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-sched.h"
15 #include "blk-mq-tag.h"
18 void blk_mq_sched_free_hctx_data(struct request_queue *q,
19 void (*exit)(struct blk_mq_hw_ctx *))
21 struct blk_mq_hw_ctx *hctx;
24 queue_for_each_hw_ctx(q, hctx, i) {
25 if (exit && hctx->sched_data)
27 kfree(hctx->sched_data);
28 hctx->sched_data = NULL;
31 EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
33 int blk_mq_sched_init_hctx_data(struct request_queue *q, size_t size,
34 int (*init)(struct blk_mq_hw_ctx *),
35 void (*exit)(struct blk_mq_hw_ctx *))
37 struct blk_mq_hw_ctx *hctx;
41 queue_for_each_hw_ctx(q, hctx, i) {
42 hctx->sched_data = kmalloc_node(size, GFP_KERNEL, hctx->numa_node);
43 if (!hctx->sched_data) {
52 * We don't want to give exit() a partially
53 * initialized sched_data. init() must clean up
56 kfree(hctx->sched_data);
57 hctx->sched_data = NULL;
65 blk_mq_sched_free_hctx_data(q, exit);
68 EXPORT_SYMBOL_GPL(blk_mq_sched_init_hctx_data);
70 static void __blk_mq_sched_assign_ioc(struct request_queue *q,
73 struct io_context *ioc)
77 spin_lock_irq(q->queue_lock);
78 icq = ioc_lookup_icq(ioc, q);
79 spin_unlock_irq(q->queue_lock);
82 icq = ioc_create_icq(ioc, q, GFP_ATOMIC);
88 if (!blk_mq_sched_get_rq_priv(q, rq, bio)) {
89 rq->rq_flags |= RQF_ELVPRIV;
90 get_io_context(icq->ioc);
97 static void blk_mq_sched_assign_ioc(struct request_queue *q,
98 struct request *rq, struct bio *bio)
100 struct io_context *ioc;
104 __blk_mq_sched_assign_ioc(q, rq, bio, ioc);
107 struct request *blk_mq_sched_get_request(struct request_queue *q,
110 struct blk_mq_alloc_data *data)
112 struct elevator_queue *e = q->elevator;
113 struct blk_mq_hw_ctx *hctx;
114 struct blk_mq_ctx *ctx;
117 blk_queue_enter_live(q);
118 ctx = blk_mq_get_ctx(q);
119 hctx = blk_mq_map_queue(q, ctx->cpu);
121 blk_mq_set_alloc_data(data, q, data->flags, ctx, hctx);
124 data->flags |= BLK_MQ_REQ_INTERNAL;
127 * Flush requests are special and go directly to the
130 if (!op_is_flush(op) && e->type->ops.mq.get_request) {
131 rq = e->type->ops.mq.get_request(q, op, data);
133 rq->rq_flags |= RQF_QUEUED;
135 rq = __blk_mq_alloc_request(data, op);
137 rq = __blk_mq_alloc_request(data, op);
139 data->hctx->tags->rqs[rq->tag] = rq;
143 if (!op_is_flush(op)) {
145 if (e && e->type->icq_cache)
146 blk_mq_sched_assign_ioc(q, rq, bio);
148 data->hctx->queued++;
156 void blk_mq_sched_put_request(struct request *rq)
158 struct request_queue *q = rq->q;
159 struct elevator_queue *e = q->elevator;
161 if (rq->rq_flags & RQF_ELVPRIV) {
162 blk_mq_sched_put_rq_priv(rq->q, rq);
164 put_io_context(rq->elv.icq->ioc);
169 if ((rq->rq_flags & RQF_QUEUED) && e && e->type->ops.mq.put_request)
170 e->type->ops.mq.put_request(rq);
172 blk_mq_finish_request(rq);
175 void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
177 struct elevator_queue *e = hctx->queue->elevator;
178 const bool has_sched_dispatch = e && e->type->ops.mq.dispatch_request;
179 bool did_work = false;
182 if (unlikely(blk_mq_hctx_stopped(hctx)))
188 * If we have previous entries on our dispatch list, grab them first for
189 * more fair dispatch.
191 if (!list_empty_careful(&hctx->dispatch)) {
192 spin_lock(&hctx->lock);
193 if (!list_empty(&hctx->dispatch))
194 list_splice_init(&hctx->dispatch, &rq_list);
195 spin_unlock(&hctx->lock);
199 * Only ask the scheduler for requests, if we didn't have residual
200 * requests from the dispatch list. This is to avoid the case where
201 * we only ever dispatch a fraction of the requests available because
202 * of low device queue depth. Once we pull requests out of the IO
203 * scheduler, we can no longer merge or sort them. So it's best to
204 * leave them there for as long as we can. Mark the hw queue as
205 * needing a restart in that case.
207 if (!list_empty(&rq_list)) {
208 blk_mq_sched_mark_restart_hctx(hctx);
209 did_work = blk_mq_dispatch_rq_list(hctx, &rq_list);
210 } else if (!has_sched_dispatch) {
211 blk_mq_flush_busy_ctxs(hctx, &rq_list);
212 blk_mq_dispatch_rq_list(hctx, &rq_list);
216 * We want to dispatch from the scheduler if we had no work left
217 * on the dispatch list, OR if we did have work but weren't able
220 if (!did_work && has_sched_dispatch) {
224 rq = e->type->ops.mq.dispatch_request(hctx);
227 list_add(&rq->queuelist, &rq_list);
228 } while (blk_mq_dispatch_rq_list(hctx, &rq_list));
232 void blk_mq_sched_move_to_dispatch(struct blk_mq_hw_ctx *hctx,
233 struct list_head *rq_list,
234 struct request *(*get_rq)(struct blk_mq_hw_ctx *))
243 list_add_tail(&rq->queuelist, rq_list);
246 EXPORT_SYMBOL_GPL(blk_mq_sched_move_to_dispatch);
248 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
249 struct request **merged_request)
253 switch (elv_merge(q, &rq, bio)) {
254 case ELEVATOR_BACK_MERGE:
255 if (!blk_mq_sched_allow_merge(q, rq, bio))
257 if (!bio_attempt_back_merge(q, rq, bio))
259 *merged_request = attempt_back_merge(q, rq);
260 if (!*merged_request)
261 elv_merged_request(q, rq, ELEVATOR_BACK_MERGE);
263 case ELEVATOR_FRONT_MERGE:
264 if (!blk_mq_sched_allow_merge(q, rq, bio))
266 if (!bio_attempt_front_merge(q, rq, bio))
268 *merged_request = attempt_front_merge(q, rq);
269 if (!*merged_request)
270 elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
276 EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
278 bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
280 struct elevator_queue *e = q->elevator;
282 if (e->type->ops.mq.bio_merge) {
283 struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
284 struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
287 return e->type->ops.mq.bio_merge(hctx, bio);
293 bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq)
295 return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq);
297 EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge);
299 void blk_mq_sched_request_inserted(struct request *rq)
301 trace_block_rq_insert(rq->q, rq);
303 EXPORT_SYMBOL_GPL(blk_mq_sched_request_inserted);
305 static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx,
309 rq->rq_flags |= RQF_SORTED;
314 * If we already have a real request tag, send directly to
317 spin_lock(&hctx->lock);
318 list_add(&rq->queuelist, &hctx->dispatch);
319 spin_unlock(&hctx->lock);
323 static void blk_mq_sched_restart_hctx(struct blk_mq_hw_ctx *hctx)
325 if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state)) {
326 clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
327 if (blk_mq_hctx_has_pending(hctx))
328 blk_mq_run_hw_queue(hctx, true);
332 void blk_mq_sched_restart_queues(struct blk_mq_hw_ctx *hctx)
334 struct request_queue *q = hctx->queue;
337 if (test_bit(QUEUE_FLAG_RESTART, &q->queue_flags)) {
338 if (test_and_clear_bit(QUEUE_FLAG_RESTART, &q->queue_flags)) {
339 queue_for_each_hw_ctx(q, hctx, i)
340 blk_mq_sched_restart_hctx(hctx);
343 blk_mq_sched_restart_hctx(hctx);
348 * Add flush/fua to the queue. If we fail getting a driver tag, then
349 * punt to the requeue list. Requeue will re-invoke us from a context
350 * that's safe to block from.
352 static void blk_mq_sched_insert_flush(struct blk_mq_hw_ctx *hctx,
353 struct request *rq, bool can_block)
355 if (blk_mq_get_driver_tag(rq, &hctx, can_block)) {
356 blk_insert_flush(rq);
357 blk_mq_run_hw_queue(hctx, true);
359 blk_mq_add_to_requeue_list(rq, false, true);
362 void blk_mq_sched_insert_request(struct request *rq, bool at_head,
363 bool run_queue, bool async, bool can_block)
365 struct request_queue *q = rq->q;
366 struct elevator_queue *e = q->elevator;
367 struct blk_mq_ctx *ctx = rq->mq_ctx;
368 struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
370 if (rq->tag == -1 && op_is_flush(rq->cmd_flags)) {
371 blk_mq_sched_insert_flush(hctx, rq, can_block);
375 if (e && blk_mq_sched_bypass_insert(hctx, rq))
378 if (e && e->type->ops.mq.insert_requests) {
381 list_add(&rq->queuelist, &list);
382 e->type->ops.mq.insert_requests(hctx, &list, at_head);
384 spin_lock(&ctx->lock);
385 __blk_mq_insert_request(hctx, rq, at_head);
386 spin_unlock(&ctx->lock);
391 blk_mq_run_hw_queue(hctx, async);
394 void blk_mq_sched_insert_requests(struct request_queue *q,
395 struct blk_mq_ctx *ctx,
396 struct list_head *list, bool run_queue_async)
398 struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
399 struct elevator_queue *e = hctx->queue->elevator;
402 struct request *rq, *next;
405 * We bypass requests that already have a driver tag assigned,
406 * which should only be flushes. Flushes are only ever inserted
407 * as single requests, so we shouldn't ever hit the
408 * WARN_ON_ONCE() below (but let's handle it just in case).
410 list_for_each_entry_safe(rq, next, list, queuelist) {
411 if (WARN_ON_ONCE(rq->tag != -1)) {
412 list_del_init(&rq->queuelist);
413 blk_mq_sched_bypass_insert(hctx, rq);
418 if (e && e->type->ops.mq.insert_requests)
419 e->type->ops.mq.insert_requests(hctx, list, false);
421 blk_mq_insert_requests(hctx, ctx, list);
423 blk_mq_run_hw_queue(hctx, run_queue_async);
426 static void blk_mq_sched_free_tags(struct blk_mq_tag_set *set,
427 struct blk_mq_hw_ctx *hctx,
428 unsigned int hctx_idx)
430 if (hctx->sched_tags) {
431 blk_mq_free_rqs(set, hctx->sched_tags, hctx_idx);
432 blk_mq_free_rq_map(hctx->sched_tags);
433 hctx->sched_tags = NULL;
437 int blk_mq_sched_setup(struct request_queue *q)
439 struct blk_mq_tag_set *set = q->tag_set;
440 struct blk_mq_hw_ctx *hctx;
444 * Default to 256, since we don't split into sync/async like the
445 * old code did. Additionally, this is a per-hw queue depth.
447 q->nr_requests = 2 * BLKDEV_MAX_RQ;
450 * We're switching to using an IO scheduler, so setup the hctx
451 * scheduler tags and switch the request map from the regular
452 * tags to scheduler tags. First allocate what we need, so we
453 * can safely fail and fallback, if needed.
456 queue_for_each_hw_ctx(q, hctx, i) {
457 hctx->sched_tags = blk_mq_alloc_rq_map(set, i, q->nr_requests, 0);
458 if (!hctx->sched_tags) {
462 ret = blk_mq_alloc_rqs(set, hctx->sched_tags, i, q->nr_requests);
468 * If we failed, free what we did allocate
471 queue_for_each_hw_ctx(q, hctx, i) {
472 if (!hctx->sched_tags)
474 blk_mq_sched_free_tags(set, hctx, i);
483 void blk_mq_sched_teardown(struct request_queue *q)
485 struct blk_mq_tag_set *set = q->tag_set;
486 struct blk_mq_hw_ctx *hctx;
489 queue_for_each_hw_ctx(q, hctx, i)
490 blk_mq_sched_free_tags(set, hctx, i);
493 int blk_mq_sched_init(struct request_queue *q)
497 mutex_lock(&q->sysfs_lock);
498 ret = elevator_init(q, NULL);
499 mutex_unlock(&q->sysfs_lock);