1 files changed, 13 insertions, 28 deletions

diff --git a/fs/notify/notification.c b/fs/notify/notification.c
index b493c37..dafd0b7 100644
--- a/fs/notify/notification.c
+++ b/fs/notify/notification.c
@@ -289,43 +289,28 @@ static void initialize_event(struct fsnotify_event *event)
 
 /*
  * Caller damn well better be holding whatever mutex is protecting the
- * old_holder->event_list.
+ * old_holder->event_list and the new_event must be a clean event which
+ * cannot be found anywhere else in the kernel.
  */
 int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
 			   struct fsnotify_event *new_event)
 {
 	struct fsnotify_event *old_event = old_holder->event;
-	struct fsnotify_event_holder *new_holder = NULL;
+	struct fsnotify_event_holder *new_holder = &new_event->holder;
+
+	enum event_spinlock_class {
+		SPINLOCK_OLD,
+		SPINLOCK_NEW,
+	};
 
 	/*
-	 * There is one fsnotify_event_holder embedded inside each fsnotify_event.
-	 * Check if we expect to be able to use that holder.  If not alloc a new
-	 * holder.
-	 * For the overflow event it's possible that something will use the in
-	 * event holder before we get the lock so we may need to jump back and
-	 * alloc a new holder, this can't happen for most events...
+	 * if the new_event's embedded holder is in use someone
+	 * screwed up and didn't give us a clean new event.
 	 */
-	if (!list_empty(&new_event->holder.event_list)) {
-alloc_holder:
-		new_holder = fsnotify_alloc_event_holder();
-		if (!new_holder)
-			return -ENOMEM;
-	}
+	BUG_ON(!list_empty(&new_holder->event_list));
 
-	spin_lock(&old_event->lock);
-	spin_lock(&new_event->lock);
-
-	if (list_empty(&new_event->holder.event_list)) {
-		if (unlikely(new_holder))
-			fsnotify_destroy_event_holder(new_holder);
-		new_holder = &new_event->holder;
-	} else if (unlikely(!new_holder)) {
-		/* between the time we checked above and got the lock the in
-		 * event holder was used, go back and get a new one */
-		spin_unlock(&new_event->lock);
-		spin_unlock(&old_event->lock);
-		goto alloc_holder;
-	}
+	spin_lock_nested(&old_event->lock, SPINLOCK_OLD);
+	spin_lock_nested(&new_event->lock, SPINLOCK_NEW);
 
 	new_holder->event = new_event;
 	list_replace_init(&old_holder->event_list, &new_holder->event_list);