xref: /openbmc/linux/block/blk-core.c (revision 6774def6)
1 /*
2  * Copyright (C) 1991, 1992 Linus Torvalds
3  * Copyright (C) 1994,      Karl Keyte: Added support for disk statistics
4  * Elevator latency, (C) 2000  Andrea Arcangeli <andrea@suse.de> SuSE
5  * Queue request tables / lock, selectable elevator, Jens Axboe <axboe@suse.de>
6  * kernel-doc documentation started by NeilBrown <neilb@cse.unsw.edu.au>
7  *	-  July2000
8  * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001
9  */
10 
11 /*
12  * This handles all read/write requests to block devices
13  */
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/backing-dev.h>
17 #include <linux/bio.h>
18 #include <linux/blkdev.h>
19 #include <linux/blk-mq.h>
20 #include <linux/highmem.h>
21 #include <linux/mm.h>
22 #include <linux/kernel_stat.h>
23 #include <linux/string.h>
24 #include <linux/init.h>
25 #include <linux/completion.h>
26 #include <linux/slab.h>
27 #include <linux/swap.h>
28 #include <linux/writeback.h>
29 #include <linux/task_io_accounting_ops.h>
30 #include <linux/fault-inject.h>
31 #include <linux/list_sort.h>
32 #include <linux/delay.h>
33 #include <linux/ratelimit.h>
34 #include <linux/pm_runtime.h>
35 
36 #define CREATE_TRACE_POINTS
37 #include <trace/events/block.h>
38 
39 #include "blk.h"
40 #include "blk-cgroup.h"
41 #include "blk-mq.h"
42 
43 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
44 EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
45 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
46 EXPORT_TRACEPOINT_SYMBOL_GPL(block_split);
47 EXPORT_TRACEPOINT_SYMBOL_GPL(block_unplug);
48 
49 DEFINE_IDA(blk_queue_ida);
50 
51 /*
52  * For the allocated request tables
53  */
54 struct kmem_cache *request_cachep = NULL;
55 
56 /*
57  * For queue allocation
58  */
59 struct kmem_cache *blk_requestq_cachep;
60 
61 /*
62  * Controlling structure to kblockd
63  */
64 static struct workqueue_struct *kblockd_workqueue;
65 
66 void blk_queue_congestion_threshold(struct request_queue *q)
67 {
68 	int nr;
69 
70 	nr = q->nr_requests - (q->nr_requests / 8) + 1;
71 	if (nr > q->nr_requests)
72 		nr = q->nr_requests;
73 	q->nr_congestion_on = nr;
74 
75 	nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
76 	if (nr < 1)
77 		nr = 1;
78 	q->nr_congestion_off = nr;
79 }
80 
81 /**
82  * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
83  * @bdev:	device
84  *
85  * Locates the passed device's request queue and returns the address of its
86  * backing_dev_info.  This function can only be called if @bdev is opened
87  * and the return value is never NULL.
88  */
89 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
90 {
91 	struct request_queue *q = bdev_get_queue(bdev);
92 
93 	return &q->backing_dev_info;
94 }
95 EXPORT_SYMBOL(blk_get_backing_dev_info);
96 
97 void blk_rq_init(struct request_queue *q, struct request *rq)
98 {
99 	memset(rq, 0, sizeof(*rq));
100 
101 	INIT_LIST_HEAD(&rq->queuelist);
102 	INIT_LIST_HEAD(&rq->timeout_list);
103 	rq->cpu = -1;
104 	rq->q = q;
105 	rq->__sector = (sector_t) -1;
106 	INIT_HLIST_NODE(&rq->hash);
107 	RB_CLEAR_NODE(&rq->rb_node);
108 	rq->cmd = rq->__cmd;
109 	rq->cmd_len = BLK_MAX_CDB;
110 	rq->tag = -1;
111 	rq->start_time = jiffies;
112 	set_start_time_ns(rq);
113 	rq->part = NULL;
114 }
115 EXPORT_SYMBOL(blk_rq_init);
116 
117 static void req_bio_endio(struct request *rq, struct bio *bio,
118 			  unsigned int nbytes, int error)
119 {
120 	if (error)
121 		clear_bit(BIO_UPTODATE, &bio->bi_flags);
122 	else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
123 		error = -EIO;
124 
125 	if (unlikely(rq->cmd_flags & REQ_QUIET))
126 		set_bit(BIO_QUIET, &bio->bi_flags);
127 
128 	bio_advance(bio, nbytes);
129 
130 	/* don't actually finish bio if it's part of flush sequence */
131 	if (bio->bi_iter.bi_size == 0 && !(rq->cmd_flags & REQ_FLUSH_SEQ))
132 		bio_endio(bio, error);
133 }
134 
135 void blk_dump_rq_flags(struct request *rq, char *msg)
136 {
137 	int bit;
138 
139 	printk(KERN_INFO "%s: dev %s: type=%x, flags=%llx\n", msg,
140 		rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type,
141 		(unsigned long long) rq->cmd_flags);
142 
143 	printk(KERN_INFO "  sector %llu, nr/cnr %u/%u\n",
144 	       (unsigned long long)blk_rq_pos(rq),
145 	       blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
146 	printk(KERN_INFO "  bio %p, biotail %p, len %u\n",
147 	       rq->bio, rq->biotail, blk_rq_bytes(rq));
148 
149 	if (rq->cmd_type == REQ_TYPE_BLOCK_PC) {
150 		printk(KERN_INFO "  cdb: ");
151 		for (bit = 0; bit < BLK_MAX_CDB; bit++)
152 			printk("%02x ", rq->cmd[bit]);
153 		printk("\n");
154 	}
155 }
156 EXPORT_SYMBOL(blk_dump_rq_flags);
157 
158 static void blk_delay_work(struct work_struct *work)
159 {
160 	struct request_queue *q;
161 
162 	q = container_of(work, struct request_queue, delay_work.work);
163 	spin_lock_irq(q->queue_lock);
164 	__blk_run_queue(q);
165 	spin_unlock_irq(q->queue_lock);
166 }
167 
168 /**
169  * blk_delay_queue - restart queueing after defined interval
170  * @q:		The &struct request_queue in question
171  * @msecs:	Delay in msecs
172  *
173  * Description:
174  *   Sometimes queueing needs to be postponed for a little while, to allow
175  *   resources to come back. This function will make sure that queueing is
176  *   restarted around the specified time. Queue lock must be held.
177  */
178 void blk_delay_queue(struct request_queue *q, unsigned long msecs)
179 {
180 	if (likely(!blk_queue_dead(q)))
181 		queue_delayed_work(kblockd_workqueue, &q->delay_work,
182 				   msecs_to_jiffies(msecs));
183 }
184 EXPORT_SYMBOL(blk_delay_queue);
185 
186 /**
187  * blk_start_queue - restart a previously stopped queue
188  * @q:    The &struct request_queue in question
189  *
190  * Description:
191  *   blk_start_queue() will clear the stop flag on the queue, and call
192  *   the request_fn for the queue if it was in a stopped state when
193  *   entered. Also see blk_stop_queue(). Queue lock must be held.
194  **/
195 void blk_start_queue(struct request_queue *q)
196 {
197 	WARN_ON(!irqs_disabled());
198 
199 	queue_flag_clear(QUEUE_FLAG_STOPPED, q);
200 	__blk_run_queue(q);
201 }
202 EXPORT_SYMBOL(blk_start_queue);
203 
204 /**
205  * blk_stop_queue - stop a queue
206  * @q:    The &struct request_queue in question
207  *
208  * Description:
209  *   The Linux block layer assumes that a block driver will consume all
210  *   entries on the request queue when the request_fn strategy is called.
211  *   Often this will not happen, because of hardware limitations (queue
212  *   depth settings). If a device driver gets a 'queue full' response,
213  *   or if it simply chooses not to queue more I/O at one point, it can
214  *   call this function to prevent the request_fn from being called until
215  *   the driver has signalled it's ready to go again. This happens by calling
216  *   blk_start_queue() to restart queue operations. Queue lock must be held.
217  **/
218 void blk_stop_queue(struct request_queue *q)
219 {
220 	cancel_delayed_work(&q->delay_work);
221 	queue_flag_set(QUEUE_FLAG_STOPPED, q);
222 }
223 EXPORT_SYMBOL(blk_stop_queue);
224 
225 /**
226  * blk_sync_queue - cancel any pending callbacks on a queue
227  * @q: the queue
228  *
229  * Description:
230  *     The block layer may perform asynchronous callback activity
231  *     on a queue, such as calling the unplug function after a timeout.
232  *     A block device may call blk_sync_queue to ensure that any
233  *     such activity is cancelled, thus allowing it to release resources
234  *     that the callbacks might use. The caller must already have made sure
235  *     that its ->make_request_fn will not re-add plugging prior to calling
236  *     this function.
237  *
238  *     This function does not cancel any asynchronous activity arising
239  *     out of elevator or throttling code. That would require elevator_exit()
240  *     and blkcg_exit_queue() to be called with queue lock initialized.
241  *
242  */
243 void blk_sync_queue(struct request_queue *q)
244 {
245 	del_timer_sync(&q->timeout);
246 
247 	if (q->mq_ops) {
248 		struct blk_mq_hw_ctx *hctx;
249 		int i;
250 
251 		queue_for_each_hw_ctx(q, hctx, i) {
252 			cancel_delayed_work_sync(&hctx->run_work);
253 			cancel_delayed_work_sync(&hctx->delay_work);
254 		}
255 	} else {
256 		cancel_delayed_work_sync(&q->delay_work);
257 	}
258 }
259 EXPORT_SYMBOL(blk_sync_queue);
260 
261 /**
262  * __blk_run_queue_uncond - run a queue whether or not it has been stopped
263  * @q:	The queue to run
264  *
265  * Description:
266  *    Invoke request handling on a queue if there are any pending requests.
267  *    May be used to restart request handling after a request has completed.
268  *    This variant runs the queue whether or not the queue has been
269  *    stopped. Must be called with the queue lock held and interrupts
270  *    disabled. See also @blk_run_queue.
271  */
272 inline void __blk_run_queue_uncond(struct request_queue *q)
273 {
274 	if (unlikely(blk_queue_dead(q)))
275 		return;
276 
277 	/*
278 	 * Some request_fn implementations, e.g. scsi_request_fn(), unlock
279 	 * the queue lock internally. As a result multiple threads may be
280 	 * running such a request function concurrently. Keep track of the
281 	 * number of active request_fn invocations such that blk_drain_queue()
282 	 * can wait until all these request_fn calls have finished.
283 	 */
284 	q->request_fn_active++;
285 	q->request_fn(q);
286 	q->request_fn_active--;
287 }
288 
289 /**
290  * __blk_run_queue - run a single device queue
291  * @q:	The queue to run
292  *
293  * Description:
294  *    See @blk_run_queue. This variant must be called with the queue lock
295  *    held and interrupts disabled.
296  */
297 void __blk_run_queue(struct request_queue *q)
298 {
299 	if (unlikely(blk_queue_stopped(q)))
300 		return;
301 
302 	__blk_run_queue_uncond(q);
303 }
304 EXPORT_SYMBOL(__blk_run_queue);
305 
306 /**
307  * blk_run_queue_async - run a single device queue in workqueue context
308  * @q:	The queue to run
309  *
310  * Description:
311  *    Tells kblockd to perform the equivalent of @blk_run_queue on behalf
312  *    of us. The caller must hold the queue lock.
313  */
314 void blk_run_queue_async(struct request_queue *q)
315 {
316 	if (likely(!blk_queue_stopped(q) && !blk_queue_dead(q)))
317 		mod_delayed_work(kblockd_workqueue, &q->delay_work, 0);
318 }
319 EXPORT_SYMBOL(blk_run_queue_async);
320 
321 /**
322  * blk_run_queue - run a single device queue
323  * @q: The queue to run
324  *
325  * Description:
326  *    Invoke request handling on this queue, if it has pending work to do.
327  *    May be used to restart queueing when a request has completed.
328  */
329 void blk_run_queue(struct request_queue *q)
330 {
331 	unsigned long flags;
332 
333 	spin_lock_irqsave(q->queue_lock, flags);
334 	__blk_run_queue(q);
335 	spin_unlock_irqrestore(q->queue_lock, flags);
336 }
337 EXPORT_SYMBOL(blk_run_queue);
338 
339 void blk_put_queue(struct request_queue *q)
340 {
341 	kobject_put(&q->kobj);
342 }
343 EXPORT_SYMBOL(blk_put_queue);
344 
345 /**
346  * __blk_drain_queue - drain requests from request_queue
347  * @q: queue to drain
348  * @drain_all: whether to drain all requests or only the ones w/ ELVPRIV
349  *
350  * Drain requests from @q.  If @drain_all is set, all requests are drained.
351  * If not, only ELVPRIV requests are drained.  The caller is responsible
352  * for ensuring that no new requests which need to be drained are queued.
353  */
354 static void __blk_drain_queue(struct request_queue *q, bool drain_all)
355 	__releases(q->queue_lock)
356 	__acquires(q->queue_lock)
357 {
358 	int i;
359 
360 	lockdep_assert_held(q->queue_lock);
361 
362 	while (true) {
363 		bool drain = false;
364 
365 		/*
366 		 * The caller might be trying to drain @q before its
367 		 * elevator is initialized.
368 		 */
369 		if (q->elevator)
370 			elv_drain_elevator(q);
371 
372 		blkcg_drain_queue(q);
373 
374 		/*
375 		 * This function might be called on a queue which failed
376 		 * driver init after queue creation or is not yet fully
377 		 * active yet.  Some drivers (e.g. fd and loop) get unhappy
378 		 * in such cases.  Kick queue iff dispatch queue has
379 		 * something on it and @q has request_fn set.
380 		 */
381 		if (!list_empty(&q->queue_head) && q->request_fn)
382 			__blk_run_queue(q);
383 
384 		drain |= q->nr_rqs_elvpriv;
385 		drain |= q->request_fn_active;
386 
387 		/*
388 		 * Unfortunately, requests are queued at and tracked from
389 		 * multiple places and there's no single counter which can
390 		 * be drained.  Check all the queues and counters.
391 		 */
392 		if (drain_all) {
393 			struct blk_flush_queue *fq = blk_get_flush_queue(q, NULL);
394 			drain |= !list_empty(&q->queue_head);
395 			for (i = 0; i < 2; i++) {
396 				drain |= q->nr_rqs[i];
397 				drain |= q->in_flight[i];
398 				if (fq)
399 				    drain |= !list_empty(&fq->flush_queue[i]);
400 			}
401 		}
402 
403 		if (!drain)
404 			break;
405 
406 		spin_unlock_irq(q->queue_lock);
407 
408 		msleep(10);
409 
410 		spin_lock_irq(q->queue_lock);
411 	}
412 
413 	/*
414 	 * With queue marked dead, any woken up waiter will fail the
415 	 * allocation path, so the wakeup chaining is lost and we're
416 	 * left with hung waiters. We need to wake up those waiters.
417 	 */
418 	if (q->request_fn) {
419 		struct request_list *rl;
420 
421 		blk_queue_for_each_rl(rl, q)
422 			for (i = 0; i < ARRAY_SIZE(rl->wait); i++)
423 				wake_up_all(&rl->wait[i]);
424 	}
425 }
426 
427 /**
428  * blk_queue_bypass_start - enter queue bypass mode
429  * @q: queue of interest
430  *
431  * In bypass mode, only the dispatch FIFO queue of @q is used.  This
432  * function makes @q enter bypass mode and drains all requests which were
433  * throttled or issued before.  On return, it's guaranteed that no request
434  * is being throttled or has ELVPRIV set and blk_queue_bypass() %true
435  * inside queue or RCU read lock.
436  */
437 void blk_queue_bypass_start(struct request_queue *q)
438 {
439 	spin_lock_irq(q->queue_lock);
440 	q->bypass_depth++;
441 	queue_flag_set(QUEUE_FLAG_BYPASS, q);
442 	spin_unlock_irq(q->queue_lock);
443 
444 	/*
445 	 * Queues start drained.  Skip actual draining till init is
446 	 * complete.  This avoids lenghty delays during queue init which
447 	 * can happen many times during boot.
448 	 */
449 	if (blk_queue_init_done(q)) {
450 		spin_lock_irq(q->queue_lock);
451 		__blk_drain_queue(q, false);
452 		spin_unlock_irq(q->queue_lock);
453 
454 		/* ensure blk_queue_bypass() is %true inside RCU read lock */
455 		synchronize_rcu();
456 	}
457 }
458 EXPORT_SYMBOL_GPL(blk_queue_bypass_start);
459 
460 /**
461  * blk_queue_bypass_end - leave queue bypass mode
462  * @q: queue of interest
463  *
464  * Leave bypass mode and restore the normal queueing behavior.
465  */
466 void blk_queue_bypass_end(struct request_queue *q)
467 {
468 	spin_lock_irq(q->queue_lock);
469 	if (!--q->bypass_depth)
470 		queue_flag_clear(QUEUE_FLAG_BYPASS, q);
471 	WARN_ON_ONCE(q->bypass_depth < 0);
472 	spin_unlock_irq(q->queue_lock);
473 }
474 EXPORT_SYMBOL_GPL(blk_queue_bypass_end);
475 
476 /**
477  * blk_cleanup_queue - shutdown a request queue
478  * @q: request queue to shutdown
479  *
480  * Mark @q DYING, drain all pending requests, mark @q DEAD, destroy and
481  * put it.  All future requests will be failed immediately with -ENODEV.
482  */
483 void blk_cleanup_queue(struct request_queue *q)
484 {
485 	spinlock_t *lock = q->queue_lock;
486 
487 	/* mark @q DYING, no new request or merges will be allowed afterwards */
488 	mutex_lock(&q->sysfs_lock);
489 	queue_flag_set_unlocked(QUEUE_FLAG_DYING, q);
490 	spin_lock_irq(lock);
491 
492 	/*
493 	 * A dying queue is permanently in bypass mode till released.  Note
494 	 * that, unlike blk_queue_bypass_start(), we aren't performing
495 	 * synchronize_rcu() after entering bypass mode to avoid the delay
496 	 * as some drivers create and destroy a lot of queues while
497 	 * probing.  This is still safe because blk_release_queue() will be
498 	 * called only after the queue refcnt drops to zero and nothing,
499 	 * RCU or not, would be traversing the queue by then.
500 	 */
501 	q->bypass_depth++;
502 	queue_flag_set(QUEUE_FLAG_BYPASS, q);
503 
504 	queue_flag_set(QUEUE_FLAG_NOMERGES, q);
505 	queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
506 	queue_flag_set(QUEUE_FLAG_DYING, q);
507 	spin_unlock_irq(lock);
508 	mutex_unlock(&q->sysfs_lock);
509 
510 	/*
511 	 * Drain all requests queued before DYING marking. Set DEAD flag to
512 	 * prevent that q->request_fn() gets invoked after draining finished.
513 	 */
514 	if (q->mq_ops) {
515 		blk_mq_freeze_queue(q);
516 		spin_lock_irq(lock);
517 	} else {
518 		spin_lock_irq(lock);
519 		__blk_drain_queue(q, true);
520 	}
521 	queue_flag_set(QUEUE_FLAG_DEAD, q);
522 	spin_unlock_irq(lock);
523 
524 	/* @q won't process any more request, flush async actions */
525 	del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);
526 	blk_sync_queue(q);
527 
528 	spin_lock_irq(lock);
529 	if (q->queue_lock != &q->__queue_lock)
530 		q->queue_lock = &q->__queue_lock;
531 	spin_unlock_irq(lock);
532 
533 	/* @q is and will stay empty, shutdown and put */
534 	blk_put_queue(q);
535 }
536 EXPORT_SYMBOL(blk_cleanup_queue);
537 
538 int blk_init_rl(struct request_list *rl, struct request_queue *q,
539 		gfp_t gfp_mask)
540 {
541 	if (unlikely(rl->rq_pool))
542 		return 0;
543 
544 	rl->q = q;
545 	rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
546 	rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
547 	init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
548 	init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
549 
550 	rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
551 					  mempool_free_slab, request_cachep,
552 					  gfp_mask, q->node);
553 	if (!rl->rq_pool)
554 		return -ENOMEM;
555 
556 	return 0;
557 }
558 
559 void blk_exit_rl(struct request_list *rl)
560 {
561 	if (rl->rq_pool)
562 		mempool_destroy(rl->rq_pool);
563 }
564 
565 struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
566 {
567 	return blk_alloc_queue_node(gfp_mask, NUMA_NO_NODE);
568 }
569 EXPORT_SYMBOL(blk_alloc_queue);
570 
571 struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
572 {
573 	struct request_queue *q;
574 	int err;
575 
576 	q = kmem_cache_alloc_node(blk_requestq_cachep,
577 				gfp_mask | __GFP_ZERO, node_id);
578 	if (!q)
579 		return NULL;
580 
581 	q->id = ida_simple_get(&blk_queue_ida, 0, 0, gfp_mask);
582 	if (q->id < 0)
583 		goto fail_q;
584 
585 	q->backing_dev_info.ra_pages =
586 			(VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
587 	q->backing_dev_info.state = 0;
588 	q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
589 	q->backing_dev_info.name = "block";
590 	q->node = node_id;
591 
592 	err = bdi_init(&q->backing_dev_info);
593 	if (err)
594 		goto fail_id;
595 
596 	setup_timer(&q->backing_dev_info.laptop_mode_wb_timer,
597 		    laptop_mode_timer_fn, (unsigned long) q);
598 	setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
599 	INIT_LIST_HEAD(&q->queue_head);
600 	INIT_LIST_HEAD(&q->timeout_list);
601 	INIT_LIST_HEAD(&q->icq_list);
602 #ifdef CONFIG_BLK_CGROUP
603 	INIT_LIST_HEAD(&q->blkg_list);
604 #endif
605 	INIT_DELAYED_WORK(&q->delay_work, blk_delay_work);
606 
607 	kobject_init(&q->kobj, &blk_queue_ktype);
608 
609 	mutex_init(&q->sysfs_lock);
610 	spin_lock_init(&q->__queue_lock);
611 
612 	/*
613 	 * By default initialize queue_lock to internal lock and driver can
614 	 * override it later if need be.
615 	 */
616 	q->queue_lock = &q->__queue_lock;
617 
618 	/*
619 	 * A queue starts its life with bypass turned on to avoid
620 	 * unnecessary bypass on/off overhead and nasty surprises during
621 	 * init.  The initial bypass will be finished when the queue is
622 	 * registered by blk_register_queue().
623 	 */
624 	q->bypass_depth = 1;
625 	__set_bit(QUEUE_FLAG_BYPASS, &q->queue_flags);
626 
627 	init_waitqueue_head(&q->mq_freeze_wq);
628 
629 	if (blkcg_init_queue(q))
630 		goto fail_bdi;
631 
632 	return q;
633 
634 fail_bdi:
635 	bdi_destroy(&q->backing_dev_info);
636 fail_id:
637 	ida_simple_remove(&blk_queue_ida, q->id);
638 fail_q:
639 	kmem_cache_free(blk_requestq_cachep, q);
640 	return NULL;
641 }
642 EXPORT_SYMBOL(blk_alloc_queue_node);
643 
644 /**
645  * blk_init_queue  - prepare a request queue for use with a block device
646  * @rfn:  The function to be called to process requests that have been
647  *        placed on the queue.
648  * @lock: Request queue spin lock
649  *
650  * Description:
651  *    If a block device wishes to use the standard request handling procedures,
652  *    which sorts requests and coalesces adjacent requests, then it must
653  *    call blk_init_queue().  The function @rfn will be called when there
654  *    are requests on the queue that need to be processed.  If the device
655  *    supports plugging, then @rfn may not be called immediately when requests
656  *    are available on the queue, but may be called at some time later instead.
657  *    Plugged queues are generally unplugged when a buffer belonging to one
658  *    of the requests on the queue is needed, or due to memory pressure.
659  *
660  *    @rfn is not required, or even expected, to remove all requests off the
661  *    queue, but only as many as it can handle at a time.  If it does leave
662  *    requests on the queue, it is responsible for arranging that the requests
663  *    get dealt with eventually.
664  *
665  *    The queue spin lock must be held while manipulating the requests on the
666  *    request queue; this lock will be taken also from interrupt context, so irq
667  *    disabling is needed for it.
668  *
669  *    Function returns a pointer to the initialized request queue, or %NULL if
670  *    it didn't succeed.
671  *
672  * Note:
673  *    blk_init_queue() must be paired with a blk_cleanup_queue() call
674  *    when the block device is deactivated (such as at module unload).
675  **/
676 
677 struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
678 {
679 	return blk_init_queue_node(rfn, lock, NUMA_NO_NODE);
680 }
681 EXPORT_SYMBOL(blk_init_queue);
682 
683 struct request_queue *
684 blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
685 {
686 	struct request_queue *uninit_q, *q;
687 
688 	uninit_q = blk_alloc_queue_node(GFP_KERNEL, node_id);
689 	if (!uninit_q)
690 		return NULL;
691 
692 	q = blk_init_allocated_queue(uninit_q, rfn, lock);
693 	if (!q)
694 		blk_cleanup_queue(uninit_q);
695 
696 	return q;
697 }
698 EXPORT_SYMBOL(blk_init_queue_node);
699 
700 struct request_queue *
701 blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
702 			 spinlock_t *lock)
703 {
704 	if (!q)
705 		return NULL;
706 
707 	q->fq = blk_alloc_flush_queue(q, NUMA_NO_NODE, 0);
708 	if (!q->fq)
709 		return NULL;
710 
711 	if (blk_init_rl(&q->root_rl, q, GFP_KERNEL))
712 		goto fail;
713 
714 	q->request_fn		= rfn;
715 	q->prep_rq_fn		= NULL;
716 	q->unprep_rq_fn		= NULL;
717 	q->queue_flags		|= QUEUE_FLAG_DEFAULT;
718 
719 	/* Override internal queue lock with supplied lock pointer */
720 	if (lock)
721 		q->queue_lock		= lock;
722 
723 	/*
724 	 * This also sets hw/phys segments, boundary and size
725 	 */
726 	blk_queue_make_request(q, blk_queue_bio);
727 
728 	q->sg_reserved_size = INT_MAX;
729 
730 	/* Protect q->elevator from elevator_change */
731 	mutex_lock(&q->sysfs_lock);
732 
733 	/* init elevator */
734 	if (elevator_init(q, NULL)) {
735 		mutex_unlock(&q->sysfs_lock);
736 		goto fail;
737 	}
738 
739 	mutex_unlock(&q->sysfs_lock);
740 
741 	return q;
742 
743 fail:
744 	blk_free_flush_queue(q->fq);
745 	return NULL;
746 }
747 EXPORT_SYMBOL(blk_init_allocated_queue);
748 
749 bool blk_get_queue(struct request_queue *q)
750 {
751 	if (likely(!blk_queue_dying(q))) {
752 		__blk_get_queue(q);
753 		return true;
754 	}
755 
756 	return false;
757 }
758 EXPORT_SYMBOL(blk_get_queue);
759 
760 static inline void blk_free_request(struct request_list *rl, struct request *rq)
761 {
762 	if (rq->cmd_flags & REQ_ELVPRIV) {
763 		elv_put_request(rl->q, rq);
764 		if (rq->elv.icq)
765 			put_io_context(rq->elv.icq->ioc);
766 	}
767 
768 	mempool_free(rq, rl->rq_pool);
769 }
770 
771 /*
772  * ioc_batching returns true if the ioc is a valid batching request and
773  * should be given priority access to a request.
774  */
775 static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
776 {
777 	if (!ioc)
778 		return 0;
779 
780 	/*
781 	 * Make sure the process is able to allocate at least 1 request
782 	 * even if the batch times out, otherwise we could theoretically
783 	 * lose wakeups.
784 	 */
785 	return ioc->nr_batch_requests == q->nr_batching ||
786 		(ioc->nr_batch_requests > 0
787 		&& time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
788 }
789 
790 /*
791  * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
792  * will cause the process to be a "batcher" on all queues in the system. This
793  * is the behaviour we want though - once it gets a wakeup it should be given
794  * a nice run.
795  */
796 static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
797 {
798 	if (!ioc || ioc_batching(q, ioc))
799 		return;
800 
801 	ioc->nr_batch_requests = q->nr_batching;
802 	ioc->last_waited = jiffies;
803 }
804 
805 static void __freed_request(struct request_list *rl, int sync)
806 {
807 	struct request_queue *q = rl->q;
808 
809 	/*
810 	 * bdi isn't aware of blkcg yet.  As all async IOs end up root
811 	 * blkcg anyway, just use root blkcg state.
812 	 */
813 	if (rl == &q->root_rl &&
814 	    rl->count[sync] < queue_congestion_off_threshold(q))
815 		blk_clear_queue_congested(q, sync);
816 
817 	if (rl->count[sync] + 1 <= q->nr_requests) {
818 		if (waitqueue_active(&rl->wait[sync]))
819 			wake_up(&rl->wait[sync]);
820 
821 		blk_clear_rl_full(rl, sync);
822 	}
823 }
824 
825 /*
826  * A request has just been released.  Account for it, update the full and
827  * congestion status, wake up any waiters.   Called under q->queue_lock.
828  */
829 static void freed_request(struct request_list *rl, unsigned int flags)
830 {
831 	struct request_queue *q = rl->q;
832 	int sync = rw_is_sync(flags);
833 
834 	q->nr_rqs[sync]--;
835 	rl->count[sync]--;
836 	if (flags & REQ_ELVPRIV)
837 		q->nr_rqs_elvpriv--;
838 
839 	__freed_request(rl, sync);
840 
841 	if (unlikely(rl->starved[sync ^ 1]))
842 		__freed_request(rl, sync ^ 1);
843 }
844 
845 int blk_update_nr_requests(struct request_queue *q, unsigned int nr)
846 {
847 	struct request_list *rl;
848 
849 	spin_lock_irq(q->queue_lock);
850 	q->nr_requests = nr;
851 	blk_queue_congestion_threshold(q);
852 
853 	/* congestion isn't cgroup aware and follows root blkcg for now */
854 	rl = &q->root_rl;
855 
856 	if (rl->count[BLK_RW_SYNC] >= queue_congestion_on_threshold(q))
857 		blk_set_queue_congested(q, BLK_RW_SYNC);
858 	else if (rl->count[BLK_RW_SYNC] < queue_congestion_off_threshold(q))
859 		blk_clear_queue_congested(q, BLK_RW_SYNC);
860 
861 	if (rl->count[BLK_RW_ASYNC] >= queue_congestion_on_threshold(q))
862 		blk_set_queue_congested(q, BLK_RW_ASYNC);
863 	else if (rl->count[BLK_RW_ASYNC] < queue_congestion_off_threshold(q))
864 		blk_clear_queue_congested(q, BLK_RW_ASYNC);
865 
866 	blk_queue_for_each_rl(rl, q) {
867 		if (rl->count[BLK_RW_SYNC] >= q->nr_requests) {
868 			blk_set_rl_full(rl, BLK_RW_SYNC);
869 		} else {
870 			blk_clear_rl_full(rl, BLK_RW_SYNC);
871 			wake_up(&rl->wait[BLK_RW_SYNC]);
872 		}
873 
874 		if (rl->count[BLK_RW_ASYNC] >= q->nr_requests) {
875 			blk_set_rl_full(rl, BLK_RW_ASYNC);
876 		} else {
877 			blk_clear_rl_full(rl, BLK_RW_ASYNC);
878 			wake_up(&rl->wait[BLK_RW_ASYNC]);
879 		}
880 	}
881 
882 	spin_unlock_irq(q->queue_lock);
883 	return 0;
884 }
885 
886 /*
887  * Determine if elevator data should be initialized when allocating the
888  * request associated with @bio.
889  */
890 static bool blk_rq_should_init_elevator(struct bio *bio)
891 {
892 	if (!bio)
893 		return true;
894 
895 	/*
896 	 * Flush requests do not use the elevator so skip initialization.
897 	 * This allows a request to share the flush and elevator data.
898 	 */
899 	if (bio->bi_rw & (REQ_FLUSH | REQ_FUA))
900 		return false;
901 
902 	return true;
903 }
904 
905 /**
906  * rq_ioc - determine io_context for request allocation
907  * @bio: request being allocated is for this bio (can be %NULL)
908  *
909  * Determine io_context to use for request allocation for @bio.  May return
910  * %NULL if %current->io_context doesn't exist.
911  */
912 static struct io_context *rq_ioc(struct bio *bio)
913 {
914 #ifdef CONFIG_BLK_CGROUP
915 	if (bio && bio->bi_ioc)
916 		return bio->bi_ioc;
917 #endif
918 	return current->io_context;
919 }
920 
921 /**
922  * __get_request - get a free request
923  * @rl: request list to allocate from
924  * @rw_flags: RW and SYNC flags
925  * @bio: bio to allocate request for (can be %NULL)
926  * @gfp_mask: allocation mask
927  *
928  * Get a free request from @q.  This function may fail under memory
929  * pressure or if @q is dead.
930  *
931  * Must be called with @q->queue_lock held and,
932  * Returns ERR_PTR on failure, with @q->queue_lock held.
933  * Returns request pointer on success, with @q->queue_lock *not held*.
934  */
935 static struct request *__get_request(struct request_list *rl, int rw_flags,
936 				     struct bio *bio, gfp_t gfp_mask)
937 {
938 	struct request_queue *q = rl->q;
939 	struct request *rq;
940 	struct elevator_type *et = q->elevator->type;
941 	struct io_context *ioc = rq_ioc(bio);
942 	struct io_cq *icq = NULL;
943 	const bool is_sync = rw_is_sync(rw_flags) != 0;
944 	int may_queue;
945 
946 	if (unlikely(blk_queue_dying(q)))
947 		return ERR_PTR(-ENODEV);
948 
949 	may_queue = elv_may_queue(q, rw_flags);
950 	if (may_queue == ELV_MQUEUE_NO)
951 		goto rq_starved;
952 
953 	if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
954 		if (rl->count[is_sync]+1 >= q->nr_requests) {
955 			/*
956 			 * The queue will fill after this allocation, so set
957 			 * it as full, and mark this process as "batching".
958 			 * This process will be allowed to complete a batch of
959 			 * requests, others will be blocked.
960 			 */
961 			if (!blk_rl_full(rl, is_sync)) {
962 				ioc_set_batching(q, ioc);
963 				blk_set_rl_full(rl, is_sync);
964 			} else {
965 				if (may_queue != ELV_MQUEUE_MUST
966 						&& !ioc_batching(q, ioc)) {
967 					/*
968 					 * The queue is full and the allocating
969 					 * process is not a "batcher", and not
970 					 * exempted by the IO scheduler
971 					 */
972 					return ERR_PTR(-ENOMEM);
973 				}
974 			}
975 		}
976 		/*
977 		 * bdi isn't aware of blkcg yet.  As all async IOs end up
978 		 * root blkcg anyway, just use root blkcg state.
979 		 */
980 		if (rl == &q->root_rl)
981 			blk_set_queue_congested(q, is_sync);
982 	}
983 
984 	/*
985 	 * Only allow batching queuers to allocate up to 50% over the defined
986 	 * limit of requests, otherwise we could have thousands of requests
987 	 * allocated with any setting of ->nr_requests
988 	 */
989 	if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
990 		return ERR_PTR(-ENOMEM);
991 
992 	q->nr_rqs[is_sync]++;
993 	rl->count[is_sync]++;
994 	rl->starved[is_sync] = 0;
995 
996 	/*
997 	 * Decide whether the new request will be managed by elevator.  If
998 	 * so, mark @rw_flags and increment elvpriv.  Non-zero elvpriv will
999 	 * prevent the current elevator from being destroyed until the new
1000 	 * request is freed.  This guarantees icq's won't be destroyed and
1001 	 * makes creating new ones safe.
1002 	 *
1003 	 * Also, lookup icq while holding queue_lock.  If it doesn't exist,
1004 	 * it will be created after releasing queue_lock.
1005 	 */
1006 	if (blk_rq_should_init_elevator(bio) && !blk_queue_bypass(q)) {
1007 		rw_flags |= REQ_ELVPRIV;
1008 		q->nr_rqs_elvpriv++;
1009 		if (et->icq_cache && ioc)
1010 			icq = ioc_lookup_icq(ioc, q);
1011 	}
1012 
1013 	if (blk_queue_io_stat(q))
1014 		rw_flags |= REQ_IO_STAT;
1015 	spin_unlock_irq(q->queue_lock);
1016 
1017 	/* allocate and init request */
1018 	rq = mempool_alloc(rl->rq_pool, gfp_mask);
1019 	if (!rq)
1020 		goto fail_alloc;
1021 
1022 	blk_rq_init(q, rq);
1023 	blk_rq_set_rl(rq, rl);
1024 	rq->cmd_flags = rw_flags | REQ_ALLOCED;
1025 
1026 	/* init elvpriv */
1027 	if (rw_flags & REQ_ELVPRIV) {
1028 		if (unlikely(et->icq_cache && !icq)) {
1029 			if (ioc)
1030 				icq = ioc_create_icq(ioc, q, gfp_mask);
1031 			if (!icq)
1032 				goto fail_elvpriv;
1033 		}
1034 
1035 		rq->elv.icq = icq;
1036 		if (unlikely(elv_set_request(q, rq, bio, gfp_mask)))
1037 			goto fail_elvpriv;
1038 
1039 		/* @rq->elv.icq holds io_context until @rq is freed */
1040 		if (icq)
1041 			get_io_context(icq->ioc);
1042 	}
1043 out:
1044 	/*
1045 	 * ioc may be NULL here, and ioc_batching will be false. That's
1046 	 * OK, if the queue is under the request limit then requests need
1047 	 * not count toward the nr_batch_requests limit. There will always
1048 	 * be some limit enforced by BLK_BATCH_TIME.
1049 	 */
1050 	if (ioc_batching(q, ioc))
1051 		ioc->nr_batch_requests--;
1052 
1053 	trace_block_getrq(q, bio, rw_flags & 1);
1054 	return rq;
1055 
1056 fail_elvpriv:
1057 	/*
1058 	 * elvpriv init failed.  ioc, icq and elvpriv aren't mempool backed
1059 	 * and may fail indefinitely under memory pressure and thus
1060 	 * shouldn't stall IO.  Treat this request as !elvpriv.  This will
1061 	 * disturb iosched and blkcg but weird is bettern than dead.
1062 	 */
1063 	printk_ratelimited(KERN_WARNING "%s: dev %s: request aux data allocation failed, iosched may be disturbed\n",
1064 			   __func__, dev_name(q->backing_dev_info.dev));
1065 
1066 	rq->cmd_flags &= ~REQ_ELVPRIV;
1067 	rq->elv.icq = NULL;
1068 
1069 	spin_lock_irq(q->queue_lock);
1070 	q->nr_rqs_elvpriv--;
1071 	spin_unlock_irq(q->queue_lock);
1072 	goto out;
1073 
1074 fail_alloc:
1075 	/*
1076 	 * Allocation failed presumably due to memory. Undo anything we
1077 	 * might have messed up.
1078 	 *
1079 	 * Allocating task should really be put onto the front of the wait
1080 	 * queue, but this is pretty rare.
1081 	 */
1082 	spin_lock_irq(q->queue_lock);
1083 	freed_request(rl, rw_flags);
1084 
1085 	/*
1086 	 * in the very unlikely event that allocation failed and no
1087 	 * requests for this direction was pending, mark us starved so that
1088 	 * freeing of a request in the other direction will notice
1089 	 * us. another possible fix would be to split the rq mempool into
1090 	 * READ and WRITE
1091 	 */
1092 rq_starved:
1093 	if (unlikely(rl->count[is_sync] == 0))
1094 		rl->starved[is_sync] = 1;
1095 	return ERR_PTR(-ENOMEM);
1096 }
1097 
1098 /**
1099  * get_request - get a free request
1100  * @q: request_queue to allocate request from
1101  * @rw_flags: RW and SYNC flags
1102  * @bio: bio to allocate request for (can be %NULL)
1103  * @gfp_mask: allocation mask
1104  *
1105  * Get a free request from @q.  If %__GFP_WAIT is set in @gfp_mask, this
1106  * function keeps retrying under memory pressure and fails iff @q is dead.
1107  *
1108  * Must be called with @q->queue_lock held and,
1109  * Returns ERR_PTR on failure, with @q->queue_lock held.
1110  * Returns request pointer on success, with @q->queue_lock *not held*.
1111  */
1112 static struct request *get_request(struct request_queue *q, int rw_flags,
1113 				   struct bio *bio, gfp_t gfp_mask)
1114 {
1115 	const bool is_sync = rw_is_sync(rw_flags) != 0;
1116 	DEFINE_WAIT(wait);
1117 	struct request_list *rl;
1118 	struct request *rq;
1119 
1120 	rl = blk_get_rl(q, bio);	/* transferred to @rq on success */
1121 retry:
1122 	rq = __get_request(rl, rw_flags, bio, gfp_mask);
1123 	if (!IS_ERR(rq))
1124 		return rq;
1125 
1126 	if (!(gfp_mask & __GFP_WAIT) || unlikely(blk_queue_dying(q))) {
1127 		blk_put_rl(rl);
1128 		return rq;
1129 	}
1130 
1131 	/* wait on @rl and retry */
1132 	prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
1133 				  TASK_UNINTERRUPTIBLE);
1134 
1135 	trace_block_sleeprq(q, bio, rw_flags & 1);
1136 
1137 	spin_unlock_irq(q->queue_lock);
1138 	io_schedule();
1139 
1140 	/*
1141 	 * After sleeping, we become a "batching" process and will be able
1142 	 * to allocate at least one request, and up to a big batch of them
1143 	 * for a small period time.  See ioc_batching, ioc_set_batching
1144 	 */
1145 	ioc_set_batching(q, current->io_context);
1146 
1147 	spin_lock_irq(q->queue_lock);
1148 	finish_wait(&rl->wait[is_sync], &wait);
1149 
1150 	goto retry;
1151 }
1152 
1153 static struct request *blk_old_get_request(struct request_queue *q, int rw,
1154 		gfp_t gfp_mask)
1155 {
1156 	struct request *rq;
1157 
1158 	BUG_ON(rw != READ && rw != WRITE);
1159 
1160 	/* create ioc upfront */
1161 	create_io_context(gfp_mask, q->node);
1162 
1163 	spin_lock_irq(q->queue_lock);
1164 	rq = get_request(q, rw, NULL, gfp_mask);
1165 	if (IS_ERR(rq))
1166 		spin_unlock_irq(q->queue_lock);
1167 	/* q->queue_lock is unlocked at this point */
1168 
1169 	return rq;
1170 }
1171 
1172 struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
1173 {
1174 	if (q->mq_ops)
1175 		return blk_mq_alloc_request(q, rw, gfp_mask, false);
1176 	else
1177 		return blk_old_get_request(q, rw, gfp_mask);
1178 }
1179 EXPORT_SYMBOL(blk_get_request);
1180 
1181 /**
1182  * blk_make_request - given a bio, allocate a corresponding struct request.
1183  * @q: target request queue
1184  * @bio:  The bio describing the memory mappings that will be submitted for IO.
1185  *        It may be a chained-bio properly constructed by block/bio layer.
1186  * @gfp_mask: gfp flags to be used for memory allocation
1187  *
1188  * blk_make_request is the parallel of generic_make_request for BLOCK_PC
1189  * type commands. Where the struct request needs to be farther initialized by
1190  * the caller. It is passed a &struct bio, which describes the memory info of
1191  * the I/O transfer.
1192  *
1193  * The caller of blk_make_request must make sure that bi_io_vec
1194  * are set to describe the memory buffers. That bio_data_dir() will return
1195  * the needed direction of the request. (And all bio's in the passed bio-chain
1196  * are properly set accordingly)
1197  *
1198  * If called under none-sleepable conditions, mapped bio buffers must not
1199  * need bouncing, by calling the appropriate masked or flagged allocator,
1200  * suitable for the target device. Otherwise the call to blk_queue_bounce will
1201  * BUG.
1202  *
1203  * WARNING: When allocating/cloning a bio-chain, careful consideration should be
1204  * given to how you allocate bios. In particular, you cannot use __GFP_WAIT for
1205  * anything but the first bio in the chain. Otherwise you risk waiting for IO
1206  * completion of a bio that hasn't been submitted yet, thus resulting in a
1207  * deadlock. Alternatively bios should be allocated using bio_kmalloc() instead
1208  * of bio_alloc(), as that avoids the mempool deadlock.
1209  * If possible a big IO should be split into smaller parts when allocation
1210  * fails. Partial allocation should not be an error, or you risk a live-lock.
1211  */
1212 struct request *blk_make_request(struct request_queue *q, struct bio *bio,
1213 				 gfp_t gfp_mask)
1214 {
1215 	struct request *rq = blk_get_request(q, bio_data_dir(bio), gfp_mask);
1216 
1217 	if (IS_ERR(rq))
1218 		return rq;
1219 
1220 	blk_rq_set_block_pc(rq);
1221 
1222 	for_each_bio(bio) {
1223 		struct bio *bounce_bio = bio;
1224 		int ret;
1225 
1226 		blk_queue_bounce(q, &bounce_bio);
1227 		ret = blk_rq_append_bio(q, rq, bounce_bio);
1228 		if (unlikely(ret)) {
1229 			blk_put_request(rq);
1230 			return ERR_PTR(ret);
1231 		}
1232 	}
1233 
1234 	return rq;
1235 }
1236 EXPORT_SYMBOL(blk_make_request);
1237 
1238 /**
1239  * blk_rq_set_block_pc - initialize a request to type BLOCK_PC
1240  * @rq:		request to be initialized
1241  *
1242  */
1243 void blk_rq_set_block_pc(struct request *rq)
1244 {
1245 	rq->cmd_type = REQ_TYPE_BLOCK_PC;
1246 	rq->__data_len = 0;
1247 	rq->__sector = (sector_t) -1;
1248 	rq->bio = rq->biotail = NULL;
1249 	memset(rq->__cmd, 0, sizeof(rq->__cmd));
1250 }
1251 EXPORT_SYMBOL(blk_rq_set_block_pc);
1252 
1253 /**
1254  * blk_requeue_request - put a request back on queue
1255  * @q:		request queue where request should be inserted
1256  * @rq:		request to be inserted
1257  *
1258  * Description:
1259  *    Drivers often keep queueing requests until the hardware cannot accept
1260  *    more, when that condition happens we need to put the request back
1261  *    on the queue. Must be called with queue lock held.
1262  */
1263 void blk_requeue_request(struct request_queue *q, struct request *rq)
1264 {
1265 	blk_delete_timer(rq);
1266 	blk_clear_rq_complete(rq);
1267 	trace_block_rq_requeue(q, rq);
1268 
1269 	if (blk_rq_tagged(rq))
1270 		blk_queue_end_tag(q, rq);
1271 
1272 	BUG_ON(blk_queued_rq(rq));
1273 
1274 	elv_requeue_request(q, rq);
1275 }
1276 EXPORT_SYMBOL(blk_requeue_request);
1277 
1278 static void add_acct_request(struct request_queue *q, struct request *rq,
1279 			     int where)
1280 {
1281 	blk_account_io_start(rq, true);
1282 	__elv_add_request(q, rq, where);
1283 }
1284 
1285 static void part_round_stats_single(int cpu, struct hd_struct *part,
1286 				    unsigned long now)
1287 {
1288 	int inflight;
1289 
1290 	if (now == part->stamp)
1291 		return;
1292 
1293 	inflight = part_in_flight(part);
1294 	if (inflight) {
1295 		__part_stat_add(cpu, part, time_in_queue,
1296 				inflight * (now - part->stamp));
1297 		__part_stat_add(cpu, part, io_ticks, (now - part->stamp));
1298 	}
1299 	part->stamp = now;
1300 }
1301 
1302 /**
1303  * part_round_stats() - Round off the performance stats on a struct disk_stats.
1304  * @cpu: cpu number for stats access
1305  * @part: target partition
1306  *
1307  * The average IO queue length and utilisation statistics are maintained
1308  * by observing the current state of the queue length and the amount of
1309  * time it has been in this state for.
1310  *
1311  * Normally, that accounting is done on IO completion, but that can result
1312  * in more than a second's worth of IO being accounted for within any one
1313  * second, leading to >100% utilisation.  To deal with that, we call this
1314  * function to do a round-off before returning the results when reading
1315  * /proc/diskstats.  This accounts immediately for all queue usage up to
1316  * the current jiffies and restarts the counters again.
1317  */
1318 void part_round_stats(int cpu, struct hd_struct *part)
1319 {
1320 	unsigned long now = jiffies;
1321 
1322 	if (part->partno)
1323 		part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1324 	part_round_stats_single(cpu, part, now);
1325 }
1326 EXPORT_SYMBOL_GPL(part_round_stats);
1327 
1328 #ifdef CONFIG_PM_RUNTIME
1329 static void blk_pm_put_request(struct request *rq)
1330 {
1331 	if (rq->q->dev && !(rq->cmd_flags & REQ_PM) && !--rq->q->nr_pending)
1332 		pm_runtime_mark_last_busy(rq->q->dev);
1333 }
1334 #else
1335 static inline void blk_pm_put_request(struct request *rq) {}
1336 #endif
1337 
1338 /*
1339  * queue lock must be held
1340  */
1341 void __blk_put_request(struct request_queue *q, struct request *req)
1342 {
1343 	if (unlikely(!q))
1344 		return;
1345 
1346 	if (q->mq_ops) {
1347 		blk_mq_free_request(req);
1348 		return;
1349 	}
1350 
1351 	blk_pm_put_request(req);
1352 
1353 	elv_completed_request(q, req);
1354 
1355 	/* this is a bio leak */
1356 	WARN_ON(req->bio != NULL);
1357 
1358 	/*
1359 	 * Request may not have originated from ll_rw_blk. if not,
1360 	 * it didn't come out of our reserved rq pools
1361 	 */
1362 	if (req->cmd_flags & REQ_ALLOCED) {
1363 		unsigned int flags = req->cmd_flags;
1364 		struct request_list *rl = blk_rq_rl(req);
1365 
1366 		BUG_ON(!list_empty(&req->queuelist));
1367 		BUG_ON(ELV_ON_HASH(req));
1368 
1369 		blk_free_request(rl, req);
1370 		freed_request(rl, flags);
1371 		blk_put_rl(rl);
1372 	}
1373 }
1374 EXPORT_SYMBOL_GPL(__blk_put_request);
1375 
1376 void blk_put_request(struct request *req)
1377 {
1378 	struct request_queue *q = req->q;
1379 
1380 	if (q->mq_ops)
1381 		blk_mq_free_request(req);
1382 	else {
1383 		unsigned long flags;
1384 
1385 		spin_lock_irqsave(q->queue_lock, flags);
1386 		__blk_put_request(q, req);
1387 		spin_unlock_irqrestore(q->queue_lock, flags);
1388 	}
1389 }
1390 EXPORT_SYMBOL(blk_put_request);
1391 
1392 /**
1393  * blk_add_request_payload - add a payload to a request
1394  * @rq: request to update
1395  * @page: page backing the payload
1396  * @len: length of the payload.
1397  *
1398  * This allows to later add a payload to an already submitted request by
1399  * a block driver.  The driver needs to take care of freeing the payload
1400  * itself.
1401  *
1402  * Note that this is a quite horrible hack and nothing but handling of
1403  * discard requests should ever use it.
1404  */
1405 void blk_add_request_payload(struct request *rq, struct page *page,
1406 		unsigned int len)
1407 {
1408 	struct bio *bio = rq->bio;
1409 
1410 	bio->bi_io_vec->bv_page = page;
1411 	bio->bi_io_vec->bv_offset = 0;
1412 	bio->bi_io_vec->bv_len = len;
1413 
1414 	bio->bi_iter.bi_size = len;
1415 	bio->bi_vcnt = 1;
1416 	bio->bi_phys_segments = 1;
1417 
1418 	rq->__data_len = rq->resid_len = len;
1419 	rq->nr_phys_segments = 1;
1420 }
1421 EXPORT_SYMBOL_GPL(blk_add_request_payload);
1422 
1423 bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
1424 			    struct bio *bio)
1425 {
1426 	const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1427 
1428 	if (!ll_back_merge_fn(q, req, bio))
1429 		return false;
1430 
1431 	trace_block_bio_backmerge(q, req, bio);
1432 
1433 	if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1434 		blk_rq_set_mixed_merge(req);
1435 
1436 	req->biotail->bi_next = bio;
1437 	req->biotail = bio;
1438 	req->__data_len += bio->bi_iter.bi_size;
1439 	req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1440 
1441 	blk_account_io_start(req, false);
1442 	return true;
1443 }
1444 
1445 bool bio_attempt_front_merge(struct request_queue *q, struct request *req,
1446 			     struct bio *bio)
1447 {
1448 	const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1449 
1450 	if (!ll_front_merge_fn(q, req, bio))
1451 		return false;
1452 
1453 	trace_block_bio_frontmerge(q, req, bio);
1454 
1455 	if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1456 		blk_rq_set_mixed_merge(req);
1457 
1458 	bio->bi_next = req->bio;
1459 	req->bio = bio;
1460 
1461 	req->__sector = bio->bi_iter.bi_sector;
1462 	req->__data_len += bio->bi_iter.bi_size;
1463 	req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1464 
1465 	blk_account_io_start(req, false);
1466 	return true;
1467 }
1468 
1469 /**
1470  * blk_attempt_plug_merge - try to merge with %current's plugged list
1471  * @q: request_queue new bio is being queued at
1472  * @bio: new bio being queued
1473  * @request_count: out parameter for number of traversed plugged requests
1474  *
1475  * Determine whether @bio being queued on @q can be merged with a request
1476  * on %current's plugged list.  Returns %true if merge was successful,
1477  * otherwise %false.
1478  *
1479  * Plugging coalesces IOs from the same issuer for the same purpose without
1480  * going through @q->queue_lock.  As such it's more of an issuing mechanism
1481  * than scheduling, and the request, while may have elvpriv data, is not
1482  * added on the elevator at this point.  In addition, we don't have
1483  * reliable access to the elevator outside queue lock.  Only check basic
1484  * merging parameters without querying the elevator.
1485  *
1486  * Caller must ensure !blk_queue_nomerges(q) beforehand.
1487  */
1488 bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
1489 			    unsigned int *request_count)
1490 {
1491 	struct blk_plug *plug;
1492 	struct request *rq;
1493 	bool ret = false;
1494 	struct list_head *plug_list;
1495 
1496 	plug = current->plug;
1497 	if (!plug)
1498 		goto out;
1499 	*request_count = 0;
1500 
1501 	if (q->mq_ops)
1502 		plug_list = &plug->mq_list;
1503 	else
1504 		plug_list = &plug->list;
1505 
1506 	list_for_each_entry_reverse(rq, plug_list, queuelist) {
1507 		int el_ret;
1508 
1509 		if (rq->q == q)
1510 			(*request_count)++;
1511 
1512 		if (rq->q != q || !blk_rq_merge_ok(rq, bio))
1513 			continue;
1514 
1515 		el_ret = blk_try_merge(rq, bio);
1516 		if (el_ret == ELEVATOR_BACK_MERGE) {
1517 			ret = bio_attempt_back_merge(q, rq, bio);
1518 			if (ret)
1519 				break;
1520 		} else if (el_ret == ELEVATOR_FRONT_MERGE) {
1521 			ret = bio_attempt_front_merge(q, rq, bio);
1522 			if (ret)
1523 				break;
1524 		}
1525 	}
1526 out:
1527 	return ret;
1528 }
1529 
1530 void init_request_from_bio(struct request *req, struct bio *bio)
1531 {
1532 	req->cmd_type = REQ_TYPE_FS;
1533 
1534 	req->cmd_flags |= bio->bi_rw & REQ_COMMON_MASK;
1535 	if (bio->bi_rw & REQ_RAHEAD)
1536 		req->cmd_flags |= REQ_FAILFAST_MASK;
1537 
1538 	req->errors = 0;
1539 	req->__sector = bio->bi_iter.bi_sector;
1540 	req->ioprio = bio_prio(bio);
1541 	blk_rq_bio_prep(req->q, req, bio);
1542 }
1543 
1544 void blk_queue_bio(struct request_queue *q, struct bio *bio)
1545 {
1546 	const bool sync = !!(bio->bi_rw & REQ_SYNC);
1547 	struct blk_plug *plug;
1548 	int el_ret, rw_flags, where = ELEVATOR_INSERT_SORT;
1549 	struct request *req;
1550 	unsigned int request_count = 0;
1551 
1552 	/*
1553 	 * low level driver can indicate that it wants pages above a
1554 	 * certain limit bounced to low memory (ie for highmem, or even
1555 	 * ISA dma in theory)
1556 	 */
1557 	blk_queue_bounce(q, &bio);
1558 
1559 	if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) {
1560 		bio_endio(bio, -EIO);
1561 		return;
1562 	}
1563 
1564 	if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) {
1565 		spin_lock_irq(q->queue_lock);
1566 		where = ELEVATOR_INSERT_FLUSH;
1567 		goto get_rq;
1568 	}
1569 
1570 	/*
1571 	 * Check if we can merge with the plugged list before grabbing
1572 	 * any locks.
1573 	 */
1574 	if (!blk_queue_nomerges(q) &&
1575 	    blk_attempt_plug_merge(q, bio, &request_count))
1576 		return;
1577 
1578 	spin_lock_irq(q->queue_lock);
1579 
1580 	el_ret = elv_merge(q, &req, bio);
1581 	if (el_ret == ELEVATOR_BACK_MERGE) {
1582 		if (bio_attempt_back_merge(q, req, bio)) {
1583 			elv_bio_merged(q, req, bio);
1584 			if (!attempt_back_merge(q, req))
1585 				elv_merged_request(q, req, el_ret);
1586 			goto out_unlock;
1587 		}
1588 	} else if (el_ret == ELEVATOR_FRONT_MERGE) {
1589 		if (bio_attempt_front_merge(q, req, bio)) {
1590 			elv_bio_merged(q, req, bio);
1591 			if (!attempt_front_merge(q, req))
1592 				elv_merged_request(q, req, el_ret);
1593 			goto out_unlock;
1594 		}
1595 	}
1596 
1597 get_rq:
1598 	/*
1599 	 * This sync check and mask will be re-done in init_request_from_bio(),
1600 	 * but we need to set it earlier to expose the sync flag to the
1601 	 * rq allocator and io schedulers.
1602 	 */
1603 	rw_flags = bio_data_dir(bio);
1604 	if (sync)
1605 		rw_flags |= REQ_SYNC;
1606 
1607 	/*
1608 	 * Grab a free request. This is might sleep but can not fail.
1609 	 * Returns with the queue unlocked.
1610 	 */
1611 	req = get_request(q, rw_flags, bio, GFP_NOIO);
1612 	if (IS_ERR(req)) {
1613 		bio_endio(bio, PTR_ERR(req));	/* @q is dead */
1614 		goto out_unlock;
1615 	}
1616 
1617 	/*
1618 	 * After dropping the lock and possibly sleeping here, our request
1619 	 * may now be mergeable after it had proven unmergeable (above).
1620 	 * We don't worry about that case for efficiency. It won't happen
1621 	 * often, and the elevators are able to handle it.
1622 	 */
1623 	init_request_from_bio(req, bio);
1624 
1625 	if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags))
1626 		req->cpu = raw_smp_processor_id();
1627 
1628 	plug = current->plug;
1629 	if (plug) {
1630 		/*
1631 		 * If this is the first request added after a plug, fire
1632 		 * of a plug trace.
1633 		 */
1634 		if (!request_count)
1635 			trace_block_plug(q);
1636 		else {
1637 			if (request_count >= BLK_MAX_REQUEST_COUNT) {
1638 				blk_flush_plug_list(plug, false);
1639 				trace_block_plug(q);
1640 			}
1641 		}
1642 		list_add_tail(&req->queuelist, &plug->list);
1643 		blk_account_io_start(req, true);
1644 	} else {
1645 		spin_lock_irq(q->queue_lock);
1646 		add_acct_request(q, req, where);
1647 		__blk_run_queue(q);
1648 out_unlock:
1649 		spin_unlock_irq(q->queue_lock);
1650 	}
1651 }
1652 EXPORT_SYMBOL_GPL(blk_queue_bio);	/* for device mapper only */
1653 
1654 /*
1655  * If bio->bi_dev is a partition, remap the location
1656  */
1657 static inline void blk_partition_remap(struct bio *bio)
1658 {
1659 	struct block_device *bdev = bio->bi_bdev;
1660 
1661 	if (bio_sectors(bio) && bdev != bdev->bd_contains) {
1662 		struct hd_struct *p = bdev->bd_part;
1663 
1664 		bio->bi_iter.bi_sector += p->start_sect;
1665 		bio->bi_bdev = bdev->bd_contains;
1666 
1667 		trace_block_bio_remap(bdev_get_queue(bio->bi_bdev), bio,
1668 				      bdev->bd_dev,
1669 				      bio->bi_iter.bi_sector - p->start_sect);
1670 	}
1671 }
1672 
1673 static void handle_bad_sector(struct bio *bio)
1674 {
1675 	char b[BDEVNAME_SIZE];
1676 
1677 	printk(KERN_INFO "attempt to access beyond end of device\n");
1678 	printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
1679 			bdevname(bio->bi_bdev, b),
1680 			bio->bi_rw,
1681 			(unsigned long long)bio_end_sector(bio),
1682 			(long long)(i_size_read(bio->bi_bdev->bd_inode) >> 9));
1683 
1684 	set_bit(BIO_EOF, &bio->bi_flags);
1685 }
1686 
1687 #ifdef CONFIG_FAIL_MAKE_REQUEST
1688 
1689 static DECLARE_FAULT_ATTR(fail_make_request);
1690 
1691 static int __init setup_fail_make_request(char *str)
1692 {
1693 	return setup_fault_attr(&fail_make_request, str);
1694 }
1695 __setup("fail_make_request=", setup_fail_make_request);
1696 
1697 static bool should_fail_request(struct hd_struct *part, unsigned int bytes)
1698 {
1699 	return part->make_it_fail && should_fail(&fail_make_request, bytes);
1700 }
1701 
1702 static int __init fail_make_request_debugfs(void)
1703 {
1704 	struct dentry *dir = fault_create_debugfs_attr("fail_make_request",
1705 						NULL, &fail_make_request);
1706 
1707 	return PTR_ERR_OR_ZERO(dir);
1708 }
1709 
1710 late_initcall(fail_make_request_debugfs);
1711 
1712 #else /* CONFIG_FAIL_MAKE_REQUEST */
1713 
1714 static inline bool should_fail_request(struct hd_struct *part,
1715 					unsigned int bytes)
1716 {
1717 	return false;
1718 }
1719 
1720 #endif /* CONFIG_FAIL_MAKE_REQUEST */
1721 
1722 /*
1723  * Check whether this bio extends beyond the end of the device.
1724  */
1725 static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1726 {
1727 	sector_t maxsector;
1728 
1729 	if (!nr_sectors)
1730 		return 0;
1731 
1732 	/* Test device or partition size, when known. */
1733 	maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
1734 	if (maxsector) {
1735 		sector_t sector = bio->bi_iter.bi_sector;
1736 
1737 		if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1738 			/*
1739 			 * This may well happen - the kernel calls bread()
1740 			 * without checking the size of the device, e.g., when
1741 			 * mounting a device.
1742 			 */
1743 			handle_bad_sector(bio);
1744 			return 1;
1745 		}
1746 	}
1747 
1748 	return 0;
1749 }
1750 
1751 static noinline_for_stack bool
1752 generic_make_request_checks(struct bio *bio)
1753 {
1754 	struct request_queue *q;
1755 	int nr_sectors = bio_sectors(bio);
1756 	int err = -EIO;
1757 	char b[BDEVNAME_SIZE];
1758 	struct hd_struct *part;
1759 
1760 	might_sleep();
1761 
1762 	if (bio_check_eod(bio, nr_sectors))
1763 		goto end_io;
1764 
1765 	q = bdev_get_queue(bio->bi_bdev);
1766 	if (unlikely(!q)) {
1767 		printk(KERN_ERR
1768 		       "generic_make_request: Trying to access "
1769 			"nonexistent block-device %s (%Lu)\n",
1770 			bdevname(bio->bi_bdev, b),
1771 			(long long) bio->bi_iter.bi_sector);
1772 		goto end_io;
1773 	}
1774 
1775 	if (likely(bio_is_rw(bio) &&
1776 		   nr_sectors > queue_max_hw_sectors(q))) {
1777 		printk(KERN_ERR "bio too big device %s (%u > %u)\n",
1778 		       bdevname(bio->bi_bdev, b),
1779 		       bio_sectors(bio),
1780 		       queue_max_hw_sectors(q));
1781 		goto end_io;
1782 	}
1783 
1784 	part = bio->bi_bdev->bd_part;
1785 	if (should_fail_request(part, bio->bi_iter.bi_size) ||
1786 	    should_fail_request(&part_to_disk(part)->part0,
1787 				bio->bi_iter.bi_size))
1788 		goto end_io;
1789 
1790 	/*
1791 	 * If this device has partitions, remap block n
1792 	 * of partition p to block n+start(p) of the disk.
1793 	 */
1794 	blk_partition_remap(bio);
1795 
1796 	if (bio_check_eod(bio, nr_sectors))
1797 		goto end_io;
1798 
1799 	/*
1800 	 * Filter flush bio's early so that make_request based
1801 	 * drivers without flush support don't have to worry
1802 	 * about them.
1803 	 */
1804 	if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
1805 		bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
1806 		if (!nr_sectors) {
1807 			err = 0;
1808 			goto end_io;
1809 		}
1810 	}
1811 
1812 	if ((bio->bi_rw & REQ_DISCARD) &&
1813 	    (!blk_queue_discard(q) ||
1814 	     ((bio->bi_rw & REQ_SECURE) && !blk_queue_secdiscard(q)))) {
1815 		err = -EOPNOTSUPP;
1816 		goto end_io;
1817 	}
1818 
1819 	if (bio->bi_rw & REQ_WRITE_SAME && !bdev_write_same(bio->bi_bdev)) {
1820 		err = -EOPNOTSUPP;
1821 		goto end_io;
1822 	}
1823 
1824 	/*
1825 	 * Various block parts want %current->io_context and lazy ioc
1826 	 * allocation ends up trading a lot of pain for a small amount of
1827 	 * memory.  Just allocate it upfront.  This may fail and block
1828 	 * layer knows how to live with it.
1829 	 */
1830 	create_io_context(GFP_ATOMIC, q->node);
1831 
1832 	if (blk_throtl_bio(q, bio))
1833 		return false;	/* throttled, will be resubmitted later */
1834 
1835 	trace_block_bio_queue(q, bio);
1836 	return true;
1837 
1838 end_io:
1839 	bio_endio(bio, err);
1840 	return false;
1841 }
1842 
1843 /**
1844  * generic_make_request - hand a buffer to its device driver for I/O
1845  * @bio:  The bio describing the location in memory and on the device.
1846  *
1847  * generic_make_request() is used to make I/O requests of block
1848  * devices. It is passed a &struct bio, which describes the I/O that needs
1849  * to be done.
1850  *
1851  * generic_make_request() does not return any status.  The
1852  * success/failure status of the request, along with notification of
1853  * completion, is delivered asynchronously through the bio->bi_end_io
1854  * function described (one day) else where.
1855  *
1856  * The caller of generic_make_request must make sure that bi_io_vec
1857  * are set to describe the memory buffer, and that bi_dev and bi_sector are
1858  * set to describe the device address, and the
1859  * bi_end_io and optionally bi_private are set to describe how
1860  * completion notification should be signaled.
1861  *
1862  * generic_make_request and the drivers it calls may use bi_next if this
1863  * bio happens to be merged with someone else, and may resubmit the bio to
1864  * a lower device by calling into generic_make_request recursively, which
1865  * means the bio should NOT be touched after the call to ->make_request_fn.
1866  */
1867 void generic_make_request(struct bio *bio)
1868 {
1869 	struct bio_list bio_list_on_stack;
1870 
1871 	if (!generic_make_request_checks(bio))
1872 		return;
1873 
1874 	/*
1875 	 * We only want one ->make_request_fn to be active at a time, else
1876 	 * stack usage with stacked devices could be a problem.  So use
1877 	 * current->bio_list to keep a list of requests submited by a
1878 	 * make_request_fn function.  current->bio_list is also used as a
1879 	 * flag to say if generic_make_request is currently active in this
1880 	 * task or not.  If it is NULL, then no make_request is active.  If
1881 	 * it is non-NULL, then a make_request is active, and new requests
1882 	 * should be added at the tail
1883 	 */
1884 	if (current->bio_list) {
1885 		bio_list_add(current->bio_list, bio);
1886 		return;
1887 	}
1888 
1889 	/* following loop may be a bit non-obvious, and so deserves some
1890 	 * explanation.
1891 	 * Before entering the loop, bio->bi_next is NULL (as all callers
1892 	 * ensure that) so we have a list with a single bio.
1893 	 * We pretend that we have just taken it off a longer list, so
1894 	 * we assign bio_list to a pointer to the bio_list_on_stack,
1895 	 * thus initialising the bio_list of new bios to be
1896 	 * added.  ->make_request() may indeed add some more bios
1897 	 * through a recursive call to generic_make_request.  If it
1898 	 * did, we find a non-NULL value in bio_list and re-enter the loop
1899 	 * from the top.  In this case we really did just take the bio
1900 	 * of the top of the list (no pretending) and so remove it from
1901 	 * bio_list, and call into ->make_request() again.
1902 	 */
1903 	BUG_ON(bio->bi_next);
1904 	bio_list_init(&bio_list_on_stack);
1905 	current->bio_list = &bio_list_on_stack;
1906 	do {
1907 		struct request_queue *q = bdev_get_queue(bio->bi_bdev);
1908 
1909 		q->make_request_fn(q, bio);
1910 
1911 		bio = bio_list_pop(current->bio_list);
1912 	} while (bio);
1913 	current->bio_list = NULL; /* deactivate */
1914 }
1915 EXPORT_SYMBOL(generic_make_request);
1916 
1917 /**
1918  * submit_bio - submit a bio to the block device layer for I/O
1919  * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1920  * @bio: The &struct bio which describes the I/O
1921  *
1922  * submit_bio() is very similar in purpose to generic_make_request(), and
1923  * uses that function to do most of the work. Both are fairly rough
1924  * interfaces; @bio must be presetup and ready for I/O.
1925  *
1926  */
1927 void submit_bio(int rw, struct bio *bio)
1928 {
1929 	bio->bi_rw |= rw;
1930 
1931 	/*
1932 	 * If it's a regular read/write or a barrier with data attached,
1933 	 * go through the normal accounting stuff before submission.
1934 	 */
1935 	if (bio_has_data(bio)) {
1936 		unsigned int count;
1937 
1938 		if (unlikely(rw & REQ_WRITE_SAME))
1939 			count = bdev_logical_block_size(bio->bi_bdev) >> 9;
1940 		else
1941 			count = bio_sectors(bio);
1942 
1943 		if (rw & WRITE) {
1944 			count_vm_events(PGPGOUT, count);
1945 		} else {
1946 			task_io_account_read(bio->bi_iter.bi_size);
1947 			count_vm_events(PGPGIN, count);
1948 		}
1949 
1950 		if (unlikely(block_dump)) {
1951 			char b[BDEVNAME_SIZE];
1952 			printk(KERN_DEBUG "%s(%d): %s block %Lu on %s (%u sectors)\n",
1953 			current->comm, task_pid_nr(current),
1954 				(rw & WRITE) ? "WRITE" : "READ",
1955 				(unsigned long long)bio->bi_iter.bi_sector,
1956 				bdevname(bio->bi_bdev, b),
1957 				count);
1958 		}
1959 	}
1960 
1961 	generic_make_request(bio);
1962 }
1963 EXPORT_SYMBOL(submit_bio);
1964 
1965 /**
1966  * blk_rq_check_limits - Helper function to check a request for the queue limit
1967  * @q:  the queue
1968  * @rq: the request being checked
1969  *
1970  * Description:
1971  *    @rq may have been made based on weaker limitations of upper-level queues
1972  *    in request stacking drivers, and it may violate the limitation of @q.
1973  *    Since the block layer and the underlying device driver trust @rq
1974  *    after it is inserted to @q, it should be checked against @q before
1975  *    the insertion using this generic function.
1976  *
1977  *    This function should also be useful for request stacking drivers
1978  *    in some cases below, so export this function.
1979  *    Request stacking drivers like request-based dm may change the queue
1980  *    limits while requests are in the queue (e.g. dm's table swapping).
1981  *    Such request stacking drivers should check those requests against
1982  *    the new queue limits again when they dispatch those requests,
1983  *    although such checkings are also done against the old queue limits
1984  *    when submitting requests.
1985  */
1986 int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1987 {
1988 	if (!rq_mergeable(rq))
1989 		return 0;
1990 
1991 	if (blk_rq_sectors(rq) > blk_queue_get_max_sectors(q, rq->cmd_flags)) {
1992 		printk(KERN_ERR "%s: over max size limit.\n", __func__);
1993 		return -EIO;
1994 	}
1995 
1996 	/*
1997 	 * queue's settings related to segment counting like q->bounce_pfn
1998 	 * may differ from that of other stacking queues.
1999 	 * Recalculate it to check the request correctly on this queue's
2000 	 * limitation.
2001 	 */
2002 	blk_recalc_rq_segments(rq);
2003 	if (rq->nr_phys_segments > queue_max_segments(q)) {
2004 		printk(KERN_ERR "%s: over max segments limit.\n", __func__);
2005 		return -EIO;
2006 	}
2007 
2008 	return 0;
2009 }
2010 EXPORT_SYMBOL_GPL(blk_rq_check_limits);
2011 
2012 /**
2013  * blk_insert_cloned_request - Helper for stacking drivers to submit a request
2014  * @q:  the queue to submit the request
2015  * @rq: the request being queued
2016  */
2017 int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
2018 {
2019 	unsigned long flags;
2020 	int where = ELEVATOR_INSERT_BACK;
2021 
2022 	if (blk_rq_check_limits(q, rq))
2023 		return -EIO;
2024 
2025 	if (rq->rq_disk &&
2026 	    should_fail_request(&rq->rq_disk->part0, blk_rq_bytes(rq)))
2027 		return -EIO;
2028 
2029 	spin_lock_irqsave(q->queue_lock, flags);
2030 	if (unlikely(blk_queue_dying(q))) {
2031 		spin_unlock_irqrestore(q->queue_lock, flags);
2032 		return -ENODEV;
2033 	}
2034 
2035 	/*
2036 	 * Submitting request must be dequeued before calling this function
2037 	 * because it will be linked to another request_queue
2038 	 */
2039 	BUG_ON(blk_queued_rq(rq));
2040 
2041 	if (rq->cmd_flags & (REQ_FLUSH|REQ_FUA))
2042 		where = ELEVATOR_INSERT_FLUSH;
2043 
2044 	add_acct_request(q, rq, where);
2045 	if (where == ELEVATOR_INSERT_FLUSH)
2046 		__blk_run_queue(q);
2047 	spin_unlock_irqrestore(q->queue_lock, flags);
2048 
2049 	return 0;
2050 }
2051 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
2052 
2053 /**
2054  * blk_rq_err_bytes - determine number of bytes till the next failure boundary
2055  * @rq: request to examine
2056  *
2057  * Description:
2058  *     A request could be merge of IOs which require different failure
2059  *     handling.  This function determines the number of bytes which
2060  *     can be failed from the beginning of the request without
2061  *     crossing into area which need to be retried further.
2062  *
2063  * Return:
2064  *     The number of bytes to fail.
2065  *
2066  * Context:
2067  *     queue_lock must be held.
2068  */
2069 unsigned int blk_rq_err_bytes(const struct request *rq)
2070 {
2071 	unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
2072 	unsigned int bytes = 0;
2073 	struct bio *bio;
2074 
2075 	if (!(rq->cmd_flags & REQ_MIXED_MERGE))
2076 		return blk_rq_bytes(rq);
2077 
2078 	/*
2079 	 * Currently the only 'mixing' which can happen is between
2080 	 * different fastfail types.  We can safely fail portions
2081 	 * which have all the failfast bits that the first one has -
2082 	 * the ones which are at least as eager to fail as the first
2083 	 * one.
2084 	 */
2085 	for (bio = rq->bio; bio; bio = bio->bi_next) {
2086 		if ((bio->bi_rw & ff) != ff)
2087 			break;
2088 		bytes += bio->bi_iter.bi_size;
2089 	}
2090 
2091 	/* this could lead to infinite loop */
2092 	BUG_ON(blk_rq_bytes(rq) && !bytes);
2093 	return bytes;
2094 }
2095 EXPORT_SYMBOL_GPL(blk_rq_err_bytes);
2096 
2097 void blk_account_io_completion(struct request *req, unsigned int bytes)
2098 {
2099 	if (blk_do_io_stat(req)) {
2100 		const int rw = rq_data_dir(req);
2101 		struct hd_struct *part;
2102 		int cpu;
2103 
2104 		cpu = part_stat_lock();
2105 		part = req->part;
2106 		part_stat_add(cpu, part, sectors[rw], bytes >> 9);
2107 		part_stat_unlock();
2108 	}
2109 }
2110 
2111 void blk_account_io_done(struct request *req)
2112 {
2113 	/*
2114 	 * Account IO completion.  flush_rq isn't accounted as a
2115 	 * normal IO on queueing nor completion.  Accounting the
2116 	 * containing request is enough.
2117 	 */
2118 	if (blk_do_io_stat(req) && !(req->cmd_flags & REQ_FLUSH_SEQ)) {
2119 		unsigned long duration = jiffies - req->start_time;
2120 		const int rw = rq_data_dir(req);
2121 		struct hd_struct *part;
2122 		int cpu;
2123 
2124 		cpu = part_stat_lock();
2125 		part = req->part;
2126 
2127 		part_stat_inc(cpu, part, ios[rw]);
2128 		part_stat_add(cpu, part, ticks[rw], duration);
2129 		part_round_stats(cpu, part);
2130 		part_dec_in_flight(part, rw);
2131 
2132 		hd_struct_put(part);
2133 		part_stat_unlock();
2134 	}
2135 }
2136 
2137 #ifdef CONFIG_PM_RUNTIME
2138 /*
2139  * Don't process normal requests when queue is suspended
2140  * or in the process of suspending/resuming
2141  */
2142 static struct request *blk_pm_peek_request(struct request_queue *q,
2143 					   struct request *rq)
2144 {
2145 	if (q->dev && (q->rpm_status == RPM_SUSPENDED ||
2146 	    (q->rpm_status != RPM_ACTIVE && !(rq->cmd_flags & REQ_PM))))
2147 		return NULL;
2148 	else
2149 		return rq;
2150 }
2151 #else
2152 static inline struct request *blk_pm_peek_request(struct request_queue *q,
2153 						  struct request *rq)
2154 {
2155 	return rq;
2156 }
2157 #endif
2158 
2159 void blk_account_io_start(struct request *rq, bool new_io)
2160 {
2161 	struct hd_struct *part;
2162 	int rw = rq_data_dir(rq);
2163 	int cpu;
2164 
2165 	if (!blk_do_io_stat(rq))
2166 		return;
2167 
2168 	cpu = part_stat_lock();
2169 
2170 	if (!new_io) {
2171 		part = rq->part;
2172 		part_stat_inc(cpu, part, merges[rw]);
2173 	} else {
2174 		part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq));
2175 		if (!hd_struct_try_get(part)) {
2176 			/*
2177 			 * The partition is already being removed,
2178 			 * the request will be accounted on the disk only
2179 			 *
2180 			 * We take a reference on disk->part0 although that
2181 			 * partition will never be deleted, so we can treat
2182 			 * it as any other partition.
2183 			 */
2184 			part = &rq->rq_disk->part0;
2185 			hd_struct_get(part);
2186 		}
2187 		part_round_stats(cpu, part);
2188 		part_inc_in_flight(part, rw);
2189 		rq->part = part;
2190 	}
2191 
2192 	part_stat_unlock();
2193 }
2194 
2195 /**
2196  * blk_peek_request - peek at the top of a request queue
2197  * @q: request queue to peek at
2198  *
2199  * Description:
2200  *     Return the request at the top of @q.  The returned request
2201  *     should be started using blk_start_request() before LLD starts
2202  *     processing it.
2203  *
2204  * Return:
2205  *     Pointer to the request at the top of @q if available.  Null
2206  *     otherwise.
2207  *
2208  * Context:
2209  *     queue_lock must be held.
2210  */
2211 struct request *blk_peek_request(struct request_queue *q)
2212 {
2213 	struct request *rq;
2214 	int ret;
2215 
2216 	while ((rq = __elv_next_request(q)) != NULL) {
2217 
2218 		rq = blk_pm_peek_request(q, rq);
2219 		if (!rq)
2220 			break;
2221 
2222 		if (!(rq->cmd_flags & REQ_STARTED)) {
2223 			/*
2224 			 * This is the first time the device driver
2225 			 * sees this request (possibly after
2226 			 * requeueing).  Notify IO scheduler.
2227 			 */
2228 			if (rq->cmd_flags & REQ_SORTED)
2229 				elv_activate_rq(q, rq);
2230 
2231 			/*
2232 			 * just mark as started even if we don't start
2233 			 * it, a request that has been delayed should
2234 			 * not be passed by new incoming requests
2235 			 */
2236 			rq->cmd_flags |= REQ_STARTED;
2237 			trace_block_rq_issue(q, rq);
2238 		}
2239 
2240 		if (!q->boundary_rq || q->boundary_rq == rq) {
2241 			q->end_sector = rq_end_sector(rq);
2242 			q->boundary_rq = NULL;
2243 		}
2244 
2245 		if (rq->cmd_flags & REQ_DONTPREP)
2246 			break;
2247 
2248 		if (q->dma_drain_size && blk_rq_bytes(rq)) {
2249 			/*
2250 			 * make sure space for the drain appears we
2251 			 * know we can do this because max_hw_segments
2252 			 * has been adjusted to be one fewer than the
2253 			 * device can handle
2254 			 */
2255 			rq->nr_phys_segments++;
2256 		}
2257 
2258 		if (!q->prep_rq_fn)
2259 			break;
2260 
2261 		ret = q->prep_rq_fn(q, rq);
2262 		if (ret == BLKPREP_OK) {
2263 			break;
2264 		} else if (ret == BLKPREP_DEFER) {
2265 			/*
2266 			 * the request may have been (partially) prepped.
2267 			 * we need to keep this request in the front to
2268 			 * avoid resource deadlock.  REQ_STARTED will
2269 			 * prevent other fs requests from passing this one.
2270 			 */
2271 			if (q->dma_drain_size && blk_rq_bytes(rq) &&
2272 			    !(rq->cmd_flags & REQ_DONTPREP)) {
2273 				/*
2274 				 * remove the space for the drain we added
2275 				 * so that we don't add it again
2276 				 */
2277 				--rq->nr_phys_segments;
2278 			}
2279 
2280 			rq = NULL;
2281 			break;
2282 		} else if (ret == BLKPREP_KILL) {
2283 			rq->cmd_flags |= REQ_QUIET;
2284 			/*
2285 			 * Mark this request as started so we don't trigger
2286 			 * any debug logic in the end I/O path.
2287 			 */
2288 			blk_start_request(rq);
2289 			__blk_end_request_all(rq, -EIO);
2290 		} else {
2291 			printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
2292 			break;
2293 		}
2294 	}
2295 
2296 	return rq;
2297 }
2298 EXPORT_SYMBOL(blk_peek_request);
2299 
2300 void blk_dequeue_request(struct request *rq)
2301 {
2302 	struct request_queue *q = rq->q;
2303 
2304 	BUG_ON(list_empty(&rq->queuelist));
2305 	BUG_ON(ELV_ON_HASH(rq));
2306 
2307 	list_del_init(&rq->queuelist);
2308 
2309 	/*
2310 	 * the time frame between a request being removed from the lists
2311 	 * and to it is freed is accounted as io that is in progress at
2312 	 * the driver side.
2313 	 */
2314 	if (blk_account_rq(rq)) {
2315 		q->in_flight[rq_is_sync(rq)]++;
2316 		set_io_start_time_ns(rq);
2317 	}
2318 }
2319 
2320 /**
2321  * blk_start_request - start request processing on the driver
2322  * @req: request to dequeue
2323  *
2324  * Description:
2325  *     Dequeue @req and start timeout timer on it.  This hands off the
2326  *     request to the driver.
2327  *
2328  *     Block internal functions which don't want to start timer should
2329  *     call blk_dequeue_request().
2330  *
2331  * Context:
2332  *     queue_lock must be held.
2333  */
2334 void blk_start_request(struct request *req)
2335 {
2336 	blk_dequeue_request(req);
2337 
2338 	/*
2339 	 * We are now handing the request to the hardware, initialize
2340 	 * resid_len to full count and add the timeout handler.
2341 	 */
2342 	req->resid_len = blk_rq_bytes(req);
2343 	if (unlikely(blk_bidi_rq(req)))
2344 		req->next_rq->resid_len = blk_rq_bytes(req->next_rq);
2345 
2346 	BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));
2347 	blk_add_timer(req);
2348 }
2349 EXPORT_SYMBOL(blk_start_request);
2350 
2351 /**
2352  * blk_fetch_request - fetch a request from a request queue
2353  * @q: request queue to fetch a request from
2354  *
2355  * Description:
2356  *     Return the request at the top of @q.  The request is started on
2357  *     return and LLD can start processing it immediately.
2358  *
2359  * Return:
2360  *     Pointer to the request at the top of @q if available.  Null
2361  *     otherwise.
2362  *
2363  * Context:
2364  *     queue_lock must be held.
2365  */
2366 struct request *blk_fetch_request(struct request_queue *q)
2367 {
2368 	struct request *rq;
2369 
2370 	rq = blk_peek_request(q);
2371 	if (rq)
2372 		blk_start_request(rq);
2373 	return rq;
2374 }
2375 EXPORT_SYMBOL(blk_fetch_request);
2376 
2377 /**
2378  * blk_update_request - Special helper function for request stacking drivers
2379  * @req:      the request being processed
2380  * @error:    %0 for success, < %0 for error
2381  * @nr_bytes: number of bytes to complete @req
2382  *
2383  * Description:
2384  *     Ends I/O on a number of bytes attached to @req, but doesn't complete
2385  *     the request structure even if @req doesn't have leftover.
2386  *     If @req has leftover, sets it up for the next range of segments.
2387  *
2388  *     This special helper function is only for request stacking drivers
2389  *     (e.g. request-based dm) so that they can handle partial completion.
2390  *     Actual device drivers should use blk_end_request instead.
2391  *
2392  *     Passing the result of blk_rq_bytes() as @nr_bytes guarantees
2393  *     %false return from this function.
2394  *
2395  * Return:
2396  *     %false - this request doesn't have any more data
2397  *     %true  - this request has more data
2398  **/
2399 bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
2400 {
2401 	int total_bytes;
2402 
2403 	trace_block_rq_complete(req->q, req, nr_bytes);
2404 
2405 	if (!req->bio)
2406 		return false;
2407 
2408 	/*
2409 	 * For fs requests, rq is just carrier of independent bio's
2410 	 * and each partial completion should be handled separately.
2411 	 * Reset per-request error on each partial completion.
2412 	 *
2413 	 * TODO: tj: This is too subtle.  It would be better to let
2414 	 * low level drivers do what they see fit.
2415 	 */
2416 	if (req->cmd_type == REQ_TYPE_FS)
2417 		req->errors = 0;
2418 
2419 	if (error && req->cmd_type == REQ_TYPE_FS &&
2420 	    !(req->cmd_flags & REQ_QUIET)) {
2421 		char *error_type;
2422 
2423 		switch (error) {
2424 		case -ENOLINK:
2425 			error_type = "recoverable transport";
2426 			break;
2427 		case -EREMOTEIO:
2428 			error_type = "critical target";
2429 			break;
2430 		case -EBADE:
2431 			error_type = "critical nexus";
2432 			break;
2433 		case -ETIMEDOUT:
2434 			error_type = "timeout";
2435 			break;
2436 		case -ENOSPC:
2437 			error_type = "critical space allocation";
2438 			break;
2439 		case -ENODATA:
2440 			error_type = "critical medium";
2441 			break;
2442 		case -EIO:
2443 		default:
2444 			error_type = "I/O";
2445 			break;
2446 		}
2447 		printk_ratelimited(KERN_ERR "%s: %s error, dev %s, sector %llu\n",
2448 				   __func__, error_type, req->rq_disk ?
2449 				   req->rq_disk->disk_name : "?",
2450 				   (unsigned long long)blk_rq_pos(req));
2451 
2452 	}
2453 
2454 	blk_account_io_completion(req, nr_bytes);
2455 
2456 	total_bytes = 0;
2457 	while (req->bio) {
2458 		struct bio *bio = req->bio;
2459 		unsigned bio_bytes = min(bio->bi_iter.bi_size, nr_bytes);
2460 
2461 		if (bio_bytes == bio->bi_iter.bi_size)
2462 			req->bio = bio->bi_next;
2463 
2464 		req_bio_endio(req, bio, bio_bytes, error);
2465 
2466 		total_bytes += bio_bytes;
2467 		nr_bytes -= bio_bytes;
2468 
2469 		if (!nr_bytes)
2470 			break;
2471 	}
2472 
2473 	/*
2474 	 * completely done
2475 	 */
2476 	if (!req->bio) {
2477 		/*
2478 		 * Reset counters so that the request stacking driver
2479 		 * can find how many bytes remain in the request
2480 		 * later.
2481 		 */
2482 		req->__data_len = 0;
2483 		return false;
2484 	}
2485 
2486 	req->__data_len -= total_bytes;
2487 
2488 	/* update sector only for requests with clear definition of sector */
2489 	if (req->cmd_type == REQ_TYPE_FS)
2490 		req->__sector += total_bytes >> 9;
2491 
2492 	/* mixed attributes always follow the first bio */
2493 	if (req->cmd_flags & REQ_MIXED_MERGE) {
2494 		req->cmd_flags &= ~REQ_FAILFAST_MASK;
2495 		req->cmd_flags |= req->bio->bi_rw & REQ_FAILFAST_MASK;
2496 	}
2497 
2498 	/*
2499 	 * If total number of sectors is less than the first segment
2500 	 * size, something has gone terribly wrong.
2501 	 */
2502 	if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
2503 		blk_dump_rq_flags(req, "request botched");
2504 		req->__data_len = blk_rq_cur_bytes(req);
2505 	}
2506 
2507 	/* recalculate the number of segments */
2508 	blk_recalc_rq_segments(req);
2509 
2510 	return true;
2511 }
2512 EXPORT_SYMBOL_GPL(blk_update_request);
2513 
2514 static bool blk_update_bidi_request(struct request *rq, int error,
2515 				    unsigned int nr_bytes,
2516 				    unsigned int bidi_bytes)
2517 {
2518 	if (blk_update_request(rq, error, nr_bytes))
2519 		return true;
2520 
2521 	/* Bidi request must be completed as a whole */
2522 	if (unlikely(blk_bidi_rq(rq)) &&
2523 	    blk_update_request(rq->next_rq, error, bidi_bytes))
2524 		return true;
2525 
2526 	if (blk_queue_add_random(rq->q))
2527 		add_disk_randomness(rq->rq_disk);
2528 
2529 	return false;
2530 }
2531 
2532 /**
2533  * blk_unprep_request - unprepare a request
2534  * @req:	the request
2535  *
2536  * This function makes a request ready for complete resubmission (or
2537  * completion).  It happens only after all error handling is complete,
2538  * so represents the appropriate moment to deallocate any resources
2539  * that were allocated to the request in the prep_rq_fn.  The queue
2540  * lock is held when calling this.
2541  */
2542 void blk_unprep_request(struct request *req)
2543 {
2544 	struct request_queue *q = req->q;
2545 
2546 	req->cmd_flags &= ~REQ_DONTPREP;
2547 	if (q->unprep_rq_fn)
2548 		q->unprep_rq_fn(q, req);
2549 }
2550 EXPORT_SYMBOL_GPL(blk_unprep_request);
2551 
2552 /*
2553  * queue lock must be held
2554  */
2555 void blk_finish_request(struct request *req, int error)
2556 {
2557 	if (blk_rq_tagged(req))
2558 		blk_queue_end_tag(req->q, req);
2559 
2560 	BUG_ON(blk_queued_rq(req));
2561 
2562 	if (unlikely(laptop_mode) && req->cmd_type == REQ_TYPE_FS)
2563 		laptop_io_completion(&req->q->backing_dev_info);
2564 
2565 	blk_delete_timer(req);
2566 
2567 	if (req->cmd_flags & REQ_DONTPREP)
2568 		blk_unprep_request(req);
2569 
2570 	blk_account_io_done(req);
2571 
2572 	if (req->end_io)
2573 		req->end_io(req, error);
2574 	else {
2575 		if (blk_bidi_rq(req))
2576 			__blk_put_request(req->next_rq->q, req->next_rq);
2577 
2578 		__blk_put_request(req->q, req);
2579 	}
2580 }
2581 EXPORT_SYMBOL(blk_finish_request);
2582 
2583 /**
2584  * blk_end_bidi_request - Complete a bidi request
2585  * @rq:         the request to complete
2586  * @error:      %0 for success, < %0 for error
2587  * @nr_bytes:   number of bytes to complete @rq
2588  * @bidi_bytes: number of bytes to complete @rq->next_rq
2589  *
2590  * Description:
2591  *     Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2592  *     Drivers that supports bidi can safely call this member for any
2593  *     type of request, bidi or uni.  In the later case @bidi_bytes is
2594  *     just ignored.
2595  *
2596  * Return:
2597  *     %false - we are done with this request
2598  *     %true  - still buffers pending for this request
2599  **/
2600 static bool blk_end_bidi_request(struct request *rq, int error,
2601 				 unsigned int nr_bytes, unsigned int bidi_bytes)
2602 {
2603 	struct request_queue *q = rq->q;
2604 	unsigned long flags;
2605 
2606 	if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2607 		return true;
2608 
2609 	spin_lock_irqsave(q->queue_lock, flags);
2610 	blk_finish_request(rq, error);
2611 	spin_unlock_irqrestore(q->queue_lock, flags);
2612 
2613 	return false;
2614 }
2615 
2616 /**
2617  * __blk_end_bidi_request - Complete a bidi request with queue lock held
2618  * @rq:         the request to complete
2619  * @error:      %0 for success, < %0 for error
2620  * @nr_bytes:   number of bytes to complete @rq
2621  * @bidi_bytes: number of bytes to complete @rq->next_rq
2622  *
2623  * Description:
2624  *     Identical to blk_end_bidi_request() except that queue lock is
2625  *     assumed to be locked on entry and remains so on return.
2626  *
2627  * Return:
2628  *     %false - we are done with this request
2629  *     %true  - still buffers pending for this request
2630  **/
2631 bool __blk_end_bidi_request(struct request *rq, int error,
2632 				   unsigned int nr_bytes, unsigned int bidi_bytes)
2633 {
2634 	if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2635 		return true;
2636 
2637 	blk_finish_request(rq, error);
2638 
2639 	return false;
2640 }
2641 
2642 /**
2643  * blk_end_request - Helper function for drivers to complete the request.
2644  * @rq:       the request being processed
2645  * @error:    %0 for success, < %0 for error
2646  * @nr_bytes: number of bytes to complete
2647  *
2648  * Description:
2649  *     Ends I/O on a number of bytes attached to @rq.
2650  *     If @rq has leftover, sets it up for the next range of segments.
2651  *
2652  * Return:
2653  *     %false - we are done with this request
2654  *     %true  - still buffers pending for this request
2655  **/
2656 bool blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2657 {
2658 	return blk_end_bidi_request(rq, error, nr_bytes, 0);
2659 }
2660 EXPORT_SYMBOL(blk_end_request);
2661 
2662 /**
2663  * blk_end_request_all - Helper function for drives to finish the request.
2664  * @rq: the request to finish
2665  * @error: %0 for success, < %0 for error
2666  *
2667  * Description:
2668  *     Completely finish @rq.
2669  */
2670 void blk_end_request_all(struct request *rq, int error)
2671 {
2672 	bool pending;
2673 	unsigned int bidi_bytes = 0;
2674 
2675 	if (unlikely(blk_bidi_rq(rq)))
2676 		bidi_bytes = blk_rq_bytes(rq->next_rq);
2677 
2678 	pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2679 	BUG_ON(pending);
2680 }
2681 EXPORT_SYMBOL(blk_end_request_all);
2682 
2683 /**
2684  * blk_end_request_cur - Helper function to finish the current request chunk.
2685  * @rq: the request to finish the current chunk for
2686  * @error: %0 for success, < %0 for error
2687  *
2688  * Description:
2689  *     Complete the current consecutively mapped chunk from @rq.
2690  *
2691  * Return:
2692  *     %false - we are done with this request
2693  *     %true  - still buffers pending for this request
2694  */
2695 bool blk_end_request_cur(struct request *rq, int error)
2696 {
2697 	return blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2698 }
2699 EXPORT_SYMBOL(blk_end_request_cur);
2700 
2701 /**
2702  * blk_end_request_err - Finish a request till the next failure boundary.
2703  * @rq: the request to finish till the next failure boundary for
2704  * @error: must be negative errno
2705  *
2706  * Description:
2707  *     Complete @rq till the next failure boundary.
2708  *
2709  * Return:
2710  *     %false - we are done with this request
2711  *     %true  - still buffers pending for this request
2712  */
2713 bool blk_end_request_err(struct request *rq, int error)
2714 {
2715 	WARN_ON(error >= 0);
2716 	return blk_end_request(rq, error, blk_rq_err_bytes(rq));
2717 }
2718 EXPORT_SYMBOL_GPL(blk_end_request_err);
2719 
2720 /**
2721  * __blk_end_request - Helper function for drivers to complete the request.
2722  * @rq:       the request being processed
2723  * @error:    %0 for success, < %0 for error
2724  * @nr_bytes: number of bytes to complete
2725  *
2726  * Description:
2727  *     Must be called with queue lock held unlike blk_end_request().
2728  *
2729  * Return:
2730  *     %false - we are done with this request
2731  *     %true  - still buffers pending for this request
2732  **/
2733 bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2734 {
2735 	return __blk_end_bidi_request(rq, error, nr_bytes, 0);
2736 }
2737 EXPORT_SYMBOL(__blk_end_request);
2738 
2739 /**
2740  * __blk_end_request_all - Helper function for drives to finish the request.
2741  * @rq: the request to finish
2742  * @error: %0 for success, < %0 for error
2743  *
2744  * Description:
2745  *     Completely finish @rq.  Must be called with queue lock held.
2746  */
2747 void __blk_end_request_all(struct request *rq, int error)
2748 {
2749 	bool pending;
2750 	unsigned int bidi_bytes = 0;
2751 
2752 	if (unlikely(blk_bidi_rq(rq)))
2753 		bidi_bytes = blk_rq_bytes(rq->next_rq);
2754 
2755 	pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2756 	BUG_ON(pending);
2757 }
2758 EXPORT_SYMBOL(__blk_end_request_all);
2759 
2760 /**
2761  * __blk_end_request_cur - Helper function to finish the current request chunk.
2762  * @rq: the request to finish the current chunk for
2763  * @error: %0 for success, < %0 for error
2764  *
2765  * Description:
2766  *     Complete the current consecutively mapped chunk from @rq.  Must
2767  *     be called with queue lock held.
2768  *
2769  * Return:
2770  *     %false - we are done with this request
2771  *     %true  - still buffers pending for this request
2772  */
2773 bool __blk_end_request_cur(struct request *rq, int error)
2774 {
2775 	return __blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2776 }
2777 EXPORT_SYMBOL(__blk_end_request_cur);
2778 
2779 /**
2780  * __blk_end_request_err - Finish a request till the next failure boundary.
2781  * @rq: the request to finish till the next failure boundary for
2782  * @error: must be negative errno
2783  *
2784  * Description:
2785  *     Complete @rq till the next failure boundary.  Must be called
2786  *     with queue lock held.
2787  *
2788  * Return:
2789  *     %false - we are done with this request
2790  *     %true  - still buffers pending for this request
2791  */
2792 bool __blk_end_request_err(struct request *rq, int error)
2793 {
2794 	WARN_ON(error >= 0);
2795 	return __blk_end_request(rq, error, blk_rq_err_bytes(rq));
2796 }
2797 EXPORT_SYMBOL_GPL(__blk_end_request_err);
2798 
2799 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2800 		     struct bio *bio)
2801 {
2802 	/* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */
2803 	rq->cmd_flags |= bio->bi_rw & REQ_WRITE;
2804 
2805 	if (bio_has_data(bio))
2806 		rq->nr_phys_segments = bio_phys_segments(q, bio);
2807 
2808 	rq->__data_len = bio->bi_iter.bi_size;
2809 	rq->bio = rq->biotail = bio;
2810 
2811 	if (bio->bi_bdev)
2812 		rq->rq_disk = bio->bi_bdev->bd_disk;
2813 }
2814 
2815 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
2816 /**
2817  * rq_flush_dcache_pages - Helper function to flush all pages in a request
2818  * @rq: the request to be flushed
2819  *
2820  * Description:
2821  *     Flush all pages in @rq.
2822  */
2823 void rq_flush_dcache_pages(struct request *rq)
2824 {
2825 	struct req_iterator iter;
2826 	struct bio_vec bvec;
2827 
2828 	rq_for_each_segment(bvec, rq, iter)
2829 		flush_dcache_page(bvec.bv_page);
2830 }
2831 EXPORT_SYMBOL_GPL(rq_flush_dcache_pages);
2832 #endif
2833 
2834 /**
2835  * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2836  * @q : the queue of the device being checked
2837  *
2838  * Description:
2839  *    Check if underlying low-level drivers of a device are busy.
2840  *    If the drivers want to export their busy state, they must set own
2841  *    exporting function using blk_queue_lld_busy() first.
2842  *
2843  *    Basically, this function is used only by request stacking drivers
2844  *    to stop dispatching requests to underlying devices when underlying
2845  *    devices are busy.  This behavior helps more I/O merging on the queue
2846  *    of the request stacking driver and prevents I/O throughput regression
2847  *    on burst I/O load.
2848  *
2849  * Return:
2850  *    0 - Not busy (The request stacking driver should dispatch request)
2851  *    1 - Busy (The request stacking driver should stop dispatching request)
2852  */
2853 int blk_lld_busy(struct request_queue *q)
2854 {
2855 	if (q->lld_busy_fn)
2856 		return q->lld_busy_fn(q);
2857 
2858 	return 0;
2859 }
2860 EXPORT_SYMBOL_GPL(blk_lld_busy);
2861 
2862 /**
2863  * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
2864  * @rq: the clone request to be cleaned up
2865  *
2866  * Description:
2867  *     Free all bios in @rq for a cloned request.
2868  */
2869 void blk_rq_unprep_clone(struct request *rq)
2870 {
2871 	struct bio *bio;
2872 
2873 	while ((bio = rq->bio) != NULL) {
2874 		rq->bio = bio->bi_next;
2875 
2876 		bio_put(bio);
2877 	}
2878 }
2879 EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
2880 
2881 /*
2882  * Copy attributes of the original request to the clone request.
2883  * The actual data parts (e.g. ->cmd, ->sense) are not copied.
2884  */
2885 static void __blk_rq_prep_clone(struct request *dst, struct request *src)
2886 {
2887 	dst->cpu = src->cpu;
2888 	dst->cmd_flags = (src->cmd_flags & REQ_CLONE_MASK) | REQ_NOMERGE;
2889 	dst->cmd_type = src->cmd_type;
2890 	dst->__sector = blk_rq_pos(src);
2891 	dst->__data_len = blk_rq_bytes(src);
2892 	dst->nr_phys_segments = src->nr_phys_segments;
2893 	dst->ioprio = src->ioprio;
2894 	dst->extra_len = src->extra_len;
2895 }
2896 
2897 /**
2898  * blk_rq_prep_clone - Helper function to setup clone request
2899  * @rq: the request to be setup
2900  * @rq_src: original request to be cloned
2901  * @bs: bio_set that bios for clone are allocated from
2902  * @gfp_mask: memory allocation mask for bio
2903  * @bio_ctr: setup function to be called for each clone bio.
2904  *           Returns %0 for success, non %0 for failure.
2905  * @data: private data to be passed to @bio_ctr
2906  *
2907  * Description:
2908  *     Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
2909  *     The actual data parts of @rq_src (e.g. ->cmd, ->sense)
2910  *     are not copied, and copying such parts is the caller's responsibility.
2911  *     Also, pages which the original bios are pointing to are not copied
2912  *     and the cloned bios just point same pages.
2913  *     So cloned bios must be completed before original bios, which means
2914  *     the caller must complete @rq before @rq_src.
2915  */
2916 int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
2917 		      struct bio_set *bs, gfp_t gfp_mask,
2918 		      int (*bio_ctr)(struct bio *, struct bio *, void *),
2919 		      void *data)
2920 {
2921 	struct bio *bio, *bio_src;
2922 
2923 	if (!bs)
2924 		bs = fs_bio_set;
2925 
2926 	blk_rq_init(NULL, rq);
2927 
2928 	__rq_for_each_bio(bio_src, rq_src) {
2929 		bio = bio_clone_fast(bio_src, gfp_mask, bs);
2930 		if (!bio)
2931 			goto free_and_out;
2932 
2933 		if (bio_ctr && bio_ctr(bio, bio_src, data))
2934 			goto free_and_out;
2935 
2936 		if (rq->bio) {
2937 			rq->biotail->bi_next = bio;
2938 			rq->biotail = bio;
2939 		} else
2940 			rq->bio = rq->biotail = bio;
2941 	}
2942 
2943 	__blk_rq_prep_clone(rq, rq_src);
2944 
2945 	return 0;
2946 
2947 free_and_out:
2948 	if (bio)
2949 		bio_put(bio);
2950 	blk_rq_unprep_clone(rq);
2951 
2952 	return -ENOMEM;
2953 }
2954 EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
2955 
2956 int kblockd_schedule_work(struct work_struct *work)
2957 {
2958 	return queue_work(kblockd_workqueue, work);
2959 }
2960 EXPORT_SYMBOL(kblockd_schedule_work);
2961 
2962 int kblockd_schedule_delayed_work(struct delayed_work *dwork,
2963 				  unsigned long delay)
2964 {
2965 	return queue_delayed_work(kblockd_workqueue, dwork, delay);
2966 }
2967 EXPORT_SYMBOL(kblockd_schedule_delayed_work);
2968 
2969 int kblockd_schedule_delayed_work_on(int cpu, struct delayed_work *dwork,
2970 				     unsigned long delay)
2971 {
2972 	return queue_delayed_work_on(cpu, kblockd_workqueue, dwork, delay);
2973 }
2974 EXPORT_SYMBOL(kblockd_schedule_delayed_work_on);
2975 
2976 /**
2977  * blk_start_plug - initialize blk_plug and track it inside the task_struct
2978  * @plug:	The &struct blk_plug that needs to be initialized
2979  *
2980  * Description:
2981  *   Tracking blk_plug inside the task_struct will help with auto-flushing the
2982  *   pending I/O should the task end up blocking between blk_start_plug() and
2983  *   blk_finish_plug(). This is important from a performance perspective, but
2984  *   also ensures that we don't deadlock. For instance, if the task is blocking
2985  *   for a memory allocation, memory reclaim could end up wanting to free a
2986  *   page belonging to that request that is currently residing in our private
2987  *   plug. By flushing the pending I/O when the process goes to sleep, we avoid
2988  *   this kind of deadlock.
2989  */
2990 void blk_start_plug(struct blk_plug *plug)
2991 {
2992 	struct task_struct *tsk = current;
2993 
2994 	INIT_LIST_HEAD(&plug->list);
2995 	INIT_LIST_HEAD(&plug->mq_list);
2996 	INIT_LIST_HEAD(&plug->cb_list);
2997 
2998 	/*
2999 	 * If this is a nested plug, don't actually assign it. It will be
3000 	 * flushed on its own.
3001 	 */
3002 	if (!tsk->plug) {
3003 		/*
3004 		 * Store ordering should not be needed here, since a potential
3005 		 * preempt will imply a full memory barrier
3006 		 */
3007 		tsk->plug = plug;
3008 	}
3009 }
3010 EXPORT_SYMBOL(blk_start_plug);
3011 
3012 static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
3013 {
3014 	struct request *rqa = container_of(a, struct request, queuelist);
3015 	struct request *rqb = container_of(b, struct request, queuelist);
3016 
3017 	return !(rqa->q < rqb->q ||
3018 		(rqa->q == rqb->q && blk_rq_pos(rqa) < blk_rq_pos(rqb)));
3019 }
3020 
3021 /*
3022  * If 'from_schedule' is true, then postpone the dispatch of requests
3023  * until a safe kblockd context. We due this to avoid accidental big
3024  * additional stack usage in driver dispatch, in places where the originally
3025  * plugger did not intend it.
3026  */
3027 static void queue_unplugged(struct request_queue *q, unsigned int depth,
3028 			    bool from_schedule)
3029 	__releases(q->queue_lock)
3030 {
3031 	trace_block_unplug(q, depth, !from_schedule);
3032 
3033 	if (from_schedule)
3034 		blk_run_queue_async(q);
3035 	else
3036 		__blk_run_queue(q);
3037 	spin_unlock(q->queue_lock);
3038 }
3039 
3040 static void flush_plug_callbacks(struct blk_plug *plug, bool from_schedule)
3041 {
3042 	LIST_HEAD(callbacks);
3043 
3044 	while (!list_empty(&plug->cb_list)) {
3045 		list_splice_init(&plug->cb_list, &callbacks);
3046 
3047 		while (!list_empty(&callbacks)) {
3048 			struct blk_plug_cb *cb = list_first_entry(&callbacks,
3049 							  struct blk_plug_cb,
3050 							  list);
3051 			list_del(&cb->list);
3052 			cb->callback(cb, from_schedule);
3053 		}
3054 	}
3055 }
3056 
3057 struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug, void *data,
3058 				      int size)
3059 {
3060 	struct blk_plug *plug = current->plug;
3061 	struct blk_plug_cb *cb;
3062 
3063 	if (!plug)
3064 		return NULL;
3065 
3066 	list_for_each_entry(cb, &plug->cb_list, list)
3067 		if (cb->callback == unplug && cb->data == data)
3068 			return cb;
3069 
3070 	/* Not currently on the callback list */
3071 	BUG_ON(size < sizeof(*cb));
3072 	cb = kzalloc(size, GFP_ATOMIC);
3073 	if (cb) {
3074 		cb->data = data;
3075 		cb->callback = unplug;
3076 		list_add(&cb->list, &plug->cb_list);
3077 	}
3078 	return cb;
3079 }
3080 EXPORT_SYMBOL(blk_check_plugged);
3081 
3082 void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
3083 {
3084 	struct request_queue *q;
3085 	unsigned long flags;
3086 	struct request *rq;
3087 	LIST_HEAD(list);
3088 	unsigned int depth;
3089 
3090 	flush_plug_callbacks(plug, from_schedule);
3091 
3092 	if (!list_empty(&plug->mq_list))
3093 		blk_mq_flush_plug_list(plug, from_schedule);
3094 
3095 	if (list_empty(&plug->list))
3096 		return;
3097 
3098 	list_splice_init(&plug->list, &list);
3099 
3100 	list_sort(NULL, &list, plug_rq_cmp);
3101 
3102 	q = NULL;
3103 	depth = 0;
3104 
3105 	/*
3106 	 * Save and disable interrupts here, to avoid doing it for every
3107 	 * queue lock we have to take.
3108 	 */
3109 	local_irq_save(flags);
3110 	while (!list_empty(&list)) {
3111 		rq = list_entry_rq(list.next);
3112 		list_del_init(&rq->queuelist);
3113 		BUG_ON(!rq->q);
3114 		if (rq->q != q) {
3115 			/*
3116 			 * This drops the queue lock
3117 			 */
3118 			if (q)
3119 				queue_unplugged(q, depth, from_schedule);
3120 			q = rq->q;
3121 			depth = 0;
3122 			spin_lock(q->queue_lock);
3123 		}
3124 
3125 		/*
3126 		 * Short-circuit if @q is dead
3127 		 */
3128 		if (unlikely(blk_queue_dying(q))) {
3129 			__blk_end_request_all(rq, -ENODEV);
3130 			continue;
3131 		}
3132 
3133 		/*
3134 		 * rq is already accounted, so use raw insert
3135 		 */
3136 		if (rq->cmd_flags & (REQ_FLUSH | REQ_FUA))
3137 			__elv_add_request(q, rq, ELEVATOR_INSERT_FLUSH);
3138 		else
3139 			__elv_add_request(q, rq, ELEVATOR_INSERT_SORT_MERGE);
3140 
3141 		depth++;
3142 	}
3143 
3144 	/*
3145 	 * This drops the queue lock
3146 	 */
3147 	if (q)
3148 		queue_unplugged(q, depth, from_schedule);
3149 
3150 	local_irq_restore(flags);
3151 }
3152 
3153 void blk_finish_plug(struct blk_plug *plug)
3154 {
3155 	blk_flush_plug_list(plug, false);
3156 
3157 	if (plug == current->plug)
3158 		current->plug = NULL;
3159 }
3160 EXPORT_SYMBOL(blk_finish_plug);
3161 
3162 #ifdef CONFIG_PM_RUNTIME
3163 /**
3164  * blk_pm_runtime_init - Block layer runtime PM initialization routine
3165  * @q: the queue of the device
3166  * @dev: the device the queue belongs to
3167  *
3168  * Description:
3169  *    Initialize runtime-PM-related fields for @q and start auto suspend for
3170  *    @dev. Drivers that want to take advantage of request-based runtime PM
3171  *    should call this function after @dev has been initialized, and its
3172  *    request queue @q has been allocated, and runtime PM for it can not happen
3173  *    yet(either due to disabled/forbidden or its usage_count > 0). In most
3174  *    cases, driver should call this function before any I/O has taken place.
3175  *
3176  *    This function takes care of setting up using auto suspend for the device,
3177  *    the autosuspend delay is set to -1 to make runtime suspend impossible
3178  *    until an updated value is either set by user or by driver. Drivers do
3179  *    not need to touch other autosuspend settings.
3180  *
3181  *    The block layer runtime PM is request based, so only works for drivers
3182  *    that use request as their IO unit instead of those directly use bio's.
3183  */
3184 void blk_pm_runtime_init(struct request_queue *q, struct device *dev)
3185 {
3186 	q->dev = dev;
3187 	q->rpm_status = RPM_ACTIVE;
3188 	pm_runtime_set_autosuspend_delay(q->dev, -1);
3189 	pm_runtime_use_autosuspend(q->dev);
3190 }
3191 EXPORT_SYMBOL(blk_pm_runtime_init);
3192 
3193 /**
3194  * blk_pre_runtime_suspend - Pre runtime suspend check
3195  * @q: the queue of the device
3196  *
3197  * Description:
3198  *    This function will check if runtime suspend is allowed for the device
3199  *    by examining if there are any requests pending in the queue. If there
3200  *    are requests pending, the device can not be runtime suspended; otherwise,
3201  *    the queue's status will be updated to SUSPENDING and the driver can
3202  *    proceed to suspend the device.
3203  *
3204  *    For the not allowed case, we mark last busy for the device so that
3205  *    runtime PM core will try to autosuspend it some time later.
3206  *
3207  *    This function should be called near the start of the device's
3208  *    runtime_suspend callback.
3209  *
3210  * Return:
3211  *    0		- OK to runtime suspend the device
3212  *    -EBUSY	- Device should not be runtime suspended
3213  */
3214 int blk_pre_runtime_suspend(struct request_queue *q)
3215 {
3216 	int ret = 0;
3217 
3218 	spin_lock_irq(q->queue_lock);
3219 	if (q->nr_pending) {
3220 		ret = -EBUSY;
3221 		pm_runtime_mark_last_busy(q->dev);
3222 	} else {
3223 		q->rpm_status = RPM_SUSPENDING;
3224 	}
3225 	spin_unlock_irq(q->queue_lock);
3226 	return ret;
3227 }
3228 EXPORT_SYMBOL(blk_pre_runtime_suspend);
3229 
3230 /**
3231  * blk_post_runtime_suspend - Post runtime suspend processing
3232  * @q: the queue of the device
3233  * @err: return value of the device's runtime_suspend function
3234  *
3235  * Description:
3236  *    Update the queue's runtime status according to the return value of the
3237  *    device's runtime suspend function and mark last busy for the device so
3238  *    that PM core will try to auto suspend the device at a later time.
3239  *
3240  *    This function should be called near the end of the device's
3241  *    runtime_suspend callback.
3242  */
3243 void blk_post_runtime_suspend(struct request_queue *q, int err)
3244 {
3245 	spin_lock_irq(q->queue_lock);
3246 	if (!err) {
3247 		q->rpm_status = RPM_SUSPENDED;
3248 	} else {
3249 		q->rpm_status = RPM_ACTIVE;
3250 		pm_runtime_mark_last_busy(q->dev);
3251 	}
3252 	spin_unlock_irq(q->queue_lock);
3253 }
3254 EXPORT_SYMBOL(blk_post_runtime_suspend);
3255 
3256 /**
3257  * blk_pre_runtime_resume - Pre runtime resume processing
3258  * @q: the queue of the device
3259  *
3260  * Description:
3261  *    Update the queue's runtime status to RESUMING in preparation for the
3262  *    runtime resume of the device.
3263  *
3264  *    This function should be called near the start of the device's
3265  *    runtime_resume callback.
3266  */
3267 void blk_pre_runtime_resume(struct request_queue *q)
3268 {
3269 	spin_lock_irq(q->queue_lock);
3270 	q->rpm_status = RPM_RESUMING;
3271 	spin_unlock_irq(q->queue_lock);
3272 }
3273 EXPORT_SYMBOL(blk_pre_runtime_resume);
3274 
3275 /**
3276  * blk_post_runtime_resume - Post runtime resume processing
3277  * @q: the queue of the device
3278  * @err: return value of the device's runtime_resume function
3279  *
3280  * Description:
3281  *    Update the queue's runtime status according to the return value of the
3282  *    device's runtime_resume function. If it is successfully resumed, process
3283  *    the requests that are queued into the device's queue when it is resuming
3284  *    and then mark last busy and initiate autosuspend for it.
3285  *
3286  *    This function should be called near the end of the device's
3287  *    runtime_resume callback.
3288  */
3289 void blk_post_runtime_resume(struct request_queue *q, int err)
3290 {
3291 	spin_lock_irq(q->queue_lock);
3292 	if (!err) {
3293 		q->rpm_status = RPM_ACTIVE;
3294 		__blk_run_queue(q);
3295 		pm_runtime_mark_last_busy(q->dev);
3296 		pm_request_autosuspend(q->dev);
3297 	} else {
3298 		q->rpm_status = RPM_SUSPENDED;
3299 	}
3300 	spin_unlock_irq(q->queue_lock);
3301 }
3302 EXPORT_SYMBOL(blk_post_runtime_resume);
3303 #endif
3304 
3305 int __init blk_dev_init(void)
3306 {
3307 	BUILD_BUG_ON(__REQ_NR_BITS > 8 *
3308 			sizeof(((struct request *)0)->cmd_flags));
3309 
3310 	/* used for unplugging and affects IO latency/throughput - HIGHPRI */
3311 	kblockd_workqueue = alloc_workqueue("kblockd",
3312 					    WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
3313 	if (!kblockd_workqueue)
3314 		panic("Failed to create kblockd\n");
3315 
3316 	request_cachep = kmem_cache_create("blkdev_requests",
3317 			sizeof(struct request), 0, SLAB_PANIC, NULL);
3318 
3319 	blk_requestq_cachep = kmem_cache_create("blkdev_queue",
3320 			sizeof(struct request_queue), 0, SLAB_PANIC, NULL);
3321 
3322 	return 0;
3323 }
3324