+ return;
+ }
+
+ /* This removes our old bs and adds the new bs. This is an operation that
+ * can fail, so we need to do it in .prepare; undoing it for abort is
+ * always possible. */
+ bdrv_ref(state->new_bs);
+ bdrv_append(state->new_bs, state->old_bs, &local_err);
+ if (local_err) {
+ error_propagate(errp, local_err);
+ return;