pacific: mds: drop locks and retry when lock set changes

src/mds/Server.cc

@@ -4071,6 +4071,24 @@ void Server::handle_client_getattr(MDRequestRef& mdr, bool is_lookup)
     } else if (ref->filelock.is_stable() ||
 	       ref->filelock.get_num_wrlocks() > 0 ||
 	       !ref->filelock.can_read(mdr->get_client())) {
+      /* Since we're taking advantage of an optimization here:
+       *
+       * We cannot suddenly, due to a changing condition, add this filelock as
+       * it can cause lock-order deadlocks. In this case, that condition is the
+       * lock state changes between request retries. If that happens, we need
+       * to check if we've acquired the other locks in this vector. If we have,
+       * then we need to drop those locks and retry.
+       */
+      if (mdr->is_rdlocked(&ref->linklock) ||
+          mdr->is_rdlocked(&ref->authlock) ||
+          mdr->is_rdlocked(&ref->xattrlock)) {
+        /* start over */
+        dout(20) << " dropping locks and restarting request because filelock state change" << dendl;
+	mds->locker->drop_locks(mdr.get());
+	mdr->drop_local_auth_pins();
+	mds->queue_waiter(new C_MDS_RetryRequest(mdcache, mdr));
+        return;
+      }
       lov.add_rdlock(&ref->filelock);
       mdr->locking_state &= ~MutationImpl::ALL_LOCKED;
     }