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

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Block multiqueue core code
  4  *
  5  * Copyright (C) 2013-2014 Jens Axboe
  6  * Copyright (C) 2013-2014 Christoph Hellwig
  7  */
  8 #include <linux/kernel.h>
  9 #include <linux/module.h>
 10 #include <linux/backing-dev.h>
 11 #include <linux/bio.h>
 12 #include <linux/blkdev.h>
 13 #include <linux/kmemleak.h>
 14 #include <linux/mm.h>
 15 #include <linux/init.h>
 16 #include <linux/slab.h>
 17 #include <linux/workqueue.h>
 18 #include <linux/smp.h>
 19 #include <linux/llist.h>
 20 #include <linux/list_sort.h>
 21 #include <linux/cpu.h>
 22 #include <linux/cache.h>
 23 #include <linux/sched/sysctl.h>
 24 #include <linux/sched/topology.h>
 25 #include <linux/sched/signal.h>
 26 #include <linux/delay.h>
 27 #include <linux/crash_dump.h>
 28 #include <linux/prefetch.h>
 29 
 30 #include <trace/events/block.h>
 31 
 32 #include <linux/blk-mq.h>
 33 #include <linux/t10-pi.h>
 34 #include "blk.h"
 35 #include "blk-mq.h"
 36 #include "blk-mq-debugfs.h"
 37 #include "blk-mq-tag.h"
 38 #include "blk-pm.h"
 39 #include "blk-stat.h"
 40 #include "blk-mq-sched.h"
 41 #include "blk-rq-qos.h"
 42 
 43 static void blk_mq_poll_stats_start(struct request_queue *q);
 44 static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb);
 45 
 46 static int blk_mq_poll_stats_bkt(const struct request *rq)
 47 {
 48         int ddir, sectors, bucket;
 49 
 50         ddir = rq_data_dir(rq);
 51         sectors = blk_rq_stats_sectors(rq);
 52 
 53         bucket = ddir + 2 * ilog2(sectors);
 54 
 55         if (bucket < 0)
 56                 return -1;
 57         else if (bucket >= BLK_MQ_POLL_STATS_BKTS)
 58                 return ddir + BLK_MQ_POLL_STATS_BKTS - 2;
 59 
 60         return bucket;
 61 }
 62 
 63 /*
 64  * Check if any of the ctx, dispatch list or elevator
 65  * have pending work in this hardware queue.
 66  */
 67 static bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx)
 68 {
 69         return !list_empty_careful(&hctx->dispatch) ||
 70                 sbitmap_any_bit_set(&hctx->ctx_map) ||
 71                         blk_mq_sched_has_work(hctx);
 72 }
 73 
 74 /*
 75  * Mark this ctx as having pending work in this hardware queue
 76  */
 77 static void blk_mq_hctx_mark_pending(struct blk_mq_hw_ctx *hctx,
 78                                      struct blk_mq_ctx *ctx)
 79 {
 80         const int bit = ctx->index_hw[hctx->type];
 81 
 82         if (!sbitmap_test_bit(&hctx->ctx_map, bit))
 83                 sbitmap_set_bit(&hctx->ctx_map, bit);
 84 }
 85 
 86 static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
 87                                       struct blk_mq_ctx *ctx)
 88 {
 89         const int bit = ctx->index_hw[hctx->type];
 90 
 91         sbitmap_clear_bit(&hctx->ctx_map, bit);
 92 }
 93 
 94 struct mq_inflight {
 95         struct hd_struct *part;
 96         unsigned int inflight[2];
 97 };
 98 
 99 static bool blk_mq_check_inflight(struct blk_mq_hw_ctx *hctx,
100                                   struct request *rq, void *priv,
101                                   bool reserved)
102 {
103         struct mq_inflight *mi = priv;
104 
105         if (rq->part == mi->part)
106                 mi->inflight[rq_data_dir(rq)]++;
107 
108         return true;
109 }
110 
111 unsigned int blk_mq_in_flight(struct request_queue *q, struct hd_struct *part)
112 {
113         struct mq_inflight mi = { .part = part };
114 
115         blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
116 
117         return mi.inflight[0] + mi.inflight[1];
118 }
119 
120 void blk_mq_in_flight_rw(struct request_queue *q, struct hd_struct *part,
121                          unsigned int inflight[2])
122 {
123         struct mq_inflight mi = { .part = part };
124 
125         blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
126         inflight[0] = mi.inflight[0];
127         inflight[1] = mi.inflight[1];
128 }
129 
130 void blk_freeze_queue_start(struct request_queue *q)
131 {
132         mutex_lock(&q->mq_freeze_lock);
133         if (++q->mq_freeze_depth == 1) {
134                 percpu_ref_kill(&q->q_usage_counter);
135                 mutex_unlock(&q->mq_freeze_lock);
136                 if (queue_is_mq(q))
137                         blk_mq_run_hw_queues(q, false);
138         } else {
139                 mutex_unlock(&q->mq_freeze_lock);
140         }
141 }
142 EXPORT_SYMBOL_GPL(blk_freeze_queue_start);
143 
144 void blk_mq_freeze_queue_wait(struct request_queue *q)
145 {
146         wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->q_usage_counter));
147 }
148 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait);
149 
150 int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
151                                      unsigned long timeout)
152 {
153         return wait_event_timeout(q->mq_freeze_wq,
154                                         percpu_ref_is_zero(&q->q_usage_counter),
155                                         timeout);
156 }
157 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait_timeout);
158 
159 /*
160  * Guarantee no request is in use, so we can change any data structure of
161  * the queue afterward.
162  */
163 void blk_freeze_queue(struct request_queue *q)
164 {
165         /*
166          * In the !blk_mq case we are only calling this to kill the
167          * q_usage_counter, otherwise this increases the freeze depth
168          * and waits for it to return to zero.  For this reason there is
169          * no blk_unfreeze_queue(), and blk_freeze_queue() is not
170          * exported to drivers as the only user for unfreeze is blk_mq.
171          */
172         blk_freeze_queue_start(q);
173         blk_mq_freeze_queue_wait(q);
174 }
175 
176 void blk_mq_freeze_queue(struct request_queue *q)
177 {
178         /*
179          * ...just an alias to keep freeze and unfreeze actions balanced
180          * in the blk_mq_* namespace
181          */
182         blk_freeze_queue(q);
183 }
184 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);
185 
186 void blk_mq_unfreeze_queue(struct request_queue *q)
187 {
188         mutex_lock(&q->mq_freeze_lock);
189         q->mq_freeze_depth--;
190         WARN_ON_ONCE(q->mq_freeze_depth < 0);
191         if (!q->mq_freeze_depth) {
192                 percpu_ref_resurrect(&q->q_usage_counter);
193                 wake_up_all(&q->mq_freeze_wq);
194         }
195         mutex_unlock(&q->mq_freeze_lock);
196 }
197 EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);
198 
199 /*
200  * FIXME: replace the scsi_internal_device_*block_nowait() calls in the
201  * mpt3sas driver such that this function can be removed.
202  */
203 void blk_mq_quiesce_queue_nowait(struct request_queue *q)
204 {
205         blk_queue_flag_set(QUEUE_FLAG_QUIESCED, q);
206 }
207 EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
208 
209 /**
210  * blk_mq_quiesce_queue() - wait until all ongoing dispatches have finished
211  * @q: request queue.
212  *
213  * Note: this function does not prevent that the struct request end_io()
214  * callback function is invoked. Once this function is returned, we make
215  * sure no dispatch can happen until the queue is unquiesced via
216  * blk_mq_unquiesce_queue().
217  */
218 void blk_mq_quiesce_queue(struct request_queue *q)
219 {
220         struct blk_mq_hw_ctx *hctx;
221         unsigned int i;
222         bool rcu = false;
223 
224         blk_mq_quiesce_queue_nowait(q);
225 
226         queue_for_each_hw_ctx(q, hctx, i) {
227                 if (hctx->flags & BLK_MQ_F_BLOCKING)
228                         synchronize_srcu(hctx->srcu);
229                 else
230                         rcu = true;
231         }
232         if (rcu)
233                 synchronize_rcu();
234 }
235 EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue);
236 
237 /*
238  * blk_mq_unquiesce_queue() - counterpart of blk_mq_quiesce_queue()
239  * @q: request queue.
240  *
241  * This function recovers queue into the state before quiescing
242  * which is done by blk_mq_quiesce_queue.
243  */
244 void blk_mq_unquiesce_queue(struct request_queue *q)
245 {
246         blk_queue_flag_clear(QUEUE_FLAG_QUIESCED, q);
247 
248         /* dispatch requests which are inserted during quiescing */
249         blk_mq_run_hw_queues(q, true);
250 }
251 EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue);
252 
253 void blk_mq_wake_waiters(struct request_queue *q)
254 {
255         struct blk_mq_hw_ctx *hctx;
256         unsigned int i;
257 
258         queue_for_each_hw_ctx(q, hctx, i)
259                 if (blk_mq_hw_queue_mapped(hctx))
260                         blk_mq_tag_wakeup_all(hctx->tags, true);
261 }
262 
263 /*
264  * Only need start/end time stamping if we have iostat or
265  * blk stats enabled, or using an IO scheduler.
266  */
267 static inline bool blk_mq_need_time_stamp(struct request *rq)
268 {
269         return (rq->rq_flags & (RQF_IO_STAT | RQF_STATS)) || rq->q->elevator;
270 }
271 
272 static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
273                 unsigned int tag, unsigned int op, u64 alloc_time_ns)
274 {
275         struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
276         struct request *rq = tags->static_rqs[tag];
277         req_flags_t rq_flags = 0;
278 
279         if (data->flags & BLK_MQ_REQ_INTERNAL) {
280                 rq->tag = -1;
281                 rq->internal_tag = tag;
282         } else {
283                 if (data->hctx->flags & BLK_MQ_F_TAG_SHARED) {
284                         rq_flags = RQF_MQ_INFLIGHT;
285                         atomic_inc(&data->hctx->nr_active);
286                 }
287                 rq->tag = tag;
288                 rq->internal_tag = -1;
289                 data->hctx->tags->rqs[rq->tag] = rq;
290         }
291 
292         /* csd/requeue_work/fifo_time is initialized before use */
293         rq->q = data->q;
294         rq->mq_ctx = data->ctx;
295         rq->mq_hctx = data->hctx;
296         rq->rq_flags = rq_flags;
297         rq->cmd_flags = op;
298         if (data->flags & BLK_MQ_REQ_PREEMPT)
299                 rq->rq_flags |= RQF_PREEMPT;
300         if (blk_queue_io_stat(data->q))
301                 rq->rq_flags |= RQF_IO_STAT;
302         INIT_LIST_HEAD(&rq->queuelist);
303         INIT_HLIST_NODE(&rq->hash);
304         RB_CLEAR_NODE(&rq->rb_node);
305         rq->rq_disk = NULL;
306         rq->part = NULL;
307 #ifdef CONFIG_BLK_RQ_ALLOC_TIME
308         rq->alloc_time_ns = alloc_time_ns;
309 #endif
310         if (blk_mq_need_time_stamp(rq))
311                 rq->start_time_ns = ktime_get_ns();
312         else
313                 rq->start_time_ns = 0;
314         rq->io_start_time_ns = 0;
315         rq->stats_sectors = 0;
316         rq->nr_phys_segments = 0;
317 #if defined(CONFIG_BLK_DEV_INTEGRITY)
318         rq->nr_integrity_segments = 0;
319 #endif
320         /* tag was already set */
321         rq->extra_len = 0;
322         WRITE_ONCE(rq->deadline, 0);
323 
324         rq->timeout = 0;
325 
326         rq->end_io = NULL;
327         rq->end_io_data = NULL;
328 
329         data->ctx->rq_dispatched[op_is_sync(op)]++;
330         refcount_set(&rq->ref, 1);
331         return rq;
332 }
333 
334 static struct request *blk_mq_get_request(struct request_queue *q,
335                                           struct bio *bio,
336                                           struct blk_mq_alloc_data *data)
337 {
338         struct elevator_queue *e = q->elevator;
339         struct request *rq;
340         unsigned int tag;
341         bool clear_ctx_on_error = false;
342         u64 alloc_time_ns = 0;
343 
344         blk_queue_enter_live(q);
345 
346         /* alloc_time includes depth and tag waits */
347         if (blk_queue_rq_alloc_time(q))
348                 alloc_time_ns = ktime_get_ns();
349 
350         data->q = q;
351         if (likely(!data->ctx)) {
352                 data->ctx = blk_mq_get_ctx(q);
353                 clear_ctx_on_error = true;
354         }
355         if (likely(!data->hctx))
356                 data->hctx = blk_mq_map_queue(q, data->cmd_flags,
357                                                 data->ctx);
358         if (data->cmd_flags & REQ_NOWAIT)
359                 data->flags |= BLK_MQ_REQ_NOWAIT;
360 
361         if (e) {
362                 data->flags |= BLK_MQ_REQ_INTERNAL;
363 
364                 /*
365                  * Flush requests are special and go directly to the
366                  * dispatch list. Don't include reserved tags in the
367                  * limiting, as it isn't useful.
368                  */
369                 if (!op_is_flush(data->cmd_flags) &&
370                     e->type->ops.limit_depth &&
371                     !(data->flags & BLK_MQ_REQ_RESERVED))
372                         e->type->ops.limit_depth(data->cmd_flags, data);
373         } else {
374                 blk_mq_tag_busy(data->hctx);
375         }
376 
377         tag = blk_mq_get_tag(data);
378         if (tag == BLK_MQ_TAG_FAIL) {
379                 if (clear_ctx_on_error)
380                         data->ctx = NULL;
381                 blk_queue_exit(q);
382                 return NULL;
383         }
384 
385         rq = blk_mq_rq_ctx_init(data, tag, data->cmd_flags, alloc_time_ns);
386         if (!op_is_flush(data->cmd_flags)) {
387                 rq->elv.icq = NULL;
388                 if (e && e->type->ops.prepare_request) {
389                         if (e->type->icq_cache)
390                                 blk_mq_sched_assign_ioc(rq);
391 
392                         e->type->ops.prepare_request(rq, bio);
393                         rq->rq_flags |= RQF_ELVPRIV;
394                 }
395         }
396         data->hctx->queued++;
397         return rq;
398 }
399 
400 struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op,
401                 blk_mq_req_flags_t flags)
402 {
403         struct blk_mq_alloc_data alloc_data = { .flags = flags, .cmd_flags = op };
404         struct request *rq;
405         int ret;
406 
407         ret = blk_queue_enter(q, flags);
408         if (ret)
409                 return ERR_PTR(ret);
410 
411         rq = blk_mq_get_request(q, NULL, &alloc_data);
412         blk_queue_exit(q);
413 
414         if (!rq)
415                 return ERR_PTR(-EWOULDBLOCK);
416 
417         rq->__data_len = 0;
418         rq->__sector = (sector_t) -1;
419         rq->bio = rq->biotail = NULL;
420         return rq;
421 }
422 EXPORT_SYMBOL(blk_mq_alloc_request);
423 
424 struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
425         unsigned int op, blk_mq_req_flags_t flags, unsigned int hctx_idx)
426 {
427         struct blk_mq_alloc_data alloc_data = { .flags = flags, .cmd_flags = op };
428         struct request *rq;
429         unsigned int cpu;
430         int ret;
431 
432         /*
433          * If the tag allocator sleeps we could get an allocation for a
434          * different hardware context.  No need to complicate the low level
435          * allocator for this for the rare use case of a command tied to
436          * a specific queue.
437          */
438         if (WARN_ON_ONCE(!(flags & BLK_MQ_REQ_NOWAIT)))
439                 return ERR_PTR(-EINVAL);
440 
441         if (hctx_idx >= q->nr_hw_queues)
442                 return ERR_PTR(-EIO);
443 
444         ret = blk_queue_enter(q, flags);
445         if (ret)
446                 return ERR_PTR(ret);
447 
448         /*
449          * Check if the hardware context is actually mapped to anything.
450          * If not tell the caller that it should skip this queue.
451          */
452         alloc_data.hctx = q->queue_hw_ctx[hctx_idx];
453         if (!blk_mq_hw_queue_mapped(alloc_data.hctx)) {
454                 blk_queue_exit(q);
455                 return ERR_PTR(-EXDEV);
456         }
457         cpu = cpumask_first_and(alloc_data.hctx->cpumask, cpu_online_mask);
458         alloc_data.ctx = __blk_mq_get_ctx(q, cpu);
459 
460         rq = blk_mq_get_request(q, NULL, &alloc_data);
461         blk_queue_exit(q);
462 
463         if (!rq)
464                 return ERR_PTR(-EWOULDBLOCK);
465 
466         return rq;
467 }
468 EXPORT_SYMBOL_GPL(blk_mq_alloc_request_hctx);
469 
470 static void __blk_mq_free_request(struct request *rq)
471 {
472         struct request_queue *q = rq->q;
473         struct blk_mq_ctx *ctx = rq->mq_ctx;
474         struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
475         const int sched_tag = rq->internal_tag;
476 
477         blk_pm_mark_last_busy(rq);
478         rq->mq_hctx = NULL;
479         if (rq->tag != -1)
480                 blk_mq_put_tag(hctx, hctx->tags, ctx, rq->tag);
481         if (sched_tag != -1)
482                 blk_mq_put_tag(hctx, hctx->sched_tags, ctx, sched_tag);
483         blk_mq_sched_restart(hctx);
484         blk_queue_exit(q);
485 }
486 
487 void blk_mq_free_request(struct request *rq)
488 {
489         struct request_queue *q = rq->q;
490         struct elevator_queue *e = q->elevator;
491         struct blk_mq_ctx *ctx = rq->mq_ctx;
492         struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
493 
494         if (rq->rq_flags & RQF_ELVPRIV) {
495                 if (e && e->type->ops.finish_request)
496                         e->type->ops.finish_request(rq);
497                 if (rq->elv.icq) {
498                         put_io_context(rq->elv.icq->ioc);
499                         rq->elv.icq = NULL;
500                 }
501         }
502 
503         ctx->rq_completed[rq_is_sync(rq)]++;
504         if (rq->rq_flags & RQF_MQ_INFLIGHT)
505                 atomic_dec(&hctx->nr_active);
506 
507         if (unlikely(laptop_mode && !blk_rq_is_passthrough(rq)))
508                 laptop_io_completion(q->backing_dev_info);
509 
510         rq_qos_done(q, rq);
511 
512         WRITE_ONCE(rq->state, MQ_RQ_IDLE);
513         if (refcount_dec_and_test(&rq->ref))
514                 __blk_mq_free_request(rq);
515 }
516 EXPORT_SYMBOL_GPL(blk_mq_free_request);
517 
518 inline void __blk_mq_end_request(struct request *rq, blk_status_t error)
519 {
520         u64 now = 0;
521 
522         if (blk_mq_need_time_stamp(rq))
523                 now = ktime_get_ns();
524 
525         if (rq->rq_flags & RQF_STATS) {
526                 blk_mq_poll_stats_start(rq->q);
527                 blk_stat_add(rq, now);
528         }
529 
530         if (rq->internal_tag != -1)
531                 blk_mq_sched_completed_request(rq, now);
532 
533         blk_account_io_done(rq, now);
534 
535         if (rq->end_io) {
536                 rq_qos_done(rq->q, rq);
537                 rq->end_io(rq, error);
538         } else {
539                 blk_mq_free_request(rq);
540         }
541 }
542 EXPORT_SYMBOL(__blk_mq_end_request);
543 
544 void blk_mq_end_request(struct request *rq, blk_status_t error)
545 {
546         if (blk_update_request(rq, error, blk_rq_bytes(rq)))
547                 BUG();
548         __blk_mq_end_request(rq, error);
549 }
550 EXPORT_SYMBOL(blk_mq_end_request);
551 
552 static void __blk_mq_complete_request_remote(void *data)
553 {
554         struct request *rq = data;
555         struct request_queue *q = rq->q;
556 
557         q->mq_ops->complete(rq);
558 }
559 
560 static void __blk_mq_complete_request(struct request *rq)
561 {
562         struct blk_mq_ctx *ctx = rq->mq_ctx;
563         struct request_queue *q = rq->q;
564         bool shared = false;
565         int cpu;
566 
567         WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);
568         /*
569          * Most of single queue controllers, there is only one irq vector
570          * for handling IO completion, and the only irq's affinity is set
571          * as all possible CPUs. On most of ARCHs, this affinity means the
572          * irq is handled on one specific CPU.
573          *
574          * So complete IO reqeust in softirq context in case of single queue
575          * for not degrading IO performance by irqsoff latency.
576          */
577         if (q->nr_hw_queues == 1) {
578                 __blk_complete_request(rq);
579                 return;
580         }
581 
582         /*
583          * For a polled request, always complete locallly, it's pointless
584          * to redirect the completion.
585          */
586         if ((rq->cmd_flags & REQ_HIPRI) ||
587             !test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags)) {
588                 q->mq_ops->complete(rq);
589                 return;
590         }
591 
592         cpu = get_cpu();
593         if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
594                 shared = cpus_share_cache(cpu, ctx->cpu);
595 
596         if (cpu != ctx->cpu && !shared && cpu_online(ctx->cpu)) {
597                 rq->csd.func = __blk_mq_complete_request_remote;
598                 rq->csd.info = rq;
599                 rq->csd.flags = 0;
600                 smp_call_function_single_async(ctx->cpu, &rq->csd);
601         } else {
602                 q->mq_ops->complete(rq);
603         }
604         put_cpu();
605 }
606 
607 static void hctx_unlock(struct blk_mq_hw_ctx *hctx, int srcu_idx)
608         __releases(hctx->srcu)
609 {
610         if (!(hctx->flags & BLK_MQ_F_BLOCKING))
611                 rcu_read_unlock();
612         else
613                 srcu_read_unlock(hctx->srcu, srcu_idx);
614 }
615 
616 static void hctx_lock(struct blk_mq_hw_ctx *hctx, int *srcu_idx)
617         __acquires(hctx->srcu)
618 {
619         if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
620                 /* shut up gcc false positive */
621                 *srcu_idx = 0;
622                 rcu_read_lock();
623         } else
624                 *srcu_idx = srcu_read_lock(hctx->srcu);
625 }
626 
627 /**
628  * blk_mq_complete_request - end I/O on a request
629  * @rq:         the request being processed
630  *
631  * Description:
632  *      Ends all I/O on a request. It does not handle partial completions.
633  *      The actual completion happens out-of-order, through a IPI handler.
634  **/
635 bool blk_mq_complete_request(struct request *rq)
636 {
637         if (unlikely(blk_should_fake_timeout(rq->q)))
638                 return false;
639         __blk_mq_complete_request(rq);
640         return true;
641 }
642 EXPORT_SYMBOL(blk_mq_complete_request);
643 
644 void blk_mq_start_request(struct request *rq)
645 {
646         struct request_queue *q = rq->q;
647 
648         trace_block_rq_issue(q, rq);
649 
650         if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags)) {
651                 rq->io_start_time_ns = ktime_get_ns();
652                 rq->stats_sectors = blk_rq_sectors(rq);
653                 rq->rq_flags |= RQF_STATS;
654                 rq_qos_issue(q, rq);
655         }
656 
657         WARN_ON_ONCE(blk_mq_rq_state(rq) != MQ_RQ_IDLE);
658 
659         blk_add_timer(rq);
660         WRITE_ONCE(rq->state, MQ_RQ_IN_FLIGHT);
661 
662         if (q->dma_drain_size && blk_rq_bytes(rq)) {
663                 /*
664                  * Make sure space for the drain appears.  We know we can do
665                  * this because max_hw_segments has been adjusted to be one
666                  * fewer than the device can handle.
667                  */
668                 rq->nr_phys_segments++;
669         }
670 
671 #ifdef CONFIG_BLK_DEV_INTEGRITY
672         if (blk_integrity_rq(rq) && req_op(rq) == REQ_OP_WRITE)
673                 q->integrity.profile->prepare_fn(rq);
674 #endif
675 }
676 EXPORT_SYMBOL(blk_mq_start_request);
677 
678 static void __blk_mq_requeue_request(struct request *rq)
679 {
680         struct request_queue *q = rq->q;
681 
682         blk_mq_put_driver_tag(rq);
683 
684         trace_block_rq_requeue(q, rq);
685         rq_qos_requeue(q, rq);
686 
687         if (blk_mq_request_started(rq)) {
688                 WRITE_ONCE(rq->state, MQ_RQ_IDLE);
689                 rq->rq_flags &= ~RQF_TIMED_OUT;
690                 if (q->dma_drain_size && blk_rq_bytes(rq))
691                         rq->nr_phys_segments--;
692         }
693 }
694 
695 void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list)
696 {
697         __blk_mq_requeue_request(rq);
698 
699         /* this request will be re-inserted to io scheduler queue */
700         blk_mq_sched_requeue_request(rq);
701 
702         BUG_ON(!list_empty(&rq->queuelist));
703         blk_mq_add_to_requeue_list(rq, true, kick_requeue_list);
704 }
705 EXPORT_SYMBOL(blk_mq_requeue_request);
706 
707 static void blk_mq_requeue_work(struct work_struct *work)
708 {
709         struct request_queue *q =
710                 container_of(work, struct request_queue, requeue_work.work);
711         LIST_HEAD(rq_list);
712         struct request *rq, *next;
713 
714         spin_lock_irq(&q->requeue_lock);
715         list_splice_init(&q->requeue_list, &rq_list);
716         spin_unlock_irq(&q->requeue_lock);
717 
718         list_for_each_entry_safe(rq, next, &rq_list, queuelist) {
719                 if (!(rq->rq_flags & (RQF_SOFTBARRIER | RQF_DONTPREP)))
720                         continue;
721 
722                 rq->rq_flags &= ~RQF_SOFTBARRIER;
723                 list_del_init(&rq->queuelist);
724                 /*
725                  * If RQF_DONTPREP, rq has contained some driver specific
726                  * data, so insert it to hctx dispatch list to avoid any
727                  * merge.
728                  */
729                 if (rq->rq_flags & RQF_DONTPREP)
730                         blk_mq_request_bypass_insert(rq, false, false);
731                 else
732                         blk_mq_sched_insert_request(rq, true, false, false);
733         }
734 
735         while (!list_empty(&rq_list)) {
736                 rq = list_entry(rq_list.next, struct request, queuelist);
737                 list_del_init(&rq->queuelist);
738                 blk_mq_sched_insert_request(rq, false, false, false);
739         }
740 
741         blk_mq_run_hw_queues(q, false);
742 }
743 
744 void blk_mq_add_to_requeue_list(struct request *rq, bool at_head,
745                                 bool kick_requeue_list)
746 {
747         struct request_queue *q = rq->q;
748         unsigned long flags;
749 
750         /*
751          * We abuse this flag that is otherwise used by the I/O scheduler to
752          * request head insertion from the workqueue.
753          */
754         BUG_ON(rq->rq_flags & RQF_SOFTBARRIER);
755 
756         spin_lock_irqsave(&q->requeue_lock, flags);
757         if (at_head) {
758                 rq->rq_flags |= RQF_SOFTBARRIER;
759                 list_add(&rq->queuelist, &q->requeue_list);
760         } else {
761                 list_add_tail(&rq->queuelist, &q->requeue_list);
762         }
763         spin_unlock_irqrestore(&q->requeue_lock, flags);
764 
765         if (kick_requeue_list)
766                 blk_mq_kick_requeue_list(q);
767 }
768 
769 void blk_mq_kick_requeue_list(struct request_queue *q)
770 {
771         kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work, 0);
772 }
773 EXPORT_SYMBOL(blk_mq_kick_requeue_list);
774 
775 void blk_mq_delay_kick_requeue_list(struct request_queue *q,
776                                     unsigned long msecs)
777 {
778         kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work,
779                                     msecs_to_jiffies(msecs));
780 }
781 EXPORT_SYMBOL(blk_mq_delay_kick_requeue_list);
782 
783 struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
784 {
785         if (tag < tags->nr_tags) {
786                 prefetch(tags->rqs[tag]);
787                 return tags->rqs[tag];
788         }
789 
790         return NULL;
791 }
792 EXPORT_SYMBOL(blk_mq_tag_to_rq);
793 
794 static bool blk_mq_rq_inflight(struct blk_mq_hw_ctx *hctx, struct request *rq,
795                                void *priv, bool reserved)
796 {
797         /*
798          * If we find a request that is inflight and the queue matches,
799          * we know the queue is busy. Return false to stop the iteration.
800          */
801         if (rq->state == MQ_RQ_IN_FLIGHT && rq->q == hctx->queue) {
802                 bool *busy = priv;
803 
804                 *busy = true;
805                 return false;
806         }
807 
808         return true;
809 }
810 
811 bool blk_mq_queue_inflight(struct request_queue *q)
812 {
813         bool busy = false;
814 
815         blk_mq_queue_tag_busy_iter(q, blk_mq_rq_inflight, &busy);
816         return busy;
817 }
818 EXPORT_SYMBOL_GPL(blk_mq_queue_inflight);
819 
820 static void blk_mq_rq_timed_out(struct request *req, bool reserved)
821 {
822         req->rq_flags |= RQF_TIMED_OUT;
823         if (req->q->mq_ops->timeout) {
824                 enum blk_eh_timer_return ret;
825 
826                 ret = req->q->mq_ops->timeout(req, reserved);
827                 if (ret == BLK_EH_DONE)
828                         return;
829                 WARN_ON_ONCE(ret != BLK_EH_RESET_TIMER);
830         }
831 
832         blk_add_timer(req);
833 }
834 
835 static bool blk_mq_req_expired(struct request *rq, unsigned long *next)
836 {
837         unsigned long deadline;
838 
839         if (blk_mq_rq_state(rq) != MQ_RQ_IN_FLIGHT)
840                 return false;
841         if (rq->rq_flags & RQF_TIMED_OUT)
842                 return false;
843 
844         deadline = READ_ONCE(rq->deadline);
845         if (time_after_eq(jiffies, deadline))
846                 return true;
847 
848         if (*next == 0)
849                 *next = deadline;
850         else if (time_after(*next, deadline))
851                 *next = deadline;
852         return false;
853 }
854 
855 static bool blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
856                 struct request *rq, void *priv, bool reserved)
857 {
858         unsigned long *next = priv;
859 
860         /*
861          * Just do a quick check if it is expired before locking the request in
862          * so we're not unnecessarilly synchronizing across CPUs.
863          */
864         if (!blk_mq_req_expired(rq, next))
865                 return true;
866 
867         /*
868          * We have reason to believe the request may be expired. Take a
869          * reference on the request to lock this request lifetime into its
870          * currently allocated context to prevent it from being reallocated in
871          * the event the completion by-passes this timeout handler.
872          *
873          * If the reference was already released, then the driver beat the
874          * timeout handler to posting a natural completion.
875          */
876         if (!refcount_inc_not_zero(&rq->ref))
877                 return true;
878 
879         /*
880          * The request is now locked and cannot be reallocated underneath the
881          * timeout handler's processing. Re-verify this exact request is truly
882          * expired; if it is not expired, then the request was completed and
883          * reallocated as a new request.
884          */
885         if (blk_mq_req_expired(rq, next))
886                 blk_mq_rq_timed_out(rq, reserved);
887 
888         if (is_flush_rq(rq, hctx))
889                 rq->end_io(rq, 0);
890         else if (refcount_dec_and_test(&rq->ref))
891                 __blk_mq_free_request(rq);
892 
893         return true;
894 }
895 
896 static void blk_mq_timeout_work(struct work_struct *work)
897 {
898         struct request_queue *q =
899                 container_of(work, struct request_queue, timeout_work);
900         unsigned long next = 0;
901         struct blk_mq_hw_ctx *hctx;
902         int i;
903 
904         /* A deadlock might occur if a request is stuck requiring a
905          * timeout at the same time a queue freeze is waiting
906          * completion, since the timeout code would not be able to
907          * acquire the queue reference here.
908          *
909          * That's why we don't use blk_queue_enter here; instead, we use
910          * percpu_ref_tryget directly, because we need to be able to
911          * obtain a reference even in the short window between the queue
912          * starting to freeze, by dropping the first reference in
913          * blk_freeze_queue_start, and the moment the last request is
914          * consumed, marked by the instant q_usage_counter reaches
915          * zero.
916          */
917         if (!percpu_ref_tryget(&q->q_usage_counter))
918                 return;
919 
920         blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &next);
921 
922         if (next != 0) {
923                 mod_timer(&q->timeout, next);
924         } else {
925                 /*
926                  * Request timeouts are handled as a forward rolling timer. If
927                  * we end up here it means that no requests are pending and
928                  * also that no request has been pending for a while. Mark
929                  * each hctx as idle.
930                  */
931                 queue_for_each_hw_ctx(q, hctx, i) {
932                         /* the hctx may be unmapped, so check it here */
933                         if (blk_mq_hw_queue_mapped(hctx))
934                                 blk_mq_tag_idle(hctx);
935                 }
936         }
937         blk_queue_exit(q);
938 }
939 
940 struct flush_busy_ctx_data {
941         struct blk_mq_hw_ctx *hctx;
942         struct list_head *list;
943 };
944 
945 static bool flush_busy_ctx(struct sbitmap *sb, unsigned int bitnr, void *data)
946 {
947         struct flush_busy_ctx_data *flush_data = data;
948         struct blk_mq_hw_ctx *hctx = flush_data->hctx;
949         struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
950         enum hctx_type type = hctx->type;
951 
952         spin_lock(&ctx->lock);
953         list_splice_tail_init(&ctx->rq_lists[type], flush_data->list);
954         sbitmap_clear_bit(sb, bitnr);
955         spin_unlock(&ctx->lock);
956         return true;
957 }
958 
959 /*
960  * Process software queues that have been marked busy, splicing them
961  * to the for-dispatch
962  */
963 void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list)
964 {
965         struct flush_busy_ctx_data data = {
966                 .hctx = hctx,
967                 .list = list,
968         };
969 
970         sbitmap_for_each_set(&hctx->ctx_map, flush_busy_ctx, &data);
971 }
972 EXPORT_SYMBOL_GPL(blk_mq_flush_busy_ctxs);
973 
974 struct dispatch_rq_data {
975         struct blk_mq_hw_ctx *hctx;
976         struct request *rq;
977 };
978 
979 static bool dispatch_rq_from_ctx(struct sbitmap *sb, unsigned int bitnr,
980                 void *data)
981 {
982         struct dispatch_rq_data *dispatch_data = data;
983         struct blk_mq_hw_ctx *hctx = dispatch_data->hctx;
984         struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
985         enum hctx_type type = hctx->type;
986 
987         spin_lock(&ctx->lock);
988         if (!list_empty(&ctx->rq_lists[type])) {
989                 dispatch_data->rq = list_entry_rq(ctx->rq_lists[type].next);
990                 list_del_init(&dispatch_data->rq->queuelist);
991                 if (list_empty(&ctx->rq_lists[type]))
992                         sbitmap_clear_bit(sb, bitnr);
993         }
994         spin_unlock(&ctx->lock);
995 
996         return !dispatch_data->rq;
997 }
998 
999 struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx,
1000                                         struct blk_mq_ctx *start)
1001 {
1002         unsigned off = start ? start->index_hw[hctx->type] : 0;
1003         struct dispatch_rq_data data = {
1004                 .hctx = hctx,
1005                 .rq   = NULL,
1006         };
1007 
1008         __sbitmap_for_each_set(&hctx->ctx_map, off,
1009                                dispatch_rq_from_ctx, &data);
1010 
1011         return data.rq;
1012 }
1013 
1014 static inline unsigned int queued_to_index(unsigned int queued)
1015 {
1016         if (!queued)
1017                 return 0;
1018 
1019         return min(BLK_MQ_MAX_DISPATCH_ORDER - 1, ilog2(queued) + 1);
1020 }
1021 
1022 bool blk_mq_get_driver_tag(struct request *rq)
1023 {
1024         struct blk_mq_alloc_data data = {
1025                 .q = rq->q,
1026                 .hctx = rq->mq_hctx,
1027                 .flags = BLK_MQ_REQ_NOWAIT,
1028                 .cmd_flags = rq->cmd_flags,
1029         };
1030         bool shared;
1031 
1032         if (rq->tag != -1)
1033                 return true;
1034 
1035         if (blk_mq_tag_is_reserved(data.hctx->sched_tags, rq->internal_tag))
1036                 data.flags |= BLK_MQ_REQ_RESERVED;
1037 
1038         shared = blk_mq_tag_busy(data.hctx);
1039         rq->tag = blk_mq_get_tag(&data);
1040         if (rq->tag >= 0) {
1041                 if (shared) {
1042                         rq->rq_flags |= RQF_MQ_INFLIGHT;
1043                         atomic_inc(&data.hctx->nr_active);
1044                 }
1045                 data.hctx->tags->rqs[rq->tag] = rq;
1046         }
1047 
1048         return rq->tag != -1;
1049 }
1050 
1051 static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode,
1052                                 int flags, void *key)
1053 {
1054         struct blk_mq_hw_ctx *hctx;
1055 
1056         hctx = container_of(wait, struct blk_mq_hw_ctx, dispatch_wait);
1057 
1058         spin_lock(&hctx->dispatch_wait_lock);
1059         if (!list_empty(&wait->entry)) {
1060                 struct sbitmap_queue *sbq;
1061 
1062                 list_del_init(&wait->entry);
1063                 sbq = &hctx->tags->bitmap_tags;
1064                 atomic_dec(&sbq->ws_active);
1065         }
1066         spin_unlock(&hctx->dispatch_wait_lock);
1067 
1068         blk_mq_run_hw_queue(hctx, true);
1069         return 1;
1070 }
1071 
1072 /*
1073  * Mark us waiting for a tag. For shared tags, this involves hooking us into
1074  * the tag wakeups. For non-shared tags, we can simply mark us needing a
1075  * restart. For both cases, take care to check the condition again after
1076  * marking us as waiting.
1077  */
1078 static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx,
1079                                  struct request *rq)
1080 {
1081         struct sbitmap_queue *sbq = &hctx->tags->bitmap_tags;
1082         struct wait_queue_head *wq;
1083         wait_queue_entry_t *wait;
1084         bool ret;
1085 
1086         if (!(hctx->flags & BLK_MQ_F_TAG_SHARED)) {
1087                 blk_mq_sched_mark_restart_hctx(hctx);
1088 
1089                 /*
1090                  * It's possible that a tag was freed in the window between the
1091                  * allocation failure and adding the hardware queue to the wait
1092                  * queue.
1093                  *
1094                  * Don't clear RESTART here, someone else could have set it.
1095                  * At most this will cost an extra queue run.
1096                  */
1097                 return blk_mq_get_driver_tag(rq);
1098         }
1099 
1100         wait = &hctx->dispatch_wait;
1101         if (!list_empty_careful(&wait->entry))
1102                 return false;
1103 
1104         wq = &bt_wait_ptr(sbq, hctx)->wait;
1105 
1106         spin_lock_irq(&wq->lock);
1107         spin_lock(&hctx->dispatch_wait_lock);
1108         if (!list_empty(&wait->entry)) {
1109                 spin_unlock(&hctx->dispatch_wait_lock);
1110                 spin_unlock_irq(&wq->lock);
1111                 return false;
1112         }
1113 
1114         atomic_inc(&sbq->ws_active);
1115         wait->flags &= ~WQ_FLAG_EXCLUSIVE;
1116         __add_wait_queue(wq, wait);
1117 
1118         /*
1119          * It's possible that a tag was freed in the window between the
1120          * allocation failure and adding the hardware queue to the wait
1121          * queue.
1122          */
1123         ret = blk_mq_get_driver_tag(rq);
1124         if (!ret) {
1125                 spin_unlock(&hctx->dispatch_wait_lock);
1126                 spin_unlock_irq(&wq->lock);
1127                 return false;
1128         }
1129 
1130         /*
1131          * We got a tag, remove ourselves from the wait queue to ensure
1132          * someone else gets the wakeup.
1133          */
1134         list_del_init(&wait->entry);
1135         atomic_dec(&sbq->ws_active);
1136         spin_unlock(&hctx->dispatch_wait_lock);
1137         spin_unlock_irq(&wq->lock);
1138 
1139         return true;
1140 }
1141 
1142 #define BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT  8
1143 #define BLK_MQ_DISPATCH_BUSY_EWMA_FACTOR  4
1144 /*
1145  * Update dispatch busy with the Exponential Weighted Moving Average(EWMA):
1146  * - EWMA is one simple way to compute running average value
1147  * - weight(7/8 and 1/8) is applied so that it can decrease exponentially
1148  * - take 4 as factor for avoiding to get too small(0) result, and this
1149  *   factor doesn't matter because EWMA decreases exponentially
1150  */
1151 static void blk_mq_update_dispatch_busy(struct blk_mq_hw_ctx *hctx, bool busy)
1152 {
1153         unsigned int ewma;
1154 
1155         if (hctx->queue->elevator)
1156                 return;
1157 
1158         ewma = hctx->dispatch_busy;
1159 
1160         if (!ewma && !busy)
1161                 return;
1162 
1163         ewma *= BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT - 1;
1164         if (busy)
1165                 ewma += 1 << BLK_MQ_DISPATCH_BUSY_EWMA_FACTOR;
1166         ewma /= BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT;
1167 
1168         hctx->dispatch_busy = ewma;
1169 }
1170 
1171 #define BLK_MQ_RESOURCE_DELAY   3               /* ms units */
1172 
1173 /*
1174  * Returns true if we did some work AND can potentially do more.
1175  */
1176 bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
1177                              bool got_budget)
1178 {
1179         struct blk_mq_hw_ctx *hctx;
1180         struct request *rq, *nxt;
1181         bool no_tag = false;
1182         int errors, queued;
1183         blk_status_t ret = BLK_STS_OK;
1184 
1185         if (list_empty(list))
1186                 return false;
1187 
1188         WARN_ON(!list_is_singular(list) && got_budget);
1189 
1190         /*
1191          * Now process all the entries, sending them to the driver.
1192          */
1193         errors = queued = 0;
1194         do {
1195                 struct blk_mq_queue_data bd;
1196 
1197                 rq = list_first_entry(list, struct request, queuelist);
1198 
1199                 hctx = rq->mq_hctx;
1200                 if (!got_budget && !blk_mq_get_dispatch_budget(hctx))
1201                         break;
1202 
1203                 if (!blk_mq_get_driver_tag(rq)) {
1204                         /*
1205                          * The initial allocation attempt failed, so we need to
1206                          * rerun the hardware queue when a tag is freed. The
1207                          * waitqueue takes care of that. If the queue is run
1208                          * before we add this entry back on the dispatch list,
1209                          * we'll re-run it below.
1210                          */
1211                         if (!blk_mq_mark_tag_wait(hctx, rq)) {
1212                                 blk_mq_put_dispatch_budget(hctx);
1213                                 /*
1214                                  * For non-shared tags, the RESTART check
1215                                  * will suffice.
1216                                  */
1217                                 if (hctx->flags & BLK_MQ_F_TAG_SHARED)
1218                                         no_tag = true;
1219                                 break;
1220                         }
1221                 }
1222 
1223                 list_del_init(&rq->queuelist);
1224 
1225                 bd.rq = rq;
1226 
1227                 /*
1228                  * Flag last if we have no more requests, or if we have more
1229                  * but can't assign a driver tag to it.
1230                  */
1231                 if (list_empty(list))
1232                         bd.last = true;
1233                 else {
1234                         nxt = list_first_entry(list, struct request, queuelist);
1235                         bd.last = !blk_mq_get_driver_tag(nxt);
1236                 }
1237 
1238                 ret = q->mq_ops->queue_rq(hctx, &bd);
1239                 if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE) {
1240                         /*
1241                          * If an I/O scheduler has been configured and we got a
1242                          * driver tag for the next request already, free it
1243                          * again.
1244                          */
1245                         if (!list_empty(list)) {
1246                                 nxt = list_first_entry(list, struct request, queuelist);
1247                                 blk_mq_put_driver_tag(nxt);
1248                         }
1249                         list_add(&rq->queuelist, list);
1250                         __blk_mq_requeue_request(rq);
1251                         break;
1252                 }
1253 
1254                 if (unlikely(ret != BLK_STS_OK)) {
1255                         errors++;
1256                         blk_mq_end_request(rq, BLK_STS_IOERR);
1257                         continue;
1258                 }
1259 
1260                 queued++;
1261         } while (!list_empty(list));
1262 
1263         hctx->dispatched[queued_to_index(queued)]++;
1264 
1265         /*
1266          * Any items that need requeuing? Stuff them into hctx->dispatch,
1267          * that is where we will continue on next queue run.
1268          */
1269         if (!list_empty(list)) {
1270                 bool needs_restart;
1271 
1272                 /*
1273                  * If we didn't flush the entire list, we could have told
1274                  * the driver there was more coming, but that turned out to
1275                  * be a lie.
1276                  */
1277                 if (q->mq_ops->commit_rqs)
1278                         q->mq_ops->commit_rqs(hctx);
1279 
1280                 spin_lock(&hctx->lock);
1281                 list_splice_tail_init(list, &hctx->dispatch);
1282                 spin_unlock(&hctx->lock);
1283 
1284                 /*
1285                  * If SCHED_RESTART was set by the caller of this function and
1286                  * it is no longer set that means that it was cleared by another
1287                  * thread and hence that a queue rerun is needed.
1288                  *
1289                  * If 'no_tag' is set, that means that we failed getting
1290                  * a driver tag with an I/O scheduler attached. If our dispatch
1291                  * waitqueue is no longer active, ensure that we run the queue
1292                  * AFTER adding our entries back to the list.
1293                  *
1294                  * If no I/O scheduler has been configured it is possible that
1295                  * the hardware queue got stopped and restarted before requests
1296                  * were pushed back onto the dispatch list. Rerun the queue to
1297                  * avoid starvation. Notes:
1298                  * - blk_mq_run_hw_queue() checks whether or not a queue has
1299                  *   been stopped before rerunning a queue.
1300                  * - Some but not all block drivers stop a queue before
1301                  *   returning BLK_STS_RESOURCE. Two exceptions are scsi-mq
1302                  *   and dm-rq.
1303                  *
1304                  * If driver returns BLK_STS_RESOURCE and SCHED_RESTART
1305                  * bit is set, run queue after a delay to avoid IO stalls
1306                  * that could otherwise occur if the queue is idle.
1307                  */
1308                 needs_restart = blk_mq_sched_needs_restart(hctx);
1309                 if (!needs_restart ||
1310                     (no_tag && list_empty_careful(&hctx->dispatch_wait.entry)))
1311                         blk_mq_run_hw_queue(hctx, true);
1312                 else if (needs_restart && (ret == BLK_STS_RESOURCE))
1313                         blk_mq_delay_run_hw_queue(hctx, BLK_MQ_RESOURCE_DELAY);
1314 
1315                 blk_mq_update_dispatch_busy(hctx, true);
1316                 return false;
1317         } else
1318                 blk_mq_update_dispatch_busy(hctx, false);
1319 
1320         /*
1321          * If the host/device is unable to accept more work, inform the
1322          * caller of that.
1323          */
1324         if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
1325                 return false;
1326 
1327         return (queued + errors) != 0;
1328 }
1329 
1330 static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
1331 {
1332         int srcu_idx;
1333 
1334         /*
1335          * We should be running this queue from one of the CPUs that
1336          * are mapped to it.
1337          *
1338          * There are at least two related races now between setting
1339          * hctx->next_cpu from blk_mq_hctx_next_cpu() and running
1340          * __blk_mq_run_hw_queue():
1341          *
1342          * - hctx->next_cpu is found offline in blk_mq_hctx_next_cpu(),
1343          *   but later it becomes online, then this warning is harmless
1344          *   at all
1345          *
1346          * - hctx->next_cpu is found online in blk_mq_hctx_next_cpu(),
1347          *   but later it becomes offline, then the warning can't be
1348          *   triggered, and we depend on blk-mq timeout handler to
1349          *   handle dispatched requests to this hctx
1350          */
1351         if (!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
1352                 cpu_online(hctx->next_cpu)) {
1353                 printk(KERN_WARNING "run queue from wrong CPU %d, hctx %s\n",
1354                         raw_smp_processor_id(),
1355                         cpumask_empty(hctx->cpumask) ? "inactive": "active");
1356                 dump_stack();
1357         }
1358 
1359         /*
1360          * We can't run the queue inline with ints disabled. Ensure that
1361          * we catch bad users of this early.
1362          */
1363         WARN_ON_ONCE(in_interrupt());
1364 
1365         might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
1366 
1367         hctx_lock(hctx, &srcu_idx);
1368         blk_mq_sched_dispatch_requests(hctx);
1369         hctx_unlock(hctx, srcu_idx);
1370 }
1371 
1372 static inline int blk_mq_first_mapped_cpu(struct blk_mq_hw_ctx *hctx)
1373 {
1374         int cpu = cpumask_first_and(hctx->cpumask, cpu_online_mask);
1375 
1376         if (cpu >= nr_cpu_ids)
1377                 cpu = cpumask_first(hctx->cpumask);
1378         return cpu;
1379 }
1380 
1381 /*
1382  * It'd be great if the workqueue API had a way to pass
1383  * in a mask and had some smarts for more clever placement.
1384  * For now we just round-robin here, switching for every
1385  * BLK_MQ_CPU_WORK_BATCH queued items.
1386  */
1387 static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
1388 {
1389         bool tried = false;
1390         int next_cpu = hctx->next_cpu;
1391 
1392         if (hctx->queue->nr_hw_queues == 1)
1393                 return WORK_CPU_UNBOUND;
1394 
1395         if (--hctx->next_cpu_batch <= 0) {
1396 select_cpu:
1397                 next_cpu = cpumask_next_and(next_cpu, hctx->cpumask,
1398                                 cpu_online_mask);
1399                 if (next_cpu >= nr_cpu_ids)
1400                         next_cpu = blk_mq_first_mapped_cpu(hctx);
1401                 hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
1402         }
1403 
1404         /*
1405          * Do unbound schedule if we can't find a online CPU for this hctx,
1406          * and it should only happen in the path of handling CPU DEAD.
1407          */
1408         if (!cpu_online(next_cpu)) {
1409                 if (!tried) {
1410                         tried = true;
1411                         goto select_cpu;
1412                 }
1413 
1414                 /*
1415                  * Make sure to re-select CPU next time once after CPUs
1416                  * in hctx->cpumask become online again.
1417                  */
1418                 hctx->next_cpu = next_cpu;
1419                 hctx->next_cpu_batch = 1;
1420                 return WORK_CPU_UNBOUND;
1421         }
1422 
1423         hctx->next_cpu = next_cpu;
1424         return next_cpu;
1425 }
1426 
1427 static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async,
1428                                         unsigned long msecs)
1429 {
1430         if (unlikely(blk_mq_hctx_stopped(hctx)))
1431                 return;
1432 
1433         if (!async && !(hctx->flags & BLK_MQ_F_BLOCKING)) {
1434                 int cpu = get_cpu();
1435                 if (cpumask_test_cpu(cpu, hctx->cpumask)) {
1436                         __blk_mq_run_hw_queue(hctx);
1437                         put_cpu();
1438                         return;
1439                 }
1440 
1441                 put_cpu();
1442         }
1443 
1444         kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work,
1445                                     msecs_to_jiffies(msecs));
1446 }
1447 
1448 void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
1449 {
1450         __blk_mq_delay_run_hw_queue(hctx, true, msecs);
1451 }
1452 EXPORT_SYMBOL(blk_mq_delay_run_hw_queue);
1453 
1454 void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
1455 {
1456         int srcu_idx;
1457         bool need_run;
1458 
1459         /*
1460          * When queue is quiesced, we may be switching io scheduler, or
1461          * updating nr_hw_queues, or other things, and we can't run queue
1462          * any more, even __blk_mq_hctx_has_pending() can't be called safely.
1463          *
1464          * And queue will be rerun in blk_mq_unquiesce_queue() if it is
1465          * quiesced.
1466          */
1467         hctx_lock(hctx, &srcu_idx);
1468         need_run = !blk_queue_quiesced(hctx->queue) &&
1469                 blk_mq_hctx_has_pending(hctx);
1470         hctx_unlock(hctx, srcu_idx);
1471 
1472         if (need_run)
1473                 __blk_mq_delay_run_hw_queue(hctx, async, 0);
1474 }
1475 EXPORT_SYMBOL(blk_mq_run_hw_queue);
1476 
1477 void blk_mq_run_hw_queues(struct request_queue *q, bool async)
1478 {
1479         struct blk_mq_hw_ctx *hctx;
1480         int i;
1481 
1482         queue_for_each_hw_ctx(q, hctx, i) {
1483                 if (blk_mq_hctx_stopped(hctx))
1484                         continue;
1485 
1486                 blk_mq_run_hw_queue(hctx, async);
1487         }
1488 }
1489 EXPORT_SYMBOL(blk_mq_run_hw_queues);
1490 
1491 /**
1492  * blk_mq_queue_stopped() - check whether one or more hctxs have been stopped
1493  * @q: request queue.
1494  *
1495  * The caller is responsible for serializing this function against
1496  * blk_mq_{start,stop}_hw_queue().
1497  */
1498 bool blk_mq_queue_stopped(struct request_queue *q)
1499 {
1500         struct blk_mq_hw_ctx *hctx;
1501         int i;
1502 
1503         queue_for_each_hw_ctx(q, hctx, i)
1504                 if (blk_mq_hctx_stopped(hctx))
1505                         return true;
1506 
1507         return false;
1508 }
1509 EXPORT_SYMBOL(blk_mq_queue_stopped);
1510 
1511 /*
1512  * This function is often used for pausing .queue_rq() by driver when
1513  * there isn't enough resource or some conditions aren't satisfied, and
1514  * BLK_STS_RESOURCE is usually returned.
1515  *
1516  * We do not guarantee that dispatch can be drained or blocked
1517  * after blk_mq_stop_hw_queue() returns. Please use
1518  * blk_mq_quiesce_queue() for that requirement.
1519  */
1520 void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx)
1521 {
1522         cancel_delayed_work(&hctx->run_work);
1523 
1524         set_bit(BLK_MQ_S_STOPPED, &hctx->state);
1525 }
1526 EXPORT_SYMBOL(blk_mq_stop_hw_queue);
1527 
1528 /*
1529  * This function is often used for pausing .queue_rq() by driver when
1530  * there isn't enough resource or some conditions aren't satisfied, and
1531  * BLK_STS_RESOURCE is usually returned.
1532  *
1533  * We do not guarantee that dispatch can be drained or blocked
1534  * after blk_mq_stop_hw_queues() returns. Please use
1535  * blk_mq_quiesce_queue() for that requirement.
1536  */
1537 void blk_mq_stop_hw_queues(struct request_queue *q)
1538 {
1539         struct blk_mq_hw_ctx *hctx;
1540         int i;
1541 
1542         queue_for_each_hw_ctx(q, hctx, i)
1543                 blk_mq_stop_hw_queue(hctx);
1544 }
1545 EXPORT_SYMBOL(blk_mq_stop_hw_queues);
1546 
1547 void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx)
1548 {
1549         clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
1550 
1551         blk_mq_run_hw_queue(hctx, false);
1552 }
1553 EXPORT_SYMBOL(blk_mq_start_hw_queue);
1554 
1555 void blk_mq_start_hw_queues(struct request_queue *q)
1556 {
1557         struct blk_mq_hw_ctx *hctx;
1558         int i;
1559 
1560         queue_for_each_hw_ctx(q, hctx, i)
1561                 blk_mq_start_hw_queue(hctx);
1562 }
1563 EXPORT_SYMBOL(blk_mq_start_hw_queues);
1564 
1565 void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
1566 {
1567         if (!blk_mq_hctx_stopped(hctx))
1568                 return;
1569 
1570         clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
1571         blk_mq_run_hw_queue(hctx, async);
1572 }
1573 EXPORT_SYMBOL_GPL(blk_mq_start_stopped_hw_queue);
1574 
1575 void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async)
1576 {
1577         struct blk_mq_hw_ctx *hctx;
1578         int i;
1579 
1580         queue_for_each_hw_ctx(q, hctx, i)
1581                 blk_mq_start_stopped_hw_queue(hctx, async);
1582 }
1583 EXPORT_SYMBOL(blk_mq_start_stopped_hw_queues);
1584 
1585 static void blk_mq_run_work_fn(struct work_struct *work)
1586 {
1587         struct blk_mq_hw_ctx *hctx;
1588 
1589         hctx = container_of(work, struct blk_mq_hw_ctx, run_work.work);
1590 
1591         /*
1592          * If we are stopped, don't run the queue.
1593          */
1594         if (test_bit(BLK_MQ_S_STOPPED, &hctx->state))
1595                 return;
1596 
1597         __blk_mq_run_hw_queue(hctx);
1598 }
1599 
1600 static inline void __blk_mq_insert_req_list(struct blk_mq_hw_ctx *hctx,
1601                                             struct request *rq,
1602                                             bool at_head)
1603 {
1604         struct blk_mq_ctx *ctx = rq->mq_ctx;
1605         enum hctx_type type = hctx->type;
1606 
1607         lockdep_assert_held(&ctx->lock);
1608 
1609         trace_block_rq_insert(hctx->queue, rq);
1610 
1611         if (at_head)
1612                 list_add(&rq->queuelist, &ctx->rq_lists[type]);
1613         else
1614                 list_add_tail(&rq->queuelist, &ctx->rq_lists[type]);
1615 }
1616 
1617 void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
1618                              bool at_head)
1619 {
1620         struct blk_mq_ctx *ctx = rq->mq_ctx;
1621 
1622         lockdep_assert_held(&ctx->lock);
1623 
1624         __blk_mq_insert_req_list(hctx, rq, at_head);
1625         blk_mq_hctx_mark_pending(hctx, ctx);
1626 }
1627 
1628 /*
1629  * Should only be used carefully, when the caller knows we want to
1630  * bypass a potential IO scheduler on the target device.
1631  */
1632 void blk_mq_request_bypass_insert(struct request *rq, bool at_head,
1633                                   bool run_queue)
1634 {
1635         struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
1636 
1637         spin_lock(&hctx->lock);
1638         if (at_head)
1639                 list_add(&rq->queuelist, &hctx->dispatch);
1640         else
1641                 list_add_tail(&rq->queuelist, &hctx->dispatch);
1642         spin_unlock(&hctx->lock);
1643 
1644         if (run_queue)
1645                 blk_mq_run_hw_queue(hctx, false);
1646 }
1647 
1648 void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
1649                             struct list_head *list)
1650 
1651 {
1652         struct request *rq;
1653         enum hctx_type type = hctx->type;
1654 
1655         /*
1656          * preemption doesn't flush plug list, so it's possible ctx->cpu is
1657          * offline now
1658          */
1659         list_for_each_entry(rq, list, queuelist) {
1660                 BUG_ON(rq->mq_ctx != ctx);
1661                 trace_block_rq_insert(hctx->queue, rq);
1662         }
1663 
1664         spin_lock(&ctx->lock);
1665         list_splice_tail_init(list, &ctx->rq_lists[type]);
1666         blk_mq_hctx_mark_pending(hctx, ctx);
1667         spin_unlock(&ctx->lock);
1668 }
1669 
1670 static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
1671 {
1672         struct request *rqa = container_of(a, struct request, queuelist);
1673         struct request *rqb = container_of(b, struct request, queuelist);
1674 
1675         if (rqa->mq_ctx < rqb->mq_ctx)
1676                 return -1;
1677         else if (rqa->mq_ctx > rqb->mq_ctx)
1678                 return 1;
1679         else if (rqa->mq_hctx < rqb->mq_hctx)
1680                 return -1;
1681         else if (rqa->mq_hctx > rqb->mq_hctx)
1682                 return 1;
1683 
1684         return blk_rq_pos(rqa) > blk_rq_pos(rqb);
1685 }
1686 
1687 void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
1688 {
1689         struct blk_mq_hw_ctx *this_hctx;
1690         struct blk_mq_ctx *this_ctx;
1691         struct request_queue *this_q;
1692         struct request *rq;
1693         LIST_HEAD(list);
1694         LIST_HEAD(rq_list);
1695         unsigned int depth;
1696 
1697         list_splice_init(&plug->mq_list, &list);
1698 
1699         if (plug->rq_count > 2 && plug->multiple_queues)
1700                 list_sort(NULL, &list, plug_rq_cmp);
1701 
1702         plug->rq_count = 0;
1703 
1704         this_q = NULL;
1705         this_hctx = NULL;
1706         this_ctx = NULL;
1707         depth = 0;
1708 
1709         while (!list_empty(&list)) {
1710                 rq = list_entry_rq(list.next);
1711                 list_del_init(&rq->queuelist);
1712                 BUG_ON(!rq->q);
1713                 if (rq->mq_hctx != this_hctx || rq->mq_ctx != this_ctx) {
1714                         if (this_hctx) {
1715                                 trace_block_unplug(this_q, depth, !from_schedule);
1716                                 blk_mq_sched_insert_requests(this_hctx, this_ctx,
1717                                                                 &rq_list,
1718                                                                 from_schedule);
1719                         }
1720 
1721                         this_q = rq->q;
1722                         this_ctx = rq->mq_ctx;
1723                         this_hctx = rq->mq_hctx;
1724                         depth = 0;
1725                 }
1726 
1727                 depth++;
1728                 list_add_tail(&rq->queuelist, &rq_list);
1729         }
1730 
1731         /*
1732          * If 'this_hctx' is set, we know we have entries to complete
1733          * on 'rq_list'. Do those.
1734          */
1735         if (this_hctx) {
1736                 trace_block_unplug(this_q, depth, !from_schedule);
1737                 blk_mq_sched_insert_requests(this_hctx, this_ctx, &rq_list,
1738                                                 from_schedule);
1739         }
1740 }
1741 
1742 static void blk_mq_bio_to_request(struct request *rq, struct bio *bio,
1743                 unsigned int nr_segs)
1744 {
1745         if (bio->bi_opf & REQ_RAHEAD)
1746                 rq->cmd_flags |= REQ_FAILFAST_MASK;
1747 
1748         rq->__sector = bio->bi_iter.bi_sector;
1749         rq->write_hint = bio->bi_write_hint;
1750         blk_rq_bio_prep(rq, bio, nr_segs);
1751 
1752         blk_account_io_start(rq, true);
1753 }
1754 
1755 static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
1756                                             struct request *rq,
1757                                             blk_qc_t *cookie, bool last)
1758 {
1759         struct request_queue *q = rq->q;
1760         struct blk_mq_queue_data bd = {
1761                 .rq = rq,
1762                 .last = last,
1763         };
1764         blk_qc_t new_cookie;
1765         blk_status_t ret;
1766 
1767         new_cookie = request_to_qc_t(hctx, rq);
1768 
1769         /*
1770          * For OK queue, we are done. For error, caller may kill it.
1771          * Any other error (busy), just add it to our list as we
1772          * previously would have done.
1773          */
1774         ret = q->mq_ops->queue_rq(hctx, &bd);
1775         switch (ret) {
1776         case BLK_STS_OK:
1777                 blk_mq_update_dispatch_busy(hctx, false);
1778                 *cookie = new_cookie;
1779                 break;
1780         case BLK_STS_RESOURCE:
1781         case BLK_STS_DEV_RESOURCE:
1782                 blk_mq_update_dispatch_busy(hctx, true);
1783                 __blk_mq_requeue_request(rq);
1784                 break;
1785         default:
1786                 blk_mq_update_dispatch_busy(hctx, false);
1787                 *cookie = BLK_QC_T_NONE;
1788                 break;
1789         }
1790 
1791         return ret;
1792 }
1793 
1794 static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
1795                                                 struct request *rq,
1796                                                 blk_qc_t *cookie,
1797                                                 bool bypass_insert, bool last)
1798 {
1799         struct request_queue *q = rq->q;
1800         bool run_queue = true;
1801 
1802         /*
1803          * RCU or SRCU read lock is needed before checking quiesced flag.
1804          *
1805          * When queue is stopped or quiesced, ignore 'bypass_insert' from
1806          * blk_mq_request_issue_directly(), and return BLK_STS_OK to caller,
1807          * and avoid driver to try to dispatch again.
1808          */
1809         if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)) {
1810                 run_queue = false;
1811                 bypass_insert = false;
1812                 goto insert;
1813         }
1814 
1815         if (q->elevator && !bypass_insert)
1816                 goto insert;
1817 
1818         if (!blk_mq_get_dispatch_budget(hctx))
1819                 goto insert;
1820 
1821         if (!blk_mq_get_driver_tag(rq)) {
1822                 blk_mq_put_dispatch_budget(hctx);
1823                 goto insert;
1824         }
1825 
1826         return __blk_mq_issue_directly(hctx, rq, cookie, last);
1827 insert:
1828         if (bypass_insert)
1829                 return BLK_STS_RESOURCE;
1830 
1831         blk_mq_request_bypass_insert(rq, false, run_queue);
1832         return BLK_STS_OK;
1833 }
1834 
1835 static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
1836                 struct request *rq, blk_qc_t *cookie)
1837 {
1838         blk_status_t ret;
1839         int srcu_idx;
1840 
1841         might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
1842 
1843         hctx_lock(hctx, &srcu_idx);
1844 
1845         ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false, true);
1846         if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
1847                 blk_mq_request_bypass_insert(rq, false, true);
1848         else if (ret != BLK_STS_OK)
1849                 blk_mq_end_request(rq, ret);
1850 
1851         hctx_unlock(hctx, srcu_idx);
1852 }
1853 
1854 blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last)
1855 {
1856         blk_status_t ret;
1857         int srcu_idx;
1858         blk_qc_t unused_cookie;
1859         struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
1860 
1861         hctx_lock(hctx, &srcu_idx);
1862         ret = __blk_mq_try_issue_directly(hctx, rq, &unused_cookie, true, last);
1863         hctx_unlock(hctx, srcu_idx);
1864 
1865         return ret;
1866 }
1867 
1868 void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
1869                 struct list_head *list)
1870 {
1871         while (!list_empty(list)) {
1872                 blk_status_t ret;
1873                 struct request *rq = list_first_entry(list, struct request,
1874                                 queuelist);
1875 
1876                 list_del_init(&rq->queuelist);
1877                 ret = blk_mq_request_issue_directly(rq, list_empty(list));
1878                 if (ret != BLK_STS_OK) {
1879                         if (ret == BLK_STS_RESOURCE ||
1880                                         ret == BLK_STS_DEV_RESOURCE) {
1881                                 blk_mq_request_bypass_insert(rq, false,
1882                                                         list_empty(list));
1883                                 break;
1884                         }
1885                         blk_mq_end_request(rq, ret);
1886                 }
1887         }
1888 
1889         /*
1890          * If we didn't flush the entire list, we could have told
1891          * the driver there was more coming, but that turned out to
1892          * be a lie.
1893          */
1894         if (!list_empty(list) && hctx->queue->mq_ops->commit_rqs)
1895                 hctx->queue->mq_ops->commit_rqs(hctx);
1896 }
1897 
1898 static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
1899 {
1900         list_add_tail(&rq->queuelist, &plug->mq_list);
1901         plug->rq_count++;
1902         if (!plug->multiple_queues && !list_is_singular(&plug->mq_list)) {
1903                 struct request *tmp;
1904 
1905                 tmp = list_first_entry(&plug->mq_list, struct request,
1906                                                 queuelist);
1907                 if (tmp->q != rq->q)
1908                         plug->multiple_queues = true;
1909         }
1910 }
1911 
1912 static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
1913 {
1914         const int is_sync = op_is_sync(bio->bi_opf);
1915         const int is_flush_fua = op_is_flush(bio->bi_opf);
1916         struct blk_mq_alloc_data data = { .flags = 0};
1917         struct request *rq;
1918         struct blk_plug *plug;
1919         struct request *same_queue_rq = NULL;
1920         unsigned int nr_segs;
1921         blk_qc_t cookie;
1922 
1923         blk_queue_bounce(q, &bio);
1924         __blk_queue_split(q, &bio, &nr_segs);
1925 
1926         if (!bio_integrity_prep(bio))
1927                 return BLK_QC_T_NONE;
1928 
1929         if (!is_flush_fua && !blk_queue_nomerges(q) &&
1930             blk_attempt_plug_merge(q, bio, nr_segs, &same_queue_rq))
1931                 return BLK_QC_T_NONE;
1932 
1933         if (blk_mq_sched_bio_merge(q, bio, nr_segs))
1934                 return BLK_QC_T_NONE;
1935 
1936         rq_qos_throttle(q, bio);
1937 
1938         data.cmd_flags = bio->bi_opf;
1939         rq = blk_mq_get_request(q, bio, &data);
1940         if (unlikely(!rq)) {
1941                 rq_qos_cleanup(q, bio);
1942                 if (bio->bi_opf & REQ_NOWAIT)
1943                         bio_wouldblock_error(bio);
1944                 return BLK_QC_T_NONE;
1945         }
1946 
1947         trace_block_getrq(q, bio, bio->bi_opf);
1948 
1949         rq_qos_track(q, rq, bio);
1950 
1951         cookie = request_to_qc_t(data.hctx, rq);
1952 
1953         blk_mq_bio_to_request(rq, bio, nr_segs);
1954 
1955         plug = blk_mq_plug(q, bio);
1956         if (unlikely(is_flush_fua)) {
1957                 /* bypass scheduler for flush rq */
1958                 blk_insert_flush(rq);
1959                 blk_mq_run_hw_queue(data.hctx, true);
1960         } else if (plug && (q->nr_hw_queues == 1 || q->mq_ops->commit_rqs ||
1961                                 !blk_queue_nonrot(q))) {
1962                 /*
1963                  * Use plugging if we have a ->commit_rqs() hook as well, as
1964                  * we know the driver uses bd->last in a smart fashion.
1965                  *
1966                  * Use normal plugging if this disk is slow HDD, as sequential
1967                  * IO may benefit a lot from plug merging.
1968                  */
1969                 unsigned int request_count = plug->rq_count;
1970                 struct request *last = NULL;
1971 
1972                 if (!request_count)
1973                         trace_block_plug(q);
1974                 else
1975                         last = list_entry_rq(plug->mq_list.prev);
1976 
1977                 if (request_count >= BLK_MAX_REQUEST_COUNT || (last &&
1978                     blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
1979                         blk_flush_plug_list(plug, false);
1980                         trace_block_plug(q);
1981                 }
1982 
1983                 blk_add_rq_to_plug(plug, rq);
1984         } else if (q->elevator) {
1985                 blk_mq_sched_insert_request(rq, false, true, true);
1986         } else if (plug && !blk_queue_nomerges(q)) {
1987                 /*
1988                  * We do limited plugging. If the bio can be merged, do that.
1989                  * Otherwise the existing request in the plug list will be
1990                  * issued. So the plug list will have one request at most
1991                  * The plug list might get flushed before this. If that happens,
1992                  * the plug list is empty, and same_queue_rq is invalid.
1993                  */
1994                 if (list_empty(&plug->mq_list))
1995                         same_queue_rq = NULL;
1996                 if (same_queue_rq) {
1997                         list_del_init(&same_queue_rq->queuelist);
1998                         plug->rq_count--;
1999                 }
2000                 blk_add_rq_to_plug(plug, rq);
2001                 trace_block_plug(q);
2002 
2003                 if (same_queue_rq) {
2004                         data.hctx = same_queue_rq->mq_hctx;
2005                         trace_block_unplug(q, 1, true);
2006                         blk_mq_try_issue_directly(data.hctx, same_queue_rq,
2007                                         &cookie);
2008                 }
2009         } else if ((q->nr_hw_queues > 1 && is_sync) ||
2010                         !data.hctx->dispatch_busy) {
2011                 blk_mq_try_issue_directly(data.hctx, rq, &cookie);
2012         } else {
2013                 blk_mq_sched_insert_request(rq, false, true, true);
2014         }
2015 
2016         return cookie;
2017 }
2018 
2019 void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
2020                      unsigned int hctx_idx)
2021 {
2022         struct page *page;
2023 
2024         if (tags->rqs && set->ops->exit_request) {
2025                 int i;
2026 
2027                 for (i = 0; i < tags->nr_tags; i++) {
2028                         struct request *rq = tags->static_rqs[i];
2029 
2030                         if (!rq)
2031                                 continue;
2032                         set->ops->exit_request(set, rq, hctx_idx);
2033                         tags->static_rqs[i] = NULL;
2034                 }
2035         }
2036 
2037         while (!list_empty(&tags->page_list)) {
2038                 page = list_first_entry(&tags->page_list, struct page, lru);
2039                 list_del_init(&page->lru);
2040                 /*
2041                  * Remove kmemleak object previously allocated in
2042                  * blk_mq_alloc_rqs().
2043                  */
2044                 kmemleak_free(page_address(page));
2045                 __free_pages(page, page->private);
2046         }
2047 }
2048 
2049 void blk_mq_free_rq_map(struct blk_mq_tags *tags)
2050 {
2051         kfree(tags->rqs);
2052         tags->rqs = NULL;
2053         kfree(tags->static_rqs);
2054         tags->static_rqs = NULL;
2055 
2056         blk_mq_free_tags(tags);
2057 }
2058 
2059 struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
2060                                         unsigned int hctx_idx,
2061                                         unsigned int nr_tags,
2062                                         unsigned int reserved_tags)
2063 {
2064         struct blk_mq_tags *tags;
2065         int node;
2066 
2067         node = blk_mq_hw_queue_to_node(&set->map[HCTX_TYPE_DEFAULT], hctx_idx);
2068         if (node == NUMA_NO_NODE)
2069                 node = set->numa_node;
2070 
2071         tags = blk_mq_init_tags(nr_tags, reserved_tags, node,
2072                                 BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags));
2073         if (!tags)
2074                 return NULL;
2075 
2076         tags->rqs = kcalloc_node(nr_tags, sizeof(struct request *),
2077                                  GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
2078                                  node);
2079         if (!tags->rqs) {
2080                 blk_mq_free_tags(tags);
2081                 return NULL;
2082         }
2083 
2084         tags->static_rqs = kcalloc_node(nr_tags, sizeof(struct request *),
2085                                         GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
2086                                         node);
2087         if (!tags->static_rqs) {
2088                 kfree(tags->rqs);
2089                 blk_mq_free_tags(tags);
2090                 return NULL;
2091         }
2092 
2093         return tags;
2094 }
2095 
2096 static size_t order_to_size(unsigned int order)
2097 {
2098         return (size_t)PAGE_SIZE << order;
2099 }
2100 
2101 static int blk_mq_init_request(struct blk_mq_tag_set *set, struct request *rq,
2102                                unsigned int hctx_idx, int node)
2103 {
2104         int ret;
2105 
2106         if (set->ops->init_request) {
2107                 ret = set->ops->init_request(set, rq, hctx_idx, node);
2108                 if (ret)
2109                         return ret;
2110         }
2111 
2112         WRITE_ONCE(rq->state, MQ_RQ_IDLE);
2113         return 0;
2114 }
2115 
2116 int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
2117                      unsigned int hctx_idx, unsigned int depth)
2118 {
2119         unsigned int i, j, entries_per_page, max_order = 4;
2120         size_t rq_size, left;
2121         int node;
2122 
2123         node = blk_mq_hw_queue_to_node(&set->map[HCTX_TYPE_DEFAULT], hctx_idx);
2124         if (node == NUMA_NO_NODE)
2125                 node = set->numa_node;
2126 
2127         INIT_LIST_HEAD(&tags->page_list);
2128 
2129         /*
2130          * rq_size is the size of the request plus driver payload, rounded
2131          * to the cacheline size
2132          */
2133         rq_size = round_up(sizeof(struct request) + set->cmd_size,
2134                                 cache_line_size());
2135         left = rq_size * depth;
2136 
2137         for (i = 0; i < depth; ) {
2138                 int this_order = max_order;
2139                 struct page *page;
2140                 int to_do;
2141                 void *p;
2142 
2143                 while (this_order && left < order_to_size(this_order - 1))
2144                         this_order--;
2145 
2146                 do {
2147                         page = alloc_pages_node(node,
2148                                 GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY | __GFP_ZERO,
2149                                 this_order);
2150                         if (page)
2151                                 break;
2152                         if (!this_order--)
2153                                 break;
2154                         if (order_to_size(this_order) < rq_size)
2155                                 break;
2156                 } while (1);
2157 
2158                 if (!page)
2159                         goto fail;
2160 
2161                 page->private = this_order;
2162                 list_add_tail(&page->lru, &tags->page_list);
2163 
2164                 p = page_address(page);
2165                 /*
2166                  * Allow kmemleak to scan these pages as they contain pointers
2167                  * to additional allocations like via ops->init_request().
2168                  */
2169                 kmemleak_alloc(p, order_to_size(this_order), 1, GFP_NOIO);
2170                 entries_per_page = order_to_size(this_order) / rq_size;
2171                 to_do = min(entries_per_page, depth - i);
2172                 left -= to_do * rq_size;
2173                 for (j = 0; j < to_do; j++) {
2174                         struct request *rq = p;
2175 
2176                         tags->static_rqs[i] = rq;
2177                         if (blk_mq_init_request(set, rq, hctx_idx, node)) {
2178                                 tags->static_rqs[i] = NULL;
2179                                 goto fail;
2180                         }
2181 
2182                         p += rq_size;
2183                         i++;
2184                 }
2185         }
2186         return 0;
2187 
2188 fail:
2189         blk_mq_free_rqs(set, tags, hctx_idx);
2190         return -ENOMEM;
2191 }
2192 
2193 /*
2194  * 'cpu' is going away. splice any existing rq_list entries from this
2195  * software queue to the hw queue dispatch list, and ensure that it
2196  * gets run.
2197  */
2198 static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node)
2199 {
2200         struct blk_mq_hw_ctx *hctx;
2201         struct blk_mq_ctx *ctx;
2202         LIST_HEAD(tmp);
2203         enum hctx_type type;
2204 
2205         hctx = hlist_entry_safe(node, struct blk_mq_hw_ctx, cpuhp_dead);
2206         ctx = __blk_mq_get_ctx(hctx->queue, cpu);
2207         type = hctx->type;
2208 
2209         spin_lock(&ctx->lock);
2210         if (!list_empty(&ctx->rq_lists[type])) {
2211                 list_splice_init(&ctx->rq_lists[type], &tmp);
2212                 blk_mq_hctx_clear_pending(hctx, ctx);
2213         }
2214         spin_unlock(&ctx->lock);
2215 
2216         if (list_empty(&tmp))
2217                 return 0;
2218 
2219         spin_lock(&hctx->lock);
2220         list_splice_tail_init(&tmp, &hctx->dispatch);
2221         spin_unlock(&hctx->lock);
2222 
2223         blk_mq_run_hw_queue(hctx, true);
2224         return 0;
2225 }
2226 
2227 static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx)
2228 {
2229         cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_DEAD,
2230                                             &hctx->cpuhp_dead);
2231 }
2232 
2233 /* hctx->ctxs will be freed in queue's release handler */
2234 static void blk_mq_exit_hctx(struct request_queue *q,
2235                 struct blk_mq_tag_set *set,
2236                 struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
2237 {
2238         if (blk_mq_hw_queue_mapped(hctx))
2239                 blk_mq_tag_idle(hctx);
2240 
2241         if (set->ops->exit_request)
2242                 set->ops->exit_request(set, hctx->fq->flush_rq, hctx_idx);
2243 
2244         if (set->ops->exit_hctx)
2245                 set->ops->exit_hctx(hctx, hctx_idx);
2246 
2247         blk_mq_remove_cpuhp(hctx);
2248 
2249         spin_lock(&q->unused_hctx_lock);
2250         list_add(&hctx->hctx_list, &q->unused_hctx_list);
2251         spin_unlock(&q->unused_hctx_lock);
2252 }
2253 
2254 static void blk_mq_exit_hw_queues(struct request_queue *q,
2255                 struct blk_mq_tag_set *set, int nr_queue)
2256 {
2257         struct blk_mq_hw_ctx *hctx;
2258         unsigned int i;
2259 
2260         queue_for_each_hw_ctx(q, hctx, i) {
2261                 if (i == nr_queue)
2262                         break;
2263                 blk_mq_debugfs_unregister_hctx(hctx);
2264                 blk_mq_exit_hctx(q, set, hctx, i);
2265         }
2266 }
2267 
2268 static int blk_mq_hw_ctx_size(struct blk_mq_tag_set *tag_set)
2269 {
2270         int hw_ctx_size = sizeof(struct blk_mq_hw_ctx);
2271 
2272         BUILD_BUG_ON(ALIGN(offsetof(struct blk_mq_hw_ctx, srcu),
2273                            __alignof__(struct blk_mq_hw_ctx)) !=
2274                      sizeof(struct blk_mq_hw_ctx));
2275 
2276         if (tag_set->flags & BLK_MQ_F_BLOCKING)
2277                 hw_ctx_size += sizeof(struct srcu_struct);
2278 
2279         return hw_ctx_size;
2280 }
2281 
2282 static int blk_mq_init_hctx(struct request_queue *q,
2283                 struct blk_mq_tag_set *set,
2284                 struct blk_mq_hw_ctx *hctx, unsigned hctx_idx)
2285 {
2286         hctx->queue_num = hctx_idx;
2287 
2288         cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD, &hctx->cpuhp_dead);
2289 
2290         hctx->tags = set->tags[hctx_idx];
2291 
2292         if (set->ops->init_hctx &&
2293             set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
2294                 goto unregister_cpu_notifier;
2295 
2296         if (blk_mq_init_request(set, hctx->fq->flush_rq, hctx_idx,
2297                                 hctx->numa_node))
2298                 goto exit_hctx;
2299         return 0;
2300 
2301  exit_hctx:
2302         if (set->ops->exit_hctx)
2303                 set->ops->exit_hctx(hctx, hctx_idx);
2304  unregister_cpu_notifier:
2305         blk_mq_remove_cpuhp(hctx);
2306         return -1;
2307 }
2308 
2309 static struct blk_mq_hw_ctx *
2310 blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set,
2311                 int node)
2312 {
2313         struct blk_mq_hw_ctx *hctx;
2314         gfp_t gfp = GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY;
2315 
2316         hctx = kzalloc_node(blk_mq_hw_ctx_size(set), gfp, node);
2317         if (!hctx)
2318                 goto fail_alloc_hctx;
2319 
2320         if (!zalloc_cpumask_var_node(&hctx->cpumask, gfp, node))
2321                 goto free_hctx;
2322 
2323         atomic_set(&hctx->nr_active, 0);
2324         if (node == NUMA_NO_NODE)
2325                 node = set->numa_node;
2326         hctx->numa_node = node;
2327 
2328         INIT_DELAYED_WORK(&hctx->run_work, blk_mq_run_work_fn);
2329         spin_lock_init(&hctx->lock);
2330         INIT_LIST_HEAD(&hctx->dispatch);
2331         hctx->queue = q;
2332         hctx->flags = set->flags & ~BLK_MQ_F_TAG_SHARED;
2333 
2334         INIT_LIST_HEAD(&hctx->hctx_list);
2335 
2336         /*
2337          * Allocate space for all possible cpus to avoid allocation at
2338          * runtime
2339          */
2340         hctx->ctxs = kmalloc_array_node(nr_cpu_ids, sizeof(void *),
2341                         gfp, node);
2342         if (!hctx->ctxs)
2343                 goto free_cpumask;
2344 
2345         if (sbitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8),
2346                                 gfp, node))
2347                 goto free_ctxs;
2348         hctx->nr_ctx = 0;
2349 
2350         spin_lock_init(&hctx->dispatch_wait_lock);
2351         init_waitqueue_func_entry(&hctx->dispatch_wait, blk_mq_dispatch_wake);
2352         INIT_LIST_HEAD(&hctx->dispatch_wait.entry);
2353 
2354         hctx->fq = blk_alloc_flush_queue(q, hctx->numa_node, set->cmd_size,
2355                         gfp);
2356         if (!hctx->fq)
2357                 goto free_bitmap;
2358 
2359         if (hctx->flags & BLK_MQ_F_BLOCKING)
2360                 init_srcu_struct(hctx->srcu);
2361         blk_mq_hctx_kobj_init(hctx);
2362 
2363         return hctx;
2364 
2365  free_bitmap:
2366         sbitmap_free(&hctx->ctx_map);
2367  free_ctxs:
2368         kfree(hctx->ctxs);
2369  free_cpumask:
2370         free_cpumask_var(hctx->cpumask);
2371  free_hctx:
2372         kfree(hctx);
2373  fail_alloc_hctx:
2374         return NULL;
2375 }
2376 
2377 static void blk_mq_init_cpu_queues(struct request_queue *q,
2378                                    unsigned int nr_hw_queues)
2379 {
2380         struct blk_mq_tag_set *set = q->tag_set;
2381         unsigned int i, j;
2382 
2383         for_each_possible_cpu(i) {
2384                 struct blk_mq_ctx *__ctx = per_cpu_ptr(q->queue_ctx, i);
2385                 struct blk_mq_hw_ctx *hctx;
2386                 int k;
2387 
2388                 __ctx->cpu = i;
2389                 spin_lock_init(&__ctx->lock);
2390                 for (k = HCTX_TYPE_DEFAULT; k < HCTX_MAX_TYPES; k++)
2391                         INIT_LIST_HEAD(&__ctx->rq_lists[k]);
2392 
2393                 __ctx->queue = q;
2394 
2395                 /*
2396                  * Set local node, IFF we have more than one hw queue. If
2397                  * not, we remain on the home node of the device
2398                  */
2399                 for (j = 0; j < set->nr_maps; j++) {
2400                         hctx = blk_mq_map_queue_type(q, j, i);
2401                         if (nr_hw_queues > 1 && hctx->numa_node == NUMA_NO_NODE)
2402                                 hctx->numa_node = local_memory_node(cpu_to_node(i));
2403                 }
2404         }
2405 }
2406 
2407 static bool __blk_mq_alloc_rq_map(struct blk_mq_tag_set *set, int hctx_idx)
2408 {
2409         int ret = 0;
2410 
2411         set->tags[hctx_idx] = blk_mq_alloc_rq_map(set, hctx_idx,
2412                                         set->queue_depth, set->reserved_tags);
2413         if (!set->tags[hctx_idx])
2414                 return false;
2415 
2416         ret = blk_mq_alloc_rqs(set, set->tags[hctx_idx], hctx_idx,
2417                                 set->queue_depth);
2418         if (!ret)
2419                 return true;
2420 
2421         blk_mq_free_rq_map(set->tags[hctx_idx]);
2422         set->tags[hctx_idx] = NULL;
2423         return false;
2424 }
2425 
2426 static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set,
2427                                          unsigned int hctx_idx)
2428 {
2429         if (set->tags && set->tags[hctx_idx]) {
2430                 blk_mq_free_rqs(set, set->tags[hctx_idx], hctx_idx);
2431                 blk_mq_free_rq_map(set->tags[hctx_idx]);
2432                 set->tags[hctx_idx] = NULL;
2433         }
2434 }
2435 
2436 static void blk_mq_map_swqueue(struct request_queue *q)
2437 {
2438         unsigned int i, j, hctx_idx;
2439         struct blk_mq_hw_ctx *hctx;
2440         struct blk_mq_ctx *ctx;
2441         struct blk_mq_tag_set *set = q->tag_set;
2442 
2443         queue_for_each_hw_ctx(q, hctx, i) {
2444                 cpumask_clear(hctx->cpumask);
2445                 hctx->nr_ctx = 0;
2446                 hctx->dispatch_from = NULL;
2447         }
2448 
2449         /*
2450          * Map software to hardware queues.
2451          *
2452          * If the cpu isn't present, the cpu is mapped to first hctx.
2453          */
2454         for_each_possible_cpu(i) {
2455                 hctx_idx = set->map[HCTX_TYPE_DEFAULT].mq_map[i];
2456                 /* unmapped hw queue can be remapped after CPU topo changed */
2457                 if (!set->tags[hctx_idx] &&
2458                     !__blk_mq_alloc_rq_map(set, hctx_idx)) {
2459                         /*
2460                          * If tags initialization fail for some hctx,
2461                          * that hctx won't be brought online.  In this
2462                          * case, remap the current ctx to hctx[0] which
2463                          * is guaranteed to always have tags allocated
2464                          */
2465                         set->map[HCTX_TYPE_DEFAULT].mq_map[i] = 0;
2466                 }
2467 
2468                 ctx = per_cpu_ptr(q->queue_ctx, i);
2469                 for (j = 0; j < set->nr_maps; j++) {
2470                         if (!set->map[j].nr_queues) {
2471                                 ctx->hctxs[j] = blk_mq_map_queue_type(q,
2472                                                 HCTX_TYPE_DEFAULT, i);
2473                                 continue;
2474                         }
2475 
2476                         hctx = blk_mq_map_queue_type(q, j, i);
2477                         ctx->hctxs[j] = hctx;
2478                         /*
2479                          * If the CPU is already set in the mask, then we've
2480                          * mapped this one already. This can happen if
2481                          * devices share queues across queue maps.
2482                          */
2483                         if (cpumask_test_cpu(i, hctx->cpumask))
2484                                 continue;
2485 
2486                         cpumask_set_cpu(i, hctx->cpumask);
2487                         hctx->type = j;
2488                         ctx->index_hw[hctx->type] = hctx->nr_ctx;
2489                         hctx->ctxs[hctx->nr_ctx++] = ctx;
2490 
2491                         /*
2492                          * If the nr_ctx type overflows, we have exceeded the
2493                          * amount of sw queues we can support.
2494                          */
2495                         BUG_ON(!hctx->nr_ctx);
2496                 }
2497 
2498                 for (; j < HCTX_MAX_TYPES; j++)
2499                         ctx->hctxs[j] = blk_mq_map_queue_type(q,
2500                                         HCTX_TYPE_DEFAULT, i);
2501         }
2502 
2503         queue_for_each_hw_ctx(q, hctx, i) {
2504                 /*
2505                  * If no software queues are mapped to this hardware queue,
2506                  * disable it and free the request entries.
2507                  */
2508                 if (!hctx->nr_ctx) {
2509                         /* Never unmap queue 0.  We need it as a
2510                          * fallback in case of a new remap fails
2511                          * allocation
2512                          */
2513                         if (i && set->tags[i])
2514                                 blk_mq_free_map_and_requests(set, i);
2515 
2516                         hctx->tags = NULL;
2517                         continue;
2518                 }
2519 
2520                 hctx->tags = set->tags[i];
2521                 WARN_ON(!hctx->tags);
2522 
2523                 /*
2524                  * Set the map size to the number of mapped software queues.
2525                  * This is more accurate and more efficient than looping
2526                  * over all possibly mapped software queues.
2527                  */
2528                 sbitmap_resize(&hctx->ctx_map, hctx->nr_ctx);
2529 
2530                 /*
2531                  * Initialize batch roundrobin counts
2532                  */
2533                 hctx->next_cpu = blk_mq_first_mapped_cpu(hctx);
2534                 hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
2535         }
2536 }
2537 
2538 /*
2539  * Caller needs to ensure that we're either frozen/quiesced, or that
2540  * the queue isn't live yet.
2541  */
2542 static void queue_set_hctx_shared(struct request_queue *q, bool shared)
2543 {
2544         struct blk_mq_hw_ctx *hctx;
2545         int i;
2546 
2547         queue_for_each_hw_ctx(q, hctx, i) {
2548                 if (shared)
2549                         hctx->flags |= BLK_MQ_F_TAG_SHARED;
2550                 else
2551                         hctx->flags &= ~BLK_MQ_F_TAG_SHARED;
2552         }
2553 }
2554 
2555 static void blk_mq_update_tag_set_depth(struct blk_mq_tag_set *set,
2556                                         bool shared)
2557 {
2558         struct request_queue *q;
2559 
2560         lockdep_assert_held(&set->tag_list_lock);
2561 
2562         list_for_each_entry(q, &set->tag_list, tag_set_list) {
2563                 blk_mq_freeze_queue(q);
2564                 queue_set_hctx_shared(q, shared);
2565                 blk_mq_unfreeze_queue(q);
2566         }
2567 }
2568 
2569 static void blk_mq_del_queue_tag_set(struct request_queue *q)
2570 {
2571         struct blk_mq_tag_set *set = q->tag_set;
2572 
2573         mutex_lock(&set->tag_list_lock);
2574         list_del_rcu(&q->tag_set_list);
2575         if (list_is_singular(&set->tag_list)) {
2576                 /* just transitioned to unshared */
2577                 set->flags &= ~BLK_MQ_F_TAG_SHARED;
2578                 /* update existing queue */
2579                 blk_mq_update_tag_set_depth(set, false);
2580         }
2581         mutex_unlock(&set->tag_list_lock);
2582         INIT_LIST_HEAD(&q->tag_set_list);
2583 }
2584 
2585 static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
2586                                      struct request_queue *q)
2587 {
2588         mutex_lock(&set->tag_list_lock);
2589 
2590         /*
2591          * Check to see if we're transitioning to shared (from 1 to 2 queues).
2592          */
2593         if (!list_empty(&set->tag_list) &&
2594             !(set->flags & BLK_MQ_F_TAG_SHARED)) {
2595                 set->flags |= BLK_MQ_F_TAG_SHARED;
2596                 /* update existing queue */
2597                 blk_mq_update_tag_set_depth(set, true);
2598         }
2599         if (set->flags & BLK_MQ_F_TAG_SHARED)
2600                 queue_set_hctx_shared(q, true);
2601         list_add_tail_rcu(&q->tag_set_list, &set->tag_list);
2602 
2603         mutex_unlock(&set->tag_list_lock);
2604 }
2605 
2606 /* All allocations will be freed in release handler of q->mq_kobj */
2607 static int blk_mq_alloc_ctxs(struct request_queue *q)
2608 {
2609         struct blk_mq_ctxs *ctxs;
2610         int cpu;
2611 
2612         ctxs = kzalloc(sizeof(*ctxs), GFP_KERNEL);
2613         if (!ctxs)
2614                 return -ENOMEM;
2615 
2616         ctxs->queue_ctx = alloc_percpu(struct blk_mq_ctx);
2617         if (!ctxs->queue_ctx)
2618                 goto fail;
2619 
2620         for_each_possible_cpu(cpu) {
2621                 struct blk_mq_ctx *ctx = per_cpu_ptr(ctxs->queue_ctx, cpu);
2622                 ctx->ctxs = ctxs;
2623         }
2624 
2625         q->mq_kobj = &ctxs->kobj;
2626         q->queue_ctx = ctxs->queue_ctx;
2627 
2628         return 0;
2629  fail:
2630         kfree(ctxs);
2631         return -ENOMEM;
2632 }
2633 
2634 /*
2635  * It is the actual release handler for mq, but we do it from
2636  * request queue's release handler for avoiding use-after-free
2637  * and headache because q->mq_kobj shouldn't have been introduced,
2638  * but we can't group ctx/kctx kobj without it.
2639  */
2640 void blk_mq_release(struct request_queue *q)
2641 {
2642         struct blk_mq_hw_ctx *hctx, *next;
2643         int i;
2644 
2645         queue_for_each_hw_ctx(q, hctx, i)
2646                 WARN_ON_ONCE(hctx && list_empty(&hctx->hctx_list));
2647 
2648         /* all hctx are in .unused_hctx_list now */
2649         list_for_each_entry_safe(hctx, next, &q->unused_hctx_list, hctx_list) {
2650                 list_del_init(&hctx->hctx_list);
2651                 kobject_put(&hctx->kobj);
2652         }
2653 
2654         kfree(q->queue_hw_ctx);
2655 
2656         /*
2657          * release .mq_kobj and sw queue's kobject now because
2658          * both share lifetime with request queue.
2659          */
2660         blk_mq_sysfs_deinit(q);
2661 }
2662 
2663 struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
2664 {
2665         struct request_queue *uninit_q, *q;
2666 
2667         uninit_q = blk_alloc_queue_node(GFP_KERNEL, set->numa_node);
2668         if (!uninit_q)
2669                 return ERR_PTR(-ENOMEM);
2670 
2671         /*
2672          * Initialize the queue without an elevator. device_add_disk() will do
2673          * the initialization.
2674          */
2675         q = blk_mq_init_allocated_queue(set, uninit_q, false);
2676         if (IS_ERR(q))
2677                 blk_cleanup_queue(uninit_q);
2678 
2679         return q;
2680 }
2681 EXPORT_SYMBOL(blk_mq_init_queue);
2682 
2683 /*
2684  * Helper for setting up a queue with mq ops, given queue depth, and
2685  * the passed in mq ops flags.
2686  */
2687 struct request_queue *blk_mq_init_sq_queue(struct blk_mq_tag_set *set,
2688                                            const struct blk_mq_ops *ops,
2689                                            unsigned int queue_depth,
2690                                            unsigned int set_flags)
2691 {
2692         struct request_queue *q;
2693         int ret;
2694 
2695         memset(set, 0, sizeof(*set));
2696         set->ops = ops;
2697         set->nr_hw_queues = 1;
2698         set->nr_maps = 1;
2699         set->queue_depth = queue_depth;
2700         set->numa_node = NUMA_NO_NODE;
2701         set->flags = set_flags;
2702 
2703         ret = blk_mq_alloc_tag_set(set);
2704         if (ret)
2705                 return ERR_PTR(ret);
2706 
2707         q = blk_mq_init_queue(set);
2708         if (IS_ERR(q)) {
2709                 blk_mq_free_tag_set(set);
2710                 return q;
2711         }
2712 
2713         return q;
2714 }
2715 EXPORT_SYMBOL(blk_mq_init_sq_queue);
2716 
2717 static struct blk_mq_hw_ctx *blk_mq_alloc_and_init_hctx(
2718                 struct blk_mq_tag_set *set, struct request_queue *q,
2719                 int hctx_idx, int node)
2720 {
2721         struct blk_mq_hw_ctx *hctx = NULL, *tmp;
2722 
2723         /* reuse dead hctx first */
2724         spin_lock(&q->unused_hctx_lock);
2725         list_for_each_entry(tmp, &q->unused_hctx_list, hctx_list) {
2726                 if (tmp->numa_node == node) {
2727                         hctx = tmp;
2728                         break;
2729                 }
2730         }
2731         if (hctx)
2732                 list_del_init(&hctx->hctx_list);
2733         spin_unlock(&q->unused_hctx_lock);
2734 
2735         if (!hctx)
2736                 hctx = blk_mq_alloc_hctx(q, set, node);
2737         if (!hctx)
2738                 goto fail;
2739 
2740         if (blk_mq_init_hctx(q, set, hctx, hctx_idx))
2741                 goto free_hctx;
2742 
2743         return hctx;
2744 
2745  free_hctx:
2746         kobject_put(&hctx->kobj);
2747  fail:
2748         return NULL;
2749 }
2750 
2751 static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
2752                                                 struct request_queue *q)
2753 {
2754         int i, j, end;
2755         struct blk_mq_hw_ctx **hctxs = q->queue_hw_ctx;
2756 
2757         if (q->nr_hw_queues < set->nr_hw_queues) {
2758                 struct blk_mq_hw_ctx **new_hctxs;
2759 
2760                 new_hctxs = kcalloc_node(set->nr_hw_queues,
2761                                        sizeof(*new_hctxs), GFP_KERNEL,
2762                                        set->numa_node);
2763                 if (!new_hctxs)
2764                         return;
2765                 if (hctxs)
2766                         memcpy(new_hctxs, hctxs, q->nr_hw_queues *
2767                                sizeof(*hctxs));
2768                 q->queue_hw_ctx = new_hctxs;
2769                 kfree(hctxs);
2770                 hctxs = new_hctxs;
2771         }
2772 
2773         /* protect against switching io scheduler  */
2774         mutex_lock(&q->sysfs_lock);
2775         for (i = 0; i < set->nr_hw_queues; i++) {
2776                 int node;
2777                 struct blk_mq_hw_ctx *hctx;
2778 
2779                 node = blk_mq_hw_queue_to_node(&set->map[HCTX_TYPE_DEFAULT], i);
2780                 /*
2781                  * If the hw queue has been mapped to another numa node,
2782                  * we need to realloc the hctx. If allocation fails, fallback
2783                  * to use the previous one.
2784                  */
2785                 if (hctxs[i] && (hctxs[i]->numa_node == node))
2786                         continue;
2787 
2788                 hctx = blk_mq_alloc_and_init_hctx(set, q, i, node);
2789                 if (hctx) {
2790                         if (hctxs[i])
2791                                 blk_mq_exit_hctx(q, set, hctxs[i], i);
2792                         hctxs[i] = hctx;
2793                 } else {
2794                         if (hctxs[i])
2795                                 pr_warn("Allocate new hctx on node %d fails,\
2796                                                 fallback to previous one on node %d\n",
2797                                                 node, hctxs[i]->numa_node);
2798                         else
2799                                 break;
2800                 }
2801         }
2802         /*
2803          * Increasing nr_hw_queues fails. Free the newly allocated
2804          * hctxs and keep the previous q->nr_hw_queues.
2805          */
2806         if (i != set->nr_hw_queues) {
2807                 j = q->nr_hw_queues;
2808                 end = i;
2809         } else {
2810                 j = i;
2811                 end = q->nr_hw_queues;
2812                 q->nr_hw_queues = set->nr_hw_queues;
2813         }
2814 
2815         for (; j < end; j++) {
2816                 struct blk_mq_hw_ctx *hctx = hctxs[j];
2817 
2818                 if (hctx) {
2819                         if (hctx->tags)
2820                                 blk_mq_free_map_and_requests(set, j);
2821                         blk_mq_exit_hctx(q, set, hctx, j);
2822                         hctxs[j] = NULL;
2823                 }
2824         }
2825         mutex_unlock(&q->sysfs_lock);
2826 }
2827 
2828 struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
2829                                                   struct request_queue *q,
2830                                                   bool elevator_init)
2831 {
2832         /* mark the queue as mq asap */
2833         q->mq_ops = set->ops;
2834 
2835         q->poll_cb = blk_stat_alloc_callback(blk_mq_poll_stats_fn,
2836                                              blk_mq_poll_stats_bkt,
2837                                              BLK_MQ_POLL_STATS_BKTS, q);
2838         if (!q->poll_cb)
2839                 goto err_exit;
2840 
2841         if (blk_mq_alloc_ctxs(q))
2842                 goto err_poll;
2843 
2844         /* init q->mq_kobj and sw queues' kobjects */
2845         blk_mq_sysfs_init(q);
2846 
2847         INIT_LIST_HEAD(&q->unused_hctx_list);
2848         spin_lock_init(&q->unused_hctx_lock);
2849 
2850         blk_mq_realloc_hw_ctxs(set, q);
2851         if (!q->nr_hw_queues)
2852                 goto err_hctxs;
2853 
2854         INIT_WORK(&q->timeout_work, blk_mq_timeout_work);
2855         blk_queue_rq_timeout(q, set->timeout ? set->timeout : 30 * HZ);
2856 
2857         q->tag_set = set;
2858 
2859         q->queue_flags |= QUEUE_FLAG_MQ_DEFAULT;
2860         if (set->nr_maps > HCTX_TYPE_POLL &&
2861             set->map[HCTX_TYPE_POLL].nr_queues)
2862                 blk_queue_flag_set(QUEUE_FLAG_POLL, q);
2863 
2864         q->sg_reserved_size = INT_MAX;
2865 
2866         INIT_DELAYED_WORK(&q->requeue_work, blk_mq_requeue_work);
2867         INIT_LIST_HEAD(&q->requeue_list);
2868         spin_lock_init(&q->requeue_lock);
2869 
2870         blk_queue_make_request(q, blk_mq_make_request);
2871 
2872         /*
2873          * Do this after blk_queue_make_request() overrides it...
2874          */
2875         q->nr_requests = set->queue_depth;
2876 
2877         /*
2878          * Default to classic polling
2879          */
2880         q->poll_nsec = BLK_MQ_POLL_CLASSIC;
2881 
2882         blk_mq_init_cpu_queues(q, set->nr_hw_queues);
2883         blk_mq_add_queue_tag_set(set, q);
2884         blk_mq_map_swqueue(q);
2885 
2886         if (elevator_init)
2887                 elevator_init_mq(q);
2888 
2889         return q;
2890 
2891 err_hctxs:
2892         kfree(q->queue_hw_ctx);
2893         q->nr_hw_queues = 0;
2894         blk_mq_sysfs_deinit(q);
2895 err_poll:
2896         blk_stat_free_callback(q->poll_cb);
2897         q->poll_cb = NULL;
2898 err_exit:
2899         q->mq_ops = NULL;
2900         return ERR_PTR(-ENOMEM);
2901 }
2902 EXPORT_SYMBOL(blk_mq_init_allocated_queue);
2903 
2904 /* tags can _not_ be used after returning from blk_mq_exit_queue */
2905 void blk_mq_exit_queue(struct request_queue *q)
2906 {
2907         struct blk_mq_tag_set   *set = q->tag_set;
2908 
2909         blk_mq_del_queue_tag_set(q);
2910         blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);
2911 }
2912 
2913 static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
2914 {
2915         int i;
2916 
2917         for (i = 0; i < set->nr_hw_queues; i++)
2918                 if (!__blk_mq_alloc_rq_map(set, i))
2919                         goto out_unwind;
2920 
2921         return 0;
2922 
2923 out_unwind:
2924         while (--i >= 0)
2925                 blk_mq_free_rq_map(set->tags[i]);
2926 
2927         return -ENOMEM;
2928 }
2929 
2930 /*
2931  * Allocate the request maps associated with this tag_set. Note that this
2932  * may reduce the depth asked for, if memory is tight. set->queue_depth
2933  * will be updated to reflect the allocated depth.
2934  */
2935 static int blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
2936 {
2937         unsigned int depth;
2938         int err;
2939 
2940         depth = set->queue_depth;
2941         do {
2942                 err = __blk_mq_alloc_rq_maps(set);
2943                 if (!err)
2944                         break;
2945 
2946                 set->queue_depth >>= 1;
2947                 if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN) {
2948                         err = -ENOMEM;
2949                         break;
2950                 }
2951         } while (set->queue_depth);
2952 
2953         if (!set->queue_depth || err) {
2954                 pr_err("blk-mq: failed to allocate request map\n");
2955                 return -ENOMEM;
2956         }
2957 
2958         if (depth != set->queue_depth)
2959                 pr_info("blk-mq: reduced tag depth (%u -> %u)\n",
2960                                                 depth, set->queue_depth);
2961 
2962         return 0;
2963 }
2964 
2965 static int blk_mq_update_queue_map(struct blk_mq_tag_set *set)
2966 {
2967         /*
2968          * blk_mq_map_queues() and multiple .map_queues() implementations
2969          * expect that set->map[HCTX_TYPE_DEFAULT].nr_queues is set to the
2970          * number of hardware queues.
2971          */
2972         if (set->nr_maps == 1)
2973                 set->map[HCTX_TYPE_DEFAULT].nr_queues = set->nr_hw_queues;
2974 
2975         if (set->ops->map_queues && !is_kdump_kernel()) {
2976                 int i;
2977 
2978                 /*
2979                  * transport .map_queues is usually done in the following
2980                  * way:
2981                  *
2982                  * for (queue = 0; queue < set->nr_hw_queues; queue++) {
2983                  *      mask = get_cpu_mask(queue)
2984                  *      for_each_cpu(cpu, mask)
2985                  *              set->map[x].mq_map[cpu] = queue;
2986                  * }
2987                  *
2988                  * When we need to remap, the table has to be cleared for
2989                  * killing stale mapping since one CPU may not be mapped
2990                  * to any hw queue.
2991                  */
2992                 for (i = 0; i < set->nr_maps; i++)
2993                         blk_mq_clear_mq_map(&set->map[i]);
2994 
2995                 return set->ops->map_queues(set);
2996         } else {
2997                 BUG_ON(set->nr_maps > 1);
2998                 return blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
2999         }
3000 }
3001 
3002 static int blk_mq_realloc_tag_set_tags(struct blk_mq_tag_set *set,
3003                                   int cur_nr_hw_queues, int new_nr_hw_queues)
3004 {
3005         struct blk_mq_tags **new_tags;
3006 
3007         if (cur_nr_hw_queues >= new_nr_hw_queues)
3008                 return 0;
3009 
3010         new_tags = kcalloc_node(new_nr_hw_queues, sizeof(struct blk_mq_tags *),
3011                                 GFP_KERNEL, set->numa_node);
3012         if (!new_tags)
3013                 return -ENOMEM;
3014 
3015         if (set->tags)
3016                 memcpy(new_tags, set->tags, cur_nr_hw_queues *
3017                        sizeof(*set->tags));
3018         kfree(set->tags);
3019         set->tags = new_tags;
3020         set->nr_hw_queues = new_nr_hw_queues;
3021 
3022         return 0;
3023 }
3024 
3025 /*
3026  * Alloc a tag set to be associated with one or more request queues.
3027  * May fail with EINVAL for various error conditions. May adjust the
3028  * requested depth down, if it's too large. In that case, the set
3029  * value will be stored in set->queue_depth.
3030  */
3031 int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
3032 {
3033         int i, ret;
3034 
3035         BUILD_BUG_ON(BLK_MQ_MAX_DEPTH > 1 << BLK_MQ_UNIQUE_TAG_BITS);
3036 
3037         if (!set->nr_hw_queues)
3038                 return -EINVAL;
3039         if (!set->queue_depth)
3040                 return -EINVAL;
3041         if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN)
3042                 return -EINVAL;
3043 
3044         if (!set->ops->queue_rq)
3045                 return -EINVAL;
3046 
3047         if (!set->ops->get_budget ^ !set->ops->put_budget)
3048                 return -EINVAL;
3049 
3050         if (set->queue_depth > BLK_MQ_MAX_DEPTH) {
3051                 pr_info("blk-mq: reduced tag depth to %u\n",
3052                         BLK_MQ_MAX_DEPTH);
3053                 set->queue_depth = BLK_MQ_MAX_DEPTH;
3054         }
3055 
3056         if (!set->nr_maps)
3057                 set->nr_maps = 1;
3058         else if (set->nr_maps > HCTX_MAX_TYPES)
3059                 return -EINVAL;
3060 
3061         /*
3062          * If a crashdump is active, then we are potentially in a very
3063          * memory constrained environment. Limit us to 1 queue and
3064          * 64 tags to prevent using too much memory.
3065          */
3066         if (is_kdump_kernel()) {
3067                 set->nr_hw_queues = 1;
3068                 set->nr_maps = 1;
3069                 set->queue_depth = min(64U, set->queue_depth);
3070         }
3071         /*
3072          * There is no use for more h/w queues than cpus if we just have
3073          * a single map
3074          */
3075         if (set->nr_maps == 1 && set->nr_hw_queues > nr_cpu_ids)
3076                 set->nr_hw_queues = nr_cpu_ids;
3077 
3078         if (blk_mq_realloc_tag_set_tags(set, 0, set->nr_hw_queues) < 0)
3079                 return -ENOMEM;
3080 
3081         ret = -ENOMEM;
3082         for (i = 0; i < set->nr_maps; i++) {
3083                 set->map[i].mq_map = kcalloc_node(nr_cpu_ids,
3084                                                   sizeof(set->map[i].mq_map[0]),
3085                                                   GFP_KERNEL, set->numa_node);
3086                 if (!set->map[i].mq_map)
3087                         goto out_free_mq_map;
3088                 set->map[i].nr_queues = is_kdump_kernel() ? 1 : set->nr_hw_queues;
3089         }
3090 
3091         ret = blk_mq_update_queue_map(set);
3092         if (ret)
3093                 goto out_free_mq_map;
3094 
3095         ret = blk_mq_alloc_rq_maps(set);
3096         if (ret)
3097                 goto out_free_mq_map;
3098 
3099         mutex_init(&set->tag_list_lock);
3100         INIT_LIST_HEAD(&set->tag_list);
3101 
3102         return 0;
3103 
3104 out_free_mq_map:
3105         for (i = 0; i < set->nr_maps; i++) {
3106                 kfree(set->map[i].mq_map);
3107                 set->map[i].mq_map = NULL;
3108         }
3109         kfree(set->tags);
3110         set->tags = NULL;
3111         return ret;
3112 }
3113 EXPORT_SYMBOL(blk_mq_alloc_tag_set);
3114 
3115 void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
3116 {
3117         int i, j;
3118 
3119         for (i = 0; i < set->nr_hw_queues; i++)
3120                 blk_mq_free_map_and_requests(set, i);
3121 
3122         for (j = 0; j < set->nr_maps; j++) {
3123                 kfree(set->map[j].mq_map);
3124                 set->map[j].mq_map = NULL;
3125         }
3126 
3127         kfree(set->tags);
3128         set->tags = NULL;
3129 }
3130 EXPORT_SYMBOL(blk_mq_free_tag_set);
3131 
3132 int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
3133 {
3134         struct blk_mq_tag_set *set = q->tag_set;
3135         struct blk_mq_hw_ctx *hctx;
3136         int i, ret;
3137 
3138         if (!set)
3139                 return -EINVAL;
3140 
3141         if (q->nr_requests == nr)
3142                 return 0;
3143 
3144         blk_mq_freeze_queue(q);
3145         blk_mq_quiesce_queue(q);
3146 
3147         ret = 0;
3148         queue_for_each_hw_ctx(q, hctx, i) {
3149                 if (!hctx->tags)
3150                         continue;
3151                 /*
3152                  * If we're using an MQ scheduler, just update the scheduler
3153                  * queue depth. This is similar to what the old code would do.
3154                  */
3155                 if (!hctx->sched_tags) {
3156                         ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
3157                                                         false);
3158                 } else {
3159                         ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
3160                                                         nr, true);
3161                 }
3162                 if (ret)
3163                         break;
3164                 if (q->elevator && q->elevator->type->ops.depth_updated)
3165                         q->elevator->type->ops.depth_updated(hctx);
3166         }
3167 
3168         if (!ret)
3169                 q->nr_requests = nr;
3170 
3171         blk_mq_unquiesce_queue(q);
3172         blk_mq_unfreeze_queue(q);
3173 
3174         return ret;
3175 }
3176 
3177 /*
3178  * request_queue and elevator_type pair.
3179  * It is just used by __blk_mq_update_nr_hw_queues to cache
3180  * the elevator_type associated with a request_queue.
3181  */
3182 struct blk_mq_qe_pair {
3183         struct list_head node;
3184         struct request_queue *q;
3185         struct elevator_type *type;
3186 };
3187 
3188 /*
3189  * Cache the elevator_type in qe pair list and switch the
3190  * io scheduler to 'none'
3191  */
3192 static bool blk_mq_elv_switch_none(struct list_head *head,
3193                 struct request_queue *q)
3194 {
3195         struct blk_mq_qe_pair *qe;
3196 
3197         if (!q->elevator)
3198                 return true;
3199 
3200         qe = kmalloc(sizeof(*qe), GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY);
3201         if (!qe)
3202                 return false;
3203 
3204         INIT_LIST_HEAD(&qe->node);
3205         qe->q = q;
3206         qe->type = q->elevator->type;
3207         list_add(&qe->node, head);
3208 
3209         mutex_lock(&q->sysfs_lock);
3210         /*
3211          * After elevator_switch_mq, the previous elevator_queue will be
3212          * released by elevator_release. The reference of the io scheduler
3213          * module get by elevator_get will also be put. So we need to get
3214          * a reference of the io scheduler module here to prevent it to be
3215          * removed.
3216          */
3217         __module_get(qe->type->elevator_owner);
3218         elevator_switch_mq(q, NULL);
3219         mutex_unlock(&q->sysfs_lock);
3220 
3221         return true;
3222 }
3223 
3224 static void blk_mq_elv_switch_back(struct list_head *head,
3225                 struct request_queue *q)
3226 {
3227         struct blk_mq_qe_pair *qe;
3228         struct elevator_type *t = NULL;
3229 
3230         list_for_each_entry(qe, head, node)
3231                 if (qe->q == q) {
3232                         t = qe->type;
3233                         break;
3234                 }
3235 
3236         if (!t)
3237                 return;
3238 
3239         list_del(&qe->node);
3240         kfree(qe);
3241 
3242         mutex_lock(&q->sysfs_lock);
3243         elevator_switch_mq(q, t);
3244         mutex_unlock(&q->sysfs_lock);
3245 }
3246 
3247 static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
3248                                                         int nr_hw_queues)
3249 {
3250         struct request_queue *q;
3251         LIST_HEAD(head);
3252         int prev_nr_hw_queues;
3253 
3254         lockdep_assert_held(&set->tag_list_lock);
3255 
3256         if (set->nr_maps == 1 && nr_hw_queues > nr_cpu_ids)
3257                 nr_hw_queues = nr_cpu_ids;
3258         if (nr_hw_queues < 1 || nr_hw_queues == set->nr_hw_queues)
3259                 return;
3260 
3261         list_for_each_entry(q, &set->tag_list, tag_set_list)
3262                 blk_mq_freeze_queue(q);
3263         /*
3264          * Switch IO scheduler to 'none', cleaning up the data associated
3265          * with the previous scheduler. We will switch back once we are done
3266          * updating the new sw to hw queue mappings.
3267          */
3268         list_for_each_entry(q, &set->tag_list, tag_set_list)
3269                 if (!blk_mq_elv_switch_none(&head, q))
3270                         goto switch_back;
3271 
3272         list_for_each_entry(q, &set->tag_list, tag_set_list) {
3273                 blk_mq_debugfs_unregister_hctxs(q);
3274                 blk_mq_sysfs_unregister(q);
3275         }
3276 
3277         if (blk_mq_realloc_tag_set_tags(set, set->nr_hw_queues, nr_hw_queues) <
3278             0)
3279                 goto reregister;
3280 
3281         prev_nr_hw_queues = set->nr_hw_queues;
3282         set->nr_hw_queues = nr_hw_queues;
3283         blk_mq_update_queue_map(set);
3284 fallback:
3285         list_for_each_entry(q, &set->tag_list, tag_set_list) {
3286                 blk_mq_realloc_hw_ctxs(set, q);
3287                 if (q->nr_hw_queues != set->nr_hw_queues) {
3288                         pr_warn("Increasing nr_hw_queues to %d fails, fallback to %d\n",
3289                                         nr_hw_queues, prev_nr_hw_queues);
3290                         set->nr_hw_queues = prev_nr_hw_queues;
3291                         blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
3292                         goto fallback;
3293                 }
3294                 blk_mq_map_swqueue(q);
3295         }
3296 
3297 reregister:
3298         list_for_each_entry(q, &set->tag_list, tag_set_list) {
3299                 blk_mq_sysfs_register(q);
3300                 blk_mq_debugfs_register_hctxs(q);
3301         }
3302 
3303 switch_back:
3304         list_for_each_entry(q, &set->tag_list, tag_set_list)
3305                 blk_mq_elv_switch_back(&head, q);
3306 
3307         list_for_each_entry(q, &set->tag_list, tag_set_list)
3308                 blk_mq_unfreeze_queue(q);
3309 }
3310 
3311 void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
3312 {
3313         mutex_lock(&set->tag_list_lock);
3314         __blk_mq_update_nr_hw_queues(set, nr_hw_queues);
3315         mutex_unlock(&set->tag_list_lock);
3316 }
3317 EXPORT_SYMBOL_GPL(blk_mq_update_nr_hw_queues);
3318 
3319 /* Enable polling stats and return whether they were already enabled. */
3320 static bool blk_poll_stats_enable(struct request_queue *q)
3321 {
3322         if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags) ||
3323             blk_queue_flag_test_and_set(QUEUE_FLAG_POLL_STATS, q))
3324                 return true;
3325         blk_stat_add_callback(q, q->poll_cb);
3326         return false;
3327 }
3328 
3329 static void blk_mq_poll_stats_start(struct request_queue *q)
3330 {
3331         /*
3332          * We don't arm the callback if polling stats are not enabled or the
3333          * callback is already active.
3334          */
3335         if (!test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags) ||
3336             blk_stat_is_active(q->poll_cb))
3337                 return;
3338 
3339         blk_stat_activate_msecs(q->poll_cb, 100);
3340 }
3341 
3342 static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb)
3343 {
3344         struct request_queue *q = cb->data;
3345         int bucket;
3346 
3347         for (bucket = 0; bucket < BLK_MQ_POLL_STATS_BKTS; bucket++) {
3348                 if (cb->stat[bucket].nr_samples)
3349                         q->poll_stat[bucket] = cb->stat[bucket];
3350         }
3351 }
3352 
3353 static unsigned long blk_mq_poll_nsecs(struct request_queue *q,
3354                                        struct blk_mq_hw_ctx *hctx,
3355                                        struct request *rq)
3356 {
3357         unsigned long ret = 0;
3358         int bucket;
3359 
3360         /*
3361          * If stats collection isn't on, don't sleep but turn it on for
3362          * future users
3363          */
3364         if (!blk_poll_stats_enable(q))
3365                 return 0;
3366 
3367         /*
3368          * As an optimistic guess, use half of the mean service time
3369          * for this type of request. We can (and should) make this smarter.
3370          * For instance, if the completion latencies are tight, we can
3371          * get closer than just half the mean. This is especially
3372          * important on devices where the completion latencies are longer
3373          * than ~10 usec. We do use the stats for the relevant IO size
3374          * if available which does lead to better estimates.
3375          */
3376         bucket = blk_mq_poll_stats_bkt(rq);
3377         if (bucket < 0)
3378                 return ret;
3379 
3380         if (q->poll_stat[bucket].nr_samples)
3381                 ret = (q->poll_stat[bucket].mean + 1) / 2;
3382 
3383         return ret;
3384 }
3385 
3386 static bool blk_mq_poll_hybrid_sleep(struct request_queue *q,
3387                                      struct blk_mq_hw_ctx *hctx,
3388                                      struct request *rq)
3389 {
3390         struct hrtimer_sleeper hs;
3391         enum hrtimer_mode mode;
3392         unsigned int nsecs;
3393         ktime_t kt;
3394 
3395         if (rq->rq_flags & RQF_MQ_POLL_SLEPT)
3396                 return false;
3397 
3398         /*
3399          * If we get here, hybrid polling is enabled. Hence poll_nsec can be:
3400          *
3401          *  0:  use half of prev avg
3402          * >0:  use this specific value
3403          */
3404         if (q->poll_nsec > 0)
3405                 nsecs = q->poll_nsec;
3406         else
3407                 nsecs = blk_mq_poll_nsecs(q, hctx, rq);
3408 
3409         if (!nsecs)
3410                 return false;
3411 
3412         rq->rq_flags |= RQF_MQ_POLL_SLEPT;
3413 
3414         /*
3415          * This will be replaced with the stats tracking code, using
3416          * 'avg_completion_time / 2' as the pre-sleep target.
3417          */
3418         kt = nsecs;
3419 
3420         mode = HRTIMER_MODE_REL;
3421         hrtimer_init_sleeper_on_stack(&hs, CLOCK_MONOTONIC, mode);
3422         hrtimer_set_expires(&hs.timer, kt);
3423 
3424         do {
3425                 if (blk_mq_rq_state(rq) == MQ_RQ_COMPLETE)
3426                         break;
3427                 set_current_state(TASK_UNINTERRUPTIBLE);
3428                 hrtimer_sleeper_start_expires(&hs, mode);
3429                 if (hs.task)
3430                         io_schedule();
3431                 hrtimer_cancel(&hs.timer);
3432                 mode = HRTIMER_MODE_ABS;
3433         } while (hs.task && !signal_pending(current));
3434 
3435         __set_current_state(TASK_RUNNING);
3436         destroy_hrtimer_on_stack(&hs.timer);
3437         return true;
3438 }
3439 
3440 static bool blk_mq_poll_hybrid(struct request_queue *q,
3441                                struct blk_mq_hw_ctx *hctx, blk_qc_t cookie)
3442 {
3443         struct request *rq;
3444 
3445         if (q->poll_nsec == BLK_MQ_POLL_CLASSIC)
3446                 return false;
3447 
3448         if (!blk_qc_t_is_internal(cookie))
3449                 rq = blk_mq_tag_to_rq(hctx->tags, blk_qc_t_to_tag(cookie));
3450         else {
3451                 rq = blk_mq_tag_to_rq(hctx->sched_tags, blk_qc_t_to_tag(cookie));
3452                 /*
3453                  * With scheduling, if the request has completed, we'll
3454                  * get a NULL return here, as we clear the sched tag when
3455                  * that happens. The request still remains valid, like always,
3456                  * so we should be safe with just the NULL check.
3457                  */
3458                 if (!rq)
3459                         return false;
3460         }
3461 
3462         return blk_mq_poll_hybrid_sleep(q, hctx, rq);
3463 }
3464 
3465 /**
3466  * blk_poll - poll for IO completions
3467  * @q:  the queue
3468  * @cookie: cookie passed back at IO submission time
3469  * @spin: whether to spin for completions
3470  *
3471  * Description:
3472  *    Poll for completions on the passed in queue. Returns number of
3473  *    completed entries found. If @spin is true, then blk_poll will continue
3474  *    looping until at least one completion is found, unless the task is
3475  *    otherwise marked running (or we need to reschedule).
3476  */
3477 int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin)
3478 {
3479         struct blk_mq_hw_ctx *hctx;
3480         long state;
3481 
3482         if (!blk_qc_t_valid(cookie) ||
3483             !test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
3484                 return 0;
3485 
3486         if (current->plug)
3487                 blk_flush_plug_list(current->plug, false);
3488 
3489         hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)];
3490 
3491         /*
3492          * If we sleep, have the caller restart the poll loop to reset
3493          * the state. Like for the other success return cases, the
3494          * caller is responsible for checking if the IO completed. If
3495          * the IO isn't complete, we'll get called again and will go
3496          * straight to the busy poll loop.
3497          */
3498         if (blk_mq_poll_hybrid(q, hctx, cookie))
3499                 return 1;
3500 
3501         hctx->poll_considered++;
3502 
3503         state = current->state;
3504         do {
3505                 int ret;
3506 
3507                 hctx->poll_invoked++;
3508 
3509                 ret = q->mq_ops->poll(hctx);
3510                 if (ret > 0) {
3511                         hctx->poll_success++;
3512                         __set_current_state(TASK_RUNNING);
3513                         return ret;
3514                 }
3515 
3516                 if (signal_pending_state(state, current))
3517                         __set_current_state(TASK_RUNNING);
3518 
3519                 if (current->state == TASK_RUNNING)
3520                         return 1;
3521                 if (ret < 0 || !spin)
3522                         break;
3523                 cpu_relax();
3524         } while (!need_resched());
3525 
3526         __set_current_state(TASK_RUNNING);
3527         return 0;
3528 }
3529 EXPORT_SYMBOL_GPL(blk_poll);
3530 
3531 unsigned int blk_mq_rq_cpu(struct request *rq)
3532 {
3533         return rq->mq_ctx->cpu;
3534 }
3535 EXPORT_SYMBOL(blk_mq_rq_cpu);
3536 
3537 static int __init blk_mq_init(void)
3538 {
3539         cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL,
3540                                 blk_mq_hctx_notify_dead);
3541         return 0;
3542 }
3543 subsys_initcall(blk_mq_init);
3544 

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