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