ANDROID: vfs: add d_canonical_path for stacked filesystem support
Inotify does not currently know when a filesystem
is acting as a wrapper around another fs. This means
that inotify watchers will miss any modifications to
the base file, as well as any made in a separate
stacked fs that points to the same file.
d_canonical_path solves this problem by allowing the fs
to map a dentry to a path in the lower fs. Inotify
can use it to find the appropriate place to watch to
be informed of all changes to a file.
Change-Id: I09563baffad1711a045e45c1bd0bd8713c2cc0b6
Signed-off-by: Daniel Rosenberg <drosen@google.com>
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 69d1ea3..6413928 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -702,6 +702,8 @@
struct fsnotify_group *group;
struct inode *inode;
struct path path;
+ struct path alteredpath;
+ struct path *canonical_path = &path;
struct fd f;
int ret;
unsigned flags = 0;
@@ -741,13 +743,22 @@
if (ret)
goto fput_and_out;
+ /* support stacked filesystems */
+ if(path.dentry && path.dentry->d_op) {
+ if (path.dentry->d_op->d_canonical_path) {
+ path.dentry->d_op->d_canonical_path(path.dentry, &alteredpath);
+ canonical_path = &alteredpath;
+ path_put(&path);
+ }
+ }
+
/* inode held in place by reference to path; group by fget on fd */
- inode = path.dentry->d_inode;
+ inode = canonical_path->dentry->d_inode;
group = f.file->private_data;
/* create/update an inode mark */
ret = inotify_update_watch(group, inode, mask);
- path_put(&path);
+ path_put(canonical_path);
fput_and_out:
fdput(f);
return ret;
@@ -814,7 +825,7 @@
BUILD_BUG_ON(IN_ISDIR != FS_ISDIR);
BUILD_BUG_ON(IN_ONESHOT != FS_IN_ONESHOT);
- BUG_ON(hweight32(ALL_INOTIFY_BITS) != 21);
+ BUG_ON(hweight32(ALL_INOTIFY_BITS) != 22);
inotify_inode_mark_cachep = KMEM_CACHE(inotify_inode_mark, SLAB_PANIC);
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 5beed7b..8f369ac 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -142,6 +142,7 @@
int (*d_manage)(struct dentry *, bool);
struct dentry *(*d_real)(struct dentry *, const struct inode *,
unsigned int);
+ void (*d_canonical_path)(const struct dentry *, struct path *);
} ____cacheline_aligned;
/*