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>
8 * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001
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>
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>
34 static int __make_request(struct request_queue *q, struct bio *bio);
37 * For the allocated request tables
39 static struct kmem_cache *request_cachep;
42 * For queue allocation
44 struct kmem_cache *blk_requestq_cachep;
47 * Controlling structure to kblockd
49 static struct workqueue_struct *kblockd_workqueue;
51 static void drive_stat_acct(struct request *rq, int new_io)
53 struct hd_struct *part;
54 int rw = rq_data_dir(rq);
57 if (!blk_fs_request(rq) || !rq->rq_disk)
60 cpu = part_stat_lock();
61 part = disk_map_sector_rcu(rq->rq_disk, rq->sector);
64 part_stat_inc(cpu, part, merges[rw]);
66 part_round_stats(cpu, part);
67 part_inc_in_flight(part);
73 void blk_queue_congestion_threshold(struct request_queue *q)
77 nr = q->nr_requests - (q->nr_requests / 8) + 1;
78 if (nr > q->nr_requests)
80 q->nr_congestion_on = nr;
82 nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
85 q->nr_congestion_off = nr;
89 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
92 * Locates the passed device's request queue and returns the address of its
95 * Will return NULL if the request queue cannot be located.
97 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
99 struct backing_dev_info *ret = NULL;
100 struct request_queue *q = bdev_get_queue(bdev);
103 ret = &q->backing_dev_info;
106 EXPORT_SYMBOL(blk_get_backing_dev_info);
108 void blk_rq_init(struct request_queue *q, struct request *rq)
110 memset(rq, 0, sizeof(*rq));
112 INIT_LIST_HEAD(&rq->queuelist);
113 INIT_LIST_HEAD(&rq->timeout_list);
116 rq->sector = rq->hard_sector = (sector_t) -1;
117 INIT_HLIST_NODE(&rq->hash);
118 RB_CLEAR_NODE(&rq->rb_node);
123 EXPORT_SYMBOL(blk_rq_init);
125 static void req_bio_endio(struct request *rq, struct bio *bio,
126 unsigned int nbytes, int error)
128 struct request_queue *q = rq->q;
130 if (&q->bar_rq != rq) {
132 clear_bit(BIO_UPTODATE, &bio->bi_flags);
133 else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
136 if (unlikely(nbytes > bio->bi_size)) {
137 printk(KERN_ERR "%s: want %u bytes done, %u left\n",
138 __func__, nbytes, bio->bi_size);
139 nbytes = bio->bi_size;
142 bio->bi_size -= nbytes;
143 bio->bi_sector += (nbytes >> 9);
145 if (bio_integrity(bio))
146 bio_integrity_advance(bio, nbytes);
148 if (bio->bi_size == 0)
149 bio_endio(bio, error);
153 * Okay, this is the barrier request in progress, just
156 if (error && !q->orderr)
161 void blk_dump_rq_flags(struct request *rq, char *msg)
165 printk(KERN_INFO "%s: dev %s: type=%x, flags=%x\n", msg,
166 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type,
169 printk(KERN_INFO " sector %llu, nr/cnr %lu/%u\n",
170 (unsigned long long)rq->sector,
172 rq->current_nr_sectors);
173 printk(KERN_INFO " bio %p, biotail %p, buffer %p, data %p, len %u\n",
174 rq->bio, rq->biotail,
175 rq->buffer, rq->data,
178 if (blk_pc_request(rq)) {
179 printk(KERN_INFO " cdb: ");
180 for (bit = 0; bit < BLK_MAX_CDB; bit++)
181 printk("%02x ", rq->cmd[bit]);
185 EXPORT_SYMBOL(blk_dump_rq_flags);
188 * "plug" the device if there are no outstanding requests: this will
189 * force the transfer to start only after we have put all the requests
192 * This is called with interrupts off and no requests on the queue and
193 * with the queue lock held.
195 void blk_plug_device(struct request_queue *q)
197 WARN_ON(!irqs_disabled());
200 * don't plug a stopped queue, it must be paired with blk_start_queue()
201 * which will restart the queueing
203 if (blk_queue_stopped(q))
206 if (!queue_flag_test_and_set(QUEUE_FLAG_PLUGGED, q)) {
207 mod_timer(&q->unplug_timer, jiffies + q->unplug_delay);
208 blk_add_trace_generic(q, NULL, 0, BLK_TA_PLUG);
211 EXPORT_SYMBOL(blk_plug_device);
214 * blk_plug_device_unlocked - plug a device without queue lock held
215 * @q: The &struct request_queue to plug
218 * Like @blk_plug_device(), but grabs the queue lock and disables
221 void blk_plug_device_unlocked(struct request_queue *q)
225 spin_lock_irqsave(q->queue_lock, flags);
227 spin_unlock_irqrestore(q->queue_lock, flags);
229 EXPORT_SYMBOL(blk_plug_device_unlocked);
232 * remove the queue from the plugged list, if present. called with
233 * queue lock held and interrupts disabled.
235 int blk_remove_plug(struct request_queue *q)
237 WARN_ON(!irqs_disabled());
239 if (!queue_flag_test_and_clear(QUEUE_FLAG_PLUGGED, q))
242 del_timer(&q->unplug_timer);
245 EXPORT_SYMBOL(blk_remove_plug);
248 * remove the plug and let it rip..
250 void __generic_unplug_device(struct request_queue *q)
252 if (unlikely(blk_queue_stopped(q)))
255 if (!blk_remove_plug(q))
260 EXPORT_SYMBOL(__generic_unplug_device);
263 * generic_unplug_device - fire a request queue
264 * @q: The &struct request_queue in question
267 * Linux uses plugging to build bigger requests queues before letting
268 * the device have at them. If a queue is plugged, the I/O scheduler
269 * is still adding and merging requests on the queue. Once the queue
270 * gets unplugged, the request_fn defined for the queue is invoked and
273 void generic_unplug_device(struct request_queue *q)
275 if (blk_queue_plugged(q)) {
276 spin_lock_irq(q->queue_lock);
277 __generic_unplug_device(q);
278 spin_unlock_irq(q->queue_lock);
281 EXPORT_SYMBOL(generic_unplug_device);
283 static void blk_backing_dev_unplug(struct backing_dev_info *bdi,
286 struct request_queue *q = bdi->unplug_io_data;
291 void blk_unplug_work(struct work_struct *work)
293 struct request_queue *q =
294 container_of(work, struct request_queue, unplug_work);
296 blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_IO, NULL,
297 q->rq.count[READ] + q->rq.count[WRITE]);
302 void blk_unplug_timeout(unsigned long data)
304 struct request_queue *q = (struct request_queue *)data;
306 blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_TIMER, NULL,
307 q->rq.count[READ] + q->rq.count[WRITE]);
309 kblockd_schedule_work(q, &q->unplug_work);
312 void blk_unplug(struct request_queue *q)
315 * devices don't necessarily have an ->unplug_fn defined
318 blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_IO, NULL,
319 q->rq.count[READ] + q->rq.count[WRITE]);
324 EXPORT_SYMBOL(blk_unplug);
326 static void blk_invoke_request_fn(struct request_queue *q)
328 if (unlikely(blk_queue_stopped(q)))
332 * one level of recursion is ok and is much faster than kicking
333 * the unplug handling
335 if (!queue_flag_test_and_set(QUEUE_FLAG_REENTER, q)) {
337 queue_flag_clear(QUEUE_FLAG_REENTER, q);
339 queue_flag_set(QUEUE_FLAG_PLUGGED, q);
340 kblockd_schedule_work(q, &q->unplug_work);
345 * blk_start_queue - restart a previously stopped queue
346 * @q: The &struct request_queue in question
349 * blk_start_queue() will clear the stop flag on the queue, and call
350 * the request_fn for the queue if it was in a stopped state when
351 * entered. Also see blk_stop_queue(). Queue lock must be held.
353 void blk_start_queue(struct request_queue *q)
355 WARN_ON(!irqs_disabled());
357 queue_flag_clear(QUEUE_FLAG_STOPPED, q);
358 blk_invoke_request_fn(q);
360 EXPORT_SYMBOL(blk_start_queue);
363 * blk_stop_queue - stop a queue
364 * @q: The &struct request_queue in question
367 * The Linux block layer assumes that a block driver will consume all
368 * entries on the request queue when the request_fn strategy is called.
369 * Often this will not happen, because of hardware limitations (queue
370 * depth settings). If a device driver gets a 'queue full' response,
371 * or if it simply chooses not to queue more I/O at one point, it can
372 * call this function to prevent the request_fn from being called until
373 * the driver has signalled it's ready to go again. This happens by calling
374 * blk_start_queue() to restart queue operations. Queue lock must be held.
376 void blk_stop_queue(struct request_queue *q)
379 queue_flag_set(QUEUE_FLAG_STOPPED, q);
381 EXPORT_SYMBOL(blk_stop_queue);
384 * blk_sync_queue - cancel any pending callbacks on a queue
388 * The block layer may perform asynchronous callback activity
389 * on a queue, such as calling the unplug function after a timeout.
390 * A block device may call blk_sync_queue to ensure that any
391 * such activity is cancelled, thus allowing it to release resources
392 * that the callbacks might use. The caller must already have made sure
393 * that its ->make_request_fn will not re-add plugging prior to calling
397 void blk_sync_queue(struct request_queue *q)
399 del_timer_sync(&q->unplug_timer);
400 kblockd_flush_work(&q->unplug_work);
402 EXPORT_SYMBOL(blk_sync_queue);
405 * __blk_run_queue - run a single device queue
406 * @q: The queue to run
409 * See @blk_run_queue. This variant must be called with the queue lock
410 * held and interrupts disabled.
413 void __blk_run_queue(struct request_queue *q)
418 * Only recurse once to avoid overrunning the stack, let the unplug
419 * handling reinvoke the handler shortly if we already got there.
421 if (!elv_queue_empty(q))
422 blk_invoke_request_fn(q);
424 EXPORT_SYMBOL(__blk_run_queue);
427 * blk_run_queue - run a single device queue
428 * @q: The queue to run
431 * Invoke request handling on this queue, if it has pending work to do.
432 * May be used to restart queueing when a request has completed. Also
433 * See @blk_start_queueing.
436 void blk_run_queue(struct request_queue *q)
440 spin_lock_irqsave(q->queue_lock, flags);
442 spin_unlock_irqrestore(q->queue_lock, flags);
444 EXPORT_SYMBOL(blk_run_queue);
446 void blk_put_queue(struct request_queue *q)
448 kobject_put(&q->kobj);
451 void blk_cleanup_queue(struct request_queue *q)
454 * We know we have process context here, so we can be a little
455 * cautious and ensure that pending block actions on this device
456 * are done before moving on. Going into this function, we should
457 * not have processes doing IO to this device.
461 mutex_lock(&q->sysfs_lock);
462 queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
463 mutex_unlock(&q->sysfs_lock);
466 elevator_exit(q->elevator);
470 EXPORT_SYMBOL(blk_cleanup_queue);
472 static int blk_init_free_list(struct request_queue *q)
474 struct request_list *rl = &q->rq;
476 rl->count[READ] = rl->count[WRITE] = 0;
477 rl->starved[READ] = rl->starved[WRITE] = 0;
479 init_waitqueue_head(&rl->wait[READ]);
480 init_waitqueue_head(&rl->wait[WRITE]);
482 rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
483 mempool_free_slab, request_cachep, q->node);
491 struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
493 return blk_alloc_queue_node(gfp_mask, -1);
495 EXPORT_SYMBOL(blk_alloc_queue);
497 struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
499 struct request_queue *q;
502 q = kmem_cache_alloc_node(blk_requestq_cachep,
503 gfp_mask | __GFP_ZERO, node_id);
507 q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug;
508 q->backing_dev_info.unplug_io_data = q;
509 err = bdi_init(&q->backing_dev_info);
511 kmem_cache_free(blk_requestq_cachep, q);
515 init_timer(&q->unplug_timer);
516 setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
517 INIT_LIST_HEAD(&q->timeout_list);
519 kobject_init(&q->kobj, &blk_queue_ktype);
521 mutex_init(&q->sysfs_lock);
522 spin_lock_init(&q->__queue_lock);
526 EXPORT_SYMBOL(blk_alloc_queue_node);
529 * blk_init_queue - prepare a request queue for use with a block device
530 * @rfn: The function to be called to process requests that have been
531 * placed on the queue.
532 * @lock: Request queue spin lock
535 * If a block device wishes to use the standard request handling procedures,
536 * which sorts requests and coalesces adjacent requests, then it must
537 * call blk_init_queue(). The function @rfn will be called when there
538 * are requests on the queue that need to be processed. If the device
539 * supports plugging, then @rfn may not be called immediately when requests
540 * are available on the queue, but may be called at some time later instead.
541 * Plugged queues are generally unplugged when a buffer belonging to one
542 * of the requests on the queue is needed, or due to memory pressure.
544 * @rfn is not required, or even expected, to remove all requests off the
545 * queue, but only as many as it can handle at a time. If it does leave
546 * requests on the queue, it is responsible for arranging that the requests
547 * get dealt with eventually.
549 * The queue spin lock must be held while manipulating the requests on the
550 * request queue; this lock will be taken also from interrupt context, so irq
551 * disabling is needed for it.
553 * Function returns a pointer to the initialized request queue, or %NULL if
557 * blk_init_queue() must be paired with a blk_cleanup_queue() call
558 * when the block device is deactivated (such as at module unload).
561 struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
563 return blk_init_queue_node(rfn, lock, -1);
565 EXPORT_SYMBOL(blk_init_queue);
567 struct request_queue *
568 blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
570 struct request_queue *q = blk_alloc_queue_node(GFP_KERNEL, node_id);
576 if (blk_init_free_list(q)) {
577 kmem_cache_free(blk_requestq_cachep, q);
582 * if caller didn't supply a lock, they get per-queue locking with
586 lock = &q->__queue_lock;
589 q->prep_rq_fn = NULL;
590 q->unplug_fn = generic_unplug_device;
591 q->queue_flags = (1 << QUEUE_FLAG_CLUSTER |
592 1 << QUEUE_FLAG_STACKABLE);
593 q->queue_lock = lock;
595 blk_queue_segment_boundary(q, 0xffffffff);
597 blk_queue_make_request(q, __make_request);
598 blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE);
600 blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
601 blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
603 q->sg_reserved_size = INT_MAX;
605 blk_set_cmd_filter_defaults(&q->cmd_filter);
610 if (!elevator_init(q, NULL)) {
611 blk_queue_congestion_threshold(q);
618 EXPORT_SYMBOL(blk_init_queue_node);
620 int blk_get_queue(struct request_queue *q)
622 if (likely(!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
623 kobject_get(&q->kobj);
630 static inline void blk_free_request(struct request_queue *q, struct request *rq)
632 if (rq->cmd_flags & REQ_ELVPRIV)
633 elv_put_request(q, rq);
634 mempool_free(rq, q->rq.rq_pool);
637 static struct request *
638 blk_alloc_request(struct request_queue *q, int rw, int priv, gfp_t gfp_mask)
640 struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
647 rq->cmd_flags = rw | REQ_ALLOCED;
650 if (unlikely(elv_set_request(q, rq, gfp_mask))) {
651 mempool_free(rq, q->rq.rq_pool);
654 rq->cmd_flags |= REQ_ELVPRIV;
661 * ioc_batching returns true if the ioc is a valid batching request and
662 * should be given priority access to a request.
664 static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
670 * Make sure the process is able to allocate at least 1 request
671 * even if the batch times out, otherwise we could theoretically
674 return ioc->nr_batch_requests == q->nr_batching ||
675 (ioc->nr_batch_requests > 0
676 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
680 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
681 * will cause the process to be a "batcher" on all queues in the system. This
682 * is the behaviour we want though - once it gets a wakeup it should be given
685 static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
687 if (!ioc || ioc_batching(q, ioc))
690 ioc->nr_batch_requests = q->nr_batching;
691 ioc->last_waited = jiffies;
694 static void __freed_request(struct request_queue *q, int rw)
696 struct request_list *rl = &q->rq;
698 if (rl->count[rw] < queue_congestion_off_threshold(q))
699 blk_clear_queue_congested(q, rw);
701 if (rl->count[rw] + 1 <= q->nr_requests) {
702 if (waitqueue_active(&rl->wait[rw]))
703 wake_up(&rl->wait[rw]);
705 blk_clear_queue_full(q, rw);
710 * A request has just been released. Account for it, update the full and
711 * congestion status, wake up any waiters. Called under q->queue_lock.
713 static void freed_request(struct request_queue *q, int rw, int priv)
715 struct request_list *rl = &q->rq;
721 __freed_request(q, rw);
723 if (unlikely(rl->starved[rw ^ 1]))
724 __freed_request(q, rw ^ 1);
727 #define blkdev_free_rq(list) list_entry((list)->next, struct request, queuelist)
729 * Get a free request, queue_lock must be held.
730 * Returns NULL on failure, with queue_lock held.
731 * Returns !NULL on success, with queue_lock *not held*.
733 static struct request *get_request(struct request_queue *q, int rw_flags,
734 struct bio *bio, gfp_t gfp_mask)
736 struct request *rq = NULL;
737 struct request_list *rl = &q->rq;
738 struct io_context *ioc = NULL;
739 const int rw = rw_flags & 0x01;
742 may_queue = elv_may_queue(q, rw_flags);
743 if (may_queue == ELV_MQUEUE_NO)
746 if (rl->count[rw]+1 >= queue_congestion_on_threshold(q)) {
747 if (rl->count[rw]+1 >= q->nr_requests) {
748 ioc = current_io_context(GFP_ATOMIC, q->node);
750 * The queue will fill after this allocation, so set
751 * it as full, and mark this process as "batching".
752 * This process will be allowed to complete a batch of
753 * requests, others will be blocked.
755 if (!blk_queue_full(q, rw)) {
756 ioc_set_batching(q, ioc);
757 blk_set_queue_full(q, rw);
759 if (may_queue != ELV_MQUEUE_MUST
760 && !ioc_batching(q, ioc)) {
762 * The queue is full and the allocating
763 * process is not a "batcher", and not
764 * exempted by the IO scheduler
770 blk_set_queue_congested(q, rw);
774 * Only allow batching queuers to allocate up to 50% over the defined
775 * limit of requests, otherwise we could have thousands of requests
776 * allocated with any setting of ->nr_requests
778 if (rl->count[rw] >= (3 * q->nr_requests / 2))
784 priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
788 spin_unlock_irq(q->queue_lock);
790 rq = blk_alloc_request(q, rw_flags, priv, gfp_mask);
793 * Allocation failed presumably due to memory. Undo anything
794 * we might have messed up.
796 * Allocating task should really be put onto the front of the
797 * wait queue, but this is pretty rare.
799 spin_lock_irq(q->queue_lock);
800 freed_request(q, rw, priv);
803 * in the very unlikely event that allocation failed and no
804 * requests for this direction was pending, mark us starved
805 * so that freeing of a request in the other direction will
806 * notice us. another possible fix would be to split the
807 * rq mempool into READ and WRITE
810 if (unlikely(rl->count[rw] == 0))
817 * ioc may be NULL here, and ioc_batching will be false. That's
818 * OK, if the queue is under the request limit then requests need
819 * not count toward the nr_batch_requests limit. There will always
820 * be some limit enforced by BLK_BATCH_TIME.
822 if (ioc_batching(q, ioc))
823 ioc->nr_batch_requests--;
825 blk_add_trace_generic(q, bio, rw, BLK_TA_GETRQ);
831 * No available requests for this queue, unplug the device and wait for some
832 * requests to become available.
834 * Called with q->queue_lock held, and returns with it unlocked.
836 static struct request *get_request_wait(struct request_queue *q, int rw_flags,
839 const int rw = rw_flags & 0x01;
842 rq = get_request(q, rw_flags, bio, GFP_NOIO);
845 struct io_context *ioc;
846 struct request_list *rl = &q->rq;
848 prepare_to_wait_exclusive(&rl->wait[rw], &wait,
849 TASK_UNINTERRUPTIBLE);
851 blk_add_trace_generic(q, bio, rw, BLK_TA_SLEEPRQ);
853 __generic_unplug_device(q);
854 spin_unlock_irq(q->queue_lock);
858 * After sleeping, we become a "batching" process and
859 * will be able to allocate at least one request, and
860 * up to a big batch of them for a small period time.
861 * See ioc_batching, ioc_set_batching
863 ioc = current_io_context(GFP_NOIO, q->node);
864 ioc_set_batching(q, ioc);
866 spin_lock_irq(q->queue_lock);
867 finish_wait(&rl->wait[rw], &wait);
869 rq = get_request(q, rw_flags, bio, GFP_NOIO);
875 struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
879 BUG_ON(rw != READ && rw != WRITE);
881 spin_lock_irq(q->queue_lock);
882 if (gfp_mask & __GFP_WAIT) {
883 rq = get_request_wait(q, rw, NULL);
885 rq = get_request(q, rw, NULL, gfp_mask);
887 spin_unlock_irq(q->queue_lock);
889 /* q->queue_lock is unlocked at this point */
893 EXPORT_SYMBOL(blk_get_request);
896 * blk_start_queueing - initiate dispatch of requests to device
897 * @q: request queue to kick into gear
899 * This is basically a helper to remove the need to know whether a queue
900 * is plugged or not if someone just wants to initiate dispatch of requests
901 * for this queue. Should be used to start queueing on a device outside
902 * of ->request_fn() context. Also see @blk_run_queue.
904 * The queue lock must be held with interrupts disabled.
906 void blk_start_queueing(struct request_queue *q)
908 if (!blk_queue_plugged(q)) {
909 if (unlikely(blk_queue_stopped(q)))
913 __generic_unplug_device(q);
915 EXPORT_SYMBOL(blk_start_queueing);
918 * blk_requeue_request - put a request back on queue
919 * @q: request queue where request should be inserted
920 * @rq: request to be inserted
923 * Drivers often keep queueing requests until the hardware cannot accept
924 * more, when that condition happens we need to put the request back
925 * on the queue. Must be called with queue lock held.
927 void blk_requeue_request(struct request_queue *q, struct request *rq)
929 blk_delete_timer(rq);
930 blk_clear_rq_complete(rq);
931 blk_add_trace_rq(q, rq, BLK_TA_REQUEUE);
933 if (blk_rq_tagged(rq))
934 blk_queue_end_tag(q, rq);
936 elv_requeue_request(q, rq);
938 EXPORT_SYMBOL(blk_requeue_request);
941 * blk_insert_request - insert a special request into a request queue
942 * @q: request queue where request should be inserted
943 * @rq: request to be inserted
944 * @at_head: insert request at head or tail of queue
945 * @data: private data
948 * Many block devices need to execute commands asynchronously, so they don't
949 * block the whole kernel from preemption during request execution. This is
950 * accomplished normally by inserting aritficial requests tagged as
951 * REQ_TYPE_SPECIAL in to the corresponding request queue, and letting them
952 * be scheduled for actual execution by the request queue.
954 * We have the option of inserting the head or the tail of the queue.
955 * Typically we use the tail for new ioctls and so forth. We use the head
956 * of the queue for things like a QUEUE_FULL message from a device, or a
957 * host that is unable to accept a particular command.
959 void blk_insert_request(struct request_queue *q, struct request *rq,
960 int at_head, void *data)
962 int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
966 * tell I/O scheduler that this isn't a regular read/write (ie it
967 * must not attempt merges on this) and that it acts as a soft
970 rq->cmd_type = REQ_TYPE_SPECIAL;
971 rq->cmd_flags |= REQ_SOFTBARRIER;
975 spin_lock_irqsave(q->queue_lock, flags);
978 * If command is tagged, release the tag
980 if (blk_rq_tagged(rq))
981 blk_queue_end_tag(q, rq);
983 drive_stat_acct(rq, 1);
984 __elv_add_request(q, rq, where, 0);
985 blk_start_queueing(q);
986 spin_unlock_irqrestore(q->queue_lock, flags);
988 EXPORT_SYMBOL(blk_insert_request);
991 * add-request adds a request to the linked list.
992 * queue lock is held and interrupts disabled, as we muck with the
993 * request queue list.
995 static inline void add_request(struct request_queue *q, struct request *req)
997 drive_stat_acct(req, 1);
1000 * elevator indicated where it wants this request to be
1001 * inserted at elevator_merge time
1003 __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
1006 static void part_round_stats_single(int cpu, struct hd_struct *part,
1009 if (now == part->stamp)
1012 if (part->in_flight) {
1013 __part_stat_add(cpu, part, time_in_queue,
1014 part->in_flight * (now - part->stamp));
1015 __part_stat_add(cpu, part, io_ticks, (now - part->stamp));
1021 * part_round_stats() - Round off the performance stats on a struct
1024 * The average IO queue length and utilisation statistics are maintained
1025 * by observing the current state of the queue length and the amount of
1026 * time it has been in this state for.
1028 * Normally, that accounting is done on IO completion, but that can result
1029 * in more than a second's worth of IO being accounted for within any one
1030 * second, leading to >100% utilisation. To deal with that, we call this
1031 * function to do a round-off before returning the results when reading
1032 * /proc/diskstats. This accounts immediately for all queue usage up to
1033 * the current jiffies and restarts the counters again.
1035 void part_round_stats(int cpu, struct hd_struct *part)
1037 unsigned long now = jiffies;
1040 part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1041 part_round_stats_single(cpu, part, now);
1043 EXPORT_SYMBOL_GPL(part_round_stats);
1046 * queue lock must be held
1048 void __blk_put_request(struct request_queue *q, struct request *req)
1052 if (unlikely(--req->ref_count))
1055 elv_completed_request(q, req);
1058 * Request may not have originated from ll_rw_blk. if not,
1059 * it didn't come out of our reserved rq pools
1061 if (req->cmd_flags & REQ_ALLOCED) {
1062 int rw = rq_data_dir(req);
1063 int priv = req->cmd_flags & REQ_ELVPRIV;
1065 BUG_ON(!list_empty(&req->queuelist));
1066 BUG_ON(!hlist_unhashed(&req->hash));
1068 blk_free_request(q, req);
1069 freed_request(q, rw, priv);
1072 EXPORT_SYMBOL_GPL(__blk_put_request);
1074 void blk_put_request(struct request *req)
1076 unsigned long flags;
1077 struct request_queue *q = req->q;
1079 spin_lock_irqsave(q->queue_lock, flags);
1080 __blk_put_request(q, req);
1081 spin_unlock_irqrestore(q->queue_lock, flags);
1083 EXPORT_SYMBOL(blk_put_request);
1085 void init_request_from_bio(struct request *req, struct bio *bio)
1087 req->cpu = bio->bi_comp_cpu;
1088 req->cmd_type = REQ_TYPE_FS;
1091 * inherit FAILFAST from bio (for read-ahead, and explicit FAILFAST)
1093 if (bio_rw_ahead(bio) || bio_failfast(bio))
1094 req->cmd_flags |= REQ_FAILFAST;
1097 * REQ_BARRIER implies no merging, but lets make it explicit
1099 if (unlikely(bio_discard(bio))) {
1100 req->cmd_flags |= REQ_DISCARD;
1101 if (bio_barrier(bio))
1102 req->cmd_flags |= REQ_SOFTBARRIER;
1103 req->q->prepare_discard_fn(req->q, req);
1104 } else if (unlikely(bio_barrier(bio)))
1105 req->cmd_flags |= (REQ_HARDBARRIER | REQ_NOMERGE);
1108 req->cmd_flags |= REQ_RW_SYNC;
1109 if (bio_rw_meta(bio))
1110 req->cmd_flags |= REQ_RW_META;
1113 req->hard_sector = req->sector = bio->bi_sector;
1114 req->ioprio = bio_prio(bio);
1115 req->start_time = jiffies;
1116 blk_rq_bio_prep(req->q, req, bio);
1119 static int __make_request(struct request_queue *q, struct bio *bio)
1121 struct request *req;
1122 int el_ret, nr_sectors, barrier, discard, err;
1123 const unsigned short prio = bio_prio(bio);
1124 const int sync = bio_sync(bio);
1127 nr_sectors = bio_sectors(bio);
1130 * low level driver can indicate that it wants pages above a
1131 * certain limit bounced to low memory (ie for highmem, or even
1132 * ISA dma in theory)
1134 blk_queue_bounce(q, &bio);
1136 barrier = bio_barrier(bio);
1137 if (unlikely(barrier) && bio_has_data(bio) &&
1138 (q->next_ordered == QUEUE_ORDERED_NONE)) {
1143 discard = bio_discard(bio);
1144 if (unlikely(discard) && !q->prepare_discard_fn) {
1149 spin_lock_irq(q->queue_lock);
1151 if (unlikely(barrier) || elv_queue_empty(q))
1154 el_ret = elv_merge(q, &req, bio);
1156 case ELEVATOR_BACK_MERGE:
1157 BUG_ON(!rq_mergeable(req));
1159 if (!ll_back_merge_fn(q, req, bio))
1162 blk_add_trace_bio(q, bio, BLK_TA_BACKMERGE);
1164 req->biotail->bi_next = bio;
1166 req->nr_sectors = req->hard_nr_sectors += nr_sectors;
1167 req->ioprio = ioprio_best(req->ioprio, prio);
1168 if (!blk_rq_cpu_valid(req))
1169 req->cpu = bio->bi_comp_cpu;
1170 drive_stat_acct(req, 0);
1171 if (!attempt_back_merge(q, req))
1172 elv_merged_request(q, req, el_ret);
1175 case ELEVATOR_FRONT_MERGE:
1176 BUG_ON(!rq_mergeable(req));
1178 if (!ll_front_merge_fn(q, req, bio))
1181 blk_add_trace_bio(q, bio, BLK_TA_FRONTMERGE);
1183 bio->bi_next = req->bio;
1187 * may not be valid. if the low level driver said
1188 * it didn't need a bounce buffer then it better
1189 * not touch req->buffer either...
1191 req->buffer = bio_data(bio);
1192 req->current_nr_sectors = bio_cur_sectors(bio);
1193 req->hard_cur_sectors = req->current_nr_sectors;
1194 req->sector = req->hard_sector = bio->bi_sector;
1195 req->nr_sectors = req->hard_nr_sectors += nr_sectors;
1196 req->ioprio = ioprio_best(req->ioprio, prio);
1197 if (!blk_rq_cpu_valid(req))
1198 req->cpu = bio->bi_comp_cpu;
1199 drive_stat_acct(req, 0);
1200 if (!attempt_front_merge(q, req))
1201 elv_merged_request(q, req, el_ret);
1204 /* ELV_NO_MERGE: elevator says don't/can't merge. */
1211 * This sync check and mask will be re-done in init_request_from_bio(),
1212 * but we need to set it earlier to expose the sync flag to the
1213 * rq allocator and io schedulers.
1215 rw_flags = bio_data_dir(bio);
1217 rw_flags |= REQ_RW_SYNC;
1220 * Grab a free request. This is might sleep but can not fail.
1221 * Returns with the queue unlocked.
1223 req = get_request_wait(q, rw_flags, bio);
1226 * After dropping the lock and possibly sleeping here, our request
1227 * may now be mergeable after it had proven unmergeable (above).
1228 * We don't worry about that case for efficiency. It won't happen
1229 * often, and the elevators are able to handle it.
1231 init_request_from_bio(req, bio);
1233 spin_lock_irq(q->queue_lock);
1234 if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) ||
1235 bio_flagged(bio, BIO_CPU_AFFINE))
1236 req->cpu = blk_cpu_to_group(smp_processor_id());
1237 if (elv_queue_empty(q))
1239 add_request(q, req);
1242 __generic_unplug_device(q);
1243 spin_unlock_irq(q->queue_lock);
1247 bio_endio(bio, err);
1252 * If bio->bi_dev is a partition, remap the location
1254 static inline void blk_partition_remap(struct bio *bio)
1256 struct block_device *bdev = bio->bi_bdev;
1258 if (bio_sectors(bio) && bdev != bdev->bd_contains) {
1259 struct hd_struct *p = bdev->bd_part;
1261 bio->bi_sector += p->start_sect;
1262 bio->bi_bdev = bdev->bd_contains;
1264 blk_add_trace_remap(bdev_get_queue(bio->bi_bdev), bio,
1265 bdev->bd_dev, bio->bi_sector,
1266 bio->bi_sector - p->start_sect);
1270 static void handle_bad_sector(struct bio *bio)
1272 char b[BDEVNAME_SIZE];
1274 printk(KERN_INFO "attempt to access beyond end of device\n");
1275 printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
1276 bdevname(bio->bi_bdev, b),
1278 (unsigned long long)bio->bi_sector + bio_sectors(bio),
1279 (long long)(bio->bi_bdev->bd_inode->i_size >> 9));
1281 set_bit(BIO_EOF, &bio->bi_flags);
1284 #ifdef CONFIG_FAIL_MAKE_REQUEST
1286 static DECLARE_FAULT_ATTR(fail_make_request);
1288 static int __init setup_fail_make_request(char *str)
1290 return setup_fault_attr(&fail_make_request, str);
1292 __setup("fail_make_request=", setup_fail_make_request);
1294 static int should_fail_request(struct bio *bio)
1296 struct hd_struct *part = bio->bi_bdev->bd_part;
1298 if (part_to_disk(part)->part0.make_it_fail || part->make_it_fail)
1299 return should_fail(&fail_make_request, bio->bi_size);
1304 static int __init fail_make_request_debugfs(void)
1306 return init_fault_attr_dentries(&fail_make_request,
1307 "fail_make_request");
1310 late_initcall(fail_make_request_debugfs);
1312 #else /* CONFIG_FAIL_MAKE_REQUEST */
1314 static inline int should_fail_request(struct bio *bio)
1319 #endif /* CONFIG_FAIL_MAKE_REQUEST */
1322 * Check whether this bio extends beyond the end of the device.
1324 static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1331 /* Test device or partition size, when known. */
1332 maxsector = bio->bi_bdev->bd_inode->i_size >> 9;
1334 sector_t sector = bio->bi_sector;
1336 if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1338 * This may well happen - the kernel calls bread()
1339 * without checking the size of the device, e.g., when
1340 * mounting a device.
1342 handle_bad_sector(bio);
1351 * generic_make_request - hand a buffer to its device driver for I/O
1352 * @bio: The bio describing the location in memory and on the device.
1354 * generic_make_request() is used to make I/O requests of block
1355 * devices. It is passed a &struct bio, which describes the I/O that needs
1358 * generic_make_request() does not return any status. The
1359 * success/failure status of the request, along with notification of
1360 * completion, is delivered asynchronously through the bio->bi_end_io
1361 * function described (one day) else where.
1363 * The caller of generic_make_request must make sure that bi_io_vec
1364 * are set to describe the memory buffer, and that bi_dev and bi_sector are
1365 * set to describe the device address, and the
1366 * bi_end_io and optionally bi_private are set to describe how
1367 * completion notification should be signaled.
1369 * generic_make_request and the drivers it calls may use bi_next if this
1370 * bio happens to be merged with someone else, and may change bi_dev and
1371 * bi_sector for remaps as it sees fit. So the values of these fields
1372 * should NOT be depended on after the call to generic_make_request.
1374 static inline void __generic_make_request(struct bio *bio)
1376 struct request_queue *q;
1377 sector_t old_sector;
1378 int ret, nr_sectors = bio_sectors(bio);
1384 if (bio_check_eod(bio, nr_sectors))
1388 * Resolve the mapping until finished. (drivers are
1389 * still free to implement/resolve their own stacking
1390 * by explicitly returning 0)
1392 * NOTE: we don't repeat the blk_size check for each new device.
1393 * Stacking drivers are expected to know what they are doing.
1398 char b[BDEVNAME_SIZE];
1400 q = bdev_get_queue(bio->bi_bdev);
1403 "generic_make_request: Trying to access "
1404 "nonexistent block-device %s (%Lu)\n",
1405 bdevname(bio->bi_bdev, b),
1406 (long long) bio->bi_sector);
1408 bio_endio(bio, err);
1412 if (unlikely(nr_sectors > q->max_hw_sectors)) {
1413 printk(KERN_ERR "bio too big device %s (%u > %u)\n",
1414 bdevname(bio->bi_bdev, b),
1420 if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
1423 if (should_fail_request(bio))
1427 * If this device has partitions, remap block n
1428 * of partition p to block n+start(p) of the disk.
1430 blk_partition_remap(bio);
1432 if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
1435 if (old_sector != -1)
1436 blk_add_trace_remap(q, bio, old_dev, bio->bi_sector,
1439 blk_add_trace_bio(q, bio, BLK_TA_QUEUE);
1441 old_sector = bio->bi_sector;
1442 old_dev = bio->bi_bdev->bd_dev;
1444 if (bio_check_eod(bio, nr_sectors))
1446 if ((bio_empty_barrier(bio) && !q->prepare_flush_fn) ||
1447 (bio_discard(bio) && !q->prepare_discard_fn)) {
1452 ret = q->make_request_fn(q, bio);
1457 * We only want one ->make_request_fn to be active at a time,
1458 * else stack usage with stacked devices could be a problem.
1459 * So use current->bio_{list,tail} to keep a list of requests
1460 * submited by a make_request_fn function.
1461 * current->bio_tail is also used as a flag to say if
1462 * generic_make_request is currently active in this task or not.
1463 * If it is NULL, then no make_request is active. If it is non-NULL,
1464 * then a make_request is active, and new requests should be added
1467 void generic_make_request(struct bio *bio)
1469 if (current->bio_tail) {
1470 /* make_request is active */
1471 *(current->bio_tail) = bio;
1472 bio->bi_next = NULL;
1473 current->bio_tail = &bio->bi_next;
1476 /* following loop may be a bit non-obvious, and so deserves some
1478 * Before entering the loop, bio->bi_next is NULL (as all callers
1479 * ensure that) so we have a list with a single bio.
1480 * We pretend that we have just taken it off a longer list, so
1481 * we assign bio_list to the next (which is NULL) and bio_tail
1482 * to &bio_list, thus initialising the bio_list of new bios to be
1483 * added. __generic_make_request may indeed add some more bios
1484 * through a recursive call to generic_make_request. If it
1485 * did, we find a non-NULL value in bio_list and re-enter the loop
1486 * from the top. In this case we really did just take the bio
1487 * of the top of the list (no pretending) and so fixup bio_list and
1488 * bio_tail or bi_next, and call into __generic_make_request again.
1490 * The loop was structured like this to make only one call to
1491 * __generic_make_request (which is important as it is large and
1492 * inlined) and to keep the structure simple.
1494 BUG_ON(bio->bi_next);
1496 current->bio_list = bio->bi_next;
1497 if (bio->bi_next == NULL)
1498 current->bio_tail = ¤t->bio_list;
1500 bio->bi_next = NULL;
1501 __generic_make_request(bio);
1502 bio = current->bio_list;
1504 current->bio_tail = NULL; /* deactivate */
1506 EXPORT_SYMBOL(generic_make_request);
1509 * submit_bio - submit a bio to the block device layer for I/O
1510 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1511 * @bio: The &struct bio which describes the I/O
1513 * submit_bio() is very similar in purpose to generic_make_request(), and
1514 * uses that function to do most of the work. Both are fairly rough
1515 * interfaces; @bio must be presetup and ready for I/O.
1518 void submit_bio(int rw, struct bio *bio)
1520 int count = bio_sectors(bio);
1525 * If it's a regular read/write or a barrier with data attached,
1526 * go through the normal accounting stuff before submission.
1528 if (bio_has_data(bio)) {
1530 count_vm_events(PGPGOUT, count);
1532 task_io_account_read(bio->bi_size);
1533 count_vm_events(PGPGIN, count);
1536 if (unlikely(block_dump)) {
1537 char b[BDEVNAME_SIZE];
1538 printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n",
1539 current->comm, task_pid_nr(current),
1540 (rw & WRITE) ? "WRITE" : "READ",
1541 (unsigned long long)bio->bi_sector,
1542 bdevname(bio->bi_bdev, b));
1546 generic_make_request(bio);
1548 EXPORT_SYMBOL(submit_bio);
1551 * blk_rq_check_limits - Helper function to check a request for the queue limit
1553 * @rq: the request being checked
1556 * @rq may have been made based on weaker limitations of upper-level queues
1557 * in request stacking drivers, and it may violate the limitation of @q.
1558 * Since the block layer and the underlying device driver trust @rq
1559 * after it is inserted to @q, it should be checked against @q before
1560 * the insertion using this generic function.
1562 * This function should also be useful for request stacking drivers
1563 * in some cases below, so export this fuction.
1564 * Request stacking drivers like request-based dm may change the queue
1565 * limits while requests are in the queue (e.g. dm's table swapping).
1566 * Such request stacking drivers should check those requests agaist
1567 * the new queue limits again when they dispatch those requests,
1568 * although such checkings are also done against the old queue limits
1569 * when submitting requests.
1571 int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1573 if (rq->nr_sectors > q->max_sectors ||
1574 rq->data_len > q->max_hw_sectors << 9) {
1575 printk(KERN_ERR "%s: over max size limit.\n", __func__);
1580 * queue's settings related to segment counting like q->bounce_pfn
1581 * may differ from that of other stacking queues.
1582 * Recalculate it to check the request correctly on this queue's
1585 blk_recalc_rq_segments(rq);
1586 if (rq->nr_phys_segments > q->max_phys_segments ||
1587 rq->nr_phys_segments > q->max_hw_segments) {
1588 printk(KERN_ERR "%s: over max segments limit.\n", __func__);
1594 EXPORT_SYMBOL_GPL(blk_rq_check_limits);
1597 * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1598 * @q: the queue to submit the request
1599 * @rq: the request being queued
1601 int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1603 unsigned long flags;
1605 if (blk_rq_check_limits(q, rq))
1608 #ifdef CONFIG_FAIL_MAKE_REQUEST
1609 if (rq->rq_disk && rq->rq_disk->part0.make_it_fail &&
1610 should_fail(&fail_make_request, blk_rq_bytes(rq)))
1614 spin_lock_irqsave(q->queue_lock, flags);
1617 * Submitting request must be dequeued before calling this function
1618 * because it will be linked to another request_queue
1620 BUG_ON(blk_queued_rq(rq));
1622 drive_stat_acct(rq, 1);
1623 __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0);
1625 spin_unlock_irqrestore(q->queue_lock, flags);
1629 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
1632 * __end_that_request_first - end I/O on a request
1633 * @req: the request being processed
1634 * @error: %0 for success, < %0 for error
1635 * @nr_bytes: number of bytes to complete
1638 * Ends I/O on a number of bytes attached to @req, and sets it up
1639 * for the next range of segments (if any) in the cluster.
1642 * %0 - we are done with this request, call end_that_request_last()
1643 * %1 - still buffers pending for this request
1645 static int __end_that_request_first(struct request *req, int error,
1648 int total_bytes, bio_nbytes, next_idx = 0;
1651 blk_add_trace_rq(req->q, req, BLK_TA_COMPLETE);
1654 * for a REQ_TYPE_BLOCK_PC request, we want to carry any eventual
1655 * sense key with us all the way through
1657 if (!blk_pc_request(req))
1660 if (error && (blk_fs_request(req) && !(req->cmd_flags & REQ_QUIET))) {
1661 printk(KERN_ERR "end_request: I/O error, dev %s, sector %llu\n",
1662 req->rq_disk ? req->rq_disk->disk_name : "?",
1663 (unsigned long long)req->sector);
1666 if (blk_fs_request(req) && req->rq_disk) {
1667 const int rw = rq_data_dir(req);
1668 struct hd_struct *part;
1671 cpu = part_stat_lock();
1672 part = disk_map_sector_rcu(req->rq_disk, req->sector);
1673 part_stat_add(cpu, part, sectors[rw], nr_bytes >> 9);
1677 total_bytes = bio_nbytes = 0;
1678 while ((bio = req->bio) != NULL) {
1682 * For an empty barrier request, the low level driver must
1683 * store a potential error location in ->sector. We pass
1684 * that back up in ->bi_sector.
1686 if (blk_empty_barrier(req))
1687 bio->bi_sector = req->sector;
1689 if (nr_bytes >= bio->bi_size) {
1690 req->bio = bio->bi_next;
1691 nbytes = bio->bi_size;
1692 req_bio_endio(req, bio, nbytes, error);
1696 int idx = bio->bi_idx + next_idx;
1698 if (unlikely(bio->bi_idx >= bio->bi_vcnt)) {
1699 blk_dump_rq_flags(req, "__end_that");
1700 printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
1701 __func__, bio->bi_idx, bio->bi_vcnt);
1705 nbytes = bio_iovec_idx(bio, idx)->bv_len;
1706 BIO_BUG_ON(nbytes > bio->bi_size);
1709 * not a complete bvec done
1711 if (unlikely(nbytes > nr_bytes)) {
1712 bio_nbytes += nr_bytes;
1713 total_bytes += nr_bytes;
1718 * advance to the next vector
1721 bio_nbytes += nbytes;
1724 total_bytes += nbytes;
1730 * end more in this run, or just return 'not-done'
1732 if (unlikely(nr_bytes <= 0))
1744 * if the request wasn't completed, update state
1747 req_bio_endio(req, bio, bio_nbytes, error);
1748 bio->bi_idx += next_idx;
1749 bio_iovec(bio)->bv_offset += nr_bytes;
1750 bio_iovec(bio)->bv_len -= nr_bytes;
1753 blk_recalc_rq_sectors(req, total_bytes >> 9);
1754 blk_recalc_rq_segments(req);
1759 * queue lock must be held
1761 static void end_that_request_last(struct request *req, int error)
1763 struct gendisk *disk = req->rq_disk;
1765 blk_delete_timer(req);
1767 if (blk_rq_tagged(req))
1768 blk_queue_end_tag(req->q, req);
1770 if (blk_queued_rq(req))
1771 blkdev_dequeue_request(req);
1773 if (unlikely(laptop_mode) && blk_fs_request(req))
1774 laptop_io_completion();
1777 * Account IO completion. bar_rq isn't accounted as a normal
1778 * IO on queueing nor completion. Accounting the containing
1779 * request is enough.
1781 if (disk && blk_fs_request(req) && req != &req->q->bar_rq) {
1782 unsigned long duration = jiffies - req->start_time;
1783 const int rw = rq_data_dir(req);
1784 struct hd_struct *part;
1787 cpu = part_stat_lock();
1788 part = disk_map_sector_rcu(disk, req->sector);
1790 part_stat_inc(cpu, part, ios[rw]);
1791 part_stat_add(cpu, part, ticks[rw], duration);
1792 part_round_stats(cpu, part);
1793 part_dec_in_flight(part);
1799 req->end_io(req, error);
1801 if (blk_bidi_rq(req))
1802 __blk_put_request(req->next_rq->q, req->next_rq);
1804 __blk_put_request(req->q, req);
1809 * blk_rq_bytes - Returns bytes left to complete in the entire request
1810 * @rq: the request being processed
1812 unsigned int blk_rq_bytes(struct request *rq)
1814 if (blk_fs_request(rq))
1815 return rq->hard_nr_sectors << 9;
1817 return rq->data_len;
1819 EXPORT_SYMBOL_GPL(blk_rq_bytes);
1822 * blk_rq_cur_bytes - Returns bytes left to complete in the current segment
1823 * @rq: the request being processed
1825 unsigned int blk_rq_cur_bytes(struct request *rq)
1827 if (blk_fs_request(rq))
1828 return rq->current_nr_sectors << 9;
1831 return rq->bio->bi_size;
1833 return rq->data_len;
1835 EXPORT_SYMBOL_GPL(blk_rq_cur_bytes);
1838 * end_request - end I/O on the current segment of the request
1839 * @req: the request being processed
1840 * @uptodate: error value or %0/%1 uptodate flag
1843 * Ends I/O on the current segment of a request. If that is the only
1844 * remaining segment, the request is also completed and freed.
1846 * This is a remnant of how older block drivers handled I/O completions.
1847 * Modern drivers typically end I/O on the full request in one go, unless
1848 * they have a residual value to account for. For that case this function
1849 * isn't really useful, unless the residual just happens to be the
1850 * full current segment. In other words, don't use this function in new
1851 * code. Use blk_end_request() or __blk_end_request() to end a request.
1853 void end_request(struct request *req, int uptodate)
1858 error = uptodate ? uptodate : -EIO;
1860 __blk_end_request(req, error, req->hard_cur_sectors << 9);
1862 EXPORT_SYMBOL(end_request);
1864 static int end_that_request_data(struct request *rq, int error,
1865 unsigned int nr_bytes, unsigned int bidi_bytes)
1868 if (__end_that_request_first(rq, error, nr_bytes))
1871 /* Bidi request must be completed as a whole */
1872 if (blk_bidi_rq(rq) &&
1873 __end_that_request_first(rq->next_rq, error, bidi_bytes))
1881 * blk_end_io - Generic end_io function to complete a request.
1882 * @rq: the request being processed
1883 * @error: %0 for success, < %0 for error
1884 * @nr_bytes: number of bytes to complete @rq
1885 * @bidi_bytes: number of bytes to complete @rq->next_rq
1886 * @drv_callback: function called between completion of bios in the request
1887 * and completion of the request.
1888 * If the callback returns non %0, this helper returns without
1889 * completion of the request.
1892 * Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
1893 * If @rq has leftover, sets it up for the next range of segments.
1896 * %0 - we are done with this request
1897 * %1 - this request is not freed yet, it still has pending buffers.
1899 static int blk_end_io(struct request *rq, int error, unsigned int nr_bytes,
1900 unsigned int bidi_bytes,
1901 int (drv_callback)(struct request *))
1903 struct request_queue *q = rq->q;
1904 unsigned long flags = 0UL;
1906 if (end_that_request_data(rq, error, nr_bytes, bidi_bytes))
1909 /* Special feature for tricky drivers */
1910 if (drv_callback && drv_callback(rq))
1913 add_disk_randomness(rq->rq_disk);
1915 spin_lock_irqsave(q->queue_lock, flags);
1916 end_that_request_last(rq, error);
1917 spin_unlock_irqrestore(q->queue_lock, flags);
1923 * blk_end_request - Helper function for drivers to complete the request.
1924 * @rq: the request being processed
1925 * @error: %0 for success, < %0 for error
1926 * @nr_bytes: number of bytes to complete
1929 * Ends I/O on a number of bytes attached to @rq.
1930 * If @rq has leftover, sets it up for the next range of segments.
1933 * %0 - we are done with this request
1934 * %1 - still buffers pending for this request
1936 int blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
1938 return blk_end_io(rq, error, nr_bytes, 0, NULL);
1940 EXPORT_SYMBOL_GPL(blk_end_request);
1943 * __blk_end_request - Helper function for drivers to complete the request.
1944 * @rq: the request being processed
1945 * @error: %0 for success, < %0 for error
1946 * @nr_bytes: number of bytes to complete
1949 * Must be called with queue lock held unlike blk_end_request().
1952 * %0 - we are done with this request
1953 * %1 - still buffers pending for this request
1955 int __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
1957 if (rq->bio && __end_that_request_first(rq, error, nr_bytes))
1960 add_disk_randomness(rq->rq_disk);
1962 end_that_request_last(rq, error);
1966 EXPORT_SYMBOL_GPL(__blk_end_request);
1969 * blk_end_bidi_request - Helper function for drivers to complete bidi request.
1970 * @rq: the bidi request being processed
1971 * @error: %0 for success, < %0 for error
1972 * @nr_bytes: number of bytes to complete @rq
1973 * @bidi_bytes: number of bytes to complete @rq->next_rq
1976 * Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
1979 * %0 - we are done with this request
1980 * %1 - still buffers pending for this request
1982 int blk_end_bidi_request(struct request *rq, int error, unsigned int nr_bytes,
1983 unsigned int bidi_bytes)
1985 return blk_end_io(rq, error, nr_bytes, bidi_bytes, NULL);
1987 EXPORT_SYMBOL_GPL(blk_end_bidi_request);
1990 * blk_update_request - Special helper function for request stacking drivers
1991 * @rq: the request being processed
1992 * @error: %0 for success, < %0 for error
1993 * @nr_bytes: number of bytes to complete @rq
1996 * Ends I/O on a number of bytes attached to @rq, but doesn't complete
1997 * the request structure even if @rq doesn't have leftover.
1998 * If @rq has leftover, sets it up for the next range of segments.
2000 * This special helper function is only for request stacking drivers
2001 * (e.g. request-based dm) so that they can handle partial completion.
2002 * Actual device drivers should use blk_end_request instead.
2004 void blk_update_request(struct request *rq, int error, unsigned int nr_bytes)
2006 if (!end_that_request_data(rq, error, nr_bytes, 0)) {
2008 * These members are not updated in end_that_request_data()
2009 * when all bios are completed.
2010 * Update them so that the request stacking driver can find
2011 * how many bytes remain in the request later.
2013 rq->nr_sectors = rq->hard_nr_sectors = 0;
2014 rq->current_nr_sectors = rq->hard_cur_sectors = 0;
2017 EXPORT_SYMBOL_GPL(blk_update_request);
2020 * blk_end_request_callback - Special helper function for tricky drivers
2021 * @rq: the request being processed
2022 * @error: %0 for success, < %0 for error
2023 * @nr_bytes: number of bytes to complete
2024 * @drv_callback: function called between completion of bios in the request
2025 * and completion of the request.
2026 * If the callback returns non %0, this helper returns without
2027 * completion of the request.
2030 * Ends I/O on a number of bytes attached to @rq.
2031 * If @rq has leftover, sets it up for the next range of segments.
2033 * This special helper function is used only for existing tricky drivers.
2034 * (e.g. cdrom_newpc_intr() of ide-cd)
2035 * This interface will be removed when such drivers are rewritten.
2036 * Don't use this interface in other places anymore.
2039 * %0 - we are done with this request
2040 * %1 - this request is not freed yet.
2041 * this request still has pending buffers or
2042 * the driver doesn't want to finish this request yet.
2044 int blk_end_request_callback(struct request *rq, int error,
2045 unsigned int nr_bytes,
2046 int (drv_callback)(struct request *))
2048 return blk_end_io(rq, error, nr_bytes, 0, drv_callback);
2050 EXPORT_SYMBOL_GPL(blk_end_request_callback);
2052 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2055 /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw, and
2056 we want BIO_RW_AHEAD (bit 1) to imply REQ_FAILFAST (bit 1). */
2057 rq->cmd_flags |= (bio->bi_rw & 3);
2059 if (bio_has_data(bio)) {
2060 rq->nr_phys_segments = bio_phys_segments(q, bio);
2061 rq->buffer = bio_data(bio);
2063 rq->current_nr_sectors = bio_cur_sectors(bio);
2064 rq->hard_cur_sectors = rq->current_nr_sectors;
2065 rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio);
2066 rq->data_len = bio->bi_size;
2068 rq->bio = rq->biotail = bio;
2071 rq->rq_disk = bio->bi_bdev->bd_disk;
2075 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2076 * @q : the queue of the device being checked
2079 * Check if underlying low-level drivers of a device are busy.
2080 * If the drivers want to export their busy state, they must set own
2081 * exporting function using blk_queue_lld_busy() first.
2083 * Basically, this function is used only by request stacking drivers
2084 * to stop dispatching requests to underlying devices when underlying
2085 * devices are busy. This behavior helps more I/O merging on the queue
2086 * of the request stacking driver and prevents I/O throughput regression
2087 * on burst I/O load.
2090 * 0 - Not busy (The request stacking driver should dispatch request)
2091 * 1 - Busy (The request stacking driver should stop dispatching request)
2093 int blk_lld_busy(struct request_queue *q)
2096 return q->lld_busy_fn(q);
2100 EXPORT_SYMBOL_GPL(blk_lld_busy);
2102 int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
2104 return queue_work(kblockd_workqueue, work);
2106 EXPORT_SYMBOL(kblockd_schedule_work);
2108 void kblockd_flush_work(struct work_struct *work)
2110 cancel_work_sync(work);
2112 EXPORT_SYMBOL(kblockd_flush_work);
2114 int __init blk_dev_init(void)
2116 kblockd_workqueue = create_workqueue("kblockd");
2117 if (!kblockd_workqueue)
2118 panic("Failed to create kblockd\n");
2120 request_cachep = kmem_cache_create("blkdev_requests",
2121 sizeof(struct request), 0, SLAB_PANIC, NULL);
2123 blk_requestq_cachep = kmem_cache_create("blkdev_queue",
2124 sizeof(struct request_queue), 0, SLAB_PANIC, NULL);