2 * blk-mq scheduling framework
4 * Copyright (C) 2016 Jens Axboe
6 #include <linux/kernel.h>
7 #include <linux/module.h>
8 #include <linux/blk-mq.h>
10 #include <trace/events/block.h>
14 #include "blk-mq-debugfs.h"
15 #include "blk-mq-sched.h"
16 #include "blk-mq-tag.h"
19 void blk_mq_sched_free_hctx_data(struct request_queue *q,
20 void (*exit)(struct blk_mq_hw_ctx *))
22 struct blk_mq_hw_ctx *hctx;
25 queue_for_each_hw_ctx(q, hctx, i) {
26 if (exit && hctx->sched_data)
28 kfree(hctx->sched_data);
29 hctx->sched_data = NULL;
32 EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
34 static void __blk_mq_sched_assign_ioc(struct request_queue *q,
37 struct io_context *ioc)
41 spin_lock_irq(q->queue_lock);
42 icq = ioc_lookup_icq(ioc, q);
43 spin_unlock_irq(q->queue_lock);
46 icq = ioc_create_icq(ioc, q, GFP_ATOMIC);
52 if (!blk_mq_sched_get_rq_priv(q, rq, bio)) {
53 rq->rq_flags |= RQF_ELVPRIV;
54 get_io_context(icq->ioc);
61 static void blk_mq_sched_assign_ioc(struct request_queue *q,
62 struct request *rq, struct bio *bio)
64 struct io_context *ioc;
68 __blk_mq_sched_assign_ioc(q, rq, bio, ioc);
71 struct request *blk_mq_sched_get_request(struct request_queue *q,
74 struct blk_mq_alloc_data *data)
76 struct elevator_queue *e = q->elevator;
79 blk_queue_enter_live(q);
81 if (likely(!data->ctx))
82 data->ctx = blk_mq_get_ctx(q);
83 if (likely(!data->hctx))
84 data->hctx = blk_mq_map_queue(q, data->ctx->cpu);
87 data->flags |= BLK_MQ_REQ_INTERNAL;
90 * Flush requests are special and go directly to the
93 if (!op_is_flush(op) && e->type->ops.mq.get_request) {
94 rq = e->type->ops.mq.get_request(q, op, data);
96 rq->rq_flags |= RQF_QUEUED;
98 rq = __blk_mq_alloc_request(data, op);
100 rq = __blk_mq_alloc_request(data, op);
104 if (!op_is_flush(op)) {
106 if (e && e->type->icq_cache)
107 blk_mq_sched_assign_ioc(q, rq, bio);
109 data->hctx->queued++;
117 void blk_mq_sched_put_request(struct request *rq)
119 struct request_queue *q = rq->q;
120 struct elevator_queue *e = q->elevator;
122 if (rq->rq_flags & RQF_ELVPRIV) {
123 blk_mq_sched_put_rq_priv(rq->q, rq);
125 put_io_context(rq->elv.icq->ioc);
130 if ((rq->rq_flags & RQF_QUEUED) && e && e->type->ops.mq.put_request)
131 e->type->ops.mq.put_request(rq);
133 blk_mq_finish_request(rq);
136 void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
138 struct request_queue *q = hctx->queue;
139 struct elevator_queue *e = q->elevator;
140 const bool has_sched_dispatch = e && e->type->ops.mq.dispatch_request;
141 bool did_work = false;
144 if (unlikely(blk_mq_hctx_stopped(hctx)))
150 * If we have previous entries on our dispatch list, grab them first for
151 * more fair dispatch.
153 if (!list_empty_careful(&hctx->dispatch)) {
154 spin_lock(&hctx->lock);
155 if (!list_empty(&hctx->dispatch))
156 list_splice_init(&hctx->dispatch, &rq_list);
157 spin_unlock(&hctx->lock);
161 * Only ask the scheduler for requests, if we didn't have residual
162 * requests from the dispatch list. This is to avoid the case where
163 * we only ever dispatch a fraction of the requests available because
164 * of low device queue depth. Once we pull requests out of the IO
165 * scheduler, we can no longer merge or sort them. So it's best to
166 * leave them there for as long as we can. Mark the hw queue as
167 * needing a restart in that case.
169 if (!list_empty(&rq_list)) {
170 blk_mq_sched_mark_restart_hctx(hctx);
171 did_work = blk_mq_dispatch_rq_list(q, &rq_list);
172 } else if (!has_sched_dispatch) {
173 blk_mq_flush_busy_ctxs(hctx, &rq_list);
174 blk_mq_dispatch_rq_list(q, &rq_list);
178 * We want to dispatch from the scheduler if we had no work left
179 * on the dispatch list, OR if we did have work but weren't able
182 if (!did_work && has_sched_dispatch) {
186 rq = e->type->ops.mq.dispatch_request(hctx);
189 list_add(&rq->queuelist, &rq_list);
190 } while (blk_mq_dispatch_rq_list(q, &rq_list));
194 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
195 struct request **merged_request)
199 switch (elv_merge(q, &rq, bio)) {
200 case ELEVATOR_BACK_MERGE:
201 if (!blk_mq_sched_allow_merge(q, rq, bio))
203 if (!bio_attempt_back_merge(q, rq, bio))
205 *merged_request = attempt_back_merge(q, rq);
206 if (!*merged_request)
207 elv_merged_request(q, rq, ELEVATOR_BACK_MERGE);
209 case ELEVATOR_FRONT_MERGE:
210 if (!blk_mq_sched_allow_merge(q, rq, bio))
212 if (!bio_attempt_front_merge(q, rq, bio))
214 *merged_request = attempt_front_merge(q, rq);
215 if (!*merged_request)
216 elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
222 EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
225 * Reverse check our software queue for entries that we could potentially
226 * merge with. Currently includes a hand-wavy stop count of 8, to not spend
227 * too much time checking for merges.
229 static bool blk_mq_attempt_merge(struct request_queue *q,
230 struct blk_mq_ctx *ctx, struct bio *bio)
235 list_for_each_entry_reverse(rq, &ctx->rq_list, queuelist) {
241 if (!blk_rq_merge_ok(rq, bio))
244 switch (blk_try_merge(rq, bio)) {
245 case ELEVATOR_BACK_MERGE:
246 if (blk_mq_sched_allow_merge(q, rq, bio))
247 merged = bio_attempt_back_merge(q, rq, bio);
249 case ELEVATOR_FRONT_MERGE:
250 if (blk_mq_sched_allow_merge(q, rq, bio))
251 merged = bio_attempt_front_merge(q, rq, bio);
253 case ELEVATOR_DISCARD_MERGE:
254 merged = bio_attempt_discard_merge(q, rq, bio);
268 bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
270 struct elevator_queue *e = q->elevator;
271 struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
272 struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
275 if (e && e->type->ops.mq.bio_merge) {
277 return e->type->ops.mq.bio_merge(hctx, bio);
280 if (hctx->flags & BLK_MQ_F_SHOULD_MERGE) {
281 /* default per sw-queue merge */
282 spin_lock(&ctx->lock);
283 ret = blk_mq_attempt_merge(q, ctx, bio);
284 spin_unlock(&ctx->lock);
291 bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq)
293 return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq);
295 EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge);
297 void blk_mq_sched_request_inserted(struct request *rq)
299 trace_block_rq_insert(rq->q, rq);
301 EXPORT_SYMBOL_GPL(blk_mq_sched_request_inserted);
303 static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx,
307 rq->rq_flags |= RQF_SORTED;
312 * If we already have a real request tag, send directly to
315 spin_lock(&hctx->lock);
316 list_add(&rq->queuelist, &hctx->dispatch);
317 spin_unlock(&hctx->lock);
321 static bool blk_mq_sched_restart_hctx(struct blk_mq_hw_ctx *hctx)
323 if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state)) {
324 clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
325 if (blk_mq_hctx_has_pending(hctx)) {
326 blk_mq_run_hw_queue(hctx, true);
334 * list_for_each_entry_rcu_rr - iterate in a round-robin fashion over rcu list
336 * @skip: the list element that will not be examined. Iteration starts at
338 * @head: head of the list to examine. This list must have at least one
339 * element, namely @skip.
340 * @member: name of the list_head structure within typeof(*pos).
342 #define list_for_each_entry_rcu_rr(pos, skip, head, member) \
343 for ((pos) = (skip); \
344 (pos = (pos)->member.next != (head) ? list_entry_rcu( \
345 (pos)->member.next, typeof(*pos), member) : \
346 list_entry_rcu((pos)->member.next->next, typeof(*pos), member)), \
350 * Called after a driver tag has been freed to check whether a hctx needs to
351 * be restarted. Restarts @hctx if its tag set is not shared. Restarts hardware
352 * queues in a round-robin fashion if the tag set of @hctx is shared with other
355 void blk_mq_sched_restart(struct blk_mq_hw_ctx *const hctx)
357 struct blk_mq_tags *const tags = hctx->tags;
358 struct blk_mq_tag_set *const set = hctx->queue->tag_set;
359 struct request_queue *const queue = hctx->queue, *q;
360 struct blk_mq_hw_ctx *hctx2;
363 if (set->flags & BLK_MQ_F_TAG_SHARED) {
365 list_for_each_entry_rcu_rr(q, queue, &set->tag_list,
367 queue_for_each_hw_ctx(q, hctx2, i)
368 if (hctx2->tags == tags &&
369 blk_mq_sched_restart_hctx(hctx2))
372 j = hctx->queue_num + 1;
373 for (i = 0; i < queue->nr_hw_queues; i++, j++) {
374 if (j == queue->nr_hw_queues)
376 hctx2 = queue->queue_hw_ctx[j];
377 if (hctx2->tags == tags &&
378 blk_mq_sched_restart_hctx(hctx2))
384 blk_mq_sched_restart_hctx(hctx);
389 * Add flush/fua to the queue. If we fail getting a driver tag, then
390 * punt to the requeue list. Requeue will re-invoke us from a context
391 * that's safe to block from.
393 static void blk_mq_sched_insert_flush(struct blk_mq_hw_ctx *hctx,
394 struct request *rq, bool can_block)
396 if (blk_mq_get_driver_tag(rq, &hctx, can_block)) {
397 blk_insert_flush(rq);
398 blk_mq_run_hw_queue(hctx, true);
400 blk_mq_add_to_requeue_list(rq, false, true);
403 void blk_mq_sched_insert_request(struct request *rq, bool at_head,
404 bool run_queue, bool async, bool can_block)
406 struct request_queue *q = rq->q;
407 struct elevator_queue *e = q->elevator;
408 struct blk_mq_ctx *ctx = rq->mq_ctx;
409 struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
411 if (rq->tag == -1 && op_is_flush(rq->cmd_flags)) {
412 blk_mq_sched_insert_flush(hctx, rq, can_block);
416 if (e && blk_mq_sched_bypass_insert(hctx, rq))
419 if (e && e->type->ops.mq.insert_requests) {
422 list_add(&rq->queuelist, &list);
423 e->type->ops.mq.insert_requests(hctx, &list, at_head);
425 spin_lock(&ctx->lock);
426 __blk_mq_insert_request(hctx, rq, at_head);
427 spin_unlock(&ctx->lock);
432 blk_mq_run_hw_queue(hctx, async);
435 void blk_mq_sched_insert_requests(struct request_queue *q,
436 struct blk_mq_ctx *ctx,
437 struct list_head *list, bool run_queue_async)
439 struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
440 struct elevator_queue *e = hctx->queue->elevator;
443 struct request *rq, *next;
446 * We bypass requests that already have a driver tag assigned,
447 * which should only be flushes. Flushes are only ever inserted
448 * as single requests, so we shouldn't ever hit the
449 * WARN_ON_ONCE() below (but let's handle it just in case).
451 list_for_each_entry_safe(rq, next, list, queuelist) {
452 if (WARN_ON_ONCE(rq->tag != -1)) {
453 list_del_init(&rq->queuelist);
454 blk_mq_sched_bypass_insert(hctx, rq);
459 if (e && e->type->ops.mq.insert_requests)
460 e->type->ops.mq.insert_requests(hctx, list, false);
462 blk_mq_insert_requests(hctx, ctx, list);
464 blk_mq_run_hw_queue(hctx, run_queue_async);
467 static void blk_mq_sched_free_tags(struct blk_mq_tag_set *set,
468 struct blk_mq_hw_ctx *hctx,
469 unsigned int hctx_idx)
471 if (hctx->sched_tags) {
472 blk_mq_free_rqs(set, hctx->sched_tags, hctx_idx);
473 blk_mq_free_rq_map(hctx->sched_tags);
474 hctx->sched_tags = NULL;
478 static int blk_mq_sched_alloc_tags(struct request_queue *q,
479 struct blk_mq_hw_ctx *hctx,
480 unsigned int hctx_idx)
482 struct blk_mq_tag_set *set = q->tag_set;
485 hctx->sched_tags = blk_mq_alloc_rq_map(set, hctx_idx, q->nr_requests,
487 if (!hctx->sched_tags)
490 ret = blk_mq_alloc_rqs(set, hctx->sched_tags, hctx_idx, q->nr_requests);
492 blk_mq_sched_free_tags(set, hctx, hctx_idx);
497 static void blk_mq_sched_tags_teardown(struct request_queue *q)
499 struct blk_mq_tag_set *set = q->tag_set;
500 struct blk_mq_hw_ctx *hctx;
503 queue_for_each_hw_ctx(q, hctx, i)
504 blk_mq_sched_free_tags(set, hctx, i);
507 int blk_mq_sched_init_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,
508 unsigned int hctx_idx)
510 struct elevator_queue *e = q->elevator;
516 ret = blk_mq_sched_alloc_tags(q, hctx, hctx_idx);
520 if (e->type->ops.mq.init_hctx) {
521 ret = e->type->ops.mq.init_hctx(hctx, hctx_idx);
523 blk_mq_sched_free_tags(q->tag_set, hctx, hctx_idx);
528 blk_mq_debugfs_register_sched_hctx(q, hctx);
533 void blk_mq_sched_exit_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,
534 unsigned int hctx_idx)
536 struct elevator_queue *e = q->elevator;
541 blk_mq_debugfs_unregister_sched_hctx(hctx);
543 if (e->type->ops.mq.exit_hctx && hctx->sched_data) {
544 e->type->ops.mq.exit_hctx(hctx, hctx_idx);
545 hctx->sched_data = NULL;
548 blk_mq_sched_free_tags(q->tag_set, hctx, hctx_idx);
551 int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
553 struct blk_mq_hw_ctx *hctx;
554 struct elevator_queue *eq;
564 * Default to 256, since we don't split into sync/async like the
565 * old code did. Additionally, this is a per-hw queue depth.
567 q->nr_requests = 2 * BLKDEV_MAX_RQ;
569 queue_for_each_hw_ctx(q, hctx, i) {
570 ret = blk_mq_sched_alloc_tags(q, hctx, i);
575 ret = e->ops.mq.init_sched(q, e);
579 blk_mq_debugfs_register_sched(q);
581 queue_for_each_hw_ctx(q, hctx, i) {
582 if (e->ops.mq.init_hctx) {
583 ret = e->ops.mq.init_hctx(hctx, i);
586 blk_mq_exit_sched(q, eq);
587 kobject_put(&eq->kobj);
591 blk_mq_debugfs_register_sched_hctx(q, hctx);
597 blk_mq_sched_tags_teardown(q);
602 void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e)
604 struct blk_mq_hw_ctx *hctx;
607 queue_for_each_hw_ctx(q, hctx, i) {
608 blk_mq_debugfs_unregister_sched_hctx(hctx);
609 if (e->type->ops.mq.exit_hctx && hctx->sched_data) {
610 e->type->ops.mq.exit_hctx(hctx, i);
611 hctx->sched_data = NULL;
614 blk_mq_debugfs_unregister_sched(q);
615 if (e->type->ops.mq.exit_sched)
616 e->type->ops.mq.exit_sched(e);
617 blk_mq_sched_tags_teardown(q);
621 int blk_mq_sched_init(struct request_queue *q)
625 mutex_lock(&q->sysfs_lock);
626 ret = elevator_init(q, NULL);
627 mutex_unlock(&q->sysfs_lock);