__fsnotify_parent() has an optimization in place to avoid unneeded take_dentry_name_snapshot(). When fsnotify_nameremove() was changed not to call __fsnotify_parent(), we left out the optimization. Kernel test robot reported a 5% performance regression in concurrent unlink() workload. Modify __fsnotify_parent() so that it can be called also to report directory modififcation events and use it from fsnotify_nameremove(). Reported-by: kernel test robot <rong.a.chen(a)intel.com&gt; Link: https://lore.kernel.org/lkml/20190505062153.GG29809@shao2-debian/ Link: https://lore.kernel.org/linux-fsdevel/20190104090357.GD22409@quack2.suse.cz/ Fixes: 5f02a8776384 ("fsnotify: annotate directory entry modification events") Signed-off-by: Amir Goldstein <amir73il(a)gmail.com&gt; --- Jan, A nicer approach reusing __fsnotify_parent() instead of copying code from it. This version does not apply cleanly to Al's for-next branch (there are some fsnotify changes in work.dcache). The conflict is trivial and resolved on my fsnotify branch [1].

diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c index df06f3da166c..265b726d6e8d 100644 --- a/fs/notify/fsnotify.c +++ b/fs/notify/fsnotify.c @@ -151,31 +151,31 @@ void __fsnotify_update_child_dentry_flags(struct inode *inode) spin_unlock(&inode->i_lock); } -/* Notify this dentry's parent about a child's events. */ +/* + * Notify this dentry's parent about an event and make sure that name is stable. + * Events "on child" are only reported if parent is watching. + * Directory modification events are also reported if super block is watching. + */ int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask) { struct dentry *parent; struct inode *p_inode; int ret = 0; + bool on_child = (mask & FS_EVENT_ON_CHILD); + __u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS); - if (!dentry) - dentry = path->dentry; - - if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED)) + if (on_child && !(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED)) return 0; parent = dget_parent(dentry); p_inode = parent->d_inode; - if (unlikely(!fsnotify_inode_watches_children(p_inode))) { + if (on_child && unlikely(!fsnotify_inode_watches_children(p_inode))) { __fsnotify_update_child_dentry_flags(p_inode); - } else if (p_inode->i_fsnotify_mask & mask & ALL_FSNOTIFY_EVENTS) { + } else if ((p_inode->i_fsnotify_mask & test_mask) || + (!on_child && (dentry->d_sb->s_fsnotify_mask & test_mask))) { struct name_snapshot name; - /* we are notifying a parent so come up with the new mask which - * specifies these are events which came from a child. */ - mask |= FS_EVENT_ON_CHILD; - take_dentry_name_snapshot(&name, dentry); if (path) ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH, diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h index 09587e2860b5..8641bf9a1eda 100644 --- a/include/linux/fsnotify.h +++ b/include/linux/fsnotify.h @@ -37,7 +37,7 @@ static inline int fsnotify_parent(const struct path *path, if (!dentry) dentry = path->dentry; - return __fsnotify_parent(path, dentry, mask); + return __fsnotify_parent(path, dentry, mask | FS_EVENT_ON_CHILD); } /* @@ -158,13 +158,11 @@ static inline void fsnotify_vfsmount_delete(struct vfsmount *mnt) * dentry->d_parent should be stable. However there are some corner cases where * inode lock is not held. So to be on the safe side and be reselient to future * callers and out of tree users of d_delete(), we do not assume that d_parent - * and d_name are stable and we use dget_parent() and + * and d_name are stable and we use __fsnotify_parent() to * take_dentry_name_snapshot() to grab stable references. */ static inline void fsnotify_nameremove(struct dentry *dentry, int isdir) { - struct dentry *parent; - struct name_snapshot name; __u32 mask = FS_DELETE; /* d_delete() of pseudo inode? (e.g. __ns_get_path() playing tricks) */ @@ -174,14 +172,7 @@ static inline void fsnotify_nameremove(struct dentry *dentry, int isdir) if (isdir) mask |= FS_ISDIR; - parent = dget_parent(dentry); - take_dentry_name_snapshot(&name, dentry); - - fsnotify(d_inode(parent), mask, d_inode(dentry), FSNOTIFY_EVENT_INODE, - name.name, 0); - - release_dentry_name_snapshot(&name); - dput(parent); + __fsnotify_parent(NULL, dentry, mask); } /* -- 2.17.1