diff options
author | Christoph Hellwig <hch@lst.de> | 2021-11-23 17:04:41 +0100 |
---|---|---|
committer | Jens Axboe <axboe@kernel.dk> | 2021-11-29 06:38:35 -0700 |
commit | 0c5bcc92d94a8f578ab2b06c1274e076cc8aecd3 (patch) | |
tree | 30139bab0795108a04306b706a351751be57fd89 /block/blk-mq.c | |
parent | a4561f9fccc57a5fd56c53e21514f63825d8ace7 (diff) | |
download | linux-0c5bcc92d94a8f578ab2b06c1274e076cc8aecd3.tar.bz2 |
blk-mq: simplify the plug handling in blk_mq_submit_bio
blk_mq_submit_bio has two different plug cases, one that uses full
plugging and a limited plugging one.
The limited plugging case is only used for a corner case that does
not matter in real life:
- no ->commit_rqs (so not NVMe)
- no shared tags (so not SCSI)
- not rotational (so no old disk or floppy driver)
- must have multiple queues (so no eMMC)
Remove the limited merging case and all the related junk to simplify
blk_mq_submit_bio and the functions called from it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211123160443.1315598-2-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 | 68 |
1 files changed, 13 insertions, 55 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c index 00df1eb031c0..4a13900b640e 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2690,11 +2690,10 @@ static inline unsigned short blk_plug_max_rq_count(struct blk_plug *plug) } static bool blk_mq_attempt_bio_merge(struct request_queue *q, - struct bio *bio, unsigned int nr_segs, - bool *same_queue_rq) + struct bio *bio, unsigned int nr_segs) { if (!blk_queue_nomerges(q) && bio_mergeable(bio)) { - if (blk_attempt_plug_merge(q, bio, nr_segs, same_queue_rq)) + if (blk_attempt_plug_merge(q, bio, nr_segs)) return true; if (blk_mq_sched_bio_merge(q, bio, nr_segs)) return true; @@ -2705,8 +2704,7 @@ static bool blk_mq_attempt_bio_merge(struct request_queue *q, static struct request *blk_mq_get_new_requests(struct request_queue *q, struct blk_plug *plug, struct bio *bio, - unsigned int nsegs, - bool *same_queue_rq) + unsigned int nsegs) { struct blk_mq_alloc_data data = { .q = q, @@ -2715,7 +2713,7 @@ static struct request *blk_mq_get_new_requests(struct request_queue *q, }; struct request *rq; - if (blk_mq_attempt_bio_merge(q, bio, nsegs, same_queue_rq)) + if (blk_mq_attempt_bio_merge(q, bio, nsegs)) return NULL; rq_qos_throttle(q, bio); @@ -2751,8 +2749,7 @@ static inline bool blk_mq_can_use_cached_rq(struct request *rq, struct bio *bio) static inline struct request *blk_mq_get_request(struct request_queue *q, struct blk_plug *plug, struct bio *bio, - unsigned int nsegs, - bool *same_queue_rq) + unsigned int nsegs) { struct request *rq; bool checked = false; @@ -2762,8 +2759,7 @@ static inline struct request *blk_mq_get_request(struct request_queue *q, if (rq && rq->q == q) { if (unlikely(!submit_bio_checks(bio))) return NULL; - if (blk_mq_attempt_bio_merge(q, bio, nsegs, - same_queue_rq)) + if (blk_mq_attempt_bio_merge(q, bio, nsegs)) return NULL; checked = true; if (!blk_mq_can_use_cached_rq(rq, bio)) @@ -2781,7 +2777,7 @@ fallback: return NULL; if (unlikely(!checked && !submit_bio_checks(bio))) goto out_put; - rq = blk_mq_get_new_requests(q, plug, bio, nsegs, same_queue_rq); + rq = blk_mq_get_new_requests(q, plug, bio, nsegs); if (rq) return rq; out_put: @@ -2808,7 +2804,6 @@ void blk_mq_submit_bio(struct bio *bio) const int is_sync = op_is_sync(bio->bi_opf); struct request *rq; struct blk_plug *plug; - bool same_queue_rq = false; unsigned int nr_segs = 1; blk_status_t ret; @@ -2823,7 +2818,7 @@ void blk_mq_submit_bio(struct bio *bio) return; plug = blk_mq_plug(q, bio); - rq = blk_mq_get_request(q, plug, bio, nr_segs, &same_queue_rq); + rq = blk_mq_get_request(q, plug, bio, nr_segs); if (unlikely(!rq)) return; @@ -2846,16 +2841,7 @@ void blk_mq_submit_bio(struct bio *bio) return; } - if (plug && (q->nr_hw_queues == 1 || - blk_mq_is_shared_tags(rq->mq_hctx->flags) || - q->mq_ops->commit_rqs || !blk_queue_nonrot(q))) { - /* - * Use plugging if we have a ->commit_rqs() hook as well, as - * we know the driver uses bd->last in a smart fashion. - * - * Use normal plugging if this disk is slow HDD, as sequential - * IO may benefit a lot from plug merging. - */ + if (plug) { unsigned int request_count = plug->rq_count; struct request *last = NULL; @@ -2873,40 +2859,12 @@ void blk_mq_submit_bio(struct bio *bio) } blk_add_rq_to_plug(plug, rq); - } else if (rq->rq_flags & RQF_ELV) { - /* Insert the request at the IO scheduler queue */ + } else if ((rq->rq_flags & RQF_ELV) || + (rq->mq_hctx->dispatch_busy && + (q->nr_hw_queues == 1 || !is_sync))) { blk_mq_sched_insert_request(rq, false, true, true); - } else if (plug && !blk_queue_nomerges(q)) { - struct request *next_rq = NULL; - - /* - * We do limited plugging. If the bio can be merged, do that. - * Otherwise the existing request in the plug list will be - * issued. So the plug list will have one request at most - * The plug list might get flushed before this. If that happens, - * the plug list is empty, and same_queue_rq is invalid. - */ - if (same_queue_rq) { - next_rq = rq_list_pop(&plug->mq_list); - plug->rq_count--; - } - blk_add_rq_to_plug(plug, rq); - trace_block_plug(q); - - if (next_rq) { - trace_block_unplug(q, 1, true); - blk_mq_try_issue_directly(next_rq->mq_hctx, next_rq); - } - } else if ((q->nr_hw_queues > 1 && is_sync) || - !rq->mq_hctx->dispatch_busy) { - /* - * There is no scheduler and we can try to send directly - * to the hardware. - */ - blk_mq_try_issue_directly(rq->mq_hctx, rq); } else { - /* Default case. */ - blk_mq_sched_insert_request(rq, false, true, true); + blk_mq_try_issue_directly(rq->mq_hctx, rq); } } |