xref: /openbmc/linux/block/blk-core.c (revision 82ced6fd)
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/highmem.h>
20 #include <linux/mm.h>
21 #include <linux/kernel_stat.h>
22 #include <linux/string.h>
23 #include <linux/init.h>
24 #include <linux/completion.h>
25 #include <linux/slab.h>
26 #include <linux/swap.h>
27 #include <linux/writeback.h>
28 #include <linux/task_io_accounting_ops.h>
29 #include <linux/blktrace_api.h>
30 #include <linux/fault-inject.h>
31 #include <trace/block.h>
32 
33 #include "blk.h"
34 
35 DEFINE_TRACE(block_plug);
36 DEFINE_TRACE(block_unplug_io);
37 DEFINE_TRACE(block_unplug_timer);
38 DEFINE_TRACE(block_getrq);
39 DEFINE_TRACE(block_sleeprq);
40 DEFINE_TRACE(block_rq_requeue);
41 DEFINE_TRACE(block_bio_backmerge);
42 DEFINE_TRACE(block_bio_frontmerge);
43 DEFINE_TRACE(block_bio_queue);
44 DEFINE_TRACE(block_rq_complete);
45 DEFINE_TRACE(block_remap);	/* Also used in drivers/md/dm.c */
46 EXPORT_TRACEPOINT_SYMBOL_GPL(block_remap);
47 
48 static int __make_request(struct request_queue *q, struct bio *bio);
49 
50 /*
51  * For the allocated request tables
52  */
53 static struct kmem_cache *request_cachep;
54 
55 /*
56  * For queue allocation
57  */
58 struct kmem_cache *blk_requestq_cachep;
59 
60 /*
61  * Controlling structure to kblockd
62  */
63 static struct workqueue_struct *kblockd_workqueue;
64 
65 static void drive_stat_acct(struct request *rq, int new_io)
66 {
67 	struct hd_struct *part;
68 	int rw = rq_data_dir(rq);
69 	int cpu;
70 
71 	if (!blk_fs_request(rq) || !blk_do_io_stat(rq))
72 		return;
73 
74 	cpu = part_stat_lock();
75 	part = disk_map_sector_rcu(rq->rq_disk, rq->sector);
76 
77 	if (!new_io)
78 		part_stat_inc(cpu, part, merges[rw]);
79 	else {
80 		part_round_stats(cpu, part);
81 		part_inc_in_flight(part);
82 	}
83 
84 	part_stat_unlock();
85 }
86 
87 void blk_queue_congestion_threshold(struct request_queue *q)
88 {
89 	int nr;
90 
91 	nr = q->nr_requests - (q->nr_requests / 8) + 1;
92 	if (nr > q->nr_requests)
93 		nr = q->nr_requests;
94 	q->nr_congestion_on = nr;
95 
96 	nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
97 	if (nr < 1)
98 		nr = 1;
99 	q->nr_congestion_off = nr;
100 }
101 
102 /**
103  * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
104  * @bdev:	device
105  *
106  * Locates the passed device's request queue and returns the address of its
107  * backing_dev_info
108  *
109  * Will return NULL if the request queue cannot be located.
110  */
111 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
112 {
113 	struct backing_dev_info *ret = NULL;
114 	struct request_queue *q = bdev_get_queue(bdev);
115 
116 	if (q)
117 		ret = &q->backing_dev_info;
118 	return ret;
119 }
120 EXPORT_SYMBOL(blk_get_backing_dev_info);
121 
122 void blk_rq_init(struct request_queue *q, struct request *rq)
123 {
124 	memset(rq, 0, sizeof(*rq));
125 
126 	INIT_LIST_HEAD(&rq->queuelist);
127 	INIT_LIST_HEAD(&rq->timeout_list);
128 	rq->cpu = -1;
129 	rq->q = q;
130 	rq->sector = rq->hard_sector = (sector_t) -1;
131 	INIT_HLIST_NODE(&rq->hash);
132 	RB_CLEAR_NODE(&rq->rb_node);
133 	rq->cmd = rq->__cmd;
134 	rq->cmd_len = BLK_MAX_CDB;
135 	rq->tag = -1;
136 	rq->ref_count = 1;
137 }
138 EXPORT_SYMBOL(blk_rq_init);
139 
140 static void req_bio_endio(struct request *rq, struct bio *bio,
141 			  unsigned int nbytes, int error)
142 {
143 	struct request_queue *q = rq->q;
144 
145 	if (&q->bar_rq != rq) {
146 		if (error)
147 			clear_bit(BIO_UPTODATE, &bio->bi_flags);
148 		else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
149 			error = -EIO;
150 
151 		if (unlikely(nbytes > bio->bi_size)) {
152 			printk(KERN_ERR "%s: want %u bytes done, %u left\n",
153 			       __func__, nbytes, bio->bi_size);
154 			nbytes = bio->bi_size;
155 		}
156 
157 		if (unlikely(rq->cmd_flags & REQ_QUIET))
158 			set_bit(BIO_QUIET, &bio->bi_flags);
159 
160 		bio->bi_size -= nbytes;
161 		bio->bi_sector += (nbytes >> 9);
162 
163 		if (bio_integrity(bio))
164 			bio_integrity_advance(bio, nbytes);
165 
166 		if (bio->bi_size == 0)
167 			bio_endio(bio, error);
168 	} else {
169 
170 		/*
171 		 * Okay, this is the barrier request in progress, just
172 		 * record the error;
173 		 */
174 		if (error && !q->orderr)
175 			q->orderr = error;
176 	}
177 }
178 
179 void blk_dump_rq_flags(struct request *rq, char *msg)
180 {
181 	int bit;
182 
183 	printk(KERN_INFO "%s: dev %s: type=%x, flags=%x\n", msg,
184 		rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type,
185 		rq->cmd_flags);
186 
187 	printk(KERN_INFO "  sector %llu, nr/cnr %lu/%u\n",
188 						(unsigned long long)rq->sector,
189 						rq->nr_sectors,
190 						rq->current_nr_sectors);
191 	printk(KERN_INFO "  bio %p, biotail %p, buffer %p, data %p, len %u\n",
192 						rq->bio, rq->biotail,
193 						rq->buffer, rq->data,
194 						rq->data_len);
195 
196 	if (blk_pc_request(rq)) {
197 		printk(KERN_INFO "  cdb: ");
198 		for (bit = 0; bit < BLK_MAX_CDB; bit++)
199 			printk("%02x ", rq->cmd[bit]);
200 		printk("\n");
201 	}
202 }
203 EXPORT_SYMBOL(blk_dump_rq_flags);
204 
205 /*
206  * "plug" the device if there are no outstanding requests: this will
207  * force the transfer to start only after we have put all the requests
208  * on the list.
209  *
210  * This is called with interrupts off and no requests on the queue and
211  * with the queue lock held.
212  */
213 void blk_plug_device(struct request_queue *q)
214 {
215 	WARN_ON(!irqs_disabled());
216 
217 	/*
218 	 * don't plug a stopped queue, it must be paired with blk_start_queue()
219 	 * which will restart the queueing
220 	 */
221 	if (blk_queue_stopped(q))
222 		return;
223 
224 	if (!queue_flag_test_and_set(QUEUE_FLAG_PLUGGED, q)) {
225 		mod_timer(&q->unplug_timer, jiffies + q->unplug_delay);
226 		trace_block_plug(q);
227 	}
228 }
229 EXPORT_SYMBOL(blk_plug_device);
230 
231 /**
232  * blk_plug_device_unlocked - plug a device without queue lock held
233  * @q:    The &struct request_queue to plug
234  *
235  * Description:
236  *   Like @blk_plug_device(), but grabs the queue lock and disables
237  *   interrupts.
238  **/
239 void blk_plug_device_unlocked(struct request_queue *q)
240 {
241 	unsigned long flags;
242 
243 	spin_lock_irqsave(q->queue_lock, flags);
244 	blk_plug_device(q);
245 	spin_unlock_irqrestore(q->queue_lock, flags);
246 }
247 EXPORT_SYMBOL(blk_plug_device_unlocked);
248 
249 /*
250  * remove the queue from the plugged list, if present. called with
251  * queue lock held and interrupts disabled.
252  */
253 int blk_remove_plug(struct request_queue *q)
254 {
255 	WARN_ON(!irqs_disabled());
256 
257 	if (!queue_flag_test_and_clear(QUEUE_FLAG_PLUGGED, q))
258 		return 0;
259 
260 	del_timer(&q->unplug_timer);
261 	return 1;
262 }
263 EXPORT_SYMBOL(blk_remove_plug);
264 
265 /*
266  * remove the plug and let it rip..
267  */
268 void __generic_unplug_device(struct request_queue *q)
269 {
270 	if (unlikely(blk_queue_stopped(q)))
271 		return;
272 	if (!blk_remove_plug(q) && !blk_queue_nonrot(q))
273 		return;
274 
275 	q->request_fn(q);
276 }
277 
278 /**
279  * generic_unplug_device - fire a request queue
280  * @q:    The &struct request_queue in question
281  *
282  * Description:
283  *   Linux uses plugging to build bigger requests queues before letting
284  *   the device have at them. If a queue is plugged, the I/O scheduler
285  *   is still adding and merging requests on the queue. Once the queue
286  *   gets unplugged, the request_fn defined for the queue is invoked and
287  *   transfers started.
288  **/
289 void generic_unplug_device(struct request_queue *q)
290 {
291 	if (blk_queue_plugged(q)) {
292 		spin_lock_irq(q->queue_lock);
293 		__generic_unplug_device(q);
294 		spin_unlock_irq(q->queue_lock);
295 	}
296 }
297 EXPORT_SYMBOL(generic_unplug_device);
298 
299 static void blk_backing_dev_unplug(struct backing_dev_info *bdi,
300 				   struct page *page)
301 {
302 	struct request_queue *q = bdi->unplug_io_data;
303 
304 	blk_unplug(q);
305 }
306 
307 void blk_unplug_work(struct work_struct *work)
308 {
309 	struct request_queue *q =
310 		container_of(work, struct request_queue, unplug_work);
311 
312 	trace_block_unplug_io(q);
313 	q->unplug_fn(q);
314 }
315 
316 void blk_unplug_timeout(unsigned long data)
317 {
318 	struct request_queue *q = (struct request_queue *)data;
319 
320 	trace_block_unplug_timer(q);
321 	kblockd_schedule_work(q, &q->unplug_work);
322 }
323 
324 void blk_unplug(struct request_queue *q)
325 {
326 	/*
327 	 * devices don't necessarily have an ->unplug_fn defined
328 	 */
329 	if (q->unplug_fn) {
330 		trace_block_unplug_io(q);
331 		q->unplug_fn(q);
332 	}
333 }
334 EXPORT_SYMBOL(blk_unplug);
335 
336 static void blk_invoke_request_fn(struct request_queue *q)
337 {
338 	if (unlikely(blk_queue_stopped(q)))
339 		return;
340 
341 	/*
342 	 * one level of recursion is ok and is much faster than kicking
343 	 * the unplug handling
344 	 */
345 	if (!queue_flag_test_and_set(QUEUE_FLAG_REENTER, q)) {
346 		q->request_fn(q);
347 		queue_flag_clear(QUEUE_FLAG_REENTER, q);
348 	} else {
349 		queue_flag_set(QUEUE_FLAG_PLUGGED, q);
350 		kblockd_schedule_work(q, &q->unplug_work);
351 	}
352 }
353 
354 /**
355  * blk_start_queue - restart a previously stopped queue
356  * @q:    The &struct request_queue in question
357  *
358  * Description:
359  *   blk_start_queue() will clear the stop flag on the queue, and call
360  *   the request_fn for the queue if it was in a stopped state when
361  *   entered. Also see blk_stop_queue(). Queue lock must be held.
362  **/
363 void blk_start_queue(struct request_queue *q)
364 {
365 	WARN_ON(!irqs_disabled());
366 
367 	queue_flag_clear(QUEUE_FLAG_STOPPED, q);
368 	blk_invoke_request_fn(q);
369 }
370 EXPORT_SYMBOL(blk_start_queue);
371 
372 /**
373  * blk_stop_queue - stop a queue
374  * @q:    The &struct request_queue in question
375  *
376  * Description:
377  *   The Linux block layer assumes that a block driver will consume all
378  *   entries on the request queue when the request_fn strategy is called.
379  *   Often this will not happen, because of hardware limitations (queue
380  *   depth settings). If a device driver gets a 'queue full' response,
381  *   or if it simply chooses not to queue more I/O at one point, it can
382  *   call this function to prevent the request_fn from being called until
383  *   the driver has signalled it's ready to go again. This happens by calling
384  *   blk_start_queue() to restart queue operations. Queue lock must be held.
385  **/
386 void blk_stop_queue(struct request_queue *q)
387 {
388 	blk_remove_plug(q);
389 	queue_flag_set(QUEUE_FLAG_STOPPED, q);
390 }
391 EXPORT_SYMBOL(blk_stop_queue);
392 
393 /**
394  * blk_sync_queue - cancel any pending callbacks on a queue
395  * @q: the queue
396  *
397  * Description:
398  *     The block layer may perform asynchronous callback activity
399  *     on a queue, such as calling the unplug function after a timeout.
400  *     A block device may call blk_sync_queue to ensure that any
401  *     such activity is cancelled, thus allowing it to release resources
402  *     that the callbacks might use. The caller must already have made sure
403  *     that its ->make_request_fn will not re-add plugging prior to calling
404  *     this function.
405  *
406  */
407 void blk_sync_queue(struct request_queue *q)
408 {
409 	del_timer_sync(&q->unplug_timer);
410 	del_timer_sync(&q->timeout);
411 	cancel_work_sync(&q->unplug_work);
412 }
413 EXPORT_SYMBOL(blk_sync_queue);
414 
415 /**
416  * __blk_run_queue - run a single device queue
417  * @q:	The queue to run
418  *
419  * Description:
420  *    See @blk_run_queue. This variant must be called with the queue lock
421  *    held and interrupts disabled.
422  *
423  */
424 void __blk_run_queue(struct request_queue *q)
425 {
426 	blk_remove_plug(q);
427 
428 	/*
429 	 * Only recurse once to avoid overrunning the stack, let the unplug
430 	 * handling reinvoke the handler shortly if we already got there.
431 	 */
432 	if (!elv_queue_empty(q))
433 		blk_invoke_request_fn(q);
434 }
435 EXPORT_SYMBOL(__blk_run_queue);
436 
437 /**
438  * blk_run_queue - run a single device queue
439  * @q: The queue to run
440  *
441  * Description:
442  *    Invoke request handling on this queue, if it has pending work to do.
443  *    May be used to restart queueing when a request has completed. Also
444  *    See @blk_start_queueing.
445  *
446  */
447 void blk_run_queue(struct request_queue *q)
448 {
449 	unsigned long flags;
450 
451 	spin_lock_irqsave(q->queue_lock, flags);
452 	__blk_run_queue(q);
453 	spin_unlock_irqrestore(q->queue_lock, flags);
454 }
455 EXPORT_SYMBOL(blk_run_queue);
456 
457 void blk_put_queue(struct request_queue *q)
458 {
459 	kobject_put(&q->kobj);
460 }
461 
462 void blk_cleanup_queue(struct request_queue *q)
463 {
464 	/*
465 	 * We know we have process context here, so we can be a little
466 	 * cautious and ensure that pending block actions on this device
467 	 * are done before moving on. Going into this function, we should
468 	 * not have processes doing IO to this device.
469 	 */
470 	blk_sync_queue(q);
471 
472 	mutex_lock(&q->sysfs_lock);
473 	queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
474 	mutex_unlock(&q->sysfs_lock);
475 
476 	if (q->elevator)
477 		elevator_exit(q->elevator);
478 
479 	blk_put_queue(q);
480 }
481 EXPORT_SYMBOL(blk_cleanup_queue);
482 
483 static int blk_init_free_list(struct request_queue *q)
484 {
485 	struct request_list *rl = &q->rq;
486 
487 	rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
488 	rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
489 	rl->elvpriv = 0;
490 	init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
491 	init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
492 
493 	rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
494 				mempool_free_slab, request_cachep, q->node);
495 
496 	if (!rl->rq_pool)
497 		return -ENOMEM;
498 
499 	return 0;
500 }
501 
502 struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
503 {
504 	return blk_alloc_queue_node(gfp_mask, -1);
505 }
506 EXPORT_SYMBOL(blk_alloc_queue);
507 
508 struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
509 {
510 	struct request_queue *q;
511 	int err;
512 
513 	q = kmem_cache_alloc_node(blk_requestq_cachep,
514 				gfp_mask | __GFP_ZERO, node_id);
515 	if (!q)
516 		return NULL;
517 
518 	q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug;
519 	q->backing_dev_info.unplug_io_data = q;
520 	err = bdi_init(&q->backing_dev_info);
521 	if (err) {
522 		kmem_cache_free(blk_requestq_cachep, q);
523 		return NULL;
524 	}
525 
526 	init_timer(&q->unplug_timer);
527 	setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
528 	INIT_LIST_HEAD(&q->timeout_list);
529 	INIT_WORK(&q->unplug_work, blk_unplug_work);
530 
531 	kobject_init(&q->kobj, &blk_queue_ktype);
532 
533 	mutex_init(&q->sysfs_lock);
534 	spin_lock_init(&q->__queue_lock);
535 
536 	return q;
537 }
538 EXPORT_SYMBOL(blk_alloc_queue_node);
539 
540 /**
541  * blk_init_queue  - prepare a request queue for use with a block device
542  * @rfn:  The function to be called to process requests that have been
543  *        placed on the queue.
544  * @lock: Request queue spin lock
545  *
546  * Description:
547  *    If a block device wishes to use the standard request handling procedures,
548  *    which sorts requests and coalesces adjacent requests, then it must
549  *    call blk_init_queue().  The function @rfn will be called when there
550  *    are requests on the queue that need to be processed.  If the device
551  *    supports plugging, then @rfn may not be called immediately when requests
552  *    are available on the queue, but may be called at some time later instead.
553  *    Plugged queues are generally unplugged when a buffer belonging to one
554  *    of the requests on the queue is needed, or due to memory pressure.
555  *
556  *    @rfn is not required, or even expected, to remove all requests off the
557  *    queue, but only as many as it can handle at a time.  If it does leave
558  *    requests on the queue, it is responsible for arranging that the requests
559  *    get dealt with eventually.
560  *
561  *    The queue spin lock must be held while manipulating the requests on the
562  *    request queue; this lock will be taken also from interrupt context, so irq
563  *    disabling is needed for it.
564  *
565  *    Function returns a pointer to the initialized request queue, or %NULL if
566  *    it didn't succeed.
567  *
568  * Note:
569  *    blk_init_queue() must be paired with a blk_cleanup_queue() call
570  *    when the block device is deactivated (such as at module unload).
571  **/
572 
573 struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
574 {
575 	return blk_init_queue_node(rfn, lock, -1);
576 }
577 EXPORT_SYMBOL(blk_init_queue);
578 
579 struct request_queue *
580 blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
581 {
582 	struct request_queue *q = blk_alloc_queue_node(GFP_KERNEL, node_id);
583 
584 	if (!q)
585 		return NULL;
586 
587 	q->node = node_id;
588 	if (blk_init_free_list(q)) {
589 		kmem_cache_free(blk_requestq_cachep, q);
590 		return NULL;
591 	}
592 
593 	/*
594 	 * if caller didn't supply a lock, they get per-queue locking with
595 	 * our embedded lock
596 	 */
597 	if (!lock)
598 		lock = &q->__queue_lock;
599 
600 	q->request_fn		= rfn;
601 	q->prep_rq_fn		= NULL;
602 	q->unplug_fn		= generic_unplug_device;
603 	q->queue_flags		= QUEUE_FLAG_DEFAULT;
604 	q->queue_lock		= lock;
605 
606 	/*
607 	 * This also sets hw/phys segments, boundary and size
608 	 */
609 	blk_queue_make_request(q, __make_request);
610 
611 	q->sg_reserved_size = INT_MAX;
612 
613 	blk_set_cmd_filter_defaults(&q->cmd_filter);
614 
615 	/*
616 	 * all done
617 	 */
618 	if (!elevator_init(q, NULL)) {
619 		blk_queue_congestion_threshold(q);
620 		return q;
621 	}
622 
623 	blk_put_queue(q);
624 	return NULL;
625 }
626 EXPORT_SYMBOL(blk_init_queue_node);
627 
628 int blk_get_queue(struct request_queue *q)
629 {
630 	if (likely(!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
631 		kobject_get(&q->kobj);
632 		return 0;
633 	}
634 
635 	return 1;
636 }
637 
638 static inline void blk_free_request(struct request_queue *q, struct request *rq)
639 {
640 	if (rq->cmd_flags & REQ_ELVPRIV)
641 		elv_put_request(q, rq);
642 	mempool_free(rq, q->rq.rq_pool);
643 }
644 
645 static struct request *
646 blk_alloc_request(struct request_queue *q, int flags, int priv, gfp_t gfp_mask)
647 {
648 	struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
649 
650 	if (!rq)
651 		return NULL;
652 
653 	blk_rq_init(q, rq);
654 
655 	rq->cmd_flags = flags | REQ_ALLOCED;
656 
657 	if (priv) {
658 		if (unlikely(elv_set_request(q, rq, gfp_mask))) {
659 			mempool_free(rq, q->rq.rq_pool);
660 			return NULL;
661 		}
662 		rq->cmd_flags |= REQ_ELVPRIV;
663 	}
664 
665 	return rq;
666 }
667 
668 /*
669  * ioc_batching returns true if the ioc is a valid batching request and
670  * should be given priority access to a request.
671  */
672 static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
673 {
674 	if (!ioc)
675 		return 0;
676 
677 	/*
678 	 * Make sure the process is able to allocate at least 1 request
679 	 * even if the batch times out, otherwise we could theoretically
680 	 * lose wakeups.
681 	 */
682 	return ioc->nr_batch_requests == q->nr_batching ||
683 		(ioc->nr_batch_requests > 0
684 		&& time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
685 }
686 
687 /*
688  * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
689  * will cause the process to be a "batcher" on all queues in the system. This
690  * is the behaviour we want though - once it gets a wakeup it should be given
691  * a nice run.
692  */
693 static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
694 {
695 	if (!ioc || ioc_batching(q, ioc))
696 		return;
697 
698 	ioc->nr_batch_requests = q->nr_batching;
699 	ioc->last_waited = jiffies;
700 }
701 
702 static void __freed_request(struct request_queue *q, int sync)
703 {
704 	struct request_list *rl = &q->rq;
705 
706 	if (rl->count[sync] < queue_congestion_off_threshold(q))
707 		blk_clear_queue_congested(q, sync);
708 
709 	if (rl->count[sync] + 1 <= q->nr_requests) {
710 		if (waitqueue_active(&rl->wait[sync]))
711 			wake_up(&rl->wait[sync]);
712 
713 		blk_clear_queue_full(q, sync);
714 	}
715 }
716 
717 /*
718  * A request has just been released.  Account for it, update the full and
719  * congestion status, wake up any waiters.   Called under q->queue_lock.
720  */
721 static void freed_request(struct request_queue *q, int sync, int priv)
722 {
723 	struct request_list *rl = &q->rq;
724 
725 	rl->count[sync]--;
726 	if (priv)
727 		rl->elvpriv--;
728 
729 	__freed_request(q, sync);
730 
731 	if (unlikely(rl->starved[sync ^ 1]))
732 		__freed_request(q, sync ^ 1);
733 }
734 
735 /*
736  * Get a free request, queue_lock must be held.
737  * Returns NULL on failure, with queue_lock held.
738  * Returns !NULL on success, with queue_lock *not held*.
739  */
740 static struct request *get_request(struct request_queue *q, int rw_flags,
741 				   struct bio *bio, gfp_t gfp_mask)
742 {
743 	struct request *rq = NULL;
744 	struct request_list *rl = &q->rq;
745 	struct io_context *ioc = NULL;
746 	const bool is_sync = rw_is_sync(rw_flags) != 0;
747 	int may_queue, priv;
748 
749 	may_queue = elv_may_queue(q, rw_flags);
750 	if (may_queue == ELV_MQUEUE_NO)
751 		goto rq_starved;
752 
753 	if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
754 		if (rl->count[is_sync]+1 >= q->nr_requests) {
755 			ioc = current_io_context(GFP_ATOMIC, q->node);
756 			/*
757 			 * The queue will fill after this allocation, so set
758 			 * it as full, and mark this process as "batching".
759 			 * This process will be allowed to complete a batch of
760 			 * requests, others will be blocked.
761 			 */
762 			if (!blk_queue_full(q, is_sync)) {
763 				ioc_set_batching(q, ioc);
764 				blk_set_queue_full(q, is_sync);
765 			} else {
766 				if (may_queue != ELV_MQUEUE_MUST
767 						&& !ioc_batching(q, ioc)) {
768 					/*
769 					 * The queue is full and the allocating
770 					 * process is not a "batcher", and not
771 					 * exempted by the IO scheduler
772 					 */
773 					goto out;
774 				}
775 			}
776 		}
777 		blk_set_queue_congested(q, is_sync);
778 	}
779 
780 	/*
781 	 * Only allow batching queuers to allocate up to 50% over the defined
782 	 * limit of requests, otherwise we could have thousands of requests
783 	 * allocated with any setting of ->nr_requests
784 	 */
785 	if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
786 		goto out;
787 
788 	rl->count[is_sync]++;
789 	rl->starved[is_sync] = 0;
790 
791 	priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
792 	if (priv)
793 		rl->elvpriv++;
794 
795 	if (blk_queue_io_stat(q))
796 		rw_flags |= REQ_IO_STAT;
797 	spin_unlock_irq(q->queue_lock);
798 
799 	rq = blk_alloc_request(q, rw_flags, priv, gfp_mask);
800 	if (unlikely(!rq)) {
801 		/*
802 		 * Allocation failed presumably due to memory. Undo anything
803 		 * we might have messed up.
804 		 *
805 		 * Allocating task should really be put onto the front of the
806 		 * wait queue, but this is pretty rare.
807 		 */
808 		spin_lock_irq(q->queue_lock);
809 		freed_request(q, is_sync, priv);
810 
811 		/*
812 		 * in the very unlikely event that allocation failed and no
813 		 * requests for this direction was pending, mark us starved
814 		 * so that freeing of a request in the other direction will
815 		 * notice us. another possible fix would be to split the
816 		 * rq mempool into READ and WRITE
817 		 */
818 rq_starved:
819 		if (unlikely(rl->count[is_sync] == 0))
820 			rl->starved[is_sync] = 1;
821 
822 		goto out;
823 	}
824 
825 	/*
826 	 * ioc may be NULL here, and ioc_batching will be false. That's
827 	 * OK, if the queue is under the request limit then requests need
828 	 * not count toward the nr_batch_requests limit. There will always
829 	 * be some limit enforced by BLK_BATCH_TIME.
830 	 */
831 	if (ioc_batching(q, ioc))
832 		ioc->nr_batch_requests--;
833 
834 	trace_block_getrq(q, bio, rw_flags & 1);
835 out:
836 	return rq;
837 }
838 
839 /*
840  * No available requests for this queue, unplug the device and wait for some
841  * requests to become available.
842  *
843  * Called with q->queue_lock held, and returns with it unlocked.
844  */
845 static struct request *get_request_wait(struct request_queue *q, int rw_flags,
846 					struct bio *bio)
847 {
848 	const bool is_sync = rw_is_sync(rw_flags) != 0;
849 	struct request *rq;
850 
851 	rq = get_request(q, rw_flags, bio, GFP_NOIO);
852 	while (!rq) {
853 		DEFINE_WAIT(wait);
854 		struct io_context *ioc;
855 		struct request_list *rl = &q->rq;
856 
857 		prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
858 				TASK_UNINTERRUPTIBLE);
859 
860 		trace_block_sleeprq(q, bio, rw_flags & 1);
861 
862 		__generic_unplug_device(q);
863 		spin_unlock_irq(q->queue_lock);
864 		io_schedule();
865 
866 		/*
867 		 * After sleeping, we become a "batching" process and
868 		 * will be able to allocate at least one request, and
869 		 * up to a big batch of them for a small period time.
870 		 * See ioc_batching, ioc_set_batching
871 		 */
872 		ioc = current_io_context(GFP_NOIO, q->node);
873 		ioc_set_batching(q, ioc);
874 
875 		spin_lock_irq(q->queue_lock);
876 		finish_wait(&rl->wait[is_sync], &wait);
877 
878 		rq = get_request(q, rw_flags, bio, GFP_NOIO);
879 	};
880 
881 	return rq;
882 }
883 
884 struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
885 {
886 	struct request *rq;
887 
888 	BUG_ON(rw != READ && rw != WRITE);
889 
890 	spin_lock_irq(q->queue_lock);
891 	if (gfp_mask & __GFP_WAIT) {
892 		rq = get_request_wait(q, rw, NULL);
893 	} else {
894 		rq = get_request(q, rw, NULL, gfp_mask);
895 		if (!rq)
896 			spin_unlock_irq(q->queue_lock);
897 	}
898 	/* q->queue_lock is unlocked at this point */
899 
900 	return rq;
901 }
902 EXPORT_SYMBOL(blk_get_request);
903 
904 /**
905  * blk_start_queueing - initiate dispatch of requests to device
906  * @q:		request queue to kick into gear
907  *
908  * This is basically a helper to remove the need to know whether a queue
909  * is plugged or not if someone just wants to initiate dispatch of requests
910  * for this queue. Should be used to start queueing on a device outside
911  * of ->request_fn() context. Also see @blk_run_queue.
912  *
913  * The queue lock must be held with interrupts disabled.
914  */
915 void blk_start_queueing(struct request_queue *q)
916 {
917 	if (!blk_queue_plugged(q)) {
918 		if (unlikely(blk_queue_stopped(q)))
919 			return;
920 		q->request_fn(q);
921 	} else
922 		__generic_unplug_device(q);
923 }
924 EXPORT_SYMBOL(blk_start_queueing);
925 
926 /**
927  * blk_requeue_request - put a request back on queue
928  * @q:		request queue where request should be inserted
929  * @rq:		request to be inserted
930  *
931  * Description:
932  *    Drivers often keep queueing requests until the hardware cannot accept
933  *    more, when that condition happens we need to put the request back
934  *    on the queue. Must be called with queue lock held.
935  */
936 void blk_requeue_request(struct request_queue *q, struct request *rq)
937 {
938 	blk_delete_timer(rq);
939 	blk_clear_rq_complete(rq);
940 	trace_block_rq_requeue(q, rq);
941 
942 	if (blk_rq_tagged(rq))
943 		blk_queue_end_tag(q, rq);
944 
945 	elv_requeue_request(q, rq);
946 }
947 EXPORT_SYMBOL(blk_requeue_request);
948 
949 /**
950  * blk_insert_request - insert a special request into a request queue
951  * @q:		request queue where request should be inserted
952  * @rq:		request to be inserted
953  * @at_head:	insert request at head or tail of queue
954  * @data:	private data
955  *
956  * Description:
957  *    Many block devices need to execute commands asynchronously, so they don't
958  *    block the whole kernel from preemption during request execution.  This is
959  *    accomplished normally by inserting aritficial requests tagged as
960  *    REQ_TYPE_SPECIAL in to the corresponding request queue, and letting them
961  *    be scheduled for actual execution by the request queue.
962  *
963  *    We have the option of inserting the head or the tail of the queue.
964  *    Typically we use the tail for new ioctls and so forth.  We use the head
965  *    of the queue for things like a QUEUE_FULL message from a device, or a
966  *    host that is unable to accept a particular command.
967  */
968 void blk_insert_request(struct request_queue *q, struct request *rq,
969 			int at_head, void *data)
970 {
971 	int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
972 	unsigned long flags;
973 
974 	/*
975 	 * tell I/O scheduler that this isn't a regular read/write (ie it
976 	 * must not attempt merges on this) and that it acts as a soft
977 	 * barrier
978 	 */
979 	rq->cmd_type = REQ_TYPE_SPECIAL;
980 	rq->cmd_flags |= REQ_SOFTBARRIER;
981 
982 	rq->special = data;
983 
984 	spin_lock_irqsave(q->queue_lock, flags);
985 
986 	/*
987 	 * If command is tagged, release the tag
988 	 */
989 	if (blk_rq_tagged(rq))
990 		blk_queue_end_tag(q, rq);
991 
992 	drive_stat_acct(rq, 1);
993 	__elv_add_request(q, rq, where, 0);
994 	blk_start_queueing(q);
995 	spin_unlock_irqrestore(q->queue_lock, flags);
996 }
997 EXPORT_SYMBOL(blk_insert_request);
998 
999 /*
1000  * add-request adds a request to the linked list.
1001  * queue lock is held and interrupts disabled, as we muck with the
1002  * request queue list.
1003  */
1004 static inline void add_request(struct request_queue *q, struct request *req)
1005 {
1006 	drive_stat_acct(req, 1);
1007 
1008 	/*
1009 	 * elevator indicated where it wants this request to be
1010 	 * inserted at elevator_merge time
1011 	 */
1012 	__elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
1013 }
1014 
1015 static void part_round_stats_single(int cpu, struct hd_struct *part,
1016 				    unsigned long now)
1017 {
1018 	if (now == part->stamp)
1019 		return;
1020 
1021 	if (part->in_flight) {
1022 		__part_stat_add(cpu, part, time_in_queue,
1023 				part->in_flight * (now - part->stamp));
1024 		__part_stat_add(cpu, part, io_ticks, (now - part->stamp));
1025 	}
1026 	part->stamp = now;
1027 }
1028 
1029 /**
1030  * part_round_stats() - Round off the performance stats on a struct disk_stats.
1031  * @cpu: cpu number for stats access
1032  * @part: target partition
1033  *
1034  * The average IO queue length and utilisation statistics are maintained
1035  * by observing the current state of the queue length and the amount of
1036  * time it has been in this state for.
1037  *
1038  * Normally, that accounting is done on IO completion, but that can result
1039  * in more than a second's worth of IO being accounted for within any one
1040  * second, leading to >100% utilisation.  To deal with that, we call this
1041  * function to do a round-off before returning the results when reading
1042  * /proc/diskstats.  This accounts immediately for all queue usage up to
1043  * the current jiffies and restarts the counters again.
1044  */
1045 void part_round_stats(int cpu, struct hd_struct *part)
1046 {
1047 	unsigned long now = jiffies;
1048 
1049 	if (part->partno)
1050 		part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1051 	part_round_stats_single(cpu, part, now);
1052 }
1053 EXPORT_SYMBOL_GPL(part_round_stats);
1054 
1055 /*
1056  * queue lock must be held
1057  */
1058 void __blk_put_request(struct request_queue *q, struct request *req)
1059 {
1060 	if (unlikely(!q))
1061 		return;
1062 	if (unlikely(--req->ref_count))
1063 		return;
1064 
1065 	elv_completed_request(q, req);
1066 
1067 	/* this is a bio leak */
1068 	WARN_ON(req->bio != NULL);
1069 
1070 	/*
1071 	 * Request may not have originated from ll_rw_blk. if not,
1072 	 * it didn't come out of our reserved rq pools
1073 	 */
1074 	if (req->cmd_flags & REQ_ALLOCED) {
1075 		int is_sync = rq_is_sync(req) != 0;
1076 		int priv = req->cmd_flags & REQ_ELVPRIV;
1077 
1078 		BUG_ON(!list_empty(&req->queuelist));
1079 		BUG_ON(!hlist_unhashed(&req->hash));
1080 
1081 		blk_free_request(q, req);
1082 		freed_request(q, is_sync, priv);
1083 	}
1084 }
1085 EXPORT_SYMBOL_GPL(__blk_put_request);
1086 
1087 void blk_put_request(struct request *req)
1088 {
1089 	unsigned long flags;
1090 	struct request_queue *q = req->q;
1091 
1092 	spin_lock_irqsave(q->queue_lock, flags);
1093 	__blk_put_request(q, req);
1094 	spin_unlock_irqrestore(q->queue_lock, flags);
1095 }
1096 EXPORT_SYMBOL(blk_put_request);
1097 
1098 void init_request_from_bio(struct request *req, struct bio *bio)
1099 {
1100 	req->cpu = bio->bi_comp_cpu;
1101 	req->cmd_type = REQ_TYPE_FS;
1102 
1103 	/*
1104 	 * inherit FAILFAST from bio (for read-ahead, and explicit FAILFAST)
1105 	 */
1106 	if (bio_rw_ahead(bio))
1107 		req->cmd_flags |= (REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
1108 				   REQ_FAILFAST_DRIVER);
1109 	if (bio_failfast_dev(bio))
1110 		req->cmd_flags |= REQ_FAILFAST_DEV;
1111 	if (bio_failfast_transport(bio))
1112 		req->cmd_flags |= REQ_FAILFAST_TRANSPORT;
1113 	if (bio_failfast_driver(bio))
1114 		req->cmd_flags |= REQ_FAILFAST_DRIVER;
1115 
1116 	/*
1117 	 * REQ_BARRIER implies no merging, but lets make it explicit
1118 	 */
1119 	if (unlikely(bio_discard(bio))) {
1120 		req->cmd_flags |= REQ_DISCARD;
1121 		if (bio_barrier(bio))
1122 			req->cmd_flags |= REQ_SOFTBARRIER;
1123 		req->q->prepare_discard_fn(req->q, req);
1124 	} else if (unlikely(bio_barrier(bio)))
1125 		req->cmd_flags |= (REQ_HARDBARRIER | REQ_NOMERGE);
1126 
1127 	if (bio_sync(bio))
1128 		req->cmd_flags |= REQ_RW_SYNC;
1129 	if (bio_rw_meta(bio))
1130 		req->cmd_flags |= REQ_RW_META;
1131 	if (bio_noidle(bio))
1132 		req->cmd_flags |= REQ_NOIDLE;
1133 
1134 	req->errors = 0;
1135 	req->hard_sector = req->sector = bio->bi_sector;
1136 	req->ioprio = bio_prio(bio);
1137 	req->start_time = jiffies;
1138 	blk_rq_bio_prep(req->q, req, bio);
1139 }
1140 
1141 /*
1142  * Only disabling plugging for non-rotational devices if it does tagging
1143  * as well, otherwise we do need the proper merging
1144  */
1145 static inline bool queue_should_plug(struct request_queue *q)
1146 {
1147 	return !(blk_queue_nonrot(q) && blk_queue_tagged(q));
1148 }
1149 
1150 static int __make_request(struct request_queue *q, struct bio *bio)
1151 {
1152 	struct request *req;
1153 	int el_ret, nr_sectors;
1154 	const unsigned short prio = bio_prio(bio);
1155 	const int sync = bio_sync(bio);
1156 	const int unplug = bio_unplug(bio);
1157 	int rw_flags;
1158 
1159 	nr_sectors = bio_sectors(bio);
1160 
1161 	/*
1162 	 * low level driver can indicate that it wants pages above a
1163 	 * certain limit bounced to low memory (ie for highmem, or even
1164 	 * ISA dma in theory)
1165 	 */
1166 	blk_queue_bounce(q, &bio);
1167 
1168 	spin_lock_irq(q->queue_lock);
1169 
1170 	if (unlikely(bio_barrier(bio)) || elv_queue_empty(q))
1171 		goto get_rq;
1172 
1173 	el_ret = elv_merge(q, &req, bio);
1174 	switch (el_ret) {
1175 	case ELEVATOR_BACK_MERGE:
1176 		BUG_ON(!rq_mergeable(req));
1177 
1178 		if (!ll_back_merge_fn(q, req, bio))
1179 			break;
1180 
1181 		trace_block_bio_backmerge(q, bio);
1182 
1183 		req->biotail->bi_next = bio;
1184 		req->biotail = bio;
1185 		req->nr_sectors = req->hard_nr_sectors += nr_sectors;
1186 		req->ioprio = ioprio_best(req->ioprio, prio);
1187 		if (!blk_rq_cpu_valid(req))
1188 			req->cpu = bio->bi_comp_cpu;
1189 		drive_stat_acct(req, 0);
1190 		if (!attempt_back_merge(q, req))
1191 			elv_merged_request(q, req, el_ret);
1192 		goto out;
1193 
1194 	case ELEVATOR_FRONT_MERGE:
1195 		BUG_ON(!rq_mergeable(req));
1196 
1197 		if (!ll_front_merge_fn(q, req, bio))
1198 			break;
1199 
1200 		trace_block_bio_frontmerge(q, bio);
1201 
1202 		bio->bi_next = req->bio;
1203 		req->bio = bio;
1204 
1205 		/*
1206 		 * may not be valid. if the low level driver said
1207 		 * it didn't need a bounce buffer then it better
1208 		 * not touch req->buffer either...
1209 		 */
1210 		req->buffer = bio_data(bio);
1211 		req->current_nr_sectors = bio_cur_sectors(bio);
1212 		req->hard_cur_sectors = req->current_nr_sectors;
1213 		req->sector = req->hard_sector = bio->bi_sector;
1214 		req->nr_sectors = req->hard_nr_sectors += nr_sectors;
1215 		req->ioprio = ioprio_best(req->ioprio, prio);
1216 		if (!blk_rq_cpu_valid(req))
1217 			req->cpu = bio->bi_comp_cpu;
1218 		drive_stat_acct(req, 0);
1219 		if (!attempt_front_merge(q, req))
1220 			elv_merged_request(q, req, el_ret);
1221 		goto out;
1222 
1223 	/* ELV_NO_MERGE: elevator says don't/can't merge. */
1224 	default:
1225 		;
1226 	}
1227 
1228 get_rq:
1229 	/*
1230 	 * This sync check and mask will be re-done in init_request_from_bio(),
1231 	 * but we need to set it earlier to expose the sync flag to the
1232 	 * rq allocator and io schedulers.
1233 	 */
1234 	rw_flags = bio_data_dir(bio);
1235 	if (sync)
1236 		rw_flags |= REQ_RW_SYNC;
1237 
1238 	/*
1239 	 * Grab a free request. This is might sleep but can not fail.
1240 	 * Returns with the queue unlocked.
1241 	 */
1242 	req = get_request_wait(q, rw_flags, bio);
1243 
1244 	/*
1245 	 * After dropping the lock and possibly sleeping here, our request
1246 	 * may now be mergeable after it had proven unmergeable (above).
1247 	 * We don't worry about that case for efficiency. It won't happen
1248 	 * often, and the elevators are able to handle it.
1249 	 */
1250 	init_request_from_bio(req, bio);
1251 
1252 	spin_lock_irq(q->queue_lock);
1253 	if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) ||
1254 	    bio_flagged(bio, BIO_CPU_AFFINE))
1255 		req->cpu = blk_cpu_to_group(smp_processor_id());
1256 	if (queue_should_plug(q) && elv_queue_empty(q))
1257 		blk_plug_device(q);
1258 	add_request(q, req);
1259 out:
1260 	if (unplug || !queue_should_plug(q))
1261 		__generic_unplug_device(q);
1262 	spin_unlock_irq(q->queue_lock);
1263 	return 0;
1264 }
1265 
1266 /*
1267  * If bio->bi_dev is a partition, remap the location
1268  */
1269 static inline void blk_partition_remap(struct bio *bio)
1270 {
1271 	struct block_device *bdev = bio->bi_bdev;
1272 
1273 	if (bio_sectors(bio) && bdev != bdev->bd_contains) {
1274 		struct hd_struct *p = bdev->bd_part;
1275 
1276 		bio->bi_sector += p->start_sect;
1277 		bio->bi_bdev = bdev->bd_contains;
1278 
1279 		trace_block_remap(bdev_get_queue(bio->bi_bdev), bio,
1280 				    bdev->bd_dev, bio->bi_sector,
1281 				    bio->bi_sector - p->start_sect);
1282 	}
1283 }
1284 
1285 static void handle_bad_sector(struct bio *bio)
1286 {
1287 	char b[BDEVNAME_SIZE];
1288 
1289 	printk(KERN_INFO "attempt to access beyond end of device\n");
1290 	printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
1291 			bdevname(bio->bi_bdev, b),
1292 			bio->bi_rw,
1293 			(unsigned long long)bio->bi_sector + bio_sectors(bio),
1294 			(long long)(bio->bi_bdev->bd_inode->i_size >> 9));
1295 
1296 	set_bit(BIO_EOF, &bio->bi_flags);
1297 }
1298 
1299 #ifdef CONFIG_FAIL_MAKE_REQUEST
1300 
1301 static DECLARE_FAULT_ATTR(fail_make_request);
1302 
1303 static int __init setup_fail_make_request(char *str)
1304 {
1305 	return setup_fault_attr(&fail_make_request, str);
1306 }
1307 __setup("fail_make_request=", setup_fail_make_request);
1308 
1309 static int should_fail_request(struct bio *bio)
1310 {
1311 	struct hd_struct *part = bio->bi_bdev->bd_part;
1312 
1313 	if (part_to_disk(part)->part0.make_it_fail || part->make_it_fail)
1314 		return should_fail(&fail_make_request, bio->bi_size);
1315 
1316 	return 0;
1317 }
1318 
1319 static int __init fail_make_request_debugfs(void)
1320 {
1321 	return init_fault_attr_dentries(&fail_make_request,
1322 					"fail_make_request");
1323 }
1324 
1325 late_initcall(fail_make_request_debugfs);
1326 
1327 #else /* CONFIG_FAIL_MAKE_REQUEST */
1328 
1329 static inline int should_fail_request(struct bio *bio)
1330 {
1331 	return 0;
1332 }
1333 
1334 #endif /* CONFIG_FAIL_MAKE_REQUEST */
1335 
1336 /*
1337  * Check whether this bio extends beyond the end of the device.
1338  */
1339 static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1340 {
1341 	sector_t maxsector;
1342 
1343 	if (!nr_sectors)
1344 		return 0;
1345 
1346 	/* Test device or partition size, when known. */
1347 	maxsector = bio->bi_bdev->bd_inode->i_size >> 9;
1348 	if (maxsector) {
1349 		sector_t sector = bio->bi_sector;
1350 
1351 		if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1352 			/*
1353 			 * This may well happen - the kernel calls bread()
1354 			 * without checking the size of the device, e.g., when
1355 			 * mounting a device.
1356 			 */
1357 			handle_bad_sector(bio);
1358 			return 1;
1359 		}
1360 	}
1361 
1362 	return 0;
1363 }
1364 
1365 /**
1366  * generic_make_request - hand a buffer to its device driver for I/O
1367  * @bio:  The bio describing the location in memory and on the device.
1368  *
1369  * generic_make_request() is used to make I/O requests of block
1370  * devices. It is passed a &struct bio, which describes the I/O that needs
1371  * to be done.
1372  *
1373  * generic_make_request() does not return any status.  The
1374  * success/failure status of the request, along with notification of
1375  * completion, is delivered asynchronously through the bio->bi_end_io
1376  * function described (one day) else where.
1377  *
1378  * The caller of generic_make_request must make sure that bi_io_vec
1379  * are set to describe the memory buffer, and that bi_dev and bi_sector are
1380  * set to describe the device address, and the
1381  * bi_end_io and optionally bi_private are set to describe how
1382  * completion notification should be signaled.
1383  *
1384  * generic_make_request and the drivers it calls may use bi_next if this
1385  * bio happens to be merged with someone else, and may change bi_dev and
1386  * bi_sector for remaps as it sees fit.  So the values of these fields
1387  * should NOT be depended on after the call to generic_make_request.
1388  */
1389 static inline void __generic_make_request(struct bio *bio)
1390 {
1391 	struct request_queue *q;
1392 	sector_t old_sector;
1393 	int ret, nr_sectors = bio_sectors(bio);
1394 	dev_t old_dev;
1395 	int err = -EIO;
1396 
1397 	might_sleep();
1398 
1399 	if (bio_check_eod(bio, nr_sectors))
1400 		goto end_io;
1401 
1402 	/*
1403 	 * Resolve the mapping until finished. (drivers are
1404 	 * still free to implement/resolve their own stacking
1405 	 * by explicitly returning 0)
1406 	 *
1407 	 * NOTE: we don't repeat the blk_size check for each new device.
1408 	 * Stacking drivers are expected to know what they are doing.
1409 	 */
1410 	old_sector = -1;
1411 	old_dev = 0;
1412 	do {
1413 		char b[BDEVNAME_SIZE];
1414 
1415 		q = bdev_get_queue(bio->bi_bdev);
1416 		if (unlikely(!q)) {
1417 			printk(KERN_ERR
1418 			       "generic_make_request: Trying to access "
1419 				"nonexistent block-device %s (%Lu)\n",
1420 				bdevname(bio->bi_bdev, b),
1421 				(long long) bio->bi_sector);
1422 			goto end_io;
1423 		}
1424 
1425 		if (unlikely(nr_sectors > q->max_hw_sectors)) {
1426 			printk(KERN_ERR "bio too big device %s (%u > %u)\n",
1427 				bdevname(bio->bi_bdev, b),
1428 				bio_sectors(bio),
1429 				q->max_hw_sectors);
1430 			goto end_io;
1431 		}
1432 
1433 		if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
1434 			goto end_io;
1435 
1436 		if (should_fail_request(bio))
1437 			goto end_io;
1438 
1439 		/*
1440 		 * If this device has partitions, remap block n
1441 		 * of partition p to block n+start(p) of the disk.
1442 		 */
1443 		blk_partition_remap(bio);
1444 
1445 		if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
1446 			goto end_io;
1447 
1448 		if (old_sector != -1)
1449 			trace_block_remap(q, bio, old_dev, bio->bi_sector,
1450 					    old_sector);
1451 
1452 		trace_block_bio_queue(q, bio);
1453 
1454 		old_sector = bio->bi_sector;
1455 		old_dev = bio->bi_bdev->bd_dev;
1456 
1457 		if (bio_check_eod(bio, nr_sectors))
1458 			goto end_io;
1459 
1460 		if (bio_discard(bio) && !q->prepare_discard_fn) {
1461 			err = -EOPNOTSUPP;
1462 			goto end_io;
1463 		}
1464 		if (bio_barrier(bio) && bio_has_data(bio) &&
1465 		    (q->next_ordered == QUEUE_ORDERED_NONE)) {
1466 			err = -EOPNOTSUPP;
1467 			goto end_io;
1468 		}
1469 
1470 		ret = q->make_request_fn(q, bio);
1471 	} while (ret);
1472 
1473 	return;
1474 
1475 end_io:
1476 	bio_endio(bio, err);
1477 }
1478 
1479 /*
1480  * We only want one ->make_request_fn to be active at a time,
1481  * else stack usage with stacked devices could be a problem.
1482  * So use current->bio_{list,tail} to keep a list of requests
1483  * submited by a make_request_fn function.
1484  * current->bio_tail is also used as a flag to say if
1485  * generic_make_request is currently active in this task or not.
1486  * If it is NULL, then no make_request is active.  If it is non-NULL,
1487  * then a make_request is active, and new requests should be added
1488  * at the tail
1489  */
1490 void generic_make_request(struct bio *bio)
1491 {
1492 	if (current->bio_tail) {
1493 		/* make_request is active */
1494 		*(current->bio_tail) = bio;
1495 		bio->bi_next = NULL;
1496 		current->bio_tail = &bio->bi_next;
1497 		return;
1498 	}
1499 	/* following loop may be a bit non-obvious, and so deserves some
1500 	 * explanation.
1501 	 * Before entering the loop, bio->bi_next is NULL (as all callers
1502 	 * ensure that) so we have a list with a single bio.
1503 	 * We pretend that we have just taken it off a longer list, so
1504 	 * we assign bio_list to the next (which is NULL) and bio_tail
1505 	 * to &bio_list, thus initialising the bio_list of new bios to be
1506 	 * added.  __generic_make_request may indeed add some more bios
1507 	 * through a recursive call to generic_make_request.  If it
1508 	 * did, we find a non-NULL value in bio_list and re-enter the loop
1509 	 * from the top.  In this case we really did just take the bio
1510 	 * of the top of the list (no pretending) and so fixup bio_list and
1511 	 * bio_tail or bi_next, and call into __generic_make_request again.
1512 	 *
1513 	 * The loop was structured like this to make only one call to
1514 	 * __generic_make_request (which is important as it is large and
1515 	 * inlined) and to keep the structure simple.
1516 	 */
1517 	BUG_ON(bio->bi_next);
1518 	do {
1519 		current->bio_list = bio->bi_next;
1520 		if (bio->bi_next == NULL)
1521 			current->bio_tail = &current->bio_list;
1522 		else
1523 			bio->bi_next = NULL;
1524 		__generic_make_request(bio);
1525 		bio = current->bio_list;
1526 	} while (bio);
1527 	current->bio_tail = NULL; /* deactivate */
1528 }
1529 EXPORT_SYMBOL(generic_make_request);
1530 
1531 /**
1532  * submit_bio - submit a bio to the block device layer for I/O
1533  * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1534  * @bio: The &struct bio which describes the I/O
1535  *
1536  * submit_bio() is very similar in purpose to generic_make_request(), and
1537  * uses that function to do most of the work. Both are fairly rough
1538  * interfaces; @bio must be presetup and ready for I/O.
1539  *
1540  */
1541 void submit_bio(int rw, struct bio *bio)
1542 {
1543 	int count = bio_sectors(bio);
1544 
1545 	bio->bi_rw |= rw;
1546 
1547 	/*
1548 	 * If it's a regular read/write or a barrier with data attached,
1549 	 * go through the normal accounting stuff before submission.
1550 	 */
1551 	if (bio_has_data(bio)) {
1552 		if (rw & WRITE) {
1553 			count_vm_events(PGPGOUT, count);
1554 		} else {
1555 			task_io_account_read(bio->bi_size);
1556 			count_vm_events(PGPGIN, count);
1557 		}
1558 
1559 		if (unlikely(block_dump)) {
1560 			char b[BDEVNAME_SIZE];
1561 			printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n",
1562 			current->comm, task_pid_nr(current),
1563 				(rw & WRITE) ? "WRITE" : "READ",
1564 				(unsigned long long)bio->bi_sector,
1565 				bdevname(bio->bi_bdev, b));
1566 		}
1567 	}
1568 
1569 	generic_make_request(bio);
1570 }
1571 EXPORT_SYMBOL(submit_bio);
1572 
1573 /**
1574  * blk_rq_check_limits - Helper function to check a request for the queue limit
1575  * @q:  the queue
1576  * @rq: the request being checked
1577  *
1578  * Description:
1579  *    @rq may have been made based on weaker limitations of upper-level queues
1580  *    in request stacking drivers, and it may violate the limitation of @q.
1581  *    Since the block layer and the underlying device driver trust @rq
1582  *    after it is inserted to @q, it should be checked against @q before
1583  *    the insertion using this generic function.
1584  *
1585  *    This function should also be useful for request stacking drivers
1586  *    in some cases below, so export this fuction.
1587  *    Request stacking drivers like request-based dm may change the queue
1588  *    limits while requests are in the queue (e.g. dm's table swapping).
1589  *    Such request stacking drivers should check those requests agaist
1590  *    the new queue limits again when they dispatch those requests,
1591  *    although such checkings are also done against the old queue limits
1592  *    when submitting requests.
1593  */
1594 int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1595 {
1596 	if (rq->nr_sectors > q->max_sectors ||
1597 	    rq->data_len > q->max_hw_sectors << 9) {
1598 		printk(KERN_ERR "%s: over max size limit.\n", __func__);
1599 		return -EIO;
1600 	}
1601 
1602 	/*
1603 	 * queue's settings related to segment counting like q->bounce_pfn
1604 	 * may differ from that of other stacking queues.
1605 	 * Recalculate it to check the request correctly on this queue's
1606 	 * limitation.
1607 	 */
1608 	blk_recalc_rq_segments(rq);
1609 	if (rq->nr_phys_segments > q->max_phys_segments ||
1610 	    rq->nr_phys_segments > q->max_hw_segments) {
1611 		printk(KERN_ERR "%s: over max segments limit.\n", __func__);
1612 		return -EIO;
1613 	}
1614 
1615 	return 0;
1616 }
1617 EXPORT_SYMBOL_GPL(blk_rq_check_limits);
1618 
1619 /**
1620  * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1621  * @q:  the queue to submit the request
1622  * @rq: the request being queued
1623  */
1624 int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1625 {
1626 	unsigned long flags;
1627 
1628 	if (blk_rq_check_limits(q, rq))
1629 		return -EIO;
1630 
1631 #ifdef CONFIG_FAIL_MAKE_REQUEST
1632 	if (rq->rq_disk && rq->rq_disk->part0.make_it_fail &&
1633 	    should_fail(&fail_make_request, blk_rq_bytes(rq)))
1634 		return -EIO;
1635 #endif
1636 
1637 	spin_lock_irqsave(q->queue_lock, flags);
1638 
1639 	/*
1640 	 * Submitting request must be dequeued before calling this function
1641 	 * because it will be linked to another request_queue
1642 	 */
1643 	BUG_ON(blk_queued_rq(rq));
1644 
1645 	drive_stat_acct(rq, 1);
1646 	__elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0);
1647 
1648 	spin_unlock_irqrestore(q->queue_lock, flags);
1649 
1650 	return 0;
1651 }
1652 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
1653 
1654 /**
1655  * blkdev_dequeue_request - dequeue request and start timeout timer
1656  * @req: request to dequeue
1657  *
1658  * Dequeue @req and start timeout timer on it.  This hands off the
1659  * request to the driver.
1660  *
1661  * Block internal functions which don't want to start timer should
1662  * call elv_dequeue_request().
1663  */
1664 void blkdev_dequeue_request(struct request *req)
1665 {
1666 	elv_dequeue_request(req->q, req);
1667 
1668 	/*
1669 	 * We are now handing the request to the hardware, add the
1670 	 * timeout handler.
1671 	 */
1672 	blk_add_timer(req);
1673 }
1674 EXPORT_SYMBOL(blkdev_dequeue_request);
1675 
1676 static void blk_account_io_completion(struct request *req, unsigned int bytes)
1677 {
1678 	if (!blk_do_io_stat(req))
1679 		return;
1680 
1681 	if (blk_fs_request(req)) {
1682 		const int rw = rq_data_dir(req);
1683 		struct hd_struct *part;
1684 		int cpu;
1685 
1686 		cpu = part_stat_lock();
1687 		part = disk_map_sector_rcu(req->rq_disk, req->sector);
1688 		part_stat_add(cpu, part, sectors[rw], bytes >> 9);
1689 		part_stat_unlock();
1690 	}
1691 }
1692 
1693 static void blk_account_io_done(struct request *req)
1694 {
1695 	if (!blk_do_io_stat(req))
1696 		return;
1697 
1698 	/*
1699 	 * Account IO completion.  bar_rq isn't accounted as a normal
1700 	 * IO on queueing nor completion.  Accounting the containing
1701 	 * request is enough.
1702 	 */
1703 	if (blk_fs_request(req) && req != &req->q->bar_rq) {
1704 		unsigned long duration = jiffies - req->start_time;
1705 		const int rw = rq_data_dir(req);
1706 		struct hd_struct *part;
1707 		int cpu;
1708 
1709 		cpu = part_stat_lock();
1710 		part = disk_map_sector_rcu(req->rq_disk, req->sector);
1711 
1712 		part_stat_inc(cpu, part, ios[rw]);
1713 		part_stat_add(cpu, part, ticks[rw], duration);
1714 		part_round_stats(cpu, part);
1715 		part_dec_in_flight(part);
1716 
1717 		part_stat_unlock();
1718 	}
1719 }
1720 
1721 /**
1722  * __end_that_request_first - end I/O on a request
1723  * @req:      the request being processed
1724  * @error:    %0 for success, < %0 for error
1725  * @nr_bytes: number of bytes to complete
1726  *
1727  * Description:
1728  *     Ends I/O on a number of bytes attached to @req, and sets it up
1729  *     for the next range of segments (if any) in the cluster.
1730  *
1731  * Return:
1732  *     %0 - we are done with this request, call end_that_request_last()
1733  *     %1 - still buffers pending for this request
1734  **/
1735 static int __end_that_request_first(struct request *req, int error,
1736 				    int nr_bytes)
1737 {
1738 	int total_bytes, bio_nbytes, next_idx = 0;
1739 	struct bio *bio;
1740 
1741 	trace_block_rq_complete(req->q, req);
1742 
1743 	/*
1744 	 * for a REQ_TYPE_BLOCK_PC request, we want to carry any eventual
1745 	 * sense key with us all the way through
1746 	 */
1747 	if (!blk_pc_request(req))
1748 		req->errors = 0;
1749 
1750 	if (error && (blk_fs_request(req) && !(req->cmd_flags & REQ_QUIET))) {
1751 		printk(KERN_ERR "end_request: I/O error, dev %s, sector %llu\n",
1752 				req->rq_disk ? req->rq_disk->disk_name : "?",
1753 				(unsigned long long)req->sector);
1754 	}
1755 
1756 	blk_account_io_completion(req, nr_bytes);
1757 
1758 	total_bytes = bio_nbytes = 0;
1759 	while ((bio = req->bio) != NULL) {
1760 		int nbytes;
1761 
1762 		if (nr_bytes >= bio->bi_size) {
1763 			req->bio = bio->bi_next;
1764 			nbytes = bio->bi_size;
1765 			req_bio_endio(req, bio, nbytes, error);
1766 			next_idx = 0;
1767 			bio_nbytes = 0;
1768 		} else {
1769 			int idx = bio->bi_idx + next_idx;
1770 
1771 			if (unlikely(idx >= bio->bi_vcnt)) {
1772 				blk_dump_rq_flags(req, "__end_that");
1773 				printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
1774 				       __func__, idx, bio->bi_vcnt);
1775 				break;
1776 			}
1777 
1778 			nbytes = bio_iovec_idx(bio, idx)->bv_len;
1779 			BIO_BUG_ON(nbytes > bio->bi_size);
1780 
1781 			/*
1782 			 * not a complete bvec done
1783 			 */
1784 			if (unlikely(nbytes > nr_bytes)) {
1785 				bio_nbytes += nr_bytes;
1786 				total_bytes += nr_bytes;
1787 				break;
1788 			}
1789 
1790 			/*
1791 			 * advance to the next vector
1792 			 */
1793 			next_idx++;
1794 			bio_nbytes += nbytes;
1795 		}
1796 
1797 		total_bytes += nbytes;
1798 		nr_bytes -= nbytes;
1799 
1800 		bio = req->bio;
1801 		if (bio) {
1802 			/*
1803 			 * end more in this run, or just return 'not-done'
1804 			 */
1805 			if (unlikely(nr_bytes <= 0))
1806 				break;
1807 		}
1808 	}
1809 
1810 	/*
1811 	 * completely done
1812 	 */
1813 	if (!req->bio)
1814 		return 0;
1815 
1816 	/*
1817 	 * if the request wasn't completed, update state
1818 	 */
1819 	if (bio_nbytes) {
1820 		req_bio_endio(req, bio, bio_nbytes, error);
1821 		bio->bi_idx += next_idx;
1822 		bio_iovec(bio)->bv_offset += nr_bytes;
1823 		bio_iovec(bio)->bv_len -= nr_bytes;
1824 	}
1825 
1826 	blk_recalc_rq_sectors(req, total_bytes >> 9);
1827 	blk_recalc_rq_segments(req);
1828 	return 1;
1829 }
1830 
1831 /*
1832  * queue lock must be held
1833  */
1834 static void end_that_request_last(struct request *req, int error)
1835 {
1836 	if (blk_rq_tagged(req))
1837 		blk_queue_end_tag(req->q, req);
1838 
1839 	if (blk_queued_rq(req))
1840 		elv_dequeue_request(req->q, req);
1841 
1842 	if (unlikely(laptop_mode) && blk_fs_request(req))
1843 		laptop_io_completion();
1844 
1845 	blk_delete_timer(req);
1846 
1847 	blk_account_io_done(req);
1848 
1849 	if (req->end_io)
1850 		req->end_io(req, error);
1851 	else {
1852 		if (blk_bidi_rq(req))
1853 			__blk_put_request(req->next_rq->q, req->next_rq);
1854 
1855 		__blk_put_request(req->q, req);
1856 	}
1857 }
1858 
1859 /**
1860  * blk_rq_bytes - Returns bytes left to complete in the entire request
1861  * @rq: the request being processed
1862  **/
1863 unsigned int blk_rq_bytes(struct request *rq)
1864 {
1865 	if (blk_fs_request(rq))
1866 		return rq->hard_nr_sectors << 9;
1867 
1868 	return rq->data_len;
1869 }
1870 EXPORT_SYMBOL_GPL(blk_rq_bytes);
1871 
1872 /**
1873  * blk_rq_cur_bytes - Returns bytes left to complete in the current segment
1874  * @rq: the request being processed
1875  **/
1876 unsigned int blk_rq_cur_bytes(struct request *rq)
1877 {
1878 	if (blk_fs_request(rq))
1879 		return rq->current_nr_sectors << 9;
1880 
1881 	if (rq->bio)
1882 		return rq->bio->bi_size;
1883 
1884 	return rq->data_len;
1885 }
1886 EXPORT_SYMBOL_GPL(blk_rq_cur_bytes);
1887 
1888 /**
1889  * end_request - end I/O on the current segment of the request
1890  * @req:	the request being processed
1891  * @uptodate:	error value or %0/%1 uptodate flag
1892  *
1893  * Description:
1894  *     Ends I/O on the current segment of a request. If that is the only
1895  *     remaining segment, the request is also completed and freed.
1896  *
1897  *     This is a remnant of how older block drivers handled I/O completions.
1898  *     Modern drivers typically end I/O on the full request in one go, unless
1899  *     they have a residual value to account for. For that case this function
1900  *     isn't really useful, unless the residual just happens to be the
1901  *     full current segment. In other words, don't use this function in new
1902  *     code. Use blk_end_request() or __blk_end_request() to end a request.
1903  **/
1904 void end_request(struct request *req, int uptodate)
1905 {
1906 	int error = 0;
1907 
1908 	if (uptodate <= 0)
1909 		error = uptodate ? uptodate : -EIO;
1910 
1911 	__blk_end_request(req, error, req->hard_cur_sectors << 9);
1912 }
1913 EXPORT_SYMBOL(end_request);
1914 
1915 static int end_that_request_data(struct request *rq, int error,
1916 				 unsigned int nr_bytes, unsigned int bidi_bytes)
1917 {
1918 	if (rq->bio) {
1919 		if (__end_that_request_first(rq, error, nr_bytes))
1920 			return 1;
1921 
1922 		/* Bidi request must be completed as a whole */
1923 		if (blk_bidi_rq(rq) &&
1924 		    __end_that_request_first(rq->next_rq, error, bidi_bytes))
1925 			return 1;
1926 	}
1927 
1928 	return 0;
1929 }
1930 
1931 /**
1932  * blk_end_io - Generic end_io function to complete a request.
1933  * @rq:           the request being processed
1934  * @error:        %0 for success, < %0 for error
1935  * @nr_bytes:     number of bytes to complete @rq
1936  * @bidi_bytes:   number of bytes to complete @rq->next_rq
1937  * @drv_callback: function called between completion of bios in the request
1938  *                and completion of the request.
1939  *                If the callback returns non %0, this helper returns without
1940  *                completion of the request.
1941  *
1942  * Description:
1943  *     Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
1944  *     If @rq has leftover, sets it up for the next range of segments.
1945  *
1946  * Return:
1947  *     %0 - we are done with this request
1948  *     %1 - this request is not freed yet, it still has pending buffers.
1949  **/
1950 static int blk_end_io(struct request *rq, int error, unsigned int nr_bytes,
1951 		      unsigned int bidi_bytes,
1952 		      int (drv_callback)(struct request *))
1953 {
1954 	struct request_queue *q = rq->q;
1955 	unsigned long flags = 0UL;
1956 
1957 	if (end_that_request_data(rq, error, nr_bytes, bidi_bytes))
1958 		return 1;
1959 
1960 	/* Special feature for tricky drivers */
1961 	if (drv_callback && drv_callback(rq))
1962 		return 1;
1963 
1964 	add_disk_randomness(rq->rq_disk);
1965 
1966 	spin_lock_irqsave(q->queue_lock, flags);
1967 	end_that_request_last(rq, error);
1968 	spin_unlock_irqrestore(q->queue_lock, flags);
1969 
1970 	return 0;
1971 }
1972 
1973 /**
1974  * blk_end_request - Helper function for drivers to complete the request.
1975  * @rq:       the request being processed
1976  * @error:    %0 for success, < %0 for error
1977  * @nr_bytes: number of bytes to complete
1978  *
1979  * Description:
1980  *     Ends I/O on a number of bytes attached to @rq.
1981  *     If @rq has leftover, sets it up for the next range of segments.
1982  *
1983  * Return:
1984  *     %0 - we are done with this request
1985  *     %1 - still buffers pending for this request
1986  **/
1987 int blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
1988 {
1989 	return blk_end_io(rq, error, nr_bytes, 0, NULL);
1990 }
1991 EXPORT_SYMBOL_GPL(blk_end_request);
1992 
1993 /**
1994  * __blk_end_request - Helper function for drivers to complete the request.
1995  * @rq:       the request being processed
1996  * @error:    %0 for success, < %0 for error
1997  * @nr_bytes: number of bytes to complete
1998  *
1999  * Description:
2000  *     Must be called with queue lock held unlike blk_end_request().
2001  *
2002  * Return:
2003  *     %0 - we are done with this request
2004  *     %1 - still buffers pending for this request
2005  **/
2006 int __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2007 {
2008 	if (rq->bio && __end_that_request_first(rq, error, nr_bytes))
2009 		return 1;
2010 
2011 	add_disk_randomness(rq->rq_disk);
2012 
2013 	end_that_request_last(rq, error);
2014 
2015 	return 0;
2016 }
2017 EXPORT_SYMBOL_GPL(__blk_end_request);
2018 
2019 /**
2020  * blk_end_bidi_request - Helper function for drivers to complete bidi request.
2021  * @rq:         the bidi request being processed
2022  * @error:      %0 for success, < %0 for error
2023  * @nr_bytes:   number of bytes to complete @rq
2024  * @bidi_bytes: number of bytes to complete @rq->next_rq
2025  *
2026  * Description:
2027  *     Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2028  *
2029  * Return:
2030  *     %0 - we are done with this request
2031  *     %1 - still buffers pending for this request
2032  **/
2033 int blk_end_bidi_request(struct request *rq, int error, unsigned int nr_bytes,
2034 			 unsigned int bidi_bytes)
2035 {
2036 	return blk_end_io(rq, error, nr_bytes, bidi_bytes, NULL);
2037 }
2038 EXPORT_SYMBOL_GPL(blk_end_bidi_request);
2039 
2040 /**
2041  * blk_update_request - Special helper function for request stacking drivers
2042  * @rq:           the request being processed
2043  * @error:        %0 for success, < %0 for error
2044  * @nr_bytes:     number of bytes to complete @rq
2045  *
2046  * Description:
2047  *     Ends I/O on a number of bytes attached to @rq, but doesn't complete
2048  *     the request structure even if @rq doesn't have leftover.
2049  *     If @rq has leftover, sets it up for the next range of segments.
2050  *
2051  *     This special helper function is only for request stacking drivers
2052  *     (e.g. request-based dm) so that they can handle partial completion.
2053  *     Actual device drivers should use blk_end_request instead.
2054  */
2055 void blk_update_request(struct request *rq, int error, unsigned int nr_bytes)
2056 {
2057 	if (!end_that_request_data(rq, error, nr_bytes, 0)) {
2058 		/*
2059 		 * These members are not updated in end_that_request_data()
2060 		 * when all bios are completed.
2061 		 * Update them so that the request stacking driver can find
2062 		 * how many bytes remain in the request later.
2063 		 */
2064 		rq->nr_sectors = rq->hard_nr_sectors = 0;
2065 		rq->current_nr_sectors = rq->hard_cur_sectors = 0;
2066 	}
2067 }
2068 EXPORT_SYMBOL_GPL(blk_update_request);
2069 
2070 /**
2071  * blk_end_request_callback - Special helper function for tricky drivers
2072  * @rq:           the request being processed
2073  * @error:        %0 for success, < %0 for error
2074  * @nr_bytes:     number of bytes to complete
2075  * @drv_callback: function called between completion of bios in the request
2076  *                and completion of the request.
2077  *                If the callback returns non %0, this helper returns without
2078  *                completion of the request.
2079  *
2080  * Description:
2081  *     Ends I/O on a number of bytes attached to @rq.
2082  *     If @rq has leftover, sets it up for the next range of segments.
2083  *
2084  *     This special helper function is used only for existing tricky drivers.
2085  *     (e.g. cdrom_newpc_intr() of ide-cd)
2086  *     This interface will be removed when such drivers are rewritten.
2087  *     Don't use this interface in other places anymore.
2088  *
2089  * Return:
2090  *     %0 - we are done with this request
2091  *     %1 - this request is not freed yet.
2092  *          this request still has pending buffers or
2093  *          the driver doesn't want to finish this request yet.
2094  **/
2095 int blk_end_request_callback(struct request *rq, int error,
2096 			     unsigned int nr_bytes,
2097 			     int (drv_callback)(struct request *))
2098 {
2099 	return blk_end_io(rq, error, nr_bytes, 0, drv_callback);
2100 }
2101 EXPORT_SYMBOL_GPL(blk_end_request_callback);
2102 
2103 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2104 		     struct bio *bio)
2105 {
2106 	/* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw, and
2107 	   we want BIO_RW_AHEAD (bit 1) to imply REQ_FAILFAST (bit 1). */
2108 	rq->cmd_flags |= (bio->bi_rw & 3);
2109 
2110 	if (bio_has_data(bio)) {
2111 		rq->nr_phys_segments = bio_phys_segments(q, bio);
2112 		rq->buffer = bio_data(bio);
2113 	}
2114 	rq->current_nr_sectors = bio_cur_sectors(bio);
2115 	rq->hard_cur_sectors = rq->current_nr_sectors;
2116 	rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio);
2117 	rq->data_len = bio->bi_size;
2118 
2119 	rq->bio = rq->biotail = bio;
2120 
2121 	if (bio->bi_bdev)
2122 		rq->rq_disk = bio->bi_bdev->bd_disk;
2123 }
2124 
2125 /**
2126  * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2127  * @q : the queue of the device being checked
2128  *
2129  * Description:
2130  *    Check if underlying low-level drivers of a device are busy.
2131  *    If the drivers want to export their busy state, they must set own
2132  *    exporting function using blk_queue_lld_busy() first.
2133  *
2134  *    Basically, this function is used only by request stacking drivers
2135  *    to stop dispatching requests to underlying devices when underlying
2136  *    devices are busy.  This behavior helps more I/O merging on the queue
2137  *    of the request stacking driver and prevents I/O throughput regression
2138  *    on burst I/O load.
2139  *
2140  * Return:
2141  *    0 - Not busy (The request stacking driver should dispatch request)
2142  *    1 - Busy (The request stacking driver should stop dispatching request)
2143  */
2144 int blk_lld_busy(struct request_queue *q)
2145 {
2146 	if (q->lld_busy_fn)
2147 		return q->lld_busy_fn(q);
2148 
2149 	return 0;
2150 }
2151 EXPORT_SYMBOL_GPL(blk_lld_busy);
2152 
2153 int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
2154 {
2155 	return queue_work(kblockd_workqueue, work);
2156 }
2157 EXPORT_SYMBOL(kblockd_schedule_work);
2158 
2159 int __init blk_dev_init(void)
2160 {
2161 	kblockd_workqueue = create_workqueue("kblockd");
2162 	if (!kblockd_workqueue)
2163 		panic("Failed to create kblockd\n");
2164 
2165 	request_cachep = kmem_cache_create("blkdev_requests",
2166 			sizeof(struct request), 0, SLAB_PANIC, NULL);
2167 
2168 	blk_requestq_cachep = kmem_cache_create("blkdev_queue",
2169 			sizeof(struct request_queue), 0, SLAB_PANIC, NULL);
2170 
2171 	return 0;
2172 }
2173 
2174