diff --git a/fs/namespace.c b/fs/namespace.c
index 27bf8665ed58..e74e63466c24 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4032,6 +4032,8 @@ void mark_mounts_for_expiry(struct list_head *mounts)
 	list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
 		if (!is_mounted(&mnt->mnt))
 			continue;
+		/* lock_mnt_tree() leaves expirable mounts alone */
+		VFS_WARN_ON_ONCE(IS_MNT_LOCKED(mnt));
 		if (!xchg(&mnt->mnt_expiry_mark, 1) ||
 			propagate_mount_busy(mnt, 1))
 			continue;
@@ -4058,7 +4060,8 @@ EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
  */
 static bool shrink_submount(struct mount *mnt)
 {
-	if (propagate_mount_busy(mnt, 1))
+	/* not the kernel's to remove either */
+	if (IS_MNT_LOCKED(mnt) || propagate_mount_busy(mnt, 1))
 		return false;
 	touch_mnt_namespace(mnt->mnt_ns);
 	umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);