summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorAmir Goldstein <amir73il@gmail.com>2024-11-15 10:30:16 -0500
committerJan Kara <jack@suse.cz>2024-12-10 12:03:16 +0100
commit318652e07fa5b1743d08eeccd69a1f47f2c15710 (patch)
tree368f2283af2d2a436bf73a8e24ad7f9f9779ea1e
parenta94204f4d48e28a711b7ed10399f749286c433e3 (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.c29
-rw-r--r--include/linux/fsnotify_backend.h3
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)