585 lines
14 KiB
C
585 lines
14 KiB
C
/*
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* blk-mq scheduling framework
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*
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* Copyright (C) 2016 Jens Axboe
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/blk-mq.h>
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#include <trace/events/block.h>
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#include "blk.h"
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#include "blk-mq.h"
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#include "blk-mq-debugfs.h"
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#include "blk-mq-sched.h"
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#include "blk-mq-tag.h"
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#include "blk-wbt.h"
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void blk_mq_sched_free_hctx_data(struct request_queue *q,
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void (*exit)(struct blk_mq_hw_ctx *))
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{
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struct blk_mq_hw_ctx *hctx;
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int i;
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queue_for_each_hw_ctx(q, hctx, i) {
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if (exit && hctx->sched_data)
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exit(hctx);
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kfree(hctx->sched_data);
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hctx->sched_data = NULL;
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}
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}
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EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
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void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio)
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{
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struct request_queue *q = rq->q;
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struct io_context *ioc = rq_ioc(bio);
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struct io_cq *icq;
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spin_lock_irq(q->queue_lock);
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icq = ioc_lookup_icq(ioc, q);
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spin_unlock_irq(q->queue_lock);
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if (!icq) {
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icq = ioc_create_icq(ioc, q, GFP_ATOMIC);
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if (!icq)
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return;
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}
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get_io_context(icq->ioc);
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rq->elv.icq = icq;
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}
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/*
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* Mark a hardware queue as needing a restart. For shared queues, maintain
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* a count of how many hardware queues are marked for restart.
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*/
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static void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx)
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{
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if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
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return;
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if (hctx->flags & BLK_MQ_F_TAG_SHARED) {
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struct request_queue *q = hctx->queue;
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if (!test_and_set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
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atomic_inc(&q->shared_hctx_restart);
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} else
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set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
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}
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static bool blk_mq_sched_restart_hctx(struct blk_mq_hw_ctx *hctx)
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{
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if (!test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
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return false;
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if (hctx->flags & BLK_MQ_F_TAG_SHARED) {
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struct request_queue *q = hctx->queue;
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if (test_and_clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
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atomic_dec(&q->shared_hctx_restart);
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} else
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clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
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if (blk_mq_hctx_has_pending(hctx)) {
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blk_mq_run_hw_queue(hctx, true);
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return true;
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}
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return false;
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}
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void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
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{
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struct request_queue *q = hctx->queue;
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struct elevator_queue *e = q->elevator;
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const bool has_sched_dispatch = e && e->type->ops.mq.dispatch_request;
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bool did_work = false;
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LIST_HEAD(rq_list);
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/* RCU or SRCU read lock is needed before checking quiesced flag */
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if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)))
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return;
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hctx->run++;
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/*
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* If we have previous entries on our dispatch list, grab them first for
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* more fair dispatch.
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*/
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if (!list_empty_careful(&hctx->dispatch)) {
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spin_lock(&hctx->lock);
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if (!list_empty(&hctx->dispatch))
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list_splice_init(&hctx->dispatch, &rq_list);
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spin_unlock(&hctx->lock);
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}
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/*
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* Only ask the scheduler for requests, if we didn't have residual
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* requests from the dispatch list. This is to avoid the case where
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* we only ever dispatch a fraction of the requests available because
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* of low device queue depth. Once we pull requests out of the IO
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* scheduler, we can no longer merge or sort them. So it's best to
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* leave them there for as long as we can. Mark the hw queue as
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* needing a restart in that case.
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*/
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if (!list_empty(&rq_list)) {
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blk_mq_sched_mark_restart_hctx(hctx);
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did_work = blk_mq_dispatch_rq_list(q, &rq_list);
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} else if (!has_sched_dispatch) {
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blk_mq_flush_busy_ctxs(hctx, &rq_list);
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blk_mq_dispatch_rq_list(q, &rq_list);
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}
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/*
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* We want to dispatch from the scheduler if we had no work left
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* on the dispatch list, OR if we did have work but weren't able
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* to make progress.
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*/
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if (!did_work && has_sched_dispatch) {
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do {
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struct request *rq;
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rq = e->type->ops.mq.dispatch_request(hctx);
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if (!rq)
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break;
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list_add(&rq->queuelist, &rq_list);
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} while (blk_mq_dispatch_rq_list(q, &rq_list));
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}
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}
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bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
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struct request **merged_request)
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{
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struct request *rq;
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switch (elv_merge(q, &rq, bio)) {
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case ELEVATOR_BACK_MERGE:
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if (!blk_mq_sched_allow_merge(q, rq, bio))
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return false;
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if (!bio_attempt_back_merge(q, rq, bio))
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return false;
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*merged_request = attempt_back_merge(q, rq);
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if (!*merged_request)
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elv_merged_request(q, rq, ELEVATOR_BACK_MERGE);
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return true;
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case ELEVATOR_FRONT_MERGE:
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if (!blk_mq_sched_allow_merge(q, rq, bio))
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return false;
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if (!bio_attempt_front_merge(q, rq, bio))
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return false;
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*merged_request = attempt_front_merge(q, rq);
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if (!*merged_request)
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elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
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return true;
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default:
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return false;
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}
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}
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EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
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/*
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* Reverse check our software queue for entries that we could potentially
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* merge with. Currently includes a hand-wavy stop count of 8, to not spend
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* too much time checking for merges.
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*/
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static bool blk_mq_attempt_merge(struct request_queue *q,
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struct blk_mq_ctx *ctx, struct bio *bio)
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{
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struct request *rq;
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int checked = 8;
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lockdep_assert_held(&ctx->lock);
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list_for_each_entry_reverse(rq, &ctx->rq_list, queuelist) {
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bool merged = false;
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if (!checked--)
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break;
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if (!blk_rq_merge_ok(rq, bio))
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continue;
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switch (blk_try_merge(rq, bio)) {
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case ELEVATOR_BACK_MERGE:
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if (blk_mq_sched_allow_merge(q, rq, bio))
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merged = bio_attempt_back_merge(q, rq, bio);
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break;
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case ELEVATOR_FRONT_MERGE:
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if (blk_mq_sched_allow_merge(q, rq, bio))
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merged = bio_attempt_front_merge(q, rq, bio);
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break;
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case ELEVATOR_DISCARD_MERGE:
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merged = bio_attempt_discard_merge(q, rq, bio);
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break;
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default:
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continue;
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}
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if (merged)
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ctx->rq_merged++;
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return merged;
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}
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return false;
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}
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bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
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{
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struct elevator_queue *e = q->elevator;
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struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
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struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
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bool ret = false;
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if (e && e->type->ops.mq.bio_merge) {
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blk_mq_put_ctx(ctx);
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return e->type->ops.mq.bio_merge(hctx, bio);
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}
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if (hctx->flags & BLK_MQ_F_SHOULD_MERGE) {
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/* default per sw-queue merge */
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spin_lock(&ctx->lock);
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ret = blk_mq_attempt_merge(q, ctx, bio);
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spin_unlock(&ctx->lock);
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}
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blk_mq_put_ctx(ctx);
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return ret;
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}
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bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq)
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{
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return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq);
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}
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EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge);
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void blk_mq_sched_request_inserted(struct request *rq)
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{
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trace_block_rq_insert(rq->q, rq);
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}
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EXPORT_SYMBOL_GPL(blk_mq_sched_request_inserted);
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static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx,
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struct request *rq)
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{
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if (rq->tag == -1) {
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rq->rq_flags |= RQF_SORTED;
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return false;
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}
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/*
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* If we already have a real request tag, send directly to
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* the dispatch list.
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*/
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spin_lock(&hctx->lock);
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list_add(&rq->queuelist, &hctx->dispatch);
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spin_unlock(&hctx->lock);
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return true;
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}
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/**
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* list_for_each_entry_rcu_rr - iterate in a round-robin fashion over rcu list
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* @pos: loop cursor.
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* @skip: the list element that will not be examined. Iteration starts at
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* @skip->next.
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* @head: head of the list to examine. This list must have at least one
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* element, namely @skip.
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* @member: name of the list_head structure within typeof(*pos).
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*/
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#define list_for_each_entry_rcu_rr(pos, skip, head, member) \
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for ((pos) = (skip); \
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(pos = (pos)->member.next != (head) ? list_entry_rcu( \
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(pos)->member.next, typeof(*pos), member) : \
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list_entry_rcu((pos)->member.next->next, typeof(*pos), member)), \
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(pos) != (skip); )
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/*
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* Called after a driver tag has been freed to check whether a hctx needs to
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* be restarted. Restarts @hctx if its tag set is not shared. Restarts hardware
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* queues in a round-robin fashion if the tag set of @hctx is shared with other
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* hardware queues.
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*/
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void blk_mq_sched_restart(struct blk_mq_hw_ctx *const hctx)
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{
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struct blk_mq_tags *const tags = hctx->tags;
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struct blk_mq_tag_set *const set = hctx->queue->tag_set;
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struct request_queue *const queue = hctx->queue, *q;
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struct blk_mq_hw_ctx *hctx2;
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unsigned int i, j;
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if (set->flags & BLK_MQ_F_TAG_SHARED) {
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/*
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* If this is 0, then we know that no hardware queues
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* have RESTART marked. We're done.
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*/
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if (!atomic_read(&queue->shared_hctx_restart))
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return;
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rcu_read_lock();
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list_for_each_entry_rcu_rr(q, queue, &set->tag_list,
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tag_set_list) {
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queue_for_each_hw_ctx(q, hctx2, i)
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if (hctx2->tags == tags &&
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blk_mq_sched_restart_hctx(hctx2))
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goto done;
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}
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j = hctx->queue_num + 1;
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for (i = 0; i < queue->nr_hw_queues; i++, j++) {
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if (j == queue->nr_hw_queues)
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j = 0;
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hctx2 = queue->queue_hw_ctx[j];
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if (hctx2->tags == tags &&
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blk_mq_sched_restart_hctx(hctx2))
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break;
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}
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done:
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rcu_read_unlock();
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} else {
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blk_mq_sched_restart_hctx(hctx);
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}
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}
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/*
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* Add flush/fua to the queue. If we fail getting a driver tag, then
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* punt to the requeue list. Requeue will re-invoke us from a context
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* that's safe to block from.
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*/
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static void blk_mq_sched_insert_flush(struct blk_mq_hw_ctx *hctx,
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struct request *rq, bool can_block)
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{
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if (blk_mq_get_driver_tag(rq, &hctx, can_block)) {
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blk_insert_flush(rq);
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blk_mq_run_hw_queue(hctx, true);
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} else
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blk_mq_add_to_requeue_list(rq, false, true);
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}
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void blk_mq_sched_insert_request(struct request *rq, bool at_head,
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bool run_queue, bool async, bool can_block)
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{
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struct request_queue *q = rq->q;
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struct elevator_queue *e = q->elevator;
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struct blk_mq_ctx *ctx = rq->mq_ctx;
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struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
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if (rq->tag == -1 && op_is_flush(rq->cmd_flags)) {
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blk_mq_sched_insert_flush(hctx, rq, can_block);
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return;
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}
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if (e && blk_mq_sched_bypass_insert(hctx, rq))
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goto run;
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if (e && e->type->ops.mq.insert_requests) {
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LIST_HEAD(list);
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list_add(&rq->queuelist, &list);
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e->type->ops.mq.insert_requests(hctx, &list, at_head);
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} else {
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spin_lock(&ctx->lock);
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__blk_mq_insert_request(hctx, rq, at_head);
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spin_unlock(&ctx->lock);
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}
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run:
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if (run_queue)
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blk_mq_run_hw_queue(hctx, async);
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}
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void blk_mq_sched_insert_requests(struct request_queue *q,
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struct blk_mq_ctx *ctx,
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struct list_head *list, bool run_queue_async)
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{
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struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
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struct elevator_queue *e = hctx->queue->elevator;
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if (e) {
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struct request *rq, *next;
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/*
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* We bypass requests that already have a driver tag assigned,
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* which should only be flushes. Flushes are only ever inserted
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* as single requests, so we shouldn't ever hit the
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* WARN_ON_ONCE() below (but let's handle it just in case).
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*/
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list_for_each_entry_safe(rq, next, list, queuelist) {
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if (WARN_ON_ONCE(rq->tag != -1)) {
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list_del_init(&rq->queuelist);
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blk_mq_sched_bypass_insert(hctx, rq);
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}
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}
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}
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if (e && e->type->ops.mq.insert_requests)
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e->type->ops.mq.insert_requests(hctx, list, false);
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else
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blk_mq_insert_requests(hctx, ctx, list);
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blk_mq_run_hw_queue(hctx, run_queue_async);
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}
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static void blk_mq_sched_free_tags(struct blk_mq_tag_set *set,
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struct blk_mq_hw_ctx *hctx,
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unsigned int hctx_idx)
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{
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if (hctx->sched_tags) {
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blk_mq_free_rqs(set, hctx->sched_tags, hctx_idx);
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blk_mq_free_rq_map(hctx->sched_tags);
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hctx->sched_tags = NULL;
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}
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}
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static int blk_mq_sched_alloc_tags(struct request_queue *q,
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struct blk_mq_hw_ctx *hctx,
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unsigned int hctx_idx)
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{
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struct blk_mq_tag_set *set = q->tag_set;
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int ret;
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hctx->sched_tags = blk_mq_alloc_rq_map(set, hctx_idx, q->nr_requests,
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set->reserved_tags);
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if (!hctx->sched_tags)
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return -ENOMEM;
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ret = blk_mq_alloc_rqs(set, hctx->sched_tags, hctx_idx, q->nr_requests);
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if (ret)
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blk_mq_sched_free_tags(set, hctx, hctx_idx);
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return ret;
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}
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static void blk_mq_sched_tags_teardown(struct request_queue *q)
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{
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struct blk_mq_tag_set *set = q->tag_set;
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struct blk_mq_hw_ctx *hctx;
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int i;
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queue_for_each_hw_ctx(q, hctx, i)
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blk_mq_sched_free_tags(set, hctx, i);
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}
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int blk_mq_sched_init_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,
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unsigned int hctx_idx)
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{
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struct elevator_queue *e = q->elevator;
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int ret;
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if (!e)
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return 0;
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ret = blk_mq_sched_alloc_tags(q, hctx, hctx_idx);
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if (ret)
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return ret;
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if (e->type->ops.mq.init_hctx) {
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ret = e->type->ops.mq.init_hctx(hctx, hctx_idx);
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if (ret) {
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blk_mq_sched_free_tags(q->tag_set, hctx, hctx_idx);
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return ret;
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}
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}
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blk_mq_debugfs_register_sched_hctx(q, hctx);
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return 0;
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}
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void blk_mq_sched_exit_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,
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unsigned int hctx_idx)
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{
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struct elevator_queue *e = q->elevator;
|
|
|
|
if (!e)
|
|
return;
|
|
|
|
blk_mq_debugfs_unregister_sched_hctx(hctx);
|
|
|
|
if (e->type->ops.mq.exit_hctx && hctx->sched_data) {
|
|
e->type->ops.mq.exit_hctx(hctx, hctx_idx);
|
|
hctx->sched_data = NULL;
|
|
}
|
|
|
|
blk_mq_sched_free_tags(q->tag_set, hctx, hctx_idx);
|
|
}
|
|
|
|
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;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Default to 256, 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 * 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;
|
|
}
|
|
|
|
int blk_mq_sched_init(struct request_queue *q)
|
|
{
|
|
int ret;
|
|
|
|
mutex_lock(&q->sysfs_lock);
|
|
ret = elevator_init(q, NULL);
|
|
mutex_unlock(&q->sysfs_lock);
|
|
|
|
return ret;
|
|
}
|