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TOMOYO Linux Cross Reference
Linux/block/blk-mq.c

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Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /*
  2  * Block multiqueue core code
  3  *
  4  * Copyright (C) 2013-2014 Jens Axboe
  5  * Copyright (C) 2013-2014 Christoph Hellwig
  6  */
  7 #include <linux/kernel.h>
  8 #include <linux/module.h>
  9 #include <linux/backing-dev.h>
 10 #include <linux/bio.h>
 11 #include <linux/blkdev.h>
 12 #include <linux/kmemleak.h>
 13 #include <linux/mm.h>
 14 #include <linux/init.h>
 15 #include <linux/slab.h>
 16 #include <linux/workqueue.h>
 17 #include <linux/smp.h>
 18 #include <linux/llist.h>
 19 #include <linux/list_sort.h>
 20 #include <linux/cpu.h>
 21 #include <linux/cache.h>
 22 #include <linux/sched/sysctl.h>
 23 #include <linux/sched/topology.h>
 24 #include <linux/sched/signal.h>
 25 #include <linux/delay.h>
 26 #include <linux/crash_dump.h>
 27 #include <linux/prefetch.h>
 28 
 29 #include <trace/events/block.h>
 30 
 31 #include <linux/blk-mq.h>
 32 #include "blk.h"
 33 #include "blk-mq.h"
 34 #include "blk-mq-debugfs.h"
 35 #include "blk-mq-tag.h"
 36 #include "blk-pm.h"
 37 #include "blk-stat.h"
 38 #include "blk-mq-sched.h"
 39 #include "blk-rq-qos.h"
 40 
 41 static void blk_mq_poll_stats_start(struct request_queue *q);
 42 static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb);
 43 
 44 static int blk_mq_poll_stats_bkt(const struct request *rq)
 45 {
 46         int ddir, bytes, bucket;
 47 
 48         ddir = rq_data_dir(rq);
 49         bytes = blk_rq_bytes(rq);
 50 
 51         bucket = ddir + 2*(ilog2(bytes) - 9);
 52 
 53         if (bucket < 0)
 54                 return -1;
 55         else if (bucket >= BLK_MQ_POLL_STATS_BKTS)
 56                 return ddir + BLK_MQ_POLL_STATS_BKTS - 2;
 57 
 58         return bucket;
 59 }
 60 
 61 /*
 62  * Check if any of the ctx's have pending work in this hardware queue
 63  */
 64 static bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx)
 65 {
 66         return !list_empty_careful(&hctx->dispatch) ||
 67                 sbitmap_any_bit_set(&hctx->ctx_map) ||
 68                         blk_mq_sched_has_work(hctx);
 69 }
 70 
 71 /*
 72  * Mark this ctx as having pending work in this hardware queue
 73  */
 74 static void blk_mq_hctx_mark_pending(struct blk_mq_hw_ctx *hctx,
 75                                      struct blk_mq_ctx *ctx)
 76 {
 77         const int bit = ctx->index_hw[hctx->type];
 78 
 79         if (!sbitmap_test_bit(&hctx->ctx_map, bit))
 80                 sbitmap_set_bit(&hctx->ctx_map, bit);
 81 }
 82 
 83 static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
 84                                       struct blk_mq_ctx *ctx)
 85 {
 86         const int bit = ctx->index_hw[hctx->type];
 87 
 88         sbitmap_clear_bit(&hctx->ctx_map, bit);
 89 }
 90 
 91 struct mq_inflight {
 92         struct hd_struct *part;
 93         unsigned int *inflight;
 94 };
 95 
 96 static bool blk_mq_check_inflight(struct blk_mq_hw_ctx *hctx,
 97                                   struct request *rq, void *priv,
 98                                   bool reserved)
 99 {
100         struct mq_inflight *mi = priv;
101 
102         /*
103          * index[0] counts the specific partition that was asked for.
104          */
105         if (rq->part == mi->part)
106                 mi->inflight[0]++;
107 
108         return true;
109 }
110 
111 unsigned int blk_mq_in_flight(struct request_queue *q, struct hd_struct *part)
112 {
113         unsigned inflight[2];
114         struct mq_inflight mi = { .part = part, .inflight = inflight, };
115 
116         inflight[0] = inflight[1] = 0;
117         blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
118 
119         return inflight[0];
120 }
121 
122 static bool blk_mq_check_inflight_rw(struct blk_mq_hw_ctx *hctx,
123                                      struct request *rq, void *priv,
124                                      bool reserved)
125 {
126         struct mq_inflight *mi = priv;
127 
128         if (rq->part == mi->part)
129                 mi->inflight[rq_data_dir(rq)]++;
130 
131         return true;
132 }
133 
134 void blk_mq_in_flight_rw(struct request_queue *q, struct hd_struct *part,
135                          unsigned int inflight[2])
136 {
137         struct mq_inflight mi = { .part = part, .inflight = inflight, };
138 
139         inflight[0] = inflight[1] = 0;
140         blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight_rw, &mi);
141 }
142 
143 void blk_freeze_queue_start(struct request_queue *q)
144 {
145         int freeze_depth;
146 
147         freeze_depth = atomic_inc_return(&q->mq_freeze_depth);
148         if (freeze_depth == 1) {
149                 percpu_ref_kill(&q->q_usage_counter);
150                 if (queue_is_mq(q))
151                         blk_mq_run_hw_queues(q, false);
152         }
153 }
154 EXPORT_SYMBOL_GPL(blk_freeze_queue_start);
155 
156 void blk_mq_freeze_queue_wait(struct request_queue *q)
157 {
158         wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->q_usage_counter));
159 }
160 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait);
161 
162 int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
163                                      unsigned long timeout)
164 {
165         return wait_event_timeout(q->mq_freeze_wq,
166                                         percpu_ref_is_zero(&q->q_usage_counter),
167                                         timeout);
168 }
169 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait_timeout);
170 
171 /*
172  * Guarantee no request is in use, so we can change any data structure of
173  * the queue afterward.
174  */
175 void blk_freeze_queue(struct request_queue *q)
176 {
177         /*
178          * In the !blk_mq case we are only calling this to kill the
179          * q_usage_counter, otherwise this increases the freeze depth
180          * and waits for it to return to zero.  For this reason there is
181          * no blk_unfreeze_queue(), and blk_freeze_queue() is not
182          * exported to drivers as the only user for unfreeze is blk_mq.
183          */
184         blk_freeze_queue_start(q);
185         blk_mq_freeze_queue_wait(q);
186 }
187 
188 void blk_mq_freeze_queue(struct request_queue *q)
189 {
190         /*
191          * ...just an alias to keep freeze and unfreeze actions balanced
192          * in the blk_mq_* namespace
193          */
194         blk_freeze_queue(q);
195 }
196 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);
197 
198 void blk_mq_unfreeze_queue(struct request_queue *q)
199 {
200         int freeze_depth;
201 
202         freeze_depth = atomic_dec_return(&q->mq_freeze_depth);
203         WARN_ON_ONCE(freeze_depth < 0);
204         if (!freeze_depth) {
205                 percpu_ref_resurrect(&q->q_usage_counter);
206                 wake_up_all(&q->mq_freeze_wq);
207         }
208 }
209 EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);
210 
211 /*
212  * FIXME: replace the scsi_internal_device_*block_nowait() calls in the
213  * mpt3sas driver such that this function can be removed.
214  */
215 void blk_mq_quiesce_queue_nowait(struct request_queue *q)
216 {
217         blk_queue_flag_set(QUEUE_FLAG_QUIESCED, q);
218 }
219 EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
220 
221 /**
222  * blk_mq_quiesce_queue() - wait until all ongoing dispatches have finished
223  * @q: request queue.
224  *
225  * Note: this function does not prevent that the struct request end_io()
226  * callback function is invoked. Once this function is returned, we make
227  * sure no dispatch can happen until the queue is unquiesced via
228  * blk_mq_unquiesce_queue().
229  */
230 void blk_mq_quiesce_queue(struct request_queue *q)
231 {
232         struct blk_mq_hw_ctx *hctx;
233         unsigned int i;
234         bool rcu = false;
235 
236         blk_mq_quiesce_queue_nowait(q);
237 
238         queue_for_each_hw_ctx(q, hctx, i) {
239                 if (hctx->flags & BLK_MQ_F_BLOCKING)
240                         synchronize_srcu(hctx->srcu);
241                 else
242                         rcu = true;
243         }
244         if (rcu)
245                 synchronize_rcu();
246 }
247 EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue);
248 
249 /*
250  * blk_mq_unquiesce_queue() - counterpart of blk_mq_quiesce_queue()
251  * @q: request queue.
252  *
253  * This function recovers queue into the state before quiescing
254  * which is done by blk_mq_quiesce_queue.
255  */
256 void blk_mq_unquiesce_queue(struct request_queue *q)
257 {
258         blk_queue_flag_clear(QUEUE_FLAG_QUIESCED, q);
259 
260         /* dispatch requests which are inserted during quiescing */
261         blk_mq_run_hw_queues(q, true);
262 }
263 EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue);
264 
265 void blk_mq_wake_waiters(struct request_queue *q)
266 {
267         struct blk_mq_hw_ctx *hctx;
268         unsigned int i;
269 
270         queue_for_each_hw_ctx(q, hctx, i)
271                 if (blk_mq_hw_queue_mapped(hctx))
272                         blk_mq_tag_wakeup_all(hctx->tags, true);
273 }
274 
275 bool blk_mq_can_queue(struct blk_mq_hw_ctx *hctx)
276 {
277         return blk_mq_has_free_tags(hctx->tags);
278 }
279 EXPORT_SYMBOL(blk_mq_can_queue);
280 
281 /*
282  * Only need start/end time stamping if we have stats enabled, or using
283  * an IO scheduler.
284  */
285 static inline bool blk_mq_need_time_stamp(struct request *rq)
286 {
287         return (rq->rq_flags & RQF_IO_STAT) || rq->q->elevator;
288 }
289 
290 static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
291                 unsigned int tag, unsigned int op)
292 {
293         struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
294         struct request *rq = tags->static_rqs[tag];
295         req_flags_t rq_flags = 0;
296 
297         if (data->flags & BLK_MQ_REQ_INTERNAL) {
298                 rq->tag = -1;
299                 rq->internal_tag = tag;
300         } else {
301                 if (data->hctx->flags & BLK_MQ_F_TAG_SHARED) {
302                         rq_flags = RQF_MQ_INFLIGHT;
303                         atomic_inc(&data->hctx->nr_active);
304                 }
305                 rq->tag = tag;
306                 rq->internal_tag = -1;
307                 data->hctx->tags->rqs[rq->tag] = rq;
308         }
309 
310         /* csd/requeue_work/fifo_time is initialized before use */
311         rq->q = data->q;
312         rq->mq_ctx = data->ctx;
313         rq->mq_hctx = data->hctx;
314         rq->rq_flags = rq_flags;
315         rq->cmd_flags = op;
316         if (data->flags & BLK_MQ_REQ_PREEMPT)
317                 rq->rq_flags |= RQF_PREEMPT;
318         if (blk_queue_io_stat(data->q))
319                 rq->rq_flags |= RQF_IO_STAT;
320         INIT_LIST_HEAD(&rq->queuelist);
321         INIT_HLIST_NODE(&rq->hash);
322         RB_CLEAR_NODE(&rq->rb_node);
323         rq->rq_disk = NULL;
324         rq->part = NULL;
325         if (blk_mq_need_time_stamp(rq))
326                 rq->start_time_ns = ktime_get_ns();
327         else
328                 rq->start_time_ns = 0;
329         rq->io_start_time_ns = 0;
330         rq->nr_phys_segments = 0;
331 #if defined(CONFIG_BLK_DEV_INTEGRITY)
332         rq->nr_integrity_segments = 0;
333 #endif
334         rq->special = NULL;
335         /* tag was already set */
336         rq->extra_len = 0;
337         WRITE_ONCE(rq->deadline, 0);
338 
339         rq->timeout = 0;
340 
341         rq->end_io = NULL;
342         rq->end_io_data = NULL;
343         rq->next_rq = NULL;
344 
345         data->ctx->rq_dispatched[op_is_sync(op)]++;
346         refcount_set(&rq->ref, 1);
347         return rq;
348 }
349 
350 static struct request *blk_mq_get_request(struct request_queue *q,
351                                           struct bio *bio,
352                                           struct blk_mq_alloc_data *data)
353 {
354         struct elevator_queue *e = q->elevator;
355         struct request *rq;
356         unsigned int tag;
357         bool put_ctx_on_error = false;
358 
359         blk_queue_enter_live(q);
360         data->q = q;
361         if (likely(!data->ctx)) {
362                 data->ctx = blk_mq_get_ctx(q);
363                 put_ctx_on_error = true;
364         }
365         if (likely(!data->hctx))
366                 data->hctx = blk_mq_map_queue(q, data->cmd_flags,
367                                                 data->ctx->cpu);
368         if (data->cmd_flags & REQ_NOWAIT)
369                 data->flags |= BLK_MQ_REQ_NOWAIT;
370 
371         if (e) {
372                 data->flags |= BLK_MQ_REQ_INTERNAL;
373 
374                 /*
375                  * Flush requests are special and go directly to the
376                  * dispatch list. Don't include reserved tags in the
377                  * limiting, as it isn't useful.
378                  */
379                 if (!op_is_flush(data->cmd_flags) &&
380                     e->type->ops.limit_depth &&
381                     !(data->flags & BLK_MQ_REQ_RESERVED))
382                         e->type->ops.limit_depth(data->cmd_flags, data);
383         } else {
384                 blk_mq_tag_busy(data->hctx);
385         }
386 
387         tag = blk_mq_get_tag(data);
388         if (tag == BLK_MQ_TAG_FAIL) {
389                 if (put_ctx_on_error) {
390                         blk_mq_put_ctx(data->ctx);
391                         data->ctx = NULL;
392                 }
393                 blk_queue_exit(q);
394                 return NULL;
395         }
396 
397         rq = blk_mq_rq_ctx_init(data, tag, data->cmd_flags);
398         if (!op_is_flush(data->cmd_flags)) {
399                 rq->elv.icq = NULL;
400                 if (e && e->type->ops.prepare_request) {
401                         if (e->type->icq_cache)
402                                 blk_mq_sched_assign_ioc(rq);
403 
404                         e->type->ops.prepare_request(rq, bio);
405                         rq->rq_flags |= RQF_ELVPRIV;
406                 }
407         }
408         data->hctx->queued++;
409         return rq;
410 }
411 
412 struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op,
413                 blk_mq_req_flags_t flags)
414 {
415         struct blk_mq_alloc_data alloc_data = { .flags = flags, .cmd_flags = op };
416         struct request *rq;
417         int ret;
418 
419         ret = blk_queue_enter(q, flags);
420         if (ret)
421                 return ERR_PTR(ret);
422 
423         rq = blk_mq_get_request(q, NULL, &alloc_data);
424         blk_queue_exit(q);
425 
426         if (!rq)
427                 return ERR_PTR(-EWOULDBLOCK);
428 
429         blk_mq_put_ctx(alloc_data.ctx);
430 
431         rq->__data_len = 0;
432         rq->__sector = (sector_t) -1;
433         rq->bio = rq->biotail = NULL;
434         return rq;
435 }
436 EXPORT_SYMBOL(blk_mq_alloc_request);
437 
438 struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
439         unsigned int op, blk_mq_req_flags_t flags, unsigned int hctx_idx)
440 {
441         struct blk_mq_alloc_data alloc_data = { .flags = flags, .cmd_flags = op };
442         struct request *rq;
443         unsigned int cpu;
444         int ret;
445 
446         /*
447          * If the tag allocator sleeps we could get an allocation for a
448          * different hardware context.  No need to complicate the low level
449          * allocator for this for the rare use case of a command tied to
450          * a specific queue.
451          */
452         if (WARN_ON_ONCE(!(flags & BLK_MQ_REQ_NOWAIT)))
453                 return ERR_PTR(-EINVAL);
454 
455         if (hctx_idx >= q->nr_hw_queues)
456                 return ERR_PTR(-EIO);
457 
458         ret = blk_queue_enter(q, flags);
459         if (ret)
460                 return ERR_PTR(ret);
461 
462         /*
463          * Check if the hardware context is actually mapped to anything.
464          * If not tell the caller that it should skip this queue.
465          */
466         alloc_data.hctx = q->queue_hw_ctx[hctx_idx];
467         if (!blk_mq_hw_queue_mapped(alloc_data.hctx)) {
468                 blk_queue_exit(q);
469                 return ERR_PTR(-EXDEV);
470         }
471         cpu = cpumask_first_and(alloc_data.hctx->cpumask, cpu_online_mask);
472         alloc_data.ctx = __blk_mq_get_ctx(q, cpu);
473 
474         rq = blk_mq_get_request(q, NULL, &alloc_data);
475         blk_queue_exit(q);
476 
477         if (!rq)
478                 return ERR_PTR(-EWOULDBLOCK);
479 
480         return rq;
481 }
482 EXPORT_SYMBOL_GPL(blk_mq_alloc_request_hctx);
483 
484 static void __blk_mq_free_request(struct request *rq)
485 {
486         struct request_queue *q = rq->q;
487         struct blk_mq_ctx *ctx = rq->mq_ctx;
488         struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
489         const int sched_tag = rq->internal_tag;
490 
491         blk_pm_mark_last_busy(rq);
492         rq->mq_hctx = NULL;
493         if (rq->tag != -1)
494                 blk_mq_put_tag(hctx, hctx->tags, ctx, rq->tag);
495         if (sched_tag != -1)
496                 blk_mq_put_tag(hctx, hctx->sched_tags, ctx, sched_tag);
497         blk_mq_sched_restart(hctx);
498         blk_queue_exit(q);
499 }
500 
501 void blk_mq_free_request(struct request *rq)
502 {
503         struct request_queue *q = rq->q;
504         struct elevator_queue *e = q->elevator;
505         struct blk_mq_ctx *ctx = rq->mq_ctx;
506         struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
507 
508         if (rq->rq_flags & RQF_ELVPRIV) {
509                 if (e && e->type->ops.finish_request)
510                         e->type->ops.finish_request(rq);
511                 if (rq->elv.icq) {
512                         put_io_context(rq->elv.icq->ioc);
513                         rq->elv.icq = NULL;
514                 }
515         }
516 
517         ctx->rq_completed[rq_is_sync(rq)]++;
518         if (rq->rq_flags & RQF_MQ_INFLIGHT)
519                 atomic_dec(&hctx->nr_active);
520 
521         if (unlikely(laptop_mode && !blk_rq_is_passthrough(rq)))
522                 laptop_io_completion(q->backing_dev_info);
523 
524         rq_qos_done(q, rq);
525 
526         WRITE_ONCE(rq->state, MQ_RQ_IDLE);
527         if (refcount_dec_and_test(&rq->ref))
528                 __blk_mq_free_request(rq);
529 }
530 EXPORT_SYMBOL_GPL(blk_mq_free_request);
531 
532 inline void __blk_mq_end_request(struct request *rq, blk_status_t error)
533 {
534         u64 now = 0;
535 
536         if (blk_mq_need_time_stamp(rq))
537                 now = ktime_get_ns();
538 
539         if (rq->rq_flags & RQF_STATS) {
540                 blk_mq_poll_stats_start(rq->q);
541                 blk_stat_add(rq, now);
542         }
543 
544         if (rq->internal_tag != -1)
545                 blk_mq_sched_completed_request(rq, now);
546 
547         blk_account_io_done(rq, now);
548 
549         if (rq->end_io) {
550                 rq_qos_done(rq->q, rq);
551                 rq->end_io(rq, error);
552         } else {
553                 if (unlikely(blk_bidi_rq(rq)))
554                         blk_mq_free_request(rq->next_rq);
555                 blk_mq_free_request(rq);
556         }
557 }
558 EXPORT_SYMBOL(__blk_mq_end_request);
559 
560 void blk_mq_end_request(struct request *rq, blk_status_t error)
561 {
562         if (blk_update_request(rq, error, blk_rq_bytes(rq)))
563                 BUG();
564         __blk_mq_end_request(rq, error);
565 }
566 EXPORT_SYMBOL(blk_mq_end_request);
567 
568 static void __blk_mq_complete_request_remote(void *data)
569 {
570         struct request *rq = data;
571         struct request_queue *q = rq->q;
572 
573         q->mq_ops->complete(rq);
574 }
575 
576 static void __blk_mq_complete_request(struct request *rq)
577 {
578         struct blk_mq_ctx *ctx = rq->mq_ctx;
579         struct request_queue *q = rq->q;
580         bool shared = false;
581         int cpu;
582 
583         WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);
584         /*
585          * Most of single queue controllers, there is only one irq vector
586          * for handling IO completion, and the only irq's affinity is set
587          * as all possible CPUs. On most of ARCHs, this affinity means the
588          * irq is handled on one specific CPU.
589          *
590          * So complete IO reqeust in softirq context in case of single queue
591          * for not degrading IO performance by irqsoff latency.
592          */
593         if (q->nr_hw_queues == 1) {
594                 __blk_complete_request(rq);
595                 return;
596         }
597 
598         /*
599          * For a polled request, always complete locallly, it's pointless
600          * to redirect the completion.
601          */
602         if ((rq->cmd_flags & REQ_HIPRI) ||
603             !test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags)) {
604                 q->mq_ops->complete(rq);
605                 return;
606         }
607 
608         cpu = get_cpu();
609         if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
610                 shared = cpus_share_cache(cpu, ctx->cpu);
611 
612         if (cpu != ctx->cpu && !shared && cpu_online(ctx->cpu)) {
613                 rq->csd.func = __blk_mq_complete_request_remote;
614                 rq->csd.info = rq;
615                 rq->csd.flags = 0;
616                 smp_call_function_single_async(ctx->cpu, &rq->csd);
617         } else {
618                 q->mq_ops->complete(rq);
619         }
620         put_cpu();
621 }
622 
623 static void hctx_unlock(struct blk_mq_hw_ctx *hctx, int srcu_idx)
624         __releases(hctx->srcu)
625 {
626         if (!(hctx->flags & BLK_MQ_F_BLOCKING))
627                 rcu_read_unlock();
628         else
629                 srcu_read_unlock(hctx->srcu, srcu_idx);
630 }
631 
632 static void hctx_lock(struct blk_mq_hw_ctx *hctx, int *srcu_idx)
633         __acquires(hctx->srcu)
634 {
635         if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
636                 /* shut up gcc false positive */
637                 *srcu_idx = 0;
638                 rcu_read_lock();
639         } else
640                 *srcu_idx = srcu_read_lock(hctx->srcu);
641 }
642 
643 /**
644  * blk_mq_complete_request - end I/O on a request
645  * @rq:         the request being processed
646  *
647  * Description:
648  *      Ends all I/O on a request. It does not handle partial completions.
649  *      The actual completion happens out-of-order, through a IPI handler.
650  **/
651 bool blk_mq_complete_request(struct request *rq)
652 {
653         if (unlikely(blk_should_fake_timeout(rq->q)))
654                 return false;
655         __blk_mq_complete_request(rq);
656         return true;
657 }
658 EXPORT_SYMBOL(blk_mq_complete_request);
659 
660 int blk_mq_request_started(struct request *rq)
661 {
662         return blk_mq_rq_state(rq) != MQ_RQ_IDLE;
663 }
664 EXPORT_SYMBOL_GPL(blk_mq_request_started);
665 
666 void blk_mq_start_request(struct request *rq)
667 {
668         struct request_queue *q = rq->q;
669 
670         blk_mq_sched_started_request(rq);
671 
672         trace_block_rq_issue(q, rq);
673 
674         if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags)) {
675                 rq->io_start_time_ns = ktime_get_ns();
676 #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
677                 rq->throtl_size = blk_rq_sectors(rq);
678 #endif
679                 rq->rq_flags |= RQF_STATS;
680                 rq_qos_issue(q, rq);
681         }
682 
683         WARN_ON_ONCE(blk_mq_rq_state(rq) != MQ_RQ_IDLE);
684 
685         blk_add_timer(rq);
686         WRITE_ONCE(rq->state, MQ_RQ_IN_FLIGHT);
687 
688         if (q->dma_drain_size && blk_rq_bytes(rq)) {
689                 /*
690                  * Make sure space for the drain appears.  We know we can do
691                  * this because max_hw_segments has been adjusted to be one
692                  * fewer than the device can handle.
693                  */
694                 rq->nr_phys_segments++;
695         }
696 }
697 EXPORT_SYMBOL(blk_mq_start_request);
698 
699 static void __blk_mq_requeue_request(struct request *rq)
700 {
701         struct request_queue *q = rq->q;
702 
703         blk_mq_put_driver_tag(rq);
704 
705         trace_block_rq_requeue(q, rq);
706         rq_qos_requeue(q, rq);
707 
708         if (blk_mq_request_started(rq)) {
709                 WRITE_ONCE(rq->state, MQ_RQ_IDLE);
710                 rq->rq_flags &= ~RQF_TIMED_OUT;
711                 if (q->dma_drain_size && blk_rq_bytes(rq))
712                         rq->nr_phys_segments--;
713         }
714 }
715 
716 void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list)
717 {
718         __blk_mq_requeue_request(rq);
719 
720         /* this request will be re-inserted to io scheduler queue */
721         blk_mq_sched_requeue_request(rq);
722 
723         BUG_ON(!list_empty(&rq->queuelist));
724         blk_mq_add_to_requeue_list(rq, true, kick_requeue_list);
725 }
726 EXPORT_SYMBOL(blk_mq_requeue_request);
727 
728 static void blk_mq_requeue_work(struct work_struct *work)
729 {
730         struct request_queue *q =
731                 container_of(work, struct request_queue, requeue_work.work);
732         LIST_HEAD(rq_list);
733         struct request *rq, *next;
734 
735         spin_lock_irq(&q->requeue_lock);
736         list_splice_init(&q->requeue_list, &rq_list);
737         spin_unlock_irq(&q->requeue_lock);
738 
739         list_for_each_entry_safe(rq, next, &rq_list, queuelist) {
740                 if (!(rq->rq_flags & RQF_SOFTBARRIER))
741                         continue;
742 
743                 rq->rq_flags &= ~RQF_SOFTBARRIER;
744                 list_del_init(&rq->queuelist);
745                 blk_mq_sched_insert_request(rq, true, false, false);
746         }
747 
748         while (!list_empty(&rq_list)) {
749                 rq = list_entry(rq_list.next, struct request, queuelist);
750                 list_del_init(&rq->queuelist);
751                 blk_mq_sched_insert_request(rq, false, false, false);
752         }
753 
754         blk_mq_run_hw_queues(q, false);
755 }
756 
757 void blk_mq_add_to_requeue_list(struct request *rq, bool at_head,
758                                 bool kick_requeue_list)
759 {
760         struct request_queue *q = rq->q;
761         unsigned long flags;
762 
763         /*
764          * We abuse this flag that is otherwise used by the I/O scheduler to
765          * request head insertion from the workqueue.
766          */
767         BUG_ON(rq->rq_flags & RQF_SOFTBARRIER);
768 
769         spin_lock_irqsave(&q->requeue_lock, flags);
770         if (at_head) {
771                 rq->rq_flags |= RQF_SOFTBARRIER;
772                 list_add(&rq->queuelist, &q->requeue_list);
773         } else {
774                 list_add_tail(&rq->queuelist, &q->requeue_list);
775         }
776         spin_unlock_irqrestore(&q->requeue_lock, flags);
777 
778         if (kick_requeue_list)
779                 blk_mq_kick_requeue_list(q);
780 }
781 EXPORT_SYMBOL(blk_mq_add_to_requeue_list);
782 
783 void blk_mq_kick_requeue_list(struct request_queue *q)
784 {
785         kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work, 0);
786 }
787 EXPORT_SYMBOL(blk_mq_kick_requeue_list);
788 
789 void blk_mq_delay_kick_requeue_list(struct request_queue *q,
790                                     unsigned long msecs)
791 {
792         kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work,
793                                     msecs_to_jiffies(msecs));
794 }
795 EXPORT_SYMBOL(blk_mq_delay_kick_requeue_list);
796 
797 struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
798 {
799         if (tag < tags->nr_tags) {
800                 prefetch(tags->rqs[tag]);
801                 return tags->rqs[tag];
802         }
803 
804         return NULL;
805 }
806 EXPORT_SYMBOL(blk_mq_tag_to_rq);
807 
808 static bool blk_mq_rq_inflight(struct blk_mq_hw_ctx *hctx, struct request *rq,
809                                void *priv, bool reserved)
810 {
811         /*
812          * If we find a request that is inflight and the queue matches,
813          * we know the queue is busy. Return false to stop the iteration.
814          */
815         if (rq->state == MQ_RQ_IN_FLIGHT && rq->q == hctx->queue) {
816                 bool *busy = priv;
817 
818                 *busy = true;
819                 return false;
820         }
821 
822         return true;
823 }
824 
825 bool blk_mq_queue_inflight(struct request_queue *q)
826 {
827         bool busy = false;
828 
829         blk_mq_queue_tag_busy_iter(q, blk_mq_rq_inflight, &busy);
830         return busy;
831 }
832 EXPORT_SYMBOL_GPL(blk_mq_queue_inflight);
833 
834 static void blk_mq_rq_timed_out(struct request *req, bool reserved)
835 {
836         req->rq_flags |= RQF_TIMED_OUT;
837         if (req->q->mq_ops->timeout) {
838                 enum blk_eh_timer_return ret;
839 
840                 ret = req->q->mq_ops->timeout(req, reserved);
841                 if (ret == BLK_EH_DONE)
842                         return;
843                 WARN_ON_ONCE(ret != BLK_EH_RESET_TIMER);
844         }
845 
846         blk_add_timer(req);
847 }
848 
849 static bool blk_mq_req_expired(struct request *rq, unsigned long *next)
850 {
851         unsigned long deadline;
852 
853         if (blk_mq_rq_state(rq) != MQ_RQ_IN_FLIGHT)
854                 return false;
855         if (rq->rq_flags & RQF_TIMED_OUT)
856                 return false;
857 
858         deadline = READ_ONCE(rq->deadline);
859         if (time_after_eq(jiffies, deadline))
860                 return true;
861 
862         if (*next == 0)
863                 *next = deadline;
864         else if (time_after(*next, deadline))
865                 *next = deadline;
866         return false;
867 }
868 
869 static bool blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
870                 struct request *rq, void *priv, bool reserved)
871 {
872         unsigned long *next = priv;
873 
874         /*
875          * Just do a quick check if it is expired before locking the request in
876          * so we're not unnecessarilly synchronizing across CPUs.
877          */
878         if (!blk_mq_req_expired(rq, next))
879                 return true;
880 
881         /*
882          * We have reason to believe the request may be expired. Take a
883          * reference on the request to lock this request lifetime into its
884          * currently allocated context to prevent it from being reallocated in
885          * the event the completion by-passes this timeout handler.
886          *
887          * If the reference was already released, then the driver beat the
888          * timeout handler to posting a natural completion.
889          */
890         if (!refcount_inc_not_zero(&rq->ref))
891                 return true;
892 
893         /*
894          * The request is now locked and cannot be reallocated underneath the
895          * timeout handler's processing. Re-verify this exact request is truly
896          * expired; if it is not expired, then the request was completed and
897          * reallocated as a new request.
898          */
899         if (blk_mq_req_expired(rq, next))
900                 blk_mq_rq_timed_out(rq, reserved);
901         if (refcount_dec_and_test(&rq->ref))
902                 __blk_mq_free_request(rq);
903 
904         return true;
905 }
906 
907 static void blk_mq_timeout_work(struct work_struct *work)
908 {
909         struct request_queue *q =
910                 container_of(work, struct request_queue, timeout_work);
911         unsigned long next = 0;
912         struct blk_mq_hw_ctx *hctx;
913         int i;
914 
915         /* A deadlock might occur if a request is stuck requiring a
916          * timeout at the same time a queue freeze is waiting
917          * completion, since the timeout code would not be able to
918          * acquire the queue reference here.
919          *
920          * That's why we don't use blk_queue_enter here; instead, we use
921          * percpu_ref_tryget directly, because we need to be able to
922          * obtain a reference even in the short window between the queue
923          * starting to freeze, by dropping the first reference in
924          * blk_freeze_queue_start, and the moment the last request is
925          * consumed, marked by the instant q_usage_counter reaches
926          * zero.
927          */
928         if (!percpu_ref_tryget(&q->q_usage_counter))
929                 return;
930 
931         blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &next);
932 
933         if (next != 0) {
934                 mod_timer(&q->timeout, next);
935         } else {
936                 /*
937                  * Request timeouts are handled as a forward rolling timer. If
938                  * we end up here it means that no requests are pending and
939                  * also that no request has been pending for a while. Mark
940                  * each hctx as idle.
941                  */
942                 queue_for_each_hw_ctx(q, hctx, i) {
943                         /* the hctx may be unmapped, so check it here */
944                         if (blk_mq_hw_queue_mapped(hctx))
945                                 blk_mq_tag_idle(hctx);
946                 }
947         }
948         blk_queue_exit(q);
949 }
950 
951 struct flush_busy_ctx_data {
952         struct blk_mq_hw_ctx *hctx;
953         struct list_head *list;
954 };
955 
956 static bool flush_busy_ctx(struct sbitmap *sb, unsigned int bitnr, void *data)
957 {
958         struct flush_busy_ctx_data *flush_data = data;
959         struct blk_mq_hw_ctx *hctx = flush_data->hctx;
960         struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
961         enum hctx_type type = hctx->type;
962 
963         spin_lock(&ctx->lock);
964         list_splice_tail_init(&ctx->rq_lists[type], flush_data->list);
965         sbitmap_clear_bit(sb, bitnr);
966         spin_unlock(&ctx->lock);
967         return true;
968 }
969 
970 /*
971  * Process software queues that have been marked busy, splicing them
972  * to the for-dispatch
973  */
974 void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list)
975 {
976         struct flush_busy_ctx_data data = {
977                 .hctx = hctx,
978                 .list = list,
979         };
980 
981         sbitmap_for_each_set(&hctx->ctx_map, flush_busy_ctx, &data);
982 }
983 EXPORT_SYMBOL_GPL(blk_mq_flush_busy_ctxs);
984 
985 struct dispatch_rq_data {
986         struct blk_mq_hw_ctx *hctx;
987         struct request *rq;
988 };
989 
990 static bool dispatch_rq_from_ctx(struct sbitmap *sb, unsigned int bitnr,
991                 void *data)
992 {
993         struct dispatch_rq_data *dispatch_data = data;
994         struct blk_mq_hw_ctx *hctx = dispatch_data->hctx;
995         struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
996         enum hctx_type type = hctx->type;
997 
998         spin_lock(&ctx->lock);
999         if (!list_empty(&ctx->rq_lists[type])) {
1000                 dispatch_data->rq = list_entry_rq(ctx->rq_lists[type].next);
1001                 list_del_init(&dispatch_data->rq->queuelist);
1002                 if (list_empty(&ctx->rq_lists[type]))
1003                         sbitmap_clear_bit(sb, bitnr);
1004         }
1005         spin_unlock(&ctx->lock);
1006 
1007         return !dispatch_data->rq;
1008 }
1009 
1010 struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx,
1011                                         struct blk_mq_ctx *start)
1012 {
1013         unsigned off = start ? start->index_hw[hctx->type] : 0;
1014         struct dispatch_rq_data data = {
1015                 .hctx = hctx,
1016                 .rq   = NULL,
1017         };
1018 
1019         __sbitmap_for_each_set(&hctx->ctx_map, off,
1020                                dispatch_rq_from_ctx, &data);
1021 
1022         return data.rq;
1023 }
1024 
1025 static inline unsigned int queued_to_index(unsigned int queued)
1026 {
1027         if (!queued)
1028                 return 0;
1029 
1030         return min(BLK_MQ_MAX_DISPATCH_ORDER - 1, ilog2(queued) + 1);
1031 }
1032 
1033 bool blk_mq_get_driver_tag(struct request *rq)
1034 {
1035         struct blk_mq_alloc_data data = {
1036                 .q = rq->q,
1037                 .hctx = rq->mq_hctx,
1038                 .flags = BLK_MQ_REQ_NOWAIT,
1039                 .cmd_flags = rq->cmd_flags,
1040         };
1041         bool shared;
1042 
1043         if (rq->tag != -1)
1044                 goto done;
1045 
1046         if (blk_mq_tag_is_reserved(data.hctx->sched_tags, rq->internal_tag))
1047                 data.flags |= BLK_MQ_REQ_RESERVED;
1048 
1049         shared = blk_mq_tag_busy(data.hctx);
1050         rq->tag = blk_mq_get_tag(&data);
1051         if (rq->tag >= 0) {
1052                 if (shared) {
1053                         rq->rq_flags |= RQF_MQ_INFLIGHT;
1054                         atomic_inc(&data.hctx->nr_active);
1055                 }
1056                 data.hctx->tags->rqs[rq->tag] = rq;
1057         }
1058 
1059 done:
1060         return rq->tag != -1;
1061 }
1062 
1063 static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode,
1064                                 int flags, void *key)
1065 {
1066         struct blk_mq_hw_ctx *hctx;
1067 
1068         hctx = container_of(wait, struct blk_mq_hw_ctx, dispatch_wait);
1069 
1070         spin_lock(&hctx->dispatch_wait_lock);
1071         list_del_init(&wait->entry);
1072         spin_unlock(&hctx->dispatch_wait_lock);
1073 
1074         blk_mq_run_hw_queue(hctx, true);
1075         return 1;
1076 }
1077 
1078 /*
1079  * Mark us waiting for a tag. For shared tags, this involves hooking us into
1080  * the tag wakeups. For non-shared tags, we can simply mark us needing a
1081  * restart. For both cases, take care to check the condition again after
1082  * marking us as waiting.
1083  */
1084 static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx,
1085                                  struct request *rq)
1086 {
1087         struct wait_queue_head *wq;
1088         wait_queue_entry_t *wait;
1089         bool ret;
1090 
1091         if (!(hctx->flags & BLK_MQ_F_TAG_SHARED)) {
1092                 if (!test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
1093                         set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
1094 
1095                 /*
1096                  * It's possible that a tag was freed in the window between the
1097                  * allocation failure and adding the hardware queue to the wait
1098                  * queue.
1099                  *
1100                  * Don't clear RESTART here, someone else could have set it.
1101                  * At most this will cost an extra queue run.
1102                  */
1103                 return blk_mq_get_driver_tag(rq);
1104         }
1105 
1106         wait = &hctx->dispatch_wait;
1107         if (!list_empty_careful(&wait->entry))
1108                 return false;
1109 
1110         wq = &bt_wait_ptr(&hctx->tags->bitmap_tags, hctx)->wait;
1111 
1112         spin_lock_irq(&wq->lock);
1113         spin_lock(&hctx->dispatch_wait_lock);
1114         if (!list_empty(&wait->entry)) {
1115                 spin_unlock(&hctx->dispatch_wait_lock);
1116                 spin_unlock_irq(&wq->lock);
1117                 return false;
1118         }
1119 
1120         wait->flags &= ~WQ_FLAG_EXCLUSIVE;
1121         __add_wait_queue(wq, wait);
1122 
1123         /*
1124          * It's possible that a tag was freed in the window between the
1125          * allocation failure and adding the hardware queue to the wait
1126          * queue.
1127          */
1128         ret = blk_mq_get_driver_tag(rq);
1129         if (!ret) {
1130                 spin_unlock(&hctx->dispatch_wait_lock);
1131                 spin_unlock_irq(&wq->lock);
1132                 return false;
1133         }
1134 
1135         /*
1136          * We got a tag, remove ourselves from the wait queue to ensure
1137          * someone else gets the wakeup.
1138          */
1139         list_del_init(&wait->entry);
1140         spin_unlock(&hctx->dispatch_wait_lock);
1141         spin_unlock_irq(&wq->lock);
1142 
1143         return true;
1144 }
1145 
1146 #define BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT  8
1147 #define BLK_MQ_DISPATCH_BUSY_EWMA_FACTOR  4
1148 /*
1149  * Update dispatch busy with the Exponential Weighted Moving Average(EWMA):
1150  * - EWMA is one simple way to compute running average value
1151  * - weight(7/8 and 1/8) is applied so that it can decrease exponentially
1152  * - take 4 as factor for avoiding to get too small(0) result, and this
1153  *   factor doesn't matter because EWMA decreases exponentially
1154  */
1155 static void blk_mq_update_dispatch_busy(struct blk_mq_hw_ctx *hctx, bool busy)
1156 {
1157         unsigned int ewma;
1158 
1159         if (hctx->queue->elevator)
1160                 return;
1161 
1162         ewma = hctx->dispatch_busy;
1163 
1164         if (!ewma && !busy)
1165                 return;
1166 
1167         ewma *= BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT - 1;
1168         if (busy)
1169                 ewma += 1 << BLK_MQ_DISPATCH_BUSY_EWMA_FACTOR;
1170         ewma /= BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT;
1171 
1172         hctx->dispatch_busy = ewma;
1173 }
1174 
1175 #define BLK_MQ_RESOURCE_DELAY   3               /* ms units */
1176 
1177 /*
1178  * Returns true if we did some work AND can potentially do more.
1179  */
1180 bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
1181                              bool got_budget)
1182 {
1183         struct blk_mq_hw_ctx *hctx;
1184         struct request *rq, *nxt;
1185         bool no_tag = false;
1186         int errors, queued;
1187         blk_status_t ret = BLK_STS_OK;
1188 
1189         if (list_empty(list))
1190                 return false;
1191 
1192         WARN_ON(!list_is_singular(list) && got_budget);
1193 
1194         /*
1195          * Now process all the entries, sending them to the driver.
1196          */
1197         errors = queued = 0;
1198         do {
1199                 struct blk_mq_queue_data bd;
1200 
1201                 rq = list_first_entry(list, struct request, queuelist);
1202 
1203                 hctx = rq->mq_hctx;
1204                 if (!got_budget && !blk_mq_get_dispatch_budget(hctx))
1205                         break;
1206 
1207                 if (!blk_mq_get_driver_tag(rq)) {
1208                         /*
1209                          * The initial allocation attempt failed, so we need to
1210                          * rerun the hardware queue when a tag is freed. The
1211                          * waitqueue takes care of that. If the queue is run
1212                          * before we add this entry back on the dispatch list,
1213                          * we'll re-run it below.
1214                          */
1215                         if (!blk_mq_mark_tag_wait(hctx, rq)) {
1216                                 blk_mq_put_dispatch_budget(hctx);
1217                                 /*
1218                                  * For non-shared tags, the RESTART check
1219                                  * will suffice.
1220                                  */
1221                                 if (hctx->flags & BLK_MQ_F_TAG_SHARED)
1222                                         no_tag = true;
1223                                 break;
1224                         }
1225                 }
1226 
1227                 list_del_init(&rq->queuelist);
1228 
1229                 bd.rq = rq;
1230 
1231                 /*
1232                  * Flag last if we have no more requests, or if we have more
1233                  * but can't assign a driver tag to it.
1234                  */
1235                 if (list_empty(list))
1236                         bd.last = true;
1237                 else {
1238                         nxt = list_first_entry(list, struct request, queuelist);
1239                         bd.last = !blk_mq_get_driver_tag(nxt);
1240                 }
1241 
1242                 ret = q->mq_ops->queue_rq(hctx, &bd);
1243                 if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE) {
1244                         /*
1245                          * If an I/O scheduler has been configured and we got a
1246                          * driver tag for the next request already, free it
1247                          * again.
1248                          */
1249                         if (!list_empty(list)) {
1250                                 nxt = list_first_entry(list, struct request, queuelist);
1251                                 blk_mq_put_driver_tag(nxt);
1252                         }
1253                         list_add(&rq->queuelist, list);
1254                         __blk_mq_requeue_request(rq);
1255                         break;
1256                 }
1257 
1258                 if (unlikely(ret != BLK_STS_OK)) {
1259                         errors++;
1260                         blk_mq_end_request(rq, BLK_STS_IOERR);
1261                         continue;
1262                 }
1263 
1264                 queued++;
1265         } while (!list_empty(list));
1266 
1267         hctx->dispatched[queued_to_index(queued)]++;
1268 
1269         /*
1270          * Any items that need requeuing? Stuff them into hctx->dispatch,
1271          * that is where we will continue on next queue run.
1272          */
1273         if (!list_empty(list)) {
1274                 bool needs_restart;
1275 
1276                 /*
1277                  * If we didn't flush the entire list, we could have told
1278                  * the driver there was more coming, but that turned out to
1279                  * be a lie.
1280                  */
1281                 if (q->mq_ops->commit_rqs)
1282                         q->mq_ops->commit_rqs(hctx);
1283 
1284                 spin_lock(&hctx->lock);
1285                 list_splice_init(list, &hctx->dispatch);
1286                 spin_unlock(&hctx->lock);
1287 
1288                 /*
1289                  * If SCHED_RESTART was set by the caller of this function and
1290                  * it is no longer set that means that it was cleared by another
1291                  * thread and hence that a queue rerun is needed.
1292                  *
1293                  * If 'no_tag' is set, that means that we failed getting
1294                  * a driver tag with an I/O scheduler attached. If our dispatch
1295                  * waitqueue is no longer active, ensure that we run the queue
1296                  * AFTER adding our entries back to the list.
1297                  *
1298                  * If no I/O scheduler has been configured it is possible that
1299                  * the hardware queue got stopped and restarted before requests
1300                  * were pushed back onto the dispatch list. Rerun the queue to
1301                  * avoid starvation. Notes:
1302                  * - blk_mq_run_hw_queue() checks whether or not a queue has
1303                  *   been stopped before rerunning a queue.
1304                  * - Some but not all block drivers stop a queue before
1305                  *   returning BLK_STS_RESOURCE. Two exceptions are scsi-mq
1306                  *   and dm-rq.
1307                  *
1308                  * If driver returns BLK_STS_RESOURCE and SCHED_RESTART
1309                  * bit is set, run queue after a delay to avoid IO stalls
1310                  * that could otherwise occur if the queue is idle.
1311                  */
1312                 needs_restart = blk_mq_sched_needs_restart(hctx);
1313                 if (!needs_restart ||
1314                     (no_tag && list_empty_careful(&hctx->dispatch_wait.entry)))
1315                         blk_mq_run_hw_queue(hctx, true);
1316                 else if (needs_restart && (ret == BLK_STS_RESOURCE))
1317                         blk_mq_delay_run_hw_queue(hctx, BLK_MQ_RESOURCE_DELAY);
1318 
1319                 blk_mq_update_dispatch_busy(hctx, true);
1320                 return false;
1321         } else
1322                 blk_mq_update_dispatch_busy(hctx, false);
1323 
1324         /*
1325          * If the host/device is unable to accept more work, inform the
1326          * caller of that.
1327          */
1328         if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
1329                 return false;
1330 
1331         return (queued + errors) != 0;
1332 }
1333 
1334 static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
1335 {
1336         int srcu_idx;
1337 
1338         /*
1339          * We should be running this queue from one of the CPUs that
1340          * are mapped to it.
1341          *
1342          * There are at least two related races now between setting
1343          * hctx->next_cpu from blk_mq_hctx_next_cpu() and running
1344          * __blk_mq_run_hw_queue():
1345          *
1346          * - hctx->next_cpu is found offline in blk_mq_hctx_next_cpu(),
1347          *   but later it becomes online, then this warning is harmless
1348          *   at all
1349          *
1350          * - hctx->next_cpu is found online in blk_mq_hctx_next_cpu(),
1351          *   but later it becomes offline, then the warning can't be
1352          *   triggered, and we depend on blk-mq timeout handler to
1353          *   handle dispatched requests to this hctx
1354          */
1355         if (!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
1356                 cpu_online(hctx->next_cpu)) {
1357                 printk(KERN_WARNING "run queue from wrong CPU %d, hctx %s\n",
1358                         raw_smp_processor_id(),
1359                         cpumask_empty(hctx->cpumask) ? "inactive": "active");
1360                 dump_stack();
1361         }
1362 
1363         /*
1364          * We can't run the queue inline with ints disabled. Ensure that
1365          * we catch bad users of this early.
1366          */
1367         WARN_ON_ONCE(in_interrupt());
1368 
1369         might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
1370 
1371         hctx_lock(hctx, &srcu_idx);
1372         blk_mq_sched_dispatch_requests(hctx);
1373         hctx_unlock(hctx, srcu_idx);
1374 }
1375 
1376 static inline int blk_mq_first_mapped_cpu(struct blk_mq_hw_ctx *hctx)
1377 {
1378         int cpu = cpumask_first_and(hctx->cpumask, cpu_online_mask);
1379 
1380         if (cpu >= nr_cpu_ids)
1381                 cpu = cpumask_first(hctx->cpumask);
1382         return cpu;
1383 }
1384 
1385 /*
1386  * It'd be great if the workqueue API had a way to pass
1387  * in a mask and had some smarts for more clever placement.
1388  * For now we just round-robin here, switching for every
1389  * BLK_MQ_CPU_WORK_BATCH queued items.
1390  */
1391 static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
1392 {
1393         bool tried = false;
1394         int next_cpu = hctx->next_cpu;
1395 
1396         if (hctx->queue->nr_hw_queues == 1)
1397                 return WORK_CPU_UNBOUND;
1398 
1399         if (--hctx->next_cpu_batch <= 0) {
1400 select_cpu:
1401                 next_cpu = cpumask_next_and(next_cpu, hctx->cpumask,
1402                                 cpu_online_mask);
1403                 if (next_cpu >= nr_cpu_ids)
1404                         next_cpu = blk_mq_first_mapped_cpu(hctx);
1405                 hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
1406         }
1407 
1408         /*
1409          * Do unbound schedule if we can't find a online CPU for this hctx,
1410          * and it should only happen in the path of handling CPU DEAD.
1411          */
1412         if (!cpu_online(next_cpu)) {
1413                 if (!tried) {
1414                         tried = true;
1415                         goto select_cpu;
1416                 }
1417 
1418                 /*
1419                  * Make sure to re-select CPU next time once after CPUs
1420                  * in hctx->cpumask become online again.
1421                  */
1422                 hctx->next_cpu = next_cpu;
1423                 hctx->next_cpu_batch = 1;
1424                 return WORK_CPU_UNBOUND;
1425         }
1426 
1427         hctx->next_cpu = next_cpu;
1428         return next_cpu;
1429 }
1430 
1431 static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async,
1432                                         unsigned long msecs)
1433 {
1434         if (unlikely(blk_mq_hctx_stopped(hctx)))
1435                 return;
1436 
1437         if (!async && !(hctx->flags & BLK_MQ_F_BLOCKING)) {
1438                 int cpu = get_cpu();
1439                 if (cpumask_test_cpu(cpu, hctx->cpumask)) {
1440                         __blk_mq_run_hw_queue(hctx);
1441                         put_cpu();
1442                         return;
1443                 }
1444 
1445                 put_cpu();
1446         }
1447 
1448         kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work,
1449                                     msecs_to_jiffies(msecs));
1450 }
1451 
1452 void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
1453 {
1454         __blk_mq_delay_run_hw_queue(hctx, true, msecs);
1455 }
1456 EXPORT_SYMBOL(blk_mq_delay_run_hw_queue);
1457 
1458 bool blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
1459 {
1460         int srcu_idx;
1461         bool need_run;
1462 
1463         /*
1464          * When queue is quiesced, we may be switching io scheduler, or
1465          * updating nr_hw_queues, or other things, and we can't run queue
1466          * any more, even __blk_mq_hctx_has_pending() can't be called safely.
1467          *
1468          * And queue will be rerun in blk_mq_unquiesce_queue() if it is
1469          * quiesced.
1470          */
1471         hctx_lock(hctx, &srcu_idx);
1472         need_run = !blk_queue_quiesced(hctx->queue) &&
1473                 blk_mq_hctx_has_pending(hctx);
1474         hctx_unlock(hctx, srcu_idx);
1475 
1476         if (need_run) {
1477                 __blk_mq_delay_run_hw_queue(hctx, async, 0);
1478                 return true;
1479         }
1480 
1481         return false;
1482 }
1483 EXPORT_SYMBOL(blk_mq_run_hw_queue);
1484 
1485 void blk_mq_run_hw_queues(struct request_queue *q, bool async)
1486 {
1487         struct blk_mq_hw_ctx *hctx;
1488         int i;
1489 
1490         queue_for_each_hw_ctx(q, hctx, i) {
1491                 if (blk_mq_hctx_stopped(hctx))
1492                         continue;
1493 
1494                 blk_mq_run_hw_queue(hctx, async);
1495         }
1496 }
1497 EXPORT_SYMBOL(blk_mq_run_hw_queues);
1498 
1499 /**
1500  * blk_mq_queue_stopped() - check whether one or more hctxs have been stopped
1501  * @q: request queue.
1502  *
1503  * The caller is responsible for serializing this function against
1504  * blk_mq_{start,stop}_hw_queue().
1505  */
1506 bool blk_mq_queue_stopped(struct request_queue *q)
1507 {
1508         struct blk_mq_hw_ctx *hctx;
1509         int i;
1510 
1511         queue_for_each_hw_ctx(q, hctx, i)
1512                 if (blk_mq_hctx_stopped(hctx))
1513                         return true;
1514 
1515         return false;
1516 }
1517 EXPORT_SYMBOL(blk_mq_queue_stopped);
1518 
1519 /*
1520  * This function is often used for pausing .queue_rq() by driver when
1521  * there isn't enough resource or some conditions aren't satisfied, and
1522  * BLK_STS_RESOURCE is usually returned.
1523  *
1524  * We do not guarantee that dispatch can be drained or blocked
1525  * after blk_mq_stop_hw_queue() returns. Please use
1526  * blk_mq_quiesce_queue() for that requirement.
1527  */
1528 void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx)
1529 {
1530         cancel_delayed_work(&hctx->run_work);
1531 
1532         set_bit(BLK_MQ_S_STOPPED, &hctx->state);
1533 }
1534 EXPORT_SYMBOL(blk_mq_stop_hw_queue);
1535 
1536 /*
1537  * This function is often used for pausing .queue_rq() by driver when
1538  * there isn't enough resource or some conditions aren't satisfied, and
1539  * BLK_STS_RESOURCE is usually returned.
1540  *
1541  * We do not guarantee that dispatch can be drained or blocked
1542  * after blk_mq_stop_hw_queues() returns. Please use
1543  * blk_mq_quiesce_queue() for that requirement.
1544  */
1545 void blk_mq_stop_hw_queues(struct request_queue *q)
1546 {
1547         struct blk_mq_hw_ctx *hctx;
1548         int i;
1549 
1550         queue_for_each_hw_ctx(q, hctx, i)
1551                 blk_mq_stop_hw_queue(hctx);
1552 }
1553 EXPORT_SYMBOL(blk_mq_stop_hw_queues);
1554 
1555 void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx)
1556 {
1557         clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
1558 
1559         blk_mq_run_hw_queue(hctx, false);
1560 }
1561 EXPORT_SYMBOL(blk_mq_start_hw_queue);
1562 
1563 void blk_mq_start_hw_queues(struct request_queue *q)
1564 {
1565         struct blk_mq_hw_ctx *hctx;
1566         int i;
1567 
1568         queue_for_each_hw_ctx(q, hctx, i)
1569                 blk_mq_start_hw_queue(hctx);
1570 }
1571 EXPORT_SYMBOL(blk_mq_start_hw_queues);
1572 
1573 void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
1574 {
1575         if (!blk_mq_hctx_stopped(hctx))
1576                 return;
1577 
1578         clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
1579         blk_mq_run_hw_queue(hctx, async);
1580 }
1581 EXPORT_SYMBOL_GPL(blk_mq_start_stopped_hw_queue);
1582 
1583 void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async)
1584 {
1585         struct blk_mq_hw_ctx *hctx;
1586         int i;
1587 
1588         queue_for_each_hw_ctx(q, hctx, i)
1589                 blk_mq_start_stopped_hw_queue(hctx, async);
1590 }
1591 EXPORT_SYMBOL(blk_mq_start_stopped_hw_queues);
1592 
1593 static void blk_mq_run_work_fn(struct work_struct *work)
1594 {
1595         struct blk_mq_hw_ctx *hctx;
1596 
1597         hctx = container_of(work, struct blk_mq_hw_ctx, run_work.work);
1598 
1599         /*
1600          * If we are stopped, don't run the queue.
1601          */
1602         if (test_bit(BLK_MQ_S_STOPPED, &hctx->state))
1603                 return;
1604 
1605         __blk_mq_run_hw_queue(hctx);
1606 }
1607 
1608 static inline void __blk_mq_insert_req_list(struct blk_mq_hw_ctx *hctx,
1609                                             struct request *rq,
1610                                             bool at_head)
1611 {
1612         struct blk_mq_ctx *ctx = rq->mq_ctx;
1613         enum hctx_type type = hctx->type;
1614 
1615         lockdep_assert_held(&ctx->lock);
1616 
1617         trace_block_rq_insert(hctx->queue, rq);
1618 
1619         if (at_head)
1620                 list_add(&rq->queuelist, &ctx->rq_lists[type]);
1621         else
1622                 list_add_tail(&rq->queuelist, &ctx->rq_lists[type]);
1623 }
1624 
1625 void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
1626                              bool at_head)
1627 {
1628         struct blk_mq_ctx *ctx = rq->mq_ctx;
1629 
1630         lockdep_assert_held(&ctx->lock);
1631 
1632         __blk_mq_insert_req_list(hctx, rq, at_head);
1633         blk_mq_hctx_mark_pending(hctx, ctx);
1634 }
1635 
1636 /*
1637  * Should only be used carefully, when the caller knows we want to
1638  * bypass a potential IO scheduler on the target device.
1639  */
1640 void blk_mq_request_bypass_insert(struct request *rq, bool run_queue)
1641 {
1642         struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
1643 
1644         spin_lock(&hctx->lock);
1645         list_add_tail(&rq->queuelist, &hctx->dispatch);
1646         spin_unlock(&hctx->lock);
1647 
1648         if (run_queue)
1649                 blk_mq_run_hw_queue(hctx, false);
1650 }
1651 
1652 void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
1653                             struct list_head *list)
1654 
1655 {
1656         struct request *rq;
1657         enum hctx_type type = hctx->type;
1658 
1659         /*
1660          * preemption doesn't flush plug list, so it's possible ctx->cpu is
1661          * offline now
1662          */
1663         list_for_each_entry(rq, list, queuelist) {
1664                 BUG_ON(rq->mq_ctx != ctx);
1665                 trace_block_rq_insert(hctx->queue, rq);
1666         }
1667 
1668         spin_lock(&ctx->lock);
1669         list_splice_tail_init(list, &ctx->rq_lists[type]);
1670         blk_mq_hctx_mark_pending(hctx, ctx);
1671         spin_unlock(&ctx->lock);
1672 }
1673 
1674 static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
1675 {
1676         struct request *rqa = container_of(a, struct request, queuelist);
1677         struct request *rqb = container_of(b, struct request, queuelist);
1678 
1679         if (rqa->mq_ctx < rqb->mq_ctx)
1680                 return -1;
1681         else if (rqa->mq_ctx > rqb->mq_ctx)
1682                 return 1;
1683         else if (rqa->mq_hctx < rqb->mq_hctx)
1684                 return -1;
1685         else if (rqa->mq_hctx > rqb->mq_hctx)
1686                 return 1;
1687 
1688         return blk_rq_pos(rqa) > blk_rq_pos(rqb);
1689 }
1690 
1691 void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
1692 {
1693         struct blk_mq_hw_ctx *this_hctx;
1694         struct blk_mq_ctx *this_ctx;
1695         struct request_queue *this_q;
1696         struct request *rq;
1697         LIST_HEAD(list);
1698         LIST_HEAD(rq_list);
1699         unsigned int depth;
1700 
1701         list_splice_init(&plug->mq_list, &list);
1702         plug->rq_count = 0;
1703 
1704         if (plug->rq_count > 2 && plug->multiple_queues)
1705                 list_sort(NULL, &list, plug_rq_cmp);
1706 
1707         this_q = NULL;
1708         this_hctx = NULL;
1709         this_ctx = NULL;
1710         depth = 0;
1711 
1712         while (!list_empty(&list)) {
1713                 rq = list_entry_rq(list.next);
1714                 list_del_init(&rq->queuelist);
1715                 BUG_ON(!rq->q);
1716                 if (rq->mq_hctx != this_hctx || rq->mq_ctx != this_ctx) {
1717                         if (this_hctx) {
1718                                 trace_block_unplug(this_q, depth, !from_schedule);
1719                                 blk_mq_sched_insert_requests(this_hctx, this_ctx,
1720                                                                 &rq_list,
1721                                                                 from_schedule);
1722                         }
1723 
1724                         this_q = rq->q;
1725                         this_ctx = rq->mq_ctx;
1726                         this_hctx = rq->mq_hctx;
1727                         depth = 0;
1728                 }
1729 
1730                 depth++;
1731                 list_add_tail(&rq->queuelist, &rq_list);
1732         }
1733 
1734         /*
1735          * If 'this_hctx' is set, we know we have entries to complete
1736          * on 'rq_list'. Do those.
1737          */
1738         if (this_hctx) {
1739                 trace_block_unplug(this_q, depth, !from_schedule);
1740                 blk_mq_sched_insert_requests(this_hctx, this_ctx, &rq_list,
1741                                                 from_schedule);
1742         }
1743 }
1744 
1745 static void blk_mq_bio_to_request(struct request *rq, struct bio *bio)
1746 {
1747         blk_init_request_from_bio(rq, bio);
1748 
1749         blk_account_io_start(rq, true);
1750 }
1751 
1752 static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
1753                                             struct request *rq,
1754                                             blk_qc_t *cookie, bool last)
1755 {
1756         struct request_queue *q = rq->q;
1757         struct blk_mq_queue_data bd = {
1758                 .rq = rq,
1759                 .last = last,
1760         };
1761         blk_qc_t new_cookie;
1762         blk_status_t ret;
1763 
1764         new_cookie = request_to_qc_t(hctx, rq);
1765 
1766         /*
1767          * For OK queue, we are done. For error, caller may kill it.
1768          * Any other error (busy), just add it to our list as we
1769          * previously would have done.
1770          */
1771         ret = q->mq_ops->queue_rq(hctx, &bd);
1772         switch (ret) {
1773         case BLK_STS_OK:
1774                 blk_mq_update_dispatch_busy(hctx, false);
1775                 *cookie = new_cookie;
1776                 break;
1777         case BLK_STS_RESOURCE:
1778         case BLK_STS_DEV_RESOURCE:
1779                 blk_mq_update_dispatch_busy(hctx, true);
1780                 __blk_mq_requeue_request(rq);
1781                 break;
1782         default:
1783                 blk_mq_update_dispatch_busy(hctx, false);
1784                 *cookie = BLK_QC_T_NONE;
1785                 break;
1786         }
1787 
1788         return ret;
1789 }
1790 
1791 blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
1792                                                 struct request *rq,
1793                                                 blk_qc_t *cookie,
1794                                                 bool bypass, bool last)
1795 {
1796         struct request_queue *q = rq->q;
1797         bool run_queue = true;
1798         blk_status_t ret = BLK_STS_RESOURCE;
1799         int srcu_idx;
1800         bool force = false;
1801 
1802         hctx_lock(hctx, &srcu_idx);
1803         /*
1804          * hctx_lock is needed before checking quiesced flag.
1805          *
1806          * When queue is stopped or quiesced, ignore 'bypass', insert
1807          * and return BLK_STS_OK to caller, and avoid driver to try to
1808          * dispatch again.
1809          */
1810         if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q))) {
1811                 run_queue = false;
1812                 bypass = false;
1813                 goto out_unlock;
1814         }
1815 
1816         if (unlikely(q->elevator && !bypass))
1817                 goto out_unlock;
1818 
1819         if (!blk_mq_get_dispatch_budget(hctx))
1820                 goto out_unlock;
1821 
1822         if (!blk_mq_get_driver_tag(rq)) {
1823                 blk_mq_put_dispatch_budget(hctx);
1824                 goto out_unlock;
1825         }
1826 
1827         /*
1828          * Always add a request that has been through
1829          *.queue_rq() to the hardware dispatch list.
1830          */
1831         force = true;
1832         ret = __blk_mq_issue_directly(hctx, rq, cookie, last);
1833 out_unlock:
1834         hctx_unlock(hctx, srcu_idx);
1835         switch (ret) {
1836         case BLK_STS_OK:
1837                 break;
1838         case BLK_STS_DEV_RESOURCE:
1839         case BLK_STS_RESOURCE:
1840                 if (force) {
1841                         blk_mq_request_bypass_insert(rq, run_queue);
1842                         /*
1843                          * We have to return BLK_STS_OK for the DM
1844                          * to avoid livelock. Otherwise, we return
1845                          * the real result to indicate whether the
1846                          * request is direct-issued successfully.
1847                          */
1848                         ret = bypass ? BLK_STS_OK : ret;
1849                 } else if (!bypass) {
1850                         blk_mq_sched_insert_request(rq, false,
1851                                                     run_queue, false);
1852                 }
1853                 break;
1854         default:
1855                 if (!bypass)
1856                         blk_mq_end_request(rq, ret);
1857                 break;
1858         }
1859 
1860         return ret;
1861 }
1862 
1863 void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
1864                 struct list_head *list)
1865 {
1866         blk_qc_t unused;
1867         blk_status_t ret = BLK_STS_OK;
1868 
1869         while (!list_empty(list)) {
1870                 struct request *rq = list_first_entry(list, struct request,
1871                                 queuelist);
1872 
1873                 list_del_init(&rq->queuelist);
1874                 if (ret == BLK_STS_OK)
1875                         ret = blk_mq_try_issue_directly(hctx, rq, &unused,
1876                                                         false,
1877                                                         list_empty(list));
1878                 else
1879                         blk_mq_sched_insert_request(rq, false, true, false);
1880         }
1881 
1882         /*
1883          * If we didn't flush the entire list, we could have told
1884          * the driver there was more coming, but that turned out to
1885          * be a lie.
1886          */
1887         if (ret != BLK_STS_OK && hctx->queue->mq_ops->commit_rqs)
1888                 hctx->queue->mq_ops->commit_rqs(hctx);
1889 }
1890 
1891 static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
1892 {
1893         list_add_tail(&rq->queuelist, &plug->mq_list);
1894         plug->rq_count++;
1895         if (!plug->multiple_queues && !list_is_singular(&plug->mq_list)) {
1896                 struct request *tmp;
1897 
1898                 tmp = list_first_entry(&plug->mq_list, struct request,
1899                                                 queuelist);
1900                 if (tmp->q != rq->q)
1901                         plug->multiple_queues = true;
1902         }
1903 }
1904 
1905 static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
1906 {
1907         const int is_sync = op_is_sync(bio->bi_opf);
1908         const int is_flush_fua = op_is_flush(bio->bi_opf);
1909         struct blk_mq_alloc_data data = { .flags = 0, .cmd_flags = bio->bi_opf };
1910         struct request *rq;
1911         struct blk_plug *plug;
1912         struct request *same_queue_rq = NULL;
1913         blk_qc_t cookie;
1914 
1915         blk_queue_bounce(q, &bio);
1916 
1917         blk_queue_split(q, &bio);
1918 
1919         if (!bio_integrity_prep(bio))
1920                 return BLK_QC_T_NONE;
1921 
1922         if (!is_flush_fua && !blk_queue_nomerges(q) &&
1923             blk_attempt_plug_merge(q, bio, &same_queue_rq))
1924                 return BLK_QC_T_NONE;
1925 
1926         if (blk_mq_sched_bio_merge(q, bio))
1927                 return BLK_QC_T_NONE;
1928 
1929         rq_qos_throttle(q, bio);
1930 
1931         rq = blk_mq_get_request(q, bio, &data);
1932         if (unlikely(!rq)) {
1933                 rq_qos_cleanup(q, bio);
1934                 if (bio->bi_opf & REQ_NOWAIT)
1935                         bio_wouldblock_error(bio);
1936                 return BLK_QC_T_NONE;
1937         }
1938 
1939         trace_block_getrq(q, bio, bio->bi_opf);
1940 
1941         rq_qos_track(q, rq, bio);
1942 
1943         cookie = request_to_qc_t(data.hctx, rq);
1944 
1945         plug = current->plug;
1946         if (unlikely(is_flush_fua)) {
1947                 blk_mq_put_ctx(data.ctx);
1948                 blk_mq_bio_to_request(rq, bio);
1949 
1950                 /* bypass scheduler for flush rq */
1951                 blk_insert_flush(rq);
1952                 blk_mq_run_hw_queue(data.hctx, true);
1953         } else if (plug && (q->nr_hw_queues == 1 || q->mq_ops->commit_rqs)) {
1954                 /*
1955                  * Use plugging if we have a ->commit_rqs() hook as well, as
1956                  * we know the driver uses bd->last in a smart fashion.
1957                  */
1958                 unsigned int request_count = plug->rq_count;
1959                 struct request *last = NULL;
1960 
1961                 blk_mq_put_ctx(data.ctx);
1962                 blk_mq_bio_to_request(rq, bio);
1963 
1964                 if (!request_count)
1965                         trace_block_plug(q);
1966                 else
1967                         last = list_entry_rq(plug->mq_list.prev);
1968 
1969                 if (request_count >= BLK_MAX_REQUEST_COUNT || (last &&
1970                     blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
1971                         blk_flush_plug_list(plug, false);
1972                         trace_block_plug(q);
1973                 }
1974 
1975                 blk_add_rq_to_plug(plug, rq);
1976         } else if (plug && !blk_queue_nomerges(q)) {
1977                 blk_mq_bio_to_request(rq, bio);
1978 
1979                 /*
1980                  * We do limited plugging. If the bio can be merged, do that.
1981                  * Otherwise the existing request in the plug list will be
1982                  * issued. So the plug list will have one request at most
1983                  * The plug list might get flushed before this. If that happens,
1984                  * the plug list is empty, and same_queue_rq is invalid.
1985                  */
1986                 if (list_empty(&plug->mq_list))
1987                         same_queue_rq = NULL;
1988                 if (same_queue_rq) {
1989                         list_del_init(&same_queue_rq->queuelist);
1990                         plug->rq_count--;
1991                 }
1992                 blk_add_rq_to_plug(plug, rq);
1993 
1994                 blk_mq_put_ctx(data.ctx);
1995 
1996                 if (same_queue_rq) {
1997                         data.hctx = same_queue_rq->mq_hctx;
1998                         blk_mq_try_issue_directly(data.hctx, same_queue_rq,
1999                                         &cookie, false, true);
2000                 }
2001         } else if ((q->nr_hw_queues > 1 && is_sync) || (!q->elevator &&
2002                         !data.hctx->dispatch_busy)) {
2003                 blk_mq_put_ctx(data.ctx);
2004                 blk_mq_bio_to_request(rq, bio);
2005                 blk_mq_try_issue_directly(data.hctx, rq, &cookie, false, true);
2006         } else {
2007                 blk_mq_put_ctx(data.ctx);
2008                 blk_mq_bio_to_request(rq, bio);
2009                 blk_mq_sched_insert_request(rq, false, true, true);
2010         }
2011 
2012         return cookie;
2013 }
2014 
2015 void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
2016                      unsigned int hctx_idx)
2017 {
2018         struct page *page;
2019 
2020         if (tags->rqs && set->ops->exit_request) {
2021                 int i;
2022 
2023                 for (i = 0; i < tags->nr_tags; i++) {
2024                         struct request *rq = tags->static_rqs[i];
2025 
2026                         if (!rq)
2027                                 continue;
2028                         set->ops->exit_request(set, rq, hctx_idx);
2029                         tags->static_rqs[i] = NULL;
2030                 }
2031         }
2032 
2033         while (!list_empty(&tags->page_list)) {
2034                 page = list_first_entry(&tags->page_list, struct page, lru);
2035                 list_del_init(&page->lru);
2036                 /*
2037                  * Remove kmemleak object previously allocated in
2038                  * blk_mq_init_rq_map().
2039                  */
2040                 kmemleak_free(page_address(page));
2041                 __free_pages(page, page->private);
2042         }
2043 }
2044 
2045 void blk_mq_free_rq_map(struct blk_mq_tags *tags)
2046 {
2047         kfree(tags->rqs);
2048         tags->rqs = NULL;
2049         kfree(tags->static_rqs);
2050         tags->static_rqs = NULL;
2051 
2052         blk_mq_free_tags(tags);
2053 }
2054 
2055 struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
2056                                         unsigned int hctx_idx,
2057                                         unsigned int nr_tags,
2058                                         unsigned int reserved_tags)
2059 {
2060         struct blk_mq_tags *tags;
2061         int node;
2062 
2063         node = blk_mq_hw_queue_to_node(&set->map[0], hctx_idx);
2064         if (node == NUMA_NO_NODE)
2065                 node = set->numa_node;
2066 
2067         tags = blk_mq_init_tags(nr_tags, reserved_tags, node,
2068                                 BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags));
2069         if (!tags)
2070                 return NULL;
2071 
2072         tags->rqs = kcalloc_node(nr_tags, sizeof(struct request *),
2073                                  GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
2074                                  node);
2075         if (!tags->rqs) {
2076                 blk_mq_free_tags(tags);
2077                 return NULL;
2078         }
2079 
2080         tags->static_rqs = kcalloc_node(nr_tags, sizeof(struct request *),
2081                                         GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
2082                                         node);
2083         if (!tags->static_rqs) {
2084                 kfree(tags->rqs);
2085                 blk_mq_free_tags(tags);
2086                 return NULL;
2087         }
2088 
2089         return tags;
2090 }
2091 
2092 static size_t order_to_size(unsigned int order)
2093 {
2094         return (size_t)PAGE_SIZE << order;
2095 }
2096 
2097 static int blk_mq_init_request(struct blk_mq_tag_set *set, struct request *rq,
2098                                unsigned int hctx_idx, int node)
2099 {
2100         int ret;
2101 
2102         if (set->ops->init_request) {
2103                 ret = set->ops->init_request(set, rq, hctx_idx, node);
2104                 if (ret)
2105                         return ret;
2106         }
2107 
2108         WRITE_ONCE(rq->state, MQ_RQ_IDLE);
2109         return 0;
2110 }
2111 
2112 int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
2113                      unsigned int hctx_idx, unsigned int depth)
2114 {
2115         unsigned int i, j, entries_per_page, max_order = 4;
2116         size_t rq_size, left;
2117         int node;
2118 
2119         node = blk_mq_hw_queue_to_node(&set->map[0], hctx_idx);
2120         if (node == NUMA_NO_NODE)
2121                 node = set->numa_node;
2122 
2123         INIT_LIST_HEAD(&tags->page_list);
2124 
2125         /*
2126          * rq_size is the size of the request plus driver payload, rounded
2127          * to the cacheline size
2128          */
2129         rq_size = round_up(sizeof(struct request) + set->cmd_size,
2130                                 cache_line_size());
2131         left = rq_size * depth;
2132 
2133         for (i = 0; i < depth; ) {
2134                 int this_order = max_order;
2135                 struct page *page;
2136                 int to_do;
2137                 void *p;
2138 
2139                 while (this_order && left < order_to_size(this_order - 1))
2140                         this_order--;
2141 
2142                 do {
2143                         page = alloc_pages_node(node,
2144                                 GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY | __GFP_ZERO,
2145                                 this_order);
2146                         if (page)
2147                                 break;
2148                         if (!this_order--)
2149                                 break;
2150                         if (order_to_size(this_order) < rq_size)
2151                                 break;
2152                 } while (1);
2153 
2154                 if (!page)
2155                         goto fail;
2156 
2157                 page->private = this_order;
2158                 list_add_tail(&page->lru, &tags->page_list);
2159 
2160                 p = page_address(page);
2161                 /*
2162                  * Allow kmemleak to scan these pages as they contain pointers
2163                  * to additional allocations like via ops->init_request().
2164                  */
2165                 kmemleak_alloc(p, order_to_size(this_order), 1, GFP_NOIO);
2166                 entries_per_page = order_to_size(this_order) / rq_size;
2167                 to_do = min(entries_per_page, depth - i);
2168                 left -= to_do * rq_size;
2169                 for (j = 0; j < to_do; j++) {
2170                         struct request *rq = p;
2171 
2172                         tags->static_rqs[i] = rq;
2173                         if (blk_mq_init_request(set, rq, hctx_idx, node)) {
2174                                 tags->static_rqs[i] = NULL;
2175                                 goto fail;
2176                         }
2177 
2178                         p += rq_size;
2179                         i++;
2180                 }
2181         }
2182         return 0;
2183 
2184 fail:
2185         blk_mq_free_rqs(set, tags, hctx_idx);
2186         return -ENOMEM;
2187 }
2188 
2189 /*
2190  * 'cpu' is going away. splice any existing rq_list entries from this
2191  * software queue to the hw queue dispatch list, and ensure that it
2192  * gets run.
2193  */
2194 static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node)
2195 {
2196         struct blk_mq_hw_ctx *hctx;
2197         struct blk_mq_ctx *ctx;
2198         LIST_HEAD(tmp);
2199         enum hctx_type type;
2200 
2201         hctx = hlist_entry_safe(node, struct blk_mq_hw_ctx, cpuhp_dead);
2202         ctx = __blk_mq_get_ctx(hctx->queue, cpu);
2203         type = hctx->type;
2204 
2205         spin_lock(&ctx->lock);
2206         if (!list_empty(&ctx->rq_lists[type])) {
2207                 list_splice_init(&ctx->rq_lists[type], &tmp);
2208                 blk_mq_hctx_clear_pending(hctx, ctx);
2209         }
2210         spin_unlock(&ctx->lock);
2211 
2212         if (list_empty(&tmp))
2213                 return 0;
2214 
2215         spin_lock(&hctx->lock);
2216         list_splice_tail_init(&tmp, &hctx->dispatch);
2217         spin_unlock(&hctx->lock);
2218 
2219         blk_mq_run_hw_queue(hctx, true);
2220         return 0;
2221 }
2222 
2223 static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx)
2224 {
2225         cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_DEAD,
2226                                             &hctx->cpuhp_dead);
2227 }
2228 
2229 /* hctx->ctxs will be freed in queue's release handler */
2230 static void blk_mq_exit_hctx(struct request_queue *q,
2231                 struct blk_mq_tag_set *set,
2232                 struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
2233 {
2234         if (blk_mq_hw_queue_mapped(hctx))
2235                 blk_mq_tag_idle(hctx);
2236 
2237         if (set->ops->exit_request)
2238                 set->ops->exit_request(set, hctx->fq->flush_rq, hctx_idx);
2239 
2240         if (set->ops->exit_hctx)
2241                 set->ops->exit_hctx(hctx, hctx_idx);
2242 
2243         if (hctx->flags & BLK_MQ_F_BLOCKING)
2244                 cleanup_srcu_struct(hctx->srcu);
2245 
2246         blk_mq_remove_cpuhp(hctx);
2247         blk_free_flush_queue(hctx->fq);
2248         sbitmap_free(&hctx->ctx_map);
2249 }
2250 
2251 static void blk_mq_exit_hw_queues(struct request_queue *q,
2252                 struct blk_mq_tag_set *set, int nr_queue)
2253 {
2254         struct blk_mq_hw_ctx *hctx;
2255         unsigned int i;
2256 
2257         queue_for_each_hw_ctx(q, hctx, i) {
2258                 if (i == nr_queue)
2259                         break;
2260                 blk_mq_debugfs_unregister_hctx(hctx);
2261                 blk_mq_exit_hctx(q, set, hctx, i);
2262         }
2263 }
2264 
2265 static int blk_mq_init_hctx(struct request_queue *q,
2266                 struct blk_mq_tag_set *set,
2267                 struct blk_mq_hw_ctx *hctx, unsigned hctx_idx)
2268 {
2269         int node;
2270 
2271         node = hctx->numa_node;
2272         if (node == NUMA_NO_NODE)
2273                 node = hctx->numa_node = set->numa_node;
2274 
2275         INIT_DELAYED_WORK(&hctx->run_work, blk_mq_run_work_fn);
2276         spin_lock_init(&hctx->lock);
2277         INIT_LIST_HEAD(&hctx->dispatch);
2278         hctx->queue = q;
2279         hctx->flags = set->flags & ~BLK_MQ_F_TAG_SHARED;
2280 
2281         cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD, &hctx->cpuhp_dead);
2282 
2283         hctx->tags = set->tags[hctx_idx];
2284 
2285         /*
2286          * Allocate space for all possible cpus to avoid allocation at
2287          * runtime
2288          */
2289         hctx->ctxs = kmalloc_array_node(nr_cpu_ids, sizeof(void *),
2290                         GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY, node);
2291         if (!hctx->ctxs)
2292                 goto unregister_cpu_notifier;
2293 
2294         if (sbitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8),
2295                                 GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY, node))
2296                 goto free_ctxs;
2297 
2298         hctx->nr_ctx = 0;
2299 
2300         spin_lock_init(&hctx->dispatch_wait_lock);
2301         init_waitqueue_func_entry(&hctx->dispatch_wait, blk_mq_dispatch_wake);
2302         INIT_LIST_HEAD(&hctx->dispatch_wait.entry);
2303 
2304         if (set->ops->init_hctx &&
2305             set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
2306                 goto free_bitmap;
2307 
2308         hctx->fq = blk_alloc_flush_queue(q, hctx->numa_node, set->cmd_size,
2309                         GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY);
2310         if (!hctx->fq)
2311                 goto exit_hctx;
2312 
2313         if (blk_mq_init_request(set, hctx->fq->flush_rq, hctx_idx, node))
2314                 goto free_fq;
2315 
2316         if (hctx->flags & BLK_MQ_F_BLOCKING)
2317                 init_srcu_struct(hctx->srcu);
2318 
2319         return 0;
2320 
2321  free_fq:
2322         kfree(hctx->fq);
2323  exit_hctx:
2324         if (set->ops->exit_hctx)
2325                 set->ops->exit_hctx(hctx, hctx_idx);
2326  free_bitmap:
2327         sbitmap_free(&hctx->ctx_map);
2328  free_ctxs:
2329         kfree(hctx->ctxs);
2330  unregister_cpu_notifier:
2331         blk_mq_remove_cpuhp(hctx);
2332         return -1;
2333 }
2334 
2335 static void blk_mq_init_cpu_queues(struct request_queue *q,
2336                                    unsigned int nr_hw_queues)
2337 {
2338         struct blk_mq_tag_set *set = q->tag_set;
2339         unsigned int i, j;
2340 
2341         for_each_possible_cpu(i) {
2342                 struct blk_mq_ctx *__ctx = per_cpu_ptr(q->queue_ctx, i);
2343                 struct blk_mq_hw_ctx *hctx;
2344                 int k;
2345 
2346                 __ctx->cpu = i;
2347                 spin_lock_init(&__ctx->lock);
2348                 for (k = HCTX_TYPE_DEFAULT; k < HCTX_MAX_TYPES; k++)
2349                         INIT_LIST_HEAD(&__ctx->rq_lists[k]);
2350 
2351                 __ctx->queue = q;
2352 
2353                 /*
2354                  * Set local node, IFF we have more than one hw queue. If
2355                  * not, we remain on the home node of the device
2356                  */
2357                 for (j = 0; j < set->nr_maps; j++) {
2358                         hctx = blk_mq_map_queue_type(q, j, i);
2359                         if (nr_hw_queues > 1 && hctx->numa_node == NUMA_NO_NODE)
2360                                 hctx->numa_node = local_memory_node(cpu_to_node(i));
2361                 }
2362         }
2363 }
2364 
2365 static bool __blk_mq_alloc_rq_map(struct blk_mq_tag_set *set, int hctx_idx)
2366 {
2367         int ret = 0;
2368 
2369         set->tags[hctx_idx] = blk_mq_alloc_rq_map(set, hctx_idx,
2370                                         set->queue_depth, set->reserved_tags);
2371         if (!set->tags[hctx_idx])
2372                 return false;
2373 
2374         ret = blk_mq_alloc_rqs(set, set->tags[hctx_idx], hctx_idx,
2375                                 set->queue_depth);
2376         if (!ret)
2377                 return true;
2378 
2379         blk_mq_free_rq_map(set->tags[hctx_idx]);
2380         set->tags[hctx_idx] = NULL;
2381         return false;
2382 }
2383 
2384 static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set,
2385                                          unsigned int hctx_idx)
2386 {
2387         if (set->tags && set->tags[hctx_idx]) {
2388                 blk_mq_free_rqs(set, set->tags[hctx_idx], hctx_idx);
2389                 blk_mq_free_rq_map(set->tags[hctx_idx]);
2390                 set->tags[hctx_idx] = NULL;
2391         }
2392 }
2393 
2394 static void blk_mq_map_swqueue(struct request_queue *q)
2395 {
2396         unsigned int i, j, hctx_idx;
2397         struct blk_mq_hw_ctx *hctx;
2398         struct blk_mq_ctx *ctx;
2399         struct blk_mq_tag_set *set = q->tag_set;
2400 
2401         /*
2402          * Avoid others reading imcomplete hctx->cpumask through sysfs
2403          */
2404         mutex_lock(&q->sysfs_lock);
2405 
2406         queue_for_each_hw_ctx(q, hctx, i) {
2407                 cpumask_clear(hctx->cpumask);
2408                 hctx->nr_ctx = 0;
2409                 hctx->dispatch_from = NULL;
2410         }
2411 
2412         /*
2413          * Map software to hardware queues.
2414          *
2415          * If the cpu isn't present, the cpu is mapped to first hctx.
2416          */
2417         for_each_possible_cpu(i) {
2418                 hctx_idx = set->map[0].mq_map[i];
2419                 /* unmapped hw queue can be remapped after CPU topo changed */
2420                 if (!set->tags[hctx_idx] &&
2421                     !__blk_mq_alloc_rq_map(set, hctx_idx)) {
2422                         /*
2423                          * If tags initialization fail for some hctx,
2424                          * that hctx won't be brought online.  In this
2425                          * case, remap the current ctx to hctx[0] which
2426                          * is guaranteed to always have tags allocated
2427                          */
2428                         set->map[0].mq_map[i] = 0;
2429                 }
2430 
2431                 ctx = per_cpu_ptr(q->queue_ctx, i);
2432                 for (j = 0; j < set->nr_maps; j++) {
2433                         if (!set->map[j].nr_queues)
2434                                 continue;
2435 
2436                         hctx = blk_mq_map_queue_type(q, j, i);
2437 
2438                         /*
2439                          * If the CPU is already set in the mask, then we've
2440                          * mapped this one already. This can happen if
2441                          * devices share queues across queue maps.
2442                          */
2443                         if (cpumask_test_cpu(i, hctx->cpumask))
2444                                 continue;
2445 
2446                         cpumask_set_cpu(i, hctx->cpumask);
2447                         hctx->type = j;
2448                         ctx->index_hw[hctx->type] = hctx->nr_ctx;
2449                         hctx->ctxs[hctx->nr_ctx++] = ctx;
2450 
2451                         /*
2452                          * If the nr_ctx type overflows, we have exceeded the
2453                          * amount of sw queues we can support.
2454                          */
2455                         BUG_ON(!hctx->nr_ctx);
2456                 }
2457         }
2458 
2459         mutex_unlock(&q->sysfs_lock);
2460 
2461         queue_for_each_hw_ctx(q, hctx, i) {
2462                 /*
2463                  * If no software queues are mapped to this hardware queue,
2464                  * disable it and free the request entries.
2465                  */
2466                 if (!hctx->nr_ctx) {
2467                         /* Never unmap queue 0.  We need it as a
2468                          * fallback in case of a new remap fails
2469                          * allocation
2470                          */
2471                         if (i && set->tags[i])
2472                                 blk_mq_free_map_and_requests(set, i);
2473 
2474                         hctx->tags = NULL;
2475                         continue;
2476                 }
2477 
2478                 hctx->tags = set->tags[i];
2479                 WARN_ON(!hctx->tags);
2480 
2481                 /*
2482                  * Set the map size to the number of mapped software queues.
2483                  * This is more accurate and more efficient than looping
2484                  * over all possibly mapped software queues.
2485                  */
2486                 sbitmap_resize(&hctx->ctx_map, hctx->nr_ctx);
2487 
2488                 /*
2489                  * Initialize batch roundrobin counts
2490                  */
2491                 hctx->next_cpu = blk_mq_first_mapped_cpu(hctx);
2492                 hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
2493         }
2494 }
2495 
2496 /*
2497  * Caller needs to ensure that we're either frozen/quiesced, or that
2498  * the queue isn't live yet.
2499  */
2500 static void queue_set_hctx_shared(struct request_queue *q, bool shared)
2501 {
2502         struct blk_mq_hw_ctx *hctx;
2503         int i;
2504 
2505         queue_for_each_hw_ctx(q, hctx, i) {
2506                 if (shared)
2507                         hctx->flags |= BLK_MQ_F_TAG_SHARED;
2508                 else
2509                         hctx->flags &= ~BLK_MQ_F_TAG_SHARED;
2510         }
2511 }
2512 
2513 static void blk_mq_update_tag_set_depth(struct blk_mq_tag_set *set,
2514                                         bool shared)
2515 {
2516         struct request_queue *q;
2517 
2518         lockdep_assert_held(&set->tag_list_lock);
2519 
2520         list_for_each_entry(q, &set->tag_list, tag_set_list) {
2521                 blk_mq_freeze_queue(q);
2522                 queue_set_hctx_shared(q, shared);
2523                 blk_mq_unfreeze_queue(q);
2524         }
2525 }
2526 
2527 static void blk_mq_del_queue_tag_set(struct request_queue *q)
2528 {
2529         struct blk_mq_tag_set *set = q->tag_set;
2530 
2531         mutex_lock(&set->tag_list_lock);
2532         list_del_rcu(&q->tag_set_list);
2533         if (list_is_singular(&set->tag_list)) {
2534                 /* just transitioned to unshared */
2535                 set->flags &= ~BLK_MQ_F_TAG_SHARED;
2536                 /* update existing queue */
2537                 blk_mq_update_tag_set_depth(set, false);
2538         }
2539         mutex_unlock(&set->tag_list_lock);
2540         INIT_LIST_HEAD(&q->tag_set_list);
2541 }
2542 
2543 static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
2544                                      struct request_queue *q)
2545 {
2546         mutex_lock(&set->tag_list_lock);
2547 
2548         /*
2549          * Check to see if we're transitioning to shared (from 1 to 2 queues).
2550          */
2551         if (!list_empty(&set->tag_list) &&
2552             !(set->flags & BLK_MQ_F_TAG_SHARED)) {
2553                 set->flags |= BLK_MQ_F_TAG_SHARED;
2554                 /* update existing queue */
2555                 blk_mq_update_tag_set_depth(set, true);
2556         }
2557         if (set->flags & BLK_MQ_F_TAG_SHARED)
2558                 queue_set_hctx_shared(q, true);
2559         list_add_tail_rcu(&q->tag_set_list, &set->tag_list);
2560 
2561         mutex_unlock(&set->tag_list_lock);
2562 }
2563 
2564 /* All allocations will be freed in release handler of q->mq_kobj */
2565 static int blk_mq_alloc_ctxs(struct request_queue *q)
2566 {
2567         struct blk_mq_ctxs *ctxs;
2568         int cpu;
2569 
2570         ctxs = kzalloc(sizeof(*ctxs), GFP_KERNEL);
2571         if (!ctxs)
2572                 return -ENOMEM;
2573 
2574         ctxs->queue_ctx = alloc_percpu(struct blk_mq_ctx);
2575         if (!ctxs->queue_ctx)
2576                 goto fail;
2577 
2578         for_each_possible_cpu(cpu) {
2579                 struct blk_mq_ctx *ctx = per_cpu_ptr(ctxs->queue_ctx, cpu);
2580                 ctx->ctxs = ctxs;
2581         }
2582 
2583         q->mq_kobj = &ctxs->kobj;
2584         q->queue_ctx = ctxs->queue_ctx;
2585 
2586         return 0;
2587  fail:
2588         kfree(ctxs);
2589         return -ENOMEM;
2590 }
2591 
2592 /*
2593  * It is the actual release handler for mq, but we do it from
2594  * request queue's release handler for avoiding use-after-free
2595  * and headache because q->mq_kobj shouldn't have been introduced,
2596  * but we can't group ctx/kctx kobj without it.
2597  */
2598 void blk_mq_release(struct request_queue *q)
2599 {
2600         struct blk_mq_hw_ctx *hctx;
2601         unsigned int i;
2602 
2603         /* hctx kobj stays in hctx */
2604         queue_for_each_hw_ctx(q, hctx, i) {
2605                 if (!hctx)
2606                         continue;
2607                 kobject_put(&hctx->kobj);
2608         }
2609 
2610         kfree(q->queue_hw_ctx);
2611 
2612         /*
2613          * release .mq_kobj and sw queue's kobject now because
2614          * both share lifetime with request queue.
2615          */
2616         blk_mq_sysfs_deinit(q);
2617 }
2618 
2619 struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
2620 {
2621         struct request_queue *uninit_q, *q;
2622 
2623         uninit_q = blk_alloc_queue_node(GFP_KERNEL, set->numa_node);
2624         if (!uninit_q)
2625                 return ERR_PTR(-ENOMEM);
2626 
2627         q = blk_mq_init_allocated_queue(set, uninit_q);
2628         if (IS_ERR(q))
2629                 blk_cleanup_queue(uninit_q);
2630 
2631         return q;
2632 }
2633 EXPORT_SYMBOL(blk_mq_init_queue);
2634 
2635 /*
2636  * Helper for setting up a queue with mq ops, given queue depth, and
2637  * the passed in mq ops flags.
2638  */
2639 struct request_queue *blk_mq_init_sq_queue(struct blk_mq_tag_set *set,
2640                                            const struct blk_mq_ops *ops,
2641                                            unsigned int queue_depth,
2642                                            unsigned int set_flags)
2643 {
2644         struct request_queue *q;
2645         int ret;
2646 
2647         memset(set, 0, sizeof(*set));
2648         set->ops = ops;
2649         set->nr_hw_queues = 1;
2650         set->nr_maps = 1;
2651         set->queue_depth = queue_depth;
2652         set->numa_node = NUMA_NO_NODE;
2653         set->flags = set_flags;
2654 
2655         ret = blk_mq_alloc_tag_set(set);
2656         if (ret)
2657                 return ERR_PTR(ret);
2658 
2659         q = blk_mq_init_queue(set);
2660         if (IS_ERR(q)) {
2661                 blk_mq_free_tag_set(set);
2662                 return q;
2663         }
2664 
2665         return q;
2666 }
2667 EXPORT_SYMBOL(blk_mq_init_sq_queue);
2668 
2669 static int blk_mq_hw_ctx_size(struct blk_mq_tag_set *tag_set)
2670 {
2671         int hw_ctx_size = sizeof(struct blk_mq_hw_ctx);
2672 
2673         BUILD_BUG_ON(ALIGN(offsetof(struct blk_mq_hw_ctx, srcu),
2674                            __alignof__(struct blk_mq_hw_ctx)) !=
2675                      sizeof(struct blk_mq_hw_ctx));
2676 
2677         if (tag_set->flags & BLK_MQ_F_BLOCKING)
2678                 hw_ctx_size += sizeof(struct srcu_struct);
2679 
2680         return hw_ctx_size;
2681 }
2682 
2683 static struct blk_mq_hw_ctx *blk_mq_alloc_and_init_hctx(
2684                 struct blk_mq_tag_set *set, struct request_queue *q,
2685                 int hctx_idx, int node)
2686 {
2687         struct blk_mq_hw_ctx *hctx;
2688 
2689         hctx = kzalloc_node(blk_mq_hw_ctx_size(set),
2690                         GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
2691                         node);
2692         if (!hctx)
2693                 return NULL;
2694 
2695         if (!zalloc_cpumask_var_node(&hctx->cpumask,
2696                                 GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
2697                                 node)) {
2698                 kfree(hctx);
2699                 return NULL;
2700         }
2701 
2702         atomic_set(&hctx->nr_active, 0);
2703         hctx->numa_node = node;
2704         hctx->queue_num = hctx_idx;
2705 
2706         if (blk_mq_init_hctx(q, set, hctx, hctx_idx)) {
2707                 free_cpumask_var(hctx->cpumask);
2708                 kfree(hctx);
2709                 return NULL;
2710         }
2711         blk_mq_hctx_kobj_init(hctx);
2712 
2713         return hctx;
2714 }
2715 
2716 static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
2717                                                 struct request_queue *q)
2718 {
2719         int i, j, end;
2720         struct blk_mq_hw_ctx **hctxs = q->queue_hw_ctx;
2721 
2722         /* protect against switching io scheduler  */
2723         mutex_lock(&q->sysfs_lock);
2724         for (i = 0; i < set->nr_hw_queues; i++) {
2725                 int node;
2726                 struct blk_mq_hw_ctx *hctx;
2727 
2728                 node = blk_mq_hw_queue_to_node(&set->map[0], i);
2729                 /*
2730                  * If the hw queue has been mapped to another numa node,
2731                  * we need to realloc the hctx. If allocation fails, fallback
2732                  * to use the previous one.
2733                  */
2734                 if (hctxs[i] && (hctxs[i]->numa_node == node))
2735                         continue;
2736 
2737                 hctx = blk_mq_alloc_and_init_hctx(set, q, i, node);
2738                 if (hctx) {
2739                         if (hctxs[i]) {
2740                                 blk_mq_exit_hctx(q, set, hctxs[i], i);
2741                                 kobject_put(&hctxs[i]->kobj);
2742                         }
2743                         hctxs[i] = hctx;
2744                 } else {
2745                         if (hctxs[i])
2746                                 pr_warn("Allocate new hctx on node %d fails,\
2747                                                 fallback to previous one on node %d\n",
2748                                                 node, hctxs[i]->numa_node);
2749                         else
2750                                 break;
2751                 }
2752         }
2753         /*
2754          * Increasing nr_hw_queues fails. Free the newly allocated
2755          * hctxs and keep the previous q->nr_hw_queues.
2756          */
2757         if (i != set->nr_hw_queues) {
2758                 j = q->nr_hw_queues;
2759                 end = i;
2760         } else {
2761                 j = i;
2762                 end = q->nr_hw_queues;
2763                 q->nr_hw_queues = set->nr_hw_queues;
2764         }
2765 
2766         for (; j < end; j++) {
2767                 struct blk_mq_hw_ctx *hctx = hctxs[j];
2768 
2769                 if (hctx) {
2770                         if (hctx->tags)
2771                                 blk_mq_free_map_and_requests(set, j);
2772                         blk_mq_exit_hctx(q, set, hctx, j);
2773                         kobject_put(&hctx->kobj);
2774                         hctxs[j] = NULL;
2775 
2776                 }
2777         }
2778         mutex_unlock(&q->sysfs_lock);
2779 }
2780 
2781 /*
2782  * Maximum number of hardware queues we support. For single sets, we'll never
2783  * have more than the CPUs (software queues). For multiple sets, the tag_set
2784  * user may have set ->nr_hw_queues larger.
2785  */
2786 static unsigned int nr_hw_queues(struct blk_mq_tag_set *set)
2787 {
2788         if (set->nr_maps == 1)
2789                 return nr_cpu_ids;
2790 
2791         return max(set->nr_hw_queues, nr_cpu_ids);
2792 }
2793 
2794 struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
2795                                                   struct request_queue *q)
2796 {
2797         /* mark the queue as mq asap */
2798         q->mq_ops = set->ops;
2799 
2800         q->poll_cb = blk_stat_alloc_callback(blk_mq_poll_stats_fn,
2801                                              blk_mq_poll_stats_bkt,
2802                                              BLK_MQ_POLL_STATS_BKTS, q);
2803         if (!q->poll_cb)
2804                 goto err_exit;
2805 
2806         if (blk_mq_alloc_ctxs(q))
2807                 goto err_exit;
2808 
2809         /* init q->mq_kobj and sw queues' kobjects */
2810         blk_mq_sysfs_init(q);
2811 
2812         q->nr_queues = nr_hw_queues(set);
2813         q->queue_hw_ctx = kcalloc_node(q->nr_queues, sizeof(*(q->queue_hw_ctx)),
2814                                                 GFP_KERNEL, set->numa_node);
2815         if (!q->queue_hw_ctx)
2816                 goto err_sys_init;
2817 
2818         blk_mq_realloc_hw_ctxs(set, q);
2819         if (!q->nr_hw_queues)
2820                 goto err_hctxs;
2821 
2822         INIT_WORK(&q->timeout_work, blk_mq_timeout_work);
2823         blk_queue_rq_timeout(q, set->timeout ? set->timeout : 30 * HZ);
2824 
2825         q->tag_set = set;
2826 
2827         q->queue_flags |= QUEUE_FLAG_MQ_DEFAULT;
2828         if (set->nr_maps > HCTX_TYPE_POLL &&
2829             set->map[HCTX_TYPE_POLL].nr_queues)
2830                 blk_queue_flag_set(QUEUE_FLAG_POLL, q);
2831 
2832         if (!(set->flags & BLK_MQ_F_SG_MERGE))
2833                 blk_queue_flag_set(QUEUE_FLAG_NO_SG_MERGE, q);
2834 
2835         q->sg_reserved_size = INT_MAX;
2836 
2837         INIT_DELAYED_WORK(&q->requeue_work, blk_mq_requeue_work);
2838         INIT_LIST_HEAD(&q->requeue_list);
2839         spin_lock_init(&q->requeue_lock);
2840 
2841         blk_queue_make_request(q, blk_mq_make_request);
2842 
2843         /*
2844          * Do this after blk_queue_make_request() overrides it...
2845          */
2846         q->nr_requests = set->queue_depth;
2847 
2848         /*
2849          * Default to classic polling
2850          */
2851         q->poll_nsec = -1;
2852 
2853         blk_mq_init_cpu_queues(q, set->nr_hw_queues);
2854         blk_mq_add_queue_tag_set(set, q);
2855         blk_mq_map_swqueue(q);
2856 
2857         if (!(set->flags & BLK_MQ_F_NO_SCHED)) {
2858                 int ret;
2859 
2860                 ret = elevator_init_mq(q);
2861                 if (ret)
2862                         return ERR_PTR(ret);
2863         }
2864 
2865         return q;
2866 
2867 err_hctxs:
2868         kfree(q->queue_hw_ctx);
2869 err_sys_init:
2870         blk_mq_sysfs_deinit(q);
2871 err_exit:
2872         q->mq_ops = NULL;
2873         return ERR_PTR(-ENOMEM);
2874 }
2875 EXPORT_SYMBOL(blk_mq_init_allocated_queue);
2876 
2877 void blk_mq_free_queue(struct request_queue *q)
2878 {
2879         struct blk_mq_tag_set   *set = q->tag_set;
2880 
2881         blk_mq_del_queue_tag_set(q);
2882         blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);
2883 }
2884 
2885 static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
2886 {
2887         int i;
2888 
2889         for (i = 0; i < set->nr_hw_queues; i++)
2890                 if (!__blk_mq_alloc_rq_map(set, i))
2891                         goto out_unwind;
2892 
2893         return 0;
2894 
2895 out_unwind:
2896         while (--i >= 0)
2897                 blk_mq_free_rq_map(set->tags[i]);
2898 
2899         return -ENOMEM;
2900 }
2901 
2902 /*
2903  * Allocate the request maps associated with this tag_set. Note that this
2904  * may reduce the depth asked for, if memory is tight. set->queue_depth
2905  * will be updated to reflect the allocated depth.
2906  */
2907 static int blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
2908 {
2909         unsigned int depth;
2910         int err;
2911 
2912         depth = set->queue_depth;
2913         do {
2914                 err = __blk_mq_alloc_rq_maps(set);
2915                 if (!err)
2916                         break;
2917 
2918                 set->queue_depth >>= 1;
2919                 if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN) {
2920                         err = -ENOMEM;
2921                         break;
2922                 }
2923         } while (set->queue_depth);
2924 
2925         if (!set->queue_depth || err) {
2926                 pr_err("blk-mq: failed to allocate request map\n");
2927                 return -ENOMEM;
2928         }
2929 
2930         if (depth != set->queue_depth)
2931                 pr_info("blk-mq: reduced tag depth (%u -> %u)\n",
2932                                                 depth, set->queue_depth);
2933 
2934         return 0;
2935 }
2936 
2937 static int blk_mq_update_queue_map(struct blk_mq_tag_set *set)
2938 {
2939         if (set->ops->map_queues && !is_kdump_kernel()) {
2940                 int i;
2941 
2942                 /*
2943                  * transport .map_queues is usually done in the following
2944                  * way:
2945                  *
2946                  * for (queue = 0; queue < set->nr_hw_queues; queue++) {
2947                  *      mask = get_cpu_mask(queue)
2948                  *      for_each_cpu(cpu, mask)
2949                  *              set->map[x].mq_map[cpu] = queue;
2950                  * }
2951                  *
2952                  * When we need to remap, the table has to be cleared for
2953                  * killing stale mapping since one CPU may not be mapped
2954                  * to any hw queue.
2955                  */
2956                 for (i = 0; i < set->nr_maps; i++)
2957                         blk_mq_clear_mq_map(&set->map[i]);
2958 
2959                 return set->ops->map_queues(set);
2960         } else {
2961                 BUG_ON(set->nr_maps > 1);
2962                 return blk_mq_map_queues(&set->map[0]);
2963         }
2964 }
2965 
2966 /*
2967  * Alloc a tag set to be associated with one or more request queues.
2968  * May fail with EINVAL for various error conditions. May adjust the
2969  * requested depth down, if it's too large. In that case, the set
2970  * value will be stored in set->queue_depth.
2971  */
2972 int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
2973 {
2974         int i, ret;
2975 
2976         BUILD_BUG_ON(BLK_MQ_MAX_DEPTH > 1 << BLK_MQ_UNIQUE_TAG_BITS);
2977 
2978         if (!set->nr_hw_queues)
2979                 return -EINVAL;
2980         if (!set->queue_depth)
2981                 return -EINVAL;
2982         if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN)
2983                 return -EINVAL;
2984 
2985         if (!set->ops->queue_rq)
2986                 return -EINVAL;
2987 
2988         if (!set->ops->get_budget ^ !set->ops->put_budget)
2989                 return -EINVAL;
2990 
2991         if (set->queue_depth > BLK_MQ_MAX_DEPTH) {
2992                 pr_info("blk-mq: reduced tag depth to %u\n",
2993                         BLK_MQ_MAX_DEPTH);
2994                 set->queue_depth = BLK_MQ_MAX_DEPTH;
2995         }
2996 
2997         if (!set->nr_maps)
2998                 set->nr_maps = 1;
2999         else if (set->nr_maps > HCTX_MAX_TYPES)
3000                 return -EINVAL;
3001 
3002         /*
3003          * If a crashdump is active, then we are potentially in a very
3004          * memory constrained environment. Limit us to 1 queue and
3005          * 64 tags to prevent using too much memory.
3006          */
3007         if (is_kdump_kernel()) {
3008                 set->nr_hw_queues = 1;
3009                 set->nr_maps = 1;
3010                 set->queue_depth = min(64U, set->queue_depth);
3011         }
3012         /*
3013          * There is no use for more h/w queues than cpus if we just have
3014          * a single map
3015          */
3016         if (set->nr_maps == 1 && set->nr_hw_queues > nr_cpu_ids)
3017                 set->nr_hw_queues = nr_cpu_ids;
3018 
3019         set->tags = kcalloc_node(nr_hw_queues(set), sizeof(struct blk_mq_tags *),
3020                                  GFP_KERNEL, set->numa_node);
3021         if (!set->tags)
3022                 return -ENOMEM;
3023 
3024         ret = -ENOMEM;
3025         for (i = 0; i < set->nr_maps; i++) {
3026                 set->map[i].mq_map = kcalloc_node(nr_cpu_ids,
3027                                                   sizeof(set->map[i].mq_map[0]),
3028                                                   GFP_KERNEL, set->numa_node);
3029                 if (!set->map[i].mq_map)
3030                         goto out_free_mq_map;
3031                 set->map[i].nr_queues = is_kdump_kernel() ? 1 : set->nr_hw_queues;
3032         }
3033 
3034         ret = blk_mq_update_queue_map(set);
3035         if (ret)
3036                 goto out_free_mq_map;
3037 
3038         ret = blk_mq_alloc_rq_maps(set);
3039         if (ret)
3040                 goto out_free_mq_map;
3041 
3042         mutex_init(&set->tag_list_lock);
3043         INIT_LIST_HEAD(&set->tag_list);
3044 
3045         return 0;
3046 
3047 out_free_mq_map:
3048         for (i = 0; i < set->nr_maps; i++) {
3049                 kfree(set->map[i].mq_map);
3050                 set->map[i].mq_map = NULL;
3051         }
3052         kfree(set->tags);
3053         set->tags = NULL;
3054         return ret;
3055 }
3056 EXPORT_SYMBOL(blk_mq_alloc_tag_set);
3057 
3058 void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
3059 {
3060         int i, j;
3061 
3062         for (i = 0; i < nr_hw_queues(set); i++)
3063                 blk_mq_free_map_and_requests(set, i);
3064 
3065         for (j = 0; j < set->nr_maps; j++) {
3066                 kfree(set->map[j].mq_map);
3067                 set->map[j].mq_map = NULL;
3068         }
3069 
3070         kfree(set->tags);
3071         set->tags = NULL;
3072 }
3073 EXPORT_SYMBOL(blk_mq_free_tag_set);
3074 
3075 int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
3076 {
3077         struct blk_mq_tag_set *set = q->tag_set;
3078         struct blk_mq_hw_ctx *hctx;
3079         int i, ret;
3080 
3081         if (!set)
3082                 return -EINVAL;
3083 
3084         blk_mq_freeze_queue(q);
3085         blk_mq_quiesce_queue(q);
3086 
3087         ret = 0;
3088         queue_for_each_hw_ctx(q, hctx, i) {
3089                 if (!hctx->tags)
3090                         continue;
3091                 /*
3092                  * If we're using an MQ scheduler, just update the scheduler
3093                  * queue depth. This is similar to what the old code would do.
3094                  */
3095                 if (!hctx->sched_tags) {
3096                         ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
3097                                                         false);
3098                 } else {
3099                         ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
3100                                                         nr, true);
3101                 }
3102                 if (ret)
3103                         break;
3104         }
3105 
3106         if (!ret)
3107                 q->nr_requests = nr;
3108 
3109         blk_mq_unquiesce_queue(q);
3110         blk_mq_unfreeze_queue(q);
3111 
3112         return ret;
3113 }
3114 
3115 /*
3116  * request_queue and elevator_type pair.
3117  * It is just used by __blk_mq_update_nr_hw_queues to cache
3118  * the elevator_type associated with a request_queue.
3119  */
3120 struct blk_mq_qe_pair {
3121         struct list_head node;
3122         struct request_queue *q;
3123         struct elevator_type *type;
3124 };
3125 
3126 /*
3127  * Cache the elevator_type in qe pair list and switch the
3128  * io scheduler to 'none'
3129  */
3130 static bool blk_mq_elv_switch_none(struct list_head *head,
3131                 struct request_queue *q)
3132 {
3133         struct blk_mq_qe_pair *qe;
3134 
3135         if (!q->elevator)
3136                 return true;
3137 
3138         qe = kmalloc(sizeof(*qe), GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY);
3139         if (!qe)
3140                 return false;
3141 
3142         INIT_LIST_HEAD(&qe->node);
3143         qe->q = q;
3144         qe->type = q->elevator->type;
3145         list_add(&qe->node, head);
3146 
3147         mutex_lock(&q->sysfs_lock);
3148         /*
3149          * After elevator_switch_mq, the previous elevator_queue will be
3150          * released by elevator_release. The reference of the io scheduler
3151          * module get by elevator_get will also be put. So we need to get
3152          * a reference of the io scheduler module here to prevent it to be
3153          * removed.
3154          */
3155         __module_get(qe->type->elevator_owner);
3156         elevator_switch_mq(q, NULL);
3157         mutex_unlock(&q->sysfs_lock);
3158 
3159         return true;
3160 }
3161 
3162 static void blk_mq_elv_switch_back(struct list_head *head,
3163                 struct request_queue *q)
3164 {
3165         struct blk_mq_qe_pair *qe;
3166         struct elevator_type *t = NULL;
3167 
3168         list_for_each_entry(qe, head, node)
3169                 if (qe->q == q) {
3170                         t = qe->type;
3171                         break;
3172                 }
3173 
3174         if (!t)
3175                 return;
3176 
3177         list_del(&qe->node);
3178         kfree(qe);
3179 
3180         mutex_lock(&q->sysfs_lock);
3181         elevator_switch_mq(q, t);
3182         mutex_unlock(&q->sysfs_lock);
3183 }
3184 
3185 static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
3186                                                         int nr_hw_queues)
3187 {
3188         struct request_queue *q;
3189         LIST_HEAD(head);
3190         int prev_nr_hw_queues;
3191 
3192         lockdep_assert_held(&set->tag_list_lock);
3193 
3194         if (set->nr_maps == 1 && nr_hw_queues > nr_cpu_ids)
3195                 nr_hw_queues = nr_cpu_ids;
3196         if (nr_hw_queues < 1 || nr_hw_queues == set->nr_hw_queues)
3197                 return;
3198 
3199         list_for_each_entry(q, &set->tag_list, tag_set_list)
3200                 blk_mq_freeze_queue(q);
3201         /*
3202          * Sync with blk_mq_queue_tag_busy_iter.
3203          */
3204         synchronize_rcu();
3205         /*
3206          * Switch IO scheduler to 'none', cleaning up the data associated
3207          * with the previous scheduler. We will switch back once we are done
3208          * updating the new sw to hw queue mappings.
3209          */
3210         list_for_each_entry(q, &set->tag_list, tag_set_list)
3211                 if (!blk_mq_elv_switch_none(&head, q))
3212                         goto switch_back;
3213 
3214         list_for_each_entry(q, &set->tag_list, tag_set_list) {
3215                 blk_mq_debugfs_unregister_hctxs(q);
3216                 blk_mq_sysfs_unregister(q);
3217         }
3218 
3219         prev_nr_hw_queues = set->nr_hw_queues;
3220         set->nr_hw_queues = nr_hw_queues;
3221         blk_mq_update_queue_map(set);
3222 fallback:
3223         list_for_each_entry(q, &set->tag_list, tag_set_list) {
3224                 blk_mq_realloc_hw_ctxs(set, q);
3225                 if (q->nr_hw_queues != set->nr_hw_queues) {
3226                         pr_warn("Increasing nr_hw_queues to %d fails, fallback to %d\n",
3227                                         nr_hw_queues, prev_nr_hw_queues);
3228                         set->nr_hw_queues = prev_nr_hw_queues;
3229                         blk_mq_map_queues(&set->map[0]);
3230                         goto fallback;
3231                 }
3232                 blk_mq_map_swqueue(q);
3233         }
3234 
3235         list_for_each_entry(q, &set->tag_list, tag_set_list) {
3236                 blk_mq_sysfs_register(q);
3237                 blk_mq_debugfs_register_hctxs(q);
3238         }
3239 
3240 switch_back:
3241         list_for_each_entry(q, &set->tag_list, tag_set_list)
3242                 blk_mq_elv_switch_back(&head, q);
3243 
3244         list_for_each_entry(q, &set->tag_list, tag_set_list)
3245                 blk_mq_unfreeze_queue(q);
3246 }
3247 
3248 void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
3249 {
3250         mutex_lock(&set->tag_list_lock);
3251         __blk_mq_update_nr_hw_queues(set, nr_hw_queues);
3252         mutex_unlock(&set->tag_list_lock);
3253 }
3254 EXPORT_SYMBOL_GPL(blk_mq_update_nr_hw_queues);
3255 
3256 /* Enable polling stats and return whether they were already enabled. */
3257 static bool blk_poll_stats_enable(struct request_queue *q)
3258 {
3259         if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags) ||
3260             blk_queue_flag_test_and_set(QUEUE_FLAG_POLL_STATS, q))
3261                 return true;
3262         blk_stat_add_callback(q, q->poll_cb);
3263         return false;
3264 }
3265 
3266 static void blk_mq_poll_stats_start(struct request_queue *q)
3267 {
3268         /*
3269          * We don't arm the callback if polling stats are not enabled or the
3270          * callback is already active.
3271          */
3272         if (!test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags) ||
3273             blk_stat_is_active(q->poll_cb))
3274                 return;
3275 
3276         blk_stat_activate_msecs(q->poll_cb, 100);
3277 }
3278 
3279 static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb)
3280 {
3281         struct request_queue *q = cb->data;
3282         int bucket;
3283 
3284         for (bucket = 0; bucket < BLK_MQ_POLL_STATS_BKTS; bucket++) {
3285                 if (cb->stat[bucket].nr_samples)
3286                         q->poll_stat[bucket] = cb->stat[bucket];
3287         }
3288 }
3289 
3290 static unsigned long blk_mq_poll_nsecs(struct request_queue *q,
3291                                        struct blk_mq_hw_ctx *hctx,
3292                                        struct request *rq)
3293 {
3294         unsigned long ret = 0;
3295         int bucket;
3296 
3297         /*
3298          * If stats collection isn't on, don't sleep but turn it on for
3299          * future users
3300          */
3301         if (!blk_poll_stats_enable(q))
3302                 return 0;
3303 
3304         /*
3305          * As an optimistic guess, use half of the mean service time
3306          * for this type of request. We can (and should) make this smarter.
3307          * For instance, if the completion latencies are tight, we can
3308          * get closer than just half the mean. This is especially
3309          * important on devices where the completion latencies are longer
3310          * than ~10 usec. We do use the stats for the relevant IO size
3311          * if available which does lead to better estimates.
3312          */
3313         bucket = blk_mq_poll_stats_bkt(rq);
3314         if (bucket < 0)
3315                 return ret;
3316 
3317         if (q->poll_stat[bucket].nr_samples)
3318                 ret = (q->poll_stat[bucket].mean + 1) / 2;
3319 
3320         return ret;
3321 }
3322 
3323 static bool blk_mq_poll_hybrid_sleep(struct request_queue *q,
3324                                      struct blk_mq_hw_ctx *hctx,
3325                                      struct request *rq)
3326 {
3327         struct hrtimer_sleeper hs;
3328         enum hrtimer_mode mode;
3329         unsigned int nsecs;
3330         ktime_t kt;
3331 
3332         if (rq->rq_flags & RQF_MQ_POLL_SLEPT)
3333                 return false;
3334 
3335         /*
3336          * If we get here, hybrid polling is enabled. Hence poll_nsec can be:
3337          *
3338          *  0:  use half of prev avg
3339          * >0:  use this specific value
3340          */
3341         if (q->poll_nsec > 0)
3342                 nsecs = q->poll_nsec;
3343         else
3344                 nsecs = blk_mq_poll_nsecs(q, hctx, rq);
3345 
3346         if (!nsecs)
3347                 return false;
3348 
3349         rq->rq_flags |= RQF_MQ_POLL_SLEPT;
3350 
3351         /*
3352          * This will be replaced with the stats tracking code, using
3353          * 'avg_completion_time / 2' as the pre-sleep target.
3354          */
3355         kt = nsecs;
3356 
3357         mode = HRTIMER_MODE_REL;
3358         hrtimer_init_on_stack(&hs.timer, CLOCK_MONOTONIC, mode);
3359         hrtimer_set_expires(&hs.timer, kt);
3360 
3361         hrtimer_init_sleeper(&hs, current);
3362         do {
3363                 if (blk_mq_rq_state(rq) == MQ_RQ_COMPLETE)
3364                         break;
3365                 set_current_state(TASK_UNINTERRUPTIBLE);
3366                 hrtimer_start_expires(&hs.timer, mode);
3367                 if (hs.task)
3368                         io_schedule();
3369                 hrtimer_cancel(&hs.timer);
3370                 mode = HRTIMER_MODE_ABS;
3371         } while (hs.task && !signal_pending(current));
3372 
3373         __set_current_state(TASK_RUNNING);
3374         destroy_hrtimer_on_stack(&hs.timer);
3375         return true;
3376 }
3377 
3378 static bool blk_mq_poll_hybrid(struct request_queue *q,
3379                                struct blk_mq_hw_ctx *hctx, blk_qc_t cookie)
3380 {
3381         struct request *rq;
3382 
3383         if (q->poll_nsec == -1)
3384                 return false;
3385 
3386         if (!blk_qc_t_is_internal(cookie))
3387                 rq = blk_mq_tag_to_rq(hctx->tags, blk_qc_t_to_tag(cookie));
3388         else {
3389                 rq = blk_mq_tag_to_rq(hctx->sched_tags, blk_qc_t_to_tag(cookie));
3390                 /*
3391                  * With scheduling, if the request has completed, we'll
3392                  * get a NULL return here, as we clear the sched tag when
3393                  * that happens. The request still remains valid, like always,
3394                  * so we should be safe with just the NULL check.
3395                  */
3396                 if (!rq)
3397                         return false;
3398         }
3399 
3400         return blk_mq_poll_hybrid_sleep(q, hctx, rq);
3401 }
3402 
3403 /**
3404  * blk_poll - poll for IO completions
3405  * @q:  the queue
3406  * @cookie: cookie passed back at IO submission time
3407  * @spin: whether to spin for completions
3408  *
3409  * Description:
3410  *    Poll for completions on the passed in queue. Returns number of
3411  *    completed entries found. If @spin is true, then blk_poll will continue
3412  *    looping until at least one completion is found, unless the task is
3413  *    otherwise marked running (or we need to reschedule).
3414  */
3415 int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin)
3416 {
3417         struct blk_mq_hw_ctx *hctx;
3418         long state;
3419 
3420         if (!blk_qc_t_valid(cookie) ||
3421             !test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
3422                 return 0;
3423 
3424         if (current->plug)
3425                 blk_flush_plug_list(current->plug, false);
3426 
3427         hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)];
3428 
3429         /*
3430          * If we sleep, have the caller restart the poll loop to reset
3431          * the state. Like for the other success return cases, the
3432          * caller is responsible for checking if the IO completed. If
3433          * the IO isn't complete, we'll get called again and will go
3434          * straight to the busy poll loop.
3435          */
3436         if (blk_mq_poll_hybrid(q, hctx, cookie))
3437                 return 1;
3438 
3439         hctx->poll_considered++;
3440 
3441         state = current->state;
3442         do {
3443                 int ret;
3444 
3445                 hctx->poll_invoked++;
3446 
3447                 ret = q->mq_ops->poll(hctx);
3448                 if (ret > 0) {
3449                         hctx->poll_success++;
3450                         __set_current_state(TASK_RUNNING);
3451                         return ret;
3452                 }
3453 
3454                 if (signal_pending_state(state, current))
3455                         __set_current_state(TASK_RUNNING);
3456 
3457                 if (current->state == TASK_RUNNING)
3458                         return 1;
3459                 if (ret < 0 || !spin)
3460                         break;
3461                 cpu_relax();
3462         } while (!need_resched());
3463 
3464         __set_current_state(TASK_RUNNING);
3465         return 0;
3466 }
3467 EXPORT_SYMBOL_GPL(blk_poll);
3468 
3469 unsigned int blk_mq_rq_cpu(struct request *rq)
3470 {
3471         return rq->mq_ctx->cpu;
3472 }
3473 EXPORT_SYMBOL(blk_mq_rq_cpu);
3474 
3475 static int __init blk_mq_init(void)
3476 {
3477         cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL,
3478                                 blk_mq_hctx_notify_dead);
3479         return 0;
3480 }
3481 subsys_initcall(blk_mq_init);
3482 

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