1 files changed, 96 insertions, 53 deletions

diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 3e594ce41010..fc0df4442f7b 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -122,26 +122,27 @@ u32 fsnotify_recalc_mask(struct hlist_head *head)
 }
 
 /*
- * Any time a mark is getting freed we end up here.
- * The caller had better be holding a reference to this mark so we don't actually
- * do the final put under the mark->lock
+ * Remove mark from inode / vfsmount list, group list, drop inode reference
+ * if we got one.
+ *
+ * Must be called with group->mark_mutex held.
  */
-void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
-				  struct fsnotify_group *group)
+void fsnotify_detach_mark(struct fsnotify_mark *mark)
 {
 	struct inode *inode = NULL;
+	struct fsnotify_group *group = mark->group;
 
 	BUG_ON(!mutex_is_locked(&group->mark_mutex));
 
 	spin_lock(&mark->lock);
 
 	/* something else already called this function on this mark */
-	if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
+	if (!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
 		spin_unlock(&mark->lock);
 		return;
 	}
 
-	mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
+	mark->flags &= ~FSNOTIFY_MARK_FLAG_ATTACHED;
 
 	if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
 		inode = mark->inode;
@@ -150,62 +151,92 @@ void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
 		fsnotify_destroy_vfsmount_mark(mark);
 	else
 		BUG();
+	/*
+	 * Note that we didn't update flags telling whether inode cares about
+	 * what's happening with children. We update these flags from
+	 * __fsnotify_parent() lazily when next event happens on one of our
+	 * children.
+	 */
 
 	list_del_init(&mark->g_list);
+
 	spin_unlock(&mark->lock);
 
 	if (inode && (mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED))
 		iput(inode);
 
+	atomic_dec(&group->num_marks);
+}
+
+/*
+ * Free fsnotify mark. The freeing is actually happening from a kthread which
+ * first waits for srcu period end. Caller must have a reference to the mark
+ * or be protected by fsnotify_mark_srcu.
+ */
+void fsnotify_free_mark(struct fsnotify_mark *mark)
+{
+	struct fsnotify_group *group = mark->group;
+
+	spin_lock(&mark->lock);
+	/* something else already called this function on this mark */
+	if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
+		spin_unlock(&mark->lock);
+		return;
+	}
+	mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
+	spin_unlock(&mark->lock);
+
 	spin_lock(&destroy_lock);
 	list_add(&mark->g_list, &destroy_list);
 	spin_unlock(&destroy_lock);
 	wake_up(&destroy_waitq);
 
 	/*
-	 * __fsnotify_update_child_dentry_flags(inode);
-	 *
-	 * I really want to call that, but we can't, we have no idea if the inode
-	 * still exists the second we drop the mark->lock.
-	 *
-	 * The next time an event arrive to this inode from one of it's children
-	 * __fsnotify_parent will see that the inode doesn't care about it's
-	 * children and will update all of these flags then.  So really this
-	 * is just a lazy update (and could be a perf win...)
+	 * Some groups like to know that marks are being freed.  This is a
+	 * callback to the group function to let it know that this mark
+	 * is being freed.
 	 */
-
-	atomic_dec(&group->num_marks);
+	if (group->ops->freeing_mark)
+		group->ops->freeing_mark(mark, group);
 }
 
 void fsnotify_destroy_mark(struct fsnotify_mark *mark,
 			   struct fsnotify_group *group)
 {
 	mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
-	fsnotify_destroy_mark_locked(mark, group);
+	fsnotify_detach_mark(mark);
 	mutex_unlock(&group->mark_mutex);
+	fsnotify_free_mark(mark);
 }
 
-/*
- * Destroy all marks in the given list. The marks must be already detached from
- * the original inode / vfsmount. Note that we can race with
- * fsnotify_clear_marks_by_group_flags(). However we hold a reference to each
- * mark so they won't get freed from under us and nobody else touches our
- * free_list list_head.
- */
-void fsnotify_destroy_marks(struct list_head *to_free)
+void fsnotify_destroy_marks(struct hlist_head *head, spinlock_t *lock)
 {
-	struct fsnotify_mark *mark, *lmark;
-	struct fsnotify_group *group;
-
-	list_for_each_entry_safe(mark, lmark, to_free, free_list) {
-		spin_lock(&mark->lock);
-		fsnotify_get_group(mark->group);
-		group = mark->group;
-		spin_unlock(&mark->lock);
+	struct fsnotify_mark *mark;
 
-		fsnotify_destroy_mark(mark, group);
+	while (1) {
+		/*
+		 * We have to be careful since we can race with e.g.
+		 * fsnotify_clear_marks_by_group() and once we drop 'lock',
+		 * mark can get removed from the obj_list and destroyed. But
+		 * we are holding mark reference so mark cannot be freed and
+		 * calling fsnotify_destroy_mark() more than once is fine.
+		 */
+		spin_lock(lock);
+		if (hlist_empty(head)) {
+			spin_unlock(lock);
+			break;
+		}
+		mark = hlist_entry(head->first, struct fsnotify_mark, obj_list);
+		/*
+		 * We don't update i_fsnotify_mask / mnt_fsnotify_mask here
+		 * since inode / mount is going away anyway. So just remove
+		 * mark from the list.
+		 */
+		hlist_del_init_rcu(&mark->obj_list);
+		fsnotify_get_mark(mark);
+		spin_unlock(lock);
+		fsnotify_destroy_mark(mark, mark->group);
 		fsnotify_put_mark(mark);
-		fsnotify_put_group(group);
 	}
 }
 
@@ -317,7 +348,7 @@ int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
 	 * inode->i_lock
 	 */
 	spin_lock(&mark->lock);
-	mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE;
+	mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE | FSNOTIFY_MARK_FLAG_ATTACHED;
 
 	fsnotify_get_group(group);
 	mark->group = group;
@@ -391,22 +422,43 @@ struct fsnotify_mark *fsnotify_find_mark(struct hlist_head *head,
 }
 
 /*
- * Clear any marks in a group in which mark->flags & flags is true.
+ * clear any marks in a group in which mark->flags & flags is true
  */
 void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group,
 					 unsigned int flags)
 {
 	struct fsnotify_mark *lmark, *mark;
+	LIST_HEAD(to_free);
 
+	/*
+	 * We have to be really careful here. Anytime we drop mark_mutex, e.g.
+	 * fsnotify_clear_marks_by_inode() can come and free marks. Even in our
+	 * to_free list so we have to use mark_mutex even when accessing that
+	 * list. And freeing mark requires us to drop mark_mutex. So we can
+	 * reliably free only the first mark in the list. That's why we first
+	 * move marks to free to to_free list in one go and then free marks in
+	 * to_free list one by one.
+	 */
 	mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
 	list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) {
-		if (mark->flags & flags) {
-			fsnotify_get_mark(mark);
-			fsnotify_destroy_mark_locked(mark, group);
-			fsnotify_put_mark(mark);
-		}
+		if (mark->flags & flags)
+			list_move(&mark->g_list, &to_free);
 	}
 	mutex_unlock(&group->mark_mutex);
+
+	while (1) {
+		mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
+		if (list_empty(&to_free)) {
+			mutex_unlock(&group->mark_mutex);
+			break;
+		}
+		mark = list_first_entry(&to_free, struct fsnotify_mark, g_list);
+		fsnotify_get_mark(mark);
+		fsnotify_detach_mark(mark);
+		mutex_unlock(&group->mark_mutex);
+		fsnotify_free_mark(mark);
+		fsnotify_put_mark(mark);
+	}
 }
 
 /*
@@ -445,7 +497,6 @@ static int fsnotify_mark_destroy(void *ignored)
 {
 	struct fsnotify_mark *mark, *next;
 	struct list_head private_destroy_list;
-	struct fsnotify_group *group;
 
 	for (;;) {
 		spin_lock(&destroy_lock);
@@ -457,14 +508,6 @@ static int fsnotify_mark_destroy(void *ignored)
 
 		list_for_each_entry_safe(mark, next, &private_destroy_list, g_list) {
 			list_del_init(&mark->g_list);
-			group = mark->group;
-			/*
-			 * Some groups like to know that marks are being freed.
-			 * This is a callback to the group function to let it
-			 * know that this mark is being freed.
-			 */
-			if (group && group->ops->freeing_mark)
-				group->ops->freeing_mark(mark, group);
 			fsnotify_put_mark(mark);
 		}