rbd-mirror: fix possible recursive lock of ImageReplayer::m_lock

If periodic status update (LambdaContext which is queued from
handle_update_mirror_image_replay_status()) races with shutdown and
ends up being the last in-flight operation that shutdown was pending
on, we attempt to recursively acquire m_lock in shut_down() because
m_in_flight_op_tracker.finish_op() is called with m_lock (and also
m_threads->timer_lock) held.  These locks are needed only for the call
to schedule_update_mirror_image_replay_status() and should be unlocked
immediately.

Fixes: https://tracker.ceph.com/issues/69978
Co-authored-by: Ilya Dryomov <[email protected]>

Signed-off-by: N Balachandran <[email protected]>

Author: nbalacha

src/tools/rbd_mirror/ImageReplayer.cc

@@ -719,10 +719,12 @@ void ImageReplayer<I>::handle_update_mirror_image_replay_status(int r) {
   auto ctx = new LambdaContext([this](int) {
       update_mirror_image_status(false, boost::none);
 
-      std::unique_lock locker{m_lock};
-      std::unique_lock timer_locker{m_threads->timer_lock};
+      {
+	std::unique_lock locker{m_lock};
+	std::unique_lock timer_locker{m_threads->timer_lock};
 
-      schedule_update_mirror_image_replay_status();
+	schedule_update_mirror_image_replay_status();
+      }
       m_in_flight_op_tracker.finish_op();
     });