tuntap: forbid calling TUNSETIFF when detached
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / block / blk-core.c
blobc973249d68cda01e0c7889ae8708e4da0f9ca4d2
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 */
12 * This handles all read/write requests to block devices
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/fault-inject.h>
30 #include <linux/list_sort.h>
31 #include <linux/delay.h>
32 #include <linux/ratelimit.h>
34 #define CREATE_TRACE_POINTS
35 #include <trace/events/block.h>
37 #include "blk.h"
38 #include "blk-cgroup.h"
40 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
41 EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
42 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
43 EXPORT_TRACEPOINT_SYMBOL_GPL(block_unplug);
45 DEFINE_IDA(blk_queue_ida);
48 * For the allocated request tables
50 static struct kmem_cache *request_cachep;
53 * For queue allocation
55 struct kmem_cache *blk_requestq_cachep;
58 * Controlling structure to kblockd
60 static struct workqueue_struct *kblockd_workqueue;
62 static void drive_stat_acct(struct request *rq, int new_io)
64 struct hd_struct *part;
65 int rw = rq_data_dir(rq);
66 int cpu;
68 if (!blk_do_io_stat(rq))
69 return;
71 cpu = part_stat_lock();
73 if (!new_io) {
74 part = rq->part;
75 part_stat_inc(cpu, part, merges[rw]);
76 } else {
77 part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq));
78 if (!hd_struct_try_get(part)) {
80 * The partition is already being removed,
81 * the request will be accounted on the disk only
83 * We take a reference on disk->part0 although that
84 * partition will never be deleted, so we can treat
85 * it as any other partition.
87 part = &rq->rq_disk->part0;
88 hd_struct_get(part);
90 part_round_stats(cpu, part);
91 part_inc_in_flight(part, rw);
92 rq->part = part;
95 part_stat_unlock();
98 void blk_queue_congestion_threshold(struct request_queue *q)
100 int nr;
102 nr = q->nr_requests - (q->nr_requests / 8) + 1;
103 if (nr > q->nr_requests)
104 nr = q->nr_requests;
105 q->nr_congestion_on = nr;
107 nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
108 if (nr < 1)
109 nr = 1;
110 q->nr_congestion_off = nr;
114 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
115 * @bdev: device
117 * Locates the passed device's request queue and returns the address of its
118 * backing_dev_info
120 * Will return NULL if the request queue cannot be located.
122 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
124 struct backing_dev_info *ret = NULL;
125 struct request_queue *q = bdev_get_queue(bdev);
127 if (q)
128 ret = &q->backing_dev_info;
129 return ret;
131 EXPORT_SYMBOL(blk_get_backing_dev_info);
133 void blk_rq_init(struct request_queue *q, struct request *rq)
135 memset(rq, 0, sizeof(*rq));
137 INIT_LIST_HEAD(&rq->queuelist);
138 INIT_LIST_HEAD(&rq->timeout_list);
139 rq->cpu = -1;
140 rq->q = q;
141 rq->__sector = (sector_t) -1;
142 INIT_HLIST_NODE(&rq->hash);
143 RB_CLEAR_NODE(&rq->rb_node);
144 rq->cmd = rq->__cmd;
145 rq->cmd_len = BLK_MAX_CDB;
146 rq->tag = -1;
147 rq->ref_count = 1;
148 rq->start_time = jiffies;
149 set_start_time_ns(rq);
150 rq->part = NULL;
152 EXPORT_SYMBOL(blk_rq_init);
154 static void req_bio_endio(struct request *rq, struct bio *bio,
155 unsigned int nbytes, int error)
157 if (error)
158 clear_bit(BIO_UPTODATE, &bio->bi_flags);
159 else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
160 error = -EIO;
162 if (unlikely(nbytes > bio->bi_size)) {
163 printk(KERN_ERR "%s: want %u bytes done, %u left\n",
164 __func__, nbytes, bio->bi_size);
165 nbytes = bio->bi_size;
168 if (unlikely(rq->cmd_flags & REQ_QUIET))
169 set_bit(BIO_QUIET, &bio->bi_flags);
171 bio->bi_size -= nbytes;
172 bio->bi_sector += (nbytes >> 9);
174 if (bio_integrity(bio))
175 bio_integrity_advance(bio, nbytes);
177 /* don't actually finish bio if it's part of flush sequence */
178 if (bio->bi_size == 0 && !(rq->cmd_flags & REQ_FLUSH_SEQ))
179 bio_endio(bio, error);
182 void blk_dump_rq_flags(struct request *rq, char *msg)
184 int bit;
186 printk(KERN_INFO "%s: dev %s: type=%x, flags=%x\n", msg,
187 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type,
188 rq->cmd_flags);
190 printk(KERN_INFO " sector %llu, nr/cnr %u/%u\n",
191 (unsigned long long)blk_rq_pos(rq),
192 blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
193 printk(KERN_INFO " bio %p, biotail %p, buffer %p, len %u\n",
194 rq->bio, rq->biotail, rq->buffer, blk_rq_bytes(rq));
196 if (rq->cmd_type == REQ_TYPE_BLOCK_PC) {
197 printk(KERN_INFO " cdb: ");
198 for (bit = 0; bit < BLK_MAX_CDB; bit++)
199 printk("%02x ", rq->cmd[bit]);
200 printk("\n");
203 EXPORT_SYMBOL(blk_dump_rq_flags);
205 static void blk_delay_work(struct work_struct *work)
207 struct request_queue *q;
209 q = container_of(work, struct request_queue, delay_work.work);
210 spin_lock_irq(q->queue_lock);
211 __blk_run_queue(q);
212 spin_unlock_irq(q->queue_lock);
216 * blk_delay_queue - restart queueing after defined interval
217 * @q: The &struct request_queue in question
218 * @msecs: Delay in msecs
220 * Description:
221 * Sometimes queueing needs to be postponed for a little while, to allow
222 * resources to come back. This function will make sure that queueing is
223 * restarted around the specified time. Queue lock must be held.
225 void blk_delay_queue(struct request_queue *q, unsigned long msecs)
227 if (likely(!blk_queue_dead(q)))
228 queue_delayed_work(kblockd_workqueue, &q->delay_work,
229 msecs_to_jiffies(msecs));
231 EXPORT_SYMBOL(blk_delay_queue);
234 * blk_start_queue - restart a previously stopped queue
235 * @q: The &struct request_queue in question
237 * Description:
238 * blk_start_queue() will clear the stop flag on the queue, and call
239 * the request_fn for the queue if it was in a stopped state when
240 * entered. Also see blk_stop_queue(). Queue lock must be held.
242 void blk_start_queue(struct request_queue *q)
244 WARN_ON(!irqs_disabled());
246 queue_flag_clear(QUEUE_FLAG_STOPPED, q);
247 __blk_run_queue(q);
249 EXPORT_SYMBOL(blk_start_queue);
252 * blk_stop_queue - stop a queue
253 * @q: The &struct request_queue in question
255 * Description:
256 * The Linux block layer assumes that a block driver will consume all
257 * entries on the request queue when the request_fn strategy is called.
258 * Often this will not happen, because of hardware limitations (queue
259 * depth settings). If a device driver gets a 'queue full' response,
260 * or if it simply chooses not to queue more I/O at one point, it can
261 * call this function to prevent the request_fn from being called until
262 * the driver has signalled it's ready to go again. This happens by calling
263 * blk_start_queue() to restart queue operations. Queue lock must be held.
265 void blk_stop_queue(struct request_queue *q)
267 cancel_delayed_work(&q->delay_work);
268 queue_flag_set(QUEUE_FLAG_STOPPED, q);
270 EXPORT_SYMBOL(blk_stop_queue);
273 * blk_sync_queue - cancel any pending callbacks on a queue
274 * @q: the queue
276 * Description:
277 * The block layer may perform asynchronous callback activity
278 * on a queue, such as calling the unplug function after a timeout.
279 * A block device may call blk_sync_queue to ensure that any
280 * such activity is cancelled, thus allowing it to release resources
281 * that the callbacks might use. The caller must already have made sure
282 * that its ->make_request_fn will not re-add plugging prior to calling
283 * this function.
285 * This function does not cancel any asynchronous activity arising
286 * out of elevator or throttling code. That would require elevaotor_exit()
287 * and blkcg_exit_queue() to be called with queue lock initialized.
290 void blk_sync_queue(struct request_queue *q)
292 del_timer_sync(&q->timeout);
293 cancel_delayed_work_sync(&q->delay_work);
295 EXPORT_SYMBOL(blk_sync_queue);
298 * __blk_run_queue_uncond - run a queue whether or not it has been stopped
299 * @q: The queue to run
301 * Description:
302 * Invoke request handling on a queue if there are any pending requests.
303 * May be used to restart request handling after a request has completed.
304 * This variant runs the queue whether or not the queue has been
305 * stopped. Must be called with the queue lock held and interrupts
306 * disabled. See also @blk_run_queue.
308 inline void __blk_run_queue_uncond(struct request_queue *q)
310 if (unlikely(blk_queue_dead(q)))
311 return;
314 * Some request_fn implementations, e.g. scsi_request_fn(), unlock
315 * the queue lock internally. As a result multiple threads may be
316 * running such a request function concurrently. Keep track of the
317 * number of active request_fn invocations such that blk_drain_queue()
318 * can wait until all these request_fn calls have finished.
320 q->request_fn_active++;
321 q->request_fn(q);
322 q->request_fn_active--;
326 * __blk_run_queue - run a single device queue
327 * @q: The queue to run
329 * Description:
330 * See @blk_run_queue. This variant must be called with the queue lock
331 * held and interrupts disabled.
333 void __blk_run_queue(struct request_queue *q)
335 if (unlikely(blk_queue_stopped(q)))
336 return;
338 __blk_run_queue_uncond(q);
340 EXPORT_SYMBOL(__blk_run_queue);
343 * blk_run_queue_async - run a single device queue in workqueue context
344 * @q: The queue to run
346 * Description:
347 * Tells kblockd to perform the equivalent of @blk_run_queue on behalf
348 * of us. The caller must hold the queue lock.
350 void blk_run_queue_async(struct request_queue *q)
352 if (likely(!blk_queue_stopped(q) && !blk_queue_dead(q)))
353 mod_delayed_work(kblockd_workqueue, &q->delay_work, 0);
355 EXPORT_SYMBOL(blk_run_queue_async);
358 * blk_run_queue - run a single device queue
359 * @q: The queue to run
361 * Description:
362 * Invoke request handling on this queue, if it has pending work to do.
363 * May be used to restart queueing when a request has completed.
365 void blk_run_queue(struct request_queue *q)
367 unsigned long flags;
369 spin_lock_irqsave(q->queue_lock, flags);
370 __blk_run_queue(q);
371 spin_unlock_irqrestore(q->queue_lock, flags);
373 EXPORT_SYMBOL(blk_run_queue);
375 void blk_put_queue(struct request_queue *q)
377 kobject_put(&q->kobj);
379 EXPORT_SYMBOL(blk_put_queue);
382 * __blk_drain_queue - drain requests from request_queue
383 * @q: queue to drain
384 * @drain_all: whether to drain all requests or only the ones w/ ELVPRIV
386 * Drain requests from @q. If @drain_all is set, all requests are drained.
387 * If not, only ELVPRIV requests are drained. The caller is responsible
388 * for ensuring that no new requests which need to be drained are queued.
390 static void __blk_drain_queue(struct request_queue *q, bool drain_all)
391 __releases(q->queue_lock)
392 __acquires(q->queue_lock)
394 int i;
396 lockdep_assert_held(q->queue_lock);
398 while (true) {
399 bool drain = false;
402 * The caller might be trying to drain @q before its
403 * elevator is initialized.
405 if (q->elevator)
406 elv_drain_elevator(q);
408 blkcg_drain_queue(q);
411 * This function might be called on a queue which failed
412 * driver init after queue creation or is not yet fully
413 * active yet. Some drivers (e.g. fd and loop) get unhappy
414 * in such cases. Kick queue iff dispatch queue has
415 * something on it and @q has request_fn set.
417 if (!list_empty(&q->queue_head) && q->request_fn)
418 __blk_run_queue(q);
420 drain |= q->nr_rqs_elvpriv;
421 drain |= q->request_fn_active;
424 * Unfortunately, requests are queued at and tracked from
425 * multiple places and there's no single counter which can
426 * be drained. Check all the queues and counters.
428 if (drain_all) {
429 drain |= !list_empty(&q->queue_head);
430 for (i = 0; i < 2; i++) {
431 drain |= q->nr_rqs[i];
432 drain |= q->in_flight[i];
433 drain |= !list_empty(&q->flush_queue[i]);
437 if (!drain)
438 break;
440 spin_unlock_irq(q->queue_lock);
442 msleep(10);
444 spin_lock_irq(q->queue_lock);
448 * With queue marked dead, any woken up waiter will fail the
449 * allocation path, so the wakeup chaining is lost and we're
450 * left with hung waiters. We need to wake up those waiters.
452 if (q->request_fn) {
453 struct request_list *rl;
455 blk_queue_for_each_rl(rl, q)
456 for (i = 0; i < ARRAY_SIZE(rl->wait); i++)
457 wake_up_all(&rl->wait[i]);
462 * blk_queue_bypass_start - enter queue bypass mode
463 * @q: queue of interest
465 * In bypass mode, only the dispatch FIFO queue of @q is used. This
466 * function makes @q enter bypass mode and drains all requests which were
467 * throttled or issued before. On return, it's guaranteed that no request
468 * is being throttled or has ELVPRIV set and blk_queue_bypass() %true
469 * inside queue or RCU read lock.
471 void blk_queue_bypass_start(struct request_queue *q)
473 bool drain;
475 spin_lock_irq(q->queue_lock);
476 drain = !q->bypass_depth++;
477 queue_flag_set(QUEUE_FLAG_BYPASS, q);
478 spin_unlock_irq(q->queue_lock);
480 if (drain) {
481 spin_lock_irq(q->queue_lock);
482 __blk_drain_queue(q, false);
483 spin_unlock_irq(q->queue_lock);
485 /* ensure blk_queue_bypass() is %true inside RCU read lock */
486 synchronize_rcu();
489 EXPORT_SYMBOL_GPL(blk_queue_bypass_start);
492 * blk_queue_bypass_end - leave queue bypass mode
493 * @q: queue of interest
495 * Leave bypass mode and restore the normal queueing behavior.
497 void blk_queue_bypass_end(struct request_queue *q)
499 spin_lock_irq(q->queue_lock);
500 if (!--q->bypass_depth)
501 queue_flag_clear(QUEUE_FLAG_BYPASS, q);
502 WARN_ON_ONCE(q->bypass_depth < 0);
503 spin_unlock_irq(q->queue_lock);
505 EXPORT_SYMBOL_GPL(blk_queue_bypass_end);
508 * blk_cleanup_queue - shutdown a request queue
509 * @q: request queue to shutdown
511 * Mark @q DYING, drain all pending requests, mark @q DEAD, destroy and
512 * put it. All future requests will be failed immediately with -ENODEV.
514 void blk_cleanup_queue(struct request_queue *q)
516 spinlock_t *lock = q->queue_lock;
518 /* mark @q DYING, no new request or merges will be allowed afterwards */
519 mutex_lock(&q->sysfs_lock);
520 queue_flag_set_unlocked(QUEUE_FLAG_DYING, q);
521 spin_lock_irq(lock);
524 * A dying queue is permanently in bypass mode till released. Note
525 * that, unlike blk_queue_bypass_start(), we aren't performing
526 * synchronize_rcu() after entering bypass mode to avoid the delay
527 * as some drivers create and destroy a lot of queues while
528 * probing. This is still safe because blk_release_queue() will be
529 * called only after the queue refcnt drops to zero and nothing,
530 * RCU or not, would be traversing the queue by then.
532 q->bypass_depth++;
533 queue_flag_set(QUEUE_FLAG_BYPASS, q);
535 queue_flag_set(QUEUE_FLAG_NOMERGES, q);
536 queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
537 queue_flag_set(QUEUE_FLAG_DYING, q);
538 spin_unlock_irq(lock);
539 mutex_unlock(&q->sysfs_lock);
542 * Drain all requests queued before DYING marking. Set DEAD flag to
543 * prevent that q->request_fn() gets invoked after draining finished.
545 spin_lock_irq(lock);
546 __blk_drain_queue(q, true);
547 queue_flag_set(QUEUE_FLAG_DEAD, q);
548 spin_unlock_irq(lock);
550 /* @q won't process any more request, flush async actions */
551 del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);
552 blk_sync_queue(q);
554 spin_lock_irq(lock);
555 if (q->queue_lock != &q->__queue_lock)
556 q->queue_lock = &q->__queue_lock;
557 spin_unlock_irq(lock);
559 /* @q is and will stay empty, shutdown and put */
560 blk_put_queue(q);
562 EXPORT_SYMBOL(blk_cleanup_queue);
564 int blk_init_rl(struct request_list *rl, struct request_queue *q,
565 gfp_t gfp_mask)
567 if (unlikely(rl->rq_pool))
568 return 0;
570 rl->q = q;
571 rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
572 rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
573 init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
574 init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
576 rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
577 mempool_free_slab, request_cachep,
578 gfp_mask, q->node);
579 if (!rl->rq_pool)
580 return -ENOMEM;
582 return 0;
585 void blk_exit_rl(struct request_list *rl)
587 if (rl->rq_pool)
588 mempool_destroy(rl->rq_pool);
591 struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
593 return blk_alloc_queue_node(gfp_mask, NUMA_NO_NODE);
595 EXPORT_SYMBOL(blk_alloc_queue);
597 struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
599 struct request_queue *q;
600 int err;
602 q = kmem_cache_alloc_node(blk_requestq_cachep,
603 gfp_mask | __GFP_ZERO, node_id);
604 if (!q)
605 return NULL;
607 q->id = ida_simple_get(&blk_queue_ida, 0, 0, gfp_mask);
608 if (q->id < 0)
609 goto fail_q;
611 q->backing_dev_info.ra_pages =
612 (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
613 q->backing_dev_info.state = 0;
614 q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
615 q->backing_dev_info.name = "block";
616 q->node = node_id;
618 err = bdi_init(&q->backing_dev_info);
619 if (err)
620 goto fail_id;
622 setup_timer(&q->backing_dev_info.laptop_mode_wb_timer,
623 laptop_mode_timer_fn, (unsigned long) q);
624 setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
625 INIT_LIST_HEAD(&q->queue_head);
626 INIT_LIST_HEAD(&q->timeout_list);
627 INIT_LIST_HEAD(&q->icq_list);
628 #ifdef CONFIG_BLK_CGROUP
629 INIT_LIST_HEAD(&q->blkg_list);
630 #endif
631 INIT_LIST_HEAD(&q->flush_queue[0]);
632 INIT_LIST_HEAD(&q->flush_queue[1]);
633 INIT_LIST_HEAD(&q->flush_data_in_flight);
634 INIT_DELAYED_WORK(&q->delay_work, blk_delay_work);
636 kobject_init(&q->kobj, &blk_queue_ktype);
638 mutex_init(&q->sysfs_lock);
639 spin_lock_init(&q->__queue_lock);
642 * By default initialize queue_lock to internal lock and driver can
643 * override it later if need be.
645 q->queue_lock = &q->__queue_lock;
648 * A queue starts its life with bypass turned on to avoid
649 * unnecessary bypass on/off overhead and nasty surprises during
650 * init. The initial bypass will be finished when the queue is
651 * registered by blk_register_queue().
653 q->bypass_depth = 1;
654 __set_bit(QUEUE_FLAG_BYPASS, &q->queue_flags);
656 if (blkcg_init_queue(q))
657 goto fail_id;
659 return q;
661 fail_id:
662 ida_simple_remove(&blk_queue_ida, q->id);
663 fail_q:
664 kmem_cache_free(blk_requestq_cachep, q);
665 return NULL;
667 EXPORT_SYMBOL(blk_alloc_queue_node);
670 * blk_init_queue - prepare a request queue for use with a block device
671 * @rfn: The function to be called to process requests that have been
672 * placed on the queue.
673 * @lock: Request queue spin lock
675 * Description:
676 * If a block device wishes to use the standard request handling procedures,
677 * which sorts requests and coalesces adjacent requests, then it must
678 * call blk_init_queue(). The function @rfn will be called when there
679 * are requests on the queue that need to be processed. If the device
680 * supports plugging, then @rfn may not be called immediately when requests
681 * are available on the queue, but may be called at some time later instead.
682 * Plugged queues are generally unplugged when a buffer belonging to one
683 * of the requests on the queue is needed, or due to memory pressure.
685 * @rfn is not required, or even expected, to remove all requests off the
686 * queue, but only as many as it can handle at a time. If it does leave
687 * requests on the queue, it is responsible for arranging that the requests
688 * get dealt with eventually.
690 * The queue spin lock must be held while manipulating the requests on the
691 * request queue; this lock will be taken also from interrupt context, so irq
692 * disabling is needed for it.
694 * Function returns a pointer to the initialized request queue, or %NULL if
695 * it didn't succeed.
697 * Note:
698 * blk_init_queue() must be paired with a blk_cleanup_queue() call
699 * when the block device is deactivated (such as at module unload).
702 struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
704 return blk_init_queue_node(rfn, lock, NUMA_NO_NODE);
706 EXPORT_SYMBOL(blk_init_queue);
708 struct request_queue *
709 blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
711 struct request_queue *uninit_q, *q;
713 uninit_q = blk_alloc_queue_node(GFP_KERNEL, node_id);
714 if (!uninit_q)
715 return NULL;
717 q = blk_init_allocated_queue(uninit_q, rfn, lock);
718 if (!q)
719 blk_cleanup_queue(uninit_q);
721 return q;
723 EXPORT_SYMBOL(blk_init_queue_node);
725 struct request_queue *
726 blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
727 spinlock_t *lock)
729 if (!q)
730 return NULL;
732 if (blk_init_rl(&q->root_rl, q, GFP_KERNEL))
733 return NULL;
735 q->request_fn = rfn;
736 q->prep_rq_fn = NULL;
737 q->unprep_rq_fn = NULL;
738 q->queue_flags |= QUEUE_FLAG_DEFAULT;
740 /* Override internal queue lock with supplied lock pointer */
741 if (lock)
742 q->queue_lock = lock;
745 * This also sets hw/phys segments, boundary and size
747 blk_queue_make_request(q, blk_queue_bio);
749 q->sg_reserved_size = INT_MAX;
751 /* init elevator */
752 if (elevator_init(q, NULL))
753 return NULL;
754 return q;
756 EXPORT_SYMBOL(blk_init_allocated_queue);
758 bool blk_get_queue(struct request_queue *q)
760 if (likely(!blk_queue_dying(q))) {
761 __blk_get_queue(q);
762 return true;
765 return false;
767 EXPORT_SYMBOL(blk_get_queue);
769 static inline void blk_free_request(struct request_list *rl, struct request *rq)
771 if (rq->cmd_flags & REQ_ELVPRIV) {
772 elv_put_request(rl->q, rq);
773 if (rq->elv.icq)
774 put_io_context(rq->elv.icq->ioc);
777 mempool_free(rq, rl->rq_pool);
781 * ioc_batching returns true if the ioc is a valid batching request and
782 * should be given priority access to a request.
784 static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
786 if (!ioc)
787 return 0;
790 * Make sure the process is able to allocate at least 1 request
791 * even if the batch times out, otherwise we could theoretically
792 * lose wakeups.
794 return ioc->nr_batch_requests == q->nr_batching ||
795 (ioc->nr_batch_requests > 0
796 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
800 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
801 * will cause the process to be a "batcher" on all queues in the system. This
802 * is the behaviour we want though - once it gets a wakeup it should be given
803 * a nice run.
805 static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
807 if (!ioc || ioc_batching(q, ioc))
808 return;
810 ioc->nr_batch_requests = q->nr_batching;
811 ioc->last_waited = jiffies;
814 static void __freed_request(struct request_list *rl, int sync)
816 struct request_queue *q = rl->q;
819 * bdi isn't aware of blkcg yet. As all async IOs end up root
820 * blkcg anyway, just use root blkcg state.
822 if (rl == &q->root_rl &&
823 rl->count[sync] < queue_congestion_off_threshold(q))
824 blk_clear_queue_congested(q, sync);
826 if (rl->count[sync] + 1 <= q->nr_requests) {
827 if (waitqueue_active(&rl->wait[sync]))
828 wake_up(&rl->wait[sync]);
830 blk_clear_rl_full(rl, sync);
835 * A request has just been released. Account for it, update the full and
836 * congestion status, wake up any waiters. Called under q->queue_lock.
838 static void freed_request(struct request_list *rl, unsigned int flags)
840 struct request_queue *q = rl->q;
841 int sync = rw_is_sync(flags);
843 q->nr_rqs[sync]--;
844 rl->count[sync]--;
845 if (flags & REQ_ELVPRIV)
846 q->nr_rqs_elvpriv--;
848 __freed_request(rl, sync);
850 if (unlikely(rl->starved[sync ^ 1]))
851 __freed_request(rl, sync ^ 1);
855 * Determine if elevator data should be initialized when allocating the
856 * request associated with @bio.
858 static bool blk_rq_should_init_elevator(struct bio *bio)
860 if (!bio)
861 return true;
864 * Flush requests do not use the elevator so skip initialization.
865 * This allows a request to share the flush and elevator data.
867 if (bio->bi_rw & (REQ_FLUSH | REQ_FUA))
868 return false;
870 return true;
874 * rq_ioc - determine io_context for request allocation
875 * @bio: request being allocated is for this bio (can be %NULL)
877 * Determine io_context to use for request allocation for @bio. May return
878 * %NULL if %current->io_context doesn't exist.
880 static struct io_context *rq_ioc(struct bio *bio)
882 #ifdef CONFIG_BLK_CGROUP
883 if (bio && bio->bi_ioc)
884 return bio->bi_ioc;
885 #endif
886 return current->io_context;
890 * __get_request - get a free request
891 * @rl: request list to allocate from
892 * @rw_flags: RW and SYNC flags
893 * @bio: bio to allocate request for (can be %NULL)
894 * @gfp_mask: allocation mask
896 * Get a free request from @q. This function may fail under memory
897 * pressure or if @q is dead.
899 * Must be callled with @q->queue_lock held and,
900 * Returns %NULL on failure, with @q->queue_lock held.
901 * Returns !%NULL on success, with @q->queue_lock *not held*.
903 static struct request *__get_request(struct request_list *rl, int rw_flags,
904 struct bio *bio, gfp_t gfp_mask)
906 struct request_queue *q = rl->q;
907 struct request *rq;
908 struct elevator_type *et = q->elevator->type;
909 struct io_context *ioc = rq_ioc(bio);
910 struct io_cq *icq = NULL;
911 const bool is_sync = rw_is_sync(rw_flags) != 0;
912 int may_queue;
914 if (unlikely(blk_queue_dying(q)))
915 return NULL;
917 may_queue = elv_may_queue(q, rw_flags);
918 if (may_queue == ELV_MQUEUE_NO)
919 goto rq_starved;
921 if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
922 if (rl->count[is_sync]+1 >= q->nr_requests) {
924 * The queue will fill after this allocation, so set
925 * it as full, and mark this process as "batching".
926 * This process will be allowed to complete a batch of
927 * requests, others will be blocked.
929 if (!blk_rl_full(rl, is_sync)) {
930 ioc_set_batching(q, ioc);
931 blk_set_rl_full(rl, is_sync);
932 } else {
933 if (may_queue != ELV_MQUEUE_MUST
934 && !ioc_batching(q, ioc)) {
936 * The queue is full and the allocating
937 * process is not a "batcher", and not
938 * exempted by the IO scheduler
940 return NULL;
945 * bdi isn't aware of blkcg yet. As all async IOs end up
946 * root blkcg anyway, just use root blkcg state.
948 if (rl == &q->root_rl)
949 blk_set_queue_congested(q, is_sync);
953 * Only allow batching queuers to allocate up to 50% over the defined
954 * limit of requests, otherwise we could have thousands of requests
955 * allocated with any setting of ->nr_requests
957 if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
958 return NULL;
960 q->nr_rqs[is_sync]++;
961 rl->count[is_sync]++;
962 rl->starved[is_sync] = 0;
965 * Decide whether the new request will be managed by elevator. If
966 * so, mark @rw_flags and increment elvpriv. Non-zero elvpriv will
967 * prevent the current elevator from being destroyed until the new
968 * request is freed. This guarantees icq's won't be destroyed and
969 * makes creating new ones safe.
971 * Also, lookup icq while holding queue_lock. If it doesn't exist,
972 * it will be created after releasing queue_lock.
974 if (blk_rq_should_init_elevator(bio) && !blk_queue_bypass(q)) {
975 rw_flags |= REQ_ELVPRIV;
976 q->nr_rqs_elvpriv++;
977 if (et->icq_cache && ioc)
978 icq = ioc_lookup_icq(ioc, q);
981 if (blk_queue_io_stat(q))
982 rw_flags |= REQ_IO_STAT;
983 spin_unlock_irq(q->queue_lock);
985 /* allocate and init request */
986 rq = mempool_alloc(rl->rq_pool, gfp_mask);
987 if (!rq)
988 goto fail_alloc;
990 blk_rq_init(q, rq);
991 blk_rq_set_rl(rq, rl);
992 rq->cmd_flags = rw_flags | REQ_ALLOCED;
994 /* init elvpriv */
995 if (rw_flags & REQ_ELVPRIV) {
996 if (unlikely(et->icq_cache && !icq)) {
997 if (ioc)
998 icq = ioc_create_icq(ioc, q, gfp_mask);
999 if (!icq)
1000 goto fail_elvpriv;
1003 rq->elv.icq = icq;
1004 if (unlikely(elv_set_request(q, rq, bio, gfp_mask)))
1005 goto fail_elvpriv;
1007 /* @rq->elv.icq holds io_context until @rq is freed */
1008 if (icq)
1009 get_io_context(icq->ioc);
1011 out:
1013 * ioc may be NULL here, and ioc_batching will be false. That's
1014 * OK, if the queue is under the request limit then requests need
1015 * not count toward the nr_batch_requests limit. There will always
1016 * be some limit enforced by BLK_BATCH_TIME.
1018 if (ioc_batching(q, ioc))
1019 ioc->nr_batch_requests--;
1021 trace_block_getrq(q, bio, rw_flags & 1);
1022 return rq;
1024 fail_elvpriv:
1026 * elvpriv init failed. ioc, icq and elvpriv aren't mempool backed
1027 * and may fail indefinitely under memory pressure and thus
1028 * shouldn't stall IO. Treat this request as !elvpriv. This will
1029 * disturb iosched and blkcg but weird is bettern than dead.
1031 printk_ratelimited(KERN_WARNING "%s: request aux data allocation failed, iosched may be disturbed\n",
1032 dev_name(q->backing_dev_info.dev));
1034 rq->cmd_flags &= ~REQ_ELVPRIV;
1035 rq->elv.icq = NULL;
1037 spin_lock_irq(q->queue_lock);
1038 q->nr_rqs_elvpriv--;
1039 spin_unlock_irq(q->queue_lock);
1040 goto out;
1042 fail_alloc:
1044 * Allocation failed presumably due to memory. Undo anything we
1045 * might have messed up.
1047 * Allocating task should really be put onto the front of the wait
1048 * queue, but this is pretty rare.
1050 spin_lock_irq(q->queue_lock);
1051 freed_request(rl, rw_flags);
1054 * in the very unlikely event that allocation failed and no
1055 * requests for this direction was pending, mark us starved so that
1056 * freeing of a request in the other direction will notice
1057 * us. another possible fix would be to split the rq mempool into
1058 * READ and WRITE
1060 rq_starved:
1061 if (unlikely(rl->count[is_sync] == 0))
1062 rl->starved[is_sync] = 1;
1063 return NULL;
1067 * get_request - get a free request
1068 * @q: request_queue to allocate request from
1069 * @rw_flags: RW and SYNC flags
1070 * @bio: bio to allocate request for (can be %NULL)
1071 * @gfp_mask: allocation mask
1073 * Get a free request from @q. If %__GFP_WAIT is set in @gfp_mask, this
1074 * function keeps retrying under memory pressure and fails iff @q is dead.
1076 * Must be callled with @q->queue_lock held and,
1077 * Returns %NULL on failure, with @q->queue_lock held.
1078 * Returns !%NULL on success, with @q->queue_lock *not held*.
1080 static struct request *get_request(struct request_queue *q, int rw_flags,
1081 struct bio *bio, gfp_t gfp_mask)
1083 const bool is_sync = rw_is_sync(rw_flags) != 0;
1084 DEFINE_WAIT(wait);
1085 struct request_list *rl;
1086 struct request *rq;
1088 rl = blk_get_rl(q, bio); /* transferred to @rq on success */
1089 retry:
1090 rq = __get_request(rl, rw_flags, bio, gfp_mask);
1091 if (rq)
1092 return rq;
1094 if (!(gfp_mask & __GFP_WAIT) || unlikely(blk_queue_dying(q))) {
1095 blk_put_rl(rl);
1096 return NULL;
1099 /* wait on @rl and retry */
1100 prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
1101 TASK_UNINTERRUPTIBLE);
1103 trace_block_sleeprq(q, bio, rw_flags & 1);
1105 spin_unlock_irq(q->queue_lock);
1106 io_schedule();
1109 * After sleeping, we become a "batching" process and will be able
1110 * to allocate at least one request, and up to a big batch of them
1111 * for a small period time. See ioc_batching, ioc_set_batching
1113 ioc_set_batching(q, current->io_context);
1115 spin_lock_irq(q->queue_lock);
1116 finish_wait(&rl->wait[is_sync], &wait);
1118 goto retry;
1121 struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
1123 struct request *rq;
1125 BUG_ON(rw != READ && rw != WRITE);
1127 /* create ioc upfront */
1128 create_io_context(gfp_mask, q->node);
1130 spin_lock_irq(q->queue_lock);
1131 rq = get_request(q, rw, NULL, gfp_mask);
1132 if (!rq)
1133 spin_unlock_irq(q->queue_lock);
1134 /* q->queue_lock is unlocked at this point */
1136 return rq;
1138 EXPORT_SYMBOL(blk_get_request);
1141 * blk_make_request - given a bio, allocate a corresponding struct request.
1142 * @q: target request queue
1143 * @bio: The bio describing the memory mappings that will be submitted for IO.
1144 * It may be a chained-bio properly constructed by block/bio layer.
1145 * @gfp_mask: gfp flags to be used for memory allocation
1147 * blk_make_request is the parallel of generic_make_request for BLOCK_PC
1148 * type commands. Where the struct request needs to be farther initialized by
1149 * the caller. It is passed a &struct bio, which describes the memory info of
1150 * the I/O transfer.
1152 * The caller of blk_make_request must make sure that bi_io_vec
1153 * are set to describe the memory buffers. That bio_data_dir() will return
1154 * the needed direction of the request. (And all bio's in the passed bio-chain
1155 * are properly set accordingly)
1157 * If called under none-sleepable conditions, mapped bio buffers must not
1158 * need bouncing, by calling the appropriate masked or flagged allocator,
1159 * suitable for the target device. Otherwise the call to blk_queue_bounce will
1160 * BUG.
1162 * WARNING: When allocating/cloning a bio-chain, careful consideration should be
1163 * given to how you allocate bios. In particular, you cannot use __GFP_WAIT for
1164 * anything but the first bio in the chain. Otherwise you risk waiting for IO
1165 * completion of a bio that hasn't been submitted yet, thus resulting in a
1166 * deadlock. Alternatively bios should be allocated using bio_kmalloc() instead
1167 * of bio_alloc(), as that avoids the mempool deadlock.
1168 * If possible a big IO should be split into smaller parts when allocation
1169 * fails. Partial allocation should not be an error, or you risk a live-lock.
1171 struct request *blk_make_request(struct request_queue *q, struct bio *bio,
1172 gfp_t gfp_mask)
1174 struct request *rq = blk_get_request(q, bio_data_dir(bio), gfp_mask);
1176 if (unlikely(!rq))
1177 return ERR_PTR(-ENOMEM);
1179 for_each_bio(bio) {
1180 struct bio *bounce_bio = bio;
1181 int ret;
1183 blk_queue_bounce(q, &bounce_bio);
1184 ret = blk_rq_append_bio(q, rq, bounce_bio);
1185 if (unlikely(ret)) {
1186 blk_put_request(rq);
1187 return ERR_PTR(ret);
1191 return rq;
1193 EXPORT_SYMBOL(blk_make_request);
1196 * blk_requeue_request - put a request back on queue
1197 * @q: request queue where request should be inserted
1198 * @rq: request to be inserted
1200 * Description:
1201 * Drivers often keep queueing requests until the hardware cannot accept
1202 * more, when that condition happens we need to put the request back
1203 * on the queue. Must be called with queue lock held.
1205 void blk_requeue_request(struct request_queue *q, struct request *rq)
1207 blk_delete_timer(rq);
1208 blk_clear_rq_complete(rq);
1209 trace_block_rq_requeue(q, rq);
1211 if (blk_rq_tagged(rq))
1212 blk_queue_end_tag(q, rq);
1214 BUG_ON(blk_queued_rq(rq));
1216 elv_requeue_request(q, rq);
1218 EXPORT_SYMBOL(blk_requeue_request);
1220 static void add_acct_request(struct request_queue *q, struct request *rq,
1221 int where)
1223 drive_stat_acct(rq, 1);
1224 __elv_add_request(q, rq, where);
1227 static void part_round_stats_single(int cpu, struct hd_struct *part,
1228 unsigned long now)
1230 if (now == part->stamp)
1231 return;
1233 if (part_in_flight(part)) {
1234 __part_stat_add(cpu, part, time_in_queue,
1235 part_in_flight(part) * (now - part->stamp));
1236 __part_stat_add(cpu, part, io_ticks, (now - part->stamp));
1238 part->stamp = now;
1242 * part_round_stats() - Round off the performance stats on a struct disk_stats.
1243 * @cpu: cpu number for stats access
1244 * @part: target partition
1246 * The average IO queue length and utilisation statistics are maintained
1247 * by observing the current state of the queue length and the amount of
1248 * time it has been in this state for.
1250 * Normally, that accounting is done on IO completion, but that can result
1251 * in more than a second's worth of IO being accounted for within any one
1252 * second, leading to >100% utilisation. To deal with that, we call this
1253 * function to do a round-off before returning the results when reading
1254 * /proc/diskstats. This accounts immediately for all queue usage up to
1255 * the current jiffies and restarts the counters again.
1257 void part_round_stats(int cpu, struct hd_struct *part)
1259 unsigned long now = jiffies;
1261 if (part->partno)
1262 part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1263 part_round_stats_single(cpu, part, now);
1265 EXPORT_SYMBOL_GPL(part_round_stats);
1268 * queue lock must be held
1270 void __blk_put_request(struct request_queue *q, struct request *req)
1272 if (unlikely(!q))
1273 return;
1274 if (unlikely(--req->ref_count))
1275 return;
1277 elv_completed_request(q, req);
1279 /* this is a bio leak */
1280 WARN_ON(req->bio != NULL);
1283 * Request may not have originated from ll_rw_blk. if not,
1284 * it didn't come out of our reserved rq pools
1286 if (req->cmd_flags & REQ_ALLOCED) {
1287 unsigned int flags = req->cmd_flags;
1288 struct request_list *rl = blk_rq_rl(req);
1290 BUG_ON(!list_empty(&req->queuelist));
1291 BUG_ON(!hlist_unhashed(&req->hash));
1293 blk_free_request(rl, req);
1294 freed_request(rl, flags);
1295 blk_put_rl(rl);
1298 EXPORT_SYMBOL_GPL(__blk_put_request);
1300 void blk_put_request(struct request *req)
1302 unsigned long flags;
1303 struct request_queue *q = req->q;
1305 spin_lock_irqsave(q->queue_lock, flags);
1306 __blk_put_request(q, req);
1307 spin_unlock_irqrestore(q->queue_lock, flags);
1309 EXPORT_SYMBOL(blk_put_request);
1312 * blk_add_request_payload - add a payload to a request
1313 * @rq: request to update
1314 * @page: page backing the payload
1315 * @len: length of the payload.
1317 * This allows to later add a payload to an already submitted request by
1318 * a block driver. The driver needs to take care of freeing the payload
1319 * itself.
1321 * Note that this is a quite horrible hack and nothing but handling of
1322 * discard requests should ever use it.
1324 void blk_add_request_payload(struct request *rq, struct page *page,
1325 unsigned int len)
1327 struct bio *bio = rq->bio;
1329 bio->bi_io_vec->bv_page = page;
1330 bio->bi_io_vec->bv_offset = 0;
1331 bio->bi_io_vec->bv_len = len;
1333 bio->bi_size = len;
1334 bio->bi_vcnt = 1;
1335 bio->bi_phys_segments = 1;
1337 rq->__data_len = rq->resid_len = len;
1338 rq->nr_phys_segments = 1;
1339 rq->buffer = bio_data(bio);
1341 EXPORT_SYMBOL_GPL(blk_add_request_payload);
1343 static bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
1344 struct bio *bio)
1346 const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1348 if (!ll_back_merge_fn(q, req, bio))
1349 return false;
1351 trace_block_bio_backmerge(q, bio);
1353 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1354 blk_rq_set_mixed_merge(req);
1356 req->biotail->bi_next = bio;
1357 req->biotail = bio;
1358 req->__data_len += bio->bi_size;
1359 req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1361 drive_stat_acct(req, 0);
1362 return true;
1365 static bool bio_attempt_front_merge(struct request_queue *q,
1366 struct request *req, struct bio *bio)
1368 const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1370 if (!ll_front_merge_fn(q, req, bio))
1371 return false;
1373 trace_block_bio_frontmerge(q, bio);
1375 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1376 blk_rq_set_mixed_merge(req);
1378 bio->bi_next = req->bio;
1379 req->bio = bio;
1382 * may not be valid. if the low level driver said
1383 * it didn't need a bounce buffer then it better
1384 * not touch req->buffer either...
1386 req->buffer = bio_data(bio);
1387 req->__sector = bio->bi_sector;
1388 req->__data_len += bio->bi_size;
1389 req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1391 drive_stat_acct(req, 0);
1392 return true;
1396 * attempt_plug_merge - try to merge with %current's plugged list
1397 * @q: request_queue new bio is being queued at
1398 * @bio: new bio being queued
1399 * @request_count: out parameter for number of traversed plugged requests
1401 * Determine whether @bio being queued on @q can be merged with a request
1402 * on %current's plugged list. Returns %true if merge was successful,
1403 * otherwise %false.
1405 * Plugging coalesces IOs from the same issuer for the same purpose without
1406 * going through @q->queue_lock. As such it's more of an issuing mechanism
1407 * than scheduling, and the request, while may have elvpriv data, is not
1408 * added on the elevator at this point. In addition, we don't have
1409 * reliable access to the elevator outside queue lock. Only check basic
1410 * merging parameters without querying the elevator.
1412 static bool attempt_plug_merge(struct request_queue *q, struct bio *bio,
1413 unsigned int *request_count)
1415 struct blk_plug *plug;
1416 struct request *rq;
1417 bool ret = false;
1419 plug = current->plug;
1420 if (!plug)
1421 goto out;
1422 *request_count = 0;
1424 list_for_each_entry_reverse(rq, &plug->list, queuelist) {
1425 int el_ret;
1427 if (rq->q == q)
1428 (*request_count)++;
1430 if (rq->q != q || !blk_rq_merge_ok(rq, bio))
1431 continue;
1433 el_ret = blk_try_merge(rq, bio);
1434 if (el_ret == ELEVATOR_BACK_MERGE) {
1435 ret = bio_attempt_back_merge(q, rq, bio);
1436 if (ret)
1437 break;
1438 } else if (el_ret == ELEVATOR_FRONT_MERGE) {
1439 ret = bio_attempt_front_merge(q, rq, bio);
1440 if (ret)
1441 break;
1444 out:
1445 return ret;
1448 void init_request_from_bio(struct request *req, struct bio *bio)
1450 req->cmd_type = REQ_TYPE_FS;
1452 req->cmd_flags |= bio->bi_rw & REQ_COMMON_MASK;
1453 if (bio->bi_rw & REQ_RAHEAD)
1454 req->cmd_flags |= REQ_FAILFAST_MASK;
1456 req->errors = 0;
1457 req->__sector = bio->bi_sector;
1458 req->ioprio = bio_prio(bio);
1459 blk_rq_bio_prep(req->q, req, bio);
1462 void blk_queue_bio(struct request_queue *q, struct bio *bio)
1464 const bool sync = !!(bio->bi_rw & REQ_SYNC);
1465 struct blk_plug *plug;
1466 int el_ret, rw_flags, where = ELEVATOR_INSERT_SORT;
1467 struct request *req;
1468 unsigned int request_count = 0;
1471 * low level driver can indicate that it wants pages above a
1472 * certain limit bounced to low memory (ie for highmem, or even
1473 * ISA dma in theory)
1475 blk_queue_bounce(q, &bio);
1477 if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) {
1478 spin_lock_irq(q->queue_lock);
1479 where = ELEVATOR_INSERT_FLUSH;
1480 goto get_rq;
1484 * Check if we can merge with the plugged list before grabbing
1485 * any locks.
1487 if (attempt_plug_merge(q, bio, &request_count))
1488 return;
1490 spin_lock_irq(q->queue_lock);
1492 el_ret = elv_merge(q, &req, bio);
1493 if (el_ret == ELEVATOR_BACK_MERGE) {
1494 if (bio_attempt_back_merge(q, req, bio)) {
1495 elv_bio_merged(q, req, bio);
1496 if (!attempt_back_merge(q, req))
1497 elv_merged_request(q, req, el_ret);
1498 goto out_unlock;
1500 } else if (el_ret == ELEVATOR_FRONT_MERGE) {
1501 if (bio_attempt_front_merge(q, req, bio)) {
1502 elv_bio_merged(q, req, bio);
1503 if (!attempt_front_merge(q, req))
1504 elv_merged_request(q, req, el_ret);
1505 goto out_unlock;
1509 get_rq:
1511 * This sync check and mask will be re-done in init_request_from_bio(),
1512 * but we need to set it earlier to expose the sync flag to the
1513 * rq allocator and io schedulers.
1515 rw_flags = bio_data_dir(bio);
1516 if (sync)
1517 rw_flags |= REQ_SYNC;
1520 * Grab a free request. This is might sleep but can not fail.
1521 * Returns with the queue unlocked.
1523 req = get_request(q, rw_flags, bio, GFP_NOIO);
1524 if (unlikely(!req)) {
1525 bio_endio(bio, -ENODEV); /* @q is dead */
1526 goto out_unlock;
1530 * After dropping the lock and possibly sleeping here, our request
1531 * may now be mergeable after it had proven unmergeable (above).
1532 * We don't worry about that case for efficiency. It won't happen
1533 * often, and the elevators are able to handle it.
1535 init_request_from_bio(req, bio);
1537 if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags))
1538 req->cpu = raw_smp_processor_id();
1540 plug = current->plug;
1541 if (plug) {
1543 * If this is the first request added after a plug, fire
1544 * of a plug trace. If others have been added before, check
1545 * if we have multiple devices in this plug. If so, make a
1546 * note to sort the list before dispatch.
1548 if (list_empty(&plug->list))
1549 trace_block_plug(q);
1550 else {
1551 if (!plug->should_sort) {
1552 struct request *__rq;
1554 __rq = list_entry_rq(plug->list.prev);
1555 if (__rq->q != q)
1556 plug->should_sort = 1;
1558 if (request_count >= BLK_MAX_REQUEST_COUNT) {
1559 blk_flush_plug_list(plug, false);
1560 trace_block_plug(q);
1563 list_add_tail(&req->queuelist, &plug->list);
1564 drive_stat_acct(req, 1);
1565 } else {
1566 spin_lock_irq(q->queue_lock);
1567 add_acct_request(q, req, where);
1568 __blk_run_queue(q);
1569 out_unlock:
1570 spin_unlock_irq(q->queue_lock);
1573 EXPORT_SYMBOL_GPL(blk_queue_bio); /* for device mapper only */
1576 * If bio->bi_dev is a partition, remap the location
1578 static inline void blk_partition_remap(struct bio *bio)
1580 struct block_device *bdev = bio->bi_bdev;
1582 if (bio_sectors(bio) && bdev != bdev->bd_contains) {
1583 struct hd_struct *p = bdev->bd_part;
1585 bio->bi_sector += p->start_sect;
1586 bio->bi_bdev = bdev->bd_contains;
1588 trace_block_bio_remap(bdev_get_queue(bio->bi_bdev), bio,
1589 bdev->bd_dev,
1590 bio->bi_sector - p->start_sect);
1594 static void handle_bad_sector(struct bio *bio)
1596 char b[BDEVNAME_SIZE];
1598 printk(KERN_INFO "attempt to access beyond end of device\n");
1599 printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
1600 bdevname(bio->bi_bdev, b),
1601 bio->bi_rw,
1602 (unsigned long long)bio->bi_sector + bio_sectors(bio),
1603 (long long)(i_size_read(bio->bi_bdev->bd_inode) >> 9));
1605 set_bit(BIO_EOF, &bio->bi_flags);
1608 #ifdef CONFIG_FAIL_MAKE_REQUEST
1610 static DECLARE_FAULT_ATTR(fail_make_request);
1612 static int __init setup_fail_make_request(char *str)
1614 return setup_fault_attr(&fail_make_request, str);
1616 __setup("fail_make_request=", setup_fail_make_request);
1618 static bool should_fail_request(struct hd_struct *part, unsigned int bytes)
1620 return part->make_it_fail && should_fail(&fail_make_request, bytes);
1623 static int __init fail_make_request_debugfs(void)
1625 struct dentry *dir = fault_create_debugfs_attr("fail_make_request",
1626 NULL, &fail_make_request);
1628 return IS_ERR(dir) ? PTR_ERR(dir) : 0;
1631 late_initcall(fail_make_request_debugfs);
1633 #else /* CONFIG_FAIL_MAKE_REQUEST */
1635 static inline bool should_fail_request(struct hd_struct *part,
1636 unsigned int bytes)
1638 return false;
1641 #endif /* CONFIG_FAIL_MAKE_REQUEST */
1644 * Check whether this bio extends beyond the end of the device.
1646 static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1648 sector_t maxsector;
1650 if (!nr_sectors)
1651 return 0;
1653 /* Test device or partition size, when known. */
1654 maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
1655 if (maxsector) {
1656 sector_t sector = bio->bi_sector;
1658 if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1660 * This may well happen - the kernel calls bread()
1661 * without checking the size of the device, e.g., when
1662 * mounting a device.
1664 handle_bad_sector(bio);
1665 return 1;
1669 return 0;
1672 static noinline_for_stack bool
1673 generic_make_request_checks(struct bio *bio)
1675 struct request_queue *q;
1676 int nr_sectors = bio_sectors(bio);
1677 int err = -EIO;
1678 char b[BDEVNAME_SIZE];
1679 struct hd_struct *part;
1681 might_sleep();
1683 if (bio_check_eod(bio, nr_sectors))
1684 goto end_io;
1686 q = bdev_get_queue(bio->bi_bdev);
1687 if (unlikely(!q)) {
1688 printk(KERN_ERR
1689 "generic_make_request: Trying to access "
1690 "nonexistent block-device %s (%Lu)\n",
1691 bdevname(bio->bi_bdev, b),
1692 (long long) bio->bi_sector);
1693 goto end_io;
1696 if (likely(bio_is_rw(bio) &&
1697 nr_sectors > queue_max_hw_sectors(q))) {
1698 printk(KERN_ERR "bio too big device %s (%u > %u)\n",
1699 bdevname(bio->bi_bdev, b),
1700 bio_sectors(bio),
1701 queue_max_hw_sectors(q));
1702 goto end_io;
1705 part = bio->bi_bdev->bd_part;
1706 if (should_fail_request(part, bio->bi_size) ||
1707 should_fail_request(&part_to_disk(part)->part0,
1708 bio->bi_size))
1709 goto end_io;
1712 * If this device has partitions, remap block n
1713 * of partition p to block n+start(p) of the disk.
1715 blk_partition_remap(bio);
1717 if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
1718 goto end_io;
1720 if (bio_check_eod(bio, nr_sectors))
1721 goto end_io;
1724 * Filter flush bio's early so that make_request based
1725 * drivers without flush support don't have to worry
1726 * about them.
1728 if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
1729 bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
1730 if (!nr_sectors) {
1731 err = 0;
1732 goto end_io;
1736 if ((bio->bi_rw & REQ_DISCARD) &&
1737 (!blk_queue_discard(q) ||
1738 ((bio->bi_rw & REQ_SECURE) && !blk_queue_secdiscard(q)))) {
1739 err = -EOPNOTSUPP;
1740 goto end_io;
1743 if (bio->bi_rw & REQ_WRITE_SAME && !bdev_write_same(bio->bi_bdev)) {
1744 err = -EOPNOTSUPP;
1745 goto end_io;
1749 * Various block parts want %current->io_context and lazy ioc
1750 * allocation ends up trading a lot of pain for a small amount of
1751 * memory. Just allocate it upfront. This may fail and block
1752 * layer knows how to live with it.
1754 create_io_context(GFP_ATOMIC, q->node);
1756 if (blk_throtl_bio(q, bio))
1757 return false; /* throttled, will be resubmitted later */
1759 trace_block_bio_queue(q, bio);
1760 return true;
1762 end_io:
1763 bio_endio(bio, err);
1764 return false;
1768 * generic_make_request - hand a buffer to its device driver for I/O
1769 * @bio: The bio describing the location in memory and on the device.
1771 * generic_make_request() is used to make I/O requests of block
1772 * devices. It is passed a &struct bio, which describes the I/O that needs
1773 * to be done.
1775 * generic_make_request() does not return any status. The
1776 * success/failure status of the request, along with notification of
1777 * completion, is delivered asynchronously through the bio->bi_end_io
1778 * function described (one day) else where.
1780 * The caller of generic_make_request must make sure that bi_io_vec
1781 * are set to describe the memory buffer, and that bi_dev and bi_sector are
1782 * set to describe the device address, and the
1783 * bi_end_io and optionally bi_private are set to describe how
1784 * completion notification should be signaled.
1786 * generic_make_request and the drivers it calls may use bi_next if this
1787 * bio happens to be merged with someone else, and may resubmit the bio to
1788 * a lower device by calling into generic_make_request recursively, which
1789 * means the bio should NOT be touched after the call to ->make_request_fn.
1791 void generic_make_request(struct bio *bio)
1793 struct bio_list bio_list_on_stack;
1795 if (!generic_make_request_checks(bio))
1796 return;
1799 * We only want one ->make_request_fn to be active at a time, else
1800 * stack usage with stacked devices could be a problem. So use
1801 * current->bio_list to keep a list of requests submited by a
1802 * make_request_fn function. current->bio_list is also used as a
1803 * flag to say if generic_make_request is currently active in this
1804 * task or not. If it is NULL, then no make_request is active. If
1805 * it is non-NULL, then a make_request is active, and new requests
1806 * should be added at the tail
1808 if (current->bio_list) {
1809 bio_list_add(current->bio_list, bio);
1810 return;
1813 /* following loop may be a bit non-obvious, and so deserves some
1814 * explanation.
1815 * Before entering the loop, bio->bi_next is NULL (as all callers
1816 * ensure that) so we have a list with a single bio.
1817 * We pretend that we have just taken it off a longer list, so
1818 * we assign bio_list to a pointer to the bio_list_on_stack,
1819 * thus initialising the bio_list of new bios to be
1820 * added. ->make_request() may indeed add some more bios
1821 * through a recursive call to generic_make_request. If it
1822 * did, we find a non-NULL value in bio_list and re-enter the loop
1823 * from the top. In this case we really did just take the bio
1824 * of the top of the list (no pretending) and so remove it from
1825 * bio_list, and call into ->make_request() again.
1827 BUG_ON(bio->bi_next);
1828 bio_list_init(&bio_list_on_stack);
1829 current->bio_list = &bio_list_on_stack;
1830 do {
1831 struct request_queue *q = bdev_get_queue(bio->bi_bdev);
1833 q->make_request_fn(q, bio);
1835 bio = bio_list_pop(current->bio_list);
1836 } while (bio);
1837 current->bio_list = NULL; /* deactivate */
1839 EXPORT_SYMBOL(generic_make_request);
1842 * submit_bio - submit a bio to the block device layer for I/O
1843 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1844 * @bio: The &struct bio which describes the I/O
1846 * submit_bio() is very similar in purpose to generic_make_request(), and
1847 * uses that function to do most of the work. Both are fairly rough
1848 * interfaces; @bio must be presetup and ready for I/O.
1851 void submit_bio(int rw, struct bio *bio)
1853 bio->bi_rw |= rw;
1856 * If it's a regular read/write or a barrier with data attached,
1857 * go through the normal accounting stuff before submission.
1859 if (bio_has_data(bio)) {
1860 unsigned int count;
1862 if (unlikely(rw & REQ_WRITE_SAME))
1863 count = bdev_logical_block_size(bio->bi_bdev) >> 9;
1864 else
1865 count = bio_sectors(bio);
1867 if (rw & WRITE) {
1868 count_vm_events(PGPGOUT, count);
1869 } else {
1870 task_io_account_read(bio->bi_size);
1871 count_vm_events(PGPGIN, count);
1874 if (unlikely(block_dump)) {
1875 char b[BDEVNAME_SIZE];
1876 printk(KERN_DEBUG "%s(%d): %s block %Lu on %s (%u sectors)\n",
1877 current->comm, task_pid_nr(current),
1878 (rw & WRITE) ? "WRITE" : "READ",
1879 (unsigned long long)bio->bi_sector,
1880 bdevname(bio->bi_bdev, b),
1881 count);
1885 generic_make_request(bio);
1887 EXPORT_SYMBOL(submit_bio);
1890 * blk_rq_check_limits - Helper function to check a request for the queue limit
1891 * @q: the queue
1892 * @rq: the request being checked
1894 * Description:
1895 * @rq may have been made based on weaker limitations of upper-level queues
1896 * in request stacking drivers, and it may violate the limitation of @q.
1897 * Since the block layer and the underlying device driver trust @rq
1898 * after it is inserted to @q, it should be checked against @q before
1899 * the insertion using this generic function.
1901 * This function should also be useful for request stacking drivers
1902 * in some cases below, so export this function.
1903 * Request stacking drivers like request-based dm may change the queue
1904 * limits while requests are in the queue (e.g. dm's table swapping).
1905 * Such request stacking drivers should check those requests agaist
1906 * the new queue limits again when they dispatch those requests,
1907 * although such checkings are also done against the old queue limits
1908 * when submitting requests.
1910 int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1912 if (!rq_mergeable(rq))
1913 return 0;
1915 if (blk_rq_sectors(rq) > blk_queue_get_max_sectors(q, rq->cmd_flags)) {
1916 printk(KERN_ERR "%s: over max size limit.\n", __func__);
1917 return -EIO;
1921 * queue's settings related to segment counting like q->bounce_pfn
1922 * may differ from that of other stacking queues.
1923 * Recalculate it to check the request correctly on this queue's
1924 * limitation.
1926 blk_recalc_rq_segments(rq);
1927 if (rq->nr_phys_segments > queue_max_segments(q)) {
1928 printk(KERN_ERR "%s: over max segments limit.\n", __func__);
1929 return -EIO;
1932 return 0;
1934 EXPORT_SYMBOL_GPL(blk_rq_check_limits);
1937 * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1938 * @q: the queue to submit the request
1939 * @rq: the request being queued
1941 int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1943 unsigned long flags;
1944 int where = ELEVATOR_INSERT_BACK;
1946 if (blk_rq_check_limits(q, rq))
1947 return -EIO;
1949 if (rq->rq_disk &&
1950 should_fail_request(&rq->rq_disk->part0, blk_rq_bytes(rq)))
1951 return -EIO;
1953 spin_lock_irqsave(q->queue_lock, flags);
1954 if (unlikely(blk_queue_dying(q))) {
1955 spin_unlock_irqrestore(q->queue_lock, flags);
1956 return -ENODEV;
1960 * Submitting request must be dequeued before calling this function
1961 * because it will be linked to another request_queue
1963 BUG_ON(blk_queued_rq(rq));
1965 if (rq->cmd_flags & (REQ_FLUSH|REQ_FUA))
1966 where = ELEVATOR_INSERT_FLUSH;
1968 add_acct_request(q, rq, where);
1969 if (where == ELEVATOR_INSERT_FLUSH)
1970 __blk_run_queue(q);
1971 spin_unlock_irqrestore(q->queue_lock, flags);
1973 return 0;
1975 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
1978 * blk_rq_err_bytes - determine number of bytes till the next failure boundary
1979 * @rq: request to examine
1981 * Description:
1982 * A request could be merge of IOs which require different failure
1983 * handling. This function determines the number of bytes which
1984 * can be failed from the beginning of the request without
1985 * crossing into area which need to be retried further.
1987 * Return:
1988 * The number of bytes to fail.
1990 * Context:
1991 * queue_lock must be held.
1993 unsigned int blk_rq_err_bytes(const struct request *rq)
1995 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
1996 unsigned int bytes = 0;
1997 struct bio *bio;
1999 if (!(rq->cmd_flags & REQ_MIXED_MERGE))
2000 return blk_rq_bytes(rq);
2003 * Currently the only 'mixing' which can happen is between
2004 * different fastfail types. We can safely fail portions
2005 * which have all the failfast bits that the first one has -
2006 * the ones which are at least as eager to fail as the first
2007 * one.
2009 for (bio = rq->bio; bio; bio = bio->bi_next) {
2010 if ((bio->bi_rw & ff) != ff)
2011 break;
2012 bytes += bio->bi_size;
2015 /* this could lead to infinite loop */
2016 BUG_ON(blk_rq_bytes(rq) && !bytes);
2017 return bytes;
2019 EXPORT_SYMBOL_GPL(blk_rq_err_bytes);
2021 static void blk_account_io_completion(struct request *req, unsigned int bytes)
2023 if (blk_do_io_stat(req)) {
2024 const int rw = rq_data_dir(req);
2025 struct hd_struct *part;
2026 int cpu;
2028 cpu = part_stat_lock();
2029 part = req->part;
2030 part_stat_add(cpu, part, sectors[rw], bytes >> 9);
2031 part_stat_unlock();
2035 static void blk_account_io_done(struct request *req)
2038 * Account IO completion. flush_rq isn't accounted as a
2039 * normal IO on queueing nor completion. Accounting the
2040 * containing request is enough.
2042 if (blk_do_io_stat(req) && !(req->cmd_flags & REQ_FLUSH_SEQ)) {
2043 unsigned long duration = jiffies - req->start_time;
2044 const int rw = rq_data_dir(req);
2045 struct hd_struct *part;
2046 int cpu;
2048 cpu = part_stat_lock();
2049 part = req->part;
2051 part_stat_inc(cpu, part, ios[rw]);
2052 part_stat_add(cpu, part, ticks[rw], duration);
2053 part_round_stats(cpu, part);
2054 part_dec_in_flight(part, rw);
2056 hd_struct_put(part);
2057 part_stat_unlock();
2062 * blk_peek_request - peek at the top of a request queue
2063 * @q: request queue to peek at
2065 * Description:
2066 * Return the request at the top of @q. The returned request
2067 * should be started using blk_start_request() before LLD starts
2068 * processing it.
2070 * Return:
2071 * Pointer to the request at the top of @q if available. Null
2072 * otherwise.
2074 * Context:
2075 * queue_lock must be held.
2077 struct request *blk_peek_request(struct request_queue *q)
2079 struct request *rq;
2080 int ret;
2082 while ((rq = __elv_next_request(q)) != NULL) {
2083 if (!(rq->cmd_flags & REQ_STARTED)) {
2085 * This is the first time the device driver
2086 * sees this request (possibly after
2087 * requeueing). Notify IO scheduler.
2089 if (rq->cmd_flags & REQ_SORTED)
2090 elv_activate_rq(q, rq);
2093 * just mark as started even if we don't start
2094 * it, a request that has been delayed should
2095 * not be passed by new incoming requests
2097 rq->cmd_flags |= REQ_STARTED;
2098 trace_block_rq_issue(q, rq);
2101 if (!q->boundary_rq || q->boundary_rq == rq) {
2102 q->end_sector = rq_end_sector(rq);
2103 q->boundary_rq = NULL;
2106 if (rq->cmd_flags & REQ_DONTPREP)
2107 break;
2109 if (q->dma_drain_size && blk_rq_bytes(rq)) {
2111 * make sure space for the drain appears we
2112 * know we can do this because max_hw_segments
2113 * has been adjusted to be one fewer than the
2114 * device can handle
2116 rq->nr_phys_segments++;
2119 if (!q->prep_rq_fn)
2120 break;
2122 ret = q->prep_rq_fn(q, rq);
2123 if (ret == BLKPREP_OK) {
2124 break;
2125 } else if (ret == BLKPREP_DEFER) {
2127 * the request may have been (partially) prepped.
2128 * we need to keep this request in the front to
2129 * avoid resource deadlock. REQ_STARTED will
2130 * prevent other fs requests from passing this one.
2132 if (q->dma_drain_size && blk_rq_bytes(rq) &&
2133 !(rq->cmd_flags & REQ_DONTPREP)) {
2135 * remove the space for the drain we added
2136 * so that we don't add it again
2138 --rq->nr_phys_segments;
2141 rq = NULL;
2142 break;
2143 } else if (ret == BLKPREP_KILL) {
2144 rq->cmd_flags |= REQ_QUIET;
2146 * Mark this request as started so we don't trigger
2147 * any debug logic in the end I/O path.
2149 blk_start_request(rq);
2150 __blk_end_request_all(rq, -EIO);
2151 } else {
2152 printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
2153 break;
2157 return rq;
2159 EXPORT_SYMBOL(blk_peek_request);
2161 void blk_dequeue_request(struct request *rq)
2163 struct request_queue *q = rq->q;
2165 BUG_ON(list_empty(&rq->queuelist));
2166 BUG_ON(ELV_ON_HASH(rq));
2168 list_del_init(&rq->queuelist);
2171 * the time frame between a request being removed from the lists
2172 * and to it is freed is accounted as io that is in progress at
2173 * the driver side.
2175 if (blk_account_rq(rq)) {
2176 q->in_flight[rq_is_sync(rq)]++;
2177 set_io_start_time_ns(rq);
2182 * blk_start_request - start request processing on the driver
2183 * @req: request to dequeue
2185 * Description:
2186 * Dequeue @req and start timeout timer on it. This hands off the
2187 * request to the driver.
2189 * Block internal functions which don't want to start timer should
2190 * call blk_dequeue_request().
2192 * Context:
2193 * queue_lock must be held.
2195 void blk_start_request(struct request *req)
2197 blk_dequeue_request(req);
2200 * We are now handing the request to the hardware, initialize
2201 * resid_len to full count and add the timeout handler.
2203 req->resid_len = blk_rq_bytes(req);
2204 if (unlikely(blk_bidi_rq(req)))
2205 req->next_rq->resid_len = blk_rq_bytes(req->next_rq);
2207 blk_add_timer(req);
2209 EXPORT_SYMBOL(blk_start_request);
2212 * blk_fetch_request - fetch a request from a request queue
2213 * @q: request queue to fetch a request from
2215 * Description:
2216 * Return the request at the top of @q. The request is started on
2217 * return and LLD can start processing it immediately.
2219 * Return:
2220 * Pointer to the request at the top of @q if available. Null
2221 * otherwise.
2223 * Context:
2224 * queue_lock must be held.
2226 struct request *blk_fetch_request(struct request_queue *q)
2228 struct request *rq;
2230 rq = blk_peek_request(q);
2231 if (rq)
2232 blk_start_request(rq);
2233 return rq;
2235 EXPORT_SYMBOL(blk_fetch_request);
2238 * blk_update_request - Special helper function for request stacking drivers
2239 * @req: the request being processed
2240 * @error: %0 for success, < %0 for error
2241 * @nr_bytes: number of bytes to complete @req
2243 * Description:
2244 * Ends I/O on a number of bytes attached to @req, but doesn't complete
2245 * the request structure even if @req doesn't have leftover.
2246 * If @req has leftover, sets it up for the next range of segments.
2248 * This special helper function is only for request stacking drivers
2249 * (e.g. request-based dm) so that they can handle partial completion.
2250 * Actual device drivers should use blk_end_request instead.
2252 * Passing the result of blk_rq_bytes() as @nr_bytes guarantees
2253 * %false return from this function.
2255 * Return:
2256 * %false - this request doesn't have any more data
2257 * %true - this request has more data
2259 bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
2261 int total_bytes, bio_nbytes, next_idx = 0;
2262 struct bio *bio;
2264 if (!req->bio)
2265 return false;
2267 trace_block_rq_complete(req->q, req);
2270 * For fs requests, rq is just carrier of independent bio's
2271 * and each partial completion should be handled separately.
2272 * Reset per-request error on each partial completion.
2274 * TODO: tj: This is too subtle. It would be better to let
2275 * low level drivers do what they see fit.
2277 if (req->cmd_type == REQ_TYPE_FS)
2278 req->errors = 0;
2280 if (error && req->cmd_type == REQ_TYPE_FS &&
2281 !(req->cmd_flags & REQ_QUIET)) {
2282 char *error_type;
2284 switch (error) {
2285 case -ENOLINK:
2286 error_type = "recoverable transport";
2287 break;
2288 case -EREMOTEIO:
2289 error_type = "critical target";
2290 break;
2291 case -EBADE:
2292 error_type = "critical nexus";
2293 break;
2294 case -EIO:
2295 default:
2296 error_type = "I/O";
2297 break;
2299 printk_ratelimited(KERN_ERR "end_request: %s error, dev %s, sector %llu\n",
2300 error_type, req->rq_disk ?
2301 req->rq_disk->disk_name : "?",
2302 (unsigned long long)blk_rq_pos(req));
2306 blk_account_io_completion(req, nr_bytes);
2308 total_bytes = bio_nbytes = 0;
2309 while ((bio = req->bio) != NULL) {
2310 int nbytes;
2312 if (nr_bytes >= bio->bi_size) {
2313 req->bio = bio->bi_next;
2314 nbytes = bio->bi_size;
2315 req_bio_endio(req, bio, nbytes, error);
2316 next_idx = 0;
2317 bio_nbytes = 0;
2318 } else {
2319 int idx = bio->bi_idx + next_idx;
2321 if (unlikely(idx >= bio->bi_vcnt)) {
2322 blk_dump_rq_flags(req, "__end_that");
2323 printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
2324 __func__, idx, bio->bi_vcnt);
2325 break;
2328 nbytes = bio_iovec_idx(bio, idx)->bv_len;
2329 BIO_BUG_ON(nbytes > bio->bi_size);
2332 * not a complete bvec done
2334 if (unlikely(nbytes > nr_bytes)) {
2335 bio_nbytes += nr_bytes;
2336 total_bytes += nr_bytes;
2337 break;
2341 * advance to the next vector
2343 next_idx++;
2344 bio_nbytes += nbytes;
2347 total_bytes += nbytes;
2348 nr_bytes -= nbytes;
2350 bio = req->bio;
2351 if (bio) {
2353 * end more in this run, or just return 'not-done'
2355 if (unlikely(nr_bytes <= 0))
2356 break;
2361 * completely done
2363 if (!req->bio) {
2365 * Reset counters so that the request stacking driver
2366 * can find how many bytes remain in the request
2367 * later.
2369 req->__data_len = 0;
2370 return false;
2374 * if the request wasn't completed, update state
2376 if (bio_nbytes) {
2377 req_bio_endio(req, bio, bio_nbytes, error);
2378 bio->bi_idx += next_idx;
2379 bio_iovec(bio)->bv_offset += nr_bytes;
2380 bio_iovec(bio)->bv_len -= nr_bytes;
2383 req->__data_len -= total_bytes;
2384 req->buffer = bio_data(req->bio);
2386 /* update sector only for requests with clear definition of sector */
2387 if (req->cmd_type == REQ_TYPE_FS)
2388 req->__sector += total_bytes >> 9;
2390 /* mixed attributes always follow the first bio */
2391 if (req->cmd_flags & REQ_MIXED_MERGE) {
2392 req->cmd_flags &= ~REQ_FAILFAST_MASK;
2393 req->cmd_flags |= req->bio->bi_rw & REQ_FAILFAST_MASK;
2397 * If total number of sectors is less than the first segment
2398 * size, something has gone terribly wrong.
2400 if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
2401 blk_dump_rq_flags(req, "request botched");
2402 req->__data_len = blk_rq_cur_bytes(req);
2405 /* recalculate the number of segments */
2406 blk_recalc_rq_segments(req);
2408 return true;
2410 EXPORT_SYMBOL_GPL(blk_update_request);
2412 static bool blk_update_bidi_request(struct request *rq, int error,
2413 unsigned int nr_bytes,
2414 unsigned int bidi_bytes)
2416 if (blk_update_request(rq, error, nr_bytes))
2417 return true;
2419 /* Bidi request must be completed as a whole */
2420 if (unlikely(blk_bidi_rq(rq)) &&
2421 blk_update_request(rq->next_rq, error, bidi_bytes))
2422 return true;
2424 if (blk_queue_add_random(rq->q))
2425 add_disk_randomness(rq->rq_disk);
2427 return false;
2431 * blk_unprep_request - unprepare a request
2432 * @req: the request
2434 * This function makes a request ready for complete resubmission (or
2435 * completion). It happens only after all error handling is complete,
2436 * so represents the appropriate moment to deallocate any resources
2437 * that were allocated to the request in the prep_rq_fn. The queue
2438 * lock is held when calling this.
2440 void blk_unprep_request(struct request *req)
2442 struct request_queue *q = req->q;
2444 req->cmd_flags &= ~REQ_DONTPREP;
2445 if (q->unprep_rq_fn)
2446 q->unprep_rq_fn(q, req);
2448 EXPORT_SYMBOL_GPL(blk_unprep_request);
2451 * queue lock must be held
2453 static void blk_finish_request(struct request *req, int error)
2455 if (blk_rq_tagged(req))
2456 blk_queue_end_tag(req->q, req);
2458 BUG_ON(blk_queued_rq(req));
2460 if (unlikely(laptop_mode) && req->cmd_type == REQ_TYPE_FS)
2461 laptop_io_completion(&req->q->backing_dev_info);
2463 blk_delete_timer(req);
2465 if (req->cmd_flags & REQ_DONTPREP)
2466 blk_unprep_request(req);
2469 blk_account_io_done(req);
2471 if (req->end_io)
2472 req->end_io(req, error);
2473 else {
2474 if (blk_bidi_rq(req))
2475 __blk_put_request(req->next_rq->q, req->next_rq);
2477 __blk_put_request(req->q, req);
2482 * blk_end_bidi_request - Complete a bidi request
2483 * @rq: the request to complete
2484 * @error: %0 for success, < %0 for error
2485 * @nr_bytes: number of bytes to complete @rq
2486 * @bidi_bytes: number of bytes to complete @rq->next_rq
2488 * Description:
2489 * Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2490 * Drivers that supports bidi can safely call this member for any
2491 * type of request, bidi or uni. In the later case @bidi_bytes is
2492 * just ignored.
2494 * Return:
2495 * %false - we are done with this request
2496 * %true - still buffers pending for this request
2498 static bool blk_end_bidi_request(struct request *rq, int error,
2499 unsigned int nr_bytes, unsigned int bidi_bytes)
2501 struct request_queue *q = rq->q;
2502 unsigned long flags;
2504 if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2505 return true;
2507 spin_lock_irqsave(q->queue_lock, flags);
2508 blk_finish_request(rq, error);
2509 spin_unlock_irqrestore(q->queue_lock, flags);
2511 return false;
2515 * __blk_end_bidi_request - Complete a bidi request with queue lock held
2516 * @rq: the request to complete
2517 * @error: %0 for success, < %0 for error
2518 * @nr_bytes: number of bytes to complete @rq
2519 * @bidi_bytes: number of bytes to complete @rq->next_rq
2521 * Description:
2522 * Identical to blk_end_bidi_request() except that queue lock is
2523 * assumed to be locked on entry and remains so on return.
2525 * Return:
2526 * %false - we are done with this request
2527 * %true - still buffers pending for this request
2529 bool __blk_end_bidi_request(struct request *rq, int error,
2530 unsigned int nr_bytes, unsigned int bidi_bytes)
2532 if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2533 return true;
2535 blk_finish_request(rq, error);
2537 return false;
2541 * blk_end_request - Helper function for drivers to complete the request.
2542 * @rq: the request being processed
2543 * @error: %0 for success, < %0 for error
2544 * @nr_bytes: number of bytes to complete
2546 * Description:
2547 * Ends I/O on a number of bytes attached to @rq.
2548 * If @rq has leftover, sets it up for the next range of segments.
2550 * Return:
2551 * %false - we are done with this request
2552 * %true - still buffers pending for this request
2554 bool blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2556 return blk_end_bidi_request(rq, error, nr_bytes, 0);
2558 EXPORT_SYMBOL(blk_end_request);
2561 * blk_end_request_all - Helper function for drives to finish the request.
2562 * @rq: the request to finish
2563 * @error: %0 for success, < %0 for error
2565 * Description:
2566 * Completely finish @rq.
2568 void blk_end_request_all(struct request *rq, int error)
2570 bool pending;
2571 unsigned int bidi_bytes = 0;
2573 if (unlikely(blk_bidi_rq(rq)))
2574 bidi_bytes = blk_rq_bytes(rq->next_rq);
2576 pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2577 BUG_ON(pending);
2579 EXPORT_SYMBOL(blk_end_request_all);
2582 * blk_end_request_cur - Helper function to finish the current request chunk.
2583 * @rq: the request to finish the current chunk for
2584 * @error: %0 for success, < %0 for error
2586 * Description:
2587 * Complete the current consecutively mapped chunk from @rq.
2589 * Return:
2590 * %false - we are done with this request
2591 * %true - still buffers pending for this request
2593 bool blk_end_request_cur(struct request *rq, int error)
2595 return blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2597 EXPORT_SYMBOL(blk_end_request_cur);
2600 * blk_end_request_err - Finish a request till the next failure boundary.
2601 * @rq: the request to finish till the next failure boundary for
2602 * @error: must be negative errno
2604 * Description:
2605 * Complete @rq till the next failure boundary.
2607 * Return:
2608 * %false - we are done with this request
2609 * %true - still buffers pending for this request
2611 bool blk_end_request_err(struct request *rq, int error)
2613 WARN_ON(error >= 0);
2614 return blk_end_request(rq, error, blk_rq_err_bytes(rq));
2616 EXPORT_SYMBOL_GPL(blk_end_request_err);
2619 * __blk_end_request - Helper function for drivers to complete the request.
2620 * @rq: the request being processed
2621 * @error: %0 for success, < %0 for error
2622 * @nr_bytes: number of bytes to complete
2624 * Description:
2625 * Must be called with queue lock held unlike blk_end_request().
2627 * Return:
2628 * %false - we are done with this request
2629 * %true - still buffers pending for this request
2631 bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2633 return __blk_end_bidi_request(rq, error, nr_bytes, 0);
2635 EXPORT_SYMBOL(__blk_end_request);
2638 * __blk_end_request_all - Helper function for drives to finish the request.
2639 * @rq: the request to finish
2640 * @error: %0 for success, < %0 for error
2642 * Description:
2643 * Completely finish @rq. Must be called with queue lock held.
2645 void __blk_end_request_all(struct request *rq, int error)
2647 bool pending;
2648 unsigned int bidi_bytes = 0;
2650 if (unlikely(blk_bidi_rq(rq)))
2651 bidi_bytes = blk_rq_bytes(rq->next_rq);
2653 pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2654 BUG_ON(pending);
2656 EXPORT_SYMBOL(__blk_end_request_all);
2659 * __blk_end_request_cur - Helper function to finish the current request chunk.
2660 * @rq: the request to finish the current chunk for
2661 * @error: %0 for success, < %0 for error
2663 * Description:
2664 * Complete the current consecutively mapped chunk from @rq. Must
2665 * be called with queue lock held.
2667 * Return:
2668 * %false - we are done with this request
2669 * %true - still buffers pending for this request
2671 bool __blk_end_request_cur(struct request *rq, int error)
2673 return __blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2675 EXPORT_SYMBOL(__blk_end_request_cur);
2678 * __blk_end_request_err - Finish a request till the next failure boundary.
2679 * @rq: the request to finish till the next failure boundary for
2680 * @error: must be negative errno
2682 * Description:
2683 * Complete @rq till the next failure boundary. Must be called
2684 * with queue lock held.
2686 * Return:
2687 * %false - we are done with this request
2688 * %true - still buffers pending for this request
2690 bool __blk_end_request_err(struct request *rq, int error)
2692 WARN_ON(error >= 0);
2693 return __blk_end_request(rq, error, blk_rq_err_bytes(rq));
2695 EXPORT_SYMBOL_GPL(__blk_end_request_err);
2697 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2698 struct bio *bio)
2700 /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */
2701 rq->cmd_flags |= bio->bi_rw & REQ_WRITE;
2703 if (bio_has_data(bio)) {
2704 rq->nr_phys_segments = bio_phys_segments(q, bio);
2705 rq->buffer = bio_data(bio);
2707 rq->__data_len = bio->bi_size;
2708 rq->bio = rq->biotail = bio;
2710 if (bio->bi_bdev)
2711 rq->rq_disk = bio->bi_bdev->bd_disk;
2714 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
2716 * rq_flush_dcache_pages - Helper function to flush all pages in a request
2717 * @rq: the request to be flushed
2719 * Description:
2720 * Flush all pages in @rq.
2722 void rq_flush_dcache_pages(struct request *rq)
2724 struct req_iterator iter;
2725 struct bio_vec *bvec;
2727 rq_for_each_segment(bvec, rq, iter)
2728 flush_dcache_page(bvec->bv_page);
2730 EXPORT_SYMBOL_GPL(rq_flush_dcache_pages);
2731 #endif
2734 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2735 * @q : the queue of the device being checked
2737 * Description:
2738 * Check if underlying low-level drivers of a device are busy.
2739 * If the drivers want to export their busy state, they must set own
2740 * exporting function using blk_queue_lld_busy() first.
2742 * Basically, this function is used only by request stacking drivers
2743 * to stop dispatching requests to underlying devices when underlying
2744 * devices are busy. This behavior helps more I/O merging on the queue
2745 * of the request stacking driver and prevents I/O throughput regression
2746 * on burst I/O load.
2748 * Return:
2749 * 0 - Not busy (The request stacking driver should dispatch request)
2750 * 1 - Busy (The request stacking driver should stop dispatching request)
2752 int blk_lld_busy(struct request_queue *q)
2754 if (q->lld_busy_fn)
2755 return q->lld_busy_fn(q);
2757 return 0;
2759 EXPORT_SYMBOL_GPL(blk_lld_busy);
2762 * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
2763 * @rq: the clone request to be cleaned up
2765 * Description:
2766 * Free all bios in @rq for a cloned request.
2768 void blk_rq_unprep_clone(struct request *rq)
2770 struct bio *bio;
2772 while ((bio = rq->bio) != NULL) {
2773 rq->bio = bio->bi_next;
2775 bio_put(bio);
2778 EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
2781 * Copy attributes of the original request to the clone request.
2782 * The actual data parts (e.g. ->cmd, ->buffer, ->sense) are not copied.
2784 static void __blk_rq_prep_clone(struct request *dst, struct request *src)
2786 dst->cpu = src->cpu;
2787 dst->cmd_flags = (src->cmd_flags & REQ_CLONE_MASK) | REQ_NOMERGE;
2788 dst->cmd_type = src->cmd_type;
2789 dst->__sector = blk_rq_pos(src);
2790 dst->__data_len = blk_rq_bytes(src);
2791 dst->nr_phys_segments = src->nr_phys_segments;
2792 dst->ioprio = src->ioprio;
2793 dst->extra_len = src->extra_len;
2797 * blk_rq_prep_clone - Helper function to setup clone request
2798 * @rq: the request to be setup
2799 * @rq_src: original request to be cloned
2800 * @bs: bio_set that bios for clone are allocated from
2801 * @gfp_mask: memory allocation mask for bio
2802 * @bio_ctr: setup function to be called for each clone bio.
2803 * Returns %0 for success, non %0 for failure.
2804 * @data: private data to be passed to @bio_ctr
2806 * Description:
2807 * Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
2808 * The actual data parts of @rq_src (e.g. ->cmd, ->buffer, ->sense)
2809 * are not copied, and copying such parts is the caller's responsibility.
2810 * Also, pages which the original bios are pointing to are not copied
2811 * and the cloned bios just point same pages.
2812 * So cloned bios must be completed before original bios, which means
2813 * the caller must complete @rq before @rq_src.
2815 int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
2816 struct bio_set *bs, gfp_t gfp_mask,
2817 int (*bio_ctr)(struct bio *, struct bio *, void *),
2818 void *data)
2820 struct bio *bio, *bio_src;
2822 if (!bs)
2823 bs = fs_bio_set;
2825 blk_rq_init(NULL, rq);
2827 __rq_for_each_bio(bio_src, rq_src) {
2828 bio = bio_clone_bioset(bio_src, gfp_mask, bs);
2829 if (!bio)
2830 goto free_and_out;
2832 if (bio_ctr && bio_ctr(bio, bio_src, data))
2833 goto free_and_out;
2835 if (rq->bio) {
2836 rq->biotail->bi_next = bio;
2837 rq->biotail = bio;
2838 } else
2839 rq->bio = rq->biotail = bio;
2842 __blk_rq_prep_clone(rq, rq_src);
2844 return 0;
2846 free_and_out:
2847 if (bio)
2848 bio_put(bio);
2849 blk_rq_unprep_clone(rq);
2851 return -ENOMEM;
2853 EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
2855 int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
2857 return queue_work(kblockd_workqueue, work);
2859 EXPORT_SYMBOL(kblockd_schedule_work);
2861 int kblockd_schedule_delayed_work(struct request_queue *q,
2862 struct delayed_work *dwork, unsigned long delay)
2864 return queue_delayed_work(kblockd_workqueue, dwork, delay);
2866 EXPORT_SYMBOL(kblockd_schedule_delayed_work);
2868 #define PLUG_MAGIC 0x91827364
2871 * blk_start_plug - initialize blk_plug and track it inside the task_struct
2872 * @plug: The &struct blk_plug that needs to be initialized
2874 * Description:
2875 * Tracking blk_plug inside the task_struct will help with auto-flushing the
2876 * pending I/O should the task end up blocking between blk_start_plug() and
2877 * blk_finish_plug(). This is important from a performance perspective, but
2878 * also ensures that we don't deadlock. For instance, if the task is blocking
2879 * for a memory allocation, memory reclaim could end up wanting to free a
2880 * page belonging to that request that is currently residing in our private
2881 * plug. By flushing the pending I/O when the process goes to sleep, we avoid
2882 * this kind of deadlock.
2884 void blk_start_plug(struct blk_plug *plug)
2886 struct task_struct *tsk = current;
2888 plug->magic = PLUG_MAGIC;
2889 INIT_LIST_HEAD(&plug->list);
2890 INIT_LIST_HEAD(&plug->cb_list);
2891 plug->should_sort = 0;
2894 * If this is a nested plug, don't actually assign it. It will be
2895 * flushed on its own.
2897 if (!tsk->plug) {
2899 * Store ordering should not be needed here, since a potential
2900 * preempt will imply a full memory barrier
2902 tsk->plug = plug;
2905 EXPORT_SYMBOL(blk_start_plug);
2907 static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
2909 struct request *rqa = container_of(a, struct request, queuelist);
2910 struct request *rqb = container_of(b, struct request, queuelist);
2912 return !(rqa->q < rqb->q ||
2913 (rqa->q == rqb->q && blk_rq_pos(rqa) < blk_rq_pos(rqb)));
2917 * If 'from_schedule' is true, then postpone the dispatch of requests
2918 * until a safe kblockd context. We due this to avoid accidental big
2919 * additional stack usage in driver dispatch, in places where the originally
2920 * plugger did not intend it.
2922 static void queue_unplugged(struct request_queue *q, unsigned int depth,
2923 bool from_schedule)
2924 __releases(q->queue_lock)
2926 trace_block_unplug(q, depth, !from_schedule);
2928 if (from_schedule)
2929 blk_run_queue_async(q);
2930 else
2931 __blk_run_queue(q);
2932 spin_unlock(q->queue_lock);
2935 static void flush_plug_callbacks(struct blk_plug *plug, bool from_schedule)
2937 LIST_HEAD(callbacks);
2939 while (!list_empty(&plug->cb_list)) {
2940 list_splice_init(&plug->cb_list, &callbacks);
2942 while (!list_empty(&callbacks)) {
2943 struct blk_plug_cb *cb = list_first_entry(&callbacks,
2944 struct blk_plug_cb,
2945 list);
2946 list_del(&cb->list);
2947 cb->callback(cb, from_schedule);
2952 struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug, void *data,
2953 int size)
2955 struct blk_plug *plug = current->plug;
2956 struct blk_plug_cb *cb;
2958 if (!plug)
2959 return NULL;
2961 list_for_each_entry(cb, &plug->cb_list, list)
2962 if (cb->callback == unplug && cb->data == data)
2963 return cb;
2965 /* Not currently on the callback list */
2966 BUG_ON(size < sizeof(*cb));
2967 cb = kzalloc(size, GFP_ATOMIC);
2968 if (cb) {
2969 cb->data = data;
2970 cb->callback = unplug;
2971 list_add(&cb->list, &plug->cb_list);
2973 return cb;
2975 EXPORT_SYMBOL(blk_check_plugged);
2977 void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
2979 struct request_queue *q;
2980 unsigned long flags;
2981 struct request *rq;
2982 LIST_HEAD(list);
2983 unsigned int depth;
2985 BUG_ON(plug->magic != PLUG_MAGIC);
2987 flush_plug_callbacks(plug, from_schedule);
2988 if (list_empty(&plug->list))
2989 return;
2991 list_splice_init(&plug->list, &list);
2993 if (plug->should_sort) {
2994 list_sort(NULL, &list, plug_rq_cmp);
2995 plug->should_sort = 0;
2998 q = NULL;
2999 depth = 0;
3002 * Save and disable interrupts here, to avoid doing it for every
3003 * queue lock we have to take.
3005 local_irq_save(flags);
3006 while (!list_empty(&list)) {
3007 rq = list_entry_rq(list.next);
3008 list_del_init(&rq->queuelist);
3009 BUG_ON(!rq->q);
3010 if (rq->q != q) {
3012 * This drops the queue lock
3014 if (q)
3015 queue_unplugged(q, depth, from_schedule);
3016 q = rq->q;
3017 depth = 0;
3018 spin_lock(q->queue_lock);
3022 * Short-circuit if @q is dead
3024 if (unlikely(blk_queue_dying(q))) {
3025 __blk_end_request_all(rq, -ENODEV);
3026 continue;
3030 * rq is already accounted, so use raw insert
3032 if (rq->cmd_flags & (REQ_FLUSH | REQ_FUA))
3033 __elv_add_request(q, rq, ELEVATOR_INSERT_FLUSH);
3034 else
3035 __elv_add_request(q, rq, ELEVATOR_INSERT_SORT_MERGE);
3037 depth++;
3041 * This drops the queue lock
3043 if (q)
3044 queue_unplugged(q, depth, from_schedule);
3046 local_irq_restore(flags);
3049 void blk_finish_plug(struct blk_plug *plug)
3051 blk_flush_plug_list(plug, false);
3053 if (plug == current->plug)
3054 current->plug = NULL;
3056 EXPORT_SYMBOL(blk_finish_plug);
3058 int __init blk_dev_init(void)
3060 BUILD_BUG_ON(__REQ_NR_BITS > 8 *
3061 sizeof(((struct request *)0)->cmd_flags));
3063 /* used for unplugging and affects IO latency/throughput - HIGHPRI */
3064 kblockd_workqueue = alloc_workqueue("kblockd",
3065 WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
3066 if (!kblockd_workqueue)
3067 panic("Failed to create kblockd\n");
3069 request_cachep = kmem_cache_create("blkdev_requests",
3070 sizeof(struct request), 0, SLAB_PANIC, NULL);
3072 blk_requestq_cachep = kmem_cache_create("blkdev_queue",
3073 sizeof(struct request_queue), 0, SLAB_PANIC, NULL);
3075 return 0;