Commit 337e89fe authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

blk-mq: introduce a blk_mq_peek_cached_request helper 



Add a new helper to check if there is suitable cached request in
blk_mq_submit_bio.  This removes open coded logic in blk_mq_submit_bio
and moves some checks that so far are in blk_mq_use_cached_rq to
be performed earlier.  This avoids the case where we first do check
with the cached request but then later end up allocating a new one
anyway and need to grab a queue reference.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDamien Le Moal <dlemoal@kernel.org>
Tested-by: default avatarDamien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20240124092658.2258309-3-hch@lst.de


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 0f299da5

block/blk-mq.c

+33 −30
Original line number Diff line number Diff line
@@ -2909,22 +2909,31 @@ static struct request *blk_mq_get_new_requests(struct request_queue *q, 
}



/*

 * Check if we can use the passed on request for submitting the passed in bio,

 * and remove it from the request list if it can be used.

 * Check if there is a suitable cached request and return it.

 */

static bool blk_mq_use_cached_rq(struct request *rq, struct blk_plug *plug,

		struct bio *bio)

static struct request *blk_mq_peek_cached_request(struct blk_plug *plug,

		struct request_queue *q, blk_opf_t opf)

{

	enum hctx_type type = blk_mq_get_hctx_type(bio->bi_opf);

	enum hctx_type hctx_type = rq->mq_hctx->type;

	enum hctx_type type = blk_mq_get_hctx_type(opf);

	struct request *rq;



	WARN_ON_ONCE(rq_list_peek(&plug->cached_rq) != rq);

	if (!plug)

		return NULL;

	rq = rq_list_peek(&plug->cached_rq);

	if (!rq || rq->q != q)

		return NULL;

	if (type != rq->mq_hctx->type &&

	    (type != HCTX_TYPE_READ || rq->mq_hctx->type != HCTX_TYPE_DEFAULT))

		return NULL;

	if (op_is_flush(rq->cmd_flags) != op_is_flush(opf))

		return NULL;

	return rq;

}



	if (type != hctx_type &&

	    !(type == HCTX_TYPE_READ && hctx_type == HCTX_TYPE_DEFAULT))

		return false;

	if (op_is_flush(rq->cmd_flags) != op_is_flush(bio->bi_opf))

		return false;

static void blk_mq_use_cached_rq(struct request *rq, struct blk_plug *plug,

		struct bio *bio)

{

	WARN_ON_ONCE(rq_list_peek(&plug->cached_rq) != rq);



	/*

	 * If any qos ->throttle() end up blocking, we will have flushed the
@@ -2937,7 +2946,6 @@ static bool blk_mq_use_cached_rq(struct request *rq, struct blk_plug *plug, 
	blk_mq_rq_time_init(rq, 0);

	rq->cmd_flags = bio->bi_opf;

	INIT_LIST_HEAD(&rq->queuelist);

	return true;

}



/**
@@ -2965,11 +2973,7 @@ void blk_mq_submit_bio(struct bio *bio) 


	bio = blk_queue_bounce(bio, q);



	if (plug) {

		rq = rq_list_peek(&plug->cached_rq);

		if (rq && rq->q != q)

			rq = NULL;

	}

	rq = blk_mq_peek_cached_request(plug, q, bio->bi_opf);

	if (rq) {

		if (unlikely(bio_may_exceed_limits(bio, &q->limits))) {

			bio = __bio_split_to_limits(bio, &q->limits, &nr_segs);
@@ -2980,10 +2984,10 @@ void blk_mq_submit_bio(struct bio *bio) 
			return;

		if (blk_mq_attempt_bio_merge(q, bio, nr_segs))

			return;

		if (blk_mq_use_cached_rq(rq, plug, bio))

		blk_mq_use_cached_rq(rq, plug, bio);

		goto done;

		percpu_ref_get(&q->q_usage_counter);

	} else {

	}



	if (unlikely(bio_queue_enter(bio)))

		return;

	if (unlikely(bio_may_exceed_limits(bio, &q->limits))) {
@@ -2993,7 +2997,6 @@ void blk_mq_submit_bio(struct bio *bio) 
	}

	if (!bio_integrity_prep(bio))

		goto queue_exit;

	}



	if (blk_mq_attempt_bio_merge(q, bio, nr_segs))

		goto queue_exit;