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blk-mq: introduce a blk_mq_peek_cached_request helper

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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: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Tested-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20240124092658.2258309-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2024-01-24 10:26:57 +01:00 committed by Jens Axboe
parent 0f299da55a
commit 337e89feb7
1 changed files with 33 additions and 30 deletions
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63
block/blk-mq.c
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@ -2909,23 +2909,32 @@ 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,
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(opf);
struct request *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;
}
static void blk_mq_use_cached_rq(struct request *rq, struct blk_plug *plug,
struct bio *bio)
{
enum hctx_type type = blk_mq_get_hctx_type(bio->bi_opf);
enum hctx_type hctx_type = rq->mq_hctx->type;
WARN_ON_ONCE(rq_list_peek(&plug->cached_rq) != 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;
/*
* If any qos ->throttle() end up blocking, we will have flushed the
* plug and hence killed the cached_rq list as well. Pop this entry
@ -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);
@ -2980,20 +2984,19 @@ 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))
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))) {
bio = __bio_split_to_limits(bio, &q->limits, &nr_segs);
if (!bio)
goto queue_exit;
}
if (!bio_integrity_prep(bio))
blk_mq_use_cached_rq(rq, plug, bio);
goto done;
}
if (unlikely(bio_queue_enter(bio)))
return;
if (unlikely(bio_may_exceed_limits(bio, &q->limits))) {
bio = __bio_split_to_limits(bio, &q->limits, &nr_segs);
if (!bio)
goto queue_exit;
}
if (!bio_integrity_prep(bio))
goto queue_exit;
if (blk_mq_attempt_bio_merge(q, bio, nr_segs))
goto queue_exit;