2 * Block multiqueue core code
4 * Copyright (C) 2013-2014 Jens Axboe
5 * Copyright (C) 2013-2014 Christoph Hellwig
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>
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>
29 #include <trace/events/block.h>
31 #include <linux/blk-mq.h>
34 #include "blk-mq-debugfs.h"
35 #include "blk-mq-tag.h"
38 #include "blk-mq-sched.h"
40 static bool blk_mq_poll(struct request_queue
*q
, blk_qc_t cookie
);
41 static void blk_mq_poll_stats_start(struct request_queue
*q
);
42 static void blk_mq_poll_stats_fn(struct blk_stat_callback
*cb
);
44 static int blk_mq_poll_stats_bkt(const struct request
*rq
)
46 int ddir
, bytes
, bucket
;
48 ddir
= rq_data_dir(rq
);
49 bytes
= blk_rq_bytes(rq
);
51 bucket
= ddir
+ 2*(ilog2(bytes
) - 9);
55 else if (bucket
>= BLK_MQ_POLL_STATS_BKTS
)
56 return ddir
+ BLK_MQ_POLL_STATS_BKTS
- 2;
62 * Check if any of the ctx's have pending work in this hardware queue
64 static bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx
*hctx
)
66 return !list_empty_careful(&hctx
->dispatch
) ||
67 sbitmap_any_bit_set(&hctx
->ctx_map
) ||
68 blk_mq_sched_has_work(hctx
);
72 * Mark this ctx as having pending work in this hardware queue
74 static void blk_mq_hctx_mark_pending(struct blk_mq_hw_ctx
*hctx
,
75 struct blk_mq_ctx
*ctx
)
77 if (!sbitmap_test_bit(&hctx
->ctx_map
, ctx
->index_hw
))
78 sbitmap_set_bit(&hctx
->ctx_map
, ctx
->index_hw
);
81 static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx
*hctx
,
82 struct blk_mq_ctx
*ctx
)
84 sbitmap_clear_bit(&hctx
->ctx_map
, ctx
->index_hw
);
88 struct hd_struct
*part
;
89 unsigned int *inflight
;
92 static void blk_mq_check_inflight(struct blk_mq_hw_ctx
*hctx
,
93 struct request
*rq
, void *priv
,
96 struct mq_inflight
*mi
= priv
;
98 if (test_bit(REQ_ATOM_STARTED
, &rq
->atomic_flags
) &&
99 !test_bit(REQ_ATOM_COMPLETE
, &rq
->atomic_flags
)) {
101 * index[0] counts the specific partition that was asked
102 * for. index[1] counts the ones that are active on the
103 * whole device, so increment that if mi->part is indeed
104 * a partition, and not a whole device.
106 if (rq
->part
== mi
->part
)
108 if (mi
->part
->partno
)
113 void blk_mq_in_flight(struct request_queue
*q
, struct hd_struct
*part
,
114 unsigned int inflight
[2])
116 struct mq_inflight mi
= { .part
= part
, .inflight
= inflight
, };
118 inflight
[0] = inflight
[1] = 0;
119 blk_mq_queue_tag_busy_iter(q
, blk_mq_check_inflight
, &mi
);
122 static void blk_mq_check_inflight_rw(struct blk_mq_hw_ctx
*hctx
,
123 struct request
*rq
, void *priv
,
126 struct mq_inflight
*mi
= priv
;
128 if (rq
->part
== mi
->part
)
129 mi
->inflight
[rq_data_dir(rq
)]++;
132 void blk_mq_in_flight_rw(struct request_queue
*q
, struct hd_struct
*part
,
133 unsigned int inflight
[2])
135 struct mq_inflight mi
= { .part
= part
, .inflight
= inflight
, };
137 inflight
[0] = inflight
[1] = 0;
138 blk_mq_queue_tag_busy_iter(q
, blk_mq_check_inflight_rw
, &mi
);
141 void blk_freeze_queue_start(struct request_queue
*q
)
145 freeze_depth
= atomic_inc_return(&q
->mq_freeze_depth
);
146 if (freeze_depth
== 1) {
147 percpu_ref_kill(&q
->q_usage_counter
);
149 blk_mq_run_hw_queues(q
, false);
152 EXPORT_SYMBOL_GPL(blk_freeze_queue_start
);
154 void blk_mq_freeze_queue_wait(struct request_queue
*q
)
156 wait_event(q
->mq_freeze_wq
, percpu_ref_is_zero(&q
->q_usage_counter
));
158 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait
);
160 int blk_mq_freeze_queue_wait_timeout(struct request_queue
*q
,
161 unsigned long timeout
)
163 return wait_event_timeout(q
->mq_freeze_wq
,
164 percpu_ref_is_zero(&q
->q_usage_counter
),
167 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait_timeout
);
170 * Guarantee no request is in use, so we can change any data structure of
171 * the queue afterward.
173 void blk_freeze_queue(struct request_queue
*q
)
176 * In the !blk_mq case we are only calling this to kill the
177 * q_usage_counter, otherwise this increases the freeze depth
178 * and waits for it to return to zero. For this reason there is
179 * no blk_unfreeze_queue(), and blk_freeze_queue() is not
180 * exported to drivers as the only user for unfreeze is blk_mq.
182 blk_freeze_queue_start(q
);
185 blk_mq_freeze_queue_wait(q
);
188 void blk_mq_freeze_queue(struct request_queue
*q
)
191 * ...just an alias to keep freeze and unfreeze actions balanced
192 * in the blk_mq_* namespace
196 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue
);
198 void blk_mq_unfreeze_queue(struct request_queue
*q
)
202 freeze_depth
= atomic_dec_return(&q
->mq_freeze_depth
);
203 WARN_ON_ONCE(freeze_depth
< 0);
205 percpu_ref_reinit(&q
->q_usage_counter
);
206 wake_up_all(&q
->mq_freeze_wq
);
209 EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue
);
212 * FIXME: replace the scsi_internal_device_*block_nowait() calls in the
213 * mpt3sas driver such that this function can be removed.
215 void blk_mq_quiesce_queue_nowait(struct request_queue
*q
)
219 spin_lock_irqsave(q
->queue_lock
, flags
);
220 queue_flag_set(QUEUE_FLAG_QUIESCED
, q
);
221 spin_unlock_irqrestore(q
->queue_lock
, flags
);
223 EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait
);
226 * blk_mq_quiesce_queue() - wait until all ongoing dispatches have finished
229 * Note: this function does not prevent that the struct request end_io()
230 * callback function is invoked. Once this function is returned, we make
231 * sure no dispatch can happen until the queue is unquiesced via
232 * blk_mq_unquiesce_queue().
234 void blk_mq_quiesce_queue(struct request_queue
*q
)
236 struct blk_mq_hw_ctx
*hctx
;
240 blk_mq_quiesce_queue_nowait(q
);
242 queue_for_each_hw_ctx(q
, hctx
, i
) {
243 if (hctx
->flags
& BLK_MQ_F_BLOCKING
)
244 synchronize_srcu(hctx
->queue_rq_srcu
);
251 EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue
);
254 * blk_mq_unquiesce_queue() - counterpart of blk_mq_quiesce_queue()
257 * This function recovers queue into the state before quiescing
258 * which is done by blk_mq_quiesce_queue.
260 void blk_mq_unquiesce_queue(struct request_queue
*q
)
264 spin_lock_irqsave(q
->queue_lock
, flags
);
265 queue_flag_clear(QUEUE_FLAG_QUIESCED
, q
);
266 spin_unlock_irqrestore(q
->queue_lock
, flags
);
268 /* dispatch requests which are inserted during quiescing */
269 blk_mq_run_hw_queues(q
, true);
271 EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue
);
273 void blk_mq_wake_waiters(struct request_queue
*q
)
275 struct blk_mq_hw_ctx
*hctx
;
278 queue_for_each_hw_ctx(q
, hctx
, i
)
279 if (blk_mq_hw_queue_mapped(hctx
))
280 blk_mq_tag_wakeup_all(hctx
->tags
, true);
283 bool blk_mq_can_queue(struct blk_mq_hw_ctx
*hctx
)
285 return blk_mq_has_free_tags(hctx
->tags
);
287 EXPORT_SYMBOL(blk_mq_can_queue
);
289 static struct request
*blk_mq_rq_ctx_init(struct blk_mq_alloc_data
*data
,
290 unsigned int tag
, unsigned int op
)
292 struct blk_mq_tags
*tags
= blk_mq_tags_from_data(data
);
293 struct request
*rq
= tags
->static_rqs
[tag
];
297 if (data
->flags
& BLK_MQ_REQ_INTERNAL
) {
299 rq
->internal_tag
= tag
;
301 if (data
->hctx
->flags
& BLK_MQ_F_TAG_SHARED
) {
302 rq
->rq_flags
= RQF_MQ_INFLIGHT
;
303 atomic_inc(&data
->hctx
->nr_active
);
306 rq
->internal_tag
= -1;
307 data
->hctx
->tags
->rqs
[rq
->tag
] = rq
;
310 INIT_LIST_HEAD(&rq
->queuelist
);
311 /* csd/requeue_work/fifo_time is initialized before use */
313 rq
->mq_ctx
= data
->ctx
;
315 if (data
->flags
& BLK_MQ_REQ_PREEMPT
)
316 rq
->rq_flags
|= RQF_PREEMPT
;
317 if (blk_queue_io_stat(data
->q
))
318 rq
->rq_flags
|= RQF_IO_STAT
;
319 /* do not touch atomic flags, it needs atomic ops against the timer */
321 INIT_HLIST_NODE(&rq
->hash
);
322 RB_CLEAR_NODE(&rq
->rb_node
);
325 rq
->start_time
= jiffies
;
326 #ifdef CONFIG_BLK_CGROUP
328 set_start_time_ns(rq
);
329 rq
->io_start_time_ns
= 0;
331 rq
->nr_phys_segments
= 0;
332 #if defined(CONFIG_BLK_DEV_INTEGRITY)
333 rq
->nr_integrity_segments
= 0;
336 /* tag was already set */
339 INIT_LIST_HEAD(&rq
->timeout_list
);
343 rq
->end_io_data
= NULL
;
346 data
->ctx
->rq_dispatched
[op_is_sync(op
)]++;
350 static struct request
*blk_mq_get_request(struct request_queue
*q
,
351 struct bio
*bio
, unsigned int op
,
352 struct blk_mq_alloc_data
*data
)
354 struct elevator_queue
*e
= q
->elevator
;
357 bool put_ctx_on_error
= false;
359 blk_queue_enter_live(q
);
361 if (likely(!data
->ctx
)) {
362 data
->ctx
= blk_mq_get_ctx(q
);
363 put_ctx_on_error
= true;
365 if (likely(!data
->hctx
))
366 data
->hctx
= blk_mq_map_queue(q
, data
->ctx
->cpu
);
368 data
->flags
|= BLK_MQ_REQ_NOWAIT
;
371 data
->flags
|= BLK_MQ_REQ_INTERNAL
;
374 * Flush requests are special and go directly to the
377 if (!op_is_flush(op
) && e
->type
->ops
.mq
.limit_depth
)
378 e
->type
->ops
.mq
.limit_depth(op
, data
);
380 blk_mq_tag_busy(data
->hctx
);
383 tag
= blk_mq_get_tag(data
);
384 if (tag
== BLK_MQ_TAG_FAIL
) {
385 if (put_ctx_on_error
) {
386 blk_mq_put_ctx(data
->ctx
);
393 rq
= blk_mq_rq_ctx_init(data
, tag
, op
);
394 if (!op_is_flush(op
)) {
396 if (e
&& e
->type
->ops
.mq
.prepare_request
) {
397 if (e
->type
->icq_cache
&& rq_ioc(bio
))
398 blk_mq_sched_assign_ioc(rq
, bio
);
400 e
->type
->ops
.mq
.prepare_request(rq
, bio
);
401 rq
->rq_flags
|= RQF_ELVPRIV
;
404 data
->hctx
->queued
++;
408 struct request
*blk_mq_alloc_request(struct request_queue
*q
, unsigned int op
,
409 blk_mq_req_flags_t flags
)
411 struct blk_mq_alloc_data alloc_data
= { .flags
= flags
};
415 ret
= blk_queue_enter(q
, flags
);
419 rq
= blk_mq_get_request(q
, NULL
, op
, &alloc_data
);
423 return ERR_PTR(-EWOULDBLOCK
);
425 blk_mq_put_ctx(alloc_data
.ctx
);
428 rq
->__sector
= (sector_t
) -1;
429 rq
->bio
= rq
->biotail
= NULL
;
432 EXPORT_SYMBOL(blk_mq_alloc_request
);
434 struct request
*blk_mq_alloc_request_hctx(struct request_queue
*q
,
435 unsigned int op
, blk_mq_req_flags_t flags
, unsigned int hctx_idx
)
437 struct blk_mq_alloc_data alloc_data
= { .flags
= flags
};
443 * If the tag allocator sleeps we could get an allocation for a
444 * different hardware context. No need to complicate the low level
445 * allocator for this for the rare use case of a command tied to
448 if (WARN_ON_ONCE(!(flags
& BLK_MQ_REQ_NOWAIT
)))
449 return ERR_PTR(-EINVAL
);
451 if (hctx_idx
>= q
->nr_hw_queues
)
452 return ERR_PTR(-EIO
);
454 ret
= blk_queue_enter(q
, flags
);
459 * Check if the hardware context is actually mapped to anything.
460 * If not tell the caller that it should skip this queue.
462 alloc_data
.hctx
= q
->queue_hw_ctx
[hctx_idx
];
463 if (!blk_mq_hw_queue_mapped(alloc_data
.hctx
)) {
465 return ERR_PTR(-EXDEV
);
467 cpu
= cpumask_first_and(alloc_data
.hctx
->cpumask
, cpu_online_mask
);
468 alloc_data
.ctx
= __blk_mq_get_ctx(q
, cpu
);
470 rq
= blk_mq_get_request(q
, NULL
, op
, &alloc_data
);
474 return ERR_PTR(-EWOULDBLOCK
);
478 EXPORT_SYMBOL_GPL(blk_mq_alloc_request_hctx
);
480 void blk_mq_free_request(struct request
*rq
)
482 struct request_queue
*q
= rq
->q
;
483 struct elevator_queue
*e
= q
->elevator
;
484 struct blk_mq_ctx
*ctx
= rq
->mq_ctx
;
485 struct blk_mq_hw_ctx
*hctx
= blk_mq_map_queue(q
, ctx
->cpu
);
486 const int sched_tag
= rq
->internal_tag
;
488 if (rq
->rq_flags
& RQF_ELVPRIV
) {
489 if (e
&& e
->type
->ops
.mq
.finish_request
)
490 e
->type
->ops
.mq
.finish_request(rq
);
492 put_io_context(rq
->elv
.icq
->ioc
);
497 ctx
->rq_completed
[rq_is_sync(rq
)]++;
498 if (rq
->rq_flags
& RQF_MQ_INFLIGHT
)
499 atomic_dec(&hctx
->nr_active
);
501 if (unlikely(laptop_mode
&& !blk_rq_is_passthrough(rq
)))
502 laptop_io_completion(q
->backing_dev_info
);
504 wbt_done(q
->rq_wb
, &rq
->issue_stat
);
507 blk_put_rl(blk_rq_rl(rq
));
509 clear_bit(REQ_ATOM_STARTED
, &rq
->atomic_flags
);
510 clear_bit(REQ_ATOM_POLL_SLEPT
, &rq
->atomic_flags
);
512 blk_mq_put_tag(hctx
, hctx
->tags
, ctx
, rq
->tag
);
514 blk_mq_put_tag(hctx
, hctx
->sched_tags
, ctx
, sched_tag
);
515 blk_mq_sched_restart(hctx
);
518 EXPORT_SYMBOL_GPL(blk_mq_free_request
);
520 inline void __blk_mq_end_request(struct request
*rq
, blk_status_t error
)
522 blk_account_io_done(rq
);
525 wbt_done(rq
->q
->rq_wb
, &rq
->issue_stat
);
526 rq
->end_io(rq
, error
);
528 if (unlikely(blk_bidi_rq(rq
)))
529 blk_mq_free_request(rq
->next_rq
);
530 blk_mq_free_request(rq
);
533 EXPORT_SYMBOL(__blk_mq_end_request
);
535 void blk_mq_end_request(struct request
*rq
, blk_status_t error
)
537 if (blk_update_request(rq
, error
, blk_rq_bytes(rq
)))
539 __blk_mq_end_request(rq
, error
);
541 EXPORT_SYMBOL(blk_mq_end_request
);
543 static void __blk_mq_complete_request_remote(void *data
)
545 struct request
*rq
= data
;
547 rq
->q
->softirq_done_fn(rq
);
550 static void __blk_mq_complete_request(struct request
*rq
)
552 struct blk_mq_ctx
*ctx
= rq
->mq_ctx
;
556 if (rq
->internal_tag
!= -1)
557 blk_mq_sched_completed_request(rq
);
558 if (rq
->rq_flags
& RQF_STATS
) {
559 blk_mq_poll_stats_start(rq
->q
);
563 if (!test_bit(QUEUE_FLAG_SAME_COMP
, &rq
->q
->queue_flags
)) {
564 rq
->q
->softirq_done_fn(rq
);
569 if (!test_bit(QUEUE_FLAG_SAME_FORCE
, &rq
->q
->queue_flags
))
570 shared
= cpus_share_cache(cpu
, ctx
->cpu
);
572 if (cpu
!= ctx
->cpu
&& !shared
&& cpu_online(ctx
->cpu
)) {
573 rq
->csd
.func
= __blk_mq_complete_request_remote
;
576 smp_call_function_single_async(ctx
->cpu
, &rq
->csd
);
578 rq
->q
->softirq_done_fn(rq
);
584 * blk_mq_complete_request - end I/O on a request
585 * @rq: the request being processed
588 * Ends all I/O on a request. It does not handle partial completions.
589 * The actual completion happens out-of-order, through a IPI handler.
591 void blk_mq_complete_request(struct request
*rq
)
593 struct request_queue
*q
= rq
->q
;
595 if (unlikely(blk_should_fake_timeout(q
)))
597 if (!blk_mark_rq_complete(rq
))
598 __blk_mq_complete_request(rq
);
600 EXPORT_SYMBOL(blk_mq_complete_request
);
602 int blk_mq_request_started(struct request
*rq
)
604 return test_bit(REQ_ATOM_STARTED
, &rq
->atomic_flags
);
606 EXPORT_SYMBOL_GPL(blk_mq_request_started
);
608 void blk_mq_start_request(struct request
*rq
)
610 struct request_queue
*q
= rq
->q
;
612 blk_mq_sched_started_request(rq
);
614 trace_block_rq_issue(q
, rq
);
616 if (test_bit(QUEUE_FLAG_STATS
, &q
->queue_flags
)) {
617 blk_stat_set_issue(&rq
->issue_stat
, blk_rq_sectors(rq
));
618 rq
->rq_flags
|= RQF_STATS
;
619 wbt_issue(q
->rq_wb
, &rq
->issue_stat
);
624 WARN_ON_ONCE(test_bit(REQ_ATOM_STARTED
, &rq
->atomic_flags
));
627 * Mark us as started and clear complete. Complete might have been
628 * set if requeue raced with timeout, which then marked it as
629 * complete. So be sure to clear complete again when we start
630 * the request, otherwise we'll ignore the completion event.
632 * Ensure that ->deadline is visible before we set STARTED, such that
633 * blk_mq_check_expired() is guaranteed to observe our ->deadline when
634 * it observes STARTED.
637 set_bit(REQ_ATOM_STARTED
, &rq
->atomic_flags
);
638 if (test_bit(REQ_ATOM_COMPLETE
, &rq
->atomic_flags
)) {
640 * Coherence order guarantees these consecutive stores to a
641 * single variable propagate in the specified order. Thus the
642 * clear_bit() is ordered _after_ the set bit. See
643 * blk_mq_check_expired().
645 * (the bits must be part of the same byte for this to be
648 clear_bit(REQ_ATOM_COMPLETE
, &rq
->atomic_flags
);
651 if (q
->dma_drain_size
&& blk_rq_bytes(rq
)) {
653 * Make sure space for the drain appears. We know we can do
654 * this because max_hw_segments has been adjusted to be one
655 * fewer than the device can handle.
657 rq
->nr_phys_segments
++;
660 EXPORT_SYMBOL(blk_mq_start_request
);
663 * When we reach here because queue is busy, REQ_ATOM_COMPLETE
664 * flag isn't set yet, so there may be race with timeout handler,
665 * but given rq->deadline is just set in .queue_rq() under
666 * this situation, the race won't be possible in reality because
667 * rq->timeout should be set as big enough to cover the window
668 * between blk_mq_start_request() called from .queue_rq() and
669 * clearing REQ_ATOM_STARTED here.
671 static void __blk_mq_requeue_request(struct request
*rq
)
673 struct request_queue
*q
= rq
->q
;
675 blk_mq_put_driver_tag(rq
);
677 trace_block_rq_requeue(q
, rq
);
678 wbt_requeue(q
->rq_wb
, &rq
->issue_stat
);
680 if (test_and_clear_bit(REQ_ATOM_STARTED
, &rq
->atomic_flags
)) {
681 if (q
->dma_drain_size
&& blk_rq_bytes(rq
))
682 rq
->nr_phys_segments
--;
686 void blk_mq_requeue_request(struct request
*rq
, bool kick_requeue_list
)
688 __blk_mq_requeue_request(rq
);
690 /* this request will be re-inserted to io scheduler queue */
691 blk_mq_sched_requeue_request(rq
);
693 BUG_ON(blk_queued_rq(rq
));
694 blk_mq_add_to_requeue_list(rq
, true, kick_requeue_list
);
696 EXPORT_SYMBOL(blk_mq_requeue_request
);
698 static void blk_mq_requeue_work(struct work_struct
*work
)
700 struct request_queue
*q
=
701 container_of(work
, struct request_queue
, requeue_work
.work
);
703 struct request
*rq
, *next
;
705 spin_lock_irq(&q
->requeue_lock
);
706 list_splice_init(&q
->requeue_list
, &rq_list
);
707 spin_unlock_irq(&q
->requeue_lock
);
709 list_for_each_entry_safe(rq
, next
, &rq_list
, queuelist
) {
710 if (!(rq
->rq_flags
& RQF_SOFTBARRIER
))
713 rq
->rq_flags
&= ~RQF_SOFTBARRIER
;
714 list_del_init(&rq
->queuelist
);
715 blk_mq_sched_insert_request(rq
, true, false, false, true);
718 while (!list_empty(&rq_list
)) {
719 rq
= list_entry(rq_list
.next
, struct request
, queuelist
);
720 list_del_init(&rq
->queuelist
);
721 blk_mq_sched_insert_request(rq
, false, false, false, true);
724 blk_mq_run_hw_queues(q
, false);
727 void blk_mq_add_to_requeue_list(struct request
*rq
, bool at_head
,
728 bool kick_requeue_list
)
730 struct request_queue
*q
= rq
->q
;
734 * We abuse this flag that is otherwise used by the I/O scheduler to
735 * request head insertion from the workqueue.
737 BUG_ON(rq
->rq_flags
& RQF_SOFTBARRIER
);
739 spin_lock_irqsave(&q
->requeue_lock
, flags
);
741 rq
->rq_flags
|= RQF_SOFTBARRIER
;
742 list_add(&rq
->queuelist
, &q
->requeue_list
);
744 list_add_tail(&rq
->queuelist
, &q
->requeue_list
);
746 spin_unlock_irqrestore(&q
->requeue_lock
, flags
);
748 if (kick_requeue_list
)
749 blk_mq_kick_requeue_list(q
);
751 EXPORT_SYMBOL(blk_mq_add_to_requeue_list
);
753 void blk_mq_kick_requeue_list(struct request_queue
*q
)
755 kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND
, &q
->requeue_work
, 0);
757 EXPORT_SYMBOL(blk_mq_kick_requeue_list
);
759 void blk_mq_delay_kick_requeue_list(struct request_queue
*q
,
762 kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND
, &q
->requeue_work
,
763 msecs_to_jiffies(msecs
));
765 EXPORT_SYMBOL(blk_mq_delay_kick_requeue_list
);
767 struct request
*blk_mq_tag_to_rq(struct blk_mq_tags
*tags
, unsigned int tag
)
769 if (tag
< tags
->nr_tags
) {
770 prefetch(tags
->rqs
[tag
]);
771 return tags
->rqs
[tag
];
776 EXPORT_SYMBOL(blk_mq_tag_to_rq
);
778 struct blk_mq_timeout_data
{
780 unsigned int next_set
;
783 void blk_mq_rq_timed_out(struct request
*req
, bool reserved
)
785 const struct blk_mq_ops
*ops
= req
->q
->mq_ops
;
786 enum blk_eh_timer_return ret
= BLK_EH_RESET_TIMER
;
789 * We know that complete is set at this point. If STARTED isn't set
790 * anymore, then the request isn't active and the "timeout" should
791 * just be ignored. This can happen due to the bitflag ordering.
792 * Timeout first checks if STARTED is set, and if it is, assumes
793 * the request is active. But if we race with completion, then
794 * both flags will get cleared. So check here again, and ignore
795 * a timeout event with a request that isn't active.
797 if (!test_bit(REQ_ATOM_STARTED
, &req
->atomic_flags
))
801 ret
= ops
->timeout(req
, reserved
);
805 __blk_mq_complete_request(req
);
807 case BLK_EH_RESET_TIMER
:
809 blk_clear_rq_complete(req
);
811 case BLK_EH_NOT_HANDLED
:
814 printk(KERN_ERR
"block: bad eh return: %d\n", ret
);
819 static void blk_mq_check_expired(struct blk_mq_hw_ctx
*hctx
,
820 struct request
*rq
, void *priv
, bool reserved
)
822 struct blk_mq_timeout_data
*data
= priv
;
823 unsigned long deadline
;
825 if (!test_bit(REQ_ATOM_STARTED
, &rq
->atomic_flags
))
829 * Ensures that if we see STARTED we must also see our
830 * up-to-date deadline, see blk_mq_start_request().
834 deadline
= READ_ONCE(rq
->deadline
);
837 * The rq being checked may have been freed and reallocated
838 * out already here, we avoid this race by checking rq->deadline
839 * and REQ_ATOM_COMPLETE flag together:
841 * - if rq->deadline is observed as new value because of
842 * reusing, the rq won't be timed out because of timing.
843 * - if rq->deadline is observed as previous value,
844 * REQ_ATOM_COMPLETE flag won't be cleared in reuse path
845 * because we put a barrier between setting rq->deadline
846 * and clearing the flag in blk_mq_start_request(), so
847 * this rq won't be timed out too.
849 if (time_after_eq(jiffies
, deadline
)) {
850 if (!blk_mark_rq_complete(rq
)) {
852 * Again coherence order ensures that consecutive reads
853 * from the same variable must be in that order. This
854 * ensures that if we see COMPLETE clear, we must then
855 * see STARTED set and we'll ignore this timeout.
857 * (There's also the MB implied by the test_and_clear())
859 blk_mq_rq_timed_out(rq
, reserved
);
861 } else if (!data
->next_set
|| time_after(data
->next
, deadline
)) {
862 data
->next
= deadline
;
867 static void blk_mq_timeout_work(struct work_struct
*work
)
869 struct request_queue
*q
=
870 container_of(work
, struct request_queue
, timeout_work
);
871 struct blk_mq_timeout_data data
= {
877 /* A deadlock might occur if a request is stuck requiring a
878 * timeout at the same time a queue freeze is waiting
879 * completion, since the timeout code would not be able to
880 * acquire the queue reference here.
882 * That's why we don't use blk_queue_enter here; instead, we use
883 * percpu_ref_tryget directly, because we need to be able to
884 * obtain a reference even in the short window between the queue
885 * starting to freeze, by dropping the first reference in
886 * blk_freeze_queue_start, and the moment the last request is
887 * consumed, marked by the instant q_usage_counter reaches
890 if (!percpu_ref_tryget(&q
->q_usage_counter
))
893 blk_mq_queue_tag_busy_iter(q
, blk_mq_check_expired
, &data
);
896 data
.next
= blk_rq_timeout(round_jiffies_up(data
.next
));
897 mod_timer(&q
->timeout
, data
.next
);
899 struct blk_mq_hw_ctx
*hctx
;
901 queue_for_each_hw_ctx(q
, hctx
, i
) {
902 /* the hctx may be unmapped, so check it here */
903 if (blk_mq_hw_queue_mapped(hctx
))
904 blk_mq_tag_idle(hctx
);
910 struct flush_busy_ctx_data
{
911 struct blk_mq_hw_ctx
*hctx
;
912 struct list_head
*list
;
915 static bool flush_busy_ctx(struct sbitmap
*sb
, unsigned int bitnr
, void *data
)
917 struct flush_busy_ctx_data
*flush_data
= data
;
918 struct blk_mq_hw_ctx
*hctx
= flush_data
->hctx
;
919 struct blk_mq_ctx
*ctx
= hctx
->ctxs
[bitnr
];
921 sbitmap_clear_bit(sb
, bitnr
);
922 spin_lock(&ctx
->lock
);
923 list_splice_tail_init(&ctx
->rq_list
, flush_data
->list
);
924 spin_unlock(&ctx
->lock
);
929 * Process software queues that have been marked busy, splicing them
930 * to the for-dispatch
932 void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx
*hctx
, struct list_head
*list
)
934 struct flush_busy_ctx_data data
= {
939 sbitmap_for_each_set(&hctx
->ctx_map
, flush_busy_ctx
, &data
);
941 EXPORT_SYMBOL_GPL(blk_mq_flush_busy_ctxs
);
943 struct dispatch_rq_data
{
944 struct blk_mq_hw_ctx
*hctx
;
948 static bool dispatch_rq_from_ctx(struct sbitmap
*sb
, unsigned int bitnr
,
951 struct dispatch_rq_data
*dispatch_data
= data
;
952 struct blk_mq_hw_ctx
*hctx
= dispatch_data
->hctx
;
953 struct blk_mq_ctx
*ctx
= hctx
->ctxs
[bitnr
];
955 spin_lock(&ctx
->lock
);
956 if (unlikely(!list_empty(&ctx
->rq_list
))) {
957 dispatch_data
->rq
= list_entry_rq(ctx
->rq_list
.next
);
958 list_del_init(&dispatch_data
->rq
->queuelist
);
959 if (list_empty(&ctx
->rq_list
))
960 sbitmap_clear_bit(sb
, bitnr
);
962 spin_unlock(&ctx
->lock
);
964 return !dispatch_data
->rq
;
967 struct request
*blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx
*hctx
,
968 struct blk_mq_ctx
*start
)
970 unsigned off
= start
? start
->index_hw
: 0;
971 struct dispatch_rq_data data
= {
976 __sbitmap_for_each_set(&hctx
->ctx_map
, off
,
977 dispatch_rq_from_ctx
, &data
);
982 static inline unsigned int queued_to_index(unsigned int queued
)
987 return min(BLK_MQ_MAX_DISPATCH_ORDER
- 1, ilog2(queued
) + 1);
990 bool blk_mq_get_driver_tag(struct request
*rq
, struct blk_mq_hw_ctx
**hctx
,
993 struct blk_mq_alloc_data data
= {
995 .hctx
= blk_mq_map_queue(rq
->q
, rq
->mq_ctx
->cpu
),
996 .flags
= wait
? 0 : BLK_MQ_REQ_NOWAIT
,
1000 might_sleep_if(wait
);
1005 if (blk_mq_tag_is_reserved(data
.hctx
->sched_tags
, rq
->internal_tag
))
1006 data
.flags
|= BLK_MQ_REQ_RESERVED
;
1008 shared
= blk_mq_tag_busy(data
.hctx
);
1009 rq
->tag
= blk_mq_get_tag(&data
);
1012 rq
->rq_flags
|= RQF_MQ_INFLIGHT
;
1013 atomic_inc(&data
.hctx
->nr_active
);
1015 data
.hctx
->tags
->rqs
[rq
->tag
] = rq
;
1021 return rq
->tag
!= -1;
1024 static int blk_mq_dispatch_wake(wait_queue_entry_t
*wait
, unsigned mode
,
1025 int flags
, void *key
)
1027 struct blk_mq_hw_ctx
*hctx
;
1029 hctx
= container_of(wait
, struct blk_mq_hw_ctx
, dispatch_wait
);
1031 list_del_init(&wait
->entry
);
1032 blk_mq_run_hw_queue(hctx
, true);
1037 * Mark us waiting for a tag. For shared tags, this involves hooking us into
1038 * the tag wakeups. For non-shared tags, we can simply mark us nedeing a
1039 * restart. For both caes, take care to check the condition again after
1040 * marking us as waiting.
1042 static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx
**hctx
,
1045 struct blk_mq_hw_ctx
*this_hctx
= *hctx
;
1046 bool shared_tags
= (this_hctx
->flags
& BLK_MQ_F_TAG_SHARED
) != 0;
1047 struct sbq_wait_state
*ws
;
1048 wait_queue_entry_t
*wait
;
1052 if (!test_bit(BLK_MQ_S_SCHED_RESTART
, &this_hctx
->state
))
1053 set_bit(BLK_MQ_S_SCHED_RESTART
, &this_hctx
->state
);
1055 wait
= &this_hctx
->dispatch_wait
;
1056 if (!list_empty_careful(&wait
->entry
))
1059 spin_lock(&this_hctx
->lock
);
1060 if (!list_empty(&wait
->entry
)) {
1061 spin_unlock(&this_hctx
->lock
);
1065 ws
= bt_wait_ptr(&this_hctx
->tags
->bitmap_tags
, this_hctx
);
1066 add_wait_queue(&ws
->wait
, wait
);
1070 * It's possible that a tag was freed in the window between the
1071 * allocation failure and adding the hardware queue to the wait
1074 ret
= blk_mq_get_driver_tag(rq
, hctx
, false);
1078 * Don't clear RESTART here, someone else could have set it.
1079 * At most this will cost an extra queue run.
1084 spin_unlock(&this_hctx
->lock
);
1089 * We got a tag, remove ourselves from the wait queue to ensure
1090 * someone else gets the wakeup.
1092 spin_lock_irq(&ws
->wait
.lock
);
1093 list_del_init(&wait
->entry
);
1094 spin_unlock_irq(&ws
->wait
.lock
);
1095 spin_unlock(&this_hctx
->lock
);
1100 bool blk_mq_dispatch_rq_list(struct request_queue
*q
, struct list_head
*list
,
1103 struct blk_mq_hw_ctx
*hctx
;
1104 struct request
*rq
, *nxt
;
1105 bool no_tag
= false;
1108 if (list_empty(list
))
1111 WARN_ON(!list_is_singular(list
) && got_budget
);
1114 * Now process all the entries, sending them to the driver.
1116 errors
= queued
= 0;
1118 struct blk_mq_queue_data bd
;
1121 rq
= list_first_entry(list
, struct request
, queuelist
);
1123 hctx
= blk_mq_map_queue(rq
->q
, rq
->mq_ctx
->cpu
);
1124 if (!got_budget
&& !blk_mq_get_dispatch_budget(hctx
))
1127 if (!blk_mq_get_driver_tag(rq
, NULL
, false)) {
1129 * The initial allocation attempt failed, so we need to
1130 * rerun the hardware queue when a tag is freed. The
1131 * waitqueue takes care of that. If the queue is run
1132 * before we add this entry back on the dispatch list,
1133 * we'll re-run it below.
1135 if (!blk_mq_mark_tag_wait(&hctx
, rq
)) {
1136 blk_mq_put_dispatch_budget(hctx
);
1138 * For non-shared tags, the RESTART check
1141 if (hctx
->flags
& BLK_MQ_F_TAG_SHARED
)
1147 list_del_init(&rq
->queuelist
);
1152 * Flag last if we have no more requests, or if we have more
1153 * but can't assign a driver tag to it.
1155 if (list_empty(list
))
1158 nxt
= list_first_entry(list
, struct request
, queuelist
);
1159 bd
.last
= !blk_mq_get_driver_tag(nxt
, NULL
, false);
1162 ret
= q
->mq_ops
->queue_rq(hctx
, &bd
);
1163 if (ret
== BLK_STS_RESOURCE
) {
1165 * If an I/O scheduler has been configured and we got a
1166 * driver tag for the next request already, free it
1169 if (!list_empty(list
)) {
1170 nxt
= list_first_entry(list
, struct request
, queuelist
);
1171 blk_mq_put_driver_tag(nxt
);
1173 list_add(&rq
->queuelist
, list
);
1174 __blk_mq_requeue_request(rq
);
1178 if (unlikely(ret
!= BLK_STS_OK
)) {
1180 blk_mq_end_request(rq
, BLK_STS_IOERR
);
1185 } while (!list_empty(list
));
1187 hctx
->dispatched
[queued_to_index(queued
)]++;
1190 * Any items that need requeuing? Stuff them into hctx->dispatch,
1191 * that is where we will continue on next queue run.
1193 if (!list_empty(list
)) {
1194 spin_lock(&hctx
->lock
);
1195 list_splice_init(list
, &hctx
->dispatch
);
1196 spin_unlock(&hctx
->lock
);
1199 * If SCHED_RESTART was set by the caller of this function and
1200 * it is no longer set that means that it was cleared by another
1201 * thread and hence that a queue rerun is needed.
1203 * If 'no_tag' is set, that means that we failed getting
1204 * a driver tag with an I/O scheduler attached. If our dispatch
1205 * waitqueue is no longer active, ensure that we run the queue
1206 * AFTER adding our entries back to the list.
1208 * If no I/O scheduler has been configured it is possible that
1209 * the hardware queue got stopped and restarted before requests
1210 * were pushed back onto the dispatch list. Rerun the queue to
1211 * avoid starvation. Notes:
1212 * - blk_mq_run_hw_queue() checks whether or not a queue has
1213 * been stopped before rerunning a queue.
1214 * - Some but not all block drivers stop a queue before
1215 * returning BLK_STS_RESOURCE. Two exceptions are scsi-mq
1218 if (!blk_mq_sched_needs_restart(hctx
) ||
1219 (no_tag
&& list_empty_careful(&hctx
->dispatch_wait
.entry
)))
1220 blk_mq_run_hw_queue(hctx
, true);
1223 return (queued
+ errors
) != 0;
1226 static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx
*hctx
)
1231 * We should be running this queue from one of the CPUs that
1234 * There are at least two related races now between setting
1235 * hctx->next_cpu from blk_mq_hctx_next_cpu() and running
1236 * __blk_mq_run_hw_queue():
1238 * - hctx->next_cpu is found offline in blk_mq_hctx_next_cpu(),
1239 * but later it becomes online, then this warning is harmless
1242 * - hctx->next_cpu is found online in blk_mq_hctx_next_cpu(),
1243 * but later it becomes offline, then the warning can't be
1244 * triggered, and we depend on blk-mq timeout handler to
1245 * handle dispatched requests to this hctx
1247 if (!cpumask_test_cpu(raw_smp_processor_id(), hctx
->cpumask
) &&
1248 cpu_online(hctx
->next_cpu
)) {
1249 printk(KERN_WARNING
"run queue from wrong CPU %d, hctx %s\n",
1250 raw_smp_processor_id(),
1251 cpumask_empty(hctx
->cpumask
) ? "inactive": "active");
1256 * We can't run the queue inline with ints disabled. Ensure that
1257 * we catch bad users of this early.
1259 WARN_ON_ONCE(in_interrupt());
1261 if (!(hctx
->flags
& BLK_MQ_F_BLOCKING
)) {
1263 blk_mq_sched_dispatch_requests(hctx
);
1268 srcu_idx
= srcu_read_lock(hctx
->queue_rq_srcu
);
1269 blk_mq_sched_dispatch_requests(hctx
);
1270 srcu_read_unlock(hctx
->queue_rq_srcu
, srcu_idx
);
1274 static inline int blk_mq_first_mapped_cpu(struct blk_mq_hw_ctx
*hctx
)
1276 int cpu
= cpumask_first_and(hctx
->cpumask
, cpu_online_mask
);
1278 if (cpu
>= nr_cpu_ids
)
1279 cpu
= cpumask_first(hctx
->cpumask
);
1284 * It'd be great if the workqueue API had a way to pass
1285 * in a mask and had some smarts for more clever placement.
1286 * For now we just round-robin here, switching for every
1287 * BLK_MQ_CPU_WORK_BATCH queued items.
1289 static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx
*hctx
)
1292 int next_cpu
= hctx
->next_cpu
;
1294 if (hctx
->queue
->nr_hw_queues
== 1)
1295 return WORK_CPU_UNBOUND
;
1297 if (--hctx
->next_cpu_batch
<= 0) {
1299 next_cpu
= cpumask_next_and(next_cpu
, hctx
->cpumask
,
1301 if (next_cpu
>= nr_cpu_ids
)
1302 next_cpu
= blk_mq_first_mapped_cpu(hctx
);
1303 hctx
->next_cpu_batch
= BLK_MQ_CPU_WORK_BATCH
;
1307 * Do unbound schedule if we can't find a online CPU for this hctx,
1308 * and it should only happen in the path of handling CPU DEAD.
1310 if (!cpu_online(next_cpu
)) {
1317 * Make sure to re-select CPU next time once after CPUs
1318 * in hctx->cpumask become online again.
1320 hctx
->next_cpu
= next_cpu
;
1321 hctx
->next_cpu_batch
= 1;
1322 return WORK_CPU_UNBOUND
;
1325 hctx
->next_cpu
= next_cpu
;
1329 static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx
*hctx
, bool async
,
1330 unsigned long msecs
)
1332 if (unlikely(blk_mq_hctx_stopped(hctx
)))
1335 if (!async
&& !(hctx
->flags
& BLK_MQ_F_BLOCKING
)) {
1336 int cpu
= get_cpu();
1337 if (cpumask_test_cpu(cpu
, hctx
->cpumask
)) {
1338 __blk_mq_run_hw_queue(hctx
);
1346 kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx
), &hctx
->run_work
,
1347 msecs_to_jiffies(msecs
));
1350 void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx
*hctx
, unsigned long msecs
)
1352 __blk_mq_delay_run_hw_queue(hctx
, true, msecs
);
1354 EXPORT_SYMBOL(blk_mq_delay_run_hw_queue
);
1356 bool blk_mq_run_hw_queue(struct blk_mq_hw_ctx
*hctx
, bool async
)
1358 if (blk_mq_hctx_has_pending(hctx
)) {
1359 __blk_mq_delay_run_hw_queue(hctx
, async
, 0);
1365 EXPORT_SYMBOL(blk_mq_run_hw_queue
);
1367 void blk_mq_run_hw_queues(struct request_queue
*q
, bool async
)
1369 struct blk_mq_hw_ctx
*hctx
;
1372 queue_for_each_hw_ctx(q
, hctx
, i
) {
1373 if (blk_mq_hctx_stopped(hctx
))
1376 blk_mq_run_hw_queue(hctx
, async
);
1379 EXPORT_SYMBOL(blk_mq_run_hw_queues
);
1382 * blk_mq_queue_stopped() - check whether one or more hctxs have been stopped
1383 * @q: request queue.
1385 * The caller is responsible for serializing this function against
1386 * blk_mq_{start,stop}_hw_queue().
1388 bool blk_mq_queue_stopped(struct request_queue
*q
)
1390 struct blk_mq_hw_ctx
*hctx
;
1393 queue_for_each_hw_ctx(q
, hctx
, i
)
1394 if (blk_mq_hctx_stopped(hctx
))
1399 EXPORT_SYMBOL(blk_mq_queue_stopped
);
1402 * This function is often used for pausing .queue_rq() by driver when
1403 * there isn't enough resource or some conditions aren't satisfied, and
1404 * BLK_STS_RESOURCE is usually returned.
1406 * We do not guarantee that dispatch can be drained or blocked
1407 * after blk_mq_stop_hw_queue() returns. Please use
1408 * blk_mq_quiesce_queue() for that requirement.
1410 void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx
*hctx
)
1412 cancel_delayed_work(&hctx
->run_work
);
1414 set_bit(BLK_MQ_S_STOPPED
, &hctx
->state
);
1416 EXPORT_SYMBOL(blk_mq_stop_hw_queue
);
1419 * This function is often used for pausing .queue_rq() by driver when
1420 * there isn't enough resource or some conditions aren't satisfied, and
1421 * BLK_STS_RESOURCE is usually returned.
1423 * We do not guarantee that dispatch can be drained or blocked
1424 * after blk_mq_stop_hw_queues() returns. Please use
1425 * blk_mq_quiesce_queue() for that requirement.
1427 void blk_mq_stop_hw_queues(struct request_queue
*q
)
1429 struct blk_mq_hw_ctx
*hctx
;
1432 queue_for_each_hw_ctx(q
, hctx
, i
)
1433 blk_mq_stop_hw_queue(hctx
);
1435 EXPORT_SYMBOL(blk_mq_stop_hw_queues
);
1437 void blk_mq_start_hw_queue(struct blk_mq_hw_ctx
*hctx
)
1439 clear_bit(BLK_MQ_S_STOPPED
, &hctx
->state
);
1441 blk_mq_run_hw_queue(hctx
, false);
1443 EXPORT_SYMBOL(blk_mq_start_hw_queue
);
1445 void blk_mq_start_hw_queues(struct request_queue
*q
)
1447 struct blk_mq_hw_ctx
*hctx
;
1450 queue_for_each_hw_ctx(q
, hctx
, i
)
1451 blk_mq_start_hw_queue(hctx
);
1453 EXPORT_SYMBOL(blk_mq_start_hw_queues
);
1455 void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx
*hctx
, bool async
)
1457 if (!blk_mq_hctx_stopped(hctx
))
1460 clear_bit(BLK_MQ_S_STOPPED
, &hctx
->state
);
1461 blk_mq_run_hw_queue(hctx
, async
);
1463 EXPORT_SYMBOL_GPL(blk_mq_start_stopped_hw_queue
);
1465 void blk_mq_start_stopped_hw_queues(struct request_queue
*q
, bool async
)
1467 struct blk_mq_hw_ctx
*hctx
;
1470 queue_for_each_hw_ctx(q
, hctx
, i
)
1471 blk_mq_start_stopped_hw_queue(hctx
, async
);
1473 EXPORT_SYMBOL(blk_mq_start_stopped_hw_queues
);
1475 static void blk_mq_run_work_fn(struct work_struct
*work
)
1477 struct blk_mq_hw_ctx
*hctx
;
1479 hctx
= container_of(work
, struct blk_mq_hw_ctx
, run_work
.work
);
1482 * If we are stopped, don't run the queue. The exception is if
1483 * BLK_MQ_S_START_ON_RUN is set. For that case, we auto-clear
1484 * the STOPPED bit and run it.
1486 if (test_bit(BLK_MQ_S_STOPPED
, &hctx
->state
)) {
1487 if (!test_bit(BLK_MQ_S_START_ON_RUN
, &hctx
->state
))
1490 clear_bit(BLK_MQ_S_START_ON_RUN
, &hctx
->state
);
1491 clear_bit(BLK_MQ_S_STOPPED
, &hctx
->state
);
1494 __blk_mq_run_hw_queue(hctx
);
1498 void blk_mq_delay_queue(struct blk_mq_hw_ctx
*hctx
, unsigned long msecs
)
1500 if (WARN_ON_ONCE(!blk_mq_hw_queue_mapped(hctx
)))
1504 * Stop the hw queue, then modify currently delayed work.
1505 * This should prevent us from running the queue prematurely.
1506 * Mark the queue as auto-clearing STOPPED when it runs.
1508 blk_mq_stop_hw_queue(hctx
);
1509 set_bit(BLK_MQ_S_START_ON_RUN
, &hctx
->state
);
1510 kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx
),
1512 msecs_to_jiffies(msecs
));
1514 EXPORT_SYMBOL(blk_mq_delay_queue
);
1516 static inline void __blk_mq_insert_req_list(struct blk_mq_hw_ctx
*hctx
,
1520 struct blk_mq_ctx
*ctx
= rq
->mq_ctx
;
1522 lockdep_assert_held(&ctx
->lock
);
1524 trace_block_rq_insert(hctx
->queue
, rq
);
1527 list_add(&rq
->queuelist
, &ctx
->rq_list
);
1529 list_add_tail(&rq
->queuelist
, &ctx
->rq_list
);
1532 void __blk_mq_insert_request(struct blk_mq_hw_ctx
*hctx
, struct request
*rq
,
1535 struct blk_mq_ctx
*ctx
= rq
->mq_ctx
;
1537 lockdep_assert_held(&ctx
->lock
);
1539 __blk_mq_insert_req_list(hctx
, rq
, at_head
);
1540 blk_mq_hctx_mark_pending(hctx
, ctx
);
1544 * Should only be used carefully, when the caller knows we want to
1545 * bypass a potential IO scheduler on the target device.
1547 void blk_mq_request_bypass_insert(struct request
*rq
, bool run_queue
)
1549 struct blk_mq_ctx
*ctx
= rq
->mq_ctx
;
1550 struct blk_mq_hw_ctx
*hctx
= blk_mq_map_queue(rq
->q
, ctx
->cpu
);
1552 spin_lock(&hctx
->lock
);
1553 list_add_tail(&rq
->queuelist
, &hctx
->dispatch
);
1554 spin_unlock(&hctx
->lock
);
1557 blk_mq_run_hw_queue(hctx
, false);
1560 void blk_mq_insert_requests(struct blk_mq_hw_ctx
*hctx
, struct blk_mq_ctx
*ctx
,
1561 struct list_head
*list
)
1565 * preemption doesn't flush plug list, so it's possible ctx->cpu is
1568 spin_lock(&ctx
->lock
);
1569 while (!list_empty(list
)) {
1572 rq
= list_first_entry(list
, struct request
, queuelist
);
1573 BUG_ON(rq
->mq_ctx
!= ctx
);
1574 list_del_init(&rq
->queuelist
);
1575 __blk_mq_insert_req_list(hctx
, rq
, false);
1577 blk_mq_hctx_mark_pending(hctx
, ctx
);
1578 spin_unlock(&ctx
->lock
);
1581 static int plug_ctx_cmp(void *priv
, struct list_head
*a
, struct list_head
*b
)
1583 struct request
*rqa
= container_of(a
, struct request
, queuelist
);
1584 struct request
*rqb
= container_of(b
, struct request
, queuelist
);
1586 return !(rqa
->mq_ctx
< rqb
->mq_ctx
||
1587 (rqa
->mq_ctx
== rqb
->mq_ctx
&&
1588 blk_rq_pos(rqa
) < blk_rq_pos(rqb
)));
1591 void blk_mq_flush_plug_list(struct blk_plug
*plug
, bool from_schedule
)
1593 struct blk_mq_ctx
*this_ctx
;
1594 struct request_queue
*this_q
;
1597 LIST_HEAD(ctx_list
);
1600 list_splice_init(&plug
->mq_list
, &list
);
1602 list_sort(NULL
, &list
, plug_ctx_cmp
);
1608 while (!list_empty(&list
)) {
1609 rq
= list_entry_rq(list
.next
);
1610 list_del_init(&rq
->queuelist
);
1612 if (rq
->mq_ctx
!= this_ctx
) {
1614 trace_block_unplug(this_q
, depth
, from_schedule
);
1615 blk_mq_sched_insert_requests(this_q
, this_ctx
,
1620 this_ctx
= rq
->mq_ctx
;
1626 list_add_tail(&rq
->queuelist
, &ctx_list
);
1630 * If 'this_ctx' is set, we know we have entries to complete
1631 * on 'ctx_list'. Do those.
1634 trace_block_unplug(this_q
, depth
, from_schedule
);
1635 blk_mq_sched_insert_requests(this_q
, this_ctx
, &ctx_list
,
1640 static void blk_mq_bio_to_request(struct request
*rq
, struct bio
*bio
)
1642 blk_init_request_from_bio(rq
, bio
);
1644 blk_rq_set_rl(rq
, blk_get_rl(rq
->q
, bio
));
1646 blk_account_io_start(rq
, true);
1649 static inline void blk_mq_queue_io(struct blk_mq_hw_ctx
*hctx
,
1650 struct blk_mq_ctx
*ctx
,
1653 spin_lock(&ctx
->lock
);
1654 __blk_mq_insert_request(hctx
, rq
, false);
1655 spin_unlock(&ctx
->lock
);
1658 static blk_qc_t
request_to_qc_t(struct blk_mq_hw_ctx
*hctx
, struct request
*rq
)
1661 return blk_tag_to_qc_t(rq
->tag
, hctx
->queue_num
, false);
1663 return blk_tag_to_qc_t(rq
->internal_tag
, hctx
->queue_num
, true);
1666 static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx
*hctx
,
1668 blk_qc_t
*cookie
, bool may_sleep
)
1670 struct request_queue
*q
= rq
->q
;
1671 struct blk_mq_queue_data bd
= {
1675 blk_qc_t new_cookie
;
1677 bool run_queue
= true;
1679 /* RCU or SRCU read lock is needed before checking quiesced flag */
1680 if (blk_mq_hctx_stopped(hctx
) || blk_queue_quiesced(q
)) {
1688 if (!blk_mq_get_dispatch_budget(hctx
))
1691 if (!blk_mq_get_driver_tag(rq
, NULL
, false)) {
1692 blk_mq_put_dispatch_budget(hctx
);
1696 new_cookie
= request_to_qc_t(hctx
, rq
);
1699 * For OK queue, we are done. For error, kill it. Any other
1700 * error (busy), just add it to our list as we previously
1703 ret
= q
->mq_ops
->queue_rq(hctx
, &bd
);
1706 *cookie
= new_cookie
;
1708 case BLK_STS_RESOURCE
:
1709 __blk_mq_requeue_request(rq
);
1712 *cookie
= BLK_QC_T_NONE
;
1713 blk_mq_end_request(rq
, ret
);
1718 blk_mq_sched_insert_request(rq
, false, run_queue
, false, may_sleep
);
1721 static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx
*hctx
,
1722 struct request
*rq
, blk_qc_t
*cookie
)
1724 if (!(hctx
->flags
& BLK_MQ_F_BLOCKING
)) {
1726 __blk_mq_try_issue_directly(hctx
, rq
, cookie
, false);
1729 unsigned int srcu_idx
;
1733 srcu_idx
= srcu_read_lock(hctx
->queue_rq_srcu
);
1734 __blk_mq_try_issue_directly(hctx
, rq
, cookie
, true);
1735 srcu_read_unlock(hctx
->queue_rq_srcu
, srcu_idx
);
1739 static blk_qc_t
blk_mq_make_request(struct request_queue
*q
, struct bio
*bio
)
1741 const int is_sync
= op_is_sync(bio
->bi_opf
);
1742 const int is_flush_fua
= op_is_flush(bio
->bi_opf
);
1743 struct blk_mq_alloc_data data
= { .flags
= 0 };
1745 unsigned int request_count
= 0;
1746 struct blk_plug
*plug
;
1747 struct request
*same_queue_rq
= NULL
;
1749 unsigned int wb_acct
;
1751 blk_queue_bounce(q
, &bio
);
1753 blk_queue_split(q
, &bio
);
1755 if (!bio_integrity_prep(bio
))
1756 return BLK_QC_T_NONE
;
1758 if (!is_flush_fua
&& !blk_queue_nomerges(q
) &&
1759 blk_attempt_plug_merge(q
, bio
, &request_count
, &same_queue_rq
))
1760 return BLK_QC_T_NONE
;
1762 if (blk_mq_sched_bio_merge(q
, bio
))
1763 return BLK_QC_T_NONE
;
1765 wb_acct
= wbt_wait(q
->rq_wb
, bio
, NULL
);
1767 trace_block_getrq(q
, bio
, bio
->bi_opf
);
1769 rq
= blk_mq_get_request(q
, bio
, bio
->bi_opf
, &data
);
1770 if (unlikely(!rq
)) {
1771 __wbt_done(q
->rq_wb
, wb_acct
);
1772 if (bio
->bi_opf
& REQ_NOWAIT
)
1773 bio_wouldblock_error(bio
);
1774 return BLK_QC_T_NONE
;
1777 wbt_track(&rq
->issue_stat
, wb_acct
);
1779 cookie
= request_to_qc_t(data
.hctx
, rq
);
1781 plug
= current
->plug
;
1782 if (unlikely(is_flush_fua
)) {
1783 blk_mq_put_ctx(data
.ctx
);
1784 blk_mq_bio_to_request(rq
, bio
);
1786 /* bypass scheduler for flush rq */
1787 blk_insert_flush(rq
);
1788 blk_mq_run_hw_queue(data
.hctx
, true);
1789 } else if (plug
&& q
->nr_hw_queues
== 1) {
1790 struct request
*last
= NULL
;
1792 blk_mq_put_ctx(data
.ctx
);
1793 blk_mq_bio_to_request(rq
, bio
);
1796 * @request_count may become stale because of schedule
1797 * out, so check the list again.
1799 if (list_empty(&plug
->mq_list
))
1801 else if (blk_queue_nomerges(q
))
1802 request_count
= blk_plug_queued_count(q
);
1805 trace_block_plug(q
);
1807 last
= list_entry_rq(plug
->mq_list
.prev
);
1809 if (request_count
>= BLK_MAX_REQUEST_COUNT
|| (last
&&
1810 blk_rq_bytes(last
) >= BLK_PLUG_FLUSH_SIZE
)) {
1811 blk_flush_plug_list(plug
, false);
1812 trace_block_plug(q
);
1815 list_add_tail(&rq
->queuelist
, &plug
->mq_list
);
1816 } else if (plug
&& !blk_queue_nomerges(q
)) {
1817 blk_mq_bio_to_request(rq
, bio
);
1820 * We do limited plugging. If the bio can be merged, do that.
1821 * Otherwise the existing request in the plug list will be
1822 * issued. So the plug list will have one request at most
1823 * The plug list might get flushed before this. If that happens,
1824 * the plug list is empty, and same_queue_rq is invalid.
1826 if (list_empty(&plug
->mq_list
))
1827 same_queue_rq
= NULL
;
1829 list_del_init(&same_queue_rq
->queuelist
);
1830 list_add_tail(&rq
->queuelist
, &plug
->mq_list
);
1832 blk_mq_put_ctx(data
.ctx
);
1834 if (same_queue_rq
) {
1835 data
.hctx
= blk_mq_map_queue(q
,
1836 same_queue_rq
->mq_ctx
->cpu
);
1837 blk_mq_try_issue_directly(data
.hctx
, same_queue_rq
,
1840 } else if (q
->nr_hw_queues
> 1 && is_sync
) {
1841 blk_mq_put_ctx(data
.ctx
);
1842 blk_mq_bio_to_request(rq
, bio
);
1843 blk_mq_try_issue_directly(data
.hctx
, rq
, &cookie
);
1844 } else if (q
->elevator
) {
1845 blk_mq_put_ctx(data
.ctx
);
1846 blk_mq_bio_to_request(rq
, bio
);
1847 blk_mq_sched_insert_request(rq
, false, true, true, true);
1849 blk_mq_put_ctx(data
.ctx
);
1850 blk_mq_bio_to_request(rq
, bio
);
1851 blk_mq_queue_io(data
.hctx
, data
.ctx
, rq
);
1852 blk_mq_run_hw_queue(data
.hctx
, true);
1858 void blk_mq_free_rqs(struct blk_mq_tag_set
*set
, struct blk_mq_tags
*tags
,
1859 unsigned int hctx_idx
)
1863 if (tags
->rqs
&& set
->ops
->exit_request
) {
1866 for (i
= 0; i
< tags
->nr_tags
; i
++) {
1867 struct request
*rq
= tags
->static_rqs
[i
];
1871 set
->ops
->exit_request(set
, rq
, hctx_idx
);
1872 tags
->static_rqs
[i
] = NULL
;
1876 while (!list_empty(&tags
->page_list
)) {
1877 page
= list_first_entry(&tags
->page_list
, struct page
, lru
);
1878 list_del_init(&page
->lru
);
1880 * Remove kmemleak object previously allocated in
1881 * blk_mq_init_rq_map().
1883 kmemleak_free(page_address(page
));
1884 __free_pages(page
, page
->private);
1888 void blk_mq_free_rq_map(struct blk_mq_tags
*tags
)
1892 kfree(tags
->static_rqs
);
1893 tags
->static_rqs
= NULL
;
1895 blk_mq_free_tags(tags
);
1898 struct blk_mq_tags
*blk_mq_alloc_rq_map(struct blk_mq_tag_set
*set
,
1899 unsigned int hctx_idx
,
1900 unsigned int nr_tags
,
1901 unsigned int reserved_tags
)
1903 struct blk_mq_tags
*tags
;
1906 node
= blk_mq_hw_queue_to_node(set
->mq_map
, hctx_idx
);
1907 if (node
== NUMA_NO_NODE
)
1908 node
= set
->numa_node
;
1910 tags
= blk_mq_init_tags(nr_tags
, reserved_tags
, node
,
1911 BLK_MQ_FLAG_TO_ALLOC_POLICY(set
->flags
));
1915 tags
->rqs
= kzalloc_node(nr_tags
* sizeof(struct request
*),
1916 GFP_NOIO
| __GFP_NOWARN
| __GFP_NORETRY
,
1919 blk_mq_free_tags(tags
);
1923 tags
->static_rqs
= kzalloc_node(nr_tags
* sizeof(struct request
*),
1924 GFP_NOIO
| __GFP_NOWARN
| __GFP_NORETRY
,
1926 if (!tags
->static_rqs
) {
1928 blk_mq_free_tags(tags
);
1935 static size_t order_to_size(unsigned int order
)
1937 return (size_t)PAGE_SIZE
<< order
;
1940 int blk_mq_alloc_rqs(struct blk_mq_tag_set
*set
, struct blk_mq_tags
*tags
,
1941 unsigned int hctx_idx
, unsigned int depth
)
1943 unsigned int i
, j
, entries_per_page
, max_order
= 4;
1944 size_t rq_size
, left
;
1947 node
= blk_mq_hw_queue_to_node(set
->mq_map
, hctx_idx
);
1948 if (node
== NUMA_NO_NODE
)
1949 node
= set
->numa_node
;
1951 INIT_LIST_HEAD(&tags
->page_list
);
1954 * rq_size is the size of the request plus driver payload, rounded
1955 * to the cacheline size
1957 rq_size
= round_up(sizeof(struct request
) + set
->cmd_size
,
1959 left
= rq_size
* depth
;
1961 for (i
= 0; i
< depth
; ) {
1962 int this_order
= max_order
;
1967 while (this_order
&& left
< order_to_size(this_order
- 1))
1971 page
= alloc_pages_node(node
,
1972 GFP_NOIO
| __GFP_NOWARN
| __GFP_NORETRY
| __GFP_ZERO
,
1978 if (order_to_size(this_order
) < rq_size
)
1985 page
->private = this_order
;
1986 list_add_tail(&page
->lru
, &tags
->page_list
);
1988 p
= page_address(page
);
1990 * Allow kmemleak to scan these pages as they contain pointers
1991 * to additional allocations like via ops->init_request().
1993 kmemleak_alloc(p
, order_to_size(this_order
), 1, GFP_NOIO
);
1994 entries_per_page
= order_to_size(this_order
) / rq_size
;
1995 to_do
= min(entries_per_page
, depth
- i
);
1996 left
-= to_do
* rq_size
;
1997 for (j
= 0; j
< to_do
; j
++) {
1998 struct request
*rq
= p
;
2000 tags
->static_rqs
[i
] = rq
;
2001 if (set
->ops
->init_request
) {
2002 if (set
->ops
->init_request(set
, rq
, hctx_idx
,
2004 tags
->static_rqs
[i
] = NULL
;
2016 blk_mq_free_rqs(set
, tags
, hctx_idx
);
2021 * 'cpu' is going away. splice any existing rq_list entries from this
2022 * software queue to the hw queue dispatch list, and ensure that it
2025 static int blk_mq_hctx_notify_dead(unsigned int cpu
, struct hlist_node
*node
)
2027 struct blk_mq_hw_ctx
*hctx
;
2028 struct blk_mq_ctx
*ctx
;
2031 hctx
= hlist_entry_safe(node
, struct blk_mq_hw_ctx
, cpuhp_dead
);
2032 ctx
= __blk_mq_get_ctx(hctx
->queue
, cpu
);
2034 spin_lock(&ctx
->lock
);
2035 if (!list_empty(&ctx
->rq_list
)) {
2036 list_splice_init(&ctx
->rq_list
, &tmp
);
2037 blk_mq_hctx_clear_pending(hctx
, ctx
);
2039 spin_unlock(&ctx
->lock
);
2041 if (list_empty(&tmp
))
2044 spin_lock(&hctx
->lock
);
2045 list_splice_tail_init(&tmp
, &hctx
->dispatch
);
2046 spin_unlock(&hctx
->lock
);
2048 blk_mq_run_hw_queue(hctx
, true);
2052 static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx
*hctx
)
2054 cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_DEAD
,
2058 /* hctx->ctxs will be freed in queue's release handler */
2059 static void blk_mq_exit_hctx(struct request_queue
*q
,
2060 struct blk_mq_tag_set
*set
,
2061 struct blk_mq_hw_ctx
*hctx
, unsigned int hctx_idx
)
2063 blk_mq_debugfs_unregister_hctx(hctx
);
2065 if (blk_mq_hw_queue_mapped(hctx
))
2066 blk_mq_tag_idle(hctx
);
2068 if (set
->ops
->exit_request
)
2069 set
->ops
->exit_request(set
, hctx
->fq
->flush_rq
, hctx_idx
);
2071 blk_mq_sched_exit_hctx(q
, hctx
, hctx_idx
);
2073 if (set
->ops
->exit_hctx
)
2074 set
->ops
->exit_hctx(hctx
, hctx_idx
);
2076 if (hctx
->flags
& BLK_MQ_F_BLOCKING
)
2077 cleanup_srcu_struct(hctx
->queue_rq_srcu
);
2079 blk_mq_remove_cpuhp(hctx
);
2080 blk_free_flush_queue(hctx
->fq
);
2081 sbitmap_free(&hctx
->ctx_map
);
2084 static void blk_mq_exit_hw_queues(struct request_queue
*q
,
2085 struct blk_mq_tag_set
*set
, int nr_queue
)
2087 struct blk_mq_hw_ctx
*hctx
;
2090 queue_for_each_hw_ctx(q
, hctx
, i
) {
2093 blk_mq_exit_hctx(q
, set
, hctx
, i
);
2097 static int blk_mq_init_hctx(struct request_queue
*q
,
2098 struct blk_mq_tag_set
*set
,
2099 struct blk_mq_hw_ctx
*hctx
, unsigned hctx_idx
)
2103 node
= hctx
->numa_node
;
2104 if (node
== NUMA_NO_NODE
)
2105 node
= hctx
->numa_node
= set
->numa_node
;
2107 INIT_DELAYED_WORK(&hctx
->run_work
, blk_mq_run_work_fn
);
2108 spin_lock_init(&hctx
->lock
);
2109 INIT_LIST_HEAD(&hctx
->dispatch
);
2111 hctx
->flags
= set
->flags
& ~BLK_MQ_F_TAG_SHARED
;
2113 cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD
, &hctx
->cpuhp_dead
);
2115 hctx
->tags
= set
->tags
[hctx_idx
];
2118 * Allocate space for all possible cpus to avoid allocation at
2121 hctx
->ctxs
= kmalloc_array_node(nr_cpu_ids
, sizeof(void *),
2124 goto unregister_cpu_notifier
;
2126 if (sbitmap_init_node(&hctx
->ctx_map
, nr_cpu_ids
, ilog2(8), GFP_KERNEL
,
2132 init_waitqueue_func_entry(&hctx
->dispatch_wait
, blk_mq_dispatch_wake
);
2133 INIT_LIST_HEAD(&hctx
->dispatch_wait
.entry
);
2135 if (set
->ops
->init_hctx
&&
2136 set
->ops
->init_hctx(hctx
, set
->driver_data
, hctx_idx
))
2139 if (blk_mq_sched_init_hctx(q
, hctx
, hctx_idx
))
2142 hctx
->fq
= blk_alloc_flush_queue(q
, hctx
->numa_node
, set
->cmd_size
);
2144 goto sched_exit_hctx
;
2146 if (set
->ops
->init_request
&&
2147 set
->ops
->init_request(set
, hctx
->fq
->flush_rq
, hctx_idx
,
2151 if (hctx
->flags
& BLK_MQ_F_BLOCKING
)
2152 init_srcu_struct(hctx
->queue_rq_srcu
);
2154 blk_mq_debugfs_register_hctx(q
, hctx
);
2161 blk_mq_sched_exit_hctx(q
, hctx
, hctx_idx
);
2163 if (set
->ops
->exit_hctx
)
2164 set
->ops
->exit_hctx(hctx
, hctx_idx
);
2166 sbitmap_free(&hctx
->ctx_map
);
2169 unregister_cpu_notifier
:
2170 blk_mq_remove_cpuhp(hctx
);
2174 static void blk_mq_init_cpu_queues(struct request_queue
*q
,
2175 unsigned int nr_hw_queues
)
2179 for_each_possible_cpu(i
) {
2180 struct blk_mq_ctx
*__ctx
= per_cpu_ptr(q
->queue_ctx
, i
);
2181 struct blk_mq_hw_ctx
*hctx
;
2184 spin_lock_init(&__ctx
->lock
);
2185 INIT_LIST_HEAD(&__ctx
->rq_list
);
2189 * Set local node, IFF we have more than one hw queue. If
2190 * not, we remain on the home node of the device
2192 hctx
= blk_mq_map_queue(q
, i
);
2193 if (nr_hw_queues
> 1 && hctx
->numa_node
== NUMA_NO_NODE
)
2194 hctx
->numa_node
= local_memory_node(cpu_to_node(i
));
2198 static bool __blk_mq_alloc_rq_map(struct blk_mq_tag_set
*set
, int hctx_idx
)
2202 set
->tags
[hctx_idx
] = blk_mq_alloc_rq_map(set
, hctx_idx
,
2203 set
->queue_depth
, set
->reserved_tags
);
2204 if (!set
->tags
[hctx_idx
])
2207 ret
= blk_mq_alloc_rqs(set
, set
->tags
[hctx_idx
], hctx_idx
,
2212 blk_mq_free_rq_map(set
->tags
[hctx_idx
]);
2213 set
->tags
[hctx_idx
] = NULL
;
2217 static void blk_mq_free_map_and_requests(struct blk_mq_tag_set
*set
,
2218 unsigned int hctx_idx
)
2220 if (set
->tags
[hctx_idx
]) {
2221 blk_mq_free_rqs(set
, set
->tags
[hctx_idx
], hctx_idx
);
2222 blk_mq_free_rq_map(set
->tags
[hctx_idx
]);
2223 set
->tags
[hctx_idx
] = NULL
;
2227 static void blk_mq_map_swqueue(struct request_queue
*q
)
2229 unsigned int i
, hctx_idx
;
2230 struct blk_mq_hw_ctx
*hctx
;
2231 struct blk_mq_ctx
*ctx
;
2232 struct blk_mq_tag_set
*set
= q
->tag_set
;
2235 * Avoid others reading imcomplete hctx->cpumask through sysfs
2237 mutex_lock(&q
->sysfs_lock
);
2239 queue_for_each_hw_ctx(q
, hctx
, i
) {
2240 cpumask_clear(hctx
->cpumask
);
2245 * Map software to hardware queues.
2247 * If the cpu isn't present, the cpu is mapped to first hctx.
2249 for_each_possible_cpu(i
) {
2250 hctx_idx
= q
->mq_map
[i
];
2251 /* unmapped hw queue can be remapped after CPU topo changed */
2252 if (!set
->tags
[hctx_idx
] &&
2253 !__blk_mq_alloc_rq_map(set
, hctx_idx
)) {
2255 * If tags initialization fail for some hctx,
2256 * that hctx won't be brought online. In this
2257 * case, remap the current ctx to hctx[0] which
2258 * is guaranteed to always have tags allocated
2263 ctx
= per_cpu_ptr(q
->queue_ctx
, i
);
2264 hctx
= blk_mq_map_queue(q
, i
);
2266 cpumask_set_cpu(i
, hctx
->cpumask
);
2267 ctx
->index_hw
= hctx
->nr_ctx
;
2268 hctx
->ctxs
[hctx
->nr_ctx
++] = ctx
;
2271 mutex_unlock(&q
->sysfs_lock
);
2273 queue_for_each_hw_ctx(q
, hctx
, i
) {
2275 * If no software queues are mapped to this hardware queue,
2276 * disable it and free the request entries.
2278 if (!hctx
->nr_ctx
) {
2279 /* Never unmap queue 0. We need it as a
2280 * fallback in case of a new remap fails
2283 if (i
&& set
->tags
[i
])
2284 blk_mq_free_map_and_requests(set
, i
);
2290 hctx
->tags
= set
->tags
[i
];
2291 WARN_ON(!hctx
->tags
);
2294 * Set the map size to the number of mapped software queues.
2295 * This is more accurate and more efficient than looping
2296 * over all possibly mapped software queues.
2298 sbitmap_resize(&hctx
->ctx_map
, hctx
->nr_ctx
);
2301 * Initialize batch roundrobin counts
2303 hctx
->next_cpu
= blk_mq_first_mapped_cpu(hctx
);
2304 hctx
->next_cpu_batch
= BLK_MQ_CPU_WORK_BATCH
;
2309 * Caller needs to ensure that we're either frozen/quiesced, or that
2310 * the queue isn't live yet.
2312 static void queue_set_hctx_shared(struct request_queue
*q
, bool shared
)
2314 struct blk_mq_hw_ctx
*hctx
;
2317 queue_for_each_hw_ctx(q
, hctx
, i
) {
2319 if (test_bit(BLK_MQ_S_SCHED_RESTART
, &hctx
->state
))
2320 atomic_inc(&q
->shared_hctx_restart
);
2321 hctx
->flags
|= BLK_MQ_F_TAG_SHARED
;
2323 if (test_bit(BLK_MQ_S_SCHED_RESTART
, &hctx
->state
))
2324 atomic_dec(&q
->shared_hctx_restart
);
2325 hctx
->flags
&= ~BLK_MQ_F_TAG_SHARED
;
2330 static void blk_mq_update_tag_set_depth(struct blk_mq_tag_set
*set
,
2333 struct request_queue
*q
;
2335 lockdep_assert_held(&set
->tag_list_lock
);
2337 list_for_each_entry(q
, &set
->tag_list
, tag_set_list
) {
2338 blk_mq_freeze_queue(q
);
2339 queue_set_hctx_shared(q
, shared
);
2340 blk_mq_unfreeze_queue(q
);
2344 static void blk_mq_del_queue_tag_set(struct request_queue
*q
)
2346 struct blk_mq_tag_set
*set
= q
->tag_set
;
2348 mutex_lock(&set
->tag_list_lock
);
2349 list_del_rcu(&q
->tag_set_list
);
2350 if (list_is_singular(&set
->tag_list
)) {
2351 /* just transitioned to unshared */
2352 set
->flags
&= ~BLK_MQ_F_TAG_SHARED
;
2353 /* update existing queue */
2354 blk_mq_update_tag_set_depth(set
, false);
2356 mutex_unlock(&set
->tag_list_lock
);
2358 INIT_LIST_HEAD(&q
->tag_set_list
);
2361 static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set
*set
,
2362 struct request_queue
*q
)
2366 mutex_lock(&set
->tag_list_lock
);
2369 * Check to see if we're transitioning to shared (from 1 to 2 queues).
2371 if (!list_empty(&set
->tag_list
) &&
2372 !(set
->flags
& BLK_MQ_F_TAG_SHARED
)) {
2373 set
->flags
|= BLK_MQ_F_TAG_SHARED
;
2374 /* update existing queue */
2375 blk_mq_update_tag_set_depth(set
, true);
2377 if (set
->flags
& BLK_MQ_F_TAG_SHARED
)
2378 queue_set_hctx_shared(q
, true);
2379 list_add_tail_rcu(&q
->tag_set_list
, &set
->tag_list
);
2381 mutex_unlock(&set
->tag_list_lock
);
2385 * It is the actual release handler for mq, but we do it from
2386 * request queue's release handler for avoiding use-after-free
2387 * and headache because q->mq_kobj shouldn't have been introduced,
2388 * but we can't group ctx/kctx kobj without it.
2390 void blk_mq_release(struct request_queue
*q
)
2392 struct blk_mq_hw_ctx
*hctx
;
2395 /* hctx kobj stays in hctx */
2396 queue_for_each_hw_ctx(q
, hctx
, i
) {
2399 kobject_put(&hctx
->kobj
);
2404 kfree(q
->queue_hw_ctx
);
2407 * release .mq_kobj and sw queue's kobject now because
2408 * both share lifetime with request queue.
2410 blk_mq_sysfs_deinit(q
);
2412 free_percpu(q
->queue_ctx
);
2415 struct request_queue
*blk_mq_init_queue(struct blk_mq_tag_set
*set
)
2417 struct request_queue
*uninit_q
, *q
;
2419 uninit_q
= blk_alloc_queue_node(GFP_KERNEL
, set
->numa_node
);
2421 return ERR_PTR(-ENOMEM
);
2423 q
= blk_mq_init_allocated_queue(set
, uninit_q
);
2425 blk_cleanup_queue(uninit_q
);
2429 EXPORT_SYMBOL(blk_mq_init_queue
);
2431 static int blk_mq_hw_ctx_size(struct blk_mq_tag_set
*tag_set
)
2433 int hw_ctx_size
= sizeof(struct blk_mq_hw_ctx
);
2435 BUILD_BUG_ON(ALIGN(offsetof(struct blk_mq_hw_ctx
, queue_rq_srcu
),
2436 __alignof__(struct blk_mq_hw_ctx
)) !=
2437 sizeof(struct blk_mq_hw_ctx
));
2439 if (tag_set
->flags
& BLK_MQ_F_BLOCKING
)
2440 hw_ctx_size
+= sizeof(struct srcu_struct
);
2445 static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set
*set
,
2446 struct request_queue
*q
)
2449 struct blk_mq_hw_ctx
**hctxs
= q
->queue_hw_ctx
;
2451 blk_mq_sysfs_unregister(q
);
2453 /* protect against switching io scheduler */
2454 mutex_lock(&q
->sysfs_lock
);
2455 for (i
= 0; i
< set
->nr_hw_queues
; i
++) {
2461 node
= blk_mq_hw_queue_to_node(q
->mq_map
, i
);
2462 hctxs
[i
] = kzalloc_node(blk_mq_hw_ctx_size(set
),
2467 if (!zalloc_cpumask_var_node(&hctxs
[i
]->cpumask
, GFP_KERNEL
,
2474 atomic_set(&hctxs
[i
]->nr_active
, 0);
2475 hctxs
[i
]->numa_node
= node
;
2476 hctxs
[i
]->queue_num
= i
;
2478 if (blk_mq_init_hctx(q
, set
, hctxs
[i
], i
)) {
2479 free_cpumask_var(hctxs
[i
]->cpumask
);
2484 blk_mq_hctx_kobj_init(hctxs
[i
]);
2486 for (j
= i
; j
< q
->nr_hw_queues
; j
++) {
2487 struct blk_mq_hw_ctx
*hctx
= hctxs
[j
];
2491 blk_mq_free_map_and_requests(set
, j
);
2492 blk_mq_exit_hctx(q
, set
, hctx
, j
);
2493 kobject_put(&hctx
->kobj
);
2498 q
->nr_hw_queues
= i
;
2499 mutex_unlock(&q
->sysfs_lock
);
2500 blk_mq_sysfs_register(q
);
2503 struct request_queue
*blk_mq_init_allocated_queue(struct blk_mq_tag_set
*set
,
2504 struct request_queue
*q
)
2506 /* mark the queue as mq asap */
2507 q
->mq_ops
= set
->ops
;
2509 q
->poll_cb
= blk_stat_alloc_callback(blk_mq_poll_stats_fn
,
2510 blk_mq_poll_stats_bkt
,
2511 BLK_MQ_POLL_STATS_BKTS
, q
);
2515 q
->queue_ctx
= alloc_percpu(struct blk_mq_ctx
);
2519 /* init q->mq_kobj and sw queues' kobjects */
2520 blk_mq_sysfs_init(q
);
2522 q
->queue_hw_ctx
= kzalloc_node(nr_cpu_ids
* sizeof(*(q
->queue_hw_ctx
)),
2523 GFP_KERNEL
, set
->numa_node
);
2524 if (!q
->queue_hw_ctx
)
2527 q
->mq_map
= set
->mq_map
;
2529 blk_mq_realloc_hw_ctxs(set
, q
);
2530 if (!q
->nr_hw_queues
)
2533 INIT_WORK(&q
->timeout_work
, blk_mq_timeout_work
);
2534 blk_queue_rq_timeout(q
, set
->timeout
? set
->timeout
: 30 * HZ
);
2536 q
->nr_queues
= nr_cpu_ids
;
2538 q
->queue_flags
|= QUEUE_FLAG_MQ_DEFAULT
;
2540 if (!(set
->flags
& BLK_MQ_F_SG_MERGE
))
2541 q
->queue_flags
|= 1 << QUEUE_FLAG_NO_SG_MERGE
;
2543 q
->sg_reserved_size
= INT_MAX
;
2545 INIT_DELAYED_WORK(&q
->requeue_work
, blk_mq_requeue_work
);
2546 INIT_LIST_HEAD(&q
->requeue_list
);
2547 spin_lock_init(&q
->requeue_lock
);
2549 blk_queue_make_request(q
, blk_mq_make_request
);
2550 if (q
->mq_ops
->poll
)
2551 q
->poll_fn
= blk_mq_poll
;
2554 * Do this after blk_queue_make_request() overrides it...
2556 q
->nr_requests
= set
->queue_depth
;
2559 * Default to classic polling
2563 if (set
->ops
->complete
)
2564 blk_queue_softirq_done(q
, set
->ops
->complete
);
2566 blk_mq_init_cpu_queues(q
, set
->nr_hw_queues
);
2567 blk_mq_add_queue_tag_set(set
, q
);
2568 blk_mq_map_swqueue(q
);
2570 if (!(set
->flags
& BLK_MQ_F_NO_SCHED
)) {
2573 ret
= blk_mq_sched_init(q
);
2575 return ERR_PTR(ret
);
2581 kfree(q
->queue_hw_ctx
);
2583 free_percpu(q
->queue_ctx
);
2586 return ERR_PTR(-ENOMEM
);
2588 EXPORT_SYMBOL(blk_mq_init_allocated_queue
);
2590 void blk_mq_free_queue(struct request_queue
*q
)
2592 struct blk_mq_tag_set
*set
= q
->tag_set
;
2594 blk_mq_del_queue_tag_set(q
);
2595 blk_mq_exit_hw_queues(q
, set
, set
->nr_hw_queues
);
2598 /* Basically redo blk_mq_init_queue with queue frozen */
2599 static void blk_mq_queue_reinit(struct request_queue
*q
)
2601 WARN_ON_ONCE(!atomic_read(&q
->mq_freeze_depth
));
2603 blk_mq_debugfs_unregister_hctxs(q
);
2604 blk_mq_sysfs_unregister(q
);
2607 * redo blk_mq_init_cpu_queues and blk_mq_init_hw_queues. FIXME: maybe
2608 * we should change hctx numa_node according to the new topology (this
2609 * involves freeing and re-allocating memory, worth doing?)
2611 blk_mq_map_swqueue(q
);
2613 blk_mq_sysfs_register(q
);
2614 blk_mq_debugfs_register_hctxs(q
);
2617 static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set
*set
)
2621 for (i
= 0; i
< set
->nr_hw_queues
; i
++)
2622 if (!__blk_mq_alloc_rq_map(set
, i
))
2629 blk_mq_free_rq_map(set
->tags
[i
]);
2635 * Allocate the request maps associated with this tag_set. Note that this
2636 * may reduce the depth asked for, if memory is tight. set->queue_depth
2637 * will be updated to reflect the allocated depth.
2639 static int blk_mq_alloc_rq_maps(struct blk_mq_tag_set
*set
)
2644 depth
= set
->queue_depth
;
2646 err
= __blk_mq_alloc_rq_maps(set
);
2650 set
->queue_depth
>>= 1;
2651 if (set
->queue_depth
< set
->reserved_tags
+ BLK_MQ_TAG_MIN
) {
2655 } while (set
->queue_depth
);
2657 if (!set
->queue_depth
|| err
) {
2658 pr_err("blk-mq: failed to allocate request map\n");
2662 if (depth
!= set
->queue_depth
)
2663 pr_info("blk-mq: reduced tag depth (%u -> %u)\n",
2664 depth
, set
->queue_depth
);
2669 static int blk_mq_update_queue_map(struct blk_mq_tag_set
*set
)
2671 if (set
->ops
->map_queues
) {
2674 * transport .map_queues is usually done in the following
2677 * for (queue = 0; queue < set->nr_hw_queues; queue++) {
2678 * mask = get_cpu_mask(queue)
2679 * for_each_cpu(cpu, mask)
2680 * set->mq_map[cpu] = queue;
2683 * When we need to remap, the table has to be cleared for
2684 * killing stale mapping since one CPU may not be mapped
2687 for_each_possible_cpu(cpu
)
2688 set
->mq_map
[cpu
] = 0;
2690 return set
->ops
->map_queues(set
);
2692 return blk_mq_map_queues(set
);
2696 * Alloc a tag set to be associated with one or more request queues.
2697 * May fail with EINVAL for various error conditions. May adjust the
2698 * requested depth down, if if it too large. In that case, the set
2699 * value will be stored in set->queue_depth.
2701 int blk_mq_alloc_tag_set(struct blk_mq_tag_set
*set
)
2705 BUILD_BUG_ON(BLK_MQ_MAX_DEPTH
> 1 << BLK_MQ_UNIQUE_TAG_BITS
);
2707 if (!set
->nr_hw_queues
)
2709 if (!set
->queue_depth
)
2711 if (set
->queue_depth
< set
->reserved_tags
+ BLK_MQ_TAG_MIN
)
2714 if (!set
->ops
->queue_rq
)
2717 if (!set
->ops
->get_budget
^ !set
->ops
->put_budget
)
2720 if (set
->queue_depth
> BLK_MQ_MAX_DEPTH
) {
2721 pr_info("blk-mq: reduced tag depth to %u\n",
2723 set
->queue_depth
= BLK_MQ_MAX_DEPTH
;
2727 * If a crashdump is active, then we are potentially in a very
2728 * memory constrained environment. Limit us to 1 queue and
2729 * 64 tags to prevent using too much memory.
2731 if (is_kdump_kernel()) {
2732 set
->nr_hw_queues
= 1;
2733 set
->queue_depth
= min(64U, set
->queue_depth
);
2736 * There is no use for more h/w queues than cpus.
2738 if (set
->nr_hw_queues
> nr_cpu_ids
)
2739 set
->nr_hw_queues
= nr_cpu_ids
;
2741 set
->tags
= kzalloc_node(nr_cpu_ids
* sizeof(struct blk_mq_tags
*),
2742 GFP_KERNEL
, set
->numa_node
);
2747 set
->mq_map
= kzalloc_node(sizeof(*set
->mq_map
) * nr_cpu_ids
,
2748 GFP_KERNEL
, set
->numa_node
);
2752 ret
= blk_mq_update_queue_map(set
);
2754 goto out_free_mq_map
;
2756 ret
= blk_mq_alloc_rq_maps(set
);
2758 goto out_free_mq_map
;
2760 mutex_init(&set
->tag_list_lock
);
2761 INIT_LIST_HEAD(&set
->tag_list
);
2773 EXPORT_SYMBOL(blk_mq_alloc_tag_set
);
2775 void blk_mq_free_tag_set(struct blk_mq_tag_set
*set
)
2779 for (i
= 0; i
< nr_cpu_ids
; i
++)
2780 blk_mq_free_map_and_requests(set
, i
);
2788 EXPORT_SYMBOL(blk_mq_free_tag_set
);
2790 int blk_mq_update_nr_requests(struct request_queue
*q
, unsigned int nr
)
2792 struct blk_mq_tag_set
*set
= q
->tag_set
;
2793 struct blk_mq_hw_ctx
*hctx
;
2799 if (q
->nr_requests
== nr
)
2802 blk_mq_freeze_queue(q
);
2805 queue_for_each_hw_ctx(q
, hctx
, i
) {
2809 * If we're using an MQ scheduler, just update the scheduler
2810 * queue depth. This is similar to what the old code would do.
2812 if (!hctx
->sched_tags
) {
2813 ret
= blk_mq_tag_update_depth(hctx
, &hctx
->tags
, nr
,
2816 ret
= blk_mq_tag_update_depth(hctx
, &hctx
->sched_tags
,
2824 q
->nr_requests
= nr
;
2826 blk_mq_unfreeze_queue(q
);
2831 static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set
*set
,
2834 struct request_queue
*q
;
2836 lockdep_assert_held(&set
->tag_list_lock
);
2838 if (nr_hw_queues
> nr_cpu_ids
)
2839 nr_hw_queues
= nr_cpu_ids
;
2840 if (nr_hw_queues
< 1 || nr_hw_queues
== set
->nr_hw_queues
)
2843 list_for_each_entry(q
, &set
->tag_list
, tag_set_list
)
2844 blk_mq_freeze_queue(q
);
2846 set
->nr_hw_queues
= nr_hw_queues
;
2847 blk_mq_update_queue_map(set
);
2848 list_for_each_entry(q
, &set
->tag_list
, tag_set_list
) {
2849 blk_mq_realloc_hw_ctxs(set
, q
);
2850 blk_mq_queue_reinit(q
);
2853 list_for_each_entry(q
, &set
->tag_list
, tag_set_list
)
2854 blk_mq_unfreeze_queue(q
);
2857 void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set
*set
, int nr_hw_queues
)
2859 mutex_lock(&set
->tag_list_lock
);
2860 __blk_mq_update_nr_hw_queues(set
, nr_hw_queues
);
2861 mutex_unlock(&set
->tag_list_lock
);
2863 EXPORT_SYMBOL_GPL(blk_mq_update_nr_hw_queues
);
2865 /* Enable polling stats and return whether they were already enabled. */
2866 static bool blk_poll_stats_enable(struct request_queue
*q
)
2868 if (test_bit(QUEUE_FLAG_POLL_STATS
, &q
->queue_flags
) ||
2869 test_and_set_bit(QUEUE_FLAG_POLL_STATS
, &q
->queue_flags
))
2871 blk_stat_add_callback(q
, q
->poll_cb
);
2875 static void blk_mq_poll_stats_start(struct request_queue
*q
)
2878 * We don't arm the callback if polling stats are not enabled or the
2879 * callback is already active.
2881 if (!test_bit(QUEUE_FLAG_POLL_STATS
, &q
->queue_flags
) ||
2882 blk_stat_is_active(q
->poll_cb
))
2885 blk_stat_activate_msecs(q
->poll_cb
, 100);
2888 static void blk_mq_poll_stats_fn(struct blk_stat_callback
*cb
)
2890 struct request_queue
*q
= cb
->data
;
2893 for (bucket
= 0; bucket
< BLK_MQ_POLL_STATS_BKTS
; bucket
++) {
2894 if (cb
->stat
[bucket
].nr_samples
)
2895 q
->poll_stat
[bucket
] = cb
->stat
[bucket
];
2899 static unsigned long blk_mq_poll_nsecs(struct request_queue
*q
,
2900 struct blk_mq_hw_ctx
*hctx
,
2903 unsigned long ret
= 0;
2907 * If stats collection isn't on, don't sleep but turn it on for
2910 if (!blk_poll_stats_enable(q
))
2914 * As an optimistic guess, use half of the mean service time
2915 * for this type of request. We can (and should) make this smarter.
2916 * For instance, if the completion latencies are tight, we can
2917 * get closer than just half the mean. This is especially
2918 * important on devices where the completion latencies are longer
2919 * than ~10 usec. We do use the stats for the relevant IO size
2920 * if available which does lead to better estimates.
2922 bucket
= blk_mq_poll_stats_bkt(rq
);
2926 if (q
->poll_stat
[bucket
].nr_samples
)
2927 ret
= (q
->poll_stat
[bucket
].mean
+ 1) / 2;
2932 static bool blk_mq_poll_hybrid_sleep(struct request_queue
*q
,
2933 struct blk_mq_hw_ctx
*hctx
,
2936 struct hrtimer_sleeper hs
;
2937 enum hrtimer_mode mode
;
2941 if (test_bit(REQ_ATOM_POLL_SLEPT
, &rq
->atomic_flags
))
2947 * -1: don't ever hybrid sleep
2948 * 0: use half of prev avg
2949 * >0: use this specific value
2951 if (q
->poll_nsec
== -1)
2953 else if (q
->poll_nsec
> 0)
2954 nsecs
= q
->poll_nsec
;
2956 nsecs
= blk_mq_poll_nsecs(q
, hctx
, rq
);
2961 set_bit(REQ_ATOM_POLL_SLEPT
, &rq
->atomic_flags
);
2964 * This will be replaced with the stats tracking code, using
2965 * 'avg_completion_time / 2' as the pre-sleep target.
2969 mode
= HRTIMER_MODE_REL
;
2970 hrtimer_init_on_stack(&hs
.timer
, CLOCK_MONOTONIC
, mode
);
2971 hrtimer_set_expires(&hs
.timer
, kt
);
2973 hrtimer_init_sleeper(&hs
, current
);
2975 if (test_bit(REQ_ATOM_COMPLETE
, &rq
->atomic_flags
))
2977 set_current_state(TASK_UNINTERRUPTIBLE
);
2978 hrtimer_start_expires(&hs
.timer
, mode
);
2981 hrtimer_cancel(&hs
.timer
);
2982 mode
= HRTIMER_MODE_ABS
;
2983 } while (hs
.task
&& !signal_pending(current
));
2985 __set_current_state(TASK_RUNNING
);
2986 destroy_hrtimer_on_stack(&hs
.timer
);
2990 static bool __blk_mq_poll(struct blk_mq_hw_ctx
*hctx
, struct request
*rq
)
2992 struct request_queue
*q
= hctx
->queue
;
2996 * If we sleep, have the caller restart the poll loop to reset
2997 * the state. Like for the other success return cases, the
2998 * caller is responsible for checking if the IO completed. If
2999 * the IO isn't complete, we'll get called again and will go
3000 * straight to the busy poll loop.
3002 if (blk_mq_poll_hybrid_sleep(q
, hctx
, rq
))
3005 hctx
->poll_considered
++;
3007 state
= current
->state
;
3008 while (!need_resched()) {
3011 hctx
->poll_invoked
++;
3013 ret
= q
->mq_ops
->poll(hctx
, rq
->tag
);
3015 hctx
->poll_success
++;
3016 set_current_state(TASK_RUNNING
);
3020 if (signal_pending_state(state
, current
))
3021 set_current_state(TASK_RUNNING
);
3023 if (current
->state
== TASK_RUNNING
)
3033 static bool blk_mq_poll(struct request_queue
*q
, blk_qc_t cookie
)
3035 struct blk_mq_hw_ctx
*hctx
;
3038 if (!test_bit(QUEUE_FLAG_POLL
, &q
->queue_flags
))
3041 hctx
= q
->queue_hw_ctx
[blk_qc_t_to_queue_num(cookie
)];
3042 if (!blk_qc_t_is_internal(cookie
))
3043 rq
= blk_mq_tag_to_rq(hctx
->tags
, blk_qc_t_to_tag(cookie
));
3045 rq
= blk_mq_tag_to_rq(hctx
->sched_tags
, blk_qc_t_to_tag(cookie
));
3047 * With scheduling, if the request has completed, we'll
3048 * get a NULL return here, as we clear the sched tag when
3049 * that happens. The request still remains valid, like always,
3050 * so we should be safe with just the NULL check.
3056 return __blk_mq_poll(hctx
, rq
);
3059 static int __init
blk_mq_init(void)
3062 * See comment in block/blk.h rq_atomic_flags enum
3064 BUILD_BUG_ON((REQ_ATOM_STARTED
/ BITS_PER_BYTE
) !=
3065 (REQ_ATOM_COMPLETE
/ BITS_PER_BYTE
));
3067 cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD
, "block/mq:dead", NULL
,
3068 blk_mq_hctx_notify_dead
);
3071 subsys_initcall(blk_mq_init
);