diff --git a/fs/dcache.c b/fs/dcache.c
index 265e0ce9769c70db65d5f9df11c4365f44c6dd29..ca02c13a84aa24d55b18bbced577ece923605665 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2833,9 +2833,9 @@ static int prepend_name(char **buffer, int *buflen, struct qstr *name)
 	u32 dlen = ACCESS_ONCE(name->len);
 	char *p;
 
-	if (*buflen < dlen + 1)
-		return -ENAMETOOLONG;
 	*buflen -= dlen + 1;
+	if (*buflen < 0)
+		return -ENAMETOOLONG;
 	p = *buffer -= dlen + 1;
 	*p++ = '/';
 	while (dlen--) {