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 void blk_mq_sched_assign_ioc(struct request *rq, struct bio *bio)
36 struct request_queue *q = rq->q;
37 struct io_context *ioc = rq_ioc(bio);
40 spin_lock_irq(q->queue_lock);
41 icq = ioc_lookup_icq(ioc, q);
42 spin_unlock_irq(q->queue_lock);
45 icq = ioc_create_icq(ioc, q, GFP_ATOMIC);
49 get_io_context(icq->ioc);
54 * Mark a hardware queue as needing a restart. For shared queues, maintain
55 * a count of how many hardware queues are marked for restart.
57 static void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx)
59 if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
62 set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
65 void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx)
67 if (!test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
69 clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
71 blk_mq_run_hw_queue(hctx, true);
75 * Only SCSI implements .get_budget and .put_budget, and SCSI restarts
76 * its queue by itself in its completion handler, so we don't need to
77 * restart queue if .get_budget() returns BLK_STS_NO_RESOURCE.
79 static void blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
81 struct request_queue *q = hctx->queue;
82 struct elevator_queue *e = q->elevator;
88 if (e->type->ops.mq.has_work &&
89 !e->type->ops.mq.has_work(hctx))
92 if (!blk_mq_get_dispatch_budget(hctx))
95 rq = e->type->ops.mq.dispatch_request(hctx);
97 blk_mq_put_dispatch_budget(hctx);
102 * Now this rq owns the budget which has to be released
103 * if this rq won't be queued to driver via .queue_rq()
104 * in blk_mq_dispatch_rq_list().
106 list_add(&rq->queuelist, &rq_list);
107 } while (blk_mq_dispatch_rq_list(q, &rq_list, true));
110 static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx,
111 struct blk_mq_ctx *ctx)
113 unsigned idx = ctx->index_hw;
115 if (++idx == hctx->nr_ctx)
118 return hctx->ctxs[idx];
122 * Only SCSI implements .get_budget and .put_budget, and SCSI restarts
123 * its queue by itself in its completion handler, so we don't need to
124 * restart queue if .get_budget() returns BLK_STS_NO_RESOURCE.
126 static void blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
128 struct request_queue *q = hctx->queue;
130 struct blk_mq_ctx *ctx = READ_ONCE(hctx->dispatch_from);
135 if (!sbitmap_any_bit_set(&hctx->ctx_map))
138 if (!blk_mq_get_dispatch_budget(hctx))
141 rq = blk_mq_dequeue_from_ctx(hctx, ctx);
143 blk_mq_put_dispatch_budget(hctx);
148 * Now this rq owns the budget which has to be released
149 * if this rq won't be queued to driver via .queue_rq()
150 * in blk_mq_dispatch_rq_list().
152 list_add(&rq->queuelist, &rq_list);
154 /* round robin for fair dispatch */
155 ctx = blk_mq_next_ctx(hctx, rq->mq_ctx);
157 } while (blk_mq_dispatch_rq_list(q, &rq_list, true));
159 WRITE_ONCE(hctx->dispatch_from, ctx);
162 void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
164 struct request_queue *q = hctx->queue;
165 struct elevator_queue *e = q->elevator;
166 const bool has_sched_dispatch = e && e->type->ops.mq.dispatch_request;
169 /* RCU or SRCU read lock is needed before checking quiesced flag */
170 if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)))
176 * If we have previous entries on our dispatch list, grab them first for
177 * more fair dispatch.
179 if (!list_empty_careful(&hctx->dispatch)) {
180 spin_lock(&hctx->lock);
181 if (!list_empty(&hctx->dispatch))
182 list_splice_init(&hctx->dispatch, &rq_list);
183 spin_unlock(&hctx->lock);
187 * Only ask the scheduler for requests, if we didn't have residual
188 * requests from the dispatch list. This is to avoid the case where
189 * we only ever dispatch a fraction of the requests available because
190 * of low device queue depth. Once we pull requests out of the IO
191 * scheduler, we can no longer merge or sort them. So it's best to
192 * leave them there for as long as we can. Mark the hw queue as
193 * needing a restart in that case.
195 * We want to dispatch from the scheduler if there was nothing
196 * on the dispatch list or we were able to dispatch from the
199 if (!list_empty(&rq_list)) {
200 blk_mq_sched_mark_restart_hctx(hctx);
201 if (blk_mq_dispatch_rq_list(q, &rq_list, false)) {
202 if (has_sched_dispatch)
203 blk_mq_do_dispatch_sched(hctx);
205 blk_mq_do_dispatch_ctx(hctx);
207 } else if (has_sched_dispatch) {
208 blk_mq_do_dispatch_sched(hctx);
209 } else if (q->mq_ops->get_budget) {
211 * If we need to get budget before queuing request, we
212 * dequeue request one by one from sw queue for avoiding
213 * to mess up I/O merge when dispatch runs out of resource.
215 * TODO: get more budgets, and dequeue more requests in
218 blk_mq_do_dispatch_ctx(hctx);
220 blk_mq_flush_busy_ctxs(hctx, &rq_list);
221 blk_mq_dispatch_rq_list(q, &rq_list, false);
225 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
226 struct request **merged_request)
230 switch (elv_merge(q, &rq, bio)) {
231 case ELEVATOR_BACK_MERGE:
232 if (!blk_mq_sched_allow_merge(q, rq, bio))
234 if (!bio_attempt_back_merge(q, rq, bio))
236 *merged_request = attempt_back_merge(q, rq);
237 if (!*merged_request)
238 elv_merged_request(q, rq, ELEVATOR_BACK_MERGE);
240 case ELEVATOR_FRONT_MERGE:
241 if (!blk_mq_sched_allow_merge(q, rq, bio))
243 if (!bio_attempt_front_merge(q, rq, bio))
245 *merged_request = attempt_front_merge(q, rq);
246 if (!*merged_request)
247 elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
249 case ELEVATOR_DISCARD_MERGE:
250 return bio_attempt_discard_merge(q, rq, bio);
255 EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
258 * Iterate list of requests and see if we can merge this bio with any
261 bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
267 list_for_each_entry_reverse(rq, list, queuelist) {
273 if (!blk_rq_merge_ok(rq, bio))
276 switch (blk_try_merge(rq, bio)) {
277 case ELEVATOR_BACK_MERGE:
278 if (blk_mq_sched_allow_merge(q, rq, bio))
279 merged = bio_attempt_back_merge(q, rq, bio);
281 case ELEVATOR_FRONT_MERGE:
282 if (blk_mq_sched_allow_merge(q, rq, bio))
283 merged = bio_attempt_front_merge(q, rq, bio);
285 case ELEVATOR_DISCARD_MERGE:
286 merged = bio_attempt_discard_merge(q, rq, bio);
297 EXPORT_SYMBOL_GPL(blk_mq_bio_list_merge);
300 * Reverse check our software queue for entries that we could potentially
301 * merge with. Currently includes a hand-wavy stop count of 8, to not spend
302 * too much time checking for merges.
304 static bool blk_mq_attempt_merge(struct request_queue *q,
305 struct blk_mq_ctx *ctx, struct bio *bio)
307 lockdep_assert_held(&ctx->lock);
309 if (blk_mq_bio_list_merge(q, &ctx->rq_list, bio)) {
317 bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
319 struct elevator_queue *e = q->elevator;
320 struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
321 struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
324 if (e && e->type->ops.mq.bio_merge) {
326 return e->type->ops.mq.bio_merge(hctx, bio);
329 if ((hctx->flags & BLK_MQ_F_SHOULD_MERGE) &&
330 !list_empty_careful(&ctx->rq_list)) {
331 /* default per sw-queue merge */
332 spin_lock(&ctx->lock);
333 ret = blk_mq_attempt_merge(q, ctx, bio);
334 spin_unlock(&ctx->lock);
341 bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq)
343 return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq);
345 EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge);
347 void blk_mq_sched_request_inserted(struct request *rq)
349 trace_block_rq_insert(rq->q, rq);
351 EXPORT_SYMBOL_GPL(blk_mq_sched_request_inserted);
353 static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx,
357 /* dispatch flush rq directly */
358 if (rq->rq_flags & RQF_FLUSH_SEQ) {
359 spin_lock(&hctx->lock);
360 list_add(&rq->queuelist, &hctx->dispatch);
361 spin_unlock(&hctx->lock);
366 rq->rq_flags |= RQF_SORTED;
371 void blk_mq_sched_insert_request(struct request *rq, bool at_head,
372 bool run_queue, bool async)
374 struct request_queue *q = rq->q;
375 struct elevator_queue *e = q->elevator;
376 struct blk_mq_ctx *ctx = rq->mq_ctx;
377 struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
379 /* flush rq in flush machinery need to be dispatched directly */
380 if (!(rq->rq_flags & RQF_FLUSH_SEQ) && op_is_flush(rq->cmd_flags)) {
381 blk_insert_flush(rq);
385 WARN_ON(e && (rq->tag != -1));
387 if (blk_mq_sched_bypass_insert(hctx, !!e, rq))
390 if (e && e->type->ops.mq.insert_requests) {
393 list_add(&rq->queuelist, &list);
394 e->type->ops.mq.insert_requests(hctx, &list, at_head);
396 spin_lock(&ctx->lock);
397 __blk_mq_insert_request(hctx, rq, at_head);
398 spin_unlock(&ctx->lock);
403 blk_mq_run_hw_queue(hctx, async);
406 void blk_mq_sched_insert_requests(struct request_queue *q,
407 struct blk_mq_ctx *ctx,
408 struct list_head *list, bool run_queue_async)
410 struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
411 struct elevator_queue *e = hctx->queue->elevator;
413 if (e && e->type->ops.mq.insert_requests)
414 e->type->ops.mq.insert_requests(hctx, list, false);
416 blk_mq_insert_requests(hctx, ctx, list);
418 blk_mq_run_hw_queue(hctx, run_queue_async);
421 static void blk_mq_sched_free_tags(struct blk_mq_tag_set *set,
422 struct blk_mq_hw_ctx *hctx,
423 unsigned int hctx_idx)
425 if (hctx->sched_tags) {
426 blk_mq_free_rqs(set, hctx->sched_tags, hctx_idx);
427 blk_mq_free_rq_map(hctx->sched_tags);
428 hctx->sched_tags = NULL;
432 static int blk_mq_sched_alloc_tags(struct request_queue *q,
433 struct blk_mq_hw_ctx *hctx,
434 unsigned int hctx_idx)
436 struct blk_mq_tag_set *set = q->tag_set;
439 hctx->sched_tags = blk_mq_alloc_rq_map(set, hctx_idx, q->nr_requests,
441 if (!hctx->sched_tags)
444 ret = blk_mq_alloc_rqs(set, hctx->sched_tags, hctx_idx, q->nr_requests);
446 blk_mq_sched_free_tags(set, hctx, hctx_idx);
451 static void blk_mq_sched_tags_teardown(struct request_queue *q)
453 struct blk_mq_tag_set *set = q->tag_set;
454 struct blk_mq_hw_ctx *hctx;
457 queue_for_each_hw_ctx(q, hctx, i)
458 blk_mq_sched_free_tags(set, hctx, i);
461 int blk_mq_sched_init_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,
462 unsigned int hctx_idx)
464 struct elevator_queue *e = q->elevator;
470 ret = blk_mq_sched_alloc_tags(q, hctx, hctx_idx);
474 if (e->type->ops.mq.init_hctx) {
475 ret = e->type->ops.mq.init_hctx(hctx, hctx_idx);
477 blk_mq_sched_free_tags(q->tag_set, hctx, hctx_idx);
482 blk_mq_debugfs_register_sched_hctx(q, hctx);
487 void blk_mq_sched_exit_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,
488 unsigned int hctx_idx)
490 struct elevator_queue *e = q->elevator;
495 blk_mq_debugfs_unregister_sched_hctx(hctx);
497 if (e->type->ops.mq.exit_hctx && hctx->sched_data) {
498 e->type->ops.mq.exit_hctx(hctx, hctx_idx);
499 hctx->sched_data = NULL;
502 blk_mq_sched_free_tags(q->tag_set, hctx, hctx_idx);
505 int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
507 struct blk_mq_hw_ctx *hctx;
508 struct elevator_queue *eq;
514 q->nr_requests = q->tag_set->queue_depth;
519 * Default to double of smaller one between hw queue_depth and 128,
520 * since we don't split into sync/async like the old code did.
521 * Additionally, this is a per-hw queue depth.
523 q->nr_requests = 2 * min_t(unsigned int, q->tag_set->queue_depth,
526 queue_for_each_hw_ctx(q, hctx, i) {
527 ret = blk_mq_sched_alloc_tags(q, hctx, i);
532 ret = e->ops.mq.init_sched(q, e);
536 blk_mq_debugfs_register_sched(q);
538 queue_for_each_hw_ctx(q, hctx, i) {
539 if (e->ops.mq.init_hctx) {
540 ret = e->ops.mq.init_hctx(hctx, i);
543 blk_mq_exit_sched(q, eq);
544 kobject_put(&eq->kobj);
548 blk_mq_debugfs_register_sched_hctx(q, hctx);
554 blk_mq_sched_tags_teardown(q);
559 void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e)
561 struct blk_mq_hw_ctx *hctx;
564 queue_for_each_hw_ctx(q, hctx, i) {
565 blk_mq_debugfs_unregister_sched_hctx(hctx);
566 if (e->type->ops.mq.exit_hctx && hctx->sched_data) {
567 e->type->ops.mq.exit_hctx(hctx, i);
568 hctx->sched_data = NULL;
571 blk_mq_debugfs_unregister_sched(q);
572 if (e->type->ops.mq.exit_sched)
573 e->type->ops.mq.exit_sched(e);
574 blk_mq_sched_tags_teardown(q);