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>
31 #include <trace/block.h>
35 DEFINE_TRACE(block_plug);
36 DEFINE_TRACE(block_unplug_io);
37 DEFINE_TRACE(block_unplug_timer);
38 DEFINE_TRACE(block_getrq);
39 DEFINE_TRACE(block_sleeprq);
40 DEFINE_TRACE(block_rq_requeue);
41 DEFINE_TRACE(block_bio_backmerge);
42 DEFINE_TRACE(block_bio_frontmerge);
43 DEFINE_TRACE(block_bio_queue);
44 DEFINE_TRACE(block_rq_complete);
45 DEFINE_TRACE(block_remap); /* Also used in drivers/md/dm.c */
46 EXPORT_TRACEPOINT_SYMBOL_GPL(block_remap);
48 static int __make_request(struct request_queue *q, struct bio *bio);
51 * For the allocated request tables
53 static struct kmem_cache *request_cachep;
56 * For queue allocation
58 struct kmem_cache *blk_requestq_cachep;
61 * Controlling structure to kblockd
63 static struct workqueue_struct *kblockd_workqueue;
65 static void drive_stat_acct(struct request *rq, int new_io)
67 struct gendisk *disk = rq->rq_disk;
68 struct hd_struct *part;
69 int rw = rq_data_dir(rq);
72 if (!blk_fs_request(rq) || !disk || !blk_do_io_stat(disk->queue))
75 cpu = part_stat_lock();
76 part = disk_map_sector_rcu(rq->rq_disk, rq->sector);
79 part_stat_inc(cpu, part, merges[rw]);
81 part_round_stats(cpu, part);
82 part_inc_in_flight(part);
88 void blk_queue_congestion_threshold(struct request_queue *q)
92 nr = q->nr_requests - (q->nr_requests / 8) + 1;
93 if (nr > q->nr_requests)
95 q->nr_congestion_on = nr;
97 nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
100 q->nr_congestion_off = nr;
104 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
107 * Locates the passed device's request queue and returns the address of its
110 * Will return NULL if the request queue cannot be located.
112 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
114 struct backing_dev_info *ret = NULL;
115 struct request_queue *q = bdev_get_queue(bdev);
118 ret = &q->backing_dev_info;
121 EXPORT_SYMBOL(blk_get_backing_dev_info);
123 void blk_rq_init(struct request_queue *q, struct request *rq)
125 memset(rq, 0, sizeof(*rq));
127 INIT_LIST_HEAD(&rq->queuelist);
128 INIT_LIST_HEAD(&rq->timeout_list);
131 rq->sector = rq->hard_sector = (sector_t) -1;
132 INIT_HLIST_NODE(&rq->hash);
133 RB_CLEAR_NODE(&rq->rb_node);
138 EXPORT_SYMBOL(blk_rq_init);
140 static void req_bio_endio(struct request *rq, struct bio *bio,
141 unsigned int nbytes, int error)
143 struct request_queue *q = rq->q;
145 if (&q->bar_rq != rq) {
147 clear_bit(BIO_UPTODATE, &bio->bi_flags);
148 else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
151 if (unlikely(nbytes > bio->bi_size)) {
152 printk(KERN_ERR "%s: want %u bytes done, %u left\n",
153 __func__, nbytes, bio->bi_size);
154 nbytes = bio->bi_size;
157 if (unlikely(rq->cmd_flags & REQ_QUIET))
158 set_bit(BIO_QUIET, &bio->bi_flags);
160 bio->bi_size -= nbytes;
161 bio->bi_sector += (nbytes >> 9);
163 if (bio_integrity(bio))
164 bio_integrity_advance(bio, nbytes);
166 if (bio->bi_size == 0)
167 bio_endio(bio, error);
171 * Okay, this is the barrier request in progress, just
174 if (error && !q->orderr)
179 void blk_dump_rq_flags(struct request *rq, char *msg)
183 printk(KERN_INFO "%s: dev %s: type=%x, flags=%x\n", msg,
184 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type,
187 printk(KERN_INFO " sector %llu, nr/cnr %lu/%u\n",
188 (unsigned long long)rq->sector,
190 rq->current_nr_sectors);
191 printk(KERN_INFO " bio %p, biotail %p, buffer %p, data %p, len %u\n",
192 rq->bio, rq->biotail,
193 rq->buffer, rq->data,
196 if (blk_pc_request(rq)) {
197 printk(KERN_INFO " cdb: ");
198 for (bit = 0; bit < BLK_MAX_CDB; bit++)
199 printk("%02x ", rq->cmd[bit]);
203 EXPORT_SYMBOL(blk_dump_rq_flags);
206 * "plug" the device if there are no outstanding requests: this will
207 * force the transfer to start only after we have put all the requests
210 * This is called with interrupts off and no requests on the queue and
211 * with the queue lock held.
213 void blk_plug_device(struct request_queue *q)
215 WARN_ON(!irqs_disabled());
218 * don't plug a stopped queue, it must be paired with blk_start_queue()
219 * which will restart the queueing
221 if (blk_queue_stopped(q))
224 if (!queue_flag_test_and_set(QUEUE_FLAG_PLUGGED, q)) {
225 mod_timer(&q->unplug_timer, jiffies + q->unplug_delay);
229 EXPORT_SYMBOL(blk_plug_device);
232 * blk_plug_device_unlocked - plug a device without queue lock held
233 * @q: The &struct request_queue to plug
236 * Like @blk_plug_device(), but grabs the queue lock and disables
239 void blk_plug_device_unlocked(struct request_queue *q)
243 spin_lock_irqsave(q->queue_lock, flags);
245 spin_unlock_irqrestore(q->queue_lock, flags);
247 EXPORT_SYMBOL(blk_plug_device_unlocked);
250 * remove the queue from the plugged list, if present. called with
251 * queue lock held and interrupts disabled.
253 int blk_remove_plug(struct request_queue *q)
255 WARN_ON(!irqs_disabled());
257 if (!queue_flag_test_and_clear(QUEUE_FLAG_PLUGGED, q))
260 del_timer(&q->unplug_timer);
263 EXPORT_SYMBOL(blk_remove_plug);
266 * remove the plug and let it rip..
268 void __generic_unplug_device(struct request_queue *q)
270 if (unlikely(blk_queue_stopped(q)))
272 if (!blk_remove_plug(q) && !blk_queue_nonrot(q))
279 * generic_unplug_device - fire a request queue
280 * @q: The &struct request_queue in question
283 * Linux uses plugging to build bigger requests queues before letting
284 * the device have at them. If a queue is plugged, the I/O scheduler
285 * is still adding and merging requests on the queue. Once the queue
286 * gets unplugged, the request_fn defined for the queue is invoked and
289 void generic_unplug_device(struct request_queue *q)
291 if (blk_queue_plugged(q)) {
292 spin_lock_irq(q->queue_lock);
293 __generic_unplug_device(q);
294 spin_unlock_irq(q->queue_lock);
297 EXPORT_SYMBOL(generic_unplug_device);
299 static void blk_backing_dev_unplug(struct backing_dev_info *bdi,
302 struct request_queue *q = bdi->unplug_io_data;
307 void blk_unplug_work(struct work_struct *work)
309 struct request_queue *q =
310 container_of(work, struct request_queue, unplug_work);
312 trace_block_unplug_io(q);
316 void blk_unplug_timeout(unsigned long data)
318 struct request_queue *q = (struct request_queue *)data;
320 trace_block_unplug_timer(q);
321 kblockd_schedule_work(q, &q->unplug_work);
324 void blk_unplug(struct request_queue *q)
327 * devices don't necessarily have an ->unplug_fn defined
330 trace_block_unplug_io(q);
334 EXPORT_SYMBOL(blk_unplug);
336 static void blk_invoke_request_fn(struct request_queue *q)
338 if (unlikely(blk_queue_stopped(q)))
342 * one level of recursion is ok and is much faster than kicking
343 * the unplug handling
345 if (!queue_flag_test_and_set(QUEUE_FLAG_REENTER, q)) {
347 queue_flag_clear(QUEUE_FLAG_REENTER, q);
349 queue_flag_set(QUEUE_FLAG_PLUGGED, q);
350 kblockd_schedule_work(q, &q->unplug_work);
355 * blk_start_queue - restart a previously stopped queue
356 * @q: The &struct request_queue in question
359 * blk_start_queue() will clear the stop flag on the queue, and call
360 * the request_fn for the queue if it was in a stopped state when
361 * entered. Also see blk_stop_queue(). Queue lock must be held.
363 void blk_start_queue(struct request_queue *q)
365 WARN_ON(!irqs_disabled());
367 queue_flag_clear(QUEUE_FLAG_STOPPED, q);
368 blk_invoke_request_fn(q);
370 EXPORT_SYMBOL(blk_start_queue);
373 * blk_stop_queue - stop a queue
374 * @q: The &struct request_queue in question
377 * The Linux block layer assumes that a block driver will consume all
378 * entries on the request queue when the request_fn strategy is called.
379 * Often this will not happen, because of hardware limitations (queue
380 * depth settings). If a device driver gets a 'queue full' response,
381 * or if it simply chooses not to queue more I/O at one point, it can
382 * call this function to prevent the request_fn from being called until
383 * the driver has signalled it's ready to go again. This happens by calling
384 * blk_start_queue() to restart queue operations. Queue lock must be held.
386 void blk_stop_queue(struct request_queue *q)
389 queue_flag_set(QUEUE_FLAG_STOPPED, q);
391 EXPORT_SYMBOL(blk_stop_queue);
394 * blk_sync_queue - cancel any pending callbacks on a queue
398 * The block layer may perform asynchronous callback activity
399 * on a queue, such as calling the unplug function after a timeout.
400 * A block device may call blk_sync_queue to ensure that any
401 * such activity is cancelled, thus allowing it to release resources
402 * that the callbacks might use. The caller must already have made sure
403 * that its ->make_request_fn will not re-add plugging prior to calling
407 void blk_sync_queue(struct request_queue *q)
409 del_timer_sync(&q->unplug_timer);
410 del_timer_sync(&q->timeout);
411 cancel_work_sync(&q->unplug_work);
413 EXPORT_SYMBOL(blk_sync_queue);
416 * __blk_run_queue - run a single device queue
417 * @q: The queue to run
420 * See @blk_run_queue. This variant must be called with the queue lock
421 * held and interrupts disabled.
424 void __blk_run_queue(struct request_queue *q)
429 * Only recurse once to avoid overrunning the stack, let the unplug
430 * handling reinvoke the handler shortly if we already got there.
432 if (!elv_queue_empty(q))
433 blk_invoke_request_fn(q);
435 EXPORT_SYMBOL(__blk_run_queue);
438 * blk_run_queue - run a single device queue
439 * @q: The queue to run
442 * Invoke request handling on this queue, if it has pending work to do.
443 * May be used to restart queueing when a request has completed. Also
444 * See @blk_start_queueing.
447 void blk_run_queue(struct request_queue *q)
451 spin_lock_irqsave(q->queue_lock, flags);
453 spin_unlock_irqrestore(q->queue_lock, flags);
455 EXPORT_SYMBOL(blk_run_queue);
457 void blk_put_queue(struct request_queue *q)
459 kobject_put(&q->kobj);
462 void blk_cleanup_queue(struct request_queue *q)
465 * We know we have process context here, so we can be a little
466 * cautious and ensure that pending block actions on this device
467 * are done before moving on. Going into this function, we should
468 * not have processes doing IO to this device.
472 mutex_lock(&q->sysfs_lock);
473 queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
474 mutex_unlock(&q->sysfs_lock);
477 elevator_exit(q->elevator);
481 EXPORT_SYMBOL(blk_cleanup_queue);
483 static int blk_init_free_list(struct request_queue *q)
485 struct request_list *rl = &q->rq;
487 rl->count[READ] = rl->count[WRITE] = 0;
488 rl->starved[READ] = rl->starved[WRITE] = 0;
490 init_waitqueue_head(&rl->wait[READ]);
491 init_waitqueue_head(&rl->wait[WRITE]);
493 rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
494 mempool_free_slab, request_cachep, q->node);
502 struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
504 return blk_alloc_queue_node(gfp_mask, -1);
506 EXPORT_SYMBOL(blk_alloc_queue);
508 struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
510 struct request_queue *q;
513 q = kmem_cache_alloc_node(blk_requestq_cachep,
514 gfp_mask | __GFP_ZERO, node_id);
518 q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug;
519 q->backing_dev_info.unplug_io_data = q;
520 err = bdi_init(&q->backing_dev_info);
522 kmem_cache_free(blk_requestq_cachep, q);
526 init_timer(&q->unplug_timer);
527 setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
528 INIT_LIST_HEAD(&q->timeout_list);
529 INIT_WORK(&q->unplug_work, blk_unplug_work);
531 kobject_init(&q->kobj, &blk_queue_ktype);
533 mutex_init(&q->sysfs_lock);
534 spin_lock_init(&q->__queue_lock);
538 EXPORT_SYMBOL(blk_alloc_queue_node);
541 * blk_init_queue - prepare a request queue for use with a block device
542 * @rfn: The function to be called to process requests that have been
543 * placed on the queue.
544 * @lock: Request queue spin lock
547 * If a block device wishes to use the standard request handling procedures,
548 * which sorts requests and coalesces adjacent requests, then it must
549 * call blk_init_queue(). The function @rfn will be called when there
550 * are requests on the queue that need to be processed. If the device
551 * supports plugging, then @rfn may not be called immediately when requests
552 * are available on the queue, but may be called at some time later instead.
553 * Plugged queues are generally unplugged when a buffer belonging to one
554 * of the requests on the queue is needed, or due to memory pressure.
556 * @rfn is not required, or even expected, to remove all requests off the
557 * queue, but only as many as it can handle at a time. If it does leave
558 * requests on the queue, it is responsible for arranging that the requests
559 * get dealt with eventually.
561 * The queue spin lock must be held while manipulating the requests on the
562 * request queue; this lock will be taken also from interrupt context, so irq
563 * disabling is needed for it.
565 * Function returns a pointer to the initialized request queue, or %NULL if
569 * blk_init_queue() must be paired with a blk_cleanup_queue() call
570 * when the block device is deactivated (such as at module unload).
573 struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
575 return blk_init_queue_node(rfn, lock, -1);
577 EXPORT_SYMBOL(blk_init_queue);
579 struct request_queue *
580 blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
582 struct request_queue *q = blk_alloc_queue_node(GFP_KERNEL, node_id);
588 if (blk_init_free_list(q)) {
589 kmem_cache_free(blk_requestq_cachep, q);
594 * if caller didn't supply a lock, they get per-queue locking with
598 lock = &q->__queue_lock;
601 q->prep_rq_fn = NULL;
602 q->unplug_fn = generic_unplug_device;
603 q->queue_flags = QUEUE_FLAG_DEFAULT;
604 q->queue_lock = lock;
607 * This also sets hw/phys segments, boundary and size
609 blk_queue_make_request(q, __make_request);
611 q->sg_reserved_size = INT_MAX;
613 blk_set_cmd_filter_defaults(&q->cmd_filter);
618 if (!elevator_init(q, NULL)) {
619 blk_queue_congestion_threshold(q);
626 EXPORT_SYMBOL(blk_init_queue_node);
628 int blk_get_queue(struct request_queue *q)
630 if (likely(!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
631 kobject_get(&q->kobj);
638 static inline void blk_free_request(struct request_queue *q, struct request *rq)
640 if (rq->cmd_flags & REQ_ELVPRIV)
641 elv_put_request(q, rq);
642 mempool_free(rq, q->rq.rq_pool);
645 static struct request *
646 blk_alloc_request(struct request_queue *q, int rw, int priv, gfp_t gfp_mask)
648 struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
655 rq->cmd_flags = rw | REQ_ALLOCED;
658 if (unlikely(elv_set_request(q, rq, gfp_mask))) {
659 mempool_free(rq, q->rq.rq_pool);
662 rq->cmd_flags |= REQ_ELVPRIV;
669 * ioc_batching returns true if the ioc is a valid batching request and
670 * should be given priority access to a request.
672 static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
678 * Make sure the process is able to allocate at least 1 request
679 * even if the batch times out, otherwise we could theoretically
682 return ioc->nr_batch_requests == q->nr_batching ||
683 (ioc->nr_batch_requests > 0
684 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
688 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
689 * will cause the process to be a "batcher" on all queues in the system. This
690 * is the behaviour we want though - once it gets a wakeup it should be given
693 static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
695 if (!ioc || ioc_batching(q, ioc))
698 ioc->nr_batch_requests = q->nr_batching;
699 ioc->last_waited = jiffies;
702 static void __freed_request(struct request_queue *q, int rw)
704 struct request_list *rl = &q->rq;
706 if (rl->count[rw] < queue_congestion_off_threshold(q))
707 blk_clear_queue_congested(q, rw);
709 if (rl->count[rw] + 1 <= q->nr_requests) {
710 if (waitqueue_active(&rl->wait[rw]))
711 wake_up(&rl->wait[rw]);
713 blk_clear_queue_full(q, rw);
718 * A request has just been released. Account for it, update the full and
719 * congestion status, wake up any waiters. Called under q->queue_lock.
721 static void freed_request(struct request_queue *q, int rw, int priv)
723 struct request_list *rl = &q->rq;
729 __freed_request(q, rw);
731 if (unlikely(rl->starved[rw ^ 1]))
732 __freed_request(q, rw ^ 1);
735 #define blkdev_free_rq(list) list_entry((list)->next, struct request, queuelist)
737 * Get a free request, queue_lock must be held.
738 * Returns NULL on failure, with queue_lock held.
739 * Returns !NULL on success, with queue_lock *not held*.
741 static struct request *get_request(struct request_queue *q, int rw_flags,
742 struct bio *bio, gfp_t gfp_mask)
744 struct request *rq = NULL;
745 struct request_list *rl = &q->rq;
746 struct io_context *ioc = NULL;
747 const int rw = rw_flags & 0x01;
750 may_queue = elv_may_queue(q, rw_flags);
751 if (may_queue == ELV_MQUEUE_NO)
754 if (rl->count[rw]+1 >= queue_congestion_on_threshold(q)) {
755 if (rl->count[rw]+1 >= q->nr_requests) {
756 ioc = current_io_context(GFP_ATOMIC, q->node);
758 * The queue will fill after this allocation, so set
759 * it as full, and mark this process as "batching".
760 * This process will be allowed to complete a batch of
761 * requests, others will be blocked.
763 if (!blk_queue_full(q, rw)) {
764 ioc_set_batching(q, ioc);
765 blk_set_queue_full(q, rw);
767 if (may_queue != ELV_MQUEUE_MUST
768 && !ioc_batching(q, ioc)) {
770 * The queue is full and the allocating
771 * process is not a "batcher", and not
772 * exempted by the IO scheduler
778 blk_set_queue_congested(q, rw);
782 * Only allow batching queuers to allocate up to 50% over the defined
783 * limit of requests, otherwise we could have thousands of requests
784 * allocated with any setting of ->nr_requests
786 if (rl->count[rw] >= (3 * q->nr_requests / 2))
792 priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
796 spin_unlock_irq(q->queue_lock);
798 rq = blk_alloc_request(q, rw_flags, priv, gfp_mask);
801 * Allocation failed presumably due to memory. Undo anything
802 * we might have messed up.
804 * Allocating task should really be put onto the front of the
805 * wait queue, but this is pretty rare.
807 spin_lock_irq(q->queue_lock);
808 freed_request(q, rw, priv);
811 * in the very unlikely event that allocation failed and no
812 * requests for this direction was pending, mark us starved
813 * so that freeing of a request in the other direction will
814 * notice us. another possible fix would be to split the
815 * rq mempool into READ and WRITE
818 if (unlikely(rl->count[rw] == 0))
825 * ioc may be NULL here, and ioc_batching will be false. That's
826 * OK, if the queue is under the request limit then requests need
827 * not count toward the nr_batch_requests limit. There will always
828 * be some limit enforced by BLK_BATCH_TIME.
830 if (ioc_batching(q, ioc))
831 ioc->nr_batch_requests--;
833 trace_block_getrq(q, bio, rw);
839 * No available requests for this queue, unplug the device and wait for some
840 * requests to become available.
842 * Called with q->queue_lock held, and returns with it unlocked.
844 static struct request *get_request_wait(struct request_queue *q, int rw_flags,
847 const int rw = rw_flags & 0x01;
850 rq = get_request(q, rw_flags, bio, GFP_NOIO);
853 struct io_context *ioc;
854 struct request_list *rl = &q->rq;
856 prepare_to_wait_exclusive(&rl->wait[rw], &wait,
857 TASK_UNINTERRUPTIBLE);
859 trace_block_sleeprq(q, bio, rw);
861 __generic_unplug_device(q);
862 spin_unlock_irq(q->queue_lock);
866 * After sleeping, we become a "batching" process and
867 * will be able to allocate at least one request, and
868 * up to a big batch of them for a small period time.
869 * See ioc_batching, ioc_set_batching
871 ioc = current_io_context(GFP_NOIO, q->node);
872 ioc_set_batching(q, ioc);
874 spin_lock_irq(q->queue_lock);
875 finish_wait(&rl->wait[rw], &wait);
877 rq = get_request(q, rw_flags, bio, GFP_NOIO);
883 struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
887 BUG_ON(rw != READ && rw != WRITE);
889 spin_lock_irq(q->queue_lock);
890 if (gfp_mask & __GFP_WAIT) {
891 rq = get_request_wait(q, rw, NULL);
893 rq = get_request(q, rw, NULL, gfp_mask);
895 spin_unlock_irq(q->queue_lock);
897 /* q->queue_lock is unlocked at this point */
901 EXPORT_SYMBOL(blk_get_request);
904 * blk_start_queueing - initiate dispatch of requests to device
905 * @q: request queue to kick into gear
907 * This is basically a helper to remove the need to know whether a queue
908 * is plugged or not if someone just wants to initiate dispatch of requests
909 * for this queue. Should be used to start queueing on a device outside
910 * of ->request_fn() context. Also see @blk_run_queue.
912 * The queue lock must be held with interrupts disabled.
914 void blk_start_queueing(struct request_queue *q)
916 if (!blk_queue_plugged(q)) {
917 if (unlikely(blk_queue_stopped(q)))
921 __generic_unplug_device(q);
923 EXPORT_SYMBOL(blk_start_queueing);
926 * blk_requeue_request - put a request back on queue
927 * @q: request queue where request should be inserted
928 * @rq: request to be inserted
931 * Drivers often keep queueing requests until the hardware cannot accept
932 * more, when that condition happens we need to put the request back
933 * on the queue. Must be called with queue lock held.
935 void blk_requeue_request(struct request_queue *q, struct request *rq)
937 blk_delete_timer(rq);
938 blk_clear_rq_complete(rq);
939 trace_block_rq_requeue(q, rq);
941 if (blk_rq_tagged(rq))
942 blk_queue_end_tag(q, rq);
944 elv_requeue_request(q, rq);
946 EXPORT_SYMBOL(blk_requeue_request);
949 * blk_insert_request - insert a special request into a request queue
950 * @q: request queue where request should be inserted
951 * @rq: request to be inserted
952 * @at_head: insert request at head or tail of queue
953 * @data: private data
956 * Many block devices need to execute commands asynchronously, so they don't
957 * block the whole kernel from preemption during request execution. This is
958 * accomplished normally by inserting aritficial requests tagged as
959 * REQ_TYPE_SPECIAL in to the corresponding request queue, and letting them
960 * be scheduled for actual execution by the request queue.
962 * We have the option of inserting the head or the tail of the queue.
963 * Typically we use the tail for new ioctls and so forth. We use the head
964 * of the queue for things like a QUEUE_FULL message from a device, or a
965 * host that is unable to accept a particular command.
967 void blk_insert_request(struct request_queue *q, struct request *rq,
968 int at_head, void *data)
970 int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
974 * tell I/O scheduler that this isn't a regular read/write (ie it
975 * must not attempt merges on this) and that it acts as a soft
978 rq->cmd_type = REQ_TYPE_SPECIAL;
979 rq->cmd_flags |= REQ_SOFTBARRIER;
983 spin_lock_irqsave(q->queue_lock, flags);
986 * If command is tagged, release the tag
988 if (blk_rq_tagged(rq))
989 blk_queue_end_tag(q, rq);
991 drive_stat_acct(rq, 1);
992 __elv_add_request(q, rq, where, 0);
993 blk_start_queueing(q);
994 spin_unlock_irqrestore(q->queue_lock, flags);
996 EXPORT_SYMBOL(blk_insert_request);
999 * add-request adds a request to the linked list.
1000 * queue lock is held and interrupts disabled, as we muck with the
1001 * request queue list.
1003 static inline void add_request(struct request_queue *q, struct request *req)
1005 drive_stat_acct(req, 1);
1008 * elevator indicated where it wants this request to be
1009 * inserted at elevator_merge time
1011 __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
1014 static void part_round_stats_single(int cpu, struct hd_struct *part,
1017 if (now == part->stamp)
1020 if (part->in_flight) {
1021 __part_stat_add(cpu, part, time_in_queue,
1022 part->in_flight * (now - part->stamp));
1023 __part_stat_add(cpu, part, io_ticks, (now - part->stamp));
1029 * part_round_stats() - Round off the performance stats on a struct disk_stats.
1030 * @cpu: cpu number for stats access
1031 * @part: target partition
1033 * The average IO queue length and utilisation statistics are maintained
1034 * by observing the current state of the queue length and the amount of
1035 * time it has been in this state for.
1037 * Normally, that accounting is done on IO completion, but that can result
1038 * in more than a second's worth of IO being accounted for within any one
1039 * second, leading to >100% utilisation. To deal with that, we call this
1040 * function to do a round-off before returning the results when reading
1041 * /proc/diskstats. This accounts immediately for all queue usage up to
1042 * the current jiffies and restarts the counters again.
1044 void part_round_stats(int cpu, struct hd_struct *part)
1046 unsigned long now = jiffies;
1049 part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1050 part_round_stats_single(cpu, part, now);
1052 EXPORT_SYMBOL_GPL(part_round_stats);
1055 * queue lock must be held
1057 void __blk_put_request(struct request_queue *q, struct request *req)
1061 if (unlikely(--req->ref_count))
1064 elv_completed_request(q, req);
1067 * Request may not have originated from ll_rw_blk. if not,
1068 * it didn't come out of our reserved rq pools
1070 if (req->cmd_flags & REQ_ALLOCED) {
1071 int rw = rq_data_dir(req);
1072 int priv = req->cmd_flags & REQ_ELVPRIV;
1074 BUG_ON(!list_empty(&req->queuelist));
1075 BUG_ON(!hlist_unhashed(&req->hash));
1077 blk_free_request(q, req);
1078 freed_request(q, rw, priv);
1081 EXPORT_SYMBOL_GPL(__blk_put_request);
1083 void blk_put_request(struct request *req)
1085 unsigned long flags;
1086 struct request_queue *q = req->q;
1088 spin_lock_irqsave(q->queue_lock, flags);
1089 __blk_put_request(q, req);
1090 spin_unlock_irqrestore(q->queue_lock, flags);
1092 EXPORT_SYMBOL(blk_put_request);
1094 void init_request_from_bio(struct request *req, struct bio *bio)
1096 req->cpu = bio->bi_comp_cpu;
1097 req->cmd_type = REQ_TYPE_FS;
1100 * inherit FAILFAST from bio (for read-ahead, and explicit FAILFAST)
1102 if (bio_rw_ahead(bio))
1103 req->cmd_flags |= (REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
1104 REQ_FAILFAST_DRIVER);
1105 if (bio_failfast_dev(bio))
1106 req->cmd_flags |= REQ_FAILFAST_DEV;
1107 if (bio_failfast_transport(bio))
1108 req->cmd_flags |= REQ_FAILFAST_TRANSPORT;
1109 if (bio_failfast_driver(bio))
1110 req->cmd_flags |= REQ_FAILFAST_DRIVER;
1113 * REQ_BARRIER implies no merging, but lets make it explicit
1115 if (unlikely(bio_discard(bio))) {
1116 req->cmd_flags |= REQ_DISCARD;
1117 if (bio_barrier(bio))
1118 req->cmd_flags |= REQ_SOFTBARRIER;
1119 req->q->prepare_discard_fn(req->q, req);
1120 } else if (unlikely(bio_barrier(bio)))
1121 req->cmd_flags |= (REQ_HARDBARRIER | REQ_NOMERGE);
1124 req->cmd_flags |= REQ_RW_SYNC;
1125 if (bio_unplug(bio))
1126 req->cmd_flags |= REQ_UNPLUG;
1127 if (bio_rw_meta(bio))
1128 req->cmd_flags |= REQ_RW_META;
1131 req->hard_sector = req->sector = bio->bi_sector;
1132 req->ioprio = bio_prio(bio);
1133 req->start_time = jiffies;
1134 blk_rq_bio_prep(req->q, req, bio);
1137 static int __make_request(struct request_queue *q, struct bio *bio)
1139 struct request *req;
1140 int el_ret, nr_sectors;
1141 const unsigned short prio = bio_prio(bio);
1142 const int sync = bio_sync(bio);
1143 const int unplug = bio_unplug(bio);
1146 nr_sectors = bio_sectors(bio);
1149 * low level driver can indicate that it wants pages above a
1150 * certain limit bounced to low memory (ie for highmem, or even
1151 * ISA dma in theory)
1153 blk_queue_bounce(q, &bio);
1155 spin_lock_irq(q->queue_lock);
1157 if (unlikely(bio_barrier(bio)) || elv_queue_empty(q))
1160 el_ret = elv_merge(q, &req, bio);
1162 case ELEVATOR_BACK_MERGE:
1163 BUG_ON(!rq_mergeable(req));
1165 if (!ll_back_merge_fn(q, req, bio))
1168 trace_block_bio_backmerge(q, bio);
1170 req->biotail->bi_next = bio;
1172 req->nr_sectors = req->hard_nr_sectors += nr_sectors;
1173 req->ioprio = ioprio_best(req->ioprio, prio);
1174 if (!blk_rq_cpu_valid(req))
1175 req->cpu = bio->bi_comp_cpu;
1176 drive_stat_acct(req, 0);
1177 if (!attempt_back_merge(q, req))
1178 elv_merged_request(q, req, el_ret);
1181 case ELEVATOR_FRONT_MERGE:
1182 BUG_ON(!rq_mergeable(req));
1184 if (!ll_front_merge_fn(q, req, bio))
1187 trace_block_bio_frontmerge(q, bio);
1189 bio->bi_next = req->bio;
1193 * may not be valid. if the low level driver said
1194 * it didn't need a bounce buffer then it better
1195 * not touch req->buffer either...
1197 req->buffer = bio_data(bio);
1198 req->current_nr_sectors = bio_cur_sectors(bio);
1199 req->hard_cur_sectors = req->current_nr_sectors;
1200 req->sector = req->hard_sector = bio->bi_sector;
1201 req->nr_sectors = req->hard_nr_sectors += nr_sectors;
1202 req->ioprio = ioprio_best(req->ioprio, prio);
1203 if (!blk_rq_cpu_valid(req))
1204 req->cpu = bio->bi_comp_cpu;
1205 drive_stat_acct(req, 0);
1206 if (!attempt_front_merge(q, req))
1207 elv_merged_request(q, req, el_ret);
1210 /* ELV_NO_MERGE: elevator says don't/can't merge. */
1217 * This sync check and mask will be re-done in init_request_from_bio(),
1218 * but we need to set it earlier to expose the sync flag to the
1219 * rq allocator and io schedulers.
1221 rw_flags = bio_data_dir(bio);
1223 rw_flags |= REQ_RW_SYNC;
1226 * Grab a free request. This is might sleep but can not fail.
1227 * Returns with the queue unlocked.
1229 req = get_request_wait(q, rw_flags, bio);
1232 * After dropping the lock and possibly sleeping here, our request
1233 * may now be mergeable after it had proven unmergeable (above).
1234 * We don't worry about that case for efficiency. It won't happen
1235 * often, and the elevators are able to handle it.
1237 init_request_from_bio(req, bio);
1239 spin_lock_irq(q->queue_lock);
1240 if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) ||
1241 bio_flagged(bio, BIO_CPU_AFFINE))
1242 req->cpu = blk_cpu_to_group(smp_processor_id());
1243 if (!blk_queue_nonrot(q) && elv_queue_empty(q))
1245 add_request(q, req);
1247 if (unplug || blk_queue_nonrot(q))
1248 __generic_unplug_device(q);
1249 spin_unlock_irq(q->queue_lock);
1254 * If bio->bi_dev is a partition, remap the location
1256 static inline void blk_partition_remap(struct bio *bio)
1258 struct block_device *bdev = bio->bi_bdev;
1260 if (bio_sectors(bio) && bdev != bdev->bd_contains) {
1261 struct hd_struct *p = bdev->bd_part;
1263 bio->bi_sector += p->start_sect;
1264 bio->bi_bdev = bdev->bd_contains;
1266 trace_block_remap(bdev_get_queue(bio->bi_bdev), bio,
1267 bdev->bd_dev, bio->bi_sector,
1268 bio->bi_sector - p->start_sect);
1272 static void handle_bad_sector(struct bio *bio)
1274 char b[BDEVNAME_SIZE];
1276 printk(KERN_INFO "attempt to access beyond end of device\n");
1277 printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
1278 bdevname(bio->bi_bdev, b),
1280 (unsigned long long)bio->bi_sector + bio_sectors(bio),
1281 (long long)(bio->bi_bdev->bd_inode->i_size >> 9));
1283 set_bit(BIO_EOF, &bio->bi_flags);
1286 #ifdef CONFIG_FAIL_MAKE_REQUEST
1288 static DECLARE_FAULT_ATTR(fail_make_request);
1290 static int __init setup_fail_make_request(char *str)
1292 return setup_fault_attr(&fail_make_request, str);
1294 __setup("fail_make_request=", setup_fail_make_request);
1296 static int should_fail_request(struct bio *bio)
1298 struct hd_struct *part = bio->bi_bdev->bd_part;
1300 if (part_to_disk(part)->part0.make_it_fail || part->make_it_fail)
1301 return should_fail(&fail_make_request, bio->bi_size);
1306 static int __init fail_make_request_debugfs(void)
1308 return init_fault_attr_dentries(&fail_make_request,
1309 "fail_make_request");
1312 late_initcall(fail_make_request_debugfs);
1314 #else /* CONFIG_FAIL_MAKE_REQUEST */
1316 static inline int should_fail_request(struct bio *bio)
1321 #endif /* CONFIG_FAIL_MAKE_REQUEST */
1324 * Check whether this bio extends beyond the end of the device.
1326 static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1333 /* Test device or partition size, when known. */
1334 maxsector = bio->bi_bdev->bd_inode->i_size >> 9;
1336 sector_t sector = bio->bi_sector;
1338 if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1340 * This may well happen - the kernel calls bread()
1341 * without checking the size of the device, e.g., when
1342 * mounting a device.
1344 handle_bad_sector(bio);
1353 * generic_make_request - hand a buffer to its device driver for I/O
1354 * @bio: The bio describing the location in memory and on the device.
1356 * generic_make_request() is used to make I/O requests of block
1357 * devices. It is passed a &struct bio, which describes the I/O that needs
1360 * generic_make_request() does not return any status. The
1361 * success/failure status of the request, along with notification of
1362 * completion, is delivered asynchronously through the bio->bi_end_io
1363 * function described (one day) else where.
1365 * The caller of generic_make_request must make sure that bi_io_vec
1366 * are set to describe the memory buffer, and that bi_dev and bi_sector are
1367 * set to describe the device address, and the
1368 * bi_end_io and optionally bi_private are set to describe how
1369 * completion notification should be signaled.
1371 * generic_make_request and the drivers it calls may use bi_next if this
1372 * bio happens to be merged with someone else, and may change bi_dev and
1373 * bi_sector for remaps as it sees fit. So the values of these fields
1374 * should NOT be depended on after the call to generic_make_request.
1376 static inline void __generic_make_request(struct bio *bio)
1378 struct request_queue *q;
1379 sector_t old_sector;
1380 int ret, nr_sectors = bio_sectors(bio);
1386 if (bio_check_eod(bio, nr_sectors))
1390 * Resolve the mapping until finished. (drivers are
1391 * still free to implement/resolve their own stacking
1392 * by explicitly returning 0)
1394 * NOTE: we don't repeat the blk_size check for each new device.
1395 * Stacking drivers are expected to know what they are doing.
1400 char b[BDEVNAME_SIZE];
1402 q = bdev_get_queue(bio->bi_bdev);
1405 "generic_make_request: Trying to access "
1406 "nonexistent block-device %s (%Lu)\n",
1407 bdevname(bio->bi_bdev, b),
1408 (long long) bio->bi_sector);
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 trace_block_remap(q, bio, old_dev, bio->bi_sector,
1439 trace_block_bio_queue(q, bio);
1441 old_sector = bio->bi_sector;
1442 old_dev = bio->bi_bdev->bd_dev;
1444 if (bio_check_eod(bio, nr_sectors))
1447 if (bio_discard(bio) && !q->prepare_discard_fn) {
1451 if (bio_barrier(bio) && bio_has_data(bio) &&
1452 (q->next_ordered == QUEUE_ORDERED_NONE)) {
1457 ret = q->make_request_fn(q, bio);
1463 bio_endio(bio, err);
1467 * We only want one ->make_request_fn to be active at a time,
1468 * else stack usage with stacked devices could be a problem.
1469 * So use current->bio_{list,tail} to keep a list of requests
1470 * submited by a make_request_fn function.
1471 * current->bio_tail is also used as a flag to say if
1472 * generic_make_request is currently active in this task or not.
1473 * If it is NULL, then no make_request is active. If it is non-NULL,
1474 * then a make_request is active, and new requests should be added
1477 void generic_make_request(struct bio *bio)
1479 if (current->bio_tail) {
1480 /* make_request is active */
1481 *(current->bio_tail) = bio;
1482 bio->bi_next = NULL;
1483 current->bio_tail = &bio->bi_next;
1486 /* following loop may be a bit non-obvious, and so deserves some
1488 * Before entering the loop, bio->bi_next is NULL (as all callers
1489 * ensure that) so we have a list with a single bio.
1490 * We pretend that we have just taken it off a longer list, so
1491 * we assign bio_list to the next (which is NULL) and bio_tail
1492 * to &bio_list, thus initialising the bio_list of new bios to be
1493 * added. __generic_make_request may indeed add some more bios
1494 * through a recursive call to generic_make_request. If it
1495 * did, we find a non-NULL value in bio_list and re-enter the loop
1496 * from the top. In this case we really did just take the bio
1497 * of the top of the list (no pretending) and so fixup bio_list and
1498 * bio_tail or bi_next, and call into __generic_make_request again.
1500 * The loop was structured like this to make only one call to
1501 * __generic_make_request (which is important as it is large and
1502 * inlined) and to keep the structure simple.
1504 BUG_ON(bio->bi_next);
1506 current->bio_list = bio->bi_next;
1507 if (bio->bi_next == NULL)
1508 current->bio_tail = ¤t->bio_list;
1510 bio->bi_next = NULL;
1511 __generic_make_request(bio);
1512 bio = current->bio_list;
1514 current->bio_tail = NULL; /* deactivate */
1516 EXPORT_SYMBOL(generic_make_request);
1519 * submit_bio - submit a bio to the block device layer for I/O
1520 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1521 * @bio: The &struct bio which describes the I/O
1523 * submit_bio() is very similar in purpose to generic_make_request(), and
1524 * uses that function to do most of the work. Both are fairly rough
1525 * interfaces; @bio must be presetup and ready for I/O.
1528 void submit_bio(int rw, struct bio *bio)
1530 int count = bio_sectors(bio);
1535 * If it's a regular read/write or a barrier with data attached,
1536 * go through the normal accounting stuff before submission.
1538 if (bio_has_data(bio)) {
1540 count_vm_events(PGPGOUT, count);
1542 task_io_account_read(bio->bi_size);
1543 count_vm_events(PGPGIN, count);
1546 if (unlikely(block_dump)) {
1547 char b[BDEVNAME_SIZE];
1548 printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n",
1549 current->comm, task_pid_nr(current),
1550 (rw & WRITE) ? "WRITE" : "READ",
1551 (unsigned long long)bio->bi_sector,
1552 bdevname(bio->bi_bdev, b));
1556 generic_make_request(bio);
1558 EXPORT_SYMBOL(submit_bio);
1561 * blk_rq_check_limits - Helper function to check a request for the queue limit
1563 * @rq: the request being checked
1566 * @rq may have been made based on weaker limitations of upper-level queues
1567 * in request stacking drivers, and it may violate the limitation of @q.
1568 * Since the block layer and the underlying device driver trust @rq
1569 * after it is inserted to @q, it should be checked against @q before
1570 * the insertion using this generic function.
1572 * This function should also be useful for request stacking drivers
1573 * in some cases below, so export this fuction.
1574 * Request stacking drivers like request-based dm may change the queue
1575 * limits while requests are in the queue (e.g. dm's table swapping).
1576 * Such request stacking drivers should check those requests agaist
1577 * the new queue limits again when they dispatch those requests,
1578 * although such checkings are also done against the old queue limits
1579 * when submitting requests.
1581 int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1583 if (rq->nr_sectors > q->max_sectors ||
1584 rq->data_len > q->max_hw_sectors << 9) {
1585 printk(KERN_ERR "%s: over max size limit.\n", __func__);
1590 * queue's settings related to segment counting like q->bounce_pfn
1591 * may differ from that of other stacking queues.
1592 * Recalculate it to check the request correctly on this queue's
1595 blk_recalc_rq_segments(rq);
1596 if (rq->nr_phys_segments > q->max_phys_segments ||
1597 rq->nr_phys_segments > q->max_hw_segments) {
1598 printk(KERN_ERR "%s: over max segments limit.\n", __func__);
1604 EXPORT_SYMBOL_GPL(blk_rq_check_limits);
1607 * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1608 * @q: the queue to submit the request
1609 * @rq: the request being queued
1611 int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1613 unsigned long flags;
1615 if (blk_rq_check_limits(q, rq))
1618 #ifdef CONFIG_FAIL_MAKE_REQUEST
1619 if (rq->rq_disk && rq->rq_disk->part0.make_it_fail &&
1620 should_fail(&fail_make_request, blk_rq_bytes(rq)))
1624 spin_lock_irqsave(q->queue_lock, flags);
1627 * Submitting request must be dequeued before calling this function
1628 * because it will be linked to another request_queue
1630 BUG_ON(blk_queued_rq(rq));
1632 drive_stat_acct(rq, 1);
1633 __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0);
1635 spin_unlock_irqrestore(q->queue_lock, flags);
1639 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
1642 * blkdev_dequeue_request - dequeue request and start timeout timer
1643 * @req: request to dequeue
1645 * Dequeue @req and start timeout timer on it. This hands off the
1646 * request to the driver.
1648 * Block internal functions which don't want to start timer should
1649 * call elv_dequeue_request().
1651 void blkdev_dequeue_request(struct request *req)
1653 elv_dequeue_request(req->q, req);
1656 * We are now handing the request to the hardware, add the
1661 EXPORT_SYMBOL(blkdev_dequeue_request);
1663 static void blk_account_io_completion(struct request *req, unsigned int bytes)
1665 struct gendisk *disk = req->rq_disk;
1667 if (!disk || !blk_do_io_stat(disk->queue))
1670 if (blk_fs_request(req)) {
1671 const int rw = rq_data_dir(req);
1672 struct hd_struct *part;
1675 cpu = part_stat_lock();
1676 part = disk_map_sector_rcu(req->rq_disk, req->sector);
1677 part_stat_add(cpu, part, sectors[rw], bytes >> 9);
1682 static void blk_account_io_done(struct request *req)
1684 struct gendisk *disk = req->rq_disk;
1686 if (!disk || !blk_do_io_stat(disk->queue))
1690 * Account IO completion. bar_rq isn't accounted as a normal
1691 * IO on queueing nor completion. Accounting the containing
1692 * request is enough.
1694 if (blk_fs_request(req) && req != &req->q->bar_rq) {
1695 unsigned long duration = jiffies - req->start_time;
1696 const int rw = rq_data_dir(req);
1697 struct hd_struct *part;
1700 cpu = part_stat_lock();
1701 part = disk_map_sector_rcu(disk, req->sector);
1703 part_stat_inc(cpu, part, ios[rw]);
1704 part_stat_add(cpu, part, ticks[rw], duration);
1705 part_round_stats(cpu, part);
1706 part_dec_in_flight(part);
1713 * __end_that_request_first - end I/O on a request
1714 * @req: the request being processed
1715 * @error: %0 for success, < %0 for error
1716 * @nr_bytes: number of bytes to complete
1719 * Ends I/O on a number of bytes attached to @req, and sets it up
1720 * for the next range of segments (if any) in the cluster.
1723 * %0 - we are done with this request, call end_that_request_last()
1724 * %1 - still buffers pending for this request
1726 static int __end_that_request_first(struct request *req, int error,
1729 int total_bytes, bio_nbytes, next_idx = 0;
1732 trace_block_rq_complete(req->q, req);
1735 * for a REQ_TYPE_BLOCK_PC request, we want to carry any eventual
1736 * sense key with us all the way through
1738 if (!blk_pc_request(req))
1741 if (error && (blk_fs_request(req) && !(req->cmd_flags & REQ_QUIET))) {
1742 printk(KERN_ERR "end_request: I/O error, dev %s, sector %llu\n",
1743 req->rq_disk ? req->rq_disk->disk_name : "?",
1744 (unsigned long long)req->sector);
1747 blk_account_io_completion(req, nr_bytes);
1749 total_bytes = bio_nbytes = 0;
1750 while ((bio = req->bio) != NULL) {
1753 if (nr_bytes >= bio->bi_size) {
1754 req->bio = bio->bi_next;
1755 nbytes = bio->bi_size;
1756 req_bio_endio(req, bio, nbytes, error);
1760 int idx = bio->bi_idx + next_idx;
1762 if (unlikely(bio->bi_idx >= bio->bi_vcnt)) {
1763 blk_dump_rq_flags(req, "__end_that");
1764 printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
1765 __func__, bio->bi_idx, bio->bi_vcnt);
1769 nbytes = bio_iovec_idx(bio, idx)->bv_len;
1770 BIO_BUG_ON(nbytes > bio->bi_size);
1773 * not a complete bvec done
1775 if (unlikely(nbytes > nr_bytes)) {
1776 bio_nbytes += nr_bytes;
1777 total_bytes += nr_bytes;
1782 * advance to the next vector
1785 bio_nbytes += nbytes;
1788 total_bytes += nbytes;
1794 * end more in this run, or just return 'not-done'
1796 if (unlikely(nr_bytes <= 0))
1808 * if the request wasn't completed, update state
1811 req_bio_endio(req, bio, bio_nbytes, error);
1812 bio->bi_idx += next_idx;
1813 bio_iovec(bio)->bv_offset += nr_bytes;
1814 bio_iovec(bio)->bv_len -= nr_bytes;
1817 blk_recalc_rq_sectors(req, total_bytes >> 9);
1818 blk_recalc_rq_segments(req);
1823 * queue lock must be held
1825 static void end_that_request_last(struct request *req, int error)
1827 if (blk_rq_tagged(req))
1828 blk_queue_end_tag(req->q, req);
1830 if (blk_queued_rq(req))
1831 elv_dequeue_request(req->q, req);
1833 if (unlikely(laptop_mode) && blk_fs_request(req))
1834 laptop_io_completion();
1836 blk_delete_timer(req);
1838 blk_account_io_done(req);
1841 req->end_io(req, error);
1843 if (blk_bidi_rq(req))
1844 __blk_put_request(req->next_rq->q, req->next_rq);
1846 __blk_put_request(req->q, req);
1851 * blk_rq_bytes - Returns bytes left to complete in the entire request
1852 * @rq: the request being processed
1854 unsigned int blk_rq_bytes(struct request *rq)
1856 if (blk_fs_request(rq))
1857 return rq->hard_nr_sectors << 9;
1859 return rq->data_len;
1861 EXPORT_SYMBOL_GPL(blk_rq_bytes);
1864 * blk_rq_cur_bytes - Returns bytes left to complete in the current segment
1865 * @rq: the request being processed
1867 unsigned int blk_rq_cur_bytes(struct request *rq)
1869 if (blk_fs_request(rq))
1870 return rq->current_nr_sectors << 9;
1873 return rq->bio->bi_size;
1875 return rq->data_len;
1877 EXPORT_SYMBOL_GPL(blk_rq_cur_bytes);
1880 * end_request - end I/O on the current segment of the request
1881 * @req: the request being processed
1882 * @uptodate: error value or %0/%1 uptodate flag
1885 * Ends I/O on the current segment of a request. If that is the only
1886 * remaining segment, the request is also completed and freed.
1888 * This is a remnant of how older block drivers handled I/O completions.
1889 * Modern drivers typically end I/O on the full request in one go, unless
1890 * they have a residual value to account for. For that case this function
1891 * isn't really useful, unless the residual just happens to be the
1892 * full current segment. In other words, don't use this function in new
1893 * code. Use blk_end_request() or __blk_end_request() to end a request.
1895 void end_request(struct request *req, int uptodate)
1900 error = uptodate ? uptodate : -EIO;
1902 __blk_end_request(req, error, req->hard_cur_sectors << 9);
1904 EXPORT_SYMBOL(end_request);
1906 static int end_that_request_data(struct request *rq, int error,
1907 unsigned int nr_bytes, unsigned int bidi_bytes)
1910 if (__end_that_request_first(rq, error, nr_bytes))
1913 /* Bidi request must be completed as a whole */
1914 if (blk_bidi_rq(rq) &&
1915 __end_that_request_first(rq->next_rq, error, bidi_bytes))
1923 * blk_end_io - Generic end_io function to complete a request.
1924 * @rq: the request being processed
1925 * @error: %0 for success, < %0 for error
1926 * @nr_bytes: number of bytes to complete @rq
1927 * @bidi_bytes: number of bytes to complete @rq->next_rq
1928 * @drv_callback: function called between completion of bios in the request
1929 * and completion of the request.
1930 * If the callback returns non %0, this helper returns without
1931 * completion of the request.
1934 * Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
1935 * If @rq has leftover, sets it up for the next range of segments.
1938 * %0 - we are done with this request
1939 * %1 - this request is not freed yet, it still has pending buffers.
1941 static int blk_end_io(struct request *rq, int error, unsigned int nr_bytes,
1942 unsigned int bidi_bytes,
1943 int (drv_callback)(struct request *))
1945 struct request_queue *q = rq->q;
1946 unsigned long flags = 0UL;
1948 if (end_that_request_data(rq, error, nr_bytes, bidi_bytes))
1951 /* Special feature for tricky drivers */
1952 if (drv_callback && drv_callback(rq))
1955 add_disk_randomness(rq->rq_disk);
1957 spin_lock_irqsave(q->queue_lock, flags);
1958 end_that_request_last(rq, error);
1959 spin_unlock_irqrestore(q->queue_lock, flags);
1965 * blk_end_request - Helper function for drivers to complete the request.
1966 * @rq: the request being processed
1967 * @error: %0 for success, < %0 for error
1968 * @nr_bytes: number of bytes to complete
1971 * Ends I/O on a number of bytes attached to @rq.
1972 * If @rq has leftover, sets it up for the next range of segments.
1975 * %0 - we are done with this request
1976 * %1 - still buffers pending for this request
1978 int blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
1980 return blk_end_io(rq, error, nr_bytes, 0, NULL);
1982 EXPORT_SYMBOL_GPL(blk_end_request);
1985 * __blk_end_request - Helper function for drivers to complete the request.
1986 * @rq: the request being processed
1987 * @error: %0 for success, < %0 for error
1988 * @nr_bytes: number of bytes to complete
1991 * Must be called with queue lock held unlike blk_end_request().
1994 * %0 - we are done with this request
1995 * %1 - still buffers pending for this request
1997 int __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
1999 if (rq->bio && __end_that_request_first(rq, error, nr_bytes))
2002 add_disk_randomness(rq->rq_disk);
2004 end_that_request_last(rq, error);
2008 EXPORT_SYMBOL_GPL(__blk_end_request);
2011 * blk_end_bidi_request - Helper function for drivers to complete bidi request.
2012 * @rq: the bidi request being processed
2013 * @error: %0 for success, < %0 for error
2014 * @nr_bytes: number of bytes to complete @rq
2015 * @bidi_bytes: number of bytes to complete @rq->next_rq
2018 * Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2021 * %0 - we are done with this request
2022 * %1 - still buffers pending for this request
2024 int blk_end_bidi_request(struct request *rq, int error, unsigned int nr_bytes,
2025 unsigned int bidi_bytes)
2027 return blk_end_io(rq, error, nr_bytes, bidi_bytes, NULL);
2029 EXPORT_SYMBOL_GPL(blk_end_bidi_request);
2032 * blk_update_request - Special helper function for request stacking drivers
2033 * @rq: the request being processed
2034 * @error: %0 for success, < %0 for error
2035 * @nr_bytes: number of bytes to complete @rq
2038 * Ends I/O on a number of bytes attached to @rq, but doesn't complete
2039 * the request structure even if @rq doesn't have leftover.
2040 * If @rq has leftover, sets it up for the next range of segments.
2042 * This special helper function is only for request stacking drivers
2043 * (e.g. request-based dm) so that they can handle partial completion.
2044 * Actual device drivers should use blk_end_request instead.
2046 void blk_update_request(struct request *rq, int error, unsigned int nr_bytes)
2048 if (!end_that_request_data(rq, error, nr_bytes, 0)) {
2050 * These members are not updated in end_that_request_data()
2051 * when all bios are completed.
2052 * Update them so that the request stacking driver can find
2053 * how many bytes remain in the request later.
2055 rq->nr_sectors = rq->hard_nr_sectors = 0;
2056 rq->current_nr_sectors = rq->hard_cur_sectors = 0;
2059 EXPORT_SYMBOL_GPL(blk_update_request);
2062 * blk_end_request_callback - Special helper function for tricky drivers
2063 * @rq: the request being processed
2064 * @error: %0 for success, < %0 for error
2065 * @nr_bytes: number of bytes to complete
2066 * @drv_callback: function called between completion of bios in the request
2067 * and completion of the request.
2068 * If the callback returns non %0, this helper returns without
2069 * completion of the request.
2072 * Ends I/O on a number of bytes attached to @rq.
2073 * If @rq has leftover, sets it up for the next range of segments.
2075 * This special helper function is used only for existing tricky drivers.
2076 * (e.g. cdrom_newpc_intr() of ide-cd)
2077 * This interface will be removed when such drivers are rewritten.
2078 * Don't use this interface in other places anymore.
2081 * %0 - we are done with this request
2082 * %1 - this request is not freed yet.
2083 * this request still has pending buffers or
2084 * the driver doesn't want to finish this request yet.
2086 int blk_end_request_callback(struct request *rq, int error,
2087 unsigned int nr_bytes,
2088 int (drv_callback)(struct request *))
2090 return blk_end_io(rq, error, nr_bytes, 0, drv_callback);
2092 EXPORT_SYMBOL_GPL(blk_end_request_callback);
2094 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2097 /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw, and
2098 we want BIO_RW_AHEAD (bit 1) to imply REQ_FAILFAST (bit 1). */
2099 rq->cmd_flags |= (bio->bi_rw & 3);
2101 if (bio_has_data(bio)) {
2102 rq->nr_phys_segments = bio_phys_segments(q, bio);
2103 rq->buffer = bio_data(bio);
2105 rq->current_nr_sectors = bio_cur_sectors(bio);
2106 rq->hard_cur_sectors = rq->current_nr_sectors;
2107 rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio);
2108 rq->data_len = bio->bi_size;
2110 rq->bio = rq->biotail = bio;
2113 rq->rq_disk = bio->bi_bdev->bd_disk;
2117 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2118 * @q : the queue of the device being checked
2121 * Check if underlying low-level drivers of a device are busy.
2122 * If the drivers want to export their busy state, they must set own
2123 * exporting function using blk_queue_lld_busy() first.
2125 * Basically, this function is used only by request stacking drivers
2126 * to stop dispatching requests to underlying devices when underlying
2127 * devices are busy. This behavior helps more I/O merging on the queue
2128 * of the request stacking driver and prevents I/O throughput regression
2129 * on burst I/O load.
2132 * 0 - Not busy (The request stacking driver should dispatch request)
2133 * 1 - Busy (The request stacking driver should stop dispatching request)
2135 int blk_lld_busy(struct request_queue *q)
2138 return q->lld_busy_fn(q);
2142 EXPORT_SYMBOL_GPL(blk_lld_busy);
2144 int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
2146 return queue_work(kblockd_workqueue, work);
2148 EXPORT_SYMBOL(kblockd_schedule_work);
2150 int __init blk_dev_init(void)
2152 kblockd_workqueue = create_workqueue("kblockd");
2153 if (!kblockd_workqueue)
2154 panic("Failed to create kblockd\n");
2156 request_cachep = kmem_cache_create("blkdev_requests",
2157 sizeof(struct request), 0, SLAB_PANIC, NULL);
2159 blk_requestq_cachep = kmem_cache_create("blkdev_queue",
2160 sizeof(struct request_queue), 0, SLAB_PANIC, NULL);