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-rw-r--r--fs/notify/notification.c13
1 files changed, 11 insertions, 2 deletions
diff --git a/fs/notify/notification.c b/fs/notify/notification.c
index 8a7a8cd041e8..1a8010e7a2a0 100644
--- a/fs/notify/notification.c
+++ b/fs/notify/notification.c
@@ -74,8 +74,17 @@ void fsnotify_destroy_event(struct fsnotify_group *group,
/* Overflow events are per-group and we don't want to free them */
if (!event || event->mask == FS_Q_OVERFLOW)
return;
- /* If the event is still queued, we have a problem... */
- WARN_ON(!list_empty(&event->list));
+ /*
+ * If the event is still queued, we have a problem... Do an unreliable
+ * lockless check first to avoid locking in the common case. The
+ * locking may be necessary for permission events which got removed
+ * from the list by a different CPU than the one freeing the event.
+ */
+ if (!list_empty(&event->list)) {
+ spin_lock(&group->notification_lock);
+ WARN_ON(!list_empty(&event->list));
+ spin_unlock(&group->notification_lock);
+ }
group->ops->free_event(event);
}