btrfs: hold a ref on the root in btrfs_search_path_in_tree

We look up an arbitrary fs root, we need to hold a ref on it while we're
doing our search.
Signed-off-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/ioctl.c

@@ -2328,6 +2328,12 @@ static noinline int btrfs_search_path_in_tree(struct btrfs_fs_info *info,
 	root = btrfs_get_fs_root(info, &key, true);
 	if (IS_ERR(root)) {
 		ret = PTR_ERR(root);
+		root = NULL;
+		goto out;
+	}
+	if (!btrfs_grab_fs_root(root)) {
+		ret = -ENOENT;
+		root = NULL;
 		goto out;
 	}
 
@@ -2378,6 +2384,7 @@ static noinline int btrfs_search_path_in_tree(struct btrfs_fs_info *info,
 	name[total_len] = '\0';
 	ret = 0;
 out:
+	btrfs_put_fs_root(root);
 	btrfs_free_path(path);
 	return ret;
 }