diff --git a/fs/namei.c b/fs/namei.c
index b8433eb..78f253c 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1248,6 +1248,8 @@
 	int err;
 	struct qstr this;
 
+	WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
+
 	err = __lookup_one_len(name, &this, base, len);
 	if (err)
 		return ERR_PTR(err);