2 * Copyright (C) 1991, 1992 Linus Torvalds
3 * Copyright (C) 1994, Karl Keyte: Added support for disk statistics
4 * Elevator latency, (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
5 * Queue request tables / lock, selectable elevator, Jens Axboe <axboe@suse.de>
6 * kernel-doc documentation started by NeilBrown <neilb@cse.unsw.edu.au>
8 * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001
12 * This handles all read/write requests to block devices
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/backing-dev.h>
17 #include <linux/bio.h>
18 #include <linux/blkdev.h>
19 #include <linux/blk-mq.h>
20 #include <linux/highmem.h>
22 #include <linux/kernel_stat.h>
23 #include <linux/string.h>
24 #include <linux/init.h>
25 #include <linux/completion.h>
26 #include <linux/slab.h>
27 #include <linux/swap.h>
28 #include <linux/writeback.h>
29 #include <linux/task_io_accounting_ops.h>
30 #include <linux/fault-inject.h>
31 #include <linux/list_sort.h>
32 #include <linux/delay.h>
33 #include <linux/ratelimit.h>
34 #include <linux/pm_runtime.h>
35 #include <linux/blk-cgroup.h>
36 #include <linux/debugfs.h>
38 #define CREATE_TRACE_POINTS
39 #include <trace/events/block.h>
43 #include "blk-mq-sched.h"
46 #ifdef CONFIG_DEBUG_FS
47 struct dentry *blk_debugfs_root;
50 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
51 EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
52 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
53 EXPORT_TRACEPOINT_SYMBOL_GPL(block_split);
54 EXPORT_TRACEPOINT_SYMBOL_GPL(block_unplug);
56 DEFINE_IDA(blk_queue_ida);
59 * For the allocated request tables
61 struct kmem_cache *request_cachep;
64 * For queue allocation
66 struct kmem_cache *blk_requestq_cachep;
69 * Controlling structure to kblockd
71 static struct workqueue_struct *kblockd_workqueue;
73 static void blk_clear_congested(struct request_list *rl, int sync)
75 #ifdef CONFIG_CGROUP_WRITEBACK
76 clear_wb_congested(rl->blkg->wb_congested, sync);
79 * If !CGROUP_WRITEBACK, all blkg's map to bdi->wb and we shouldn't
80 * flip its congestion state for events on other blkcgs.
82 if (rl == &rl->q->root_rl)
83 clear_wb_congested(rl->q->backing_dev_info->wb.congested, sync);
87 static void blk_set_congested(struct request_list *rl, int sync)
89 #ifdef CONFIG_CGROUP_WRITEBACK
90 set_wb_congested(rl->blkg->wb_congested, sync);
92 /* see blk_clear_congested() */
93 if (rl == &rl->q->root_rl)
94 set_wb_congested(rl->q->backing_dev_info->wb.congested, sync);
98 void blk_queue_congestion_threshold(struct request_queue *q)
102 nr = q->nr_requests - (q->nr_requests / 8) + 1;
103 if (nr > q->nr_requests)
105 q->nr_congestion_on = nr;
107 nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
110 q->nr_congestion_off = nr;
113 void blk_rq_init(struct request_queue *q, struct request *rq)
115 memset(rq, 0, sizeof(*rq));
117 INIT_LIST_HEAD(&rq->queuelist);
118 INIT_LIST_HEAD(&rq->timeout_list);
121 rq->__sector = (sector_t) -1;
122 INIT_HLIST_NODE(&rq->hash);
123 RB_CLEAR_NODE(&rq->rb_node);
125 rq->internal_tag = -1;
126 rq->start_time = jiffies;
127 set_start_time_ns(rq);
130 EXPORT_SYMBOL(blk_rq_init);
132 static void req_bio_endio(struct request *rq, struct bio *bio,
133 unsigned int nbytes, int error)
136 bio->bi_error = error;
138 if (unlikely(rq->rq_flags & RQF_QUIET))
139 bio_set_flag(bio, BIO_QUIET);
141 bio_advance(bio, nbytes);
143 /* don't actually finish bio if it's part of flush sequence */
144 if (bio->bi_iter.bi_size == 0 && !(rq->rq_flags & RQF_FLUSH_SEQ))
148 void blk_dump_rq_flags(struct request *rq, char *msg)
150 printk(KERN_INFO "%s: dev %s: flags=%llx\n", msg,
151 rq->rq_disk ? rq->rq_disk->disk_name : "?",
152 (unsigned long long) rq->cmd_flags);
154 printk(KERN_INFO " sector %llu, nr/cnr %u/%u\n",
155 (unsigned long long)blk_rq_pos(rq),
156 blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
157 printk(KERN_INFO " bio %p, biotail %p, len %u\n",
158 rq->bio, rq->biotail, blk_rq_bytes(rq));
160 EXPORT_SYMBOL(blk_dump_rq_flags);
162 static void blk_delay_work(struct work_struct *work)
164 struct request_queue *q;
166 q = container_of(work, struct request_queue, delay_work.work);
167 spin_lock_irq(q->queue_lock);
169 spin_unlock_irq(q->queue_lock);
173 * blk_delay_queue - restart queueing after defined interval
174 * @q: The &struct request_queue in question
175 * @msecs: Delay in msecs
178 * Sometimes queueing needs to be postponed for a little while, to allow
179 * resources to come back. This function will make sure that queueing is
180 * restarted around the specified time. Queue lock must be held.
182 void blk_delay_queue(struct request_queue *q, unsigned long msecs)
184 if (likely(!blk_queue_dead(q)))
185 queue_delayed_work(kblockd_workqueue, &q->delay_work,
186 msecs_to_jiffies(msecs));
188 EXPORT_SYMBOL(blk_delay_queue);
191 * blk_start_queue_async - asynchronously restart a previously stopped queue
192 * @q: The &struct request_queue in question
195 * blk_start_queue_async() will clear the stop flag on the queue, and
196 * ensure that the request_fn for the queue is run from an async
199 void blk_start_queue_async(struct request_queue *q)
201 queue_flag_clear(QUEUE_FLAG_STOPPED, q);
202 blk_run_queue_async(q);
204 EXPORT_SYMBOL(blk_start_queue_async);
207 * blk_start_queue - restart a previously stopped queue
208 * @q: The &struct request_queue in question
211 * blk_start_queue() will clear the stop flag on the queue, and call
212 * the request_fn for the queue if it was in a stopped state when
213 * entered. Also see blk_stop_queue(). Queue lock must be held.
215 void blk_start_queue(struct request_queue *q)
217 WARN_ON(!irqs_disabled());
219 queue_flag_clear(QUEUE_FLAG_STOPPED, q);
222 EXPORT_SYMBOL(blk_start_queue);
225 * blk_stop_queue - stop a queue
226 * @q: The &struct request_queue in question
229 * The Linux block layer assumes that a block driver will consume all
230 * entries on the request queue when the request_fn strategy is called.
231 * Often this will not happen, because of hardware limitations (queue
232 * depth settings). If a device driver gets a 'queue full' response,
233 * or if it simply chooses not to queue more I/O at one point, it can
234 * call this function to prevent the request_fn from being called until
235 * the driver has signalled it's ready to go again. This happens by calling
236 * blk_start_queue() to restart queue operations. Queue lock must be held.
238 void blk_stop_queue(struct request_queue *q)
240 cancel_delayed_work(&q->delay_work);
241 queue_flag_set(QUEUE_FLAG_STOPPED, q);
243 EXPORT_SYMBOL(blk_stop_queue);
246 * blk_sync_queue - cancel any pending callbacks on a queue
250 * The block layer may perform asynchronous callback activity
251 * on a queue, such as calling the unplug function after a timeout.
252 * A block device may call blk_sync_queue to ensure that any
253 * such activity is cancelled, thus allowing it to release resources
254 * that the callbacks might use. The caller must already have made sure
255 * that its ->make_request_fn will not re-add plugging prior to calling
258 * This function does not cancel any asynchronous activity arising
259 * out of elevator or throttling code. That would require elevator_exit()
260 * and blkcg_exit_queue() to be called with queue lock initialized.
263 void blk_sync_queue(struct request_queue *q)
265 del_timer_sync(&q->timeout);
268 struct blk_mq_hw_ctx *hctx;
271 queue_for_each_hw_ctx(q, hctx, i) {
272 cancel_work_sync(&hctx->run_work);
273 cancel_delayed_work_sync(&hctx->delay_work);
276 cancel_delayed_work_sync(&q->delay_work);
279 EXPORT_SYMBOL(blk_sync_queue);
282 * __blk_run_queue_uncond - run a queue whether or not it has been stopped
283 * @q: The queue to run
286 * Invoke request handling on a queue if there are any pending requests.
287 * May be used to restart request handling after a request has completed.
288 * This variant runs the queue whether or not the queue has been
289 * stopped. Must be called with the queue lock held and interrupts
290 * disabled. See also @blk_run_queue.
292 inline void __blk_run_queue_uncond(struct request_queue *q)
294 if (unlikely(blk_queue_dead(q)))
298 * Some request_fn implementations, e.g. scsi_request_fn(), unlock
299 * the queue lock internally. As a result multiple threads may be
300 * running such a request function concurrently. Keep track of the
301 * number of active request_fn invocations such that blk_drain_queue()
302 * can wait until all these request_fn calls have finished.
304 q->request_fn_active++;
306 q->request_fn_active--;
308 EXPORT_SYMBOL_GPL(__blk_run_queue_uncond);
311 * __blk_run_queue - run a single device queue
312 * @q: The queue to run
315 * See @blk_run_queue. This variant must be called with the queue lock
316 * held and interrupts disabled.
318 void __blk_run_queue(struct request_queue *q)
320 if (unlikely(blk_queue_stopped(q)))
323 __blk_run_queue_uncond(q);
325 EXPORT_SYMBOL(__blk_run_queue);
328 * blk_run_queue_async - run a single device queue in workqueue context
329 * @q: The queue to run
332 * Tells kblockd to perform the equivalent of @blk_run_queue on behalf
333 * of us. The caller must hold the queue lock.
335 void blk_run_queue_async(struct request_queue *q)
337 if (likely(!blk_queue_stopped(q) && !blk_queue_dead(q)))
338 mod_delayed_work(kblockd_workqueue, &q->delay_work, 0);
340 EXPORT_SYMBOL(blk_run_queue_async);
343 * blk_run_queue - run a single device queue
344 * @q: The queue to run
347 * Invoke request handling on this queue, if it has pending work to do.
348 * May be used to restart queueing when a request has completed.
350 void blk_run_queue(struct request_queue *q)
354 spin_lock_irqsave(q->queue_lock, flags);
356 spin_unlock_irqrestore(q->queue_lock, flags);
358 EXPORT_SYMBOL(blk_run_queue);
360 void blk_put_queue(struct request_queue *q)
362 kobject_put(&q->kobj);
364 EXPORT_SYMBOL(blk_put_queue);
367 * __blk_drain_queue - drain requests from request_queue
369 * @drain_all: whether to drain all requests or only the ones w/ ELVPRIV
371 * Drain requests from @q. If @drain_all is set, all requests are drained.
372 * If not, only ELVPRIV requests are drained. The caller is responsible
373 * for ensuring that no new requests which need to be drained are queued.
375 static void __blk_drain_queue(struct request_queue *q, bool drain_all)
376 __releases(q->queue_lock)
377 __acquires(q->queue_lock)
381 lockdep_assert_held(q->queue_lock);
387 * The caller might be trying to drain @q before its
388 * elevator is initialized.
391 elv_drain_elevator(q);
393 blkcg_drain_queue(q);
396 * This function might be called on a queue which failed
397 * driver init after queue creation or is not yet fully
398 * active yet. Some drivers (e.g. fd and loop) get unhappy
399 * in such cases. Kick queue iff dispatch queue has
400 * something on it and @q has request_fn set.
402 if (!list_empty(&q->queue_head) && q->request_fn)
405 drain |= q->nr_rqs_elvpriv;
406 drain |= q->request_fn_active;
409 * Unfortunately, requests are queued at and tracked from
410 * multiple places and there's no single counter which can
411 * be drained. Check all the queues and counters.
414 struct blk_flush_queue *fq = blk_get_flush_queue(q, NULL);
415 drain |= !list_empty(&q->queue_head);
416 for (i = 0; i < 2; i++) {
417 drain |= q->nr_rqs[i];
418 drain |= q->in_flight[i];
420 drain |= !list_empty(&fq->flush_queue[i]);
427 spin_unlock_irq(q->queue_lock);
431 spin_lock_irq(q->queue_lock);
435 * With queue marked dead, any woken up waiter will fail the
436 * allocation path, so the wakeup chaining is lost and we're
437 * left with hung waiters. We need to wake up those waiters.
440 struct request_list *rl;
442 blk_queue_for_each_rl(rl, q)
443 for (i = 0; i < ARRAY_SIZE(rl->wait); i++)
444 wake_up_all(&rl->wait[i]);
449 * blk_queue_bypass_start - enter queue bypass mode
450 * @q: queue of interest
452 * In bypass mode, only the dispatch FIFO queue of @q is used. This
453 * function makes @q enter bypass mode and drains all requests which were
454 * throttled or issued before. On return, it's guaranteed that no request
455 * is being throttled or has ELVPRIV set and blk_queue_bypass() %true
456 * inside queue or RCU read lock.
458 void blk_queue_bypass_start(struct request_queue *q)
460 spin_lock_irq(q->queue_lock);
462 queue_flag_set(QUEUE_FLAG_BYPASS, q);
463 spin_unlock_irq(q->queue_lock);
466 * Queues start drained. Skip actual draining till init is
467 * complete. This avoids lenghty delays during queue init which
468 * can happen many times during boot.
470 if (blk_queue_init_done(q)) {
471 spin_lock_irq(q->queue_lock);
472 __blk_drain_queue(q, false);
473 spin_unlock_irq(q->queue_lock);
475 /* ensure blk_queue_bypass() is %true inside RCU read lock */
479 EXPORT_SYMBOL_GPL(blk_queue_bypass_start);
482 * blk_queue_bypass_end - leave queue bypass mode
483 * @q: queue of interest
485 * Leave bypass mode and restore the normal queueing behavior.
487 void blk_queue_bypass_end(struct request_queue *q)
489 spin_lock_irq(q->queue_lock);
490 if (!--q->bypass_depth)
491 queue_flag_clear(QUEUE_FLAG_BYPASS, q);
492 WARN_ON_ONCE(q->bypass_depth < 0);
493 spin_unlock_irq(q->queue_lock);
495 EXPORT_SYMBOL_GPL(blk_queue_bypass_end);
497 void blk_set_queue_dying(struct request_queue *q)
499 spin_lock_irq(q->queue_lock);
500 queue_flag_set(QUEUE_FLAG_DYING, q);
501 spin_unlock_irq(q->queue_lock);
504 * When queue DYING flag is set, we need to block new req
505 * entering queue, so we call blk_freeze_queue_start() to
506 * prevent I/O from crossing blk_queue_enter().
508 blk_freeze_queue_start(q);
511 blk_mq_wake_waiters(q);
513 struct request_list *rl;
515 spin_lock_irq(q->queue_lock);
516 blk_queue_for_each_rl(rl, q) {
518 wake_up(&rl->wait[BLK_RW_SYNC]);
519 wake_up(&rl->wait[BLK_RW_ASYNC]);
522 spin_unlock_irq(q->queue_lock);
525 EXPORT_SYMBOL_GPL(blk_set_queue_dying);
528 * blk_cleanup_queue - shutdown a request queue
529 * @q: request queue to shutdown
531 * Mark @q DYING, drain all pending requests, mark @q DEAD, destroy and
532 * put it. All future requests will be failed immediately with -ENODEV.
534 void blk_cleanup_queue(struct request_queue *q)
536 spinlock_t *lock = q->queue_lock;
538 /* mark @q DYING, no new request or merges will be allowed afterwards */
539 mutex_lock(&q->sysfs_lock);
540 blk_set_queue_dying(q);
544 * A dying queue is permanently in bypass mode till released. Note
545 * that, unlike blk_queue_bypass_start(), we aren't performing
546 * synchronize_rcu() after entering bypass mode to avoid the delay
547 * as some drivers create and destroy a lot of queues while
548 * probing. This is still safe because blk_release_queue() will be
549 * called only after the queue refcnt drops to zero and nothing,
550 * RCU or not, would be traversing the queue by then.
553 queue_flag_set(QUEUE_FLAG_BYPASS, q);
555 queue_flag_set(QUEUE_FLAG_NOMERGES, q);
556 queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
557 queue_flag_set(QUEUE_FLAG_DYING, q);
558 spin_unlock_irq(lock);
559 mutex_unlock(&q->sysfs_lock);
562 * Drain all requests queued before DYING marking. Set DEAD flag to
563 * prevent that q->request_fn() gets invoked after draining finished.
568 __blk_drain_queue(q, true);
569 queue_flag_set(QUEUE_FLAG_DEAD, q);
570 spin_unlock_irq(lock);
572 /* for synchronous bio-based driver finish in-flight integrity i/o */
573 blk_flush_integrity();
575 /* @q won't process any more request, flush async actions */
576 del_timer_sync(&q->backing_dev_info->laptop_mode_wb_timer);
580 blk_mq_free_queue(q);
581 percpu_ref_exit(&q->q_usage_counter);
584 if (q->queue_lock != &q->__queue_lock)
585 q->queue_lock = &q->__queue_lock;
586 spin_unlock_irq(lock);
588 /* @q is and will stay empty, shutdown and put */
591 EXPORT_SYMBOL(blk_cleanup_queue);
593 /* Allocate memory local to the request queue */
594 static void *alloc_request_simple(gfp_t gfp_mask, void *data)
596 struct request_queue *q = data;
598 return kmem_cache_alloc_node(request_cachep, gfp_mask, q->node);
601 static void free_request_simple(void *element, void *data)
603 kmem_cache_free(request_cachep, element);
606 static void *alloc_request_size(gfp_t gfp_mask, void *data)
608 struct request_queue *q = data;
611 rq = kmalloc_node(sizeof(struct request) + q->cmd_size, gfp_mask,
613 if (rq && q->init_rq_fn && q->init_rq_fn(q, rq, gfp_mask) < 0) {
620 static void free_request_size(void *element, void *data)
622 struct request_queue *q = data;
625 q->exit_rq_fn(q, element);
629 int blk_init_rl(struct request_list *rl, struct request_queue *q,
632 if (unlikely(rl->rq_pool))
636 rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
637 rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
638 init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
639 init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
642 rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ,
643 alloc_request_size, free_request_size,
644 q, gfp_mask, q->node);
646 rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ,
647 alloc_request_simple, free_request_simple,
648 q, gfp_mask, q->node);
656 void blk_exit_rl(struct request_list *rl)
659 mempool_destroy(rl->rq_pool);
662 struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
664 return blk_alloc_queue_node(gfp_mask, NUMA_NO_NODE);
666 EXPORT_SYMBOL(blk_alloc_queue);
668 int blk_queue_enter(struct request_queue *q, bool nowait)
673 if (percpu_ref_tryget_live(&q->q_usage_counter))
680 * read pair of barrier in blk_freeze_queue_start(),
681 * we need to order reading __PERCPU_REF_DEAD flag of
682 * .q_usage_counter and reading .mq_freeze_depth or
683 * queue dying flag, otherwise the following wait may
684 * never return if the two reads are reordered.
688 ret = wait_event_interruptible(q->mq_freeze_wq,
689 !atomic_read(&q->mq_freeze_depth) ||
691 if (blk_queue_dying(q))
698 void blk_queue_exit(struct request_queue *q)
700 percpu_ref_put(&q->q_usage_counter);
703 static void blk_queue_usage_counter_release(struct percpu_ref *ref)
705 struct request_queue *q =
706 container_of(ref, struct request_queue, q_usage_counter);
708 wake_up_all(&q->mq_freeze_wq);
711 static void blk_rq_timed_out_timer(unsigned long data)
713 struct request_queue *q = (struct request_queue *)data;
715 kblockd_schedule_work(&q->timeout_work);
718 struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
720 struct request_queue *q;
722 q = kmem_cache_alloc_node(blk_requestq_cachep,
723 gfp_mask | __GFP_ZERO, node_id);
727 q->id = ida_simple_get(&blk_queue_ida, 0, 0, gfp_mask);
731 q->bio_split = bioset_create(BIO_POOL_SIZE, 0);
735 q->backing_dev_info = bdi_alloc_node(gfp_mask, node_id);
736 if (!q->backing_dev_info)
739 q->stats = blk_alloc_queue_stats();
743 q->backing_dev_info->ra_pages =
744 (VM_MAX_READAHEAD * 1024) / PAGE_SIZE;
745 q->backing_dev_info->capabilities = BDI_CAP_CGROUP_WRITEBACK;
746 q->backing_dev_info->name = "block";
749 setup_timer(&q->backing_dev_info->laptop_mode_wb_timer,
750 laptop_mode_timer_fn, (unsigned long) q);
751 setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
752 INIT_LIST_HEAD(&q->queue_head);
753 INIT_LIST_HEAD(&q->timeout_list);
754 INIT_LIST_HEAD(&q->icq_list);
755 #ifdef CONFIG_BLK_CGROUP
756 INIT_LIST_HEAD(&q->blkg_list);
758 INIT_DELAYED_WORK(&q->delay_work, blk_delay_work);
760 kobject_init(&q->kobj, &blk_queue_ktype);
762 mutex_init(&q->sysfs_lock);
763 spin_lock_init(&q->__queue_lock);
766 * By default initialize queue_lock to internal lock and driver can
767 * override it later if need be.
769 q->queue_lock = &q->__queue_lock;
772 * A queue starts its life with bypass turned on to avoid
773 * unnecessary bypass on/off overhead and nasty surprises during
774 * init. The initial bypass will be finished when the queue is
775 * registered by blk_register_queue().
778 __set_bit(QUEUE_FLAG_BYPASS, &q->queue_flags);
780 init_waitqueue_head(&q->mq_freeze_wq);
783 * Init percpu_ref in atomic mode so that it's faster to shutdown.
784 * See blk_register_queue() for details.
786 if (percpu_ref_init(&q->q_usage_counter,
787 blk_queue_usage_counter_release,
788 PERCPU_REF_INIT_ATOMIC, GFP_KERNEL))
791 if (blkcg_init_queue(q))
797 percpu_ref_exit(&q->q_usage_counter);
799 blk_free_queue_stats(q->stats);
801 bdi_put(q->backing_dev_info);
803 bioset_free(q->bio_split);
805 ida_simple_remove(&blk_queue_ida, q->id);
807 kmem_cache_free(blk_requestq_cachep, q);
810 EXPORT_SYMBOL(blk_alloc_queue_node);
813 * blk_init_queue - prepare a request queue for use with a block device
814 * @rfn: The function to be called to process requests that have been
815 * placed on the queue.
816 * @lock: Request queue spin lock
819 * If a block device wishes to use the standard request handling procedures,
820 * which sorts requests and coalesces adjacent requests, then it must
821 * call blk_init_queue(). The function @rfn will be called when there
822 * are requests on the queue that need to be processed. If the device
823 * supports plugging, then @rfn may not be called immediately when requests
824 * are available on the queue, but may be called at some time later instead.
825 * Plugged queues are generally unplugged when a buffer belonging to one
826 * of the requests on the queue is needed, or due to memory pressure.
828 * @rfn is not required, or even expected, to remove all requests off the
829 * queue, but only as many as it can handle at a time. If it does leave
830 * requests on the queue, it is responsible for arranging that the requests
831 * get dealt with eventually.
833 * The queue spin lock must be held while manipulating the requests on the
834 * request queue; this lock will be taken also from interrupt context, so irq
835 * disabling is needed for it.
837 * Function returns a pointer to the initialized request queue, or %NULL if
841 * blk_init_queue() must be paired with a blk_cleanup_queue() call
842 * when the block device is deactivated (such as at module unload).
845 struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
847 return blk_init_queue_node(rfn, lock, NUMA_NO_NODE);
849 EXPORT_SYMBOL(blk_init_queue);
851 struct request_queue *
852 blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
854 struct request_queue *q;
856 q = blk_alloc_queue_node(GFP_KERNEL, node_id);
862 q->queue_lock = lock;
863 if (blk_init_allocated_queue(q) < 0) {
864 blk_cleanup_queue(q);
870 EXPORT_SYMBOL(blk_init_queue_node);
872 static blk_qc_t blk_queue_bio(struct request_queue *q, struct bio *bio);
875 int blk_init_allocated_queue(struct request_queue *q)
877 q->fq = blk_alloc_flush_queue(q, NUMA_NO_NODE, q->cmd_size);
881 if (q->init_rq_fn && q->init_rq_fn(q, q->fq->flush_rq, GFP_KERNEL))
882 goto out_free_flush_queue;
884 if (blk_init_rl(&q->root_rl, q, GFP_KERNEL))
885 goto out_exit_flush_rq;
887 INIT_WORK(&q->timeout_work, blk_timeout_work);
888 q->queue_flags |= QUEUE_FLAG_DEFAULT;
891 * This also sets hw/phys segments, boundary and size
893 blk_queue_make_request(q, blk_queue_bio);
895 q->sg_reserved_size = INT_MAX;
897 /* Protect q->elevator from elevator_change */
898 mutex_lock(&q->sysfs_lock);
901 if (elevator_init(q, NULL)) {
902 mutex_unlock(&q->sysfs_lock);
903 goto out_exit_flush_rq;
906 mutex_unlock(&q->sysfs_lock);
911 q->exit_rq_fn(q, q->fq->flush_rq);
912 out_free_flush_queue:
913 blk_free_flush_queue(q->fq);
916 EXPORT_SYMBOL(blk_init_allocated_queue);
918 bool blk_get_queue(struct request_queue *q)
920 if (likely(!blk_queue_dying(q))) {
927 EXPORT_SYMBOL(blk_get_queue);
929 static inline void blk_free_request(struct request_list *rl, struct request *rq)
931 if (rq->rq_flags & RQF_ELVPRIV) {
932 elv_put_request(rl->q, rq);
934 put_io_context(rq->elv.icq->ioc);
937 mempool_free(rq, rl->rq_pool);
941 * ioc_batching returns true if the ioc is a valid batching request and
942 * should be given priority access to a request.
944 static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
950 * Make sure the process is able to allocate at least 1 request
951 * even if the batch times out, otherwise we could theoretically
954 return ioc->nr_batch_requests == q->nr_batching ||
955 (ioc->nr_batch_requests > 0
956 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
960 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
961 * will cause the process to be a "batcher" on all queues in the system. This
962 * is the behaviour we want though - once it gets a wakeup it should be given
965 static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
967 if (!ioc || ioc_batching(q, ioc))
970 ioc->nr_batch_requests = q->nr_batching;
971 ioc->last_waited = jiffies;
974 static void __freed_request(struct request_list *rl, int sync)
976 struct request_queue *q = rl->q;
978 if (rl->count[sync] < queue_congestion_off_threshold(q))
979 blk_clear_congested(rl, sync);
981 if (rl->count[sync] + 1 <= q->nr_requests) {
982 if (waitqueue_active(&rl->wait[sync]))
983 wake_up(&rl->wait[sync]);
985 blk_clear_rl_full(rl, sync);
990 * A request has just been released. Account for it, update the full and
991 * congestion status, wake up any waiters. Called under q->queue_lock.
993 static void freed_request(struct request_list *rl, bool sync,
994 req_flags_t rq_flags)
996 struct request_queue *q = rl->q;
1000 if (rq_flags & RQF_ELVPRIV)
1001 q->nr_rqs_elvpriv--;
1003 __freed_request(rl, sync);
1005 if (unlikely(rl->starved[sync ^ 1]))
1006 __freed_request(rl, sync ^ 1);
1009 int blk_update_nr_requests(struct request_queue *q, unsigned int nr)
1011 struct request_list *rl;
1012 int on_thresh, off_thresh;
1014 spin_lock_irq(q->queue_lock);
1015 q->nr_requests = nr;
1016 blk_queue_congestion_threshold(q);
1017 on_thresh = queue_congestion_on_threshold(q);
1018 off_thresh = queue_congestion_off_threshold(q);
1020 blk_queue_for_each_rl(rl, q) {
1021 if (rl->count[BLK_RW_SYNC] >= on_thresh)
1022 blk_set_congested(rl, BLK_RW_SYNC);
1023 else if (rl->count[BLK_RW_SYNC] < off_thresh)
1024 blk_clear_congested(rl, BLK_RW_SYNC);
1026 if (rl->count[BLK_RW_ASYNC] >= on_thresh)
1027 blk_set_congested(rl, BLK_RW_ASYNC);
1028 else if (rl->count[BLK_RW_ASYNC] < off_thresh)
1029 blk_clear_congested(rl, BLK_RW_ASYNC);
1031 if (rl->count[BLK_RW_SYNC] >= q->nr_requests) {
1032 blk_set_rl_full(rl, BLK_RW_SYNC);
1034 blk_clear_rl_full(rl, BLK_RW_SYNC);
1035 wake_up(&rl->wait[BLK_RW_SYNC]);
1038 if (rl->count[BLK_RW_ASYNC] >= q->nr_requests) {
1039 blk_set_rl_full(rl, BLK_RW_ASYNC);
1041 blk_clear_rl_full(rl, BLK_RW_ASYNC);
1042 wake_up(&rl->wait[BLK_RW_ASYNC]);
1046 spin_unlock_irq(q->queue_lock);
1051 * __get_request - get a free request
1052 * @rl: request list to allocate from
1053 * @op: operation and flags
1054 * @bio: bio to allocate request for (can be %NULL)
1055 * @gfp_mask: allocation mask
1057 * Get a free request from @q. This function may fail under memory
1058 * pressure or if @q is dead.
1060 * Must be called with @q->queue_lock held and,
1061 * Returns ERR_PTR on failure, with @q->queue_lock held.
1062 * Returns request pointer on success, with @q->queue_lock *not held*.
1064 static struct request *__get_request(struct request_list *rl, unsigned int op,
1065 struct bio *bio, gfp_t gfp_mask)
1067 struct request_queue *q = rl->q;
1069 struct elevator_type *et = q->elevator->type;
1070 struct io_context *ioc = rq_ioc(bio);
1071 struct io_cq *icq = NULL;
1072 const bool is_sync = op_is_sync(op);
1074 req_flags_t rq_flags = RQF_ALLOCED;
1076 if (unlikely(blk_queue_dying(q)))
1077 return ERR_PTR(-ENODEV);
1079 may_queue = elv_may_queue(q, op);
1080 if (may_queue == ELV_MQUEUE_NO)
1083 if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
1084 if (rl->count[is_sync]+1 >= q->nr_requests) {
1086 * The queue will fill after this allocation, so set
1087 * it as full, and mark this process as "batching".
1088 * This process will be allowed to complete a batch of
1089 * requests, others will be blocked.
1091 if (!blk_rl_full(rl, is_sync)) {
1092 ioc_set_batching(q, ioc);
1093 blk_set_rl_full(rl, is_sync);
1095 if (may_queue != ELV_MQUEUE_MUST
1096 && !ioc_batching(q, ioc)) {
1098 * The queue is full and the allocating
1099 * process is not a "batcher", and not
1100 * exempted by the IO scheduler
1102 return ERR_PTR(-ENOMEM);
1106 blk_set_congested(rl, is_sync);
1110 * Only allow batching queuers to allocate up to 50% over the defined
1111 * limit of requests, otherwise we could have thousands of requests
1112 * allocated with any setting of ->nr_requests
1114 if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
1115 return ERR_PTR(-ENOMEM);
1117 q->nr_rqs[is_sync]++;
1118 rl->count[is_sync]++;
1119 rl->starved[is_sync] = 0;
1122 * Decide whether the new request will be managed by elevator. If
1123 * so, mark @rq_flags and increment elvpriv. Non-zero elvpriv will
1124 * prevent the current elevator from being destroyed until the new
1125 * request is freed. This guarantees icq's won't be destroyed and
1126 * makes creating new ones safe.
1128 * Flush requests do not use the elevator so skip initialization.
1129 * This allows a request to share the flush and elevator data.
1131 * Also, lookup icq while holding queue_lock. If it doesn't exist,
1132 * it will be created after releasing queue_lock.
1134 if (!op_is_flush(op) && !blk_queue_bypass(q)) {
1135 rq_flags |= RQF_ELVPRIV;
1136 q->nr_rqs_elvpriv++;
1137 if (et->icq_cache && ioc)
1138 icq = ioc_lookup_icq(ioc, q);
1141 if (blk_queue_io_stat(q))
1142 rq_flags |= RQF_IO_STAT;
1143 spin_unlock_irq(q->queue_lock);
1145 /* allocate and init request */
1146 rq = mempool_alloc(rl->rq_pool, gfp_mask);
1151 blk_rq_set_rl(rq, rl);
1153 rq->rq_flags = rq_flags;
1156 if (rq_flags & RQF_ELVPRIV) {
1157 if (unlikely(et->icq_cache && !icq)) {
1159 icq = ioc_create_icq(ioc, q, gfp_mask);
1165 if (unlikely(elv_set_request(q, rq, bio, gfp_mask)))
1168 /* @rq->elv.icq holds io_context until @rq is freed */
1170 get_io_context(icq->ioc);
1174 * ioc may be NULL here, and ioc_batching will be false. That's
1175 * OK, if the queue is under the request limit then requests need
1176 * not count toward the nr_batch_requests limit. There will always
1177 * be some limit enforced by BLK_BATCH_TIME.
1179 if (ioc_batching(q, ioc))
1180 ioc->nr_batch_requests--;
1182 trace_block_getrq(q, bio, op);
1187 * elvpriv init failed. ioc, icq and elvpriv aren't mempool backed
1188 * and may fail indefinitely under memory pressure and thus
1189 * shouldn't stall IO. Treat this request as !elvpriv. This will
1190 * disturb iosched and blkcg but weird is bettern than dead.
1192 printk_ratelimited(KERN_WARNING "%s: dev %s: request aux data allocation failed, iosched may be disturbed\n",
1193 __func__, dev_name(q->backing_dev_info->dev));
1195 rq->rq_flags &= ~RQF_ELVPRIV;
1198 spin_lock_irq(q->queue_lock);
1199 q->nr_rqs_elvpriv--;
1200 spin_unlock_irq(q->queue_lock);
1205 * Allocation failed presumably due to memory. Undo anything we
1206 * might have messed up.
1208 * Allocating task should really be put onto the front of the wait
1209 * queue, but this is pretty rare.
1211 spin_lock_irq(q->queue_lock);
1212 freed_request(rl, is_sync, rq_flags);
1215 * in the very unlikely event that allocation failed and no
1216 * requests for this direction was pending, mark us starved so that
1217 * freeing of a request in the other direction will notice
1218 * us. another possible fix would be to split the rq mempool into
1222 if (unlikely(rl->count[is_sync] == 0))
1223 rl->starved[is_sync] = 1;
1224 return ERR_PTR(-ENOMEM);
1228 * get_request - get a free request
1229 * @q: request_queue to allocate request from
1230 * @op: operation and flags
1231 * @bio: bio to allocate request for (can be %NULL)
1232 * @gfp_mask: allocation mask
1234 * Get a free request from @q. If %__GFP_DIRECT_RECLAIM is set in @gfp_mask,
1235 * this function keeps retrying under memory pressure and fails iff @q is dead.
1237 * Must be called with @q->queue_lock held and,
1238 * Returns ERR_PTR on failure, with @q->queue_lock held.
1239 * Returns request pointer on success, with @q->queue_lock *not held*.
1241 static struct request *get_request(struct request_queue *q, unsigned int op,
1242 struct bio *bio, gfp_t gfp_mask)
1244 const bool is_sync = op_is_sync(op);
1246 struct request_list *rl;
1249 rl = blk_get_rl(q, bio); /* transferred to @rq on success */
1251 rq = __get_request(rl, op, bio, gfp_mask);
1255 if (!gfpflags_allow_blocking(gfp_mask) || unlikely(blk_queue_dying(q))) {
1260 /* wait on @rl and retry */
1261 prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
1262 TASK_UNINTERRUPTIBLE);
1264 trace_block_sleeprq(q, bio, op);
1266 spin_unlock_irq(q->queue_lock);
1270 * After sleeping, we become a "batching" process and will be able
1271 * to allocate at least one request, and up to a big batch of them
1272 * for a small period time. See ioc_batching, ioc_set_batching
1274 ioc_set_batching(q, current->io_context);
1276 spin_lock_irq(q->queue_lock);
1277 finish_wait(&rl->wait[is_sync], &wait);
1282 static struct request *blk_old_get_request(struct request_queue *q, int rw,
1287 /* create ioc upfront */
1288 create_io_context(gfp_mask, q->node);
1290 spin_lock_irq(q->queue_lock);
1291 rq = get_request(q, rw, NULL, gfp_mask);
1293 spin_unlock_irq(q->queue_lock);
1297 /* q->queue_lock is unlocked at this point */
1299 rq->__sector = (sector_t) -1;
1300 rq->bio = rq->biotail = NULL;
1304 struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
1307 return blk_mq_alloc_request(q, rw,
1308 (gfp_mask & __GFP_DIRECT_RECLAIM) ?
1309 0 : BLK_MQ_REQ_NOWAIT);
1311 return blk_old_get_request(q, rw, gfp_mask);
1313 EXPORT_SYMBOL(blk_get_request);
1316 * blk_requeue_request - put a request back on queue
1317 * @q: request queue where request should be inserted
1318 * @rq: request to be inserted
1321 * Drivers often keep queueing requests until the hardware cannot accept
1322 * more, when that condition happens we need to put the request back
1323 * on the queue. Must be called with queue lock held.
1325 void blk_requeue_request(struct request_queue *q, struct request *rq)
1327 blk_delete_timer(rq);
1328 blk_clear_rq_complete(rq);
1329 trace_block_rq_requeue(q, rq);
1330 wbt_requeue(q->rq_wb, &rq->issue_stat);
1332 if (rq->rq_flags & RQF_QUEUED)
1333 blk_queue_end_tag(q, rq);
1335 BUG_ON(blk_queued_rq(rq));
1337 elv_requeue_request(q, rq);
1339 EXPORT_SYMBOL(blk_requeue_request);
1341 static void add_acct_request(struct request_queue *q, struct request *rq,
1344 blk_account_io_start(rq, true);
1345 __elv_add_request(q, rq, where);
1348 static void part_round_stats_single(int cpu, struct hd_struct *part,
1353 if (now == part->stamp)
1356 inflight = part_in_flight(part);
1358 __part_stat_add(cpu, part, time_in_queue,
1359 inflight * (now - part->stamp));
1360 __part_stat_add(cpu, part, io_ticks, (now - part->stamp));
1366 * part_round_stats() - Round off the performance stats on a struct disk_stats.
1367 * @cpu: cpu number for stats access
1368 * @part: target partition
1370 * The average IO queue length and utilisation statistics are maintained
1371 * by observing the current state of the queue length and the amount of
1372 * time it has been in this state for.
1374 * Normally, that accounting is done on IO completion, but that can result
1375 * in more than a second's worth of IO being accounted for within any one
1376 * second, leading to >100% utilisation. To deal with that, we call this
1377 * function to do a round-off before returning the results when reading
1378 * /proc/diskstats. This accounts immediately for all queue usage up to
1379 * the current jiffies and restarts the counters again.
1381 void part_round_stats(int cpu, struct hd_struct *part)
1383 unsigned long now = jiffies;
1386 part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1387 part_round_stats_single(cpu, part, now);
1389 EXPORT_SYMBOL_GPL(part_round_stats);
1392 static void blk_pm_put_request(struct request *rq)
1394 if (rq->q->dev && !(rq->rq_flags & RQF_PM) && !--rq->q->nr_pending)
1395 pm_runtime_mark_last_busy(rq->q->dev);
1398 static inline void blk_pm_put_request(struct request *rq) {}
1402 * queue lock must be held
1404 void __blk_put_request(struct request_queue *q, struct request *req)
1406 req_flags_t rq_flags = req->rq_flags;
1412 blk_mq_free_request(req);
1416 blk_pm_put_request(req);
1418 elv_completed_request(q, req);
1420 /* this is a bio leak */
1421 WARN_ON(req->bio != NULL);
1423 wbt_done(q->rq_wb, &req->issue_stat);
1426 * Request may not have originated from ll_rw_blk. if not,
1427 * it didn't come out of our reserved rq pools
1429 if (rq_flags & RQF_ALLOCED) {
1430 struct request_list *rl = blk_rq_rl(req);
1431 bool sync = op_is_sync(req->cmd_flags);
1433 BUG_ON(!list_empty(&req->queuelist));
1434 BUG_ON(ELV_ON_HASH(req));
1436 blk_free_request(rl, req);
1437 freed_request(rl, sync, rq_flags);
1441 EXPORT_SYMBOL_GPL(__blk_put_request);
1443 void blk_put_request(struct request *req)
1445 struct request_queue *q = req->q;
1448 blk_mq_free_request(req);
1450 unsigned long flags;
1452 spin_lock_irqsave(q->queue_lock, flags);
1453 __blk_put_request(q, req);
1454 spin_unlock_irqrestore(q->queue_lock, flags);
1457 EXPORT_SYMBOL(blk_put_request);
1459 bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
1462 const int ff = bio->bi_opf & REQ_FAILFAST_MASK;
1464 if (!ll_back_merge_fn(q, req, bio))
1467 trace_block_bio_backmerge(q, req, bio);
1469 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1470 blk_rq_set_mixed_merge(req);
1472 req->biotail->bi_next = bio;
1474 req->__data_len += bio->bi_iter.bi_size;
1475 req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1477 blk_account_io_start(req, false);
1481 bool bio_attempt_front_merge(struct request_queue *q, struct request *req,
1484 const int ff = bio->bi_opf & REQ_FAILFAST_MASK;
1486 if (!ll_front_merge_fn(q, req, bio))
1489 trace_block_bio_frontmerge(q, req, bio);
1491 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1492 blk_rq_set_mixed_merge(req);
1494 bio->bi_next = req->bio;
1497 req->__sector = bio->bi_iter.bi_sector;
1498 req->__data_len += bio->bi_iter.bi_size;
1499 req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1501 blk_account_io_start(req, false);
1505 bool bio_attempt_discard_merge(struct request_queue *q, struct request *req,
1508 unsigned short segments = blk_rq_nr_discard_segments(req);
1510 if (segments >= queue_max_discard_segments(q))
1512 if (blk_rq_sectors(req) + bio_sectors(bio) >
1513 blk_rq_get_max_sectors(req, blk_rq_pos(req)))
1516 req->biotail->bi_next = bio;
1518 req->__data_len += bio->bi_iter.bi_size;
1519 req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1520 req->nr_phys_segments = segments + 1;
1522 blk_account_io_start(req, false);
1525 req_set_nomerge(q, req);
1530 * blk_attempt_plug_merge - try to merge with %current's plugged list
1531 * @q: request_queue new bio is being queued at
1532 * @bio: new bio being queued
1533 * @request_count: out parameter for number of traversed plugged requests
1534 * @same_queue_rq: pointer to &struct request that gets filled in when
1535 * another request associated with @q is found on the plug list
1536 * (optional, may be %NULL)
1538 * Determine whether @bio being queued on @q can be merged with a request
1539 * on %current's plugged list. Returns %true if merge was successful,
1542 * Plugging coalesces IOs from the same issuer for the same purpose without
1543 * going through @q->queue_lock. As such it's more of an issuing mechanism
1544 * than scheduling, and the request, while may have elvpriv data, is not
1545 * added on the elevator at this point. In addition, we don't have
1546 * reliable access to the elevator outside queue lock. Only check basic
1547 * merging parameters without querying the elevator.
1549 * Caller must ensure !blk_queue_nomerges(q) beforehand.
1551 bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
1552 unsigned int *request_count,
1553 struct request **same_queue_rq)
1555 struct blk_plug *plug;
1557 struct list_head *plug_list;
1559 plug = current->plug;
1565 plug_list = &plug->mq_list;
1567 plug_list = &plug->list;
1569 list_for_each_entry_reverse(rq, plug_list, queuelist) {
1570 bool merged = false;
1575 * Only blk-mq multiple hardware queues case checks the
1576 * rq in the same queue, there should be only one such
1580 *same_queue_rq = rq;
1583 if (rq->q != q || !blk_rq_merge_ok(rq, bio))
1586 switch (blk_try_merge(rq, bio)) {
1587 case ELEVATOR_BACK_MERGE:
1588 merged = bio_attempt_back_merge(q, rq, bio);
1590 case ELEVATOR_FRONT_MERGE:
1591 merged = bio_attempt_front_merge(q, rq, bio);
1593 case ELEVATOR_DISCARD_MERGE:
1594 merged = bio_attempt_discard_merge(q, rq, bio);
1607 unsigned int blk_plug_queued_count(struct request_queue *q)
1609 struct blk_plug *plug;
1611 struct list_head *plug_list;
1612 unsigned int ret = 0;
1614 plug = current->plug;
1619 plug_list = &plug->mq_list;
1621 plug_list = &plug->list;
1623 list_for_each_entry(rq, plug_list, queuelist) {
1631 void init_request_from_bio(struct request *req, struct bio *bio)
1633 if (bio->bi_opf & REQ_RAHEAD)
1634 req->cmd_flags |= REQ_FAILFAST_MASK;
1637 req->__sector = bio->bi_iter.bi_sector;
1638 blk_rq_set_prio(req, rq_ioc(bio));
1639 if (ioprio_valid(bio_prio(bio)))
1640 req->ioprio = bio_prio(bio);
1641 blk_rq_bio_prep(req->q, req, bio);
1644 static blk_qc_t blk_queue_bio(struct request_queue *q, struct bio *bio)
1646 struct blk_plug *plug;
1647 int where = ELEVATOR_INSERT_SORT;
1648 struct request *req, *free;
1649 unsigned int request_count = 0;
1650 unsigned int wb_acct;
1653 * low level driver can indicate that it wants pages above a
1654 * certain limit bounced to low memory (ie for highmem, or even
1655 * ISA dma in theory)
1657 blk_queue_bounce(q, &bio);
1659 blk_queue_split(q, &bio, q->bio_split);
1661 if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) {
1662 bio->bi_error = -EIO;
1664 return BLK_QC_T_NONE;
1667 if (op_is_flush(bio->bi_opf)) {
1668 spin_lock_irq(q->queue_lock);
1669 where = ELEVATOR_INSERT_FLUSH;
1674 * Check if we can merge with the plugged list before grabbing
1677 if (!blk_queue_nomerges(q)) {
1678 if (blk_attempt_plug_merge(q, bio, &request_count, NULL))
1679 return BLK_QC_T_NONE;
1681 request_count = blk_plug_queued_count(q);
1683 spin_lock_irq(q->queue_lock);
1685 switch (elv_merge(q, &req, bio)) {
1686 case ELEVATOR_BACK_MERGE:
1687 if (!bio_attempt_back_merge(q, req, bio))
1689 elv_bio_merged(q, req, bio);
1690 free = attempt_back_merge(q, req);
1692 __blk_put_request(q, free);
1694 elv_merged_request(q, req, ELEVATOR_BACK_MERGE);
1696 case ELEVATOR_FRONT_MERGE:
1697 if (!bio_attempt_front_merge(q, req, bio))
1699 elv_bio_merged(q, req, bio);
1700 free = attempt_front_merge(q, req);
1702 __blk_put_request(q, free);
1704 elv_merged_request(q, req, ELEVATOR_FRONT_MERGE);
1711 wb_acct = wbt_wait(q->rq_wb, bio, q->queue_lock);
1714 * Grab a free request. This is might sleep but can not fail.
1715 * Returns with the queue unlocked.
1717 req = get_request(q, bio->bi_opf, bio, GFP_NOIO);
1719 __wbt_done(q->rq_wb, wb_acct);
1720 bio->bi_error = PTR_ERR(req);
1725 wbt_track(&req->issue_stat, wb_acct);
1728 * After dropping the lock and possibly sleeping here, our request
1729 * may now be mergeable after it had proven unmergeable (above).
1730 * We don't worry about that case for efficiency. It won't happen
1731 * often, and the elevators are able to handle it.
1733 init_request_from_bio(req, bio);
1735 if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags))
1736 req->cpu = raw_smp_processor_id();
1738 plug = current->plug;
1741 * If this is the first request added after a plug, fire
1744 * @request_count may become stale because of schedule
1745 * out, so check plug list again.
1747 if (!request_count || list_empty(&plug->list))
1748 trace_block_plug(q);
1750 struct request *last = list_entry_rq(plug->list.prev);
1751 if (request_count >= BLK_MAX_REQUEST_COUNT ||
1752 blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE) {
1753 blk_flush_plug_list(plug, false);
1754 trace_block_plug(q);
1757 list_add_tail(&req->queuelist, &plug->list);
1758 blk_account_io_start(req, true);
1760 spin_lock_irq(q->queue_lock);
1761 add_acct_request(q, req, where);
1764 spin_unlock_irq(q->queue_lock);
1767 return BLK_QC_T_NONE;
1771 * If bio->bi_dev is a partition, remap the location
1773 static inline void blk_partition_remap(struct bio *bio)
1775 struct block_device *bdev = bio->bi_bdev;
1778 * Zone reset does not include bi_size so bio_sectors() is always 0.
1779 * Include a test for the reset op code and perform the remap if needed.
1781 if (bdev != bdev->bd_contains &&
1782 (bio_sectors(bio) || bio_op(bio) == REQ_OP_ZONE_RESET)) {
1783 struct hd_struct *p = bdev->bd_part;
1785 bio->bi_iter.bi_sector += p->start_sect;
1786 bio->bi_bdev = bdev->bd_contains;
1788 trace_block_bio_remap(bdev_get_queue(bio->bi_bdev), bio,
1790 bio->bi_iter.bi_sector - p->start_sect);
1794 static void handle_bad_sector(struct bio *bio)
1796 char b[BDEVNAME_SIZE];
1798 printk(KERN_INFO "attempt to access beyond end of device\n");
1799 printk(KERN_INFO "%s: rw=%d, want=%Lu, limit=%Lu\n",
1800 bdevname(bio->bi_bdev, b),
1802 (unsigned long long)bio_end_sector(bio),
1803 (long long)(i_size_read(bio->bi_bdev->bd_inode) >> 9));
1806 #ifdef CONFIG_FAIL_MAKE_REQUEST
1808 static DECLARE_FAULT_ATTR(fail_make_request);
1810 static int __init setup_fail_make_request(char *str)
1812 return setup_fault_attr(&fail_make_request, str);
1814 __setup("fail_make_request=", setup_fail_make_request);
1816 static bool should_fail_request(struct hd_struct *part, unsigned int bytes)
1818 return part->make_it_fail && should_fail(&fail_make_request, bytes);
1821 static int __init fail_make_request_debugfs(void)
1823 struct dentry *dir = fault_create_debugfs_attr("fail_make_request",
1824 NULL, &fail_make_request);
1826 return PTR_ERR_OR_ZERO(dir);
1829 late_initcall(fail_make_request_debugfs);
1831 #else /* CONFIG_FAIL_MAKE_REQUEST */
1833 static inline bool should_fail_request(struct hd_struct *part,
1839 #endif /* CONFIG_FAIL_MAKE_REQUEST */
1842 * Check whether this bio extends beyond the end of the device.
1844 static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1851 /* Test device or partition size, when known. */
1852 maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
1854 sector_t sector = bio->bi_iter.bi_sector;
1856 if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1858 * This may well happen - the kernel calls bread()
1859 * without checking the size of the device, e.g., when
1860 * mounting a device.
1862 handle_bad_sector(bio);
1870 static noinline_for_stack bool
1871 generic_make_request_checks(struct bio *bio)
1873 struct request_queue *q;
1874 int nr_sectors = bio_sectors(bio);
1876 char b[BDEVNAME_SIZE];
1877 struct hd_struct *part;
1881 if (bio_check_eod(bio, nr_sectors))
1884 q = bdev_get_queue(bio->bi_bdev);
1887 "generic_make_request: Trying to access "
1888 "nonexistent block-device %s (%Lu)\n",
1889 bdevname(bio->bi_bdev, b),
1890 (long long) bio->bi_iter.bi_sector);
1894 part = bio->bi_bdev->bd_part;
1895 if (should_fail_request(part, bio->bi_iter.bi_size) ||
1896 should_fail_request(&part_to_disk(part)->part0,
1897 bio->bi_iter.bi_size))
1901 * If this device has partitions, remap block n
1902 * of partition p to block n+start(p) of the disk.
1904 blk_partition_remap(bio);
1906 if (bio_check_eod(bio, nr_sectors))
1910 * Filter flush bio's early so that make_request based
1911 * drivers without flush support don't have to worry
1914 if (op_is_flush(bio->bi_opf) &&
1915 !test_bit(QUEUE_FLAG_WC, &q->queue_flags)) {
1916 bio->bi_opf &= ~(REQ_PREFLUSH | REQ_FUA);
1923 switch (bio_op(bio)) {
1924 case REQ_OP_DISCARD:
1925 if (!blk_queue_discard(q))
1928 case REQ_OP_SECURE_ERASE:
1929 if (!blk_queue_secure_erase(q))
1932 case REQ_OP_WRITE_SAME:
1933 if (!bdev_write_same(bio->bi_bdev))
1936 case REQ_OP_ZONE_REPORT:
1937 case REQ_OP_ZONE_RESET:
1938 if (!bdev_is_zoned(bio->bi_bdev))
1941 case REQ_OP_WRITE_ZEROES:
1942 if (!bdev_write_zeroes_sectors(bio->bi_bdev))
1950 * Various block parts want %current->io_context and lazy ioc
1951 * allocation ends up trading a lot of pain for a small amount of
1952 * memory. Just allocate it upfront. This may fail and block
1953 * layer knows how to live with it.
1955 create_io_context(GFP_ATOMIC, q->node);
1957 if (!blkcg_bio_issue_check(q, bio))
1960 if (!bio_flagged(bio, BIO_TRACE_COMPLETION)) {
1961 trace_block_bio_queue(q, bio);
1962 /* Now that enqueuing has been traced, we need to trace
1963 * completion as well.
1965 bio_set_flag(bio, BIO_TRACE_COMPLETION);
1972 bio->bi_error = err;
1978 * generic_make_request - hand a buffer to its device driver for I/O
1979 * @bio: The bio describing the location in memory and on the device.
1981 * generic_make_request() is used to make I/O requests of block
1982 * devices. It is passed a &struct bio, which describes the I/O that needs
1985 * generic_make_request() does not return any status. The
1986 * success/failure status of the request, along with notification of
1987 * completion, is delivered asynchronously through the bio->bi_end_io
1988 * function described (one day) else where.
1990 * The caller of generic_make_request must make sure that bi_io_vec
1991 * are set to describe the memory buffer, and that bi_dev and bi_sector are
1992 * set to describe the device address, and the
1993 * bi_end_io and optionally bi_private are set to describe how
1994 * completion notification should be signaled.
1996 * generic_make_request and the drivers it calls may use bi_next if this
1997 * bio happens to be merged with someone else, and may resubmit the bio to
1998 * a lower device by calling into generic_make_request recursively, which
1999 * means the bio should NOT be touched after the call to ->make_request_fn.
2001 blk_qc_t generic_make_request(struct bio *bio)
2004 * bio_list_on_stack[0] contains bios submitted by the current
2006 * bio_list_on_stack[1] contains bios that were submitted before
2007 * the current make_request_fn, but that haven't been processed
2010 struct bio_list bio_list_on_stack[2];
2011 blk_qc_t ret = BLK_QC_T_NONE;
2013 if (!generic_make_request_checks(bio))
2017 * We only want one ->make_request_fn to be active at a time, else
2018 * stack usage with stacked devices could be a problem. So use
2019 * current->bio_list to keep a list of requests submited by a
2020 * make_request_fn function. current->bio_list is also used as a
2021 * flag to say if generic_make_request is currently active in this
2022 * task or not. If it is NULL, then no make_request is active. If
2023 * it is non-NULL, then a make_request is active, and new requests
2024 * should be added at the tail
2026 if (current->bio_list) {
2027 bio_list_add(¤t->bio_list[0], bio);
2031 /* following loop may be a bit non-obvious, and so deserves some
2033 * Before entering the loop, bio->bi_next is NULL (as all callers
2034 * ensure that) so we have a list with a single bio.
2035 * We pretend that we have just taken it off a longer list, so
2036 * we assign bio_list to a pointer to the bio_list_on_stack,
2037 * thus initialising the bio_list of new bios to be
2038 * added. ->make_request() may indeed add some more bios
2039 * through a recursive call to generic_make_request. If it
2040 * did, we find a non-NULL value in bio_list and re-enter the loop
2041 * from the top. In this case we really did just take the bio
2042 * of the top of the list (no pretending) and so remove it from
2043 * bio_list, and call into ->make_request() again.
2045 BUG_ON(bio->bi_next);
2046 bio_list_init(&bio_list_on_stack[0]);
2047 current->bio_list = bio_list_on_stack;
2049 struct request_queue *q = bdev_get_queue(bio->bi_bdev);
2051 if (likely(blk_queue_enter(q, false) == 0)) {
2052 struct bio_list lower, same;
2054 /* Create a fresh bio_list for all subordinate requests */
2055 bio_list_on_stack[1] = bio_list_on_stack[0];
2056 bio_list_init(&bio_list_on_stack[0]);
2057 ret = q->make_request_fn(q, bio);
2061 /* sort new bios into those for a lower level
2062 * and those for the same level
2064 bio_list_init(&lower);
2065 bio_list_init(&same);
2066 while ((bio = bio_list_pop(&bio_list_on_stack[0])) != NULL)
2067 if (q == bdev_get_queue(bio->bi_bdev))
2068 bio_list_add(&same, bio);
2070 bio_list_add(&lower, bio);
2071 /* now assemble so we handle the lowest level first */
2072 bio_list_merge(&bio_list_on_stack[0], &lower);
2073 bio_list_merge(&bio_list_on_stack[0], &same);
2074 bio_list_merge(&bio_list_on_stack[0], &bio_list_on_stack[1]);
2078 bio = bio_list_pop(&bio_list_on_stack[0]);
2080 current->bio_list = NULL; /* deactivate */
2085 EXPORT_SYMBOL(generic_make_request);
2088 * submit_bio - submit a bio to the block device layer for I/O
2089 * @bio: The &struct bio which describes the I/O
2091 * submit_bio() is very similar in purpose to generic_make_request(), and
2092 * uses that function to do most of the work. Both are fairly rough
2093 * interfaces; @bio must be presetup and ready for I/O.
2096 blk_qc_t submit_bio(struct bio *bio)
2099 * If it's a regular read/write or a barrier with data attached,
2100 * go through the normal accounting stuff before submission.
2102 if (bio_has_data(bio)) {
2105 if (unlikely(bio_op(bio) == REQ_OP_WRITE_SAME))
2106 count = bdev_logical_block_size(bio->bi_bdev) >> 9;
2108 count = bio_sectors(bio);
2110 if (op_is_write(bio_op(bio))) {
2111 count_vm_events(PGPGOUT, count);
2113 task_io_account_read(bio->bi_iter.bi_size);
2114 count_vm_events(PGPGIN, count);
2117 if (unlikely(block_dump)) {
2118 char b[BDEVNAME_SIZE];
2119 printk(KERN_DEBUG "%s(%d): %s block %Lu on %s (%u sectors)\n",
2120 current->comm, task_pid_nr(current),
2121 op_is_write(bio_op(bio)) ? "WRITE" : "READ",
2122 (unsigned long long)bio->bi_iter.bi_sector,
2123 bdevname(bio->bi_bdev, b),
2128 return generic_make_request(bio);
2130 EXPORT_SYMBOL(submit_bio);
2133 * blk_cloned_rq_check_limits - Helper function to check a cloned request
2134 * for new the queue limits
2136 * @rq: the request being checked
2139 * @rq may have been made based on weaker limitations of upper-level queues
2140 * in request stacking drivers, and it may violate the limitation of @q.
2141 * Since the block layer and the underlying device driver trust @rq
2142 * after it is inserted to @q, it should be checked against @q before
2143 * the insertion using this generic function.
2145 * Request stacking drivers like request-based dm may change the queue
2146 * limits when retrying requests on other queues. Those requests need
2147 * to be checked against the new queue limits again during dispatch.
2149 static int blk_cloned_rq_check_limits(struct request_queue *q,
2152 if (blk_rq_sectors(rq) > blk_queue_get_max_sectors(q, req_op(rq))) {
2153 printk(KERN_ERR "%s: over max size limit.\n", __func__);
2158 * queue's settings related to segment counting like q->bounce_pfn
2159 * may differ from that of other stacking queues.
2160 * Recalculate it to check the request correctly on this queue's
2163 blk_recalc_rq_segments(rq);
2164 if (rq->nr_phys_segments > queue_max_segments(q)) {
2165 printk(KERN_ERR "%s: over max segments limit.\n", __func__);
2173 * blk_insert_cloned_request - Helper for stacking drivers to submit a request
2174 * @q: the queue to submit the request
2175 * @rq: the request being queued
2177 int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
2179 unsigned long flags;
2180 int where = ELEVATOR_INSERT_BACK;
2182 if (blk_cloned_rq_check_limits(q, rq))
2186 should_fail_request(&rq->rq_disk->part0, blk_rq_bytes(rq)))
2190 if (blk_queue_io_stat(q))
2191 blk_account_io_start(rq, true);
2192 blk_mq_sched_insert_request(rq, false, true, false, false);
2196 spin_lock_irqsave(q->queue_lock, flags);
2197 if (unlikely(blk_queue_dying(q))) {
2198 spin_unlock_irqrestore(q->queue_lock, flags);
2203 * Submitting request must be dequeued before calling this function
2204 * because it will be linked to another request_queue
2206 BUG_ON(blk_queued_rq(rq));
2208 if (op_is_flush(rq->cmd_flags))
2209 where = ELEVATOR_INSERT_FLUSH;
2211 add_acct_request(q, rq, where);
2212 if (where == ELEVATOR_INSERT_FLUSH)
2214 spin_unlock_irqrestore(q->queue_lock, flags);
2218 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
2221 * blk_rq_err_bytes - determine number of bytes till the next failure boundary
2222 * @rq: request to examine
2225 * A request could be merge of IOs which require different failure
2226 * handling. This function determines the number of bytes which
2227 * can be failed from the beginning of the request without
2228 * crossing into area which need to be retried further.
2231 * The number of bytes to fail.
2234 * queue_lock must be held.
2236 unsigned int blk_rq_err_bytes(const struct request *rq)
2238 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
2239 unsigned int bytes = 0;
2242 if (!(rq->rq_flags & RQF_MIXED_MERGE))
2243 return blk_rq_bytes(rq);
2246 * Currently the only 'mixing' which can happen is between
2247 * different fastfail types. We can safely fail portions
2248 * which have all the failfast bits that the first one has -
2249 * the ones which are at least as eager to fail as the first
2252 for (bio = rq->bio; bio; bio = bio->bi_next) {
2253 if ((bio->bi_opf & ff) != ff)
2255 bytes += bio->bi_iter.bi_size;
2258 /* this could lead to infinite loop */
2259 BUG_ON(blk_rq_bytes(rq) && !bytes);
2262 EXPORT_SYMBOL_GPL(blk_rq_err_bytes);
2264 void blk_account_io_completion(struct request *req, unsigned int bytes)
2266 if (blk_do_io_stat(req)) {
2267 const int rw = rq_data_dir(req);
2268 struct hd_struct *part;
2271 cpu = part_stat_lock();
2273 part_stat_add(cpu, part, sectors[rw], bytes >> 9);
2278 void blk_account_io_done(struct request *req)
2281 * Account IO completion. flush_rq isn't accounted as a
2282 * normal IO on queueing nor completion. Accounting the
2283 * containing request is enough.
2285 if (blk_do_io_stat(req) && !(req->rq_flags & RQF_FLUSH_SEQ)) {
2286 unsigned long duration = jiffies - req->start_time;
2287 const int rw = rq_data_dir(req);
2288 struct hd_struct *part;
2291 cpu = part_stat_lock();
2294 part_stat_inc(cpu, part, ios[rw]);
2295 part_stat_add(cpu, part, ticks[rw], duration);
2296 part_round_stats(cpu, part);
2297 part_dec_in_flight(part, rw);
2299 hd_struct_put(part);
2306 * Don't process normal requests when queue is suspended
2307 * or in the process of suspending/resuming
2309 static struct request *blk_pm_peek_request(struct request_queue *q,
2312 if (q->dev && (q->rpm_status == RPM_SUSPENDED ||
2313 (q->rpm_status != RPM_ACTIVE && !(rq->rq_flags & RQF_PM))))
2319 static inline struct request *blk_pm_peek_request(struct request_queue *q,
2326 void blk_account_io_start(struct request *rq, bool new_io)
2328 struct hd_struct *part;
2329 int rw = rq_data_dir(rq);
2332 if (!blk_do_io_stat(rq))
2335 cpu = part_stat_lock();
2339 part_stat_inc(cpu, part, merges[rw]);
2341 part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq));
2342 if (!hd_struct_try_get(part)) {
2344 * The partition is already being removed,
2345 * the request will be accounted on the disk only
2347 * We take a reference on disk->part0 although that
2348 * partition will never be deleted, so we can treat
2349 * it as any other partition.
2351 part = &rq->rq_disk->part0;
2352 hd_struct_get(part);
2354 part_round_stats(cpu, part);
2355 part_inc_in_flight(part, rw);
2363 * blk_peek_request - peek at the top of a request queue
2364 * @q: request queue to peek at
2367 * Return the request at the top of @q. The returned request
2368 * should be started using blk_start_request() before LLD starts
2372 * Pointer to the request at the top of @q if available. Null
2376 * queue_lock must be held.
2378 struct request *blk_peek_request(struct request_queue *q)
2383 while ((rq = __elv_next_request(q)) != NULL) {
2385 rq = blk_pm_peek_request(q, rq);
2389 if (!(rq->rq_flags & RQF_STARTED)) {
2391 * This is the first time the device driver
2392 * sees this request (possibly after
2393 * requeueing). Notify IO scheduler.
2395 if (rq->rq_flags & RQF_SORTED)
2396 elv_activate_rq(q, rq);
2399 * just mark as started even if we don't start
2400 * it, a request that has been delayed should
2401 * not be passed by new incoming requests
2403 rq->rq_flags |= RQF_STARTED;
2404 trace_block_rq_issue(q, rq);
2407 if (!q->boundary_rq || q->boundary_rq == rq) {
2408 q->end_sector = rq_end_sector(rq);
2409 q->boundary_rq = NULL;
2412 if (rq->rq_flags & RQF_DONTPREP)
2415 if (q->dma_drain_size && blk_rq_bytes(rq)) {
2417 * make sure space for the drain appears we
2418 * know we can do this because max_hw_segments
2419 * has been adjusted to be one fewer than the
2422 rq->nr_phys_segments++;
2428 ret = q->prep_rq_fn(q, rq);
2429 if (ret == BLKPREP_OK) {
2431 } else if (ret == BLKPREP_DEFER) {
2433 * the request may have been (partially) prepped.
2434 * we need to keep this request in the front to
2435 * avoid resource deadlock. RQF_STARTED will
2436 * prevent other fs requests from passing this one.
2438 if (q->dma_drain_size && blk_rq_bytes(rq) &&
2439 !(rq->rq_flags & RQF_DONTPREP)) {
2441 * remove the space for the drain we added
2442 * so that we don't add it again
2444 --rq->nr_phys_segments;
2449 } else if (ret == BLKPREP_KILL || ret == BLKPREP_INVALID) {
2450 int err = (ret == BLKPREP_INVALID) ? -EREMOTEIO : -EIO;
2452 rq->rq_flags |= RQF_QUIET;
2454 * Mark this request as started so we don't trigger
2455 * any debug logic in the end I/O path.
2457 blk_start_request(rq);
2458 __blk_end_request_all(rq, err);
2460 printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
2467 EXPORT_SYMBOL(blk_peek_request);
2469 void blk_dequeue_request(struct request *rq)
2471 struct request_queue *q = rq->q;
2473 BUG_ON(list_empty(&rq->queuelist));
2474 BUG_ON(ELV_ON_HASH(rq));
2476 list_del_init(&rq->queuelist);
2479 * the time frame between a request being removed from the lists
2480 * and to it is freed is accounted as io that is in progress at
2483 if (blk_account_rq(rq)) {
2484 q->in_flight[rq_is_sync(rq)]++;
2485 set_io_start_time_ns(rq);
2490 * blk_start_request - start request processing on the driver
2491 * @req: request to dequeue
2494 * Dequeue @req and start timeout timer on it. This hands off the
2495 * request to the driver.
2497 * Block internal functions which don't want to start timer should
2498 * call blk_dequeue_request().
2501 * queue_lock must be held.
2503 void blk_start_request(struct request *req)
2505 blk_dequeue_request(req);
2507 if (test_bit(QUEUE_FLAG_STATS, &req->q->queue_flags)) {
2508 blk_stat_set_issue(&req->issue_stat, blk_rq_sectors(req));
2509 req->rq_flags |= RQF_STATS;
2510 wbt_issue(req->q->rq_wb, &req->issue_stat);
2513 BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));
2516 EXPORT_SYMBOL(blk_start_request);
2519 * blk_fetch_request - fetch a request from a request queue
2520 * @q: request queue to fetch a request from
2523 * Return the request at the top of @q. The request is started on
2524 * return and LLD can start processing it immediately.
2527 * Pointer to the request at the top of @q if available. Null
2531 * queue_lock must be held.
2533 struct request *blk_fetch_request(struct request_queue *q)
2537 rq = blk_peek_request(q);
2539 blk_start_request(rq);
2542 EXPORT_SYMBOL(blk_fetch_request);
2545 * blk_update_request - Special helper function for request stacking drivers
2546 * @req: the request being processed
2547 * @error: %0 for success, < %0 for error
2548 * @nr_bytes: number of bytes to complete @req
2551 * Ends I/O on a number of bytes attached to @req, but doesn't complete
2552 * the request structure even if @req doesn't have leftover.
2553 * If @req has leftover, sets it up for the next range of segments.
2555 * This special helper function is only for request stacking drivers
2556 * (e.g. request-based dm) so that they can handle partial completion.
2557 * Actual device drivers should use blk_end_request instead.
2559 * Passing the result of blk_rq_bytes() as @nr_bytes guarantees
2560 * %false return from this function.
2563 * %false - this request doesn't have any more data
2564 * %true - this request has more data
2566 bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
2570 trace_block_rq_complete(req->q, req, nr_bytes);
2576 * For fs requests, rq is just carrier of independent bio's
2577 * and each partial completion should be handled separately.
2578 * Reset per-request error on each partial completion.
2580 * TODO: tj: This is too subtle. It would be better to let
2581 * low level drivers do what they see fit.
2583 if (!blk_rq_is_passthrough(req))
2586 if (error && !blk_rq_is_passthrough(req) &&
2587 !(req->rq_flags & RQF_QUIET)) {
2592 error_type = "recoverable transport";
2595 error_type = "critical target";
2598 error_type = "critical nexus";
2601 error_type = "timeout";
2604 error_type = "critical space allocation";
2607 error_type = "critical medium";
2614 printk_ratelimited(KERN_ERR "%s: %s error, dev %s, sector %llu\n",
2615 __func__, error_type, req->rq_disk ?
2616 req->rq_disk->disk_name : "?",
2617 (unsigned long long)blk_rq_pos(req));
2621 blk_account_io_completion(req, nr_bytes);
2625 struct bio *bio = req->bio;
2626 unsigned bio_bytes = min(bio->bi_iter.bi_size, nr_bytes);
2628 if (bio_bytes == bio->bi_iter.bi_size)
2629 req->bio = bio->bi_next;
2631 /* Completion has already been traced */
2632 bio_clear_flag(bio, BIO_TRACE_COMPLETION);
2633 req_bio_endio(req, bio, bio_bytes, error);
2635 total_bytes += bio_bytes;
2636 nr_bytes -= bio_bytes;
2647 * Reset counters so that the request stacking driver
2648 * can find how many bytes remain in the request
2651 req->__data_len = 0;
2655 WARN_ON_ONCE(req->rq_flags & RQF_SPECIAL_PAYLOAD);
2657 req->__data_len -= total_bytes;
2659 /* update sector only for requests with clear definition of sector */
2660 if (!blk_rq_is_passthrough(req))
2661 req->__sector += total_bytes >> 9;
2663 /* mixed attributes always follow the first bio */
2664 if (req->rq_flags & RQF_MIXED_MERGE) {
2665 req->cmd_flags &= ~REQ_FAILFAST_MASK;
2666 req->cmd_flags |= req->bio->bi_opf & REQ_FAILFAST_MASK;
2670 * If total number of sectors is less than the first segment
2671 * size, something has gone terribly wrong.
2673 if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
2674 blk_dump_rq_flags(req, "request botched");
2675 req->__data_len = blk_rq_cur_bytes(req);
2678 /* recalculate the number of segments */
2679 blk_recalc_rq_segments(req);
2683 EXPORT_SYMBOL_GPL(blk_update_request);
2685 static bool blk_update_bidi_request(struct request *rq, int error,
2686 unsigned int nr_bytes,
2687 unsigned int bidi_bytes)
2689 if (blk_update_request(rq, error, nr_bytes))
2692 /* Bidi request must be completed as a whole */
2693 if (unlikely(blk_bidi_rq(rq)) &&
2694 blk_update_request(rq->next_rq, error, bidi_bytes))
2697 if (blk_queue_add_random(rq->q))
2698 add_disk_randomness(rq->rq_disk);
2704 * blk_unprep_request - unprepare a request
2707 * This function makes a request ready for complete resubmission (or
2708 * completion). It happens only after all error handling is complete,
2709 * so represents the appropriate moment to deallocate any resources
2710 * that were allocated to the request in the prep_rq_fn. The queue
2711 * lock is held when calling this.
2713 void blk_unprep_request(struct request *req)
2715 struct request_queue *q = req->q;
2717 req->rq_flags &= ~RQF_DONTPREP;
2718 if (q->unprep_rq_fn)
2719 q->unprep_rq_fn(q, req);
2721 EXPORT_SYMBOL_GPL(blk_unprep_request);
2724 * queue lock must be held
2726 void blk_finish_request(struct request *req, int error)
2728 struct request_queue *q = req->q;
2730 if (req->rq_flags & RQF_STATS)
2733 if (req->rq_flags & RQF_QUEUED)
2734 blk_queue_end_tag(q, req);
2736 BUG_ON(blk_queued_rq(req));
2738 if (unlikely(laptop_mode) && !blk_rq_is_passthrough(req))
2739 laptop_io_completion(req->q->backing_dev_info);
2741 blk_delete_timer(req);
2743 if (req->rq_flags & RQF_DONTPREP)
2744 blk_unprep_request(req);
2746 blk_account_io_done(req);
2749 wbt_done(req->q->rq_wb, &req->issue_stat);
2750 req->end_io(req, error);
2752 if (blk_bidi_rq(req))
2753 __blk_put_request(req->next_rq->q, req->next_rq);
2755 __blk_put_request(q, req);
2758 EXPORT_SYMBOL(blk_finish_request);
2761 * blk_end_bidi_request - Complete a bidi request
2762 * @rq: the request to complete
2763 * @error: %0 for success, < %0 for error
2764 * @nr_bytes: number of bytes to complete @rq
2765 * @bidi_bytes: number of bytes to complete @rq->next_rq
2768 * Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2769 * Drivers that supports bidi can safely call this member for any
2770 * type of request, bidi or uni. In the later case @bidi_bytes is
2774 * %false - we are done with this request
2775 * %true - still buffers pending for this request
2777 static bool blk_end_bidi_request(struct request *rq, int error,
2778 unsigned int nr_bytes, unsigned int bidi_bytes)
2780 struct request_queue *q = rq->q;
2781 unsigned long flags;
2783 if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2786 spin_lock_irqsave(q->queue_lock, flags);
2787 blk_finish_request(rq, error);
2788 spin_unlock_irqrestore(q->queue_lock, flags);
2794 * __blk_end_bidi_request - Complete a bidi request with queue lock held
2795 * @rq: the request to complete
2796 * @error: %0 for success, < %0 for error
2797 * @nr_bytes: number of bytes to complete @rq
2798 * @bidi_bytes: number of bytes to complete @rq->next_rq
2801 * Identical to blk_end_bidi_request() except that queue lock is
2802 * assumed to be locked on entry and remains so on return.
2805 * %false - we are done with this request
2806 * %true - still buffers pending for this request
2808 bool __blk_end_bidi_request(struct request *rq, int error,
2809 unsigned int nr_bytes, unsigned int bidi_bytes)
2811 if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2814 blk_finish_request(rq, error);
2820 * blk_end_request - Helper function for drivers to complete the request.
2821 * @rq: the request being processed
2822 * @error: %0 for success, < %0 for error
2823 * @nr_bytes: number of bytes to complete
2826 * Ends I/O on a number of bytes attached to @rq.
2827 * If @rq has leftover, sets it up for the next range of segments.
2830 * %false - we are done with this request
2831 * %true - still buffers pending for this request
2833 bool blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2835 return blk_end_bidi_request(rq, error, nr_bytes, 0);
2837 EXPORT_SYMBOL(blk_end_request);
2840 * blk_end_request_all - Helper function for drives to finish the request.
2841 * @rq: the request to finish
2842 * @error: %0 for success, < %0 for error
2845 * Completely finish @rq.
2847 void blk_end_request_all(struct request *rq, int error)
2850 unsigned int bidi_bytes = 0;
2852 if (unlikely(blk_bidi_rq(rq)))
2853 bidi_bytes = blk_rq_bytes(rq->next_rq);
2855 pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2858 EXPORT_SYMBOL(blk_end_request_all);
2861 * __blk_end_request - Helper function for drivers to complete the request.
2862 * @rq: the request being processed
2863 * @error: %0 for success, < %0 for error
2864 * @nr_bytes: number of bytes to complete
2867 * Must be called with queue lock held unlike blk_end_request().
2870 * %false - we are done with this request
2871 * %true - still buffers pending for this request
2873 bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2875 return __blk_end_bidi_request(rq, error, nr_bytes, 0);
2877 EXPORT_SYMBOL(__blk_end_request);
2880 * __blk_end_request_all - Helper function for drives to finish the request.
2881 * @rq: the request to finish
2882 * @error: %0 for success, < %0 for error
2885 * Completely finish @rq. Must be called with queue lock held.
2887 void __blk_end_request_all(struct request *rq, int error)
2890 unsigned int bidi_bytes = 0;
2892 if (unlikely(blk_bidi_rq(rq)))
2893 bidi_bytes = blk_rq_bytes(rq->next_rq);
2895 pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2898 EXPORT_SYMBOL(__blk_end_request_all);
2901 * __blk_end_request_cur - Helper function to finish the current request chunk.
2902 * @rq: the request to finish the current chunk for
2903 * @error: %0 for success, < %0 for error
2906 * Complete the current consecutively mapped chunk from @rq. Must
2907 * be called with queue lock held.
2910 * %false - we are done with this request
2911 * %true - still buffers pending for this request
2913 bool __blk_end_request_cur(struct request *rq, int error)
2915 return __blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2917 EXPORT_SYMBOL(__blk_end_request_cur);
2919 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2922 if (bio_has_data(bio))
2923 rq->nr_phys_segments = bio_phys_segments(q, bio);
2925 rq->__data_len = bio->bi_iter.bi_size;
2926 rq->bio = rq->biotail = bio;
2929 rq->rq_disk = bio->bi_bdev->bd_disk;
2932 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
2934 * rq_flush_dcache_pages - Helper function to flush all pages in a request
2935 * @rq: the request to be flushed
2938 * Flush all pages in @rq.
2940 void rq_flush_dcache_pages(struct request *rq)
2942 struct req_iterator iter;
2943 struct bio_vec bvec;
2945 rq_for_each_segment(bvec, rq, iter)
2946 flush_dcache_page(bvec.bv_page);
2948 EXPORT_SYMBOL_GPL(rq_flush_dcache_pages);
2952 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2953 * @q : the queue of the device being checked
2956 * Check if underlying low-level drivers of a device are busy.
2957 * If the drivers want to export their busy state, they must set own
2958 * exporting function using blk_queue_lld_busy() first.
2960 * Basically, this function is used only by request stacking drivers
2961 * to stop dispatching requests to underlying devices when underlying
2962 * devices are busy. This behavior helps more I/O merging on the queue
2963 * of the request stacking driver and prevents I/O throughput regression
2964 * on burst I/O load.
2967 * 0 - Not busy (The request stacking driver should dispatch request)
2968 * 1 - Busy (The request stacking driver should stop dispatching request)
2970 int blk_lld_busy(struct request_queue *q)
2973 return q->lld_busy_fn(q);
2977 EXPORT_SYMBOL_GPL(blk_lld_busy);
2980 * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
2981 * @rq: the clone request to be cleaned up
2984 * Free all bios in @rq for a cloned request.
2986 void blk_rq_unprep_clone(struct request *rq)
2990 while ((bio = rq->bio) != NULL) {
2991 rq->bio = bio->bi_next;
2996 EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
2999 * Copy attributes of the original request to the clone request.
3000 * The actual data parts (e.g. ->cmd, ->sense) are not copied.
3002 static void __blk_rq_prep_clone(struct request *dst, struct request *src)
3004 dst->cpu = src->cpu;
3005 dst->__sector = blk_rq_pos(src);
3006 dst->__data_len = blk_rq_bytes(src);
3007 dst->nr_phys_segments = src->nr_phys_segments;
3008 dst->ioprio = src->ioprio;
3009 dst->extra_len = src->extra_len;
3013 * blk_rq_prep_clone - Helper function to setup clone request
3014 * @rq: the request to be setup
3015 * @rq_src: original request to be cloned
3016 * @bs: bio_set that bios for clone are allocated from
3017 * @gfp_mask: memory allocation mask for bio
3018 * @bio_ctr: setup function to be called for each clone bio.
3019 * Returns %0 for success, non %0 for failure.
3020 * @data: private data to be passed to @bio_ctr
3023 * Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
3024 * The actual data parts of @rq_src (e.g. ->cmd, ->sense)
3025 * are not copied, and copying such parts is the caller's responsibility.
3026 * Also, pages which the original bios are pointing to are not copied
3027 * and the cloned bios just point same pages.
3028 * So cloned bios must be completed before original bios, which means
3029 * the caller must complete @rq before @rq_src.
3031 int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
3032 struct bio_set *bs, gfp_t gfp_mask,
3033 int (*bio_ctr)(struct bio *, struct bio *, void *),
3036 struct bio *bio, *bio_src;
3041 __rq_for_each_bio(bio_src, rq_src) {
3042 bio = bio_clone_fast(bio_src, gfp_mask, bs);
3046 if (bio_ctr && bio_ctr(bio, bio_src, data))
3050 rq->biotail->bi_next = bio;
3053 rq->bio = rq->biotail = bio;
3056 __blk_rq_prep_clone(rq, rq_src);
3063 blk_rq_unprep_clone(rq);
3067 EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
3069 int kblockd_schedule_work(struct work_struct *work)
3071 return queue_work(kblockd_workqueue, work);
3073 EXPORT_SYMBOL(kblockd_schedule_work);
3075 int kblockd_schedule_work_on(int cpu, struct work_struct *work)
3077 return queue_work_on(cpu, kblockd_workqueue, work);
3079 EXPORT_SYMBOL(kblockd_schedule_work_on);
3081 int kblockd_schedule_delayed_work(struct delayed_work *dwork,
3082 unsigned long delay)
3084 return queue_delayed_work(kblockd_workqueue, dwork, delay);
3086 EXPORT_SYMBOL(kblockd_schedule_delayed_work);
3088 int kblockd_schedule_delayed_work_on(int cpu, struct delayed_work *dwork,
3089 unsigned long delay)
3091 return queue_delayed_work_on(cpu, kblockd_workqueue, dwork, delay);
3093 EXPORT_SYMBOL(kblockd_schedule_delayed_work_on);
3096 * blk_start_plug - initialize blk_plug and track it inside the task_struct
3097 * @plug: The &struct blk_plug that needs to be initialized
3100 * Tracking blk_plug inside the task_struct will help with auto-flushing the
3101 * pending I/O should the task end up blocking between blk_start_plug() and
3102 * blk_finish_plug(). This is important from a performance perspective, but
3103 * also ensures that we don't deadlock. For instance, if the task is blocking
3104 * for a memory allocation, memory reclaim could end up wanting to free a
3105 * page belonging to that request that is currently residing in our private
3106 * plug. By flushing the pending I/O when the process goes to sleep, we avoid
3107 * this kind of deadlock.
3109 void blk_start_plug(struct blk_plug *plug)
3111 struct task_struct *tsk = current;
3114 * If this is a nested plug, don't actually assign it.
3119 INIT_LIST_HEAD(&plug->list);
3120 INIT_LIST_HEAD(&plug->mq_list);
3121 INIT_LIST_HEAD(&plug->cb_list);
3123 * Store ordering should not be needed here, since a potential
3124 * preempt will imply a full memory barrier
3128 EXPORT_SYMBOL(blk_start_plug);
3130 static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
3132 struct request *rqa = container_of(a, struct request, queuelist);
3133 struct request *rqb = container_of(b, struct request, queuelist);
3135 return !(rqa->q < rqb->q ||
3136 (rqa->q == rqb->q && blk_rq_pos(rqa) < blk_rq_pos(rqb)));
3140 * If 'from_schedule' is true, then postpone the dispatch of requests
3141 * until a safe kblockd context. We due this to avoid accidental big
3142 * additional stack usage in driver dispatch, in places where the originally
3143 * plugger did not intend it.
3145 static void queue_unplugged(struct request_queue *q, unsigned int depth,
3147 __releases(q->queue_lock)
3149 trace_block_unplug(q, depth, !from_schedule);
3152 blk_run_queue_async(q);
3155 spin_unlock(q->queue_lock);
3158 static void flush_plug_callbacks(struct blk_plug *plug, bool from_schedule)
3160 LIST_HEAD(callbacks);
3162 while (!list_empty(&plug->cb_list)) {
3163 list_splice_init(&plug->cb_list, &callbacks);
3165 while (!list_empty(&callbacks)) {
3166 struct blk_plug_cb *cb = list_first_entry(&callbacks,
3169 list_del(&cb->list);
3170 cb->callback(cb, from_schedule);
3175 struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug, void *data,
3178 struct blk_plug *plug = current->plug;
3179 struct blk_plug_cb *cb;
3184 list_for_each_entry(cb, &plug->cb_list, list)
3185 if (cb->callback == unplug && cb->data == data)
3188 /* Not currently on the callback list */
3189 BUG_ON(size < sizeof(*cb));
3190 cb = kzalloc(size, GFP_ATOMIC);
3193 cb->callback = unplug;
3194 list_add(&cb->list, &plug->cb_list);
3198 EXPORT_SYMBOL(blk_check_plugged);
3200 void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
3202 struct request_queue *q;
3203 unsigned long flags;
3208 flush_plug_callbacks(plug, from_schedule);
3210 if (!list_empty(&plug->mq_list))
3211 blk_mq_flush_plug_list(plug, from_schedule);
3213 if (list_empty(&plug->list))
3216 list_splice_init(&plug->list, &list);
3218 list_sort(NULL, &list, plug_rq_cmp);
3224 * Save and disable interrupts here, to avoid doing it for every
3225 * queue lock we have to take.
3227 local_irq_save(flags);
3228 while (!list_empty(&list)) {
3229 rq = list_entry_rq(list.next);
3230 list_del_init(&rq->queuelist);
3234 * This drops the queue lock
3237 queue_unplugged(q, depth, from_schedule);
3240 spin_lock(q->queue_lock);
3244 * Short-circuit if @q is dead
3246 if (unlikely(blk_queue_dying(q))) {
3247 __blk_end_request_all(rq, -ENODEV);
3252 * rq is already accounted, so use raw insert
3254 if (op_is_flush(rq->cmd_flags))
3255 __elv_add_request(q, rq, ELEVATOR_INSERT_FLUSH);
3257 __elv_add_request(q, rq, ELEVATOR_INSERT_SORT_MERGE);
3263 * This drops the queue lock
3266 queue_unplugged(q, depth, from_schedule);
3268 local_irq_restore(flags);
3271 void blk_finish_plug(struct blk_plug *plug)
3273 if (plug != current->plug)
3275 blk_flush_plug_list(plug, false);
3277 current->plug = NULL;
3279 EXPORT_SYMBOL(blk_finish_plug);
3283 * blk_pm_runtime_init - Block layer runtime PM initialization routine
3284 * @q: the queue of the device
3285 * @dev: the device the queue belongs to
3288 * Initialize runtime-PM-related fields for @q and start auto suspend for
3289 * @dev. Drivers that want to take advantage of request-based runtime PM
3290 * should call this function after @dev has been initialized, and its
3291 * request queue @q has been allocated, and runtime PM for it can not happen
3292 * yet(either due to disabled/forbidden or its usage_count > 0). In most
3293 * cases, driver should call this function before any I/O has taken place.
3295 * This function takes care of setting up using auto suspend for the device,
3296 * the autosuspend delay is set to -1 to make runtime suspend impossible
3297 * until an updated value is either set by user or by driver. Drivers do
3298 * not need to touch other autosuspend settings.
3300 * The block layer runtime PM is request based, so only works for drivers
3301 * that use request as their IO unit instead of those directly use bio's.
3303 void blk_pm_runtime_init(struct request_queue *q, struct device *dev)
3306 q->rpm_status = RPM_ACTIVE;
3307 pm_runtime_set_autosuspend_delay(q->dev, -1);
3308 pm_runtime_use_autosuspend(q->dev);
3310 EXPORT_SYMBOL(blk_pm_runtime_init);
3313 * blk_pre_runtime_suspend - Pre runtime suspend check
3314 * @q: the queue of the device
3317 * This function will check if runtime suspend is allowed for the device
3318 * by examining if there are any requests pending in the queue. If there
3319 * are requests pending, the device can not be runtime suspended; otherwise,
3320 * the queue's status will be updated to SUSPENDING and the driver can
3321 * proceed to suspend the device.
3323 * For the not allowed case, we mark last busy for the device so that
3324 * runtime PM core will try to autosuspend it some time later.
3326 * This function should be called near the start of the device's
3327 * runtime_suspend callback.
3330 * 0 - OK to runtime suspend the device
3331 * -EBUSY - Device should not be runtime suspended
3333 int blk_pre_runtime_suspend(struct request_queue *q)
3340 spin_lock_irq(q->queue_lock);
3341 if (q->nr_pending) {
3343 pm_runtime_mark_last_busy(q->dev);
3345 q->rpm_status = RPM_SUSPENDING;
3347 spin_unlock_irq(q->queue_lock);
3350 EXPORT_SYMBOL(blk_pre_runtime_suspend);
3353 * blk_post_runtime_suspend - Post runtime suspend processing
3354 * @q: the queue of the device
3355 * @err: return value of the device's runtime_suspend function
3358 * Update the queue's runtime status according to the return value of the
3359 * device's runtime suspend function and mark last busy for the device so
3360 * that PM core will try to auto suspend the device at a later time.
3362 * This function should be called near the end of the device's
3363 * runtime_suspend callback.
3365 void blk_post_runtime_suspend(struct request_queue *q, int err)
3370 spin_lock_irq(q->queue_lock);
3372 q->rpm_status = RPM_SUSPENDED;
3374 q->rpm_status = RPM_ACTIVE;
3375 pm_runtime_mark_last_busy(q->dev);
3377 spin_unlock_irq(q->queue_lock);
3379 EXPORT_SYMBOL(blk_post_runtime_suspend);
3382 * blk_pre_runtime_resume - Pre runtime resume processing
3383 * @q: the queue of the device
3386 * Update the queue's runtime status to RESUMING in preparation for the
3387 * runtime resume of the device.
3389 * This function should be called near the start of the device's
3390 * runtime_resume callback.
3392 void blk_pre_runtime_resume(struct request_queue *q)
3397 spin_lock_irq(q->queue_lock);
3398 q->rpm_status = RPM_RESUMING;
3399 spin_unlock_irq(q->queue_lock);
3401 EXPORT_SYMBOL(blk_pre_runtime_resume);
3404 * blk_post_runtime_resume - Post runtime resume processing
3405 * @q: the queue of the device
3406 * @err: return value of the device's runtime_resume function
3409 * Update the queue's runtime status according to the return value of the
3410 * device's runtime_resume function. If it is successfully resumed, process
3411 * the requests that are queued into the device's queue when it is resuming
3412 * and then mark last busy and initiate autosuspend for it.
3414 * This function should be called near the end of the device's
3415 * runtime_resume callback.
3417 void blk_post_runtime_resume(struct request_queue *q, int err)
3422 spin_lock_irq(q->queue_lock);
3424 q->rpm_status = RPM_ACTIVE;
3426 pm_runtime_mark_last_busy(q->dev);
3427 pm_request_autosuspend(q->dev);
3429 q->rpm_status = RPM_SUSPENDED;
3431 spin_unlock_irq(q->queue_lock);
3433 EXPORT_SYMBOL(blk_post_runtime_resume);
3436 * blk_set_runtime_active - Force runtime status of the queue to be active
3437 * @q: the queue of the device
3439 * If the device is left runtime suspended during system suspend the resume
3440 * hook typically resumes the device and corrects runtime status
3441 * accordingly. However, that does not affect the queue runtime PM status
3442 * which is still "suspended". This prevents processing requests from the
3445 * This function can be used in driver's resume hook to correct queue
3446 * runtime PM status and re-enable peeking requests from the queue. It
3447 * should be called before first request is added to the queue.
3449 void blk_set_runtime_active(struct request_queue *q)
3451 spin_lock_irq(q->queue_lock);
3452 q->rpm_status = RPM_ACTIVE;
3453 pm_runtime_mark_last_busy(q->dev);
3454 pm_request_autosuspend(q->dev);
3455 spin_unlock_irq(q->queue_lock);
3457 EXPORT_SYMBOL(blk_set_runtime_active);
3460 int __init blk_dev_init(void)
3462 BUILD_BUG_ON(REQ_OP_LAST >= (1 << REQ_OP_BITS));
3463 BUILD_BUG_ON(REQ_OP_BITS + REQ_FLAG_BITS > 8 *
3464 FIELD_SIZEOF(struct request, cmd_flags));
3465 BUILD_BUG_ON(REQ_OP_BITS + REQ_FLAG_BITS > 8 *
3466 FIELD_SIZEOF(struct bio, bi_opf));
3468 /* used for unplugging and affects IO latency/throughput - HIGHPRI */
3469 kblockd_workqueue = alloc_workqueue("kblockd",
3470 WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
3471 if (!kblockd_workqueue)
3472 panic("Failed to create kblockd\n");
3474 request_cachep = kmem_cache_create("blkdev_requests",
3475 sizeof(struct request), 0, SLAB_PANIC, NULL);
3477 blk_requestq_cachep = kmem_cache_create("request_queue",
3478 sizeof(struct request_queue), 0, SLAB_PANIC, NULL);
3480 #ifdef CONFIG_DEBUG_FS
3481 blk_debugfs_root = debugfs_create_dir("block", NULL);