- 5.16.15

[packages/kernel.git] / kernel-aufs5.patch

SPDX-License-Identifier: GPL-2.0
aufs5.x-rcN kbuild patch

diff --git a/fs/Kconfig b/fs/Kconfig
index a6313a969bc5f..aca4b89d41a14 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -312,6 +312,7 @@ source "fs/sysv/Kconfig"
 source "fs/ufs/Kconfig"
 source "fs/erofs/Kconfig"
 source "fs/vboxsf/Kconfig"
+source "fs/aufs/Kconfig"
 
 endif # MISC_FILESYSTEMS
 
diff --git a/fs/Makefile b/fs/Makefile
index 84c5e4cdfee5a..b4fcdad8412ed 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -138,3 +138,4 @@ obj-$(CONFIG_EFIVAR_FS)             += efivarfs/
 obj-$(CONFIG_EROFS_FS)         += erofs/
 obj-$(CONFIG_VBOXSF_FS)                += vboxsf/
 obj-$(CONFIG_ZONEFS_FS)                += zonefs/
+obj-$(CONFIG_AUFS_FS)           += aufs/
SPDX-License-Identifier: GPL-2.0
aufs5.x-rcN base patch

diff --git a/MAINTAINERS b/MAINTAINERS
index 5250298d28170..6b11c93d6750a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3169,6 +3169,19 @@ F:       include/uapi/linux/audit.h
 F:     kernel/audit*
 F:     lib/*audit.c
 
+AUFS (advanced multi layered unification filesystem) FILESYSTEM
+M:     "J. R. Okajima" <hooanon05g@gmail.com>
+L:     aufs-users@lists.sourceforge.net (members only)
+L:     linux-unionfs@vger.kernel.org
+S:     Supported
+W:     http://aufs.sourceforge.net
+T:     git://github.com/sfjro/aufs4-linux.git
+F:     Documentation/ABI/testing/debugfs-aufs
+F:     Documentation/ABI/testing/sysfs-aufs
+F:     Documentation/filesystems/aufs/
+F:     fs/aufs/
+F:     include/uapi/linux/aufs_type.h
+
 AUXILIARY DISPLAY DRIVERS
 M:     Miguel Ojeda <ojeda@kernel.org>
 S:     Maintained
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index a154cab6cd989..52776d48e306a 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -635,6 +635,24 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
        return error;
 }
 
+/*
+ * for AUFS
+ * no get/put for file.
+ */
+struct file *loop_backing_file(struct super_block *sb)
+{
+       struct file *ret;
+       struct loop_device *l;
+
+       ret = NULL;
+       if (MAJOR(sb->s_dev) == LOOP_MAJOR) {
+               l = sb->s_bdev->bd_disk->private_data;
+               ret = l->lo_backing_file;
+       }
+       return ret;
+}
+EXPORT_SYMBOL_GPL(loop_backing_file);
+
 /* loop sysfs attributes */
 
 static ssize_t loop_attr_show(struct device *dev, char *page,
diff --git a/fs/dcache.c b/fs/dcache.c
index cf871a81f4fdc..bc5095b734f58 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1320,7 +1320,7 @@ enum d_walk_ret {
  *
  * The @enter() callbacks are called with d_lock held.
  */
-static void d_walk(struct dentry *parent, void *data,
+void d_walk(struct dentry *parent, void *data,
                   enum d_walk_ret (*enter)(void *, struct dentry *))
 {
        struct dentry *this_parent;
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 9c6c6a3e2de51..02382fa9bd341 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -33,7 +33,7 @@
 
 #define SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT | O_NOATIME)
 
-static int setfl(int fd, struct file * filp, unsigned long arg)
+int setfl(int fd, struct file *filp, unsigned long arg)
 {
        struct inode * inode = file_inode(filp);
        int error = 0;
@@ -64,6 +64,8 @@ static int setfl(int fd, struct file * filp, unsigned long arg)
 
        if (filp->f_op->check_flags)
                error = filp->f_op->check_flags(arg);
+       if (!error && filp->f_op->setfl)
+               error = filp->f_op->setfl(filp, arg);
        if (error)
                return error;
 
diff --git a/fs/namespace.c b/fs/namespace.c
index 659a8f39c61af..1283670737826 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -808,6 +808,12 @@ static inline int check_mnt(struct mount *mnt)
        return mnt->mnt_ns == current->nsproxy->mnt_ns;
 }
 
+/* for aufs, CONFIG_AUFS_BR_FUSE */
+int is_current_mnt_ns(struct vfsmount *mnt)
+{
+       return check_mnt(real_mount(mnt));
+}
+
 /*
  * vfsmount lock must be held for write
  */
diff --git a/fs/splice.c b/fs/splice.c
index 5dbce4dcc1a7d..3e6ba363b7775 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -759,8 +759,8 @@ static int warn_unsupported(struct file *file, const char *op)
 /*
  * Attempt to initiate a splice from pipe to file.
  */
-static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
-                          loff_t *ppos, size_t len, unsigned int flags)
+long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
+                   loff_t *ppos, size_t len, unsigned int flags)
 {
        if (unlikely(!out->f_op->splice_write))
                return warn_unsupported(out, "write");
@@ -770,9 +770,9 @@ static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 /*
  * Attempt to initiate a splice from a file to a pipe.
  */
-static long do_splice_to(struct file *in, loff_t *ppos,
-                        struct pipe_inode_info *pipe, size_t len,
-                        unsigned int flags)
+long do_splice_to(struct file *in, loff_t *ppos,
+                 struct pipe_inode_info *pipe, size_t len,
+                 unsigned int flags)
 {
        unsigned int p_space;
        int ret;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1cb616fc11053..02ce64c28ef15 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1378,6 +1378,7 @@ extern void fasync_free(struct fasync_struct *);
 /* can be called from interrupts */
 extern void kill_fasync(struct fasync_struct **, int, int);
 
+extern int setfl(int fd, struct file *filp, unsigned long arg);
 extern void __f_setown(struct file *filp, struct pid *, enum pid_type, int force);
 extern int f_setown(struct file *filp, unsigned long arg, int force);
 extern void f_delown(struct file *filp);
@@ -2091,6 +2092,7 @@ struct file_operations {
        ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
        unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
        int (*check_flags)(int);
+       int (*setfl)(struct file *, unsigned long);
        int (*flock) (struct file *, int, struct file_lock *);
        ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
        ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
@@ -2614,6 +2616,7 @@ extern int current_umask(void);
 extern void ihold(struct inode * inode);
 extern void iput(struct inode *);
 extern int generic_update_time(struct inode *, struct timespec64 *, int);
+extern int update_time(struct inode *, struct timespec64 *, int);
 
 /* /sys/fs */
 extern struct kobject *fs_kobj;
@@ -2777,6 +2780,7 @@ static inline bool sb_is_blkdev_sb(struct super_block *sb)
 }
 
 void emergency_thaw_all(void);
+extern int __sync_filesystem(struct super_block *, int);
 extern int sync_filesystem(struct super_block *);
 extern const struct file_operations def_blk_fops;
 extern const struct file_operations def_chr_fops;
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 467b94257105e..dab20282c82e2 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -248,6 +248,8 @@ static inline int lockdep_match_key(struct lockdep_map *lock,
        return lock->key == key;
 }
 
+struct lock_class *lockdep_hlock_class(struct held_lock *hlock);
+
 /*
  * Acquire a lock.
  *
diff --git a/include/linux/mnt_namespace.h b/include/linux/mnt_namespace.h
index 8f882f5881e87..6b9808f098435 100644
--- a/include/linux/mnt_namespace.h
+++ b/include/linux/mnt_namespace.h
@@ -7,12 +7,15 @@ struct mnt_namespace;
 struct fs_struct;
 struct user_namespace;
 struct ns_common;
+struct vfsmount;
 
 extern struct mnt_namespace *copy_mnt_ns(unsigned long, struct mnt_namespace *,
                struct user_namespace *, struct fs_struct *);
 extern void put_mnt_ns(struct mnt_namespace *ns);
 extern struct ns_common *from_mnt_ns(struct mnt_namespace *);
 
+extern int is_current_mnt_ns(struct vfsmount *mnt);
+
 extern const struct file_operations proc_mounts_operations;
 extern const struct file_operations proc_mountinfo_operations;
 extern const struct file_operations proc_mountstats_operations;
diff --git a/include/linux/splice.h b/include/linux/splice.h
index a55179fd60fc3..8e21c53cf8831 100644
--- a/include/linux/splice.h
+++ b/include/linux/splice.h
@@ -93,4 +93,10 @@ extern void splice_shrink_spd(struct splice_pipe_desc *);
 
 extern const struct pipe_buf_operations page_cache_pipe_buf_ops;
 extern const struct pipe_buf_operations default_pipe_buf_ops;
+
+extern long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
+                          loff_t *ppos, size_t len, unsigned int flags);
+extern long do_splice_to(struct file *in, loff_t *ppos,
+                        struct pipe_inode_info *pipe, size_t len,
+                        unsigned int flags);
 #endif
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 2270ec68f10a1..fbb8e650c1749 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -189,7 +189,7 @@ static
 struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
 static DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
 
-static inline struct lock_class *hlock_class(struct held_lock *hlock)
+inline struct lock_class *lockdep_hlock_class(struct held_lock *hlock)
 {
        unsigned int class_idx = hlock->class_idx;
 
@@ -210,6 +210,7 @@ static inline struct lock_class *hlock_class(struct held_lock *hlock)
         */
        return lock_classes + class_idx;
 }
+#define hlock_class(hlock) lockdep_hlock_class(hlock)
 
 #ifdef CONFIG_LOCK_STAT
 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
SPDX-License-Identifier: GPL-2.0
aufs5.x-rcN mmap patch

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 13eda8de29981..24fd5e986cb79 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2191,7 +2191,7 @@ static int map_files_get_link(struct dentry *dentry, struct path *path)
        rc = -ENOENT;
        vma = find_exact_vma(mm, vm_start, vm_end);
        if (vma && vma->vm_file) {
-               *path = vma->vm_file->f_path;
+               *path = vma_pr_or_file(vma)->f_path;
                path_get(path);
                rc = 0;
        }
diff --git a/fs/proc/nommu.c b/fs/proc/nommu.c
index 13452b32e2bd5..38acccfef9d49 100644
--- a/fs/proc/nommu.c
+++ b/fs/proc/nommu.c
@@ -40,7 +40,10 @@ static int nommu_region_show(struct seq_file *m, struct vm_region *region)
        file = region->vm_file;
 
        if (file) {
-               struct inode *inode = file_inode(region->vm_file);
+               struct inode *inode;
+
+               file = vmr_pr_or_file(region);
+               inode = file_inode(file);
                dev = inode->i_sb->s_dev;
                ino = inode->i_ino;
        }
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index ad667dbc96f5c..d50423613c8ed 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -280,7 +280,10 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
        const char *name = NULL;
 
        if (file) {
-               struct inode *inode = file_inode(vma->vm_file);
+               struct inode *inode;
+
+               file = vma_pr_or_file(vma);
+               inode = file_inode(file);
                dev = inode->i_sb->s_dev;
                ino = inode->i_ino;
                pgoff = ((loff_t)vma->vm_pgoff) << PAGE_SHIFT;
@@ -1869,7 +1872,7 @@ static int show_numa_map(struct seq_file *m, void *v)
        struct proc_maps_private *proc_priv = &numa_priv->proc_maps;
        struct vm_area_struct *vma = v;
        struct numa_maps *md = &numa_priv->md;
-       struct file *file = vma->vm_file;
+       struct file *file = vma_pr_or_file(vma);
        struct mm_struct *mm = vma->vm_mm;
        struct mempolicy *pol;
        char buffer[64];
diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index a6d21fc0033c6..02c2de31196e0 100644
--- a/fs/proc/task_nommu.c
+++ b/fs/proc/task_nommu.c
@@ -155,7 +155,10 @@ static int nommu_vma_show(struct seq_file *m, struct vm_area_struct *vma)
        file = vma->vm_file;
 
        if (file) {
-               struct inode *inode = file_inode(vma->vm_file);
+               struct inode *inode;
+
+               file = vma_pr_or_file(vma);
+               inode = file_inode(file);
                dev = inode->i_sb->s_dev;
                ino = inode->i_ino;
                pgoff = (loff_t)vma->vm_pgoff << PAGE_SHIFT;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a7e4a9e7d807a..30699240b45d6 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1926,6 +1926,28 @@ static inline void unmap_shared_mapping_range(struct address_space *mapping,
        unmap_mapping_range(mapping, holebegin, holelen, 0);
 }
 
+extern void vma_do_file_update_time(struct vm_area_struct *, const char[], int);
+extern struct file *vma_do_pr_or_file(struct vm_area_struct *, const char[],
+                                     int);
+extern void vma_do_get_file(struct vm_area_struct *, const char[], int);
+extern void vma_do_fput(struct vm_area_struct *, const char[], int);
+
+#define vma_file_update_time(vma)      vma_do_file_update_time(vma, __func__, \
+                                                               __LINE__)
+#define vma_pr_or_file(vma)            vma_do_pr_or_file(vma, __func__, \
+                                                         __LINE__)
+#define vma_get_file(vma)              vma_do_get_file(vma, __func__, __LINE__)
+#define vma_fput(vma)                  vma_do_fput(vma, __func__, __LINE__)
+
+#ifndef CONFIG_MMU
+extern struct file *vmr_do_pr_or_file(struct vm_region *, const char[], int);
+extern void vmr_do_fput(struct vm_region *, const char[], int);
+
+#define vmr_pr_or_file(region)         vmr_do_pr_or_file(region, __func__, \
+                                                         __LINE__)
+#define vmr_fput(region)               vmr_do_fput(region, __func__, __LINE__)
+#endif /* !CONFIG_MMU */
+
 extern int access_process_vm(struct task_struct *tsk, unsigned long addr,
                void *buf, int len, unsigned int gup_flags);
 extern int access_remote_vm(struct mm_struct *mm, unsigned long addr,
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index c3a6e62096006..45f5754d51cd1 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -370,6 +370,7 @@ struct vm_region {
        unsigned long   vm_top;         /* region allocated to here */
        unsigned long   vm_pgoff;       /* the offset in vm_file corresponding to vm_start */
        struct file     *vm_file;       /* the backing file or NULL */
+       struct file     *vm_prfile;     /* the virtual backing file or NULL */
 
        int             vm_usage;       /* region usage count (access under nommu_region_sem) */
        bool            vm_icache_flushed : 1; /* true if the icache has been flushed for
@@ -449,6 +450,7 @@ struct vm_area_struct {
        unsigned long vm_pgoff;         /* Offset (within vm_file) in PAGE_SIZE
                                           units */
        struct file * vm_file;          /* File we map to (can be NULL). */
+       struct file *vm_prfile;         /* shadow of vm_file */
        void * vm_private_data;         /* was vm_pte (shared mem) */
 
 #ifdef CONFIG_SWAP
diff --git a/kernel/fork.c b/kernel/fork.c
index 3244cc56b697d..ae63cce182fdc 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -572,7 +572,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
                if (file) {
                        struct address_space *mapping = file->f_mapping;
 
-                       get_file(file);
+                       vma_get_file(tmp);
                        i_mmap_lock_write(mapping);
                        if (tmp->vm_flags & VM_SHARED)
                                mapping_allow_writable(mapping);
diff --git a/mm/Makefile b/mm/Makefile
index d6c0042e3aa0d..1f11c655a632b 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -52,7 +52,7 @@ obj-y                 := filemap.o mempool.o oom_kill.o fadvise.o \
                           mm_init.o percpu.o slab_common.o \
                           compaction.o vmacache.o \
                           interval_tree.o list_lru.o workingset.o \
-                          debug.o gup.o mmap_lock.o $(mmu-y)
+                          prfile.o debug.o gup.o mmap_lock.o $(mmu-y)
 
 # Give 'page_alloc' its own module-parameter namespace
 page-alloc-y := page_alloc.o
diff --git a/mm/filemap.c b/mm/filemap.c
index daa0e23a6ee66..1c1f517516f26 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3358,7 +3358,7 @@ vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
        vm_fault_t ret = VM_FAULT_LOCKED;
 
        sb_start_pagefault(mapping->host->i_sb);
-       file_update_time(vmf->vma->vm_file);
+       vma_file_update_time(vmf->vma);
        lock_page(page);
        if (page->mapping != mapping) {
                unlock_page(page);
diff --git a/mm/mmap.c b/mm/mmap.c
index bfb0ea164a90a..6bbc17d4733df 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -183,7 +183,7 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
        if (vma->vm_ops && vma->vm_ops->close)
                vma->vm_ops->close(vma);
        if (vma->vm_file)
-               fput(vma->vm_file);
+               vma_fput(vma);
        mpol_put(vma_policy(vma));
        vm_area_free(vma);
        return next;
@@ -952,7 +952,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
        if (remove_next) {
                if (file) {
                        uprobe_munmap(next, next->vm_start, next->vm_end);
-                       fput(file);
+                       vma_fput(vma);
                }
                if (next->anon_vma)
                        anon_vma_merge(vma, next);
@@ -1872,7 +1872,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
        return addr;
 
 unmap_and_free_vma:
-       fput(vma->vm_file);
+       vma_fput(vma);
        vma->vm_file = NULL;
 
        /* Undo any partial mapping done by a device driver. */
@@ -2730,7 +2730,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
                goto out_free_mpol;
 
        if (new->vm_file)
-               get_file(new->vm_file);
+               vma_get_file(new);
 
        if (new->vm_ops && new->vm_ops->open)
                new->vm_ops->open(new);
@@ -2749,7 +2749,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
        if (new->vm_ops && new->vm_ops->close)
                new->vm_ops->close(new);
        if (new->vm_file)
-               fput(new->vm_file);
+               vma_fput(new);
        unlink_anon_vmas(new);
  out_free_mpol:
        mpol_put(vma_policy(new));
@@ -2944,7 +2944,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
        struct vm_area_struct *vma;
        unsigned long populate = 0;
        unsigned long ret = -EINVAL;
-       struct file *file;
+       struct file *file, *prfile;
 
        pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. See Documentation/vm/remap_file_pages.rst.\n",
                     current->comm, current->pid);
@@ -3000,10 +3000,27 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
        if (vma->vm_flags & VM_LOCKED)
                flags |= MAP_LOCKED;
 
-       file = get_file(vma->vm_file);
+       vma_get_file(vma);
+       file = vma->vm_file;
+       prfile = vma->vm_prfile;
        ret = do_mmap(vma->vm_file, start, size,
                        prot, flags, pgoff, &populate, NULL);
+       if (!IS_ERR_VALUE(ret) && file && prfile) {
+               struct vm_area_struct *new_vma;
+
+               new_vma = find_vma(mm, ret);
+               if (!new_vma->vm_prfile)
+                       new_vma->vm_prfile = prfile;
+               if (new_vma != vma)
+                       get_file(prfile);
+       }
+       /*
+        * two fput()s instead of vma_fput(vma),
+        * coz vma may not be available anymore.
+        */
        fput(file);
+       if (prfile)
+               fput(prfile);
 out:
        mmap_write_unlock(mm);
        if (populate)
@@ -3284,7 +3301,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
                if (anon_vma_clone(new_vma, vma))
                        goto out_free_mempol;
                if (new_vma->vm_file)
-                       get_file(new_vma->vm_file);
+                       vma_get_file(new_vma);
                if (new_vma->vm_ops && new_vma->vm_ops->open)
                        new_vma->vm_ops->open(new_vma);
                vma_link(mm, new_vma, prev, rb_link, rb_parent);
diff --git a/mm/nommu.c b/mm/nommu.c
index 55a9e48a7a026..8dc77ce96335a 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -522,7 +522,7 @@ static void __put_nommu_region(struct vm_region *region)
                up_write(&nommu_region_sem);
 
                if (region->vm_file)
-                       fput(region->vm_file);
+                       vmr_fput(region);
 
                /* IO memory and memory shared directly out of the pagecache
                 * from ramfs/tmpfs mustn't be released here */
@@ -654,7 +654,7 @@ static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma)
        if (vma->vm_ops && vma->vm_ops->close)
                vma->vm_ops->close(vma);
        if (vma->vm_file)
-               fput(vma->vm_file);
+               vma_fput(vma);
        put_nommu_region(vma->vm_region);
        vm_area_free(vma);
 }
@@ -1174,7 +1174,7 @@ unsigned long do_mmap(struct file *file,
                                        goto error_just_free;
                                }
                        }
-                       fput(region->vm_file);
+                       vmr_fput(region);
                        kmem_cache_free(vm_region_jar, region);
                        region = pregion;
                        result = start;
@@ -1251,10 +1251,10 @@ unsigned long do_mmap(struct file *file,
        up_write(&nommu_region_sem);
 error:
        if (region->vm_file)
-               fput(region->vm_file);
+               vmr_fput(region);
        kmem_cache_free(vm_region_jar, region);
        if (vma->vm_file)
-               fput(vma->vm_file);
+               vma_fput(vma);
        vm_area_free(vma);
        return ret;
 
diff --git a/mm/prfile.c b/mm/prfile.c
new file mode 100644
index 0000000000000..511543ab1b418
--- /dev/null
+++ b/mm/prfile.c
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Mainly for aufs which mmap(2) different file and wants to print different
+ * path in /proc/PID/maps.
+ * Call these functions via macros defined in linux/mm.h.
+ *
+ * See Documentation/filesystems/aufs/design/06mmap.txt
+ *
+ * Copyright (c) 2014-2021 Junjro R. Okajima
+ * Copyright (c) 2014 Ian Campbell
+ */
+
+#include <linux/mm.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+
+/* #define PRFILE_TRACE */
+static inline void prfile_trace(struct file *f, struct file *pr,
+                             const char func[], int line, const char func2[])
+{
+#ifdef PRFILE_TRACE
+       if (pr)
+               pr_info("%s:%d: %s, %pD2\n", func, line, func2, f);
+#endif
+}
+
+void vma_do_file_update_time(struct vm_area_struct *vma, const char func[],
+                            int line)
+{
+       struct file *f = vma->vm_file, *pr = vma->vm_prfile;
+
+       prfile_trace(f, pr, func, line, __func__);
+       file_update_time(f);
+       if (f && pr)
+               file_update_time(pr);
+}
+
+struct file *vma_do_pr_or_file(struct vm_area_struct *vma, const char func[],
+                              int line)
+{
+       struct file *f = vma->vm_file, *pr = vma->vm_prfile;
+
+       prfile_trace(f, pr, func, line, __func__);
+       return (f && pr) ? pr : f;
+}
+
+void vma_do_get_file(struct vm_area_struct *vma, const char func[], int line)
+{
+       struct file *f = vma->vm_file, *pr = vma->vm_prfile;
+
+       prfile_trace(f, pr, func, line, __func__);
+       get_file(f);
+       if (f && pr)
+               get_file(pr);
+}
+
+void vma_do_fput(struct vm_area_struct *vma, const char func[], int line)
+{
+       struct file *f = vma->vm_file, *pr = vma->vm_prfile;
+
+       prfile_trace(f, pr, func, line, __func__);
+       fput(f);
+       if (f && pr)
+               fput(pr);
+}
+
+#ifndef CONFIG_MMU
+struct file *vmr_do_pr_or_file(struct vm_region *region, const char func[],
+                              int line)
+{
+       struct file *f = region->vm_file, *pr = region->vm_prfile;
+
+       prfile_trace(f, pr, func, line, __func__);
+       return (f && pr) ? pr : f;
+}
+
+void vmr_do_fput(struct vm_region *region, const char func[], int line)
+{
+       struct file *f = region->vm_file, *pr = region->vm_prfile;
+
+       prfile_trace(f, pr, func, line, __func__);
+       fput(f);
+       if (f && pr)
+               fput(pr);
+}
+#endif /* !CONFIG_MMU */
SPDX-License-Identifier: GPL-2.0
aufs5.x-rcN standalone patch

diff --git a/fs/dcache.c b/fs/dcache.c
index bc5095b734f58..9508bd57a3bc0 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1425,6 +1425,7 @@ void d_walk(struct dentry *parent, void *data,
        seq = 1;
        goto again;
 }
+EXPORT_SYMBOL_GPL(d_walk);
 
 struct check_mount {
        struct vfsmount *mnt;
@@ -2970,6 +2971,7 @@ void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
 
        write_sequnlock(&rename_lock);
 }
+EXPORT_SYMBOL_GPL(d_exchange);
 
 /**
  * d_ancestor - search for an ancestor
diff --git a/fs/exec.c b/fs/exec.c
index 537d92c41105b..0ab811e0fdaae 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -111,6 +111,7 @@ bool path_noexec(const struct path *path)
        return (path->mnt->mnt_flags & MNT_NOEXEC) ||
               (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
 }
+EXPORT_SYMBOL_GPL(path_noexec);
 
 #ifdef CONFIG_USELIB
 /*
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 02382fa9bd341..3418c60b90146 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -86,6 +86,7 @@ int setfl(int fd, struct file *filp, unsigned long arg)
  out:
        return error;
 }
+EXPORT_SYMBOL_GPL(setfl);
 
 static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
                      int force)
diff --git a/fs/file_table.c b/fs/file_table.c
index 45437f8e1003e..786af52904fcf 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -161,6 +161,7 @@ struct file *alloc_empty_file(int flags, const struct cred *cred)
        }
        return ERR_PTR(-ENFILE);
 }
+EXPORT_SYMBOL_GPL(alloc_empty_file);
 
 /*
  * Variant of alloc_empty_file() that doesn't check and modify nr_files.
@@ -375,6 +376,7 @@ void __fput_sync(struct file *file)
 }
 
 EXPORT_SYMBOL(fput);
+EXPORT_SYMBOL_GPL(__fput_sync);
 
 void __init files_init(void)
 {
diff --git a/fs/namespace.c b/fs/namespace.c
index 1283670737826..db99365620118 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -439,6 +439,7 @@ void __mnt_drop_write(struct vfsmount *mnt)
        mnt_dec_writers(real_mount(mnt));
        preempt_enable();
 }
+EXPORT_SYMBOL_GPL(__mnt_drop_write);
 
 /**
  * mnt_drop_write - give up write access to a mount
@@ -813,6 +814,7 @@ int is_current_mnt_ns(struct vfsmount *mnt)
 {
        return check_mnt(real_mount(mnt));
 }
+EXPORT_SYMBOL_GPL(is_current_mnt_ns);
 
 /*
  * vfsmount lock must be held for write
@@ -2011,6 +2013,7 @@ int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
        }
        return 0;
 }
+EXPORT_SYMBOL_GPL(iterate_mounts);
 
 static void lock_mnt_tree(struct mount *mnt)
 {
diff --git a/fs/notify/group.c b/fs/notify/group.c
index 6a297efc47887..ed394ccb10e00 100644
--- a/fs/notify/group.c
+++ b/fs/notify/group.c
@@ -100,6 +100,7 @@ void fsnotify_get_group(struct fsnotify_group *group)
 {
        refcount_inc(&group->refcnt);
 }
+EXPORT_SYMBOL_GPL(fsnotify_get_group);
 
 /*
  * Drop a reference to a group.  Free it if it's through.
diff --git a/fs/open.c b/fs/open.c
index f732fb94600ce..ca33d86e73fd2 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -65,6 +65,7 @@ int do_truncate(struct user_namespace *mnt_userns, struct dentry *dentry,
        inode_unlock(dentry->d_inode);
        return ret;
 }
+EXPORT_SYMBOL_GPL(do_truncate);
 
 long vfs_truncate(const struct path *path, loff_t length)
 {
diff --git a/fs/read_write.c b/fs/read_write.c
index 0074afa7ecb3e..612cf04d9f6b9 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -488,6 +488,7 @@ ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
        inc_syscr(current);
        return ret;
 }
+EXPORT_SYMBOL_GPL(vfs_read);
 
 static ssize_t new_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos)
 {
@@ -598,6 +599,7 @@ ssize_t vfs_write(struct file *file, const char __user *buf, size_t count, loff_
        file_end_write(file);
        return ret;
 }
+EXPORT_SYMBOL_GPL(vfs_write);
 
 /* file_ppos returns &file->f_pos or NULL if file is stream */
 static inline loff_t *file_ppos(struct file *file)
diff --git a/fs/splice.c b/fs/splice.c
index 3e6ba363b7775..7c1be373eb7cd 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -766,6 +766,7 @@ long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
                return warn_unsupported(out, "write");
        return out->f_op->splice_write(pipe, out, ppos, len, flags);
 }
+EXPORT_SYMBOL_GPL(do_splice_from);
 
 /*
  * Attempt to initiate a splice from a file to a pipe.
@@ -795,6 +796,7 @@ long do_splice_to(struct file *in, loff_t *ppos,
                return warn_unsupported(in, "read");
        return in->f_op->splice_read(in, ppos, pipe, len, flags);
 }
+EXPORT_SYMBOL_GPL(do_splice_to);
 
 /**
  * splice_direct_to_actor - splices data directly between two non-pipes
diff --git a/fs/xattr.c b/fs/xattr.c
index 5c8c5175b385c..ff7e9ff774b73 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -384,6 +384,7 @@ vfs_getxattr_alloc(struct user_namespace *mnt_userns, struct dentry *dentry,
        *xattr_value = value;
        return error;
 }
+EXPORT_SYMBOL_GPL(vfs_getxattr_alloc);
 
 ssize_t
 __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index fbb8e650c1749..49c4d11b08938 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -210,6 +210,7 @@ inline struct lock_class *lockdep_hlock_class(struct held_lock *hlock)
         */
        return lock_classes + class_idx;
 }
+EXPORT_SYMBOL_GPL(lockdep_hlock_class);
 #define hlock_class(hlock) lockdep_hlock_class(hlock)
 
 #ifdef CONFIG_LOCK_STAT
diff --git a/kernel/task_work.c b/kernel/task_work.c
index 1698fbe6f0e13..081b05acadf82 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -167,3 +167,4 @@ void task_work_run(void)
                } while (work);
        }
 }
+EXPORT_SYMBOL_GPL(task_work_run);
diff --git a/security/security.c b/security/security.c
index c88167a414b41..125724525d5c0 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1148,6 +1148,7 @@ int security_path_rmdir(const struct path *dir, struct dentry *dentry)
                return 0;
        return call_int_hook(path_rmdir, 0, dir, dentry);
 }
+EXPORT_SYMBOL_GPL(security_path_rmdir);
 
 int security_path_unlink(const struct path *dir, struct dentry *dentry)
 {
@@ -1164,6 +1165,7 @@ int security_path_symlink(const struct path *dir, struct dentry *dentry,
                return 0;
        return call_int_hook(path_symlink, 0, dir, dentry, old_name);
 }
+EXPORT_SYMBOL_GPL(security_path_symlink);
 
 int security_path_link(struct dentry *old_dentry, const struct path *new_dir,
                       struct dentry *new_dentry)
@@ -1172,6 +1174,7 @@ int security_path_link(struct dentry *old_dentry, const struct path *new_dir,
                return 0;
        return call_int_hook(path_link, 0, old_dentry, new_dir, new_dentry);
 }
+EXPORT_SYMBOL_GPL(security_path_link);
 
 int security_path_rename(const struct path *old_dir, struct dentry *old_dentry,
                         const struct path *new_dir, struct dentry *new_dentry,
@@ -1199,6 +1202,7 @@ int security_path_truncate(const struct path *path)
                return 0;
        return call_int_hook(path_truncate, 0, path);
 }
+EXPORT_SYMBOL_GPL(security_path_truncate);
 
 int security_path_chmod(const struct path *path, umode_t mode)
 {
@@ -1206,6 +1210,7 @@ int security_path_chmod(const struct path *path, umode_t mode)
                return 0;
        return call_int_hook(path_chmod, 0, path, mode);
 }
+EXPORT_SYMBOL_GPL(security_path_chmod);
 
 int security_path_chown(const struct path *path, kuid_t uid, kgid_t gid)
 {
@@ -1213,6 +1218,7 @@ int security_path_chown(const struct path *path, kuid_t uid, kgid_t gid)
                return 0;
        return call_int_hook(path_chown, 0, path, uid, gid);
 }
+EXPORT_SYMBOL_GPL(security_path_chown);
 
 int security_path_chroot(const struct path *path)
 {
@@ -1313,6 +1319,7 @@ int security_inode_permission(struct inode *inode, int mask)
                return 0;
        return call_int_hook(inode_permission, 0, inode, mask);
 }
+EXPORT_SYMBOL_GPL(security_inode_permission);
 
 int security_inode_setattr(struct dentry *dentry, struct iattr *attr)
 {
@@ -1510,6 +1517,7 @@ int security_file_permission(struct file *file, int mask)
 
        return fsnotify_perm(file, mask);
 }
+EXPORT_SYMBOL_GPL(security_file_permission);
 
 int security_file_alloc(struct file *file)
 {
diff -urN /usr/share/empty/Documentation/ABI/testing/debugfs-aufs linux/Documentation/ABI/testing/debugfs-aufs
--- /usr/share/empty/Documentation/ABI/testing/debugfs-aufs     1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/ABI/testing/debugfs-aufs        2021-12-03 15:38:59.926647310 +0100
@@ -0,0 +1,55 @@
+What:          /debug/aufs/si_<id>/
+Date:          March 2009
+Contact:       J. R. Okajima <hooanon05g@gmail.com>
+Description:
+               Under /debug/aufs, a directory named si_<id> is created
+               per aufs mount, where <id> is a unique id generated
+               internally.
+
+What:          /debug/aufs/si_<id>/plink
+Date:          Apr 2013
+Contact:       J. R. Okajima <hooanon05g@gmail.com>
+Description:
+               It has three lines and shows the information about the
+               pseudo-link. The first line is a single number
+               representing a number of buckets. The second line is a
+               number of pseudo-links per buckets (separated by a
+               blank). The last line is a single number representing a
+               total number of psedo-links.
+               When the aufs mount option 'noplink' is specified, it
+               will show "1\n0\n0\n".
+
+What:          /debug/aufs/si_<id>/xib
+Date:          March 2009
+Contact:       J. R. Okajima <hooanon05g@gmail.com>
+Description:
+               It shows the consumed blocks by xib (External Inode Number
+               Bitmap), its block size and file size.
+               When the aufs mount option 'noxino' is specified, it
+               will be empty. About XINO files, see the aufs manual.
+
+What:          /debug/aufs/si_<id>/xi<branch-index>
+Date:          March 2009
+Contact:       J. R. Okajima <hooanon05g@gmail.com>
+Description:
+               It shows the consumed blocks by xino (External Inode Number
+               Translation Table), its link count, block size and file
+               size.
+               Due to the file size limit, there may exist multiple
+               xino files per branch.  In this case, "-N" is added to
+               the filename and it corresponds to the index of the
+               internal xino array.  "-0" is omitted.
+               When the aufs mount option 'noxino' is specified, Those
+               entries won't exist.  About XINO files, see the aufs
+               manual.
+
+What:          /debug/aufs/si_<id>/xigen
+Date:          March 2009
+Contact:       J. R. Okajima <hooanon05g@gmail.com>
+Description:
+               It shows the consumed blocks by xigen (External Inode
+               Generation Table), its block size and file size.
+               If CONFIG_AUFS_EXPORT is disabled, this entry will not
+               be created.
+               When the aufs mount option 'noxino' is specified, it
+               will be empty. About XINO files, see the aufs manual.
diff -urN /usr/share/empty/Documentation/ABI/testing/sysfs-aufs linux/Documentation/ABI/testing/sysfs-aufs
--- /usr/share/empty/Documentation/ABI/testing/sysfs-aufs       1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/ABI/testing/sysfs-aufs  2021-12-03 15:38:59.926647310 +0100
@@ -0,0 +1,31 @@
+What:          /sys/fs/aufs/si_<id>/
+Date:          March 2009
+Contact:       J. R. Okajima <hooanon05g@gmail.com>
+Description:
+               Under /sys/fs/aufs, a directory named si_<id> is created
+               per aufs mount, where <id> is a unique id generated
+               internally.
+
+What:          /sys/fs/aufs/si_<id>/br<idx>
+Date:          March 2009
+Contact:       J. R. Okajima <hooanon05g@gmail.com>
+Description:
+               It shows the abolute path of a member directory (which
+               is called branch) in aufs, and its permission.
+
+What:          /sys/fs/aufs/si_<id>/brid<idx>
+Date:          July 2013
+Contact:       J. R. Okajima <hooanon05g@gmail.com>
+Description:
+               It shows the id of a member directory (which is called
+               branch) in aufs.
+
+What:          /sys/fs/aufs/si_<id>/xi_path
+Date:          March 2009
+Contact:       J. R. Okajima <hooanon05g@gmail.com>
+Description:
+               It shows the abolute path of XINO (External Inode Number
+               Bitmap, Translation Table and Generation Table) file
+               even if it is the default path.
+               When the aufs mount option 'noxino' is specified, it
+               will be empty. About XINO files, see the aufs manual.
diff -urN /usr/share/empty/Documentation/filesystems/aufs/design/01intro.txt linux/Documentation/filesystems/aufs/design/01intro.txt
--- /usr/share/empty/Documentation/filesystems/aufs/design/01intro.txt  1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/filesystems/aufs/design/01intro.txt     2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,171 @@
+
+# Copyright (C) 2005-2021 Junjiro R. Okajima
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Introduction
+----------------------------------------
+
+aufs [ei ju: ef es] | /ey-yoo-ef-es/ | [a u f s]
+1. abbrev. for "advanced multi-layered unification filesystem".
+2. abbrev. for "another unionfs".
+3. abbrev. for "auf das" in German which means "on the" in English.
+   Ex. "Butter aufs Brot"(G) means "butter onto bread"(E).
+   But "Filesystem aufs Filesystem" is hard to understand.
+4. abbrev. for "African Urban Fashion Show".
+
+AUFS is a filesystem with features:
+- multi layered stackable unification filesystem, the member directory
+  is called as a branch.
+- branch permission and attribute, 'readonly', 'real-readonly',
+  'readwrite', 'whiteout-able', 'link-able whiteout', etc. and their
+  combination.
+- internal "file copy-on-write".
+- logical deletion, whiteout.
+- dynamic branch manipulation, adding, deleting and changing permission.
+- allow bypassing aufs, user's direct branch access.
+- external inode number translation table and bitmap which maintains the
+  persistent aufs inode number.
+- seekable directory, including NFS readdir.
+- file mapping, mmap and sharing pages.
+- pseudo-link, hardlink over branches.
+- loopback mounted filesystem as a branch.
+- several policies to select one among multiple writable branches.
+- revert a single systemcall when an error occurs in aufs.
+- and more...
+
+
+Multi Layered Stackable Unification Filesystem
+----------------------------------------------------------------------
+Most people already knows what it is.
+It is a filesystem which unifies several directories and provides a
+merged single directory. When users access a file, the access will be
+passed/re-directed/converted (sorry, I am not sure which English word is
+correct) to the real file on the member filesystem. The member
+filesystem is called 'lower filesystem' or 'branch' and has a mode
+'readonly' and 'readwrite.' And the deletion for a file on the lower
+readonly branch is handled by creating 'whiteout' on the upper writable
+branch.
+
+On LKML, there have been discussions about UnionMount (Jan Blunck,
+Bharata B Rao and Valerie Aurora) and Unionfs (Erez Zadok). They took
+different approaches to implement the merged-view.
+The former tries putting it into VFS, and the latter implements as a
+separate filesystem.
+(If I misunderstand about these implementations, please let me know and
+I shall correct it. Because it is a long time ago when I read their
+source files last time).
+
+UnionMount's approach will be able to small, but may be hard to share
+branches between several UnionMount since the whiteout in it is
+implemented in the inode on branch filesystem and always
+shared. According to Bharata's post, readdir does not seems to be
+finished yet.
+There are several missing features known in this implementations such as
+- for users, the inode number may change silently. eg. copy-up.
+- link(2) may break by copy-up.
+- read(2) may get an obsoleted filedata (fstat(2) too).
+- fcntl(F_SETLK) may be broken by copy-up.
+- unnecessary copy-up may happen, for example mmap(MAP_PRIVATE) after
+  open(O_RDWR).
+
+In linux-3.18, "overlay" filesystem (formerly known as "overlayfs") was
+merged into mainline. This is another implementation of UnionMount as a
+separated filesystem. All the limitations and known problems which
+UnionMount are equally inherited to "overlay" filesystem.
+
+Unionfs has a longer history. When I started implementing a stackable
+filesystem (Aug 2005), it already existed. It has virtual super_block,
+inode, dentry and file objects and they have an array pointing lower
+same kind objects. After contributing many patches for Unionfs, I
+re-started my project AUFS (Jun 2006).
+
+In AUFS, the structure of filesystem resembles to Unionfs, but I
+implemented my own ideas, approaches and enhancements and it became
+totally different one.
+
+Comparing DM snapshot and fs based implementation
+- the number of bytes to be copied between devices is much smaller.
+- the type of filesystem must be one and only.
+- the fs must be writable, no readonly fs, even for the lower original
+  device. so the compression fs will not be usable. but if we use
+  loopback mount, we may address this issue.
+  for instance,
+       mount /cdrom/squashfs.img /sq
+       losetup /sq/ext2.img
+       losetup /somewhere/cow
+       dmsetup "snapshot /dev/loop0 /dev/loop1 ..."
+- it will be difficult (or needs more operations) to extract the
+  difference between the original device and COW.
+- DM snapshot-merge may help a lot when users try merging. in the
+  fs-layer union, users will use rsync(1).
+
+You may want to read my old paper "Filesystems in LiveCD"
+(http://aufs.sourceforge.net/aufs2/report/sq/sq.pdf).
+
+
+Several characters/aspects/persona of aufs
+----------------------------------------------------------------------
+
+Aufs has several characters, aspects or persona.
+1. a filesystem, callee of VFS helper
+2. sub-VFS, caller of VFS helper for branches
+3. a virtual filesystem which maintains persistent inode number
+4. reader/writer of files on branches such like an application
+
+1. Callee of VFS Helper
+As an ordinary linux filesystem, aufs is a callee of VFS. For instance,
+unlink(2) from an application reaches sys_unlink() kernel function and
+then vfs_unlink() is called. vfs_unlink() is one of VFS helper and it
+calls filesystem specific unlink operation. Actually aufs implements the
+unlink operation but it behaves like a redirector.
+
+2. Caller of VFS Helper for Branches
+aufs_unlink() passes the unlink request to the branch filesystem as if
+it were called from VFS. So the called unlink operation of the branch
+filesystem acts as usual. As a caller of VFS helper, aufs should handle
+every necessary pre/post operation for the branch filesystem.
+- acquire the lock for the parent dir on a branch
+- lookup in a branch
+- revalidate dentry on a branch
+- mnt_want_write() for a branch
+- vfs_unlink() for a branch
+- mnt_drop_write() for a branch
+- release the lock on a branch
+
+3. Persistent Inode Number
+One of the most important issue for a filesystem is to maintain inode
+numbers. This is particularly important to support exporting a
+filesystem via NFS. Aufs is a virtual filesystem which doesn't have a
+backend block device for its own. But some storage is necessary to
+keep and maintain the inode numbers. It may be a large space and may not
+suit to keep in memory. Aufs rents some space from its first writable
+branch filesystem (by default) and creates file(s) on it. These files
+are created by aufs internally and removed soon (currently) keeping
+opened.
+Note: Because these files are removed, they are totally gone after
+      unmounting aufs. It means the inode numbers are not persistent
+      across unmount or reboot. I have a plan to make them really
+      persistent which will be important for aufs on NFS server.
+
+4. Read/Write Files Internally (copy-on-write)
+Because a branch can be readonly, when you write a file on it, aufs will
+"copy-up" it to the upper writable branch internally. And then write the
+originally requested thing to the file. Generally kernel doesn't
+open/read/write file actively. In aufs, even a single write may cause a
+internal "file copy". This behaviour is very similar to cp(1) command.
+
+Some people may think it is better to pass such work to user space
+helper, instead of doing in kernel space. Actually I am still thinking
+about it. But currently I have implemented it in kernel space.
diff -urN /usr/share/empty/Documentation/filesystems/aufs/design/02struct.txt linux/Documentation/filesystems/aufs/design/02struct.txt
--- /usr/share/empty/Documentation/filesystems/aufs/design/02struct.txt 1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/filesystems/aufs/design/02struct.txt    2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,258 @@
+
+# Copyright (C) 2005-2021 Junjiro R. Okajima
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Basic Aufs Internal Structure
+
+Superblock/Inode/Dentry/File Objects
+----------------------------------------------------------------------
+As like an ordinary filesystem, aufs has its own
+superblock/inode/dentry/file objects. All these objects have a
+dynamically allocated array and store the same kind of pointers to the
+lower filesystem, branch.
+For example, when you build a union with one readwrite branch and one
+readonly, mounted /au, /rw and /ro respectively.
+- /au = /rw + /ro
+- /ro/fileA exists but /rw/fileA
+
+Aufs lookup operation finds /ro/fileA and gets dentry for that. These
+pointers are stored in a aufs dentry. The array in aufs dentry will be,
+- [0] = NULL (because /rw/fileA doesn't exist)
+- [1] = /ro/fileA
+
+This style of an array is essentially same to the aufs
+superblock/inode/dentry/file objects.
+
+Because aufs supports manipulating branches, ie. add/delete/change
+branches dynamically, these objects has its own generation. When
+branches are changed, the generation in aufs superblock is
+incremented. And a generation in other object are compared when it is
+accessed. When a generation in other objects are obsoleted, aufs
+refreshes the internal array.
+
+
+Superblock
+----------------------------------------------------------------------
+Additionally aufs superblock has some data for policies to select one
+among multiple writable branches, XIB files, pseudo-links and kobject.
+See below in detail.
+About the policies which supports copy-down a directory, see
+wbr_policy.txt too.
+
+
+Branch and XINO(External Inode Number Translation Table)
+----------------------------------------------------------------------
+Every branch has its own xino (external inode number translation table)
+file. The xino file is created and unlinked by aufs internally. When two
+members of a union exist on the same filesystem, they share the single
+xino file.
+The struct of a xino file is simple, just a sequence of aufs inode
+numbers which is indexed by the lower inode number.
+In the above sample, assume the inode number of /ro/fileA is i111 and
+aufs assigns the inode number i999 for fileA. Then aufs writes 999 as
+4(8) bytes at 111 * 4(8) bytes offset in the xino file.
+
+When the inode numbers are not contiguous, the xino file will be sparse
+which has a hole in it and doesn't consume as much disk space as it
+might appear. If your branch filesystem consumes disk space for such
+holes, then you should specify 'xino=' option at mounting aufs.
+
+Aufs has a mount option to free the disk blocks for such holes in XINO
+files on tmpfs or ramdisk. But it is not so effective actually. If you
+meet a problem of disk shortage due to XINO files, then you should try
+"tmpfs-ino.patch" (and "vfs-ino.patch" too) in aufs4-standalone.git.
+The patch localizes the assignment inumbers per tmpfs-mount and avoid
+the holes in XINO files.
+
+Also a writable branch has three kinds of "whiteout bases". All these
+are existed when the branch is joined to aufs, and their names are
+whiteout-ed doubly, so that users will never see their names in aufs
+hierarchy.
+1. a regular file which will be hardlinked to all whiteouts.
+2. a directory to store a pseudo-link.
+3. a directory to store an "orphan"-ed file temporary.
+
+1. Whiteout Base
+   When you remove a file on a readonly branch, aufs handles it as a
+   logical deletion and creates a whiteout on the upper writable branch
+   as a hardlink of this file in order not to consume inode on the
+   writable branch.
+2. Pseudo-link Dir
+   See below, Pseudo-link.
+3. Step-Parent Dir
+   When "fileC" exists on the lower readonly branch only and it is
+   opened and removed with its parent dir, and then user writes
+   something into it, then aufs copies-up fileC to this
+   directory. Because there is no other dir to store fileC. After
+   creating a file under this dir, the file is unlinked.
+
+Because aufs supports manipulating branches, ie. add/delete/change
+dynamically, a branch has its own id. When the branch order changes,
+aufs finds the new index by searching the branch id.
+
+
+Pseudo-link
+----------------------------------------------------------------------
+Assume "fileA" exists on the lower readonly branch only and it is
+hardlinked to "fileB" on the branch. When you write something to fileA,
+aufs copies-up it to the upper writable branch. Additionally aufs
+creates a hardlink under the Pseudo-link Directory of the writable
+branch. The inode of a pseudo-link is kept in aufs super_block as a
+simple list. If fileB is read after unlinking fileA, aufs returns
+filedata from the pseudo-link instead of the lower readonly
+branch. Because the pseudo-link is based upon the inode, to keep the
+inode number by xino (see above) is essentially necessary.
+
+All the hardlinks under the Pseudo-link Directory of the writable branch
+should be restored in a proper location later. Aufs provides a utility
+to do this. The userspace helpers executed at remounting and unmounting
+aufs by default.
+During this utility is running, it puts aufs into the pseudo-link
+maintenance mode. In this mode, only the process which began the
+maintenance mode (and its child processes) is allowed to operate in
+aufs. Some other processes which are not related to the pseudo-link will
+be allowed to run too, but the rest have to return an error or wait
+until the maintenance mode ends. If a process already acquires an inode
+mutex (in VFS), it has to return an error.
+
+
+XIB(external inode number bitmap)
+----------------------------------------------------------------------
+Addition to the xino file per a branch, aufs has an external inode number
+bitmap in a superblock object. It is also an internal file such like a
+xino file.
+It is a simple bitmap to mark whether the aufs inode number is in-use or
+not.
+To reduce the file I/O, aufs prepares a single memory page to cache xib.
+
+As well as XINO files, aufs has a feature to truncate/refresh XIB to
+reduce the number of consumed disk blocks for these files.
+
+
+Virtual or Vertical Dir, and Readdir in Userspace
+----------------------------------------------------------------------
+In order to support multiple layers (branches), aufs readdir operation
+constructs a virtual dir block on memory. For readdir, aufs calls
+vfs_readdir() internally for each dir on branches, merges their entries
+with eliminating the whiteout-ed ones, and sets it to file (dir)
+object. So the file object has its entry list until it is closed. The
+entry list will be updated when the file position is zero and becomes
+obsoleted. This decision is made in aufs automatically.
+
+The dynamically allocated memory block for the name of entries has a
+unit of 512 bytes (by default) and stores the names contiguously (no
+padding). Another block for each entry is handled by kmem_cache too.
+During building dir blocks, aufs creates hash list and judging whether
+the entry is whiteouted by its upper branch or already listed.
+The merged result is cached in the corresponding inode object and
+maintained by a customizable life-time option.
+
+Some people may call it can be a security hole or invite DoS attack
+since the opened and once readdir-ed dir (file object) holds its entry
+list and becomes a pressure for system memory. But I'd say it is similar
+to files under /proc or /sys. The virtual files in them also holds a
+memory page (generally) while they are opened. When an idea to reduce
+memory for them is introduced, it will be applied to aufs too.
+For those who really hate this situation, I've developed readdir(3)
+library which operates this merging in userspace. You just need to set
+LD_PRELOAD environment variable, and aufs will not consume no memory in
+kernel space for readdir(3).
+
+
+Workqueue
+----------------------------------------------------------------------
+Aufs sometimes requires privilege access to a branch. For instance,
+in copy-up/down operation. When a user process is going to make changes
+to a file which exists in the lower readonly branch only, and the mode
+of one of ancestor directories may not be writable by a user
+process. Here aufs copy-up the file with its ancestors and they may
+require privilege to set its owner/group/mode/etc.
+This is a typical case of a application character of aufs (see
+Introduction).
+
+Aufs uses workqueue synchronously for this case. It creates its own
+workqueue. The workqueue is a kernel thread and has privilege. Aufs
+passes the request to call mkdir or write (for example), and wait for
+its completion. This approach solves a problem of a signal handler
+simply.
+If aufs didn't adopt the workqueue and changed the privilege of the
+process, then the process may receive the unexpected SIGXFSZ or other
+signals.
+
+Also aufs uses the system global workqueue ("events" kernel thread) too
+for asynchronous tasks, such like handling inotify/fsnotify, re-creating a
+whiteout base and etc. This is unrelated to a privilege.
+Most of aufs operation tries acquiring a rw_semaphore for aufs
+superblock at the beginning, at the same time waits for the completion
+of all queued asynchronous tasks.
+
+
+Whiteout
+----------------------------------------------------------------------
+The whiteout in aufs is very similar to Unionfs's. That is represented
+by its filename. UnionMount takes an approach of a file mode, but I am
+afraid several utilities (find(1) or something) will have to support it.
+
+Basically the whiteout represents "logical deletion" which stops aufs to
+lookup further, but also it represents "dir is opaque" which also stop
+further lookup.
+
+In aufs, rmdir(2) and rename(2) for dir uses whiteout alternatively.
+In order to make several functions in a single systemcall to be
+revertible, aufs adopts an approach to rename a directory to a temporary
+unique whiteouted name.
+For example, in rename(2) dir where the target dir already existed, aufs
+renames the target dir to a temporary unique whiteouted name before the
+actual rename on a branch, and then handles other actions (make it opaque,
+update the attributes, etc). If an error happens in these actions, aufs
+simply renames the whiteouted name back and returns an error. If all are
+succeeded, aufs registers a function to remove the whiteouted unique
+temporary name completely and asynchronously to the system global
+workqueue.
+
+
+Copy-up
+----------------------------------------------------------------------
+It is a well-known feature or concept.
+When user modifies a file on a readonly branch, aufs operate "copy-up"
+internally and makes change to the new file on the upper writable branch.
+When the trigger systemcall does not update the timestamps of the parent
+dir, aufs reverts it after copy-up.
+
+
+Move-down (aufs3.9 and later)
+----------------------------------------------------------------------
+"Copy-up" is one of the essential feature in aufs. It copies a file from
+the lower readonly branch to the upper writable branch when a user
+changes something about the file.
+"Move-down" is an opposite action of copy-up. Basically this action is
+ran manually instead of automatically and internally.
+For desgin and implementation, aufs has to consider these issues.
+- whiteout for the file may exist on the lower branch.
+- ancestor directories may not exist on the lower branch.
+- diropq for the ancestor directories may exist on the upper branch.
+- free space on the lower branch will reduce.
+- another access to the file may happen during moving-down, including
+  UDBA (see "Revalidate Dentry and UDBA").
+- the file should not be hard-linked nor pseudo-linked. they should be
+  handled by auplink utility later.
+
+Sometimes users want to move-down a file from the upper writable branch
+to the lower readonly or writable branch. For instance,
+- the free space of the upper writable branch is going to run out.
+- create a new intermediate branch between the upper and lower branch.
+- etc.
+
+For this purpose, use "aumvdown" command in aufs-util.git.
diff -urN /usr/share/empty/Documentation/filesystems/aufs/design/03atomic_open.txt linux/Documentation/filesystems/aufs/design/03atomic_open.txt
--- /usr/share/empty/Documentation/filesystems/aufs/design/03atomic_open.txt    1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/filesystems/aufs/design/03atomic_open.txt       2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,85 @@
+
+# Copyright (C) 2015-2021 Junjiro R. Okajima
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Support for a branch who has its ->atomic_open()
+----------------------------------------------------------------------
+The filesystems who implement its ->atomic_open() are not majority. For
+example NFSv4 does, and aufs should call NFSv4 ->atomic_open,
+particularly for open(O_CREAT|O_EXCL, 0400) case. Other than
+->atomic_open(), NFSv4 returns an error for this open(2). While I am not
+sure whether all filesystems who have ->atomic_open() behave like this,
+but NFSv4 surely returns the error.
+
+In order to support ->atomic_open() for aufs, there are a few
+approaches.
+
+A. Introduce aufs_atomic_open()
+   - calls one of VFS:do_last(), lookup_open() or atomic_open() for
+     branch fs.
+B. Introduce aufs_atomic_open() calling create, open and chmod. this is
+   an aufs user Pip Cet's approach
+   - calls aufs_create(), VFS finish_open() and notify_change().
+   - pass fake-mode to finish_open(), and then correct the mode by
+     notify_change().
+C. Extend aufs_open() to call branch fs's ->atomic_open()
+   - no aufs_atomic_open().
+   - aufs_lookup() registers the TID to an aufs internal object.
+   - aufs_create() does nothing when the matching TID is registered, but
+     registers the mode.
+   - aufs_open() calls branch fs's ->atomic_open() when the matching
+     TID is registered.
+D. Extend aufs_open() to re-try branch fs's ->open() with superuser's
+   credential
+   - no aufs_atomic_open().
+   - aufs_create() registers the TID to an internal object. this info
+     represents "this process created this file just now."
+   - when aufs gets EACCES from branch fs's ->open(), then confirm the
+     registered TID and re-try open() with superuser's credential.
+
+Pros and cons for each approach.
+
+A.
+   - straightforward but highly depends upon VFS internal.
+   - the atomic behavaiour is kept.
+   - some of parameters such as nameidata are hard to reproduce for
+     branch fs.
+   - large overhead.
+B.
+   - easy to implement.
+   - the atomic behavaiour is lost.
+C.
+   - the atomic behavaiour is kept.
+   - dirty and tricky.
+   - VFS checks whether the file is created correctly after calling
+     ->create(), which means this approach doesn't work.
+D.
+   - easy to implement.
+   - the atomic behavaiour is lost.
+   - to open a file with superuser's credential and give it to a user
+     process is a bad idea, since the file object keeps the credential
+     in it. It may affect LSM or something. This approach doesn't work
+     either.
+
+The approach A is ideal, but it hard to implement. So here is a
+variation of A, which is to be implemented.
+
+A-1. Introduce aufs_atomic_open()
+     - calls branch fs ->atomic_open() if exists. otherwise calls
+       vfs_create() and finish_open().
+     - the demerit is that the several checks after branch fs
+       ->atomic_open() are lost. in the ordinary case, the checks are
+       done by VFS:do_last(), lookup_open() and atomic_open(). some can
+       be implemented in aufs, but not all I am afraid.
diff -urN /usr/share/empty/Documentation/filesystems/aufs/design/03lookup.txt linux/Documentation/filesystems/aufs/design/03lookup.txt
--- /usr/share/empty/Documentation/filesystems/aufs/design/03lookup.txt 1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/filesystems/aufs/design/03lookup.txt    2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,113 @@
+
+# Copyright (C) 2005-2021 Junjiro R. Okajima
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Lookup in a Branch
+----------------------------------------------------------------------
+Since aufs has a character of sub-VFS (see Introduction), it operates
+lookup for branches as VFS does. It may be a heavy work. But almost all
+lookup operation in aufs is the simplest case, ie. lookup only an entry
+directly connected to its parent. Digging down the directory hierarchy
+is unnecessary. VFS has a function lookup_one_len() for that use, and
+aufs calls it.
+
+When a branch is a remote filesystem, aufs basically relies upon its
+->d_revalidate(), also aufs forces the hardest revalidate tests for
+them.
+For d_revalidate, aufs implements three levels of revalidate tests. See
+"Revalidate Dentry and UDBA" in detail.
+
+
+Test Only the Highest One for the Directory Permission (dirperm1 option)
+----------------------------------------------------------------------
+Let's try case study.
+- aufs has two branches, upper readwrite and lower readonly.
+  /au = /rw + /ro
+- "dirA" exists under /ro, but /rw. and its mode is 0700.
+- user invoked "chmod a+rx /au/dirA"
+- the internal copy-up is activated and "/rw/dirA" is created and its
+  permission bits are set to world readable.
+- then "/au/dirA" becomes world readable?
+
+In this case, /ro/dirA is still 0700 since it exists in readonly branch,
+or it may be a natively readonly filesystem. If aufs respects the lower
+branch, it should not respond readdir request from other users. But user
+allowed it by chmod. Should really aufs rejects showing the entries
+under /ro/dirA?
+
+To be honest, I don't have a good solution for this case. So aufs
+implements 'dirperm1' and 'nodirperm1' mount options, and leave it to
+users.
+When dirperm1 is specified, aufs checks only the highest one for the
+directory permission, and shows the entries. Otherwise, as usual, checks
+every dir existing on all branches and rejects the request.
+
+As a side effect, dirperm1 option improves the performance of aufs
+because the number of permission check is reduced when the number of
+branch is many.
+
+
+Revalidate Dentry and UDBA (User's Direct Branch Access)
+----------------------------------------------------------------------
+Generally VFS helpers re-validate a dentry as a part of lookup.
+0. digging down the directory hierarchy.
+1. lock the parent dir by its i_mutex.
+2. lookup the final (child) entry.
+3. revalidate it.
+4. call the actual operation (create, unlink, etc.)
+5. unlock the parent dir
+
+If the filesystem implements its ->d_revalidate() (step 3), then it is
+called. Actually aufs implements it and checks the dentry on a branch is
+still valid.
+But it is not enough. Because aufs has to release the lock for the
+parent dir on a branch at the end of ->lookup() (step 2) and
+->d_revalidate() (step 3) while the i_mutex of the aufs dir is still
+held by VFS.
+If the file on a branch is changed directly, eg. bypassing aufs, after
+aufs released the lock, then the subsequent operation may cause
+something unpleasant result.
+
+This situation is a result of VFS architecture, ->lookup() and
+->d_revalidate() is separated. But I never say it is wrong. It is a good
+design from VFS's point of view. It is just not suitable for sub-VFS
+character in aufs.
+
+Aufs supports such case by three level of revalidation which is
+selectable by user.
+1. Simple Revalidate
+   Addition to the native flow in VFS's, confirm the child-parent
+   relationship on the branch just after locking the parent dir on the
+   branch in the "actual operation" (step 4). When this validation
+   fails, aufs returns EBUSY. ->d_revalidate() (step 3) in aufs still
+   checks the validation of the dentry on branches.
+2. Monitor Changes Internally by Inotify/Fsnotify
+   Addition to above, in the "actual operation" (step 4) aufs re-lookup
+   the dentry on the branch, and returns EBUSY if it finds different
+   dentry.
+   Additionally, aufs sets the inotify/fsnotify watch for every dir on branches
+   during it is in cache. When the event is notified, aufs registers a
+   function to kernel 'events' thread by schedule_work(). And the
+   function sets some special status to the cached aufs dentry and inode
+   private data. If they are not cached, then aufs has nothing to
+   do. When the same file is accessed through aufs (step 0-3) later,
+   aufs will detect the status and refresh all necessary data.
+   In this mode, aufs has to ignore the event which is fired by aufs
+   itself.
+3. No Extra Validation
+   This is the simplest test and doesn't add any additional revalidation
+   test, and skip the revalidation in step 4. It is useful and improves
+   aufs performance when system surely hide the aufs branches from user,
+   by over-mounting something (or another method).
diff -urN /usr/share/empty/Documentation/filesystems/aufs/design/04branch.txt linux/Documentation/filesystems/aufs/design/04branch.txt
--- /usr/share/empty/Documentation/filesystems/aufs/design/04branch.txt 1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/filesystems/aufs/design/04branch.txt    2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,74 @@
+
+# Copyright (C) 2005-2021 Junjiro R. Okajima
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Branch Manipulation
+
+Since aufs supports dynamic branch manipulation, ie. add/remove a branch
+and changing its permission/attribute, there are a lot of works to do.
+
+
+Add a Branch
+----------------------------------------------------------------------
+o Confirm the adding dir exists outside of aufs, including loopback
+  mount, and its various attributes.
+o Initialize the xino file and whiteout bases if necessary.
+  See struct.txt.
+
+o Check the owner/group/mode of the directory
+  When the owner/group/mode of the adding directory differs from the
+  existing branch, aufs issues a warning because it may impose a
+  security risk.
+  For example, when a upper writable branch has a world writable empty
+  top directory, a malicious user can create any files on the writable
+  branch directly, like copy-up and modify manually. If something like
+  /etc/{passwd,shadow} exists on the lower readonly branch but the upper
+  writable branch, and the writable branch is world-writable, then a
+  malicious guy may create /etc/passwd on the writable branch directly
+  and the infected file will be valid in aufs.
+  I am afraid it can be a security issue, but aufs can do nothing except
+  producing a warning.
+
+
+Delete a Branch
+----------------------------------------------------------------------
+o Confirm the deleting branch is not busy
+  To be general, there is one merit to adopt "remount" interface to
+  manipulate branches. It is to discard caches. At deleting a branch,
+  aufs checks the still cached (and connected) dentries and inodes. If
+  there are any, then they are all in-use. An inode without its
+  corresponding dentry can be alive alone (for example, inotify/fsnotify case).
+
+  For the cached one, aufs checks whether the same named entry exists on
+  other branches.
+  If the cached one is a directory, because aufs provides a merged view
+  to users, as long as one dir is left on any branch aufs can show the
+  dir to users. In this case, the branch can be removed from aufs.
+  Otherwise aufs rejects deleting the branch.
+
+  If any file on the deleting branch is opened by aufs, then aufs
+  rejects deleting.
+
+
+Modify the Permission of a Branch
+----------------------------------------------------------------------
+o Re-initialize or remove the xino file and whiteout bases if necessary.
+  See struct.txt.
+
+o rw --> ro: Confirm the modifying branch is not busy
+  Aufs rejects the request if any of these conditions are true.
+  - a file on the branch is mmap-ed.
+  - a regular file on the branch is opened for write and there is no
+    same named entry on the upper branch.
diff -urN /usr/share/empty/Documentation/filesystems/aufs/design/05wbr_policy.txt linux/Documentation/filesystems/aufs/design/05wbr_policy.txt
--- /usr/share/empty/Documentation/filesystems/aufs/design/05wbr_policy.txt     1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/filesystems/aufs/design/05wbr_policy.txt        2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,64 @@
+
+# Copyright (C) 2005-2021 Junjiro R. Okajima
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Policies to Select One among Multiple Writable Branches
+----------------------------------------------------------------------
+When the number of writable branch is more than one, aufs has to decide
+the target branch for file creation or copy-up. By default, the highest
+writable branch which has the parent (or ancestor) dir of the target
+file is chosen (top-down-parent policy).
+By user's request, aufs implements some other policies to select the
+writable branch, for file creation several policies, round-robin,
+most-free-space, and other policies. For copy-up, top-down-parent,
+bottom-up-parent, bottom-up and others.
+
+As expected, the round-robin policy selects the branch in circular. When
+you have two writable branches and creates 10 new files, 5 files will be
+created for each branch. mkdir(2) systemcall is an exception. When you
+create 10 new directories, all will be created on the same branch.
+And the most-free-space policy selects the one which has most free
+space among the writable branches. The amount of free space will be
+checked by aufs internally, and users can specify its time interval.
+
+The policies for copy-up is more simple,
+top-down-parent is equivalent to the same named on in create policy,
+bottom-up-parent selects the writable branch where the parent dir
+exists and the nearest upper one from the copyup-source,
+bottom-up selects the nearest upper writable branch from the
+copyup-source, regardless the existence of the parent dir.
+
+There are some rules or exceptions to apply these policies.
+- If there is a readonly branch above the policy-selected branch and
+  the parent dir is marked as opaque (a variation of whiteout), or the
+  target (creating) file is whiteout-ed on the upper readonly branch,
+  then the result of the policy is ignored and the target file will be
+  created on the nearest upper writable branch than the readonly branch.
+- If there is a writable branch above the policy-selected branch and
+  the parent dir is marked as opaque or the target file is whiteouted
+  on the branch, then the result of the policy is ignored and the target
+  file will be created on the highest one among the upper writable
+  branches who has diropq or whiteout. In case of whiteout, aufs removes
+  it as usual.
+- link(2) and rename(2) systemcalls are exceptions in every policy.
+  They try selecting the branch where the source exists as possible
+  since copyup a large file will take long time. If it can't be,
+  ie. the branch where the source exists is readonly, then they will
+  follow the copyup policy.
+- There is an exception for rename(2) when the target exists.
+  If the rename target exists, aufs compares the index of the branches
+  where the source and the target exists and selects the higher
+  one. If the selected branch is readonly, then aufs follows the
+  copyup policy.
diff -urN /usr/share/empty/Documentation/filesystems/aufs/design/06dirren.dot linux/Documentation/filesystems/aufs/design/06dirren.dot
--- /usr/share/empty/Documentation/filesystems/aufs/design/06dirren.dot 1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/filesystems/aufs/design/06dirren.dot    2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,31 @@
+
+// to view this graph, run dot(1) command in GRAPHVIZ.
+
+digraph G {
+node [shape=box];
+whinfo [label="detailed info file\n(lower_brid_root-hinum, h_inum, namelen, old name)"];
+
+node [shape=oval];
+
+aufs_rename -> whinfo [label="store/remove"];
+
+node [shape=oval];
+inode_list [label="h_inum list in branch\ncache"];
+
+node [shape=box];
+whinode [label="h_inum list file"];
+
+node [shape=oval];
+brmgmt [label="br_add/del/mod/umount"];
+
+brmgmt -> inode_list [label="create/remove"];
+brmgmt -> whinode [label="load/store"];
+
+inode_list -> whinode [style=dashed,dir=both];
+
+aufs_rename -> inode_list [label="add/del"];
+
+aufs_lookup -> inode_list [label="search"];
+
+aufs_lookup -> whinfo [label="load/remove"];
+}
diff -urN /usr/share/empty/Documentation/filesystems/aufs/design/06dirren.txt linux/Documentation/filesystems/aufs/design/06dirren.txt
--- /usr/share/empty/Documentation/filesystems/aufs/design/06dirren.txt 1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/filesystems/aufs/design/06dirren.txt    2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,102 @@
+
+# Copyright (C) 2017-2021 Junjiro R. Okajima
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Special handling for renaming a directory (DIRREN)
+----------------------------------------------------------------------
+First, let's assume we have a simple usecase.
+
+- /u = /rw + /ro
+- /rw/dirA exists
+- /ro/dirA and /ro/dirA/file exist too
+- there is no dirB on both branches
+- a user issues rename("dirA", "dirB")
+
+Now, what should aufs behave against this rename(2)?
+There are a few possible cases.
+
+A. returns EROFS.
+   since dirA exists on a readonly branch which cannot be renamed.
+B. returns EXDEV.
+   it is possible to copy-up dirA (only the dir itself), but the child
+   entries ("file" in this case) should not be. it must be a bad
+   approach to copy-up recursively.
+C. returns a success.
+   even the branch /ro is readonly, aufs tries renaming it. Obviously it
+   is a violation of aufs' policy.
+D. construct an extra information which indicates that /ro/dirA should
+   be handled as the name of dirB.
+   overlayfs has a similar feature called REDIRECT.
+
+Until now, aufs implements the case B only which returns EXDEV, and
+expects the userspace application behaves like mv(1) which tries
+issueing rename(2) recursively.
+
+A new aufs feature called DIRREN is introduced which implements the case
+D. There are several "extra information" added.
+
+1. detailed info per renamed directory
+   path: /rw/dirB/$AUFS_WH_DR_INFO_PFX.<lower branch-id>
+2. the inode-number list of directories on a branch
+   path: /rw/dirB/$AUFS_WH_DR_BRHINO
+
+The filename of "detailed info per directory" represents the lower
+branch, and its format is
+- a type of the branch id
+  one of these.
+  + uuid (not implemented yet)
+  + fsid
+  + dev
+- the inode-number of the branch root dir
+
+And it contains these info in a single regular file.
+- magic number
+- branch's inode-number of the logically renamed dir
+- the name of the before-renamed dir
+
+The "detailed info per directory" file is created in aufs rename(2), and
+loaded in any lookup.
+The info is considered in lookup for the matching case only. Here
+"matching" means that the root of branch (in the info filename) is same
+to the current looking-up branch. After looking-up the before-renamed
+name, the inode-number is compared. And the matched dentry is used.
+
+The "inode-number list of directories" is a regular file which contains
+simply the inode-numbers on the branch. The file is created or updated
+in removing the branch, and loaded in adding the branch. Its lifetime is
+equal to the branch.
+The list is refered in lookup, and when the current target inode is
+found in the list, the aufs tries loading the "detailed info per
+directory" and get the changed and valid name of the dir.
+
+Theoretically these "extra informaiton" may be able to be put into XATTR
+in the dir inode. But aufs doesn't choose this way because
+1. XATTR may not be supported by the branch (or its configuration)
+2. XATTR may have its size limit.
+3. XATTR may be less easy to convert than a regular file, when the
+   format of the info is changed in the future.
+At the same time, I agree that the regular file approach is much slower
+than XATTR approach. So, in the future, aufs may take the XATTR or other
+better approach.
+
+This DIRREN feature is enabled by aufs configuration, and is activated
+by a new mount option.
+
+For the more complicated case, there is a work with UDBA option, which
+is to dected the direct access to the branches (by-passing aufs) and to
+maintain the cashes in aufs. Since a single cached aufs dentry may
+contains two names, before- and after-rename, the name comparision in
+UDBA handler may not work correctly. In this case, the behaviour will be
+equivalen to udba=reval case.
diff -urN /usr/share/empty/Documentation/filesystems/aufs/design/06fhsm.txt linux/Documentation/filesystems/aufs/design/06fhsm.txt
--- /usr/share/empty/Documentation/filesystems/aufs/design/06fhsm.txt   1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/filesystems/aufs/design/06fhsm.txt      2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,120 @@
+
+# Copyright (C) 2011-2021 Junjiro R. Okajima
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+
+
+File-based Hierarchical Storage Management (FHSM)
+----------------------------------------------------------------------
+Hierarchical Storage Management (or HSM) is a well-known feature in the
+storage world. Aufs provides this feature as file-based with multiple
+writable branches, based upon the principle of "Colder, the Lower".
+Here the word "colder" means that the less used files, and "lower" means
+that the position in the order of the stacked branches vertically.
+These multiple writable branches are prioritized, ie. the topmost one
+should be the fastest drive and be used heavily.
+
+o Characters in aufs FHSM story
+- aufs itself and a new branch attribute.
+- a new ioctl interface to move-down and to establish a connection with
+  the daemon ("move-down" is a converse of "copy-up").
+- userspace tool and daemon.
+
+The userspace daemon establishes a connection with aufs and waits for
+the notification. The notified information is very similar to struct
+statfs containing the number of consumed blocks and inodes.
+When the consumed blocks/inodes of a branch exceeds the user-specified
+upper watermark, the daemon activates its move-down process until the
+consumed blocks/inodes reaches the user-specified lower watermark.
+
+The actual move-down is done by aufs based upon the request from
+user-space since we need to maintain the inode number and the internal
+pointer arrays in aufs.
+
+Currently aufs FHSM handles the regular files only. Additionally they
+must not be hard-linked nor pseudo-linked.
+
+
+o Cowork of aufs and the user-space daemon
+  During the userspace daemon established the connection, aufs sends a
+  small notification to it whenever aufs writes something into the
+  writable branch. But it may cost high since aufs issues statfs(2)
+  internally. So user can specify a new option to cache the
+  info. Actually the notification is controlled by these factors.
+  + the specified cache time.
+  + classified as "force" by aufs internally.
+  Until the specified time expires, aufs doesn't send the info
+  except the forced cases. When aufs decide forcing, the info is always
+  notified to userspace.
+  For example, the number of free inodes is generally large enough and
+  the shortage of it happens rarely. So aufs doesn't force the
+  notification when creating a new file, directory and others. This is
+  the typical case which aufs doesn't force.
+  When aufs writes the actual filedata and the files consumes any of new
+  blocks, the aufs forces notifying.
+
+
+o Interfaces in aufs
+- New branch attribute.
+  + fhsm
+    Specifies that the branch is managed by FHSM feature. In other word,
+    participant in the FHSM.
+    When nofhsm is set to the branch, it will not be the source/target
+    branch of the move-down operation. This attribute is set
+    independently from coo and moo attributes, and if you want full
+    FHSM, you should specify them as well.
+- New mount option.
+  + fhsm_sec
+    Specifies a second to suppress many less important info to be
+    notified.
+- New ioctl.
+  + AUFS_CTL_FHSM_FD
+    create a new file descriptor which userspace can read the notification
+    (a subset of struct statfs) from aufs.
+- Module parameter 'brs'
+  It has to be set to 1. Otherwise the new mount option 'fhsm' will not
+  be set.
+- mount helpers /sbin/mount.aufs and /sbin/umount.aufs
+  When there are two or more branches with fhsm attributes,
+  /sbin/mount.aufs invokes the user-space daemon and /sbin/umount.aufs
+  terminates it. As a result of remounting and branch-manipulation, the
+  number of branches with fhsm attribute can be one. In this case,
+  /sbin/mount.aufs will terminate the user-space daemon.
+
+
+Finally the operation is done as these steps in kernel-space.
+- make sure that,
+  + no one else is using the file.
+  + the file is not hard-linked.
+  + the file is not pseudo-linked.
+  + the file is a regular file.
+  + the parent dir is not opaqued.
+- find the target writable branch.
+- make sure the file is not whiteout-ed by the upper (than the target)
+  branch.
+- make the parent dir on the target branch.
+- mutex lock the inode on the branch.
+- unlink the whiteout on the target branch (if exists).
+- lookup and create the whiteout-ed temporary name on the target branch.
+- copy the file as the whiteout-ed temporary name on the target branch.
+- rename the whiteout-ed temporary name to the original name.
+- unlink the file on the source branch.
+- maintain the internal pointer array and the external inode number
+  table (XINO).
+- maintain the timestamps and other attributes of the parent dir and the
+  file.
+
+And of course, in every step, an error may happen. So the operation
+should restore the original file state after an error happens.
diff -urN /usr/share/empty/Documentation/filesystems/aufs/design/06mmap.txt linux/Documentation/filesystems/aufs/design/06mmap.txt
--- /usr/share/empty/Documentation/filesystems/aufs/design/06mmap.txt   1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/filesystems/aufs/design/06mmap.txt      2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,72 @@
+
+# Copyright (C) 2005-2021 Junjiro R. Okajima
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+mmap(2) -- File Memory Mapping
+----------------------------------------------------------------------
+In aufs, the file-mapped pages are handled by a branch fs directly, no
+interaction with aufs. It means aufs_mmap() calls the branch fs's
+->mmap().
+This approach is simple and good, but there is one problem.
+Under /proc, several entries show the mmapped files by its path (with
+device and inode number), and the printed path will be the path on the
+branch fs's instead of virtual aufs's.
+This is not a problem in most cases, but some utilities lsof(1) (and its
+user) may expect the path on aufs.
+
+To address this issue, aufs adds a new member called vm_prfile in struct
+vm_area_struct (and struct vm_region). The original vm_file points to
+the file on the branch fs in order to handle everything correctly as
+usual. The new vm_prfile points to a virtual file in aufs, and the
+show-functions in procfs refers to vm_prfile if it is set.
+Also we need to maintain several other places where touching vm_file
+such like
+- fork()/clone() copies vma and the reference count of vm_file is
+  incremented.
+- merging vma maintains the ref count too.
+
+This is not a good approach. It just fakes the printed path. But it
+leaves all behaviour around f_mapping unchanged. This is surely an
+advantage.
+Actually aufs had adopted another complicated approach which calls
+generic_file_mmap() and handles struct vm_operations_struct. In this
+approach, aufs met a hard problem and I could not solve it without
+switching the approach.
+
+There may be one more another approach which is
+- bind-mount the branch-root onto the aufs-root internally
+- grab the new vfsmount (ie. struct mount)
+- lazy-umount the branch-root internally
+- in open(2) the aufs-file, open the branch-file with the hidden
+  vfsmount (instead of the original branch's vfsmount)
+- ideally this "bind-mount and lazy-umount" should be done atomically,
+  but it may be possible from userspace by the mount helper.
+
+Adding the internal hidden vfsmount and using it in opening a file, the
+file path under /proc will be printed correctly. This approach looks
+smarter, but is not possible I am afraid.
+- aufs-root may be bind-mount later. when it happens, another hidden
+  vfsmount will be required.
+- it is hard to get the chance to bind-mount and lazy-umount
+  + in kernel-space, FS can have vfsmount in open(2) via
+    file->f_path, and aufs can know its vfsmount. But several locks are
+    already acquired, and if aufs tries to bind-mount and lazy-umount
+    here, then it may cause a deadlock.
+  + in user-space, bind-mount doesn't invoke the mount helper.
+- since /proc shows dev and ino, aufs has to give vma these info. it
+  means a new member vm_prinode will be necessary. this is essentially
+  equivalent to vm_prfile described above.
+
+I have to give up this "looks-smater" approach.
diff -urN /usr/share/empty/Documentation/filesystems/aufs/design/06xattr.txt linux/Documentation/filesystems/aufs/design/06xattr.txt
--- /usr/share/empty/Documentation/filesystems/aufs/design/06xattr.txt  1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/filesystems/aufs/design/06xattr.txt     2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,96 @@
+
+# Copyright (C) 2014-2021 Junjiro R. Okajima
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+
+
+Listing XATTR/EA and getting the value
+----------------------------------------------------------------------
+For the inode standard attributes (owner, group, timestamps, etc.), aufs
+shows the values from the topmost existing file. This behaviour is good
+for the non-dir entries since the bahaviour exactly matches the shown
+information. But for the directories, aufs considers all the same named
+entries on the lower branches. Which means, if one of the lower entry
+rejects readdir call, then aufs returns an error even if the topmost
+entry allows it. This behaviour is necessary to respect the branch fs's
+security, but can make users confused since the user-visible standard
+attributes don't match the behaviour.
+To address this issue, aufs has a mount option called dirperm1 which
+checks the permission for the topmost entry only, and ignores the lower
+entry's permission.
+
+A similar issue can happen around XATTR.
+getxattr(2) and listxattr(2) families behave as if dirperm1 option is
+always set. Otherwise these very unpleasant situation would happen.
+- listxattr(2) may return the duplicated entries.
+- users may not be able to remove or reset the XATTR forever,
+
+
+XATTR/EA support in the internal (copy,move)-(up,down)
+----------------------------------------------------------------------
+Generally the extended attributes of inode are categorized as these.
+- "security" for LSM and capability.
+- "system" for posix ACL, 'acl' mount option is required for the branch
+  fs generally.
+- "trusted" for userspace, CAP_SYS_ADMIN is required.
+- "user" for userspace, 'user_xattr' mount option is required for the
+  branch fs generally.
+
+Moreover there are some other categories. Aufs handles these rather
+unpopular categories as the ordinary ones, ie. there is no special
+condition nor exception.
+
+In copy-up, the support for XATTR on the dst branch may differ from the
+src branch. In this case, the copy-up operation will get an error and
+the original user operation which triggered the copy-up will fail. It
+can happen that even all copy-up will fail.
+When both of src and dst branches support XATTR and if an error occurs
+during copying XATTR, then the copy-up should fail obviously. That is a
+good reason and aufs should return an error to userspace. But when only
+the src branch support that XATTR, aufs should not return an error.
+For example, the src branch supports ACL but the dst branch doesn't
+because the dst branch may natively un-support it or temporary
+un-support it due to "noacl" mount option. Of course, the dst branch fs
+may NOT return an error even if the XATTR is not supported. It is
+totally up to the branch fs.
+
+Anyway when the aufs internal copy-up gets an error from the dst branch
+fs, then aufs tries removing the just copied entry and returns the error
+to the userspace. The worst case of this situation will be all copy-up
+will fail.
+
+For the copy-up operation, there two basic approaches.
+- copy the specified XATTR only (by category above), and return the
+  error unconditionally if it happens.
+- copy all XATTR, and ignore the error on the specified category only.
+
+In order to support XATTR and to implement the correct behaviour, aufs
+chooses the latter approach and introduces some new branch attributes,
+"icexsec", "icexsys", "icextr", "icexusr", and "icexoth".
+They correspond to the XATTR namespaces (see above). Additionally, to be
+convenient, "icex" is also provided which means all "icex*" attributes
+are set (here the word "icex" stands for "ignore copy-error on XATTR").
+
+The meaning of these attributes is to ignore the error from setting
+XATTR on that branch.
+Note that aufs tries copying all XATTR unconditionally, and ignores the
+error from the dst branch according to the specified attributes.
+
+Some XATTR may have its default value. The default value may come from
+the parent dir or the environment. If the default value is set at the
+file creating-time, it will be overwritten by copy-up.
+Some contradiction may happen I am afraid.
+Do we need another attribute to stop copying XATTR? I am unsure. For
+now, aufs implements the branch attributes to ignore the error.
diff -urN /usr/share/empty/Documentation/filesystems/aufs/design/07export.txt linux/Documentation/filesystems/aufs/design/07export.txt
--- /usr/share/empty/Documentation/filesystems/aufs/design/07export.txt 1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/filesystems/aufs/design/07export.txt    2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,58 @@
+
+# Copyright (C) 2005-2021 Junjiro R. Okajima
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Export Aufs via NFS
+----------------------------------------------------------------------
+Here is an approach.
+- like xino/xib, add a new file 'xigen' which stores aufs inode
+  generation.
+- iget_locked(): initialize aufs inode generation for a new inode, and
+  store it in xigen file.
+- destroy_inode(): increment aufs inode generation and store it in xigen
+  file. it is necessary even if it is not unlinked, because any data of
+  inode may be changed by UDBA.
+- encode_fh(): for a root dir, simply return FILEID_ROOT. otherwise
+  build file handle by
+  + branch id (4 bytes)
+  + superblock generation (4 bytes)
+  + inode number (4 or 8 bytes)
+  + parent dir inode number (4 or 8 bytes)
+  + inode generation (4 bytes))
+  + return value of exportfs_encode_fh() for the parent on a branch (4
+    bytes)
+  + file handle for a branch (by exportfs_encode_fh())
+- fh_to_dentry():
+  + find the index of a branch from its id in handle, and check it is
+    still exist in aufs.
+  + 1st level: get the inode number from handle and search it in cache.
+  + 2nd level: if not found in cache, get the parent inode number from
+    the handle and search it in cache. and then open the found parent
+    dir, find the matching inode number by vfs_readdir() and get its
+    name, and call lookup_one_len() for the target dentry.
+  + 3rd level: if the parent dir is not cached, call
+    exportfs_decode_fh() for a branch and get the parent on a branch,
+    build a pathname of it, convert it a pathname in aufs, call
+    path_lookup(). now aufs gets a parent dir dentry, then handle it as
+    the 2nd level.
+  + to open the dir, aufs needs struct vfsmount. aufs keeps vfsmount
+    for every branch, but not itself. to get this, (currently) aufs
+    searches in current->nsproxy->mnt_ns list. it may not be a good
+    idea, but I didn't get other approach.
+  + test the generation of the gotten inode.
+- every inode operation: they may get EBUSY due to UDBA. in this case,
+  convert it into ESTALE for NFSD.
+- readdir(): call lockdep_on/off() because filldir in NFSD calls
+  lookup_one_len(), vfs_getattr(), encode_fh() and others.
diff -urN /usr/share/empty/Documentation/filesystems/aufs/design/08shwh.txt linux/Documentation/filesystems/aufs/design/08shwh.txt
--- /usr/share/empty/Documentation/filesystems/aufs/design/08shwh.txt   1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/filesystems/aufs/design/08shwh.txt      2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,52 @@
+
+# Copyright (C) 2005-2021 Junjiro R. Okajima
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Show Whiteout Mode (shwh)
+----------------------------------------------------------------------
+Generally aufs hides the name of whiteouts. But in some cases, to show
+them is very useful for users. For instance, creating a new middle layer
+(branch) by merging existing layers.
+
+(borrowing aufs1 HOW-TO from a user, Michael Towers)
+When you have three branches,
+- Bottom: 'system', squashfs (underlying base system), read-only
+- Middle: 'mods', squashfs, read-only
+- Top: 'overlay', ram (tmpfs), read-write
+
+The top layer is loaded at boot time and saved at shutdown, to preserve
+the changes made to the system during the session.
+When larger changes have been made, or smaller changes have accumulated,
+the size of the saved top layer data grows. At this point, it would be
+nice to be able to merge the two overlay branches ('mods' and 'overlay')
+and rewrite the 'mods' squashfs, clearing the top layer and thus
+restoring save and load speed.
+
+This merging is simplified by the use of another aufs mount, of just the
+two overlay branches using the 'shwh' option.
+# mount -t aufs -o ro,shwh,br:/livesys/overlay=ro+wh:/livesys/mods=rr+wh \
+       aufs /livesys/merge_union
+
+A merged view of these two branches is then available at
+/livesys/merge_union, and the new feature is that the whiteouts are
+visible!
+Note that in 'shwh' mode the aufs mount must be 'ro', which will disable
+writing to all branches. Also the default mode for all branches is 'ro'.
+It is now possible to save the combined contents of the two overlay
+branches to a new squashfs, e.g.:
+# mksquashfs /livesys/merge_union /path/to/newmods.squash
+
+This new squashfs archive can be stored on the boot device and the
+initramfs will use it to replace the old one at the next boot.
diff -urN /usr/share/empty/Documentation/filesystems/aufs/design/10dynop.txt linux/Documentation/filesystems/aufs/design/10dynop.txt
--- /usr/share/empty/Documentation/filesystems/aufs/design/10dynop.txt  1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/filesystems/aufs/design/10dynop.txt     2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,47 @@
+
+# Copyright (C) 2010-2021 Junjiro R. Okajima
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Dynamically customizable FS operations
+----------------------------------------------------------------------
+Generally FS operations (struct inode_operations, struct
+address_space_operations, struct file_operations, etc.) are defined as
+"static const", but it never means that FS have only one set of
+operation. Some FS have multiple sets of them. For instance, ext2 has
+three sets, one for XIP, for NOBH, and for normal.
+Since aufs overrides and redirects these operations, sometimes aufs has
+to change its behaviour according to the branch FS type. More importantly
+VFS acts differently if a function (member in the struct) is set or
+not. It means aufs should have several sets of operations and select one
+among them according to the branch FS definition.
+
+In order to solve this problem and not to affect the behaviour of VFS,
+aufs defines these operations dynamically. For instance, aufs defines
+dummy direct_IO function for struct address_space_operations, but it may
+not be set to the address_space_operations actually. When the branch FS
+doesn't have it, aufs doesn't set it to its address_space_operations
+while the function definition itself is still alive. So the behaviour
+itself will not change, and it will return an error when direct_IO is
+not set.
+
+The lifetime of these dynamically generated operation object is
+maintained by aufs branch object. When the branch is removed from aufs,
+the reference counter of the object is decremented. When it reaches
+zero, the dynamically generated operation object will be freed.
+
+This approach is designed to support AIO (io_submit), Direct I/O and
+XIP (DAX) mainly.
+Currently this approach is applied to address_space_operations for
+regular files only.
diff -urN /usr/share/empty/Documentation/filesystems/aufs/README linux/Documentation/filesystems/aufs/README
--- /usr/share/empty/Documentation/filesystems/aufs/README      1970-01-01 01:00:00.000000000 +0100
+++ linux/Documentation/filesystems/aufs/README 2021-12-03 15:40:58.233313963 +0100
@@ -0,0 +1,396 @@
+
+Aufs5 -- advanced multi layered unification filesystem version 5.x
+http://aufs.sf.net
+Junjiro R. Okajima
+
+
+0. Introduction
+----------------------------------------
+In the early days, aufs was entirely re-designed and re-implemented
+Unionfs Version 1.x series. Adding many original ideas, approaches,
+improvements and implementations, it became totally different from
+Unionfs while keeping the basic features.
+Later, Unionfs Version 2.x series began taking some of the same
+approaches to aufs1's.
+Unionfs was being developed by Professor Erez Zadok at Stony Brook
+University and his team.
+
+Aufs5 supports linux-v5.0 and later, If you want older kernel version
+support,
+- for linux-v4.x series, try aufs4-linux.git or aufs4-standalone.git
+- for linux-v3.x series, try aufs3-linux.git or aufs3-standalone.git
+- for linux-v2.6.16 and later, try aufs2-2.6.git, aufs2-standalone.git
+  or aufs1 from CVS on SourceForge.
+
+Note: it becomes clear that "Aufs was rejected. Let's give it up."
+      According to Christoph Hellwig, linux rejects all union-type
+      filesystems but UnionMount.
+<http://marc.info/?l=linux-kernel&m=123938533724484&w=2>
+
+PS. Al Viro seems have a plan to merge aufs as well as overlayfs and
+    UnionMount, and he pointed out an issue around a directory mutex
+    lock and aufs addressed it. But it is still unsure whether aufs will
+    be merged (or any other union solution).
+<http://marc.info/?l=linux-kernel&m=136312705029295&w=1>
+
+
+1. Features
+----------------------------------------
+- unite several directories into a single virtual filesystem. The member
+  directory is called as a branch.
+- you can specify the permission flags to the branch, which are 'readonly',
+  'readwrite' and 'whiteout-able.'
+- by upper writable branch, internal copyup and whiteout, files/dirs on
+  readonly branch are modifiable logically.
+- dynamic branch manipulation, add, del.
+- etc...
+
+Also there are many enhancements in aufs, such as:
+- test only the highest one for the directory permission (dirperm1)
+- copyup on open (coo=)
+- 'move' policy for copy-up between two writable branches, after
+  checking free space.
+- xattr, acl
+- readdir(3) in userspace.
+- keep inode number by external inode number table
+- keep the timestamps of file/dir in internal copyup operation
+- seekable directory, supporting NFS readdir.
+- whiteout is hardlinked in order to reduce the consumption of inodes
+  on branch
+- do not copyup, nor create a whiteout when it is unnecessary
+- revert a single systemcall when an error occurs in aufs
+- remount interface instead of ioctl
+- maintain /etc/mtab by an external command, /sbin/mount.aufs.
+- loopback mounted filesystem as a branch
+- kernel thread for removing the dir who has a plenty of whiteouts
+- support copyup sparse file (a file which has a 'hole' in it)
+- default permission flags for branches
+- selectable permission flags for ro branch, whether whiteout can
+  exist or not
+- export via NFS.
+- support <sysfs>/fs/aufs and <debugfs>/aufs.
+- support multiple writable branches, some policies to select one
+  among multiple writable branches.
+- a new semantics for link(2) and rename(2) to support multiple
+  writable branches.
+- no glibc changes are required.
+- pseudo hardlink (hardlink over branches)
+- allow a direct access manually to a file on branch, e.g. bypassing aufs.
+  including NFS or remote filesystem branch.
+- userspace wrapper for pathconf(3)/fpathconf(3) with _PC_LINK_MAX.
+- and more...
+
+Currently these features are dropped temporary from aufs5.
+See design/08plan.txt in detail.
+- nested mount, i.e. aufs as readonly no-whiteout branch of another aufs
+  (robr)
+- statistics of aufs thread (/sys/fs/aufs/stat)
+
+Features or just an idea in the future (see also design/*.txt),
+- reorder the branch index without del/re-add.
+- permanent xino files for NFSD
+- an option for refreshing the opened files after add/del branches
+- light version, without branch manipulation. (unnecessary?)
+- copyup in userspace
+- inotify in userspace
+- readv/writev
+
+
+2. Download
+----------------------------------------
+There are three GIT trees for aufs5, aufs5-linux.git,
+aufs5-standalone.git, and aufs-util.git. Note that there is no "5" in
+"aufs-util.git."
+While the aufs-util is always necessary, you need either of aufs5-linux
+or aufs5-standalone.
+
+The aufs5-linux tree includes the whole linux mainline GIT tree,
+git://git.kernel.org/.../torvalds/linux.git.
+And you cannot select CONFIG_AUFS_FS=m for this version, eg. you cannot
+build aufs5 as an external kernel module.
+Several extra patches are not included in this tree. Only
+aufs5-standalone tree contains them. They are described in the later
+section "Configuration and Compilation."
+
+On the other hand, the aufs5-standalone tree has only aufs source files
+and necessary patches, and you can select CONFIG_AUFS_FS=m.
+But you need to apply all aufs patches manually.
+
+You will find GIT branches whose name is in form of "aufs5.x" where "x"
+represents the linux kernel version, "linux-5.x". For instance,
+"aufs5.0" is for linux-5.0. For latest "linux-5.x-rcN", use
+"aufs5.x-rcN" branch.
+
+o aufs5-linux tree
+$ git clone --reference /your/linux/git/tree \
+       git://github.com/sfjro/aufs5-linux.git aufs5-linux.git
+- if you don't have linux GIT tree, then remove "--reference ..."
+$ cd aufs5-linux.git
+$ git checkout origin/aufs5.0
+
+Or You may want to directly git-pull aufs into your linux GIT tree, and
+leave the patch-work to GIT.
+$ cd /your/linux/git/tree
+$ git remote add aufs5 git://github.com/sfjro/aufs5-linux.git
+$ git fetch aufs5
+$ git checkout -b my5.0 v5.0
+$ (add your local change...)
+$ git pull aufs5 aufs5.0
+- now you have v5.0 + your_changes + aufs5.0 in you my5.0 branch.
+- you may need to solve some conflicts between your_changes and
+  aufs5.0. in this case, git-rerere is recommended so that you can
+  solve the similar conflicts automatically when you upgrade to 5.1 or
+  later in the future.
+
+o aufs5-standalone tree
+$ git clone git://github.com/sfjro/aufs5-standalone.git aufs5-standalone.git
+$ cd aufs5-standalone.git
+$ git checkout origin/aufs5.0
+
+o aufs-util tree
+$ git clone git://git.code.sf.net/p/aufs/aufs-util aufs-util.git
+- note that the public aufs-util.git is on SourceForge instead of
+  GitHUB.
+$ cd aufs-util.git
+$ git checkout origin/aufs5.0
+
+Note: The 5.x-rcN branch is to be used with `rc' kernel versions ONLY.
+The minor version number, 'x' in '5.x', of aufs may not always
+follow the minor version number of the kernel.
+Because changes in the kernel that cause the use of a new
+minor version number do not always require changes to aufs-util.
+
+Since aufs-util has its own minor version number, you may not be
+able to find a GIT branch in aufs-util for your kernel's
+exact minor version number.
+In this case, you should git-checkout the branch for the
+nearest lower number.
+
+For (an unreleased) example:
+If you are using "linux-5.10" and the "aufs5.10" branch
+does not exist in aufs-util repository, then "aufs5.9", "aufs5.8"
+or something numerically smaller is the branch for your kernel.
+
+Also you can view all branches by
+       $ git branch -a
+
+
+3. Configuration and Compilation
+----------------------------------------
+Make sure you have git-checkout'ed the correct branch.
+
+For aufs5-linux tree,
+- enable CONFIG_AUFS_FS.
+- set other aufs configurations if necessary.
+- for aufs5.13 and later
+  Because aufs is not only an ordinary filesystem (callee of VFS), but
+  also a caller of VFS functions for branch filesystems, subclassing of
+  the internal locks for LOCKDEP is necessary. LOCKDEP is a debugging
+  feature of linux kernel. If you enable CONFIG_LOCKDEP, then you will
+  need to customize some LOCKDEP numbers. Here are what I use on my
+  test environment.
+       CONFIG_LOCKDEP_BITS=21
+       CONFIG_LOCKDEP_CHAINS_BITS=21
+       CONFIG_LOCKDEP_STACK_TRACE_BITS=24
+
+For aufs5-standalone tree,
+There are several ways to build.
+
+1.
+- apply ./aufs5-kbuild.patch to your kernel source files.
+- apply ./aufs5-base.patch too.
+- apply ./aufs5-mmap.patch too.
+- apply ./aufs5-standalone.patch too, if you have a plan to set
+  CONFIG_AUFS_FS=m. otherwise you don't need ./aufs5-standalone.patch.
+- copy ./{Documentation,fs,include/uapi/linux/aufs_type.h} files to your
+  kernel source tree. Never copy $PWD/include/uapi/linux/Kbuild.
+- enable CONFIG_AUFS_FS, you can select either
+  =m or =y.
+- and build your kernel as usual.
+- install the built kernel.
+- install the header files too by "make headers_install" to the
+  directory where you specify. By default, it is $PWD/usr.
+  "make help" shows a brief note for headers_install.
+- and reboot your system.
+
+2.
+- module only (CONFIG_AUFS_FS=m).
+- apply ./aufs5-base.patch to your kernel source files.
+- apply ./aufs5-mmap.patch too.
+- apply ./aufs5-standalone.patch too.
+- build your kernel, don't forget "make headers_install", and reboot.
+- edit ./config.mk and set other aufs configurations if necessary.
+  Note: You should read $PWD/fs/aufs/Kconfig carefully which describes
+  every aufs configurations.
+- build the module by simple "make".
+- you can specify ${KDIR} make variable which points to your kernel
+  source tree.
+- install the files
+  + run "make install" to install the aufs module, or copy the built
+    $PWD/aufs.ko to /lib/modules/... and run depmod -a (or reboot simply).
+  + run "make install_headers" (instead of headers_install) to install
+    the modified aufs header file (you can specify DESTDIR which is
+    available in aufs standalone version's Makefile only), or copy
+    $PWD/usr/include/linux/aufs_type.h to /usr/include/linux or wherever
+    you like manually. By default, the target directory is $PWD/usr.
+- no need to apply aufs5-kbuild.patch, nor copying source files to your
+  kernel source tree.
+
+Note: The header file aufs_type.h is necessary to build aufs-util
+      as well as "make headers_install" in the kernel source tree.
+      headers_install is subject to be forgotten, but it is essentially
+      necessary, not only for building aufs-util.
+      You may not meet problems without headers_install in some older
+      version though.
+
+And then,
+- read README in aufs-util, build and install it
+- note that your distribution may contain an obsoleted version of
+  aufs_type.h in /usr/include/linux or something. When you build aufs
+  utilities, make sure that your compiler refers the correct aufs header
+  file which is built by "make headers_install."
+- if you want to use readdir(3) in userspace or pathconf(3) wrapper,
+  then run "make install_ulib" too. And refer to the aufs manual in
+  detail.
+
+There several other patches in aufs5-standalone.git. They are all
+optional. When you meet some problems, they will help you.
+- aufs5-loopback.patch
+  Supports a nested loopback mount in a branch-fs. This patch is
+  unnecessary until aufs produces a message like "you may want to try
+  another patch for loopback file".
+- vfs-ino.patch
+  Modifies a system global kernel internal function get_next_ino() in
+  order to stop assigning 0 for an inode-number. Not directly related to
+  aufs, but recommended generally.
+- tmpfs-idr.patch
+  Keeps the tmpfs inode number as the lowest value. Effective to reduce
+  the size of aufs XINO files for tmpfs branch. Also it prevents the
+  duplication of inode number, which is important for backup tools and
+  other utilities. When you find aufs XINO files for tmpfs branch
+  growing too much, try this patch.
+
+
+4. Usage
+----------------------------------------
+At first, make sure aufs-util are installed, and please read the aufs
+manual, aufs.5 in aufs-util.git tree.
+$ man -l aufs.5
+
+And then,
+$ mkdir /tmp/rw /tmp/aufs
+# mount -t aufs -o br=/tmp/rw:${HOME} none /tmp/aufs
+
+Here is another example. The result is equivalent.
+# mount -t aufs -o br=/tmp/rw=rw:${HOME}=ro none /tmp/aufs
+  Or
+# mount -t aufs -o br:/tmp/rw none /tmp/aufs
+# mount -o remount,append:${HOME} /tmp/aufs
+
+Then, you can see whole tree of your home dir through /tmp/aufs. If
+you modify a file under /tmp/aufs, the one on your home directory is
+not affected, instead the same named file will be newly created under
+/tmp/rw. And all of your modification to a file will be applied to
+the one under /tmp/rw. This is called the file based Copy on Write
+(COW) method.
+Aufs mount options are described in aufs.5.
+If you run chroot or something and make your aufs as a root directory,
+then you need to customize the shutdown script. See the aufs manual in
+detail.
+
+Additionally, there are some sample usages of aufs which are a
+diskless system with network booting, and LiveCD over NFS.
+See sample dir in CVS tree on SourceForge.
+
+
+5. Contact
+----------------------------------------
+When you have any problems or strange behaviour in aufs, please let me
+know with:
+- /proc/mounts (instead of the output of mount(8))
+- /sys/module/aufs/*
+- /sys/fs/aufs/* (if you have them)
+- /debug/aufs/* (if you have them)
+- linux kernel version
+  if your kernel is not plain, for example modified by distributor,
+  the url where i can download its source is necessary too.
+- aufs version which was printed at loading the module or booting the
+  system, instead of the date you downloaded.
+- configuration (define/undefine CONFIG_AUFS_xxx)
+- kernel configuration or /proc/config.gz (if you have it)
+- LSM (linux security module, if you are using)
+- behaviour which you think to be incorrect
+- actual operation, reproducible one is better
+- mailto: aufs-users at lists.sourceforge.net
+
+Usually, I don't watch the Public Areas(Bugs, Support Requests, Patches,
+and Feature Requests) on SourceForge. Please join and write to
+aufs-users ML.
+
+
+6. Acknowledgements
+----------------------------------------
+Thanks to everyone who have tried and are using aufs, whoever
+have reported a bug or any feedback.
+
+Especially donators:
+Tomas Matejicek(slax.org) made a donation (much more than once).
+       Since Apr 2010, Tomas M (the author of Slax and Linux Live
+       scripts) is making "doubling" donations.
+       Unfortunately I cannot list all of the donators, but I really
+       appreciate.
+       It ends Aug 2010, but the ordinary donation URL is still available.
+       <http://sourceforge.net/donate/index.php?group_id=167503>
+Dai Itasaka made a donation (2007/8).
+Chuck Smith made a donation (2008/4, 10 and 12).
+Henk Schoneveld made a donation (2008/9).
+Chih-Wei Huang, ASUS, CTC donated Eee PC 4G (2008/10).
+Francois Dupoux made a donation (2008/11).
+Bruno Cesar Ribas and Luis Carlos Erpen de Bona, C3SL serves public
+       aufs2 GIT tree (2009/2).
+William Grant made a donation (2009/3).
+Patrick Lane made a donation (2009/4).
+The Mail Archive (mail-archive.com) made donations (2009/5).
+Nippy Networks (Ed Wildgoose) made a donation (2009/7).
+New Dream Network, LLC (www.dreamhost.com) made a donation (2009/11).
+Pavel Pronskiy made a donation (2011/2).
+Iridium and Inmarsat satellite phone retailer (www.mailasail.com), Nippy
+       Networks (Ed Wildgoose) made a donation for hardware (2011/3).
+Max Lekomcev (DOM-TV project) made a donation (2011/7, 12, 2012/3, 6 and
+11).
+Sam Liddicott made a donation (2011/9).
+Era Scarecrow made a donation (2013/4).
+Bor Ratajc made a donation (2013/4).
+Alessandro Gorreta made a donation (2013/4).
+POIRETTE Marc made a donation (2013/4).
+Alessandro Gorreta made a donation (2013/4).
+lauri kasvandik made a donation (2013/5).
+"pemasu from Finland" made a donation (2013/7).
+The Parted Magic Project made a donation (2013/9 and 11).
+Pavel Barta made a donation (2013/10).
+Nikolay Pertsev made a donation (2014/5).
+James B made a donation (2014/7 and 2015/7).
+Stefano Di Biase made a donation (2014/8).
+Daniel Epellei made a donation (2015/1).
+OmegaPhil made a donation (2016/1, 2018/4).
+Tomasz Szewczyk made a donation (2016/4).
+James Burry made a donation (2016/12).
+Carsten Rose made a donation (2018/9).
+Porteus Kiosk made a donation (2018/10).
+
+Thank you very much.
+Donations are always, including future donations, very important and
+helpful for me to keep on developing aufs.
+
+
+7.
+----------------------------------------
+If you are an experienced user, no explanation is needed. Aufs is
+just a linux filesystem.
+
+
+Enjoy!
+
+# Local variables: ;
+# mode: text;
+# End: ;
diff -urN /usr/share/empty/fs/aufs/aufs.h linux/fs/aufs/aufs.h
--- /usr/share/empty/fs/aufs/aufs.h     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/aufs.h        2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * all header files
+ */
+
+#ifndef __AUFS_H__
+#define __AUFS_H__
+
+#ifdef __KERNEL__
+
+#define AuStub(type, name, body, ...) \
+       static inline type name(__VA_ARGS__) { body; }
+
+#define AuStubVoid(name, ...) \
+       AuStub(void, name, , __VA_ARGS__)
+#define AuStubInt0(name, ...) \
+       AuStub(int, name, return 0, __VA_ARGS__)
+
+#include "debug.h"
+
+#include "branch.h"
+#include "cpup.h"
+#include "dcsub.h"
+#include "dbgaufs.h"
+#include "dentry.h"
+#include "dir.h"
+#include "dirren.h"
+#include "dynop.h"
+#include "file.h"
+#include "fstype.h"
+#include "hbl.h"
+#include "inode.h"
+#include "lcnt.h"
+#include "loop.h"
+#include "module.h"
+#include "opts.h"
+#include "rwsem.h"
+#include "super.h"
+#include "sysaufs.h"
+#include "vfsub.h"
+#include "whout.h"
+#include "wkq.h"
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_H__ */
diff -urN /usr/share/empty/fs/aufs/branch.c linux/fs/aufs/branch.c
--- /usr/share/empty/fs/aufs/branch.c   1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/branch.c      2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,1427 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * branch management
+ */
+
+#include <linux/compat.h>
+#include <linux/statfs.h>
+#include "aufs.h"
+
+/*
+ * free a single branch
+ */
+static void au_br_do_free(struct au_branch *br)
+{
+       int i;
+       struct au_wbr *wbr;
+       struct au_dykey **key;
+
+       au_hnotify_fin_br(br);
+       /* always, regardless the mount option */
+       au_dr_hino_free(&br->br_dirren);
+       au_xino_put(br);
+
+       AuLCntZero(au_lcnt_read(&br->br_nfiles, /*do_rev*/0));
+       au_lcnt_fin(&br->br_nfiles, /*do_sync*/0);
+       AuLCntZero(au_lcnt_read(&br->br_count, /*do_rev*/0));
+       au_lcnt_fin(&br->br_count, /*do_sync*/0);
+
+       wbr = br->br_wbr;
+       if (wbr) {
+               for (i = 0; i < AuBrWh_Last; i++)
+                       dput(wbr->wbr_wh[i]);
+               AuDebugOn(atomic_read(&wbr->wbr_wh_running));
+               AuRwDestroy(&wbr->wbr_wh_rwsem);
+       }
+
+       if (br->br_fhsm) {
+               au_br_fhsm_fin(br->br_fhsm);
+               au_kfree_try_rcu(br->br_fhsm);
+       }
+
+       key = br->br_dykey;
+       for (i = 0; i < AuBrDynOp; i++, key++)
+               if (*key)
+                       au_dy_put(*key);
+               else
+                       break;
+
+       /* recursive lock, s_umount of branch's */
+       /* synchronize_rcu(); */ /* why? */
+       lockdep_off();
+       path_put(&br->br_path);
+       lockdep_on();
+       au_kfree_rcu(wbr);
+       au_lcnt_wait_for_fin(&br->br_nfiles);
+       au_lcnt_wait_for_fin(&br->br_count);
+       /* I don't know why, but percpu_refcount requires this */
+       /* synchronize_rcu(); */
+       au_kfree_rcu(br);
+}
+
+/*
+ * frees all branches
+ */
+void au_br_free(struct au_sbinfo *sbinfo)
+{
+       aufs_bindex_t bmax;
+       struct au_branch **br;
+
+       AuRwMustWriteLock(&sbinfo->si_rwsem);
+
+       bmax = sbinfo->si_bbot + 1;
+       br = sbinfo->si_branch;
+       while (bmax--)
+               au_br_do_free(*br++);
+}
+
+/*
+ * find the index of a branch which is specified by @br_id.
+ */
+int au_br_index(struct super_block *sb, aufs_bindex_t br_id)
+{
+       aufs_bindex_t bindex, bbot;
+
+       bbot = au_sbbot(sb);
+       for (bindex = 0; bindex <= bbot; bindex++)
+               if (au_sbr_id(sb, bindex) == br_id)
+                       return bindex;
+       return -1;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * add a branch
+ */
+
+static int test_overlap(struct super_block *sb, struct dentry *h_adding,
+                       struct dentry *h_root)
+{
+       if (unlikely(h_adding == h_root
+                    || au_test_loopback_overlap(sb, h_adding)))
+               return 1;
+       if (h_adding->d_sb != h_root->d_sb)
+               return 0;
+       return au_test_subdir(h_adding, h_root)
+               || au_test_subdir(h_root, h_adding);
+}
+
+/*
+ * returns a newly allocated branch. @new_nbranch is a number of branches
+ * after adding a branch.
+ */
+static struct au_branch *au_br_alloc(struct super_block *sb, int new_nbranch,
+                                    int perm)
+{
+       struct au_branch *add_branch;
+       struct dentry *root;
+       struct inode *inode;
+       int err;
+
+       err = -ENOMEM;
+       add_branch = kzalloc(sizeof(*add_branch), GFP_NOFS);
+       if (unlikely(!add_branch))
+               goto out;
+       add_branch->br_xino = au_xino_alloc(/*nfile*/1);
+       if (unlikely(!add_branch->br_xino))
+               goto out_br;
+       err = au_hnotify_init_br(add_branch, perm);
+       if (unlikely(err))
+               goto out_xino;
+
+       if (au_br_writable(perm)) {
+               /* may be freed separately at changing the branch permission */
+               add_branch->br_wbr = kzalloc(sizeof(*add_branch->br_wbr),
+                                            GFP_NOFS);
+               if (unlikely(!add_branch->br_wbr))
+                       goto out_hnotify;
+       }
+
+       if (au_br_fhsm(perm)) {
+               err = au_fhsm_br_alloc(add_branch);
+               if (unlikely(err))
+                       goto out_wbr;
+       }
+
+       root = sb->s_root;
+       err = au_sbr_realloc(au_sbi(sb), new_nbranch, /*may_shrink*/0);
+       if (!err)
+               err = au_di_realloc(au_di(root), new_nbranch, /*may_shrink*/0);
+       if (!err) {
+               inode = d_inode(root);
+               err = au_hinode_realloc(au_ii(inode), new_nbranch,
+                                       /*may_shrink*/0);
+       }
+       if (!err)
+               return add_branch; /* success */
+
+out_wbr:
+       au_kfree_rcu(add_branch->br_wbr);
+out_hnotify:
+       au_hnotify_fin_br(add_branch);
+out_xino:
+       au_xino_put(add_branch);
+out_br:
+       au_kfree_rcu(add_branch);
+out:
+       return ERR_PTR(err);
+}
+
+/*
+ * test if the branch permission is legal or not.
+ */
+static int test_br(struct inode *inode, int brperm, char *path)
+{
+       int err;
+
+       err = (au_br_writable(brperm) && IS_RDONLY(inode));
+       if (!err)
+               goto out;
+
+       err = -EINVAL;
+       pr_err("write permission for readonly mount or inode, %s\n", path);
+
+out:
+       return err;
+}
+
+/*
+ * returns:
+ * 0: success, the caller will add it
+ * plus: success, it is already unified, the caller should ignore it
+ * minus: error
+ */
+static int test_add(struct super_block *sb, struct au_opt_add *add, int remount)
+{
+       int err;
+       aufs_bindex_t bbot, bindex;
+       struct dentry *root, *h_dentry;
+       struct inode *inode, *h_inode;
+
+       root = sb->s_root;
+       bbot = au_sbbot(sb);
+       if (unlikely(bbot >= 0
+                    && au_find_dbindex(root, add->path.dentry) >= 0)) {
+               err = 1;
+               if (!remount) {
+                       err = -EINVAL;
+                       pr_err("%s duplicated\n", add->pathname);
+               }
+               goto out;
+       }
+
+       err = -ENOSPC; /* -E2BIG; */
+       if (unlikely(AUFS_BRANCH_MAX <= add->bindex
+                    || AUFS_BRANCH_MAX - 1 <= bbot)) {
+               pr_err("number of branches exceeded %s\n", add->pathname);
+               goto out;
+       }
+
+       err = -EDOM;
+       if (unlikely(add->bindex < 0 || bbot + 1 < add->bindex)) {
+               pr_err("bad index %d\n", add->bindex);
+               goto out;
+       }
+
+       inode = d_inode(add->path.dentry);
+       err = -ENOENT;
+       if (unlikely(!inode->i_nlink)) {
+               pr_err("no existence %s\n", add->pathname);
+               goto out;
+       }
+
+       err = -EINVAL;
+       if (unlikely(inode->i_sb == sb)) {
+               pr_err("%s must be outside\n", add->pathname);
+               goto out;
+       }
+
+       if (unlikely(au_test_fs_unsuppoted(inode->i_sb))) {
+               pr_err("unsupported filesystem, %s (%s)\n",
+                      add->pathname, au_sbtype(inode->i_sb));
+               goto out;
+       }
+
+       if (unlikely(inode->i_sb->s_stack_depth)) {
+               pr_err("already stacked, %s (%s)\n",
+                      add->pathname, au_sbtype(inode->i_sb));
+               goto out;
+       }
+
+       err = test_br(d_inode(add->path.dentry), add->perm, add->pathname);
+       if (unlikely(err))
+               goto out;
+
+       if (bbot < 0)
+               return 0; /* success */
+
+       err = -EINVAL;
+       for (bindex = 0; bindex <= bbot; bindex++)
+               if (unlikely(test_overlap(sb, add->path.dentry,
+                                         au_h_dptr(root, bindex)))) {
+                       pr_err("%s is overlapped\n", add->pathname);
+                       goto out;
+               }
+
+       err = 0;
+       if (au_opt_test(au_mntflags(sb), WARN_PERM)) {
+               h_dentry = au_h_dptr(root, 0);
+               h_inode = d_inode(h_dentry);
+               if ((h_inode->i_mode & S_IALLUGO) != (inode->i_mode & S_IALLUGO)
+                   || !uid_eq(h_inode->i_uid, inode->i_uid)
+                   || !gid_eq(h_inode->i_gid, inode->i_gid))
+                       pr_warn("uid/gid/perm %s %u/%u/0%o, %u/%u/0%o\n",
+                               add->pathname,
+                               i_uid_read(inode), i_gid_read(inode),
+                               (inode->i_mode & S_IALLUGO),
+                               i_uid_read(h_inode), i_gid_read(h_inode),
+                               (h_inode->i_mode & S_IALLUGO));
+       }
+
+out:
+       return err;
+}
+
+/*
+ * initialize or clean the whiteouts for an adding branch
+ */
+static int au_br_init_wh(struct super_block *sb, struct au_branch *br,
+                        int new_perm)
+{
+       int err, old_perm;
+       aufs_bindex_t bindex;
+       struct inode *h_inode;
+       struct au_wbr *wbr;
+       struct au_hinode *hdir;
+       struct dentry *h_dentry;
+
+       err = vfsub_mnt_want_write(au_br_mnt(br));
+       if (unlikely(err))
+               goto out;
+
+       wbr = br->br_wbr;
+       old_perm = br->br_perm;
+       br->br_perm = new_perm;
+       hdir = NULL;
+       h_inode = NULL;
+       bindex = au_br_index(sb, br->br_id);
+       if (0 <= bindex) {
+               hdir = au_hi(d_inode(sb->s_root), bindex);
+               au_hn_inode_lock_nested(hdir, AuLsc_I_PARENT);
+       } else {
+               h_dentry = au_br_dentry(br);
+               h_inode = d_inode(h_dentry);
+               inode_lock_nested(h_inode, AuLsc_I_PARENT);
+       }
+       if (!wbr)
+               err = au_wh_init(br, sb);
+       else {
+               wbr_wh_write_lock(wbr);
+               err = au_wh_init(br, sb);
+               wbr_wh_write_unlock(wbr);
+       }
+       if (hdir)
+               au_hn_inode_unlock(hdir);
+       else
+               inode_unlock(h_inode);
+       vfsub_mnt_drop_write(au_br_mnt(br));
+       br->br_perm = old_perm;
+
+       if (!err && wbr && !au_br_writable(new_perm)) {
+               au_kfree_rcu(wbr);
+               br->br_wbr = NULL;
+       }
+
+out:
+       return err;
+}
+
+static int au_wbr_init(struct au_branch *br, struct super_block *sb,
+                      int perm)
+{
+       int err;
+       struct kstatfs kst;
+       struct au_wbr *wbr;
+
+       wbr = br->br_wbr;
+       au_rw_init(&wbr->wbr_wh_rwsem);
+       atomic_set(&wbr->wbr_wh_running, 0);
+
+       /*
+        * a limit for rmdir/rename a dir
+        * cf. AUFS_MAX_NAMELEN in include/uapi/linux/aufs_type.h
+        */
+       err = vfs_statfs(&br->br_path, &kst);
+       if (unlikely(err))
+               goto out;
+       err = -EINVAL;
+       if (kst.f_namelen >= NAME_MAX)
+               err = au_br_init_wh(sb, br, perm);
+       else
+               pr_err("%pd(%s), unsupported namelen %ld\n",
+                      au_br_dentry(br),
+                      au_sbtype(au_br_dentry(br)->d_sb), kst.f_namelen);
+
+out:
+       return err;
+}
+
+/* initialize a new branch */
+static int au_br_init(struct au_branch *br, struct super_block *sb,
+                     struct au_opt_add *add)
+{
+       int err;
+       struct au_branch *brbase;
+       struct file *xf;
+       struct inode *h_inode;
+
+       err = 0;
+       br->br_perm = add->perm;
+       br->br_path = add->path; /* set first, path_get() later */
+       spin_lock_init(&br->br_dykey_lock);
+       au_lcnt_init(&br->br_nfiles, /*release*/NULL);
+       au_lcnt_init(&br->br_count, /*release*/NULL);
+       br->br_id = au_new_br_id(sb);
+       AuDebugOn(br->br_id < 0);
+
+       /* always, regardless the given option */
+       err = au_dr_br_init(sb, br, &add->path);
+       if (unlikely(err))
+               goto out_err;
+
+       if (au_br_writable(add->perm)) {
+               err = au_wbr_init(br, sb, add->perm);
+               if (unlikely(err))
+                       goto out_err;
+       }
+
+       if (au_opt_test(au_mntflags(sb), XINO)) {
+               brbase = au_sbr(sb, 0);
+               xf = au_xino_file(brbase->br_xino, /*idx*/-1);
+               AuDebugOn(!xf);
+               h_inode = d_inode(add->path.dentry);
+               err = au_xino_init_br(sb, br, h_inode->i_ino, &xf->f_path);
+               if (unlikely(err)) {
+                       AuDebugOn(au_xino_file(br->br_xino, /*idx*/-1));
+                       goto out_err;
+               }
+       }
+
+       sysaufs_br_init(br);
+       path_get(&br->br_path);
+       goto out; /* success */
+
+out_err:
+       memset(&br->br_path, 0, sizeof(br->br_path));
+out:
+       return err;
+}
+
+static void au_br_do_add_brp(struct au_sbinfo *sbinfo, aufs_bindex_t bindex,
+                            struct au_branch *br, aufs_bindex_t bbot,
+                            aufs_bindex_t amount)
+{
+       struct au_branch **brp;
+
+       AuRwMustWriteLock(&sbinfo->si_rwsem);
+
+       brp = sbinfo->si_branch + bindex;
+       memmove(brp + 1, brp, sizeof(*brp) * amount);
+       *brp = br;
+       sbinfo->si_bbot++;
+       if (unlikely(bbot < 0))
+               sbinfo->si_bbot = 0;
+}
+
+static void au_br_do_add_hdp(struct au_dinfo *dinfo, aufs_bindex_t bindex,
+                            aufs_bindex_t bbot, aufs_bindex_t amount)
+{
+       struct au_hdentry *hdp;
+
+       AuRwMustWriteLock(&dinfo->di_rwsem);
+
+       hdp = au_hdentry(dinfo, bindex);
+       memmove(hdp + 1, hdp, sizeof(*hdp) * amount);
+       au_h_dentry_init(hdp);
+       dinfo->di_bbot++;
+       if (unlikely(bbot < 0))
+               dinfo->di_btop = 0;
+}
+
+static void au_br_do_add_hip(struct au_iinfo *iinfo, aufs_bindex_t bindex,
+                            aufs_bindex_t bbot, aufs_bindex_t amount)
+{
+       struct au_hinode *hip;
+
+       AuRwMustWriteLock(&iinfo->ii_rwsem);
+
+       hip = au_hinode(iinfo, bindex);
+       memmove(hip + 1, hip, sizeof(*hip) * amount);
+       au_hinode_init(hip);
+       iinfo->ii_bbot++;
+       if (unlikely(bbot < 0))
+               iinfo->ii_btop = 0;
+}
+
+static void au_br_do_add(struct super_block *sb, struct au_branch *br,
+                        aufs_bindex_t bindex)
+{
+       struct dentry *root, *h_dentry;
+       struct inode *root_inode, *h_inode;
+       aufs_bindex_t bbot, amount;
+
+       root = sb->s_root;
+       root_inode = d_inode(root);
+       bbot = au_sbbot(sb);
+       amount = bbot + 1 - bindex;
+       h_dentry = au_br_dentry(br);
+       au_sbilist_lock();
+       au_br_do_add_brp(au_sbi(sb), bindex, br, bbot, amount);
+       au_br_do_add_hdp(au_di(root), bindex, bbot, amount);
+       au_br_do_add_hip(au_ii(root_inode), bindex, bbot, amount);
+       au_set_h_dptr(root, bindex, dget(h_dentry));
+       h_inode = d_inode(h_dentry);
+       au_set_h_iptr(root_inode, bindex, au_igrab(h_inode), /*flags*/0);
+       au_sbilist_unlock();
+}
+
+int au_br_add(struct super_block *sb, struct au_opt_add *add, int remount)
+{
+       int err;
+       aufs_bindex_t bbot, add_bindex;
+       struct dentry *root, *h_dentry;
+       struct inode *root_inode;
+       struct au_branch *add_branch;
+
+       root = sb->s_root;
+       root_inode = d_inode(root);
+       IMustLock(root_inode);
+       IiMustWriteLock(root_inode);
+       err = test_add(sb, add, remount);
+       if (unlikely(err < 0))
+               goto out;
+       if (err) {
+               err = 0;
+               goto out; /* success */
+       }
+
+       bbot = au_sbbot(sb);
+       add_branch = au_br_alloc(sb, bbot + 2, add->perm);
+       err = PTR_ERR(add_branch);
+       if (IS_ERR(add_branch))
+               goto out;
+
+       err = au_br_init(add_branch, sb, add);
+       if (unlikely(err)) {
+               au_br_do_free(add_branch);
+               goto out;
+       }
+
+       add_bindex = add->bindex;
+       sysaufs_brs_del(sb, add_bindex);        /* remove successors */
+       au_br_do_add(sb, add_branch, add_bindex);
+       sysaufs_brs_add(sb, add_bindex);        /* append successors */
+       dbgaufs_brs_add(sb, add_bindex, /*topdown*/0);  /* rename successors */
+
+       h_dentry = add->path.dentry;
+       if (!add_bindex) {
+               au_cpup_attr_all(root_inode, /*force*/1);
+               sb->s_maxbytes = h_dentry->d_sb->s_maxbytes;
+       } else
+               au_add_nlink(root_inode, d_inode(h_dentry));
+
+out:
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static unsigned long long au_farray_cb(struct super_block *sb, void *a,
+                                      unsigned long long max __maybe_unused,
+                                      void *arg)
+{
+       unsigned long long n;
+       struct file **p, *f;
+       struct hlist_bl_head *files;
+       struct hlist_bl_node *pos;
+       struct au_finfo *finfo;
+
+       n = 0;
+       p = a;
+       files = &au_sbi(sb)->si_files;
+       hlist_bl_lock(files);
+       hlist_bl_for_each_entry(finfo, pos, files, fi_hlist) {
+               f = finfo->fi_file;
+               if (file_count(f)
+                   && !special_file(file_inode(f)->i_mode)) {
+                       get_file(f);
+                       *p++ = f;
+                       n++;
+                       AuDebugOn(n > max);
+               }
+       }
+       hlist_bl_unlock(files);
+
+       return n;
+}
+
+static struct file **au_farray_alloc(struct super_block *sb,
+                                    unsigned long long *max)
+{
+       struct au_sbinfo *sbi;
+
+       sbi = au_sbi(sb);
+       *max = au_lcnt_read(&sbi->si_nfiles, /*do_rev*/1);
+       return au_array_alloc(max, au_farray_cb, sb, /*arg*/NULL);
+}
+
+static void au_farray_free(struct file **a, unsigned long long max)
+{
+       unsigned long long ull;
+
+       for (ull = 0; ull < max; ull++)
+               if (a[ull])
+                       fput(a[ull]);
+       kvfree(a);
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * delete a branch
+ */
+
+/* to show the line number, do not make it inlined function */
+#define AuVerbose(do_info, fmt, ...) do { \
+       if (do_info) \
+               pr_info(fmt, ##__VA_ARGS__); \
+} while (0)
+
+static int au_test_ibusy(struct inode *inode, aufs_bindex_t btop,
+                        aufs_bindex_t bbot)
+{
+       return (inode && !S_ISDIR(inode->i_mode)) || btop == bbot;
+}
+
+static int au_test_dbusy(struct dentry *dentry, aufs_bindex_t btop,
+                        aufs_bindex_t bbot)
+{
+       return au_test_ibusy(d_inode(dentry), btop, bbot);
+}
+
+/*
+ * test if the branch is deletable or not.
+ */
+static int test_dentry_busy(struct dentry *root, aufs_bindex_t bindex,
+                           unsigned int sigen, const unsigned int verbose)
+{
+       int err, i, j, ndentry;
+       aufs_bindex_t btop, bbot;
+       struct au_dcsub_pages dpages;
+       struct au_dpage *dpage;
+       struct dentry *d;
+
+       err = au_dpages_init(&dpages, GFP_NOFS);
+       if (unlikely(err))
+               goto out;
+       err = au_dcsub_pages(&dpages, root, NULL, NULL);
+       if (unlikely(err))
+               goto out_dpages;
+
+       for (i = 0; !err && i < dpages.ndpage; i++) {
+               dpage = dpages.dpages + i;
+               ndentry = dpage->ndentry;
+               for (j = 0; !err && j < ndentry; j++) {
+                       d = dpage->dentries[j];
+                       AuDebugOn(au_dcount(d) <= 0);
+                       if (!au_digen_test(d, sigen)) {
+                               di_read_lock_child(d, AuLock_IR);
+                               if (unlikely(au_dbrange_test(d))) {
+                                       di_read_unlock(d, AuLock_IR);
+                                       continue;
+                               }
+                       } else {
+                               di_write_lock_child(d);
+                               if (unlikely(au_dbrange_test(d))) {
+                                       di_write_unlock(d);
+                                       continue;
+                               }
+                               err = au_reval_dpath(d, sigen);
+                               if (!err)
+                                       di_downgrade_lock(d, AuLock_IR);
+                               else {
+                                       di_write_unlock(d);
+                                       break;
+                               }
+                       }
+
+                       /* AuDbgDentry(d); */
+                       btop = au_dbtop(d);
+                       bbot = au_dbbot(d);
+                       if (btop <= bindex
+                           && bindex <= bbot
+                           && au_h_dptr(d, bindex)
+                           && au_test_dbusy(d, btop, bbot)) {
+                               err = -EBUSY;
+                               AuVerbose(verbose, "busy %pd\n", d);
+                               AuDbgDentry(d);
+                       }
+                       di_read_unlock(d, AuLock_IR);
+               }
+       }
+
+out_dpages:
+       au_dpages_free(&dpages);
+out:
+       return err;
+}
+
+static int test_inode_busy(struct super_block *sb, aufs_bindex_t bindex,
+                          unsigned int sigen, const unsigned int verbose)
+{
+       int err;
+       unsigned long long max, ull;
+       struct inode *i, **array;
+       aufs_bindex_t btop, bbot;
+
+       array = au_iarray_alloc(sb, &max);
+       err = PTR_ERR(array);
+       if (IS_ERR(array))
+               goto out;
+
+       err = 0;
+       AuDbg("b%d\n", bindex);
+       for (ull = 0; !err && ull < max; ull++) {
+               i = array[ull];
+               if (unlikely(!i))
+                       break;
+               if (i->i_ino == AUFS_ROOT_INO)
+                       continue;
+
+               /* AuDbgInode(i); */
+               if (au_iigen(i, NULL) == sigen)
+                       ii_read_lock_child(i);
+               else {
+                       ii_write_lock_child(i);
+                       err = au_refresh_hinode_self(i);
+                       au_iigen_dec(i);
+                       if (!err)
+                               ii_downgrade_lock(i);
+                       else {
+                               ii_write_unlock(i);
+                               break;
+                       }
+               }
+
+               btop = au_ibtop(i);
+               bbot = au_ibbot(i);
+               if (btop <= bindex
+                   && bindex <= bbot
+                   && au_h_iptr(i, bindex)
+                   && au_test_ibusy(i, btop, bbot)) {
+                       err = -EBUSY;
+                       AuVerbose(verbose, "busy i%lu\n", i->i_ino);
+                       AuDbgInode(i);
+               }
+               ii_read_unlock(i);
+       }
+       au_iarray_free(array, max);
+
+out:
+       return err;
+}
+
+static int test_children_busy(struct dentry *root, aufs_bindex_t bindex,
+                             const unsigned int verbose)
+{
+       int err;
+       unsigned int sigen;
+
+       sigen = au_sigen(root->d_sb);
+       DiMustNoWaiters(root);
+       IiMustNoWaiters(d_inode(root));
+       di_write_unlock(root);
+       err = test_dentry_busy(root, bindex, sigen, verbose);
+       if (!err)
+               err = test_inode_busy(root->d_sb, bindex, sigen, verbose);
+       di_write_lock_child(root); /* aufs_write_lock() calls ..._child() */
+
+       return err;
+}
+
+static int test_dir_busy(struct file *file, aufs_bindex_t br_id,
+                        struct file **to_free, int *idx)
+{
+       int err;
+       unsigned char matched, root;
+       aufs_bindex_t bindex, bbot;
+       struct au_fidir *fidir;
+       struct au_hfile *hfile;
+
+       err = 0;
+       root = IS_ROOT(file->f_path.dentry);
+       if (root) {
+               get_file(file);
+               to_free[*idx] = file;
+               (*idx)++;
+               goto out;
+       }
+
+       matched = 0;
+       fidir = au_fi(file)->fi_hdir;
+       AuDebugOn(!fidir);
+       bbot = au_fbbot_dir(file);
+       for (bindex = au_fbtop(file); bindex <= bbot; bindex++) {
+               hfile = fidir->fd_hfile + bindex;
+               if (!hfile->hf_file)
+                       continue;
+
+               if (hfile->hf_br->br_id == br_id) {
+                       matched = 1;
+                       break;
+               }
+       }
+       if (matched)
+               err = -EBUSY;
+
+out:
+       return err;
+}
+
+static int test_file_busy(struct super_block *sb, aufs_bindex_t br_id,
+                         struct file **to_free, int opened)
+{
+       int err, idx;
+       unsigned long long ull, max;
+       aufs_bindex_t btop;
+       struct file *file, **array;
+       struct dentry *root;
+       struct au_hfile *hfile;
+
+       array = au_farray_alloc(sb, &max);
+       err = PTR_ERR(array);
+       if (IS_ERR(array))
+               goto out;
+
+       err = 0;
+       idx = 0;
+       root = sb->s_root;
+       di_write_unlock(root);
+       for (ull = 0; ull < max; ull++) {
+               file = array[ull];
+               if (unlikely(!file))
+                       break;
+
+               /* AuDbg("%pD\n", file); */
+               fi_read_lock(file);
+               btop = au_fbtop(file);
+               if (!d_is_dir(file->f_path.dentry)) {
+                       hfile = &au_fi(file)->fi_htop;
+                       if (hfile->hf_br->br_id == br_id)
+                               err = -EBUSY;
+               } else
+                       err = test_dir_busy(file, br_id, to_free, &idx);
+               fi_read_unlock(file);
+               if (unlikely(err))
+                       break;
+       }
+       di_write_lock_child(root);
+       au_farray_free(array, max);
+       AuDebugOn(idx > opened);
+
+out:
+       return err;
+}
+
+static void br_del_file(struct file **to_free, unsigned long long opened,
+                       aufs_bindex_t br_id)
+{
+       unsigned long long ull;
+       aufs_bindex_t bindex, btop, bbot, bfound;
+       struct file *file;
+       struct au_fidir *fidir;
+       struct au_hfile *hfile;
+
+       for (ull = 0; ull < opened; ull++) {
+               file = to_free[ull];
+               if (unlikely(!file))
+                       break;
+
+               /* AuDbg("%pD\n", file); */
+               AuDebugOn(!d_is_dir(file->f_path.dentry));
+               bfound = -1;
+               fidir = au_fi(file)->fi_hdir;
+               AuDebugOn(!fidir);
+               fi_write_lock(file);
+               btop = au_fbtop(file);
+               bbot = au_fbbot_dir(file);
+               for (bindex = btop; bindex <= bbot; bindex++) {
+                       hfile = fidir->fd_hfile + bindex;
+                       if (!hfile->hf_file)
+                               continue;
+
+                       if (hfile->hf_br->br_id == br_id) {
+                               bfound = bindex;
+                               break;
+                       }
+               }
+               AuDebugOn(bfound < 0);
+               au_set_h_fptr(file, bfound, NULL);
+               if (bfound == btop) {
+                       for (btop++; btop <= bbot; btop++)
+                               if (au_hf_dir(file, btop)) {
+                                       au_set_fbtop(file, btop);
+                                       break;
+                               }
+               }
+               fi_write_unlock(file);
+       }
+}
+
+static void au_br_do_del_brp(struct au_sbinfo *sbinfo,
+                            const aufs_bindex_t bindex,
+                            const aufs_bindex_t bbot)
+{
+       struct au_branch **brp, **p;
+
+       AuRwMustWriteLock(&sbinfo->si_rwsem);
+
+       brp = sbinfo->si_branch + bindex;
+       if (bindex < bbot)
+               memmove(brp, brp + 1, sizeof(*brp) * (bbot - bindex));
+       sbinfo->si_branch[0 + bbot] = NULL;
+       sbinfo->si_bbot--;
+
+       p = au_krealloc(sbinfo->si_branch, sizeof(*p) * bbot, AuGFP_SBILIST,
+                       /*may_shrink*/1);
+       if (p)
+               sbinfo->si_branch = p;
+       /* harmless error */
+}
+
+static void au_br_do_del_hdp(struct au_dinfo *dinfo, const aufs_bindex_t bindex,
+                            const aufs_bindex_t bbot)
+{
+       struct au_hdentry *hdp, *p;
+
+       AuRwMustWriteLock(&dinfo->di_rwsem);
+
+       hdp = au_hdentry(dinfo, bindex);
+       if (bindex < bbot)
+               memmove(hdp, hdp + 1, sizeof(*hdp) * (bbot - bindex));
+       /* au_h_dentry_init(au_hdentry(dinfo, bbot); */
+       dinfo->di_bbot--;
+
+       p = au_krealloc(dinfo->di_hdentry, sizeof(*p) * bbot, AuGFP_SBILIST,
+                       /*may_shrink*/1);
+       if (p)
+               dinfo->di_hdentry = p;
+       /* harmless error */
+}
+
+static void au_br_do_del_hip(struct au_iinfo *iinfo, const aufs_bindex_t bindex,
+                            const aufs_bindex_t bbot)
+{
+       struct au_hinode *hip, *p;
+
+       AuRwMustWriteLock(&iinfo->ii_rwsem);
+
+       hip = au_hinode(iinfo, bindex);
+       if (bindex < bbot)
+               memmove(hip, hip + 1, sizeof(*hip) * (bbot - bindex));
+       /* au_hinode_init(au_hinode(iinfo, bbot)); */
+       iinfo->ii_bbot--;
+
+       p = au_krealloc(iinfo->ii_hinode, sizeof(*p) * bbot, AuGFP_SBILIST,
+                       /*may_shrink*/1);
+       if (p)
+               iinfo->ii_hinode = p;
+       /* harmless error */
+}
+
+static void au_br_do_del(struct super_block *sb, aufs_bindex_t bindex,
+                        struct au_branch *br)
+{
+       aufs_bindex_t bbot;
+       struct au_sbinfo *sbinfo;
+       struct dentry *root, *h_root;
+       struct inode *inode, *h_inode;
+       struct au_hinode *hinode;
+
+       SiMustWriteLock(sb);
+
+       root = sb->s_root;
+       inode = d_inode(root);
+       sbinfo = au_sbi(sb);
+       bbot = sbinfo->si_bbot;
+
+       h_root = au_h_dptr(root, bindex);
+       hinode = au_hi(inode, bindex);
+       h_inode = au_igrab(hinode->hi_inode);
+       au_hiput(hinode);
+
+       au_sbilist_lock();
+       au_br_do_del_brp(sbinfo, bindex, bbot);
+       au_br_do_del_hdp(au_di(root), bindex, bbot);
+       au_br_do_del_hip(au_ii(inode), bindex, bbot);
+       au_sbilist_unlock();
+
+       /* ignore an error */
+       au_dr_br_fin(sb, br); /* always, regardless the mount option */
+
+       dput(h_root);
+       iput(h_inode);
+       au_br_do_free(br);
+}
+
+static unsigned long long empty_cb(struct super_block *sb, void *array,
+                                  unsigned long long max, void *arg)
+{
+       return max;
+}
+
+int au_br_del(struct super_block *sb, struct au_opt_del *del, int remount)
+{
+       int err, rerr, i;
+       unsigned long long opened;
+       unsigned int mnt_flags;
+       aufs_bindex_t bindex, bbot, br_id;
+       unsigned char do_wh, verbose;
+       struct au_branch *br;
+       struct au_wbr *wbr;
+       struct dentry *root;
+       struct file **to_free;
+
+       err = 0;
+       opened = 0;
+       to_free = NULL;
+       root = sb->s_root;
+       bindex = au_find_dbindex(root, del->h_path.dentry);
+       if (bindex < 0) {
+               if (remount)
+                       goto out; /* success */
+               err = -ENOENT;
+               pr_err("%s no such branch\n", del->pathname);
+               goto out;
+       }
+       AuDbg("bindex b%d\n", bindex);
+
+       err = -EBUSY;
+       mnt_flags = au_mntflags(sb);
+       verbose = !!au_opt_test(mnt_flags, VERBOSE);
+       bbot = au_sbbot(sb);
+       if (unlikely(!bbot)) {
+               AuVerbose(verbose, "no more branches left\n");
+               goto out;
+       }
+
+       br = au_sbr(sb, bindex);
+       AuDebugOn(!path_equal(&br->br_path, &del->h_path));
+       if (unlikely(au_lcnt_read(&br->br_count, /*do_rev*/1))) {
+               AuVerbose(verbose, "br %pd2 is busy now\n", del->h_path.dentry);
+               goto out;
+       }
+
+       br_id = br->br_id;
+       opened = au_lcnt_read(&br->br_nfiles, /*do_rev*/1);
+       if (unlikely(opened)) {
+               to_free = au_array_alloc(&opened, empty_cb, sb, NULL);
+               err = PTR_ERR(to_free);
+               if (IS_ERR(to_free))
+                       goto out;
+
+               err = test_file_busy(sb, br_id, to_free, opened);
+               if (unlikely(err)) {
+                       AuVerbose(verbose, "%llu file(s) opened\n", opened);
+                       goto out;
+               }
+       }
+
+       wbr = br->br_wbr;
+       do_wh = wbr && (wbr->wbr_whbase || wbr->wbr_plink || wbr->wbr_orph);
+       if (do_wh) {
+               /* instead of WbrWhMustWriteLock(wbr) */
+               SiMustWriteLock(sb);
+               for (i = 0; i < AuBrWh_Last; i++) {
+                       dput(wbr->wbr_wh[i]);
+                       wbr->wbr_wh[i] = NULL;
+               }
+       }
+
+       err = test_children_busy(root, bindex, verbose);
+       if (unlikely(err)) {
+               if (do_wh)
+                       goto out_wh;
+               goto out;
+       }
+
+       err = 0;
+       if (to_free) {
+               /*
+                * now we confirmed the branch is deletable.
+                * let's free the remaining opened dirs on the branch.
+                */
+               di_write_unlock(root);
+               br_del_file(to_free, opened, br_id);
+               di_write_lock_child(root);
+       }
+
+       sysaufs_brs_del(sb, bindex);    /* remove successors */
+       dbgaufs_xino_del(br);           /* remove one */
+       au_br_do_del(sb, bindex, br);
+       sysaufs_brs_add(sb, bindex);    /* append successors */
+       dbgaufs_brs_add(sb, bindex, /*topdown*/1);      /* rename successors */
+
+       if (!bindex) {
+               au_cpup_attr_all(d_inode(root), /*force*/1);
+               sb->s_maxbytes = au_sbr_sb(sb, 0)->s_maxbytes;
+       } else
+               au_sub_nlink(d_inode(root), d_inode(del->h_path.dentry));
+       if (au_opt_test(mnt_flags, PLINK))
+               au_plink_half_refresh(sb, br_id);
+
+       goto out; /* success */
+
+out_wh:
+       /* revert */
+       rerr = au_br_init_wh(sb, br, br->br_perm);
+       if (rerr)
+               pr_warn("failed re-creating base whiteout, %s. (%d)\n",
+                       del->pathname, rerr);
+out:
+       if (to_free)
+               au_farray_free(to_free, opened);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_ibusy(struct super_block *sb, struct aufs_ibusy __user *arg)
+{
+       int err;
+       aufs_bindex_t btop, bbot;
+       struct aufs_ibusy ibusy;
+       struct inode *inode, *h_inode;
+
+       err = -EPERM;
+       if (unlikely(!capable(CAP_SYS_ADMIN)))
+               goto out;
+
+       err = copy_from_user(&ibusy, arg, sizeof(ibusy));
+       if (!err)
+               /* VERIFY_WRITE */
+               err = !access_ok(&arg->h_ino, sizeof(arg->h_ino));
+       if (unlikely(err)) {
+               err = -EFAULT;
+               AuTraceErr(err);
+               goto out;
+       }
+
+       err = -EINVAL;
+       si_read_lock(sb, AuLock_FLUSH);
+       if (unlikely(ibusy.bindex < 0 || ibusy.bindex > au_sbbot(sb)))
+               goto out_unlock;
+
+       err = 0;
+       ibusy.h_ino = 0; /* invalid */
+       inode = ilookup(sb, ibusy.ino);
+       if (!inode
+           || inode->i_ino == AUFS_ROOT_INO
+           || au_is_bad_inode(inode))
+               goto out_unlock;
+
+       ii_read_lock_child(inode);
+       btop = au_ibtop(inode);
+       bbot = au_ibbot(inode);
+       if (btop <= ibusy.bindex && ibusy.bindex <= bbot) {
+               h_inode = au_h_iptr(inode, ibusy.bindex);
+               if (h_inode && au_test_ibusy(inode, btop, bbot))
+                       ibusy.h_ino = h_inode->i_ino;
+       }
+       ii_read_unlock(inode);
+       iput(inode);
+
+out_unlock:
+       si_read_unlock(sb);
+       if (!err) {
+               err = __put_user(ibusy.h_ino, &arg->h_ino);
+               if (unlikely(err)) {
+                       err = -EFAULT;
+                       AuTraceErr(err);
+               }
+       }
+out:
+       return err;
+}
+
+long au_ibusy_ioctl(struct file *file, unsigned long arg)
+{
+       return au_ibusy(file->f_path.dentry->d_sb, (void __user *)arg);
+}
+
+#ifdef CONFIG_COMPAT
+long au_ibusy_compat_ioctl(struct file *file, unsigned long arg)
+{
+       return au_ibusy(file->f_path.dentry->d_sb, compat_ptr(arg));
+}
+#endif
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * change a branch permission
+ */
+
+static void au_warn_ima(void)
+{
+#ifdef CONFIG_IMA
+       /* since it doesn't support mark_files_ro() */
+       AuWarn1("RW -> RO makes IMA to produce wrong message\n");
+#endif
+}
+
+static int do_need_sigen_inc(int a, int b)
+{
+       return au_br_whable(a) && !au_br_whable(b);
+}
+
+static int need_sigen_inc(int old, int new)
+{
+       return do_need_sigen_inc(old, new)
+               || do_need_sigen_inc(new, old);
+}
+
+static int au_br_mod_files_ro(struct super_block *sb, aufs_bindex_t bindex)
+{
+       int err, do_warn;
+       unsigned int mnt_flags;
+       unsigned long long ull, max;
+       aufs_bindex_t br_id;
+       unsigned char verbose, writer;
+       struct file *file, *hf, **array;
+       struct au_hfile *hfile;
+       struct inode *h_inode;
+
+       mnt_flags = au_mntflags(sb);
+       verbose = !!au_opt_test(mnt_flags, VERBOSE);
+
+       array = au_farray_alloc(sb, &max);
+       err = PTR_ERR(array);
+       if (IS_ERR(array))
+               goto out;
+
+       do_warn = 0;
+       br_id = au_sbr_id(sb, bindex);
+       for (ull = 0; ull < max; ull++) {
+               file = array[ull];
+               if (unlikely(!file))
+                       break;
+
+               /* AuDbg("%pD\n", file); */
+               fi_read_lock(file);
+               if (unlikely(au_test_mmapped(file))) {
+                       err = -EBUSY;
+                       AuVerbose(verbose, "mmapped %pD\n", file);
+                       AuDbgFile(file);
+                       FiMustNoWaiters(file);
+                       fi_read_unlock(file);
+                       goto out_array;
+               }
+
+               hfile = &au_fi(file)->fi_htop;
+               hf = hfile->hf_file;
+               if (!d_is_reg(file->f_path.dentry)
+                   || !(file->f_mode & FMODE_WRITE)
+                   || hfile->hf_br->br_id != br_id
+                   || !(hf->f_mode & FMODE_WRITE))
+                       array[ull] = NULL;
+               else {
+                       do_warn = 1;
+                       get_file(file);
+               }
+
+               FiMustNoWaiters(file);
+               fi_read_unlock(file);
+               fput(file);
+       }
+
+       err = 0;
+       if (do_warn)
+               au_warn_ima();
+
+       for (ull = 0; ull < max; ull++) {
+               file = array[ull];
+               if (!file)
+                       continue;
+
+               /* todo: already flushed? */
+               /*
+                * fs/super.c:mark_files_ro() is gone, but aufs keeps its
+                * approach which resets f_mode and calls mnt_drop_write() and
+                * file_release_write() for each file, because the branch
+                * attribute in aufs world is totally different from the native
+                * fs rw/ro mode.
+               */
+               /* fi_read_lock(file); */
+               hfile = &au_fi(file)->fi_htop;
+               hf = hfile->hf_file;
+               /* fi_read_unlock(file); */
+               spin_lock(&hf->f_lock);
+               writer = !!(hf->f_mode & FMODE_WRITER);
+               hf->f_mode &= ~(FMODE_WRITE | FMODE_WRITER);
+               spin_unlock(&hf->f_lock);
+               if (writer) {
+                       h_inode = file_inode(hf);
+                       if (hf->f_mode & FMODE_READ)
+                               i_readcount_inc(h_inode);
+                       put_write_access(h_inode);
+                       __mnt_drop_write(hf->f_path.mnt);
+               }
+       }
+
+out_array:
+       au_farray_free(array, max);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+int au_br_mod(struct super_block *sb, struct au_opt_mod *mod, int remount,
+             int *do_refresh)
+{
+       int err, rerr;
+       aufs_bindex_t bindex;
+       struct dentry *root;
+       struct au_branch *br;
+       struct au_br_fhsm *bf;
+
+       root = sb->s_root;
+       bindex = au_find_dbindex(root, mod->h_root);
+       if (bindex < 0) {
+               if (remount)
+                       return 0; /* success */
+               err = -ENOENT;
+               pr_err("%s no such branch\n", mod->path);
+               goto out;
+       }
+       AuDbg("bindex b%d\n", bindex);
+
+       err = test_br(d_inode(mod->h_root), mod->perm, mod->path);
+       if (unlikely(err))
+               goto out;
+
+       br = au_sbr(sb, bindex);
+       AuDebugOn(mod->h_root != au_br_dentry(br));
+       if (br->br_perm == mod->perm)
+               return 0; /* success */
+
+       /* pre-allocate for non-fhsm --> fhsm */
+       bf = NULL;
+       if (!au_br_fhsm(br->br_perm) && au_br_fhsm(mod->perm)) {
+               err = au_fhsm_br_alloc(br);
+               if (unlikely(err))
+                       goto out;
+               bf = br->br_fhsm;
+               br->br_fhsm = NULL;
+       }
+
+       if (au_br_writable(br->br_perm)) {
+               /* remove whiteout base */
+               err = au_br_init_wh(sb, br, mod->perm);
+               if (unlikely(err))
+                       goto out_bf;
+
+               if (!au_br_writable(mod->perm)) {
+                       /* rw --> ro, file might be mmapped */
+                       DiMustNoWaiters(root);
+                       IiMustNoWaiters(d_inode(root));
+                       di_write_unlock(root);
+                       err = au_br_mod_files_ro(sb, bindex);
+                       /* aufs_write_lock() calls ..._child() */
+                       di_write_lock_child(root);
+
+                       if (unlikely(err)) {
+                               rerr = -ENOMEM;
+                               br->br_wbr = kzalloc(sizeof(*br->br_wbr),
+                                                    GFP_NOFS);
+                               if (br->br_wbr)
+                                       rerr = au_wbr_init(br, sb, br->br_perm);
+                               if (unlikely(rerr)) {
+                                       AuIOErr("nested error %d (%d)\n",
+                                               rerr, err);
+                                       br->br_perm = mod->perm;
+                               }
+                       }
+               }
+       } else if (au_br_writable(mod->perm)) {
+               /* ro --> rw */
+               err = -ENOMEM;
+               br->br_wbr = kzalloc(sizeof(*br->br_wbr), GFP_NOFS);
+               if (br->br_wbr) {
+                       err = au_wbr_init(br, sb, mod->perm);
+                       if (unlikely(err)) {
+                               au_kfree_rcu(br->br_wbr);
+                               br->br_wbr = NULL;
+                       }
+               }
+       }
+       if (unlikely(err))
+               goto out_bf;
+
+       if (au_br_fhsm(br->br_perm)) {
+               if (!au_br_fhsm(mod->perm)) {
+                       /* fhsm --> non-fhsm */
+                       au_br_fhsm_fin(br->br_fhsm);
+                       au_kfree_rcu(br->br_fhsm);
+                       br->br_fhsm = NULL;
+               }
+       } else if (au_br_fhsm(mod->perm))
+               /* non-fhsm --> fhsm */
+               br->br_fhsm = bf;
+
+       *do_refresh |= need_sigen_inc(br->br_perm, mod->perm);
+       br->br_perm = mod->perm;
+       goto out; /* success */
+
+out_bf:
+       au_kfree_try_rcu(bf);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+int au_br_stfs(struct au_branch *br, struct aufs_stfs *stfs)
+{
+       int err;
+       struct kstatfs kstfs;
+
+       err = vfs_statfs(&br->br_path, &kstfs);
+       if (!err) {
+               stfs->f_blocks = kstfs.f_blocks;
+               stfs->f_bavail = kstfs.f_bavail;
+               stfs->f_files = kstfs.f_files;
+               stfs->f_ffree = kstfs.f_ffree;
+       }
+
+       return err;
+}
diff -urN /usr/share/empty/fs/aufs/branch.h linux/fs/aufs/branch.h
--- /usr/share/empty/fs/aufs/branch.h   1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/branch.h      2021-12-03 15:40:58.233313963 +0100
@@ -0,0 +1,375 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * branch filesystems and xino for them
+ */
+
+#ifndef __AUFS_BRANCH_H__
+#define __AUFS_BRANCH_H__
+
+#ifdef __KERNEL__
+
+#include <linux/mount.h>
+#include "dirren.h"
+#include "dynop.h"
+#include "lcnt.h"
+#include "rwsem.h"
+#include "super.h"
+
+/* ---------------------------------------------------------------------- */
+
+/* a xino file */
+struct au_xino {
+       struct file             **xi_file;
+       unsigned int            xi_nfile;
+
+       struct {
+               spinlock_t              spin;
+               ino_t                   *array;
+               int                     total;
+               /* reserved for future use */
+               /* unsigned long        *bitmap; */
+               wait_queue_head_t       wqh;
+       } xi_nondir;
+
+       struct mutex            xi_mtx; /* protects xi_file array */
+       struct hlist_bl_head    xi_writing;
+
+       atomic_t                xi_truncating;
+
+       struct kref             xi_kref;
+};
+
+/* File-based Hierarchical Storage Management */
+struct au_br_fhsm {
+#ifdef CONFIG_AUFS_FHSM
+       struct mutex            bf_lock;
+       unsigned long           bf_jiffy;
+       struct aufs_stfs        bf_stfs;
+       int                     bf_readable;
+#endif
+};
+
+/* members for writable branch only */
+enum {AuBrWh_BASE, AuBrWh_PLINK, AuBrWh_ORPH, AuBrWh_Last};
+struct au_wbr {
+       struct au_rwsem         wbr_wh_rwsem;
+       struct dentry           *wbr_wh[AuBrWh_Last];
+       atomic_t                wbr_wh_running;
+#define wbr_whbase             wbr_wh[AuBrWh_BASE]     /* whiteout base */
+#define wbr_plink              wbr_wh[AuBrWh_PLINK]    /* pseudo-link dir */
+#define wbr_orph               wbr_wh[AuBrWh_ORPH]     /* dir for orphans */
+
+       /* mfs mode */
+       unsigned long long      wbr_bytes;
+};
+
+/* ext2 has 3 types of operations at least, ext3 has 4 */
+#define AuBrDynOp (AuDyLast * 4)
+
+#ifdef CONFIG_AUFS_HFSNOTIFY
+/* support for asynchronous destruction */
+struct au_br_hfsnotify {
+       struct fsnotify_group   *hfsn_group;
+};
+#endif
+
+/* sysfs entries */
+struct au_brsysfs {
+       char                    name[16];
+       struct attribute        attr;
+};
+
+enum {
+       AuBrSysfs_BR,
+       AuBrSysfs_BRID,
+       AuBrSysfs_Last
+};
+
+/* protected by superblock rwsem */
+struct au_branch {
+       struct au_xino          *br_xino;
+
+       aufs_bindex_t           br_id;
+
+       int                     br_perm;
+       struct path             br_path;
+       spinlock_t              br_dykey_lock;
+       struct au_dykey         *br_dykey[AuBrDynOp];
+       au_lcnt_t               br_nfiles;      /* opened files */
+       au_lcnt_t               br_count;       /* in-use for other */
+
+       struct au_wbr           *br_wbr;
+       struct au_br_fhsm       *br_fhsm;
+
+#ifdef CONFIG_AUFS_HFSNOTIFY
+       struct au_br_hfsnotify  *br_hfsn;
+#endif
+
+#ifdef CONFIG_SYSFS
+       /* entries under sysfs per mount-point */
+       struct au_brsysfs       br_sysfs[AuBrSysfs_Last];
+#endif
+
+#ifdef CONFIG_DEBUG_FS
+       struct dentry            *br_dbgaufs; /* xino */
+#endif
+
+       struct au_dr_br         br_dirren;
+};
+
+/* ---------------------------------------------------------------------- */
+
+static inline struct vfsmount *au_br_mnt(struct au_branch *br)
+{
+       return br->br_path.mnt;
+}
+
+static inline struct dentry *au_br_dentry(struct au_branch *br)
+{
+       return br->br_path.dentry;
+}
+
+static inline struct user_namespace *au_br_userns(struct au_branch *br)
+{
+       return mnt_user_ns(br->br_path.mnt);
+}
+
+static inline struct super_block *au_br_sb(struct au_branch *br)
+{
+       return au_br_mnt(br)->mnt_sb;
+}
+
+static inline int au_br_rdonly(struct au_branch *br)
+{
+       return (sb_rdonly(au_br_sb(br))
+               || !au_br_writable(br->br_perm))
+               ? -EROFS : 0;
+}
+
+static inline int au_br_hnotifyable(int brperm __maybe_unused)
+{
+#ifdef CONFIG_AUFS_HNOTIFY
+       return !(brperm & AuBrPerm_RR);
+#else
+       return 0;
+#endif
+}
+
+static inline int au_br_test_oflag(int oflag, struct au_branch *br)
+{
+       int err, exec_flag;
+
+       err = 0;
+       exec_flag = oflag & __FMODE_EXEC;
+       if (unlikely(exec_flag && path_noexec(&br->br_path)))
+               err = -EACCES;
+
+       return err;
+}
+
+static inline void au_xino_get(struct au_branch *br)
+{
+       struct au_xino *xi;
+
+       xi = br->br_xino;
+       if (xi)
+               kref_get(&xi->xi_kref);
+}
+
+static inline int au_xino_count(struct au_branch *br)
+{
+       int v;
+       struct au_xino *xi;
+
+       v = 0;
+       xi = br->br_xino;
+       if (xi)
+               v = kref_read(&xi->xi_kref);
+
+       return v;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* branch.c */
+struct au_sbinfo;
+void au_br_free(struct au_sbinfo *sinfo);
+int au_br_index(struct super_block *sb, aufs_bindex_t br_id);
+struct au_opt_add;
+int au_br_add(struct super_block *sb, struct au_opt_add *add, int remount);
+struct au_opt_del;
+int au_br_del(struct super_block *sb, struct au_opt_del *del, int remount);
+long au_ibusy_ioctl(struct file *file, unsigned long arg);
+#ifdef CONFIG_COMPAT
+long au_ibusy_compat_ioctl(struct file *file, unsigned long arg);
+#endif
+struct au_opt_mod;
+int au_br_mod(struct super_block *sb, struct au_opt_mod *mod, int remount,
+             int *do_refresh);
+struct aufs_stfs;
+int au_br_stfs(struct au_branch *br, struct aufs_stfs *stfs);
+
+/* xino.c */
+static const loff_t au_loff_max = LLONG_MAX;
+
+aufs_bindex_t au_xi_root(struct super_block *sb, struct dentry *dentry);
+struct file *au_xino_create(struct super_block *sb, char *fpath, int silent,
+                           int wbrtop);
+struct file *au_xino_create2(struct super_block *sb, struct path *base,
+                            struct file *copy_src);
+struct au_xi_new {
+       struct au_xino *xi;     /* switch between xino and xigen */
+       int idx;
+       struct path *base;
+       struct file *copy_src;
+};
+struct file *au_xi_new(struct super_block *sb, struct au_xi_new *xinew);
+
+int au_xino_read(struct super_block *sb, aufs_bindex_t bindex, ino_t h_ino,
+                ino_t *ino);
+int au_xino_write(struct super_block *sb, aufs_bindex_t bindex, ino_t h_ino,
+                 ino_t ino);
+ssize_t xino_fread(struct file *file, void *buf, size_t size, loff_t *pos);
+ssize_t xino_fwrite(struct file *file, void *buf, size_t size, loff_t *pos);
+
+int au_xib_trunc(struct super_block *sb);
+int au_xino_trunc(struct super_block *sb, aufs_bindex_t bindex, int idx_begin);
+
+struct au_xino *au_xino_alloc(unsigned int nfile);
+int au_xino_put(struct au_branch *br);
+struct file *au_xino_file1(struct au_xino *xi);
+
+struct au_opt_xino;
+void au_xino_clr(struct super_block *sb);
+int au_xino_set(struct super_block *sb, struct au_opt_xino *xiopt, int remount);
+struct file *au_xino_def(struct super_block *sb);
+int au_xino_init_br(struct super_block *sb, struct au_branch *br, ino_t hino,
+                   struct path *base);
+
+ino_t au_xino_new_ino(struct super_block *sb);
+void au_xino_delete_inode(struct inode *inode, const int unlinked);
+
+void au_xinondir_leave(struct super_block *sb, aufs_bindex_t bindex,
+                      ino_t h_ino, int idx);
+int au_xinondir_enter(struct super_block *sb, aufs_bindex_t bindex, ino_t h_ino,
+                     int *idx);
+
+int au_xino_path(struct seq_file *seq, struct file *file);
+
+/* ---------------------------------------------------------------------- */
+
+/* @idx is signed to accept -1 meaning the first file */
+static inline struct file *au_xino_file(struct au_xino *xi, int idx)
+{
+       struct file *file;
+
+       file = NULL;
+       if (!xi)
+               goto out;
+
+       if (idx >= 0) {
+               if (idx < xi->xi_nfile)
+                       file = xi->xi_file[idx];
+       } else
+               file = au_xino_file1(xi);
+
+out:
+       return file;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* Superblock to branch */
+static inline
+aufs_bindex_t au_sbr_id(struct super_block *sb, aufs_bindex_t bindex)
+{
+       return au_sbr(sb, bindex)->br_id;
+}
+
+static inline
+struct vfsmount *au_sbr_mnt(struct super_block *sb, aufs_bindex_t bindex)
+{
+       return au_br_mnt(au_sbr(sb, bindex));
+}
+
+static inline
+struct user_namespace *au_sbr_userns(struct super_block *sb, aufs_bindex_t bindex)
+{
+       return au_br_userns(au_sbr(sb, bindex));
+}
+
+static inline
+struct super_block *au_sbr_sb(struct super_block *sb, aufs_bindex_t bindex)
+{
+       return au_br_sb(au_sbr(sb, bindex));
+}
+
+static inline int au_sbr_perm(struct super_block *sb, aufs_bindex_t bindex)
+{
+       return au_sbr(sb, bindex)->br_perm;
+}
+
+static inline int au_sbr_whable(struct super_block *sb, aufs_bindex_t bindex)
+{
+       return au_br_whable(au_sbr_perm(sb, bindex));
+}
+
+/* ---------------------------------------------------------------------- */
+
+#define wbr_wh_read_lock(wbr)  au_rw_read_lock(&(wbr)->wbr_wh_rwsem)
+#define wbr_wh_write_lock(wbr) au_rw_write_lock(&(wbr)->wbr_wh_rwsem)
+#define wbr_wh_read_trylock(wbr)       au_rw_read_trylock(&(wbr)->wbr_wh_rwsem)
+#define wbr_wh_write_trylock(wbr) au_rw_write_trylock(&(wbr)->wbr_wh_rwsem)
+/*
+#define wbr_wh_read_trylock_nested(wbr) \
+       au_rw_read_trylock_nested(&(wbr)->wbr_wh_rwsem)
+#define wbr_wh_write_trylock_nested(wbr) \
+       au_rw_write_trylock_nested(&(wbr)->wbr_wh_rwsem)
+*/
+
+#define wbr_wh_read_unlock(wbr)        au_rw_read_unlock(&(wbr)->wbr_wh_rwsem)
+#define wbr_wh_write_unlock(wbr)       au_rw_write_unlock(&(wbr)->wbr_wh_rwsem)
+#define wbr_wh_downgrade_lock(wbr)     au_rw_dgrade_lock(&(wbr)->wbr_wh_rwsem)
+
+#define WbrWhMustNoWaiters(wbr)        AuRwMustNoWaiters(&(wbr)->wbr_wh_rwsem)
+#define WbrWhMustAnyLock(wbr)  AuRwMustAnyLock(&(wbr)->wbr_wh_rwsem)
+#define WbrWhMustWriteLock(wbr)        AuRwMustWriteLock(&(wbr)->wbr_wh_rwsem)
+
+/* ---------------------------------------------------------------------- */
+
+#ifdef CONFIG_AUFS_FHSM
+static inline void au_br_fhsm_init(struct au_br_fhsm *brfhsm)
+{
+       mutex_init(&brfhsm->bf_lock);
+       brfhsm->bf_jiffy = 0;
+       brfhsm->bf_readable = 0;
+}
+
+static inline void au_br_fhsm_fin(struct au_br_fhsm *brfhsm)
+{
+       mutex_destroy(&brfhsm->bf_lock);
+}
+#else
+AuStubVoid(au_br_fhsm_init, struct au_br_fhsm *brfhsm)
+AuStubVoid(au_br_fhsm_fin, struct au_br_fhsm *brfhsm)
+#endif
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_BRANCH_H__ */
diff -urN /usr/share/empty/fs/aufs/conf.mk linux/fs/aufs/conf.mk
--- /usr/share/empty/fs/aufs/conf.mk    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/conf.mk       2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,40 @@
+# SPDX-License-Identifier: GPL-2.0
+
+AuConfStr = CONFIG_AUFS_FS=${CONFIG_AUFS_FS}
+
+define AuConf
+ifdef ${1}
+AuConfStr += ${1}=${${1}}
+endif
+endef
+
+AuConfAll = BRANCH_MAX_127 BRANCH_MAX_511 BRANCH_MAX_1023 BRANCH_MAX_32767 \
+       SBILIST \
+       HNOTIFY HFSNOTIFY \
+       EXPORT INO_T_64 \
+       XATTR \
+       FHSM \
+       RDU \
+       DIRREN \
+       SHWH \
+       BR_RAMFS \
+       BR_FUSE POLL \
+       BR_HFSPLUS \
+       BDEV_LOOP \
+       DEBUG MAGIC_SYSRQ
+$(foreach i, ${AuConfAll}, \
+       $(eval $(call AuConf,CONFIG_AUFS_${i})))
+
+AuConfName = ${obj}/conf.str
+${AuConfName}.tmp: FORCE
+       @echo ${AuConfStr} | tr ' ' '\n' | sed -e 's/^/"/' -e 's/$$/\\n"/' > $@
+${AuConfName}: ${AuConfName}.tmp
+       @diff -q $< $@ > /dev/null 2>&1 || { \
+       echo '  GEN    ' $@; \
+       cp -p $< $@; \
+       }
+FORCE:
+clean-files += ${AuConfName} ${AuConfName}.tmp
+${obj}/sysfs.o: ${AuConfName}
+
+-include ${srctree}/${src}/conf_priv.mk
diff -urN /usr/share/empty/fs/aufs/cpup.c linux/fs/aufs/cpup.c
--- /usr/share/empty/fs/aufs/cpup.c     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/cpup.c        2021-12-03 15:40:58.233313963 +0100
@@ -0,0 +1,1459 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * copy-up functions, see wbr_policy.c for copy-down
+ */
+
+#include <linux/fs_stack.h>
+#include <linux/mm.h>
+#include <linux/task_work.h>
+#include "aufs.h"
+
+void au_cpup_attr_flags(struct inode *dst, unsigned int iflags)
+{
+       const unsigned int mask = S_DEAD | S_SWAPFILE | S_PRIVATE
+               | S_NOATIME | S_NOCMTIME | S_AUTOMOUNT;
+
+       BUILD_BUG_ON(sizeof(iflags) != sizeof(dst->i_flags));
+
+       dst->i_flags |= iflags & ~mask;
+       if (au_test_fs_notime(dst->i_sb))
+               dst->i_flags |= S_NOATIME | S_NOCMTIME;
+}
+
+void au_cpup_attr_timesizes(struct inode *inode)
+{
+       struct inode *h_inode;
+
+       h_inode = au_h_iptr(inode, au_ibtop(inode));
+       fsstack_copy_attr_times(inode, h_inode);
+       fsstack_copy_inode_size(inode, h_inode);
+}
+
+void au_cpup_attr_nlink(struct inode *inode, int force)
+{
+       struct inode *h_inode;
+       struct super_block *sb;
+       aufs_bindex_t bindex, bbot;
+
+       sb = inode->i_sb;
+       bindex = au_ibtop(inode);
+       h_inode = au_h_iptr(inode, bindex);
+       if (!force
+           && !S_ISDIR(h_inode->i_mode)
+           && au_opt_test(au_mntflags(sb), PLINK)
+           && au_plink_test(inode))
+               return;
+
+       /*
+        * 0 can happen in revalidating.
+        * h_inode->i_mutex may not be held here, but it is harmless since once
+        * i_nlink reaches 0, it will never become positive except O_TMPFILE
+        * case.
+        * todo: O_TMPFILE+linkat(AT_SYMLINK_FOLLOW) bypassing aufs may cause
+        *       the incorrect link count.
+        */
+       set_nlink(inode, h_inode->i_nlink);
+
+       /*
+        * fewer nlink makes find(1) noisy, but larger nlink doesn't.
+        * it may includes whplink directory.
+        */
+       if (S_ISDIR(h_inode->i_mode)) {
+               bbot = au_ibbot(inode);
+               for (bindex++; bindex <= bbot; bindex++) {
+                       h_inode = au_h_iptr(inode, bindex);
+                       if (h_inode)
+                               au_add_nlink(inode, h_inode);
+               }
+       }
+}
+
+void au_cpup_attr_changeable(struct inode *inode)
+{
+       struct inode *h_inode;
+
+       h_inode = au_h_iptr(inode, au_ibtop(inode));
+       inode->i_mode = h_inode->i_mode;
+       inode->i_uid = h_inode->i_uid;
+       inode->i_gid = h_inode->i_gid;
+       au_cpup_attr_timesizes(inode);
+       au_cpup_attr_flags(inode, h_inode->i_flags);
+}
+
+void au_cpup_igen(struct inode *inode, struct inode *h_inode)
+{
+       struct au_iinfo *iinfo = au_ii(inode);
+
+       IiMustWriteLock(inode);
+
+       iinfo->ii_higen = h_inode->i_generation;
+       iinfo->ii_hsb1 = h_inode->i_sb;
+}
+
+void au_cpup_attr_all(struct inode *inode, int force)
+{
+       struct inode *h_inode;
+
+       h_inode = au_h_iptr(inode, au_ibtop(inode));
+       au_cpup_attr_changeable(inode);
+       if (inode->i_nlink > 0)
+               au_cpup_attr_nlink(inode, force);
+       inode->i_rdev = h_inode->i_rdev;
+       inode->i_blkbits = h_inode->i_blkbits;
+       au_cpup_igen(inode, h_inode);
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* Note: dt_dentry and dt_h_dentry are not dget/dput-ed */
+
+/* keep the timestamps of the parent dir when cpup */
+void au_dtime_store(struct au_dtime *dt, struct dentry *dentry,
+                   struct path *h_path)
+{
+       struct inode *h_inode;
+
+       dt->dt_dentry = dentry;
+       dt->dt_h_path = *h_path;
+       h_inode = d_inode(h_path->dentry);
+       dt->dt_atime = h_inode->i_atime;
+       dt->dt_mtime = h_inode->i_mtime;
+       /* smp_mb(); */
+}
+
+void au_dtime_revert(struct au_dtime *dt)
+{
+       struct iattr attr;
+       int err;
+
+       attr.ia_atime = dt->dt_atime;
+       attr.ia_mtime = dt->dt_mtime;
+       attr.ia_valid = ATTR_FORCE | ATTR_MTIME | ATTR_MTIME_SET
+               | ATTR_ATIME | ATTR_ATIME_SET;
+
+       /* no delegation since this is a directory */
+       err = vfsub_notify_change(&dt->dt_h_path, &attr, /*delegated*/NULL);
+       if (unlikely(err))
+               pr_warn("restoring timestamps failed(%d). ignored\n", err);
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* internal use only */
+struct au_cpup_reg_attr {
+       int             valid;
+       struct kstat    st;
+       unsigned int    iflags; /* inode->i_flags */
+};
+
+static noinline_for_stack
+int cpup_iattr(struct dentry *dst, aufs_bindex_t bindex, struct path *h_src,
+              struct au_cpup_reg_attr *h_src_attr)
+{
+       int err, sbits, icex;
+       unsigned int mnt_flags;
+       unsigned char verbose;
+       struct iattr ia;
+       struct path h_path;
+       struct inode *h_isrc, *h_idst;
+       struct kstat *h_st;
+       struct au_branch *br;
+
+       br = au_sbr(dst->d_sb, bindex);
+       h_path.mnt = au_br_mnt(br);
+       h_path.dentry = au_h_dptr(dst, bindex);
+       h_idst = d_inode(h_path.dentry);
+       h_isrc = d_inode(h_src->dentry);
+       ia.ia_valid = ATTR_FORCE | ATTR_UID | ATTR_GID
+               | ATTR_ATIME | ATTR_MTIME
+               | ATTR_ATIME_SET | ATTR_MTIME_SET;
+       if (h_src_attr && h_src_attr->valid) {
+               h_st = &h_src_attr->st;
+               ia.ia_uid = h_st->uid;
+               ia.ia_gid = h_st->gid;
+               ia.ia_atime = h_st->atime;
+               ia.ia_mtime = h_st->mtime;
+               if (h_idst->i_mode != h_st->mode
+                   && !S_ISLNK(h_idst->i_mode)) {
+                       ia.ia_valid |= ATTR_MODE;
+                       ia.ia_mode = h_st->mode;
+               }
+               sbits = !!(h_st->mode & (S_ISUID | S_ISGID));
+               au_cpup_attr_flags(h_idst, h_src_attr->iflags);
+       } else {
+               ia.ia_uid = h_isrc->i_uid;
+               ia.ia_gid = h_isrc->i_gid;
+               ia.ia_atime = h_isrc->i_atime;
+               ia.ia_mtime = h_isrc->i_mtime;
+               if (h_idst->i_mode != h_isrc->i_mode
+                   && !S_ISLNK(h_idst->i_mode)) {
+                       ia.ia_valid |= ATTR_MODE;
+                       ia.ia_mode = h_isrc->i_mode;
+               }
+               sbits = !!(h_isrc->i_mode & (S_ISUID | S_ISGID));
+               au_cpup_attr_flags(h_idst, h_isrc->i_flags);
+       }
+       /* no delegation since it is just created */
+       err = vfsub_notify_change(&h_path, &ia, /*delegated*/NULL);
+
+       /* is this nfs only? */
+       if (!err && sbits && au_test_nfs(h_path.dentry->d_sb)) {
+               ia.ia_valid = ATTR_FORCE | ATTR_MODE;
+               ia.ia_mode = h_isrc->i_mode;
+               err = vfsub_notify_change(&h_path, &ia, /*delegated*/NULL);
+       }
+
+       icex = br->br_perm & AuBrAttr_ICEX;
+       if (!err) {
+               mnt_flags = au_mntflags(dst->d_sb);
+               verbose = !!au_opt_test(mnt_flags, VERBOSE);
+               err = au_cpup_xattr(&h_path, h_src, icex, verbose);
+       }
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_do_copy_file(struct file *dst, struct file *src, loff_t len,
+                          char *buf, unsigned long blksize)
+{
+       int err;
+       size_t sz, rbytes, wbytes;
+       unsigned char all_zero;
+       char *p, *zp;
+       struct inode *h_inode;
+       /* reduce stack usage */
+       struct iattr *ia;
+
+       zp = page_address(ZERO_PAGE(0));
+       if (unlikely(!zp))
+               return -ENOMEM; /* possible? */
+
+       err = 0;
+       all_zero = 0;
+       while (len) {
+               AuDbg("len %lld\n", len);
+               sz = blksize;
+               if (len < blksize)
+                       sz = len;
+
+               rbytes = 0;
+               /* todo: signal_pending? */
+               while (!rbytes || err == -EAGAIN || err == -EINTR) {
+                       rbytes = vfsub_read_k(src, buf, sz, &src->f_pos);
+                       err = rbytes;
+               }
+               if (unlikely(err < 0))
+                       break;
+
+               all_zero = 0;
+               if (len >= rbytes && rbytes == blksize)
+                       all_zero = !memcmp(buf, zp, rbytes);
+               if (!all_zero) {
+                       wbytes = rbytes;
+                       p = buf;
+                       while (wbytes) {
+                               size_t b;
+
+                               b = vfsub_write_k(dst, p, wbytes, &dst->f_pos);
+                               err = b;
+                               /* todo: signal_pending? */
+                               if (unlikely(err == -EAGAIN || err == -EINTR))
+                                       continue;
+                               if (unlikely(err < 0))
+                                       break;
+                               wbytes -= b;
+                               p += b;
+                       }
+                       if (unlikely(err < 0))
+                               break;
+               } else {
+                       loff_t res;
+
+                       AuLabel(hole);
+                       res = vfsub_llseek(dst, rbytes, SEEK_CUR);
+                       err = res;
+                       if (unlikely(res < 0))
+                               break;
+               }
+               len -= rbytes;
+               err = 0;
+       }
+
+       /* the last block may be a hole */
+       if (!err && all_zero) {
+               AuLabel(last hole);
+
+               err = 1;
+               if (au_test_nfs(dst->f_path.dentry->d_sb)) {
+                       /* nfs requires this step to make last hole */
+                       /* is this only nfs? */
+                       do {
+                               /* todo: signal_pending? */
+                               err = vfsub_write_k(dst, "\0", 1, &dst->f_pos);
+                       } while (err == -EAGAIN || err == -EINTR);
+                       if (err == 1)
+                               dst->f_pos--;
+               }
+
+               if (err == 1) {
+                       ia = (void *)buf;
+                       ia->ia_size = dst->f_pos;
+                       ia->ia_valid = ATTR_SIZE | ATTR_FILE;
+                       ia->ia_file = dst;
+                       h_inode = file_inode(dst);
+                       inode_lock_nested(h_inode, AuLsc_I_CHILD2);
+                       /* no delegation since it is just created */
+                       err = vfsub_notify_change(&dst->f_path, ia,
+                                                 /*delegated*/NULL);
+                       inode_unlock(h_inode);
+               }
+       }
+
+       return err;
+}
+
+int au_copy_file(struct file *dst, struct file *src, loff_t len)
+{
+       int err;
+       unsigned long blksize;
+       unsigned char do_kfree;
+       char *buf;
+       struct super_block *h_sb;
+
+       err = -ENOMEM;
+       h_sb = file_inode(dst)->i_sb;
+       blksize = h_sb->s_blocksize;
+       if (!blksize || PAGE_SIZE < blksize)
+               blksize = PAGE_SIZE;
+       AuDbg("blksize %lu\n", blksize);
+       do_kfree = (blksize != PAGE_SIZE && blksize >= sizeof(struct iattr *));
+       if (do_kfree)
+               buf = kmalloc(blksize, GFP_NOFS);
+       else
+               buf = (void *)__get_free_page(GFP_NOFS);
+       if (unlikely(!buf))
+               goto out;
+
+       if (len > (1 << 22))
+               AuDbg("copying a large file %lld\n", (long long)len);
+
+       src->f_pos = 0;
+       dst->f_pos = 0;
+       err = au_do_copy_file(dst, src, len, buf, blksize);
+       if (do_kfree) {
+               AuDebugOn(!au_kfree_do_sz_test(blksize));
+               au_kfree_do_rcu(buf);
+       } else
+               free_page((unsigned long)buf);
+
+out:
+       return err;
+}
+
+static int au_do_copy(struct file *dst, struct file *src, loff_t len)
+{
+       int err;
+       struct super_block *h_src_sb;
+       struct inode *h_src_inode;
+
+       h_src_inode = file_inode(src);
+       h_src_sb = h_src_inode->i_sb;
+
+       /* XFS acquires inode_lock */
+       if (!au_test_xfs(h_src_sb))
+               err = au_copy_file(dst, src, len);
+       else {
+               inode_unlock_shared(h_src_inode);
+               err = au_copy_file(dst, src, len);
+               inode_lock_shared_nested(h_src_inode, AuLsc_I_CHILD);
+       }
+
+       return err;
+}
+
+static int au_clone_or_copy(struct file *dst, struct file *src, loff_t len)
+{
+       int err;
+       loff_t lo;
+       struct super_block *h_src_sb;
+       struct inode *h_src_inode;
+
+       h_src_inode = file_inode(src);
+       h_src_sb = h_src_inode->i_sb;
+       if (h_src_sb != file_inode(dst)->i_sb
+           || !dst->f_op->remap_file_range) {
+               err = au_do_copy(dst, src, len);
+               goto out;
+       }
+
+       if (!au_test_nfs(h_src_sb)) {
+               inode_unlock_shared(h_src_inode);
+               lo = vfsub_clone_file_range(src, dst, len);
+               inode_lock_shared_nested(h_src_inode, AuLsc_I_CHILD);
+       } else
+               lo = vfsub_clone_file_range(src, dst, len);
+       if (lo == len) {
+               err = 0;
+               goto out; /* success */
+       } else if (lo >= 0)
+               /* todo: possible? */
+               /* paritially succeeded */
+               AuDbg("lo %lld, len %lld. Retrying.\n", lo, len);
+       else if (lo != -EOPNOTSUPP) {
+               /* older XFS has a condition in cloning */
+               err = lo;
+               goto out;
+       }
+
+       /* the backend fs on NFS may not support cloning */
+       err = au_do_copy(dst, src, len);
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/*
+ * to support a sparse file which is opened with O_APPEND,
+ * we need to close the file.
+ */
+static int au_cp_regular(struct au_cp_generic *cpg)
+{
+       int err, i;
+       enum { SRC, DST };
+       struct {
+               aufs_bindex_t bindex;
+               unsigned int flags;
+               struct dentry *dentry;
+               int force_wr;
+               struct file *file;
+       } *f, file[] = {
+               {
+                       .bindex = cpg->bsrc,
+                       .flags = O_RDONLY | O_NOATIME | O_LARGEFILE,
+               },
+               {
+                       .bindex = cpg->bdst,
+                       .flags = O_WRONLY | O_NOATIME | O_LARGEFILE,
+                       .force_wr = !!au_ftest_cpup(cpg->flags, RWDST),
+               }
+       };
+       struct au_branch *br;
+       struct super_block *sb, *h_src_sb;
+       struct inode *h_src_inode;
+       struct task_struct *tsk = current;
+
+       /* bsrc branch can be ro/rw. */
+       sb = cpg->dentry->d_sb;
+       f = file;
+       for (i = 0; i < 2; i++, f++) {
+               f->dentry = au_h_dptr(cpg->dentry, f->bindex);
+               f->file = au_h_open(cpg->dentry, f->bindex, f->flags,
+                                   /*file*/NULL, f->force_wr);
+               if (IS_ERR(f->file)) {
+                       err = PTR_ERR(f->file);
+                       if (i == SRC)
+                               goto out;
+                       else
+                               goto out_src;
+               }
+       }
+
+       /* try stopping to update while we copyup */
+       h_src_inode = d_inode(file[SRC].dentry);
+       h_src_sb = h_src_inode->i_sb;
+       if (!au_test_nfs(h_src_sb))
+               IMustLock(h_src_inode);
+       err = au_clone_or_copy(file[DST].file, file[SRC].file, cpg->len);
+
+       /* i wonder if we had O_NO_DELAY_FPUT flag */
+       if (tsk->flags & PF_KTHREAD)
+               __fput_sync(file[DST].file);
+       else {
+               /* it happened actually */
+               fput(file[DST].file);
+               /*
+                * too bad.
+                * we have to call both since we don't know which place the file
+                * was added to.
+                */
+               task_work_run();
+               flush_delayed_fput();
+       }
+       br = au_sbr(sb, file[DST].bindex);
+       au_lcnt_dec(&br->br_nfiles);
+
+out_src:
+       fput(file[SRC].file);
+       br = au_sbr(sb, file[SRC].bindex);
+       au_lcnt_dec(&br->br_nfiles);
+out:
+       return err;
+}
+
+static int au_do_cpup_regular(struct au_cp_generic *cpg,
+                             struct au_cpup_reg_attr *h_src_attr)
+{
+       int err, rerr;
+       loff_t l;
+       struct path h_path;
+       struct inode *h_src_inode, *h_dst_inode;
+
+       err = 0;
+       h_src_inode = au_h_iptr(d_inode(cpg->dentry), cpg->bsrc);
+       l = i_size_read(h_src_inode);
+       if (cpg->len == -1 || l < cpg->len)
+               cpg->len = l;
+       if (cpg->len) {
+               /* try stopping to update while we are referencing */
+               inode_lock_shared_nested(h_src_inode, AuLsc_I_CHILD);
+               au_pin_hdir_unlock(cpg->pin);
+
+               h_path.dentry = au_h_dptr(cpg->dentry, cpg->bsrc);
+               h_path.mnt = au_sbr_mnt(cpg->dentry->d_sb, cpg->bsrc);
+               h_src_attr->iflags = h_src_inode->i_flags;
+               if (!au_test_nfs(h_src_inode->i_sb))
+                       err = vfsub_getattr(&h_path, &h_src_attr->st);
+               else {
+                       inode_unlock_shared(h_src_inode);
+                       err = vfsub_getattr(&h_path, &h_src_attr->st);
+                       inode_lock_shared_nested(h_src_inode, AuLsc_I_CHILD);
+               }
+               if (unlikely(err)) {
+                       inode_unlock_shared(h_src_inode);
+                       goto out;
+               }
+               h_src_attr->valid = 1;
+               if (!au_test_nfs(h_src_inode->i_sb)) {
+                       err = au_cp_regular(cpg);
+                       inode_unlock_shared(h_src_inode);
+               } else {
+                       inode_unlock_shared(h_src_inode);
+                       err = au_cp_regular(cpg);
+               }
+               rerr = au_pin_hdir_relock(cpg->pin);
+               if (!err && rerr)
+                       err = rerr;
+       }
+       if (!err && (h_src_inode->i_state & I_LINKABLE)) {
+               h_path.dentry = au_h_dptr(cpg->dentry, cpg->bdst);
+               h_dst_inode = d_inode(h_path.dentry);
+               spin_lock(&h_dst_inode->i_lock);
+               h_dst_inode->i_state |= I_LINKABLE;
+               spin_unlock(&h_dst_inode->i_lock);
+       }
+
+out:
+       return err;
+}
+
+static int au_do_cpup_symlink(struct path *h_path, struct dentry *h_src,
+                             struct inode *h_dir)
+{
+       int err;
+       DEFINE_DELAYED_CALL(done);
+       const char *sym;
+
+       sym = vfs_get_link(h_src, &done);
+       err = PTR_ERR(sym);
+       if (IS_ERR(sym))
+               goto out;
+
+       err = vfsub_symlink(h_dir, h_path, sym);
+
+out:
+       do_delayed_call(&done);
+       return err;
+}
+
+/*
+ * regardless 'acl' option, reset all ACL.
+ * All ACL will be copied up later from the original entry on the lower branch.
+ */
+static int au_reset_acl(struct inode *h_dir, struct path *h_path, umode_t mode)
+{
+       int err;
+       struct dentry *h_dentry;
+       struct inode *h_inode;
+       struct user_namespace *h_userns;
+
+       h_userns = mnt_user_ns(h_path->mnt);
+       h_dentry = h_path->dentry;
+       h_inode = d_inode(h_dentry);
+       /* forget_all_cached_acls(h_inode)); */
+       err = vfsub_removexattr(h_userns, h_dentry, XATTR_NAME_POSIX_ACL_ACCESS);
+       AuTraceErr(err);
+       if (err == -EOPNOTSUPP)
+               err = 0;
+       if (!err)
+               err = vfsub_acl_chmod(h_userns, h_inode, mode);
+
+       AuTraceErr(err);
+       return err;
+}
+
+static int au_do_cpup_dir(struct au_cp_generic *cpg, struct dentry *dst_parent,
+                         struct inode *h_dir, struct path *h_path)
+{
+       int err;
+       struct inode *dir, *inode;
+       struct user_namespace *h_userns;
+
+       h_userns = mnt_user_ns(h_path->mnt);
+       err = vfsub_removexattr(h_userns, h_path->dentry,
+                               XATTR_NAME_POSIX_ACL_DEFAULT);
+       AuTraceErr(err);
+       if (err == -EOPNOTSUPP)
+               err = 0;
+       if (unlikely(err))
+               goto out;
+
+       /*
+        * strange behaviour from the users view,
+        * particularly setattr case
+        */
+       dir = d_inode(dst_parent);
+       if (au_ibtop(dir) == cpg->bdst)
+               au_cpup_attr_nlink(dir, /*force*/1);
+       inode = d_inode(cpg->dentry);
+       au_cpup_attr_nlink(inode, /*force*/1);
+
+out:
+       return err;
+}
+
+static noinline_for_stack
+int cpup_entry(struct au_cp_generic *cpg, struct dentry *dst_parent,
+              struct au_cpup_reg_attr *h_src_attr)
+{
+       int err;
+       umode_t mode;
+       unsigned int mnt_flags;
+       unsigned char isdir, isreg, force;
+       const unsigned char do_dt = !!au_ftest_cpup(cpg->flags, DTIME);
+       struct au_dtime dt;
+       struct path h_path;
+       struct dentry *h_src, *h_dst, *h_parent;
+       struct inode *h_inode, *h_dir;
+       struct super_block *sb;
+
+       /* bsrc branch can be ro/rw. */
+       h_src = au_h_dptr(cpg->dentry, cpg->bsrc);
+       h_inode = d_inode(h_src);
+       AuDebugOn(h_inode != au_h_iptr(d_inode(cpg->dentry), cpg->bsrc));
+
+       /* try stopping to be referenced while we are creating */
+       h_dst = au_h_dptr(cpg->dentry, cpg->bdst);
+       if (au_ftest_cpup(cpg->flags, RENAME))
+               AuDebugOn(strncmp(h_dst->d_name.name, AUFS_WH_PFX,
+                                 AUFS_WH_PFX_LEN));
+       h_parent = h_dst->d_parent; /* dir inode is locked */
+       h_dir = d_inode(h_parent);
+       IMustLock(h_dir);
+       AuDebugOn(h_parent != h_dst->d_parent);
+
+       sb = cpg->dentry->d_sb;
+       h_path.mnt = au_sbr_mnt(sb, cpg->bdst);
+       if (do_dt) {
+               h_path.dentry = h_parent;
+               au_dtime_store(&dt, dst_parent, &h_path);
+       }
+       h_path.dentry = h_dst;
+
+       isreg = 0;
+       isdir = 0;
+       mode = h_inode->i_mode;
+       switch (mode & S_IFMT) {
+       case S_IFREG:
+               isreg = 1;
+               err = vfsub_create(h_dir, &h_path, 0600, /*want_excl*/true);
+               if (!err)
+                       err = au_do_cpup_regular(cpg, h_src_attr);
+               break;
+       case S_IFDIR:
+               isdir = 1;
+               err = vfsub_mkdir(h_dir, &h_path, mode);
+               if (!err)
+                       err = au_do_cpup_dir(cpg, dst_parent, h_dir, &h_path);
+               break;
+       case S_IFLNK:
+               err = au_do_cpup_symlink(&h_path, h_src, h_dir);
+               break;
+       case S_IFCHR:
+       case S_IFBLK:
+               AuDebugOn(!capable(CAP_MKNOD));
+               fallthrough;
+       case S_IFIFO:
+       case S_IFSOCK:
+               err = vfsub_mknod(h_dir, &h_path, mode, h_inode->i_rdev);
+               break;
+       default:
+               AuIOErr("Unknown inode type 0%o\n", mode);
+               err = -EIO;
+       }
+       if (!err)
+               err = au_reset_acl(h_dir, &h_path, mode);
+
+       mnt_flags = au_mntflags(sb);
+       if (!au_opt_test(mnt_flags, UDBA_NONE)
+           && !isdir
+           && au_opt_test(mnt_flags, XINO)
+           && (h_inode->i_nlink == 1
+               || (h_inode->i_state & I_LINKABLE))
+           /* todo: unnecessary? */
+           /* && d_inode(cpg->dentry)->i_nlink == 1 */
+           && cpg->bdst < cpg->bsrc
+           && !au_ftest_cpup(cpg->flags, KEEPLINO))
+               au_xino_write(sb, cpg->bsrc, h_inode->i_ino, /*ino*/0);
+               /* ignore this error */
+
+       if (!err) {
+               force = 0;
+               if (isreg) {
+                       force = !!cpg->len;
+                       if (cpg->len == -1)
+                               force = !!i_size_read(h_inode);
+               }
+               au_fhsm_wrote(sb, cpg->bdst, force);
+       }
+
+       if (do_dt)
+               au_dtime_revert(&dt);
+       return err;
+}
+
+static int au_do_ren_after_cpup(struct au_cp_generic *cpg, struct path *h_path)
+{
+       int err;
+       struct dentry *dentry, *h_dentry, *h_parent, *parent;
+       struct path h_ppath;
+       struct inode *h_dir;
+       aufs_bindex_t bdst;
+
+       dentry = cpg->dentry;
+       bdst = cpg->bdst;
+       h_ppath.mnt = au_sbr_mnt(dentry->d_sb, bdst);
+       h_dentry = au_h_dptr(dentry, bdst);
+       if (!au_ftest_cpup(cpg->flags, OVERWRITE)) {
+               dget(h_dentry);
+               au_set_h_dptr(dentry, bdst, NULL);
+               err = au_lkup_neg(dentry, bdst, /*wh*/0);
+               if (!err)
+                       h_path->dentry = dget(au_h_dptr(dentry, bdst));
+               au_set_h_dptr(dentry, bdst, h_dentry);
+       } else {
+               err = 0;
+               parent = dget_parent(dentry);
+               h_ppath.dentry = au_h_dptr(parent, bdst);
+               dput(parent);
+               h_path->dentry = vfsub_lkup_one(&dentry->d_name, &h_ppath);
+               if (IS_ERR(h_path->dentry))
+                       err = PTR_ERR(h_path->dentry);
+       }
+       if (unlikely(err))
+               goto out;
+
+       h_parent = h_dentry->d_parent; /* dir inode is locked */
+       h_dir = d_inode(h_parent);
+       IMustLock(h_dir);
+       AuDbg("%pd %pd\n", h_dentry, h_path->dentry);
+       /* no delegation since it is just created */
+       err = vfsub_rename(h_dir, h_dentry, h_dir, h_path, /*delegated*/NULL,
+                          /*flags*/0);
+       dput(h_path->dentry);
+
+out:
+       return err;
+}
+
+/*
+ * copyup the @dentry from @bsrc to @bdst.
+ * the caller must set the both of lower dentries.
+ * @len is for truncating when it is -1 copyup the entire file.
+ * in link/rename cases, @dst_parent may be different from the real one.
+ * basic->bsrc can be larger than basic->bdst.
+ * aufs doesn't touch the credential so
+ * security_inode_copy_up{,_xattr}() are unnecessary.
+ */
+static int au_cpup_single(struct au_cp_generic *cpg, struct dentry *dst_parent)
+{
+       int err, rerr;
+       aufs_bindex_t old_ibtop;
+       unsigned char isdir, plink;
+       struct dentry *h_src, *h_dst, *h_parent;
+       struct inode *dst_inode, *h_dir, *inode, *delegated, *src_inode;
+       struct super_block *sb;
+       struct au_branch *br;
+       struct path h_src_path;
+       /* to reduce stack size */
+       struct {
+               struct au_dtime dt;
+               struct path h_path;
+               struct au_cpup_reg_attr h_src_attr;
+       } *a;
+
+       err = -ENOMEM;
+       a = kmalloc(sizeof(*a), GFP_NOFS);
+       if (unlikely(!a))
+               goto out;
+       a->h_src_attr.valid = 0;
+
+       sb = cpg->dentry->d_sb;
+       br = au_sbr(sb, cpg->bdst);
+       a->h_path.mnt = au_br_mnt(br);
+       h_dst = au_h_dptr(cpg->dentry, cpg->bdst);
+       h_parent = h_dst->d_parent; /* dir inode is locked */
+       h_dir = d_inode(h_parent);
+       IMustLock(h_dir);
+
+       h_src = au_h_dptr(cpg->dentry, cpg->bsrc);
+       inode = d_inode(cpg->dentry);
+
+       if (!dst_parent)
+               dst_parent = dget_parent(cpg->dentry);
+       else
+               dget(dst_parent);
+
+       plink = !!au_opt_test(au_mntflags(sb), PLINK);
+       dst_inode = au_h_iptr(inode, cpg->bdst);
+       if (dst_inode) {
+               if (unlikely(!plink)) {
+                       err = -EIO;
+                       AuIOErr("hi%lu(i%lu) exists on b%d "
+                               "but plink is disabled\n",
+                               dst_inode->i_ino, inode->i_ino, cpg->bdst);
+                       goto out_parent;
+               }
+
+               if (dst_inode->i_nlink) {
+                       const int do_dt = au_ftest_cpup(cpg->flags, DTIME);
+
+                       h_src = au_plink_lkup(inode, cpg->bdst);
+                       err = PTR_ERR(h_src);
+                       if (IS_ERR(h_src))
+                               goto out_parent;
+                       if (unlikely(d_is_negative(h_src))) {
+                               err = -EIO;
+                               AuIOErr("i%lu exists on b%d "
+                                       "but not pseudo-linked\n",
+                                       inode->i_ino, cpg->bdst);
+                               dput(h_src);
+                               goto out_parent;
+                       }
+
+                       if (do_dt) {
+                               a->h_path.dentry = h_parent;
+                               au_dtime_store(&a->dt, dst_parent, &a->h_path);
+                       }
+
+                       a->h_path.dentry = h_dst;
+                       delegated = NULL;
+                       err = vfsub_link(h_src, h_dir, &a->h_path, &delegated);
+                       if (!err && au_ftest_cpup(cpg->flags, RENAME))
+                               err = au_do_ren_after_cpup(cpg, &a->h_path);
+                       if (do_dt)
+                               au_dtime_revert(&a->dt);
+                       if (unlikely(err == -EWOULDBLOCK)) {
+                               pr_warn("cannot retry for NFSv4 delegation"
+                                       " for an internal link\n");
+                               iput(delegated);
+                       }
+                       dput(h_src);
+                       goto out_parent;
+               } else
+                       /* todo: cpup_wh_file? */
+                       /* udba work */
+                       au_update_ibrange(inode, /*do_put_zero*/1);
+       }
+
+       isdir = S_ISDIR(inode->i_mode);
+       old_ibtop = au_ibtop(inode);
+       err = cpup_entry(cpg, dst_parent, &a->h_src_attr);
+       if (unlikely(err))
+               goto out_rev;
+       dst_inode = d_inode(h_dst);
+       inode_lock_nested(dst_inode, AuLsc_I_CHILD2);
+       /* todo: necessary? */
+       /* au_pin_hdir_unlock(cpg->pin); */
+
+       h_src_path.dentry = h_src;
+       h_src_path.mnt = au_sbr_mnt(sb, cpg->bsrc);
+       err = cpup_iattr(cpg->dentry, cpg->bdst, &h_src_path, &a->h_src_attr);
+       if (unlikely(err)) {
+               /* todo: necessary? */
+               /* au_pin_hdir_relock(cpg->pin); */ /* ignore an error */
+               inode_unlock(dst_inode);
+               goto out_rev;
+       }
+
+       if (cpg->bdst < old_ibtop) {
+               if (S_ISREG(inode->i_mode)) {
+                       err = au_dy_iaop(inode, cpg->bdst, dst_inode);
+                       if (unlikely(err)) {
+                               /* ignore an error */
+                               /* au_pin_hdir_relock(cpg->pin); */
+                               inode_unlock(dst_inode);
+                               goto out_rev;
+                       }
+               }
+               au_set_ibtop(inode, cpg->bdst);
+       } else
+               au_set_ibbot(inode, cpg->bdst);
+       au_set_h_iptr(inode, cpg->bdst, au_igrab(dst_inode),
+                     au_hi_flags(inode, isdir));
+
+       /* todo: necessary? */
+       /* err = au_pin_hdir_relock(cpg->pin); */
+       inode_unlock(dst_inode);
+       if (unlikely(err))
+               goto out_rev;
+
+       src_inode = d_inode(h_src);
+       if (!isdir
+           && (src_inode->i_nlink > 1
+               || src_inode->i_state & I_LINKABLE)
+           && plink)
+               au_plink_append(inode, cpg->bdst, h_dst);
+
+       if (au_ftest_cpup(cpg->flags, RENAME)) {
+               a->h_path.dentry = h_dst;
+               err = au_do_ren_after_cpup(cpg, &a->h_path);
+       }
+       if (!err)
+               goto out_parent; /* success */
+
+       /* revert */
+out_rev:
+       a->h_path.dentry = h_parent;
+       au_dtime_store(&a->dt, dst_parent, &a->h_path);
+       a->h_path.dentry = h_dst;
+       rerr = 0;
+       if (d_is_positive(h_dst)) {
+               if (!isdir) {
+                       /* no delegation since it is just created */
+                       rerr = vfsub_unlink(h_dir, &a->h_path,
+                                           /*delegated*/NULL, /*force*/0);
+               } else
+                       rerr = vfsub_rmdir(h_dir, &a->h_path);
+       }
+       au_dtime_revert(&a->dt);
+       if (rerr) {
+               AuIOErr("failed removing broken entry(%d, %d)\n", err, rerr);
+               err = -EIO;
+       }
+out_parent:
+       dput(dst_parent);
+       au_kfree_rcu(a);
+out:
+       return err;
+}
+
+#if 0 /* reserved */
+struct au_cpup_single_args {
+       int *errp;
+       struct au_cp_generic *cpg;
+       struct dentry *dst_parent;
+};
+
+static void au_call_cpup_single(void *args)
+{
+       struct au_cpup_single_args *a = args;
+
+       au_pin_hdir_acquire_nest(a->cpg->pin);
+       *a->errp = au_cpup_single(a->cpg, a->dst_parent);
+       au_pin_hdir_release(a->cpg->pin);
+}
+#endif
+
+/*
+ * prevent SIGXFSZ in copy-up.
+ * testing CAP_MKNOD is for generic fs,
+ * but CAP_FSETID is for xfs only, currently.
+ */
+static int au_cpup_sio_test(struct au_pin *pin, umode_t mode)
+{
+       int do_sio;
+       struct super_block *sb;
+       struct inode *h_dir;
+
+       do_sio = 0;
+       sb = au_pinned_parent(pin)->d_sb;
+       if (!au_wkq_test()
+           && (!au_sbi(sb)->si_plink_maint_pid
+               || au_plink_maint(sb, AuLock_NOPLM))) {
+               switch (mode & S_IFMT) {
+               case S_IFREG:
+                       /* no condition about RLIMIT_FSIZE and the file size */
+                       do_sio = 1;
+                       break;
+               case S_IFCHR:
+               case S_IFBLK:
+                       do_sio = !capable(CAP_MKNOD);
+                       break;
+               }
+               if (!do_sio)
+                       do_sio = ((mode & (S_ISUID | S_ISGID))
+                                 && !capable(CAP_FSETID));
+               /* this workaround may be removed in the future */
+               if (!do_sio) {
+                       h_dir = au_pinned_h_dir(pin);
+                       do_sio = h_dir->i_mode & S_ISVTX;
+               }
+       }
+
+       return do_sio;
+}
+
+#if 0 /* reserved */
+int au_sio_cpup_single(struct au_cp_generic *cpg, struct dentry *dst_parent)
+{
+       int err, wkq_err;
+       struct dentry *h_dentry;
+
+       h_dentry = au_h_dptr(cpg->dentry, cpg->bsrc);
+       if (!au_cpup_sio_test(pin, d_inode(h_dentry)->i_mode))
+               err = au_cpup_single(cpg, dst_parent);
+       else {
+               struct au_cpup_single_args args = {
+                       .errp           = &err,
+                       .cpg            = cpg,
+                       .dst_parent     = dst_parent
+               };
+               wkq_err = au_wkq_wait(au_call_cpup_single, &args);
+               if (unlikely(wkq_err))
+                       err = wkq_err;
+       }
+
+       return err;
+}
+#endif
+
+/*
+ * copyup the @dentry from the first active lower branch to @bdst,
+ * using au_cpup_single().
+ */
+static int au_cpup_simple(struct au_cp_generic *cpg)
+{
+       int err;
+       unsigned int flags_orig;
+       struct dentry *dentry;
+
+       AuDebugOn(cpg->bsrc < 0);
+
+       dentry = cpg->dentry;
+       DiMustWriteLock(dentry);
+
+       err = au_lkup_neg(dentry, cpg->bdst, /*wh*/1);
+       if (!err) {
+               flags_orig = cpg->flags;
+               au_fset_cpup(cpg->flags, RENAME);
+               err = au_cpup_single(cpg, NULL);
+               cpg->flags = flags_orig;
+               if (!err)
+                       return 0; /* success */
+
+               /* revert */
+               au_set_h_dptr(dentry, cpg->bdst, NULL);
+               au_set_dbtop(dentry, cpg->bsrc);
+       }
+
+       return err;
+}
+
+struct au_cpup_simple_args {
+       int *errp;
+       struct au_cp_generic *cpg;
+};
+
+static void au_call_cpup_simple(void *args)
+{
+       struct au_cpup_simple_args *a = args;
+
+       au_pin_hdir_acquire_nest(a->cpg->pin);
+       *a->errp = au_cpup_simple(a->cpg);
+       au_pin_hdir_release(a->cpg->pin);
+}
+
+static int au_do_sio_cpup_simple(struct au_cp_generic *cpg)
+{
+       int err, wkq_err;
+       struct dentry *dentry, *parent;
+       struct file *h_file;
+       struct inode *h_dir;
+       struct user_namespace *h_userns;
+
+       dentry = cpg->dentry;
+       h_file = NULL;
+       if (au_ftest_cpup(cpg->flags, HOPEN)) {
+               AuDebugOn(cpg->bsrc < 0);
+               h_file = au_h_open_pre(dentry, cpg->bsrc, /*force_wr*/0);
+               err = PTR_ERR(h_file);
+               if (IS_ERR(h_file))
+                       goto out;
+       }
+
+       parent = dget_parent(dentry);
+       h_dir = au_h_iptr(d_inode(parent), cpg->bdst);
+       h_userns = au_sbr_userns(dentry->d_sb, cpg->bdst);
+       if (!au_test_h_perm_sio(h_userns, h_dir, MAY_EXEC | MAY_WRITE)
+           && !au_cpup_sio_test(cpg->pin, d_inode(dentry)->i_mode))
+               err = au_cpup_simple(cpg);
+       else {
+               struct au_cpup_simple_args args = {
+                       .errp           = &err,
+                       .cpg            = cpg
+               };
+               wkq_err = au_wkq_wait(au_call_cpup_simple, &args);
+               if (unlikely(wkq_err))
+                       err = wkq_err;
+       }
+
+       dput(parent);
+       if (h_file)
+               au_h_open_post(dentry, cpg->bsrc, h_file);
+
+out:
+       return err;
+}
+
+int au_sio_cpup_simple(struct au_cp_generic *cpg)
+{
+       aufs_bindex_t bsrc, bbot;
+       struct dentry *dentry, *h_dentry;
+
+       if (cpg->bsrc < 0) {
+               dentry = cpg->dentry;
+               bbot = au_dbbot(dentry);
+               for (bsrc = cpg->bdst + 1; bsrc <= bbot; bsrc++) {
+                       h_dentry = au_h_dptr(dentry, bsrc);
+                       if (h_dentry) {
+                               AuDebugOn(d_is_negative(h_dentry));
+                               break;
+                       }
+               }
+               AuDebugOn(bsrc > bbot);
+               cpg->bsrc = bsrc;
+       }
+       AuDebugOn(cpg->bsrc <= cpg->bdst);
+       return au_do_sio_cpup_simple(cpg);
+}
+
+int au_sio_cpdown_simple(struct au_cp_generic *cpg)
+{
+       AuDebugOn(cpg->bdst <= cpg->bsrc);
+       return au_do_sio_cpup_simple(cpg);
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * copyup the deleted file for writing.
+ */
+static int au_do_cpup_wh(struct au_cp_generic *cpg, struct dentry *wh_dentry,
+                        struct file *file)
+{
+       int err;
+       unsigned int flags_orig;
+       aufs_bindex_t bsrc_orig;
+       struct au_dinfo *dinfo;
+       struct {
+               struct au_hdentry *hd;
+               struct dentry *h_dentry;
+       } hdst, hsrc;
+
+       dinfo = au_di(cpg->dentry);
+       AuRwMustWriteLock(&dinfo->di_rwsem);
+
+       bsrc_orig = cpg->bsrc;
+       cpg->bsrc = dinfo->di_btop;
+       hdst.hd = au_hdentry(dinfo, cpg->bdst);
+       hdst.h_dentry = hdst.hd->hd_dentry;
+       hdst.hd->hd_dentry = wh_dentry;
+       dinfo->di_btop = cpg->bdst;
+
+       hsrc.h_dentry = NULL;
+       if (file) {
+               hsrc.hd = au_hdentry(dinfo, cpg->bsrc);
+               hsrc.h_dentry = hsrc.hd->hd_dentry;
+               hsrc.hd->hd_dentry = au_hf_top(file)->f_path.dentry;
+       }
+       flags_orig = cpg->flags;
+       cpg->flags = !AuCpup_DTIME;
+       err = au_cpup_single(cpg, /*h_parent*/NULL);
+       cpg->flags = flags_orig;
+       if (file) {
+               if (!err)
+                       err = au_reopen_nondir(file);
+               hsrc.hd->hd_dentry = hsrc.h_dentry;
+       }
+       hdst.hd->hd_dentry = hdst.h_dentry;
+       dinfo->di_btop = cpg->bsrc;
+       cpg->bsrc = bsrc_orig;
+
+       return err;
+}
+
+static int au_cpup_wh(struct au_cp_generic *cpg, struct file *file)
+{
+       int err;
+       aufs_bindex_t bdst;
+       struct au_dtime dt;
+       struct dentry *dentry, *parent, *h_parent, *wh_dentry;
+       struct au_branch *br;
+       struct path h_path;
+
+       dentry = cpg->dentry;
+       bdst = cpg->bdst;
+       br = au_sbr(dentry->d_sb, bdst);
+       parent = dget_parent(dentry);
+       h_parent = au_h_dptr(parent, bdst);
+       wh_dentry = au_whtmp_lkup(h_parent, br, &dentry->d_name);
+       err = PTR_ERR(wh_dentry);
+       if (IS_ERR(wh_dentry))
+               goto out;
+
+       h_path.dentry = h_parent;
+       h_path.mnt = au_br_mnt(br);
+       au_dtime_store(&dt, parent, &h_path);
+       err = au_do_cpup_wh(cpg, wh_dentry, file);
+       if (unlikely(err))
+               goto out_wh;
+
+       dget(wh_dentry);
+       h_path.dentry = wh_dentry;
+       if (!d_is_dir(wh_dentry)) {
+               /* no delegation since it is just created */
+               err = vfsub_unlink(d_inode(h_parent), &h_path,
+                                  /*delegated*/NULL, /*force*/0);
+       } else
+               err = vfsub_rmdir(d_inode(h_parent), &h_path);
+       if (unlikely(err)) {
+               AuIOErr("failed remove copied-up tmp file %pd(%d)\n",
+                       wh_dentry, err);
+               err = -EIO;
+       }
+       au_dtime_revert(&dt);
+       au_set_hi_wh(d_inode(dentry), bdst, wh_dentry);
+
+out_wh:
+       dput(wh_dentry);
+out:
+       dput(parent);
+       return err;
+}
+
+struct au_cpup_wh_args {
+       int *errp;
+       struct au_cp_generic *cpg;
+       struct file *file;
+};
+
+static void au_call_cpup_wh(void *args)
+{
+       struct au_cpup_wh_args *a = args;
+
+       au_pin_hdir_acquire_nest(a->cpg->pin);
+       *a->errp = au_cpup_wh(a->cpg, a->file);
+       au_pin_hdir_release(a->cpg->pin);
+}
+
+int au_sio_cpup_wh(struct au_cp_generic *cpg, struct file *file)
+{
+       int err, wkq_err;
+       aufs_bindex_t bdst;
+       struct dentry *dentry, *parent, *h_orph, *h_parent;
+       struct inode *dir, *h_dir, *h_tmpdir;
+       struct au_wbr *wbr;
+       struct au_pin wh_pin, *pin_orig;
+       struct user_namespace *h_userns;
+
+       dentry = cpg->dentry;
+       bdst = cpg->bdst;
+       parent = dget_parent(dentry);
+       dir = d_inode(parent);
+       h_orph = NULL;
+       h_parent = NULL;
+       h_dir = au_igrab(au_h_iptr(dir, bdst));
+       h_tmpdir = h_dir;
+       pin_orig = NULL;
+       if (!h_dir->i_nlink) {
+               wbr = au_sbr(dentry->d_sb, bdst)->br_wbr;
+               h_orph = wbr->wbr_orph;
+
+               h_parent = dget(au_h_dptr(parent, bdst));
+               au_set_h_dptr(parent, bdst, dget(h_orph));
+               h_tmpdir = d_inode(h_orph);
+               au_set_h_iptr(dir, bdst, au_igrab(h_tmpdir), /*flags*/0);
+
+               inode_lock_nested(h_tmpdir, AuLsc_I_PARENT3);
+               /* todo: au_h_open_pre()? */
+
+               pin_orig = cpg->pin;
+               au_pin_init(&wh_pin, dentry, bdst, AuLsc_DI_PARENT,
+                           AuLsc_I_PARENT3, cpg->pin->udba, AuPin_DI_LOCKED);
+               cpg->pin = &wh_pin;
+       }
+
+       h_userns = au_sbr_userns(dentry->d_sb, bdst);
+       if (!au_test_h_perm_sio(h_userns, h_tmpdir, MAY_EXEC | MAY_WRITE)
+           && !au_cpup_sio_test(cpg->pin, d_inode(dentry)->i_mode))
+               err = au_cpup_wh(cpg, file);
+       else {
+               struct au_cpup_wh_args args = {
+                       .errp   = &err,
+                       .cpg    = cpg,
+                       .file   = file
+               };
+               wkq_err = au_wkq_wait(au_call_cpup_wh, &args);
+               if (unlikely(wkq_err))
+                       err = wkq_err;
+       }
+
+       if (h_orph) {
+               inode_unlock(h_tmpdir);
+               /* todo: au_h_open_post()? */
+               au_set_h_iptr(dir, bdst, au_igrab(h_dir), /*flags*/0);
+               au_set_h_dptr(parent, bdst, h_parent);
+               AuDebugOn(!pin_orig);
+               cpg->pin = pin_orig;
+       }
+       iput(h_dir);
+       dput(parent);
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * generic routine for both of copy-up and copy-down.
+ */
+/* cf. revalidate function in file.c */
+int au_cp_dirs(struct dentry *dentry, aufs_bindex_t bdst,
+              int (*cp)(struct dentry *dentry, aufs_bindex_t bdst,
+                        struct au_pin *pin,
+                        struct dentry *h_parent, void *arg),
+              void *arg)
+{
+       int err;
+       struct au_pin pin;
+       struct dentry *d, *parent, *h_parent, *real_parent, *h_dentry;
+
+       err = 0;
+       parent = dget_parent(dentry);
+       if (IS_ROOT(parent))
+               goto out;
+
+       au_pin_init(&pin, dentry, bdst, AuLsc_DI_PARENT2, AuLsc_I_PARENT2,
+                   au_opt_udba(dentry->d_sb), AuPin_MNT_WRITE);
+
+       /* do not use au_dpage */
+       real_parent = parent;
+       while (1) {
+               dput(parent);
+               parent = dget_parent(dentry);
+               h_parent = au_h_dptr(parent, bdst);
+               if (h_parent)
+                       goto out; /* success */
+
+               /* find top dir which is necessary to cpup */
+               do {
+                       d = parent;
+                       dput(parent);
+                       parent = dget_parent(d);
+                       di_read_lock_parent3(parent, !AuLock_IR);
+                       h_parent = au_h_dptr(parent, bdst);
+                       di_read_unlock(parent, !AuLock_IR);
+               } while (!h_parent);
+
+               if (d != real_parent)
+                       di_write_lock_child3(d);
+
+               /* somebody else might create while we were sleeping */
+               h_dentry = au_h_dptr(d, bdst);
+               if (!h_dentry || d_is_negative(h_dentry)) {
+                       if (h_dentry)
+                               au_update_dbtop(d);
+
+                       au_pin_set_dentry(&pin, d);
+                       err = au_do_pin(&pin);
+                       if (!err) {
+                               err = cp(d, bdst, &pin, h_parent, arg);
+                               au_unpin(&pin);
+                       }
+               }
+
+               if (d != real_parent)
+                       di_write_unlock(d);
+               if (unlikely(err))
+                       break;
+       }
+
+out:
+       dput(parent);
+       return err;
+}
+
+static int au_cpup_dir(struct dentry *dentry, aufs_bindex_t bdst,
+                      struct au_pin *pin,
+                      struct dentry *h_parent __maybe_unused,
+                      void *arg __maybe_unused)
+{
+       struct au_cp_generic cpg = {
+               .dentry = dentry,
+               .bdst   = bdst,
+               .bsrc   = -1,
+               .len    = 0,
+               .pin    = pin,
+               .flags  = AuCpup_DTIME
+       };
+       return au_sio_cpup_simple(&cpg);
+}
+
+int au_cpup_dirs(struct dentry *dentry, aufs_bindex_t bdst)
+{
+       return au_cp_dirs(dentry, bdst, au_cpup_dir, NULL);
+}
+
+int au_test_and_cpup_dirs(struct dentry *dentry, aufs_bindex_t bdst)
+{
+       int err;
+       struct dentry *parent;
+       struct inode *dir;
+
+       parent = dget_parent(dentry);
+       dir = d_inode(parent);
+       err = 0;
+       if (au_h_iptr(dir, bdst))
+               goto out;
+
+       di_read_unlock(parent, AuLock_IR);
+       di_write_lock_parent(parent);
+       /* someone else might change our inode while we were sleeping */
+       if (!au_h_iptr(dir, bdst))
+               err = au_cpup_dirs(dentry, bdst);
+       di_downgrade_lock(parent, AuLock_IR);
+
+out:
+       dput(parent);
+       return err;
+}
diff -urN /usr/share/empty/fs/aufs/cpup.h linux/fs/aufs/cpup.h
--- /usr/share/empty/fs/aufs/cpup.h     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/cpup.h        2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,100 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * copy-up/down functions
+ */
+
+#ifndef __AUFS_CPUP_H__
+#define __AUFS_CPUP_H__
+
+#ifdef __KERNEL__
+
+#include <linux/path.h>
+
+struct inode;
+struct file;
+struct au_pin;
+
+void au_cpup_attr_flags(struct inode *dst, unsigned int iflags);
+void au_cpup_attr_timesizes(struct inode *inode);
+void au_cpup_attr_nlink(struct inode *inode, int force);
+void au_cpup_attr_changeable(struct inode *inode);
+void au_cpup_igen(struct inode *inode, struct inode *h_inode);
+void au_cpup_attr_all(struct inode *inode, int force);
+
+/* ---------------------------------------------------------------------- */
+
+struct au_cp_generic {
+       struct dentry   *dentry;
+       aufs_bindex_t   bdst, bsrc;
+       loff_t          len;
+       struct au_pin   *pin;
+       unsigned int    flags;
+};
+
+/* cpup flags */
+#define AuCpup_DTIME           1               /* do dtime_store/revert */
+#define AuCpup_KEEPLINO                (1 << 1)        /* do not clear the lower xino,
+                                                  for link(2) */
+#define AuCpup_RENAME          (1 << 2)        /* rename after cpup */
+#define AuCpup_HOPEN           (1 << 3)        /* call h_open_pre/post() in
+                                                  cpup */
+#define AuCpup_OVERWRITE       (1 << 4)        /* allow overwriting the
+                                                  existing entry */
+#define AuCpup_RWDST           (1 << 5)        /* force write target even if
+                                                  the branch is marked as RO */
+
+#ifndef CONFIG_AUFS_BR_HFSPLUS
+#undef AuCpup_HOPEN
+#define AuCpup_HOPEN           0
+#endif
+
+#define au_ftest_cpup(flags, name)     ((flags) & AuCpup_##name)
+#define au_fset_cpup(flags, name) \
+       do { (flags) |= AuCpup_##name; } while (0)
+#define au_fclr_cpup(flags, name) \
+       do { (flags) &= ~AuCpup_##name; } while (0)
+
+int au_copy_file(struct file *dst, struct file *src, loff_t len);
+int au_sio_cpup_simple(struct au_cp_generic *cpg);
+int au_sio_cpdown_simple(struct au_cp_generic *cpg);
+int au_sio_cpup_wh(struct au_cp_generic *cpg, struct file *file);
+
+int au_cp_dirs(struct dentry *dentry, aufs_bindex_t bdst,
+              int (*cp)(struct dentry *dentry, aufs_bindex_t bdst,
+                        struct au_pin *pin,
+                        struct dentry *h_parent, void *arg),
+              void *arg);
+int au_cpup_dirs(struct dentry *dentry, aufs_bindex_t bdst);
+int au_test_and_cpup_dirs(struct dentry *dentry, aufs_bindex_t bdst);
+
+/* ---------------------------------------------------------------------- */
+
+/* keep timestamps when copyup */
+struct au_dtime {
+       struct dentry *dt_dentry;
+       struct path dt_h_path;
+       struct timespec64 dt_atime, dt_mtime;
+};
+void au_dtime_store(struct au_dtime *dt, struct dentry *dentry,
+                   struct path *h_path);
+void au_dtime_revert(struct au_dtime *dt);
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_CPUP_H__ */
diff -urN /usr/share/empty/fs/aufs/dbgaufs.c linux/fs/aufs/dbgaufs.c
--- /usr/share/empty/fs/aufs/dbgaufs.c  1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/dbgaufs.c     2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,526 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * debugfs interface
+ */
+
+#include <linux/debugfs.h>
+#include "aufs.h"
+
+#ifndef CONFIG_SYSFS
+#error DEBUG_FS depends upon SYSFS
+#endif
+
+static struct dentry *dbgaufs;
+static const mode_t dbgaufs_mode = 0444;
+
+/* 20 is max digits length of ulong 64 */
+struct dbgaufs_arg {
+       int n;
+       char a[20 * 4];
+};
+
+/*
+ * common function for all XINO files
+ */
+static int dbgaufs_xi_release(struct inode *inode __maybe_unused,
+                             struct file *file)
+{
+       void *p;
+
+       p = file->private_data;
+       if (p) {
+               /* this is struct dbgaufs_arg */
+               AuDebugOn(!au_kfree_sz_test(p));
+               au_kfree_do_rcu(p);
+       }
+       return 0;
+}
+
+static int dbgaufs_xi_open(struct file *xf, struct file *file, int do_fcnt,
+                          int cnt)
+{
+       int err;
+       struct kstat st;
+       struct dbgaufs_arg *p;
+
+       err = -ENOMEM;
+       p = kmalloc(sizeof(*p), GFP_NOFS);
+       if (unlikely(!p))
+               goto out;
+
+       err = 0;
+       p->n = 0;
+       file->private_data = p;
+       if (!xf)
+               goto out;
+
+       err = vfsub_getattr(&xf->f_path, &st);
+       if (!err) {
+               if (do_fcnt)
+                       p->n = snprintf
+                               (p->a, sizeof(p->a), "%d, %llux%u %lld\n",
+                                cnt, st.blocks, st.blksize,
+                                (long long)st.size);
+               else
+                       p->n = snprintf(p->a, sizeof(p->a), "%llux%u %lld\n",
+                                       st.blocks, st.blksize,
+                                       (long long)st.size);
+               AuDebugOn(p->n >= sizeof(p->a));
+       } else {
+               p->n = snprintf(p->a, sizeof(p->a), "err %d\n", err);
+               err = 0;
+       }
+
+out:
+       return err;
+}
+
+static ssize_t dbgaufs_xi_read(struct file *file, char __user *buf,
+                              size_t count, loff_t *ppos)
+{
+       struct dbgaufs_arg *p;
+
+       p = file->private_data;
+       return simple_read_from_buffer(buf, count, ppos, p->a, p->n);
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct dbgaufs_plink_arg {
+       int n;
+       char a[];
+};
+
+static int dbgaufs_plink_release(struct inode *inode __maybe_unused,
+                                struct file *file)
+{
+       free_page((unsigned long)file->private_data);
+       return 0;
+}
+
+static int dbgaufs_plink_open(struct inode *inode, struct file *file)
+{
+       int err, i, limit;
+       unsigned long n, sum;
+       struct dbgaufs_plink_arg *p;
+       struct au_sbinfo *sbinfo;
+       struct super_block *sb;
+       struct hlist_bl_head *hbl;
+
+       err = -ENOMEM;
+       p = (void *)get_zeroed_page(GFP_NOFS);
+       if (unlikely(!p))
+               goto out;
+
+       err = -EFBIG;
+       sbinfo = inode->i_private;
+       sb = sbinfo->si_sb;
+       si_noflush_read_lock(sb);
+       if (au_opt_test(au_mntflags(sb), PLINK)) {
+               limit = PAGE_SIZE - sizeof(p->n);
+
+               /* the number of buckets */
+               n = snprintf(p->a + p->n, limit, "%d\n", AuPlink_NHASH);
+               p->n += n;
+               limit -= n;
+
+               sum = 0;
+               for (i = 0, hbl = sbinfo->si_plink; i < AuPlink_NHASH;
+                    i++, hbl++) {
+                       n = au_hbl_count(hbl);
+                       sum += n;
+
+                       n = snprintf(p->a + p->n, limit, "%lu ", n);
+                       p->n += n;
+                       limit -= n;
+                       if (unlikely(limit <= 0))
+                               goto out_free;
+               }
+               p->a[p->n - 1] = '\n';
+
+               /* the sum of plinks */
+               n = snprintf(p->a + p->n, limit, "%lu\n", sum);
+               p->n += n;
+               limit -= n;
+               if (unlikely(limit <= 0))
+                       goto out_free;
+       } else {
+#define str "1\n0\n0\n"
+               p->n = sizeof(str) - 1;
+               strcpy(p->a, str);
+#undef str
+       }
+       si_read_unlock(sb);
+
+       err = 0;
+       file->private_data = p;
+       goto out; /* success */
+
+out_free:
+       free_page((unsigned long)p);
+out:
+       return err;
+}
+
+static ssize_t dbgaufs_plink_read(struct file *file, char __user *buf,
+                                 size_t count, loff_t *ppos)
+{
+       struct dbgaufs_plink_arg *p;
+
+       p = file->private_data;
+       return simple_read_from_buffer(buf, count, ppos, p->a, p->n);
+}
+
+static const struct file_operations dbgaufs_plink_fop = {
+       .owner          = THIS_MODULE,
+       .open           = dbgaufs_plink_open,
+       .release        = dbgaufs_plink_release,
+       .read           = dbgaufs_plink_read
+};
+
+/* ---------------------------------------------------------------------- */
+
+static int dbgaufs_xib_open(struct inode *inode, struct file *file)
+{
+       int err;
+       struct au_sbinfo *sbinfo;
+       struct super_block *sb;
+
+       sbinfo = inode->i_private;
+       sb = sbinfo->si_sb;
+       si_noflush_read_lock(sb);
+       err = dbgaufs_xi_open(sbinfo->si_xib, file, /*do_fcnt*/0, /*cnt*/0);
+       si_read_unlock(sb);
+       return err;
+}
+
+static const struct file_operations dbgaufs_xib_fop = {
+       .owner          = THIS_MODULE,
+       .open           = dbgaufs_xib_open,
+       .release        = dbgaufs_xi_release,
+       .read           = dbgaufs_xi_read
+};
+
+/* ---------------------------------------------------------------------- */
+
+#define DbgaufsXi_PREFIX "xi"
+
+static int dbgaufs_xino_open(struct inode *inode, struct file *file)
+{
+       int err, idx;
+       long l;
+       aufs_bindex_t bindex;
+       char *p, a[sizeof(DbgaufsXi_PREFIX) + 8];
+       struct au_sbinfo *sbinfo;
+       struct super_block *sb;
+       struct au_xino *xi;
+       struct file *xf;
+       struct qstr *name;
+       struct au_branch *br;
+
+       err = -ENOENT;
+       name = &file->f_path.dentry->d_name;
+       if (unlikely(name->len < sizeof(DbgaufsXi_PREFIX)
+                    || memcmp(name->name, DbgaufsXi_PREFIX,
+                              sizeof(DbgaufsXi_PREFIX) - 1)))
+               goto out;
+
+       AuDebugOn(name->len >= sizeof(a));
+       memcpy(a, name->name, name->len);
+       a[name->len] = '\0';
+       p = strchr(a, '-');
+       if (p)
+               *p = '\0';
+       err = kstrtol(a + sizeof(DbgaufsXi_PREFIX) - 1, 10, &l);
+       if (unlikely(err))
+               goto out;
+       bindex = l;
+       idx = 0;
+       if (p) {
+               err = kstrtol(p + 1, 10, &l);
+               if (unlikely(err))
+                       goto out;
+               idx = l;
+       }
+
+       err = -ENOENT;
+       sbinfo = inode->i_private;
+       sb = sbinfo->si_sb;
+       si_noflush_read_lock(sb);
+       if (unlikely(bindex < 0 || bindex > au_sbbot(sb)))
+               goto out_si;
+       br = au_sbr(sb, bindex);
+       xi = br->br_xino;
+       if (unlikely(idx >= xi->xi_nfile))
+               goto out_si;
+       xf = au_xino_file(xi, idx);
+       if (xf)
+               err = dbgaufs_xi_open(xf, file, /*do_fcnt*/1,
+                                     au_xino_count(br));
+
+out_si:
+       si_read_unlock(sb);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+static const struct file_operations dbgaufs_xino_fop = {
+       .owner          = THIS_MODULE,
+       .open           = dbgaufs_xino_open,
+       .release        = dbgaufs_xi_release,
+       .read           = dbgaufs_xi_read
+};
+
+void dbgaufs_xino_del(struct au_branch *br)
+{
+       struct dentry *dbgaufs;
+
+       dbgaufs = br->br_dbgaufs;
+       if (!dbgaufs)
+               return;
+
+       br->br_dbgaufs = NULL;
+       /* debugfs acquires the parent i_mutex */
+       lockdep_off();
+       debugfs_remove(dbgaufs);
+       lockdep_on();
+}
+
+void dbgaufs_brs_del(struct super_block *sb, aufs_bindex_t bindex)
+{
+       aufs_bindex_t bbot;
+       struct au_branch *br;
+
+       if (!au_sbi(sb)->si_dbgaufs)
+               return;
+
+       bbot = au_sbbot(sb);
+       for (; bindex <= bbot; bindex++) {
+               br = au_sbr(sb, bindex);
+               dbgaufs_xino_del(br);
+       }
+}
+
+static void dbgaufs_br_do_add(struct super_block *sb, aufs_bindex_t bindex,
+                             unsigned int idx, struct dentry *parent,
+                             struct au_sbinfo *sbinfo)
+{
+       struct au_branch *br;
+       struct dentry *d;
+       /* "xi" bindex(5) "-" idx(2) NULL */
+       char name[sizeof(DbgaufsXi_PREFIX) + 8];
+
+       if (!idx)
+               snprintf(name, sizeof(name), DbgaufsXi_PREFIX "%d", bindex);
+       else
+               snprintf(name, sizeof(name), DbgaufsXi_PREFIX "%d-%u",
+                        bindex, idx);
+       br = au_sbr(sb, bindex);
+       if (br->br_dbgaufs) {
+               struct qstr qstr = QSTR_INIT(name, strlen(name));
+
+               if (!au_qstreq(&br->br_dbgaufs->d_name, &qstr)) {
+                       /* debugfs acquires the parent i_mutex */
+                       lockdep_off();
+                       d = debugfs_rename(parent, br->br_dbgaufs, parent,
+                                          name);
+                       lockdep_on();
+                       if (unlikely(!d))
+                               pr_warn("failed renaming %pd/%s, ignored.\n",
+                                       parent, name);
+               }
+       } else {
+               lockdep_off();
+               br->br_dbgaufs = debugfs_create_file(name, dbgaufs_mode, parent,
+                                                    sbinfo, &dbgaufs_xino_fop);
+               lockdep_on();
+               if (unlikely(!br->br_dbgaufs))
+                       pr_warn("failed creating %pd/%s, ignored.\n",
+                               parent, name);
+       }
+}
+
+static void dbgaufs_br_add(struct super_block *sb, aufs_bindex_t bindex,
+                          struct dentry *parent, struct au_sbinfo *sbinfo)
+{
+       struct au_branch *br;
+       struct au_xino *xi;
+       unsigned int u;
+
+       br = au_sbr(sb, bindex);
+       xi = br->br_xino;
+       for (u = 0; u < xi->xi_nfile; u++)
+               dbgaufs_br_do_add(sb, bindex, u, parent, sbinfo);
+}
+
+void dbgaufs_brs_add(struct super_block *sb, aufs_bindex_t bindex, int topdown)
+{
+       struct au_sbinfo *sbinfo;
+       struct dentry *parent;
+       aufs_bindex_t bbot;
+
+       if (!au_opt_test(au_mntflags(sb), XINO))
+               return;
+
+       sbinfo = au_sbi(sb);
+       parent = sbinfo->si_dbgaufs;
+       if (!parent)
+               return;
+
+       bbot = au_sbbot(sb);
+       if (topdown)
+               for (; bindex <= bbot; bindex++)
+                       dbgaufs_br_add(sb, bindex, parent, sbinfo);
+       else
+               for (; bbot >= bindex; bbot--)
+                       dbgaufs_br_add(sb, bbot, parent, sbinfo);
+}
+
+/* ---------------------------------------------------------------------- */
+
+#ifdef CONFIG_AUFS_EXPORT
+static int dbgaufs_xigen_open(struct inode *inode, struct file *file)
+{
+       int err;
+       struct au_sbinfo *sbinfo;
+       struct super_block *sb;
+
+       sbinfo = inode->i_private;
+       sb = sbinfo->si_sb;
+       si_noflush_read_lock(sb);
+       err = dbgaufs_xi_open(sbinfo->si_xigen, file, /*do_fcnt*/0, /*cnt*/0);
+       si_read_unlock(sb);
+       return err;
+}
+
+static const struct file_operations dbgaufs_xigen_fop = {
+       .owner          = THIS_MODULE,
+       .open           = dbgaufs_xigen_open,
+       .release        = dbgaufs_xi_release,
+       .read           = dbgaufs_xi_read
+};
+
+static int dbgaufs_xigen_init(struct au_sbinfo *sbinfo)
+{
+       int err;
+
+       /*
+        * This function is a dynamic '__init' function actually,
+        * so the tiny check for si_rwsem is unnecessary.
+        */
+       /* AuRwMustWriteLock(&sbinfo->si_rwsem); */
+
+       err = -EIO;
+       sbinfo->si_dbgaufs_xigen = debugfs_create_file
+               ("xigen", dbgaufs_mode, sbinfo->si_dbgaufs, sbinfo,
+                &dbgaufs_xigen_fop);
+       if (sbinfo->si_dbgaufs_xigen)
+               err = 0;
+
+       return err;
+}
+#else
+static int dbgaufs_xigen_init(struct au_sbinfo *sbinfo)
+{
+       return 0;
+}
+#endif /* CONFIG_AUFS_EXPORT */
+
+/* ---------------------------------------------------------------------- */
+
+void dbgaufs_si_fin(struct au_sbinfo *sbinfo)
+{
+       /*
+        * This function is a dynamic '__fin' function actually,
+        * so the tiny check for si_rwsem is unnecessary.
+        */
+       /* AuRwMustWriteLock(&sbinfo->si_rwsem); */
+
+       debugfs_remove_recursive(sbinfo->si_dbgaufs);
+       sbinfo->si_dbgaufs = NULL;
+}
+
+int dbgaufs_si_init(struct au_sbinfo *sbinfo)
+{
+       int err;
+       char name[SysaufsSiNameLen];
+
+       /*
+        * This function is a dynamic '__init' function actually,
+        * so the tiny check for si_rwsem is unnecessary.
+        */
+       /* AuRwMustWriteLock(&sbinfo->si_rwsem); */
+
+       err = -ENOENT;
+       if (!dbgaufs) {
+               AuErr1("/debug/aufs is uninitialized\n");
+               goto out;
+       }
+
+       err = -EIO;
+       sysaufs_name(sbinfo, name);
+       sbinfo->si_dbgaufs = debugfs_create_dir(name, dbgaufs);
+       if (unlikely(!sbinfo->si_dbgaufs))
+               goto out;
+
+       /* regardless plink/noplink option */
+       sbinfo->si_dbgaufs_plink = debugfs_create_file
+               ("plink", dbgaufs_mode, sbinfo->si_dbgaufs, sbinfo,
+                &dbgaufs_plink_fop);
+       if (unlikely(!sbinfo->si_dbgaufs_plink))
+               goto out_dir;
+
+       /* regardless xino/noxino option */
+       sbinfo->si_dbgaufs_xib = debugfs_create_file
+               ("xib", dbgaufs_mode, sbinfo->si_dbgaufs, sbinfo,
+                &dbgaufs_xib_fop);
+       if (unlikely(!sbinfo->si_dbgaufs_xib))
+               goto out_dir;
+
+       err = dbgaufs_xigen_init(sbinfo);
+       if (!err)
+               goto out; /* success */
+
+out_dir:
+       dbgaufs_si_fin(sbinfo);
+out:
+       if (unlikely(err))
+               pr_err("debugfs/aufs failed\n");
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void dbgaufs_fin(void)
+{
+       debugfs_remove(dbgaufs);
+}
+
+int __init dbgaufs_init(void)
+{
+       int err;
+
+       err = -EIO;
+       dbgaufs = debugfs_create_dir(AUFS_NAME, NULL);
+       if (dbgaufs)
+               err = 0;
+       return err;
+}
diff -urN /usr/share/empty/fs/aufs/dbgaufs.h linux/fs/aufs/dbgaufs.h
--- /usr/share/empty/fs/aufs/dbgaufs.h  1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/dbgaufs.h     2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * debugfs interface
+ */
+
+#ifndef __DBGAUFS_H__
+#define __DBGAUFS_H__
+
+#ifdef __KERNEL__
+
+struct super_block;
+struct au_sbinfo;
+struct au_branch;
+
+#ifdef CONFIG_DEBUG_FS
+/* dbgaufs.c */
+void dbgaufs_xino_del(struct au_branch *br);
+void dbgaufs_brs_del(struct super_block *sb, aufs_bindex_t bindex);
+void dbgaufs_brs_add(struct super_block *sb, aufs_bindex_t bindex, int topdown);
+void dbgaufs_si_fin(struct au_sbinfo *sbinfo);
+int dbgaufs_si_init(struct au_sbinfo *sbinfo);
+void dbgaufs_fin(void);
+int __init dbgaufs_init(void);
+#else
+AuStubVoid(dbgaufs_xino_del, struct au_branch *br)
+AuStubVoid(dbgaufs_brs_del, struct super_block *sb, aufs_bindex_t bindex)
+AuStubVoid(dbgaufs_brs_add, struct super_block *sb, aufs_bindex_t bindex,
+          int topdown)
+AuStubVoid(dbgaufs_si_fin, struct au_sbinfo *sbinfo)
+AuStubInt0(dbgaufs_si_init, struct au_sbinfo *sbinfo)
+AuStubVoid(dbgaufs_fin, void)
+AuStubInt0(__init dbgaufs_init, void)
+#endif /* CONFIG_DEBUG_FS */
+
+#endif /* __KERNEL__ */
+#endif /* __DBGAUFS_H__ */
diff -urN /usr/share/empty/fs/aufs/dcsub.c linux/fs/aufs/dcsub.c
--- /usr/share/empty/fs/aufs/dcsub.c    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/dcsub.c       2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,225 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * sub-routines for dentry cache
+ */
+
+#include "aufs.h"
+
+static void au_dpage_free(struct au_dpage *dpage)
+{
+       int i;
+       struct dentry **p;
+
+       p = dpage->dentries;
+       for (i = 0; i < dpage->ndentry; i++)
+               dput(*p++);
+       free_page((unsigned long)dpage->dentries);
+}
+
+int au_dpages_init(struct au_dcsub_pages *dpages, gfp_t gfp)
+{
+       int err;
+       void *p;
+
+       err = -ENOMEM;
+       dpages->dpages = kmalloc(sizeof(*dpages->dpages), gfp);
+       if (unlikely(!dpages->dpages))
+               goto out;
+
+       p = (void *)__get_free_page(gfp);
+       if (unlikely(!p))
+               goto out_dpages;
+
+       dpages->dpages[0].ndentry = 0;
+       dpages->dpages[0].dentries = p;
+       dpages->ndpage = 1;
+       return 0; /* success */
+
+out_dpages:
+       au_kfree_try_rcu(dpages->dpages);
+out:
+       return err;
+}
+
+void au_dpages_free(struct au_dcsub_pages *dpages)
+{
+       int i;
+       struct au_dpage *p;
+
+       p = dpages->dpages;
+       for (i = 0; i < dpages->ndpage; i++)
+               au_dpage_free(p++);
+       au_kfree_try_rcu(dpages->dpages);
+}
+
+static int au_dpages_append(struct au_dcsub_pages *dpages,
+                           struct dentry *dentry, gfp_t gfp)
+{
+       int err, sz;
+       struct au_dpage *dpage;
+       void *p;
+
+       dpage = dpages->dpages + dpages->ndpage - 1;
+       sz = PAGE_SIZE / sizeof(dentry);
+       if (unlikely(dpage->ndentry >= sz)) {
+               AuLabel(new dpage);
+               err = -ENOMEM;
+               sz = dpages->ndpage * sizeof(*dpages->dpages);
+               p = au_kzrealloc(dpages->dpages, sz,
+                                sz + sizeof(*dpages->dpages), gfp,
+                                /*may_shrink*/0);
+               if (unlikely(!p))
+                       goto out;
+
+               dpages->dpages = p;
+               dpage = dpages->dpages + dpages->ndpage;
+               p = (void *)__get_free_page(gfp);
+               if (unlikely(!p))
+                       goto out;
+
+               dpage->ndentry = 0;
+               dpage->dentries = p;
+               dpages->ndpage++;
+       }
+
+       AuDebugOn(au_dcount(dentry) <= 0);
+       dpage->dentries[dpage->ndentry++] = dget_dlock(dentry);
+       return 0; /* success */
+
+out:
+       return err;
+}
+
+/* todo: BAD approach */
+/* copied from linux/fs/dcache.c */
+enum d_walk_ret {
+       D_WALK_CONTINUE,
+       D_WALK_QUIT,
+       D_WALK_NORETRY,
+       D_WALK_SKIP,
+};
+
+extern void d_walk(struct dentry *parent, void *data,
+                  enum d_walk_ret (*enter)(void *, struct dentry *));
+
+struct ac_dpages_arg {
+       int err;
+       struct au_dcsub_pages *dpages;
+       struct super_block *sb;
+       au_dpages_test test;
+       void *arg;
+};
+
+static enum d_walk_ret au_call_dpages_append(void *_arg, struct dentry *dentry)
+{
+       enum d_walk_ret ret;
+       struct ac_dpages_arg *arg = _arg;
+
+       ret = D_WALK_CONTINUE;
+       if (dentry->d_sb == arg->sb
+           && !IS_ROOT(dentry)
+           && au_dcount(dentry) > 0
+           && au_di(dentry)
+           && (!arg->test || arg->test(dentry, arg->arg))) {
+               arg->err = au_dpages_append(arg->dpages, dentry, GFP_ATOMIC);
+               if (unlikely(arg->err))
+                       ret = D_WALK_QUIT;
+       }
+
+       return ret;
+}
+
+int au_dcsub_pages(struct au_dcsub_pages *dpages, struct dentry *root,
+                  au_dpages_test test, void *arg)
+{
+       struct ac_dpages_arg args = {
+               .err    = 0,
+               .dpages = dpages,
+               .sb     = root->d_sb,
+               .test   = test,
+               .arg    = arg
+       };
+
+       d_walk(root, &args, au_call_dpages_append);
+
+       return args.err;
+}
+
+int au_dcsub_pages_rev(struct au_dcsub_pages *dpages, struct dentry *dentry,
+                      int do_include, au_dpages_test test, void *arg)
+{
+       int err;
+
+       err = 0;
+       write_seqlock(&rename_lock);
+       spin_lock(&dentry->d_lock);
+       if (do_include
+           && au_dcount(dentry) > 0
+           && (!test || test(dentry, arg)))
+               err = au_dpages_append(dpages, dentry, GFP_ATOMIC);
+       spin_unlock(&dentry->d_lock);
+       if (unlikely(err))
+               goto out;
+
+       /*
+        * RCU for vfsmount is unnecessary since this is a traverse in a single
+        * mount
+        */
+       while (!IS_ROOT(dentry)) {
+               dentry = dentry->d_parent; /* rename_lock is locked */
+               spin_lock(&dentry->d_lock);
+               if (au_dcount(dentry) > 0
+                   && (!test || test(dentry, arg)))
+                       err = au_dpages_append(dpages, dentry, GFP_ATOMIC);
+               spin_unlock(&dentry->d_lock);
+               if (unlikely(err))
+                       break;
+       }
+
+out:
+       write_sequnlock(&rename_lock);
+       return err;
+}
+
+static inline int au_dcsub_dpages_aufs(struct dentry *dentry, void *arg)
+{
+       return au_di(dentry) && dentry->d_sb == arg;
+}
+
+int au_dcsub_pages_rev_aufs(struct au_dcsub_pages *dpages,
+                           struct dentry *dentry, int do_include)
+{
+       return au_dcsub_pages_rev(dpages, dentry, do_include,
+                                 au_dcsub_dpages_aufs, dentry->d_sb);
+}
+
+int au_test_subdir(struct dentry *d1, struct dentry *d2)
+{
+       struct path path[2] = {
+               {
+                       .dentry = d1
+               },
+               {
+                       .dentry = d2
+               }
+       };
+
+       return path_is_under(path + 0, path + 1);
+}
diff -urN /usr/share/empty/fs/aufs/dcsub.h linux/fs/aufs/dcsub.h
--- /usr/share/empty/fs/aufs/dcsub.h    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/dcsub.h       2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,137 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * sub-routines for dentry cache
+ */
+
+#ifndef __AUFS_DCSUB_H__
+#define __AUFS_DCSUB_H__
+
+#ifdef __KERNEL__
+
+#include <linux/dcache.h>
+#include <linux/fs.h>
+
+struct au_dpage {
+       int ndentry;
+       struct dentry **dentries;
+};
+
+struct au_dcsub_pages {
+       int ndpage;
+       struct au_dpage *dpages;
+};
+
+/* ---------------------------------------------------------------------- */
+
+/* dcsub.c */
+int au_dpages_init(struct au_dcsub_pages *dpages, gfp_t gfp);
+void au_dpages_free(struct au_dcsub_pages *dpages);
+typedef int (*au_dpages_test)(struct dentry *dentry, void *arg);
+int au_dcsub_pages(struct au_dcsub_pages *dpages, struct dentry *root,
+                  au_dpages_test test, void *arg);
+int au_dcsub_pages_rev(struct au_dcsub_pages *dpages, struct dentry *dentry,
+                      int do_include, au_dpages_test test, void *arg);
+int au_dcsub_pages_rev_aufs(struct au_dcsub_pages *dpages,
+                           struct dentry *dentry, int do_include);
+int au_test_subdir(struct dentry *d1, struct dentry *d2);
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * todo: in linux-3.13, several similar (but faster) helpers are added to
+ * include/linux/dcache.h. Try them (in the future).
+ */
+
+static inline int au_d_hashed_positive(struct dentry *d)
+{
+       int err;
+       struct inode *inode = d_inode(d);
+
+       err = 0;
+       if (unlikely(d_unhashed(d)
+                    || d_is_negative(d)
+                    || !inode->i_nlink))
+               err = -ENOENT;
+       return err;
+}
+
+static inline int au_d_linkable(struct dentry *d)
+{
+       int err;
+       struct inode *inode = d_inode(d);
+
+       err = au_d_hashed_positive(d);
+       if (err
+           && d_is_positive(d)
+           && (inode->i_state & I_LINKABLE))
+               err = 0;
+       return err;
+}
+
+static inline int au_d_alive(struct dentry *d)
+{
+       int err;
+       struct inode *inode;
+
+       err = 0;
+       if (!IS_ROOT(d))
+               err = au_d_hashed_positive(d);
+       else {
+               inode = d_inode(d);
+               if (unlikely(d_unlinked(d)
+                            || d_is_negative(d)
+                            || !inode->i_nlink))
+                       err = -ENOENT;
+       }
+       return err;
+}
+
+static inline int au_alive_dir(struct dentry *d)
+{
+       int err;
+
+       err = au_d_alive(d);
+       if (unlikely(err || IS_DEADDIR(d_inode(d))))
+               err = -ENOENT;
+       return err;
+}
+
+static inline int au_qstreq(struct qstr *a, struct qstr *b)
+{
+       return a->len == b->len
+               && !memcmp(a->name, b->name, a->len);
+}
+
+/*
+ * by the commit
+ * 360f547 2015-01-25 dcache: let the dentry count go down to zero without
+ *                     taking d_lock
+ * the type of d_lockref.count became int, but the inlined function d_count()
+ * still returns unsigned int.
+ * I don't know why. Maybe it is for every d_count() users?
+ * Anyway au_dcount() lives on.
+ */
+static inline int au_dcount(struct dentry *d)
+{
+       return (int)d_count(d);
+}
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_DCSUB_H__ */
diff -urN /usr/share/empty/fs/aufs/debug.c linux/fs/aufs/debug.c
--- /usr/share/empty/fs/aufs/debug.c    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/debug.c       2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,444 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * debug print functions
+ */
+
+#include <linux/iversion.h>
+#include "aufs.h"
+
+/* Returns 0, or -errno.  arg is in kp->arg. */
+static int param_atomic_t_set(const char *val, const struct kernel_param *kp)
+{
+       int err, n;
+
+       err = kstrtoint(val, 0, &n);
+       if (!err) {
+               if (n > 0)
+                       au_debug_on();
+               else
+                       au_debug_off();
+       }
+       return err;
+}
+
+/* Returns length written or -errno.  Buffer is 4k (ie. be short!) */
+static int param_atomic_t_get(char *buffer, const struct kernel_param *kp)
+{
+       atomic_t *a;
+
+       a = kp->arg;
+       return sprintf(buffer, "%d", atomic_read(a));
+}
+
+static struct kernel_param_ops param_ops_atomic_t = {
+       .set = param_atomic_t_set,
+       .get = param_atomic_t_get
+       /* void (*free)(void *arg) */
+};
+
+atomic_t aufs_debug = ATOMIC_INIT(0);
+MODULE_PARM_DESC(debug, "debug print");
+module_param_named(debug, aufs_debug, atomic_t, 0664);
+
+DEFINE_MUTEX(au_dbg_mtx);      /* just to serialize the dbg msgs */
+char *au_plevel = KERN_DEBUG;
+#define dpri(fmt, ...) do {                                    \
+       if ((au_plevel                                          \
+            && strcmp(au_plevel, KERN_DEBUG))                  \
+           || au_debug_test())                                 \
+               printk("%s" fmt, au_plevel, ##__VA_ARGS__);     \
+} while (0)
+
+/* ---------------------------------------------------------------------- */
+
+void au_dpri_whlist(struct au_nhash *whlist)
+{
+       unsigned long ul, n;
+       struct hlist_head *head;
+       struct au_vdir_wh *pos;
+
+       n = whlist->nh_num;
+       head = whlist->nh_head;
+       for (ul = 0; ul < n; ul++) {
+               hlist_for_each_entry(pos, head, wh_hash)
+                       dpri("b%d, %.*s, %d\n",
+                            pos->wh_bindex,
+                            pos->wh_str.len, pos->wh_str.name,
+                            pos->wh_str.len);
+               head++;
+       }
+}
+
+void au_dpri_vdir(struct au_vdir *vdir)
+{
+       unsigned long ul;
+       union au_vdir_deblk_p p;
+       unsigned char *o;
+
+       if (!vdir || IS_ERR(vdir)) {
+               dpri("err %ld\n", PTR_ERR(vdir));
+               return;
+       }
+
+       dpri("deblk %u, nblk %lu, deblk %p, last{%lu, %p}, ver %llu\n",
+            vdir->vd_deblk_sz, vdir->vd_nblk, vdir->vd_deblk,
+            vdir->vd_last.ul, vdir->vd_last.p.deblk, vdir->vd_version);
+       for (ul = 0; ul < vdir->vd_nblk; ul++) {
+               p.deblk = vdir->vd_deblk[ul];
+               o = p.deblk;
+               dpri("[%lu]: %p\n", ul, o);
+       }
+}
+
+static int do_pri_inode(aufs_bindex_t bindex, struct inode *inode, int hn,
+                       struct dentry *wh)
+{
+       char *n = NULL;
+       int l = 0;
+
+       if (!inode || IS_ERR(inode)) {
+               dpri("i%d: err %ld\n", bindex, PTR_ERR(inode));
+               return -1;
+       }
+
+       /* the type of i_blocks depends upon CONFIG_LBDAF */
+       BUILD_BUG_ON(sizeof(inode->i_blocks) != sizeof(unsigned long)
+                    && sizeof(inode->i_blocks) != sizeof(u64));
+       if (wh) {
+               n = (void *)wh->d_name.name;
+               l = wh->d_name.len;
+       }
+
+       dpri("i%d: %p, i%lu, %s, cnt %d, nl %u, 0%o, sz %llu, blk %llu,"
+            " hn %d, ct %lld, np %lu, st 0x%lx, f 0x%x, v %llu, g %x%s%.*s\n",
+            bindex, inode,
+            inode->i_ino, inode->i_sb ? au_sbtype(inode->i_sb) : "??",
+            atomic_read(&inode->i_count), inode->i_nlink, inode->i_mode,
+            i_size_read(inode), (unsigned long long)inode->i_blocks,
+            hn, (long long)timespec64_to_ns(&inode->i_ctime) & 0x0ffff,
+            inode->i_mapping ? inode->i_mapping->nrpages : 0,
+            inode->i_state, inode->i_flags, inode_peek_iversion(inode),
+            inode->i_generation,
+            l ? ", wh " : "", l, n);
+       return 0;
+}
+
+void au_dpri_inode(struct inode *inode)
+{
+       struct au_iinfo *iinfo;
+       struct au_hinode *hi;
+       aufs_bindex_t bindex;
+       int err, hn;
+
+       err = do_pri_inode(-1, inode, -1, NULL);
+       if (err || !au_test_aufs(inode->i_sb) || au_is_bad_inode(inode))
+               return;
+
+       iinfo = au_ii(inode);
+       dpri("i-1: btop %d, bbot %d, gen %d\n",
+            iinfo->ii_btop, iinfo->ii_bbot, au_iigen(inode, NULL));
+       if (iinfo->ii_btop < 0)
+               return;
+       hn = 0;
+       for (bindex = iinfo->ii_btop; bindex <= iinfo->ii_bbot; bindex++) {
+               hi = au_hinode(iinfo, bindex);
+               hn = !!au_hn(hi);
+               do_pri_inode(bindex, hi->hi_inode, hn, hi->hi_whdentry);
+       }
+}
+
+void au_dpri_dalias(struct inode *inode)
+{
+       struct dentry *d;
+
+       spin_lock(&inode->i_lock);
+       hlist_for_each_entry(d, &inode->i_dentry, d_u.d_alias)
+               au_dpri_dentry(d);
+       spin_unlock(&inode->i_lock);
+}
+
+static int do_pri_dentry(aufs_bindex_t bindex, struct dentry *dentry)
+{
+       struct dentry *wh = NULL;
+       int hn;
+       struct inode *inode;
+       struct au_iinfo *iinfo;
+       struct au_hinode *hi;
+
+       if (!dentry || IS_ERR(dentry)) {
+               dpri("d%d: err %ld\n", bindex, PTR_ERR(dentry));
+               return -1;
+       }
+       /* do not call dget_parent() here */
+       /* note: access d_xxx without d_lock */
+       dpri("d%d: %p, %pd2?, %s, cnt %d, flags 0x%x, %shashed\n",
+            bindex, dentry, dentry,
+            dentry->d_sb ? au_sbtype(dentry->d_sb) : "??",
+            au_dcount(dentry), dentry->d_flags,
+            d_unhashed(dentry) ? "un" : "");
+       hn = -1;
+       inode = NULL;
+       if (d_is_positive(dentry))
+               inode = d_inode(dentry);
+       if (inode
+           && au_test_aufs(dentry->d_sb)
+           && bindex >= 0
+           && !au_is_bad_inode(inode)) {
+               iinfo = au_ii(inode);
+               hi = au_hinode(iinfo, bindex);
+               hn = !!au_hn(hi);
+               wh = hi->hi_whdentry;
+       }
+       do_pri_inode(bindex, inode, hn, wh);
+       return 0;
+}
+
+void au_dpri_dentry(struct dentry *dentry)
+{
+       struct au_dinfo *dinfo;
+       aufs_bindex_t bindex;
+       int err;
+
+       err = do_pri_dentry(-1, dentry);
+       if (err || !au_test_aufs(dentry->d_sb))
+               return;
+
+       dinfo = au_di(dentry);
+       if (!dinfo)
+               return;
+       dpri("d-1: btop %d, bbot %d, bwh %d, bdiropq %d, gen %d, tmp %d\n",
+            dinfo->di_btop, dinfo->di_bbot,
+            dinfo->di_bwh, dinfo->di_bdiropq, au_digen(dentry),
+            dinfo->di_tmpfile);
+       if (dinfo->di_btop < 0)
+               return;
+       for (bindex = dinfo->di_btop; bindex <= dinfo->di_bbot; bindex++)
+               do_pri_dentry(bindex, au_hdentry(dinfo, bindex)->hd_dentry);
+}
+
+static int do_pri_file(aufs_bindex_t bindex, struct file *file)
+{
+       char a[32];
+
+       if (!file || IS_ERR(file)) {
+               dpri("f%d: err %ld\n", bindex, PTR_ERR(file));
+               return -1;
+       }
+       a[0] = 0;
+       if (bindex < 0
+           && !IS_ERR_OR_NULL(file->f_path.dentry)
+           && au_test_aufs(file->f_path.dentry->d_sb)
+           && au_fi(file))
+               snprintf(a, sizeof(a), ", gen %d, mmapped %d",
+                        au_figen(file), atomic_read(&au_fi(file)->fi_mmapped));
+       dpri("f%d: mode 0x%x, flags 0%o, cnt %ld, v %llu, pos %llu%s\n",
+            bindex, file->f_mode, file->f_flags, (long)file_count(file),
+            file->f_version, file->f_pos, a);
+       if (!IS_ERR_OR_NULL(file->f_path.dentry))
+               do_pri_dentry(bindex, file->f_path.dentry);
+       return 0;
+}
+
+void au_dpri_file(struct file *file)
+{
+       struct au_finfo *finfo;
+       struct au_fidir *fidir;
+       struct au_hfile *hfile;
+       aufs_bindex_t bindex;
+       int err;
+
+       err = do_pri_file(-1, file);
+       if (err
+           || IS_ERR_OR_NULL(file->f_path.dentry)
+           || !au_test_aufs(file->f_path.dentry->d_sb))
+               return;
+
+       finfo = au_fi(file);
+       if (!finfo)
+               return;
+       if (finfo->fi_btop < 0)
+               return;
+       fidir = finfo->fi_hdir;
+       if (!fidir)
+               do_pri_file(finfo->fi_btop, finfo->fi_htop.hf_file);
+       else
+               for (bindex = finfo->fi_btop;
+                    bindex >= 0 && bindex <= fidir->fd_bbot;
+                    bindex++) {
+                       hfile = fidir->fd_hfile + bindex;
+                       do_pri_file(bindex, hfile ? hfile->hf_file : NULL);
+               }
+}
+
+static int do_pri_br(aufs_bindex_t bindex, struct au_branch *br)
+{
+       struct vfsmount *mnt;
+       struct super_block *sb;
+
+       if (!br || IS_ERR(br))
+               goto out;
+       mnt = au_br_mnt(br);
+       if (!mnt || IS_ERR(mnt))
+               goto out;
+       sb = mnt->mnt_sb;
+       if (!sb || IS_ERR(sb))
+               goto out;
+
+       dpri("s%d: {perm 0x%x, id %d, wbr %p}, "
+            "%s, dev 0x%02x%02x, flags 0x%lx, cnt %d, active %d, "
+            "xino %d\n",
+            bindex, br->br_perm, br->br_id, br->br_wbr,
+            au_sbtype(sb), MAJOR(sb->s_dev), MINOR(sb->s_dev),
+            sb->s_flags, sb->s_count,
+            atomic_read(&sb->s_active),
+            !!au_xino_file(br->br_xino, /*idx*/-1));
+       return 0;
+
+out:
+       dpri("s%d: err %ld\n", bindex, PTR_ERR(br));
+       return -1;
+}
+
+void au_dpri_sb(struct super_block *sb)
+{
+       struct au_sbinfo *sbinfo;
+       aufs_bindex_t bindex;
+       int err;
+       /* to reduce stack size */
+       struct {
+               struct vfsmount mnt;
+               struct au_branch fake;
+       } *a;
+
+       /* this function can be called from magic sysrq */
+       a = kzalloc(sizeof(*a), GFP_ATOMIC);
+       if (unlikely(!a)) {
+               dpri("no memory\n");
+               return;
+       }
+
+       a->mnt.mnt_sb = sb;
+       a->fake.br_path.mnt = &a->mnt;
+       err = do_pri_br(-1, &a->fake);
+       au_kfree_rcu(a);
+       dpri("dev 0x%x\n", sb->s_dev);
+       if (err || !au_test_aufs(sb))
+               return;
+
+       sbinfo = au_sbi(sb);
+       if (!sbinfo)
+               return;
+       dpri("nw %d, gen %u, kobj %d\n",
+            atomic_read(&sbinfo->si_nowait.nw_len), sbinfo->si_generation,
+            kref_read(&sbinfo->si_kobj.kref));
+       for (bindex = 0; bindex <= sbinfo->si_bbot; bindex++)
+               do_pri_br(bindex, sbinfo->si_branch[0 + bindex]);
+}
+
+/* ---------------------------------------------------------------------- */
+
+void __au_dbg_verify_dinode(struct dentry *dentry, const char *func, int line)
+{
+       struct inode *h_inode, *inode = d_inode(dentry);
+       struct dentry *h_dentry;
+       aufs_bindex_t bindex, bbot, bi;
+
+       if (!inode /* || au_di(dentry)->di_lsc == AuLsc_DI_TMP */)
+               return;
+
+       bbot = au_dbbot(dentry);
+       bi = au_ibbot(inode);
+       if (bi < bbot)
+               bbot = bi;
+       bindex = au_dbtop(dentry);
+       bi = au_ibtop(inode);
+       if (bi > bindex)
+               bindex = bi;
+
+       for (; bindex <= bbot; bindex++) {
+               h_dentry = au_h_dptr(dentry, bindex);
+               if (!h_dentry)
+                       continue;
+               h_inode = au_h_iptr(inode, bindex);
+               if (unlikely(h_inode != d_inode(h_dentry))) {
+                       au_debug_on();
+                       AuDbg("b%d, %s:%d\n", bindex, func, line);
+                       AuDbgDentry(dentry);
+                       AuDbgInode(inode);
+                       au_debug_off();
+                       if (au_test_fuse(h_inode->i_sb))
+                               WARN_ON_ONCE(1);
+                       else
+                               BUG();
+               }
+       }
+}
+
+void au_dbg_verify_gen(struct dentry *parent, unsigned int sigen)
+{
+       int err, i, j;
+       struct au_dcsub_pages dpages;
+       struct au_dpage *dpage;
+       struct dentry **dentries;
+
+       err = au_dpages_init(&dpages, GFP_NOFS);
+       AuDebugOn(err);
+       err = au_dcsub_pages_rev_aufs(&dpages, parent, /*do_include*/1);
+       AuDebugOn(err);
+       for (i = dpages.ndpage - 1; !err && i >= 0; i--) {
+               dpage = dpages.dpages + i;
+               dentries = dpage->dentries;
+               for (j = dpage->ndentry - 1; !err && j >= 0; j--)
+                       AuDebugOn(au_digen_test(dentries[j], sigen));
+       }
+       au_dpages_free(&dpages);
+}
+
+void au_dbg_verify_kthread(void)
+{
+       if (au_wkq_test()) {
+               au_dbg_blocked();
+               /*
+                * It may be recursive, but udba=notify between two aufs mounts,
+                * where a single ro branch is shared, is not a problem.
+                */
+               /* WARN_ON(1); */
+       }
+}
+
+/* ---------------------------------------------------------------------- */
+
+int __init au_debug_init(void)
+{
+       aufs_bindex_t bindex;
+       struct au_vdir_destr destr;
+
+       bindex = -1;
+       AuDebugOn(bindex >= 0);
+
+       destr.len = -1;
+       AuDebugOn(destr.len < NAME_MAX);
+
+#ifdef CONFIG_4KSTACKS
+       pr_warn("CONFIG_4KSTACKS is defined.\n");
+#endif
+
+       return 0;
+}
diff -urN /usr/share/empty/fs/aufs/debug.h linux/fs/aufs/debug.h
--- /usr/share/empty/fs/aufs/debug.h    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/debug.h       2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,226 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * debug print functions
+ */
+
+#ifndef __AUFS_DEBUG_H__
+#define __AUFS_DEBUG_H__
+
+#ifdef __KERNEL__
+
+#include <linux/atomic.h>
+#include <linux/module.h>
+#include <linux/kallsyms.h>
+#include <linux/sysrq.h>
+
+#ifdef CONFIG_AUFS_DEBUG
+#define AuDebugOn(a)           BUG_ON(a)
+
+/* module parameter */
+extern atomic_t aufs_debug;
+static inline void au_debug_on(void)
+{
+       atomic_inc(&aufs_debug);
+}
+static inline void au_debug_off(void)
+{
+       atomic_dec_if_positive(&aufs_debug);
+}
+
+static inline int au_debug_test(void)
+{
+       return atomic_read(&aufs_debug) > 0;
+}
+#else
+#define AuDebugOn(a)           do {} while (0)
+AuStubVoid(au_debug_on, void)
+AuStubVoid(au_debug_off, void)
+AuStubInt0(au_debug_test, void)
+#endif /* CONFIG_AUFS_DEBUG */
+
+#define param_check_atomic_t(name, p) __param_check(name, p, atomic_t)
+
+/* ---------------------------------------------------------------------- */
+
+/* debug print */
+
+#define AuDbg(fmt, ...) do { \
+       if (au_debug_test()) \
+               pr_debug("DEBUG: " fmt, ##__VA_ARGS__); \
+} while (0)
+#define AuLabel(l)             AuDbg(#l "\n")
+#define AuIOErr(fmt, ...)      pr_err("I/O Error, " fmt, ##__VA_ARGS__)
+#define AuWarn1(fmt, ...) do { \
+       static unsigned char _c; \
+       if (!_c++) \
+               pr_warn(fmt, ##__VA_ARGS__); \
+} while (0)
+
+#define AuErr1(fmt, ...) do { \
+       static unsigned char _c; \
+       if (!_c++) \
+               pr_err(fmt, ##__VA_ARGS__); \
+} while (0)
+
+#define AuIOErr1(fmt, ...) do { \
+       static unsigned char _c; \
+       if (!_c++) \
+               AuIOErr(fmt, ##__VA_ARGS__); \
+} while (0)
+
+#define AuUnsupportMsg "This operation is not supported." \
+                       " Please report this application to aufs-users ML."
+#define AuUnsupport(fmt, ...) do { \
+       pr_err(AuUnsupportMsg "\n" fmt, ##__VA_ARGS__); \
+       dump_stack(); \
+} while (0)
+
+#define AuTraceErr(e) do { \
+       if (unlikely((e) < 0)) \
+               AuDbg("err %d\n", (int)(e)); \
+} while (0)
+
+#define AuTraceErrPtr(p) do { \
+       if (IS_ERR(p)) \
+               AuDbg("err %ld\n", PTR_ERR(p)); \
+} while (0)
+
+/* dirty macros for debug print, use with "%.*s" and caution */
+#define AuLNPair(qstr)         (qstr)->len, (qstr)->name
+
+/* ---------------------------------------------------------------------- */
+
+struct dentry;
+#ifdef CONFIG_AUFS_DEBUG
+extern struct mutex au_dbg_mtx;
+extern char *au_plevel;
+struct au_nhash;
+void au_dpri_whlist(struct au_nhash *whlist);
+struct au_vdir;
+void au_dpri_vdir(struct au_vdir *vdir);
+struct inode;
+void au_dpri_inode(struct inode *inode);
+void au_dpri_dalias(struct inode *inode);
+void au_dpri_dentry(struct dentry *dentry);
+struct file;
+void au_dpri_file(struct file *filp);
+struct super_block;
+void au_dpri_sb(struct super_block *sb);
+
+#define au_dbg_verify_dinode(d) __au_dbg_verify_dinode(d, __func__, __LINE__)
+void __au_dbg_verify_dinode(struct dentry *dentry, const char *func, int line);
+void au_dbg_verify_gen(struct dentry *parent, unsigned int sigen);
+void au_dbg_verify_kthread(void);
+
+int __init au_debug_init(void);
+
+#define AuDbgWhlist(w) do { \
+       mutex_lock(&au_dbg_mtx); \
+       AuDbg(#w "\n"); \
+       au_dpri_whlist(w); \
+       mutex_unlock(&au_dbg_mtx); \
+} while (0)
+
+#define AuDbgVdir(v) do { \
+       mutex_lock(&au_dbg_mtx); \
+       AuDbg(#v "\n"); \
+       au_dpri_vdir(v); \
+       mutex_unlock(&au_dbg_mtx); \
+} while (0)
+
+#define AuDbgInode(i) do { \
+       mutex_lock(&au_dbg_mtx); \
+       AuDbg(#i "\n"); \
+       au_dpri_inode(i); \
+       mutex_unlock(&au_dbg_mtx); \
+} while (0)
+
+#define AuDbgDAlias(i) do { \
+       mutex_lock(&au_dbg_mtx); \
+       AuDbg(#i "\n"); \
+       au_dpri_dalias(i); \
+       mutex_unlock(&au_dbg_mtx); \
+} while (0)
+
+#define AuDbgDentry(d) do { \
+       mutex_lock(&au_dbg_mtx); \
+       AuDbg(#d "\n"); \
+       au_dpri_dentry(d); \
+       mutex_unlock(&au_dbg_mtx); \
+} while (0)
+
+#define AuDbgFile(f) do { \
+       mutex_lock(&au_dbg_mtx); \
+       AuDbg(#f "\n"); \
+       au_dpri_file(f); \
+       mutex_unlock(&au_dbg_mtx); \
+} while (0)
+
+#define AuDbgSb(sb) do { \
+       mutex_lock(&au_dbg_mtx); \
+       AuDbg(#sb "\n"); \
+       au_dpri_sb(sb); \
+       mutex_unlock(&au_dbg_mtx); \
+} while (0)
+
+#define AuDbgSym(addr) do {                            \
+       char sym[KSYM_SYMBOL_LEN];                      \
+       sprint_symbol(sym, (unsigned long)addr);        \
+       AuDbg("%s\n", sym);                             \
+} while (0)
+#else
+AuStubVoid(au_dbg_verify_dinode, struct dentry *dentry)
+AuStubVoid(au_dbg_verify_gen, struct dentry *parent, unsigned int sigen)
+AuStubVoid(au_dbg_verify_kthread, void)
+AuStubInt0(__init au_debug_init, void)
+
+#define AuDbgWhlist(w)         do {} while (0)
+#define AuDbgVdir(v)           do {} while (0)
+#define AuDbgInode(i)          do {} while (0)
+#define AuDbgDAlias(i)         do {} while (0)
+#define AuDbgDentry(d)         do {} while (0)
+#define AuDbgFile(f)           do {} while (0)
+#define AuDbgSb(sb)            do {} while (0)
+#define AuDbgSym(addr)         do {} while (0)
+#endif /* CONFIG_AUFS_DEBUG */
+
+/* ---------------------------------------------------------------------- */
+
+#ifdef CONFIG_AUFS_MAGIC_SYSRQ
+int __init au_sysrq_init(void);
+void au_sysrq_fin(void);
+
+#ifdef CONFIG_HW_CONSOLE
+#define au_dbg_blocked() do { \
+       WARN_ON(1); \
+       handle_sysrq('w'); \
+} while (0)
+#else
+AuStubVoid(au_dbg_blocked, void)
+#endif
+
+#else
+AuStubInt0(__init au_sysrq_init, void)
+AuStubVoid(au_sysrq_fin, void)
+AuStubVoid(au_dbg_blocked, void)
+#endif /* CONFIG_AUFS_MAGIC_SYSRQ */
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_DEBUG_H__ */
diff -urN /usr/share/empty/fs/aufs/dentry.c linux/fs/aufs/dentry.c
--- /usr/share/empty/fs/aufs/dentry.c   1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/dentry.c      2021-12-03 15:40:58.233313963 +0100
@@ -0,0 +1,1169 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * lookup and dentry operations
+ */
+
+#include <linux/iversion.h>
+#include <linux/namei.h>
+#include "aufs.h"
+
+/*
+ * returns positive/negative dentry, NULL or an error.
+ * NULL means whiteout-ed or not-found.
+ */
+static struct dentry*
+au_do_lookup(struct dentry *h_parent, struct dentry *dentry,
+            aufs_bindex_t bindex, struct au_do_lookup_args *args)
+{
+       struct dentry *h_dentry;
+       struct inode *h_inode;
+       struct au_branch *br;
+       struct user_namespace *h_userns;
+       struct path h_path;
+       int wh_found, opq;
+       unsigned char wh_able;
+       const unsigned char allow_neg = !!au_ftest_lkup(args->flags, ALLOW_NEG);
+       const unsigned char ignore_perm = !!au_ftest_lkup(args->flags,
+                                                         IGNORE_PERM);
+
+       wh_found = 0;
+       br = au_sbr(dentry->d_sb, bindex);
+       h_path.dentry = h_parent;
+       h_path.mnt = au_br_mnt(br);
+       h_userns = au_br_userns(br);
+       wh_able = !!au_br_whable(br->br_perm);
+       if (wh_able)
+               wh_found = au_wh_test(h_userns, &h_path, &args->whname,
+                                     ignore_perm);
+       h_dentry = ERR_PTR(wh_found);
+       if (!wh_found)
+               goto real_lookup;
+       if (unlikely(wh_found < 0))
+               goto out;
+
+       /* We found a whiteout */
+       /* au_set_dbbot(dentry, bindex); */
+       au_set_dbwh(dentry, bindex);
+       if (!allow_neg)
+               return NULL; /* success */
+
+real_lookup:
+       if (!ignore_perm)
+               h_dentry = vfsub_lkup_one(args->name, &h_path);
+       else
+               h_dentry = au_sio_lkup_one(h_userns, args->name, &h_path);
+       if (IS_ERR(h_dentry)) {
+               if (PTR_ERR(h_dentry) == -ENAMETOOLONG
+                   && !allow_neg)
+                       h_dentry = NULL;
+               goto out;
+       }
+
+       h_inode = d_inode(h_dentry);
+       if (d_is_negative(h_dentry)) {
+               if (!allow_neg)
+                       goto out_neg;
+       } else if (wh_found
+                  || (args->type && args->type != (h_inode->i_mode & S_IFMT)))
+               goto out_neg;
+       else if (au_ftest_lkup(args->flags, DIRREN)
+                /* && h_inode */
+                && !au_dr_lkup_h_ino(args, bindex, h_inode->i_ino)) {
+               AuDbg("b%d %pd ignored hi%llu\n", bindex, h_dentry,
+                     (unsigned long long)h_inode->i_ino);
+               goto out_neg;
+       }
+
+       if (au_dbbot(dentry) <= bindex)
+               au_set_dbbot(dentry, bindex);
+       if (au_dbtop(dentry) < 0 || bindex < au_dbtop(dentry))
+               au_set_dbtop(dentry, bindex);
+       au_set_h_dptr(dentry, bindex, h_dentry);
+
+       if (!d_is_dir(h_dentry)
+           || !wh_able
+           || (d_really_is_positive(dentry) && !d_is_dir(dentry)))
+               goto out; /* success */
+
+       h_path.dentry = h_dentry;
+       inode_lock_shared_nested(h_inode, AuLsc_I_CHILD);
+       opq = au_diropq_test(h_userns, &h_path);
+       inode_unlock_shared(h_inode);
+       if (opq > 0)
+               au_set_dbdiropq(dentry, bindex);
+       else if (unlikely(opq < 0)) {
+               au_set_h_dptr(dentry, bindex, NULL);
+               h_dentry = ERR_PTR(opq);
+       }
+       goto out;
+
+out_neg:
+       dput(h_dentry);
+       h_dentry = NULL;
+out:
+       return h_dentry;
+}
+
+static int au_test_shwh(struct super_block *sb, const struct qstr *name)
+{
+       if (unlikely(!au_opt_test(au_mntflags(sb), SHWH)
+                    && !strncmp(name->name, AUFS_WH_PFX, AUFS_WH_PFX_LEN)))
+               return -EPERM;
+       return 0;
+}
+
+/*
+ * returns the number of lower positive dentries,
+ * otherwise an error.
+ * can be called at unlinking with @type is zero.
+ */
+int au_lkup_dentry(struct dentry *dentry, aufs_bindex_t btop,
+                  unsigned int flags)
+{
+       int npositive, err;
+       aufs_bindex_t bindex, btail, bdiropq;
+       unsigned char isdir, dirperm1, dirren;
+       struct au_do_lookup_args args = {
+               .flags          = flags,
+               .name           = &dentry->d_name
+       };
+       struct dentry *parent;
+       struct super_block *sb;
+
+       sb = dentry->d_sb;
+       err = au_test_shwh(sb, args.name);
+       if (unlikely(err))
+               goto out;
+
+       err = au_wh_name_alloc(&args.whname, args.name);
+       if (unlikely(err))
+               goto out;
+
+       isdir = !!d_is_dir(dentry);
+       dirperm1 = !!au_opt_test(au_mntflags(sb), DIRPERM1);
+       dirren = !!au_opt_test(au_mntflags(sb), DIRREN);
+       if (dirren)
+               au_fset_lkup(args.flags, DIRREN);
+
+       npositive = 0;
+       parent = dget_parent(dentry);
+       btail = au_dbtaildir(parent);
+       for (bindex = btop; bindex <= btail; bindex++) {
+               struct dentry *h_parent, *h_dentry;
+               struct inode *h_inode, *h_dir;
+               struct au_branch *br;
+
+               h_dentry = au_h_dptr(dentry, bindex);
+               if (h_dentry) {
+                       if (d_is_positive(h_dentry))
+                               npositive++;
+                       break;
+               }
+               h_parent = au_h_dptr(parent, bindex);
+               if (!h_parent || !d_is_dir(h_parent))
+                       continue;
+
+               if (dirren) {
+                       /* if the inum matches, then use the prepared name */
+                       err = au_dr_lkup_name(&args, bindex);
+                       if (unlikely(err))
+                               goto out_parent;
+               }
+
+               h_dir = d_inode(h_parent);
+               inode_lock_shared_nested(h_dir, AuLsc_I_PARENT);
+               h_dentry = au_do_lookup(h_parent, dentry, bindex, &args);
+               inode_unlock_shared(h_dir);
+               err = PTR_ERR(h_dentry);
+               if (IS_ERR(h_dentry))
+                       goto out_parent;
+               if (h_dentry)
+                       au_fclr_lkup(args.flags, ALLOW_NEG);
+               if (dirperm1)
+                       au_fset_lkup(args.flags, IGNORE_PERM);
+
+               if (au_dbwh(dentry) == bindex)
+                       break;
+               if (!h_dentry)
+                       continue;
+               if (d_is_negative(h_dentry))
+                       continue;
+               h_inode = d_inode(h_dentry);
+               npositive++;
+               if (!args.type)
+                       args.type = h_inode->i_mode & S_IFMT;
+               if (args.type != S_IFDIR)
+                       break;
+               else if (isdir) {
+                       /* the type of lower may be different */
+                       bdiropq = au_dbdiropq(dentry);
+                       if (bdiropq >= 0 && bdiropq <= bindex)
+                               break;
+               }
+               br = au_sbr(sb, bindex);
+               if (dirren
+                   && au_dr_hino_test_add(&br->br_dirren, h_inode->i_ino,
+                                          /*add_ent*/NULL)) {
+                       /* prepare next name to lookup */
+                       err = au_dr_lkup(&args, dentry, bindex);
+                       if (unlikely(err))
+                               goto out_parent;
+               }
+       }
+
+       if (npositive) {
+               AuLabel(positive);
+               au_update_dbtop(dentry);
+       }
+       err = npositive;
+       if (unlikely(!au_opt_test(au_mntflags(sb), UDBA_NONE)
+                    && au_dbtop(dentry) < 0)) {
+               err = -EIO;
+               AuIOErr("both of real entry and whiteout found, %pd, err %d\n",
+                       dentry, err);
+       }
+
+out_parent:
+       dput(parent);
+       au_kfree_try_rcu(args.whname.name);
+       if (dirren)
+               au_dr_lkup_fin(&args);
+out:
+       return err;
+}
+
+struct dentry *au_sio_lkup_one(struct user_namespace *userns, struct qstr *name,
+                              struct path *ppath)
+{
+       struct dentry *dentry;
+       int wkq_err;
+
+       if (!au_test_h_perm_sio(userns, d_inode(ppath->dentry), MAY_EXEC))
+               dentry = vfsub_lkup_one(name, ppath);
+       else {
+               struct vfsub_lkup_one_args args = {
+                       .errp   = &dentry,
+                       .name   = name,
+                       .ppath  = ppath
+               };
+
+               wkq_err = au_wkq_wait(vfsub_call_lkup_one, &args);
+               if (unlikely(wkq_err))
+                       dentry = ERR_PTR(wkq_err);
+       }
+
+       return dentry;
+}
+
+/*
+ * lookup @dentry on @bindex which should be negative.
+ */
+int au_lkup_neg(struct dentry *dentry, aufs_bindex_t bindex, int wh)
+{
+       int err;
+       struct dentry *parent, *h_dentry;
+       struct au_branch *br;
+       struct user_namespace *h_userns;
+       struct path h_ppath;
+
+       parent = dget_parent(dentry);
+       br = au_sbr(dentry->d_sb, bindex);
+       h_ppath.dentry = au_h_dptr(parent, bindex);
+       h_ppath.mnt = au_br_mnt(br);
+       h_userns = au_br_userns(br);
+       if (wh)
+               h_dentry = au_whtmp_lkup(h_ppath.dentry, br, &dentry->d_name);
+       else
+               h_dentry = au_sio_lkup_one(h_userns, &dentry->d_name, &h_ppath);
+       err = PTR_ERR(h_dentry);
+       if (IS_ERR(h_dentry))
+               goto out;
+       if (unlikely(d_is_positive(h_dentry))) {
+               err = -EIO;
+               AuIOErr("%pd should be negative on b%d.\n", h_dentry, bindex);
+               dput(h_dentry);
+               goto out;
+       }
+
+       err = 0;
+       if (bindex < au_dbtop(dentry))
+               au_set_dbtop(dentry, bindex);
+       if (au_dbbot(dentry) < bindex)
+               au_set_dbbot(dentry, bindex);
+       au_set_h_dptr(dentry, bindex, h_dentry);
+
+out:
+       dput(parent);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* subset of struct inode */
+struct au_iattr {
+       unsigned long           i_ino;
+       /* unsigned int         i_nlink; */
+       kuid_t                  i_uid;
+       kgid_t                  i_gid;
+       u64                     i_version;
+/*
+       loff_t                  i_size;
+       blkcnt_t                i_blocks;
+*/
+       umode_t                 i_mode;
+};
+
+static void au_iattr_save(struct au_iattr *ia, struct inode *h_inode)
+{
+       ia->i_ino = h_inode->i_ino;
+       /* ia->i_nlink = h_inode->i_nlink; */
+       ia->i_uid = h_inode->i_uid;
+       ia->i_gid = h_inode->i_gid;
+       ia->i_version = inode_query_iversion(h_inode);
+/*
+       ia->i_size = h_inode->i_size;
+       ia->i_blocks = h_inode->i_blocks;
+*/
+       ia->i_mode = (h_inode->i_mode & S_IFMT);
+}
+
+static int au_iattr_test(struct au_iattr *ia, struct inode *h_inode)
+{
+       return ia->i_ino != h_inode->i_ino
+               /* || ia->i_nlink != h_inode->i_nlink */
+               || !uid_eq(ia->i_uid, h_inode->i_uid)
+               || !gid_eq(ia->i_gid, h_inode->i_gid)
+               || !inode_eq_iversion(h_inode, ia->i_version)
+/*
+               || ia->i_size != h_inode->i_size
+               || ia->i_blocks != h_inode->i_blocks
+*/
+               || ia->i_mode != (h_inode->i_mode & S_IFMT);
+}
+
+static int au_h_verify_dentry(struct dentry *h_dentry, struct dentry *h_parent,
+                             struct au_branch *br)
+{
+       int err;
+       struct au_iattr ia;
+       struct inode *h_inode;
+       struct dentry *h_d;
+       struct super_block *h_sb;
+       struct path h_ppath;
+
+       err = 0;
+       memset(&ia, -1, sizeof(ia));
+       h_sb = h_dentry->d_sb;
+       h_inode = NULL;
+       if (d_is_positive(h_dentry)) {
+               h_inode = d_inode(h_dentry);
+               au_iattr_save(&ia, h_inode);
+       } else if (au_test_nfs(h_sb) || au_test_fuse(h_sb))
+               /* nfs d_revalidate may return 0 for negative dentry */
+               /* fuse d_revalidate always return 0 for negative dentry */
+               goto out;
+
+       /* main purpose is namei.c:cached_lookup() and d_revalidate */
+       h_ppath.dentry = h_parent;
+       h_ppath.mnt = au_br_mnt(br);
+       h_d = vfsub_lkup_one(&h_dentry->d_name, &h_ppath);
+       err = PTR_ERR(h_d);
+       if (IS_ERR(h_d))
+               goto out;
+
+       err = 0;
+       if (unlikely(h_d != h_dentry
+                    || d_inode(h_d) != h_inode
+                    || (h_inode && au_iattr_test(&ia, h_inode))))
+               err = au_busy_or_stale();
+       dput(h_d);
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+int au_h_verify(struct dentry *h_dentry, unsigned int udba, struct inode *h_dir,
+               struct dentry *h_parent, struct au_branch *br)
+{
+       int err;
+
+       err = 0;
+       if (udba == AuOpt_UDBA_REVAL
+           && !au_test_fs_remote(h_dentry->d_sb)) {
+               IMustLock(h_dir);
+               err = (d_inode(h_dentry->d_parent) != h_dir);
+       } else if (udba != AuOpt_UDBA_NONE)
+               err = au_h_verify_dentry(h_dentry, h_parent, br);
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_do_refresh_hdentry(struct dentry *dentry, struct dentry *parent)
+{
+       int err;
+       aufs_bindex_t new_bindex, bindex, bbot, bwh, bdiropq;
+       struct au_hdentry tmp, *p, *q;
+       struct au_dinfo *dinfo;
+       struct super_block *sb;
+
+       DiMustWriteLock(dentry);
+
+       sb = dentry->d_sb;
+       dinfo = au_di(dentry);
+       bbot = dinfo->di_bbot;
+       bwh = dinfo->di_bwh;
+       bdiropq = dinfo->di_bdiropq;
+       bindex = dinfo->di_btop;
+       p = au_hdentry(dinfo, bindex);
+       for (; bindex <= bbot; bindex++, p++) {
+               if (!p->hd_dentry)
+                       continue;
+
+               new_bindex = au_br_index(sb, p->hd_id);
+               if (new_bindex == bindex)
+                       continue;
+
+               if (dinfo->di_bwh == bindex)
+                       bwh = new_bindex;
+               if (dinfo->di_bdiropq == bindex)
+                       bdiropq = new_bindex;
+               if (new_bindex < 0) {
+                       au_hdput(p);
+                       p->hd_dentry = NULL;
+                       continue;
+               }
+
+               /* swap two lower dentries, and loop again */
+               q = au_hdentry(dinfo, new_bindex);
+               tmp = *q;
+               *q = *p;
+               *p = tmp;
+               if (tmp.hd_dentry) {
+                       bindex--;
+                       p--;
+               }
+       }
+
+       dinfo->di_bwh = -1;
+       if (bwh >= 0 && bwh <= au_sbbot(sb) && au_sbr_whable(sb, bwh))
+               dinfo->di_bwh = bwh;
+
+       dinfo->di_bdiropq = -1;
+       if (bdiropq >= 0
+           && bdiropq <= au_sbbot(sb)
+           && au_sbr_whable(sb, bdiropq))
+               dinfo->di_bdiropq = bdiropq;
+
+       err = -EIO;
+       dinfo->di_btop = -1;
+       dinfo->di_bbot = -1;
+       bbot = au_dbbot(parent);
+       bindex = 0;
+       p = au_hdentry(dinfo, bindex);
+       for (; bindex <= bbot; bindex++, p++)
+               if (p->hd_dentry) {
+                       dinfo->di_btop = bindex;
+                       break;
+               }
+
+       if (dinfo->di_btop >= 0) {
+               bindex = bbot;
+               p = au_hdentry(dinfo, bindex);
+               for (; bindex >= 0; bindex--, p--)
+                       if (p->hd_dentry) {
+                               dinfo->di_bbot = bindex;
+                               err = 0;
+                               break;
+                       }
+       }
+
+       return err;
+}
+
+static void au_do_hide(struct dentry *dentry)
+{
+       struct inode *inode;
+
+       if (d_really_is_positive(dentry)) {
+               inode = d_inode(dentry);
+               if (!d_is_dir(dentry)) {
+                       if (inode->i_nlink && !d_unhashed(dentry))
+                               drop_nlink(inode);
+               } else {
+                       clear_nlink(inode);
+                       /* stop next lookup */
+                       inode->i_flags |= S_DEAD;
+               }
+               smp_mb(); /* necessary? */
+       }
+       d_drop(dentry);
+}
+
+static int au_hide_children(struct dentry *parent)
+{
+       int err, i, j, ndentry;
+       struct au_dcsub_pages dpages;
+       struct au_dpage *dpage;
+       struct dentry *dentry;
+
+       err = au_dpages_init(&dpages, GFP_NOFS);
+       if (unlikely(err))
+               goto out;
+       err = au_dcsub_pages(&dpages, parent, NULL, NULL);
+       if (unlikely(err))
+               goto out_dpages;
+
+       /* in reverse order */
+       for (i = dpages.ndpage - 1; i >= 0; i--) {
+               dpage = dpages.dpages + i;
+               ndentry = dpage->ndentry;
+               for (j = ndentry - 1; j >= 0; j--) {
+                       dentry = dpage->dentries[j];
+                       if (dentry != parent)
+                               au_do_hide(dentry);
+               }
+       }
+
+out_dpages:
+       au_dpages_free(&dpages);
+out:
+       return err;
+}
+
+static void au_hide(struct dentry *dentry)
+{
+       int err;
+
+       AuDbgDentry(dentry);
+       if (d_is_dir(dentry)) {
+               /* shrink_dcache_parent(dentry); */
+               err = au_hide_children(dentry);
+               if (unlikely(err))
+                       AuIOErr("%pd, failed hiding children, ignored %d\n",
+                               dentry, err);
+       }
+       au_do_hide(dentry);
+}
+
+/*
+ * By adding a dirty branch, a cached dentry may be affected in various ways.
+ *
+ * a dirty branch is added
+ * - on the top of layers
+ * - in the middle of layers
+ * - to the bottom of layers
+ *
+ * on the added branch there exists
+ * - a whiteout
+ * - a diropq
+ * - a same named entry
+ *   + exist
+ *     * negative --> positive
+ *     * positive --> positive
+ *      - type is unchanged
+ *      - type is changed
+ *   + doesn't exist
+ *     * negative --> negative
+ *     * positive --> negative (rejected by au_br_del() for non-dir case)
+ * - none
+ */
+static int au_refresh_by_dinfo(struct dentry *dentry, struct au_dinfo *dinfo,
+                              struct au_dinfo *tmp)
+{
+       int err;
+       aufs_bindex_t bindex, bbot;
+       struct {
+               struct dentry *dentry;
+               struct inode *inode;
+               mode_t mode;
+       } orig_h, tmp_h = {
+               .dentry = NULL
+       };
+       struct au_hdentry *hd;
+       struct inode *inode, *h_inode;
+       struct dentry *h_dentry;
+
+       err = 0;
+       AuDebugOn(dinfo->di_btop < 0);
+       orig_h.mode = 0;
+       orig_h.dentry = au_hdentry(dinfo, dinfo->di_btop)->hd_dentry;
+       orig_h.inode = NULL;
+       if (d_is_positive(orig_h.dentry)) {
+               orig_h.inode = d_inode(orig_h.dentry);
+               orig_h.mode = orig_h.inode->i_mode & S_IFMT;
+       }
+       if (tmp->di_btop >= 0) {
+               tmp_h.dentry = au_hdentry(tmp, tmp->di_btop)->hd_dentry;
+               if (d_is_positive(tmp_h.dentry)) {
+                       tmp_h.inode = d_inode(tmp_h.dentry);
+                       tmp_h.mode = tmp_h.inode->i_mode & S_IFMT;
+               }
+       }
+
+       inode = NULL;
+       if (d_really_is_positive(dentry))
+               inode = d_inode(dentry);
+       if (!orig_h.inode) {
+               AuDbg("negative originally\n");
+               if (inode) {
+                       au_hide(dentry);
+                       goto out;
+               }
+               AuDebugOn(inode);
+               AuDebugOn(dinfo->di_btop != dinfo->di_bbot);
+               AuDebugOn(dinfo->di_bdiropq != -1);
+
+               if (!tmp_h.inode) {
+                       AuDbg("negative --> negative\n");
+                       /* should have only one negative lower */
+                       if (tmp->di_btop >= 0
+                           && tmp->di_btop < dinfo->di_btop) {
+                               AuDebugOn(tmp->di_btop != tmp->di_bbot);
+                               AuDebugOn(dinfo->di_btop != dinfo->di_bbot);
+                               au_set_h_dptr(dentry, dinfo->di_btop, NULL);
+                               au_di_cp(dinfo, tmp);
+                               hd = au_hdentry(tmp, tmp->di_btop);
+                               au_set_h_dptr(dentry, tmp->di_btop,
+                                             dget(hd->hd_dentry));
+                       }
+                       au_dbg_verify_dinode(dentry);
+               } else {
+                       AuDbg("negative --> positive\n");
+                       /*
+                        * similar to the behaviour of creating with bypassing
+                        * aufs.
+                        * unhash it in order to force an error in the
+                        * succeeding create operation.
+                        * we should not set S_DEAD here.
+                        */
+                       d_drop(dentry);
+                       /* au_di_swap(tmp, dinfo); */
+                       au_dbg_verify_dinode(dentry);
+               }
+       } else {
+               AuDbg("positive originally\n");
+               /* inode may be NULL */
+               AuDebugOn(inode && (inode->i_mode & S_IFMT) != orig_h.mode);
+               if (!tmp_h.inode) {
+                       AuDbg("positive --> negative\n");
+                       /* or bypassing aufs */
+                       au_hide(dentry);
+                       if (tmp->di_bwh >= 0 && tmp->di_bwh <= dinfo->di_btop)
+                               dinfo->di_bwh = tmp->di_bwh;
+                       if (inode)
+                               err = au_refresh_hinode_self(inode);
+                       au_dbg_verify_dinode(dentry);
+               } else if (orig_h.mode == tmp_h.mode) {
+                       AuDbg("positive --> positive, same type\n");
+                       if (!S_ISDIR(orig_h.mode)
+                           && dinfo->di_btop > tmp->di_btop) {
+                               /*
+                                * similar to the behaviour of removing and
+                                * creating.
+                                */
+                               au_hide(dentry);
+                               if (inode)
+                                       err = au_refresh_hinode_self(inode);
+                               au_dbg_verify_dinode(dentry);
+                       } else {
+                               /* fill empty slots */
+                               if (dinfo->di_btop > tmp->di_btop)
+                                       dinfo->di_btop = tmp->di_btop;
+                               if (dinfo->di_bbot < tmp->di_bbot)
+                                       dinfo->di_bbot = tmp->di_bbot;
+                               dinfo->di_bwh = tmp->di_bwh;
+                               dinfo->di_bdiropq = tmp->di_bdiropq;
+                               bbot = dinfo->di_bbot;
+                               bindex = tmp->di_btop;
+                               hd = au_hdentry(tmp, bindex);
+                               for (; bindex <= bbot; bindex++, hd++) {
+                                       if (au_h_dptr(dentry, bindex))
+                                               continue;
+                                       h_dentry = hd->hd_dentry;
+                                       if (!h_dentry)
+                                               continue;
+                                       AuDebugOn(d_is_negative(h_dentry));
+                                       h_inode = d_inode(h_dentry);
+                                       AuDebugOn(orig_h.mode
+                                                 != (h_inode->i_mode
+                                                     & S_IFMT));
+                                       au_set_h_dptr(dentry, bindex,
+                                                     dget(h_dentry));
+                               }
+                               if (inode)
+                                       err = au_refresh_hinode(inode, dentry);
+                               au_dbg_verify_dinode(dentry);
+                       }
+               } else {
+                       AuDbg("positive --> positive, different type\n");
+                       /* similar to the behaviour of removing and creating */
+                       au_hide(dentry);
+                       if (inode)
+                               err = au_refresh_hinode_self(inode);
+                       au_dbg_verify_dinode(dentry);
+               }
+       }
+
+out:
+       return err;
+}
+
+void au_refresh_dop(struct dentry *dentry, int force_reval)
+{
+       const struct dentry_operations *dop
+               = force_reval ? &aufs_dop : dentry->d_sb->s_d_op;
+       static const unsigned int mask
+               = DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE;
+
+       BUILD_BUG_ON(sizeof(mask) != sizeof(dentry->d_flags));
+
+       if (dentry->d_op == dop)
+               return;
+
+       AuDbg("%pd\n", dentry);
+       spin_lock(&dentry->d_lock);
+       if (dop == &aufs_dop)
+               dentry->d_flags |= mask;
+       else
+               dentry->d_flags &= ~mask;
+       dentry->d_op = dop;
+       spin_unlock(&dentry->d_lock);
+}
+
+int au_refresh_dentry(struct dentry *dentry, struct dentry *parent)
+{
+       int err, ebrange, nbr;
+       unsigned int sigen;
+       struct au_dinfo *dinfo, *tmp;
+       struct super_block *sb;
+       struct inode *inode;
+
+       DiMustWriteLock(dentry);
+       AuDebugOn(IS_ROOT(dentry));
+       AuDebugOn(d_really_is_negative(parent));
+
+       sb = dentry->d_sb;
+       sigen = au_sigen(sb);
+       err = au_digen_test(parent, sigen);
+       if (unlikely(err))
+               goto out;
+
+       nbr = au_sbbot(sb) + 1;
+       dinfo = au_di(dentry);
+       err = au_di_realloc(dinfo, nbr, /*may_shrink*/0);
+       if (unlikely(err))
+               goto out;
+       ebrange = au_dbrange_test(dentry);
+       if (!ebrange)
+               ebrange = au_do_refresh_hdentry(dentry, parent);
+
+       if (d_unhashed(dentry) || ebrange /* || dinfo->di_tmpfile */) {
+               AuDebugOn(au_dbtop(dentry) < 0 && au_dbbot(dentry) >= 0);
+               if (d_really_is_positive(dentry)) {
+                       inode = d_inode(dentry);
+                       err = au_refresh_hinode_self(inode);
+               }
+               au_dbg_verify_dinode(dentry);
+               if (!err)
+                       goto out_dgen; /* success */
+               goto out;
+       }
+
+       /* temporary dinfo */
+       AuDbgDentry(dentry);
+       err = -ENOMEM;
+       tmp = au_di_alloc(sb, AuLsc_DI_TMP);
+       if (unlikely(!tmp))
+               goto out;
+       au_di_swap(tmp, dinfo);
+       /* returns the number of positive dentries */
+       /*
+        * if current working dir is removed, it returns an error.
+        * but the dentry is legal.
+        */
+       err = au_lkup_dentry(dentry, /*btop*/0, AuLkup_ALLOW_NEG);
+       AuDbgDentry(dentry);
+       au_di_swap(tmp, dinfo);
+       if (err == -ENOENT)
+               err = 0;
+       if (err >= 0) {
+               /* compare/refresh by dinfo */
+               AuDbgDentry(dentry);
+               err = au_refresh_by_dinfo(dentry, dinfo, tmp);
+               au_dbg_verify_dinode(dentry);
+               AuTraceErr(err);
+       }
+       au_di_realloc(dinfo, nbr, /*may_shrink*/1); /* harmless if err */
+       au_rw_write_unlock(&tmp->di_rwsem);
+       au_di_free(tmp);
+       if (unlikely(err))
+               goto out;
+
+out_dgen:
+       au_update_digen(dentry);
+out:
+       if (unlikely(err && !(dentry->d_flags & DCACHE_NFSFS_RENAMED))) {
+               AuIOErr("failed refreshing %pd, %d\n", dentry, err);
+               AuDbgDentry(dentry);
+       }
+       AuTraceErr(err);
+       return err;
+}
+
+static int au_do_h_d_reval(struct dentry *h_dentry, unsigned int flags,
+                          struct dentry *dentry, aufs_bindex_t bindex)
+{
+       int err, valid;
+
+       err = 0;
+       if (!(h_dentry->d_flags & DCACHE_OP_REVALIDATE))
+               goto out;
+
+       AuDbg("b%d\n", bindex);
+       /*
+        * gave up supporting LOOKUP_CREATE/OPEN for lower fs,
+        * due to whiteout and branch permission.
+        */
+       flags &= ~(/*LOOKUP_PARENT |*/ LOOKUP_OPEN | LOOKUP_CREATE
+                  | LOOKUP_FOLLOW | LOOKUP_EXCL);
+       /* it may return tri-state */
+       valid = h_dentry->d_op->d_revalidate(h_dentry, flags);
+
+       if (unlikely(valid < 0))
+               err = valid;
+       else if (!valid)
+               err = -EINVAL;
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/* todo: remove this */
+static int h_d_revalidate(struct dentry *dentry, struct inode *inode,
+                         unsigned int flags, int do_udba, int dirren)
+{
+       int err;
+       umode_t mode, h_mode;
+       aufs_bindex_t bindex, btail, btop, ibs, ibe;
+       unsigned char plus, unhashed, is_root, h_plus, h_nfs, tmpfile;
+       struct inode *h_inode, *h_cached_inode;
+       struct dentry *h_dentry;
+       struct qstr *name, *h_name;
+
+       err = 0;
+       plus = 0;
+       mode = 0;
+       ibs = -1;
+       ibe = -1;
+       unhashed = !!d_unhashed(dentry);
+       is_root = !!IS_ROOT(dentry);
+       name = &dentry->d_name;
+       tmpfile = au_di(dentry)->di_tmpfile;
+
+       /*
+        * Theoretically, REVAL test should be unnecessary in case of
+        * {FS,I}NOTIFY.
+        * But {fs,i}notify doesn't fire some necessary events,
+        *      IN_ATTRIB for atime/nlink/pageio
+        * Let's do REVAL test too.
+        */
+       if (do_udba && inode) {
+               mode = (inode->i_mode & S_IFMT);
+               plus = (inode->i_nlink > 0);
+               ibs = au_ibtop(inode);
+               ibe = au_ibbot(inode);
+       }
+
+       btop = au_dbtop(dentry);
+       btail = btop;
+       if (inode && S_ISDIR(inode->i_mode))
+               btail = au_dbtaildir(dentry);
+       for (bindex = btop; bindex <= btail; bindex++) {
+               h_dentry = au_h_dptr(dentry, bindex);
+               if (!h_dentry)
+                       continue;
+
+               AuDbg("b%d, %pd\n", bindex, h_dentry);
+               h_nfs = !!au_test_nfs(h_dentry->d_sb);
+               spin_lock(&h_dentry->d_lock);
+               h_name = &h_dentry->d_name;
+               if (unlikely(do_udba
+                            && !is_root
+                            && ((!h_nfs
+                                 && (unhashed != !!d_unhashed(h_dentry)
+                                     || (!tmpfile && !dirren
+                                         && !au_qstreq(name, h_name))
+                                         ))
+                                || (h_nfs
+                                    && !(flags & LOOKUP_OPEN)
+                                    && (h_dentry->d_flags
+                                        & DCACHE_NFSFS_RENAMED)))
+                           )) {
+                       int h_unhashed;
+
+                       h_unhashed = d_unhashed(h_dentry);
+                       spin_unlock(&h_dentry->d_lock);
+                       AuDbg("unhash 0x%x 0x%x, %pd %pd\n",
+                             unhashed, h_unhashed, dentry, h_dentry);
+                       goto err;
+               }
+               spin_unlock(&h_dentry->d_lock);
+
+               err = au_do_h_d_reval(h_dentry, flags, dentry, bindex);
+               if (unlikely(err))
+                       /* do not goto err, to keep the errno */
+                       break;
+
+               /* todo: plink too? */
+               if (!do_udba)
+                       continue;
+
+               /* UDBA tests */
+               if (unlikely(!!inode != d_is_positive(h_dentry)))
+                       goto err;
+
+               h_inode = NULL;
+               if (d_is_positive(h_dentry))
+                       h_inode = d_inode(h_dentry);
+               h_plus = plus;
+               h_mode = mode;
+               h_cached_inode = h_inode;
+               if (h_inode) {
+                       h_mode = (h_inode->i_mode & S_IFMT);
+                       h_plus = (h_inode->i_nlink > 0);
+               }
+               if (inode && ibs <= bindex && bindex <= ibe)
+                       h_cached_inode = au_h_iptr(inode, bindex);
+
+               if (!h_nfs) {
+                       if (unlikely(plus != h_plus && !tmpfile))
+                               goto err;
+               } else {
+                       if (unlikely(!(h_dentry->d_flags & DCACHE_NFSFS_RENAMED)
+                                    && !is_root
+                                    && !IS_ROOT(h_dentry)
+                                    && unhashed != d_unhashed(h_dentry)))
+                               goto err;
+               }
+               if (unlikely(mode != h_mode
+                            || h_cached_inode != h_inode))
+                       goto err;
+               continue;
+
+err:
+               err = -EINVAL;
+               break;
+       }
+
+       AuTraceErr(err);
+       return err;
+}
+
+/* todo: consolidate with do_refresh() and au_reval_for_attr() */
+static int simple_reval_dpath(struct dentry *dentry, unsigned int sigen)
+{
+       int err;
+       struct dentry *parent;
+
+       if (!au_digen_test(dentry, sigen))
+               return 0;
+
+       parent = dget_parent(dentry);
+       di_read_lock_parent(parent, AuLock_IR);
+       AuDebugOn(au_digen_test(parent, sigen));
+       au_dbg_verify_gen(parent, sigen);
+       err = au_refresh_dentry(dentry, parent);
+       di_read_unlock(parent, AuLock_IR);
+       dput(parent);
+       AuTraceErr(err);
+       return err;
+}
+
+int au_reval_dpath(struct dentry *dentry, unsigned int sigen)
+{
+       int err;
+       struct dentry *d, *parent;
+
+       if (!au_ftest_si(au_sbi(dentry->d_sb), FAILED_REFRESH_DIR))
+               return simple_reval_dpath(dentry, sigen);
+
+       /* slow loop, keep it simple and stupid */
+       /* cf: au_cpup_dirs() */
+       err = 0;
+       parent = NULL;
+       while (au_digen_test(dentry, sigen)) {
+               d = dentry;
+               while (1) {
+                       dput(parent);
+                       parent = dget_parent(d);
+                       if (!au_digen_test(parent, sigen))
+                               break;
+                       d = parent;
+               }
+
+               if (d != dentry)
+                       di_write_lock_child2(d);
+
+               /* someone might update our dentry while we were sleeping */
+               if (au_digen_test(d, sigen)) {
+                       /*
+                        * todo: consolidate with simple_reval_dpath(),
+                        * do_refresh() and au_reval_for_attr().
+                        */
+                       di_read_lock_parent(parent, AuLock_IR);
+                       err = au_refresh_dentry(d, parent);
+                       di_read_unlock(parent, AuLock_IR);
+               }
+
+               if (d != dentry)
+                       di_write_unlock(d);
+               dput(parent);
+               if (unlikely(err))
+                       break;
+       }
+
+       return err;
+}
+
+/*
+ * if valid returns 1, otherwise 0.
+ */
+static int aufs_d_revalidate(struct dentry *dentry, unsigned int flags)
+{
+       int valid, err;
+       unsigned int sigen;
+       unsigned char do_udba, dirren;
+       struct super_block *sb;
+       struct inode *inode;
+
+       /* todo: support rcu-walk? */
+       if (flags & LOOKUP_RCU)
+               return -ECHILD;
+
+       valid = 0;
+       if (unlikely(!au_di(dentry)))
+               goto out;
+
+       valid = 1;
+       sb = dentry->d_sb;
+       /*
+        * todo: very ugly
+        * i_mutex of parent dir may be held,
+        * but we should not return 'invalid' due to busy.
+        */
+       err = aufs_read_lock(dentry, AuLock_FLUSH | AuLock_DW | AuLock_NOPLM);
+       if (unlikely(err)) {
+               valid = err;
+               AuTraceErr(err);
+               goto out;
+       }
+       inode = NULL;
+       if (d_really_is_positive(dentry))
+               inode = d_inode(dentry);
+       if (unlikely(inode && au_is_bad_inode(inode))) {
+               err = -EINVAL;
+               AuTraceErr(err);
+               goto out_dgrade;
+       }
+       if (unlikely(au_dbrange_test(dentry))) {
+               err = -EINVAL;
+               AuTraceErr(err);
+               goto out_dgrade;
+       }
+
+       sigen = au_sigen(sb);
+       if (au_digen_test(dentry, sigen)) {
+               AuDebugOn(IS_ROOT(dentry));
+               err = au_reval_dpath(dentry, sigen);
+               if (unlikely(err)) {
+                       AuTraceErr(err);
+                       goto out_dgrade;
+               }
+       }
+       di_downgrade_lock(dentry, AuLock_IR);
+
+       err = -EINVAL;
+       if (!(flags & (LOOKUP_OPEN | LOOKUP_EMPTY))
+           && inode
+           && !(inode->i_state && I_LINKABLE)
+           && (IS_DEADDIR(inode) || !inode->i_nlink)) {
+               AuTraceErr(err);
+               goto out_inval;
+       }
+
+       do_udba = !au_opt_test(au_mntflags(sb), UDBA_NONE);
+       if (do_udba && inode) {
+               aufs_bindex_t btop = au_ibtop(inode);
+               struct inode *h_inode;
+
+               if (btop >= 0) {
+                       h_inode = au_h_iptr(inode, btop);
+                       if (h_inode && au_test_higen(inode, h_inode)) {
+                               AuTraceErr(err);
+                               goto out_inval;
+                       }
+               }
+       }
+
+       dirren = !!au_opt_test(au_mntflags(sb), DIRREN);
+       err = h_d_revalidate(dentry, inode, flags, do_udba, dirren);
+       if (unlikely(!err && do_udba && au_dbtop(dentry) < 0)) {
+               err = -EIO;
+               AuDbg("both of real entry and whiteout found, %p, err %d\n",
+                     dentry, err);
+       }
+       goto out_inval;
+
+out_dgrade:
+       di_downgrade_lock(dentry, AuLock_IR);
+out_inval:
+       aufs_read_unlock(dentry, AuLock_IR);
+       AuTraceErr(err);
+       valid = !err;
+out:
+       if (!valid) {
+               AuDbg("%pd invalid, %d\n", dentry, valid);
+               d_drop(dentry);
+       }
+       return valid;
+}
+
+static void aufs_d_release(struct dentry *dentry)
+{
+       if (au_di(dentry)) {
+               au_di_fin(dentry);
+               au_hn_di_reinit(dentry);
+       }
+}
+
+const struct dentry_operations aufs_dop = {
+       .d_revalidate           = aufs_d_revalidate,
+       .d_weak_revalidate      = aufs_d_revalidate,
+       .d_release              = aufs_d_release
+};
+
+/* aufs_dop without d_revalidate */
+const struct dentry_operations aufs_dop_noreval = {
+       .d_release              = aufs_d_release
+};
diff -urN /usr/share/empty/fs/aufs/dentry.h linux/fs/aufs/dentry.h
--- /usr/share/empty/fs/aufs/dentry.h   1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/dentry.h      2021-12-03 15:40:58.233313963 +0100
@@ -0,0 +1,269 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * lookup and dentry operations
+ */
+
+#ifndef __AUFS_DENTRY_H__
+#define __AUFS_DENTRY_H__
+
+#ifdef __KERNEL__
+
+#include <linux/dcache.h>
+#include "dirren.h"
+#include "rwsem.h"
+
+struct au_hdentry {
+       struct dentry           *hd_dentry;
+       aufs_bindex_t           hd_id;
+};
+
+struct au_dinfo {
+       atomic_t                di_generation;
+
+       struct au_rwsem         di_rwsem;
+       aufs_bindex_t           di_btop, di_bbot, di_bwh, di_bdiropq;
+       unsigned char           di_tmpfile; /* to allow the different name */
+       struct au_hdentry       *di_hdentry;
+       struct rcu_head         rcu;
+} ____cacheline_aligned_in_smp;
+
+/* ---------------------------------------------------------------------- */
+
+/* flags for au_lkup_dentry() */
+#define AuLkup_ALLOW_NEG       1
+#define AuLkup_IGNORE_PERM     (1 << 1)
+#define AuLkup_DIRREN          (1 << 2)
+#define au_ftest_lkup(flags, name)     ((flags) & AuLkup_##name)
+#define au_fset_lkup(flags, name) \
+       do { (flags) |= AuLkup_##name; } while (0)
+#define au_fclr_lkup(flags, name) \
+       do { (flags) &= ~AuLkup_##name; } while (0)
+
+#ifndef CONFIG_AUFS_DIRREN
+#undef AuLkup_DIRREN
+#define AuLkup_DIRREN 0
+#endif
+
+struct au_do_lookup_args {
+       unsigned int            flags;
+       mode_t                  type;
+       struct qstr             whname, *name;
+       struct au_dr_lookup     dirren;
+};
+
+/* ---------------------------------------------------------------------- */
+
+/* dentry.c */
+extern const struct dentry_operations aufs_dop, aufs_dop_noreval;
+struct au_branch;
+struct dentry *au_sio_lkup_one(struct user_namespace *userns, struct qstr *name,
+                              struct path *ppath);
+int au_h_verify(struct dentry *h_dentry, unsigned int udba, struct inode *h_dir,
+               struct dentry *h_parent, struct au_branch *br);
+
+int au_lkup_dentry(struct dentry *dentry, aufs_bindex_t btop,
+                  unsigned int flags);
+int au_lkup_neg(struct dentry *dentry, aufs_bindex_t bindex, int wh);
+int au_refresh_dentry(struct dentry *dentry, struct dentry *parent);
+int au_reval_dpath(struct dentry *dentry, unsigned int sigen);
+void au_refresh_dop(struct dentry *dentry, int force_reval);
+
+/* dinfo.c */
+void au_di_init_once(void *_di);
+struct au_dinfo *au_di_alloc(struct super_block *sb, unsigned int lsc);
+void au_di_free(struct au_dinfo *dinfo);
+void au_di_swap(struct au_dinfo *a, struct au_dinfo *b);
+void au_di_cp(struct au_dinfo *dst, struct au_dinfo *src);
+int au_di_init(struct dentry *dentry);
+void au_di_fin(struct dentry *dentry);
+int au_di_realloc(struct au_dinfo *dinfo, int nbr, int may_shrink);
+
+void di_read_lock(struct dentry *d, int flags, unsigned int lsc);
+void di_read_unlock(struct dentry *d, int flags);
+void di_downgrade_lock(struct dentry *d, int flags);
+void di_write_lock(struct dentry *d, unsigned int lsc);
+void di_write_unlock(struct dentry *d);
+void di_write_lock2_child(struct dentry *d1, struct dentry *d2, int isdir);
+void di_write_lock2_parent(struct dentry *d1, struct dentry *d2, int isdir);
+void di_write_unlock2(struct dentry *d1, struct dentry *d2);
+
+struct dentry *au_h_dptr(struct dentry *dentry, aufs_bindex_t bindex);
+struct dentry *au_h_d_alias(struct dentry *dentry, aufs_bindex_t bindex);
+aufs_bindex_t au_dbtail(struct dentry *dentry);
+aufs_bindex_t au_dbtaildir(struct dentry *dentry);
+
+void au_set_h_dptr(struct dentry *dentry, aufs_bindex_t bindex,
+                  struct dentry *h_dentry);
+int au_digen_test(struct dentry *dentry, unsigned int sigen);
+int au_dbrange_test(struct dentry *dentry);
+void au_update_digen(struct dentry *dentry);
+void au_update_dbrange(struct dentry *dentry, int do_put_zero);
+void au_update_dbtop(struct dentry *dentry);
+void au_update_dbbot(struct dentry *dentry);
+int au_find_dbindex(struct dentry *dentry, struct dentry *h_dentry);
+
+/* ---------------------------------------------------------------------- */
+
+static inline struct au_dinfo *au_di(struct dentry *dentry)
+{
+       return dentry->d_fsdata;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* lock subclass for dinfo */
+enum {
+       AuLsc_DI_CHILD,         /* child first */
+       AuLsc_DI_CHILD2,        /* rename(2), link(2), and cpup at hnotify */
+       AuLsc_DI_CHILD3,        /* copyup dirs */
+       AuLsc_DI_PARENT,
+       AuLsc_DI_PARENT2,
+       AuLsc_DI_PARENT3,
+       AuLsc_DI_TMP            /* temp for replacing dinfo */
+};
+
+/*
+ * di_read_lock_child, di_write_lock_child,
+ * di_read_lock_child2, di_write_lock_child2,
+ * di_read_lock_child3, di_write_lock_child3,
+ * di_read_lock_parent, di_write_lock_parent,
+ * di_read_lock_parent2, di_write_lock_parent2,
+ * di_read_lock_parent3, di_write_lock_parent3,
+ */
+#define AuReadLockFunc(name, lsc) \
+static inline void di_read_lock_##name(struct dentry *d, int flags) \
+{ di_read_lock(d, flags, AuLsc_DI_##lsc); }
+
+#define AuWriteLockFunc(name, lsc) \
+static inline void di_write_lock_##name(struct dentry *d) \
+{ di_write_lock(d, AuLsc_DI_##lsc); }
+
+#define AuRWLockFuncs(name, lsc) \
+       AuReadLockFunc(name, lsc) \
+       AuWriteLockFunc(name, lsc)
+
+AuRWLockFuncs(child, CHILD);
+AuRWLockFuncs(child2, CHILD2);
+AuRWLockFuncs(child3, CHILD3);
+AuRWLockFuncs(parent, PARENT);
+AuRWLockFuncs(parent2, PARENT2);
+AuRWLockFuncs(parent3, PARENT3);
+
+#undef AuReadLockFunc
+#undef AuWriteLockFunc
+#undef AuRWLockFuncs
+
+#define DiMustNoWaiters(d)     AuRwMustNoWaiters(&au_di(d)->di_rwsem)
+#define DiMustAnyLock(d)       AuRwMustAnyLock(&au_di(d)->di_rwsem)
+#define DiMustWriteLock(d)     AuRwMustWriteLock(&au_di(d)->di_rwsem)
+
+/* ---------------------------------------------------------------------- */
+
+/* todo: memory barrier? */
+static inline unsigned int au_digen(struct dentry *d)
+{
+       return atomic_read(&au_di(d)->di_generation);
+}
+
+static inline void au_h_dentry_init(struct au_hdentry *hdentry)
+{
+       hdentry->hd_dentry = NULL;
+}
+
+static inline struct au_hdentry *au_hdentry(struct au_dinfo *di,
+                                           aufs_bindex_t bindex)
+{
+       return di->di_hdentry + bindex;
+}
+
+static inline void au_hdput(struct au_hdentry *hd)
+{
+       if (hd)
+               dput(hd->hd_dentry);
+}
+
+static inline aufs_bindex_t au_dbtop(struct dentry *dentry)
+{
+       DiMustAnyLock(dentry);
+       return au_di(dentry)->di_btop;
+}
+
+static inline aufs_bindex_t au_dbbot(struct dentry *dentry)
+{
+       DiMustAnyLock(dentry);
+       return au_di(dentry)->di_bbot;
+}
+
+static inline aufs_bindex_t au_dbwh(struct dentry *dentry)
+{
+       DiMustAnyLock(dentry);
+       return au_di(dentry)->di_bwh;
+}
+
+static inline aufs_bindex_t au_dbdiropq(struct dentry *dentry)
+{
+       DiMustAnyLock(dentry);
+       return au_di(dentry)->di_bdiropq;
+}
+
+/* todo: hard/soft set? */
+static inline void au_set_dbtop(struct dentry *dentry, aufs_bindex_t bindex)
+{
+       DiMustWriteLock(dentry);
+       au_di(dentry)->di_btop = bindex;
+}
+
+static inline void au_set_dbbot(struct dentry *dentry, aufs_bindex_t bindex)
+{
+       DiMustWriteLock(dentry);
+       au_di(dentry)->di_bbot = bindex;
+}
+
+static inline void au_set_dbwh(struct dentry *dentry, aufs_bindex_t bindex)
+{
+       DiMustWriteLock(dentry);
+       /* dbwh can be outside of btop - bbot range */
+       au_di(dentry)->di_bwh = bindex;
+}
+
+static inline void au_set_dbdiropq(struct dentry *dentry, aufs_bindex_t bindex)
+{
+       DiMustWriteLock(dentry);
+       au_di(dentry)->di_bdiropq = bindex;
+}
+
+/* ---------------------------------------------------------------------- */
+
+#ifdef CONFIG_AUFS_HNOTIFY
+static inline void au_digen_dec(struct dentry *d)
+{
+       atomic_dec(&au_di(d)->di_generation);
+}
+
+static inline void au_hn_di_reinit(struct dentry *dentry)
+{
+       dentry->d_fsdata = NULL;
+}
+#else
+AuStubVoid(au_hn_di_reinit, struct dentry *dentry __maybe_unused)
+#endif /* CONFIG_AUFS_HNOTIFY */
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_DENTRY_H__ */
diff -urN /usr/share/empty/fs/aufs/dinfo.c linux/fs/aufs/dinfo.c
--- /usr/share/empty/fs/aufs/dinfo.c    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/dinfo.c       2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,554 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * dentry private data
+ */
+
+#include "aufs.h"
+
+void au_di_init_once(void *_dinfo)
+{
+       struct au_dinfo *dinfo = _dinfo;
+
+       au_rw_init(&dinfo->di_rwsem);
+}
+
+struct au_dinfo *au_di_alloc(struct super_block *sb, unsigned int lsc)
+{
+       struct au_dinfo *dinfo;
+       int nbr, i;
+
+       dinfo = au_cache_alloc_dinfo();
+       if (unlikely(!dinfo))
+               goto out;
+
+       nbr = au_sbbot(sb) + 1;
+       if (nbr <= 0)
+               nbr = 1;
+       dinfo->di_hdentry = kcalloc(nbr, sizeof(*dinfo->di_hdentry), GFP_NOFS);
+       if (dinfo->di_hdentry) {
+               au_rw_write_lock_nested(&dinfo->di_rwsem, lsc);
+               dinfo->di_btop = -1;
+               dinfo->di_bbot = -1;
+               dinfo->di_bwh = -1;
+               dinfo->di_bdiropq = -1;
+               dinfo->di_tmpfile = 0;
+               for (i = 0; i < nbr; i++)
+                       dinfo->di_hdentry[i].hd_id = -1;
+               goto out;
+       }
+
+       au_cache_free_dinfo(dinfo);
+       dinfo = NULL;
+
+out:
+       return dinfo;
+}
+
+void au_di_free(struct au_dinfo *dinfo)
+{
+       struct au_hdentry *p;
+       aufs_bindex_t bbot, bindex;
+
+       /* dentry may not be revalidated */
+       bindex = dinfo->di_btop;
+       if (bindex >= 0) {
+               bbot = dinfo->di_bbot;
+               p = au_hdentry(dinfo, bindex);
+               while (bindex++ <= bbot)
+                       au_hdput(p++);
+       }
+       au_kfree_try_rcu(dinfo->di_hdentry);
+       au_cache_free_dinfo(dinfo);
+}
+
+void au_di_swap(struct au_dinfo *a, struct au_dinfo *b)
+{
+       struct au_hdentry *p;
+       aufs_bindex_t bi;
+
+       AuRwMustWriteLock(&a->di_rwsem);
+       AuRwMustWriteLock(&b->di_rwsem);
+
+#define DiSwap(v, name)                                \
+       do {                                    \
+               v = a->di_##name;               \
+               a->di_##name = b->di_##name;    \
+               b->di_##name = v;               \
+       } while (0)
+
+       DiSwap(p, hdentry);
+       DiSwap(bi, btop);
+       DiSwap(bi, bbot);
+       DiSwap(bi, bwh);
+       DiSwap(bi, bdiropq);
+       /* smp_mb(); */
+
+#undef DiSwap
+}
+
+void au_di_cp(struct au_dinfo *dst, struct au_dinfo *src)
+{
+       AuRwMustWriteLock(&dst->di_rwsem);
+       AuRwMustWriteLock(&src->di_rwsem);
+
+       dst->di_btop = src->di_btop;
+       dst->di_bbot = src->di_bbot;
+       dst->di_bwh = src->di_bwh;
+       dst->di_bdiropq = src->di_bdiropq;
+       /* smp_mb(); */
+}
+
+int au_di_init(struct dentry *dentry)
+{
+       int err;
+       struct super_block *sb;
+       struct au_dinfo *dinfo;
+
+       err = 0;
+       sb = dentry->d_sb;
+       dinfo = au_di_alloc(sb, AuLsc_DI_CHILD);
+       if (dinfo) {
+               atomic_set(&dinfo->di_generation, au_sigen(sb));
+               /* smp_mb(); */ /* atomic_set */
+               dentry->d_fsdata = dinfo;
+       } else
+               err = -ENOMEM;
+
+       return err;
+}
+
+void au_di_fin(struct dentry *dentry)
+{
+       struct au_dinfo *dinfo;
+
+       dinfo = au_di(dentry);
+       AuRwDestroy(&dinfo->di_rwsem);
+       au_di_free(dinfo);
+}
+
+int au_di_realloc(struct au_dinfo *dinfo, int nbr, int may_shrink)
+{
+       int err, sz;
+       struct au_hdentry *hdp;
+
+       AuRwMustWriteLock(&dinfo->di_rwsem);
+
+       err = -ENOMEM;
+       sz = sizeof(*hdp) * (dinfo->di_bbot + 1);
+       if (!sz)
+               sz = sizeof(*hdp);
+       hdp = au_kzrealloc(dinfo->di_hdentry, sz, sizeof(*hdp) * nbr, GFP_NOFS,
+                          may_shrink);
+       if (hdp) {
+               dinfo->di_hdentry = hdp;
+               err = 0;
+       }
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static void do_ii_write_lock(struct inode *inode, unsigned int lsc)
+{
+       switch (lsc) {
+       case AuLsc_DI_CHILD:
+               ii_write_lock_child(inode);
+               break;
+       case AuLsc_DI_CHILD2:
+               ii_write_lock_child2(inode);
+               break;
+       case AuLsc_DI_CHILD3:
+               ii_write_lock_child3(inode);
+               break;
+       case AuLsc_DI_PARENT:
+               ii_write_lock_parent(inode);
+               break;
+       case AuLsc_DI_PARENT2:
+               ii_write_lock_parent2(inode);
+               break;
+       case AuLsc_DI_PARENT3:
+               ii_write_lock_parent3(inode);
+               break;
+       default:
+               BUG();
+       }
+}
+
+static void do_ii_read_lock(struct inode *inode, unsigned int lsc)
+{
+       switch (lsc) {
+       case AuLsc_DI_CHILD:
+               ii_read_lock_child(inode);
+               break;
+       case AuLsc_DI_CHILD2:
+               ii_read_lock_child2(inode);
+               break;
+       case AuLsc_DI_CHILD3:
+               ii_read_lock_child3(inode);
+               break;
+       case AuLsc_DI_PARENT:
+               ii_read_lock_parent(inode);
+               break;
+       case AuLsc_DI_PARENT2:
+               ii_read_lock_parent2(inode);
+               break;
+       case AuLsc_DI_PARENT3:
+               ii_read_lock_parent3(inode);
+               break;
+       default:
+               BUG();
+       }
+}
+
+void di_read_lock(struct dentry *d, int flags, unsigned int lsc)
+{
+       struct inode *inode;
+
+       au_rw_read_lock_nested(&au_di(d)->di_rwsem, lsc);
+       if (d_really_is_positive(d)) {
+               inode = d_inode(d);
+               if (au_ftest_lock(flags, IW))
+                       do_ii_write_lock(inode, lsc);
+               else if (au_ftest_lock(flags, IR))
+                       do_ii_read_lock(inode, lsc);
+       }
+}
+
+void di_read_unlock(struct dentry *d, int flags)
+{
+       struct inode *inode;
+
+       if (d_really_is_positive(d)) {
+               inode = d_inode(d);
+               if (au_ftest_lock(flags, IW)) {
+                       au_dbg_verify_dinode(d);
+                       ii_write_unlock(inode);
+               } else if (au_ftest_lock(flags, IR)) {
+                       au_dbg_verify_dinode(d);
+                       ii_read_unlock(inode);
+               }
+       }
+       au_rw_read_unlock(&au_di(d)->di_rwsem);
+}
+
+void di_downgrade_lock(struct dentry *d, int flags)
+{
+       if (d_really_is_positive(d) && au_ftest_lock(flags, IR))
+               ii_downgrade_lock(d_inode(d));
+       au_rw_dgrade_lock(&au_di(d)->di_rwsem);
+}
+
+void di_write_lock(struct dentry *d, unsigned int lsc)
+{
+       au_rw_write_lock_nested(&au_di(d)->di_rwsem, lsc);
+       if (d_really_is_positive(d))
+               do_ii_write_lock(d_inode(d), lsc);
+}
+
+void di_write_unlock(struct dentry *d)
+{
+       au_dbg_verify_dinode(d);
+       if (d_really_is_positive(d))
+               ii_write_unlock(d_inode(d));
+       au_rw_write_unlock(&au_di(d)->di_rwsem);
+}
+
+void di_write_lock2_child(struct dentry *d1, struct dentry *d2, int isdir)
+{
+       AuDebugOn(d1 == d2
+                 || d_inode(d1) == d_inode(d2)
+                 || d1->d_sb != d2->d_sb);
+
+       if ((isdir && au_test_subdir(d1, d2))
+           || d1 < d2) {
+               di_write_lock_child(d1);
+               di_write_lock_child2(d2);
+       } else {
+               di_write_lock_child(d2);
+               di_write_lock_child2(d1);
+       }
+}
+
+void di_write_lock2_parent(struct dentry *d1, struct dentry *d2, int isdir)
+{
+       AuDebugOn(d1 == d2
+                 || d_inode(d1) == d_inode(d2)
+                 || d1->d_sb != d2->d_sb);
+
+       if ((isdir && au_test_subdir(d1, d2))
+           || d1 < d2) {
+               di_write_lock_parent(d1);
+               di_write_lock_parent2(d2);
+       } else {
+               di_write_lock_parent(d2);
+               di_write_lock_parent2(d1);
+       }
+}
+
+void di_write_unlock2(struct dentry *d1, struct dentry *d2)
+{
+       di_write_unlock(d1);
+       if (d_inode(d1) == d_inode(d2))
+               au_rw_write_unlock(&au_di(d2)->di_rwsem);
+       else
+               di_write_unlock(d2);
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct dentry *au_h_dptr(struct dentry *dentry, aufs_bindex_t bindex)
+{
+       struct dentry *d;
+
+       DiMustAnyLock(dentry);
+
+       if (au_dbtop(dentry) < 0 || bindex < au_dbtop(dentry))
+               return NULL;
+       AuDebugOn(bindex < 0);
+       d = au_hdentry(au_di(dentry), bindex)->hd_dentry;
+       AuDebugOn(d && au_dcount(d) <= 0);
+       return d;
+}
+
+/*
+ * extended version of au_h_dptr().
+ * returns a hashed and positive (or linkable) h_dentry in bindex, NULL, or
+ * error.
+ */
+struct dentry *au_h_d_alias(struct dentry *dentry, aufs_bindex_t bindex)
+{
+       struct dentry *h_dentry;
+       struct inode *inode, *h_inode;
+
+       AuDebugOn(d_really_is_negative(dentry));
+
+       h_dentry = NULL;
+       if (au_dbtop(dentry) <= bindex
+           && bindex <= au_dbbot(dentry))
+               h_dentry = au_h_dptr(dentry, bindex);
+       if (h_dentry && !au_d_linkable(h_dentry)) {
+               dget(h_dentry);
+               goto out; /* success */
+       }
+
+       inode = d_inode(dentry);
+       AuDebugOn(bindex < au_ibtop(inode));
+       AuDebugOn(au_ibbot(inode) < bindex);
+       h_inode = au_h_iptr(inode, bindex);
+       h_dentry = d_find_alias(h_inode);
+       if (h_dentry) {
+               if (!IS_ERR(h_dentry)) {
+                       if (!au_d_linkable(h_dentry))
+                               goto out; /* success */
+                       dput(h_dentry);
+               } else
+                       goto out;
+       }
+
+       if (au_opt_test(au_mntflags(dentry->d_sb), PLINK)) {
+               h_dentry = au_plink_lkup(inode, bindex);
+               AuDebugOn(!h_dentry);
+               if (!IS_ERR(h_dentry)) {
+                       if (!au_d_hashed_positive(h_dentry))
+                               goto out; /* success */
+                       dput(h_dentry);
+                       h_dentry = NULL;
+               }
+       }
+
+out:
+       AuDbgDentry(h_dentry);
+       return h_dentry;
+}
+
+aufs_bindex_t au_dbtail(struct dentry *dentry)
+{
+       aufs_bindex_t bbot, bwh;
+
+       bbot = au_dbbot(dentry);
+       if (0 <= bbot) {
+               bwh = au_dbwh(dentry);
+               if (!bwh)
+                       return bwh;
+               if (0 < bwh && bwh < bbot)
+                       return bwh - 1;
+       }
+       return bbot;
+}
+
+aufs_bindex_t au_dbtaildir(struct dentry *dentry)
+{
+       aufs_bindex_t bbot, bopq;
+
+       bbot = au_dbtail(dentry);
+       if (0 <= bbot) {
+               bopq = au_dbdiropq(dentry);
+               if (0 <= bopq && bopq < bbot)
+                       bbot = bopq;
+       }
+       return bbot;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void au_set_h_dptr(struct dentry *dentry, aufs_bindex_t bindex,
+                  struct dentry *h_dentry)
+{
+       struct au_dinfo *dinfo;
+       struct au_hdentry *hd;
+       struct au_branch *br;
+
+       DiMustWriteLock(dentry);
+
+       dinfo = au_di(dentry);
+       hd = au_hdentry(dinfo, bindex);
+       au_hdput(hd);
+       hd->hd_dentry = h_dentry;
+       if (h_dentry) {
+               br = au_sbr(dentry->d_sb, bindex);
+               hd->hd_id = br->br_id;
+       }
+}
+
+int au_dbrange_test(struct dentry *dentry)
+{
+       int err;
+       aufs_bindex_t btop, bbot;
+
+       err = 0;
+       btop = au_dbtop(dentry);
+       bbot = au_dbbot(dentry);
+       if (btop >= 0)
+               AuDebugOn(bbot < 0 && btop > bbot);
+       else {
+               err = -EIO;
+               AuDebugOn(bbot >= 0);
+       }
+
+       return err;
+}
+
+int au_digen_test(struct dentry *dentry, unsigned int sigen)
+{
+       int err;
+
+       err = 0;
+       if (unlikely(au_digen(dentry) != sigen
+                    || au_iigen_test(d_inode(dentry), sigen)))
+               err = -EIO;
+
+       return err;
+}
+
+void au_update_digen(struct dentry *dentry)
+{
+       atomic_set(&au_di(dentry)->di_generation, au_sigen(dentry->d_sb));
+       /* smp_mb(); */ /* atomic_set */
+}
+
+void au_update_dbrange(struct dentry *dentry, int do_put_zero)
+{
+       struct au_dinfo *dinfo;
+       struct dentry *h_d;
+       struct au_hdentry *hdp;
+       aufs_bindex_t bindex, bbot;
+
+       DiMustWriteLock(dentry);
+
+       dinfo = au_di(dentry);
+       if (!dinfo || dinfo->di_btop < 0)
+               return;
+
+       if (do_put_zero) {
+               bbot = dinfo->di_bbot;
+               bindex = dinfo->di_btop;
+               hdp = au_hdentry(dinfo, bindex);
+               for (; bindex <= bbot; bindex++, hdp++) {
+                       h_d = hdp->hd_dentry;
+                       if (h_d && d_is_negative(h_d))
+                               au_set_h_dptr(dentry, bindex, NULL);
+               }
+       }
+
+       dinfo->di_btop = 0;
+       hdp = au_hdentry(dinfo, dinfo->di_btop);
+       for (; dinfo->di_btop <= dinfo->di_bbot; dinfo->di_btop++, hdp++)
+               if (hdp->hd_dentry)
+                       break;
+       if (dinfo->di_btop > dinfo->di_bbot) {
+               dinfo->di_btop = -1;
+               dinfo->di_bbot = -1;
+               return;
+       }
+
+       hdp = au_hdentry(dinfo, dinfo->di_bbot);
+       for (; dinfo->di_bbot >= 0; dinfo->di_bbot--, hdp--)
+               if (hdp->hd_dentry)
+                       break;
+       AuDebugOn(dinfo->di_btop > dinfo->di_bbot || dinfo->di_bbot < 0);
+}
+
+void au_update_dbtop(struct dentry *dentry)
+{
+       aufs_bindex_t bindex, bbot;
+       struct dentry *h_dentry;
+
+       bbot = au_dbbot(dentry);
+       for (bindex = au_dbtop(dentry); bindex <= bbot; bindex++) {
+               h_dentry = au_h_dptr(dentry, bindex);
+               if (!h_dentry)
+                       continue;
+               if (d_is_positive(h_dentry)) {
+                       au_set_dbtop(dentry, bindex);
+                       return;
+               }
+               au_set_h_dptr(dentry, bindex, NULL);
+       }
+}
+
+void au_update_dbbot(struct dentry *dentry)
+{
+       aufs_bindex_t bindex, btop;
+       struct dentry *h_dentry;
+
+       btop = au_dbtop(dentry);
+       for (bindex = au_dbbot(dentry); bindex >= btop; bindex--) {
+               h_dentry = au_h_dptr(dentry, bindex);
+               if (!h_dentry)
+                       continue;
+               if (d_is_positive(h_dentry)) {
+                       au_set_dbbot(dentry, bindex);
+                       return;
+               }
+               au_set_h_dptr(dentry, bindex, NULL);
+       }
+}
+
+int au_find_dbindex(struct dentry *dentry, struct dentry *h_dentry)
+{
+       aufs_bindex_t bindex, bbot;
+
+       bbot = au_dbbot(dentry);
+       for (bindex = au_dbtop(dentry); bindex <= bbot; bindex++)
+               if (au_h_dptr(dentry, bindex) == h_dentry)
+                       return bindex;
+       return -1;
+}
diff -urN /usr/share/empty/fs/aufs/dir.c linux/fs/aufs/dir.c
--- /usr/share/empty/fs/aufs/dir.c      1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/dir.c 2021-12-03 15:40:58.233313963 +0100
@@ -0,0 +1,765 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * directory operations
+ */
+
+#include <linux/fs_stack.h>
+#include <linux/iversion.h>
+#include "aufs.h"
+
+void au_add_nlink(struct inode *dir, struct inode *h_dir)
+{
+       unsigned int nlink;
+
+       AuDebugOn(!S_ISDIR(dir->i_mode) || !S_ISDIR(h_dir->i_mode));
+
+       nlink = dir->i_nlink;
+       nlink += h_dir->i_nlink - 2;
+       if (h_dir->i_nlink < 2)
+               nlink += 2;
+       smp_mb(); /* for i_nlink */
+       /* 0 can happen in revaliding */
+       set_nlink(dir, nlink);
+}
+
+void au_sub_nlink(struct inode *dir, struct inode *h_dir)
+{
+       unsigned int nlink;
+
+       AuDebugOn(!S_ISDIR(dir->i_mode) || !S_ISDIR(h_dir->i_mode));
+
+       nlink = dir->i_nlink;
+       nlink -= h_dir->i_nlink - 2;
+       if (h_dir->i_nlink < 2)
+               nlink -= 2;
+       smp_mb(); /* for i_nlink */
+       /* nlink == 0 means the branch-fs is broken */
+       set_nlink(dir, nlink);
+}
+
+loff_t au_dir_size(struct file *file, struct dentry *dentry)
+{
+       loff_t sz;
+       aufs_bindex_t bindex, bbot;
+       struct file *h_file;
+       struct dentry *h_dentry;
+
+       sz = 0;
+       if (file) {
+               AuDebugOn(!d_is_dir(file->f_path.dentry));
+
+               bbot = au_fbbot_dir(file);
+               for (bindex = au_fbtop(file);
+                    bindex <= bbot && sz < KMALLOC_MAX_SIZE;
+                    bindex++) {
+                       h_file = au_hf_dir(file, bindex);
+                       if (h_file && file_inode(h_file))
+                               sz += vfsub_f_size_read(h_file);
+               }
+       } else {
+               AuDebugOn(!dentry);
+               AuDebugOn(!d_is_dir(dentry));
+
+               bbot = au_dbtaildir(dentry);
+               for (bindex = au_dbtop(dentry);
+                    bindex <= bbot && sz < KMALLOC_MAX_SIZE;
+                    bindex++) {
+                       h_dentry = au_h_dptr(dentry, bindex);
+                       if (h_dentry && d_is_positive(h_dentry))
+                               sz += i_size_read(d_inode(h_dentry));
+               }
+       }
+       if (sz < KMALLOC_MAX_SIZE)
+               sz = roundup_pow_of_two(sz);
+       if (sz > KMALLOC_MAX_SIZE)
+               sz = KMALLOC_MAX_SIZE;
+       else if (sz < NAME_MAX) {
+               BUILD_BUG_ON(AUFS_RDBLK_DEF < NAME_MAX);
+               sz = AUFS_RDBLK_DEF;
+       }
+       return sz;
+}
+
+struct au_dir_ts_arg {
+       struct dentry *dentry;
+       aufs_bindex_t brid;
+};
+
+static void au_do_dir_ts(void *arg)
+{
+       struct au_dir_ts_arg *a = arg;
+       struct au_dtime dt;
+       struct path h_path;
+       struct inode *dir, *h_dir;
+       struct super_block *sb;
+       struct au_branch *br;
+       struct au_hinode *hdir;
+       int err;
+       aufs_bindex_t btop, bindex;
+
+       sb = a->dentry->d_sb;
+       if (d_really_is_negative(a->dentry))
+               goto out;
+       /* no dir->i_mutex lock */
+       aufs_read_lock(a->dentry, AuLock_DW); /* noflush */
+
+       dir = d_inode(a->dentry);
+       btop = au_ibtop(dir);
+       bindex = au_br_index(sb, a->brid);
+       if (bindex < btop)
+               goto out_unlock;
+
+       br = au_sbr(sb, bindex);
+       h_path.dentry = au_h_dptr(a->dentry, bindex);
+       if (!h_path.dentry)
+               goto out_unlock;
+       h_path.mnt = au_br_mnt(br);
+       au_dtime_store(&dt, a->dentry, &h_path);
+
+       br = au_sbr(sb, btop);
+       if (!au_br_writable(br->br_perm))
+               goto out_unlock;
+       h_path.dentry = au_h_dptr(a->dentry, btop);
+       h_path.mnt = au_br_mnt(br);
+       err = vfsub_mnt_want_write(h_path.mnt);
+       if (err)
+               goto out_unlock;
+       hdir = au_hi(dir, btop);
+       au_hn_inode_lock_nested(hdir, AuLsc_I_PARENT);
+       h_dir = au_h_iptr(dir, btop);
+       if (h_dir->i_nlink
+           && timespec64_compare(&h_dir->i_mtime, &dt.dt_mtime) < 0) {
+               dt.dt_h_path = h_path;
+               au_dtime_revert(&dt);
+       }
+       au_hn_inode_unlock(hdir);
+       vfsub_mnt_drop_write(h_path.mnt);
+       au_cpup_attr_timesizes(dir);
+
+out_unlock:
+       aufs_read_unlock(a->dentry, AuLock_DW);
+out:
+       dput(a->dentry);
+       au_nwt_done(&au_sbi(sb)->si_nowait);
+       au_kfree_try_rcu(arg);
+}
+
+void au_dir_ts(struct inode *dir, aufs_bindex_t bindex)
+{
+       int perm, wkq_err;
+       aufs_bindex_t btop;
+       struct au_dir_ts_arg *arg;
+       struct dentry *dentry;
+       struct super_block *sb;
+
+       IMustLock(dir);
+
+       dentry = d_find_any_alias(dir);
+       AuDebugOn(!dentry);
+       sb = dentry->d_sb;
+       btop = au_ibtop(dir);
+       if (btop == bindex) {
+               au_cpup_attr_timesizes(dir);
+               goto out;
+       }
+
+       perm = au_sbr_perm(sb, btop);
+       if (!au_br_writable(perm))
+               goto out;
+
+       arg = kmalloc(sizeof(*arg), GFP_NOFS);
+       if (!arg)
+               goto out;
+
+       arg->dentry = dget(dentry); /* will be dput-ted by au_do_dir_ts() */
+       arg->brid = au_sbr_id(sb, bindex);
+       wkq_err = au_wkq_nowait(au_do_dir_ts, arg, sb, /*flags*/0);
+       if (unlikely(wkq_err)) {
+               pr_err("wkq %d\n", wkq_err);
+               dput(dentry);
+               au_kfree_try_rcu(arg);
+       }
+
+out:
+       dput(dentry);
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int reopen_dir(struct file *file)
+{
+       int err;
+       unsigned int flags;
+       aufs_bindex_t bindex, btail, btop;
+       struct dentry *dentry, *h_dentry;
+       struct file *h_file;
+
+       /* open all lower dirs */
+       dentry = file->f_path.dentry;
+       btop = au_dbtop(dentry);
+       for (bindex = au_fbtop(file); bindex < btop; bindex++)
+               au_set_h_fptr(file, bindex, NULL);
+       au_set_fbtop(file, btop);
+
+       btail = au_dbtaildir(dentry);
+       for (bindex = au_fbbot_dir(file); btail < bindex; bindex--)
+               au_set_h_fptr(file, bindex, NULL);
+       au_set_fbbot_dir(file, btail);
+
+       flags = vfsub_file_flags(file);
+       for (bindex = btop; bindex <= btail; bindex++) {
+               h_dentry = au_h_dptr(dentry, bindex);
+               if (!h_dentry)
+                       continue;
+               h_file = au_hf_dir(file, bindex);
+               if (h_file)
+                       continue;
+
+               h_file = au_h_open(dentry, bindex, flags, file, /*force_wr*/0);
+               err = PTR_ERR(h_file);
+               if (IS_ERR(h_file))
+                       goto out; /* close all? */
+               au_set_h_fptr(file, bindex, h_file);
+       }
+       au_update_figen(file);
+       /* todo: necessary? */
+       /* file->f_ra = h_file->f_ra; */
+       err = 0;
+
+out:
+       return err;
+}
+
+static int do_open_dir(struct file *file, int flags, struct file *h_file)
+{
+       int err;
+       aufs_bindex_t bindex, btail;
+       struct dentry *dentry, *h_dentry;
+       struct vfsmount *mnt;
+
+       FiMustWriteLock(file);
+       AuDebugOn(h_file);
+
+       err = 0;
+       mnt = file->f_path.mnt;
+       dentry = file->f_path.dentry;
+       file->f_version = inode_query_iversion(d_inode(dentry));
+       bindex = au_dbtop(dentry);
+       au_set_fbtop(file, bindex);
+       btail = au_dbtaildir(dentry);
+       au_set_fbbot_dir(file, btail);
+       for (; !err && bindex <= btail; bindex++) {
+               h_dentry = au_h_dptr(dentry, bindex);
+               if (!h_dentry)
+                       continue;
+
+               err = vfsub_test_mntns(mnt, h_dentry->d_sb);
+               if (unlikely(err))
+                       break;
+               h_file = au_h_open(dentry, bindex, flags, file, /*force_wr*/0);
+               if (IS_ERR(h_file)) {
+                       err = PTR_ERR(h_file);
+                       break;
+               }
+               au_set_h_fptr(file, bindex, h_file);
+       }
+       au_update_figen(file);
+       /* todo: necessary? */
+       /* file->f_ra = h_file->f_ra; */
+       if (!err)
+               return 0; /* success */
+
+       /* close all */
+       for (bindex = au_fbtop(file); bindex <= btail; bindex++)
+               au_set_h_fptr(file, bindex, NULL);
+       au_set_fbtop(file, -1);
+       au_set_fbbot_dir(file, -1);
+
+       return err;
+}
+
+static int aufs_open_dir(struct inode *inode __maybe_unused,
+                        struct file *file)
+{
+       int err;
+       struct super_block *sb;
+       struct au_fidir *fidir;
+
+       err = -ENOMEM;
+       sb = file->f_path.dentry->d_sb;
+       si_read_lock(sb, AuLock_FLUSH);
+       fidir = au_fidir_alloc(sb);
+       if (fidir) {
+               struct au_do_open_args args = {
+                       .open   = do_open_dir,
+                       .fidir  = fidir
+               };
+               err = au_do_open(file, &args);
+               if (unlikely(err))
+                       au_kfree_rcu(fidir);
+       }
+       si_read_unlock(sb);
+       return err;
+}
+
+static int aufs_release_dir(struct inode *inode __maybe_unused,
+                           struct file *file)
+{
+       struct au_vdir *vdir_cache;
+       struct au_finfo *finfo;
+       struct au_fidir *fidir;
+       struct au_hfile *hf;
+       aufs_bindex_t bindex, bbot;
+
+       finfo = au_fi(file);
+       fidir = finfo->fi_hdir;
+       if (fidir) {
+               au_hbl_del(&finfo->fi_hlist,
+                          &au_sbi(file->f_path.dentry->d_sb)->si_files);
+               vdir_cache = fidir->fd_vdir_cache; /* lock-free */
+               if (vdir_cache)
+                       au_vdir_free(vdir_cache);
+
+               bindex = finfo->fi_btop;
+               if (bindex >= 0) {
+                       hf = fidir->fd_hfile + bindex;
+                       /*
+                        * calls fput() instead of filp_close(),
+                        * since no dnotify or lock for the lower file.
+                        */
+                       bbot = fidir->fd_bbot;
+                       for (; bindex <= bbot; bindex++, hf++)
+                               if (hf->hf_file)
+                                       au_hfput(hf, /*execed*/0);
+               }
+               au_kfree_rcu(fidir);
+               finfo->fi_hdir = NULL;
+       }
+       au_finfo_fin(file);
+       return 0;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_do_flush_dir(struct file *file, fl_owner_t id)
+{
+       int err;
+       aufs_bindex_t bindex, bbot;
+       struct file *h_file;
+
+       err = 0;
+       bbot = au_fbbot_dir(file);
+       for (bindex = au_fbtop(file); !err && bindex <= bbot; bindex++) {
+               h_file = au_hf_dir(file, bindex);
+               if (h_file)
+                       err = vfsub_flush(h_file, id);
+       }
+       return err;
+}
+
+static int aufs_flush_dir(struct file *file, fl_owner_t id)
+{
+       return au_do_flush(file, id, au_do_flush_dir);
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_do_fsync_dir_no_file(struct dentry *dentry, int datasync)
+{
+       int err;
+       aufs_bindex_t bbot, bindex;
+       struct inode *inode;
+       struct super_block *sb;
+
+       err = 0;
+       sb = dentry->d_sb;
+       inode = d_inode(dentry);
+       IMustLock(inode);
+       bbot = au_dbbot(dentry);
+       for (bindex = au_dbtop(dentry); !err && bindex <= bbot; bindex++) {
+               struct path h_path;
+
+               if (au_test_ro(sb, bindex, inode))
+                       continue;
+               h_path.dentry = au_h_dptr(dentry, bindex);
+               if (!h_path.dentry)
+                       continue;
+
+               h_path.mnt = au_sbr_mnt(sb, bindex);
+               err = vfsub_fsync(NULL, &h_path, datasync);
+       }
+
+       return err;
+}
+
+static int au_do_fsync_dir(struct file *file, int datasync)
+{
+       int err;
+       aufs_bindex_t bbot, bindex;
+       struct file *h_file;
+       struct super_block *sb;
+       struct inode *inode;
+
+       err = au_reval_and_lock_fdi(file, reopen_dir, /*wlock*/1, /*fi_lsc*/0);
+       if (unlikely(err))
+               goto out;
+
+       inode = file_inode(file);
+       sb = inode->i_sb;
+       bbot = au_fbbot_dir(file);
+       for (bindex = au_fbtop(file); !err && bindex <= bbot; bindex++) {
+               h_file = au_hf_dir(file, bindex);
+               if (!h_file || au_test_ro(sb, bindex, inode))
+                       continue;
+
+               err = vfsub_fsync(h_file, &h_file->f_path, datasync);
+       }
+
+out:
+       return err;
+}
+
+/*
+ * @file may be NULL
+ */
+static int aufs_fsync_dir(struct file *file, loff_t start, loff_t end,
+                         int datasync)
+{
+       int err;
+       struct dentry *dentry;
+       struct inode *inode;
+       struct super_block *sb;
+
+       err = 0;
+       dentry = file->f_path.dentry;
+       inode = d_inode(dentry);
+       inode_lock(inode);
+       sb = dentry->d_sb;
+       si_noflush_read_lock(sb);
+       if (file)
+               err = au_do_fsync_dir(file, datasync);
+       else {
+               di_write_lock_child(dentry);
+               err = au_do_fsync_dir_no_file(dentry, datasync);
+       }
+       au_cpup_attr_timesizes(inode);
+       di_write_unlock(dentry);
+       if (file)
+               fi_write_unlock(file);
+
+       si_read_unlock(sb);
+       inode_unlock(inode);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int aufs_iterate_shared(struct file *file, struct dir_context *ctx)
+{
+       int err;
+       struct dentry *dentry;
+       struct inode *inode, *h_inode;
+       struct super_block *sb;
+
+       AuDbg("%pD, ctx{%ps, %llu}\n", file, ctx->actor, ctx->pos);
+
+       dentry = file->f_path.dentry;
+       inode = d_inode(dentry);
+       IMustLock(inode);
+
+       sb = dentry->d_sb;
+       si_read_lock(sb, AuLock_FLUSH);
+       err = au_reval_and_lock_fdi(file, reopen_dir, /*wlock*/1, /*fi_lsc*/0);
+       if (unlikely(err))
+               goto out;
+       err = au_alive_dir(dentry);
+       if (!err)
+               err = au_vdir_init(file);
+       di_downgrade_lock(dentry, AuLock_IR);
+       if (unlikely(err))
+               goto out_unlock;
+
+       h_inode = au_h_iptr(inode, au_ibtop(inode));
+       if (!au_test_nfsd()) {
+               err = au_vdir_fill_de(file, ctx);
+               fsstack_copy_attr_atime(inode, h_inode);
+       } else {
+               /*
+                * nfsd filldir may call lookup_one_len(), vfs_getattr(),
+                * encode_fh() and others.
+                */
+               atomic_inc(&h_inode->i_count);
+               di_read_unlock(dentry, AuLock_IR);
+               si_read_unlock(sb);
+               err = au_vdir_fill_de(file, ctx);
+               fsstack_copy_attr_atime(inode, h_inode);
+               fi_write_unlock(file);
+               iput(h_inode);
+
+               AuTraceErr(err);
+               return err;
+       }
+
+out_unlock:
+       di_read_unlock(dentry, AuLock_IR);
+       fi_write_unlock(file);
+out:
+       si_read_unlock(sb);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+#define AuTestEmpty_WHONLY     1
+#define AuTestEmpty_CALLED     (1 << 1)
+#define AuTestEmpty_SHWH       (1 << 2)
+#define au_ftest_testempty(flags, name)        ((flags) & AuTestEmpty_##name)
+#define au_fset_testempty(flags, name) \
+       do { (flags) |= AuTestEmpty_##name; } while (0)
+#define au_fclr_testempty(flags, name) \
+       do { (flags) &= ~AuTestEmpty_##name; } while (0)
+
+#ifndef CONFIG_AUFS_SHWH
+#undef AuTestEmpty_SHWH
+#define AuTestEmpty_SHWH       0
+#endif
+
+struct test_empty_arg {
+       struct dir_context ctx;
+       struct au_nhash *whlist;
+       unsigned int flags;
+       int err;
+       aufs_bindex_t bindex;
+};
+
+static int test_empty_cb(struct dir_context *ctx, const char *__name,
+                        int namelen, loff_t offset __maybe_unused, u64 ino,
+                        unsigned int d_type)
+{
+       struct test_empty_arg *arg = container_of(ctx, struct test_empty_arg,
+                                                 ctx);
+       char *name = (void *)__name;
+
+       arg->err = 0;
+       au_fset_testempty(arg->flags, CALLED);
+       /* smp_mb(); */
+       if (name[0] == '.'
+           && (namelen == 1 || (name[1] == '.' && namelen == 2)))
+               goto out; /* success */
+
+       if (namelen <= AUFS_WH_PFX_LEN
+           || memcmp(name, AUFS_WH_PFX, AUFS_WH_PFX_LEN)) {
+               if (au_ftest_testempty(arg->flags, WHONLY)
+                   && !au_nhash_test_known_wh(arg->whlist, name, namelen))
+                       arg->err = -ENOTEMPTY;
+               goto out;
+       }
+
+       name += AUFS_WH_PFX_LEN;
+       namelen -= AUFS_WH_PFX_LEN;
+       if (!au_nhash_test_known_wh(arg->whlist, name, namelen))
+               arg->err = au_nhash_append_wh
+                       (arg->whlist, name, namelen, ino, d_type, arg->bindex,
+                        au_ftest_testempty(arg->flags, SHWH));
+
+out:
+       /* smp_mb(); */
+       AuTraceErr(arg->err);
+       return arg->err;
+}
+
+static int do_test_empty(struct dentry *dentry, struct test_empty_arg *arg)
+{
+       int err;
+       struct file *h_file;
+       struct au_branch *br;
+
+       h_file = au_h_open(dentry, arg->bindex,
+                          O_RDONLY | O_NONBLOCK | O_DIRECTORY | O_LARGEFILE,
+                          /*file*/NULL, /*force_wr*/0);
+       err = PTR_ERR(h_file);
+       if (IS_ERR(h_file))
+               goto out;
+
+       err = 0;
+       if (!au_opt_test(au_mntflags(dentry->d_sb), UDBA_NONE)
+           && !file_inode(h_file)->i_nlink)
+               goto out_put;
+
+       do {
+               arg->err = 0;
+               au_fclr_testempty(arg->flags, CALLED);
+               /* smp_mb(); */
+               err = vfsub_iterate_dir(h_file, &arg->ctx);
+               if (err >= 0)
+                       err = arg->err;
+       } while (!err && au_ftest_testempty(arg->flags, CALLED));
+
+out_put:
+       fput(h_file);
+       br = au_sbr(dentry->d_sb, arg->bindex);
+       au_lcnt_dec(&br->br_nfiles);
+out:
+       return err;
+}
+
+struct do_test_empty_args {
+       int *errp;
+       struct dentry *dentry;
+       struct test_empty_arg *arg;
+};
+
+static void call_do_test_empty(void *args)
+{
+       struct do_test_empty_args *a = args;
+       *a->errp = do_test_empty(a->dentry, a->arg);
+}
+
+static int sio_test_empty(struct dentry *dentry, struct test_empty_arg *arg)
+{
+       int err, wkq_err;
+       struct dentry *h_dentry;
+       struct inode *h_inode;
+       struct user_namespace *h_userns;
+
+       h_userns = au_sbr_userns(dentry->d_sb, arg->bindex);
+       h_dentry = au_h_dptr(dentry, arg->bindex);
+       h_inode = d_inode(h_dentry);
+       /* todo: i_mode changes anytime? */
+       inode_lock_shared_nested(h_inode, AuLsc_I_CHILD);
+       err = au_test_h_perm_sio(h_userns, h_inode, MAY_EXEC | MAY_READ);
+       inode_unlock_shared(h_inode);
+       if (!err)
+               err = do_test_empty(dentry, arg);
+       else {
+               struct do_test_empty_args args = {
+                       .errp   = &err,
+                       .dentry = dentry,
+                       .arg    = arg
+               };
+               unsigned int flags = arg->flags;
+
+               wkq_err = au_wkq_wait(call_do_test_empty, &args);
+               if (unlikely(wkq_err))
+                       err = wkq_err;
+               arg->flags = flags;
+       }
+
+       return err;
+}
+
+int au_test_empty_lower(struct dentry *dentry)
+{
+       int err;
+       unsigned int rdhash;
+       aufs_bindex_t bindex, btop, btail;
+       struct au_nhash whlist;
+       struct test_empty_arg arg = {
+               .ctx = {
+                       .actor = test_empty_cb
+               }
+       };
+       int (*test_empty)(struct dentry *dentry, struct test_empty_arg *arg);
+
+       SiMustAnyLock(dentry->d_sb);
+
+       rdhash = au_sbi(dentry->d_sb)->si_rdhash;
+       if (!rdhash)
+               rdhash = au_rdhash_est(au_dir_size(/*file*/NULL, dentry));
+       err = au_nhash_alloc(&whlist, rdhash, GFP_NOFS);
+       if (unlikely(err))
+               goto out;
+
+       arg.flags = 0;
+       arg.whlist = &whlist;
+       btop = au_dbtop(dentry);
+       if (au_opt_test(au_mntflags(dentry->d_sb), SHWH))
+               au_fset_testempty(arg.flags, SHWH);
+       test_empty = do_test_empty;
+       if (au_opt_test(au_mntflags(dentry->d_sb), DIRPERM1))
+               test_empty = sio_test_empty;
+       arg.bindex = btop;
+       err = test_empty(dentry, &arg);
+       if (unlikely(err))
+               goto out_whlist;
+
+       au_fset_testempty(arg.flags, WHONLY);
+       btail = au_dbtaildir(dentry);
+       for (bindex = btop + 1; !err && bindex <= btail; bindex++) {
+               struct dentry *h_dentry;
+
+               h_dentry = au_h_dptr(dentry, bindex);
+               if (h_dentry && d_is_positive(h_dentry)) {
+                       arg.bindex = bindex;
+                       err = test_empty(dentry, &arg);
+               }
+       }
+
+out_whlist:
+       au_nhash_wh_free(&whlist);
+out:
+       return err;
+}
+
+int au_test_empty(struct dentry *dentry, struct au_nhash *whlist)
+{
+       int err;
+       struct test_empty_arg arg = {
+               .ctx = {
+                       .actor = test_empty_cb
+               }
+       };
+       aufs_bindex_t bindex, btail;
+
+       err = 0;
+       arg.whlist = whlist;
+       arg.flags = AuTestEmpty_WHONLY;
+       if (au_opt_test(au_mntflags(dentry->d_sb), SHWH))
+               au_fset_testempty(arg.flags, SHWH);
+       btail = au_dbtaildir(dentry);
+       for (bindex = au_dbtop(dentry); !err && bindex <= btail; bindex++) {
+               struct dentry *h_dentry;
+
+               h_dentry = au_h_dptr(dentry, bindex);
+               if (h_dentry && d_is_positive(h_dentry)) {
+                       arg.bindex = bindex;
+                       err = sio_test_empty(dentry, &arg);
+               }
+       }
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+const struct file_operations aufs_dir_fop = {
+       .owner          = THIS_MODULE,
+       .llseek         = default_llseek,
+       .read           = generic_read_dir,
+       .iterate_shared = aufs_iterate_shared,
+       .unlocked_ioctl = aufs_ioctl_dir,
+#ifdef CONFIG_COMPAT
+       .compat_ioctl   = aufs_compat_ioctl_dir,
+#endif
+       .open           = aufs_open_dir,
+       .release        = aufs_release_dir,
+       .flush          = aufs_flush_dir,
+       .fsync          = aufs_fsync_dir
+};
diff -urN /usr/share/empty/fs/aufs/dir.h linux/fs/aufs/dir.h
--- /usr/share/empty/fs/aufs/dir.h      1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/dir.h 2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,134 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * directory operations
+ */
+
+#ifndef __AUFS_DIR_H__
+#define __AUFS_DIR_H__
+
+#ifdef __KERNEL__
+
+#include <linux/fs.h>
+
+/* ---------------------------------------------------------------------- */
+
+/* need to be faster and smaller */
+
+struct au_nhash {
+       unsigned int            nh_num;
+       struct hlist_head       *nh_head;
+};
+
+struct au_vdir_destr {
+       unsigned char   len;
+       unsigned char   name[];
+} __packed;
+
+struct au_vdir_dehstr {
+       struct hlist_node       hash;
+       struct au_vdir_destr    *str;
+       struct rcu_head         rcu;
+} ____cacheline_aligned_in_smp;
+
+struct au_vdir_de {
+       ino_t                   de_ino;
+       unsigned char           de_type;
+       /* caution: packed */
+       struct au_vdir_destr    de_str;
+} __packed;
+
+struct au_vdir_wh {
+       struct hlist_node       wh_hash;
+#ifdef CONFIG_AUFS_SHWH
+       ino_t                   wh_ino;
+       aufs_bindex_t           wh_bindex;
+       unsigned char           wh_type;
+#else
+       aufs_bindex_t           wh_bindex;
+#endif
+       /* caution: packed */
+       struct au_vdir_destr    wh_str;
+} __packed;
+
+union au_vdir_deblk_p {
+       unsigned char           *deblk;
+       struct au_vdir_de       *de;
+};
+
+struct au_vdir {
+       unsigned char   **vd_deblk;
+       unsigned long   vd_nblk;
+       struct {
+               unsigned long           ul;
+               union au_vdir_deblk_p   p;
+       } vd_last;
+
+       u64             vd_version;
+       unsigned int    vd_deblk_sz;
+       unsigned long   vd_jiffy;
+       struct rcu_head rcu;
+} ____cacheline_aligned_in_smp;
+
+/* ---------------------------------------------------------------------- */
+
+/* dir.c */
+extern const struct file_operations aufs_dir_fop;
+void au_add_nlink(struct inode *dir, struct inode *h_dir);
+void au_sub_nlink(struct inode *dir, struct inode *h_dir);
+loff_t au_dir_size(struct file *file, struct dentry *dentry);
+void au_dir_ts(struct inode *dir, aufs_bindex_t bsrc);
+int au_test_empty_lower(struct dentry *dentry);
+int au_test_empty(struct dentry *dentry, struct au_nhash *whlist);
+
+/* vdir.c */
+unsigned int au_rdhash_est(loff_t sz);
+int au_nhash_alloc(struct au_nhash *nhash, unsigned int num_hash, gfp_t gfp);
+void au_nhash_wh_free(struct au_nhash *whlist);
+int au_nhash_test_longer_wh(struct au_nhash *whlist, aufs_bindex_t btgt,
+                           int limit);
+int au_nhash_test_known_wh(struct au_nhash *whlist, char *name, int nlen);
+int au_nhash_append_wh(struct au_nhash *whlist, char *name, int nlen, ino_t ino,
+                      unsigned int d_type, aufs_bindex_t bindex,
+                      unsigned char shwh);
+void au_vdir_free(struct au_vdir *vdir);
+int au_vdir_init(struct file *file);
+int au_vdir_fill_de(struct file *file, struct dir_context *ctx);
+
+/* ioctl.c */
+long aufs_ioctl_dir(struct file *file, unsigned int cmd, unsigned long arg);
+
+#ifdef CONFIG_AUFS_RDU
+/* rdu.c */
+long au_rdu_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
+#ifdef CONFIG_COMPAT
+long au_rdu_compat_ioctl(struct file *file, unsigned int cmd,
+                        unsigned long arg);
+#endif
+#else
+AuStub(long, au_rdu_ioctl, return -EINVAL, struct file *file,
+       unsigned int cmd, unsigned long arg)
+#ifdef CONFIG_COMPAT
+AuStub(long, au_rdu_compat_ioctl, return -EINVAL, struct file *file,
+       unsigned int cmd, unsigned long arg)
+#endif
+#endif
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_DIR_H__ */
diff -urN /usr/share/empty/fs/aufs/dirren.c linux/fs/aufs/dirren.c
--- /usr/share/empty/fs/aufs/dirren.c   1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/dirren.c      2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,1315 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2017-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * special handling in renaming a directory
+ * in order to support looking-up the before-renamed name on the lower readonly
+ * branches
+ */
+
+#include <linux/byteorder/generic.h>
+#include "aufs.h"
+
+static void au_dr_hino_del(struct au_dr_br *dr, struct au_dr_hino *ent)
+{
+       int idx;
+
+       idx = au_dr_ihash(ent->dr_h_ino);
+       au_hbl_del(&ent->dr_hnode, dr->dr_h_ino + idx);
+}
+
+static int au_dr_hino_test_empty(struct au_dr_br *dr)
+{
+       int ret, i;
+       struct hlist_bl_head *hbl;
+
+       ret = 1;
+       for (i = 0; ret && i < AuDirren_NHASH; i++) {
+               hbl = dr->dr_h_ino + i;
+               hlist_bl_lock(hbl);
+               ret &= hlist_bl_empty(hbl);
+               hlist_bl_unlock(hbl);
+       }
+
+       return ret;
+}
+
+static struct au_dr_hino *au_dr_hino_find(struct au_dr_br *dr, ino_t ino)
+{
+       struct au_dr_hino *found, *ent;
+       struct hlist_bl_head *hbl;
+       struct hlist_bl_node *pos;
+       int idx;
+
+       found = NULL;
+       idx = au_dr_ihash(ino);
+       hbl = dr->dr_h_ino + idx;
+       hlist_bl_lock(hbl);
+       hlist_bl_for_each_entry(ent, pos, hbl, dr_hnode)
+               if (ent->dr_h_ino == ino) {
+                       found = ent;
+                       break;
+               }
+       hlist_bl_unlock(hbl);
+
+       return found;
+}
+
+int au_dr_hino_test_add(struct au_dr_br *dr, ino_t ino,
+                       struct au_dr_hino *add_ent)
+{
+       int found, idx;
+       struct hlist_bl_head *hbl;
+       struct hlist_bl_node *pos;
+       struct au_dr_hino *ent;
+
+       found = 0;
+       idx = au_dr_ihash(ino);
+       hbl = dr->dr_h_ino + idx;
+#if 0 /* debug print */
+       {
+               struct hlist_bl_node *tmp;
+
+               hlist_bl_for_each_entry_safe(ent, pos, tmp, hbl, dr_hnode)
+                       AuDbg("hi%llu\n", (unsigned long long)ent->dr_h_ino);
+       }
+#endif
+       hlist_bl_lock(hbl);
+       hlist_bl_for_each_entry(ent, pos, hbl, dr_hnode)
+               if (ent->dr_h_ino == ino) {
+                       found = 1;
+                       break;
+               }
+       if (!found && add_ent)
+               hlist_bl_add_head(&add_ent->dr_hnode, hbl);
+       hlist_bl_unlock(hbl);
+
+       if (!found && add_ent)
+               AuDbg("i%llu added\n", (unsigned long long)add_ent->dr_h_ino);
+
+       return found;
+}
+
+void au_dr_hino_free(struct au_dr_br *dr)
+{
+       int i;
+       struct hlist_bl_head *hbl;
+       struct hlist_bl_node *pos, *tmp;
+       struct au_dr_hino *ent;
+
+       /* SiMustWriteLock(sb); */
+
+       for (i = 0; i < AuDirren_NHASH; i++) {
+               hbl = dr->dr_h_ino + i;
+               /* no spinlock since sbinfo must be write-locked */
+               hlist_bl_for_each_entry_safe(ent, pos, tmp, hbl, dr_hnode)
+                       au_kfree_rcu(ent);
+               INIT_HLIST_BL_HEAD(hbl);
+       }
+}
+
+/* returns the number of inodes or an error */
+static int au_dr_hino_store(struct super_block *sb, struct au_branch *br,
+                           struct file *hinofile)
+{
+       int err, i;
+       ssize_t ssz;
+       loff_t pos, oldsize;
+       __be64 u64;
+       struct inode *hinoinode;
+       struct hlist_bl_head *hbl;
+       struct hlist_bl_node *n1, *n2;
+       struct au_dr_hino *ent;
+
+       SiMustWriteLock(sb);
+       AuDebugOn(!au_br_writable(br->br_perm));
+
+       hinoinode = file_inode(hinofile);
+       oldsize = i_size_read(hinoinode);
+
+       err = 0;
+       pos = 0;
+       hbl = br->br_dirren.dr_h_ino;
+       for (i = 0; !err && i < AuDirren_NHASH; i++, hbl++) {
+               /* no bit-lock since sbinfo must be write-locked */
+               hlist_bl_for_each_entry_safe(ent, n1, n2, hbl, dr_hnode) {
+                       AuDbg("hi%llu, %pD2\n",
+                             (unsigned long long)ent->dr_h_ino, hinofile);
+                       u64 = cpu_to_be64(ent->dr_h_ino);
+                       ssz = vfsub_write_k(hinofile, &u64, sizeof(u64), &pos);
+                       if (ssz == sizeof(u64))
+                               continue;
+
+                       /* write error */
+                       pr_err("ssz %zd, %pD2\n", ssz, hinofile);
+                       err = -ENOSPC;
+                       if (ssz < 0)
+                               err = ssz;
+                       break;
+               }
+       }
+       /* regardless the error */
+       if (pos < oldsize) {
+               err = vfsub_trunc(&hinofile->f_path, pos, /*attr*/0, hinofile);
+               AuTraceErr(err);
+       }
+
+       AuTraceErr(err);
+       return err;
+}
+
+static int au_dr_hino_load(struct au_dr_br *dr, struct file *hinofile)
+{
+       int err, hidx;
+       ssize_t ssz;
+       size_t sz, n;
+       loff_t pos;
+       uint64_t u64;
+       struct au_dr_hino *ent;
+       struct inode *hinoinode;
+       struct hlist_bl_head *hbl;
+
+       err = 0;
+       pos = 0;
+       hbl = dr->dr_h_ino;
+       hinoinode = file_inode(hinofile);
+       sz = i_size_read(hinoinode);
+       AuDebugOn(sz % sizeof(u64));
+       n = sz / sizeof(u64);
+       while (n--) {
+               ssz = vfsub_read_k(hinofile, &u64, sizeof(u64), &pos);
+               if (unlikely(ssz != sizeof(u64))) {
+                       pr_err("ssz %zd, %pD2\n", ssz, hinofile);
+                       err = -EINVAL;
+                       if (ssz < 0)
+                               err = ssz;
+                       goto out_free;
+               }
+
+               ent = kmalloc(sizeof(*ent), GFP_NOFS);
+               if (!ent) {
+                       err = -ENOMEM;
+                       AuTraceErr(err);
+                       goto out_free;
+               }
+               ent->dr_h_ino = be64_to_cpu((__force __be64)u64);
+               AuDbg("hi%llu, %pD2\n",
+                     (unsigned long long)ent->dr_h_ino, hinofile);
+               hidx = au_dr_ihash(ent->dr_h_ino);
+               au_hbl_add(&ent->dr_hnode, hbl + hidx);
+       }
+       goto out; /* success */
+
+out_free:
+       au_dr_hino_free(dr);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/*
+ * @bindex/@br is a switch to distinguish whether suspending hnotify or not.
+ * @path is a switch to distinguish load and store.
+ */
+static int au_dr_hino(struct super_block *sb, aufs_bindex_t bindex,
+                     struct au_branch *br, const struct path *path)
+{
+       int err, flags;
+       unsigned char load, suspend;
+       struct file *hinofile;
+       struct au_hinode *hdir;
+       struct inode *dir, *delegated;
+       struct path hinopath;
+       struct qstr hinoname = QSTR_INIT(AUFS_WH_DR_BRHINO,
+                                        sizeof(AUFS_WH_DR_BRHINO) - 1);
+
+       AuDebugOn(bindex < 0 && !br);
+       AuDebugOn(bindex >= 0 && br);
+
+       err = -EINVAL;
+       suspend = !br;
+       if (suspend)
+               br = au_sbr(sb, bindex);
+       load = !!path;
+       if (!load) {
+               path = &br->br_path;
+               AuDebugOn(!au_br_writable(br->br_perm));
+               if (unlikely(!au_br_writable(br->br_perm)))
+                       goto out;
+       }
+
+       hdir = NULL;
+       if (suspend) {
+               dir = d_inode(sb->s_root);
+               hdir = au_hinode(au_ii(dir), bindex);
+               dir = hdir->hi_inode;
+               au_hn_inode_lock_nested(hdir, AuLsc_I_CHILD);
+       } else {
+               dir = d_inode(path->dentry);
+               inode_lock_nested(dir, AuLsc_I_CHILD);
+       }
+       hinopath.mnt = path->mnt;
+       hinopath.dentry = vfsub_lkup_one(&hinoname, (struct path *)path);
+       err = PTR_ERR(hinopath.dentry);
+       if (IS_ERR(hinopath.dentry))
+               goto out_unlock;
+
+       err = 0;
+       flags = O_RDONLY;
+       if (load) {
+               if (d_is_negative(hinopath.dentry))
+                       goto out_dput; /* success */
+       } else {
+               if (au_dr_hino_test_empty(&br->br_dirren)) {
+                       if (d_is_positive(hinopath.dentry)) {
+                               delegated = NULL;
+                               err = vfsub_unlink(dir, &hinopath, &delegated,
+                                                  /*force*/0);
+                               AuTraceErr(err);
+                               if (unlikely(err))
+                                       pr_err("ignored err %d, %pd2\n",
+                                              err, hinopath.dentry);
+                               if (unlikely(err == -EWOULDBLOCK))
+                                       iput(delegated);
+                               err = 0;
+                       }
+                       goto out_dput;
+               } else if (!d_is_positive(hinopath.dentry)) {
+                       err = vfsub_create(dir, &hinopath, 0600,
+                                          /*want_excl*/false);
+                       AuTraceErr(err);
+                       if (unlikely(err))
+                               goto out_dput;
+               }
+               flags = O_WRONLY;
+       }
+       hinofile = vfsub_dentry_open(&hinopath, flags);
+       if (suspend)
+               au_hn_inode_unlock(hdir);
+       else
+               inode_unlock(dir);
+       dput(hinopath.dentry);
+       AuTraceErrPtr(hinofile);
+       if (IS_ERR(hinofile)) {
+               err = PTR_ERR(hinofile);
+               goto out;
+       }
+
+       if (load)
+               err = au_dr_hino_load(&br->br_dirren, hinofile);
+       else
+               err = au_dr_hino_store(sb, br, hinofile);
+       fput(hinofile);
+       goto out;
+
+out_dput:
+       dput(hinopath.dentry);
+out_unlock:
+       if (suspend)
+               au_hn_inode_unlock(hdir);
+       else
+               inode_unlock(dir);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_dr_brid_init(struct au_dr_brid *brid, const struct path *path)
+{
+       int err;
+       struct kstatfs kstfs;
+       dev_t dev;
+       struct dentry *dentry;
+       struct super_block *sb;
+
+       err = vfs_statfs((void *)path, &kstfs);
+       AuTraceErr(err);
+       if (unlikely(err))
+               goto out;
+
+       /* todo: support for UUID */
+
+       if (kstfs.f_fsid.val[0] || kstfs.f_fsid.val[1]) {
+               brid->type = AuBrid_FSID;
+               brid->fsid = kstfs.f_fsid;
+       } else {
+               dentry = path->dentry;
+               sb = dentry->d_sb;
+               dev = sb->s_dev;
+               if (dev) {
+                       brid->type = AuBrid_DEV;
+                       brid->dev = dev;
+               }
+       }
+
+out:
+       return err;
+}
+
+int au_dr_br_init(struct super_block *sb, struct au_branch *br,
+                 const struct path *path)
+{
+       int err, i;
+       struct au_dr_br *dr;
+       struct hlist_bl_head *hbl;
+
+       dr = &br->br_dirren;
+       hbl = dr->dr_h_ino;
+       for (i = 0; i < AuDirren_NHASH; i++, hbl++)
+               INIT_HLIST_BL_HEAD(hbl);
+
+       err = au_dr_brid_init(&dr->dr_brid, path);
+       if (unlikely(err))
+               goto out;
+
+       if (au_opt_test(au_mntflags(sb), DIRREN))
+               err = au_dr_hino(sb, /*bindex*/-1, br, path);
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+int au_dr_br_fin(struct super_block *sb, struct au_branch *br)
+{
+       int err;
+
+       err = 0;
+       if (au_br_writable(br->br_perm))
+               err = au_dr_hino(sb, /*bindex*/-1, br, /*path*/NULL);
+       if (!err)
+               au_dr_hino_free(&br->br_dirren);
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_brid_str(struct au_dr_brid *brid, struct inode *h_inode,
+                      char *buf, size_t sz)
+{
+       int err;
+       unsigned int major, minor;
+       char *p;
+
+       p = buf;
+       err = snprintf(p, sz, "%d_", brid->type);
+       AuDebugOn(err > sz);
+       p += err;
+       sz -= err;
+       switch (brid->type) {
+       case AuBrid_Unset:
+               return -EINVAL;
+       case AuBrid_UUID:
+               err = snprintf(p, sz, "%pU", brid->uuid.b);
+               break;
+       case AuBrid_FSID:
+               err = snprintf(p, sz, "%08x-%08x",
+                              brid->fsid.val[0], brid->fsid.val[1]);
+               break;
+       case AuBrid_DEV:
+               major = MAJOR(brid->dev);
+               minor = MINOR(brid->dev);
+               if (major <= 0xff && minor <= 0xff)
+                       err = snprintf(p, sz, "%02x%02x", major, minor);
+               else
+                       err = snprintf(p, sz, "%03x:%05x", major, minor);
+               break;
+       }
+       AuDebugOn(err > sz);
+       p += err;
+       sz -= err;
+       err = snprintf(p, sz, "_%llu", (unsigned long long)h_inode->i_ino);
+       AuDebugOn(err > sz);
+       p += err;
+       sz -= err;
+
+       return p - buf;
+}
+
+static int au_drinfo_name(struct au_branch *br, char *name, int len)
+{
+       int rlen;
+       struct dentry *br_dentry;
+       struct inode *br_inode;
+
+       br_dentry = au_br_dentry(br);
+       br_inode = d_inode(br_dentry);
+       rlen = au_brid_str(&br->br_dirren.dr_brid, br_inode, name, len);
+       AuDebugOn(rlen >= AUFS_DIRREN_ENV_VAL_SZ);
+       AuDebugOn(rlen > len);
+
+       return rlen;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * from the given @h_dentry, construct drinfo at @*fdata.
+ * when the size of @*fdata is not enough, reallocate and return new @fdata and
+ * @allocated.
+ */
+static int au_drinfo_construct(struct au_drinfo_fdata **fdata,
+                              struct dentry *h_dentry,
+                              unsigned char *allocated)
+{
+       int err, v;
+       struct au_drinfo_fdata *f, *p;
+       struct au_drinfo *drinfo;
+       struct inode *h_inode;
+       struct qstr *qname;
+
+       err = 0;
+       f = *fdata;
+       h_inode = d_inode(h_dentry);
+       qname = &h_dentry->d_name;
+       drinfo = &f->drinfo;
+       drinfo->ino = (__force uint64_t)cpu_to_be64(h_inode->i_ino);
+       drinfo->oldnamelen = qname->len;
+       if (*allocated < sizeof(*f) + qname->len) {
+               v = roundup_pow_of_two(*allocated + qname->len);
+               p = au_krealloc(f, v, GFP_NOFS, /*may_shrink*/0);
+               if (unlikely(!p)) {
+                       err = -ENOMEM;
+                       AuTraceErr(err);
+                       goto out;
+               }
+               f = p;
+               *fdata = f;
+               *allocated = v;
+               drinfo = &f->drinfo;
+       }
+       memcpy(drinfo->oldname, qname->name, qname->len);
+       AuDbg("i%llu, %.*s\n",
+             be64_to_cpu((__force __be64)drinfo->ino), drinfo->oldnamelen,
+             drinfo->oldname);
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/* callers have to free the return value */
+static struct au_drinfo *au_drinfo_read_k(struct file *file, ino_t h_ino)
+{
+       struct au_drinfo *ret, *drinfo;
+       struct au_drinfo_fdata fdata;
+       int len;
+       loff_t pos;
+       ssize_t ssz;
+
+       ret = ERR_PTR(-EIO);
+       pos = 0;
+       ssz = vfsub_read_k(file, &fdata, sizeof(fdata), &pos);
+       if (unlikely(ssz != sizeof(fdata))) {
+               AuIOErr("ssz %zd, %u, %pD2\n",
+                       ssz, (unsigned int)sizeof(fdata), file);
+               goto out;
+       }
+
+       fdata.magic = ntohl((__force __be32)fdata.magic);
+       switch (fdata.magic) {
+       case AUFS_DRINFO_MAGIC_V1:
+               break;
+       default:
+               AuIOErr("magic-num 0x%x, 0x%x, %pD2\n",
+                       fdata.magic, AUFS_DRINFO_MAGIC_V1, file);
+               goto out;
+       }
+
+       drinfo = &fdata.drinfo;
+       len = drinfo->oldnamelen;
+       if (!len) {
+               AuIOErr("broken drinfo %pD2\n", file);
+               goto out;
+       }
+
+       ret = NULL;
+       drinfo->ino = be64_to_cpu((__force __be64)drinfo->ino);
+       if (unlikely(h_ino && drinfo->ino != h_ino)) {
+               AuDbg("ignored i%llu, i%llu, %pD2\n",
+                     (unsigned long long)drinfo->ino,
+                     (unsigned long long)h_ino, file);
+               goto out; /* success */
+       }
+
+       ret = kmalloc(sizeof(*ret) + len, GFP_NOFS);
+       if (unlikely(!ret)) {
+               ret = ERR_PTR(-ENOMEM);
+               AuTraceErrPtr(ret);
+               goto out;
+       }
+
+       *ret = *drinfo;
+       ssz = vfsub_read_k(file, (void *)ret->oldname, len, &pos);
+       if (unlikely(ssz != len)) {
+               au_kfree_rcu(ret);
+               ret = ERR_PTR(-EIO);
+               AuIOErr("ssz %zd, %u, %pD2\n", ssz, len, file);
+               goto out;
+       }
+
+       AuDbg("oldname %.*s\n", ret->oldnamelen, ret->oldname);
+
+out:
+       return ret;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* in order to be revertible */
+struct au_drinfo_rev_elm {
+       int                     created;
+       struct dentry           *info_dentry;
+       struct au_drinfo        *info_last;
+};
+
+struct au_drinfo_rev {
+       unsigned char                   already;
+       aufs_bindex_t                   nelm;
+       struct au_drinfo_rev_elm        elm[];
+};
+
+/* todo: isn't it too large? */
+struct au_drinfo_store {
+       struct path h_ppath;
+       struct dentry *h_dentry;
+       struct au_drinfo_fdata *fdata;
+       char *infoname;                 /* inside of whname, just after PFX */
+       char whname[sizeof(AUFS_WH_DR_INFO_PFX) + AUFS_DIRREN_ENV_VAL_SZ];
+       aufs_bindex_t btgt, btail;
+       unsigned char no_sio,
+               allocated,              /* current size of *fdata */
+               infonamelen,            /* room size for p */
+               whnamelen,              /* length of the generated name */
+               renameback;             /* renamed back */
+};
+
+/* on rename(2) error, the caller should revert it using @elm */
+static int au_drinfo_do_store(struct au_drinfo_store *w,
+                             struct au_drinfo_rev_elm *elm)
+{
+       int err, len;
+       ssize_t ssz;
+       loff_t pos;
+       struct path infopath = {
+               .mnt = w->h_ppath.mnt
+       };
+       struct inode *h_dir, *h_inode, *delegated;
+       struct file *infofile;
+       struct qstr *qname;
+
+       AuDebugOn(elm
+                 && memcmp(elm, page_address(ZERO_PAGE(0)), sizeof(*elm)));
+
+       infopath.dentry = vfsub_lookup_one_len(w->whname, &w->h_ppath,
+                                              w->whnamelen);
+       AuTraceErrPtr(infopath.dentry);
+       if (IS_ERR(infopath.dentry)) {
+               err = PTR_ERR(infopath.dentry);
+               goto out;
+       }
+
+       err = 0;
+       h_dir = d_inode(w->h_ppath.dentry);
+       if (elm && d_is_negative(infopath.dentry)) {
+               err = vfsub_create(h_dir, &infopath, 0600, /*want_excl*/true);
+               AuTraceErr(err);
+               if (unlikely(err))
+                       goto out_dput;
+               elm->created = 1;
+               elm->info_dentry = dget(infopath.dentry);
+       }
+
+       infofile = vfsub_dentry_open(&infopath, O_RDWR);
+       AuTraceErrPtr(infofile);
+       if (IS_ERR(infofile)) {
+               err = PTR_ERR(infofile);
+               goto out_dput;
+       }
+
+       h_inode = d_inode(infopath.dentry);
+       if (elm && i_size_read(h_inode)) {
+               h_inode = d_inode(w->h_dentry);
+               elm->info_last = au_drinfo_read_k(infofile, h_inode->i_ino);
+               AuTraceErrPtr(elm->info_last);
+               if (IS_ERR(elm->info_last)) {
+                       err = PTR_ERR(elm->info_last);
+                       elm->info_last = NULL;
+                       AuDebugOn(elm->info_dentry);
+                       goto out_fput;
+               }
+       }
+
+       if (elm && w->renameback) {
+               delegated = NULL;
+               err = vfsub_unlink(h_dir, &infopath, &delegated, /*force*/0);
+               AuTraceErr(err);
+               if (unlikely(err == -EWOULDBLOCK))
+                       iput(delegated);
+               goto out_fput;
+       }
+
+       pos = 0;
+       qname = &w->h_dentry->d_name;
+       len = sizeof(*w->fdata) + qname->len;
+       if (!elm)
+               len = sizeof(*w->fdata) + w->fdata->drinfo.oldnamelen;
+       ssz = vfsub_write_k(infofile, w->fdata, len, &pos);
+       if (ssz == len) {
+               AuDbg("hi%llu, %.*s\n", w->fdata->drinfo.ino,
+                     w->fdata->drinfo.oldnamelen, w->fdata->drinfo.oldname);
+               goto out_fput; /* success */
+       } else {
+               err = -EIO;
+               if (ssz < 0)
+                       err = ssz;
+               /* the caller should revert it using @elm */
+       }
+
+out_fput:
+       fput(infofile);
+out_dput:
+       dput(infopath.dentry);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+struct au_call_drinfo_do_store_args {
+       int *errp;
+       struct au_drinfo_store *w;
+       struct au_drinfo_rev_elm *elm;
+};
+
+static void au_call_drinfo_do_store(void *args)
+{
+       struct au_call_drinfo_do_store_args *a = args;
+
+       *a->errp = au_drinfo_do_store(a->w, a->elm);
+}
+
+static int au_drinfo_store_sio(struct au_drinfo_store *w,
+                              struct au_drinfo_rev_elm *elm)
+{
+       int err, wkq_err;
+
+       if (w->no_sio)
+               err = au_drinfo_do_store(w, elm);
+       else {
+               struct au_call_drinfo_do_store_args a = {
+                       .errp   = &err,
+                       .w      = w,
+                       .elm    = elm
+               };
+               wkq_err = au_wkq_wait(au_call_drinfo_do_store, &a);
+               if (unlikely(wkq_err))
+                       err = wkq_err;
+       }
+       AuTraceErr(err);
+
+       return err;
+}
+
+static int au_drinfo_store_work_init(struct au_drinfo_store *w,
+                                    aufs_bindex_t btgt)
+{
+       int err;
+
+       memset(w, 0, sizeof(*w));
+       w->allocated = roundup_pow_of_two(sizeof(*w->fdata) + 40);
+       strcpy(w->whname, AUFS_WH_DR_INFO_PFX);
+       w->infoname = w->whname + sizeof(AUFS_WH_DR_INFO_PFX) - 1;
+       w->infonamelen = sizeof(w->whname) - sizeof(AUFS_WH_DR_INFO_PFX);
+       w->btgt = btgt;
+       w->no_sio = !!uid_eq(current_fsuid(), GLOBAL_ROOT_UID);
+
+       err = -ENOMEM;
+       w->fdata = kcalloc(1, w->allocated, GFP_NOFS);
+       if (unlikely(!w->fdata)) {
+               AuTraceErr(err);
+               goto out;
+       }
+       w->fdata->magic = (__force uint32_t)htonl(AUFS_DRINFO_MAGIC_V1);
+       err = 0;
+
+out:
+       return err;
+}
+
+static void au_drinfo_store_work_fin(struct au_drinfo_store *w)
+{
+       au_kfree_rcu(w->fdata);
+}
+
+static void au_drinfo_store_rev(struct au_drinfo_rev *rev,
+                               struct au_drinfo_store *w)
+{
+       struct au_drinfo_rev_elm *elm;
+       struct inode *h_dir, *delegated;
+       int err, nelm;
+       struct path infopath = {
+               .mnt = w->h_ppath.mnt
+       };
+
+       h_dir = d_inode(w->h_ppath.dentry);
+       IMustLock(h_dir);
+
+       err = 0;
+       elm = rev->elm;
+       for (nelm = rev->nelm; nelm > 0; nelm--, elm++) {
+               AuDebugOn(elm->created && elm->info_last);
+               if (elm->created) {
+                       AuDbg("here\n");
+                       delegated = NULL;
+                       infopath.dentry = elm->info_dentry;
+                       err = vfsub_unlink(h_dir, &infopath, &delegated,
+                                          !w->no_sio);
+                       AuTraceErr(err);
+                       if (unlikely(err == -EWOULDBLOCK))
+                               iput(delegated);
+                       dput(elm->info_dentry);
+               } else if (elm->info_last) {
+                       AuDbg("here\n");
+                       w->fdata->drinfo = *elm->info_last;
+                       memcpy(w->fdata->drinfo.oldname,
+                              elm->info_last->oldname,
+                              elm->info_last->oldnamelen);
+                       err = au_drinfo_store_sio(w, /*elm*/NULL);
+                       au_kfree_rcu(elm->info_last);
+               }
+               if (unlikely(err))
+                       AuIOErr("%d, %s\n", err, w->whname);
+               /* go on even if err */
+       }
+}
+
+/* caller has to call au_dr_rename_fin() later */
+static int au_drinfo_store(struct dentry *dentry, aufs_bindex_t btgt,
+                          struct qstr *dst_name, void *_rev)
+{
+       int err, sz, nelm;
+       aufs_bindex_t bindex, btail;
+       struct au_drinfo_store work;
+       struct au_drinfo_rev *rev, **p;
+       struct au_drinfo_rev_elm *elm;
+       struct super_block *sb;
+       struct au_branch *br;
+       struct au_hinode *hdir;
+
+       err = au_drinfo_store_work_init(&work, btgt);
+       AuTraceErr(err);
+       if (unlikely(err))
+               goto out;
+
+       err = -ENOMEM;
+       btail = au_dbtaildir(dentry);
+       nelm = btail - btgt;
+       sz = sizeof(*rev) + sizeof(*elm) * nelm;
+       rev = kcalloc(1, sz, GFP_NOFS);
+       if (unlikely(!rev)) {
+               AuTraceErr(err);
+               goto out_args;
+       }
+       rev->nelm = nelm;
+       elm = rev->elm;
+       p = _rev;
+       *p = rev;
+
+       err = 0;
+       sb = dentry->d_sb;
+       work.h_ppath.dentry = au_h_dptr(dentry, btgt);
+       work.h_ppath.mnt = au_sbr_mnt(sb, btgt);
+       hdir = au_hi(d_inode(dentry), btgt);
+       au_hn_inode_lock_nested(hdir, AuLsc_I_CHILD);
+       for (bindex = btgt + 1; bindex <= btail; bindex++, elm++) {
+               work.h_dentry = au_h_dptr(dentry, bindex);
+               if (!work.h_dentry)
+                       continue;
+
+               err = au_drinfo_construct(&work.fdata, work.h_dentry,
+                                         &work.allocated);
+               AuTraceErr(err);
+               if (unlikely(err))
+                       break;
+
+               work.renameback = au_qstreq(&work.h_dentry->d_name, dst_name);
+               br = au_sbr(sb, bindex);
+               work.whnamelen = sizeof(AUFS_WH_DR_INFO_PFX) - 1;
+               work.whnamelen += au_drinfo_name(br, work.infoname,
+                                                work.infonamelen);
+               AuDbg("whname %.*s, i%llu, %.*s\n",
+                     work.whnamelen, work.whname,
+                     be64_to_cpu((__force __be64)work.fdata->drinfo.ino),
+                     work.fdata->drinfo.oldnamelen,
+                     work.fdata->drinfo.oldname);
+
+               err = au_drinfo_store_sio(&work, elm);
+               AuTraceErr(err);
+               if (unlikely(err))
+                       break;
+       }
+       if (unlikely(err)) {
+               /* revert all drinfo */
+               au_drinfo_store_rev(rev, &work);
+               au_kfree_try_rcu(rev);
+               *p = NULL;
+       }
+       au_hn_inode_unlock(hdir);
+
+out_args:
+       au_drinfo_store_work_fin(&work);
+out:
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+int au_dr_rename(struct dentry *src, aufs_bindex_t bindex,
+                struct qstr *dst_name, void *_rev)
+{
+       int err, already;
+       ino_t ino;
+       struct super_block *sb;
+       struct au_branch *br;
+       struct au_dr_br *dr;
+       struct dentry *h_dentry;
+       struct inode *h_inode;
+       struct au_dr_hino *ent;
+       struct au_drinfo_rev *rev, **p;
+
+       AuDbg("bindex %d\n", bindex);
+
+       err = -ENOMEM;
+       ent = kmalloc(sizeof(*ent), GFP_NOFS);
+       if (unlikely(!ent))
+               goto out;
+
+       sb = src->d_sb;
+       br = au_sbr(sb, bindex);
+       dr = &br->br_dirren;
+       h_dentry = au_h_dptr(src, bindex);
+       h_inode = d_inode(h_dentry);
+       ino = h_inode->i_ino;
+       ent->dr_h_ino = ino;
+       already = au_dr_hino_test_add(dr, ino, ent);
+       AuDbg("b%d, hi%llu, already %d\n",
+             bindex, (unsigned long long)ino, already);
+
+       err = au_drinfo_store(src, bindex, dst_name, _rev);
+       AuTraceErr(err);
+       if (!err) {
+               p = _rev;
+               rev = *p;
+               rev->already = already;
+               goto out; /* success */
+       }
+
+       /* revert */
+       if (!already)
+               au_dr_hino_del(dr, ent);
+       au_kfree_rcu(ent);
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+void au_dr_rename_fin(struct dentry *src, aufs_bindex_t btgt, void *_rev)
+{
+       struct au_drinfo_rev *rev;
+       struct au_drinfo_rev_elm *elm;
+       int nelm;
+
+       rev = _rev;
+       elm = rev->elm;
+       for (nelm = rev->nelm; nelm > 0; nelm--, elm++) {
+               dput(elm->info_dentry);
+               au_kfree_rcu(elm->info_last);
+       }
+       au_kfree_try_rcu(rev);
+}
+
+void au_dr_rename_rev(struct dentry *src, aufs_bindex_t btgt, void *_rev)
+{
+       int err;
+       struct au_drinfo_store work;
+       struct au_drinfo_rev *rev = _rev;
+       struct super_block *sb;
+       struct au_branch *br;
+       struct inode *h_inode;
+       struct au_dr_br *dr;
+       struct au_dr_hino *ent;
+
+       err = au_drinfo_store_work_init(&work, btgt);
+       if (unlikely(err))
+               goto out;
+
+       sb = src->d_sb;
+       br = au_sbr(sb, btgt);
+       work.h_ppath.dentry = au_h_dptr(src, btgt);
+       work.h_ppath.mnt = au_br_mnt(br);
+       au_drinfo_store_rev(rev, &work);
+       au_drinfo_store_work_fin(&work);
+       if (rev->already)
+               goto out;
+
+       dr = &br->br_dirren;
+       h_inode = d_inode(work.h_ppath.dentry);
+       ent = au_dr_hino_find(dr, h_inode->i_ino);
+       BUG_ON(!ent);
+       au_dr_hino_del(dr, ent);
+       au_kfree_rcu(ent);
+
+out:
+       au_kfree_try_rcu(rev);
+       if (unlikely(err))
+               pr_err("failed to remove dirren info\n");
+}
+
+/* ---------------------------------------------------------------------- */
+
+static struct au_drinfo *au_drinfo_do_load(struct path *h_ppath,
+                                          char *whname, int whnamelen,
+                                          struct dentry **info_dentry)
+{
+       struct au_drinfo *drinfo;
+       struct file *f;
+       struct inode *h_dir;
+       struct path infopath;
+       int unlocked;
+
+       AuDbg("%pd/%.*s\n", h_ppath->dentry, whnamelen, whname);
+
+       *info_dentry = NULL;
+       drinfo = NULL;
+       unlocked = 0;
+       h_dir = d_inode(h_ppath->dentry);
+       inode_lock_shared_nested(h_dir, AuLsc_I_PARENT);
+       infopath.dentry = vfsub_lookup_one_len(whname, h_ppath, whnamelen);
+       if (IS_ERR(infopath.dentry)) {
+               drinfo = (void *)infopath.dentry;
+               goto out;
+       }
+
+       if (d_is_negative(infopath.dentry))
+               goto out_dput; /* success */
+
+       infopath.mnt = h_ppath->mnt;
+       f = vfsub_dentry_open(&infopath, O_RDONLY);
+       inode_unlock_shared(h_dir);
+       unlocked = 1;
+       if (IS_ERR(f)) {
+               drinfo = (void *)f;
+               goto out_dput;
+       }
+
+       drinfo = au_drinfo_read_k(f, /*h_ino*/0);
+       if (IS_ERR_OR_NULL(drinfo))
+               goto out_fput;
+
+       AuDbg("oldname %.*s\n", drinfo->oldnamelen, drinfo->oldname);
+       *info_dentry = dget(infopath.dentry); /* keep it alive */
+
+out_fput:
+       fput(f);
+out_dput:
+       dput(infopath.dentry);
+out:
+       if (!unlocked)
+               inode_unlock_shared(h_dir);
+       AuTraceErrPtr(drinfo);
+       return drinfo;
+}
+
+struct au_drinfo_do_load_args {
+       struct au_drinfo **drinfop;
+       struct path *h_ppath;
+       char *whname;
+       int whnamelen;
+       struct dentry **info_dentry;
+};
+
+static void au_call_drinfo_do_load(void *args)
+{
+       struct au_drinfo_do_load_args *a = args;
+
+       *a->drinfop = au_drinfo_do_load(a->h_ppath, a->whname, a->whnamelen,
+                                       a->info_dentry);
+}
+
+struct au_drinfo_load {
+       struct path h_ppath;
+       struct qstr *qname;
+       unsigned char no_sio;
+
+       aufs_bindex_t ninfo;
+       struct au_drinfo **drinfo;
+};
+
+static int au_drinfo_load(struct au_drinfo_load *w, aufs_bindex_t bindex,
+                         struct au_branch *br)
+{
+       int err, wkq_err, whnamelen, e;
+       char whname[sizeof(AUFS_WH_DR_INFO_PFX) + AUFS_DIRREN_ENV_VAL_SZ]
+               = AUFS_WH_DR_INFO_PFX;
+       struct au_drinfo *drinfo;
+       struct qstr oldname;
+       struct inode *h_dir, *delegated;
+       struct dentry *info_dentry;
+       struct path infopath;
+
+       whnamelen = sizeof(AUFS_WH_DR_INFO_PFX) - 1;
+       whnamelen += au_drinfo_name(br, whname + whnamelen,
+                                   sizeof(whname) - whnamelen);
+       if (w->no_sio)
+               drinfo = au_drinfo_do_load(&w->h_ppath, whname, whnamelen,
+                                          &info_dentry);
+       else {
+               struct au_drinfo_do_load_args args = {
+                       .drinfop        = &drinfo,
+                       .h_ppath        = &w->h_ppath,
+                       .whname         = whname,
+                       .whnamelen      = whnamelen,
+                       .info_dentry    = &info_dentry
+               };
+               wkq_err = au_wkq_wait(au_call_drinfo_do_load, &args);
+               if (unlikely(wkq_err))
+                       drinfo = ERR_PTR(wkq_err);
+       }
+       err = PTR_ERR(drinfo);
+       if (IS_ERR_OR_NULL(drinfo))
+               goto out;
+
+       err = 0;
+       oldname.len = drinfo->oldnamelen;
+       oldname.name = drinfo->oldname;
+       if (au_qstreq(w->qname, &oldname)) {
+               /* the name is renamed back */
+               au_kfree_rcu(drinfo);
+               drinfo = NULL;
+
+               infopath.dentry = info_dentry;
+               infopath.mnt = w->h_ppath.mnt;
+               h_dir = d_inode(w->h_ppath.dentry);
+               delegated = NULL;
+               inode_lock_nested(h_dir, AuLsc_I_PARENT);
+               e = vfsub_unlink(h_dir, &infopath, &delegated, !w->no_sio);
+               inode_unlock(h_dir);
+               if (unlikely(e))
+                       AuIOErr("ignored %d, %pd2\n", e, &infopath.dentry);
+               if (unlikely(e == -EWOULDBLOCK))
+                       iput(delegated);
+       }
+       au_kfree_rcu(w->drinfo[bindex]);
+       w->drinfo[bindex] = drinfo;
+       dput(info_dentry);
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static void au_dr_lkup_free(struct au_drinfo **drinfo, int n)
+{
+       struct au_drinfo **p = drinfo;
+
+       while (n-- > 0)
+               au_kfree_rcu(*drinfo++);
+       au_kfree_try_rcu(p);
+}
+
+int au_dr_lkup(struct au_do_lookup_args *lkup, struct dentry *dentry,
+              aufs_bindex_t btgt)
+{
+       int err, ninfo;
+       struct au_drinfo_load w;
+       aufs_bindex_t bindex, bbot;
+       struct au_branch *br;
+       struct inode *h_dir;
+       struct au_dr_hino *ent;
+       struct super_block *sb;
+
+       AuDbg("%.*s, name %.*s, whname %.*s, b%d\n",
+             AuLNPair(&dentry->d_name), AuLNPair(&lkup->dirren.dr_name),
+             AuLNPair(&lkup->whname), btgt);
+
+       sb = dentry->d_sb;
+       bbot = au_sbbot(sb);
+       w.ninfo = bbot + 1;
+       if (!lkup->dirren.drinfo) {
+               lkup->dirren.drinfo = kcalloc(w.ninfo,
+                                             sizeof(*lkup->dirren.drinfo),
+                                             GFP_NOFS);
+               if (unlikely(!lkup->dirren.drinfo)) {
+                       err = -ENOMEM;
+                       goto out;
+               }
+               lkup->dirren.ninfo = w.ninfo;
+       }
+       w.drinfo = lkup->dirren.drinfo;
+       w.no_sio = !!uid_eq(current_fsuid(), GLOBAL_ROOT_UID);
+       w.h_ppath.dentry = au_h_dptr(dentry, btgt);
+       AuDebugOn(!w.h_ppath.dentry);
+       w.h_ppath.mnt = au_sbr_mnt(sb, btgt);
+       w.qname = &dentry->d_name;
+
+       ninfo = 0;
+       for (bindex = btgt + 1; bindex <= bbot; bindex++) {
+               br = au_sbr(sb, bindex);
+               err = au_drinfo_load(&w, bindex, br);
+               if (unlikely(err))
+                       goto out_free;
+               if (w.drinfo[bindex])
+                       ninfo++;
+       }
+       if (!ninfo) {
+               br = au_sbr(sb, btgt);
+               h_dir = d_inode(w.h_ppath.dentry);
+               ent = au_dr_hino_find(&br->br_dirren, h_dir->i_ino);
+               AuDebugOn(!ent);
+               au_dr_hino_del(&br->br_dirren, ent);
+               au_kfree_rcu(ent);
+       }
+       goto out; /* success */
+
+out_free:
+       au_dr_lkup_free(lkup->dirren.drinfo, lkup->dirren.ninfo);
+       lkup->dirren.ninfo = 0;
+       lkup->dirren.drinfo = NULL;
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+void au_dr_lkup_fin(struct au_do_lookup_args *lkup)
+{
+       au_dr_lkup_free(lkup->dirren.drinfo, lkup->dirren.ninfo);
+}
+
+int au_dr_lkup_name(struct au_do_lookup_args *lkup, aufs_bindex_t btgt)
+{
+       int err;
+       struct au_drinfo *drinfo;
+
+       err = 0;
+       if (!lkup->dirren.drinfo)
+               goto out;
+       AuDebugOn(lkup->dirren.ninfo <= btgt);
+       drinfo = lkup->dirren.drinfo[btgt];
+       if (!drinfo)
+               goto out;
+
+       au_kfree_try_rcu(lkup->whname.name);
+       lkup->whname.name = NULL;
+       lkup->dirren.dr_name.len = drinfo->oldnamelen;
+       lkup->dirren.dr_name.name = drinfo->oldname;
+       lkup->name = &lkup->dirren.dr_name;
+       err = au_wh_name_alloc(&lkup->whname, lkup->name);
+       if (!err)
+               AuDbg("name %.*s, whname %.*s, b%d\n",
+                     AuLNPair(lkup->name), AuLNPair(&lkup->whname),
+                     btgt);
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+int au_dr_lkup_h_ino(struct au_do_lookup_args *lkup, aufs_bindex_t bindex,
+                    ino_t h_ino)
+{
+       int match;
+       struct au_drinfo *drinfo;
+
+       match = 1;
+       if (!lkup->dirren.drinfo)
+               goto out;
+       AuDebugOn(lkup->dirren.ninfo <= bindex);
+       drinfo = lkup->dirren.drinfo[bindex];
+       if (!drinfo)
+               goto out;
+
+       match = (drinfo->ino == h_ino);
+       AuDbg("match %d\n", match);
+
+out:
+       return match;
+}
+
+/* ---------------------------------------------------------------------- */
+
+int au_dr_opt_set(struct super_block *sb)
+{
+       int err;
+       aufs_bindex_t bindex, bbot;
+       struct au_branch *br;
+
+       err = 0;
+       bbot = au_sbbot(sb);
+       for (bindex = 0; !err && bindex <= bbot; bindex++) {
+               br = au_sbr(sb, bindex);
+               err = au_dr_hino(sb, bindex, /*br*/NULL, &br->br_path);
+       }
+
+       return err;
+}
+
+int au_dr_opt_flush(struct super_block *sb)
+{
+       int err;
+       aufs_bindex_t bindex, bbot;
+       struct au_branch *br;
+
+       err = 0;
+       bbot = au_sbbot(sb);
+       for (bindex = 0; !err && bindex <= bbot; bindex++) {
+               br = au_sbr(sb, bindex);
+               if (au_br_writable(br->br_perm))
+                       err = au_dr_hino(sb, bindex, /*br*/NULL, /*path*/NULL);
+       }
+
+       return err;
+}
+
+int au_dr_opt_clr(struct super_block *sb, int no_flush)
+{
+       int err;
+       aufs_bindex_t bindex, bbot;
+       struct au_branch *br;
+
+       err = 0;
+       if (!no_flush) {
+               err = au_dr_opt_flush(sb);
+               if (unlikely(err))
+                       goto out;
+       }
+
+       bbot = au_sbbot(sb);
+       for (bindex = 0; bindex <= bbot; bindex++) {
+               br = au_sbr(sb, bindex);
+               au_dr_hino_free(&br->br_dirren);
+       }
+
+out:
+       return err;
+}
diff -urN /usr/share/empty/fs/aufs/dirren.h linux/fs/aufs/dirren.h
--- /usr/share/empty/fs/aufs/dirren.h   1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/dirren.h      2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,140 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2017-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * renamed dir info
+ */
+
+#ifndef __AUFS_DIRREN_H__
+#define __AUFS_DIRREN_H__
+
+#ifdef __KERNEL__
+
+#include <linux/dcache.h>
+#include <linux/statfs.h>
+#include <linux/uuid.h>
+#include "hbl.h"
+
+#define AuDirren_NHASH 100
+
+#ifdef CONFIG_AUFS_DIRREN
+enum au_brid_type {
+       AuBrid_Unset,
+       AuBrid_UUID,
+       AuBrid_FSID,
+       AuBrid_DEV
+};
+
+struct au_dr_brid {
+       enum au_brid_type       type;
+       union {
+               uuid_t  uuid;   /* unimplemented yet */
+               fsid_t  fsid;
+               dev_t   dev;
+       };
+};
+
+/* 20 is the max digits length of ulong 64 */
+/* brid-type "_" uuid "_" inum */
+#define AUFS_DIRREN_FNAME_SZ   (1 + 1 + UUID_STRING_LEN + 20)
+#define AUFS_DIRREN_ENV_VAL_SZ (AUFS_DIRREN_FNAME_SZ + 1 + 20)
+
+struct au_dr_hino {
+       struct hlist_bl_node    dr_hnode;
+       ino_t                   dr_h_ino;
+};
+
+struct au_dr_br {
+       struct hlist_bl_head    dr_h_ino[AuDirren_NHASH];
+       struct au_dr_brid       dr_brid;
+};
+
+struct au_dr_lookup {
+       /* dr_name is pointed by struct au_do_lookup_args.name */
+       struct qstr             dr_name; /* subset of dr_info */
+       aufs_bindex_t           ninfo;
+       struct au_drinfo        **drinfo;
+};
+#else
+struct au_dr_hino;
+/* empty */
+struct au_dr_br { };
+struct au_dr_lookup { };
+#endif
+
+/* ---------------------------------------------------------------------- */
+
+struct au_branch;
+struct au_do_lookup_args;
+struct au_hinode;
+#ifdef CONFIG_AUFS_DIRREN
+int au_dr_hino_test_add(struct au_dr_br *dr, ino_t h_ino,
+                       struct au_dr_hino *add_ent);
+void au_dr_hino_free(struct au_dr_br *dr);
+int au_dr_br_init(struct super_block *sb, struct au_branch *br,
+                 const struct path *path);
+int au_dr_br_fin(struct super_block *sb, struct au_branch *br);
+int au_dr_rename(struct dentry *src, aufs_bindex_t bindex,
+                struct qstr *dst_name, void *_rev);
+void au_dr_rename_fin(struct dentry *src, aufs_bindex_t btgt, void *rev);
+void au_dr_rename_rev(struct dentry *src, aufs_bindex_t bindex, void *rev);
+int au_dr_lkup(struct au_do_lookup_args *lkup, struct dentry *dentry,
+              aufs_bindex_t bindex);
+int au_dr_lkup_name(struct au_do_lookup_args *lkup, aufs_bindex_t btgt);
+int au_dr_lkup_h_ino(struct au_do_lookup_args *lkup, aufs_bindex_t bindex,
+                    ino_t h_ino);
+void au_dr_lkup_fin(struct au_do_lookup_args *lkup);
+int au_dr_opt_set(struct super_block *sb);
+int au_dr_opt_flush(struct super_block *sb);
+int au_dr_opt_clr(struct super_block *sb, int no_flush);
+#else
+AuStubInt0(au_dr_hino_test_add, struct au_dr_br *dr, ino_t h_ino,
+          struct au_dr_hino *add_ent);
+AuStubVoid(au_dr_hino_free, struct au_dr_br *dr);
+AuStubInt0(au_dr_br_init, struct super_block *sb, struct au_branch *br,
+          const struct path *path);
+AuStubInt0(au_dr_br_fin, struct super_block *sb, struct au_branch *br);
+AuStubInt0(au_dr_rename, struct dentry *src, aufs_bindex_t bindex,
+          struct qstr *dst_name, void *_rev);
+AuStubVoid(au_dr_rename_fin, struct dentry *src, aufs_bindex_t btgt, void *rev);
+AuStubVoid(au_dr_rename_rev, struct dentry *src, aufs_bindex_t bindex,
+          void *rev);
+AuStubInt0(au_dr_lkup, struct au_do_lookup_args *lkup, struct dentry *dentry,
+          aufs_bindex_t bindex);
+AuStubInt0(au_dr_lkup_name, struct au_do_lookup_args *lkup, aufs_bindex_t btgt);
+AuStubInt0(au_dr_lkup_h_ino, struct au_do_lookup_args *lkup,
+          aufs_bindex_t bindex, ino_t h_ino);
+AuStubVoid(au_dr_lkup_fin, struct au_do_lookup_args *lkup);
+AuStubInt0(au_dr_opt_set, struct super_block *sb);
+AuStubInt0(au_dr_opt_flush, struct super_block *sb);
+AuStubInt0(au_dr_opt_clr, struct super_block *sb, int no_flush);
+#endif
+
+/* ---------------------------------------------------------------------- */
+
+#ifdef CONFIG_AUFS_DIRREN
+static inline int au_dr_ihash(ino_t h_ino)
+{
+       return h_ino % AuDirren_NHASH;
+}
+#else
+AuStubInt0(au_dr_ihash, ino_t h_ino);
+#endif
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_DIRREN_H__ */
diff -urN /usr/share/empty/fs/aufs/dynop.c linux/fs/aufs/dynop.c
--- /usr/share/empty/fs/aufs/dynop.c    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/dynop.c       2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,368 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2010-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * dynamically customizable operations for regular files
+ */
+
+#include "aufs.h"
+
+#define DyPrSym(key)   AuDbgSym(key->dk_op.dy_hop)
+
+/*
+ * How large will these lists be?
+ * Usually just a few elements, 20-30 at most for each, I guess.
+ */
+static struct hlist_bl_head dynop[AuDyLast];
+
+static struct au_dykey *dy_gfind_get(struct hlist_bl_head *hbl,
+                                    const void *h_op)
+{
+       struct au_dykey *key, *tmp;
+       struct hlist_bl_node *pos;
+
+       key = NULL;
+       hlist_bl_lock(hbl);
+       hlist_bl_for_each_entry(tmp, pos, hbl, dk_hnode)
+               if (tmp->dk_op.dy_hop == h_op) {
+                       if (kref_get_unless_zero(&tmp->dk_kref))
+                               key = tmp;
+                       break;
+               }
+       hlist_bl_unlock(hbl);
+
+       return key;
+}
+
+static struct au_dykey *dy_bradd(struct au_branch *br, struct au_dykey *key)
+{
+       struct au_dykey **k, *found;
+       const void *h_op = key->dk_op.dy_hop;
+       int i;
+
+       found = NULL;
+       k = br->br_dykey;
+       for (i = 0; i < AuBrDynOp; i++)
+               if (k[i]) {
+                       if (k[i]->dk_op.dy_hop == h_op) {
+                               found = k[i];
+                               break;
+                       }
+               } else
+                       break;
+       if (!found) {
+               spin_lock(&br->br_dykey_lock);
+               for (; i < AuBrDynOp; i++)
+                       if (k[i]) {
+                               if (k[i]->dk_op.dy_hop == h_op) {
+                                       found = k[i];
+                                       break;
+                               }
+                       } else {
+                               k[i] = key;
+                               break;
+                       }
+               spin_unlock(&br->br_dykey_lock);
+               BUG_ON(i == AuBrDynOp); /* expand the array */
+       }
+
+       return found;
+}
+
+/* kref_get() if @key is already added */
+static struct au_dykey *dy_gadd(struct hlist_bl_head *hbl, struct au_dykey *key)
+{
+       struct au_dykey *tmp, *found;
+       struct hlist_bl_node *pos;
+       const void *h_op = key->dk_op.dy_hop;
+
+       found = NULL;
+       hlist_bl_lock(hbl);
+       hlist_bl_for_each_entry(tmp, pos, hbl, dk_hnode)
+               if (tmp->dk_op.dy_hop == h_op) {
+                       if (kref_get_unless_zero(&tmp->dk_kref))
+                               found = tmp;
+                       break;
+               }
+       if (!found)
+               hlist_bl_add_head(&key->dk_hnode, hbl);
+       hlist_bl_unlock(hbl);
+
+       if (!found)
+               DyPrSym(key);
+       return found;
+}
+
+static void dy_free_rcu(struct rcu_head *rcu)
+{
+       struct au_dykey *key;
+
+       key = container_of(rcu, struct au_dykey, dk_rcu);
+       DyPrSym(key);
+       kfree(key);
+}
+
+static void dy_free(struct kref *kref)
+{
+       struct au_dykey *key;
+       struct hlist_bl_head *hbl;
+
+       key = container_of(kref, struct au_dykey, dk_kref);
+       hbl = dynop + key->dk_op.dy_type;
+       au_hbl_del(&key->dk_hnode, hbl);
+       call_rcu(&key->dk_rcu, dy_free_rcu);
+}
+
+void au_dy_put(struct au_dykey *key)
+{
+       kref_put(&key->dk_kref, dy_free);
+}
+
+/* ---------------------------------------------------------------------- */
+
+#define DyDbgSize(cnt, op)     AuDebugOn(cnt != sizeof(op)/sizeof(void *))
+
+#ifdef CONFIG_AUFS_DEBUG
+#define DyDbgDeclare(cnt)      unsigned int cnt = 0
+#define DyDbgInc(cnt)          do { cnt++; } while (0)
+#else
+#define DyDbgDeclare(cnt)      do {} while (0)
+#define DyDbgInc(cnt)          do {} while (0)
+#endif
+
+#define DySet(func, dst, src, h_op, h_sb) do {                         \
+       DyDbgInc(cnt);                                                  \
+       if (h_op->func) {                                               \
+               if (src.func)                                           \
+                       dst.func = src.func;                            \
+               else                                                    \
+                       AuDbg("%s %s\n", au_sbtype(h_sb), #func);       \
+       }                                                               \
+} while (0)
+
+#define DySetForce(func, dst, src) do {                \
+       AuDebugOn(!src.func);                   \
+       DyDbgInc(cnt);                          \
+       dst.func = src.func;                    \
+} while (0)
+
+#define DySetAop(func) \
+       DySet(func, dyaop->da_op, aufs_aop, h_aop, h_sb)
+#define DySetAopForce(func) \
+       DySetForce(func, dyaop->da_op, aufs_aop)
+
+static void dy_aop(struct au_dykey *key, const void *h_op,
+                  struct super_block *h_sb __maybe_unused)
+{
+       struct au_dyaop *dyaop = (void *)key;
+       const struct address_space_operations *h_aop = h_op;
+       DyDbgDeclare(cnt);
+
+       AuDbg("%s\n", au_sbtype(h_sb));
+
+       DySetAop(writepage);
+       DySetAopForce(readpage);        /* force */
+       DySetAop(writepages);
+       DySetAop(set_page_dirty);
+       DySetAop(readpages);
+       DySetAop(readahead);
+       DySetAop(write_begin);
+       DySetAop(write_end);
+       DySetAop(bmap);
+       DySetAop(invalidatepage);
+       DySetAop(releasepage);
+       DySetAop(freepage);
+       /* this one will be changed according to an aufs mount option */
+       DySetAop(direct_IO);
+       DySetAop(migratepage);
+       DySetAop(isolate_page);
+       DySetAop(putback_page);
+       DySetAop(launder_page);
+       DySetAop(is_partially_uptodate);
+       DySetAop(is_dirty_writeback);
+       DySetAop(error_remove_page);
+       DySetAop(swap_activate);
+       DySetAop(swap_deactivate);
+
+       DyDbgSize(cnt, *h_aop);
+}
+
+/* ---------------------------------------------------------------------- */
+
+static void dy_bug(struct kref *kref)
+{
+       BUG();
+}
+
+static struct au_dykey *dy_get(struct au_dynop *op, struct au_branch *br)
+{
+       struct au_dykey *key, *old;
+       struct hlist_bl_head *hbl;
+       struct op {
+               unsigned int sz;
+               void (*set)(struct au_dykey *key, const void *h_op,
+                           struct super_block *h_sb __maybe_unused);
+       };
+       static const struct op a[] = {
+               [AuDy_AOP] = {
+                       .sz     = sizeof(struct au_dyaop),
+                       .set    = dy_aop
+               }
+       };
+       const struct op *p;
+
+       hbl = dynop + op->dy_type;
+       key = dy_gfind_get(hbl, op->dy_hop);
+       if (key)
+               goto out_add; /* success */
+
+       p = a + op->dy_type;
+       key = kzalloc(p->sz, GFP_NOFS);
+       if (unlikely(!key)) {
+               key = ERR_PTR(-ENOMEM);
+               goto out;
+       }
+
+       key->dk_op.dy_hop = op->dy_hop;
+       kref_init(&key->dk_kref);
+       p->set(key, op->dy_hop, au_br_sb(br));
+       old = dy_gadd(hbl, key);
+       if (old) {
+               au_kfree_rcu(key);
+               key = old;
+       }
+
+out_add:
+       old = dy_bradd(br, key);
+       if (old)
+               /* its ref-count should never be zero here */
+               kref_put(&key->dk_kref, dy_bug);
+out:
+       return key;
+}
+
+/* ---------------------------------------------------------------------- */
+/*
+ * Aufs prohibits O_DIRECT by default even if the branch supports it.
+ * This behaviour is necessary to return an error from open(O_DIRECT) instead
+ * of the succeeding I/O. The dio mount option enables O_DIRECT and makes
+ * open(O_DIRECT) always succeed, but the succeeding I/O may return an error.
+ * See the aufs manual in detail.
+ */
+static void dy_adx(struct au_dyaop *dyaop, int do_dx)
+{
+       if (!do_dx)
+               dyaop->da_op.direct_IO = NULL;
+       else
+               dyaop->da_op.direct_IO = aufs_aop.direct_IO;
+}
+
+static struct au_dyaop *dy_aget(struct au_branch *br,
+                               const struct address_space_operations *h_aop,
+                               int do_dx)
+{
+       struct au_dyaop *dyaop;
+       struct au_dynop op;
+
+       op.dy_type = AuDy_AOP;
+       op.dy_haop = h_aop;
+       dyaop = (void *)dy_get(&op, br);
+       if (IS_ERR(dyaop))
+               goto out;
+       dy_adx(dyaop, do_dx);
+
+out:
+       return dyaop;
+}
+
+int au_dy_iaop(struct inode *inode, aufs_bindex_t bindex,
+               struct inode *h_inode)
+{
+       int err, do_dx;
+       struct super_block *sb;
+       struct au_branch *br;
+       struct au_dyaop *dyaop;
+
+       AuDebugOn(!S_ISREG(h_inode->i_mode));
+       IiMustWriteLock(inode);
+
+       sb = inode->i_sb;
+       br = au_sbr(sb, bindex);
+       do_dx = !!au_opt_test(au_mntflags(sb), DIO);
+       dyaop = dy_aget(br, h_inode->i_mapping->a_ops, do_dx);
+       err = PTR_ERR(dyaop);
+       if (IS_ERR(dyaop))
+               /* unnecessary to call dy_fput() */
+               goto out;
+
+       err = 0;
+       inode->i_mapping->a_ops = &dyaop->da_op;
+
+out:
+       return err;
+}
+
+/*
+ * Is it safe to replace a_ops during the inode/file is in operation?
+ * Yes, I hope so.
+ */
+int au_dy_irefresh(struct inode *inode)
+{
+       int err;
+       aufs_bindex_t btop;
+       struct inode *h_inode;
+
+       err = 0;
+       if (S_ISREG(inode->i_mode)) {
+               btop = au_ibtop(inode);
+               h_inode = au_h_iptr(inode, btop);
+               err = au_dy_iaop(inode, btop, h_inode);
+       }
+       return err;
+}
+
+void au_dy_arefresh(int do_dx)
+{
+       struct hlist_bl_head *hbl;
+       struct hlist_bl_node *pos;
+       struct au_dykey *key;
+
+       hbl = dynop + AuDy_AOP;
+       hlist_bl_lock(hbl);
+       hlist_bl_for_each_entry(key, pos, hbl, dk_hnode)
+               dy_adx((void *)key, do_dx);
+       hlist_bl_unlock(hbl);
+}
+
+/* ---------------------------------------------------------------------- */
+
+void __init au_dy_init(void)
+{
+       int i;
+
+       for (i = 0; i < AuDyLast; i++)
+               INIT_HLIST_BL_HEAD(dynop + i);
+}
+
+void au_dy_fin(void)
+{
+       int i;
+
+       for (i = 0; i < AuDyLast; i++)
+               WARN_ON(!hlist_bl_empty(dynop + i));
+}
diff -urN /usr/share/empty/fs/aufs/dynop.h linux/fs/aufs/dynop.h
--- /usr/share/empty/fs/aufs/dynop.h    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/dynop.h       2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2010-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * dynamically customizable operations (for regular files only)
+ */
+
+#ifndef __AUFS_DYNOP_H__
+#define __AUFS_DYNOP_H__
+
+#ifdef __KERNEL__
+
+#include <linux/fs.h>
+#include <linux/kref.h>
+
+enum {AuDy_AOP, AuDyLast};
+
+struct au_dynop {
+       int                                             dy_type;
+       union {
+               const void                              *dy_hop;
+               const struct address_space_operations   *dy_haop;
+       };
+};
+
+struct au_dykey {
+       union {
+               struct hlist_bl_node    dk_hnode;
+               struct rcu_head         dk_rcu;
+       };
+       struct au_dynop         dk_op;
+
+       /*
+        * during I am in the branch local array, kref is gotten. when the
+        * branch is removed, kref is put.
+        */
+       struct kref             dk_kref;
+};
+
+/* stop unioning since their sizes are very different from each other */
+struct au_dyaop {
+       struct au_dykey                 da_key;
+       struct address_space_operations da_op; /* not const */
+};
+/* make sure that 'struct au_dykey *' can be any type */
+static_assert(!offsetof(struct au_dyaop, da_key));
+
+/* ---------------------------------------------------------------------- */
+
+/* dynop.c */
+struct au_branch;
+void au_dy_put(struct au_dykey *key);
+int au_dy_iaop(struct inode *inode, aufs_bindex_t bindex,
+               struct inode *h_inode);
+int au_dy_irefresh(struct inode *inode);
+void au_dy_arefresh(int do_dio);
+
+void __init au_dy_init(void);
+void au_dy_fin(void);
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_DYNOP_H__ */
diff -urN /usr/share/empty/fs/aufs/export.c linux/fs/aufs/export.c
--- /usr/share/empty/fs/aufs/export.c   1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/export.c      2021-12-03 15:40:58.233313963 +0100
@@ -0,0 +1,831 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * export via nfs
+ */
+
+#include <linux/exportfs.h>
+#include <linux/fs_struct.h>
+#include <linux/namei.h>
+#include <linux/nsproxy.h>
+#include <linux/random.h>
+#include <linux/writeback.h>
+#include "aufs.h"
+
+union conv {
+#ifdef CONFIG_AUFS_INO_T_64
+       __u32 a[2];
+#else
+       __u32 a[1];
+#endif
+       ino_t ino;
+};
+
+static ino_t decode_ino(__u32 *a)
+{
+       union conv u;
+
+       BUILD_BUG_ON(sizeof(u.ino) != sizeof(u.a));
+       u.a[0] = a[0];
+#ifdef CONFIG_AUFS_INO_T_64
+       u.a[1] = a[1];
+#endif
+       return u.ino;
+}
+
+static void encode_ino(__u32 *a, ino_t ino)
+{
+       union conv u;
+
+       u.ino = ino;
+       a[0] = u.a[0];
+#ifdef CONFIG_AUFS_INO_T_64
+       a[1] = u.a[1];
+#endif
+}
+
+/* NFS file handle */
+enum {
+       Fh_br_id,
+       Fh_sigen,
+#ifdef CONFIG_AUFS_INO_T_64
+       /* support 64bit inode number */
+       Fh_ino1,
+       Fh_ino2,
+       Fh_dir_ino1,
+       Fh_dir_ino2,
+#else
+       Fh_ino1,
+       Fh_dir_ino1,
+#endif
+       Fh_igen,
+       Fh_h_type,
+       Fh_tail,
+
+       Fh_ino = Fh_ino1,
+       Fh_dir_ino = Fh_dir_ino1
+};
+
+static int au_test_anon(struct dentry *dentry)
+{
+       /* note: read d_flags without d_lock */
+       return !!(dentry->d_flags & DCACHE_DISCONNECTED);
+}
+
+int au_test_nfsd(void)
+{
+       int ret;
+       struct task_struct *tsk = current;
+       char comm[sizeof(tsk->comm)];
+
+       ret = 0;
+       if (tsk->flags & PF_KTHREAD) {
+               get_task_comm(comm, tsk);
+               ret = !strcmp(comm, "nfsd");
+       }
+
+       return ret;
+}
+
+/* ---------------------------------------------------------------------- */
+/* inode generation external table */
+
+void au_xigen_inc(struct inode *inode)
+{
+       loff_t pos;
+       ssize_t sz;
+       __u32 igen;
+       struct super_block *sb;
+       struct au_sbinfo *sbinfo;
+
+       sb = inode->i_sb;
+       AuDebugOn(!au_opt_test(au_mntflags(sb), XINO));
+
+       sbinfo = au_sbi(sb);
+       pos = inode->i_ino;
+       pos *= sizeof(igen);
+       igen = inode->i_generation + 1;
+       sz = xino_fwrite(sbinfo->si_xigen, &igen, sizeof(igen), &pos);
+       if (sz == sizeof(igen))
+               return; /* success */
+
+       if (unlikely(sz >= 0))
+               AuIOErr("xigen error (%zd)\n", sz);
+}
+
+int au_xigen_new(struct inode *inode)
+{
+       int err;
+       loff_t pos;
+       ssize_t sz;
+       struct super_block *sb;
+       struct au_sbinfo *sbinfo;
+       struct file *file;
+
+       err = 0;
+       /* todo: dirty, at mount time */
+       if (inode->i_ino == AUFS_ROOT_INO)
+               goto out;
+       sb = inode->i_sb;
+       SiMustAnyLock(sb);
+       if (unlikely(!au_opt_test(au_mntflags(sb), XINO)))
+               goto out;
+
+       err = -EFBIG;
+       pos = inode->i_ino;
+       if (unlikely(au_loff_max / sizeof(inode->i_generation) - 1 < pos)) {
+               AuIOErr1("too large i%lld\n", pos);
+               goto out;
+       }
+       pos *= sizeof(inode->i_generation);
+
+       err = 0;
+       sbinfo = au_sbi(sb);
+       file = sbinfo->si_xigen;
+       BUG_ON(!file);
+
+       if (vfsub_f_size_read(file)
+           < pos + sizeof(inode->i_generation)) {
+               inode->i_generation = atomic_inc_return(&sbinfo->si_xigen_next);
+               sz = xino_fwrite(file, &inode->i_generation,
+                                sizeof(inode->i_generation), &pos);
+       } else
+               sz = xino_fread(file, &inode->i_generation,
+                               sizeof(inode->i_generation), &pos);
+       if (sz == sizeof(inode->i_generation))
+               goto out; /* success */
+
+       err = sz;
+       if (unlikely(sz >= 0)) {
+               err = -EIO;
+               AuIOErr("xigen error (%zd)\n", sz);
+       }
+
+out:
+       return err;
+}
+
+int au_xigen_set(struct super_block *sb, struct path *path)
+{
+       int err;
+       struct au_sbinfo *sbinfo;
+       struct file *file;
+
+       SiMustWriteLock(sb);
+
+       sbinfo = au_sbi(sb);
+       file = au_xino_create2(sb, path, sbinfo->si_xigen);
+       err = PTR_ERR(file);
+       if (IS_ERR(file))
+               goto out;
+       err = 0;
+       if (sbinfo->si_xigen)
+               fput(sbinfo->si_xigen);
+       sbinfo->si_xigen = file;
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+void au_xigen_clr(struct super_block *sb)
+{
+       struct au_sbinfo *sbinfo;
+
+       SiMustWriteLock(sb);
+
+       sbinfo = au_sbi(sb);
+       if (sbinfo->si_xigen) {
+               fput(sbinfo->si_xigen);
+               sbinfo->si_xigen = NULL;
+       }
+}
+
+/* ---------------------------------------------------------------------- */
+
+static struct dentry *decode_by_ino(struct super_block *sb, ino_t ino,
+                                   ino_t dir_ino)
+{
+       struct dentry *dentry, *d;
+       struct inode *inode;
+       unsigned int sigen;
+
+       dentry = NULL;
+       inode = ilookup(sb, ino);
+       if (!inode)
+               goto out;
+
+       dentry = ERR_PTR(-ESTALE);
+       sigen = au_sigen(sb);
+       if (unlikely(au_is_bad_inode(inode)
+                    || IS_DEADDIR(inode)
+                    || sigen != au_iigen(inode, NULL)))
+               goto out_iput;
+
+       dentry = NULL;
+       if (!dir_ino || S_ISDIR(inode->i_mode))
+               dentry = d_find_alias(inode);
+       else {
+               spin_lock(&inode->i_lock);
+               hlist_for_each_entry(d, &inode->i_dentry, d_u.d_alias) {
+                       spin_lock(&d->d_lock);
+                       if (!au_test_anon(d)
+                           && d_inode(d->d_parent)->i_ino == dir_ino) {
+                               dentry = dget_dlock(d);
+                               spin_unlock(&d->d_lock);
+                               break;
+                       }
+                       spin_unlock(&d->d_lock);
+               }
+               spin_unlock(&inode->i_lock);
+       }
+       if (unlikely(dentry && au_digen_test(dentry, sigen))) {
+               /* need to refresh */
+               dput(dentry);
+               dentry = NULL;
+       }
+
+out_iput:
+       iput(inode);
+out:
+       AuTraceErrPtr(dentry);
+       return dentry;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* todo: dirty? */
+/* if exportfs_decode_fh() passed vfsmount*, we could be happy */
+
+struct au_compare_mnt_args {
+       /* input */
+       struct super_block *sb;
+
+       /* output */
+       struct vfsmount *mnt;
+};
+
+static int au_compare_mnt(struct vfsmount *mnt, void *arg)
+{
+       struct au_compare_mnt_args *a = arg;
+
+       if (mnt->mnt_sb != a->sb)
+               return 0;
+       a->mnt = mntget(mnt);
+       return 1;
+}
+
+static struct vfsmount *au_mnt_get(struct super_block *sb)
+{
+       int err;
+       struct path root;
+       struct au_compare_mnt_args args = {
+               .sb = sb
+       };
+
+       get_fs_root(current->fs, &root);
+       rcu_read_lock();
+       err = iterate_mounts(au_compare_mnt, &args, root.mnt);
+       rcu_read_unlock();
+       path_put(&root);
+       AuDebugOn(!err);
+       AuDebugOn(!args.mnt);
+       return args.mnt;
+}
+
+struct au_nfsd_si_lock {
+       unsigned int sigen;
+       aufs_bindex_t bindex, br_id;
+       unsigned char force_lock;
+};
+
+static int si_nfsd_read_lock(struct super_block *sb,
+                            struct au_nfsd_si_lock *nsi_lock)
+{
+       int err;
+       aufs_bindex_t bindex;
+
+       si_read_lock(sb, AuLock_FLUSH);
+
+       /* branch id may be wrapped around */
+       err = 0;
+       bindex = au_br_index(sb, nsi_lock->br_id);
+       if (bindex >= 0 && nsi_lock->sigen + AUFS_BRANCH_MAX > au_sigen(sb))
+               goto out; /* success */
+
+       err = -ESTALE;
+       bindex = -1;
+       if (!nsi_lock->force_lock)
+               si_read_unlock(sb);
+
+out:
+       nsi_lock->bindex = bindex;
+       return err;
+}
+
+struct find_name_by_ino {
+       struct dir_context ctx;
+       int called, found;
+       ino_t ino;
+       char *name;
+       int namelen;
+};
+
+static int
+find_name_by_ino(struct dir_context *ctx, const char *name, int namelen,
+                loff_t offset, u64 ino, unsigned int d_type)
+{
+       struct find_name_by_ino *a = container_of(ctx, struct find_name_by_ino,
+                                                 ctx);
+
+       a->called++;
+       if (a->ino != ino)
+               return 0;
+
+       memcpy(a->name, name, namelen);
+       a->namelen = namelen;
+       a->found = 1;
+       return 1;
+}
+
+static struct dentry *au_lkup_by_ino(struct path *path, ino_t ino,
+                                    struct au_nfsd_si_lock *nsi_lock)
+{
+       struct dentry *dentry, *parent;
+       struct file *file;
+       struct inode *dir;
+       struct find_name_by_ino arg = {
+               .ctx = {
+                       .actor = find_name_by_ino
+               }
+       };
+       int err;
+
+       parent = path->dentry;
+       if (nsi_lock)
+               si_read_unlock(parent->d_sb);
+       file = vfsub_dentry_open(path, au_dir_roflags);
+       dentry = (void *)file;
+       if (IS_ERR(file))
+               goto out;
+
+       dentry = ERR_PTR(-ENOMEM);
+       arg.name = (void *)__get_free_page(GFP_NOFS);
+       if (unlikely(!arg.name))
+               goto out_file;
+       arg.ino = ino;
+       arg.found = 0;
+       do {
+               arg.called = 0;
+               /* smp_mb(); */
+               err = vfsub_iterate_dir(file, &arg.ctx);
+       } while (!err && !arg.found && arg.called);
+       dentry = ERR_PTR(err);
+       if (unlikely(err))
+               goto out_name;
+       /* instead of ENOENT */
+       dentry = ERR_PTR(-ESTALE);
+       if (!arg.found)
+               goto out_name;
+
+       /* do not call vfsub_lkup_one() */
+       dir = d_inode(parent);
+       dentry = vfsub_lookup_one_len_unlocked(arg.name, path, arg.namelen);
+       AuTraceErrPtr(dentry);
+       if (IS_ERR(dentry))
+               goto out_name;
+       AuDebugOn(au_test_anon(dentry));
+       if (unlikely(d_really_is_negative(dentry))) {
+               dput(dentry);
+               dentry = ERR_PTR(-ENOENT);
+       }
+
+out_name:
+       free_page((unsigned long)arg.name);
+out_file:
+       fput(file);
+out:
+       if (unlikely(nsi_lock
+                    && si_nfsd_read_lock(parent->d_sb, nsi_lock) < 0))
+               if (!IS_ERR(dentry)) {
+                       dput(dentry);
+                       dentry = ERR_PTR(-ESTALE);
+               }
+       AuTraceErrPtr(dentry);
+       return dentry;
+}
+
+static struct dentry *decode_by_dir_ino(struct super_block *sb, ino_t ino,
+                                       ino_t dir_ino,
+                                       struct au_nfsd_si_lock *nsi_lock)
+{
+       struct dentry *dentry;
+       struct path path;
+
+       if (dir_ino != AUFS_ROOT_INO) {
+               path.dentry = decode_by_ino(sb, dir_ino, 0);
+               dentry = path.dentry;
+               if (!path.dentry || IS_ERR(path.dentry))
+                       goto out;
+               AuDebugOn(au_test_anon(path.dentry));
+       } else
+               path.dentry = dget(sb->s_root);
+
+       path.mnt = au_mnt_get(sb);
+       dentry = au_lkup_by_ino(&path, ino, nsi_lock);
+       path_put(&path);
+
+out:
+       AuTraceErrPtr(dentry);
+       return dentry;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int h_acceptable(void *expv, struct dentry *dentry)
+{
+       return 1;
+}
+
+static char *au_build_path(struct dentry *h_parent, struct path *h_rootpath,
+                          char *buf, int len, struct super_block *sb)
+{
+       char *p;
+       int n;
+       struct path path;
+
+       p = d_path(h_rootpath, buf, len);
+       if (IS_ERR(p))
+               goto out;
+       n = strlen(p);
+
+       path.mnt = h_rootpath->mnt;
+       path.dentry = h_parent;
+       p = d_path(&path, buf, len);
+       if (IS_ERR(p))
+               goto out;
+       if (n != 1)
+               p += n;
+
+       path.mnt = au_mnt_get(sb);
+       path.dentry = sb->s_root;
+       p = d_path(&path, buf, len - strlen(p));
+       mntput(path.mnt);
+       if (IS_ERR(p))
+               goto out;
+       if (n != 1)
+               p[strlen(p)] = '/';
+
+out:
+       AuTraceErrPtr(p);
+       return p;
+}
+
+static
+struct dentry *decode_by_path(struct super_block *sb, ino_t ino, __u32 *fh,
+                             int fh_len, struct au_nfsd_si_lock *nsi_lock)
+{
+       struct dentry *dentry, *h_parent, *root;
+       struct super_block *h_sb;
+       char *pathname, *p;
+       struct vfsmount *h_mnt;
+       struct au_branch *br;
+       int err;
+       struct path path;
+
+       br = au_sbr(sb, nsi_lock->bindex);
+       h_mnt = au_br_mnt(br);
+       h_sb = h_mnt->mnt_sb;
+       /* todo: call lower fh_to_dentry()? fh_to_parent()? */
+       lockdep_off();
+       h_parent = exportfs_decode_fh(h_mnt, (void *)(fh + Fh_tail),
+                                     fh_len - Fh_tail, fh[Fh_h_type],
+                                     h_acceptable, /*context*/NULL);
+       lockdep_on();
+       dentry = h_parent;
+       if (unlikely(!h_parent || IS_ERR(h_parent))) {
+               AuWarn1("%s decode_fh failed, %ld\n",
+                       au_sbtype(h_sb), PTR_ERR(h_parent));
+               goto out;
+       }
+       dentry = NULL;
+       if (unlikely(au_test_anon(h_parent))) {
+               AuWarn1("%s decode_fh returned a disconnected dentry\n",
+                       au_sbtype(h_sb));
+               goto out_h_parent;
+       }
+
+       dentry = ERR_PTR(-ENOMEM);
+       pathname = (void *)__get_free_page(GFP_NOFS);
+       if (unlikely(!pathname))
+               goto out_h_parent;
+
+       root = sb->s_root;
+       path.mnt = h_mnt;
+       di_read_lock_parent(root, !AuLock_IR);
+       path.dentry = au_h_dptr(root, nsi_lock->bindex);
+       di_read_unlock(root, !AuLock_IR);
+       p = au_build_path(h_parent, &path, pathname, PAGE_SIZE, sb);
+       dentry = (void *)p;
+       if (IS_ERR(p))
+               goto out_pathname;
+
+       si_read_unlock(sb);
+       err = vfsub_kern_path(p, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &path);
+       dentry = ERR_PTR(err);
+       if (unlikely(err))
+               goto out_relock;
+
+       dentry = ERR_PTR(-ENOENT);
+       AuDebugOn(au_test_anon(path.dentry));
+       if (unlikely(d_really_is_negative(path.dentry)))
+               goto out_path;
+
+       if (ino != d_inode(path.dentry)->i_ino)
+               dentry = au_lkup_by_ino(&path, ino, /*nsi_lock*/NULL);
+       else
+               dentry = dget(path.dentry);
+
+out_path:
+       path_put(&path);
+out_relock:
+       if (unlikely(si_nfsd_read_lock(sb, nsi_lock) < 0))
+               if (!IS_ERR(dentry)) {
+                       dput(dentry);
+                       dentry = ERR_PTR(-ESTALE);
+               }
+out_pathname:
+       free_page((unsigned long)pathname);
+out_h_parent:
+       dput(h_parent);
+out:
+       AuTraceErrPtr(dentry);
+       return dentry;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static struct dentry *
+aufs_fh_to_dentry(struct super_block *sb, struct fid *fid, int fh_len,
+                 int fh_type)
+{
+       struct dentry *dentry;
+       __u32 *fh = fid->raw;
+       struct au_branch *br;
+       ino_t ino, dir_ino;
+       struct au_nfsd_si_lock nsi_lock = {
+               .force_lock     = 0
+       };
+
+       dentry = ERR_PTR(-ESTALE);
+       /* it should never happen, but the file handle is unreliable */
+       if (unlikely(fh_len < Fh_tail))
+               goto out;
+       nsi_lock.sigen = fh[Fh_sigen];
+       nsi_lock.br_id = fh[Fh_br_id];
+
+       /* branch id may be wrapped around */
+       br = NULL;
+       if (unlikely(si_nfsd_read_lock(sb, &nsi_lock)))
+               goto out;
+       nsi_lock.force_lock = 1;
+
+       /* is this inode still cached? */
+       ino = decode_ino(fh + Fh_ino);
+       /* it should never happen */
+       if (unlikely(ino == AUFS_ROOT_INO))
+               goto out_unlock;
+
+       dir_ino = decode_ino(fh + Fh_dir_ino);
+       dentry = decode_by_ino(sb, ino, dir_ino);
+       if (IS_ERR(dentry))
+               goto out_unlock;
+       if (dentry)
+               goto accept;
+
+       /* is the parent dir cached? */
+       br = au_sbr(sb, nsi_lock.bindex);
+       au_lcnt_inc(&br->br_nfiles);
+       dentry = decode_by_dir_ino(sb, ino, dir_ino, &nsi_lock);
+       if (IS_ERR(dentry))
+               goto out_unlock;
+       if (dentry)
+               goto accept;
+
+       /* lookup path */
+       dentry = decode_by_path(sb, ino, fh, fh_len, &nsi_lock);
+       if (IS_ERR(dentry))
+               goto out_unlock;
+       if (unlikely(!dentry))
+               /* todo?: make it ESTALE */
+               goto out_unlock;
+
+accept:
+       if (!au_digen_test(dentry, au_sigen(sb))
+           && d_inode(dentry)->i_generation == fh[Fh_igen])
+               goto out_unlock; /* success */
+
+       dput(dentry);
+       dentry = ERR_PTR(-ESTALE);
+out_unlock:
+       if (br)
+               au_lcnt_dec(&br->br_nfiles);
+       si_read_unlock(sb);
+out:
+       AuTraceErrPtr(dentry);
+       return dentry;
+}
+
+#if 0 /* reserved for future use */
+/* support subtreecheck option */
+static struct dentry *aufs_fh_to_parent(struct super_block *sb, struct fid *fid,
+                                       int fh_len, int fh_type)
+{
+       struct dentry *parent;
+       __u32 *fh = fid->raw;
+       ino_t dir_ino;
+
+       dir_ino = decode_ino(fh + Fh_dir_ino);
+       parent = decode_by_ino(sb, dir_ino, 0);
+       if (IS_ERR(parent))
+               goto out;
+       if (!parent)
+               parent = decode_by_path(sb, au_br_index(sb, fh[Fh_br_id]),
+                                       dir_ino, fh, fh_len);
+
+out:
+       AuTraceErrPtr(parent);
+       return parent;
+}
+#endif
+
+/* ---------------------------------------------------------------------- */
+
+static int aufs_encode_fh(struct inode *inode, __u32 *fh, int *max_len,
+                         struct inode *dir)
+{
+       int err;
+       aufs_bindex_t bindex;
+       struct super_block *sb, *h_sb;
+       struct dentry *dentry, *parent, *h_parent;
+       struct inode *h_dir;
+       struct au_branch *br;
+
+       err = -ENOSPC;
+       if (unlikely(*max_len <= Fh_tail)) {
+               AuWarn1("NFSv2 client (max_len %d)?\n", *max_len);
+               goto out;
+       }
+
+       err = FILEID_ROOT;
+       if (inode->i_ino == AUFS_ROOT_INO) {
+               AuDebugOn(inode->i_ino != AUFS_ROOT_INO);
+               goto out;
+       }
+
+       h_parent = NULL;
+       sb = inode->i_sb;
+       err = si_read_lock(sb, AuLock_FLUSH);
+       if (unlikely(err))
+               goto out;
+
+#ifdef CONFIG_AUFS_DEBUG
+       if (unlikely(!au_opt_test(au_mntflags(sb), XINO)))
+               AuWarn1("NFS-exporting requires xino\n");
+#endif
+       err = -EIO;
+       parent = NULL;
+       ii_read_lock_child(inode);
+       bindex = au_ibtop(inode);
+       if (!dir) {
+               dentry = d_find_any_alias(inode);
+               if (unlikely(!dentry))
+                       goto out_unlock;
+               AuDebugOn(au_test_anon(dentry));
+               parent = dget_parent(dentry);
+               dput(dentry);
+               if (unlikely(!parent))
+                       goto out_unlock;
+               if (d_really_is_positive(parent))
+                       dir = d_inode(parent);
+       }
+
+       ii_read_lock_parent(dir);
+       h_dir = au_h_iptr(dir, bindex);
+       ii_read_unlock(dir);
+       if (unlikely(!h_dir))
+               goto out_parent;
+       h_parent = d_find_any_alias(h_dir);
+       if (unlikely(!h_parent))
+               goto out_hparent;
+
+       err = -EPERM;
+       br = au_sbr(sb, bindex);
+       h_sb = au_br_sb(br);
+       if (unlikely(!h_sb->s_export_op)) {
+               AuErr1("%s branch is not exportable\n", au_sbtype(h_sb));
+               goto out_hparent;
+       }
+
+       fh[Fh_br_id] = br->br_id;
+       fh[Fh_sigen] = au_sigen(sb);
+       encode_ino(fh + Fh_ino, inode->i_ino);
+       encode_ino(fh + Fh_dir_ino, dir->i_ino);
+       fh[Fh_igen] = inode->i_generation;
+
+       *max_len -= Fh_tail;
+       fh[Fh_h_type] = exportfs_encode_fh(h_parent, (void *)(fh + Fh_tail),
+                                          max_len,
+                                          /*connectable or subtreecheck*/0);
+       err = fh[Fh_h_type];
+       *max_len += Fh_tail;
+       /* todo: macros? */
+       if (err != FILEID_INVALID)
+               err = 99;
+       else
+               AuWarn1("%s encode_fh failed\n", au_sbtype(h_sb));
+
+out_hparent:
+       dput(h_parent);
+out_parent:
+       dput(parent);
+out_unlock:
+       ii_read_unlock(inode);
+       si_read_unlock(sb);
+out:
+       if (unlikely(err < 0))
+               err = FILEID_INVALID;
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int aufs_commit_metadata(struct inode *inode)
+{
+       int err;
+       aufs_bindex_t bindex;
+       struct super_block *sb;
+       struct inode *h_inode;
+       int (*f)(struct inode *inode);
+
+       sb = inode->i_sb;
+       si_read_lock(sb, AuLock_FLUSH | AuLock_NOPLMW);
+       ii_write_lock_child(inode);
+       bindex = au_ibtop(inode);
+       AuDebugOn(bindex < 0);
+       h_inode = au_h_iptr(inode, bindex);
+
+       f = h_inode->i_sb->s_export_op->commit_metadata;
+       if (f)
+               err = f(h_inode);
+       else
+               err = sync_inode_metadata(h_inode, /*wait*/1);
+
+       au_cpup_attr_timesizes(inode);
+       ii_write_unlock(inode);
+       si_read_unlock(sb);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static struct export_operations aufs_export_op = {
+       .fh_to_dentry           = aufs_fh_to_dentry,
+       /* .fh_to_parent        = aufs_fh_to_parent, */
+       .encode_fh              = aufs_encode_fh,
+       .commit_metadata        = aufs_commit_metadata
+};
+
+void au_export_init(struct super_block *sb)
+{
+       struct au_sbinfo *sbinfo;
+       __u32 u;
+
+       BUILD_BUG_ON_MSG(IS_BUILTIN(CONFIG_AUFS_FS)
+                        && IS_MODULE(CONFIG_EXPORTFS),
+                        AUFS_NAME ": unsupported configuration "
+                        "CONFIG_EXPORTFS=m and CONFIG_AUFS_FS=y");
+
+       sb->s_export_op = &aufs_export_op;
+       sbinfo = au_sbi(sb);
+       sbinfo->si_xigen = NULL;
+       get_random_bytes(&u, sizeof(u));
+       BUILD_BUG_ON(sizeof(u) != sizeof(int));
+       atomic_set(&sbinfo->si_xigen_next, u);
+}
diff -urN /usr/share/empty/fs/aufs/fhsm.c linux/fs/aufs/fhsm.c
--- /usr/share/empty/fs/aufs/fhsm.c     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/fhsm.c        2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,427 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2011-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+/*
+ * File-based Hierarchy Storage Management
+ */
+
+#include <linux/anon_inodes.h>
+#include <linux/poll.h>
+#include <linux/seq_file.h>
+#include <linux/statfs.h>
+#include "aufs.h"
+
+static aufs_bindex_t au_fhsm_bottom(struct super_block *sb)
+{
+       struct au_sbinfo *sbinfo;
+       struct au_fhsm *fhsm;
+
+       SiMustAnyLock(sb);
+
+       sbinfo = au_sbi(sb);
+       fhsm = &sbinfo->si_fhsm;
+       AuDebugOn(!fhsm);
+       return fhsm->fhsm_bottom;
+}
+
+void au_fhsm_set_bottom(struct super_block *sb, aufs_bindex_t bindex)
+{
+       struct au_sbinfo *sbinfo;
+       struct au_fhsm *fhsm;
+
+       SiMustWriteLock(sb);
+
+       sbinfo = au_sbi(sb);
+       fhsm = &sbinfo->si_fhsm;
+       AuDebugOn(!fhsm);
+       fhsm->fhsm_bottom = bindex;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_fhsm_test_jiffy(struct au_sbinfo *sbinfo, struct au_branch *br)
+{
+       struct au_br_fhsm *bf;
+
+       bf = br->br_fhsm;
+       MtxMustLock(&bf->bf_lock);
+
+       return !bf->bf_readable
+               || time_after(jiffies,
+                             bf->bf_jiffy + sbinfo->si_fhsm.fhsm_expire);
+}
+
+/* ---------------------------------------------------------------------- */
+
+static void au_fhsm_notify(struct super_block *sb, int val)
+{
+       struct au_sbinfo *sbinfo;
+       struct au_fhsm *fhsm;
+
+       SiMustAnyLock(sb);
+
+       sbinfo = au_sbi(sb);
+       fhsm = &sbinfo->si_fhsm;
+       if (au_fhsm_pid(fhsm)
+           && atomic_read(&fhsm->fhsm_readable) != -1) {
+               atomic_set(&fhsm->fhsm_readable, val);
+               if (val)
+                       wake_up(&fhsm->fhsm_wqh);
+       }
+}
+
+static int au_fhsm_stfs(struct super_block *sb, aufs_bindex_t bindex,
+                       struct aufs_stfs *rstfs, int do_lock, int do_notify)
+{
+       int err;
+       struct au_branch *br;
+       struct au_br_fhsm *bf;
+
+       br = au_sbr(sb, bindex);
+       AuDebugOn(au_br_rdonly(br));
+       bf = br->br_fhsm;
+       AuDebugOn(!bf);
+
+       if (do_lock)
+               mutex_lock(&bf->bf_lock);
+       else
+               MtxMustLock(&bf->bf_lock);
+
+       /* sb->s_root for NFS is unreliable */
+       err = au_br_stfs(br, &bf->bf_stfs);
+       if (unlikely(err)) {
+               AuErr1("FHSM failed (%d), b%d, ignored.\n", bindex, err);
+               goto out;
+       }
+
+       bf->bf_jiffy = jiffies;
+       bf->bf_readable = 1;
+       if (do_notify)
+               au_fhsm_notify(sb, /*val*/1);
+       if (rstfs)
+               *rstfs = bf->bf_stfs;
+
+out:
+       if (do_lock)
+               mutex_unlock(&bf->bf_lock);
+       au_fhsm_notify(sb, /*val*/1);
+
+       return err;
+}
+
+void au_fhsm_wrote(struct super_block *sb, aufs_bindex_t bindex, int force)
+{
+       int err;
+       struct au_sbinfo *sbinfo;
+       struct au_fhsm *fhsm;
+       struct au_branch *br;
+       struct au_br_fhsm *bf;
+
+       AuDbg("b%d, force %d\n", bindex, force);
+       SiMustAnyLock(sb);
+
+       sbinfo = au_sbi(sb);
+       fhsm = &sbinfo->si_fhsm;
+       if (!au_ftest_si(sbinfo, FHSM)
+           || fhsm->fhsm_bottom == bindex)
+               return;
+
+       br = au_sbr(sb, bindex);
+       bf = br->br_fhsm;
+       AuDebugOn(!bf);
+       mutex_lock(&bf->bf_lock);
+       if (force
+           || au_fhsm_pid(fhsm)
+           || au_fhsm_test_jiffy(sbinfo, br))
+               err = au_fhsm_stfs(sb, bindex, /*rstfs*/NULL, /*do_lock*/0,
+                                 /*do_notify*/1);
+       mutex_unlock(&bf->bf_lock);
+}
+
+void au_fhsm_wrote_all(struct super_block *sb, int force)
+{
+       aufs_bindex_t bindex, bbot;
+       struct au_branch *br;
+
+       /* exclude the bottom */
+       bbot = au_fhsm_bottom(sb);
+       for (bindex = 0; bindex < bbot; bindex++) {
+               br = au_sbr(sb, bindex);
+               if (au_br_fhsm(br->br_perm))
+                       au_fhsm_wrote(sb, bindex, force);
+       }
+}
+
+/* ---------------------------------------------------------------------- */
+
+static __poll_t au_fhsm_poll(struct file *file, struct poll_table_struct *wait)
+{
+       __poll_t mask;
+       struct au_sbinfo *sbinfo;
+       struct au_fhsm *fhsm;
+
+       mask = 0;
+       sbinfo = file->private_data;
+       fhsm = &sbinfo->si_fhsm;
+       poll_wait(file, &fhsm->fhsm_wqh, wait);
+       if (atomic_read(&fhsm->fhsm_readable))
+               mask = EPOLLIN /* | EPOLLRDNORM */;
+
+       if (!mask)
+               AuDbg("mask 0x%x\n", mask);
+       return mask;
+}
+
+static int au_fhsm_do_read_one(struct aufs_stbr __user *stbr,
+                             struct aufs_stfs *stfs, __s16 brid)
+{
+       int err;
+
+       err = copy_to_user(&stbr->stfs, stfs, sizeof(*stfs));
+       if (!err)
+               err = __put_user(brid, &stbr->brid);
+       if (unlikely(err))
+               err = -EFAULT;
+
+       return err;
+}
+
+static ssize_t au_fhsm_do_read(struct super_block *sb,
+                              struct aufs_stbr __user *stbr, size_t count)
+{
+       ssize_t err;
+       int nstbr;
+       aufs_bindex_t bindex, bbot;
+       struct au_branch *br;
+       struct au_br_fhsm *bf;
+
+       /* except the bottom branch */
+       err = 0;
+       nstbr = 0;
+       bbot = au_fhsm_bottom(sb);
+       for (bindex = 0; !err && bindex < bbot; bindex++) {
+               br = au_sbr(sb, bindex);
+               if (!au_br_fhsm(br->br_perm))
+                       continue;
+
+               bf = br->br_fhsm;
+               mutex_lock(&bf->bf_lock);
+               if (bf->bf_readable) {
+                       err = -EFAULT;
+                       if (count >= sizeof(*stbr))
+                               err = au_fhsm_do_read_one(stbr++, &bf->bf_stfs,
+                                                         br->br_id);
+                       if (!err) {
+                               bf->bf_readable = 0;
+                               count -= sizeof(*stbr);
+                               nstbr++;
+                       }
+               }
+               mutex_unlock(&bf->bf_lock);
+       }
+       if (!err)
+               err = sizeof(*stbr) * nstbr;
+
+       return err;
+}
+
+static ssize_t au_fhsm_read(struct file *file, char __user *buf, size_t count,
+                          loff_t *pos)
+{
+       ssize_t err;
+       int readable;
+       aufs_bindex_t nfhsm, bindex, bbot;
+       struct au_sbinfo *sbinfo;
+       struct au_fhsm *fhsm;
+       struct au_branch *br;
+       struct super_block *sb;
+
+       err = 0;
+       sbinfo = file->private_data;
+       fhsm = &sbinfo->si_fhsm;
+need_data:
+       spin_lock_irq(&fhsm->fhsm_wqh.lock);
+       if (!atomic_read(&fhsm->fhsm_readable)) {
+               if (vfsub_file_flags(file) & O_NONBLOCK)
+                       err = -EAGAIN;
+               else
+                       err = wait_event_interruptible_locked_irq
+                               (fhsm->fhsm_wqh,
+                                atomic_read(&fhsm->fhsm_readable));
+       }
+       spin_unlock_irq(&fhsm->fhsm_wqh.lock);
+       if (unlikely(err))
+               goto out;
+
+       /* sb may already be dead */
+       au_rw_read_lock(&sbinfo->si_rwsem);
+       readable = atomic_read(&fhsm->fhsm_readable);
+       if (readable > 0) {
+               sb = sbinfo->si_sb;
+               AuDebugOn(!sb);
+               /* exclude the bottom branch */
+               nfhsm = 0;
+               bbot = au_fhsm_bottom(sb);
+               for (bindex = 0; bindex < bbot; bindex++) {
+                       br = au_sbr(sb, bindex);
+                       if (au_br_fhsm(br->br_perm))
+                               nfhsm++;
+               }
+               err = -EMSGSIZE;
+               if (nfhsm * sizeof(struct aufs_stbr) <= count) {
+                       atomic_set(&fhsm->fhsm_readable, 0);
+                       err = au_fhsm_do_read(sbinfo->si_sb, (void __user *)buf,
+                                            count);
+               }
+       }
+       au_rw_read_unlock(&sbinfo->si_rwsem);
+       if (!readable)
+               goto need_data;
+
+out:
+       return err;
+}
+
+static int au_fhsm_release(struct inode *inode, struct file *file)
+{
+       struct au_sbinfo *sbinfo;
+       struct au_fhsm *fhsm;
+
+       /* sb may already be dead */
+       sbinfo = file->private_data;
+       fhsm = &sbinfo->si_fhsm;
+       spin_lock(&fhsm->fhsm_spin);
+       fhsm->fhsm_pid = 0;
+       spin_unlock(&fhsm->fhsm_spin);
+       kobject_put(&sbinfo->si_kobj);
+
+       return 0;
+}
+
+static const struct file_operations au_fhsm_fops = {
+       .owner          = THIS_MODULE,
+       .llseek         = noop_llseek,
+       .read           = au_fhsm_read,
+       .poll           = au_fhsm_poll,
+       .release        = au_fhsm_release
+};
+
+int au_fhsm_fd(struct super_block *sb, int oflags)
+{
+       int err, fd;
+       struct au_sbinfo *sbinfo;
+       struct au_fhsm *fhsm;
+
+       err = -EPERM;
+       if (unlikely(!capable(CAP_SYS_ADMIN)))
+               goto out;
+
+       err = -EINVAL;
+       if (unlikely(oflags & ~(O_CLOEXEC | O_NONBLOCK)))
+               goto out;
+
+       err = 0;
+       sbinfo = au_sbi(sb);
+       fhsm = &sbinfo->si_fhsm;
+       spin_lock(&fhsm->fhsm_spin);
+       if (!fhsm->fhsm_pid)
+               fhsm->fhsm_pid = current->pid;
+       else
+               err = -EBUSY;
+       spin_unlock(&fhsm->fhsm_spin);
+       if (unlikely(err))
+               goto out;
+
+       oflags |= O_RDONLY;
+       /* oflags |= FMODE_NONOTIFY; */
+       fd = anon_inode_getfd("[aufs_fhsm]", &au_fhsm_fops, sbinfo, oflags);
+       err = fd;
+       if (unlikely(fd < 0))
+               goto out_pid;
+
+       /* succeed regardless 'fhsm' status */
+       kobject_get(&sbinfo->si_kobj);
+       si_noflush_read_lock(sb);
+       if (au_ftest_si(sbinfo, FHSM))
+               au_fhsm_wrote_all(sb, /*force*/0);
+       si_read_unlock(sb);
+       goto out; /* success */
+
+out_pid:
+       spin_lock(&fhsm->fhsm_spin);
+       fhsm->fhsm_pid = 0;
+       spin_unlock(&fhsm->fhsm_spin);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+int au_fhsm_br_alloc(struct au_branch *br)
+{
+       int err;
+
+       err = 0;
+       br->br_fhsm = kmalloc(sizeof(*br->br_fhsm), GFP_NOFS);
+       if (br->br_fhsm)
+               au_br_fhsm_init(br->br_fhsm);
+       else
+               err = -ENOMEM;
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void au_fhsm_fin(struct super_block *sb)
+{
+       au_fhsm_notify(sb, /*val*/-1);
+}
+
+void au_fhsm_init(struct au_sbinfo *sbinfo)
+{
+       struct au_fhsm *fhsm;
+
+       fhsm = &sbinfo->si_fhsm;
+       spin_lock_init(&fhsm->fhsm_spin);
+       init_waitqueue_head(&fhsm->fhsm_wqh);
+       atomic_set(&fhsm->fhsm_readable, 0);
+       fhsm->fhsm_expire
+               = msecs_to_jiffies(AUFS_FHSM_CACHE_DEF_SEC * MSEC_PER_SEC);
+       fhsm->fhsm_bottom = -1;
+}
+
+void au_fhsm_set(struct au_sbinfo *sbinfo, unsigned int sec)
+{
+       sbinfo->si_fhsm.fhsm_expire
+               = msecs_to_jiffies(sec * MSEC_PER_SEC);
+}
+
+void au_fhsm_show(struct seq_file *seq, struct au_sbinfo *sbinfo)
+{
+       unsigned int u;
+
+       if (!au_ftest_si(sbinfo, FHSM))
+               return;
+
+       u = jiffies_to_msecs(sbinfo->si_fhsm.fhsm_expire) / MSEC_PER_SEC;
+       if (u != AUFS_FHSM_CACHE_DEF_SEC)
+               seq_printf(seq, ",fhsm_sec=%u", u);
+}
diff -urN /usr/share/empty/fs/aufs/file.c linux/fs/aufs/file.c
--- /usr/share/empty/fs/aufs/file.c     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/file.c        2021-12-03 15:38:59.936647310 +0100
@@ -0,0 +1,863 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * handling file/dir, and address_space operation
+ */
+
+#ifdef CONFIG_AUFS_DEBUG
+#include <linux/migrate.h>
+#endif
+#include <linux/pagemap.h>
+#include "aufs.h"
+
+/* drop flags for writing */
+unsigned int au_file_roflags(unsigned int flags)
+{
+       flags &= ~(O_WRONLY | O_RDWR | O_APPEND | O_CREAT | O_TRUNC);
+       flags |= O_RDONLY | O_NOATIME;
+       return flags;
+}
+
+/* common functions to regular file and dir */
+struct file *au_h_open(struct dentry *dentry, aufs_bindex_t bindex, int flags,
+                      struct file *file, int force_wr)
+{
+       struct file *h_file;
+       struct dentry *h_dentry;
+       struct inode *h_inode;
+       struct super_block *sb;
+       struct au_branch *br;
+       struct path h_path;
+       int err;
+
+       /* a race condition can happen between open and unlink/rmdir */
+       h_file = ERR_PTR(-ENOENT);
+       h_dentry = au_h_dptr(dentry, bindex);
+       if (au_test_nfsd() && (!h_dentry || d_is_negative(h_dentry)))
+               goto out;
+       h_inode = d_inode(h_dentry);
+       spin_lock(&h_dentry->d_lock);
+       err = (!d_unhashed(dentry) && d_unlinked(h_dentry))
+               /* || !d_inode(dentry)->i_nlink */
+               ;
+       spin_unlock(&h_dentry->d_lock);
+       if (unlikely(err))
+               goto out;
+
+       sb = dentry->d_sb;
+       br = au_sbr(sb, bindex);
+       err = au_br_test_oflag(flags, br);
+       h_file = ERR_PTR(err);
+       if (unlikely(err))
+               goto out;
+
+       /* drop flags for writing */
+       if (au_test_ro(sb, bindex, d_inode(dentry))) {
+               if (force_wr && !(flags & O_WRONLY))
+                       force_wr = 0;
+               flags = au_file_roflags(flags);
+               if (force_wr) {
+                       h_file = ERR_PTR(-EROFS);
+                       flags = au_file_roflags(flags);
+                       if (unlikely(vfsub_native_ro(h_inode)
+                                    || IS_APPEND(h_inode)))
+                               goto out;
+                       flags &= ~O_ACCMODE;
+                       flags |= O_WRONLY;
+               }
+       }
+       flags &= ~O_CREAT;
+       au_lcnt_inc(&br->br_nfiles);
+       h_path.dentry = h_dentry;
+       h_path.mnt = au_br_mnt(br);
+       h_file = vfsub_dentry_open(&h_path, flags);
+       if (IS_ERR(h_file))
+               goto out_br;
+
+       if (flags & __FMODE_EXEC) {
+               err = deny_write_access(h_file);
+               if (unlikely(err)) {
+                       fput(h_file);
+                       h_file = ERR_PTR(err);
+                       goto out_br;
+               }
+       }
+       fsnotify_open(h_file);
+       goto out; /* success */
+
+out_br:
+       au_lcnt_dec(&br->br_nfiles);
+out:
+       return h_file;
+}
+
+static int au_cmoo(struct dentry *dentry)
+{
+       int err, cmoo, matched;
+       unsigned int udba;
+       struct path h_path;
+       struct au_pin pin;
+       struct au_cp_generic cpg = {
+               .dentry = dentry,
+               .bdst   = -1,
+               .bsrc   = -1,
+               .len    = -1,
+               .pin    = &pin,
+               .flags  = AuCpup_DTIME | AuCpup_HOPEN
+       };
+       struct inode *delegated;
+       struct super_block *sb;
+       struct au_sbinfo *sbinfo;
+       struct au_fhsm *fhsm;
+       pid_t pid;
+       struct au_branch *br;
+       struct dentry *parent;
+       struct au_hinode *hdir;
+
+       DiMustWriteLock(dentry);
+       IiMustWriteLock(d_inode(dentry));
+
+       err = 0;
+       if (IS_ROOT(dentry))
+               goto out;
+       cpg.bsrc = au_dbtop(dentry);
+       if (!cpg.bsrc)
+               goto out;
+
+       sb = dentry->d_sb;
+       sbinfo = au_sbi(sb);
+       fhsm = &sbinfo->si_fhsm;
+       pid = au_fhsm_pid(fhsm);
+       rcu_read_lock();
+       matched = (pid
+                  && (current->pid == pid
+                      || rcu_dereference(current->real_parent)->pid == pid));
+       rcu_read_unlock();
+       if (matched)
+               goto out;
+
+       br = au_sbr(sb, cpg.bsrc);
+       cmoo = au_br_cmoo(br->br_perm);
+       if (!cmoo)
+               goto out;
+       if (!d_is_reg(dentry))
+               cmoo &= AuBrAttr_COO_ALL;
+       if (!cmoo)
+               goto out;
+
+       parent = dget_parent(dentry);
+       di_write_lock_parent(parent);
+       err = au_wbr_do_copyup_bu(dentry, cpg.bsrc - 1);
+       cpg.bdst = err;
+       if (unlikely(err < 0)) {
+               err = 0;        /* there is no upper writable branch */
+               goto out_dgrade;
+       }
+       AuDbg("bsrc %d, bdst %d\n", cpg.bsrc, cpg.bdst);
+
+       /* do not respect the coo attrib for the target branch */
+       err = au_cpup_dirs(dentry, cpg.bdst);
+       if (unlikely(err))
+               goto out_dgrade;
+
+       di_downgrade_lock(parent, AuLock_IR);
+       udba = au_opt_udba(sb);
+       err = au_pin(&pin, dentry, cpg.bdst, udba,
+                    AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+       if (unlikely(err))
+               goto out_parent;
+
+       err = au_sio_cpup_simple(&cpg);
+       au_unpin(&pin);
+       if (unlikely(err))
+               goto out_parent;
+       if (!(cmoo & AuBrWAttr_MOO))
+               goto out_parent; /* success */
+
+       err = au_pin(&pin, dentry, cpg.bsrc, udba,
+                    AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+       if (unlikely(err))
+               goto out_parent;
+
+       h_path.mnt = au_br_mnt(br);
+       h_path.dentry = au_h_dptr(dentry, cpg.bsrc);
+       hdir = au_hi(d_inode(parent), cpg.bsrc);
+       delegated = NULL;
+       err = vfsub_unlink(hdir->hi_inode, &h_path, &delegated, /*force*/1);
+       au_unpin(&pin);
+       /* todo: keep h_dentry or not? */
+       if (unlikely(err == -EWOULDBLOCK)) {
+               pr_warn("cannot retry for NFSv4 delegation"
+                       " for an internal unlink\n");
+               iput(delegated);
+       }
+       if (unlikely(err)) {
+               pr_err("unlink %pd after coo failed (%d), ignored\n",
+                      dentry, err);
+               err = 0;
+       }
+       goto out_parent; /* success */
+
+out_dgrade:
+       di_downgrade_lock(parent, AuLock_IR);
+out_parent:
+       di_read_unlock(parent, AuLock_IR);
+       dput(parent);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+int au_do_open(struct file *file, struct au_do_open_args *args)
+{
+       int err, aopen = args->aopen;
+       struct dentry *dentry;
+       struct au_finfo *finfo;
+
+       if (!aopen)
+               err = au_finfo_init(file, args->fidir);
+       else {
+               lockdep_off();
+               err = au_finfo_init(file, args->fidir);
+               lockdep_on();
+       }
+       if (unlikely(err))
+               goto out;
+
+       dentry = file->f_path.dentry;
+       AuDebugOn(IS_ERR_OR_NULL(dentry));
+       di_write_lock_child(dentry);
+       err = au_cmoo(dentry);
+       di_downgrade_lock(dentry, AuLock_IR);
+       if (!err) {
+               if (!aopen)
+                       err = args->open(file, vfsub_file_flags(file), NULL);
+               else {
+                       lockdep_off();
+                       err = args->open(file, vfsub_file_flags(file),
+                                        args->h_file);
+                       lockdep_on();
+               }
+       }
+       di_read_unlock(dentry, AuLock_IR);
+
+       finfo = au_fi(file);
+       if (!err) {
+               finfo->fi_file = file;
+               au_hbl_add(&finfo->fi_hlist,
+                          &au_sbi(file->f_path.dentry->d_sb)->si_files);
+       }
+       if (!aopen)
+               fi_write_unlock(file);
+       else {
+               lockdep_off();
+               fi_write_unlock(file);
+               lockdep_on();
+       }
+       if (unlikely(err)) {
+               finfo->fi_hdir = NULL;
+               au_finfo_fin(file);
+       }
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+int au_reopen_nondir(struct file *file)
+{
+       int err;
+       aufs_bindex_t btop;
+       struct dentry *dentry;
+       struct au_branch *br;
+       struct file *h_file, *h_file_tmp;
+
+       dentry = file->f_path.dentry;
+       btop = au_dbtop(dentry);
+       br = au_sbr(dentry->d_sb, btop);
+       h_file_tmp = NULL;
+       if (au_fbtop(file) == btop) {
+               h_file = au_hf_top(file);
+               if (file->f_mode == h_file->f_mode)
+                       return 0; /* success */
+               h_file_tmp = h_file;
+               get_file(h_file_tmp);
+               au_lcnt_inc(&br->br_nfiles);
+               au_set_h_fptr(file, btop, NULL);
+       }
+       AuDebugOn(au_fi(file)->fi_hdir);
+       /*
+        * it can happen
+        * file exists on both of rw and ro
+        * open --> dbtop and fbtop are both 0
+        * prepend a branch as rw, "rw" become ro
+        * remove rw/file
+        * delete the top branch, "rw" becomes rw again
+        *      --> dbtop is 1, fbtop is still 0
+        * write --> fbtop is 0 but dbtop is 1
+        */
+       /* AuDebugOn(au_fbtop(file) < btop); */
+
+       h_file = au_h_open(dentry, btop, vfsub_file_flags(file) & ~O_TRUNC,
+                          file, /*force_wr*/0);
+       err = PTR_ERR(h_file);
+       if (IS_ERR(h_file)) {
+               if (h_file_tmp) {
+                       /* revert */
+                       au_set_h_fptr(file, btop, h_file_tmp);
+                       h_file_tmp = NULL;
+               }
+               goto out; /* todo: close all? */
+       }
+
+       err = 0;
+       au_set_fbtop(file, btop);
+       au_set_h_fptr(file, btop, h_file);
+       au_update_figen(file);
+       /* todo: necessary? */
+       /* file->f_ra = h_file->f_ra; */
+
+out:
+       if (h_file_tmp) {
+               fput(h_file_tmp);
+               au_lcnt_dec(&br->br_nfiles);
+       }
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_reopen_wh(struct file *file, aufs_bindex_t btgt,
+                       struct dentry *hi_wh)
+{
+       int err;
+       aufs_bindex_t btop;
+       struct au_dinfo *dinfo;
+       struct dentry *h_dentry;
+       struct au_hdentry *hdp;
+
+       dinfo = au_di(file->f_path.dentry);
+       AuRwMustWriteLock(&dinfo->di_rwsem);
+
+       btop = dinfo->di_btop;
+       dinfo->di_btop = btgt;
+       hdp = au_hdentry(dinfo, btgt);
+       h_dentry = hdp->hd_dentry;
+       hdp->hd_dentry = hi_wh;
+       err = au_reopen_nondir(file);
+       hdp->hd_dentry = h_dentry;
+       dinfo->di_btop = btop;
+
+       return err;
+}
+
+static int au_ready_to_write_wh(struct file *file, loff_t len,
+                               aufs_bindex_t bcpup, struct au_pin *pin)
+{
+       int err;
+       struct inode *inode, *h_inode;
+       struct dentry *h_dentry, *hi_wh;
+       struct au_cp_generic cpg = {
+               .dentry = file->f_path.dentry,
+               .bdst   = bcpup,
+               .bsrc   = -1,
+               .len    = len,
+               .pin    = pin
+       };
+
+       au_update_dbtop(cpg.dentry);
+       inode = d_inode(cpg.dentry);
+       h_inode = NULL;
+       if (au_dbtop(cpg.dentry) <= bcpup
+           && au_dbbot(cpg.dentry) >= bcpup) {
+               h_dentry = au_h_dptr(cpg.dentry, bcpup);
+               if (h_dentry && d_is_positive(h_dentry))
+                       h_inode = d_inode(h_dentry);
+       }
+       hi_wh = au_hi_wh(inode, bcpup);
+       if (!hi_wh && !h_inode)
+               err = au_sio_cpup_wh(&cpg, file);
+       else
+               /* already copied-up after unlink */
+               err = au_reopen_wh(file, bcpup, hi_wh);
+
+       if (!err
+           && (inode->i_nlink > 1
+               || (inode->i_state & I_LINKABLE))
+           && au_opt_test(au_mntflags(cpg.dentry->d_sb), PLINK))
+               au_plink_append(inode, bcpup, au_h_dptr(cpg.dentry, bcpup));
+
+       return err;
+}
+
+/*
+ * prepare the @file for writing.
+ */
+int au_ready_to_write(struct file *file, loff_t len, struct au_pin *pin)
+{
+       int err;
+       aufs_bindex_t dbtop;
+       struct dentry *parent;
+       struct inode *inode;
+       struct super_block *sb;
+       struct file *h_file;
+       struct au_cp_generic cpg = {
+               .dentry = file->f_path.dentry,
+               .bdst   = -1,
+               .bsrc   = -1,
+               .len    = len,
+               .pin    = pin,
+               .flags  = AuCpup_DTIME
+       };
+
+       sb = cpg.dentry->d_sb;
+       inode = d_inode(cpg.dentry);
+       cpg.bsrc = au_fbtop(file);
+       err = au_test_ro(sb, cpg.bsrc, inode);
+       if (!err && (au_hf_top(file)->f_mode & FMODE_WRITE)) {
+               err = au_pin(pin, cpg.dentry, cpg.bsrc, AuOpt_UDBA_NONE,
+                            /*flags*/0);
+               goto out;
+       }
+
+       /* need to cpup or reopen */
+       parent = dget_parent(cpg.dentry);
+       di_write_lock_parent(parent);
+       err = AuWbrCopyup(au_sbi(sb), cpg.dentry);
+       cpg.bdst = err;
+       if (unlikely(err < 0))
+               goto out_dgrade;
+       err = 0;
+
+       if (!d_unhashed(cpg.dentry) && !au_h_dptr(parent, cpg.bdst)) {
+               err = au_cpup_dirs(cpg.dentry, cpg.bdst);
+               if (unlikely(err))
+                       goto out_dgrade;
+       }
+
+       err = au_pin(pin, cpg.dentry, cpg.bdst, AuOpt_UDBA_NONE,
+                    AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+       if (unlikely(err))
+               goto out_dgrade;
+
+       dbtop = au_dbtop(cpg.dentry);
+       if (dbtop <= cpg.bdst)
+               cpg.bsrc = cpg.bdst;
+
+       if (dbtop <= cpg.bdst           /* just reopen */
+           || !d_unhashed(cpg.dentry)  /* copyup and reopen */
+               ) {
+               h_file = au_h_open_pre(cpg.dentry, cpg.bsrc, /*force_wr*/0);
+               if (IS_ERR(h_file))
+                       err = PTR_ERR(h_file);
+               else {
+                       di_downgrade_lock(parent, AuLock_IR);
+                       if (dbtop > cpg.bdst)
+                               err = au_sio_cpup_simple(&cpg);
+                       if (!err)
+                               err = au_reopen_nondir(file);
+                       au_h_open_post(cpg.dentry, cpg.bsrc, h_file);
+               }
+       } else {                        /* copyup as wh and reopen */
+               /*
+                * since writable hfsplus branch is not supported,
+                * h_open_pre/post() are unnecessary.
+                */
+               err = au_ready_to_write_wh(file, len, cpg.bdst, pin);
+               di_downgrade_lock(parent, AuLock_IR);
+       }
+
+       if (!err) {
+               au_pin_set_parent_lflag(pin, /*lflag*/0);
+               goto out_dput; /* success */
+       }
+       au_unpin(pin);
+       goto out_unlock;
+
+out_dgrade:
+       di_downgrade_lock(parent, AuLock_IR);
+out_unlock:
+       di_read_unlock(parent, AuLock_IR);
+out_dput:
+       dput(parent);
+out:
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+int au_do_flush(struct file *file, fl_owner_t id,
+               int (*flush)(struct file *file, fl_owner_t id))
+{
+       int err;
+       struct super_block *sb;
+       struct inode *inode;
+
+       inode = file_inode(file);
+       sb = inode->i_sb;
+       si_noflush_read_lock(sb);
+       fi_read_lock(file);
+       ii_read_lock_child(inode);
+
+       err = flush(file, id);
+       au_cpup_attr_timesizes(inode);
+
+       ii_read_unlock(inode);
+       fi_read_unlock(file);
+       si_read_unlock(sb);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_file_refresh_by_inode(struct file *file, int *need_reopen)
+{
+       int err;
+       struct au_pin pin;
+       struct au_finfo *finfo;
+       struct dentry *parent, *hi_wh;
+       struct inode *inode;
+       struct super_block *sb;
+       struct au_cp_generic cpg = {
+               .dentry = file->f_path.dentry,
+               .bdst   = -1,
+               .bsrc   = -1,
+               .len    = -1,
+               .pin    = &pin,
+               .flags  = AuCpup_DTIME
+       };
+
+       FiMustWriteLock(file);
+
+       err = 0;
+       finfo = au_fi(file);
+       sb = cpg.dentry->d_sb;
+       inode = d_inode(cpg.dentry);
+       cpg.bdst = au_ibtop(inode);
+       if (cpg.bdst == finfo->fi_btop || IS_ROOT(cpg.dentry))
+               goto out;
+
+       parent = dget_parent(cpg.dentry);
+       if (au_test_ro(sb, cpg.bdst, inode)) {
+               di_read_lock_parent(parent, !AuLock_IR);
+               err = AuWbrCopyup(au_sbi(sb), cpg.dentry);
+               cpg.bdst = err;
+               di_read_unlock(parent, !AuLock_IR);
+               if (unlikely(err < 0))
+                       goto out_parent;
+               err = 0;
+       }
+
+       di_read_lock_parent(parent, AuLock_IR);
+       hi_wh = au_hi_wh(inode, cpg.bdst);
+       if (!S_ISDIR(inode->i_mode)
+           && au_opt_test(au_mntflags(sb), PLINK)
+           && au_plink_test(inode)
+           && !d_unhashed(cpg.dentry)
+           && cpg.bdst < au_dbtop(cpg.dentry)) {
+               err = au_test_and_cpup_dirs(cpg.dentry, cpg.bdst);
+               if (unlikely(err))
+                       goto out_unlock;
+
+               /* always superio. */
+               err = au_pin(&pin, cpg.dentry, cpg.bdst, AuOpt_UDBA_NONE,
+                            AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+               if (!err) {
+                       err = au_sio_cpup_simple(&cpg);
+                       au_unpin(&pin);
+               }
+       } else if (hi_wh) {
+               /* already copied-up after unlink */
+               err = au_reopen_wh(file, cpg.bdst, hi_wh);
+               *need_reopen = 0;
+       }
+
+out_unlock:
+       di_read_unlock(parent, AuLock_IR);
+out_parent:
+       dput(parent);
+out:
+       return err;
+}
+
+static void au_do_refresh_dir(struct file *file)
+{
+       aufs_bindex_t bindex, bbot, new_bindex, brid;
+       struct au_hfile *p, tmp, *q;
+       struct au_finfo *finfo;
+       struct super_block *sb;
+       struct au_fidir *fidir;
+
+       FiMustWriteLock(file);
+
+       sb = file->f_path.dentry->d_sb;
+       finfo = au_fi(file);
+       fidir = finfo->fi_hdir;
+       AuDebugOn(!fidir);
+       p = fidir->fd_hfile + finfo->fi_btop;
+       brid = p->hf_br->br_id;
+       bbot = fidir->fd_bbot;
+       for (bindex = finfo->fi_btop; bindex <= bbot; bindex++, p++) {
+               if (!p->hf_file)
+                       continue;
+
+               new_bindex = au_br_index(sb, p->hf_br->br_id);
+               if (new_bindex == bindex)
+                       continue;
+               if (new_bindex < 0) {
+                       au_set_h_fptr(file, bindex, NULL);
+                       continue;
+               }
+
+               /* swap two lower inode, and loop again */
+               q = fidir->fd_hfile + new_bindex;
+               tmp = *q;
+               *q = *p;
+               *p = tmp;
+               if (tmp.hf_file) {
+                       bindex--;
+                       p--;
+               }
+       }
+
+       p = fidir->fd_hfile;
+       if (!au_test_mmapped(file) && !d_unlinked(file->f_path.dentry)) {
+               bbot = au_sbbot(sb);
+               for (finfo->fi_btop = 0; finfo->fi_btop <= bbot;
+                    finfo->fi_btop++, p++)
+                       if (p->hf_file) {
+                               if (file_inode(p->hf_file))
+                                       break;
+                               au_hfput(p, /*execed*/0);
+                       }
+       } else {
+               bbot = au_br_index(sb, brid);
+               for (finfo->fi_btop = 0; finfo->fi_btop < bbot;
+                    finfo->fi_btop++, p++)
+                       if (p->hf_file)
+                               au_hfput(p, /*execed*/0);
+               bbot = au_sbbot(sb);
+       }
+
+       p = fidir->fd_hfile + bbot;
+       for (fidir->fd_bbot = bbot; fidir->fd_bbot >= finfo->fi_btop;
+            fidir->fd_bbot--, p--)
+               if (p->hf_file) {
+                       if (file_inode(p->hf_file))
+                               break;
+                       au_hfput(p, /*execed*/0);
+               }
+       AuDebugOn(fidir->fd_bbot < finfo->fi_btop);
+}
+
+/*
+ * after branch manipulating, refresh the file.
+ */
+static int refresh_file(struct file *file, int (*reopen)(struct file *file))
+{
+       int err, need_reopen, nbr;
+       aufs_bindex_t bbot, bindex;
+       struct dentry *dentry;
+       struct super_block *sb;
+       struct au_finfo *finfo;
+       struct au_hfile *hfile;
+
+       dentry = file->f_path.dentry;
+       sb = dentry->d_sb;
+       nbr = au_sbbot(sb) + 1;
+       finfo = au_fi(file);
+       if (!finfo->fi_hdir) {
+               hfile = &finfo->fi_htop;
+               AuDebugOn(!hfile->hf_file);
+               bindex = au_br_index(sb, hfile->hf_br->br_id);
+               AuDebugOn(bindex < 0);
+               if (bindex != finfo->fi_btop)
+                       au_set_fbtop(file, bindex);
+       } else {
+               err = au_fidir_realloc(finfo, nbr, /*may_shrink*/0);
+               if (unlikely(err))
+                       goto out;
+               au_do_refresh_dir(file);
+       }
+
+       err = 0;
+       need_reopen = 1;
+       if (!au_test_mmapped(file))
+               err = au_file_refresh_by_inode(file, &need_reopen);
+       if (finfo->fi_hdir)
+               /* harmless if err */
+               au_fidir_realloc(finfo, nbr, /*may_shrink*/1);
+       if (!err && need_reopen && !d_unlinked(dentry))
+               err = reopen(file);
+       if (!err) {
+               au_update_figen(file);
+               goto out; /* success */
+       }
+
+       /* error, close all lower files */
+       if (finfo->fi_hdir) {
+               bbot = au_fbbot_dir(file);
+               for (bindex = au_fbtop(file); bindex <= bbot; bindex++)
+                       au_set_h_fptr(file, bindex, NULL);
+       }
+
+out:
+       return err;
+}
+
+/* common function to regular file and dir */
+int au_reval_and_lock_fdi(struct file *file, int (*reopen)(struct file *file),
+                         int wlock, unsigned int fi_lsc)
+{
+       int err;
+       unsigned int sigen, figen;
+       aufs_bindex_t btop;
+       unsigned char pseudo_link;
+       struct dentry *dentry;
+       struct inode *inode;
+
+       err = 0;
+       dentry = file->f_path.dentry;
+       inode = d_inode(dentry);
+       sigen = au_sigen(dentry->d_sb);
+       fi_write_lock_nested(file, fi_lsc);
+       figen = au_figen(file);
+       if (!fi_lsc)
+               di_write_lock_child(dentry);
+       else
+               di_write_lock_child2(dentry);
+       btop = au_dbtop(dentry);
+       pseudo_link = (btop != au_ibtop(inode));
+       if (sigen == figen && !pseudo_link && au_fbtop(file) == btop) {
+               if (!wlock) {
+                       di_downgrade_lock(dentry, AuLock_IR);
+                       fi_downgrade_lock(file);
+               }
+               goto out; /* success */
+       }
+
+       AuDbg("sigen %d, figen %d\n", sigen, figen);
+       if (au_digen_test(dentry, sigen)) {
+               err = au_reval_dpath(dentry, sigen);
+               AuDebugOn(!err && au_digen_test(dentry, sigen));
+       }
+
+       if (!err)
+               err = refresh_file(file, reopen);
+       if (!err) {
+               if (!wlock) {
+                       di_downgrade_lock(dentry, AuLock_IR);
+                       fi_downgrade_lock(file);
+               }
+       } else {
+               di_write_unlock(dentry);
+               fi_write_unlock(file);
+       }
+
+out:
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* cf. aufs_nopage() */
+/* for madvise(2) */
+static int aufs_readpage(struct file *file __maybe_unused, struct page *page)
+{
+       unlock_page(page);
+       return 0;
+}
+
+/* it will never be called, but necessary to support O_DIRECT */
+static ssize_t aufs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
+{ BUG(); return 0; }
+
+/* they will never be called. */
+#ifdef CONFIG_AUFS_DEBUG
+static int aufs_write_begin(struct file *file, struct address_space *mapping,
+                           loff_t pos, unsigned len, unsigned flags,
+                           struct page **pagep, void **fsdata)
+{ AuUnsupport(); return 0; }
+static int aufs_write_end(struct file *file, struct address_space *mapping,
+                         loff_t pos, unsigned len, unsigned copied,
+                         struct page *page, void *fsdata)
+{ AuUnsupport(); return 0; }
+static int aufs_writepage(struct page *page, struct writeback_control *wbc)
+{ AuUnsupport(); return 0; }
+
+static int aufs_set_page_dirty(struct page *page)
+{ AuUnsupport(); return 0; }
+static void aufs_invalidatepage(struct page *page, unsigned int offset,
+                               unsigned int length)
+{ AuUnsupport(); }
+static int aufs_releasepage(struct page *page, gfp_t gfp)
+{ AuUnsupport(); return 0; }
+#if 0 /* called by memory compaction regardless file */
+static int aufs_migratepage(struct address_space *mapping, struct page *newpage,
+                           struct page *page, enum migrate_mode mode)
+{ AuUnsupport(); return 0; }
+#endif
+static bool aufs_isolate_page(struct page *page, isolate_mode_t mode)
+{ AuUnsupport(); return true; }
+static void aufs_putback_page(struct page *page)
+{ AuUnsupport(); }
+static int aufs_launder_page(struct page *page)
+{ AuUnsupport(); return 0; }
+static int aufs_is_partially_uptodate(struct page *page,
+                                     unsigned long from,
+                                     unsigned long count)
+{ AuUnsupport(); return 0; }
+static void aufs_is_dirty_writeback(struct page *page, bool *dirty,
+                                   bool *writeback)
+{ AuUnsupport(); }
+static int aufs_error_remove_page(struct address_space *mapping,
+                                 struct page *page)
+{ AuUnsupport(); return 0; }
+static int aufs_swap_activate(struct swap_info_struct *sis, struct file *file,
+                             sector_t *span)
+{ AuUnsupport(); return 0; }
+static void aufs_swap_deactivate(struct file *file)
+{ AuUnsupport(); }
+#endif /* CONFIG_AUFS_DEBUG */
+
+const struct address_space_operations aufs_aop = {
+       .readpage               = aufs_readpage,
+       .direct_IO              = aufs_direct_IO,
+#ifdef CONFIG_AUFS_DEBUG
+       .writepage              = aufs_writepage,
+       /* no writepages, because of writepage */
+       .set_page_dirty         = aufs_set_page_dirty,
+       /* no readpages, because of readpage */
+       .write_begin            = aufs_write_begin,
+       .write_end              = aufs_write_end,
+       /* no bmap, no block device */
+       .invalidatepage         = aufs_invalidatepage,
+       .releasepage            = aufs_releasepage,
+       /* is fallback_migrate_page ok? */
+       /* .migratepage         = aufs_migratepage, */
+       .isolate_page           = aufs_isolate_page,
+       .putback_page           = aufs_putback_page,
+       .launder_page           = aufs_launder_page,
+       .is_partially_uptodate  = aufs_is_partially_uptodate,
+       .is_dirty_writeback     = aufs_is_dirty_writeback,
+       .error_remove_page      = aufs_error_remove_page,
+       .swap_activate          = aufs_swap_activate,
+       .swap_deactivate        = aufs_swap_deactivate
+#endif /* CONFIG_AUFS_DEBUG */
+};
diff -urN /usr/share/empty/fs/aufs/file.h linux/fs/aufs/file.h
--- /usr/share/empty/fs/aufs/file.h     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/file.h        2021-12-03 15:38:59.936647310 +0100
@@ -0,0 +1,342 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * file operations
+ */
+
+#ifndef __AUFS_FILE_H__
+#define __AUFS_FILE_H__
+
+#ifdef __KERNEL__
+
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/mm_types.h>
+#include <linux/poll.h>
+#include "rwsem.h"
+
+struct au_branch;
+struct au_hfile {
+       struct file             *hf_file;
+       struct au_branch        *hf_br;
+};
+
+struct au_vdir;
+struct au_fidir {
+       aufs_bindex_t           fd_bbot;
+       aufs_bindex_t           fd_nent;
+       struct au_vdir          *fd_vdir_cache;
+       struct au_hfile         fd_hfile[];
+};
+
+static inline int au_fidir_sz(int nent)
+{
+       AuDebugOn(nent < 0);
+       return sizeof(struct au_fidir) + sizeof(struct au_hfile) * nent;
+}
+
+struct au_finfo {
+       atomic_t                fi_generation;
+
+       struct au_rwsem         fi_rwsem;
+       aufs_bindex_t           fi_btop;
+
+       /* do not union them */
+       struct {                                /* for non-dir */
+               struct au_hfile                 fi_htop;
+               atomic_t                        fi_mmapped;
+       };
+       struct au_fidir         *fi_hdir;       /* for dir only */
+
+       struct hlist_bl_node    fi_hlist;
+       struct file             *fi_file;       /* very ugly */
+       struct rcu_head         rcu;
+} ____cacheline_aligned_in_smp;
+
+/* ---------------------------------------------------------------------- */
+
+/* file.c */
+extern const struct address_space_operations aufs_aop;
+unsigned int au_file_roflags(unsigned int flags);
+struct file *au_h_open(struct dentry *dentry, aufs_bindex_t bindex, int flags,
+                      struct file *file, int force_wr);
+struct au_do_open_args {
+       int             aopen;
+       int             (*open)(struct file *file, int flags,
+                               struct file *h_file);
+       struct au_fidir *fidir;
+       struct file     *h_file;
+};
+int au_do_open(struct file *file, struct au_do_open_args *args);
+int au_reopen_nondir(struct file *file);
+struct au_pin;
+int au_ready_to_write(struct file *file, loff_t len, struct au_pin *pin);
+int au_reval_and_lock_fdi(struct file *file, int (*reopen)(struct file *file),
+                         int wlock, unsigned int fi_lsc);
+int au_do_flush(struct file *file, fl_owner_t id,
+               int (*flush)(struct file *file, fl_owner_t id));
+
+/* poll.c */
+#ifdef CONFIG_AUFS_POLL
+__poll_t aufs_poll(struct file *file, struct poll_table_struct *pt);
+#endif
+
+#ifdef CONFIG_AUFS_BR_HFSPLUS
+/* hfsplus.c */
+struct file *au_h_open_pre(struct dentry *dentry, aufs_bindex_t bindex,
+                          int force_wr);
+void au_h_open_post(struct dentry *dentry, aufs_bindex_t bindex,
+                   struct file *h_file);
+#else
+AuStub(struct file *, au_h_open_pre, return NULL, struct dentry *dentry,
+       aufs_bindex_t bindex, int force_wr)
+AuStubVoid(au_h_open_post, struct dentry *dentry, aufs_bindex_t bindex,
+          struct file *h_file);
+#endif
+
+/* f_op.c */
+extern const struct file_operations aufs_file_fop;
+int au_do_open_nondir(struct file *file, int flags, struct file *h_file);
+int aufs_release_nondir(struct inode *inode __maybe_unused, struct file *file);
+struct file *au_read_pre(struct file *file, int keep_fi, unsigned int lsc);
+
+/* finfo.c */
+void au_hfput(struct au_hfile *hf, int execed);
+void au_set_h_fptr(struct file *file, aufs_bindex_t bindex,
+                  struct file *h_file);
+
+void au_update_figen(struct file *file);
+struct au_fidir *au_fidir_alloc(struct super_block *sb);
+int au_fidir_realloc(struct au_finfo *finfo, int nbr, int may_shrink);
+
+void au_fi_init_once(void *_fi);
+void au_finfo_fin(struct file *file);
+int au_finfo_init(struct file *file, struct au_fidir *fidir);
+
+/* ioctl.c */
+long aufs_ioctl_nondir(struct file *file, unsigned int cmd, unsigned long arg);
+#ifdef CONFIG_COMPAT
+long aufs_compat_ioctl_dir(struct file *file, unsigned int cmd,
+                          unsigned long arg);
+long aufs_compat_ioctl_nondir(struct file *file, unsigned int cmd,
+                             unsigned long arg);
+#endif
+
+/* ---------------------------------------------------------------------- */
+
+static inline struct au_finfo *au_fi(struct file *file)
+{
+       return file->private_data;
+}
+
+/* ---------------------------------------------------------------------- */
+
+#define fi_read_lock(f)        au_rw_read_lock(&au_fi(f)->fi_rwsem)
+#define fi_write_lock(f)       au_rw_write_lock(&au_fi(f)->fi_rwsem)
+#define fi_read_trylock(f)     au_rw_read_trylock(&au_fi(f)->fi_rwsem)
+#define fi_write_trylock(f)    au_rw_write_trylock(&au_fi(f)->fi_rwsem)
+/*
+#define fi_read_trylock_nested(f) \
+       au_rw_read_trylock_nested(&au_fi(f)->fi_rwsem)
+#define fi_write_trylock_nested(f) \
+       au_rw_write_trylock_nested(&au_fi(f)->fi_rwsem)
+*/
+
+#define fi_read_unlock(f)      au_rw_read_unlock(&au_fi(f)->fi_rwsem)
+#define fi_write_unlock(f)     au_rw_write_unlock(&au_fi(f)->fi_rwsem)
+#define fi_downgrade_lock(f)   au_rw_dgrade_lock(&au_fi(f)->fi_rwsem)
+
+/* lock subclass for finfo */
+enum {
+       AuLsc_FI_1,
+       AuLsc_FI_2
+};
+
+static inline void fi_read_lock_nested(struct file *f, unsigned int lsc)
+{
+       au_rw_read_lock_nested(&au_fi(f)->fi_rwsem, lsc);
+}
+
+static inline void fi_write_lock_nested(struct file *f, unsigned int lsc)
+{
+       au_rw_write_lock_nested(&au_fi(f)->fi_rwsem, lsc);
+}
+
+/*
+ * fi_read_lock_1, fi_write_lock_1,
+ * fi_read_lock_2, fi_write_lock_2
+ */
+#define AuReadLockFunc(name) \
+static inline void fi_read_lock_##name(struct file *f) \
+{ fi_read_lock_nested(f, AuLsc_FI_##name); }
+
+#define AuWriteLockFunc(name) \
+static inline void fi_write_lock_##name(struct file *f) \
+{ fi_write_lock_nested(f, AuLsc_FI_##name); }
+
+#define AuRWLockFuncs(name) \
+       AuReadLockFunc(name) \
+       AuWriteLockFunc(name)
+
+AuRWLockFuncs(1);
+AuRWLockFuncs(2);
+
+#undef AuReadLockFunc
+#undef AuWriteLockFunc
+#undef AuRWLockFuncs
+
+#define FiMustNoWaiters(f)     AuRwMustNoWaiters(&au_fi(f)->fi_rwsem)
+#define FiMustAnyLock(f)       AuRwMustAnyLock(&au_fi(f)->fi_rwsem)
+#define FiMustWriteLock(f)     AuRwMustWriteLock(&au_fi(f)->fi_rwsem)
+
+/* ---------------------------------------------------------------------- */
+
+/* todo: hard/soft set? */
+static inline aufs_bindex_t au_fbtop(struct file *file)
+{
+       FiMustAnyLock(file);
+       return au_fi(file)->fi_btop;
+}
+
+static inline aufs_bindex_t au_fbbot_dir(struct file *file)
+{
+       FiMustAnyLock(file);
+       AuDebugOn(!au_fi(file)->fi_hdir);
+       return au_fi(file)->fi_hdir->fd_bbot;
+}
+
+static inline struct au_vdir *au_fvdir_cache(struct file *file)
+{
+       FiMustAnyLock(file);
+       AuDebugOn(!au_fi(file)->fi_hdir);
+       return au_fi(file)->fi_hdir->fd_vdir_cache;
+}
+
+static inline void au_set_fbtop(struct file *file, aufs_bindex_t bindex)
+{
+       FiMustWriteLock(file);
+       au_fi(file)->fi_btop = bindex;
+}
+
+static inline void au_set_fbbot_dir(struct file *file, aufs_bindex_t bindex)
+{
+       FiMustWriteLock(file);
+       AuDebugOn(!au_fi(file)->fi_hdir);
+       au_fi(file)->fi_hdir->fd_bbot = bindex;
+}
+
+static inline void au_set_fvdir_cache(struct file *file,
+                                     struct au_vdir *vdir_cache)
+{
+       FiMustWriteLock(file);
+       AuDebugOn(!au_fi(file)->fi_hdir);
+       au_fi(file)->fi_hdir->fd_vdir_cache = vdir_cache;
+}
+
+static inline struct file *au_hf_top(struct file *file)
+{
+       FiMustAnyLock(file);
+       AuDebugOn(au_fi(file)->fi_hdir);
+       return au_fi(file)->fi_htop.hf_file;
+}
+
+static inline struct file *au_hf_dir(struct file *file, aufs_bindex_t bindex)
+{
+       FiMustAnyLock(file);
+       AuDebugOn(!au_fi(file)->fi_hdir);
+       return au_fi(file)->fi_hdir->fd_hfile[0 + bindex].hf_file;
+}
+
+/* todo: memory barrier? */
+static inline unsigned int au_figen(struct file *f)
+{
+       return atomic_read(&au_fi(f)->fi_generation);
+}
+
+static inline void au_set_mmapped(struct file *f)
+{
+       if (atomic_inc_return(&au_fi(f)->fi_mmapped))
+               return;
+       pr_warn("fi_mmapped wrapped around\n");
+       while (!atomic_inc_return(&au_fi(f)->fi_mmapped))
+               ;
+}
+
+static inline void au_unset_mmapped(struct file *f)
+{
+       atomic_dec(&au_fi(f)->fi_mmapped);
+}
+
+static inline int au_test_mmapped(struct file *f)
+{
+       return atomic_read(&au_fi(f)->fi_mmapped);
+}
+
+/* customize vma->vm_file */
+
+static inline void au_do_vm_file_reset(struct vm_area_struct *vma,
+                                      struct file *file)
+{
+       struct file *f;
+
+       f = vma->vm_file;
+       get_file(file);
+       vma->vm_file = file;
+       fput(f);
+}
+
+#ifdef CONFIG_MMU
+#define AuDbgVmRegion(file, vma) do {} while (0)
+
+static inline void au_vm_file_reset(struct vm_area_struct *vma,
+                                   struct file *file)
+{
+       au_do_vm_file_reset(vma, file);
+}
+#else
+#define AuDbgVmRegion(file, vma) \
+       AuDebugOn((vma)->vm_region && (vma)->vm_region->vm_file != (file))
+
+static inline void au_vm_file_reset(struct vm_area_struct *vma,
+                                   struct file *file)
+{
+       struct file *f;
+
+       au_do_vm_file_reset(vma, file);
+       f = vma->vm_region->vm_file;
+       get_file(file);
+       vma->vm_region->vm_file = file;
+       fput(f);
+}
+#endif /* CONFIG_MMU */
+
+/* handle vma->vm_prfile */
+static inline void au_vm_prfile_set(struct vm_area_struct *vma,
+                                   struct file *file)
+{
+       get_file(file);
+       vma->vm_prfile = file;
+#ifndef CONFIG_MMU
+       get_file(file);
+       vma->vm_region->vm_prfile = file;
+#endif
+}
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_FILE_H__ */
diff -urN /usr/share/empty/fs/aufs/finfo.c linux/fs/aufs/finfo.c
--- /usr/share/empty/fs/aufs/finfo.c    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/finfo.c       2021-12-03 15:38:59.936647310 +0100
@@ -0,0 +1,149 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * file private data
+ */
+
+#include "aufs.h"
+
+void au_hfput(struct au_hfile *hf, int execed)
+{
+       if (execed)
+               allow_write_access(hf->hf_file);
+       fput(hf->hf_file);
+       hf->hf_file = NULL;
+       au_lcnt_dec(&hf->hf_br->br_nfiles);
+       hf->hf_br = NULL;
+}
+
+void au_set_h_fptr(struct file *file, aufs_bindex_t bindex, struct file *val)
+{
+       struct au_finfo *finfo = au_fi(file);
+       struct au_hfile *hf;
+       struct au_fidir *fidir;
+
+       fidir = finfo->fi_hdir;
+       if (!fidir) {
+               AuDebugOn(finfo->fi_btop != bindex);
+               hf = &finfo->fi_htop;
+       } else
+               hf = fidir->fd_hfile + bindex;
+
+       if (hf && hf->hf_file)
+               au_hfput(hf, vfsub_file_execed(file));
+       if (val) {
+               FiMustWriteLock(file);
+               AuDebugOn(IS_ERR_OR_NULL(file->f_path.dentry));
+               hf->hf_file = val;
+               hf->hf_br = au_sbr(file->f_path.dentry->d_sb, bindex);
+       }
+}
+
+void au_update_figen(struct file *file)
+{
+       atomic_set(&au_fi(file)->fi_generation, au_digen(file->f_path.dentry));
+       /* smp_mb(); */ /* atomic_set */
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct au_fidir *au_fidir_alloc(struct super_block *sb)
+{
+       struct au_fidir *fidir;
+       int nbr;
+
+       nbr = au_sbbot(sb) + 1;
+       if (nbr < 2)
+               nbr = 2; /* initial allocate for 2 branches */
+       fidir = kzalloc(au_fidir_sz(nbr), GFP_NOFS);
+       if (fidir) {
+               fidir->fd_bbot = -1;
+               fidir->fd_nent = nbr;
+       }
+
+       return fidir;
+}
+
+int au_fidir_realloc(struct au_finfo *finfo, int nbr, int may_shrink)
+{
+       int err;
+       struct au_fidir *fidir, *p;
+
+       AuRwMustWriteLock(&finfo->fi_rwsem);
+       fidir = finfo->fi_hdir;
+       AuDebugOn(!fidir);
+
+       err = -ENOMEM;
+       p = au_kzrealloc(fidir, au_fidir_sz(fidir->fd_nent), au_fidir_sz(nbr),
+                        GFP_NOFS, may_shrink);
+       if (p) {
+               p->fd_nent = nbr;
+               finfo->fi_hdir = p;
+               err = 0;
+       }
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void au_finfo_fin(struct file *file)
+{
+       struct au_finfo *finfo;
+
+       au_lcnt_dec(&au_sbi(file->f_path.dentry->d_sb)->si_nfiles);
+
+       finfo = au_fi(file);
+       AuDebugOn(finfo->fi_hdir);
+       AuRwDestroy(&finfo->fi_rwsem);
+       au_cache_free_finfo(finfo);
+}
+
+void au_fi_init_once(void *_finfo)
+{
+       struct au_finfo *finfo = _finfo;
+
+       au_rw_init(&finfo->fi_rwsem);
+}
+
+int au_finfo_init(struct file *file, struct au_fidir *fidir)
+{
+       int err;
+       struct au_finfo *finfo;
+       struct dentry *dentry;
+
+       err = -ENOMEM;
+       dentry = file->f_path.dentry;
+       finfo = au_cache_alloc_finfo();
+       if (unlikely(!finfo))
+               goto out;
+
+       err = 0;
+       au_lcnt_inc(&au_sbi(dentry->d_sb)->si_nfiles);
+       au_rw_write_lock(&finfo->fi_rwsem);
+       finfo->fi_btop = -1;
+       finfo->fi_hdir = fidir;
+       atomic_set(&finfo->fi_generation, au_digen(dentry));
+       /* smp_mb(); */ /* atomic_set */
+
+       file->private_data = finfo;
+
+out:
+       return err;
+}
diff -urN /usr/share/empty/fs/aufs/f_op.c linux/fs/aufs/f_op.c
--- /usr/share/empty/fs/aufs/f_op.c     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/f_op.c        2021-12-03 15:38:59.933313976 +0100
@@ -0,0 +1,771 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * file and vm operations
+ */
+
+#include <linux/aio.h>
+#include <linux/fs_stack.h>
+#include <linux/mman.h>
+#include <linux/security.h>
+#include "aufs.h"
+
+int au_do_open_nondir(struct file *file, int flags, struct file *h_file)
+{
+       int err;
+       aufs_bindex_t bindex;
+       struct dentry *dentry, *h_dentry;
+       struct au_finfo *finfo;
+       struct inode *h_inode;
+
+       FiMustWriteLock(file);
+
+       err = 0;
+       dentry = file->f_path.dentry;
+       AuDebugOn(IS_ERR_OR_NULL(dentry));
+       finfo = au_fi(file);
+       memset(&finfo->fi_htop, 0, sizeof(finfo->fi_htop));
+       atomic_set(&finfo->fi_mmapped, 0);
+       bindex = au_dbtop(dentry);
+       if (!h_file) {
+               h_dentry = au_h_dptr(dentry, bindex);
+               err = vfsub_test_mntns(file->f_path.mnt, h_dentry->d_sb);
+               if (unlikely(err))
+                       goto out;
+               h_file = au_h_open(dentry, bindex, flags, file, /*force_wr*/0);
+               if (IS_ERR(h_file)) {
+                       err = PTR_ERR(h_file);
+                       goto out;
+               }
+       } else {
+               h_dentry = h_file->f_path.dentry;
+               err = vfsub_test_mntns(file->f_path.mnt, h_dentry->d_sb);
+               if (unlikely(err))
+                       goto out;
+               /* br ref is already inc-ed */
+       }
+
+       if ((flags & __O_TMPFILE)
+           && !(flags & O_EXCL)) {
+               h_inode = file_inode(h_file);
+               spin_lock(&h_inode->i_lock);
+               h_inode->i_state |= I_LINKABLE;
+               spin_unlock(&h_inode->i_lock);
+       }
+       au_set_fbtop(file, bindex);
+       au_set_h_fptr(file, bindex, h_file);
+       au_update_figen(file);
+       /* todo: necessary? */
+       /* file->f_ra = h_file->f_ra; */
+
+out:
+       return err;
+}
+
+static int aufs_open_nondir(struct inode *inode __maybe_unused,
+                           struct file *file)
+{
+       int err;
+       struct super_block *sb;
+       struct au_do_open_args args = {
+               .open   = au_do_open_nondir
+       };
+
+       AuDbg("%pD, f_flags 0x%x, f_mode 0x%x\n",
+             file, vfsub_file_flags(file), file->f_mode);
+
+       sb = file->f_path.dentry->d_sb;
+       si_read_lock(sb, AuLock_FLUSH);
+       err = au_do_open(file, &args);
+       si_read_unlock(sb);
+       return err;
+}
+
+int aufs_release_nondir(struct inode *inode __maybe_unused, struct file *file)
+{
+       struct au_finfo *finfo;
+       aufs_bindex_t bindex;
+
+       finfo = au_fi(file);
+       au_hbl_del(&finfo->fi_hlist,
+                  &au_sbi(file->f_path.dentry->d_sb)->si_files);
+       bindex = finfo->fi_btop;
+       if (bindex >= 0)
+               au_set_h_fptr(file, bindex, NULL);
+
+       au_finfo_fin(file);
+       return 0;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_do_flush_nondir(struct file *file, fl_owner_t id)
+{
+       int err;
+       struct file *h_file;
+
+       err = 0;
+       h_file = au_hf_top(file);
+       if (h_file)
+               err = vfsub_flush(h_file, id);
+       return err;
+}
+
+static int aufs_flush_nondir(struct file *file, fl_owner_t id)
+{
+       return au_do_flush(file, id, au_do_flush_nondir);
+}
+
+/* ---------------------------------------------------------------------- */
+/*
+ * read and write functions acquire [fdi]_rwsem once, but release before
+ * mmap_sem. This is because to stop a race condition between mmap(2).
+ * Releasing these aufs-rwsem should be safe, no branch-management (by keeping
+ * si_rwsem), no harmful copy-up should happen. Actually copy-up may happen in
+ * read functions after [fdi]_rwsem are released, but it should be harmless.
+ */
+
+/* Callers should call au_read_post() or fput() in the end */
+struct file *au_read_pre(struct file *file, int keep_fi, unsigned int lsc)
+{
+       struct file *h_file;
+       int err;
+
+       err = au_reval_and_lock_fdi(file, au_reopen_nondir, /*wlock*/0, lsc);
+       if (!err) {
+               di_read_unlock(file->f_path.dentry, AuLock_IR);
+               h_file = au_hf_top(file);
+               get_file(h_file);
+               if (!keep_fi)
+                       fi_read_unlock(file);
+       } else
+               h_file = ERR_PTR(err);
+
+       return h_file;
+}
+
+static void au_read_post(struct inode *inode, struct file *h_file)
+{
+       /* update without lock, I don't think it a problem */
+       fsstack_copy_attr_atime(inode, file_inode(h_file));
+       fput(h_file);
+}
+
+struct au_write_pre {
+       /* input */
+       unsigned int lsc;
+
+       /* output */
+       blkcnt_t blks;
+       aufs_bindex_t btop;
+};
+
+/*
+ * return with iinfo is write-locked
+ * callers should call au_write_post() or iinfo_write_unlock() + fput() in the
+ * end
+ */
+static struct file *au_write_pre(struct file *file, int do_ready,
+                                struct au_write_pre *wpre)
+{
+       struct file *h_file;
+       struct dentry *dentry;
+       int err;
+       unsigned int lsc;
+       struct au_pin pin;
+
+       lsc = 0;
+       if (wpre)
+               lsc = wpre->lsc;
+       err = au_reval_and_lock_fdi(file, au_reopen_nondir, /*wlock*/1, lsc);
+       h_file = ERR_PTR(err);
+       if (unlikely(err))
+               goto out;
+
+       dentry = file->f_path.dentry;
+       if (do_ready) {
+               err = au_ready_to_write(file, -1, &pin);
+               if (unlikely(err)) {
+                       h_file = ERR_PTR(err);
+                       di_write_unlock(dentry);
+                       goto out_fi;
+               }
+       }
+
+       di_downgrade_lock(dentry, /*flags*/0);
+       if (wpre)
+               wpre->btop = au_fbtop(file);
+       h_file = au_hf_top(file);
+       get_file(h_file);
+       if (wpre)
+               wpre->blks = file_inode(h_file)->i_blocks;
+       if (do_ready)
+               au_unpin(&pin);
+       di_read_unlock(dentry, /*flags*/0);
+
+out_fi:
+       fi_write_unlock(file);
+out:
+       return h_file;
+}
+
+static void au_write_post(struct inode *inode, struct file *h_file,
+                         struct au_write_pre *wpre, ssize_t written)
+{
+       struct inode *h_inode;
+
+       au_cpup_attr_timesizes(inode);
+       AuDebugOn(au_ibtop(inode) != wpre->btop);
+       h_inode = file_inode(h_file);
+       inode->i_mode = h_inode->i_mode;
+       ii_write_unlock(inode);
+       /* AuDbg("blks %llu, %llu\n", (u64)blks, (u64)h_inode->i_blocks); */
+       if (written > 0)
+               au_fhsm_wrote(inode->i_sb, wpre->btop,
+                             /*force*/h_inode->i_blocks > wpre->blks);
+       fput(h_file);
+}
+
+/*
+ * todo: very ugly
+ * it locks both of i_mutex and si_rwsem for read in safe.
+ * if the plink maintenance mode continues forever (that is the problem),
+ * may loop forever.
+ */
+static void au_mtx_and_read_lock(struct inode *inode)
+{
+       int err;
+       struct super_block *sb = inode->i_sb;
+
+       while (1) {
+               inode_lock(inode);
+               err = si_read_lock(sb, AuLock_FLUSH | AuLock_NOPLM);
+               if (!err)
+                       break;
+               inode_unlock(inode);
+               si_read_lock(sb, AuLock_NOPLMW);
+               si_read_unlock(sb);
+       }
+}
+
+static ssize_t au_do_iter(struct file *h_file, int rw, struct kiocb *kio,
+                         struct iov_iter *iov_iter)
+{
+       ssize_t err;
+       struct file *file;
+       ssize_t (*iter)(struct kiocb *, struct iov_iter *);
+
+       err = security_file_permission(h_file, rw);
+       if (unlikely(err))
+               goto out;
+
+       err = -ENOSYS;  /* the branch doesn't have its ->(read|write)_iter() */
+       iter = NULL;
+       if (rw == MAY_READ)
+               iter = h_file->f_op->read_iter;
+       else if (rw == MAY_WRITE)
+               iter = h_file->f_op->write_iter;
+
+       file = kio->ki_filp;
+       kio->ki_filp = h_file;
+       if (iter) {
+               lockdep_off();
+               err = iter(kio, iov_iter);
+               lockdep_on();
+       } else
+               /* currently there is no such fs */
+               WARN_ON_ONCE(1);
+       kio->ki_filp = file;
+
+out:
+       return err;
+}
+
+static ssize_t aufs_read_iter(struct kiocb *kio, struct iov_iter *iov_iter)
+{
+       ssize_t err;
+       struct file *file, *h_file;
+       struct inode *inode;
+       struct super_block *sb;
+
+       file = kio->ki_filp;
+       inode = file_inode(file);
+       sb = inode->i_sb;
+       si_read_lock(sb, AuLock_FLUSH | AuLock_NOPLMW);
+
+       h_file = au_read_pre(file, /*keep_fi*/1, /*lsc*/0);
+       err = PTR_ERR(h_file);
+       if (IS_ERR(h_file))
+               goto out;
+
+       if (au_test_loopback_kthread()) {
+               au_warn_loopback(h_file->f_path.dentry->d_sb);
+               if (file->f_mapping != h_file->f_mapping) {
+                       file->f_mapping = h_file->f_mapping;
+                       smp_mb(); /* unnecessary? */
+               }
+       }
+       fi_read_unlock(file);
+
+       err = au_do_iter(h_file, MAY_READ, kio, iov_iter);
+       /* todo: necessary? */
+       /* file->f_ra = h_file->f_ra; */
+       au_read_post(inode, h_file);
+
+out:
+       si_read_unlock(sb);
+       return err;
+}
+
+static ssize_t aufs_write_iter(struct kiocb *kio, struct iov_iter *iov_iter)
+{
+       ssize_t err;
+       struct au_write_pre wpre;
+       struct inode *inode;
+       struct file *file, *h_file;
+
+       file = kio->ki_filp;
+       inode = file_inode(file);
+       au_mtx_and_read_lock(inode);
+
+       wpre.lsc = 0;
+       h_file = au_write_pre(file, /*do_ready*/1, &wpre);
+       err = PTR_ERR(h_file);
+       if (IS_ERR(h_file))
+               goto out;
+
+       err = au_do_iter(h_file, MAY_WRITE, kio, iov_iter);
+       au_write_post(inode, h_file, &wpre, err);
+
+out:
+       si_read_unlock(inode->i_sb);
+       inode_unlock(inode);
+       return err;
+}
+
+/*
+ * We may be able to remove aufs_splice_{read,write}() since almost all FSes
+ * don't have their own .splice_{read,write} implimentations, and they use
+ * generic_file_splice_read() and iter_file_splice_write() who can act like the
+ * simple converters to f_op->iter_read() and ->iter_write().
+ * But we keep our own implementations because some non-mainlined FSes may have
+ * their own .splice_{read,write} implimentations and aufs doesn't want to take
+ * away an opportunity to co-work with aufs from them.
+ */
+static ssize_t aufs_splice_read(struct file *file, loff_t *ppos,
+                               struct pipe_inode_info *pipe, size_t len,
+                               unsigned int flags)
+{
+       ssize_t err;
+       struct file *h_file;
+       struct inode *inode;
+       struct super_block *sb;
+
+       inode = file_inode(file);
+       sb = inode->i_sb;
+       si_read_lock(sb, AuLock_FLUSH | AuLock_NOPLMW);
+
+       h_file = au_read_pre(file, /*keep_fi*/0, /*lsc*/0);
+       err = PTR_ERR(h_file);
+       if (IS_ERR(h_file))
+               goto out;
+
+       err = vfsub_splice_to(h_file, ppos, pipe, len, flags);
+       /* todo: necessary? */
+       /* file->f_ra = h_file->f_ra; */
+       au_read_post(inode, h_file);
+
+out:
+       si_read_unlock(sb);
+       return err;
+}
+
+static ssize_t
+aufs_splice_write(struct pipe_inode_info *pipe, struct file *file, loff_t *ppos,
+                 size_t len, unsigned int flags)
+{
+       ssize_t err;
+       struct au_write_pre wpre;
+       struct inode *inode;
+       struct file *h_file;
+
+       inode = file_inode(file);
+       au_mtx_and_read_lock(inode);
+
+       wpre.lsc = 0;
+       h_file = au_write_pre(file, /*do_ready*/1, &wpre);
+       err = PTR_ERR(h_file);
+       if (IS_ERR(h_file))
+               goto out;
+
+       err = vfsub_splice_from(pipe, h_file, ppos, len, flags);
+       au_write_post(inode, h_file, &wpre, err);
+
+out:
+       si_read_unlock(inode->i_sb);
+       inode_unlock(inode);
+       return err;
+}
+
+static long aufs_fallocate(struct file *file, int mode, loff_t offset,
+                          loff_t len)
+{
+       long err;
+       struct au_write_pre wpre;
+       struct inode *inode;
+       struct file *h_file;
+
+       inode = file_inode(file);
+       au_mtx_and_read_lock(inode);
+
+       wpre.lsc = 0;
+       h_file = au_write_pre(file, /*do_ready*/1, &wpre);
+       err = PTR_ERR(h_file);
+       if (IS_ERR(h_file))
+               goto out;
+
+       lockdep_off();
+       err = vfs_fallocate(h_file, mode, offset, len);
+       lockdep_on();
+       au_write_post(inode, h_file, &wpre, /*written*/1);
+
+out:
+       si_read_unlock(inode->i_sb);
+       inode_unlock(inode);
+       return err;
+}
+
+static ssize_t aufs_copy_file_range(struct file *src, loff_t src_pos,
+                                   struct file *dst, loff_t dst_pos,
+                                   size_t len, unsigned int flags)
+{
+       ssize_t err;
+       struct au_write_pre wpre;
+       enum { SRC, DST };
+       struct {
+               struct inode *inode;
+               struct file *h_file;
+               struct super_block *h_sb;
+       } a[2];
+#define a_src  a[SRC]
+#define a_dst  a[DST]
+
+       err = -EINVAL;
+       a_src.inode = file_inode(src);
+       if (unlikely(!S_ISREG(a_src.inode->i_mode)))
+               goto out;
+       a_dst.inode = file_inode(dst);
+       if (unlikely(!S_ISREG(a_dst.inode->i_mode)))
+               goto out;
+
+       au_mtx_and_read_lock(a_dst.inode);
+       /*
+        * in order to match the order in di_write_lock2_{child,parent}(),
+        * use f_path.dentry for this comparison.
+        */
+       if (src->f_path.dentry < dst->f_path.dentry) {
+               a_src.h_file = au_read_pre(src, /*keep_fi*/1, AuLsc_FI_1);
+               err = PTR_ERR(a_src.h_file);
+               if (IS_ERR(a_src.h_file))
+                       goto out_si;
+
+               wpre.lsc = AuLsc_FI_2;
+               a_dst.h_file = au_write_pre(dst, /*do_ready*/1, &wpre);
+               err = PTR_ERR(a_dst.h_file);
+               if (IS_ERR(a_dst.h_file)) {
+                       au_read_post(a_src.inode, a_src.h_file);
+                       goto out_si;
+               }
+       } else {
+               wpre.lsc = AuLsc_FI_1;
+               a_dst.h_file = au_write_pre(dst, /*do_ready*/1, &wpre);
+               err = PTR_ERR(a_dst.h_file);
+               if (IS_ERR(a_dst.h_file))
+                       goto out_si;
+
+               a_src.h_file = au_read_pre(src, /*keep_fi*/1, AuLsc_FI_2);
+               err = PTR_ERR(a_src.h_file);
+               if (IS_ERR(a_src.h_file)) {
+                       au_write_post(a_dst.inode, a_dst.h_file, &wpre,
+                                     /*written*/0);
+                       goto out_si;
+               }
+       }
+
+       err = -EXDEV;
+       a_src.h_sb = file_inode(a_src.h_file)->i_sb;
+       a_dst.h_sb = file_inode(a_dst.h_file)->i_sb;
+       if (unlikely(a_src.h_sb != a_dst.h_sb)) {
+               AuDbgFile(src);
+               AuDbgFile(dst);
+               goto out_file;
+       }
+
+       err = vfsub_copy_file_range(a_src.h_file, src_pos, a_dst.h_file,
+                                   dst_pos, len, flags);
+
+out_file:
+       au_write_post(a_dst.inode, a_dst.h_file, &wpre, err);
+       fi_read_unlock(src);
+       au_read_post(a_src.inode, a_src.h_file);
+out_si:
+       si_read_unlock(a_dst.inode->i_sb);
+       inode_unlock(a_dst.inode);
+out:
+       return err;
+#undef a_src
+#undef a_dst
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * The locking order around current->mmap_sem.
+ * - in most and regular cases
+ *   file I/O syscall -- aufs_read() or something
+ *     -- si_rwsem for read -- mmap_sem
+ *     (Note that [fdi]i_rwsem are released before mmap_sem).
+ * - in mmap case
+ *   mmap(2) -- mmap_sem -- aufs_mmap() -- si_rwsem for read -- [fdi]i_rwsem
+ * This AB-BA order is definitely bad, but is not a problem since "si_rwsem for
+ * read" allows multiple processes to acquire it and [fdi]i_rwsem are not held
+ * in file I/O. Aufs needs to stop lockdep in aufs_mmap() though.
+ * It means that when aufs acquires si_rwsem for write, the process should never
+ * acquire mmap_sem.
+ *
+ * Actually aufs_iterate() holds [fdi]i_rwsem before mmap_sem, but this is not a
+ * problem either since any directory is not able to be mmap-ed.
+ * The similar scenario is applied to aufs_readlink() too.
+ */
+
+#if 0 /* stop calling security_file_mmap() */
+/* cf. linux/include/linux/mman.h: calc_vm_prot_bits() */
+#define AuConv_VM_PROT(f, b)   _calc_vm_trans(f, VM_##b, PROT_##b)
+
+static unsigned long au_arch_prot_conv(unsigned long flags)
+{
+       /* currently ppc64 only */
+#ifdef CONFIG_PPC64
+       /* cf. linux/arch/powerpc/include/asm/mman.h */
+       AuDebugOn(arch_calc_vm_prot_bits(-1) != VM_SAO);
+       return AuConv_VM_PROT(flags, SAO);
+#else
+       AuDebugOn(arch_calc_vm_prot_bits(-1));
+       return 0;
+#endif
+}
+
+static unsigned long au_prot_conv(unsigned long flags)
+{
+       return AuConv_VM_PROT(flags, READ)
+               | AuConv_VM_PROT(flags, WRITE)
+               | AuConv_VM_PROT(flags, EXEC)
+               | au_arch_prot_conv(flags);
+}
+
+/* cf. linux/include/linux/mman.h: calc_vm_flag_bits() */
+#define AuConv_VM_MAP(f, b)    _calc_vm_trans(f, VM_##b, MAP_##b)
+
+static unsigned long au_flag_conv(unsigned long flags)
+{
+       return AuConv_VM_MAP(flags, GROWSDOWN)
+               | AuConv_VM_MAP(flags, DENYWRITE)
+               | AuConv_VM_MAP(flags, LOCKED);
+}
+#endif
+
+static int aufs_mmap(struct file *file, struct vm_area_struct *vma)
+{
+       int err;
+       const unsigned char wlock
+               = (file->f_mode & FMODE_WRITE) && (vma->vm_flags & VM_SHARED);
+       struct super_block *sb;
+       struct file *h_file;
+       struct inode *inode;
+
+       AuDbgVmRegion(file, vma);
+
+       inode = file_inode(file);
+       sb = inode->i_sb;
+       lockdep_off();
+       si_read_lock(sb, AuLock_NOPLMW);
+
+       h_file = au_write_pre(file, wlock, /*wpre*/NULL);
+       lockdep_on();
+       err = PTR_ERR(h_file);
+       if (IS_ERR(h_file))
+               goto out;
+
+       err = 0;
+       au_set_mmapped(file);
+       au_vm_file_reset(vma, h_file);
+       /*
+        * we cannot call security_mmap_file() here since it may acquire
+        * mmap_sem or i_mutex.
+        *
+        * err = security_mmap_file(h_file, au_prot_conv(vma->vm_flags),
+        *                       au_flag_conv(vma->vm_flags));
+        */
+       if (!err)
+               err = call_mmap(h_file, vma);
+       if (!err) {
+               au_vm_prfile_set(vma, file);
+               fsstack_copy_attr_atime(inode, file_inode(h_file));
+               goto out_fput; /* success */
+       }
+       au_unset_mmapped(file);
+       au_vm_file_reset(vma, file);
+
+out_fput:
+       lockdep_off();
+       ii_write_unlock(inode);
+       lockdep_on();
+       fput(h_file);
+out:
+       lockdep_off();
+       si_read_unlock(sb);
+       lockdep_on();
+       AuTraceErr(err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int aufs_fsync_nondir(struct file *file, loff_t start, loff_t end,
+                            int datasync)
+{
+       int err;
+       struct au_write_pre wpre;
+       struct inode *inode;
+       struct file *h_file;
+
+       err = 0; /* -EBADF; */ /* posix? */
+       if (unlikely(!(file->f_mode & FMODE_WRITE)))
+               goto out;
+
+       inode = file_inode(file);
+       au_mtx_and_read_lock(inode);
+
+       wpre.lsc = 0;
+       h_file = au_write_pre(file, /*do_ready*/1, &wpre);
+       err = PTR_ERR(h_file);
+       if (IS_ERR(h_file))
+               goto out_unlock;
+
+       err = vfsub_fsync(h_file, &h_file->f_path, datasync);
+       au_write_post(inode, h_file, &wpre, /*written*/0);
+
+out_unlock:
+       si_read_unlock(inode->i_sb);
+       inode_unlock(inode);
+out:
+       return err;
+}
+
+static int aufs_fasync(int fd, struct file *file, int flag)
+{
+       int err;
+       struct file *h_file;
+       struct super_block *sb;
+
+       sb = file->f_path.dentry->d_sb;
+       si_read_lock(sb, AuLock_FLUSH | AuLock_NOPLMW);
+
+       h_file = au_read_pre(file, /*keep_fi*/0, /*lsc*/0);
+       err = PTR_ERR(h_file);
+       if (IS_ERR(h_file))
+               goto out;
+
+       if (h_file->f_op->fasync)
+               err = h_file->f_op->fasync(fd, h_file, flag);
+       fput(h_file); /* instead of au_read_post() */
+
+out:
+       si_read_unlock(sb);
+       return err;
+}
+
+static int aufs_setfl(struct file *file, unsigned long arg)
+{
+       int err;
+       struct file *h_file;
+       struct super_block *sb;
+
+       sb = file->f_path.dentry->d_sb;
+       si_read_lock(sb, AuLock_FLUSH | AuLock_NOPLMW);
+
+       h_file = au_read_pre(file, /*keep_fi*/0, /*lsc*/0);
+       err = PTR_ERR(h_file);
+       if (IS_ERR(h_file))
+               goto out;
+
+       /* stop calling h_file->fasync */
+       arg |= vfsub_file_flags(file) & FASYNC;
+       err = setfl(/*unused fd*/-1, h_file, arg);
+       fput(h_file); /* instead of au_read_post() */
+
+out:
+       si_read_unlock(sb);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* no one supports this operation, currently */
+#if 0 /* reserved for future use */
+static ssize_t aufs_sendpage(struct file *file, struct page *page, int offset,
+                            size_t len, loff_t *pos, int more)
+{
+}
+#endif
+
+/* ---------------------------------------------------------------------- */
+
+const struct file_operations aufs_file_fop = {
+       .owner          = THIS_MODULE,
+
+       .llseek         = default_llseek,
+
+       .read_iter      = aufs_read_iter,
+       .write_iter     = aufs_write_iter,
+
+#ifdef CONFIG_AUFS_POLL
+       .poll           = aufs_poll,
+#endif
+       .unlocked_ioctl = aufs_ioctl_nondir,
+#ifdef CONFIG_COMPAT
+       .compat_ioctl   = aufs_compat_ioctl_nondir,
+#endif
+       .mmap           = aufs_mmap,
+       .open           = aufs_open_nondir,
+       .flush          = aufs_flush_nondir,
+       .release        = aufs_release_nondir,
+       .fsync          = aufs_fsync_nondir,
+       .fasync         = aufs_fasync,
+       /* .sendpage    = aufs_sendpage, */
+       .setfl          = aufs_setfl,
+       .splice_write   = aufs_splice_write,
+       .splice_read    = aufs_splice_read,
+#if 0 /* reserved for future use */
+       .aio_splice_write = aufs_aio_splice_write,
+       .aio_splice_read  = aufs_aio_splice_read,
+#endif
+       .fallocate      = aufs_fallocate,
+       .copy_file_range = aufs_copy_file_range
+};
diff -urN /usr/share/empty/fs/aufs/fstype.h linux/fs/aufs/fstype.h
--- /usr/share/empty/fs/aufs/fstype.h   1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/fstype.h      2021-12-03 15:38:59.936647310 +0100
@@ -0,0 +1,401 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * judging filesystem type
+ */
+
+#ifndef __AUFS_FSTYPE_H__
+#define __AUFS_FSTYPE_H__
+
+#ifdef __KERNEL__
+
+#include <linux/fs.h>
+#include <linux/magic.h>
+#include <linux/nfs_fs.h>
+#include <linux/romfs_fs.h>
+
+static inline int au_test_aufs(struct super_block *sb)
+{
+       return sb->s_magic == AUFS_SUPER_MAGIC;
+}
+
+static inline const char *au_sbtype(struct super_block *sb)
+{
+       return sb->s_type->name;
+}
+
+static inline int au_test_iso9660(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_ISO9660_FS)
+       return sb->s_magic == ISOFS_SUPER_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_romfs(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_ROMFS_FS)
+       return sb->s_magic == ROMFS_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_cramfs(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_CRAMFS)
+       return sb->s_magic == CRAMFS_MAGIC;
+#endif
+       return 0;
+}
+
+static inline int au_test_nfs(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_NFS_FS)
+       return sb->s_magic == NFS_SUPER_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_fuse(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_FUSE_FS)
+       return sb->s_magic == FUSE_SUPER_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_xfs(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_XFS_FS)
+       return sb->s_magic == XFS_SB_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_tmpfs(struct super_block *sb __maybe_unused)
+{
+#ifdef CONFIG_TMPFS
+       return sb->s_magic == TMPFS_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_ecryptfs(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_ECRYPT_FS)
+       return !strcmp(au_sbtype(sb), "ecryptfs");
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_ramfs(struct super_block *sb)
+{
+       return sb->s_magic == RAMFS_MAGIC;
+}
+
+static inline int au_test_ubifs(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_UBIFS_FS)
+       return sb->s_magic == UBIFS_SUPER_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_procfs(struct super_block *sb __maybe_unused)
+{
+#ifdef CONFIG_PROC_FS
+       return sb->s_magic == PROC_SUPER_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_sysfs(struct super_block *sb __maybe_unused)
+{
+#ifdef CONFIG_SYSFS
+       return sb->s_magic == SYSFS_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_configfs(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_CONFIGFS_FS)
+       return sb->s_magic == CONFIGFS_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_minix(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_MINIX_FS)
+       return sb->s_magic == MINIX3_SUPER_MAGIC
+               || sb->s_magic == MINIX2_SUPER_MAGIC
+               || sb->s_magic == MINIX2_SUPER_MAGIC2
+               || sb->s_magic == MINIX_SUPER_MAGIC
+               || sb->s_magic == MINIX_SUPER_MAGIC2;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_fat(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_FAT_FS)
+       return sb->s_magic == MSDOS_SUPER_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_msdos(struct super_block *sb)
+{
+       return au_test_fat(sb);
+}
+
+static inline int au_test_vfat(struct super_block *sb)
+{
+       return au_test_fat(sb);
+}
+
+static inline int au_test_securityfs(struct super_block *sb __maybe_unused)
+{
+#ifdef CONFIG_SECURITYFS
+       return sb->s_magic == SECURITYFS_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_squashfs(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_SQUASHFS)
+       return sb->s_magic == SQUASHFS_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_btrfs(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_BTRFS_FS)
+       return sb->s_magic == BTRFS_SUPER_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_xenfs(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_XENFS)
+       return sb->s_magic == XENFS_SUPER_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_debugfs(struct super_block *sb __maybe_unused)
+{
+#ifdef CONFIG_DEBUG_FS
+       return sb->s_magic == DEBUGFS_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_nilfs(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_NILFS)
+       return sb->s_magic == NILFS_SUPER_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+static inline int au_test_hfsplus(struct super_block *sb __maybe_unused)
+{
+#if IS_ENABLED(CONFIG_HFSPLUS_FS)
+       return sb->s_magic == HFSPLUS_SUPER_MAGIC;
+#else
+       return 0;
+#endif
+}
+
+/* ---------------------------------------------------------------------- */
+/*
+ * they can't be an aufs branch.
+ */
+static inline int au_test_fs_unsuppoted(struct super_block *sb)
+{
+       return
+#ifndef CONFIG_AUFS_BR_RAMFS
+               au_test_ramfs(sb) ||
+#endif
+               au_test_procfs(sb)
+               || au_test_sysfs(sb)
+               || au_test_configfs(sb)
+               || au_test_debugfs(sb)
+               || au_test_securityfs(sb)
+               || au_test_xenfs(sb)
+               || au_test_ecryptfs(sb)
+               /* || !strcmp(au_sbtype(sb), "unionfs") */
+               || au_test_aufs(sb); /* will be supported in next version */
+}
+
+static inline int au_test_fs_remote(struct super_block *sb)
+{
+       return !au_test_tmpfs(sb)
+#ifdef CONFIG_AUFS_BR_RAMFS
+               && !au_test_ramfs(sb)
+#endif
+               && !(sb->s_type->fs_flags & FS_REQUIRES_DEV);
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * Note: these functions (below) are created after reading ->getattr() in all
+ * filesystems under linux/fs. it means we have to do so in every update...
+ */
+
+/*
+ * some filesystems require getattr to refresh the inode attributes before
+ * referencing.
+ * in most cases, we can rely on the inode attribute in NFS (or every remote fs)
+ * and leave the work for d_revalidate()
+ */
+static inline int au_test_fs_refresh_iattr(struct super_block *sb)
+{
+       return au_test_nfs(sb)
+               || au_test_fuse(sb)
+               /* || au_test_btrfs(sb) */      /* untested */
+               ;
+}
+
+/*
+ * filesystems which don't maintain i_size or i_blocks.
+ */
+static inline int au_test_fs_bad_iattr_size(struct super_block *sb)
+{
+       return au_test_xfs(sb)
+               || au_test_btrfs(sb)
+               || au_test_ubifs(sb)
+               || au_test_hfsplus(sb)  /* maintained, but incorrect */
+               /* || au_test_minix(sb) */      /* untested */
+               ;
+}
+
+/*
+ * filesystems which don't store the correct value in some of their inode
+ * attributes.
+ */
+static inline int au_test_fs_bad_iattr(struct super_block *sb)
+{
+       return au_test_fs_bad_iattr_size(sb)
+               || au_test_fat(sb)
+               || au_test_msdos(sb)
+               || au_test_vfat(sb);
+}
+
+/* they don't check i_nlink in link(2) */
+static inline int au_test_fs_no_limit_nlink(struct super_block *sb)
+{
+       return au_test_tmpfs(sb)
+#ifdef CONFIG_AUFS_BR_RAMFS
+               || au_test_ramfs(sb)
+#endif
+               || au_test_ubifs(sb)
+               || au_test_hfsplus(sb);
+}
+
+/*
+ * filesystems which sets S_NOATIME and S_NOCMTIME.
+ */
+static inline int au_test_fs_notime(struct super_block *sb)
+{
+       return au_test_nfs(sb)
+               || au_test_fuse(sb)
+               || au_test_ubifs(sb)
+               ;
+}
+
+/* temporary support for i#1 in cramfs */
+static inline int au_test_fs_unique_ino(struct inode *inode)
+{
+       if (au_test_cramfs(inode->i_sb))
+               return inode->i_ino != 1;
+       return 1;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * the filesystem where the xino files placed must support i/o after unlink and
+ * maintain i_size and i_blocks.
+ */
+static inline int au_test_fs_bad_xino(struct super_block *sb)
+{
+       return au_test_fs_remote(sb)
+               || au_test_fs_bad_iattr_size(sb)
+               /* don't want unnecessary work for xino */
+               || au_test_aufs(sb)
+               || au_test_ecryptfs(sb)
+               || au_test_nilfs(sb);
+}
+
+static inline int au_test_fs_trunc_xino(struct super_block *sb)
+{
+       return au_test_tmpfs(sb)
+               || au_test_ramfs(sb);
+}
+
+/*
+ * test if the @sb is real-readonly.
+ */
+static inline int au_test_fs_rr(struct super_block *sb)
+{
+       return au_test_squashfs(sb)
+               || au_test_iso9660(sb)
+               || au_test_cramfs(sb)
+               || au_test_romfs(sb);
+}
+
+/*
+ * test if the @inode is nfs with 'noacl' option
+ * NFS always sets SB_POSIXACL regardless its mount option 'noacl.'
+ */
+static inline int au_test_nfs_noacl(struct inode *inode)
+{
+       return au_test_nfs(inode->i_sb)
+               /* && IS_POSIXACL(inode) */
+               && !nfs_server_capable(inode, NFS_CAP_ACLS);
+}
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_FSTYPE_H__ */
diff -urN /usr/share/empty/fs/aufs/hbl.h linux/fs/aufs/hbl.h
--- /usr/share/empty/fs/aufs/hbl.h      1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/hbl.h 2021-12-03 15:38:59.936647310 +0100
@@ -0,0 +1,65 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2017-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * helpers for hlist_bl.h
+ */
+
+#ifndef __AUFS_HBL_H__
+#define __AUFS_HBL_H__
+
+#ifdef __KERNEL__
+
+#include <linux/list_bl.h>
+
+static inline void au_hbl_add(struct hlist_bl_node *node,
+                             struct hlist_bl_head *hbl)
+{
+       hlist_bl_lock(hbl);
+       hlist_bl_add_head(node, hbl);
+       hlist_bl_unlock(hbl);
+}
+
+static inline void au_hbl_del(struct hlist_bl_node *node,
+                             struct hlist_bl_head *hbl)
+{
+       hlist_bl_lock(hbl);
+       hlist_bl_del(node);
+       hlist_bl_unlock(hbl);
+}
+
+#define au_hbl_for_each(pos, head)                                     \
+       for (pos = hlist_bl_first(head);                                \
+            pos;                                                       \
+            pos = pos->next)
+
+static inline unsigned long au_hbl_count(struct hlist_bl_head *hbl)
+{
+       unsigned long cnt;
+       struct hlist_bl_node *pos;
+
+       cnt = 0;
+       hlist_bl_lock(hbl);
+       au_hbl_for_each(pos, hbl)
+               cnt++;
+       hlist_bl_unlock(hbl);
+       return cnt;
+}
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_HBL_H__ */
diff -urN /usr/share/empty/fs/aufs/hfsnotify.c linux/fs/aufs/hfsnotify.c
--- /usr/share/empty/fs/aufs/hfsnotify.c        1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/hfsnotify.c   2022-01-13 12:42:15.929566135 +0100
@@ -0,0 +1,289 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * fsnotify for the lower directories
+ */
+
+#include "aufs.h"
+
+/* FS_IN_IGNORED is unnecessary */
+static const __u32 AuHfsnMask = (FS_MOVED_TO | FS_MOVED_FROM | FS_DELETE
+                                | FS_CREATE | FS_EVENT_ON_CHILD);
+static DECLARE_WAIT_QUEUE_HEAD(au_hfsn_wq);
+static __cacheline_aligned_in_smp atomic64_t au_hfsn_ifree = ATOMIC64_INIT(0);
+
+static void au_hfsn_free_mark(struct fsnotify_mark *mark)
+{
+       struct au_hnotify *hn = container_of(mark, struct au_hnotify,
+                                            hn_mark);
+       /* AuDbg("here\n"); */
+       au_cache_free_hnotify(hn);
+       smp_mb__before_atomic(); /* for atomic64_dec */
+       if (atomic64_dec_and_test(&au_hfsn_ifree))
+               wake_up(&au_hfsn_wq);
+}
+
+static int au_hfsn_alloc(struct au_hinode *hinode)
+{
+       int err;
+       struct au_hnotify *hn;
+       struct super_block *sb;
+       struct au_branch *br;
+       struct fsnotify_mark *mark;
+       aufs_bindex_t bindex;
+
+       hn = hinode->hi_notify;
+       sb = hn->hn_aufs_inode->i_sb;
+       bindex = au_br_index(sb, hinode->hi_id);
+       br = au_sbr(sb, bindex);
+       AuDebugOn(!br->br_hfsn);
+
+       mark = &hn->hn_mark;
+       fsnotify_init_mark(mark, br->br_hfsn->hfsn_group);
+       mark->mask = AuHfsnMask;
+       /*
+        * by udba rename or rmdir, aufs assign a new inode to the known
+        * h_inode, so specify 1 to allow dups.
+        */
+       lockdep_off();
+       err = fsnotify_add_inode_mark(mark, hinode->hi_inode, /*allow_dups*/1);
+       lockdep_on();
+
+       return err;
+}
+
+static int au_hfsn_free(struct au_hinode *hinode, struct au_hnotify *hn)
+{
+       struct fsnotify_mark *mark;
+       unsigned long long ull;
+       struct fsnotify_group *group;
+
+       ull = atomic64_inc_return(&au_hfsn_ifree);
+       BUG_ON(!ull);
+
+       mark = &hn->hn_mark;
+       spin_lock(&mark->lock);
+       group = mark->group;
+       fsnotify_get_group(group);
+       spin_unlock(&mark->lock);
+       lockdep_off();
+       fsnotify_destroy_mark(mark, group);
+       fsnotify_put_mark(mark);
+       fsnotify_put_group(group);
+       lockdep_on();
+
+       /* free hn by myself */
+       return 0;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static void au_hfsn_ctl(struct au_hinode *hinode, int do_set)
+{
+       struct fsnotify_mark *mark;
+
+       mark = &hinode->hi_notify->hn_mark;
+       spin_lock(&mark->lock);
+       if (do_set) {
+               AuDebugOn(mark->mask & AuHfsnMask);
+               mark->mask |= AuHfsnMask;
+       } else {
+               AuDebugOn(!(mark->mask & AuHfsnMask));
+               mark->mask &= ~AuHfsnMask;
+       }
+       spin_unlock(&mark->lock);
+       /* fsnotify_recalc_inode_mask(hinode->hi_inode); */
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* #define AuDbgHnotify */
+#ifdef AuDbgHnotify
+static char *au_hfsn_name(u32 mask)
+{
+#ifdef CONFIG_AUFS_DEBUG
+#define test_ret(flag)                         \
+       do {                                    \
+               if (mask & flag)                \
+                       return #flag;           \
+       } while (0)
+       test_ret(FS_ACCESS);
+       test_ret(FS_MODIFY);
+       test_ret(FS_ATTRIB);
+       test_ret(FS_CLOSE_WRITE);
+       test_ret(FS_CLOSE_NOWRITE);
+       test_ret(FS_OPEN);
+       test_ret(FS_MOVED_FROM);
+       test_ret(FS_MOVED_TO);
+       test_ret(FS_CREATE);
+       test_ret(FS_DELETE);
+       test_ret(FS_DELETE_SELF);
+       test_ret(FS_MOVE_SELF);
+       test_ret(FS_UNMOUNT);
+       test_ret(FS_Q_OVERFLOW);
+       test_ret(FS_IN_IGNORED);
+       test_ret(FS_ISDIR);
+       test_ret(FS_IN_ONESHOT);
+       test_ret(FS_EVENT_ON_CHILD);
+       return "";
+#undef test_ret
+#else
+       return "??";
+#endif
+}
+#endif
+
+/* ---------------------------------------------------------------------- */
+
+static void au_hfsn_free_group(struct fsnotify_group *group)
+{
+       struct au_br_hfsnotify *hfsn = group->private;
+
+       /* AuDbg("here\n"); */
+       au_kfree_try_rcu(hfsn);
+}
+
+static int au_hfsn_handle_event(struct fsnotify_group *group,
+                               u32 mask, const void *data, int data_type,
+                               struct inode *dir,
+                               const struct qstr *file_name, u32 cookie,
+                               struct fsnotify_iter_info *iter_info)
+{
+       int err;
+       struct au_hnotify *hnotify;
+       struct inode *h_dir, *h_inode;
+       struct fsnotify_mark *inode_mark;
+
+       AuDebugOn(!(data_type == FSNOTIFY_EVENT_INODE
+                   || data_type == FSNOTIFY_EVENT_DENTRY));
+
+       err = 0;
+       /* if FS_UNMOUNT happens, there must be another bug */
+       AuDebugOn(mask & FS_UNMOUNT);
+       if (mask & (FS_IN_IGNORED | FS_UNMOUNT))
+               goto out;
+
+       h_dir = dir;
+       h_inode = NULL;
+#ifdef AuDbgHnotify
+       au_debug_on();
+       if (1 || h_child_qstr.len != sizeof(AUFS_XINO_FNAME) - 1
+           || strncmp(h_child_qstr.name, AUFS_XINO_FNAME, h_child_qstr.len)) {
+               AuDbg("i%lu, mask 0x%x %s, hcname %.*s, hi%lu\n",
+                     h_dir->i_ino, mask, au_hfsn_name(mask),
+                     AuLNPair(&h_child_qstr), h_inode ? h_inode->i_ino : 0);
+               /* WARN_ON(1); */
+       }
+       au_debug_off();
+#endif
+
+       inode_mark = fsnotify_iter_inode_mark(iter_info);
+       AuDebugOn(!inode_mark);
+       hnotify = container_of(inode_mark, struct au_hnotify, hn_mark);
+       err = au_hnotify(h_dir, hnotify, mask, file_name, h_inode);
+
+out:
+       return err;
+}
+
+static struct fsnotify_ops au_hfsn_ops = {
+       .handle_event           = au_hfsn_handle_event,
+       .free_group_priv        = au_hfsn_free_group,
+       .free_mark              = au_hfsn_free_mark
+};
+
+/* ---------------------------------------------------------------------- */
+
+static void au_hfsn_fin_br(struct au_branch *br)
+{
+       struct au_br_hfsnotify *hfsn;
+
+       hfsn = br->br_hfsn;
+       if (hfsn) {
+               lockdep_off();
+               fsnotify_put_group(hfsn->hfsn_group);
+               lockdep_on();
+       }
+}
+
+static int au_hfsn_init_br(struct au_branch *br, int perm)
+{
+       int err;
+       struct fsnotify_group *group;
+       struct au_br_hfsnotify *hfsn;
+
+       err = 0;
+       br->br_hfsn = NULL;
+       if (!au_br_hnotifyable(perm))
+               goto out;
+
+       err = -ENOMEM;
+       hfsn = kmalloc(sizeof(*hfsn), GFP_NOFS);
+       if (unlikely(!hfsn))
+               goto out;
+
+       err = 0;
+       group = fsnotify_alloc_group(&au_hfsn_ops);
+       if (IS_ERR(group)) {
+               err = PTR_ERR(group);
+               pr_err("fsnotify_alloc_group() failed, %d\n", err);
+               goto out_hfsn;
+       }
+
+       group->private = hfsn;
+       hfsn->hfsn_group = group;
+       br->br_hfsn = hfsn;
+       goto out; /* success */
+
+out_hfsn:
+       au_kfree_try_rcu(hfsn);
+out:
+       return err;
+}
+
+static int au_hfsn_reset_br(unsigned int udba, struct au_branch *br, int perm)
+{
+       int err;
+
+       err = 0;
+       if (!br->br_hfsn)
+               err = au_hfsn_init_br(br, perm);
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static void au_hfsn_fin(void)
+{
+       AuDbg("au_hfsn_ifree %lld\n", (long long)atomic64_read(&au_hfsn_ifree));
+       wait_event(au_hfsn_wq, !atomic64_read(&au_hfsn_ifree));
+}
+
+const struct au_hnotify_op au_hnotify_op = {
+       .ctl            = au_hfsn_ctl,
+       .alloc          = au_hfsn_alloc,
+       .free           = au_hfsn_free,
+
+       .fin            = au_hfsn_fin,
+
+       .reset_br       = au_hfsn_reset_br,
+       .fin_br         = au_hfsn_fin_br,
+       .init_br        = au_hfsn_init_br
+};
diff -urN /usr/share/empty/fs/aufs/hfsplus.c linux/fs/aufs/hfsplus.c
--- /usr/share/empty/fs/aufs/hfsplus.c  1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/hfsplus.c     2021-12-03 15:38:59.936647310 +0100
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2010-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * special support for filesystems which acquires an inode mutex
+ * at final closing a file, eg, hfsplus.
+ *
+ * This trick is very simple and stupid, just to open the file before really
+ * necessary open to tell hfsplus that this is not the final closing.
+ * The caller should call au_h_open_pre() after acquiring the inode mutex,
+ * and au_h_open_post() after releasing it.
+ */
+
+#include "aufs.h"
+
+struct file *au_h_open_pre(struct dentry *dentry, aufs_bindex_t bindex,
+                          int force_wr)
+{
+       struct file *h_file;
+       struct dentry *h_dentry;
+
+       h_dentry = au_h_dptr(dentry, bindex);
+       AuDebugOn(!h_dentry);
+       AuDebugOn(d_is_negative(h_dentry));
+
+       h_file = NULL;
+       if (au_test_hfsplus(h_dentry->d_sb)
+           && d_is_reg(h_dentry))
+               h_file = au_h_open(dentry, bindex,
+                                  O_RDONLY | O_NOATIME | O_LARGEFILE,
+                                  /*file*/NULL, force_wr);
+       return h_file;
+}
+
+void au_h_open_post(struct dentry *dentry, aufs_bindex_t bindex,
+                   struct file *h_file)
+{
+       struct au_branch *br;
+
+       if (h_file) {
+               fput(h_file);
+               br = au_sbr(dentry->d_sb, bindex);
+               au_lcnt_dec(&br->br_nfiles);
+       }
+}
diff -urN /usr/share/empty/fs/aufs/hnotify.c linux/fs/aufs/hnotify.c
--- /usr/share/empty/fs/aufs/hnotify.c  1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/hnotify.c     2021-12-03 15:38:59.936647310 +0100
@@ -0,0 +1,715 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * abstraction to notify the direct changes on lower directories
+ */
+
+/* #include <linux/iversion.h> */
+#include "aufs.h"
+
+int au_hn_alloc(struct au_hinode *hinode, struct inode *inode)
+{
+       int err;
+       struct au_hnotify *hn;
+
+       err = -ENOMEM;
+       hn = au_cache_alloc_hnotify();
+       if (hn) {
+               hn->hn_aufs_inode = inode;
+               hinode->hi_notify = hn;
+               err = au_hnotify_op.alloc(hinode);
+               AuTraceErr(err);
+               if (unlikely(err)) {
+                       hinode->hi_notify = NULL;
+                       au_cache_free_hnotify(hn);
+                       /*
+                        * The upper dir was removed by udba, but the same named
+                        * dir left. In this case, aufs assigns a new inode
+                        * number and set the monitor again.
+                        * For the lower dir, the old monitor is still left.
+                        */
+                       if (err == -EEXIST)
+                               err = 0;
+               }
+       }
+
+       AuTraceErr(err);
+       return err;
+}
+
+void au_hn_free(struct au_hinode *hinode)
+{
+       struct au_hnotify *hn;
+
+       hn = hinode->hi_notify;
+       if (hn) {
+               hinode->hi_notify = NULL;
+               if (au_hnotify_op.free(hinode, hn))
+                       au_cache_free_hnotify(hn);
+       }
+}
+
+/* ---------------------------------------------------------------------- */
+
+void au_hn_ctl(struct au_hinode *hinode, int do_set)
+{
+       if (hinode->hi_notify)
+               au_hnotify_op.ctl(hinode, do_set);
+}
+
+void au_hn_reset(struct inode *inode, unsigned int flags)
+{
+       aufs_bindex_t bindex, bbot;
+       struct inode *hi;
+       struct dentry *iwhdentry;
+
+       bbot = au_ibbot(inode);
+       for (bindex = au_ibtop(inode); bindex <= bbot; bindex++) {
+               hi = au_h_iptr(inode, bindex);
+               if (!hi)
+                       continue;
+
+               /* inode_lock_nested(hi, AuLsc_I_CHILD); */
+               iwhdentry = au_hi_wh(inode, bindex);
+               if (iwhdentry)
+                       dget(iwhdentry);
+               au_igrab(hi);
+               au_set_h_iptr(inode, bindex, NULL, 0);
+               au_set_h_iptr(inode, bindex, au_igrab(hi),
+                             flags & ~AuHi_XINO);
+               iput(hi);
+               dput(iwhdentry);
+               /* inode_unlock(hi); */
+       }
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int hn_xino(struct inode *inode, struct inode *h_inode)
+{
+       int err;
+       aufs_bindex_t bindex, bbot, bfound, btop;
+       struct inode *h_i;
+
+       err = 0;
+       if (unlikely(inode->i_ino == AUFS_ROOT_INO)) {
+               pr_warn("branch root dir was changed\n");
+               goto out;
+       }
+
+       bfound = -1;
+       bbot = au_ibbot(inode);
+       btop = au_ibtop(inode);
+#if 0 /* reserved for future use */
+       if (bindex == bbot) {
+               /* keep this ino in rename case */
+               goto out;
+       }
+#endif
+       for (bindex = btop; bindex <= bbot; bindex++)
+               if (au_h_iptr(inode, bindex) == h_inode) {
+                       bfound = bindex;
+                       break;
+               }
+       if (bfound < 0)
+               goto out;
+
+       for (bindex = btop; bindex <= bbot; bindex++) {
+               h_i = au_h_iptr(inode, bindex);
+               if (!h_i)
+                       continue;
+
+               err = au_xino_write(inode->i_sb, bindex, h_i->i_ino, /*ino*/0);
+               /* ignore this error */
+               /* bad action? */
+       }
+
+       /* children inode number will be broken */
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+static int hn_gen_tree(struct dentry *dentry)
+{
+       int err, i, j, ndentry;
+       struct au_dcsub_pages dpages;
+       struct au_dpage *dpage;
+       struct dentry **dentries;
+
+       err = au_dpages_init(&dpages, GFP_NOFS);
+       if (unlikely(err))
+               goto out;
+       err = au_dcsub_pages(&dpages, dentry, NULL, NULL);
+       if (unlikely(err))
+               goto out_dpages;
+
+       for (i = 0; i < dpages.ndpage; i++) {
+               dpage = dpages.dpages + i;
+               dentries = dpage->dentries;
+               ndentry = dpage->ndentry;
+               for (j = 0; j < ndentry; j++) {
+                       struct dentry *d;
+
+                       d = dentries[j];
+                       if (IS_ROOT(d))
+                               continue;
+
+                       au_digen_dec(d);
+                       if (d_really_is_positive(d))
+                               /* todo: reset children xino?
+                                  cached children only? */
+                               au_iigen_dec(d_inode(d));
+               }
+       }
+
+out_dpages:
+       au_dpages_free(&dpages);
+out:
+       return err;
+}
+
+/*
+ * return 0 if processed.
+ */
+static int hn_gen_by_inode(char *name, unsigned int nlen, struct inode *inode,
+                          const unsigned int isdir)
+{
+       int err;
+       struct dentry *d;
+       struct qstr *dname;
+
+       err = 1;
+       if (unlikely(inode->i_ino == AUFS_ROOT_INO)) {
+               pr_warn("branch root dir was changed\n");
+               err = 0;
+               goto out;
+       }
+
+       if (!isdir) {
+               AuDebugOn(!name);
+               au_iigen_dec(inode);
+               spin_lock(&inode->i_lock);
+               hlist_for_each_entry(d, &inode->i_dentry, d_u.d_alias) {
+                       spin_lock(&d->d_lock);
+                       dname = &d->d_name;
+                       if (dname->len != nlen
+                           && memcmp(dname->name, name, nlen)) {
+                               spin_unlock(&d->d_lock);
+                               continue;
+                       }
+                       err = 0;
+                       au_digen_dec(d);
+                       spin_unlock(&d->d_lock);
+                       break;
+               }
+               spin_unlock(&inode->i_lock);
+       } else {
+               au_fset_si(au_sbi(inode->i_sb), FAILED_REFRESH_DIR);
+               d = d_find_any_alias(inode);
+               if (!d) {
+                       au_iigen_dec(inode);
+                       goto out;
+               }
+
+               spin_lock(&d->d_lock);
+               dname = &d->d_name;
+               if (dname->len == nlen && !memcmp(dname->name, name, nlen)) {
+                       spin_unlock(&d->d_lock);
+                       err = hn_gen_tree(d);
+                       spin_lock(&d->d_lock);
+               }
+               spin_unlock(&d->d_lock);
+               dput(d);
+       }
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+static int hn_gen_by_name(struct dentry *dentry, const unsigned int isdir)
+{
+       int err;
+
+       if (IS_ROOT(dentry)) {
+               pr_warn("branch root dir was changed\n");
+               return 0;
+       }
+
+       err = 0;
+       if (!isdir) {
+               au_digen_dec(dentry);
+               if (d_really_is_positive(dentry))
+                       au_iigen_dec(d_inode(dentry));
+       } else {
+               au_fset_si(au_sbi(dentry->d_sb), FAILED_REFRESH_DIR);
+               if (d_really_is_positive(dentry))
+                       err = hn_gen_tree(dentry);
+       }
+
+       AuTraceErr(err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* hnotify job flags */
+#define AuHnJob_XINO0          1
+#define AuHnJob_GEN            (1 << 1)
+#define AuHnJob_DIRENT         (1 << 2)
+#define AuHnJob_ISDIR          (1 << 3)
+#define AuHnJob_TRYXINO0       (1 << 4)
+#define AuHnJob_MNTPNT         (1 << 5)
+#define au_ftest_hnjob(flags, name)    ((flags) & AuHnJob_##name)
+#define au_fset_hnjob(flags, name) \
+       do { (flags) |= AuHnJob_##name; } while (0)
+#define au_fclr_hnjob(flags, name) \
+       do { (flags) &= ~AuHnJob_##name; } while (0)
+
+enum {
+       AuHn_CHILD,
+       AuHn_PARENT,
+       AuHnLast
+};
+
+struct au_hnotify_args {
+       struct inode *h_dir, *dir, *h_child_inode;
+       u32 mask;
+       unsigned int flags[AuHnLast];
+       unsigned int h_child_nlen;
+       char h_child_name[];
+};
+
+struct hn_job_args {
+       unsigned int flags;
+       struct inode *inode, *h_inode, *dir, *h_dir;
+       struct dentry *dentry;
+       char *h_name;
+       int h_nlen;
+};
+
+static int hn_job(struct hn_job_args *a)
+{
+       const unsigned int isdir = au_ftest_hnjob(a->flags, ISDIR);
+       int e;
+
+       /* reset xino */
+       if (au_ftest_hnjob(a->flags, XINO0) && a->inode)
+               hn_xino(a->inode, a->h_inode); /* ignore this error */
+
+       if (au_ftest_hnjob(a->flags, TRYXINO0)
+           && a->inode
+           && a->h_inode) {
+               inode_lock_shared_nested(a->h_inode, AuLsc_I_CHILD);
+               if (!a->h_inode->i_nlink
+                   && !(a->h_inode->i_state & I_LINKABLE))
+                       hn_xino(a->inode, a->h_inode); /* ignore this error */
+               inode_unlock_shared(a->h_inode);
+       }
+
+       /* make the generation obsolete */
+       if (au_ftest_hnjob(a->flags, GEN)) {
+               e = -1;
+               if (a->inode)
+                       e = hn_gen_by_inode(a->h_name, a->h_nlen, a->inode,
+                                             isdir);
+               if (e && a->dentry)
+                       hn_gen_by_name(a->dentry, isdir);
+               /* ignore this error */
+       }
+
+       /* make dir entries obsolete */
+       if (au_ftest_hnjob(a->flags, DIRENT) && a->inode) {
+               struct au_vdir *vdir;
+
+               vdir = au_ivdir(a->inode);
+               if (vdir)
+                       vdir->vd_jiffy = 0;
+               /* IMustLock(a->inode); */
+               /* inode_inc_iversion(a->inode); */
+       }
+
+       /* can do nothing but warn */
+       if (au_ftest_hnjob(a->flags, MNTPNT)
+           && a->dentry
+           && d_mountpoint(a->dentry))
+               pr_warn("mount-point %pd is removed or renamed\n", a->dentry);
+
+       return 0;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static struct dentry *lookup_wlock_by_name(char *name, unsigned int nlen,
+                                          struct inode *dir)
+{
+       struct dentry *dentry, *d, *parent;
+       struct qstr *dname;
+
+       parent = d_find_any_alias(dir);
+       if (!parent)
+               return NULL;
+
+       dentry = NULL;
+       spin_lock(&parent->d_lock);
+       list_for_each_entry(d, &parent->d_subdirs, d_child) {
+               /* AuDbg("%pd\n", d); */
+               spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
+               dname = &d->d_name;
+               if (dname->len != nlen || memcmp(dname->name, name, nlen))
+                       goto cont_unlock;
+               if (au_di(d))
+                       au_digen_dec(d);
+               else
+                       goto cont_unlock;
+               if (au_dcount(d) > 0) {
+                       dentry = dget_dlock(d);
+                       spin_unlock(&d->d_lock);
+                       break;
+               }
+
+cont_unlock:
+               spin_unlock(&d->d_lock);
+       }
+       spin_unlock(&parent->d_lock);
+       dput(parent);
+
+       if (dentry)
+               di_write_lock_child(dentry);
+
+       return dentry;
+}
+
+static struct inode *lookup_wlock_by_ino(struct super_block *sb,
+                                        aufs_bindex_t bindex, ino_t h_ino)
+{
+       struct inode *inode;
+       ino_t ino;
+       int err;
+
+       inode = NULL;
+       err = au_xino_read(sb, bindex, h_ino, &ino);
+       if (!err && ino)
+               inode = ilookup(sb, ino);
+       if (!inode)
+               goto out;
+
+       if (unlikely(inode->i_ino == AUFS_ROOT_INO)) {
+               pr_warn("wrong root branch\n");
+               iput(inode);
+               inode = NULL;
+               goto out;
+       }
+
+       ii_write_lock_child(inode);
+
+out:
+       return inode;
+}
+
+static void au_hn_bh(void *_args)
+{
+       struct au_hnotify_args *a = _args;
+       struct super_block *sb;
+       aufs_bindex_t bindex, bbot, bfound;
+       unsigned char xino, try_iput;
+       int err;
+       struct inode *inode;
+       ino_t h_ino;
+       struct hn_job_args args;
+       struct dentry *dentry;
+       struct au_sbinfo *sbinfo;
+
+       AuDebugOn(!_args);
+       AuDebugOn(!a->h_dir);
+       AuDebugOn(!a->dir);
+       AuDebugOn(!a->mask);
+       AuDbg("mask 0x%x, i%lu, hi%lu, hci%lu\n",
+             a->mask, a->dir->i_ino, a->h_dir->i_ino,
+             a->h_child_inode ? a->h_child_inode->i_ino : 0);
+
+       inode = NULL;
+       dentry = NULL;
+       /*
+        * do not lock a->dir->i_mutex here
+        * because of d_revalidate() may cause a deadlock.
+        */
+       sb = a->dir->i_sb;
+       AuDebugOn(!sb);
+       sbinfo = au_sbi(sb);
+       AuDebugOn(!sbinfo);
+       si_write_lock(sb, AuLock_NOPLMW);
+
+       if (au_opt_test(sbinfo->si_mntflags, DIRREN))
+               switch (a->mask & FS_EVENTS_POSS_ON_CHILD) {
+               case FS_MOVED_FROM:
+               case FS_MOVED_TO:
+                       AuWarn1("DIRREN with UDBA may not work correctly "
+                               "for the direct rename(2)\n");
+               }
+
+       ii_read_lock_parent(a->dir);
+       bfound = -1;
+       bbot = au_ibbot(a->dir);
+       for (bindex = au_ibtop(a->dir); bindex <= bbot; bindex++)
+               if (au_h_iptr(a->dir, bindex) == a->h_dir) {
+                       bfound = bindex;
+                       break;
+               }
+       ii_read_unlock(a->dir);
+       if (unlikely(bfound < 0))
+               goto out;
+
+       xino = !!au_opt_test(au_mntflags(sb), XINO);
+       h_ino = 0;
+       if (a->h_child_inode)
+               h_ino = a->h_child_inode->i_ino;
+
+       if (a->h_child_nlen
+           && (au_ftest_hnjob(a->flags[AuHn_CHILD], GEN)
+               || au_ftest_hnjob(a->flags[AuHn_CHILD], MNTPNT)))
+               dentry = lookup_wlock_by_name(a->h_child_name, a->h_child_nlen,
+                                             a->dir);
+       try_iput = 0;
+       if (dentry && d_really_is_positive(dentry))
+               inode = d_inode(dentry);
+       if (xino && !inode && h_ino
+           && (au_ftest_hnjob(a->flags[AuHn_CHILD], XINO0)
+               || au_ftest_hnjob(a->flags[AuHn_CHILD], TRYXINO0)
+               || au_ftest_hnjob(a->flags[AuHn_CHILD], GEN))) {
+               inode = lookup_wlock_by_ino(sb, bfound, h_ino);
+               try_iput = 1;
+       }
+
+       args.flags = a->flags[AuHn_CHILD];
+       args.dentry = dentry;
+       args.inode = inode;
+       args.h_inode = a->h_child_inode;
+       args.dir = a->dir;
+       args.h_dir = a->h_dir;
+       args.h_name = a->h_child_name;
+       args.h_nlen = a->h_child_nlen;
+       err = hn_job(&args);
+       if (dentry) {
+               if (au_di(dentry))
+                       di_write_unlock(dentry);
+               dput(dentry);
+       }
+       if (inode && try_iput) {
+               ii_write_unlock(inode);
+               iput(inode);
+       }
+
+       ii_write_lock_parent(a->dir);
+       args.flags = a->flags[AuHn_PARENT];
+       args.dentry = NULL;
+       args.inode = a->dir;
+       args.h_inode = a->h_dir;
+       args.dir = NULL;
+       args.h_dir = NULL;
+       args.h_name = NULL;
+       args.h_nlen = 0;
+       err = hn_job(&args);
+       ii_write_unlock(a->dir);
+
+out:
+       iput(a->h_child_inode);
+       iput(a->h_dir);
+       iput(a->dir);
+       si_write_unlock(sb);
+       au_nwt_done(&sbinfo->si_nowait);
+       au_kfree_rcu(a);
+}
+
+/* ---------------------------------------------------------------------- */
+
+int au_hnotify(struct inode *h_dir, struct au_hnotify *hnotify, u32 mask,
+              const struct qstr *h_child_qstr, struct inode *h_child_inode)
+{
+       int err, len;
+       unsigned int flags[AuHnLast], f;
+       unsigned char isdir, isroot, wh;
+       struct inode *dir;
+       struct au_hnotify_args *args;
+       char *p, *h_child_name;
+
+       err = 0;
+       AuDebugOn(!hnotify || !hnotify->hn_aufs_inode);
+       dir = igrab(hnotify->hn_aufs_inode);
+       if (!dir)
+               goto out;
+
+       isroot = (dir->i_ino == AUFS_ROOT_INO);
+       wh = 0;
+       h_child_name = (void *)h_child_qstr->name;
+       len = h_child_qstr->len;
+       if (h_child_name) {
+               if (len > AUFS_WH_PFX_LEN
+                   && !memcmp(h_child_name, AUFS_WH_PFX, AUFS_WH_PFX_LEN)) {
+                       h_child_name += AUFS_WH_PFX_LEN;
+                       len -= AUFS_WH_PFX_LEN;
+                       wh = 1;
+               }
+       }
+
+       isdir = 0;
+       if (h_child_inode)
+               isdir = !!S_ISDIR(h_child_inode->i_mode);
+       flags[AuHn_PARENT] = AuHnJob_ISDIR;
+       flags[AuHn_CHILD] = 0;
+       if (isdir)
+               flags[AuHn_CHILD] = AuHnJob_ISDIR;
+       au_fset_hnjob(flags[AuHn_PARENT], DIRENT);
+       au_fset_hnjob(flags[AuHn_CHILD], GEN);
+       switch (mask & ALL_FSNOTIFY_DIRENT_EVENTS) {
+       case FS_MOVED_FROM:
+       case FS_MOVED_TO:
+               au_fset_hnjob(flags[AuHn_CHILD], XINO0);
+               au_fset_hnjob(flags[AuHn_CHILD], MNTPNT);
+               fallthrough;
+       case FS_CREATE:
+               AuDebugOn(!h_child_name);
+               break;
+
+       case FS_DELETE:
+               /*
+                * aufs never be able to get this child inode.
+                * revalidation should be in d_revalidate()
+                * by checking i_nlink, i_generation or d_unhashed().
+                */
+               AuDebugOn(!h_child_name);
+               au_fset_hnjob(flags[AuHn_CHILD], TRYXINO0);
+               au_fset_hnjob(flags[AuHn_CHILD], MNTPNT);
+               break;
+
+       default:
+               AuDebugOn(1);
+       }
+
+       if (wh)
+               h_child_inode = NULL;
+
+       err = -ENOMEM;
+       /* iput() and kfree() will be called in au_hnotify() */
+       args = kmalloc(sizeof(*args) + len + 1, GFP_NOFS);
+       if (unlikely(!args)) {
+               AuErr1("no memory\n");
+               iput(dir);
+               goto out;
+       }
+       args->flags[AuHn_PARENT] = flags[AuHn_PARENT];
+       args->flags[AuHn_CHILD] = flags[AuHn_CHILD];
+       args->mask = mask;
+       args->dir = dir;
+       args->h_dir = igrab(h_dir);
+       if (h_child_inode)
+               h_child_inode = igrab(h_child_inode); /* can be NULL */
+       args->h_child_inode = h_child_inode;
+       args->h_child_nlen = len;
+       if (len) {
+               p = (void *)args;
+               p += sizeof(*args);
+               memcpy(p, h_child_name, len);
+               p[len] = 0;
+       }
+
+       /* NFS fires the event for silly-renamed one from kworker */
+       f = 0;
+       if (!dir->i_nlink
+           || (au_test_nfs(h_dir->i_sb) && (mask & FS_DELETE)))
+               f = AuWkq_NEST;
+       err = au_wkq_nowait(au_hn_bh, args, dir->i_sb, f);
+       if (unlikely(err)) {
+               pr_err("wkq %d\n", err);
+               iput(args->h_child_inode);
+               iput(args->h_dir);
+               iput(args->dir);
+               au_kfree_rcu(args);
+       }
+
+out:
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+int au_hnotify_reset_br(unsigned int udba, struct au_branch *br, int perm)
+{
+       int err;
+
+       AuDebugOn(!(udba & AuOptMask_UDBA));
+
+       err = 0;
+       if (au_hnotify_op.reset_br)
+               err = au_hnotify_op.reset_br(udba, br, perm);
+
+       return err;
+}
+
+int au_hnotify_init_br(struct au_branch *br, int perm)
+{
+       int err;
+
+       err = 0;
+       if (au_hnotify_op.init_br)
+               err = au_hnotify_op.init_br(br, perm);
+
+       return err;
+}
+
+void au_hnotify_fin_br(struct au_branch *br)
+{
+       if (au_hnotify_op.fin_br)
+               au_hnotify_op.fin_br(br);
+}
+
+static void au_hn_destroy_cache(void)
+{
+       kmem_cache_destroy(au_cache[AuCache_HNOTIFY]);
+       au_cache[AuCache_HNOTIFY] = NULL;
+}
+
+int __init au_hnotify_init(void)
+{
+       int err;
+
+       err = -ENOMEM;
+       au_cache[AuCache_HNOTIFY] = AuCache(au_hnotify);
+       if (au_cache[AuCache_HNOTIFY]) {
+               err = 0;
+               if (au_hnotify_op.init)
+                       err = au_hnotify_op.init();
+               if (unlikely(err))
+                       au_hn_destroy_cache();
+       }
+       AuTraceErr(err);
+       return err;
+}
+
+void au_hnotify_fin(void)
+{
+       if (au_hnotify_op.fin)
+               au_hnotify_op.fin();
+
+       /* cf. au_cache_fin() */
+       if (au_cache[AuCache_HNOTIFY])
+               au_hn_destroy_cache();
+}
diff -urN /usr/share/empty/fs/aufs/iinfo.c linux/fs/aufs/iinfo.c
--- /usr/share/empty/fs/aufs/iinfo.c    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/iinfo.c       2021-12-03 15:38:59.936647310 +0100
@@ -0,0 +1,286 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * inode private data
+ */
+
+#include "aufs.h"
+
+struct inode *au_h_iptr(struct inode *inode, aufs_bindex_t bindex)
+{
+       struct inode *h_inode;
+       struct au_hinode *hinode;
+
+       IiMustAnyLock(inode);
+
+       hinode = au_hinode(au_ii(inode), bindex);
+       h_inode = hinode->hi_inode;
+       AuDebugOn(h_inode && atomic_read(&h_inode->i_count) <= 0);
+       return h_inode;
+}
+
+/* todo: hard/soft set? */
+void au_hiput(struct au_hinode *hinode)
+{
+       au_hn_free(hinode);
+       dput(hinode->hi_whdentry);
+       iput(hinode->hi_inode);
+}
+
+unsigned int au_hi_flags(struct inode *inode, int isdir)
+{
+       unsigned int flags;
+       const unsigned int mnt_flags = au_mntflags(inode->i_sb);
+
+       flags = 0;
+       if (au_opt_test(mnt_flags, XINO))
+               au_fset_hi(flags, XINO);
+       if (isdir && au_opt_test(mnt_flags, UDBA_HNOTIFY))
+               au_fset_hi(flags, HNOTIFY);
+       return flags;
+}
+
+void au_set_h_iptr(struct inode *inode, aufs_bindex_t bindex,
+                  struct inode *h_inode, unsigned int flags)
+{
+       struct au_hinode *hinode;
+       struct inode *hi;
+       struct au_iinfo *iinfo = au_ii(inode);
+
+       IiMustWriteLock(inode);
+
+       hinode = au_hinode(iinfo, bindex);
+       hi = hinode->hi_inode;
+       AuDebugOn(h_inode && atomic_read(&h_inode->i_count) <= 0);
+
+       if (hi)
+               au_hiput(hinode);
+       hinode->hi_inode = h_inode;
+       if (h_inode) {
+               int err;
+               struct super_block *sb = inode->i_sb;
+               struct au_branch *br;
+
+               AuDebugOn(inode->i_mode
+                         && (h_inode->i_mode & S_IFMT)
+                         != (inode->i_mode & S_IFMT));
+               if (bindex == iinfo->ii_btop)
+                       au_cpup_igen(inode, h_inode);
+               br = au_sbr(sb, bindex);
+               hinode->hi_id = br->br_id;
+               if (au_ftest_hi(flags, XINO)) {
+                       err = au_xino_write(sb, bindex, h_inode->i_ino,
+                                           inode->i_ino);
+                       if (unlikely(err))
+                               AuIOErr1("failed au_xino_write() %d\n", err);
+               }
+
+               if (au_ftest_hi(flags, HNOTIFY)
+                   && au_br_hnotifyable(br->br_perm)) {
+                       err = au_hn_alloc(hinode, inode);
+                       if (unlikely(err))
+                               AuIOErr1("au_hn_alloc() %d\n", err);
+               }
+       }
+}
+
+void au_set_hi_wh(struct inode *inode, aufs_bindex_t bindex,
+                 struct dentry *h_wh)
+{
+       struct au_hinode *hinode;
+
+       IiMustWriteLock(inode);
+
+       hinode = au_hinode(au_ii(inode), bindex);
+       AuDebugOn(hinode->hi_whdentry);
+       hinode->hi_whdentry = h_wh;
+}
+
+void au_update_iigen(struct inode *inode, int half)
+{
+       struct au_iinfo *iinfo;
+       struct au_iigen *iigen;
+       unsigned int sigen;
+
+       sigen = au_sigen(inode->i_sb);
+       iinfo = au_ii(inode);
+       iigen = &iinfo->ii_generation;
+       spin_lock(&iigen->ig_spin);
+       iigen->ig_generation = sigen;
+       if (half)
+               au_ig_fset(iigen->ig_flags, HALF_REFRESHED);
+       else
+               au_ig_fclr(iigen->ig_flags, HALF_REFRESHED);
+       spin_unlock(&iigen->ig_spin);
+}
+
+/* it may be called at remount time, too */
+void au_update_ibrange(struct inode *inode, int do_put_zero)
+{
+       struct au_iinfo *iinfo;
+       aufs_bindex_t bindex, bbot;
+
+       AuDebugOn(au_is_bad_inode(inode));
+       IiMustWriteLock(inode);
+
+       iinfo = au_ii(inode);
+       if (do_put_zero && iinfo->ii_btop >= 0) {
+               for (bindex = iinfo->ii_btop; bindex <= iinfo->ii_bbot;
+                    bindex++) {
+                       struct inode *h_i;
+
+                       h_i = au_hinode(iinfo, bindex)->hi_inode;
+                       if (h_i
+                           && !h_i->i_nlink
+                           && !(h_i->i_state & I_LINKABLE))
+                               au_set_h_iptr(inode, bindex, NULL, 0);
+               }
+       }
+
+       iinfo->ii_btop = -1;
+       iinfo->ii_bbot = -1;
+       bbot = au_sbbot(inode->i_sb);
+       for (bindex = 0; bindex <= bbot; bindex++)
+               if (au_hinode(iinfo, bindex)->hi_inode) {
+                       iinfo->ii_btop = bindex;
+                       break;
+               }
+       if (iinfo->ii_btop >= 0)
+               for (bindex = bbot; bindex >= iinfo->ii_btop; bindex--)
+                       if (au_hinode(iinfo, bindex)->hi_inode) {
+                               iinfo->ii_bbot = bindex;
+                               break;
+                       }
+       AuDebugOn(iinfo->ii_btop > iinfo->ii_bbot);
+}
+
+/* ---------------------------------------------------------------------- */
+
+void au_icntnr_init_once(void *_c)
+{
+       struct au_icntnr *c = _c;
+       struct au_iinfo *iinfo = &c->iinfo;
+
+       spin_lock_init(&iinfo->ii_generation.ig_spin);
+       au_rw_init(&iinfo->ii_rwsem);
+       inode_init_once(&c->vfs_inode);
+}
+
+void au_hinode_init(struct au_hinode *hinode)
+{
+       hinode->hi_inode = NULL;
+       hinode->hi_id = -1;
+       au_hn_init(hinode);
+       hinode->hi_whdentry = NULL;
+}
+
+int au_iinfo_init(struct inode *inode)
+{
+       struct au_iinfo *iinfo;
+       struct super_block *sb;
+       struct au_hinode *hi;
+       int nbr, i;
+
+       sb = inode->i_sb;
+       iinfo = &(container_of(inode, struct au_icntnr, vfs_inode)->iinfo);
+       nbr = au_sbbot(sb) + 1;
+       if (unlikely(nbr <= 0))
+               nbr = 1;
+       hi = kmalloc_array(nbr, sizeof(*iinfo->ii_hinode), GFP_NOFS);
+       if (hi) {
+               au_lcnt_inc(&au_sbi(sb)->si_ninodes);
+
+               iinfo->ii_hinode = hi;
+               for (i = 0; i < nbr; i++, hi++)
+                       au_hinode_init(hi);
+
+               iinfo->ii_generation.ig_generation = au_sigen(sb);
+               iinfo->ii_btop = -1;
+               iinfo->ii_bbot = -1;
+               iinfo->ii_vdir = NULL;
+               return 0;
+       }
+       return -ENOMEM;
+}
+
+int au_hinode_realloc(struct au_iinfo *iinfo, int nbr, int may_shrink)
+{
+       int err, i;
+       struct au_hinode *hip;
+
+       AuRwMustWriteLock(&iinfo->ii_rwsem);
+
+       err = -ENOMEM;
+       hip = au_krealloc(iinfo->ii_hinode, sizeof(*hip) * nbr, GFP_NOFS,
+                         may_shrink);
+       if (hip) {
+               iinfo->ii_hinode = hip;
+               i = iinfo->ii_bbot + 1;
+               hip += i;
+               for (; i < nbr; i++, hip++)
+                       au_hinode_init(hip);
+               err = 0;
+       }
+
+       return err;
+}
+
+void au_iinfo_fin(struct inode *inode)
+{
+       struct au_iinfo *iinfo;
+       struct au_hinode *hi;
+       struct super_block *sb;
+       aufs_bindex_t bindex, bbot;
+       const unsigned char unlinked = !inode->i_nlink;
+
+       AuDebugOn(au_is_bad_inode(inode));
+
+       sb = inode->i_sb;
+       au_lcnt_dec(&au_sbi(sb)->si_ninodes);
+       if (si_pid_test(sb))
+               au_xino_delete_inode(inode, unlinked);
+       else {
+               /*
+                * it is safe to hide the dependency between sbinfo and
+                * sb->s_umount.
+                */
+               lockdep_off();
+               si_noflush_read_lock(sb);
+               au_xino_delete_inode(inode, unlinked);
+               si_read_unlock(sb);
+               lockdep_on();
+       }
+
+       iinfo = au_ii(inode);
+       if (iinfo->ii_vdir)
+               au_vdir_free(iinfo->ii_vdir);
+
+       bindex = iinfo->ii_btop;
+       if (bindex >= 0) {
+               hi = au_hinode(iinfo, bindex);
+               bbot = iinfo->ii_bbot;
+               while (bindex++ <= bbot) {
+                       if (hi->hi_inode)
+                               au_hiput(hi);
+                       hi++;
+               }
+       }
+       au_kfree_rcu(iinfo->ii_hinode);
+       AuRwDestroy(&iinfo->ii_rwsem);
+}
diff -urN /usr/share/empty/fs/aufs/inode.c linux/fs/aufs/inode.c
--- /usr/share/empty/fs/aufs/inode.c    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/inode.c       2021-12-03 15:40:58.236647297 +0100
@@ -0,0 +1,531 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * inode functions
+ */
+
+#include <linux/iversion.h>
+#include "aufs.h"
+
+struct inode *au_igrab(struct inode *inode)
+{
+       if (inode) {
+               AuDebugOn(!atomic_read(&inode->i_count));
+               ihold(inode);
+       }
+       return inode;
+}
+
+static void au_refresh_hinode_attr(struct inode *inode, int do_version)
+{
+       au_cpup_attr_all(inode, /*force*/0);
+       au_update_iigen(inode, /*half*/1);
+       if (do_version)
+               inode_inc_iversion(inode);
+}
+
+static int au_ii_refresh(struct inode *inode, int *update)
+{
+       int err, e, nbr;
+       umode_t type;
+       aufs_bindex_t bindex, new_bindex;
+       struct super_block *sb;
+       struct au_iinfo *iinfo;
+       struct au_hinode *p, *q, tmp;
+
+       AuDebugOn(au_is_bad_inode(inode));
+       IiMustWriteLock(inode);
+
+       *update = 0;
+       sb = inode->i_sb;
+       nbr = au_sbbot(sb) + 1;
+       type = inode->i_mode & S_IFMT;
+       iinfo = au_ii(inode);
+       err = au_hinode_realloc(iinfo, nbr, /*may_shrink*/0);
+       if (unlikely(err))
+               goto out;
+
+       AuDebugOn(iinfo->ii_btop < 0);
+       p = au_hinode(iinfo, iinfo->ii_btop);
+       for (bindex = iinfo->ii_btop; bindex <= iinfo->ii_bbot;
+            bindex++, p++) {
+               if (!p->hi_inode)
+                       continue;
+
+               AuDebugOn(type != (p->hi_inode->i_mode & S_IFMT));
+               new_bindex = au_br_index(sb, p->hi_id);
+               if (new_bindex == bindex)
+                       continue;
+
+               if (new_bindex < 0) {
+                       *update = 1;
+                       au_hiput(p);
+                       p->hi_inode = NULL;
+                       continue;
+               }
+
+               if (new_bindex < iinfo->ii_btop)
+                       iinfo->ii_btop = new_bindex;
+               if (iinfo->ii_bbot < new_bindex)
+                       iinfo->ii_bbot = new_bindex;
+               /* swap two lower inode, and loop again */
+               q = au_hinode(iinfo, new_bindex);
+               tmp = *q;
+               *q = *p;
+               *p = tmp;
+               if (tmp.hi_inode) {
+                       bindex--;
+                       p--;
+               }
+       }
+       au_update_ibrange(inode, /*do_put_zero*/0);
+       au_hinode_realloc(iinfo, nbr, /*may_shrink*/1); /* harmless if err */
+       e = au_dy_irefresh(inode);
+       if (unlikely(e && !err))
+               err = e;
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+void au_refresh_iop(struct inode *inode, int force_getattr)
+{
+       int type;
+       struct au_sbinfo *sbi = au_sbi(inode->i_sb);
+       const struct inode_operations *iop
+               = force_getattr ? aufs_iop : sbi->si_iop_array;
+
+       if (inode->i_op == iop)
+               return;
+
+       switch (inode->i_mode & S_IFMT) {
+       case S_IFDIR:
+               type = AuIop_DIR;
+               break;
+       case S_IFLNK:
+               type = AuIop_SYMLINK;
+               break;
+       default:
+               type = AuIop_OTHER;
+               break;
+       }
+
+       inode->i_op = iop + type;
+       /* unnecessary smp_wmb() */
+}
+
+int au_refresh_hinode_self(struct inode *inode)
+{
+       int err, update;
+
+       err = au_ii_refresh(inode, &update);
+       if (!err)
+               au_refresh_hinode_attr(inode, update && S_ISDIR(inode->i_mode));
+
+       AuTraceErr(err);
+       return err;
+}
+
+int au_refresh_hinode(struct inode *inode, struct dentry *dentry)
+{
+       int err, e, update;
+       unsigned int flags;
+       umode_t mode;
+       aufs_bindex_t bindex, bbot;
+       unsigned char isdir;
+       struct au_hinode *p;
+       struct au_iinfo *iinfo;
+
+       err = au_ii_refresh(inode, &update);
+       if (unlikely(err))
+               goto out;
+
+       update = 0;
+       iinfo = au_ii(inode);
+       p = au_hinode(iinfo, iinfo->ii_btop);
+       mode = (inode->i_mode & S_IFMT);
+       isdir = S_ISDIR(mode);
+       flags = au_hi_flags(inode, isdir);
+       bbot = au_dbbot(dentry);
+       for (bindex = au_dbtop(dentry); bindex <= bbot; bindex++) {
+               struct inode *h_i, *h_inode;
+               struct dentry *h_d;
+
+               h_d = au_h_dptr(dentry, bindex);
+               if (!h_d || d_is_negative(h_d))
+                       continue;
+
+               h_inode = d_inode(h_d);
+               AuDebugOn(mode != (h_inode->i_mode & S_IFMT));
+               if (iinfo->ii_btop <= bindex && bindex <= iinfo->ii_bbot) {
+                       h_i = au_h_iptr(inode, bindex);
+                       if (h_i) {
+                               if (h_i == h_inode)
+                                       continue;
+                               err = -EIO;
+                               break;
+                       }
+               }
+               if (bindex < iinfo->ii_btop)
+                       iinfo->ii_btop = bindex;
+               if (iinfo->ii_bbot < bindex)
+                       iinfo->ii_bbot = bindex;
+               au_set_h_iptr(inode, bindex, au_igrab(h_inode), flags);
+               update = 1;
+       }
+       au_update_ibrange(inode, /*do_put_zero*/0);
+       e = au_dy_irefresh(inode);
+       if (unlikely(e && !err))
+               err = e;
+       if (!err)
+               au_refresh_hinode_attr(inode, update && isdir);
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+static int set_inode(struct inode *inode, struct dentry *dentry)
+{
+       int err;
+       unsigned int flags;
+       umode_t mode;
+       aufs_bindex_t bindex, btop, btail;
+       unsigned char isdir;
+       struct dentry *h_dentry;
+       struct inode *h_inode;
+       struct au_iinfo *iinfo;
+       const struct inode_operations *iop;
+
+       IiMustWriteLock(inode);
+
+       err = 0;
+       isdir = 0;
+       iop = au_sbi(inode->i_sb)->si_iop_array;
+       btop = au_dbtop(dentry);
+       h_dentry = au_h_dptr(dentry, btop);
+       h_inode = d_inode(h_dentry);
+       mode = h_inode->i_mode;
+       switch (mode & S_IFMT) {
+       case S_IFREG:
+               btail = au_dbtail(dentry);
+               inode->i_op = iop + AuIop_OTHER;
+               inode->i_fop = &aufs_file_fop;
+               err = au_dy_iaop(inode, btop, h_inode);
+               if (unlikely(err))
+                       goto out;
+               break;
+       case S_IFDIR:
+               isdir = 1;
+               btail = au_dbtaildir(dentry);
+               inode->i_op = iop + AuIop_DIR;
+               inode->i_fop = &aufs_dir_fop;
+               break;
+       case S_IFLNK:
+               btail = au_dbtail(dentry);
+               inode->i_op = iop + AuIop_SYMLINK;
+               break;
+       case S_IFBLK:
+       case S_IFCHR:
+       case S_IFIFO:
+       case S_IFSOCK:
+               btail = au_dbtail(dentry);
+               inode->i_op = iop + AuIop_OTHER;
+               init_special_inode(inode, mode, h_inode->i_rdev);
+               break;
+       default:
+               AuIOErr("Unknown file type 0%o\n", mode);
+               err = -EIO;
+               goto out;
+       }
+
+       /* do not set hnotify for whiteouted dirs (SHWH mode) */
+       flags = au_hi_flags(inode, isdir);
+       if (au_opt_test(au_mntflags(dentry->d_sb), SHWH)
+           && au_ftest_hi(flags, HNOTIFY)
+           && dentry->d_name.len > AUFS_WH_PFX_LEN
+           && !memcmp(dentry->d_name.name, AUFS_WH_PFX, AUFS_WH_PFX_LEN))
+               au_fclr_hi(flags, HNOTIFY);
+       iinfo = au_ii(inode);
+       iinfo->ii_btop = btop;
+       iinfo->ii_bbot = btail;
+       for (bindex = btop; bindex <= btail; bindex++) {
+               h_dentry = au_h_dptr(dentry, bindex);
+               if (h_dentry)
+                       au_set_h_iptr(inode, bindex,
+                                     au_igrab(d_inode(h_dentry)), flags);
+       }
+       au_cpup_attr_all(inode, /*force*/1);
+       /*
+        * to force calling aufs_get_acl() every time,
+        * do not call cache_no_acl() for aufs inode.
+        */
+
+out:
+       return err;
+}
+
+/*
+ * successful returns with iinfo write_locked
+ * minus: errno
+ * zero: success, matched
+ * plus: no error, but unmatched
+ */
+static int reval_inode(struct inode *inode, struct dentry *dentry)
+{
+       int err;
+       unsigned int gen, igflags;
+       aufs_bindex_t bindex, bbot;
+       struct inode *h_inode, *h_dinode;
+       struct dentry *h_dentry;
+
+       /*
+        * before this function, if aufs got any iinfo lock, it must be only
+        * one, the parent dir.
+        * it can happen by UDBA and the obsoleted inode number.
+        */
+       err = -EIO;
+       if (unlikely(inode->i_ino == parent_ino(dentry)))
+               goto out;
+
+       err = 1;
+       ii_write_lock_new_child(inode);
+       h_dentry = au_h_dptr(dentry, au_dbtop(dentry));
+       h_dinode = d_inode(h_dentry);
+       bbot = au_ibbot(inode);
+       for (bindex = au_ibtop(inode); bindex <= bbot; bindex++) {
+               h_inode = au_h_iptr(inode, bindex);
+               if (!h_inode || h_inode != h_dinode)
+                       continue;
+
+               err = 0;
+               gen = au_iigen(inode, &igflags);
+               if (gen == au_digen(dentry)
+                   && !au_ig_ftest(igflags, HALF_REFRESHED))
+                       break;
+
+               /* fully refresh inode using dentry */
+               err = au_refresh_hinode(inode, dentry);
+               if (!err)
+                       au_update_iigen(inode, /*half*/0);
+               break;
+       }
+
+       if (unlikely(err))
+               ii_write_unlock(inode);
+out:
+       return err;
+}
+
+int au_ino(struct super_block *sb, aufs_bindex_t bindex, ino_t h_ino,
+          unsigned int d_type, ino_t *ino)
+{
+       int err, idx;
+       const int isnondir = d_type != DT_DIR;
+
+       /* prevent hardlinked inode number from race condition */
+       if (isnondir) {
+               err = au_xinondir_enter(sb, bindex, h_ino, &idx);
+               if (unlikely(err))
+                       goto out;
+       }
+
+       err = au_xino_read(sb, bindex, h_ino, ino);
+       if (unlikely(err))
+               goto out_xinondir;
+
+       if (!*ino) {
+               err = -EIO;
+               *ino = au_xino_new_ino(sb);
+               if (unlikely(!*ino))
+                       goto out_xinondir;
+               err = au_xino_write(sb, bindex, h_ino, *ino);
+               if (unlikely(err))
+                       goto out_xinondir;
+       }
+
+out_xinondir:
+       if (isnondir && idx >= 0)
+               au_xinondir_leave(sb, bindex, h_ino, idx);
+out:
+       return err;
+}
+
+/* successful returns with iinfo write_locked */
+/* todo: return with unlocked? */
+struct inode *au_new_inode(struct dentry *dentry, int must_new)
+{
+       struct inode *inode, *h_inode;
+       struct dentry *h_dentry;
+       struct super_block *sb;
+       ino_t h_ino, ino;
+       int err, idx, hlinked;
+       aufs_bindex_t btop;
+
+       sb = dentry->d_sb;
+       btop = au_dbtop(dentry);
+       h_dentry = au_h_dptr(dentry, btop);
+       h_inode = d_inode(h_dentry);
+       h_ino = h_inode->i_ino;
+       hlinked = !d_is_dir(h_dentry) && h_inode->i_nlink > 1;
+
+new_ino:
+       /*
+        * stop 'race'-ing between hardlinks under different
+        * parents.
+        */
+       if (hlinked) {
+               err = au_xinondir_enter(sb, btop, h_ino, &idx);
+               inode = ERR_PTR(err);
+               if (unlikely(err))
+                       goto out;
+       }
+
+       err = au_xino_read(sb, btop, h_ino, &ino);
+       inode = ERR_PTR(err);
+       if (unlikely(err))
+               goto out_xinondir;
+
+       if (!ino) {
+               ino = au_xino_new_ino(sb);
+               if (unlikely(!ino)) {
+                       inode = ERR_PTR(-EIO);
+                       goto out_xinondir;
+               }
+       }
+
+       AuDbg("i%lu\n", (unsigned long)ino);
+       inode = au_iget_locked(sb, ino);
+       err = PTR_ERR(inode);
+       if (IS_ERR(inode))
+               goto out_xinondir;
+
+       AuDbg("%lx, new %d\n", inode->i_state, !!(inode->i_state & I_NEW));
+       if (inode->i_state & I_NEW) {
+               ii_write_lock_new_child(inode);
+               err = set_inode(inode, dentry);
+               if (!err) {
+                       unlock_new_inode(inode);
+                       goto out_xinondir; /* success */
+               }
+
+               /*
+                * iget_failed() calls iput(), but we need to call
+                * ii_write_unlock() after iget_failed(). so dirty hack for
+                * i_count.
+                */
+               atomic_inc(&inode->i_count);
+               iget_failed(inode);
+               ii_write_unlock(inode);
+               au_xino_write(sb, btop, h_ino, /*ino*/0);
+               /* ignore this error */
+               goto out_iput;
+       } else if (!must_new && !IS_DEADDIR(inode) && inode->i_nlink) {
+               /*
+                * horrible race condition between lookup, readdir and copyup
+                * (or something).
+                */
+               if (hlinked && idx >= 0)
+                       au_xinondir_leave(sb, btop, h_ino, idx);
+               err = reval_inode(inode, dentry);
+               if (unlikely(err < 0)) {
+                       hlinked = 0;
+                       goto out_iput;
+               }
+               if (!err)
+                       goto out; /* success */
+               else if (hlinked && idx >= 0) {
+                       err = au_xinondir_enter(sb, btop, h_ino, &idx);
+                       if (unlikely(err)) {
+                               iput(inode);
+                               inode = ERR_PTR(err);
+                               goto out;
+                       }
+               }
+       }
+
+       if (unlikely(au_test_fs_unique_ino(h_inode)))
+               AuWarn1("Warning: Un-notified UDBA or repeatedly renamed dir,"
+                       " b%d, %s, %pd, hi%lu, i%lu.\n",
+                       btop, au_sbtype(h_dentry->d_sb), dentry,
+                       (unsigned long)h_ino, (unsigned long)ino);
+       ino = 0;
+       err = au_xino_write(sb, btop, h_ino, /*ino*/0);
+       if (!err) {
+               iput(inode);
+               if (hlinked && idx >= 0)
+                       au_xinondir_leave(sb, btop, h_ino, idx);
+               goto new_ino;
+       }
+
+out_iput:
+       iput(inode);
+       inode = ERR_PTR(err);
+out_xinondir:
+       if (hlinked && idx >= 0)
+               au_xinondir_leave(sb, btop, h_ino, idx);
+out:
+       return inode;
+}
+
+/* ---------------------------------------------------------------------- */
+
+int au_test_ro(struct super_block *sb, aufs_bindex_t bindex,
+              struct inode *inode)
+{
+       int err;
+       struct inode *hi;
+
+       err = au_br_rdonly(au_sbr(sb, bindex));
+
+       /* pseudo-link after flushed may happen out of bounds */
+       if (!err
+           && inode
+           && au_ibtop(inode) <= bindex
+           && bindex <= au_ibbot(inode)) {
+               /*
+                * permission check is unnecessary since vfsub routine
+                * will be called later
+                */
+               hi = au_h_iptr(inode, bindex);
+               if (hi)
+                       err = IS_IMMUTABLE(hi) ? -EROFS : 0;
+       }
+
+       return err;
+}
+
+int au_test_h_perm(struct user_namespace *h_userns, struct inode *h_inode,
+                  int mask)
+{
+       if (uid_eq(current_fsuid(), GLOBAL_ROOT_UID))
+               return 0;
+       return inode_permission(h_userns, h_inode, mask);
+}
+
+int au_test_h_perm_sio(struct user_namespace *h_userns, struct inode *h_inode,
+                      int mask)
+{
+       if (au_test_nfs(h_inode->i_sb)
+           && (mask & MAY_WRITE)
+           && S_ISDIR(h_inode->i_mode))
+               mask |= MAY_READ; /* force permission check */
+       return au_test_h_perm(h_userns, h_inode, mask);
+}
diff -urN /usr/share/empty/fs/aufs/inode.h linux/fs/aufs/inode.h
--- /usr/share/empty/fs/aufs/inode.h    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/inode.h       2021-12-03 15:40:58.236647297 +0100
@@ -0,0 +1,705 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * inode operations
+ */
+
+#ifndef __AUFS_INODE_H__
+#define __AUFS_INODE_H__
+
+#ifdef __KERNEL__
+
+#include <linux/fsnotify.h>
+#include "rwsem.h"
+
+struct vfsmount;
+
+struct au_hnotify {
+#ifdef CONFIG_AUFS_HNOTIFY
+#ifdef CONFIG_AUFS_HFSNOTIFY
+       /* never use fsnotify_add_vfsmount_mark() */
+       struct fsnotify_mark            hn_mark;
+#endif
+       struct inode            *hn_aufs_inode; /* no get/put */
+       struct rcu_head         rcu;
+#endif
+} ____cacheline_aligned_in_smp;
+
+struct au_hinode {
+       struct inode            *hi_inode;
+       aufs_bindex_t           hi_id;
+#ifdef CONFIG_AUFS_HNOTIFY
+       struct au_hnotify       *hi_notify;
+#endif
+
+       /* reference to the copied-up whiteout with get/put */
+       struct dentry           *hi_whdentry;
+};
+
+/* ig_flags */
+#define AuIG_HALF_REFRESHED            1
+#define au_ig_ftest(flags, name)       ((flags) & AuIG_##name)
+#define au_ig_fset(flags, name) \
+       do { (flags) |= AuIG_##name; } while (0)
+#define au_ig_fclr(flags, name) \
+       do { (flags) &= ~AuIG_##name; } while (0)
+
+struct au_iigen {
+       spinlock_t      ig_spin;
+       __u32           ig_generation, ig_flags;
+};
+
+struct au_vdir;
+struct au_iinfo {
+       struct au_iigen         ii_generation;
+       struct super_block      *ii_hsb1;       /* no get/put */
+
+       struct au_rwsem         ii_rwsem;
+       aufs_bindex_t           ii_btop, ii_bbot;
+       __u32                   ii_higen;
+       struct au_hinode        *ii_hinode;
+       struct au_vdir          *ii_vdir;
+};
+
+struct au_icntnr {
+       struct au_iinfo         iinfo;
+       struct inode            vfs_inode;
+       struct hlist_bl_node    plink;
+       struct rcu_head         rcu;
+} ____cacheline_aligned_in_smp;
+
+/* au_pin flags */
+#define AuPin_DI_LOCKED                1
+#define AuPin_MNT_WRITE                (1 << 1)
+#define au_ftest_pin(flags, name)      ((flags) & AuPin_##name)
+#define au_fset_pin(flags, name) \
+       do { (flags) |= AuPin_##name; } while (0)
+#define au_fclr_pin(flags, name) \
+       do { (flags) &= ~AuPin_##name; } while (0)
+
+struct au_pin {
+       /* input */
+       struct dentry *dentry;
+       unsigned int udba;
+       unsigned char lsc_di, lsc_hi, flags;
+       aufs_bindex_t bindex;
+
+       /* output */
+       struct dentry *parent;
+       struct au_hinode *hdir;
+       struct vfsmount *h_mnt;
+
+       /* temporary unlock/relock for copyup */
+       struct dentry *h_dentry, *h_parent;
+       struct au_branch *br;
+       struct task_struct *task;
+};
+
+void au_pin_hdir_unlock(struct au_pin *p);
+int au_pin_hdir_lock(struct au_pin *p);
+int au_pin_hdir_relock(struct au_pin *p);
+void au_pin_hdir_acquire_nest(struct au_pin *p);
+void au_pin_hdir_release(struct au_pin *p);
+
+/* ---------------------------------------------------------------------- */
+
+static inline struct au_iinfo *au_ii(struct inode *inode)
+{
+       BUG_ON(is_bad_inode(inode));
+       return &(container_of(inode, struct au_icntnr, vfs_inode)->iinfo);
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* inode.c */
+struct inode *au_igrab(struct inode *inode);
+void au_refresh_iop(struct inode *inode, int force_getattr);
+int au_refresh_hinode_self(struct inode *inode);
+int au_refresh_hinode(struct inode *inode, struct dentry *dentry);
+int au_ino(struct super_block *sb, aufs_bindex_t bindex, ino_t h_ino,
+          unsigned int d_type, ino_t *ino);
+struct inode *au_new_inode(struct dentry *dentry, int must_new);
+int au_test_ro(struct super_block *sb, aufs_bindex_t bindex,
+              struct inode *inode);
+int au_test_h_perm(struct user_namespace *h_userns, struct inode *h_inode,
+                  int mask);
+int au_test_h_perm_sio(struct user_namespace *h_userns, struct inode *h_inode,
+                      int mask);
+
+static inline int au_wh_ino(struct super_block *sb, aufs_bindex_t bindex,
+                           ino_t h_ino, unsigned int d_type, ino_t *ino)
+{
+#ifdef CONFIG_AUFS_SHWH
+       return au_ino(sb, bindex, h_ino, d_type, ino);
+#else
+       return 0;
+#endif
+}
+
+/* i_op.c */
+enum {
+       AuIop_SYMLINK,
+       AuIop_DIR,
+       AuIop_OTHER,
+       AuIop_Last
+};
+extern struct inode_operations aufs_iop[AuIop_Last], /* not const */
+       aufs_iop_nogetattr[AuIop_Last];
+
+/* au_wr_dir flags */
+#define AuWrDir_ADD_ENTRY      1
+#define AuWrDir_ISDIR          (1 << 1)
+#define AuWrDir_TMPFILE                (1 << 2)
+#define au_ftest_wrdir(flags, name)    ((flags) & AuWrDir_##name)
+#define au_fset_wrdir(flags, name) \
+       do { (flags) |= AuWrDir_##name; } while (0)
+#define au_fclr_wrdir(flags, name) \
+       do { (flags) &= ~AuWrDir_##name; } while (0)
+
+struct au_wr_dir_args {
+       aufs_bindex_t force_btgt;
+       unsigned char flags;
+};
+int au_wr_dir(struct dentry *dentry, struct dentry *src_dentry,
+             struct au_wr_dir_args *args);
+
+struct dentry *au_pinned_h_parent(struct au_pin *pin);
+void au_pin_init(struct au_pin *pin, struct dentry *dentry,
+                aufs_bindex_t bindex, int lsc_di, int lsc_hi,
+                unsigned int udba, unsigned char flags);
+int au_pin(struct au_pin *pin, struct dentry *dentry, aufs_bindex_t bindex,
+          unsigned int udba, unsigned char flags) __must_check;
+int au_do_pin(struct au_pin *pin) __must_check;
+void au_unpin(struct au_pin *pin);
+int au_reval_for_attr(struct dentry *dentry, unsigned int sigen);
+
+#define AuIcpup_DID_CPUP       1
+#define au_ftest_icpup(flags, name)    ((flags) & AuIcpup_##name)
+#define au_fset_icpup(flags, name) \
+       do { (flags) |= AuIcpup_##name; } while (0)
+#define au_fclr_icpup(flags, name) \
+       do { (flags) &= ~AuIcpup_##name; } while (0)
+
+struct au_icpup_args {
+       unsigned char flags;
+       unsigned char pin_flags;
+       aufs_bindex_t btgt;
+       unsigned int udba;
+       struct au_pin pin;
+       struct path h_path;
+       struct inode *h_inode;
+};
+
+int au_pin_and_icpup(struct dentry *dentry, struct iattr *ia,
+                    struct au_icpup_args *a);
+
+int au_h_path_getattr(struct dentry *dentry, struct inode *inode, int force,
+                     struct path *h_path, int locked);
+
+/* i_op_add.c */
+int au_may_add(struct dentry *dentry, aufs_bindex_t bindex,
+              struct dentry *h_parent, int isdir);
+int aufs_mknod(struct user_namespace *userns, struct inode *dir,
+              struct dentry *dentry, umode_t mode, dev_t dev);
+int aufs_symlink(struct user_namespace *userns, struct inode *dir,
+                struct dentry *dentry, const char *symname);
+int aufs_create(struct user_namespace *userns, struct inode *dir,
+               struct dentry *dentry, umode_t mode, bool want_excl);
+struct vfsub_aopen_args;
+int au_aopen_or_create(struct inode *dir, struct dentry *dentry,
+                      struct vfsub_aopen_args *args);
+int aufs_tmpfile(struct user_namespace *userns, struct inode *dir,
+                struct dentry *dentry, umode_t mode);
+int aufs_link(struct dentry *src_dentry, struct inode *dir,
+             struct dentry *dentry);
+int aufs_mkdir(struct user_namespace *userns, struct inode *dir,
+              struct dentry *dentry, umode_t mode);
+
+/* i_op_del.c */
+int au_wr_dir_need_wh(struct dentry *dentry, int isdir, aufs_bindex_t *bcpup);
+int au_may_del(struct dentry *dentry, aufs_bindex_t bindex,
+              struct dentry *h_parent, int isdir);
+int aufs_unlink(struct inode *dir, struct dentry *dentry);
+int aufs_rmdir(struct inode *dir, struct dentry *dentry);
+
+/* i_op_ren.c */
+int au_wbr(struct dentry *dentry, aufs_bindex_t btgt);
+int aufs_rename(struct user_namespace *userns,
+               struct inode *_src_dir, struct dentry *_src_dentry,
+               struct inode *_dst_dir, struct dentry *_dst_dentry,
+               unsigned int _flags);
+
+/* iinfo.c */
+struct inode *au_h_iptr(struct inode *inode, aufs_bindex_t bindex);
+void au_hiput(struct au_hinode *hinode);
+void au_set_hi_wh(struct inode *inode, aufs_bindex_t bindex,
+                 struct dentry *h_wh);
+unsigned int au_hi_flags(struct inode *inode, int isdir);
+
+/* hinode flags */
+#define AuHi_XINO      1
+#define AuHi_HNOTIFY   (1 << 1)
+#define au_ftest_hi(flags, name)       ((flags) & AuHi_##name)
+#define au_fset_hi(flags, name) \
+       do { (flags) |= AuHi_##name; } while (0)
+#define au_fclr_hi(flags, name) \
+       do { (flags) &= ~AuHi_##name; } while (0)
+
+#ifndef CONFIG_AUFS_HNOTIFY
+#undef AuHi_HNOTIFY
+#define AuHi_HNOTIFY   0
+#endif
+
+void au_set_h_iptr(struct inode *inode, aufs_bindex_t bindex,
+                  struct inode *h_inode, unsigned int flags);
+
+void au_update_iigen(struct inode *inode, int half);
+void au_update_ibrange(struct inode *inode, int do_put_zero);
+
+void au_icntnr_init_once(void *_c);
+void au_hinode_init(struct au_hinode *hinode);
+int au_iinfo_init(struct inode *inode);
+void au_iinfo_fin(struct inode *inode);
+int au_hinode_realloc(struct au_iinfo *iinfo, int nbr, int may_shrink);
+
+#ifdef CONFIG_PROC_FS
+/* plink.c */
+int au_plink_maint(struct super_block *sb, int flags);
+struct au_sbinfo;
+void au_plink_maint_leave(struct au_sbinfo *sbinfo);
+int au_plink_maint_enter(struct super_block *sb);
+#ifdef CONFIG_AUFS_DEBUG
+void au_plink_list(struct super_block *sb);
+#else
+AuStubVoid(au_plink_list, struct super_block *sb)
+#endif
+int au_plink_test(struct inode *inode);
+struct dentry *au_plink_lkup(struct inode *inode, aufs_bindex_t bindex);
+void au_plink_append(struct inode *inode, aufs_bindex_t bindex,
+                    struct dentry *h_dentry);
+void au_plink_put(struct super_block *sb, int verbose);
+void au_plink_clean(struct super_block *sb, int verbose);
+void au_plink_half_refresh(struct super_block *sb, aufs_bindex_t br_id);
+#else
+AuStubInt0(au_plink_maint, struct super_block *sb, int flags);
+AuStubVoid(au_plink_maint_leave, struct au_sbinfo *sbinfo);
+AuStubInt0(au_plink_maint_enter, struct super_block *sb);
+AuStubVoid(au_plink_list, struct super_block *sb);
+AuStubInt0(au_plink_test, struct inode *inode);
+AuStub(struct dentry *, au_plink_lkup, return NULL,
+       struct inode *inode, aufs_bindex_t bindex);
+AuStubVoid(au_plink_append, struct inode *inode, aufs_bindex_t bindex,
+          struct dentry *h_dentry);
+AuStubVoid(au_plink_put, struct super_block *sb, int verbose);
+AuStubVoid(au_plink_clean, struct super_block *sb, int verbose);
+AuStubVoid(au_plink_half_refresh, struct super_block *sb, aufs_bindex_t br_id);
+#endif /* CONFIG_PROC_FS */
+
+#ifdef CONFIG_AUFS_XATTR
+/* xattr.c */
+int au_cpup_xattr(struct path *h_dst, struct path *h_src, int ignore_flags,
+                 unsigned int verbose);
+ssize_t aufs_listxattr(struct dentry *dentry, char *list, size_t size);
+void au_xattr_init(struct super_block *sb);
+#else
+AuStubInt0(au_cpup_xattr, struct path *h_dst, struct path *h_src,
+          int ignore_flags, unsigned int verbose);
+AuStubVoid(au_xattr_init, struct super_block *sb);
+#endif
+
+#ifdef CONFIG_FS_POSIX_ACL
+struct posix_acl *aufs_get_acl(struct inode *inode, int type, bool rcu);
+int aufs_set_acl(struct user_namespace *userns, struct inode *inode,
+                struct posix_acl *acl, int type);
+#endif
+
+#if IS_ENABLED(CONFIG_AUFS_XATTR) || IS_ENABLED(CONFIG_FS_POSIX_ACL)
+enum {
+       AU_XATTR_SET,
+       AU_ACL_SET
+};
+
+struct au_sxattr {
+       int type;
+       union {
+               struct {
+                       const char      *name;
+                       const void      *value;
+                       size_t          size;
+                       int             flags;
+               } set;
+               struct {
+                       struct posix_acl *acl;
+                       int             type;
+               } acl_set;
+       } u;
+};
+ssize_t au_sxattr(struct dentry *dentry, struct inode *inode,
+                 struct au_sxattr *arg);
+#endif
+
+/* ---------------------------------------------------------------------- */
+
+/* lock subclass for iinfo */
+enum {
+       AuLsc_II_CHILD,         /* child first */
+       AuLsc_II_CHILD2,        /* rename(2), link(2), and cpup at hnotify */
+       AuLsc_II_CHILD3,        /* copyup dirs */
+       AuLsc_II_PARENT,        /* see AuLsc_I_PARENT in vfsub.h */
+       AuLsc_II_PARENT2,
+       AuLsc_II_PARENT3,       /* copyup dirs */
+       AuLsc_II_NEW_CHILD
+};
+
+/*
+ * ii_read_lock_child, ii_write_lock_child,
+ * ii_read_lock_child2, ii_write_lock_child2,
+ * ii_read_lock_child3, ii_write_lock_child3,
+ * ii_read_lock_parent, ii_write_lock_parent,
+ * ii_read_lock_parent2, ii_write_lock_parent2,
+ * ii_read_lock_parent3, ii_write_lock_parent3,
+ * ii_read_lock_new_child, ii_write_lock_new_child,
+ */
+#define AuReadLockFunc(name, lsc) \
+static inline void ii_read_lock_##name(struct inode *i) \
+{ \
+       au_rw_read_lock_nested(&au_ii(i)->ii_rwsem, AuLsc_II_##lsc); \
+}
+
+#define AuWriteLockFunc(name, lsc) \
+static inline void ii_write_lock_##name(struct inode *i) \
+{ \
+       au_rw_write_lock_nested(&au_ii(i)->ii_rwsem, AuLsc_II_##lsc); \
+}
+
+#define AuRWLockFuncs(name, lsc) \
+       AuReadLockFunc(name, lsc) \
+       AuWriteLockFunc(name, lsc)
+
+AuRWLockFuncs(child, CHILD);
+AuRWLockFuncs(child2, CHILD2);
+AuRWLockFuncs(child3, CHILD3);
+AuRWLockFuncs(parent, PARENT);
+AuRWLockFuncs(parent2, PARENT2);
+AuRWLockFuncs(parent3, PARENT3);
+AuRWLockFuncs(new_child, NEW_CHILD);
+
+#undef AuReadLockFunc
+#undef AuWriteLockFunc
+#undef AuRWLockFuncs
+
+#define ii_read_unlock(i)      au_rw_read_unlock(&au_ii(i)->ii_rwsem)
+#define ii_write_unlock(i)     au_rw_write_unlock(&au_ii(i)->ii_rwsem)
+#define ii_downgrade_lock(i)   au_rw_dgrade_lock(&au_ii(i)->ii_rwsem)
+
+#define IiMustNoWaiters(i)     AuRwMustNoWaiters(&au_ii(i)->ii_rwsem)
+#define IiMustAnyLock(i)       AuRwMustAnyLock(&au_ii(i)->ii_rwsem)
+#define IiMustWriteLock(i)     AuRwMustWriteLock(&au_ii(i)->ii_rwsem)
+
+/* ---------------------------------------------------------------------- */
+
+static inline void au_icntnr_init(struct au_icntnr *c)
+{
+#ifdef CONFIG_AUFS_DEBUG
+       c->vfs_inode.i_mode = 0;
+#endif
+}
+
+static inline unsigned int au_iigen(struct inode *inode, unsigned int *igflags)
+{
+       unsigned int gen;
+       struct au_iinfo *iinfo;
+       struct au_iigen *iigen;
+
+       iinfo = au_ii(inode);
+       iigen = &iinfo->ii_generation;
+       spin_lock(&iigen->ig_spin);
+       if (igflags)
+               *igflags = iigen->ig_flags;
+       gen = iigen->ig_generation;
+       spin_unlock(&iigen->ig_spin);
+
+       return gen;
+}
+
+/* tiny test for inode number */
+/* tmpfs generation is too rough */
+static inline int au_test_higen(struct inode *inode, struct inode *h_inode)
+{
+       struct au_iinfo *iinfo;
+
+       iinfo = au_ii(inode);
+       AuRwMustAnyLock(&iinfo->ii_rwsem);
+       return !(iinfo->ii_hsb1 == h_inode->i_sb
+                && iinfo->ii_higen == h_inode->i_generation);
+}
+
+static inline void au_iigen_dec(struct inode *inode)
+{
+       struct au_iinfo *iinfo;
+       struct au_iigen *iigen;
+
+       iinfo = au_ii(inode);
+       iigen = &iinfo->ii_generation;
+       spin_lock(&iigen->ig_spin);
+       iigen->ig_generation--;
+       spin_unlock(&iigen->ig_spin);
+}
+
+static inline int au_iigen_test(struct inode *inode, unsigned int sigen)
+{
+       int err;
+
+       err = 0;
+       if (unlikely(inode && au_iigen(inode, NULL) != sigen))
+               err = -EIO;
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static inline struct au_hinode *au_hinode(struct au_iinfo *iinfo,
+                                         aufs_bindex_t bindex)
+{
+       return iinfo->ii_hinode + bindex;
+}
+
+static inline int au_is_bad_inode(struct inode *inode)
+{
+       return !!(is_bad_inode(inode) || !au_hinode(au_ii(inode), 0));
+}
+
+static inline aufs_bindex_t au_ii_br_id(struct inode *inode,
+                                       aufs_bindex_t bindex)
+{
+       IiMustAnyLock(inode);
+       return au_hinode(au_ii(inode), bindex)->hi_id;
+}
+
+static inline aufs_bindex_t au_ibtop(struct inode *inode)
+{
+       IiMustAnyLock(inode);
+       return au_ii(inode)->ii_btop;
+}
+
+static inline aufs_bindex_t au_ibbot(struct inode *inode)
+{
+       IiMustAnyLock(inode);
+       return au_ii(inode)->ii_bbot;
+}
+
+static inline struct au_vdir *au_ivdir(struct inode *inode)
+{
+       IiMustAnyLock(inode);
+       return au_ii(inode)->ii_vdir;
+}
+
+static inline struct dentry *au_hi_wh(struct inode *inode, aufs_bindex_t bindex)
+{
+       IiMustAnyLock(inode);
+       return au_hinode(au_ii(inode), bindex)->hi_whdentry;
+}
+
+static inline void au_set_ibtop(struct inode *inode, aufs_bindex_t bindex)
+{
+       IiMustWriteLock(inode);
+       au_ii(inode)->ii_btop = bindex;
+}
+
+static inline void au_set_ibbot(struct inode *inode, aufs_bindex_t bindex)
+{
+       IiMustWriteLock(inode);
+       au_ii(inode)->ii_bbot = bindex;
+}
+
+static inline void au_set_ivdir(struct inode *inode, struct au_vdir *vdir)
+{
+       IiMustWriteLock(inode);
+       au_ii(inode)->ii_vdir = vdir;
+}
+
+static inline struct au_hinode *au_hi(struct inode *inode, aufs_bindex_t bindex)
+{
+       IiMustAnyLock(inode);
+       return au_hinode(au_ii(inode), bindex);
+}
+
+/* ---------------------------------------------------------------------- */
+
+static inline struct dentry *au_pinned_parent(struct au_pin *pin)
+{
+       if (pin)
+               return pin->parent;
+       return NULL;
+}
+
+static inline struct inode *au_pinned_h_dir(struct au_pin *pin)
+{
+       if (pin && pin->hdir)
+               return pin->hdir->hi_inode;
+       return NULL;
+}
+
+static inline struct au_hinode *au_pinned_hdir(struct au_pin *pin)
+{
+       if (pin)
+               return pin->hdir;
+       return NULL;
+}
+
+static inline void au_pin_set_dentry(struct au_pin *pin, struct dentry *dentry)
+{
+       if (pin)
+               pin->dentry = dentry;
+}
+
+static inline void au_pin_set_parent_lflag(struct au_pin *pin,
+                                          unsigned char lflag)
+{
+       if (pin) {
+               if (lflag)
+                       au_fset_pin(pin->flags, DI_LOCKED);
+               else
+                       au_fclr_pin(pin->flags, DI_LOCKED);
+       }
+}
+
+#if 0 /* reserved */
+static inline void au_pin_set_parent(struct au_pin *pin, struct dentry *parent)
+{
+       if (pin) {
+               dput(pin->parent);
+               pin->parent = dget(parent);
+       }
+}
+#endif
+
+/* ---------------------------------------------------------------------- */
+
+struct au_branch;
+#ifdef CONFIG_AUFS_HNOTIFY
+struct au_hnotify_op {
+       void (*ctl)(struct au_hinode *hinode, int do_set);
+       int (*alloc)(struct au_hinode *hinode);
+
+       /*
+        * if it returns true, the caller should free hinode->hi_notify,
+        * otherwise ->free() frees it.
+        */
+       int (*free)(struct au_hinode *hinode,
+                   struct au_hnotify *hn) __must_check;
+
+       void (*fin)(void);
+       int (*init)(void);
+
+       int (*reset_br)(unsigned int udba, struct au_branch *br, int perm);
+       void (*fin_br)(struct au_branch *br);
+       int (*init_br)(struct au_branch *br, int perm);
+};
+
+/* hnotify.c */
+int au_hn_alloc(struct au_hinode *hinode, struct inode *inode);
+void au_hn_free(struct au_hinode *hinode);
+void au_hn_ctl(struct au_hinode *hinode, int do_set);
+void au_hn_reset(struct inode *inode, unsigned int flags);
+int au_hnotify(struct inode *h_dir, struct au_hnotify *hnotify, u32 mask,
+              const struct qstr *h_child_qstr, struct inode *h_child_inode);
+int au_hnotify_reset_br(unsigned int udba, struct au_branch *br, int perm);
+int au_hnotify_init_br(struct au_branch *br, int perm);
+void au_hnotify_fin_br(struct au_branch *br);
+int __init au_hnotify_init(void);
+void au_hnotify_fin(void);
+
+/* hfsnotify.c */
+extern const struct au_hnotify_op au_hnotify_op;
+
+static inline
+void au_hn_init(struct au_hinode *hinode)
+{
+       hinode->hi_notify = NULL;
+}
+
+static inline struct au_hnotify *au_hn(struct au_hinode *hinode)
+{
+       return hinode->hi_notify;
+}
+
+#else
+AuStub(int, au_hn_alloc, return -EOPNOTSUPP,
+       struct au_hinode *hinode __maybe_unused,
+       struct inode *inode __maybe_unused)
+AuStub(struct au_hnotify *, au_hn, return NULL, struct au_hinode *hinode)
+AuStubVoid(au_hn_free, struct au_hinode *hinode __maybe_unused)
+AuStubVoid(au_hn_ctl, struct au_hinode *hinode __maybe_unused,
+          int do_set __maybe_unused)
+AuStubVoid(au_hn_reset, struct inode *inode __maybe_unused,
+          unsigned int flags __maybe_unused)
+AuStubInt0(au_hnotify_reset_br, unsigned int udba __maybe_unused,
+          struct au_branch *br __maybe_unused,
+          int perm __maybe_unused)
+AuStubInt0(au_hnotify_init_br, struct au_branch *br __maybe_unused,
+          int perm __maybe_unused)
+AuStubVoid(au_hnotify_fin_br, struct au_branch *br __maybe_unused)
+AuStubInt0(__init au_hnotify_init, void)
+AuStubVoid(au_hnotify_fin, void)
+AuStubVoid(au_hn_init, struct au_hinode *hinode __maybe_unused)
+#endif /* CONFIG_AUFS_HNOTIFY */
+
+static inline void au_hn_suspend(struct au_hinode *hdir)
+{
+       au_hn_ctl(hdir, /*do_set*/0);
+}
+
+static inline void au_hn_resume(struct au_hinode *hdir)
+{
+       au_hn_ctl(hdir, /*do_set*/1);
+}
+
+static inline void au_hn_inode_lock(struct au_hinode *hdir)
+{
+       inode_lock(hdir->hi_inode);
+       au_hn_suspend(hdir);
+}
+
+static inline void au_hn_inode_lock_nested(struct au_hinode *hdir,
+                                         unsigned int sc __maybe_unused)
+{
+       inode_lock_nested(hdir->hi_inode, sc);
+       au_hn_suspend(hdir);
+}
+
+#if 0 /* unused */
+#include "vfsub.h"
+static inline void au_hn_inode_lock_shared_nested(struct au_hinode *hdir,
+                                                 unsigned int sc)
+{
+       inode_lock_shared_nested(hdir->hi_inode, sc);
+       au_hn_suspend(hdir);
+}
+#endif
+
+static inline void au_hn_inode_unlock(struct au_hinode *hdir)
+{
+       au_hn_resume(hdir);
+       inode_unlock(hdir->hi_inode);
+}
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_INODE_H__ */
diff -urN /usr/share/empty/fs/aufs/ioctl.c linux/fs/aufs/ioctl.c
--- /usr/share/empty/fs/aufs/ioctl.c    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/ioctl.c       2021-12-03 15:38:59.936647310 +0100
@@ -0,0 +1,220 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * ioctl
+ * plink-management and readdir in userspace.
+ * assist the pathconf(3) wrapper library.
+ * move-down
+ * File-based Hierarchical Storage Management.
+ */
+
+#include <linux/compat.h>
+#include <linux/file.h>
+#include "aufs.h"
+
+static int au_wbr_fd(struct path *path, struct aufs_wbr_fd __user *arg)
+{
+       int err, fd;
+       aufs_bindex_t wbi, bindex, bbot;
+       struct file *h_file;
+       struct super_block *sb;
+       struct dentry *root;
+       struct au_branch *br;
+       struct aufs_wbr_fd wbrfd = {
+               .oflags = au_dir_roflags,
+               .brid   = -1
+       };
+       const int valid = O_RDONLY | O_NONBLOCK | O_LARGEFILE | O_DIRECTORY
+               | O_NOATIME | O_CLOEXEC;
+
+       AuDebugOn(wbrfd.oflags & ~valid);
+
+       if (arg) {
+               err = copy_from_user(&wbrfd, arg, sizeof(wbrfd));
+               if (unlikely(err)) {
+                       err = -EFAULT;
+                       goto out;
+               }
+
+               err = -EINVAL;
+               AuDbg("wbrfd{0%o, %d}\n", wbrfd.oflags, wbrfd.brid);
+               wbrfd.oflags |= au_dir_roflags;
+               AuDbg("0%o\n", wbrfd.oflags);
+               if (unlikely(wbrfd.oflags & ~valid))
+                       goto out;
+       }
+
+       fd = get_unused_fd_flags(0);
+       err = fd;
+       if (unlikely(fd < 0))
+               goto out;
+
+       h_file = ERR_PTR(-EINVAL);
+       wbi = 0;
+       br = NULL;
+       sb = path->dentry->d_sb;
+       root = sb->s_root;
+       aufs_read_lock(root, AuLock_IR);
+       bbot = au_sbbot(sb);
+       if (wbrfd.brid >= 0) {
+               wbi = au_br_index(sb, wbrfd.brid);
+               if (unlikely(wbi < 0 || wbi > bbot))
+                       goto out_unlock;
+       }
+
+       h_file = ERR_PTR(-ENOENT);
+       br = au_sbr(sb, wbi);
+       if (!au_br_writable(br->br_perm)) {
+               if (arg)
+                       goto out_unlock;
+
+               bindex = wbi + 1;
+               wbi = -1;
+               for (; bindex <= bbot; bindex++) {
+                       br = au_sbr(sb, bindex);
+                       if (au_br_writable(br->br_perm)) {
+                               wbi = bindex;
+                               br = au_sbr(sb, wbi);
+                               break;
+                       }
+               }
+       }
+       AuDbg("wbi %d\n", wbi);
+       if (wbi >= 0)
+               h_file = au_h_open(root, wbi, wbrfd.oflags, NULL,
+                                  /*force_wr*/0);
+
+out_unlock:
+       aufs_read_unlock(root, AuLock_IR);
+       err = PTR_ERR(h_file);
+       if (IS_ERR(h_file))
+               goto out_fd;
+
+       au_lcnt_dec(&br->br_nfiles); /* cf. au_h_open() */
+       fd_install(fd, h_file);
+       err = fd;
+       goto out; /* success */
+
+out_fd:
+       put_unused_fd(fd);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+long aufs_ioctl_dir(struct file *file, unsigned int cmd, unsigned long arg)
+{
+       long err;
+       struct dentry *dentry;
+
+       switch (cmd) {
+       case AUFS_CTL_RDU:
+       case AUFS_CTL_RDU_INO:
+               err = au_rdu_ioctl(file, cmd, arg);
+               break;
+
+       case AUFS_CTL_WBR_FD:
+               err = au_wbr_fd(&file->f_path, (void __user *)arg);
+               break;
+
+       case AUFS_CTL_IBUSY:
+               err = au_ibusy_ioctl(file, arg);
+               break;
+
+       case AUFS_CTL_BRINFO:
+               err = au_brinfo_ioctl(file, arg);
+               break;
+
+       case AUFS_CTL_FHSM_FD:
+               dentry = file->f_path.dentry;
+               if (IS_ROOT(dentry))
+                       err = au_fhsm_fd(dentry->d_sb, arg);
+               else
+                       err = -ENOTTY;
+               break;
+
+       default:
+               /* do not call the lower */
+               AuDbg("0x%x\n", cmd);
+               err = -ENOTTY;
+       }
+
+       AuTraceErr(err);
+       return err;
+}
+
+long aufs_ioctl_nondir(struct file *file, unsigned int cmd, unsigned long arg)
+{
+       long err;
+
+       switch (cmd) {
+       case AUFS_CTL_MVDOWN:
+               err = au_mvdown(file->f_path.dentry, (void __user *)arg);
+               break;
+
+       case AUFS_CTL_WBR_FD:
+               err = au_wbr_fd(&file->f_path, (void __user *)arg);
+               break;
+
+       default:
+               /* do not call the lower */
+               AuDbg("0x%x\n", cmd);
+               err = -ENOTTY;
+       }
+
+       AuTraceErr(err);
+       return err;
+}
+
+#ifdef CONFIG_COMPAT
+long aufs_compat_ioctl_dir(struct file *file, unsigned int cmd,
+                          unsigned long arg)
+{
+       long err;
+
+       switch (cmd) {
+       case AUFS_CTL_RDU:
+       case AUFS_CTL_RDU_INO:
+               err = au_rdu_compat_ioctl(file, cmd, arg);
+               break;
+
+       case AUFS_CTL_IBUSY:
+               err = au_ibusy_compat_ioctl(file, arg);
+               break;
+
+       case AUFS_CTL_BRINFO:
+               err = au_brinfo_compat_ioctl(file, arg);
+               break;
+
+       default:
+               err = aufs_ioctl_dir(file, cmd, arg);
+       }
+
+       AuTraceErr(err);
+       return err;
+}
+
+long aufs_compat_ioctl_nondir(struct file *file, unsigned int cmd,
+                             unsigned long arg)
+{
+       return aufs_ioctl_nondir(file, cmd, (unsigned long)compat_ptr(arg));
+}
+#endif
diff -urN /usr/share/empty/fs/aufs/i_op_add.c linux/fs/aufs/i_op_add.c
--- /usr/share/empty/fs/aufs/i_op_add.c 1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/i_op_add.c    2021-12-03 15:40:58.236647297 +0100
@@ -0,0 +1,941 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * inode operations (add entry)
+ */
+
+#include <linux/iversion.h>
+#include "aufs.h"
+
+/*
+ * final procedure of adding a new entry, except link(2).
+ * remove whiteout, instantiate, copyup the parent dir's times and size
+ * and update version.
+ * if it failed, re-create the removed whiteout.
+ */
+static int epilog(struct inode *dir, aufs_bindex_t bindex,
+                 struct dentry *wh_dentry, struct dentry *dentry)
+{
+       int err, rerr;
+       aufs_bindex_t bwh;
+       struct path h_path;
+       struct super_block *sb;
+       struct inode *inode, *h_dir;
+       struct dentry *wh;
+
+       bwh = -1;
+       sb = dir->i_sb;
+       if (wh_dentry) {
+               h_dir = d_inode(wh_dentry->d_parent); /* dir inode is locked */
+               IMustLock(h_dir);
+               AuDebugOn(au_h_iptr(dir, bindex) != h_dir);
+               bwh = au_dbwh(dentry);
+               h_path.dentry = wh_dentry;
+               h_path.mnt = au_sbr_mnt(sb, bindex);
+               err = au_wh_unlink_dentry(au_h_iptr(dir, bindex), &h_path,
+                                         dentry);
+               if (unlikely(err))
+                       goto out;
+       }
+
+       inode = au_new_inode(dentry, /*must_new*/1);
+       if (!IS_ERR(inode)) {
+               d_instantiate(dentry, inode);
+               dir = d_inode(dentry->d_parent); /* dir inode is locked */
+               IMustLock(dir);
+               au_dir_ts(dir, bindex);
+               inode_inc_iversion(dir);
+               au_fhsm_wrote(sb, bindex, /*force*/0);
+               return 0; /* success */
+       }
+
+       err = PTR_ERR(inode);
+       if (!wh_dentry)
+               goto out;
+
+       /* revert */
+       /* dir inode is locked */
+       wh = au_wh_create(dentry, bwh, wh_dentry->d_parent);
+       rerr = PTR_ERR(wh);
+       if (IS_ERR(wh)) {
+               AuIOErr("%pd reverting whiteout failed(%d, %d)\n",
+                       dentry, err, rerr);
+               err = -EIO;
+       } else
+               dput(wh);
+
+out:
+       return err;
+}
+
+static int au_d_may_add(struct dentry *dentry)
+{
+       int err;
+
+       err = 0;
+       if (unlikely(d_unhashed(dentry)))
+               err = -ENOENT;
+       if (unlikely(d_really_is_positive(dentry)))
+               err = -EEXIST;
+       return err;
+}
+
+/*
+ * simple tests for the adding inode operations.
+ * following the checks in vfs, plus the parent-child relationship.
+ */
+int au_may_add(struct dentry *dentry, aufs_bindex_t bindex,
+              struct dentry *h_parent, int isdir)
+{
+       int err;
+       umode_t h_mode;
+       struct dentry *h_dentry;
+       struct inode *h_inode;
+
+       err = -ENAMETOOLONG;
+       if (unlikely(dentry->d_name.len > AUFS_MAX_NAMELEN))
+               goto out;
+
+       h_dentry = au_h_dptr(dentry, bindex);
+       if (d_really_is_negative(dentry)) {
+               err = -EEXIST;
+               if (unlikely(d_is_positive(h_dentry)))
+                       goto out;
+       } else {
+               /* rename(2) case */
+               err = -EIO;
+               if (unlikely(d_is_negative(h_dentry)))
+                       goto out;
+               h_inode = d_inode(h_dentry);
+               if (unlikely(!h_inode->i_nlink))
+                       goto out;
+
+               h_mode = h_inode->i_mode;
+               if (!isdir) {
+                       err = -EISDIR;
+                       if (unlikely(S_ISDIR(h_mode)))
+                               goto out;
+               } else if (unlikely(!S_ISDIR(h_mode))) {
+                       err = -ENOTDIR;
+                       goto out;
+               }
+       }
+
+       err = 0;
+       /* expected parent dir is locked */
+       if (unlikely(h_parent != h_dentry->d_parent))
+               err = -EIO;
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/*
+ * initial procedure of adding a new entry.
+ * prepare writable branch and the parent dir, lock it,
+ * and lookup whiteout for the new entry.
+ */
+static struct dentry*
+lock_hdir_lkup_wh(struct dentry *dentry, struct au_dtime *dt,
+                 struct dentry *src_dentry, struct au_pin *pin,
+                 struct au_wr_dir_args *wr_dir_args)
+{
+       struct dentry *wh_dentry, *h_parent;
+       struct super_block *sb;
+       struct au_branch *br;
+       int err;
+       unsigned int udba;
+       aufs_bindex_t bcpup;
+
+       AuDbg("%pd\n", dentry);
+
+       err = au_wr_dir(dentry, src_dentry, wr_dir_args);
+       bcpup = err;
+       wh_dentry = ERR_PTR(err);
+       if (unlikely(err < 0))
+               goto out;
+
+       sb = dentry->d_sb;
+       udba = au_opt_udba(sb);
+       err = au_pin(pin, dentry, bcpup, udba,
+                    AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+       wh_dentry = ERR_PTR(err);
+       if (unlikely(err))
+               goto out;
+
+       h_parent = au_pinned_h_parent(pin);
+       if (udba != AuOpt_UDBA_NONE
+           && au_dbtop(dentry) == bcpup)
+               err = au_may_add(dentry, bcpup, h_parent,
+                                au_ftest_wrdir(wr_dir_args->flags, ISDIR));
+       else if (unlikely(dentry->d_name.len > AUFS_MAX_NAMELEN))
+               err = -ENAMETOOLONG;
+       wh_dentry = ERR_PTR(err);
+       if (unlikely(err))
+               goto out_unpin;
+
+       br = au_sbr(sb, bcpup);
+       if (dt) {
+               struct path tmp = {
+                       .dentry = h_parent,
+                       .mnt    = au_br_mnt(br)
+               };
+               au_dtime_store(dt, au_pinned_parent(pin), &tmp);
+       }
+
+       wh_dentry = NULL;
+       if (bcpup != au_dbwh(dentry))
+               goto out; /* success */
+
+       /*
+        * ENAMETOOLONG here means that if we allowed create such name, then it
+        * would not be able to removed in the future. So we don't allow such
+        * name here and we don't handle ENAMETOOLONG differently here.
+        */
+       wh_dentry = au_wh_lkup(h_parent, &dentry->d_name, br);
+
+out_unpin:
+       if (IS_ERR(wh_dentry))
+               au_unpin(pin);
+out:
+       return wh_dentry;
+}
+
+/* ---------------------------------------------------------------------- */
+
+enum { Mknod, Symlink, Creat };
+struct simple_arg {
+       int type;
+       union {
+               struct {
+                       umode_t                 mode;
+                       bool                    want_excl;
+                       bool                    try_aopen;
+                       struct vfsub_aopen_args *aopen;
+               } c;
+               struct {
+                       const char *symname;
+               } s;
+               struct {
+                       umode_t mode;
+                       dev_t dev;
+               } m;
+       } u;
+};
+
+static int add_simple(struct inode *dir, struct dentry *dentry,
+                     struct simple_arg *arg)
+{
+       int err, rerr;
+       aufs_bindex_t btop;
+       unsigned char created;
+       const unsigned char try_aopen
+               = (arg->type == Creat && arg->u.c.try_aopen);
+       struct vfsub_aopen_args *aopen = arg->u.c.aopen;
+       struct dentry *wh_dentry, *parent;
+       struct inode *h_dir;
+       struct super_block *sb;
+       struct au_branch *br;
+       /* to reduce stack size */
+       struct {
+               struct au_dtime dt;
+               struct au_pin pin;
+               struct path h_path;
+               struct au_wr_dir_args wr_dir_args;
+       } *a;
+
+       AuDbg("%pd\n", dentry);
+       IMustLock(dir);
+
+       err = -ENOMEM;
+       a = kmalloc(sizeof(*a), GFP_NOFS);
+       if (unlikely(!a))
+               goto out;
+       a->wr_dir_args.force_btgt = -1;
+       a->wr_dir_args.flags = AuWrDir_ADD_ENTRY;
+
+       parent = dentry->d_parent; /* dir inode is locked */
+       if (!try_aopen) {
+               err = aufs_read_lock(dentry, AuLock_DW | AuLock_GEN);
+               if (unlikely(err))
+                       goto out_free;
+       }
+       err = au_d_may_add(dentry);
+       if (unlikely(err))
+               goto out_unlock;
+       if (!try_aopen)
+               di_write_lock_parent(parent);
+       wh_dentry = lock_hdir_lkup_wh(dentry, &a->dt, /*src_dentry*/NULL,
+                                     &a->pin, &a->wr_dir_args);
+       err = PTR_ERR(wh_dentry);
+       if (IS_ERR(wh_dentry))
+               goto out_parent;
+
+       btop = au_dbtop(dentry);
+       sb = dentry->d_sb;
+       br = au_sbr(sb, btop);
+       a->h_path.dentry = au_h_dptr(dentry, btop);
+       a->h_path.mnt = au_br_mnt(br);
+       h_dir = au_pinned_h_dir(&a->pin);
+       switch (arg->type) {
+       case Creat:
+               if (!try_aopen || !h_dir->i_op->atomic_open) {
+                       err = vfsub_create(h_dir, &a->h_path, arg->u.c.mode,
+                                          arg->u.c.want_excl);
+                       created = !err;
+                       if (!err && try_aopen)
+                               aopen->file->f_mode |= FMODE_CREATED;
+               } else {
+                       aopen->br = br;
+                       err = vfsub_atomic_open(h_dir, a->h_path.dentry, aopen);
+                       AuDbg("err %d\n", err);
+                       AuDbgFile(aopen->file);
+                       created = err >= 0
+                               && !!(aopen->file->f_mode & FMODE_CREATED);
+               }
+               break;
+       case Symlink:
+               err = vfsub_symlink(h_dir, &a->h_path, arg->u.s.symname);
+               created = !err;
+               break;
+       case Mknod:
+               err = vfsub_mknod(h_dir, &a->h_path, arg->u.m.mode,
+                                 arg->u.m.dev);
+               created = !err;
+               break;
+       default:
+               BUG();
+       }
+       if (unlikely(err < 0))
+               goto out_unpin;
+
+       err = epilog(dir, btop, wh_dentry, dentry);
+       if (!err)
+               goto out_unpin; /* success */
+
+       /* revert */
+       if (created /* && d_is_positive(a->h_path.dentry) */) {
+               /* no delegation since it is just created */
+               rerr = vfsub_unlink(h_dir, &a->h_path, /*delegated*/NULL,
+                                   /*force*/0);
+               if (rerr) {
+                       AuIOErr("%pd revert failure(%d, %d)\n",
+                               dentry, err, rerr);
+                       err = -EIO;
+               }
+               au_dtime_revert(&a->dt);
+       }
+       if (try_aopen && h_dir->i_op->atomic_open
+           && (aopen->file->f_mode & FMODE_OPENED))
+               /* aopen->file is still opened */
+               au_lcnt_dec(&aopen->br->br_nfiles);
+
+out_unpin:
+       au_unpin(&a->pin);
+       dput(wh_dentry);
+out_parent:
+       if (!try_aopen)
+               di_write_unlock(parent);
+out_unlock:
+       if (unlikely(err)) {
+               au_update_dbtop(dentry);
+               d_drop(dentry);
+       }
+       if (!try_aopen)
+               aufs_read_unlock(dentry, AuLock_DW);
+out_free:
+       au_kfree_rcu(a);
+out:
+       return err;
+}
+
+int aufs_mknod(struct user_namespace *userns, struct inode *dir,
+              struct dentry *dentry, umode_t mode, dev_t dev)
+{
+       struct simple_arg arg = {
+               .type = Mknod,
+               .u.m = {
+                       .mode   = mode,
+                       .dev    = dev
+               }
+       };
+       return add_simple(dir, dentry, &arg);
+}
+
+int aufs_symlink(struct user_namespace *userns, struct inode *dir,
+                struct dentry *dentry, const char *symname)
+{
+       struct simple_arg arg = {
+               .type = Symlink,
+               .u.s.symname = symname
+       };
+       return add_simple(dir, dentry, &arg);
+}
+
+int aufs_create(struct user_namespace *userns, struct inode *dir,
+               struct dentry *dentry, umode_t mode, bool want_excl)
+{
+       struct simple_arg arg = {
+               .type = Creat,
+               .u.c = {
+                       .mode           = mode,
+                       .want_excl      = want_excl
+               }
+       };
+       return add_simple(dir, dentry, &arg);
+}
+
+int au_aopen_or_create(struct inode *dir, struct dentry *dentry,
+                      struct vfsub_aopen_args *aopen_args)
+{
+       struct simple_arg arg = {
+               .type = Creat,
+               .u.c = {
+                       .mode           = aopen_args->create_mode,
+                       .want_excl      = aopen_args->open_flag & O_EXCL,
+                       .try_aopen      = true,
+                       .aopen          = aopen_args
+               }
+       };
+       return add_simple(dir, dentry, &arg);
+}
+
+int aufs_tmpfile(struct user_namespace *userns, struct inode *dir,
+                struct dentry *dentry, umode_t mode)
+{
+       int err;
+       aufs_bindex_t bindex;
+       struct super_block *sb;
+       struct dentry *parent, *h_parent, *h_dentry;
+       struct inode *h_dir, *inode;
+       struct vfsmount *h_mnt;
+       struct user_namespace *h_userns;
+       struct au_wr_dir_args wr_dir_args = {
+               .force_btgt     = -1,
+               .flags          = AuWrDir_TMPFILE
+       };
+
+       /* copy-up may happen */
+       inode_lock(dir);
+
+       sb = dir->i_sb;
+       err = si_read_lock(sb, AuLock_FLUSH | AuLock_NOPLM);
+       if (unlikely(err))
+               goto out;
+
+       err = au_di_init(dentry);
+       if (unlikely(err))
+               goto out_si;
+
+       err = -EBUSY;
+       parent = d_find_any_alias(dir);
+       AuDebugOn(!parent);
+       di_write_lock_parent(parent);
+       if (unlikely(d_inode(parent) != dir))
+               goto out_parent;
+
+       err = au_digen_test(parent, au_sigen(sb));
+       if (unlikely(err))
+               goto out_parent;
+
+       bindex = au_dbtop(parent);
+       au_set_dbtop(dentry, bindex);
+       au_set_dbbot(dentry, bindex);
+       err = au_wr_dir(dentry, /*src_dentry*/NULL, &wr_dir_args);
+       bindex = err;
+       if (unlikely(err < 0))
+               goto out_parent;
+
+       err = -EOPNOTSUPP;
+       h_dir = au_h_iptr(dir, bindex);
+       if (unlikely(!h_dir->i_op->tmpfile))
+               goto out_parent;
+
+       h_mnt = au_sbr_mnt(sb, bindex);
+       err = vfsub_mnt_want_write(h_mnt);
+       if (unlikely(err))
+               goto out_parent;
+
+       h_userns = mnt_user_ns(h_mnt);
+       h_parent = au_h_dptr(parent, bindex);
+       h_dentry = vfs_tmpfile(h_userns, h_parent, mode, /*open_flag*/0);
+       if (IS_ERR(h_dentry)) {
+               err = PTR_ERR(h_dentry);
+               goto out_mnt;
+       }
+
+       au_set_dbtop(dentry, bindex);
+       au_set_dbbot(dentry, bindex);
+       au_set_h_dptr(dentry, bindex, dget(h_dentry));
+       inode = au_new_inode(dentry, /*must_new*/1);
+       if (IS_ERR(inode)) {
+               err = PTR_ERR(inode);
+               au_set_h_dptr(dentry, bindex, NULL);
+               au_set_dbtop(dentry, -1);
+               au_set_dbbot(dentry, -1);
+       } else {
+               if (!inode->i_nlink)
+                       set_nlink(inode, 1);
+               d_tmpfile(dentry, inode);
+               au_di(dentry)->di_tmpfile = 1;
+
+               /* update without i_mutex */
+               if (au_ibtop(dir) == au_dbtop(dentry))
+                       au_cpup_attr_timesizes(dir);
+       }
+       dput(h_dentry);
+
+out_mnt:
+       vfsub_mnt_drop_write(h_mnt);
+out_parent:
+       di_write_unlock(parent);
+       dput(parent);
+       di_write_unlock(dentry);
+       if (unlikely(err)) {
+               au_di_fin(dentry);
+               dentry->d_fsdata = NULL;
+       }
+out_si:
+       si_read_unlock(sb);
+out:
+       inode_unlock(dir);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct au_link_args {
+       aufs_bindex_t bdst, bsrc;
+       struct au_pin pin;
+       struct path h_path;
+       struct dentry *src_parent, *parent;
+};
+
+static int au_cpup_before_link(struct dentry *src_dentry,
+                              struct au_link_args *a)
+{
+       int err;
+       struct dentry *h_src_dentry;
+       struct au_cp_generic cpg = {
+               .dentry = src_dentry,
+               .bdst   = a->bdst,
+               .bsrc   = a->bsrc,
+               .len    = -1,
+               .pin    = &a->pin,
+               .flags  = AuCpup_DTIME | AuCpup_HOPEN /* | AuCpup_KEEPLINO */
+       };
+
+       di_read_lock_parent(a->src_parent, AuLock_IR);
+       err = au_test_and_cpup_dirs(src_dentry, a->bdst);
+       if (unlikely(err))
+               goto out;
+
+       h_src_dentry = au_h_dptr(src_dentry, a->bsrc);
+       err = au_pin(&a->pin, src_dentry, a->bdst,
+                    au_opt_udba(src_dentry->d_sb),
+                    AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+       if (unlikely(err))
+               goto out;
+
+       err = au_sio_cpup_simple(&cpg);
+       au_unpin(&a->pin);
+
+out:
+       di_read_unlock(a->src_parent, AuLock_IR);
+       return err;
+}
+
+static int au_cpup_or_link(struct dentry *src_dentry, struct dentry *dentry,
+                          struct au_link_args *a)
+{
+       int err;
+       unsigned char plink;
+       aufs_bindex_t bbot;
+       struct dentry *h_src_dentry;
+       struct inode *h_inode, *inode, *delegated;
+       struct super_block *sb;
+       struct file *h_file;
+
+       plink = 0;
+       h_inode = NULL;
+       sb = src_dentry->d_sb;
+       inode = d_inode(src_dentry);
+       if (au_ibtop(inode) <= a->bdst)
+               h_inode = au_h_iptr(inode, a->bdst);
+       if (!h_inode || !h_inode->i_nlink) {
+               /* copyup src_dentry as the name of dentry. */
+               bbot = au_dbbot(dentry);
+               if (bbot < a->bsrc)
+                       au_set_dbbot(dentry, a->bsrc);
+               au_set_h_dptr(dentry, a->bsrc,
+                             dget(au_h_dptr(src_dentry, a->bsrc)));
+               dget(a->h_path.dentry);
+               au_set_h_dptr(dentry, a->bdst, NULL);
+               AuDbg("temporary d_inode...\n");
+               spin_lock(&dentry->d_lock);
+               dentry->d_inode = d_inode(src_dentry); /* tmp */
+               spin_unlock(&dentry->d_lock);
+               h_file = au_h_open_pre(dentry, a->bsrc, /*force_wr*/0);
+               if (IS_ERR(h_file))
+                       err = PTR_ERR(h_file);
+               else {
+                       struct au_cp_generic cpg = {
+                               .dentry = dentry,
+                               .bdst   = a->bdst,
+                               .bsrc   = -1,
+                               .len    = -1,
+                               .pin    = &a->pin,
+                               .flags  = AuCpup_KEEPLINO
+                       };
+                       err = au_sio_cpup_simple(&cpg);
+                       au_h_open_post(dentry, a->bsrc, h_file);
+                       if (!err) {
+                               dput(a->h_path.dentry);
+                               a->h_path.dentry = au_h_dptr(dentry, a->bdst);
+                       } else
+                               au_set_h_dptr(dentry, a->bdst,
+                                             a->h_path.dentry);
+               }
+               spin_lock(&dentry->d_lock);
+               dentry->d_inode = NULL; /* restore */
+               spin_unlock(&dentry->d_lock);
+               AuDbg("temporary d_inode...done\n");
+               au_set_h_dptr(dentry, a->bsrc, NULL);
+               au_set_dbbot(dentry, bbot);
+       } else {
+               /* the inode of src_dentry already exists on a.bdst branch */
+               h_src_dentry = d_find_alias(h_inode);
+               if (!h_src_dentry && au_plink_test(inode)) {
+                       plink = 1;
+                       h_src_dentry = au_plink_lkup(inode, a->bdst);
+                       err = PTR_ERR(h_src_dentry);
+                       if (IS_ERR(h_src_dentry))
+                               goto out;
+
+                       if (unlikely(d_is_negative(h_src_dentry))) {
+                               dput(h_src_dentry);
+                               h_src_dentry = NULL;
+                       }
+
+               }
+               if (h_src_dentry) {
+                       delegated = NULL;
+                       err = vfsub_link(h_src_dentry, au_pinned_h_dir(&a->pin),
+                                        &a->h_path, &delegated);
+                       if (unlikely(err == -EWOULDBLOCK)) {
+                               pr_warn("cannot retry for NFSv4 delegation"
+                                       " for an internal link\n");
+                               iput(delegated);
+                       }
+                       dput(h_src_dentry);
+               } else {
+                       AuIOErr("no dentry found for hi%lu on b%d\n",
+                               h_inode->i_ino, a->bdst);
+                       err = -EIO;
+               }
+       }
+
+       if (!err && !plink)
+               au_plink_append(inode, a->bdst, a->h_path.dentry);
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+int aufs_link(struct dentry *src_dentry, struct inode *dir,
+             struct dentry *dentry)
+{
+       int err, rerr;
+       struct au_dtime dt;
+       struct au_link_args *a;
+       struct dentry *wh_dentry, *h_src_dentry;
+       struct inode *inode, *delegated;
+       struct super_block *sb;
+       struct au_wr_dir_args wr_dir_args = {
+               /* .force_btgt  = -1, */
+               .flags          = AuWrDir_ADD_ENTRY
+       };
+
+       IMustLock(dir);
+       inode = d_inode(src_dentry);
+       IMustLock(inode);
+
+       err = -ENOMEM;
+       a = kzalloc(sizeof(*a), GFP_NOFS);
+       if (unlikely(!a))
+               goto out;
+
+       a->parent = dentry->d_parent; /* dir inode is locked */
+       err = aufs_read_and_write_lock2(dentry, src_dentry,
+                                       AuLock_NOPLM | AuLock_GEN);
+       if (unlikely(err))
+               goto out_kfree;
+       err = au_d_linkable(src_dentry);
+       if (unlikely(err))
+               goto out_unlock;
+       err = au_d_may_add(dentry);
+       if (unlikely(err))
+               goto out_unlock;
+
+       a->src_parent = dget_parent(src_dentry);
+       wr_dir_args.force_btgt = au_ibtop(inode);
+
+       di_write_lock_parent(a->parent);
+       wr_dir_args.force_btgt = au_wbr(dentry, wr_dir_args.force_btgt);
+       wh_dentry = lock_hdir_lkup_wh(dentry, &dt, src_dentry, &a->pin,
+                                     &wr_dir_args);
+       err = PTR_ERR(wh_dentry);
+       if (IS_ERR(wh_dentry))
+               goto out_parent;
+
+       err = 0;
+       sb = dentry->d_sb;
+       a->bdst = au_dbtop(dentry);
+       a->h_path.dentry = au_h_dptr(dentry, a->bdst);
+       a->h_path.mnt = au_sbr_mnt(sb, a->bdst);
+       a->bsrc = au_ibtop(inode);
+       h_src_dentry = au_h_d_alias(src_dentry, a->bsrc);
+       if (!h_src_dentry && au_di(src_dentry)->di_tmpfile)
+               h_src_dentry = dget(au_hi_wh(inode, a->bsrc));
+       if (!h_src_dentry) {
+               a->bsrc = au_dbtop(src_dentry);
+               h_src_dentry = au_h_d_alias(src_dentry, a->bsrc);
+               AuDebugOn(!h_src_dentry);
+       } else if (IS_ERR(h_src_dentry)) {
+               err = PTR_ERR(h_src_dentry);
+               goto out_parent;
+       }
+
+       /*
+        * aufs doesn't touch the credential so
+        * security_dentry_create_files_as() is unnecessary.
+        */
+       if (au_opt_test(au_mntflags(sb), PLINK)) {
+               if (a->bdst < a->bsrc
+                   /* && h_src_dentry->d_sb != a->h_path.dentry->d_sb */)
+                       err = au_cpup_or_link(src_dentry, dentry, a);
+               else {
+                       delegated = NULL;
+                       err = vfsub_link(h_src_dentry, au_pinned_h_dir(&a->pin),
+                                        &a->h_path, &delegated);
+                       if (unlikely(err == -EWOULDBLOCK)) {
+                               pr_warn("cannot retry for NFSv4 delegation"
+                                       " for an internal link\n");
+                               iput(delegated);
+                       }
+               }
+               dput(h_src_dentry);
+       } else {
+               /*
+                * copyup src_dentry to the branch we process,
+                * and then link(2) to it.
+                */
+               dput(h_src_dentry);
+               if (a->bdst < a->bsrc
+                   /* && h_src_dentry->d_sb != a->h_path.dentry->d_sb */) {
+                       au_unpin(&a->pin);
+                       di_write_unlock(a->parent);
+                       err = au_cpup_before_link(src_dentry, a);
+                       di_write_lock_parent(a->parent);
+                       if (!err)
+                               err = au_pin(&a->pin, dentry, a->bdst,
+                                            au_opt_udba(sb),
+                                            AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+                       if (unlikely(err))
+                               goto out_wh;
+               }
+               if (!err) {
+                       h_src_dentry = au_h_dptr(src_dentry, a->bdst);
+                       err = -ENOENT;
+                       if (h_src_dentry && d_is_positive(h_src_dentry)) {
+                               delegated = NULL;
+                               err = vfsub_link(h_src_dentry,
+                                                au_pinned_h_dir(&a->pin),
+                                                &a->h_path, &delegated);
+                               if (unlikely(err == -EWOULDBLOCK)) {
+                                       pr_warn("cannot retry"
+                                               " for NFSv4 delegation"
+                                               " for an internal link\n");
+                                       iput(delegated);
+                               }
+                       }
+               }
+       }
+       if (unlikely(err))
+               goto out_unpin;
+
+       if (wh_dentry) {
+               a->h_path.dentry = wh_dentry;
+               err = au_wh_unlink_dentry(au_pinned_h_dir(&a->pin), &a->h_path,
+                                         dentry);
+               if (unlikely(err))
+                       goto out_revert;
+       }
+
+       au_dir_ts(dir, a->bdst);
+       inode_inc_iversion(dir);
+       inc_nlink(inode);
+       inode->i_ctime = dir->i_ctime;
+       d_instantiate(dentry, au_igrab(inode));
+       if (d_unhashed(a->h_path.dentry))
+               /* some filesystem calls d_drop() */
+               d_drop(dentry);
+       /* some filesystems consume an inode even hardlink */
+       au_fhsm_wrote(sb, a->bdst, /*force*/0);
+       goto out_unpin; /* success */
+
+out_revert:
+       /* no delegation since it is just created */
+       rerr = vfsub_unlink(au_pinned_h_dir(&a->pin), &a->h_path,
+                           /*delegated*/NULL, /*force*/0);
+       if (unlikely(rerr)) {
+               AuIOErr("%pd reverting failed(%d, %d)\n", dentry, err, rerr);
+               err = -EIO;
+       }
+       au_dtime_revert(&dt);
+out_unpin:
+       au_unpin(&a->pin);
+out_wh:
+       dput(wh_dentry);
+out_parent:
+       di_write_unlock(a->parent);
+       dput(a->src_parent);
+out_unlock:
+       if (unlikely(err)) {
+               au_update_dbtop(dentry);
+               d_drop(dentry);
+       }
+       aufs_read_and_write_unlock2(dentry, src_dentry);
+out_kfree:
+       au_kfree_rcu(a);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+int aufs_mkdir(struct user_namespace *userns, struct inode *dir,
+              struct dentry *dentry, umode_t mode)
+{
+       int err, rerr;
+       aufs_bindex_t bindex;
+       unsigned char diropq;
+       struct path h_path;
+       struct dentry *wh_dentry, *parent, *opq_dentry;
+       struct inode *h_inode;
+       struct super_block *sb;
+       struct {
+               struct au_pin pin;
+               struct au_dtime dt;
+       } *a; /* reduce the stack usage */
+       struct au_wr_dir_args wr_dir_args = {
+               .force_btgt     = -1,
+               .flags          = AuWrDir_ADD_ENTRY | AuWrDir_ISDIR
+       };
+
+       IMustLock(dir);
+
+       err = -ENOMEM;
+       a = kmalloc(sizeof(*a), GFP_NOFS);
+       if (unlikely(!a))
+               goto out;
+
+       err = aufs_read_lock(dentry, AuLock_DW | AuLock_GEN);
+       if (unlikely(err))
+               goto out_free;
+       err = au_d_may_add(dentry);
+       if (unlikely(err))
+               goto out_unlock;
+
+       parent = dentry->d_parent; /* dir inode is locked */
+       di_write_lock_parent(parent);
+       wh_dentry = lock_hdir_lkup_wh(dentry, &a->dt, /*src_dentry*/NULL,
+                                     &a->pin, &wr_dir_args);
+       err = PTR_ERR(wh_dentry);
+       if (IS_ERR(wh_dentry))
+               goto out_parent;
+
+       sb = dentry->d_sb;
+       bindex = au_dbtop(dentry);
+       h_path.dentry = au_h_dptr(dentry, bindex);
+       h_path.mnt = au_sbr_mnt(sb, bindex);
+       err = vfsub_mkdir(au_pinned_h_dir(&a->pin), &h_path, mode);
+       if (unlikely(err))
+               goto out_unpin;
+
+       /* make the dir opaque */
+       diropq = 0;
+       h_inode = d_inode(h_path.dentry);
+       if (wh_dentry
+           || au_opt_test(au_mntflags(sb), ALWAYS_DIROPQ)) {
+               inode_lock_nested(h_inode, AuLsc_I_CHILD);
+               opq_dentry = au_diropq_create(dentry, bindex);
+               inode_unlock(h_inode);
+               err = PTR_ERR(opq_dentry);
+               if (IS_ERR(opq_dentry))
+                       goto out_dir;
+               dput(opq_dentry);
+               diropq = 1;
+       }
+
+       err = epilog(dir, bindex, wh_dentry, dentry);
+       if (!err) {
+               inc_nlink(dir);
+               goto out_unpin; /* success */
+       }
+
+       /* revert */
+       if (diropq) {
+               AuLabel(revert opq);
+               inode_lock_nested(h_inode, AuLsc_I_CHILD);
+               rerr = au_diropq_remove(dentry, bindex);
+               inode_unlock(h_inode);
+               if (rerr) {
+                       AuIOErr("%pd reverting diropq failed(%d, %d)\n",
+                               dentry, err, rerr);
+                       err = -EIO;
+               }
+       }
+
+out_dir:
+       AuLabel(revert dir);
+       rerr = vfsub_rmdir(au_pinned_h_dir(&a->pin), &h_path);
+       if (rerr) {
+               AuIOErr("%pd reverting dir failed(%d, %d)\n",
+                       dentry, err, rerr);
+               err = -EIO;
+       }
+       au_dtime_revert(&a->dt);
+out_unpin:
+       au_unpin(&a->pin);
+       dput(wh_dentry);
+out_parent:
+       di_write_unlock(parent);
+out_unlock:
+       if (unlikely(err)) {
+               au_update_dbtop(dentry);
+               d_drop(dentry);
+       }
+       aufs_read_unlock(dentry, AuLock_DW);
+out_free:
+       au_kfree_rcu(a);
+out:
+       return err;
+}
diff -urN /usr/share/empty/fs/aufs/i_op.c linux/fs/aufs/i_op.c
--- /usr/share/empty/fs/aufs/i_op.c     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/i_op.c        2021-12-03 15:40:58.236647297 +0100
@@ -0,0 +1,1513 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * inode operations (except add/del/rename)
+ */
+
+#include <linux/device_cgroup.h>
+#include <linux/fs_stack.h>
+#include <linux/iversion.h>
+#include <linux/namei.h>
+#include <linux/security.h>
+#include "aufs.h"
+
+static int h_permission(struct inode *h_inode, int mask,
+                       struct path *h_path, int brperm)
+{
+       int err;
+       const unsigned char write_mask = !!(mask & (MAY_WRITE | MAY_APPEND));
+       struct user_namespace *h_userns;
+
+       err = -EPERM;
+       if (write_mask && IS_IMMUTABLE(h_inode))
+               goto out;
+
+       err = -EACCES;
+       if (((mask & MAY_EXEC)
+            && S_ISREG(h_inode->i_mode)
+            && (path_noexec(h_path)
+                || !(h_inode->i_mode & 0111))))
+               goto out;
+
+       /*
+        * - skip the lower fs test in the case of write to ro branch.
+        * - nfs dir permission write check is optimized, but a policy for
+        *   link/rename requires a real check.
+        * - nfs always sets SB_POSIXACL regardless its mount option 'noacl.'
+        *   in this case, generic_permission() returns -EOPNOTSUPP.
+        */
+       h_userns = mnt_user_ns(h_path->mnt);
+       if ((write_mask && !au_br_writable(brperm))
+           || (au_test_nfs(h_inode->i_sb) && S_ISDIR(h_inode->i_mode)
+               && write_mask && !(mask & MAY_READ))
+           || !h_inode->i_op->permission) {
+               /* AuLabel(generic_permission); */
+               /* AuDbg("get_acl %ps\n", h_inode->i_op->get_acl); */
+               err = generic_permission(h_userns, h_inode, mask);
+               if (err == -EOPNOTSUPP && au_test_nfs_noacl(h_inode))
+                       err = h_inode->i_op->permission(h_userns, h_inode,
+                                                       mask);
+               AuTraceErr(err);
+       } else {
+               /* AuLabel(h_inode->permission); */
+               err = h_inode->i_op->permission(h_userns, h_inode, mask);
+               AuTraceErr(err);
+       }
+
+       if (!err)
+               err = devcgroup_inode_permission(h_inode, mask);
+       if (!err)
+               err = security_inode_permission(h_inode, mask);
+
+out:
+       return err;
+}
+
+static int aufs_permission(struct user_namespace *userns, struct inode *inode,
+                          int mask)
+{
+       int err;
+       aufs_bindex_t bindex, bbot;
+       const unsigned char isdir = !!S_ISDIR(inode->i_mode),
+               write_mask = !!(mask & (MAY_WRITE | MAY_APPEND));
+       struct inode *h_inode;
+       struct super_block *sb;
+       struct au_branch *br;
+
+       /* todo: support rcu-walk? */
+       if (mask & MAY_NOT_BLOCK)
+               return -ECHILD;
+
+       sb = inode->i_sb;
+       si_read_lock(sb, AuLock_FLUSH);
+       ii_read_lock_child(inode);
+#if 0 /* reserved for future use */
+       /*
+        * This test may be rather 'too much' since the test is essentially done
+        * in the aufs_lookup().  Theoretically it is possible that the inode
+        * generation doesn't match to the superblock's here.  But it isn't a
+        * big deal I suppose.
+        */
+       err = au_iigen_test(inode, au_sigen(sb));
+       if (unlikely(err))
+               goto out;
+#endif
+
+       if (!isdir
+           || write_mask
+           || au_opt_test(au_mntflags(sb), DIRPERM1)) {
+               err = au_busy_or_stale();
+               h_inode = au_h_iptr(inode, au_ibtop(inode));
+               if (unlikely(!h_inode
+                            || (h_inode->i_mode & S_IFMT)
+                            != (inode->i_mode & S_IFMT)))
+                       goto out;
+
+               err = 0;
+               bindex = au_ibtop(inode);
+               br = au_sbr(sb, bindex);
+               err = h_permission(h_inode, mask, &br->br_path, br->br_perm);
+               if (write_mask
+                   && !err
+                   && !special_file(h_inode->i_mode)) {
+                       /* test whether the upper writable branch exists */
+                       err = -EROFS;
+                       for (; bindex >= 0; bindex--)
+                               if (!au_br_rdonly(au_sbr(sb, bindex))) {
+                                       err = 0;
+                                       break;
+                               }
+               }
+               goto out;
+       }
+
+       /* non-write to dir */
+       err = 0;
+       bbot = au_ibbot(inode);
+       for (bindex = au_ibtop(inode); !err && bindex <= bbot; bindex++) {
+               h_inode = au_h_iptr(inode, bindex);
+               if (h_inode) {
+                       err = au_busy_or_stale();
+                       if (unlikely(!S_ISDIR(h_inode->i_mode)))
+                               break;
+
+                       br = au_sbr(sb, bindex);
+                       err = h_permission(h_inode, mask, &br->br_path,
+                                          br->br_perm);
+               }
+       }
+
+out:
+       ii_read_unlock(inode);
+       si_read_unlock(sb);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static struct dentry *aufs_lookup(struct inode *dir, struct dentry *dentry,
+                                 unsigned int flags)
+{
+       struct dentry *ret, *parent;
+       struct inode *inode;
+       struct super_block *sb;
+       int err, npositive;
+
+       IMustLock(dir);
+
+       /* todo: support rcu-walk? */
+       ret = ERR_PTR(-ECHILD);
+       if (flags & LOOKUP_RCU)
+               goto out;
+
+       ret = ERR_PTR(-ENAMETOOLONG);
+       if (unlikely(dentry->d_name.len > AUFS_MAX_NAMELEN))
+               goto out;
+
+       sb = dir->i_sb;
+       err = si_read_lock(sb, AuLock_FLUSH | AuLock_NOPLM);
+       ret = ERR_PTR(err);
+       if (unlikely(err))
+               goto out;
+
+       err = au_di_init(dentry);
+       ret = ERR_PTR(err);
+       if (unlikely(err))
+               goto out_si;
+
+       inode = NULL;
+       npositive = 0; /* suppress a warning */
+       parent = dentry->d_parent; /* dir inode is locked */
+       di_read_lock_parent(parent, AuLock_IR);
+       err = au_alive_dir(parent);
+       if (!err)
+               err = au_digen_test(parent, au_sigen(sb));
+       if (!err) {
+               /* regardless LOOKUP_CREATE, always ALLOW_NEG */
+               npositive = au_lkup_dentry(dentry, au_dbtop(parent),
+                                          AuLkup_ALLOW_NEG);
+               err = npositive;
+       }
+       di_read_unlock(parent, AuLock_IR);
+       ret = ERR_PTR(err);
+       if (unlikely(err < 0))
+               goto out_unlock;
+
+       if (npositive) {
+               inode = au_new_inode(dentry, /*must_new*/0);
+               if (IS_ERR(inode)) {
+                       ret = (void *)inode;
+                       inode = NULL;
+                       goto out_unlock;
+               }
+       }
+
+       if (inode)
+               atomic_inc(&inode->i_count);
+       ret = d_splice_alias(inode, dentry);
+#if 0 /* reserved for future use */
+       if (unlikely(d_need_lookup(dentry))) {
+               spin_lock(&dentry->d_lock);
+               dentry->d_flags &= ~DCACHE_NEED_LOOKUP;
+               spin_unlock(&dentry->d_lock);
+       } else
+#endif
+       if (inode) {
+               if (!IS_ERR(ret)) {
+                       iput(inode);
+                       if (ret && ret != dentry)
+                               ii_write_unlock(inode);
+               } else {
+                       ii_write_unlock(inode);
+                       iput(inode);
+                       inode = NULL;
+               }
+       }
+
+out_unlock:
+       di_write_unlock(dentry);
+out_si:
+       si_read_unlock(sb);
+out:
+       return ret;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * very dirty and complicated aufs ->atomic_open().
+ * aufs_atomic_open()
+ * + au_aopen_or_create()
+ *   + add_simple()
+ *     + vfsub_atomic_open()
+ *       + branch fs ->atomic_open()
+ *        may call the actual 'open' for h_file
+ *       + inc br_nfiles only if opened
+ * + au_aopen_no_open() or au_aopen_do_open()
+ *
+ * au_aopen_do_open()
+ * + finish_open()
+ *   + au_do_aopen()
+ *     + au_do_open() the body of all 'open'
+ *       + au_do_open_nondir()
+ *        set the passed h_file
+ *
+ * au_aopen_no_open()
+ * + finish_no_open()
+ */
+
+struct aopen_node {
+       struct hlist_bl_node hblist;
+       struct file *file, *h_file;
+};
+
+static int au_do_aopen(struct inode *inode, struct file *file)
+{
+       struct hlist_bl_head *aopen;
+       struct hlist_bl_node *pos;
+       struct aopen_node *node;
+       struct au_do_open_args args = {
+               .aopen  = 1,
+               .open   = au_do_open_nondir
+       };
+
+       aopen = &au_sbi(inode->i_sb)->si_aopen;
+       hlist_bl_lock(aopen);
+       hlist_bl_for_each_entry(node, pos, aopen, hblist)
+               if (node->file == file) {
+                       args.h_file = node->h_file;
+                       break;
+               }
+       hlist_bl_unlock(aopen);
+       /* AuDebugOn(!args.h_file); */
+
+       return au_do_open(file, &args);
+}
+
+static int au_aopen_do_open(struct file *file, struct dentry *dentry,
+                           struct aopen_node *aopen_node)
+{
+       int err;
+       struct hlist_bl_head *aopen;
+
+       AuLabel(here);
+       aopen = &au_sbi(dentry->d_sb)->si_aopen;
+       au_hbl_add(&aopen_node->hblist, aopen);
+       err = finish_open(file, dentry, au_do_aopen);
+       au_hbl_del(&aopen_node->hblist, aopen);
+       /* AuDbgFile(file); */
+       AuDbg("%pd%s%s\n", dentry,
+             (file->f_mode & FMODE_CREATED) ? " created" : "",
+             (file->f_mode & FMODE_OPENED) ? " opened" : "");
+
+       AuTraceErr(err);
+       return err;
+}
+
+static int au_aopen_no_open(struct file *file, struct dentry *dentry)
+{
+       int err;
+
+       AuLabel(here);
+       dget(dentry);
+       err = finish_no_open(file, dentry);
+
+       AuTraceErr(err);
+       return err;
+}
+
+static int aufs_atomic_open(struct inode *dir, struct dentry *dentry,
+                           struct file *file, unsigned int open_flag,
+                           umode_t create_mode)
+{
+       int err, did_open;
+       unsigned int lkup_flags;
+       aufs_bindex_t bindex;
+       struct super_block *sb;
+       struct dentry *parent, *d;
+       struct vfsub_aopen_args args = {
+               .open_flag      = open_flag,
+               .create_mode    = create_mode
+       };
+       struct aopen_node aopen_node = {
+               .file   = file
+       };
+
+       IMustLock(dir);
+       AuDbg("open_flag 0%o\n", open_flag);
+       AuDbgDentry(dentry);
+
+       err = 0;
+       if (!au_di(dentry)) {
+               lkup_flags = LOOKUP_OPEN;
+               if (open_flag & O_CREAT)
+                       lkup_flags |= LOOKUP_CREATE;
+               d = aufs_lookup(dir, dentry, lkup_flags);
+               if (IS_ERR(d)) {
+                       err = PTR_ERR(d);
+                       AuTraceErr(err);
+                       goto out;
+               } else if (d) {
+                       /*
+                        * obsoleted dentry found.
+                        * another error will be returned later.
+                        */
+                       d_drop(d);
+                       AuDbgDentry(d);
+                       dput(d);
+               }
+               AuDbgDentry(dentry);
+       }
+
+       if (d_is_positive(dentry)
+           || d_unhashed(dentry)
+           || d_unlinked(dentry)
+           || !(open_flag & O_CREAT)) {
+               err = au_aopen_no_open(file, dentry);
+               goto out; /* success */
+       }
+
+       err = aufs_read_lock(dentry, AuLock_DW | AuLock_FLUSH | AuLock_GEN);
+       if (unlikely(err))
+               goto out;
+
+       sb = dentry->d_sb;
+       parent = dentry->d_parent;      /* dir is locked */
+       di_write_lock_parent(parent);
+       err = au_lkup_dentry(dentry, /*btop*/0, AuLkup_ALLOW_NEG);
+       if (unlikely(err < 0))
+               goto out_parent;
+
+       AuDbgDentry(dentry);
+       if (d_is_positive(dentry)) {
+               err = au_aopen_no_open(file, dentry);
+               goto out_parent; /* success */
+       }
+
+       args.file = alloc_empty_file(file->f_flags, current_cred());
+       err = PTR_ERR(args.file);
+       if (IS_ERR(args.file))
+               goto out_parent;
+
+       bindex = au_dbtop(dentry);
+       err = au_aopen_or_create(dir, dentry, &args);
+       AuTraceErr(err);
+       AuDbgFile(args.file);
+       file->f_mode = args.file->f_mode & ~FMODE_OPENED;
+       did_open = !!(args.file->f_mode & FMODE_OPENED);
+       if (!did_open) {
+               fput(args.file);
+               args.file = NULL;
+       }
+       di_write_unlock(parent);
+       di_write_unlock(dentry);
+       if (unlikely(err < 0)) {
+               if (args.file)
+                       fput(args.file);
+               goto out_sb;
+       }
+
+       if (!did_open)
+               err = au_aopen_no_open(file, dentry);
+       else {
+               aopen_node.h_file = args.file;
+               err = au_aopen_do_open(file, dentry, &aopen_node);
+       }
+       if (unlikely(err < 0)) {
+               if (args.file)
+                       fput(args.file);
+               if (did_open)
+                       au_lcnt_dec(&args.br->br_nfiles);
+       }
+       goto out_sb; /* success */
+
+out_parent:
+       di_write_unlock(parent);
+       di_write_unlock(dentry);
+out_sb:
+       si_read_unlock(sb);
+out:
+       AuTraceErr(err);
+       AuDbgFile(file);
+       return err;
+}
+
+
+/* ---------------------------------------------------------------------- */
+
+static int au_wr_dir_cpup(struct dentry *dentry, struct dentry *parent,
+                         const unsigned char add_entry, aufs_bindex_t bcpup,
+                         aufs_bindex_t btop)
+{
+       int err;
+       struct dentry *h_parent;
+       struct inode *h_dir;
+
+       if (add_entry)
+               IMustLock(d_inode(parent));
+       else
+               di_write_lock_parent(parent);
+
+       err = 0;
+       if (!au_h_dptr(parent, bcpup)) {
+               if (btop > bcpup)
+                       err = au_cpup_dirs(dentry, bcpup);
+               else if (btop < bcpup)
+                       err = au_cpdown_dirs(dentry, bcpup);
+               else
+                       BUG();
+       }
+       if (!err && add_entry && !au_ftest_wrdir(add_entry, TMPFILE)) {
+               h_parent = au_h_dptr(parent, bcpup);
+               h_dir = d_inode(h_parent);
+               inode_lock_shared_nested(h_dir, AuLsc_I_PARENT);
+               err = au_lkup_neg(dentry, bcpup, /*wh*/0);
+               /* todo: no unlock here */
+               inode_unlock_shared(h_dir);
+
+               AuDbg("bcpup %d\n", bcpup);
+               if (!err) {
+                       if (d_really_is_negative(dentry))
+                               au_set_h_dptr(dentry, btop, NULL);
+                       au_update_dbrange(dentry, /*do_put_zero*/0);
+               }
+       }
+
+       if (!add_entry)
+               di_write_unlock(parent);
+       if (!err)
+               err = bcpup; /* success */
+
+       AuTraceErr(err);
+       return err;
+}
+
+/*
+ * decide the branch and the parent dir where we will create a new entry.
+ * returns new bindex or an error.
+ * copyup the parent dir if needed.
+ */
+int au_wr_dir(struct dentry *dentry, struct dentry *src_dentry,
+             struct au_wr_dir_args *args)
+{
+       int err;
+       unsigned int flags;
+       aufs_bindex_t bcpup, btop, src_btop;
+       const unsigned char add_entry
+               = au_ftest_wrdir(args->flags, ADD_ENTRY)
+               | au_ftest_wrdir(args->flags, TMPFILE);
+       struct super_block *sb;
+       struct dentry *parent;
+       struct au_sbinfo *sbinfo;
+
+       sb = dentry->d_sb;
+       sbinfo = au_sbi(sb);
+       parent = dget_parent(dentry);
+       btop = au_dbtop(dentry);
+       bcpup = btop;
+       if (args->force_btgt < 0) {
+               if (src_dentry) {
+                       src_btop = au_dbtop(src_dentry);
+                       if (src_btop < btop)
+                               bcpup = src_btop;
+               } else if (add_entry) {
+                       flags = 0;
+                       if (au_ftest_wrdir(args->flags, ISDIR))
+                               au_fset_wbr(flags, DIR);
+                       err = AuWbrCreate(sbinfo, dentry, flags);
+                       bcpup = err;
+               }
+
+               if (bcpup < 0 || au_test_ro(sb, bcpup, d_inode(dentry))) {
+                       if (add_entry)
+                               err = AuWbrCopyup(sbinfo, dentry);
+                       else {
+                               if (!IS_ROOT(dentry)) {
+                                       di_read_lock_parent(parent, !AuLock_IR);
+                                       err = AuWbrCopyup(sbinfo, dentry);
+                                       di_read_unlock(parent, !AuLock_IR);
+                               } else
+                                       err = AuWbrCopyup(sbinfo, dentry);
+                       }
+                       bcpup = err;
+                       if (unlikely(err < 0))
+                               goto out;
+               }
+       } else {
+               bcpup = args->force_btgt;
+               AuDebugOn(au_test_ro(sb, bcpup, d_inode(dentry)));
+       }
+
+       AuDbg("btop %d, bcpup %d\n", btop, bcpup);
+       err = bcpup;
+       if (bcpup == btop)
+               goto out; /* success */
+
+       /* copyup the new parent into the branch we process */
+       err = au_wr_dir_cpup(dentry, parent, add_entry, bcpup, btop);
+       if (err >= 0) {
+               if (d_really_is_negative(dentry)) {
+                       au_set_h_dptr(dentry, btop, NULL);
+                       au_set_dbtop(dentry, bcpup);
+                       au_set_dbbot(dentry, bcpup);
+               }
+               AuDebugOn(add_entry
+                         && !au_ftest_wrdir(args->flags, TMPFILE)
+                         && !au_h_dptr(dentry, bcpup));
+       }
+
+out:
+       dput(parent);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void au_pin_hdir_unlock(struct au_pin *p)
+{
+       if (p->hdir)
+               au_hn_inode_unlock(p->hdir);
+}
+
+int au_pin_hdir_lock(struct au_pin *p)
+{
+       int err;
+
+       err = 0;
+       if (!p->hdir)
+               goto out;
+
+       /* even if an error happens later, keep this lock */
+       au_hn_inode_lock_nested(p->hdir, p->lsc_hi);
+
+       err = -EBUSY;
+       if (unlikely(p->hdir->hi_inode != d_inode(p->h_parent)))
+               goto out;
+
+       err = 0;
+       if (p->h_dentry)
+               err = au_h_verify(p->h_dentry, p->udba, p->hdir->hi_inode,
+                                 p->h_parent, p->br);
+
+out:
+       return err;
+}
+
+int au_pin_hdir_relock(struct au_pin *p)
+{
+       int err, i;
+       struct inode *h_i;
+       struct dentry *h_d[] = {
+               p->h_dentry,
+               p->h_parent
+       };
+
+       err = au_pin_hdir_lock(p);
+       if (unlikely(err))
+               goto out;
+
+       for (i = 0; !err && i < sizeof(h_d)/sizeof(*h_d); i++) {
+               if (!h_d[i])
+                       continue;
+               if (d_is_positive(h_d[i])) {
+                       h_i = d_inode(h_d[i]);
+                       err = !h_i->i_nlink;
+               }
+       }
+
+out:
+       return err;
+}
+
+static void au_pin_hdir_set_owner(struct au_pin *p, struct task_struct *task)
+{
+       atomic_long_set(&p->hdir->hi_inode->i_rwsem.owner, (long)task);
+}
+
+void au_pin_hdir_acquire_nest(struct au_pin *p)
+{
+       if (p->hdir) {
+               rwsem_acquire_nest(&p->hdir->hi_inode->i_rwsem.dep_map,
+                                  p->lsc_hi, 0, NULL, _RET_IP_);
+               au_pin_hdir_set_owner(p, current);
+       }
+}
+
+void au_pin_hdir_release(struct au_pin *p)
+{
+       if (p->hdir) {
+               au_pin_hdir_set_owner(p, p->task);
+               rwsem_release(&p->hdir->hi_inode->i_rwsem.dep_map, _RET_IP_);
+       }
+}
+
+struct dentry *au_pinned_h_parent(struct au_pin *pin)
+{
+       if (pin && pin->parent)
+               return au_h_dptr(pin->parent, pin->bindex);
+       return NULL;
+}
+
+void au_unpin(struct au_pin *p)
+{
+       if (p->hdir)
+               au_pin_hdir_unlock(p);
+       if (p->h_mnt && au_ftest_pin(p->flags, MNT_WRITE))
+               vfsub_mnt_drop_write(p->h_mnt);
+       if (!p->hdir)
+               return;
+
+       if (!au_ftest_pin(p->flags, DI_LOCKED))
+               di_read_unlock(p->parent, AuLock_IR);
+       iput(p->hdir->hi_inode);
+       dput(p->parent);
+       p->parent = NULL;
+       p->hdir = NULL;
+       p->h_mnt = NULL;
+       /* do not clear p->task */
+}
+
+int au_do_pin(struct au_pin *p)
+{
+       int err;
+       struct super_block *sb;
+       struct inode *h_dir;
+
+       err = 0;
+       sb = p->dentry->d_sb;
+       p->br = au_sbr(sb, p->bindex);
+       if (IS_ROOT(p->dentry)) {
+               if (au_ftest_pin(p->flags, MNT_WRITE)) {
+                       p->h_mnt = au_br_mnt(p->br);
+                       err = vfsub_mnt_want_write(p->h_mnt);
+                       if (unlikely(err)) {
+                               au_fclr_pin(p->flags, MNT_WRITE);
+                               goto out_err;
+                       }
+               }
+               goto out;
+       }
+
+       p->h_dentry = NULL;
+       if (p->bindex <= au_dbbot(p->dentry))
+               p->h_dentry = au_h_dptr(p->dentry, p->bindex);
+
+       p->parent = dget_parent(p->dentry);
+       if (!au_ftest_pin(p->flags, DI_LOCKED))
+               di_read_lock(p->parent, AuLock_IR, p->lsc_di);
+
+       h_dir = NULL;
+       p->h_parent = au_h_dptr(p->parent, p->bindex);
+       p->hdir = au_hi(d_inode(p->parent), p->bindex);
+       if (p->hdir)
+               h_dir = p->hdir->hi_inode;
+
+       /*
+        * udba case, or
+        * if DI_LOCKED is not set, then p->parent may be different
+        * and h_parent can be NULL.
+        */
+       if (unlikely(!p->hdir || !h_dir || !p->h_parent)) {
+               err = -EBUSY;
+               if (!au_ftest_pin(p->flags, DI_LOCKED))
+                       di_read_unlock(p->parent, AuLock_IR);
+               dput(p->parent);
+               p->parent = NULL;
+               goto out_err;
+       }
+
+       if (au_ftest_pin(p->flags, MNT_WRITE)) {
+               p->h_mnt = au_br_mnt(p->br);
+               err = vfsub_mnt_want_write(p->h_mnt);
+               if (unlikely(err)) {
+                       au_fclr_pin(p->flags, MNT_WRITE);
+                       if (!au_ftest_pin(p->flags, DI_LOCKED))
+                               di_read_unlock(p->parent, AuLock_IR);
+                       dput(p->parent);
+                       p->parent = NULL;
+                       goto out_err;
+               }
+       }
+
+       au_igrab(h_dir);
+       err = au_pin_hdir_lock(p);
+       if (!err)
+               goto out; /* success */
+
+       au_unpin(p);
+
+out_err:
+       pr_err("err %d\n", err);
+       err = au_busy_or_stale();
+out:
+       return err;
+}
+
+void au_pin_init(struct au_pin *p, struct dentry *dentry,
+                aufs_bindex_t bindex, int lsc_di, int lsc_hi,
+                unsigned int udba, unsigned char flags)
+{
+       p->dentry = dentry;
+       p->udba = udba;
+       p->lsc_di = lsc_di;
+       p->lsc_hi = lsc_hi;
+       p->flags = flags;
+       p->bindex = bindex;
+
+       p->parent = NULL;
+       p->hdir = NULL;
+       p->h_mnt = NULL;
+
+       p->h_dentry = NULL;
+       p->h_parent = NULL;
+       p->br = NULL;
+       p->task = current;
+}
+
+int au_pin(struct au_pin *pin, struct dentry *dentry, aufs_bindex_t bindex,
+          unsigned int udba, unsigned char flags)
+{
+       au_pin_init(pin, dentry, bindex, AuLsc_DI_PARENT, AuLsc_I_PARENT2,
+                   udba, flags);
+       return au_do_pin(pin);
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * ->setattr() and ->getattr() are called in various cases.
+ * chmod, stat: dentry is revalidated.
+ * fchmod, fstat: file and dentry are not revalidated, additionally they may be
+ *               unhashed.
+ * for ->setattr(), ia->ia_file is passed from ftruncate only.
+ */
+/* todo: consolidate with do_refresh() and simple_reval_dpath() */
+int au_reval_for_attr(struct dentry *dentry, unsigned int sigen)
+{
+       int err;
+       struct dentry *parent;
+
+       err = 0;
+       if (au_digen_test(dentry, sigen)) {
+               parent = dget_parent(dentry);
+               di_read_lock_parent(parent, AuLock_IR);
+               err = au_refresh_dentry(dentry, parent);
+               di_read_unlock(parent, AuLock_IR);
+               dput(parent);
+       }
+
+       AuTraceErr(err);
+       return err;
+}
+
+int au_pin_and_icpup(struct dentry *dentry, struct iattr *ia,
+                    struct au_icpup_args *a)
+{
+       int err;
+       loff_t sz;
+       aufs_bindex_t btop, ibtop;
+       struct dentry *hi_wh, *parent;
+       struct inode *inode;
+       struct au_wr_dir_args wr_dir_args = {
+               .force_btgt     = -1,
+               .flags          = 0
+       };
+
+       if (d_is_dir(dentry))
+               au_fset_wrdir(wr_dir_args.flags, ISDIR);
+       /* plink or hi_wh() case */
+       btop = au_dbtop(dentry);
+       inode = d_inode(dentry);
+       ibtop = au_ibtop(inode);
+       if (btop != ibtop && !au_test_ro(inode->i_sb, ibtop, inode))
+               wr_dir_args.force_btgt = ibtop;
+       err = au_wr_dir(dentry, /*src_dentry*/NULL, &wr_dir_args);
+       if (unlikely(err < 0))
+               goto out;
+       a->btgt = err;
+       if (err != btop)
+               au_fset_icpup(a->flags, DID_CPUP);
+
+       err = 0;
+       a->pin_flags = AuPin_MNT_WRITE;
+       parent = NULL;
+       if (!IS_ROOT(dentry)) {
+               au_fset_pin(a->pin_flags, DI_LOCKED);
+               parent = dget_parent(dentry);
+               di_write_lock_parent(parent);
+       }
+
+       err = au_pin(&a->pin, dentry, a->btgt, a->udba, a->pin_flags);
+       if (unlikely(err))
+               goto out_parent;
+
+       sz = -1;
+       a->h_path.dentry = au_h_dptr(dentry, btop);
+       a->h_inode = d_inode(a->h_path.dentry);
+       if (ia && (ia->ia_valid & ATTR_SIZE)) {
+               inode_lock_shared_nested(a->h_inode, AuLsc_I_CHILD);
+               if (ia->ia_size < i_size_read(a->h_inode))
+                       sz = ia->ia_size;
+               inode_unlock_shared(a->h_inode);
+       }
+
+       hi_wh = NULL;
+       if (au_ftest_icpup(a->flags, DID_CPUP) && d_unlinked(dentry)) {
+               hi_wh = au_hi_wh(inode, a->btgt);
+               if (!hi_wh) {
+                       struct au_cp_generic cpg = {
+                               .dentry = dentry,
+                               .bdst   = a->btgt,
+                               .bsrc   = -1,
+                               .len    = sz,
+                               .pin    = &a->pin
+                       };
+                       err = au_sio_cpup_wh(&cpg, /*file*/NULL);
+                       if (unlikely(err))
+                               goto out_unlock;
+                       hi_wh = au_hi_wh(inode, a->btgt);
+                       /* todo: revalidate hi_wh? */
+               }
+       }
+
+       if (parent) {
+               au_pin_set_parent_lflag(&a->pin, /*lflag*/0);
+               di_downgrade_lock(parent, AuLock_IR);
+               dput(parent);
+               parent = NULL;
+       }
+       if (!au_ftest_icpup(a->flags, DID_CPUP))
+               goto out; /* success */
+
+       if (!d_unhashed(dentry)) {
+               struct au_cp_generic cpg = {
+                       .dentry = dentry,
+                       .bdst   = a->btgt,
+                       .bsrc   = btop,
+                       .len    = sz,
+                       .pin    = &a->pin,
+                       .flags  = AuCpup_DTIME | AuCpup_HOPEN
+               };
+               err = au_sio_cpup_simple(&cpg);
+               if (!err)
+                       a->h_path.dentry = au_h_dptr(dentry, a->btgt);
+       } else if (!hi_wh)
+               a->h_path.dentry = au_h_dptr(dentry, a->btgt);
+       else
+               a->h_path.dentry = hi_wh; /* do not dget here */
+
+out_unlock:
+       a->h_inode = d_inode(a->h_path.dentry);
+       if (!err)
+               goto out; /* success */
+       au_unpin(&a->pin);
+out_parent:
+       if (parent) {
+               di_write_unlock(parent);
+               dput(parent);
+       }
+out:
+       if (!err)
+               inode_lock_nested(a->h_inode, AuLsc_I_CHILD);
+       return err;
+}
+
+static int aufs_setattr(struct user_namespace *userns, struct dentry *dentry,
+                       struct iattr *ia)
+{
+       int err;
+       struct inode *inode, *delegated;
+       struct super_block *sb;
+       struct file *file;
+       struct au_icpup_args *a;
+       struct user_namespace *h_userns;
+
+       inode = d_inode(dentry);
+       IMustLock(inode);
+
+       err = setattr_prepare(userns, dentry, ia);
+       if (unlikely(err))
+               goto out;
+
+       err = -ENOMEM;
+       a = kzalloc(sizeof(*a), GFP_NOFS);
+       if (unlikely(!a))
+               goto out;
+
+       if (ia->ia_valid & (ATTR_KILL_SUID | ATTR_KILL_SGID))
+               ia->ia_valid &= ~ATTR_MODE;
+
+       file = NULL;
+       sb = dentry->d_sb;
+       err = si_read_lock(sb, AuLock_FLUSH | AuLock_NOPLM);
+       if (unlikely(err))
+               goto out_kfree;
+
+       if (ia->ia_valid & ATTR_FILE) {
+               /* currently ftruncate(2) only */
+               AuDebugOn(!d_is_reg(dentry));
+               file = ia->ia_file;
+               err = au_reval_and_lock_fdi(file, au_reopen_nondir, /*wlock*/1,
+                                           /*fi_lsc*/0);
+               if (unlikely(err))
+                       goto out_si;
+               ia->ia_file = au_hf_top(file);
+               a->udba = AuOpt_UDBA_NONE;
+       } else {
+               /* fchmod() doesn't pass ia_file */
+               a->udba = au_opt_udba(sb);
+               di_write_lock_child(dentry);
+               /* no d_unlinked(), to set UDBA_NONE for root */
+               if (d_unhashed(dentry))
+                       a->udba = AuOpt_UDBA_NONE;
+               if (a->udba != AuOpt_UDBA_NONE) {
+                       AuDebugOn(IS_ROOT(dentry));
+                       err = au_reval_for_attr(dentry, au_sigen(sb));
+                       if (unlikely(err))
+                               goto out_dentry;
+               }
+       }
+
+       err = au_pin_and_icpup(dentry, ia, a);
+       if (unlikely(err < 0))
+               goto out_dentry;
+       if (au_ftest_icpup(a->flags, DID_CPUP)) {
+               ia->ia_file = NULL;
+               ia->ia_valid &= ~ATTR_FILE;
+       }
+
+       a->h_path.mnt = au_sbr_mnt(sb, a->btgt);
+       if ((ia->ia_valid & (ATTR_MODE | ATTR_CTIME))
+           == (ATTR_MODE | ATTR_CTIME)) {
+               err = security_path_chmod(&a->h_path, ia->ia_mode);
+               if (unlikely(err))
+                       goto out_unlock;
+       } else if ((ia->ia_valid & (ATTR_UID | ATTR_GID))
+                  && (ia->ia_valid & ATTR_CTIME)) {
+               err = security_path_chown(&a->h_path, ia->ia_uid, ia->ia_gid);
+               if (unlikely(err))
+                       goto out_unlock;
+       }
+
+       if (ia->ia_valid & ATTR_SIZE) {
+               struct file *f;
+
+               if (ia->ia_size < i_size_read(inode))
+                       /* unmap only */
+                       truncate_setsize(inode, ia->ia_size);
+
+               f = NULL;
+               if (ia->ia_valid & ATTR_FILE)
+                       f = ia->ia_file;
+               inode_unlock(a->h_inode);
+               err = vfsub_trunc(&a->h_path, ia->ia_size, ia->ia_valid, f);
+               inode_lock_nested(a->h_inode, AuLsc_I_CHILD);
+       } else {
+               delegated = NULL;
+               while (1) {
+                       err = vfsub_notify_change(&a->h_path, ia, &delegated);
+                       if (delegated) {
+                               err = break_deleg_wait(&delegated);
+                               if (!err)
+                                       continue;
+                       }
+                       break;
+               }
+       }
+       /*
+        * regardless aufs 'acl' option setting.
+        * why don't all acl-aware fs call this func from their ->setattr()?
+        */
+       if (!err && (ia->ia_valid & ATTR_MODE)) {
+               h_userns = mnt_user_ns(a->h_path.mnt);
+               err = vfsub_acl_chmod(h_userns, a->h_inode, ia->ia_mode);
+       }
+       if (!err)
+               au_cpup_attr_changeable(inode);
+
+out_unlock:
+       inode_unlock(a->h_inode);
+       au_unpin(&a->pin);
+       if (unlikely(err))
+               au_update_dbtop(dentry);
+out_dentry:
+       di_write_unlock(dentry);
+       if (file) {
+               fi_write_unlock(file);
+               ia->ia_file = file;
+               ia->ia_valid |= ATTR_FILE;
+       }
+out_si:
+       si_read_unlock(sb);
+out_kfree:
+       au_kfree_rcu(a);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+#if IS_ENABLED(CONFIG_AUFS_XATTR) || IS_ENABLED(CONFIG_FS_POSIX_ACL)
+static int au_h_path_to_set_attr(struct dentry *dentry,
+                                struct au_icpup_args *a, struct path *h_path)
+{
+       int err;
+       struct super_block *sb;
+
+       sb = dentry->d_sb;
+       a->udba = au_opt_udba(sb);
+       /* no d_unlinked(), to set UDBA_NONE for root */
+       if (d_unhashed(dentry))
+               a->udba = AuOpt_UDBA_NONE;
+       if (a->udba != AuOpt_UDBA_NONE) {
+               AuDebugOn(IS_ROOT(dentry));
+               err = au_reval_for_attr(dentry, au_sigen(sb));
+               if (unlikely(err))
+                       goto out;
+       }
+       err = au_pin_and_icpup(dentry, /*ia*/NULL, a);
+       if (unlikely(err < 0))
+               goto out;
+
+       h_path->dentry = a->h_path.dentry;
+       h_path->mnt = au_sbr_mnt(sb, a->btgt);
+
+out:
+       return err;
+}
+
+ssize_t au_sxattr(struct dentry *dentry, struct inode *inode,
+                 struct au_sxattr *arg)
+{
+       int err;
+       struct path h_path;
+       struct super_block *sb;
+       struct au_icpup_args *a;
+       struct inode *h_inode;
+       struct user_namespace *h_userns;
+
+       IMustLock(inode);
+
+       err = -ENOMEM;
+       a = kzalloc(sizeof(*a), GFP_NOFS);
+       if (unlikely(!a))
+               goto out;
+
+       sb = dentry->d_sb;
+       err = si_read_lock(sb, AuLock_FLUSH | AuLock_NOPLM);
+       if (unlikely(err))
+               goto out_kfree;
+
+       h_path.dentry = NULL;   /* silence gcc */
+       di_write_lock_child(dentry);
+       err = au_h_path_to_set_attr(dentry, a, &h_path);
+       if (unlikely(err))
+               goto out_di;
+       h_userns = mnt_user_ns(h_path.mnt);
+
+       inode_unlock(a->h_inode);
+       switch (arg->type) {
+       case AU_XATTR_SET:
+               AuDebugOn(d_is_negative(h_path.dentry));
+               err = vfsub_setxattr(h_userns, h_path.dentry,
+                                    arg->u.set.name, arg->u.set.value,
+                                    arg->u.set.size, arg->u.set.flags);
+               break;
+       case AU_ACL_SET:
+               err = -EOPNOTSUPP;
+               h_inode = d_inode(h_path.dentry);
+               if (h_inode->i_op->set_acl) {
+                       /* this will call posix_acl_update_mode */
+                       err = h_inode->i_op->set_acl(h_userns, h_inode,
+                                                    arg->u.acl_set.acl,
+                                                    arg->u.acl_set.type);
+               }
+               break;
+       }
+       if (!err)
+               au_cpup_attr_timesizes(inode);
+
+       au_unpin(&a->pin);
+       if (unlikely(err))
+               au_update_dbtop(dentry);
+
+out_di:
+       di_write_unlock(dentry);
+       si_read_unlock(sb);
+out_kfree:
+       au_kfree_rcu(a);
+out:
+       AuTraceErr(err);
+       return err;
+}
+#endif
+
+static void au_refresh_iattr(struct inode *inode, struct kstat *st,
+                            unsigned int nlink)
+{
+       unsigned int n;
+
+       inode->i_mode = st->mode;
+       /* don't i_[ug]id_write() here */
+       inode->i_uid = st->uid;
+       inode->i_gid = st->gid;
+       inode->i_atime = st->atime;
+       inode->i_mtime = st->mtime;
+       inode->i_ctime = st->ctime;
+
+       au_cpup_attr_nlink(inode, /*force*/0);
+       if (S_ISDIR(inode->i_mode)) {
+               n = inode->i_nlink;
+               n -= nlink;
+               n += st->nlink;
+               smp_mb(); /* for i_nlink */
+               /* 0 can happen */
+               set_nlink(inode, n);
+       }
+
+       spin_lock(&inode->i_lock);
+       inode->i_blocks = st->blocks;
+       i_size_write(inode, st->size);
+       spin_unlock(&inode->i_lock);
+}
+
+/*
+ * common routine for aufs_getattr() and au_getxattr().
+ * returns zero or negative (an error).
+ * @dentry will be read-locked in success.
+ */
+int au_h_path_getattr(struct dentry *dentry, struct inode *inode, int force,
+                     struct path *h_path, int locked)
+{
+       int err;
+       unsigned int mnt_flags, sigen;
+       unsigned char udba_none;
+       aufs_bindex_t bindex;
+       struct super_block *sb, *h_sb;
+
+       h_path->mnt = NULL;
+       h_path->dentry = NULL;
+
+       err = 0;
+       sb = dentry->d_sb;
+       mnt_flags = au_mntflags(sb);
+       udba_none = !!au_opt_test(mnt_flags, UDBA_NONE);
+
+       if (unlikely(locked))
+               goto body; /* skip locking dinfo */
+
+       /* support fstat(2) */
+       if (!d_unlinked(dentry) && !udba_none) {
+               sigen = au_sigen(sb);
+               err = au_digen_test(dentry, sigen);
+               if (!err) {
+                       di_read_lock_child(dentry, AuLock_IR);
+                       err = au_dbrange_test(dentry);
+                       if (unlikely(err)) {
+                               di_read_unlock(dentry, AuLock_IR);
+                               goto out;
+                       }
+               } else {
+                       AuDebugOn(IS_ROOT(dentry));
+                       di_write_lock_child(dentry);
+                       err = au_dbrange_test(dentry);
+                       if (!err)
+                               err = au_reval_for_attr(dentry, sigen);
+                       if (!err)
+                               di_downgrade_lock(dentry, AuLock_IR);
+                       else {
+                               di_write_unlock(dentry);
+                               goto out;
+                       }
+               }
+       } else
+               di_read_lock_child(dentry, AuLock_IR);
+
+body:
+       if (!inode) {
+               inode = d_inode(dentry);
+               if (unlikely(!inode))
+                       goto out;
+       }
+       bindex = au_ibtop(inode);
+       h_path->mnt = au_sbr_mnt(sb, bindex);
+       h_sb = h_path->mnt->mnt_sb;
+       if (!force
+           && !au_test_fs_bad_iattr(h_sb)
+           && udba_none)
+               goto out; /* success */
+
+       if (au_dbtop(dentry) == bindex)
+               h_path->dentry = au_h_dptr(dentry, bindex);
+       else if (au_opt_test(mnt_flags, PLINK) && au_plink_test(inode)) {
+               h_path->dentry = au_plink_lkup(inode, bindex);
+               if (IS_ERR(h_path->dentry))
+                       /* pretending success */
+                       h_path->dentry = NULL;
+               else
+                       dput(h_path->dentry);
+       }
+
+out:
+       return err;
+}
+
+static int aufs_getattr(struct user_namespace *userns, const struct path *path,
+                       struct kstat *st, u32 request, unsigned int query)
+{
+       int err;
+       unsigned char positive;
+       struct path h_path;
+       struct dentry *dentry;
+       struct inode *inode;
+       struct super_block *sb;
+
+       dentry = path->dentry;
+       inode = d_inode(dentry);
+       sb = dentry->d_sb;
+       err = si_read_lock(sb, AuLock_FLUSH | AuLock_NOPLM);
+       if (unlikely(err))
+               goto out;
+       err = au_h_path_getattr(dentry, /*inode*/NULL, /*force*/0, &h_path,
+                               /*locked*/0);
+       if (unlikely(err))
+               goto out_si;
+       if (unlikely(!h_path.dentry))
+               /* illegally overlapped or something */
+               goto out_fill; /* pretending success */
+
+       positive = d_is_positive(h_path.dentry);
+       if (positive)
+               /* no vfsub version */
+               err = vfs_getattr(&h_path, st, request, query);
+       if (!err) {
+               if (positive)
+                       au_refresh_iattr(inode, st,
+                                        d_inode(h_path.dentry)->i_nlink);
+               goto out_fill; /* success */
+       }
+       AuTraceErr(err);
+       goto out_di;
+
+out_fill:
+       generic_fillattr(userns, inode, st);
+out_di:
+       di_read_unlock(dentry, AuLock_IR);
+out_si:
+       si_read_unlock(sb);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static const char *aufs_get_link(struct dentry *dentry, struct inode *inode,
+                                struct delayed_call *done)
+{
+       const char *ret;
+       struct dentry *h_dentry;
+       struct inode *h_inode;
+       int err;
+       aufs_bindex_t bindex;
+
+       ret = NULL; /* suppress a warning */
+       err = -ECHILD;
+       if (!dentry)
+               goto out;
+
+       err = aufs_read_lock(dentry, AuLock_IR | AuLock_GEN);
+       if (unlikely(err))
+               goto out;
+
+       err = au_d_hashed_positive(dentry);
+       if (unlikely(err))
+               goto out_unlock;
+
+       err = -EINVAL;
+       inode = d_inode(dentry);
+       bindex = au_ibtop(inode);
+       h_inode = au_h_iptr(inode, bindex);
+       if (unlikely(!h_inode->i_op->get_link))
+               goto out_unlock;
+
+       err = -EBUSY;
+       h_dentry = NULL;
+       if (au_dbtop(dentry) <= bindex) {
+               h_dentry = au_h_dptr(dentry, bindex);
+               if (h_dentry)
+                       dget(h_dentry);
+       }
+       if (!h_dentry) {
+               h_dentry = d_find_any_alias(h_inode);
+               if (IS_ERR(h_dentry)) {
+                       err = PTR_ERR(h_dentry);
+                       goto out_unlock;
+               }
+       }
+       if (unlikely(!h_dentry))
+               goto out_unlock;
+
+       err = 0;
+       AuDbg("%ps\n", h_inode->i_op->get_link);
+       AuDbgDentry(h_dentry);
+       ret = vfs_get_link(h_dentry, done);
+       dput(h_dentry);
+       if (IS_ERR(ret))
+               err = PTR_ERR(ret);
+
+out_unlock:
+       aufs_read_unlock(dentry, AuLock_IR);
+out:
+       if (unlikely(err))
+               ret = ERR_PTR(err);
+       AuTraceErrPtr(ret);
+       return ret;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_is_special(struct inode *inode)
+{
+       return (inode->i_mode & (S_IFBLK | S_IFCHR | S_IFIFO | S_IFSOCK));
+}
+
+static int aufs_update_time(struct inode *inode, struct timespec64 *ts,
+                           int flags)
+{
+       int err;
+       aufs_bindex_t bindex;
+       struct super_block *sb;
+       struct inode *h_inode;
+       struct vfsmount *h_mnt;
+
+       sb = inode->i_sb;
+       WARN_ONCE((flags & S_ATIME) && !IS_NOATIME(inode),
+                 "unexpected s_flags 0x%lx", sb->s_flags);
+
+       /* mmap_sem might be acquired already, cf. aufs_mmap() */
+       lockdep_off();
+       si_read_lock(sb, AuLock_FLUSH);
+       ii_write_lock_child(inode);
+
+       err = 0;
+       bindex = au_ibtop(inode);
+       h_inode = au_h_iptr(inode, bindex);
+       if (!au_test_ro(sb, bindex, inode)) {
+               h_mnt = au_sbr_mnt(sb, bindex);
+               err = vfsub_mnt_want_write(h_mnt);
+               if (!err) {
+                       err = vfsub_update_time(h_inode, ts, flags);
+                       vfsub_mnt_drop_write(h_mnt);
+               }
+       } else if (au_is_special(h_inode)) {
+               /*
+                * Never copy-up here.
+                * These special files may already be opened and used for
+                * communicating. If we copied it up, then the communication
+                * would be corrupted.
+                */
+               AuWarn1("timestamps for i%lu are ignored "
+                       "since it is on readonly branch (hi%lu).\n",
+                       inode->i_ino, h_inode->i_ino);
+       } else if (flags & ~S_ATIME) {
+               err = -EIO;
+               AuIOErr1("unexpected flags 0x%x\n", flags);
+               AuDebugOn(1);
+       }
+
+       if (!err)
+               au_cpup_attr_timesizes(inode);
+       ii_write_unlock(inode);
+       si_read_unlock(sb);
+       lockdep_on();
+
+       if (!err && (flags & S_VERSION))
+               inode_inc_iversion(inode);
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* no getattr version will be set by module.c:aufs_init() */
+struct inode_operations aufs_iop_nogetattr[AuIop_Last],
+       aufs_iop[] = {
+       [AuIop_SYMLINK] = {
+               .permission     = aufs_permission,
+#ifdef CONFIG_FS_POSIX_ACL
+               .get_acl        = aufs_get_acl,
+               .set_acl        = aufs_set_acl, /* unsupport for symlink? */
+#endif
+
+               .setattr        = aufs_setattr,
+               .getattr        = aufs_getattr,
+
+#ifdef CONFIG_AUFS_XATTR
+               .listxattr      = aufs_listxattr,
+#endif
+
+               .get_link       = aufs_get_link,
+
+               /* .update_time = aufs_update_time */
+       },
+       [AuIop_DIR] = {
+               .create         = aufs_create,
+               .lookup         = aufs_lookup,
+               .link           = aufs_link,
+               .unlink         = aufs_unlink,
+               .symlink        = aufs_symlink,
+               .mkdir          = aufs_mkdir,
+               .rmdir          = aufs_rmdir,
+               .mknod          = aufs_mknod,
+               .rename         = aufs_rename,
+
+               .permission     = aufs_permission,
+#ifdef CONFIG_FS_POSIX_ACL
+               .get_acl        = aufs_get_acl,
+               .set_acl        = aufs_set_acl,
+#endif
+
+               .setattr        = aufs_setattr,
+               .getattr        = aufs_getattr,
+
+#ifdef CONFIG_AUFS_XATTR
+               .listxattr      = aufs_listxattr,
+#endif
+
+               .update_time    = aufs_update_time,
+               .atomic_open    = aufs_atomic_open,
+               .tmpfile        = aufs_tmpfile
+       },
+       [AuIop_OTHER] = {
+               .permission     = aufs_permission,
+#ifdef CONFIG_FS_POSIX_ACL
+               .get_acl        = aufs_get_acl,
+               .set_acl        = aufs_set_acl,
+#endif
+
+               .setattr        = aufs_setattr,
+               .getattr        = aufs_getattr,
+
+#ifdef CONFIG_AUFS_XATTR
+               .listxattr      = aufs_listxattr,
+#endif
+
+               .update_time    = aufs_update_time
+       }
+};
diff -urN /usr/share/empty/fs/aufs/i_op_del.c linux/fs/aufs/i_op_del.c
--- /usr/share/empty/fs/aufs/i_op_del.c 1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/i_op_del.c    2021-12-03 15:40:58.236647297 +0100
@@ -0,0 +1,522 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * inode operations (del entry)
+ */
+
+#include <linux/iversion.h>
+#include "aufs.h"
+
+/*
+ * decide if a new whiteout for @dentry is necessary or not.
+ * when it is necessary, prepare the parent dir for the upper branch whose
+ * branch index is @bcpup for creation. the actual creation of the whiteout will
+ * be done by caller.
+ * return value:
+ * 0: wh is unnecessary
+ * plus: wh is necessary
+ * minus: error
+ */
+int au_wr_dir_need_wh(struct dentry *dentry, int isdir, aufs_bindex_t *bcpup)
+{
+       int need_wh, err;
+       aufs_bindex_t btop;
+       struct super_block *sb;
+
+       sb = dentry->d_sb;
+       btop = au_dbtop(dentry);
+       if (*bcpup < 0) {
+               *bcpup = btop;
+               if (au_test_ro(sb, btop, d_inode(dentry))) {
+                       err = AuWbrCopyup(au_sbi(sb), dentry);
+                       *bcpup = err;
+                       if (unlikely(err < 0))
+                               goto out;
+               }
+       } else
+               AuDebugOn(btop < *bcpup
+                         || au_test_ro(sb, *bcpup, d_inode(dentry)));
+       AuDbg("bcpup %d, btop %d\n", *bcpup, btop);
+
+       if (*bcpup != btop) {
+               err = au_cpup_dirs(dentry, *bcpup);
+               if (unlikely(err))
+                       goto out;
+               need_wh = 1;
+       } else {
+               struct au_dinfo *dinfo, *tmp;
+
+               need_wh = -ENOMEM;
+               dinfo = au_di(dentry);
+               tmp = au_di_alloc(sb, AuLsc_DI_TMP);
+               if (tmp) {
+                       au_di_cp(tmp, dinfo);
+                       au_di_swap(tmp, dinfo);
+                       /* returns the number of positive dentries */
+                       need_wh = au_lkup_dentry(dentry, btop + 1,
+                                                /* AuLkup_IGNORE_PERM */ 0);
+                       au_di_swap(tmp, dinfo);
+                       au_rw_write_unlock(&tmp->di_rwsem);
+                       au_di_free(tmp);
+               }
+       }
+       AuDbg("need_wh %d\n", need_wh);
+       err = need_wh;
+
+out:
+       return err;
+}
+
+/*
+ * simple tests for the del-entry operations.
+ * following the checks in vfs, plus the parent-child relationship.
+ */
+int au_may_del(struct dentry *dentry, aufs_bindex_t bindex,
+              struct dentry *h_parent, int isdir)
+{
+       int err;
+       umode_t h_mode;
+       struct dentry *h_dentry, *h_latest;
+       struct inode *h_inode;
+       struct path h_ppath;
+       struct super_block *sb;
+       struct au_branch *br;
+       struct user_namespace *h_userns;
+
+       h_dentry = au_h_dptr(dentry, bindex);
+       if (d_really_is_positive(dentry)) {
+               err = -ENOENT;
+               if (unlikely(d_is_negative(h_dentry)))
+                       goto out;
+               h_inode = d_inode(h_dentry);
+               if (unlikely(!h_inode->i_nlink))
+                       goto out;
+
+               h_mode = h_inode->i_mode;
+               if (!isdir) {
+                       err = -EISDIR;
+                       if (unlikely(S_ISDIR(h_mode)))
+                               goto out;
+               } else if (unlikely(!S_ISDIR(h_mode))) {
+                       err = -ENOTDIR;
+                       goto out;
+               }
+       } else {
+               /* rename(2) case */
+               err = -EIO;
+               if (unlikely(d_is_positive(h_dentry)))
+                       goto out;
+       }
+
+       err = -ENOENT;
+       /* expected parent dir is locked */
+       if (unlikely(h_parent != h_dentry->d_parent))
+               goto out;
+       err = 0;
+
+       /*
+        * rmdir a dir may break the consistency on some filesystem.
+        * let's try heavy test.
+        */
+       err = -EACCES;
+       sb = dentry->d_sb;
+       br = au_sbr(sb, bindex);
+       h_userns = au_br_userns(br);
+       if (unlikely(!au_opt_test(au_mntflags(sb), DIRPERM1)
+                    && au_test_h_perm(h_userns, d_inode(h_parent),
+                                      MAY_EXEC | MAY_WRITE)))
+               goto out;
+
+       h_ppath.dentry = h_parent;
+       h_ppath.mnt = au_br_mnt(br);
+       h_latest = au_sio_lkup_one(h_userns, &dentry->d_name, &h_ppath);
+       err = -EIO;
+       if (IS_ERR(h_latest))
+               goto out;
+       if (h_latest == h_dentry)
+               err = 0;
+       dput(h_latest);
+
+out:
+       return err;
+}
+
+/*
+ * decide the branch where we operate for @dentry. the branch index will be set
+ * @rbcpup. after deciding it, 'pin' it and store the timestamps of the parent
+ * dir for reverting.
+ * when a new whiteout is necessary, create it.
+ */
+static struct dentry*
+lock_hdir_create_wh(struct dentry *dentry, int isdir, aufs_bindex_t *rbcpup,
+                   struct au_dtime *dt, struct au_pin *pin)
+{
+       struct dentry *wh_dentry;
+       struct super_block *sb;
+       struct path h_path;
+       int err, need_wh;
+       unsigned int udba;
+       aufs_bindex_t bcpup;
+
+       need_wh = au_wr_dir_need_wh(dentry, isdir, rbcpup);
+       wh_dentry = ERR_PTR(need_wh);
+       if (unlikely(need_wh < 0))
+               goto out;
+
+       sb = dentry->d_sb;
+       udba = au_opt_udba(sb);
+       bcpup = *rbcpup;
+       err = au_pin(pin, dentry, bcpup, udba,
+                    AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+       wh_dentry = ERR_PTR(err);
+       if (unlikely(err))
+               goto out;
+
+       h_path.dentry = au_pinned_h_parent(pin);
+       if (udba != AuOpt_UDBA_NONE
+           && au_dbtop(dentry) == bcpup) {
+               err = au_may_del(dentry, bcpup, h_path.dentry, isdir);
+               wh_dentry = ERR_PTR(err);
+               if (unlikely(err))
+                       goto out_unpin;
+       }
+
+       h_path.mnt = au_sbr_mnt(sb, bcpup);
+       au_dtime_store(dt, au_pinned_parent(pin), &h_path);
+       wh_dentry = NULL;
+       if (!need_wh)
+               goto out; /* success, no need to create whiteout */
+
+       wh_dentry = au_wh_create(dentry, bcpup, h_path.dentry);
+       if (IS_ERR(wh_dentry))
+               goto out_unpin;
+
+       /* returns with the parent is locked and wh_dentry is dget-ed */
+       goto out; /* success */
+
+out_unpin:
+       au_unpin(pin);
+out:
+       return wh_dentry;
+}
+
+/*
+ * when removing a dir, rename it to a unique temporary whiteout-ed name first
+ * in order to be revertible and save time for removing many child whiteouts
+ * under the dir.
+ * returns 1 when there are too many child whiteout and caller should remove
+ * them asynchronously. returns 0 when the number of children is enough small to
+ * remove now or the branch fs is a remote fs.
+ * otherwise return an error.
+ */
+static int renwh_and_rmdir(struct dentry *dentry, aufs_bindex_t bindex,
+                          struct au_nhash *whlist, struct inode *dir)
+{
+       int rmdir_later, err, dirwh;
+       struct dentry *h_dentry;
+       struct super_block *sb;
+       struct inode *inode;
+
+       sb = dentry->d_sb;
+       SiMustAnyLock(sb);
+       h_dentry = au_h_dptr(dentry, bindex);
+       err = au_whtmp_ren(h_dentry, au_sbr(sb, bindex));
+       if (unlikely(err))
+               goto out;
+
+       /* stop monitoring */
+       inode = d_inode(dentry);
+       au_hn_free(au_hi(inode, bindex));
+
+       if (!au_test_fs_remote(h_dentry->d_sb)) {
+               dirwh = au_sbi(sb)->si_dirwh;
+               rmdir_later = (dirwh <= 1);
+               if (!rmdir_later)
+                       rmdir_later = au_nhash_test_longer_wh(whlist, bindex,
+                                                             dirwh);
+               if (rmdir_later)
+                       return rmdir_later;
+       }
+
+       err = au_whtmp_rmdir(dir, bindex, h_dentry, whlist);
+       if (unlikely(err)) {
+               AuIOErr("rmdir %pd, b%d failed, %d. ignored\n",
+                       h_dentry, bindex, err);
+               err = 0;
+       }
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/*
+ * final procedure for deleting a entry.
+ * maintain dentry and iattr.
+ */
+static void epilog(struct inode *dir, struct dentry *dentry,
+                  aufs_bindex_t bindex)
+{
+       struct inode *inode;
+
+       inode = d_inode(dentry);
+       d_drop(dentry);
+       inode->i_ctime = dir->i_ctime;
+
+       au_dir_ts(dir, bindex);
+       inode_inc_iversion(dir);
+}
+
+/*
+ * when an error happened, remove the created whiteout and revert everything.
+ */
+static int do_revert(int err, struct inode *dir, aufs_bindex_t bindex,
+                    aufs_bindex_t bwh, struct dentry *wh_dentry,
+                    struct dentry *dentry, struct au_dtime *dt)
+{
+       int rerr;
+       struct path h_path = {
+               .dentry = wh_dentry,
+               .mnt    = au_sbr_mnt(dir->i_sb, bindex)
+       };
+
+       rerr = au_wh_unlink_dentry(au_h_iptr(dir, bindex), &h_path, dentry);
+       if (!rerr) {
+               au_set_dbwh(dentry, bwh);
+               au_dtime_revert(dt);
+               return 0;
+       }
+
+       AuIOErr("%pd reverting whiteout failed(%d, %d)\n", dentry, err, rerr);
+       return -EIO;
+}
+
+/* ---------------------------------------------------------------------- */
+
+int aufs_unlink(struct inode *dir, struct dentry *dentry)
+{
+       int err;
+       aufs_bindex_t bwh, bindex, btop;
+       struct inode *inode, *h_dir, *delegated;
+       struct dentry *parent, *wh_dentry;
+       /* to reduce stack size */
+       struct {
+               struct au_dtime dt;
+               struct au_pin pin;
+               struct path h_path;
+       } *a;
+
+       IMustLock(dir);
+
+       err = -ENOMEM;
+       a = kmalloc(sizeof(*a), GFP_NOFS);
+       if (unlikely(!a))
+               goto out;
+
+       err = aufs_read_lock(dentry, AuLock_DW | AuLock_GEN);
+       if (unlikely(err))
+               goto out_free;
+       err = au_d_hashed_positive(dentry);
+       if (unlikely(err))
+               goto out_unlock;
+       inode = d_inode(dentry);
+       IMustLock(inode);
+       err = -EISDIR;
+       if (unlikely(d_is_dir(dentry)))
+               goto out_unlock; /* possible? */
+
+       btop = au_dbtop(dentry);
+       bwh = au_dbwh(dentry);
+       bindex = -1;
+       parent = dentry->d_parent; /* dir inode is locked */
+       di_write_lock_parent(parent);
+       wh_dentry = lock_hdir_create_wh(dentry, /*isdir*/0, &bindex, &a->dt,
+                                       &a->pin);
+       err = PTR_ERR(wh_dentry);
+       if (IS_ERR(wh_dentry))
+               goto out_parent;
+
+       a->h_path.mnt = au_sbr_mnt(dentry->d_sb, btop);
+       a->h_path.dentry = au_h_dptr(dentry, btop);
+       dget(a->h_path.dentry);
+       if (bindex == btop) {
+               h_dir = au_pinned_h_dir(&a->pin);
+               delegated = NULL;
+               err = vfsub_unlink(h_dir, &a->h_path, &delegated, /*force*/0);
+               if (unlikely(err == -EWOULDBLOCK)) {
+                       pr_warn("cannot retry for NFSv4 delegation"
+                               " for an internal unlink\n");
+                       iput(delegated);
+               }
+       } else {
+               /* dir inode is locked */
+               h_dir = d_inode(wh_dentry->d_parent);
+               IMustLock(h_dir);
+               err = 0;
+       }
+
+       if (!err) {
+               vfsub_drop_nlink(inode);
+               epilog(dir, dentry, bindex);
+
+               /* update target timestamps */
+               if (bindex == btop) {
+                       vfsub_update_h_iattr(&a->h_path, /*did*/NULL);
+                       /*ignore*/
+                       inode->i_ctime = d_inode(a->h_path.dentry)->i_ctime;
+               } else
+                       /* todo: this timestamp may be reverted later */
+                       inode->i_ctime = h_dir->i_ctime;
+               goto out_unpin; /* success */
+       }
+
+       /* revert */
+       if (wh_dentry) {
+               int rerr;
+
+               rerr = do_revert(err, dir, bindex, bwh, wh_dentry, dentry,
+                                &a->dt);
+               if (rerr)
+                       err = rerr;
+       }
+
+out_unpin:
+       au_unpin(&a->pin);
+       dput(wh_dentry);
+       dput(a->h_path.dentry);
+out_parent:
+       di_write_unlock(parent);
+out_unlock:
+       aufs_read_unlock(dentry, AuLock_DW);
+out_free:
+       au_kfree_rcu(a);
+out:
+       return err;
+}
+
+int aufs_rmdir(struct inode *dir, struct dentry *dentry)
+{
+       int err, rmdir_later;
+       aufs_bindex_t bwh, bindex, btop;
+       struct inode *inode;
+       struct dentry *parent, *wh_dentry, *h_dentry;
+       struct au_whtmp_rmdir *args;
+       /* to reduce stack size */
+       struct {
+               struct au_dtime dt;
+               struct au_pin pin;
+       } *a;
+
+       IMustLock(dir);
+
+       err = -ENOMEM;
+       a = kmalloc(sizeof(*a), GFP_NOFS);
+       if (unlikely(!a))
+               goto out;
+
+       err = aufs_read_lock(dentry, AuLock_DW | AuLock_FLUSH | AuLock_GEN);
+       if (unlikely(err))
+               goto out_free;
+       err = au_alive_dir(dentry);
+       if (unlikely(err))
+               goto out_unlock;
+       inode = d_inode(dentry);
+       IMustLock(inode);
+       err = -ENOTDIR;
+       if (unlikely(!d_is_dir(dentry)))
+               goto out_unlock; /* possible? */
+
+       err = -ENOMEM;
+       args = au_whtmp_rmdir_alloc(dir->i_sb, GFP_NOFS);
+       if (unlikely(!args))
+               goto out_unlock;
+
+       parent = dentry->d_parent; /* dir inode is locked */
+       di_write_lock_parent(parent);
+       err = au_test_empty(dentry, &args->whlist);
+       if (unlikely(err))
+               goto out_parent;
+
+       btop = au_dbtop(dentry);
+       bwh = au_dbwh(dentry);
+       bindex = -1;
+       wh_dentry = lock_hdir_create_wh(dentry, /*isdir*/1, &bindex, &a->dt,
+                                       &a->pin);
+       err = PTR_ERR(wh_dentry);
+       if (IS_ERR(wh_dentry))
+               goto out_parent;
+
+       h_dentry = au_h_dptr(dentry, btop);
+       dget(h_dentry);
+       rmdir_later = 0;
+       if (bindex == btop) {
+               err = renwh_and_rmdir(dentry, btop, &args->whlist, dir);
+               if (err > 0) {
+                       rmdir_later = err;
+                       err = 0;
+               }
+       } else {
+               /* stop monitoring */
+               au_hn_free(au_hi(inode, btop));
+
+               /* dir inode is locked */
+               IMustLock(d_inode(wh_dentry->d_parent));
+               err = 0;
+       }
+
+       if (!err) {
+               vfsub_dead_dir(inode);
+               au_set_dbdiropq(dentry, -1);
+               epilog(dir, dentry, bindex);
+
+               if (rmdir_later) {
+                       au_whtmp_kick_rmdir(dir, btop, h_dentry, args);
+                       args = NULL;
+               }
+
+               goto out_unpin; /* success */
+       }
+
+       /* revert */
+       AuLabel(revert);
+       if (wh_dentry) {
+               int rerr;
+
+               rerr = do_revert(err, dir, bindex, bwh, wh_dentry, dentry,
+                                &a->dt);
+               if (rerr)
+                       err = rerr;
+       }
+
+out_unpin:
+       au_unpin(&a->pin);
+       dput(wh_dentry);
+       dput(h_dentry);
+out_parent:
+       di_write_unlock(parent);
+       if (args)
+               au_whtmp_rmdir_free(args);
+out_unlock:
+       aufs_read_unlock(dentry, AuLock_DW);
+out_free:
+       au_kfree_rcu(a);
+out:
+       AuTraceErr(err);
+       return err;
+}
diff -urN /usr/share/empty/fs/aufs/i_op_ren.c linux/fs/aufs/i_op_ren.c
--- /usr/share/empty/fs/aufs/i_op_ren.c 1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/i_op_ren.c    2021-12-03 15:40:58.236647297 +0100
@@ -0,0 +1,1257 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * inode operation (rename entry)
+ * todo: this is crazy monster
+ */
+
+#include <linux/iversion.h>
+#include "aufs.h"
+
+enum { AuSRC, AuDST, AuSrcDst };
+enum { AuPARENT, AuCHILD, AuParentChild };
+
+#define AuRen_ISDIR_SRC                1
+#define AuRen_ISDIR_DST                (1 << 1)
+#define AuRen_ISSAMEDIR                (1 << 2)
+#define AuRen_WHSRC            (1 << 3)
+#define AuRen_WHDST            (1 << 4)
+#define AuRen_MNT_WRITE                (1 << 5)
+#define AuRen_DT_DSTDIR                (1 << 6)
+#define AuRen_DIROPQ_SRC       (1 << 7)
+#define AuRen_DIROPQ_DST       (1 << 8)
+#define AuRen_DIRREN           (1 << 9)
+#define AuRen_DROPPED_SRC      (1 << 10)
+#define AuRen_DROPPED_DST      (1 << 11)
+#define au_ftest_ren(flags, name)      ((flags) & AuRen_##name)
+#define au_fset_ren(flags, name) \
+       do { (flags) |= AuRen_##name; } while (0)
+#define au_fclr_ren(flags, name) \
+       do { (flags) &= ~AuRen_##name; } while (0)
+
+#ifndef CONFIG_AUFS_DIRREN
+#undef AuRen_DIRREN
+#define AuRen_DIRREN           0
+#endif
+
+struct au_ren_args {
+       struct {
+               struct dentry *dentry, *h_dentry, *parent, *h_parent,
+                       *wh_dentry;
+               struct inode *dir, *inode;
+               struct au_hinode *hdir, *hinode;
+               struct au_dtime dt[AuParentChild];
+               aufs_bindex_t btop, bdiropq;
+       } sd[AuSrcDst];
+
+#define src_dentry     sd[AuSRC].dentry
+#define src_dir                sd[AuSRC].dir
+#define src_inode      sd[AuSRC].inode
+#define src_h_dentry   sd[AuSRC].h_dentry
+#define src_parent     sd[AuSRC].parent
+#define src_h_parent   sd[AuSRC].h_parent
+#define src_wh_dentry  sd[AuSRC].wh_dentry
+#define src_hdir       sd[AuSRC].hdir
+#define src_hinode     sd[AuSRC].hinode
+#define src_h_dir      sd[AuSRC].hdir->hi_inode
+#define src_dt         sd[AuSRC].dt
+#define src_btop       sd[AuSRC].btop
+#define src_bdiropq    sd[AuSRC].bdiropq
+
+#define dst_dentry     sd[AuDST].dentry
+#define dst_dir                sd[AuDST].dir
+#define dst_inode      sd[AuDST].inode
+#define dst_h_dentry   sd[AuDST].h_dentry
+#define dst_parent     sd[AuDST].parent
+#define dst_h_parent   sd[AuDST].h_parent
+#define dst_wh_dentry  sd[AuDST].wh_dentry
+#define dst_hdir       sd[AuDST].hdir
+#define dst_hinode     sd[AuDST].hinode
+#define dst_h_dir      sd[AuDST].hdir->hi_inode
+#define dst_dt         sd[AuDST].dt
+#define dst_btop       sd[AuDST].btop
+#define dst_bdiropq    sd[AuDST].bdiropq
+
+       struct dentry *h_trap;
+       struct au_branch *br;
+       struct path h_path;
+       struct au_nhash whlist;
+       aufs_bindex_t btgt, src_bwh;
+
+       struct {
+               unsigned short auren_flags;
+               unsigned char flags;    /* syscall parameter */
+               unsigned char exchange;
+       } __packed;
+
+       struct au_whtmp_rmdir *thargs;
+       struct dentry *h_dst;
+       struct au_hinode *h_root;
+};
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * functions for reverting.
+ * when an error happened in a single rename systemcall, we should revert
+ * everything as if nothing happened.
+ * we don't need to revert the copied-up/down the parent dir since they are
+ * harmless.
+ */
+
+#define RevertFailure(fmt, ...) do { \
+       AuIOErr("revert failure: " fmt " (%d, %d)\n", \
+               ##__VA_ARGS__, err, rerr); \
+       err = -EIO; \
+} while (0)
+
+static void au_ren_do_rev_diropq(int err, struct au_ren_args *a, int idx)
+{
+       int rerr;
+       struct dentry *d;
+#define src_or_dst(member) a->sd[idx].member
+
+       d = src_or_dst(dentry); /* {src,dst}_dentry */
+       au_hn_inode_lock_nested(src_or_dst(hinode), AuLsc_I_CHILD);
+       rerr = au_diropq_remove(d, a->btgt);
+       au_hn_inode_unlock(src_or_dst(hinode));
+       au_set_dbdiropq(d, src_or_dst(bdiropq));
+       if (rerr)
+               RevertFailure("remove diropq %pd", d);
+
+#undef src_or_dst_
+}
+
+static void au_ren_rev_diropq(int err, struct au_ren_args *a)
+{
+       if (au_ftest_ren(a->auren_flags, DIROPQ_SRC))
+               au_ren_do_rev_diropq(err, a, AuSRC);
+       if (au_ftest_ren(a->auren_flags, DIROPQ_DST))
+               au_ren_do_rev_diropq(err, a, AuDST);
+}
+
+static void au_ren_rev_rename(int err, struct au_ren_args *a)
+{
+       int rerr;
+       struct inode *delegated;
+       struct path h_ppath = {
+               .dentry = a->src_h_parent,
+               .mnt    = a->h_path.mnt
+       };
+
+       a->h_path.dentry = vfsub_lkup_one(&a->src_dentry->d_name, &h_ppath);
+       rerr = PTR_ERR(a->h_path.dentry);
+       if (IS_ERR(a->h_path.dentry)) {
+               RevertFailure("lkup one %pd", a->src_dentry);
+               return;
+       }
+
+       delegated = NULL;
+       rerr = vfsub_rename(a->dst_h_dir,
+                           au_h_dptr(a->src_dentry, a->btgt),
+                           a->src_h_dir, &a->h_path, &delegated, a->flags);
+       if (unlikely(rerr == -EWOULDBLOCK)) {
+               pr_warn("cannot retry for NFSv4 delegation"
+                       " for an internal rename\n");
+               iput(delegated);
+       }
+       d_drop(a->h_path.dentry);
+       dput(a->h_path.dentry);
+       /* au_set_h_dptr(a->src_dentry, a->btgt, NULL); */
+       if (rerr)
+               RevertFailure("rename %pd", a->src_dentry);
+}
+
+static void au_ren_rev_whtmp(int err, struct au_ren_args *a)
+{
+       int rerr;
+       struct inode *delegated;
+       struct path h_ppath = {
+               .dentry = a->dst_h_parent,
+               .mnt    = a->h_path.mnt
+       };
+
+       a->h_path.dentry = vfsub_lkup_one(&a->dst_dentry->d_name, &h_ppath);
+       rerr = PTR_ERR(a->h_path.dentry);
+       if (IS_ERR(a->h_path.dentry)) {
+               RevertFailure("lkup one %pd", a->dst_dentry);
+               return;
+       }
+       if (d_is_positive(a->h_path.dentry)) {
+               d_drop(a->h_path.dentry);
+               dput(a->h_path.dentry);
+               return;
+       }
+
+       delegated = NULL;
+       rerr = vfsub_rename(a->dst_h_dir, a->h_dst, a->dst_h_dir, &a->h_path,
+                           &delegated, a->flags);
+       if (unlikely(rerr == -EWOULDBLOCK)) {
+               pr_warn("cannot retry for NFSv4 delegation"
+                       " for an internal rename\n");
+               iput(delegated);
+       }
+       d_drop(a->h_path.dentry);
+       dput(a->h_path.dentry);
+       if (!rerr)
+               au_set_h_dptr(a->dst_dentry, a->btgt, dget(a->h_dst));
+       else
+               RevertFailure("rename %pd", a->h_dst);
+}
+
+static void au_ren_rev_whsrc(int err, struct au_ren_args *a)
+{
+       int rerr;
+
+       a->h_path.dentry = a->src_wh_dentry;
+       rerr = au_wh_unlink_dentry(a->src_h_dir, &a->h_path, a->src_dentry);
+       au_set_dbwh(a->src_dentry, a->src_bwh);
+       if (rerr)
+               RevertFailure("unlink %pd", a->src_wh_dentry);
+}
+#undef RevertFailure
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * when we have to copyup the renaming entry, do it with the rename-target name
+ * in order to minimize the cost (the later actual rename is unnecessary).
+ * otherwise rename it on the target branch.
+ */
+static int au_ren_or_cpup(struct au_ren_args *a)
+{
+       int err;
+       struct dentry *d;
+       struct inode *delegated;
+
+       d = a->src_dentry;
+       if (au_dbtop(d) == a->btgt) {
+               a->h_path.dentry = a->dst_h_dentry;
+               AuDebugOn(au_dbtop(d) != a->btgt);
+               delegated = NULL;
+               err = vfsub_rename(a->src_h_dir, au_h_dptr(d, a->btgt),
+                                  a->dst_h_dir, &a->h_path, &delegated,
+                                  a->flags);
+               if (unlikely(err == -EWOULDBLOCK)) {
+                       pr_warn("cannot retry for NFSv4 delegation"
+                               " for an internal rename\n");
+                       iput(delegated);
+               }
+       } else
+               BUG();
+
+       if (!err && a->h_dst)
+               /* it will be set to dinfo later */
+               dget(a->h_dst);
+
+       return err;
+}
+
+/* cf. aufs_rmdir() */
+static int au_ren_del_whtmp(struct au_ren_args *a)
+{
+       int err;
+       struct inode *dir;
+
+       dir = a->dst_dir;
+       SiMustAnyLock(dir->i_sb);
+       if (!au_nhash_test_longer_wh(&a->whlist, a->btgt,
+                                    au_sbi(dir->i_sb)->si_dirwh)
+           || au_test_fs_remote(a->h_dst->d_sb)) {
+               err = au_whtmp_rmdir(dir, a->btgt, a->h_dst, &a->whlist);
+               if (unlikely(err))
+                       pr_warn("failed removing whtmp dir %pd (%d), "
+                               "ignored.\n", a->h_dst, err);
+       } else {
+               au_nhash_wh_free(&a->thargs->whlist);
+               a->thargs->whlist = a->whlist;
+               a->whlist.nh_num = 0;
+               au_whtmp_kick_rmdir(dir, a->btgt, a->h_dst, a->thargs);
+               dput(a->h_dst);
+               a->thargs = NULL;
+       }
+
+       return 0;
+}
+
+/* make it 'opaque' dir. */
+static int au_ren_do_diropq(struct au_ren_args *a, int idx)
+{
+       int err;
+       struct dentry *d, *diropq;
+#define src_or_dst(member) a->sd[idx].member
+
+       err = 0;
+       d = src_or_dst(dentry); /* {src,dst}_dentry */
+       src_or_dst(bdiropq) = au_dbdiropq(d);
+       src_or_dst(hinode) = au_hi(src_or_dst(inode), a->btgt);
+       au_hn_inode_lock_nested(src_or_dst(hinode), AuLsc_I_CHILD);
+       diropq = au_diropq_create(d, a->btgt);
+       au_hn_inode_unlock(src_or_dst(hinode));
+       if (IS_ERR(diropq))
+               err = PTR_ERR(diropq);
+       else
+               dput(diropq);
+
+#undef src_or_dst_
+       return err;
+}
+
+static int au_ren_diropq(struct au_ren_args *a)
+{
+       int err;
+       unsigned char always;
+       struct dentry *d;
+
+       err = 0;
+       d = a->dst_dentry; /* already renamed on the branch */
+       always = !!au_opt_test(au_mntflags(d->d_sb), ALWAYS_DIROPQ);
+       if (au_ftest_ren(a->auren_flags, ISDIR_SRC)
+           && !au_ftest_ren(a->auren_flags, DIRREN)
+           && a->btgt != au_dbdiropq(a->src_dentry)
+           && (a->dst_wh_dentry
+               || a->btgt <= au_dbdiropq(d)
+               /* hide the lower to keep xino */
+               /* the lowers may not be a dir, but we hide them anyway */
+               || a->btgt < au_dbbot(d)
+               || always)) {
+               AuDbg("here\n");
+               err = au_ren_do_diropq(a, AuSRC);
+               if (unlikely(err))
+                       goto out;
+               au_fset_ren(a->auren_flags, DIROPQ_SRC);
+       }
+       if (!a->exchange)
+               goto out; /* success */
+
+       d = a->src_dentry; /* already renamed on the branch */
+       if (au_ftest_ren(a->auren_flags, ISDIR_DST)
+           && a->btgt != au_dbdiropq(a->dst_dentry)
+           && (a->btgt < au_dbdiropq(d)
+               || a->btgt < au_dbbot(d)
+               || always)) {
+               AuDbgDentry(a->src_dentry);
+               AuDbgDentry(a->dst_dentry);
+               err = au_ren_do_diropq(a, AuDST);
+               if (unlikely(err))
+                       goto out_rev_src;
+               au_fset_ren(a->auren_flags, DIROPQ_DST);
+       }
+       goto out; /* success */
+
+out_rev_src:
+       AuDbg("err %d, reverting src\n", err);
+       au_ren_rev_diropq(err, a);
+out:
+       return err;
+}
+
+static int do_rename(struct au_ren_args *a)
+{
+       int err;
+       struct dentry *d, *h_d;
+
+       if (!a->exchange) {
+               /* prepare workqueue args for asynchronous rmdir */
+               h_d = a->dst_h_dentry;
+               if (au_ftest_ren(a->auren_flags, ISDIR_DST)
+                   /* && !au_ftest_ren(a->auren_flags, DIRREN) */
+                   && d_is_positive(h_d)) {
+                       err = -ENOMEM;
+                       a->thargs = au_whtmp_rmdir_alloc(a->src_dentry->d_sb,
+                                                        GFP_NOFS);
+                       if (unlikely(!a->thargs))
+                               goto out;
+                       a->h_dst = dget(h_d);
+               }
+
+               /* create whiteout for src_dentry */
+               if (au_ftest_ren(a->auren_flags, WHSRC)) {
+                       a->src_bwh = au_dbwh(a->src_dentry);
+                       AuDebugOn(a->src_bwh >= 0);
+                       a->src_wh_dentry = au_wh_create(a->src_dentry, a->btgt,
+                                                       a->src_h_parent);
+                       err = PTR_ERR(a->src_wh_dentry);
+                       if (IS_ERR(a->src_wh_dentry))
+                               goto out_thargs;
+               }
+
+               /* lookup whiteout for dentry */
+               if (au_ftest_ren(a->auren_flags, WHDST)) {
+                       h_d = au_wh_lkup(a->dst_h_parent,
+                                        &a->dst_dentry->d_name, a->br);
+                       err = PTR_ERR(h_d);
+                       if (IS_ERR(h_d))
+                               goto out_whsrc;
+                       if (d_is_negative(h_d))
+                               dput(h_d);
+                       else
+                               a->dst_wh_dentry = h_d;
+               }
+
+               /* rename dentry to tmpwh */
+               if (a->thargs) {
+                       err = au_whtmp_ren(a->dst_h_dentry, a->br);
+                       if (unlikely(err))
+                               goto out_whdst;
+
+                       d = a->dst_dentry;
+                       au_set_h_dptr(d, a->btgt, NULL);
+                       err = au_lkup_neg(d, a->btgt, /*wh*/0);
+                       if (unlikely(err))
+                               goto out_whtmp;
+                       a->dst_h_dentry = au_h_dptr(d, a->btgt);
+               }
+       }
+
+       BUG_ON(d_is_positive(a->dst_h_dentry) && a->src_btop != a->btgt);
+#if 0 /* debugging */
+       BUG_ON(!au_ftest_ren(a->auren_flags, DIRREN)
+              && d_is_positive(a->dst_h_dentry)
+              && a->src_btop != a->btgt);
+#endif
+
+       /* rename by vfs_rename or cpup */
+       err = au_ren_or_cpup(a);
+       if (unlikely(err))
+               /* leave the copied-up one */
+               goto out_whtmp;
+
+       /* make dir opaque */
+       err = au_ren_diropq(a);
+       if (unlikely(err))
+               goto out_rename;
+
+       /* update target timestamps */
+       if (a->exchange) {
+               AuDebugOn(au_dbtop(a->dst_dentry) != a->btgt);
+               a->h_path.dentry = au_h_dptr(a->dst_dentry, a->btgt);
+               vfsub_update_h_iattr(&a->h_path, /*did*/NULL); /*ignore*/
+               a->dst_inode->i_ctime = d_inode(a->h_path.dentry)->i_ctime;
+       }
+       AuDebugOn(au_dbtop(a->src_dentry) != a->btgt);
+       a->h_path.dentry = au_h_dptr(a->src_dentry, a->btgt);
+       vfsub_update_h_iattr(&a->h_path, /*did*/NULL); /*ignore*/
+       a->src_inode->i_ctime = d_inode(a->h_path.dentry)->i_ctime;
+
+       if (!a->exchange) {
+               /* remove whiteout for dentry */
+               if (a->dst_wh_dentry) {
+                       a->h_path.dentry = a->dst_wh_dentry;
+                       err = au_wh_unlink_dentry(a->dst_h_dir, &a->h_path,
+                                                 a->dst_dentry);
+                       if (unlikely(err))
+                               goto out_diropq;
+               }
+
+               /* remove whtmp */
+               if (a->thargs)
+                       au_ren_del_whtmp(a); /* ignore this error */
+
+               au_fhsm_wrote(a->src_dentry->d_sb, a->btgt, /*force*/0);
+       }
+       err = 0;
+       goto out_success;
+
+out_diropq:
+       au_ren_rev_diropq(err, a);
+out_rename:
+       au_ren_rev_rename(err, a);
+       dput(a->h_dst);
+out_whtmp:
+       if (a->thargs)
+               au_ren_rev_whtmp(err, a);
+out_whdst:
+       dput(a->dst_wh_dentry);
+       a->dst_wh_dentry = NULL;
+out_whsrc:
+       if (a->src_wh_dentry)
+               au_ren_rev_whsrc(err, a);
+out_success:
+       dput(a->src_wh_dentry);
+       dput(a->dst_wh_dentry);
+out_thargs:
+       if (a->thargs) {
+               dput(a->h_dst);
+               au_whtmp_rmdir_free(a->thargs);
+               a->thargs = NULL;
+       }
+out:
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * test if @dentry dir can be rename destination or not.
+ * success means, it is a logically empty dir.
+ */
+static int may_rename_dstdir(struct dentry *dentry, struct au_nhash *whlist)
+{
+       return au_test_empty(dentry, whlist);
+}
+
+/*
+ * test if @a->src_dentry dir can be rename source or not.
+ * if it can, return 0.
+ * success means,
+ * - it is a logically empty dir.
+ * - or, it exists on writable branch and has no children including whiteouts
+ *   on the lower branch unless DIRREN is on.
+ */
+static int may_rename_srcdir(struct au_ren_args *a)
+{
+       int err;
+       unsigned int rdhash;
+       aufs_bindex_t btop, btgt;
+       struct dentry *dentry;
+       struct super_block *sb;
+       struct au_sbinfo *sbinfo;
+
+       dentry = a->src_dentry;
+       sb = dentry->d_sb;
+       sbinfo = au_sbi(sb);
+       if (au_opt_test(sbinfo->si_mntflags, DIRREN))
+               au_fset_ren(a->auren_flags, DIRREN);
+
+       btgt = a->btgt;
+       btop = au_dbtop(dentry);
+       if (btop != btgt) {
+               struct au_nhash whlist;
+
+               SiMustAnyLock(sb);
+               rdhash = sbinfo->si_rdhash;
+               if (!rdhash)
+                       rdhash = au_rdhash_est(au_dir_size(/*file*/NULL,
+                                                          dentry));
+               err = au_nhash_alloc(&whlist, rdhash, GFP_NOFS);
+               if (unlikely(err))
+                       goto out;
+               err = au_test_empty(dentry, &whlist);
+               au_nhash_wh_free(&whlist);
+               goto out;
+       }
+
+       if (btop == au_dbtaildir(dentry))
+               return 0; /* success */
+
+       err = au_test_empty_lower(dentry);
+
+out:
+       if (err == -ENOTEMPTY) {
+               if (au_ftest_ren(a->auren_flags, DIRREN)) {
+                       err = 0;
+               } else {
+                       AuWarn1("renaming dir who has child(ren) on multiple "
+                               "branches, is not supported\n");
+                       err = -EXDEV;
+               }
+       }
+       return err;
+}
+
+/* side effect: sets whlist and h_dentry */
+static int au_ren_may_dir(struct au_ren_args *a)
+{
+       int err;
+       unsigned int rdhash;
+       struct dentry *d;
+
+       d = a->dst_dentry;
+       SiMustAnyLock(d->d_sb);
+
+       err = 0;
+       if (au_ftest_ren(a->auren_flags, ISDIR_DST) && a->dst_inode) {
+               rdhash = au_sbi(d->d_sb)->si_rdhash;
+               if (!rdhash)
+                       rdhash = au_rdhash_est(au_dir_size(/*file*/NULL, d));
+               err = au_nhash_alloc(&a->whlist, rdhash, GFP_NOFS);
+               if (unlikely(err))
+                       goto out;
+
+               if (!a->exchange) {
+                       au_set_dbtop(d, a->dst_btop);
+                       err = may_rename_dstdir(d, &a->whlist);
+                       au_set_dbtop(d, a->btgt);
+               } else
+                       err = may_rename_srcdir(a);
+       }
+       a->dst_h_dentry = au_h_dptr(d, au_dbtop(d));
+       if (unlikely(err))
+               goto out;
+
+       d = a->src_dentry;
+       a->src_h_dentry = au_h_dptr(d, au_dbtop(d));
+       if (au_ftest_ren(a->auren_flags, ISDIR_SRC)) {
+               err = may_rename_srcdir(a);
+               if (unlikely(err)) {
+                       au_nhash_wh_free(&a->whlist);
+                       a->whlist.nh_num = 0;
+               }
+       }
+out:
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * simple tests for rename.
+ * following the checks in vfs, plus the parent-child relationship.
+ */
+static int au_may_ren(struct au_ren_args *a)
+{
+       int err, isdir;
+       struct inode *h_inode;
+
+       if (a->src_btop == a->btgt) {
+               err = au_may_del(a->src_dentry, a->btgt, a->src_h_parent,
+                                au_ftest_ren(a->auren_flags, ISDIR_SRC));
+               if (unlikely(err))
+                       goto out;
+               err = -EINVAL;
+               if (unlikely(a->src_h_dentry == a->h_trap))
+                       goto out;
+       }
+
+       err = 0;
+       if (a->dst_btop != a->btgt)
+               goto out;
+
+       err = -ENOTEMPTY;
+       if (unlikely(a->dst_h_dentry == a->h_trap))
+               goto out;
+
+       err = -EIO;
+       isdir = !!au_ftest_ren(a->auren_flags, ISDIR_DST);
+       if (d_really_is_negative(a->dst_dentry)) {
+               if (d_is_negative(a->dst_h_dentry))
+                       err = au_may_add(a->dst_dentry, a->btgt,
+                                        a->dst_h_parent, isdir);
+       } else {
+               if (unlikely(d_is_negative(a->dst_h_dentry)))
+                       goto out;
+               h_inode = d_inode(a->dst_h_dentry);
+               if (h_inode->i_nlink)
+                       err = au_may_del(a->dst_dentry, a->btgt,
+                                        a->dst_h_parent, isdir);
+       }
+
+out:
+       if (unlikely(err == -ENOENT || err == -EEXIST))
+               err = -EIO;
+       AuTraceErr(err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * locking order
+ * (VFS)
+ * - src_dir and dir by lock_rename()
+ * - inode if exists
+ * (aufs)
+ * - lock all
+ *   + src_dentry and dentry by aufs_read_and_write_lock2() which calls,
+ *     + si_read_lock
+ *     + di_write_lock2_child()
+ *       + di_write_lock_child()
+ *        + ii_write_lock_child()
+ *       + di_write_lock_child2()
+ *        + ii_write_lock_child2()
+ *     + src_parent and parent
+ *       + di_write_lock_parent()
+ *        + ii_write_lock_parent()
+ *       + di_write_lock_parent2()
+ *        + ii_write_lock_parent2()
+ *   + lower src_dir and dir by vfsub_lock_rename()
+ *   + verify the every relationships between child and parent. if any
+ *     of them failed, unlock all and return -EBUSY.
+ */
+static void au_ren_unlock(struct au_ren_args *a)
+{
+       vfsub_unlock_rename(a->src_h_parent, a->src_hdir,
+                           a->dst_h_parent, a->dst_hdir);
+       if (au_ftest_ren(a->auren_flags, DIRREN)
+           && a->h_root)
+               au_hn_inode_unlock(a->h_root);
+       if (au_ftest_ren(a->auren_flags, MNT_WRITE))
+               vfsub_mnt_drop_write(au_br_mnt(a->br));
+}
+
+static int au_ren_lock(struct au_ren_args *a)
+{
+       int err;
+       unsigned int udba;
+
+       err = 0;
+       a->src_h_parent = au_h_dptr(a->src_parent, a->btgt);
+       a->src_hdir = au_hi(a->src_dir, a->btgt);
+       a->dst_h_parent = au_h_dptr(a->dst_parent, a->btgt);
+       a->dst_hdir = au_hi(a->dst_dir, a->btgt);
+
+       err = vfsub_mnt_want_write(au_br_mnt(a->br));
+       if (unlikely(err))
+               goto out;
+       au_fset_ren(a->auren_flags, MNT_WRITE);
+       if (au_ftest_ren(a->auren_flags, DIRREN)) {
+               struct dentry *root;
+               struct inode *dir;
+
+               /*
+                * sbinfo is already locked, so this ii_read_lock is
+                * unnecessary. but our debugging feature checks it.
+                */
+               root = a->src_inode->i_sb->s_root;
+               if (root != a->src_parent && root != a->dst_parent) {
+                       dir = d_inode(root);
+                       ii_read_lock_parent3(dir);
+                       a->h_root = au_hi(dir, a->btgt);
+                       ii_read_unlock(dir);
+                       au_hn_inode_lock_nested(a->h_root, AuLsc_I_PARENT3);
+               }
+       }
+       a->h_trap = vfsub_lock_rename(a->src_h_parent, a->src_hdir,
+                                     a->dst_h_parent, a->dst_hdir);
+       udba = au_opt_udba(a->src_dentry->d_sb);
+       if (unlikely(a->src_hdir->hi_inode != d_inode(a->src_h_parent)
+                    || a->dst_hdir->hi_inode != d_inode(a->dst_h_parent)))
+               err = au_busy_or_stale();
+       if (!err && au_dbtop(a->src_dentry) == a->btgt)
+               err = au_h_verify(a->src_h_dentry, udba,
+                                 d_inode(a->src_h_parent), a->src_h_parent,
+                                 a->br);
+       if (!err && au_dbtop(a->dst_dentry) == a->btgt)
+               err = au_h_verify(a->dst_h_dentry, udba,
+                                 d_inode(a->dst_h_parent), a->dst_h_parent,
+                                 a->br);
+       if (!err)
+               goto out; /* success */
+
+       err = au_busy_or_stale();
+       au_ren_unlock(a);
+
+out:
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static void au_ren_refresh_dir(struct au_ren_args *a)
+{
+       struct inode *dir;
+
+       dir = a->dst_dir;
+       inode_inc_iversion(dir);
+       if (au_ftest_ren(a->auren_flags, ISDIR_SRC)) {
+               /* is this updating defined in POSIX? */
+               au_cpup_attr_timesizes(a->src_inode);
+               au_cpup_attr_nlink(dir, /*force*/1);
+       }
+       au_dir_ts(dir, a->btgt);
+
+       if (a->exchange) {
+               dir = a->src_dir;
+               inode_inc_iversion(dir);
+               if (au_ftest_ren(a->auren_flags, ISDIR_DST)) {
+                       /* is this updating defined in POSIX? */
+                       au_cpup_attr_timesizes(a->dst_inode);
+                       au_cpup_attr_nlink(dir, /*force*/1);
+               }
+               au_dir_ts(dir, a->btgt);
+       }
+
+       if (au_ftest_ren(a->auren_flags, ISSAMEDIR))
+               return;
+
+       dir = a->src_dir;
+       inode_inc_iversion(dir);
+       if (au_ftest_ren(a->auren_flags, ISDIR_SRC))
+               au_cpup_attr_nlink(dir, /*force*/1);
+       au_dir_ts(dir, a->btgt);
+}
+
+static void au_ren_refresh(struct au_ren_args *a)
+{
+       aufs_bindex_t bbot, bindex;
+       struct dentry *d, *h_d;
+       struct inode *i, *h_i;
+       struct super_block *sb;
+
+       d = a->dst_dentry;
+       d_drop(d);
+       if (a->h_dst)
+               /* already dget-ed by au_ren_or_cpup() */
+               au_set_h_dptr(d, a->btgt, a->h_dst);
+
+       i = a->dst_inode;
+       if (i) {
+               if (!a->exchange) {
+                       if (!au_ftest_ren(a->auren_flags, ISDIR_DST))
+                               vfsub_drop_nlink(i);
+                       else {
+                               vfsub_dead_dir(i);
+                               au_cpup_attr_timesizes(i);
+                       }
+                       au_update_dbrange(d, /*do_put_zero*/1);
+               } else
+                       au_cpup_attr_nlink(i, /*force*/1);
+       } else {
+               bbot = a->btgt;
+               for (bindex = au_dbtop(d); bindex < bbot; bindex++)
+                       au_set_h_dptr(d, bindex, NULL);
+               bbot = au_dbbot(d);
+               for (bindex = a->btgt + 1; bindex <= bbot; bindex++)
+                       au_set_h_dptr(d, bindex, NULL);
+               au_update_dbrange(d, /*do_put_zero*/0);
+       }
+
+       if (a->exchange
+           || au_ftest_ren(a->auren_flags, DIRREN)) {
+               d_drop(a->src_dentry);
+               if (au_ftest_ren(a->auren_flags, DIRREN))
+                       au_set_dbwh(a->src_dentry, -1);
+               return;
+       }
+
+       d = a->src_dentry;
+       au_set_dbwh(d, -1);
+       bbot = au_dbbot(d);
+       for (bindex = a->btgt + 1; bindex <= bbot; bindex++) {
+               h_d = au_h_dptr(d, bindex);
+               if (h_d)
+                       au_set_h_dptr(d, bindex, NULL);
+       }
+       au_set_dbbot(d, a->btgt);
+
+       sb = d->d_sb;
+       i = a->src_inode;
+       if (au_opt_test(au_mntflags(sb), PLINK) && au_plink_test(i))
+               return; /* success */
+
+       bbot = au_ibbot(i);
+       for (bindex = a->btgt + 1; bindex <= bbot; bindex++) {
+               h_i = au_h_iptr(i, bindex);
+               if (h_i) {
+                       au_xino_write(sb, bindex, h_i->i_ino, /*ino*/0);
+                       /* ignore this error */
+                       au_set_h_iptr(i, bindex, NULL, 0);
+               }
+       }
+       au_set_ibbot(i, a->btgt);
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* mainly for link(2) and rename(2) */
+int au_wbr(struct dentry *dentry, aufs_bindex_t btgt)
+{
+       aufs_bindex_t bdiropq, bwh;
+       struct dentry *parent;
+       struct au_branch *br;
+
+       parent = dentry->d_parent;
+       IMustLock(d_inode(parent)); /* dir is locked */
+
+       bdiropq = au_dbdiropq(parent);
+       bwh = au_dbwh(dentry);
+       br = au_sbr(dentry->d_sb, btgt);
+       if (au_br_rdonly(br)
+           || (0 <= bdiropq && bdiropq < btgt)
+           || (0 <= bwh && bwh < btgt))
+               btgt = -1;
+
+       AuDbg("btgt %d\n", btgt);
+       return btgt;
+}
+
+/* sets src_btop, dst_btop and btgt */
+static int au_ren_wbr(struct au_ren_args *a)
+{
+       int err;
+       struct au_wr_dir_args wr_dir_args = {
+               /* .force_btgt  = -1, */
+               .flags          = AuWrDir_ADD_ENTRY
+       };
+
+       a->src_btop = au_dbtop(a->src_dentry);
+       a->dst_btop = au_dbtop(a->dst_dentry);
+       if (au_ftest_ren(a->auren_flags, ISDIR_SRC)
+           || au_ftest_ren(a->auren_flags, ISDIR_DST))
+               au_fset_wrdir(wr_dir_args.flags, ISDIR);
+       wr_dir_args.force_btgt = a->src_btop;
+       if (a->dst_inode && a->dst_btop < a->src_btop)
+               wr_dir_args.force_btgt = a->dst_btop;
+       wr_dir_args.force_btgt = au_wbr(a->dst_dentry, wr_dir_args.force_btgt);
+       err = au_wr_dir(a->dst_dentry, a->src_dentry, &wr_dir_args);
+       a->btgt = err;
+       if (a->exchange)
+               au_update_dbtop(a->dst_dentry);
+
+       return err;
+}
+
+static void au_ren_dt(struct au_ren_args *a)
+{
+       a->h_path.dentry = a->src_h_parent;
+       au_dtime_store(a->src_dt + AuPARENT, a->src_parent, &a->h_path);
+       if (!au_ftest_ren(a->auren_flags, ISSAMEDIR)) {
+               a->h_path.dentry = a->dst_h_parent;
+               au_dtime_store(a->dst_dt + AuPARENT, a->dst_parent, &a->h_path);
+       }
+
+       au_fclr_ren(a->auren_flags, DT_DSTDIR);
+       if (!au_ftest_ren(a->auren_flags, ISDIR_SRC)
+           && !a->exchange)
+               return;
+
+       a->h_path.dentry = a->src_h_dentry;
+       au_dtime_store(a->src_dt + AuCHILD, a->src_dentry, &a->h_path);
+       if (d_is_positive(a->dst_h_dentry)) {
+               au_fset_ren(a->auren_flags, DT_DSTDIR);
+               a->h_path.dentry = a->dst_h_dentry;
+               au_dtime_store(a->dst_dt + AuCHILD, a->dst_dentry, &a->h_path);
+       }
+}
+
+static void au_ren_rev_dt(int err, struct au_ren_args *a)
+{
+       struct dentry *h_d;
+       struct inode *h_inode;
+
+       au_dtime_revert(a->src_dt + AuPARENT);
+       if (!au_ftest_ren(a->auren_flags, ISSAMEDIR))
+               au_dtime_revert(a->dst_dt + AuPARENT);
+
+       if (au_ftest_ren(a->auren_flags, ISDIR_SRC) && err != -EIO) {
+               h_d = a->src_dt[AuCHILD].dt_h_path.dentry;
+               h_inode = d_inode(h_d);
+               inode_lock_nested(h_inode, AuLsc_I_CHILD);
+               au_dtime_revert(a->src_dt + AuCHILD);
+               inode_unlock(h_inode);
+
+               if (au_ftest_ren(a->auren_flags, DT_DSTDIR)) {
+                       h_d = a->dst_dt[AuCHILD].dt_h_path.dentry;
+                       h_inode = d_inode(h_d);
+                       inode_lock_nested(h_inode, AuLsc_I_CHILD);
+                       au_dtime_revert(a->dst_dt + AuCHILD);
+                       inode_unlock(h_inode);
+               }
+       }
+}
+
+/* ---------------------------------------------------------------------- */
+
+int aufs_rename(struct user_namespace *userns,
+               struct inode *_src_dir, struct dentry *_src_dentry,
+               struct inode *_dst_dir, struct dentry *_dst_dentry,
+               unsigned int _flags)
+{
+       int err, lock_flags;
+       void *rev;
+       /* reduce stack space */
+       struct au_ren_args *a;
+       struct au_pin pin;
+
+       AuDbg("%pd, %pd, 0x%x\n", _src_dentry, _dst_dentry, _flags);
+       IMustLock(_src_dir);
+       IMustLock(_dst_dir);
+
+       err = -EINVAL;
+       if (unlikely(_flags & RENAME_WHITEOUT))
+               goto out;
+
+       err = -ENOMEM;
+       BUILD_BUG_ON(sizeof(*a) > PAGE_SIZE);
+       a = kzalloc(sizeof(*a), GFP_NOFS);
+       if (unlikely(!a))
+               goto out;
+
+       a->flags = _flags;
+       BUILD_BUG_ON(sizeof(a->exchange) == sizeof(u8)
+                    && RENAME_EXCHANGE > U8_MAX);
+       a->exchange = _flags & RENAME_EXCHANGE;
+       a->src_dir = _src_dir;
+       a->src_dentry = _src_dentry;
+       a->src_inode = NULL;
+       if (d_really_is_positive(a->src_dentry))
+               a->src_inode = d_inode(a->src_dentry);
+       a->src_parent = a->src_dentry->d_parent; /* dir inode is locked */
+       a->dst_dir = _dst_dir;
+       a->dst_dentry = _dst_dentry;
+       a->dst_inode = NULL;
+       if (d_really_is_positive(a->dst_dentry))
+               a->dst_inode = d_inode(a->dst_dentry);
+       a->dst_parent = a->dst_dentry->d_parent; /* dir inode is locked */
+       if (a->dst_inode) {
+               /*
+                * if EXCHANGE && src is non-dir && dst is dir,
+                * dst is not locked.
+                */
+               /* IMustLock(a->dst_inode); */
+               au_igrab(a->dst_inode);
+       }
+
+       err = -ENOTDIR;
+       lock_flags = AuLock_FLUSH | AuLock_NOPLM | AuLock_GEN;
+       if (d_is_dir(a->src_dentry)) {
+               au_fset_ren(a->auren_flags, ISDIR_SRC);
+               if (unlikely(!a->exchange
+                            && d_really_is_positive(a->dst_dentry)
+                            && !d_is_dir(a->dst_dentry)))
+                       goto out_free;
+               lock_flags |= AuLock_DIRS;
+       }
+       if (a->dst_inode && d_is_dir(a->dst_dentry)) {
+               au_fset_ren(a->auren_flags, ISDIR_DST);
+               if (unlikely(!a->exchange
+                            && d_really_is_positive(a->src_dentry)
+                            && !d_is_dir(a->src_dentry)))
+                       goto out_free;
+               lock_flags |= AuLock_DIRS;
+       }
+       err = aufs_read_and_write_lock2(a->dst_dentry, a->src_dentry,
+                                       lock_flags);
+       if (unlikely(err))
+               goto out_free;
+
+       err = au_d_hashed_positive(a->src_dentry);
+       if (unlikely(err))
+               goto out_unlock;
+       err = -ENOENT;
+       if (a->dst_inode) {
+               /*
+                * If it is a dir, VFS unhash it before this
+                * function. It means we cannot rely upon d_unhashed().
+                */
+               if (unlikely(!a->dst_inode->i_nlink))
+                       goto out_unlock;
+               if (!au_ftest_ren(a->auren_flags, ISDIR_DST)) {
+                       err = au_d_hashed_positive(a->dst_dentry);
+                       if (unlikely(err && !a->exchange))
+                               goto out_unlock;
+               } else if (unlikely(IS_DEADDIR(a->dst_inode)))
+                       goto out_unlock;
+       } else if (unlikely(d_unhashed(a->dst_dentry)))
+               goto out_unlock;
+
+       /*
+        * is it possible?
+        * yes, it happened (in linux-3.3-rcN) but I don't know why.
+        * there may exist a problem somewhere else.
+        */
+       err = -EINVAL;
+       if (unlikely(d_inode(a->dst_parent) == d_inode(a->src_dentry)))
+               goto out_unlock;
+
+       au_fset_ren(a->auren_flags, ISSAMEDIR); /* temporary */
+       di_write_lock_parent(a->dst_parent);
+
+       /* which branch we process */
+       err = au_ren_wbr(a);
+       if (unlikely(err < 0))
+               goto out_parent;
+       a->br = au_sbr(a->dst_dentry->d_sb, a->btgt);
+       a->h_path.mnt = au_br_mnt(a->br);
+
+       /* are they available to be renamed */
+       err = au_ren_may_dir(a);
+       if (unlikely(err))
+               goto out_children;
+
+       /* prepare the writable parent dir on the same branch */
+       if (a->dst_btop == a->btgt) {
+               au_fset_ren(a->auren_flags, WHDST);
+       } else {
+               err = au_cpup_dirs(a->dst_dentry, a->btgt);
+               if (unlikely(err))
+                       goto out_children;
+       }
+
+       err = 0;
+       if (!a->exchange) {
+               if (a->src_dir != a->dst_dir) {
+                       /*
+                        * this temporary unlock is safe,
+                        * because both dir->i_mutex are locked.
+                        */
+                       di_write_unlock(a->dst_parent);
+                       di_write_lock_parent(a->src_parent);
+                       err = au_wr_dir_need_wh(a->src_dentry,
+                                               au_ftest_ren(a->auren_flags,
+                                                            ISDIR_SRC),
+                                               &a->btgt);
+                       di_write_unlock(a->src_parent);
+                       di_write_lock2_parent(a->src_parent, a->dst_parent,
+                                             /*isdir*/1);
+                       au_fclr_ren(a->auren_flags, ISSAMEDIR);
+               } else
+                       err = au_wr_dir_need_wh(a->src_dentry,
+                                               au_ftest_ren(a->auren_flags,
+                                                            ISDIR_SRC),
+                                               &a->btgt);
+       }
+       if (unlikely(err < 0))
+               goto out_children;
+       if (err)
+               au_fset_ren(a->auren_flags, WHSRC);
+
+       /* cpup src */
+       if (a->src_btop != a->btgt) {
+               err = au_pin(&pin, a->src_dentry, a->btgt,
+                            au_opt_udba(a->src_dentry->d_sb),
+                            AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+               if (!err) {
+                       struct au_cp_generic cpg = {
+                               .dentry = a->src_dentry,
+                               .bdst   = a->btgt,
+                               .bsrc   = a->src_btop,
+                               .len    = -1,
+                               .pin    = &pin,
+                               .flags  = AuCpup_DTIME | AuCpup_HOPEN
+                       };
+                       AuDebugOn(au_dbtop(a->src_dentry) != a->src_btop);
+                       err = au_sio_cpup_simple(&cpg);
+                       au_unpin(&pin);
+               }
+               if (unlikely(err))
+                       goto out_children;
+               a->src_btop = a->btgt;
+               a->src_h_dentry = au_h_dptr(a->src_dentry, a->btgt);
+               if (!a->exchange)
+                       au_fset_ren(a->auren_flags, WHSRC);
+       }
+
+       /* cpup dst */
+       if (a->exchange && a->dst_inode
+           && a->dst_btop != a->btgt) {
+               err = au_pin(&pin, a->dst_dentry, a->btgt,
+                            au_opt_udba(a->dst_dentry->d_sb),
+                            AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+               if (!err) {
+                       struct au_cp_generic cpg = {
+                               .dentry = a->dst_dentry,
+                               .bdst   = a->btgt,
+                               .bsrc   = a->dst_btop,
+                               .len    = -1,
+                               .pin    = &pin,
+                               .flags  = AuCpup_DTIME | AuCpup_HOPEN
+                       };
+                       err = au_sio_cpup_simple(&cpg);
+                       au_unpin(&pin);
+               }
+               if (unlikely(err))
+                       goto out_children;
+               a->dst_btop = a->btgt;
+               a->dst_h_dentry = au_h_dptr(a->dst_dentry, a->btgt);
+       }
+
+       /* lock them all */
+       err = au_ren_lock(a);
+       if (unlikely(err))
+               /* leave the copied-up one */
+               goto out_children;
+
+       if (!a->exchange) {
+               if (!au_opt_test(au_mntflags(a->dst_dir->i_sb), UDBA_NONE))
+                       err = au_may_ren(a);
+               else if (unlikely(a->dst_dentry->d_name.len > AUFS_MAX_NAMELEN))
+                       err = -ENAMETOOLONG;
+               if (unlikely(err))
+                       goto out_hdir;
+       }
+
+       /* store timestamps to be revertible */
+       au_ren_dt(a);
+
+       /* store dirren info */
+       if (au_ftest_ren(a->auren_flags, DIRREN)) {
+               err = au_dr_rename(a->src_dentry, a->btgt,
+                                  &a->dst_dentry->d_name, &rev);
+               AuTraceErr(err);
+               if (unlikely(err))
+                       goto out_dt;
+       }
+
+       /* here we go */
+       err = do_rename(a);
+       if (unlikely(err))
+               goto out_dirren;
+
+       if (au_ftest_ren(a->auren_flags, DIRREN))
+               au_dr_rename_fin(a->src_dentry, a->btgt, rev);
+
+       /* update dir attributes */
+       au_ren_refresh_dir(a);
+
+       /* dput/iput all lower dentries */
+       au_ren_refresh(a);
+
+       goto out_hdir; /* success */
+
+out_dirren:
+       if (au_ftest_ren(a->auren_flags, DIRREN))
+               au_dr_rename_rev(a->src_dentry, a->btgt, rev);
+out_dt:
+       au_ren_rev_dt(err, a);
+out_hdir:
+       au_ren_unlock(a);
+out_children:
+       au_nhash_wh_free(&a->whlist);
+       if (err && a->dst_inode && a->dst_btop != a->btgt) {
+               AuDbg("btop %d, btgt %d\n", a->dst_btop, a->btgt);
+               au_set_h_dptr(a->dst_dentry, a->btgt, NULL);
+               au_set_dbtop(a->dst_dentry, a->dst_btop);
+       }
+out_parent:
+       if (!err) {
+               if (d_unhashed(a->src_dentry))
+                       au_fset_ren(a->auren_flags, DROPPED_SRC);
+               if (d_unhashed(a->dst_dentry))
+                       au_fset_ren(a->auren_flags, DROPPED_DST);
+               if (!a->exchange)
+                       d_move(a->src_dentry, a->dst_dentry);
+               else {
+                       d_exchange(a->src_dentry, a->dst_dentry);
+                       if (au_ftest_ren(a->auren_flags, DROPPED_DST))
+                               d_drop(a->dst_dentry);
+               }
+               if (au_ftest_ren(a->auren_flags, DROPPED_SRC))
+                       d_drop(a->src_dentry);
+       } else {
+               au_update_dbtop(a->dst_dentry);
+               if (!a->dst_inode)
+                       d_drop(a->dst_dentry);
+       }
+       if (au_ftest_ren(a->auren_flags, ISSAMEDIR))
+               di_write_unlock(a->dst_parent);
+       else
+               di_write_unlock2(a->src_parent, a->dst_parent);
+out_unlock:
+       aufs_read_and_write_unlock2(a->dst_dentry, a->src_dentry);
+out_free:
+       iput(a->dst_inode);
+       if (a->thargs)
+               au_whtmp_rmdir_free(a->thargs);
+       au_kfree_rcu(a);
+out:
+       AuTraceErr(err);
+       return err;
+}
diff -urN /usr/share/empty/fs/aufs/Kconfig linux/fs/aufs/Kconfig
--- /usr/share/empty/fs/aufs/Kconfig    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/Kconfig       2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,199 @@
+# SPDX-License-Identifier: GPL-2.0
+config AUFS_FS
+       tristate "Aufs (Advanced multi layered unification filesystem) support"
+       help
+       Aufs is a stackable unification filesystem such as Unionfs,
+       which unifies several directories and provides a merged single
+       directory.
+       In the early days, aufs was entirely re-designed and
+       re-implemented Unionfs Version 1.x series. Introducing many
+       original ideas, approaches and improvements, it becomes totally
+       different from Unionfs while keeping the basic features.
+
+if AUFS_FS
+choice
+       prompt "Maximum number of branches"
+       default AUFS_BRANCH_MAX_127
+       help
+       Specifies the maximum number of branches (or member directories)
+       in a single aufs. The larger value consumes more system
+       resources and has a minor impact to performance.
+config AUFS_BRANCH_MAX_127
+       bool "127"
+       help
+       Specifies the maximum number of branches (or member directories)
+       in a single aufs. The larger value consumes more system
+       resources and has a minor impact to performance.
+config AUFS_BRANCH_MAX_511
+       bool "511"
+       help
+       Specifies the maximum number of branches (or member directories)
+       in a single aufs. The larger value consumes more system
+       resources and has a minor impact to performance.
+config AUFS_BRANCH_MAX_1023
+       bool "1023"
+       help
+       Specifies the maximum number of branches (or member directories)
+       in a single aufs. The larger value consumes more system
+       resources and has a minor impact to performance.
+config AUFS_BRANCH_MAX_32767
+       bool "32767"
+       help
+       Specifies the maximum number of branches (or member directories)
+       in a single aufs. The larger value consumes more system
+       resources and has a minor impact to performance.
+endchoice
+
+config AUFS_SBILIST
+       bool
+       depends on AUFS_MAGIC_SYSRQ || PROC_FS
+       default y
+       help
+       Automatic configuration for internal use.
+       When aufs supports Magic SysRq or /proc, enabled automatically.
+
+config AUFS_HNOTIFY
+       bool "Detect direct branch access (bypassing aufs)"
+       help
+       If you want to modify files on branches directly, eg. bypassing aufs,
+       and want aufs to detect the changes of them fully, then enable this
+       option and use 'udba=notify' mount option.
+       Currently there is only one available configuration, "fsnotify".
+       It will have a negative impact to the performance.
+       See detail in aufs.5.
+
+choice
+       prompt "method" if AUFS_HNOTIFY
+       default AUFS_HFSNOTIFY
+config AUFS_HFSNOTIFY
+       bool "fsnotify"
+       select FSNOTIFY
+endchoice
+
+config AUFS_EXPORT
+       bool "NFS-exportable aufs"
+       depends on EXPORTFS
+       help
+       If you want to export your mounted aufs via NFS, then enable this
+       option. There are several requirements for this configuration.
+       See detail in aufs.5.
+
+config AUFS_INO_T_64
+       bool
+       depends on AUFS_EXPORT
+       depends on 64BIT && !(ALPHA || S390)
+       default y
+       help
+       Automatic configuration for internal use.
+       /* typedef unsigned long/int __kernel_ino_t */
+       /* alpha and s390x are int */
+
+config AUFS_XATTR
+       bool "support for XATTR/EA (including Security Labels)"
+       help
+       If your branch fs supports XATTR/EA and you want to make them
+       available in aufs too, then enable this opsion and specify the
+       branch attributes for EA.
+       See detail in aufs.5.
+
+config AUFS_FHSM
+       bool "File-based Hierarchical Storage Management"
+       help
+       Hierarchical Storage Management (or HSM) is a well-known feature
+       in the storage world. Aufs provides this feature as file-based.
+       with multiple branches.
+       These multiple branches are prioritized, ie. the topmost one
+       should be the fastest drive and be used heavily.
+
+config AUFS_RDU
+       bool "Readdir in userspace"
+       help
+       Aufs has two methods to provide a merged view for a directory,
+       by a user-space library and by kernel-space natively. The latter
+       is always enabled but sometimes large and slow.
+       If you enable this option, install the library in aufs2-util
+       package, and set some environment variables for your readdir(3),
+       then the work will be handled in user-space which generally
+       shows better performance in most cases.
+       See detail in aufs.5.
+
+config AUFS_DIRREN
+       bool "Workaround for rename(2)-ing a directory"
+       help
+       By default, aufs returns EXDEV error in renameing a dir who has
+       his child on the lower branch, since it is a bad idea to issue
+       rename(2) internally for every lower branch. But user may not
+       accept this behaviour. So here is a workaround to allow such
+       rename(2) and store some extra infromation on the writable
+       branch. Obviously this costs high (and I don't like it).
+       To use this feature, you need to enable this configuration AND
+       to specify the mount option `dirren.'
+       See details in aufs.5 and the design documents.
+
+config AUFS_SHWH
+       bool "Show whiteouts"
+       help
+       If you want to make the whiteouts in aufs visible, then enable
+       this option and specify 'shwh' mount option. Although it may
+       sounds like philosophy or something, but in technically it
+       simply shows the name of whiteout with keeping its behaviour.
+
+config AUFS_BR_RAMFS
+       bool "Ramfs (initramfs/rootfs) as an aufs branch"
+       help
+       If you want to use ramfs as an aufs branch fs, then enable this
+       option. Generally tmpfs is recommended.
+       Aufs prohibited them to be a branch fs by default, because
+       initramfs becomes unusable after switch_root or something
+       generally. If you sets initramfs as an aufs branch and boot your
+       system by switch_root, you will meet a problem easily since the
+       files in initramfs may be inaccessible.
+       Unless you are going to use ramfs as an aufs branch fs without
+       switch_root or something, leave it N.
+
+config AUFS_BR_FUSE
+       bool "Fuse fs as an aufs branch"
+       depends on FUSE_FS
+       select AUFS_POLL
+       help
+       If you want to use fuse-based userspace filesystem as an aufs
+       branch fs, then enable this option.
+       It implements the internal poll(2) operation which is
+       implemented by fuse only (curretnly).
+
+config AUFS_POLL
+       bool
+       help
+       Automatic configuration for internal use.
+
+config AUFS_BR_HFSPLUS
+       bool "Hfsplus as an aufs branch"
+       depends on HFSPLUS_FS
+       default y
+       help
+       If you want to use hfsplus fs as an aufs branch fs, then enable
+       this option. This option introduces a small overhead at
+       copying-up a file on hfsplus.
+
+config AUFS_BDEV_LOOP
+       bool
+       depends on BLK_DEV_LOOP
+       default y
+       help
+       Automatic configuration for internal use.
+       Convert =[ym] into =y.
+
+config AUFS_DEBUG
+       bool "Debug aufs"
+       help
+       Enable this to compile aufs internal debug code.
+       It will have a negative impact to the performance.
+
+config AUFS_MAGIC_SYSRQ
+       bool
+       depends on AUFS_DEBUG && MAGIC_SYSRQ
+       default y
+       help
+       Automatic configuration for internal use.
+       When aufs supports Magic SysRq, enabled automatically.
+endif
diff -urN /usr/share/empty/fs/aufs/lcnt.h linux/fs/aufs/lcnt.h
--- /usr/share/empty/fs/aufs/lcnt.h     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/lcnt.h        2021-12-03 15:38:59.936647310 +0100
@@ -0,0 +1,186 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2018-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * simple long counter wrapper
+ */
+
+#ifndef __AUFS_LCNT_H__
+#define __AUFS_LCNT_H__
+
+#ifdef __KERNEL__
+
+#include "debug.h"
+
+#define AuLCntATOMIC   1
+#define AuLCntPCPUCNT  2
+/*
+ * why does percpu_refcount require extra synchronize_rcu()s in
+ * au_br_do_free()
+ */
+#define AuLCntPCPUREF  3
+
+/* #define AuLCntChosen        AuLCntATOMIC */
+#define AuLCntChosen   AuLCntPCPUCNT
+/* #define AuLCntChosen        AuLCntPCPUREF */
+
+#if AuLCntChosen == AuLCntATOMIC
+#include <linux/atomic.h>
+
+typedef atomic_long_t au_lcnt_t;
+
+static inline int au_lcnt_init(au_lcnt_t *cnt, void *release __maybe_unused)
+{
+       atomic_long_set(cnt, 0);
+       return 0;
+}
+
+static inline void au_lcnt_wait_for_fin(au_lcnt_t *cnt __maybe_unused)
+{
+       /* empty */
+}
+
+static inline void au_lcnt_fin(au_lcnt_t *cnt __maybe_unused,
+                              int do_sync __maybe_unused)
+{
+       /* empty */
+}
+
+static inline void au_lcnt_inc(au_lcnt_t *cnt)
+{
+       atomic_long_inc(cnt);
+}
+
+static inline void au_lcnt_dec(au_lcnt_t *cnt)
+{
+       atomic_long_dec(cnt);
+}
+
+static inline long au_lcnt_read(au_lcnt_t *cnt, int do_rev __maybe_unused)
+{
+       return atomic_long_read(cnt);
+}
+#endif
+
+#if AuLCntChosen == AuLCntPCPUCNT
+#include <linux/percpu_counter.h>
+
+typedef struct percpu_counter au_lcnt_t;
+
+static inline int au_lcnt_init(au_lcnt_t *cnt, void *release __maybe_unused)
+{
+       return percpu_counter_init(cnt, 0, GFP_NOFS);
+}
+
+static inline void au_lcnt_wait_for_fin(au_lcnt_t *cnt __maybe_unused)
+{
+       /* empty */
+}
+
+static inline void au_lcnt_fin(au_lcnt_t *cnt, int do_sync __maybe_unused)
+{
+       percpu_counter_destroy(cnt);
+}
+
+static inline void au_lcnt_inc(au_lcnt_t *cnt)
+{
+       percpu_counter_inc(cnt);
+}
+
+static inline void au_lcnt_dec(au_lcnt_t *cnt)
+{
+       percpu_counter_dec(cnt);
+}
+
+static inline long au_lcnt_read(au_lcnt_t *cnt, int do_rev __maybe_unused)
+{
+       s64 n;
+
+       n = percpu_counter_sum(cnt);
+       BUG_ON(n < 0);
+       if (LONG_MAX != LLONG_MAX
+           && n > LONG_MAX)
+               AuWarn1("%s\n", "wrap-around");
+
+       return n;
+}
+#endif
+
+#if AuLCntChosen == AuLCntPCPUREF
+#include <linux/percpu-refcount.h>
+
+typedef struct percpu_ref au_lcnt_t;
+
+static inline int au_lcnt_init(au_lcnt_t *cnt, percpu_ref_func_t *release)
+{
+       if (!release)
+               release = percpu_ref_exit;
+       return percpu_ref_init(cnt, release, /*percpu mode*/0, GFP_NOFS);
+}
+
+static inline void au_lcnt_wait_for_fin(au_lcnt_t *cnt __maybe_unused)
+{
+       synchronize_rcu();
+}
+
+static inline void au_lcnt_fin(au_lcnt_t *cnt, int do_sync)
+{
+       percpu_ref_kill(cnt);
+       if (do_sync)
+               au_lcnt_wait_for_fin(cnt);
+}
+
+static inline void au_lcnt_inc(au_lcnt_t *cnt)
+{
+       percpu_ref_get(cnt);
+}
+
+static inline void au_lcnt_dec(au_lcnt_t *cnt)
+{
+       percpu_ref_put(cnt);
+}
+
+/*
+ * avoid calling this func as possible.
+ */
+static inline long au_lcnt_read(au_lcnt_t *cnt, int do_rev)
+{
+       long l;
+
+       percpu_ref_switch_to_atomic_sync(cnt);
+       l = atomic_long_read(&cnt->count);
+       if (do_rev)
+               percpu_ref_switch_to_percpu(cnt);
+
+       /* percpu_ref is initialized by 1 instead of 0 */
+       return l - 1;
+}
+#endif
+
+#ifdef CONFIG_AUFS_DEBUG
+#define AuLCntZero(val) do {                   \
+       long l = val;                           \
+       if (l)                                  \
+               AuDbg("%s = %ld\n", #val, l);   \
+} while (0)
+#else
+#define AuLCntZero(val)                do {} while (0)
+#endif
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_LCNT_H__ */
diff -urN /usr/share/empty/fs/aufs/loop.c linux/fs/aufs/loop.c
--- /usr/share/empty/fs/aufs/loop.c     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/loop.c        2021-12-03 15:38:59.936647310 +0100
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * support for loopback block device as a branch
+ */
+
+#include "aufs.h"
+
+/* added into drivers/block/loop.c */
+static struct file *(*backing_file_func)(struct super_block *sb);
+
+/*
+ * test if two lower dentries have overlapping branches.
+ */
+int au_test_loopback_overlap(struct super_block *sb, struct dentry *h_adding)
+{
+       struct super_block *h_sb;
+       struct file *backing_file;
+
+       if (unlikely(!backing_file_func)) {
+               /* don't load "loop" module here */
+               backing_file_func = symbol_get(loop_backing_file);
+               if (unlikely(!backing_file_func))
+                       /* "loop" module is not loaded */
+                       return 0;
+       }
+
+       h_sb = h_adding->d_sb;
+       backing_file = backing_file_func(h_sb);
+       if (!backing_file)
+               return 0;
+
+       h_adding = backing_file->f_path.dentry;
+       /*
+        * h_adding can be local NFS.
+        * in this case aufs cannot detect the loop.
+        */
+       if (unlikely(h_adding->d_sb == sb))
+               return 1;
+       return !!au_test_subdir(h_adding, sb->s_root);
+}
+
+/* true if a kernel thread named 'loop[0-9].*' accesses a file */
+int au_test_loopback_kthread(void)
+{
+       int ret;
+       struct task_struct *tsk = current;
+       char c, comm[sizeof(tsk->comm)];
+
+       ret = 0;
+       if (tsk->flags & PF_KTHREAD) {
+               get_task_comm(comm, tsk);
+               c = comm[4];
+               ret = ('0' <= c && c <= '9'
+                      && !strncmp(comm, "loop", 4));
+       }
+
+       return ret;
+}
+
+/* ---------------------------------------------------------------------- */
+
+#define au_warn_loopback_step  16
+static int au_warn_loopback_nelem = au_warn_loopback_step;
+static unsigned long *au_warn_loopback_array;
+
+void au_warn_loopback(struct super_block *h_sb)
+{
+       int i, new_nelem;
+       unsigned long *a, magic;
+       static DEFINE_SPINLOCK(spin);
+
+       magic = h_sb->s_magic;
+       spin_lock(&spin);
+       a = au_warn_loopback_array;
+       for (i = 0; i < au_warn_loopback_nelem && *a; i++)
+               if (a[i] == magic) {
+                       spin_unlock(&spin);
+                       return;
+               }
+
+       /* h_sb is new to us, print it */
+       if (i < au_warn_loopback_nelem) {
+               a[i] = magic;
+               goto pr;
+       }
+
+       /* expand the array */
+       new_nelem = au_warn_loopback_nelem + au_warn_loopback_step;
+       a = au_kzrealloc(au_warn_loopback_array,
+                        au_warn_loopback_nelem * sizeof(unsigned long),
+                        new_nelem * sizeof(unsigned long), GFP_ATOMIC,
+                        /*may_shrink*/0);
+       if (a) {
+               au_warn_loopback_nelem = new_nelem;
+               au_warn_loopback_array = a;
+               a[i] = magic;
+               goto pr;
+       }
+
+       spin_unlock(&spin);
+       AuWarn1("realloc failed, ignored\n");
+       return;
+
+pr:
+       spin_unlock(&spin);
+       pr_warn("you may want to try another patch for loopback file "
+               "on %s(0x%lx) branch\n", au_sbtype(h_sb), magic);
+}
+
+int au_loopback_init(void)
+{
+       int err;
+       struct super_block *sb __maybe_unused;
+
+       BUILD_BUG_ON(sizeof(sb->s_magic) != sizeof(*au_warn_loopback_array));
+
+       err = 0;
+       au_warn_loopback_array = kcalloc(au_warn_loopback_step,
+                                        sizeof(unsigned long), GFP_NOFS);
+       if (unlikely(!au_warn_loopback_array))
+               err = -ENOMEM;
+
+       return err;
+}
+
+void au_loopback_fin(void)
+{
+       if (backing_file_func)
+               symbol_put(loop_backing_file);
+       au_kfree_try_rcu(au_warn_loopback_array);
+}
diff -urN /usr/share/empty/fs/aufs/loop.h linux/fs/aufs/loop.h
--- /usr/share/empty/fs/aufs/loop.h     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/loop.h        2021-12-03 15:38:59.936647310 +0100
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * support for loopback mount as a branch
+ */
+
+#ifndef __AUFS_LOOP_H__
+#define __AUFS_LOOP_H__
+
+#ifdef __KERNEL__
+
+struct dentry;
+struct super_block;
+
+#ifdef CONFIG_AUFS_BDEV_LOOP
+/* drivers/block/loop.c */
+struct file *loop_backing_file(struct super_block *sb);
+
+/* loop.c */
+int au_test_loopback_overlap(struct super_block *sb, struct dentry *h_adding);
+int au_test_loopback_kthread(void);
+void au_warn_loopback(struct super_block *h_sb);
+
+int au_loopback_init(void);
+void au_loopback_fin(void);
+#else
+AuStub(struct file *, loop_backing_file, return NULL, struct super_block *sb)
+
+AuStubInt0(au_test_loopback_overlap, struct super_block *sb,
+          struct dentry *h_adding)
+AuStubInt0(au_test_loopback_kthread, void)
+AuStubVoid(au_warn_loopback, struct super_block *h_sb)
+
+AuStubInt0(au_loopback_init, void)
+AuStubVoid(au_loopback_fin, void)
+#endif /* BLK_DEV_LOOP */
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_LOOP_H__ */
diff -urN /usr/share/empty/fs/aufs/magic.mk linux/fs/aufs/magic.mk
--- /usr/share/empty/fs/aufs/magic.mk   1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/magic.mk      2021-12-03 15:38:59.936647310 +0100
@@ -0,0 +1,31 @@
+# SPDX-License-Identifier: GPL-2.0
+
+# defined in ${srctree}/fs/fuse/inode.c
+# tristate
+ifdef CONFIG_FUSE_FS
+ccflags-y += -DFUSE_SUPER_MAGIC=0x65735546
+endif
+
+# defined in ${srctree}/fs/xfs/xfs_sb.h
+# tristate
+ifdef CONFIG_XFS_FS
+ccflags-y += -DXFS_SB_MAGIC=0x58465342
+endif
+
+# defined in ${srctree}/fs/configfs/mount.c
+# tristate
+ifdef CONFIG_CONFIGFS_FS
+ccflags-y += -DCONFIGFS_MAGIC=0x62656570
+endif
+
+# defined in ${srctree}/fs/ubifs/ubifs.h
+# tristate
+ifdef CONFIG_UBIFS_FS
+ccflags-y += -DUBIFS_SUPER_MAGIC=0x24051905
+endif
+
+# defined in ${srctree}/fs/hfsplus/hfsplus_raw.h
+# tristate
+ifdef CONFIG_HFSPLUS_FS
+ccflags-y += -DHFSPLUS_SUPER_MAGIC=0x482b
+endif
diff -urN /usr/share/empty/fs/aufs/Makefile linux/fs/aufs/Makefile
--- /usr/share/empty/fs/aufs/Makefile   1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/Makefile      2021-12-03 15:38:59.929980643 +0100
@@ -0,0 +1,46 @@
+# SPDX-License-Identifier: GPL-2.0
+
+include ${src}/magic.mk
+ifeq (${CONFIG_AUFS_FS},m)
+include ${src}/conf.mk
+endif
+-include ${src}/priv_def.mk
+
+# cf. include/linux/kernel.h
+# enable pr_debug
+ccflags-y += -DDEBUG
+# sparse requires the full pathname
+ifdef M
+ccflags-y += -include ${M}/../../include/uapi/linux/aufs_type.h
+else
+ccflags-y += -include ${srctree}/include/uapi/linux/aufs_type.h
+endif
+
+obj-$(CONFIG_AUFS_FS) += aufs.o
+aufs-y := module.o sbinfo.o super.o branch.o xino.o sysaufs.o opts.o \
+       wkq.o vfsub.o dcsub.o \
+       cpup.o whout.o wbr_policy.o \
+       dinfo.o dentry.o \
+       dynop.o \
+       finfo.o file.o f_op.o \
+       dir.o vdir.o \
+       iinfo.o inode.o i_op.o i_op_add.o i_op_del.o i_op_ren.o \
+       mvdown.o ioctl.o
+
+# all are boolean
+aufs-$(CONFIG_PROC_FS) += procfs.o plink.o
+aufs-$(CONFIG_SYSFS) += sysfs.o
+aufs-$(CONFIG_DEBUG_FS) += dbgaufs.o
+aufs-$(CONFIG_AUFS_BDEV_LOOP) += loop.o
+aufs-$(CONFIG_AUFS_HNOTIFY) += hnotify.o
+aufs-$(CONFIG_AUFS_HFSNOTIFY) += hfsnotify.o
+aufs-$(CONFIG_AUFS_EXPORT) += export.o
+aufs-$(CONFIG_AUFS_XATTR) += xattr.o
+aufs-$(CONFIG_FS_POSIX_ACL) += posix_acl.o
+aufs-$(CONFIG_AUFS_DIRREN) += dirren.o
+aufs-$(CONFIG_AUFS_FHSM) += fhsm.o
+aufs-$(CONFIG_AUFS_POLL) += poll.o
+aufs-$(CONFIG_AUFS_RDU) += rdu.o
+aufs-$(CONFIG_AUFS_BR_HFSPLUS) += hfsplus.o
+aufs-$(CONFIG_AUFS_DEBUG) += debug.o
+aufs-$(CONFIG_AUFS_MAGIC_SYSRQ) += sysrq.o
diff -urN /usr/share/empty/fs/aufs/module.c linux/fs/aufs/module.c
--- /usr/share/empty/fs/aufs/module.c   1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/module.c      2021-12-03 15:38:59.936647310 +0100
@@ -0,0 +1,273 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * module global variables and operations
+ */
+
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include "aufs.h"
+
+/* shrinkable realloc */
+void *au_krealloc(void *p, unsigned int new_sz, gfp_t gfp, int may_shrink)
+{
+       size_t sz;
+       int diff;
+
+       sz = 0;
+       diff = -1;
+       if (p) {
+#if 0 /* unused */
+               if (!new_sz) {
+                       au_kfree_rcu(p);
+                       p = NULL;
+                       goto out;
+               }
+#else
+               AuDebugOn(!new_sz);
+#endif
+               sz = ksize(p);
+               diff = au_kmidx_sub(sz, new_sz);
+       }
+       if (sz && !diff)
+               goto out;
+
+       if (sz < new_sz)
+               /* expand or SLOB */
+               p = krealloc(p, new_sz, gfp);
+       else if (new_sz < sz && may_shrink) {
+               /* shrink */
+               void *q;
+
+               q = kmalloc(new_sz, gfp);
+               if (q) {
+                       if (p) {
+                               memcpy(q, p, new_sz);
+                               au_kfree_try_rcu(p);
+                       }
+                       p = q;
+               } else
+                       p = NULL;
+       }
+
+out:
+       return p;
+}
+
+void *au_kzrealloc(void *p, unsigned int nused, unsigned int new_sz, gfp_t gfp,
+                  int may_shrink)
+{
+       p = au_krealloc(p, new_sz, gfp, may_shrink);
+       if (p && new_sz > nused)
+               memset(p + nused, 0, new_sz - nused);
+       return p;
+}
+
+/* ---------------------------------------------------------------------- */
+/*
+ * aufs caches
+ */
+struct kmem_cache *au_cache[AuCache_Last];
+
+static void au_cache_fin(void)
+{
+       int i;
+
+       /*
+        * Make sure all delayed rcu free inodes are flushed before we
+        * destroy cache.
+        */
+       rcu_barrier();
+
+       /* excluding AuCache_HNOTIFY */
+       BUILD_BUG_ON(AuCache_HNOTIFY + 1 != AuCache_Last);
+       for (i = 0; i < AuCache_HNOTIFY; i++) {
+               kmem_cache_destroy(au_cache[i]);
+               au_cache[i] = NULL;
+       }
+}
+
+static int __init au_cache_init(void)
+{
+       au_cache[AuCache_DINFO] = AuCacheCtor(au_dinfo, au_di_init_once);
+       if (au_cache[AuCache_DINFO])
+               /* SLAB_DESTROY_BY_RCU */
+               au_cache[AuCache_ICNTNR] = AuCacheCtor(au_icntnr,
+                                                      au_icntnr_init_once);
+       if (au_cache[AuCache_ICNTNR])
+               au_cache[AuCache_FINFO] = AuCacheCtor(au_finfo,
+                                                     au_fi_init_once);
+       if (au_cache[AuCache_FINFO])
+               au_cache[AuCache_VDIR] = AuCache(au_vdir);
+       if (au_cache[AuCache_VDIR])
+               au_cache[AuCache_DEHSTR] = AuCache(au_vdir_dehstr);
+       if (au_cache[AuCache_DEHSTR])
+               return 0;
+
+       au_cache_fin();
+       return -ENOMEM;
+}
+
+/* ---------------------------------------------------------------------- */
+
+int au_dir_roflags;
+
+#ifdef CONFIG_AUFS_SBILIST
+/*
+ * iterate_supers_type() doesn't protect us from
+ * remounting (branch management)
+ */
+struct hlist_bl_head au_sbilist;
+#endif
+
+/*
+ * functions for module interface.
+ */
+MODULE_LICENSE("GPL");
+/* MODULE_LICENSE("GPL v2"); */
+MODULE_AUTHOR("Junjiro R. Okajima <aufs-users@lists.sourceforge.net>");
+MODULE_DESCRIPTION(AUFS_NAME
+       " -- Advanced multi layered unification filesystem");
+MODULE_VERSION(AUFS_VERSION);
+MODULE_ALIAS_FS(AUFS_NAME);
+
+/* this module parameter has no meaning when SYSFS is disabled */
+int sysaufs_brs = 1;
+MODULE_PARM_DESC(brs, "use <sysfs>/fs/aufs/si_*/brN");
+module_param_named(brs, sysaufs_brs, int, 0444);
+
+/* this module parameter has no meaning when USER_NS is disabled */
+bool au_userns;
+MODULE_PARM_DESC(allow_userns, "allow unprivileged to mount under userns");
+module_param_named(allow_userns, au_userns, bool, 0444);
+
+/* ---------------------------------------------------------------------- */
+
+static char au_esc_chars[0x20 + 3]; /* 0x01-0x20, backslash, del, and NULL */
+
+int au_seq_path(struct seq_file *seq, struct path *path)
+{
+       int err;
+
+       err = seq_path(seq, path, au_esc_chars);
+       if (err >= 0)
+               err = 0;
+       else
+               err = -ENOMEM;
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int __init aufs_init(void)
+{
+       int err, i;
+       char *p;
+
+       p = au_esc_chars;
+       for (i = 1; i <= ' '; i++)
+               *p++ = i;
+       *p++ = '\\';
+       *p++ = '\x7f';
+       *p = 0;
+
+       au_dir_roflags = au_file_roflags(O_DIRECTORY | O_LARGEFILE);
+
+       memcpy(aufs_iop_nogetattr, aufs_iop, sizeof(aufs_iop));
+       for (i = 0; i < AuIop_Last; i++)
+               aufs_iop_nogetattr[i].getattr = NULL;
+
+       memset(au_cache, 0, sizeof(au_cache));  /* including hnotify */
+
+       au_sbilist_init();
+       sysaufs_brs_init();
+       au_debug_init();
+       au_dy_init();
+       err = sysaufs_init();
+       if (unlikely(err))
+               goto out;
+       err = dbgaufs_init();
+       if (unlikely(err))
+               goto out_sysaufs;
+       err = au_procfs_init();
+       if (unlikely(err))
+               goto out_dbgaufs;
+       err = au_wkq_init();
+       if (unlikely(err))
+               goto out_procfs;
+       err = au_loopback_init();
+       if (unlikely(err))
+               goto out_wkq;
+       err = au_hnotify_init();
+       if (unlikely(err))
+               goto out_loopback;
+       err = au_sysrq_init();
+       if (unlikely(err))
+               goto out_hin;
+       err = au_cache_init();
+       if (unlikely(err))
+               goto out_sysrq;
+
+       aufs_fs_type.fs_flags |= au_userns ? FS_USERNS_MOUNT : 0;
+       err = register_filesystem(&aufs_fs_type);
+       if (unlikely(err))
+               goto out_cache;
+
+       /* since we define pr_fmt, call printk directly */
+       printk(KERN_INFO AUFS_NAME " " AUFS_VERSION "\n");
+       goto out; /* success */
+
+out_cache:
+       au_cache_fin();
+out_sysrq:
+       au_sysrq_fin();
+out_hin:
+       au_hnotify_fin();
+out_loopback:
+       au_loopback_fin();
+out_wkq:
+       au_wkq_fin();
+out_procfs:
+       au_procfs_fin();
+out_dbgaufs:
+       dbgaufs_fin();
+out_sysaufs:
+       sysaufs_fin();
+       au_dy_fin();
+out:
+       return err;
+}
+
+static void __exit aufs_exit(void)
+{
+       unregister_filesystem(&aufs_fs_type);
+       au_cache_fin();
+       au_sysrq_fin();
+       au_hnotify_fin();
+       au_loopback_fin();
+       au_wkq_fin();
+       au_procfs_fin();
+       dbgaufs_fin();
+       sysaufs_fin();
+       au_dy_fin();
+}
+
+module_init(aufs_init);
+module_exit(aufs_exit);
diff -urN /usr/share/empty/fs/aufs/module.h linux/fs/aufs/module.h
--- /usr/share/empty/fs/aufs/module.h   1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/module.h      2021-12-03 15:40:58.236647297 +0100
@@ -0,0 +1,166 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * module initialization and module-global
+ */
+
+#ifndef __AUFS_MODULE_H__
+#define __AUFS_MODULE_H__
+
+#ifdef __KERNEL__
+
+#include <linux/slab.h>
+#include "debug.h"
+#include "dentry.h"
+#include "dir.h"
+#include "file.h"
+#include "inode.h"
+
+struct path;
+struct seq_file;
+
+/* module parameters */
+extern int sysaufs_brs;
+extern bool au_userns;
+
+/* ---------------------------------------------------------------------- */
+
+extern int au_dir_roflags;
+
+void *au_krealloc(void *p, unsigned int new_sz, gfp_t gfp, int may_shrink);
+void *au_kzrealloc(void *p, unsigned int nused, unsigned int new_sz, gfp_t gfp,
+                  int may_shrink);
+
+/*
+ * Comparing the size of the object with sizeof(struct rcu_head)
+ * case 1: object is always larger
+ *     --> au_kfree_rcu() or au_kfree_do_rcu()
+ * case 2: object is always smaller
+ *     --> au_kfree_small()
+ * case 3: object can be any size
+ *     --> au_kfree_try_rcu()
+ */
+
+static inline void au_kfree_do_rcu(const void *p)
+{
+       struct {
+               struct rcu_head rcu;
+       } *a = (void *)p;
+
+       kfree_rcu(a, rcu);
+}
+
+#define au_kfree_rcu(_p) do {                                          \
+               typeof(_p) p = (_p);                                    \
+               BUILD_BUG_ON(sizeof(*p) < sizeof(struct rcu_head));     \
+               if (p)                                                  \
+                       au_kfree_do_rcu(p);                             \
+       } while (0)
+
+#define au_kfree_do_sz_test(sz)        (sz >= sizeof(struct rcu_head))
+#define au_kfree_sz_test(p)    (p && au_kfree_do_sz_test(ksize(p)))
+
+static inline void au_kfree_try_rcu(const void *p)
+{
+       if (!p)
+               return;
+       if (au_kfree_sz_test(p))
+               au_kfree_do_rcu(p);
+       else
+               kfree(p);
+}
+
+static inline void au_kfree_small(const void *p)
+{
+       if (!p)
+               return;
+       AuDebugOn(au_kfree_sz_test(p));
+       kfree(p);
+}
+
+static inline int au_kmidx_sub(size_t sz, size_t new_sz)
+{
+#ifndef CONFIG_SLOB
+       return __kmalloc_index(sz, false) - __kmalloc_index(new_sz, false);
+#else
+       return -1; /* SLOB is untested */
+#endif
+}
+
+int au_seq_path(struct seq_file *seq, struct path *path);
+
+#ifdef CONFIG_PROC_FS
+/* procfs.c */
+int __init au_procfs_init(void);
+void au_procfs_fin(void);
+#else
+AuStubInt0(au_procfs_init, void);
+AuStubVoid(au_procfs_fin, void);
+#endif
+
+/* ---------------------------------------------------------------------- */
+
+/* kmem cache */
+enum {
+       AuCache_DINFO,
+       AuCache_ICNTNR,
+       AuCache_FINFO,
+       AuCache_VDIR,
+       AuCache_DEHSTR,
+       AuCache_HNOTIFY, /* must be last */
+       AuCache_Last
+};
+
+extern struct kmem_cache *au_cache[AuCache_Last];
+
+#define AuCacheFlags           (SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD)
+#define AuCache(type)          KMEM_CACHE(type, AuCacheFlags)
+#define AuCacheCtor(type, ctor)        \
+       kmem_cache_create(#type, sizeof(struct type), \
+                         __alignof__(struct type), AuCacheFlags, ctor)
+
+#define AuCacheFuncs(name, index)                                      \
+       static inline struct au_##name *au_cache_alloc_##name(void)     \
+       { return kmem_cache_alloc(au_cache[AuCache_##index], GFP_NOFS); } \
+       static inline void au_cache_free_##name##_norcu(struct au_##name *p) \
+       { kmem_cache_free(au_cache[AuCache_##index], p); }              \
+                                                                       \
+       static inline void au_cache_free_##name##_rcu_cb(struct rcu_head *rcu) \
+       { void *p = rcu;                                                \
+               p -= offsetof(struct au_##name, rcu);                   \
+               kmem_cache_free(au_cache[AuCache_##index], p); }        \
+       static inline void au_cache_free_##name##_rcu(struct au_##name *p) \
+       { BUILD_BUG_ON(sizeof(struct au_##name) < sizeof(struct rcu_head)); \
+               call_rcu(&p->rcu, au_cache_free_##name##_rcu_cb); }     \
+                                                                       \
+       static inline void au_cache_free_##name(struct au_##name *p)    \
+       { /* au_cache_free_##name##_norcu(p); */                        \
+               au_cache_free_##name##_rcu(p); }
+
+AuCacheFuncs(dinfo, DINFO);
+AuCacheFuncs(icntnr, ICNTNR);
+AuCacheFuncs(finfo, FINFO);
+AuCacheFuncs(vdir, VDIR);
+AuCacheFuncs(vdir_dehstr, DEHSTR);
+#ifdef CONFIG_AUFS_HNOTIFY
+AuCacheFuncs(hnotify, HNOTIFY);
+#endif
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_MODULE_H__ */
diff -urN /usr/share/empty/fs/aufs/mvdown.c linux/fs/aufs/mvdown.c
--- /usr/share/empty/fs/aufs/mvdown.c   1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/mvdown.c      2021-12-03 15:38:59.939980643 +0100
@@ -0,0 +1,706 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2011-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * move-down, opposite of copy-up
+ */
+
+#include "aufs.h"
+
+struct au_mvd_args {
+       struct {
+               struct super_block *h_sb;
+               struct dentry *h_parent;
+               struct au_hinode *hdir;
+               struct inode *h_dir, *h_inode;
+               struct au_pin pin;
+       } info[AUFS_MVDOWN_NARRAY];
+
+       struct aufs_mvdown mvdown;
+       struct dentry *dentry, *parent;
+       struct inode *inode, *dir;
+       struct super_block *sb;
+       aufs_bindex_t bopq, bwh, bfound;
+       unsigned char rename_lock;
+};
+
+#define mvd_errno              mvdown.au_errno
+#define mvd_bsrc               mvdown.stbr[AUFS_MVDOWN_UPPER].bindex
+#define mvd_src_brid           mvdown.stbr[AUFS_MVDOWN_UPPER].brid
+#define mvd_bdst               mvdown.stbr[AUFS_MVDOWN_LOWER].bindex
+#define mvd_dst_brid           mvdown.stbr[AUFS_MVDOWN_LOWER].brid
+
+#define mvd_h_src_sb           info[AUFS_MVDOWN_UPPER].h_sb
+#define mvd_h_src_parent       info[AUFS_MVDOWN_UPPER].h_parent
+#define mvd_hdir_src           info[AUFS_MVDOWN_UPPER].hdir
+#define mvd_h_src_dir          info[AUFS_MVDOWN_UPPER].h_dir
+#define mvd_h_src_inode                info[AUFS_MVDOWN_UPPER].h_inode
+#define mvd_pin_src            info[AUFS_MVDOWN_UPPER].pin
+
+#define mvd_h_dst_sb           info[AUFS_MVDOWN_LOWER].h_sb
+#define mvd_h_dst_parent       info[AUFS_MVDOWN_LOWER].h_parent
+#define mvd_hdir_dst           info[AUFS_MVDOWN_LOWER].hdir
+#define mvd_h_dst_dir          info[AUFS_MVDOWN_LOWER].h_dir
+#define mvd_h_dst_inode                info[AUFS_MVDOWN_LOWER].h_inode
+#define mvd_pin_dst            info[AUFS_MVDOWN_LOWER].pin
+
+#define AU_MVD_PR(flag, ...) do {                      \
+               if (flag)                               \
+                       pr_err(__VA_ARGS__);            \
+       } while (0)
+
+static int find_lower_writable(struct au_mvd_args *a)
+{
+       struct super_block *sb;
+       aufs_bindex_t bindex, bbot;
+       struct au_branch *br;
+
+       sb = a->sb;
+       bindex = a->mvd_bsrc;
+       bbot = au_sbbot(sb);
+       if (a->mvdown.flags & AUFS_MVDOWN_FHSM_LOWER)
+               for (bindex++; bindex <= bbot; bindex++) {
+                       br = au_sbr(sb, bindex);
+                       if (au_br_fhsm(br->br_perm)
+                           && !sb_rdonly(au_br_sb(br)))
+                               return bindex;
+               }
+       else if (!(a->mvdown.flags & AUFS_MVDOWN_ROLOWER))
+               for (bindex++; bindex <= bbot; bindex++) {
+                       br = au_sbr(sb, bindex);
+                       if (!au_br_rdonly(br))
+                               return bindex;
+               }
+       else
+               for (bindex++; bindex <= bbot; bindex++) {
+                       br = au_sbr(sb, bindex);
+                       if (!sb_rdonly(au_br_sb(br))) {
+                               if (au_br_rdonly(br))
+                                       a->mvdown.flags
+                                               |= AUFS_MVDOWN_ROLOWER_R;
+                               return bindex;
+                       }
+               }
+
+       return -1;
+}
+
+/* make the parent dir on bdst */
+static int au_do_mkdir(const unsigned char dmsg, struct au_mvd_args *a)
+{
+       int err;
+
+       err = 0;
+       a->mvd_hdir_src = au_hi(a->dir, a->mvd_bsrc);
+       a->mvd_hdir_dst = au_hi(a->dir, a->mvd_bdst);
+       a->mvd_h_src_parent = au_h_dptr(a->parent, a->mvd_bsrc);
+       a->mvd_h_dst_parent = NULL;
+       if (au_dbbot(a->parent) >= a->mvd_bdst)
+               a->mvd_h_dst_parent = au_h_dptr(a->parent, a->mvd_bdst);
+       if (!a->mvd_h_dst_parent) {
+               err = au_cpdown_dirs(a->dentry, a->mvd_bdst);
+               if (unlikely(err)) {
+                       AU_MVD_PR(dmsg, "cpdown_dirs failed\n");
+                       goto out;
+               }
+               a->mvd_h_dst_parent = au_h_dptr(a->parent, a->mvd_bdst);
+       }
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/* lock them all */
+static int au_do_lock(const unsigned char dmsg, struct au_mvd_args *a)
+{
+       int err;
+       struct dentry *h_trap;
+
+       a->mvd_h_src_sb = au_sbr_sb(a->sb, a->mvd_bsrc);
+       a->mvd_h_dst_sb = au_sbr_sb(a->sb, a->mvd_bdst);
+       err = au_pin(&a->mvd_pin_dst, a->dentry, a->mvd_bdst,
+                    au_opt_udba(a->sb),
+                    AuPin_MNT_WRITE | AuPin_DI_LOCKED);
+       AuTraceErr(err);
+       if (unlikely(err)) {
+               AU_MVD_PR(dmsg, "pin_dst failed\n");
+               goto out;
+       }
+
+       if (a->mvd_h_src_sb != a->mvd_h_dst_sb) {
+               a->rename_lock = 0;
+               au_pin_init(&a->mvd_pin_src, a->dentry, a->mvd_bsrc,
+                           AuLsc_DI_PARENT, AuLsc_I_PARENT3,
+                           au_opt_udba(a->sb),
+                           AuPin_MNT_WRITE | AuPin_DI_LOCKED);
+               err = au_do_pin(&a->mvd_pin_src);
+               AuTraceErr(err);
+               a->mvd_h_src_dir = d_inode(a->mvd_h_src_parent);
+               if (unlikely(err)) {
+                       AU_MVD_PR(dmsg, "pin_src failed\n");
+                       goto out_dst;
+               }
+               goto out; /* success */
+       }
+
+       a->rename_lock = 1;
+       au_pin_hdir_unlock(&a->mvd_pin_dst);
+       err = au_pin(&a->mvd_pin_src, a->dentry, a->mvd_bsrc,
+                    au_opt_udba(a->sb),
+                    AuPin_MNT_WRITE | AuPin_DI_LOCKED);
+       AuTraceErr(err);
+       a->mvd_h_src_dir = d_inode(a->mvd_h_src_parent);
+       if (unlikely(err)) {
+               AU_MVD_PR(dmsg, "pin_src failed\n");
+               au_pin_hdir_lock(&a->mvd_pin_dst);
+               goto out_dst;
+       }
+       au_pin_hdir_unlock(&a->mvd_pin_src);
+       h_trap = vfsub_lock_rename(a->mvd_h_src_parent, a->mvd_hdir_src,
+                                  a->mvd_h_dst_parent, a->mvd_hdir_dst);
+       if (h_trap) {
+               err = (h_trap != a->mvd_h_src_parent);
+               if (err)
+                       err = (h_trap != a->mvd_h_dst_parent);
+       }
+       BUG_ON(err); /* it should never happen */
+       if (unlikely(a->mvd_h_src_dir != au_pinned_h_dir(&a->mvd_pin_src))) {
+               err = -EBUSY;
+               AuTraceErr(err);
+               vfsub_unlock_rename(a->mvd_h_src_parent, a->mvd_hdir_src,
+                                   a->mvd_h_dst_parent, a->mvd_hdir_dst);
+               au_pin_hdir_lock(&a->mvd_pin_src);
+               au_unpin(&a->mvd_pin_src);
+               au_pin_hdir_lock(&a->mvd_pin_dst);
+               goto out_dst;
+       }
+       goto out; /* success */
+
+out_dst:
+       au_unpin(&a->mvd_pin_dst);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+static void au_do_unlock(const unsigned char dmsg, struct au_mvd_args *a)
+{
+       if (!a->rename_lock)
+               au_unpin(&a->mvd_pin_src);
+       else {
+               vfsub_unlock_rename(a->mvd_h_src_parent, a->mvd_hdir_src,
+                                   a->mvd_h_dst_parent, a->mvd_hdir_dst);
+               au_pin_hdir_lock(&a->mvd_pin_src);
+               au_unpin(&a->mvd_pin_src);
+               au_pin_hdir_lock(&a->mvd_pin_dst);
+       }
+       au_unpin(&a->mvd_pin_dst);
+}
+
+/* copy-down the file */
+static int au_do_cpdown(const unsigned char dmsg, struct au_mvd_args *a)
+{
+       int err;
+       struct au_cp_generic cpg = {
+               .dentry = a->dentry,
+               .bdst   = a->mvd_bdst,
+               .bsrc   = a->mvd_bsrc,
+               .len    = -1,
+               .pin    = &a->mvd_pin_dst,
+               .flags  = AuCpup_DTIME | AuCpup_HOPEN
+       };
+
+       AuDbg("b%d, b%d\n", cpg.bsrc, cpg.bdst);
+       if (a->mvdown.flags & AUFS_MVDOWN_OWLOWER)
+               au_fset_cpup(cpg.flags, OVERWRITE);
+       if (a->mvdown.flags & AUFS_MVDOWN_ROLOWER)
+               au_fset_cpup(cpg.flags, RWDST);
+       err = au_sio_cpdown_simple(&cpg);
+       if (unlikely(err))
+               AU_MVD_PR(dmsg, "cpdown failed\n");
+
+       AuTraceErr(err);
+       return err;
+}
+
+/*
+ * unlink the whiteout on bdst if exist which may be created by UDBA while we
+ * were sleeping
+ */
+static int au_do_unlink_wh(const unsigned char dmsg, struct au_mvd_args *a)
+{
+       int err;
+       struct path h_path;
+       struct au_branch *br;
+       struct inode *delegated;
+
+       br = au_sbr(a->sb, a->mvd_bdst);
+       h_path.dentry = au_wh_lkup(a->mvd_h_dst_parent, &a->dentry->d_name, br);
+       err = PTR_ERR(h_path.dentry);
+       if (IS_ERR(h_path.dentry)) {
+               AU_MVD_PR(dmsg, "wh_lkup failed\n");
+               goto out;
+       }
+
+       err = 0;
+       if (d_is_positive(h_path.dentry)) {
+               h_path.mnt = au_br_mnt(br);
+               delegated = NULL;
+               err = vfsub_unlink(d_inode(a->mvd_h_dst_parent), &h_path,
+                                  &delegated, /*force*/0);
+               if (unlikely(err == -EWOULDBLOCK)) {
+                       pr_warn("cannot retry for NFSv4 delegation"
+                               " for an internal unlink\n");
+                       iput(delegated);
+               }
+               if (unlikely(err))
+                       AU_MVD_PR(dmsg, "wh_unlink failed\n");
+       }
+       dput(h_path.dentry);
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/*
+ * unlink the topmost h_dentry
+ */
+static int au_do_unlink(const unsigned char dmsg, struct au_mvd_args *a)
+{
+       int err;
+       struct path h_path;
+       struct inode *delegated;
+
+       h_path.mnt = au_sbr_mnt(a->sb, a->mvd_bsrc);
+       h_path.dentry = au_h_dptr(a->dentry, a->mvd_bsrc);
+       delegated = NULL;
+       err = vfsub_unlink(a->mvd_h_src_dir, &h_path, &delegated, /*force*/0);
+       if (unlikely(err == -EWOULDBLOCK)) {
+               pr_warn("cannot retry for NFSv4 delegation"
+                       " for an internal unlink\n");
+               iput(delegated);
+       }
+       if (unlikely(err))
+               AU_MVD_PR(dmsg, "unlink failed\n");
+
+       AuTraceErr(err);
+       return err;
+}
+
+/* Since mvdown succeeded, we ignore an error of this function */
+static void au_do_stfs(const unsigned char dmsg, struct au_mvd_args *a)
+{
+       int err;
+       struct au_branch *br;
+
+       a->mvdown.flags |= AUFS_MVDOWN_STFS_FAILED;
+       br = au_sbr(a->sb, a->mvd_bsrc);
+       err = au_br_stfs(br, &a->mvdown.stbr[AUFS_MVDOWN_UPPER].stfs);
+       if (!err) {
+               br = au_sbr(a->sb, a->mvd_bdst);
+               a->mvdown.stbr[AUFS_MVDOWN_LOWER].brid = br->br_id;
+               err = au_br_stfs(br, &a->mvdown.stbr[AUFS_MVDOWN_LOWER].stfs);
+       }
+       if (!err)
+               a->mvdown.flags &= ~AUFS_MVDOWN_STFS_FAILED;
+       else
+               AU_MVD_PR(dmsg, "statfs failed (%d), ignored\n", err);
+}
+
+/*
+ * copy-down the file and unlink the bsrc file.
+ * - unlink the bdst whout if exist
+ * - copy-down the file (with whtmp name and rename)
+ * - unlink the bsrc file
+ */
+static int au_do_mvdown(const unsigned char dmsg, struct au_mvd_args *a)
+{
+       int err;
+
+       err = au_do_mkdir(dmsg, a);
+       if (!err)
+               err = au_do_lock(dmsg, a);
+       if (unlikely(err))
+               goto out;
+
+       /*
+        * do not revert the activities we made on bdst since they should be
+        * harmless in aufs.
+        */
+
+       err = au_do_cpdown(dmsg, a);
+       if (!err)
+               err = au_do_unlink_wh(dmsg, a);
+       if (!err && !(a->mvdown.flags & AUFS_MVDOWN_KUPPER))
+               err = au_do_unlink(dmsg, a);
+       if (unlikely(err))
+               goto out_unlock;
+
+       AuDbg("%pd2, 0x%x, %d --> %d\n",
+             a->dentry, a->mvdown.flags, a->mvd_bsrc, a->mvd_bdst);
+       if (find_lower_writable(a) < 0)
+               a->mvdown.flags |= AUFS_MVDOWN_BOTTOM;
+
+       if (a->mvdown.flags & AUFS_MVDOWN_STFS)
+               au_do_stfs(dmsg, a);
+
+       /* maintain internal array */
+       if (!(a->mvdown.flags & AUFS_MVDOWN_KUPPER)) {
+               au_set_h_dptr(a->dentry, a->mvd_bsrc, NULL);
+               au_set_dbtop(a->dentry, a->mvd_bdst);
+               au_set_h_iptr(a->inode, a->mvd_bsrc, NULL, /*flags*/0);
+               au_set_ibtop(a->inode, a->mvd_bdst);
+       } else {
+               /* hide the lower */
+               au_set_h_dptr(a->dentry, a->mvd_bdst, NULL);
+               au_set_dbbot(a->dentry, a->mvd_bsrc);
+               au_set_h_iptr(a->inode, a->mvd_bdst, NULL, /*flags*/0);
+               au_set_ibbot(a->inode, a->mvd_bsrc);
+       }
+       if (au_dbbot(a->dentry) < a->mvd_bdst)
+               au_set_dbbot(a->dentry, a->mvd_bdst);
+       if (au_ibbot(a->inode) < a->mvd_bdst)
+               au_set_ibbot(a->inode, a->mvd_bdst);
+
+out_unlock:
+       au_do_unlock(dmsg, a);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* make sure the file is idle */
+static int au_mvd_args_busy(const unsigned char dmsg, struct au_mvd_args *a)
+{
+       int err, plinked;
+
+       err = 0;
+       plinked = !!au_opt_test(au_mntflags(a->sb), PLINK);
+       if (au_dbtop(a->dentry) == a->mvd_bsrc
+           && au_dcount(a->dentry) == 1
+           && atomic_read(&a->inode->i_count) == 1
+           /* && a->mvd_h_src_inode->i_nlink == 1 */
+           && (!plinked || !au_plink_test(a->inode))
+           && a->inode->i_nlink == 1)
+               goto out;
+
+       err = -EBUSY;
+       AU_MVD_PR(dmsg,
+                 "b%d, d{b%d, c%d?}, i{c%d?, l%u}, hi{l%u}, p{%d, %d}\n",
+                 a->mvd_bsrc, au_dbtop(a->dentry), au_dcount(a->dentry),
+                 atomic_read(&a->inode->i_count), a->inode->i_nlink,
+                 a->mvd_h_src_inode->i_nlink,
+                 plinked, plinked ? au_plink_test(a->inode) : 0);
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/* make sure the parent dir is fine */
+static int au_mvd_args_parent(const unsigned char dmsg,
+                             struct au_mvd_args *a)
+{
+       int err;
+       aufs_bindex_t bindex;
+
+       err = 0;
+       if (unlikely(au_alive_dir(a->parent))) {
+               err = -ENOENT;
+               AU_MVD_PR(dmsg, "parent dir is dead\n");
+               goto out;
+       }
+
+       a->bopq = au_dbdiropq(a->parent);
+       bindex = au_wbr_nonopq(a->dentry, a->mvd_bdst);
+       AuDbg("b%d\n", bindex);
+       if (unlikely((bindex >= 0 && bindex < a->mvd_bdst)
+                    || (a->bopq != -1 && a->bopq < a->mvd_bdst))) {
+               err = -EINVAL;
+               a->mvd_errno = EAU_MVDOWN_OPAQUE;
+               AU_MVD_PR(dmsg, "ancestor is opaque b%d, b%d\n",
+                         a->bopq, a->mvd_bdst);
+       }
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+static int au_mvd_args_intermediate(const unsigned char dmsg,
+                                   struct au_mvd_args *a)
+{
+       int err;
+       struct au_dinfo *dinfo, *tmp;
+
+       /* lookup the next lower positive entry */
+       err = -ENOMEM;
+       tmp = au_di_alloc(a->sb, AuLsc_DI_TMP);
+       if (unlikely(!tmp))
+               goto out;
+
+       a->bfound = -1;
+       a->bwh = -1;
+       dinfo = au_di(a->dentry);
+       au_di_cp(tmp, dinfo);
+       au_di_swap(tmp, dinfo);
+
+       /* returns the number of positive dentries */
+       err = au_lkup_dentry(a->dentry, a->mvd_bsrc + 1,
+                            /* AuLkup_IGNORE_PERM */ 0);
+       if (!err)
+               a->bwh = au_dbwh(a->dentry);
+       else if (err > 0)
+               a->bfound = au_dbtop(a->dentry);
+
+       au_di_swap(tmp, dinfo);
+       au_rw_write_unlock(&tmp->di_rwsem);
+       au_di_free(tmp);
+       if (unlikely(err < 0))
+               AU_MVD_PR(dmsg, "failed look-up lower\n");
+
+       /*
+        * here, we have these cases.
+        * bfound == -1
+        *      no positive dentry under bsrc. there are more sub-cases.
+        *      bwh < 0
+        *              there no whiteout, we can safely move-down.
+        *      bwh <= bsrc
+        *              impossible
+        *      bsrc < bwh && bwh < bdst
+        *              there is a whiteout on RO branch. cannot proceed.
+        *      bwh == bdst
+        *              there is a whiteout on the RW target branch. it should
+        *              be removed.
+        *      bdst < bwh
+        *              there is a whiteout somewhere unrelated branch.
+        * -1 < bfound && bfound <= bsrc
+        *      impossible.
+        * bfound < bdst
+        *      found, but it is on RO branch between bsrc and bdst. cannot
+        *      proceed.
+        * bfound == bdst
+        *      found, replace it if AUFS_MVDOWN_FORCE is set. otherwise return
+        *      error.
+        * bdst < bfound
+        *      found, after we create the file on bdst, it will be hidden.
+        */
+
+       AuDebugOn(a->bfound == -1
+                 && a->bwh != -1
+                 && a->bwh <= a->mvd_bsrc);
+       AuDebugOn(-1 < a->bfound
+                 && a->bfound <= a->mvd_bsrc);
+
+       err = -EINVAL;
+       if (a->bfound == -1
+           && a->mvd_bsrc < a->bwh
+           && a->bwh != -1
+           && a->bwh < a->mvd_bdst) {
+               a->mvd_errno = EAU_MVDOWN_WHITEOUT;
+               AU_MVD_PR(dmsg, "bsrc %d, bdst %d, bfound %d, bwh %d\n",
+                         a->mvd_bsrc, a->mvd_bdst, a->bfound, a->bwh);
+               goto out;
+       } else if (a->bfound != -1 && a->bfound < a->mvd_bdst) {
+               a->mvd_errno = EAU_MVDOWN_UPPER;
+               AU_MVD_PR(dmsg, "bdst %d, bfound %d\n",
+                         a->mvd_bdst, a->bfound);
+               goto out;
+       }
+
+       err = 0; /* success */
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+static int au_mvd_args_exist(const unsigned char dmsg, struct au_mvd_args *a)
+{
+       int err;
+
+       err = 0;
+       if (!(a->mvdown.flags & AUFS_MVDOWN_OWLOWER)
+           && a->bfound == a->mvd_bdst)
+               err = -EEXIST;
+       AuTraceErr(err);
+       return err;
+}
+
+static int au_mvd_args(const unsigned char dmsg, struct au_mvd_args *a)
+{
+       int err;
+       struct au_branch *br;
+
+       err = -EISDIR;
+       if (unlikely(S_ISDIR(a->inode->i_mode)))
+               goto out;
+
+       err = -EINVAL;
+       if (!(a->mvdown.flags & AUFS_MVDOWN_BRID_UPPER))
+               a->mvd_bsrc = au_ibtop(a->inode);
+       else {
+               a->mvd_bsrc = au_br_index(a->sb, a->mvd_src_brid);
+               if (unlikely(a->mvd_bsrc < 0
+                            || (a->mvd_bsrc < au_dbtop(a->dentry)
+                                || au_dbbot(a->dentry) < a->mvd_bsrc
+                                || !au_h_dptr(a->dentry, a->mvd_bsrc))
+                            || (a->mvd_bsrc < au_ibtop(a->inode)
+                                || au_ibbot(a->inode) < a->mvd_bsrc
+                                || !au_h_iptr(a->inode, a->mvd_bsrc)))) {
+                       a->mvd_errno = EAU_MVDOWN_NOUPPER;
+                       AU_MVD_PR(dmsg, "no upper\n");
+                       goto out;
+               }
+       }
+       if (unlikely(a->mvd_bsrc == au_sbbot(a->sb))) {
+               a->mvd_errno = EAU_MVDOWN_BOTTOM;
+               AU_MVD_PR(dmsg, "on the bottom\n");
+               goto out;
+       }
+       a->mvd_h_src_inode = au_h_iptr(a->inode, a->mvd_bsrc);
+       br = au_sbr(a->sb, a->mvd_bsrc);
+       err = au_br_rdonly(br);
+       if (!(a->mvdown.flags & AUFS_MVDOWN_ROUPPER)) {
+               if (unlikely(err))
+                       goto out;
+       } else if (!(vfsub_native_ro(a->mvd_h_src_inode)
+                    || IS_APPEND(a->mvd_h_src_inode))) {
+               if (err)
+                       a->mvdown.flags |= AUFS_MVDOWN_ROUPPER_R;
+               /* go on */
+       } else
+               goto out;
+
+       err = -EINVAL;
+       if (!(a->mvdown.flags & AUFS_MVDOWN_BRID_LOWER)) {
+               a->mvd_bdst = find_lower_writable(a);
+               if (unlikely(a->mvd_bdst < 0)) {
+                       a->mvd_errno = EAU_MVDOWN_BOTTOM;
+                       AU_MVD_PR(dmsg, "no writable lower branch\n");
+                       goto out;
+               }
+       } else {
+               a->mvd_bdst = au_br_index(a->sb, a->mvd_dst_brid);
+               if (unlikely(a->mvd_bdst < 0
+                            || au_sbbot(a->sb) < a->mvd_bdst)) {
+                       a->mvd_errno = EAU_MVDOWN_NOLOWERBR;
+                       AU_MVD_PR(dmsg, "no lower brid\n");
+                       goto out;
+               }
+       }
+
+       err = au_mvd_args_busy(dmsg, a);
+       if (!err)
+               err = au_mvd_args_parent(dmsg, a);
+       if (!err)
+               err = au_mvd_args_intermediate(dmsg, a);
+       if (!err)
+               err = au_mvd_args_exist(dmsg, a);
+       if (!err)
+               AuDbg("b%d, b%d\n", a->mvd_bsrc, a->mvd_bdst);
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+int au_mvdown(struct dentry *dentry, struct aufs_mvdown __user *uarg)
+{
+       int err, e;
+       unsigned char dmsg;
+       struct au_mvd_args *args;
+       struct inode *inode;
+
+       inode = d_inode(dentry);
+       err = -EPERM;
+       if (unlikely(!capable(CAP_SYS_ADMIN)))
+               goto out;
+
+       err = -ENOMEM;
+       args = kmalloc(sizeof(*args), GFP_NOFS);
+       if (unlikely(!args))
+               goto out;
+
+       err = copy_from_user(&args->mvdown, uarg, sizeof(args->mvdown));
+       if (!err)
+               /* VERIFY_WRITE */
+               err = !access_ok(uarg, sizeof(*uarg));
+       if (unlikely(err)) {
+               err = -EFAULT;
+               AuTraceErr(err);
+               goto out_free;
+       }
+       AuDbg("flags 0x%x\n", args->mvdown.flags);
+       args->mvdown.flags &= ~(AUFS_MVDOWN_ROLOWER_R | AUFS_MVDOWN_ROUPPER_R);
+       args->mvdown.au_errno = 0;
+       args->dentry = dentry;
+       args->inode = inode;
+       args->sb = dentry->d_sb;
+
+       err = -ENOENT;
+       dmsg = !!(args->mvdown.flags & AUFS_MVDOWN_DMSG);
+       args->parent = dget_parent(dentry);
+       args->dir = d_inode(args->parent);
+       inode_lock_nested(args->dir, I_MUTEX_PARENT);
+       dput(args->parent);
+       if (unlikely(args->parent != dentry->d_parent)) {
+               AU_MVD_PR(dmsg, "parent dir is moved\n");
+               goto out_dir;
+       }
+
+       inode_lock_nested(inode, I_MUTEX_CHILD);
+       err = aufs_read_lock(dentry, AuLock_DW | AuLock_FLUSH | AuLock_NOPLMW);
+       if (unlikely(err))
+               goto out_inode;
+
+       di_write_lock_parent(args->parent);
+       err = au_mvd_args(dmsg, args);
+       if (unlikely(err))
+               goto out_parent;
+
+       err = au_do_mvdown(dmsg, args);
+       if (unlikely(err))
+               goto out_parent;
+
+       au_cpup_attr_timesizes(args->dir);
+       au_cpup_attr_timesizes(inode);
+       if (!(args->mvdown.flags & AUFS_MVDOWN_KUPPER))
+               au_cpup_igen(inode, au_h_iptr(inode, args->mvd_bdst));
+       /* au_digen_dec(dentry); */
+
+out_parent:
+       di_write_unlock(args->parent);
+       aufs_read_unlock(dentry, AuLock_DW);
+out_inode:
+       inode_unlock(inode);
+out_dir:
+       inode_unlock(args->dir);
+out_free:
+       e = copy_to_user(uarg, &args->mvdown, sizeof(args->mvdown));
+       if (unlikely(e))
+               err = -EFAULT;
+       au_kfree_rcu(args);
+out:
+       AuTraceErr(err);
+       return err;
+}
diff -urN /usr/share/empty/fs/aufs/opts.c linux/fs/aufs/opts.c
--- /usr/share/empty/fs/aufs/opts.c     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/opts.c        2021-12-03 15:38:59.939980643 +0100
@@ -0,0 +1,1880 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * mount options/flags
+ */
+
+#include <linux/namei.h>
+#include <linux/types.h> /* a distribution requires */
+#include <linux/parser.h>
+#include "aufs.h"
+
+/* ---------------------------------------------------------------------- */
+
+enum {
+       Opt_br,
+       Opt_add, Opt_del, Opt_mod, Opt_append, Opt_prepend,
+       Opt_idel, Opt_imod,
+       Opt_dirwh, Opt_rdcache, Opt_rdblk, Opt_rdhash,
+       Opt_rdblk_def, Opt_rdhash_def,
+       Opt_xino, Opt_noxino,
+       Opt_trunc_xino, Opt_trunc_xino_v, Opt_notrunc_xino,
+       Opt_trunc_xino_path, Opt_itrunc_xino,
+       Opt_trunc_xib, Opt_notrunc_xib,
+       Opt_shwh, Opt_noshwh,
+       Opt_plink, Opt_noplink, Opt_list_plink,
+       Opt_udba,
+       Opt_dio, Opt_nodio,
+       Opt_diropq_a, Opt_diropq_w,
+       Opt_warn_perm, Opt_nowarn_perm,
+       Opt_wbr_copyup, Opt_wbr_create,
+       Opt_fhsm_sec,
+       Opt_verbose, Opt_noverbose,
+       Opt_sum, Opt_nosum, Opt_wsum,
+       Opt_dirperm1, Opt_nodirperm1,
+       Opt_dirren, Opt_nodirren,
+       Opt_acl, Opt_noacl,
+       Opt_tail, Opt_ignore, Opt_ignore_silent, Opt_err
+};
+
+static match_table_t options = {
+       {Opt_br, "br=%s"},
+       {Opt_br, "br:%s"},
+
+       {Opt_add, "add=%d:%s"},
+       {Opt_add, "add:%d:%s"},
+       {Opt_add, "ins=%d:%s"},
+       {Opt_add, "ins:%d:%s"},
+       {Opt_append, "append=%s"},
+       {Opt_append, "append:%s"},
+       {Opt_prepend, "prepend=%s"},
+       {Opt_prepend, "prepend:%s"},
+
+       {Opt_del, "del=%s"},
+       {Opt_del, "del:%s"},
+       /* {Opt_idel, "idel:%d"}, */
+       {Opt_mod, "mod=%s"},
+       {Opt_mod, "mod:%s"},
+       /* {Opt_imod, "imod:%d:%s"}, */
+
+       {Opt_dirwh, "dirwh=%d"},
+
+       {Opt_xino, "xino=%s"},
+       {Opt_noxino, "noxino"},
+       {Opt_trunc_xino, "trunc_xino"},
+       {Opt_trunc_xino_v, "trunc_xino_v=%d:%d"},
+       {Opt_notrunc_xino, "notrunc_xino"},
+       {Opt_trunc_xino_path, "trunc_xino=%s"},
+       {Opt_itrunc_xino, "itrunc_xino=%d"},
+       /* {Opt_zxino, "zxino=%s"}, */
+       {Opt_trunc_xib, "trunc_xib"},
+       {Opt_notrunc_xib, "notrunc_xib"},
+
+#ifdef CONFIG_PROC_FS
+       {Opt_plink, "plink"},
+#else
+       {Opt_ignore_silent, "plink"},
+#endif
+
+       {Opt_noplink, "noplink"},
+
+#ifdef CONFIG_AUFS_DEBUG
+       {Opt_list_plink, "list_plink"},
+#endif
+
+       {Opt_udba, "udba=%s"},
+
+       {Opt_dio, "dio"},
+       {Opt_nodio, "nodio"},
+
+#ifdef CONFIG_AUFS_DIRREN
+       {Opt_dirren, "dirren"},
+       {Opt_nodirren, "nodirren"},
+#else
+       {Opt_ignore, "dirren"},
+       {Opt_ignore_silent, "nodirren"},
+#endif
+
+#ifdef CONFIG_AUFS_FHSM
+       {Opt_fhsm_sec, "fhsm_sec=%d"},
+#else
+       {Opt_ignore, "fhsm_sec=%d"},
+#endif
+
+       {Opt_diropq_a, "diropq=always"},
+       {Opt_diropq_a, "diropq=a"},
+       {Opt_diropq_w, "diropq=whiteouted"},
+       {Opt_diropq_w, "diropq=w"},
+
+       {Opt_warn_perm, "warn_perm"},
+       {Opt_nowarn_perm, "nowarn_perm"},
+
+       /* keep them temporary */
+       {Opt_ignore_silent, "nodlgt"},
+       {Opt_ignore, "clean_plink"},
+
+#ifdef CONFIG_AUFS_SHWH
+       {Opt_shwh, "shwh"},
+#endif
+       {Opt_noshwh, "noshwh"},
+
+       {Opt_dirperm1, "dirperm1"},
+       {Opt_nodirperm1, "nodirperm1"},
+
+       {Opt_verbose, "verbose"},
+       {Opt_verbose, "v"},
+       {Opt_noverbose, "noverbose"},
+       {Opt_noverbose, "quiet"},
+       {Opt_noverbose, "q"},
+       {Opt_noverbose, "silent"},
+
+       {Opt_sum, "sum"},
+       {Opt_nosum, "nosum"},
+       {Opt_wsum, "wsum"},
+
+       {Opt_rdcache, "rdcache=%d"},
+       {Opt_rdblk, "rdblk=%d"},
+       {Opt_rdblk_def, "rdblk=def"},
+       {Opt_rdhash, "rdhash=%d"},
+       {Opt_rdhash_def, "rdhash=def"},
+
+       {Opt_wbr_create, "create=%s"},
+       {Opt_wbr_create, "create_policy=%s"},
+       {Opt_wbr_copyup, "cpup=%s"},
+       {Opt_wbr_copyup, "copyup=%s"},
+       {Opt_wbr_copyup, "copyup_policy=%s"},
+
+       /* generic VFS flag */
+#ifdef CONFIG_FS_POSIX_ACL
+       {Opt_acl, "acl"},
+       {Opt_noacl, "noacl"},
+#else
+       {Opt_ignore, "acl"},
+       {Opt_ignore_silent, "noacl"},
+#endif
+
+       /* internal use for the scripts */
+       {Opt_ignore_silent, "si=%s"},
+
+       {Opt_br, "dirs=%s"},
+       {Opt_ignore, "debug=%d"},
+       {Opt_ignore, "delete=whiteout"},
+       {Opt_ignore, "delete=all"},
+       {Opt_ignore, "imap=%s"},
+
+       /* temporary workaround, due to old mount(8)? */
+       {Opt_ignore_silent, "relatime"},
+
+       {Opt_err, NULL}
+};
+
+/* ---------------------------------------------------------------------- */
+
+static const char *au_parser_pattern(int val, match_table_t tbl)
+{
+       struct match_token *p;
+
+       p = tbl;
+       while (p->pattern) {
+               if (p->token == val)
+                       return p->pattern;
+               p++;
+       }
+       BUG();
+       return "??";
+}
+
+static const char *au_optstr(int *val, match_table_t tbl)
+{
+       struct match_token *p;
+       int v;
+
+       v = *val;
+       if (!v)
+               goto out;
+       p = tbl;
+       while (p->pattern) {
+               if (p->token
+                   && (v & p->token) == p->token) {
+                       *val &= ~p->token;
+                       return p->pattern;
+               }
+               p++;
+       }
+
+out:
+       return NULL;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static match_table_t brperm = {
+       {AuBrPerm_RO, AUFS_BRPERM_RO},
+       {AuBrPerm_RR, AUFS_BRPERM_RR},
+       {AuBrPerm_RW, AUFS_BRPERM_RW},
+       {0, NULL}
+};
+
+static match_table_t brattr = {
+       /* general */
+       {AuBrAttr_COO_REG, AUFS_BRATTR_COO_REG},
+       {AuBrAttr_COO_ALL, AUFS_BRATTR_COO_ALL},
+       /* 'unpin' attrib is meaningless since linux-3.18-rc1 */
+       {AuBrAttr_UNPIN, AUFS_BRATTR_UNPIN},
+#ifdef CONFIG_AUFS_FHSM
+       {AuBrAttr_FHSM, AUFS_BRATTR_FHSM},
+#endif
+#ifdef CONFIG_AUFS_XATTR
+       {AuBrAttr_ICEX, AUFS_BRATTR_ICEX},
+       {AuBrAttr_ICEX_SEC, AUFS_BRATTR_ICEX_SEC},
+       {AuBrAttr_ICEX_SYS, AUFS_BRATTR_ICEX_SYS},
+       {AuBrAttr_ICEX_TR, AUFS_BRATTR_ICEX_TR},
+       {AuBrAttr_ICEX_USR, AUFS_BRATTR_ICEX_USR},
+       {AuBrAttr_ICEX_OTH, AUFS_BRATTR_ICEX_OTH},
+#endif
+
+       /* ro/rr branch */
+       {AuBrRAttr_WH, AUFS_BRRATTR_WH},
+
+       /* rw branch */
+       {AuBrWAttr_MOO, AUFS_BRWATTR_MOO},
+       {AuBrWAttr_NoLinkWH, AUFS_BRWATTR_NLWH},
+
+       {0, NULL}
+};
+
+static int br_attr_val(char *str, match_table_t table, substring_t args[])
+{
+       int attr, v;
+       char *p;
+
+       attr = 0;
+       do {
+               p = strchr(str, '+');
+               if (p)
+                       *p = 0;
+               v = match_token(str, table, args);
+               if (v) {
+                       if (v & AuBrAttr_CMOO_Mask)
+                               attr &= ~AuBrAttr_CMOO_Mask;
+                       attr |= v;
+               } else {
+                       if (p)
+                               *p = '+';
+                       pr_warn("ignored branch attribute %s\n", str);
+                       break;
+               }
+               if (p)
+                       str = p + 1;
+       } while (p);
+
+       return attr;
+}
+
+static int au_do_optstr_br_attr(au_br_perm_str_t *str, int perm)
+{
+       int sz;
+       const char *p;
+       char *q;
+
+       q = str->a;
+       *q = 0;
+       p = au_optstr(&perm, brattr);
+       if (p) {
+               sz = strlen(p);
+               memcpy(q, p, sz + 1);
+               q += sz;
+       } else
+               goto out;
+
+       do {
+               p = au_optstr(&perm, brattr);
+               if (p) {
+                       *q++ = '+';
+                       sz = strlen(p);
+                       memcpy(q, p, sz + 1);
+                       q += sz;
+               }
+       } while (p);
+
+out:
+       return q - str->a;
+}
+
+static int noinline_for_stack br_perm_val(char *perm)
+{
+       int val, bad, sz;
+       char *p;
+       substring_t args[MAX_OPT_ARGS];
+       au_br_perm_str_t attr;
+
+       p = strchr(perm, '+');
+       if (p)
+               *p = 0;
+       val = match_token(perm, brperm, args);
+       if (!val) {
+               if (p)
+                       *p = '+';
+               pr_warn("ignored branch permission %s\n", perm);
+               val = AuBrPerm_RO;
+               goto out;
+       }
+       if (!p)
+               goto out;
+
+       val |= br_attr_val(p + 1, brattr, args);
+
+       bad = 0;
+       switch (val & AuBrPerm_Mask) {
+       case AuBrPerm_RO:
+       case AuBrPerm_RR:
+               bad = val & AuBrWAttr_Mask;
+               val &= ~AuBrWAttr_Mask;
+               break;
+       case AuBrPerm_RW:
+               bad = val & AuBrRAttr_Mask;
+               val &= ~AuBrRAttr_Mask;
+               break;
+       }
+
+       /*
+        * 'unpin' attrib becomes meaningless since linux-3.18-rc1, but aufs
+        * does not treat it as an error, just warning.
+        * this is a tiny guard for the user operation.
+        */
+       if (val & AuBrAttr_UNPIN) {
+               bad |= AuBrAttr_UNPIN;
+               val &= ~AuBrAttr_UNPIN;
+       }
+
+       if (unlikely(bad)) {
+               sz = au_do_optstr_br_attr(&attr, bad);
+               AuDebugOn(!sz);
+               pr_warn("ignored branch attribute %s\n", attr.a);
+       }
+
+out:
+       return val;
+}
+
+void au_optstr_br_perm(au_br_perm_str_t *str, int perm)
+{
+       au_br_perm_str_t attr;
+       const char *p;
+       char *q;
+       int sz;
+
+       q = str->a;
+       p = au_optstr(&perm, brperm);
+       AuDebugOn(!p || !*p);
+       sz = strlen(p);
+       memcpy(q, p, sz + 1);
+       q += sz;
+
+       sz = au_do_optstr_br_attr(&attr, perm);
+       if (sz) {
+               *q++ = '+';
+               memcpy(q, attr.a, sz + 1);
+       }
+
+       AuDebugOn(strlen(str->a) >= sizeof(str->a));
+}
+
+/* ---------------------------------------------------------------------- */
+
+static match_table_t udbalevel = {
+       {AuOpt_UDBA_REVAL, "reval"},
+       {AuOpt_UDBA_NONE, "none"},
+#ifdef CONFIG_AUFS_HNOTIFY
+       {AuOpt_UDBA_HNOTIFY, "notify"}, /* abstraction */
+#ifdef CONFIG_AUFS_HFSNOTIFY
+       {AuOpt_UDBA_HNOTIFY, "fsnotify"},
+#endif
+#endif
+       {-1, NULL}
+};
+
+static int noinline_for_stack udba_val(char *str)
+{
+       substring_t args[MAX_OPT_ARGS];
+
+       return match_token(str, udbalevel, args);
+}
+
+const char *au_optstr_udba(int udba)
+{
+       return au_parser_pattern(udba, udbalevel);
+}
+
+/* ---------------------------------------------------------------------- */
+
+static match_table_t au_wbr_create_policy = {
+       {AuWbrCreate_TDP, "tdp"},
+       {AuWbrCreate_TDP, "top-down-parent"},
+       {AuWbrCreate_RR, "rr"},
+       {AuWbrCreate_RR, "round-robin"},
+       {AuWbrCreate_MFS, "mfs"},
+       {AuWbrCreate_MFS, "most-free-space"},
+       {AuWbrCreate_MFSV, "mfs:%d"},
+       {AuWbrCreate_MFSV, "most-free-space:%d"},
+
+       /* top-down regardless the parent, and then mfs */
+       {AuWbrCreate_TDMFS, "tdmfs:%d"},
+       {AuWbrCreate_TDMFSV, "tdmfs:%d:%d"},
+
+       {AuWbrCreate_MFSRR, "mfsrr:%d"},
+       {AuWbrCreate_MFSRRV, "mfsrr:%d:%d"},
+       {AuWbrCreate_PMFS, "pmfs"},
+       {AuWbrCreate_PMFSV, "pmfs:%d"},
+       {AuWbrCreate_PMFSRR, "pmfsrr:%d"},
+       {AuWbrCreate_PMFSRRV, "pmfsrr:%d:%d"},
+
+       {-1, NULL}
+};
+
+static int au_wbr_mfs_wmark(substring_t *arg, char *str,
+                           struct au_opt_wbr_create *create)
+{
+       int err;
+       unsigned long long ull;
+
+       err = 0;
+       if (!match_u64(arg, &ull))
+               create->mfsrr_watermark = ull;
+       else {
+               pr_err("bad integer in %s\n", str);
+               err = -EINVAL;
+       }
+
+       return err;
+}
+
+static int au_wbr_mfs_sec(substring_t *arg, char *str,
+                         struct au_opt_wbr_create *create)
+{
+       int n, err;
+
+       err = 0;
+       if (!match_int(arg, &n) && 0 <= n && n <= AUFS_MFS_MAX_SEC)
+               create->mfs_second = n;
+       else {
+               pr_err("bad integer in %s\n", str);
+               err = -EINVAL;
+       }
+
+       return err;
+}
+
+static int noinline_for_stack
+au_wbr_create_val(char *str, struct au_opt_wbr_create *create)
+{
+       int err, e;
+       substring_t args[MAX_OPT_ARGS];
+
+       err = match_token(str, au_wbr_create_policy, args);
+       create->wbr_create = err;
+       switch (err) {
+       case AuWbrCreate_MFSRRV:
+       case AuWbrCreate_TDMFSV:
+       case AuWbrCreate_PMFSRRV:
+               e = au_wbr_mfs_wmark(&args[0], str, create);
+               if (!e)
+                       e = au_wbr_mfs_sec(&args[1], str, create);
+               if (unlikely(e))
+                       err = e;
+               break;
+       case AuWbrCreate_MFSRR:
+       case AuWbrCreate_TDMFS:
+       case AuWbrCreate_PMFSRR:
+               e = au_wbr_mfs_wmark(&args[0], str, create);
+               if (unlikely(e)) {
+                       err = e;
+                       break;
+               }
+               fallthrough;
+       case AuWbrCreate_MFS:
+       case AuWbrCreate_PMFS:
+               create->mfs_second = AUFS_MFS_DEF_SEC;
+               break;
+       case AuWbrCreate_MFSV:
+       case AuWbrCreate_PMFSV:
+               e = au_wbr_mfs_sec(&args[0], str, create);
+               if (unlikely(e))
+                       err = e;
+               break;
+       }
+
+       return err;
+}
+
+const char *au_optstr_wbr_create(int wbr_create)
+{
+       return au_parser_pattern(wbr_create, au_wbr_create_policy);
+}
+
+static match_table_t au_wbr_copyup_policy = {
+       {AuWbrCopyup_TDP, "tdp"},
+       {AuWbrCopyup_TDP, "top-down-parent"},
+       {AuWbrCopyup_BUP, "bup"},
+       {AuWbrCopyup_BUP, "bottom-up-parent"},
+       {AuWbrCopyup_BU, "bu"},
+       {AuWbrCopyup_BU, "bottom-up"},
+       {-1, NULL}
+};
+
+static int noinline_for_stack au_wbr_copyup_val(char *str)
+{
+       substring_t args[MAX_OPT_ARGS];
+
+       return match_token(str, au_wbr_copyup_policy, args);
+}
+
+const char *au_optstr_wbr_copyup(int wbr_copyup)
+{
+       return au_parser_pattern(wbr_copyup, au_wbr_copyup_policy);
+}
+
+/* ---------------------------------------------------------------------- */
+
+static const int lkup_dirflags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
+
+static void dump_opts(struct au_opts *opts)
+{
+#ifdef CONFIG_AUFS_DEBUG
+       /* reduce stack space */
+       union {
+               struct au_opt_add *add;
+               struct au_opt_del *del;
+               struct au_opt_mod *mod;
+               struct au_opt_xino *xino;
+               struct au_opt_xino_itrunc *xino_itrunc;
+               struct au_opt_wbr_create *create;
+       } u;
+       struct au_opt *opt;
+
+       opt = opts->opt;
+       while (opt->type != Opt_tail) {
+               switch (opt->type) {
+               case Opt_add:
+                       u.add = &opt->add;
+                       AuDbg("add {b%d, %s, 0x%x, %p}\n",
+                                 u.add->bindex, u.add->pathname, u.add->perm,
+                                 u.add->path.dentry);
+                       break;
+               case Opt_del:
+               case Opt_idel:
+                       u.del = &opt->del;
+                       AuDbg("del {%s, %p}\n",
+                             u.del->pathname, u.del->h_path.dentry);
+                       break;
+               case Opt_mod:
+               case Opt_imod:
+                       u.mod = &opt->mod;
+                       AuDbg("mod {%s, 0x%x, %p}\n",
+                                 u.mod->path, u.mod->perm, u.mod->h_root);
+                       break;
+               case Opt_append:
+                       u.add = &opt->add;
+                       AuDbg("append {b%d, %s, 0x%x, %p}\n",
+                                 u.add->bindex, u.add->pathname, u.add->perm,
+                                 u.add->path.dentry);
+                       break;
+               case Opt_prepend:
+                       u.add = &opt->add;
+                       AuDbg("prepend {b%d, %s, 0x%x, %p}\n",
+                                 u.add->bindex, u.add->pathname, u.add->perm,
+                                 u.add->path.dentry);
+                       break;
+               case Opt_dirwh:
+                       AuDbg("dirwh %d\n", opt->dirwh);
+                       break;
+               case Opt_rdcache:
+                       AuDbg("rdcache %d\n", opt->rdcache);
+                       break;
+               case Opt_rdblk:
+                       AuDbg("rdblk %u\n", opt->rdblk);
+                       break;
+               case Opt_rdblk_def:
+                       AuDbg("rdblk_def\n");
+                       break;
+               case Opt_rdhash:
+                       AuDbg("rdhash %u\n", opt->rdhash);
+                       break;
+               case Opt_rdhash_def:
+                       AuDbg("rdhash_def\n");
+                       break;
+               case Opt_xino:
+                       u.xino = &opt->xino;
+                       AuDbg("xino {%s %pD}\n", u.xino->path, u.xino->file);
+                       break;
+               case Opt_trunc_xino:
+                       AuLabel(trunc_xino);
+                       break;
+               case Opt_notrunc_xino:
+                       AuLabel(notrunc_xino);
+                       break;
+               case Opt_trunc_xino_path:
+               case Opt_itrunc_xino:
+                       u.xino_itrunc = &opt->xino_itrunc;
+                       AuDbg("trunc_xino %d\n", u.xino_itrunc->bindex);
+                       break;
+               case Opt_noxino:
+                       AuLabel(noxino);
+                       break;
+               case Opt_trunc_xib:
+                       AuLabel(trunc_xib);
+                       break;
+               case Opt_notrunc_xib:
+                       AuLabel(notrunc_xib);
+                       break;
+               case Opt_shwh:
+                       AuLabel(shwh);
+                       break;
+               case Opt_noshwh:
+                       AuLabel(noshwh);
+                       break;
+               case Opt_dirperm1:
+                       AuLabel(dirperm1);
+                       break;
+               case Opt_nodirperm1:
+                       AuLabel(nodirperm1);
+                       break;
+               case Opt_plink:
+                       AuLabel(plink);
+                       break;
+               case Opt_noplink:
+                       AuLabel(noplink);
+                       break;
+               case Opt_list_plink:
+                       AuLabel(list_plink);
+                       break;
+               case Opt_udba:
+                       AuDbg("udba %d, %s\n",
+                                 opt->udba, au_optstr_udba(opt->udba));
+                       break;
+               case Opt_dio:
+                       AuLabel(dio);
+                       break;
+               case Opt_nodio:
+                       AuLabel(nodio);
+                       break;
+               case Opt_diropq_a:
+                       AuLabel(diropq_a);
+                       break;
+               case Opt_diropq_w:
+                       AuLabel(diropq_w);
+                       break;
+               case Opt_warn_perm:
+                       AuLabel(warn_perm);
+                       break;
+               case Opt_nowarn_perm:
+                       AuLabel(nowarn_perm);
+                       break;
+               case Opt_verbose:
+                       AuLabel(verbose);
+                       break;
+               case Opt_noverbose:
+                       AuLabel(noverbose);
+                       break;
+               case Opt_sum:
+                       AuLabel(sum);
+                       break;
+               case Opt_nosum:
+                       AuLabel(nosum);
+                       break;
+               case Opt_wsum:
+                       AuLabel(wsum);
+                       break;
+               case Opt_wbr_create:
+                       u.create = &opt->wbr_create;
+                       AuDbg("create %d, %s\n", u.create->wbr_create,
+                                 au_optstr_wbr_create(u.create->wbr_create));
+                       switch (u.create->wbr_create) {
+                       case AuWbrCreate_MFSV:
+                       case AuWbrCreate_PMFSV:
+                               AuDbg("%d sec\n", u.create->mfs_second);
+                               break;
+                       case AuWbrCreate_MFSRR:
+                       case AuWbrCreate_TDMFS:
+                               AuDbg("%llu watermark\n",
+                                         u.create->mfsrr_watermark);
+                               break;
+                       case AuWbrCreate_MFSRRV:
+                       case AuWbrCreate_TDMFSV:
+                       case AuWbrCreate_PMFSRRV:
+                               AuDbg("%llu watermark, %d sec\n",
+                                         u.create->mfsrr_watermark,
+                                         u.create->mfs_second);
+                               break;
+                       }
+                       break;
+               case Opt_wbr_copyup:
+                       AuDbg("copyup %d, %s\n", opt->wbr_copyup,
+                                 au_optstr_wbr_copyup(opt->wbr_copyup));
+                       break;
+               case Opt_fhsm_sec:
+                       AuDbg("fhsm_sec %u\n", opt->fhsm_second);
+                       break;
+               case Opt_dirren:
+                       AuLabel(dirren);
+                       break;
+               case Opt_nodirren:
+                       AuLabel(nodirren);
+                       break;
+               case Opt_acl:
+                       AuLabel(acl);
+                       break;
+               case Opt_noacl:
+                       AuLabel(noacl);
+                       break;
+               default:
+                       BUG();
+               }
+               opt++;
+       }
+#endif
+}
+
+void au_opts_free(struct au_opts *opts)
+{
+       struct au_opt *opt;
+
+       opt = opts->opt;
+       while (opt->type != Opt_tail) {
+               switch (opt->type) {
+               case Opt_add:
+               case Opt_append:
+               case Opt_prepend:
+                       path_put(&opt->add.path);
+                       break;
+               case Opt_del:
+               case Opt_idel:
+                       path_put(&opt->del.h_path);
+                       break;
+               case Opt_mod:
+               case Opt_imod:
+                       dput(opt->mod.h_root);
+                       break;
+               case Opt_xino:
+                       fput(opt->xino.file);
+                       break;
+               }
+               opt++;
+       }
+}
+
+static int opt_add(struct au_opt *opt, char *opt_str, unsigned long sb_flags,
+                  aufs_bindex_t bindex)
+{
+       int err;
+       struct au_opt_add *add = &opt->add;
+       char *p;
+
+       add->bindex = bindex;
+       add->perm = AuBrPerm_RO;
+       add->pathname = opt_str;
+       p = strchr(opt_str, '=');
+       if (p) {
+               *p++ = 0;
+               if (*p)
+                       add->perm = br_perm_val(p);
+       }
+
+       err = vfsub_kern_path(add->pathname, lkup_dirflags, &add->path);
+       if (!err) {
+               if (!p) {
+                       add->perm = AuBrPerm_RO;
+                       if (au_test_fs_rr(add->path.dentry->d_sb))
+                               add->perm = AuBrPerm_RR;
+                       else if (!bindex && !(sb_flags & SB_RDONLY))
+                               add->perm = AuBrPerm_RW;
+               }
+               opt->type = Opt_add;
+               goto out;
+       }
+       pr_err("lookup failed %s (%d)\n", add->pathname, err);
+       err = -EINVAL;
+
+out:
+       return err;
+}
+
+static int au_opts_parse_del(struct au_opt_del *del, substring_t args[])
+{
+       int err;
+
+       del->pathname = args[0].from;
+       AuDbg("del path %s\n", del->pathname);
+
+       err = vfsub_kern_path(del->pathname, lkup_dirflags, &del->h_path);
+       if (unlikely(err))
+               pr_err("lookup failed %s (%d)\n", del->pathname, err);
+
+       return err;
+}
+
+#if 0 /* reserved for future use */
+static int au_opts_parse_idel(struct super_block *sb, aufs_bindex_t bindex,
+                             struct au_opt_del *del, substring_t args[])
+{
+       int err;
+       struct dentry *root;
+
+       err = -EINVAL;
+       root = sb->s_root;
+       aufs_read_lock(root, AuLock_FLUSH);
+       if (bindex < 0 || au_sbbot(sb) < bindex) {
+               pr_err("out of bounds, %d\n", bindex);
+               goto out;
+       }
+
+       err = 0;
+       del->h_path.dentry = dget(au_h_dptr(root, bindex));
+       del->h_path.mnt = mntget(au_sbr_mnt(sb, bindex));
+
+out:
+       aufs_read_unlock(root, !AuLock_IR);
+       return err;
+}
+#endif
+
+static int noinline_for_stack
+au_opts_parse_mod(struct au_opt_mod *mod, substring_t args[])
+{
+       int err;
+       struct path path;
+       char *p;
+
+       err = -EINVAL;
+       mod->path = args[0].from;
+       p = strchr(mod->path, '=');
+       if (unlikely(!p)) {
+               pr_err("no permission %s\n", args[0].from);
+               goto out;
+       }
+
+       *p++ = 0;
+       err = vfsub_kern_path(mod->path, lkup_dirflags, &path);
+       if (unlikely(err)) {
+               pr_err("lookup failed %s (%d)\n", mod->path, err);
+               goto out;
+       }
+
+       mod->perm = br_perm_val(p);
+       AuDbg("mod path %s, perm 0x%x, %s\n", mod->path, mod->perm, p);
+       mod->h_root = dget(path.dentry);
+       path_put(&path);
+
+out:
+       return err;
+}
+
+#if 0 /* reserved for future use */
+static int au_opts_parse_imod(struct super_block *sb, aufs_bindex_t bindex,
+                             struct au_opt_mod *mod, substring_t args[])
+{
+       int err;
+       struct dentry *root;
+
+       err = -EINVAL;
+       root = sb->s_root;
+       aufs_read_lock(root, AuLock_FLUSH);
+       if (bindex < 0 || au_sbbot(sb) < bindex) {
+               pr_err("out of bounds, %d\n", bindex);
+               goto out;
+       }
+
+       err = 0;
+       mod->perm = br_perm_val(args[1].from);
+       AuDbg("mod path %s, perm 0x%x, %s\n",
+             mod->path, mod->perm, args[1].from);
+       mod->h_root = dget(au_h_dptr(root, bindex));
+
+out:
+       aufs_read_unlock(root, !AuLock_IR);
+       return err;
+}
+#endif
+
+static int au_opts_parse_xino(struct super_block *sb, struct au_opt_xino *xino,
+                             substring_t args[])
+{
+       int err;
+       struct file *file;
+
+       file = au_xino_create(sb, args[0].from, /*silent*/0, /*wbrtop*/0);
+       err = PTR_ERR(file);
+       if (IS_ERR(file))
+               goto out;
+
+       err = -EINVAL;
+       if (unlikely(file->f_path.dentry->d_sb == sb)) {
+               fput(file);
+               pr_err("%s must be outside\n", args[0].from);
+               goto out;
+       }
+
+       err = 0;
+       xino->file = file;
+       xino->path = args[0].from;
+
+out:
+       return err;
+}
+
+static int noinline_for_stack
+au_opts_parse_xino_itrunc_path(struct super_block *sb,
+                              struct au_opt_xino_itrunc *xino_itrunc,
+                              substring_t args[])
+{
+       int err;
+       aufs_bindex_t bbot, bindex;
+       struct path path;
+       struct dentry *root;
+
+       err = vfsub_kern_path(args[0].from, lkup_dirflags, &path);
+       if (unlikely(err)) {
+               pr_err("lookup failed %s (%d)\n", args[0].from, err);
+               goto out;
+       }
+
+       xino_itrunc->bindex = -1;
+       root = sb->s_root;
+       aufs_read_lock(root, AuLock_FLUSH);
+       bbot = au_sbbot(sb);
+       for (bindex = 0; bindex <= bbot; bindex++) {
+               if (au_h_dptr(root, bindex) == path.dentry) {
+                       xino_itrunc->bindex = bindex;
+                       break;
+               }
+       }
+       aufs_read_unlock(root, !AuLock_IR);
+       path_put(&path);
+
+       if (unlikely(xino_itrunc->bindex < 0)) {
+               pr_err("no such branch %s\n", args[0].from);
+               err = -EINVAL;
+       }
+
+out:
+       return err;
+}
+
+/* called without aufs lock */
+int au_opts_parse(struct super_block *sb, char *str, struct au_opts *opts)
+{
+       int err, n, token;
+       aufs_bindex_t bindex;
+       unsigned char skipped;
+       struct dentry *root;
+       struct au_opt *opt, *opt_tail;
+       char *opt_str;
+       /* reduce the stack space */
+       union {
+               struct au_opt_xino_itrunc *xino_itrunc;
+               struct au_opt_wbr_create *create;
+       } u;
+       struct {
+               substring_t args[MAX_OPT_ARGS];
+       } *a;
+
+       err = -ENOMEM;
+       a = kmalloc(sizeof(*a), GFP_NOFS);
+       if (unlikely(!a))
+               goto out;
+
+       root = sb->s_root;
+       err = 0;
+       bindex = 0;
+       opt = opts->opt;
+       opt_tail = opt + opts->max_opt - 1;
+       opt->type = Opt_tail;
+       while (!err && (opt_str = strsep(&str, ",")) && *opt_str) {
+               err = -EINVAL;
+               skipped = 0;
+               token = match_token(opt_str, options, a->args);
+               switch (token) {
+               case Opt_br:
+                       err = 0;
+                       while (!err && (opt_str = strsep(&a->args[0].from, ":"))
+                              && *opt_str) {
+                               err = opt_add(opt, opt_str, opts->sb_flags,
+                                             bindex++);
+                               if (unlikely(!err && ++opt > opt_tail)) {
+                                       err = -E2BIG;
+                                       break;
+                               }
+                               opt->type = Opt_tail;
+                               skipped = 1;
+                       }
+                       break;
+               case Opt_add:
+                       if (unlikely(match_int(&a->args[0], &n))) {
+                               pr_err("bad integer in %s\n", opt_str);
+                               break;
+                       }
+                       bindex = n;
+                       err = opt_add(opt, a->args[1].from, opts->sb_flags,
+                                     bindex);
+                       if (!err)
+                               opt->type = token;
+                       break;
+               case Opt_append:
+                       err = opt_add(opt, a->args[0].from, opts->sb_flags,
+                                     /*dummy bindex*/1);
+                       if (!err)
+                               opt->type = token;
+                       break;
+               case Opt_prepend:
+                       err = opt_add(opt, a->args[0].from, opts->sb_flags,
+                                     /*bindex*/0);
+                       if (!err)
+                               opt->type = token;
+                       break;
+               case Opt_del:
+                       err = au_opts_parse_del(&opt->del, a->args);
+                       if (!err)
+                               opt->type = token;
+                       break;
+#if 0 /* reserved for future use */
+               case Opt_idel:
+                       del->pathname = "(indexed)";
+                       if (unlikely(match_int(&args[0], &n))) {
+                               pr_err("bad integer in %s\n", opt_str);
+                               break;
+                       }
+                       err = au_opts_parse_idel(sb, n, &opt->del, a->args);
+                       if (!err)
+                               opt->type = token;
+                       break;
+#endif
+               case Opt_mod:
+                       err = au_opts_parse_mod(&opt->mod, a->args);
+                       if (!err)
+                               opt->type = token;
+                       break;
+#ifdef IMOD /* reserved for future use */
+               case Opt_imod:
+                       u.mod->path = "(indexed)";
+                       if (unlikely(match_int(&a->args[0], &n))) {
+                               pr_err("bad integer in %s\n", opt_str);
+                               break;
+                       }
+                       err = au_opts_parse_imod(sb, n, &opt->mod, a->args);
+                       if (!err)
+                               opt->type = token;
+                       break;
+#endif
+               case Opt_xino:
+                       err = au_opts_parse_xino(sb, &opt->xino, a->args);
+                       if (!err)
+                               opt->type = token;
+                       break;
+
+               case Opt_trunc_xino_path:
+                       err = au_opts_parse_xino_itrunc_path
+                               (sb, &opt->xino_itrunc, a->args);
+                       if (!err)
+                               opt->type = token;
+                       break;
+
+               case Opt_itrunc_xino:
+                       u.xino_itrunc = &opt->xino_itrunc;
+                       if (unlikely(match_int(&a->args[0], &n))) {
+                               pr_err("bad integer in %s\n", opt_str);
+                               break;
+                       }
+                       u.xino_itrunc->bindex = n;
+                       aufs_read_lock(root, AuLock_FLUSH);
+                       if (n < 0 || au_sbbot(sb) < n) {
+                               pr_err("out of bounds, %d\n", n);
+                               aufs_read_unlock(root, !AuLock_IR);
+                               break;
+                       }
+                       aufs_read_unlock(root, !AuLock_IR);
+                       err = 0;
+                       opt->type = token;
+                       break;
+
+               case Opt_dirwh:
+                       if (unlikely(match_int(&a->args[0], &opt->dirwh)))
+                               break;
+                       err = 0;
+                       opt->type = token;
+                       break;
+
+               case Opt_rdcache:
+                       if (unlikely(match_int(&a->args[0], &n))) {
+                               pr_err("bad integer in %s\n", opt_str);
+                               break;
+                       }
+                       if (unlikely(n > AUFS_RDCACHE_MAX)) {
+                               pr_err("rdcache must be smaller than %d\n",
+                                      AUFS_RDCACHE_MAX);
+                               break;
+                       }
+                       opt->rdcache = n;
+                       err = 0;
+                       opt->type = token;
+                       break;
+               case Opt_rdblk:
+                       if (unlikely(match_int(&a->args[0], &n)
+                                    || n < 0
+                                    || n > KMALLOC_MAX_SIZE)) {
+                               pr_err("bad integer in %s\n", opt_str);
+                               break;
+                       }
+                       if (unlikely(n && n < NAME_MAX)) {
+                               pr_err("rdblk must be larger than %d\n",
+                                      NAME_MAX);
+                               break;
+                       }
+                       opt->rdblk = n;
+                       err = 0;
+                       opt->type = token;
+                       break;
+               case Opt_rdhash:
+                       if (unlikely(match_int(&a->args[0], &n)
+                                    || n < 0
+                                    || n * sizeof(struct hlist_head)
+                                    > KMALLOC_MAX_SIZE)) {
+                               pr_err("bad integer in %s\n", opt_str);
+                               break;
+                       }
+                       opt->rdhash = n;
+                       err = 0;
+                       opt->type = token;
+                       break;
+
+               case Opt_trunc_xino:
+               case Opt_notrunc_xino:
+               case Opt_noxino:
+               case Opt_trunc_xib:
+               case Opt_notrunc_xib:
+               case Opt_shwh:
+               case Opt_noshwh:
+               case Opt_dirperm1:
+               case Opt_nodirperm1:
+               case Opt_plink:
+               case Opt_noplink:
+               case Opt_list_plink:
+               case Opt_dio:
+               case Opt_nodio:
+               case Opt_diropq_a:
+               case Opt_diropq_w:
+               case Opt_warn_perm:
+               case Opt_nowarn_perm:
+               case Opt_verbose:
+               case Opt_noverbose:
+               case Opt_sum:
+               case Opt_nosum:
+               case Opt_wsum:
+               case Opt_rdblk_def:
+               case Opt_rdhash_def:
+               case Opt_dirren:
+               case Opt_nodirren:
+               case Opt_acl:
+               case Opt_noacl:
+                       err = 0;
+                       opt->type = token;
+                       break;
+
+               case Opt_udba:
+                       opt->udba = udba_val(a->args[0].from);
+                       if (opt->udba >= 0) {
+                               err = 0;
+                               opt->type = token;
+                       } else
+                               pr_err("wrong value, %s\n", opt_str);
+                       break;
+
+               case Opt_wbr_create:
+                       u.create = &opt->wbr_create;
+                       u.create->wbr_create
+                               = au_wbr_create_val(a->args[0].from, u.create);
+                       if (u.create->wbr_create >= 0) {
+                               err = 0;
+                               opt->type = token;
+                       } else
+                               pr_err("wrong value, %s\n", opt_str);
+                       break;
+               case Opt_wbr_copyup:
+                       opt->wbr_copyup = au_wbr_copyup_val(a->args[0].from);
+                       if (opt->wbr_copyup >= 0) {
+                               err = 0;
+                               opt->type = token;
+                       } else
+                               pr_err("wrong value, %s\n", opt_str);
+                       break;
+
+               case Opt_fhsm_sec:
+                       if (unlikely(match_int(&a->args[0], &n)
+                                    || n < 0)) {
+                               pr_err("bad integer in %s\n", opt_str);
+                               break;
+                       }
+                       if (sysaufs_brs) {
+                               opt->fhsm_second = n;
+                               opt->type = token;
+                       } else
+                               pr_warn("ignored %s\n", opt_str);
+                       err = 0;
+                       break;
+
+               case Opt_ignore:
+                       pr_warn("ignored %s\n", opt_str);
+                       fallthrough;
+               case Opt_ignore_silent:
+                       skipped = 1;
+                       err = 0;
+                       break;
+               case Opt_err:
+                       pr_err("unknown option %s\n", opt_str);
+                       break;
+               }
+
+               if (!err && !skipped) {
+                       if (unlikely(++opt > opt_tail)) {
+                               err = -E2BIG;
+                               opt--;
+                               opt->type = Opt_tail;
+                               break;
+                       }
+                       opt->type = Opt_tail;
+               }
+       }
+
+       au_kfree_rcu(a);
+       dump_opts(opts);
+       if (unlikely(err))
+               au_opts_free(opts);
+
+out:
+       return err;
+}
+
+static int au_opt_wbr_create(struct super_block *sb,
+                            struct au_opt_wbr_create *create)
+{
+       int err;
+       struct au_sbinfo *sbinfo;
+
+       SiMustWriteLock(sb);
+
+       err = 1; /* handled */
+       sbinfo = au_sbi(sb);
+       if (sbinfo->si_wbr_create_ops->fin) {
+               err = sbinfo->si_wbr_create_ops->fin(sb);
+               if (!err)
+                       err = 1;
+       }
+
+       sbinfo->si_wbr_create = create->wbr_create;
+       sbinfo->si_wbr_create_ops = au_wbr_create_ops + create->wbr_create;
+       switch (create->wbr_create) {
+       case AuWbrCreate_MFSRRV:
+       case AuWbrCreate_MFSRR:
+       case AuWbrCreate_TDMFS:
+       case AuWbrCreate_TDMFSV:
+       case AuWbrCreate_PMFSRR:
+       case AuWbrCreate_PMFSRRV:
+               sbinfo->si_wbr_mfs.mfsrr_watermark = create->mfsrr_watermark;
+               fallthrough;
+       case AuWbrCreate_MFS:
+       case AuWbrCreate_MFSV:
+       case AuWbrCreate_PMFS:
+       case AuWbrCreate_PMFSV:
+               sbinfo->si_wbr_mfs.mfs_expire
+                       = msecs_to_jiffies(create->mfs_second * MSEC_PER_SEC);
+               break;
+       }
+
+       if (sbinfo->si_wbr_create_ops->init)
+               sbinfo->si_wbr_create_ops->init(sb); /* ignore */
+
+       return err;
+}
+
+/*
+ * returns,
+ * plus: processed without an error
+ * zero: unprocessed
+ */
+static int au_opt_simple(struct super_block *sb, struct au_opt *opt,
+                        struct au_opts *opts)
+{
+       int err;
+       struct au_sbinfo *sbinfo;
+
+       SiMustWriteLock(sb);
+
+       err = 1; /* handled */
+       sbinfo = au_sbi(sb);
+       switch (opt->type) {
+       case Opt_udba:
+               sbinfo->si_mntflags &= ~AuOptMask_UDBA;
+               sbinfo->si_mntflags |= opt->udba;
+               opts->given_udba |= opt->udba;
+               break;
+
+       case Opt_plink:
+               au_opt_set(sbinfo->si_mntflags, PLINK);
+               break;
+       case Opt_noplink:
+               if (au_opt_test(sbinfo->si_mntflags, PLINK))
+                       au_plink_put(sb, /*verbose*/1);
+               au_opt_clr(sbinfo->si_mntflags, PLINK);
+               break;
+       case Opt_list_plink:
+               if (au_opt_test(sbinfo->si_mntflags, PLINK))
+                       au_plink_list(sb);
+               break;
+
+       case Opt_dio:
+               au_opt_set(sbinfo->si_mntflags, DIO);
+               au_fset_opts(opts->flags, REFRESH_DYAOP);
+               break;
+       case Opt_nodio:
+               au_opt_clr(sbinfo->si_mntflags, DIO);
+               au_fset_opts(opts->flags, REFRESH_DYAOP);
+               break;
+
+       case Opt_fhsm_sec:
+               au_fhsm_set(sbinfo, opt->fhsm_second);
+               break;
+
+       case Opt_diropq_a:
+               au_opt_set(sbinfo->si_mntflags, ALWAYS_DIROPQ);
+               break;
+       case Opt_diropq_w:
+               au_opt_clr(sbinfo->si_mntflags, ALWAYS_DIROPQ);
+               break;
+
+       case Opt_warn_perm:
+               au_opt_set(sbinfo->si_mntflags, WARN_PERM);
+               break;
+       case Opt_nowarn_perm:
+               au_opt_clr(sbinfo->si_mntflags, WARN_PERM);
+               break;
+
+       case Opt_verbose:
+               au_opt_set(sbinfo->si_mntflags, VERBOSE);
+               break;
+       case Opt_noverbose:
+               au_opt_clr(sbinfo->si_mntflags, VERBOSE);
+               break;
+
+       case Opt_sum:
+               au_opt_set(sbinfo->si_mntflags, SUM);
+               break;
+       case Opt_wsum:
+               au_opt_clr(sbinfo->si_mntflags, SUM);
+               au_opt_set(sbinfo->si_mntflags, SUM_W);
+               break;
+       case Opt_nosum:
+               au_opt_clr(sbinfo->si_mntflags, SUM);
+               au_opt_clr(sbinfo->si_mntflags, SUM_W);
+               break;
+
+       case Opt_wbr_create:
+               err = au_opt_wbr_create(sb, &opt->wbr_create);
+               break;
+       case Opt_wbr_copyup:
+               sbinfo->si_wbr_copyup = opt->wbr_copyup;
+               sbinfo->si_wbr_copyup_ops = au_wbr_copyup_ops + opt->wbr_copyup;
+               break;
+
+       case Opt_dirwh:
+               sbinfo->si_dirwh = opt->dirwh;
+               break;
+
+       case Opt_rdcache:
+               sbinfo->si_rdcache
+                       = msecs_to_jiffies(opt->rdcache * MSEC_PER_SEC);
+               break;
+       case Opt_rdblk:
+               sbinfo->si_rdblk = opt->rdblk;
+               break;
+       case Opt_rdblk_def:
+               sbinfo->si_rdblk = AUFS_RDBLK_DEF;
+               break;
+       case Opt_rdhash:
+               sbinfo->si_rdhash = opt->rdhash;
+               break;
+       case Opt_rdhash_def:
+               sbinfo->si_rdhash = AUFS_RDHASH_DEF;
+               break;
+
+       case Opt_shwh:
+               au_opt_set(sbinfo->si_mntflags, SHWH);
+               break;
+       case Opt_noshwh:
+               au_opt_clr(sbinfo->si_mntflags, SHWH);
+               break;
+
+       case Opt_dirperm1:
+               au_opt_set(sbinfo->si_mntflags, DIRPERM1);
+               break;
+       case Opt_nodirperm1:
+               au_opt_clr(sbinfo->si_mntflags, DIRPERM1);
+               break;
+
+       case Opt_trunc_xino:
+               au_opt_set(sbinfo->si_mntflags, TRUNC_XINO);
+               break;
+       case Opt_notrunc_xino:
+               au_opt_clr(sbinfo->si_mntflags, TRUNC_XINO);
+               break;
+
+       case Opt_trunc_xino_path:
+       case Opt_itrunc_xino:
+               err = au_xino_trunc(sb, opt->xino_itrunc.bindex,
+                                   /*idx_begin*/0);
+               if (!err)
+                       err = 1;
+               break;
+
+       case Opt_trunc_xib:
+               au_fset_opts(opts->flags, TRUNC_XIB);
+               break;
+       case Opt_notrunc_xib:
+               au_fclr_opts(opts->flags, TRUNC_XIB);
+               break;
+
+       case Opt_dirren:
+               err = 1;
+               if (!au_opt_test(sbinfo->si_mntflags, DIRREN)) {
+                       err = au_dr_opt_set(sb);
+                       if (!err)
+                               err = 1;
+               }
+               if (err == 1)
+                       au_opt_set(sbinfo->si_mntflags, DIRREN);
+               break;
+       case Opt_nodirren:
+               err = 1;
+               if (au_opt_test(sbinfo->si_mntflags, DIRREN)) {
+                       err = au_dr_opt_clr(sb, au_ftest_opts(opts->flags,
+                                                             DR_FLUSHED));
+                       if (!err)
+                               err = 1;
+               }
+               if (err == 1)
+                       au_opt_clr(sbinfo->si_mntflags, DIRREN);
+               break;
+
+       case Opt_acl:
+               sb->s_flags |= SB_POSIXACL;
+               break;
+       case Opt_noacl:
+               sb->s_flags &= ~SB_POSIXACL;
+               break;
+
+       default:
+               err = 0;
+               break;
+       }
+
+       return err;
+}
+
+/*
+ * returns tri-state.
+ * plus: processed without an error
+ * zero: unprocessed
+ * minus: error
+ */
+static int au_opt_br(struct super_block *sb, struct au_opt *opt,
+                    struct au_opts *opts)
+{
+       int err, do_refresh;
+
+       err = 0;
+       switch (opt->type) {
+       case Opt_append:
+               opt->add.bindex = au_sbbot(sb) + 1;
+               if (opt->add.bindex < 0)
+                       opt->add.bindex = 0;
+               goto add;
+               /* Always goto add, not fallthrough */
+       case Opt_prepend:
+               opt->add.bindex = 0;
+               fallthrough;
+       add: /* indented label */
+       case Opt_add:
+               err = au_br_add(sb, &opt->add,
+                               au_ftest_opts(opts->flags, REMOUNT));
+               if (!err) {
+                       err = 1;
+                       au_fset_opts(opts->flags, REFRESH);
+               }
+               break;
+
+       case Opt_del:
+       case Opt_idel:
+               err = au_br_del(sb, &opt->del,
+                               au_ftest_opts(opts->flags, REMOUNT));
+               if (!err) {
+                       err = 1;
+                       au_fset_opts(opts->flags, TRUNC_XIB);
+                       au_fset_opts(opts->flags, REFRESH);
+               }
+               break;
+
+       case Opt_mod:
+       case Opt_imod:
+               err = au_br_mod(sb, &opt->mod,
+                               au_ftest_opts(opts->flags, REMOUNT),
+                               &do_refresh);
+               if (!err) {
+                       err = 1;
+                       if (do_refresh)
+                               au_fset_opts(opts->flags, REFRESH);
+               }
+               break;
+       }
+       return err;
+}
+
+static int au_opt_xino(struct super_block *sb, struct au_opt *opt,
+                      struct au_opt_xino **opt_xino,
+                      struct au_opts *opts)
+{
+       int err;
+
+       err = 0;
+       switch (opt->type) {
+       case Opt_xino:
+               err = au_xino_set(sb, &opt->xino,
+                                 !!au_ftest_opts(opts->flags, REMOUNT));
+               if (unlikely(err))
+                       break;
+
+               *opt_xino = &opt->xino;
+               break;
+
+       case Opt_noxino:
+               au_xino_clr(sb);
+               *opt_xino = (void *)-1;
+               break;
+       }
+
+       return err;
+}
+
+int au_opts_verify(struct super_block *sb, unsigned long sb_flags,
+                  unsigned int pending)
+{
+       int err, fhsm;
+       aufs_bindex_t bindex, bbot;
+       unsigned char do_plink, skip, do_free, can_no_dreval;
+       struct au_branch *br;
+       struct au_wbr *wbr;
+       struct dentry *root, *dentry;
+       struct inode *dir, *h_dir;
+       struct au_sbinfo *sbinfo;
+       struct au_hinode *hdir;
+
+       SiMustAnyLock(sb);
+
+       sbinfo = au_sbi(sb);
+       AuDebugOn(!(sbinfo->si_mntflags & AuOptMask_UDBA));
+
+       if (!(sb_flags & SB_RDONLY)) {
+               if (unlikely(!au_br_writable(au_sbr_perm(sb, 0))))
+                       pr_warn("first branch should be rw\n");
+               if (unlikely(au_opt_test(sbinfo->si_mntflags, SHWH)))
+                       pr_warn_once("shwh should be used with ro\n");
+       }
+
+       if (au_opt_test((sbinfo->si_mntflags | pending), UDBA_HNOTIFY)
+           && !au_opt_test(sbinfo->si_mntflags, XINO))
+               pr_warn_once("udba=*notify requires xino\n");
+
+       if (au_opt_test(sbinfo->si_mntflags, DIRPERM1))
+               pr_warn_once("dirperm1 breaks the protection"
+                            " by the permission bits on the lower branch\n");
+
+       err = 0;
+       fhsm = 0;
+       root = sb->s_root;
+       dir = d_inode(root);
+       do_plink = !!au_opt_test(sbinfo->si_mntflags, PLINK);
+       can_no_dreval = !!au_opt_test((sbinfo->si_mntflags | pending),
+                                     UDBA_NONE);
+       bbot = au_sbbot(sb);
+       for (bindex = 0; !err && bindex <= bbot; bindex++) {
+               skip = 0;
+               h_dir = au_h_iptr(dir, bindex);
+               br = au_sbr(sb, bindex);
+
+               if ((br->br_perm & AuBrAttr_ICEX)
+                   && !h_dir->i_op->listxattr)
+                       br->br_perm &= ~AuBrAttr_ICEX;
+#if 0 /* untested */
+               if ((br->br_perm & AuBrAttr_ICEX_SEC)
+                   && (au_br_sb(br)->s_flags & SB_NOSEC))
+                       br->br_perm &= ~AuBrAttr_ICEX_SEC;
+#endif
+
+               do_free = 0;
+               wbr = br->br_wbr;
+               if (wbr)
+                       wbr_wh_read_lock(wbr);
+
+               if (!au_br_writable(br->br_perm)) {
+                       do_free = !!wbr;
+                       skip = (!wbr
+                               || (!wbr->wbr_whbase
+                                   && !wbr->wbr_plink
+                                   && !wbr->wbr_orph));
+               } else if (!au_br_wh_linkable(br->br_perm)) {
+                       /* skip = (!br->br_whbase && !br->br_orph); */
+                       skip = (!wbr || !wbr->wbr_whbase);
+                       if (skip && wbr) {
+                               if (do_plink)
+                                       skip = !!wbr->wbr_plink;
+                               else
+                                       skip = !wbr->wbr_plink;
+                       }
+               } else {
+                       /* skip = (br->br_whbase && br->br_ohph); */
+                       skip = (wbr && wbr->wbr_whbase);
+                       if (skip) {
+                               if (do_plink)
+                                       skip = !!wbr->wbr_plink;
+                               else
+                                       skip = !wbr->wbr_plink;
+                       }
+               }
+               if (wbr)
+                       wbr_wh_read_unlock(wbr);
+
+               if (can_no_dreval) {
+                       dentry = br->br_path.dentry;
+                       spin_lock(&dentry->d_lock);
+                       if (dentry->d_flags &
+                           (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE))
+                               can_no_dreval = 0;
+                       spin_unlock(&dentry->d_lock);
+               }
+
+               if (au_br_fhsm(br->br_perm)) {
+                       fhsm++;
+                       AuDebugOn(!br->br_fhsm);
+               }
+
+               if (skip)
+                       continue;
+
+               hdir = au_hi(dir, bindex);
+               au_hn_inode_lock_nested(hdir, AuLsc_I_PARENT);
+               if (wbr)
+                       wbr_wh_write_lock(wbr);
+               err = au_wh_init(br, sb);
+               if (wbr)
+                       wbr_wh_write_unlock(wbr);
+               au_hn_inode_unlock(hdir);
+
+               if (!err && do_free) {
+                       au_kfree_rcu(wbr);
+                       br->br_wbr = NULL;
+               }
+       }
+
+       if (can_no_dreval)
+               au_fset_si(sbinfo, NO_DREVAL);
+       else
+               au_fclr_si(sbinfo, NO_DREVAL);
+
+       if (fhsm >= 2) {
+               au_fset_si(sbinfo, FHSM);
+               for (bindex = bbot; bindex >= 0; bindex--) {
+                       br = au_sbr(sb, bindex);
+                       if (au_br_fhsm(br->br_perm)) {
+                               au_fhsm_set_bottom(sb, bindex);
+                               break;
+                       }
+               }
+       } else {
+               au_fclr_si(sbinfo, FHSM);
+               au_fhsm_set_bottom(sb, -1);
+       }
+
+       return err;
+}
+
+int au_opts_mount(struct super_block *sb, struct au_opts *opts)
+{
+       int err;
+       unsigned int tmp;
+       aufs_bindex_t bindex, bbot;
+       struct au_opt *opt;
+       struct au_opt_xino *opt_xino, xino;
+       struct au_sbinfo *sbinfo;
+       struct au_branch *br;
+       struct inode *dir;
+
+       SiMustWriteLock(sb);
+
+       err = 0;
+       opt_xino = NULL;
+       opt = opts->opt;
+       while (err >= 0 && opt->type != Opt_tail)
+               err = au_opt_simple(sb, opt++, opts);
+       if (err > 0)
+               err = 0;
+       else if (unlikely(err < 0))
+               goto out;
+
+       /* disable xino and udba temporary */
+       sbinfo = au_sbi(sb);
+       tmp = sbinfo->si_mntflags;
+       au_opt_clr(sbinfo->si_mntflags, XINO);
+       au_opt_set_udba(sbinfo->si_mntflags, UDBA_REVAL);
+
+       opt = opts->opt;
+       while (err >= 0 && opt->type != Opt_tail)
+               err = au_opt_br(sb, opt++, opts);
+       if (err > 0)
+               err = 0;
+       else if (unlikely(err < 0))
+               goto out;
+
+       bbot = au_sbbot(sb);
+       if (unlikely(bbot < 0)) {
+               err = -EINVAL;
+               pr_err("no branches\n");
+               goto out;
+       }
+
+       if (au_opt_test(tmp, XINO))
+               au_opt_set(sbinfo->si_mntflags, XINO);
+       opt = opts->opt;
+       while (!err && opt->type != Opt_tail)
+               err = au_opt_xino(sb, opt++, &opt_xino, opts);
+       if (unlikely(err))
+               goto out;
+
+       err = au_opts_verify(sb, sb->s_flags, tmp);
+       if (unlikely(err))
+               goto out;
+
+       /* restore xino */
+       if (au_opt_test(tmp, XINO) && !opt_xino) {
+               xino.file = au_xino_def(sb);
+               err = PTR_ERR(xino.file);
+               if (IS_ERR(xino.file))
+                       goto out;
+
+               err = au_xino_set(sb, &xino, /*remount*/0);
+               fput(xino.file);
+               if (unlikely(err))
+                       goto out;
+       }
+
+       /* restore udba */
+       tmp &= AuOptMask_UDBA;
+       sbinfo->si_mntflags &= ~AuOptMask_UDBA;
+       sbinfo->si_mntflags |= tmp;
+       bbot = au_sbbot(sb);
+       for (bindex = 0; bindex <= bbot; bindex++) {
+               br = au_sbr(sb, bindex);
+               err = au_hnotify_reset_br(tmp, br, br->br_perm);
+               if (unlikely(err))
+                       AuIOErr("hnotify failed on br %d, %d, ignored\n",
+                               bindex, err);
+               /* go on even if err */
+       }
+       if (au_opt_test(tmp, UDBA_HNOTIFY)) {
+               dir = d_inode(sb->s_root);
+               au_hn_reset(dir, au_hi_flags(dir, /*isdir*/1) & ~AuHi_XINO);
+       }
+
+out:
+       return err;
+}
+
+int au_opts_remount(struct super_block *sb, struct au_opts *opts)
+{
+       int err, rerr;
+       unsigned char no_dreval;
+       struct inode *dir;
+       struct au_opt_xino *opt_xino;
+       struct au_opt *opt;
+       struct au_sbinfo *sbinfo;
+
+       SiMustWriteLock(sb);
+
+       err = au_dr_opt_flush(sb);
+       if (unlikely(err))
+               goto out;
+       au_fset_opts(opts->flags, DR_FLUSHED);
+
+       dir = d_inode(sb->s_root);
+       sbinfo = au_sbi(sb);
+       opt_xino = NULL;
+       opt = opts->opt;
+       while (err >= 0 && opt->type != Opt_tail) {
+               err = au_opt_simple(sb, opt, opts);
+               if (!err)
+                       err = au_opt_br(sb, opt, opts);
+               if (!err)
+                       err = au_opt_xino(sb, opt, &opt_xino, opts);
+               opt++;
+       }
+       if (err > 0)
+               err = 0;
+       AuTraceErr(err);
+       /* go on even err */
+
+       no_dreval = !!au_ftest_si(sbinfo, NO_DREVAL);
+       rerr = au_opts_verify(sb, opts->sb_flags, /*pending*/0);
+       if (unlikely(rerr && !err))
+               err = rerr;
+
+       if (no_dreval != !!au_ftest_si(sbinfo, NO_DREVAL))
+               au_fset_opts(opts->flags, REFRESH_IDOP);
+
+       if (au_ftest_opts(opts->flags, TRUNC_XIB)) {
+               rerr = au_xib_trunc(sb);
+               if (unlikely(rerr && !err))
+                       err = rerr;
+       }
+
+       /* will be handled by the caller */
+       if (!au_ftest_opts(opts->flags, REFRESH)
+           && (opts->given_udba
+               || au_opt_test(sbinfo->si_mntflags, XINO)
+               || au_ftest_opts(opts->flags, REFRESH_IDOP)
+                   ))
+               au_fset_opts(opts->flags, REFRESH);
+
+       AuDbg("status 0x%x\n", opts->flags);
+
+out:
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+unsigned int au_opt_udba(struct super_block *sb)
+{
+       return au_mntflags(sb) & AuOptMask_UDBA;
+}
diff -urN /usr/share/empty/fs/aufs/opts.h linux/fs/aufs/opts.h
--- /usr/share/empty/fs/aufs/opts.h     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/opts.h        2021-12-03 15:38:59.939980643 +0100
@@ -0,0 +1,225 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * mount options/flags
+ */
+
+#ifndef __AUFS_OPTS_H__
+#define __AUFS_OPTS_H__
+
+#ifdef __KERNEL__
+
+#include <linux/path.h>
+
+struct file;
+
+/* ---------------------------------------------------------------------- */
+
+/* mount flags */
+#define AuOpt_XINO             1               /* external inode number bitmap
+                                                  and translation table */
+#define AuOpt_TRUNC_XINO       (1 << 1)        /* truncate xino files */
+#define AuOpt_UDBA_NONE                (1 << 2)        /* users direct branch access */
+#define AuOpt_UDBA_REVAL       (1 << 3)
+#define AuOpt_UDBA_HNOTIFY     (1 << 4)
+#define AuOpt_SHWH             (1 << 5)        /* show whiteout */
+#define AuOpt_PLINK            (1 << 6)        /* pseudo-link */
+#define AuOpt_DIRPERM1         (1 << 7)        /* ignore the lower dir's perm
+                                                  bits */
+#define AuOpt_ALWAYS_DIROPQ    (1 << 9)        /* policy to creating diropq */
+#define AuOpt_SUM              (1 << 10)       /* summation for statfs(2) */
+#define AuOpt_SUM_W            (1 << 11)       /* unimplemented */
+#define AuOpt_WARN_PERM                (1 << 12)       /* warn when add-branch */
+#define AuOpt_VERBOSE          (1 << 13)       /* print the cause of error */
+#define AuOpt_DIO              (1 << 14)       /* direct io */
+#define AuOpt_DIRREN           (1 << 15)       /* directory rename */
+
+#ifndef CONFIG_AUFS_HNOTIFY
+#undef AuOpt_UDBA_HNOTIFY
+#define AuOpt_UDBA_HNOTIFY     0
+#endif
+#ifndef CONFIG_AUFS_DIRREN
+#undef AuOpt_DIRREN
+#define AuOpt_DIRREN           0
+#endif
+#ifndef CONFIG_AUFS_SHWH
+#undef AuOpt_SHWH
+#define AuOpt_SHWH             0
+#endif
+
+#define AuOpt_Def      (AuOpt_XINO \
+                        | AuOpt_UDBA_REVAL \
+                        | AuOpt_PLINK \
+                        /* | AuOpt_DIRPERM1 */ \
+                        | AuOpt_WARN_PERM)
+#define AuOptMask_UDBA (AuOpt_UDBA_NONE \
+                        | AuOpt_UDBA_REVAL \
+                        | AuOpt_UDBA_HNOTIFY)
+
+#define au_opt_test(flags, name)       (flags & AuOpt_##name)
+#define au_opt_set(flags, name) do { \
+       BUILD_BUG_ON(AuOpt_##name & AuOptMask_UDBA); \
+       ((flags) |= AuOpt_##name); \
+} while (0)
+#define au_opt_set_udba(flags, name) do { \
+       (flags) &= ~AuOptMask_UDBA; \
+       ((flags) |= AuOpt_##name); \
+} while (0)
+#define au_opt_clr(flags, name) do { \
+       ((flags) &= ~AuOpt_##name); \
+} while (0)
+
+static inline unsigned int au_opts_plink(unsigned int mntflags)
+{
+#ifdef CONFIG_PROC_FS
+       return mntflags;
+#else
+       return mntflags & ~AuOpt_PLINK;
+#endif
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* policies to select one among multiple writable branches */
+enum {
+       AuWbrCreate_TDP,        /* top down parent */
+       AuWbrCreate_RR,         /* round robin */
+       AuWbrCreate_MFS,        /* most free space */
+       AuWbrCreate_MFSV,       /* mfs with seconds */
+       AuWbrCreate_MFSRR,      /* mfs then rr */
+       AuWbrCreate_MFSRRV,     /* mfs then rr with seconds */
+       AuWbrCreate_TDMFS,      /* top down regardless parent and mfs */
+       AuWbrCreate_TDMFSV,     /* top down regardless parent and mfs */
+       AuWbrCreate_PMFS,       /* parent and mfs */
+       AuWbrCreate_PMFSV,      /* parent and mfs with seconds */
+       AuWbrCreate_PMFSRR,     /* parent, mfs and round-robin */
+       AuWbrCreate_PMFSRRV,    /* plus seconds */
+
+       AuWbrCreate_Def = AuWbrCreate_TDP
+};
+
+enum {
+       AuWbrCopyup_TDP,        /* top down parent */
+       AuWbrCopyup_BUP,        /* bottom up parent */
+       AuWbrCopyup_BU,         /* bottom up */
+
+       AuWbrCopyup_Def = AuWbrCopyup_TDP
+};
+
+/* ---------------------------------------------------------------------- */
+
+struct au_opt_add {
+       aufs_bindex_t   bindex;
+       char            *pathname;
+       int             perm;
+       struct path     path;
+};
+
+struct au_opt_del {
+       char            *pathname;
+       struct path     h_path;
+};
+
+struct au_opt_mod {
+       char            *path;
+       int             perm;
+       struct dentry   *h_root;
+};
+
+struct au_opt_xino {
+       char            *path;
+       struct file     *file;
+};
+
+struct au_opt_xino_itrunc {
+       aufs_bindex_t   bindex;
+};
+
+struct au_opt_wbr_create {
+       int                     wbr_create;
+       int                     mfs_second;
+       unsigned long long      mfsrr_watermark;
+};
+
+struct au_opt {
+       int type;
+       union {
+               struct au_opt_xino      xino;
+               struct au_opt_xino_itrunc xino_itrunc;
+               struct au_opt_add       add;
+               struct au_opt_del       del;
+               struct au_opt_mod       mod;
+               int                     dirwh;
+               int                     rdcache;
+               unsigned int            rdblk;
+               unsigned int            rdhash;
+               int                     udba;
+               struct au_opt_wbr_create wbr_create;
+               int                     wbr_copyup;
+               unsigned int            fhsm_second;
+       };
+};
+
+/* opts flags */
+#define AuOpts_REMOUNT         1
+#define AuOpts_REFRESH         (1 << 1)
+#define AuOpts_TRUNC_XIB       (1 << 2)
+#define AuOpts_REFRESH_DYAOP   (1 << 3)
+#define AuOpts_REFRESH_IDOP    (1 << 4)
+#define AuOpts_DR_FLUSHED      (1 << 5)
+#define au_ftest_opts(flags, name)     ((flags) & AuOpts_##name)
+#define au_fset_opts(flags, name) \
+       do { (flags) |= AuOpts_##name; } while (0)
+#define au_fclr_opts(flags, name) \
+       do { (flags) &= ~AuOpts_##name; } while (0)
+
+#ifndef CONFIG_AUFS_DIRREN
+#undef AuOpts_DR_FLUSHED
+#define AuOpts_DR_FLUSHED      0
+#endif
+
+struct au_opts {
+       struct au_opt   *opt;
+       int             max_opt;
+
+       unsigned int    given_udba;
+       unsigned int    flags;
+       unsigned long   sb_flags;
+};
+
+/* ---------------------------------------------------------------------- */
+
+/* opts.c */
+void au_optstr_br_perm(au_br_perm_str_t *str, int perm);
+const char *au_optstr_udba(int udba);
+const char *au_optstr_wbr_copyup(int wbr_copyup);
+const char *au_optstr_wbr_create(int wbr_create);
+
+void au_opts_free(struct au_opts *opts);
+struct super_block;
+int au_opts_parse(struct super_block *sb, char *str, struct au_opts *opts);
+int au_opts_verify(struct super_block *sb, unsigned long sb_flags,
+                  unsigned int pending);
+int au_opts_mount(struct super_block *sb, struct au_opts *opts);
+int au_opts_remount(struct super_block *sb, struct au_opts *opts);
+
+unsigned int au_opt_udba(struct super_block *sb);
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_OPTS_H__ */
diff -urN /usr/share/empty/fs/aufs/plink.c linux/fs/aufs/plink.c
--- /usr/share/empty/fs/aufs/plink.c    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/plink.c       2021-12-03 15:38:59.939980643 +0100
@@ -0,0 +1,516 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * pseudo-link
+ */
+
+#include "aufs.h"
+
+/*
+ * the pseudo-link maintenance mode.
+ * during a user process maintains the pseudo-links,
+ * prohibit adding a new plink and branch manipulation.
+ *
+ * Flags
+ * NOPLM:
+ *     For entry functions which will handle plink, and i_mutex is already held
+ *     in VFS.
+ *     They cannot wait and should return an error at once.
+ *     Callers has to check the error.
+ * NOPLMW:
+ *     For entry functions which will handle plink, but i_mutex is not held
+ *     in VFS.
+ *     They can wait the plink maintenance mode to finish.
+ *
+ * They behave like F_SETLK and F_SETLKW.
+ * If the caller never handle plink, then both flags are unnecessary.
+ */
+
+int au_plink_maint(struct super_block *sb, int flags)
+{
+       int err;
+       pid_t pid, ppid;
+       struct task_struct *parent, *prev;
+       struct au_sbinfo *sbi;
+
+       SiMustAnyLock(sb);
+
+       err = 0;
+       if (!au_opt_test(au_mntflags(sb), PLINK))
+               goto out;
+
+       sbi = au_sbi(sb);
+       pid = sbi->si_plink_maint_pid;
+       if (!pid || pid == current->pid)
+               goto out;
+
+       /* todo: it highly depends upon /sbin/mount.aufs */
+       prev = NULL;
+       parent = current;
+       ppid = 0;
+       rcu_read_lock();
+       while (1) {
+               parent = rcu_dereference(parent->real_parent);
+               if (parent == prev)
+                       break;
+               ppid = task_pid_vnr(parent);
+               if (pid == ppid) {
+                       rcu_read_unlock();
+                       goto out;
+               }
+               prev = parent;
+       }
+       rcu_read_unlock();
+
+       if (au_ftest_lock(flags, NOPLMW)) {
+               /* if there is no i_mutex lock in VFS, we don't need to wait */
+               /* AuDebugOn(!lockdep_depth(current)); */
+               while (sbi->si_plink_maint_pid) {
+                       si_read_unlock(sb);
+                       /* gave up wake_up_bit() */
+                       wait_event(sbi->si_plink_wq, !sbi->si_plink_maint_pid);
+
+                       if (au_ftest_lock(flags, FLUSH))
+                               au_nwt_flush(&sbi->si_nowait);
+                       si_noflush_read_lock(sb);
+               }
+       } else if (au_ftest_lock(flags, NOPLM)) {
+               AuDbg("ppid %d, pid %d\n", ppid, pid);
+               err = -EAGAIN;
+       }
+
+out:
+       return err;
+}
+
+void au_plink_maint_leave(struct au_sbinfo *sbinfo)
+{
+       spin_lock(&sbinfo->si_plink_maint_lock);
+       sbinfo->si_plink_maint_pid = 0;
+       spin_unlock(&sbinfo->si_plink_maint_lock);
+       wake_up_all(&sbinfo->si_plink_wq);
+}
+
+int au_plink_maint_enter(struct super_block *sb)
+{
+       int err;
+       struct au_sbinfo *sbinfo;
+
+       err = 0;
+       sbinfo = au_sbi(sb);
+       /* make sure i am the only one in this fs */
+       si_write_lock(sb, AuLock_FLUSH);
+       if (au_opt_test(au_mntflags(sb), PLINK)) {
+               spin_lock(&sbinfo->si_plink_maint_lock);
+               if (!sbinfo->si_plink_maint_pid)
+                       sbinfo->si_plink_maint_pid = current->pid;
+               else
+                       err = -EBUSY;
+               spin_unlock(&sbinfo->si_plink_maint_lock);
+       }
+       si_write_unlock(sb);
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+#ifdef CONFIG_AUFS_DEBUG
+void au_plink_list(struct super_block *sb)
+{
+       int i;
+       struct au_sbinfo *sbinfo;
+       struct hlist_bl_head *hbl;
+       struct hlist_bl_node *pos;
+       struct au_icntnr *icntnr;
+
+       SiMustAnyLock(sb);
+
+       sbinfo = au_sbi(sb);
+       AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
+       AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));
+
+       for (i = 0; i < AuPlink_NHASH; i++) {
+               hbl = sbinfo->si_plink + i;
+               hlist_bl_lock(hbl);
+               hlist_bl_for_each_entry(icntnr, pos, hbl, plink)
+                       AuDbg("%lu\n", icntnr->vfs_inode.i_ino);
+               hlist_bl_unlock(hbl);
+       }
+}
+#endif
+
+/* is the inode pseudo-linked? */
+int au_plink_test(struct inode *inode)
+{
+       int found, i;
+       struct au_sbinfo *sbinfo;
+       struct hlist_bl_head *hbl;
+       struct hlist_bl_node *pos;
+       struct au_icntnr *icntnr;
+
+       sbinfo = au_sbi(inode->i_sb);
+       AuRwMustAnyLock(&sbinfo->si_rwsem);
+       AuDebugOn(!au_opt_test(au_mntflags(inode->i_sb), PLINK));
+       AuDebugOn(au_plink_maint(inode->i_sb, AuLock_NOPLM));
+
+       found = 0;
+       i = au_plink_hash(inode->i_ino);
+       hbl =  sbinfo->si_plink + i;
+       hlist_bl_lock(hbl);
+       hlist_bl_for_each_entry(icntnr, pos, hbl, plink)
+               if (&icntnr->vfs_inode == inode) {
+                       found = 1;
+                       break;
+               }
+       hlist_bl_unlock(hbl);
+       return found;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * generate a name for plink.
+ * the file will be stored under AUFS_WH_PLINKDIR.
+ */
+/* 20 is max digits length of ulong 64 */
+#define PLINK_NAME_LEN ((20 + 1) * 2)
+
+static int plink_name(char *name, int len, struct inode *inode,
+                     aufs_bindex_t bindex)
+{
+       int rlen;
+       struct inode *h_inode;
+
+       h_inode = au_h_iptr(inode, bindex);
+       rlen = snprintf(name, len, "%lu.%lu", inode->i_ino, h_inode->i_ino);
+       return rlen;
+}
+
+struct au_do_plink_lkup_args {
+       struct dentry **errp;
+       struct qstr *tgtname;
+       struct path *h_ppath;
+};
+
+static struct dentry *au_do_plink_lkup(struct qstr *tgtname,
+                                      struct path *h_ppath)
+{
+       struct dentry *h_dentry;
+       struct inode *h_inode;
+
+       h_inode = d_inode(h_ppath->dentry);
+       inode_lock_shared_nested(h_inode, AuLsc_I_CHILD2);
+       h_dentry = vfsub_lkup_one(tgtname, h_ppath);
+       inode_unlock_shared(h_inode);
+
+       return h_dentry;
+}
+
+static void au_call_do_plink_lkup(void *args)
+{
+       struct au_do_plink_lkup_args *a = args;
+       *a->errp = au_do_plink_lkup(a->tgtname, a->h_ppath);
+}
+
+/* lookup the plink-ed @inode under the branch at @bindex */
+struct dentry *au_plink_lkup(struct inode *inode, aufs_bindex_t bindex)
+{
+       struct dentry *h_dentry;
+       struct au_branch *br;
+       struct path h_ppath;
+       int wkq_err;
+       char a[PLINK_NAME_LEN];
+       struct qstr tgtname = QSTR_INIT(a, 0);
+
+       AuDebugOn(au_plink_maint(inode->i_sb, AuLock_NOPLM));
+
+       br = au_sbr(inode->i_sb, bindex);
+       h_ppath.dentry = br->br_wbr->wbr_plink;
+       h_ppath.mnt = au_br_mnt(br);
+       tgtname.len = plink_name(a, sizeof(a), inode, bindex);
+
+       if (!uid_eq(current_fsuid(), GLOBAL_ROOT_UID)) {
+               struct au_do_plink_lkup_args args = {
+                       .errp           = &h_dentry,
+                       .tgtname        = &tgtname,
+                       .h_ppath        = &h_ppath
+               };
+
+               wkq_err = au_wkq_wait(au_call_do_plink_lkup, &args);
+               if (unlikely(wkq_err))
+                       h_dentry = ERR_PTR(wkq_err);
+       } else
+               h_dentry = au_do_plink_lkup(&tgtname, &h_ppath);
+
+       return h_dentry;
+}
+
+/* create a pseudo-link */
+static int do_whplink(struct qstr *tgt, struct path *h_ppath,
+                     struct dentry *h_dentry)
+{
+       int err;
+       struct path h_path;
+       struct inode *h_dir, *delegated;
+
+       h_dir = d_inode(h_ppath->dentry);
+       inode_lock_nested(h_dir, AuLsc_I_CHILD2);
+       h_path.mnt = h_ppath->mnt;
+again:
+       h_path.dentry = vfsub_lkup_one(tgt, h_ppath);
+       err = PTR_ERR(h_path.dentry);
+       if (IS_ERR(h_path.dentry))
+               goto out;
+
+       err = 0;
+       /* wh.plink dir is not monitored */
+       /* todo: is it really safe? */
+       if (d_is_positive(h_path.dentry)
+           && d_inode(h_path.dentry) != d_inode(h_dentry)) {
+               delegated = NULL;
+               err = vfsub_unlink(h_dir, &h_path, &delegated, /*force*/0);
+               if (unlikely(err == -EWOULDBLOCK)) {
+                       pr_warn("cannot retry for NFSv4 delegation"
+                               " for an internal unlink\n");
+                       iput(delegated);
+               }
+               dput(h_path.dentry);
+               h_path.dentry = NULL;
+               if (!err)
+                       goto again;
+       }
+       if (!err && d_is_negative(h_path.dentry)) {
+               delegated = NULL;
+               err = vfsub_link(h_dentry, h_dir, &h_path, &delegated);
+               if (unlikely(err == -EWOULDBLOCK)) {
+                       pr_warn("cannot retry for NFSv4 delegation"
+                               " for an internal link\n");
+                       iput(delegated);
+               }
+       }
+       dput(h_path.dentry);
+
+out:
+       inode_unlock(h_dir);
+       return err;
+}
+
+struct do_whplink_args {
+       int *errp;
+       struct qstr *tgt;
+       struct path *h_ppath;
+       struct dentry *h_dentry;
+};
+
+static void call_do_whplink(void *args)
+{
+       struct do_whplink_args *a = args;
+       *a->errp = do_whplink(a->tgt, a->h_ppath, a->h_dentry);
+}
+
+static int whplink(struct dentry *h_dentry, struct inode *inode,
+                  aufs_bindex_t bindex)
+{
+       int err, wkq_err;
+       struct au_branch *br;
+       struct au_wbr *wbr;
+       struct path h_ppath;
+       char a[PLINK_NAME_LEN];
+       struct qstr tgtname = QSTR_INIT(a, 0);
+
+       br = au_sbr(inode->i_sb, bindex);
+       wbr = br->br_wbr;
+       h_ppath.dentry = wbr->wbr_plink;
+       h_ppath.mnt = au_br_mnt(br);
+       tgtname.len = plink_name(a, sizeof(a), inode, bindex);
+
+       /* always superio. */
+       if (!uid_eq(current_fsuid(), GLOBAL_ROOT_UID)) {
+               struct do_whplink_args args = {
+                       .errp           = &err,
+                       .tgt            = &tgtname,
+                       .h_ppath        = &h_ppath,
+                       .h_dentry       = h_dentry
+               };
+               wkq_err = au_wkq_wait(call_do_whplink, &args);
+               if (unlikely(wkq_err))
+                       err = wkq_err;
+       } else
+               err = do_whplink(&tgtname, &h_ppath, h_dentry);
+
+       return err;
+}
+
+/*
+ * create a new pseudo-link for @h_dentry on @bindex.
+ * the linked inode is held in aufs @inode.
+ */
+void au_plink_append(struct inode *inode, aufs_bindex_t bindex,
+                    struct dentry *h_dentry)
+{
+       struct super_block *sb;
+       struct au_sbinfo *sbinfo;
+       struct hlist_bl_head *hbl;
+       struct hlist_bl_node *pos;
+       struct au_icntnr *icntnr;
+       int found, err, cnt, i;
+
+       sb = inode->i_sb;
+       sbinfo = au_sbi(sb);
+       AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
+       AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));
+
+       found = au_plink_test(inode);
+       if (found)
+               return;
+
+       i = au_plink_hash(inode->i_ino);
+       hbl = sbinfo->si_plink + i;
+       au_igrab(inode);
+
+       hlist_bl_lock(hbl);
+       hlist_bl_for_each_entry(icntnr, pos, hbl, plink) {
+               if (&icntnr->vfs_inode == inode) {
+                       found = 1;
+                       break;
+               }
+       }
+       if (!found) {
+               icntnr = container_of(inode, struct au_icntnr, vfs_inode);
+               hlist_bl_add_head(&icntnr->plink, hbl);
+       }
+       hlist_bl_unlock(hbl);
+       if (!found) {
+               cnt = au_hbl_count(hbl);
+#define msg "unexpectedly unbalanced or too many pseudo-links"
+               if (cnt > AUFS_PLINK_WARN)
+                       AuWarn1(msg ", %d\n", cnt);
+#undef msg
+               err = whplink(h_dentry, inode, bindex);
+               if (unlikely(err)) {
+                       pr_warn("err %d, damaged pseudo link.\n", err);
+                       au_hbl_del(&icntnr->plink, hbl);
+                       iput(&icntnr->vfs_inode);
+               }
+       } else
+               iput(&icntnr->vfs_inode);
+}
+
+/* free all plinks */
+void au_plink_put(struct super_block *sb, int verbose)
+{
+       int i, warned;
+       struct au_sbinfo *sbinfo;
+       struct hlist_bl_head *hbl;
+       struct hlist_bl_node *pos, *tmp;
+       struct au_icntnr *icntnr;
+
+       SiMustWriteLock(sb);
+
+       sbinfo = au_sbi(sb);
+       AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
+       AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));
+
+       /* no spin_lock since sbinfo is write-locked */
+       warned = 0;
+       for (i = 0; i < AuPlink_NHASH; i++) {
+               hbl = sbinfo->si_plink + i;
+               if (!warned && verbose && !hlist_bl_empty(hbl)) {
+                       pr_warn("pseudo-link is not flushed");
+                       warned = 1;
+               }
+               hlist_bl_for_each_entry_safe(icntnr, pos, tmp, hbl, plink)
+                       iput(&icntnr->vfs_inode);
+               INIT_HLIST_BL_HEAD(hbl);
+       }
+}
+
+void au_plink_clean(struct super_block *sb, int verbose)
+{
+       struct dentry *root;
+
+       root = sb->s_root;
+       aufs_write_lock(root);
+       if (au_opt_test(au_mntflags(sb), PLINK))
+               au_plink_put(sb, verbose);
+       aufs_write_unlock(root);
+}
+
+static int au_plink_do_half_refresh(struct inode *inode, aufs_bindex_t br_id)
+{
+       int do_put;
+       aufs_bindex_t btop, bbot, bindex;
+
+       do_put = 0;
+       btop = au_ibtop(inode);
+       bbot = au_ibbot(inode);
+       if (btop >= 0) {
+               for (bindex = btop; bindex <= bbot; bindex++) {
+                       if (!au_h_iptr(inode, bindex)
+                           || au_ii_br_id(inode, bindex) != br_id)
+                               continue;
+                       au_set_h_iptr(inode, bindex, NULL, 0);
+                       do_put = 1;
+                       break;
+               }
+               if (do_put)
+                       for (bindex = btop; bindex <= bbot; bindex++)
+                               if (au_h_iptr(inode, bindex)) {
+                                       do_put = 0;
+                                       break;
+                               }
+       } else
+               do_put = 1;
+
+       return do_put;
+}
+
+/* free the plinks on a branch specified by @br_id */
+void au_plink_half_refresh(struct super_block *sb, aufs_bindex_t br_id)
+{
+       struct au_sbinfo *sbinfo;
+       struct hlist_bl_head *hbl;
+       struct hlist_bl_node *pos, *tmp;
+       struct au_icntnr *icntnr;
+       struct inode *inode;
+       int i, do_put;
+
+       SiMustWriteLock(sb);
+
+       sbinfo = au_sbi(sb);
+       AuDebugOn(!au_opt_test(au_mntflags(sb), PLINK));
+       AuDebugOn(au_plink_maint(sb, AuLock_NOPLM));
+
+       /* no bit_lock since sbinfo is write-locked */
+       for (i = 0; i < AuPlink_NHASH; i++) {
+               hbl = sbinfo->si_plink + i;
+               hlist_bl_for_each_entry_safe(icntnr, pos, tmp, hbl, plink) {
+                       inode = au_igrab(&icntnr->vfs_inode);
+                       ii_write_lock_child(inode);
+                       do_put = au_plink_do_half_refresh(inode, br_id);
+                       if (do_put) {
+                               hlist_bl_del(&icntnr->plink);
+                               iput(inode);
+                       }
+                       ii_write_unlock(inode);
+                       iput(inode);
+               }
+       }
+}
diff -urN /usr/share/empty/fs/aufs/poll.c linux/fs/aufs/poll.c
--- /usr/share/empty/fs/aufs/poll.c     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/poll.c        2021-12-03 15:38:59.939980643 +0100
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * poll operation
+ * There is only one filesystem which implements ->poll operation, currently.
+ */
+
+#include "aufs.h"
+
+__poll_t aufs_poll(struct file *file, struct poll_table_struct *pt)
+{
+       __poll_t mask;
+       struct file *h_file;
+       struct super_block *sb;
+
+       /* We should pretend an error happened. */
+       mask = EPOLLERR /* | EPOLLIN | EPOLLOUT */;
+       sb = file->f_path.dentry->d_sb;
+       si_read_lock(sb, AuLock_FLUSH | AuLock_NOPLMW);
+
+       h_file = au_read_pre(file, /*keep_fi*/0, /*lsc*/0);
+       if (IS_ERR(h_file)) {
+               AuDbg("h_file %ld\n", PTR_ERR(h_file));
+               goto out;
+       }
+
+       mask = vfs_poll(h_file, pt);
+       fput(h_file); /* instead of au_read_post() */
+
+out:
+       si_read_unlock(sb);
+       if (mask & EPOLLERR)
+               AuDbg("mask 0x%x\n", mask);
+       return mask;
+}
diff -urN /usr/share/empty/fs/aufs/posix_acl.c linux/fs/aufs/posix_acl.c
--- /usr/share/empty/fs/aufs/posix_acl.c        1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/posix_acl.c   2021-12-03 15:40:58.236647297 +0100
@@ -0,0 +1,111 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2014-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * posix acl operations
+ */
+
+#include <linux/fs.h>
+#include "aufs.h"
+
+struct posix_acl *aufs_get_acl(struct inode *inode, int type, bool rcu)
+{
+       struct posix_acl *acl;
+       int err;
+       aufs_bindex_t bindex;
+       struct inode *h_inode;
+       struct super_block *sb;
+
+       acl = ERR_PTR(-ECHILD);
+       if (rcu)
+               goto out;
+
+       acl = NULL;
+       sb = inode->i_sb;
+       si_read_lock(sb, AuLock_FLUSH);
+       ii_read_lock_child(inode);
+       if (!(sb->s_flags & SB_POSIXACL))
+               goto unlock;
+
+       bindex = au_ibtop(inode);
+       h_inode = au_h_iptr(inode, bindex);
+       if (unlikely(!h_inode
+                    || ((h_inode->i_mode & S_IFMT)
+                        != (inode->i_mode & S_IFMT)))) {
+               err = au_busy_or_stale();
+               acl = ERR_PTR(err);
+               goto unlock;
+       }
+
+       /* always topmost only */
+       acl = get_acl(h_inode, type);
+       if (IS_ERR(acl))
+               forget_cached_acl(inode, type);
+       else
+               set_cached_acl(inode, type, acl);
+
+unlock:
+       ii_read_unlock(inode);
+       si_read_unlock(sb);
+
+out:
+       AuTraceErrPtr(acl);
+       return acl;
+}
+
+int aufs_set_acl(struct user_namespace *userns, struct inode *inode,
+                struct posix_acl *acl, int type)
+{
+       int err;
+       ssize_t ssz;
+       struct dentry *dentry;
+       struct au_sxattr arg = {
+               .type = AU_ACL_SET,
+               .u.acl_set = {
+                       .acl    = acl,
+                       .type   = type
+               },
+       };
+
+       IMustLock(inode);
+
+       if (inode->i_ino == AUFS_ROOT_INO)
+               dentry = dget(inode->i_sb->s_root);
+       else {
+               dentry = d_find_alias(inode);
+               if (!dentry)
+                       dentry = d_find_any_alias(inode);
+               if (!dentry) {
+                       pr_warn("cannot handle this inode, "
+                               "please report to aufs-users ML\n");
+                       err = -ENOENT;
+                       goto out;
+               }
+       }
+
+       ssz = au_sxattr(dentry, inode, &arg);
+       /* forget even it if succeeds since the branch might set differently */
+       forget_cached_acl(inode, type);
+       dput(dentry);
+       err = ssz;
+       if (ssz >= 0)
+               err = 0;
+
+out:
+       return err;
+}
diff -urN /usr/share/empty/fs/aufs/procfs.c linux/fs/aufs/procfs.c
--- /usr/share/empty/fs/aufs/procfs.c   1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/procfs.c      2021-12-03 15:38:59.939980643 +0100
@@ -0,0 +1,170 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2010-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * procfs interfaces
+ */
+
+#include <linux/proc_fs.h>
+#include "aufs.h"
+
+static int au_procfs_plm_release(struct inode *inode, struct file *file)
+{
+       struct au_sbinfo *sbinfo;
+
+       sbinfo = file->private_data;
+       if (sbinfo) {
+               au_plink_maint_leave(sbinfo);
+               kobject_put(&sbinfo->si_kobj);
+       }
+
+       return 0;
+}
+
+static void au_procfs_plm_write_clean(struct file *file)
+{
+       struct au_sbinfo *sbinfo;
+
+       sbinfo = file->private_data;
+       if (sbinfo)
+               au_plink_clean(sbinfo->si_sb, /*verbose*/0);
+}
+
+static int au_procfs_plm_write_si(struct file *file, unsigned long id)
+{
+       int err;
+       struct super_block *sb;
+       struct au_sbinfo *sbinfo;
+       struct hlist_bl_node *pos;
+
+       err = -EBUSY;
+       if (unlikely(file->private_data))
+               goto out;
+
+       sb = NULL;
+       /* don't use au_sbilist_lock() here */
+       hlist_bl_lock(&au_sbilist);
+       hlist_bl_for_each_entry(sbinfo, pos, &au_sbilist, si_list)
+               if (id == sysaufs_si_id(sbinfo)) {
+                       if (kobject_get_unless_zero(&sbinfo->si_kobj))
+                               sb = sbinfo->si_sb;
+                       break;
+               }
+       hlist_bl_unlock(&au_sbilist);
+
+       err = -EINVAL;
+       if (unlikely(!sb))
+               goto out;
+
+       err = au_plink_maint_enter(sb);
+       if (!err)
+               /* keep kobject_get() */
+               file->private_data = sbinfo;
+       else
+               kobject_put(&sbinfo->si_kobj);
+out:
+       return err;
+}
+
+/*
+ * Accept a valid "si=xxxx" only.
+ * Once it is accepted successfully, accept "clean" too.
+ */
+static ssize_t au_procfs_plm_write(struct file *file, const char __user *ubuf,
+                                  size_t count, loff_t *ppos)
+{
+       ssize_t err;
+       unsigned long id;
+       /* last newline is allowed */
+       char buf[3 + sizeof(unsigned long) * 2 + 1];
+
+       err = -EACCES;
+       if (unlikely(!capable(CAP_SYS_ADMIN)))
+               goto out;
+
+       err = -EINVAL;
+       if (unlikely(count > sizeof(buf)))
+               goto out;
+
+       err = copy_from_user(buf, ubuf, count);
+       if (unlikely(err)) {
+               err = -EFAULT;
+               goto out;
+       }
+       buf[count] = 0;
+
+       err = -EINVAL;
+       if (!strcmp("clean", buf)) {
+               au_procfs_plm_write_clean(file);
+               goto out_success;
+       } else if (unlikely(strncmp("si=", buf, 3)))
+               goto out;
+
+       err = kstrtoul(buf + 3, 16, &id);
+       if (unlikely(err))
+               goto out;
+
+       err = au_procfs_plm_write_si(file, id);
+       if (unlikely(err))
+               goto out;
+
+out_success:
+       err = count; /* success */
+out:
+       return err;
+}
+
+static const struct proc_ops au_procfs_plm_op = {
+       .proc_write     = au_procfs_plm_write,
+       .proc_release   = au_procfs_plm_release
+};
+
+/* ---------------------------------------------------------------------- */
+
+static struct proc_dir_entry *au_procfs_dir;
+
+void au_procfs_fin(void)
+{
+       remove_proc_entry(AUFS_PLINK_MAINT_NAME, au_procfs_dir);
+       remove_proc_entry(AUFS_PLINK_MAINT_DIR, NULL);
+}
+
+int __init au_procfs_init(void)
+{
+       int err;
+       struct proc_dir_entry *entry;
+
+       err = -ENOMEM;
+       au_procfs_dir = proc_mkdir(AUFS_PLINK_MAINT_DIR, NULL);
+       if (unlikely(!au_procfs_dir))
+               goto out;
+
+       entry = proc_create(AUFS_PLINK_MAINT_NAME, S_IFREG | 0200,
+                           au_procfs_dir, &au_procfs_plm_op);
+       if (unlikely(!entry))
+               goto out_dir;
+
+       err = 0;
+       goto out; /* success */
+
+
+out_dir:
+       remove_proc_entry(AUFS_PLINK_MAINT_DIR, NULL);
+out:
+       return err;
+}
diff -urN /usr/share/empty/fs/aufs/rdu.c linux/fs/aufs/rdu.c
--- /usr/share/empty/fs/aufs/rdu.c      1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/rdu.c 2021-12-03 15:38:59.939980643 +0100
@@ -0,0 +1,384 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * readdir in userspace.
+ */
+
+#include <linux/compat.h>
+#include <linux/fs_stack.h>
+#include <linux/security.h>
+#include "aufs.h"
+
+/* bits for struct aufs_rdu.flags */
+#define        AuRdu_CALLED    1
+#define        AuRdu_CONT      (1 << 1)
+#define        AuRdu_FULL      (1 << 2)
+#define au_ftest_rdu(flags, name)      ((flags) & AuRdu_##name)
+#define au_fset_rdu(flags, name) \
+       do { (flags) |= AuRdu_##name; } while (0)
+#define au_fclr_rdu(flags, name) \
+       do { (flags) &= ~AuRdu_##name; } while (0)
+
+struct au_rdu_arg {
+       struct dir_context              ctx;
+       struct aufs_rdu                 *rdu;
+       union au_rdu_ent_ul             ent;
+       unsigned long                   end;
+
+       struct super_block              *sb;
+       int                             err;
+};
+
+static int au_rdu_fill(struct dir_context *ctx, const char *name, int nlen,
+                      loff_t offset, u64 h_ino, unsigned int d_type)
+{
+       int err, len;
+       struct au_rdu_arg *arg = container_of(ctx, struct au_rdu_arg, ctx);
+       struct aufs_rdu *rdu = arg->rdu;
+       struct au_rdu_ent ent;
+
+       err = 0;
+       arg->err = 0;
+       au_fset_rdu(rdu->cookie.flags, CALLED);
+       len = au_rdu_len(nlen);
+       if (arg->ent.ul + len  < arg->end) {
+               ent.ino = h_ino;
+               ent.bindex = rdu->cookie.bindex;
+               ent.type = d_type;
+               ent.nlen = nlen;
+               if (unlikely(nlen > AUFS_MAX_NAMELEN))
+                       ent.type = DT_UNKNOWN;
+
+               /* unnecessary to support mmap_sem since this is a dir */
+               err = -EFAULT;
+               if (copy_to_user(arg->ent.e, &ent, sizeof(ent)))
+                       goto out;
+               if (copy_to_user(arg->ent.e->name, name, nlen))
+                       goto out;
+               /* the terminating NULL */
+               if (__put_user(0, arg->ent.e->name + nlen))
+                       goto out;
+               err = 0;
+               /* AuDbg("%p, %.*s\n", arg->ent.p, nlen, name); */
+               arg->ent.ul += len;
+               rdu->rent++;
+       } else {
+               err = -EFAULT;
+               au_fset_rdu(rdu->cookie.flags, FULL);
+               rdu->full = 1;
+               rdu->tail = arg->ent;
+       }
+
+out:
+       /* AuTraceErr(err); */
+       return err;
+}
+
+static int au_rdu_do(struct file *h_file, struct au_rdu_arg *arg)
+{
+       int err;
+       loff_t offset;
+       struct au_rdu_cookie *cookie = &arg->rdu->cookie;
+
+       /* we don't have to care (FMODE_32BITHASH | FMODE_64BITHASH) for ext4 */
+       offset = vfsub_llseek(h_file, cookie->h_pos, SEEK_SET);
+       err = offset;
+       if (unlikely(offset != cookie->h_pos))
+               goto out;
+
+       err = 0;
+       do {
+               arg->err = 0;
+               au_fclr_rdu(cookie->flags, CALLED);
+               /* smp_mb(); */
+               err = vfsub_iterate_dir(h_file, &arg->ctx);
+               if (err >= 0)
+                       err = arg->err;
+       } while (!err
+                && au_ftest_rdu(cookie->flags, CALLED)
+                && !au_ftest_rdu(cookie->flags, FULL));
+       cookie->h_pos = h_file->f_pos;
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+static int au_rdu(struct file *file, struct aufs_rdu *rdu)
+{
+       int err;
+       aufs_bindex_t bbot;
+       struct au_rdu_arg arg = {
+               .ctx = {
+                       .actor = au_rdu_fill
+               }
+       };
+       struct dentry *dentry;
+       struct inode *inode;
+       struct file *h_file;
+       struct au_rdu_cookie *cookie = &rdu->cookie;
+
+       /* VERIFY_WRITE */
+       err = !access_ok(rdu->ent.e, rdu->sz);
+       if (unlikely(err)) {
+               err = -EFAULT;
+               AuTraceErr(err);
+               goto out;
+       }
+       rdu->rent = 0;
+       rdu->tail = rdu->ent;
+       rdu->full = 0;
+       arg.rdu = rdu;
+       arg.ent = rdu->ent;
+       arg.end = arg.ent.ul;
+       arg.end += rdu->sz;
+
+       err = -ENOTDIR;
+       if (unlikely(!file->f_op->iterate && !file->f_op->iterate_shared))
+               goto out;
+
+       err = security_file_permission(file, MAY_READ);
+       AuTraceErr(err);
+       if (unlikely(err))
+               goto out;
+
+       dentry = file->f_path.dentry;
+       inode = d_inode(dentry);
+       inode_lock_shared(inode);
+
+       arg.sb = inode->i_sb;
+       err = si_read_lock(arg.sb, AuLock_FLUSH | AuLock_NOPLM);
+       if (unlikely(err))
+               goto out_mtx;
+       err = au_alive_dir(dentry);
+       if (unlikely(err))
+               goto out_si;
+       /* todo: reval? */
+       fi_read_lock(file);
+
+       err = -EAGAIN;
+       if (unlikely(au_ftest_rdu(cookie->flags, CONT)
+                    && cookie->generation != au_figen(file)))
+               goto out_unlock;
+
+       err = 0;
+       if (!rdu->blk) {
+               rdu->blk = au_sbi(arg.sb)->si_rdblk;
+               if (!rdu->blk)
+                       rdu->blk = au_dir_size(file, /*dentry*/NULL);
+       }
+       bbot = au_fbtop(file);
+       if (cookie->bindex < bbot)
+               cookie->bindex = bbot;
+       bbot = au_fbbot_dir(file);
+       /* AuDbg("b%d, b%d\n", cookie->bindex, bbot); */
+       for (; !err && cookie->bindex <= bbot;
+            cookie->bindex++, cookie->h_pos = 0) {
+               h_file = au_hf_dir(file, cookie->bindex);
+               if (!h_file)
+                       continue;
+
+               au_fclr_rdu(cookie->flags, FULL);
+               err = au_rdu_do(h_file, &arg);
+               AuTraceErr(err);
+               if (unlikely(au_ftest_rdu(cookie->flags, FULL) || err))
+                       break;
+       }
+       AuDbg("rent %llu\n", rdu->rent);
+
+       if (!err && !au_ftest_rdu(cookie->flags, CONT)) {
+               rdu->shwh = !!au_opt_test(au_sbi(arg.sb)->si_mntflags, SHWH);
+               au_fset_rdu(cookie->flags, CONT);
+               cookie->generation = au_figen(file);
+       }
+
+       ii_read_lock_child(inode);
+       fsstack_copy_attr_atime(inode, au_h_iptr(inode, au_ibtop(inode)));
+       ii_read_unlock(inode);
+
+out_unlock:
+       fi_read_unlock(file);
+out_si:
+       si_read_unlock(arg.sb);
+out_mtx:
+       inode_unlock_shared(inode);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+static int au_rdu_ino(struct file *file, struct aufs_rdu *rdu)
+{
+       int err;
+       ino_t ino;
+       unsigned long long nent;
+       union au_rdu_ent_ul *u;
+       struct au_rdu_ent ent;
+       struct super_block *sb;
+
+       err = 0;
+       nent = rdu->nent;
+       u = &rdu->ent;
+       sb = file->f_path.dentry->d_sb;
+       si_read_lock(sb, AuLock_FLUSH);
+       while (nent-- > 0) {
+               /* unnecessary to support mmap_sem since this is a dir */
+               err = copy_from_user(&ent, u->e, sizeof(ent));
+               if (!err)
+                       /* VERIFY_WRITE */
+                       err = !access_ok(&u->e->ino, sizeof(ino));
+               if (unlikely(err)) {
+                       err = -EFAULT;
+                       AuTraceErr(err);
+                       break;
+               }
+
+               /* AuDbg("b%d, i%llu\n", ent.bindex, ent.ino); */
+               if (!ent.wh)
+                       err = au_ino(sb, ent.bindex, ent.ino, ent.type, &ino);
+               else
+                       err = au_wh_ino(sb, ent.bindex, ent.ino, ent.type,
+                                       &ino);
+               if (unlikely(err)) {
+                       AuTraceErr(err);
+                       break;
+               }
+
+               err = __put_user(ino, &u->e->ino);
+               if (unlikely(err)) {
+                       err = -EFAULT;
+                       AuTraceErr(err);
+                       break;
+               }
+               u->ul += au_rdu_len(ent.nlen);
+       }
+       si_read_unlock(sb);
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_rdu_verify(struct aufs_rdu *rdu)
+{
+       AuDbg("rdu{%llu, %p, %u | %u | %llu, %u, %u | "
+             "%llu, b%d, 0x%x, g%u}\n",
+             rdu->sz, rdu->ent.e, rdu->verify[AufsCtlRduV_SZ],
+             rdu->blk,
+             rdu->rent, rdu->shwh, rdu->full,
+             rdu->cookie.h_pos, rdu->cookie.bindex, rdu->cookie.flags,
+             rdu->cookie.generation);
+
+       if (rdu->verify[AufsCtlRduV_SZ] == sizeof(*rdu))
+               return 0;
+
+       AuDbg("%u:%u\n",
+             rdu->verify[AufsCtlRduV_SZ], (unsigned int)sizeof(*rdu));
+       return -EINVAL;
+}
+
+long au_rdu_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+       long err, e;
+       struct aufs_rdu rdu;
+       void __user *p = (void __user *)arg;
+
+       err = copy_from_user(&rdu, p, sizeof(rdu));
+       if (unlikely(err)) {
+               err = -EFAULT;
+               AuTraceErr(err);
+               goto out;
+       }
+       err = au_rdu_verify(&rdu);
+       if (unlikely(err))
+               goto out;
+
+       switch (cmd) {
+       case AUFS_CTL_RDU:
+               err = au_rdu(file, &rdu);
+               if (unlikely(err))
+                       break;
+
+               e = copy_to_user(p, &rdu, sizeof(rdu));
+               if (unlikely(e)) {
+                       err = -EFAULT;
+                       AuTraceErr(err);
+               }
+               break;
+       case AUFS_CTL_RDU_INO:
+               err = au_rdu_ino(file, &rdu);
+               break;
+
+       default:
+               /* err = -ENOTTY; */
+               err = -EINVAL;
+       }
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+#ifdef CONFIG_COMPAT
+long au_rdu_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+       long err, e;
+       struct aufs_rdu rdu;
+       void __user *p = compat_ptr(arg);
+
+       /* todo: get_user()? */
+       err = copy_from_user(&rdu, p, sizeof(rdu));
+       if (unlikely(err)) {
+               err = -EFAULT;
+               AuTraceErr(err);
+               goto out;
+       }
+       rdu.ent.e = compat_ptr(rdu.ent.ul);
+       err = au_rdu_verify(&rdu);
+       if (unlikely(err))
+               goto out;
+
+       switch (cmd) {
+       case AUFS_CTL_RDU:
+               err = au_rdu(file, &rdu);
+               if (unlikely(err))
+                       break;
+
+               rdu.ent.ul = ptr_to_compat(rdu.ent.e);
+               rdu.tail.ul = ptr_to_compat(rdu.tail.e);
+               e = copy_to_user(p, &rdu, sizeof(rdu));
+               if (unlikely(e)) {
+                       err = -EFAULT;
+                       AuTraceErr(err);
+               }
+               break;
+       case AUFS_CTL_RDU_INO:
+               err = au_rdu_ino(file, &rdu);
+               break;
+
+       default:
+               /* err = -ENOTTY; */
+               err = -EINVAL;
+       }
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+#endif
diff -urN /usr/share/empty/fs/aufs/rwsem.h linux/fs/aufs/rwsem.h
--- /usr/share/empty/fs/aufs/rwsem.h    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/rwsem.h       2021-12-03 15:40:58.236647297 +0100
@@ -0,0 +1,85 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * simple read-write semaphore wrappers
+ */
+
+#ifndef __AUFS_RWSEM_H__
+#define __AUFS_RWSEM_H__
+
+#ifdef __KERNEL__
+
+#include "debug.h"
+
+/* in the future, the name 'au_rwsem' will be totally gone */
+#define au_rwsem       rw_semaphore
+
+/* to debug easier, do not make them inlined functions */
+#define AuRwMustNoWaiters(rw)  AuDebugOn(rwsem_is_contended(rw))
+
+#ifdef CONFIG_LOCKDEP
+/* rwsem_is_locked() is unusable */
+#define AuRwMustReadLock(rw)   AuDebugOn(IS_ENABLED(CONFIG_LOCKDEP)    \
+                                         && !lockdep_recursing(current) \
+                                         && debug_locks                \
+                                         && !lockdep_is_held_type(rw, 1))
+#define AuRwMustWriteLock(rw)  AuDebugOn(IS_ENABLED(CONFIG_LOCKDEP)    \
+                                         && !lockdep_recursing(current) \
+                                         && debug_locks                \
+                                         && !lockdep_is_held_type(rw, 0))
+#define AuRwMustAnyLock(rw)    AuDebugOn(IS_ENABLED(CONFIG_LOCKDEP)    \
+                                         && !lockdep_recursing(current) \
+                                         && debug_locks                \
+                                         && !lockdep_is_held(rw))
+#define AuRwDestroy(rw)                AuDebugOn(IS_ENABLED(CONFIG_LOCKDEP)    \
+                                         && !lockdep_recursing(current) \
+                                         && debug_locks                \
+                                         && lockdep_is_held(rw))
+#else
+#define AuRwMustReadLock(rw)   do {} while (0)
+#define AuRwMustWriteLock(rw)  do {} while (0)
+#define AuRwMustAnyLock(rw)    do {} while (0)
+#define AuRwDestroy(rw)                do {} while (0)
+#endif
+
+#define au_rw_init(rw) init_rwsem(rw)
+
+#define au_rw_init_wlock(rw) do {              \
+               au_rw_init(rw);                 \
+               down_write(rw);                 \
+       } while (0)
+
+#define au_rw_init_wlock_nested(rw, lsc) do {  \
+               au_rw_init(rw);                 \
+               down_write_nested(rw, lsc);     \
+       } while (0)
+
+#define au_rw_read_lock(rw)            down_read(rw)
+#define au_rw_read_lock_nested(rw, lsc)        down_read_nested(rw, lsc)
+#define au_rw_read_unlock(rw)          up_read(rw)
+#define au_rw_dgrade_lock(rw)          downgrade_write(rw)
+#define au_rw_write_lock(rw)           down_write(rw)
+#define au_rw_write_lock_nested(rw, lsc) down_write_nested(rw, lsc)
+#define au_rw_write_unlock(rw)         up_write(rw)
+/* why is not _nested version defined? */
+#define au_rw_read_trylock(rw)         down_read_trylock(rw)
+#define au_rw_write_trylock(rw)                down_write_trylock(rw)
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_RWSEM_H__ */
diff -urN /usr/share/empty/fs/aufs/sbinfo.c linux/fs/aufs/sbinfo.c
--- /usr/share/empty/fs/aufs/sbinfo.c   1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/sbinfo.c      2021-12-03 15:38:59.939980643 +0100
@@ -0,0 +1,314 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * superblock private data
+ */
+
+#include <linux/iversion.h>
+#include "aufs.h"
+
+/*
+ * they are necessary regardless sysfs is disabled.
+ */
+void au_si_free(struct kobject *kobj)
+{
+       int i;
+       struct au_sbinfo *sbinfo;
+       char *locked __maybe_unused; /* debug only */
+
+       sbinfo = container_of(kobj, struct au_sbinfo, si_kobj);
+       for (i = 0; i < AuPlink_NHASH; i++)
+               AuDebugOn(!hlist_bl_empty(sbinfo->si_plink + i));
+       AuDebugOn(atomic_read(&sbinfo->si_nowait.nw_len));
+
+       AuLCntZero(au_lcnt_read(&sbinfo->si_ninodes, /*do_rev*/0));
+       au_lcnt_fin(&sbinfo->si_ninodes, /*do_sync*/0);
+       AuLCntZero(au_lcnt_read(&sbinfo->si_nfiles, /*do_rev*/0));
+       au_lcnt_fin(&sbinfo->si_nfiles, /*do_sync*/0);
+
+       dbgaufs_si_fin(sbinfo);
+       au_rw_write_lock(&sbinfo->si_rwsem);
+       au_br_free(sbinfo);
+       au_rw_write_unlock(&sbinfo->si_rwsem);
+
+       au_kfree_try_rcu(sbinfo->si_branch);
+       mutex_destroy(&sbinfo->si_xib_mtx);
+       AuRwDestroy(&sbinfo->si_rwsem);
+
+       au_lcnt_wait_for_fin(&sbinfo->si_ninodes);
+       /* si_nfiles is waited too */
+       au_kfree_rcu(sbinfo);
+}
+
+int au_si_alloc(struct super_block *sb)
+{
+       int err, i;
+       struct au_sbinfo *sbinfo;
+
+       err = -ENOMEM;
+       sbinfo = kzalloc(sizeof(*sbinfo), GFP_NOFS);
+       if (unlikely(!sbinfo))
+               goto out;
+
+       /* will be reallocated separately */
+       sbinfo->si_branch = kzalloc(sizeof(*sbinfo->si_branch), GFP_NOFS);
+       if (unlikely(!sbinfo->si_branch))
+               goto out_sbinfo;
+
+       err = sysaufs_si_init(sbinfo);
+       if (!err) {
+               dbgaufs_si_null(sbinfo);
+               err = dbgaufs_si_init(sbinfo);
+               if (unlikely(err))
+                       kobject_put(&sbinfo->si_kobj);
+       }
+       if (unlikely(err))
+               goto out_br;
+
+       au_nwt_init(&sbinfo->si_nowait);
+       au_rw_init_wlock(&sbinfo->si_rwsem);
+
+       au_lcnt_init(&sbinfo->si_ninodes, /*release*/NULL);
+       au_lcnt_init(&sbinfo->si_nfiles, /*release*/NULL);
+
+       sbinfo->si_bbot = -1;
+       sbinfo->si_last_br_id = AUFS_BRANCH_MAX / 2;
+
+       sbinfo->si_wbr_copyup = AuWbrCopyup_Def;
+       sbinfo->si_wbr_create = AuWbrCreate_Def;
+       sbinfo->si_wbr_copyup_ops = au_wbr_copyup_ops + sbinfo->si_wbr_copyup;
+       sbinfo->si_wbr_create_ops = au_wbr_create_ops + sbinfo->si_wbr_create;
+
+       au_fhsm_init(sbinfo);
+
+       sbinfo->si_mntflags = au_opts_plink(AuOpt_Def);
+
+       sbinfo->si_xino_jiffy = jiffies;
+       sbinfo->si_xino_expire
+               = msecs_to_jiffies(AUFS_XINO_DEF_SEC * MSEC_PER_SEC);
+       mutex_init(&sbinfo->si_xib_mtx);
+       /* leave si_xib_last_pindex and si_xib_next_bit */
+
+       INIT_HLIST_BL_HEAD(&sbinfo->si_aopen);
+
+       sbinfo->si_rdcache = msecs_to_jiffies(AUFS_RDCACHE_DEF * MSEC_PER_SEC);
+       sbinfo->si_rdblk = AUFS_RDBLK_DEF;
+       sbinfo->si_rdhash = AUFS_RDHASH_DEF;
+       sbinfo->si_dirwh = AUFS_DIRWH_DEF;
+
+       for (i = 0; i < AuPlink_NHASH; i++)
+               INIT_HLIST_BL_HEAD(sbinfo->si_plink + i);
+       init_waitqueue_head(&sbinfo->si_plink_wq);
+       spin_lock_init(&sbinfo->si_plink_maint_lock);
+
+       INIT_HLIST_BL_HEAD(&sbinfo->si_files);
+
+       /* with getattr by default */
+       sbinfo->si_iop_array = aufs_iop;
+
+       /* leave other members for sysaufs and si_mnt. */
+       sbinfo->si_sb = sb;
+       sb->s_fs_info = sbinfo;
+       si_pid_set(sb);
+       return 0; /* success */
+
+out_br:
+       au_kfree_try_rcu(sbinfo->si_branch);
+out_sbinfo:
+       au_kfree_rcu(sbinfo);
+out:
+       return err;
+}
+
+int au_sbr_realloc(struct au_sbinfo *sbinfo, int nbr, int may_shrink)
+{
+       int err, sz;
+       struct au_branch **brp;
+
+       AuRwMustWriteLock(&sbinfo->si_rwsem);
+
+       err = -ENOMEM;
+       sz = sizeof(*brp) * (sbinfo->si_bbot + 1);
+       if (unlikely(!sz))
+               sz = sizeof(*brp);
+       brp = au_kzrealloc(sbinfo->si_branch, sz, sizeof(*brp) * nbr, GFP_NOFS,
+                          may_shrink);
+       if (brp) {
+               sbinfo->si_branch = brp;
+               err = 0;
+       }
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+unsigned int au_sigen_inc(struct super_block *sb)
+{
+       unsigned int gen;
+       struct inode *inode;
+
+       SiMustWriteLock(sb);
+
+       gen = ++au_sbi(sb)->si_generation;
+       au_update_digen(sb->s_root);
+       inode = d_inode(sb->s_root);
+       au_update_iigen(inode, /*half*/0);
+       inode_inc_iversion(inode);
+       return gen;
+}
+
+aufs_bindex_t au_new_br_id(struct super_block *sb)
+{
+       aufs_bindex_t br_id;
+       int i;
+       struct au_sbinfo *sbinfo;
+
+       SiMustWriteLock(sb);
+
+       sbinfo = au_sbi(sb);
+       for (i = 0; i <= AUFS_BRANCH_MAX; i++) {
+               br_id = ++sbinfo->si_last_br_id;
+               AuDebugOn(br_id < 0);
+               if (br_id && au_br_index(sb, br_id) < 0)
+                       return br_id;
+       }
+
+       return -1;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* it is ok that new 'nwt' tasks are appended while we are sleeping */
+int si_read_lock(struct super_block *sb, int flags)
+{
+       int err;
+
+       err = 0;
+       if (au_ftest_lock(flags, FLUSH))
+               au_nwt_flush(&au_sbi(sb)->si_nowait);
+
+       si_noflush_read_lock(sb);
+       err = au_plink_maint(sb, flags);
+       if (unlikely(err))
+               si_read_unlock(sb);
+
+       return err;
+}
+
+int si_write_lock(struct super_block *sb, int flags)
+{
+       int err;
+
+       if (au_ftest_lock(flags, FLUSH))
+               au_nwt_flush(&au_sbi(sb)->si_nowait);
+
+       si_noflush_write_lock(sb);
+       err = au_plink_maint(sb, flags);
+       if (unlikely(err))
+               si_write_unlock(sb);
+
+       return err;
+}
+
+/* dentry and super_block lock. call at entry point */
+int aufs_read_lock(struct dentry *dentry, int flags)
+{
+       int err;
+       struct super_block *sb;
+
+       sb = dentry->d_sb;
+       err = si_read_lock(sb, flags);
+       if (unlikely(err))
+               goto out;
+
+       if (au_ftest_lock(flags, DW))
+               di_write_lock_child(dentry);
+       else
+               di_read_lock_child(dentry, flags);
+
+       if (au_ftest_lock(flags, GEN)) {
+               err = au_digen_test(dentry, au_sigen(sb));
+               if (!au_opt_test(au_mntflags(sb), UDBA_NONE))
+                       AuDebugOn(!err && au_dbrange_test(dentry));
+               else if (!err)
+                       err = au_dbrange_test(dentry);
+               if (unlikely(err))
+                       aufs_read_unlock(dentry, flags);
+       }
+
+out:
+       return err;
+}
+
+void aufs_read_unlock(struct dentry *dentry, int flags)
+{
+       if (au_ftest_lock(flags, DW))
+               di_write_unlock(dentry);
+       else
+               di_read_unlock(dentry, flags);
+       si_read_unlock(dentry->d_sb);
+}
+
+void aufs_write_lock(struct dentry *dentry)
+{
+       si_write_lock(dentry->d_sb, AuLock_FLUSH | AuLock_NOPLMW);
+       di_write_lock_child(dentry);
+}
+
+void aufs_write_unlock(struct dentry *dentry)
+{
+       di_write_unlock(dentry);
+       si_write_unlock(dentry->d_sb);
+}
+
+int aufs_read_and_write_lock2(struct dentry *d1, struct dentry *d2, int flags)
+{
+       int err;
+       unsigned int sigen;
+       struct super_block *sb;
+
+       sb = d1->d_sb;
+       err = si_read_lock(sb, flags);
+       if (unlikely(err))
+               goto out;
+
+       di_write_lock2_child(d1, d2, au_ftest_lock(flags, DIRS));
+
+       if (au_ftest_lock(flags, GEN)) {
+               sigen = au_sigen(sb);
+               err = au_digen_test(d1, sigen);
+               AuDebugOn(!err && au_dbrange_test(d1));
+               if (!err) {
+                       err = au_digen_test(d2, sigen);
+                       AuDebugOn(!err && au_dbrange_test(d2));
+               }
+               if (unlikely(err))
+                       aufs_read_and_write_unlock2(d1, d2);
+       }
+
+out:
+       return err;
+}
+
+void aufs_read_and_write_unlock2(struct dentry *d1, struct dentry *d2)
+{
+       di_write_unlock2(d1, d2);
+       si_read_unlock(d1->d_sb);
+}
diff -urN /usr/share/empty/fs/aufs/super.c linux/fs/aufs/super.c
--- /usr/share/empty/fs/aufs/super.c    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/super.c       2022-01-13 12:42:15.932899468 +0100
@@ -0,0 +1,1050 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * mount and super_block operations
+ */
+
+#include <linux/iversion.h>
+#include <linux/mm.h>
+#include <linux/seq_file.h>
+#include <linux/statfs.h>
+#include <linux/vmalloc.h>
+#include "aufs.h"
+
+/*
+ * super_operations
+ */
+static struct inode *aufs_alloc_inode(struct super_block *sb __maybe_unused)
+{
+       struct au_icntnr *c;
+
+       c = au_cache_alloc_icntnr();
+       if (c) {
+               au_icntnr_init(c);
+               inode_set_iversion(&c->vfs_inode, 1); /* sigen(sb); */
+               c->iinfo.ii_hinode = NULL;
+               return &c->vfs_inode;
+       }
+       return NULL;
+}
+
+static void aufs_destroy_inode(struct inode *inode)
+{
+       if (!au_is_bad_inode(inode))
+               au_iinfo_fin(inode);
+}
+
+static void aufs_free_inode(struct inode *inode)
+{
+       au_cache_free_icntnr(container_of(inode, struct au_icntnr, vfs_inode));
+}
+
+struct inode *au_iget_locked(struct super_block *sb, ino_t ino)
+{
+       struct inode *inode;
+       int err;
+
+       inode = iget_locked(sb, ino);
+       if (unlikely(!inode)) {
+               inode = ERR_PTR(-ENOMEM);
+               goto out;
+       }
+       if (!(inode->i_state & I_NEW))
+               goto out;
+
+       err = au_xigen_new(inode);
+       if (!err)
+               err = au_iinfo_init(inode);
+       if (!err)
+               inode_inc_iversion(inode);
+       else {
+               iget_failed(inode);
+               inode = ERR_PTR(err);
+       }
+
+out:
+       /* never return NULL */
+       AuDebugOn(!inode);
+       AuTraceErrPtr(inode);
+       return inode;
+}
+
+/* lock free root dinfo */
+static int au_show_brs(struct seq_file *seq, struct super_block *sb)
+{
+       int err;
+       aufs_bindex_t bindex, bbot;
+       struct path path;
+       struct au_hdentry *hdp;
+       struct au_branch *br;
+       au_br_perm_str_t perm;
+
+       err = 0;
+       bbot = au_sbbot(sb);
+       bindex = 0;
+       hdp = au_hdentry(au_di(sb->s_root), bindex);
+       for (; !err && bindex <= bbot; bindex++, hdp++) {
+               br = au_sbr(sb, bindex);
+               path.mnt = au_br_mnt(br);
+               path.dentry = hdp->hd_dentry;
+               err = au_seq_path(seq, &path);
+               if (!err) {
+                       au_optstr_br_perm(&perm, br->br_perm);
+                       seq_printf(seq, "=%s", perm.a);
+                       if (bindex != bbot)
+                               seq_putc(seq, ':');
+               }
+       }
+       if (unlikely(err || seq_has_overflowed(seq)))
+               err = -E2BIG;
+
+       return err;
+}
+
+static void au_gen_fmt(char *fmt, int len __maybe_unused, const char *pat,
+                      const char *append)
+{
+       char *p;
+
+       p = fmt;
+       while (*pat != ':')
+               *p++ = *pat++;
+       *p++ = *pat++;
+       strcpy(p, append);
+       AuDebugOn(strlen(fmt) >= len);
+}
+
+static void au_show_wbr_create(struct seq_file *m, int v,
+                              struct au_sbinfo *sbinfo)
+{
+       const char *pat;
+       char fmt[32];
+       struct au_wbr_mfs *mfs;
+
+       AuRwMustAnyLock(&sbinfo->si_rwsem);
+
+       seq_puts(m, ",create=");
+       pat = au_optstr_wbr_create(v);
+       mfs = &sbinfo->si_wbr_mfs;
+       switch (v) {
+       case AuWbrCreate_TDP:
+       case AuWbrCreate_RR:
+       case AuWbrCreate_MFS:
+       case AuWbrCreate_PMFS:
+               seq_puts(m, pat);
+               break;
+       case AuWbrCreate_MFSRR:
+       case AuWbrCreate_TDMFS:
+       case AuWbrCreate_PMFSRR:
+               au_gen_fmt(fmt, sizeof(fmt), pat, "%llu");
+               seq_printf(m, fmt, mfs->mfsrr_watermark);
+               break;
+       case AuWbrCreate_MFSV:
+       case AuWbrCreate_PMFSV:
+               au_gen_fmt(fmt, sizeof(fmt), pat, "%lu");
+               seq_printf(m, fmt,
+                          jiffies_to_msecs(mfs->mfs_expire)
+                          / MSEC_PER_SEC);
+               break;
+       case AuWbrCreate_MFSRRV:
+       case AuWbrCreate_TDMFSV:
+       case AuWbrCreate_PMFSRRV:
+               au_gen_fmt(fmt, sizeof(fmt), pat, "%llu:%lu");
+               seq_printf(m, fmt, mfs->mfsrr_watermark,
+                          jiffies_to_msecs(mfs->mfs_expire) / MSEC_PER_SEC);
+               break;
+       default:
+               BUG();
+       }
+}
+
+static int au_show_xino(struct seq_file *seq, struct super_block *sb)
+{
+#ifdef CONFIG_SYSFS
+       return 0;
+#else
+       int err;
+       const int len = sizeof(AUFS_XINO_FNAME) - 1;
+       aufs_bindex_t bindex, brid;
+       struct qstr *name;
+       struct file *f;
+       struct dentry *d, *h_root;
+       struct au_branch *br;
+
+       AuRwMustAnyLock(&sbinfo->si_rwsem);
+
+       err = 0;
+       f = au_sbi(sb)->si_xib;
+       if (!f)
+               goto out;
+
+       /* stop printing the default xino path on the first writable branch */
+       h_root = NULL;
+       bindex = au_xi_root(sb, f->f_path.dentry);
+       if (bindex >= 0) {
+               br = au_sbr_sb(sb, bindex);
+               h_root = au_br_dentry(br);
+       }
+
+       d = f->f_path.dentry;
+       name = &d->d_name;
+       /* safe ->d_parent because the file is unlinked */
+       if (d->d_parent == h_root
+           && name->len == len
+           && !memcmp(name->name, AUFS_XINO_FNAME, len))
+               goto out;
+
+       seq_puts(seq, ",xino=");
+       err = au_xino_path(seq, f);
+
+out:
+       return err;
+#endif
+}
+
+/* seq_file will re-call me in case of too long string */
+static int aufs_show_options(struct seq_file *m, struct dentry *dentry)
+{
+       int err;
+       unsigned int mnt_flags, v;
+       struct super_block *sb;
+       struct au_sbinfo *sbinfo;
+
+#define AuBool(name, str) do { \
+       v = au_opt_test(mnt_flags, name); \
+       if (v != au_opt_test(AuOpt_Def, name)) \
+               seq_printf(m, ",%s" #str, v ? "" : "no"); \
+} while (0)
+
+#define AuStr(name, str) do { \
+       v = mnt_flags & AuOptMask_##name; \
+       if (v != (AuOpt_Def & AuOptMask_##name)) \
+               seq_printf(m, "," #str "=%s", au_optstr_##str(v)); \
+} while (0)
+
+#define AuUInt(name, str, val) do { \
+       if (val != AUFS_##name##_DEF) \
+               seq_printf(m, "," #str "=%u", val); \
+} while (0)
+
+       sb = dentry->d_sb;
+       if (sb->s_flags & SB_POSIXACL)
+               seq_puts(m, ",acl");
+#if 0 /* reserved for future use */
+       if (sb->s_flags & SB_I_VERSION)
+               seq_puts(m, ",i_version");
+#endif
+
+       /* lock free root dinfo */
+       si_noflush_read_lock(sb);
+       sbinfo = au_sbi(sb);
+       seq_printf(m, ",si=%lx", sysaufs_si_id(sbinfo));
+
+       mnt_flags = au_mntflags(sb);
+       if (au_opt_test(mnt_flags, XINO)) {
+               err = au_show_xino(m, sb);
+               if (unlikely(err))
+                       goto out;
+       } else
+               seq_puts(m, ",noxino");
+
+       AuBool(TRUNC_XINO, trunc_xino);
+       AuStr(UDBA, udba);
+       AuBool(SHWH, shwh);
+       AuBool(PLINK, plink);
+       AuBool(DIO, dio);
+       AuBool(DIRPERM1, dirperm1);
+
+       v = sbinfo->si_wbr_create;
+       if (v != AuWbrCreate_Def)
+               au_show_wbr_create(m, v, sbinfo);
+
+       v = sbinfo->si_wbr_copyup;
+       if (v != AuWbrCopyup_Def)
+               seq_printf(m, ",cpup=%s", au_optstr_wbr_copyup(v));
+
+       v = au_opt_test(mnt_flags, ALWAYS_DIROPQ);
+       if (v != au_opt_test(AuOpt_Def, ALWAYS_DIROPQ))
+               seq_printf(m, ",diropq=%c", v ? 'a' : 'w');
+
+       AuUInt(DIRWH, dirwh, sbinfo->si_dirwh);
+
+       v = jiffies_to_msecs(sbinfo->si_rdcache) / MSEC_PER_SEC;
+       AuUInt(RDCACHE, rdcache, v);
+
+       AuUInt(RDBLK, rdblk, sbinfo->si_rdblk);
+       AuUInt(RDHASH, rdhash, sbinfo->si_rdhash);
+
+       au_fhsm_show(m, sbinfo);
+
+       AuBool(DIRREN, dirren);
+       AuBool(SUM, sum);
+       /* AuBool(SUM_W, wsum); */
+       AuBool(WARN_PERM, warn_perm);
+       AuBool(VERBOSE, verbose);
+
+out:
+       /* be sure to print "br:" last */
+       if (!sysaufs_brs) {
+               seq_puts(m, ",br:");
+               au_show_brs(m, sb);
+       }
+       si_read_unlock(sb);
+       return 0;
+
+#undef AuBool
+#undef AuStr
+#undef AuUInt
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* sum mode which returns the summation for statfs(2) */
+
+static u64 au_add_till_max(u64 a, u64 b)
+{
+       u64 old;
+
+       old = a;
+       a += b;
+       if (old <= a)
+               return a;
+       return ULLONG_MAX;
+}
+
+static u64 au_mul_till_max(u64 a, long mul)
+{
+       u64 old;
+
+       old = a;
+       a *= mul;
+       if (old <= a)
+               return a;
+       return ULLONG_MAX;
+}
+
+static int au_statfs_sum(struct super_block *sb, struct kstatfs *buf)
+{
+       int err;
+       long bsize, factor;
+       u64 blocks, bfree, bavail, files, ffree;
+       aufs_bindex_t bbot, bindex, i;
+       unsigned char shared;
+       struct path h_path;
+       struct super_block *h_sb;
+
+       err = 0;
+       bsize = LONG_MAX;
+       files = 0;
+       ffree = 0;
+       blocks = 0;
+       bfree = 0;
+       bavail = 0;
+       bbot = au_sbbot(sb);
+       for (bindex = 0; bindex <= bbot; bindex++) {
+               h_path.mnt = au_sbr_mnt(sb, bindex);
+               h_sb = h_path.mnt->mnt_sb;
+               shared = 0;
+               for (i = 0; !shared && i < bindex; i++)
+                       shared = (au_sbr_sb(sb, i) == h_sb);
+               if (shared)
+                       continue;
+
+               /* sb->s_root for NFS is unreliable */
+               h_path.dentry = h_path.mnt->mnt_root;
+               err = vfs_statfs(&h_path, buf);
+               if (unlikely(err))
+                       goto out;
+
+               if (bsize > buf->f_bsize) {
+                       /*
+                        * we will reduce bsize, so we have to expand blocks
+                        * etc. to match them again
+                        */
+                       factor = (bsize / buf->f_bsize);
+                       blocks = au_mul_till_max(blocks, factor);
+                       bfree = au_mul_till_max(bfree, factor);
+                       bavail = au_mul_till_max(bavail, factor);
+                       bsize = buf->f_bsize;
+               }
+
+               factor = (buf->f_bsize / bsize);
+               blocks = au_add_till_max(blocks,
+                               au_mul_till_max(buf->f_blocks, factor));
+               bfree = au_add_till_max(bfree,
+                               au_mul_till_max(buf->f_bfree, factor));
+               bavail = au_add_till_max(bavail,
+                               au_mul_till_max(buf->f_bavail, factor));
+               files = au_add_till_max(files, buf->f_files);
+               ffree = au_add_till_max(ffree, buf->f_ffree);
+       }
+
+       buf->f_bsize = bsize;
+       buf->f_blocks = blocks;
+       buf->f_bfree = bfree;
+       buf->f_bavail = bavail;
+       buf->f_files = files;
+       buf->f_ffree = ffree;
+       buf->f_frsize = 0;
+
+out:
+       return err;
+}
+
+static int aufs_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+       int err;
+       struct path h_path;
+       struct super_block *sb;
+
+       /* lock free root dinfo */
+       sb = dentry->d_sb;
+       si_noflush_read_lock(sb);
+       if (!au_opt_test(au_mntflags(sb), SUM)) {
+               /* sb->s_root for NFS is unreliable */
+               h_path.mnt = au_sbr_mnt(sb, 0);
+               h_path.dentry = h_path.mnt->mnt_root;
+               err = vfs_statfs(&h_path, buf);
+       } else
+               err = au_statfs_sum(sb, buf);
+       si_read_unlock(sb);
+
+       if (!err) {
+               buf->f_type = AUFS_SUPER_MAGIC;
+               buf->f_namelen = AUFS_MAX_NAMELEN;
+               memset(&buf->f_fsid, 0, sizeof(buf->f_fsid));
+       }
+       /* buf->f_bsize = buf->f_blocks = buf->f_bfree = buf->f_bavail = -1; */
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int aufs_sync_fs(struct super_block *sb, int wait)
+{
+       int err, e;
+       aufs_bindex_t bbot, bindex;
+       struct au_branch *br;
+       struct super_block *h_sb;
+
+       err = 0;
+       si_noflush_read_lock(sb);
+       bbot = au_sbbot(sb);
+       for (bindex = 0; bindex <= bbot; bindex++) {
+               br = au_sbr(sb, bindex);
+               if (!au_br_writable(br->br_perm))
+                       continue;
+
+               h_sb = au_sbr_sb(sb, bindex);
+               e = vfsub_sync_filesystem(h_sb);
+               if (unlikely(e && !err))
+                       err = e;
+               /* go on even if an error happens */
+       }
+       si_read_unlock(sb);
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* final actions when unmounting a file system */
+static void aufs_put_super(struct super_block *sb)
+{
+       struct au_sbinfo *sbinfo;
+
+       sbinfo = au_sbi(sb);
+       if (sbinfo)
+               kobject_put(&sbinfo->si_kobj);
+}
+
+/* ---------------------------------------------------------------------- */
+
+void *au_array_alloc(unsigned long long *hint, au_arraycb_t cb,
+                    struct super_block *sb, void *arg)
+{
+       void *array;
+       unsigned long long n, sz;
+
+       array = NULL;
+       n = 0;
+       if (!*hint)
+               goto out;
+
+       if (*hint > ULLONG_MAX / sizeof(array)) {
+               array = ERR_PTR(-EMFILE);
+               pr_err("hint %llu\n", *hint);
+               goto out;
+       }
+
+       sz = sizeof(array) * *hint;
+       array = kzalloc(sz, GFP_NOFS);
+       if (unlikely(!array))
+               array = vzalloc(sz);
+       if (unlikely(!array)) {
+               array = ERR_PTR(-ENOMEM);
+               goto out;
+       }
+
+       n = cb(sb, array, *hint, arg);
+       AuDebugOn(n > *hint);
+
+out:
+       *hint = n;
+       return array;
+}
+
+static unsigned long long au_iarray_cb(struct super_block *sb, void *a,
+                                      unsigned long long max __maybe_unused,
+                                      void *arg)
+{
+       unsigned long long n;
+       struct inode **p, *inode;
+       struct list_head *head;
+
+       n = 0;
+       p = a;
+       head = arg;
+       spin_lock(&sb->s_inode_list_lock);
+       list_for_each_entry(inode, head, i_sb_list) {
+               if (!au_is_bad_inode(inode)
+                   && au_ii(inode)->ii_btop >= 0) {
+                       spin_lock(&inode->i_lock);
+                       if (atomic_read(&inode->i_count)) {
+                               au_igrab(inode);
+                               *p++ = inode;
+                               n++;
+                               AuDebugOn(n > max);
+                       }
+                       spin_unlock(&inode->i_lock);
+               }
+       }
+       spin_unlock(&sb->s_inode_list_lock);
+
+       return n;
+}
+
+struct inode **au_iarray_alloc(struct super_block *sb, unsigned long long *max)
+{
+       struct au_sbinfo *sbi;
+
+       sbi = au_sbi(sb);
+       *max = au_lcnt_read(&sbi->si_ninodes, /*do_rev*/1);
+       return au_array_alloc(max, au_iarray_cb, sb, &sb->s_inodes);
+}
+
+void au_iarray_free(struct inode **a, unsigned long long max)
+{
+       unsigned long long ull;
+
+       for (ull = 0; ull < max; ull++)
+               iput(a[ull]);
+       kvfree(a);
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * refresh dentry and inode at remount time.
+ */
+/* todo: consolidate with simple_reval_dpath() and au_reval_for_attr() */
+static int au_do_refresh(struct dentry *dentry, unsigned int dir_flags,
+                     struct dentry *parent)
+{
+       int err;
+
+       di_write_lock_child(dentry);
+       di_read_lock_parent(parent, AuLock_IR);
+       err = au_refresh_dentry(dentry, parent);
+       if (!err && dir_flags)
+               au_hn_reset(d_inode(dentry), dir_flags);
+       di_read_unlock(parent, AuLock_IR);
+       di_write_unlock(dentry);
+
+       return err;
+}
+
+static int au_do_refresh_d(struct dentry *dentry, unsigned int sigen,
+                          struct au_sbinfo *sbinfo,
+                          const unsigned int dir_flags, unsigned int do_idop)
+{
+       int err;
+       struct dentry *parent;
+
+       err = 0;
+       parent = dget_parent(dentry);
+       if (!au_digen_test(parent, sigen) && au_digen_test(dentry, sigen)) {
+               if (d_really_is_positive(dentry)) {
+                       if (!d_is_dir(dentry))
+                               err = au_do_refresh(dentry, /*dir_flags*/0,
+                                                parent);
+                       else {
+                               err = au_do_refresh(dentry, dir_flags, parent);
+                               if (unlikely(err))
+                                       au_fset_si(sbinfo, FAILED_REFRESH_DIR);
+                       }
+               } else
+                       err = au_do_refresh(dentry, /*dir_flags*/0, parent);
+               AuDbgDentry(dentry);
+       }
+       dput(parent);
+
+       if (!err) {
+               if (do_idop)
+                       au_refresh_dop(dentry, /*force_reval*/0);
+       } else
+               au_refresh_dop(dentry, /*force_reval*/1);
+
+       AuTraceErr(err);
+       return err;
+}
+
+static int au_refresh_d(struct super_block *sb, unsigned int do_idop)
+{
+       int err, i, j, ndentry, e;
+       unsigned int sigen;
+       struct au_dcsub_pages dpages;
+       struct au_dpage *dpage;
+       struct dentry **dentries, *d;
+       struct au_sbinfo *sbinfo;
+       struct dentry *root = sb->s_root;
+       const unsigned int dir_flags = au_hi_flags(d_inode(root), /*isdir*/1);
+
+       if (do_idop)
+               au_refresh_dop(root, /*force_reval*/0);
+
+       err = au_dpages_init(&dpages, GFP_NOFS);
+       if (unlikely(err))
+               goto out;
+       err = au_dcsub_pages(&dpages, root, NULL, NULL);
+       if (unlikely(err))
+               goto out_dpages;
+
+       sigen = au_sigen(sb);
+       sbinfo = au_sbi(sb);
+       for (i = 0; i < dpages.ndpage; i++) {
+               dpage = dpages.dpages + i;
+               dentries = dpage->dentries;
+               ndentry = dpage->ndentry;
+               for (j = 0; j < ndentry; j++) {
+                       d = dentries[j];
+                       e = au_do_refresh_d(d, sigen, sbinfo, dir_flags,
+                                           do_idop);
+                       if (unlikely(e && !err))
+                               err = e;
+                       /* go on even err */
+               }
+       }
+
+out_dpages:
+       au_dpages_free(&dpages);
+out:
+       return err;
+}
+
+static int au_refresh_i(struct super_block *sb, unsigned int do_idop)
+{
+       int err, e;
+       unsigned int sigen;
+       unsigned long long max, ull;
+       struct inode *inode, **array;
+
+       array = au_iarray_alloc(sb, &max);
+       err = PTR_ERR(array);
+       if (IS_ERR(array))
+               goto out;
+
+       err = 0;
+       sigen = au_sigen(sb);
+       for (ull = 0; ull < max; ull++) {
+               inode = array[ull];
+               if (unlikely(!inode))
+                       break;
+
+               e = 0;
+               ii_write_lock_child(inode);
+               if (au_iigen(inode, NULL) != sigen) {
+                       e = au_refresh_hinode_self(inode);
+                       if (unlikely(e)) {
+                               au_refresh_iop(inode, /*force_getattr*/1);
+                               pr_err("error %d, i%lu\n", e, inode->i_ino);
+                               if (!err)
+                                       err = e;
+                               /* go on even if err */
+                       }
+               }
+               if (!e && do_idop)
+                       au_refresh_iop(inode, /*force_getattr*/0);
+               ii_write_unlock(inode);
+       }
+
+       au_iarray_free(array, max);
+
+out:
+       return err;
+}
+
+static void au_remount_refresh(struct super_block *sb, unsigned int do_idop)
+{
+       int err, e;
+       unsigned int udba;
+       aufs_bindex_t bindex, bbot;
+       struct dentry *root;
+       struct inode *inode;
+       struct au_branch *br;
+       struct au_sbinfo *sbi;
+
+       au_sigen_inc(sb);
+       sbi = au_sbi(sb);
+       au_fclr_si(sbi, FAILED_REFRESH_DIR);
+
+       root = sb->s_root;
+       DiMustNoWaiters(root);
+       inode = d_inode(root);
+       IiMustNoWaiters(inode);
+
+       udba = au_opt_udba(sb);
+       bbot = au_sbbot(sb);
+       for (bindex = 0; bindex <= bbot; bindex++) {
+               br = au_sbr(sb, bindex);
+               err = au_hnotify_reset_br(udba, br, br->br_perm);
+               if (unlikely(err))
+                       AuIOErr("hnotify failed on br %d, %d, ignored\n",
+                               bindex, err);
+               /* go on even if err */
+       }
+       au_hn_reset(inode, au_hi_flags(inode, /*isdir*/1));
+
+       if (do_idop) {
+               if (au_ftest_si(sbi, NO_DREVAL)) {
+                       AuDebugOn(sb->s_d_op == &aufs_dop_noreval);
+                       sb->s_d_op = &aufs_dop_noreval;
+                       AuDebugOn(sbi->si_iop_array == aufs_iop_nogetattr);
+                       sbi->si_iop_array = aufs_iop_nogetattr;
+               } else {
+                       AuDebugOn(sb->s_d_op == &aufs_dop);
+                       sb->s_d_op = &aufs_dop;
+                       AuDebugOn(sbi->si_iop_array == aufs_iop);
+                       sbi->si_iop_array = aufs_iop;
+               }
+               pr_info("reset to %ps and %ps\n",
+                       sb->s_d_op, sbi->si_iop_array);
+       }
+
+       di_write_unlock(root);
+       err = au_refresh_d(sb, do_idop);
+       e = au_refresh_i(sb, do_idop);
+       if (unlikely(e && !err))
+               err = e;
+       /* aufs_write_lock() calls ..._child() */
+       di_write_lock_child(root);
+
+       au_cpup_attr_all(inode, /*force*/1);
+
+       if (unlikely(err))
+               AuIOErr("refresh failed, ignored, %d\n", err);
+}
+
+/* stop extra interpretation of errno in mount(8), and strange error messages */
+static int cvt_err(int err)
+{
+       AuTraceErr(err);
+
+       switch (err) {
+       case -ENOENT:
+       case -ENOTDIR:
+       case -EEXIST:
+       case -EIO:
+               err = -EINVAL;
+       }
+       return err;
+}
+
+static int aufs_remount_fs(struct super_block *sb, int *flags, char *data)
+{
+       int err, do_dx;
+       unsigned int mntflags;
+       struct au_opts opts = {
+               .opt = NULL
+       };
+       struct dentry *root;
+       struct inode *inode;
+       struct au_sbinfo *sbinfo;
+
+       err = 0;
+       root = sb->s_root;
+       if (!data || !*data) {
+               err = si_write_lock(sb, AuLock_FLUSH | AuLock_NOPLM);
+               if (!err) {
+                       di_write_lock_child(root);
+                       err = au_opts_verify(sb, *flags, /*pending*/0);
+                       aufs_write_unlock(root);
+               }
+               goto out;
+       }
+
+       err = -ENOMEM;
+       opts.opt = (void *)__get_free_page(GFP_NOFS);
+       if (unlikely(!opts.opt))
+               goto out;
+       opts.max_opt = PAGE_SIZE / sizeof(*opts.opt);
+       opts.flags = AuOpts_REMOUNT;
+       opts.sb_flags = *flags;
+
+       /* parse it before aufs lock */
+       err = au_opts_parse(sb, data, &opts);
+       if (unlikely(err))
+               goto out_opts;
+
+       sbinfo = au_sbi(sb);
+       inode = d_inode(root);
+       inode_lock(inode);
+       err = si_write_lock(sb, AuLock_FLUSH | AuLock_NOPLM);
+       if (unlikely(err))
+               goto out_mtx;
+       di_write_lock_child(root);
+
+       /* au_opts_remount() may return an error */
+       err = au_opts_remount(sb, &opts);
+       au_opts_free(&opts);
+
+       if (au_ftest_opts(opts.flags, REFRESH))
+               au_remount_refresh(sb, au_ftest_opts(opts.flags, REFRESH_IDOP));
+
+       if (au_ftest_opts(opts.flags, REFRESH_DYAOP)) {
+               mntflags = au_mntflags(sb);
+               do_dx = !!au_opt_test(mntflags, DIO);
+               au_dy_arefresh(do_dx);
+       }
+
+       au_fhsm_wrote_all(sb, /*force*/1); /* ?? */
+       aufs_write_unlock(root);
+
+out_mtx:
+       inode_unlock(inode);
+out_opts:
+       free_page((unsigned long)opts.opt);
+out:
+       err = cvt_err(err);
+       AuTraceErr(err);
+       return err;
+}
+
+static const struct super_operations aufs_sop = {
+       .alloc_inode    = aufs_alloc_inode,
+       .destroy_inode  = aufs_destroy_inode,
+       .free_inode     = aufs_free_inode,
+       /* always deleting, no clearing */
+       .drop_inode     = generic_delete_inode,
+       .show_options   = aufs_show_options,
+       .statfs         = aufs_statfs,
+       .put_super      = aufs_put_super,
+       .sync_fs        = aufs_sync_fs,
+       .remount_fs     = aufs_remount_fs
+};
+
+/* ---------------------------------------------------------------------- */
+
+static int alloc_root(struct super_block *sb)
+{
+       int err;
+       struct inode *inode;
+       struct dentry *root;
+
+       err = -ENOMEM;
+       inode = au_iget_locked(sb, AUFS_ROOT_INO);
+       err = PTR_ERR(inode);
+       if (IS_ERR(inode))
+               goto out;
+
+       inode->i_op = aufs_iop + AuIop_DIR; /* with getattr by default */
+       inode->i_fop = &aufs_dir_fop;
+       inode->i_mode = S_IFDIR;
+       set_nlink(inode, 2);
+       unlock_new_inode(inode);
+
+       root = d_make_root(inode);
+       if (unlikely(!root))
+               goto out;
+       err = PTR_ERR(root);
+       if (IS_ERR(root))
+               goto out;
+
+       err = au_di_init(root);
+       if (!err) {
+               sb->s_root = root;
+               return 0; /* success */
+       }
+       dput(root);
+
+out:
+       return err;
+}
+
+static int aufs_fill_super(struct super_block *sb, void *raw_data,
+                          int silent __maybe_unused)
+{
+       int err;
+       struct au_opts opts = {
+               .opt = NULL
+       };
+       struct au_sbinfo *sbinfo;
+       struct dentry *root;
+       struct inode *inode;
+       char *arg = raw_data;
+
+       if (unlikely(!arg || !*arg)) {
+               err = -EINVAL;
+               pr_err("no arg\n");
+               goto out;
+       }
+
+       err = -ENOMEM;
+       opts.opt = (void *)__get_free_page(GFP_NOFS);
+       if (unlikely(!opts.opt))
+               goto out;
+       opts.max_opt = PAGE_SIZE / sizeof(*opts.opt);
+       opts.sb_flags = sb->s_flags;
+
+       err = au_si_alloc(sb);
+       if (unlikely(err))
+               goto out_opts;
+       sbinfo = au_sbi(sb);
+
+       /* all timestamps always follow the ones on the branch */
+       sb->s_flags |= SB_NOATIME | SB_NODIRATIME;
+       sb->s_flags |= SB_I_VERSION; /* do we really need this? */
+       sb->s_op = &aufs_sop;
+       sb->s_d_op = &aufs_dop;
+       sb->s_magic = AUFS_SUPER_MAGIC;
+       sb->s_maxbytes = 0;
+       sb->s_stack_depth = 1;
+       au_export_init(sb);
+       au_xattr_init(sb);
+
+       err = alloc_root(sb);
+       if (unlikely(err)) {
+               si_write_unlock(sb);
+               goto out_info;
+       }
+       root = sb->s_root;
+       inode = d_inode(root);
+
+       /*
+        * actually we can parse options regardless aufs lock here.
+        * but at remount time, parsing must be done before aufs lock.
+        * so we follow the same rule.
+        */
+       ii_write_lock_parent(inode);
+       aufs_write_unlock(root);
+       err = au_opts_parse(sb, arg, &opts);
+       if (unlikely(err))
+               goto out_root;
+
+       /* lock vfs_inode first, then aufs. */
+       inode_lock(inode);
+       aufs_write_lock(root);
+       err = au_opts_mount(sb, &opts);
+       au_opts_free(&opts);
+       if (!err && au_ftest_si(sbinfo, NO_DREVAL)) {
+               sb->s_d_op = &aufs_dop_noreval;
+               pr_info("%ps\n", sb->s_d_op);
+               au_refresh_dop(root, /*force_reval*/0);
+               sbinfo->si_iop_array = aufs_iop_nogetattr;
+               au_refresh_iop(inode, /*force_getattr*/0);
+       }
+       aufs_write_unlock(root);
+       inode_unlock(inode);
+       if (!err)
+               goto out_opts; /* success */
+
+out_root:
+       dput(root);
+       sb->s_root = NULL;
+out_info:
+       kobject_put(&sbinfo->si_kobj);
+       sb->s_fs_info = NULL;
+out_opts:
+       free_page((unsigned long)opts.opt);
+out:
+       AuTraceErr(err);
+       err = cvt_err(err);
+       AuTraceErr(err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static struct dentry *aufs_mount(struct file_system_type *fs_type, int flags,
+                                const char *dev_name __maybe_unused,
+                                void *raw_data)
+{
+       struct dentry *root;
+
+       /* all timestamps always follow the ones on the branch */
+       /* mnt->mnt_flags |= MNT_NOATIME | MNT_NODIRATIME; */
+       root = mount_nodev(fs_type, flags, raw_data, aufs_fill_super);
+       if (IS_ERR(root))
+               goto out;
+
+       au_sbilist_add(root->d_sb);
+
+out:
+       return root;
+}
+
+static void aufs_kill_sb(struct super_block *sb)
+{
+       struct au_sbinfo *sbinfo;
+
+       sbinfo = au_sbi(sb);
+       if (sbinfo) {
+               au_sbilist_del(sb);
+               aufs_write_lock(sb->s_root);
+               au_fhsm_fin(sb);
+               if (sbinfo->si_wbr_create_ops->fin)
+                       sbinfo->si_wbr_create_ops->fin(sb);
+               if (au_opt_test(sbinfo->si_mntflags, UDBA_HNOTIFY)) {
+                       au_opt_set_udba(sbinfo->si_mntflags, UDBA_NONE);
+                       au_remount_refresh(sb, /*do_idop*/0);
+               }
+               if (au_opt_test(sbinfo->si_mntflags, PLINK))
+                       au_plink_put(sb, /*verbose*/1);
+               au_xino_clr(sb);
+               au_dr_opt_flush(sb);
+               sbinfo->si_sb = NULL;
+               aufs_write_unlock(sb->s_root);
+               au_nwt_flush(&sbinfo->si_nowait);
+       }
+       kill_anon_super(sb);
+}
+
+struct file_system_type aufs_fs_type = {
+       .name           = AUFS_FSTYPE,
+       /* a race between rename and others */
+       .fs_flags       = FS_RENAME_DOES_D_MOVE
+                               /* untested */
+                               /*| FS_ALLOW_IDMAP*/
+                               ,
+       .mount          = aufs_mount,
+       .kill_sb        = aufs_kill_sb,
+       /* no need to __module_get() and module_put(). */
+       .owner          = THIS_MODULE,
+};
diff -urN /usr/share/empty/fs/aufs/super.h linux/fs/aufs/super.h
--- /usr/share/empty/fs/aufs/super.h    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/super.h       2021-12-03 15:38:59.939980643 +0100
@@ -0,0 +1,587 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * super_block operations
+ */
+
+#ifndef __AUFS_SUPER_H__
+#define __AUFS_SUPER_H__
+
+#ifdef __KERNEL__
+
+#include <linux/fs.h>
+#include <linux/kobject.h>
+#include "hbl.h"
+#include "lcnt.h"
+#include "rwsem.h"
+#include "wkq.h"
+
+/* policies to select one among multiple writable branches */
+struct au_wbr_copyup_operations {
+       int (*copyup)(struct dentry *dentry);
+};
+
+#define AuWbr_DIR      1               /* target is a dir */
+#define AuWbr_PARENT   (1 << 1)        /* always require a parent */
+
+#define au_ftest_wbr(flags, name)      ((flags) & AuWbr_##name)
+#define au_fset_wbr(flags, name)       { (flags) |= AuWbr_##name; }
+#define au_fclr_wbr(flags, name)       { (flags) &= ~AuWbr_##name; }
+
+struct au_wbr_create_operations {
+       int (*create)(struct dentry *dentry, unsigned int flags);
+       int (*init)(struct super_block *sb);
+       int (*fin)(struct super_block *sb);
+};
+
+struct au_wbr_mfs {
+       struct mutex    mfs_lock; /* protect this structure */
+       unsigned long   mfs_jiffy;
+       unsigned long   mfs_expire;
+       aufs_bindex_t   mfs_bindex;
+
+       unsigned long long      mfsrr_bytes;
+       unsigned long long      mfsrr_watermark;
+};
+
+#define AuPlink_NHASH 100
+static inline int au_plink_hash(ino_t ino)
+{
+       return ino % AuPlink_NHASH;
+}
+
+/* File-based Hierarchical Storage Management */
+struct au_fhsm {
+#ifdef CONFIG_AUFS_FHSM
+       /* allow only one process who can receive the notification */
+       spinlock_t              fhsm_spin;
+       pid_t                   fhsm_pid;
+       wait_queue_head_t       fhsm_wqh;
+       atomic_t                fhsm_readable;
+
+       /* these are protected by si_rwsem */
+       unsigned long           fhsm_expire;
+       aufs_bindex_t           fhsm_bottom;
+#endif
+};
+
+struct au_branch;
+struct au_sbinfo {
+       /* nowait tasks in the system-wide workqueue */
+       struct au_nowait_tasks  si_nowait;
+
+       /*
+        * tried sb->s_umount, but failed due to the dependency between i_mutex.
+        * rwsem for au_sbinfo is necessary.
+        */
+       struct au_rwsem         si_rwsem;
+
+       /*
+        * dirty approach to protect sb->sb_inodes and ->s_files (gone) from
+        * remount.
+        */
+       au_lcnt_t               si_ninodes, si_nfiles;
+
+       /* branch management */
+       unsigned int            si_generation;
+
+       /* see AuSi_ flags */
+       unsigned char           au_si_status;
+
+       aufs_bindex_t           si_bbot;
+
+       /* dirty trick to keep br_id plus */
+       unsigned int            si_last_br_id :
+                               sizeof(aufs_bindex_t) * BITS_PER_BYTE - 1;
+       struct au_branch        **si_branch;
+
+       /* policy to select a writable branch */
+       unsigned char           si_wbr_copyup;
+       unsigned char           si_wbr_create;
+       struct au_wbr_copyup_operations *si_wbr_copyup_ops;
+       struct au_wbr_create_operations *si_wbr_create_ops;
+
+       /* round robin */
+       atomic_t                si_wbr_rr_next;
+
+       /* most free space */
+       struct au_wbr_mfs       si_wbr_mfs;
+
+       /* File-based Hierarchical Storage Management */
+       struct au_fhsm          si_fhsm;
+
+       /* mount flags */
+       /* include/asm-ia64/siginfo.h defines a macro named si_flags */
+       unsigned int            si_mntflags;
+
+       /* external inode number (bitmap and translation table) */
+       loff_t                  si_ximaxent;    /* max entries in a xino */
+
+       struct file             *si_xib;
+       struct mutex            si_xib_mtx; /* protect xib members */
+       unsigned long           *si_xib_buf;
+       unsigned long           si_xib_last_pindex;
+       int                     si_xib_next_bit;
+
+       unsigned long           si_xino_jiffy;
+       unsigned long           si_xino_expire;
+       /* reserved for future use */
+       /* unsigned long long   si_xib_limit; */        /* Max xib file size */
+
+#ifdef CONFIG_AUFS_EXPORT
+       /* i_generation */
+       /* todo: make xigen file an array to support many inode numbers */
+       struct file             *si_xigen;
+       atomic_t                si_xigen_next;
+#endif
+
+       /* dirty trick to support atomic_open */
+       struct hlist_bl_head    si_aopen;
+
+       /* vdir parameters */
+       unsigned long           si_rdcache;     /* max cache time in jiffies */
+       unsigned int            si_rdblk;       /* deblk size */
+       unsigned int            si_rdhash;      /* hash size */
+
+       /*
+        * If the number of whiteouts are larger than si_dirwh, leave all of
+        * them after au_whtmp_ren to reduce the cost of rmdir(2).
+        * future fsck.aufs or kernel thread will remove them later.
+        * Otherwise, remove all whiteouts and the dir in rmdir(2).
+        */
+       unsigned int            si_dirwh;
+
+       /* pseudo_link list */
+       struct hlist_bl_head    si_plink[AuPlink_NHASH];
+       wait_queue_head_t       si_plink_wq;
+       spinlock_t              si_plink_maint_lock;
+       pid_t                   si_plink_maint_pid;
+
+       /* file list */
+       struct hlist_bl_head    si_files;
+
+       /* with/without getattr, brother of sb->s_d_op */
+       const struct inode_operations *si_iop_array;
+
+       /*
+        * sysfs and lifetime management.
+        * this is not a small structure and it may be a waste of memory in case
+        * of sysfs is disabled, particularly when many aufs-es are mounted.
+        * but using sysfs is majority.
+        */
+       struct kobject          si_kobj;
+#ifdef CONFIG_DEBUG_FS
+       struct dentry            *si_dbgaufs;
+       struct dentry            *si_dbgaufs_plink;
+       struct dentry            *si_dbgaufs_xib;
+#ifdef CONFIG_AUFS_EXPORT
+       struct dentry            *si_dbgaufs_xigen;
+#endif
+#endif
+
+#ifdef CONFIG_AUFS_SBILIST
+       struct hlist_bl_node    si_list;
+#endif
+
+       /* dirty, necessary for unmounting, sysfs and sysrq */
+       struct super_block      *si_sb;
+};
+
+/* sbinfo status flags */
+/*
+ * set true when refresh_dirs() failed at remount time.
+ * then try refreshing dirs at access time again.
+ * if it is false, refreshing dirs at access time is unnecessary
+ */
+#define AuSi_FAILED_REFRESH_DIR        1
+#define AuSi_FHSM              (1 << 1)        /* fhsm is active now */
+#define AuSi_NO_DREVAL         (1 << 2)        /* disable all d_revalidate */
+
+#ifndef CONFIG_AUFS_FHSM
+#undef AuSi_FHSM
+#define AuSi_FHSM              0
+#endif
+
+static inline unsigned char au_do_ftest_si(struct au_sbinfo *sbi,
+                                          unsigned int flag)
+{
+       AuRwMustAnyLock(&sbi->si_rwsem);
+       return sbi->au_si_status & flag;
+}
+#define au_ftest_si(sbinfo, name)      au_do_ftest_si(sbinfo, AuSi_##name)
+#define au_fset_si(sbinfo, name) do { \
+       AuRwMustWriteLock(&(sbinfo)->si_rwsem); \
+       (sbinfo)->au_si_status |= AuSi_##name; \
+} while (0)
+#define au_fclr_si(sbinfo, name) do { \
+       AuRwMustWriteLock(&(sbinfo)->si_rwsem); \
+       (sbinfo)->au_si_status &= ~AuSi_##name; \
+} while (0)
+
+/* ---------------------------------------------------------------------- */
+
+/* policy to select one among writable branches */
+#define AuWbrCopyup(sbinfo, ...) \
+       ((sbinfo)->si_wbr_copyup_ops->copyup(__VA_ARGS__))
+#define AuWbrCreate(sbinfo, ...) \
+       ((sbinfo)->si_wbr_create_ops->create(__VA_ARGS__))
+
+/* flags for si_read_lock()/aufs_read_lock()/di_read_lock() */
+#define AuLock_DW              1               /* write-lock dentry */
+#define AuLock_IR              (1 << 1)        /* read-lock inode */
+#define AuLock_IW              (1 << 2)        /* write-lock inode */
+#define AuLock_FLUSH           (1 << 3)        /* wait for 'nowait' tasks */
+#define AuLock_DIRS            (1 << 4)        /* target is a pair of dirs */
+                                               /* except RENAME_EXCHANGE */
+#define AuLock_NOPLM           (1 << 5)        /* return err in plm mode */
+#define AuLock_NOPLMW          (1 << 6)        /* wait for plm mode ends */
+#define AuLock_GEN             (1 << 7)        /* test digen/iigen */
+#define au_ftest_lock(flags, name)     ((flags) & AuLock_##name)
+#define au_fset_lock(flags, name) \
+       do { (flags) |= AuLock_##name; } while (0)
+#define au_fclr_lock(flags, name) \
+       do { (flags) &= ~AuLock_##name; } while (0)
+
+/* ---------------------------------------------------------------------- */
+
+/* super.c */
+extern struct file_system_type aufs_fs_type;
+struct inode *au_iget_locked(struct super_block *sb, ino_t ino);
+typedef unsigned long long (*au_arraycb_t)(struct super_block *sb, void *array,
+                                          unsigned long long max, void *arg);
+void *au_array_alloc(unsigned long long *hint, au_arraycb_t cb,
+                    struct super_block *sb, void *arg);
+struct inode **au_iarray_alloc(struct super_block *sb, unsigned long long *max);
+void au_iarray_free(struct inode **a, unsigned long long max);
+
+/* sbinfo.c */
+void au_si_free(struct kobject *kobj);
+int au_si_alloc(struct super_block *sb);
+int au_sbr_realloc(struct au_sbinfo *sbinfo, int nbr, int may_shrink);
+
+unsigned int au_sigen_inc(struct super_block *sb);
+aufs_bindex_t au_new_br_id(struct super_block *sb);
+
+int si_read_lock(struct super_block *sb, int flags);
+int si_write_lock(struct super_block *sb, int flags);
+int aufs_read_lock(struct dentry *dentry, int flags);
+void aufs_read_unlock(struct dentry *dentry, int flags);
+void aufs_write_lock(struct dentry *dentry);
+void aufs_write_unlock(struct dentry *dentry);
+int aufs_read_and_write_lock2(struct dentry *d1, struct dentry *d2, int flags);
+void aufs_read_and_write_unlock2(struct dentry *d1, struct dentry *d2);
+
+/* wbr_policy.c */
+extern struct au_wbr_copyup_operations au_wbr_copyup_ops[];
+extern struct au_wbr_create_operations au_wbr_create_ops[];
+int au_cpdown_dirs(struct dentry *dentry, aufs_bindex_t bdst);
+int au_wbr_nonopq(struct dentry *dentry, aufs_bindex_t bindex);
+int au_wbr_do_copyup_bu(struct dentry *dentry, aufs_bindex_t btop);
+
+/* mvdown.c */
+int au_mvdown(struct dentry *dentry, struct aufs_mvdown __user *arg);
+
+#ifdef CONFIG_AUFS_FHSM
+/* fhsm.c */
+
+static inline pid_t au_fhsm_pid(struct au_fhsm *fhsm)
+{
+       pid_t pid;
+
+       spin_lock(&fhsm->fhsm_spin);
+       pid = fhsm->fhsm_pid;
+       spin_unlock(&fhsm->fhsm_spin);
+
+       return pid;
+}
+
+void au_fhsm_wrote(struct super_block *sb, aufs_bindex_t bindex, int force);
+void au_fhsm_wrote_all(struct super_block *sb, int force);
+int au_fhsm_fd(struct super_block *sb, int oflags);
+int au_fhsm_br_alloc(struct au_branch *br);
+void au_fhsm_set_bottom(struct super_block *sb, aufs_bindex_t bindex);
+void au_fhsm_fin(struct super_block *sb);
+void au_fhsm_init(struct au_sbinfo *sbinfo);
+void au_fhsm_set(struct au_sbinfo *sbinfo, unsigned int sec);
+void au_fhsm_show(struct seq_file *seq, struct au_sbinfo *sbinfo);
+#else
+AuStubVoid(au_fhsm_wrote, struct super_block *sb, aufs_bindex_t bindex,
+          int force)
+AuStubVoid(au_fhsm_wrote_all, struct super_block *sb, int force)
+AuStub(int, au_fhsm_fd, return -EOPNOTSUPP, struct super_block *sb, int oflags)
+AuStub(pid_t, au_fhsm_pid, return 0, struct au_fhsm *fhsm)
+AuStubInt0(au_fhsm_br_alloc, struct au_branch *br)
+AuStubVoid(au_fhsm_set_bottom, struct super_block *sb, aufs_bindex_t bindex)
+AuStubVoid(au_fhsm_fin, struct super_block *sb)
+AuStubVoid(au_fhsm_init, struct au_sbinfo *sbinfo)
+AuStubVoid(au_fhsm_set, struct au_sbinfo *sbinfo, unsigned int sec)
+AuStubVoid(au_fhsm_show, struct seq_file *seq, struct au_sbinfo *sbinfo)
+#endif
+
+/* ---------------------------------------------------------------------- */
+
+static inline struct au_sbinfo *au_sbi(struct super_block *sb)
+{
+       return sb->s_fs_info;
+}
+
+/* ---------------------------------------------------------------------- */
+
+#ifdef CONFIG_AUFS_EXPORT
+int au_test_nfsd(void);
+void au_export_init(struct super_block *sb);
+void au_xigen_inc(struct inode *inode);
+int au_xigen_new(struct inode *inode);
+int au_xigen_set(struct super_block *sb, struct path *path);
+void au_xigen_clr(struct super_block *sb);
+
+static inline int au_busy_or_stale(void)
+{
+       if (!au_test_nfsd())
+               return -EBUSY;
+       return -ESTALE;
+}
+#else
+AuStubInt0(au_test_nfsd, void)
+AuStubVoid(au_export_init, struct super_block *sb)
+AuStubVoid(au_xigen_inc, struct inode *inode)
+AuStubInt0(au_xigen_new, struct inode *inode)
+AuStubInt0(au_xigen_set, struct super_block *sb, struct path *path)
+AuStubVoid(au_xigen_clr, struct super_block *sb)
+AuStub(int, au_busy_or_stale, return -EBUSY, void)
+#endif /* CONFIG_AUFS_EXPORT */
+
+/* ---------------------------------------------------------------------- */
+
+#ifdef CONFIG_AUFS_SBILIST
+/* module.c */
+extern struct hlist_bl_head au_sbilist;
+
+static inline void au_sbilist_init(void)
+{
+       INIT_HLIST_BL_HEAD(&au_sbilist);
+}
+
+static inline void au_sbilist_add(struct super_block *sb)
+{
+       au_hbl_add(&au_sbi(sb)->si_list, &au_sbilist);
+}
+
+static inline void au_sbilist_del(struct super_block *sb)
+{
+       au_hbl_del(&au_sbi(sb)->si_list, &au_sbilist);
+}
+
+#ifdef CONFIG_AUFS_MAGIC_SYSRQ
+static inline void au_sbilist_lock(void)
+{
+       hlist_bl_lock(&au_sbilist);
+}
+
+static inline void au_sbilist_unlock(void)
+{
+       hlist_bl_unlock(&au_sbilist);
+}
+#define AuGFP_SBILIST  GFP_ATOMIC
+#else
+AuStubVoid(au_sbilist_lock, void)
+AuStubVoid(au_sbilist_unlock, void)
+#define AuGFP_SBILIST  GFP_NOFS
+#endif /* CONFIG_AUFS_MAGIC_SYSRQ */
+#else
+AuStubVoid(au_sbilist_init, void)
+AuStubVoid(au_sbilist_add, struct super_block *sb)
+AuStubVoid(au_sbilist_del, struct super_block *sb)
+AuStubVoid(au_sbilist_lock, void)
+AuStubVoid(au_sbilist_unlock, void)
+#define AuGFP_SBILIST  GFP_NOFS
+#endif
+
+/* ---------------------------------------------------------------------- */
+
+static inline void dbgaufs_si_null(struct au_sbinfo *sbinfo)
+{
+       /*
+        * This function is a dynamic '__init' function actually,
+        * so the tiny check for si_rwsem is unnecessary.
+        */
+       /* AuRwMustWriteLock(&sbinfo->si_rwsem); */
+#ifdef CONFIG_DEBUG_FS
+       sbinfo->si_dbgaufs = NULL;
+       sbinfo->si_dbgaufs_plink = NULL;
+       sbinfo->si_dbgaufs_xib = NULL;
+#ifdef CONFIG_AUFS_EXPORT
+       sbinfo->si_dbgaufs_xigen = NULL;
+#endif
+#endif
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* current->atomic_flags */
+/* this value should never corrupt the ones defined in linux/sched.h */
+#define PFA_AUFS       0x10
+
+TASK_PFA_TEST(AUFS, test_aufs) /* task_test_aufs */
+TASK_PFA_SET(AUFS, aufs)       /* task_set_aufs */
+TASK_PFA_CLEAR(AUFS, aufs)     /* task_clear_aufs */
+
+static inline int si_pid_test(struct super_block *sb)
+{
+       return !!task_test_aufs(current);
+}
+
+static inline void si_pid_clr(struct super_block *sb)
+{
+       AuDebugOn(!task_test_aufs(current));
+       task_clear_aufs(current);
+}
+
+static inline void si_pid_set(struct super_block *sb)
+{
+       AuDebugOn(task_test_aufs(current));
+       task_set_aufs(current);
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* lock superblock. mainly for entry point functions */
+#define __si_read_lock(sb)     au_rw_read_lock(&au_sbi(sb)->si_rwsem)
+#define __si_write_lock(sb)    au_rw_write_lock(&au_sbi(sb)->si_rwsem)
+#define __si_read_trylock(sb)  au_rw_read_trylock(&au_sbi(sb)->si_rwsem)
+#define __si_write_trylock(sb) au_rw_write_trylock(&au_sbi(sb)->si_rwsem)
+/*
+#define __si_read_trylock_nested(sb) \
+       au_rw_read_trylock_nested(&au_sbi(sb)->si_rwsem)
+#define __si_write_trylock_nested(sb) \
+       au_rw_write_trylock_nested(&au_sbi(sb)->si_rwsem)
+*/
+
+#define __si_read_unlock(sb)   au_rw_read_unlock(&au_sbi(sb)->si_rwsem)
+#define __si_write_unlock(sb)  au_rw_write_unlock(&au_sbi(sb)->si_rwsem)
+#define __si_downgrade_lock(sb)        au_rw_dgrade_lock(&au_sbi(sb)->si_rwsem)
+
+#define SiMustNoWaiters(sb)    AuRwMustNoWaiters(&au_sbi(sb)->si_rwsem)
+#define SiMustAnyLock(sb)      AuRwMustAnyLock(&au_sbi(sb)->si_rwsem)
+#define SiMustWriteLock(sb)    AuRwMustWriteLock(&au_sbi(sb)->si_rwsem)
+
+static inline void si_noflush_read_lock(struct super_block *sb)
+{
+       __si_read_lock(sb);
+       si_pid_set(sb);
+}
+
+static inline int si_noflush_read_trylock(struct super_block *sb)
+{
+       int locked;
+
+       locked = __si_read_trylock(sb);
+       if (locked)
+               si_pid_set(sb);
+       return locked;
+}
+
+static inline void si_noflush_write_lock(struct super_block *sb)
+{
+       __si_write_lock(sb);
+       si_pid_set(sb);
+}
+
+static inline int si_noflush_write_trylock(struct super_block *sb)
+{
+       int locked;
+
+       locked = __si_write_trylock(sb);
+       if (locked)
+               si_pid_set(sb);
+       return locked;
+}
+
+#if 0 /* reserved */
+static inline int si_read_trylock(struct super_block *sb, int flags)
+{
+       if (au_ftest_lock(flags, FLUSH))
+               au_nwt_flush(&au_sbi(sb)->si_nowait);
+       return si_noflush_read_trylock(sb);
+}
+#endif
+
+static inline void si_read_unlock(struct super_block *sb)
+{
+       si_pid_clr(sb);
+       __si_read_unlock(sb);
+}
+
+#if 0 /* reserved */
+static inline int si_write_trylock(struct super_block *sb, int flags)
+{
+       if (au_ftest_lock(flags, FLUSH))
+               au_nwt_flush(&au_sbi(sb)->si_nowait);
+       return si_noflush_write_trylock(sb);
+}
+#endif
+
+static inline void si_write_unlock(struct super_block *sb)
+{
+       si_pid_clr(sb);
+       __si_write_unlock(sb);
+}
+
+#if 0 /* reserved */
+static inline void si_downgrade_lock(struct super_block *sb)
+{
+       __si_downgrade_lock(sb);
+}
+#endif
+
+/* ---------------------------------------------------------------------- */
+
+static inline aufs_bindex_t au_sbbot(struct super_block *sb)
+{
+       SiMustAnyLock(sb);
+       return au_sbi(sb)->si_bbot;
+}
+
+static inline unsigned int au_mntflags(struct super_block *sb)
+{
+       SiMustAnyLock(sb);
+       return au_sbi(sb)->si_mntflags;
+}
+
+static inline unsigned int au_sigen(struct super_block *sb)
+{
+       SiMustAnyLock(sb);
+       return au_sbi(sb)->si_generation;
+}
+
+static inline struct au_branch *au_sbr(struct super_block *sb,
+                                      aufs_bindex_t bindex)
+{
+       SiMustAnyLock(sb);
+       return au_sbi(sb)->si_branch[0 + bindex];
+}
+
+static inline loff_t au_xi_maxent(struct super_block *sb)
+{
+       SiMustAnyLock(sb);
+       return au_sbi(sb)->si_ximaxent;
+}
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_SUPER_H__ */
diff -urN /usr/share/empty/fs/aufs/sysaufs.c linux/fs/aufs/sysaufs.c
--- /usr/share/empty/fs/aufs/sysaufs.c  1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/sysaufs.c     2021-12-03 15:38:59.939980643 +0100
@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * sysfs interface and lifetime management
+ * they are necessary regardless sysfs is disabled.
+ */
+
+#include <linux/random.h>
+#include "aufs.h"
+
+unsigned long sysaufs_si_mask;
+struct kset *sysaufs_kset;
+
+#define AuSiAttr(_name) { \
+       .attr   = { .name = __stringify(_name), .mode = 0444 }, \
+       .show   = sysaufs_si_##_name,                           \
+}
+
+static struct sysaufs_si_attr sysaufs_si_attr_xi_path = AuSiAttr(xi_path);
+struct attribute *sysaufs_si_attrs[] = {
+       &sysaufs_si_attr_xi_path.attr,
+       NULL,
+};
+
+static const struct sysfs_ops au_sbi_ops = {
+       .show   = sysaufs_si_show
+};
+
+static struct kobj_type au_sbi_ktype = {
+       .release        = au_si_free,
+       .sysfs_ops      = &au_sbi_ops,
+       .default_attrs  = sysaufs_si_attrs
+};
+
+/* ---------------------------------------------------------------------- */
+
+int sysaufs_si_init(struct au_sbinfo *sbinfo)
+{
+       int err;
+
+       sbinfo->si_kobj.kset = sysaufs_kset;
+       /* cf. sysaufs_name() */
+       err = kobject_init_and_add
+               (&sbinfo->si_kobj, &au_sbi_ktype, /*&sysaufs_kset->kobj*/NULL,
+                SysaufsSiNamePrefix "%lx", sysaufs_si_id(sbinfo));
+
+       return err;
+}
+
+void sysaufs_fin(void)
+{
+       sysfs_remove_group(&sysaufs_kset->kobj, sysaufs_attr_group);
+       kset_unregister(sysaufs_kset);
+}
+
+int __init sysaufs_init(void)
+{
+       int err;
+
+       do {
+               get_random_bytes(&sysaufs_si_mask, sizeof(sysaufs_si_mask));
+       } while (!sysaufs_si_mask);
+
+       err = -EINVAL;
+       sysaufs_kset = kset_create_and_add(AUFS_NAME, NULL, fs_kobj);
+       if (unlikely(!sysaufs_kset))
+               goto out;
+       err = PTR_ERR(sysaufs_kset);
+       if (IS_ERR(sysaufs_kset))
+               goto out;
+       err = sysfs_create_group(&sysaufs_kset->kobj, sysaufs_attr_group);
+       if (unlikely(err))
+               kset_unregister(sysaufs_kset);
+
+out:
+       return err;
+}
diff -urN /usr/share/empty/fs/aufs/sysaufs.h linux/fs/aufs/sysaufs.h
--- /usr/share/empty/fs/aufs/sysaufs.h  1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/sysaufs.h     2021-12-03 15:38:59.939980643 +0100
@@ -0,0 +1,102 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * sysfs interface and mount lifetime management
+ */
+
+#ifndef __SYSAUFS_H__
+#define __SYSAUFS_H__
+
+#ifdef __KERNEL__
+
+#include <linux/sysfs.h>
+#include "module.h"
+
+struct super_block;
+struct au_sbinfo;
+
+struct sysaufs_si_attr {
+       struct attribute attr;
+       int (*show)(struct seq_file *seq, struct super_block *sb);
+};
+
+/* ---------------------------------------------------------------------- */
+
+/* sysaufs.c */
+extern unsigned long sysaufs_si_mask;
+extern struct kset *sysaufs_kset;
+extern struct attribute *sysaufs_si_attrs[];
+int sysaufs_si_init(struct au_sbinfo *sbinfo);
+int __init sysaufs_init(void);
+void sysaufs_fin(void);
+
+/* ---------------------------------------------------------------------- */
+
+/* some people doesn't like to show a pointer in kernel */
+static inline unsigned long sysaufs_si_id(struct au_sbinfo *sbinfo)
+{
+       return sysaufs_si_mask ^ (unsigned long)sbinfo;
+}
+
+#define SysaufsSiNamePrefix    "si_"
+#define SysaufsSiNameLen       (sizeof(SysaufsSiNamePrefix) + 16)
+static inline void sysaufs_name(struct au_sbinfo *sbinfo, char *name)
+{
+       snprintf(name, SysaufsSiNameLen, SysaufsSiNamePrefix "%lx",
+                sysaufs_si_id(sbinfo));
+}
+
+struct au_branch;
+#ifdef CONFIG_SYSFS
+/* sysfs.c */
+extern struct attribute_group *sysaufs_attr_group;
+
+int sysaufs_si_xi_path(struct seq_file *seq, struct super_block *sb);
+ssize_t sysaufs_si_show(struct kobject *kobj, struct attribute *attr,
+                        char *buf);
+long au_brinfo_ioctl(struct file *file, unsigned long arg);
+#ifdef CONFIG_COMPAT
+long au_brinfo_compat_ioctl(struct file *file, unsigned long arg);
+#endif
+
+void sysaufs_br_init(struct au_branch *br);
+void sysaufs_brs_add(struct super_block *sb, aufs_bindex_t bindex);
+void sysaufs_brs_del(struct super_block *sb, aufs_bindex_t bindex);
+
+#define sysaufs_brs_init()     do {} while (0)
+
+#else
+#define sysaufs_attr_group     NULL
+
+AuStubInt0(sysaufs_si_xi_path, struct seq_file *seq, struct super_block *sb)
+AuStub(ssize_t, sysaufs_si_show, return 0, struct kobject *kobj,
+       struct attribute *attr, char *buf)
+AuStubVoid(sysaufs_br_init, struct au_branch *br)
+AuStubVoid(sysaufs_brs_add, struct super_block *sb, aufs_bindex_t bindex)
+AuStubVoid(sysaufs_brs_del, struct super_block *sb, aufs_bindex_t bindex)
+
+static inline void sysaufs_brs_init(void)
+{
+       sysaufs_brs = 0;
+}
+
+#endif /* CONFIG_SYSFS */
+
+#endif /* __KERNEL__ */
+#endif /* __SYSAUFS_H__ */
diff -urN /usr/share/empty/fs/aufs/sysfs.c linux/fs/aufs/sysfs.c
--- /usr/share/empty/fs/aufs/sysfs.c    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/sysfs.c       2021-12-03 15:38:59.939980643 +0100
@@ -0,0 +1,374 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * sysfs interface
+ */
+
+#include <linux/compat.h>
+#include <linux/seq_file.h>
+#include "aufs.h"
+
+#ifdef CONFIG_AUFS_FS_MODULE
+/* this entry violates the "one line per file" policy of sysfs */
+static ssize_t config_show(struct kobject *kobj, struct kobj_attribute *attr,
+                          char *buf)
+{
+       ssize_t err;
+       static char *conf =
+/* this file is generated at compiling */
+#include "conf.str"
+               ;
+
+       err = snprintf(buf, PAGE_SIZE, conf);
+       if (unlikely(err >= PAGE_SIZE))
+               err = -EFBIG;
+       return err;
+}
+
+static struct kobj_attribute au_config_attr = __ATTR_RO(config);
+#endif
+
+static struct attribute *au_attr[] = {
+#ifdef CONFIG_AUFS_FS_MODULE
+       &au_config_attr.attr,
+#endif
+       NULL,   /* need to NULL terminate the list of attributes */
+};
+
+static struct attribute_group sysaufs_attr_group_body = {
+       .attrs = au_attr
+};
+
+struct attribute_group *sysaufs_attr_group = &sysaufs_attr_group_body;
+
+/* ---------------------------------------------------------------------- */
+
+int sysaufs_si_xi_path(struct seq_file *seq, struct super_block *sb)
+{
+       int err;
+
+       SiMustAnyLock(sb);
+
+       err = 0;
+       if (au_opt_test(au_mntflags(sb), XINO)) {
+               err = au_xino_path(seq, au_sbi(sb)->si_xib);
+               seq_putc(seq, '\n');
+       }
+       return err;
+}
+
+/*
+ * the lifetime of branch is independent from the entry under sysfs.
+ * sysfs handles the lifetime of the entry, and never call ->show() after it is
+ * unlinked.
+ */
+static int sysaufs_si_br(struct seq_file *seq, struct super_block *sb,
+                        aufs_bindex_t bindex, int idx)
+{
+       int err;
+       struct path path;
+       struct dentry *root;
+       struct au_branch *br;
+       au_br_perm_str_t perm;
+
+       AuDbg("b%d\n", bindex);
+
+       err = 0;
+       root = sb->s_root;
+       di_read_lock_parent(root, !AuLock_IR);
+       br = au_sbr(sb, bindex);
+
+       switch (idx) {
+       case AuBrSysfs_BR:
+               path.mnt = au_br_mnt(br);
+               path.dentry = au_h_dptr(root, bindex);
+               err = au_seq_path(seq, &path);
+               if (!err) {
+                       au_optstr_br_perm(&perm, br->br_perm);
+                       seq_printf(seq, "=%s\n", perm.a);
+               }
+               break;
+       case AuBrSysfs_BRID:
+               seq_printf(seq, "%d\n", br->br_id);
+               break;
+       }
+       di_read_unlock(root, !AuLock_IR);
+       if (unlikely(err || seq_has_overflowed(seq)))
+               err = -E2BIG;
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static struct seq_file *au_seq(char *p, ssize_t len)
+{
+       struct seq_file *seq;
+
+       seq = kzalloc(sizeof(*seq), GFP_NOFS);
+       if (seq) {
+               /* mutex_init(&seq.lock); */
+               seq->buf = p;
+               seq->size = len;
+               return seq; /* success */
+       }
+
+       seq = ERR_PTR(-ENOMEM);
+       return seq;
+}
+
+#define SysaufsBr_PREFIX       "br"
+#define SysaufsBrid_PREFIX     "brid"
+
+/* todo: file size may exceed PAGE_SIZE */
+ssize_t sysaufs_si_show(struct kobject *kobj, struct attribute *attr,
+                       char *buf)
+{
+       ssize_t err;
+       int idx;
+       long l;
+       aufs_bindex_t bbot;
+       struct au_sbinfo *sbinfo;
+       struct super_block *sb;
+       struct seq_file *seq;
+       char *name;
+       struct attribute **cattr;
+
+       sbinfo = container_of(kobj, struct au_sbinfo, si_kobj);
+       sb = sbinfo->si_sb;
+
+       /*
+        * prevent a race condition between sysfs and aufs.
+        * for instance, sysfs_file_read() calls sysfs_get_active_two() which
+        * prohibits maintaining the sysfs entries.
+        * hew we acquire read lock after sysfs_get_active_two().
+        * on the other hand, the remount process may maintain the sysfs/aufs
+        * entries after acquiring write lock.
+        * it can cause a deadlock.
+        * simply we gave up processing read here.
+        */
+       err = -EBUSY;
+       if (unlikely(!si_noflush_read_trylock(sb)))
+               goto out;
+
+       seq = au_seq(buf, PAGE_SIZE);
+       err = PTR_ERR(seq);
+       if (IS_ERR(seq))
+               goto out_unlock;
+
+       name = (void *)attr->name;
+       cattr = sysaufs_si_attrs;
+       while (*cattr) {
+               if (!strcmp(name, (*cattr)->name)) {
+                       err = container_of(*cattr, struct sysaufs_si_attr, attr)
+                               ->show(seq, sb);
+                       goto out_seq;
+               }
+               cattr++;
+       }
+
+       if (!strncmp(name, SysaufsBrid_PREFIX,
+                    sizeof(SysaufsBrid_PREFIX) - 1)) {
+               idx = AuBrSysfs_BRID;
+               name += sizeof(SysaufsBrid_PREFIX) - 1;
+       } else if (!strncmp(name, SysaufsBr_PREFIX,
+                           sizeof(SysaufsBr_PREFIX) - 1)) {
+               idx = AuBrSysfs_BR;
+               name += sizeof(SysaufsBr_PREFIX) - 1;
+       } else
+                 BUG();
+
+       err = kstrtol(name, 10, &l);
+       if (!err) {
+               bbot = au_sbbot(sb);
+               if (l <= bbot)
+                       err = sysaufs_si_br(seq, sb, (aufs_bindex_t)l, idx);
+               else
+                       err = -ENOENT;
+       }
+
+out_seq:
+       if (!err) {
+               err = seq->count;
+               /* sysfs limit */
+               if (unlikely(err == PAGE_SIZE))
+                       err = -EFBIG;
+       }
+       au_kfree_rcu(seq);
+out_unlock:
+       si_read_unlock(sb);
+out:
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_brinfo(struct super_block *sb, union aufs_brinfo __user *arg)
+{
+       int err;
+       int16_t brid;
+       aufs_bindex_t bindex, bbot;
+       size_t sz;
+       char *buf;
+       struct seq_file *seq;
+       struct au_branch *br;
+
+       si_read_lock(sb, AuLock_FLUSH);
+       bbot = au_sbbot(sb);
+       err = bbot + 1;
+       if (!arg)
+               goto out;
+
+       err = -ENOMEM;
+       buf = (void *)__get_free_page(GFP_NOFS);
+       if (unlikely(!buf))
+               goto out;
+
+       seq = au_seq(buf, PAGE_SIZE);
+       err = PTR_ERR(seq);
+       if (IS_ERR(seq))
+               goto out_buf;
+
+       sz = sizeof(*arg) - offsetof(union aufs_brinfo, path);
+       for (bindex = 0; bindex <= bbot; bindex++, arg++) {
+               /* VERIFY_WRITE */
+               err = !access_ok(arg, sizeof(*arg));
+               if (unlikely(err))
+                       break;
+
+               br = au_sbr(sb, bindex);
+               brid = br->br_id;
+               BUILD_BUG_ON(sizeof(brid) != sizeof(arg->id));
+               err = __put_user(brid, &arg->id);
+               if (unlikely(err))
+                       break;
+
+               BUILD_BUG_ON(sizeof(br->br_perm) != sizeof(arg->perm));
+               err = __put_user(br->br_perm, &arg->perm);
+               if (unlikely(err))
+                       break;
+
+               err = au_seq_path(seq, &br->br_path);
+               if (unlikely(err))
+                       break;
+               seq_putc(seq, '\0');
+               if (!seq_has_overflowed(seq)) {
+                       err = copy_to_user(arg->path, seq->buf, seq->count);
+                       seq->count = 0;
+                       if (unlikely(err))
+                               break;
+               } else {
+                       err = -E2BIG;
+                       goto out_seq;
+               }
+       }
+       if (unlikely(err))
+               err = -EFAULT;
+
+out_seq:
+       au_kfree_rcu(seq);
+out_buf:
+       free_page((unsigned long)buf);
+out:
+       si_read_unlock(sb);
+       return err;
+}
+
+long au_brinfo_ioctl(struct file *file, unsigned long arg)
+{
+       return au_brinfo(file->f_path.dentry->d_sb, (void __user *)arg);
+}
+
+#ifdef CONFIG_COMPAT
+long au_brinfo_compat_ioctl(struct file *file, unsigned long arg)
+{
+       return au_brinfo(file->f_path.dentry->d_sb, compat_ptr(arg));
+}
+#endif
+
+/* ---------------------------------------------------------------------- */
+
+void sysaufs_br_init(struct au_branch *br)
+{
+       int i;
+       struct au_brsysfs *br_sysfs;
+       struct attribute *attr;
+
+       br_sysfs = br->br_sysfs;
+       for (i = 0; i < ARRAY_SIZE(br->br_sysfs); i++) {
+               attr = &br_sysfs->attr;
+               sysfs_attr_init(attr);
+               attr->name = br_sysfs->name;
+               attr->mode = 0444;
+               br_sysfs++;
+       }
+}
+
+void sysaufs_brs_del(struct super_block *sb, aufs_bindex_t bindex)
+{
+       struct au_branch *br;
+       struct kobject *kobj;
+       struct au_brsysfs *br_sysfs;
+       int i;
+       aufs_bindex_t bbot;
+
+       if (!sysaufs_brs)
+               return;
+
+       kobj = &au_sbi(sb)->si_kobj;
+       bbot = au_sbbot(sb);
+       for (; bindex <= bbot; bindex++) {
+               br = au_sbr(sb, bindex);
+               br_sysfs = br->br_sysfs;
+               for (i = 0; i < ARRAY_SIZE(br->br_sysfs); i++) {
+                       sysfs_remove_file(kobj, &br_sysfs->attr);
+                       br_sysfs++;
+               }
+       }
+}
+
+void sysaufs_brs_add(struct super_block *sb, aufs_bindex_t bindex)
+{
+       int err, i;
+       aufs_bindex_t bbot;
+       struct kobject *kobj;
+       struct au_branch *br;
+       struct au_brsysfs *br_sysfs;
+
+       if (!sysaufs_brs)
+               return;
+
+       kobj = &au_sbi(sb)->si_kobj;
+       bbot = au_sbbot(sb);
+       for (; bindex <= bbot; bindex++) {
+               br = au_sbr(sb, bindex);
+               br_sysfs = br->br_sysfs;
+               snprintf(br_sysfs[AuBrSysfs_BR].name, sizeof(br_sysfs->name),
+                        SysaufsBr_PREFIX "%d", bindex);
+               snprintf(br_sysfs[AuBrSysfs_BRID].name, sizeof(br_sysfs->name),
+                        SysaufsBrid_PREFIX "%d", bindex);
+               for (i = 0; i < ARRAY_SIZE(br->br_sysfs); i++) {
+                       err = sysfs_create_file(kobj, &br_sysfs->attr);
+                       if (unlikely(err))
+                               pr_warn("failed %s under sysfs(%d)\n",
+                                       br_sysfs->name, err);
+                       br_sysfs++;
+               }
+       }
+}
diff -urN /usr/share/empty/fs/aufs/sysrq.c linux/fs/aufs/sysrq.c
--- /usr/share/empty/fs/aufs/sysrq.c    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/sysrq.c       2021-12-03 15:38:59.939980643 +0100
@@ -0,0 +1,149 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * magic sysrq handler
+ */
+
+/* #include <linux/sysrq.h> */
+#include <linux/writeback.h>
+#include "aufs.h"
+
+/* ---------------------------------------------------------------------- */
+
+static void sysrq_sb(struct super_block *sb)
+{
+       char *plevel;
+       struct au_sbinfo *sbinfo;
+       struct file *file;
+       struct hlist_bl_head *files;
+       struct hlist_bl_node *pos;
+       struct au_finfo *finfo;
+       struct inode *i;
+
+       plevel = au_plevel;
+       au_plevel = KERN_WARNING;
+
+       /* since we define pr_fmt, call printk directly */
+#define pr(str) printk(KERN_WARNING AUFS_NAME ": " str)
+
+       sbinfo = au_sbi(sb);
+       printk(KERN_WARNING "si=%lx\n", sysaufs_si_id(sbinfo));
+       pr("superblock\n");
+       au_dpri_sb(sb);
+
+#if 0 /* reserved */
+       do {
+               int err, i, j, ndentry;
+               struct au_dcsub_pages dpages;
+               struct au_dpage *dpage;
+
+               err = au_dpages_init(&dpages, GFP_ATOMIC);
+               if (unlikely(err))
+                       break;
+               err = au_dcsub_pages(&dpages, sb->s_root, NULL, NULL);
+               if (!err)
+                       for (i = 0; i < dpages.ndpage; i++) {
+                               dpage = dpages.dpages + i;
+                               ndentry = dpage->ndentry;
+                               for (j = 0; j < ndentry; j++)
+                                       au_dpri_dentry(dpage->dentries[j]);
+                       }
+               au_dpages_free(&dpages);
+       } while (0);
+#endif
+
+       pr("isolated inode\n");
+       spin_lock(&sb->s_inode_list_lock);
+       list_for_each_entry(i, &sb->s_inodes, i_sb_list) {
+               spin_lock(&i->i_lock);
+               if (hlist_empty(&i->i_dentry))
+                       au_dpri_inode(i);
+               spin_unlock(&i->i_lock);
+       }
+       spin_unlock(&sb->s_inode_list_lock);
+
+       pr("files\n");
+       files = &au_sbi(sb)->si_files;
+       hlist_bl_lock(files);
+       hlist_bl_for_each_entry(finfo, pos, files, fi_hlist) {
+               umode_t mode;
+
+               file = finfo->fi_file;
+               mode = file_inode(file)->i_mode;
+               if (!special_file(mode))
+                       au_dpri_file(file);
+       }
+       hlist_bl_unlock(files);
+       pr("done\n");
+
+#undef pr
+       au_plevel = plevel;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* module parameter */
+static char *aufs_sysrq_key = "a";
+module_param_named(sysrq, aufs_sysrq_key, charp, 0444);
+MODULE_PARM_DESC(sysrq, "MagicSysRq key for " AUFS_NAME);
+
+static void au_sysrq(int key __maybe_unused)
+{
+       struct au_sbinfo *sbinfo;
+       struct hlist_bl_node *pos;
+
+       lockdep_off();
+       au_sbilist_lock();
+       hlist_bl_for_each_entry(sbinfo, pos, &au_sbilist, si_list)
+               sysrq_sb(sbinfo->si_sb);
+       au_sbilist_unlock();
+       lockdep_on();
+}
+
+static struct sysrq_key_op au_sysrq_op = {
+       .handler        = au_sysrq,
+       .help_msg       = "Aufs",
+       .action_msg     = "Aufs",
+       .enable_mask    = SYSRQ_ENABLE_DUMP
+};
+
+/* ---------------------------------------------------------------------- */
+
+int __init au_sysrq_init(void)
+{
+       int err;
+       char key;
+
+       err = -1;
+       key = *aufs_sysrq_key;
+       if ('a' <= key && key <= 'z')
+               err = register_sysrq_key(key, &au_sysrq_op);
+       if (unlikely(err))
+               pr_err("err %d, sysrq=%c\n", err, key);
+       return err;
+}
+
+void au_sysrq_fin(void)
+{
+       int err;
+
+       err = unregister_sysrq_key(*aufs_sysrq_key, &au_sysrq_op);
+       if (unlikely(err))
+               pr_err("err %d (ignored)\n", err);
+}
diff -urN /usr/share/empty/fs/aufs/vdir.c linux/fs/aufs/vdir.c
--- /usr/share/empty/fs/aufs/vdir.c     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/vdir.c        2021-12-03 15:38:59.939980643 +0100
@@ -0,0 +1,896 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * virtual or vertical directory
+ */
+
+#include <linux/iversion.h>
+#include "aufs.h"
+
+static unsigned int calc_size(int nlen)
+{
+       return ALIGN(sizeof(struct au_vdir_de) + nlen, sizeof(ino_t));
+}
+
+static int set_deblk_end(union au_vdir_deblk_p *p,
+                        union au_vdir_deblk_p *deblk_end)
+{
+       if (calc_size(0) <= deblk_end->deblk - p->deblk) {
+               p->de->de_str.len = 0;
+               /* smp_mb(); */
+               return 0;
+       }
+       return -1; /* error */
+}
+
+/* returns true or false */
+static int is_deblk_end(union au_vdir_deblk_p *p,
+                       union au_vdir_deblk_p *deblk_end)
+{
+       if (calc_size(0) <= deblk_end->deblk - p->deblk)
+               return !p->de->de_str.len;
+       return 1;
+}
+
+static unsigned char *last_deblk(struct au_vdir *vdir)
+{
+       return vdir->vd_deblk[vdir->vd_nblk - 1];
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* estimate the appropriate size for name hash table */
+unsigned int au_rdhash_est(loff_t sz)
+{
+       unsigned int n;
+
+       n = UINT_MAX;
+       sz >>= 10;
+       if (sz < n)
+               n = sz;
+       if (sz < AUFS_RDHASH_DEF)
+               n = AUFS_RDHASH_DEF;
+       /* pr_info("n %u\n", n); */
+       return n;
+}
+
+/*
+ * the allocated memory has to be freed by
+ * au_nhash_wh_free() or au_nhash_de_free().
+ */
+int au_nhash_alloc(struct au_nhash *nhash, unsigned int num_hash, gfp_t gfp)
+{
+       struct hlist_head *head;
+       unsigned int u;
+       size_t sz;
+
+       sz = sizeof(*nhash->nh_head) * num_hash;
+       head = kmalloc(sz, gfp);
+       if (head) {
+               nhash->nh_num = num_hash;
+               nhash->nh_head = head;
+               for (u = 0; u < num_hash; u++)
+                       INIT_HLIST_HEAD(head++);
+               return 0; /* success */
+       }
+
+       return -ENOMEM;
+}
+
+static void nhash_count(struct hlist_head *head)
+{
+#if 0 /* debugging */
+       unsigned long n;
+       struct hlist_node *pos;
+
+       n = 0;
+       hlist_for_each(pos, head)
+               n++;
+       pr_info("%lu\n", n);
+#endif
+}
+
+static void au_nhash_wh_do_free(struct hlist_head *head)
+{
+       struct au_vdir_wh *pos;
+       struct hlist_node *node;
+
+       hlist_for_each_entry_safe(pos, node, head, wh_hash)
+               au_kfree_rcu(pos);
+}
+
+static void au_nhash_de_do_free(struct hlist_head *head)
+{
+       struct au_vdir_dehstr *pos;
+       struct hlist_node *node;
+
+       hlist_for_each_entry_safe(pos, node, head, hash)
+               au_cache_free_vdir_dehstr(pos);
+}
+
+static void au_nhash_do_free(struct au_nhash *nhash,
+                            void (*free)(struct hlist_head *head))
+{
+       unsigned int n;
+       struct hlist_head *head;
+
+       n = nhash->nh_num;
+       if (!n)
+               return;
+
+       head = nhash->nh_head;
+       while (n-- > 0) {
+               nhash_count(head);
+               free(head++);
+       }
+       au_kfree_try_rcu(nhash->nh_head);
+}
+
+void au_nhash_wh_free(struct au_nhash *whlist)
+{
+       au_nhash_do_free(whlist, au_nhash_wh_do_free);
+}
+
+static void au_nhash_de_free(struct au_nhash *delist)
+{
+       au_nhash_do_free(delist, au_nhash_de_do_free);
+}
+
+/* ---------------------------------------------------------------------- */
+
+int au_nhash_test_longer_wh(struct au_nhash *whlist, aufs_bindex_t btgt,
+                           int limit)
+{
+       int num;
+       unsigned int u, n;
+       struct hlist_head *head;
+       struct au_vdir_wh *pos;
+
+       num = 0;
+       n = whlist->nh_num;
+       head = whlist->nh_head;
+       for (u = 0; u < n; u++, head++)
+               hlist_for_each_entry(pos, head, wh_hash)
+                       if (pos->wh_bindex == btgt && ++num > limit)
+                               return 1;
+       return 0;
+}
+
+static struct hlist_head *au_name_hash(struct au_nhash *nhash,
+                                      unsigned char *name,
+                                      unsigned int len)
+{
+       unsigned int v;
+       /* const unsigned int magic_bit = 12; */
+
+       AuDebugOn(!nhash->nh_num || !nhash->nh_head);
+
+       v = 0;
+       if (len > 8)
+               len = 8;
+       while (len--)
+               v += *name++;
+       /* v = hash_long(v, magic_bit); */
+       v %= nhash->nh_num;
+       return nhash->nh_head + v;
+}
+
+static int au_nhash_test_name(struct au_vdir_destr *str, const char *name,
+                             int nlen)
+{
+       return str->len == nlen && !memcmp(str->name, name, nlen);
+}
+
+/* returns found or not */
+int au_nhash_test_known_wh(struct au_nhash *whlist, char *name, int nlen)
+{
+       struct hlist_head *head;
+       struct au_vdir_wh *pos;
+       struct au_vdir_destr *str;
+
+       head = au_name_hash(whlist, name, nlen);
+       hlist_for_each_entry(pos, head, wh_hash) {
+               str = &pos->wh_str;
+               AuDbg("%.*s\n", str->len, str->name);
+               if (au_nhash_test_name(str, name, nlen))
+                       return 1;
+       }
+       return 0;
+}
+
+/* returns found(true) or not */
+static int test_known(struct au_nhash *delist, char *name, int nlen)
+{
+       struct hlist_head *head;
+       struct au_vdir_dehstr *pos;
+       struct au_vdir_destr *str;
+
+       head = au_name_hash(delist, name, nlen);
+       hlist_for_each_entry(pos, head, hash) {
+               str = pos->str;
+               AuDbg("%.*s\n", str->len, str->name);
+               if (au_nhash_test_name(str, name, nlen))
+                       return 1;
+       }
+       return 0;
+}
+
+static void au_shwh_init_wh(struct au_vdir_wh *wh, ino_t ino,
+                           unsigned char d_type)
+{
+#ifdef CONFIG_AUFS_SHWH
+       wh->wh_ino = ino;
+       wh->wh_type = d_type;
+#endif
+}
+
+/* ---------------------------------------------------------------------- */
+
+int au_nhash_append_wh(struct au_nhash *whlist, char *name, int nlen, ino_t ino,
+                      unsigned int d_type, aufs_bindex_t bindex,
+                      unsigned char shwh)
+{
+       int err;
+       struct au_vdir_destr *str;
+       struct au_vdir_wh *wh;
+
+       AuDbg("%.*s\n", nlen, name);
+       AuDebugOn(!whlist->nh_num || !whlist->nh_head);
+
+       err = -ENOMEM;
+       wh = kmalloc(sizeof(*wh) + nlen, GFP_NOFS);
+       if (unlikely(!wh))
+               goto out;
+
+       err = 0;
+       wh->wh_bindex = bindex;
+       if (shwh)
+               au_shwh_init_wh(wh, ino, d_type);
+       str = &wh->wh_str;
+       str->len = nlen;
+       memcpy(str->name, name, nlen);
+       hlist_add_head(&wh->wh_hash, au_name_hash(whlist, name, nlen));
+       /* smp_mb(); */
+
+out:
+       return err;
+}
+
+static int append_deblk(struct au_vdir *vdir)
+{
+       int err;
+       unsigned long ul;
+       const unsigned int deblk_sz = vdir->vd_deblk_sz;
+       union au_vdir_deblk_p p, deblk_end;
+       unsigned char **o;
+
+       err = -ENOMEM;
+       o = au_krealloc(vdir->vd_deblk, sizeof(*o) * (vdir->vd_nblk + 1),
+                       GFP_NOFS, /*may_shrink*/0);
+       if (unlikely(!o))
+               goto out;
+
+       vdir->vd_deblk = o;
+       p.deblk = kmalloc(deblk_sz, GFP_NOFS);
+       if (p.deblk) {
+               ul = vdir->vd_nblk++;
+               vdir->vd_deblk[ul] = p.deblk;
+               vdir->vd_last.ul = ul;
+               vdir->vd_last.p.deblk = p.deblk;
+               deblk_end.deblk = p.deblk + deblk_sz;
+               err = set_deblk_end(&p, &deblk_end);
+       }
+
+out:
+       return err;
+}
+
+static int append_de(struct au_vdir *vdir, char *name, int nlen, ino_t ino,
+                    unsigned int d_type, struct au_nhash *delist)
+{
+       int err;
+       unsigned int sz;
+       const unsigned int deblk_sz = vdir->vd_deblk_sz;
+       union au_vdir_deblk_p p, *room, deblk_end;
+       struct au_vdir_dehstr *dehstr;
+
+       p.deblk = last_deblk(vdir);
+       deblk_end.deblk = p.deblk + deblk_sz;
+       room = &vdir->vd_last.p;
+       AuDebugOn(room->deblk < p.deblk || deblk_end.deblk <= room->deblk
+                 || !is_deblk_end(room, &deblk_end));
+
+       sz = calc_size(nlen);
+       if (unlikely(sz > deblk_end.deblk - room->deblk)) {
+               err = append_deblk(vdir);
+               if (unlikely(err))
+                       goto out;
+
+               p.deblk = last_deblk(vdir);
+               deblk_end.deblk = p.deblk + deblk_sz;
+               /* smp_mb(); */
+               AuDebugOn(room->deblk != p.deblk);
+       }
+
+       err = -ENOMEM;
+       dehstr = au_cache_alloc_vdir_dehstr();
+       if (unlikely(!dehstr))
+               goto out;
+
+       dehstr->str = &room->de->de_str;
+       hlist_add_head(&dehstr->hash, au_name_hash(delist, name, nlen));
+       room->de->de_ino = ino;
+       room->de->de_type = d_type;
+       room->de->de_str.len = nlen;
+       memcpy(room->de->de_str.name, name, nlen);
+
+       err = 0;
+       room->deblk += sz;
+       if (unlikely(set_deblk_end(room, &deblk_end)))
+               err = append_deblk(vdir);
+       /* smp_mb(); */
+
+out:
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void au_vdir_free(struct au_vdir *vdir)
+{
+       unsigned char **deblk;
+
+       deblk = vdir->vd_deblk;
+       while (vdir->vd_nblk--)
+               au_kfree_try_rcu(*deblk++);
+       au_kfree_try_rcu(vdir->vd_deblk);
+       au_cache_free_vdir(vdir);
+}
+
+static struct au_vdir *alloc_vdir(struct file *file)
+{
+       struct au_vdir *vdir;
+       struct super_block *sb;
+       int err;
+
+       sb = file->f_path.dentry->d_sb;
+       SiMustAnyLock(sb);
+
+       err = -ENOMEM;
+       vdir = au_cache_alloc_vdir();
+       if (unlikely(!vdir))
+               goto out;
+
+       vdir->vd_deblk = kzalloc(sizeof(*vdir->vd_deblk), GFP_NOFS);
+       if (unlikely(!vdir->vd_deblk))
+               goto out_free;
+
+       vdir->vd_deblk_sz = au_sbi(sb)->si_rdblk;
+       if (!vdir->vd_deblk_sz) {
+               /* estimate the appropriate size for deblk */
+               vdir->vd_deblk_sz = au_dir_size(file, /*dentry*/NULL);
+               /* pr_info("vd_deblk_sz %u\n", vdir->vd_deblk_sz); */
+       }
+       vdir->vd_nblk = 0;
+       vdir->vd_version = 0;
+       vdir->vd_jiffy = 0;
+       err = append_deblk(vdir);
+       if (!err)
+               return vdir; /* success */
+
+       au_kfree_try_rcu(vdir->vd_deblk);
+
+out_free:
+       au_cache_free_vdir(vdir);
+out:
+       vdir = ERR_PTR(err);
+       return vdir;
+}
+
+static int reinit_vdir(struct au_vdir *vdir)
+{
+       int err;
+       union au_vdir_deblk_p p, deblk_end;
+
+       while (vdir->vd_nblk > 1) {
+               au_kfree_try_rcu(vdir->vd_deblk[vdir->vd_nblk - 1]);
+               /* vdir->vd_deblk[vdir->vd_nblk - 1] = NULL; */
+               vdir->vd_nblk--;
+       }
+       p.deblk = vdir->vd_deblk[0];
+       deblk_end.deblk = p.deblk + vdir->vd_deblk_sz;
+       err = set_deblk_end(&p, &deblk_end);
+       /* keep vd_dblk_sz */
+       vdir->vd_last.ul = 0;
+       vdir->vd_last.p.deblk = vdir->vd_deblk[0];
+       vdir->vd_version = 0;
+       vdir->vd_jiffy = 0;
+       /* smp_mb(); */
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+#define AuFillVdir_CALLED      1
+#define AuFillVdir_WHABLE      (1 << 1)
+#define AuFillVdir_SHWH                (1 << 2)
+#define au_ftest_fillvdir(flags, name) ((flags) & AuFillVdir_##name)
+#define au_fset_fillvdir(flags, name) \
+       do { (flags) |= AuFillVdir_##name; } while (0)
+#define au_fclr_fillvdir(flags, name) \
+       do { (flags) &= ~AuFillVdir_##name; } while (0)
+
+#ifndef CONFIG_AUFS_SHWH
+#undef AuFillVdir_SHWH
+#define AuFillVdir_SHWH                0
+#endif
+
+struct fillvdir_arg {
+       struct dir_context      ctx;
+       struct file             *file;
+       struct au_vdir          *vdir;
+       struct au_nhash         delist;
+       struct au_nhash         whlist;
+       aufs_bindex_t           bindex;
+       unsigned int            flags;
+       int                     err;
+};
+
+static int fillvdir(struct dir_context *ctx, const char *__name, int nlen,
+                   loff_t offset __maybe_unused, u64 h_ino,
+                   unsigned int d_type)
+{
+       struct fillvdir_arg *arg = container_of(ctx, struct fillvdir_arg, ctx);
+       char *name = (void *)__name;
+       struct super_block *sb;
+       ino_t ino;
+       const unsigned char shwh = !!au_ftest_fillvdir(arg->flags, SHWH);
+
+       arg->err = 0;
+       sb = arg->file->f_path.dentry->d_sb;
+       au_fset_fillvdir(arg->flags, CALLED);
+       /* smp_mb(); */
+       if (nlen <= AUFS_WH_PFX_LEN
+           || memcmp(name, AUFS_WH_PFX, AUFS_WH_PFX_LEN)) {
+               if (test_known(&arg->delist, name, nlen)
+                   || au_nhash_test_known_wh(&arg->whlist, name, nlen))
+                       goto out; /* already exists or whiteouted */
+
+               arg->err = au_ino(sb, arg->bindex, h_ino, d_type, &ino);
+               if (!arg->err) {
+                       if (unlikely(nlen > AUFS_MAX_NAMELEN))
+                               d_type = DT_UNKNOWN;
+                       arg->err = append_de(arg->vdir, name, nlen, ino,
+                                            d_type, &arg->delist);
+               }
+       } else if (au_ftest_fillvdir(arg->flags, WHABLE)) {
+               name += AUFS_WH_PFX_LEN;
+               nlen -= AUFS_WH_PFX_LEN;
+               if (au_nhash_test_known_wh(&arg->whlist, name, nlen))
+                       goto out; /* already whiteouted */
+
+               ino = 0; /* just to suppress a warning */
+               if (shwh)
+                       arg->err = au_wh_ino(sb, arg->bindex, h_ino, d_type,
+                                            &ino);
+               if (!arg->err) {
+                       if (nlen <= AUFS_MAX_NAMELEN + AUFS_WH_PFX_LEN)
+                               d_type = DT_UNKNOWN;
+                       arg->err = au_nhash_append_wh
+                               (&arg->whlist, name, nlen, ino, d_type,
+                                arg->bindex, shwh);
+               }
+       }
+
+out:
+       if (!arg->err)
+               arg->vdir->vd_jiffy = jiffies;
+       /* smp_mb(); */
+       AuTraceErr(arg->err);
+       return arg->err;
+}
+
+static int au_handle_shwh(struct super_block *sb, struct au_vdir *vdir,
+                         struct au_nhash *whlist, struct au_nhash *delist)
+{
+#ifdef CONFIG_AUFS_SHWH
+       int err;
+       unsigned int nh, u;
+       struct hlist_head *head;
+       struct au_vdir_wh *pos;
+       struct hlist_node *n;
+       char *p, *o;
+       struct au_vdir_destr *destr;
+
+       AuDebugOn(!au_opt_test(au_mntflags(sb), SHWH));
+
+       err = -ENOMEM;
+       o = p = (void *)__get_free_page(GFP_NOFS);
+       if (unlikely(!p))
+               goto out;
+
+       err = 0;
+       nh = whlist->nh_num;
+       memcpy(p, AUFS_WH_PFX, AUFS_WH_PFX_LEN);
+       p += AUFS_WH_PFX_LEN;
+       for (u = 0; u < nh; u++) {
+               head = whlist->nh_head + u;
+               hlist_for_each_entry_safe(pos, n, head, wh_hash) {
+                       destr = &pos->wh_str;
+                       memcpy(p, destr->name, destr->len);
+                       err = append_de(vdir, o, destr->len + AUFS_WH_PFX_LEN,
+                                       pos->wh_ino, pos->wh_type, delist);
+                       if (unlikely(err))
+                               break;
+               }
+       }
+
+       free_page((unsigned long)o);
+
+out:
+       AuTraceErr(err);
+       return err;
+#else
+       return 0;
+#endif
+}
+
+static int au_do_read_vdir(struct fillvdir_arg *arg)
+{
+       int err;
+       unsigned int rdhash;
+       loff_t offset;
+       aufs_bindex_t bbot, bindex, btop;
+       unsigned char shwh;
+       struct file *hf, *file;
+       struct super_block *sb;
+
+       file = arg->file;
+       sb = file->f_path.dentry->d_sb;
+       SiMustAnyLock(sb);
+
+       rdhash = au_sbi(sb)->si_rdhash;
+       if (!rdhash)
+               rdhash = au_rdhash_est(au_dir_size(file, /*dentry*/NULL));
+       err = au_nhash_alloc(&arg->delist, rdhash, GFP_NOFS);
+       if (unlikely(err))
+               goto out;
+       err = au_nhash_alloc(&arg->whlist, rdhash, GFP_NOFS);
+       if (unlikely(err))
+               goto out_delist;
+
+       err = 0;
+       arg->flags = 0;
+       shwh = 0;
+       if (au_opt_test(au_mntflags(sb), SHWH)) {
+               shwh = 1;
+               au_fset_fillvdir(arg->flags, SHWH);
+       }
+       btop = au_fbtop(file);
+       bbot = au_fbbot_dir(file);
+       for (bindex = btop; !err && bindex <= bbot; bindex++) {
+               hf = au_hf_dir(file, bindex);
+               if (!hf)
+                       continue;
+
+               offset = vfsub_llseek(hf, 0, SEEK_SET);
+               err = offset;
+               if (unlikely(offset))
+                       break;
+
+               arg->bindex = bindex;
+               au_fclr_fillvdir(arg->flags, WHABLE);
+               if (shwh
+                   || (bindex != bbot
+                       && au_br_whable(au_sbr_perm(sb, bindex))))
+                       au_fset_fillvdir(arg->flags, WHABLE);
+               do {
+                       arg->err = 0;
+                       au_fclr_fillvdir(arg->flags, CALLED);
+                       /* smp_mb(); */
+                       err = vfsub_iterate_dir(hf, &arg->ctx);
+                       if (err >= 0)
+                               err = arg->err;
+               } while (!err && au_ftest_fillvdir(arg->flags, CALLED));
+
+               /*
+                * dir_relax() may be good for concurrency, but aufs should not
+                * use it since it will cause a lockdep problem.
+                */
+       }
+
+       if (!err && shwh)
+               err = au_handle_shwh(sb, arg->vdir, &arg->whlist, &arg->delist);
+
+       au_nhash_wh_free(&arg->whlist);
+
+out_delist:
+       au_nhash_de_free(&arg->delist);
+out:
+       return err;
+}
+
+static int read_vdir(struct file *file, int may_read)
+{
+       int err;
+       unsigned long expire;
+       unsigned char do_read;
+       struct fillvdir_arg arg = {
+               .ctx = {
+                       .actor = fillvdir
+               }
+       };
+       struct inode *inode;
+       struct au_vdir *vdir, *allocated;
+
+       err = 0;
+       inode = file_inode(file);
+       IMustLock(inode);
+       IiMustWriteLock(inode);
+       SiMustAnyLock(inode->i_sb);
+
+       allocated = NULL;
+       do_read = 0;
+       expire = au_sbi(inode->i_sb)->si_rdcache;
+       vdir = au_ivdir(inode);
+       if (!vdir) {
+               do_read = 1;
+               vdir = alloc_vdir(file);
+               err = PTR_ERR(vdir);
+               if (IS_ERR(vdir))
+                       goto out;
+               err = 0;
+               allocated = vdir;
+       } else if (may_read
+                  && (!inode_eq_iversion(inode, vdir->vd_version)
+                      || time_after(jiffies, vdir->vd_jiffy + expire))) {
+               do_read = 1;
+               err = reinit_vdir(vdir);
+               if (unlikely(err))
+                       goto out;
+       }
+
+       if (!do_read)
+               return 0; /* success */
+
+       arg.file = file;
+       arg.vdir = vdir;
+       err = au_do_read_vdir(&arg);
+       if (!err) {
+               /* file->f_pos = 0; */ /* todo: ctx->pos? */
+               vdir->vd_version = inode_query_iversion(inode);
+               vdir->vd_last.ul = 0;
+               vdir->vd_last.p.deblk = vdir->vd_deblk[0];
+               if (allocated)
+                       au_set_ivdir(inode, allocated);
+       } else if (allocated)
+               au_vdir_free(allocated);
+
+out:
+       return err;
+}
+
+static int copy_vdir(struct au_vdir *tgt, struct au_vdir *src)
+{
+       int err, rerr;
+       unsigned long ul, n;
+       const unsigned int deblk_sz = src->vd_deblk_sz;
+
+       AuDebugOn(tgt->vd_nblk != 1);
+
+       err = -ENOMEM;
+       if (tgt->vd_nblk < src->vd_nblk) {
+               unsigned char **p;
+
+               p = au_krealloc(tgt->vd_deblk, sizeof(*p) * src->vd_nblk,
+                               GFP_NOFS, /*may_shrink*/0);
+               if (unlikely(!p))
+                       goto out;
+               tgt->vd_deblk = p;
+       }
+
+       if (tgt->vd_deblk_sz != deblk_sz) {
+               unsigned char *p;
+
+               tgt->vd_deblk_sz = deblk_sz;
+               p = au_krealloc(tgt->vd_deblk[0], deblk_sz, GFP_NOFS,
+                               /*may_shrink*/1);
+               if (unlikely(!p))
+                       goto out;
+               tgt->vd_deblk[0] = p;
+       }
+       memcpy(tgt->vd_deblk[0], src->vd_deblk[0], deblk_sz);
+       tgt->vd_version = src->vd_version;
+       tgt->vd_jiffy = src->vd_jiffy;
+
+       n = src->vd_nblk;
+       for (ul = 1; ul < n; ul++) {
+               tgt->vd_deblk[ul] = kmemdup(src->vd_deblk[ul], deblk_sz,
+                                           GFP_NOFS);
+               if (unlikely(!tgt->vd_deblk[ul]))
+                       goto out;
+               tgt->vd_nblk++;
+       }
+       tgt->vd_nblk = n;
+       tgt->vd_last.ul = tgt->vd_last.ul;
+       tgt->vd_last.p.deblk = tgt->vd_deblk[tgt->vd_last.ul];
+       tgt->vd_last.p.deblk += src->vd_last.p.deblk
+               - src->vd_deblk[src->vd_last.ul];
+       /* smp_mb(); */
+       return 0; /* success */
+
+out:
+       rerr = reinit_vdir(tgt);
+       BUG_ON(rerr);
+       return err;
+}
+
+int au_vdir_init(struct file *file)
+{
+       int err;
+       struct inode *inode;
+       struct au_vdir *vdir_cache, *allocated;
+
+       /* test file->f_pos here instead of ctx->pos */
+       err = read_vdir(file, !file->f_pos);
+       if (unlikely(err))
+               goto out;
+
+       allocated = NULL;
+       vdir_cache = au_fvdir_cache(file);
+       if (!vdir_cache) {
+               vdir_cache = alloc_vdir(file);
+               err = PTR_ERR(vdir_cache);
+               if (IS_ERR(vdir_cache))
+                       goto out;
+               allocated = vdir_cache;
+       } else if (!file->f_pos && vdir_cache->vd_version != file->f_version) {
+               /* test file->f_pos here instead of ctx->pos */
+               err = reinit_vdir(vdir_cache);
+               if (unlikely(err))
+                       goto out;
+       } else
+               return 0; /* success */
+
+       inode = file_inode(file);
+       err = copy_vdir(vdir_cache, au_ivdir(inode));
+       if (!err) {
+               file->f_version = inode_query_iversion(inode);
+               if (allocated)
+                       au_set_fvdir_cache(file, allocated);
+       } else if (allocated)
+               au_vdir_free(allocated);
+
+out:
+       return err;
+}
+
+static loff_t calc_offset(struct au_vdir *vdir)
+{
+       loff_t offset;
+       union au_vdir_deblk_p p;
+
+       p.deblk = vdir->vd_deblk[vdir->vd_last.ul];
+       offset = vdir->vd_last.p.deblk - p.deblk;
+       offset += vdir->vd_deblk_sz * vdir->vd_last.ul;
+       return offset;
+}
+
+/* returns true or false */
+static int seek_vdir(struct file *file, struct dir_context *ctx)
+{
+       int valid;
+       unsigned int deblk_sz;
+       unsigned long ul, n;
+       loff_t offset;
+       union au_vdir_deblk_p p, deblk_end;
+       struct au_vdir *vdir_cache;
+
+       valid = 1;
+       vdir_cache = au_fvdir_cache(file);
+       offset = calc_offset(vdir_cache);
+       AuDbg("offset %lld\n", offset);
+       if (ctx->pos == offset)
+               goto out;
+
+       vdir_cache->vd_last.ul = 0;
+       vdir_cache->vd_last.p.deblk = vdir_cache->vd_deblk[0];
+       if (!ctx->pos)
+               goto out;
+
+       valid = 0;
+       deblk_sz = vdir_cache->vd_deblk_sz;
+       ul = div64_u64(ctx->pos, deblk_sz);
+       AuDbg("ul %lu\n", ul);
+       if (ul >= vdir_cache->vd_nblk)
+               goto out;
+
+       n = vdir_cache->vd_nblk;
+       for (; ul < n; ul++) {
+               p.deblk = vdir_cache->vd_deblk[ul];
+               deblk_end.deblk = p.deblk + deblk_sz;
+               offset = ul;
+               offset *= deblk_sz;
+               while (!is_deblk_end(&p, &deblk_end) && offset < ctx->pos) {
+                       unsigned int l;
+
+                       l = calc_size(p.de->de_str.len);
+                       offset += l;
+                       p.deblk += l;
+               }
+               if (!is_deblk_end(&p, &deblk_end)) {
+                       valid = 1;
+                       vdir_cache->vd_last.ul = ul;
+                       vdir_cache->vd_last.p = p;
+                       break;
+               }
+       }
+
+out:
+       /* smp_mb(); */
+       if (!valid)
+               AuDbg("valid %d\n", !valid);
+       return valid;
+}
+
+int au_vdir_fill_de(struct file *file, struct dir_context *ctx)
+{
+       unsigned int l, deblk_sz;
+       union au_vdir_deblk_p deblk_end;
+       struct au_vdir *vdir_cache;
+       struct au_vdir_de *de;
+
+       if (!seek_vdir(file, ctx))
+               return 0;
+
+       vdir_cache = au_fvdir_cache(file);
+       deblk_sz = vdir_cache->vd_deblk_sz;
+       while (1) {
+               deblk_end.deblk = vdir_cache->vd_deblk[vdir_cache->vd_last.ul];
+               deblk_end.deblk += deblk_sz;
+               while (!is_deblk_end(&vdir_cache->vd_last.p, &deblk_end)) {
+                       de = vdir_cache->vd_last.p.de;
+                       AuDbg("%.*s, off%lld, i%lu, dt%d\n",
+                             de->de_str.len, de->de_str.name, ctx->pos,
+                             (unsigned long)de->de_ino, de->de_type);
+                       if (unlikely(!dir_emit(ctx, de->de_str.name,
+                                              de->de_str.len, de->de_ino,
+                                              de->de_type))) {
+                               /* todo: ignore the error caused by udba? */
+                               /* return err; */
+                               return 0;
+                       }
+
+                       l = calc_size(de->de_str.len);
+                       vdir_cache->vd_last.p.deblk += l;
+                       ctx->pos += l;
+               }
+               if (vdir_cache->vd_last.ul < vdir_cache->vd_nblk - 1) {
+                       vdir_cache->vd_last.ul++;
+                       vdir_cache->vd_last.p.deblk
+                               = vdir_cache->vd_deblk[vdir_cache->vd_last.ul];
+                       ctx->pos = deblk_sz * vdir_cache->vd_last.ul;
+                       continue;
+               }
+               break;
+       }
+
+       /* smp_mb(); */
+       return 0;
+}
diff -urN /usr/share/empty/fs/aufs/vfsub.c linux/fs/aufs/vfsub.c
--- /usr/share/empty/fs/aufs/vfsub.c    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/vfsub.c       2022-01-13 12:42:15.932899468 +0100
@@ -0,0 +1,919 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * sub-routines for VFS
+ */
+
+#include <linux/mnt_namespace.h>
+#include <linux/namei.h>
+#include <linux/nsproxy.h>
+#include <linux/security.h>
+#include <linux/splice.h>
+#include "aufs.h"
+
+#ifdef CONFIG_AUFS_BR_FUSE
+int vfsub_test_mntns(struct vfsmount *mnt, struct super_block *h_sb)
+{
+       if (!au_test_fuse(h_sb) || !au_userns)
+               return 0;
+
+       return is_current_mnt_ns(mnt) ? 0 : -EACCES;
+}
+#endif
+
+int vfsub_sync_filesystem(struct super_block *h_sb)
+{
+       int err;
+
+       lockdep_off();
+       down_read(&h_sb->s_umount);
+       err = sync_filesystem(h_sb);
+       up_read(&h_sb->s_umount);
+       lockdep_on();
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+int vfsub_update_h_iattr(struct path *h_path, int *did)
+{
+       int err;
+       struct kstat st;
+       struct super_block *h_sb;
+
+       /*
+        * Always needs h_path->mnt for LSM or FUSE branch.
+        */
+       AuDebugOn(!h_path->mnt);
+
+       /* for remote fs, leave work for its getattr or d_revalidate */
+       /* for bad i_attr fs, handle them in aufs_getattr() */
+       /* still some fs may acquire i_mutex. we need to skip them */
+       err = 0;
+       if (!did)
+               did = &err;
+       h_sb = h_path->dentry->d_sb;
+       *did = (!au_test_fs_remote(h_sb) && au_test_fs_refresh_iattr(h_sb));
+       if (*did)
+               err = vfsub_getattr(h_path, &st);
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct file *vfsub_dentry_open(struct path *path, int flags)
+{
+       return dentry_open(path, flags /* | __FMODE_NONOTIFY */,
+                          current_cred());
+}
+
+struct file *vfsub_filp_open(const char *path, int oflags, int mode)
+{
+       struct file *file;
+
+       lockdep_off();
+       file = filp_open(path,
+                        oflags /* | __FMODE_NONOTIFY */,
+                        mode);
+       lockdep_on();
+       if (IS_ERR(file))
+               goto out;
+       vfsub_update_h_iattr(&file->f_path, /*did*/NULL); /*ignore*/
+
+out:
+       return file;
+}
+
+/*
+ * Ideally this function should call VFS:do_last() in order to keep all its
+ * checkings. But it is very hard for aufs to regenerate several VFS internal
+ * structure such as nameidata. This is a second (or third) best approach.
+ * cf. linux/fs/namei.c:do_last(), lookup_open() and atomic_open().
+ */
+int vfsub_atomic_open(struct inode *dir, struct dentry *dentry,
+                     struct vfsub_aopen_args *args)
+{
+       int err;
+       struct au_branch *br = args->br;
+       struct file *file = args->file;
+       /* copied from linux/fs/namei.c:atomic_open() */
+       struct dentry *const DENTRY_NOT_SET = (void *)-1UL;
+
+       IMustLock(dir);
+       AuDebugOn(!dir->i_op->atomic_open);
+
+       err = au_br_test_oflag(args->open_flag, br);
+       if (unlikely(err))
+               goto out;
+
+       au_lcnt_inc(&br->br_nfiles);
+       file->f_path.dentry = DENTRY_NOT_SET;
+       file->f_path.mnt = au_br_mnt(br);
+       AuDbg("%ps\n", dir->i_op->atomic_open);
+       err = dir->i_op->atomic_open(dir, dentry, file, args->open_flag,
+                                    args->create_mode);
+       if (unlikely(err < 0)) {
+               au_lcnt_dec(&br->br_nfiles);
+               goto out;
+       }
+
+       /* temporary workaround for nfsv4 branch */
+       if (au_test_nfs(dir->i_sb))
+               nfs_mark_for_revalidate(dir);
+
+       if (file->f_mode & FMODE_CREATED)
+               fsnotify_create(dir, dentry);
+       if (!(file->f_mode & FMODE_OPENED)) {
+               au_lcnt_dec(&br->br_nfiles);
+               goto out;
+       }
+
+       /* todo: call VFS:may_open() here */
+       /* todo: ima_file_check() too? */
+       if (!err && (args->open_flag & __FMODE_EXEC))
+               err = deny_write_access(file);
+       if (!err)
+               fsnotify_open(file);
+       else
+               au_lcnt_dec(&br->br_nfiles);
+       /* note that the file is created and still opened */
+
+out:
+       return err;
+}
+
+int vfsub_kern_path(const char *name, unsigned int flags, struct path *path)
+{
+       int err;
+
+       err = kern_path(name, flags, path);
+       if (!err && d_is_positive(path->dentry))
+               vfsub_update_h_iattr(path, /*did*/NULL); /*ignore*/
+       return err;
+}
+
+struct dentry *vfsub_lookup_one_len_unlocked(const char *name,
+                                            struct path *ppath, int len)
+{
+       struct path path;
+
+       path.dentry = lookup_one_len_unlocked(name, ppath->dentry, len);
+       if (IS_ERR(path.dentry))
+               goto out;
+       if (d_is_positive(path.dentry)) {
+               path.mnt = ppath->mnt;
+               vfsub_update_h_iattr(&path, /*did*/NULL); /*ignore*/
+       }
+
+out:
+       AuTraceErrPtr(path.dentry);
+       return path.dentry;
+}
+
+struct dentry *vfsub_lookup_one_len(const char *name, struct path *ppath,
+                                   int len)
+{
+       struct path path;
+
+       /* VFS checks it too, but by WARN_ON_ONCE() */
+       IMustLock(d_inode(ppath->dentry));
+
+       path.dentry = lookup_one_len(name, ppath->dentry, len);
+       if (IS_ERR(path.dentry))
+               goto out;
+       if (d_is_positive(path.dentry)) {
+               path.mnt = ppath->mnt;
+               vfsub_update_h_iattr(&path, /*did*/NULL); /*ignore*/
+       }
+
+out:
+       AuTraceErrPtr(path.dentry);
+       return path.dentry;
+}
+
+void vfsub_call_lkup_one(void *args)
+{
+       struct vfsub_lkup_one_args *a = args;
+       *a->errp = vfsub_lkup_one(a->name, a->ppath);
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct dentry *vfsub_lock_rename(struct dentry *d1, struct au_hinode *hdir1,
+                                struct dentry *d2, struct au_hinode *hdir2)
+{
+       struct dentry *d;
+
+       lockdep_off();
+       d = lock_rename(d1, d2);
+       lockdep_on();
+       au_hn_suspend(hdir1);
+       if (hdir1 != hdir2)
+               au_hn_suspend(hdir2);
+
+       return d;
+}
+
+void vfsub_unlock_rename(struct dentry *d1, struct au_hinode *hdir1,
+                        struct dentry *d2, struct au_hinode *hdir2)
+{
+       au_hn_resume(hdir1);
+       if (hdir1 != hdir2)
+               au_hn_resume(hdir2);
+       lockdep_off();
+       unlock_rename(d1, d2);
+       lockdep_on();
+}
+
+/* ---------------------------------------------------------------------- */
+
+int vfsub_create(struct inode *dir, struct path *path, int mode, bool want_excl)
+{
+       int err;
+       struct dentry *d;
+       struct user_namespace *userns;
+
+       IMustLock(dir);
+
+       d = path->dentry;
+       path->dentry = d->d_parent;
+       err = security_path_mknod(path, d, mode, 0);
+       path->dentry = d;
+       if (unlikely(err))
+               goto out;
+       userns = mnt_user_ns(path->mnt);
+
+       lockdep_off();
+       err = vfs_create(userns, dir, path->dentry, mode, want_excl);
+       lockdep_on();
+       if (!err) {
+               struct path tmp = *path;
+               int did;
+
+               vfsub_update_h_iattr(&tmp, &did);
+               if (did) {
+                       tmp.dentry = path->dentry->d_parent;
+                       vfsub_update_h_iattr(&tmp, /*did*/NULL);
+               }
+               /*ignore*/
+       }
+
+out:
+       return err;
+}
+
+int vfsub_symlink(struct inode *dir, struct path *path, const char *symname)
+{
+       int err;
+       struct dentry *d;
+       struct user_namespace *userns;
+
+       IMustLock(dir);
+
+       d = path->dentry;
+       path->dentry = d->d_parent;
+       err = security_path_symlink(path, d, symname);
+       path->dentry = d;
+       if (unlikely(err))
+               goto out;
+       userns = mnt_user_ns(path->mnt);
+
+       lockdep_off();
+       err = vfs_symlink(userns, dir, path->dentry, symname);
+       lockdep_on();
+       if (!err) {
+               struct path tmp = *path;
+               int did;
+
+               vfsub_update_h_iattr(&tmp, &did);
+               if (did) {
+                       tmp.dentry = path->dentry->d_parent;
+                       vfsub_update_h_iattr(&tmp, /*did*/NULL);
+               }
+               /*ignore*/
+       }
+
+out:
+       return err;
+}
+
+int vfsub_mknod(struct inode *dir, struct path *path, int mode, dev_t dev)
+{
+       int err;
+       struct dentry *d;
+       struct user_namespace *userns;
+
+       IMustLock(dir);
+
+       d = path->dentry;
+       path->dentry = d->d_parent;
+       err = security_path_mknod(path, d, mode, new_encode_dev(dev));
+       path->dentry = d;
+       if (unlikely(err))
+               goto out;
+       userns = mnt_user_ns(path->mnt);
+
+       lockdep_off();
+       err = vfs_mknod(userns, dir, path->dentry, mode, dev);
+       lockdep_on();
+       if (!err) {
+               struct path tmp = *path;
+               int did;
+
+               vfsub_update_h_iattr(&tmp, &did);
+               if (did) {
+                       tmp.dentry = path->dentry->d_parent;
+                       vfsub_update_h_iattr(&tmp, /*did*/NULL);
+               }
+               /*ignore*/
+       }
+
+out:
+       return err;
+}
+
+static int au_test_nlink(struct inode *inode)
+{
+       const unsigned int link_max = UINT_MAX >> 1; /* rough margin */
+
+       if (!au_test_fs_no_limit_nlink(inode->i_sb)
+           || inode->i_nlink < link_max)
+               return 0;
+       return -EMLINK;
+}
+
+int vfsub_link(struct dentry *src_dentry, struct inode *dir, struct path *path,
+              struct inode **delegated_inode)
+{
+       int err;
+       struct dentry *d;
+       struct user_namespace *userns;
+
+       IMustLock(dir);
+
+       err = au_test_nlink(d_inode(src_dentry));
+       if (unlikely(err))
+               return err;
+
+       /* we don't call may_linkat() */
+       d = path->dentry;
+       path->dentry = d->d_parent;
+       err = security_path_link(src_dentry, path, d);
+       path->dentry = d;
+       if (unlikely(err))
+               goto out;
+       userns = mnt_user_ns(path->mnt);
+
+       lockdep_off();
+       err = vfs_link(src_dentry, userns, dir, path->dentry, delegated_inode);
+       lockdep_on();
+       if (!err) {
+               struct path tmp = *path;
+               int did;
+
+               /* fuse has different memory inode for the same inumber */
+               vfsub_update_h_iattr(&tmp, &did);
+               if (did) {
+                       tmp.dentry = path->dentry->d_parent;
+                       vfsub_update_h_iattr(&tmp, /*did*/NULL);
+                       tmp.dentry = src_dentry;
+                       vfsub_update_h_iattr(&tmp, /*did*/NULL);
+               }
+               /*ignore*/
+       }
+
+out:
+       return err;
+}
+
+int vfsub_rename(struct inode *src_dir, struct dentry *src_dentry,
+                struct inode *dir, struct path *path,
+                struct inode **delegated_inode, unsigned int flags)
+{
+       int err;
+       struct renamedata rd;
+       struct path tmp = {
+               .mnt    = path->mnt
+       };
+       struct dentry *d;
+
+       IMustLock(dir);
+       IMustLock(src_dir);
+
+       d = path->dentry;
+       path->dentry = d->d_parent;
+       tmp.dentry = src_dentry->d_parent;
+       err = security_path_rename(&tmp, src_dentry, path, d, /*flags*/0);
+       path->dentry = d;
+       if (unlikely(err))
+               goto out;
+
+       rd.old_mnt_userns = mnt_user_ns(path->mnt);
+       rd.old_dir = src_dir;
+       rd.old_dentry = src_dentry;
+       rd.new_mnt_userns = rd.old_mnt_userns;
+       rd.new_dir = dir;
+       rd.new_dentry = path->dentry;
+       rd.delegated_inode = delegated_inode;
+       rd.flags = flags;
+       lockdep_off();
+       err = vfs_rename(&rd);
+       lockdep_on();
+       if (!err) {
+               int did;
+
+               tmp.dentry = d->d_parent;
+               vfsub_update_h_iattr(&tmp, &did);
+               if (did) {
+                       tmp.dentry = src_dentry;
+                       vfsub_update_h_iattr(&tmp, /*did*/NULL);
+                       tmp.dentry = src_dentry->d_parent;
+                       vfsub_update_h_iattr(&tmp, /*did*/NULL);
+               }
+               /*ignore*/
+       }
+
+out:
+       return err;
+}
+
+int vfsub_mkdir(struct inode *dir, struct path *path, int mode)
+{
+       int err;
+       struct dentry *d;
+       struct user_namespace *userns;
+
+       IMustLock(dir);
+
+       d = path->dentry;
+       path->dentry = d->d_parent;
+       err = security_path_mkdir(path, d, mode);
+       path->dentry = d;
+       if (unlikely(err))
+               goto out;
+       userns = mnt_user_ns(path->mnt);
+
+       lockdep_off();
+       err = vfs_mkdir(userns, dir, path->dentry, mode);
+       lockdep_on();
+       if (!err) {
+               struct path tmp = *path;
+               int did;
+
+               vfsub_update_h_iattr(&tmp, &did);
+               if (did) {
+                       tmp.dentry = path->dentry->d_parent;
+                       vfsub_update_h_iattr(&tmp, /*did*/NULL);
+               }
+               /*ignore*/
+       }
+
+out:
+       return err;
+}
+
+int vfsub_rmdir(struct inode *dir, struct path *path)
+{
+       int err;
+       struct dentry *d;
+       struct user_namespace *userns;
+
+       IMustLock(dir);
+
+       d = path->dentry;
+       path->dentry = d->d_parent;
+       err = security_path_rmdir(path, d);
+       path->dentry = d;
+       if (unlikely(err))
+               goto out;
+       userns = mnt_user_ns(path->mnt);
+
+       lockdep_off();
+       err = vfs_rmdir(userns, dir, path->dentry);
+       lockdep_on();
+       if (!err) {
+               struct path tmp = {
+                       .dentry = path->dentry->d_parent,
+                       .mnt    = path->mnt
+               };
+
+               vfsub_update_h_iattr(&tmp, /*did*/NULL); /*ignore*/
+       }
+
+out:
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* todo: support mmap_sem? */
+ssize_t vfsub_read_u(struct file *file, char __user *ubuf, size_t count,
+                    loff_t *ppos)
+{
+       ssize_t err;
+
+       lockdep_off();
+       err = vfs_read(file, ubuf, count, ppos);
+       lockdep_on();
+       if (err >= 0)
+               vfsub_update_h_iattr(&file->f_path, /*did*/NULL); /*ignore*/
+       return err;
+}
+
+ssize_t vfsub_read_k(struct file *file, void *kbuf, size_t count,
+                    loff_t *ppos)
+{
+       ssize_t err;
+
+       lockdep_off();
+       err = kernel_read(file, kbuf, count, ppos);
+       lockdep_on();
+       AuTraceErr(err);
+       if (err >= 0)
+               vfsub_update_h_iattr(&file->f_path, /*did*/NULL); /*ignore*/
+       return err;
+}
+
+ssize_t vfsub_write_u(struct file *file, const char __user *ubuf, size_t count,
+                     loff_t *ppos)
+{
+       ssize_t err;
+
+       lockdep_off();
+       err = vfs_write(file, ubuf, count, ppos);
+       lockdep_on();
+       if (err >= 0)
+               vfsub_update_h_iattr(&file->f_path, /*did*/NULL); /*ignore*/
+       return err;
+}
+
+ssize_t vfsub_write_k(struct file *file, void *kbuf, size_t count, loff_t *ppos)
+{
+       ssize_t err;
+
+       lockdep_off();
+       err = kernel_write(file, kbuf, count, ppos);
+       lockdep_on();
+       if (err >= 0)
+               vfsub_update_h_iattr(&file->f_path, /*did*/NULL); /*ignore*/
+       return err;
+}
+
+int vfsub_flush(struct file *file, fl_owner_t id)
+{
+       int err;
+
+       err = 0;
+       if (file->f_op->flush) {
+               if (!au_test_nfs(file->f_path.dentry->d_sb))
+                       err = file->f_op->flush(file, id);
+               else {
+                       lockdep_off();
+                       err = file->f_op->flush(file, id);
+                       lockdep_on();
+               }
+               if (!err)
+                       vfsub_update_h_iattr(&file->f_path, /*did*/NULL);
+               /*ignore*/
+       }
+       return err;
+}
+
+int vfsub_iterate_dir(struct file *file, struct dir_context *ctx)
+{
+       int err;
+
+       AuDbg("%pD, ctx{%ps, %llu}\n", file, ctx->actor, ctx->pos);
+
+       lockdep_off();
+       err = iterate_dir(file, ctx);
+       lockdep_on();
+       if (err >= 0)
+               vfsub_update_h_iattr(&file->f_path, /*did*/NULL); /*ignore*/
+
+       return err;
+}
+
+long vfsub_splice_to(struct file *in, loff_t *ppos,
+                    struct pipe_inode_info *pipe, size_t len,
+                    unsigned int flags)
+{
+       long err;
+
+       lockdep_off();
+       err = do_splice_to(in, ppos, pipe, len, flags);
+       lockdep_on();
+       file_accessed(in);
+       if (err >= 0)
+               vfsub_update_h_iattr(&in->f_path, /*did*/NULL); /*ignore*/
+       return err;
+}
+
+long vfsub_splice_from(struct pipe_inode_info *pipe, struct file *out,
+                      loff_t *ppos, size_t len, unsigned int flags)
+{
+       long err;
+
+       lockdep_off();
+       err = do_splice_from(pipe, out, ppos, len, flags);
+       lockdep_on();
+       if (err >= 0)
+               vfsub_update_h_iattr(&out->f_path, /*did*/NULL); /*ignore*/
+       return err;
+}
+
+int vfsub_fsync(struct file *file, struct path *path, int datasync)
+{
+       int err;
+
+       /* file can be NULL */
+       lockdep_off();
+       err = vfs_fsync(file, datasync);
+       lockdep_on();
+       if (!err) {
+               if (!path) {
+                       AuDebugOn(!file);
+                       path = &file->f_path;
+               }
+               vfsub_update_h_iattr(path, /*did*/NULL); /*ignore*/
+       }
+       return err;
+}
+
+/* cf. open.c:do_sys_truncate() and do_sys_ftruncate() */
+int vfsub_trunc(struct path *h_path, loff_t length, unsigned int attr,
+               struct file *h_file)
+{
+       int err;
+       struct inode *h_inode;
+       struct super_block *h_sb;
+       struct user_namespace *h_userns;
+
+       if (!h_file) {
+               err = vfsub_truncate(h_path, length);
+               goto out;
+       }
+
+       h_inode = d_inode(h_path->dentry);
+       h_sb = h_inode->i_sb;
+       lockdep_off();
+       sb_start_write(h_sb);
+       lockdep_on();
+       err = security_path_truncate(h_path);
+       if (!err) {
+               h_userns = mnt_user_ns(h_path->mnt);
+               lockdep_off();
+               err = do_truncate(h_userns, h_path->dentry, length, attr,
+                                 h_file);
+               lockdep_on();
+       }
+       lockdep_off();
+       sb_end_write(h_sb);
+       lockdep_on();
+
+out:
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct au_vfsub_mkdir_args {
+       int *errp;
+       struct inode *dir;
+       struct path *path;
+       int mode;
+};
+
+static void au_call_vfsub_mkdir(void *args)
+{
+       struct au_vfsub_mkdir_args *a = args;
+       *a->errp = vfsub_mkdir(a->dir, a->path, a->mode);
+}
+
+int vfsub_sio_mkdir(struct inode *dir, struct path *path, int mode)
+{
+       int err, do_sio, wkq_err;
+       struct user_namespace *userns;
+
+       userns = mnt_user_ns(path->mnt);
+       do_sio = au_test_h_perm_sio(userns, dir, MAY_EXEC | MAY_WRITE);
+       if (!do_sio) {
+               lockdep_off();
+               err = vfsub_mkdir(dir, path, mode);
+               lockdep_on();
+       } else {
+               struct au_vfsub_mkdir_args args = {
+                       .errp   = &err,
+                       .dir    = dir,
+                       .path   = path,
+                       .mode   = mode
+               };
+               wkq_err = au_wkq_wait(au_call_vfsub_mkdir, &args);
+               if (unlikely(wkq_err))
+                       err = wkq_err;
+       }
+
+       return err;
+}
+
+struct au_vfsub_rmdir_args {
+       int *errp;
+       struct inode *dir;
+       struct path *path;
+};
+
+static void au_call_vfsub_rmdir(void *args)
+{
+       struct au_vfsub_rmdir_args *a = args;
+       *a->errp = vfsub_rmdir(a->dir, a->path);
+}
+
+int vfsub_sio_rmdir(struct inode *dir, struct path *path)
+{
+       int err, do_sio, wkq_err;
+       struct user_namespace *userns;
+
+       userns = mnt_user_ns(path->mnt);
+       do_sio = au_test_h_perm_sio(userns, dir, MAY_EXEC | MAY_WRITE);
+       if (!do_sio) {
+               lockdep_off();
+               err = vfsub_rmdir(dir, path);
+               lockdep_on();
+       } else {
+               struct au_vfsub_rmdir_args args = {
+                       .errp   = &err,
+                       .dir    = dir,
+                       .path   = path
+               };
+               wkq_err = au_wkq_wait(au_call_vfsub_rmdir, &args);
+               if (unlikely(wkq_err))
+                       err = wkq_err;
+       }
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct notify_change_args {
+       int *errp;
+       struct path *path;
+       struct iattr *ia;
+       struct inode **delegated_inode;
+};
+
+static void call_notify_change(void *args)
+{
+       struct notify_change_args *a = args;
+       struct inode *h_inode;
+       struct user_namespace *userns;
+
+       h_inode = d_inode(a->path->dentry);
+       IMustLock(h_inode);
+
+       *a->errp = -EPERM;
+       if (!IS_IMMUTABLE(h_inode) && !IS_APPEND(h_inode)) {
+               userns = mnt_user_ns(a->path->mnt);
+               lockdep_off();
+               *a->errp = notify_change(userns, a->path->dentry, a->ia,
+                                        a->delegated_inode);
+               lockdep_on();
+               if (!*a->errp)
+                       vfsub_update_h_iattr(a->path, /*did*/NULL); /*ignore*/
+       }
+       AuTraceErr(*a->errp);
+}
+
+int vfsub_notify_change(struct path *path, struct iattr *ia,
+                       struct inode **delegated_inode)
+{
+       int err;
+       struct notify_change_args args = {
+               .errp                   = &err,
+               .path                   = path,
+               .ia                     = ia,
+               .delegated_inode        = delegated_inode
+       };
+
+       call_notify_change(&args);
+
+       return err;
+}
+
+int vfsub_sio_notify_change(struct path *path, struct iattr *ia,
+                           struct inode **delegated_inode)
+{
+       int err, wkq_err;
+       struct notify_change_args args = {
+               .errp                   = &err,
+               .path                   = path,
+               .ia                     = ia,
+               .delegated_inode        = delegated_inode
+       };
+
+       wkq_err = au_wkq_wait(call_notify_change, &args);
+       if (unlikely(wkq_err))
+               err = wkq_err;
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct unlink_args {
+       int *errp;
+       struct inode *dir;
+       struct path *path;
+       struct inode **delegated_inode;
+};
+
+static void call_unlink(void *args)
+{
+       struct unlink_args *a = args;
+       struct dentry *d = a->path->dentry;
+       struct inode *h_inode;
+       struct user_namespace *userns;
+       const int stop_sillyrename = (au_test_nfs(d->d_sb)
+                                     && au_dcount(d) == 1);
+
+       IMustLock(a->dir);
+
+       a->path->dentry = d->d_parent;
+       *a->errp = security_path_unlink(a->path, d);
+       a->path->dentry = d;
+       if (unlikely(*a->errp))
+               return;
+
+       if (!stop_sillyrename)
+               dget(d);
+       h_inode = NULL;
+       if (d_is_positive(d)) {
+               h_inode = d_inode(d);
+               ihold(h_inode);
+       }
+
+       userns = mnt_user_ns(a->path->mnt);
+       lockdep_off();
+       *a->errp = vfs_unlink(userns, a->dir, d, a->delegated_inode);
+       lockdep_on();
+       if (!*a->errp) {
+               struct path tmp = {
+                       .dentry = d->d_parent,
+                       .mnt    = a->path->mnt
+               };
+               vfsub_update_h_iattr(&tmp, /*did*/NULL); /*ignore*/
+       }
+
+       if (!stop_sillyrename)
+               dput(d);
+       if (h_inode)
+               iput(h_inode);
+
+       AuTraceErr(*a->errp);
+}
+
+/*
+ * @dir: must be locked.
+ * @dentry: target dentry.
+ */
+int vfsub_unlink(struct inode *dir, struct path *path,
+                struct inode **delegated_inode, int force)
+{
+       int err;
+       struct unlink_args args = {
+               .errp                   = &err,
+               .dir                    = dir,
+               .path                   = path,
+               .delegated_inode        = delegated_inode
+       };
+
+       if (!force)
+               call_unlink(&args);
+       else {
+               int wkq_err;
+
+               wkq_err = au_wkq_wait(call_unlink, &args);
+               if (unlikely(wkq_err))
+                       err = wkq_err;
+       }
+
+       return err;
+}
diff -urN /usr/share/empty/fs/aufs/vfsub.h linux/fs/aufs/vfsub.h
--- /usr/share/empty/fs/aufs/vfsub.h    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/vfsub.h       2022-01-13 12:42:15.932899468 +0100
@@ -0,0 +1,358 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * sub-routines for VFS
+ */
+
+#ifndef __AUFS_VFSUB_H__
+#define __AUFS_VFSUB_H__
+
+#ifdef __KERNEL__
+
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/posix_acl.h>
+#include <linux/xattr.h>
+#include "debug.h"
+
+/* copied from linux/fs/internal.h */
+/* todo: BAD approach!! */
+extern void __mnt_drop_write(struct vfsmount *);
+extern struct file *alloc_empty_file(int, const struct cred *);
+
+/* ---------------------------------------------------------------------- */
+
+/* lock subclass for lower inode */
+/* default MAX_LOCKDEP_SUBCLASSES(8) is not enough */
+/* reduce? gave up. */
+enum {
+       AuLsc_I_Begin = I_MUTEX_PARENT2, /* 5 */
+       AuLsc_I_PARENT,         /* lower inode, parent first */
+       AuLsc_I_PARENT2,        /* copyup dirs */
+       AuLsc_I_PARENT3,        /* copyup wh */
+       AuLsc_I_CHILD,
+       AuLsc_I_CHILD2,
+       AuLsc_I_End
+};
+
+/* to debug easier, do not make them inlined functions */
+#define MtxMustLock(mtx)       AuDebugOn(!mutex_is_locked(mtx))
+#define IMustLock(i)           AuDebugOn(!inode_is_locked(i))
+
+/* ---------------------------------------------------------------------- */
+
+static inline void vfsub_drop_nlink(struct inode *inode)
+{
+       AuDebugOn(!inode->i_nlink);
+       drop_nlink(inode);
+}
+
+static inline void vfsub_dead_dir(struct inode *inode)
+{
+       AuDebugOn(!S_ISDIR(inode->i_mode));
+       inode->i_flags |= S_DEAD;
+       clear_nlink(inode);
+}
+
+static inline int vfsub_native_ro(struct inode *inode)
+{
+       return sb_rdonly(inode->i_sb)
+               || IS_RDONLY(inode)
+               /* || IS_APPEND(inode) */
+               || IS_IMMUTABLE(inode);
+}
+
+#ifdef CONFIG_AUFS_BR_FUSE
+int vfsub_test_mntns(struct vfsmount *mnt, struct super_block *h_sb);
+#else
+AuStubInt0(vfsub_test_mntns, struct vfsmount *mnt, struct super_block *h_sb);
+#endif
+
+int vfsub_sync_filesystem(struct super_block *h_sb);
+
+/* ---------------------------------------------------------------------- */
+
+int vfsub_update_h_iattr(struct path *h_path, int *did);
+struct file *vfsub_dentry_open(struct path *path, int flags);
+struct file *vfsub_filp_open(const char *path, int oflags, int mode);
+struct au_branch;
+struct vfsub_aopen_args {
+       struct file             *file;
+       unsigned int            open_flag;
+       umode_t                 create_mode;
+       struct au_branch        *br;
+};
+int vfsub_atomic_open(struct inode *dir, struct dentry *dentry,
+                     struct vfsub_aopen_args *args);
+int vfsub_kern_path(const char *name, unsigned int flags, struct path *path);
+
+struct dentry *vfsub_lookup_one_len_unlocked(const char *name,
+                                            struct path *ppath, int len);
+struct dentry *vfsub_lookup_one_len(const char *name, struct path *ppath,
+                                   int len);
+
+struct vfsub_lkup_one_args {
+       struct dentry **errp;
+       struct qstr *name;
+       struct path *ppath;
+};
+
+static inline struct dentry *vfsub_lkup_one(struct qstr *name,
+                                           struct path *ppath)
+{
+       return vfsub_lookup_one_len(name->name, ppath, name->len);
+}
+
+void vfsub_call_lkup_one(void *args);
+
+/* ---------------------------------------------------------------------- */
+
+static inline int vfsub_mnt_want_write(struct vfsmount *mnt)
+{
+       int err;
+
+       lockdep_off();
+       err = mnt_want_write(mnt);
+       lockdep_on();
+       return err;
+}
+
+static inline void vfsub_mnt_drop_write(struct vfsmount *mnt)
+{
+       lockdep_off();
+       mnt_drop_write(mnt);
+       lockdep_on();
+}
+
+#if 0 /* reserved */
+static inline void vfsub_mnt_drop_write_file(struct file *file)
+{
+       lockdep_off();
+       mnt_drop_write_file(file);
+       lockdep_on();
+}
+#endif
+
+/* ---------------------------------------------------------------------- */
+
+struct au_hinode;
+struct dentry *vfsub_lock_rename(struct dentry *d1, struct au_hinode *hdir1,
+                                struct dentry *d2, struct au_hinode *hdir2);
+void vfsub_unlock_rename(struct dentry *d1, struct au_hinode *hdir1,
+                        struct dentry *d2, struct au_hinode *hdir2);
+
+int vfsub_create(struct inode *dir, struct path *path, int mode,
+                bool want_excl);
+int vfsub_symlink(struct inode *dir, struct path *path,
+                 const char *symname);
+int vfsub_mknod(struct inode *dir, struct path *path, int mode, dev_t dev);
+int vfsub_link(struct dentry *src_dentry, struct inode *dir,
+              struct path *path, struct inode **delegated_inode);
+int vfsub_rename(struct inode *src_hdir, struct dentry *src_dentry,
+                struct inode *hdir, struct path *path,
+                struct inode **delegated_inode, unsigned int flags);
+int vfsub_mkdir(struct inode *dir, struct path *path, int mode);
+int vfsub_rmdir(struct inode *dir, struct path *path);
+
+/* ---------------------------------------------------------------------- */
+
+ssize_t vfsub_read_u(struct file *file, char __user *ubuf, size_t count,
+                    loff_t *ppos);
+ssize_t vfsub_read_k(struct file *file, void *kbuf, size_t count,
+                       loff_t *ppos);
+ssize_t vfsub_write_u(struct file *file, const char __user *ubuf, size_t count,
+                     loff_t *ppos);
+ssize_t vfsub_write_k(struct file *file, void *kbuf, size_t count,
+                     loff_t *ppos);
+int vfsub_flush(struct file *file, fl_owner_t id);
+int vfsub_iterate_dir(struct file *file, struct dir_context *ctx);
+
+static inline loff_t vfsub_f_size_read(struct file *file)
+{
+       return i_size_read(file_inode(file));
+}
+
+static inline unsigned int vfsub_file_flags(struct file *file)
+{
+       unsigned int flags;
+
+       spin_lock(&file->f_lock);
+       flags = file->f_flags;
+       spin_unlock(&file->f_lock);
+
+       return flags;
+}
+
+static inline int vfsub_file_execed(struct file *file)
+{
+       /* todo: direct access f_flags */
+       return !!(vfsub_file_flags(file) & __FMODE_EXEC);
+}
+
+#if 0 /* reserved */
+static inline void vfsub_file_accessed(struct file *h_file)
+{
+       file_accessed(h_file);
+       vfsub_update_h_iattr(&h_file->f_path, /*did*/NULL); /*ignore*/
+}
+#endif
+
+#if 0 /* reserved */
+static inline void vfsub_touch_atime(struct vfsmount *h_mnt,
+                                    struct dentry *h_dentry)
+{
+       struct path h_path = {
+               .dentry = h_dentry,
+               .mnt    = h_mnt
+       };
+       touch_atime(&h_path);
+       vfsub_update_h_iattr(&h_path, /*did*/NULL); /*ignore*/
+}
+#endif
+
+static inline int vfsub_update_time(struct inode *h_inode,
+                                   struct timespec64 *ts, int flags)
+{
+       return inode_update_time(h_inode, ts, flags);
+       /* no vfsub_update_h_iattr() since we don't have struct path */
+}
+
+#ifdef CONFIG_FS_POSIX_ACL
+static inline int vfsub_acl_chmod(struct user_namespace *h_userns,
+                                 struct inode *h_inode, umode_t h_mode)
+{
+       int err;
+
+       err = posix_acl_chmod(h_userns, h_inode, h_mode);
+       if (err == -EOPNOTSUPP)
+               err = 0;
+       return err;
+}
+#else
+AuStubInt0(vfsub_acl_chmod, struct user_namespace *h_userns,
+          struct inode *h_inode, umode_t h_mode);
+#endif
+
+long vfsub_splice_to(struct file *in, loff_t *ppos,
+                    struct pipe_inode_info *pipe, size_t len,
+                    unsigned int flags);
+long vfsub_splice_from(struct pipe_inode_info *pipe, struct file *out,
+                      loff_t *ppos, size_t len, unsigned int flags);
+
+static inline long vfsub_truncate(struct path *path, loff_t length)
+{
+       long err;
+
+       lockdep_off();
+       err = vfs_truncate(path, length);
+       lockdep_on();
+       return err;
+}
+
+int vfsub_trunc(struct path *h_path, loff_t length, unsigned int attr,
+               struct file *h_file);
+int vfsub_fsync(struct file *file, struct path *path, int datasync);
+
+/*
+ * re-use branch fs's ioctl(FICLONE) while aufs itself doesn't support such
+ * ioctl.
+ */
+static inline loff_t vfsub_clone_file_range(struct file *src, struct file *dst,
+                                           loff_t len)
+{
+       loff_t err;
+
+       lockdep_off();
+       err = vfs_clone_file_range(src, 0, dst, 0, len, /*remap_flags*/0);
+       lockdep_on();
+
+       return err;
+}
+
+/* copy_file_range(2) is a systemcall */
+static inline ssize_t vfsub_copy_file_range(struct file *src, loff_t src_pos,
+                                           struct file *dst, loff_t dst_pos,
+                                           size_t len, unsigned int flags)
+{
+       ssize_t ssz;
+
+       lockdep_off();
+       ssz = vfs_copy_file_range(src, src_pos, dst, dst_pos, len, flags);
+       lockdep_on();
+
+       return ssz;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static inline loff_t vfsub_llseek(struct file *file, loff_t offset, int origin)
+{
+       loff_t err;
+
+       lockdep_off();
+       err = vfs_llseek(file, offset, origin);
+       lockdep_on();
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+int vfsub_sio_mkdir(struct inode *dir, struct path *path, int mode);
+int vfsub_sio_rmdir(struct inode *dir, struct path *path);
+int vfsub_sio_notify_change(struct path *path, struct iattr *ia,
+                           struct inode **delegated_inode);
+int vfsub_notify_change(struct path *path, struct iattr *ia,
+                       struct inode **delegated_inode);
+int vfsub_unlink(struct inode *dir, struct path *path,
+                struct inode **delegated_inode, int force);
+
+static inline int vfsub_getattr(const struct path *path, struct kstat *st)
+{
+       return vfs_getattr(path, st, STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
+}
+
+/* ---------------------------------------------------------------------- */
+
+static inline int vfsub_setxattr(struct user_namespace *userns,
+                                struct dentry *dentry, const char *name,
+                                const void *value, size_t size, int flags)
+{
+       int err;
+
+       lockdep_off();
+       err = vfs_setxattr(userns, dentry, name, value, size, flags);
+       lockdep_on();
+
+       return err;
+}
+
+static inline int vfsub_removexattr(struct user_namespace *userns,
+                                   struct dentry *dentry, const char *name)
+{
+       int err;
+
+       lockdep_off();
+       err = vfs_removexattr(userns, dentry, name);
+       lockdep_on();
+
+       return err;
+}
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_VFSUB_H__ */
diff -urN /usr/share/empty/fs/aufs/wbr_policy.c linux/fs/aufs/wbr_policy.c
--- /usr/share/empty/fs/aufs/wbr_policy.c       1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/wbr_policy.c  2021-12-03 15:38:59.939980643 +0100
@@ -0,0 +1,830 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * policies for selecting one among multiple writable branches
+ */
+
+#include <linux/statfs.h>
+#include "aufs.h"
+
+/* subset of cpup_attr() */
+static noinline_for_stack
+int au_cpdown_attr(struct path *h_path, struct dentry *h_src)
+{
+       int err, sbits;
+       struct iattr ia;
+       struct inode *h_isrc;
+
+       h_isrc = d_inode(h_src);
+       ia.ia_valid = ATTR_FORCE | ATTR_MODE | ATTR_UID | ATTR_GID;
+       ia.ia_mode = h_isrc->i_mode;
+       ia.ia_uid = h_isrc->i_uid;
+       ia.ia_gid = h_isrc->i_gid;
+       sbits = !!(ia.ia_mode & (S_ISUID | S_ISGID));
+       au_cpup_attr_flags(d_inode(h_path->dentry), h_isrc->i_flags);
+       /* no delegation since it is just created */
+       err = vfsub_sio_notify_change(h_path, &ia, /*delegated*/NULL);
+
+       /* is this nfs only? */
+       if (!err && sbits && au_test_nfs(h_path->dentry->d_sb)) {
+               ia.ia_valid = ATTR_FORCE | ATTR_MODE;
+               ia.ia_mode = h_isrc->i_mode;
+               err = vfsub_sio_notify_change(h_path, &ia, /*delegated*/NULL);
+       }
+
+       return err;
+}
+
+#define AuCpdown_PARENT_OPQ    1
+#define AuCpdown_WHED          (1 << 1)
+#define AuCpdown_MADE_DIR      (1 << 2)
+#define AuCpdown_DIROPQ                (1 << 3)
+#define au_ftest_cpdown(flags, name)   ((flags) & AuCpdown_##name)
+#define au_fset_cpdown(flags, name) \
+       do { (flags) |= AuCpdown_##name; } while (0)
+#define au_fclr_cpdown(flags, name) \
+       do { (flags) &= ~AuCpdown_##name; } while (0)
+
+static int au_cpdown_dir_opq(struct dentry *dentry, aufs_bindex_t bdst,
+                            unsigned int *flags)
+{
+       int err;
+       struct dentry *opq_dentry;
+
+       opq_dentry = au_diropq_create(dentry, bdst);
+       err = PTR_ERR(opq_dentry);
+       if (IS_ERR(opq_dentry))
+               goto out;
+       dput(opq_dentry);
+       au_fset_cpdown(*flags, DIROPQ);
+
+out:
+       return err;
+}
+
+static int au_cpdown_dir_wh(struct dentry *dentry, struct dentry *h_parent,
+                           struct inode *dir, aufs_bindex_t bdst)
+{
+       int err;
+       struct path h_path;
+       struct au_branch *br;
+
+       br = au_sbr(dentry->d_sb, bdst);
+       h_path.dentry = au_wh_lkup(h_parent, &dentry->d_name, br);
+       err = PTR_ERR(h_path.dentry);
+       if (IS_ERR(h_path.dentry))
+               goto out;
+
+       err = 0;
+       if (d_is_positive(h_path.dentry)) {
+               h_path.mnt = au_br_mnt(br);
+               err = au_wh_unlink_dentry(au_h_iptr(dir, bdst), &h_path,
+                                         dentry);
+       }
+       dput(h_path.dentry);
+
+out:
+       return err;
+}
+
+static int au_cpdown_dir(struct dentry *dentry, aufs_bindex_t bdst,
+                        struct au_pin *pin,
+                        struct dentry *h_parent, void *arg)
+{
+       int err, rerr;
+       aufs_bindex_t bopq, btop;
+       struct path h_path;
+       struct dentry *parent;
+       struct inode *h_dir, *h_inode, *inode, *dir;
+       unsigned int *flags = arg;
+
+       btop = au_dbtop(dentry);
+       /* dentry is di-locked */
+       parent = dget_parent(dentry);
+       dir = d_inode(parent);
+       h_dir = d_inode(h_parent);
+       AuDebugOn(h_dir != au_h_iptr(dir, bdst));
+       IMustLock(h_dir);
+
+       err = au_lkup_neg(dentry, bdst, /*wh*/0);
+       if (unlikely(err < 0))
+               goto out;
+       h_path.dentry = au_h_dptr(dentry, bdst);
+       h_path.mnt = au_sbr_mnt(dentry->d_sb, bdst);
+       err = vfsub_sio_mkdir(au_h_iptr(dir, bdst), &h_path, 0755);
+       if (unlikely(err))
+               goto out_put;
+       au_fset_cpdown(*flags, MADE_DIR);
+
+       bopq = au_dbdiropq(dentry);
+       au_fclr_cpdown(*flags, WHED);
+       au_fclr_cpdown(*flags, DIROPQ);
+       if (au_dbwh(dentry) == bdst)
+               au_fset_cpdown(*flags, WHED);
+       if (!au_ftest_cpdown(*flags, PARENT_OPQ) && bopq <= bdst)
+               au_fset_cpdown(*flags, PARENT_OPQ);
+       h_inode = d_inode(h_path.dentry);
+       inode_lock_nested(h_inode, AuLsc_I_CHILD);
+       if (au_ftest_cpdown(*flags, WHED)) {
+               err = au_cpdown_dir_opq(dentry, bdst, flags);
+               if (unlikely(err)) {
+                       inode_unlock(h_inode);
+                       goto out_dir;
+               }
+       }
+
+       err = au_cpdown_attr(&h_path, au_h_dptr(dentry, btop));
+       inode_unlock(h_inode);
+       if (unlikely(err))
+               goto out_opq;
+
+       if (au_ftest_cpdown(*flags, WHED)) {
+               err = au_cpdown_dir_wh(dentry, h_parent, dir, bdst);
+               if (unlikely(err))
+                       goto out_opq;
+       }
+
+       inode = d_inode(dentry);
+       if (au_ibbot(inode) < bdst)
+               au_set_ibbot(inode, bdst);
+       au_set_h_iptr(inode, bdst, au_igrab(h_inode),
+                     au_hi_flags(inode, /*isdir*/1));
+       au_fhsm_wrote(dentry->d_sb, bdst, /*force*/0);
+       goto out; /* success */
+
+       /* revert */
+out_opq:
+       if (au_ftest_cpdown(*flags, DIROPQ)) {
+               inode_lock_nested(h_inode, AuLsc_I_CHILD);
+               rerr = au_diropq_remove(dentry, bdst);
+               inode_unlock(h_inode);
+               if (unlikely(rerr)) {
+                       AuIOErr("failed removing diropq for %pd b%d (%d)\n",
+                               dentry, bdst, rerr);
+                       err = -EIO;
+                       goto out;
+               }
+       }
+out_dir:
+       if (au_ftest_cpdown(*flags, MADE_DIR)) {
+               rerr = vfsub_sio_rmdir(au_h_iptr(dir, bdst), &h_path);
+               if (unlikely(rerr)) {
+                       AuIOErr("failed removing %pd b%d (%d)\n",
+                               dentry, bdst, rerr);
+                       err = -EIO;
+               }
+       }
+out_put:
+       au_set_h_dptr(dentry, bdst, NULL);
+       if (au_dbbot(dentry) == bdst)
+               au_update_dbbot(dentry);
+out:
+       dput(parent);
+       return err;
+}
+
+int au_cpdown_dirs(struct dentry *dentry, aufs_bindex_t bdst)
+{
+       int err;
+       unsigned int flags;
+
+       flags = 0;
+       err = au_cp_dirs(dentry, bdst, au_cpdown_dir, &flags);
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* policies for create */
+
+int au_wbr_nonopq(struct dentry *dentry, aufs_bindex_t bindex)
+{
+       int err, i, j, ndentry;
+       aufs_bindex_t bopq;
+       struct au_dcsub_pages dpages;
+       struct au_dpage *dpage;
+       struct dentry **dentries, *parent, *d;
+
+       err = au_dpages_init(&dpages, GFP_NOFS);
+       if (unlikely(err))
+               goto out;
+       parent = dget_parent(dentry);
+       err = au_dcsub_pages_rev_aufs(&dpages, parent, /*do_include*/0);
+       if (unlikely(err))
+               goto out_free;
+
+       err = bindex;
+       for (i = 0; i < dpages.ndpage; i++) {
+               dpage = dpages.dpages + i;
+               dentries = dpage->dentries;
+               ndentry = dpage->ndentry;
+               for (j = 0; j < ndentry; j++) {
+                       d = dentries[j];
+                       di_read_lock_parent2(d, !AuLock_IR);
+                       bopq = au_dbdiropq(d);
+                       di_read_unlock(d, !AuLock_IR);
+                       if (bopq >= 0 && bopq < err)
+                               err = bopq;
+               }
+       }
+
+out_free:
+       dput(parent);
+       au_dpages_free(&dpages);
+out:
+       return err;
+}
+
+static int au_wbr_bu(struct super_block *sb, aufs_bindex_t bindex)
+{
+       for (; bindex >= 0; bindex--)
+               if (!au_br_rdonly(au_sbr(sb, bindex)))
+                       return bindex;
+       return -EROFS;
+}
+
+/* top down parent */
+static int au_wbr_create_tdp(struct dentry *dentry,
+                            unsigned int flags __maybe_unused)
+{
+       int err;
+       aufs_bindex_t btop, bindex;
+       struct super_block *sb;
+       struct dentry *parent, *h_parent;
+
+       sb = dentry->d_sb;
+       btop = au_dbtop(dentry);
+       err = btop;
+       if (!au_br_rdonly(au_sbr(sb, btop)))
+               goto out;
+
+       err = -EROFS;
+       parent = dget_parent(dentry);
+       for (bindex = au_dbtop(parent); bindex < btop; bindex++) {
+               h_parent = au_h_dptr(parent, bindex);
+               if (!h_parent || d_is_negative(h_parent))
+                       continue;
+
+               if (!au_br_rdonly(au_sbr(sb, bindex))) {
+                       err = bindex;
+                       break;
+               }
+       }
+       dput(parent);
+
+       /* bottom up here */
+       if (unlikely(err < 0)) {
+               err = au_wbr_bu(sb, btop - 1);
+               if (err >= 0)
+                       err = au_wbr_nonopq(dentry, err);
+       }
+
+out:
+       AuDbg("b%d\n", err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* an exception for the policy other than tdp */
+static int au_wbr_create_exp(struct dentry *dentry)
+{
+       int err;
+       aufs_bindex_t bwh, bdiropq;
+       struct dentry *parent;
+
+       err = -1;
+       bwh = au_dbwh(dentry);
+       parent = dget_parent(dentry);
+       bdiropq = au_dbdiropq(parent);
+       if (bwh >= 0) {
+               if (bdiropq >= 0)
+                       err = min(bdiropq, bwh);
+               else
+                       err = bwh;
+               AuDbg("%d\n", err);
+       } else if (bdiropq >= 0) {
+               err = bdiropq;
+               AuDbg("%d\n", err);
+       }
+       dput(parent);
+
+       if (err >= 0)
+               err = au_wbr_nonopq(dentry, err);
+
+       if (err >= 0 && au_br_rdonly(au_sbr(dentry->d_sb, err)))
+               err = -1;
+
+       AuDbg("%d\n", err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* round robin */
+static int au_wbr_create_init_rr(struct super_block *sb)
+{
+       int err;
+
+       err = au_wbr_bu(sb, au_sbbot(sb));
+       atomic_set(&au_sbi(sb)->si_wbr_rr_next, -err); /* less important */
+       /* smp_mb(); */
+
+       AuDbg("b%d\n", err);
+       return err;
+}
+
+static int au_wbr_create_rr(struct dentry *dentry, unsigned int flags)
+{
+       int err, nbr;
+       unsigned int u;
+       aufs_bindex_t bindex, bbot;
+       struct super_block *sb;
+       atomic_t *next;
+
+       err = au_wbr_create_exp(dentry);
+       if (err >= 0)
+               goto out;
+
+       sb = dentry->d_sb;
+       next = &au_sbi(sb)->si_wbr_rr_next;
+       bbot = au_sbbot(sb);
+       nbr = bbot + 1;
+       for (bindex = 0; bindex <= bbot; bindex++) {
+               if (!au_ftest_wbr(flags, DIR)) {
+                       err = atomic_dec_return(next) + 1;
+                       /* modulo for 0 is meaningless */
+                       if (unlikely(!err))
+                               err = atomic_dec_return(next) + 1;
+               } else
+                       err = atomic_read(next);
+               AuDbg("%d\n", err);
+               u = err;
+               err = u % nbr;
+               AuDbg("%d\n", err);
+               if (!au_br_rdonly(au_sbr(sb, err)))
+                       break;
+               err = -EROFS;
+       }
+
+       if (err >= 0)
+               err = au_wbr_nonopq(dentry, err);
+
+out:
+       AuDbg("%d\n", err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* most free space */
+static void au_mfs(struct dentry *dentry, struct dentry *parent)
+{
+       struct super_block *sb;
+       struct au_branch *br;
+       struct au_wbr_mfs *mfs;
+       struct dentry *h_parent;
+       aufs_bindex_t bindex, bbot;
+       int err;
+       unsigned long long b, bavail;
+       struct path h_path;
+       /* reduce the stack usage */
+       struct kstatfs *st;
+
+       st = kmalloc(sizeof(*st), GFP_NOFS);
+       if (unlikely(!st)) {
+               AuWarn1("failed updating mfs(%d), ignored\n", -ENOMEM);
+               return;
+       }
+
+       bavail = 0;
+       sb = dentry->d_sb;
+       mfs = &au_sbi(sb)->si_wbr_mfs;
+       MtxMustLock(&mfs->mfs_lock);
+       mfs->mfs_bindex = -EROFS;
+       mfs->mfsrr_bytes = 0;
+       if (!parent) {
+               bindex = 0;
+               bbot = au_sbbot(sb);
+       } else {
+               bindex = au_dbtop(parent);
+               bbot = au_dbtaildir(parent);
+       }
+
+       for (; bindex <= bbot; bindex++) {
+               if (parent) {
+                       h_parent = au_h_dptr(parent, bindex);
+                       if (!h_parent || d_is_negative(h_parent))
+                               continue;
+               }
+               br = au_sbr(sb, bindex);
+               if (au_br_rdonly(br))
+                       continue;
+
+               /* sb->s_root for NFS is unreliable */
+               h_path.mnt = au_br_mnt(br);
+               h_path.dentry = h_path.mnt->mnt_root;
+               err = vfs_statfs(&h_path, st);
+               if (unlikely(err)) {
+                       AuWarn1("failed statfs, b%d, %d\n", bindex, err);
+                       continue;
+               }
+
+               /* when the available size is equal, select the lower one */
+               BUILD_BUG_ON(sizeof(b) < sizeof(st->f_bavail)
+                            || sizeof(b) < sizeof(st->f_bsize));
+               b = st->f_bavail * st->f_bsize;
+               br->br_wbr->wbr_bytes = b;
+               if (b >= bavail) {
+                       bavail = b;
+                       mfs->mfs_bindex = bindex;
+                       mfs->mfs_jiffy = jiffies;
+               }
+       }
+
+       mfs->mfsrr_bytes = bavail;
+       AuDbg("b%d\n", mfs->mfs_bindex);
+       au_kfree_rcu(st);
+}
+
+static int au_wbr_create_mfs(struct dentry *dentry, unsigned int flags)
+{
+       int err;
+       struct dentry *parent;
+       struct super_block *sb;
+       struct au_wbr_mfs *mfs;
+
+       err = au_wbr_create_exp(dentry);
+       if (err >= 0)
+               goto out;
+
+       sb = dentry->d_sb;
+       parent = NULL;
+       if (au_ftest_wbr(flags, PARENT))
+               parent = dget_parent(dentry);
+       mfs = &au_sbi(sb)->si_wbr_mfs;
+       mutex_lock(&mfs->mfs_lock);
+       if (time_after(jiffies, mfs->mfs_jiffy + mfs->mfs_expire)
+           || mfs->mfs_bindex < 0
+           || au_br_rdonly(au_sbr(sb, mfs->mfs_bindex)))
+               au_mfs(dentry, parent);
+       mutex_unlock(&mfs->mfs_lock);
+       err = mfs->mfs_bindex;
+       dput(parent);
+
+       if (err >= 0)
+               err = au_wbr_nonopq(dentry, err);
+
+out:
+       AuDbg("b%d\n", err);
+       return err;
+}
+
+static int au_wbr_create_init_mfs(struct super_block *sb)
+{
+       struct au_wbr_mfs *mfs;
+
+       mfs = &au_sbi(sb)->si_wbr_mfs;
+       mutex_init(&mfs->mfs_lock);
+       mfs->mfs_jiffy = 0;
+       mfs->mfs_bindex = -EROFS;
+
+       return 0;
+}
+
+static int au_wbr_create_fin_mfs(struct super_block *sb __maybe_unused)
+{
+       mutex_destroy(&au_sbi(sb)->si_wbr_mfs.mfs_lock);
+       return 0;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* top down regardless parent, and then mfs */
+static int au_wbr_create_tdmfs(struct dentry *dentry,
+                              unsigned int flags __maybe_unused)
+{
+       int err;
+       aufs_bindex_t bwh, btail, bindex, bfound, bmfs;
+       unsigned long long watermark;
+       struct super_block *sb;
+       struct au_wbr_mfs *mfs;
+       struct au_branch *br;
+       struct dentry *parent;
+
+       sb = dentry->d_sb;
+       mfs = &au_sbi(sb)->si_wbr_mfs;
+       mutex_lock(&mfs->mfs_lock);
+       if (time_after(jiffies, mfs->mfs_jiffy + mfs->mfs_expire)
+           || mfs->mfs_bindex < 0)
+               au_mfs(dentry, /*parent*/NULL);
+       watermark = mfs->mfsrr_watermark;
+       bmfs = mfs->mfs_bindex;
+       mutex_unlock(&mfs->mfs_lock);
+
+       /* another style of au_wbr_create_exp() */
+       bwh = au_dbwh(dentry);
+       parent = dget_parent(dentry);
+       btail = au_dbtaildir(parent);
+       if (bwh >= 0 && bwh < btail)
+               btail = bwh;
+
+       err = au_wbr_nonopq(dentry, btail);
+       if (unlikely(err < 0))
+               goto out;
+       btail = err;
+       bfound = -1;
+       for (bindex = 0; bindex <= btail; bindex++) {
+               br = au_sbr(sb, bindex);
+               if (au_br_rdonly(br))
+                       continue;
+               if (br->br_wbr->wbr_bytes > watermark) {
+                       bfound = bindex;
+                       break;
+               }
+       }
+       err = bfound;
+       if (err < 0)
+               err = bmfs;
+
+out:
+       dput(parent);
+       AuDbg("b%d\n", err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* most free space and then round robin */
+static int au_wbr_create_mfsrr(struct dentry *dentry, unsigned int flags)
+{
+       int err;
+       struct au_wbr_mfs *mfs;
+
+       err = au_wbr_create_mfs(dentry, flags);
+       if (err >= 0) {
+               mfs = &au_sbi(dentry->d_sb)->si_wbr_mfs;
+               mutex_lock(&mfs->mfs_lock);
+               if (mfs->mfsrr_bytes < mfs->mfsrr_watermark)
+                       err = au_wbr_create_rr(dentry, flags);
+               mutex_unlock(&mfs->mfs_lock);
+       }
+
+       AuDbg("b%d\n", err);
+       return err;
+}
+
+static int au_wbr_create_init_mfsrr(struct super_block *sb)
+{
+       int err;
+
+       au_wbr_create_init_mfs(sb); /* ignore */
+       err = au_wbr_create_init_rr(sb);
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* top down parent and most free space */
+static int au_wbr_create_pmfs(struct dentry *dentry, unsigned int flags)
+{
+       int err, e2;
+       unsigned long long b;
+       aufs_bindex_t bindex, btop, bbot;
+       struct super_block *sb;
+       struct dentry *parent, *h_parent;
+       struct au_branch *br;
+
+       err = au_wbr_create_tdp(dentry, flags);
+       if (unlikely(err < 0))
+               goto out;
+       parent = dget_parent(dentry);
+       btop = au_dbtop(parent);
+       bbot = au_dbtaildir(parent);
+       if (btop == bbot)
+               goto out_parent; /* success */
+
+       e2 = au_wbr_create_mfs(dentry, flags);
+       if (e2 < 0)
+               goto out_parent; /* success */
+
+       /* when the available size is equal, select upper one */
+       sb = dentry->d_sb;
+       br = au_sbr(sb, err);
+       b = br->br_wbr->wbr_bytes;
+       AuDbg("b%d, %llu\n", err, b);
+
+       for (bindex = btop; bindex <= bbot; bindex++) {
+               h_parent = au_h_dptr(parent, bindex);
+               if (!h_parent || d_is_negative(h_parent))
+                       continue;
+
+               br = au_sbr(sb, bindex);
+               if (!au_br_rdonly(br) && br->br_wbr->wbr_bytes > b) {
+                       b = br->br_wbr->wbr_bytes;
+                       err = bindex;
+                       AuDbg("b%d, %llu\n", err, b);
+               }
+       }
+
+       if (err >= 0)
+               err = au_wbr_nonopq(dentry, err);
+
+out_parent:
+       dput(parent);
+out:
+       AuDbg("b%d\n", err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * - top down parent
+ * - most free space with parent
+ * - most free space round-robin regardless parent
+ */
+static int au_wbr_create_pmfsrr(struct dentry *dentry, unsigned int flags)
+{
+       int err;
+       unsigned long long watermark;
+       struct super_block *sb;
+       struct au_branch *br;
+       struct au_wbr_mfs *mfs;
+
+       err = au_wbr_create_pmfs(dentry, flags | AuWbr_PARENT);
+       if (unlikely(err < 0))
+               goto out;
+
+       sb = dentry->d_sb;
+       br = au_sbr(sb, err);
+       mfs = &au_sbi(sb)->si_wbr_mfs;
+       mutex_lock(&mfs->mfs_lock);
+       watermark = mfs->mfsrr_watermark;
+       mutex_unlock(&mfs->mfs_lock);
+       if (br->br_wbr->wbr_bytes < watermark)
+               /* regardless the parent dir */
+               err = au_wbr_create_mfsrr(dentry, flags);
+
+out:
+       AuDbg("b%d\n", err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* policies for copyup */
+
+/* top down parent */
+static int au_wbr_copyup_tdp(struct dentry *dentry)
+{
+       return au_wbr_create_tdp(dentry, /*flags, anything is ok*/0);
+}
+
+/* bottom up parent */
+static int au_wbr_copyup_bup(struct dentry *dentry)
+{
+       int err;
+       aufs_bindex_t bindex, btop;
+       struct dentry *parent, *h_parent;
+       struct super_block *sb;
+
+       err = -EROFS;
+       sb = dentry->d_sb;
+       parent = dget_parent(dentry);
+       btop = au_dbtop(parent);
+       for (bindex = au_dbtop(dentry); bindex >= btop; bindex--) {
+               h_parent = au_h_dptr(parent, bindex);
+               if (!h_parent || d_is_negative(h_parent))
+                       continue;
+
+               if (!au_br_rdonly(au_sbr(sb, bindex))) {
+                       err = bindex;
+                       break;
+               }
+       }
+       dput(parent);
+
+       /* bottom up here */
+       if (unlikely(err < 0))
+               err = au_wbr_bu(sb, btop - 1);
+
+       AuDbg("b%d\n", err);
+       return err;
+}
+
+/* bottom up */
+int au_wbr_do_copyup_bu(struct dentry *dentry, aufs_bindex_t btop)
+{
+       int err;
+
+       err = au_wbr_bu(dentry->d_sb, btop);
+       AuDbg("b%d\n", err);
+       if (err > btop)
+               err = au_wbr_nonopq(dentry, err);
+
+       AuDbg("b%d\n", err);
+       return err;
+}
+
+static int au_wbr_copyup_bu(struct dentry *dentry)
+{
+       int err;
+       aufs_bindex_t btop;
+
+       btop = au_dbtop(dentry);
+       err = au_wbr_do_copyup_bu(dentry, btop);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct au_wbr_copyup_operations au_wbr_copyup_ops[] = {
+       [AuWbrCopyup_TDP] = {
+               .copyup = au_wbr_copyup_tdp
+       },
+       [AuWbrCopyup_BUP] = {
+               .copyup = au_wbr_copyup_bup
+       },
+       [AuWbrCopyup_BU] = {
+               .copyup = au_wbr_copyup_bu
+       }
+};
+
+struct au_wbr_create_operations au_wbr_create_ops[] = {
+       [AuWbrCreate_TDP] = {
+               .create = au_wbr_create_tdp
+       },
+       [AuWbrCreate_RR] = {
+               .create = au_wbr_create_rr,
+               .init   = au_wbr_create_init_rr
+       },
+       [AuWbrCreate_MFS] = {
+               .create = au_wbr_create_mfs,
+               .init   = au_wbr_create_init_mfs,
+               .fin    = au_wbr_create_fin_mfs
+       },
+       [AuWbrCreate_MFSV] = {
+               .create = au_wbr_create_mfs,
+               .init   = au_wbr_create_init_mfs,
+               .fin    = au_wbr_create_fin_mfs
+       },
+       [AuWbrCreate_MFSRR] = {
+               .create = au_wbr_create_mfsrr,
+               .init   = au_wbr_create_init_mfsrr,
+               .fin    = au_wbr_create_fin_mfs
+       },
+       [AuWbrCreate_MFSRRV] = {
+               .create = au_wbr_create_mfsrr,
+               .init   = au_wbr_create_init_mfsrr,
+               .fin    = au_wbr_create_fin_mfs
+       },
+       [AuWbrCreate_TDMFS] = {
+               .create = au_wbr_create_tdmfs,
+               .init   = au_wbr_create_init_mfs,
+               .fin    = au_wbr_create_fin_mfs
+       },
+       [AuWbrCreate_TDMFSV] = {
+               .create = au_wbr_create_tdmfs,
+               .init   = au_wbr_create_init_mfs,
+               .fin    = au_wbr_create_fin_mfs
+       },
+       [AuWbrCreate_PMFS] = {
+               .create = au_wbr_create_pmfs,
+               .init   = au_wbr_create_init_mfs,
+               .fin    = au_wbr_create_fin_mfs
+       },
+       [AuWbrCreate_PMFSV] = {
+               .create = au_wbr_create_pmfs,
+               .init   = au_wbr_create_init_mfs,
+               .fin    = au_wbr_create_fin_mfs
+       },
+       [AuWbrCreate_PMFSRR] = {
+               .create = au_wbr_create_pmfsrr,
+               .init   = au_wbr_create_init_mfsrr,
+               .fin    = au_wbr_create_fin_mfs
+       },
+       [AuWbrCreate_PMFSRRV] = {
+               .create = au_wbr_create_pmfsrr,
+               .init   = au_wbr_create_init_mfsrr,
+               .fin    = au_wbr_create_fin_mfs
+       }
+};
diff -urN /usr/share/empty/fs/aufs/whout.c linux/fs/aufs/whout.c
--- /usr/share/empty/fs/aufs/whout.c    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/whout.c       2021-12-03 15:40:58.236647297 +0100
@@ -0,0 +1,1072 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * whiteout for logical deletion and opaque directory
+ */
+
+#include "aufs.h"
+
+#define WH_MASK                        0444
+
+/*
+ * If a directory contains this file, then it is opaque.  We start with the
+ * .wh. flag so that it is blocked by lookup.
+ */
+static struct qstr diropq_name = QSTR_INIT(AUFS_WH_DIROPQ,
+                                          sizeof(AUFS_WH_DIROPQ) - 1);
+
+/*
+ * generate whiteout name, which is NOT terminated by NULL.
+ * @name: original d_name.name
+ * @len: original d_name.len
+ * @wh: whiteout qstr
+ * returns zero when succeeds, otherwise error.
+ * succeeded value as wh->name should be freed by kfree().
+ */
+int au_wh_name_alloc(struct qstr *wh, const struct qstr *name)
+{
+       char *p;
+
+       if (unlikely(name->len > PATH_MAX - AUFS_WH_PFX_LEN))
+               return -ENAMETOOLONG;
+
+       wh->len = name->len + AUFS_WH_PFX_LEN;
+       p = kmalloc(wh->len, GFP_NOFS);
+       wh->name = p;
+       if (p) {
+               memcpy(p, AUFS_WH_PFX, AUFS_WH_PFX_LEN);
+               memcpy(p + AUFS_WH_PFX_LEN, name->name, name->len);
+               /* smp_mb(); */
+               return 0;
+       }
+       return -ENOMEM;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * test if the @wh_name exists under @h_ppath.
+ * @try_sio specifies the necessary of super-io.
+ */
+int au_wh_test(struct user_namespace *h_userns, struct path *h_ppath,
+              struct qstr *wh_name, int try_sio)
+{
+       int err;
+       struct dentry *wh_dentry;
+
+       if (!try_sio)
+               wh_dentry = vfsub_lkup_one(wh_name, h_ppath);
+       else
+               wh_dentry = au_sio_lkup_one(h_userns, wh_name, h_ppath);
+       err = PTR_ERR(wh_dentry);
+       if (IS_ERR(wh_dentry)) {
+               if (err == -ENAMETOOLONG)
+                       err = 0;
+               goto out;
+       }
+
+       err = 0;
+       if (d_is_negative(wh_dentry))
+               goto out_wh; /* success */
+
+       err = 1;
+       if (d_is_reg(wh_dentry))
+               goto out_wh; /* success */
+
+       err = -EIO;
+       AuIOErr("%pd Invalid whiteout entry type 0%o.\n",
+               wh_dentry, d_inode(wh_dentry)->i_mode);
+
+out_wh:
+       dput(wh_dentry);
+out:
+       return err;
+}
+
+/*
+ * test if the @h_path->dentry sets opaque or not.
+ */
+int au_diropq_test(struct user_namespace *h_userns, struct path *h_path)
+{
+       int err;
+       struct inode *h_dir;
+
+       h_dir = d_inode(h_path->dentry);
+       err = au_wh_test(h_userns, h_path, &diropq_name,
+                        au_test_h_perm_sio(h_userns, h_dir, MAY_EXEC));
+       return err;
+}
+
+/*
+ * returns a negative dentry whose name is unique and temporary.
+ */
+struct dentry *au_whtmp_lkup(struct dentry *h_parent, struct au_branch *br,
+                            struct qstr *prefix)
+{
+       struct dentry *dentry;
+       int i;
+       char defname[NAME_MAX - AUFS_MAX_NAMELEN + DNAME_INLINE_LEN + 1],
+               *name, *p;
+       /* strict atomic_t is unnecessary here */
+       static unsigned short cnt;
+       struct qstr qs;
+       struct path h_ppath;
+       struct user_namespace *h_userns;
+
+       BUILD_BUG_ON(sizeof(cnt) * 2 > AUFS_WH_TMP_LEN);
+
+       name = defname;
+       qs.len = sizeof(defname) - DNAME_INLINE_LEN + prefix->len - 1;
+       if (unlikely(prefix->len > DNAME_INLINE_LEN)) {
+               dentry = ERR_PTR(-ENAMETOOLONG);
+               if (unlikely(qs.len > NAME_MAX))
+                       goto out;
+               dentry = ERR_PTR(-ENOMEM);
+               name = kmalloc(qs.len + 1, GFP_NOFS);
+               if (unlikely(!name))
+                       goto out;
+       }
+
+       /* doubly whiteout-ed */
+       memcpy(name, AUFS_WH_PFX AUFS_WH_PFX, AUFS_WH_PFX_LEN * 2);
+       p = name + AUFS_WH_PFX_LEN * 2;
+       memcpy(p, prefix->name, prefix->len);
+       p += prefix->len;
+       *p++ = '.';
+       AuDebugOn(name + qs.len + 1 - p <= AUFS_WH_TMP_LEN);
+
+       h_ppath.dentry = h_parent;
+       h_ppath.mnt = au_br_mnt(br);
+       h_userns = au_br_userns(br);
+       qs.name = name;
+       for (i = 0; i < 3; i++) {
+               sprintf(p, "%.*x", AUFS_WH_TMP_LEN, cnt++);
+               dentry = au_sio_lkup_one(h_userns, &qs, &h_ppath);
+               if (IS_ERR(dentry) || d_is_negative(dentry))
+                       goto out_name;
+               dput(dentry);
+       }
+       /* pr_warn("could not get random name\n"); */
+       dentry = ERR_PTR(-EEXIST);
+       AuDbg("%.*s\n", AuLNPair(&qs));
+       BUG();
+
+out_name:
+       if (name != defname)
+               au_kfree_try_rcu(name);
+out:
+       AuTraceErrPtr(dentry);
+       return dentry;
+}
+
+/*
+ * rename the @h_dentry on @br to the whiteouted temporary name.
+ */
+int au_whtmp_ren(struct dentry *h_dentry, struct au_branch *br)
+{
+       int err;
+       struct path h_path = {
+               .mnt = au_br_mnt(br)
+       };
+       struct inode *h_dir, *delegated;
+       struct dentry *h_parent;
+
+       h_parent = h_dentry->d_parent; /* dir inode is locked */
+       h_dir = d_inode(h_parent);
+       IMustLock(h_dir);
+
+       h_path.dentry = au_whtmp_lkup(h_parent, br, &h_dentry->d_name);
+       err = PTR_ERR(h_path.dentry);
+       if (IS_ERR(h_path.dentry))
+               goto out;
+
+       /* under the same dir, no need to lock_rename() */
+       delegated = NULL;
+       err = vfsub_rename(h_dir, h_dentry, h_dir, &h_path, &delegated,
+                          /*flags*/0);
+       AuTraceErr(err);
+       if (unlikely(err == -EWOULDBLOCK)) {
+               pr_warn("cannot retry for NFSv4 delegation"
+                       " for an internal rename\n");
+               iput(delegated);
+       }
+       dput(h_path.dentry);
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+/*
+ * functions for removing a whiteout
+ */
+
+static int do_unlink_wh(struct inode *h_dir, struct path *h_path)
+{
+       int err, force;
+       struct inode *delegated;
+
+       /*
+        * forces superio when the dir has a sticky bit.
+        * this may be a violation of unix fs semantics.
+        */
+       force = (h_dir->i_mode & S_ISVTX)
+               && !uid_eq(current_fsuid(), d_inode(h_path->dentry)->i_uid);
+       delegated = NULL;
+       err = vfsub_unlink(h_dir, h_path, &delegated, force);
+       if (unlikely(err == -EWOULDBLOCK)) {
+               pr_warn("cannot retry for NFSv4 delegation"
+                       " for an internal unlink\n");
+               iput(delegated);
+       }
+       return err;
+}
+
+int au_wh_unlink_dentry(struct inode *h_dir, struct path *h_path,
+                       struct dentry *dentry)
+{
+       int err;
+
+       err = do_unlink_wh(h_dir, h_path);
+       if (!err && dentry)
+               au_set_dbwh(dentry, -1);
+
+       return err;
+}
+
+static int unlink_wh_name(struct path *h_ppath, struct qstr *wh)
+{
+       int err;
+       struct path h_path;
+
+       err = 0;
+       h_path.dentry = vfsub_lkup_one(wh, h_ppath);
+       if (IS_ERR(h_path.dentry))
+               err = PTR_ERR(h_path.dentry);
+       else {
+               if (d_is_reg(h_path.dentry)) {
+                       h_path.mnt = h_ppath->mnt;
+                       err = do_unlink_wh(d_inode(h_ppath->dentry), &h_path);
+               }
+               dput(h_path.dentry);
+       }
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+/*
+ * initialize/clean whiteout for a branch
+ */
+
+static void au_wh_clean(struct inode *h_dir, struct path *whpath,
+                       const int isdir)
+{
+       int err;
+       struct inode *delegated;
+
+       if (d_is_negative(whpath->dentry))
+               return;
+
+       if (isdir)
+               err = vfsub_rmdir(h_dir, whpath);
+       else {
+               delegated = NULL;
+               err = vfsub_unlink(h_dir, whpath, &delegated, /*force*/0);
+               if (unlikely(err == -EWOULDBLOCK)) {
+                       pr_warn("cannot retry for NFSv4 delegation"
+                               " for an internal unlink\n");
+                       iput(delegated);
+               }
+       }
+       if (unlikely(err))
+               pr_warn("failed removing %pd (%d), ignored.\n",
+                       whpath->dentry, err);
+}
+
+static int test_linkable(struct dentry *h_root)
+{
+       struct inode *h_dir = d_inode(h_root);
+
+       if (h_dir->i_op->link)
+               return 0;
+
+       pr_err("%pd (%s) doesn't support link(2), use noplink and rw+nolwh\n",
+              h_root, au_sbtype(h_root->d_sb));
+       return -ENOSYS; /* the branch doesn't have its ->link() */
+}
+
+/* todo: should this mkdir be done in /sbin/mount.aufs helper? */
+static int au_whdir(struct inode *h_dir, struct path *path)
+{
+       int err;
+
+       err = -EEXIST;
+       if (d_is_negative(path->dentry)) {
+               int mode = 0700;
+
+               if (au_test_nfs(path->dentry->d_sb))
+                       mode |= 0111;
+               err = vfsub_mkdir(h_dir, path, mode);
+       } else if (d_is_dir(path->dentry))
+               err = 0;
+       else
+               pr_err("unknown %pd exists\n", path->dentry);
+
+       return err;
+}
+
+struct au_wh_base {
+       const struct qstr *name;
+       struct dentry *dentry;
+};
+
+static void au_wh_init_ro(struct inode *h_dir, struct au_wh_base base[],
+                         struct path *h_path)
+{
+       h_path->dentry = base[AuBrWh_BASE].dentry;
+       au_wh_clean(h_dir, h_path, /*isdir*/0);
+       h_path->dentry = base[AuBrWh_PLINK].dentry;
+       au_wh_clean(h_dir, h_path, /*isdir*/1);
+       h_path->dentry = base[AuBrWh_ORPH].dentry;
+       au_wh_clean(h_dir, h_path, /*isdir*/1);
+}
+
+/*
+ * returns tri-state,
+ * minus: error, caller should print the message
+ * zero: success
+ * plus: error, caller should NOT print the message
+ */
+static int au_wh_init_rw_nolink(struct dentry *h_root, struct au_wbr *wbr,
+                               int do_plink, struct au_wh_base base[],
+                               struct path *h_path)
+{
+       int err;
+       struct inode *h_dir;
+
+       h_dir = d_inode(h_root);
+       h_path->dentry = base[AuBrWh_BASE].dentry;
+       au_wh_clean(h_dir, h_path, /*isdir*/0);
+       h_path->dentry = base[AuBrWh_PLINK].dentry;
+       if (do_plink) {
+               err = test_linkable(h_root);
+               if (unlikely(err)) {
+                       err = 1;
+                       goto out;
+               }
+
+               err = au_whdir(h_dir, h_path);
+               if (unlikely(err))
+                       goto out;
+               wbr->wbr_plink = dget(base[AuBrWh_PLINK].dentry);
+       } else
+               au_wh_clean(h_dir, h_path, /*isdir*/1);
+       h_path->dentry = base[AuBrWh_ORPH].dentry;
+       err = au_whdir(h_dir, h_path);
+       if (unlikely(err))
+               goto out;
+       wbr->wbr_orph = dget(base[AuBrWh_ORPH].dentry);
+
+out:
+       return err;
+}
+
+/*
+ * for the moment, aufs supports the branch filesystem which does not support
+ * link(2). testing on FAT which does not support i_op->setattr() fully either,
+ * copyup failed. finally, such filesystem will not be used as the writable
+ * branch.
+ *
+ * returns tri-state, see above.
+ */
+static int au_wh_init_rw(struct dentry *h_root, struct au_wbr *wbr,
+                        int do_plink, struct au_wh_base base[],
+                        struct path *h_path)
+{
+       int err;
+       struct inode *h_dir;
+
+       WbrWhMustWriteLock(wbr);
+
+       err = test_linkable(h_root);
+       if (unlikely(err)) {
+               err = 1;
+               goto out;
+       }
+
+       /*
+        * todo: should this create be done in /sbin/mount.aufs helper?
+        */
+       err = -EEXIST;
+       h_dir = d_inode(h_root);
+       if (d_is_negative(base[AuBrWh_BASE].dentry)) {
+               h_path->dentry = base[AuBrWh_BASE].dentry;
+               err = vfsub_create(h_dir, h_path, WH_MASK, /*want_excl*/true);
+       } else if (d_is_reg(base[AuBrWh_BASE].dentry))
+               err = 0;
+       else
+               pr_err("unknown %pd2 exists\n", base[AuBrWh_BASE].dentry);
+       if (unlikely(err))
+               goto out;
+
+       h_path->dentry = base[AuBrWh_PLINK].dentry;
+       if (do_plink) {
+               err = au_whdir(h_dir, h_path);
+               if (unlikely(err))
+                       goto out;
+               wbr->wbr_plink = dget(base[AuBrWh_PLINK].dentry);
+       } else
+               au_wh_clean(h_dir, h_path, /*isdir*/1);
+       wbr->wbr_whbase = dget(base[AuBrWh_BASE].dentry);
+
+       h_path->dentry = base[AuBrWh_ORPH].dentry;
+       err = au_whdir(h_dir, h_path);
+       if (unlikely(err))
+               goto out;
+       wbr->wbr_orph = dget(base[AuBrWh_ORPH].dentry);
+
+out:
+       return err;
+}
+
+/*
+ * initialize the whiteout base file/dir for @br.
+ */
+int au_wh_init(struct au_branch *br, struct super_block *sb)
+{
+       int err, i;
+       const unsigned char do_plink
+               = !!au_opt_test(au_mntflags(sb), PLINK);
+       struct inode *h_dir;
+       struct path path = br->br_path;
+       struct dentry *h_root = path.dentry;
+       struct au_wbr *wbr = br->br_wbr;
+       static const struct qstr base_name[] = {
+               [AuBrWh_BASE] = QSTR_INIT(AUFS_BASE_NAME,
+                                         sizeof(AUFS_BASE_NAME) - 1),
+               [AuBrWh_PLINK] = QSTR_INIT(AUFS_PLINKDIR_NAME,
+                                          sizeof(AUFS_PLINKDIR_NAME) - 1),
+               [AuBrWh_ORPH] = QSTR_INIT(AUFS_ORPHDIR_NAME,
+                                         sizeof(AUFS_ORPHDIR_NAME) - 1)
+       };
+       struct au_wh_base base[] = {
+               [AuBrWh_BASE] = {
+                       .name   = base_name + AuBrWh_BASE,
+                       .dentry = NULL
+               },
+               [AuBrWh_PLINK] = {
+                       .name   = base_name + AuBrWh_PLINK,
+                       .dentry = NULL
+               },
+               [AuBrWh_ORPH] = {
+                       .name   = base_name + AuBrWh_ORPH,
+                       .dentry = NULL
+               }
+       };
+
+       if (wbr)
+               WbrWhMustWriteLock(wbr);
+
+       for (i = 0; i < AuBrWh_Last; i++) {
+               /* doubly whiteouted */
+               struct dentry *d;
+
+               d = au_wh_lkup(h_root, (void *)base[i].name, br);
+               err = PTR_ERR(d);
+               if (IS_ERR(d))
+                       goto out;
+
+               base[i].dentry = d;
+               AuDebugOn(wbr
+                         && wbr->wbr_wh[i]
+                         && wbr->wbr_wh[i] != base[i].dentry);
+       }
+
+       if (wbr)
+               for (i = 0; i < AuBrWh_Last; i++) {
+                       dput(wbr->wbr_wh[i]);
+                       wbr->wbr_wh[i] = NULL;
+               }
+
+       err = 0;
+       if (!au_br_writable(br->br_perm)) {
+               h_dir = d_inode(h_root);
+               au_wh_init_ro(h_dir, base, &path);
+       } else if (!au_br_wh_linkable(br->br_perm)) {
+               err = au_wh_init_rw_nolink(h_root, wbr, do_plink, base, &path);
+               if (err > 0)
+                       goto out;
+               else if (err)
+                       goto out_err;
+       } else {
+               err = au_wh_init_rw(h_root, wbr, do_plink, base, &path);
+               if (err > 0)
+                       goto out;
+               else if (err)
+                       goto out_err;
+       }
+       goto out; /* success */
+
+out_err:
+       pr_err("an error(%d) on the writable branch %pd(%s)\n",
+              err, h_root, au_sbtype(h_root->d_sb));
+out:
+       for (i = 0; i < AuBrWh_Last; i++)
+               dput(base[i].dentry);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+/*
+ * whiteouts are all hard-linked usually.
+ * when its link count reaches a ceiling, we create a new whiteout base
+ * asynchronously.
+ */
+
+struct reinit_br_wh {
+       struct super_block *sb;
+       struct au_branch *br;
+};
+
+static void reinit_br_wh(void *arg)
+{
+       int err;
+       aufs_bindex_t bindex;
+       struct path h_path;
+       struct reinit_br_wh *a = arg;
+       struct au_wbr *wbr;
+       struct inode *dir, *delegated;
+       struct dentry *h_root;
+       struct au_hinode *hdir;
+
+       err = 0;
+       wbr = a->br->br_wbr;
+       /* big aufs lock */
+       si_noflush_write_lock(a->sb);
+       if (!au_br_writable(a->br->br_perm))
+               goto out;
+       bindex = au_br_index(a->sb, a->br->br_id);
+       if (unlikely(bindex < 0))
+               goto out;
+
+       di_read_lock_parent(a->sb->s_root, AuLock_IR);
+       dir = d_inode(a->sb->s_root);
+       hdir = au_hi(dir, bindex);
+       h_root = au_h_dptr(a->sb->s_root, bindex);
+       AuDebugOn(h_root != au_br_dentry(a->br));
+
+       au_hn_inode_lock_nested(hdir, AuLsc_I_PARENT);
+       wbr_wh_write_lock(wbr);
+       err = au_h_verify(wbr->wbr_whbase, au_opt_udba(a->sb), hdir->hi_inode,
+                         h_root, a->br);
+       if (!err) {
+               h_path.dentry = wbr->wbr_whbase;
+               h_path.mnt = au_br_mnt(a->br);
+               delegated = NULL;
+               err = vfsub_unlink(hdir->hi_inode, &h_path, &delegated,
+                                  /*force*/0);
+               if (unlikely(err == -EWOULDBLOCK)) {
+                       pr_warn("cannot retry for NFSv4 delegation"
+                               " for an internal unlink\n");
+                       iput(delegated);
+               }
+       } else {
+               pr_warn("%pd is moved, ignored\n", wbr->wbr_whbase);
+               err = 0;
+       }
+       dput(wbr->wbr_whbase);
+       wbr->wbr_whbase = NULL;
+       if (!err)
+               err = au_wh_init(a->br, a->sb);
+       wbr_wh_write_unlock(wbr);
+       au_hn_inode_unlock(hdir);
+       di_read_unlock(a->sb->s_root, AuLock_IR);
+       if (!err)
+               au_fhsm_wrote(a->sb, bindex, /*force*/0);
+
+out:
+       if (wbr)
+               atomic_dec(&wbr->wbr_wh_running);
+       au_lcnt_dec(&a->br->br_count);
+       si_write_unlock(a->sb);
+       au_nwt_done(&au_sbi(a->sb)->si_nowait);
+       au_kfree_rcu(a);
+       if (unlikely(err))
+               AuIOErr("err %d\n", err);
+}
+
+static void kick_reinit_br_wh(struct super_block *sb, struct au_branch *br)
+{
+       int do_dec, wkq_err;
+       struct reinit_br_wh *arg;
+
+       do_dec = 1;
+       if (atomic_inc_return(&br->br_wbr->wbr_wh_running) != 1)
+               goto out;
+
+       /* ignore ENOMEM */
+       arg = kmalloc(sizeof(*arg), GFP_NOFS);
+       if (arg) {
+               /*
+                * dec(wh_running), kfree(arg) and dec(br_count)
+                * in reinit function
+                */
+               arg->sb = sb;
+               arg->br = br;
+               au_lcnt_inc(&br->br_count);
+               wkq_err = au_wkq_nowait(reinit_br_wh, arg, sb, /*flags*/0);
+               if (unlikely(wkq_err)) {
+                       atomic_dec(&br->br_wbr->wbr_wh_running);
+                       au_lcnt_dec(&br->br_count);
+                       au_kfree_rcu(arg);
+               }
+               do_dec = 0;
+       }
+
+out:
+       if (do_dec)
+               atomic_dec(&br->br_wbr->wbr_wh_running);
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * create the whiteout @wh.
+ */
+static int link_or_create_wh(struct super_block *sb, aufs_bindex_t bindex,
+                            struct dentry *wh)
+{
+       int err;
+       struct path h_path = {
+               .dentry = wh
+       };
+       struct au_branch *br;
+       struct au_wbr *wbr;
+       struct dentry *h_parent;
+       struct inode *h_dir, *delegated;
+
+       h_parent = wh->d_parent; /* dir inode is locked */
+       h_dir = d_inode(h_parent);
+       IMustLock(h_dir);
+
+       br = au_sbr(sb, bindex);
+       h_path.mnt = au_br_mnt(br);
+       wbr = br->br_wbr;
+       wbr_wh_read_lock(wbr);
+       if (wbr->wbr_whbase) {
+               delegated = NULL;
+               err = vfsub_link(wbr->wbr_whbase, h_dir, &h_path, &delegated);
+               if (unlikely(err == -EWOULDBLOCK)) {
+                       pr_warn("cannot retry for NFSv4 delegation"
+                               " for an internal link\n");
+                       iput(delegated);
+               }
+               if (!err || err != -EMLINK)
+                       goto out;
+
+               /* link count full. re-initialize br_whbase. */
+               kick_reinit_br_wh(sb, br);
+       }
+
+       /* return this error in this context */
+       err = vfsub_create(h_dir, &h_path, WH_MASK, /*want_excl*/true);
+       if (!err)
+               au_fhsm_wrote(sb, bindex, /*force*/0);
+
+out:
+       wbr_wh_read_unlock(wbr);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * create or remove the diropq.
+ */
+static struct dentry *do_diropq(struct dentry *dentry, aufs_bindex_t bindex,
+                               unsigned int flags)
+{
+       struct dentry *opq_dentry;
+       struct super_block *sb;
+       struct au_branch *br;
+       struct path h_path;
+       int err;
+
+       sb = dentry->d_sb;
+       br = au_sbr(sb, bindex);
+       h_path.dentry = au_h_dptr(dentry, bindex);
+       h_path.mnt = au_br_mnt(br);
+       opq_dentry = vfsub_lkup_one(&diropq_name, &h_path);
+       if (IS_ERR(opq_dentry))
+               goto out;
+
+       if (au_ftest_diropq(flags, CREATE)) {
+               err = link_or_create_wh(sb, bindex, opq_dentry);
+               if (!err) {
+                       au_set_dbdiropq(dentry, bindex);
+                       goto out; /* success */
+               }
+       } else {
+               h_path.dentry = opq_dentry;
+               err = do_unlink_wh(au_h_iptr(d_inode(dentry), bindex), &h_path);
+               if (!err)
+                       au_set_dbdiropq(dentry, -1);
+       }
+       dput(opq_dentry);
+       opq_dentry = ERR_PTR(err);
+
+out:
+       return opq_dentry;
+}
+
+struct do_diropq_args {
+       struct dentry **errp;
+       struct dentry *dentry;
+       aufs_bindex_t bindex;
+       unsigned int flags;
+};
+
+static void call_do_diropq(void *args)
+{
+       struct do_diropq_args *a = args;
+       *a->errp = do_diropq(a->dentry, a->bindex, a->flags);
+}
+
+struct dentry *au_diropq_sio(struct dentry *dentry, aufs_bindex_t bindex,
+                            unsigned int flags)
+{
+       struct dentry *diropq, *h_dentry;
+       struct user_namespace *h_userns;
+
+       h_userns = au_sbr_userns(dentry->d_sb, bindex);
+       h_dentry = au_h_dptr(dentry, bindex);
+       if (!au_test_h_perm_sio(h_userns, d_inode(h_dentry),
+                               MAY_EXEC | MAY_WRITE))
+               diropq = do_diropq(dentry, bindex, flags);
+       else {
+               int wkq_err;
+               struct do_diropq_args args = {
+                       .errp           = &diropq,
+                       .dentry         = dentry,
+                       .bindex         = bindex,
+                       .flags          = flags
+               };
+
+               wkq_err = au_wkq_wait(call_do_diropq, &args);
+               if (unlikely(wkq_err))
+                       diropq = ERR_PTR(wkq_err);
+       }
+
+       return diropq;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * lookup whiteout dentry.
+ * @h_parent: lower parent dentry which must exist and be locked
+ * @base_name: name of dentry which will be whiteouted
+ * returns dentry for whiteout.
+ */
+struct dentry *au_wh_lkup(struct dentry *h_parent, struct qstr *base_name,
+                         struct au_branch *br)
+{
+       int err;
+       struct qstr wh_name;
+       struct dentry *wh_dentry;
+       struct path h_path;
+
+       err = au_wh_name_alloc(&wh_name, base_name);
+       wh_dentry = ERR_PTR(err);
+       if (!err) {
+               h_path.dentry = h_parent;
+               h_path.mnt = au_br_mnt(br);
+               wh_dentry = vfsub_lkup_one(&wh_name, &h_path);
+               au_kfree_try_rcu(wh_name.name);
+       }
+       return wh_dentry;
+}
+
+/*
+ * link/create a whiteout for @dentry on @bindex.
+ */
+struct dentry *au_wh_create(struct dentry *dentry, aufs_bindex_t bindex,
+                           struct dentry *h_parent)
+{
+       struct dentry *wh_dentry;
+       struct super_block *sb;
+       int err;
+
+       sb = dentry->d_sb;
+       wh_dentry = au_wh_lkup(h_parent, &dentry->d_name, au_sbr(sb, bindex));
+       if (!IS_ERR(wh_dentry) && d_is_negative(wh_dentry)) {
+               err = link_or_create_wh(sb, bindex, wh_dentry);
+               if (!err) {
+                       au_set_dbwh(dentry, bindex);
+                       au_fhsm_wrote(sb, bindex, /*force*/0);
+               } else {
+                       dput(wh_dentry);
+                       wh_dentry = ERR_PTR(err);
+               }
+       }
+
+       return wh_dentry;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* Delete all whiteouts in this directory on branch bindex. */
+static int del_wh_children(struct path *h_path, struct au_nhash *whlist,
+                          aufs_bindex_t bindex)
+{
+       int err;
+       unsigned long ul, n;
+       struct qstr wh_name;
+       char *p;
+       struct hlist_head *head;
+       struct au_vdir_wh *pos;
+       struct au_vdir_destr *str;
+
+       err = -ENOMEM;
+       p = (void *)__get_free_page(GFP_NOFS);
+       wh_name.name = p;
+       if (unlikely(!wh_name.name))
+               goto out;
+
+       err = 0;
+       memcpy(p, AUFS_WH_PFX, AUFS_WH_PFX_LEN);
+       p += AUFS_WH_PFX_LEN;
+       n = whlist->nh_num;
+       head = whlist->nh_head;
+       for (ul = 0; !err && ul < n; ul++, head++) {
+               hlist_for_each_entry(pos, head, wh_hash) {
+                       if (pos->wh_bindex != bindex)
+                               continue;
+
+                       str = &pos->wh_str;
+                       if (str->len + AUFS_WH_PFX_LEN <= PATH_MAX) {
+                               memcpy(p, str->name, str->len);
+                               wh_name.len = AUFS_WH_PFX_LEN + str->len;
+                               err = unlink_wh_name(h_path, &wh_name);
+                               if (!err)
+                                       continue;
+                               break;
+                       }
+                       AuIOErr("whiteout name too long %.*s\n",
+                               str->len, str->name);
+                       err = -EIO;
+                       break;
+               }
+       }
+       free_page((unsigned long)wh_name.name);
+
+out:
+       return err;
+}
+
+struct del_wh_children_args {
+       int *errp;
+       struct path *h_path;
+       struct au_nhash *whlist;
+       aufs_bindex_t bindex;
+};
+
+static void call_del_wh_children(void *args)
+{
+       struct del_wh_children_args *a = args;
+       *a->errp = del_wh_children(a->h_path, a->whlist, a->bindex);
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct au_whtmp_rmdir *au_whtmp_rmdir_alloc(struct super_block *sb, gfp_t gfp)
+{
+       struct au_whtmp_rmdir *whtmp;
+       int err;
+       unsigned int rdhash;
+
+       SiMustAnyLock(sb);
+
+       whtmp = kzalloc(sizeof(*whtmp), gfp);
+       if (unlikely(!whtmp)) {
+               whtmp = ERR_PTR(-ENOMEM);
+               goto out;
+       }
+
+       /* no estimation for dir size */
+       rdhash = au_sbi(sb)->si_rdhash;
+       if (!rdhash)
+               rdhash = AUFS_RDHASH_DEF;
+       err = au_nhash_alloc(&whtmp->whlist, rdhash, gfp);
+       if (unlikely(err)) {
+               au_kfree_rcu(whtmp);
+               whtmp = ERR_PTR(err);
+       }
+
+out:
+       return whtmp;
+}
+
+void au_whtmp_rmdir_free(struct au_whtmp_rmdir *whtmp)
+{
+       if (whtmp->br)
+               au_lcnt_dec(&whtmp->br->br_count);
+       dput(whtmp->wh_dentry);
+       iput(whtmp->dir);
+       au_nhash_wh_free(&whtmp->whlist);
+       au_kfree_rcu(whtmp);
+}
+
+/*
+ * rmdir the whiteouted temporary named dir @h_dentry.
+ * @whlist: whiteouted children.
+ */
+int au_whtmp_rmdir(struct inode *dir, aufs_bindex_t bindex,
+                  struct dentry *wh_dentry, struct au_nhash *whlist)
+{
+       int err;
+       unsigned int h_nlink;
+       struct path wh_path;
+       struct inode *wh_inode, *h_dir;
+       struct au_branch *br;
+       struct user_namespace *h_userns;
+
+       h_dir = d_inode(wh_dentry->d_parent); /* dir inode is locked */
+       IMustLock(h_dir);
+
+       br = au_sbr(dir->i_sb, bindex);
+       wh_path.dentry = wh_dentry;
+       wh_path.mnt = au_br_mnt(br);
+       h_userns = au_br_userns(br);
+       wh_inode = d_inode(wh_dentry);
+       inode_lock_nested(wh_inode, AuLsc_I_CHILD);
+
+       /*
+        * someone else might change some whiteouts while we were sleeping.
+        * it means this whlist may have an obsoleted entry.
+        */
+       if (!au_test_h_perm_sio(h_userns, wh_inode, MAY_EXEC | MAY_WRITE))
+               err = del_wh_children(&wh_path, whlist, bindex);
+       else {
+               int wkq_err;
+               struct del_wh_children_args args = {
+                       .errp           = &err,
+                       .h_path         = &wh_path,
+                       .whlist         = whlist,
+                       .bindex         = bindex
+               };
+
+               wkq_err = au_wkq_wait(call_del_wh_children, &args);
+               if (unlikely(wkq_err))
+                       err = wkq_err;
+       }
+       inode_unlock(wh_inode);
+
+       if (!err) {
+               h_nlink = h_dir->i_nlink;
+               err = vfsub_rmdir(h_dir, &wh_path);
+               /* some fs doesn't change the parent nlink in some cases */
+               h_nlink -= h_dir->i_nlink;
+       }
+
+       if (!err) {
+               if (au_ibtop(dir) == bindex) {
+                       /* todo: dir->i_mutex is necessary */
+                       au_cpup_attr_timesizes(dir);
+                       if (h_nlink)
+                               vfsub_drop_nlink(dir);
+               }
+               return 0; /* success */
+       }
+
+       pr_warn("failed removing %pd(%d), ignored\n", wh_dentry, err);
+       return err;
+}
+
+static void call_rmdir_whtmp(void *args)
+{
+       int err;
+       aufs_bindex_t bindex;
+       struct au_whtmp_rmdir *a = args;
+       struct super_block *sb;
+       struct dentry *h_parent;
+       struct inode *h_dir;
+       struct au_hinode *hdir;
+
+       /* rmdir by nfsd may cause deadlock with this i_mutex */
+       /* inode_lock(a->dir); */
+       err = -EROFS;
+       sb = a->dir->i_sb;
+       si_read_lock(sb, !AuLock_FLUSH);
+       if (!au_br_writable(a->br->br_perm))
+               goto out;
+       bindex = au_br_index(sb, a->br->br_id);
+       if (unlikely(bindex < 0))
+               goto out;
+
+       err = -EIO;
+       ii_write_lock_parent(a->dir);
+       h_parent = dget_parent(a->wh_dentry);
+       h_dir = d_inode(h_parent);
+       hdir = au_hi(a->dir, bindex);
+       err = vfsub_mnt_want_write(au_br_mnt(a->br));
+       if (unlikely(err))
+               goto out_mnt;
+       au_hn_inode_lock_nested(hdir, AuLsc_I_PARENT);
+       err = au_h_verify(a->wh_dentry, au_opt_udba(sb), h_dir, h_parent,
+                         a->br);
+       if (!err)
+               err = au_whtmp_rmdir(a->dir, bindex, a->wh_dentry, &a->whlist);
+       au_hn_inode_unlock(hdir);
+       vfsub_mnt_drop_write(au_br_mnt(a->br));
+
+out_mnt:
+       dput(h_parent);
+       ii_write_unlock(a->dir);
+out:
+       /* inode_unlock(a->dir); */
+       au_whtmp_rmdir_free(a);
+       si_read_unlock(sb);
+       au_nwt_done(&au_sbi(sb)->si_nowait);
+       if (unlikely(err))
+               AuIOErr("err %d\n", err);
+}
+
+void au_whtmp_kick_rmdir(struct inode *dir, aufs_bindex_t bindex,
+                        struct dentry *wh_dentry, struct au_whtmp_rmdir *args)
+{
+       int wkq_err;
+       struct super_block *sb;
+
+       IMustLock(dir);
+
+       /* all post-process will be done in do_rmdir_whtmp(). */
+       sb = dir->i_sb;
+       args->dir = au_igrab(dir);
+       args->br = au_sbr(sb, bindex);
+       au_lcnt_inc(&args->br->br_count);
+       args->wh_dentry = dget(wh_dentry);
+       wkq_err = au_wkq_nowait(call_rmdir_whtmp, args, sb, /*flags*/0);
+       if (unlikely(wkq_err)) {
+               pr_warn("rmdir error %pd (%d), ignored\n", wh_dentry, wkq_err);
+               au_whtmp_rmdir_free(args);
+       }
+}
diff -urN /usr/share/empty/fs/aufs/whout.h linux/fs/aufs/whout.h
--- /usr/share/empty/fs/aufs/whout.h    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/whout.h       2021-12-03 15:40:58.236647297 +0100
@@ -0,0 +1,87 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * whiteout for logical deletion and opaque directory
+ */
+
+#ifndef __AUFS_WHOUT_H__
+#define __AUFS_WHOUT_H__
+
+#ifdef __KERNEL__
+
+#include "dir.h"
+
+/* whout.c */
+int au_wh_name_alloc(struct qstr *wh, const struct qstr *name);
+int au_wh_test(struct user_namespace *h_userns, struct path *h_ppath,
+              struct qstr *wh_name, int try_sio);
+int au_diropq_test(struct user_namespace *h_userns, struct path *h_path);
+struct au_branch;
+struct dentry *au_whtmp_lkup(struct dentry *h_parent, struct au_branch *br,
+                            struct qstr *prefix);
+int au_whtmp_ren(struct dentry *h_dentry, struct au_branch *br);
+int au_wh_unlink_dentry(struct inode *h_dir, struct path *h_path,
+                       struct dentry *dentry);
+int au_wh_init(struct au_branch *br, struct super_block *sb);
+
+/* diropq flags */
+#define AuDiropq_CREATE        1
+#define au_ftest_diropq(flags, name)   ((flags) & AuDiropq_##name)
+#define au_fset_diropq(flags, name) \
+       do { (flags) |= AuDiropq_##name; } while (0)
+#define au_fclr_diropq(flags, name) \
+       do { (flags) &= ~AuDiropq_##name; } while (0)
+
+struct dentry *au_diropq_sio(struct dentry *dentry, aufs_bindex_t bindex,
+                            unsigned int flags);
+struct dentry *au_wh_lkup(struct dentry *h_parent, struct qstr *base_name,
+                         struct au_branch *br);
+struct dentry *au_wh_create(struct dentry *dentry, aufs_bindex_t bindex,
+                           struct dentry *h_parent);
+
+/* real rmdir for the whiteout-ed dir */
+struct au_whtmp_rmdir {
+       struct inode *dir;
+       struct au_branch *br;
+       struct dentry *wh_dentry;
+       struct au_nhash whlist;
+};
+
+struct au_whtmp_rmdir *au_whtmp_rmdir_alloc(struct super_block *sb, gfp_t gfp);
+void au_whtmp_rmdir_free(struct au_whtmp_rmdir *whtmp);
+int au_whtmp_rmdir(struct inode *dir, aufs_bindex_t bindex,
+                  struct dentry *wh_dentry, struct au_nhash *whlist);
+void au_whtmp_kick_rmdir(struct inode *dir, aufs_bindex_t bindex,
+                        struct dentry *wh_dentry, struct au_whtmp_rmdir *args);
+
+/* ---------------------------------------------------------------------- */
+
+static inline struct dentry *au_diropq_create(struct dentry *dentry,
+                                             aufs_bindex_t bindex)
+{
+       return au_diropq_sio(dentry, bindex, AuDiropq_CREATE);
+}
+
+static inline int au_diropq_remove(struct dentry *dentry, aufs_bindex_t bindex)
+{
+       return PTR_ERR(au_diropq_sio(dentry, bindex, !AuDiropq_CREATE));
+}
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_WHOUT_H__ */
diff -urN /usr/share/empty/fs/aufs/wkq.c linux/fs/aufs/wkq.c
--- /usr/share/empty/fs/aufs/wkq.c      1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/wkq.c 2021-12-03 15:38:59.943313977 +0100
@@ -0,0 +1,372 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * workqueue for asynchronous/super-io operations
+ * todo: try new credential scheme
+ */
+
+#include <linux/module.h>
+#include "aufs.h"
+
+/* internal workqueue named AUFS_WKQ_NAME */
+
+static struct workqueue_struct *au_wkq;
+
+struct au_wkinfo {
+       struct work_struct wk;
+       struct kobject *kobj;
+
+       unsigned int flags; /* see wkq.h */
+
+       au_wkq_func_t func;
+       void *args;
+
+#ifdef CONFIG_LOCKDEP
+       int dont_check;
+       struct held_lock **hlock;
+#endif
+
+       struct completion *comp;
+};
+
+/* ---------------------------------------------------------------------- */
+/*
+ * Aufs passes some operations to the workqueue such as the internal copyup.
+ * This scheme looks rather unnatural for LOCKDEP debugging feature, since the
+ * job run by workqueue depends upon the locks acquired in the other task.
+ * Delegating a small operation to the workqueue, aufs passes its lockdep
+ * information too. And the job in the workqueue restores the info in order to
+ * pretend as if it acquired those locks. This is just to make LOCKDEP work
+ * correctly and expectedly.
+ */
+
+#ifndef CONFIG_LOCKDEP
+AuStubInt0(au_wkq_lockdep_alloc, struct au_wkinfo *wkinfo);
+AuStubVoid(au_wkq_lockdep_free, struct au_wkinfo *wkinfo);
+AuStubVoid(au_wkq_lockdep_pre, struct au_wkinfo *wkinfo);
+AuStubVoid(au_wkq_lockdep_post, struct au_wkinfo *wkinfo);
+AuStubVoid(au_wkq_lockdep_init, struct au_wkinfo *wkinfo);
+#else
+static void au_wkq_lockdep_init(struct au_wkinfo *wkinfo)
+{
+       wkinfo->hlock = NULL;
+       wkinfo->dont_check = 0;
+}
+
+/*
+ * 1: matched
+ * 0: unmatched
+ */
+static int au_wkq_lockdep_test(struct lock_class_key *key, const char *name)
+{
+       static DEFINE_SPINLOCK(spin);
+       static struct {
+               char *name;
+               struct lock_class_key *key;
+       } a[] = {
+               { .name = "&sbinfo->si_rwsem" },
+               { .name = "&finfo->fi_rwsem" },
+               { .name = "&dinfo->di_rwsem" },
+               { .name = "&iinfo->ii_rwsem" }
+       };
+       static int set;
+       int i;
+
+       /* lockless read from 'set.' see below */
+       if (set == ARRAY_SIZE(a)) {
+               for (i = 0; i < ARRAY_SIZE(a); i++)
+                       if (a[i].key == key)
+                               goto match;
+               goto unmatch;
+       }
+
+       spin_lock(&spin);
+       if (set)
+               for (i = 0; i < ARRAY_SIZE(a); i++)
+                       if (a[i].key == key) {
+                               spin_unlock(&spin);
+                               goto match;
+                       }
+       for (i = 0; i < ARRAY_SIZE(a); i++) {
+               if (a[i].key) {
+                       if (unlikely(a[i].key == key)) { /* rare but possible */
+                               spin_unlock(&spin);
+                               goto match;
+                       } else
+                               continue;
+               }
+               if (strstr(a[i].name, name)) {
+                       /*
+                        * the order of these three lines is important for the
+                        * lockless read above.
+                        */
+                       a[i].key = key;
+                       spin_unlock(&spin);
+                       set++;
+                       /* AuDbg("%d, %s\n", set, name); */
+                       goto match;
+               }
+       }
+       spin_unlock(&spin);
+       goto unmatch;
+
+match:
+       return 1;
+unmatch:
+       return 0;
+}
+
+static int au_wkq_lockdep_alloc(struct au_wkinfo *wkinfo)
+{
+       int err, n;
+       struct task_struct *curr;
+       struct held_lock **hl, *held_locks, *p;
+
+       err = 0;
+       curr = current;
+       wkinfo->dont_check = lockdep_recursing(curr);
+       if (wkinfo->dont_check)
+               goto out;
+       n = curr->lockdep_depth;
+       if (!n)
+               goto out;
+
+       err = -ENOMEM;
+       wkinfo->hlock = kmalloc_array(n + 1, sizeof(*wkinfo->hlock), GFP_NOFS);
+       if (unlikely(!wkinfo->hlock))
+               goto out;
+
+       err = 0;
+#if 0 /* left for debugging */
+       if (0 && au_debug_test())
+               lockdep_print_held_locks(curr);
+#endif
+       held_locks = curr->held_locks;
+       hl = wkinfo->hlock;
+       while (n--) {
+               p = held_locks++;
+               if (au_wkq_lockdep_test(p->instance->key, p->instance->name))
+                       *hl++ = p;
+       }
+       *hl = NULL;
+
+out:
+       return err;
+}
+
+static void au_wkq_lockdep_free(struct au_wkinfo *wkinfo)
+{
+       au_kfree_try_rcu(wkinfo->hlock);
+}
+
+static void au_wkq_lockdep_pre(struct au_wkinfo *wkinfo)
+{
+       struct held_lock *p, **hl = wkinfo->hlock;
+       int subclass;
+
+       if (wkinfo->dont_check)
+               lockdep_off();
+       if (!hl)
+               return;
+       while ((p = *hl++)) { /* assignment */
+               subclass = lockdep_hlock_class(p)->subclass;
+               /* AuDbg("%s, %d\n", p->instance->name, subclass); */
+               if (p->read)
+                       rwsem_acquire_read(p->instance, subclass, 0,
+                                          /*p->acquire_ip*/_RET_IP_);
+               else
+                       rwsem_acquire(p->instance, subclass, 0,
+                                     /*p->acquire_ip*/_RET_IP_);
+       }
+}
+
+static void au_wkq_lockdep_post(struct au_wkinfo *wkinfo)
+{
+       struct held_lock *p, **hl = wkinfo->hlock;
+
+       if (wkinfo->dont_check)
+               lockdep_on();
+       if (!hl)
+               return;
+       while ((p = *hl++)) /* assignment */
+               rwsem_release(p->instance, /*p->acquire_ip*/_RET_IP_);
+}
+#endif
+
+static void wkq_func(struct work_struct *wk)
+{
+       struct au_wkinfo *wkinfo = container_of(wk, struct au_wkinfo, wk);
+
+       AuDebugOn(!uid_eq(current_fsuid(), GLOBAL_ROOT_UID));
+       AuDebugOn(rlimit(RLIMIT_FSIZE) != RLIM_INFINITY);
+
+       au_wkq_lockdep_pre(wkinfo);
+       wkinfo->func(wkinfo->args);
+       au_wkq_lockdep_post(wkinfo);
+       if (au_ftest_wkq(wkinfo->flags, WAIT))
+               complete(wkinfo->comp);
+       else {
+               kobject_put(wkinfo->kobj);
+               module_put(THIS_MODULE); /* todo: ?? */
+               au_kfree_rcu(wkinfo);
+       }
+}
+
+/*
+ * Since struct completion is large, try allocating it dynamically.
+ */
+#define AuWkqCompDeclare(name) struct completion *comp = NULL
+
+static int au_wkq_comp_alloc(struct au_wkinfo *wkinfo, struct completion **comp)
+{
+       *comp = kmalloc(sizeof(**comp), GFP_NOFS);
+       if (*comp) {
+               init_completion(*comp);
+               wkinfo->comp = *comp;
+               return 0;
+       }
+       return -ENOMEM;
+}
+
+static void au_wkq_comp_free(struct completion *comp)
+{
+       au_kfree_rcu(comp);
+}
+
+static void au_wkq_run(struct au_wkinfo *wkinfo)
+{
+       if (au_ftest_wkq(wkinfo->flags, NEST)) {
+               if (au_wkq_test()) {
+                       AuWarn1("wkq from wkq, unless silly-rename on NFS,"
+                               " due to a dead dir by UDBA,"
+                               " or async xino write?\n");
+                       AuDebugOn(au_ftest_wkq(wkinfo->flags, WAIT));
+               }
+       } else
+               au_dbg_verify_kthread();
+
+       if (au_ftest_wkq(wkinfo->flags, WAIT)) {
+               INIT_WORK_ONSTACK(&wkinfo->wk, wkq_func);
+               queue_work(au_wkq, &wkinfo->wk);
+       } else {
+               INIT_WORK(&wkinfo->wk, wkq_func);
+               schedule_work(&wkinfo->wk);
+       }
+}
+
+/*
+ * Be careful. It is easy to make deadlock happen.
+ * processA: lock, wkq and wait
+ * processB: wkq and wait, lock in wkq
+ * --> deadlock
+ */
+int au_wkq_do_wait(unsigned int flags, au_wkq_func_t func, void *args)
+{
+       int err;
+       AuWkqCompDeclare(comp);
+       struct au_wkinfo wkinfo = {
+               .flags  = flags,
+               .func   = func,
+               .args   = args
+       };
+
+       err = au_wkq_comp_alloc(&wkinfo, &comp);
+       if (unlikely(err))
+               goto out;
+       err = au_wkq_lockdep_alloc(&wkinfo);
+       if (unlikely(err))
+               goto out_comp;
+       if (!err) {
+               au_wkq_run(&wkinfo);
+               /* no timeout, no interrupt */
+               wait_for_completion(wkinfo.comp);
+       }
+       au_wkq_lockdep_free(&wkinfo);
+
+out_comp:
+       au_wkq_comp_free(comp);
+out:
+       destroy_work_on_stack(&wkinfo.wk);
+       return err;
+}
+
+/*
+ * Note: dget/dput() in func for aufs dentries are not supported. It will be a
+ * problem in a concurrent umounting.
+ */
+int au_wkq_nowait(au_wkq_func_t func, void *args, struct super_block *sb,
+                 unsigned int flags)
+{
+       int err;
+       struct au_wkinfo *wkinfo;
+
+       atomic_inc(&au_sbi(sb)->si_nowait.nw_len);
+
+       /*
+        * wkq_func() must free this wkinfo.
+        * it highly depends upon the implementation of workqueue.
+        */
+       err = 0;
+       wkinfo = kmalloc(sizeof(*wkinfo), GFP_NOFS);
+       if (wkinfo) {
+               wkinfo->kobj = &au_sbi(sb)->si_kobj;
+               wkinfo->flags = flags & ~AuWkq_WAIT;
+               wkinfo->func = func;
+               wkinfo->args = args;
+               wkinfo->comp = NULL;
+               au_wkq_lockdep_init(wkinfo);
+               kobject_get(wkinfo->kobj);
+               __module_get(THIS_MODULE); /* todo: ?? */
+
+               au_wkq_run(wkinfo);
+       } else {
+               err = -ENOMEM;
+               au_nwt_done(&au_sbi(sb)->si_nowait);
+       }
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void au_nwt_init(struct au_nowait_tasks *nwt)
+{
+       atomic_set(&nwt->nw_len, 0);
+       /* smp_mb(); */ /* atomic_set */
+       init_waitqueue_head(&nwt->nw_wq);
+}
+
+void au_wkq_fin(void)
+{
+       destroy_workqueue(au_wkq);
+}
+
+int __init au_wkq_init(void)
+{
+       int err;
+
+       err = 0;
+       au_wkq = alloc_workqueue(AUFS_WKQ_NAME, 0, WQ_DFL_ACTIVE);
+       if (IS_ERR(au_wkq))
+               err = PTR_ERR(au_wkq);
+       else if (!au_wkq)
+               err = -ENOMEM;
+
+       return err;
+}
diff -urN /usr/share/empty/fs/aufs/wkq.h linux/fs/aufs/wkq.h
--- /usr/share/empty/fs/aufs/wkq.h      1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/wkq.h 2021-12-03 15:38:59.943313977 +0100
@@ -0,0 +1,89 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * workqueue for asynchronous/super-io operations
+ * todo: try new credentials management scheme
+ */
+
+#ifndef __AUFS_WKQ_H__
+#define __AUFS_WKQ_H__
+
+#ifdef __KERNEL__
+
+#include <linux/wait.h>
+
+struct super_block;
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * in the next operation, wait for the 'nowait' tasks in system-wide workqueue
+ */
+struct au_nowait_tasks {
+       atomic_t                nw_len;
+       wait_queue_head_t       nw_wq;
+};
+
+/* ---------------------------------------------------------------------- */
+
+typedef void (*au_wkq_func_t)(void *args);
+
+/* wkq flags */
+#define AuWkq_WAIT     1
+#define AuWkq_NEST     (1 << 1)
+#define au_ftest_wkq(flags, name)      ((flags) & AuWkq_##name)
+#define au_fset_wkq(flags, name) \
+       do { (flags) |= AuWkq_##name; } while (0)
+#define au_fclr_wkq(flags, name) \
+       do { (flags) &= ~AuWkq_##name; } while (0)
+
+/* wkq.c */
+int au_wkq_do_wait(unsigned int flags, au_wkq_func_t func, void *args);
+int au_wkq_nowait(au_wkq_func_t func, void *args, struct super_block *sb,
+                 unsigned int flags);
+void au_nwt_init(struct au_nowait_tasks *nwt);
+int __init au_wkq_init(void);
+void au_wkq_fin(void);
+
+/* ---------------------------------------------------------------------- */
+
+static inline int au_wkq_test(void)
+{
+       return current->flags & PF_WQ_WORKER;
+}
+
+static inline int au_wkq_wait(au_wkq_func_t func, void *args)
+{
+       return au_wkq_do_wait(AuWkq_WAIT, func, args);
+}
+
+static inline void au_nwt_done(struct au_nowait_tasks *nwt)
+{
+       if (atomic_dec_and_test(&nwt->nw_len))
+               wake_up_all(&nwt->nw_wq);
+}
+
+static inline int au_nwt_flush(struct au_nowait_tasks *nwt)
+{
+       wait_event(nwt->nw_wq, !atomic_read(&nwt->nw_len));
+       return 0;
+}
+
+#endif /* __KERNEL__ */
+#endif /* __AUFS_WKQ_H__ */
diff -urN /usr/share/empty/fs/aufs/xattr.c linux/fs/aufs/xattr.c
--- /usr/share/empty/fs/aufs/xattr.c    1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/xattr.c       2021-12-03 15:40:58.236647297 +0100
@@ -0,0 +1,368 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2014-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * handling xattr functions
+ */
+
+#include <linux/fs.h>
+#include <linux/posix_acl_xattr.h>
+#include <linux/xattr.h>
+#include "aufs.h"
+
+static int au_xattr_ignore(int err, char *name, unsigned int ignore_flags)
+{
+       if (!ignore_flags)
+               goto out;
+       switch (err) {
+       case -ENOMEM:
+       case -EDQUOT:
+               goto out;
+       }
+
+       if ((ignore_flags & AuBrAttr_ICEX) == AuBrAttr_ICEX) {
+               err = 0;
+               goto out;
+       }
+
+#define cmp(brattr, prefix) do {                                       \
+               if (!strncmp(name, XATTR_##prefix##_PREFIX,             \
+                            XATTR_##prefix##_PREFIX_LEN)) {            \
+                       if (ignore_flags & AuBrAttr_ICEX_##brattr)      \
+                               err = 0;                                \
+                       goto out;                                       \
+               }                                                       \
+       } while (0)
+
+       cmp(SEC, SECURITY);
+       cmp(SYS, SYSTEM);
+       cmp(TR, TRUSTED);
+       cmp(USR, USER);
+#undef cmp
+
+       if (ignore_flags & AuBrAttr_ICEX_OTH)
+               err = 0;
+
+out:
+       return err;
+}
+
+static const int au_xattr_out_of_list = AuBrAttr_ICEX_OTH << 1;
+
+static int au_do_cpup_xattr(struct path *h_dst, struct path *h_src,
+                           char *name, char **buf, unsigned int ignore_flags,
+                           unsigned int verbose)
+{
+       int err;
+       ssize_t ssz;
+       struct inode *h_idst;
+       struct dentry *h_dst_dentry, *h_src_dentry;
+       struct user_namespace *h_dst_userns, *h_src_userns;
+
+       h_src_userns = mnt_user_ns(h_src->mnt);
+       h_src_dentry = h_src->dentry;
+       ssz = vfs_getxattr_alloc(h_src_userns, h_src_dentry, name, buf, 0,
+                                GFP_NOFS);
+       err = ssz;
+       if (unlikely(err <= 0)) {
+               if (err == -ENODATA
+                   || (err == -EOPNOTSUPP
+                       && ((ignore_flags & au_xattr_out_of_list)
+                           || (au_test_nfs_noacl(d_inode(h_src_dentry))
+                               && (!strcmp(name, XATTR_NAME_POSIX_ACL_ACCESS)
+                                   || !strcmp(name,
+                                              XATTR_NAME_POSIX_ACL_DEFAULT))))
+                           ))
+                       err = 0;
+               if (err && (verbose || au_debug_test()))
+                       pr_err("%s, err %d\n", name, err);
+               goto out;
+       }
+
+       /* unlock it temporary */
+       h_dst_userns = mnt_user_ns(h_dst->mnt);
+       h_dst_dentry = h_dst->dentry;
+       h_idst = d_inode(h_dst_dentry);
+       inode_unlock(h_idst);
+       err = vfsub_setxattr(h_dst_userns, h_dst_dentry, name, *buf, ssz,
+                            /*flags*/0);
+       inode_lock_nested(h_idst, AuLsc_I_CHILD2);
+       if (unlikely(err)) {
+               if (verbose || au_debug_test())
+                       pr_err("%s, err %d\n", name, err);
+               err = au_xattr_ignore(err, name, ignore_flags);
+       }
+
+out:
+       return err;
+}
+
+int au_cpup_xattr(struct path *h_dst, struct path *h_src, int ignore_flags,
+                 unsigned int verbose)
+{
+       int err, unlocked, acl_access, acl_default;
+       ssize_t ssz;
+       struct dentry *h_dst_dentry, *h_src_dentry;
+       struct inode *h_isrc, *h_idst;
+       char *value, *p, *o, *e;
+
+       /* try stopping to update the source inode while we are referencing */
+       /* there should not be the parent-child relationship between them */
+       h_dst_dentry = h_dst->dentry;
+       h_idst = d_inode(h_dst_dentry);
+       h_src_dentry = h_src->dentry;
+       h_isrc = d_inode(h_src_dentry);
+       inode_unlock(h_idst);
+       inode_lock_shared_nested(h_isrc, AuLsc_I_CHILD);
+       inode_lock_nested(h_idst, AuLsc_I_CHILD2);
+       unlocked = 0;
+
+       /* some filesystems don't list POSIX ACL, for example tmpfs */
+       ssz = vfs_listxattr(h_src_dentry, NULL, 0);
+       err = ssz;
+       if (unlikely(err < 0)) {
+               AuTraceErr(err);
+               if (err == -ENODATA
+                   || err == -EOPNOTSUPP)
+                       err = 0;        /* ignore */
+               goto out;
+       }
+
+       err = 0;
+       p = NULL;
+       o = NULL;
+       if (ssz) {
+               err = -ENOMEM;
+               p = kmalloc(ssz, GFP_NOFS);
+               o = p;
+               if (unlikely(!p))
+                       goto out;
+               err = vfs_listxattr(h_src_dentry, p, ssz);
+       }
+       inode_unlock_shared(h_isrc);
+       unlocked = 1;
+       AuDbg("err %d, ssz %zd\n", err, ssz);
+       if (unlikely(err < 0))
+               goto out_free;
+
+       err = 0;
+       e = p + ssz;
+       value = NULL;
+       acl_access = 0;
+       acl_default = 0;
+       while (!err && p < e) {
+               acl_access |= !strncmp(p, XATTR_NAME_POSIX_ACL_ACCESS,
+                                      sizeof(XATTR_NAME_POSIX_ACL_ACCESS) - 1);
+               acl_default |= !strncmp(p, XATTR_NAME_POSIX_ACL_DEFAULT,
+                                       sizeof(XATTR_NAME_POSIX_ACL_DEFAULT)
+                                       - 1);
+               err = au_do_cpup_xattr(h_dst, h_src, p, &value, ignore_flags,
+                                      verbose);
+               p += strlen(p) + 1;
+       }
+       AuTraceErr(err);
+       ignore_flags |= au_xattr_out_of_list;
+       if (!err && !acl_access) {
+               err = au_do_cpup_xattr(h_dst, h_src,
+                                      XATTR_NAME_POSIX_ACL_ACCESS, &value,
+                                      ignore_flags, verbose);
+               AuTraceErr(err);
+       }
+       if (!err && !acl_default) {
+               err = au_do_cpup_xattr(h_dst, h_src,
+                                      XATTR_NAME_POSIX_ACL_DEFAULT, &value,
+                                      ignore_flags, verbose);
+               AuTraceErr(err);
+       }
+
+       au_kfree_try_rcu(value);
+
+out_free:
+       au_kfree_try_rcu(o);
+out:
+       if (!unlocked)
+               inode_unlock_shared(h_isrc);
+       AuTraceErr(err);
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_smack_reentering(struct super_block *sb)
+{
+#if IS_ENABLED(CONFIG_SECURITY_SMACK) || IS_ENABLED(CONFIG_SECURITY_SELINUX)
+       /*
+        * as a part of lookup, smack_d_instantiate() is called, and it calls
+        * i_op->getxattr(). ouch.
+        */
+       return si_pid_test(sb);
+#else
+       return 0;
+#endif
+}
+
+enum {
+       AU_XATTR_LIST,
+       AU_XATTR_GET
+};
+
+struct au_lgxattr {
+       int type;
+       union {
+               struct {
+                       char    *list;
+                       size_t  size;
+               } list;
+               struct {
+                       const char      *name;
+                       void            *value;
+                       size_t          size;
+               } get;
+       } u;
+};
+
+static ssize_t au_lgxattr(struct dentry *dentry, struct inode *inode,
+                         struct au_lgxattr *arg)
+{
+       ssize_t err;
+       int reenter;
+       struct path h_path;
+       struct super_block *sb;
+
+       sb = dentry->d_sb;
+       reenter = au_smack_reentering(sb);
+       if (!reenter) {
+               err = si_read_lock(sb, AuLock_FLUSH | AuLock_NOPLM);
+               if (unlikely(err))
+                       goto out;
+       }
+       err = au_h_path_getattr(dentry, inode, /*force*/1, &h_path, reenter);
+       if (unlikely(err))
+               goto out_si;
+       if (unlikely(!h_path.dentry))
+               /* illegally overlapped or something */
+               goto out_di; /* pretending success */
+
+       /* always topmost entry only */
+       switch (arg->type) {
+       case AU_XATTR_LIST:
+               err = vfs_listxattr(h_path.dentry,
+                                   arg->u.list.list, arg->u.list.size);
+               break;
+       case AU_XATTR_GET:
+               AuDebugOn(d_is_negative(h_path.dentry));
+               err = vfs_getxattr(mnt_user_ns(h_path.mnt), h_path.dentry,
+                                  arg->u.get.name, arg->u.get.value,
+                                  arg->u.get.size);
+               break;
+       }
+
+out_di:
+       if (!reenter)
+               di_read_unlock(dentry, AuLock_IR);
+out_si:
+       if (!reenter)
+               si_read_unlock(sb);
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+ssize_t aufs_listxattr(struct dentry *dentry, char *list, size_t size)
+{
+       struct au_lgxattr arg = {
+               .type = AU_XATTR_LIST,
+               .u.list = {
+                       .list   = list,
+                       .size   = size
+               },
+       };
+
+       return au_lgxattr(dentry, /*inode*/NULL, &arg);
+}
+
+static ssize_t au_getxattr(struct dentry *dentry, struct inode *inode,
+                          const char *name, void *value, size_t size)
+{
+       struct au_lgxattr arg = {
+               .type = AU_XATTR_GET,
+               .u.get = {
+                       .name   = name,
+                       .value  = value,
+                       .size   = size
+               },
+       };
+
+       return au_lgxattr(dentry, inode, &arg);
+}
+
+static int au_setxattr(struct dentry *dentry, struct inode *inode,
+                      const char *name, const void *value, size_t size,
+                      int flags)
+{
+       struct au_sxattr arg = {
+               .type = AU_XATTR_SET,
+               .u.set = {
+                       .name   = name,
+                       .value  = value,
+                       .size   = size,
+                       .flags  = flags
+               },
+       };
+
+       return au_sxattr(dentry, inode, &arg);
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_xattr_get(const struct xattr_handler *handler,
+                       struct dentry *dentry, struct inode *inode,
+                       const char *name, void *buffer, size_t size)
+{
+       return au_getxattr(dentry, inode, name, buffer, size);
+}
+
+static int au_xattr_set(const struct xattr_handler *handler,
+                       struct user_namespace *userns,
+                       struct dentry *dentry, struct inode *inode,
+                       const char *name, const void *value, size_t size,
+                       int flags)
+{
+       return au_setxattr(dentry, inode, name, value, size, flags);
+}
+
+static const struct xattr_handler au_xattr_handler = {
+       .name   = "",
+       .prefix = "",
+       .get    = au_xattr_get,
+       .set    = au_xattr_set
+};
+
+static const struct xattr_handler *au_xattr_handlers[] = {
+#ifdef CONFIG_FS_POSIX_ACL
+       &posix_acl_access_xattr_handler,
+       &posix_acl_default_xattr_handler,
+#endif
+       &au_xattr_handler, /* must be last */
+       NULL
+};
+
+void au_xattr_init(struct super_block *sb)
+{
+       sb->s_xattr = au_xattr_handlers;
+}
diff -urN /usr/share/empty/fs/aufs/xino.c linux/fs/aufs/xino.c
--- /usr/share/empty/fs/aufs/xino.c     1970-01-01 01:00:00.000000000 +0100
+++ linux/fs/aufs/xino.c        2021-12-03 15:40:58.236647297 +0100
@@ -0,0 +1,1926 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * external inode number translation table and bitmap
+ *
+ * things to consider
+ * - the lifetime
+ *   + au_xino object
+ *   + XINO files (xino, xib, xigen)
+ *   + dynamic debugfs entries (xiN)
+ *   + static debugfs entries (xib, xigen)
+ *   + static sysfs entry (xi_path)
+ * - several entry points to handle them.
+ *   + mount(2) without xino option (default)
+ *   + mount(2) with xino option
+ *   + mount(2) with noxino option
+ *   + umount(2)
+ *   + remount with add/del branches
+ *   + remount with xino/noxino options
+ */
+
+#include <linux/seq_file.h>
+#include <linux/statfs.h>
+#include "aufs.h"
+
+static aufs_bindex_t sbr_find_shared(struct super_block *sb, aufs_bindex_t btop,
+                                    aufs_bindex_t bbot,
+                                    struct super_block *h_sb)
+{
+       /* todo: try binary-search if the branches are many */
+       for (; btop <= bbot; btop++)
+               if (h_sb == au_sbr_sb(sb, btop))
+                       return btop;
+       return -1;
+}
+
+/*
+ * find another branch who is on the same filesystem of the specified
+ * branch{@btgt}. search until @bbot.
+ */
+static aufs_bindex_t is_sb_shared(struct super_block *sb, aufs_bindex_t btgt,
+                                 aufs_bindex_t bbot)
+{
+       aufs_bindex_t bindex;
+       struct super_block *tgt_sb;
+
+       tgt_sb = au_sbr_sb(sb, btgt);
+       bindex = sbr_find_shared(sb, /*btop*/0, btgt - 1, tgt_sb);
+       if (bindex < 0)
+               bindex = sbr_find_shared(sb, btgt + 1, bbot, tgt_sb);
+
+       return bindex;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * stop unnecessary notify events at creating xino files
+ */
+
+aufs_bindex_t au_xi_root(struct super_block *sb, struct dentry *dentry)
+{
+       aufs_bindex_t bfound, bindex, bbot;
+       struct dentry *parent;
+       struct au_branch *br;
+
+       bfound = -1;
+       parent = dentry->d_parent; /* safe d_parent access */
+       bbot = au_sbbot(sb);
+       for (bindex = 0; bindex <= bbot; bindex++) {
+               br = au_sbr(sb, bindex);
+               if (au_br_dentry(br) == parent) {
+                       bfound = bindex;
+                       break;
+               }
+       }
+
+       AuDbg("bfound b%d\n", bfound);
+       return bfound;
+}
+
+struct au_xino_lock_dir {
+       struct au_hinode *hdir;
+       struct dentry *parent;
+       struct inode *dir;
+};
+
+static struct dentry *au_dget_parent_lock(struct dentry *dentry,
+                                         unsigned int lsc)
+{
+       struct dentry *parent;
+       struct inode *dir;
+
+       parent = dget_parent(dentry);
+       dir = d_inode(parent);
+       inode_lock_nested(dir, lsc);
+#if 0 /* it should not happen */
+       spin_lock(&dentry->d_lock);
+       if (unlikely(dentry->d_parent != parent)) {
+               spin_unlock(&dentry->d_lock);
+               inode_unlock(dir);
+               dput(parent);
+               parent = NULL;
+               goto out;
+       }
+       spin_unlock(&dentry->d_lock);
+
+out:
+#endif
+       return parent;
+}
+
+static void au_xino_lock_dir(struct super_block *sb, struct path *xipath,
+                            struct au_xino_lock_dir *ldir)
+{
+       aufs_bindex_t bindex;
+
+       ldir->hdir = NULL;
+       bindex = au_xi_root(sb, xipath->dentry);
+       if (bindex >= 0) {
+               /* rw branch root */
+               ldir->hdir = au_hi(d_inode(sb->s_root), bindex);
+               au_hn_inode_lock_nested(ldir->hdir, AuLsc_I_PARENT);
+       } else {
+               /* other */
+               ldir->parent = au_dget_parent_lock(xipath->dentry,
+                                                  AuLsc_I_PARENT);
+               ldir->dir = d_inode(ldir->parent);
+       }
+}
+
+static void au_xino_unlock_dir(struct au_xino_lock_dir *ldir)
+{
+       if (ldir->hdir)
+               au_hn_inode_unlock(ldir->hdir);
+       else {
+               inode_unlock(ldir->dir);
+               dput(ldir->parent);
+       }
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * create and set a new xino file
+ */
+struct file *au_xino_create(struct super_block *sb, char *fpath, int silent,
+                           int wbrtop)
+{
+       struct file *file;
+       struct dentry *h_parent, *d;
+       struct inode *h_dir, *inode;
+       int err;
+       static DEFINE_MUTEX(mtx);
+
+       /*
+        * at mount-time, and the xino file is the default path,
+        * hnotify is disabled so we have no notify events to ignore.
+        * when a user specified the xino, we cannot get au_hdir to be ignored.
+        */
+       if (!wbrtop)
+               mutex_lock(&mtx);
+       file = vfsub_filp_open(fpath, O_RDWR | O_CREAT | O_EXCL | O_LARGEFILE
+                              /* | __FMODE_NONOTIFY */,
+                              0666);
+       if (IS_ERR(file)) {
+               if (!wbrtop)
+                       mutex_unlock(&mtx);
+               if (!silent)
+                       pr_err("open %s(%ld)\n", fpath, PTR_ERR(file));
+               return file;
+       }
+
+       /* keep file count */
+       err = 0;
+       d = file->f_path.dentry;
+       h_parent = au_dget_parent_lock(d, AuLsc_I_PARENT);
+       if (!wbrtop)
+               mutex_unlock(&mtx);
+       /* mnt_want_write() is unnecessary here */
+       h_dir = d_inode(h_parent);
+       inode = file_inode(file);
+       /* no delegation since it is just created */
+       if (inode->i_nlink)
+               err = vfsub_unlink(h_dir, &file->f_path, /*delegated*/NULL,
+                                  /*force*/0);
+       inode_unlock(h_dir);
+       dput(h_parent);
+       if (unlikely(err)) {
+               if (!silent)
+                       pr_err("unlink %s(%d)\n", fpath, err);
+               goto out;
+       }
+
+       err = -EINVAL;
+       if (unlikely(sb == d->d_sb)) {
+               if (!silent)
+                       pr_err("%s must be outside\n", fpath);
+               goto out;
+       }
+       if (unlikely(au_test_fs_bad_xino(d->d_sb))) {
+               if (!silent)
+                       pr_err("xino doesn't support %s(%s)\n",
+                              fpath, au_sbtype(d->d_sb));
+               goto out;
+       }
+       return file; /* success */
+
+out:
+       fput(file);
+       file = ERR_PTR(err);
+       return file;
+}
+
+/*
+ * create a new xinofile at the same place/path as @base.
+ */
+struct file *au_xino_create2(struct super_block *sb, struct path *base,
+                            struct file *copy_src)
+{
+       struct file *file;
+       struct dentry *dentry;
+       struct inode *dir, *delegated;
+       struct qstr *name;
+       struct path ppath, path;
+       int err, do_unlock;
+       struct au_xino_lock_dir ldir;
+
+       do_unlock = 1;
+       au_xino_lock_dir(sb, base, &ldir);
+       dentry = base->dentry;
+       ppath.dentry = dentry->d_parent; /* dir inode is locked */
+       ppath.mnt = base->mnt;
+       dir = d_inode(ppath.dentry);
+       IMustLock(dir);
+
+       name = &dentry->d_name;
+       path.dentry = vfsub_lookup_one_len(name->name, &ppath, name->len);
+       if (IS_ERR(path.dentry)) {
+               file = (void *)path.dentry;
+               pr_err("%pd lookup err %ld\n", dentry, PTR_ERR(path.dentry));
+               goto out;
+       }
+
+       /* no need to mnt_want_write() since we call dentry_open() later */
+       err = vfs_create(mnt_user_ns(base->mnt), dir, path.dentry, 0666, NULL);
+       if (unlikely(err)) {
+               file = ERR_PTR(err);
+               pr_err("%pd create err %d\n", dentry, err);
+               goto out_dput;
+       }
+
+       path.mnt = base->mnt;
+       file = vfsub_dentry_open(&path,
+                                O_RDWR | O_CREAT | O_EXCL | O_LARGEFILE
+                                /* | __FMODE_NONOTIFY */);
+       if (IS_ERR(file)) {
+               pr_err("%pd open err %ld\n", dentry, PTR_ERR(file));
+               goto out_dput;
+       }
+
+       delegated = NULL;
+       err = vfsub_unlink(dir, &file->f_path, &delegated, /*force*/0);
+       au_xino_unlock_dir(&ldir);
+       do_unlock = 0;
+       if (unlikely(err == -EWOULDBLOCK)) {
+               pr_warn("cannot retry for NFSv4 delegation"
+                       " for an internal unlink\n");
+               iput(delegated);
+       }
+       if (unlikely(err)) {
+               pr_err("%pd unlink err %d\n", dentry, err);
+               goto out_fput;
+       }
+
+       if (copy_src) {
+               /* no one can touch copy_src xino */
+               err = au_copy_file(file, copy_src, vfsub_f_size_read(copy_src));
+               if (unlikely(err)) {
+                       pr_err("%pd copy err %d\n", dentry, err);
+                       goto out_fput;
+               }
+       }
+       goto out_dput; /* success */
+
+out_fput:
+       fput(file);
+       file = ERR_PTR(err);
+out_dput:
+       dput(path.dentry);
+out:
+       if (do_unlock)
+               au_xino_unlock_dir(&ldir);
+       return file;
+}
+
+struct file *au_xino_file1(struct au_xino *xi)
+{
+       struct file *file;
+       unsigned int u, nfile;
+
+       file = NULL;
+       nfile = xi->xi_nfile;
+       for (u = 0; u < nfile; u++) {
+               file = xi->xi_file[u];
+               if (file)
+                       break;
+       }
+
+       return file;
+}
+
+static int au_xino_file_set(struct au_xino *xi, int idx, struct file *file)
+{
+       int err;
+       struct file *f;
+       void *p;
+
+       if (file)
+               get_file(file);
+
+       err = 0;
+       f = NULL;
+       if (idx < xi->xi_nfile) {
+               f = xi->xi_file[idx];
+               if (f)
+                       fput(f);
+       } else {
+               p = au_kzrealloc(xi->xi_file,
+                                sizeof(*xi->xi_file) * xi->xi_nfile,
+                                sizeof(*xi->xi_file) * (idx + 1),
+                                GFP_NOFS, /*may_shrink*/0);
+               if (p) {
+                       MtxMustLock(&xi->xi_mtx);
+                       xi->xi_file = p;
+                       xi->xi_nfile = idx + 1;
+               } else {
+                       err = -ENOMEM;
+                       if (file)
+                               fput(file);
+                       goto out;
+               }
+       }
+       xi->xi_file[idx] = file;
+
+out:
+       return err;
+}
+
+/*
+ * if @xinew->xi is not set, then create new xigen file.
+ */
+struct file *au_xi_new(struct super_block *sb, struct au_xi_new *xinew)
+{
+       struct file *file;
+       int err;
+
+       SiMustAnyLock(sb);
+
+       file = au_xino_create2(sb, xinew->base, xinew->copy_src);
+       if (IS_ERR(file)) {
+               err = PTR_ERR(file);
+               pr_err("%s[%d], err %d\n",
+                      xinew->xi ? "xino" : "xigen",
+                      xinew->idx, err);
+               goto out;
+       }
+
+       if (xinew->xi)
+               err = au_xino_file_set(xinew->xi, xinew->idx, file);
+       else {
+               BUG();
+               /* todo: make xigen file an array */
+               /* err = au_xigen_file_set(sb, xinew->idx, file); */
+       }
+       fput(file);
+       if (unlikely(err))
+               file = ERR_PTR(err);
+
+out:
+       return file;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * truncate xino files
+ */
+static int au_xino_do_trunc(struct super_block *sb, aufs_bindex_t bindex,
+                           int idx, struct kstatfs *st)
+{
+       int err;
+       blkcnt_t blocks;
+       struct file *file, *new_xino;
+       struct au_xi_new xinew = {
+               .idx = idx
+       };
+
+       err = 0;
+       xinew.xi = au_sbr(sb, bindex)->br_xino;
+       file = au_xino_file(xinew.xi, idx);
+       if (!file)
+               goto out;
+
+       xinew.base = &file->f_path;
+       err = vfs_statfs(xinew.base, st);
+       if (unlikely(err)) {
+               AuErr1("statfs err %d, ignored\n", err);
+               err = 0;
+               goto out;
+       }
+
+       blocks = file_inode(file)->i_blocks;
+       pr_info("begin truncating xino(b%d-%d), ib%llu, %llu/%llu free blks\n",
+               bindex, idx, (u64)blocks, st->f_bfree, st->f_blocks);
+
+       xinew.copy_src = file;
+       new_xino = au_xi_new(sb, &xinew);
+       if (IS_ERR(new_xino)) {
+               err = PTR_ERR(new_xino);
+               pr_err("xino(b%d-%d), err %d, ignored\n", bindex, idx, err);
+               goto out;
+       }
+
+       err = vfs_statfs(&new_xino->f_path, st);
+       if (!err)
+               pr_info("end truncating xino(b%d-%d), ib%llu, %llu/%llu free blks\n",
+                       bindex, idx, (u64)file_inode(new_xino)->i_blocks,
+                       st->f_bfree, st->f_blocks);
+       else {
+               AuErr1("statfs err %d, ignored\n", err);
+               err = 0;
+       }
+
+out:
+       return err;
+}
+
+int au_xino_trunc(struct super_block *sb, aufs_bindex_t bindex, int idx_begin)
+{
+       int err, i;
+       unsigned long jiffy;
+       aufs_bindex_t bbot;
+       struct kstatfs *st;
+       struct au_branch *br;
+       struct au_xino *xi;
+
+       err = -ENOMEM;
+       st = kmalloc(sizeof(*st), GFP_NOFS);
+       if (unlikely(!st))
+               goto out;
+
+       err = -EINVAL;
+       bbot = au_sbbot(sb);
+       if (unlikely(bindex < 0 || bbot < bindex))
+               goto out_st;
+
+       err = 0;
+       jiffy = jiffies;
+       br = au_sbr(sb, bindex);
+       xi = br->br_xino;
+       for (i = idx_begin; !err && i < xi->xi_nfile; i++)
+               err = au_xino_do_trunc(sb, bindex, i, st);
+       if (!err)
+               au_sbi(sb)->si_xino_jiffy = jiffy;
+
+out_st:
+       au_kfree_rcu(st);
+out:
+       return err;
+}
+
+struct xino_do_trunc_args {
+       struct super_block *sb;
+       struct au_branch *br;
+       int idx;
+};
+
+static void xino_do_trunc(void *_args)
+{
+       struct xino_do_trunc_args *args = _args;
+       struct super_block *sb;
+       struct au_branch *br;
+       struct inode *dir;
+       int err, idx;
+       aufs_bindex_t bindex;
+
+       err = 0;
+       sb = args->sb;
+       dir = d_inode(sb->s_root);
+       br = args->br;
+       idx = args->idx;
+
+       si_noflush_write_lock(sb);
+       ii_read_lock_parent(dir);
+       bindex = au_br_index(sb, br->br_id);
+       err = au_xino_trunc(sb, bindex, idx);
+       ii_read_unlock(dir);
+       if (unlikely(err))
+               pr_warn("err b%d, (%d)\n", bindex, err);
+       atomic_dec(&br->br_xino->xi_truncating);
+       au_lcnt_dec(&br->br_count);
+       si_write_unlock(sb);
+       au_nwt_done(&au_sbi(sb)->si_nowait);
+       au_kfree_rcu(args);
+}
+
+/*
+ * returns the index in the xi_file array whose corresponding file is necessary
+ * to truncate, or -1 which means no need to truncate.
+ */
+static int xino_trunc_test(struct super_block *sb, struct au_branch *br)
+{
+       int err;
+       unsigned int u;
+       struct kstatfs st;
+       struct au_sbinfo *sbinfo;
+       struct au_xino *xi;
+       struct file *file;
+
+       /* todo: si_xino_expire and the ratio should be customizable */
+       sbinfo = au_sbi(sb);
+       if (time_before(jiffies,
+                       sbinfo->si_xino_jiffy + sbinfo->si_xino_expire))
+               return -1;
+
+       /* truncation border */
+       xi = br->br_xino;
+       for (u = 0; u < xi->xi_nfile; u++) {
+               file = au_xino_file(xi, u);
+               if (!file)
+                       continue;
+
+               err = vfs_statfs(&file->f_path, &st);
+               if (unlikely(err)) {
+                       AuErr1("statfs err %d, ignored\n", err);
+                       return -1;
+               }
+               if (div64_u64(st.f_bfree * 100, st.f_blocks)
+                   >= AUFS_XINO_DEF_TRUNC)
+                       return u;
+       }
+
+       return -1;
+}
+
+static void xino_try_trunc(struct super_block *sb, struct au_branch *br)
+{
+       int idx;
+       struct xino_do_trunc_args *args;
+       int wkq_err;
+
+       idx = xino_trunc_test(sb, br);
+       if (idx < 0)
+               return;
+
+       if (atomic_inc_return(&br->br_xino->xi_truncating) > 1)
+               goto out;
+
+       /* lock and kfree() will be called in trunc_xino() */
+       args = kmalloc(sizeof(*args), GFP_NOFS);
+       if (unlikely(!args)) {
+               AuErr1("no memory\n");
+               goto out;
+       }
+
+       au_lcnt_inc(&br->br_count);
+       args->sb = sb;
+       args->br = br;
+       args->idx = idx;
+       wkq_err = au_wkq_nowait(xino_do_trunc, args, sb, /*flags*/0);
+       if (!wkq_err)
+               return; /* success */
+
+       pr_err("wkq %d\n", wkq_err);
+       au_lcnt_dec(&br->br_count);
+       au_kfree_rcu(args);
+
+out:
+       atomic_dec(&br->br_xino->xi_truncating);
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct au_xi_calc {
+       int idx;
+       loff_t pos;
+};
+
+static void au_xi_calc(struct super_block *sb, ino_t h_ino,
+                      struct au_xi_calc *calc)
+{
+       loff_t maxent;
+
+       maxent = au_xi_maxent(sb);
+       calc->idx = div64_u64_rem(h_ino, maxent, &calc->pos);
+       calc->pos *= sizeof(ino_t);
+}
+
+static int au_xino_do_new_async(struct super_block *sb, struct au_branch *br,
+                               struct au_xi_calc *calc)
+{
+       int err;
+       struct file *file;
+       struct au_xino *xi = br->br_xino;
+       struct au_xi_new xinew = {
+               .xi = xi
+       };
+
+       SiMustAnyLock(sb);
+
+       err = 0;
+       if (!xi)
+               goto out;
+
+       mutex_lock(&xi->xi_mtx);
+       file = au_xino_file(xi, calc->idx);
+       if (file)
+               goto out_mtx;
+
+       file = au_xino_file(xi, /*idx*/-1);
+       AuDebugOn(!file);
+       xinew.idx = calc->idx;
+       xinew.base = &file->f_path;
+       /* xinew.copy_src = NULL; */
+       file = au_xi_new(sb, &xinew);
+       if (IS_ERR(file))
+               err = PTR_ERR(file);
+
+out_mtx:
+       mutex_unlock(&xi->xi_mtx);
+out:
+       return err;
+}
+
+struct au_xino_do_new_async_args {
+       struct super_block *sb;
+       struct au_branch *br;
+       struct au_xi_calc calc;
+       ino_t ino;
+};
+
+struct au_xi_writing {
+       struct hlist_bl_node node;
+       ino_t h_ino, ino;
+};
+
+static int au_xino_do_write(struct file *file, struct au_xi_calc *calc,
+                           ino_t ino);
+
+static void au_xino_call_do_new_async(void *args)
+{
+       struct au_xino_do_new_async_args *a = args;
+       struct au_branch *br;
+       struct super_block *sb;
+       struct au_sbinfo *sbi;
+       struct inode *root;
+       struct file *file;
+       struct au_xi_writing *del, *p;
+       struct hlist_bl_head *hbl;
+       struct hlist_bl_node *pos;
+       int err;
+
+       br = a->br;
+       sb = a->sb;
+       sbi = au_sbi(sb);
+       si_noflush_read_lock(sb);
+       root = d_inode(sb->s_root);
+       ii_read_lock_child(root);
+       err = au_xino_do_new_async(sb, br, &a->calc);
+       if (unlikely(err)) {
+               AuIOErr("err %d\n", err);
+               goto out;
+       }
+
+       file = au_xino_file(br->br_xino, a->calc.idx);
+       AuDebugOn(!file);
+       err = au_xino_do_write(file, &a->calc, a->ino);
+       if (unlikely(err)) {
+               AuIOErr("err %d\n", err);
+               goto out;
+       }
+
+       del = NULL;
+       hbl = &br->br_xino->xi_writing;
+       hlist_bl_lock(hbl);
+       au_hbl_for_each(pos, hbl) {
+               p = container_of(pos, struct au_xi_writing, node);
+               if (p->ino == a->ino) {
+                       del = p;
+                       hlist_bl_del(&p->node);
+                       break;
+               }
+       }
+       hlist_bl_unlock(hbl);
+       au_kfree_rcu(del);
+
+out:
+       au_lcnt_dec(&br->br_count);
+       ii_read_unlock(root);
+       si_read_unlock(sb);
+       au_nwt_done(&sbi->si_nowait);
+       au_kfree_rcu(a);
+}
+
+/*
+ * create a new xino file asynchronously
+ */
+static int au_xino_new_async(struct super_block *sb, struct au_branch *br,
+                            struct au_xi_calc *calc, ino_t ino)
+{
+       int err;
+       struct au_xino_do_new_async_args *arg;
+
+       err = -ENOMEM;
+       arg = kmalloc(sizeof(*arg), GFP_NOFS);
+       if (unlikely(!arg))
+               goto out;
+
+       arg->sb = sb;
+       arg->br = br;
+       arg->calc = *calc;
+       arg->ino = ino;
+       au_lcnt_inc(&br->br_count);
+       err = au_wkq_nowait(au_xino_call_do_new_async, arg, sb, AuWkq_NEST);
+       if (unlikely(err)) {
+               pr_err("wkq %d\n", err);
+               au_lcnt_dec(&br->br_count);
+               au_kfree_rcu(arg);
+       }
+
+out:
+       return err;
+}
+
+/*
+ * read @ino from xinofile for the specified branch{@sb, @bindex}
+ * at the position of @h_ino.
+ */
+int au_xino_read(struct super_block *sb, aufs_bindex_t bindex, ino_t h_ino,
+                ino_t *ino)
+{
+       int err;
+       ssize_t sz;
+       struct au_xi_calc calc;
+       struct au_sbinfo *sbinfo;
+       struct file *file;
+       struct au_xino *xi;
+       struct hlist_bl_head *hbl;
+       struct hlist_bl_node *pos;
+       struct au_xi_writing *p;
+
+       *ino = 0;
+       if (!au_opt_test(au_mntflags(sb), XINO))
+               return 0; /* no xino */
+
+       err = 0;
+       au_xi_calc(sb, h_ino, &calc);
+       xi = au_sbr(sb, bindex)->br_xino;
+       file = au_xino_file(xi, calc.idx);
+       if (!file) {
+               hbl = &xi->xi_writing;
+               hlist_bl_lock(hbl);
+               au_hbl_for_each(pos, hbl) {
+                       p = container_of(pos, struct au_xi_writing, node);
+                       if (p->h_ino == h_ino) {
+                               AuDbg("hi%llu, i%llu, found\n",
+                                     (u64)p->h_ino, (u64)p->ino);
+                               *ino = p->ino;
+                               break;
+                       }
+               }
+               hlist_bl_unlock(hbl);
+               return 0;
+       } else if (vfsub_f_size_read(file) < calc.pos + sizeof(*ino))
+               return 0; /* no xino */
+
+       sbinfo = au_sbi(sb);
+       sz = xino_fread(file, ino, sizeof(*ino), &calc.pos);
+       if (sz == sizeof(*ino))
+               return 0; /* success */
+
+       err = sz;
+       if (unlikely(sz >= 0)) {
+               err = -EIO;
+               AuIOErr("xino read error (%zd)\n", sz);
+       }
+       return err;
+}
+
+static int au_xino_do_write(struct file *file, struct au_xi_calc *calc,
+                           ino_t ino)
+{
+       ssize_t sz;
+
+       sz = xino_fwrite(file, &ino, sizeof(ino), &calc->pos);
+       if (sz == sizeof(ino))
+               return 0; /* success */
+
+       AuIOErr("write failed (%zd)\n", sz);
+       return -EIO;
+}
+
+/*
+ * write @ino to the xinofile for the specified branch{@sb, @bindex}
+ * at the position of @h_ino.
+ * even if @ino is zero, it is written to the xinofile and means no entry.
+ * if the size of the xino file on a specific filesystem exceeds the watermark,
+ * try truncating it.
+ */
+int au_xino_write(struct super_block *sb, aufs_bindex_t bindex, ino_t h_ino,
+                 ino_t ino)
+{
+       int err;
+       unsigned int mnt_flags;
+       struct au_xi_calc calc;
+       struct file *file;
+       struct au_branch *br;
+       struct au_xino *xi;
+       struct au_xi_writing *p;
+
+       SiMustAnyLock(sb);
+
+       mnt_flags = au_mntflags(sb);
+       if (!au_opt_test(mnt_flags, XINO))
+               return 0;
+
+       au_xi_calc(sb, h_ino, &calc);
+       br = au_sbr(sb, bindex);
+       xi = br->br_xino;
+       file = au_xino_file(xi, calc.idx);
+       if (!file) {
+               /* store the inum pair into the list */
+               p = kmalloc(sizeof(*p), GFP_NOFS | __GFP_NOFAIL);
+               p->h_ino = h_ino;
+               p->ino = ino;
+               au_hbl_add(&p->node, &xi->xi_writing);
+
+               /* create and write a new xino file asynchronously */
+               err = au_xino_new_async(sb, br, &calc, ino);
+               if (!err)
+                       return 0; /* success */
+               goto out;
+       }
+
+       err = au_xino_do_write(file, &calc, ino);
+       if (!err) {
+               br = au_sbr(sb, bindex);
+               if (au_opt_test(mnt_flags, TRUNC_XINO)
+                   && au_test_fs_trunc_xino(au_br_sb(br)))
+                       xino_try_trunc(sb, br);
+               return 0; /* success */
+       }
+
+out:
+       AuIOErr("write failed (%d)\n", err);
+       return -EIO;
+}
+
+static ssize_t xino_fread_wkq(struct file *file, void *buf, size_t size,
+                             loff_t *pos);
+
+/* todo: unnecessary to support mmap_sem since kernel-space? */
+ssize_t xino_fread(struct file *file, void *kbuf, size_t size, loff_t *pos)
+{
+       ssize_t err;
+       int i;
+       const int prevent_endless = 10;
+
+       i = 0;
+       do {
+               err = vfsub_read_k(file, kbuf, size, pos);
+               if (err == -EINTR
+                   && !au_wkq_test()
+                   && fatal_signal_pending(current)) {
+                       err = xino_fread_wkq(file, kbuf, size, pos);
+                       BUG_ON(err == -EINTR);
+               }
+       } while (i++ < prevent_endless
+                && (err == -EAGAIN || err == -EINTR));
+
+#if 0 /* reserved for future use */
+       if (err > 0)
+               fsnotify_access(file->f_path.dentry);
+#endif
+
+       return err;
+}
+
+struct xino_fread_args {
+       ssize_t *errp;
+       struct file *file;
+       void *buf;
+       size_t size;
+       loff_t *pos;
+};
+
+static void call_xino_fread(void *args)
+{
+       struct xino_fread_args *a = args;
+       *a->errp = xino_fread(a->file, a->buf, a->size, a->pos);
+}
+
+static ssize_t xino_fread_wkq(struct file *file, void *buf, size_t size,
+                             loff_t *pos)
+{
+       ssize_t err;
+       int wkq_err;
+       struct xino_fread_args args = {
+               .errp   = &err,
+               .file   = file,
+               .buf    = buf,
+               .size   = size,
+               .pos    = pos
+       };
+
+       wkq_err = au_wkq_wait(call_xino_fread, &args);
+       if (unlikely(wkq_err))
+               err = wkq_err;
+
+       return err;
+}
+
+static ssize_t xino_fwrite_wkq(struct file *file, void *buf, size_t size,
+                              loff_t *pos);
+
+static ssize_t do_xino_fwrite(struct file *file, void *kbuf, size_t size,
+                             loff_t *pos)
+{
+       ssize_t err;
+       int i;
+       const int prevent_endless = 10;
+
+       i = 0;
+       do {
+               err = vfsub_write_k(file, kbuf, size, pos);
+               if (err == -EINTR
+                   && !au_wkq_test()
+                   && fatal_signal_pending(current)) {
+                       err = xino_fwrite_wkq(file, kbuf, size, pos);
+                       BUG_ON(err == -EINTR);
+               }
+       } while (i++ < prevent_endless
+                && (err == -EAGAIN || err == -EINTR));
+
+#if 0 /* reserved for future use */
+       if (err > 0)
+               fsnotify_modify(file->f_path.dentry);
+#endif
+
+       return err;
+}
+
+struct do_xino_fwrite_args {
+       ssize_t *errp;
+       struct file *file;
+       void *buf;
+       size_t size;
+       loff_t *pos;
+};
+
+static void call_do_xino_fwrite(void *args)
+{
+       struct do_xino_fwrite_args *a = args;
+       *a->errp = do_xino_fwrite(a->file, a->buf, a->size, a->pos);
+}
+
+static ssize_t xino_fwrite_wkq(struct file *file, void *buf, size_t size,
+                              loff_t *pos)
+{
+       ssize_t err;
+       int wkq_err;
+       struct do_xino_fwrite_args args = {
+               .errp   = &err,
+               .file   = file,
+               .buf    = buf,
+               .size   = size,
+               .pos    = pos
+       };
+
+       /*
+        * it breaks RLIMIT_FSIZE and normal user's limit,
+        * users should care about quota and real 'filesystem full.'
+        */
+       wkq_err = au_wkq_wait(call_do_xino_fwrite, &args);
+       if (unlikely(wkq_err))
+               err = wkq_err;
+
+       return err;
+}
+
+ssize_t xino_fwrite(struct file *file, void *buf, size_t size, loff_t *pos)
+{
+       ssize_t err;
+
+       if (rlimit(RLIMIT_FSIZE) == RLIM_INFINITY) {
+               lockdep_off();
+               err = do_xino_fwrite(file, buf, size, pos);
+               lockdep_on();
+       } else {
+               lockdep_off();
+               err = xino_fwrite_wkq(file, buf, size, pos);
+               lockdep_on();
+       }
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * inode number bitmap
+ */
+static const int page_bits = (int)PAGE_SIZE * BITS_PER_BYTE;
+static ino_t xib_calc_ino(unsigned long pindex, int bit)
+{
+       ino_t ino;
+
+       AuDebugOn(bit < 0 || page_bits <= bit);
+       ino = AUFS_FIRST_INO + pindex * page_bits + bit;
+       return ino;
+}
+
+static void xib_calc_bit(ino_t ino, unsigned long *pindex, int *bit)
+{
+       AuDebugOn(ino < AUFS_FIRST_INO);
+       ino -= AUFS_FIRST_INO;
+       *pindex = ino / page_bits;
+       *bit = ino % page_bits;
+}
+
+static int xib_pindex(struct super_block *sb, unsigned long pindex)
+{
+       int err;
+       loff_t pos;
+       ssize_t sz;
+       struct au_sbinfo *sbinfo;
+       struct file *xib;
+       unsigned long *p;
+
+       sbinfo = au_sbi(sb);
+       MtxMustLock(&sbinfo->si_xib_mtx);
+       AuDebugOn(pindex > ULONG_MAX / PAGE_SIZE
+                 || !au_opt_test(sbinfo->si_mntflags, XINO));
+
+       if (pindex == sbinfo->si_xib_last_pindex)
+               return 0;
+
+       xib = sbinfo->si_xib;
+       p = sbinfo->si_xib_buf;
+       pos = sbinfo->si_xib_last_pindex;
+       pos *= PAGE_SIZE;
+       sz = xino_fwrite(xib, p, PAGE_SIZE, &pos);
+       if (unlikely(sz != PAGE_SIZE))
+               goto out;
+
+       pos = pindex;
+       pos *= PAGE_SIZE;
+       if (vfsub_f_size_read(xib) >= pos + PAGE_SIZE)
+               sz = xino_fread(xib, p, PAGE_SIZE, &pos);
+       else {
+               memset(p, 0, PAGE_SIZE);
+               sz = xino_fwrite(xib, p, PAGE_SIZE, &pos);
+       }
+       if (sz == PAGE_SIZE) {
+               sbinfo->si_xib_last_pindex = pindex;
+               return 0; /* success */
+       }
+
+out:
+       AuIOErr1("write failed (%zd)\n", sz);
+       err = sz;
+       if (sz >= 0)
+               err = -EIO;
+       return err;
+}
+
+static void au_xib_clear_bit(struct inode *inode)
+{
+       int err, bit;
+       unsigned long pindex;
+       struct super_block *sb;
+       struct au_sbinfo *sbinfo;
+
+       AuDebugOn(inode->i_nlink);
+
+       sb = inode->i_sb;
+       xib_calc_bit(inode->i_ino, &pindex, &bit);
+       AuDebugOn(page_bits <= bit);
+       sbinfo = au_sbi(sb);
+       mutex_lock(&sbinfo->si_xib_mtx);
+       err = xib_pindex(sb, pindex);
+       if (!err) {
+               clear_bit(bit, sbinfo->si_xib_buf);
+               sbinfo->si_xib_next_bit = bit;
+       }
+       mutex_unlock(&sbinfo->si_xib_mtx);
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * truncate a xino bitmap file
+ */
+
+/* todo: slow */
+static int do_xib_restore(struct super_block *sb, struct file *file, void *page)
+{
+       int err, bit;
+       ssize_t sz;
+       unsigned long pindex;
+       loff_t pos, pend;
+       struct au_sbinfo *sbinfo;
+       ino_t *ino;
+       unsigned long *p;
+
+       err = 0;
+       sbinfo = au_sbi(sb);
+       MtxMustLock(&sbinfo->si_xib_mtx);
+       p = sbinfo->si_xib_buf;
+       pend = vfsub_f_size_read(file);
+       pos = 0;
+       while (pos < pend) {
+               sz = xino_fread(file, page, PAGE_SIZE, &pos);
+               err = sz;
+               if (unlikely(sz <= 0))
+                       goto out;
+
+               err = 0;
+               for (ino = page; sz > 0; ino++, sz -= sizeof(ino)) {
+                       if (unlikely(*ino < AUFS_FIRST_INO))
+                               continue;
+
+                       xib_calc_bit(*ino, &pindex, &bit);
+                       AuDebugOn(page_bits <= bit);
+                       err = xib_pindex(sb, pindex);
+                       if (!err)
+                               set_bit(bit, p);
+                       else
+                               goto out;
+               }
+       }
+
+out:
+       return err;
+}
+
+static int xib_restore(struct super_block *sb)
+{
+       int err, i;
+       unsigned int nfile;
+       aufs_bindex_t bindex, bbot;
+       void *page;
+       struct au_branch *br;
+       struct au_xino *xi;
+       struct file *file;
+
+       err = -ENOMEM;
+       page = (void *)__get_free_page(GFP_NOFS);
+       if (unlikely(!page))
+               goto out;
+
+       err = 0;
+       bbot = au_sbbot(sb);
+       for (bindex = 0; !err && bindex <= bbot; bindex++)
+               if (!bindex || is_sb_shared(sb, bindex, bindex - 1) < 0) {
+                       br = au_sbr(sb, bindex);
+                       xi = br->br_xino;
+                       nfile = xi->xi_nfile;
+                       for (i = 0; i < nfile; i++) {
+                               file = au_xino_file(xi, i);
+                               if (file)
+                                       err = do_xib_restore(sb, file, page);
+                       }
+               } else
+                       AuDbg("skip shared b%d\n", bindex);
+       free_page((unsigned long)page);
+
+out:
+       return err;
+}
+
+int au_xib_trunc(struct super_block *sb)
+{
+       int err;
+       ssize_t sz;
+       loff_t pos;
+       struct au_sbinfo *sbinfo;
+       unsigned long *p;
+       struct file *file;
+
+       SiMustWriteLock(sb);
+
+       err = 0;
+       sbinfo = au_sbi(sb);
+       if (!au_opt_test(sbinfo->si_mntflags, XINO))
+               goto out;
+
+       file = sbinfo->si_xib;
+       if (vfsub_f_size_read(file) <= PAGE_SIZE)
+               goto out;
+
+       file = au_xino_create2(sb, &sbinfo->si_xib->f_path, NULL);
+       err = PTR_ERR(file);
+       if (IS_ERR(file))
+               goto out;
+       fput(sbinfo->si_xib);
+       sbinfo->si_xib = file;
+
+       p = sbinfo->si_xib_buf;
+       memset(p, 0, PAGE_SIZE);
+       pos = 0;
+       sz = xino_fwrite(sbinfo->si_xib, p, PAGE_SIZE, &pos);
+       if (unlikely(sz != PAGE_SIZE)) {
+               err = sz;
+               AuIOErr("err %d\n", err);
+               if (sz >= 0)
+                       err = -EIO;
+               goto out;
+       }
+
+       mutex_lock(&sbinfo->si_xib_mtx);
+       /* mnt_want_write() is unnecessary here */
+       err = xib_restore(sb);
+       mutex_unlock(&sbinfo->si_xib_mtx);
+
+out:
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct au_xino *au_xino_alloc(unsigned int nfile)
+{
+       struct au_xino *xi;
+
+       xi = kzalloc(sizeof(*xi), GFP_NOFS);
+       if (unlikely(!xi))
+               goto out;
+       xi->xi_nfile = nfile;
+       xi->xi_file = kcalloc(nfile, sizeof(*xi->xi_file), GFP_NOFS);
+       if (unlikely(!xi->xi_file))
+               goto out_free;
+
+       xi->xi_nondir.total = 8; /* initial size */
+       xi->xi_nondir.array = kcalloc(xi->xi_nondir.total, sizeof(ino_t),
+                                     GFP_NOFS);
+       if (unlikely(!xi->xi_nondir.array))
+               goto out_file;
+
+       spin_lock_init(&xi->xi_nondir.spin);
+       init_waitqueue_head(&xi->xi_nondir.wqh);
+       mutex_init(&xi->xi_mtx);
+       INIT_HLIST_BL_HEAD(&xi->xi_writing);
+       atomic_set(&xi->xi_truncating, 0);
+       kref_init(&xi->xi_kref);
+       goto out; /* success */
+
+out_file:
+       au_kfree_try_rcu(xi->xi_file);
+out_free:
+       au_kfree_rcu(xi);
+       xi = NULL;
+out:
+       return xi;
+}
+
+static int au_xino_init(struct au_branch *br, int idx, struct file *file)
+{
+       int err;
+       struct au_xino *xi;
+
+       err = 0;
+       xi = au_xino_alloc(idx + 1);
+       if (unlikely(!xi)) {
+               err = -ENOMEM;
+               goto out;
+       }
+
+       if (file)
+               get_file(file);
+       xi->xi_file[idx] = file;
+       AuDebugOn(br->br_xino);
+       br->br_xino = xi;
+
+out:
+       return err;
+}
+
+static void au_xino_release(struct kref *kref)
+{
+       struct au_xino *xi;
+       int i;
+       unsigned long ul;
+       struct hlist_bl_head *hbl;
+       struct hlist_bl_node *pos, *n;
+       struct au_xi_writing *p;
+
+       xi = container_of(kref, struct au_xino, xi_kref);
+       for (i = 0; i < xi->xi_nfile; i++)
+               if (xi->xi_file[i])
+                       fput(xi->xi_file[i]);
+       for (i = xi->xi_nondir.total - 1; i >= 0; i--)
+               AuDebugOn(xi->xi_nondir.array[i]);
+       mutex_destroy(&xi->xi_mtx);
+       hbl = &xi->xi_writing;
+       ul = au_hbl_count(hbl);
+       if (unlikely(ul)) {
+               pr_warn("xi_writing %lu\n", ul);
+               hlist_bl_lock(hbl);
+               hlist_bl_for_each_entry_safe(p, pos, n, hbl, node) {
+                       hlist_bl_del(&p->node);
+                       /* kmemleak reported au_kfree_rcu() doesn't free it */
+                       kfree(p);
+               }
+               hlist_bl_unlock(hbl);
+       }
+       au_kfree_try_rcu(xi->xi_file);
+       au_kfree_try_rcu(xi->xi_nondir.array);
+       au_kfree_rcu(xi);
+}
+
+int au_xino_put(struct au_branch *br)
+{
+       int ret;
+       struct au_xino *xi;
+
+       ret = 0;
+       xi = br->br_xino;
+       if (xi) {
+               br->br_xino = NULL;
+               ret = kref_put(&xi->xi_kref, au_xino_release);
+       }
+
+       return ret;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * xino mount option handlers
+ */
+
+/* xino bitmap */
+static void xino_clear_xib(struct super_block *sb)
+{
+       struct au_sbinfo *sbinfo;
+
+       SiMustWriteLock(sb);
+
+       sbinfo = au_sbi(sb);
+       if (sbinfo->si_xib)
+               fput(sbinfo->si_xib);
+       sbinfo->si_xib = NULL;
+       if (sbinfo->si_xib_buf)
+               free_page((unsigned long)sbinfo->si_xib_buf);
+       sbinfo->si_xib_buf = NULL;
+}
+
+static int au_xino_set_xib(struct super_block *sb, struct path *path)
+{
+       int err;
+       loff_t pos;
+       struct au_sbinfo *sbinfo;
+       struct file *file;
+       struct super_block *xi_sb;
+
+       SiMustWriteLock(sb);
+
+       sbinfo = au_sbi(sb);
+       file = au_xino_create2(sb, path, sbinfo->si_xib);
+       err = PTR_ERR(file);
+       if (IS_ERR(file))
+               goto out;
+       if (sbinfo->si_xib)
+               fput(sbinfo->si_xib);
+       sbinfo->si_xib = file;
+       xi_sb = file_inode(file)->i_sb;
+       sbinfo->si_ximaxent = xi_sb->s_maxbytes;
+       if (unlikely(sbinfo->si_ximaxent < PAGE_SIZE)) {
+               err = -EIO;
+               pr_err("s_maxbytes(%llu) on %s is too small\n",
+                      (u64)sbinfo->si_ximaxent, au_sbtype(xi_sb));
+               goto out_unset;
+       }
+       sbinfo->si_ximaxent /= sizeof(ino_t);
+
+       err = -ENOMEM;
+       if (!sbinfo->si_xib_buf)
+               sbinfo->si_xib_buf = (void *)get_zeroed_page(GFP_NOFS);
+       if (unlikely(!sbinfo->si_xib_buf))
+               goto out_unset;
+
+       sbinfo->si_xib_last_pindex = 0;
+       sbinfo->si_xib_next_bit = 0;
+       if (vfsub_f_size_read(file) < PAGE_SIZE) {
+               pos = 0;
+               err = xino_fwrite(file, sbinfo->si_xib_buf, PAGE_SIZE, &pos);
+               if (unlikely(err != PAGE_SIZE))
+                       goto out_free;
+       }
+       err = 0;
+       goto out; /* success */
+
+out_free:
+       if (sbinfo->si_xib_buf)
+               free_page((unsigned long)sbinfo->si_xib_buf);
+       sbinfo->si_xib_buf = NULL;
+       if (err >= 0)
+               err = -EIO;
+out_unset:
+       fput(sbinfo->si_xib);
+       sbinfo->si_xib = NULL;
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+/* xino for each branch */
+static void xino_clear_br(struct super_block *sb)
+{
+       aufs_bindex_t bindex, bbot;
+       struct au_branch *br;
+
+       bbot = au_sbbot(sb);
+       for (bindex = 0; bindex <= bbot; bindex++) {
+               br = au_sbr(sb, bindex);
+               AuDebugOn(!br);
+               au_xino_put(br);
+       }
+}
+
+static void au_xino_set_br_shared(struct super_block *sb, struct au_branch *br,
+                                 aufs_bindex_t bshared)
+{
+       struct au_branch *brshared;
+
+       brshared = au_sbr(sb, bshared);
+       AuDebugOn(!brshared->br_xino);
+       AuDebugOn(!brshared->br_xino->xi_file);
+       if (br->br_xino != brshared->br_xino) {
+               au_xino_get(brshared);
+               au_xino_put(br);
+               br->br_xino = brshared->br_xino;
+       }
+}
+
+struct au_xino_do_set_br {
+       struct au_branch *br;
+       ino_t h_ino;
+       aufs_bindex_t bshared;
+};
+
+static int au_xino_do_set_br(struct super_block *sb, struct path *path,
+                            struct au_xino_do_set_br *args)
+{
+       int err;
+       struct au_xi_calc calc;
+       struct file *file;
+       struct au_branch *br;
+       struct au_xi_new xinew = {
+               .base = path
+       };
+
+       br = args->br;
+       xinew.xi = br->br_xino;
+       au_xi_calc(sb, args->h_ino, &calc);
+       xinew.copy_src = au_xino_file(xinew.xi, calc.idx);
+       if (args->bshared >= 0)
+               /* shared xino */
+               au_xino_set_br_shared(sb, br, args->bshared);
+       else if (!xinew.xi) {
+               /* new xino */
+               err = au_xino_init(br, calc.idx, xinew.copy_src);
+               if (unlikely(err))
+                       goto out;
+       }
+
+       /* force re-creating */
+       xinew.xi = br->br_xino;
+       xinew.idx = calc.idx;
+       mutex_lock(&xinew.xi->xi_mtx);
+       file = au_xi_new(sb, &xinew);
+       mutex_unlock(&xinew.xi->xi_mtx);
+       err = PTR_ERR(file);
+       if (IS_ERR(file))
+               goto out;
+       AuDebugOn(!file);
+
+       err = au_xino_do_write(file, &calc, AUFS_ROOT_INO);
+       if (unlikely(err))
+               au_xino_put(br);
+
+out:
+       AuTraceErr(err);
+       return err;
+}
+
+static int au_xino_set_br(struct super_block *sb, struct path *path)
+{
+       int err;
+       aufs_bindex_t bindex, bbot;
+       struct au_xino_do_set_br args;
+       struct inode *inode;
+
+       SiMustWriteLock(sb);
+
+       bbot = au_sbbot(sb);
+       inode = d_inode(sb->s_root);
+       for (bindex = 0; bindex <= bbot; bindex++) {
+               args.h_ino = au_h_iptr(inode, bindex)->i_ino;
+               args.br = au_sbr(sb, bindex);
+               args.bshared = is_sb_shared(sb, bindex, bindex - 1);
+               err = au_xino_do_set_br(sb, path, &args);
+               if (unlikely(err))
+                       break;
+       }
+
+       AuTraceErr(err);
+       return err;
+}
+
+void au_xino_clr(struct super_block *sb)
+{
+       struct au_sbinfo *sbinfo;
+
+       au_xigen_clr(sb);
+       xino_clear_xib(sb);
+       xino_clear_br(sb);
+       dbgaufs_brs_del(sb, 0);
+       sbinfo = au_sbi(sb);
+       /* lvalue, do not call au_mntflags() */
+       au_opt_clr(sbinfo->si_mntflags, XINO);
+}
+
+int au_xino_set(struct super_block *sb, struct au_opt_xino *xiopt, int remount)
+{
+       int err, skip;
+       struct dentry *dentry, *parent, *cur_dentry, *cur_parent;
+       struct qstr *dname, *cur_name;
+       struct file *cur_xino;
+       struct au_sbinfo *sbinfo;
+       struct path *path, *cur_path;
+
+       SiMustWriteLock(sb);
+
+       err = 0;
+       sbinfo = au_sbi(sb);
+       path = &xiopt->file->f_path;
+       dentry = path->dentry;
+       parent = dget_parent(dentry);
+       if (remount) {
+               skip = 0;
+               cur_xino = sbinfo->si_xib;
+               if (cur_xino) {
+                       cur_path = &cur_xino->f_path;
+                       cur_dentry = cur_path->dentry;
+                       cur_parent = dget_parent(cur_dentry);
+                       cur_name = &cur_dentry->d_name;
+                       dname = &dentry->d_name;
+                       skip = (cur_parent == parent
+                               && au_qstreq(dname, cur_name));
+                       dput(cur_parent);
+               }
+               if (skip)
+                       goto out;
+       }
+
+       au_opt_set(sbinfo->si_mntflags, XINO);
+       err = au_xino_set_xib(sb, path);
+       /* si_x{read,write} are set */
+       if (!err)
+               err = au_xigen_set(sb, path);
+       if (!err)
+               err = au_xino_set_br(sb, path);
+       if (!err) {
+               dbgaufs_brs_add(sb, 0, /*topdown*/1);
+               goto out; /* success */
+       }
+
+       /* reset all */
+       AuIOErr("failed setting xino(%d).\n", err);
+       au_xino_clr(sb);
+
+out:
+       dput(parent);
+       return err;
+}
+
+/*
+ * create a xinofile at the default place/path.
+ */
+struct file *au_xino_def(struct super_block *sb)
+{
+       struct file *file;
+       char *page, *p;
+       struct au_branch *br;
+       struct super_block *h_sb;
+       struct path path;
+       aufs_bindex_t bbot, bindex, bwr;
+
+       br = NULL;
+       bbot = au_sbbot(sb);
+       bwr = -1;
+       for (bindex = 0; bindex <= bbot; bindex++) {
+               br = au_sbr(sb, bindex);
+               if (au_br_writable(br->br_perm)
+                   && !au_test_fs_bad_xino(au_br_sb(br))) {
+                       bwr = bindex;
+                       break;
+               }
+       }
+
+       if (bwr >= 0) {
+               file = ERR_PTR(-ENOMEM);
+               page = (void *)__get_free_page(GFP_NOFS);
+               if (unlikely(!page))
+                       goto out;
+               path.mnt = au_br_mnt(br);
+               path.dentry = au_h_dptr(sb->s_root, bwr);
+               p = d_path(&path, page, PATH_MAX - sizeof(AUFS_XINO_FNAME));
+               file = (void *)p;
+               if (!IS_ERR(p)) {
+                       strcat(p, "/" AUFS_XINO_FNAME);
+                       AuDbg("%s\n", p);
+                       file = au_xino_create(sb, p, /*silent*/0, /*wbrtop*/1);
+               }
+               free_page((unsigned long)page);
+       } else {
+               file = au_xino_create(sb, AUFS_XINO_DEFPATH, /*silent*/0,
+                                     /*wbrtop*/0);
+               if (IS_ERR(file))
+                       goto out;
+               h_sb = file->f_path.dentry->d_sb;
+               if (unlikely(au_test_fs_bad_xino(h_sb))) {
+                       pr_err("xino doesn't support %s(%s)\n",
+                              AUFS_XINO_DEFPATH, au_sbtype(h_sb));
+                       fput(file);
+                       file = ERR_PTR(-EINVAL);
+               }
+       }
+
+out:
+       return file;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * initialize the xinofile for the specified branch @br
+ * at the place/path where @base_file indicates.
+ * test whether another branch is on the same filesystem or not,
+ * if found then share the xinofile with another branch.
+ */
+int au_xino_init_br(struct super_block *sb, struct au_branch *br, ino_t h_ino,
+                   struct path *base)
+{
+       int err;
+       struct au_xino_do_set_br args = {
+               .h_ino  = h_ino,
+               .br     = br
+       };
+
+       args.bshared = sbr_find_shared(sb, /*btop*/0, au_sbbot(sb),
+                                      au_br_sb(br));
+       err = au_xino_do_set_br(sb, base, &args);
+       if (unlikely(err))
+               au_xino_put(br);
+
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * get an unused inode number from bitmap
+ */
+ino_t au_xino_new_ino(struct super_block *sb)
+{
+       ino_t ino;
+       unsigned long *p, pindex, ul, pend;
+       struct au_sbinfo *sbinfo;
+       struct file *file;
+       int free_bit, err;
+
+       if (!au_opt_test(au_mntflags(sb), XINO))
+               return iunique(sb, AUFS_FIRST_INO);
+
+       sbinfo = au_sbi(sb);
+       mutex_lock(&sbinfo->si_xib_mtx);
+       p = sbinfo->si_xib_buf;
+       free_bit = sbinfo->si_xib_next_bit;
+       if (free_bit < page_bits && !test_bit(free_bit, p))
+               goto out; /* success */
+       free_bit = find_first_zero_bit(p, page_bits);
+       if (free_bit < page_bits)
+               goto out; /* success */
+
+       pindex = sbinfo->si_xib_last_pindex;
+       for (ul = pindex - 1; ul < ULONG_MAX; ul--) {
+               err = xib_pindex(sb, ul);
+               if (unlikely(err))
+                       goto out_err;
+               free_bit = find_first_zero_bit(p, page_bits);
+               if (free_bit < page_bits)
+                       goto out; /* success */
+       }
+
+       file = sbinfo->si_xib;
+       pend = vfsub_f_size_read(file) / PAGE_SIZE;
+       for (ul = pindex + 1; ul <= pend; ul++) {
+               err = xib_pindex(sb, ul);
+               if (unlikely(err))
+                       goto out_err;
+               free_bit = find_first_zero_bit(p, page_bits);
+               if (free_bit < page_bits)
+                       goto out; /* success */
+       }
+       BUG();
+
+out:
+       set_bit(free_bit, p);
+       sbinfo->si_xib_next_bit = free_bit + 1;
+       pindex = sbinfo->si_xib_last_pindex;
+       mutex_unlock(&sbinfo->si_xib_mtx);
+       ino = xib_calc_ino(pindex, free_bit);
+       AuDbg("i%lu\n", (unsigned long)ino);
+       return ino;
+out_err:
+       mutex_unlock(&sbinfo->si_xib_mtx);
+       AuDbg("i0\n");
+       return 0;
+}
+
+/* for s_op->delete_inode() */
+void au_xino_delete_inode(struct inode *inode, const int unlinked)
+{
+       int err;
+       unsigned int mnt_flags;
+       aufs_bindex_t bindex, bbot, bi;
+       unsigned char try_trunc;
+       struct au_iinfo *iinfo;
+       struct super_block *sb;
+       struct au_hinode *hi;
+       struct inode *h_inode;
+       struct au_branch *br;
+       struct au_xi_calc calc;
+       struct file *file;
+
+       AuDebugOn(au_is_bad_inode(inode));
+
+       sb = inode->i_sb;
+       mnt_flags = au_mntflags(sb);
+       if (!au_opt_test(mnt_flags, XINO)
+           || inode->i_ino == AUFS_ROOT_INO)
+               return;
+
+       if (unlinked) {
+               au_xigen_inc(inode);
+               au_xib_clear_bit(inode);
+       }
+
+       iinfo = au_ii(inode);
+       bindex = iinfo->ii_btop;
+       if (bindex < 0)
+               return;
+
+       try_trunc = !!au_opt_test(mnt_flags, TRUNC_XINO);
+       hi = au_hinode(iinfo, bindex);
+       bbot = iinfo->ii_bbot;
+       for (; bindex <= bbot; bindex++, hi++) {
+               h_inode = hi->hi_inode;
+               if (!h_inode
+                   || (!unlinked && h_inode->i_nlink))
+                       continue;
+
+               /* inode may not be revalidated */
+               bi = au_br_index(sb, hi->hi_id);
+               if (bi < 0)
+                       continue;
+
+               br = au_sbr(sb, bi);
+               au_xi_calc(sb, h_inode->i_ino, &calc);
+               file = au_xino_file(br->br_xino, calc.idx);
+               if (IS_ERR_OR_NULL(file))
+                       continue;
+
+               err = au_xino_do_write(file, &calc, /*ino*/0);
+               if (!err && try_trunc
+                   && au_test_fs_trunc_xino(au_br_sb(br)))
+                       xino_try_trunc(sb, br);
+       }
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_xinondir_find(struct au_xino *xi, ino_t h_ino)
+{
+       int found, total, i;
+
+       found = -1;
+       total = xi->xi_nondir.total;
+       for (i = 0; i < total; i++) {
+               if (xi->xi_nondir.array[i] != h_ino)
+                       continue;
+               found = i;
+               break;
+       }
+
+       return found;
+}
+
+static int au_xinondir_expand(struct au_xino *xi)
+{
+       int err, sz;
+       ino_t *p;
+
+       BUILD_BUG_ON(KMALLOC_MAX_SIZE > INT_MAX);
+
+       err = -ENOMEM;
+       sz = xi->xi_nondir.total * sizeof(ino_t);
+       if (unlikely(sz > KMALLOC_MAX_SIZE / 2))
+               goto out;
+       p = au_kzrealloc(xi->xi_nondir.array, sz, sz << 1, GFP_ATOMIC,
+                        /*may_shrink*/0);
+       if (p) {
+               xi->xi_nondir.array = p;
+               xi->xi_nondir.total <<= 1;
+               AuDbg("xi_nondir.total %d\n", xi->xi_nondir.total);
+               err = 0;
+       }
+
+out:
+       return err;
+}
+
+void au_xinondir_leave(struct super_block *sb, aufs_bindex_t bindex,
+                      ino_t h_ino, int idx)
+{
+       struct au_xino *xi;
+
+       AuDebugOn(!au_opt_test(au_mntflags(sb), XINO));
+       xi = au_sbr(sb, bindex)->br_xino;
+       AuDebugOn(idx < 0 || xi->xi_nondir.total <= idx);
+
+       spin_lock(&xi->xi_nondir.spin);
+       AuDebugOn(xi->xi_nondir.array[idx] != h_ino);
+       xi->xi_nondir.array[idx] = 0;
+       spin_unlock(&xi->xi_nondir.spin);
+       wake_up_all(&xi->xi_nondir.wqh);
+}
+
+int au_xinondir_enter(struct super_block *sb, aufs_bindex_t bindex, ino_t h_ino,
+                     int *idx)
+{
+       int err, found, empty;
+       struct au_xino *xi;
+
+       err = 0;
+       *idx = -1;
+       if (!au_opt_test(au_mntflags(sb), XINO))
+               goto out; /* no xino */
+
+       xi = au_sbr(sb, bindex)->br_xino;
+
+again:
+       spin_lock(&xi->xi_nondir.spin);
+       found = au_xinondir_find(xi, h_ino);
+       if (found == -1) {
+               empty = au_xinondir_find(xi, /*h_ino*/0);
+               if (empty == -1) {
+                       empty = xi->xi_nondir.total;
+                       err = au_xinondir_expand(xi);
+                       if (unlikely(err))
+                               goto out_unlock;
+               }
+               xi->xi_nondir.array[empty] = h_ino;
+               *idx = empty;
+       } else {
+               spin_unlock(&xi->xi_nondir.spin);
+               wait_event(xi->xi_nondir.wqh,
+                          xi->xi_nondir.array[found] != h_ino);
+               goto again;
+       }
+
+out_unlock:
+       spin_unlock(&xi->xi_nondir.spin);
+out:
+       return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+int au_xino_path(struct seq_file *seq, struct file *file)
+{
+       int err;
+
+       err = au_seq_path(seq, &file->f_path);
+       if (unlikely(err))
+               goto out;
+
+#define Deleted "\\040(deleted)"
+       seq->count -= sizeof(Deleted) - 1;
+       AuDebugOn(memcmp(seq->buf + seq->count, Deleted,
+                        sizeof(Deleted) - 1));
+#undef Deleted
+
+out:
+       return err;
+}
diff -urN /usr/share/empty/include/uapi/linux/aufs_type.h linux/include/uapi/linux/aufs_type.h
--- /usr/share/empty/include/uapi/linux/aufs_type.h     1970-01-01 01:00:00.000000000 +0100
+++ linux/include/uapi/linux/aufs_type.h        2022-01-13 12:42:15.932899468 +0100
@@ -0,0 +1,452 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Copyright (C) 2005-2021 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __AUFS_TYPE_H__
+#define __AUFS_TYPE_H__
+
+#define AUFS_NAME      "aufs"
+
+#ifdef __KERNEL__
+/*
+ * define it before including all other headers.
+ * sched.h may use pr_* macros before defining "current", so define the
+ * no-current version first, and re-define later.
+ */
+#define pr_fmt(fmt)    AUFS_NAME " %s:%d: " fmt, __func__, __LINE__
+#include <linux/sched.h>
+#undef pr_fmt
+#define pr_fmt(fmt) \
+               AUFS_NAME " %s:%d:%.*s[%d]: " fmt, __func__, __LINE__, \
+               (int)sizeof(current->comm), current->comm, current->pid
+#include <linux/limits.h>
+#else
+#include <stdint.h>
+#include <sys/types.h>
+#include <limits.h>
+#endif /* __KERNEL__ */
+
+#define AUFS_VERSION   "5.x-rcN-20211129"
+
+/* todo? move this to linux-2.6.19/include/magic.h */
+#define AUFS_SUPER_MAGIC       ('a' << 24 | 'u' << 16 | 'f' << 8 | 's')
+
+/* ---------------------------------------------------------------------- */
+
+#ifdef __KERNEL__
+#ifdef CONFIG_AUFS_BRANCH_MAX_127
+typedef int8_t aufs_bindex_t;
+#define AUFS_BRANCH_MAX 127
+#else
+typedef int16_t aufs_bindex_t;
+#ifdef CONFIG_AUFS_BRANCH_MAX_511
+#define AUFS_BRANCH_MAX 511
+#elif defined(CONFIG_AUFS_BRANCH_MAX_1023)
+#define AUFS_BRANCH_MAX 1023
+#elif defined(CONFIG_AUFS_BRANCH_MAX_32767)
+#define AUFS_BRANCH_MAX 32767
+#endif
+#endif
+
+#ifndef AUFS_BRANCH_MAX
+#error unknown CONFIG_AUFS_BRANCH_MAX value
+#endif
+#endif /* __KERNEL__ */
+
+/* ---------------------------------------------------------------------- */
+
+#define AUFS_FSTYPE            AUFS_NAME
+
+#define AUFS_ROOT_INO          2
+#define AUFS_FIRST_INO         11
+
+#define AUFS_WH_PFX            ".wh."
+#define AUFS_WH_PFX_LEN                ((int)sizeof(AUFS_WH_PFX) - 1)
+#define AUFS_WH_TMP_LEN                4
+/* a limit for rmdir/rename a dir and copyup */
+#define AUFS_MAX_NAMELEN       (NAME_MAX \
+                               - AUFS_WH_PFX_LEN * 2   /* doubly whiteouted */\
+                               - 1                     /* dot */\
+                               - AUFS_WH_TMP_LEN)      /* hex */
+#define AUFS_XINO_FNAME                "." AUFS_NAME ".xino"
+#define AUFS_XINO_DEFPATH      "/tmp/" AUFS_XINO_FNAME
+#define AUFS_XINO_DEF_SEC      30 /* seconds */
+#define AUFS_XINO_DEF_TRUNC    45 /* percentage */
+#define AUFS_DIRWH_DEF         3
+#define AUFS_RDCACHE_DEF       10 /* seconds */
+#define AUFS_RDCACHE_MAX       3600 /* seconds */
+#define AUFS_RDBLK_DEF         512 /* bytes */
+#define AUFS_RDHASH_DEF                32
+#define AUFS_WKQ_NAME          AUFS_NAME "d"
+#define AUFS_MFS_DEF_SEC       30 /* seconds */
+#define AUFS_MFS_MAX_SEC       3600 /* seconds */
+#define AUFS_FHSM_CACHE_DEF_SEC        30 /* seconds */
+#define AUFS_PLINK_WARN                50 /* number of plinks in a single bucket */
+
+/* pseudo-link maintenace under /proc */
+#define AUFS_PLINK_MAINT_NAME  "plink_maint"
+#define AUFS_PLINK_MAINT_DIR   "fs/" AUFS_NAME
+#define AUFS_PLINK_MAINT_PATH  AUFS_PLINK_MAINT_DIR "/" AUFS_PLINK_MAINT_NAME
+
+/* dirren, renamed dir */
+#define AUFS_DR_INFO_PFX       AUFS_WH_PFX ".dr."
+#define AUFS_DR_BRHINO_NAME    AUFS_WH_PFX "hino"
+/* whiteouted doubly */
+#define AUFS_WH_DR_INFO_PFX    AUFS_WH_PFX AUFS_DR_INFO_PFX
+#define AUFS_WH_DR_BRHINO      AUFS_WH_PFX AUFS_DR_BRHINO_NAME
+
+#define AUFS_DIROPQ_NAME       AUFS_WH_PFX ".opq" /* whiteouted doubly */
+#define AUFS_WH_DIROPQ         AUFS_WH_PFX AUFS_DIROPQ_NAME
+
+#define AUFS_BASE_NAME         AUFS_WH_PFX AUFS_NAME
+#define AUFS_PLINKDIR_NAME     AUFS_WH_PFX "plnk"
+#define AUFS_ORPHDIR_NAME      AUFS_WH_PFX "orph"
+
+/* doubly whiteouted */
+#define AUFS_WH_BASE           AUFS_WH_PFX AUFS_BASE_NAME
+#define AUFS_WH_PLINKDIR       AUFS_WH_PFX AUFS_PLINKDIR_NAME
+#define AUFS_WH_ORPHDIR                AUFS_WH_PFX AUFS_ORPHDIR_NAME
+
+/* branch permissions and attributes */
+#define AUFS_BRPERM_RW         "rw"
+#define AUFS_BRPERM_RO         "ro"
+#define AUFS_BRPERM_RR         "rr"
+#define AUFS_BRATTR_COO_REG    "coo_reg"
+#define AUFS_BRATTR_COO_ALL    "coo_all"
+#define AUFS_BRATTR_FHSM       "fhsm"
+#define AUFS_BRATTR_UNPIN      "unpin"
+#define AUFS_BRATTR_ICEX       "icex"
+#define AUFS_BRATTR_ICEX_SEC   "icexsec"
+#define AUFS_BRATTR_ICEX_SYS   "icexsys"
+#define AUFS_BRATTR_ICEX_TR    "icextr"
+#define AUFS_BRATTR_ICEX_USR   "icexusr"
+#define AUFS_BRATTR_ICEX_OTH   "icexoth"
+#define AUFS_BRRATTR_WH                "wh"
+#define AUFS_BRWATTR_NLWH      "nolwh"
+#define AUFS_BRWATTR_MOO       "moo"
+
+#define AuBrPerm_RW            1               /* writable, hardlinkable wh */
+#define AuBrPerm_RO            (1 << 1)        /* readonly */
+#define AuBrPerm_RR            (1 << 2)        /* natively readonly */
+#define AuBrPerm_Mask          (AuBrPerm_RW | AuBrPerm_RO | AuBrPerm_RR)
+
+#define AuBrAttr_COO_REG       (1 << 3)        /* copy-up on open */
+#define AuBrAttr_COO_ALL       (1 << 4)
+#define AuBrAttr_COO_Mask      (AuBrAttr_COO_REG | AuBrAttr_COO_ALL)
+
+#define AuBrAttr_FHSM          (1 << 5)        /* file-based hsm */
+#define AuBrAttr_UNPIN         (1 << 6)        /* rename-able top dir of
+                                                  branch. meaningless since
+                                                  linux-3.18-rc1 */
+
+/* ignore error in copying XATTR */
+#define AuBrAttr_ICEX_SEC      (1 << 7)
+#define AuBrAttr_ICEX_SYS      (1 << 8)
+#define AuBrAttr_ICEX_TR       (1 << 9)
+#define AuBrAttr_ICEX_USR      (1 << 10)
+#define AuBrAttr_ICEX_OTH      (1 << 11)
+#define AuBrAttr_ICEX          (AuBrAttr_ICEX_SEC      \
+                                | AuBrAttr_ICEX_SYS    \
+                                | AuBrAttr_ICEX_TR     \
+                                | AuBrAttr_ICEX_USR    \
+                                | AuBrAttr_ICEX_OTH)
+
+#define AuBrRAttr_WH           (1 << 12)       /* whiteout-able */
+#define AuBrRAttr_Mask         AuBrRAttr_WH
+
+#define AuBrWAttr_NoLinkWH     (1 << 13)       /* un-hardlinkable whiteouts */
+#define AuBrWAttr_MOO          (1 << 14)       /* move-up on open */
+#define AuBrWAttr_Mask         (AuBrWAttr_NoLinkWH | AuBrWAttr_MOO)
+
+#define AuBrAttr_CMOO_Mask     (AuBrAttr_COO_Mask | AuBrWAttr_MOO)
+
+/* #warning test userspace */
+#ifdef __KERNEL__
+#ifndef CONFIG_AUFS_FHSM
+#undef AuBrAttr_FHSM
+#define AuBrAttr_FHSM          0
+#endif
+#ifndef CONFIG_AUFS_XATTR
+#undef AuBrAttr_ICEX
+#define AuBrAttr_ICEX          0
+#undef AuBrAttr_ICEX_SEC
+#define AuBrAttr_ICEX_SEC      0
+#undef AuBrAttr_ICEX_SYS
+#define AuBrAttr_ICEX_SYS      0
+#undef AuBrAttr_ICEX_TR
+#define AuBrAttr_ICEX_TR       0
+#undef AuBrAttr_ICEX_USR
+#define AuBrAttr_ICEX_USR      0
+#undef AuBrAttr_ICEX_OTH
+#define AuBrAttr_ICEX_OTH      0
+#endif
+#endif
+
+/* the longest combination */
+/* AUFS_BRATTR_ICEX and AUFS_BRATTR_ICEX_TR don't affect here */
+#define AuBrPermStrSz  sizeof(AUFS_BRPERM_RW                   \
+                              "+" AUFS_BRATTR_COO_REG          \
+                              "+" AUFS_BRATTR_FHSM             \
+                              "+" AUFS_BRATTR_UNPIN            \
+                              "+" AUFS_BRATTR_ICEX_SEC         \
+                              "+" AUFS_BRATTR_ICEX_SYS         \
+                              "+" AUFS_BRATTR_ICEX_USR         \
+                              "+" AUFS_BRATTR_ICEX_OTH         \
+                              "+" AUFS_BRWATTR_NLWH)
+
+typedef struct {
+       char a[AuBrPermStrSz];
+} au_br_perm_str_t;
+
+static inline int au_br_writable(int brperm)
+{
+       return brperm & AuBrPerm_RW;
+}
+
+static inline int au_br_whable(int brperm)
+{
+       return brperm & (AuBrPerm_RW | AuBrRAttr_WH);
+}
+
+static inline int au_br_wh_linkable(int brperm)
+{
+       return !(brperm & AuBrWAttr_NoLinkWH);
+}
+
+static inline int au_br_cmoo(int brperm)
+{
+       return brperm & AuBrAttr_CMOO_Mask;
+}
+
+static inline int au_br_fhsm(int brperm)
+{
+       return brperm & AuBrAttr_FHSM;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* ioctl */
+enum {
+       /* readdir in userspace */
+       AuCtl_RDU,
+       AuCtl_RDU_INO,
+
+       AuCtl_WBR_FD,   /* pathconf wrapper */
+       AuCtl_IBUSY,    /* busy inode */
+       AuCtl_MVDOWN,   /* move-down */
+       AuCtl_BR,       /* info about branches */
+       AuCtl_FHSM_FD   /* connection for fhsm */
+};
+
+/* borrowed from linux/include/linux/kernel.h */
+#ifndef ALIGN
+#ifdef _GNU_SOURCE
+#define ALIGN(x, a)            __ALIGN_MASK(x, (typeof(x))(a)-1)
+#else
+#define ALIGN(x, a)            (((x) + (a) - 1) & ~((a) - 1))
+#endif
+#define __ALIGN_MASK(x, mask)  (((x)+(mask))&~(mask))
+#endif
+
+/* borrowed from linux/include/linux/compiler-gcc3.h */
+#ifndef __aligned
+#define __aligned(x)                   __attribute__((aligned(x)))
+#endif
+
+#ifdef __KERNEL__
+#ifndef __packed
+#define __packed                       __attribute__((packed))
+#endif
+#endif
+
+struct au_rdu_cookie {
+       uint64_t        h_pos;
+       int16_t         bindex;
+       uint8_t         flags;
+       uint8_t         pad;
+       uint32_t        generation;
+} __aligned(8);
+
+struct au_rdu_ent {
+       uint64_t        ino;
+       int16_t         bindex;
+       uint8_t         type;
+       uint8_t         nlen;
+       uint8_t         wh;
+       char            name[];
+} __aligned(8);
+
+static inline int au_rdu_len(int nlen)
+{
+       /* include the terminating NULL */
+       return ALIGN(sizeof(struct au_rdu_ent) + nlen + 1,
+                    sizeof(uint64_t));
+}
+
+union au_rdu_ent_ul {
+       struct au_rdu_ent __user        *e;
+       uint64_t                        ul;
+};
+
+enum {
+       AufsCtlRduV_SZ,
+       AufsCtlRduV_End
+};
+
+struct aufs_rdu {
+       /* input */
+       union {
+               uint64_t        sz;     /* AuCtl_RDU */
+               uint64_t        nent;   /* AuCtl_RDU_INO */
+       };
+       union au_rdu_ent_ul     ent;
+       uint16_t                verify[AufsCtlRduV_End];
+
+       /* input/output */
+       uint32_t                blk;
+
+       /* output */
+       union au_rdu_ent_ul     tail;
+       /* number of entries which were added in a single call */
+       uint64_t                rent;
+       uint8_t                 full;
+       uint8_t                 shwh;
+
+       struct au_rdu_cookie    cookie;
+} __aligned(8);
+
+/* ---------------------------------------------------------------------- */
+
+/* dirren. the branch is identified by the filename who contains this */
+struct au_drinfo {
+       uint64_t ino;
+       union {
+               uint8_t oldnamelen;
+               uint64_t _padding;
+       };
+       uint8_t oldname[];
+} __aligned(8);
+
+struct au_drinfo_fdata {
+       uint32_t magic;
+       struct au_drinfo drinfo;
+} __aligned(8);
+
+#define AUFS_DRINFO_MAGIC_V1   ('a' << 24 | 'd' << 16 | 'r' << 8 | 0x01)
+/* future */
+#define AUFS_DRINFO_MAGIC_V2   ('a' << 24 | 'd' << 16 | 'r' << 8 | 0x02)
+
+/* ---------------------------------------------------------------------- */
+
+struct aufs_wbr_fd {
+       uint32_t        oflags;
+       int16_t         brid;
+} __aligned(8);
+
+/* ---------------------------------------------------------------------- */
+
+struct aufs_ibusy {
+       uint64_t        ino, h_ino;
+       int16_t         bindex;
+} __aligned(8);
+
+/* ---------------------------------------------------------------------- */
+
+/* error code for move-down */
+/* the actual message strings are implemented in aufs-util.git */
+enum {
+       EAU_MVDOWN_OPAQUE = 1,
+       EAU_MVDOWN_WHITEOUT,
+       EAU_MVDOWN_UPPER,
+       EAU_MVDOWN_BOTTOM,
+       EAU_MVDOWN_NOUPPER,
+       EAU_MVDOWN_NOLOWERBR,
+       EAU_Last
+};
+
+/* flags for move-down */
+#define AUFS_MVDOWN_DMSG       1
+#define AUFS_MVDOWN_OWLOWER    (1 << 1)        /* overwrite lower */
+#define AUFS_MVDOWN_KUPPER     (1 << 2)        /* keep upper */
+#define AUFS_MVDOWN_ROLOWER    (1 << 3)        /* do even if lower is RO */
+#define AUFS_MVDOWN_ROLOWER_R  (1 << 4)        /* did on lower RO */
+#define AUFS_MVDOWN_ROUPPER    (1 << 5)        /* do even if upper is RO */
+#define AUFS_MVDOWN_ROUPPER_R  (1 << 6)        /* did on upper RO */
+#define AUFS_MVDOWN_BRID_UPPER (1 << 7)        /* upper brid */
+#define AUFS_MVDOWN_BRID_LOWER (1 << 8)        /* lower brid */
+#define AUFS_MVDOWN_FHSM_LOWER (1 << 9)        /* find fhsm attr for lower */
+#define AUFS_MVDOWN_STFS       (1 << 10)       /* req. stfs */
+#define AUFS_MVDOWN_STFS_FAILED        (1 << 11)       /* output: stfs is unusable */
+#define AUFS_MVDOWN_BOTTOM     (1 << 12)       /* output: no more lowers */
+
+/* index for move-down */
+enum {
+       AUFS_MVDOWN_UPPER,
+       AUFS_MVDOWN_LOWER,
+       AUFS_MVDOWN_NARRAY
+};
+
+/*
+ * additional info of move-down
+ * number of free blocks and inodes.
+ * subset of struct kstatfs, but smaller and always 64bit.
+ */
+struct aufs_stfs {
+       uint64_t        f_blocks;
+       uint64_t        f_bavail;
+       uint64_t        f_files;
+       uint64_t        f_ffree;
+};
+
+struct aufs_stbr {
+       int16_t                 brid;   /* optional input */
+       int16_t                 bindex; /* output */
+       struct aufs_stfs        stfs;   /* output when AUFS_MVDOWN_STFS set */
+} __aligned(8);
+
+struct aufs_mvdown {
+       uint32_t                flags;                  /* input/output */
+       struct aufs_stbr        stbr[AUFS_MVDOWN_NARRAY]; /* input/output */
+       int8_t                  au_errno;               /* output */
+} __aligned(8);
+
+/* ---------------------------------------------------------------------- */
+
+union aufs_brinfo {
+       /* PATH_MAX may differ between kernel-space and user-space */
+       char    _spacer[4096];
+       struct {
+               int16_t id;
+               int     perm;
+               char    path[];
+       };
+} __aligned(8);
+
+/* ---------------------------------------------------------------------- */
+
+#define AuCtlType              'A'
+#define AUFS_CTL_RDU           _IOWR(AuCtlType, AuCtl_RDU, struct aufs_rdu)
+#define AUFS_CTL_RDU_INO       _IOWR(AuCtlType, AuCtl_RDU_INO, struct aufs_rdu)
+#define AUFS_CTL_WBR_FD                _IOW(AuCtlType, AuCtl_WBR_FD, \
+                                    struct aufs_wbr_fd)
+#define AUFS_CTL_IBUSY         _IOWR(AuCtlType, AuCtl_IBUSY, struct aufs_ibusy)
+#define AUFS_CTL_MVDOWN                _IOWR(AuCtlType, AuCtl_MVDOWN, \
+                                     struct aufs_mvdown)
+#define AUFS_CTL_BRINFO                _IOW(AuCtlType, AuCtl_BR, union aufs_brinfo)
+#define AUFS_CTL_FHSM_FD       _IOW(AuCtlType, AuCtl_FHSM_FD, int)
+
+#endif /* __AUFS_TYPE_H__ */
SPDX-License-Identifier: GPL-2.0
aufs5.x-rcN loopback patch

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 52776d48e306a..64112f1cf8b18 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -509,6 +509,15 @@ static inline void loop_update_dio(struct loop_device *lo)
                                lo->use_dio);
 }
 
+static struct file *loop_real_file(struct file *file)
+{
+       struct file *f = NULL;
+
+       if (file->f_path.dentry->d_sb->s_op->real_loop)
+               f = file->f_path.dentry->d_sb->s_op->real_loop(file);
+       return f;
+}
+
 static void loop_reread_partitions(struct loop_device *lo)
 {
        int rc;
@@ -566,6 +575,7 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
 {
        struct file *file = fget(arg);
        struct file *old_file;
+       struct file *f, *virt_file = NULL, *old_virt_file;
        int error;
        bool partscan;
        bool is_loop;
@@ -585,11 +595,19 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
        if (!(lo->lo_flags & LO_FLAGS_READ_ONLY))
                goto out_err;
 
+       f = loop_real_file(file);
+       if (f) {
+               virt_file = file;
+               file = f;
+               get_file(file);
+       }
+
        error = loop_validate_file(file, bdev);
        if (error)
                goto out_err;
 
        old_file = lo->lo_backing_file;
+       old_virt_file = lo->lo_backing_virt_file;
 
        error = -EINVAL;
 
@@ -602,6 +620,7 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
        blk_mq_freeze_queue(lo->lo_queue);
        mapping_set_gfp_mask(old_file->f_mapping, lo->old_gfp_mask);
        lo->lo_backing_file = file;
+       lo->lo_backing_virt_file = virt_file;
        lo->old_gfp_mask = mapping_gfp_mask(file->f_mapping);
        mapping_set_gfp_mask(file->f_mapping,
                             lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
@@ -624,6 +643,8 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
         * dependency.
         */
        fput(old_file);
+       if (old_virt_file)
+               fput(old_virt_file);
        if (partscan)
                loop_reread_partitions(lo);
        return 0;
@@ -632,6 +653,8 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
        loop_global_unlock(lo, is_loop);
 out_putf:
        fput(file);
+       if (virt_file)
+               fput(virt_file);
        return error;
 }
 
@@ -965,6 +988,7 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
                          const struct loop_config *config)
 {
        struct file *file = fget(config->fd);
+       struct file *f, *virt_file = NULL;
        struct inode *inode;
        struct address_space *mapping;
        int error;
@@ -980,6 +1004,13 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
        /* This is safe, since we have a reference from open(). */
        __module_get(THIS_MODULE);
 
+       f = loop_real_file(file);
+       if (f) {
+               virt_file = file;
+               file = f;
+               get_file(file);
+       }
+
        /*
         * If we don't hold exclusive handle for the device, upgrade to it
         * here to avoid changing device under exclusive owner.
@@ -1045,6 +1076,7 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
        lo->use_dio = lo->lo_flags & LO_FLAGS_DIRECT_IO;
        lo->lo_device = bdev;
        lo->lo_backing_file = file;
+       lo->lo_backing_virt_file = virt_file;
        lo->old_gfp_mask = mapping_gfp_mask(mapping);
        mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
 
@@ -1095,6 +1127,8 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
                bd_abort_claiming(bdev, loop_configure);
 out_putf:
        fput(file);
+       if (virt_file)
+               fput(virt_file);
        /* This is safe: open() is still holding a reference. */
        module_put(THIS_MODULE);
        return error;
@@ -1103,6 +1137,7 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
 static int __loop_clr_fd(struct loop_device *lo, bool release)
 {
        struct file *filp = NULL;
+       struct file *virt_filp = lo->lo_backing_virt_file;
        gfp_t gfp = lo->old_gfp_mask;
        int err = 0;
        bool partscan = false;
@@ -1153,6 +1188,7 @@ static int __loop_clr_fd(struct loop_device *lo, bool release)
 
        spin_lock_irq(&lo->lo_lock);
        lo->lo_backing_file = NULL;
+       lo->lo_backing_virt_file = NULL;
        spin_unlock_irq(&lo->lo_lock);
 
        lo->lo_device = NULL;
@@ -1220,6 +1256,8 @@ static int __loop_clr_fd(struct loop_device *lo, bool release)
         */
        if (filp)
                fput(filp);
+       if (virt_filp)
+               fput(virt_filp);
        return err;
 }
 
diff --git a/drivers/block/loop.h b/drivers/block/loop.h
index 082d4b6bfc6a6..61feca64688df 100644
--- a/drivers/block/loop.h
+++ b/drivers/block/loop.h
@@ -34,7 +34,7 @@ struct loop_device {
        int             lo_flags;
        char            lo_file_name[LO_NAME_SIZE];
 
-       struct file *   lo_backing_file;
+       struct file     *lo_backing_file, *lo_backing_virt_file;
        struct block_device *lo_device;
 
        gfp_t           old_gfp_mask;
diff --git a/fs/aufs/f_op.c b/fs/aufs/f_op.c
index 99ceca1440449..e49dfe8550329 100644
--- a/fs/aufs/f_op.c
+++ b/fs/aufs/f_op.c
@@ -304,7 +304,7 @@ static ssize_t aufs_read_iter(struct kiocb *kio, struct iov_iter *iov_iter)
        if (IS_ERR(h_file))
                goto out;
 
-       if (au_test_loopback_kthread()) {
+       if (0 && au_test_loopback_kthread()) {
                au_warn_loopback(h_file->f_path.dentry->d_sb);
                if (file->f_mapping != h_file->f_mapping) {
                        file->f_mapping = h_file->f_mapping;
diff --git a/fs/aufs/loop.c b/fs/aufs/loop.c
index 74347bd75b380..5ef888a1d53f4 100644
--- a/fs/aufs/loop.c
+++ b/fs/aufs/loop.c
@@ -133,3 +133,19 @@ void au_loopback_fin(void)
                symbol_put(loop_backing_file);
        au_kfree_try_rcu(au_warn_loopback_array);
 }
+
+/* ---------------------------------------------------------------------- */
+
+/* support the loopback block device insude aufs */
+
+struct file *aufs_real_loop(struct file *file)
+{
+       struct file *f;
+
+       BUG_ON(!au_test_aufs(file->f_path.dentry->d_sb));
+       fi_read_lock(file);
+       f = au_hf_top(file);
+       fi_read_unlock(file);
+       AuDebugOn(!f);
+       return f;
+}
diff --git a/fs/aufs/loop.h b/fs/aufs/loop.h
index 7293bee427f96..3345c098d0d47 100644
--- a/fs/aufs/loop.h
+++ b/fs/aufs/loop.h
@@ -26,6 +26,8 @@ void au_warn_loopback(struct super_block *h_sb);
 
 int au_loopback_init(void);
 void au_loopback_fin(void);
+
+struct file *aufs_real_loop(struct file *file);
 #else
 AuStub(struct file *, loop_backing_file, return NULL, struct super_block *sb)
 
@@ -36,6 +38,8 @@ AuStubVoid(au_warn_loopback, struct super_block *h_sb)
 
 AuStubInt0(au_loopback_init, void)
 AuStubVoid(au_loopback_fin, void)
+
+AuStub(struct file *, aufs_real_loop, return NULL, struct file *file)
 #endif /* BLK_DEV_LOOP */
 
 #endif /* __KERNEL__ */
diff --git a/fs/aufs/super.c b/fs/aufs/super.c
index cfa90537d9d38..028ee1ceeed1a 100644
--- a/fs/aufs/super.c
+++ b/fs/aufs/super.c
@@ -844,7 +844,10 @@ static const struct super_operations aufs_sop = {
        .statfs         = aufs_statfs,
        .put_super      = aufs_put_super,
        .sync_fs        = aufs_sync_fs,
-       .remount_fs     = aufs_remount_fs
+       .remount_fs     = aufs_remount_fs,
+#ifdef CONFIG_AUFS_BDEV_LOOP
+       .real_loop      = aufs_real_loop
+#endif
 };
 
 /* ---------------------------------------------------------------------- */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 02ce64c28ef15..eed5ad4a414ac 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2225,6 +2225,10 @@ struct super_operations {
                                  struct shrink_control *);
        long (*free_cached_objects)(struct super_block *,
                                    struct shrink_control *);
+#if IS_ENABLED(CONFIG_BLK_DEV_LOOP) || IS_ENABLED(CONFIG_BLK_DEV_LOOP_MODULE)
+       /* and aufs */
+       struct file *(*real_loop)(struct file *);
+#endif
 };
 
 /*