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

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

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