diff options
| author | Christoph Hellwig <hch@lst.de> | 2024-01-24 10:26:58 +0100 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2024-02-05 10:06:53 -0700 |
| commit | 72e84e909eb5354e1e405c968dfdc4dcc23d41cc (patch) | |
| tree | 9081ada23cb175ac725495cb63b731f77e087a9c /block/blk-mq.c | |
| parent | 337e89feb7c29043dacd851b6ac28542a9a8aacf (diff) | |
| download | lwn-72e84e909eb5354e1e405c968dfdc4dcc23d41cc.tar.gz lwn-72e84e909eb5354e1e405c968dfdc4dcc23d41cc.zip | |
blk-mq: special case cached requests less
Share the main merge / split / integrity preparation code between the
cached request vs newly allocated request cases, and add comments
explaining the cached request handling.
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/20240124092658.2258309-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-mq.c')
| -rw-r--r-- | block/blk-mq.c | 41 |
1 files changed, 22 insertions, 19 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c index ad57a259e975..c53a196f579e 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2967,29 +2967,24 @@ void blk_mq_submit_bio(struct bio *bio) struct blk_plug *plug = blk_mq_plug(bio); const int is_sync = op_is_sync(bio->bi_opf); struct blk_mq_hw_ctx *hctx; - struct request *rq = NULL; unsigned int nr_segs = 1; + struct request *rq; blk_status_t ret; bio = blk_queue_bounce(bio, q); + /* + * If the plug has a cached request for this queue, try use it. + * + * The cached request already holds a q_usage_counter reference and we + * don't have to acquire a new one if we use it. + */ 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); - if (!bio) - return; - } - if (!bio_integrity_prep(bio)) - return; - if (blk_mq_attempt_bio_merge(q, bio, nr_segs)) + if (!rq) { + if (unlikely(bio_queue_enter(bio))) return; - 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) @@ -3001,11 +2996,14 @@ void blk_mq_submit_bio(struct bio *bio) if (blk_mq_attempt_bio_merge(q, bio, nr_segs)) goto queue_exit; - rq = blk_mq_get_new_requests(q, plug, bio, nr_segs); - if (unlikely(!rq)) - goto queue_exit; + if (!rq) { + rq = blk_mq_get_new_requests(q, plug, bio, nr_segs); + if (unlikely(!rq)) + goto queue_exit; + } else { + blk_mq_use_cached_rq(rq, plug, bio); + } -done: trace_block_getrq(bio); rq_qos_track(q, rq, bio); @@ -3039,7 +3037,12 @@ done: return; queue_exit: - blk_queue_exit(q); + /* + * Don't drop the queue reference if we were trying to use a cached + * request and thus didn't acquire one. + */ + if (!rq) + blk_queue_exit(q); } #ifdef CONFIG_BLK_MQ_STACKING |