--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -508,8 +508,10 @@ xfs_qm_shrink_scan(
 	INIT_LIST_HEAD(&isol.buffers);
 	INIT_LIST_HEAD(&isol.dispose);
 
+	mutex_lock(&qi->qi_tree_lock);
 	freed = list_lru_shrink_walk(&qi->qi_lru, sc,
 				     xfs_qm_dquot_isolate, &isol);
+	mutex_unlock(&qi->qi_tree_lock);
 
 	error = xfs_buf_delwri_submit(&isol.buffers);
 	if (error)