inotify: fix coalesce duplicate events into a single event in special case

If we do rename a dir entry, like this:

  rename("/tmp/ino7UrgoJ.rename1", "/tmp/ino7UrgoJ.rename2")
  rename("/tmp/ino7UrgoJ.rename2", "/tmp/ino7UrgoJ")

The duplicate events should be coalesced into a single event. But those two
events do not be coalesced into a single event, due to some bad check in
event_compare(). It can not match the two NULL inodes as the same event.
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Eric Paris <eparis@redhat.com>

fs/notify/notification.c

@@ -143,7 +143,7 @@ static bool event_compare(struct fsnotify_event *old, struct fsnotify_event *new
 			/* remember, after old was put on the wait_q we aren't
 			 * allowed to look at the inode any more, only thing
 			 * left to check was if the file_name is the same */
-			if (old->name_len &&
+			if (!old->name_len ||
 			    !strcmp(old->file_name, new->file_name))
 				return true;
 			break;