linux-kernel - Re: [PATCH 5/6] aio: implement IOCB_CMD_FSYNC and IOCB_CMD

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Date:   Fri, 6 Apr 2018 03:59:48 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Christoph Hellwig <hch@....de>
Cc:     Avi Kivity <avi@...lladb.com>, linux-aio@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-api@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] aio: implement IOCB_CMD_FSYNC and IOCB_CMD_FDSYNC

On Wed, Mar 28, 2018 at 09:26:38AM +0200, Christoph Hellwig wrote:
> +static int aio_fsync(struct fsync_iocb *req, struct iocb *iocb, bool datasync)
> +{
> +	int ret;
> +
> +	if (iocb->aio_buf)
> +		return -EINVAL;
> +	if (iocb->aio_offset || iocb->aio_nbytes || iocb->aio_rw_flags)
> +		return -EINVAL;
> +
> +	req->file = fget(iocb->aio_fildes);
> +	if (unlikely(!req->file))
> +		return -EBADF;
> +
> +	ret = -EINVAL;
> +	if (!req->file->f_op->fsync)
> +		goto out_fput;
> +
> +	req->datasync = datasync;
> +	INIT_WORK(&req->work, aio_fsync_work);
> +	schedule_work(&req->work);
> +	return -EIOCBQUEUED;
> +out_fput:
> +	if (unlikely(ret && ret != -EIOCBQUEUED))

Really?  The only way to get there is if we got NULL ->f_op->fsync.
So this "if (unlikely(...))" is actually if (true) and I'm not
sure we want that separated anyway - simply

	if (unlikely(!req->file->f_op->fsync)) {
		fput(req->file);
		return -EINVAL;
	}

> +		fput(req->file);

> +	return ret;
> +}