Merge pull request #6048 from XinzeChi/wip-filestore-qlock

filestore: fix peek_queue for OpSequencer

Reviewed-by: Sage Weil <sage@redhat.com>

src/os/FileStore.h

@@ -263,6 +263,7 @@ private:
       q.push_back(o);
     }
     Op *peek_queue() {
+      Mutex::Locker l(qlock);
       assert(apply_lock.is_locked());
       return q.front();
     }