| From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 |
| From: Alessio Balsini <balsini@google.com> |
| Date: Tue, 27 Oct 2020 13:24:03 +0000 |
| Subject: 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. |
| |
| [CPNOTE: 20/07/21] Lee: Requested status from Alessio via the bug |
| |
| Original-Change-Id: I09563baffad1711a045e45c1bd0bd8713c2cc0b6 |
| |
| 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 |
| 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> |
| Change-Id: Ifb6719eaa466ab9cc98ab4b02866de16f7c73cbf |
| [maennich: folded into this patch: |
| ffea51ec1f7a ("ANDROID: vfs: d_canonical_path cleanup #if 0")] |
| Signed-off-by: Matthias Maennich <maennich@google.com> |
| --- |
| fs/notify/inotify/inotify_user.c | 16 ++++++++++++++-- |
| include/linux/dcache.h | 1 + |
| 2 files changed, 15 insertions(+), 2 deletions(-) |
| |
| diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c |
| --- a/fs/notify/inotify/inotify_user.c |
| +++ b/fs/notify/inotify/inotify_user.c |
| @@ -712,6 +712,8 @@ 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; |
| @@ -758,13 +760,23 @@ 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 |
| --- a/include/linux/dcache.h |
| +++ b/include/linux/dcache.h |
| @@ -149,6 +149,7 @@ 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; |
| |
| /* |