Re: [PATCH 4/4] block: move plug rq alloc into helper and ensure queue match

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

On Wed, Nov 03, 2021 at 12:32:22PM -0600, Jens Axboe wrote:
> +	if (plug && !rq_list_empty(plug->cached_rq)) {
> +		rq = rq_list_peek(&plug->cached_rq);

No need for the empty check plus peek.  This could be simplified
down to:

	if (!plug)
		return NULL;
	rq = rq_list_peek(&plug->cached_rq);
	if (!rq || rq->q != q)
		return NULL;

	rq_qos_throttle(q, bio);
	plug->cached_rq = rq_list_next(rq);
	INIT_LIST_HEAD(&rq->queuelist);
	return rq;