xref: /openbmc/linux/block/blk-mq.c (revision 9a234a2a)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Block multiqueue core code
4  *
5  * Copyright (C) 2013-2014 Jens Axboe
6  * Copyright (C) 2013-2014 Christoph Hellwig
7  */
8 #include <linux/kernel.h>
9 #include <linux/module.h>
10 #include <linux/backing-dev.h>
11 #include <linux/bio.h>
12 #include <linux/blkdev.h>
13 #include <linux/blk-integrity.h>
14 #include <linux/kmemleak.h>
15 #include <linux/mm.h>
16 #include <linux/init.h>
17 #include <linux/slab.h>
18 #include <linux/workqueue.h>
19 #include <linux/smp.h>
20 #include <linux/interrupt.h>
21 #include <linux/llist.h>
22 #include <linux/cpu.h>
23 #include <linux/cache.h>
24 #include <linux/sched/sysctl.h>
25 #include <linux/sched/topology.h>
26 #include <linux/sched/signal.h>
27 #include <linux/delay.h>
28 #include <linux/crash_dump.h>
29 #include <linux/prefetch.h>
30 #include <linux/blk-crypto.h>
31 #include <linux/part_stat.h>
32 
33 #include <trace/events/block.h>
34 
35 #include <linux/blk-mq.h>
36 #include <linux/t10-pi.h>
37 #include "blk.h"
38 #include "blk-mq.h"
39 #include "blk-mq-debugfs.h"
40 #include "blk-mq-tag.h"
41 #include "blk-pm.h"
42 #include "blk-stat.h"
43 #include "blk-mq-sched.h"
44 #include "blk-rq-qos.h"
45 #include "blk-ioprio.h"
46 
47 static DEFINE_PER_CPU(struct llist_head, blk_cpu_done);
48 
49 static void blk_mq_poll_stats_start(struct request_queue *q);
50 static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb);
51 
52 static int blk_mq_poll_stats_bkt(const struct request *rq)
53 {
54 	int ddir, sectors, bucket;
55 
56 	ddir = rq_data_dir(rq);
57 	sectors = blk_rq_stats_sectors(rq);
58 
59 	bucket = ddir + 2 * ilog2(sectors);
60 
61 	if (bucket < 0)
62 		return -1;
63 	else if (bucket >= BLK_MQ_POLL_STATS_BKTS)
64 		return ddir + BLK_MQ_POLL_STATS_BKTS - 2;
65 
66 	return bucket;
67 }
68 
69 #define BLK_QC_T_SHIFT		16
70 #define BLK_QC_T_INTERNAL	(1U << 31)
71 
72 static inline struct blk_mq_hw_ctx *blk_qc_to_hctx(struct request_queue *q,
73 		blk_qc_t qc)
74 {
75 	return xa_load(&q->hctx_table,
76 			(qc & ~BLK_QC_T_INTERNAL) >> BLK_QC_T_SHIFT);
77 }
78 
79 static inline struct request *blk_qc_to_rq(struct blk_mq_hw_ctx *hctx,
80 		blk_qc_t qc)
81 {
82 	unsigned int tag = qc & ((1U << BLK_QC_T_SHIFT) - 1);
83 
84 	if (qc & BLK_QC_T_INTERNAL)
85 		return blk_mq_tag_to_rq(hctx->sched_tags, tag);
86 	return blk_mq_tag_to_rq(hctx->tags, tag);
87 }
88 
89 static inline blk_qc_t blk_rq_to_qc(struct request *rq)
90 {
91 	return (rq->mq_hctx->queue_num << BLK_QC_T_SHIFT) |
92 		(rq->tag != -1 ?
93 		 rq->tag : (rq->internal_tag | BLK_QC_T_INTERNAL));
94 }
95 
96 /*
97  * Check if any of the ctx, dispatch list or elevator
98  * have pending work in this hardware queue.
99  */
100 static bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx)
101 {
102 	return !list_empty_careful(&hctx->dispatch) ||
103 		sbitmap_any_bit_set(&hctx->ctx_map) ||
104 			blk_mq_sched_has_work(hctx);
105 }
106 
107 /*
108  * Mark this ctx as having pending work in this hardware queue
109  */
110 static void blk_mq_hctx_mark_pending(struct blk_mq_hw_ctx *hctx,
111 				     struct blk_mq_ctx *ctx)
112 {
113 	const int bit = ctx->index_hw[hctx->type];
114 
115 	if (!sbitmap_test_bit(&hctx->ctx_map, bit))
116 		sbitmap_set_bit(&hctx->ctx_map, bit);
117 }
118 
119 static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
120 				      struct blk_mq_ctx *ctx)
121 {
122 	const int bit = ctx->index_hw[hctx->type];
123 
124 	sbitmap_clear_bit(&hctx->ctx_map, bit);
125 }
126 
127 struct mq_inflight {
128 	struct block_device *part;
129 	unsigned int inflight[2];
130 };
131 
132 static bool blk_mq_check_inflight(struct request *rq, void *priv)
133 {
134 	struct mq_inflight *mi = priv;
135 
136 	if (rq->part && blk_do_io_stat(rq) &&
137 	    (!mi->part->bd_partno || rq->part == mi->part) &&
138 	    blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT)
139 		mi->inflight[rq_data_dir(rq)]++;
140 
141 	return true;
142 }
143 
144 unsigned int blk_mq_in_flight(struct request_queue *q,
145 		struct block_device *part)
146 {
147 	struct mq_inflight mi = { .part = part };
148 
149 	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
150 
151 	return mi.inflight[0] + mi.inflight[1];
152 }
153 
154 void blk_mq_in_flight_rw(struct request_queue *q, struct block_device *part,
155 		unsigned int inflight[2])
156 {
157 	struct mq_inflight mi = { .part = part };
158 
159 	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
160 	inflight[0] = mi.inflight[0];
161 	inflight[1] = mi.inflight[1];
162 }
163 
164 void blk_freeze_queue_start(struct request_queue *q)
165 {
166 	mutex_lock(&q->mq_freeze_lock);
167 	if (++q->mq_freeze_depth == 1) {
168 		percpu_ref_kill(&q->q_usage_counter);
169 		mutex_unlock(&q->mq_freeze_lock);
170 		if (queue_is_mq(q))
171 			blk_mq_run_hw_queues(q, false);
172 	} else {
173 		mutex_unlock(&q->mq_freeze_lock);
174 	}
175 }
176 EXPORT_SYMBOL_GPL(blk_freeze_queue_start);
177 
178 void blk_mq_freeze_queue_wait(struct request_queue *q)
179 {
180 	wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->q_usage_counter));
181 }
182 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait);
183 
184 int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
185 				     unsigned long timeout)
186 {
187 	return wait_event_timeout(q->mq_freeze_wq,
188 					percpu_ref_is_zero(&q->q_usage_counter),
189 					timeout);
190 }
191 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait_timeout);
192 
193 /*
194  * Guarantee no request is in use, so we can change any data structure of
195  * the queue afterward.
196  */
197 void blk_freeze_queue(struct request_queue *q)
198 {
199 	/*
200 	 * In the !blk_mq case we are only calling this to kill the
201 	 * q_usage_counter, otherwise this increases the freeze depth
202 	 * and waits for it to return to zero.  For this reason there is
203 	 * no blk_unfreeze_queue(), and blk_freeze_queue() is not
204 	 * exported to drivers as the only user for unfreeze is blk_mq.
205 	 */
206 	blk_freeze_queue_start(q);
207 	blk_mq_freeze_queue_wait(q);
208 }
209 
210 void blk_mq_freeze_queue(struct request_queue *q)
211 {
212 	/*
213 	 * ...just an alias to keep freeze and unfreeze actions balanced
214 	 * in the blk_mq_* namespace
215 	 */
216 	blk_freeze_queue(q);
217 }
218 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);
219 
220 void __blk_mq_unfreeze_queue(struct request_queue *q, bool force_atomic)
221 {
222 	mutex_lock(&q->mq_freeze_lock);
223 	if (force_atomic)
224 		q->q_usage_counter.data->force_atomic = true;
225 	q->mq_freeze_depth--;
226 	WARN_ON_ONCE(q->mq_freeze_depth < 0);
227 	if (!q->mq_freeze_depth) {
228 		percpu_ref_resurrect(&q->q_usage_counter);
229 		wake_up_all(&q->mq_freeze_wq);
230 	}
231 	mutex_unlock(&q->mq_freeze_lock);
232 }
233 
234 void blk_mq_unfreeze_queue(struct request_queue *q)
235 {
236 	__blk_mq_unfreeze_queue(q, false);
237 }
238 EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);
239 
240 /*
241  * FIXME: replace the scsi_internal_device_*block_nowait() calls in the
242  * mpt3sas driver such that this function can be removed.
243  */
244 void blk_mq_quiesce_queue_nowait(struct request_queue *q)
245 {
246 	unsigned long flags;
247 
248 	spin_lock_irqsave(&q->queue_lock, flags);
249 	if (!q->quiesce_depth++)
250 		blk_queue_flag_set(QUEUE_FLAG_QUIESCED, q);
251 	spin_unlock_irqrestore(&q->queue_lock, flags);
252 }
253 EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
254 
255 /**
256  * blk_mq_wait_quiesce_done() - wait until in-progress quiesce is done
257  * @q: request queue.
258  *
259  * Note: it is driver's responsibility for making sure that quiesce has
260  * been started.
261  */
262 void blk_mq_wait_quiesce_done(struct request_queue *q)
263 {
264 	if (blk_queue_has_srcu(q))
265 		synchronize_srcu(q->srcu);
266 	else
267 		synchronize_rcu();
268 }
269 EXPORT_SYMBOL_GPL(blk_mq_wait_quiesce_done);
270 
271 /**
272  * blk_mq_quiesce_queue() - wait until all ongoing dispatches have finished
273  * @q: request queue.
274  *
275  * Note: this function does not prevent that the struct request end_io()
276  * callback function is invoked. Once this function is returned, we make
277  * sure no dispatch can happen until the queue is unquiesced via
278  * blk_mq_unquiesce_queue().
279  */
280 void blk_mq_quiesce_queue(struct request_queue *q)
281 {
282 	blk_mq_quiesce_queue_nowait(q);
283 	blk_mq_wait_quiesce_done(q);
284 }
285 EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue);
286 
287 /*
288  * blk_mq_unquiesce_queue() - counterpart of blk_mq_quiesce_queue()
289  * @q: request queue.
290  *
291  * This function recovers queue into the state before quiescing
292  * which is done by blk_mq_quiesce_queue.
293  */
294 void blk_mq_unquiesce_queue(struct request_queue *q)
295 {
296 	unsigned long flags;
297 	bool run_queue = false;
298 
299 	spin_lock_irqsave(&q->queue_lock, flags);
300 	if (WARN_ON_ONCE(q->quiesce_depth <= 0)) {
301 		;
302 	} else if (!--q->quiesce_depth) {
303 		blk_queue_flag_clear(QUEUE_FLAG_QUIESCED, q);
304 		run_queue = true;
305 	}
306 	spin_unlock_irqrestore(&q->queue_lock, flags);
307 
308 	/* dispatch requests which are inserted during quiescing */
309 	if (run_queue)
310 		blk_mq_run_hw_queues(q, true);
311 }
312 EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue);
313 
314 void blk_mq_wake_waiters(struct request_queue *q)
315 {
316 	struct blk_mq_hw_ctx *hctx;
317 	unsigned long i;
318 
319 	queue_for_each_hw_ctx(q, hctx, i)
320 		if (blk_mq_hw_queue_mapped(hctx))
321 			blk_mq_tag_wakeup_all(hctx->tags, true);
322 }
323 
324 void blk_rq_init(struct request_queue *q, struct request *rq)
325 {
326 	memset(rq, 0, sizeof(*rq));
327 
328 	INIT_LIST_HEAD(&rq->queuelist);
329 	rq->q = q;
330 	rq->__sector = (sector_t) -1;
331 	INIT_HLIST_NODE(&rq->hash);
332 	RB_CLEAR_NODE(&rq->rb_node);
333 	rq->tag = BLK_MQ_NO_TAG;
334 	rq->internal_tag = BLK_MQ_NO_TAG;
335 	rq->start_time_ns = ktime_get_ns();
336 	rq->part = NULL;
337 	blk_crypto_rq_set_defaults(rq);
338 }
339 EXPORT_SYMBOL(blk_rq_init);
340 
341 static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
342 		struct blk_mq_tags *tags, unsigned int tag, u64 alloc_time_ns)
343 {
344 	struct blk_mq_ctx *ctx = data->ctx;
345 	struct blk_mq_hw_ctx *hctx = data->hctx;
346 	struct request_queue *q = data->q;
347 	struct request *rq = tags->static_rqs[tag];
348 
349 	rq->q = q;
350 	rq->mq_ctx = ctx;
351 	rq->mq_hctx = hctx;
352 	rq->cmd_flags = data->cmd_flags;
353 
354 	if (data->flags & BLK_MQ_REQ_PM)
355 		data->rq_flags |= RQF_PM;
356 	if (blk_queue_io_stat(q))
357 		data->rq_flags |= RQF_IO_STAT;
358 	rq->rq_flags = data->rq_flags;
359 
360 	if (!(data->rq_flags & RQF_ELV)) {
361 		rq->tag = tag;
362 		rq->internal_tag = BLK_MQ_NO_TAG;
363 	} else {
364 		rq->tag = BLK_MQ_NO_TAG;
365 		rq->internal_tag = tag;
366 	}
367 	rq->timeout = 0;
368 
369 	if (blk_mq_need_time_stamp(rq))
370 		rq->start_time_ns = ktime_get_ns();
371 	else
372 		rq->start_time_ns = 0;
373 	rq->part = NULL;
374 #ifdef CONFIG_BLK_RQ_ALLOC_TIME
375 	rq->alloc_time_ns = alloc_time_ns;
376 #endif
377 	rq->io_start_time_ns = 0;
378 	rq->stats_sectors = 0;
379 	rq->nr_phys_segments = 0;
380 #if defined(CONFIG_BLK_DEV_INTEGRITY)
381 	rq->nr_integrity_segments = 0;
382 #endif
383 	rq->end_io = NULL;
384 	rq->end_io_data = NULL;
385 
386 	blk_crypto_rq_set_defaults(rq);
387 	INIT_LIST_HEAD(&rq->queuelist);
388 	/* tag was already set */
389 	WRITE_ONCE(rq->deadline, 0);
390 	req_ref_set(rq, 1);
391 
392 	if (rq->rq_flags & RQF_ELV) {
393 		struct elevator_queue *e = data->q->elevator;
394 
395 		INIT_HLIST_NODE(&rq->hash);
396 		RB_CLEAR_NODE(&rq->rb_node);
397 
398 		if (!op_is_flush(data->cmd_flags) &&
399 		    e->type->ops.prepare_request) {
400 			e->type->ops.prepare_request(rq);
401 			rq->rq_flags |= RQF_ELVPRIV;
402 		}
403 	}
404 
405 	return rq;
406 }
407 
408 static inline struct request *
409 __blk_mq_alloc_requests_batch(struct blk_mq_alloc_data *data,
410 		u64 alloc_time_ns)
411 {
412 	unsigned int tag, tag_offset;
413 	struct blk_mq_tags *tags;
414 	struct request *rq;
415 	unsigned long tag_mask;
416 	int i, nr = 0;
417 
418 	tag_mask = blk_mq_get_tags(data, data->nr_tags, &tag_offset);
419 	if (unlikely(!tag_mask))
420 		return NULL;
421 
422 	tags = blk_mq_tags_from_data(data);
423 	for (i = 0; tag_mask; i++) {
424 		if (!(tag_mask & (1UL << i)))
425 			continue;
426 		tag = tag_offset + i;
427 		prefetch(tags->static_rqs[tag]);
428 		tag_mask &= ~(1UL << i);
429 		rq = blk_mq_rq_ctx_init(data, tags, tag, alloc_time_ns);
430 		rq_list_add(data->cached_rq, rq);
431 		nr++;
432 	}
433 	/* caller already holds a reference, add for remainder */
434 	percpu_ref_get_many(&data->q->q_usage_counter, nr - 1);
435 	data->nr_tags -= nr;
436 
437 	return rq_list_pop(data->cached_rq);
438 }
439 
440 static struct request *__blk_mq_alloc_requests(struct blk_mq_alloc_data *data)
441 {
442 	struct request_queue *q = data->q;
443 	u64 alloc_time_ns = 0;
444 	struct request *rq;
445 	unsigned int tag;
446 
447 	/* alloc_time includes depth and tag waits */
448 	if (blk_queue_rq_alloc_time(q))
449 		alloc_time_ns = ktime_get_ns();
450 
451 	if (data->cmd_flags & REQ_NOWAIT)
452 		data->flags |= BLK_MQ_REQ_NOWAIT;
453 
454 	if (q->elevator) {
455 		struct elevator_queue *e = q->elevator;
456 
457 		data->rq_flags |= RQF_ELV;
458 
459 		/*
460 		 * Flush/passthrough requests are special and go directly to the
461 		 * dispatch list. Don't include reserved tags in the
462 		 * limiting, as it isn't useful.
463 		 */
464 		if (!op_is_flush(data->cmd_flags) &&
465 		    !blk_op_is_passthrough(data->cmd_flags) &&
466 		    e->type->ops.limit_depth &&
467 		    !(data->flags & BLK_MQ_REQ_RESERVED))
468 			e->type->ops.limit_depth(data->cmd_flags, data);
469 	}
470 
471 retry:
472 	data->ctx = blk_mq_get_ctx(q);
473 	data->hctx = blk_mq_map_queue(q, data->cmd_flags, data->ctx);
474 	if (!(data->rq_flags & RQF_ELV))
475 		blk_mq_tag_busy(data->hctx);
476 
477 	if (data->flags & BLK_MQ_REQ_RESERVED)
478 		data->rq_flags |= RQF_RESV;
479 
480 	/*
481 	 * Try batched alloc if we want more than 1 tag.
482 	 */
483 	if (data->nr_tags > 1) {
484 		rq = __blk_mq_alloc_requests_batch(data, alloc_time_ns);
485 		if (rq)
486 			return rq;
487 		data->nr_tags = 1;
488 	}
489 
490 	/*
491 	 * Waiting allocations only fail because of an inactive hctx.  In that
492 	 * case just retry the hctx assignment and tag allocation as CPU hotplug
493 	 * should have migrated us to an online CPU by now.
494 	 */
495 	tag = blk_mq_get_tag(data);
496 	if (tag == BLK_MQ_NO_TAG) {
497 		if (data->flags & BLK_MQ_REQ_NOWAIT)
498 			return NULL;
499 		/*
500 		 * Give up the CPU and sleep for a random short time to
501 		 * ensure that thread using a realtime scheduling class
502 		 * are migrated off the CPU, and thus off the hctx that
503 		 * is going away.
504 		 */
505 		msleep(3);
506 		goto retry;
507 	}
508 
509 	return blk_mq_rq_ctx_init(data, blk_mq_tags_from_data(data), tag,
510 					alloc_time_ns);
511 }
512 
513 static struct request *blk_mq_rq_cache_fill(struct request_queue *q,
514 					    struct blk_plug *plug,
515 					    blk_opf_t opf,
516 					    blk_mq_req_flags_t flags)
517 {
518 	struct blk_mq_alloc_data data = {
519 		.q		= q,
520 		.flags		= flags,
521 		.cmd_flags	= opf,
522 		.nr_tags	= plug->nr_ios,
523 		.cached_rq	= &plug->cached_rq,
524 	};
525 	struct request *rq;
526 
527 	if (blk_queue_enter(q, flags))
528 		return NULL;
529 
530 	plug->nr_ios = 1;
531 
532 	rq = __blk_mq_alloc_requests(&data);
533 	if (unlikely(!rq))
534 		blk_queue_exit(q);
535 	return rq;
536 }
537 
538 static struct request *blk_mq_alloc_cached_request(struct request_queue *q,
539 						   blk_opf_t opf,
540 						   blk_mq_req_flags_t flags)
541 {
542 	struct blk_plug *plug = current->plug;
543 	struct request *rq;
544 
545 	if (!plug)
546 		return NULL;
547 	if (rq_list_empty(plug->cached_rq)) {
548 		if (plug->nr_ios == 1)
549 			return NULL;
550 		rq = blk_mq_rq_cache_fill(q, plug, opf, flags);
551 		if (rq)
552 			goto got_it;
553 		return NULL;
554 	}
555 	rq = rq_list_peek(&plug->cached_rq);
556 	if (!rq || rq->q != q)
557 		return NULL;
558 
559 	if (blk_mq_get_hctx_type(opf) != rq->mq_hctx->type)
560 		return NULL;
561 	if (op_is_flush(rq->cmd_flags) != op_is_flush(opf))
562 		return NULL;
563 
564 	plug->cached_rq = rq_list_next(rq);
565 got_it:
566 	rq->cmd_flags = opf;
567 	INIT_LIST_HEAD(&rq->queuelist);
568 	return rq;
569 }
570 
571 struct request *blk_mq_alloc_request(struct request_queue *q, blk_opf_t opf,
572 		blk_mq_req_flags_t flags)
573 {
574 	struct request *rq;
575 
576 	rq = blk_mq_alloc_cached_request(q, opf, flags);
577 	if (!rq) {
578 		struct blk_mq_alloc_data data = {
579 			.q		= q,
580 			.flags		= flags,
581 			.cmd_flags	= opf,
582 			.nr_tags	= 1,
583 		};
584 		int ret;
585 
586 		ret = blk_queue_enter(q, flags);
587 		if (ret)
588 			return ERR_PTR(ret);
589 
590 		rq = __blk_mq_alloc_requests(&data);
591 		if (!rq)
592 			goto out_queue_exit;
593 	}
594 	rq->__data_len = 0;
595 	rq->__sector = (sector_t) -1;
596 	rq->bio = rq->biotail = NULL;
597 	return rq;
598 out_queue_exit:
599 	blk_queue_exit(q);
600 	return ERR_PTR(-EWOULDBLOCK);
601 }
602 EXPORT_SYMBOL(blk_mq_alloc_request);
603 
604 struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
605 	blk_opf_t opf, blk_mq_req_flags_t flags, unsigned int hctx_idx)
606 {
607 	struct blk_mq_alloc_data data = {
608 		.q		= q,
609 		.flags		= flags,
610 		.cmd_flags	= opf,
611 		.nr_tags	= 1,
612 	};
613 	u64 alloc_time_ns = 0;
614 	struct request *rq;
615 	unsigned int cpu;
616 	unsigned int tag;
617 	int ret;
618 
619 	/* alloc_time includes depth and tag waits */
620 	if (blk_queue_rq_alloc_time(q))
621 		alloc_time_ns = ktime_get_ns();
622 
623 	/*
624 	 * If the tag allocator sleeps we could get an allocation for a
625 	 * different hardware context.  No need to complicate the low level
626 	 * allocator for this for the rare use case of a command tied to
627 	 * a specific queue.
628 	 */
629 	if (WARN_ON_ONCE(!(flags & (BLK_MQ_REQ_NOWAIT | BLK_MQ_REQ_RESERVED))))
630 		return ERR_PTR(-EINVAL);
631 
632 	if (hctx_idx >= q->nr_hw_queues)
633 		return ERR_PTR(-EIO);
634 
635 	ret = blk_queue_enter(q, flags);
636 	if (ret)
637 		return ERR_PTR(ret);
638 
639 	/*
640 	 * Check if the hardware context is actually mapped to anything.
641 	 * If not tell the caller that it should skip this queue.
642 	 */
643 	ret = -EXDEV;
644 	data.hctx = xa_load(&q->hctx_table, hctx_idx);
645 	if (!blk_mq_hw_queue_mapped(data.hctx))
646 		goto out_queue_exit;
647 	cpu = cpumask_first_and(data.hctx->cpumask, cpu_online_mask);
648 	if (cpu >= nr_cpu_ids)
649 		goto out_queue_exit;
650 	data.ctx = __blk_mq_get_ctx(q, cpu);
651 
652 	if (!q->elevator)
653 		blk_mq_tag_busy(data.hctx);
654 	else
655 		data.rq_flags |= RQF_ELV;
656 
657 	if (flags & BLK_MQ_REQ_RESERVED)
658 		data.rq_flags |= RQF_RESV;
659 
660 	ret = -EWOULDBLOCK;
661 	tag = blk_mq_get_tag(&data);
662 	if (tag == BLK_MQ_NO_TAG)
663 		goto out_queue_exit;
664 	rq = blk_mq_rq_ctx_init(&data, blk_mq_tags_from_data(&data), tag,
665 					alloc_time_ns);
666 	rq->__data_len = 0;
667 	rq->__sector = (sector_t) -1;
668 	rq->bio = rq->biotail = NULL;
669 	return rq;
670 
671 out_queue_exit:
672 	blk_queue_exit(q);
673 	return ERR_PTR(ret);
674 }
675 EXPORT_SYMBOL_GPL(blk_mq_alloc_request_hctx);
676 
677 static void __blk_mq_free_request(struct request *rq)
678 {
679 	struct request_queue *q = rq->q;
680 	struct blk_mq_ctx *ctx = rq->mq_ctx;
681 	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
682 	const int sched_tag = rq->internal_tag;
683 
684 	blk_crypto_free_request(rq);
685 	blk_pm_mark_last_busy(rq);
686 	rq->mq_hctx = NULL;
687 	if (rq->tag != BLK_MQ_NO_TAG)
688 		blk_mq_put_tag(hctx->tags, ctx, rq->tag);
689 	if (sched_tag != BLK_MQ_NO_TAG)
690 		blk_mq_put_tag(hctx->sched_tags, ctx, sched_tag);
691 	blk_mq_sched_restart(hctx);
692 	blk_queue_exit(q);
693 }
694 
695 void blk_mq_free_request(struct request *rq)
696 {
697 	struct request_queue *q = rq->q;
698 	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
699 
700 	if ((rq->rq_flags & RQF_ELVPRIV) &&
701 	    q->elevator->type->ops.finish_request)
702 		q->elevator->type->ops.finish_request(rq);
703 
704 	if (rq->rq_flags & RQF_MQ_INFLIGHT)
705 		__blk_mq_dec_active_requests(hctx);
706 
707 	if (unlikely(laptop_mode && !blk_rq_is_passthrough(rq)))
708 		laptop_io_completion(q->disk->bdi);
709 
710 	rq_qos_done(q, rq);
711 
712 	WRITE_ONCE(rq->state, MQ_RQ_IDLE);
713 	if (req_ref_put_and_test(rq))
714 		__blk_mq_free_request(rq);
715 }
716 EXPORT_SYMBOL_GPL(blk_mq_free_request);
717 
718 void blk_mq_free_plug_rqs(struct blk_plug *plug)
719 {
720 	struct request *rq;
721 
722 	while ((rq = rq_list_pop(&plug->cached_rq)) != NULL)
723 		blk_mq_free_request(rq);
724 }
725 
726 void blk_dump_rq_flags(struct request *rq, char *msg)
727 {
728 	printk(KERN_INFO "%s: dev %s: flags=%llx\n", msg,
729 		rq->q->disk ? rq->q->disk->disk_name : "?",
730 		(__force unsigned long long) rq->cmd_flags);
731 
732 	printk(KERN_INFO "  sector %llu, nr/cnr %u/%u\n",
733 	       (unsigned long long)blk_rq_pos(rq),
734 	       blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
735 	printk(KERN_INFO "  bio %p, biotail %p, len %u\n",
736 	       rq->bio, rq->biotail, blk_rq_bytes(rq));
737 }
738 EXPORT_SYMBOL(blk_dump_rq_flags);
739 
740 static void req_bio_endio(struct request *rq, struct bio *bio,
741 			  unsigned int nbytes, blk_status_t error)
742 {
743 	if (unlikely(error)) {
744 		bio->bi_status = error;
745 	} else if (req_op(rq) == REQ_OP_ZONE_APPEND) {
746 		/*
747 		 * Partial zone append completions cannot be supported as the
748 		 * BIO fragments may end up not being written sequentially.
749 		 */
750 		if (bio->bi_iter.bi_size != nbytes)
751 			bio->bi_status = BLK_STS_IOERR;
752 		else
753 			bio->bi_iter.bi_sector = rq->__sector;
754 	}
755 
756 	bio_advance(bio, nbytes);
757 
758 	if (unlikely(rq->rq_flags & RQF_QUIET))
759 		bio_set_flag(bio, BIO_QUIET);
760 	/* don't actually finish bio if it's part of flush sequence */
761 	if (bio->bi_iter.bi_size == 0 && !(rq->rq_flags & RQF_FLUSH_SEQ))
762 		bio_endio(bio);
763 }
764 
765 static void blk_account_io_completion(struct request *req, unsigned int bytes)
766 {
767 	if (req->part && blk_do_io_stat(req)) {
768 		const int sgrp = op_stat_group(req_op(req));
769 
770 		part_stat_lock();
771 		part_stat_add(req->part, sectors[sgrp], bytes >> 9);
772 		part_stat_unlock();
773 	}
774 }
775 
776 static void blk_print_req_error(struct request *req, blk_status_t status)
777 {
778 	printk_ratelimited(KERN_ERR
779 		"%s error, dev %s, sector %llu op 0x%x:(%s) flags 0x%x "
780 		"phys_seg %u prio class %u\n",
781 		blk_status_to_str(status),
782 		req->q->disk ? req->q->disk->disk_name : "?",
783 		blk_rq_pos(req), (__force u32)req_op(req),
784 		blk_op_str(req_op(req)),
785 		(__force u32)(req->cmd_flags & ~REQ_OP_MASK),
786 		req->nr_phys_segments,
787 		IOPRIO_PRIO_CLASS(req->ioprio));
788 }
789 
790 /*
791  * Fully end IO on a request. Does not support partial completions, or
792  * errors.
793  */
794 static void blk_complete_request(struct request *req)
795 {
796 	const bool is_flush = (req->rq_flags & RQF_FLUSH_SEQ) != 0;
797 	int total_bytes = blk_rq_bytes(req);
798 	struct bio *bio = req->bio;
799 
800 	trace_block_rq_complete(req, BLK_STS_OK, total_bytes);
801 
802 	if (!bio)
803 		return;
804 
805 #ifdef CONFIG_BLK_DEV_INTEGRITY
806 	if (blk_integrity_rq(req) && req_op(req) == REQ_OP_READ)
807 		req->q->integrity.profile->complete_fn(req, total_bytes);
808 #endif
809 
810 	blk_account_io_completion(req, total_bytes);
811 
812 	do {
813 		struct bio *next = bio->bi_next;
814 
815 		/* Completion has already been traced */
816 		bio_clear_flag(bio, BIO_TRACE_COMPLETION);
817 
818 		if (req_op(req) == REQ_OP_ZONE_APPEND)
819 			bio->bi_iter.bi_sector = req->__sector;
820 
821 		if (!is_flush)
822 			bio_endio(bio);
823 		bio = next;
824 	} while (bio);
825 
826 	/*
827 	 * Reset counters so that the request stacking driver
828 	 * can find how many bytes remain in the request
829 	 * later.
830 	 */
831 	if (!req->end_io) {
832 		req->bio = NULL;
833 		req->__data_len = 0;
834 	}
835 }
836 
837 /**
838  * blk_update_request - Complete multiple bytes without completing the request
839  * @req:      the request being processed
840  * @error:    block status code
841  * @nr_bytes: number of bytes to complete for @req
842  *
843  * Description:
844  *     Ends I/O on a number of bytes attached to @req, but doesn't complete
845  *     the request structure even if @req doesn't have leftover.
846  *     If @req has leftover, sets it up for the next range of segments.
847  *
848  *     Passing the result of blk_rq_bytes() as @nr_bytes guarantees
849  *     %false return from this function.
850  *
851  * Note:
852  *	The RQF_SPECIAL_PAYLOAD flag is ignored on purpose in this function
853  *      except in the consistency check at the end of this function.
854  *
855  * Return:
856  *     %false - this request doesn't have any more data
857  *     %true  - this request has more data
858  **/
859 bool blk_update_request(struct request *req, blk_status_t error,
860 		unsigned int nr_bytes)
861 {
862 	int total_bytes;
863 
864 	trace_block_rq_complete(req, error, nr_bytes);
865 
866 	if (!req->bio)
867 		return false;
868 
869 #ifdef CONFIG_BLK_DEV_INTEGRITY
870 	if (blk_integrity_rq(req) && req_op(req) == REQ_OP_READ &&
871 	    error == BLK_STS_OK)
872 		req->q->integrity.profile->complete_fn(req, nr_bytes);
873 #endif
874 
875 	if (unlikely(error && !blk_rq_is_passthrough(req) &&
876 		     !(req->rq_flags & RQF_QUIET)) &&
877 		     !test_bit(GD_DEAD, &req->q->disk->state)) {
878 		blk_print_req_error(req, error);
879 		trace_block_rq_error(req, error, nr_bytes);
880 	}
881 
882 	blk_account_io_completion(req, nr_bytes);
883 
884 	total_bytes = 0;
885 	while (req->bio) {
886 		struct bio *bio = req->bio;
887 		unsigned bio_bytes = min(bio->bi_iter.bi_size, nr_bytes);
888 
889 		if (bio_bytes == bio->bi_iter.bi_size)
890 			req->bio = bio->bi_next;
891 
892 		/* Completion has already been traced */
893 		bio_clear_flag(bio, BIO_TRACE_COMPLETION);
894 		req_bio_endio(req, bio, bio_bytes, error);
895 
896 		total_bytes += bio_bytes;
897 		nr_bytes -= bio_bytes;
898 
899 		if (!nr_bytes)
900 			break;
901 	}
902 
903 	/*
904 	 * completely done
905 	 */
906 	if (!req->bio) {
907 		/*
908 		 * Reset counters so that the request stacking driver
909 		 * can find how many bytes remain in the request
910 		 * later.
911 		 */
912 		req->__data_len = 0;
913 		return false;
914 	}
915 
916 	req->__data_len -= total_bytes;
917 
918 	/* update sector only for requests with clear definition of sector */
919 	if (!blk_rq_is_passthrough(req))
920 		req->__sector += total_bytes >> 9;
921 
922 	/* mixed attributes always follow the first bio */
923 	if (req->rq_flags & RQF_MIXED_MERGE) {
924 		req->cmd_flags &= ~REQ_FAILFAST_MASK;
925 		req->cmd_flags |= req->bio->bi_opf & REQ_FAILFAST_MASK;
926 	}
927 
928 	if (!(req->rq_flags & RQF_SPECIAL_PAYLOAD)) {
929 		/*
930 		 * If total number of sectors is less than the first segment
931 		 * size, something has gone terribly wrong.
932 		 */
933 		if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
934 			blk_dump_rq_flags(req, "request botched");
935 			req->__data_len = blk_rq_cur_bytes(req);
936 		}
937 
938 		/* recalculate the number of segments */
939 		req->nr_phys_segments = blk_recalc_rq_segments(req);
940 	}
941 
942 	return true;
943 }
944 EXPORT_SYMBOL_GPL(blk_update_request);
945 
946 static void __blk_account_io_done(struct request *req, u64 now)
947 {
948 	const int sgrp = op_stat_group(req_op(req));
949 
950 	part_stat_lock();
951 	update_io_ticks(req->part, jiffies, true);
952 	part_stat_inc(req->part, ios[sgrp]);
953 	part_stat_add(req->part, nsecs[sgrp], now - req->start_time_ns);
954 	part_stat_unlock();
955 }
956 
957 static inline void blk_account_io_done(struct request *req, u64 now)
958 {
959 	/*
960 	 * Account IO completion.  flush_rq isn't accounted as a
961 	 * normal IO on queueing nor completion.  Accounting the
962 	 * containing request is enough.
963 	 */
964 	if (blk_do_io_stat(req) && req->part &&
965 	    !(req->rq_flags & RQF_FLUSH_SEQ))
966 		__blk_account_io_done(req, now);
967 }
968 
969 static void __blk_account_io_start(struct request *rq)
970 {
971 	/*
972 	 * All non-passthrough requests are created from a bio with one
973 	 * exception: when a flush command that is part of a flush sequence
974 	 * generated by the state machine in blk-flush.c is cloned onto the
975 	 * lower device by dm-multipath we can get here without a bio.
976 	 */
977 	if (rq->bio)
978 		rq->part = rq->bio->bi_bdev;
979 	else
980 		rq->part = rq->q->disk->part0;
981 
982 	part_stat_lock();
983 	update_io_ticks(rq->part, jiffies, false);
984 	part_stat_unlock();
985 }
986 
987 static inline void blk_account_io_start(struct request *req)
988 {
989 	if (blk_do_io_stat(req))
990 		__blk_account_io_start(req);
991 }
992 
993 static inline void __blk_mq_end_request_acct(struct request *rq, u64 now)
994 {
995 	if (rq->rq_flags & RQF_STATS) {
996 		blk_mq_poll_stats_start(rq->q);
997 		blk_stat_add(rq, now);
998 	}
999 
1000 	blk_mq_sched_completed_request(rq, now);
1001 	blk_account_io_done(rq, now);
1002 }
1003 
1004 inline void __blk_mq_end_request(struct request *rq, blk_status_t error)
1005 {
1006 	if (blk_mq_need_time_stamp(rq))
1007 		__blk_mq_end_request_acct(rq, ktime_get_ns());
1008 
1009 	if (rq->end_io) {
1010 		rq_qos_done(rq->q, rq);
1011 		if (rq->end_io(rq, error) == RQ_END_IO_FREE)
1012 			blk_mq_free_request(rq);
1013 	} else {
1014 		blk_mq_free_request(rq);
1015 	}
1016 }
1017 EXPORT_SYMBOL(__blk_mq_end_request);
1018 
1019 void blk_mq_end_request(struct request *rq, blk_status_t error)
1020 {
1021 	if (blk_update_request(rq, error, blk_rq_bytes(rq)))
1022 		BUG();
1023 	__blk_mq_end_request(rq, error);
1024 }
1025 EXPORT_SYMBOL(blk_mq_end_request);
1026 
1027 #define TAG_COMP_BATCH		32
1028 
1029 static inline void blk_mq_flush_tag_batch(struct blk_mq_hw_ctx *hctx,
1030 					  int *tag_array, int nr_tags)
1031 {
1032 	struct request_queue *q = hctx->queue;
1033 
1034 	/*
1035 	 * All requests should have been marked as RQF_MQ_INFLIGHT, so
1036 	 * update hctx->nr_active in batch
1037 	 */
1038 	if (hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)
1039 		__blk_mq_sub_active_requests(hctx, nr_tags);
1040 
1041 	blk_mq_put_tags(hctx->tags, tag_array, nr_tags);
1042 	percpu_ref_put_many(&q->q_usage_counter, nr_tags);
1043 }
1044 
1045 void blk_mq_end_request_batch(struct io_comp_batch *iob)
1046 {
1047 	int tags[TAG_COMP_BATCH], nr_tags = 0;
1048 	struct blk_mq_hw_ctx *cur_hctx = NULL;
1049 	struct request *rq;
1050 	u64 now = 0;
1051 
1052 	if (iob->need_ts)
1053 		now = ktime_get_ns();
1054 
1055 	while ((rq = rq_list_pop(&iob->req_list)) != NULL) {
1056 		prefetch(rq->bio);
1057 		prefetch(rq->rq_next);
1058 
1059 		blk_complete_request(rq);
1060 		if (iob->need_ts)
1061 			__blk_mq_end_request_acct(rq, now);
1062 
1063 		rq_qos_done(rq->q, rq);
1064 
1065 		/*
1066 		 * If end_io handler returns NONE, then it still has
1067 		 * ownership of the request.
1068 		 */
1069 		if (rq->end_io && rq->end_io(rq, 0) == RQ_END_IO_NONE)
1070 			continue;
1071 
1072 		WRITE_ONCE(rq->state, MQ_RQ_IDLE);
1073 		if (!req_ref_put_and_test(rq))
1074 			continue;
1075 
1076 		blk_crypto_free_request(rq);
1077 		blk_pm_mark_last_busy(rq);
1078 
1079 		if (nr_tags == TAG_COMP_BATCH || cur_hctx != rq->mq_hctx) {
1080 			if (cur_hctx)
1081 				blk_mq_flush_tag_batch(cur_hctx, tags, nr_tags);
1082 			nr_tags = 0;
1083 			cur_hctx = rq->mq_hctx;
1084 		}
1085 		tags[nr_tags++] = rq->tag;
1086 	}
1087 
1088 	if (nr_tags)
1089 		blk_mq_flush_tag_batch(cur_hctx, tags, nr_tags);
1090 }
1091 EXPORT_SYMBOL_GPL(blk_mq_end_request_batch);
1092 
1093 static void blk_complete_reqs(struct llist_head *list)
1094 {
1095 	struct llist_node *entry = llist_reverse_order(llist_del_all(list));
1096 	struct request *rq, *next;
1097 
1098 	llist_for_each_entry_safe(rq, next, entry, ipi_list)
1099 		rq->q->mq_ops->complete(rq);
1100 }
1101 
1102 static __latent_entropy void blk_done_softirq(struct softirq_action *h)
1103 {
1104 	blk_complete_reqs(this_cpu_ptr(&blk_cpu_done));
1105 }
1106 
1107 static int blk_softirq_cpu_dead(unsigned int cpu)
1108 {
1109 	blk_complete_reqs(&per_cpu(blk_cpu_done, cpu));
1110 	return 0;
1111 }
1112 
1113 static void __blk_mq_complete_request_remote(void *data)
1114 {
1115 	__raise_softirq_irqoff(BLOCK_SOFTIRQ);
1116 }
1117 
1118 static inline bool blk_mq_complete_need_ipi(struct request *rq)
1119 {
1120 	int cpu = raw_smp_processor_id();
1121 
1122 	if (!IS_ENABLED(CONFIG_SMP) ||
1123 	    !test_bit(QUEUE_FLAG_SAME_COMP, &rq->q->queue_flags))
1124 		return false;
1125 	/*
1126 	 * With force threaded interrupts enabled, raising softirq from an SMP
1127 	 * function call will always result in waking the ksoftirqd thread.
1128 	 * This is probably worse than completing the request on a different
1129 	 * cache domain.
1130 	 */
1131 	if (force_irqthreads())
1132 		return false;
1133 
1134 	/* same CPU or cache domain?  Complete locally */
1135 	if (cpu == rq->mq_ctx->cpu ||
1136 	    (!test_bit(QUEUE_FLAG_SAME_FORCE, &rq->q->queue_flags) &&
1137 	     cpus_share_cache(cpu, rq->mq_ctx->cpu)))
1138 		return false;
1139 
1140 	/* don't try to IPI to an offline CPU */
1141 	return cpu_online(rq->mq_ctx->cpu);
1142 }
1143 
1144 static void blk_mq_complete_send_ipi(struct request *rq)
1145 {
1146 	struct llist_head *list;
1147 	unsigned int cpu;
1148 
1149 	cpu = rq->mq_ctx->cpu;
1150 	list = &per_cpu(blk_cpu_done, cpu);
1151 	if (llist_add(&rq->ipi_list, list)) {
1152 		INIT_CSD(&rq->csd, __blk_mq_complete_request_remote, rq);
1153 		smp_call_function_single_async(cpu, &rq->csd);
1154 	}
1155 }
1156 
1157 static void blk_mq_raise_softirq(struct request *rq)
1158 {
1159 	struct llist_head *list;
1160 
1161 	preempt_disable();
1162 	list = this_cpu_ptr(&blk_cpu_done);
1163 	if (llist_add(&rq->ipi_list, list))
1164 		raise_softirq(BLOCK_SOFTIRQ);
1165 	preempt_enable();
1166 }
1167 
1168 bool blk_mq_complete_request_remote(struct request *rq)
1169 {
1170 	WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);
1171 
1172 	/*
1173 	 * For request which hctx has only one ctx mapping,
1174 	 * or a polled request, always complete locally,
1175 	 * it's pointless to redirect the completion.
1176 	 */
1177 	if (rq->mq_hctx->nr_ctx == 1 ||
1178 		rq->cmd_flags & REQ_POLLED)
1179 		return false;
1180 
1181 	if (blk_mq_complete_need_ipi(rq)) {
1182 		blk_mq_complete_send_ipi(rq);
1183 		return true;
1184 	}
1185 
1186 	if (rq->q->nr_hw_queues == 1) {
1187 		blk_mq_raise_softirq(rq);
1188 		return true;
1189 	}
1190 	return false;
1191 }
1192 EXPORT_SYMBOL_GPL(blk_mq_complete_request_remote);
1193 
1194 /**
1195  * blk_mq_complete_request - end I/O on a request
1196  * @rq:		the request being processed
1197  *
1198  * Description:
1199  *	Complete a request by scheduling the ->complete_rq operation.
1200  **/
1201 void blk_mq_complete_request(struct request *rq)
1202 {
1203 	if (!blk_mq_complete_request_remote(rq))
1204 		rq->q->mq_ops->complete(rq);
1205 }
1206 EXPORT_SYMBOL(blk_mq_complete_request);
1207 
1208 /**
1209  * blk_mq_start_request - Start processing a request
1210  * @rq: Pointer to request to be started
1211  *
1212  * Function used by device drivers to notify the block layer that a request
1213  * is going to be processed now, so blk layer can do proper initializations
1214  * such as starting the timeout timer.
1215  */
1216 void blk_mq_start_request(struct request *rq)
1217 {
1218 	struct request_queue *q = rq->q;
1219 
1220 	trace_block_rq_issue(rq);
1221 
1222 	if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags)) {
1223 		rq->io_start_time_ns = ktime_get_ns();
1224 		rq->stats_sectors = blk_rq_sectors(rq);
1225 		rq->rq_flags |= RQF_STATS;
1226 		rq_qos_issue(q, rq);
1227 	}
1228 
1229 	WARN_ON_ONCE(blk_mq_rq_state(rq) != MQ_RQ_IDLE);
1230 
1231 	blk_add_timer(rq);
1232 	WRITE_ONCE(rq->state, MQ_RQ_IN_FLIGHT);
1233 
1234 #ifdef CONFIG_BLK_DEV_INTEGRITY
1235 	if (blk_integrity_rq(rq) && req_op(rq) == REQ_OP_WRITE)
1236 		q->integrity.profile->prepare_fn(rq);
1237 #endif
1238 	if (rq->bio && rq->bio->bi_opf & REQ_POLLED)
1239 	        WRITE_ONCE(rq->bio->bi_cookie, blk_rq_to_qc(rq));
1240 }
1241 EXPORT_SYMBOL(blk_mq_start_request);
1242 
1243 /*
1244  * Allow 2x BLK_MAX_REQUEST_COUNT requests on plug queue for multiple
1245  * queues. This is important for md arrays to benefit from merging
1246  * requests.
1247  */
1248 static inline unsigned short blk_plug_max_rq_count(struct blk_plug *plug)
1249 {
1250 	if (plug->multiple_queues)
1251 		return BLK_MAX_REQUEST_COUNT * 2;
1252 	return BLK_MAX_REQUEST_COUNT;
1253 }
1254 
1255 static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
1256 {
1257 	struct request *last = rq_list_peek(&plug->mq_list);
1258 
1259 	if (!plug->rq_count) {
1260 		trace_block_plug(rq->q);
1261 	} else if (plug->rq_count >= blk_plug_max_rq_count(plug) ||
1262 		   (!blk_queue_nomerges(rq->q) &&
1263 		    blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
1264 		blk_mq_flush_plug_list(plug, false);
1265 		last = NULL;
1266 		trace_block_plug(rq->q);
1267 	}
1268 
1269 	if (!plug->multiple_queues && last && last->q != rq->q)
1270 		plug->multiple_queues = true;
1271 	if (!plug->has_elevator && (rq->rq_flags & RQF_ELV))
1272 		plug->has_elevator = true;
1273 	rq->rq_next = NULL;
1274 	rq_list_add(&plug->mq_list, rq);
1275 	plug->rq_count++;
1276 }
1277 
1278 /**
1279  * blk_execute_rq_nowait - insert a request to I/O scheduler for execution
1280  * @rq:		request to insert
1281  * @at_head:    insert request at head or tail of queue
1282  *
1283  * Description:
1284  *    Insert a fully prepared request at the back of the I/O scheduler queue
1285  *    for execution.  Don't wait for completion.
1286  *
1287  * Note:
1288  *    This function will invoke @done directly if the queue is dead.
1289  */
1290 void blk_execute_rq_nowait(struct request *rq, bool at_head)
1291 {
1292 	WARN_ON(irqs_disabled());
1293 	WARN_ON(!blk_rq_is_passthrough(rq));
1294 
1295 	blk_account_io_start(rq);
1296 
1297 	/*
1298 	 * As plugging can be enabled for passthrough requests on a zoned
1299 	 * device, directly accessing the plug instead of using blk_mq_plug()
1300 	 * should not have any consequences.
1301 	 */
1302 	if (current->plug)
1303 		blk_add_rq_to_plug(current->plug, rq);
1304 	else
1305 		blk_mq_sched_insert_request(rq, at_head, true, false);
1306 }
1307 EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);
1308 
1309 struct blk_rq_wait {
1310 	struct completion done;
1311 	blk_status_t ret;
1312 };
1313 
1314 static enum rq_end_io_ret blk_end_sync_rq(struct request *rq, blk_status_t ret)
1315 {
1316 	struct blk_rq_wait *wait = rq->end_io_data;
1317 
1318 	wait->ret = ret;
1319 	complete(&wait->done);
1320 	return RQ_END_IO_NONE;
1321 }
1322 
1323 bool blk_rq_is_poll(struct request *rq)
1324 {
1325 	if (!rq->mq_hctx)
1326 		return false;
1327 	if (rq->mq_hctx->type != HCTX_TYPE_POLL)
1328 		return false;
1329 	if (WARN_ON_ONCE(!rq->bio))
1330 		return false;
1331 	return true;
1332 }
1333 EXPORT_SYMBOL_GPL(blk_rq_is_poll);
1334 
1335 static void blk_rq_poll_completion(struct request *rq, struct completion *wait)
1336 {
1337 	do {
1338 		bio_poll(rq->bio, NULL, 0);
1339 		cond_resched();
1340 	} while (!completion_done(wait));
1341 }
1342 
1343 /**
1344  * blk_execute_rq - insert a request into queue for execution
1345  * @rq:		request to insert
1346  * @at_head:    insert request at head or tail of queue
1347  *
1348  * Description:
1349  *    Insert a fully prepared request at the back of the I/O scheduler queue
1350  *    for execution and wait for completion.
1351  * Return: The blk_status_t result provided to blk_mq_end_request().
1352  */
1353 blk_status_t blk_execute_rq(struct request *rq, bool at_head)
1354 {
1355 	struct blk_rq_wait wait = {
1356 		.done = COMPLETION_INITIALIZER_ONSTACK(wait.done),
1357 	};
1358 
1359 	WARN_ON(irqs_disabled());
1360 	WARN_ON(!blk_rq_is_passthrough(rq));
1361 
1362 	rq->end_io_data = &wait;
1363 	rq->end_io = blk_end_sync_rq;
1364 
1365 	blk_account_io_start(rq);
1366 	blk_mq_sched_insert_request(rq, at_head, true, false);
1367 
1368 	if (blk_rq_is_poll(rq)) {
1369 		blk_rq_poll_completion(rq, &wait.done);
1370 	} else {
1371 		/*
1372 		 * Prevent hang_check timer from firing at us during very long
1373 		 * I/O
1374 		 */
1375 		unsigned long hang_check = sysctl_hung_task_timeout_secs;
1376 
1377 		if (hang_check)
1378 			while (!wait_for_completion_io_timeout(&wait.done,
1379 					hang_check * (HZ/2)))
1380 				;
1381 		else
1382 			wait_for_completion_io(&wait.done);
1383 	}
1384 
1385 	return wait.ret;
1386 }
1387 EXPORT_SYMBOL(blk_execute_rq);
1388 
1389 static void __blk_mq_requeue_request(struct request *rq)
1390 {
1391 	struct request_queue *q = rq->q;
1392 
1393 	blk_mq_put_driver_tag(rq);
1394 
1395 	trace_block_rq_requeue(rq);
1396 	rq_qos_requeue(q, rq);
1397 
1398 	if (blk_mq_request_started(rq)) {
1399 		WRITE_ONCE(rq->state, MQ_RQ_IDLE);
1400 		rq->rq_flags &= ~RQF_TIMED_OUT;
1401 	}
1402 }
1403 
1404 void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list)
1405 {
1406 	__blk_mq_requeue_request(rq);
1407 
1408 	/* this request will be re-inserted to io scheduler queue */
1409 	blk_mq_sched_requeue_request(rq);
1410 
1411 	blk_mq_add_to_requeue_list(rq, true, kick_requeue_list);
1412 }
1413 EXPORT_SYMBOL(blk_mq_requeue_request);
1414 
1415 static void blk_mq_requeue_work(struct work_struct *work)
1416 {
1417 	struct request_queue *q =
1418 		container_of(work, struct request_queue, requeue_work.work);
1419 	LIST_HEAD(rq_list);
1420 	struct request *rq, *next;
1421 
1422 	spin_lock_irq(&q->requeue_lock);
1423 	list_splice_init(&q->requeue_list, &rq_list);
1424 	spin_unlock_irq(&q->requeue_lock);
1425 
1426 	list_for_each_entry_safe(rq, next, &rq_list, queuelist) {
1427 		if (!(rq->rq_flags & (RQF_SOFTBARRIER | RQF_DONTPREP)))
1428 			continue;
1429 
1430 		rq->rq_flags &= ~RQF_SOFTBARRIER;
1431 		list_del_init(&rq->queuelist);
1432 		/*
1433 		 * If RQF_DONTPREP, rq has contained some driver specific
1434 		 * data, so insert it to hctx dispatch list to avoid any
1435 		 * merge.
1436 		 */
1437 		if (rq->rq_flags & RQF_DONTPREP)
1438 			blk_mq_request_bypass_insert(rq, false, false);
1439 		else
1440 			blk_mq_sched_insert_request(rq, true, false, false);
1441 	}
1442 
1443 	while (!list_empty(&rq_list)) {
1444 		rq = list_entry(rq_list.next, struct request, queuelist);
1445 		list_del_init(&rq->queuelist);
1446 		blk_mq_sched_insert_request(rq, false, false, false);
1447 	}
1448 
1449 	blk_mq_run_hw_queues(q, false);
1450 }
1451 
1452 void blk_mq_add_to_requeue_list(struct request *rq, bool at_head,
1453 				bool kick_requeue_list)
1454 {
1455 	struct request_queue *q = rq->q;
1456 	unsigned long flags;
1457 
1458 	/*
1459 	 * We abuse this flag that is otherwise used by the I/O scheduler to
1460 	 * request head insertion from the workqueue.
1461 	 */
1462 	BUG_ON(rq->rq_flags & RQF_SOFTBARRIER);
1463 
1464 	spin_lock_irqsave(&q->requeue_lock, flags);
1465 	if (at_head) {
1466 		rq->rq_flags |= RQF_SOFTBARRIER;
1467 		list_add(&rq->queuelist, &q->requeue_list);
1468 	} else {
1469 		list_add_tail(&rq->queuelist, &q->requeue_list);
1470 	}
1471 	spin_unlock_irqrestore(&q->requeue_lock, flags);
1472 
1473 	if (kick_requeue_list)
1474 		blk_mq_kick_requeue_list(q);
1475 }
1476 
1477 void blk_mq_kick_requeue_list(struct request_queue *q)
1478 {
1479 	kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work, 0);
1480 }
1481 EXPORT_SYMBOL(blk_mq_kick_requeue_list);
1482 
1483 void blk_mq_delay_kick_requeue_list(struct request_queue *q,
1484 				    unsigned long msecs)
1485 {
1486 	kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work,
1487 				    msecs_to_jiffies(msecs));
1488 }
1489 EXPORT_SYMBOL(blk_mq_delay_kick_requeue_list);
1490 
1491 static bool blk_mq_rq_inflight(struct request *rq, void *priv)
1492 {
1493 	/*
1494 	 * If we find a request that isn't idle we know the queue is busy
1495 	 * as it's checked in the iter.
1496 	 * Return false to stop the iteration.
1497 	 */
1498 	if (blk_mq_request_started(rq)) {
1499 		bool *busy = priv;
1500 
1501 		*busy = true;
1502 		return false;
1503 	}
1504 
1505 	return true;
1506 }
1507 
1508 bool blk_mq_queue_inflight(struct request_queue *q)
1509 {
1510 	bool busy = false;
1511 
1512 	blk_mq_queue_tag_busy_iter(q, blk_mq_rq_inflight, &busy);
1513 	return busy;
1514 }
1515 EXPORT_SYMBOL_GPL(blk_mq_queue_inflight);
1516 
1517 static void blk_mq_rq_timed_out(struct request *req)
1518 {
1519 	req->rq_flags |= RQF_TIMED_OUT;
1520 	if (req->q->mq_ops->timeout) {
1521 		enum blk_eh_timer_return ret;
1522 
1523 		ret = req->q->mq_ops->timeout(req);
1524 		if (ret == BLK_EH_DONE)
1525 			return;
1526 		WARN_ON_ONCE(ret != BLK_EH_RESET_TIMER);
1527 	}
1528 
1529 	blk_add_timer(req);
1530 }
1531 
1532 static bool blk_mq_req_expired(struct request *rq, unsigned long *next)
1533 {
1534 	unsigned long deadline;
1535 
1536 	if (blk_mq_rq_state(rq) != MQ_RQ_IN_FLIGHT)
1537 		return false;
1538 	if (rq->rq_flags & RQF_TIMED_OUT)
1539 		return false;
1540 
1541 	deadline = READ_ONCE(rq->deadline);
1542 	if (time_after_eq(jiffies, deadline))
1543 		return true;
1544 
1545 	if (*next == 0)
1546 		*next = deadline;
1547 	else if (time_after(*next, deadline))
1548 		*next = deadline;
1549 	return false;
1550 }
1551 
1552 void blk_mq_put_rq_ref(struct request *rq)
1553 {
1554 	if (is_flush_rq(rq)) {
1555 		if (rq->end_io(rq, 0) == RQ_END_IO_FREE)
1556 			blk_mq_free_request(rq);
1557 	} else if (req_ref_put_and_test(rq)) {
1558 		__blk_mq_free_request(rq);
1559 	}
1560 }
1561 
1562 static bool blk_mq_check_expired(struct request *rq, void *priv)
1563 {
1564 	unsigned long *next = priv;
1565 
1566 	/*
1567 	 * blk_mq_queue_tag_busy_iter() has locked the request, so it cannot
1568 	 * be reallocated underneath the timeout handler's processing, then
1569 	 * the expire check is reliable. If the request is not expired, then
1570 	 * it was completed and reallocated as a new request after returning
1571 	 * from blk_mq_check_expired().
1572 	 */
1573 	if (blk_mq_req_expired(rq, next))
1574 		blk_mq_rq_timed_out(rq);
1575 	return true;
1576 }
1577 
1578 static void blk_mq_timeout_work(struct work_struct *work)
1579 {
1580 	struct request_queue *q =
1581 		container_of(work, struct request_queue, timeout_work);
1582 	unsigned long next = 0;
1583 	struct blk_mq_hw_ctx *hctx;
1584 	unsigned long i;
1585 
1586 	/* A deadlock might occur if a request is stuck requiring a
1587 	 * timeout at the same time a queue freeze is waiting
1588 	 * completion, since the timeout code would not be able to
1589 	 * acquire the queue reference here.
1590 	 *
1591 	 * That's why we don't use blk_queue_enter here; instead, we use
1592 	 * percpu_ref_tryget directly, because we need to be able to
1593 	 * obtain a reference even in the short window between the queue
1594 	 * starting to freeze, by dropping the first reference in
1595 	 * blk_freeze_queue_start, and the moment the last request is
1596 	 * consumed, marked by the instant q_usage_counter reaches
1597 	 * zero.
1598 	 */
1599 	if (!percpu_ref_tryget(&q->q_usage_counter))
1600 		return;
1601 
1602 	blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &next);
1603 
1604 	if (next != 0) {
1605 		mod_timer(&q->timeout, next);
1606 	} else {
1607 		/*
1608 		 * Request timeouts are handled as a forward rolling timer. If
1609 		 * we end up here it means that no requests are pending and
1610 		 * also that no request has been pending for a while. Mark
1611 		 * each hctx as idle.
1612 		 */
1613 		queue_for_each_hw_ctx(q, hctx, i) {
1614 			/* the hctx may be unmapped, so check it here */
1615 			if (blk_mq_hw_queue_mapped(hctx))
1616 				blk_mq_tag_idle(hctx);
1617 		}
1618 	}
1619 	blk_queue_exit(q);
1620 }
1621 
1622 struct flush_busy_ctx_data {
1623 	struct blk_mq_hw_ctx *hctx;
1624 	struct list_head *list;
1625 };
1626 
1627 static bool flush_busy_ctx(struct sbitmap *sb, unsigned int bitnr, void *data)
1628 {
1629 	struct flush_busy_ctx_data *flush_data = data;
1630 	struct blk_mq_hw_ctx *hctx = flush_data->hctx;
1631 	struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
1632 	enum hctx_type type = hctx->type;
1633 
1634 	spin_lock(&ctx->lock);
1635 	list_splice_tail_init(&ctx->rq_lists[type], flush_data->list);
1636 	sbitmap_clear_bit(sb, bitnr);
1637 	spin_unlock(&ctx->lock);
1638 	return true;
1639 }
1640 
1641 /*
1642  * Process software queues that have been marked busy, splicing them
1643  * to the for-dispatch
1644  */
1645 void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list)
1646 {
1647 	struct flush_busy_ctx_data data = {
1648 		.hctx = hctx,
1649 		.list = list,
1650 	};
1651 
1652 	sbitmap_for_each_set(&hctx->ctx_map, flush_busy_ctx, &data);
1653 }
1654 EXPORT_SYMBOL_GPL(blk_mq_flush_busy_ctxs);
1655 
1656 struct dispatch_rq_data {
1657 	struct blk_mq_hw_ctx *hctx;
1658 	struct request *rq;
1659 };
1660 
1661 static bool dispatch_rq_from_ctx(struct sbitmap *sb, unsigned int bitnr,
1662 		void *data)
1663 {
1664 	struct dispatch_rq_data *dispatch_data = data;
1665 	struct blk_mq_hw_ctx *hctx = dispatch_data->hctx;
1666 	struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
1667 	enum hctx_type type = hctx->type;
1668 
1669 	spin_lock(&ctx->lock);
1670 	if (!list_empty(&ctx->rq_lists[type])) {
1671 		dispatch_data->rq = list_entry_rq(ctx->rq_lists[type].next);
1672 		list_del_init(&dispatch_data->rq->queuelist);
1673 		if (list_empty(&ctx->rq_lists[type]))
1674 			sbitmap_clear_bit(sb, bitnr);
1675 	}
1676 	spin_unlock(&ctx->lock);
1677 
1678 	return !dispatch_data->rq;
1679 }
1680 
1681 struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx,
1682 					struct blk_mq_ctx *start)
1683 {
1684 	unsigned off = start ? start->index_hw[hctx->type] : 0;
1685 	struct dispatch_rq_data data = {
1686 		.hctx = hctx,
1687 		.rq   = NULL,
1688 	};
1689 
1690 	__sbitmap_for_each_set(&hctx->ctx_map, off,
1691 			       dispatch_rq_from_ctx, &data);
1692 
1693 	return data.rq;
1694 }
1695 
1696 static bool __blk_mq_alloc_driver_tag(struct request *rq)
1697 {
1698 	struct sbitmap_queue *bt = &rq->mq_hctx->tags->bitmap_tags;
1699 	unsigned int tag_offset = rq->mq_hctx->tags->nr_reserved_tags;
1700 	int tag;
1701 
1702 	blk_mq_tag_busy(rq->mq_hctx);
1703 
1704 	if (blk_mq_tag_is_reserved(rq->mq_hctx->sched_tags, rq->internal_tag)) {
1705 		bt = &rq->mq_hctx->tags->breserved_tags;
1706 		tag_offset = 0;
1707 	} else {
1708 		if (!hctx_may_queue(rq->mq_hctx, bt))
1709 			return false;
1710 	}
1711 
1712 	tag = __sbitmap_queue_get(bt);
1713 	if (tag == BLK_MQ_NO_TAG)
1714 		return false;
1715 
1716 	rq->tag = tag + tag_offset;
1717 	return true;
1718 }
1719 
1720 bool __blk_mq_get_driver_tag(struct blk_mq_hw_ctx *hctx, struct request *rq)
1721 {
1722 	if (rq->tag == BLK_MQ_NO_TAG && !__blk_mq_alloc_driver_tag(rq))
1723 		return false;
1724 
1725 	if ((hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED) &&
1726 			!(rq->rq_flags & RQF_MQ_INFLIGHT)) {
1727 		rq->rq_flags |= RQF_MQ_INFLIGHT;
1728 		__blk_mq_inc_active_requests(hctx);
1729 	}
1730 	hctx->tags->rqs[rq->tag] = rq;
1731 	return true;
1732 }
1733 
1734 static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode,
1735 				int flags, void *key)
1736 {
1737 	struct blk_mq_hw_ctx *hctx;
1738 
1739 	hctx = container_of(wait, struct blk_mq_hw_ctx, dispatch_wait);
1740 
1741 	spin_lock(&hctx->dispatch_wait_lock);
1742 	if (!list_empty(&wait->entry)) {
1743 		struct sbitmap_queue *sbq;
1744 
1745 		list_del_init(&wait->entry);
1746 		sbq = &hctx->tags->bitmap_tags;
1747 		atomic_dec(&sbq->ws_active);
1748 	}
1749 	spin_unlock(&hctx->dispatch_wait_lock);
1750 
1751 	blk_mq_run_hw_queue(hctx, true);
1752 	return 1;
1753 }
1754 
1755 /*
1756  * Mark us waiting for a tag. For shared tags, this involves hooking us into
1757  * the tag wakeups. For non-shared tags, we can simply mark us needing a
1758  * restart. For both cases, take care to check the condition again after
1759  * marking us as waiting.
1760  */
1761 static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx,
1762 				 struct request *rq)
1763 {
1764 	struct sbitmap_queue *sbq = &hctx->tags->bitmap_tags;
1765 	struct wait_queue_head *wq;
1766 	wait_queue_entry_t *wait;
1767 	bool ret;
1768 
1769 	if (!(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) {
1770 		blk_mq_sched_mark_restart_hctx(hctx);
1771 
1772 		/*
1773 		 * It's possible that a tag was freed in the window between the
1774 		 * allocation failure and adding the hardware queue to the wait
1775 		 * queue.
1776 		 *
1777 		 * Don't clear RESTART here, someone else could have set it.
1778 		 * At most this will cost an extra queue run.
1779 		 */
1780 		return blk_mq_get_driver_tag(rq);
1781 	}
1782 
1783 	wait = &hctx->dispatch_wait;
1784 	if (!list_empty_careful(&wait->entry))
1785 		return false;
1786 
1787 	wq = &bt_wait_ptr(sbq, hctx)->wait;
1788 
1789 	spin_lock_irq(&wq->lock);
1790 	spin_lock(&hctx->dispatch_wait_lock);
1791 	if (!list_empty(&wait->entry)) {
1792 		spin_unlock(&hctx->dispatch_wait_lock);
1793 		spin_unlock_irq(&wq->lock);
1794 		return false;
1795 	}
1796 
1797 	atomic_inc(&sbq->ws_active);
1798 	wait->flags &= ~WQ_FLAG_EXCLUSIVE;
1799 	__add_wait_queue(wq, wait);
1800 
1801 	/*
1802 	 * It's possible that a tag was freed in the window between the
1803 	 * allocation failure and adding the hardware queue to the wait
1804 	 * queue.
1805 	 */
1806 	ret = blk_mq_get_driver_tag(rq);
1807 	if (!ret) {
1808 		spin_unlock(&hctx->dispatch_wait_lock);
1809 		spin_unlock_irq(&wq->lock);
1810 		return false;
1811 	}
1812 
1813 	/*
1814 	 * We got a tag, remove ourselves from the wait queue to ensure
1815 	 * someone else gets the wakeup.
1816 	 */
1817 	list_del_init(&wait->entry);
1818 	atomic_dec(&sbq->ws_active);
1819 	spin_unlock(&hctx->dispatch_wait_lock);
1820 	spin_unlock_irq(&wq->lock);
1821 
1822 	return true;
1823 }
1824 
1825 #define BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT  8
1826 #define BLK_MQ_DISPATCH_BUSY_EWMA_FACTOR  4
1827 /*
1828  * Update dispatch busy with the Exponential Weighted Moving Average(EWMA):
1829  * - EWMA is one simple way to compute running average value
1830  * - weight(7/8 and 1/8) is applied so that it can decrease exponentially
1831  * - take 4 as factor for avoiding to get too small(0) result, and this
1832  *   factor doesn't matter because EWMA decreases exponentially
1833  */
1834 static void blk_mq_update_dispatch_busy(struct blk_mq_hw_ctx *hctx, bool busy)
1835 {
1836 	unsigned int ewma;
1837 
1838 	ewma = hctx->dispatch_busy;
1839 
1840 	if (!ewma && !busy)
1841 		return;
1842 
1843 	ewma *= BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT - 1;
1844 	if (busy)
1845 		ewma += 1 << BLK_MQ_DISPATCH_BUSY_EWMA_FACTOR;
1846 	ewma /= BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT;
1847 
1848 	hctx->dispatch_busy = ewma;
1849 }
1850 
1851 #define BLK_MQ_RESOURCE_DELAY	3		/* ms units */
1852 
1853 static void blk_mq_handle_dev_resource(struct request *rq,
1854 				       struct list_head *list)
1855 {
1856 	struct request *next =
1857 		list_first_entry_or_null(list, struct request, queuelist);
1858 
1859 	/*
1860 	 * If an I/O scheduler has been configured and we got a driver tag for
1861 	 * the next request already, free it.
1862 	 */
1863 	if (next)
1864 		blk_mq_put_driver_tag(next);
1865 
1866 	list_add(&rq->queuelist, list);
1867 	__blk_mq_requeue_request(rq);
1868 }
1869 
1870 static void blk_mq_handle_zone_resource(struct request *rq,
1871 					struct list_head *zone_list)
1872 {
1873 	/*
1874 	 * If we end up here it is because we cannot dispatch a request to a
1875 	 * specific zone due to LLD level zone-write locking or other zone
1876 	 * related resource not being available. In this case, set the request
1877 	 * aside in zone_list for retrying it later.
1878 	 */
1879 	list_add(&rq->queuelist, zone_list);
1880 	__blk_mq_requeue_request(rq);
1881 }
1882 
1883 enum prep_dispatch {
1884 	PREP_DISPATCH_OK,
1885 	PREP_DISPATCH_NO_TAG,
1886 	PREP_DISPATCH_NO_BUDGET,
1887 };
1888 
1889 static enum prep_dispatch blk_mq_prep_dispatch_rq(struct request *rq,
1890 						  bool need_budget)
1891 {
1892 	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
1893 	int budget_token = -1;
1894 
1895 	if (need_budget) {
1896 		budget_token = blk_mq_get_dispatch_budget(rq->q);
1897 		if (budget_token < 0) {
1898 			blk_mq_put_driver_tag(rq);
1899 			return PREP_DISPATCH_NO_BUDGET;
1900 		}
1901 		blk_mq_set_rq_budget_token(rq, budget_token);
1902 	}
1903 
1904 	if (!blk_mq_get_driver_tag(rq)) {
1905 		/*
1906 		 * The initial allocation attempt failed, so we need to
1907 		 * rerun the hardware queue when a tag is freed. The
1908 		 * waitqueue takes care of that. If the queue is run
1909 		 * before we add this entry back on the dispatch list,
1910 		 * we'll re-run it below.
1911 		 */
1912 		if (!blk_mq_mark_tag_wait(hctx, rq)) {
1913 			/*
1914 			 * All budgets not got from this function will be put
1915 			 * together during handling partial dispatch
1916 			 */
1917 			if (need_budget)
1918 				blk_mq_put_dispatch_budget(rq->q, budget_token);
1919 			return PREP_DISPATCH_NO_TAG;
1920 		}
1921 	}
1922 
1923 	return PREP_DISPATCH_OK;
1924 }
1925 
1926 /* release all allocated budgets before calling to blk_mq_dispatch_rq_list */
1927 static void blk_mq_release_budgets(struct request_queue *q,
1928 		struct list_head *list)
1929 {
1930 	struct request *rq;
1931 
1932 	list_for_each_entry(rq, list, queuelist) {
1933 		int budget_token = blk_mq_get_rq_budget_token(rq);
1934 
1935 		if (budget_token >= 0)
1936 			blk_mq_put_dispatch_budget(q, budget_token);
1937 	}
1938 }
1939 
1940 /*
1941  * Returns true if we did some work AND can potentially do more.
1942  */
1943 bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
1944 			     unsigned int nr_budgets)
1945 {
1946 	enum prep_dispatch prep;
1947 	struct request_queue *q = hctx->queue;
1948 	struct request *rq, *nxt;
1949 	int errors, queued;
1950 	blk_status_t ret = BLK_STS_OK;
1951 	LIST_HEAD(zone_list);
1952 	bool needs_resource = false;
1953 
1954 	if (list_empty(list))
1955 		return false;
1956 
1957 	/*
1958 	 * Now process all the entries, sending them to the driver.
1959 	 */
1960 	errors = queued = 0;
1961 	do {
1962 		struct blk_mq_queue_data bd;
1963 
1964 		rq = list_first_entry(list, struct request, queuelist);
1965 
1966 		WARN_ON_ONCE(hctx != rq->mq_hctx);
1967 		prep = blk_mq_prep_dispatch_rq(rq, !nr_budgets);
1968 		if (prep != PREP_DISPATCH_OK)
1969 			break;
1970 
1971 		list_del_init(&rq->queuelist);
1972 
1973 		bd.rq = rq;
1974 
1975 		/*
1976 		 * Flag last if we have no more requests, or if we have more
1977 		 * but can't assign a driver tag to it.
1978 		 */
1979 		if (list_empty(list))
1980 			bd.last = true;
1981 		else {
1982 			nxt = list_first_entry(list, struct request, queuelist);
1983 			bd.last = !blk_mq_get_driver_tag(nxt);
1984 		}
1985 
1986 		/*
1987 		 * once the request is queued to lld, no need to cover the
1988 		 * budget any more
1989 		 */
1990 		if (nr_budgets)
1991 			nr_budgets--;
1992 		ret = q->mq_ops->queue_rq(hctx, &bd);
1993 		switch (ret) {
1994 		case BLK_STS_OK:
1995 			queued++;
1996 			break;
1997 		case BLK_STS_RESOURCE:
1998 			needs_resource = true;
1999 			fallthrough;
2000 		case BLK_STS_DEV_RESOURCE:
2001 			blk_mq_handle_dev_resource(rq, list);
2002 			goto out;
2003 		case BLK_STS_ZONE_RESOURCE:
2004 			/*
2005 			 * Move the request to zone_list and keep going through
2006 			 * the dispatch list to find more requests the drive can
2007 			 * accept.
2008 			 */
2009 			blk_mq_handle_zone_resource(rq, &zone_list);
2010 			needs_resource = true;
2011 			break;
2012 		default:
2013 			errors++;
2014 			blk_mq_end_request(rq, ret);
2015 		}
2016 	} while (!list_empty(list));
2017 out:
2018 	if (!list_empty(&zone_list))
2019 		list_splice_tail_init(&zone_list, list);
2020 
2021 	/* If we didn't flush the entire list, we could have told the driver
2022 	 * there was more coming, but that turned out to be a lie.
2023 	 */
2024 	if ((!list_empty(list) || errors || needs_resource ||
2025 	     ret == BLK_STS_DEV_RESOURCE) && q->mq_ops->commit_rqs && queued)
2026 		q->mq_ops->commit_rqs(hctx);
2027 	/*
2028 	 * Any items that need requeuing? Stuff them into hctx->dispatch,
2029 	 * that is where we will continue on next queue run.
2030 	 */
2031 	if (!list_empty(list)) {
2032 		bool needs_restart;
2033 		/* For non-shared tags, the RESTART check will suffice */
2034 		bool no_tag = prep == PREP_DISPATCH_NO_TAG &&
2035 			(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED);
2036 
2037 		if (nr_budgets)
2038 			blk_mq_release_budgets(q, list);
2039 
2040 		spin_lock(&hctx->lock);
2041 		list_splice_tail_init(list, &hctx->dispatch);
2042 		spin_unlock(&hctx->lock);
2043 
2044 		/*
2045 		 * Order adding requests to hctx->dispatch and checking
2046 		 * SCHED_RESTART flag. The pair of this smp_mb() is the one
2047 		 * in blk_mq_sched_restart(). Avoid restart code path to
2048 		 * miss the new added requests to hctx->dispatch, meantime
2049 		 * SCHED_RESTART is observed here.
2050 		 */
2051 		smp_mb();
2052 
2053 		/*
2054 		 * If SCHED_RESTART was set by the caller of this function and
2055 		 * it is no longer set that means that it was cleared by another
2056 		 * thread and hence that a queue rerun is needed.
2057 		 *
2058 		 * If 'no_tag' is set, that means that we failed getting
2059 		 * a driver tag with an I/O scheduler attached. If our dispatch
2060 		 * waitqueue is no longer active, ensure that we run the queue
2061 		 * AFTER adding our entries back to the list.
2062 		 *
2063 		 * If no I/O scheduler has been configured it is possible that
2064 		 * the hardware queue got stopped and restarted before requests
2065 		 * were pushed back onto the dispatch list. Rerun the queue to
2066 		 * avoid starvation. Notes:
2067 		 * - blk_mq_run_hw_queue() checks whether or not a queue has
2068 		 *   been stopped before rerunning a queue.
2069 		 * - Some but not all block drivers stop a queue before
2070 		 *   returning BLK_STS_RESOURCE. Two exceptions are scsi-mq
2071 		 *   and dm-rq.
2072 		 *
2073 		 * If driver returns BLK_STS_RESOURCE and SCHED_RESTART
2074 		 * bit is set, run queue after a delay to avoid IO stalls
2075 		 * that could otherwise occur if the queue is idle.  We'll do
2076 		 * similar if we couldn't get budget or couldn't lock a zone
2077 		 * and SCHED_RESTART is set.
2078 		 */
2079 		needs_restart = blk_mq_sched_needs_restart(hctx);
2080 		if (prep == PREP_DISPATCH_NO_BUDGET)
2081 			needs_resource = true;
2082 		if (!needs_restart ||
2083 		    (no_tag && list_empty_careful(&hctx->dispatch_wait.entry)))
2084 			blk_mq_run_hw_queue(hctx, true);
2085 		else if (needs_resource)
2086 			blk_mq_delay_run_hw_queue(hctx, BLK_MQ_RESOURCE_DELAY);
2087 
2088 		blk_mq_update_dispatch_busy(hctx, true);
2089 		return false;
2090 	} else
2091 		blk_mq_update_dispatch_busy(hctx, false);
2092 
2093 	return (queued + errors) != 0;
2094 }
2095 
2096 /**
2097  * __blk_mq_run_hw_queue - Run a hardware queue.
2098  * @hctx: Pointer to the hardware queue to run.
2099  *
2100  * Send pending requests to the hardware.
2101  */
2102 static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
2103 {
2104 	/*
2105 	 * We can't run the queue inline with ints disabled. Ensure that
2106 	 * we catch bad users of this early.
2107 	 */
2108 	WARN_ON_ONCE(in_interrupt());
2109 
2110 	blk_mq_run_dispatch_ops(hctx->queue,
2111 			blk_mq_sched_dispatch_requests(hctx));
2112 }
2113 
2114 static inline int blk_mq_first_mapped_cpu(struct blk_mq_hw_ctx *hctx)
2115 {
2116 	int cpu = cpumask_first_and(hctx->cpumask, cpu_online_mask);
2117 
2118 	if (cpu >= nr_cpu_ids)
2119 		cpu = cpumask_first(hctx->cpumask);
2120 	return cpu;
2121 }
2122 
2123 /*
2124  * It'd be great if the workqueue API had a way to pass
2125  * in a mask and had some smarts for more clever placement.
2126  * For now we just round-robin here, switching for every
2127  * BLK_MQ_CPU_WORK_BATCH queued items.
2128  */
2129 static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
2130 {
2131 	bool tried = false;
2132 	int next_cpu = hctx->next_cpu;
2133 
2134 	if (hctx->queue->nr_hw_queues == 1)
2135 		return WORK_CPU_UNBOUND;
2136 
2137 	if (--hctx->next_cpu_batch <= 0) {
2138 select_cpu:
2139 		next_cpu = cpumask_next_and(next_cpu, hctx->cpumask,
2140 				cpu_online_mask);
2141 		if (next_cpu >= nr_cpu_ids)
2142 			next_cpu = blk_mq_first_mapped_cpu(hctx);
2143 		hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
2144 	}
2145 
2146 	/*
2147 	 * Do unbound schedule if we can't find a online CPU for this hctx,
2148 	 * and it should only happen in the path of handling CPU DEAD.
2149 	 */
2150 	if (!cpu_online(next_cpu)) {
2151 		if (!tried) {
2152 			tried = true;
2153 			goto select_cpu;
2154 		}
2155 
2156 		/*
2157 		 * Make sure to re-select CPU next time once after CPUs
2158 		 * in hctx->cpumask become online again.
2159 		 */
2160 		hctx->next_cpu = next_cpu;
2161 		hctx->next_cpu_batch = 1;
2162 		return WORK_CPU_UNBOUND;
2163 	}
2164 
2165 	hctx->next_cpu = next_cpu;
2166 	return next_cpu;
2167 }
2168 
2169 /**
2170  * __blk_mq_delay_run_hw_queue - Run (or schedule to run) a hardware queue.
2171  * @hctx: Pointer to the hardware queue to run.
2172  * @async: If we want to run the queue asynchronously.
2173  * @msecs: Milliseconds of delay to wait before running the queue.
2174  *
2175  * If !@async, try to run the queue now. Else, run the queue asynchronously and
2176  * with a delay of @msecs.
2177  */
2178 static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async,
2179 					unsigned long msecs)
2180 {
2181 	if (unlikely(blk_mq_hctx_stopped(hctx)))
2182 		return;
2183 
2184 	if (!async && !(hctx->flags & BLK_MQ_F_BLOCKING)) {
2185 		if (cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask)) {
2186 			__blk_mq_run_hw_queue(hctx);
2187 			return;
2188 		}
2189 	}
2190 
2191 	kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work,
2192 				    msecs_to_jiffies(msecs));
2193 }
2194 
2195 /**
2196  * blk_mq_delay_run_hw_queue - Run a hardware queue asynchronously.
2197  * @hctx: Pointer to the hardware queue to run.
2198  * @msecs: Milliseconds of delay to wait before running the queue.
2199  *
2200  * Run a hardware queue asynchronously with a delay of @msecs.
2201  */
2202 void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
2203 {
2204 	__blk_mq_delay_run_hw_queue(hctx, true, msecs);
2205 }
2206 EXPORT_SYMBOL(blk_mq_delay_run_hw_queue);
2207 
2208 /**
2209  * blk_mq_run_hw_queue - Start to run a hardware queue.
2210  * @hctx: Pointer to the hardware queue to run.
2211  * @async: If we want to run the queue asynchronously.
2212  *
2213  * Check if the request queue is not in a quiesced state and if there are
2214  * pending requests to be sent. If this is true, run the queue to send requests
2215  * to hardware.
2216  */
2217 void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
2218 {
2219 	bool need_run;
2220 
2221 	/*
2222 	 * When queue is quiesced, we may be switching io scheduler, or
2223 	 * updating nr_hw_queues, or other things, and we can't run queue
2224 	 * any more, even __blk_mq_hctx_has_pending() can't be called safely.
2225 	 *
2226 	 * And queue will be rerun in blk_mq_unquiesce_queue() if it is
2227 	 * quiesced.
2228 	 */
2229 	__blk_mq_run_dispatch_ops(hctx->queue, false,
2230 		need_run = !blk_queue_quiesced(hctx->queue) &&
2231 		blk_mq_hctx_has_pending(hctx));
2232 
2233 	if (need_run)
2234 		__blk_mq_delay_run_hw_queue(hctx, async, 0);
2235 }
2236 EXPORT_SYMBOL(blk_mq_run_hw_queue);
2237 
2238 /*
2239  * Return prefered queue to dispatch from (if any) for non-mq aware IO
2240  * scheduler.
2241  */
2242 static struct blk_mq_hw_ctx *blk_mq_get_sq_hctx(struct request_queue *q)
2243 {
2244 	struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
2245 	/*
2246 	 * If the IO scheduler does not respect hardware queues when
2247 	 * dispatching, we just don't bother with multiple HW queues and
2248 	 * dispatch from hctx for the current CPU since running multiple queues
2249 	 * just causes lock contention inside the scheduler and pointless cache
2250 	 * bouncing.
2251 	 */
2252 	struct blk_mq_hw_ctx *hctx = ctx->hctxs[HCTX_TYPE_DEFAULT];
2253 
2254 	if (!blk_mq_hctx_stopped(hctx))
2255 		return hctx;
2256 	return NULL;
2257 }
2258 
2259 /**
2260  * blk_mq_run_hw_queues - Run all hardware queues in a request queue.
2261  * @q: Pointer to the request queue to run.
2262  * @async: If we want to run the queue asynchronously.
2263  */
2264 void blk_mq_run_hw_queues(struct request_queue *q, bool async)
2265 {
2266 	struct blk_mq_hw_ctx *hctx, *sq_hctx;
2267 	unsigned long i;
2268 
2269 	sq_hctx = NULL;
2270 	if (blk_queue_sq_sched(q))
2271 		sq_hctx = blk_mq_get_sq_hctx(q);
2272 	queue_for_each_hw_ctx(q, hctx, i) {
2273 		if (blk_mq_hctx_stopped(hctx))
2274 			continue;
2275 		/*
2276 		 * Dispatch from this hctx either if there's no hctx preferred
2277 		 * by IO scheduler or if it has requests that bypass the
2278 		 * scheduler.
2279 		 */
2280 		if (!sq_hctx || sq_hctx == hctx ||
2281 		    !list_empty_careful(&hctx->dispatch))
2282 			blk_mq_run_hw_queue(hctx, async);
2283 	}
2284 }
2285 EXPORT_SYMBOL(blk_mq_run_hw_queues);
2286 
2287 /**
2288  * blk_mq_delay_run_hw_queues - Run all hardware queues asynchronously.
2289  * @q: Pointer to the request queue to run.
2290  * @msecs: Milliseconds of delay to wait before running the queues.
2291  */
2292 void blk_mq_delay_run_hw_queues(struct request_queue *q, unsigned long msecs)
2293 {
2294 	struct blk_mq_hw_ctx *hctx, *sq_hctx;
2295 	unsigned long i;
2296 
2297 	sq_hctx = NULL;
2298 	if (blk_queue_sq_sched(q))
2299 		sq_hctx = blk_mq_get_sq_hctx(q);
2300 	queue_for_each_hw_ctx(q, hctx, i) {
2301 		if (blk_mq_hctx_stopped(hctx))
2302 			continue;
2303 		/*
2304 		 * If there is already a run_work pending, leave the
2305 		 * pending delay untouched. Otherwise, a hctx can stall
2306 		 * if another hctx is re-delaying the other's work
2307 		 * before the work executes.
2308 		 */
2309 		if (delayed_work_pending(&hctx->run_work))
2310 			continue;
2311 		/*
2312 		 * Dispatch from this hctx either if there's no hctx preferred
2313 		 * by IO scheduler or if it has requests that bypass the
2314 		 * scheduler.
2315 		 */
2316 		if (!sq_hctx || sq_hctx == hctx ||
2317 		    !list_empty_careful(&hctx->dispatch))
2318 			blk_mq_delay_run_hw_queue(hctx, msecs);
2319 	}
2320 }
2321 EXPORT_SYMBOL(blk_mq_delay_run_hw_queues);
2322 
2323 /*
2324  * This function is often used for pausing .queue_rq() by driver when
2325  * there isn't enough resource or some conditions aren't satisfied, and
2326  * BLK_STS_RESOURCE is usually returned.
2327  *
2328  * We do not guarantee that dispatch can be drained or blocked
2329  * after blk_mq_stop_hw_queue() returns. Please use
2330  * blk_mq_quiesce_queue() for that requirement.
2331  */
2332 void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx)
2333 {
2334 	cancel_delayed_work(&hctx->run_work);
2335 
2336 	set_bit(BLK_MQ_S_STOPPED, &hctx->state);
2337 }
2338 EXPORT_SYMBOL(blk_mq_stop_hw_queue);
2339 
2340 /*
2341  * This function is often used for pausing .queue_rq() by driver when
2342  * there isn't enough resource or some conditions aren't satisfied, and
2343  * BLK_STS_RESOURCE is usually returned.
2344  *
2345  * We do not guarantee that dispatch can be drained or blocked
2346  * after blk_mq_stop_hw_queues() returns. Please use
2347  * blk_mq_quiesce_queue() for that requirement.
2348  */
2349 void blk_mq_stop_hw_queues(struct request_queue *q)
2350 {
2351 	struct blk_mq_hw_ctx *hctx;
2352 	unsigned long i;
2353 
2354 	queue_for_each_hw_ctx(q, hctx, i)
2355 		blk_mq_stop_hw_queue(hctx);
2356 }
2357 EXPORT_SYMBOL(blk_mq_stop_hw_queues);
2358 
2359 void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx)
2360 {
2361 	clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
2362 
2363 	blk_mq_run_hw_queue(hctx, false);
2364 }
2365 EXPORT_SYMBOL(blk_mq_start_hw_queue);
2366 
2367 void blk_mq_start_hw_queues(struct request_queue *q)
2368 {
2369 	struct blk_mq_hw_ctx *hctx;
2370 	unsigned long i;
2371 
2372 	queue_for_each_hw_ctx(q, hctx, i)
2373 		blk_mq_start_hw_queue(hctx);
2374 }
2375 EXPORT_SYMBOL(blk_mq_start_hw_queues);
2376 
2377 void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
2378 {
2379 	if (!blk_mq_hctx_stopped(hctx))
2380 		return;
2381 
2382 	clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
2383 	blk_mq_run_hw_queue(hctx, async);
2384 }
2385 EXPORT_SYMBOL_GPL(blk_mq_start_stopped_hw_queue);
2386 
2387 void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async)
2388 {
2389 	struct blk_mq_hw_ctx *hctx;
2390 	unsigned long i;
2391 
2392 	queue_for_each_hw_ctx(q, hctx, i)
2393 		blk_mq_start_stopped_hw_queue(hctx, async);
2394 }
2395 EXPORT_SYMBOL(blk_mq_start_stopped_hw_queues);
2396 
2397 static void blk_mq_run_work_fn(struct work_struct *work)
2398 {
2399 	struct blk_mq_hw_ctx *hctx;
2400 
2401 	hctx = container_of(work, struct blk_mq_hw_ctx, run_work.work);
2402 
2403 	/*
2404 	 * If we are stopped, don't run the queue.
2405 	 */
2406 	if (blk_mq_hctx_stopped(hctx))
2407 		return;
2408 
2409 	__blk_mq_run_hw_queue(hctx);
2410 }
2411 
2412 static inline void __blk_mq_insert_req_list(struct blk_mq_hw_ctx *hctx,
2413 					    struct request *rq,
2414 					    bool at_head)
2415 {
2416 	struct blk_mq_ctx *ctx = rq->mq_ctx;
2417 	enum hctx_type type = hctx->type;
2418 
2419 	lockdep_assert_held(&ctx->lock);
2420 
2421 	trace_block_rq_insert(rq);
2422 
2423 	if (at_head)
2424 		list_add(&rq->queuelist, &ctx->rq_lists[type]);
2425 	else
2426 		list_add_tail(&rq->queuelist, &ctx->rq_lists[type]);
2427 }
2428 
2429 void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
2430 			     bool at_head)
2431 {
2432 	struct blk_mq_ctx *ctx = rq->mq_ctx;
2433 
2434 	lockdep_assert_held(&ctx->lock);
2435 
2436 	__blk_mq_insert_req_list(hctx, rq, at_head);
2437 	blk_mq_hctx_mark_pending(hctx, ctx);
2438 }
2439 
2440 /**
2441  * blk_mq_request_bypass_insert - Insert a request at dispatch list.
2442  * @rq: Pointer to request to be inserted.
2443  * @at_head: true if the request should be inserted at the head of the list.
2444  * @run_queue: If we should run the hardware queue after inserting the request.
2445  *
2446  * Should only be used carefully, when the caller knows we want to
2447  * bypass a potential IO scheduler on the target device.
2448  */
2449 void blk_mq_request_bypass_insert(struct request *rq, bool at_head,
2450 				  bool run_queue)
2451 {
2452 	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
2453 
2454 	spin_lock(&hctx->lock);
2455 	if (at_head)
2456 		list_add(&rq->queuelist, &hctx->dispatch);
2457 	else
2458 		list_add_tail(&rq->queuelist, &hctx->dispatch);
2459 	spin_unlock(&hctx->lock);
2460 
2461 	if (run_queue)
2462 		blk_mq_run_hw_queue(hctx, false);
2463 }
2464 
2465 void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
2466 			    struct list_head *list)
2467 
2468 {
2469 	struct request *rq;
2470 	enum hctx_type type = hctx->type;
2471 
2472 	/*
2473 	 * preemption doesn't flush plug list, so it's possible ctx->cpu is
2474 	 * offline now
2475 	 */
2476 	list_for_each_entry(rq, list, queuelist) {
2477 		BUG_ON(rq->mq_ctx != ctx);
2478 		trace_block_rq_insert(rq);
2479 	}
2480 
2481 	spin_lock(&ctx->lock);
2482 	list_splice_tail_init(list, &ctx->rq_lists[type]);
2483 	blk_mq_hctx_mark_pending(hctx, ctx);
2484 	spin_unlock(&ctx->lock);
2485 }
2486 
2487 static void blk_mq_commit_rqs(struct blk_mq_hw_ctx *hctx, int *queued,
2488 			      bool from_schedule)
2489 {
2490 	if (hctx->queue->mq_ops->commit_rqs) {
2491 		trace_block_unplug(hctx->queue, *queued, !from_schedule);
2492 		hctx->queue->mq_ops->commit_rqs(hctx);
2493 	}
2494 	*queued = 0;
2495 }
2496 
2497 static void blk_mq_bio_to_request(struct request *rq, struct bio *bio,
2498 		unsigned int nr_segs)
2499 {
2500 	int err;
2501 
2502 	if (bio->bi_opf & REQ_RAHEAD)
2503 		rq->cmd_flags |= REQ_FAILFAST_MASK;
2504 
2505 	rq->__sector = bio->bi_iter.bi_sector;
2506 	blk_rq_bio_prep(rq, bio, nr_segs);
2507 
2508 	/* This can't fail, since GFP_NOIO includes __GFP_DIRECT_RECLAIM. */
2509 	err = blk_crypto_rq_bio_prep(rq, bio, GFP_NOIO);
2510 	WARN_ON_ONCE(err);
2511 
2512 	blk_account_io_start(rq);
2513 }
2514 
2515 static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
2516 					    struct request *rq, bool last)
2517 {
2518 	struct request_queue *q = rq->q;
2519 	struct blk_mq_queue_data bd = {
2520 		.rq = rq,
2521 		.last = last,
2522 	};
2523 	blk_status_t ret;
2524 
2525 	/*
2526 	 * For OK queue, we are done. For error, caller may kill it.
2527 	 * Any other error (busy), just add it to our list as we
2528 	 * previously would have done.
2529 	 */
2530 	ret = q->mq_ops->queue_rq(hctx, &bd);
2531 	switch (ret) {
2532 	case BLK_STS_OK:
2533 		blk_mq_update_dispatch_busy(hctx, false);
2534 		break;
2535 	case BLK_STS_RESOURCE:
2536 	case BLK_STS_DEV_RESOURCE:
2537 		blk_mq_update_dispatch_busy(hctx, true);
2538 		__blk_mq_requeue_request(rq);
2539 		break;
2540 	default:
2541 		blk_mq_update_dispatch_busy(hctx, false);
2542 		break;
2543 	}
2544 
2545 	return ret;
2546 }
2547 
2548 static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
2549 						struct request *rq,
2550 						bool bypass_insert, bool last)
2551 {
2552 	struct request_queue *q = rq->q;
2553 	bool run_queue = true;
2554 	int budget_token;
2555 
2556 	/*
2557 	 * RCU or SRCU read lock is needed before checking quiesced flag.
2558 	 *
2559 	 * When queue is stopped or quiesced, ignore 'bypass_insert' from
2560 	 * blk_mq_request_issue_directly(), and return BLK_STS_OK to caller,
2561 	 * and avoid driver to try to dispatch again.
2562 	 */
2563 	if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)) {
2564 		run_queue = false;
2565 		bypass_insert = false;
2566 		goto insert;
2567 	}
2568 
2569 	if ((rq->rq_flags & RQF_ELV) && !bypass_insert)
2570 		goto insert;
2571 
2572 	budget_token = blk_mq_get_dispatch_budget(q);
2573 	if (budget_token < 0)
2574 		goto insert;
2575 
2576 	blk_mq_set_rq_budget_token(rq, budget_token);
2577 
2578 	if (!blk_mq_get_driver_tag(rq)) {
2579 		blk_mq_put_dispatch_budget(q, budget_token);
2580 		goto insert;
2581 	}
2582 
2583 	return __blk_mq_issue_directly(hctx, rq, last);
2584 insert:
2585 	if (bypass_insert)
2586 		return BLK_STS_RESOURCE;
2587 
2588 	blk_mq_sched_insert_request(rq, false, run_queue, false);
2589 
2590 	return BLK_STS_OK;
2591 }
2592 
2593 /**
2594  * blk_mq_try_issue_directly - Try to send a request directly to device driver.
2595  * @hctx: Pointer of the associated hardware queue.
2596  * @rq: Pointer to request to be sent.
2597  *
2598  * If the device has enough resources to accept a new request now, send the
2599  * request directly to device driver. Else, insert at hctx->dispatch queue, so
2600  * we can try send it another time in the future. Requests inserted at this
2601  * queue have higher priority.
2602  */
2603 static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
2604 		struct request *rq)
2605 {
2606 	blk_status_t ret =
2607 		__blk_mq_try_issue_directly(hctx, rq, false, true);
2608 
2609 	if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
2610 		blk_mq_request_bypass_insert(rq, false, true);
2611 	else if (ret != BLK_STS_OK)
2612 		blk_mq_end_request(rq, ret);
2613 }
2614 
2615 static blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last)
2616 {
2617 	return __blk_mq_try_issue_directly(rq->mq_hctx, rq, true, last);
2618 }
2619 
2620 static void blk_mq_plug_issue_direct(struct blk_plug *plug, bool from_schedule)
2621 {
2622 	struct blk_mq_hw_ctx *hctx = NULL;
2623 	struct request *rq;
2624 	int queued = 0;
2625 	int errors = 0;
2626 
2627 	while ((rq = rq_list_pop(&plug->mq_list))) {
2628 		bool last = rq_list_empty(plug->mq_list);
2629 		blk_status_t ret;
2630 
2631 		if (hctx != rq->mq_hctx) {
2632 			if (hctx)
2633 				blk_mq_commit_rqs(hctx, &queued, from_schedule);
2634 			hctx = rq->mq_hctx;
2635 		}
2636 
2637 		ret = blk_mq_request_issue_directly(rq, last);
2638 		switch (ret) {
2639 		case BLK_STS_OK:
2640 			queued++;
2641 			break;
2642 		case BLK_STS_RESOURCE:
2643 		case BLK_STS_DEV_RESOURCE:
2644 			blk_mq_request_bypass_insert(rq, false, true);
2645 			blk_mq_commit_rqs(hctx, &queued, from_schedule);
2646 			return;
2647 		default:
2648 			blk_mq_end_request(rq, ret);
2649 			errors++;
2650 			break;
2651 		}
2652 	}
2653 
2654 	/*
2655 	 * If we didn't flush the entire list, we could have told the driver
2656 	 * there was more coming, but that turned out to be a lie.
2657 	 */
2658 	if (errors)
2659 		blk_mq_commit_rqs(hctx, &queued, from_schedule);
2660 }
2661 
2662 static void __blk_mq_flush_plug_list(struct request_queue *q,
2663 				     struct blk_plug *plug)
2664 {
2665 	if (blk_queue_quiesced(q))
2666 		return;
2667 	q->mq_ops->queue_rqs(&plug->mq_list);
2668 }
2669 
2670 static void blk_mq_dispatch_plug_list(struct blk_plug *plug, bool from_sched)
2671 {
2672 	struct blk_mq_hw_ctx *this_hctx = NULL;
2673 	struct blk_mq_ctx *this_ctx = NULL;
2674 	struct request *requeue_list = NULL;
2675 	unsigned int depth = 0;
2676 	LIST_HEAD(list);
2677 
2678 	do {
2679 		struct request *rq = rq_list_pop(&plug->mq_list);
2680 
2681 		if (!this_hctx) {
2682 			this_hctx = rq->mq_hctx;
2683 			this_ctx = rq->mq_ctx;
2684 		} else if (this_hctx != rq->mq_hctx || this_ctx != rq->mq_ctx) {
2685 			rq_list_add(&requeue_list, rq);
2686 			continue;
2687 		}
2688 		list_add_tail(&rq->queuelist, &list);
2689 		depth++;
2690 	} while (!rq_list_empty(plug->mq_list));
2691 
2692 	plug->mq_list = requeue_list;
2693 	trace_block_unplug(this_hctx->queue, depth, !from_sched);
2694 	blk_mq_sched_insert_requests(this_hctx, this_ctx, &list, from_sched);
2695 }
2696 
2697 void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
2698 {
2699 	struct request *rq;
2700 
2701 	if (rq_list_empty(plug->mq_list))
2702 		return;
2703 	plug->rq_count = 0;
2704 
2705 	if (!plug->multiple_queues && !plug->has_elevator && !from_schedule) {
2706 		struct request_queue *q;
2707 
2708 		rq = rq_list_peek(&plug->mq_list);
2709 		q = rq->q;
2710 
2711 		/*
2712 		 * Peek first request and see if we have a ->queue_rqs() hook.
2713 		 * If we do, we can dispatch the whole plug list in one go. We
2714 		 * already know at this point that all requests belong to the
2715 		 * same queue, caller must ensure that's the case.
2716 		 *
2717 		 * Since we pass off the full list to the driver at this point,
2718 		 * we do not increment the active request count for the queue.
2719 		 * Bypass shared tags for now because of that.
2720 		 */
2721 		if (q->mq_ops->queue_rqs &&
2722 		    !(rq->mq_hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) {
2723 			blk_mq_run_dispatch_ops(q,
2724 				__blk_mq_flush_plug_list(q, plug));
2725 			if (rq_list_empty(plug->mq_list))
2726 				return;
2727 		}
2728 
2729 		blk_mq_run_dispatch_ops(q,
2730 				blk_mq_plug_issue_direct(plug, false));
2731 		if (rq_list_empty(plug->mq_list))
2732 			return;
2733 	}
2734 
2735 	do {
2736 		blk_mq_dispatch_plug_list(plug, from_schedule);
2737 	} while (!rq_list_empty(plug->mq_list));
2738 }
2739 
2740 void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
2741 		struct list_head *list)
2742 {
2743 	int queued = 0;
2744 	int errors = 0;
2745 
2746 	while (!list_empty(list)) {
2747 		blk_status_t ret;
2748 		struct request *rq = list_first_entry(list, struct request,
2749 				queuelist);
2750 
2751 		list_del_init(&rq->queuelist);
2752 		ret = blk_mq_request_issue_directly(rq, list_empty(list));
2753 		if (ret != BLK_STS_OK) {
2754 			errors++;
2755 			if (ret == BLK_STS_RESOURCE ||
2756 					ret == BLK_STS_DEV_RESOURCE) {
2757 				blk_mq_request_bypass_insert(rq, false,
2758 							list_empty(list));
2759 				break;
2760 			}
2761 			blk_mq_end_request(rq, ret);
2762 		} else
2763 			queued++;
2764 	}
2765 
2766 	/*
2767 	 * If we didn't flush the entire list, we could have told
2768 	 * the driver there was more coming, but that turned out to
2769 	 * be a lie.
2770 	 */
2771 	if ((!list_empty(list) || errors) &&
2772 	     hctx->queue->mq_ops->commit_rqs && queued)
2773 		hctx->queue->mq_ops->commit_rqs(hctx);
2774 }
2775 
2776 static bool blk_mq_attempt_bio_merge(struct request_queue *q,
2777 				     struct bio *bio, unsigned int nr_segs)
2778 {
2779 	if (!blk_queue_nomerges(q) && bio_mergeable(bio)) {
2780 		if (blk_attempt_plug_merge(q, bio, nr_segs))
2781 			return true;
2782 		if (blk_mq_sched_bio_merge(q, bio, nr_segs))
2783 			return true;
2784 	}
2785 	return false;
2786 }
2787 
2788 static struct request *blk_mq_get_new_requests(struct request_queue *q,
2789 					       struct blk_plug *plug,
2790 					       struct bio *bio,
2791 					       unsigned int nsegs)
2792 {
2793 	struct blk_mq_alloc_data data = {
2794 		.q		= q,
2795 		.nr_tags	= 1,
2796 		.cmd_flags	= bio->bi_opf,
2797 	};
2798 	struct request *rq;
2799 
2800 	if (unlikely(bio_queue_enter(bio)))
2801 		return NULL;
2802 
2803 	if (blk_mq_attempt_bio_merge(q, bio, nsegs))
2804 		goto queue_exit;
2805 
2806 	rq_qos_throttle(q, bio);
2807 
2808 	if (plug) {
2809 		data.nr_tags = plug->nr_ios;
2810 		plug->nr_ios = 1;
2811 		data.cached_rq = &plug->cached_rq;
2812 	}
2813 
2814 	rq = __blk_mq_alloc_requests(&data);
2815 	if (rq)
2816 		return rq;
2817 	rq_qos_cleanup(q, bio);
2818 	if (bio->bi_opf & REQ_NOWAIT)
2819 		bio_wouldblock_error(bio);
2820 queue_exit:
2821 	blk_queue_exit(q);
2822 	return NULL;
2823 }
2824 
2825 static inline struct request *blk_mq_get_cached_request(struct request_queue *q,
2826 		struct blk_plug *plug, struct bio **bio, unsigned int nsegs)
2827 {
2828 	struct request *rq;
2829 
2830 	if (!plug)
2831 		return NULL;
2832 	rq = rq_list_peek(&plug->cached_rq);
2833 	if (!rq || rq->q != q)
2834 		return NULL;
2835 
2836 	if (blk_mq_attempt_bio_merge(q, *bio, nsegs)) {
2837 		*bio = NULL;
2838 		return NULL;
2839 	}
2840 
2841 	if (blk_mq_get_hctx_type((*bio)->bi_opf) != rq->mq_hctx->type)
2842 		return NULL;
2843 	if (op_is_flush(rq->cmd_flags) != op_is_flush((*bio)->bi_opf))
2844 		return NULL;
2845 
2846 	/*
2847 	 * If any qos ->throttle() end up blocking, we will have flushed the
2848 	 * plug and hence killed the cached_rq list as well. Pop this entry
2849 	 * before we throttle.
2850 	 */
2851 	plug->cached_rq = rq_list_next(rq);
2852 	rq_qos_throttle(q, *bio);
2853 
2854 	rq->cmd_flags = (*bio)->bi_opf;
2855 	INIT_LIST_HEAD(&rq->queuelist);
2856 	return rq;
2857 }
2858 
2859 static void bio_set_ioprio(struct bio *bio)
2860 {
2861 	/* Nobody set ioprio so far? Initialize it based on task's nice value */
2862 	if (IOPRIO_PRIO_CLASS(bio->bi_ioprio) == IOPRIO_CLASS_NONE)
2863 		bio->bi_ioprio = get_current_ioprio();
2864 	blkcg_set_ioprio(bio);
2865 }
2866 
2867 /**
2868  * blk_mq_submit_bio - Create and send a request to block device.
2869  * @bio: Bio pointer.
2870  *
2871  * Builds up a request structure from @q and @bio and send to the device. The
2872  * request may not be queued directly to hardware if:
2873  * * This request can be merged with another one
2874  * * We want to place request at plug queue for possible future merging
2875  * * There is an IO scheduler active at this queue
2876  *
2877  * It will not queue the request if there is an error with the bio, or at the
2878  * request creation.
2879  */
2880 void blk_mq_submit_bio(struct bio *bio)
2881 {
2882 	struct request_queue *q = bdev_get_queue(bio->bi_bdev);
2883 	struct blk_plug *plug = blk_mq_plug(bio);
2884 	const int is_sync = op_is_sync(bio->bi_opf);
2885 	struct request *rq;
2886 	unsigned int nr_segs = 1;
2887 	blk_status_t ret;
2888 
2889 	bio = blk_queue_bounce(bio, q);
2890 	if (bio_may_exceed_limits(bio, &q->limits))
2891 		bio = __bio_split_to_limits(bio, &q->limits, &nr_segs);
2892 
2893 	if (!bio_integrity_prep(bio))
2894 		return;
2895 
2896 	bio_set_ioprio(bio);
2897 
2898 	rq = blk_mq_get_cached_request(q, plug, &bio, nr_segs);
2899 	if (!rq) {
2900 		if (!bio)
2901 			return;
2902 		rq = blk_mq_get_new_requests(q, plug, bio, nr_segs);
2903 		if (unlikely(!rq))
2904 			return;
2905 	}
2906 
2907 	trace_block_getrq(bio);
2908 
2909 	rq_qos_track(q, rq, bio);
2910 
2911 	blk_mq_bio_to_request(rq, bio, nr_segs);
2912 
2913 	ret = blk_crypto_init_request(rq);
2914 	if (ret != BLK_STS_OK) {
2915 		bio->bi_status = ret;
2916 		bio_endio(bio);
2917 		blk_mq_free_request(rq);
2918 		return;
2919 	}
2920 
2921 	if (op_is_flush(bio->bi_opf)) {
2922 		blk_insert_flush(rq);
2923 		return;
2924 	}
2925 
2926 	if (plug)
2927 		blk_add_rq_to_plug(plug, rq);
2928 	else if ((rq->rq_flags & RQF_ELV) ||
2929 		 (rq->mq_hctx->dispatch_busy &&
2930 		  (q->nr_hw_queues == 1 || !is_sync)))
2931 		blk_mq_sched_insert_request(rq, false, true, true);
2932 	else
2933 		blk_mq_run_dispatch_ops(rq->q,
2934 				blk_mq_try_issue_directly(rq->mq_hctx, rq));
2935 }
2936 
2937 #ifdef CONFIG_BLK_MQ_STACKING
2938 /**
2939  * blk_insert_cloned_request - Helper for stacking drivers to submit a request
2940  * @rq: the request being queued
2941  */
2942 blk_status_t blk_insert_cloned_request(struct request *rq)
2943 {
2944 	struct request_queue *q = rq->q;
2945 	unsigned int max_sectors = blk_queue_get_max_sectors(q, req_op(rq));
2946 	blk_status_t ret;
2947 
2948 	if (blk_rq_sectors(rq) > max_sectors) {
2949 		/*
2950 		 * SCSI device does not have a good way to return if
2951 		 * Write Same/Zero is actually supported. If a device rejects
2952 		 * a non-read/write command (discard, write same,etc.) the
2953 		 * low-level device driver will set the relevant queue limit to
2954 		 * 0 to prevent blk-lib from issuing more of the offending
2955 		 * operations. Commands queued prior to the queue limit being
2956 		 * reset need to be completed with BLK_STS_NOTSUPP to avoid I/O
2957 		 * errors being propagated to upper layers.
2958 		 */
2959 		if (max_sectors == 0)
2960 			return BLK_STS_NOTSUPP;
2961 
2962 		printk(KERN_ERR "%s: over max size limit. (%u > %u)\n",
2963 			__func__, blk_rq_sectors(rq), max_sectors);
2964 		return BLK_STS_IOERR;
2965 	}
2966 
2967 	/*
2968 	 * The queue settings related to segment counting may differ from the
2969 	 * original queue.
2970 	 */
2971 	rq->nr_phys_segments = blk_recalc_rq_segments(rq);
2972 	if (rq->nr_phys_segments > queue_max_segments(q)) {
2973 		printk(KERN_ERR "%s: over max segments limit. (%hu > %hu)\n",
2974 			__func__, rq->nr_phys_segments, queue_max_segments(q));
2975 		return BLK_STS_IOERR;
2976 	}
2977 
2978 	if (q->disk && should_fail_request(q->disk->part0, blk_rq_bytes(rq)))
2979 		return BLK_STS_IOERR;
2980 
2981 	if (blk_crypto_insert_cloned_request(rq))
2982 		return BLK_STS_IOERR;
2983 
2984 	blk_account_io_start(rq);
2985 
2986 	/*
2987 	 * Since we have a scheduler attached on the top device,
2988 	 * bypass a potential scheduler on the bottom device for
2989 	 * insert.
2990 	 */
2991 	blk_mq_run_dispatch_ops(q,
2992 			ret = blk_mq_request_issue_directly(rq, true));
2993 	if (ret)
2994 		blk_account_io_done(rq, ktime_get_ns());
2995 	return ret;
2996 }
2997 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
2998 
2999 /**
3000  * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
3001  * @rq: the clone request to be cleaned up
3002  *
3003  * Description:
3004  *     Free all bios in @rq for a cloned request.
3005  */
3006 void blk_rq_unprep_clone(struct request *rq)
3007 {
3008 	struct bio *bio;
3009 
3010 	while ((bio = rq->bio) != NULL) {
3011 		rq->bio = bio->bi_next;
3012 
3013 		bio_put(bio);
3014 	}
3015 }
3016 EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
3017 
3018 /**
3019  * blk_rq_prep_clone - Helper function to setup clone request
3020  * @rq: the request to be setup
3021  * @rq_src: original request to be cloned
3022  * @bs: bio_set that bios for clone are allocated from
3023  * @gfp_mask: memory allocation mask for bio
3024  * @bio_ctr: setup function to be called for each clone bio.
3025  *           Returns %0 for success, non %0 for failure.
3026  * @data: private data to be passed to @bio_ctr
3027  *
3028  * Description:
3029  *     Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
3030  *     Also, pages which the original bios are pointing to are not copied
3031  *     and the cloned bios just point same pages.
3032  *     So cloned bios must be completed before original bios, which means
3033  *     the caller must complete @rq before @rq_src.
3034  */
3035 int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
3036 		      struct bio_set *bs, gfp_t gfp_mask,
3037 		      int (*bio_ctr)(struct bio *, struct bio *, void *),
3038 		      void *data)
3039 {
3040 	struct bio *bio, *bio_src;
3041 
3042 	if (!bs)
3043 		bs = &fs_bio_set;
3044 
3045 	__rq_for_each_bio(bio_src, rq_src) {
3046 		bio = bio_alloc_clone(rq->q->disk->part0, bio_src, gfp_mask,
3047 				      bs);
3048 		if (!bio)
3049 			goto free_and_out;
3050 
3051 		if (bio_ctr && bio_ctr(bio, bio_src, data))
3052 			goto free_and_out;
3053 
3054 		if (rq->bio) {
3055 			rq->biotail->bi_next = bio;
3056 			rq->biotail = bio;
3057 		} else {
3058 			rq->bio = rq->biotail = bio;
3059 		}
3060 		bio = NULL;
3061 	}
3062 
3063 	/* Copy attributes of the original request to the clone request. */
3064 	rq->__sector = blk_rq_pos(rq_src);
3065 	rq->__data_len = blk_rq_bytes(rq_src);
3066 	if (rq_src->rq_flags & RQF_SPECIAL_PAYLOAD) {
3067 		rq->rq_flags |= RQF_SPECIAL_PAYLOAD;
3068 		rq->special_vec = rq_src->special_vec;
3069 	}
3070 	rq->nr_phys_segments = rq_src->nr_phys_segments;
3071 	rq->ioprio = rq_src->ioprio;
3072 
3073 	if (rq->bio && blk_crypto_rq_bio_prep(rq, rq->bio, gfp_mask) < 0)
3074 		goto free_and_out;
3075 
3076 	return 0;
3077 
3078 free_and_out:
3079 	if (bio)
3080 		bio_put(bio);
3081 	blk_rq_unprep_clone(rq);
3082 
3083 	return -ENOMEM;
3084 }
3085 EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
3086 #endif /* CONFIG_BLK_MQ_STACKING */
3087 
3088 /*
3089  * Steal bios from a request and add them to a bio list.
3090  * The request must not have been partially completed before.
3091  */
3092 void blk_steal_bios(struct bio_list *list, struct request *rq)
3093 {
3094 	if (rq->bio) {
3095 		if (list->tail)
3096 			list->tail->bi_next = rq->bio;
3097 		else
3098 			list->head = rq->bio;
3099 		list->tail = rq->biotail;
3100 
3101 		rq->bio = NULL;
3102 		rq->biotail = NULL;
3103 	}
3104 
3105 	rq->__data_len = 0;
3106 }
3107 EXPORT_SYMBOL_GPL(blk_steal_bios);
3108 
3109 static size_t order_to_size(unsigned int order)
3110 {
3111 	return (size_t)PAGE_SIZE << order;
3112 }
3113 
3114 /* called before freeing request pool in @tags */
3115 static void blk_mq_clear_rq_mapping(struct blk_mq_tags *drv_tags,
3116 				    struct blk_mq_tags *tags)
3117 {
3118 	struct page *page;
3119 	unsigned long flags;
3120 
3121 	/*
3122 	 * There is no need to clear mapping if driver tags is not initialized
3123 	 * or the mapping belongs to the driver tags.
3124 	 */
3125 	if (!drv_tags || drv_tags == tags)
3126 		return;
3127 
3128 	list_for_each_entry(page, &tags->page_list, lru) {
3129 		unsigned long start = (unsigned long)page_address(page);
3130 		unsigned long end = start + order_to_size(page->private);
3131 		int i;
3132 
3133 		for (i = 0; i < drv_tags->nr_tags; i++) {
3134 			struct request *rq = drv_tags->rqs[i];
3135 			unsigned long rq_addr = (unsigned long)rq;
3136 
3137 			if (rq_addr >= start && rq_addr < end) {
3138 				WARN_ON_ONCE(req_ref_read(rq) != 0);
3139 				cmpxchg(&drv_tags->rqs[i], rq, NULL);
3140 			}
3141 		}
3142 	}
3143 
3144 	/*
3145 	 * Wait until all pending iteration is done.
3146 	 *
3147 	 * Request reference is cleared and it is guaranteed to be observed
3148 	 * after the ->lock is released.
3149 	 */
3150 	spin_lock_irqsave(&drv_tags->lock, flags);
3151 	spin_unlock_irqrestore(&drv_tags->lock, flags);
3152 }
3153 
3154 void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
3155 		     unsigned int hctx_idx)
3156 {
3157 	struct blk_mq_tags *drv_tags;
3158 	struct page *page;
3159 
3160 	if (list_empty(&tags->page_list))
3161 		return;
3162 
3163 	if (blk_mq_is_shared_tags(set->flags))
3164 		drv_tags = set->shared_tags;
3165 	else
3166 		drv_tags = set->tags[hctx_idx];
3167 
3168 	if (tags->static_rqs && set->ops->exit_request) {
3169 		int i;
3170 
3171 		for (i = 0; i < tags->nr_tags; i++) {
3172 			struct request *rq = tags->static_rqs[i];
3173 
3174 			if (!rq)
3175 				continue;
3176 			set->ops->exit_request(set, rq, hctx_idx);
3177 			tags->static_rqs[i] = NULL;
3178 		}
3179 	}
3180 
3181 	blk_mq_clear_rq_mapping(drv_tags, tags);
3182 
3183 	while (!list_empty(&tags->page_list)) {
3184 		page = list_first_entry(&tags->page_list, struct page, lru);
3185 		list_del_init(&page->lru);
3186 		/*
3187 		 * Remove kmemleak object previously allocated in
3188 		 * blk_mq_alloc_rqs().
3189 		 */
3190 		kmemleak_free(page_address(page));
3191 		__free_pages(page, page->private);
3192 	}
3193 }
3194 
3195 void blk_mq_free_rq_map(struct blk_mq_tags *tags)
3196 {
3197 	kfree(tags->rqs);
3198 	tags->rqs = NULL;
3199 	kfree(tags->static_rqs);
3200 	tags->static_rqs = NULL;
3201 
3202 	blk_mq_free_tags(tags);
3203 }
3204 
3205 static enum hctx_type hctx_idx_to_type(struct blk_mq_tag_set *set,
3206 		unsigned int hctx_idx)
3207 {
3208 	int i;
3209 
3210 	for (i = 0; i < set->nr_maps; i++) {
3211 		unsigned int start = set->map[i].queue_offset;
3212 		unsigned int end = start + set->map[i].nr_queues;
3213 
3214 		if (hctx_idx >= start && hctx_idx < end)
3215 			break;
3216 	}
3217 
3218 	if (i >= set->nr_maps)
3219 		i = HCTX_TYPE_DEFAULT;
3220 
3221 	return i;
3222 }
3223 
3224 static int blk_mq_get_hctx_node(struct blk_mq_tag_set *set,
3225 		unsigned int hctx_idx)
3226 {
3227 	enum hctx_type type = hctx_idx_to_type(set, hctx_idx);
3228 
3229 	return blk_mq_hw_queue_to_node(&set->map[type], hctx_idx);
3230 }
3231 
3232 static struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
3233 					       unsigned int hctx_idx,
3234 					       unsigned int nr_tags,
3235 					       unsigned int reserved_tags)
3236 {
3237 	int node = blk_mq_get_hctx_node(set, hctx_idx);
3238 	struct blk_mq_tags *tags;
3239 
3240 	if (node == NUMA_NO_NODE)
3241 		node = set->numa_node;
3242 
3243 	tags = blk_mq_init_tags(nr_tags, reserved_tags, node,
3244 				BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags));
3245 	if (!tags)
3246 		return NULL;
3247 
3248 	tags->rqs = kcalloc_node(nr_tags, sizeof(struct request *),
3249 				 GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
3250 				 node);
3251 	if (!tags->rqs) {
3252 		blk_mq_free_tags(tags);
3253 		return NULL;
3254 	}
3255 
3256 	tags->static_rqs = kcalloc_node(nr_tags, sizeof(struct request *),
3257 					GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
3258 					node);
3259 	if (!tags->static_rqs) {
3260 		kfree(tags->rqs);
3261 		blk_mq_free_tags(tags);
3262 		return NULL;
3263 	}
3264 
3265 	return tags;
3266 }
3267 
3268 static int blk_mq_init_request(struct blk_mq_tag_set *set, struct request *rq,
3269 			       unsigned int hctx_idx, int node)
3270 {
3271 	int ret;
3272 
3273 	if (set->ops->init_request) {
3274 		ret = set->ops->init_request(set, rq, hctx_idx, node);
3275 		if (ret)
3276 			return ret;
3277 	}
3278 
3279 	WRITE_ONCE(rq->state, MQ_RQ_IDLE);
3280 	return 0;
3281 }
3282 
3283 static int blk_mq_alloc_rqs(struct blk_mq_tag_set *set,
3284 			    struct blk_mq_tags *tags,
3285 			    unsigned int hctx_idx, unsigned int depth)
3286 {
3287 	unsigned int i, j, entries_per_page, max_order = 4;
3288 	int node = blk_mq_get_hctx_node(set, hctx_idx);
3289 	size_t rq_size, left;
3290 
3291 	if (node == NUMA_NO_NODE)
3292 		node = set->numa_node;
3293 
3294 	INIT_LIST_HEAD(&tags->page_list);
3295 
3296 	/*
3297 	 * rq_size is the size of the request plus driver payload, rounded
3298 	 * to the cacheline size
3299 	 */
3300 	rq_size = round_up(sizeof(struct request) + set->cmd_size,
3301 				cache_line_size());
3302 	left = rq_size * depth;
3303 
3304 	for (i = 0; i < depth; ) {
3305 		int this_order = max_order;
3306 		struct page *page;
3307 		int to_do;
3308 		void *p;
3309 
3310 		while (this_order && left < order_to_size(this_order - 1))
3311 			this_order--;
3312 
3313 		do {
3314 			page = alloc_pages_node(node,
3315 				GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY | __GFP_ZERO,
3316 				this_order);
3317 			if (page)
3318 				break;
3319 			if (!this_order--)
3320 				break;
3321 			if (order_to_size(this_order) < rq_size)
3322 				break;
3323 		} while (1);
3324 
3325 		if (!page)
3326 			goto fail;
3327 
3328 		page->private = this_order;
3329 		list_add_tail(&page->lru, &tags->page_list);
3330 
3331 		p = page_address(page);
3332 		/*
3333 		 * Allow kmemleak to scan these pages as they contain pointers
3334 		 * to additional allocations like via ops->init_request().
3335 		 */
3336 		kmemleak_alloc(p, order_to_size(this_order), 1, GFP_NOIO);
3337 		entries_per_page = order_to_size(this_order) / rq_size;
3338 		to_do = min(entries_per_page, depth - i);
3339 		left -= to_do * rq_size;
3340 		for (j = 0; j < to_do; j++) {
3341 			struct request *rq = p;
3342 
3343 			tags->static_rqs[i] = rq;
3344 			if (blk_mq_init_request(set, rq, hctx_idx, node)) {
3345 				tags->static_rqs[i] = NULL;
3346 				goto fail;
3347 			}
3348 
3349 			p += rq_size;
3350 			i++;
3351 		}
3352 	}
3353 	return 0;
3354 
3355 fail:
3356 	blk_mq_free_rqs(set, tags, hctx_idx);
3357 	return -ENOMEM;
3358 }
3359 
3360 struct rq_iter_data {
3361 	struct blk_mq_hw_ctx *hctx;
3362 	bool has_rq;
3363 };
3364 
3365 static bool blk_mq_has_request(struct request *rq, void *data)
3366 {
3367 	struct rq_iter_data *iter_data = data;
3368 
3369 	if (rq->mq_hctx != iter_data->hctx)
3370 		return true;
3371 	iter_data->has_rq = true;
3372 	return false;
3373 }
3374 
3375 static bool blk_mq_hctx_has_requests(struct blk_mq_hw_ctx *hctx)
3376 {
3377 	struct blk_mq_tags *tags = hctx->sched_tags ?
3378 			hctx->sched_tags : hctx->tags;
3379 	struct rq_iter_data data = {
3380 		.hctx	= hctx,
3381 	};
3382 
3383 	blk_mq_all_tag_iter(tags, blk_mq_has_request, &data);
3384 	return data.has_rq;
3385 }
3386 
3387 static inline bool blk_mq_last_cpu_in_hctx(unsigned int cpu,
3388 		struct blk_mq_hw_ctx *hctx)
3389 {
3390 	if (cpumask_first_and(hctx->cpumask, cpu_online_mask) != cpu)
3391 		return false;
3392 	if (cpumask_next_and(cpu, hctx->cpumask, cpu_online_mask) < nr_cpu_ids)
3393 		return false;
3394 	return true;
3395 }
3396 
3397 static int blk_mq_hctx_notify_offline(unsigned int cpu, struct hlist_node *node)
3398 {
3399 	struct blk_mq_hw_ctx *hctx = hlist_entry_safe(node,
3400 			struct blk_mq_hw_ctx, cpuhp_online);
3401 
3402 	if (!cpumask_test_cpu(cpu, hctx->cpumask) ||
3403 	    !blk_mq_last_cpu_in_hctx(cpu, hctx))
3404 		return 0;
3405 
3406 	/*
3407 	 * Prevent new request from being allocated on the current hctx.
3408 	 *
3409 	 * The smp_mb__after_atomic() Pairs with the implied barrier in
3410 	 * test_and_set_bit_lock in sbitmap_get().  Ensures the inactive flag is
3411 	 * seen once we return from the tag allocator.
3412 	 */
3413 	set_bit(BLK_MQ_S_INACTIVE, &hctx->state);
3414 	smp_mb__after_atomic();
3415 
3416 	/*
3417 	 * Try to grab a reference to the queue and wait for any outstanding
3418 	 * requests.  If we could not grab a reference the queue has been
3419 	 * frozen and there are no requests.
3420 	 */
3421 	if (percpu_ref_tryget(&hctx->queue->q_usage_counter)) {
3422 		while (blk_mq_hctx_has_requests(hctx))
3423 			msleep(5);
3424 		percpu_ref_put(&hctx->queue->q_usage_counter);
3425 	}
3426 
3427 	return 0;
3428 }
3429 
3430 static int blk_mq_hctx_notify_online(unsigned int cpu, struct hlist_node *node)
3431 {
3432 	struct blk_mq_hw_ctx *hctx = hlist_entry_safe(node,
3433 			struct blk_mq_hw_ctx, cpuhp_online);
3434 
3435 	if (cpumask_test_cpu(cpu, hctx->cpumask))
3436 		clear_bit(BLK_MQ_S_INACTIVE, &hctx->state);
3437 	return 0;
3438 }
3439 
3440 /*
3441  * 'cpu' is going away. splice any existing rq_list entries from this
3442  * software queue to the hw queue dispatch list, and ensure that it
3443  * gets run.
3444  */
3445 static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node)
3446 {
3447 	struct blk_mq_hw_ctx *hctx;
3448 	struct blk_mq_ctx *ctx;
3449 	LIST_HEAD(tmp);
3450 	enum hctx_type type;
3451 
3452 	hctx = hlist_entry_safe(node, struct blk_mq_hw_ctx, cpuhp_dead);
3453 	if (!cpumask_test_cpu(cpu, hctx->cpumask))
3454 		return 0;
3455 
3456 	ctx = __blk_mq_get_ctx(hctx->queue, cpu);
3457 	type = hctx->type;
3458 
3459 	spin_lock(&ctx->lock);
3460 	if (!list_empty(&ctx->rq_lists[type])) {
3461 		list_splice_init(&ctx->rq_lists[type], &tmp);
3462 		blk_mq_hctx_clear_pending(hctx, ctx);
3463 	}
3464 	spin_unlock(&ctx->lock);
3465 
3466 	if (list_empty(&tmp))
3467 		return 0;
3468 
3469 	spin_lock(&hctx->lock);
3470 	list_splice_tail_init(&tmp, &hctx->dispatch);
3471 	spin_unlock(&hctx->lock);
3472 
3473 	blk_mq_run_hw_queue(hctx, true);
3474 	return 0;
3475 }
3476 
3477 static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx)
3478 {
3479 	if (!(hctx->flags & BLK_MQ_F_STACKING))
3480 		cpuhp_state_remove_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE,
3481 						    &hctx->cpuhp_online);
3482 	cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_DEAD,
3483 					    &hctx->cpuhp_dead);
3484 }
3485 
3486 /*
3487  * Before freeing hw queue, clearing the flush request reference in
3488  * tags->rqs[] for avoiding potential UAF.
3489  */
3490 static void blk_mq_clear_flush_rq_mapping(struct blk_mq_tags *tags,
3491 		unsigned int queue_depth, struct request *flush_rq)
3492 {
3493 	int i;
3494 	unsigned long flags;
3495 
3496 	/* The hw queue may not be mapped yet */
3497 	if (!tags)
3498 		return;
3499 
3500 	WARN_ON_ONCE(req_ref_read(flush_rq) != 0);
3501 
3502 	for (i = 0; i < queue_depth; i++)
3503 		cmpxchg(&tags->rqs[i], flush_rq, NULL);
3504 
3505 	/*
3506 	 * Wait until all pending iteration is done.
3507 	 *
3508 	 * Request reference is cleared and it is guaranteed to be observed
3509 	 * after the ->lock is released.
3510 	 */
3511 	spin_lock_irqsave(&tags->lock, flags);
3512 	spin_unlock_irqrestore(&tags->lock, flags);
3513 }
3514 
3515 /* hctx->ctxs will be freed in queue's release handler */
3516 static void blk_mq_exit_hctx(struct request_queue *q,
3517 		struct blk_mq_tag_set *set,
3518 		struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
3519 {
3520 	struct request *flush_rq = hctx->fq->flush_rq;
3521 
3522 	if (blk_mq_hw_queue_mapped(hctx))
3523 		blk_mq_tag_idle(hctx);
3524 
3525 	if (blk_queue_init_done(q))
3526 		blk_mq_clear_flush_rq_mapping(set->tags[hctx_idx],
3527 				set->queue_depth, flush_rq);
3528 	if (set->ops->exit_request)
3529 		set->ops->exit_request(set, flush_rq, hctx_idx);
3530 
3531 	if (set->ops->exit_hctx)
3532 		set->ops->exit_hctx(hctx, hctx_idx);
3533 
3534 	blk_mq_remove_cpuhp(hctx);
3535 
3536 	xa_erase(&q->hctx_table, hctx_idx);
3537 
3538 	spin_lock(&q->unused_hctx_lock);
3539 	list_add(&hctx->hctx_list, &q->unused_hctx_list);
3540 	spin_unlock(&q->unused_hctx_lock);
3541 }
3542 
3543 static void blk_mq_exit_hw_queues(struct request_queue *q,
3544 		struct blk_mq_tag_set *set, int nr_queue)
3545 {
3546 	struct blk_mq_hw_ctx *hctx;
3547 	unsigned long i;
3548 
3549 	queue_for_each_hw_ctx(q, hctx, i) {
3550 		if (i == nr_queue)
3551 			break;
3552 		blk_mq_exit_hctx(q, set, hctx, i);
3553 	}
3554 }
3555 
3556 static int blk_mq_init_hctx(struct request_queue *q,
3557 		struct blk_mq_tag_set *set,
3558 		struct blk_mq_hw_ctx *hctx, unsigned hctx_idx)
3559 {
3560 	hctx->queue_num = hctx_idx;
3561 
3562 	if (!(hctx->flags & BLK_MQ_F_STACKING))
3563 		cpuhp_state_add_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE,
3564 				&hctx->cpuhp_online);
3565 	cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD, &hctx->cpuhp_dead);
3566 
3567 	hctx->tags = set->tags[hctx_idx];
3568 
3569 	if (set->ops->init_hctx &&
3570 	    set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
3571 		goto unregister_cpu_notifier;
3572 
3573 	if (blk_mq_init_request(set, hctx->fq->flush_rq, hctx_idx,
3574 				hctx->numa_node))
3575 		goto exit_hctx;
3576 
3577 	if (xa_insert(&q->hctx_table, hctx_idx, hctx, GFP_KERNEL))
3578 		goto exit_flush_rq;
3579 
3580 	return 0;
3581 
3582  exit_flush_rq:
3583 	if (set->ops->exit_request)
3584 		set->ops->exit_request(set, hctx->fq->flush_rq, hctx_idx);
3585  exit_hctx:
3586 	if (set->ops->exit_hctx)
3587 		set->ops->exit_hctx(hctx, hctx_idx);
3588  unregister_cpu_notifier:
3589 	blk_mq_remove_cpuhp(hctx);
3590 	return -1;
3591 }
3592 
3593 static struct blk_mq_hw_ctx *
3594 blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set,
3595 		int node)
3596 {
3597 	struct blk_mq_hw_ctx *hctx;
3598 	gfp_t gfp = GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY;
3599 
3600 	hctx = kzalloc_node(sizeof(struct blk_mq_hw_ctx), gfp, node);
3601 	if (!hctx)
3602 		goto fail_alloc_hctx;
3603 
3604 	if (!zalloc_cpumask_var_node(&hctx->cpumask, gfp, node))
3605 		goto free_hctx;
3606 
3607 	atomic_set(&hctx->nr_active, 0);
3608 	if (node == NUMA_NO_NODE)
3609 		node = set->numa_node;
3610 	hctx->numa_node = node;
3611 
3612 	INIT_DELAYED_WORK(&hctx->run_work, blk_mq_run_work_fn);
3613 	spin_lock_init(&hctx->lock);
3614 	INIT_LIST_HEAD(&hctx->dispatch);
3615 	hctx->queue = q;
3616 	hctx->flags = set->flags & ~BLK_MQ_F_TAG_QUEUE_SHARED;
3617 
3618 	INIT_LIST_HEAD(&hctx->hctx_list);
3619 
3620 	/*
3621 	 * Allocate space for all possible cpus to avoid allocation at
3622 	 * runtime
3623 	 */
3624 	hctx->ctxs = kmalloc_array_node(nr_cpu_ids, sizeof(void *),
3625 			gfp, node);
3626 	if (!hctx->ctxs)
3627 		goto free_cpumask;
3628 
3629 	if (sbitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8),
3630 				gfp, node, false, false))
3631 		goto free_ctxs;
3632 	hctx->nr_ctx = 0;
3633 
3634 	spin_lock_init(&hctx->dispatch_wait_lock);
3635 	init_waitqueue_func_entry(&hctx->dispatch_wait, blk_mq_dispatch_wake);
3636 	INIT_LIST_HEAD(&hctx->dispatch_wait.entry);
3637 
3638 	hctx->fq = blk_alloc_flush_queue(hctx->numa_node, set->cmd_size, gfp);
3639 	if (!hctx->fq)
3640 		goto free_bitmap;
3641 
3642 	blk_mq_hctx_kobj_init(hctx);
3643 
3644 	return hctx;
3645 
3646  free_bitmap:
3647 	sbitmap_free(&hctx->ctx_map);
3648  free_ctxs:
3649 	kfree(hctx->ctxs);
3650  free_cpumask:
3651 	free_cpumask_var(hctx->cpumask);
3652  free_hctx:
3653 	kfree(hctx);
3654  fail_alloc_hctx:
3655 	return NULL;
3656 }
3657 
3658 static void blk_mq_init_cpu_queues(struct request_queue *q,
3659 				   unsigned int nr_hw_queues)
3660 {
3661 	struct blk_mq_tag_set *set = q->tag_set;
3662 	unsigned int i, j;
3663 
3664 	for_each_possible_cpu(i) {
3665 		struct blk_mq_ctx *__ctx = per_cpu_ptr(q->queue_ctx, i);
3666 		struct blk_mq_hw_ctx *hctx;
3667 		int k;
3668 
3669 		__ctx->cpu = i;
3670 		spin_lock_init(&__ctx->lock);
3671 		for (k = HCTX_TYPE_DEFAULT; k < HCTX_MAX_TYPES; k++)
3672 			INIT_LIST_HEAD(&__ctx->rq_lists[k]);
3673 
3674 		__ctx->queue = q;
3675 
3676 		/*
3677 		 * Set local node, IFF we have more than one hw queue. If
3678 		 * not, we remain on the home node of the device
3679 		 */
3680 		for (j = 0; j < set->nr_maps; j++) {
3681 			hctx = blk_mq_map_queue_type(q, j, i);
3682 			if (nr_hw_queues > 1 && hctx->numa_node == NUMA_NO_NODE)
3683 				hctx->numa_node = cpu_to_node(i);
3684 		}
3685 	}
3686 }
3687 
3688 struct blk_mq_tags *blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
3689 					     unsigned int hctx_idx,
3690 					     unsigned int depth)
3691 {
3692 	struct blk_mq_tags *tags;
3693 	int ret;
3694 
3695 	tags = blk_mq_alloc_rq_map(set, hctx_idx, depth, set->reserved_tags);
3696 	if (!tags)
3697 		return NULL;
3698 
3699 	ret = blk_mq_alloc_rqs(set, tags, hctx_idx, depth);
3700 	if (ret) {
3701 		blk_mq_free_rq_map(tags);
3702 		return NULL;
3703 	}
3704 
3705 	return tags;
3706 }
3707 
3708 static bool __blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
3709 				       int hctx_idx)
3710 {
3711 	if (blk_mq_is_shared_tags(set->flags)) {
3712 		set->tags[hctx_idx] = set->shared_tags;
3713 
3714 		return true;
3715 	}
3716 
3717 	set->tags[hctx_idx] = blk_mq_alloc_map_and_rqs(set, hctx_idx,
3718 						       set->queue_depth);
3719 
3720 	return set->tags[hctx_idx];
3721 }
3722 
3723 void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
3724 			     struct blk_mq_tags *tags,
3725 			     unsigned int hctx_idx)
3726 {
3727 	if (tags) {
3728 		blk_mq_free_rqs(set, tags, hctx_idx);
3729 		blk_mq_free_rq_map(tags);
3730 	}
3731 }
3732 
3733 static void __blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
3734 				      unsigned int hctx_idx)
3735 {
3736 	if (!blk_mq_is_shared_tags(set->flags))
3737 		blk_mq_free_map_and_rqs(set, set->tags[hctx_idx], hctx_idx);
3738 
3739 	set->tags[hctx_idx] = NULL;
3740 }
3741 
3742 static void blk_mq_map_swqueue(struct request_queue *q)
3743 {
3744 	unsigned int j, hctx_idx;
3745 	unsigned long i;
3746 	struct blk_mq_hw_ctx *hctx;
3747 	struct blk_mq_ctx *ctx;
3748 	struct blk_mq_tag_set *set = q->tag_set;
3749 
3750 	queue_for_each_hw_ctx(q, hctx, i) {
3751 		cpumask_clear(hctx->cpumask);
3752 		hctx->nr_ctx = 0;
3753 		hctx->dispatch_from = NULL;
3754 	}
3755 
3756 	/*
3757 	 * Map software to hardware queues.
3758 	 *
3759 	 * If the cpu isn't present, the cpu is mapped to first hctx.
3760 	 */
3761 	for_each_possible_cpu(i) {
3762 
3763 		ctx = per_cpu_ptr(q->queue_ctx, i);
3764 		for (j = 0; j < set->nr_maps; j++) {
3765 			if (!set->map[j].nr_queues) {
3766 				ctx->hctxs[j] = blk_mq_map_queue_type(q,
3767 						HCTX_TYPE_DEFAULT, i);
3768 				continue;
3769 			}
3770 			hctx_idx = set->map[j].mq_map[i];
3771 			/* unmapped hw queue can be remapped after CPU topo changed */
3772 			if (!set->tags[hctx_idx] &&
3773 			    !__blk_mq_alloc_map_and_rqs(set, hctx_idx)) {
3774 				/*
3775 				 * If tags initialization fail for some hctx,
3776 				 * that hctx won't be brought online.  In this
3777 				 * case, remap the current ctx to hctx[0] which
3778 				 * is guaranteed to always have tags allocated
3779 				 */
3780 				set->map[j].mq_map[i] = 0;
3781 			}
3782 
3783 			hctx = blk_mq_map_queue_type(q, j, i);
3784 			ctx->hctxs[j] = hctx;
3785 			/*
3786 			 * If the CPU is already set in the mask, then we've
3787 			 * mapped this one already. This can happen if
3788 			 * devices share queues across queue maps.
3789 			 */
3790 			if (cpumask_test_cpu(i, hctx->cpumask))
3791 				continue;
3792 
3793 			cpumask_set_cpu(i, hctx->cpumask);
3794 			hctx->type = j;
3795 			ctx->index_hw[hctx->type] = hctx->nr_ctx;
3796 			hctx->ctxs[hctx->nr_ctx++] = ctx;
3797 
3798 			/*
3799 			 * If the nr_ctx type overflows, we have exceeded the
3800 			 * amount of sw queues we can support.
3801 			 */
3802 			BUG_ON(!hctx->nr_ctx);
3803 		}
3804 
3805 		for (; j < HCTX_MAX_TYPES; j++)
3806 			ctx->hctxs[j] = blk_mq_map_queue_type(q,
3807 					HCTX_TYPE_DEFAULT, i);
3808 	}
3809 
3810 	queue_for_each_hw_ctx(q, hctx, i) {
3811 		/*
3812 		 * If no software queues are mapped to this hardware queue,
3813 		 * disable it and free the request entries.
3814 		 */
3815 		if (!hctx->nr_ctx) {
3816 			/* Never unmap queue 0.  We need it as a
3817 			 * fallback in case of a new remap fails
3818 			 * allocation
3819 			 */
3820 			if (i)
3821 				__blk_mq_free_map_and_rqs(set, i);
3822 
3823 			hctx->tags = NULL;
3824 			continue;
3825 		}
3826 
3827 		hctx->tags = set->tags[i];
3828 		WARN_ON(!hctx->tags);
3829 
3830 		/*
3831 		 * Set the map size to the number of mapped software queues.
3832 		 * This is more accurate and more efficient than looping
3833 		 * over all possibly mapped software queues.
3834 		 */
3835 		sbitmap_resize(&hctx->ctx_map, hctx->nr_ctx);
3836 
3837 		/*
3838 		 * Initialize batch roundrobin counts
3839 		 */
3840 		hctx->next_cpu = blk_mq_first_mapped_cpu(hctx);
3841 		hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
3842 	}
3843 }
3844 
3845 /*
3846  * Caller needs to ensure that we're either frozen/quiesced, or that
3847  * the queue isn't live yet.
3848  */
3849 static void queue_set_hctx_shared(struct request_queue *q, bool shared)
3850 {
3851 	struct blk_mq_hw_ctx *hctx;
3852 	unsigned long i;
3853 
3854 	queue_for_each_hw_ctx(q, hctx, i) {
3855 		if (shared) {
3856 			hctx->flags |= BLK_MQ_F_TAG_QUEUE_SHARED;
3857 		} else {
3858 			blk_mq_tag_idle(hctx);
3859 			hctx->flags &= ~BLK_MQ_F_TAG_QUEUE_SHARED;
3860 		}
3861 	}
3862 }
3863 
3864 static void blk_mq_update_tag_set_shared(struct blk_mq_tag_set *set,
3865 					 bool shared)
3866 {
3867 	struct request_queue *q;
3868 
3869 	lockdep_assert_held(&set->tag_list_lock);
3870 
3871 	list_for_each_entry(q, &set->tag_list, tag_set_list) {
3872 		blk_mq_freeze_queue(q);
3873 		queue_set_hctx_shared(q, shared);
3874 		blk_mq_unfreeze_queue(q);
3875 	}
3876 }
3877 
3878 static void blk_mq_del_queue_tag_set(struct request_queue *q)
3879 {
3880 	struct blk_mq_tag_set *set = q->tag_set;
3881 
3882 	mutex_lock(&set->tag_list_lock);
3883 	list_del(&q->tag_set_list);
3884 	if (list_is_singular(&set->tag_list)) {
3885 		/* just transitioned to unshared */
3886 		set->flags &= ~BLK_MQ_F_TAG_QUEUE_SHARED;
3887 		/* update existing queue */
3888 		blk_mq_update_tag_set_shared(set, false);
3889 	}
3890 	mutex_unlock(&set->tag_list_lock);
3891 	INIT_LIST_HEAD(&q->tag_set_list);
3892 }
3893 
3894 static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
3895 				     struct request_queue *q)
3896 {
3897 	mutex_lock(&set->tag_list_lock);
3898 
3899 	/*
3900 	 * Check to see if we're transitioning to shared (from 1 to 2 queues).
3901 	 */
3902 	if (!list_empty(&set->tag_list) &&
3903 	    !(set->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) {
3904 		set->flags |= BLK_MQ_F_TAG_QUEUE_SHARED;
3905 		/* update existing queue */
3906 		blk_mq_update_tag_set_shared(set, true);
3907 	}
3908 	if (set->flags & BLK_MQ_F_TAG_QUEUE_SHARED)
3909 		queue_set_hctx_shared(q, true);
3910 	list_add_tail(&q->tag_set_list, &set->tag_list);
3911 
3912 	mutex_unlock(&set->tag_list_lock);
3913 }
3914 
3915 /* All allocations will be freed in release handler of q->mq_kobj */
3916 static int blk_mq_alloc_ctxs(struct request_queue *q)
3917 {
3918 	struct blk_mq_ctxs *ctxs;
3919 	int cpu;
3920 
3921 	ctxs = kzalloc(sizeof(*ctxs), GFP_KERNEL);
3922 	if (!ctxs)
3923 		return -ENOMEM;
3924 
3925 	ctxs->queue_ctx = alloc_percpu(struct blk_mq_ctx);
3926 	if (!ctxs->queue_ctx)
3927 		goto fail;
3928 
3929 	for_each_possible_cpu(cpu) {
3930 		struct blk_mq_ctx *ctx = per_cpu_ptr(ctxs->queue_ctx, cpu);
3931 		ctx->ctxs = ctxs;
3932 	}
3933 
3934 	q->mq_kobj = &ctxs->kobj;
3935 	q->queue_ctx = ctxs->queue_ctx;
3936 
3937 	return 0;
3938  fail:
3939 	kfree(ctxs);
3940 	return -ENOMEM;
3941 }
3942 
3943 /*
3944  * It is the actual release handler for mq, but we do it from
3945  * request queue's release handler for avoiding use-after-free
3946  * and headache because q->mq_kobj shouldn't have been introduced,
3947  * but we can't group ctx/kctx kobj without it.
3948  */
3949 void blk_mq_release(struct request_queue *q)
3950 {
3951 	struct blk_mq_hw_ctx *hctx, *next;
3952 	unsigned long i;
3953 
3954 	queue_for_each_hw_ctx(q, hctx, i)
3955 		WARN_ON_ONCE(hctx && list_empty(&hctx->hctx_list));
3956 
3957 	/* all hctx are in .unused_hctx_list now */
3958 	list_for_each_entry_safe(hctx, next, &q->unused_hctx_list, hctx_list) {
3959 		list_del_init(&hctx->hctx_list);
3960 		kobject_put(&hctx->kobj);
3961 	}
3962 
3963 	xa_destroy(&q->hctx_table);
3964 
3965 	/*
3966 	 * release .mq_kobj and sw queue's kobject now because
3967 	 * both share lifetime with request queue.
3968 	 */
3969 	blk_mq_sysfs_deinit(q);
3970 }
3971 
3972 static struct request_queue *blk_mq_init_queue_data(struct blk_mq_tag_set *set,
3973 		void *queuedata)
3974 {
3975 	struct request_queue *q;
3976 	int ret;
3977 
3978 	q = blk_alloc_queue(set->numa_node, set->flags & BLK_MQ_F_BLOCKING);
3979 	if (!q)
3980 		return ERR_PTR(-ENOMEM);
3981 	q->queuedata = queuedata;
3982 	ret = blk_mq_init_allocated_queue(set, q);
3983 	if (ret) {
3984 		blk_put_queue(q);
3985 		return ERR_PTR(ret);
3986 	}
3987 	return q;
3988 }
3989 
3990 struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
3991 {
3992 	return blk_mq_init_queue_data(set, NULL);
3993 }
3994 EXPORT_SYMBOL(blk_mq_init_queue);
3995 
3996 /**
3997  * blk_mq_destroy_queue - shutdown a request queue
3998  * @q: request queue to shutdown
3999  *
4000  * This shuts down a request queue allocated by blk_mq_init_queue() and drops
4001  * the initial reference.  All future requests will failed with -ENODEV.
4002  *
4003  * Context: can sleep
4004  */
4005 void blk_mq_destroy_queue(struct request_queue *q)
4006 {
4007 	WARN_ON_ONCE(!queue_is_mq(q));
4008 	WARN_ON_ONCE(blk_queue_registered(q));
4009 
4010 	might_sleep();
4011 
4012 	blk_queue_flag_set(QUEUE_FLAG_DYING, q);
4013 	blk_queue_start_drain(q);
4014 	blk_freeze_queue(q);
4015 
4016 	blk_sync_queue(q);
4017 	blk_mq_cancel_work_sync(q);
4018 	blk_mq_exit_queue(q);
4019 
4020 	/* @q is and will stay empty, shutdown and put */
4021 	blk_put_queue(q);
4022 }
4023 EXPORT_SYMBOL(blk_mq_destroy_queue);
4024 
4025 struct gendisk *__blk_mq_alloc_disk(struct blk_mq_tag_set *set, void *queuedata,
4026 		struct lock_class_key *lkclass)
4027 {
4028 	struct request_queue *q;
4029 	struct gendisk *disk;
4030 
4031 	q = blk_mq_init_queue_data(set, queuedata);
4032 	if (IS_ERR(q))
4033 		return ERR_CAST(q);
4034 
4035 	disk = __alloc_disk_node(q, set->numa_node, lkclass);
4036 	if (!disk) {
4037 		blk_mq_destroy_queue(q);
4038 		return ERR_PTR(-ENOMEM);
4039 	}
4040 	set_bit(GD_OWNS_QUEUE, &disk->state);
4041 	return disk;
4042 }
4043 EXPORT_SYMBOL(__blk_mq_alloc_disk);
4044 
4045 struct gendisk *blk_mq_alloc_disk_for_queue(struct request_queue *q,
4046 		struct lock_class_key *lkclass)
4047 {
4048 	if (!blk_get_queue(q))
4049 		return NULL;
4050 	return __alloc_disk_node(q, NUMA_NO_NODE, lkclass);
4051 }
4052 EXPORT_SYMBOL(blk_mq_alloc_disk_for_queue);
4053 
4054 static struct blk_mq_hw_ctx *blk_mq_alloc_and_init_hctx(
4055 		struct blk_mq_tag_set *set, struct request_queue *q,
4056 		int hctx_idx, int node)
4057 {
4058 	struct blk_mq_hw_ctx *hctx = NULL, *tmp;
4059 
4060 	/* reuse dead hctx first */
4061 	spin_lock(&q->unused_hctx_lock);
4062 	list_for_each_entry(tmp, &q->unused_hctx_list, hctx_list) {
4063 		if (tmp->numa_node == node) {
4064 			hctx = tmp;
4065 			break;
4066 		}
4067 	}
4068 	if (hctx)
4069 		list_del_init(&hctx->hctx_list);
4070 	spin_unlock(&q->unused_hctx_lock);
4071 
4072 	if (!hctx)
4073 		hctx = blk_mq_alloc_hctx(q, set, node);
4074 	if (!hctx)
4075 		goto fail;
4076 
4077 	if (blk_mq_init_hctx(q, set, hctx, hctx_idx))
4078 		goto free_hctx;
4079 
4080 	return hctx;
4081 
4082  free_hctx:
4083 	kobject_put(&hctx->kobj);
4084  fail:
4085 	return NULL;
4086 }
4087 
4088 static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
4089 						struct request_queue *q)
4090 {
4091 	struct blk_mq_hw_ctx *hctx;
4092 	unsigned long i, j;
4093 
4094 	/* protect against switching io scheduler  */
4095 	mutex_lock(&q->sysfs_lock);
4096 	for (i = 0; i < set->nr_hw_queues; i++) {
4097 		int old_node;
4098 		int node = blk_mq_get_hctx_node(set, i);
4099 		struct blk_mq_hw_ctx *old_hctx = xa_load(&q->hctx_table, i);
4100 
4101 		if (old_hctx) {
4102 			old_node = old_hctx->numa_node;
4103 			blk_mq_exit_hctx(q, set, old_hctx, i);
4104 		}
4105 
4106 		if (!blk_mq_alloc_and_init_hctx(set, q, i, node)) {
4107 			if (!old_hctx)
4108 				break;
4109 			pr_warn("Allocate new hctx on node %d fails, fallback to previous one on node %d\n",
4110 					node, old_node);
4111 			hctx = blk_mq_alloc_and_init_hctx(set, q, i, old_node);
4112 			WARN_ON_ONCE(!hctx);
4113 		}
4114 	}
4115 	/*
4116 	 * Increasing nr_hw_queues fails. Free the newly allocated
4117 	 * hctxs and keep the previous q->nr_hw_queues.
4118 	 */
4119 	if (i != set->nr_hw_queues) {
4120 		j = q->nr_hw_queues;
4121 	} else {
4122 		j = i;
4123 		q->nr_hw_queues = set->nr_hw_queues;
4124 	}
4125 
4126 	xa_for_each_start(&q->hctx_table, j, hctx, j)
4127 		blk_mq_exit_hctx(q, set, hctx, j);
4128 	mutex_unlock(&q->sysfs_lock);
4129 }
4130 
4131 static void blk_mq_update_poll_flag(struct request_queue *q)
4132 {
4133 	struct blk_mq_tag_set *set = q->tag_set;
4134 
4135 	if (set->nr_maps > HCTX_TYPE_POLL &&
4136 	    set->map[HCTX_TYPE_POLL].nr_queues)
4137 		blk_queue_flag_set(QUEUE_FLAG_POLL, q);
4138 	else
4139 		blk_queue_flag_clear(QUEUE_FLAG_POLL, q);
4140 }
4141 
4142 int blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
4143 		struct request_queue *q)
4144 {
4145 	WARN_ON_ONCE(blk_queue_has_srcu(q) !=
4146 			!!(set->flags & BLK_MQ_F_BLOCKING));
4147 
4148 	/* mark the queue as mq asap */
4149 	q->mq_ops = set->ops;
4150 
4151 	q->poll_cb = blk_stat_alloc_callback(blk_mq_poll_stats_fn,
4152 					     blk_mq_poll_stats_bkt,
4153 					     BLK_MQ_POLL_STATS_BKTS, q);
4154 	if (!q->poll_cb)
4155 		goto err_exit;
4156 
4157 	if (blk_mq_alloc_ctxs(q))
4158 		goto err_poll;
4159 
4160 	/* init q->mq_kobj and sw queues' kobjects */
4161 	blk_mq_sysfs_init(q);
4162 
4163 	INIT_LIST_HEAD(&q->unused_hctx_list);
4164 	spin_lock_init(&q->unused_hctx_lock);
4165 
4166 	xa_init(&q->hctx_table);
4167 
4168 	blk_mq_realloc_hw_ctxs(set, q);
4169 	if (!q->nr_hw_queues)
4170 		goto err_hctxs;
4171 
4172 	INIT_WORK(&q->timeout_work, blk_mq_timeout_work);
4173 	blk_queue_rq_timeout(q, set->timeout ? set->timeout : 30 * HZ);
4174 
4175 	q->tag_set = set;
4176 
4177 	q->queue_flags |= QUEUE_FLAG_MQ_DEFAULT;
4178 	blk_mq_update_poll_flag(q);
4179 
4180 	INIT_DELAYED_WORK(&q->requeue_work, blk_mq_requeue_work);
4181 	INIT_LIST_HEAD(&q->requeue_list);
4182 	spin_lock_init(&q->requeue_lock);
4183 
4184 	q->nr_requests = set->queue_depth;
4185 
4186 	/*
4187 	 * Default to classic polling
4188 	 */
4189 	q->poll_nsec = BLK_MQ_POLL_CLASSIC;
4190 
4191 	blk_mq_init_cpu_queues(q, set->nr_hw_queues);
4192 	blk_mq_add_queue_tag_set(set, q);
4193 	blk_mq_map_swqueue(q);
4194 	return 0;
4195 
4196 err_hctxs:
4197 	blk_mq_release(q);
4198 err_poll:
4199 	blk_stat_free_callback(q->poll_cb);
4200 	q->poll_cb = NULL;
4201 err_exit:
4202 	q->mq_ops = NULL;
4203 	return -ENOMEM;
4204 }
4205 EXPORT_SYMBOL(blk_mq_init_allocated_queue);
4206 
4207 /* tags can _not_ be used after returning from blk_mq_exit_queue */
4208 void blk_mq_exit_queue(struct request_queue *q)
4209 {
4210 	struct blk_mq_tag_set *set = q->tag_set;
4211 
4212 	/* Checks hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED. */
4213 	blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);
4214 	/* May clear BLK_MQ_F_TAG_QUEUE_SHARED in hctx->flags. */
4215 	blk_mq_del_queue_tag_set(q);
4216 }
4217 
4218 static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
4219 {
4220 	int i;
4221 
4222 	if (blk_mq_is_shared_tags(set->flags)) {
4223 		set->shared_tags = blk_mq_alloc_map_and_rqs(set,
4224 						BLK_MQ_NO_HCTX_IDX,
4225 						set->queue_depth);
4226 		if (!set->shared_tags)
4227 			return -ENOMEM;
4228 	}
4229 
4230 	for (i = 0; i < set->nr_hw_queues; i++) {
4231 		if (!__blk_mq_alloc_map_and_rqs(set, i))
4232 			goto out_unwind;
4233 		cond_resched();
4234 	}
4235 
4236 	return 0;
4237 
4238 out_unwind:
4239 	while (--i >= 0)
4240 		__blk_mq_free_map_and_rqs(set, i);
4241 
4242 	if (blk_mq_is_shared_tags(set->flags)) {
4243 		blk_mq_free_map_and_rqs(set, set->shared_tags,
4244 					BLK_MQ_NO_HCTX_IDX);
4245 	}
4246 
4247 	return -ENOMEM;
4248 }
4249 
4250 /*
4251  * Allocate the request maps associated with this tag_set. Note that this
4252  * may reduce the depth asked for, if memory is tight. set->queue_depth
4253  * will be updated to reflect the allocated depth.
4254  */
4255 static int blk_mq_alloc_set_map_and_rqs(struct blk_mq_tag_set *set)
4256 {
4257 	unsigned int depth;
4258 	int err;
4259 
4260 	depth = set->queue_depth;
4261 	do {
4262 		err = __blk_mq_alloc_rq_maps(set);
4263 		if (!err)
4264 			break;
4265 
4266 		set->queue_depth >>= 1;
4267 		if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN) {
4268 			err = -ENOMEM;
4269 			break;
4270 		}
4271 	} while (set->queue_depth);
4272 
4273 	if (!set->queue_depth || err) {
4274 		pr_err("blk-mq: failed to allocate request map\n");
4275 		return -ENOMEM;
4276 	}
4277 
4278 	if (depth != set->queue_depth)
4279 		pr_info("blk-mq: reduced tag depth (%u -> %u)\n",
4280 						depth, set->queue_depth);
4281 
4282 	return 0;
4283 }
4284 
4285 static void blk_mq_update_queue_map(struct blk_mq_tag_set *set)
4286 {
4287 	/*
4288 	 * blk_mq_map_queues() and multiple .map_queues() implementations
4289 	 * expect that set->map[HCTX_TYPE_DEFAULT].nr_queues is set to the
4290 	 * number of hardware queues.
4291 	 */
4292 	if (set->nr_maps == 1)
4293 		set->map[HCTX_TYPE_DEFAULT].nr_queues = set->nr_hw_queues;
4294 
4295 	if (set->ops->map_queues && !is_kdump_kernel()) {
4296 		int i;
4297 
4298 		/*
4299 		 * transport .map_queues is usually done in the following
4300 		 * way:
4301 		 *
4302 		 * for (queue = 0; queue < set->nr_hw_queues; queue++) {
4303 		 * 	mask = get_cpu_mask(queue)
4304 		 * 	for_each_cpu(cpu, mask)
4305 		 * 		set->map[x].mq_map[cpu] = queue;
4306 		 * }
4307 		 *
4308 		 * When we need to remap, the table has to be cleared for
4309 		 * killing stale mapping since one CPU may not be mapped
4310 		 * to any hw queue.
4311 		 */
4312 		for (i = 0; i < set->nr_maps; i++)
4313 			blk_mq_clear_mq_map(&set->map[i]);
4314 
4315 		set->ops->map_queues(set);
4316 	} else {
4317 		BUG_ON(set->nr_maps > 1);
4318 		blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
4319 	}
4320 }
4321 
4322 static int blk_mq_realloc_tag_set_tags(struct blk_mq_tag_set *set,
4323 				  int cur_nr_hw_queues, int new_nr_hw_queues)
4324 {
4325 	struct blk_mq_tags **new_tags;
4326 
4327 	if (cur_nr_hw_queues >= new_nr_hw_queues)
4328 		return 0;
4329 
4330 	new_tags = kcalloc_node(new_nr_hw_queues, sizeof(struct blk_mq_tags *),
4331 				GFP_KERNEL, set->numa_node);
4332 	if (!new_tags)
4333 		return -ENOMEM;
4334 
4335 	if (set->tags)
4336 		memcpy(new_tags, set->tags, cur_nr_hw_queues *
4337 		       sizeof(*set->tags));
4338 	kfree(set->tags);
4339 	set->tags = new_tags;
4340 	set->nr_hw_queues = new_nr_hw_queues;
4341 
4342 	return 0;
4343 }
4344 
4345 static int blk_mq_alloc_tag_set_tags(struct blk_mq_tag_set *set,
4346 				int new_nr_hw_queues)
4347 {
4348 	return blk_mq_realloc_tag_set_tags(set, 0, new_nr_hw_queues);
4349 }
4350 
4351 /*
4352  * Alloc a tag set to be associated with one or more request queues.
4353  * May fail with EINVAL for various error conditions. May adjust the
4354  * requested depth down, if it's too large. In that case, the set
4355  * value will be stored in set->queue_depth.
4356  */
4357 int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
4358 {
4359 	int i, ret;
4360 
4361 	BUILD_BUG_ON(BLK_MQ_MAX_DEPTH > 1 << BLK_MQ_UNIQUE_TAG_BITS);
4362 
4363 	if (!set->nr_hw_queues)
4364 		return -EINVAL;
4365 	if (!set->queue_depth)
4366 		return -EINVAL;
4367 	if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN)
4368 		return -EINVAL;
4369 
4370 	if (!set->ops->queue_rq)
4371 		return -EINVAL;
4372 
4373 	if (!set->ops->get_budget ^ !set->ops->put_budget)
4374 		return -EINVAL;
4375 
4376 	if (set->queue_depth > BLK_MQ_MAX_DEPTH) {
4377 		pr_info("blk-mq: reduced tag depth to %u\n",
4378 			BLK_MQ_MAX_DEPTH);
4379 		set->queue_depth = BLK_MQ_MAX_DEPTH;
4380 	}
4381 
4382 	if (!set->nr_maps)
4383 		set->nr_maps = 1;
4384 	else if (set->nr_maps > HCTX_MAX_TYPES)
4385 		return -EINVAL;
4386 
4387 	/*
4388 	 * If a crashdump is active, then we are potentially in a very
4389 	 * memory constrained environment. Limit us to 1 queue and
4390 	 * 64 tags to prevent using too much memory.
4391 	 */
4392 	if (is_kdump_kernel()) {
4393 		set->nr_hw_queues = 1;
4394 		set->nr_maps = 1;
4395 		set->queue_depth = min(64U, set->queue_depth);
4396 	}
4397 	/*
4398 	 * There is no use for more h/w queues than cpus if we just have
4399 	 * a single map
4400 	 */
4401 	if (set->nr_maps == 1 && set->nr_hw_queues > nr_cpu_ids)
4402 		set->nr_hw_queues = nr_cpu_ids;
4403 
4404 	if (blk_mq_alloc_tag_set_tags(set, set->nr_hw_queues) < 0)
4405 		return -ENOMEM;
4406 
4407 	ret = -ENOMEM;
4408 	for (i = 0; i < set->nr_maps; i++) {
4409 		set->map[i].mq_map = kcalloc_node(nr_cpu_ids,
4410 						  sizeof(set->map[i].mq_map[0]),
4411 						  GFP_KERNEL, set->numa_node);
4412 		if (!set->map[i].mq_map)
4413 			goto out_free_mq_map;
4414 		set->map[i].nr_queues = is_kdump_kernel() ? 1 : set->nr_hw_queues;
4415 	}
4416 
4417 	blk_mq_update_queue_map(set);
4418 
4419 	ret = blk_mq_alloc_set_map_and_rqs(set);
4420 	if (ret)
4421 		goto out_free_mq_map;
4422 
4423 	mutex_init(&set->tag_list_lock);
4424 	INIT_LIST_HEAD(&set->tag_list);
4425 
4426 	return 0;
4427 
4428 out_free_mq_map:
4429 	for (i = 0; i < set->nr_maps; i++) {
4430 		kfree(set->map[i].mq_map);
4431 		set->map[i].mq_map = NULL;
4432 	}
4433 	kfree(set->tags);
4434 	set->tags = NULL;
4435 	return ret;
4436 }
4437 EXPORT_SYMBOL(blk_mq_alloc_tag_set);
4438 
4439 /* allocate and initialize a tagset for a simple single-queue device */
4440 int blk_mq_alloc_sq_tag_set(struct blk_mq_tag_set *set,
4441 		const struct blk_mq_ops *ops, unsigned int queue_depth,
4442 		unsigned int set_flags)
4443 {
4444 	memset(set, 0, sizeof(*set));
4445 	set->ops = ops;
4446 	set->nr_hw_queues = 1;
4447 	set->nr_maps = 1;
4448 	set->queue_depth = queue_depth;
4449 	set->numa_node = NUMA_NO_NODE;
4450 	set->flags = set_flags;
4451 	return blk_mq_alloc_tag_set(set);
4452 }
4453 EXPORT_SYMBOL_GPL(blk_mq_alloc_sq_tag_set);
4454 
4455 void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
4456 {
4457 	int i, j;
4458 
4459 	for (i = 0; i < set->nr_hw_queues; i++)
4460 		__blk_mq_free_map_and_rqs(set, i);
4461 
4462 	if (blk_mq_is_shared_tags(set->flags)) {
4463 		blk_mq_free_map_and_rqs(set, set->shared_tags,
4464 					BLK_MQ_NO_HCTX_IDX);
4465 	}
4466 
4467 	for (j = 0; j < set->nr_maps; j++) {
4468 		kfree(set->map[j].mq_map);
4469 		set->map[j].mq_map = NULL;
4470 	}
4471 
4472 	kfree(set->tags);
4473 	set->tags = NULL;
4474 }
4475 EXPORT_SYMBOL(blk_mq_free_tag_set);
4476 
4477 int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
4478 {
4479 	struct blk_mq_tag_set *set = q->tag_set;
4480 	struct blk_mq_hw_ctx *hctx;
4481 	int ret;
4482 	unsigned long i;
4483 
4484 	if (!set)
4485 		return -EINVAL;
4486 
4487 	if (q->nr_requests == nr)
4488 		return 0;
4489 
4490 	blk_mq_freeze_queue(q);
4491 	blk_mq_quiesce_queue(q);
4492 
4493 	ret = 0;
4494 	queue_for_each_hw_ctx(q, hctx, i) {
4495 		if (!hctx->tags)
4496 			continue;
4497 		/*
4498 		 * If we're using an MQ scheduler, just update the scheduler
4499 		 * queue depth. This is similar to what the old code would do.
4500 		 */
4501 		if (hctx->sched_tags) {
4502 			ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
4503 						      nr, true);
4504 		} else {
4505 			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
4506 						      false);
4507 		}
4508 		if (ret)
4509 			break;
4510 		if (q->elevator && q->elevator->type->ops.depth_updated)
4511 			q->elevator->type->ops.depth_updated(hctx);
4512 	}
4513 	if (!ret) {
4514 		q->nr_requests = nr;
4515 		if (blk_mq_is_shared_tags(set->flags)) {
4516 			if (q->elevator)
4517 				blk_mq_tag_update_sched_shared_tags(q);
4518 			else
4519 				blk_mq_tag_resize_shared_tags(set, nr);
4520 		}
4521 	}
4522 
4523 	blk_mq_unquiesce_queue(q);
4524 	blk_mq_unfreeze_queue(q);
4525 
4526 	return ret;
4527 }
4528 
4529 /*
4530  * request_queue and elevator_type pair.
4531  * It is just used by __blk_mq_update_nr_hw_queues to cache
4532  * the elevator_type associated with a request_queue.
4533  */
4534 struct blk_mq_qe_pair {
4535 	struct list_head node;
4536 	struct request_queue *q;
4537 	struct elevator_type *type;
4538 };
4539 
4540 /*
4541  * Cache the elevator_type in qe pair list and switch the
4542  * io scheduler to 'none'
4543  */
4544 static bool blk_mq_elv_switch_none(struct list_head *head,
4545 		struct request_queue *q)
4546 {
4547 	struct blk_mq_qe_pair *qe;
4548 
4549 	if (!q->elevator)
4550 		return true;
4551 
4552 	qe = kmalloc(sizeof(*qe), GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY);
4553 	if (!qe)
4554 		return false;
4555 
4556 	/* q->elevator needs protection from ->sysfs_lock */
4557 	mutex_lock(&q->sysfs_lock);
4558 
4559 	INIT_LIST_HEAD(&qe->node);
4560 	qe->q = q;
4561 	qe->type = q->elevator->type;
4562 	list_add(&qe->node, head);
4563 
4564 	/*
4565 	 * After elevator_switch, the previous elevator_queue will be
4566 	 * released by elevator_release. The reference of the io scheduler
4567 	 * module get by elevator_get will also be put. So we need to get
4568 	 * a reference of the io scheduler module here to prevent it to be
4569 	 * removed.
4570 	 */
4571 	__module_get(qe->type->elevator_owner);
4572 	elevator_switch(q, NULL);
4573 	mutex_unlock(&q->sysfs_lock);
4574 
4575 	return true;
4576 }
4577 
4578 static struct blk_mq_qe_pair *blk_lookup_qe_pair(struct list_head *head,
4579 						struct request_queue *q)
4580 {
4581 	struct blk_mq_qe_pair *qe;
4582 
4583 	list_for_each_entry(qe, head, node)
4584 		if (qe->q == q)
4585 			return qe;
4586 
4587 	return NULL;
4588 }
4589 
4590 static void blk_mq_elv_switch_back(struct list_head *head,
4591 				  struct request_queue *q)
4592 {
4593 	struct blk_mq_qe_pair *qe;
4594 	struct elevator_type *t;
4595 
4596 	qe = blk_lookup_qe_pair(head, q);
4597 	if (!qe)
4598 		return;
4599 	t = qe->type;
4600 	list_del(&qe->node);
4601 	kfree(qe);
4602 
4603 	mutex_lock(&q->sysfs_lock);
4604 	elevator_switch(q, t);
4605 	mutex_unlock(&q->sysfs_lock);
4606 }
4607 
4608 static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
4609 							int nr_hw_queues)
4610 {
4611 	struct request_queue *q;
4612 	LIST_HEAD(head);
4613 	int prev_nr_hw_queues;
4614 
4615 	lockdep_assert_held(&set->tag_list_lock);
4616 
4617 	if (set->nr_maps == 1 && nr_hw_queues > nr_cpu_ids)
4618 		nr_hw_queues = nr_cpu_ids;
4619 	if (nr_hw_queues < 1)
4620 		return;
4621 	if (set->nr_maps == 1 && nr_hw_queues == set->nr_hw_queues)
4622 		return;
4623 
4624 	list_for_each_entry(q, &set->tag_list, tag_set_list)
4625 		blk_mq_freeze_queue(q);
4626 	/*
4627 	 * Switch IO scheduler to 'none', cleaning up the data associated
4628 	 * with the previous scheduler. We will switch back once we are done
4629 	 * updating the new sw to hw queue mappings.
4630 	 */
4631 	list_for_each_entry(q, &set->tag_list, tag_set_list)
4632 		if (!blk_mq_elv_switch_none(&head, q))
4633 			goto switch_back;
4634 
4635 	list_for_each_entry(q, &set->tag_list, tag_set_list) {
4636 		blk_mq_debugfs_unregister_hctxs(q);
4637 		blk_mq_sysfs_unregister_hctxs(q);
4638 	}
4639 
4640 	prev_nr_hw_queues = set->nr_hw_queues;
4641 	if (blk_mq_realloc_tag_set_tags(set, set->nr_hw_queues, nr_hw_queues) <
4642 	    0)
4643 		goto reregister;
4644 
4645 	set->nr_hw_queues = nr_hw_queues;
4646 fallback:
4647 	blk_mq_update_queue_map(set);
4648 	list_for_each_entry(q, &set->tag_list, tag_set_list) {
4649 		blk_mq_realloc_hw_ctxs(set, q);
4650 		blk_mq_update_poll_flag(q);
4651 		if (q->nr_hw_queues != set->nr_hw_queues) {
4652 			int i = prev_nr_hw_queues;
4653 
4654 			pr_warn("Increasing nr_hw_queues to %d fails, fallback to %d\n",
4655 					nr_hw_queues, prev_nr_hw_queues);
4656 			for (; i < set->nr_hw_queues; i++)
4657 				__blk_mq_free_map_and_rqs(set, i);
4658 
4659 			set->nr_hw_queues = prev_nr_hw_queues;
4660 			blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
4661 			goto fallback;
4662 		}
4663 		blk_mq_map_swqueue(q);
4664 	}
4665 
4666 reregister:
4667 	list_for_each_entry(q, &set->tag_list, tag_set_list) {
4668 		blk_mq_sysfs_register_hctxs(q);
4669 		blk_mq_debugfs_register_hctxs(q);
4670 	}
4671 
4672 switch_back:
4673 	list_for_each_entry(q, &set->tag_list, tag_set_list)
4674 		blk_mq_elv_switch_back(&head, q);
4675 
4676 	list_for_each_entry(q, &set->tag_list, tag_set_list)
4677 		blk_mq_unfreeze_queue(q);
4678 }
4679 
4680 void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
4681 {
4682 	mutex_lock(&set->tag_list_lock);
4683 	__blk_mq_update_nr_hw_queues(set, nr_hw_queues);
4684 	mutex_unlock(&set->tag_list_lock);
4685 }
4686 EXPORT_SYMBOL_GPL(blk_mq_update_nr_hw_queues);
4687 
4688 /* Enable polling stats and return whether they were already enabled. */
4689 static bool blk_poll_stats_enable(struct request_queue *q)
4690 {
4691 	if (q->poll_stat)
4692 		return true;
4693 
4694 	return blk_stats_alloc_enable(q);
4695 }
4696 
4697 static void blk_mq_poll_stats_start(struct request_queue *q)
4698 {
4699 	/*
4700 	 * We don't arm the callback if polling stats are not enabled or the
4701 	 * callback is already active.
4702 	 */
4703 	if (!q->poll_stat || blk_stat_is_active(q->poll_cb))
4704 		return;
4705 
4706 	blk_stat_activate_msecs(q->poll_cb, 100);
4707 }
4708 
4709 static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb)
4710 {
4711 	struct request_queue *q = cb->data;
4712 	int bucket;
4713 
4714 	for (bucket = 0; bucket < BLK_MQ_POLL_STATS_BKTS; bucket++) {
4715 		if (cb->stat[bucket].nr_samples)
4716 			q->poll_stat[bucket] = cb->stat[bucket];
4717 	}
4718 }
4719 
4720 static unsigned long blk_mq_poll_nsecs(struct request_queue *q,
4721 				       struct request *rq)
4722 {
4723 	unsigned long ret = 0;
4724 	int bucket;
4725 
4726 	/*
4727 	 * If stats collection isn't on, don't sleep but turn it on for
4728 	 * future users
4729 	 */
4730 	if (!blk_poll_stats_enable(q))
4731 		return 0;
4732 
4733 	/*
4734 	 * As an optimistic guess, use half of the mean service time
4735 	 * for this type of request. We can (and should) make this smarter.
4736 	 * For instance, if the completion latencies are tight, we can
4737 	 * get closer than just half the mean. This is especially
4738 	 * important on devices where the completion latencies are longer
4739 	 * than ~10 usec. We do use the stats for the relevant IO size
4740 	 * if available which does lead to better estimates.
4741 	 */
4742 	bucket = blk_mq_poll_stats_bkt(rq);
4743 	if (bucket < 0)
4744 		return ret;
4745 
4746 	if (q->poll_stat[bucket].nr_samples)
4747 		ret = (q->poll_stat[bucket].mean + 1) / 2;
4748 
4749 	return ret;
4750 }
4751 
4752 static bool blk_mq_poll_hybrid(struct request_queue *q, blk_qc_t qc)
4753 {
4754 	struct blk_mq_hw_ctx *hctx = blk_qc_to_hctx(q, qc);
4755 	struct request *rq = blk_qc_to_rq(hctx, qc);
4756 	struct hrtimer_sleeper hs;
4757 	enum hrtimer_mode mode;
4758 	unsigned int nsecs;
4759 	ktime_t kt;
4760 
4761 	/*
4762 	 * If a request has completed on queue that uses an I/O scheduler, we
4763 	 * won't get back a request from blk_qc_to_rq.
4764 	 */
4765 	if (!rq || (rq->rq_flags & RQF_MQ_POLL_SLEPT))
4766 		return false;
4767 
4768 	/*
4769 	 * If we get here, hybrid polling is enabled. Hence poll_nsec can be:
4770 	 *
4771 	 *  0:	use half of prev avg
4772 	 * >0:	use this specific value
4773 	 */
4774 	if (q->poll_nsec > 0)
4775 		nsecs = q->poll_nsec;
4776 	else
4777 		nsecs = blk_mq_poll_nsecs(q, rq);
4778 
4779 	if (!nsecs)
4780 		return false;
4781 
4782 	rq->rq_flags |= RQF_MQ_POLL_SLEPT;
4783 
4784 	/*
4785 	 * This will be replaced with the stats tracking code, using
4786 	 * 'avg_completion_time / 2' as the pre-sleep target.
4787 	 */
4788 	kt = nsecs;
4789 
4790 	mode = HRTIMER_MODE_REL;
4791 	hrtimer_init_sleeper_on_stack(&hs, CLOCK_MONOTONIC, mode);
4792 	hrtimer_set_expires(&hs.timer, kt);
4793 
4794 	do {
4795 		if (blk_mq_rq_state(rq) == MQ_RQ_COMPLETE)
4796 			break;
4797 		set_current_state(TASK_UNINTERRUPTIBLE);
4798 		hrtimer_sleeper_start_expires(&hs, mode);
4799 		if (hs.task)
4800 			io_schedule();
4801 		hrtimer_cancel(&hs.timer);
4802 		mode = HRTIMER_MODE_ABS;
4803 	} while (hs.task && !signal_pending(current));
4804 
4805 	__set_current_state(TASK_RUNNING);
4806 	destroy_hrtimer_on_stack(&hs.timer);
4807 
4808 	/*
4809 	 * If we sleep, have the caller restart the poll loop to reset the
4810 	 * state.  Like for the other success return cases, the caller is
4811 	 * responsible for checking if the IO completed.  If the IO isn't
4812 	 * complete, we'll get called again and will go straight to the busy
4813 	 * poll loop.
4814 	 */
4815 	return true;
4816 }
4817 
4818 static int blk_mq_poll_classic(struct request_queue *q, blk_qc_t cookie,
4819 			       struct io_comp_batch *iob, unsigned int flags)
4820 {
4821 	struct blk_mq_hw_ctx *hctx = blk_qc_to_hctx(q, cookie);
4822 	long state = get_current_state();
4823 	int ret;
4824 
4825 	do {
4826 		ret = q->mq_ops->poll(hctx, iob);
4827 		if (ret > 0) {
4828 			__set_current_state(TASK_RUNNING);
4829 			return ret;
4830 		}
4831 
4832 		if (signal_pending_state(state, current))
4833 			__set_current_state(TASK_RUNNING);
4834 		if (task_is_running(current))
4835 			return 1;
4836 
4837 		if (ret < 0 || (flags & BLK_POLL_ONESHOT))
4838 			break;
4839 		cpu_relax();
4840 	} while (!need_resched());
4841 
4842 	__set_current_state(TASK_RUNNING);
4843 	return 0;
4844 }
4845 
4846 int blk_mq_poll(struct request_queue *q, blk_qc_t cookie, struct io_comp_batch *iob,
4847 		unsigned int flags)
4848 {
4849 	if (!(flags & BLK_POLL_NOSLEEP) &&
4850 	    q->poll_nsec != BLK_MQ_POLL_CLASSIC) {
4851 		if (blk_mq_poll_hybrid(q, cookie))
4852 			return 1;
4853 	}
4854 	return blk_mq_poll_classic(q, cookie, iob, flags);
4855 }
4856 
4857 unsigned int blk_mq_rq_cpu(struct request *rq)
4858 {
4859 	return rq->mq_ctx->cpu;
4860 }
4861 EXPORT_SYMBOL(blk_mq_rq_cpu);
4862 
4863 void blk_mq_cancel_work_sync(struct request_queue *q)
4864 {
4865 	if (queue_is_mq(q)) {
4866 		struct blk_mq_hw_ctx *hctx;
4867 		unsigned long i;
4868 
4869 		cancel_delayed_work_sync(&q->requeue_work);
4870 
4871 		queue_for_each_hw_ctx(q, hctx, i)
4872 			cancel_delayed_work_sync(&hctx->run_work);
4873 	}
4874 }
4875 
4876 static int __init blk_mq_init(void)
4877 {
4878 	int i;
4879 
4880 	for_each_possible_cpu(i)
4881 		init_llist_head(&per_cpu(blk_cpu_done, i));
4882 	open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
4883 
4884 	cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD,
4885 				  "block/softirq:dead", NULL,
4886 				  blk_softirq_cpu_dead);
4887 	cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL,
4888 				blk_mq_hctx_notify_dead);
4889 	cpuhp_setup_state_multi(CPUHP_AP_BLK_MQ_ONLINE, "block/mq:online",
4890 				blk_mq_hctx_notify_online,
4891 				blk_mq_hctx_notify_offline);
4892 	return 0;
4893 }
4894 subsys_initcall(blk_mq_init);
4895