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

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  1 /*
  2  * Block multiqueue core code
  3  *
  4  * Copyright (C) 2013-2014 Jens Axboe
  5  * Copyright (C) 2013-2014 Christoph Hellwig
  6  */
  7 #include <linux/kernel.h>
  8 #include <linux/module.h>
  9 #include <linux/backing-dev.h>
 10 #include <linux/bio.h>
 11 #include <linux/blkdev.h>
 12 #include <linux/kmemleak.h>
 13 #include <linux/mm.h>
 14 #include <linux/init.h>
 15 #include <linux/slab.h>
 16 #include <linux/workqueue.h>
 17 #include <linux/smp.h>
 18 #include <linux/llist.h>
 19 #include <linux/list_sort.h>
 20 #include <linux/cpu.h>
 21 #include <linux/cache.h>
 22 #include <linux/sched/sysctl.h>
 23 #include <linux/delay.h>
 24 #include <linux/crash_dump.h>
 25 
 26 #include <trace/events/block.h>
 27 
 28 #include <linux/blk-mq.h>
 29 #include "blk.h"
 30 #include "blk-mq.h"
 31 #include "blk-mq-tag.h"
 32 
 33 static DEFINE_MUTEX(all_q_mutex);
 34 static LIST_HEAD(all_q_list);
 35 
 36 static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx);
 37 
 38 /*
 39  * Check if any of the ctx's have pending work in this hardware queue
 40  */
 41 static bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx)
 42 {
 43         unsigned int i;
 44 
 45         for (i = 0; i < hctx->ctx_map.size; i++)
 46                 if (hctx->ctx_map.map[i].word)
 47                         return true;
 48 
 49         return false;
 50 }
 51 
 52 static inline struct blk_align_bitmap *get_bm(struct blk_mq_hw_ctx *hctx,
 53                                               struct blk_mq_ctx *ctx)
 54 {
 55         return &hctx->ctx_map.map[ctx->index_hw / hctx->ctx_map.bits_per_word];
 56 }
 57 
 58 #define CTX_TO_BIT(hctx, ctx)   \
 59         ((ctx)->index_hw & ((hctx)->ctx_map.bits_per_word - 1))
 60 
 61 /*
 62  * Mark this ctx as having pending work in this hardware queue
 63  */
 64 static void blk_mq_hctx_mark_pending(struct blk_mq_hw_ctx *hctx,
 65                                      struct blk_mq_ctx *ctx)
 66 {
 67         struct blk_align_bitmap *bm = get_bm(hctx, ctx);
 68 
 69         if (!test_bit(CTX_TO_BIT(hctx, ctx), &bm->word))
 70                 set_bit(CTX_TO_BIT(hctx, ctx), &bm->word);
 71 }
 72 
 73 static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
 74                                       struct blk_mq_ctx *ctx)
 75 {
 76         struct blk_align_bitmap *bm = get_bm(hctx, ctx);
 77 
 78         clear_bit(CTX_TO_BIT(hctx, ctx), &bm->word);
 79 }
 80 
 81 void blk_mq_freeze_queue_start(struct request_queue *q)
 82 {
 83         int freeze_depth;
 84 
 85         freeze_depth = atomic_inc_return(&q->mq_freeze_depth);
 86         if (freeze_depth == 1) {
 87                 percpu_ref_kill(&q->q_usage_counter);
 88                 blk_mq_run_hw_queues(q, false);
 89         }
 90 }
 91 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_start);
 92 
 93 static void blk_mq_freeze_queue_wait(struct request_queue *q)
 94 {
 95         wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->q_usage_counter));
 96 }
 97 
 98 /*
 99  * Guarantee no request is in use, so we can change any data structure of
100  * the queue afterward.
101  */
102 void blk_freeze_queue(struct request_queue *q)
103 {
104         /*
105          * In the !blk_mq case we are only calling this to kill the
106          * q_usage_counter, otherwise this increases the freeze depth
107          * and waits for it to return to zero.  For this reason there is
108          * no blk_unfreeze_queue(), and blk_freeze_queue() is not
109          * exported to drivers as the only user for unfreeze is blk_mq.
110          */
111         blk_mq_freeze_queue_start(q);
112         blk_mq_freeze_queue_wait(q);
113 }
114 
115 void blk_mq_freeze_queue(struct request_queue *q)
116 {
117         /*
118          * ...just an alias to keep freeze and unfreeze actions balanced
119          * in the blk_mq_* namespace
120          */
121         blk_freeze_queue(q);
122 }
123 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);
124 
125 void blk_mq_unfreeze_queue(struct request_queue *q)
126 {
127         int freeze_depth;
128 
129         freeze_depth = atomic_dec_return(&q->mq_freeze_depth);
130         WARN_ON_ONCE(freeze_depth < 0);
131         if (!freeze_depth) {
132                 percpu_ref_reinit(&q->q_usage_counter);
133                 wake_up_all(&q->mq_freeze_wq);
134         }
135 }
136 EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);
137 
138 void blk_mq_wake_waiters(struct request_queue *q)
139 {
140         struct blk_mq_hw_ctx *hctx;
141         unsigned int i;
142 
143         queue_for_each_hw_ctx(q, hctx, i)
144                 if (blk_mq_hw_queue_mapped(hctx))
145                         blk_mq_tag_wakeup_all(hctx->tags, true);
146 
147         /*
148          * If we are called because the queue has now been marked as
149          * dying, we need to ensure that processes currently waiting on
150          * the queue are notified as well.
151          */
152         wake_up_all(&q->mq_freeze_wq);
153 }
154 
155 bool blk_mq_can_queue(struct blk_mq_hw_ctx *hctx)
156 {
157         return blk_mq_has_free_tags(hctx->tags);
158 }
159 EXPORT_SYMBOL(blk_mq_can_queue);
160 
161 static void blk_mq_rq_ctx_init(struct request_queue *q, struct blk_mq_ctx *ctx,
162                                struct request *rq, int op,
163                                unsigned int op_flags)
164 {
165         if (blk_queue_io_stat(q))
166                 op_flags |= REQ_IO_STAT;
167 
168         INIT_LIST_HEAD(&rq->queuelist);
169         /* csd/requeue_work/fifo_time is initialized before use */
170         rq->q = q;
171         rq->mq_ctx = ctx;
172         req_set_op_attrs(rq, op, op_flags);
173         /* do not touch atomic flags, it needs atomic ops against the timer */
174         rq->cpu = -1;
175         INIT_HLIST_NODE(&rq->hash);
176         RB_CLEAR_NODE(&rq->rb_node);
177         rq->rq_disk = NULL;
178         rq->part = NULL;
179         rq->start_time = jiffies;
180 #ifdef CONFIG_BLK_CGROUP
181         rq->rl = NULL;
182         set_start_time_ns(rq);
183         rq->io_start_time_ns = 0;
184 #endif
185         rq->nr_phys_segments = 0;
186 #if defined(CONFIG_BLK_DEV_INTEGRITY)
187         rq->nr_integrity_segments = 0;
188 #endif
189         rq->special = NULL;
190         /* tag was already set */
191         rq->errors = 0;
192 
193         rq->cmd = rq->__cmd;
194 
195         rq->extra_len = 0;
196         rq->sense_len = 0;
197         rq->resid_len = 0;
198         rq->sense = NULL;
199 
200         INIT_LIST_HEAD(&rq->timeout_list);
201         rq->timeout = 0;
202 
203         rq->end_io = NULL;
204         rq->end_io_data = NULL;
205         rq->next_rq = NULL;
206 
207         ctx->rq_dispatched[rw_is_sync(op, op_flags)]++;
208 }
209 
210 static struct request *
211 __blk_mq_alloc_request(struct blk_mq_alloc_data *data, int op, int op_flags)
212 {
213         struct request *rq;
214         unsigned int tag;
215 
216         tag = blk_mq_get_tag(data);
217         if (tag != BLK_MQ_TAG_FAIL) {
218                 rq = data->hctx->tags->rqs[tag];
219 
220                 if (blk_mq_tag_busy(data->hctx)) {
221                         rq->cmd_flags = REQ_MQ_INFLIGHT;
222                         atomic_inc(&data->hctx->nr_active);
223                 }
224 
225                 rq->tag = tag;
226                 blk_mq_rq_ctx_init(data->q, data->ctx, rq, op, op_flags);
227                 return rq;
228         }
229 
230         return NULL;
231 }
232 
233 struct request *blk_mq_alloc_request(struct request_queue *q, int rw,
234                 unsigned int flags)
235 {
236         struct blk_mq_ctx *ctx;
237         struct blk_mq_hw_ctx *hctx;
238         struct request *rq;
239         struct blk_mq_alloc_data alloc_data;
240         int ret;
241 
242         ret = blk_queue_enter(q, flags & BLK_MQ_REQ_NOWAIT);
243         if (ret)
244                 return ERR_PTR(ret);
245 
246         ctx = blk_mq_get_ctx(q);
247         hctx = q->mq_ops->map_queue(q, ctx->cpu);
248         blk_mq_set_alloc_data(&alloc_data, q, flags, ctx, hctx);
249 
250         rq = __blk_mq_alloc_request(&alloc_data, rw, 0);
251         if (!rq && !(flags & BLK_MQ_REQ_NOWAIT)) {
252                 __blk_mq_run_hw_queue(hctx);
253                 blk_mq_put_ctx(ctx);
254 
255                 ctx = blk_mq_get_ctx(q);
256                 hctx = q->mq_ops->map_queue(q, ctx->cpu);
257                 blk_mq_set_alloc_data(&alloc_data, q, flags, ctx, hctx);
258                 rq =  __blk_mq_alloc_request(&alloc_data, rw, 0);
259                 ctx = alloc_data.ctx;
260         }
261         blk_mq_put_ctx(ctx);
262         if (!rq) {
263                 blk_queue_exit(q);
264                 return ERR_PTR(-EWOULDBLOCK);
265         }
266 
267         rq->__data_len = 0;
268         rq->__sector = (sector_t) -1;
269         rq->bio = rq->biotail = NULL;
270         return rq;
271 }
272 EXPORT_SYMBOL(blk_mq_alloc_request);
273 
274 struct request *blk_mq_alloc_request_hctx(struct request_queue *q, int rw,
275                 unsigned int flags, unsigned int hctx_idx)
276 {
277         struct blk_mq_hw_ctx *hctx;
278         struct blk_mq_ctx *ctx;
279         struct request *rq;
280         struct blk_mq_alloc_data alloc_data;
281         int ret;
282 
283         /*
284          * If the tag allocator sleeps we could get an allocation for a
285          * different hardware context.  No need to complicate the low level
286          * allocator for this for the rare use case of a command tied to
287          * a specific queue.
288          */
289         if (WARN_ON_ONCE(!(flags & BLK_MQ_REQ_NOWAIT)))
290                 return ERR_PTR(-EINVAL);
291 
292         if (hctx_idx >= q->nr_hw_queues)
293                 return ERR_PTR(-EIO);
294 
295         ret = blk_queue_enter(q, true);
296         if (ret)
297                 return ERR_PTR(ret);
298 
299         /*
300          * Check if the hardware context is actually mapped to anything.
301          * If not tell the caller that it should skip this queue.
302          */
303         hctx = q->queue_hw_ctx[hctx_idx];
304         if (!blk_mq_hw_queue_mapped(hctx)) {
305                 ret = -EXDEV;
306                 goto out_queue_exit;
307         }
308         ctx = __blk_mq_get_ctx(q, cpumask_first(hctx->cpumask));
309 
310         blk_mq_set_alloc_data(&alloc_data, q, flags, ctx, hctx);
311         rq = __blk_mq_alloc_request(&alloc_data, rw, 0);
312         if (!rq) {
313                 ret = -EWOULDBLOCK;
314                 goto out_queue_exit;
315         }
316 
317         return rq;
318 
319 out_queue_exit:
320         blk_queue_exit(q);
321         return ERR_PTR(ret);
322 }
323 EXPORT_SYMBOL_GPL(blk_mq_alloc_request_hctx);
324 
325 static void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx,
326                                   struct blk_mq_ctx *ctx, struct request *rq)
327 {
328         const int tag = rq->tag;
329         struct request_queue *q = rq->q;
330 
331         if (rq->cmd_flags & REQ_MQ_INFLIGHT)
332                 atomic_dec(&hctx->nr_active);
333         rq->cmd_flags = 0;
334 
335         clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
336         blk_mq_put_tag(hctx, tag, &ctx->last_tag);
337         blk_queue_exit(q);
338 }
339 
340 void blk_mq_free_hctx_request(struct blk_mq_hw_ctx *hctx, struct request *rq)
341 {
342         struct blk_mq_ctx *ctx = rq->mq_ctx;
343 
344         ctx->rq_completed[rq_is_sync(rq)]++;
345         __blk_mq_free_request(hctx, ctx, rq);
346 
347 }
348 EXPORT_SYMBOL_GPL(blk_mq_free_hctx_request);
349 
350 void blk_mq_free_request(struct request *rq)
351 {
352         struct blk_mq_hw_ctx *hctx;
353         struct request_queue *q = rq->q;
354 
355         hctx = q->mq_ops->map_queue(q, rq->mq_ctx->cpu);
356         blk_mq_free_hctx_request(hctx, rq);
357 }
358 EXPORT_SYMBOL_GPL(blk_mq_free_request);
359 
360 inline void __blk_mq_end_request(struct request *rq, int error)
361 {
362         blk_account_io_done(rq);
363 
364         if (rq->end_io) {
365                 rq->end_io(rq, error);
366         } else {
367                 if (unlikely(blk_bidi_rq(rq)))
368                         blk_mq_free_request(rq->next_rq);
369                 blk_mq_free_request(rq);
370         }
371 }
372 EXPORT_SYMBOL(__blk_mq_end_request);
373 
374 void blk_mq_end_request(struct request *rq, int error)
375 {
376         if (blk_update_request(rq, error, blk_rq_bytes(rq)))
377                 BUG();
378         __blk_mq_end_request(rq, error);
379 }
380 EXPORT_SYMBOL(blk_mq_end_request);
381 
382 static void __blk_mq_complete_request_remote(void *data)
383 {
384         struct request *rq = data;
385 
386         rq->q->softirq_done_fn(rq);
387 }
388 
389 static void blk_mq_ipi_complete_request(struct request *rq)
390 {
391         struct blk_mq_ctx *ctx = rq->mq_ctx;
392         bool shared = false;
393         int cpu;
394 
395         if (!test_bit(QUEUE_FLAG_SAME_COMP, &rq->q->queue_flags)) {
396                 rq->q->softirq_done_fn(rq);
397                 return;
398         }
399 
400         cpu = get_cpu();
401         if (!test_bit(QUEUE_FLAG_SAME_FORCE, &rq->q->queue_flags))
402                 shared = cpus_share_cache(cpu, ctx->cpu);
403 
404         if (cpu != ctx->cpu && !shared && cpu_online(ctx->cpu)) {
405                 rq->csd.func = __blk_mq_complete_request_remote;
406                 rq->csd.info = rq;
407                 rq->csd.flags = 0;
408                 smp_call_function_single_async(ctx->cpu, &rq->csd);
409         } else {
410                 rq->q->softirq_done_fn(rq);
411         }
412         put_cpu();
413 }
414 
415 static void __blk_mq_complete_request(struct request *rq)
416 {
417         struct request_queue *q = rq->q;
418 
419         if (!q->softirq_done_fn)
420                 blk_mq_end_request(rq, rq->errors);
421         else
422                 blk_mq_ipi_complete_request(rq);
423 }
424 
425 /**
426  * blk_mq_complete_request - end I/O on a request
427  * @rq:         the request being processed
428  *
429  * Description:
430  *      Ends all I/O on a request. It does not handle partial completions.
431  *      The actual completion happens out-of-order, through a IPI handler.
432  **/
433 void blk_mq_complete_request(struct request *rq, int error)
434 {
435         struct request_queue *q = rq->q;
436 
437         if (unlikely(blk_should_fake_timeout(q)))
438                 return;
439         if (!blk_mark_rq_complete(rq)) {
440                 rq->errors = error;
441                 __blk_mq_complete_request(rq);
442         }
443 }
444 EXPORT_SYMBOL(blk_mq_complete_request);
445 
446 int blk_mq_request_started(struct request *rq)
447 {
448         return test_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
449 }
450 EXPORT_SYMBOL_GPL(blk_mq_request_started);
451 
452 void blk_mq_start_request(struct request *rq)
453 {
454         struct request_queue *q = rq->q;
455 
456         trace_block_rq_issue(q, rq);
457 
458         rq->resid_len = blk_rq_bytes(rq);
459         if (unlikely(blk_bidi_rq(rq)))
460                 rq->next_rq->resid_len = blk_rq_bytes(rq->next_rq);
461 
462         blk_add_timer(rq);
463 
464         /*
465          * Ensure that ->deadline is visible before set the started
466          * flag and clear the completed flag.
467          */
468         smp_mb__before_atomic();
469 
470         /*
471          * Mark us as started and clear complete. Complete might have been
472          * set if requeue raced with timeout, which then marked it as
473          * complete. So be sure to clear complete again when we start
474          * the request, otherwise we'll ignore the completion event.
475          */
476         if (!test_bit(REQ_ATOM_STARTED, &rq->atomic_flags))
477                 set_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
478         if (test_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags))
479                 clear_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags);
480 
481         if (q->dma_drain_size && blk_rq_bytes(rq)) {
482                 /*
483                  * Make sure space for the drain appears.  We know we can do
484                  * this because max_hw_segments has been adjusted to be one
485                  * fewer than the device can handle.
486                  */
487                 rq->nr_phys_segments++;
488         }
489 }
490 EXPORT_SYMBOL(blk_mq_start_request);
491 
492 static void __blk_mq_requeue_request(struct request *rq)
493 {
494         struct request_queue *q = rq->q;
495 
496         trace_block_rq_requeue(q, rq);
497 
498         if (test_and_clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags)) {
499                 if (q->dma_drain_size && blk_rq_bytes(rq))
500                         rq->nr_phys_segments--;
501         }
502 }
503 
504 void blk_mq_requeue_request(struct request *rq)
505 {
506         __blk_mq_requeue_request(rq);
507 
508         BUG_ON(blk_queued_rq(rq));
509         blk_mq_add_to_requeue_list(rq, true);
510 }
511 EXPORT_SYMBOL(blk_mq_requeue_request);
512 
513 static void blk_mq_requeue_work(struct work_struct *work)
514 {
515         struct request_queue *q =
516                 container_of(work, struct request_queue, requeue_work);
517         LIST_HEAD(rq_list);
518         struct request *rq, *next;
519         unsigned long flags;
520 
521         spin_lock_irqsave(&q->requeue_lock, flags);
522         list_splice_init(&q->requeue_list, &rq_list);
523         spin_unlock_irqrestore(&q->requeue_lock, flags);
524 
525         list_for_each_entry_safe(rq, next, &rq_list, queuelist) {
526                 if (!(rq->cmd_flags & REQ_SOFTBARRIER))
527                         continue;
528 
529                 rq->cmd_flags &= ~REQ_SOFTBARRIER;
530                 list_del_init(&rq->queuelist);
531                 blk_mq_insert_request(rq, true, false, false);
532         }
533 
534         while (!list_empty(&rq_list)) {
535                 rq = list_entry(rq_list.next, struct request, queuelist);
536                 list_del_init(&rq->queuelist);
537                 blk_mq_insert_request(rq, false, false, false);
538         }
539 
540         /*
541          * Use the start variant of queue running here, so that running
542          * the requeue work will kick stopped queues.
543          */
544         blk_mq_start_hw_queues(q);
545 }
546 
547 void blk_mq_add_to_requeue_list(struct request *rq, bool at_head)
548 {
549         struct request_queue *q = rq->q;
550         unsigned long flags;
551 
552         /*
553          * We abuse this flag that is otherwise used by the I/O scheduler to
554          * request head insertation from the workqueue.
555          */
556         BUG_ON(rq->cmd_flags & REQ_SOFTBARRIER);
557 
558         spin_lock_irqsave(&q->requeue_lock, flags);
559         if (at_head) {
560                 rq->cmd_flags |= REQ_SOFTBARRIER;
561                 list_add(&rq->queuelist, &q->requeue_list);
562         } else {
563                 list_add_tail(&rq->queuelist, &q->requeue_list);
564         }
565         spin_unlock_irqrestore(&q->requeue_lock, flags);
566 }
567 EXPORT_SYMBOL(blk_mq_add_to_requeue_list);
568 
569 void blk_mq_cancel_requeue_work(struct request_queue *q)
570 {
571         cancel_work_sync(&q->requeue_work);
572 }
573 EXPORT_SYMBOL_GPL(blk_mq_cancel_requeue_work);
574 
575 void blk_mq_kick_requeue_list(struct request_queue *q)
576 {
577         kblockd_schedule_work(&q->requeue_work);
578 }
579 EXPORT_SYMBOL(blk_mq_kick_requeue_list);
580 
581 void blk_mq_abort_requeue_list(struct request_queue *q)
582 {
583         unsigned long flags;
584         LIST_HEAD(rq_list);
585 
586         spin_lock_irqsave(&q->requeue_lock, flags);
587         list_splice_init(&q->requeue_list, &rq_list);
588         spin_unlock_irqrestore(&q->requeue_lock, flags);
589 
590         while (!list_empty(&rq_list)) {
591                 struct request *rq;
592 
593                 rq = list_first_entry(&rq_list, struct request, queuelist);
594                 list_del_init(&rq->queuelist);
595                 rq->errors = -EIO;
596                 blk_mq_end_request(rq, rq->errors);
597         }
598 }
599 EXPORT_SYMBOL(blk_mq_abort_requeue_list);
600 
601 struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
602 {
603         if (tag < tags->nr_tags)
604                 return tags->rqs[tag];
605 
606         return NULL;
607 }
608 EXPORT_SYMBOL(blk_mq_tag_to_rq);
609 
610 struct blk_mq_timeout_data {
611         unsigned long next;
612         unsigned int next_set;
613 };
614 
615 void blk_mq_rq_timed_out(struct request *req, bool reserved)
616 {
617         struct blk_mq_ops *ops = req->q->mq_ops;
618         enum blk_eh_timer_return ret = BLK_EH_RESET_TIMER;
619 
620         /*
621          * We know that complete is set at this point. If STARTED isn't set
622          * anymore, then the request isn't active and the "timeout" should
623          * just be ignored. This can happen due to the bitflag ordering.
624          * Timeout first checks if STARTED is set, and if it is, assumes
625          * the request is active. But if we race with completion, then
626          * we both flags will get cleared. So check here again, and ignore
627          * a timeout event with a request that isn't active.
628          */
629         if (!test_bit(REQ_ATOM_STARTED, &req->atomic_flags))
630                 return;
631 
632         if (ops->timeout)
633                 ret = ops->timeout(req, reserved);
634 
635         switch (ret) {
636         case BLK_EH_HANDLED:
637                 __blk_mq_complete_request(req);
638                 break;
639         case BLK_EH_RESET_TIMER:
640                 blk_add_timer(req);
641                 blk_clear_rq_complete(req);
642                 break;
643         case BLK_EH_NOT_HANDLED:
644                 break;
645         default:
646                 printk(KERN_ERR "block: bad eh return: %d\n", ret);
647                 break;
648         }
649 }
650 
651 static void blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
652                 struct request *rq, void *priv, bool reserved)
653 {
654         struct blk_mq_timeout_data *data = priv;
655 
656         if (!test_bit(REQ_ATOM_STARTED, &rq->atomic_flags)) {
657                 /*
658                  * If a request wasn't started before the queue was
659                  * marked dying, kill it here or it'll go unnoticed.
660                  */
661                 if (unlikely(blk_queue_dying(rq->q))) {
662                         rq->errors = -EIO;
663                         blk_mq_end_request(rq, rq->errors);
664                 }
665                 return;
666         }
667 
668         if (time_after_eq(jiffies, rq->deadline)) {
669                 if (!blk_mark_rq_complete(rq))
670                         blk_mq_rq_timed_out(rq, reserved);
671         } else if (!data->next_set || time_after(data->next, rq->deadline)) {
672                 data->next = rq->deadline;
673                 data->next_set = 1;
674         }
675 }
676 
677 static void blk_mq_timeout_work(struct work_struct *work)
678 {
679         struct request_queue *q =
680                 container_of(work, struct request_queue, timeout_work);
681         struct blk_mq_timeout_data data = {
682                 .next           = 0,
683                 .next_set       = 0,
684         };
685         int i;
686 
687         /* A deadlock might occur if a request is stuck requiring a
688          * timeout at the same time a queue freeze is waiting
689          * completion, since the timeout code would not be able to
690          * acquire the queue reference here.
691          *
692          * That's why we don't use blk_queue_enter here; instead, we use
693          * percpu_ref_tryget directly, because we need to be able to
694          * obtain a reference even in the short window between the queue
695          * starting to freeze, by dropping the first reference in
696          * blk_mq_freeze_queue_start, and the moment the last request is
697          * consumed, marked by the instant q_usage_counter reaches
698          * zero.
699          */
700         if (!percpu_ref_tryget(&q->q_usage_counter))
701                 return;
702 
703         blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &data);
704 
705         if (data.next_set) {
706                 data.next = blk_rq_timeout(round_jiffies_up(data.next));
707                 mod_timer(&q->timeout, data.next);
708         } else {
709                 struct blk_mq_hw_ctx *hctx;
710 
711                 queue_for_each_hw_ctx(q, hctx, i) {
712                         /* the hctx may be unmapped, so check it here */
713                         if (blk_mq_hw_queue_mapped(hctx))
714                                 blk_mq_tag_idle(hctx);
715                 }
716         }
717         blk_queue_exit(q);
718 }
719 
720 /*
721  * Reverse check our software queue for entries that we could potentially
722  * merge with. Currently includes a hand-wavy stop count of 8, to not spend
723  * too much time checking for merges.
724  */
725 static bool blk_mq_attempt_merge(struct request_queue *q,
726                                  struct blk_mq_ctx *ctx, struct bio *bio)
727 {
728         struct request *rq;
729         int checked = 8;
730 
731         list_for_each_entry_reverse(rq, &ctx->rq_list, queuelist) {
732                 int el_ret;
733 
734                 if (!checked--)
735                         break;
736 
737                 if (!blk_rq_merge_ok(rq, bio))
738                         continue;
739 
740                 el_ret = blk_try_merge(rq, bio);
741                 if (el_ret == ELEVATOR_BACK_MERGE) {
742                         if (bio_attempt_back_merge(q, rq, bio)) {
743                                 ctx->rq_merged++;
744                                 return true;
745                         }
746                         break;
747                 } else if (el_ret == ELEVATOR_FRONT_MERGE) {
748                         if (bio_attempt_front_merge(q, rq, bio)) {
749                                 ctx->rq_merged++;
750                                 return true;
751                         }
752                         break;
753                 }
754         }
755 
756         return false;
757 }
758 
759 /*
760  * Process software queues that have been marked busy, splicing them
761  * to the for-dispatch
762  */
763 static void flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list)
764 {
765         struct blk_mq_ctx *ctx;
766         int i;
767 
768         for (i = 0; i < hctx->ctx_map.size; i++) {
769                 struct blk_align_bitmap *bm = &hctx->ctx_map.map[i];
770                 unsigned int off, bit;
771 
772                 if (!bm->word)
773                         continue;
774 
775                 bit = 0;
776                 off = i * hctx->ctx_map.bits_per_word;
777                 do {
778                         bit = find_next_bit(&bm->word, bm->depth, bit);
779                         if (bit >= bm->depth)
780                                 break;
781 
782                         ctx = hctx->ctxs[bit + off];
783                         clear_bit(bit, &bm->word);
784                         spin_lock(&ctx->lock);
785                         list_splice_tail_init(&ctx->rq_list, list);
786                         spin_unlock(&ctx->lock);
787 
788                         bit++;
789                 } while (1);
790         }
791 }
792 
793 /*
794  * Run this hardware queue, pulling any software queues mapped to it in.
795  * Note that this function currently has various problems around ordering
796  * of IO. In particular, we'd like FIFO behaviour on handling existing
797  * items on the hctx->dispatch list. Ignore that for now.
798  */
799 static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
800 {
801         struct request_queue *q = hctx->queue;
802         struct request *rq;
803         LIST_HEAD(rq_list);
804         LIST_HEAD(driver_list);
805         struct list_head *dptr;
806         int queued;
807 
808         if (unlikely(test_bit(BLK_MQ_S_STOPPED, &hctx->state)))
809                 return;
810 
811         WARN_ON(!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
812                 cpu_online(hctx->next_cpu));
813 
814         hctx->run++;
815 
816         /*
817          * Touch any software queue that has pending entries.
818          */
819         flush_busy_ctxs(hctx, &rq_list);
820 
821         /*
822          * If we have previous entries on our dispatch list, grab them
823          * and stuff them at the front for more fair dispatch.
824          */
825         if (!list_empty_careful(&hctx->dispatch)) {
826                 spin_lock(&hctx->lock);
827                 if (!list_empty(&hctx->dispatch))
828                         list_splice_init(&hctx->dispatch, &rq_list);
829                 spin_unlock(&hctx->lock);
830         }
831 
832         /*
833          * Start off with dptr being NULL, so we start the first request
834          * immediately, even if we have more pending.
835          */
836         dptr = NULL;
837 
838         /*
839          * Now process all the entries, sending them to the driver.
840          */
841         queued = 0;
842         while (!list_empty(&rq_list)) {
843                 struct blk_mq_queue_data bd;
844                 int ret;
845 
846                 rq = list_first_entry(&rq_list, struct request, queuelist);
847                 list_del_init(&rq->queuelist);
848 
849                 bd.rq = rq;
850                 bd.list = dptr;
851                 bd.last = list_empty(&rq_list);
852 
853                 ret = q->mq_ops->queue_rq(hctx, &bd);
854                 switch (ret) {
855                 case BLK_MQ_RQ_QUEUE_OK:
856                         queued++;
857                         break;
858                 case BLK_MQ_RQ_QUEUE_BUSY:
859                         list_add(&rq->queuelist, &rq_list);
860                         __blk_mq_requeue_request(rq);
861                         break;
862                 default:
863                         pr_err("blk-mq: bad return on queue: %d\n", ret);
864                 case BLK_MQ_RQ_QUEUE_ERROR:
865                         rq->errors = -EIO;
866                         blk_mq_end_request(rq, rq->errors);
867                         break;
868                 }
869 
870                 if (ret == BLK_MQ_RQ_QUEUE_BUSY)
871                         break;
872 
873                 /*
874                  * We've done the first request. If we have more than 1
875                  * left in the list, set dptr to defer issue.
876                  */
877                 if (!dptr && rq_list.next != rq_list.prev)
878                         dptr = &driver_list;
879         }
880 
881         if (!queued)
882                 hctx->dispatched[0]++;
883         else if (queued < (1 << (BLK_MQ_MAX_DISPATCH_ORDER - 1)))
884                 hctx->dispatched[ilog2(queued) + 1]++;
885 
886         /*
887          * Any items that need requeuing? Stuff them into hctx->dispatch,
888          * that is where we will continue on next queue run.
889          */
890         if (!list_empty(&rq_list)) {
891                 spin_lock(&hctx->lock);
892                 list_splice(&rq_list, &hctx->dispatch);
893                 spin_unlock(&hctx->lock);
894                 /*
895                  * the queue is expected stopped with BLK_MQ_RQ_QUEUE_BUSY, but
896                  * it's possible the queue is stopped and restarted again
897                  * before this. Queue restart will dispatch requests. And since
898                  * requests in rq_list aren't added into hctx->dispatch yet,
899                  * the requests in rq_list might get lost.
900                  *
901                  * blk_mq_run_hw_queue() already checks the STOPPED bit
902                  **/
903                 blk_mq_run_hw_queue(hctx, true);
904         }
905 }
906 
907 /*
908  * It'd be great if the workqueue API had a way to pass
909  * in a mask and had some smarts for more clever placement.
910  * For now we just round-robin here, switching for every
911  * BLK_MQ_CPU_WORK_BATCH queued items.
912  */
913 static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
914 {
915         if (hctx->queue->nr_hw_queues == 1)
916                 return WORK_CPU_UNBOUND;
917 
918         if (--hctx->next_cpu_batch <= 0) {
919                 int cpu = hctx->next_cpu, next_cpu;
920 
921                 next_cpu = cpumask_next(hctx->next_cpu, hctx->cpumask);
922                 if (next_cpu >= nr_cpu_ids)
923                         next_cpu = cpumask_first(hctx->cpumask);
924 
925                 hctx->next_cpu = next_cpu;
926                 hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
927 
928                 return cpu;
929         }
930 
931         return hctx->next_cpu;
932 }
933 
934 void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
935 {
936         if (unlikely(test_bit(BLK_MQ_S_STOPPED, &hctx->state) ||
937             !blk_mq_hw_queue_mapped(hctx)))
938                 return;
939 
940         if (!async) {
941                 int cpu = get_cpu();
942                 if (cpumask_test_cpu(cpu, hctx->cpumask)) {
943                         __blk_mq_run_hw_queue(hctx);
944                         put_cpu();
945                         return;
946                 }
947 
948                 put_cpu();
949         }
950 
951         kblockd_schedule_delayed_work_on(blk_mq_hctx_next_cpu(hctx),
952                         &hctx->run_work, 0);
953 }
954 
955 void blk_mq_run_hw_queues(struct request_queue *q, bool async)
956 {
957         struct blk_mq_hw_ctx *hctx;
958         int i;
959 
960         queue_for_each_hw_ctx(q, hctx, i) {
961                 if ((!blk_mq_hctx_has_pending(hctx) &&
962                     list_empty_careful(&hctx->dispatch)) ||
963                     test_bit(BLK_MQ_S_STOPPED, &hctx->state))
964                         continue;
965 
966                 blk_mq_run_hw_queue(hctx, async);
967         }
968 }
969 EXPORT_SYMBOL(blk_mq_run_hw_queues);
970 
971 void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx)
972 {
973         cancel_delayed_work(&hctx->run_work);
974         cancel_delayed_work(&hctx->delay_work);
975         set_bit(BLK_MQ_S_STOPPED, &hctx->state);
976 }
977 EXPORT_SYMBOL(blk_mq_stop_hw_queue);
978 
979 void blk_mq_stop_hw_queues(struct request_queue *q)
980 {
981         struct blk_mq_hw_ctx *hctx;
982         int i;
983 
984         queue_for_each_hw_ctx(q, hctx, i)
985                 blk_mq_stop_hw_queue(hctx);
986 }
987 EXPORT_SYMBOL(blk_mq_stop_hw_queues);
988 
989 void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx)
990 {
991         clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
992 
993         blk_mq_run_hw_queue(hctx, false);
994 }
995 EXPORT_SYMBOL(blk_mq_start_hw_queue);
996 
997 void blk_mq_start_hw_queues(struct request_queue *q)
998 {
999         struct blk_mq_hw_ctx *hctx;
1000         int i;
1001 
1002         queue_for_each_hw_ctx(q, hctx, i)
1003                 blk_mq_start_hw_queue(hctx);
1004 }
1005 EXPORT_SYMBOL(blk_mq_start_hw_queues);
1006 
1007 void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async)
1008 {
1009         struct blk_mq_hw_ctx *hctx;
1010         int i;
1011 
1012         queue_for_each_hw_ctx(q, hctx, i) {
1013                 if (!test_bit(BLK_MQ_S_STOPPED, &hctx->state))
1014                         continue;
1015 
1016                 clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
1017                 blk_mq_run_hw_queue(hctx, async);
1018         }
1019 }
1020 EXPORT_SYMBOL(blk_mq_start_stopped_hw_queues);
1021 
1022 static void blk_mq_run_work_fn(struct work_struct *work)
1023 {
1024         struct blk_mq_hw_ctx *hctx;
1025 
1026         hctx = container_of(work, struct blk_mq_hw_ctx, run_work.work);
1027 
1028         __blk_mq_run_hw_queue(hctx);
1029 }
1030 
1031 static void blk_mq_delay_work_fn(struct work_struct *work)
1032 {
1033         struct blk_mq_hw_ctx *hctx;
1034 
1035         hctx = container_of(work, struct blk_mq_hw_ctx, delay_work.work);
1036 
1037         if (test_and_clear_bit(BLK_MQ_S_STOPPED, &hctx->state))
1038                 __blk_mq_run_hw_queue(hctx);
1039 }
1040 
1041 void blk_mq_delay_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
1042 {
1043         if (unlikely(!blk_mq_hw_queue_mapped(hctx)))
1044                 return;
1045 
1046         kblockd_schedule_delayed_work_on(blk_mq_hctx_next_cpu(hctx),
1047                         &hctx->delay_work, msecs_to_jiffies(msecs));
1048 }
1049 EXPORT_SYMBOL(blk_mq_delay_queue);
1050 
1051 static inline void __blk_mq_insert_req_list(struct blk_mq_hw_ctx *hctx,
1052                                             struct request *rq,
1053                                             bool at_head)
1054 {
1055         struct blk_mq_ctx *ctx = rq->mq_ctx;
1056 
1057         trace_block_rq_insert(hctx->queue, rq);
1058 
1059         if (at_head)
1060                 list_add(&rq->queuelist, &ctx->rq_list);
1061         else
1062                 list_add_tail(&rq->queuelist, &ctx->rq_list);
1063 }
1064 
1065 static void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx,
1066                                     struct request *rq, bool at_head)
1067 {
1068         struct blk_mq_ctx *ctx = rq->mq_ctx;
1069 
1070         __blk_mq_insert_req_list(hctx, rq, at_head);
1071         blk_mq_hctx_mark_pending(hctx, ctx);
1072 }
1073 
1074 void blk_mq_insert_request(struct request *rq, bool at_head, bool run_queue,
1075                            bool async)
1076 {
1077         struct blk_mq_ctx *ctx = rq->mq_ctx;
1078         struct request_queue *q = rq->q;
1079         struct blk_mq_hw_ctx *hctx;
1080 
1081         hctx = q->mq_ops->map_queue(q, ctx->cpu);
1082 
1083         spin_lock(&ctx->lock);
1084         __blk_mq_insert_request(hctx, rq, at_head);
1085         spin_unlock(&ctx->lock);
1086 
1087         if (run_queue)
1088                 blk_mq_run_hw_queue(hctx, async);
1089 }
1090 
1091 static void blk_mq_insert_requests(struct request_queue *q,
1092                                      struct blk_mq_ctx *ctx,
1093                                      struct list_head *list,
1094                                      int depth,
1095                                      bool from_schedule)
1096 
1097 {
1098         struct blk_mq_hw_ctx *hctx;
1099 
1100         trace_block_unplug(q, depth, !from_schedule);
1101 
1102         hctx = q->mq_ops->map_queue(q, ctx->cpu);
1103 
1104         /*
1105          * preemption doesn't flush plug list, so it's possible ctx->cpu is
1106          * offline now
1107          */
1108         spin_lock(&ctx->lock);
1109         while (!list_empty(list)) {
1110                 struct request *rq;
1111 
1112                 rq = list_first_entry(list, struct request, queuelist);
1113                 BUG_ON(rq->mq_ctx != ctx);
1114                 list_del_init(&rq->queuelist);
1115                 __blk_mq_insert_req_list(hctx, rq, false);
1116         }
1117         blk_mq_hctx_mark_pending(hctx, ctx);
1118         spin_unlock(&ctx->lock);
1119 
1120         blk_mq_run_hw_queue(hctx, from_schedule);
1121 }
1122 
1123 static int plug_ctx_cmp(void *priv, struct list_head *a, struct list_head *b)
1124 {
1125         struct request *rqa = container_of(a, struct request, queuelist);
1126         struct request *rqb = container_of(b, struct request, queuelist);
1127 
1128         return !(rqa->mq_ctx < rqb->mq_ctx ||
1129                  (rqa->mq_ctx == rqb->mq_ctx &&
1130                   blk_rq_pos(rqa) < blk_rq_pos(rqb)));
1131 }
1132 
1133 void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
1134 {
1135         struct blk_mq_ctx *this_ctx;
1136         struct request_queue *this_q;
1137         struct request *rq;
1138         LIST_HEAD(list);
1139         LIST_HEAD(ctx_list);
1140         unsigned int depth;
1141 
1142         list_splice_init(&plug->mq_list, &list);
1143 
1144         list_sort(NULL, &list, plug_ctx_cmp);
1145 
1146         this_q = NULL;
1147         this_ctx = NULL;
1148         depth = 0;
1149 
1150         while (!list_empty(&list)) {
1151                 rq = list_entry_rq(list.next);
1152                 list_del_init(&rq->queuelist);
1153                 BUG_ON(!rq->q);
1154                 if (rq->mq_ctx != this_ctx) {
1155                         if (this_ctx) {
1156                                 blk_mq_insert_requests(this_q, this_ctx,
1157                                                         &ctx_list, depth,
1158                                                         from_schedule);
1159                         }
1160 
1161                         this_ctx = rq->mq_ctx;
1162                         this_q = rq->q;
1163                         depth = 0;
1164                 }
1165 
1166                 depth++;
1167                 list_add_tail(&rq->queuelist, &ctx_list);
1168         }
1169 
1170         /*
1171          * If 'this_ctx' is set, we know we have entries to complete
1172          * on 'ctx_list'. Do those.
1173          */
1174         if (this_ctx) {
1175                 blk_mq_insert_requests(this_q, this_ctx, &ctx_list, depth,
1176                                        from_schedule);
1177         }
1178 }
1179 
1180 static void blk_mq_bio_to_request(struct request *rq, struct bio *bio)
1181 {
1182         init_request_from_bio(rq, bio);
1183 
1184         blk_account_io_start(rq, 1);
1185 }
1186 
1187 static inline bool hctx_allow_merges(struct blk_mq_hw_ctx *hctx)
1188 {
1189         return (hctx->flags & BLK_MQ_F_SHOULD_MERGE) &&
1190                 !blk_queue_nomerges(hctx->queue);
1191 }
1192 
1193 static inline bool blk_mq_merge_queue_io(struct blk_mq_hw_ctx *hctx,
1194                                          struct blk_mq_ctx *ctx,
1195                                          struct request *rq, struct bio *bio)
1196 {
1197         if (!hctx_allow_merges(hctx) || !bio_mergeable(bio)) {
1198                 blk_mq_bio_to_request(rq, bio);
1199                 spin_lock(&ctx->lock);
1200 insert_rq:
1201                 __blk_mq_insert_request(hctx, rq, false);
1202                 spin_unlock(&ctx->lock);
1203                 return false;
1204         } else {
1205                 struct request_queue *q = hctx->queue;
1206 
1207                 spin_lock(&ctx->lock);
1208                 if (!blk_mq_attempt_merge(q, ctx, bio)) {
1209                         blk_mq_bio_to_request(rq, bio);
1210                         goto insert_rq;
1211                 }
1212 
1213                 spin_unlock(&ctx->lock);
1214                 __blk_mq_free_request(hctx, ctx, rq);
1215                 return true;
1216         }
1217 }
1218 
1219 struct blk_map_ctx {
1220         struct blk_mq_hw_ctx *hctx;
1221         struct blk_mq_ctx *ctx;
1222 };
1223 
1224 static struct request *blk_mq_map_request(struct request_queue *q,
1225                                           struct bio *bio,
1226                                           struct blk_map_ctx *data)
1227 {
1228         struct blk_mq_hw_ctx *hctx;
1229         struct blk_mq_ctx *ctx;
1230         struct request *rq;
1231         int op = bio_data_dir(bio);
1232         int op_flags = 0;
1233         struct blk_mq_alloc_data alloc_data;
1234 
1235         blk_queue_enter_live(q);
1236         ctx = blk_mq_get_ctx(q);
1237         hctx = q->mq_ops->map_queue(q, ctx->cpu);
1238 
1239         if (rw_is_sync(bio_op(bio), bio->bi_opf))
1240                 op_flags |= REQ_SYNC;
1241 
1242         trace_block_getrq(q, bio, op);
1243         blk_mq_set_alloc_data(&alloc_data, q, BLK_MQ_REQ_NOWAIT, ctx, hctx);
1244         rq = __blk_mq_alloc_request(&alloc_data, op, op_flags);
1245         if (unlikely(!rq)) {
1246                 __blk_mq_run_hw_queue(hctx);
1247                 blk_mq_put_ctx(ctx);
1248                 trace_block_sleeprq(q, bio, op);
1249 
1250                 ctx = blk_mq_get_ctx(q);
1251                 hctx = q->mq_ops->map_queue(q, ctx->cpu);
1252                 blk_mq_set_alloc_data(&alloc_data, q, 0, ctx, hctx);
1253                 rq = __blk_mq_alloc_request(&alloc_data, op, op_flags);
1254                 ctx = alloc_data.ctx;
1255                 hctx = alloc_data.hctx;
1256         }
1257 
1258         hctx->queued++;
1259         data->hctx = hctx;
1260         data->ctx = ctx;
1261         return rq;
1262 }
1263 
1264 static int blk_mq_direct_issue_request(struct request *rq, blk_qc_t *cookie)
1265 {
1266         int ret;
1267         struct request_queue *q = rq->q;
1268         struct blk_mq_hw_ctx *hctx = q->mq_ops->map_queue(q,
1269                         rq->mq_ctx->cpu);
1270         struct blk_mq_queue_data bd = {
1271                 .rq = rq,
1272                 .list = NULL,
1273                 .last = 1
1274         };
1275         blk_qc_t new_cookie = blk_tag_to_qc_t(rq->tag, hctx->queue_num);
1276 
1277         /*
1278          * For OK queue, we are done. For error, kill it. Any other
1279          * error (busy), just add it to our list as we previously
1280          * would have done
1281          */
1282         ret = q->mq_ops->queue_rq(hctx, &bd);
1283         if (ret == BLK_MQ_RQ_QUEUE_OK) {
1284                 *cookie = new_cookie;
1285                 return 0;
1286         }
1287 
1288         __blk_mq_requeue_request(rq);
1289 
1290         if (ret == BLK_MQ_RQ_QUEUE_ERROR) {
1291                 *cookie = BLK_QC_T_NONE;
1292                 rq->errors = -EIO;
1293                 blk_mq_end_request(rq, rq->errors);
1294                 return 0;
1295         }
1296 
1297         return -1;
1298 }
1299 
1300 /*
1301  * Multiple hardware queue variant. This will not use per-process plugs,
1302  * but will attempt to bypass the hctx queueing if we can go straight to
1303  * hardware for SYNC IO.
1304  */
1305 static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
1306 {
1307         const int is_sync = rw_is_sync(bio_op(bio), bio->bi_opf);
1308         const int is_flush_fua = bio->bi_opf & (REQ_PREFLUSH | REQ_FUA);
1309         struct blk_map_ctx data;
1310         struct request *rq;
1311         unsigned int request_count = 0;
1312         struct blk_plug *plug;
1313         struct request *same_queue_rq = NULL;
1314         blk_qc_t cookie;
1315 
1316         blk_queue_bounce(q, &bio);
1317 
1318         if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) {
1319                 bio_io_error(bio);
1320                 return BLK_QC_T_NONE;
1321         }
1322 
1323         blk_queue_split(q, &bio, q->bio_split);
1324 
1325         if (!is_flush_fua && !blk_queue_nomerges(q) &&
1326             blk_attempt_plug_merge(q, bio, &request_count, &same_queue_rq))
1327                 return BLK_QC_T_NONE;
1328 
1329         rq = blk_mq_map_request(q, bio, &data);
1330         if (unlikely(!rq))
1331                 return BLK_QC_T_NONE;
1332 
1333         cookie = blk_tag_to_qc_t(rq->tag, data.hctx->queue_num);
1334 
1335         if (unlikely(is_flush_fua)) {
1336                 blk_mq_bio_to_request(rq, bio);
1337                 blk_insert_flush(rq);
1338                 goto run_queue;
1339         }
1340 
1341         plug = current->plug;
1342         /*
1343          * If the driver supports defer issued based on 'last', then
1344          * queue it up like normal since we can potentially save some
1345          * CPU this way.
1346          */
1347         if (((plug && !blk_queue_nomerges(q)) || is_sync) &&
1348             !(data.hctx->flags & BLK_MQ_F_DEFER_ISSUE)) {
1349                 struct request *old_rq = NULL;
1350 
1351                 blk_mq_bio_to_request(rq, bio);
1352 
1353                 /*
1354                  * We do limited pluging. If the bio can be merged, do that.
1355                  * Otherwise the existing request in the plug list will be
1356                  * issued. So the plug list will have one request at most
1357                  */
1358                 if (plug) {
1359                         /*
1360                          * The plug list might get flushed before this. If that
1361                          * happens, same_queue_rq is invalid and plug list is
1362                          * empty
1363                          */
1364                         if (same_queue_rq && !list_empty(&plug->mq_list)) {
1365                                 old_rq = same_queue_rq;
1366                                 list_del_init(&old_rq->queuelist);
1367                         }
1368                         list_add_tail(&rq->queuelist, &plug->mq_list);
1369                 } else /* is_sync */
1370                         old_rq = rq;
1371                 blk_mq_put_ctx(data.ctx);
1372                 if (!old_rq)
1373                         goto done;
1374                 if (test_bit(BLK_MQ_S_STOPPED, &data.hctx->state) ||
1375                     blk_mq_direct_issue_request(old_rq, &cookie) != 0)
1376                         blk_mq_insert_request(old_rq, false, true, true);
1377                 goto done;
1378         }
1379 
1380         if (!blk_mq_merge_queue_io(data.hctx, data.ctx, rq, bio)) {
1381                 /*
1382                  * For a SYNC request, send it to the hardware immediately. For
1383                  * an ASYNC request, just ensure that we run it later on. The
1384                  * latter allows for merging opportunities and more efficient
1385                  * dispatching.
1386                  */
1387 run_queue:
1388                 blk_mq_run_hw_queue(data.hctx, !is_sync || is_flush_fua);
1389         }
1390         blk_mq_put_ctx(data.ctx);
1391 done:
1392         return cookie;
1393 }
1394 
1395 /*
1396  * Single hardware queue variant. This will attempt to use any per-process
1397  * plug for merging and IO deferral.
1398  */
1399 static blk_qc_t blk_sq_make_request(struct request_queue *q, struct bio *bio)
1400 {
1401         const int is_sync = rw_is_sync(bio_op(bio), bio->bi_opf);
1402         const int is_flush_fua = bio->bi_opf & (REQ_PREFLUSH | REQ_FUA);
1403         struct blk_plug *plug;
1404         unsigned int request_count = 0;
1405         struct blk_map_ctx data;
1406         struct request *rq;
1407         blk_qc_t cookie;
1408 
1409         blk_queue_bounce(q, &bio);
1410 
1411         if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) {
1412                 bio_io_error(bio);
1413                 return BLK_QC_T_NONE;
1414         }
1415 
1416         blk_queue_split(q, &bio, q->bio_split);
1417 
1418         if (!is_flush_fua && !blk_queue_nomerges(q)) {
1419                 if (blk_attempt_plug_merge(q, bio, &request_count, NULL))
1420                         return BLK_QC_T_NONE;
1421         } else
1422                 request_count = blk_plug_queued_count(q);
1423 
1424         rq = blk_mq_map_request(q, bio, &data);
1425         if (unlikely(!rq))
1426                 return BLK_QC_T_NONE;
1427 
1428         cookie = blk_tag_to_qc_t(rq->tag, data.hctx->queue_num);
1429 
1430         if (unlikely(is_flush_fua)) {
1431                 blk_mq_bio_to_request(rq, bio);
1432                 blk_insert_flush(rq);
1433                 goto run_queue;
1434         }
1435 
1436         /*
1437          * A task plug currently exists. Since this is completely lockless,
1438          * utilize that to temporarily store requests until the task is
1439          * either done or scheduled away.
1440          */
1441         plug = current->plug;
1442         if (plug) {
1443                 blk_mq_bio_to_request(rq, bio);
1444                 if (!request_count)
1445                         trace_block_plug(q);
1446 
1447                 blk_mq_put_ctx(data.ctx);
1448 
1449                 if (request_count >= BLK_MAX_REQUEST_COUNT) {
1450                         blk_flush_plug_list(plug, false);
1451                         trace_block_plug(q);
1452                 }
1453 
1454                 list_add_tail(&rq->queuelist, &plug->mq_list);
1455                 return cookie;
1456         }
1457 
1458         if (!blk_mq_merge_queue_io(data.hctx, data.ctx, rq, bio)) {
1459                 /*
1460                  * For a SYNC request, send it to the hardware immediately. For
1461                  * an ASYNC request, just ensure that we run it later on. The
1462                  * latter allows for merging opportunities and more efficient
1463                  * dispatching.
1464                  */
1465 run_queue:
1466                 blk_mq_run_hw_queue(data.hctx, !is_sync || is_flush_fua);
1467         }
1468 
1469         blk_mq_put_ctx(data.ctx);
1470         return cookie;
1471 }
1472 
1473 /*
1474  * Default mapping to a software queue, since we use one per CPU.
1475  */
1476 struct blk_mq_hw_ctx *blk_mq_map_queue(struct request_queue *q, const int cpu)
1477 {
1478         return q->queue_hw_ctx[q->mq_map[cpu]];
1479 }
1480 EXPORT_SYMBOL(blk_mq_map_queue);
1481 
1482 static void blk_mq_free_rq_map(struct blk_mq_tag_set *set,
1483                 struct blk_mq_tags *tags, unsigned int hctx_idx)
1484 {
1485         struct page *page;
1486 
1487         if (tags->rqs && set->ops->exit_request) {
1488                 int i;
1489 
1490                 for (i = 0; i < tags->nr_tags; i++) {
1491                         if (!tags->rqs[i])
1492                                 continue;
1493                         set->ops->exit_request(set->driver_data, tags->rqs[i],
1494                                                 hctx_idx, i);
1495                         tags->rqs[i] = NULL;
1496                 }
1497         }
1498 
1499         while (!list_empty(&tags->page_list)) {
1500                 page = list_first_entry(&tags->page_list, struct page, lru);
1501                 list_del_init(&page->lru);
1502                 /*
1503                  * Remove kmemleak object previously allocated in
1504                  * blk_mq_init_rq_map().
1505                  */
1506                 kmemleak_free(page_address(page));
1507                 __free_pages(page, page->private);
1508         }
1509 
1510         kfree(tags->rqs);
1511 
1512         blk_mq_free_tags(tags);
1513 }
1514 
1515 static size_t order_to_size(unsigned int order)
1516 {
1517         return (size_t)PAGE_SIZE << order;
1518 }
1519 
1520 static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set,
1521                 unsigned int hctx_idx)
1522 {
1523         struct blk_mq_tags *tags;
1524         unsigned int i, j, entries_per_page, max_order = 4;
1525         size_t rq_size, left;
1526 
1527         tags = blk_mq_init_tags(set->queue_depth, set->reserved_tags,
1528                                 set->numa_node,
1529                                 BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags));
1530         if (!tags)
1531                 return NULL;
1532 
1533         INIT_LIST_HEAD(&tags->page_list);
1534 
1535         tags->rqs = kzalloc_node(set->queue_depth * sizeof(struct request *),
1536                                  GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY,
1537                                  set->numa_node);
1538         if (!tags->rqs) {
1539                 blk_mq_free_tags(tags);
1540                 return NULL;
1541         }
1542 
1543         /*
1544          * rq_size is the size of the request plus driver payload, rounded
1545          * to the cacheline size
1546          */
1547         rq_size = round_up(sizeof(struct request) + set->cmd_size,
1548                                 cache_line_size());
1549         left = rq_size * set->queue_depth;
1550 
1551         for (i = 0; i < set->queue_depth; ) {
1552                 int this_order = max_order;
1553                 struct page *page;
1554                 int to_do;
1555                 void *p;
1556 
1557                 while (this_order && left < order_to_size(this_order - 1))
1558                         this_order--;
1559 
1560                 do {
1561                         page = alloc_pages_node(set->numa_node,
1562                                 GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY | __GFP_ZERO,
1563                                 this_order);
1564                         if (page)
1565                                 break;
1566                         if (!this_order--)
1567                                 break;
1568                         if (order_to_size(this_order) < rq_size)
1569                                 break;
1570                 } while (1);
1571 
1572                 if (!page)
1573                         goto fail;
1574 
1575                 page->private = this_order;
1576                 list_add_tail(&page->lru, &tags->page_list);
1577 
1578                 p = page_address(page);
1579                 /*
1580                  * Allow kmemleak to scan these pages as they contain pointers
1581                  * to additional allocations like via ops->init_request().
1582                  */
1583                 kmemleak_alloc(p, order_to_size(this_order), 1, GFP_KERNEL);
1584                 entries_per_page = order_to_size(this_order) / rq_size;
1585                 to_do = min(entries_per_page, set->queue_depth - i);
1586                 left -= to_do * rq_size;
1587                 for (j = 0; j < to_do; j++) {
1588                         tags->rqs[i] = p;
1589                         if (set->ops->init_request) {
1590                                 if (set->ops->init_request(set->driver_data,
1591                                                 tags->rqs[i], hctx_idx, i,
1592                                                 set->numa_node)) {
1593                                         tags->rqs[i] = NULL;
1594                                         goto fail;
1595                                 }
1596                         }
1597 
1598                         p += rq_size;
1599                         i++;
1600                 }
1601         }
1602         return tags;
1603 
1604 fail:
1605         blk_mq_free_rq_map(set, tags, hctx_idx);
1606         return NULL;
1607 }
1608 
1609 static void blk_mq_free_bitmap(struct blk_mq_ctxmap *bitmap)
1610 {
1611         kfree(bitmap->map);
1612 }
1613 
1614 static int blk_mq_alloc_bitmap(struct blk_mq_ctxmap *bitmap, int node)
1615 {
1616         unsigned int bpw = 8, total, num_maps, i;
1617 
1618         bitmap->bits_per_word = bpw;
1619 
1620         num_maps = ALIGN(nr_cpu_ids, bpw) / bpw;
1621         bitmap->map = kzalloc_node(num_maps * sizeof(struct blk_align_bitmap),
1622                                         GFP_KERNEL, node);
1623         if (!bitmap->map)
1624                 return -ENOMEM;
1625 
1626         total = nr_cpu_ids;
1627         for (i = 0; i < num_maps; i++) {
1628                 bitmap->map[i].depth = min(total, bitmap->bits_per_word);
1629                 total -= bitmap->map[i].depth;
1630         }
1631 
1632         return 0;
1633 }
1634 
1635 /*
1636  * 'cpu' is going away. splice any existing rq_list entries from this
1637  * software queue to the hw queue dispatch list, and ensure that it
1638  * gets run.
1639  */
1640 static int blk_mq_hctx_cpu_offline(struct blk_mq_hw_ctx *hctx, int cpu)
1641 {
1642         struct blk_mq_ctx *ctx;
1643         LIST_HEAD(tmp);
1644 
1645         ctx = __blk_mq_get_ctx(hctx->queue, cpu);
1646 
1647         spin_lock(&ctx->lock);
1648         if (!list_empty(&ctx->rq_list)) {
1649                 list_splice_init(&ctx->rq_list, &tmp);
1650                 blk_mq_hctx_clear_pending(hctx, ctx);
1651         }
1652         spin_unlock(&ctx->lock);
1653 
1654         if (list_empty(&tmp))
1655                 return NOTIFY_OK;
1656 
1657         spin_lock(&hctx->lock);
1658         list_splice_tail_init(&tmp, &hctx->dispatch);
1659         spin_unlock(&hctx->lock);
1660 
1661         blk_mq_run_hw_queue(hctx, true);
1662         return NOTIFY_OK;
1663 }
1664 
1665 static int blk_mq_hctx_notify(void *data, unsigned long action,
1666                               unsigned int cpu)
1667 {
1668         struct blk_mq_hw_ctx *hctx = data;
1669 
1670         if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
1671                 return blk_mq_hctx_cpu_offline(hctx, cpu);
1672 
1673         /*
1674          * In case of CPU online, tags may be reallocated
1675          * in blk_mq_map_swqueue() after mapping is updated.
1676          */
1677 
1678         return NOTIFY_OK;
1679 }
1680 
1681 /* hctx->ctxs will be freed in queue's release handler */
1682 static void blk_mq_exit_hctx(struct request_queue *q,
1683                 struct blk_mq_tag_set *set,
1684                 struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
1685 {
1686         unsigned flush_start_tag = set->queue_depth;
1687 
1688         blk_mq_tag_idle(hctx);
1689 
1690         if (set->ops->exit_request)
1691                 set->ops->exit_request(set->driver_data,
1692                                        hctx->fq->flush_rq, hctx_idx,
1693                                        flush_start_tag + hctx_idx);
1694 
1695         if (set->ops->exit_hctx)
1696                 set->ops->exit_hctx(hctx, hctx_idx);
1697 
1698         blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
1699         blk_free_flush_queue(hctx->fq);
1700         blk_mq_free_bitmap(&hctx->ctx_map);
1701 }
1702 
1703 static void blk_mq_exit_hw_queues(struct request_queue *q,
1704                 struct blk_mq_tag_set *set, int nr_queue)
1705 {
1706         struct blk_mq_hw_ctx *hctx;
1707         unsigned int i;
1708 
1709         queue_for_each_hw_ctx(q, hctx, i) {
1710                 if (i == nr_queue)
1711                         break;
1712                 blk_mq_exit_hctx(q, set, hctx, i);
1713         }
1714 }
1715 
1716 static void blk_mq_free_hw_queues(struct request_queue *q,
1717                 struct blk_mq_tag_set *set)
1718 {
1719         struct blk_mq_hw_ctx *hctx;
1720         unsigned int i;
1721 
1722         queue_for_each_hw_ctx(q, hctx, i)
1723                 free_cpumask_var(hctx->cpumask);
1724 }
1725 
1726 static int blk_mq_init_hctx(struct request_queue *q,
1727                 struct blk_mq_tag_set *set,
1728                 struct blk_mq_hw_ctx *hctx, unsigned hctx_idx)
1729 {
1730         int node;
1731         unsigned flush_start_tag = set->queue_depth;
1732 
1733         node = hctx->numa_node;
1734         if (node == NUMA_NO_NODE)
1735                 node = hctx->numa_node = set->numa_node;
1736 
1737         INIT_DELAYED_WORK(&hctx->run_work, blk_mq_run_work_fn);
1738         INIT_DELAYED_WORK(&hctx->delay_work, blk_mq_delay_work_fn);
1739         spin_lock_init(&hctx->lock);
1740         INIT_LIST_HEAD(&hctx->dispatch);
1741         hctx->queue = q;
1742         hctx->queue_num = hctx_idx;
1743         hctx->flags = set->flags & ~BLK_MQ_F_TAG_SHARED;
1744 
1745         blk_mq_init_cpu_notifier(&hctx->cpu_notifier,
1746                                         blk_mq_hctx_notify, hctx);
1747         blk_mq_register_cpu_notifier(&hctx->cpu_notifier);
1748 
1749         hctx->tags = set->tags[hctx_idx];
1750 
1751         /*
1752          * Allocate space for all possible cpus to avoid allocation at
1753          * runtime
1754          */
1755         hctx->ctxs = kmalloc_node(nr_cpu_ids * sizeof(void *),
1756                                         GFP_KERNEL, node);
1757         if (!hctx->ctxs)
1758                 goto unregister_cpu_notifier;
1759 
1760         if (blk_mq_alloc_bitmap(&hctx->ctx_map, node))
1761                 goto free_ctxs;
1762 
1763         hctx->nr_ctx = 0;
1764 
1765         if (set->ops->init_hctx &&
1766             set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
1767                 goto free_bitmap;
1768 
1769         hctx->fq = blk_alloc_flush_queue(q, hctx->numa_node, set->cmd_size);
1770         if (!hctx->fq)
1771                 goto exit_hctx;
1772 
1773         if (set->ops->init_request &&
1774             set->ops->init_request(set->driver_data,
1775                                    hctx->fq->flush_rq, hctx_idx,
1776                                    flush_start_tag + hctx_idx, node))
1777                 goto free_fq;
1778 
1779         return 0;
1780 
1781  free_fq:
1782         kfree(hctx->fq);
1783  exit_hctx:
1784         if (set->ops->exit_hctx)
1785                 set->ops->exit_hctx(hctx, hctx_idx);
1786  free_bitmap:
1787         blk_mq_free_bitmap(&hctx->ctx_map);
1788  free_ctxs:
1789         kfree(hctx->ctxs);
1790  unregister_cpu_notifier:
1791         blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
1792 
1793         return -1;
1794 }
1795 
1796 static void blk_mq_init_cpu_queues(struct request_queue *q,
1797                                    unsigned int nr_hw_queues)
1798 {
1799         unsigned int i;
1800 
1801         for_each_possible_cpu(i) {
1802                 struct blk_mq_ctx *__ctx = per_cpu_ptr(q->queue_ctx, i);
1803                 struct blk_mq_hw_ctx *hctx;
1804 
1805                 memset(__ctx, 0, sizeof(*__ctx));
1806                 __ctx->cpu = i;
1807                 spin_lock_init(&__ctx->lock);
1808                 INIT_LIST_HEAD(&__ctx->rq_list);
1809                 __ctx->queue = q;
1810 
1811                 /* If the cpu isn't online, the cpu is mapped to first hctx */
1812                 if (!cpu_online(i))
1813                         continue;
1814 
1815                 hctx = q->mq_ops->map_queue(q, i);
1816 
1817                 /*
1818                  * Set local node, IFF we have more than one hw queue. If
1819                  * not, we remain on the home node of the device
1820                  */
1821                 if (nr_hw_queues > 1 && hctx->numa_node == NUMA_NO_NODE)
1822                         hctx->numa_node = local_memory_node(cpu_to_node(i));
1823         }
1824 }
1825 
1826 static void blk_mq_map_swqueue(struct request_queue *q,
1827                                const struct cpumask *online_mask)
1828 {
1829         unsigned int i;
1830         struct blk_mq_hw_ctx *hctx;
1831         struct blk_mq_ctx *ctx;
1832         struct blk_mq_tag_set *set = q->tag_set;
1833 
1834         /*
1835          * Avoid others reading imcomplete hctx->cpumask through sysfs
1836          */
1837         mutex_lock(&q->sysfs_lock);
1838 
1839         queue_for_each_hw_ctx(q, hctx, i) {
1840                 cpumask_clear(hctx->cpumask);
1841                 hctx->nr_ctx = 0;
1842         }
1843 
1844         /*
1845          * Map software to hardware queues
1846          */
1847         for_each_possible_cpu(i) {
1848                 /* If the cpu isn't online, the cpu is mapped to first hctx */
1849                 if (!cpumask_test_cpu(i, online_mask))
1850                         continue;
1851 
1852                 ctx = per_cpu_ptr(q->queue_ctx, i);
1853                 hctx = q->mq_ops->map_queue(q, i);
1854 
1855                 cpumask_set_cpu(i, hctx->cpumask);
1856                 ctx->index_hw = hctx->nr_ctx;
1857                 hctx->ctxs[hctx->nr_ctx++] = ctx;
1858         }
1859 
1860         mutex_unlock(&q->sysfs_lock);
1861 
1862         queue_for_each_hw_ctx(q, hctx, i) {
1863                 struct blk_mq_ctxmap *map = &hctx->ctx_map;
1864 
1865                 /*
1866                  * If no software queues are mapped to this hardware queue,
1867                  * disable it and free the request entries.
1868                  */
1869                 if (!hctx->nr_ctx) {
1870                         if (set->tags[i]) {
1871                                 blk_mq_free_rq_map(set, set->tags[i], i);
1872                                 set->tags[i] = NULL;
1873                         }
1874                         hctx->tags = NULL;
1875                         continue;
1876                 }
1877 
1878                 /* unmapped hw queue can be remapped after CPU topo changed */
1879                 if (!set->tags[i])
1880                         set->tags[i] = blk_mq_init_rq_map(set, i);
1881                 hctx->tags = set->tags[i];
1882                 WARN_ON(!hctx->tags);
1883 
1884                 cpumask_copy(hctx->tags->cpumask, hctx->cpumask);
1885                 /*
1886                  * Set the map size to the number of mapped software queues.
1887                  * This is more accurate and more efficient than looping
1888                  * over all possibly mapped software queues.
1889                  */
1890                 map->size = DIV_ROUND_UP(hctx->nr_ctx, map->bits_per_word);
1891 
1892                 /*
1893                  * Initialize batch roundrobin counts
1894                  */
1895                 hctx->next_cpu = cpumask_first(hctx->cpumask);
1896                 hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
1897         }
1898 }
1899 
1900 static void queue_set_hctx_shared(struct request_queue *q, bool shared)
1901 {
1902         struct blk_mq_hw_ctx *hctx;
1903         int i;
1904 
1905         queue_for_each_hw_ctx(q, hctx, i) {
1906                 if (shared)
1907                         hctx->flags |= BLK_MQ_F_TAG_SHARED;
1908                 else
1909                         hctx->flags &= ~BLK_MQ_F_TAG_SHARED;
1910         }
1911 }
1912 
1913 static void blk_mq_update_tag_set_depth(struct blk_mq_tag_set *set, bool shared)
1914 {
1915         struct request_queue *q;
1916 
1917         list_for_each_entry(q, &set->tag_list, tag_set_list) {
1918                 blk_mq_freeze_queue(q);
1919                 queue_set_hctx_shared(q, shared);
1920                 blk_mq_unfreeze_queue(q);
1921         }
1922 }
1923 
1924 static void blk_mq_del_queue_tag_set(struct request_queue *q)
1925 {
1926         struct blk_mq_tag_set *set = q->tag_set;
1927 
1928         mutex_lock(&set->tag_list_lock);
1929         list_del_init(&q->tag_set_list);
1930         if (list_is_singular(&set->tag_list)) {
1931                 /* just transitioned to unshared */
1932                 set->flags &= ~BLK_MQ_F_TAG_SHARED;
1933                 /* update existing queue */
1934                 blk_mq_update_tag_set_depth(set, false);
1935         }
1936         mutex_unlock(&set->tag_list_lock);
1937 }
1938 
1939 static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
1940                                      struct request_queue *q)
1941 {
1942         q->tag_set = set;
1943 
1944         mutex_lock(&set->tag_list_lock);
1945 
1946         /* Check to see if we're transitioning to shared (from 1 to 2 queues). */
1947         if (!list_empty(&set->tag_list) && !(set->flags & BLK_MQ_F_TAG_SHARED)) {
1948                 set->flags |= BLK_MQ_F_TAG_SHARED;
1949                 /* update existing queue */
1950                 blk_mq_update_tag_set_depth(set, true);
1951         }
1952         if (set->flags & BLK_MQ_F_TAG_SHARED)
1953                 queue_set_hctx_shared(q, true);
1954         list_add_tail(&q->tag_set_list, &set->tag_list);
1955 
1956         mutex_unlock(&set->tag_list_lock);
1957 }
1958 
1959 /*
1960  * It is the actual release handler for mq, but we do it from
1961  * request queue's release handler for avoiding use-after-free
1962  * and headache because q->mq_kobj shouldn't have been introduced,
1963  * but we can't group ctx/kctx kobj without it.
1964  */
1965 void blk_mq_release(struct request_queue *q)
1966 {
1967         struct blk_mq_hw_ctx *hctx;
1968         unsigned int i;
1969 
1970         /* hctx kobj stays in hctx */
1971         queue_for_each_hw_ctx(q, hctx, i) {
1972                 if (!hctx)
1973                         continue;
1974                 kfree(hctx->ctxs);
1975                 kfree(hctx);
1976         }
1977 
1978         kfree(q->mq_map);
1979         q->mq_map = NULL;
1980 
1981         kfree(q->queue_hw_ctx);
1982 
1983         /* ctx kobj stays in queue_ctx */
1984         free_percpu(q->queue_ctx);
1985 }
1986 
1987 struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
1988 {
1989         struct request_queue *uninit_q, *q;
1990 
1991         uninit_q = blk_alloc_queue_node(GFP_KERNEL, set->numa_node);
1992         if (!uninit_q)
1993                 return ERR_PTR(-ENOMEM);
1994 
1995         q = blk_mq_init_allocated_queue(set, uninit_q);
1996         if (IS_ERR(q))
1997                 blk_cleanup_queue(uninit_q);
1998 
1999         return q;
2000 }
2001 EXPORT_SYMBOL(blk_mq_init_queue);
2002 
2003 static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
2004                                                 struct request_queue *q)
2005 {
2006         int i, j;
2007         struct blk_mq_hw_ctx **hctxs = q->queue_hw_ctx;
2008 
2009         blk_mq_sysfs_unregister(q);
2010         for (i = 0; i < set->nr_hw_queues; i++) {
2011                 int node;
2012 
2013                 if (hctxs[i])
2014                         continue;
2015 
2016                 node = blk_mq_hw_queue_to_node(q->mq_map, i);
2017                 hctxs[i] = kzalloc_node(sizeof(struct blk_mq_hw_ctx),
2018                                         GFP_KERNEL, node);
2019                 if (!hctxs[i])
2020                         break;
2021 
2022                 if (!zalloc_cpumask_var_node(&hctxs[i]->cpumask, GFP_KERNEL,
2023                                                 node)) {
2024                         kfree(hctxs[i]);
2025                         hctxs[i] = NULL;
2026                         break;
2027                 }
2028 
2029                 atomic_set(&hctxs[i]->nr_active, 0);
2030                 hctxs[i]->numa_node = node;
2031                 hctxs[i]->queue_num = i;
2032 
2033                 if (blk_mq_init_hctx(q, set, hctxs[i], i)) {
2034                         free_cpumask_var(hctxs[i]->cpumask);
2035                         kfree(hctxs[i]);
2036                         hctxs[i] = NULL;
2037                         break;
2038                 }
2039                 blk_mq_hctx_kobj_init(hctxs[i]);
2040         }
2041         for (j = i; j < q->nr_hw_queues; j++) {
2042                 struct blk_mq_hw_ctx *hctx = hctxs[j];
2043 
2044                 if (hctx) {
2045                         if (hctx->tags) {
2046                                 blk_mq_free_rq_map(set, hctx->tags, j);
2047                                 set->tags[j] = NULL;
2048                         }
2049                         blk_mq_exit_hctx(q, set, hctx, j);
2050                         free_cpumask_var(hctx->cpumask);
2051                         kobject_put(&hctx->kobj);
2052                         kfree(hctx->ctxs);
2053                         kfree(hctx);
2054                         hctxs[j] = NULL;
2055 
2056                 }
2057         }
2058         q->nr_hw_queues = i;
2059         blk_mq_sysfs_register(q);
2060 }
2061 
2062 struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
2063                                                   struct request_queue *q)
2064 {
2065         /* mark the queue as mq asap */
2066         q->mq_ops = set->ops;
2067 
2068         q->queue_ctx = alloc_percpu(struct blk_mq_ctx);
2069         if (!q->queue_ctx)
2070                 goto err_exit;
2071 
2072         q->queue_hw_ctx = kzalloc_node(nr_cpu_ids * sizeof(*(q->queue_hw_ctx)),
2073                                                 GFP_KERNEL, set->numa_node);
2074         if (!q->queue_hw_ctx)
2075                 goto err_percpu;
2076 
2077         q->mq_map = blk_mq_make_queue_map(set);
2078         if (!q->mq_map)
2079                 goto err_map;
2080 
2081         blk_mq_realloc_hw_ctxs(set, q);
2082         if (!q->nr_hw_queues)
2083                 goto err_hctxs;
2084 
2085         INIT_WORK(&q->timeout_work, blk_mq_timeout_work);
2086         blk_queue_rq_timeout(q, set->timeout ? set->timeout : 30 * HZ);
2087 
2088         q->nr_queues = nr_cpu_ids;
2089 
2090         q->queue_flags |= QUEUE_FLAG_MQ_DEFAULT;
2091 
2092         if (!(set->flags & BLK_MQ_F_SG_MERGE))
2093                 q->queue_flags |= 1 << QUEUE_FLAG_NO_SG_MERGE;
2094 
2095         q->sg_reserved_size = INT_MAX;
2096 
2097         INIT_WORK(&q->requeue_work, blk_mq_requeue_work);
2098         INIT_LIST_HEAD(&q->requeue_list);
2099         spin_lock_init(&q->requeue_lock);
2100 
2101         if (q->nr_hw_queues > 1)
2102                 blk_queue_make_request(q, blk_mq_make_request);
2103         else
2104                 blk_queue_make_request(q, blk_sq_make_request);
2105 
2106         /*
2107          * Do this after blk_queue_make_request() overrides it...
2108          */
2109         q->nr_requests = set->queue_depth;
2110 
2111         if (set->ops->complete)
2112                 blk_queue_softirq_done(q, set->ops->complete);
2113 
2114         blk_mq_init_cpu_queues(q, set->nr_hw_queues);
2115 
2116         get_online_cpus();
2117         mutex_lock(&all_q_mutex);
2118 
2119         list_add_tail(&q->all_q_node, &all_q_list);
2120         blk_mq_add_queue_tag_set(set, q);
2121         blk_mq_map_swqueue(q, cpu_online_mask);
2122 
2123         mutex_unlock(&all_q_mutex);
2124         put_online_cpus();
2125 
2126         return q;
2127 
2128 err_hctxs:
2129         kfree(q->mq_map);
2130 err_map:
2131         kfree(q->queue_hw_ctx);
2132 err_percpu:
2133         free_percpu(q->queue_ctx);
2134 err_exit:
2135         q->mq_ops = NULL;
2136         return ERR_PTR(-ENOMEM);
2137 }
2138 EXPORT_SYMBOL(blk_mq_init_allocated_queue);
2139 
2140 void blk_mq_free_queue(struct request_queue *q)
2141 {
2142         struct blk_mq_tag_set   *set = q->tag_set;
2143 
2144         mutex_lock(&all_q_mutex);
2145         list_del_init(&q->all_q_node);
2146         mutex_unlock(&all_q_mutex);
2147 
2148         blk_mq_del_queue_tag_set(q);
2149 
2150         blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);
2151         blk_mq_free_hw_queues(q, set);
2152 }
2153 
2154 /* Basically redo blk_mq_init_queue with queue frozen */
2155 static void blk_mq_queue_reinit(struct request_queue *q,
2156                                 const struct cpumask *online_mask)
2157 {
2158         WARN_ON_ONCE(!atomic_read(&q->mq_freeze_depth));
2159 
2160         blk_mq_sysfs_unregister(q);
2161 
2162         blk_mq_update_queue_map(q->mq_map, q->nr_hw_queues, online_mask);
2163 
2164         /*
2165          * redo blk_mq_init_cpu_queues and blk_mq_init_hw_queues. FIXME: maybe
2166          * we should change hctx numa_node according to new topology (this
2167          * involves free and re-allocate memory, worthy doing?)
2168          */
2169 
2170         blk_mq_map_swqueue(q, online_mask);
2171 
2172         blk_mq_sysfs_register(q);
2173 }
2174 
2175 static int blk_mq_queue_reinit_notify(struct notifier_block *nb,
2176                                       unsigned long action, void *hcpu)
2177 {
2178         struct request_queue *q;
2179         int cpu = (unsigned long)hcpu;
2180         /*
2181          * New online cpumask which is going to be set in this hotplug event.
2182          * Declare this cpumasks as global as cpu-hotplug operation is invoked
2183          * one-by-one and dynamically allocating this could result in a failure.
2184          */
2185         static struct cpumask online_new;
2186 
2187         /*
2188          * Before hotadded cpu starts handling requests, new mappings must
2189          * be established.  Otherwise, these requests in hw queue might
2190          * never be dispatched.
2191          *
2192          * For example, there is a single hw queue (hctx) and two CPU queues
2193          * (ctx0 for CPU0, and ctx1 for CPU1).
2194          *
2195          * Now CPU1 is just onlined and a request is inserted into
2196          * ctx1->rq_list and set bit0 in pending bitmap as ctx1->index_hw is
2197          * still zero.
2198          *
2199          * And then while running hw queue, flush_busy_ctxs() finds bit0 is
2200          * set in pending bitmap and tries to retrieve requests in
2201          * hctx->ctxs[0]->rq_list.  But htx->ctxs[0] is a pointer to ctx0,
2202          * so the request in ctx1->rq_list is ignored.
2203          */
2204         switch (action & ~CPU_TASKS_FROZEN) {
2205         case CPU_DEAD:
2206         case CPU_UP_CANCELED:
2207                 cpumask_copy(&online_new, cpu_online_mask);
2208                 break;
2209         case CPU_UP_PREPARE:
2210                 cpumask_copy(&online_new, cpu_online_mask);
2211                 cpumask_set_cpu(cpu, &online_new);
2212                 break;
2213         default:
2214                 return NOTIFY_OK;
2215         }
2216 
2217         mutex_lock(&all_q_mutex);
2218 
2219         /*
2220          * We need to freeze and reinit all existing queues.  Freezing
2221          * involves synchronous wait for an RCU grace period and doing it
2222          * one by one may take a long time.  Start freezing all queues in
2223          * one swoop and then wait for the completions so that freezing can
2224          * take place in parallel.
2225          */
2226         list_for_each_entry(q, &all_q_list, all_q_node)
2227                 blk_mq_freeze_queue_start(q);
2228         list_for_each_entry(q, &all_q_list, all_q_node) {
2229                 blk_mq_freeze_queue_wait(q);
2230 
2231                 /*
2232                  * timeout handler can't touch hw queue during the
2233                  * reinitialization
2234                  */
2235                 del_timer_sync(&q->timeout);
2236         }
2237 
2238         list_for_each_entry(q, &all_q_list, all_q_node)
2239                 blk_mq_queue_reinit(q, &online_new);
2240 
2241         list_for_each_entry(q, &all_q_list, all_q_node)
2242                 blk_mq_unfreeze_queue(q);
2243 
2244         mutex_unlock(&all_q_mutex);
2245         return NOTIFY_OK;
2246 }
2247 
2248 static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
2249 {
2250         int i;
2251 
2252         for (i = 0; i < set->nr_hw_queues; i++) {
2253                 set->tags[i] = blk_mq_init_rq_map(set, i);
2254                 if (!set->tags[i])
2255                         goto out_unwind;
2256         }
2257 
2258         return 0;
2259 
2260 out_unwind:
2261         while (--i >= 0)
2262                 blk_mq_free_rq_map(set, set->tags[i], i);
2263 
2264         return -ENOMEM;
2265 }
2266 
2267 /*
2268  * Allocate the request maps associated with this tag_set. Note that this
2269  * may reduce the depth asked for, if memory is tight. set->queue_depth
2270  * will be updated to reflect the allocated depth.
2271  */
2272 static int blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
2273 {
2274         unsigned int depth;
2275         int err;
2276 
2277         depth = set->queue_depth;
2278         do {
2279                 err = __blk_mq_alloc_rq_maps(set);
2280                 if (!err)
2281                         break;
2282 
2283                 set->queue_depth >>= 1;
2284                 if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN) {
2285                         err = -ENOMEM;
2286                         break;
2287                 }
2288         } while (set->queue_depth);
2289 
2290         if (!set->queue_depth || err) {
2291                 pr_err("blk-mq: failed to allocate request map\n");
2292                 return -ENOMEM;
2293         }
2294 
2295         if (depth != set->queue_depth)
2296                 pr_info("blk-mq: reduced tag depth (%u -> %u)\n",
2297                                                 depth, set->queue_depth);
2298 
2299         return 0;
2300 }
2301 
2302 struct cpumask *blk_mq_tags_cpumask(struct blk_mq_tags *tags)
2303 {
2304         return tags->cpumask;
2305 }
2306 EXPORT_SYMBOL_GPL(blk_mq_tags_cpumask);
2307 
2308 /*
2309  * Alloc a tag set to be associated with one or more request queues.
2310  * May fail with EINVAL for various error conditions. May adjust the
2311  * requested depth down, if if it too large. In that case, the set
2312  * value will be stored in set->queue_depth.
2313  */
2314 int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
2315 {
2316         BUILD_BUG_ON(BLK_MQ_MAX_DEPTH > 1 << BLK_MQ_UNIQUE_TAG_BITS);
2317 
2318         if (!set->nr_hw_queues)
2319                 return -EINVAL;
2320         if (!set->queue_depth)
2321                 return -EINVAL;
2322         if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN)
2323                 return -EINVAL;
2324 
2325         if (!set->ops->queue_rq || !set->ops->map_queue)
2326                 return -EINVAL;
2327 
2328         if (set->queue_depth > BLK_MQ_MAX_DEPTH) {
2329                 pr_info("blk-mq: reduced tag depth to %u\n",
2330                         BLK_MQ_MAX_DEPTH);
2331                 set->queue_depth = BLK_MQ_MAX_DEPTH;
2332         }
2333 
2334         /*
2335          * If a crashdump is active, then we are potentially in a very
2336          * memory constrained environment. Limit us to 1 queue and
2337          * 64 tags to prevent using too much memory.
2338          */
2339         if (is_kdump_kernel()) {
2340                 set->nr_hw_queues = 1;
2341                 set->queue_depth = min(64U, set->queue_depth);
2342         }
2343         /*
2344          * There is no use for more h/w queues than cpus.
2345          */
2346         if (set->nr_hw_queues > nr_cpu_ids)
2347                 set->nr_hw_queues = nr_cpu_ids;
2348 
2349         set->tags = kzalloc_node(nr_cpu_ids * sizeof(struct blk_mq_tags *),
2350                                  GFP_KERNEL, set->numa_node);
2351         if (!set->tags)
2352                 return -ENOMEM;
2353 
2354         if (blk_mq_alloc_rq_maps(set))
2355                 goto enomem;
2356 
2357         mutex_init(&set->tag_list_lock);
2358         INIT_LIST_HEAD(&set->tag_list);
2359 
2360         return 0;
2361 enomem:
2362         kfree(set->tags);
2363         set->tags = NULL;
2364         return -ENOMEM;
2365 }
2366 EXPORT_SYMBOL(blk_mq_alloc_tag_set);
2367 
2368 void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
2369 {
2370         int i;
2371 
2372         for (i = 0; i < nr_cpu_ids; i++) {
2373                 if (set->tags[i])
2374                         blk_mq_free_rq_map(set, set->tags[i], i);
2375         }
2376 
2377         kfree(set->tags);
2378         set->tags = NULL;
2379 }
2380 EXPORT_SYMBOL(blk_mq_free_tag_set);
2381 
2382 int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
2383 {
2384         struct blk_mq_tag_set *set = q->tag_set;
2385         struct blk_mq_hw_ctx *hctx;
2386         int i, ret;
2387 
2388         if (!set || nr > set->queue_depth)
2389                 return -EINVAL;
2390 
2391         ret = 0;
2392         queue_for_each_hw_ctx(q, hctx, i) {
2393                 if (!hctx->tags)
2394                         continue;
2395                 ret = blk_mq_tag_update_depth(hctx->tags, nr);
2396                 if (ret)
2397                         break;
2398         }
2399 
2400         if (!ret)
2401                 q->nr_requests = nr;
2402 
2403         return ret;
2404 }
2405 
2406 void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
2407 {
2408         struct request_queue *q;
2409 
2410         if (nr_hw_queues > nr_cpu_ids)
2411                 nr_hw_queues = nr_cpu_ids;
2412         if (nr_hw_queues < 1 || nr_hw_queues == set->nr_hw_queues)
2413                 return;
2414 
2415         list_for_each_entry(q, &set->tag_list, tag_set_list)
2416                 blk_mq_freeze_queue(q);
2417 
2418         set->nr_hw_queues = nr_hw_queues;
2419         list_for_each_entry(q, &set->tag_list, tag_set_list) {
2420                 blk_mq_realloc_hw_ctxs(set, q);
2421 
2422                 if (q->nr_hw_queues > 1)
2423                         blk_queue_make_request(q, blk_mq_make_request);
2424                 else
2425                         blk_queue_make_request(q, blk_sq_make_request);
2426 
2427                 blk_mq_queue_reinit(q, cpu_online_mask);
2428         }
2429 
2430         list_for_each_entry(q, &set->tag_list, tag_set_list)
2431                 blk_mq_unfreeze_queue(q);
2432 }
2433 EXPORT_SYMBOL_GPL(blk_mq_update_nr_hw_queues);
2434 
2435 void blk_mq_disable_hotplug(void)
2436 {
2437         mutex_lock(&all_q_mutex);
2438 }
2439 
2440 void blk_mq_enable_hotplug(void)
2441 {
2442         mutex_unlock(&all_q_mutex);
2443 }
2444 
2445 static int __init blk_mq_init(void)
2446 {
2447         blk_mq_cpu_init();
2448 
2449         hotcpu_notifier(blk_mq_queue_reinit_notify, 0);
2450 
2451         return 0;
2452 }
2453 subsys_initcall(blk_mq_init);
2454 

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