From f37e05049bf8197901ec042818a64110e59fac41 Mon Sep 17 00:00:00 2001 From: Alessio Balsini Date: Tue, 27 Oct 2020 13:24:03 +0000 Subject: [PATCH] ANDROID: vfs: d_canonical_path for stacked FS 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. Original-Change-Id: I09563baffad1711a045e45c1bd0bd8713c2cc0b6 Test: FileObserverTest and FileObserverTestLegacyPath on Cuttlefish Bug: 171780975 Signed-off-by: Daniel Rosenberg [astrachan: Folded 34df4102216e ("ANDROID: fsnotify: Notify lower fs of open") into this patch] Signed-off-by: Alistair Strachan Signed-off-by: Yongqin Liu Signed-off-by: Alessio Balsini Change-Id: Ifb6719eaa466ab9cc98ab4b02866de16f7c73cbf --- fs/notify/inotify/inotify_user.c | 16 ++++++++++++++-- include/linux/dcache.h | 1 + include/linux/fsnotify.h | 15 +++++++++++++++ 3 files changed, 30 insertions(+), 2 deletions(-) diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c index 186722ba3894..8755e49c6ee8 100644 --- a/fs/notify/inotify/inotify_user.c +++ b/fs/notify/inotify/inotify_user.c @@ -703,6 +703,8 @@ SYSCALL_DEFINE3(inotify_add_watch, int, fd, const char __user *, pathname, 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; @@ -749,13 +751,23 @@ SYSCALL_DEFINE3(inotify_add_watch, int, fd, const char __user *, pathname, 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, + &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; diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 6f95c3300cbb..49d0b6f732f2 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -147,6 +147,7 @@ struct dentry_operations { struct vfsmount *(*d_automount)(struct path *); int (*d_manage)(const struct path *, bool); struct dentry *(*d_real)(struct dentry *, const struct inode *); + void (*d_canonical_path)(const struct path *, struct path *); } ____cacheline_aligned; /* diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h index f8acddcf54fb..53314522c7f3 100644 --- a/include/linux/fsnotify.h +++ b/include/linux/fsnotify.h @@ -260,12 +260,27 @@ static inline void fsnotify_modify(struct file *file) */ static inline void fsnotify_open(struct file *file) { +#if 0 + const struct path *path = &file->f_path; + struct inode *inode = file_inode(file); + struct path lower_path; +#endif __u32 mask = FS_OPEN; if (file->f_flags & __FMODE_EXEC) mask |= FS_OPEN_EXEC; fsnotify_file(file, mask); +#if 0 + 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_path(inode, path, mask); +#endif } /*