diff options
| author | Amir Goldstein <amir73il@gmail.com> | 2024-11-15 10:30:16 -0500 |
|---|---|---|
| committer | Jan Kara <jack@suse.cz> | 2024-12-10 12:03:16 +0100 |
| commit | 318652e07fa5b1743d08eeccd69a1f47f2c15710 (patch) | |
| tree | 368f2283af2d2a436bf73a8e24ad7f9f9779ea1e | |
| parent | a94204f4d48e28a711b7ed10399f749286c433e3 (diff) | |
fsnotify: check if file is actually being watched for pre-content events on open
So far, we set FMODE_NONOTIFY_ flags at open time if we know that there
are no permission event watchers at all on the filesystem, but lack of
FMODE_NONOTIFY_ flags does not mean that the file is actually watched.
For pre-content events, it is possible to optimize things so that we
don't bother trying to send pre-content events if file was not watched
(through sb, mnt, parent or inode itself) on open. Set FMODE_NONOTIFY_
flags according to that.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/2ddcc9f8d1fde48d085318a6b5a889289d8871d8.1731684329.git.josef@toxicpanda.com
| -rw-r--r-- | fs/notify/fsnotify.c | 29 | ||||
| -rw-r--r-- | include/linux/fsnotify_backend.h | 3 |
2 files changed, 29 insertions, 3 deletions
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c index 569ec356e4ce..9e483fface1e 100644 --- a/fs/notify/fsnotify.c +++ b/fs/notify/fsnotify.c @@ -193,7 +193,7 @@ static bool fsnotify_event_needs_parent(struct inode *inode, __u32 mnt_mask, return mask & marks_mask; } -/* Are there any inode/mount/sb objects that are interested in this event? */ +/* Are there any inode/mount/sb objects that watch for these events? */ static inline bool fsnotify_object_watched(struct inode *inode, __u32 mnt_mask, __u32 mask) { @@ -632,7 +632,9 @@ EXPORT_SYMBOL_GPL(fsnotify); */ void file_set_fsnotify_mode(struct file *file) { - struct super_block *sb = file->f_path.dentry->d_sb; + struct dentry *dentry = file->f_path.dentry, *parent; + struct super_block *sb = dentry->d_sb; + __u32 mnt_mask, p_mask; /* Is it a file opened by fanotify? */ if (FMODE_FSNOTIFY_NONE(file->f_mode)) @@ -653,11 +655,32 @@ void file_set_fsnotify_mode(struct file *file) * If there are permission event watchers but no pre-content event * watchers, set FMODE_NONOTIFY | FMODE_NONOTIFY_PERM to indicate that. */ - if (likely(!fsnotify_sb_has_priority_watchers(sb, + if ((!d_is_dir(dentry) && !d_is_reg(dentry)) || + likely(!fsnotify_sb_has_priority_watchers(sb, FSNOTIFY_PRIO_PRE_CONTENT))) { file->f_mode |= FMODE_NONOTIFY | FMODE_NONOTIFY_PERM; return; } + + /* + * OK, there are some pre-content watchers. Check if anybody is + * watching for pre-content events on *this* file. + */ + mnt_mask = READ_ONCE(real_mount(file->f_path.mnt)->mnt_fsnotify_mask); + if (unlikely(fsnotify_object_watched(d_inode(dentry), mnt_mask, + FSNOTIFY_PRE_CONTENT_EVENTS))) + return; + + /* Is parent watching for pre-content events on this file? */ + if (dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED) { + parent = dget_parent(dentry); + p_mask = fsnotify_inode_watches_children(d_inode(parent)); + dput(parent); + if (p_mask & FSNOTIFY_PRE_CONTENT_EVENTS) + return; + } + /* Nobody watching for pre-content events from this file */ + file->f_mode |= FMODE_NONOTIFY | FMODE_NONOTIFY_PERM; } #endif diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h index 3ecf7768e577..9c105244815d 100644 --- a/include/linux/fsnotify_backend.h +++ b/include/linux/fsnotify_backend.h @@ -77,6 +77,9 @@ */ #define ALL_FSNOTIFY_DIRENT_EVENTS (FS_CREATE | FS_DELETE | FS_MOVE | FS_RENAME) +/* Pre-content events can be used to fill file content */ +#define FSNOTIFY_PRE_CONTENT_EVENTS 0 + #define ALL_FSNOTIFY_PERM_EVENTS (FS_OPEN_PERM | FS_ACCESS_PERM | \ FS_OPEN_EXEC_PERM) |