1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (C) 1991, 1992 Linus Torvalds
4 * Copyright (C) 1994, Karl Keyte: Added support for disk statistics
5 * Elevator latency, (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
6 * Queue request tables / lock, selectable elevator, Jens Axboe <axboe@suse.de>
7 * kernel-doc documentation started by NeilBrown <neilb@cse.unsw.edu.au>
9 * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001
13 * This handles all read/write requests to block devices
15 #include <linux/kernel.h>
16 #include <linux/module.h>
17 #include <linux/bio.h>
18 #include <linux/blkdev.h>
19 #include <linux/blk-mq.h>
20 #include <linux/blk-pm.h>
21 #include <linux/blk-integrity.h>
22 #include <linux/highmem.h>
24 #include <linux/pagemap.h>
25 #include <linux/kernel_stat.h>
26 #include <linux/string.h>
27 #include <linux/init.h>
28 #include <linux/completion.h>
29 #include <linux/slab.h>
30 #include <linux/swap.h>
31 #include <linux/writeback.h>
32 #include <linux/task_io_accounting_ops.h>
33 #include <linux/fault-inject.h>
34 #include <linux/list_sort.h>
35 #include <linux/delay.h>
36 #include <linux/ratelimit.h>
37 #include <linux/pm_runtime.h>
38 #include <linux/blk-cgroup.h>
39 #include <linux/t10-pi.h>
40 #include <linux/debugfs.h>
41 #include <linux/bpf.h>
42 #include <linux/psi.h>
43 #include <linux/sched/sysctl.h>
44 #include <linux/blk-crypto.h>
46 #define CREATE_TRACE_POINTS
47 #include <trace/events/block.h>
51 #include "blk-mq-sched.h"
53 #include "blk-throttle.h"
55 struct dentry *blk_debugfs_root;
57 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
58 EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
59 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
60 EXPORT_TRACEPOINT_SYMBOL_GPL(block_split);
61 EXPORT_TRACEPOINT_SYMBOL_GPL(block_unplug);
62 EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_insert);
64 DEFINE_IDA(blk_queue_ida);
67 * For queue allocation
69 struct kmem_cache *blk_requestq_cachep;
72 * Controlling structure to kblockd
74 static struct workqueue_struct *kblockd_workqueue;
77 * blk_queue_flag_set - atomically set a queue flag
78 * @flag: flag to be set
81 void blk_queue_flag_set(unsigned int flag, struct request_queue *q)
83 set_bit(flag, &q->queue_flags);
85 EXPORT_SYMBOL(blk_queue_flag_set);
88 * blk_queue_flag_clear - atomically clear a queue flag
89 * @flag: flag to be cleared
92 void blk_queue_flag_clear(unsigned int flag, struct request_queue *q)
94 clear_bit(flag, &q->queue_flags);
96 EXPORT_SYMBOL(blk_queue_flag_clear);
99 * blk_queue_flag_test_and_set - atomically test and set a queue flag
100 * @flag: flag to be set
103 * Returns the previous value of @flag - 0 if the flag was not set and 1 if
104 * the flag was already set.
106 bool blk_queue_flag_test_and_set(unsigned int flag, struct request_queue *q)
108 return test_and_set_bit(flag, &q->queue_flags);
110 EXPORT_SYMBOL_GPL(blk_queue_flag_test_and_set);
112 void blk_rq_init(struct request_queue *q, struct request *rq)
114 memset(rq, 0, sizeof(*rq));
116 INIT_LIST_HEAD(&rq->queuelist);
118 rq->__sector = (sector_t) -1;
119 INIT_HLIST_NODE(&rq->hash);
120 RB_CLEAR_NODE(&rq->rb_node);
121 rq->tag = BLK_MQ_NO_TAG;
122 rq->internal_tag = BLK_MQ_NO_TAG;
123 rq->start_time_ns = ktime_get_ns();
125 blk_crypto_rq_set_defaults(rq);
127 EXPORT_SYMBOL(blk_rq_init);
129 #define REQ_OP_NAME(name) [REQ_OP_##name] = #name
130 static const char *const blk_op_name[] = {
134 REQ_OP_NAME(DISCARD),
135 REQ_OP_NAME(SECURE_ERASE),
136 REQ_OP_NAME(ZONE_RESET),
137 REQ_OP_NAME(ZONE_RESET_ALL),
138 REQ_OP_NAME(ZONE_OPEN),
139 REQ_OP_NAME(ZONE_CLOSE),
140 REQ_OP_NAME(ZONE_FINISH),
141 REQ_OP_NAME(ZONE_APPEND),
142 REQ_OP_NAME(WRITE_SAME),
143 REQ_OP_NAME(WRITE_ZEROES),
145 REQ_OP_NAME(DRV_OUT),
150 * blk_op_str - Return string XXX in the REQ_OP_XXX.
153 * Description: Centralize block layer function to convert REQ_OP_XXX into
154 * string format. Useful in the debugging and tracing bio or request. For
155 * invalid REQ_OP_XXX it returns string "UNKNOWN".
157 inline const char *blk_op_str(unsigned int op)
159 const char *op_str = "UNKNOWN";
161 if (op < ARRAY_SIZE(blk_op_name) && blk_op_name[op])
162 op_str = blk_op_name[op];
166 EXPORT_SYMBOL_GPL(blk_op_str);
168 static const struct {
172 [BLK_STS_OK] = { 0, "" },
173 [BLK_STS_NOTSUPP] = { -EOPNOTSUPP, "operation not supported" },
174 [BLK_STS_TIMEOUT] = { -ETIMEDOUT, "timeout" },
175 [BLK_STS_NOSPC] = { -ENOSPC, "critical space allocation" },
176 [BLK_STS_TRANSPORT] = { -ENOLINK, "recoverable transport" },
177 [BLK_STS_TARGET] = { -EREMOTEIO, "critical target" },
178 [BLK_STS_NEXUS] = { -EBADE, "critical nexus" },
179 [BLK_STS_MEDIUM] = { -ENODATA, "critical medium" },
180 [BLK_STS_PROTECTION] = { -EILSEQ, "protection" },
181 [BLK_STS_RESOURCE] = { -ENOMEM, "kernel resource" },
182 [BLK_STS_DEV_RESOURCE] = { -EBUSY, "device resource" },
183 [BLK_STS_AGAIN] = { -EAGAIN, "nonblocking retry" },
185 /* device mapper special case, should not leak out: */
186 [BLK_STS_DM_REQUEUE] = { -EREMCHG, "dm internal retry" },
188 /* zone device specific errors */
189 [BLK_STS_ZONE_OPEN_RESOURCE] = { -ETOOMANYREFS, "open zones exceeded" },
190 [BLK_STS_ZONE_ACTIVE_RESOURCE] = { -EOVERFLOW, "active zones exceeded" },
192 /* everything else not covered above: */
193 [BLK_STS_IOERR] = { -EIO, "I/O" },
196 blk_status_t errno_to_blk_status(int errno)
200 for (i = 0; i < ARRAY_SIZE(blk_errors); i++) {
201 if (blk_errors[i].errno == errno)
202 return (__force blk_status_t)i;
205 return BLK_STS_IOERR;
207 EXPORT_SYMBOL_GPL(errno_to_blk_status);
209 int blk_status_to_errno(blk_status_t status)
211 int idx = (__force int)status;
213 if (WARN_ON_ONCE(idx >= ARRAY_SIZE(blk_errors)))
215 return blk_errors[idx].errno;
217 EXPORT_SYMBOL_GPL(blk_status_to_errno);
219 void blk_print_req_error(struct request *req, blk_status_t status)
221 int idx = (__force int)status;
223 if (WARN_ON_ONCE(idx >= ARRAY_SIZE(blk_errors)))
226 printk_ratelimited(KERN_ERR
227 "%s error, dev %s, sector %llu op 0x%x:(%s) flags 0x%x "
228 "phys_seg %u prio class %u\n",
229 blk_errors[idx].name,
230 req->rq_disk ? req->rq_disk->disk_name : "?",
231 blk_rq_pos(req), req_op(req), blk_op_str(req_op(req)),
232 req->cmd_flags & ~REQ_OP_MASK,
233 req->nr_phys_segments,
234 IOPRIO_PRIO_CLASS(req->ioprio));
237 void blk_dump_rq_flags(struct request *rq, char *msg)
239 printk(KERN_INFO "%s: dev %s: flags=%llx\n", msg,
240 rq->rq_disk ? rq->rq_disk->disk_name : "?",
241 (unsigned long long) rq->cmd_flags);
243 printk(KERN_INFO " sector %llu, nr/cnr %u/%u\n",
244 (unsigned long long)blk_rq_pos(rq),
245 blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
246 printk(KERN_INFO " bio %p, biotail %p, len %u\n",
247 rq->bio, rq->biotail, blk_rq_bytes(rq));
249 EXPORT_SYMBOL(blk_dump_rq_flags);
252 * blk_sync_queue - cancel any pending callbacks on a queue
256 * The block layer may perform asynchronous callback activity
257 * on a queue, such as calling the unplug function after a timeout.
258 * A block device may call blk_sync_queue to ensure that any
259 * such activity is cancelled, thus allowing it to release resources
260 * that the callbacks might use. The caller must already have made sure
261 * that its ->submit_bio will not re-add plugging prior to calling
264 * This function does not cancel any asynchronous activity arising
265 * out of elevator or throttling code. That would require elevator_exit()
266 * and blkcg_exit_queue() to be called with queue lock initialized.
269 void blk_sync_queue(struct request_queue *q)
271 del_timer_sync(&q->timeout);
272 cancel_work_sync(&q->timeout_work);
274 EXPORT_SYMBOL(blk_sync_queue);
277 * blk_set_pm_only - increment pm_only counter
278 * @q: request queue pointer
280 void blk_set_pm_only(struct request_queue *q)
282 atomic_inc(&q->pm_only);
284 EXPORT_SYMBOL_GPL(blk_set_pm_only);
286 void blk_clear_pm_only(struct request_queue *q)
290 pm_only = atomic_dec_return(&q->pm_only);
291 WARN_ON_ONCE(pm_only < 0);
293 wake_up_all(&q->mq_freeze_wq);
295 EXPORT_SYMBOL_GPL(blk_clear_pm_only);
298 * blk_put_queue - decrement the request_queue refcount
299 * @q: the request_queue structure to decrement the refcount for
301 * Decrements the refcount of the request_queue kobject. When this reaches 0
302 * we'll have blk_release_queue() called.
304 * Context: Any context, but the last reference must not be dropped from
307 void blk_put_queue(struct request_queue *q)
309 kobject_put(&q->kobj);
311 EXPORT_SYMBOL(blk_put_queue);
313 void blk_queue_start_drain(struct request_queue *q)
316 * When queue DYING flag is set, we need to block new req
317 * entering queue, so we call blk_freeze_queue_start() to
318 * prevent I/O from crossing blk_queue_enter().
320 blk_freeze_queue_start(q);
322 blk_mq_wake_waiters(q);
323 /* Make blk_queue_enter() reexamine the DYING flag. */
324 wake_up_all(&q->mq_freeze_wq);
327 void blk_set_queue_dying(struct request_queue *q)
329 blk_queue_flag_set(QUEUE_FLAG_DYING, q);
330 blk_queue_start_drain(q);
332 EXPORT_SYMBOL_GPL(blk_set_queue_dying);
335 * blk_cleanup_queue - shutdown a request queue
336 * @q: request queue to shutdown
338 * Mark @q DYING, drain all pending requests, mark @q DEAD, destroy and
339 * put it. All future requests will be failed immediately with -ENODEV.
343 void blk_cleanup_queue(struct request_queue *q)
345 /* cannot be called from atomic context */
348 WARN_ON_ONCE(blk_queue_registered(q));
350 /* mark @q DYING, no new request or merges will be allowed afterwards */
351 blk_set_queue_dying(q);
353 blk_queue_flag_set(QUEUE_FLAG_NOMERGES, q);
354 blk_queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
357 * Drain all requests queued before DYING marking. Set DEAD flag to
358 * prevent that blk_mq_run_hw_queues() accesses the hardware queues
359 * after draining finished.
363 blk_queue_flag_set(QUEUE_FLAG_DEAD, q);
367 blk_mq_exit_queue(q);
370 * In theory, request pool of sched_tags belongs to request queue.
371 * However, the current implementation requires tag_set for freeing
372 * requests, so free the pool now.
374 * Queue has become frozen, there can't be any in-queue requests, so
375 * it is safe to free requests now.
377 mutex_lock(&q->sysfs_lock);
379 blk_mq_sched_free_rqs(q);
380 mutex_unlock(&q->sysfs_lock);
382 percpu_ref_exit(&q->q_usage_counter);
384 /* @q is and will stay empty, shutdown and put */
387 EXPORT_SYMBOL(blk_cleanup_queue);
390 * blk_queue_enter() - try to increase q->q_usage_counter
391 * @q: request queue pointer
392 * @flags: BLK_MQ_REQ_NOWAIT and/or BLK_MQ_REQ_PM
394 int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
396 const bool pm = flags & BLK_MQ_REQ_PM;
398 while (!blk_try_enter_queue(q, pm)) {
399 if (flags & BLK_MQ_REQ_NOWAIT)
403 * read pair of barrier in blk_freeze_queue_start(), we need to
404 * order reading __PERCPU_REF_DEAD flag of .q_usage_counter and
405 * reading .mq_freeze_depth or queue dying flag, otherwise the
406 * following wait may never return if the two reads are
410 wait_event(q->mq_freeze_wq,
411 (!q->mq_freeze_depth &&
412 blk_pm_resume_queue(pm, q)) ||
414 if (blk_queue_dying(q))
421 int __bio_queue_enter(struct request_queue *q, struct bio *bio)
423 while (!blk_try_enter_queue(q, false)) {
424 struct gendisk *disk = bio->bi_bdev->bd_disk;
426 if (bio->bi_opf & REQ_NOWAIT) {
427 if (test_bit(GD_DEAD, &disk->state))
429 bio_wouldblock_error(bio);
434 * read pair of barrier in blk_freeze_queue_start(), we need to
435 * order reading __PERCPU_REF_DEAD flag of .q_usage_counter and
436 * reading .mq_freeze_depth or queue dying flag, otherwise the
437 * following wait may never return if the two reads are
441 wait_event(q->mq_freeze_wq,
442 (!q->mq_freeze_depth &&
443 blk_pm_resume_queue(false, q)) ||
444 test_bit(GD_DEAD, &disk->state));
445 if (test_bit(GD_DEAD, &disk->state))
455 void blk_queue_exit(struct request_queue *q)
457 percpu_ref_put(&q->q_usage_counter);
460 static void blk_queue_usage_counter_release(struct percpu_ref *ref)
462 struct request_queue *q =
463 container_of(ref, struct request_queue, q_usage_counter);
465 wake_up_all(&q->mq_freeze_wq);
468 static void blk_rq_timed_out_timer(struct timer_list *t)
470 struct request_queue *q = from_timer(q, t, timeout);
472 kblockd_schedule_work(&q->timeout_work);
475 static void blk_timeout_work(struct work_struct *work)
479 struct request_queue *blk_alloc_queue(int node_id)
481 struct request_queue *q;
484 q = kmem_cache_alloc_node(blk_requestq_cachep,
485 GFP_KERNEL | __GFP_ZERO, node_id);
489 q->last_merge = NULL;
491 q->id = ida_simple_get(&blk_queue_ida, 0, 0, GFP_KERNEL);
495 ret = bioset_init(&q->bio_split, BIO_POOL_SIZE, 0, 0);
499 q->stats = blk_alloc_queue_stats();
505 atomic_set(&q->nr_active_requests_shared_tags, 0);
507 timer_setup(&q->timeout, blk_rq_timed_out_timer, 0);
508 INIT_WORK(&q->timeout_work, blk_timeout_work);
509 INIT_LIST_HEAD(&q->icq_list);
510 #ifdef CONFIG_BLK_CGROUP
511 INIT_LIST_HEAD(&q->blkg_list);
514 kobject_init(&q->kobj, &blk_queue_ktype);
516 mutex_init(&q->debugfs_mutex);
517 mutex_init(&q->sysfs_lock);
518 mutex_init(&q->sysfs_dir_lock);
519 spin_lock_init(&q->queue_lock);
521 init_waitqueue_head(&q->mq_freeze_wq);
522 mutex_init(&q->mq_freeze_lock);
525 * Init percpu_ref in atomic mode so that it's faster to shutdown.
526 * See blk_register_queue() for details.
528 if (percpu_ref_init(&q->q_usage_counter,
529 blk_queue_usage_counter_release,
530 PERCPU_REF_INIT_ATOMIC, GFP_KERNEL))
533 if (blkcg_init_queue(q))
536 blk_queue_dma_alignment(q, 511);
537 blk_set_default_limits(&q->limits);
538 q->nr_requests = BLKDEV_DEFAULT_RQ;
543 percpu_ref_exit(&q->q_usage_counter);
545 blk_free_queue_stats(q->stats);
547 bioset_exit(&q->bio_split);
549 ida_simple_remove(&blk_queue_ida, q->id);
551 kmem_cache_free(blk_requestq_cachep, q);
556 * blk_get_queue - increment the request_queue refcount
557 * @q: the request_queue structure to increment the refcount for
559 * Increment the refcount of the request_queue kobject.
561 * Context: Any context.
563 bool blk_get_queue(struct request_queue *q)
565 if (likely(!blk_queue_dying(q))) {
572 EXPORT_SYMBOL(blk_get_queue);
574 static void handle_bad_sector(struct bio *bio, sector_t maxsector)
576 char b[BDEVNAME_SIZE];
578 pr_info_ratelimited("%s: attempt to access beyond end of device\n"
579 "%s: rw=%d, want=%llu, limit=%llu\n",
581 bio_devname(bio, b), bio->bi_opf,
582 bio_end_sector(bio), maxsector);
585 #ifdef CONFIG_FAIL_MAKE_REQUEST
587 static DECLARE_FAULT_ATTR(fail_make_request);
589 static int __init setup_fail_make_request(char *str)
591 return setup_fault_attr(&fail_make_request, str);
593 __setup("fail_make_request=", setup_fail_make_request);
595 static bool should_fail_request(struct block_device *part, unsigned int bytes)
597 return part->bd_make_it_fail && should_fail(&fail_make_request, bytes);
600 static int __init fail_make_request_debugfs(void)
602 struct dentry *dir = fault_create_debugfs_attr("fail_make_request",
603 NULL, &fail_make_request);
605 return PTR_ERR_OR_ZERO(dir);
608 late_initcall(fail_make_request_debugfs);
610 #else /* CONFIG_FAIL_MAKE_REQUEST */
612 static inline bool should_fail_request(struct block_device *part,
618 #endif /* CONFIG_FAIL_MAKE_REQUEST */
620 static inline bool bio_check_ro(struct bio *bio)
622 if (op_is_write(bio_op(bio)) && bdev_read_only(bio->bi_bdev)) {
623 char b[BDEVNAME_SIZE];
625 if (op_is_flush(bio->bi_opf) && !bio_sectors(bio))
629 "Trying to write to read-only block-device %s (partno %d)\n",
630 bio_devname(bio, b), bio->bi_bdev->bd_partno);
631 /* Older lvm-tools actually trigger this */
638 static noinline int should_fail_bio(struct bio *bio)
640 if (should_fail_request(bdev_whole(bio->bi_bdev), bio->bi_iter.bi_size))
644 ALLOW_ERROR_INJECTION(should_fail_bio, ERRNO);
647 * Check whether this bio extends beyond the end of the device or partition.
648 * This may well happen - the kernel calls bread() without checking the size of
649 * the device, e.g., when mounting a file system.
651 static inline int bio_check_eod(struct bio *bio)
653 sector_t maxsector = bdev_nr_sectors(bio->bi_bdev);
654 unsigned int nr_sectors = bio_sectors(bio);
656 if (nr_sectors && maxsector &&
657 (nr_sectors > maxsector ||
658 bio->bi_iter.bi_sector > maxsector - nr_sectors)) {
659 handle_bad_sector(bio, maxsector);
666 * Remap block n of partition p to block n+start(p) of the disk.
668 static int blk_partition_remap(struct bio *bio)
670 struct block_device *p = bio->bi_bdev;
672 if (unlikely(should_fail_request(p, bio->bi_iter.bi_size)))
674 if (bio_sectors(bio)) {
675 bio->bi_iter.bi_sector += p->bd_start_sect;
676 trace_block_bio_remap(bio, p->bd_dev,
677 bio->bi_iter.bi_sector -
680 bio_set_flag(bio, BIO_REMAPPED);
685 * Check write append to a zoned block device.
687 static inline blk_status_t blk_check_zone_append(struct request_queue *q,
690 sector_t pos = bio->bi_iter.bi_sector;
691 int nr_sectors = bio_sectors(bio);
693 /* Only applicable to zoned block devices */
694 if (!blk_queue_is_zoned(q))
695 return BLK_STS_NOTSUPP;
697 /* The bio sector must point to the start of a sequential zone */
698 if (pos & (blk_queue_zone_sectors(q) - 1) ||
699 !blk_queue_zone_is_seq(q, pos))
700 return BLK_STS_IOERR;
703 * Not allowed to cross zone boundaries. Otherwise, the BIO will be
704 * split and could result in non-contiguous sectors being written in
707 if (nr_sectors > q->limits.chunk_sectors)
708 return BLK_STS_IOERR;
710 /* Make sure the BIO is small enough and will not get split */
711 if (nr_sectors > q->limits.max_zone_append_sectors)
712 return BLK_STS_IOERR;
714 bio->bi_opf |= REQ_NOMERGE;
719 noinline_for_stack bool submit_bio_checks(struct bio *bio)
721 struct block_device *bdev = bio->bi_bdev;
722 struct request_queue *q = bdev_get_queue(bdev);
723 blk_status_t status = BLK_STS_IOERR;
724 struct blk_plug *plug;
728 plug = blk_mq_plug(q, bio);
729 if (plug && plug->nowait)
730 bio->bi_opf |= REQ_NOWAIT;
733 * For a REQ_NOWAIT based request, return -EOPNOTSUPP
734 * if queue does not support NOWAIT.
736 if ((bio->bi_opf & REQ_NOWAIT) && !blk_queue_nowait(q))
739 if (should_fail_bio(bio))
741 if (unlikely(bio_check_ro(bio)))
743 if (!bio_flagged(bio, BIO_REMAPPED)) {
744 if (unlikely(bio_check_eod(bio)))
746 if (bdev->bd_partno && unlikely(blk_partition_remap(bio)))
751 * Filter flush bio's early so that bio based drivers without flush
752 * support don't have to worry about them.
754 if (op_is_flush(bio->bi_opf) &&
755 !test_bit(QUEUE_FLAG_WC, &q->queue_flags)) {
756 bio->bi_opf &= ~(REQ_PREFLUSH | REQ_FUA);
757 if (!bio_sectors(bio)) {
763 if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
764 bio_clear_polled(bio);
766 switch (bio_op(bio)) {
768 if (!blk_queue_discard(q))
771 case REQ_OP_SECURE_ERASE:
772 if (!blk_queue_secure_erase(q))
775 case REQ_OP_WRITE_SAME:
776 if (!q->limits.max_write_same_sectors)
779 case REQ_OP_ZONE_APPEND:
780 status = blk_check_zone_append(q, bio);
781 if (status != BLK_STS_OK)
784 case REQ_OP_ZONE_RESET:
785 case REQ_OP_ZONE_OPEN:
786 case REQ_OP_ZONE_CLOSE:
787 case REQ_OP_ZONE_FINISH:
788 if (!blk_queue_is_zoned(q))
791 case REQ_OP_ZONE_RESET_ALL:
792 if (!blk_queue_is_zoned(q) || !blk_queue_zone_resetall(q))
795 case REQ_OP_WRITE_ZEROES:
796 if (!q->limits.max_write_zeroes_sectors)
804 * Various block parts want %current->io_context, so allocate it up
805 * front rather than dealing with lots of pain to allocate it only
806 * where needed. This may fail and the block layer knows how to live
809 if (unlikely(!current->io_context))
810 create_task_io_context(current, GFP_ATOMIC, q->node);
812 if (blk_throtl_bio(bio))
815 blk_cgroup_bio_start(bio);
816 blkcg_bio_issue_init(bio);
818 if (!bio_flagged(bio, BIO_TRACE_COMPLETION)) {
819 trace_block_bio_queue(bio);
820 /* Now that enqueuing has been traced, we need to trace
821 * completion as well.
823 bio_set_flag(bio, BIO_TRACE_COMPLETION);
828 status = BLK_STS_NOTSUPP;
830 bio->bi_status = status;
835 static void __submit_bio_fops(struct gendisk *disk, struct bio *bio)
837 if (unlikely(bio_queue_enter(bio) != 0))
839 if (submit_bio_checks(bio) && blk_crypto_bio_prep(&bio))
840 disk->fops->submit_bio(bio);
841 blk_queue_exit(disk->queue);
844 static void __submit_bio(struct bio *bio)
846 struct gendisk *disk = bio->bi_bdev->bd_disk;
848 if (!disk->fops->submit_bio)
849 blk_mq_submit_bio(bio);
851 __submit_bio_fops(disk, bio);
855 * The loop in this function may be a bit non-obvious, and so deserves some
858 * - Before entering the loop, bio->bi_next is NULL (as all callers ensure
859 * that), so we have a list with a single bio.
860 * - We pretend that we have just taken it off a longer list, so we assign
861 * bio_list to a pointer to the bio_list_on_stack, thus initialising the
862 * bio_list of new bios to be added. ->submit_bio() may indeed add some more
863 * bios through a recursive call to submit_bio_noacct. If it did, we find a
864 * non-NULL value in bio_list and re-enter the loop from the top.
865 * - In this case we really did just take the bio of the top of the list (no
866 * pretending) and so remove it from bio_list, and call into ->submit_bio()
869 * bio_list_on_stack[0] contains bios submitted by the current ->submit_bio.
870 * bio_list_on_stack[1] contains bios that were submitted before the current
871 * ->submit_bio_bio, but that haven't been processed yet.
873 static void __submit_bio_noacct(struct bio *bio)
875 struct bio_list bio_list_on_stack[2];
877 BUG_ON(bio->bi_next);
879 bio_list_init(&bio_list_on_stack[0]);
880 current->bio_list = bio_list_on_stack;
883 struct request_queue *q = bdev_get_queue(bio->bi_bdev);
884 struct bio_list lower, same;
887 * Create a fresh bio_list for all subordinate requests.
889 bio_list_on_stack[1] = bio_list_on_stack[0];
890 bio_list_init(&bio_list_on_stack[0]);
895 * Sort new bios into those for a lower level and those for the
898 bio_list_init(&lower);
899 bio_list_init(&same);
900 while ((bio = bio_list_pop(&bio_list_on_stack[0])) != NULL)
901 if (q == bdev_get_queue(bio->bi_bdev))
902 bio_list_add(&same, bio);
904 bio_list_add(&lower, bio);
907 * Now assemble so we handle the lowest level first.
909 bio_list_merge(&bio_list_on_stack[0], &lower);
910 bio_list_merge(&bio_list_on_stack[0], &same);
911 bio_list_merge(&bio_list_on_stack[0], &bio_list_on_stack[1]);
912 } while ((bio = bio_list_pop(&bio_list_on_stack[0])));
914 current->bio_list = NULL;
917 static void __submit_bio_noacct_mq(struct bio *bio)
919 struct bio_list bio_list[2] = { };
921 current->bio_list = bio_list;
925 } while ((bio = bio_list_pop(&bio_list[0])));
927 current->bio_list = NULL;
931 * submit_bio_noacct - re-submit a bio to the block device layer for I/O
932 * @bio: The bio describing the location in memory and on the device.
934 * This is a version of submit_bio() that shall only be used for I/O that is
935 * resubmitted to lower level drivers by stacking block drivers. All file
936 * systems and other upper level users of the block layer should use
937 * submit_bio() instead.
939 void submit_bio_noacct(struct bio *bio)
942 * We only want one ->submit_bio to be active at a time, else stack
943 * usage with stacked devices could be a problem. Use current->bio_list
944 * to collect a list of requests submited by a ->submit_bio method while
945 * it is active, and then process them after it returned.
947 if (current->bio_list)
948 bio_list_add(¤t->bio_list[0], bio);
949 else if (!bio->bi_bdev->bd_disk->fops->submit_bio)
950 __submit_bio_noacct_mq(bio);
952 __submit_bio_noacct(bio);
954 EXPORT_SYMBOL(submit_bio_noacct);
957 * submit_bio - submit a bio to the block device layer for I/O
958 * @bio: The &struct bio which describes the I/O
960 * submit_bio() is used to submit I/O requests to block devices. It is passed a
961 * fully set up &struct bio that describes the I/O that needs to be done. The
962 * bio will be send to the device described by the bi_bdev field.
964 * The success/failure status of the request, along with notification of
965 * completion, is delivered asynchronously through the ->bi_end_io() callback
966 * in @bio. The bio must NOT be touched by thecaller until ->bi_end_io() has
969 void submit_bio(struct bio *bio)
971 if (blkcg_punt_bio_submit(bio))
975 * If it's a regular read/write or a barrier with data attached,
976 * go through the normal accounting stuff before submission.
978 if (bio_has_data(bio)) {
981 if (unlikely(bio_op(bio) == REQ_OP_WRITE_SAME))
982 count = queue_logical_block_size(
983 bdev_get_queue(bio->bi_bdev)) >> 9;
985 count = bio_sectors(bio);
987 if (op_is_write(bio_op(bio))) {
988 count_vm_events(PGPGOUT, count);
990 task_io_account_read(bio->bi_iter.bi_size);
991 count_vm_events(PGPGIN, count);
996 * If we're reading data that is part of the userspace workingset, count
997 * submission time as memory stall. When the device is congested, or
998 * the submitting cgroup IO-throttled, submission can be a significant
999 * part of overall IO time.
1001 if (unlikely(bio_op(bio) == REQ_OP_READ &&
1002 bio_flagged(bio, BIO_WORKINGSET))) {
1003 unsigned long pflags;
1005 psi_memstall_enter(&pflags);
1006 submit_bio_noacct(bio);
1007 psi_memstall_leave(&pflags);
1011 submit_bio_noacct(bio);
1013 EXPORT_SYMBOL(submit_bio);
1016 * bio_poll - poll for BIO completions
1017 * @bio: bio to poll for
1018 * @flags: BLK_POLL_* flags that control the behavior
1020 * Poll for completions on queue associated with the bio. Returns number of
1021 * completed entries found.
1023 * Note: the caller must either be the context that submitted @bio, or
1024 * be in a RCU critical section to prevent freeing of @bio.
1026 int bio_poll(struct bio *bio, struct io_comp_batch *iob, unsigned int flags)
1028 struct request_queue *q = bdev_get_queue(bio->bi_bdev);
1029 blk_qc_t cookie = READ_ONCE(bio->bi_cookie);
1032 if (cookie == BLK_QC_T_NONE ||
1033 !test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
1037 blk_flush_plug(current->plug, false);
1039 if (blk_queue_enter(q, BLK_MQ_REQ_NOWAIT))
1041 if (WARN_ON_ONCE(!queue_is_mq(q)))
1042 ret = 0; /* not yet implemented, should not happen */
1044 ret = blk_mq_poll(q, cookie, iob, flags);
1048 EXPORT_SYMBOL_GPL(bio_poll);
1051 * Helper to implement file_operations.iopoll. Requires the bio to be stored
1052 * in iocb->private, and cleared before freeing the bio.
1054 int iocb_bio_iopoll(struct kiocb *kiocb, struct io_comp_batch *iob,
1061 * Note: the bio cache only uses SLAB_TYPESAFE_BY_RCU, so bio can
1062 * point to a freshly allocated bio at this point. If that happens
1063 * we have a few cases to consider:
1065 * 1) the bio is beeing initialized and bi_bdev is NULL. We can just
1066 * simply nothing in this case
1067 * 2) the bio points to a not poll enabled device. bio_poll will catch
1069 * 3) the bio points to a poll capable device, including but not
1070 * limited to the one that the original bio pointed to. In this
1071 * case we will call into the actual poll method and poll for I/O,
1072 * even if we don't need to, but it won't cause harm either.
1074 * For cases 2) and 3) above the RCU grace period ensures that bi_bdev
1075 * is still allocated. Because partitions hold a reference to the whole
1076 * device bdev and thus disk, the disk is also still valid. Grabbing
1077 * a reference to the queue in bio_poll() ensures the hctxs and requests
1078 * are still valid as well.
1081 bio = READ_ONCE(kiocb->private);
1082 if (bio && bio->bi_bdev)
1083 ret = bio_poll(bio, iob, flags);
1088 EXPORT_SYMBOL_GPL(iocb_bio_iopoll);
1091 * blk_cloned_rq_check_limits - Helper function to check a cloned request
1092 * for the new queue limits
1094 * @rq: the request being checked
1097 * @rq may have been made based on weaker limitations of upper-level queues
1098 * in request stacking drivers, and it may violate the limitation of @q.
1099 * Since the block layer and the underlying device driver trust @rq
1100 * after it is inserted to @q, it should be checked against @q before
1101 * the insertion using this generic function.
1103 * Request stacking drivers like request-based dm may change the queue
1104 * limits when retrying requests on other queues. Those requests need
1105 * to be checked against the new queue limits again during dispatch.
1107 static blk_status_t blk_cloned_rq_check_limits(struct request_queue *q,
1110 unsigned int max_sectors = blk_queue_get_max_sectors(q, req_op(rq));
1112 if (blk_rq_sectors(rq) > max_sectors) {
1114 * SCSI device does not have a good way to return if
1115 * Write Same/Zero is actually supported. If a device rejects
1116 * a non-read/write command (discard, write same,etc.) the
1117 * low-level device driver will set the relevant queue limit to
1118 * 0 to prevent blk-lib from issuing more of the offending
1119 * operations. Commands queued prior to the queue limit being
1120 * reset need to be completed with BLK_STS_NOTSUPP to avoid I/O
1121 * errors being propagated to upper layers.
1123 if (max_sectors == 0)
1124 return BLK_STS_NOTSUPP;
1126 printk(KERN_ERR "%s: over max size limit. (%u > %u)\n",
1127 __func__, blk_rq_sectors(rq), max_sectors);
1128 return BLK_STS_IOERR;
1132 * The queue settings related to segment counting may differ from the
1135 rq->nr_phys_segments = blk_recalc_rq_segments(rq);
1136 if (rq->nr_phys_segments > queue_max_segments(q)) {
1137 printk(KERN_ERR "%s: over max segments limit. (%hu > %hu)\n",
1138 __func__, rq->nr_phys_segments, queue_max_segments(q));
1139 return BLK_STS_IOERR;
1146 * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1147 * @q: the queue to submit the request
1148 * @rq: the request being queued
1150 blk_status_t blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1154 ret = blk_cloned_rq_check_limits(q, rq);
1155 if (ret != BLK_STS_OK)
1159 should_fail_request(rq->rq_disk->part0, blk_rq_bytes(rq)))
1160 return BLK_STS_IOERR;
1162 if (blk_crypto_insert_cloned_request(rq))
1163 return BLK_STS_IOERR;
1165 blk_account_io_start(rq);
1168 * Since we have a scheduler attached on the top device,
1169 * bypass a potential scheduler on the bottom device for
1172 return blk_mq_request_issue_directly(rq, true);
1174 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
1177 * blk_rq_err_bytes - determine number of bytes till the next failure boundary
1178 * @rq: request to examine
1181 * A request could be merge of IOs which require different failure
1182 * handling. This function determines the number of bytes which
1183 * can be failed from the beginning of the request without
1184 * crossing into area which need to be retried further.
1187 * The number of bytes to fail.
1189 unsigned int blk_rq_err_bytes(const struct request *rq)
1191 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
1192 unsigned int bytes = 0;
1195 if (!(rq->rq_flags & RQF_MIXED_MERGE))
1196 return blk_rq_bytes(rq);
1199 * Currently the only 'mixing' which can happen is between
1200 * different fastfail types. We can safely fail portions
1201 * which have all the failfast bits that the first one has -
1202 * the ones which are at least as eager to fail as the first
1205 for (bio = rq->bio; bio; bio = bio->bi_next) {
1206 if ((bio->bi_opf & ff) != ff)
1208 bytes += bio->bi_iter.bi_size;
1211 /* this could lead to infinite loop */
1212 BUG_ON(blk_rq_bytes(rq) && !bytes);
1215 EXPORT_SYMBOL_GPL(blk_rq_err_bytes);
1217 static void update_io_ticks(struct block_device *part, unsigned long now,
1220 unsigned long stamp;
1222 stamp = READ_ONCE(part->bd_stamp);
1223 if (unlikely(time_after(now, stamp))) {
1224 if (likely(cmpxchg(&part->bd_stamp, stamp, now) == stamp))
1225 __part_stat_add(part, io_ticks, end ? now - stamp : 1);
1227 if (part->bd_partno) {
1228 part = bdev_whole(part);
1233 void __blk_account_io_done(struct request *req, u64 now)
1235 const int sgrp = op_stat_group(req_op(req));
1238 update_io_ticks(req->part, jiffies, true);
1239 part_stat_inc(req->part, ios[sgrp]);
1240 part_stat_add(req->part, nsecs[sgrp], now - req->start_time_ns);
1244 void __blk_account_io_start(struct request *rq)
1246 /* passthrough requests can hold bios that do not have ->bi_bdev set */
1247 if (rq->bio && rq->bio->bi_bdev)
1248 rq->part = rq->bio->bi_bdev;
1250 rq->part = rq->rq_disk->part0;
1253 update_io_ticks(rq->part, jiffies, false);
1257 static unsigned long __part_start_io_acct(struct block_device *part,
1258 unsigned int sectors, unsigned int op)
1260 const int sgrp = op_stat_group(op);
1261 unsigned long now = READ_ONCE(jiffies);
1264 update_io_ticks(part, now, false);
1265 part_stat_inc(part, ios[sgrp]);
1266 part_stat_add(part, sectors[sgrp], sectors);
1267 part_stat_local_inc(part, in_flight[op_is_write(op)]);
1274 * bio_start_io_acct - start I/O accounting for bio based drivers
1275 * @bio: bio to start account for
1277 * Returns the start time that should be passed back to bio_end_io_acct().
1279 unsigned long bio_start_io_acct(struct bio *bio)
1281 return __part_start_io_acct(bio->bi_bdev, bio_sectors(bio), bio_op(bio));
1283 EXPORT_SYMBOL_GPL(bio_start_io_acct);
1285 unsigned long disk_start_io_acct(struct gendisk *disk, unsigned int sectors,
1288 return __part_start_io_acct(disk->part0, sectors, op);
1290 EXPORT_SYMBOL(disk_start_io_acct);
1292 static void __part_end_io_acct(struct block_device *part, unsigned int op,
1293 unsigned long start_time)
1295 const int sgrp = op_stat_group(op);
1296 unsigned long now = READ_ONCE(jiffies);
1297 unsigned long duration = now - start_time;
1300 update_io_ticks(part, now, true);
1301 part_stat_add(part, nsecs[sgrp], jiffies_to_nsecs(duration));
1302 part_stat_local_dec(part, in_flight[op_is_write(op)]);
1306 void bio_end_io_acct_remapped(struct bio *bio, unsigned long start_time,
1307 struct block_device *orig_bdev)
1309 __part_end_io_acct(orig_bdev, bio_op(bio), start_time);
1311 EXPORT_SYMBOL_GPL(bio_end_io_acct_remapped);
1313 void disk_end_io_acct(struct gendisk *disk, unsigned int op,
1314 unsigned long start_time)
1316 __part_end_io_acct(disk->part0, op, start_time);
1318 EXPORT_SYMBOL(disk_end_io_acct);
1321 * Steal bios from a request and add them to a bio list.
1322 * The request must not have been partially completed before.
1324 void blk_steal_bios(struct bio_list *list, struct request *rq)
1328 list->tail->bi_next = rq->bio;
1330 list->head = rq->bio;
1331 list->tail = rq->biotail;
1339 EXPORT_SYMBOL_GPL(blk_steal_bios);
1341 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
1343 * rq_flush_dcache_pages - Helper function to flush all pages in a request
1344 * @rq: the request to be flushed
1347 * Flush all pages in @rq.
1349 void rq_flush_dcache_pages(struct request *rq)
1351 struct req_iterator iter;
1352 struct bio_vec bvec;
1354 rq_for_each_segment(bvec, rq, iter)
1355 flush_dcache_page(bvec.bv_page);
1357 EXPORT_SYMBOL_GPL(rq_flush_dcache_pages);
1361 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
1362 * @q : the queue of the device being checked
1365 * Check if underlying low-level drivers of a device are busy.
1366 * If the drivers want to export their busy state, they must set own
1367 * exporting function using blk_queue_lld_busy() first.
1369 * Basically, this function is used only by request stacking drivers
1370 * to stop dispatching requests to underlying devices when underlying
1371 * devices are busy. This behavior helps more I/O merging on the queue
1372 * of the request stacking driver and prevents I/O throughput regression
1373 * on burst I/O load.
1376 * 0 - Not busy (The request stacking driver should dispatch request)
1377 * 1 - Busy (The request stacking driver should stop dispatching request)
1379 int blk_lld_busy(struct request_queue *q)
1381 if (queue_is_mq(q) && q->mq_ops->busy)
1382 return q->mq_ops->busy(q);
1386 EXPORT_SYMBOL_GPL(blk_lld_busy);
1389 * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
1390 * @rq: the clone request to be cleaned up
1393 * Free all bios in @rq for a cloned request.
1395 void blk_rq_unprep_clone(struct request *rq)
1399 while ((bio = rq->bio) != NULL) {
1400 rq->bio = bio->bi_next;
1405 EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
1408 * blk_rq_prep_clone - Helper function to setup clone request
1409 * @rq: the request to be setup
1410 * @rq_src: original request to be cloned
1411 * @bs: bio_set that bios for clone are allocated from
1412 * @gfp_mask: memory allocation mask for bio
1413 * @bio_ctr: setup function to be called for each clone bio.
1414 * Returns %0 for success, non %0 for failure.
1415 * @data: private data to be passed to @bio_ctr
1418 * Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
1419 * Also, pages which the original bios are pointing to are not copied
1420 * and the cloned bios just point same pages.
1421 * So cloned bios must be completed before original bios, which means
1422 * the caller must complete @rq before @rq_src.
1424 int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
1425 struct bio_set *bs, gfp_t gfp_mask,
1426 int (*bio_ctr)(struct bio *, struct bio *, void *),
1429 struct bio *bio, *bio_src;
1434 __rq_for_each_bio(bio_src, rq_src) {
1435 bio = bio_clone_fast(bio_src, gfp_mask, bs);
1439 if (bio_ctr && bio_ctr(bio, bio_src, data))
1443 rq->biotail->bi_next = bio;
1446 rq->bio = rq->biotail = bio;
1451 /* Copy attributes of the original request to the clone request. */
1452 rq->__sector = blk_rq_pos(rq_src);
1453 rq->__data_len = blk_rq_bytes(rq_src);
1454 if (rq_src->rq_flags & RQF_SPECIAL_PAYLOAD) {
1455 rq->rq_flags |= RQF_SPECIAL_PAYLOAD;
1456 rq->special_vec = rq_src->special_vec;
1458 rq->nr_phys_segments = rq_src->nr_phys_segments;
1459 rq->ioprio = rq_src->ioprio;
1461 if (rq->bio && blk_crypto_rq_bio_prep(rq, rq->bio, gfp_mask) < 0)
1469 blk_rq_unprep_clone(rq);
1473 EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
1475 int kblockd_schedule_work(struct work_struct *work)
1477 return queue_work(kblockd_workqueue, work);
1479 EXPORT_SYMBOL(kblockd_schedule_work);
1481 int kblockd_mod_delayed_work_on(int cpu, struct delayed_work *dwork,
1482 unsigned long delay)
1484 return mod_delayed_work_on(cpu, kblockd_workqueue, dwork, delay);
1486 EXPORT_SYMBOL(kblockd_mod_delayed_work_on);
1488 void blk_start_plug_nr_ios(struct blk_plug *plug, unsigned short nr_ios)
1490 struct task_struct *tsk = current;
1493 * If this is a nested plug, don't actually assign it.
1498 plug->mq_list = NULL;
1499 plug->cached_rq = NULL;
1500 plug->nr_ios = min_t(unsigned short, nr_ios, BLK_MAX_REQUEST_COUNT);
1502 plug->multiple_queues = false;
1503 plug->has_elevator = false;
1504 plug->nowait = false;
1505 INIT_LIST_HEAD(&plug->cb_list);
1508 * Store ordering should not be needed here, since a potential
1509 * preempt will imply a full memory barrier
1515 * blk_start_plug - initialize blk_plug and track it inside the task_struct
1516 * @plug: The &struct blk_plug that needs to be initialized
1519 * blk_start_plug() indicates to the block layer an intent by the caller
1520 * to submit multiple I/O requests in a batch. The block layer may use
1521 * this hint to defer submitting I/Os from the caller until blk_finish_plug()
1522 * is called. However, the block layer may choose to submit requests
1523 * before a call to blk_finish_plug() if the number of queued I/Os
1524 * exceeds %BLK_MAX_REQUEST_COUNT, or if the size of the I/O is larger than
1525 * %BLK_PLUG_FLUSH_SIZE. The queued I/Os may also be submitted early if
1526 * the task schedules (see below).
1528 * Tracking blk_plug inside the task_struct will help with auto-flushing the
1529 * pending I/O should the task end up blocking between blk_start_plug() and
1530 * blk_finish_plug(). This is important from a performance perspective, but
1531 * also ensures that we don't deadlock. For instance, if the task is blocking
1532 * for a memory allocation, memory reclaim could end up wanting to free a
1533 * page belonging to that request that is currently residing in our private
1534 * plug. By flushing the pending I/O when the process goes to sleep, we avoid
1535 * this kind of deadlock.
1537 void blk_start_plug(struct blk_plug *plug)
1539 blk_start_plug_nr_ios(plug, 1);
1541 EXPORT_SYMBOL(blk_start_plug);
1543 static void flush_plug_callbacks(struct blk_plug *plug, bool from_schedule)
1545 LIST_HEAD(callbacks);
1547 while (!list_empty(&plug->cb_list)) {
1548 list_splice_init(&plug->cb_list, &callbacks);
1550 while (!list_empty(&callbacks)) {
1551 struct blk_plug_cb *cb = list_first_entry(&callbacks,
1554 list_del(&cb->list);
1555 cb->callback(cb, from_schedule);
1560 struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug, void *data,
1563 struct blk_plug *plug = current->plug;
1564 struct blk_plug_cb *cb;
1569 list_for_each_entry(cb, &plug->cb_list, list)
1570 if (cb->callback == unplug && cb->data == data)
1573 /* Not currently on the callback list */
1574 BUG_ON(size < sizeof(*cb));
1575 cb = kzalloc(size, GFP_ATOMIC);
1578 cb->callback = unplug;
1579 list_add(&cb->list, &plug->cb_list);
1583 EXPORT_SYMBOL(blk_check_plugged);
1585 void blk_flush_plug(struct blk_plug *plug, bool from_schedule)
1587 if (!list_empty(&plug->cb_list))
1588 flush_plug_callbacks(plug, from_schedule);
1589 if (!rq_list_empty(plug->mq_list))
1590 blk_mq_flush_plug_list(plug, from_schedule);
1592 * Unconditionally flush out cached requests, even if the unplug
1593 * event came from schedule. Since we know hold references to the
1594 * queue for cached requests, we don't want a blocked task holding
1595 * up a queue freeze/quiesce event.
1597 if (unlikely(!rq_list_empty(plug->cached_rq)))
1598 blk_mq_free_plug_rqs(plug);
1602 * blk_finish_plug - mark the end of a batch of submitted I/O
1603 * @plug: The &struct blk_plug passed to blk_start_plug()
1606 * Indicate that a batch of I/O submissions is complete. This function
1607 * must be paired with an initial call to blk_start_plug(). The intent
1608 * is to allow the block layer to optimize I/O submission. See the
1609 * documentation for blk_start_plug() for more information.
1611 void blk_finish_plug(struct blk_plug *plug)
1613 if (plug == current->plug) {
1614 blk_flush_plug(plug, false);
1615 current->plug = NULL;
1618 EXPORT_SYMBOL(blk_finish_plug);
1620 void blk_io_schedule(void)
1622 /* Prevent hang_check timer from firing at us during very long I/O */
1623 unsigned long timeout = sysctl_hung_task_timeout_secs * HZ / 2;
1626 io_schedule_timeout(timeout);
1630 EXPORT_SYMBOL_GPL(blk_io_schedule);
1632 int __init blk_dev_init(void)
1634 BUILD_BUG_ON(REQ_OP_LAST >= (1 << REQ_OP_BITS));
1635 BUILD_BUG_ON(REQ_OP_BITS + REQ_FLAG_BITS > 8 *
1636 sizeof_field(struct request, cmd_flags));
1637 BUILD_BUG_ON(REQ_OP_BITS + REQ_FLAG_BITS > 8 *
1638 sizeof_field(struct bio, bi_opf));
1640 /* used for unplugging and affects IO latency/throughput - HIGHPRI */
1641 kblockd_workqueue = alloc_workqueue("kblockd",
1642 WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
1643 if (!kblockd_workqueue)
1644 panic("Failed to create kblockd\n");
1646 blk_requestq_cachep = kmem_cache_create("request_queue",
1647 sizeof(struct request_queue), 0, SLAB_PANIC, NULL);
1649 blk_debugfs_root = debugfs_create_dir("block", NULL);