diff --git a/fs/namespace.c b/fs/namespace.c
index fe37680..061e5ed 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1176,17 +1176,6 @@
 #endif
 }
 
-static int lives_below_in_same_fs(struct dentry *d, struct dentry *dentry)
-{
-	while (1) {
-		if (d == dentry)
-			return 1;
-		if (d == NULL || d == d->d_parent)
-			return 0;
-		d = d->d_parent;
-	}
-}
-
 struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
 					int flag)
 {
@@ -1203,7 +1192,7 @@
 
 	p = mnt;
 	list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
-		if (!lives_below_in_same_fs(r->mnt_mountpoint, dentry))
+		if (!is_subdir(r->mnt_mountpoint, dentry))
 			continue;
 
 		for (s = r; s; s = next_mnt(s, r)) {