summaryrefslogtreecommitdiff
path: root/block/blk-core.c
blob: 27fb1357ad4b81bd5940ede8908a37e56abfa158 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 1991, 1992 Linus Torvalds
 * Copyright (C) 1994,      Karl Keyte: Added support for disk statistics
 * Elevator latency, (C) 2000  Andrea Arcangeli <andrea@suse.de> SuSE
 * Queue request tables / lock, selectable elevator, Jens Axboe <axboe@suse.de>
 * kernel-doc documentation started by NeilBrown <neilb@cse.unsw.edu.au>
 *	-  July2000
 * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001
 */

/*
 * This handles all read/write requests to block devices
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/blk-pm.h>
#include <linux/blk-integrity.h>
#include <linux/highmem.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/kernel_stat.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/completion.h>
#include <linux/slab.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/fault-inject.h>
#include <linux/list_sort.h>
#include <linux/delay.h>
#include <linux/ratelimit.h>
#include <linux/pm_runtime.h>
#include <linux/t10-pi.h>
#include <linux/debugfs.h>
#include <linux/bpf.h>
#include <linux/psi.h>
#include <linux/part_stat.h>
#include <linux/sched/sysctl.h>
#include <linux/blk-crypto.h>

#define CREATE_TRACE_POINTS
#include <trace/events/block.h>

#include "blk.h"
#include "blk-mq-sched.h"
#include "blk-pm.h"
#include "blk-cgroup.h"
#include "blk-throttle.h"

struct dentry *blk_debugfs_root;

EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
EXPORT_TRACEPOINT_SYMBOL_GPL(block_split);
EXPORT_TRACEPOINT_SYMBOL_GPL(block_unplug);
EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_insert);

DEFINE_IDA(blk_queue_ida);

/*
 * For queue allocation
 */
struct kmem_cache *blk_requestq_cachep;
struct kmem_cache *blk_requestq_srcu_cachep;

/*
 * Controlling structure to kblockd
 */
static struct workqueue_struct *kblockd_workqueue;

/**
 * blk_queue_flag_set - atomically set a queue flag
 * @flag: flag to be set
 * @q: request queue
 */
void blk_queue_flag_set(unsigned int flag, struct request_queue *q)
{
	set_bit(flag, &q->queue_flags);
}
EXPORT_SYMBOL(blk_queue_flag_set);

/**
 * blk_queue_flag_clear - atomically clear a queue flag
 * @flag: flag to be cleared
 * @q: request queue
 */
void blk_queue_flag_clear(unsigned int flag, struct request_queue *q)
{
	clear_bit(flag, &q->queue_flags);
}
EXPORT_SYMBOL(blk_queue_flag_clear);

/**
 * blk_queue_flag_test_and_set - atomically test and set a queue flag
 * @flag: flag to be set
 * @q: request queue
 *
 * Returns the previous value of @flag - 0 if the flag was not set and 1 if
 * the flag was already set.
 */
bool blk_queue_flag_test_and_set(unsigned int flag, struct request_queue *q)
{
	return test_and_set_bit(flag, &q->queue_flags);
}
EXPORT_SYMBOL_GPL(blk_queue_flag_test_and_set);

#define REQ_OP_NAME(name) [REQ_OP_##name] = #name
static const char *const blk_op_name[] = {
	REQ_OP_NAME(READ),
	REQ_OP_NAME(WRITE),
	REQ_OP_NAME(FLUSH),
	REQ_OP_NAME(DISCARD),
	REQ_OP_NAME(SECURE_ERASE),
	REQ_OP_NAME(ZONE_RESET),
	REQ_OP_NAME(ZONE_RESET_ALL),
	REQ_OP_NAME(ZONE_OPEN),
	REQ_OP_NAME(ZONE_CLOSE),
	REQ_OP_NAME(ZONE_FINISH),
	REQ_OP_NAME(ZONE_APPEND),
	REQ_OP_NAME(WRITE_ZEROES),
	REQ_OP_NAME(DRV_IN),
	REQ_OP_NAME(DRV_OUT),
};
#undef REQ_OP_NAME

/**
 * blk_op_str - Return string XXX in the REQ_OP_XXX.
 * @op: REQ_OP_XXX.
 *
 * Description: Centralize block layer function to convert REQ_OP_XXX into
 * string format. Useful in the debugging and tracing bio or request. For
 * invalid REQ_OP_XXX it returns string "UNKNOWN".
 */
inline const char *blk_op_str(unsigned int op)
{
	const char *op_str = "UNKNOWN";

	if (op < ARRAY_SIZE(blk_op_name) && blk_op_name[op])
		op_str = blk_op_name[op];

	return op_str;
}
EXPORT_SYMBOL_GPL(blk_op_str);

static const struct {
	int		errno;
	const char	*name;
} blk_errors[] = {
	[BLK_STS_OK]		= { 0,		"" },
	[BLK_STS_NOTSUPP]	= { -EOPNOTSUPP, "operation not supported" },
	[BLK_STS_TIMEOUT]	= { -ETIMEDOUT,	"timeout" },
	[BLK_STS_NOSPC]		= { -ENOSPC,	"critical space allocation" },
	[BLK_STS_TRANSPORT]	= { -ENOLINK,	"recoverable transport" },
	[BLK_STS_TARGET]	= { -EREMOTEIO,	"critical target" },
	[BLK_STS_NEXUS]		= { -EBADE,	"critical nexus" },
	[BLK_STS_MEDIUM]	= { -ENODATA,	"critical medium" },
	[BLK_STS_PROTECTION]	= { -EILSEQ,	"protection" },
	[BLK_STS_RESOURCE]	= { -ENOMEM,	"kernel resource" },
	[BLK_STS_DEV_RESOURCE]	= { -EBUSY,	"device resource" },
	[BLK_STS_AGAIN]		= { -EAGAIN,	"nonblocking retry" },
	[BLK_STS_OFFLINE]	= { -ENODEV,	"device offline" },

	/* device mapper special case, should not leak out: */
	[BLK_STS_DM_REQUEUE]	= { -EREMCHG, "dm internal retry" },

	/* zone device specific errors */
	[BLK_STS_ZONE_OPEN_RESOURCE]	= { -ETOOMANYREFS, "open zones exceeded" },
	[BLK_STS_ZONE_ACTIVE_RESOURCE]	= { -EOVERFLOW, "active zones exceeded" },

	/* everything else not covered above: */
	[BLK_STS_IOERR]		= { -EIO,	"I/O" },
};

blk_status_t errno_to_blk_status(int errno)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(blk_errors); i++) {
		if (blk_errors[i].errno == errno)
			return (__force blk_status_t)i;
	}

	return BLK_STS_IOERR;
}
EXPORT_SYMBOL_GPL(errno_to_blk_status);

int blk_status_to_errno(blk_status_t status)
{
	int idx = (__force int)status;

	if (WARN_ON_ONCE(idx >= ARRAY_SIZE(blk_errors)))
		return -EIO;
	return blk_errors[idx].errno;
}
EXPORT_SYMBOL_GPL(blk_status_to_errno);

const char *blk_status_to_str(blk_status_t status)
{
	int idx = (__force int)status;

	if (WARN_ON_ONCE(idx >= ARRAY_SIZE(blk_errors)))
		return "<null>";
	return blk_errors[idx].name;
}

/**
 * blk_sync_queue - cancel any pending callbacks on a queue
 * @q: the queue
 *
 * Description:
 *     The block layer may perform asynchronous callback activity
 *     on a queue, such as calling the unplug function after a timeout.
 *     A block device may call blk_sync_queue to ensure that any
 *     such activity is cancelled, thus allowing it to release resources
 *     that the callbacks might use. The caller must already have made sure
 *     that its ->submit_bio will not re-add plugging prior to calling
 *     this function.
 *
 *     This function does not cancel any asynchronous activity arising
 *     out of elevator or throttling code. That would require elevator_exit()
 *     and blkcg_exit_queue() to be called with queue lock initialized.
 *
 */
void blk_sync_queue(struct request_queue *q)
{
	del_timer_sync(&q->timeout);
	cancel_work_sync(&q->timeout_work);
}
EXPORT_SYMBOL(blk_sync_queue);

/**
 * blk_set_pm_only - increment pm_only counter
 * @q: request queue pointer
 */
void blk_set_pm_only(struct request_queue *q)
{
	atomic_inc(&q->pm_only);
}
EXPORT_SYMBOL_GPL(blk_set_pm_only);

void blk_clear_pm_only(struct request_queue *q)
{
	int pm_only;

	pm_only = atomic_dec_return(&q->pm_only);
	WARN_ON_ONCE(pm_only < 0);
	if (pm_only == 0)
		wake_up_all(&q->mq_freeze_wq);
}
EXPORT_SYMBOL_GPL(blk_clear_pm_only);

/**
 * blk_put_queue - decrement the request_queue refcount
 * @q: the request_queue structure to decrement the refcount for
 *
 * Decrements the refcount of the request_queue kobject. When this reaches 0
 * we'll have blk_release_queue() called.
 *
 * Context: Any context, but the last reference must not be dropped from
 *          atomic context.
 */
void blk_put_queue(struct request_queue *q)
{
	kobject_put(&q->kobj);
}
EXPORT_SYMBOL(blk_put_queue);

void blk_queue_start_drain(struct request_queue *q)
{
	/*
	 * When queue DYING flag is set, we need to block new req
	 * entering queue, so we call blk_freeze_queue_start() to
	 * prevent I/O from crossing blk_queue_enter().
	 */
	blk_freeze_queue_start(q);
	if (queue_is_mq(q))
		blk_mq_wake_waiters(q);
	/* Make blk_queue_enter() reexamine the DYING flag. */
	wake_up_all(&q->mq_freeze_wq);
}

/**
 * blk_cleanup_queue - shutdown a request queue
 * @q: request queue to shutdown
 *
 * Mark @q DYING, drain all pending requests, mark @q DEAD, destroy and
 * put it.  All future requests will be failed immediately with -ENODEV.
 *
 * Context: can sleep
 */
void blk_cleanup_queue(struct request_queue *q)
{
	/* cannot be called from atomic context */
	might_sleep();

	WARN_ON_ONCE(blk_queue_registered(q));

	/* mark @q DYING, no new request or merges will be allowed afterwards */
	blk_queue_flag_set(QUEUE_FLAG_DYING, q);
	blk_queue_start_drain(q);

	blk_queue_flag_set(QUEUE_FLAG_NOMERGES, q);
	blk_queue_flag_set(QUEUE_FLAG_NOXMERGES, q);

	/*
	 * Drain all requests queued before DYING marking. Set DEAD flag to
	 * prevent that blk_mq_run_hw_queues() accesses the hardware queues
	 * after draining finished.
	 */
	blk_freeze_queue(q);

	blk_queue_flag_set(QUEUE_FLAG_DEAD, q);

	blk_sync_queue(q);
	if (queue_is_mq(q)) {
		blk_mq_cancel_work_sync(q);
		blk_mq_exit_queue(q);
	}

	/* @q is and will stay empty, shutdown and put */
	blk_put_queue(q);
}
EXPORT_SYMBOL(blk_cleanup_queue);

/**
 * blk_queue_enter() - try to increase q->q_usage_counter
 * @q: request queue pointer
 * @flags: BLK_MQ_REQ_NOWAIT and/or BLK_MQ_REQ_PM
 */
int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
{
	const bool pm = flags & BLK_MQ_REQ_PM;

	while (!blk_try_enter_queue(q, pm)) {
		if (flags & BLK_MQ_REQ_NOWAIT)
			return -EBUSY;

		/*
		 * read pair of barrier in blk_freeze_queue_start(), we need to
		 * order reading __PERCPU_REF_DEAD flag of .q_usage_counter and
		 * reading .mq_freeze_depth or queue dying flag, otherwise the
		 * following wait may never return if the two reads are
		 * reordered.
		 */
		smp_rmb();
		wait_event(q->mq_freeze_wq,
			   (!q->mq_freeze_depth &&
			    blk_pm_resume_queue(pm, q)) ||
			   blk_queue_dying(q));
		if (blk_queue_dying(q))
			return -ENODEV;
	}

	return 0;
}

int __bio_queue_enter(struct request_queue *q, struct bio *bio)
{
	while (!blk_try_enter_queue(q, false)) {
		struct gendisk *disk = bio->bi_bdev->bd_disk;

		if (bio->bi_opf & REQ_NOWAIT) {
			if (test_bit(GD_DEAD, &disk->state))
				goto dead;
			bio_wouldblock_error(bio);
			return -EBUSY;
		}

		/*
		 * read pair of barrier in blk_freeze_queue_start(), we need to
		 * order reading __PERCPU_REF_DEAD flag of .q_usage_counter and
		 * reading .mq_freeze_depth or queue dying flag, otherwise the
		 * following wait may never return if the two reads are
		 * reordered.
		 */
		smp_rmb();
		wait_event(q->mq_freeze_wq,
			   (!q->mq_freeze_depth &&
			    blk_pm_resume_queue(false, q)) ||
			   test_bit(GD_DEAD, &disk->state));
		if (test_bit(GD_DEAD, &disk->state))
			goto dead;
	}

	return 0;
dead:
	bio_io_error(bio);
	return -ENODEV;
}

void blk_queue_exit(struct request_queue *q)
{
	percpu_ref_put(&q->q_usage_counter);
}

static void blk_queue_usage_counter_release(struct percpu_ref *ref)
{
	struct request_queue *q =
		container_of(ref, struct request_queue, q_usage_counter);

	wake_up_all(&q->mq_freeze_wq);
}

static void blk_rq_timed_out_timer(struct timer_list *t)
{
	struct request_queue *q = from_timer(q, t, timeout);

	kblockd_schedule_work(&q->timeout_work);
}

static void blk_timeout_work(struct work_struct *work)
{
}

struct request_queue *blk_alloc_queue(int node_id, bool alloc_srcu)
{
	struct request_queue *q;
	int ret;

	q = kmem_cache_alloc_node(blk_get_queue_kmem_cache(alloc_srcu),
			GFP_KERNEL | __GFP_ZERO, node_id);
	if (!q)
		return NULL;

	if (alloc_srcu) {
		blk_queue_flag_set(QUEUE_FLAG_HAS_SRCU, q);
		if (init_srcu_struct(q->srcu) != 0)
			goto fail_q;
	}

	q->last_merge = NULL;

	q->id = ida_simple_get(&blk_queue_ida, 0, 0, GFP_KERNEL);
	if (q->id < 0)
		goto fail_srcu;

	ret = bioset_init(&q->bio_split, BIO_POOL_SIZE, 0, 0);
	if (ret)
		goto fail_id;

	q->stats = blk_alloc_queue_stats();
	if (!q->stats)
		goto fail_split;

	q->node = node_id;

	atomic_set(&q->nr_active_requests_shared_tags, 0);

	timer_setup(&q->timeout, blk_rq_timed_out_timer, 0);
	INIT_WORK(&q->timeout_work, blk_timeout_work);
	INIT_LIST_HEAD(&q->icq_list);

	kobject_init(&q->kobj, &blk_queue_ktype);

	mutex_init(&q->debugfs_mutex);
	mutex_init(&q->sysfs_lock);
	mutex_init(&q->sysfs_dir_lock);
	spin_lock_init(&q->queue_lock);

	init_waitqueue_head(&q->mq_freeze_wq);
	mutex_init(&q->mq_freeze_lock);

	/*
	 * Init percpu_ref in atomic mode so that it's faster to shutdown.
	 * See blk_register_queue() for details.
	 */
	if (percpu_ref_init(&q->q_usage_counter,
				blk_queue_usage_counter_release,
				PERCPU_REF_INIT_ATOMIC, GFP_KERNEL))
		goto fail_stats;

	blk_queue_dma_alignment(q, 511);
	blk_set_default_limits(&q->limits);
	q->nr_requests = BLKDEV_DEFAULT_RQ;

	return q;

fail_stats:
	blk_free_queue_stats(q->stats);
fail_split:
	bioset_exit(&q->bio_split);
fail_id:
	ida_simple_remove(&blk_queue_ida, q->id);
fail_srcu:
	if (alloc_srcu)
		cleanup_srcu_struct(q->srcu);
fail_q:
	kmem_cache_free(blk_get_queue_kmem_cache(alloc_srcu), q);
	return NULL;
}

/**
 * blk_get_queue - increment the request_queue refcount
 * @q: the request_queue structure to increment the refcount for
 *
 * Increment the refcount of the request_queue kobject.
 *
 * Context: Any context.
 */
bool blk_get_queue(struct request_queue *q)
{
	if (likely(!blk_queue_dying(q))) {
		__blk_get_queue(q);
		return true;
	}

	return false;
}
EXPORT_SYMBOL(blk_get_queue);

#ifdef CONFIG_FAIL_MAKE_REQUEST

static DECLARE_FAULT_ATTR(fail_make_request);

static int __init setup_fail_make_request(char *str)
{
	return setup_fault_attr(&fail_make_request, str);
}
__setup("fail_make_request=", setup_fail_make_request);

bool should_fail_request(struct block_device *part, unsigned int bytes)
{
	return part->bd_make_it_fail && should_fail(&fail_make_request, bytes);
}

static int __init fail_make_request_debugfs(void)
{
	struct dentry *dir = fault_create_debugfs_attr("fail_make_request",
						NULL, &fail_make_request);

	return PTR_ERR_OR_ZERO(dir);
}

late_initcall(fail_make_request_debugfs);
#endif /* CONFIG_FAIL_MAKE_REQUEST */

static inline bool bio_check_ro(struct bio *bio)
{
	if (op_is_write(bio_op(bio)) && bdev_read_only(bio->bi_bdev)) {
		if (op_is_flush(bio->bi_opf) && !bio_sectors(bio))
			return false;
		pr_warn("Trying to write to read-only block-device %pg\n",
			bio->bi_bdev);
		/* Older lvm-tools actually trigger this */
		return false;
	}

	return false;
}

static noinline int should_fail_bio(struct bio *bio)
{
	if (should_fail_request(bdev_whole(bio->bi_bdev), bio->bi_iter.bi_size))
		return -EIO;
	return 0;
}
ALLOW_ERROR_INJECTION(should_fail_bio, ERRNO);

/*
 * Check whether this bio extends beyond the end of the device or partition.
 * This may well happen - the kernel calls bread() without checking the size of
 * the device, e.g., when mounting a file system.
 */
static inline int bio_check_eod(struct bio *bio)
{
	sector_t maxsector = bdev_nr_sectors(bio->bi_bdev);
	unsigned int nr_sectors = bio_sectors(bio);

	if (nr_sectors && maxsector &&
	    (nr_sectors > maxsector ||
	     bio->bi_iter.bi_sector > maxsector - nr_sectors)) {
		pr_info_ratelimited("%s: attempt to access beyond end of device\n"
				    "%pg: rw=%d, sector=%llu, nr_sectors = %u limit=%llu\n",
				    current->comm, bio->bi_bdev, bio->bi_opf,
				    bio->bi_iter.bi_sector, nr_sectors, maxsector);
		return -EIO;
	}
	return 0;
}

/*
 * Remap block n of partition p to block n+start(p) of the disk.
 */
static int blk_partition_remap(struct bio *bio)
{
	struct block_device *p = bio->bi_bdev;

	if (unlikely(should_fail_request(p, bio->bi_iter.bi_size)))
		return -EIO;
	if (bio_sectors(bio)) {
		bio->bi_iter.bi_sector += p->bd_start_sect;
		trace_block_bio_remap(bio, p->bd_dev,
				      bio->bi_iter.bi_sector -
				      p->bd_start_sect);
	}
	bio_set_flag(bio, BIO_REMAPPED);
	return 0;
}

/*
 * Check write append to a zoned block device.
 */
static inline blk_status_t blk_check_zone_append(struct request_queue *q,
						 struct bio *bio)
{
	sector_t pos = bio->bi_iter.bi_sector;
	int nr_sectors = bio_sectors(bio);

	/* Only applicable to zoned block devices */
	if (!blk_queue_is_zoned(q))
		return BLK_STS_NOTSUPP;

	/* The bio sector must point to the start of a sequential zone */
	if (pos & (blk_queue_zone_sectors(q) - 1) ||
	    !blk_queue_zone_is_seq(q, pos))
		return BLK_STS_IOERR;

	/*
	 * Not allowed to cross zone boundaries. Otherwise, the BIO will be
	 * split and could result in non-contiguous sectors being written in
	 * different zones.
	 */
	if (nr_sectors > q->limits.chunk_sectors)
		return BLK_STS_IOERR;

	/* Make sure the BIO is small enough and will not get split */
	if (nr_sectors > q->limits.max_zone_append_sectors)
		return BLK_STS_IOERR;

	bio->bi_opf |= REQ_NOMERGE;

	return BLK_STS_OK;
}

static void __submit_bio(struct bio *bio)
{
	struct gendisk *disk = bio->bi_bdev->bd_disk;

	if (unlikely(!blk_crypto_bio_prep(&bio)))
		return;

	if (!disk->fops->submit_bio) {
		blk_mq_submit_bio(bio);
	} else if (likely(bio_queue_enter(bio) == 0)) {
		disk->fops->submit_bio(bio);
		blk_queue_exit(disk->queue);
	}
}

/*
 * The loop in this function may be a bit non-obvious, and so deserves some
 * explanation:
 *
 *  - Before entering the loop, bio->bi_next is NULL (as all callers ensure
 *    that), so we have a list with a single bio.
 *  - We pretend that we have just taken it off a longer list, so we assign
 *    bio_list to a pointer to the bio_list_on_stack, thus initialising the
 *    bio_list of new bios to be added.  ->submit_bio() may indeed add some more
 *    bios through a recursive call to submit_bio_noacct.  If it did, we find a
 *    non-NULL value in bio_list and re-enter the loop from the top.
 *  - In this case we really did just take the bio of the top of the list (no
 *    pretending) and so remove it from bio_list, and call into ->submit_bio()
 *    again.
 *
 * bio_list_on_stack[0] contains bios submitted by the current ->submit_bio.
 * bio_list_on_stack[1] contains bios that were submitted before the current
 *	->submit_bio, but that haven't been processed yet.
 */
static void __submit_bio_noacct(struct bio *bio)
{
	struct bio_list bio_list_on_stack[2];

	BUG_ON(bio->bi_next);

	bio_list_init(&bio_list_on_stack[0]);
	current->bio_list = bio_list_on_stack;

	do {
		struct request_queue *q = bdev_get_queue(bio->bi_bdev);
		struct bio_list lower, same;

		/*
		 * Create a fresh bio_list for all subordinate requests.
		 */
		bio_list_on_stack[1] = bio_list_on_stack[0];
		bio_list_init(&bio_list_on_stack[0]);

		__submit_bio(bio);

		/*
		 * Sort new bios into those for a lower level and those for the
		 * same level.
		 */
		bio_list_init(&lower);
		bio_list_init(&same);
		while ((bio = bio_list_pop(&bio_list_on_stack[0])) != NULL)
			if (q == bdev_get_queue(bio->bi_bdev))
				bio_list_add(&same, bio);
			else
				bio_list_add(&lower, bio);

		/*
		 * Now assemble so we handle the lowest level first.
		 */
		bio_list_merge(&bio_list_on_stack[0], &lower);
		bio_list_merge(&bio_list_on_stack[0], &same);
		bio_list_merge(&bio_list_on_stack[0], &bio_list_on_stack[1]);
	} while ((bio = bio_list_pop(&bio_list_on_stack[0])));

	current->bio_list = NULL;
}

static void __submit_bio_noacct_mq(struct bio *bio)
{
	struct bio_list bio_list[2] = { };

	current->bio_list = bio_list;

	do {
		__submit_bio(bio);
	} while ((bio = bio_list_pop(&bio_list[0])));

	current->bio_list = NULL;
}

void submit_bio_noacct_nocheck(struct bio *bio)
{
	/*
	 * We only want one ->submit_bio to be active at a time, else stack
	 * usage with stacked devices could be a problem.  Use current->bio_list
	 * to collect a list of requests submited by a ->submit_bio method while
	 * it is active, and then process them after it returned.
	 */
	if (current->bio_list)
		bio_list_add(&current->bio_list[0], bio);
	else if (!bio->bi_bdev->bd_disk->fops->submit_bio)
		__submit_bio_noacct_mq(bio);
	else
		__submit_bio_noacct(bio);
}

/**
 * submit_bio_noacct - re-submit a bio to the block device layer for I/O
 * @bio:  The bio describing the location in memory and on the device.
 *
 * This is a version of submit_bio() that shall only be used for I/O that is
 * resubmitted to lower level drivers by stacking block drivers.  All file
 * systems and other upper level users of the block layer should use
 * submit_bio() instead.
 */
void submit_bio_noacct(struct bio *bio)
{
	struct block_device *bdev = bio->bi_bdev;
	struct request_queue *q = bdev_get_queue(bdev);
	blk_status_t status = BLK_STS_IOERR;
	struct blk_plug *plug;

	might_sleep();

	plug = blk_mq_plug(q, bio);
	if (plug && plug->nowait)
		bio->bi_opf |= REQ_NOWAIT;

	/*
	 * For a REQ_NOWAIT based request, return -EOPNOTSUPP
	 * if queue does not support NOWAIT.
	 */
	if ((bio->bi_opf & REQ_NOWAIT) && !blk_queue_nowait(q))
		goto not_supported;

	if (should_fail_bio(bio))
		goto end_io;
	if (unlikely(bio_check_ro(bio)))
		goto end_io;
	if (!bio_flagged(bio, BIO_REMAPPED)) {
		if (unlikely(bio_check_eod(bio)))
			goto end_io;
		if (bdev->bd_partno && unlikely(blk_partition_remap(bio)))
			goto end_io;
	}

	/*
	 * Filter flush bio's early so that bio based drivers without flush
	 * support don't have to worry about them.
	 */
	if (op_is_flush(bio->bi_opf) &&
	    !test_bit(QUEUE_FLAG_WC, &q->queue_flags)) {
		bio->bi_opf &= ~(REQ_PREFLUSH | REQ_FUA);
		if (!bio_sectors(bio)) {
			status = BLK_STS_OK;
			goto end_io;
		}
	}

	if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
		bio_clear_polled(bio);

	switch (bio_op(bio)) {
	case REQ_OP_DISCARD:
		if (!bdev_max_discard_sectors(bdev))
			goto not_supported;
		break;
	case REQ_OP_SECURE_ERASE:
		if (!bdev_max_secure_erase_sectors(bdev))
			goto not_supported;
		break;
	case REQ_OP_ZONE_APPEND:
		status = blk_check_zone_append(q, bio);
		if (status != BLK_STS_OK)
			goto end_io;
		break;
	case REQ_OP_ZONE_RESET:
	case REQ_OP_ZONE_OPEN:
	case REQ_OP_ZONE_CLOSE:
	case REQ_OP_ZONE_FINISH:
		if (!blk_queue_is_zoned(q))
			goto not_supported;
		break;
	case REQ_OP_ZONE_RESET_ALL:
		if (!blk_queue_is_zoned(q) || !blk_queue_zone_resetall(q))
			goto not_supported;
		break;
	case REQ_OP_WRITE_ZEROES:
		if (!q->limits.max_write_zeroes_sectors)
			goto not_supported;
		break;
	default:
		break;
	}

	if (blk_throtl_bio(bio))
		return;

	blk_cgroup_bio_start(bio);
	blkcg_bio_issue_init(bio);

	if (!bio_flagged(bio, BIO_TRACE_COMPLETION)) {
		trace_block_bio_queue(bio);
		/* Now that enqueuing has been traced, we need to trace
		 * completion as well.
		 */
		bio_set_flag(bio, BIO_TRACE_COMPLETION);
	}
	submit_bio_noacct_nocheck(bio);
	return;

not_supported:
	status = BLK_STS_NOTSUPP;
end_io:
	bio->bi_status = status;
	bio_endio(bio);
}
EXPORT_SYMBOL(submit_bio_noacct);

/**
 * submit_bio - submit a bio to the block device layer for I/O
 * @bio: The &struct bio which describes the I/O
 *
 * submit_bio() is used to submit I/O requests to block devices.  It is passed a
 * fully set up &struct bio that describes the I/O that needs to be done.  The
 * bio will be send to the device described by the bi_bdev field.
 *
 * The success/failure status of the request, along with notification of
 * completion, is delivered asynchronously through the ->bi_end_io() callback
 * in @bio.  The bio must NOT be touched by thecaller until ->bi_end_io() has
 * been called.
 */
void submit_bio(struct bio *bio)
{
	if (blkcg_punt_bio_submit(bio))
		return;

	if (bio_op(bio) == REQ_OP_READ) {
		task_io_account_read(bio->bi_iter.bi_size);
		count_vm_events(PGPGIN, bio_sectors(bio));
	} else if (bio_op(bio) == REQ_OP_WRITE) {
		count_vm_events(PGPGOUT, bio_sectors(bio));
	}

	/*
	 * If we're reading data that is part of the userspace workingset, count
	 * submission time as memory stall.  When the device is congested, or
	 * the submitting cgroup IO-throttled, submission can be a significant
	 * part of overall IO time.
	 */
	if (unlikely(bio_op(bio) == REQ_OP_READ &&
	    bio_flagged(bio, BIO_WORKINGSET))) {
		unsigned long pflags;

		psi_memstall_enter(&pflags);
		submit_bio_noacct(bio);
		psi_memstall_leave(&pflags);
		return;
	}

	submit_bio_noacct(bio);
}
EXPORT_SYMBOL(submit_bio);

/**
 * bio_poll - poll for BIO completions
 * @bio: bio to poll for
 * @iob: batches of IO
 * @flags: BLK_POLL_* flags that control the behavior
 *
 * Poll for completions on queue associated with the bio. Returns number of
 * completed entries found.
 *
 * Note: the caller must either be the context that submitted @bio, or
 * be in a RCU critical section to prevent freeing of @bio.
 */
int bio_poll(struct bio *bio, struct io_comp_batch *iob, unsigned int flags)
{
	struct request_queue *q = bdev_get_queue(bio->bi_bdev);
	blk_qc_t cookie = READ_ONCE(bio->bi_cookie);
	int ret = 0;

	if (cookie == BLK_QC_T_NONE ||
	    !test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
		return 0;

	blk_flush_plug(current->plug, false);

	if (bio_queue_enter(bio))
		return 0;
	if (queue_is_mq(q)) {
		ret = blk_mq_poll(q, cookie, iob, flags);
	} else {
		struct gendisk *disk = q->disk;

		if (disk && disk->fops->poll_bio)
			ret = disk->fops->poll_bio(bio, iob, flags);
	}
	blk_queue_exit(q);
	return ret;
}
EXPORT_SYMBOL_GPL(bio_poll);

/*
 * Helper to implement file_operations.iopoll.  Requires the bio to be stored
 * in iocb->private, and cleared before freeing the bio.
 */
int iocb_bio_iopoll(struct kiocb *kiocb, struct io_comp_batch *iob,
		    unsigned int flags)
{
	struct bio *bio;
	int ret = 0;

	/*
	 * Note: the bio cache only uses SLAB_TYPESAFE_BY_RCU, so bio can
	 * point to a freshly allocated bio at this point.  If that happens
	 * we have a few cases to consider:
	 *
	 *  1) the bio is beeing initialized and bi_bdev is NULL.  We can just
	 *     simply nothing in this case
	 *  2) the bio points to a not poll enabled device.  bio_poll will catch
	 *     this and return 0
	 *  3) the bio points to a poll capable device, including but not
	 *     limited to the one that the original bio pointed to.  In this
	 *     case we will call into the actual poll method and poll for I/O,
	 *     even if we don't need to, but it won't cause harm either.
	 *
	 * For cases 2) and 3) above the RCU grace period ensures that bi_bdev
	 * is still allocated. Because partitions hold a reference to the whole
	 * device bdev and thus disk, the disk is also still valid.  Grabbing
	 * a reference to the queue in bio_poll() ensures the hctxs and requests
	 * are still valid as well.
	 */
	rcu_read_lock();
	bio = READ_ONCE(kiocb->private);
	if (bio && bio->bi_bdev)
		ret = bio_poll(bio, iob, flags);
	rcu_read_unlock();

	return ret;
}
EXPORT_SYMBOL_GPL(iocb_bio_iopoll);

void update_io_ticks(struct block_device *part, unsigned long now, bool end)
{
	unsigned long stamp;
again:
	stamp = READ_ONCE(part->bd_stamp);
	if (unlikely(time_after(now, stamp))) {
		if (likely(cmpxchg(&part->bd_stamp, stamp, now) == stamp))
			__part_stat_add(part, io_ticks, end ? now - stamp : 1);
	}
	if (part->bd_partno) {
		part = bdev_whole(part);
		goto again;
	}
}

unsigned long bdev_start_io_acct(struct block_device *bdev,
				 unsigned int sectors, unsigned int op,
				 unsigned long start_time)
{
	const int sgrp = op_stat_group(op);

	part_stat_lock();
	update_io_ticks(bdev, start_time, false);
	part_stat_inc(bdev, ios[sgrp]);
	part_stat_add(bdev, sectors[sgrp], sectors);
	part_stat_local_inc(bdev, in_flight[op_is_write(op)]);
	part_stat_unlock();

	return start_time;
}
EXPORT_SYMBOL(bdev_start_io_acct);

/**
 * bio_start_io_acct_time - start I/O accounting for bio based drivers
 * @bio:	bio to start account for
 * @start_time:	start time that should be passed back to bio_end_io_acct().
 */
void bio_start_io_acct_time(struct bio *bio, unsigned long start_time)
{
	bdev_start_io_acct(bio->bi_bdev, bio_sectors(bio),
			   bio_op(bio), start_time);
}
EXPORT_SYMBOL_GPL(bio_start_io_acct_time);

/**
 * bio_start_io_acct - start I/O accounting for bio based drivers
 * @bio:	bio to start account for
 *
 * Returns the start time that should be passed back to bio_end_io_acct().
 */
unsigned long bio_start_io_acct(struct bio *bio)
{
	return bdev_start_io_acct(bio->bi_bdev, bio_sectors(bio),
				  bio_op(bio), jiffies);
}
EXPORT_SYMBOL_GPL(bio_start_io_acct);

void bdev_end_io_acct(struct block_device *bdev, unsigned int op,
		      unsigned long start_time)
{
	const int sgrp = op_stat_group(op);
	unsigned long now = READ_ONCE(jiffies);
	unsigned long duration = now - start_time;

	part_stat_lock();
	update_io_ticks(bdev, now, true);
	part_stat_add(bdev, nsecs[sgrp], jiffies_to_nsecs(duration));
	part_stat_local_dec(bdev, in_flight[op_is_write(op)]);
	part_stat_unlock();
}
EXPORT_SYMBOL(bdev_end_io_acct);

void bio_end_io_acct_remapped(struct bio *bio, unsigned long start_time,
			      struct block_device *orig_bdev)
{
	bdev_end_io_acct(orig_bdev, bio_op(bio), start_time);
}
EXPORT_SYMBOL_GPL(bio_end_io_acct_remapped);

/**
 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
 * @q : the queue of the device being checked
 *
 * Description:
 *    Check if underlying low-level drivers of a device are busy.
 *    If the drivers want to export their busy state, they must set own
 *    exporting function using blk_queue_lld_busy() first.
 *
 *    Basically, this function is used only by request stacking drivers
 *    to stop dispatching requests to underlying devices when underlying
 *    devices are busy.  This behavior helps more I/O merging on the queue
 *    of the request stacking driver and prevents I/O throughput regression
 *    on burst I/O load.
 *
 * Return:
 *    0 - Not busy (The request stacking driver should dispatch request)
 *    1 - Busy (The request stacking driver should stop dispatching request)
 */
int blk_lld_busy(struct request_queue *q)
{
	if (queue_is_mq(q) && q->mq_ops->busy)
		return q->mq_ops->busy(q);

	return 0;
}
EXPORT_SYMBOL_GPL(blk_lld_busy);

int kblockd_schedule_work(struct work_struct *work)
{
	return queue_work(kblockd_workqueue, work);
}
EXPORT_SYMBOL(kblockd_schedule_work);

int kblockd_mod_delayed_work_on(int cpu, struct delayed_work *dwork,
				unsigned long delay)
{
	return mod_delayed_work_on(cpu, kblockd_workqueue, dwork, delay);
}
EXPORT_SYMBOL(kblockd_mod_delayed_work_on);

void blk_start_plug_nr_ios(struct blk_plug *plug, unsigned short nr_ios)
{
	struct task_struct *tsk = current;

	/*
	 * If this is a nested plug, don't actually assign it.
	 */
	if (tsk->plug)
		return;

	plug->mq_list = NULL;
	plug->cached_rq = NULL;
	plug->nr_ios = min_t(unsigned short, nr_ios, BLK_MAX_REQUEST_COUNT);
	plug->rq_count = 0;
	plug->multiple_queues = false;
	plug->has_elevator = false;
	plug->nowait = false;
	INIT_LIST_HEAD(&plug->cb_list);

	/*
	 * Store ordering should not be needed here, since a potential
	 * preempt will imply a full memory barrier
	 */
	tsk->plug = plug;
}

/**
 * blk_start_plug - initialize blk_plug and track it inside the task_struct
 * @plug:	The &struct blk_plug that needs to be initialized
 *
 * Description:
 *   blk_start_plug() indicates to the block layer an intent by the caller
 *   to submit multiple I/O requests in a batch.  The block layer may use
 *   this hint to defer submitting I/Os from the caller until blk_finish_plug()
 *   is called.  However, the block layer may choose to submit requests
 *   before a call to blk_finish_plug() if the number of queued I/Os
 *   exceeds %BLK_MAX_REQUEST_COUNT, or if the size of the I/O is larger than
 *   %BLK_PLUG_FLUSH_SIZE.  The queued I/Os may also be submitted early if
 *   the task schedules (see below).
 *
 *   Tracking blk_plug inside the task_struct will help with auto-flushing the
 *   pending I/O should the task end up blocking between blk_start_plug() and
 *   blk_finish_plug(). This is important from a performance perspective, but
 *   also ensures that we don't deadlock. For instance, if the task is blocking
 *   for a memory allocation, memory reclaim could end up wanting to free a
 *   page belonging to that request that is currently residing in our private
 *   plug. By flushing the pending I/O when the process goes to sleep, we avoid
 *   this kind of deadlock.
 */
void blk_start_plug(struct blk_plug *plug)
{
	blk_start_plug_nr_ios(plug, 1);
}
EXPORT_SYMBOL(blk_start_plug);

static void flush_plug_callbacks(struct blk_plug *plug, bool from_schedule)
{
	LIST_HEAD(callbacks);

	while (!list_empty(&plug->cb_list)) {
		list_splice_init(&plug->cb_list, &callbacks);

		while (!list_empty(&callbacks)) {
			struct blk_plug_cb *cb = list_first_entry(&callbacks,
							  struct blk_plug_cb,
							  list);
			list_del(&cb->list);
			cb->callback(cb, from_schedule);
		}
	}
}

struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug, void *data,
				      int size)
{
	struct blk_plug *plug = current->plug;
	struct blk_plug_cb *cb;

	if (!plug)
		return NULL;

	list_for_each_entry(cb, &plug->cb_list, list)
		if (cb->callback == unplug && cb->data == data)
			return cb;

	/* Not currently on the callback list */
	BUG_ON(size < sizeof(*cb));
	cb = kzalloc(size, GFP_ATOMIC);
	if (cb) {
		cb->data = data;
		cb->callback = unplug;
		list_add(&cb->list, &plug->cb_list);
	}
	return cb;
}
EXPORT_SYMBOL(blk_check_plugged);

void __blk_flush_plug(struct blk_plug *plug, bool from_schedule)
{
	if (!list_empty(&plug->cb_list))
		flush_plug_callbacks(plug, from_schedule);
	if (!rq_list_empty(plug->mq_list))
		blk_mq_flush_plug_list(plug, from_schedule);
	/*
	 * Unconditionally flush out cached requests, even if the unplug
	 * event came from schedule. Since we know hold references to the
	 * queue for cached requests, we don't want a blocked task holding
	 * up a queue freeze/quiesce event.
	 */
	if (unlikely(!rq_list_empty(plug->cached_rq)))
		blk_mq_free_plug_rqs(plug);
}

/**
 * blk_finish_plug - mark the end of a batch of submitted I/O
 * @plug:	The &struct blk_plug passed to blk_start_plug()
 *
 * Description:
 * Indicate that a batch of I/O submissions is complete.  This function
 * must be paired with an initial call to blk_start_plug().  The intent
 * is to allow the block layer to optimize I/O submission.  See the
 * documentation for blk_start_plug() for more information.
 */
void blk_finish_plug(struct blk_plug *plug)
{
	if (plug == current->plug) {
		__blk_flush_plug(plug, false);
		current->plug = NULL;
	}
}
EXPORT_SYMBOL(blk_finish_plug);

void blk_io_schedule(void)
{
	/* Prevent hang_check timer from firing at us during very long I/O */
	unsigned long timeout = sysctl_hung_task_timeout_secs * HZ / 2;

	if (timeout)
		io_schedule_timeout(timeout);
	else
		io_schedule();
}
EXPORT_SYMBOL_GPL(blk_io_schedule);

int __init blk_dev_init(void)
{
	BUILD_BUG_ON(REQ_OP_LAST >= (1 << REQ_OP_BITS));
	BUILD_BUG_ON(REQ_OP_BITS + REQ_FLAG_BITS > 8 *
			sizeof_field(struct request, cmd_flags));
	BUILD_BUG_ON(REQ_OP_BITS + REQ_FLAG_BITS > 8 *
			sizeof_field(struct bio, bi_opf));
	BUILD_BUG_ON(ALIGN(offsetof(struct request_queue, srcu),
			   __alignof__(struct request_queue)) !=
		     sizeof(struct request_queue));

	/* used for unplugging and affects IO latency/throughput - HIGHPRI */
	kblockd_workqueue = alloc_workqueue("kblockd",
					    WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
	if (!kblockd_workqueue)
		panic("Failed to create kblockd\n");

	blk_requestq_cachep = kmem_cache_create("request_queue",
			sizeof(struct request_queue), 0, SLAB_PANIC, NULL);

	blk_requestq_srcu_cachep = kmem_cache_create("request_queue_srcu",
			sizeof(struct request_queue) +
			sizeof(struct srcu_struct), 0, SLAB_PANIC, NULL);

	blk_debugfs_root = debugfs_create_dir("block", NULL);

	return 0;
}