inotify: tail drop inotify q_overflow events

In f44aebcc the tail drop logic of events with no file backing
(q_overflow and in_ignored) was reversed so IN_IGNORED events would
never be tail dropped.  This now means that Q_OVERFLOW events are NOT
tail dropped.  The fix is to not tail drop IN_IGNORED, but to tail drop
Q_OVERFLOW.
Signed-off-by: NEric Paris <eparis@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/notify/notification.c

@@ -153,6 +153,10 @@ static bool event_compare(struct fsnotify_event *old, struct fsnotify_event *new
 				return true;
 			break;
 		case (FSNOTIFY_EVENT_NONE):
+			if (old->mask & FS_Q_OVERFLOW)
+				return true;
+			else if (old->mask & FS_IN_IGNORED)
+				return false;
 			return false;
 		};
 	}