From 07068d5b8ed8fa6759b2826ba9197e49b69a1fc3 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 22 May 2014 10:40:51 -0600 Subject: [PATCH] blk-mq: split make request handler for multi and single queue We want slightly different behavior from them: - On single queue devices, we currently use the per-process plug for deferred IO and for merging. - On multi queue devices, we don't use the per-process plug, but we want to go straight to hardware for SYNC IO. Split blk_mq_make_request() into a blk_sq_make_request() for single queue devices, and retain blk_mq_make_request() for multi queue devices. Then we don't need multiple checks for q->nr_hw_queues in the request mapping. Signed-off-by: Jens Axboe --- block/blk-mq.c | 209 +++++++++++++++++++++++++++++++++++++------------ 1 file changed, 158 insertions(+), 51 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 103aa1dbc000..54e78863c083 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1072,43 +1072,57 @@ static void blk_mq_bio_to_request(struct request *rq, struct bio *bio) blk_account_io_start(rq, 1); } -static void blk_mq_make_request(struct request_queue *q, struct bio *bio) +static inline bool blk_mq_merge_queue_io(struct blk_mq_hw_ctx *hctx, + struct blk_mq_ctx *ctx, + struct request *rq, struct bio *bio) +{ + struct request_queue *q = hctx->queue; + + if (!(hctx->flags & BLK_MQ_F_SHOULD_MERGE)) { + blk_mq_bio_to_request(rq, bio); + spin_lock(&ctx->lock); +insert_rq: + __blk_mq_insert_request(hctx, rq, false); + spin_unlock(&ctx->lock); + return false; + } else { + spin_lock(&ctx->lock); + if (!blk_mq_attempt_merge(q, ctx, bio)) { + blk_mq_bio_to_request(rq, bio); + goto insert_rq; + } + + spin_unlock(&ctx->lock); + __blk_mq_free_request(hctx, ctx, rq); + return true; + } +} + +struct blk_map_ctx { + struct blk_mq_hw_ctx *hctx; + struct blk_mq_ctx *ctx; +}; + +static struct request *blk_mq_map_request(struct request_queue *q, + struct bio *bio, + struct blk_map_ctx *data) { struct blk_mq_hw_ctx *hctx; struct blk_mq_ctx *ctx; - const int is_sync = rw_is_sync(bio->bi_rw); - const int is_flush_fua = bio->bi_rw & (REQ_FLUSH | REQ_FUA); - int rw = bio_data_dir(bio); struct request *rq; - unsigned int use_plug, request_count = 0; + int rw = bio_data_dir(bio); - /* - * If we have multiple hardware queues, just go directly to - * one of those for sync IO. - */ - use_plug = !is_flush_fua && ((q->nr_hw_queues == 1) || !is_sync); - - blk_queue_bounce(q, &bio); - - if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) { + if (unlikely(blk_mq_queue_enter(q))) { bio_endio(bio, -EIO); - return; - } - - if (use_plug && !blk_queue_nomerges(q) && - blk_attempt_plug_merge(q, bio, &request_count)) - return; - - if (blk_mq_queue_enter(q)) { - bio_endio(bio, -EIO); - return; + return NULL; } ctx = blk_mq_get_ctx(q); hctx = q->mq_ops->map_queue(q, ctx->cpu); - if (is_sync) + if (rw_is_sync(bio->bi_rw)) rw |= REQ_SYNC; + trace_block_getrq(q, bio, rw); rq = __blk_mq_alloc_request(hctx, ctx, GFP_ATOMIC, false); if (likely(rq)) @@ -1123,6 +1137,109 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio) } hctx->queued++; + data->hctx = hctx; + data->ctx = ctx; + return rq; +} + +/* + * Multiple hardware queue variant. This will not use per-process plugs, + * but will attempt to bypass the hctx queueing if we can go straight to + * hardware for SYNC IO. + */ +static void blk_mq_make_request(struct request_queue *q, struct bio *bio) +{ + const int is_sync = rw_is_sync(bio->bi_rw); + const int is_flush_fua = bio->bi_rw & (REQ_FLUSH | REQ_FUA); + struct blk_map_ctx data; + struct request *rq; + + blk_queue_bounce(q, &bio); + + if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) { + bio_endio(bio, -EIO); + return; + } + + rq = blk_mq_map_request(q, bio, &data); + if (unlikely(!rq)) + return; + + if (unlikely(is_flush_fua)) { + blk_mq_bio_to_request(rq, bio); + blk_insert_flush(rq); + goto run_queue; + } + + if (is_sync) { + int ret; + + blk_mq_bio_to_request(rq, bio); + blk_mq_start_request(rq, true); + + /* + * For OK queue, we are done. For error, kill it. Any other + * error (busy), just add it to our list as we previously + * would have done + */ + ret = q->mq_ops->queue_rq(data.hctx, rq); + if (ret == BLK_MQ_RQ_QUEUE_OK) + goto done; + else { + __blk_mq_requeue_request(rq); + + if (ret == BLK_MQ_RQ_QUEUE_ERROR) { + rq->errors = -EIO; + blk_mq_end_io(rq, rq->errors); + goto done; + } + } + } + + if (!blk_mq_merge_queue_io(data.hctx, data.ctx, rq, bio)) { + /* + * For a SYNC request, send it to the hardware immediately. For + * an ASYNC request, just ensure that we run it later on. The + * latter allows for merging opportunities and more efficient + * dispatching. + */ +run_queue: + blk_mq_run_hw_queue(data.hctx, !is_sync || is_flush_fua); + } +done: + blk_mq_put_ctx(data.ctx); +} + +/* + * Single hardware queue variant. This will attempt to use any per-process + * plug for merging and IO deferral. + */ +static void blk_sq_make_request(struct request_queue *q, struct bio *bio) +{ + const int is_sync = rw_is_sync(bio->bi_rw); + const int is_flush_fua = bio->bi_rw & (REQ_FLUSH | REQ_FUA); + unsigned int use_plug, request_count = 0; + struct blk_map_ctx data; + struct request *rq; + + /* + * If we have multiple hardware queues, just go directly to + * one of those for sync IO. + */ + use_plug = !is_flush_fua && !is_sync; + + blk_queue_bounce(q, &bio); + + if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) { + bio_endio(bio, -EIO); + return; + } + + if (use_plug && !blk_queue_nomerges(q) && + blk_attempt_plug_merge(q, bio, &request_count)) + return; + + rq = blk_mq_map_request(q, bio, &data); if (unlikely(is_flush_fua)) { blk_mq_bio_to_request(rq, bio); @@ -1147,37 +1264,23 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio) trace_block_plug(q); } list_add_tail(&rq->queuelist, &plug->mq_list); - blk_mq_put_ctx(ctx); + blk_mq_put_ctx(data.ctx); return; } } - if (!(hctx->flags & BLK_MQ_F_SHOULD_MERGE)) { - blk_mq_bio_to_request(rq, bio); - spin_lock(&ctx->lock); -insert_rq: - __blk_mq_insert_request(hctx, rq, false); - spin_unlock(&ctx->lock); - } else { - spin_lock(&ctx->lock); - if (!blk_mq_attempt_merge(q, ctx, bio)) { - blk_mq_bio_to_request(rq, bio); - goto insert_rq; - } - - spin_unlock(&ctx->lock); - __blk_mq_free_request(hctx, ctx, rq); + if (!blk_mq_merge_queue_io(data.hctx, data.ctx, rq, bio)) { + /* + * For a SYNC request, send it to the hardware immediately. For + * an ASYNC request, just ensure that we run it later on. The + * latter allows for merging opportunities and more efficient + * dispatching. + */ +run_queue: + blk_mq_run_hw_queue(data.hctx, !is_sync || is_flush_fua); } - - /* - * For a SYNC request, send it to the hardware immediately. For an - * ASYNC request, just ensure that we run it later on. The latter - * allows for merging opportunities and more efficient dispatching. - */ -run_queue: - blk_mq_run_hw_queue(hctx, !is_sync || is_flush_fua); - blk_mq_put_ctx(ctx); + blk_mq_put_ctx(data.ctx); } /* @@ -1670,7 +1773,11 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set) q->sg_reserved_size = INT_MAX; - blk_queue_make_request(q, blk_mq_make_request); + if (q->nr_hw_queues > 1) + blk_queue_make_request(q, blk_mq_make_request); + else + blk_queue_make_request(q, blk_sq_make_request); + blk_queue_rq_timed_out(q, blk_mq_rq_timed_out); if (set->timeout) blk_queue_rq_timeout(q, set->timeout);