From eb9e939dacee9e2422d62e9a8089e4ce4227ea64 Mon Sep 17 00:00:00 2001 From: Daniel Rosenberg Date: Thu, 11 Feb 2016 16:44:15 -0800 Subject: [PATCH] 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. Bug: 70706497 Bug: 120446149 Change-Id: I09563baffad1711a045e45c1bd0bd8713c2cc0b6 Signed-off-by: Daniel Rosenberg [astrachan: Folded 34df4102216e ("ANDROID: fsnotify: Notify lower fs of open") into this patch] Signed-off-by: Alistair Strachan --- fs/notify/inotify/inotify_user.c | 15 +++++++++++++-- include/linux/dcache.h | 1 + include/linux/fsnotify.h | 7 +++++++ 3 files changed, 21 insertions(+), 2 deletions(-) diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c index aca7bd8dcacd..f9a95fb1008f 100644 --- a/fs/notify/inotify/inotify_user.c +++ b/fs/notify/inotify/inotify_user.c @@ -699,6 +699,8 @@ 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; @@ -742,13 +744,22 @@ 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 ef4b70f64f33..2dc6915d7abf 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -146,6 +146,7 @@ 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 fd1ce10553bf..61b72519f2f2 100644 --- a/include/linux/fsnotify.h +++ b/include/linux/fsnotify.h @@ -210,12 +210,19 @@ 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); }