1 // SPDX-License-Identifier: GPL-2.0
2 /*
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>
8  *	-  July2000
9  * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001
10  */
11 
12 /*
13  * This handles all read/write requests to block devices
14  */
15 #include <linux/kernel.h>
16 #include <linux/module.h>
17 #include <linux/bio.h>
18 #include <linux/blkdev.h>
19 #include <linux/blk-pm.h>
20 #include <linux/blk-integrity.h>
21 #include <linux/highmem.h>
22 #include <linux/mm.h>
23 #include <linux/pagemap.h>
24 #include <linux/kernel_stat.h>
25 #include <linux/string.h>
26 #include <linux/init.h>
27 #include <linux/completion.h>
28 #include <linux/slab.h>
29 #include <linux/swap.h>
30 #include <linux/writeback.h>
31 #include <linux/task_io_accounting_ops.h>
32 #include <linux/fault-inject.h>
33 #include <linux/list_sort.h>
34 #include <linux/delay.h>
35 #include <linux/ratelimit.h>
36 #include <linux/pm_runtime.h>
37 #include <linux/t10-pi.h>
38 #include <linux/debugfs.h>
39 #include <linux/bpf.h>
40 #include <linux/part_stat.h>
41 #include <linux/sched/sysctl.h>
42 #include <linux/blk-crypto.h>
43 
44 #define CREATE_TRACE_POINTS
45 #include <trace/events/block.h>
46 
47 #include "blk.h"
48 #include "blk-mq-sched.h"
49 #include "blk-pm.h"
50 #include "blk-cgroup.h"
51 #include "blk-throttle.h"
52 
53 struct dentry *blk_debugfs_root;
54 
55 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
56 EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
57 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
58 EXPORT_TRACEPOINT_SYMBOL_GPL(block_split);
59 EXPORT_TRACEPOINT_SYMBOL_GPL(block_unplug);
60 EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_insert);
61 
62 DEFINE_IDA(blk_queue_ida);
63 
64 /*
65  * For queue allocation
66  */
67 struct kmem_cache *blk_requestq_cachep;
68 struct kmem_cache *blk_requestq_srcu_cachep;
69 
70 /*
71  * Controlling structure to kblockd
72  */
73 static struct workqueue_struct *kblockd_workqueue;
74 
75 /**
76  * blk_queue_flag_set - atomically set a queue flag
77  * @flag: flag to be set
78  * @q: request queue
79  */
blk_queue_flag_set(unsigned int flag,struct request_queue * q)80 void blk_queue_flag_set(unsigned int flag, struct request_queue *q)
81 {
82 	set_bit(flag, &q->queue_flags);
83 }
84 EXPORT_SYMBOL(blk_queue_flag_set);
85 
86 /**
87  * blk_queue_flag_clear - atomically clear a queue flag
88  * @flag: flag to be cleared
89  * @q: request queue
90  */
blk_queue_flag_clear(unsigned int flag,struct request_queue * q)91 void blk_queue_flag_clear(unsigned int flag, struct request_queue *q)
92 {
93 	clear_bit(flag, &q->queue_flags);
94 }
95 EXPORT_SYMBOL(blk_queue_flag_clear);
96 
97 /**
98  * blk_queue_flag_test_and_set - atomically test and set a queue flag
99  * @flag: flag to be set
100  * @q: request queue
101  *
102  * Returns the previous value of @flag - 0 if the flag was not set and 1 if
103  * the flag was already set.
104  */
blk_queue_flag_test_and_set(unsigned int flag,struct request_queue * q)105 bool blk_queue_flag_test_and_set(unsigned int flag, struct request_queue *q)
106 {
107 	return test_and_set_bit(flag, &q->queue_flags);
108 }
109 EXPORT_SYMBOL_GPL(blk_queue_flag_test_and_set);
110 
111 #define REQ_OP_NAME(name) [REQ_OP_##name] = #name
112 static const char *const blk_op_name[] = {
113 	REQ_OP_NAME(READ),
114 	REQ_OP_NAME(WRITE),
115 	REQ_OP_NAME(FLUSH),
116 	REQ_OP_NAME(DISCARD),
117 	REQ_OP_NAME(SECURE_ERASE),
118 	REQ_OP_NAME(ZONE_RESET),
119 	REQ_OP_NAME(ZONE_RESET_ALL),
120 	REQ_OP_NAME(ZONE_OPEN),
121 	REQ_OP_NAME(ZONE_CLOSE),
122 	REQ_OP_NAME(ZONE_FINISH),
123 	REQ_OP_NAME(ZONE_APPEND),
124 	REQ_OP_NAME(WRITE_ZEROES),
125 	REQ_OP_NAME(DRV_IN),
126 	REQ_OP_NAME(DRV_OUT),
127 };
128 #undef REQ_OP_NAME
129 
130 /**
131  * blk_op_str - Return string XXX in the REQ_OP_XXX.
132  * @op: REQ_OP_XXX.
133  *
134  * Description: Centralize block layer function to convert REQ_OP_XXX into
135  * string format. Useful in the debugging and tracing bio or request. For
136  * invalid REQ_OP_XXX it returns string "UNKNOWN".
137  */
blk_op_str(enum req_op op)138 inline const char *blk_op_str(enum req_op op)
139 {
140 	const char *op_str = "UNKNOWN";
141 
142 	if (op < ARRAY_SIZE(blk_op_name) && blk_op_name[op])
143 		op_str = blk_op_name[op];
144 
145 	return op_str;
146 }
147 EXPORT_SYMBOL_GPL(blk_op_str);
148 
149 static const struct {
150 	int		errno;
151 	const char	*name;
152 } blk_errors[] = {
153 	[BLK_STS_OK]		= { 0,		"" },
154 	[BLK_STS_NOTSUPP]	= { -EOPNOTSUPP, "operation not supported" },
155 	[BLK_STS_TIMEOUT]	= { -ETIMEDOUT,	"timeout" },
156 	[BLK_STS_NOSPC]		= { -ENOSPC,	"critical space allocation" },
157 	[BLK_STS_TRANSPORT]	= { -ENOLINK,	"recoverable transport" },
158 	[BLK_STS_TARGET]	= { -EREMOTEIO,	"critical target" },
159 	[BLK_STS_NEXUS]		= { -EBADE,	"critical nexus" },
160 	[BLK_STS_MEDIUM]	= { -ENODATA,	"critical medium" },
161 	[BLK_STS_PROTECTION]	= { -EILSEQ,	"protection" },
162 	[BLK_STS_RESOURCE]	= { -ENOMEM,	"kernel resource" },
163 	[BLK_STS_DEV_RESOURCE]	= { -EBUSY,	"device resource" },
164 	[BLK_STS_AGAIN]		= { -EAGAIN,	"nonblocking retry" },
165 	[BLK_STS_OFFLINE]	= { -ENODEV,	"device offline" },
166 
167 	/* device mapper special case, should not leak out: */
168 	[BLK_STS_DM_REQUEUE]	= { -EREMCHG, "dm internal retry" },
169 
170 	/* zone device specific errors */
171 	[BLK_STS_ZONE_OPEN_RESOURCE]	= { -ETOOMANYREFS, "open zones exceeded" },
172 	[BLK_STS_ZONE_ACTIVE_RESOURCE]	= { -EOVERFLOW, "active zones exceeded" },
173 
174 	/* everything else not covered above: */
175 	[BLK_STS_IOERR]		= { -EIO,	"I/O" },
176 };
177 
errno_to_blk_status(int errno)178 blk_status_t errno_to_blk_status(int errno)
179 {
180 	int i;
181 
182 	for (i = 0; i < ARRAY_SIZE(blk_errors); i++) {
183 		if (blk_errors[i].errno == errno)
184 			return (__force blk_status_t)i;
185 	}
186 
187 	return BLK_STS_IOERR;
188 }
189 EXPORT_SYMBOL_GPL(errno_to_blk_status);
190 
blk_status_to_errno(blk_status_t status)191 int blk_status_to_errno(blk_status_t status)
192 {
193 	int idx = (__force int)status;
194 
195 	if (WARN_ON_ONCE(idx >= ARRAY_SIZE(blk_errors)))
196 		return -EIO;
197 	return blk_errors[idx].errno;
198 }
199 EXPORT_SYMBOL_GPL(blk_status_to_errno);
200 
blk_status_to_str(blk_status_t status)201 const char *blk_status_to_str(blk_status_t status)
202 {
203 	int idx = (__force int)status;
204 
205 	if (WARN_ON_ONCE(idx >= ARRAY_SIZE(blk_errors)))
206 		return "<null>";
207 	return blk_errors[idx].name;
208 }
209 
210 /**
211  * blk_sync_queue - cancel any pending callbacks on a queue
212  * @q: the queue
213  *
214  * Description:
215  *     The block layer may perform asynchronous callback activity
216  *     on a queue, such as calling the unplug function after a timeout.
217  *     A block device may call blk_sync_queue to ensure that any
218  *     such activity is cancelled, thus allowing it to release resources
219  *     that the callbacks might use. The caller must already have made sure
220  *     that its ->submit_bio will not re-add plugging prior to calling
221  *     this function.
222  *
223  *     This function does not cancel any asynchronous activity arising
224  *     out of elevator or throttling code. That would require elevator_exit()
225  *     and blkcg_exit_queue() to be called with queue lock initialized.
226  *
227  */
blk_sync_queue(struct request_queue * q)228 void blk_sync_queue(struct request_queue *q)
229 {
230 	del_timer_sync(&q->timeout);
231 	cancel_work_sync(&q->timeout_work);
232 }
233 EXPORT_SYMBOL(blk_sync_queue);
234 
235 /**
236  * blk_set_pm_only - increment pm_only counter
237  * @q: request queue pointer
238  */
blk_set_pm_only(struct request_queue * q)239 void blk_set_pm_only(struct request_queue *q)
240 {
241 	atomic_inc(&q->pm_only);
242 }
243 EXPORT_SYMBOL_GPL(blk_set_pm_only);
244 
blk_clear_pm_only(struct request_queue * q)245 void blk_clear_pm_only(struct request_queue *q)
246 {
247 	int pm_only;
248 
249 	pm_only = atomic_dec_return(&q->pm_only);
250 	WARN_ON_ONCE(pm_only < 0);
251 	if (pm_only == 0)
252 		wake_up_all(&q->mq_freeze_wq);
253 }
254 EXPORT_SYMBOL_GPL(blk_clear_pm_only);
255 
256 /**
257  * blk_put_queue - decrement the request_queue refcount
258  * @q: the request_queue structure to decrement the refcount for
259  *
260  * Decrements the refcount of the request_queue kobject. When this reaches 0
261  * we'll have blk_release_queue() called.
262  *
263  * Context: Any context, but the last reference must not be dropped from
264  *          atomic context.
265  */
blk_put_queue(struct request_queue * q)266 void blk_put_queue(struct request_queue *q)
267 {
268 	kobject_put(&q->kobj);
269 }
270 EXPORT_SYMBOL(blk_put_queue);
271 
blk_queue_start_drain(struct request_queue * q)272 void blk_queue_start_drain(struct request_queue *q)
273 {
274 	/*
275 	 * When queue DYING flag is set, we need to block new req
276 	 * entering queue, so we call blk_freeze_queue_start() to
277 	 * prevent I/O from crossing blk_queue_enter().
278 	 */
279 	blk_freeze_queue_start(q);
280 	if (queue_is_mq(q))
281 		blk_mq_wake_waiters(q);
282 	/* Make blk_queue_enter() reexamine the DYING flag. */
283 	wake_up_all(&q->mq_freeze_wq);
284 }
285 
286 /**
287  * blk_queue_enter() - try to increase q->q_usage_counter
288  * @q: request queue pointer
289  * @flags: BLK_MQ_REQ_NOWAIT and/or BLK_MQ_REQ_PM
290  */
blk_queue_enter(struct request_queue * q,blk_mq_req_flags_t flags)291 int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
292 {
293 	const bool pm = flags & BLK_MQ_REQ_PM;
294 
295 	while (!blk_try_enter_queue(q, pm)) {
296 		if (flags & BLK_MQ_REQ_NOWAIT)
297 			return -EAGAIN;
298 
299 		/*
300 		 * read pair of barrier in blk_freeze_queue_start(), we need to
301 		 * order reading __PERCPU_REF_DEAD flag of .q_usage_counter and
302 		 * reading .mq_freeze_depth or queue dying flag, otherwise the
303 		 * following wait may never return if the two reads are
304 		 * reordered.
305 		 */
306 		smp_rmb();
307 		wait_event(q->mq_freeze_wq,
308 			   (!q->mq_freeze_depth &&
309 			    blk_pm_resume_queue(pm, q)) ||
310 			   blk_queue_dying(q));
311 		if (blk_queue_dying(q))
312 			return -ENODEV;
313 	}
314 
315 	return 0;
316 }
317 
__bio_queue_enter(struct request_queue * q,struct bio * bio)318 int __bio_queue_enter(struct request_queue *q, struct bio *bio)
319 {
320 	while (!blk_try_enter_queue(q, false)) {
321 		struct gendisk *disk = bio->bi_bdev->bd_disk;
322 
323 		if (bio->bi_opf & REQ_NOWAIT) {
324 			if (test_bit(GD_DEAD, &disk->state))
325 				goto dead;
326 			bio_wouldblock_error(bio);
327 			return -EAGAIN;
328 		}
329 
330 		/*
331 		 * read pair of barrier in blk_freeze_queue_start(), we need to
332 		 * order reading __PERCPU_REF_DEAD flag of .q_usage_counter and
333 		 * reading .mq_freeze_depth or queue dying flag, otherwise the
334 		 * following wait may never return if the two reads are
335 		 * reordered.
336 		 */
337 		smp_rmb();
338 		wait_event(q->mq_freeze_wq,
339 			   (!q->mq_freeze_depth &&
340 			    blk_pm_resume_queue(false, q)) ||
341 			   test_bit(GD_DEAD, &disk->state));
342 		if (test_bit(GD_DEAD, &disk->state))
343 			goto dead;
344 	}
345 
346 	return 0;
347 dead:
348 	bio_io_error(bio);
349 	return -ENODEV;
350 }
351 
blk_queue_exit(struct request_queue * q)352 void blk_queue_exit(struct request_queue *q)
353 {
354 	percpu_ref_put(&q->q_usage_counter);
355 }
356 
blk_queue_usage_counter_release(struct percpu_ref * ref)357 static void blk_queue_usage_counter_release(struct percpu_ref *ref)
358 {
359 	struct request_queue *q =
360 		container_of(ref, struct request_queue, q_usage_counter);
361 
362 	wake_up_all(&q->mq_freeze_wq);
363 }
364 
blk_rq_timed_out_timer(struct timer_list * t)365 static void blk_rq_timed_out_timer(struct timer_list *t)
366 {
367 	struct request_queue *q = from_timer(q, t, timeout);
368 
369 	kblockd_schedule_work(&q->timeout_work);
370 }
371 
blk_timeout_work(struct work_struct * work)372 static void blk_timeout_work(struct work_struct *work)
373 {
374 }
375 
blk_alloc_queue(int node_id,bool alloc_srcu)376 struct request_queue *blk_alloc_queue(int node_id, bool alloc_srcu)
377 {
378 	struct request_queue *q;
379 
380 	q = kmem_cache_alloc_node(blk_get_queue_kmem_cache(alloc_srcu),
381 			GFP_KERNEL | __GFP_ZERO, node_id);
382 	if (!q)
383 		return NULL;
384 
385 	if (alloc_srcu) {
386 		blk_queue_flag_set(QUEUE_FLAG_HAS_SRCU, q);
387 		if (init_srcu_struct(q->srcu) != 0)
388 			goto fail_q;
389 	}
390 
391 	q->last_merge = NULL;
392 
393 	q->id = ida_alloc(&blk_queue_ida, GFP_KERNEL);
394 	if (q->id < 0)
395 		goto fail_srcu;
396 
397 	q->stats = blk_alloc_queue_stats();
398 	if (!q->stats)
399 		goto fail_id;
400 
401 	q->node = node_id;
402 
403 	atomic_set(&q->nr_active_requests_shared_tags, 0);
404 
405 	timer_setup(&q->timeout, blk_rq_timed_out_timer, 0);
406 	INIT_WORK(&q->timeout_work, blk_timeout_work);
407 	INIT_LIST_HEAD(&q->icq_list);
408 
409 	kobject_init(&q->kobj, &blk_queue_ktype);
410 
411 	mutex_init(&q->debugfs_mutex);
412 	mutex_init(&q->sysfs_lock);
413 	mutex_init(&q->sysfs_dir_lock);
414 	spin_lock_init(&q->queue_lock);
415 
416 	init_waitqueue_head(&q->mq_freeze_wq);
417 	mutex_init(&q->mq_freeze_lock);
418 
419 	/*
420 	 * Init percpu_ref in atomic mode so that it's faster to shutdown.
421 	 * See blk_register_queue() for details.
422 	 */
423 	if (percpu_ref_init(&q->q_usage_counter,
424 				blk_queue_usage_counter_release,
425 				PERCPU_REF_INIT_ATOMIC, GFP_KERNEL))
426 		goto fail_stats;
427 
428 	blk_set_default_limits(&q->limits);
429 	q->nr_requests = BLKDEV_DEFAULT_RQ;
430 
431 	return q;
432 
433 fail_stats:
434 	blk_free_queue_stats(q->stats);
435 fail_id:
436 	ida_free(&blk_queue_ida, q->id);
437 fail_srcu:
438 	if (alloc_srcu)
439 		cleanup_srcu_struct(q->srcu);
440 fail_q:
441 	kmem_cache_free(blk_get_queue_kmem_cache(alloc_srcu), q);
442 	return NULL;
443 }
444 
445 /**
446  * blk_get_queue - increment the request_queue refcount
447  * @q: the request_queue structure to increment the refcount for
448  *
449  * Increment the refcount of the request_queue kobject.
450  *
451  * Context: Any context.
452  */
blk_get_queue(struct request_queue * q)453 bool blk_get_queue(struct request_queue *q)
454 {
455 	if (unlikely(blk_queue_dying(q)))
456 		return false;
457 	kobject_get(&q->kobj);
458 	return true;
459 }
460 EXPORT_SYMBOL(blk_get_queue);
461 
462 #ifdef CONFIG_FAIL_MAKE_REQUEST
463 
464 static DECLARE_FAULT_ATTR(fail_make_request);
465 
setup_fail_make_request(char * str)466 static int __init setup_fail_make_request(char *str)
467 {
468 	return setup_fault_attr(&fail_make_request, str);
469 }
470 __setup("fail_make_request=", setup_fail_make_request);
471 
should_fail_request(struct block_device * part,unsigned int bytes)472 bool should_fail_request(struct block_device *part, unsigned int bytes)
473 {
474 	return part->bd_make_it_fail && should_fail(&fail_make_request, bytes);
475 }
476 
fail_make_request_debugfs(void)477 static int __init fail_make_request_debugfs(void)
478 {
479 	struct dentry *dir = fault_create_debugfs_attr("fail_make_request",
480 						NULL, &fail_make_request);
481 
482 	return PTR_ERR_OR_ZERO(dir);
483 }
484 
485 late_initcall(fail_make_request_debugfs);
486 #endif /* CONFIG_FAIL_MAKE_REQUEST */
487 
bio_check_ro(struct bio * bio)488 static inline void bio_check_ro(struct bio *bio)
489 {
490 	if (op_is_write(bio_op(bio)) && bdev_read_only(bio->bi_bdev)) {
491 		if (op_is_flush(bio->bi_opf) && !bio_sectors(bio))
492 			return;
493 		pr_warn("Trying to write to read-only block-device %pg\n",
494 			bio->bi_bdev);
495 		/* Older lvm-tools actually trigger this */
496 	}
497 }
498 
should_fail_bio(struct bio * bio)499 static noinline int should_fail_bio(struct bio *bio)
500 {
501 	if (should_fail_request(bdev_whole(bio->bi_bdev), bio->bi_iter.bi_size))
502 		return -EIO;
503 	return 0;
504 }
505 ALLOW_ERROR_INJECTION(should_fail_bio, ERRNO);
506 
507 /*
508  * Check whether this bio extends beyond the end of the device or partition.
509  * This may well happen - the kernel calls bread() without checking the size of
510  * the device, e.g., when mounting a file system.
511  */
bio_check_eod(struct bio * bio)512 static inline int bio_check_eod(struct bio *bio)
513 {
514 	sector_t maxsector = bdev_nr_sectors(bio->bi_bdev);
515 	unsigned int nr_sectors = bio_sectors(bio);
516 
517 	if (nr_sectors && maxsector &&
518 	    (nr_sectors > maxsector ||
519 	     bio->bi_iter.bi_sector > maxsector - nr_sectors)) {
520 		pr_info_ratelimited("%s: attempt to access beyond end of device\n"
521 				    "%pg: rw=%d, sector=%llu, nr_sectors = %u limit=%llu\n",
522 				    current->comm, bio->bi_bdev, bio->bi_opf,
523 				    bio->bi_iter.bi_sector, nr_sectors, maxsector);
524 		return -EIO;
525 	}
526 	return 0;
527 }
528 
529 /*
530  * Remap block n of partition p to block n+start(p) of the disk.
531  */
blk_partition_remap(struct bio * bio)532 static int blk_partition_remap(struct bio *bio)
533 {
534 	struct block_device *p = bio->bi_bdev;
535 
536 	if (unlikely(should_fail_request(p, bio->bi_iter.bi_size)))
537 		return -EIO;
538 	if (bio_sectors(bio)) {
539 		bio->bi_iter.bi_sector += p->bd_start_sect;
540 		trace_block_bio_remap(bio, p->bd_dev,
541 				      bio->bi_iter.bi_sector -
542 				      p->bd_start_sect);
543 	}
544 	bio_set_flag(bio, BIO_REMAPPED);
545 	return 0;
546 }
547 
548 /*
549  * Check write append to a zoned block device.
550  */
blk_check_zone_append(struct request_queue * q,struct bio * bio)551 static inline blk_status_t blk_check_zone_append(struct request_queue *q,
552 						 struct bio *bio)
553 {
554 	int nr_sectors = bio_sectors(bio);
555 
556 	/* Only applicable to zoned block devices */
557 	if (!bdev_is_zoned(bio->bi_bdev))
558 		return BLK_STS_NOTSUPP;
559 
560 	/* The bio sector must point to the start of a sequential zone */
561 	if (bio->bi_iter.bi_sector & (bdev_zone_sectors(bio->bi_bdev) - 1) ||
562 	    !bio_zone_is_seq(bio))
563 		return BLK_STS_IOERR;
564 
565 	/*
566 	 * Not allowed to cross zone boundaries. Otherwise, the BIO will be
567 	 * split and could result in non-contiguous sectors being written in
568 	 * different zones.
569 	 */
570 	if (nr_sectors > q->limits.chunk_sectors)
571 		return BLK_STS_IOERR;
572 
573 	/* Make sure the BIO is small enough and will not get split */
574 	if (nr_sectors > q->limits.max_zone_append_sectors)
575 		return BLK_STS_IOERR;
576 
577 	bio->bi_opf |= REQ_NOMERGE;
578 
579 	return BLK_STS_OK;
580 }
581 
__submit_bio(struct bio * bio)582 static void __submit_bio(struct bio *bio)
583 {
584 	struct gendisk *disk = bio->bi_bdev->bd_disk;
585 
586 	if (unlikely(!blk_crypto_bio_prep(&bio)))
587 		return;
588 
589 	if (!disk->fops->submit_bio) {
590 		blk_mq_submit_bio(bio);
591 	} else if (likely(bio_queue_enter(bio) == 0)) {
592 		disk->fops->submit_bio(bio);
593 		blk_queue_exit(disk->queue);
594 	}
595 }
596 
597 /*
598  * The loop in this function may be a bit non-obvious, and so deserves some
599  * explanation:
600  *
601  *  - Before entering the loop, bio->bi_next is NULL (as all callers ensure
602  *    that), so we have a list with a single bio.
603  *  - We pretend that we have just taken it off a longer list, so we assign
604  *    bio_list to a pointer to the bio_list_on_stack, thus initialising the
605  *    bio_list of new bios to be added.  ->submit_bio() may indeed add some more
606  *    bios through a recursive call to submit_bio_noacct.  If it did, we find a
607  *    non-NULL value in bio_list and re-enter the loop from the top.
608  *  - In this case we really did just take the bio of the top of the list (no
609  *    pretending) and so remove it from bio_list, and call into ->submit_bio()
610  *    again.
611  *
612  * bio_list_on_stack[0] contains bios submitted by the current ->submit_bio.
613  * bio_list_on_stack[1] contains bios that were submitted before the current
614  *	->submit_bio, but that haven't been processed yet.
615  */
__submit_bio_noacct(struct bio * bio)616 static void __submit_bio_noacct(struct bio *bio)
617 {
618 	struct bio_list bio_list_on_stack[2];
619 
620 	BUG_ON(bio->bi_next);
621 
622 	bio_list_init(&bio_list_on_stack[0]);
623 	current->bio_list = bio_list_on_stack;
624 
625 	do {
626 		struct request_queue *q = bdev_get_queue(bio->bi_bdev);
627 		struct bio_list lower, same;
628 
629 		/*
630 		 * Create a fresh bio_list for all subordinate requests.
631 		 */
632 		bio_list_on_stack[1] = bio_list_on_stack[0];
633 		bio_list_init(&bio_list_on_stack[0]);
634 
635 		__submit_bio(bio);
636 
637 		/*
638 		 * Sort new bios into those for a lower level and those for the
639 		 * same level.
640 		 */
641 		bio_list_init(&lower);
642 		bio_list_init(&same);
643 		while ((bio = bio_list_pop(&bio_list_on_stack[0])) != NULL)
644 			if (q == bdev_get_queue(bio->bi_bdev))
645 				bio_list_add(&same, bio);
646 			else
647 				bio_list_add(&lower, bio);
648 
649 		/*
650 		 * Now assemble so we handle the lowest level first.
651 		 */
652 		bio_list_merge(&bio_list_on_stack[0], &lower);
653 		bio_list_merge(&bio_list_on_stack[0], &same);
654 		bio_list_merge(&bio_list_on_stack[0], &bio_list_on_stack[1]);
655 	} while ((bio = bio_list_pop(&bio_list_on_stack[0])));
656 
657 	current->bio_list = NULL;
658 }
659 
__submit_bio_noacct_mq(struct bio * bio)660 static void __submit_bio_noacct_mq(struct bio *bio)
661 {
662 	struct bio_list bio_list[2] = { };
663 
664 	current->bio_list = bio_list;
665 
666 	do {
667 		__submit_bio(bio);
668 	} while ((bio = bio_list_pop(&bio_list[0])));
669 
670 	current->bio_list = NULL;
671 }
672 
submit_bio_noacct_nocheck(struct bio * bio)673 void submit_bio_noacct_nocheck(struct bio *bio)
674 {
675 	/*
676 	 * We only want one ->submit_bio to be active at a time, else stack
677 	 * usage with stacked devices could be a problem.  Use current->bio_list
678 	 * to collect a list of requests submited by a ->submit_bio method while
679 	 * it is active, and then process them after it returned.
680 	 */
681 	if (current->bio_list)
682 		bio_list_add(&current->bio_list[0], bio);
683 	else if (!bio->bi_bdev->bd_disk->fops->submit_bio)
684 		__submit_bio_noacct_mq(bio);
685 	else
686 		__submit_bio_noacct(bio);
687 }
688 
689 /**
690  * submit_bio_noacct - re-submit a bio to the block device layer for I/O
691  * @bio:  The bio describing the location in memory and on the device.
692  *
693  * This is a version of submit_bio() that shall only be used for I/O that is
694  * resubmitted to lower level drivers by stacking block drivers.  All file
695  * systems and other upper level users of the block layer should use
696  * submit_bio() instead.
697  */
submit_bio_noacct(struct bio * bio)698 void submit_bio_noacct(struct bio *bio)
699 {
700 	struct block_device *bdev = bio->bi_bdev;
701 	struct request_queue *q = bdev_get_queue(bdev);
702 	blk_status_t status = BLK_STS_IOERR;
703 	struct blk_plug *plug;
704 
705 	might_sleep();
706 
707 	plug = blk_mq_plug(bio);
708 	if (plug && plug->nowait)
709 		bio->bi_opf |= REQ_NOWAIT;
710 
711 	/*
712 	 * For a REQ_NOWAIT based request, return -EOPNOTSUPP
713 	 * if queue does not support NOWAIT.
714 	 */
715 	if ((bio->bi_opf & REQ_NOWAIT) && !bdev_nowait(bdev))
716 		goto not_supported;
717 
718 	if (should_fail_bio(bio))
719 		goto end_io;
720 	bio_check_ro(bio);
721 	if (!bio_flagged(bio, BIO_REMAPPED)) {
722 		if (unlikely(bio_check_eod(bio)))
723 			goto end_io;
724 		if (bdev->bd_partno && unlikely(blk_partition_remap(bio)))
725 			goto end_io;
726 	}
727 
728 	/*
729 	 * Filter flush bio's early so that bio based drivers without flush
730 	 * support don't have to worry about them.
731 	 */
732 	if (op_is_flush(bio->bi_opf) &&
733 	    !test_bit(QUEUE_FLAG_WC, &q->queue_flags)) {
734 		bio->bi_opf &= ~(REQ_PREFLUSH | REQ_FUA);
735 		if (!bio_sectors(bio)) {
736 			status = BLK_STS_OK;
737 			goto end_io;
738 		}
739 	}
740 
741 	if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
742 		bio_clear_polled(bio);
743 
744 	switch (bio_op(bio)) {
745 	case REQ_OP_DISCARD:
746 		if (!bdev_max_discard_sectors(bdev))
747 			goto not_supported;
748 		break;
749 	case REQ_OP_SECURE_ERASE:
750 		if (!bdev_max_secure_erase_sectors(bdev))
751 			goto not_supported;
752 		break;
753 	case REQ_OP_ZONE_APPEND:
754 		status = blk_check_zone_append(q, bio);
755 		if (status != BLK_STS_OK)
756 			goto end_io;
757 		break;
758 	case REQ_OP_ZONE_RESET:
759 	case REQ_OP_ZONE_OPEN:
760 	case REQ_OP_ZONE_CLOSE:
761 	case REQ_OP_ZONE_FINISH:
762 		if (!bdev_is_zoned(bio->bi_bdev))
763 			goto not_supported;
764 		break;
765 	case REQ_OP_ZONE_RESET_ALL:
766 		if (!bdev_is_zoned(bio->bi_bdev) || !blk_queue_zone_resetall(q))
767 			goto not_supported;
768 		break;
769 	case REQ_OP_WRITE_ZEROES:
770 		if (!q->limits.max_write_zeroes_sectors)
771 			goto not_supported;
772 		break;
773 	default:
774 		break;
775 	}
776 
777 	if (blk_throtl_bio(bio))
778 		return;
779 
780 	blk_cgroup_bio_start(bio);
781 	blkcg_bio_issue_init(bio);
782 
783 	if (!bio_flagged(bio, BIO_TRACE_COMPLETION)) {
784 		trace_block_bio_queue(bio);
785 		/* Now that enqueuing has been traced, we need to trace
786 		 * completion as well.
787 		 */
788 		bio_set_flag(bio, BIO_TRACE_COMPLETION);
789 	}
790 	submit_bio_noacct_nocheck(bio);
791 	return;
792 
793 not_supported:
794 	status = BLK_STS_NOTSUPP;
795 end_io:
796 	bio->bi_status = status;
797 	bio_endio(bio);
798 }
799 EXPORT_SYMBOL(submit_bio_noacct);
800 
801 /**
802  * submit_bio - submit a bio to the block device layer for I/O
803  * @bio: The &struct bio which describes the I/O
804  *
805  * submit_bio() is used to submit I/O requests to block devices.  It is passed a
806  * fully set up &struct bio that describes the I/O that needs to be done.  The
807  * bio will be send to the device described by the bi_bdev field.
808  *
809  * The success/failure status of the request, along with notification of
810  * completion, is delivered asynchronously through the ->bi_end_io() callback
811  * in @bio.  The bio must NOT be touched by the caller until ->bi_end_io() has
812  * been called.
813  */
submit_bio(struct bio * bio)814 void submit_bio(struct bio *bio)
815 {
816 	if (blkcg_punt_bio_submit(bio))
817 		return;
818 
819 	if (bio_op(bio) == REQ_OP_READ) {
820 		task_io_account_read(bio->bi_iter.bi_size);
821 		count_vm_events(PGPGIN, bio_sectors(bio));
822 	} else if (bio_op(bio) == REQ_OP_WRITE) {
823 		count_vm_events(PGPGOUT, bio_sectors(bio));
824 	}
825 
826 	submit_bio_noacct(bio);
827 }
828 EXPORT_SYMBOL(submit_bio);
829 
830 /**
831  * bio_poll - poll for BIO completions
832  * @bio: bio to poll for
833  * @iob: batches of IO
834  * @flags: BLK_POLL_* flags that control the behavior
835  *
836  * Poll for completions on queue associated with the bio. Returns number of
837  * completed entries found.
838  *
839  * Note: the caller must either be the context that submitted @bio, or
840  * be in a RCU critical section to prevent freeing of @bio.
841  */
bio_poll(struct bio * bio,struct io_comp_batch * iob,unsigned int flags)842 int bio_poll(struct bio *bio, struct io_comp_batch *iob, unsigned int flags)
843 {
844 	struct request_queue *q = bdev_get_queue(bio->bi_bdev);
845 	blk_qc_t cookie = READ_ONCE(bio->bi_cookie);
846 	int ret = 0;
847 
848 	if (cookie == BLK_QC_T_NONE ||
849 	    !test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
850 		return 0;
851 
852 	/*
853 	 * As the requests that require a zone lock are not plugged in the
854 	 * first place, directly accessing the plug instead of using
855 	 * blk_mq_plug() should not have any consequences during flushing for
856 	 * zoned devices.
857 	 */
858 	blk_flush_plug(current->plug, false);
859 
860 	if (bio_queue_enter(bio))
861 		return 0;
862 	if (queue_is_mq(q)) {
863 		ret = blk_mq_poll(q, cookie, iob, flags);
864 	} else {
865 		struct gendisk *disk = q->disk;
866 
867 		if (disk && disk->fops->poll_bio)
868 			ret = disk->fops->poll_bio(bio, iob, flags);
869 	}
870 	blk_queue_exit(q);
871 	return ret;
872 }
873 EXPORT_SYMBOL_GPL(bio_poll);
874 
875 /*
876  * Helper to implement file_operations.iopoll.  Requires the bio to be stored
877  * in iocb->private, and cleared before freeing the bio.
878  */
iocb_bio_iopoll(struct kiocb * kiocb,struct io_comp_batch * iob,unsigned int flags)879 int iocb_bio_iopoll(struct kiocb *kiocb, struct io_comp_batch *iob,
880 		    unsigned int flags)
881 {
882 	struct bio *bio;
883 	int ret = 0;
884 
885 	/*
886 	 * Note: the bio cache only uses SLAB_TYPESAFE_BY_RCU, so bio can
887 	 * point to a freshly allocated bio at this point.  If that happens
888 	 * we have a few cases to consider:
889 	 *
890 	 *  1) the bio is beeing initialized and bi_bdev is NULL.  We can just
891 	 *     simply nothing in this case
892 	 *  2) the bio points to a not poll enabled device.  bio_poll will catch
893 	 *     this and return 0
894 	 *  3) the bio points to a poll capable device, including but not
895 	 *     limited to the one that the original bio pointed to.  In this
896 	 *     case we will call into the actual poll method and poll for I/O,
897 	 *     even if we don't need to, but it won't cause harm either.
898 	 *
899 	 * For cases 2) and 3) above the RCU grace period ensures that bi_bdev
900 	 * is still allocated. Because partitions hold a reference to the whole
901 	 * device bdev and thus disk, the disk is also still valid.  Grabbing
902 	 * a reference to the queue in bio_poll() ensures the hctxs and requests
903 	 * are still valid as well.
904 	 */
905 	rcu_read_lock();
906 	bio = READ_ONCE(kiocb->private);
907 	if (bio && bio->bi_bdev)
908 		ret = bio_poll(bio, iob, flags);
909 	rcu_read_unlock();
910 
911 	return ret;
912 }
913 EXPORT_SYMBOL_GPL(iocb_bio_iopoll);
914 
update_io_ticks(struct block_device * part,unsigned long now,bool end)915 void update_io_ticks(struct block_device *part, unsigned long now, bool end)
916 {
917 	unsigned long stamp;
918 again:
919 	stamp = READ_ONCE(part->bd_stamp);
920 	if (unlikely(time_after(now, stamp))) {
921 		if (likely(try_cmpxchg(&part->bd_stamp, &stamp, now)))
922 			__part_stat_add(part, io_ticks, end ? now - stamp : 1);
923 	}
924 	if (part->bd_partno) {
925 		part = bdev_whole(part);
926 		goto again;
927 	}
928 }
929 
bdev_start_io_acct(struct block_device * bdev,unsigned int sectors,enum req_op op,unsigned long start_time)930 unsigned long bdev_start_io_acct(struct block_device *bdev,
931 				 unsigned int sectors, enum req_op op,
932 				 unsigned long start_time)
933 {
934 	const int sgrp = op_stat_group(op);
935 
936 	part_stat_lock();
937 	update_io_ticks(bdev, start_time, false);
938 	part_stat_inc(bdev, ios[sgrp]);
939 	part_stat_add(bdev, sectors[sgrp], sectors);
940 	part_stat_local_inc(bdev, in_flight[op_is_write(op)]);
941 	part_stat_unlock();
942 
943 	return start_time;
944 }
945 EXPORT_SYMBOL(bdev_start_io_acct);
946 
947 /**
948  * bio_start_io_acct_time - start I/O accounting for bio based drivers
949  * @bio:	bio to start account for
950  * @start_time:	start time that should be passed back to bio_end_io_acct().
951  */
bio_start_io_acct_time(struct bio * bio,unsigned long start_time)952 void bio_start_io_acct_time(struct bio *bio, unsigned long start_time)
953 {
954 	bdev_start_io_acct(bio->bi_bdev, bio_sectors(bio),
955 			   bio_op(bio), start_time);
956 }
957 EXPORT_SYMBOL_GPL(bio_start_io_acct_time);
958 
959 /**
960  * bio_start_io_acct - start I/O accounting for bio based drivers
961  * @bio:	bio to start account for
962  *
963  * Returns the start time that should be passed back to bio_end_io_acct().
964  */
bio_start_io_acct(struct bio * bio)965 unsigned long bio_start_io_acct(struct bio *bio)
966 {
967 	return bdev_start_io_acct(bio->bi_bdev, bio_sectors(bio),
968 				  bio_op(bio), jiffies);
969 }
970 EXPORT_SYMBOL_GPL(bio_start_io_acct);
971 
bdev_end_io_acct(struct block_device * bdev,enum req_op op,unsigned long start_time)972 void bdev_end_io_acct(struct block_device *bdev, enum req_op op,
973 		      unsigned long start_time)
974 {
975 	const int sgrp = op_stat_group(op);
976 	unsigned long now = READ_ONCE(jiffies);
977 	unsigned long duration = now - start_time;
978 
979 	part_stat_lock();
980 	update_io_ticks(bdev, now, true);
981 	part_stat_add(bdev, nsecs[sgrp], jiffies_to_nsecs(duration));
982 	part_stat_local_dec(bdev, in_flight[op_is_write(op)]);
983 	part_stat_unlock();
984 }
985 EXPORT_SYMBOL(bdev_end_io_acct);
986 
bio_end_io_acct_remapped(struct bio * bio,unsigned long start_time,struct block_device * orig_bdev)987 void bio_end_io_acct_remapped(struct bio *bio, unsigned long start_time,
988 			      struct block_device *orig_bdev)
989 {
990 	bdev_end_io_acct(orig_bdev, bio_op(bio), start_time);
991 }
992 EXPORT_SYMBOL_GPL(bio_end_io_acct_remapped);
993 
994 /**
995  * blk_lld_busy - Check if underlying low-level drivers of a device are busy
996  * @q : the queue of the device being checked
997  *
998  * Description:
999  *    Check if underlying low-level drivers of a device are busy.
1000  *    If the drivers want to export their busy state, they must set own
1001  *    exporting function using blk_queue_lld_busy() first.
1002  *
1003  *    Basically, this function is used only by request stacking drivers
1004  *    to stop dispatching requests to underlying devices when underlying
1005  *    devices are busy.  This behavior helps more I/O merging on the queue
1006  *    of the request stacking driver and prevents I/O throughput regression
1007  *    on burst I/O load.
1008  *
1009  * Return:
1010  *    0 - Not busy (The request stacking driver should dispatch request)
1011  *    1 - Busy (The request stacking driver should stop dispatching request)
1012  */
blk_lld_busy(struct request_queue * q)1013 int blk_lld_busy(struct request_queue *q)
1014 {
1015 	if (queue_is_mq(q) && q->mq_ops->busy)
1016 		return q->mq_ops->busy(q);
1017 
1018 	return 0;
1019 }
1020 EXPORT_SYMBOL_GPL(blk_lld_busy);
1021 
kblockd_schedule_work(struct work_struct * work)1022 int kblockd_schedule_work(struct work_struct *work)
1023 {
1024 	return queue_work(kblockd_workqueue, work);
1025 }
1026 EXPORT_SYMBOL(kblockd_schedule_work);
1027 
kblockd_mod_delayed_work_on(int cpu,struct delayed_work * dwork,unsigned long delay)1028 int kblockd_mod_delayed_work_on(int cpu, struct delayed_work *dwork,
1029 				unsigned long delay)
1030 {
1031 	return mod_delayed_work_on(cpu, kblockd_workqueue, dwork, delay);
1032 }
1033 EXPORT_SYMBOL(kblockd_mod_delayed_work_on);
1034 
blk_start_plug_nr_ios(struct blk_plug * plug,unsigned short nr_ios)1035 void blk_start_plug_nr_ios(struct blk_plug *plug, unsigned short nr_ios)
1036 {
1037 	struct task_struct *tsk = current;
1038 
1039 	/*
1040 	 * If this is a nested plug, don't actually assign it.
1041 	 */
1042 	if (tsk->plug)
1043 		return;
1044 
1045 	plug->mq_list = NULL;
1046 	plug->cached_rq = NULL;
1047 	plug->nr_ios = min_t(unsigned short, nr_ios, BLK_MAX_REQUEST_COUNT);
1048 	plug->rq_count = 0;
1049 	plug->multiple_queues = false;
1050 	plug->has_elevator = false;
1051 	plug->nowait = false;
1052 	INIT_LIST_HEAD(&plug->cb_list);
1053 
1054 	/*
1055 	 * Store ordering should not be needed here, since a potential
1056 	 * preempt will imply a full memory barrier
1057 	 */
1058 	tsk->plug = plug;
1059 }
1060 
1061 /**
1062  * blk_start_plug - initialize blk_plug and track it inside the task_struct
1063  * @plug:	The &struct blk_plug that needs to be initialized
1064  *
1065  * Description:
1066  *   blk_start_plug() indicates to the block layer an intent by the caller
1067  *   to submit multiple I/O requests in a batch.  The block layer may use
1068  *   this hint to defer submitting I/Os from the caller until blk_finish_plug()
1069  *   is called.  However, the block layer may choose to submit requests
1070  *   before a call to blk_finish_plug() if the number of queued I/Os
1071  *   exceeds %BLK_MAX_REQUEST_COUNT, or if the size of the I/O is larger than
1072  *   %BLK_PLUG_FLUSH_SIZE.  The queued I/Os may also be submitted early if
1073  *   the task schedules (see below).
1074  *
1075  *   Tracking blk_plug inside the task_struct will help with auto-flushing the
1076  *   pending I/O should the task end up blocking between blk_start_plug() and
1077  *   blk_finish_plug(). This is important from a performance perspective, but
1078  *   also ensures that we don't deadlock. For instance, if the task is blocking
1079  *   for a memory allocation, memory reclaim could end up wanting to free a
1080  *   page belonging to that request that is currently residing in our private
1081  *   plug. By flushing the pending I/O when the process goes to sleep, we avoid
1082  *   this kind of deadlock.
1083  */
blk_start_plug(struct blk_plug * plug)1084 void blk_start_plug(struct blk_plug *plug)
1085 {
1086 	blk_start_plug_nr_ios(plug, 1);
1087 }
1088 EXPORT_SYMBOL(blk_start_plug);
1089 
flush_plug_callbacks(struct blk_plug * plug,bool from_schedule)1090 static void flush_plug_callbacks(struct blk_plug *plug, bool from_schedule)
1091 {
1092 	LIST_HEAD(callbacks);
1093 
1094 	while (!list_empty(&plug->cb_list)) {
1095 		list_splice_init(&plug->cb_list, &callbacks);
1096 
1097 		while (!list_empty(&callbacks)) {
1098 			struct blk_plug_cb *cb = list_first_entry(&callbacks,
1099 							  struct blk_plug_cb,
1100 							  list);
1101 			list_del(&cb->list);
1102 			cb->callback(cb, from_schedule);
1103 		}
1104 	}
1105 }
1106 
blk_check_plugged(blk_plug_cb_fn unplug,void * data,int size)1107 struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug, void *data,
1108 				      int size)
1109 {
1110 	struct blk_plug *plug = current->plug;
1111 	struct blk_plug_cb *cb;
1112 
1113 	if (!plug)
1114 		return NULL;
1115 
1116 	list_for_each_entry(cb, &plug->cb_list, list)
1117 		if (cb->callback == unplug && cb->data == data)
1118 			return cb;
1119 
1120 	/* Not currently on the callback list */
1121 	BUG_ON(size < sizeof(*cb));
1122 	cb = kzalloc(size, GFP_ATOMIC);
1123 	if (cb) {
1124 		cb->data = data;
1125 		cb->callback = unplug;
1126 		list_add(&cb->list, &plug->cb_list);
1127 	}
1128 	return cb;
1129 }
1130 EXPORT_SYMBOL(blk_check_plugged);
1131 
__blk_flush_plug(struct blk_plug * plug,bool from_schedule)1132 void __blk_flush_plug(struct blk_plug *plug, bool from_schedule)
1133 {
1134 	if (!list_empty(&plug->cb_list))
1135 		flush_plug_callbacks(plug, from_schedule);
1136 	if (!rq_list_empty(plug->mq_list))
1137 		blk_mq_flush_plug_list(plug, from_schedule);
1138 	/*
1139 	 * Unconditionally flush out cached requests, even if the unplug
1140 	 * event came from schedule. Since we know hold references to the
1141 	 * queue for cached requests, we don't want a blocked task holding
1142 	 * up a queue freeze/quiesce event.
1143 	 */
1144 	if (unlikely(!rq_list_empty(plug->cached_rq)))
1145 		blk_mq_free_plug_rqs(plug);
1146 }
1147 
1148 /**
1149  * blk_finish_plug - mark the end of a batch of submitted I/O
1150  * @plug:	The &struct blk_plug passed to blk_start_plug()
1151  *
1152  * Description:
1153  * Indicate that a batch of I/O submissions is complete.  This function
1154  * must be paired with an initial call to blk_start_plug().  The intent
1155  * is to allow the block layer to optimize I/O submission.  See the
1156  * documentation for blk_start_plug() for more information.
1157  */
blk_finish_plug(struct blk_plug * plug)1158 void blk_finish_plug(struct blk_plug *plug)
1159 {
1160 	if (plug == current->plug) {
1161 		__blk_flush_plug(plug, false);
1162 		current->plug = NULL;
1163 	}
1164 }
1165 EXPORT_SYMBOL(blk_finish_plug);
1166 
blk_io_schedule(void)1167 void blk_io_schedule(void)
1168 {
1169 	/* Prevent hang_check timer from firing at us during very long I/O */
1170 	unsigned long timeout = sysctl_hung_task_timeout_secs * HZ / 2;
1171 
1172 	if (timeout)
1173 		io_schedule_timeout(timeout);
1174 	else
1175 		io_schedule();
1176 }
1177 EXPORT_SYMBOL_GPL(blk_io_schedule);
1178 
blk_dev_init(void)1179 int __init blk_dev_init(void)
1180 {
1181 	BUILD_BUG_ON((__force u32)REQ_OP_LAST >= (1 << REQ_OP_BITS));
1182 	BUILD_BUG_ON(REQ_OP_BITS + REQ_FLAG_BITS > 8 *
1183 			sizeof_field(struct request, cmd_flags));
1184 	BUILD_BUG_ON(REQ_OP_BITS + REQ_FLAG_BITS > 8 *
1185 			sizeof_field(struct bio, bi_opf));
1186 	BUILD_BUG_ON(ALIGN(offsetof(struct request_queue, srcu),
1187 			   __alignof__(struct request_queue)) !=
1188 		     sizeof(struct request_queue));
1189 
1190 	/* used for unplugging and affects IO latency/throughput - HIGHPRI */
1191 	kblockd_workqueue = alloc_workqueue("kblockd",
1192 					    WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
1193 	if (!kblockd_workqueue)
1194 		panic("Failed to create kblockd\n");
1195 
1196 	blk_requestq_cachep = kmem_cache_create("request_queue",
1197 			sizeof(struct request_queue), 0, SLAB_PANIC, NULL);
1198 
1199 	blk_requestq_srcu_cachep = kmem_cache_create("request_queue_srcu",
1200 			sizeof(struct request_queue) +
1201 			sizeof(struct srcu_struct), 0, SLAB_PANIC, NULL);
1202 
1203 	blk_debugfs_root = debugfs_create_dir("block", NULL);
1204 
1205 	return 0;
1206 }
1207