From: Amir Goldstein <amir73il@xxxxxxxxx> 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@xxxxxxxxx> Signed-off-by: Jan Kara <jack@xxxxxxx> Link: https://patch.msgid.link/2ddcc9f8d1fde48d085318a6b5a889289d8871d8.1731684329.git.josef@xxxxxxxxxxxxxx --- fs/notify/fsnotify.c | 27 +++++++++++++++++++++++++-- include/linux/fsnotify_backend.h | 3 +++ 2 files changed, 28 insertions(+), 2 deletions(-) diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c index 569ec356e4ce..dd1dffd89fd6 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)) @@ -658,6 +660,27 @@ void file_set_fsnotify_mode(struct file *file) file->f_mode |= FMODE_NONOTIFY | FMODE_NONOTIFY_PERM; return; } + + /* + * OK, there are some pre-content watchers. Check if anybody can be + * watching for pre-content events on *this* file. + */ + mnt_mask = READ_ONCE(real_mount(file->f_path.mnt)->mnt_fsnotify_mask); + if (likely(!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED) && + !fsnotify_object_watched(d_inode(dentry), mnt_mask, + FSNOTIFY_PRE_CONTENT_EVENTS))) { + file->f_mode |= FMODE_NONOTIFY | FMODE_NONOTIFY_PERM; + return; + } + + /* Even parent is not watching for pre-content events on this file? */ + parent = dget_parent(dentry); + p_mask = fsnotify_inode_watches_children(d_inode(parent)); + dput(parent); + if (!(p_mask & FSNOTIFY_PRE_CONTENT_EVENTS)) { + file->f_mode |= FMODE_NONOTIFY | FMODE_NONOTIFY_PERM; + return; + } } #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) -- 2.35.3
