// SPDX-License-Identifier: GPL-2.0 /* * 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 request_queue *q = rq->q; struct io_context *ioc; struct io_cq *icq; /* * May not have an IO context if it's a passthrough request */ ioc = current->io_context; if (!ioc) return; 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); 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.has_work && !e->type->ops.has_work(hctx)) break; if (!blk_mq_get_dispatch_budget(hctx)) break; rq = e->type->ops.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 short idx = ctx->index_hw[hctx->type]; 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.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, unsigned int nr_segs, 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(rq, bio, nr_segs)) 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(rq, bio, nr_segs)) 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, unsigned int nr_segs) { 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(rq, bio, nr_segs); break; case ELEVATOR_FRONT_MERGE: if (blk_mq_sched_allow_merge(q, rq, bio)) merged = bio_attempt_front_merge(rq, bio, nr_segs); 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_hw_ctx *hctx, struct blk_mq_ctx *ctx, struct bio *bio, unsigned int nr_segs) { enum hctx_type type = hctx->type; lockdep_assert_held(&ctx->lock); if (blk_mq_bio_list_merge(q, &ctx->rq_lists[type], bio, nr_segs)) { ctx->rq_merged++; return true; } return false; } bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio, unsigned int nr_segs) { 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, bio->bi_opf, ctx); bool ret = false; enum hctx_type type; if (e && e->type->ops.bio_merge) return e->type->ops.bio_merge(hctx, bio, nr_segs); type = hctx->type; if ((hctx->flags & BLK_MQ_F_SHOULD_MERGE) && !list_empty_careful(&ctx->rq_lists[type])) { /* default per sw-queue merge */ spin_lock(&ctx->lock); ret = blk_mq_attempt_merge(q, hctx, ctx, bio, nr_segs); spin_unlock(&ctx->lock); } 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 = rq->mq_hctx; /* 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.insert_requests) { LIST_HEAD(list); list_add(&rq->queuelist, &list); e->type->ops.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 blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx, struct list_head *list, bool run_queue_async) { struct elevator_queue *e; struct request_queue *q = hctx->queue; /* * blk_mq_sched_insert_requests() is called from flush plug * context only, and hold one usage counter to prevent queue * from being released. */ percpu_ref_get(&q->q_usage_counter); e = hctx->queue->elevator; if (e && e->type->ops.insert_requests) e->type->ops.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)) goto out; } blk_mq_insert_requests(hctx, ctx, list); } blk_mq_run_hw_queue(hctx, run_queue_async); out: percpu_ref_put(&q->q_usage_counter); } 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; } /* called in queue's release handler, tagset has gone away */ static void blk_mq_sched_tags_teardown(struct request_queue *q) { struct blk_mq_hw_ctx *hctx; int i; queue_for_each_hw_ctx(q, hctx, i) { if (hctx->sched_tags) { blk_mq_free_rq_map(hctx->sched_tags); hctx->sched_tags = NULL; } } } 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.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.init_hctx) { ret = e->ops.init_hctx(hctx, i); if (ret) { eq = q->elevator; blk_mq_sched_free_requests(q); 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_free_requests(q); blk_mq_sched_tags_teardown(q); q->elevator = NULL; return ret; } /* * called in either blk_queue_cleanup or elevator_switch, tagset * is required for freeing requests */ void blk_mq_sched_free_requests(struct request_queue *q) { struct blk_mq_hw_ctx *hctx; int i; lockdep_assert_held(&q->sysfs_lock); queue_for_each_hw_ctx(q, hctx, i) { if (hctx->sched_tags) blk_mq_free_rqs(q->tag_set, hctx->sched_tags, i); } } 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.exit_hctx && hctx->sched_data) { e->type->ops.exit_hctx(hctx, i); hctx->sched_data = NULL; } } blk_mq_debugfs_unregister_sched(q); if (e->type->ops.exit_sched) e->type->ops.exit_sched(e); blk_mq_sched_tags_teardown(q); q->elevator = NULL; }