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ANDROID: vfs: d_canonical_path for stacked FS

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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: Icc7ff8f4798bf907d5c9ce32065a0471db751a26
Test: FileObserverTest and FileObserverTestLegacyPath on Cuttlefish
Bug: 171780975
Signed-off-by: Daniel Rosenberg <drosen@google.com>
[astrachan: Folded 34df4102216e ("ANDROID: fsnotify: Notify lower fs of
 astrachan:           open") into this patch]
Signed-off-by: Alistair Strachan <astrachan@google.com>
Signed-off-by: Yongqin Liu <yongqin.liu@linaro.org>
Signed-off-by: Alessio Balsini <balsini@google.com>
Git-commit: f37e05049bf8197901ec042818a64110e59fac41
Git-repo: https://android.googlesource.com/kernel/common/
Signed-off-by: Pradeep P V K <ppvk@codeaurora.org>
This commit is contained in:
Alessio Balsini 2020-10-27 13:24:03 +00:00 committed by Pradeep P V K
parent af6e75fdb0
commit 596207b5c5
1 changed files with 0 additions and 7 deletions
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7
include/linux/fsnotify.h
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@ -210,19 +210,12 @@ static inline void fsnotify_modify(struct file *file)
static inline void fsnotify_open(struct file *file)
{
const struct path *path = &file->f_path;
struct path lower_path;
struct inode *inode = file_inode(file);
__u32 mask = FS_OPEN;
if (S_ISDIR(inode->i_mode))
mask |= FS_ISDIR;
if (path->dentry->d_op && path->dentry->d_op->d_canonical_path) {
path->dentry->d_op->d_canonical_path(path, &lower_path);
fsnotify_parent(&lower_path, NULL, mask);
fsnotify(lower_path.dentry->d_inode, mask, &lower_path, FSNOTIFY_EVENT_PATH, NULL, 0);
path_put(&lower_path);
}
fsnotify_parent(path, NULL, mask);
fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
}