diff options
Diffstat (limited to 'block/blk-mq-sched.c')
| -rw-r--r-- | block/blk-mq-sched.c | 546 |
1 files changed, 546 insertions, 0 deletions
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c new file mode 100644 index 000000000..d89a757cb --- /dev/null +++ b/block/blk-mq-sched.c @@ -0,0 +1,546 @@ +/* + * blk-mq scheduling framework + * + * Copyright (C) 2016 Jens Axboe + */ +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/blk-mq.h> + +#include <trace/events/block.h> + +#include "blk.h" +#include "blk-mq.h" +#include "blk-mq-debugfs.h" +#include "blk-mq-sched.h" +#include "blk-mq-tag.h" +#include "blk-wbt.h" + +void blk_mq_sched_free_hctx_data(struct request_queue *q, + void (*exit)(struct blk_mq_hw_ctx *)) +{ + struct blk_mq_hw_ctx *hctx; + int i; + + queue_for_each_hw_ctx(q, hctx, i) { + if (exit && hctx->sched_data) + exit(hctx); + kfree(hctx->sched_data); + hctx->sched_data = NULL; + } +} +EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data); + +void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio) +{ + struct request_queue *q = rq->q; + struct io_context *ioc = rq_ioc(bio); + struct io_cq *icq; + + spin_lock_irq(q->queue_lock); + icq = ioc_lookup_icq(ioc, q); + spin_unlock_irq(q->queue_lock); + + if (!icq) { + icq = ioc_create_icq(ioc, q, GFP_ATOMIC); + if (!icq) + return; + } + get_io_context(icq->ioc); + rq->elv.icq = icq; +} + +/* + * Mark a hardware queue as needing a restart. For shared queues, maintain + * a count of how many hardware queues are marked for restart. + */ +void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx) +{ + if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state)) + return; + + set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state); +} +EXPORT_SYMBOL_GPL(blk_mq_sched_mark_restart_hctx); + +void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx) +{ + if (!test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state)) + return; + clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state); + + /* + * Order clearing SCHED_RESTART and list_empty_careful(&hctx->dispatch) + * in blk_mq_run_hw_queue(). Its pair is the barrier in + * blk_mq_dispatch_rq_list(). So dispatch code won't see SCHED_RESTART, + * meantime new request added to hctx->dispatch is missed to check in + * blk_mq_run_hw_queue(). + */ + smp_mb(); + + blk_mq_run_hw_queue(hctx, true); +} + +/* + * Only SCSI implements .get_budget and .put_budget, and SCSI restarts + * its queue by itself in its completion handler, so we don't need to + * restart queue if .get_budget() returns BLK_STS_NO_RESOURCE. + */ +static void blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) +{ + struct request_queue *q = hctx->queue; + struct elevator_queue *e = q->elevator; + LIST_HEAD(rq_list); + + do { + struct request *rq; + + if (e->type->ops.mq.has_work && + !e->type->ops.mq.has_work(hctx)) + break; + + if (!blk_mq_get_dispatch_budget(hctx)) + break; + + rq = e->type->ops.mq.dispatch_request(hctx); + if (!rq) { + blk_mq_put_dispatch_budget(hctx); + break; + } + + /* + * Now this rq owns the budget which has to be released + * if this rq won't be queued to driver via .queue_rq() + * in blk_mq_dispatch_rq_list(). + */ + list_add(&rq->queuelist, &rq_list); + } while (blk_mq_dispatch_rq_list(q, &rq_list, true)); +} + +static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx, + struct blk_mq_ctx *ctx) +{ + unsigned idx = ctx->index_hw; + + if (++idx == hctx->nr_ctx) + idx = 0; + + return hctx->ctxs[idx]; +} + +/* + * Only SCSI implements .get_budget and .put_budget, and SCSI restarts + * its queue by itself in its completion handler, so we don't need to + * restart queue if .get_budget() returns BLK_STS_NO_RESOURCE. + */ +static void blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx) +{ + struct request_queue *q = hctx->queue; + LIST_HEAD(rq_list); + struct blk_mq_ctx *ctx = READ_ONCE(hctx->dispatch_from); + + do { + struct request *rq; + + if (!sbitmap_any_bit_set(&hctx->ctx_map)) + break; + + if (!blk_mq_get_dispatch_budget(hctx)) + break; + + rq = blk_mq_dequeue_from_ctx(hctx, ctx); + if (!rq) { + blk_mq_put_dispatch_budget(hctx); + break; + } + + /* + * Now this rq owns the budget which has to be released + * if this rq won't be queued to driver via .queue_rq() + * in blk_mq_dispatch_rq_list(). + */ + list_add(&rq->queuelist, &rq_list); + + /* round robin for fair dispatch */ + ctx = blk_mq_next_ctx(hctx, rq->mq_ctx); + + } while (blk_mq_dispatch_rq_list(q, &rq_list, true)); + + WRITE_ONCE(hctx->dispatch_from, ctx); +} + +void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) +{ + struct request_queue *q = hctx->queue; + struct elevator_queue *e = q->elevator; + const bool has_sched_dispatch = e && e->type->ops.mq.dispatch_request; + LIST_HEAD(rq_list); + + /* RCU or SRCU read lock is needed before checking quiesced flag */ + if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q))) + return; + + hctx->run++; + + /* + * If we have previous entries on our dispatch list, grab them first for + * more fair dispatch. + */ + if (!list_empty_careful(&hctx->dispatch)) { + spin_lock(&hctx->lock); + if (!list_empty(&hctx->dispatch)) + list_splice_init(&hctx->dispatch, &rq_list); + spin_unlock(&hctx->lock); + } + + /* + * Only ask the scheduler for requests, if we didn't have residual + * requests from the dispatch list. This is to avoid the case where + * we only ever dispatch a fraction of the requests available because + * of low device queue depth. Once we pull requests out of the IO + * scheduler, we can no longer merge or sort them. So it's best to + * leave them there for as long as we can. Mark the hw queue as + * needing a restart in that case. + * + * We want to dispatch from the scheduler if there was nothing + * on the dispatch list or we were able to dispatch from the + * dispatch list. + */ + if (!list_empty(&rq_list)) { + blk_mq_sched_mark_restart_hctx(hctx); + if (blk_mq_dispatch_rq_list(q, &rq_list, false)) { + if (has_sched_dispatch) + blk_mq_do_dispatch_sched(hctx); + else + blk_mq_do_dispatch_ctx(hctx); + } + } else if (has_sched_dispatch) { + blk_mq_do_dispatch_sched(hctx); + } else if (hctx->dispatch_busy) { + /* dequeue request one by one from sw queue if queue is busy */ + blk_mq_do_dispatch_ctx(hctx); + } else { + blk_mq_flush_busy_ctxs(hctx, &rq_list); + blk_mq_dispatch_rq_list(q, &rq_list, false); + } +} + +bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio, + struct request **merged_request) +{ + struct request *rq; + + switch (elv_merge(q, &rq, bio)) { + case ELEVATOR_BACK_MERGE: + if (!blk_mq_sched_allow_merge(q, rq, bio)) + return false; + if (!bio_attempt_back_merge(q, rq, bio)) + return false; + *merged_request = attempt_back_merge(q, rq); + if (!*merged_request) + elv_merged_request(q, rq, ELEVATOR_BACK_MERGE); + return true; + case ELEVATOR_FRONT_MERGE: + if (!blk_mq_sched_allow_merge(q, rq, bio)) + return false; + if (!bio_attempt_front_merge(q, rq, bio)) + return false; + *merged_request = attempt_front_merge(q, rq); + if (!*merged_request) + elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE); + return true; + case ELEVATOR_DISCARD_MERGE: + return bio_attempt_discard_merge(q, rq, bio); + default: + return false; + } +} +EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge); + +/* + * Iterate list of requests and see if we can merge this bio with any + * of them. + */ +bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list, + struct bio *bio) +{ + struct request *rq; + int checked = 8; + + list_for_each_entry_reverse(rq, list, queuelist) { + bool merged = false; + + if (!checked--) + break; + + if (!blk_rq_merge_ok(rq, bio)) + continue; + + switch (blk_try_merge(rq, bio)) { + case ELEVATOR_BACK_MERGE: + if (blk_mq_sched_allow_merge(q, rq, bio)) + merged = bio_attempt_back_merge(q, rq, bio); + break; + case ELEVATOR_FRONT_MERGE: + if (blk_mq_sched_allow_merge(q, rq, bio)) + merged = bio_attempt_front_merge(q, rq, bio); + break; + case ELEVATOR_DISCARD_MERGE: + merged = bio_attempt_discard_merge(q, rq, bio); + break; + default: + continue; + } + + return merged; + } + + return false; +} +EXPORT_SYMBOL_GPL(blk_mq_bio_list_merge); + +/* + * Reverse check our software queue for entries that we could potentially + * merge with. Currently includes a hand-wavy stop count of 8, to not spend + * too much time checking for merges. + */ +static bool blk_mq_attempt_merge(struct request_queue *q, + struct blk_mq_ctx *ctx, struct bio *bio) +{ + lockdep_assert_held(&ctx->lock); + + if (blk_mq_bio_list_merge(q, &ctx->rq_list, bio)) { + ctx->rq_merged++; + return true; + } + + return false; +} + +bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio) +{ + struct elevator_queue *e = q->elevator; + struct blk_mq_ctx *ctx = blk_mq_get_ctx(q); + struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu); + bool ret = false; + + if (e && e->type->ops.mq.bio_merge) { + blk_mq_put_ctx(ctx); + return e->type->ops.mq.bio_merge(hctx, bio); + } + + if ((hctx->flags & BLK_MQ_F_SHOULD_MERGE) && + !list_empty_careful(&ctx->rq_list)) { + /* default per sw-queue merge */ + spin_lock(&ctx->lock); + ret = blk_mq_attempt_merge(q, ctx, bio); + spin_unlock(&ctx->lock); + } + + blk_mq_put_ctx(ctx); + return ret; +} + +bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq) +{ + return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq); +} +EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge); + +void blk_mq_sched_request_inserted(struct request *rq) +{ + trace_block_rq_insert(rq->q, rq); +} +EXPORT_SYMBOL_GPL(blk_mq_sched_request_inserted); + +static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx, + bool has_sched, + struct request *rq) +{ + /* dispatch flush rq directly */ + if (rq->rq_flags & RQF_FLUSH_SEQ) { + spin_lock(&hctx->lock); + list_add(&rq->queuelist, &hctx->dispatch); + spin_unlock(&hctx->lock); + return true; + } + + if (has_sched) + rq->rq_flags |= RQF_SORTED; + + return false; +} + +void blk_mq_sched_insert_request(struct request *rq, bool at_head, + bool run_queue, bool async) +{ + struct request_queue *q = rq->q; + struct elevator_queue *e = q->elevator; + struct blk_mq_ctx *ctx = rq->mq_ctx; + struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu); + + /* flush rq in flush machinery need to be dispatched directly */ + if (!(rq->rq_flags & RQF_FLUSH_SEQ) && op_is_flush(rq->cmd_flags)) { + blk_insert_flush(rq); + goto run; + } + + WARN_ON(e && (rq->tag != -1)); + + if (blk_mq_sched_bypass_insert(hctx, !!e, rq)) + goto run; + + if (e && e->type->ops.mq.insert_requests) { + LIST_HEAD(list); + + list_add(&rq->queuelist, &list); + e->type->ops.mq.insert_requests(hctx, &list, at_head); + } else { + spin_lock(&ctx->lock); + __blk_mq_insert_request(hctx, rq, at_head); + spin_unlock(&ctx->lock); + } + +run: + if (run_queue) + blk_mq_run_hw_queue(hctx, async); +} + +void blk_mq_sched_insert_requests(struct request_queue *q, + struct blk_mq_ctx *ctx, + struct list_head *list, bool run_queue_async) +{ + struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu); + struct elevator_queue *e = hctx->queue->elevator; + + if (e && e->type->ops.mq.insert_requests) + e->type->ops.mq.insert_requests(hctx, list, false); + else { + /* + * try to issue requests directly if the hw queue isn't + * busy in case of 'none' scheduler, and this way may save + * us one extra enqueue & dequeue to sw queue. + */ + if (!hctx->dispatch_busy && !e && !run_queue_async) { + blk_mq_try_issue_list_directly(hctx, list); + if (list_empty(list)) + return; + } + blk_mq_insert_requests(hctx, ctx, list); + } + + blk_mq_run_hw_queue(hctx, run_queue_async); +} + +static void blk_mq_sched_free_tags(struct blk_mq_tag_set *set, + struct blk_mq_hw_ctx *hctx, + unsigned int hctx_idx) +{ + if (hctx->sched_tags) { + blk_mq_free_rqs(set, hctx->sched_tags, hctx_idx); + blk_mq_free_rq_map(hctx->sched_tags); + hctx->sched_tags = NULL; + } +} + +static int blk_mq_sched_alloc_tags(struct request_queue *q, + struct blk_mq_hw_ctx *hctx, + unsigned int hctx_idx) +{ + struct blk_mq_tag_set *set = q->tag_set; + int ret; + + hctx->sched_tags = blk_mq_alloc_rq_map(set, hctx_idx, q->nr_requests, + set->reserved_tags); + if (!hctx->sched_tags) + return -ENOMEM; + + ret = blk_mq_alloc_rqs(set, hctx->sched_tags, hctx_idx, q->nr_requests); + if (ret) + blk_mq_sched_free_tags(set, hctx, hctx_idx); + + return ret; +} + +static void blk_mq_sched_tags_teardown(struct request_queue *q) +{ + struct blk_mq_tag_set *set = q->tag_set; + struct blk_mq_hw_ctx *hctx; + int i; + + queue_for_each_hw_ctx(q, hctx, i) + blk_mq_sched_free_tags(set, hctx, i); +} + +int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e) +{ + struct blk_mq_hw_ctx *hctx; + struct elevator_queue *eq; + unsigned int i; + int ret; + + if (!e) { + q->elevator = NULL; + q->nr_requests = q->tag_set->queue_depth; + return 0; + } + + /* + * Default to double of smaller one between hw queue_depth and 128, + * since we don't split into sync/async like the old code did. + * Additionally, this is a per-hw queue depth. + */ + q->nr_requests = 2 * min_t(unsigned int, q->tag_set->queue_depth, + BLKDEV_MAX_RQ); + + queue_for_each_hw_ctx(q, hctx, i) { + ret = blk_mq_sched_alloc_tags(q, hctx, i); + if (ret) + goto err; + } + + ret = e->ops.mq.init_sched(q, e); + if (ret) + goto err; + + blk_mq_debugfs_register_sched(q); + + queue_for_each_hw_ctx(q, hctx, i) { + if (e->ops.mq.init_hctx) { + ret = e->ops.mq.init_hctx(hctx, i); + if (ret) { + eq = q->elevator; + blk_mq_exit_sched(q, eq); + kobject_put(&eq->kobj); + return ret; + } + } + blk_mq_debugfs_register_sched_hctx(q, hctx); + } + + return 0; + +err: + blk_mq_sched_tags_teardown(q); + q->elevator = NULL; + return ret; +} + +void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e) +{ + struct blk_mq_hw_ctx *hctx; + unsigned int i; + + queue_for_each_hw_ctx(q, hctx, i) { + blk_mq_debugfs_unregister_sched_hctx(hctx); + if (e->type->ops.mq.exit_hctx && hctx->sched_data) { + e->type->ops.mq.exit_hctx(hctx, i); + hctx->sched_data = NULL; + } + } + blk_mq_debugfs_unregister_sched(q); + if (e->type->ops.mq.exit_sched) + e->type->ops.mq.exit_sched(e); + blk_mq_sched_tags_teardown(q); + q->elevator = NULL; +} |