- up to 3.5.2

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

diff --git a/Documentation/filesystems/00-INDEX b/Documentation/filesystems/00-INDEX
index 8c624a1..4aa288b 100644
--- a/Documentation/filesystems/00-INDEX
+++ b/Documentation/filesystems/00-INDEX
@@ -110,6 +110,8 @@ udf.txt
        - info and mount options for the UDF filesystem.
 ufs.txt
        - info on the ufs filesystem.
+unionfs/
+       - info on the unionfs filesystem
 vfat.txt
        - info on using the VFAT filesystem used in Windows NT and Windows 95
 vfs.txt
diff --git a/Documentation/filesystems/unionfs/00-INDEX b/Documentation/filesystems/unionfs/00-INDEX
new file mode 100644
index 0000000..96fdf67
--- /dev/null
+++ b/Documentation/filesystems/unionfs/00-INDEX
@@ -0,0 +1,10 @@
+00-INDEX
+       - this file.
+concepts.txt
+       - A brief introduction of concepts.
+issues.txt
+       - A summary of known issues with unionfs.
+rename.txt
+       - Information regarding rename operations.
+usage.txt
+       - Usage information and examples.
diff --git a/Documentation/filesystems/unionfs/concepts.txt b/Documentation/filesystems/unionfs/concepts.txt
new file mode 100644
index 0000000..b853788
--- /dev/null
+++ b/Documentation/filesystems/unionfs/concepts.txt
@@ -0,0 +1,287 @@
+Unionfs 2.x CONCEPTS:
+=====================
+
+This file describes the concepts needed by a namespace unification file
+system.
+
+
+Branch Priority:
+================
+
+Each branch is assigned a unique priority - starting from 0 (highest
+priority).  No two branches can have the same priority.
+
+
+Branch Mode:
+============
+
+Each branch is assigned a mode - read-write or read-only. This allows
+directories on media mounted read-write to be used in a read-only manner.
+
+
+Whiteouts:
+==========
+
+A whiteout removes a file name from the namespace. Whiteouts are needed when
+one attempts to remove a file on a read-only branch.
+
+Suppose we have a two-branch union, where branch 0 is read-write and branch
+1 is read-only. And a file 'foo' on branch 1:
+
+./b0/
+./b1/
+./b1/foo
+
+The unified view would simply be:
+
+./union/
+./union/foo
+
+Since 'foo' is stored on a read-only branch, it cannot be removed. A
+whiteout is used to remove the name 'foo' from the unified namespace. Again,
+since branch 1 is read-only, the whiteout cannot be created there. So, we
+try on a higher priority (lower numerically) branch and create the whiteout
+there.
+
+./b0/
+./b0/.wh.foo
+./b1/
+./b1/foo
+
+Later, when Unionfs traverses branches (due to lookup or readdir), it
+eliminate 'foo' from the namespace (as well as the whiteout itself.)
+
+
+Opaque Directories:
+===================
+
+Assume we have a unionfs mount comprising of two branches.  Branch 0 is
+empty; branch 1 has the directory /a and file /a/f.  Let's say we mount a
+union of branch 0 as read-write and branch 1 as read-only.  Now, let's say
+we try to perform the following operation in the union:
+
+       rm -fr a
+
+Because branch 1 is not writable, we cannot physically remove the file /a/f
+or the directory /a.  So instead, we will create a whiteout in branch 0
+named /.wh.a, masking out the name "a" from branch 1.  Next, let's say we
+try to create a directory named "a" as follows:
+
+       mkdir a
+
+Because we have a whiteout for "a" already, Unionfs behaves as if "a"
+doesn't exist, and thus will delete the whiteout and replace it with an
+actual directory named "a".
+
+The problem now is that if you try to "ls" in the union, Unionfs will
+perform is normal directory name unification, for *all* directories named
+"a" in all branches.  This will cause the file /a/f from branch 1 to
+re-appear in the union's namespace, which violates Unix semantics.
+
+To avoid this problem, we have a different form of whiteouts for
+directories, called "opaque directories" (same as BSD Union Mount does).
+Whenever we replace a whiteout with a directory, that directory is marked as
+opaque.  In Unionfs 2.x, it means that we create a file named
+/a/.wh.__dir_opaque in branch 0, after having created directory /a there.
+When unionfs notices that a directory is opaque, it stops all namespace
+operations (including merging readdir contents) at that opaque directory.
+This prevents re-exposing names from masked out directories.
+
+
+Duplicate Elimination:
+======================
+
+It is possible for files on different branches to have the same name.
+Unionfs then has to select which instance of the file to show to the user.
+Given the fact that each branch has a priority associated with it, the
+simplest solution is to take the instance from the highest priority
+(numerically lowest value) and "hide" the others.
+
+
+Unlinking:
+=========
+
+Unlink operation on non-directory instances is optimized to remove the
+maximum possible objects in case multiple underlying branches have the same
+file name.  The unlink operation will first try to delete file instances
+from highest priority branch and then move further to delete from remaining
+branches in order of their decreasing priority.  Consider a case (F..D..F),
+where F is a file and D is a directory of the same name; here, some
+intermediate branch could have an empty directory instance with the same
+name, so this operation also tries to delete this directory instance and
+proceed further to delete from next possible lower priority branch.  The
+unionfs unlink operation will smoothly delete the files with same name from
+all possible underlying branches.  In case if some error occurs, it creates
+whiteout in highest priority branch that will hide file instance in rest of
+the branches.  An error could occur either if an unlink operations in any of
+the underlying branch failed or if a branch has no write permission.
+
+This unlinking policy is known as "delete all" and it has the benefit of
+overall reducing the number of inodes used by duplicate files, and further
+reducing the total number of inodes consumed by whiteouts.  The cost is of
+extra processing, but testing shows this extra processing is well worth the
+savings.
+
+
+Copyup:
+=======
+
+When a change is made to the contents of a file's data or meta-data, they
+have to be stored somewhere.  The best way is to create a copy of the
+original file on a branch that is writable, and then redirect the write
+though to this copy.  The copy must be made on a higher priority branch so
+that lookup and readdir return this newer "version" of the file rather than
+the original (see duplicate elimination).
+
+An entire unionfs mount can be read-only or read-write.  If it's read-only,
+then none of the branches will be written to, even if some of the branches
+are physically writeable.  If the unionfs mount is read-write, then the
+leftmost (highest priority) branch must be writeable (for copyup to take
+place); the remaining branches can be any mix of read-write and read-only.
+
+In a writeable mount, unionfs will create new files/dir in the leftmost
+branch.  If one tries to modify a file in a read-only branch/media, unionfs
+will copyup the file to the leftmost branch and modify it there.  If you try
+to modify a file from a writeable branch which is not the leftmost branch,
+then unionfs will modify it in that branch; this is useful if you, say,
+unify differnet packages (e.g., apache, sendmail, ftpd, etc.) and you want
+changes to specific package files to remain logically in the directory where
+they came from.
+
+Cache Coherency:
+================
+
+Unionfs users often want to be able to modify files and directories directly
+on the lower branches, and have those changes be visible at the Unionfs
+level.  This means that data (e.g., pages) and meta-data (dentries, inodes,
+open files, etc.) have to be synchronized between the upper and lower
+layers.  In other words, the newest changes from a layer below have to be
+propagated to the Unionfs layer above.  If the two layers are not in sync, a
+cache incoherency ensues, which could lead to application failures and even
+oopses.  The Linux kernel, however, has a rather limited set of mechanisms
+to ensure this inter-layer cache coherency---so Unionfs has to do most of
+the hard work on its own.
+
+Maintaining Invariants:
+
+The way Unionfs ensures cache coherency is as follows.  At each entry point
+to a Unionfs file system method, we call a utility function to validate the
+primary objects of this method.  Generally, we call unionfs_file_revalidate
+on open files, and __unionfs_d_revalidate_chain on dentries (which also
+validates inodes).  These utility functions check to see whether the upper
+Unionfs object is in sync with any of the lower objects that it represents.
+The checks we perform include whether the Unionfs superblock has a newer
+generation number, or if any of the lower objects mtime's or ctime's are
+newer.  (Note: generation numbers change when branch-management commands are
+issued, so in a way, maintaining cache coherency is also very important for
+branch-management.)  If indeed we determine that any Unionfs object is no
+longer in sync with its lower counterparts, then we rebuild that object
+similarly to how we do so for branch-management.
+
+While rebuilding Unionfs's objects, we also purge any page mappings and
+truncate inode pages (see fs/unionfs/dentry.c:purge_inode_data).  This is to
+ensure that Unionfs will re-get the newer data from the lower branches.  We
+perform this purging only if the Unionfs operation in question is a reading
+operation; if Unionfs is performing a data writing operation (e.g., ->write,
+->commit_write, etc.) then we do NOT flush the lower mappings/pages: this is
+because (1) a self-deadlock could occur and (2) the upper Unionfs pages are
+considered more authoritative anyway, as they are newer and will overwrite
+any lower pages.
+
+Unionfs maintains the following important invariant regarding mtime's,
+ctime's, and atime's: the upper inode object's times are the max() of all of
+the lower ones.  For non-directory objects, there's only one object below,
+so the mapping is simple; for directory objects, there could me multiple
+lower objects and we have to sync up with the newest one of all the lower
+ones.  This invariant is important to maintain, especially for directories
+(besides, we need this to be POSIX compliant).  A union could comprise
+multiple writable branches, each of which could change.  If we don't reflect
+the newest possible mtime/ctime, some applications could fail.  For example,
+NFSv2/v3 exports check for newer directory mtimes on the server to determine
+if the client-side attribute cache should be purged.
+
+To maintain these important invariants, of course, Unionfs carefully
+synchronizes upper and lower times in various places.  For example, if we
+copy-up a file to a top-level branch, the parent directory where the file
+was copied up to will now have a new mtime: so after a successful copy-up,
+we sync up with the new top-level branch's parent directory mtime.
+
+Implementation:
+
+This cache-coherency implementation is efficient because it defers any
+synchronizing between the upper and lower layers until absolutely needed.
+Consider the example a common situation where users perform a lot of lower
+changes, such as untarring a whole package.  While these take place,
+typically the user doesn't access the files via Unionfs; only after the
+lower changes are done, does the user try to access the lower files.  With
+our cache-coherency implementation, the entirety of the changes to the lower
+branches will not result in a single CPU cycle spent at the Unionfs level
+until the user invokes a system call that goes through Unionfs.
+
+We have considered two alternate cache-coherency designs.  (1) Using the
+dentry/inode notify functionality to register interest in finding out about
+any lower changes.  This is a somewhat limited and also a heavy-handed
+approach which could result in many notifications to the Unionfs layer upon
+each small change at the lower layer (imagine a file being modified multiple
+times in rapid succession).  (2) Rewriting the VFS to support explicit
+callbacks from lower objects to upper objects.  We began exploring such an
+implementation, but found it to be very complicated--it would have resulted
+in massive VFS/MM changes which are unlikely to be accepted by the LKML
+community.  We therefore believe that our current cache-coherency design and
+implementation represent the best approach at this time.
+
+Limitations:
+
+Our implementation works in that as long as a user process will have caused
+Unionfs to be called, directly or indirectly, even to just do
+->d_revalidate; then we will have purged the current Unionfs data and the
+process will see the new data.  For example, a process that continually
+re-reads the same file's data will see the NEW data as soon as the lower
+file had changed, upon the next read(2) syscall (even if the file is still
+open!)  However, this doesn't work when the process re-reads the open file's
+data via mmap(2) (unless the user unmaps/closes the file and remaps/reopens
+it).  Once we respond to ->readpage(s), then the kernel maps the page into
+the process's address space and there doesn't appear to be a way to force
+the kernel to invalidate those pages/mappings, and force the process to
+re-issue ->readpage.  If there's a way to invalidate active mappings and
+force a ->readpage, let us know please (invalidate_inode_pages2 doesn't do
+the trick).
+
+Our current Unionfs code has to perform many file-revalidation calls.  It
+would be really nice if the VFS would export an optional file system hook
+->file_revalidate (similarly to dentry->d_revalidate) that will be called
+before each VFS op that has a "struct file" in it.
+
+Certain file systems have micro-second granularity (or better) for inode
+times, and asynchronous actions could cause those times to change with some
+small delay.  In such cases, Unionfs may see a changed inode time that only
+differs by a tiny fraction of a second: such a change may be a false
+positive indication that the lower object has changed, whereas if unionfs
+waits a little longer, that false indication will not be seen.  (These false
+positives are harmless, because they would at most cause unionfs to
+re-validate an object that may need no revalidation, and print a debugging
+message that clutters the console/logs.)  Therefore, to minimize the chances
+of these situations, we delay the detection of changed times by a small
+factor of a few seconds, called UNIONFS_MIN_CC_TIME (which defaults to 3
+seconds, as does NFS).  This means that we will detect the change, only a
+couple of seconds later, if indeed the time change persists in the lower
+file object.  This delayed detection has an added performance benefit: we
+reduce the number of times that unionfs has to revalidate objects, in case
+there's a lot of concurrent activity on both the upper and lower objects,
+for the same file(s).  Lastly, this delayed time attribute detection is
+similar to how NFS clients operate (e.g., acregmin).
+
+Finally, there is no way currently in Linux to prevent lower directories
+from being moved around (i.e., topology changes); there's no way to prevent
+modifications to directory sub-trees of whole file systems which are mounted
+read-write.  It is therefore possible for in-flight operations in unionfs to
+take place, while a lower directory is being moved around.  Therefore, if
+you try to, say, create a new file in a directory through unionfs, while the
+directory is being moved around directly, then the new file may get created
+in the new location where that directory was moved to.  This is a somewhat
+similar behaviour in NFS: an NFS client could be creating a new file while
+th NFS server is moving th directory around; the file will get successfully
+created in the new location.  (The one exception in unionfs is that if the
+branch is marked read-only by unionfs, then a copyup will take place.)
+
+For more information, see <http://unionfs.filesystems.org/>.
diff --git a/Documentation/filesystems/unionfs/issues.txt b/Documentation/filesystems/unionfs/issues.txt
new file mode 100644
index 0000000..f4b7e7e
--- /dev/null
+++ b/Documentation/filesystems/unionfs/issues.txt
@@ -0,0 +1,28 @@
+KNOWN Unionfs 2.x ISSUES:
+=========================
+
+1. Unionfs should not use lookup_one_len() on the underlying f/s as it
+   confuses NFSv4.  Currently, unionfs_lookup() passes lookup intents to the
+   lower file-system, this eliminates part of the problem.  The remaining
+   calls to lookup_one_len may need to be changed to pass an intent.  We are
+   currently introducing VFS changes to fs/namei.c's do_path_lookup() to
+   allow proper file lookup and opening in stackable file systems.
+
+2. Lockdep (a debugging feature) isn't aware of stacking, and so it
+   incorrectly complains about locking problems.  The problem boils down to
+   this: Lockdep considers all objects of a certain type to be in the same
+   class, for example, all inodes.  Lockdep doesn't like to see a lock held
+   on two inodes within the same task, and warns that it could lead to a
+   deadlock.  However, stackable file systems do precisely that: they lock
+   an upper object, and then a lower object, in a strict order to avoid
+   locking problems; in addition, Unionfs, as a fan-out file system, may
+   have to lock several lower inodes.  We are currently looking into Lockdep
+   to see how to make it aware of stackable file systems.  For now, we
+   temporarily disable lockdep when calling vfs methods on lower objects,
+   but only for those places where lockdep complained.  While this solution
+   may seem unclean, it is not without precedent: other places in the kernel
+   also do similar temporary disabling, of course after carefully having
+   checked that it is the right thing to do.  Anyway, you get any warnings
+   from Lockdep, please report them to the Unionfs maintainers.
+
+For more information, see <http://unionfs.filesystems.org/>.
diff --git a/Documentation/filesystems/unionfs/rename.txt b/Documentation/filesystems/unionfs/rename.txt
new file mode 100644
index 0000000..e20bb82
--- /dev/null
+++ b/Documentation/filesystems/unionfs/rename.txt
@@ -0,0 +1,31 @@
+Rename is a complex beast. The following table shows which rename(2) operations
+should succeed and which should fail.
+
+o: success
+E: error (either unionfs or vfs)
+X: EXDEV
+
+none = file does not exist
+file = file is a file
+dir  = file is a empty directory
+child= file is a non-empty directory
+wh   = file is a directory containing only whiteouts; this makes it logically
+               empty
+
+                      none    file    dir     child   wh
+file                  o       o       E       E       E
+dir                   o       E       o       E       o
+child                 X       E       X       E       X
+wh                    o       E       o       E       o
+
+
+Renaming directories:
+=====================
+
+Whenever a empty (either physically or logically) directory is being renamed,
+the following sequence of events should take place:
+
+1) Remove whiteouts from both source and destination directory
+2) Rename source to destination
+3) Make destination opaque to prevent anything under it from showing up
+
diff --git a/Documentation/filesystems/unionfs/usage.txt b/Documentation/filesystems/unionfs/usage.txt
new file mode 100644
index 0000000..1adde69
--- /dev/null
+++ b/Documentation/filesystems/unionfs/usage.txt
@@ -0,0 +1,134 @@
+Unionfs is a stackable unification file system, which can appear to merge
+the contents of several directories (branches), while keeping their physical
+content separate.  Unionfs is useful for unified source tree management,
+merged contents of split CD-ROM, merged separate software package
+directories, data grids, and more.  Unionfs allows any mix of read-only and
+read-write branches, as well as insertion and deletion of branches anywhere
+in the fan-out.  To maintain Unix semantics, Unionfs handles elimination of
+duplicates, partial-error conditions, and more.
+
+GENERAL SYNTAX
+==============
+
+# mount -t unionfs -o <OPTIONS>,<BRANCH-OPTIONS> none MOUNTPOINT
+
+OPTIONS can be any legal combination of:
+
+- ro           # mount file system read-only
+- rw           # mount file system read-write
+- remount      # remount the file system (see Branch Management below)
+- incgen       # increment generation no. (see Cache Consistency below)
+
+BRANCH-OPTIONS can be either (1) a list of branches given to the "dirs="
+option, or (2) a list of individual branch manipulation commands, combined
+with the "remount" option, and is further described in the "Branch
+Management" section below.
+
+The syntax for the "dirs=" mount option is:
+
+       dirs=branch[=ro|=rw][:...]
+
+The "dirs=" option takes a colon-delimited list of directories to compose
+the union, with an optional branch mode for each of those directories.
+Directories that come earlier (specified first, on the left) in the list
+have a higher precedence than those which come later.  Additionally,
+read-only or read-write permissions of the branch can be specified by
+appending =ro or =rw (default) to each directory.  See the Copyup section in
+concepts.txt, for a description of Unionfs's behavior when mixing read-only
+and read-write branches and mounts.
+
+Syntax:
+
+       dirs=/branch1[=ro|=rw]:/branch2[=ro|=rw]:...:/branchN[=ro|=rw]
+
+Example:
+
+       dirs=/writable_branch=rw:/read-only_branch=ro
+
+
+BRANCH MANAGEMENT
+=================
+
+Once you mount your union for the first time, using the "dirs=" option, you
+can then change the union's overall mode or reconfigure the branches, using
+the remount option, as follows.
+
+To downgrade a union from read-write to read-only:
+
+# mount -t unionfs -o remount,ro none MOUNTPOINT
+
+To upgrade a union from read-only to read-write:
+
+# mount -t unionfs -o remount,rw none MOUNTPOINT
+
+To delete a branch /foo, regardless where it is in the current union:
+
+# mount -t unionfs -o remount,del=/foo none MOUNTPOINT
+
+To insert (add) a branch /foo before /bar:
+
+# mount -t unionfs -o remount,add=/bar:/foo none MOUNTPOINT
+
+To insert (add) a branch /foo (with the "rw" mode flag) before /bar:
+
+# mount -t unionfs -o remount,add=/bar:/foo=rw none MOUNTPOINT
+
+To insert (add) a branch /foo (in "rw" mode) at the very beginning (i.e., a
+new highest-priority branch), you can use the above syntax, or use a short
+hand version as follows:
+
+# mount -t unionfs -o remount,add=/foo none MOUNTPOINT
+
+To append a branch to the very end (new lowest-priority branch):
+
+# mount -t unionfs -o remount,add=:/foo none MOUNTPOINT
+
+To append a branch to the very end (new lowest-priority branch), in
+read-only mode:
+
+# mount -t unionfs -o remount,add=:/foo=ro none MOUNTPOINT
+
+Finally, to change the mode of one existing branch, say /foo, from read-only
+to read-write, and change /bar from read-write to read-only:
+
+# mount -t unionfs -o remount,mode=/foo=rw,mode=/bar=ro none MOUNTPOINT
+
+Note: in Unionfs 2.x, you cannot set the leftmost branch to readonly because
+then Unionfs won't have any writable place for copyups to take place.
+Moreover, the VFS can get confused when it tries to modify something in a
+file system mounted read-write, but isn't permitted to write to it.
+Instead, you should set the whole union as readonly, as described above.
+If, however, you must set the leftmost branch as readonly, perhaps so you
+can get a snapshot of it at a point in time, then you should insert a new
+writable top-level branch, and mark the one you want as readonly.  This can
+be accomplished as follows, assuming that /foo is your current leftmost
+branch:
+
+# mount -t tmpfs -o size=NNN /new
+# mount -t unionfs -o remount,add=/new,mode=/foo=ro none MOUNTPOINT
+<do what you want safely in /foo>
+# mount -t unionfs -o remount,del=/new,mode=/foo=rw none MOUNTPOINT
+<check if there's anything in /new you want to preserve>
+# umount /new
+
+CACHE CONSISTENCY
+=================
+
+If you modify any file on any of the lower branches directly, while there is
+a Unionfs 2.x mounted above any of those branches, you should tell Unionfs
+to purge its caches and re-get the objects.  To do that, you have to
+increment the generation number of the superblock using the following
+command:
+
+# mount -t unionfs -o remount,incgen none MOUNTPOINT
+
+Note that the older way of incrementing the generation number using an
+ioctl, is no longer supported in Unionfs 2.0 and newer.  Ioctls in general
+are not encouraged.  Plus, an ioctl is per-file concept, whereas the
+generation number is a per-file-system concept.  Worse, such an ioctl
+requires an open file, which then has to be invalidated by the very nature
+of the generation number increase (read: the old generation increase ioctl
+was pretty racy).
+
+
+For more information, see <http://unionfs.filesystems.org/>.
diff --git a/MAINTAINERS b/MAINTAINERS
index 9a648eb..81b24a8 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6765,6 +6765,14 @@ F:       Documentation/cdrom/
 F:     drivers/cdrom/cdrom.c
 F:     include/linux/cdrom.h
 
+UNIONFS
+P:     Erez Zadok
+M:     ezk@cs.sunysb.edu
+L:     unionfs@filesystems.org
+W:     http://unionfs.filesystems.org/
+T:     git git.kernel.org/pub/scm/linux/kernel/git/ezk/unionfs.git
+S:     Maintained
+
 UNSORTED BLOCK IMAGES (UBI)
 M:     Artem Bityutskiy <dedekind1@gmail.com>
 W:     http://www.linux-mtd.infradead.org/
diff --git a/fs/Kconfig b/fs/Kconfig
index d621f02..c12677d 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -194,6 +194,7 @@ if MISC_FILESYSTEMS
 source "fs/adfs/Kconfig"
 source "fs/affs/Kconfig"
 source "fs/ecryptfs/Kconfig"
+source "fs/unionfs/Kconfig"
 source "fs/hfs/Kconfig"
 source "fs/hfsplus/Kconfig"
 source "fs/befs/Kconfig"
diff --git a/fs/Makefile b/fs/Makefile
index 93804d4..3ff10bb 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -83,6 +83,7 @@ obj-$(CONFIG_ISO9660_FS)      += isofs/
 obj-$(CONFIG_HFSPLUS_FS)       += hfsplus/ # Before hfs to find wrapped HFS+
 obj-$(CONFIG_HFS_FS)           += hfs/
 obj-$(CONFIG_ECRYPT_FS)                += ecryptfs/
+obj-$(CONFIG_UNION_FS)         += unionfs/
 obj-$(CONFIG_VXFS_FS)          += freevxfs/
 obj-$(CONFIG_NFS_FS)           += nfs/
 obj-$(CONFIG_EXPORTFS)         += exportfs/
diff --git a/fs/namei.c b/fs/namei.c
index 208c6aa..050eded 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -491,6 +491,7 @@ void release_open_intent(struct nameidata *nd)
                        fput(file);
        }
 }
+EXPORT_SYMBOL_GPL(release_open_intent);
 
 static inline int d_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
@@ -1804,6 +1805,42 @@ struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
        return __lookup_hash(&this, base, NULL);
 }
 
+/* pass nameidata from caller (useful for NFS) */
+struct dentry *lookup_one_len_nd(const char *name, struct dentry *base,
+                                int len, struct nameidata *nd)
+{
+       struct qstr this;
+       unsigned long hash;
+       unsigned int c;
+
+       WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
+
+       this.name = name;
+       this.len = len;
+       if (!len)
+               return ERR_PTR(-EACCES);
+
+       hash = init_name_hash();
+       while (len--) {
+               c = *(const unsigned char *)name++;
+               if (c == '/' || c == '\0')
+                       return ERR_PTR(-EACCES);
+               hash = partial_name_hash(c, hash);
+       }
+       this.hash = end_name_hash(hash);
+       /*
+        * See if the low-level filesystem might want
+        * to use its own hash..
+        */
+       if (base->d_flags & DCACHE_OP_HASH) {
+               int err = base->d_op->d_hash(base, base->d_inode, &this);
+               if (err < 0)
+                       return ERR_PTR(err);
+       }
+
+       return __lookup_hash(&this, base, nd);
+}
+
 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
                 struct path *path, int *empty)
 {
@@ -3384,6 +3421,7 @@ EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
 EXPORT_SYMBOL(getname);
 EXPORT_SYMBOL(lock_rename);
 EXPORT_SYMBOL(lookup_one_len);
+EXPORT_SYMBOL(lookup_one_len_nd);
 EXPORT_SYMBOL(page_follow_link_light);
 EXPORT_SYMBOL(page_put_link);
 EXPORT_SYMBOL(page_readlink);
diff --git a/fs/splice.c b/fs/splice.c
index 1ec0493..3215728 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1084,8 +1084,8 @@ EXPORT_SYMBOL(generic_splice_sendpage);
 /*
  * 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 vfs_splice_from(struct pipe_inode_info *pipe, struct file *out,
+                    loff_t *ppos, size_t len, unsigned int flags)
 {
        ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
                                loff_t *, size_t, unsigned int);
@@ -1108,13 +1108,14 @@ static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 
        return splice_write(pipe, out, ppos, len, flags);
 }
+EXPORT_SYMBOL_GPL(vfs_splice_from);
 
 /*
  * 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 vfs_splice_to(struct file *in, loff_t *ppos,
+                  struct pipe_inode_info *pipe, size_t len,
+                  unsigned int flags)
 {
        ssize_t (*splice_read)(struct file *, loff_t *,
                               struct pipe_inode_info *, size_t, unsigned int);
@@ -1134,6 +1135,7 @@ static long do_splice_to(struct file *in, loff_t *ppos,
 
        return splice_read(in, ppos, pipe, len, flags);
 }
+EXPORT_SYMBOL_GPL(vfs_splice_to);
 
 /**
  * splice_direct_to_actor - splices data directly between two non-pipes
@@ -1203,7 +1205,7 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
                size_t read_len;
                loff_t pos = sd->pos, prev_pos = pos;
 
-               ret = do_splice_to(in, &pos, pipe, len, flags);
+               ret = vfs_splice_to(in, &pos, pipe, len, flags);
                if (unlikely(ret <= 0))
                        goto out_release;
 
@@ -1262,8 +1264,8 @@ static int direct_splice_actor(struct pipe_inode_info *pipe,
 {
        struct file *file = sd->u.file;
 
-       return do_splice_from(pipe, file, &file->f_pos, sd->total_len,
-                             sd->flags);
+       return vfs_splice_from(pipe, file, &file->f_pos, sd->total_len,
+                              sd->flags);
 }
 
 /**
@@ -1348,7 +1350,7 @@ static long do_splice(struct file *in, loff_t __user *off_in,
                } else
                        off = &out->f_pos;
 
-               ret = do_splice_from(ipipe, out, off, len, flags);
+               ret = vfs_splice_from(ipipe, out, off, len, flags);
 
                if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
                        ret = -EFAULT;
@@ -1368,7 +1370,7 @@ static long do_splice(struct file *in, loff_t __user *off_in,
                } else
                        off = &in->f_pos;
 
-               ret = do_splice_to(in, off, opipe, len, flags);
+               ret = vfs_splice_to(in, off, opipe, len, flags);
 
                if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
                        ret = -EFAULT;
diff --git a/fs/unionfs/Kconfig b/fs/unionfs/Kconfig
new file mode 100644
index 0000000..f3c1ac4
--- /dev/null
+++ b/fs/unionfs/Kconfig
@@ -0,0 +1,24 @@
+config UNION_FS
+       tristate "Union file system (EXPERIMENTAL)"
+       depends on EXPERIMENTAL
+       help
+         Unionfs is a stackable unification file system, which appears to
+         merge the contents of several directories (branches), while keeping
+         their physical content separate.
+
+         See <http://unionfs.filesystems.org> for details
+
+config UNION_FS_XATTR
+       bool "Unionfs extended attributes"
+       depends on UNION_FS
+       help
+         Extended attributes are name:value pairs associated with inodes by
+         the kernel or by users (see the attr(5) manual page).
+
+         If unsure, say N.
+
+config UNION_FS_DEBUG
+       bool "Debug Unionfs"
+       depends on UNION_FS
+       help
+         If you say Y here, you can turn on debugging output from Unionfs.
diff --git a/fs/unionfs/Makefile b/fs/unionfs/Makefile
new file mode 100644
index 0000000..60b6060
--- /dev/null
+++ b/fs/unionfs/Makefile
@@ -0,0 +1,17 @@
+UNIONFS_VERSION="2.5.11 (for 3.3.0-rc3)"
+
+EXTRA_CFLAGS += -DUNIONFS_VERSION=\"$(UNIONFS_VERSION)\"
+
+obj-$(CONFIG_UNION_FS) += unionfs.o
+
+unionfs-y := subr.o dentry.o file.o inode.o main.o super.o \
+       rdstate.o copyup.o dirhelper.o rename.o unlink.o \
+       lookup.o commonfops.o dirfops.o sioq.o mmap.o whiteout.o
+
+unionfs-$(CONFIG_UNION_FS_XATTR) += xattr.o
+
+unionfs-$(CONFIG_UNION_FS_DEBUG) += debug.o
+
+ifeq ($(CONFIG_UNION_FS_DEBUG),y)
+EXTRA_CFLAGS += -DDEBUG
+endif
diff --git a/fs/unionfs/commonfops.c b/fs/unionfs/commonfops.c
new file mode 100644
index 0000000..71cacfe
--- /dev/null
+++ b/fs/unionfs/commonfops.c
@@ -0,0 +1,901 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/*
+ * 1) Copyup the file
+ * 2) Rename the file to '.unionfs<original inode#><counter>' - obviously
+ * stolen from NFS's silly rename
+ */
+static int copyup_deleted_file(struct file *file, struct dentry *dentry,
+                              struct dentry *parent, int bstart, int bindex)
+{
+       static unsigned int counter;
+       const int i_inosize = sizeof(dentry->d_inode->i_ino) * 2;
+       const int countersize = sizeof(counter) * 2;
+       const int nlen = sizeof(".unionfs") + i_inosize + countersize - 1;
+       char name[nlen + 1];
+       int err;
+       struct dentry *tmp_dentry = NULL;
+       struct dentry *lower_dentry;
+       struct dentry *lower_dir_dentry = NULL;
+
+       lower_dentry = unionfs_lower_dentry_idx(dentry, bstart);
+
+       sprintf(name, ".unionfs%*.*lx",
+               i_inosize, i_inosize, lower_dentry->d_inode->i_ino);
+
+       /*
+        * Loop, looking for an unused temp name to copyup to.
+        *
+        * It's somewhat silly that we look for a free temp tmp name in the
+        * source branch (bstart) instead of the dest branch (bindex), where
+        * the final name will be created.  We _will_ catch it if somehow
+        * the name exists in the dest branch, but it'd be nice to catch it
+        * sooner than later.
+        */
+retry:
+       tmp_dentry = NULL;
+       do {
+               char *suffix = name + nlen - countersize;
+
+               dput(tmp_dentry);
+               counter++;
+               sprintf(suffix, "%*.*x", countersize, countersize, counter);
+
+               pr_debug("unionfs: trying to rename %s to %s\n",
+                        dentry->d_name.name, name);
+
+               tmp_dentry = lookup_lck_len(name, lower_dentry->d_parent,
+                                           nlen);
+               if (IS_ERR(tmp_dentry)) {
+                       err = PTR_ERR(tmp_dentry);
+                       goto out;
+               }
+       } while (tmp_dentry->d_inode != NULL);  /* need negative dentry */
+       dput(tmp_dentry);
+
+       err = copyup_named_file(parent->d_inode, file, name, bstart, bindex,
+                               i_size_read(file->f_path.dentry->d_inode));
+       if (err) {
+               if (unlikely(err == -EEXIST))
+                       goto retry;
+               goto out;
+       }
+
+       /* bring it to the same state as an unlinked file */
+       lower_dentry = unionfs_lower_dentry_idx(dentry, dbstart(dentry));
+       if (!unionfs_lower_inode_idx(dentry->d_inode, bindex)) {
+               atomic_inc(&lower_dentry->d_inode->i_count);
+               unionfs_set_lower_inode_idx(dentry->d_inode, bindex,
+                                           lower_dentry->d_inode);
+       }
+       lower_dir_dentry = lock_parent(lower_dentry);
+       err = vfs_unlink(lower_dir_dentry->d_inode, lower_dentry);
+       unlock_dir(lower_dir_dentry);
+
+out:
+       if (!err)
+               unionfs_check_dentry(dentry);
+       return err;
+}
+
+/*
+ * put all references held by upper struct file and free lower file pointer
+ * array
+ */
+static void cleanup_file(struct file *file)
+{
+       int bindex, bstart, bend;
+       struct file **lower_files;
+       struct file *lower_file;
+       struct super_block *sb = file->f_path.dentry->d_sb;
+
+       lower_files = UNIONFS_F(file)->lower_files;
+       bstart = fbstart(file);
+       bend = fbend(file);
+
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               int i;  /* holds (possibly) updated branch index */
+               int old_bid;
+
+               lower_file = unionfs_lower_file_idx(file, bindex);
+               if (!lower_file)
+                       continue;
+
+               /*
+                * Find new index of matching branch with an open
+                * file, since branches could have been added or
+                * deleted causing the one with open files to shift.
+                */
+               old_bid = UNIONFS_F(file)->saved_branch_ids[bindex];
+               i = branch_id_to_idx(sb, old_bid);
+               if (unlikely(i < 0)) {
+                       printk(KERN_ERR "unionfs: no superblock for "
+                              "file %p\n", file);
+                       continue;
+               }
+
+               /* decrement count of open files */
+               branchput(sb, i);
+               /*
+                * fput will perform an mntput for us on the correct branch.
+                * Although we're using the file's old branch configuration,
+                * bindex, which is the old index, correctly points to the
+                * right branch in the file's branch list.  In other words,
+                * we're going to mntput the correct branch even if branches
+                * have been added/removed.
+                */
+               fput(lower_file);
+               UNIONFS_F(file)->lower_files[bindex] = NULL;
+               UNIONFS_F(file)->saved_branch_ids[bindex] = -1;
+       }
+
+       UNIONFS_F(file)->lower_files = NULL;
+       kfree(lower_files);
+       kfree(UNIONFS_F(file)->saved_branch_ids);
+       /* set to NULL because caller needs to know if to kfree on error */
+       UNIONFS_F(file)->saved_branch_ids = NULL;
+}
+
+/* open all lower files for a given file */
+static int open_all_files(struct file *file)
+{
+       int bindex, bstart, bend, err = 0;
+       struct file *lower_file;
+       struct dentry *lower_dentry;
+       struct dentry *dentry = file->f_path.dentry;
+       struct super_block *sb = dentry->d_sb;
+
+       bstart = dbstart(dentry);
+       bend = dbend(dentry);
+
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               if (!lower_dentry)
+                       continue;
+
+               dget(lower_dentry);
+               unionfs_mntget(dentry, bindex);
+               branchget(sb, bindex);
+
+               lower_file =
+                       dentry_open(lower_dentry,
+                                   unionfs_lower_mnt_idx(dentry, bindex),
+                                   file->f_flags, current_cred());
+               if (IS_ERR(lower_file)) {
+                       branchput(sb, bindex);
+                       err = PTR_ERR(lower_file);
+                       goto out;
+               } else {
+                       unionfs_set_lower_file_idx(file, bindex, lower_file);
+               }
+       }
+out:
+       return err;
+}
+
+/* open the highest priority file for a given upper file */
+static int open_highest_file(struct file *file, bool willwrite)
+{
+       int bindex, bstart, bend, err = 0;
+       struct file *lower_file;
+       struct dentry *lower_dentry;
+       struct dentry *dentry = file->f_path.dentry;
+       struct dentry *parent = dget_parent(dentry);
+       struct inode *parent_inode = parent->d_inode;
+       struct super_block *sb = dentry->d_sb;
+
+       bstart = dbstart(dentry);
+       bend = dbend(dentry);
+
+       lower_dentry = unionfs_lower_dentry(dentry);
+       if (willwrite && IS_WRITE_FLAG(file->f_flags) && is_robranch(dentry)) {
+               for (bindex = bstart - 1; bindex >= 0; bindex--) {
+                       err = copyup_file(parent_inode, file, bstart, bindex,
+                                         i_size_read(dentry->d_inode));
+                       if (!err)
+                               break;
+               }
+               atomic_set(&UNIONFS_F(file)->generation,
+                          atomic_read(&UNIONFS_I(dentry->d_inode)->
+                                      generation));
+               goto out;
+       }
+
+       dget(lower_dentry);
+       unionfs_mntget(dentry, bstart);
+       lower_file = dentry_open(lower_dentry,
+                                unionfs_lower_mnt_idx(dentry, bstart),
+                                file->f_flags, current_cred());
+       if (IS_ERR(lower_file)) {
+               err = PTR_ERR(lower_file);
+               goto out;
+       }
+       branchget(sb, bstart);
+       unionfs_set_lower_file(file, lower_file);
+       /* Fix up the position. */
+       lower_file->f_pos = file->f_pos;
+
+       memcpy(&lower_file->f_ra, &file->f_ra, sizeof(struct file_ra_state));
+out:
+       dput(parent);
+       return err;
+}
+
+/* perform a delayed copyup of a read-write file on a read-only branch */
+static int do_delayed_copyup(struct file *file, struct dentry *parent)
+{
+       int bindex, bstart, bend, err = 0;
+       struct dentry *dentry = file->f_path.dentry;
+       struct inode *parent_inode = parent->d_inode;
+
+       bstart = fbstart(file);
+       bend = fbend(file);
+
+       BUG_ON(!S_ISREG(dentry->d_inode->i_mode));
+
+       unionfs_check_file(file);
+       for (bindex = bstart - 1; bindex >= 0; bindex--) {
+               if (!d_deleted(dentry))
+                       err = copyup_file(parent_inode, file, bstart,
+                                         bindex,
+                                         i_size_read(dentry->d_inode));
+               else
+                       err = copyup_deleted_file(file, dentry, parent,
+                                                 bstart, bindex);
+               /* if succeeded, set lower open-file flags and break */
+               if (!err) {
+                       struct file *lower_file;
+                       lower_file = unionfs_lower_file_idx(file, bindex);
+                       lower_file->f_flags = file->f_flags;
+                       break;
+               }
+       }
+       if (err || (bstart <= fbstart(file)))
+               goto out;
+       bend = fbend(file);
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               if (unionfs_lower_file_idx(file, bindex)) {
+                       branchput(dentry->d_sb, bindex);
+                       fput(unionfs_lower_file_idx(file, bindex));
+                       unionfs_set_lower_file_idx(file, bindex, NULL);
+               }
+       }
+       path_put_lowers(dentry, bstart, bend, false);
+       iput_lowers(dentry->d_inode, bstart, bend, false);
+       /* for reg file, we only open it "once" */
+       fbend(file) = fbstart(file);
+       dbend(dentry) = dbstart(dentry);
+       ibend(dentry->d_inode) = ibstart(dentry->d_inode);
+
+out:
+       unionfs_check_file(file);
+       return err;
+}
+
+/*
+ * Helper function for unionfs_file_revalidate/locked.
+ * Expects dentry/parent to be locked already, and revalidated.
+ */
+static int __unionfs_file_revalidate(struct file *file, struct dentry *dentry,
+                                    struct dentry *parent,
+                                    struct super_block *sb, int sbgen,
+                                    int dgen, bool willwrite)
+{
+       int fgen;
+       int bstart, bend, orig_brid;
+       int size;
+       int err = 0;
+
+       fgen = atomic_read(&UNIONFS_F(file)->generation);
+
+       /*
+        * There are two cases we are interested in.  The first is if the
+        * generation is lower than the super-block.  The second is if
+        * someone has copied up this file from underneath us, we also need
+        * to refresh things.
+        */
+       if (d_deleted(dentry) ||
+           (sbgen <= fgen &&
+            dbstart(dentry) == fbstart(file) &&
+            unionfs_lower_file(file)))
+               goto out_may_copyup;
+
+       /* save orig branch ID */
+       orig_brid = UNIONFS_F(file)->saved_branch_ids[fbstart(file)];
+
+       /* First we throw out the existing files. */
+       cleanup_file(file);
+
+       /* Now we reopen the file(s) as in unionfs_open. */
+       bstart = fbstart(file) = dbstart(dentry);
+       bend = fbend(file) = dbend(dentry);
+
+       size = sizeof(struct file *) * sbmax(sb);
+       UNIONFS_F(file)->lower_files = kzalloc(size, GFP_KERNEL);
+       if (unlikely(!UNIONFS_F(file)->lower_files)) {
+               err = -ENOMEM;
+               goto out;
+       }
+       size = sizeof(int) * sbmax(sb);
+       UNIONFS_F(file)->saved_branch_ids = kzalloc(size, GFP_KERNEL);
+       if (unlikely(!UNIONFS_F(file)->saved_branch_ids)) {
+               err = -ENOMEM;
+               goto out;
+       }
+
+       if (S_ISDIR(dentry->d_inode->i_mode)) {
+               /* We need to open all the files. */
+               err = open_all_files(file);
+               if (err)
+                       goto out;
+       } else {
+               int new_brid;
+               /* We only open the highest priority branch. */
+               err = open_highest_file(file, willwrite);
+               if (err)
+                       goto out;
+               new_brid = UNIONFS_F(file)->saved_branch_ids[fbstart(file)];
+               if (unlikely(new_brid != orig_brid && sbgen > fgen)) {
+                       /*
+                        * If we re-opened the file on a different branch
+                        * than the original one, and this was due to a new
+                        * branch inserted, then update the mnt counts of
+                        * the old and new branches accordingly.
+                        */
+                       unionfs_mntget(dentry, bstart);
+                       unionfs_mntput(sb->s_root,
+                                      branch_id_to_idx(sb, orig_brid));
+               }
+               /* regular files have only one open lower file */
+               fbend(file) = fbstart(file);
+       }
+       atomic_set(&UNIONFS_F(file)->generation,
+                  atomic_read(&UNIONFS_I(dentry->d_inode)->generation));
+
+out_may_copyup:
+       /* Copyup on the first write to a file on a readonly branch. */
+       if (willwrite && IS_WRITE_FLAG(file->f_flags) &&
+           !IS_WRITE_FLAG(unionfs_lower_file(file)->f_flags) &&
+           is_robranch(dentry)) {
+               pr_debug("unionfs: do delay copyup of \"%s\"\n",
+                        dentry->d_name.name);
+               err = do_delayed_copyup(file, parent);
+               /* regular files have only one open lower file */
+               if (!err && !S_ISDIR(dentry->d_inode->i_mode))
+                       fbend(file) = fbstart(file);
+       }
+
+out:
+       if (err) {
+               kfree(UNIONFS_F(file)->lower_files);
+               kfree(UNIONFS_F(file)->saved_branch_ids);
+       }
+       return err;
+}
+
+/*
+ * Revalidate the struct file
+ * @file: file to revalidate
+ * @parent: parent dentry (locked by caller)
+ * @willwrite: true if caller may cause changes to the file; false otherwise.
+ * Caller must lock/unlock dentry's branch configuration.
+ */
+int unionfs_file_revalidate(struct file *file, struct dentry *parent,
+                           bool willwrite)
+{
+       struct super_block *sb;
+       struct dentry *dentry;
+       int sbgen, dgen;
+       int err = 0;
+
+       dentry = file->f_path.dentry;
+       sb = dentry->d_sb;
+       verify_locked(dentry);
+       verify_locked(parent);
+
+       /*
+        * First revalidate the dentry inside struct file,
+        * but not unhashed dentries.
+        */
+       if (!d_deleted(dentry) &&
+           !__unionfs_d_revalidate(dentry, parent, willwrite)) {
+               err = -ESTALE;
+               goto out;
+       }
+
+       sbgen = atomic_read(&UNIONFS_SB(sb)->generation);
+       dgen = atomic_read(&UNIONFS_D(dentry)->generation);
+
+       if (unlikely(sbgen > dgen)) { /* XXX: should never happen */
+               pr_debug("unionfs: failed to revalidate dentry (%s)\n",
+                        dentry->d_name.name);
+               err = -ESTALE;
+               goto out;
+       }
+
+       err = __unionfs_file_revalidate(file, dentry, parent, sb,
+                                       sbgen, dgen, willwrite);
+out:
+       return err;
+}
+
+/* unionfs_open helper function: open a directory */
+static int __open_dir(struct inode *inode, struct file *file,
+                     struct dentry *parent)
+{
+       struct dentry *lower_dentry;
+       struct file *lower_file;
+       int bindex, bstart, bend;
+       struct vfsmount *lower_mnt;
+       struct dentry *dentry = file->f_path.dentry;
+
+       bstart = fbstart(file) = dbstart(dentry);
+       bend = fbend(file) = dbend(dentry);
+
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_dentry =
+                       unionfs_lower_dentry_idx(dentry, bindex);
+               if (!lower_dentry)
+                       continue;
+
+               dget(lower_dentry);
+               lower_mnt = unionfs_mntget(dentry, bindex);
+               if (!lower_mnt)
+                       lower_mnt = unionfs_mntget(parent, bindex);
+               lower_file = dentry_open(lower_dentry, lower_mnt, file->f_flags,
+                                        current_cred());
+               if (IS_ERR(lower_file))
+                       return PTR_ERR(lower_file);
+
+               unionfs_set_lower_file_idx(file, bindex, lower_file);
+               if (!unionfs_lower_mnt_idx(dentry, bindex))
+                       unionfs_set_lower_mnt_idx(dentry, bindex, lower_mnt);
+
+               /*
+                * The branchget goes after the open, because otherwise
+                * we would miss the reference on release.
+                */
+               branchget(inode->i_sb, bindex);
+       }
+
+       return 0;
+}
+
+/* unionfs_open helper function: open a file */
+static int __open_file(struct inode *inode, struct file *file,
+                      struct dentry *parent)
+{
+       struct dentry *lower_dentry;
+       struct file *lower_file;
+       int lower_flags;
+       int bindex, bstart, bend;
+       struct dentry *dentry = file->f_path.dentry;
+       struct vfsmount *lower_mnt;
+
+       lower_dentry = unionfs_lower_dentry(dentry);
+       lower_flags = file->f_flags;
+
+       bstart = fbstart(file) = dbstart(dentry);
+       bend = fbend(file) = dbend(dentry);
+
+       /*
+        * check for the permission for lower file.  If the error is
+        * COPYUP_ERR, copyup the file.
+        */
+       if (lower_dentry->d_inode && is_robranch(dentry)) {
+               /*
+                * if the open will change the file, copy it up otherwise
+                * defer it.
+                */
+               if (lower_flags & O_TRUNC) {
+                       int size = 0;
+                       int err = -EROFS;
+
+                       /* copyup the file */
+                       for (bindex = bstart - 1; bindex >= 0; bindex--) {
+                               err = copyup_file(parent->d_inode, file,
+                                                 bstart, bindex, size);
+                               if (!err) {
+                                       /* only one regular file open */
+                                       fbend(file) = fbstart(file);
+                                       break;
+                               }
+                       }
+                       return err;
+               } else {
+                       /*
+                        * turn off writeable flags, to force delayed copyup
+                        * by caller.
+                        */
+                       lower_flags &= ~(OPEN_WRITE_FLAGS);
+               }
+       }
+
+       dget(lower_dentry);
+
+       /*
+        * dentry_open will decrement mnt refcnt if err.
+        * otherwise fput() will do an mntput() for us upon file close.
+        */
+       lower_mnt = unionfs_mntget(dentry, bstart);
+       lower_file = dentry_open(lower_dentry, lower_mnt, lower_flags,
+                                current_cred());
+       if (IS_ERR(lower_file))
+               return PTR_ERR(lower_file);
+
+       unionfs_set_lower_file(file, lower_file);
+       branchget(inode->i_sb, bstart);
+
+       return 0;
+}
+
+int unionfs_open(struct inode *inode, struct file *file)
+{
+       int err = 0;
+       struct file *lower_file = NULL;
+       struct dentry *dentry = file->f_path.dentry;
+       struct dentry *parent;
+       int bindex = 0, bstart = 0, bend = 0;
+       int size;
+       int valid = 0;
+
+       unionfs_read_lock(inode->i_sb, UNIONFS_SMUTEX_PARENT);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       /* don't open unhashed/deleted files */
+       if (d_deleted(dentry)) {
+               err = -ENOENT;
+               goto out_nofree;
+       }
+
+       /* XXX: should I change 'false' below to the 'willwrite' flag? */
+       valid = __unionfs_d_revalidate(dentry, parent, false);
+       if (unlikely(!valid)) {
+               err = -ESTALE;
+               goto out_nofree;
+       }
+
+       file->private_data =
+               kzalloc(sizeof(struct unionfs_file_info), GFP_KERNEL);
+       if (unlikely(!UNIONFS_F(file))) {
+               err = -ENOMEM;
+               goto out_nofree;
+       }
+       fbstart(file) = -1;
+       fbend(file) = -1;
+       atomic_set(&UNIONFS_F(file)->generation,
+                  atomic_read(&UNIONFS_I(inode)->generation));
+
+       size = sizeof(struct file *) * sbmax(inode->i_sb);
+       UNIONFS_F(file)->lower_files = kzalloc(size, GFP_KERNEL);
+       if (unlikely(!UNIONFS_F(file)->lower_files)) {
+               err = -ENOMEM;
+               goto out;
+       }
+       size = sizeof(int) * sbmax(inode->i_sb);
+       UNIONFS_F(file)->saved_branch_ids = kzalloc(size, GFP_KERNEL);
+       if (unlikely(!UNIONFS_F(file)->saved_branch_ids)) {
+               err = -ENOMEM;
+               goto out;
+       }
+
+       bstart = fbstart(file) = dbstart(dentry);
+       bend = fbend(file) = dbend(dentry);
+
+       /*
+        * open all directories and make the unionfs file struct point to
+        * these lower file structs
+        */
+       if (S_ISDIR(inode->i_mode))
+               err = __open_dir(inode, file, parent); /* open a dir */
+       else
+               err = __open_file(inode, file, parent); /* open a file */
+
+       /* freeing the allocated resources, and fput the opened files */
+       if (err) {
+               for (bindex = bstart; bindex <= bend; bindex++) {
+                       lower_file = unionfs_lower_file_idx(file, bindex);
+                       if (!lower_file)
+                               continue;
+
+                       branchput(dentry->d_sb, bindex);
+                       /* fput calls dput for lower_dentry */
+                       fput(lower_file);
+               }
+       }
+
+out:
+       if (err) {
+               kfree(UNIONFS_F(file)->lower_files);
+               kfree(UNIONFS_F(file)->saved_branch_ids);
+               kfree(UNIONFS_F(file));
+       }
+out_nofree:
+       if (!err) {
+               unionfs_postcopyup_setmnt(dentry);
+               unionfs_copy_attr_times(inode);
+               unionfs_check_file(file);
+               unionfs_check_inode(inode);
+       }
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(inode->i_sb);
+       return err;
+}
+
+/*
+ * release all lower object references & free the file info structure
+ *
+ * No need to grab sb info's rwsem.
+ */
+int unionfs_file_release(struct inode *inode, struct file *file)
+{
+       struct file *lower_file = NULL;
+       struct unionfs_file_info *fileinfo;
+       struct unionfs_inode_info *inodeinfo;
+       struct super_block *sb = inode->i_sb;
+       struct dentry *dentry = file->f_path.dentry;
+       struct dentry *parent;
+       int bindex, bstart, bend;
+       int err = 0;
+
+       /*
+        * Since mm/memory.c:might_fault() (under PROVE_LOCKING) was
+        * modified in 2.6.29-rc1 to call might_lock_read on mmap_sem, this
+        * has been causing false positives in file system stacking layers.
+        * In particular, our ->mmap is called after sys_mmap2 already holds
+        * mmap_sem, then we lock our own mutexes; but earlier, it's
+        * possible for lockdep to have locked our mutexes first, and then
+        * we call a lower ->readdir which could call might_fault.  The
+        * different ordering of the locks is what lockdep complains about
+        * -- unnecessarily.  Therefore, we have no choice but to tell
+        * lockdep to temporarily turn off lockdep here.  Note: the comments
+        * inside might_sleep also suggest that it would have been
+        * nicer to only annotate paths that needs that might_lock_read.
+        */
+       lockdep_off();
+       unionfs_read_lock(sb, UNIONFS_SMUTEX_PARENT);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       /*
+        * We try to revalidate, but the VFS ignores return return values
+        * from file->release, so we must always try to succeed here,
+        * including to do the kfree and dput below.  So if revalidation
+        * failed, all we can do is print some message and keep going.
+        */
+       err = unionfs_file_revalidate(file, parent,
+                                     UNIONFS_F(file)->wrote_to_file);
+       if (!err)
+               unionfs_check_file(file);
+       fileinfo = UNIONFS_F(file);
+       BUG_ON(file->f_path.dentry->d_inode != inode);
+       inodeinfo = UNIONFS_I(inode);
+
+       /* fput all the lower files */
+       bstart = fbstart(file);
+       bend = fbend(file);
+
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_file = unionfs_lower_file_idx(file, bindex);
+
+               if (lower_file) {
+                       unionfs_set_lower_file_idx(file, bindex, NULL);
+                       fput(lower_file);
+                       branchput(sb, bindex);
+               }
+
+               /* if there are no more refs to the dentry, dput it */
+               if (d_deleted(dentry)) {
+                       dput(unionfs_lower_dentry_idx(dentry, bindex));
+                       unionfs_set_lower_dentry_idx(dentry, bindex, NULL);
+               }
+       }
+
+       kfree(fileinfo->lower_files);
+       kfree(fileinfo->saved_branch_ids);
+
+       if (fileinfo->rdstate) {
+               fileinfo->rdstate->access = jiffies;
+               spin_lock(&inodeinfo->rdlock);
+               inodeinfo->rdcount++;
+               list_add_tail(&fileinfo->rdstate->cache,
+                             &inodeinfo->readdircache);
+               mark_inode_dirty(inode);
+               spin_unlock(&inodeinfo->rdlock);
+               fileinfo->rdstate = NULL;
+       }
+       kfree(fileinfo);
+
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(sb);
+       lockdep_on();
+       return err;
+}
+
+/* pass the ioctl to the lower fs */
+static long do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+       struct file *lower_file;
+       int err;
+
+       lower_file = unionfs_lower_file(file);
+
+       err = -ENOTTY;
+       if (!lower_file || !lower_file->f_op)
+               goto out;
+       if (lower_file->f_op->unlocked_ioctl) {
+               err = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);
+#ifdef CONFIG_COMPAT
+       } else if (lower_file->f_op->compat_ioctl) {
+               err = lower_file->f_op->compat_ioctl(lower_file, cmd, arg);
+#endif
+       }
+
+out:
+       return err;
+}
+
+/*
+ * return to user-space the branch indices containing the file in question
+ *
+ * We use fd_set and therefore we are limited to the number of the branches
+ * to FD_SETSIZE, which is currently 1024 - plenty for most people
+ */
+static int unionfs_ioctl_queryfile(struct file *file, struct dentry *parent,
+                                  unsigned int cmd, unsigned long arg)
+{
+       int err = 0;
+       fd_set branchlist;
+       int bstart = 0, bend = 0, bindex = 0;
+       int orig_bstart, orig_bend;
+       struct dentry *dentry, *lower_dentry;
+       struct vfsmount *mnt;
+
+       dentry = file->f_path.dentry;
+       orig_bstart = dbstart(dentry);
+       orig_bend = dbend(dentry);
+       err = unionfs_partial_lookup(dentry, parent);
+       if (err)
+               goto out;
+       bstart = dbstart(dentry);
+       bend = dbend(dentry);
+
+       FD_ZERO(&branchlist);
+
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               if (!lower_dentry)
+                       continue;
+               if (likely(lower_dentry->d_inode))
+                       FD_SET(bindex, &branchlist);
+               /* purge any lower objects after partial_lookup */
+               if (bindex < orig_bstart || bindex > orig_bend) {
+                       dput(lower_dentry);
+                       unionfs_set_lower_dentry_idx(dentry, bindex, NULL);
+                       iput(unionfs_lower_inode_idx(dentry->d_inode, bindex));
+                       unionfs_set_lower_inode_idx(dentry->d_inode, bindex,
+                                                   NULL);
+                       mnt = unionfs_lower_mnt_idx(dentry, bindex);
+                       if (!mnt)
+                               continue;
+                       unionfs_mntput(dentry, bindex);
+                       unionfs_set_lower_mnt_idx(dentry, bindex, NULL);
+               }
+       }
+       /* restore original dentry's offsets */
+       dbstart(dentry) = orig_bstart;
+       dbend(dentry) = orig_bend;
+       ibstart(dentry->d_inode) = orig_bstart;
+       ibend(dentry->d_inode) = orig_bend;
+
+       err = copy_to_user((void __user *)arg, &branchlist, sizeof(fd_set));
+       if (unlikely(err))
+               err = -EFAULT;
+
+out:
+       return err < 0 ? err : bend;
+}
+
+long unionfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+       long err;
+       struct dentry *dentry = file->f_path.dentry;
+       struct dentry *parent;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_PARENT);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       err = unionfs_file_revalidate(file, parent, true);
+       if (unlikely(err))
+               goto out;
+
+       /* check if asked for local commands */
+       switch (cmd) {
+       case UNIONFS_IOCTL_INCGEN:
+               /* Increment the superblock generation count */
+               pr_info("unionfs: incgen ioctl deprecated; "
+                       "use \"-o remount,incgen\"\n");
+               err = -ENOSYS;
+               break;
+
+       case UNIONFS_IOCTL_QUERYFILE:
+               /* Return list of branches containing the given file */
+               err = unionfs_ioctl_queryfile(file, parent, cmd, arg);
+               break;
+
+       default:
+               /* pass the ioctl down */
+               err = do_ioctl(file, cmd, arg);
+               break;
+       }
+
+out:
+       unionfs_check_file(file);
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
+
+int unionfs_flush(struct file *file, fl_owner_t id)
+{
+       int err = 0;
+       struct file *lower_file = NULL;
+       struct dentry *dentry = file->f_path.dentry;
+       struct dentry *parent;
+       int bindex, bstart, bend;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_PARENT);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       err = unionfs_file_revalidate(file, parent,
+                                     UNIONFS_F(file)->wrote_to_file);
+       if (unlikely(err))
+               goto out;
+       unionfs_check_file(file);
+
+       bstart = fbstart(file);
+       bend = fbend(file);
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_file = unionfs_lower_file_idx(file, bindex);
+
+               if (lower_file && lower_file->f_op &&
+                   lower_file->f_op->flush) {
+                       err = lower_file->f_op->flush(lower_file, id);
+                       if (err)
+                               goto out;
+               }
+
+       }
+
+out:
+       if (!err)
+               unionfs_check_file(file);
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
diff --git a/fs/unionfs/copyup.c b/fs/unionfs/copyup.c
new file mode 100644
index 0000000..078ca27
--- /dev/null
+++ b/fs/unionfs/copyup.c
@@ -0,0 +1,899 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/*
+ * For detailed explanation of copyup see:
+ * Documentation/filesystems/unionfs/concepts.txt
+ */
+
+#ifdef CONFIG_UNION_FS_XATTR
+/* copyup all extended attrs for a given dentry */
+static int copyup_xattrs(struct dentry *old_lower_dentry,
+                        struct dentry *new_lower_dentry)
+{
+       int err = 0;
+       ssize_t list_size = -1;
+       char *name_list = NULL;
+       char *attr_value = NULL;
+       char *name_list_buf = NULL;
+
+       /* query the actual size of the xattr list */
+       list_size = vfs_listxattr(old_lower_dentry, NULL, 0);
+       if (list_size <= 0) {
+               err = list_size;
+               goto out;
+       }
+
+       /* allocate space for the actual list */
+       name_list = unionfs_xattr_alloc(list_size + 1, XATTR_LIST_MAX);
+       if (unlikely(!name_list || IS_ERR(name_list))) {
+               err = PTR_ERR(name_list);
+               goto out;
+       }
+
+       name_list_buf = name_list; /* save for kfree at end */
+
+       /* now get the actual xattr list of the source file */
+       list_size = vfs_listxattr(old_lower_dentry, name_list, list_size);
+       if (list_size <= 0) {
+               err = list_size;
+               goto out;
+       }
+
+       /* allocate space to hold each xattr's value */
+       attr_value = unionfs_xattr_alloc(XATTR_SIZE_MAX, XATTR_SIZE_MAX);
+       if (unlikely(!attr_value || IS_ERR(attr_value))) {
+               err = PTR_ERR(name_list);
+               goto out;
+       }
+
+       /* in a loop, get and set each xattr from src to dst file */
+       while (*name_list) {
+               ssize_t size;
+
+               /* Lock here since vfs_getxattr doesn't lock for us */
+               mutex_lock(&old_lower_dentry->d_inode->i_mutex);
+               size = vfs_getxattr(old_lower_dentry, name_list,
+                                   attr_value, XATTR_SIZE_MAX);
+               mutex_unlock(&old_lower_dentry->d_inode->i_mutex);
+               if (size < 0) {
+                       err = size;
+                       goto out;
+               }
+               if (size > XATTR_SIZE_MAX) {
+                       err = -E2BIG;
+                       goto out;
+               }
+               /* Don't lock here since vfs_setxattr does it for us. */
+               err = vfs_setxattr(new_lower_dentry, name_list, attr_value,
+                                  size, 0);
+               /*
+                * Selinux depends on "security.*" xattrs, so to maintain
+                * the security of copied-up files, if Selinux is active,
+                * then we must copy these xattrs as well.  So we need to
+                * temporarily get FOWNER privileges.
+                * XXX: move entire copyup code to SIOQ.
+                */
+               if (err == -EPERM && !capable(CAP_FOWNER)) {
+                       const struct cred *old_creds;
+                       struct cred *new_creds;
+
+                       new_creds = prepare_creds();
+                       if (unlikely(!new_creds)) {
+                               err = -ENOMEM;
+                               goto out;
+                       }
+                       cap_raise(new_creds->cap_effective, CAP_FOWNER);
+                       old_creds = override_creds(new_creds);
+                       err = vfs_setxattr(new_lower_dentry, name_list,
+                                          attr_value, size, 0);
+                       revert_creds(old_creds);
+               }
+               if (err < 0)
+                       goto out;
+               name_list += strlen(name_list) + 1;
+       }
+out:
+       unionfs_xattr_kfree(name_list_buf);
+       unionfs_xattr_kfree(attr_value);
+       /* Ignore if xattr isn't supported */
+       if (err == -ENOTSUPP || err == -EOPNOTSUPP)
+               err = 0;
+       return err;
+}
+#endif /* CONFIG_UNION_FS_XATTR */
+
+/*
+ * Determine the mode based on the copyup flags, and the existing dentry.
+ *
+ * Handle file systems which may not support certain options.  For example
+ * jffs2 doesn't allow one to chmod a symlink.  So we ignore such harmless
+ * errors, rather than propagating them up, which results in copyup errors
+ * and errors returned back to users.
+ */
+static int copyup_permissions(struct super_block *sb,
+                             struct dentry *old_lower_dentry,
+                             struct dentry *new_lower_dentry)
+{
+       struct inode *i = old_lower_dentry->d_inode;
+       struct iattr newattrs;
+       int err;
+
+       newattrs.ia_atime = i->i_atime;
+       newattrs.ia_mtime = i->i_mtime;
+       newattrs.ia_ctime = i->i_ctime;
+       newattrs.ia_gid = i->i_gid;
+       newattrs.ia_uid = i->i_uid;
+       newattrs.ia_valid = ATTR_CTIME | ATTR_ATIME | ATTR_MTIME |
+               ATTR_ATIME_SET | ATTR_MTIME_SET | ATTR_FORCE |
+               ATTR_GID | ATTR_UID;
+       mutex_lock(&new_lower_dentry->d_inode->i_mutex);
+       err = notify_change(new_lower_dentry, &newattrs);
+       if (err)
+               goto out;
+
+       /* now try to change the mode and ignore EOPNOTSUPP on symlinks */
+       newattrs.ia_mode = i->i_mode;
+       newattrs.ia_valid = ATTR_MODE | ATTR_FORCE;
+       err = notify_change(new_lower_dentry, &newattrs);
+       if (err == -EOPNOTSUPP &&
+           S_ISLNK(new_lower_dentry->d_inode->i_mode)) {
+               printk(KERN_WARNING
+                      "unionfs: changing \"%s\" symlink mode unsupported\n",
+                      new_lower_dentry->d_name.name);
+               err = 0;
+       }
+
+out:
+       mutex_unlock(&new_lower_dentry->d_inode->i_mutex);
+       return err;
+}
+
+/*
+ * create the new device/file/directory - use copyup_permission to copyup
+ * times, and mode
+ *
+ * if the object being copied up is a regular file, the file is only created,
+ * the contents have to be copied up separately
+ */
+static int __copyup_ndentry(struct dentry *old_lower_dentry,
+                           struct dentry *new_lower_dentry,
+                           struct dentry *new_lower_parent_dentry,
+                           char *symbuf)
+{
+       int err = 0;
+       umode_t old_mode = old_lower_dentry->d_inode->i_mode;
+       struct sioq_args args;
+
+       if (S_ISDIR(old_mode)) {
+               args.mkdir.parent = new_lower_parent_dentry->d_inode;
+               args.mkdir.dentry = new_lower_dentry;
+               args.mkdir.mode = old_mode;
+
+               run_sioq(__unionfs_mkdir, &args);
+               err = args.err;
+       } else if (S_ISLNK(old_mode)) {
+               args.symlink.parent = new_lower_parent_dentry->d_inode;
+               args.symlink.dentry = new_lower_dentry;
+               args.symlink.symbuf = symbuf;
+
+               run_sioq(__unionfs_symlink, &args);
+               err = args.err;
+       } else if (S_ISBLK(old_mode) || S_ISCHR(old_mode) ||
+                  S_ISFIFO(old_mode) || S_ISSOCK(old_mode)) {
+               args.mknod.parent = new_lower_parent_dentry->d_inode;
+               args.mknod.dentry = new_lower_dentry;
+               args.mknod.mode = old_mode;
+               args.mknod.dev = old_lower_dentry->d_inode->i_rdev;
+
+               run_sioq(__unionfs_mknod, &args);
+               err = args.err;
+       } else if (S_ISREG(old_mode)) {
+               struct nameidata nd;
+               err = init_lower_nd(&nd, LOOKUP_CREATE);
+               if (unlikely(err < 0))
+                       goto out;
+               args.create.nd = &nd;
+               args.create.parent = new_lower_parent_dentry->d_inode;
+               args.create.dentry = new_lower_dentry;
+               args.create.mode = old_mode;
+
+               run_sioq(__unionfs_create, &args);
+               err = args.err;
+               release_lower_nd(&nd, err);
+       } else {
+               printk(KERN_CRIT "unionfs: unknown inode type %d\n",
+                      old_mode);
+               BUG();
+       }
+
+out:
+       return err;
+}
+
+static int __copyup_reg_data(struct dentry *dentry,
+                            struct dentry *new_lower_dentry, int new_bindex,
+                            struct dentry *old_lower_dentry, int old_bindex,
+                            struct file **copyup_file, loff_t len)
+{
+       struct super_block *sb = dentry->d_sb;
+       struct file *input_file;
+       struct file *output_file;
+       struct vfsmount *output_mnt;
+       mm_segment_t old_fs;
+       char *buf = NULL;
+       ssize_t read_bytes, write_bytes;
+       loff_t size;
+       int err = 0;
+
+       /* open old file */
+       unionfs_mntget(dentry, old_bindex);
+       branchget(sb, old_bindex);
+       /* dentry_open calls dput and mntput if it returns an error */
+       input_file = dentry_open(old_lower_dentry,
+                                unionfs_lower_mnt_idx(dentry, old_bindex),
+                                O_RDONLY | O_LARGEFILE, current_cred());
+       if (IS_ERR(input_file)) {
+               dput(old_lower_dentry);
+               err = PTR_ERR(input_file);
+               goto out;
+       }
+       if (unlikely(!input_file->f_op || !input_file->f_op->read)) {
+               err = -EINVAL;
+               goto out_close_in;
+       }
+
+       /* open new file */
+       dget(new_lower_dentry);
+       output_mnt = unionfs_mntget(sb->s_root, new_bindex);
+       branchget(sb, new_bindex);
+       output_file = dentry_open(new_lower_dentry, output_mnt,
+                                 O_RDWR | O_LARGEFILE, current_cred());
+       if (IS_ERR(output_file)) {
+               err = PTR_ERR(output_file);
+               goto out_close_in2;
+       }
+       if (unlikely(!output_file->f_op || !output_file->f_op->write)) {
+               err = -EINVAL;
+               goto out_close_out;
+       }
+
+       /* allocating a buffer */
+       buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+       if (unlikely(!buf)) {
+               err = -ENOMEM;
+               goto out_close_out;
+       }
+
+       input_file->f_pos = 0;
+       output_file->f_pos = 0;
+
+       old_fs = get_fs();
+       set_fs(KERNEL_DS);
+
+       size = len;
+       err = 0;
+       do {
+               if (len >= PAGE_SIZE)
+                       size = PAGE_SIZE;
+               else if ((len < PAGE_SIZE) && (len > 0))
+                       size = len;
+
+               len -= PAGE_SIZE;
+
+               read_bytes =
+                       input_file->f_op->read(input_file,
+                                              (char __user *)buf, size,
+                                              &input_file->f_pos);
+               if (read_bytes <= 0) {
+                       err = read_bytes;
+                       break;
+               }
+
+               /* see Documentation/filesystems/unionfs/issues.txt */
+               lockdep_off();
+               write_bytes =
+                       output_file->f_op->write(output_file,
+                                                (char __user *)buf,
+                                                read_bytes,
+                                                &output_file->f_pos);
+               lockdep_on();
+               if ((write_bytes < 0) || (write_bytes < read_bytes)) {
+                       err = write_bytes;
+                       break;
+               }
+       } while ((read_bytes > 0) && (len > 0));
+
+       set_fs(old_fs);
+
+       kfree(buf);
+
+#if 0
+       /* XXX: code no longer needed? */
+       if (!err)
+               err = output_file->f_op->fsync(output_file, 0);
+#endif
+
+       if (err)
+               goto out_close_out;
+
+       if (copyup_file) {
+               *copyup_file = output_file;
+               goto out_close_in;
+       }
+
+out_close_out:
+       fput(output_file);
+
+out_close_in2:
+       branchput(sb, new_bindex);
+
+out_close_in:
+       fput(input_file);
+
+out:
+       branchput(sb, old_bindex);
+
+       return err;
+}
+
+/*
+ * dput the lower references for old and new dentry & clear a lower dentry
+ * pointer
+ */
+static void __clear(struct dentry *dentry, struct dentry *old_lower_dentry,
+                   int old_bstart, int old_bend,
+                   struct dentry *new_lower_dentry, int new_bindex)
+{
+       /* get rid of the lower dentry and all its traces */
+       unionfs_set_lower_dentry_idx(dentry, new_bindex, NULL);
+       dbstart(dentry) = old_bstart;
+       dbend(dentry) = old_bend;
+
+       dput(new_lower_dentry);
+       dput(old_lower_dentry);
+}
+
+/*
+ * Copy up a dentry to a file of specified name.
+ *
+ * @dir: used to pull the ->i_sb to access other branches
+ * @dentry: the non-negative dentry whose lower_inode we should copy
+ * @bstart: the branch of the lower_inode to copy from
+ * @new_bindex: the branch to create the new file in
+ * @name: the name of the file to create
+ * @namelen: length of @name
+ * @copyup_file: the "struct file" to return (optional)
+ * @len: how many bytes to copy-up?
+ */
+int copyup_dentry(struct inode *dir, struct dentry *dentry, int bstart,
+                 int new_bindex, const char *name, int namelen,
+                 struct file **copyup_file, loff_t len)
+{
+       struct dentry *new_lower_dentry;
+       struct dentry *old_lower_dentry = NULL;
+       struct super_block *sb;
+       int err = 0;
+       int old_bindex;
+       int old_bstart;
+       int old_bend;
+       struct dentry *new_lower_parent_dentry = NULL;
+       mm_segment_t oldfs;
+       char *symbuf = NULL;
+
+       verify_locked(dentry);
+
+       old_bindex = bstart;
+       old_bstart = dbstart(dentry);
+       old_bend = dbend(dentry);
+
+       BUG_ON(new_bindex < 0);
+       BUG_ON(new_bindex >= old_bindex);
+
+       sb = dir->i_sb;
+
+       err = is_robranch_super(sb, new_bindex);
+       if (err)
+               goto out;
+
+       /* Create the directory structure above this dentry. */
+       new_lower_dentry = create_parents(dir, dentry, name, new_bindex);
+       if (IS_ERR(new_lower_dentry)) {
+               err = PTR_ERR(new_lower_dentry);
+               goto out;
+       }
+
+       old_lower_dentry = unionfs_lower_dentry_idx(dentry, old_bindex);
+       /* we conditionally dput this old_lower_dentry at end of function */
+       dget(old_lower_dentry);
+
+       /* For symlinks, we must read the link before we lock the directory. */
+       if (S_ISLNK(old_lower_dentry->d_inode->i_mode)) {
+
+               symbuf = kmalloc(PATH_MAX, GFP_KERNEL);
+               if (unlikely(!symbuf)) {
+                       __clear(dentry, old_lower_dentry,
+                               old_bstart, old_bend,
+                               new_lower_dentry, new_bindex);
+                       err = -ENOMEM;
+                       goto out_free;
+               }
+
+               oldfs = get_fs();
+               set_fs(KERNEL_DS);
+               err = old_lower_dentry->d_inode->i_op->readlink(
+                       old_lower_dentry,
+                       (char __user *)symbuf,
+                       PATH_MAX);
+               set_fs(oldfs);
+               if (err < 0) {
+                       __clear(dentry, old_lower_dentry,
+                               old_bstart, old_bend,
+                               new_lower_dentry, new_bindex);
+                       goto out_free;
+               }
+               symbuf[err] = '\0';
+       }
+
+       /* Now we lock the parent, and create the object in the new branch. */
+       new_lower_parent_dentry = lock_parent(new_lower_dentry);
+
+       /* create the new inode */
+       err = __copyup_ndentry(old_lower_dentry, new_lower_dentry,
+                              new_lower_parent_dentry, symbuf);
+
+       if (err) {
+               __clear(dentry, old_lower_dentry,
+                       old_bstart, old_bend,
+                       new_lower_dentry, new_bindex);
+               goto out_unlock;
+       }
+
+       /* We actually copyup the file here. */
+       if (S_ISREG(old_lower_dentry->d_inode->i_mode))
+               err = __copyup_reg_data(dentry, new_lower_dentry, new_bindex,
+                                       old_lower_dentry, old_bindex,
+                                       copyup_file, len);
+       if (err)
+               goto out_unlink;
+
+       /* Set permissions. */
+       err = copyup_permissions(sb, old_lower_dentry, new_lower_dentry);
+       if (err)
+               goto out_unlink;
+
+#ifdef CONFIG_UNION_FS_XATTR
+       /* Selinux uses extended attributes for permissions. */
+       err = copyup_xattrs(old_lower_dentry, new_lower_dentry);
+       if (err)
+               goto out_unlink;
+#endif /* CONFIG_UNION_FS_XATTR */
+
+       /* do not allow files getting deleted to be re-interposed */
+       if (!d_deleted(dentry))
+               unionfs_reinterpose(dentry);
+
+       goto out_unlock;
+
+out_unlink:
+       /*
+        * copyup failed, because we possibly ran out of space or
+        * quota, or something else happened so let's unlink; we don't
+        * really care about the return value of vfs_unlink
+        */
+       vfs_unlink(new_lower_parent_dentry->d_inode, new_lower_dentry);
+
+       if (copyup_file) {
+               /* need to close the file */
+
+               fput(*copyup_file);
+               branchput(sb, new_bindex);
+       }
+
+       /*
+        * TODO: should we reset the error to something like -EIO?
+        *
+        * If we don't reset, the user may get some nonsensical errors, but
+        * on the other hand, if we reset to EIO, we guarantee that the user
+        * will get a "confusing" error message.
+        */
+
+out_unlock:
+       unlock_dir(new_lower_parent_dentry);
+
+out_free:
+       /*
+        * If old_lower_dentry was not a file, then we need to dput it.  If
+        * it was a file, then it was already dput indirectly by other
+        * functions we call above which operate on regular files.
+        */
+       if (old_lower_dentry && old_lower_dentry->d_inode &&
+           !S_ISREG(old_lower_dentry->d_inode->i_mode))
+               dput(old_lower_dentry);
+       kfree(symbuf);
+
+       if (err) {
+               /*
+                * if directory creation succeeded, but inode copyup failed,
+                * then purge new dentries.
+                */
+               if (dbstart(dentry) < old_bstart &&
+                   ibstart(dentry->d_inode) > dbstart(dentry))
+                       __clear(dentry, NULL, old_bstart, old_bend,
+                               unionfs_lower_dentry(dentry), dbstart(dentry));
+               goto out;
+       }
+       if (!S_ISDIR(dentry->d_inode->i_mode)) {
+               unionfs_postcopyup_release(dentry);
+               if (!unionfs_lower_inode(dentry->d_inode)) {
+                       /*
+                        * If we got here, then we copied up to an
+                        * unlinked-open file, whose name is .unionfsXXXXX.
+                        */
+                       struct inode *inode = new_lower_dentry->d_inode;
+                       atomic_inc(&inode->i_count);
+                       unionfs_set_lower_inode_idx(dentry->d_inode,
+                                                   ibstart(dentry->d_inode),
+                                                   inode);
+               }
+       }
+       unionfs_postcopyup_setmnt(dentry);
+       /* sync inode times from copied-up inode to our inode */
+       unionfs_copy_attr_times(dentry->d_inode);
+       unionfs_check_inode(dir);
+       unionfs_check_dentry(dentry);
+out:
+       return err;
+}
+
+/*
+ * This function creates a copy of a file represented by 'file' which
+ * currently resides in branch 'bstart' to branch 'new_bindex.'  The copy
+ * will be named "name".
+ */
+int copyup_named_file(struct inode *dir, struct file *file, char *name,
+                     int bstart, int new_bindex, loff_t len)
+{
+       int err = 0;
+       struct file *output_file = NULL;
+
+       err = copyup_dentry(dir, file->f_path.dentry, bstart, new_bindex,
+                           name, strlen(name), &output_file, len);
+       if (!err) {
+               fbstart(file) = new_bindex;
+               unionfs_set_lower_file_idx(file, new_bindex, output_file);
+       }
+
+       return err;
+}
+
+/*
+ * This function creates a copy of a file represented by 'file' which
+ * currently resides in branch 'bstart' to branch 'new_bindex'.
+ */
+int copyup_file(struct inode *dir, struct file *file, int bstart,
+               int new_bindex, loff_t len)
+{
+       int err = 0;
+       struct file *output_file = NULL;
+       struct dentry *dentry = file->f_path.dentry;
+
+       err = copyup_dentry(dir, dentry, bstart, new_bindex,
+                           dentry->d_name.name, dentry->d_name.len,
+                           &output_file, len);
+       if (!err) {
+               fbstart(file) = new_bindex;
+               unionfs_set_lower_file_idx(file, new_bindex, output_file);
+       }
+
+       return err;
+}
+
+/* purge a dentry's lower-branch states (dput/mntput, etc.) */
+static void __cleanup_dentry(struct dentry *dentry, int bindex,
+                            int old_bstart, int old_bend)
+{
+       int loop_start;
+       int loop_end;
+       int new_bstart = -1;
+       int new_bend = -1;
+       int i;
+
+       loop_start = min(old_bstart, bindex);
+       loop_end = max(old_bend, bindex);
+
+       /*
+        * This loop sets the bstart and bend for the new dentry by
+        * traversing from left to right.  It also dputs all negative
+        * dentries except bindex
+        */
+       for (i = loop_start; i <= loop_end; i++) {
+               if (!unionfs_lower_dentry_idx(dentry, i))
+                       continue;
+
+               if (i == bindex) {
+                       new_bend = i;
+                       if (new_bstart < 0)
+                               new_bstart = i;
+                       continue;
+               }
+
+               if (!unionfs_lower_dentry_idx(dentry, i)->d_inode) {
+                       dput(unionfs_lower_dentry_idx(dentry, i));
+                       unionfs_set_lower_dentry_idx(dentry, i, NULL);
+
+                       unionfs_mntput(dentry, i);
+                       unionfs_set_lower_mnt_idx(dentry, i, NULL);
+               } else {
+                       if (new_bstart < 0)
+                               new_bstart = i;
+                       new_bend = i;
+               }
+       }
+
+       if (new_bstart < 0)
+               new_bstart = bindex;
+       if (new_bend < 0)
+               new_bend = bindex;
+       dbstart(dentry) = new_bstart;
+       dbend(dentry) = new_bend;
+
+}
+
+/* set lower inode ptr and update bstart & bend if necessary */
+static void __set_inode(struct dentry *upper, struct dentry *lower,
+                       int bindex)
+{
+       unionfs_set_lower_inode_idx(upper->d_inode, bindex,
+                                   igrab(lower->d_inode));
+       if (likely(ibstart(upper->d_inode) > bindex))
+               ibstart(upper->d_inode) = bindex;
+       if (likely(ibend(upper->d_inode) < bindex))
+               ibend(upper->d_inode) = bindex;
+
+}
+
+/* set lower dentry ptr and update bstart & bend if necessary */
+static void __set_dentry(struct dentry *upper, struct dentry *lower,
+                        int bindex)
+{
+       unionfs_set_lower_dentry_idx(upper, bindex, lower);
+       if (likely(dbstart(upper) > bindex))
+               dbstart(upper) = bindex;
+       if (likely(dbend(upper) < bindex))
+               dbend(upper) = bindex;
+}
+
+/*
+ * This function replicates the directory structure up-to given dentry
+ * in the bindex branch.
+ */
+struct dentry *create_parents(struct inode *dir, struct dentry *dentry,
+                             const char *name, int bindex)
+{
+       int err;
+       struct dentry *child_dentry;
+       struct dentry *parent_dentry;
+       struct dentry *lower_parent_dentry = NULL;
+       struct dentry *lower_dentry = NULL;
+       const char *childname;
+       unsigned int childnamelen;
+       int nr_dentry;
+       int count = 0;
+       int old_bstart;
+       int old_bend;
+       struct dentry **path = NULL;
+       struct super_block *sb;
+
+       verify_locked(dentry);
+
+       err = is_robranch_super(dir->i_sb, bindex);
+       if (err) {
+               lower_dentry = ERR_PTR(err);
+               goto out;
+       }
+
+       old_bstart = dbstart(dentry);
+       old_bend = dbend(dentry);
+
+       lower_dentry = ERR_PTR(-ENOMEM);
+
+       /* There is no sense allocating any less than the minimum. */
+       nr_dentry = 1;
+       path = kmalloc(nr_dentry * sizeof(struct dentry *), GFP_KERNEL);
+       if (unlikely(!path))
+               goto out;
+
+       /* assume the negative dentry of unionfs as the parent dentry */
+       parent_dentry = dentry;
+
+       /*
+        * This loop finds the first parent that exists in the given branch.
+        * We start building the directory structure from there.  At the end
+        * of the loop, the following should hold:
+        *  - child_dentry is the first nonexistent child
+        *  - parent_dentry is the first existent parent
+        *  - path[0] is the = deepest child
+        *  - path[count] is the first child to create
+        */
+       do {
+               child_dentry = parent_dentry;
+
+               /* find the parent directory dentry in unionfs */
+               parent_dentry = dget_parent(child_dentry);
+
+               /* find out the lower_parent_dentry in the given branch */
+               lower_parent_dentry =
+                       unionfs_lower_dentry_idx(parent_dentry, bindex);
+
+               /* grow path table */
+               if (count == nr_dentry) {
+                       void *p;
+
+                       nr_dentry *= 2;
+                       p = krealloc(path, nr_dentry * sizeof(struct dentry *),
+                                    GFP_KERNEL);
+                       if (unlikely(!p)) {
+                               lower_dentry = ERR_PTR(-ENOMEM);
+                               goto out;
+                       }
+                       path = p;
+               }
+
+               /* store the child dentry */
+               path[count++] = child_dentry;
+       } while (!lower_parent_dentry);
+       count--;
+
+       sb = dentry->d_sb;
+
+       /*
+        * This code goes between the begin/end labels and basically
+        * emulates a while(child_dentry != dentry), only cleaner and
+        * shorter than what would be a much longer while loop.
+        */
+begin:
+       /* get lower parent dir in the current branch */
+       lower_parent_dentry = unionfs_lower_dentry_idx(parent_dentry, bindex);
+       dput(parent_dentry);
+
+       /* init the values to lookup */
+       childname = child_dentry->d_name.name;
+       childnamelen = child_dentry->d_name.len;
+
+       if (child_dentry != dentry) {
+               /* lookup child in the underlying file system */
+               lower_dentry = lookup_lck_len(childname, lower_parent_dentry,
+                                             childnamelen);
+               if (IS_ERR(lower_dentry))
+                       goto out;
+       } else {
+               /*
+                * Is the name a whiteout of the child name ?  lookup the
+                * whiteout child in the underlying file system
+                */
+               lower_dentry = lookup_lck_len(name, lower_parent_dentry,
+                                             strlen(name));
+               if (IS_ERR(lower_dentry))
+                       goto out;
+
+               /* Replace the current dentry (if any) with the new one */
+               dput(unionfs_lower_dentry_idx(dentry, bindex));
+               unionfs_set_lower_dentry_idx(dentry, bindex,
+                                            lower_dentry);
+
+               __cleanup_dentry(dentry, bindex, old_bstart, old_bend);
+               goto out;
+       }
+
+       if (lower_dentry->d_inode) {
+               /*
+                * since this already exists we dput to avoid
+                * multiple references on the same dentry
+                */
+               dput(lower_dentry);
+       } else {
+               struct sioq_args args;
+
+               /* it's a negative dentry, create a new dir */
+               lower_parent_dentry = lock_parent(lower_dentry);
+
+               args.mkdir.parent = lower_parent_dentry->d_inode;
+               args.mkdir.dentry = lower_dentry;
+               args.mkdir.mode = child_dentry->d_inode->i_mode;
+
+               run_sioq(__unionfs_mkdir, &args);
+               err = args.err;
+
+               if (!err)
+                       err = copyup_permissions(dir->i_sb, child_dentry,
+                                                lower_dentry);
+               unlock_dir(lower_parent_dentry);
+               if (err) {
+                       dput(lower_dentry);
+                       lower_dentry = ERR_PTR(err);
+                       goto out;
+               }
+
+       }
+
+       __set_inode(child_dentry, lower_dentry, bindex);
+       __set_dentry(child_dentry, lower_dentry, bindex);
+       /*
+        * update times of this dentry, but also the parent, because if
+        * we changed, the parent may have changed too.
+        */
+       fsstack_copy_attr_times(parent_dentry->d_inode,
+                               lower_parent_dentry->d_inode);
+       unionfs_copy_attr_times(child_dentry->d_inode);
+
+       parent_dentry = child_dentry;
+       child_dentry = path[--count];
+       goto begin;
+out:
+       /* cleanup any leftover locks from the do/while loop above */
+       if (IS_ERR(lower_dentry))
+               while (count)
+                       dput(path[count--]);
+       kfree(path);
+       return lower_dentry;
+}
+
+/*
+ * Post-copyup helper to ensure we have valid mnts: set lower mnt of
+ * dentry+parents to the first parent node that has an mnt.
+ */
+void unionfs_postcopyup_setmnt(struct dentry *dentry)
+{
+       struct dentry *parent, *hasone;
+       int bindex = dbstart(dentry);
+
+       if (unionfs_lower_mnt_idx(dentry, bindex))
+               return;
+       hasone = dentry->d_parent;
+       /* this loop should stop at root dentry */
+       while (!unionfs_lower_mnt_idx(hasone, bindex))
+               hasone = hasone->d_parent;
+       parent = dentry;
+       while (!unionfs_lower_mnt_idx(parent, bindex)) {
+               unionfs_set_lower_mnt_idx(parent, bindex,
+                                         unionfs_mntget(hasone, bindex));
+               parent = parent->d_parent;
+       }
+}
+
+/*
+ * Post-copyup helper to release all non-directory source objects of a
+ * copied-up file.  Regular files should have only one lower object.
+ */
+void unionfs_postcopyup_release(struct dentry *dentry)
+{
+       int bstart, bend;
+
+       BUG_ON(S_ISDIR(dentry->d_inode->i_mode));
+       bstart = dbstart(dentry);
+       bend = dbend(dentry);
+
+       path_put_lowers(dentry, bstart + 1, bend, false);
+       iput_lowers(dentry->d_inode, bstart + 1, bend, false);
+
+       dbend(dentry) = bstart;
+       ibend(dentry->d_inode) = ibstart(dentry->d_inode) = bstart;
+}
diff --git a/fs/unionfs/debug.c b/fs/unionfs/debug.c
new file mode 100644
index 0000000..21ce90c
--- /dev/null
+++ b/fs/unionfs/debug.c
@@ -0,0 +1,551 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+#include "../mount.h"
+
+/*
+ * Helper debugging functions for maintainers (and for users to report back
+ * useful information back to maintainers)
+ */
+
+/* it's always useful to know what part of the code called us */
+#define PRINT_CALLER(fname, fxn, line)                                 \
+       do {                                                            \
+               if (!printed_caller) {                                  \
+                       pr_debug("PC:%s:%s:%d\n", (fname), (fxn), (line)); \
+                       printed_caller = 1;                             \
+               }                                                       \
+       } while (0)
+
+/*
+ * __unionfs_check_{inode,dentry,file} perform exhaustive sanity checking on
+ * the fan-out of various Unionfs objects.  We check that no lower objects
+ * exist  outside the start/end branch range; that all objects within are
+ * non-NULL (with some allowed exceptions); that for every lower file
+ * there's a lower dentry+inode; that the start/end ranges match for all
+ * corresponding lower objects; that open files/symlinks have only one lower
+ * objects, but directories can have several; and more.
+ */
+void __unionfs_check_inode(const struct inode *inode,
+                          const char *fname, const char *fxn, int line)
+{
+       int bindex;
+       int istart, iend;
+       struct inode *lower_inode;
+       struct super_block *sb;
+       int printed_caller = 0;
+       void *poison_ptr;
+
+       /* for inodes now */
+       BUG_ON(!inode);
+       sb = inode->i_sb;
+       istart = ibstart(inode);
+       iend = ibend(inode);
+       /* don't check inode if no lower branches */
+       if (istart < 0 && iend < 0)
+               return;
+       if (unlikely(istart > iend)) {
+               PRINT_CALLER(fname, fxn, line);
+               pr_debug(" Ci0: inode=%p istart/end=%d:%d\n",
+                        inode, istart, iend);
+       }
+       if (unlikely((istart == -1 && iend != -1) ||
+                    (istart != -1 && iend == -1))) {
+               PRINT_CALLER(fname, fxn, line);
+               pr_debug(" Ci1: inode=%p istart/end=%d:%d\n",
+                        inode, istart, iend);
+       }
+       if (!S_ISDIR(inode->i_mode)) {
+               if (unlikely(iend != istart)) {
+                       PRINT_CALLER(fname, fxn, line);
+                       pr_debug(" Ci2: inode=%p istart=%d iend=%d\n",
+                                inode, istart, iend);
+               }
+       }
+
+       for (bindex = sbstart(sb); bindex < sbmax(sb); bindex++) {
+               if (unlikely(!UNIONFS_I(inode))) {
+                       PRINT_CALLER(fname, fxn, line);
+                       pr_debug(" Ci3: no inode_info %p\n", inode);
+                       return;
+               }
+               if (unlikely(!UNIONFS_I(inode)->lower_inodes)) {
+                       PRINT_CALLER(fname, fxn, line);
+                       pr_debug(" Ci4: no lower_inodes %p\n", inode);
+                       return;
+               }
+               lower_inode = unionfs_lower_inode_idx(inode, bindex);
+               if (lower_inode) {
+                       memset(&poison_ptr, POISON_INUSE, sizeof(void *));
+                       if (unlikely(bindex < istart || bindex > iend)) {
+                               PRINT_CALLER(fname, fxn, line);
+                               pr_debug(" Ci5: inode/linode=%p:%p bindex=%d "
+                                        "istart/end=%d:%d\n", inode,
+                                        lower_inode, bindex, istart, iend);
+                       } else if (unlikely(lower_inode == poison_ptr)) {
+                               /* freed inode! */
+                               PRINT_CALLER(fname, fxn, line);
+                               pr_debug(" Ci6: inode/linode=%p:%p bindex=%d "
+                                        "istart/end=%d:%d\n", inode,
+                                        lower_inode, bindex, istart, iend);
+                       }
+                       continue;
+               }
+               /* if we get here, then lower_inode == NULL */
+               if (bindex < istart || bindex > iend)
+                       continue;
+               /*
+                * directories can have NULL lower inodes in b/t start/end,
+                * but NOT if at the start/end range.
+                */
+               if (unlikely(S_ISDIR(inode->i_mode) &&
+                            bindex > istart && bindex < iend))
+                       continue;
+               PRINT_CALLER(fname, fxn, line);
+               pr_debug(" Ci7: inode/linode=%p:%p "
+                        "bindex=%d istart/end=%d:%d\n",
+                        inode, lower_inode, bindex, istart, iend);
+       }
+}
+
+void __unionfs_check_dentry(const struct dentry *dentry,
+                           const char *fname, const char *fxn, int line)
+{
+       int bindex;
+       int dstart, dend, istart, iend;
+       struct dentry *lower_dentry;
+       struct inode *inode, *lower_inode;
+       struct super_block *sb;
+       struct vfsmount *lower_mnt;
+       int printed_caller = 0;
+       void *poison_ptr;
+
+       BUG_ON(!dentry);
+       sb = dentry->d_sb;
+       inode = dentry->d_inode;
+       dstart = dbstart(dentry);
+       dend = dbend(dentry);
+       /* don't check dentry/mnt if no lower branches */
+       if (dstart < 0 && dend < 0)
+               goto check_inode;
+       BUG_ON(dstart > dend);
+
+       if (unlikely((dstart == -1 && dend != -1) ||
+                    (dstart != -1 && dend == -1))) {
+               PRINT_CALLER(fname, fxn, line);
+               pr_debug(" CD0: dentry=%p dstart/end=%d:%d\n",
+                        dentry, dstart, dend);
+       }
+       /*
+        * check for NULL dentries inside the start/end range, or
+        * non-NULL dentries outside the start/end range.
+        */
+       for (bindex = sbstart(sb); bindex < sbmax(sb); bindex++) {
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               if (lower_dentry) {
+                       if (unlikely(bindex < dstart || bindex > dend)) {
+                               PRINT_CALLER(fname, fxn, line);
+                               pr_debug(" CD1: dentry/lower=%p:%p(%p) "
+                                        "bindex=%d dstart/end=%d:%d\n",
+                                        dentry, lower_dentry,
+                                        (lower_dentry ? lower_dentry->d_inode :
+                                         (void *) -1L),
+                                        bindex, dstart, dend);
+                       }
+               } else {        /* lower_dentry == NULL */
+                       if (bindex < dstart || bindex > dend)
+                               continue;
+                       /*
+                        * Directories can have NULL lower inodes in b/t
+                        * start/end, but NOT if at the start/end range.
+                        * Ignore this rule, however, if this is a NULL
+                        * dentry or a deleted dentry.
+                        */
+                       if (unlikely(!d_deleted((struct dentry *) dentry) &&
+                                    inode &&
+                                    !(inode && S_ISDIR(inode->i_mode) &&
+                                      bindex > dstart && bindex < dend))) {
+                               PRINT_CALLER(fname, fxn, line);
+                               pr_debug(" CD2: dentry/lower=%p:%p(%p) "
+                                        "bindex=%d dstart/end=%d:%d\n",
+                                        dentry, lower_dentry,
+                                        (lower_dentry ?
+                                         lower_dentry->d_inode :
+                                         (void *) -1L),
+                                        bindex, dstart, dend);
+                       }
+               }
+       }
+
+       /* check for vfsmounts same as for dentries */
+       for (bindex = sbstart(sb); bindex < sbmax(sb); bindex++) {
+               lower_mnt = unionfs_lower_mnt_idx(dentry, bindex);
+               if (lower_mnt) {
+                       if (unlikely(bindex < dstart || bindex > dend)) {
+                               PRINT_CALLER(fname, fxn, line);
+                               pr_debug(" CM0: dentry/lmnt=%p:%p bindex=%d "
+                                        "dstart/end=%d:%d\n", dentry,
+                                        lower_mnt, bindex, dstart, dend);
+                       }
+               } else {        /* lower_mnt == NULL */
+                       if (bindex < dstart || bindex > dend)
+                               continue;
+                       /*
+                        * Directories can have NULL lower inodes in b/t
+                        * start/end, but NOT if at the start/end range.
+                        * Ignore this rule, however, if this is a NULL
+                        * dentry.
+                        */
+                       if (unlikely(inode &&
+                                    !(inode && S_ISDIR(inode->i_mode) &&
+                                      bindex > dstart && bindex < dend))) {
+                               PRINT_CALLER(fname, fxn, line);
+                               pr_debug(" CM1: dentry/lmnt=%p:%p "
+                                        "bindex=%d dstart/end=%d:%d\n",
+                                        dentry, lower_mnt, bindex,
+                                        dstart, dend);
+                       }
+               }
+       }
+
+check_inode:
+       /* for inodes now */
+       if (!inode)
+               return;
+       istart = ibstart(inode);
+       iend = ibend(inode);
+       /* don't check inode if no lower branches */
+       if (istart < 0 && iend < 0)
+               return;
+       BUG_ON(istart > iend);
+       if (unlikely((istart == -1 && iend != -1) ||
+                    (istart != -1 && iend == -1))) {
+               PRINT_CALLER(fname, fxn, line);
+               pr_debug(" CI0: dentry/inode=%p:%p istart/end=%d:%d\n",
+                        dentry, inode, istart, iend);
+       }
+       if (unlikely(istart != dstart)) {
+               PRINT_CALLER(fname, fxn, line);
+               pr_debug(" CI1: dentry/inode=%p:%p istart=%d dstart=%d\n",
+                        dentry, inode, istart, dstart);
+       }
+       if (unlikely(iend != dend)) {
+               PRINT_CALLER(fname, fxn, line);
+               pr_debug(" CI2: dentry/inode=%p:%p iend=%d dend=%d\n",
+                        dentry, inode, iend, dend);
+       }
+
+       if (!S_ISDIR(inode->i_mode)) {
+               if (unlikely(dend != dstart)) {
+                       PRINT_CALLER(fname, fxn, line);
+                       pr_debug(" CI3: dentry/inode=%p:%p dstart=%d dend=%d\n",
+                                dentry, inode, dstart, dend);
+               }
+               if (unlikely(iend != istart)) {
+                       PRINT_CALLER(fname, fxn, line);
+                       pr_debug(" CI4: dentry/inode=%p:%p istart=%d iend=%d\n",
+                                dentry, inode, istart, iend);
+               }
+       }
+
+       for (bindex = sbstart(sb); bindex < sbmax(sb); bindex++) {
+               lower_inode = unionfs_lower_inode_idx(inode, bindex);
+               if (lower_inode) {
+                       memset(&poison_ptr, POISON_INUSE, sizeof(void *));
+                       if (unlikely(bindex < istart || bindex > iend)) {
+                               PRINT_CALLER(fname, fxn, line);
+                               pr_debug(" CI5: dentry/linode=%p:%p bindex=%d "
+                                        "istart/end=%d:%d\n", dentry,
+                                        lower_inode, bindex, istart, iend);
+                       } else if (unlikely(lower_inode == poison_ptr)) {
+                               /* freed inode! */
+                               PRINT_CALLER(fname, fxn, line);
+                               pr_debug(" CI6: dentry/linode=%p:%p bindex=%d "
+                                        "istart/end=%d:%d\n", dentry,
+                                        lower_inode, bindex, istart, iend);
+                       }
+                       continue;
+               }
+               /* if we get here, then lower_inode == NULL */
+               if (bindex < istart || bindex > iend)
+                       continue;
+               /*
+                * directories can have NULL lower inodes in b/t start/end,
+                * but NOT if at the start/end range.
+                */
+               if (unlikely(S_ISDIR(inode->i_mode) &&
+                            bindex > istart && bindex < iend))
+                       continue;
+               PRINT_CALLER(fname, fxn, line);
+               pr_debug(" CI7: dentry/linode=%p:%p "
+                        "bindex=%d istart/end=%d:%d\n",
+                        dentry, lower_inode, bindex, istart, iend);
+       }
+
+       /*
+        * If it's a directory, then intermediate objects b/t start/end can
+        * be NULL.  But, check that all three are NULL: lower dentry, mnt,
+        * and inode.
+        */
+       if (dstart >= 0 && dend >= 0 && S_ISDIR(inode->i_mode))
+               for (bindex = dstart+1; bindex < dend; bindex++) {
+                       lower_inode = unionfs_lower_inode_idx(inode, bindex);
+                       lower_dentry = unionfs_lower_dentry_idx(dentry,
+                                                               bindex);
+                       lower_mnt = unionfs_lower_mnt_idx(dentry, bindex);
+                       if (unlikely(!((lower_inode && lower_dentry &&
+                                       lower_mnt) ||
+                                      (!lower_inode &&
+                                       !lower_dentry && !lower_mnt)))) {
+                               PRINT_CALLER(fname, fxn, line);
+                               pr_debug(" Cx: lmnt/ldentry/linode=%p:%p:%p "
+                                        "bindex=%d dstart/end=%d:%d\n",
+                                        lower_mnt, lower_dentry, lower_inode,
+                                        bindex, dstart, dend);
+                       }
+               }
+       /* check if lower inode is newer than upper one (it shouldn't) */
+       if (unlikely(is_newer_lower(dentry) && !is_negative_lower(dentry))) {
+               PRINT_CALLER(fname, fxn, line);
+               for (bindex = ibstart(inode); bindex <= ibend(inode);
+                    bindex++) {
+                       lower_inode = unionfs_lower_inode_idx(inode, bindex);
+                       if (unlikely(!lower_inode))
+                               continue;
+                       pr_debug(" CI8: bindex=%d mtime/lmtime=%lu.%lu/%lu.%lu "
+                                "ctime/lctime=%lu.%lu/%lu.%lu\n",
+                                bindex,
+                                inode->i_mtime.tv_sec,
+                                inode->i_mtime.tv_nsec,
+                                lower_inode->i_mtime.tv_sec,
+                                lower_inode->i_mtime.tv_nsec,
+                                inode->i_ctime.tv_sec,
+                                inode->i_ctime.tv_nsec,
+                                lower_inode->i_ctime.tv_sec,
+                                lower_inode->i_ctime.tv_nsec);
+               }
+       }
+}
+
+void __unionfs_check_file(const struct file *file,
+                         const char *fname, const char *fxn, int line)
+{
+       int bindex;
+       int dstart, dend, fstart, fend;
+       struct dentry *dentry;
+       struct file *lower_file;
+       struct inode *inode;
+       struct super_block *sb;
+       int printed_caller = 0;
+
+       BUG_ON(!file);
+       dentry = file->f_path.dentry;
+       sb = dentry->d_sb;
+       dstart = dbstart(dentry);
+       dend = dbend(dentry);
+       BUG_ON(dstart > dend);
+       fstart = fbstart(file);
+       fend = fbend(file);
+       BUG_ON(fstart > fend);
+
+       if (unlikely((fstart == -1 && fend != -1) ||
+                    (fstart != -1 && fend == -1))) {
+               PRINT_CALLER(fname, fxn, line);
+               pr_debug(" CF0: file/dentry=%p:%p fstart/end=%d:%d\n",
+                        file, dentry, fstart, fend);
+       }
+       /* d_deleted dentries can be ignored for this test */
+       if (unlikely(fstart != dstart) && !d_deleted(dentry)) {
+               PRINT_CALLER(fname, fxn, line);
+               pr_debug(" CF1: file/dentry=%p:%p fstart=%d dstart=%d\n",
+                        file, dentry, fstart, dstart);
+       }
+       if (unlikely(fend != dend) && !d_deleted(dentry)) {
+               PRINT_CALLER(fname, fxn, line);
+               pr_debug(" CF2: file/dentry=%p:%p fend=%d dend=%d\n",
+                        file, dentry, fend, dend);
+       }
+       inode = dentry->d_inode;
+       if (!S_ISDIR(inode->i_mode)) {
+               if (unlikely(fend != fstart)) {
+                       PRINT_CALLER(fname, fxn, line);
+                       pr_debug(" CF3: file/inode=%p:%p fstart=%d fend=%d\n",
+                                file, inode, fstart, fend);
+               }
+               if (unlikely(dend != dstart)) {
+                       PRINT_CALLER(fname, fxn, line);
+                       pr_debug(" CF4: file/dentry=%p:%p dstart=%d dend=%d\n",
+                                file, dentry, dstart, dend);
+               }
+       }
+
+       /*
+        * check for NULL dentries inside the start/end range, or
+        * non-NULL dentries outside the start/end range.
+        */
+       for (bindex = sbstart(sb); bindex < sbmax(sb); bindex++) {
+               lower_file = unionfs_lower_file_idx(file, bindex);
+               if (lower_file) {
+                       if (unlikely(bindex < fstart || bindex > fend)) {
+                               PRINT_CALLER(fname, fxn, line);
+                               pr_debug(" CF5: file/lower=%p:%p bindex=%d "
+                                        "fstart/end=%d:%d\n", file,
+                                        lower_file, bindex, fstart, fend);
+                       }
+               } else {        /* lower_file == NULL */
+                       if (bindex >= fstart && bindex <= fend) {
+                               /*
+                                * directories can have NULL lower inodes in
+                                * b/t start/end, but NOT if at the
+                                * start/end range.
+                                */
+                               if (unlikely(!(S_ISDIR(inode->i_mode) &&
+                                              bindex > fstart &&
+                                              bindex < fend))) {
+                                       PRINT_CALLER(fname, fxn, line);
+                                       pr_debug(" CF6: file/lower=%p:%p "
+                                                "bindex=%d fstart/end=%d:%d\n",
+                                                file, lower_file, bindex,
+                                                fstart, fend);
+                               }
+                       }
+               }
+       }
+
+       __unionfs_check_dentry(dentry, fname, fxn, line);
+}
+
+void __unionfs_check_nd(const struct nameidata *nd,
+                       const char *fname, const char *fxn, int line)
+{
+       struct file *file;
+       int printed_caller = 0;
+
+       if (unlikely(!nd))
+               return;
+       if (nd->flags & LOOKUP_OPEN) {
+               file = nd->intent.open.file;
+               if (unlikely(file->f_path.dentry &&
+                            strcmp(file->f_path.dentry->d_sb->s_type->name,
+                                   UNIONFS_NAME))) {
+                       PRINT_CALLER(fname, fxn, line);
+                       pr_debug(" CND1: lower_file of type %s\n",
+                                file->f_path.dentry->d_sb->s_type->name);
+               }
+       }
+}
+
+static unsigned int __mnt_get_count(struct vfsmount *mnt)
+{
+       struct mount *m = real_mount(mnt);
+#ifdef CONFIG_SMP
+       unsigned int count = 0;
+       int cpu;
+
+       for_each_possible_cpu(cpu) {
+               count += per_cpu_ptr(m->mnt_pcp, cpu)->mnt_count;
+       }
+
+       return count;
+#else
+       return m->mnt_count;
+#endif
+}
+
+/* useful to track vfsmount leaks that could cause EBUSY on unmount */
+void __show_branch_counts(const struct super_block *sb,
+                         const char *file, const char *fxn, int line)
+{
+       int i;
+       struct vfsmount *mnt;
+
+       pr_debug("BC:");
+       for (i = 0; i < sbmax(sb); i++) {
+               if (likely(sb->s_root))
+                       mnt = UNIONFS_D(sb->s_root)->lower_paths[i].mnt;
+               else
+                       mnt = NULL;
+               printk(KERN_CONT "%d:",
+                      (mnt ? __mnt_get_count(mnt) : -99));
+       }
+       printk(KERN_CONT "%s:%s:%d\n", file, fxn, line);
+}
+
+void __show_inode_times(const struct inode *inode,
+                       const char *file, const char *fxn, int line)
+{
+       struct inode *lower_inode;
+       int bindex;
+
+       for (bindex = ibstart(inode); bindex <= ibend(inode); bindex++) {
+               lower_inode = unionfs_lower_inode_idx(inode, bindex);
+               if (unlikely(!lower_inode))
+                       continue;
+               pr_debug("IT(%lu:%d): %s:%s:%d "
+                        "um=%lu/%lu lm=%lu/%lu uc=%lu/%lu lc=%lu/%lu\n",
+                        inode->i_ino, bindex,
+                        file, fxn, line,
+                        inode->i_mtime.tv_sec, inode->i_mtime.tv_nsec,
+                        lower_inode->i_mtime.tv_sec,
+                        lower_inode->i_mtime.tv_nsec,
+                        inode->i_ctime.tv_sec, inode->i_ctime.tv_nsec,
+                        lower_inode->i_ctime.tv_sec,
+                        lower_inode->i_ctime.tv_nsec);
+       }
+}
+
+void __show_dinode_times(const struct dentry *dentry,
+                       const char *file, const char *fxn, int line)
+{
+       struct inode *inode = dentry->d_inode;
+       struct inode *lower_inode;
+       int bindex;
+
+       for (bindex = ibstart(inode); bindex <= ibend(inode); bindex++) {
+               lower_inode = unionfs_lower_inode_idx(inode, bindex);
+               if (!lower_inode)
+                       continue;
+               pr_debug("DT(%s:%lu:%d): %s:%s:%d "
+                        "um=%lu/%lu lm=%lu/%lu uc=%lu/%lu lc=%lu/%lu\n",
+                        dentry->d_name.name, inode->i_ino, bindex,
+                        file, fxn, line,
+                        inode->i_mtime.tv_sec, inode->i_mtime.tv_nsec,
+                        lower_inode->i_mtime.tv_sec,
+                        lower_inode->i_mtime.tv_nsec,
+                        inode->i_ctime.tv_sec, inode->i_ctime.tv_nsec,
+                        lower_inode->i_ctime.tv_sec,
+                        lower_inode->i_ctime.tv_nsec);
+       }
+}
+
+void __show_inode_counts(const struct inode *inode,
+                       const char *file, const char *fxn, int line)
+{
+       struct inode *lower_inode;
+       int bindex;
+
+       if (unlikely(!inode)) {
+               pr_debug("SiC: Null inode\n");
+               return;
+       }
+       for (bindex = sbstart(inode->i_sb); bindex <= sbend(inode->i_sb);
+            bindex++) {
+               lower_inode = unionfs_lower_inode_idx(inode, bindex);
+               if (unlikely(!lower_inode))
+                       continue;
+               pr_debug("SIC(%lu:%d:%d): lc=%d %s:%s:%d\n",
+                        inode->i_ino, bindex,
+                        atomic_read(&(inode)->i_count),
+                        atomic_read(&(lower_inode)->i_count),
+                        file, fxn, line);
+       }
+}
diff --git a/fs/unionfs/dentry.c b/fs/unionfs/dentry.c
new file mode 100644
index 0000000..1628dad
--- /dev/null
+++ b/fs/unionfs/dentry.c
@@ -0,0 +1,409 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+bool is_negative_lower(const struct dentry *dentry)
+{
+       int bindex;
+       struct dentry *lower_dentry;
+
+       BUG_ON(!dentry);
+       /* cache coherency: check if file was deleted on lower branch */
+       if (dbstart(dentry) < 0)
+               return true;
+       for (bindex = dbstart(dentry); bindex <= dbend(dentry); bindex++) {
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               /* unhashed (i.e., unlinked) lower dentries don't count */
+               if (lower_dentry && lower_dentry->d_inode &&
+                   !d_deleted(lower_dentry) &&
+                   !(lower_dentry->d_flags & DCACHE_NFSFS_RENAMED))
+                       return false;
+       }
+       return true;
+}
+
+static inline void __dput_lowers(struct dentry *dentry, int start, int end)
+{
+       struct dentry *lower_dentry;
+       int bindex;
+
+       if (start < 0)
+               return;
+       for (bindex = start; bindex <= end; bindex++) {
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               if (!lower_dentry)
+                       continue;
+               unionfs_set_lower_dentry_idx(dentry, bindex, NULL);
+               dput(lower_dentry);
+       }
+}
+
+/*
+ * Purge and invalidate as many data pages of a unionfs inode.  This is
+ * called when the lower inode has changed, and we want to force processes
+ * to re-get the new data.
+ */
+static inline void purge_inode_data(struct inode *inode)
+{
+       /* remove all non-private mappings */
+       unmap_mapping_range(inode->i_mapping, 0, 0, 0);
+       /* invalidate as many pages as possible */
+       invalidate_mapping_pages(inode->i_mapping, 0, -1);
+       /*
+        * Don't try to truncate_inode_pages here, because this could lead
+        * to a deadlock between some of address_space ops and dentry
+        * revalidation: the address space op is invoked with a lock on our
+        * own page, and truncate_inode_pages will block on locked pages.
+        */
+}
+
+/*
+ * Revalidate a single file/symlink/special dentry.  Assume that info nodes
+ * of the @dentry and its @parent are locked.  Assume parent is valid,
+ * otherwise return false (and let's hope the VFS will try to re-lookup this
+ * dentry).  Returns true if valid, false otherwise.
+ */
+bool __unionfs_d_revalidate(struct dentry *dentry, struct dentry *parent,
+                           bool willwrite)
+{
+       bool valid = true;      /* default is valid */
+       struct dentry *lower_dentry;
+       struct dentry *result;
+       int bindex, bstart, bend;
+       int sbgen, dgen, pdgen;
+       int positive = 0;
+       int interpose_flag;
+
+       verify_locked(dentry);
+       verify_locked(parent);
+
+       /* if the dentry is unhashed, do NOT revalidate */
+       if (d_deleted(dentry))
+               goto out;
+
+       dgen = atomic_read(&UNIONFS_D(dentry)->generation);
+
+       if (is_newer_lower(dentry)) {
+               /* root dentry is always valid */
+               if (IS_ROOT(dentry)) {
+                       unionfs_copy_attr_times(dentry->d_inode);
+               } else {
+                       /*
+                        * reset generation number to zero, guaranteed to be
+                        * "old"
+                        */
+                       dgen = 0;
+                       atomic_set(&UNIONFS_D(dentry)->generation, dgen);
+               }
+               if (!willwrite)
+                       purge_inode_data(dentry->d_inode);
+       }
+
+       sbgen = atomic_read(&UNIONFS_SB(dentry->d_sb)->generation);
+
+       BUG_ON(dbstart(dentry) == -1);
+       if (dentry->d_inode)
+               positive = 1;
+
+       /* if our dentry is valid, then validate all lower ones */
+       if (sbgen == dgen)
+               goto validate_lowers;
+
+       /* The root entry should always be valid */
+       BUG_ON(IS_ROOT(dentry));
+
+       /* We can't work correctly if our parent isn't valid. */
+       pdgen = atomic_read(&UNIONFS_D(parent)->generation);
+
+       /* Free the pointers for our inodes and this dentry. */
+       path_put_lowers_all(dentry, false);
+
+       interpose_flag = INTERPOSE_REVAL_NEG;
+       if (positive) {
+               interpose_flag = INTERPOSE_REVAL;
+               iput_lowers_all(dentry->d_inode, true);
+       }
+
+       if (realloc_dentry_private_data(dentry) != 0) {
+               valid = false;
+               goto out;
+       }
+
+       result = unionfs_lookup_full(dentry, parent, interpose_flag);
+       if (result) {
+               if (IS_ERR(result)) {
+                       valid = false;
+                       goto out;
+               }
+               /*
+                * current unionfs_lookup_backend() doesn't return
+                * a valid dentry
+                */
+               dput(dentry);
+               dentry = result;
+       }
+
+       if (unlikely(positive && is_negative_lower(dentry))) {
+               /* call make_bad_inode here ? */
+               d_drop(dentry);
+               valid = false;
+               goto out;
+       }
+
+       /*
+        * if we got here then we have revalidated our dentry and all lower
+        * ones, so we can return safely.
+        */
+       if (!valid)             /* lower dentry revalidation failed */
+               goto out;
+
+       /*
+        * If the parent's gen no.  matches the superblock's gen no., then
+        * we can update our denty's gen no.  If they didn't match, then it
+        * was OK to revalidate this dentry with a stale parent, but we'll
+        * purposely not update our dentry's gen no. (so it can be redone);
+        * and, we'll mark our parent dentry as invalid so it'll force it
+        * (and our dentry) to be revalidated.
+        */
+       if (pdgen == sbgen)
+               atomic_set(&UNIONFS_D(dentry)->generation, sbgen);
+       goto out;
+
+validate_lowers:
+
+       /* The revalidation must occur across all branches */
+       bstart = dbstart(dentry);
+       bend = dbend(dentry);
+       BUG_ON(bstart == -1);
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               int err;
+               struct nameidata lower_nd;
+
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               if (!lower_dentry || !lower_dentry->d_op
+                   || !lower_dentry->d_op->d_revalidate)
+                       continue;
+               /*
+                * Don't pass nameidata to lower file system, because we
+                * don't want an arbitrary lower file being opened or
+                * returned to us: it may be useless to us because of the
+                * fanout nature of unionfs (cf. file/directory open-file
+                * invariants).  We will open lower files as and when needed
+                * later on.
+                */
+               err = init_lower_nd(&lower_nd, LOOKUP_OPEN);
+               if (unlikely(err < 0)) {
+                       valid = false;
+                       break;
+               }
+               if (!lower_dentry->d_op->d_revalidate(lower_dentry, &lower_nd))
+                       valid = false;
+               release_lower_nd(&lower_nd, err);
+       }
+
+       if (!dentry->d_inode ||
+           ibstart(dentry->d_inode) < 0 ||
+           ibend(dentry->d_inode) < 0) {
+               valid = false;
+               goto out;
+       }
+
+       if (valid) {
+               /*
+                * If we get here, and we copy the meta-data from the lower
+                * inode to our inode, then it is vital that we have already
+                * purged all unionfs-level file data.  We do that in the
+                * caller (__unionfs_d_revalidate) by calling
+                * purge_inode_data.
+                */
+               unionfs_copy_attr_all(dentry->d_inode,
+                                     unionfs_lower_inode(dentry->d_inode));
+               fsstack_copy_inode_size(dentry->d_inode,
+                                       unionfs_lower_inode(dentry->d_inode));
+       }
+
+out:
+       return valid;
+}
+
+/*
+ * Determine if the lower inode objects have changed from below the unionfs
+ * inode.  Return true if changed, false otherwise.
+ *
+ * We check if the mtime or ctime have changed.  However, the inode times
+ * can be changed by anyone without much protection, including
+ * asynchronously.  This can sometimes cause unionfs to find that the lower
+ * file system doesn't change its inode times quick enough, resulting in a
+ * false positive indication (which is harmless, it just makes unionfs do
+ * extra work in re-validating the objects).  To minimize the chances of
+ * these situations, we still consider such small time changes valid, but we
+ * don't print debugging messages unless the time changes are greater than
+ * UNIONFS_MIN_CC_TIME (which defaults to 3 seconds, as with NFS's acregmin)
+ * because significant changes are more likely due to users manually
+ * touching lower files.
+ */
+bool is_newer_lower(const struct dentry *dentry)
+{
+       int bindex;
+       struct inode *inode;
+       struct inode *lower_inode;
+
+       /* ignore if we're called on semi-initialized dentries/inodes */
+       if (!dentry || !UNIONFS_D(dentry))
+               return false;
+       inode = dentry->d_inode;
+       if (!inode || !UNIONFS_I(inode)->lower_inodes ||
+           ibstart(inode) < 0 || ibend(inode) < 0)
+               return false;
+
+       for (bindex = ibstart(inode); bindex <= ibend(inode); bindex++) {
+               lower_inode = unionfs_lower_inode_idx(inode, bindex);
+               if (!lower_inode)
+                       continue;
+
+               /* check if mtime/ctime have changed */
+               if (unlikely(timespec_compare(&inode->i_mtime,
+                                             &lower_inode->i_mtime) < 0)) {
+                       if ((lower_inode->i_mtime.tv_sec -
+                            inode->i_mtime.tv_sec) > UNIONFS_MIN_CC_TIME) {
+                               pr_info("unionfs: new lower inode mtime "
+                                       "(bindex=%d, name=%s)\n", bindex,
+                                       dentry->d_name.name);
+                               show_dinode_times(dentry);
+                       }
+                       return true;
+               }
+               if (unlikely(timespec_compare(&inode->i_ctime,
+                                             &lower_inode->i_ctime) < 0)) {
+                       if ((lower_inode->i_ctime.tv_sec -
+                            inode->i_ctime.tv_sec) > UNIONFS_MIN_CC_TIME) {
+                               pr_info("unionfs: new lower inode ctime "
+                                       "(bindex=%d, name=%s)\n", bindex,
+                                       dentry->d_name.name);
+                               show_dinode_times(dentry);
+                       }
+                       return true;
+               }
+       }
+
+       /*
+        * Last check: if this is a positive dentry, but somehow all lower
+        * dentries are negative or unhashed, then this dentry needs to be
+        * revalidated, because someone probably deleted the objects from
+        * the lower branches directly.
+        */
+       if (is_negative_lower(dentry))
+               return true;
+
+       return false;           /* default: lower is not newer */
+}
+
+static int unionfs_d_revalidate(struct dentry *dentry,
+                               struct nameidata *nd)
+{
+       bool valid = true;
+       int err = 1;            /* 1 means valid for the VFS */
+       struct dentry *parent;
+
+       if (nd && nd->flags & LOOKUP_RCU)
+               return -ECHILD;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       valid = __unionfs_d_revalidate(dentry, parent, false);
+       if (valid) {
+               unionfs_postcopyup_setmnt(dentry);
+               unionfs_check_dentry(dentry);
+       } else {
+               d_drop(dentry);
+               err = valid;
+       }
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+
+       return err;
+}
+
+static void unionfs_d_release(struct dentry *dentry)
+{
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       if (unlikely(!UNIONFS_D(dentry)))
+               goto out;       /* skip if no lower branches */
+       /* must lock our branch configuration here */
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       unionfs_check_dentry(dentry);
+       /* this could be a negative dentry, so check first */
+       if (dbstart(dentry) < 0) {
+               unionfs_unlock_dentry(dentry);
+               goto out;       /* due to a (normal) failed lookup */
+       }
+
+       /* Release all the lower dentries */
+       path_put_lowers_all(dentry, true);
+
+       unionfs_unlock_dentry(dentry);
+
+out:
+       free_dentry_private_data(dentry);
+       unionfs_read_unlock(dentry->d_sb);
+       return;
+}
+
+/*
+ * Called when we're removing the last reference to our dentry.  So we
+ * should drop all lower references too.
+ */
+static void unionfs_d_iput(struct dentry *dentry, struct inode *inode)
+{
+       int rc;
+
+       BUG_ON(!dentry);
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       if (!UNIONFS_D(dentry) || dbstart(dentry) < 0)
+               goto drop_lower_inodes;
+       path_put_lowers_all(dentry, false);
+
+drop_lower_inodes:
+       rc = atomic_read(&inode->i_count);
+       if (rc == 1 && inode->i_nlink == 1 && ibstart(inode) >= 0) {
+               /* see Documentation/filesystems/unionfs/issues.txt */
+               lockdep_off();
+               iput(unionfs_lower_inode(inode));
+               lockdep_on();
+               unionfs_set_lower_inode(inode, NULL);
+               /* XXX: may need to set start/end to -1? */
+       }
+
+       iput(inode);
+
+       unionfs_unlock_dentry(dentry);
+       unionfs_read_unlock(dentry->d_sb);
+}
+
+struct dentry_operations unionfs_dops = {
+       .d_revalidate   = unionfs_d_revalidate,
+       .d_release      = unionfs_d_release,
+       .d_iput         = unionfs_d_iput,
+};
diff --git a/fs/unionfs/dirfops.c b/fs/unionfs/dirfops.c
new file mode 100644
index 0000000..72a9c1a
--- /dev/null
+++ b/fs/unionfs/dirfops.c
@@ -0,0 +1,302 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/* Make sure our rdstate is playing by the rules. */
+static void verify_rdstate_offset(struct unionfs_dir_state *rdstate)
+{
+       BUG_ON(rdstate->offset >= DIREOF);
+       BUG_ON(rdstate->cookie >= MAXRDCOOKIE);
+}
+
+struct unionfs_getdents_callback {
+       struct unionfs_dir_state *rdstate;
+       void *dirent;
+       int entries_written;
+       int filldir_called;
+       int filldir_error;
+       filldir_t filldir;
+       struct super_block *sb;
+};
+
+/* based on generic filldir in fs/readir.c */
+static int unionfs_filldir(void *dirent, const char *oname, int namelen,
+                          loff_t offset, u64 ino, unsigned int d_type)
+{
+       struct unionfs_getdents_callback *buf = dirent;
+       struct filldir_node *found = NULL;
+       int err = 0;
+       int is_whiteout;
+       char *name = (char *) oname;
+
+       buf->filldir_called++;
+
+       is_whiteout = is_whiteout_name(&name, &namelen);
+
+       found = find_filldir_node(buf->rdstate, name, namelen, is_whiteout);
+
+       if (found) {
+               /*
+                * If we had non-whiteout entry in dir cache, then mark it
+                * as a whiteout and but leave it in the dir cache.
+                */
+               if (is_whiteout && !found->whiteout)
+                       found->whiteout = is_whiteout;
+               goto out;
+       }
+
+       /* if 'name' isn't a whiteout, filldir it. */
+       if (!is_whiteout) {
+               off_t pos = rdstate2offset(buf->rdstate);
+               u64 unionfs_ino = ino;
+
+               err = buf->filldir(buf->dirent, name, namelen, pos,
+                                  unionfs_ino, d_type);
+               buf->rdstate->offset++;
+               verify_rdstate_offset(buf->rdstate);
+       }
+       /*
+        * If we did fill it, stuff it in our hash, otherwise return an
+        * error.
+        */
+       if (err) {
+               buf->filldir_error = err;
+               goto out;
+       }
+       buf->entries_written++;
+       err = add_filldir_node(buf->rdstate, name, namelen,
+                              buf->rdstate->bindex, is_whiteout);
+       if (err)
+               buf->filldir_error = err;
+
+out:
+       return err;
+}
+
+static int unionfs_readdir(struct file *file, void *dirent, filldir_t filldir)
+{
+       int err = 0;
+       struct file *lower_file = NULL;
+       struct dentry *dentry = file->f_path.dentry;
+       struct dentry *parent;
+       struct inode *inode = NULL;
+       struct unionfs_getdents_callback buf;
+       struct unionfs_dir_state *uds;
+       int bend;
+       loff_t offset;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_PARENT);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       err = unionfs_file_revalidate(file, parent, false);
+       if (unlikely(err))
+               goto out;
+
+       inode = dentry->d_inode;
+
+       uds = UNIONFS_F(file)->rdstate;
+       if (!uds) {
+               if (file->f_pos == DIREOF) {
+                       goto out;
+               } else if (file->f_pos > 0) {
+                       uds = find_rdstate(inode, file->f_pos);
+                       if (unlikely(!uds)) {
+                               err = -ESTALE;
+                               goto out;
+                       }
+                       UNIONFS_F(file)->rdstate = uds;
+               } else {
+                       init_rdstate(file);
+                       uds = UNIONFS_F(file)->rdstate;
+               }
+       }
+       bend = fbend(file);
+
+       while (uds->bindex <= bend) {
+               lower_file = unionfs_lower_file_idx(file, uds->bindex);
+               if (!lower_file) {
+                       uds->bindex++;
+                       uds->dirpos = 0;
+                       continue;
+               }
+
+               /* prepare callback buffer */
+               buf.filldir_called = 0;
+               buf.filldir_error = 0;
+               buf.entries_written = 0;
+               buf.dirent = dirent;
+               buf.filldir = filldir;
+               buf.rdstate = uds;
+               buf.sb = inode->i_sb;
+
+               /* Read starting from where we last left off. */
+               offset = vfs_llseek(lower_file, uds->dirpos, SEEK_SET);
+               if (offset < 0) {
+                       err = offset;
+                       goto out;
+               }
+               err = vfs_readdir(lower_file, unionfs_filldir, &buf);
+
+               /* Save the position for when we continue. */
+               offset = vfs_llseek(lower_file, 0, SEEK_CUR);
+               if (offset < 0) {
+                       err = offset;
+                       goto out;
+               }
+               uds->dirpos = offset;
+
+               /* Copy the atime. */
+               fsstack_copy_attr_atime(inode,
+                                       lower_file->f_path.dentry->d_inode);
+
+               if (err < 0)
+                       goto out;
+
+               if (buf.filldir_error)
+                       break;
+
+               if (!buf.entries_written) {
+                       uds->bindex++;
+                       uds->dirpos = 0;
+               }
+       }
+
+       if (!buf.filldir_error && uds->bindex >= bend) {
+               /* Save the number of hash entries for next time. */
+               UNIONFS_I(inode)->hashsize = uds->hashentries;
+               free_rdstate(uds);
+               UNIONFS_F(file)->rdstate = NULL;
+               file->f_pos = DIREOF;
+       } else {
+               file->f_pos = rdstate2offset(uds);
+       }
+
+out:
+       if (!err)
+               unionfs_check_file(file);
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
+
+/*
+ * This is not meant to be a generic repositioning function.  If you do
+ * things that aren't supported, then we return EINVAL.
+ *
+ * What is allowed:
+ *  (1) seeking to the same position that you are currently at
+ *     This really has no effect, but returns where you are.
+ *  (2) seeking to the beginning of the file
+ *     This throws out all state, and lets you begin again.
+ */
+static loff_t unionfs_dir_llseek(struct file *file, loff_t offset, int origin)
+{
+       struct unionfs_dir_state *rdstate;
+       struct dentry *dentry = file->f_path.dentry;
+       struct dentry *parent;
+       loff_t err;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_PARENT);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       err = unionfs_file_revalidate(file, parent, false);
+       if (unlikely(err))
+               goto out;
+
+       rdstate = UNIONFS_F(file)->rdstate;
+
+       /*
+        * we let users seek to their current position, but not anywhere
+        * else.
+        */
+       if (!offset) {
+               switch (origin) {
+               case SEEK_SET:
+                       if (rdstate) {
+                               free_rdstate(rdstate);
+                               UNIONFS_F(file)->rdstate = NULL;
+                       }
+                       init_rdstate(file);
+                       err = 0;
+                       break;
+               case SEEK_CUR:
+                       err = file->f_pos;
+                       break;
+               case SEEK_END:
+                       /* Unsupported, because we would break everything.  */
+                       err = -EINVAL;
+                       break;
+               }
+       } else {
+               switch (origin) {
+               case SEEK_SET:
+                       if (rdstate) {
+                               if (offset == rdstate2offset(rdstate))
+                                       err = offset;
+                               else if (file->f_pos == DIREOF)
+                                       err = DIREOF;
+                               else
+                                       err = -EINVAL;
+                       } else {
+                               struct inode *inode;
+                               inode = dentry->d_inode;
+                               rdstate = find_rdstate(inode, offset);
+                               if (rdstate) {
+                                       UNIONFS_F(file)->rdstate = rdstate;
+                                       err = rdstate->offset;
+                               } else {
+                                       err = -EINVAL;
+                               }
+                       }
+                       break;
+               case SEEK_CUR:
+               case SEEK_END:
+                       /* Unsupported, because we would break everything.  */
+                       err = -EINVAL;
+                       break;
+               }
+       }
+
+out:
+       if (!err)
+               unionfs_check_file(file);
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
+
+/*
+ * Trimmed directory options, we shouldn't pass everything down since
+ * we don't want to operate on partial directories.
+ */
+struct file_operations unionfs_dir_fops = {
+       .llseek         = unionfs_dir_llseek,
+       .read           = generic_read_dir,
+       .readdir        = unionfs_readdir,
+       .unlocked_ioctl = unionfs_ioctl,
+       .open           = unionfs_open,
+       .release        = unionfs_file_release,
+       .flush          = unionfs_flush,
+       .fsync          = unionfs_fsync,
+       .fasync         = unionfs_fasync,
+};
diff --git a/fs/unionfs/dirhelper.c b/fs/unionfs/dirhelper.c
new file mode 100644
index 0000000..62ec9af
--- /dev/null
+++ b/fs/unionfs/dirhelper.c
@@ -0,0 +1,158 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+#define RD_NONE 0
+#define RD_CHECK_EMPTY 1
+/* The callback structure for check_empty. */
+struct unionfs_rdutil_callback {
+       int err;
+       int filldir_called;
+       struct unionfs_dir_state *rdstate;
+       int mode;
+};
+
+/* This filldir function makes sure only whiteouts exist within a directory. */
+static int readdir_util_callback(void *dirent, const char *oname, int namelen,
+                                loff_t offset, u64 ino, unsigned int d_type)
+{
+       int err = 0;
+       struct unionfs_rdutil_callback *buf = dirent;
+       int is_whiteout;
+       struct filldir_node *found;
+       char *name = (char *) oname;
+
+       buf->filldir_called = 1;
+
+       if (name[0] == '.' && (namelen == 1 ||
+                              (name[1] == '.' && namelen == 2)))
+               goto out;
+
+       is_whiteout = is_whiteout_name(&name, &namelen);
+
+       found = find_filldir_node(buf->rdstate, name, namelen, is_whiteout);
+       /* If it was found in the table there was a previous whiteout. */
+       if (found)
+               goto out;
+
+       /*
+        * if it wasn't found and isn't a whiteout, the directory isn't
+        * empty.
+        */
+       err = -ENOTEMPTY;
+       if ((buf->mode == RD_CHECK_EMPTY) && !is_whiteout)
+               goto out;
+
+       err = add_filldir_node(buf->rdstate, name, namelen,
+                              buf->rdstate->bindex, is_whiteout);
+
+out:
+       buf->err = err;
+       return err;
+}
+
+/* Is a directory logically empty? */
+int check_empty(struct dentry *dentry, struct dentry *parent,
+               struct unionfs_dir_state **namelist)
+{
+       int err = 0;
+       struct dentry *lower_dentry = NULL;
+       struct vfsmount *mnt;
+       struct super_block *sb;
+       struct file *lower_file;
+       struct unionfs_rdutil_callback *buf = NULL;
+       int bindex, bstart, bend, bopaque;
+
+       sb = dentry->d_sb;
+
+
+       BUG_ON(!S_ISDIR(dentry->d_inode->i_mode));
+
+       err = unionfs_partial_lookup(dentry, parent);
+       if (err)
+               goto out;
+
+       bstart = dbstart(dentry);
+       bend = dbend(dentry);
+       bopaque = dbopaque(dentry);
+       if (0 <= bopaque && bopaque < bend)
+               bend = bopaque;
+
+       buf = kmalloc(sizeof(struct unionfs_rdutil_callback), GFP_KERNEL);
+       if (unlikely(!buf)) {
+               err = -ENOMEM;
+               goto out;
+       }
+       buf->err = 0;
+       buf->mode = RD_CHECK_EMPTY;
+       buf->rdstate = alloc_rdstate(dentry->d_inode, bstart);
+       if (unlikely(!buf->rdstate)) {
+               err = -ENOMEM;
+               goto out;
+       }
+
+       /* Process the lower directories with rdutil_callback as a filldir. */
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               if (!lower_dentry)
+                       continue;
+               if (!lower_dentry->d_inode)
+                       continue;
+               if (!S_ISDIR(lower_dentry->d_inode->i_mode))
+                       continue;
+
+               dget(lower_dentry);
+               mnt = unionfs_mntget(dentry, bindex);
+               branchget(sb, bindex);
+               lower_file = dentry_open(lower_dentry, mnt, O_RDONLY, current_cred());
+               if (IS_ERR(lower_file)) {
+                       err = PTR_ERR(lower_file);
+                       branchput(sb, bindex);
+                       goto out;
+               }
+
+               do {
+                       buf->filldir_called = 0;
+                       buf->rdstate->bindex = bindex;
+                       err = vfs_readdir(lower_file,
+                                         readdir_util_callback, buf);
+                       if (buf->err)
+                               err = buf->err;
+               } while ((err >= 0) && buf->filldir_called);
+
+               /* fput calls dput for lower_dentry */
+               fput(lower_file);
+               branchput(sb, bindex);
+
+               if (err < 0)
+                       goto out;
+       }
+
+out:
+       if (buf) {
+               if (namelist && !err)
+                       *namelist = buf->rdstate;
+               else if (buf->rdstate)
+                       free_rdstate(buf->rdstate);
+               kfree(buf);
+       }
+
+
+       return err;
+}
diff --git a/fs/unionfs/fanout.h b/fs/unionfs/fanout.h
new file mode 100644
index 0000000..ae1b86a
--- /dev/null
+++ b/fs/unionfs/fanout.h
@@ -0,0 +1,407 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _FANOUT_H_
+#define _FANOUT_H_
+
+/*
+ * Inode to private data
+ *
+ * Since we use containers and the struct inode is _inside_ the
+ * unionfs_inode_info structure, UNIONFS_I will always (given a non-NULL
+ * inode pointer), return a valid non-NULL pointer.
+ */
+static inline struct unionfs_inode_info *UNIONFS_I(const struct inode *inode)
+{
+       return container_of(inode, struct unionfs_inode_info, vfs_inode);
+}
+
+#define ibstart(ino) (UNIONFS_I(ino)->bstart)
+#define ibend(ino) (UNIONFS_I(ino)->bend)
+
+/* Dentry to private data */
+#define UNIONFS_D(dent) ((struct unionfs_dentry_info *)(dent)->d_fsdata)
+#define dbstart(dent) (UNIONFS_D(dent)->bstart)
+#define dbend(dent) (UNIONFS_D(dent)->bend)
+#define dbopaque(dent) (UNIONFS_D(dent)->bopaque)
+
+/* Superblock to private data */
+#define UNIONFS_SB(super) ((struct unionfs_sb_info *)(super)->s_fs_info)
+#define sbstart(sb) 0
+#define sbend(sb) (UNIONFS_SB(sb)->bend)
+#define sbmax(sb) (UNIONFS_SB(sb)->bend + 1)
+#define sbhbid(sb) (UNIONFS_SB(sb)->high_branch_id)
+
+/* File to private Data */
+#define UNIONFS_F(file) ((struct unionfs_file_info *)((file)->private_data))
+#define fbstart(file) (UNIONFS_F(file)->bstart)
+#define fbend(file) (UNIONFS_F(file)->bend)
+
+/* macros to manipulate branch IDs in stored in our superblock */
+static inline int branch_id(struct super_block *sb, int index)
+{
+       BUG_ON(!sb || index < 0);
+       return UNIONFS_SB(sb)->data[index].branch_id;
+}
+
+static inline void set_branch_id(struct super_block *sb, int index, int val)
+{
+       BUG_ON(!sb || index < 0);
+       UNIONFS_SB(sb)->data[index].branch_id = val;
+}
+
+static inline void new_branch_id(struct super_block *sb, int index)
+{
+       BUG_ON(!sb || index < 0);
+       set_branch_id(sb, index, ++UNIONFS_SB(sb)->high_branch_id);
+}
+
+/*
+ * Find new index of matching branch with an existing superblock of a known
+ * (possibly old) id.  This is needed because branches could have been
+ * added/deleted causing the branches of any open files to shift.
+ *
+ * @sb: the new superblock which may have new/different branch IDs
+ * @id: the old/existing id we're looking for
+ * Returns index of newly found branch (0 or greater), -1 otherwise.
+ */
+static inline int branch_id_to_idx(struct super_block *sb, int id)
+{
+       int i;
+       for (i = 0; i < sbmax(sb); i++) {
+               if (branch_id(sb, i) == id)
+                       return i;
+       }
+       /* in the non-ODF code, this should really never happen */
+       printk(KERN_WARNING "unionfs: cannot find branch with id %d\n", id);
+       return -1;
+}
+
+/* File to lower file. */
+static inline struct file *unionfs_lower_file(const struct file *f)
+{
+       BUG_ON(!f);
+       return UNIONFS_F(f)->lower_files[fbstart(f)];
+}
+
+static inline struct file *unionfs_lower_file_idx(const struct file *f,
+                                                 int index)
+{
+       BUG_ON(!f || index < 0);
+       return UNIONFS_F(f)->lower_files[index];
+}
+
+static inline void unionfs_set_lower_file_idx(struct file *f, int index,
+                                             struct file *val)
+{
+       BUG_ON(!f || index < 0);
+       UNIONFS_F(f)->lower_files[index] = val;
+       /* save branch ID (may be redundant?) */
+       UNIONFS_F(f)->saved_branch_ids[index] =
+               branch_id((f)->f_path.dentry->d_sb, index);
+}
+
+static inline void unionfs_set_lower_file(struct file *f, struct file *val)
+{
+       BUG_ON(!f);
+       unionfs_set_lower_file_idx((f), fbstart(f), (val));
+}
+
+/* Inode to lower inode. */
+static inline struct inode *unionfs_lower_inode(const struct inode *i)
+{
+       BUG_ON(!i);
+       return UNIONFS_I(i)->lower_inodes[ibstart(i)];
+}
+
+static inline struct inode *unionfs_lower_inode_idx(const struct inode *i,
+                                                   int index)
+{
+       BUG_ON(!i || index < 0);
+       return UNIONFS_I(i)->lower_inodes[index];
+}
+
+static inline void unionfs_set_lower_inode_idx(struct inode *i, int index,
+                                              struct inode *val)
+{
+       BUG_ON(!i || index < 0);
+       UNIONFS_I(i)->lower_inodes[index] = val;
+}
+
+static inline void unionfs_set_lower_inode(struct inode *i, struct inode *val)
+{
+       BUG_ON(!i);
+       UNIONFS_I(i)->lower_inodes[ibstart(i)] = val;
+}
+
+/* Superblock to lower superblock. */
+static inline struct super_block *unionfs_lower_super(
+                                       const struct super_block *sb)
+{
+       BUG_ON(!sb);
+       return UNIONFS_SB(sb)->data[sbstart(sb)].sb;
+}
+
+static inline struct super_block *unionfs_lower_super_idx(
+                                       const struct super_block *sb,
+                                       int index)
+{
+       BUG_ON(!sb || index < 0);
+       return UNIONFS_SB(sb)->data[index].sb;
+}
+
+static inline void unionfs_set_lower_super_idx(struct super_block *sb,
+                                              int index,
+                                              struct super_block *val)
+{
+       BUG_ON(!sb || index < 0);
+       UNIONFS_SB(sb)->data[index].sb = val;
+}
+
+static inline void unionfs_set_lower_super(struct super_block *sb,
+                                          struct super_block *val)
+{
+       BUG_ON(!sb);
+       UNIONFS_SB(sb)->data[sbstart(sb)].sb = val;
+}
+
+/* Branch count macros. */
+static inline int branch_count(const struct super_block *sb, int index)
+{
+       BUG_ON(!sb || index < 0);
+       return atomic_read(&UNIONFS_SB(sb)->data[index].open_files);
+}
+
+static inline void set_branch_count(struct super_block *sb, int index, int val)
+{
+       BUG_ON(!sb || index < 0);
+       atomic_set(&UNIONFS_SB(sb)->data[index].open_files, val);
+}
+
+static inline void branchget(struct super_block *sb, int index)
+{
+       BUG_ON(!sb || index < 0);
+       atomic_inc(&UNIONFS_SB(sb)->data[index].open_files);
+}
+
+static inline void branchput(struct super_block *sb, int index)
+{
+       BUG_ON(!sb || index < 0);
+       atomic_dec(&UNIONFS_SB(sb)->data[index].open_files);
+}
+
+/* Dentry macros */
+static inline void unionfs_set_lower_dentry_idx(struct dentry *dent, int index,
+                                               struct dentry *val)
+{
+       BUG_ON(!dent || index < 0);
+       UNIONFS_D(dent)->lower_paths[index].dentry = val;
+}
+
+static inline struct dentry *unionfs_lower_dentry_idx(
+                               const struct dentry *dent,
+                               int index)
+{
+       BUG_ON(!dent || index < 0);
+       return UNIONFS_D(dent)->lower_paths[index].dentry;
+}
+
+static inline struct dentry *unionfs_lower_dentry(const struct dentry *dent)
+{
+       BUG_ON(!dent);
+       return unionfs_lower_dentry_idx(dent, dbstart(dent));
+}
+
+static inline void unionfs_set_lower_mnt_idx(struct dentry *dent, int index,
+                                            struct vfsmount *mnt)
+{
+       BUG_ON(!dent || index < 0);
+       UNIONFS_D(dent)->lower_paths[index].mnt = mnt;
+}
+
+static inline struct vfsmount *unionfs_lower_mnt_idx(
+                                       const struct dentry *dent,
+                                       int index)
+{
+       BUG_ON(!dent || index < 0);
+       return UNIONFS_D(dent)->lower_paths[index].mnt;
+}
+
+static inline struct vfsmount *unionfs_lower_mnt(const struct dentry *dent)
+{
+       BUG_ON(!dent);
+       return unionfs_lower_mnt_idx(dent, dbstart(dent));
+}
+
+/* Macros for locking a dentry. */
+enum unionfs_dentry_lock_class {
+       UNIONFS_DMUTEX_NORMAL,
+       UNIONFS_DMUTEX_ROOT,
+       UNIONFS_DMUTEX_PARENT,
+       UNIONFS_DMUTEX_CHILD,
+       UNIONFS_DMUTEX_WHITEOUT,
+       UNIONFS_DMUTEX_REVAL_PARENT, /* for file/dentry revalidate */
+       UNIONFS_DMUTEX_REVAL_CHILD,   /* for file/dentry revalidate */
+};
+
+static inline void unionfs_lock_dentry(struct dentry *d,
+                                      unsigned int subclass)
+{
+       BUG_ON(!d);
+       mutex_lock_nested(&UNIONFS_D(d)->lock, subclass);
+}
+
+static inline void unionfs_unlock_dentry(struct dentry *d)
+{
+       BUG_ON(!d);
+       mutex_unlock(&UNIONFS_D(d)->lock);
+}
+
+static inline struct dentry *unionfs_lock_parent(struct dentry *d,
+                                                unsigned int subclass)
+{
+       struct dentry *p;
+
+       BUG_ON(!d);
+       p = dget_parent(d);
+       if (p != d)
+               mutex_lock_nested(&UNIONFS_D(p)->lock, subclass);
+       return p;
+}
+
+static inline void unionfs_unlock_parent(struct dentry *d, struct dentry *p)
+{
+       BUG_ON(!d);
+       BUG_ON(!p);
+       if (p != d) {
+               BUG_ON(!mutex_is_locked(&UNIONFS_D(p)->lock));
+               mutex_unlock(&UNIONFS_D(p)->lock);
+       }
+       dput(p);
+}
+
+static inline void verify_locked(struct dentry *d)
+{
+       BUG_ON(!d);
+       BUG_ON(!mutex_is_locked(&UNIONFS_D(d)->lock));
+}
+
+/* macros to put lower objects */
+
+/*
+ * iput lower inodes of an unionfs dentry, from bstart to bend.  If
+ * @free_lower is true, then also kfree the memory used to hold the lower
+ * object pointers.
+ */
+static inline void iput_lowers(struct inode *inode,
+                              int bstart, int bend, bool free_lower)
+{
+       struct inode *lower_inode;
+       int bindex;
+
+       BUG_ON(!inode);
+       BUG_ON(!UNIONFS_I(inode));
+       BUG_ON(bstart < 0);
+
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_inode = unionfs_lower_inode_idx(inode, bindex);
+               if (lower_inode) {
+                       unionfs_set_lower_inode_idx(inode, bindex, NULL);
+                       /* see Documentation/filesystems/unionfs/issues.txt */
+                       lockdep_off();
+                       iput(lower_inode);
+                       lockdep_on();
+               }
+       }
+
+       if (free_lower) {
+               kfree(UNIONFS_I(inode)->lower_inodes);
+               UNIONFS_I(inode)->lower_inodes = NULL;
+       }
+}
+
+/* iput all lower inodes, and reset start/end branch indices to -1 */
+static inline void iput_lowers_all(struct inode *inode, bool free_lower)
+{
+       int bstart, bend;
+
+       BUG_ON(!inode);
+       BUG_ON(!UNIONFS_I(inode));
+       bstart = ibstart(inode);
+       bend = ibend(inode);
+       BUG_ON(bstart < 0);
+
+       iput_lowers(inode, bstart, bend, free_lower);
+       ibstart(inode) = ibend(inode) = -1;
+}
+
+/*
+ * dput/mntput all lower dentries and vfsmounts of an unionfs dentry, from
+ * bstart to bend.  If @free_lower is true, then also kfree the memory used
+ * to hold the lower object pointers.
+ *
+ * XXX: implement using path_put VFS macros
+ */
+static inline void path_put_lowers(struct dentry *dentry,
+                                  int bstart, int bend, bool free_lower)
+{
+       struct dentry *lower_dentry;
+       struct vfsmount *lower_mnt;
+       int bindex;
+
+       BUG_ON(!dentry);
+       BUG_ON(!UNIONFS_D(dentry));
+       BUG_ON(bstart < 0);
+
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               if (lower_dentry) {
+                       unionfs_set_lower_dentry_idx(dentry, bindex, NULL);
+                       dput(lower_dentry);
+               }
+               lower_mnt = unionfs_lower_mnt_idx(dentry, bindex);
+               if (lower_mnt) {
+                       unionfs_set_lower_mnt_idx(dentry, bindex, NULL);
+                       mntput(lower_mnt);
+               }
+       }
+
+       if (free_lower) {
+               kfree(UNIONFS_D(dentry)->lower_paths);
+               UNIONFS_D(dentry)->lower_paths = NULL;
+       }
+}
+
+/*
+ * dput/mntput all lower dentries and vfsmounts, and reset start/end branch
+ * indices to -1.
+ */
+static inline void path_put_lowers_all(struct dentry *dentry, bool free_lower)
+{
+       int bstart, bend;
+
+       BUG_ON(!dentry);
+       BUG_ON(!UNIONFS_D(dentry));
+       bstart = dbstart(dentry);
+       bend = dbend(dentry);
+       BUG_ON(bstart < 0);
+
+       path_put_lowers(dentry, bstart, bend, free_lower);
+       dbstart(dentry) = dbend(dentry) = -1;
+}
+
+#endif /* not _FANOUT_H */
diff --git a/fs/unionfs/file.c b/fs/unionfs/file.c
new file mode 100644
index 0000000..f583c8f
--- /dev/null
+++ b/fs/unionfs/file.c
@@ -0,0 +1,386 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+static ssize_t unionfs_read(struct file *file, char __user *buf,
+                           size_t count, loff_t *ppos)
+{
+       int err;
+       struct file *lower_file;
+       struct dentry *dentry = file->f_path.dentry;
+       struct dentry *parent;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_PARENT);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       err = unionfs_file_revalidate(file, parent, false);
+       if (unlikely(err))
+               goto out;
+
+       lower_file = unionfs_lower_file(file);
+       err = vfs_read(lower_file, buf, count, ppos);
+       /* update our inode atime upon a successful lower read */
+       if (err >= 0) {
+               fsstack_copy_attr_atime(dentry->d_inode,
+                                       lower_file->f_path.dentry->d_inode);
+               unionfs_check_file(file);
+       }
+
+out:
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
+
+static ssize_t unionfs_write(struct file *file, const char __user *buf,
+                            size_t count, loff_t *ppos)
+{
+       int err = 0;
+       struct file *lower_file;
+       struct dentry *dentry = file->f_path.dentry;
+       struct dentry *parent;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_PARENT);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       err = unionfs_file_revalidate(file, parent, true);
+       if (unlikely(err))
+               goto out;
+
+       lower_file = unionfs_lower_file(file);
+       err = vfs_write(lower_file, buf, count, ppos);
+       /* update our inode times+sizes upon a successful lower write */
+       if (err >= 0) {
+               fsstack_copy_inode_size(dentry->d_inode,
+                                       lower_file->f_path.dentry->d_inode);
+               fsstack_copy_attr_times(dentry->d_inode,
+                                       lower_file->f_path.dentry->d_inode);
+               UNIONFS_F(file)->wrote_to_file = true; /* for delayed copyup */
+               unionfs_check_file(file);
+       }
+
+out:
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
+
+static int unionfs_file_readdir(struct file *file, void *dirent,
+                               filldir_t filldir)
+{
+       return -ENOTDIR;
+}
+
+static int unionfs_mmap(struct file *file, struct vm_area_struct *vma)
+{
+       int err = 0;
+       bool willwrite;
+       struct file *lower_file;
+       struct dentry *dentry = file->f_path.dentry;
+       struct dentry *parent;
+       const struct vm_operations_struct *saved_vm_ops = NULL;
+
+       /*
+        * Since mm/memory.c:might_fault() (under PROVE_LOCKING) was
+        * modified in 2.6.29-rc1 to call might_lock_read on mmap_sem, this
+        * has been causing false positives in file system stacking layers.
+        * In particular, our ->mmap is called after sys_mmap2 already holds
+        * mmap_sem, then we lock our own mutexes; but earlier, it's
+        * possible for lockdep to have locked our mutexes first, and then
+        * we call a lower ->readdir which could call might_fault.  The
+        * different ordering of the locks is what lockdep complains about
+        * -- unnecessarily.  Therefore, we have no choice but to tell
+        * lockdep to temporarily turn off lockdep here.  Note: the comments
+        * inside might_sleep also suggest that it would have been
+        * nicer to only annotate paths that needs that might_lock_read.
+        */
+       lockdep_off();
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_PARENT);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       /* This might be deferred to mmap's writepage */
+       willwrite = ((vma->vm_flags | VM_SHARED | VM_WRITE) == vma->vm_flags);
+       err = unionfs_file_revalidate(file, parent, willwrite);
+       if (unlikely(err))
+               goto out;
+       unionfs_check_file(file);
+
+       /*
+        * File systems which do not implement ->writepage may use
+        * generic_file_readonly_mmap as their ->mmap op.  If you call
+        * generic_file_readonly_mmap with VM_WRITE, you'd get an -EINVAL.
+        * But we cannot call the lower ->mmap op, so we can't tell that
+        * writeable mappings won't work.  Therefore, our only choice is to
+        * check if the lower file system supports the ->writepage, and if
+        * not, return EINVAL (the same error that
+        * generic_file_readonly_mmap returns in that case).
+        */
+       lower_file = unionfs_lower_file(file);
+       if (willwrite && !lower_file->f_mapping->a_ops->writepage) {
+               err = -EINVAL;
+               printk(KERN_ERR "unionfs: branch %d file system does not "
+                      "support writeable mmap\n", fbstart(file));
+               goto out;
+       }
+
+       /*
+        * find and save lower vm_ops.
+        *
+        * XXX: the VFS should have a cleaner way of finding the lower vm_ops
+        */
+       if (!UNIONFS_F(file)->lower_vm_ops) {
+               err = lower_file->f_op->mmap(lower_file, vma);
+               if (err) {
+                       printk(KERN_ERR "unionfs: lower mmap failed %d\n", err);
+                       goto out;
+               }
+               saved_vm_ops = vma->vm_ops;
+               err = vm_munmap(vma->vm_start,
+                               vma->vm_end - vma->vm_start);
+               if (err) {
+                       printk(KERN_ERR "unionfs: vm_munmap failed %d\n", err);
+                       goto out;
+               }
+       }
+
+       file->f_mapping->a_ops = &unionfs_dummy_aops;
+       err = generic_file_mmap(file, vma);
+       file->f_mapping->a_ops = &unionfs_aops;
+       if (err) {
+               printk(KERN_ERR "unionfs: generic_file_mmap failed %d\n", err);
+               goto out;
+       }
+       vma->vm_ops = &unionfs_vm_ops;
+       if (!UNIONFS_F(file)->lower_vm_ops)
+               UNIONFS_F(file)->lower_vm_ops = saved_vm_ops;
+
+out:
+       if (!err) {
+               /* copyup could cause parent dir times to change */
+               unionfs_copy_attr_times(parent->d_inode);
+               unionfs_check_file(file);
+       }
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       lockdep_on();
+       return err;
+}
+
+int unionfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
+{
+       int bindex, bstart, bend;
+       struct file *lower_file;
+       struct dentry *dentry = file->f_path.dentry;
+       struct dentry *lower_dentry;
+       struct dentry *parent;
+       struct inode *lower_inode, *inode;
+       int err = -EINVAL;
+
+       lockdep_off();
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_PARENT);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       err = unionfs_file_revalidate(file, parent, true);
+       if (unlikely(err))
+               goto out;
+       unionfs_check_file(file);
+
+       err = generic_file_fsync(file, start, end, datasync);
+       if (err)
+               goto out;
+
+       bstart = fbstart(file);
+       bend = fbend(file);
+       if (bstart < 0 || bend < 0)
+               goto out;
+
+       inode = dentry->d_inode;
+       if (unlikely(!inode)) {
+               printk(KERN_ERR
+                      "unionfs: null lower inode in unionfs_fsync\n");
+               goto out;
+       }
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_inode = unionfs_lower_inode_idx(inode, bindex);
+               if (!lower_inode || !lower_inode->i_fop->fsync)
+                       continue;
+               lower_file = unionfs_lower_file_idx(file, bindex);
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               err = vfs_fsync_range(lower_file, start, end, datasync);
+               if (!err && bindex == bstart)
+                       fsstack_copy_attr_times(inode, lower_inode);
+               if (err)
+                       goto out;
+       }
+
+out:
+       if (!err)
+               unionfs_check_file(file);
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       lockdep_on();
+       return err;
+}
+
+int unionfs_fasync(int fd, struct file *file, int flag)
+{
+       int bindex, bstart, bend;
+       struct file *lower_file;
+       struct dentry *dentry = file->f_path.dentry;
+       struct dentry *parent;
+       struct inode *lower_inode, *inode;
+       int err = 0;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_PARENT);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       err = unionfs_file_revalidate(file, parent, true);
+       if (unlikely(err))
+               goto out;
+       unionfs_check_file(file);
+
+       bstart = fbstart(file);
+       bend = fbend(file);
+       if (bstart < 0 || bend < 0)
+               goto out;
+
+       inode = dentry->d_inode;
+       if (unlikely(!inode)) {
+               printk(KERN_ERR
+                      "unionfs: null lower inode in unionfs_fasync\n");
+               goto out;
+       }
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_inode = unionfs_lower_inode_idx(inode, bindex);
+               if (!lower_inode || !lower_inode->i_fop->fasync)
+                       continue;
+               lower_file = unionfs_lower_file_idx(file, bindex);
+               mutex_lock(&lower_inode->i_mutex);
+               err = lower_inode->i_fop->fasync(fd, lower_file, flag);
+               if (!err && bindex == bstart)
+                       fsstack_copy_attr_times(inode, lower_inode);
+               mutex_unlock(&lower_inode->i_mutex);
+               if (err)
+                       goto out;
+       }
+
+out:
+       if (!err)
+               unionfs_check_file(file);
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
+
+static ssize_t unionfs_splice_read(struct file *file, loff_t *ppos,
+                                  struct pipe_inode_info *pipe, size_t len,
+                                  unsigned int flags)
+{
+       ssize_t err;
+       struct file *lower_file;
+       struct dentry *dentry = file->f_path.dentry;
+       struct dentry *parent;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_PARENT);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       err = unionfs_file_revalidate(file, parent, false);
+       if (unlikely(err))
+               goto out;
+
+       lower_file = unionfs_lower_file(file);
+       err = vfs_splice_to(lower_file, ppos, pipe, len, flags);
+       /* update our inode atime upon a successful lower splice-read */
+       if (err >= 0) {
+               fsstack_copy_attr_atime(dentry->d_inode,
+                                       lower_file->f_path.dentry->d_inode);
+               unionfs_check_file(file);
+       }
+
+out:
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
+
+static ssize_t unionfs_splice_write(struct pipe_inode_info *pipe,
+                                   struct file *file, loff_t *ppos,
+                                   size_t len, unsigned int flags)
+{
+       ssize_t err = 0;
+       struct file *lower_file;
+       struct dentry *dentry = file->f_path.dentry;
+       struct dentry *parent;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_PARENT);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       err = unionfs_file_revalidate(file, parent, true);
+       if (unlikely(err))
+               goto out;
+
+       lower_file = unionfs_lower_file(file);
+       err = vfs_splice_from(pipe, lower_file, ppos, len, flags);
+       /* update our inode times+sizes upon a successful lower write */
+       if (err >= 0) {
+               fsstack_copy_inode_size(dentry->d_inode,
+                                       lower_file->f_path.dentry->d_inode);
+               fsstack_copy_attr_times(dentry->d_inode,
+                                       lower_file->f_path.dentry->d_inode);
+               unionfs_check_file(file);
+       }
+
+out:
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
+
+struct file_operations unionfs_main_fops = {
+       .llseek         = generic_file_llseek,
+       .read           = unionfs_read,
+       .write          = unionfs_write,
+       .readdir        = unionfs_file_readdir,
+       .unlocked_ioctl = unionfs_ioctl,
+#ifdef CONFIG_COMPAT
+       .compat_ioctl   = unionfs_ioctl,
+#endif
+       .mmap           = unionfs_mmap,
+       .open           = unionfs_open,
+       .flush          = unionfs_flush,
+       .release        = unionfs_file_release,
+       .fsync          = unionfs_fsync,
+       .fasync         = unionfs_fasync,
+       .splice_read    = unionfs_splice_read,
+       .splice_write   = unionfs_splice_write,
+};
diff --git a/fs/unionfs/inode.c b/fs/unionfs/inode.c
new file mode 100644
index 0000000..dd522c2
--- /dev/null
+++ b/fs/unionfs/inode.c
@@ -0,0 +1,1085 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/*
+ * Find a writeable branch to create new object in.  Checks all writeble
+ * branches of the parent inode, from istart to iend order; if none are
+ * suitable, also tries branch 0 (which may require a copyup).
+ *
+ * Return a lower_dentry we can use to create object in, or ERR_PTR.
+ */
+static struct dentry *find_writeable_branch(struct inode *parent,
+                                           struct dentry *dentry)
+{
+       int err = -EINVAL;
+       int bindex, istart, iend;
+       struct dentry *lower_dentry = NULL;
+
+       istart = ibstart(parent);
+       iend = ibend(parent);
+       if (istart < 0)
+               goto out;
+
+begin:
+       for (bindex = istart; bindex <= iend; bindex++) {
+               /* skip non-writeable branches */
+               err = is_robranch_super(dentry->d_sb, bindex);
+               if (err) {
+                       err = -EROFS;
+                       continue;
+               }
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               if (!lower_dentry)
+                       continue;
+               /*
+                * check for whiteouts in writeable branch, and remove them
+                * if necessary.
+                */
+               err = check_unlink_whiteout(dentry, lower_dentry, bindex);
+               if (err > 0)    /* ignore if whiteout found and removed */
+                       err = 0;
+               if (err)
+                       continue;
+               /* if get here, we can write to the branch */
+               break;
+       }
+       /*
+        * If istart wasn't already branch 0, and we got any error, then try
+        * branch 0 (which may require copyup)
+        */
+       if (err && istart > 0) {
+               istart = iend = 0;
+               goto begin;
+       }
+
+       /*
+        * If we tried even branch 0, and still got an error, abort.  But if
+        * the error was an EROFS, then we should try to copyup.
+        */
+       if (err && err != -EROFS)
+               goto out;
+
+       /*
+        * If we get here, then check if copyup needed.  If lower_dentry is
+        * NULL, create the entire dentry directory structure in branch 0.
+        */
+       if (!lower_dentry) {
+               bindex = 0;
+               lower_dentry = create_parents(parent, dentry,
+                                             dentry->d_name.name, bindex);
+               if (IS_ERR(lower_dentry)) {
+                       err = PTR_ERR(lower_dentry);
+                       goto out;
+               }
+       }
+       err = 0;                /* all's well */
+out:
+       if (err)
+               return ERR_PTR(err);
+       return lower_dentry;
+}
+
+static int unionfs_create(struct inode *dir, struct dentry *dentry,
+                         umode_t mode, struct nameidata *nd_unused)
+{
+       int err = 0;
+       struct dentry *lower_dentry = NULL;
+       struct dentry *lower_parent_dentry = NULL;
+       struct dentry *parent;
+       int valid = 0;
+       struct nameidata lower_nd;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       valid = __unionfs_d_revalidate(dentry, parent, false);
+       if (unlikely(!valid)) {
+               err = -ESTALE;  /* same as what real_lookup does */
+               goto out;
+       }
+
+       lower_dentry = find_writeable_branch(dir, dentry);
+       if (IS_ERR(lower_dentry)) {
+               err = PTR_ERR(lower_dentry);
+               goto out;
+       }
+
+       lower_parent_dentry = lock_parent(lower_dentry);
+       if (IS_ERR(lower_parent_dentry)) {
+               err = PTR_ERR(lower_parent_dentry);
+               goto out_unlock;
+       }
+
+       err = init_lower_nd(&lower_nd, LOOKUP_CREATE);
+       if (unlikely(err < 0))
+               goto out_unlock;
+       err = vfs_create(lower_parent_dentry->d_inode, lower_dentry, mode,
+                        &lower_nd);
+       release_lower_nd(&lower_nd, err);
+
+       if (!err) {
+               err = PTR_ERR(unionfs_interpose(dentry, dir->i_sb, 0));
+               if (!err) {
+                       unionfs_copy_attr_times(dir);
+                       fsstack_copy_inode_size(dir,
+                                               lower_parent_dentry->d_inode);
+                       /* update no. of links on parent directory */
+                       set_nlink(dir, unionfs_get_nlinks(dir));
+               }
+       }
+
+out_unlock:
+       unlock_dir(lower_parent_dentry);
+out:
+       if (!err) {
+               unionfs_postcopyup_setmnt(dentry);
+               unionfs_check_inode(dir);
+               unionfs_check_dentry(dentry);
+       }
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
+
+/*
+ * unionfs_lookup is the only special function which takes a dentry, yet we
+ * do NOT want to call __unionfs_d_revalidate_chain because by definition,
+ * we don't have a valid dentry here yet.
+ */
+static struct dentry *unionfs_lookup(struct inode *dir,
+                                    struct dentry *dentry,
+                                    struct nameidata *nd_unused)
+{
+       struct dentry *ret, *parent;
+       int err = 0;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+
+       /*
+        * As long as we lock/dget the parent, then can skip validating the
+        * parent now; we may have to rebuild this dentry on the next
+        * ->d_revalidate, however.
+        */
+
+       /* allocate dentry private data.  We free it in ->d_release */
+       err = new_dentry_private_data(dentry, UNIONFS_DMUTEX_CHILD);
+       if (unlikely(err)) {
+               ret = ERR_PTR(err);
+               goto out;
+       }
+
+       ret = unionfs_lookup_full(dentry, parent, INTERPOSE_LOOKUP);
+
+       if (!IS_ERR(ret)) {
+               if (ret)
+                       dentry = ret;
+               /* lookup_full can return multiple positive dentries */
+               if (dentry->d_inode && !S_ISDIR(dentry->d_inode->i_mode)) {
+                       BUG_ON(dbstart(dentry) < 0);
+                       unionfs_postcopyup_release(dentry);
+               }
+               unionfs_copy_attr_times(dentry->d_inode);
+       }
+
+       unionfs_check_inode(dir);
+       if (!IS_ERR(ret))
+               unionfs_check_dentry(dentry);
+       unionfs_check_dentry(parent);
+       unionfs_unlock_dentry(dentry); /* locked in new_dentry_private data */
+
+out:
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+
+       return ret;
+}
+
+static int unionfs_link(struct dentry *old_dentry, struct inode *dir,
+                       struct dentry *new_dentry)
+{
+       int err = 0;
+       struct dentry *lower_old_dentry = NULL;
+       struct dentry *lower_new_dentry = NULL;
+       struct dentry *lower_dir_dentry = NULL;
+       struct dentry *old_parent, *new_parent;
+       char *name = NULL;
+       bool valid;
+
+       unionfs_read_lock(old_dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       old_parent = dget_parent(old_dentry);
+       new_parent = dget_parent(new_dentry);
+       unionfs_double_lock_parents(old_parent, new_parent);
+       unionfs_double_lock_dentry(old_dentry, new_dentry);
+
+       valid = __unionfs_d_revalidate(old_dentry, old_parent, false);
+       if (unlikely(!valid)) {
+               err = -ESTALE;
+               goto out;
+       }
+       if (new_dentry->d_inode) {
+               valid = __unionfs_d_revalidate(new_dentry, new_parent, false);
+               if (unlikely(!valid)) {
+                       err = -ESTALE;
+                       goto out;
+               }
+       }
+
+       lower_new_dentry = unionfs_lower_dentry(new_dentry);
+
+       /* check for a whiteout in new dentry branch, and delete it */
+       err = check_unlink_whiteout(new_dentry, lower_new_dentry,
+                                   dbstart(new_dentry));
+       if (err > 0) {         /* whiteout found and removed successfully */
+               lower_dir_dentry = dget_parent(lower_new_dentry);
+               fsstack_copy_attr_times(dir, lower_dir_dentry->d_inode);
+               dput(lower_dir_dentry);
+               set_nlink(dir, unionfs_get_nlinks(dir));
+               err = 0;
+       }
+       if (err)
+               goto out;
+
+       /* check if parent hierachy is needed, then link in same branch */
+       if (dbstart(old_dentry) != dbstart(new_dentry)) {
+               lower_new_dentry = create_parents(dir, new_dentry,
+                                                 new_dentry->d_name.name,
+                                                 dbstart(old_dentry));
+               err = PTR_ERR(lower_new_dentry);
+               if (IS_COPYUP_ERR(err))
+                       goto docopyup;
+               if (!lower_new_dentry || IS_ERR(lower_new_dentry))
+                       goto out;
+       }
+       lower_new_dentry = unionfs_lower_dentry(new_dentry);
+       lower_old_dentry = unionfs_lower_dentry(old_dentry);
+
+       BUG_ON(dbstart(old_dentry) != dbstart(new_dentry));
+       lower_dir_dentry = lock_parent(lower_new_dentry);
+       err = is_robranch(old_dentry);
+       if (!err) {
+               /* see Documentation/filesystems/unionfs/issues.txt */
+               lockdep_off();
+               err = vfs_link(lower_old_dentry, lower_dir_dentry->d_inode,
+                              lower_new_dentry);
+               lockdep_on();
+       }
+       unlock_dir(lower_dir_dentry);
+
+docopyup:
+       if (IS_COPYUP_ERR(err)) {
+               int old_bstart = dbstart(old_dentry);
+               int bindex;
+
+               for (bindex = old_bstart - 1; bindex >= 0; bindex--) {
+                       err = copyup_dentry(old_parent->d_inode,
+                                           old_dentry, old_bstart,
+                                           bindex, old_dentry->d_name.name,
+                                           old_dentry->d_name.len, NULL,
+                                           i_size_read(old_dentry->d_inode));
+                       if (err)
+                               continue;
+                       lower_new_dentry =
+                               create_parents(dir, new_dentry,
+                                              new_dentry->d_name.name,
+                                              bindex);
+                       lower_old_dentry = unionfs_lower_dentry(old_dentry);
+                       lower_dir_dentry = lock_parent(lower_new_dentry);
+                       /* see Documentation/filesystems/unionfs/issues.txt */
+                       lockdep_off();
+                       /* do vfs_link */
+                       err = vfs_link(lower_old_dentry,
+                                      lower_dir_dentry->d_inode,
+                                      lower_new_dentry);
+                       lockdep_on();
+                       unlock_dir(lower_dir_dentry);
+                       goto check_link;
+               }
+               goto out;
+       }
+
+check_link:
+       if (err || !lower_new_dentry->d_inode)
+               goto out;
+
+       /* Its a hard link, so use the same inode */
+       new_dentry->d_inode = igrab(old_dentry->d_inode);
+       d_add(new_dentry, new_dentry->d_inode);
+       unionfs_copy_attr_all(dir, lower_new_dentry->d_parent->d_inode);
+       fsstack_copy_inode_size(dir, lower_new_dentry->d_parent->d_inode);
+
+       /* propagate number of hard-links */
+       set_nlink(old_dentry->d_inode,
+                 unionfs_get_nlinks(old_dentry->d_inode));
+       /* new dentry's ctime may have changed due to hard-link counts */
+       unionfs_copy_attr_times(new_dentry->d_inode);
+
+out:
+       if (!new_dentry->d_inode)
+               d_drop(new_dentry);
+
+       kfree(name);
+       if (!err)
+               unionfs_postcopyup_setmnt(new_dentry);
+
+       unionfs_check_inode(dir);
+       unionfs_check_dentry(new_dentry);
+       unionfs_check_dentry(old_dentry);
+
+       unionfs_double_unlock_dentry(old_dentry, new_dentry);
+       unionfs_double_unlock_parents(old_parent, new_parent);
+       dput(new_parent);
+       dput(old_parent);
+       unionfs_read_unlock(old_dentry->d_sb);
+
+       return err;
+}
+
+static int unionfs_symlink(struct inode *dir, struct dentry *dentry,
+                          const char *symname)
+{
+       int err = 0;
+       struct dentry *lower_dentry = NULL;
+       struct dentry *wh_dentry = NULL;
+       struct dentry *lower_parent_dentry = NULL;
+       struct dentry *parent;
+       char *name = NULL;
+       int valid = 0;
+       umode_t mode;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       valid = __unionfs_d_revalidate(dentry, parent, false);
+       if (unlikely(!valid)) {
+               err = -ESTALE;
+               goto out;
+       }
+
+       /*
+        * It's only a bug if this dentry was not negative and couldn't be
+        * revalidated (shouldn't happen).
+        */
+       BUG_ON(!valid && dentry->d_inode);
+
+       lower_dentry = find_writeable_branch(dir, dentry);
+       if (IS_ERR(lower_dentry)) {
+               err = PTR_ERR(lower_dentry);
+               goto out;
+       }
+
+       lower_parent_dentry = lock_parent(lower_dentry);
+       if (IS_ERR(lower_parent_dentry)) {
+               err = PTR_ERR(lower_parent_dentry);
+               goto out_unlock;
+       }
+
+       mode = S_IALLUGO;
+       err = vfs_symlink(lower_parent_dentry->d_inode, lower_dentry, symname);
+       if (!err) {
+               err = PTR_ERR(unionfs_interpose(dentry, dir->i_sb, 0));
+               if (!err) {
+                       unionfs_copy_attr_times(dir);
+                       fsstack_copy_inode_size(dir,
+                                               lower_parent_dentry->d_inode);
+                       /* update no. of links on parent directory */
+                       set_nlink(dir, unionfs_get_nlinks(dir));
+               }
+       }
+
+out_unlock:
+       unlock_dir(lower_parent_dentry);
+out:
+       dput(wh_dentry);
+       kfree(name);
+
+       if (!err) {
+               unionfs_postcopyup_setmnt(dentry);
+               unionfs_check_inode(dir);
+               unionfs_check_dentry(dentry);
+       }
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
+
+static int unionfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
+{
+       int err = 0;
+       struct dentry *lower_dentry = NULL;
+       struct dentry *lower_parent_dentry = NULL;
+       struct dentry *parent;
+       int bindex = 0, bstart;
+       char *name = NULL;
+       int valid;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       valid = __unionfs_d_revalidate(dentry, parent, false);
+       if (unlikely(!valid)) {
+               err = -ESTALE;  /* same as what real_lookup does */
+               goto out;
+       }
+
+       bstart = dbstart(dentry);
+
+       lower_dentry = unionfs_lower_dentry(dentry);
+
+       /* check for a whiteout in new dentry branch, and delete it */
+       err = check_unlink_whiteout(dentry, lower_dentry, bstart);
+       if (err > 0)           /* whiteout found and removed successfully */
+               err = 0;
+       if (err) {
+               /* exit if the error returned was NOT -EROFS */
+               if (!IS_COPYUP_ERR(err))
+                       goto out;
+               bstart--;
+       }
+
+       /* check if copyup's needed, and mkdir */
+       for (bindex = bstart; bindex >= 0; bindex--) {
+               int i;
+               int bend = dbend(dentry);
+
+               if (is_robranch_super(dentry->d_sb, bindex))
+                       continue;
+
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               if (!lower_dentry) {
+                       lower_dentry = create_parents(dir, dentry,
+                                                     dentry->d_name.name,
+                                                     bindex);
+                       if (!lower_dentry || IS_ERR(lower_dentry)) {
+                               printk(KERN_ERR "unionfs: lower dentry "
+                                      " NULL for bindex = %d\n", bindex);
+                               continue;
+                       }
+               }
+
+               lower_parent_dentry = lock_parent(lower_dentry);
+
+               if (IS_ERR(lower_parent_dentry)) {
+                       err = PTR_ERR(lower_parent_dentry);
+                       goto out;
+               }
+
+               err = vfs_mkdir(lower_parent_dentry->d_inode, lower_dentry,
+                               mode);
+
+               unlock_dir(lower_parent_dentry);
+
+               /* did the mkdir succeed? */
+               if (err)
+                       break;
+
+               for (i = bindex + 1; i <= bend; i++) {
+                       /* XXX: use path_put_lowers? */
+                       if (unionfs_lower_dentry_idx(dentry, i)) {
+                               dput(unionfs_lower_dentry_idx(dentry, i));
+                               unionfs_set_lower_dentry_idx(dentry, i, NULL);
+                       }
+               }
+               dbend(dentry) = bindex;
+
+               /*
+                * Only INTERPOSE_LOOKUP can return a value other than 0 on
+                * err.
+                */
+               err = PTR_ERR(unionfs_interpose(dentry, dir->i_sb, 0));
+               if (!err) {
+                       unionfs_copy_attr_times(dir);
+                       fsstack_copy_inode_size(dir,
+                                               lower_parent_dentry->d_inode);
+
+                       /* update number of links on parent directory */
+                       set_nlink(dir, unionfs_get_nlinks(dir));
+               }
+
+               err = make_dir_opaque(dentry, dbstart(dentry));
+               if (err) {
+                       printk(KERN_ERR "unionfs: mkdir: error creating "
+                              ".wh.__dir_opaque: %d\n", err);
+                       goto out;
+               }
+
+               /* we are done! */
+               break;
+       }
+
+out:
+       if (!dentry->d_inode)
+               d_drop(dentry);
+
+       kfree(name);
+
+       if (!err) {
+               unionfs_copy_attr_times(dentry->d_inode);
+               unionfs_postcopyup_setmnt(dentry);
+       }
+       unionfs_check_inode(dir);
+       unionfs_check_dentry(dentry);
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+
+       return err;
+}
+
+static int unionfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
+                        dev_t dev)
+{
+       int err = 0;
+       struct dentry *lower_dentry = NULL;
+       struct dentry *wh_dentry = NULL;
+       struct dentry *lower_parent_dentry = NULL;
+       struct dentry *parent;
+       char *name = NULL;
+       int valid = 0;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       valid = __unionfs_d_revalidate(dentry, parent, false);
+       if (unlikely(!valid)) {
+               err = -ESTALE;
+               goto out;
+       }
+
+       /*
+        * It's only a bug if this dentry was not negative and couldn't be
+        * revalidated (shouldn't happen).
+        */
+       BUG_ON(!valid && dentry->d_inode);
+
+       lower_dentry = find_writeable_branch(dir, dentry);
+       if (IS_ERR(lower_dentry)) {
+               err = PTR_ERR(lower_dentry);
+               goto out;
+       }
+
+       lower_parent_dentry = lock_parent(lower_dentry);
+       if (IS_ERR(lower_parent_dentry)) {
+               err = PTR_ERR(lower_parent_dentry);
+               goto out_unlock;
+       }
+
+       err = vfs_mknod(lower_parent_dentry->d_inode, lower_dentry, mode, dev);
+       if (!err) {
+               err = PTR_ERR(unionfs_interpose(dentry, dir->i_sb, 0));
+               if (!err) {
+                       unionfs_copy_attr_times(dir);
+                       fsstack_copy_inode_size(dir,
+                                               lower_parent_dentry->d_inode);
+                       /* update no. of links on parent directory */
+                       set_nlink(dir, unionfs_get_nlinks(dir));
+               }
+       }
+
+out_unlock:
+       unlock_dir(lower_parent_dentry);
+out:
+       dput(wh_dentry);
+       kfree(name);
+
+       if (!err) {
+               unionfs_postcopyup_setmnt(dentry);
+               unionfs_check_inode(dir);
+               unionfs_check_dentry(dentry);
+       }
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
+
+/* requires sb, dentry, and parent to already be locked */
+static int __unionfs_readlink(struct dentry *dentry, char __user *buf,
+                             int bufsiz)
+{
+       int err;
+       struct dentry *lower_dentry;
+
+       lower_dentry = unionfs_lower_dentry(dentry);
+
+       if (!lower_dentry->d_inode->i_op ||
+           !lower_dentry->d_inode->i_op->readlink) {
+               err = -EINVAL;
+               goto out;
+       }
+
+       err = lower_dentry->d_inode->i_op->readlink(lower_dentry,
+                                                   buf, bufsiz);
+       if (err >= 0)
+               fsstack_copy_attr_atime(dentry->d_inode,
+                                       lower_dentry->d_inode);
+
+out:
+       return err;
+}
+
+static int unionfs_readlink(struct dentry *dentry, char __user *buf,
+                           int bufsiz)
+{
+       int err;
+       struct dentry *parent;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       if (unlikely(!__unionfs_d_revalidate(dentry, parent, false))) {
+               err = -ESTALE;
+               goto out;
+       }
+
+       err = __unionfs_readlink(dentry, buf, bufsiz);
+
+out:
+       unionfs_check_dentry(dentry);
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+
+       return err;
+}
+
+static void *unionfs_follow_link(struct dentry *dentry, struct nameidata *nd)
+{
+       char *buf;
+       int len = PAGE_SIZE, err;
+       mm_segment_t old_fs;
+       struct dentry *parent;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       /* This is freed by the put_link method assuming a successful call. */
+       buf = kmalloc(len, GFP_KERNEL);
+       if (unlikely(!buf)) {
+               err = -ENOMEM;
+               goto out;
+       }
+
+       /* read the symlink, and then we will follow it */
+       old_fs = get_fs();
+       set_fs(KERNEL_DS);
+       err = __unionfs_readlink(dentry, buf, len);
+       set_fs(old_fs);
+       if (err < 0) {
+               kfree(buf);
+               buf = NULL;
+               goto out;
+       }
+       buf[err] = 0;
+       nd_set_link(nd, buf);
+       err = 0;
+
+out:
+       if (err >= 0) {
+               unionfs_check_nd(nd);
+               unionfs_check_dentry(dentry);
+       }
+
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+
+       return ERR_PTR(err);
+}
+
+/* this @nd *IS* still used */
+static void unionfs_put_link(struct dentry *dentry, struct nameidata *nd,
+                            void *cookie)
+{
+       struct dentry *parent;
+       char *buf;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       if (unlikely(!__unionfs_d_revalidate(dentry, parent, false)))
+               printk(KERN_ERR
+                      "unionfs: put_link failed to revalidate dentry\n");
+
+       unionfs_check_dentry(dentry);
+#if 0
+       /* XXX: can't run this check b/c this fxn can receive a poisoned 'nd' PTR */
+       unionfs_check_nd(nd);
+#endif
+       buf = nd_get_link(nd);
+       if (!IS_ERR(buf))
+               kfree(buf);
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+}
+
+/*
+ * This is a variant of fs/namei.c:permission() or inode_permission() which
+ * skips over EROFS tests (because we perform copyup on EROFS).
+ */
+static int __inode_permission(struct inode *inode, int mask)
+{
+       int retval;
+
+       /* nobody gets write access to an immutable file */
+       if ((mask & MAY_WRITE) && IS_IMMUTABLE(inode))
+               return -EACCES;
+
+       /* Ordinary permission routines do not understand MAY_APPEND. */
+       if (inode->i_op && inode->i_op->permission) {
+               retval = inode->i_op->permission(inode, mask);
+               if (!retval) {
+                       /*
+                        * Exec permission on a regular file is denied if none
+                        * of the execute bits are set.
+                        *
+                        * This check should be done by the ->permission()
+                        * method.
+                        */
+                       if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode) &&
+                           !(inode->i_mode & S_IXUGO))
+                               return -EACCES;
+               }
+       } else {
+               retval = generic_permission(inode, mask);
+       }
+       if (retval)
+               return retval;
+
+       return security_inode_permission(inode,
+                       mask & (MAY_READ|MAY_WRITE|MAY_EXEC|MAY_APPEND));
+}
+
+/*
+ * Don't grab the superblock read-lock in unionfs_permission, which prevents
+ * a deadlock with the branch-management "add branch" code (which grabbed
+ * the write lock).  It is safe to not grab the read lock here, because even
+ * with branch management taking place, there is no chance that
+ * unionfs_permission, or anything it calls, will use stale branch
+ * information.
+ */
+static int unionfs_permission(struct inode *inode, int mask)
+{
+       struct inode *lower_inode = NULL;
+       int err = 0;
+       int bindex, bstart, bend;
+       int is_file;
+       const int write_mask = (mask & MAY_WRITE) && !(mask & MAY_READ);
+       struct inode *inode_grabbed;
+
+       inode_grabbed = igrab(inode);
+       is_file = !S_ISDIR(inode->i_mode);
+
+       if (!UNIONFS_I(inode)->lower_inodes) {
+               if (is_file)    /* dirs can be unlinked but chdir'ed to */
+                       err = -ESTALE;  /* force revalidate */
+               goto out;
+       }
+       bstart = ibstart(inode);
+       bend = ibend(inode);
+       if (unlikely(bstart < 0 || bend < 0)) {
+               /*
+                * With branch-management, we can get a stale inode here.
+                * If so, we return ESTALE back to link_path_walk, which
+                * would discard the dcache entry and re-lookup the
+                * dentry+inode.  This should be equivalent to issuing
+                * __unionfs_d_revalidate_chain on nd.dentry here.
+                */
+               if (is_file)    /* dirs can be unlinked but chdir'ed to */
+                       err = -ESTALE;  /* force revalidate */
+               goto out;
+       }
+
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_inode = unionfs_lower_inode_idx(inode, bindex);
+               if (!lower_inode)
+                       continue;
+
+               /*
+                * check the condition for D-F-D underlying files/directories,
+                * we don't have to check for files, if we are checking for
+                * directories.
+                */
+               if (!is_file && !S_ISDIR(lower_inode->i_mode))
+                       continue;
+
+               /*
+                * We check basic permissions, but we ignore any conditions
+                * such as readonly file systems or branches marked as
+                * readonly, because those conditions should lead to a
+                * copyup taking place later on.  However, if user never had
+                * access to the file, then no copyup could ever take place.
+                */
+               err = __inode_permission(lower_inode, mask);
+               if (err && err != -EACCES && err != EPERM && bindex > 0) {
+                       umode_t mode = lower_inode->i_mode;
+                       if ((is_robranch_super(inode->i_sb, bindex) ||
+                            __is_rdonly(lower_inode)) &&
+                           (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
+                               err = 0;
+                       if (IS_COPYUP_ERR(err))
+                               err = 0;
+               }
+
+               /*
+                * NFS HACK: NFSv2/3 return EACCES on readonly-exported,
+                * locally readonly-mounted file systems, instead of EROFS
+                * like other file systems do.  So we have no choice here
+                * but to intercept this and ignore it for NFS branches
+                * marked readonly.  Specifically, we avoid using NFS's own
+                * "broken" ->permission method, and rely on
+                * generic_permission() to do basic checking for us.
+                */
+               if (err && err == -EACCES &&
+                   is_robranch_super(inode->i_sb, bindex) &&
+                   lower_inode->i_sb->s_magic == NFS_SUPER_MAGIC)
+                       err = generic_permission(lower_inode, mask);
+
+               /*
+                * The permissions are an intersection of the overall directory
+                * permissions, so we fail if one fails.
+                */
+               if (err)
+                       goto out;
+
+               /* only the leftmost file matters. */
+               if (is_file || write_mask) {
+                       if (is_file && write_mask) {
+                               err = get_write_access(lower_inode);
+                               if (!err)
+                                       put_write_access(lower_inode);
+                       }
+                       break;
+               }
+       }
+       /* sync times which may have changed (asynchronously) below */
+       unionfs_copy_attr_times(inode);
+
+out:
+       unionfs_check_inode(inode);
+       iput(inode_grabbed);
+       return err;
+}
+
+static int unionfs_setattr(struct dentry *dentry, struct iattr *ia)
+{
+       int err = 0;
+       struct dentry *lower_dentry;
+       struct dentry *parent;
+       struct inode *inode;
+       struct inode *lower_inode;
+       int bstart, bend, bindex;
+       loff_t size;
+       struct iattr lower_ia;
+
+       /* check if user has permission to change inode */
+       err = inode_change_ok(dentry->d_inode, ia);
+       if (err)
+               goto out_err;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       if (unlikely(!__unionfs_d_revalidate(dentry, parent, false))) {
+               err = -ESTALE;
+               goto out;
+       }
+
+       bstart = dbstart(dentry);
+       bend = dbend(dentry);
+       inode = dentry->d_inode;
+
+       /*
+        * mode change is for clearing setuid/setgid. Allow lower filesystem
+        * to reinterpret it in its own way.
+        */
+       if (ia->ia_valid & (ATTR_KILL_SUID | ATTR_KILL_SGID))
+               ia->ia_valid &= ~ATTR_MODE;
+
+       lower_dentry = unionfs_lower_dentry(dentry);
+       if (!lower_dentry) { /* should never happen after above revalidate */
+               err = -EINVAL;
+               goto out;
+       }
+
+       /*
+        * Get the lower inode directly from lower dentry, in case ibstart
+        * is -1 (which happens when the file is open but unlinked.
+        */
+       lower_inode = lower_dentry->d_inode;
+
+       /* check if user has permission to change lower inode */
+       err = inode_change_ok(lower_inode, ia);
+       if (err)
+               goto out;
+
+       /* copyup if the file is on a read only branch */
+       if (is_robranch_super(dentry->d_sb, bstart)
+           || __is_rdonly(lower_inode)) {
+               /* check if we have a branch to copy up to */
+               if (bstart <= 0) {
+                       err = -EACCES;
+                       goto out;
+               }
+
+               if (ia->ia_valid & ATTR_SIZE)
+                       size = ia->ia_size;
+               else
+                       size = i_size_read(inode);
+               /* copyup to next available branch */
+               for (bindex = bstart - 1; bindex >= 0; bindex--) {
+                       err = copyup_dentry(parent->d_inode,
+                                           dentry, bstart, bindex,
+                                           dentry->d_name.name,
+                                           dentry->d_name.len,
+                                           NULL, size);
+                       if (!err)
+                               break;
+               }
+               if (err)
+                       goto out;
+               /* get updated lower_dentry/inode after copyup */
+               lower_dentry = unionfs_lower_dentry(dentry);
+               lower_inode = unionfs_lower_inode(inode);
+               /*
+                * check for whiteouts in writeable branch, and remove them
+                * if necessary.
+                */
+               if (lower_dentry) {
+                       err = check_unlink_whiteout(dentry, lower_dentry,
+                                                   bindex);
+                       if (err > 0) /* ignore if whiteout found and removed */
+                               err = 0;
+               }
+       }
+
+       /*
+        * If shrinking, first truncate upper level to cancel writing dirty
+        * pages beyond the new eof; and also if its' maxbytes is more
+        * limiting (fail with -EFBIG before making any change to the lower
+        * level).  There is no need to vmtruncate the upper level
+        * afterwards in the other cases: we fsstack_copy_inode_size from
+        * the lower level.
+        */
+       if (ia->ia_valid & ATTR_SIZE) {
+               size = i_size_read(inode);
+               if (ia->ia_size < size || (ia->ia_size > size &&
+                   inode->i_sb->s_maxbytes < lower_inode->i_sb->s_maxbytes)) {
+                       err = vmtruncate(inode, ia->ia_size);
+                       if (err)
+                               goto out;
+               }
+       }
+
+       /* notify the (possibly copied-up) lower inode */
+       /*
+        * Note: we use lower_dentry->d_inode, because lower_inode may be
+        * unlinked (no inode->i_sb and i_ino==0.  This happens if someone
+        * tries to open(), unlink(), then ftruncate() a file.
+        */
+       /* prepare our own lower struct iattr (with our own lower file) */
+       memcpy(&lower_ia, ia, sizeof(lower_ia));
+       if (ia->ia_valid & ATTR_FILE) {
+               lower_ia.ia_file = unionfs_lower_file(ia->ia_file);
+               BUG_ON(!lower_ia.ia_file); // XXX?
+       }
+
+       mutex_lock(&lower_dentry->d_inode->i_mutex);
+       err = notify_change(lower_dentry, &lower_ia);
+       mutex_unlock(&lower_dentry->d_inode->i_mutex);
+       if (err)
+               goto out;
+
+       /* get attributes from the first lower inode */
+       if (ibstart(inode) >= 0)
+               unionfs_copy_attr_all(inode, lower_inode);
+       /*
+        * unionfs_copy_attr_all will copy the lower times to our inode if
+        * the lower ones are newer (useful for cache coherency).  However,
+        * ->setattr is the only place in which we may have to copy the
+        * lower inode times absolutely, to support utimes(2).
+        */
+       if (ia->ia_valid & ATTR_MTIME_SET)
+               inode->i_mtime = lower_inode->i_mtime;
+       if (ia->ia_valid & ATTR_CTIME)
+               inode->i_ctime = lower_inode->i_ctime;
+       if (ia->ia_valid & ATTR_ATIME_SET)
+               inode->i_atime = lower_inode->i_atime;
+       fsstack_copy_inode_size(inode, lower_inode);
+
+out:
+       if (!err)
+               unionfs_check_dentry(dentry);
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+out_err:
+       return err;
+}
+
+struct inode_operations unionfs_symlink_iops = {
+       .readlink       = unionfs_readlink,
+       .permission     = unionfs_permission,
+       .follow_link    = unionfs_follow_link,
+       .setattr        = unionfs_setattr,
+       .put_link       = unionfs_put_link,
+};
+
+struct inode_operations unionfs_dir_iops = {
+       .create         = unionfs_create,
+       .lookup         = unionfs_lookup,
+       .link           = unionfs_link,
+       .unlink         = unionfs_unlink,
+       .symlink        = unionfs_symlink,
+       .mkdir          = unionfs_mkdir,
+       .rmdir          = unionfs_rmdir,
+       .mknod          = unionfs_mknod,
+       .rename         = unionfs_rename,
+       .permission     = unionfs_permission,
+       .setattr        = unionfs_setattr,
+#ifdef CONFIG_UNION_FS_XATTR
+       .setxattr       = unionfs_setxattr,
+       .getxattr       = unionfs_getxattr,
+       .removexattr    = unionfs_removexattr,
+       .listxattr      = unionfs_listxattr,
+#endif /* CONFIG_UNION_FS_XATTR */
+};
+
+struct inode_operations unionfs_main_iops = {
+       .permission     = unionfs_permission,
+       .setattr        = unionfs_setattr,
+#ifdef CONFIG_UNION_FS_XATTR
+       .setxattr       = unionfs_setxattr,
+       .getxattr       = unionfs_getxattr,
+       .removexattr    = unionfs_removexattr,
+       .listxattr      = unionfs_listxattr,
+#endif /* CONFIG_UNION_FS_XATTR */
+};
diff --git a/fs/unionfs/lookup.c b/fs/unionfs/lookup.c
new file mode 100644
index 0000000..041d674
--- /dev/null
+++ b/fs/unionfs/lookup.c
@@ -0,0 +1,570 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/*
+ * Lookup one path component @name relative to a <base,mnt> path pair.
+ * Behaves nearly the same as lookup_one_len (i.e., return negative dentry
+ * on ENOENT), but uses the @mnt passed, so it can cross bind mounts and
+ * other lower mounts properly.  If @new_mnt is non-null, will fill in the
+ * new mnt there.  Caller is responsible to dput/mntput/path_put returned
+ * @dentry and @new_mnt.
+ */
+struct dentry *__lookup_one(struct dentry *base, struct vfsmount *mnt,
+                           const char *name, struct vfsmount **new_mnt)
+{
+       struct dentry *dentry = NULL;
+       struct path lower_path = {NULL, NULL};
+       int err;
+
+       /* we use flags=0 to get basic lookup */
+       err = vfs_path_lookup(base, mnt, name, 0, &lower_path);
+
+       switch (err) {
+       case 0: /* no error */
+               dentry = lower_path.dentry;
+               if (new_mnt)
+                       *new_mnt = lower_path.mnt; /* rc already inc'ed */
+               break;
+       case -ENOENT:
+                /*
+                 * We don't consider ENOENT an error, and we want to return
+                 * a negative dentry (ala lookup_one_len).  As we know
+                 * there was no inode for this name before (-ENOENT), then
+                 * it's safe to call lookup_one_len (which doesn't take a
+                 * vfsmount).
+                 */
+               dentry = lookup_lck_len(name, base, strlen(name));
+               if (new_mnt)
+                       *new_mnt = mntget(lower_path.mnt);
+               break;
+       default: /* all other real errors */
+               dentry = ERR_PTR(err);
+               break;
+       }
+
+       return dentry;
+}
+
+/*
+ * This is a utility function that fills in a unionfs dentry.
+ * Caller must lock this dentry with unionfs_lock_dentry.
+ *
+ * Returns: 0 (ok), or -ERRNO if an error occurred.
+ * XXX: get rid of _partial_lookup and make callers call _lookup_full directly
+ */
+int unionfs_partial_lookup(struct dentry *dentry, struct dentry *parent)
+{
+       struct dentry *tmp;
+       int err = -ENOSYS;
+
+       tmp = unionfs_lookup_full(dentry, parent, INTERPOSE_PARTIAL);
+
+       if (!tmp) {
+               err = 0;
+               goto out;
+       }
+       if (IS_ERR(tmp)) {
+               err = PTR_ERR(tmp);
+               goto out;
+       }
+       /* XXX: need to change the interface */
+       BUG_ON(tmp != dentry);
+out:
+       return err;
+}
+
+/* The dentry cache is just so we have properly sized dentries. */
+static struct kmem_cache *unionfs_dentry_cachep;
+int unionfs_init_dentry_cache(void)
+{
+       unionfs_dentry_cachep =
+               kmem_cache_create("unionfs_dentry",
+                                 sizeof(struct unionfs_dentry_info),
+                                 0, SLAB_RECLAIM_ACCOUNT, NULL);
+
+       return (unionfs_dentry_cachep ? 0 : -ENOMEM);
+}
+
+void unionfs_destroy_dentry_cache(void)
+{
+       if (unionfs_dentry_cachep)
+               kmem_cache_destroy(unionfs_dentry_cachep);
+}
+
+void free_dentry_private_data(struct dentry *dentry)
+{
+       if (!dentry || !dentry->d_fsdata)
+               return;
+       kfree(UNIONFS_D(dentry)->lower_paths);
+       UNIONFS_D(dentry)->lower_paths = NULL;
+       kmem_cache_free(unionfs_dentry_cachep, dentry->d_fsdata);
+       dentry->d_fsdata = NULL;
+}
+
+static inline int __realloc_dentry_private_data(struct dentry *dentry)
+{
+       struct unionfs_dentry_info *info = UNIONFS_D(dentry);
+       void *p;
+       int size;
+
+       BUG_ON(!info);
+
+       size = sizeof(struct path) * sbmax(dentry->d_sb);
+       p = krealloc(info->lower_paths, size, GFP_ATOMIC);
+       if (unlikely(!p))
+               return -ENOMEM;
+
+       info->lower_paths = p;
+
+       info->bstart = -1;
+       info->bend = -1;
+       info->bopaque = -1;
+       info->bcount = sbmax(dentry->d_sb);
+       atomic_set(&info->generation,
+                       atomic_read(&UNIONFS_SB(dentry->d_sb)->generation));
+
+       memset(info->lower_paths, 0, size);
+
+       return 0;
+}
+
+/* UNIONFS_D(dentry)->lock must be locked */
+int realloc_dentry_private_data(struct dentry *dentry)
+{
+       if (!__realloc_dentry_private_data(dentry))
+               return 0;
+
+       kfree(UNIONFS_D(dentry)->lower_paths);
+       free_dentry_private_data(dentry);
+       return -ENOMEM;
+}
+
+/* allocate new dentry private data */
+int new_dentry_private_data(struct dentry *dentry, int subclass)
+{
+       struct unionfs_dentry_info *info = UNIONFS_D(dentry);
+
+       BUG_ON(info);
+
+       info = kmem_cache_alloc(unionfs_dentry_cachep, GFP_ATOMIC);
+       if (unlikely(!info))
+               return -ENOMEM;
+
+       mutex_init(&info->lock);
+       mutex_lock_nested(&info->lock, subclass);
+
+       info->lower_paths = NULL;
+
+       dentry->d_fsdata = info;
+
+       if (!__realloc_dentry_private_data(dentry))
+               return 0;
+
+       mutex_unlock(&info->lock);
+       free_dentry_private_data(dentry);
+       return -ENOMEM;
+}
+
+/*
+ * scan through the lower dentry objects, and set bstart to reflect the
+ * starting branch
+ */
+void update_bstart(struct dentry *dentry)
+{
+       int bindex;
+       int bstart = dbstart(dentry);
+       int bend = dbend(dentry);
+       struct dentry *lower_dentry;
+
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               if (!lower_dentry)
+                       continue;
+               if (lower_dentry->d_inode) {
+                       dbstart(dentry) = bindex;
+                       break;
+               }
+               dput(lower_dentry);
+               unionfs_set_lower_dentry_idx(dentry, bindex, NULL);
+       }
+}
+
+
+/*
+ * Initialize a nameidata structure (the intent part) we can pass to a lower
+ * file system.  Returns 0 on success or -error (only -ENOMEM possible).
+ * Inside that nd structure, this function may also return an allocated
+ * struct file (for open intents).  The caller, when done with this nd, must
+ * kfree the intent file (using release_lower_nd).
+ *
+ * XXX: this code, and the callers of this code, should be redone using
+ * vfs_path_lookup() when (1) the nameidata structure is refactored into a
+ * separate intent-structure, and (2) open_namei() is broken into a VFS-only
+ * function and a method that other file systems can call.
+ */
+int init_lower_nd(struct nameidata *nd, unsigned int flags)
+{
+       int err = 0;
+#ifdef ALLOC_LOWER_ND_FILE
+       /*
+        * XXX: one day we may need to have the lower return an open file
+        * for us.  It is not needed in 2.6.23-rc1 for nfs2/nfs3, but may
+        * very well be needed for nfs4.
+        */
+       struct file *file;
+#endif /* ALLOC_LOWER_ND_FILE */
+
+       memset(nd, 0, sizeof(struct nameidata));
+       if (!flags)
+               return err;
+
+       switch (flags) {
+       case LOOKUP_CREATE:
+               nd->intent.open.flags |= O_CREAT;
+               /* fall through: shared code for create/open cases */
+       case LOOKUP_OPEN:
+               nd->flags = flags;
+               nd->intent.open.flags |= (FMODE_READ | FMODE_WRITE);
+#ifdef ALLOC_LOWER_ND_FILE
+               file = kzalloc(sizeof(struct file), GFP_KERNEL);
+               if (unlikely(!file)) {
+                       err = -ENOMEM;
+                       break; /* exit switch statement and thus return */
+               }
+               nd->intent.open.file = file;
+#endif /* ALLOC_LOWER_ND_FILE */
+               break;
+       default:
+               /*
+                * We should never get here, for now.
+                * We can add new cases here later on.
+                */
+               pr_debug("unionfs: unknown nameidata flag 0x%x\n", flags);
+               BUG();
+               break;
+       }
+
+       return err;
+}
+
+void release_lower_nd(struct nameidata *nd, int err)
+{
+       if (!nd->intent.open.file)
+               return;
+       else if (!err)
+               release_open_intent(nd);
+#ifdef ALLOC_LOWER_ND_FILE
+       kfree(nd->intent.open.file);
+#endif /* ALLOC_LOWER_ND_FILE */
+}
+
+/*
+ * Main (and complex) driver function for Unionfs's lookup
+ *
+ * Returns: NULL (ok), ERR_PTR if an error occurred, or a non-null non-error
+ * PTR if d_splice returned a different dentry.
+ *
+ * If lookupmode is INTERPOSE_PARTIAL/REVAL/REVAL_NEG, the passed dentry's
+ * inode info must be locked.  If lookupmode is INTERPOSE_LOOKUP (i.e., a
+ * newly looked-up dentry), then unionfs_lookup_backend will return a locked
+ * dentry's info, which the caller must unlock.
+ */
+struct dentry *unionfs_lookup_full(struct dentry *dentry,
+                                  struct dentry *parent, int lookupmode)
+{
+       int err = 0;
+       struct dentry *lower_dentry = NULL;
+       struct vfsmount *lower_mnt;
+       struct vfsmount *lower_dir_mnt;
+       struct dentry *wh_lower_dentry = NULL;
+       struct dentry *lower_dir_dentry = NULL;
+       struct dentry *d_interposed = NULL;
+       int bindex, bstart, bend, bopaque;
+       int opaque, num_positive = 0;
+       const char *name;
+       int namelen;
+       int pos_start, pos_end;
+
+       /*
+        * We should already have a lock on this dentry in the case of a
+        * partial lookup, or a revalidation.  Otherwise it is returned from
+        * new_dentry_private_data already locked.
+        */
+       verify_locked(dentry);
+       verify_locked(parent);
+
+       /* must initialize dentry operations */
+       if (lookupmode == INTERPOSE_LOOKUP)
+               d_set_d_op(dentry, &unionfs_dops);
+
+       /* We never partial lookup the root directory. */
+       if (IS_ROOT(dentry))
+               goto out;
+
+       name = dentry->d_name.name;
+       namelen = dentry->d_name.len;
+
+       /* No dentries should get created for possible whiteout names. */
+       if (!is_validname(name)) {
+               err = -EPERM;
+               goto out_free;
+       }
+
+       /* Now start the actual lookup procedure. */
+       bstart = dbstart(parent);
+       bend = dbend(parent);
+       bopaque = dbopaque(parent);
+       BUG_ON(bstart < 0);
+
+       /* adjust bend to bopaque if needed */
+       if ((bopaque >= 0) && (bopaque < bend))
+               bend = bopaque;
+
+       /* lookup all possible dentries */
+       for (bindex = bstart; bindex <= bend; bindex++) {
+
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               lower_mnt = unionfs_lower_mnt_idx(dentry, bindex);
+
+               /* skip if we already have a positive lower dentry */
+               if (lower_dentry) {
+                       if (dbstart(dentry) < 0)
+                               dbstart(dentry) = bindex;
+                       if (bindex > dbend(dentry))
+                               dbend(dentry) = bindex;
+                       if (lower_dentry->d_inode)
+                               num_positive++;
+                       continue;
+               }
+
+               lower_dir_dentry =
+                       unionfs_lower_dentry_idx(parent, bindex);
+               /* if the lower dentry's parent does not exist, skip this */
+               if (!lower_dir_dentry || !lower_dir_dentry->d_inode)
+                       continue;
+
+               /* also skip it if the parent isn't a directory. */
+               if (!S_ISDIR(lower_dir_dentry->d_inode->i_mode))
+                       continue; /* XXX: should be BUG_ON */
+
+               /* check for whiteouts: stop lookup if found */
+               wh_lower_dentry = lookup_whiteout(name, lower_dir_dentry);
+               if (IS_ERR(wh_lower_dentry)) {
+                       err = PTR_ERR(wh_lower_dentry);
+                       goto out_free;
+               }
+               if (wh_lower_dentry->d_inode) {
+                       dbend(dentry) = dbopaque(dentry) = bindex;
+                       if (dbstart(dentry) < 0)
+                               dbstart(dentry) = bindex;
+                       dput(wh_lower_dentry);
+                       break;
+               }
+               dput(wh_lower_dentry);
+
+               /* Now do regular lookup; lookup @name */
+               lower_dir_mnt = unionfs_lower_mnt_idx(parent, bindex);
+               lower_mnt = NULL; /* XXX: needed? */
+
+               lower_dentry = __lookup_one(lower_dir_dentry, lower_dir_mnt,
+                                           name, &lower_mnt);
+
+               if (IS_ERR(lower_dentry)) {
+                       err = PTR_ERR(lower_dentry);
+                       goto out_free;
+               }
+               unionfs_set_lower_dentry_idx(dentry, bindex, lower_dentry);
+               if (!lower_mnt)
+                       lower_mnt = unionfs_mntget(dentry->d_sb->s_root,
+                                                  bindex);
+               unionfs_set_lower_mnt_idx(dentry, bindex, lower_mnt);
+
+               /* adjust dbstart/end */
+               if (dbstart(dentry) < 0)
+                       dbstart(dentry) = bindex;
+               if (bindex > dbend(dentry))
+                       dbend(dentry) = bindex;
+               /*
+                * We always store the lower dentries above, and update
+                * dbstart/dbend, even if the whole unionfs dentry is
+                * negative (i.e., no lower inodes).
+                */
+               if (!lower_dentry->d_inode)
+                       continue;
+               num_positive++;
+
+               /*
+                * check if we just found an opaque directory, if so, stop
+                * lookups here.
+                */
+               if (!S_ISDIR(lower_dentry->d_inode->i_mode))
+                       continue;
+               opaque = is_opaque_dir(dentry, bindex);
+               if (opaque < 0) {
+                       err = opaque;
+                       goto out_free;
+               } else if (opaque) {
+                       dbend(dentry) = dbopaque(dentry) = bindex;
+                       break;
+               }
+               dbend(dentry) = bindex;
+
+               /* update parent directory's atime with the bindex */
+               fsstack_copy_attr_atime(parent->d_inode,
+                                       lower_dir_dentry->d_inode);
+       }
+
+       /* sanity checks, then decide if to process a negative dentry */
+       BUG_ON(dbstart(dentry) < 0 && dbend(dentry) >= 0);
+       BUG_ON(dbstart(dentry) >= 0 && dbend(dentry) < 0);
+
+       if (num_positive > 0)
+               goto out_positive;
+
+       /*** handle NEGATIVE dentries ***/
+
+       /*
+        * If negative, keep only first lower negative dentry, to save on
+        * memory.
+        */
+       if (dbstart(dentry) < dbend(dentry)) {
+               path_put_lowers(dentry, dbstart(dentry) + 1,
+                               dbend(dentry), false);
+               dbend(dentry) = dbstart(dentry);
+       }
+       if (lookupmode == INTERPOSE_PARTIAL)
+               goto out;
+       if (lookupmode == INTERPOSE_LOOKUP) {
+               /*
+                * If all we found was a whiteout in the first available
+                * branch, then create a negative dentry for a possibly new
+                * file to be created.
+                */
+               if (dbopaque(dentry) < 0)
+                       goto out;
+               /* XXX: need to get mnt here */
+               bindex = dbstart(dentry);
+               if (unionfs_lower_dentry_idx(dentry, bindex))
+                       goto out;
+               lower_dir_dentry =
+                       unionfs_lower_dentry_idx(parent, bindex);
+               if (!lower_dir_dentry || !lower_dir_dentry->d_inode)
+                       goto out;
+               if (!S_ISDIR(lower_dir_dentry->d_inode->i_mode))
+                       goto out; /* XXX: should be BUG_ON */
+               /* XXX: do we need to cross bind mounts here? */
+               lower_dentry = lookup_lck_len(name, lower_dir_dentry, namelen);
+               if (IS_ERR(lower_dentry)) {
+                       err = PTR_ERR(lower_dentry);
+                       goto out;
+               }
+               /* XXX: need to mntget/mntput as needed too! */
+               unionfs_set_lower_dentry_idx(dentry, bindex, lower_dentry);
+               /* XXX: wrong mnt for crossing bind mounts! */
+               lower_mnt = unionfs_mntget(dentry->d_sb->s_root, bindex);
+               unionfs_set_lower_mnt_idx(dentry, bindex, lower_mnt);
+
+               goto out;
+       }
+
+       /* if we're revalidating a positive dentry, don't make it negative */
+       if (lookupmode != INTERPOSE_REVAL)
+               d_add(dentry, NULL);
+
+       goto out;
+
+out_positive:
+       /*** handle POSITIVE dentries ***/
+
+       /*
+        * This unionfs dentry is positive (at least one lower inode
+        * exists), so scan entire dentry from beginning to end, and remove
+        * any negative lower dentries, if any.  Then, update dbstart/dbend
+        * to reflect the start/end of positive dentries.
+        */
+       pos_start = pos_end = -1;
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_dentry = unionfs_lower_dentry_idx(dentry,
+                                                       bindex);
+               if (lower_dentry && lower_dentry->d_inode) {
+                       if (pos_start < 0)
+                               pos_start = bindex;
+                       if (bindex > pos_end)
+                               pos_end = bindex;
+                       continue;
+               }
+               path_put_lowers(dentry, bindex, bindex, false);
+       }
+       if (pos_start >= 0)
+               dbstart(dentry) = pos_start;
+       if (pos_end >= 0)
+               dbend(dentry) = pos_end;
+
+       /* Partial lookups need to re-interpose, or throw away older negs. */
+       if (lookupmode == INTERPOSE_PARTIAL) {
+               if (dentry->d_inode) {
+                       unionfs_reinterpose(dentry);
+                       goto out;
+               }
+
+               /*
+                * This dentry was positive, so it is as if we had a
+                * negative revalidation.
+                */
+               lookupmode = INTERPOSE_REVAL_NEG;
+               update_bstart(dentry);
+       }
+
+       /*
+        * Interpose can return a dentry if d_splice returned a different
+        * dentry.
+        */
+       d_interposed = unionfs_interpose(dentry, dentry->d_sb, lookupmode);
+       if (IS_ERR(d_interposed))
+               err = PTR_ERR(d_interposed);
+       else if (d_interposed)
+               dentry = d_interposed;
+
+       if (!err)
+               goto out;
+       d_drop(dentry);
+
+out_free:
+       /* should dput/mntput all the underlying dentries on error condition */
+       if (dbstart(dentry) >= 0)
+               path_put_lowers_all(dentry, false);
+       /* free lower_paths unconditionally */
+       kfree(UNIONFS_D(dentry)->lower_paths);
+       UNIONFS_D(dentry)->lower_paths = NULL;
+
+out:
+       if (dentry && UNIONFS_D(dentry)) {
+               BUG_ON(dbstart(dentry) < 0 && dbend(dentry) >= 0);
+               BUG_ON(dbstart(dentry) >= 0 && dbend(dentry) < 0);
+       }
+       if (d_interposed && UNIONFS_D(d_interposed)) {
+               BUG_ON(dbstart(d_interposed) < 0 && dbend(d_interposed) >= 0);
+               BUG_ON(dbstart(d_interposed) >= 0 && dbend(d_interposed) < 0);
+       }
+
+       if (!err && d_interposed)
+               return d_interposed;
+       return ERR_PTR(err);
+}
diff --git a/fs/unionfs/main.c b/fs/unionfs/main.c
new file mode 100644
index 0000000..ee78f1d
--- /dev/null
+++ b/fs/unionfs/main.c
@@ -0,0 +1,752 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+
+static void unionfs_fill_inode(struct dentry *dentry,
+                              struct inode *inode)
+{
+       struct inode *lower_inode;
+       struct dentry *lower_dentry;
+       int bindex, bstart, bend;
+
+       bstart = dbstart(dentry);
+       bend = dbend(dentry);
+
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               if (!lower_dentry) {
+                       unionfs_set_lower_inode_idx(inode, bindex, NULL);
+                       continue;
+               }
+
+               /* Initialize the lower inode to the new lower inode. */
+               if (!lower_dentry->d_inode)
+                       continue;
+
+               unionfs_set_lower_inode_idx(inode, bindex,
+                                           igrab(lower_dentry->d_inode));
+       }
+
+       ibstart(inode) = dbstart(dentry);
+       ibend(inode) = dbend(dentry);
+
+       /* Use attributes from the first branch. */
+       lower_inode = unionfs_lower_inode(inode);
+
+       /* Use different set of inode ops for symlinks & directories */
+       if (S_ISLNK(lower_inode->i_mode))
+               inode->i_op = &unionfs_symlink_iops;
+       else if (S_ISDIR(lower_inode->i_mode))
+               inode->i_op = &unionfs_dir_iops;
+
+       /* Use different set of file ops for directories */
+       if (S_ISDIR(lower_inode->i_mode))
+               inode->i_fop = &unionfs_dir_fops;
+
+       /* properly initialize special inodes */
+       if (S_ISBLK(lower_inode->i_mode) || S_ISCHR(lower_inode->i_mode) ||
+           S_ISFIFO(lower_inode->i_mode) || S_ISSOCK(lower_inode->i_mode))
+               init_special_inode(inode, lower_inode->i_mode,
+                                  lower_inode->i_rdev);
+
+       /* all well, copy inode attributes */
+       unionfs_copy_attr_all(inode, lower_inode);
+       fsstack_copy_inode_size(inode, lower_inode);
+}
+
+/*
+ * Connect a unionfs inode dentry/inode with several lower ones.  This is
+ * the classic stackable file system "vnode interposition" action.
+ *
+ * @sb: unionfs's super_block
+ */
+struct dentry *unionfs_interpose(struct dentry *dentry, struct super_block *sb,
+                                int flag)
+{
+       int err = 0;
+       struct inode *inode;
+       int need_fill_inode = 1;
+       struct dentry *spliced = NULL;
+
+       verify_locked(dentry);
+
+       /*
+        * We allocate our new inode below by calling unionfs_iget,
+        * which will initialize some of the new inode's fields
+        */
+
+       /*
+        * On revalidate we've already got our own inode and just need
+        * to fix it up.
+        */
+       if (flag == INTERPOSE_REVAL) {
+               inode = dentry->d_inode;
+               UNIONFS_I(inode)->bstart = -1;
+               UNIONFS_I(inode)->bend = -1;
+               atomic_set(&UNIONFS_I(inode)->generation,
+                          atomic_read(&UNIONFS_SB(sb)->generation));
+
+               UNIONFS_I(inode)->lower_inodes =
+                       kcalloc(sbmax(sb), sizeof(struct inode *), GFP_KERNEL);
+               if (unlikely(!UNIONFS_I(inode)->lower_inodes)) {
+                       err = -ENOMEM;
+                       goto out;
+               }
+       } else {
+               /* get unique inode number for unionfs */
+               inode = unionfs_iget(sb, iunique(sb, UNIONFS_ROOT_INO));
+               if (IS_ERR(inode)) {
+                       err = PTR_ERR(inode);
+                       goto out;
+               }
+               if (atomic_read(&inode->i_count) > 1)
+                       goto skip;
+       }
+
+       need_fill_inode = 0;
+       unionfs_fill_inode(dentry, inode);
+
+skip:
+       /* only (our) lookup wants to do a d_add */
+       switch (flag) {
+       case INTERPOSE_DEFAULT:
+               /* for operations which create new inodes */
+               d_add(dentry, inode);
+               break;
+       case INTERPOSE_REVAL_NEG:
+               d_instantiate(dentry, inode);
+               break;
+       case INTERPOSE_LOOKUP:
+               spliced = d_splice_alias(inode, dentry);
+               if (spliced && spliced != dentry) {
+                       /*
+                        * d_splice can return a dentry if it was
+                        * disconnected and had to be moved.  We must ensure
+                        * that the private data of the new dentry is
+                        * correct and that the inode info was filled
+                        * properly.  Finally we must return this new
+                        * dentry.
+                        */
+                       d_set_d_op(spliced, &unionfs_dops);
+                       spliced->d_fsdata = dentry->d_fsdata;
+                       dentry->d_fsdata = NULL;
+                       dentry = spliced;
+                       if (need_fill_inode) {
+                               need_fill_inode = 0;
+                               unionfs_fill_inode(dentry, inode);
+                       }
+                       goto out_spliced;
+               } else if (!spliced) {
+                       if (need_fill_inode) {
+                               need_fill_inode = 0;
+                               unionfs_fill_inode(dentry, inode);
+                               goto out_spliced;
+                       }
+               }
+               break;
+       case INTERPOSE_REVAL:
+               /* Do nothing. */
+               break;
+       default:
+               printk(KERN_CRIT "unionfs: invalid interpose flag passed!\n");
+               BUG();
+       }
+       goto out;
+
+out_spliced:
+       if (!err)
+               return spliced;
+out:
+       return ERR_PTR(err);
+}
+
+/* like interpose above, but for an already existing dentry */
+void unionfs_reinterpose(struct dentry *dentry)
+{
+       struct dentry *lower_dentry;
+       struct inode *inode;
+       int bindex, bstart, bend;
+
+       verify_locked(dentry);
+
+       /* This is pre-allocated inode */
+       inode = dentry->d_inode;
+
+       bstart = dbstart(dentry);
+       bend = dbend(dentry);
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               if (!lower_dentry)
+                       continue;
+
+               if (!lower_dentry->d_inode)
+                       continue;
+               if (unionfs_lower_inode_idx(inode, bindex))
+                       continue;
+               unionfs_set_lower_inode_idx(inode, bindex,
+                                           igrab(lower_dentry->d_inode));
+       }
+       ibstart(inode) = dbstart(dentry);
+       ibend(inode) = dbend(dentry);
+}
+
+/*
+ * make sure the branch we just looked up (nd) makes sense:
+ *
+ * 1) we're not trying to stack unionfs on top of unionfs
+ * 2) it exists
+ * 3) is a directory
+ */
+int check_branch(const struct path *path)
+{
+       /* XXX: remove in ODF code -- stacking unions allowed there */
+       if (!strcmp(path->dentry->d_sb->s_type->name, UNIONFS_NAME))
+               return -EINVAL;
+       if (!path->dentry->d_inode)
+               return -ENOENT;
+       if (!S_ISDIR(path->dentry->d_inode->i_mode))
+               return -ENOTDIR;
+       return 0;
+}
+
+/* checks if two lower_dentries have overlapping branches */
+static int is_branch_overlap(struct dentry *dent1, struct dentry *dent2)
+{
+       struct dentry *dent = NULL;
+
+       dent = dent1;
+       while ((dent != dent2) && (dent->d_parent != dent))
+               dent = dent->d_parent;
+
+       if (dent == dent2)
+               return 1;
+
+       dent = dent2;
+       while ((dent != dent1) && (dent->d_parent != dent))
+               dent = dent->d_parent;
+
+       return (dent == dent1);
+}
+
+/*
+ * Parse "ro" or "rw" options, but default to "rw" if no mode options was
+ * specified.  Fill the mode bits in @perms.  If encounter an unknown
+ * string, return -EINVAL.  Otherwise return 0.
+ */
+int parse_branch_mode(const char *name, int *perms)
+{
+       if (!name || !strcmp(name, "rw")) {
+               *perms = MAY_READ | MAY_WRITE;
+               return 0;
+       }
+       if (!strcmp(name, "ro")) {
+               *perms = MAY_READ;
+               return 0;
+       }
+       return -EINVAL;
+}
+
+/*
+ * parse the dirs= mount argument
+ *
+ * We don't need to lock the superblock private data's rwsem, as we get
+ * called only by unionfs_read_super - it is still a long time before anyone
+ * can even get a reference to us.
+ */
+static int parse_dirs_option(struct super_block *sb, struct unionfs_dentry_info
+                            *lower_root_info, char *options)
+{
+       struct path path;
+       char *name;
+       int err = 0;
+       int branches = 1;
+       int bindex = 0;
+       int i = 0;
+       int j = 0;
+       struct dentry *dent1;
+       struct dentry *dent2;
+
+       if (options[0] == '\0') {
+               printk(KERN_ERR "unionfs: no branches specified\n");
+               err = -EINVAL;
+               goto out_return;
+       }
+
+       /*
+        * Each colon means we have a separator, this is really just a rough
+        * guess, since strsep will handle empty fields for us.
+        */
+       for (i = 0; options[i]; i++)
+               if (options[i] == ':')
+                       branches++;
+
+       /* allocate space for underlying pointers to lower dentry */
+       UNIONFS_SB(sb)->data =
+               kcalloc(branches, sizeof(struct unionfs_data), GFP_KERNEL);
+       if (unlikely(!UNIONFS_SB(sb)->data)) {
+               err = -ENOMEM;
+               goto out_return;
+       }
+
+       lower_root_info->lower_paths =
+               kcalloc(branches, sizeof(struct path), GFP_KERNEL);
+       if (unlikely(!lower_root_info->lower_paths)) {
+               err = -ENOMEM;
+               /* free the underlying pointer array */
+               kfree(UNIONFS_SB(sb)->data);
+               UNIONFS_SB(sb)->data = NULL;
+               goto out_return;
+       }
+
+       /* now parsing a string such as "b1:b2=rw:b3=ro:b4" */
+       branches = 0;
+       while ((name = strsep(&options, ":")) != NULL) {
+               int perms;
+               char *mode = strchr(name, '=');
+
+               if (!name)
+                       continue;
+               if (!*name) {   /* bad use of ':' (extra colons) */
+                       err = -EINVAL;
+                       goto out;
+               }
+
+               branches++;
+
+               /* strip off '=' if any */
+               if (mode)
+                       *mode++ = '\0';
+
+               err = parse_branch_mode(mode, &perms);
+               if (err) {
+                       printk(KERN_ERR "unionfs: invalid mode \"%s\" for "
+                              "branch %d\n", mode, bindex);
+                       goto out;
+               }
+               /* ensure that leftmost branch is writeable */
+               if (!bindex && !(perms & MAY_WRITE)) {
+                       printk(KERN_ERR "unionfs: leftmost branch cannot be "
+                              "read-only (use \"-o ro\" to create a "
+                              "read-only union)\n");
+                       err = -EINVAL;
+                       goto out;
+               }
+
+               err = kern_path(name, LOOKUP_FOLLOW, &path);
+               if (err) {
+                       printk(KERN_ERR "unionfs: error accessing "
+                              "lower directory '%s' (error %d)\n",
+                              name, err);
+                       goto out;
+               }
+
+               err = check_branch(&path);
+               if (err) {
+                       printk(KERN_ERR "unionfs: lower directory "
+                              "'%s' is not a valid branch\n", name);
+                       path_put(&path);
+                       goto out;
+               }
+
+               lower_root_info->lower_paths[bindex].dentry = path.dentry;
+               lower_root_info->lower_paths[bindex].mnt = path.mnt;
+
+               set_branchperms(sb, bindex, perms);
+               set_branch_count(sb, bindex, 0);
+               new_branch_id(sb, bindex);
+
+               if (lower_root_info->bstart < 0)
+                       lower_root_info->bstart = bindex;
+               lower_root_info->bend = bindex;
+               bindex++;
+       }
+
+       if (branches == 0) {
+               printk(KERN_ERR "unionfs: no branches specified\n");
+               err = -EINVAL;
+               goto out;
+       }
+
+       BUG_ON(branches != (lower_root_info->bend + 1));
+
+       /*
+        * Ensure that no overlaps exist in the branches.
+        *
+        * This test is required because the Linux kernel has no support
+        * currently for ensuring coherency between stackable layers and
+        * branches.  If we were to allow overlapping branches, it would be
+        * possible, for example, to delete a file via one branch, which
+        * would not be reflected in another branch.  Such incoherency could
+        * lead to inconsistencies and even kernel oopses.  Rather than
+        * implement hacks to work around some of these cache-coherency
+        * problems, we prevent branch overlapping, for now.  A complete
+        * solution will involve proper kernel/VFS support for cache
+        * coherency, at which time we could safely remove this
+        * branch-overlapping test.
+        */
+       for (i = 0; i < branches; i++) {
+               dent1 = lower_root_info->lower_paths[i].dentry;
+               for (j = i + 1; j < branches; j++) {
+                       dent2 = lower_root_info->lower_paths[j].dentry;
+                       if (is_branch_overlap(dent1, dent2)) {
+                               printk(KERN_ERR "unionfs: branches %d and "
+                                      "%d overlap\n", i, j);
+                               err = -EINVAL;
+                               goto out;
+                       }
+               }
+       }
+
+out:
+       if (err) {
+               for (i = 0; i < branches; i++)
+                       path_put(&lower_root_info->lower_paths[i]);
+
+               kfree(lower_root_info->lower_paths);
+               kfree(UNIONFS_SB(sb)->data);
+
+               /*
+                * MUST clear the pointers to prevent potential double free if
+                * the caller dies later on
+                */
+               lower_root_info->lower_paths = NULL;
+               UNIONFS_SB(sb)->data = NULL;
+       }
+out_return:
+       return err;
+}
+
+/*
+ * Parse mount options.  See the manual page for usage instructions.
+ *
+ * Returns the dentry object of the lower-level (lower) directory;
+ * We want to mount our stackable file system on top of that lower directory.
+ */
+static struct unionfs_dentry_info *unionfs_parse_options(
+                                        struct super_block *sb,
+                                        char *options)
+{
+       struct unionfs_dentry_info *lower_root_info;
+       char *optname;
+       int err = 0;
+       int bindex;
+       int dirsfound = 0;
+
+       /* allocate private data area */
+       err = -ENOMEM;
+       lower_root_info =
+               kzalloc(sizeof(struct unionfs_dentry_info), GFP_KERNEL);
+       if (unlikely(!lower_root_info))
+               goto out_error;
+       lower_root_info->bstart = -1;
+       lower_root_info->bend = -1;
+       lower_root_info->bopaque = -1;
+
+       while ((optname = strsep(&options, ",")) != NULL) {
+               char *optarg;
+
+               if (!optname || !*optname)
+                       continue;
+
+               optarg = strchr(optname, '=');
+               if (optarg)
+                       *optarg++ = '\0';
+
+               /*
+                * All of our options take an argument now. Insert ones that
+                * don't, above this check.
+                */
+               if (!optarg) {
+                       printk(KERN_ERR "unionfs: %s requires an argument\n",
+                              optname);
+                       err = -EINVAL;
+                       goto out_error;
+               }
+
+               if (!strcmp("dirs", optname)) {
+                       if (++dirsfound > 1) {
+                               printk(KERN_ERR
+                                      "unionfs: multiple dirs specified\n");
+                               err = -EINVAL;
+                               goto out_error;
+                       }
+                       err = parse_dirs_option(sb, lower_root_info, optarg);
+                       if (err)
+                               goto out_error;
+                       continue;
+               }
+
+               err = -EINVAL;
+               printk(KERN_ERR
+                      "unionfs: unrecognized option '%s'\n", optname);
+               goto out_error;
+       }
+       if (dirsfound != 1) {
+               printk(KERN_ERR "unionfs: dirs option required\n");
+               err = -EINVAL;
+               goto out_error;
+       }
+       goto out;
+
+out_error:
+       if (lower_root_info && lower_root_info->lower_paths) {
+               for (bindex = lower_root_info->bstart;
+                    bindex >= 0 && bindex <= lower_root_info->bend;
+                    bindex++)
+                       path_put(&lower_root_info->lower_paths[bindex]);
+       }
+
+       kfree(lower_root_info->lower_paths);
+       kfree(lower_root_info);
+
+       kfree(UNIONFS_SB(sb)->data);
+       UNIONFS_SB(sb)->data = NULL;
+
+       lower_root_info = ERR_PTR(err);
+out:
+       return lower_root_info;
+}
+
+/*
+ * There is no need to lock the unionfs_super_info's rwsem as there is no
+ * way anyone can have a reference to the superblock at this point in time.
+ */
+static int unionfs_read_super(struct super_block *sb, void *raw_data,
+                             int silent)
+{
+       int err = 0;
+       struct unionfs_dentry_info *lower_root_info = NULL;
+       int bindex, bstart, bend;
+       struct inode *inode = NULL;
+
+       if (!raw_data) {
+               printk(KERN_ERR
+                      "unionfs: read_super: missing data argument\n");
+               err = -EINVAL;
+               goto out;
+       }
+
+       /* Allocate superblock private data */
+       sb->s_fs_info = kzalloc(sizeof(struct unionfs_sb_info), GFP_KERNEL);
+       if (unlikely(!UNIONFS_SB(sb))) {
+               printk(KERN_CRIT "unionfs: read_super: out of memory\n");
+               err = -ENOMEM;
+               goto out;
+       }
+
+       UNIONFS_SB(sb)->bend = -1;
+       atomic_set(&UNIONFS_SB(sb)->generation, 1);
+       init_rwsem(&UNIONFS_SB(sb)->rwsem);
+       UNIONFS_SB(sb)->high_branch_id = -1; /* -1 == invalid branch ID */
+
+       lower_root_info = unionfs_parse_options(sb, raw_data);
+       if (IS_ERR(lower_root_info)) {
+               printk(KERN_ERR
+                      "unionfs: read_super: error while parsing options "
+                      "(err = %ld)\n", PTR_ERR(lower_root_info));
+               err = PTR_ERR(lower_root_info);
+               lower_root_info = NULL;
+               goto out_free;
+       }
+       if (lower_root_info->bstart == -1) {
+               err = -ENOENT;
+               goto out_free;
+       }
+
+       /* set the lower superblock field of upper superblock */
+       bstart = lower_root_info->bstart;
+       BUG_ON(bstart != 0);
+       sbend(sb) = bend = lower_root_info->bend;
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               struct dentry *d = lower_root_info->lower_paths[bindex].dentry;
+               atomic_inc(&d->d_sb->s_active);
+               unionfs_set_lower_super_idx(sb, bindex, d->d_sb);
+       }
+
+       /* max Bytes is the maximum bytes from highest priority branch */
+       sb->s_maxbytes = unionfs_lower_super_idx(sb, 0)->s_maxbytes;
+
+       /*
+        * Our c/m/atime granularity is 1 ns because we may stack on file
+        * systems whose granularity is as good.  This is important for our
+        * time-based cache coherency.
+        */
+       sb->s_time_gran = 1;
+
+       sb->s_op = &unionfs_sops;
+
+       /* get a new inode and allocate our root dentry */
+       inode = unionfs_iget(sb, iunique(sb, UNIONFS_ROOT_INO));
+       if (IS_ERR(inode)) {
+               err = PTR_ERR(inode);
+               goto out_dput;
+       }
+       sb->s_root = d_make_root(inode);
+       if (unlikely(!sb->s_root)) {
+               err = -ENOMEM;
+               goto out_dput;
+       }
+       d_set_d_op(sb->s_root, &unionfs_dops);
+
+       /* link the upper and lower dentries */
+       sb->s_root->d_fsdata = NULL;
+       err = new_dentry_private_data(sb->s_root, UNIONFS_DMUTEX_ROOT);
+       if (unlikely(err))
+               goto out_freedpd;
+
+       /* if get here: cannot have error */
+
+       /* Set the lower dentries for s_root */
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               struct dentry *d;
+               struct vfsmount *m;
+
+               d = lower_root_info->lower_paths[bindex].dentry;
+               m = lower_root_info->lower_paths[bindex].mnt;
+
+               unionfs_set_lower_dentry_idx(sb->s_root, bindex, d);
+               unionfs_set_lower_mnt_idx(sb->s_root, bindex, m);
+       }
+       dbstart(sb->s_root) = bstart;
+       dbend(sb->s_root) = bend;
+
+       /* Set the generation number to one, since this is for the mount. */
+       atomic_set(&UNIONFS_D(sb->s_root)->generation, 1);
+
+       if (atomic_read(&inode->i_count) <= 1)
+               unionfs_fill_inode(sb->s_root, inode);
+
+       /*
+        * No need to call interpose because we already have a positive
+        * dentry, which was instantiated by d_alloc_root.  Just need to
+        * d_rehash it.
+        */
+       d_rehash(sb->s_root);
+
+       unionfs_unlock_dentry(sb->s_root);
+       goto out; /* all is well */
+
+out_freedpd:
+       if (UNIONFS_D(sb->s_root)) {
+               kfree(UNIONFS_D(sb->s_root)->lower_paths);
+               free_dentry_private_data(sb->s_root);
+       }
+       dput(sb->s_root);
+
+out_iput:
+       iput(inode);
+
+out_dput:
+       if (lower_root_info && !IS_ERR(lower_root_info)) {
+               for (bindex = lower_root_info->bstart;
+                    bindex <= lower_root_info->bend; bindex++) {
+                       struct dentry *d;
+                       d = lower_root_info->lower_paths[bindex].dentry;
+                       /* drop refs we took earlier */
+                       atomic_dec(&d->d_sb->s_active);
+                       path_put(&lower_root_info->lower_paths[bindex]);
+               }
+               kfree(lower_root_info->lower_paths);
+               kfree(lower_root_info);
+               lower_root_info = NULL;
+       }
+
+out_free:
+       kfree(UNIONFS_SB(sb)->data);
+       kfree(UNIONFS_SB(sb));
+       sb->s_fs_info = NULL;
+
+out:
+       if (lower_root_info && !IS_ERR(lower_root_info)) {
+               kfree(lower_root_info->lower_paths);
+               kfree(lower_root_info);
+       }
+       return err;
+}
+
+static struct dentry *unionfs_mount(struct file_system_type *fs_type,
+                                   int flags, const char *dev_name,
+                                   void *raw_data)
+{
+       struct dentry *dentry;
+
+       dentry = mount_nodev(fs_type, flags, raw_data, unionfs_read_super);
+       if (!IS_ERR(dentry))
+               UNIONFS_SB(dentry->d_sb)->dev_name =
+                       kstrdup(dev_name, GFP_KERNEL);
+       return dentry;
+}
+
+static struct file_system_type unionfs_fs_type = {
+       .owner          = THIS_MODULE,
+       .name           = UNIONFS_NAME,
+       .mount          = unionfs_mount,
+       .kill_sb        = generic_shutdown_super,
+       .fs_flags       = FS_REVAL_DOT,
+};
+
+static int __init init_unionfs_fs(void)
+{
+       int err;
+
+       pr_info("Registering unionfs " UNIONFS_VERSION "\n");
+
+       err = unionfs_init_filldir_cache();
+       if (unlikely(err))
+               goto out;
+       err = unionfs_init_inode_cache();
+       if (unlikely(err))
+               goto out;
+       err = unionfs_init_dentry_cache();
+       if (unlikely(err))
+               goto out;
+       err = init_sioq();
+       if (unlikely(err))
+               goto out;
+       err = register_filesystem(&unionfs_fs_type);
+out:
+       if (unlikely(err)) {
+               stop_sioq();
+               unionfs_destroy_filldir_cache();
+               unionfs_destroy_inode_cache();
+               unionfs_destroy_dentry_cache();
+       }
+       return err;
+}
+
+static void __exit exit_unionfs_fs(void)
+{
+       stop_sioq();
+       unionfs_destroy_filldir_cache();
+       unionfs_destroy_inode_cache();
+       unionfs_destroy_dentry_cache();
+       unregister_filesystem(&unionfs_fs_type);
+       pr_info("Completed unionfs module unload\n");
+}
+
+MODULE_AUTHOR("Erez Zadok, Filesystems and Storage Lab, Stony Brook University"
+             " (http://www.fsl.cs.sunysb.edu)");
+MODULE_DESCRIPTION("Unionfs " UNIONFS_VERSION
+                  " (http://unionfs.filesystems.org)");
+MODULE_LICENSE("GPL");
+
+module_init(init_unionfs_fs);
+module_exit(exit_unionfs_fs);
diff --git a/fs/unionfs/mmap.c b/fs/unionfs/mmap.c
new file mode 100644
index 0000000..bcc5652
--- /dev/null
+++ b/fs/unionfs/mmap.c
@@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2006      Shaya Potter
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+
+/*
+ * XXX: we need a dummy readpage handler because generic_file_mmap (which we
+ * use in unionfs_mmap) checks for the existence of
+ * mapping->a_ops->readpage, else it returns -ENOEXEC.  The VFS will need to
+ * be fixed to allow a file system to define vm_ops->fault without any
+ * address_space_ops whatsoever.
+ *
+ * Otherwise, we don't want to use our readpage method at all.
+ */
+static int unionfs_readpage(struct file *file, struct page *page)
+{
+       BUG();
+       return -EINVAL;
+}
+
+static int unionfs_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+       int err;
+       struct file *file, *lower_file;
+       const struct vm_operations_struct *lower_vm_ops;
+       struct vm_area_struct lower_vma;
+
+       BUG_ON(!vma);
+       memcpy(&lower_vma, vma, sizeof(struct vm_area_struct));
+       file = lower_vma.vm_file;
+       lower_vm_ops = UNIONFS_F(file)->lower_vm_ops;
+       BUG_ON(!lower_vm_ops);
+
+       lower_file = unionfs_lower_file(file);
+       BUG_ON(!lower_file);
+       /*
+        * XXX: vm_ops->fault may be called in parallel.  Because we have to
+        * resort to temporarily changing the vma->vm_file to point to the
+        * lower file, a concurrent invocation of unionfs_fault could see a
+        * different value.  In this workaround, we keep a different copy of
+        * the vma structure in our stack, so we never expose a different
+        * value of the vma->vm_file called to us, even temporarily.  A
+        * better fix would be to change the calling semantics of ->fault to
+        * take an explicit file pointer.
+        */
+       lower_vma.vm_file = lower_file;
+       err = lower_vm_ops->fault(&lower_vma, vmf);
+       return err;
+}
+
+/*
+ * XXX: the default address_space_ops for unionfs is empty.  We cannot set
+ * our inode->i_mapping->a_ops to NULL because too many code paths expect
+ * the a_ops vector to be non-NULL.
+ */
+struct address_space_operations unionfs_aops = {
+       /* empty on purpose */
+};
+
+/*
+ * XXX: we need a second, dummy address_space_ops vector, to be used
+ * temporarily during unionfs_mmap, because the latter calls
+ * generic_file_mmap, which checks if ->readpage exists, else returns
+ * -ENOEXEC.
+ */
+struct address_space_operations unionfs_dummy_aops = {
+       .readpage       = unionfs_readpage,
+};
+
+struct vm_operations_struct unionfs_vm_ops = {
+       .fault          = unionfs_fault,
+};
diff --git a/fs/unionfs/rdstate.c b/fs/unionfs/rdstate.c
new file mode 100644
index 0000000..59b7333
--- /dev/null
+++ b/fs/unionfs/rdstate.c
@@ -0,0 +1,285 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/* This file contains the routines for maintaining readdir state. */
+
+/*
+ * There are two structures here, rdstate which is a hash table
+ * of the second structure which is a filldir_node.
+ */
+
+/*
+ * This is a struct kmem_cache for filldir nodes, because we allocate a lot
+ * of them and they shouldn't waste memory.  If the node has a small name
+ * (as defined by the dentry structure), then we use an inline name to
+ * preserve kmalloc space.
+ */
+static struct kmem_cache *unionfs_filldir_cachep;
+
+int unionfs_init_filldir_cache(void)
+{
+       unionfs_filldir_cachep =
+               kmem_cache_create("unionfs_filldir",
+                                 sizeof(struct filldir_node), 0,
+                                 SLAB_RECLAIM_ACCOUNT, NULL);
+
+       return (unionfs_filldir_cachep ? 0 : -ENOMEM);
+}
+
+void unionfs_destroy_filldir_cache(void)
+{
+       if (unionfs_filldir_cachep)
+               kmem_cache_destroy(unionfs_filldir_cachep);
+}
+
+/*
+ * This is a tuning parameter that tells us roughly how big to make the
+ * hash table in directory entries per page.  This isn't perfect, but
+ * at least we get a hash table size that shouldn't be too overloaded.
+ * The following averages are based on my home directory.
+ * 14.44693    Overall
+ * 12.29       Single Page Directories
+ * 117.93      Multi-page directories
+ */
+#define DENTPAGE 4096
+#define DENTPERONEPAGE 12
+#define DENTPERPAGE 118
+#define MINHASHSIZE 1
+static int guesstimate_hash_size(struct inode *inode)
+{
+       struct inode *lower_inode;
+       int bindex;
+       int hashsize = MINHASHSIZE;
+
+       if (UNIONFS_I(inode)->hashsize > 0)
+               return UNIONFS_I(inode)->hashsize;
+
+       for (bindex = ibstart(inode); bindex <= ibend(inode); bindex++) {
+               lower_inode = unionfs_lower_inode_idx(inode, bindex);
+               if (!lower_inode)
+                       continue;
+
+               if (i_size_read(lower_inode) == DENTPAGE)
+                       hashsize += DENTPERONEPAGE;
+               else
+                       hashsize += (i_size_read(lower_inode) / DENTPAGE) *
+                               DENTPERPAGE;
+       }
+
+       return hashsize;
+}
+
+int init_rdstate(struct file *file)
+{
+       BUG_ON(sizeof(loff_t) !=
+              (sizeof(unsigned int) + sizeof(unsigned int)));
+       BUG_ON(UNIONFS_F(file)->rdstate != NULL);
+
+       UNIONFS_F(file)->rdstate = alloc_rdstate(file->f_path.dentry->d_inode,
+                                                fbstart(file));
+
+       return (UNIONFS_F(file)->rdstate ? 0 : -ENOMEM);
+}
+
+struct unionfs_dir_state *find_rdstate(struct inode *inode, loff_t fpos)
+{
+       struct unionfs_dir_state *rdstate = NULL;
+       struct list_head *pos;
+
+       spin_lock(&UNIONFS_I(inode)->rdlock);
+       list_for_each(pos, &UNIONFS_I(inode)->readdircache) {
+               struct unionfs_dir_state *r =
+                       list_entry(pos, struct unionfs_dir_state, cache);
+               if (fpos == rdstate2offset(r)) {
+                       UNIONFS_I(inode)->rdcount--;
+                       list_del(&r->cache);
+                       rdstate = r;
+                       break;
+               }
+       }
+       spin_unlock(&UNIONFS_I(inode)->rdlock);
+       return rdstate;
+}
+
+struct unionfs_dir_state *alloc_rdstate(struct inode *inode, int bindex)
+{
+       int i = 0;
+       int hashsize;
+       unsigned long mallocsize = sizeof(struct unionfs_dir_state);
+       struct unionfs_dir_state *rdstate;
+
+       hashsize = guesstimate_hash_size(inode);
+       mallocsize += hashsize * sizeof(struct list_head);
+       mallocsize = __roundup_pow_of_two(mallocsize);
+
+       /* This should give us about 500 entries anyway. */
+       if (mallocsize > PAGE_SIZE)
+               mallocsize = PAGE_SIZE;
+
+       hashsize = (mallocsize - sizeof(struct unionfs_dir_state)) /
+               sizeof(struct list_head);
+
+       rdstate = kmalloc(mallocsize, GFP_KERNEL);
+       if (unlikely(!rdstate))
+               return NULL;
+
+       spin_lock(&UNIONFS_I(inode)->rdlock);
+       if (UNIONFS_I(inode)->cookie >= (MAXRDCOOKIE - 1))
+               UNIONFS_I(inode)->cookie = 1;
+       else
+               UNIONFS_I(inode)->cookie++;
+
+       rdstate->cookie = UNIONFS_I(inode)->cookie;
+       spin_unlock(&UNIONFS_I(inode)->rdlock);
+       rdstate->offset = 1;
+       rdstate->access = jiffies;
+       rdstate->bindex = bindex;
+       rdstate->dirpos = 0;
+       rdstate->hashentries = 0;
+       rdstate->size = hashsize;
+       for (i = 0; i < rdstate->size; i++)
+               INIT_LIST_HEAD(&rdstate->list[i]);
+
+       return rdstate;
+}
+
+static void free_filldir_node(struct filldir_node *node)
+{
+       if (node->namelen >= DNAME_INLINE_LEN)
+               kfree(node->name);
+       kmem_cache_free(unionfs_filldir_cachep, node);
+}
+
+void free_rdstate(struct unionfs_dir_state *state)
+{
+       struct filldir_node *tmp;
+       int i;
+
+       for (i = 0; i < state->size; i++) {
+               struct list_head *head = &(state->list[i]);
+               struct list_head *pos, *n;
+
+               /* traverse the list and deallocate space */
+               list_for_each_safe(pos, n, head) {
+                       tmp = list_entry(pos, struct filldir_node, file_list);
+                       list_del(&tmp->file_list);
+                       free_filldir_node(tmp);
+               }
+       }
+
+       kfree(state);
+}
+
+struct filldir_node *find_filldir_node(struct unionfs_dir_state *rdstate,
+                                      const char *name, int namelen,
+                                      int is_whiteout)
+{
+       int index;
+       unsigned int hash;
+       struct list_head *head;
+       struct list_head *pos;
+       struct filldir_node *cursor = NULL;
+       int found = 0;
+
+       BUG_ON(namelen <= 0);
+
+       hash = full_name_hash(name, namelen);
+       index = hash % rdstate->size;
+
+       head = &(rdstate->list[index]);
+       list_for_each(pos, head) {
+               cursor = list_entry(pos, struct filldir_node, file_list);
+
+               if (cursor->namelen == namelen && cursor->hash == hash &&
+                   !strncmp(cursor->name, name, namelen)) {
+                       /*
+                        * a duplicate exists, and hence no need to create
+                        * entry to the list
+                        */
+                       found = 1;
+
+                       /*
+                        * if a duplicate is found in this branch, and is
+                        * not due to the caller looking for an entry to
+                        * whiteout, then the file system may be corrupted.
+                        */
+                       if (unlikely(!is_whiteout &&
+                                    cursor->bindex == rdstate->bindex))
+                               printk(KERN_ERR "unionfs: filldir: possible "
+                                      "I/O error: a file is duplicated "
+                                      "in the same branch %d: %s\n",
+                                      rdstate->bindex, cursor->name);
+                       break;
+               }
+       }
+
+       if (!found)
+               cursor = NULL;
+
+       return cursor;
+}
+
+int add_filldir_node(struct unionfs_dir_state *rdstate, const char *name,
+                    int namelen, int bindex, int whiteout)
+{
+       struct filldir_node *new;
+       unsigned int hash;
+       int index;
+       int err = 0;
+       struct list_head *head;
+
+       BUG_ON(namelen <= 0);
+
+       hash = full_name_hash(name, namelen);
+       index = hash % rdstate->size;
+       head = &(rdstate->list[index]);
+
+       new = kmem_cache_alloc(unionfs_filldir_cachep, GFP_KERNEL);
+       if (unlikely(!new)) {
+               err = -ENOMEM;
+               goto out;
+       }
+
+       INIT_LIST_HEAD(&new->file_list);
+       new->namelen = namelen;
+       new->hash = hash;
+       new->bindex = bindex;
+       new->whiteout = whiteout;
+
+       if (namelen < DNAME_INLINE_LEN) {
+               new->name = new->iname;
+       } else {
+               new->name = kmalloc(namelen + 1, GFP_KERNEL);
+               if (unlikely(!new->name)) {
+                       kmem_cache_free(unionfs_filldir_cachep, new);
+                       new = NULL;
+                       goto out;
+               }
+       }
+
+       memcpy(new->name, name, namelen);
+       new->name[namelen] = '\0';
+
+       rdstate->hashentries++;
+
+       list_add(&(new->file_list), head);
+out:
+       return err;
+}
diff --git a/fs/unionfs/rename.c b/fs/unionfs/rename.c
new file mode 100644
index 0000000..ce85b84
--- /dev/null
+++ b/fs/unionfs/rename.c
@@ -0,0 +1,522 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/*
+ * This is a helper function for rename, used when rename ends up with hosed
+ * over dentries and we need to revert.
+ */
+static int unionfs_refresh_lower_dentry(struct dentry *dentry,
+                                       struct dentry *parent, int bindex)
+{
+       struct dentry *lower_dentry;
+       struct dentry *lower_parent;
+       int err = 0;
+       struct nameidata lower_nd;
+
+       verify_locked(dentry);
+
+       lower_parent = unionfs_lower_dentry_idx(parent, bindex);
+
+       BUG_ON(!S_ISDIR(lower_parent->d_inode->i_mode));
+
+       err = init_lower_nd(&lower_nd, LOOKUP_OPEN);
+       if (unlikely(err < 0))
+               goto out;
+       lower_dentry = lookup_one_len_nd(dentry->d_name.name, lower_parent,
+                                        dentry->d_name.len, &lower_nd);
+       release_lower_nd(&lower_nd, err);
+       if (IS_ERR(lower_dentry)) {
+               err = PTR_ERR(lower_dentry);
+               goto out;
+       }
+
+       dput(unionfs_lower_dentry_idx(dentry, bindex));
+       iput(unionfs_lower_inode_idx(dentry->d_inode, bindex));
+       unionfs_set_lower_inode_idx(dentry->d_inode, bindex, NULL);
+
+       if (!lower_dentry->d_inode) {
+               dput(lower_dentry);
+               unionfs_set_lower_dentry_idx(dentry, bindex, NULL);
+       } else {
+               unionfs_set_lower_dentry_idx(dentry, bindex, lower_dentry);
+               unionfs_set_lower_inode_idx(dentry->d_inode, bindex,
+                                           igrab(lower_dentry->d_inode));
+       }
+
+out:
+       return err;
+}
+
+static int __unionfs_rename(struct inode *old_dir, struct dentry *old_dentry,
+                           struct dentry *old_parent,
+                           struct inode *new_dir, struct dentry *new_dentry,
+                           struct dentry *new_parent,
+                           int bindex)
+{
+       int err = 0;
+       struct dentry *lower_old_dentry;
+       struct dentry *lower_new_dentry;
+       struct dentry *lower_old_dir_dentry;
+       struct dentry *lower_new_dir_dentry;
+       struct dentry *trap;
+
+       lower_new_dentry = unionfs_lower_dentry_idx(new_dentry, bindex);
+       lower_old_dentry = unionfs_lower_dentry_idx(old_dentry, bindex);
+
+       if (!lower_new_dentry) {
+               lower_new_dentry =
+                       create_parents(new_parent->d_inode,
+                                      new_dentry, new_dentry->d_name.name,
+                                      bindex);
+               if (IS_ERR(lower_new_dentry)) {
+                       err = PTR_ERR(lower_new_dentry);
+                       if (IS_COPYUP_ERR(err))
+                               goto out;
+                       printk(KERN_ERR "unionfs: error creating directory "
+                              "tree for rename, bindex=%d err=%d\n",
+                              bindex, err);
+                       goto out;
+               }
+       }
+
+       /* check for and remove whiteout, if any */
+       err = check_unlink_whiteout(new_dentry, lower_new_dentry, bindex);
+       if (err > 0) /* ignore if whiteout found and successfully removed */
+               err = 0;
+       if (err)
+               goto out;
+
+       /* check of old_dentry branch is writable */
+       err = is_robranch_super(old_dentry->d_sb, bindex);
+       if (err)
+               goto out;
+
+       dget(lower_old_dentry);
+       dget(lower_new_dentry);
+       lower_old_dir_dentry = dget_parent(lower_old_dentry);
+       lower_new_dir_dentry = dget_parent(lower_new_dentry);
+
+       trap = lock_rename(lower_old_dir_dentry, lower_new_dir_dentry);
+       /* source should not be ancenstor of target */
+       if (trap == lower_old_dentry) {
+               err = -EINVAL;
+               goto out_err_unlock;
+       }
+       /* target should not be ancenstor of source */
+       if (trap == lower_new_dentry) {
+               err = -ENOTEMPTY;
+               goto out_err_unlock;
+       }
+       err = vfs_rename(lower_old_dir_dentry->d_inode, lower_old_dentry,
+                        lower_new_dir_dentry->d_inode, lower_new_dentry);
+out_err_unlock:
+       if (!err) {
+               /* update parent dir times */
+               fsstack_copy_attr_times(old_dir, lower_old_dir_dentry->d_inode);
+               fsstack_copy_attr_times(new_dir, lower_new_dir_dentry->d_inode);
+       }
+       unlock_rename(lower_old_dir_dentry, lower_new_dir_dentry);
+
+       dput(lower_old_dir_dentry);
+       dput(lower_new_dir_dentry);
+       dput(lower_old_dentry);
+       dput(lower_new_dentry);
+
+out:
+       if (!err) {
+               /* Fixup the new_dentry. */
+               if (bindex < dbstart(new_dentry))
+                       dbstart(new_dentry) = bindex;
+               else if (bindex > dbend(new_dentry))
+                       dbend(new_dentry) = bindex;
+       }
+
+       return err;
+}
+
+/*
+ * Main rename code.  This is sufficiently complex, that it's documented in
+ * Documentation/filesystems/unionfs/rename.txt.  This routine calls
+ * __unionfs_rename() above to perform some of the work.
+ */
+static int do_unionfs_rename(struct inode *old_dir,
+                            struct dentry *old_dentry,
+                            struct dentry *old_parent,
+                            struct inode *new_dir,
+                            struct dentry *new_dentry,
+                            struct dentry *new_parent)
+{
+       int err = 0;
+       int bindex;
+       int old_bstart, old_bend;
+       int new_bstart, new_bend;
+       int do_copyup = -1;
+       int local_err = 0;
+       int eio = 0;
+       int revert = 0;
+
+       old_bstart = dbstart(old_dentry);
+       old_bend = dbend(old_dentry);
+
+       new_bstart = dbstart(new_dentry);
+       new_bend = dbend(new_dentry);
+
+       /* Rename source to destination. */
+       err = __unionfs_rename(old_dir, old_dentry, old_parent,
+                              new_dir, new_dentry, new_parent,
+                              old_bstart);
+       if (err) {
+               if (!IS_COPYUP_ERR(err))
+                       goto out;
+               do_copyup = old_bstart - 1;
+       } else {
+               revert = 1;
+       }
+
+       /*
+        * Unlink all instances of destination that exist to the left of
+        * bstart of source. On error, revert back, goto out.
+        */
+       for (bindex = old_bstart - 1; bindex >= new_bstart; bindex--) {
+               struct dentry *unlink_dentry;
+               struct dentry *unlink_dir_dentry;
+
+               BUG_ON(bindex < 0);
+               unlink_dentry = unionfs_lower_dentry_idx(new_dentry, bindex);
+               if (!unlink_dentry)
+                       continue;
+
+               unlink_dir_dentry = lock_parent(unlink_dentry);
+               err = is_robranch_super(old_dir->i_sb, bindex);
+               if (!err)
+                       err = vfs_unlink(unlink_dir_dentry->d_inode,
+                                        unlink_dentry);
+
+               fsstack_copy_attr_times(new_parent->d_inode,
+                                       unlink_dir_dentry->d_inode);
+               /* propagate number of hard-links */
+               set_nlink(new_parent->d_inode,
+                         unionfs_get_nlinks(new_parent->d_inode));
+
+               unlock_dir(unlink_dir_dentry);
+               if (!err) {
+                       if (bindex != new_bstart) {
+                               dput(unlink_dentry);
+                               unionfs_set_lower_dentry_idx(new_dentry,
+                                                            bindex, NULL);
+                       }
+               } else if (IS_COPYUP_ERR(err)) {
+                       do_copyup = bindex - 1;
+               } else if (revert) {
+                       goto revert;
+               }
+       }
+
+       if (do_copyup != -1) {
+               for (bindex = do_copyup; bindex >= 0; bindex--) {
+                       /*
+                        * copyup the file into some left directory, so that
+                        * you can rename it
+                        */
+                       err = copyup_dentry(old_parent->d_inode,
+                                           old_dentry, old_bstart, bindex,
+                                           old_dentry->d_name.name,
+                                           old_dentry->d_name.len, NULL,
+                                           i_size_read(old_dentry->d_inode));
+                       /* if copyup failed, try next branch to the left */
+                       if (err)
+                               continue;
+                       /*
+                        * create whiteout before calling __unionfs_rename
+                        * because the latter will change the old_dentry's
+                        * lower name and parent dir, resulting in the
+                        * whiteout getting created in the wrong dir.
+                        */
+                       err = create_whiteout(old_dentry, bindex);
+                       if (err) {
+                               printk(KERN_ERR "unionfs: can't create a "
+                                      "whiteout for %s in rename (err=%d)\n",
+                                      old_dentry->d_name.name, err);
+                               continue;
+                       }
+                       err = __unionfs_rename(old_dir, old_dentry, old_parent,
+                                              new_dir, new_dentry, new_parent,
+                                              bindex);
+                       break;
+               }
+       }
+
+       /* make it opaque */
+       if (S_ISDIR(old_dentry->d_inode->i_mode)) {
+               err = make_dir_opaque(old_dentry, dbstart(old_dentry));
+               if (err)
+                       goto revert;
+       }
+
+       /*
+        * Create whiteout for source, only if:
+        * (1) There is more than one underlying instance of source.
+        * (We did a copy_up is taken care of above).
+        */
+       if ((old_bstart != old_bend) && (do_copyup == -1)) {
+               err = create_whiteout(old_dentry, old_bstart);
+               if (err) {
+                       /* can't fix anything now, so we exit with -EIO */
+                       printk(KERN_ERR "unionfs: can't create a whiteout for "
+                              "%s in rename!\n", old_dentry->d_name.name);
+                       err = -EIO;
+               }
+       }
+
+out:
+       return err;
+
+revert:
+       /* Do revert here. */
+       local_err = unionfs_refresh_lower_dentry(new_dentry, new_parent,
+                                                old_bstart);
+       if (local_err) {
+               printk(KERN_ERR "unionfs: revert failed in rename: "
+                      "the new refresh failed\n");
+               eio = -EIO;
+       }
+
+       local_err = unionfs_refresh_lower_dentry(old_dentry, old_parent,
+                                                old_bstart);
+       if (local_err) {
+               printk(KERN_ERR "unionfs: revert failed in rename: "
+                      "the old refresh failed\n");
+               eio = -EIO;
+               goto revert_out;
+       }
+
+       if (!unionfs_lower_dentry_idx(new_dentry, bindex) ||
+           !unionfs_lower_dentry_idx(new_dentry, bindex)->d_inode) {
+               printk(KERN_ERR "unionfs: revert failed in rename: "
+                      "the object disappeared from under us!\n");
+               eio = -EIO;
+               goto revert_out;
+       }
+
+       if (unionfs_lower_dentry_idx(old_dentry, bindex) &&
+           unionfs_lower_dentry_idx(old_dentry, bindex)->d_inode) {
+               printk(KERN_ERR "unionfs: revert failed in rename: "
+                      "the object was created underneath us!\n");
+               eio = -EIO;
+               goto revert_out;
+       }
+
+       local_err = __unionfs_rename(new_dir, new_dentry, new_parent,
+                                    old_dir, old_dentry, old_parent,
+                                    old_bstart);
+
+       /* If we can't fix it, then we cop-out with -EIO. */
+       if (local_err) {
+               printk(KERN_ERR "unionfs: revert failed in rename!\n");
+               eio = -EIO;
+       }
+
+       local_err = unionfs_refresh_lower_dentry(new_dentry, new_parent,
+                                                bindex);
+       if (local_err)
+               eio = -EIO;
+       local_err = unionfs_refresh_lower_dentry(old_dentry, old_parent,
+                                                bindex);
+       if (local_err)
+               eio = -EIO;
+
+revert_out:
+       if (eio)
+               err = eio;
+       return err;
+}
+
+/*
+ * We can't copyup a directory, because it may involve huge numbers of
+ * children, etc.  Doing that in the kernel would be bad, so instead we
+ * return EXDEV to the user-space utility that caused this, and let the
+ * user-space recurse and ask us to copy up each file separately.
+ */
+static int may_rename_dir(struct dentry *dentry, struct dentry *parent)
+{
+       int err, bstart;
+
+       err = check_empty(dentry, parent, NULL);
+       if (err == -ENOTEMPTY) {
+               if (is_robranch(dentry))
+                       return -EXDEV;
+       } else if (err) {
+               return err;
+       }
+
+       bstart = dbstart(dentry);
+       if (dbend(dentry) == bstart || dbopaque(dentry) == bstart)
+               return 0;
+
+       dbstart(dentry) = bstart + 1;
+       err = check_empty(dentry, parent, NULL);
+       dbstart(dentry) = bstart;
+       if (err == -ENOTEMPTY)
+               err = -EXDEV;
+       return err;
+}
+
+/*
+ * The locking rules in unionfs_rename are complex.  We could use a simpler
+ * superblock-level name-space lock for renames and copy-ups.
+ */
+int unionfs_rename(struct inode *old_dir, struct dentry *old_dentry,
+                  struct inode *new_dir, struct dentry *new_dentry)
+{
+       int err = 0;
+       struct dentry *wh_dentry;
+       struct dentry *old_parent, *new_parent;
+       int valid = true;
+
+       unionfs_read_lock(old_dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       old_parent = dget_parent(old_dentry);
+       new_parent = dget_parent(new_dentry);
+       /* un/lock parent dentries only if they differ from old/new_dentry */
+       if (old_parent != old_dentry &&
+           old_parent != new_dentry)
+               unionfs_lock_dentry(old_parent, UNIONFS_DMUTEX_REVAL_PARENT);
+       if (new_parent != old_dentry &&
+           new_parent != new_dentry &&
+           new_parent != old_parent)
+               unionfs_lock_dentry(new_parent, UNIONFS_DMUTEX_REVAL_CHILD);
+       unionfs_double_lock_dentry(old_dentry, new_dentry);
+
+       valid = __unionfs_d_revalidate(old_dentry, old_parent, false);
+       if (!valid) {
+               err = -ESTALE;
+               goto out;
+       }
+       if (!d_deleted(new_dentry) && new_dentry->d_inode) {
+               valid = __unionfs_d_revalidate(new_dentry, new_parent, false);
+               if (!valid) {
+                       err = -ESTALE;
+                       goto out;
+               }
+       }
+
+       if (!S_ISDIR(old_dentry->d_inode->i_mode))
+               err = unionfs_partial_lookup(old_dentry, old_parent);
+       else
+               err = may_rename_dir(old_dentry, old_parent);
+
+       if (err)
+               goto out;
+
+       err = unionfs_partial_lookup(new_dentry, new_parent);
+       if (err)
+               goto out;
+
+       /*
+        * if new_dentry is already lower because of whiteout,
+        * simply override it even if the whited-out dir is not empty.
+        */
+       wh_dentry = find_first_whiteout(new_dentry);
+       if (!IS_ERR(wh_dentry)) {
+               dput(wh_dentry);
+       } else if (new_dentry->d_inode) {
+               if (S_ISDIR(old_dentry->d_inode->i_mode) !=
+                   S_ISDIR(new_dentry->d_inode->i_mode)) {
+                       err = S_ISDIR(old_dentry->d_inode->i_mode) ?
+                               -ENOTDIR : -EISDIR;
+                       goto out;
+               }
+
+               if (S_ISDIR(new_dentry->d_inode->i_mode)) {
+                       struct unionfs_dir_state *namelist = NULL;
+                       /* check if this unionfs directory is empty or not */
+                       err = check_empty(new_dentry, new_parent, &namelist);
+                       if (err)
+                               goto out;
+
+                       if (!is_robranch(new_dentry))
+                               err = delete_whiteouts(new_dentry,
+                                                      dbstart(new_dentry),
+                                                      namelist);
+
+                       free_rdstate(namelist);
+
+                       if (err)
+                               goto out;
+               }
+       }
+
+       err = do_unionfs_rename(old_dir, old_dentry, old_parent,
+                               new_dir, new_dentry, new_parent);
+       if (err)
+               goto out;
+
+       /*
+        * force re-lookup since the dir on ro branch is not renamed, and
+        * lower dentries still indicate the un-renamed ones.
+        */
+       if (S_ISDIR(old_dentry->d_inode->i_mode))
+               atomic_dec(&UNIONFS_D(old_dentry)->generation);
+       else
+               unionfs_postcopyup_release(old_dentry);
+       if (new_dentry->d_inode && !S_ISDIR(new_dentry->d_inode->i_mode)) {
+               unionfs_postcopyup_release(new_dentry);
+               unionfs_postcopyup_setmnt(new_dentry);
+               if (!unionfs_lower_inode(new_dentry->d_inode)) {
+                       /*
+                        * If we get here, it means that no copyup was
+                        * needed, and that a file by the old name already
+                        * existing on the destination branch; that file got
+                        * renamed earlier in this function, so all we need
+                        * to do here is set the lower inode.
+                        */
+                       struct inode *inode;
+                       inode = unionfs_lower_inode(old_dentry->d_inode);
+                       igrab(inode);
+                       unionfs_set_lower_inode_idx(new_dentry->d_inode,
+                                                   dbstart(new_dentry),
+                                                   inode);
+               }
+       }
+       /* if all of this renaming succeeded, update our times */
+       unionfs_copy_attr_times(old_dentry->d_inode);
+       unionfs_copy_attr_times(new_dentry->d_inode);
+       unionfs_check_inode(old_dir);
+       unionfs_check_inode(new_dir);
+       unionfs_check_dentry(old_dentry);
+       unionfs_check_dentry(new_dentry);
+
+out:
+       if (err)                /* clear the new_dentry stuff created */
+               d_drop(new_dentry);
+
+       unionfs_double_unlock_dentry(old_dentry, new_dentry);
+       if (new_parent != old_dentry &&
+           new_parent != new_dentry &&
+           new_parent != old_parent)
+               unionfs_unlock_dentry(new_parent);
+       if (old_parent != old_dentry &&
+           old_parent != new_dentry)
+               unionfs_unlock_dentry(old_parent);
+       dput(new_parent);
+       dput(old_parent);
+       unionfs_read_unlock(old_dentry->d_sb);
+
+       return err;
+}
diff --git a/fs/unionfs/sioq.c b/fs/unionfs/sioq.c
new file mode 100644
index 0000000..b923742
--- /dev/null
+++ b/fs/unionfs/sioq.c
@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2006-2011 Erez Zadok
+ * Copyright (c) 2006      Charles P. Wright
+ * Copyright (c) 2006-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2006      Junjiro Okajima
+ * Copyright (c) 2006      David P. Quigley
+ * Copyright (c) 2006-2011 Stony Brook University
+ * Copyright (c) 2006-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/*
+ * Super-user IO work Queue - sometimes we need to perform actions which
+ * would fail due to the unix permissions on the parent directory (e.g.,
+ * rmdir a directory which appears empty, but in reality contains
+ * whiteouts).
+ */
+
+static struct workqueue_struct *superio_workqueue;
+
+int __init init_sioq(void)
+{
+       int err;
+
+       superio_workqueue = create_workqueue("unionfs_siod");
+       if (!IS_ERR(superio_workqueue))
+               return 0;
+
+       err = PTR_ERR(superio_workqueue);
+       printk(KERN_ERR "unionfs: create_workqueue failed %d\n", err);
+       superio_workqueue = NULL;
+       return err;
+}
+
+void stop_sioq(void)
+{
+       if (superio_workqueue)
+               destroy_workqueue(superio_workqueue);
+}
+
+void run_sioq(work_func_t func, struct sioq_args *args)
+{
+       INIT_WORK(&args->work, func);
+
+       init_completion(&args->comp);
+       while (!queue_work(superio_workqueue, &args->work)) {
+               /* TODO: do accounting if needed */
+               schedule();
+       }
+       wait_for_completion(&args->comp);
+}
+
+void __unionfs_create(struct work_struct *work)
+{
+       struct sioq_args *args = container_of(work, struct sioq_args, work);
+       struct create_args *c = &args->create;
+
+       args->err = vfs_create(c->parent, c->dentry, c->mode, c->nd);
+       complete(&args->comp);
+}
+
+void __unionfs_mkdir(struct work_struct *work)
+{
+       struct sioq_args *args = container_of(work, struct sioq_args, work);
+       struct mkdir_args *m = &args->mkdir;
+
+       args->err = vfs_mkdir(m->parent, m->dentry, m->mode);
+       complete(&args->comp);
+}
+
+void __unionfs_mknod(struct work_struct *work)
+{
+       struct sioq_args *args = container_of(work, struct sioq_args, work);
+       struct mknod_args *m = &args->mknod;
+
+       args->err = vfs_mknod(m->parent, m->dentry, m->mode, m->dev);
+       complete(&args->comp);
+}
+
+void __unionfs_symlink(struct work_struct *work)
+{
+       struct sioq_args *args = container_of(work, struct sioq_args, work);
+       struct symlink_args *s = &args->symlink;
+
+       args->err = vfs_symlink(s->parent, s->dentry, s->symbuf);
+       complete(&args->comp);
+}
+
+void __unionfs_unlink(struct work_struct *work)
+{
+       struct sioq_args *args = container_of(work, struct sioq_args, work);
+       struct unlink_args *u = &args->unlink;
+
+       args->err = vfs_unlink(u->parent, u->dentry);
+       complete(&args->comp);
+}
diff --git a/fs/unionfs/sioq.h b/fs/unionfs/sioq.h
new file mode 100644
index 0000000..c2dfb94
--- /dev/null
+++ b/fs/unionfs/sioq.h
@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2006-2011 Erez Zadok
+ * Copyright (c) 2006      Charles P. Wright
+ * Copyright (c) 2006-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2006      Junjiro Okajima
+ * Copyright (c) 2006      David P. Quigley
+ * Copyright (c) 2006-2011 Stony Brook University
+ * Copyright (c) 2006-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _SIOQ_H
+#define _SIOQ_H
+
+struct deletewh_args {
+       struct unionfs_dir_state *namelist;
+       struct dentry *dentry;
+       int bindex;
+};
+
+struct is_opaque_args {
+       struct dentry *dentry;
+};
+
+struct create_args {
+       struct inode *parent;
+       struct dentry *dentry;
+       umode_t mode;
+       struct nameidata *nd;
+};
+
+struct mkdir_args {
+       struct inode *parent;
+       struct dentry *dentry;
+       umode_t mode;
+};
+
+struct mknod_args {
+       struct inode *parent;
+       struct dentry *dentry;
+       umode_t mode;
+       dev_t dev;
+};
+
+struct symlink_args {
+       struct inode *parent;
+       struct dentry *dentry;
+       char *symbuf;
+};
+
+struct unlink_args {
+       struct inode *parent;
+       struct dentry *dentry;
+};
+
+
+struct sioq_args {
+       struct completion comp;
+       struct work_struct work;
+       int err;
+       void *ret;
+
+       union {
+               struct deletewh_args deletewh;
+               struct is_opaque_args is_opaque;
+               struct create_args create;
+               struct mkdir_args mkdir;
+               struct mknod_args mknod;
+               struct symlink_args symlink;
+               struct unlink_args unlink;
+       };
+};
+
+/* Extern definitions for SIOQ functions */
+extern int __init init_sioq(void);
+extern void stop_sioq(void);
+extern void run_sioq(work_func_t func, struct sioq_args *args);
+
+/* Extern definitions for our privilege escalation helpers */
+extern void __unionfs_create(struct work_struct *work);
+extern void __unionfs_mkdir(struct work_struct *work);
+extern void __unionfs_mknod(struct work_struct *work);
+extern void __unionfs_symlink(struct work_struct *work);
+extern void __unionfs_unlink(struct work_struct *work);
+extern void __delete_whiteouts(struct work_struct *work);
+extern void __is_opaque_dir(struct work_struct *work);
+
+#endif /* not _SIOQ_H */
diff --git a/fs/unionfs/subr.c b/fs/unionfs/subr.c
new file mode 100644
index 0000000..e7fc5a5
--- /dev/null
+++ b/fs/unionfs/subr.c
@@ -0,0 +1,95 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/*
+ * returns the right n_link value based on the inode type
+ */
+int unionfs_get_nlinks(const struct inode *inode)
+{
+       /* don't bother to do all the work since we're unlinked */
+       if (inode->i_nlink == 0)
+               return 0;
+
+       if (!S_ISDIR(inode->i_mode))
+               return unionfs_lower_inode(inode)->i_nlink;
+
+       /*
+        * For directories, we return 1. The only place that could cares
+        * about links is readdir, and there's d_type there so even that
+        * doesn't matter.
+        */
+       return 1;
+}
+
+/* copy a/m/ctime from the lower branch with the newest times */
+void unionfs_copy_attr_times(struct inode *upper)
+{
+       int bindex;
+       struct inode *lower;
+
+       if (!upper)
+               return;
+       if (ibstart(upper) < 0) {
+#ifdef CONFIG_UNION_FS_DEBUG
+               WARN_ON(ibstart(upper) < 0);
+#endif /* CONFIG_UNION_FS_DEBUG */
+               return;
+       }
+       for (bindex = ibstart(upper); bindex <= ibend(upper); bindex++) {
+               lower = unionfs_lower_inode_idx(upper, bindex);
+               if (!lower)
+                       continue; /* not all lower dir objects may exist */
+               if (unlikely(timespec_compare(&upper->i_mtime,
+                                             &lower->i_mtime) < 0))
+                       upper->i_mtime = lower->i_mtime;
+               if (unlikely(timespec_compare(&upper->i_ctime,
+                                             &lower->i_ctime) < 0))
+                       upper->i_ctime = lower->i_ctime;
+               if (unlikely(timespec_compare(&upper->i_atime,
+                                             &lower->i_atime) < 0))
+                       upper->i_atime = lower->i_atime;
+       }
+}
+
+/*
+ * A unionfs/fanout version of fsstack_copy_attr_all.  Uses a
+ * unionfs_get_nlinks to properly calcluate the number of links to a file.
+ * Also, copies the max() of all a/m/ctimes for all lower inodes (which is
+ * important if the lower inode is a directory type)
+ */
+void unionfs_copy_attr_all(struct inode *dest,
+                          const struct inode *src)
+{
+       dest->i_mode = src->i_mode;
+       dest->i_uid = src->i_uid;
+       dest->i_gid = src->i_gid;
+       dest->i_rdev = src->i_rdev;
+
+       unionfs_copy_attr_times(dest);
+
+       dest->i_blkbits = src->i_blkbits;
+       dest->i_flags = src->i_flags;
+
+       /*
+        * Update the nlinks AFTER updating the above fields, because the
+        * get_links callback may depend on them.
+        */
+       set_nlink(dest, unionfs_get_nlinks(dest));
+}
diff --git a/fs/unionfs/super.c b/fs/unionfs/super.c
new file mode 100644
index 0000000..b99f14d
--- /dev/null
+++ b/fs/unionfs/super.c
@@ -0,0 +1,1030 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/*
+ * The inode cache is used with alloc_inode for both our inode info and the
+ * vfs inode.
+ */
+static struct kmem_cache *unionfs_inode_cachep;
+
+struct inode *unionfs_iget(struct super_block *sb, unsigned long ino)
+{
+       int size;
+       struct unionfs_inode_info *info;
+       struct inode *inode;
+
+       inode = iget_locked(sb, ino);
+       if (!inode)
+               return ERR_PTR(-ENOMEM);
+       if (!(inode->i_state & I_NEW))
+               return inode;
+
+       info = UNIONFS_I(inode);
+       memset(info, 0, offsetof(struct unionfs_inode_info, vfs_inode));
+       info->bstart = -1;
+       info->bend = -1;
+       atomic_set(&info->generation,
+                  atomic_read(&UNIONFS_SB(inode->i_sb)->generation));
+       spin_lock_init(&info->rdlock);
+       info->rdcount = 1;
+       info->hashsize = -1;
+       INIT_LIST_HEAD(&info->readdircache);
+
+       size = sbmax(inode->i_sb) * sizeof(struct inode *);
+       info->lower_inodes = kzalloc(size, GFP_KERNEL);
+       if (unlikely(!info->lower_inodes)) {
+               printk(KERN_CRIT "unionfs: no kernel memory when allocating "
+                      "lower-pointer array!\n");
+               iget_failed(inode);
+               return ERR_PTR(-ENOMEM);
+       }
+
+       inode->i_version++;
+       inode->i_op = &unionfs_main_iops;
+       inode->i_fop = &unionfs_main_fops;
+
+       inode->i_mapping->a_ops = &unionfs_aops;
+
+       /*
+        * reset times so unionfs_copy_attr_all can keep out time invariants
+        * right (upper inode time being the max of all lower ones).
+        */
+       inode->i_atime.tv_sec = inode->i_atime.tv_nsec = 0;
+       inode->i_mtime.tv_sec = inode->i_mtime.tv_nsec = 0;
+       inode->i_ctime.tv_sec = inode->i_ctime.tv_nsec = 0;
+       unlock_new_inode(inode);
+       return inode;
+}
+
+/*
+ * final actions when unmounting a file system
+ *
+ * No need to lock rwsem.
+ */
+static void unionfs_put_super(struct super_block *sb)
+{
+       int bindex, bstart, bend;
+       struct unionfs_sb_info *spd;
+       int leaks = 0;
+
+       spd = UNIONFS_SB(sb);
+       if (!spd)
+               return;
+
+       bstart = sbstart(sb);
+       bend = sbend(sb);
+
+       /* Make sure we have no leaks of branchget/branchput. */
+       for (bindex = bstart; bindex <= bend; bindex++)
+               if (unlikely(branch_count(sb, bindex) != 0)) {
+                       printk(KERN_CRIT
+                              "unionfs: branch %d has %d references left!\n",
+                              bindex, branch_count(sb, bindex));
+                       leaks = 1;
+               }
+       WARN_ON(leaks != 0);
+
+       /* decrement lower super references */
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               struct super_block *s;
+               s = unionfs_lower_super_idx(sb, bindex);
+               unionfs_set_lower_super_idx(sb, bindex, NULL);
+               atomic_dec(&s->s_active);
+       }
+
+       kfree(spd->dev_name);
+       kfree(spd->data);
+       kfree(spd);
+       sb->s_fs_info = NULL;
+}
+
+/*
+ * Since people use this to answer the "How big of a file can I write?"
+ * question, we report the size of the highest priority branch as the size of
+ * the union.
+ */
+static int unionfs_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+       int err = 0;
+       struct super_block *sb;
+       struct dentry *lower_dentry;
+       struct dentry *parent;
+       struct path lower_path;
+       bool valid;
+
+       sb = dentry->d_sb;
+
+       unionfs_read_lock(sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       valid = __unionfs_d_revalidate(dentry, parent, false);
+       if (unlikely(!valid)) {
+               err = -ESTALE;
+               goto out;
+       }
+       unionfs_check_dentry(dentry);
+
+       lower_dentry = unionfs_lower_dentry(sb->s_root);
+       lower_path.dentry = lower_dentry;
+       lower_path.mnt = unionfs_mntget(sb->s_root, 0);
+       err = vfs_statfs(&lower_path, buf);
+       mntput(lower_path.mnt);
+
+       /* set return buf to our f/s to avoid confusing user-level utils */
+       buf->f_type = UNIONFS_SUPER_MAGIC;
+       /*
+        * Our maximum file name can is shorter by a few bytes because every
+        * file name could potentially be whited-out.
+        *
+        * XXX: this restriction goes away with ODF.
+        */
+       unionfs_set_max_namelen(&buf->f_namelen);
+
+       /*
+        * reset two fields to avoid confusing user-land.
+        * XXX: is this still necessary?
+        */
+       memset(&buf->f_fsid, 0, sizeof(__kernel_fsid_t));
+       memset(&buf->f_spare, 0, sizeof(buf->f_spare));
+
+out:
+       unionfs_check_dentry(dentry);
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(sb);
+       return err;
+}
+
+/* handle mode changing during remount */
+static noinline_for_stack int do_remount_mode_option(
+                                       char *optarg,
+                                       int cur_branches,
+                                       struct unionfs_data *new_data,
+                                       struct path *new_lower_paths)
+{
+       int err = -EINVAL;
+       int perms, idx;
+       char *modename = strchr(optarg, '=');
+       struct path path;
+
+       /* by now, optarg contains the branch name */
+       if (!*optarg) {
+               printk(KERN_ERR
+                      "unionfs: no branch specified for mode change\n");
+               goto out;
+       }
+       if (!modename) {
+               printk(KERN_ERR "unionfs: branch \"%s\" requires a mode\n",
+                      optarg);
+               goto out;
+       }
+       *modename++ = '\0';
+       err = parse_branch_mode(modename, &perms);
+       if (err) {
+               printk(KERN_ERR "unionfs: invalid mode \"%s\" for \"%s\"\n",
+                      modename, optarg);
+               goto out;
+       }
+
+       /*
+        * Find matching branch index.  For now, this assumes that nothing
+        * has been mounted on top of this Unionfs stack.  Once we have /odf
+        * and cache-coherency resolved, we'll address the branch-path
+        * uniqueness.
+        */
+       err = kern_path(optarg, LOOKUP_FOLLOW, &path);
+       if (err) {
+               printk(KERN_ERR "unionfs: error accessing "
+                      "lower directory \"%s\" (error %d)\n",
+                      optarg, err);
+               goto out;
+       }
+       for (idx = 0; idx < cur_branches; idx++)
+               if (path.mnt == new_lower_paths[idx].mnt &&
+                   path.dentry == new_lower_paths[idx].dentry)
+                       break;
+       path_put(&path);        /* no longer needed */
+       if (idx == cur_branches) {
+               err = -ENOENT;  /* err may have been reset above */
+               printk(KERN_ERR "unionfs: branch \"%s\" "
+                      "not found\n", optarg);
+               goto out;
+       }
+       /* check/change mode for existing branch */
+       /* we don't warn if perms==branchperms */
+       new_data[idx].branchperms = perms;
+       err = 0;
+out:
+       return err;
+}
+
+/* handle branch deletion during remount */
+static noinline_for_stack int do_remount_del_option(
+                                       char *optarg, int cur_branches,
+                                       struct unionfs_data *new_data,
+                                       struct path *new_lower_paths)
+{
+       int err = -EINVAL;
+       int idx;
+       struct path path;
+
+       /* optarg contains the branch name to delete */
+
+       /*
+        * Find matching branch index.  For now, this assumes that nothing
+        * has been mounted on top of this Unionfs stack.  Once we have /odf
+        * and cache-coherency resolved, we'll address the branch-path
+        * uniqueness.
+        */
+       err = kern_path(optarg, LOOKUP_FOLLOW, &path);
+       if (err) {
+               printk(KERN_ERR "unionfs: error accessing "
+                      "lower directory \"%s\" (error %d)\n",
+                      optarg, err);
+               goto out;
+       }
+       for (idx = 0; idx < cur_branches; idx++)
+               if (path.mnt == new_lower_paths[idx].mnt &&
+                   path.dentry == new_lower_paths[idx].dentry)
+                       break;
+       path_put(&path);        /* no longer needed */
+       if (idx == cur_branches) {
+               printk(KERN_ERR "unionfs: branch \"%s\" "
+                      "not found\n", optarg);
+               err = -ENOENT;
+               goto out;
+       }
+       /* check if there are any open files on the branch to be deleted */
+       if (atomic_read(&new_data[idx].open_files) > 0) {
+               err = -EBUSY;
+               goto out;
+       }
+
+       /*
+        * Now we have to delete the branch.  First, release any handles it
+        * has.  Then, move the remaining array indexes past "idx" in
+        * new_data and new_lower_paths one to the left.  Finally, adjust
+        * cur_branches.
+        */
+       path_put(&new_lower_paths[idx]);
+
+       if (idx < cur_branches - 1) {
+               /* if idx==cur_branches-1, we delete last branch: easy */
+               memmove(&new_data[idx], &new_data[idx+1],
+                       (cur_branches - 1 - idx) *
+                       sizeof(struct unionfs_data));
+               memmove(&new_lower_paths[idx], &new_lower_paths[idx+1],
+                       (cur_branches - 1 - idx) * sizeof(struct path));
+       }
+
+       err = 0;
+out:
+       return err;
+}
+
+/* handle branch insertion during remount */
+static noinline_for_stack int do_remount_add_option(
+                                       char *optarg, int cur_branches,
+                                       struct unionfs_data *new_data,
+                                       struct path *new_lower_paths,
+                                       int *high_branch_id)
+{
+       int err = -EINVAL;
+       int perms;
+       int idx = 0;            /* default: insert at beginning */
+       char *new_branch , *modename = NULL;
+       struct path path;
+
+       /*
+        * optarg can be of several forms:
+        *
+        * /bar:/foo            insert /foo before /bar
+        * /bar:/foo=ro         insert /foo in ro mode before /bar
+        * /foo                 insert /foo in the beginning (prepend)
+        * :/foo                insert /foo at the end (append)
+        */
+       if (*optarg == ':') {   /* append? */
+               new_branch = optarg + 1; /* skip ':' */
+               idx = cur_branches;
+               goto found_insertion_point;
+       }
+       new_branch = strchr(optarg, ':');
+       if (!new_branch) {      /* prepend? */
+               new_branch = optarg;
+               goto found_insertion_point;
+       }
+       *new_branch++ = '\0';   /* holds path+mode of new branch */
+
+       /*
+        * Find matching branch index.  For now, this assumes that nothing
+        * has been mounted on top of this Unionfs stack.  Once we have /odf
+        * and cache-coherency resolved, we'll address the branch-path
+        * uniqueness.
+        */
+       err = kern_path(optarg, LOOKUP_FOLLOW, &path);
+       if (err) {
+               printk(KERN_ERR "unionfs: error accessing "
+                      "lower directory \"%s\" (error %d)\n",
+                      optarg, err);
+               goto out;
+       }
+       for (idx = 0; idx < cur_branches; idx++)
+               if (path.mnt == new_lower_paths[idx].mnt &&
+                   path.dentry == new_lower_paths[idx].dentry)
+                       break;
+       path_put(&path);        /* no longer needed */
+       if (idx == cur_branches) {
+               printk(KERN_ERR "unionfs: branch \"%s\" "
+                      "not found\n", optarg);
+               err = -ENOENT;
+               goto out;
+       }
+
+       /*
+        * At this point idx will hold the index where the new branch should
+        * be inserted before.
+        */
+found_insertion_point:
+       /* find the mode for the new branch */
+       if (new_branch)
+               modename = strchr(new_branch, '=');
+       if (modename)
+               *modename++ = '\0';
+       if (!new_branch || !*new_branch) {
+               printk(KERN_ERR "unionfs: null new branch\n");
+               err = -EINVAL;
+               goto out;
+       }
+       err = parse_branch_mode(modename, &perms);
+       if (err) {
+               printk(KERN_ERR "unionfs: invalid mode \"%s\" for "
+                      "branch \"%s\"\n", modename, new_branch);
+               goto out;
+       }
+       err = kern_path(new_branch, LOOKUP_FOLLOW, &path);
+       if (err) {
+               printk(KERN_ERR "unionfs: error accessing "
+                      "lower directory \"%s\" (error %d)\n",
+                      new_branch, err);
+               goto out;
+       }
+       /*
+        * It's probably safe to check_mode the new branch to insert.  Note:
+        * we don't allow inserting branches which are unionfs's by
+        * themselves (check_branch returns EINVAL in that case).  This is
+        * because this code base doesn't support stacking unionfs: the ODF
+        * code base supports that correctly.
+        */
+       err = check_branch(&path);
+       if (err) {
+               printk(KERN_ERR "unionfs: lower directory "
+                      "\"%s\" is not a valid branch\n", optarg);
+               path_put(&path);
+               goto out;
+       }
+
+       /*
+        * Now we have to insert the new branch.  But first, move the bits
+        * to make space for the new branch, if needed.  Finally, adjust
+        * cur_branches.
+        * We don't release nd here; it's kept until umount/remount.
+        */
+       if (idx < cur_branches) {
+               /* if idx==cur_branches, we append: easy */
+               memmove(&new_data[idx+1], &new_data[idx],
+                       (cur_branches - idx) * sizeof(struct unionfs_data));
+               memmove(&new_lower_paths[idx+1], &new_lower_paths[idx],
+                       (cur_branches - idx) * sizeof(struct path));
+       }
+       new_lower_paths[idx].dentry = path.dentry;
+       new_lower_paths[idx].mnt = path.mnt;
+
+       new_data[idx].sb = path.dentry->d_sb;
+       atomic_set(&new_data[idx].open_files, 0);
+       new_data[idx].branchperms = perms;
+       new_data[idx].branch_id = ++*high_branch_id; /* assign new branch ID */
+
+       err = 0;
+out:
+       return err;
+}
+
+
+/*
+ * Support branch management options on remount.
+ *
+ * See Documentation/filesystems/unionfs/ for details.
+ *
+ * @flags: numeric mount options
+ * @options: mount options string
+ *
+ * This function can rearrange a mounted union dynamically, adding and
+ * removing branches, including changing branch modes.  Clearly this has to
+ * be done safely and atomically.  Luckily, the VFS already calls this
+ * function with lock_super(sb) and lock_kernel() held, preventing
+ * concurrent mixing of new mounts, remounts, and unmounts.  Moreover,
+ * do_remount_sb(), our caller function, already called shrink_dcache_sb(sb)
+ * to purge dentries/inodes from our superblock, and also called
+ * fsync_super(sb) to purge any dirty pages.  So we're good.
+ *
+ * XXX: however, our remount code may also need to invalidate mapped pages
+ * so as to force them to be re-gotten from the (newly reconfigured) lower
+ * branches.  This has to wait for proper mmap and cache coherency support
+ * in the VFS.
+ *
+ */
+static int unionfs_remount_fs(struct super_block *sb, int *flags,
+                             char *options)
+{
+       int err = 0;
+       int i;
+       char *optionstmp, *tmp_to_free; /* kstrdup'ed of "options" */
+       char *optname;
+       int cur_branches = 0;   /* no. of current branches */
+       int new_branches = 0;   /* no. of branches actually left in the end */
+       int add_branches;       /* est. no. of branches to add */
+       int del_branches;       /* est. no. of branches to del */
+       int max_branches;       /* max possible no. of branches */
+       struct unionfs_data *new_data = NULL, *tmp_data = NULL;
+       struct path *new_lower_paths = NULL, *tmp_lower_paths = NULL;
+       struct inode **new_lower_inodes = NULL;
+       int new_high_branch_id; /* new high branch ID */
+       int size;               /* memory allocation size, temp var */
+       int old_ibstart, old_ibend;
+
+       unionfs_write_lock(sb);
+
+       /*
+        * The VFS will take care of "ro" and "rw" flags, and we can safely
+        * ignore MS_SILENT, but anything else left over is an error.  So we
+        * need to check if any other flags may have been passed (none are
+        * allowed/supported as of now).
+        */
+       if ((*flags & ~(MS_RDONLY | MS_SILENT)) != 0) {
+               printk(KERN_ERR
+                      "unionfs: remount flags 0x%x unsupported\n", *flags);
+               err = -EINVAL;
+               goto out_error;
+       }
+
+       /*
+        * If 'options' is NULL, it's probably because the user just changed
+        * the union to a "ro" or "rw" and the VFS took care of it.  So
+        * nothing to do and we're done.
+        */
+       if (!options || options[0] == '\0')
+               goto out_error;
+
+       /*
+        * Find out how many branches we will have in the end, counting
+        * "add" and "del" commands.  Copy the "options" string because
+        * strsep modifies the string and we need it later.
+        */
+       tmp_to_free = kstrdup(options, GFP_KERNEL);
+       optionstmp = tmp_to_free;
+       if (unlikely(!optionstmp)) {
+               err = -ENOMEM;
+               goto out_free;
+       }
+       cur_branches = sbmax(sb); /* current no. branches */
+       new_branches = sbmax(sb);
+       del_branches = 0;
+       add_branches = 0;
+       new_high_branch_id = sbhbid(sb); /* save current high_branch_id */
+       while ((optname = strsep(&optionstmp, ",")) != NULL) {
+               char *optarg;
+
+               if (!optname || !*optname)
+                       continue;
+
+               optarg = strchr(optname, '=');
+               if (optarg)
+                       *optarg++ = '\0';
+
+               if (!strcmp("add", optname))
+                       add_branches++;
+               else if (!strcmp("del", optname))
+                       del_branches++;
+       }
+       kfree(tmp_to_free);
+       /* after all changes, will we have at least one branch left? */
+       if ((new_branches + add_branches - del_branches) < 1) {
+               printk(KERN_ERR
+                      "unionfs: no branches left after remount\n");
+               err = -EINVAL;
+               goto out_free;
+       }
+
+       /*
+        * Since we haven't actually parsed all the add/del options, nor
+        * have we checked them for errors, we don't know for sure how many
+        * branches we will have after all changes have taken place.  In
+        * fact, the total number of branches left could be less than what
+        * we have now.  So we need to allocate space for a temporary
+        * placeholder that is at least as large as the maximum number of
+        * branches we *could* have, which is the current number plus all
+        * the additions.  Once we're done with these temp placeholders, we
+        * may have to re-allocate the final size, copy over from the temp,
+        * and then free the temps (done near the end of this function).
+        */
+       max_branches = cur_branches + add_branches;
+       /* allocate space for new pointers to lower dentry */
+       tmp_data = kcalloc(max_branches,
+                          sizeof(struct unionfs_data), GFP_KERNEL);
+       if (unlikely(!tmp_data)) {
+               err = -ENOMEM;
+               goto out_free;
+       }
+       /* allocate space for new pointers to lower paths */
+       tmp_lower_paths = kcalloc(max_branches,
+                                 sizeof(struct path), GFP_KERNEL);
+       if (unlikely(!tmp_lower_paths)) {
+               err = -ENOMEM;
+               goto out_free;
+       }
+       /* copy current info into new placeholders, incrementing refcnts */
+       memcpy(tmp_data, UNIONFS_SB(sb)->data,
+              cur_branches * sizeof(struct unionfs_data));
+       memcpy(tmp_lower_paths, UNIONFS_D(sb->s_root)->lower_paths,
+              cur_branches * sizeof(struct path));
+       for (i = 0; i < cur_branches; i++)
+               path_get(&tmp_lower_paths[i]); /* drop refs at end of fxn */
+
+       /*******************************************************************
+        * For each branch command, do kern_path on the requested branch,
+        * and apply the change to a temp branch list.  To handle errors, we
+        * already dup'ed the old arrays (above), and increased the refcnts
+        * on various f/s objects.  So now we can do all the kern_path'ss
+        * and branch-management commands on the new arrays.  If it fail mid
+        * way, we free the tmp arrays and *put all objects.  If we succeed,
+        * then we free old arrays and *put its objects, and then replace
+        * the arrays with the new tmp list (we may have to re-allocate the
+        * memory because the temp lists could have been larger than what we
+        * actually needed).
+        *******************************************************************/
+
+       while ((optname = strsep(&options, ",")) != NULL) {
+               char *optarg;
+
+               if (!optname || !*optname)
+                       continue;
+               /*
+                * At this stage optname holds a comma-delimited option, but
+                * without the commas.  Next, we need to break the string on
+                * the '=' symbol to separate CMD=ARG, where ARG itself can
+                * be KEY=VAL.  For example, in mode=/foo=rw, CMD is "mode",
+                * KEY is "/foo", and VAL is "rw".
+                */
+               optarg = strchr(optname, '=');
+               if (optarg)
+                       *optarg++ = '\0';
+               /* incgen remount option (instead of old ioctl) */
+               if (!strcmp("incgen", optname)) {
+                       err = 0;
+                       goto out_no_change;
+               }
+
+               /*
+                * All of our options take an argument now.  (Insert ones
+                * that don't above this check.)  So at this stage optname
+                * contains the CMD part and optarg contains the ARG part.
+                */
+               if (!optarg || !*optarg) {
+                       printk(KERN_ERR "unionfs: all remount options require "
+                              "an argument (%s)\n", optname);
+                       err = -EINVAL;
+                       goto out_release;
+               }
+
+               if (!strcmp("add", optname)) {
+                       err = do_remount_add_option(optarg, new_branches,
+                                                   tmp_data,
+                                                   tmp_lower_paths,
+                                                   &new_high_branch_id);
+                       if (err)
+                               goto out_release;
+                       new_branches++;
+                       if (new_branches > UNIONFS_MAX_BRANCHES) {
+                               printk(KERN_ERR "unionfs: command exceeds "
+                                      "%d branches\n", UNIONFS_MAX_BRANCHES);
+                               err = -E2BIG;
+                               goto out_release;
+                       }
+                       continue;
+               }
+               if (!strcmp("del", optname)) {
+                       err = do_remount_del_option(optarg, new_branches,
+                                                   tmp_data,
+                                                   tmp_lower_paths);
+                       if (err)
+                               goto out_release;
+                       new_branches--;
+                       continue;
+               }
+               if (!strcmp("mode", optname)) {
+                       err = do_remount_mode_option(optarg, new_branches,
+                                                    tmp_data,
+                                                    tmp_lower_paths);
+                       if (err)
+                               goto out_release;
+                       continue;
+               }
+
+               /*
+                * When you use "mount -o remount,ro", mount(8) will
+                * reportedly pass the original dirs= string from
+                * /proc/mounts.  So for now, we have to ignore dirs= and
+                * not consider it an error, unless we want to allow users
+                * to pass dirs= in remount.  Note that to allow the VFS to
+                * actually process the ro/rw remount options, we have to
+                * return 0 from this function.
+                */
+               if (!strcmp("dirs", optname)) {
+                       printk(KERN_WARNING
+                              "unionfs: remount ignoring option \"%s\"\n",
+                              optname);
+                       continue;
+               }
+
+               err = -EINVAL;
+               printk(KERN_ERR
+                      "unionfs: unrecognized option \"%s\"\n", optname);
+               goto out_release;
+       }
+
+out_no_change:
+
+       /******************************************************************
+        * WE'RE ALMOST DONE: check if leftmost branch might be read-only,
+        * see if we need to allocate a small-sized new vector, copy the
+        * vectors to their correct place, release the refcnt of the older
+        * ones, and return.  Also handle invalidating any pages that will
+        * have to be re-read.
+        *******************************************************************/
+
+       if (!(tmp_data[0].branchperms & MAY_WRITE)) {
+               printk(KERN_ERR "unionfs: leftmost branch cannot be read-only "
+                      "(use \"remount,ro\" to create a read-only union)\n");
+               err = -EINVAL;
+               goto out_release;
+       }
+
+       /* (re)allocate space for new pointers to lower dentry */
+       size = new_branches * sizeof(struct unionfs_data);
+       new_data = krealloc(tmp_data, size, GFP_KERNEL);
+       if (unlikely(!new_data)) {
+               err = -ENOMEM;
+               goto out_release;
+       }
+
+       /* allocate space for new pointers to lower paths */
+       size = new_branches * sizeof(struct path);
+       new_lower_paths = krealloc(tmp_lower_paths, size, GFP_KERNEL);
+       if (unlikely(!new_lower_paths)) {
+               err = -ENOMEM;
+               goto out_release;
+       }
+
+       /* allocate space for new pointers to lower inodes */
+       new_lower_inodes = kcalloc(new_branches,
+                                  sizeof(struct inode *), GFP_KERNEL);
+       if (unlikely(!new_lower_inodes)) {
+               err = -ENOMEM;
+               goto out_release;
+       }
+
+       /*
+        * OK, just before we actually put the new set of branches in place,
+        * we need to ensure that our own f/s has no dirty objects left.
+        * Luckily, do_remount_sb() already calls shrink_dcache_sb(sb) and
+        * fsync_super(sb), taking care of dentries, inodes, and dirty
+        * pages.  So all that's left is for us to invalidate any leftover
+        * (non-dirty) pages to ensure that they will be re-read from the
+        * new lower branches (and to support mmap).
+        */
+
+       /*
+        * Once we finish the remounting successfully, our superblock
+        * generation number will have increased.  This will be detected by
+        * our dentry-revalidation code upon subsequent f/s operations
+        * through unionfs.  The revalidation code will rebuild the union of
+        * lower inodes for a given unionfs inode and invalidate any pages
+        * of such "stale" inodes (by calling our purge_inode_data
+        * function).  This revalidation will happen lazily and
+        * incrementally, as users perform operations on cached inodes.  We
+        * would like to encourage this revalidation to happen sooner if
+        * possible, so we like to try to invalidate as many other pages in
+        * our superblock as we can.  We used to call drop_pagecache_sb() or
+        * a variant thereof, but either method was racy (drop_caches alone
+        * is known to be racy).  So now we let the revalidation happen on a
+        * per file basis in ->d_revalidate.
+        */
+
+       /* grab new lower super references; release old ones */
+       for (i = 0; i < new_branches; i++)
+               atomic_inc(&new_data[i].sb->s_active);
+       for (i = 0; i < sbmax(sb); i++)
+               atomic_dec(&UNIONFS_SB(sb)->data[i].sb->s_active);
+
+       /* copy new vectors into their correct place */
+       tmp_data = UNIONFS_SB(sb)->data;
+       UNIONFS_SB(sb)->data = new_data;
+       new_data = NULL;        /* so don't free good pointers below */
+       tmp_lower_paths = UNIONFS_D(sb->s_root)->lower_paths;
+       UNIONFS_D(sb->s_root)->lower_paths = new_lower_paths;
+       new_lower_paths = NULL; /* so don't free good pointers below */
+
+       /* update our unionfs_sb_info and root dentry index of last branch */
+       i = sbmax(sb);          /* save no. of branches to release at end */
+       sbend(sb) = new_branches - 1;
+       dbend(sb->s_root) = new_branches - 1;
+       old_ibstart = ibstart(sb->s_root->d_inode);
+       old_ibend = ibend(sb->s_root->d_inode);
+       ibend(sb->s_root->d_inode) = new_branches - 1;
+       UNIONFS_D(sb->s_root)->bcount = new_branches;
+       new_branches = i; /* no. of branches to release below */
+
+       /*
+        * Update lower inodes: 3 steps
+        * 1. grab ref on all new lower inodes
+        */
+       for (i = dbstart(sb->s_root); i <= dbend(sb->s_root); i++) {
+               struct dentry *lower_dentry =
+                       unionfs_lower_dentry_idx(sb->s_root, i);
+               igrab(lower_dentry->d_inode);
+               new_lower_inodes[i] = lower_dentry->d_inode;
+       }
+       /* 2. release reference on all older lower inodes */
+       iput_lowers(sb->s_root->d_inode, old_ibstart, old_ibend, true);
+       /* 3. update root dentry's inode to new lower_inodes array */
+       UNIONFS_I(sb->s_root->d_inode)->lower_inodes = new_lower_inodes;
+       new_lower_inodes = NULL;
+
+       /* maxbytes may have changed */
+       sb->s_maxbytes = unionfs_lower_super_idx(sb, 0)->s_maxbytes;
+       /* update high branch ID */
+       sbhbid(sb) = new_high_branch_id;
+
+       /* update our sb->generation for revalidating objects */
+       i = atomic_inc_return(&UNIONFS_SB(sb)->generation);
+       atomic_set(&UNIONFS_D(sb->s_root)->generation, i);
+       atomic_set(&UNIONFS_I(sb->s_root->d_inode)->generation, i);
+       if (!(*flags & MS_SILENT))
+               pr_info("unionfs: %s: new generation number %d\n",
+                       UNIONFS_SB(sb)->dev_name, i);
+       /* finally, update the root dentry's times */
+       unionfs_copy_attr_times(sb->s_root->d_inode);
+       err = 0;                /* reset to success */
+
+       /*
+        * The code above falls through to the next label, and releases the
+        * refcnts of the older ones (stored in tmp_*): if we fell through
+        * here, it means success.  However, if we jump directly to this
+        * label from any error above, then an error occurred after we
+        * grabbed various refcnts, and so we have to release the
+        * temporarily constructed structures.
+        */
+out_release:
+       /* no need to cleanup/release anything in tmp_data */
+       if (tmp_lower_paths)
+               for (i = 0; i < new_branches; i++)
+                       path_put(&tmp_lower_paths[i]);
+out_free:
+       kfree(tmp_lower_paths);
+       kfree(tmp_data);
+       kfree(new_lower_paths);
+       kfree(new_data);
+       kfree(new_lower_inodes);
+out_error:
+       unionfs_check_dentry(sb->s_root);
+       unionfs_write_unlock(sb);
+       return err;
+}
+
+/*
+ * Called by iput() when the inode reference count reached zero
+ * and the inode is not hashed anywhere.  Used to clear anything
+ * that needs to be, before the inode is completely destroyed and put
+ * on the inode free list.
+ *
+ * No need to lock sb info's rwsem.
+ */
+static void unionfs_evict_inode(struct inode *inode)
+{
+       int bindex, bstart, bend;
+       struct inode *lower_inode;
+       struct list_head *pos, *n;
+       struct unionfs_dir_state *rdstate;
+
+       truncate_inode_pages(&inode->i_data, 0);
+       clear_inode(inode);
+
+       list_for_each_safe(pos, n, &UNIONFS_I(inode)->readdircache) {
+               rdstate = list_entry(pos, struct unionfs_dir_state, cache);
+               list_del(&rdstate->cache);
+               free_rdstate(rdstate);
+       }
+
+       /*
+        * Decrement a reference to a lower_inode, which was incremented
+        * by our read_inode when it was created initially.
+        */
+       bstart = ibstart(inode);
+       bend = ibend(inode);
+       if (bstart >= 0) {
+               for (bindex = bstart; bindex <= bend; bindex++) {
+                       lower_inode = unionfs_lower_inode_idx(inode, bindex);
+                       if (!lower_inode)
+                               continue;
+                       unionfs_set_lower_inode_idx(inode, bindex, NULL);
+                       /* see Documentation/filesystems/unionfs/issues.txt */
+                       lockdep_off();
+                       iput(lower_inode);
+                       lockdep_on();
+               }
+       }
+
+       kfree(UNIONFS_I(inode)->lower_inodes);
+       UNIONFS_I(inode)->lower_inodes = NULL;
+}
+
+static struct inode *unionfs_alloc_inode(struct super_block *sb)
+{
+       struct unionfs_inode_info *i;
+
+       i = kmem_cache_alloc(unionfs_inode_cachep, GFP_KERNEL);
+       if (unlikely(!i))
+               return NULL;
+
+       /* memset everything up to the inode to 0 */
+       memset(i, 0, offsetof(struct unionfs_inode_info, vfs_inode));
+
+       i->vfs_inode.i_version = 1;
+       return &i->vfs_inode;
+}
+
+static void unionfs_destroy_inode(struct inode *inode)
+{
+       kmem_cache_free(unionfs_inode_cachep, UNIONFS_I(inode));
+}
+
+/* unionfs inode cache constructor */
+static void init_once(void *obj)
+{
+       struct unionfs_inode_info *i = obj;
+
+       inode_init_once(&i->vfs_inode);
+}
+
+int unionfs_init_inode_cache(void)
+{
+       int err = 0;
+
+       unionfs_inode_cachep =
+               kmem_cache_create("unionfs_inode_cache",
+                                 sizeof(struct unionfs_inode_info), 0,
+                                 SLAB_RECLAIM_ACCOUNT, init_once);
+       if (unlikely(!unionfs_inode_cachep))
+               err = -ENOMEM;
+       return err;
+}
+
+/* unionfs inode cache destructor */
+void unionfs_destroy_inode_cache(void)
+{
+       if (unionfs_inode_cachep)
+               kmem_cache_destroy(unionfs_inode_cachep);
+}
+
+/*
+ * Called when we have a dirty inode, right here we only throw out
+ * parts of our readdir list that are too old.
+ *
+ * No need to grab sb info's rwsem.
+ */
+static int unionfs_write_inode(struct inode *inode,
+                              struct writeback_control *wbc)
+{
+       struct list_head *pos, *n;
+       struct unionfs_dir_state *rdstate;
+
+       spin_lock(&UNIONFS_I(inode)->rdlock);
+       list_for_each_safe(pos, n, &UNIONFS_I(inode)->readdircache) {
+               rdstate = list_entry(pos, struct unionfs_dir_state, cache);
+               /* We keep this list in LRU order. */
+               if ((rdstate->access + RDCACHE_JIFFIES) > jiffies)
+                       break;
+               UNIONFS_I(inode)->rdcount--;
+               list_del(&rdstate->cache);
+               free_rdstate(rdstate);
+       }
+       spin_unlock(&UNIONFS_I(inode)->rdlock);
+
+       return 0;
+}
+
+/*
+ * Used only in nfs, to kill any pending RPC tasks, so that subsequent
+ * code can actually succeed and won't leave tasks that need handling.
+ */
+static void unionfs_umount_begin(struct super_block *sb)
+{
+       struct super_block *lower_sb;
+       int bindex, bstart, bend;
+
+       unionfs_read_lock(sb, UNIONFS_SMUTEX_CHILD);
+
+       bstart = sbstart(sb);
+       bend = sbend(sb);
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_sb = unionfs_lower_super_idx(sb, bindex);
+
+               if (lower_sb && lower_sb->s_op &&
+                   lower_sb->s_op->umount_begin)
+                       lower_sb->s_op->umount_begin(lower_sb);
+       }
+
+       unionfs_read_unlock(sb);
+}
+
+static int unionfs_show_options(struct seq_file *m, struct dentry *root)
+{
+       struct super_block *sb = root->d_sb;
+       int ret = 0;
+       char *tmp_page;
+       char *path;
+       int bindex, bstart, bend;
+       int perms;
+
+       /* to prevent a silly lockdep warning with namespace_sem */
+       lockdep_off();
+       unionfs_read_lock(sb, UNIONFS_SMUTEX_CHILD);
+       unionfs_lock_dentry(sb->s_root, UNIONFS_DMUTEX_CHILD);
+
+       tmp_page = (char *) __get_free_page(GFP_KERNEL);
+       if (unlikely(!tmp_page)) {
+               ret = -ENOMEM;
+               goto out;
+       }
+
+       bstart = sbstart(sb);
+       bend = sbend(sb);
+
+       seq_printf(m, ",dirs=");
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               struct path p;
+               p.dentry = unionfs_lower_dentry_idx(sb->s_root, bindex);
+               p.mnt = unionfs_lower_mnt_idx(sb->s_root, bindex);
+               path = d_path(&p, tmp_page, PAGE_SIZE);
+               if (IS_ERR(path)) {
+                       ret = PTR_ERR(path);
+                       goto out;
+               }
+
+               perms = branchperms(sb, bindex);
+
+               seq_printf(m, "%s=%s", path,
+                          perms & MAY_WRITE ? "rw" : "ro");
+               if (bindex != bend)
+                       seq_printf(m, ":");
+       }
+
+out:
+       free_page((unsigned long) tmp_page);
+
+       unionfs_unlock_dentry(sb->s_root);
+       unionfs_read_unlock(sb);
+       lockdep_on();
+
+       return ret;
+}
+
+struct super_operations unionfs_sops = {
+       .put_super      = unionfs_put_super,
+       .statfs         = unionfs_statfs,
+       .remount_fs     = unionfs_remount_fs,
+       .evict_inode    = unionfs_evict_inode,
+       .umount_begin   = unionfs_umount_begin,
+       .show_options   = unionfs_show_options,
+       .write_inode    = unionfs_write_inode,
+       .alloc_inode    = unionfs_alloc_inode,
+       .destroy_inode  = unionfs_destroy_inode,
+};
diff --git a/fs/unionfs/union.h b/fs/unionfs/union.h
new file mode 100644
index 0000000..8e7fcfb
--- /dev/null
+++ b/fs/unionfs/union.h
@@ -0,0 +1,681 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _UNION_H_
+#define _UNION_H_
+
+#include <linux/dcache.h>
+#include <linux/file.h>
+#include <linux/list.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/page-flags.h>
+#include <linux/pagemap.h>
+#include <linux/poll.h>
+#include <linux/security.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/statfs.h>
+#include <linux/string.h>
+#include <linux/vmalloc.h>
+#include <linux/writeback.h>
+#include <linux/buffer_head.h>
+#include <linux/xattr.h>
+#include <linux/fs_stack.h>
+#include <linux/magic.h>
+#include <linux/log2.h>
+#include <linux/poison.h>
+#include <linux/mman.h>
+#include <linux/backing-dev.h>
+#include <linux/splice.h>
+#include <linux/sched.h>
+
+
+
+#include <linux/union_fs.h>
+
+/* the file system name */
+#define UNIONFS_NAME "unionfs"
+
+/* unionfs root inode number */
+#define UNIONFS_ROOT_INO     1
+
+/* number of times we try to get a unique temporary file name */
+#define GET_TMPNAM_MAX_RETRY   5
+
+/* maximum number of branches we support, to avoid memory blowup */
+#define UNIONFS_MAX_BRANCHES   128
+
+/* minimum time (seconds) required for time-based cache-coherency */
+#define UNIONFS_MIN_CC_TIME    3
+
+/* Operations vectors defined in specific files. */
+extern struct file_operations unionfs_main_fops;
+extern struct file_operations unionfs_dir_fops;
+extern struct inode_operations unionfs_main_iops;
+extern struct inode_operations unionfs_dir_iops;
+extern struct inode_operations unionfs_symlink_iops;
+extern struct super_operations unionfs_sops;
+extern struct dentry_operations unionfs_dops;
+extern struct address_space_operations unionfs_aops, unionfs_dummy_aops;
+extern struct vm_operations_struct unionfs_vm_ops;
+
+/* How long should an entry be allowed to persist */
+#define RDCACHE_JIFFIES        (5*HZ)
+
+/* compatibility with Real-Time patches */
+#ifdef CONFIG_PREEMPT_RT
+# define unionfs_rw_semaphore  compat_rw_semaphore
+#else /* not CONFIG_PREEMPT_RT */
+# define unionfs_rw_semaphore  rw_semaphore
+#endif /* not CONFIG_PREEMPT_RT */
+
+/* file private data. */
+struct unionfs_file_info {
+       int bstart;
+       int bend;
+       atomic_t generation;
+
+       struct unionfs_dir_state *rdstate;
+       struct file **lower_files;
+       int *saved_branch_ids; /* IDs of branches when file was opened */
+       const struct vm_operations_struct *lower_vm_ops;
+       bool wrote_to_file;     /* for delayed copyup */
+};
+
+/* unionfs inode data in memory */
+struct unionfs_inode_info {
+       int bstart;
+       int bend;
+       atomic_t generation;
+       /* Stuff for readdir over NFS. */
+       spinlock_t rdlock;
+       struct list_head readdircache;
+       int rdcount;
+       int hashsize;
+       int cookie;
+
+       /* The lower inodes */
+       struct inode **lower_inodes;
+
+       struct inode vfs_inode;
+};
+
+/* unionfs dentry data in memory */
+struct unionfs_dentry_info {
+       /*
+        * The semaphore is used to lock the dentry as soon as we get into a
+        * unionfs function from the VFS.  Our lock ordering is that children
+        * go before their parents.
+        */
+       struct mutex lock;
+       int bstart;
+       int bend;
+       int bopaque;
+       int bcount;
+       atomic_t generation;
+       struct path *lower_paths;
+};
+
+/* These are the pointers to our various objects. */
+struct unionfs_data {
+       struct super_block *sb; /* lower super_block */
+       atomic_t open_files;    /* number of open files on branch */
+       int branchperms;
+       int branch_id;          /* unique branch ID at re/mount time */
+};
+
+/* unionfs super-block data in memory */
+struct unionfs_sb_info {
+       int bend;
+
+       atomic_t generation;
+
+       /*
+        * This rwsem is used to make sure that a branch management
+        * operation...
+        *   1) will not begin before all currently in-flight operations
+        *      complete.
+        *   2) any new operations do not execute until the currently
+        *      running branch management operation completes.
+        *
+        * The write_lock_owner records the PID of the task which grabbed
+        * the rw_sem for writing.  If the same task also tries to grab the
+        * read lock, we allow it.  This prevents a self-deadlock when
+        * branch-management is used on a pivot_root'ed union, because we
+        * have to ->lookup paths which belong to the same union.
+        */
+       struct unionfs_rw_semaphore rwsem;
+       pid_t write_lock_owner; /* PID of rw_sem owner (write lock) */
+       int high_branch_id;     /* last unique branch ID given */
+       char *dev_name;         /* to identify different unions in pr_debug */
+       struct unionfs_data *data;
+};
+
+/*
+ * structure for making the linked list of entries by readdir on left branch
+ * to compare with entries on right branch
+ */
+struct filldir_node {
+       struct list_head file_list;     /* list for directory entries */
+       char *name;             /* name entry */
+       int hash;               /* name hash */
+       int namelen;            /* name len since name is not 0 terminated */
+
+       /*
+        * we can check for duplicate whiteouts and files in the same branch
+        * in order to return -EIO.
+        */
+       int bindex;
+
+       /* is this a whiteout entry? */
+       int whiteout;
+
+       /* Inline name, so we don't need to separately kmalloc small ones */
+       char iname[DNAME_INLINE_LEN];
+};
+
+/* Directory hash table. */
+struct unionfs_dir_state {
+       unsigned int cookie;    /* the cookie, based off of rdversion */
+       unsigned int offset;    /* The entry we have returned. */
+       int bindex;
+       loff_t dirpos;          /* offset within the lower level directory */
+       int size;               /* How big is the hash table? */
+       int hashentries;        /* How many entries have been inserted? */
+       unsigned long access;
+
+       /* This cache list is used when the inode keeps us around. */
+       struct list_head cache;
+       struct list_head list[0];
+};
+
+/* externs needed for fanout.h or sioq.h */
+extern int unionfs_get_nlinks(const struct inode *inode);
+extern void unionfs_copy_attr_times(struct inode *upper);
+extern void unionfs_copy_attr_all(struct inode *dest, const struct inode *src);
+
+/* include miscellaneous macros */
+#include "fanout.h"
+#include "sioq.h"
+
+/* externs for cache creation/deletion routines */
+extern void unionfs_destroy_filldir_cache(void);
+extern int unionfs_init_filldir_cache(void);
+extern int unionfs_init_inode_cache(void);
+extern void unionfs_destroy_inode_cache(void);
+extern int unionfs_init_dentry_cache(void);
+extern void unionfs_destroy_dentry_cache(void);
+
+/* Initialize and free readdir-specific  state. */
+extern int init_rdstate(struct file *file);
+extern struct unionfs_dir_state *alloc_rdstate(struct inode *inode,
+                                              int bindex);
+extern struct unionfs_dir_state *find_rdstate(struct inode *inode,
+                                             loff_t fpos);
+extern void free_rdstate(struct unionfs_dir_state *state);
+extern int add_filldir_node(struct unionfs_dir_state *rdstate,
+                           const char *name, int namelen, int bindex,
+                           int whiteout);
+extern struct filldir_node *find_filldir_node(struct unionfs_dir_state *rdstate,
+                                             const char *name, int namelen,
+                                             int is_whiteout);
+
+extern struct dentry **alloc_new_dentries(int objs);
+extern struct unionfs_data *alloc_new_data(int objs);
+
+/* We can only use 32-bits of offset for rdstate --- blech! */
+#define DIREOF (0xfffff)
+#define RDOFFBITS 20           /* This is the number of bits in DIREOF. */
+#define MAXRDCOOKIE (0xfff)
+/* Turn an rdstate into an offset. */
+static inline off_t rdstate2offset(struct unionfs_dir_state *buf)
+{
+       off_t tmp;
+
+       tmp = ((buf->cookie & MAXRDCOOKIE) << RDOFFBITS)
+               | (buf->offset & DIREOF);
+       return tmp;
+}
+
+/* Macros for locking a super_block. */
+enum unionfs_super_lock_class {
+       UNIONFS_SMUTEX_NORMAL,
+       UNIONFS_SMUTEX_PARENT,  /* when locking on behalf of file */
+       UNIONFS_SMUTEX_CHILD,   /* when locking on behalf of dentry */
+};
+static inline void unionfs_read_lock(struct super_block *sb, int subclass)
+{
+       if (UNIONFS_SB(sb)->write_lock_owner &&
+           UNIONFS_SB(sb)->write_lock_owner == current->pid)
+               return;
+       down_read_nested(&UNIONFS_SB(sb)->rwsem, subclass);
+}
+static inline void unionfs_read_unlock(struct super_block *sb)
+{
+       if (UNIONFS_SB(sb)->write_lock_owner &&
+           UNIONFS_SB(sb)->write_lock_owner == current->pid)
+               return;
+       up_read(&UNIONFS_SB(sb)->rwsem);
+}
+static inline void unionfs_write_lock(struct super_block *sb)
+{
+       down_write(&UNIONFS_SB(sb)->rwsem);
+       UNIONFS_SB(sb)->write_lock_owner = current->pid;
+}
+static inline void unionfs_write_unlock(struct super_block *sb)
+{
+       up_write(&UNIONFS_SB(sb)->rwsem);
+       UNIONFS_SB(sb)->write_lock_owner = 0;
+}
+
+static inline void unionfs_double_lock_dentry(struct dentry *d1,
+                                             struct dentry *d2)
+{
+       BUG_ON(d1 == d2);
+       if (d1 < d2) {
+               unionfs_lock_dentry(d1, UNIONFS_DMUTEX_PARENT);
+               unionfs_lock_dentry(d2, UNIONFS_DMUTEX_CHILD);
+       } else {
+               unionfs_lock_dentry(d2, UNIONFS_DMUTEX_PARENT);
+               unionfs_lock_dentry(d1, UNIONFS_DMUTEX_CHILD);
+       }
+}
+
+static inline void unionfs_double_unlock_dentry(struct dentry *d1,
+                                               struct dentry *d2)
+{
+       BUG_ON(d1 == d2);
+       if (d1 < d2) { /* unlock in reverse order than double_lock_dentry */
+               unionfs_unlock_dentry(d1);
+               unionfs_unlock_dentry(d2);
+       } else {
+               unionfs_unlock_dentry(d2);
+               unionfs_unlock_dentry(d1);
+       }
+}
+
+static inline void unionfs_double_lock_parents(struct dentry *p1,
+                                              struct dentry *p2)
+{
+       if (p1 == p2) {
+               unionfs_lock_dentry(p1, UNIONFS_DMUTEX_REVAL_PARENT);
+               return;
+       }
+       if (p1 < p2) {
+               unionfs_lock_dentry(p1, UNIONFS_DMUTEX_REVAL_PARENT);
+               unionfs_lock_dentry(p2, UNIONFS_DMUTEX_REVAL_CHILD);
+       } else {
+               unionfs_lock_dentry(p2, UNIONFS_DMUTEX_REVAL_PARENT);
+               unionfs_lock_dentry(p1, UNIONFS_DMUTEX_REVAL_CHILD);
+       }
+}
+
+static inline void unionfs_double_unlock_parents(struct dentry *p1,
+                                                struct dentry *p2)
+{
+       if (p1 == p2) {
+               unionfs_unlock_dentry(p1);
+               return;
+       }
+       if (p1 < p2) { /* unlock in reverse order of double_lock_parents */
+               unionfs_unlock_dentry(p1);
+               unionfs_unlock_dentry(p2);
+       } else {
+               unionfs_unlock_dentry(p2);
+               unionfs_unlock_dentry(p1);
+       }
+}
+
+extern int new_dentry_private_data(struct dentry *dentry, int subclass);
+extern int realloc_dentry_private_data(struct dentry *dentry);
+extern void free_dentry_private_data(struct dentry *dentry);
+extern void update_bstart(struct dentry *dentry);
+extern int init_lower_nd(struct nameidata *nd, unsigned int flags);
+extern void release_lower_nd(struct nameidata *nd, int err);
+
+/*
+ * EXTERNALS:
+ */
+
+/* replicates the directory structure up to given dentry in given branch */
+extern struct dentry *create_parents(struct inode *dir, struct dentry *dentry,
+                                    const char *name, int bindex);
+
+/* partial lookup */
+extern int unionfs_partial_lookup(struct dentry *dentry,
+                                 struct dentry *parent);
+extern struct dentry *unionfs_lookup_full(struct dentry *dentry,
+                                         struct dentry *parent,
+                                         int lookupmode);
+
+/* copies a file from dbstart to newbindex branch */
+extern int copyup_file(struct inode *dir, struct file *file, int bstart,
+                      int newbindex, loff_t size);
+extern int copyup_named_file(struct inode *dir, struct file *file,
+                            char *name, int bstart, int new_bindex,
+                            loff_t len);
+/* copies a dentry from dbstart to newbindex branch */
+extern int copyup_dentry(struct inode *dir, struct dentry *dentry,
+                        int bstart, int new_bindex, const char *name,
+                        int namelen, struct file **copyup_file, loff_t len);
+/* helper functions for post-copyup actions */
+extern void unionfs_postcopyup_setmnt(struct dentry *dentry);
+extern void unionfs_postcopyup_release(struct dentry *dentry);
+
+/* Is this directory empty: 0 if it is empty, -ENOTEMPTY if not. */
+extern int check_empty(struct dentry *dentry, struct dentry *parent,
+                      struct unionfs_dir_state **namelist);
+/* whiteout and opaque directory helpers */
+extern char *alloc_whname(const char *name, int len);
+extern bool is_whiteout_name(char **namep, int *namelenp);
+extern bool is_validname(const char *name);
+extern struct dentry *lookup_whiteout(const char *name,
+                                     struct dentry *lower_parent);
+extern struct dentry *find_first_whiteout(struct dentry *dentry);
+extern int unlink_whiteout(struct dentry *wh_dentry);
+extern int check_unlink_whiteout(struct dentry *dentry,
+                                struct dentry *lower_dentry, int bindex);
+extern int create_whiteout(struct dentry *dentry, int start);
+extern int delete_whiteouts(struct dentry *dentry, int bindex,
+                           struct unionfs_dir_state *namelist);
+extern int is_opaque_dir(struct dentry *dentry, int bindex);
+extern int make_dir_opaque(struct dentry *dir, int bindex);
+extern void unionfs_set_max_namelen(long *namelen);
+
+extern void unionfs_reinterpose(struct dentry *this_dentry);
+extern struct super_block *unionfs_duplicate_super(struct super_block *sb);
+
+/* Locking functions. */
+extern int unionfs_setlk(struct file *file, int cmd, struct file_lock *fl);
+extern int unionfs_getlk(struct file *file, struct file_lock *fl);
+
+/* Common file operations. */
+extern int unionfs_file_revalidate(struct file *file, struct dentry *parent,
+                                  bool willwrite);
+extern int unionfs_open(struct inode *inode, struct file *file);
+extern int unionfs_file_release(struct inode *inode, struct file *file);
+extern int unionfs_flush(struct file *file, fl_owner_t id);
+extern long unionfs_ioctl(struct file *file, unsigned int cmd,
+                         unsigned long arg);
+extern int unionfs_fsync(struct file *file, loff_t start, loff_t end,
+                        int datasync);
+extern int unionfs_fasync(int fd, struct file *file, int flag);
+
+/* Inode operations */
+extern struct inode *unionfs_iget(struct super_block *sb, unsigned long ino);
+extern int unionfs_rename(struct inode *old_dir, struct dentry *old_dentry,
+                         struct inode *new_dir, struct dentry *new_dentry);
+extern int unionfs_unlink(struct inode *dir, struct dentry *dentry);
+extern int unionfs_rmdir(struct inode *dir, struct dentry *dentry);
+
+extern bool __unionfs_d_revalidate(struct dentry *dentry,
+                                  struct dentry *parent, bool willwrite);
+extern bool is_negative_lower(const struct dentry *dentry);
+extern bool is_newer_lower(const struct dentry *dentry);
+extern void purge_sb_data(struct super_block *sb);
+
+/* The values for unionfs_interpose's flag. */
+#define INTERPOSE_DEFAULT      0
+#define INTERPOSE_LOOKUP       1
+#define INTERPOSE_REVAL                2
+#define INTERPOSE_REVAL_NEG    3
+#define INTERPOSE_PARTIAL      4
+
+extern struct dentry *unionfs_interpose(struct dentry *this_dentry,
+                                       struct super_block *sb, int flag);
+
+#ifdef CONFIG_UNION_FS_XATTR
+/* Extended attribute functions. */
+extern void *unionfs_xattr_alloc(size_t size, size_t limit);
+static inline void unionfs_xattr_kfree(const void *p)
+{
+       kfree(p);
+}
+extern ssize_t unionfs_getxattr(struct dentry *dentry, const char *name,
+                               void *value, size_t size);
+extern int unionfs_removexattr(struct dentry *dentry, const char *name);
+extern ssize_t unionfs_listxattr(struct dentry *dentry, char *list,
+                                size_t size);
+extern int unionfs_setxattr(struct dentry *dentry, const char *name,
+                           const void *value, size_t size, int flags);
+#endif /* CONFIG_UNION_FS_XATTR */
+
+/* The root directory is unhashed, but isn't deleted. */
+static inline int d_deleted(struct dentry *d)
+{
+       return d_unhashed(d) && (d != d->d_sb->s_root);
+}
+
+/* unionfs_permission, check if we should bypass error to facilitate copyup */
+#define IS_COPYUP_ERR(err) ((err) == -EROFS)
+
+/* unionfs_open, check if we need to copyup the file */
+#define OPEN_WRITE_FLAGS (O_WRONLY | O_RDWR | O_APPEND)
+#define IS_WRITE_FLAG(flag) ((flag) & OPEN_WRITE_FLAGS)
+
+static inline int branchperms(const struct super_block *sb, int index)
+{
+       BUG_ON(index < 0);
+       return UNIONFS_SB(sb)->data[index].branchperms;
+}
+
+static inline int set_branchperms(struct super_block *sb, int index, int perms)
+{
+       BUG_ON(index < 0);
+       UNIONFS_SB(sb)->data[index].branchperms = perms;
+       return perms;
+}
+
+/* check if readonly lower inode, but possibly unlinked (no inode->i_sb) */
+static inline int __is_rdonly(const struct inode *inode)
+{
+       /* if unlinked, can't be readonly (?) */
+       if (!inode->i_sb)
+               return 0;
+       return IS_RDONLY(inode);
+
+}
+/* Is this file on a read-only branch? */
+static inline int is_robranch_super(const struct super_block *sb, int index)
+{
+       int ret;
+
+       ret = (!(branchperms(sb, index) & MAY_WRITE)) ? -EROFS : 0;
+       return ret;
+}
+
+/* Is this file on a read-only branch? */
+static inline int is_robranch_idx(const struct dentry *dentry, int index)
+{
+       struct super_block *lower_sb;
+
+       BUG_ON(index < 0);
+
+       if (!(branchperms(dentry->d_sb, index) & MAY_WRITE))
+               return -EROFS;
+
+       lower_sb = unionfs_lower_super_idx(dentry->d_sb, index);
+       BUG_ON(lower_sb == NULL);
+       /*
+        * test sb flags directly, not IS_RDONLY(lower_inode) because the
+        * lower_dentry could be a negative.
+        */
+       if (lower_sb->s_flags & MS_RDONLY)
+               return -EROFS;
+
+       return 0;
+}
+
+static inline int is_robranch(const struct dentry *dentry)
+{
+       int index;
+
+       index = UNIONFS_D(dentry)->bstart;
+       BUG_ON(index < 0);
+
+       return is_robranch_idx(dentry, index);
+}
+
+/*
+ * EXTERNALS:
+ */
+extern int check_branch(const struct path *path);
+extern int parse_branch_mode(const char *name, int *perms);
+
+/* locking helpers */
+static inline struct dentry *lock_parent(struct dentry *dentry)
+{
+       struct dentry *dir = dget_parent(dentry);
+       mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
+       return dir;
+}
+static inline struct dentry *lock_parent_wh(struct dentry *dentry)
+{
+       struct dentry *dir = dget_parent(dentry);
+
+       mutex_lock_nested(&dir->d_inode->i_mutex, UNIONFS_DMUTEX_WHITEOUT);
+       return dir;
+}
+
+static inline void unlock_dir(struct dentry *dir)
+{
+       mutex_unlock(&dir->d_inode->i_mutex);
+       dput(dir);
+}
+
+/* lock base inode mutex before calling lookup_one_len */
+static inline struct dentry *lookup_lck_len(const char *name,
+                                           struct dentry *base, int len)
+{
+       struct dentry *d;
+       struct nameidata lower_nd;
+       int err;
+
+       err = init_lower_nd(&lower_nd, LOOKUP_OPEN);
+       if (unlikely(err < 0)) {
+               d = ERR_PTR(err);
+               goto out;
+       }
+       mutex_lock(&base->d_inode->i_mutex);
+       d = lookup_one_len_nd(name, base, len, &lower_nd);
+       release_lower_nd(&lower_nd, err);
+       mutex_unlock(&base->d_inode->i_mutex);
+out:
+       return d;
+}
+
+static inline struct vfsmount *unionfs_mntget(struct dentry *dentry,
+                                             int bindex)
+{
+       struct vfsmount *mnt;
+
+       BUG_ON(!dentry || bindex < 0);
+
+       mnt = mntget(unionfs_lower_mnt_idx(dentry, bindex));
+#ifdef CONFIG_UNION_FS_DEBUG
+       if (!mnt)
+               pr_debug("unionfs: mntget: mnt=%p bindex=%d\n",
+                        mnt, bindex);
+#endif /* CONFIG_UNION_FS_DEBUG */
+
+       return mnt;
+}
+
+static inline void unionfs_mntput(struct dentry *dentry, int bindex)
+{
+       struct vfsmount *mnt;
+
+       if (!dentry && bindex < 0)
+               return;
+       BUG_ON(!dentry || bindex < 0);
+
+       mnt = unionfs_lower_mnt_idx(dentry, bindex);
+#ifdef CONFIG_UNION_FS_DEBUG
+       /*
+        * Directories can have NULL lower objects in between start/end, but
+        * NOT if at the start/end range.  We cannot verify that this dentry
+        * is a type=DIR, because it may already be a negative dentry.  But
+        * if dbstart is greater than dbend, we know that this couldn't have
+        * been a regular file: it had to have been a directory.
+        */
+       if (!mnt && !(bindex > dbstart(dentry) && bindex < dbend(dentry)))
+               pr_debug("unionfs: mntput: mnt=%p bindex=%d\n", mnt, bindex);
+#endif /* CONFIG_UNION_FS_DEBUG */
+       mntput(mnt);
+}
+
+#ifdef CONFIG_UNION_FS_DEBUG
+
+/* useful for tracking code reachability */
+#define UDBG pr_debug("DBG:%s:%s:%d\n", __FILE__, __func__, __LINE__)
+
+#define unionfs_check_inode(i) __unionfs_check_inode((i),      \
+       __FILE__, __func__, __LINE__)
+#define unionfs_check_dentry(d)        __unionfs_check_dentry((d),     \
+       __FILE__, __func__, __LINE__)
+#define unionfs_check_file(f)  __unionfs_check_file((f),       \
+       __FILE__, __func__, __LINE__)
+#define unionfs_check_nd(n)    __unionfs_check_nd((n),         \
+       __FILE__, __func__, __LINE__)
+#define show_branch_counts(sb) __show_branch_counts((sb),      \
+       __FILE__, __func__, __LINE__)
+#define show_inode_times(i)    __show_inode_times((i),         \
+       __FILE__, __func__, __LINE__)
+#define show_dinode_times(d)   __show_dinode_times((d),        \
+       __FILE__, __func__, __LINE__)
+#define show_inode_counts(i)   __show_inode_counts((i),        \
+       __FILE__, __func__, __LINE__)
+
+extern void __unionfs_check_inode(const struct inode *inode, const char *fname,
+                                 const char *fxn, int line);
+extern void __unionfs_check_dentry(const struct dentry *dentry,
+                                  const char *fname, const char *fxn,
+                                  int line);
+extern void __unionfs_check_file(const struct file *file,
+                                const char *fname, const char *fxn, int line);
+extern void __unionfs_check_nd(const struct nameidata *nd,
+                              const char *fname, const char *fxn, int line);
+extern void __show_branch_counts(const struct super_block *sb,
+                                const char *file, const char *fxn, int line);
+extern void __show_inode_times(const struct inode *inode,
+                              const char *file, const char *fxn, int line);
+extern void __show_dinode_times(const struct dentry *dentry,
+                               const char *file, const char *fxn, int line);
+extern void __show_inode_counts(const struct inode *inode,
+                               const char *file, const char *fxn, int line);
+
+#else /* not CONFIG_UNION_FS_DEBUG */
+
+/* we leave useful hooks for these check functions throughout the code */
+#define unionfs_check_inode(i)         do { } while (0)
+#define unionfs_check_dentry(d)                do { } while (0)
+#define unionfs_check_file(f)          do { } while (0)
+#define unionfs_check_nd(n)            do { } while (0)
+#define show_branch_counts(sb)         do { } while (0)
+#define show_inode_times(i)            do { } while (0)
+#define show_dinode_times(d)           do { } while (0)
+#define show_inode_counts(i)           do { } while (0)
+#define UDBG                           do { } while (0)
+
+#endif /* not CONFIG_UNION_FS_DEBUG */
+
+#endif /* not _UNION_H_ */
diff --git a/fs/unionfs/unlink.c b/fs/unionfs/unlink.c
new file mode 100644
index 0000000..25943a5
--- /dev/null
+++ b/fs/unionfs/unlink.c
@@ -0,0 +1,278 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/*
+ * Helper function for Unionfs's unlink operation.
+ *
+ * The main goal of this function is to optimize the unlinking of non-dir
+ * objects in unionfs by deleting all possible lower inode objects from the
+ * underlying branches having same dentry name as the non-dir dentry on
+ * which this unlink operation is called.  This way we delete as many lower
+ * inodes as possible, and save space.  Whiteouts need to be created in
+ * branch0 only if unlinking fails on any of the lower branch other than
+ * branch0, or if a lower branch is marked read-only.
+ *
+ * Also, while unlinking a file, if we encounter any dir type entry in any
+ * intermediate branch, then we remove the directory by calling vfs_rmdir.
+ * The following special cases are also handled:
+
+ * (1) If an error occurs in branch0 during vfs_unlink, then we return
+ *     appropriate error.
+ *
+ * (2) If we get an error during unlink in any of other lower branch other
+ *     than branch0, then we create a whiteout in branch0.
+ *
+ * (3) If a whiteout already exists in any intermediate branch, we delete
+ *     all possible inodes only up to that branch (this is an "opaqueness"
+ *     as as per Documentation/filesystems/unionfs/concepts.txt).
+ *
+ */
+static int unionfs_unlink_whiteout(struct inode *dir, struct dentry *dentry,
+                                  struct dentry *parent)
+{
+       struct dentry *lower_dentry;
+       struct dentry *lower_dir_dentry;
+       int bindex;
+       int err = 0;
+
+       err = unionfs_partial_lookup(dentry, parent);
+       if (err)
+               goto out;
+
+       /* trying to unlink all possible valid instances */
+       for (bindex = dbstart(dentry); bindex <= dbend(dentry); bindex++) {
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+               if (!lower_dentry || !lower_dentry->d_inode)
+                       continue;
+
+               lower_dir_dentry = lock_parent(lower_dentry);
+
+               /* avoid destroying the lower inode if the object is in use */
+               dget(lower_dentry);
+               err = is_robranch_super(dentry->d_sb, bindex);
+               if (!err) {
+                       /* see Documentation/filesystems/unionfs/issues.txt */
+                       lockdep_off();
+                       if (!S_ISDIR(lower_dentry->d_inode->i_mode))
+                               err = vfs_unlink(lower_dir_dentry->d_inode,
+                                                               lower_dentry);
+                       else
+                               err = vfs_rmdir(lower_dir_dentry->d_inode,
+                                                               lower_dentry);
+                       lockdep_on();
+               }
+
+               /* if lower object deletion succeeds, update inode's times */
+               if (!err)
+                       unionfs_copy_attr_times(dentry->d_inode);
+               dput(lower_dentry);
+               fsstack_copy_attr_times(dir, lower_dir_dentry->d_inode);
+               unlock_dir(lower_dir_dentry);
+
+               if (err)
+                       break;
+       }
+
+       /*
+        * Create the whiteout in branch 0 (highest priority) only if (a)
+        * there was an error in any intermediate branch other than branch 0
+        * due to failure of vfs_unlink/vfs_rmdir or (b) a branch marked or
+        * mounted read-only.
+        */
+       if (err) {
+               if ((bindex == 0) ||
+                   ((bindex == dbstart(dentry)) &&
+                    (!IS_COPYUP_ERR(err))))
+                       goto out;
+               else {
+                       if (!IS_COPYUP_ERR(err))
+                               pr_debug("unionfs: lower object deletion "
+                                            "failed in branch:%d\n", bindex);
+                       err = create_whiteout(dentry, sbstart(dentry->d_sb));
+               }
+       }
+
+out:
+       if (!err)
+               inode_dec_link_count(dentry->d_inode);
+
+       /* We don't want to leave negative leftover dentries for revalidate. */
+       if (!err && (dbopaque(dentry) != -1))
+               update_bstart(dentry);
+
+       return err;
+}
+
+int unionfs_unlink(struct inode *dir, struct dentry *dentry)
+{
+       int err = 0;
+       struct inode *inode = dentry->d_inode;
+       struct dentry *parent;
+       int valid;
+
+       BUG_ON(S_ISDIR(inode->i_mode));
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       valid = __unionfs_d_revalidate(dentry, parent, false);
+       if (unlikely(!valid)) {
+               err = -ESTALE;
+               goto out;
+       }
+       unionfs_check_dentry(dentry);
+
+       err = unionfs_unlink_whiteout(dir, dentry, parent);
+       /* call d_drop so the system "forgets" about us */
+       if (!err) {
+               unionfs_postcopyup_release(dentry);
+               unionfs_postcopyup_setmnt(parent);
+               if (inode->i_nlink == 0) /* drop lower inodes */
+                       iput_lowers_all(inode, false);
+               d_drop(dentry);
+               /*
+                * if unlink/whiteout succeeded, parent dir mtime has
+                * changed
+                */
+               unionfs_copy_attr_times(dir);
+       }
+
+out:
+       if (!err) {
+               unionfs_check_dentry(dentry);
+               unionfs_check_inode(dir);
+       }
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
+
+static int unionfs_rmdir_first(struct inode *dir, struct dentry *dentry,
+                              struct unionfs_dir_state *namelist)
+{
+       int err;
+       struct dentry *lower_dentry;
+       struct dentry *lower_dir_dentry = NULL;
+
+       /* Here we need to remove whiteout entries. */
+       err = delete_whiteouts(dentry, dbstart(dentry), namelist);
+       if (err)
+               goto out;
+
+       lower_dentry = unionfs_lower_dentry(dentry);
+
+       lower_dir_dentry = lock_parent(lower_dentry);
+
+       /* avoid destroying the lower inode if the file is in use */
+       dget(lower_dentry);
+       err = is_robranch(dentry);
+       if (!err)
+               err = vfs_rmdir(lower_dir_dentry->d_inode, lower_dentry);
+       dput(lower_dentry);
+
+       fsstack_copy_attr_times(dir, lower_dir_dentry->d_inode);
+       /* propagate number of hard-links */
+       set_nlink(dentry->d_inode, unionfs_get_nlinks(dentry->d_inode));
+
+out:
+       if (lower_dir_dentry)
+               unlock_dir(lower_dir_dentry);
+       return err;
+}
+
+int unionfs_rmdir(struct inode *dir, struct dentry *dentry)
+{
+       int err = 0;
+       struct unionfs_dir_state *namelist = NULL;
+       struct dentry *parent;
+       int dstart, dend;
+       bool valid;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       valid = __unionfs_d_revalidate(dentry, parent, false);
+       if (unlikely(!valid)) {
+               err = -ESTALE;
+               goto out;
+       }
+       unionfs_check_dentry(dentry);
+
+       /* check if this unionfs directory is empty or not */
+       err = check_empty(dentry, parent, &namelist);
+       if (err)
+               goto out;
+
+       err = unionfs_rmdir_first(dir, dentry, namelist);
+       dstart = dbstart(dentry);
+       dend = dbend(dentry);
+       /*
+        * We create a whiteout for the directory if there was an error to
+        * rmdir the first directory entry in the union.  Otherwise, we
+        * create a whiteout only if there is no chance that a lower
+        * priority branch might also have the same named directory.  IOW,
+        * if there is not another same-named directory at a lower priority
+        * branch, then we don't need to create a whiteout for it.
+        */
+       if (!err) {
+               if (dstart < dend)
+                       err = create_whiteout(dentry, dstart);
+       } else {
+               int new_err;
+
+               if (dstart == 0)
+                       goto out;
+
+               /* exit if the error returned was NOT -EROFS */
+               if (!IS_COPYUP_ERR(err))
+                       goto out;
+
+               new_err = create_whiteout(dentry, dstart - 1);
+               if (new_err != -EEXIST)
+                       err = new_err;
+       }
+
+out:
+       /*
+        * Drop references to lower dentry/inode so storage space for them
+        * can be reclaimed.  Then, call d_drop so the system "forgets"
+        * about us.
+        */
+       if (!err) {
+               iput_lowers_all(dentry->d_inode, false);
+               dput(unionfs_lower_dentry_idx(dentry, dstart));
+               unionfs_set_lower_dentry_idx(dentry, dstart, NULL);
+               d_drop(dentry);
+               /* update our lower vfsmnts, in case a copyup took place */
+               unionfs_postcopyup_setmnt(dentry);
+               unionfs_check_dentry(dentry);
+               unionfs_check_inode(dir);
+       }
+
+       if (namelist)
+               free_rdstate(namelist);
+
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
diff --git a/fs/unionfs/whiteout.c b/fs/unionfs/whiteout.c
new file mode 100644
index 0000000..582cef2
--- /dev/null
+++ b/fs/unionfs/whiteout.c
@@ -0,0 +1,601 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/*
+ * whiteout and opaque directory helpers
+ */
+
+/* What do we use for whiteouts. */
+#define UNIONFS_WHPFX ".wh."
+#define UNIONFS_WHLEN 4
+/*
+ * If a directory contains this file, then it is opaque.  We start with the
+ * .wh. flag so that it is blocked by lookup.
+ */
+#define UNIONFS_DIR_OPAQUE_NAME "__dir_opaque"
+#define UNIONFS_DIR_OPAQUE UNIONFS_WHPFX UNIONFS_DIR_OPAQUE_NAME
+
+/* construct whiteout filename */
+char *alloc_whname(const char *name, int len)
+{
+       char *buf;
+
+       buf = kmalloc(len + UNIONFS_WHLEN + 1, GFP_KERNEL);
+       if (unlikely(!buf))
+               return ERR_PTR(-ENOMEM);
+
+       strcpy(buf, UNIONFS_WHPFX);
+       strlcat(buf, name, len + UNIONFS_WHLEN + 1);
+
+       return buf;
+}
+
+/*
+ * XXX: this can be inline or CPP macro, but is here to keep all whiteout
+ * code in one place.
+ */
+void unionfs_set_max_namelen(long *namelen)
+{
+       *namelen -= UNIONFS_WHLEN;
+}
+
+/* check if @namep is a whiteout, update @namep and @namelenp accordingly */
+bool is_whiteout_name(char **namep, int *namelenp)
+{
+       if (*namelenp > UNIONFS_WHLEN &&
+           !strncmp(*namep, UNIONFS_WHPFX, UNIONFS_WHLEN)) {
+               *namep += UNIONFS_WHLEN;
+               *namelenp -= UNIONFS_WHLEN;
+               return true;
+       }
+       return false;
+}
+
+/* is the filename valid == !(whiteout for a file or opaque dir marker) */
+bool is_validname(const char *name)
+{
+       if (!strncmp(name, UNIONFS_WHPFX, UNIONFS_WHLEN))
+               return false;
+       if (!strncmp(name, UNIONFS_DIR_OPAQUE_NAME,
+                    sizeof(UNIONFS_DIR_OPAQUE_NAME) - 1))
+               return false;
+       return true;
+}
+
+/*
+ * Look for a whiteout @name in @lower_parent directory.  If error, return
+ * ERR_PTR.  Caller must dput() the returned dentry if not an error.
+ *
+ * XXX: some callers can reuse the whname allocated buffer to avoid repeated
+ * free then re-malloc calls.  Need to provide a different API for those
+ * callers.
+ */
+struct dentry *lookup_whiteout(const char *name, struct dentry *lower_parent)
+{
+       char *whname = NULL;
+       int err = 0, namelen;
+       struct dentry *wh_dentry = NULL;
+
+       namelen = strlen(name);
+       whname = alloc_whname(name, namelen);
+       if (unlikely(IS_ERR(whname))) {
+               err = PTR_ERR(whname);
+               goto out;
+       }
+
+       /* check if whiteout exists in this branch: lookup .wh.foo */
+       wh_dentry = lookup_lck_len(whname, lower_parent, strlen(whname));
+       if (IS_ERR(wh_dentry)) {
+               err = PTR_ERR(wh_dentry);
+               goto out;
+       }
+
+       /* check if negative dentry (ENOENT) */
+       if (!wh_dentry->d_inode)
+               goto out;
+
+       /* whiteout found: check if valid type */
+       if (!S_ISREG(wh_dentry->d_inode->i_mode)) {
+               printk(KERN_ERR "unionfs: invalid whiteout %s entry type %d\n",
+                      whname, wh_dentry->d_inode->i_mode);
+               dput(wh_dentry);
+               err = -EIO;
+               goto out;
+       }
+
+out:
+       kfree(whname);
+       if (err)
+               wh_dentry = ERR_PTR(err);
+       return wh_dentry;
+}
+
+/* find and return first whiteout in parent directory, else ENOENT */
+struct dentry *find_first_whiteout(struct dentry *dentry)
+{
+       int bindex, bstart, bend;
+       struct dentry *parent, *lower_parent, *wh_dentry;
+
+       parent = dget_parent(dentry);
+
+       bstart = dbstart(parent);
+       bend = dbend(parent);
+       wh_dentry = ERR_PTR(-ENOENT);
+
+       for (bindex = bstart; bindex <= bend; bindex++) {
+               lower_parent = unionfs_lower_dentry_idx(parent, bindex);
+               if (!lower_parent)
+                       continue;
+               wh_dentry = lookup_whiteout(dentry->d_name.name, lower_parent);
+               if (IS_ERR(wh_dentry))
+                       continue;
+               if (wh_dentry->d_inode)
+                       break;
+               dput(wh_dentry);
+               wh_dentry = ERR_PTR(-ENOENT);
+       }
+
+       dput(parent);
+
+       return wh_dentry;
+}
+
+/*
+ * Unlink a whiteout dentry.  Returns 0 or -errno.  Caller must hold and
+ * release dentry reference.
+ */
+int unlink_whiteout(struct dentry *wh_dentry)
+{
+       int err;
+       struct dentry *lower_dir_dentry;
+
+       /* dget and lock parent dentry */
+       lower_dir_dentry = lock_parent_wh(wh_dentry);
+
+       /* see Documentation/filesystems/unionfs/issues.txt */
+       lockdep_off();
+       err = vfs_unlink(lower_dir_dentry->d_inode, wh_dentry);
+       lockdep_on();
+       unlock_dir(lower_dir_dentry);
+
+       /*
+        * Whiteouts are special files and should be deleted no matter what
+        * (as if they never existed), in order to allow this create
+        * operation to succeed.  This is especially important in sticky
+        * directories: a whiteout may have been created by one user, but
+        * the newly created file may be created by another user.
+        * Therefore, in order to maintain Unix semantics, if the vfs_unlink
+        * above failed, then we have to try to directly unlink the
+        * whiteout.  Note: in the ODF version of unionfs, whiteout are
+        * handled much more cleanly.
+        */
+       if (err == -EPERM) {
+               struct inode *inode = lower_dir_dentry->d_inode;
+               err = inode->i_op->unlink(inode, wh_dentry);
+       }
+       if (err)
+               printk(KERN_ERR "unionfs: could not unlink whiteout %s, "
+                      "err = %d\n", wh_dentry->d_name.name, err);
+
+       return err;
+
+}
+
+/*
+ * Helper function when creating new objects (create, symlink, mknod, etc.).
+ * Checks to see if there's a whiteout in @lower_dentry's parent directory,
+ * whose name is taken from @dentry.  Then tries to remove that whiteout, if
+ * found.  If <dentry,bindex> is a branch marked readonly, return -EROFS.
+ * If it finds both a regular file and a whiteout, delete whiteout (this
+ * should never happen).
+ *
+ * Return 0 if no whiteout was found.  Return 1 if one was found and
+ * successfully removed.  Therefore a value >= 0 tells the caller that
+ * @lower_dentry belongs to a good branch to create the new object in).
+ * Return -ERRNO if an error occurred during whiteout lookup or in trying to
+ * unlink the whiteout.
+ */
+int check_unlink_whiteout(struct dentry *dentry, struct dentry *lower_dentry,
+                         int bindex)
+{
+       int err;
+       struct dentry *wh_dentry = NULL;
+       struct dentry *lower_dir_dentry = NULL;
+
+       /* look for whiteout dentry first */
+       lower_dir_dentry = dget_parent(lower_dentry);
+       wh_dentry = lookup_whiteout(dentry->d_name.name, lower_dir_dentry);
+       dput(lower_dir_dentry);
+       if (IS_ERR(wh_dentry)) {
+               err = PTR_ERR(wh_dentry);
+               goto out;
+       }
+
+       if (!wh_dentry->d_inode) { /* no whiteout exists*/
+               err = 0;
+               goto out_dput;
+       }
+
+       /* check if regular file and whiteout were both found */
+       if (unlikely(lower_dentry->d_inode))
+               printk(KERN_WARNING "unionfs: removing whiteout; regular "
+                      "file exists in directory %s (branch %d)\n",
+                      lower_dir_dentry->d_name.name, bindex);
+
+       /* check if branch is writeable */
+       err = is_robranch_super(dentry->d_sb, bindex);
+       if (err)
+               goto out_dput;
+
+       /* .wh.foo has been found, so let's unlink it */
+       err = unlink_whiteout(wh_dentry);
+       if (!err)
+               err = 1; /* a whiteout was found and successfully removed */
+out_dput:
+       dput(wh_dentry);
+out:
+       return err;
+}
+
+/*
+ * Pass an unionfs dentry and an index.  It will try to create a whiteout
+ * for the filename in dentry, and will try in branch 'index'.  On error,
+ * it will proceed to a branch to the left.
+ */
+int create_whiteout(struct dentry *dentry, int start)
+{
+       int bstart, bend, bindex;
+       struct dentry *lower_dir_dentry;
+       struct dentry *lower_dentry;
+       struct dentry *lower_wh_dentry;
+       struct nameidata nd;
+       char *name = NULL;
+       int err = -EINVAL;
+
+       verify_locked(dentry);
+
+       bstart = dbstart(dentry);
+       bend = dbend(dentry);
+
+       /* create dentry's whiteout equivalent */
+       name = alloc_whname(dentry->d_name.name, dentry->d_name.len);
+       if (unlikely(IS_ERR(name))) {
+               err = PTR_ERR(name);
+               goto out;
+       }
+
+       for (bindex = start; bindex >= 0; bindex--) {
+               lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+
+               if (!lower_dentry) {
+                       /*
+                        * if lower dentry is not present, create the
+                        * entire lower dentry directory structure and go
+                        * ahead.  Since we want to just create whiteout, we
+                        * only want the parent dentry, and hence get rid of
+                        * this dentry.
+                        */
+                       lower_dentry = create_parents(dentry->d_inode,
+                                                     dentry,
+                                                     dentry->d_name.name,
+                                                     bindex);
+                       if (!lower_dentry || IS_ERR(lower_dentry)) {
+                               int ret = PTR_ERR(lower_dentry);
+                               if (!IS_COPYUP_ERR(ret))
+                                       printk(KERN_ERR
+                                              "unionfs: create_parents for "
+                                              "whiteout failed: bindex=%d "
+                                              "err=%d\n", bindex, ret);
+                               continue;
+                       }
+               }
+
+               lower_wh_dentry =
+                       lookup_lck_len(name, lower_dentry->d_parent,
+                                      dentry->d_name.len + UNIONFS_WHLEN);
+               if (IS_ERR(lower_wh_dentry))
+                       continue;
+
+               /*
+                * The whiteout already exists. This used to be impossible,
+                * but now is possible because of opaqueness.
+                */
+               if (lower_wh_dentry->d_inode) {
+                       dput(lower_wh_dentry);
+                       err = 0;
+                       goto out;
+               }
+
+               err = init_lower_nd(&nd, LOOKUP_CREATE);
+               if (unlikely(err < 0))
+                       goto out;
+               lower_dir_dentry = lock_parent_wh(lower_wh_dentry);
+               err = is_robranch_super(dentry->d_sb, bindex);
+               if (!err)
+                       err = vfs_create(lower_dir_dentry->d_inode,
+                                        lower_wh_dentry,
+                                        current_umask() & S_IRUGO,
+                                        &nd);
+               unlock_dir(lower_dir_dentry);
+               dput(lower_wh_dentry);
+               release_lower_nd(&nd, err);
+
+               if (!err || !IS_COPYUP_ERR(err))
+                       break;
+       }
+
+       /* set dbopaque so that lookup will not proceed after this branch */
+       if (!err)
+               dbopaque(dentry) = bindex;
+
+out:
+       kfree(name);
+       return err;
+}
+
+/*
+ * Delete all of the whiteouts in a given directory for rmdir.
+ *
+ * lower directory inode should be locked
+ */
+static int do_delete_whiteouts(struct dentry *dentry, int bindex,
+                              struct unionfs_dir_state *namelist)
+{
+       int err = 0;
+       struct dentry *lower_dir_dentry = NULL;
+       struct dentry *lower_dentry;
+       char *name = NULL, *p;
+       struct inode *lower_dir;
+       int i;
+       struct list_head *pos;
+       struct filldir_node *cursor;
+
+       /* Find out lower parent dentry */
+       lower_dir_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+       BUG_ON(!S_ISDIR(lower_dir_dentry->d_inode->i_mode));
+       lower_dir = lower_dir_dentry->d_inode;
+       BUG_ON(!S_ISDIR(lower_dir->i_mode));
+
+       err = -ENOMEM;
+       name = __getname();
+       if (unlikely(!name))
+               goto out;
+       strcpy(name, UNIONFS_WHPFX);
+       p = name + UNIONFS_WHLEN;
+
+       err = 0;
+       for (i = 0; !err && i < namelist->size; i++) {
+               list_for_each(pos, &namelist->list[i]) {
+                       cursor =
+                               list_entry(pos, struct filldir_node,
+                                          file_list);
+                       /* Only operate on whiteouts in this branch. */
+                       if (cursor->bindex != bindex)
+                               continue;
+                       if (!cursor->whiteout)
+                               continue;
+
+                       strlcpy(p, cursor->name, PATH_MAX - UNIONFS_WHLEN);
+                       lower_dentry =
+                               lookup_lck_len(name, lower_dir_dentry,
+                                              cursor->namelen +
+                                              UNIONFS_WHLEN);
+                       if (IS_ERR(lower_dentry)) {
+                               err = PTR_ERR(lower_dentry);
+                               break;
+                       }
+                       if (lower_dentry->d_inode)
+                               err = vfs_unlink(lower_dir, lower_dentry);
+                       dput(lower_dentry);
+                       if (err)
+                               break;
+               }
+       }
+
+       __putname(name);
+
+       /* After all of the removals, we should copy the attributes once. */
+       fsstack_copy_attr_times(dentry->d_inode, lower_dir_dentry->d_inode);
+
+out:
+       return err;
+}
+
+
+void __delete_whiteouts(struct work_struct *work)
+{
+       struct sioq_args *args = container_of(work, struct sioq_args, work);
+       struct deletewh_args *d = &args->deletewh;
+
+       args->err = do_delete_whiteouts(d->dentry, d->bindex, d->namelist);
+       complete(&args->comp);
+}
+
+/* delete whiteouts in a dir (for rmdir operation) using sioq if necessary */
+int delete_whiteouts(struct dentry *dentry, int bindex,
+                    struct unionfs_dir_state *namelist)
+{
+       int err;
+       struct super_block *sb;
+       struct dentry *lower_dir_dentry;
+       struct inode *lower_dir;
+       struct sioq_args args;
+
+       sb = dentry->d_sb;
+
+       BUG_ON(!S_ISDIR(dentry->d_inode->i_mode));
+       BUG_ON(bindex < dbstart(dentry));
+       BUG_ON(bindex > dbend(dentry));
+       err = is_robranch_super(sb, bindex);
+       if (err)
+               goto out;
+
+       lower_dir_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+       BUG_ON(!S_ISDIR(lower_dir_dentry->d_inode->i_mode));
+       lower_dir = lower_dir_dentry->d_inode;
+       BUG_ON(!S_ISDIR(lower_dir->i_mode));
+
+       if (!inode_permission(lower_dir, MAY_WRITE | MAY_EXEC)) {
+               err = do_delete_whiteouts(dentry, bindex, namelist);
+       } else {
+               args.deletewh.namelist = namelist;
+               args.deletewh.dentry = dentry;
+               args.deletewh.bindex = bindex;
+               run_sioq(__delete_whiteouts, &args);
+               err = args.err;
+       }
+
+out:
+       return err;
+}
+
+/****************************************************************************
+ * Opaque directory helpers                                                 *
+ ****************************************************************************/
+
+/*
+ * is_opaque_dir: returns 0 if it is NOT an opaque dir, 1 if it is, and
+ * -errno if an error occurred trying to figure this out.
+ */
+int is_opaque_dir(struct dentry *dentry, int bindex)
+{
+       int err = 0;
+       struct dentry *lower_dentry;
+       struct dentry *wh_lower_dentry;
+       struct inode *lower_inode;
+       struct sioq_args args;
+       struct nameidata lower_nd;
+
+       lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+       lower_inode = lower_dentry->d_inode;
+
+       BUG_ON(!S_ISDIR(lower_inode->i_mode));
+
+       mutex_lock(&lower_inode->i_mutex);
+
+       if (!inode_permission(lower_inode, MAY_EXEC)) {
+               err = init_lower_nd(&lower_nd, LOOKUP_OPEN);
+               if (unlikely(err < 0)) {
+                       mutex_unlock(&lower_inode->i_mutex);
+                       goto out;
+               }
+               wh_lower_dentry =
+                       lookup_one_len_nd(UNIONFS_DIR_OPAQUE, lower_dentry,
+                                         sizeof(UNIONFS_DIR_OPAQUE) - 1,
+                                         &lower_nd);
+               release_lower_nd(&lower_nd, err);
+       } else {
+               args.is_opaque.dentry = lower_dentry;
+               run_sioq(__is_opaque_dir, &args);
+               wh_lower_dentry = args.ret;
+       }
+
+       mutex_unlock(&lower_inode->i_mutex);
+
+       if (IS_ERR(wh_lower_dentry)) {
+               err = PTR_ERR(wh_lower_dentry);
+               goto out;
+       }
+
+       /* This is an opaque dir iff wh_lower_dentry is positive */
+       err = !!wh_lower_dentry->d_inode;
+
+       dput(wh_lower_dentry);
+out:
+       return err;
+}
+
+void __is_opaque_dir(struct work_struct *work)
+{
+       struct sioq_args *args = container_of(work, struct sioq_args, work);
+       struct nameidata lower_nd;
+       int err;
+
+       err = init_lower_nd(&lower_nd, LOOKUP_OPEN);
+       if (unlikely(err < 0))
+               return;
+       args->ret = lookup_one_len_nd(UNIONFS_DIR_OPAQUE,
+                                     args->is_opaque.dentry,
+                                     sizeof(UNIONFS_DIR_OPAQUE) - 1,
+                                     &lower_nd);
+       release_lower_nd(&lower_nd, err);
+       complete(&args->comp);
+}
+
+int make_dir_opaque(struct dentry *dentry, int bindex)
+{
+       int err = 0;
+       struct dentry *lower_dentry, *diropq;
+       struct inode *lower_dir;
+       struct nameidata nd;
+       const struct cred *old_creds;
+       struct cred *new_creds;
+
+       /*
+        * Opaque directory whiteout markers are special files (like regular
+        * whiteouts), and should appear to the users as if they don't
+        * exist.  They should be created/deleted regardless of directory
+        * search/create permissions, but only for the duration of this
+        * creation of the .wh.__dir_opaque: file.  Note, this does not
+        * circumvent normal ->permission).
+        */
+       new_creds = prepare_creds();
+       if (unlikely(!new_creds)) {
+               err = -ENOMEM;
+               goto out_err;
+       }
+       cap_raise(new_creds->cap_effective, CAP_DAC_READ_SEARCH);
+       cap_raise(new_creds->cap_effective, CAP_DAC_OVERRIDE);
+       old_creds = override_creds(new_creds);
+
+       lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+       lower_dir = lower_dentry->d_inode;
+       BUG_ON(!S_ISDIR(dentry->d_inode->i_mode) ||
+              !S_ISDIR(lower_dir->i_mode));
+
+       mutex_lock(&lower_dir->i_mutex);
+       err = init_lower_nd(&nd, LOOKUP_OPEN);
+       if (unlikely(err < 0))
+               goto out;
+       diropq = lookup_one_len_nd(UNIONFS_DIR_OPAQUE, lower_dentry,
+                                  sizeof(UNIONFS_DIR_OPAQUE) - 1, &nd);
+       release_lower_nd(&nd, err);
+       if (IS_ERR(diropq)) {
+               err = PTR_ERR(diropq);
+               goto out;
+       }
+
+       err = init_lower_nd(&nd, LOOKUP_CREATE);
+       if (unlikely(err < 0))
+               goto out;
+       if (!diropq->d_inode)
+               err = vfs_create(lower_dir, diropq, S_IRUGO, &nd);
+       if (!err)
+               dbopaque(dentry) = bindex;
+       release_lower_nd(&nd, err);
+
+       dput(diropq);
+
+out:
+       mutex_unlock(&lower_dir->i_mutex);
+       revert_creds(old_creds);
+out_err:
+       return err;
+}
diff --git a/fs/unionfs/xattr.c b/fs/unionfs/xattr.c
new file mode 100644
index 0000000..a93d803
--- /dev/null
+++ b/fs/unionfs/xattr.c
@@ -0,0 +1,173 @@
+/*
+ * Copyright (c) 2003-2011 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2011 Stony Brook University
+ * Copyright (c) 2003-2011 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/* This is lifted from fs/xattr.c */
+void *unionfs_xattr_alloc(size_t size, size_t limit)
+{
+       void *ptr;
+
+       if (size > limit)
+               return ERR_PTR(-E2BIG);
+
+       if (!size)              /* size request, no buffer is needed */
+               return NULL;
+
+       ptr = kmalloc(size, GFP_KERNEL);
+       if (unlikely(!ptr))
+               return ERR_PTR(-ENOMEM);
+       return ptr;
+}
+
+/*
+ * BKL held by caller.
+ * dentry->d_inode->i_mutex locked
+ */
+ssize_t unionfs_getxattr(struct dentry *dentry, const char *name, void *value,
+                        size_t size)
+{
+       struct dentry *lower_dentry = NULL;
+       struct dentry *parent;
+       int err = -EOPNOTSUPP;
+       bool valid;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       valid = __unionfs_d_revalidate(dentry, parent, false);
+       if (unlikely(!valid)) {
+               err = -ESTALE;
+               goto out;
+       }
+
+       lower_dentry = unionfs_lower_dentry(dentry);
+
+       err = vfs_getxattr(lower_dentry, (char *) name, value, size);
+
+out:
+       unionfs_check_dentry(dentry);
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
+
+/*
+ * BKL held by caller.
+ * dentry->d_inode->i_mutex locked
+ */
+int unionfs_setxattr(struct dentry *dentry, const char *name,
+                    const void *value, size_t size, int flags)
+{
+       struct dentry *lower_dentry = NULL;
+       struct dentry *parent;
+       int err = -EOPNOTSUPP;
+       bool valid;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       valid = __unionfs_d_revalidate(dentry, parent, false);
+       if (unlikely(!valid)) {
+               err = -ESTALE;
+               goto out;
+       }
+
+       lower_dentry = unionfs_lower_dentry(dentry);
+
+       err = vfs_setxattr(lower_dentry, (char *) name, (void *) value,
+                          size, flags);
+
+out:
+       unionfs_check_dentry(dentry);
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
+
+/*
+ * BKL held by caller.
+ * dentry->d_inode->i_mutex locked
+ */
+int unionfs_removexattr(struct dentry *dentry, const char *name)
+{
+       struct dentry *lower_dentry = NULL;
+       struct dentry *parent;
+       int err = -EOPNOTSUPP;
+       bool valid;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       valid = __unionfs_d_revalidate(dentry, parent, false);
+       if (unlikely(!valid)) {
+               err = -ESTALE;
+               goto out;
+       }
+
+       lower_dentry = unionfs_lower_dentry(dentry);
+
+       err = vfs_removexattr(lower_dentry, (char *) name);
+
+out:
+       unionfs_check_dentry(dentry);
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
+
+/*
+ * BKL held by caller.
+ * dentry->d_inode->i_mutex locked
+ */
+ssize_t unionfs_listxattr(struct dentry *dentry, char *list, size_t size)
+{
+       struct dentry *lower_dentry = NULL;
+       struct dentry *parent;
+       int err = -EOPNOTSUPP;
+       char *encoded_list = NULL;
+       bool valid;
+
+       unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_CHILD);
+       parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+       unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+       valid = __unionfs_d_revalidate(dentry, parent, false);
+       if (unlikely(!valid)) {
+               err = -ESTALE;
+               goto out;
+       }
+
+       lower_dentry = unionfs_lower_dentry(dentry);
+
+       encoded_list = list;
+       err = vfs_listxattr(lower_dentry, encoded_list, size);
+
+out:
+       unionfs_check_dentry(dentry);
+       unionfs_unlock_dentry(dentry);
+       unionfs_unlock_parent(dentry, parent);
+       unionfs_read_unlock(dentry->d_sb);
+       return err;
+}
diff --git a/include/linux/fs_stack.h b/include/linux/fs_stack.h
index da317c7..64f1ced 100644
--- a/include/linux/fs_stack.h
+++ b/include/linux/fs_stack.h
@@ -1,7 +1,19 @@
+/*
+ * Copyright (c) 2006-2009 Erez Zadok
+ * Copyright (c) 2006-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2006-2009 Stony Brook University
+ * Copyright (c) 2006-2009 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
 #ifndef _LINUX_FS_STACK_H
 #define _LINUX_FS_STACK_H
 
-/* This file defines generic functions used primarily by stackable
+/*
+ * This file defines generic functions used primarily by stackable
  * filesystems; none of these functions require i_mutex to be held.
  */
 
diff --git a/include/linux/magic.h b/include/linux/magic.h
index 2d4beab..39f5798 100644
--- a/include/linux/magic.h
+++ b/include/linux/magic.h
@@ -50,6 +50,8 @@
 #define REISER2FS_SUPER_MAGIC_STRING   "ReIsEr2Fs"
 #define REISER2FS_JR_SUPER_MAGIC_STRING        "ReIsEr3Fs"
 
+#define UNIONFS_SUPER_MAGIC 0xf15f083d
+
 #define SMB_SUPER_MAGIC                0x517B
 #define USBDEVICE_SUPER_MAGIC  0x9fa2
 #define CGROUP_SUPER_MAGIC     0x27e0eb
diff --git a/include/linux/namei.h b/include/linux/namei.h
index ffc0213..99802c3 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -84,8 +84,11 @@ extern int vfs_path_lookup(struct dentry *, struct vfsmount *,
 
 extern struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
                int (*open)(struct inode *, struct file *));
+extern void release_open_intent(struct nameidata *);
 
 extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
+extern struct dentry *lookup_one_len_nd(const char *, struct dentry *, int,
+                                     struct nameidata *nd);
 
 extern int follow_down_one(struct path *);
 extern int follow_down(struct path *);
diff --git a/include/linux/splice.h b/include/linux/splice.h
index 26e5b61..28213e6 100644
--- a/include/linux/splice.h
+++ b/include/linux/splice.h
@@ -81,6 +81,11 @@ extern ssize_t splice_to_pipe(struct pipe_inode_info *,
                              struct splice_pipe_desc *);
 extern ssize_t splice_direct_to_actor(struct file *, struct splice_desc *,
                                      splice_direct_actor *);
+extern long vfs_splice_from(struct pipe_inode_info *pipe, struct file *out,
+                           loff_t *ppos, size_t len, unsigned int flags);
+extern long vfs_splice_to(struct file *in, loff_t *ppos,
+                         struct pipe_inode_info *pipe, size_t len,
+                         unsigned int flags);
 
 /*
  * for dynamic pipe sizing
diff --git a/include/linux/union_fs.h b/include/linux/union_fs.h
new file mode 100644
index 0000000..c84d97e
--- /dev/null
+++ b/include/linux/union_fs.h
@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2003-2009 Erez Zadok
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2003-2009 Stony Brook University
+ * Copyright (c) 2003-2009 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _LINUX_UNION_FS_H
+#define _LINUX_UNION_FS_H
+
+/*
+ * DEFINITIONS FOR USER AND KERNEL CODE:
+ */
+# define UNIONFS_IOCTL_INCGEN          _IOR(0x15, 11, int)
+# define UNIONFS_IOCTL_QUERYFILE       _IOR(0x15, 15, int)
+
+#endif /* _LINUX_UNIONFS_H */
+
diff --git a/security/security.c b/security/security.c
index d754249..f7e8373 100644
--- a/security/security.c
+++ b/security/security.c
@@ -538,6 +538,7 @@ int security_inode_permission(struct inode *inode, int mask)
                return 0;
        return security_ops->inode_permission(inode, mask);
 }
+EXPORT_SYMBOL(security_inode_permission);
 
 int security_inode_setattr(struct dentry *dentry, struct iattr *attr)
 {