static noinline long btrfs_ioctl_start_sync(struct btrfs_root *root,
					    void __user *argp)
{
	struct btrfs_trans_handle *trans;
	u64 transid;
	int ret;

	trans = btrfs_attach_transaction_barrier(root);
	if (IS_ERR(trans)) {
		if (PTR_ERR(trans) != -ENOENT)
			return PTR_ERR(trans);

		/* No running transaction, don't bother */
		transid = root->fs_info->last_trans_committed;
		goto out;
	}
	transid = trans->transid;
	ret = btrfs_commit_transaction_async(trans, root, 0);
	if (ret) {
		btrfs_end_transaction(trans, root);
		return ret;
	}
out:
	if (argp)
		if (copy_to_user(argp, &transid, sizeof(transid)))
			return -EFAULT;
	return 0;
}
Unknown