btrfs_find_root
ret = btrfs_find_root(tree_root, key, path,
ret = btrfs_find_root(tree_root, &root->root_key, path,
ret = btrfs_find_root(fs_info->tree_root, &key, path, NULL, NULL);
int btrfs_find_root(struct btrfs_root *root, const struct btrfs_key *search_key,