backref_in_log
ret = backref_in_log(wc->log, search_key, btrfs_ino(dir), &victim_name);
ret = backref_in_log(log_root, search_key, btrfs_ino(dir), &victim_name);
ret = backref_in_log(root->log_root, &search_key, 0, &name);
ret = backref_in_log(root->log_root, &search_key, wc->log_key.objectid, &name);