1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * blk-mq scheduling framework
4  *
5  * Copyright (C) 2016 Jens Axboe
6  */
7 #include <linux/kernel.h>
8 #include <linux/module.h>
9 #include <linux/blk-mq.h>
10 #include <linux/list_sort.h>
11 
12 #include <trace/events/block.h>
13 
14 #include "blk.h"
15 #include "blk-mq.h"
16 #include "blk-mq-debugfs.h"
17 #include "blk-mq-sched.h"
18 #include "blk-mq-tag.h"
19 #include "blk-wbt.h"
20 
21 /*
22  * Mark a hardware queue as needing a restart.
23  */
blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx * hctx)24 void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx)
25 {
26 	if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
27 		return;
28 
29 	set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
30 }
31 EXPORT_SYMBOL_GPL(blk_mq_sched_mark_restart_hctx);
32 
__blk_mq_sched_restart(struct blk_mq_hw_ctx * hctx)33 void __blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx)
34 {
35 	clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
36 
37 	/*
38 	 * Order clearing SCHED_RESTART and list_empty_careful(&hctx->dispatch)
39 	 * in blk_mq_run_hw_queue(). Its pair is the barrier in
40 	 * blk_mq_dispatch_rq_list(). So dispatch code won't see SCHED_RESTART,
41 	 * meantime new request added to hctx->dispatch is missed to check in
42 	 * blk_mq_run_hw_queue().
43 	 */
44 	smp_mb();
45 
46 	blk_mq_run_hw_queue(hctx, true);
47 }
48 
sched_rq_cmp(void * priv,const struct list_head * a,const struct list_head * b)49 static int sched_rq_cmp(void *priv, const struct list_head *a,
50 			const struct list_head *b)
51 {
52 	struct request *rqa = container_of(a, struct request, queuelist);
53 	struct request *rqb = container_of(b, struct request, queuelist);
54 
55 	return rqa->mq_hctx > rqb->mq_hctx;
56 }
57 
blk_mq_dispatch_hctx_list(struct list_head * rq_list)58 static bool blk_mq_dispatch_hctx_list(struct list_head *rq_list)
59 {
60 	struct blk_mq_hw_ctx *hctx =
61 		list_first_entry(rq_list, struct request, queuelist)->mq_hctx;
62 	struct request *rq;
63 	LIST_HEAD(hctx_list);
64 	unsigned int count = 0;
65 
66 	list_for_each_entry(rq, rq_list, queuelist) {
67 		if (rq->mq_hctx != hctx) {
68 			list_cut_before(&hctx_list, rq_list, &rq->queuelist);
69 			goto dispatch;
70 		}
71 		count++;
72 	}
73 	list_splice_tail_init(rq_list, &hctx_list);
74 
75 dispatch:
76 	return blk_mq_dispatch_rq_list(hctx, &hctx_list, count);
77 }
78 
79 #define BLK_MQ_BUDGET_DELAY	3		/* ms units */
80 
81 /*
82  * Only SCSI implements .get_budget and .put_budget, and SCSI restarts
83  * its queue by itself in its completion handler, so we don't need to
84  * restart queue if .get_budget() fails to get the budget.
85  *
86  * Returns -EAGAIN if hctx->dispatch was found non-empty and run_work has to
87  * be run again.  This is necessary to avoid starving flushes.
88  */
__blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx * hctx)89 static int __blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
90 {
91 	struct request_queue *q = hctx->queue;
92 	struct elevator_queue *e = q->elevator;
93 	bool multi_hctxs = false, run_queue = false;
94 	bool dispatched = false, busy = false;
95 	unsigned int max_dispatch;
96 	LIST_HEAD(rq_list);
97 	int count = 0;
98 
99 	if (hctx->dispatch_busy)
100 		max_dispatch = 1;
101 	else
102 		max_dispatch = hctx->queue->nr_requests;
103 
104 	do {
105 		struct request *rq;
106 		int budget_token;
107 
108 		if (e->type->ops.has_work && !e->type->ops.has_work(hctx))
109 			break;
110 
111 		if (!list_empty_careful(&hctx->dispatch)) {
112 			busy = true;
113 			break;
114 		}
115 
116 		budget_token = blk_mq_get_dispatch_budget(q);
117 		if (budget_token < 0)
118 			break;
119 
120 		rq = e->type->ops.dispatch_request(hctx);
121 		if (!rq) {
122 			blk_mq_put_dispatch_budget(q, budget_token);
123 			/*
124 			 * We're releasing without dispatching. Holding the
125 			 * budget could have blocked any "hctx"s with the
126 			 * same queue and if we didn't dispatch then there's
127 			 * no guarantee anyone will kick the queue.  Kick it
128 			 * ourselves.
129 			 */
130 			run_queue = true;
131 			break;
132 		}
133 
134 		blk_mq_set_rq_budget_token(rq, budget_token);
135 
136 		/*
137 		 * Now this rq owns the budget which has to be released
138 		 * if this rq won't be queued to driver via .queue_rq()
139 		 * in blk_mq_dispatch_rq_list().
140 		 */
141 		list_add_tail(&rq->queuelist, &rq_list);
142 		count++;
143 		if (rq->mq_hctx != hctx)
144 			multi_hctxs = true;
145 
146 		/*
147 		 * If we cannot get tag for the request, stop dequeueing
148 		 * requests from the IO scheduler. We are unlikely to be able
149 		 * to submit them anyway and it creates false impression for
150 		 * scheduling heuristics that the device can take more IO.
151 		 */
152 		if (!blk_mq_get_driver_tag(rq))
153 			break;
154 	} while (count < max_dispatch);
155 
156 	if (!count) {
157 		if (run_queue)
158 			blk_mq_delay_run_hw_queues(q, BLK_MQ_BUDGET_DELAY);
159 	} else if (multi_hctxs) {
160 		/*
161 		 * Requests from different hctx may be dequeued from some
162 		 * schedulers, such as bfq and deadline.
163 		 *
164 		 * Sort the requests in the list according to their hctx,
165 		 * dispatch batching requests from same hctx at a time.
166 		 */
167 		list_sort(NULL, &rq_list, sched_rq_cmp);
168 		do {
169 			dispatched |= blk_mq_dispatch_hctx_list(&rq_list);
170 		} while (!list_empty(&rq_list));
171 	} else {
172 		dispatched = blk_mq_dispatch_rq_list(hctx, &rq_list, count);
173 	}
174 
175 	if (busy)
176 		return -EAGAIN;
177 	return !!dispatched;
178 }
179 
blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx * hctx)180 static int blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
181 {
182 	unsigned long end = jiffies + HZ;
183 	int ret;
184 
185 	do {
186 		ret = __blk_mq_do_dispatch_sched(hctx);
187 		if (ret != 1)
188 			break;
189 		if (need_resched() || time_is_before_jiffies(end)) {
190 			blk_mq_delay_run_hw_queue(hctx, 0);
191 			break;
192 		}
193 	} while (1);
194 
195 	return ret;
196 }
197 
blk_mq_next_ctx(struct blk_mq_hw_ctx * hctx,struct blk_mq_ctx * ctx)198 static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx,
199 					  struct blk_mq_ctx *ctx)
200 {
201 	unsigned short idx = ctx->index_hw[hctx->type];
202 
203 	if (++idx == hctx->nr_ctx)
204 		idx = 0;
205 
206 	return hctx->ctxs[idx];
207 }
208 
209 /*
210  * Only SCSI implements .get_budget and .put_budget, and SCSI restarts
211  * its queue by itself in its completion handler, so we don't need to
212  * restart queue if .get_budget() fails to get the budget.
213  *
214  * Returns -EAGAIN if hctx->dispatch was found non-empty and run_work has to
215  * be run again.  This is necessary to avoid starving flushes.
216  */
blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx * hctx)217 static int blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
218 {
219 	struct request_queue *q = hctx->queue;
220 	LIST_HEAD(rq_list);
221 	struct blk_mq_ctx *ctx = READ_ONCE(hctx->dispatch_from);
222 	int ret = 0;
223 	struct request *rq;
224 
225 	do {
226 		int budget_token;
227 
228 		if (!list_empty_careful(&hctx->dispatch)) {
229 			ret = -EAGAIN;
230 			break;
231 		}
232 
233 		if (!sbitmap_any_bit_set(&hctx->ctx_map))
234 			break;
235 
236 		budget_token = blk_mq_get_dispatch_budget(q);
237 		if (budget_token < 0)
238 			break;
239 
240 		rq = blk_mq_dequeue_from_ctx(hctx, ctx);
241 		if (!rq) {
242 			blk_mq_put_dispatch_budget(q, budget_token);
243 			/*
244 			 * We're releasing without dispatching. Holding the
245 			 * budget could have blocked any "hctx"s with the
246 			 * same queue and if we didn't dispatch then there's
247 			 * no guarantee anyone will kick the queue.  Kick it
248 			 * ourselves.
249 			 */
250 			blk_mq_delay_run_hw_queues(q, BLK_MQ_BUDGET_DELAY);
251 			break;
252 		}
253 
254 		blk_mq_set_rq_budget_token(rq, budget_token);
255 
256 		/*
257 		 * Now this rq owns the budget which has to be released
258 		 * if this rq won't be queued to driver via .queue_rq()
259 		 * in blk_mq_dispatch_rq_list().
260 		 */
261 		list_add(&rq->queuelist, &rq_list);
262 
263 		/* round robin for fair dispatch */
264 		ctx = blk_mq_next_ctx(hctx, rq->mq_ctx);
265 
266 	} while (blk_mq_dispatch_rq_list(rq->mq_hctx, &rq_list, 1));
267 
268 	WRITE_ONCE(hctx->dispatch_from, ctx);
269 	return ret;
270 }
271 
__blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx * hctx)272 static int __blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
273 {
274 	struct request_queue *q = hctx->queue;
275 	const bool has_sched = q->elevator;
276 	int ret = 0;
277 	LIST_HEAD(rq_list);
278 
279 	/*
280 	 * If we have previous entries on our dispatch list, grab them first for
281 	 * more fair dispatch.
282 	 */
283 	if (!list_empty_careful(&hctx->dispatch)) {
284 		spin_lock(&hctx->lock);
285 		if (!list_empty(&hctx->dispatch))
286 			list_splice_init(&hctx->dispatch, &rq_list);
287 		spin_unlock(&hctx->lock);
288 	}
289 
290 	/*
291 	 * Only ask the scheduler for requests, if we didn't have residual
292 	 * requests from the dispatch list. This is to avoid the case where
293 	 * we only ever dispatch a fraction of the requests available because
294 	 * of low device queue depth. Once we pull requests out of the IO
295 	 * scheduler, we can no longer merge or sort them. So it's best to
296 	 * leave them there for as long as we can. Mark the hw queue as
297 	 * needing a restart in that case.
298 	 *
299 	 * We want to dispatch from the scheduler if there was nothing
300 	 * on the dispatch list or we were able to dispatch from the
301 	 * dispatch list.
302 	 */
303 	if (!list_empty(&rq_list)) {
304 		blk_mq_sched_mark_restart_hctx(hctx);
305 		if (blk_mq_dispatch_rq_list(hctx, &rq_list, 0)) {
306 			if (has_sched)
307 				ret = blk_mq_do_dispatch_sched(hctx);
308 			else
309 				ret = blk_mq_do_dispatch_ctx(hctx);
310 		}
311 	} else if (has_sched) {
312 		ret = blk_mq_do_dispatch_sched(hctx);
313 	} else if (hctx->dispatch_busy) {
314 		/* dequeue request one by one from sw queue if queue is busy */
315 		ret = blk_mq_do_dispatch_ctx(hctx);
316 	} else {
317 		blk_mq_flush_busy_ctxs(hctx, &rq_list);
318 		blk_mq_dispatch_rq_list(hctx, &rq_list, 0);
319 	}
320 
321 	return ret;
322 }
323 
blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx * hctx)324 void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
325 {
326 	struct request_queue *q = hctx->queue;
327 
328 	/* RCU or SRCU read lock is needed before checking quiesced flag */
329 	if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)))
330 		return;
331 
332 	hctx->run++;
333 
334 	/*
335 	 * A return of -EAGAIN is an indication that hctx->dispatch is not
336 	 * empty and we must run again in order to avoid starving flushes.
337 	 */
338 	if (__blk_mq_sched_dispatch_requests(hctx) == -EAGAIN) {
339 		if (__blk_mq_sched_dispatch_requests(hctx) == -EAGAIN)
340 			blk_mq_run_hw_queue(hctx, true);
341 	}
342 }
343 
blk_mq_sched_bio_merge(struct request_queue * q,struct bio * bio,unsigned int nr_segs)344 bool blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
345 		unsigned int nr_segs)
346 {
347 	struct elevator_queue *e = q->elevator;
348 	struct blk_mq_ctx *ctx;
349 	struct blk_mq_hw_ctx *hctx;
350 	bool ret = false;
351 	enum hctx_type type;
352 
353 	if (e && e->type->ops.bio_merge) {
354 		ret = e->type->ops.bio_merge(q, bio, nr_segs);
355 		goto out_put;
356 	}
357 
358 	ctx = blk_mq_get_ctx(q);
359 	hctx = blk_mq_map_queue(q, bio->bi_opf, ctx);
360 	type = hctx->type;
361 	if (!(hctx->flags & BLK_MQ_F_SHOULD_MERGE) ||
362 	    list_empty_careful(&ctx->rq_lists[type]))
363 		goto out_put;
364 
365 	/* default per sw-queue merge */
366 	spin_lock(&ctx->lock);
367 	/*
368 	 * Reverse check our software queue for entries that we could
369 	 * potentially merge with. Currently includes a hand-wavy stop
370 	 * count of 8, to not spend too much time checking for merges.
371 	 */
372 	if (blk_bio_list_merge(q, &ctx->rq_lists[type], bio, nr_segs))
373 		ret = true;
374 
375 	spin_unlock(&ctx->lock);
376 out_put:
377 	return ret;
378 }
379 
blk_mq_sched_try_insert_merge(struct request_queue * q,struct request * rq,struct list_head * free)380 bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq,
381 				   struct list_head *free)
382 {
383 	return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq, free);
384 }
385 EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge);
386 
blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx * hctx,struct request * rq)387 static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx,
388 				       struct request *rq)
389 {
390 	/*
391 	 * dispatch flush and passthrough rq directly
392 	 *
393 	 * passthrough request has to be added to hctx->dispatch directly.
394 	 * For some reason, device may be in one situation which can't
395 	 * handle FS request, so STS_RESOURCE is always returned and the
396 	 * FS request will be added to hctx->dispatch. However passthrough
397 	 * request may be required at that time for fixing the problem. If
398 	 * passthrough request is added to scheduler queue, there isn't any
399 	 * chance to dispatch it given we prioritize requests in hctx->dispatch.
400 	 */
401 	if ((rq->rq_flags & RQF_FLUSH_SEQ) || blk_rq_is_passthrough(rq))
402 		return true;
403 
404 	return false;
405 }
406 
blk_mq_sched_insert_request(struct request * rq,bool at_head,bool run_queue,bool async)407 void blk_mq_sched_insert_request(struct request *rq, bool at_head,
408 				 bool run_queue, bool async)
409 {
410 	struct request_queue *q = rq->q;
411 	struct elevator_queue *e = q->elevator;
412 	struct blk_mq_ctx *ctx = rq->mq_ctx;
413 	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
414 
415 	WARN_ON(e && (rq->tag != BLK_MQ_NO_TAG));
416 
417 	if (blk_mq_sched_bypass_insert(hctx, rq)) {
418 		/*
419 		 * Firstly normal IO request is inserted to scheduler queue or
420 		 * sw queue, meantime we add flush request to dispatch queue(
421 		 * hctx->dispatch) directly and there is at most one in-flight
422 		 * flush request for each hw queue, so it doesn't matter to add
423 		 * flush request to tail or front of the dispatch queue.
424 		 *
425 		 * Secondly in case of NCQ, flush request belongs to non-NCQ
426 		 * command, and queueing it will fail when there is any
427 		 * in-flight normal IO request(NCQ command). When adding flush
428 		 * rq to the front of hctx->dispatch, it is easier to introduce
429 		 * extra time to flush rq's latency because of S_SCHED_RESTART
430 		 * compared with adding to the tail of dispatch queue, then
431 		 * chance of flush merge is increased, and less flush requests
432 		 * will be issued to controller. It is observed that ~10% time
433 		 * is saved in blktests block/004 on disk attached to AHCI/NCQ
434 		 * drive when adding flush rq to the front of hctx->dispatch.
435 		 *
436 		 * Simply queue flush rq to the front of hctx->dispatch so that
437 		 * intensive flush workloads can benefit in case of NCQ HW.
438 		 */
439 		at_head = (rq->rq_flags & RQF_FLUSH_SEQ) ? true : at_head;
440 		blk_mq_request_bypass_insert(rq, at_head, false);
441 		goto run;
442 	}
443 
444 	if (e) {
445 		LIST_HEAD(list);
446 
447 		list_add(&rq->queuelist, &list);
448 		e->type->ops.insert_requests(hctx, &list, at_head);
449 	} else {
450 		spin_lock(&ctx->lock);
451 		__blk_mq_insert_request(hctx, rq, at_head);
452 		spin_unlock(&ctx->lock);
453 	}
454 
455 run:
456 	if (run_queue)
457 		blk_mq_run_hw_queue(hctx, async);
458 }
459 
blk_mq_sched_insert_requests(struct blk_mq_hw_ctx * hctx,struct blk_mq_ctx * ctx,struct list_head * list,bool run_queue_async)460 void blk_mq_sched_insert_requests(struct blk_mq_hw_ctx *hctx,
461 				  struct blk_mq_ctx *ctx,
462 				  struct list_head *list, bool run_queue_async)
463 {
464 	struct elevator_queue *e;
465 	struct request_queue *q = hctx->queue;
466 
467 	/*
468 	 * blk_mq_sched_insert_requests() is called from flush plug
469 	 * context only, and hold one usage counter to prevent queue
470 	 * from being released.
471 	 */
472 	percpu_ref_get(&q->q_usage_counter);
473 
474 	e = hctx->queue->elevator;
475 	if (e) {
476 		e->type->ops.insert_requests(hctx, list, false);
477 	} else {
478 		/*
479 		 * try to issue requests directly if the hw queue isn't
480 		 * busy in case of 'none' scheduler, and this way may save
481 		 * us one extra enqueue & dequeue to sw queue.
482 		 */
483 		if (!hctx->dispatch_busy && !run_queue_async) {
484 			blk_mq_run_dispatch_ops(hctx->queue,
485 				blk_mq_try_issue_list_directly(hctx, list));
486 			if (list_empty(list))
487 				goto out;
488 		}
489 		blk_mq_insert_requests(hctx, ctx, list);
490 	}
491 
492 	blk_mq_run_hw_queue(hctx, run_queue_async);
493  out:
494 	percpu_ref_put(&q->q_usage_counter);
495 }
496 
blk_mq_sched_alloc_map_and_rqs(struct request_queue * q,struct blk_mq_hw_ctx * hctx,unsigned int hctx_idx)497 static int blk_mq_sched_alloc_map_and_rqs(struct request_queue *q,
498 					  struct blk_mq_hw_ctx *hctx,
499 					  unsigned int hctx_idx)
500 {
501 	if (blk_mq_is_shared_tags(q->tag_set->flags)) {
502 		hctx->sched_tags = q->sched_shared_tags;
503 		return 0;
504 	}
505 
506 	hctx->sched_tags = blk_mq_alloc_map_and_rqs(q->tag_set, hctx_idx,
507 						    q->nr_requests);
508 
509 	if (!hctx->sched_tags)
510 		return -ENOMEM;
511 	return 0;
512 }
513 
blk_mq_exit_sched_shared_tags(struct request_queue * queue)514 static void blk_mq_exit_sched_shared_tags(struct request_queue *queue)
515 {
516 	blk_mq_free_rq_map(queue->sched_shared_tags);
517 	queue->sched_shared_tags = NULL;
518 }
519 
520 /* called in queue's release handler, tagset has gone away */
blk_mq_sched_tags_teardown(struct request_queue * q,unsigned int flags)521 static void blk_mq_sched_tags_teardown(struct request_queue *q, unsigned int flags)
522 {
523 	struct blk_mq_hw_ctx *hctx;
524 	unsigned long i;
525 
526 	queue_for_each_hw_ctx(q, hctx, i) {
527 		if (hctx->sched_tags) {
528 			if (!blk_mq_is_shared_tags(flags))
529 				blk_mq_free_rq_map(hctx->sched_tags);
530 			hctx->sched_tags = NULL;
531 		}
532 	}
533 
534 	if (blk_mq_is_shared_tags(flags))
535 		blk_mq_exit_sched_shared_tags(q);
536 }
537 
blk_mq_init_sched_shared_tags(struct request_queue * queue)538 static int blk_mq_init_sched_shared_tags(struct request_queue *queue)
539 {
540 	struct blk_mq_tag_set *set = queue->tag_set;
541 
542 	/*
543 	 * Set initial depth at max so that we don't need to reallocate for
544 	 * updating nr_requests.
545 	 */
546 	queue->sched_shared_tags = blk_mq_alloc_map_and_rqs(set,
547 						BLK_MQ_NO_HCTX_IDX,
548 						MAX_SCHED_RQ);
549 	if (!queue->sched_shared_tags)
550 		return -ENOMEM;
551 
552 	blk_mq_tag_update_sched_shared_tags(queue);
553 
554 	return 0;
555 }
556 
557 /* caller must have a reference to @e, will grab another one if successful */
blk_mq_init_sched(struct request_queue * q,struct elevator_type * e)558 int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
559 {
560 	unsigned int flags = q->tag_set->flags;
561 	struct blk_mq_hw_ctx *hctx;
562 	struct elevator_queue *eq;
563 	unsigned long i;
564 	int ret;
565 
566 	/*
567 	 * Default to double of smaller one between hw queue_depth and 128,
568 	 * since we don't split into sync/async like the old code did.
569 	 * Additionally, this is a per-hw queue depth.
570 	 */
571 	q->nr_requests = 2 * min_t(unsigned int, q->tag_set->queue_depth,
572 				   BLKDEV_DEFAULT_RQ);
573 
574 	if (blk_mq_is_shared_tags(flags)) {
575 		ret = blk_mq_init_sched_shared_tags(q);
576 		if (ret)
577 			return ret;
578 	}
579 
580 	queue_for_each_hw_ctx(q, hctx, i) {
581 		ret = blk_mq_sched_alloc_map_and_rqs(q, hctx, i);
582 		if (ret)
583 			goto err_free_map_and_rqs;
584 	}
585 
586 	ret = e->ops.init_sched(q, e);
587 	if (ret)
588 		goto err_free_map_and_rqs;
589 
590 	mutex_lock(&q->debugfs_mutex);
591 	blk_mq_debugfs_register_sched(q);
592 	mutex_unlock(&q->debugfs_mutex);
593 
594 	queue_for_each_hw_ctx(q, hctx, i) {
595 		if (e->ops.init_hctx) {
596 			ret = e->ops.init_hctx(hctx, i);
597 			if (ret) {
598 				eq = q->elevator;
599 				blk_mq_sched_free_rqs(q);
600 				blk_mq_exit_sched(q, eq);
601 				kobject_put(&eq->kobj);
602 				return ret;
603 			}
604 		}
605 		mutex_lock(&q->debugfs_mutex);
606 		blk_mq_debugfs_register_sched_hctx(q, hctx);
607 		mutex_unlock(&q->debugfs_mutex);
608 	}
609 
610 	return 0;
611 
612 err_free_map_and_rqs:
613 	blk_mq_sched_free_rqs(q);
614 	blk_mq_sched_tags_teardown(q, flags);
615 
616 	q->elevator = NULL;
617 	return ret;
618 }
619 
620 /*
621  * called in either blk_queue_cleanup or elevator_switch, tagset
622  * is required for freeing requests
623  */
blk_mq_sched_free_rqs(struct request_queue * q)624 void blk_mq_sched_free_rqs(struct request_queue *q)
625 {
626 	struct blk_mq_hw_ctx *hctx;
627 	unsigned long i;
628 
629 	if (blk_mq_is_shared_tags(q->tag_set->flags)) {
630 		blk_mq_free_rqs(q->tag_set, q->sched_shared_tags,
631 				BLK_MQ_NO_HCTX_IDX);
632 	} else {
633 		queue_for_each_hw_ctx(q, hctx, i) {
634 			if (hctx->sched_tags)
635 				blk_mq_free_rqs(q->tag_set,
636 						hctx->sched_tags, i);
637 		}
638 	}
639 }
640 
blk_mq_exit_sched(struct request_queue * q,struct elevator_queue * e)641 void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e)
642 {
643 	struct blk_mq_hw_ctx *hctx;
644 	unsigned long i;
645 	unsigned int flags = 0;
646 
647 	queue_for_each_hw_ctx(q, hctx, i) {
648 		mutex_lock(&q->debugfs_mutex);
649 		blk_mq_debugfs_unregister_sched_hctx(hctx);
650 		mutex_unlock(&q->debugfs_mutex);
651 
652 		if (e->type->ops.exit_hctx && hctx->sched_data) {
653 			e->type->ops.exit_hctx(hctx, i);
654 			hctx->sched_data = NULL;
655 		}
656 		flags = hctx->flags;
657 	}
658 
659 	mutex_lock(&q->debugfs_mutex);
660 	blk_mq_debugfs_unregister_sched(q);
661 	mutex_unlock(&q->debugfs_mutex);
662 
663 	if (e->type->ops.exit_sched)
664 		e->type->ops.exit_sched(e);
665 	blk_mq_sched_tags_teardown(q, flags);
666 	q->elevator = NULL;
667 }
668