From b0c34c08a36aafbbb2240d384935343feefb68f3 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Thu, 30 Aug 2012 16:13:49 +0200 Subject: [PATCH 01/13] vfs: add i_op->dentry_open() Patch-mainline: not yet Add a new inode operation i_op->dentry_open(). This is for stacked filesystems that want to return a struct file from a different filesystem. Signed-off-by: Miklos Szeredi --- Documentation/filesystems/Locking | 2 ++ Documentation/filesystems/vfs.txt | 7 +++++++ fs/namei.c | 9 ++++++--- fs/open.c | 23 +++++++++++++++++++++-- include/linux/fs.h | 2 ++ 5 files changed, 38 insertions(+), 5 deletions(-) --- a/Documentation/filesystems/Locking +++ b/Documentation/filesystems/Locking @@ -66,6 +66,7 @@ d_manage: no no yes (ref-walk) maybe struct file *, unsigned open_flag, umode_t create_mode, int *opened); int (*tmpfile) (struct inode *, struct dentry *, umode_t); + int (*dentry_open)(struct dentry *, struct file *, const struct cred *); locking rules: all may block @@ -93,6 +94,7 @@ removexattr: yes update_time: no atomic_open: yes tmpfile: no +dentry_open: no Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on victim. --- a/Documentation/filesystems/vfs.txt +++ b/Documentation/filesystems/vfs.txt @@ -362,6 +362,7 @@ struct inode_operations { int (*atomic_open)(struct inode *, struct dentry *, struct file *, unsigned open_flag, umode_t create_mode, int *opened); int (*tmpfile) (struct inode *, struct dentry *, umode_t); + int (*dentry_open)(struct dentry *, struct file *, const struct cred *); }; Again, all methods are called without any locks being held, unless @@ -681,6 +682,12 @@ struct address_space_operations { but instead uses bmap to find out where the blocks in the file are and uses those addresses directly. + dentry_open: this is an alternative to f_op->open(), the difference is that + this method may open a file not necessarily originating from the same + filesystem as the one i_op->open() was called on. It may be + useful for stacking filesystems which want to allow native I/O directly + on underlying files. + invalidatepage: If a page has PagePrivate set, then invalidatepage will be called when part or all of the page is to be removed --- a/fs/namei.c +++ b/fs/namei.c @@ -2915,9 +2915,12 @@ static int do_last(struct nameidata *nd, error = may_open(&nd->path, acc_mode, open_flag); if (error) goto out; - file->f_path.mnt = nd->path.mnt; - error = finish_open(file, nd->path.dentry, NULL, opened); - if (error) { + + BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */ + error = vfs_open(&nd->path, file, current_cred()); + if (!error) { + *opened |= FILE_OPENED; + } else { if (error == -EOPENSTALE) goto stale_open; goto out; --- a/fs/open.c +++ b/fs/open.c @@ -800,8 +800,7 @@ struct file *dentry_open(const struct pa f = get_empty_filp(); if (!IS_ERR(f)) { f->f_flags = flags; - f->f_path = *path; - error = do_dentry_open(f, NULL, cred); + error = vfs_open(path, f, cred); if (!error) { /* from now on we need fput() to dispose of f */ error = open_check_o_direct(f); @@ -818,6 +817,26 @@ struct file *dentry_open(const struct pa } EXPORT_SYMBOL(dentry_open); +/** + * vfs_open - open the file at the given path + * @path: path to open + * @filp: newly allocated file with f_flag initialized + * @cred: credentials to use + */ +int vfs_open(const struct path *path, struct file *filp, + const struct cred *cred) +{ + struct inode *inode = path->dentry->d_inode; + + if (inode->i_op->dentry_open) + return inode->i_op->dentry_open(path->dentry, filp, cred); + else { + filp->f_path = *path; + return do_dentry_open(filp, NULL, cred); + } +} +EXPORT_SYMBOL(vfs_open); + static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op) { int lookup_flags = 0; --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1585,6 +1585,7 @@ struct inode_operations { umode_t create_mode, int *opened); int (*tmpfile) (struct inode *, struct dentry *, umode_t); int (*set_acl)(struct inode *, struct posix_acl *, int); + int (*dentry_open)(struct dentry *, struct file *, const struct cred *); } ____cacheline_aligned; ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector, @@ -2019,6 +2020,7 @@ extern struct file *file_open_name(struc extern struct file *filp_open(const char *, int, umode_t); extern struct file *file_open_root(struct dentry *, struct vfsmount *, const char *, int); +extern int vfs_open(const struct path *, struct file *, const struct cred *); extern struct file * dentry_open(const struct path *, int, const struct cred *); extern int filp_close(struct file *, fl_owner_t id);