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/fault-inject.h>
30 #include <linux/list_sort.h>
32 #define CREATE_TRACE_POINTS
33 #include <trace/events/block.h>
37 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
38 EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
39 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
41 static int __make_request(struct request_queue *q, struct bio *bio);
44 * For the allocated request tables
46 static struct kmem_cache *request_cachep;
49 * For queue allocation
51 struct kmem_cache *blk_requestq_cachep;
54 * Controlling structure to kblockd
56 static struct workqueue_struct *kblockd_workqueue;
58 static void drive_stat_acct(struct request *rq, int new_io)
60 struct hd_struct *part;
61 int rw = rq_data_dir(rq);
64 if (!blk_do_io_stat(rq))
67 cpu = part_stat_lock();
71 part_stat_inc(cpu, part, merges[rw]);
73 part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq));
74 if (!hd_struct_try_get(part)) {
76 * The partition is already being removed,
77 * the request will be accounted on the disk only
79 * We take a reference on disk->part0 although that
80 * partition will never be deleted, so we can treat
81 * it as any other partition.
83 part = &rq->rq_disk->part0;
86 part_round_stats(cpu, part);
87 part_inc_in_flight(part, rw);
94 void blk_queue_congestion_threshold(struct request_queue *q)
98 nr = q->nr_requests - (q->nr_requests / 8) + 1;
99 if (nr > q->nr_requests)
101 q->nr_congestion_on = nr;
103 nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
106 q->nr_congestion_off = nr;
110 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
113 * Locates the passed device's request queue and returns the address of its
116 * Will return NULL if the request queue cannot be located.
118 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
120 struct backing_dev_info *ret = NULL;
121 struct request_queue *q = bdev_get_queue(bdev);
124 ret = &q->backing_dev_info;
127 EXPORT_SYMBOL(blk_get_backing_dev_info);
129 void blk_rq_init(struct request_queue *q, struct request *rq)
131 memset(rq, 0, sizeof(*rq));
133 INIT_LIST_HEAD(&rq->queuelist);
134 INIT_LIST_HEAD(&rq->timeout_list);
137 rq->__sector = (sector_t) -1;
138 INIT_HLIST_NODE(&rq->hash);
139 RB_CLEAR_NODE(&rq->rb_node);
141 rq->cmd_len = BLK_MAX_CDB;
144 rq->start_time = jiffies;
145 set_start_time_ns(rq);
148 EXPORT_SYMBOL(blk_rq_init);
150 static void req_bio_endio(struct request *rq, struct bio *bio,
151 unsigned int nbytes, int error)
154 clear_bit(BIO_UPTODATE, &bio->bi_flags);
155 else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
158 if (unlikely(nbytes > bio->bi_size)) {
159 printk(KERN_ERR "%s: want %u bytes done, %u left\n",
160 __func__, nbytes, bio->bi_size);
161 nbytes = bio->bi_size;
164 if (unlikely(rq->cmd_flags & REQ_QUIET))
165 set_bit(BIO_QUIET, &bio->bi_flags);
167 bio->bi_size -= nbytes;
168 bio->bi_sector += (nbytes >> 9);
170 if (bio_integrity(bio))
171 bio_integrity_advance(bio, nbytes);
173 /* don't actually finish bio if it's part of flush sequence */
174 if (bio->bi_size == 0 && !(rq->cmd_flags & REQ_FLUSH_SEQ))
175 bio_endio(bio, error);
178 void blk_dump_rq_flags(struct request *rq, char *msg)
182 printk(KERN_INFO "%s: dev %s: type=%x, flags=%x\n", msg,
183 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type,
186 printk(KERN_INFO " sector %llu, nr/cnr %u/%u\n",
187 (unsigned long long)blk_rq_pos(rq),
188 blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
189 printk(KERN_INFO " bio %p, biotail %p, buffer %p, len %u\n",
190 rq->bio, rq->biotail, rq->buffer, blk_rq_bytes(rq));
192 if (rq->cmd_type == REQ_TYPE_BLOCK_PC) {
193 printk(KERN_INFO " cdb: ");
194 for (bit = 0; bit < BLK_MAX_CDB; bit++)
195 printk("%02x ", rq->cmd[bit]);
199 EXPORT_SYMBOL(blk_dump_rq_flags);
201 static void blk_delay_work(struct work_struct *work)
203 struct request_queue *q;
205 q = container_of(work, struct request_queue, delay_work.work);
206 spin_lock_irq(q->queue_lock);
208 spin_unlock_irq(q->queue_lock);
212 * blk_delay_queue - restart queueing after defined interval
213 * @q: The &struct request_queue in question
214 * @msecs: Delay in msecs
217 * Sometimes queueing needs to be postponed for a little while, to allow
218 * resources to come back. This function will make sure that queueing is
219 * restarted around the specified time.
221 void blk_delay_queue(struct request_queue *q, unsigned long msecs)
223 queue_delayed_work(kblockd_workqueue, &q->delay_work,
224 msecs_to_jiffies(msecs));
226 EXPORT_SYMBOL(blk_delay_queue);
229 * blk_start_queue - restart a previously stopped queue
230 * @q: The &struct request_queue in question
233 * blk_start_queue() will clear the stop flag on the queue, and call
234 * the request_fn for the queue if it was in a stopped state when
235 * entered. Also see blk_stop_queue(). Queue lock must be held.
237 void blk_start_queue(struct request_queue *q)
239 WARN_ON(!irqs_disabled());
241 queue_flag_clear(QUEUE_FLAG_STOPPED, q);
244 EXPORT_SYMBOL(blk_start_queue);
247 * blk_stop_queue - stop a queue
248 * @q: The &struct request_queue in question
251 * The Linux block layer assumes that a block driver will consume all
252 * entries on the request queue when the request_fn strategy is called.
253 * Often this will not happen, because of hardware limitations (queue
254 * depth settings). If a device driver gets a 'queue full' response,
255 * or if it simply chooses not to queue more I/O at one point, it can
256 * call this function to prevent the request_fn from being called until
257 * the driver has signalled it's ready to go again. This happens by calling
258 * blk_start_queue() to restart queue operations. Queue lock must be held.
260 void blk_stop_queue(struct request_queue *q)
262 __cancel_delayed_work(&q->delay_work);
263 queue_flag_set(QUEUE_FLAG_STOPPED, q);
265 EXPORT_SYMBOL(blk_stop_queue);
268 * blk_sync_queue - cancel any pending callbacks on a queue
272 * The block layer may perform asynchronous callback activity
273 * on a queue, such as calling the unplug function after a timeout.
274 * A block device may call blk_sync_queue to ensure that any
275 * such activity is cancelled, thus allowing it to release resources
276 * that the callbacks might use. The caller must already have made sure
277 * that its ->make_request_fn will not re-add plugging prior to calling
280 * This function does not cancel any asynchronous activity arising
281 * out of elevator or throttling code. That would require elevaotor_exit()
282 * and blk_throtl_exit() to be called with queue lock initialized.
285 void blk_sync_queue(struct request_queue *q)
287 del_timer_sync(&q->timeout);
288 cancel_delayed_work_sync(&q->delay_work);
290 EXPORT_SYMBOL(blk_sync_queue);
293 * __blk_run_queue - run a single device queue
294 * @q: The queue to run
297 * See @blk_run_queue. This variant must be called with the queue lock
298 * held and interrupts disabled.
300 void __blk_run_queue(struct request_queue *q)
302 if (unlikely(blk_queue_stopped(q)))
307 EXPORT_SYMBOL(__blk_run_queue);
310 * blk_run_queue_async - run a single device queue in workqueue context
311 * @q: The queue to run
314 * Tells kblockd to perform the equivalent of @blk_run_queue on behalf
317 void blk_run_queue_async(struct request_queue *q)
319 if (likely(!blk_queue_stopped(q))) {
320 __cancel_delayed_work(&q->delay_work);
321 queue_delayed_work(kblockd_workqueue, &q->delay_work, 0);
324 EXPORT_SYMBOL(blk_run_queue_async);
327 * blk_run_queue - run a single device queue
328 * @q: The queue to run
331 * Invoke request handling on this queue, if it has pending work to do.
332 * May be used to restart queueing when a request has completed.
334 void blk_run_queue(struct request_queue *q)
338 spin_lock_irqsave(q->queue_lock, flags);
340 spin_unlock_irqrestore(q->queue_lock, flags);
342 EXPORT_SYMBOL(blk_run_queue);
344 void blk_put_queue(struct request_queue *q)
346 kobject_put(&q->kobj);
348 EXPORT_SYMBOL(blk_put_queue);
351 * Note: If a driver supplied the queue lock, it should not zap that lock
352 * unexpectedly as some queue cleanup components like elevator_exit() and
353 * blk_throtl_exit() need queue lock.
355 void blk_cleanup_queue(struct request_queue *q)
358 * We know we have process context here, so we can be a little
359 * cautious and ensure that pending block actions on this device
360 * are done before moving on. Going into this function, we should
361 * not have processes doing IO to this device.
365 del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);
366 mutex_lock(&q->sysfs_lock);
367 queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
368 mutex_unlock(&q->sysfs_lock);
371 elevator_exit(q->elevator);
377 EXPORT_SYMBOL(blk_cleanup_queue);
379 static int blk_init_free_list(struct request_queue *q)
381 struct request_list *rl = &q->rq;
383 if (unlikely(rl->rq_pool))
386 rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
387 rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
389 init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
390 init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
392 rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
393 mempool_free_slab, request_cachep, q->node);
401 struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
403 return blk_alloc_queue_node(gfp_mask, -1);
405 EXPORT_SYMBOL(blk_alloc_queue);
407 struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
409 struct request_queue *q;
412 q = kmem_cache_alloc_node(blk_requestq_cachep,
413 gfp_mask | __GFP_ZERO, node_id);
417 q->backing_dev_info.ra_pages =
418 (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
419 q->backing_dev_info.state = 0;
420 q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
421 q->backing_dev_info.name = "block";
423 err = bdi_init(&q->backing_dev_info);
425 kmem_cache_free(blk_requestq_cachep, q);
429 if (blk_throtl_init(q)) {
430 kmem_cache_free(blk_requestq_cachep, q);
434 setup_timer(&q->backing_dev_info.laptop_mode_wb_timer,
435 laptop_mode_timer_fn, (unsigned long) q);
436 setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
437 INIT_LIST_HEAD(&q->timeout_list);
438 INIT_LIST_HEAD(&q->flush_queue[0]);
439 INIT_LIST_HEAD(&q->flush_queue[1]);
440 INIT_LIST_HEAD(&q->flush_data_in_flight);
441 INIT_DELAYED_WORK(&q->delay_work, blk_delay_work);
443 kobject_init(&q->kobj, &blk_queue_ktype);
445 mutex_init(&q->sysfs_lock);
446 spin_lock_init(&q->__queue_lock);
449 * By default initialize queue_lock to internal lock and driver can
450 * override it later if need be.
452 q->queue_lock = &q->__queue_lock;
456 EXPORT_SYMBOL(blk_alloc_queue_node);
459 * blk_init_queue - prepare a request queue for use with a block device
460 * @rfn: The function to be called to process requests that have been
461 * placed on the queue.
462 * @lock: Request queue spin lock
465 * If a block device wishes to use the standard request handling procedures,
466 * which sorts requests and coalesces adjacent requests, then it must
467 * call blk_init_queue(). The function @rfn will be called when there
468 * are requests on the queue that need to be processed. If the device
469 * supports plugging, then @rfn may not be called immediately when requests
470 * are available on the queue, but may be called at some time later instead.
471 * Plugged queues are generally unplugged when a buffer belonging to one
472 * of the requests on the queue is needed, or due to memory pressure.
474 * @rfn is not required, or even expected, to remove all requests off the
475 * queue, but only as many as it can handle at a time. If it does leave
476 * requests on the queue, it is responsible for arranging that the requests
477 * get dealt with eventually.
479 * The queue spin lock must be held while manipulating the requests on the
480 * request queue; this lock will be taken also from interrupt context, so irq
481 * disabling is needed for it.
483 * Function returns a pointer to the initialized request queue, or %NULL if
487 * blk_init_queue() must be paired with a blk_cleanup_queue() call
488 * when the block device is deactivated (such as at module unload).
491 struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
493 return blk_init_queue_node(rfn, lock, -1);
495 EXPORT_SYMBOL(blk_init_queue);
497 struct request_queue *
498 blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
500 struct request_queue *uninit_q, *q;
502 uninit_q = blk_alloc_queue_node(GFP_KERNEL, node_id);
506 q = blk_init_allocated_queue_node(uninit_q, rfn, lock, node_id);
508 blk_cleanup_queue(uninit_q);
512 EXPORT_SYMBOL(blk_init_queue_node);
514 struct request_queue *
515 blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
518 return blk_init_allocated_queue_node(q, rfn, lock, -1);
520 EXPORT_SYMBOL(blk_init_allocated_queue);
522 struct request_queue *
523 blk_init_allocated_queue_node(struct request_queue *q, request_fn_proc *rfn,
524 spinlock_t *lock, int node_id)
530 if (blk_init_free_list(q))
534 q->prep_rq_fn = NULL;
535 q->unprep_rq_fn = NULL;
536 q->queue_flags = QUEUE_FLAG_DEFAULT;
538 /* Override internal queue lock with supplied lock pointer */
540 q->queue_lock = lock;
543 * This also sets hw/phys segments, boundary and size
545 blk_queue_make_request(q, __make_request);
547 q->sg_reserved_size = INT_MAX;
552 if (!elevator_init(q, NULL)) {
553 blk_queue_congestion_threshold(q);
559 EXPORT_SYMBOL(blk_init_allocated_queue_node);
561 int blk_get_queue(struct request_queue *q)
563 if (likely(!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
564 kobject_get(&q->kobj);
570 EXPORT_SYMBOL(blk_get_queue);
572 static inline void blk_free_request(struct request_queue *q, struct request *rq)
574 if (rq->cmd_flags & REQ_ELVPRIV)
575 elv_put_request(q, rq);
576 mempool_free(rq, q->rq.rq_pool);
579 static struct request *
580 blk_alloc_request(struct request_queue *q, int flags, int priv, gfp_t gfp_mask)
582 struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
589 rq->cmd_flags = flags | REQ_ALLOCED;
592 if (unlikely(elv_set_request(q, rq, gfp_mask))) {
593 mempool_free(rq, q->rq.rq_pool);
596 rq->cmd_flags |= REQ_ELVPRIV;
603 * ioc_batching returns true if the ioc is a valid batching request and
604 * should be given priority access to a request.
606 static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
612 * Make sure the process is able to allocate at least 1 request
613 * even if the batch times out, otherwise we could theoretically
616 return ioc->nr_batch_requests == q->nr_batching ||
617 (ioc->nr_batch_requests > 0
618 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
622 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
623 * will cause the process to be a "batcher" on all queues in the system. This
624 * is the behaviour we want though - once it gets a wakeup it should be given
627 static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
629 if (!ioc || ioc_batching(q, ioc))
632 ioc->nr_batch_requests = q->nr_batching;
633 ioc->last_waited = jiffies;
636 static void __freed_request(struct request_queue *q, int sync)
638 struct request_list *rl = &q->rq;
640 if (rl->count[sync] < queue_congestion_off_threshold(q))
641 blk_clear_queue_congested(q, sync);
643 if (rl->count[sync] + 1 <= q->nr_requests) {
644 if (waitqueue_active(&rl->wait[sync]))
645 wake_up(&rl->wait[sync]);
647 blk_clear_queue_full(q, sync);
652 * A request has just been released. Account for it, update the full and
653 * congestion status, wake up any waiters. Called under q->queue_lock.
655 static void freed_request(struct request_queue *q, int sync, int priv)
657 struct request_list *rl = &q->rq;
663 __freed_request(q, sync);
665 if (unlikely(rl->starved[sync ^ 1]))
666 __freed_request(q, sync ^ 1);
670 * Determine if elevator data should be initialized when allocating the
671 * request associated with @bio.
673 static bool blk_rq_should_init_elevator(struct bio *bio)
679 * Flush requests do not use the elevator so skip initialization.
680 * This allows a request to share the flush and elevator data.
682 if (bio->bi_rw & (REQ_FLUSH | REQ_FUA))
689 * Get a free request, queue_lock must be held.
690 * Returns NULL on failure, with queue_lock held.
691 * Returns !NULL on success, with queue_lock *not held*.
693 static struct request *get_request(struct request_queue *q, int rw_flags,
694 struct bio *bio, gfp_t gfp_mask)
696 struct request *rq = NULL;
697 struct request_list *rl = &q->rq;
698 struct io_context *ioc = NULL;
699 const bool is_sync = rw_is_sync(rw_flags) != 0;
700 int may_queue, priv = 0;
702 may_queue = elv_may_queue(q, rw_flags);
703 if (may_queue == ELV_MQUEUE_NO)
706 if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
707 if (rl->count[is_sync]+1 >= q->nr_requests) {
708 ioc = current_io_context(GFP_ATOMIC, q->node);
710 * The queue will fill after this allocation, so set
711 * it as full, and mark this process as "batching".
712 * This process will be allowed to complete a batch of
713 * requests, others will be blocked.
715 if (!blk_queue_full(q, is_sync)) {
716 ioc_set_batching(q, ioc);
717 blk_set_queue_full(q, is_sync);
719 if (may_queue != ELV_MQUEUE_MUST
720 && !ioc_batching(q, ioc)) {
722 * The queue is full and the allocating
723 * process is not a "batcher", and not
724 * exempted by the IO scheduler
730 blk_set_queue_congested(q, is_sync);
734 * Only allow batching queuers to allocate up to 50% over the defined
735 * limit of requests, otherwise we could have thousands of requests
736 * allocated with any setting of ->nr_requests
738 if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
741 rl->count[is_sync]++;
742 rl->starved[is_sync] = 0;
744 if (blk_rq_should_init_elevator(bio)) {
745 priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
750 if (blk_queue_io_stat(q))
751 rw_flags |= REQ_IO_STAT;
752 spin_unlock_irq(q->queue_lock);
754 rq = blk_alloc_request(q, rw_flags, priv, gfp_mask);
757 * Allocation failed presumably due to memory. Undo anything
758 * we might have messed up.
760 * Allocating task should really be put onto the front of the
761 * wait queue, but this is pretty rare.
763 spin_lock_irq(q->queue_lock);
764 freed_request(q, is_sync, priv);
767 * in the very unlikely event that allocation failed and no
768 * requests for this direction was pending, mark us starved
769 * so that freeing of a request in the other direction will
770 * notice us. another possible fix would be to split the
771 * rq mempool into READ and WRITE
774 if (unlikely(rl->count[is_sync] == 0))
775 rl->starved[is_sync] = 1;
781 * ioc may be NULL here, and ioc_batching will be false. That's
782 * OK, if the queue is under the request limit then requests need
783 * not count toward the nr_batch_requests limit. There will always
784 * be some limit enforced by BLK_BATCH_TIME.
786 if (ioc_batching(q, ioc))
787 ioc->nr_batch_requests--;
789 trace_block_getrq(q, bio, rw_flags & 1);
795 * No available requests for this queue, wait for some requests to become
798 * Called with q->queue_lock held, and returns with it unlocked.
800 static struct request *get_request_wait(struct request_queue *q, int rw_flags,
803 const bool is_sync = rw_is_sync(rw_flags) != 0;
806 rq = get_request(q, rw_flags, bio, GFP_NOIO);
809 struct io_context *ioc;
810 struct request_list *rl = &q->rq;
812 prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
813 TASK_UNINTERRUPTIBLE);
815 trace_block_sleeprq(q, bio, rw_flags & 1);
817 spin_unlock_irq(q->queue_lock);
821 * After sleeping, we become a "batching" process and
822 * will be able to allocate at least one request, and
823 * up to a big batch of them for a small period time.
824 * See ioc_batching, ioc_set_batching
826 ioc = current_io_context(GFP_NOIO, q->node);
827 ioc_set_batching(q, ioc);
829 spin_lock_irq(q->queue_lock);
830 finish_wait(&rl->wait[is_sync], &wait);
832 rq = get_request(q, rw_flags, bio, GFP_NOIO);
838 struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
842 BUG_ON(rw != READ && rw != WRITE);
844 spin_lock_irq(q->queue_lock);
845 if (gfp_mask & __GFP_WAIT) {
846 rq = get_request_wait(q, rw, NULL);
848 rq = get_request(q, rw, NULL, gfp_mask);
850 spin_unlock_irq(q->queue_lock);
852 /* q->queue_lock is unlocked at this point */
856 EXPORT_SYMBOL(blk_get_request);
859 * blk_make_request - given a bio, allocate a corresponding struct request.
860 * @q: target request queue
861 * @bio: The bio describing the memory mappings that will be submitted for IO.
862 * It may be a chained-bio properly constructed by block/bio layer.
863 * @gfp_mask: gfp flags to be used for memory allocation
865 * blk_make_request is the parallel of generic_make_request for BLOCK_PC
866 * type commands. Where the struct request needs to be farther initialized by
867 * the caller. It is passed a &struct bio, which describes the memory info of
870 * The caller of blk_make_request must make sure that bi_io_vec
871 * are set to describe the memory buffers. That bio_data_dir() will return
872 * the needed direction of the request. (And all bio's in the passed bio-chain
873 * are properly set accordingly)
875 * If called under none-sleepable conditions, mapped bio buffers must not
876 * need bouncing, by calling the appropriate masked or flagged allocator,
877 * suitable for the target device. Otherwise the call to blk_queue_bounce will
880 * WARNING: When allocating/cloning a bio-chain, careful consideration should be
881 * given to how you allocate bios. In particular, you cannot use __GFP_WAIT for
882 * anything but the first bio in the chain. Otherwise you risk waiting for IO
883 * completion of a bio that hasn't been submitted yet, thus resulting in a
884 * deadlock. Alternatively bios should be allocated using bio_kmalloc() instead
885 * of bio_alloc(), as that avoids the mempool deadlock.
886 * If possible a big IO should be split into smaller parts when allocation
887 * fails. Partial allocation should not be an error, or you risk a live-lock.
889 struct request *blk_make_request(struct request_queue *q, struct bio *bio,
892 struct request *rq = blk_get_request(q, bio_data_dir(bio), gfp_mask);
895 return ERR_PTR(-ENOMEM);
898 struct bio *bounce_bio = bio;
901 blk_queue_bounce(q, &bounce_bio);
902 ret = blk_rq_append_bio(q, rq, bounce_bio);
911 EXPORT_SYMBOL(blk_make_request);
914 * blk_requeue_request - put a request back on queue
915 * @q: request queue where request should be inserted
916 * @rq: request to be inserted
919 * Drivers often keep queueing requests until the hardware cannot accept
920 * more, when that condition happens we need to put the request back
921 * on the queue. Must be called with queue lock held.
923 void blk_requeue_request(struct request_queue *q, struct request *rq)
925 blk_delete_timer(rq);
926 blk_clear_rq_complete(rq);
927 trace_block_rq_requeue(q, rq);
929 if (blk_rq_tagged(rq))
930 blk_queue_end_tag(q, rq);
932 BUG_ON(blk_queued_rq(rq));
934 elv_requeue_request(q, rq);
936 EXPORT_SYMBOL(blk_requeue_request);
938 static void add_acct_request(struct request_queue *q, struct request *rq,
941 drive_stat_acct(rq, 1);
942 __elv_add_request(q, rq, where);
946 * blk_insert_request - insert a special request into a request queue
947 * @q: request queue where request should be inserted
948 * @rq: request to be inserted
949 * @at_head: insert request at head or tail of queue
950 * @data: private data
953 * Many block devices need to execute commands asynchronously, so they don't
954 * block the whole kernel from preemption during request execution. This is
955 * accomplished normally by inserting aritficial requests tagged as
956 * REQ_TYPE_SPECIAL in to the corresponding request queue, and letting them
957 * be scheduled for actual execution by the request queue.
959 * We have the option of inserting the head or the tail of the queue.
960 * Typically we use the tail for new ioctls and so forth. We use the head
961 * of the queue for things like a QUEUE_FULL message from a device, or a
962 * host that is unable to accept a particular command.
964 void blk_insert_request(struct request_queue *q, struct request *rq,
965 int at_head, void *data)
967 int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
971 * tell I/O scheduler that this isn't a regular read/write (ie it
972 * must not attempt merges on this) and that it acts as a soft
975 rq->cmd_type = REQ_TYPE_SPECIAL;
979 spin_lock_irqsave(q->queue_lock, flags);
982 * If command is tagged, release the tag
984 if (blk_rq_tagged(rq))
985 blk_queue_end_tag(q, rq);
987 add_acct_request(q, rq, where);
989 spin_unlock_irqrestore(q->queue_lock, flags);
991 EXPORT_SYMBOL(blk_insert_request);
993 static void part_round_stats_single(int cpu, struct hd_struct *part,
996 if (now == part->stamp)
999 if (part_in_flight(part)) {
1000 __part_stat_add(cpu, part, time_in_queue,
1001 part_in_flight(part) * (now - part->stamp));
1002 __part_stat_add(cpu, part, io_ticks, (now - part->stamp));
1008 * part_round_stats() - Round off the performance stats on a struct disk_stats.
1009 * @cpu: cpu number for stats access
1010 * @part: target partition
1012 * The average IO queue length and utilisation statistics are maintained
1013 * by observing the current state of the queue length and the amount of
1014 * time it has been in this state for.
1016 * Normally, that accounting is done on IO completion, but that can result
1017 * in more than a second's worth of IO being accounted for within any one
1018 * second, leading to >100% utilisation. To deal with that, we call this
1019 * function to do a round-off before returning the results when reading
1020 * /proc/diskstats. This accounts immediately for all queue usage up to
1021 * the current jiffies and restarts the counters again.
1023 void part_round_stats(int cpu, struct hd_struct *part)
1025 unsigned long now = jiffies;
1028 part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1029 part_round_stats_single(cpu, part, now);
1031 EXPORT_SYMBOL_GPL(part_round_stats);
1034 * queue lock must be held
1036 void __blk_put_request(struct request_queue *q, struct request *req)
1040 if (unlikely(--req->ref_count))
1043 elv_completed_request(q, req);
1045 /* this is a bio leak */
1046 WARN_ON(req->bio != NULL);
1049 * Request may not have originated from ll_rw_blk. if not,
1050 * it didn't come out of our reserved rq pools
1052 if (req->cmd_flags & REQ_ALLOCED) {
1053 int is_sync = rq_is_sync(req) != 0;
1054 int priv = req->cmd_flags & REQ_ELVPRIV;
1056 BUG_ON(!list_empty(&req->queuelist));
1057 BUG_ON(!hlist_unhashed(&req->hash));
1059 blk_free_request(q, req);
1060 freed_request(q, is_sync, priv);
1063 EXPORT_SYMBOL_GPL(__blk_put_request);
1065 void blk_put_request(struct request *req)
1067 unsigned long flags;
1068 struct request_queue *q = req->q;
1070 spin_lock_irqsave(q->queue_lock, flags);
1071 __blk_put_request(q, req);
1072 spin_unlock_irqrestore(q->queue_lock, flags);
1074 EXPORT_SYMBOL(blk_put_request);
1077 * blk_add_request_payload - add a payload to a request
1078 * @rq: request to update
1079 * @page: page backing the payload
1080 * @len: length of the payload.
1082 * This allows to later add a payload to an already submitted request by
1083 * a block driver. The driver needs to take care of freeing the payload
1086 * Note that this is a quite horrible hack and nothing but handling of
1087 * discard requests should ever use it.
1089 void blk_add_request_payload(struct request *rq, struct page *page,
1092 struct bio *bio = rq->bio;
1094 bio->bi_io_vec->bv_page = page;
1095 bio->bi_io_vec->bv_offset = 0;
1096 bio->bi_io_vec->bv_len = len;
1100 bio->bi_phys_segments = 1;
1102 rq->__data_len = rq->resid_len = len;
1103 rq->nr_phys_segments = 1;
1104 rq->buffer = bio_data(bio);
1106 EXPORT_SYMBOL_GPL(blk_add_request_payload);
1108 static bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
1111 const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1113 if (!ll_back_merge_fn(q, req, bio))
1116 trace_block_bio_backmerge(q, bio);
1118 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1119 blk_rq_set_mixed_merge(req);
1121 req->biotail->bi_next = bio;
1123 req->__data_len += bio->bi_size;
1124 req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1126 drive_stat_acct(req, 0);
1127 elv_bio_merged(q, req, bio);
1131 static bool bio_attempt_front_merge(struct request_queue *q,
1132 struct request *req, struct bio *bio)
1134 const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1136 if (!ll_front_merge_fn(q, req, bio))
1139 trace_block_bio_frontmerge(q, bio);
1141 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1142 blk_rq_set_mixed_merge(req);
1144 bio->bi_next = req->bio;
1148 * may not be valid. if the low level driver said
1149 * it didn't need a bounce buffer then it better
1150 * not touch req->buffer either...
1152 req->buffer = bio_data(bio);
1153 req->__sector = bio->bi_sector;
1154 req->__data_len += bio->bi_size;
1155 req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1157 drive_stat_acct(req, 0);
1158 elv_bio_merged(q, req, bio);
1163 * Attempts to merge with the plugged list in the current process. Returns
1164 * true if merge was successful, otherwise false.
1166 static bool attempt_plug_merge(struct task_struct *tsk, struct request_queue *q,
1169 struct blk_plug *plug;
1177 list_for_each_entry_reverse(rq, &plug->list, queuelist) {
1183 el_ret = elv_try_merge(rq, bio);
1184 if (el_ret == ELEVATOR_BACK_MERGE) {
1185 ret = bio_attempt_back_merge(q, rq, bio);
1188 } else if (el_ret == ELEVATOR_FRONT_MERGE) {
1189 ret = bio_attempt_front_merge(q, rq, bio);
1198 void init_request_from_bio(struct request *req, struct bio *bio)
1200 req->cpu = bio->bi_comp_cpu;
1201 req->cmd_type = REQ_TYPE_FS;
1203 req->cmd_flags |= bio->bi_rw & REQ_COMMON_MASK;
1204 if (bio->bi_rw & REQ_RAHEAD)
1205 req->cmd_flags |= REQ_FAILFAST_MASK;
1208 req->__sector = bio->bi_sector;
1209 req->ioprio = bio_prio(bio);
1210 blk_rq_bio_prep(req->q, req, bio);
1213 static int __make_request(struct request_queue *q, struct bio *bio)
1215 const bool sync = !!(bio->bi_rw & REQ_SYNC);
1216 struct blk_plug *plug;
1217 int el_ret, rw_flags, where = ELEVATOR_INSERT_SORT;
1218 struct request *req;
1221 * low level driver can indicate that it wants pages above a
1222 * certain limit bounced to low memory (ie for highmem, or even
1223 * ISA dma in theory)
1225 blk_queue_bounce(q, &bio);
1227 if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) {
1228 spin_lock_irq(q->queue_lock);
1229 where = ELEVATOR_INSERT_FLUSH;
1234 * Check if we can merge with the plugged list before grabbing
1237 if (attempt_plug_merge(current, q, bio))
1240 spin_lock_irq(q->queue_lock);
1242 el_ret = elv_merge(q, &req, bio);
1243 if (el_ret == ELEVATOR_BACK_MERGE) {
1244 if (bio_attempt_back_merge(q, req, bio)) {
1245 if (!attempt_back_merge(q, req))
1246 elv_merged_request(q, req, el_ret);
1249 } else if (el_ret == ELEVATOR_FRONT_MERGE) {
1250 if (bio_attempt_front_merge(q, req, bio)) {
1251 if (!attempt_front_merge(q, req))
1252 elv_merged_request(q, req, el_ret);
1259 * This sync check and mask will be re-done in init_request_from_bio(),
1260 * but we need to set it earlier to expose the sync flag to the
1261 * rq allocator and io schedulers.
1263 rw_flags = bio_data_dir(bio);
1265 rw_flags |= REQ_SYNC;
1268 * Grab a free request. This is might sleep but can not fail.
1269 * Returns with the queue unlocked.
1271 req = get_request_wait(q, rw_flags, bio);
1274 * After dropping the lock and possibly sleeping here, our request
1275 * may now be mergeable after it had proven unmergeable (above).
1276 * We don't worry about that case for efficiency. It won't happen
1277 * often, and the elevators are able to handle it.
1279 init_request_from_bio(req, bio);
1281 if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) ||
1282 bio_flagged(bio, BIO_CPU_AFFINE)) {
1283 req->cpu = blk_cpu_to_group(get_cpu());
1287 plug = current->plug;
1290 * If this is the first request added after a plug, fire
1291 * of a plug trace. If others have been added before, check
1292 * if we have multiple devices in this plug. If so, make a
1293 * note to sort the list before dispatch.
1295 if (list_empty(&plug->list))
1296 trace_block_plug(q);
1297 else if (!plug->should_sort) {
1298 struct request *__rq;
1300 __rq = list_entry_rq(plug->list.prev);
1302 plug->should_sort = 1;
1304 list_add_tail(&req->queuelist, &plug->list);
1305 drive_stat_acct(req, 1);
1307 spin_lock_irq(q->queue_lock);
1308 add_acct_request(q, req, where);
1311 spin_unlock_irq(q->queue_lock);
1318 * If bio->bi_dev is a partition, remap the location
1320 static inline void blk_partition_remap(struct bio *bio)
1322 struct block_device *bdev = bio->bi_bdev;
1324 if (bio_sectors(bio) && bdev != bdev->bd_contains) {
1325 struct hd_struct *p = bdev->bd_part;
1327 bio->bi_sector += p->start_sect;
1328 bio->bi_bdev = bdev->bd_contains;
1330 trace_block_bio_remap(bdev_get_queue(bio->bi_bdev), bio,
1332 bio->bi_sector - p->start_sect);
1336 static void handle_bad_sector(struct bio *bio)
1338 char b[BDEVNAME_SIZE];
1340 printk(KERN_INFO "attempt to access beyond end of device\n");
1341 printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
1342 bdevname(bio->bi_bdev, b),
1344 (unsigned long long)bio->bi_sector + bio_sectors(bio),
1345 (long long)(i_size_read(bio->bi_bdev->bd_inode) >> 9));
1347 set_bit(BIO_EOF, &bio->bi_flags);
1350 #ifdef CONFIG_FAIL_MAKE_REQUEST
1352 static DECLARE_FAULT_ATTR(fail_make_request);
1354 static int __init setup_fail_make_request(char *str)
1356 return setup_fault_attr(&fail_make_request, str);
1358 __setup("fail_make_request=", setup_fail_make_request);
1360 static int should_fail_request(struct bio *bio)
1362 struct hd_struct *part = bio->bi_bdev->bd_part;
1364 if (part_to_disk(part)->part0.make_it_fail || part->make_it_fail)
1365 return should_fail(&fail_make_request, bio->bi_size);
1370 static int __init fail_make_request_debugfs(void)
1372 return init_fault_attr_dentries(&fail_make_request,
1373 "fail_make_request");
1376 late_initcall(fail_make_request_debugfs);
1378 #else /* CONFIG_FAIL_MAKE_REQUEST */
1380 static inline int should_fail_request(struct bio *bio)
1385 #endif /* CONFIG_FAIL_MAKE_REQUEST */
1388 * Check whether this bio extends beyond the end of the device.
1390 static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1397 /* Test device or partition size, when known. */
1398 maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
1400 sector_t sector = bio->bi_sector;
1402 if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1404 * This may well happen - the kernel calls bread()
1405 * without checking the size of the device, e.g., when
1406 * mounting a device.
1408 handle_bad_sector(bio);
1417 * generic_make_request - hand a buffer to its device driver for I/O
1418 * @bio: The bio describing the location in memory and on the device.
1420 * generic_make_request() is used to make I/O requests of block
1421 * devices. It is passed a &struct bio, which describes the I/O that needs
1424 * generic_make_request() does not return any status. The
1425 * success/failure status of the request, along with notification of
1426 * completion, is delivered asynchronously through the bio->bi_end_io
1427 * function described (one day) else where.
1429 * The caller of generic_make_request must make sure that bi_io_vec
1430 * are set to describe the memory buffer, and that bi_dev and bi_sector are
1431 * set to describe the device address, and the
1432 * bi_end_io and optionally bi_private are set to describe how
1433 * completion notification should be signaled.
1435 * generic_make_request and the drivers it calls may use bi_next if this
1436 * bio happens to be merged with someone else, and may change bi_dev and
1437 * bi_sector for remaps as it sees fit. So the values of these fields
1438 * should NOT be depended on after the call to generic_make_request.
1440 static inline void __generic_make_request(struct bio *bio)
1442 struct request_queue *q;
1443 sector_t old_sector;
1444 int ret, nr_sectors = bio_sectors(bio);
1450 if (bio_check_eod(bio, nr_sectors))
1454 * Resolve the mapping until finished. (drivers are
1455 * still free to implement/resolve their own stacking
1456 * by explicitly returning 0)
1458 * NOTE: we don't repeat the blk_size check for each new device.
1459 * Stacking drivers are expected to know what they are doing.
1464 char b[BDEVNAME_SIZE];
1466 q = bdev_get_queue(bio->bi_bdev);
1469 "generic_make_request: Trying to access "
1470 "nonexistent block-device %s (%Lu)\n",
1471 bdevname(bio->bi_bdev, b),
1472 (long long) bio->bi_sector);
1476 if (unlikely(!(bio->bi_rw & REQ_DISCARD) &&
1477 nr_sectors > queue_max_hw_sectors(q))) {
1478 printk(KERN_ERR "bio too big device %s (%u > %u)\n",
1479 bdevname(bio->bi_bdev, b),
1481 queue_max_hw_sectors(q));
1485 if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
1488 if (should_fail_request(bio))
1492 * If this device has partitions, remap block n
1493 * of partition p to block n+start(p) of the disk.
1495 blk_partition_remap(bio);
1497 if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
1500 if (old_sector != -1)
1501 trace_block_bio_remap(q, bio, old_dev, old_sector);
1503 old_sector = bio->bi_sector;
1504 old_dev = bio->bi_bdev->bd_dev;
1506 if (bio_check_eod(bio, nr_sectors))
1510 * Filter flush bio's early so that make_request based
1511 * drivers without flush support don't have to worry
1514 if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
1515 bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
1522 if ((bio->bi_rw & REQ_DISCARD) &&
1523 (!blk_queue_discard(q) ||
1524 ((bio->bi_rw & REQ_SECURE) &&
1525 !blk_queue_secdiscard(q)))) {
1530 if (blk_throtl_bio(q, &bio))
1534 * If bio = NULL, bio has been throttled and will be submitted
1540 trace_block_bio_queue(q, bio);
1542 ret = q->make_request_fn(q, bio);
1548 bio_endio(bio, err);
1552 * We only want one ->make_request_fn to be active at a time,
1553 * else stack usage with stacked devices could be a problem.
1554 * So use current->bio_list to keep a list of requests
1555 * submited by a make_request_fn function.
1556 * current->bio_list is also used as a flag to say if
1557 * generic_make_request is currently active in this task or not.
1558 * If it is NULL, then no make_request is active. If it is non-NULL,
1559 * then a make_request is active, and new requests should be added
1562 void generic_make_request(struct bio *bio)
1564 struct bio_list bio_list_on_stack;
1566 if (current->bio_list) {
1567 /* make_request is active */
1568 bio_list_add(current->bio_list, bio);
1571 /* following loop may be a bit non-obvious, and so deserves some
1573 * Before entering the loop, bio->bi_next is NULL (as all callers
1574 * ensure that) so we have a list with a single bio.
1575 * We pretend that we have just taken it off a longer list, so
1576 * we assign bio_list to a pointer to the bio_list_on_stack,
1577 * thus initialising the bio_list of new bios to be
1578 * added. __generic_make_request may indeed add some more bios
1579 * through a recursive call to generic_make_request. If it
1580 * did, we find a non-NULL value in bio_list and re-enter the loop
1581 * from the top. In this case we really did just take the bio
1582 * of the top of the list (no pretending) and so remove it from
1583 * bio_list, and call into __generic_make_request again.
1585 * The loop was structured like this to make only one call to
1586 * __generic_make_request (which is important as it is large and
1587 * inlined) and to keep the structure simple.
1589 BUG_ON(bio->bi_next);
1590 bio_list_init(&bio_list_on_stack);
1591 current->bio_list = &bio_list_on_stack;
1593 __generic_make_request(bio);
1594 bio = bio_list_pop(current->bio_list);
1596 current->bio_list = NULL; /* deactivate */
1598 EXPORT_SYMBOL(generic_make_request);
1601 * submit_bio - submit a bio to the block device layer for I/O
1602 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1603 * @bio: The &struct bio which describes the I/O
1605 * submit_bio() is very similar in purpose to generic_make_request(), and
1606 * uses that function to do most of the work. Both are fairly rough
1607 * interfaces; @bio must be presetup and ready for I/O.
1610 void submit_bio(int rw, struct bio *bio)
1612 int count = bio_sectors(bio);
1617 * If it's a regular read/write or a barrier with data attached,
1618 * go through the normal accounting stuff before submission.
1620 if (bio_has_data(bio) && !(rw & REQ_DISCARD)) {
1622 count_vm_events(PGPGOUT, count);
1624 task_io_account_read(bio->bi_size);
1625 count_vm_events(PGPGIN, count);
1628 if (unlikely(block_dump)) {
1629 char b[BDEVNAME_SIZE];
1630 printk(KERN_DEBUG "%s(%d): %s block %Lu on %s (%u sectors)\n",
1631 current->comm, task_pid_nr(current),
1632 (rw & WRITE) ? "WRITE" : "READ",
1633 (unsigned long long)bio->bi_sector,
1634 bdevname(bio->bi_bdev, b),
1639 generic_make_request(bio);
1641 EXPORT_SYMBOL(submit_bio);
1644 * blk_rq_check_limits - Helper function to check a request for the queue limit
1646 * @rq: the request being checked
1649 * @rq may have been made based on weaker limitations of upper-level queues
1650 * in request stacking drivers, and it may violate the limitation of @q.
1651 * Since the block layer and the underlying device driver trust @rq
1652 * after it is inserted to @q, it should be checked against @q before
1653 * the insertion using this generic function.
1655 * This function should also be useful for request stacking drivers
1656 * in some cases below, so export this function.
1657 * Request stacking drivers like request-based dm may change the queue
1658 * limits while requests are in the queue (e.g. dm's table swapping).
1659 * Such request stacking drivers should check those requests agaist
1660 * the new queue limits again when they dispatch those requests,
1661 * although such checkings are also done against the old queue limits
1662 * when submitting requests.
1664 int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1666 if (rq->cmd_flags & REQ_DISCARD)
1669 if (blk_rq_sectors(rq) > queue_max_sectors(q) ||
1670 blk_rq_bytes(rq) > queue_max_hw_sectors(q) << 9) {
1671 printk(KERN_ERR "%s: over max size limit.\n", __func__);
1676 * queue's settings related to segment counting like q->bounce_pfn
1677 * may differ from that of other stacking queues.
1678 * Recalculate it to check the request correctly on this queue's
1681 blk_recalc_rq_segments(rq);
1682 if (rq->nr_phys_segments > queue_max_segments(q)) {
1683 printk(KERN_ERR "%s: over max segments limit.\n", __func__);
1689 EXPORT_SYMBOL_GPL(blk_rq_check_limits);
1692 * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1693 * @q: the queue to submit the request
1694 * @rq: the request being queued
1696 int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1698 unsigned long flags;
1700 if (blk_rq_check_limits(q, rq))
1703 #ifdef CONFIG_FAIL_MAKE_REQUEST
1704 if (rq->rq_disk && rq->rq_disk->part0.make_it_fail &&
1705 should_fail(&fail_make_request, blk_rq_bytes(rq)))
1709 spin_lock_irqsave(q->queue_lock, flags);
1712 * Submitting request must be dequeued before calling this function
1713 * because it will be linked to another request_queue
1715 BUG_ON(blk_queued_rq(rq));
1717 add_acct_request(q, rq, ELEVATOR_INSERT_BACK);
1718 spin_unlock_irqrestore(q->queue_lock, flags);
1722 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
1725 * blk_rq_err_bytes - determine number of bytes till the next failure boundary
1726 * @rq: request to examine
1729 * A request could be merge of IOs which require different failure
1730 * handling. This function determines the number of bytes which
1731 * can be failed from the beginning of the request without
1732 * crossing into area which need to be retried further.
1735 * The number of bytes to fail.
1738 * queue_lock must be held.
1740 unsigned int blk_rq_err_bytes(const struct request *rq)
1742 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
1743 unsigned int bytes = 0;
1746 if (!(rq->cmd_flags & REQ_MIXED_MERGE))
1747 return blk_rq_bytes(rq);
1750 * Currently the only 'mixing' which can happen is between
1751 * different fastfail types. We can safely fail portions
1752 * which have all the failfast bits that the first one has -
1753 * the ones which are at least as eager to fail as the first
1756 for (bio = rq->bio; bio; bio = bio->bi_next) {
1757 if ((bio->bi_rw & ff) != ff)
1759 bytes += bio->bi_size;
1762 /* this could lead to infinite loop */
1763 BUG_ON(blk_rq_bytes(rq) && !bytes);
1766 EXPORT_SYMBOL_GPL(blk_rq_err_bytes);
1768 static void blk_account_io_completion(struct request *req, unsigned int bytes)
1770 if (blk_do_io_stat(req)) {
1771 const int rw = rq_data_dir(req);
1772 struct hd_struct *part;
1775 cpu = part_stat_lock();
1777 part_stat_add(cpu, part, sectors[rw], bytes >> 9);
1782 static void blk_account_io_done(struct request *req)
1785 * Account IO completion. flush_rq isn't accounted as a
1786 * normal IO on queueing nor completion. Accounting the
1787 * containing request is enough.
1789 if (blk_do_io_stat(req) && !(req->cmd_flags & REQ_FLUSH_SEQ)) {
1790 unsigned long duration = jiffies - req->start_time;
1791 const int rw = rq_data_dir(req);
1792 struct hd_struct *part;
1795 cpu = part_stat_lock();
1798 part_stat_inc(cpu, part, ios[rw]);
1799 part_stat_add(cpu, part, ticks[rw], duration);
1800 part_round_stats(cpu, part);
1801 part_dec_in_flight(part, rw);
1803 hd_struct_put(part);
1809 * blk_peek_request - peek at the top of a request queue
1810 * @q: request queue to peek at
1813 * Return the request at the top of @q. The returned request
1814 * should be started using blk_start_request() before LLD starts
1818 * Pointer to the request at the top of @q if available. Null
1822 * queue_lock must be held.
1824 struct request *blk_peek_request(struct request_queue *q)
1829 while ((rq = __elv_next_request(q)) != NULL) {
1830 if (!(rq->cmd_flags & REQ_STARTED)) {
1832 * This is the first time the device driver
1833 * sees this request (possibly after
1834 * requeueing). Notify IO scheduler.
1836 if (rq->cmd_flags & REQ_SORTED)
1837 elv_activate_rq(q, rq);
1840 * just mark as started even if we don't start
1841 * it, a request that has been delayed should
1842 * not be passed by new incoming requests
1844 rq->cmd_flags |= REQ_STARTED;
1845 trace_block_rq_issue(q, rq);
1848 if (!q->boundary_rq || q->boundary_rq == rq) {
1849 q->end_sector = rq_end_sector(rq);
1850 q->boundary_rq = NULL;
1853 if (rq->cmd_flags & REQ_DONTPREP)
1856 if (q->dma_drain_size && blk_rq_bytes(rq)) {
1858 * make sure space for the drain appears we
1859 * know we can do this because max_hw_segments
1860 * has been adjusted to be one fewer than the
1863 rq->nr_phys_segments++;
1869 ret = q->prep_rq_fn(q, rq);
1870 if (ret == BLKPREP_OK) {
1872 } else if (ret == BLKPREP_DEFER) {
1874 * the request may have been (partially) prepped.
1875 * we need to keep this request in the front to
1876 * avoid resource deadlock. REQ_STARTED will
1877 * prevent other fs requests from passing this one.
1879 if (q->dma_drain_size && blk_rq_bytes(rq) &&
1880 !(rq->cmd_flags & REQ_DONTPREP)) {
1882 * remove the space for the drain we added
1883 * so that we don't add it again
1885 --rq->nr_phys_segments;
1890 } else if (ret == BLKPREP_KILL) {
1891 rq->cmd_flags |= REQ_QUIET;
1893 * Mark this request as started so we don't trigger
1894 * any debug logic in the end I/O path.
1896 blk_start_request(rq);
1897 __blk_end_request_all(rq, -EIO);
1899 printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
1906 EXPORT_SYMBOL(blk_peek_request);
1908 void blk_dequeue_request(struct request *rq)
1910 struct request_queue *q = rq->q;
1912 BUG_ON(list_empty(&rq->queuelist));
1913 BUG_ON(ELV_ON_HASH(rq));
1915 list_del_init(&rq->queuelist);
1918 * the time frame between a request being removed from the lists
1919 * and to it is freed is accounted as io that is in progress at
1922 if (blk_account_rq(rq)) {
1923 q->in_flight[rq_is_sync(rq)]++;
1924 set_io_start_time_ns(rq);
1929 * blk_start_request - start request processing on the driver
1930 * @req: request to dequeue
1933 * Dequeue @req and start timeout timer on it. This hands off the
1934 * request to the driver.
1936 * Block internal functions which don't want to start timer should
1937 * call blk_dequeue_request().
1940 * queue_lock must be held.
1942 void blk_start_request(struct request *req)
1944 blk_dequeue_request(req);
1947 * We are now handing the request to the hardware, initialize
1948 * resid_len to full count and add the timeout handler.
1950 req->resid_len = blk_rq_bytes(req);
1951 if (unlikely(blk_bidi_rq(req)))
1952 req->next_rq->resid_len = blk_rq_bytes(req->next_rq);
1956 EXPORT_SYMBOL(blk_start_request);
1959 * blk_fetch_request - fetch a request from a request queue
1960 * @q: request queue to fetch a request from
1963 * Return the request at the top of @q. The request is started on
1964 * return and LLD can start processing it immediately.
1967 * Pointer to the request at the top of @q if available. Null
1971 * queue_lock must be held.
1973 struct request *blk_fetch_request(struct request_queue *q)
1977 rq = blk_peek_request(q);
1979 blk_start_request(rq);
1982 EXPORT_SYMBOL(blk_fetch_request);
1985 * blk_update_request - Special helper function for request stacking drivers
1986 * @req: the request being processed
1987 * @error: %0 for success, < %0 for error
1988 * @nr_bytes: number of bytes to complete @req
1991 * Ends I/O on a number of bytes attached to @req, but doesn't complete
1992 * the request structure even if @req doesn't have leftover.
1993 * If @req has leftover, sets it up for the next range of segments.
1995 * This special helper function is only for request stacking drivers
1996 * (e.g. request-based dm) so that they can handle partial completion.
1997 * Actual device drivers should use blk_end_request instead.
1999 * Passing the result of blk_rq_bytes() as @nr_bytes guarantees
2000 * %false return from this function.
2003 * %false - this request doesn't have any more data
2004 * %true - this request has more data
2006 bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
2008 int total_bytes, bio_nbytes, next_idx = 0;
2014 trace_block_rq_complete(req->q, req);
2017 * For fs requests, rq is just carrier of independent bio's
2018 * and each partial completion should be handled separately.
2019 * Reset per-request error on each partial completion.
2021 * TODO: tj: This is too subtle. It would be better to let
2022 * low level drivers do what they see fit.
2024 if (req->cmd_type == REQ_TYPE_FS)
2027 if (error && req->cmd_type == REQ_TYPE_FS &&
2028 !(req->cmd_flags & REQ_QUIET)) {
2033 error_type = "recoverable transport";
2036 error_type = "critical target";
2039 error_type = "critical nexus";
2046 printk(KERN_ERR "end_request: %s error, dev %s, sector %llu\n",
2047 error_type, req->rq_disk ? req->rq_disk->disk_name : "?",
2048 (unsigned long long)blk_rq_pos(req));
2051 blk_account_io_completion(req, nr_bytes);
2053 total_bytes = bio_nbytes = 0;
2054 while ((bio = req->bio) != NULL) {
2057 if (nr_bytes >= bio->bi_size) {
2058 req->bio = bio->bi_next;
2059 nbytes = bio->bi_size;
2060 req_bio_endio(req, bio, nbytes, error);
2064 int idx = bio->bi_idx + next_idx;
2066 if (unlikely(idx >= bio->bi_vcnt)) {
2067 blk_dump_rq_flags(req, "__end_that");
2068 printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
2069 __func__, idx, bio->bi_vcnt);
2073 nbytes = bio_iovec_idx(bio, idx)->bv_len;
2074 BIO_BUG_ON(nbytes > bio->bi_size);
2077 * not a complete bvec done
2079 if (unlikely(nbytes > nr_bytes)) {
2080 bio_nbytes += nr_bytes;
2081 total_bytes += nr_bytes;
2086 * advance to the next vector
2089 bio_nbytes += nbytes;
2092 total_bytes += nbytes;
2098 * end more in this run, or just return 'not-done'
2100 if (unlikely(nr_bytes <= 0))
2110 * Reset counters so that the request stacking driver
2111 * can find how many bytes remain in the request
2114 req->__data_len = 0;
2119 * if the request wasn't completed, update state
2122 req_bio_endio(req, bio, bio_nbytes, error);
2123 bio->bi_idx += next_idx;
2124 bio_iovec(bio)->bv_offset += nr_bytes;
2125 bio_iovec(bio)->bv_len -= nr_bytes;
2128 req->__data_len -= total_bytes;
2129 req->buffer = bio_data(req->bio);
2131 /* update sector only for requests with clear definition of sector */
2132 if (req->cmd_type == REQ_TYPE_FS || (req->cmd_flags & REQ_DISCARD))
2133 req->__sector += total_bytes >> 9;
2135 /* mixed attributes always follow the first bio */
2136 if (req->cmd_flags & REQ_MIXED_MERGE) {
2137 req->cmd_flags &= ~REQ_FAILFAST_MASK;
2138 req->cmd_flags |= req->bio->bi_rw & REQ_FAILFAST_MASK;
2142 * If total number of sectors is less than the first segment
2143 * size, something has gone terribly wrong.
2145 if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
2146 blk_dump_rq_flags(req, "request botched");
2147 req->__data_len = blk_rq_cur_bytes(req);
2150 /* recalculate the number of segments */
2151 blk_recalc_rq_segments(req);
2155 EXPORT_SYMBOL_GPL(blk_update_request);
2157 static bool blk_update_bidi_request(struct request *rq, int error,
2158 unsigned int nr_bytes,
2159 unsigned int bidi_bytes)
2161 if (blk_update_request(rq, error, nr_bytes))
2164 /* Bidi request must be completed as a whole */
2165 if (unlikely(blk_bidi_rq(rq)) &&
2166 blk_update_request(rq->next_rq, error, bidi_bytes))
2169 if (blk_queue_add_random(rq->q))
2170 add_disk_randomness(rq->rq_disk);
2176 * blk_unprep_request - unprepare a request
2179 * This function makes a request ready for complete resubmission (or
2180 * completion). It happens only after all error handling is complete,
2181 * so represents the appropriate moment to deallocate any resources
2182 * that were allocated to the request in the prep_rq_fn. The queue
2183 * lock is held when calling this.
2185 void blk_unprep_request(struct request *req)
2187 struct request_queue *q = req->q;
2189 req->cmd_flags &= ~REQ_DONTPREP;
2190 if (q->unprep_rq_fn)
2191 q->unprep_rq_fn(q, req);
2193 EXPORT_SYMBOL_GPL(blk_unprep_request);
2196 * queue lock must be held
2198 static void blk_finish_request(struct request *req, int error)
2200 if (blk_rq_tagged(req))
2201 blk_queue_end_tag(req->q, req);
2203 BUG_ON(blk_queued_rq(req));
2205 if (unlikely(laptop_mode) && req->cmd_type == REQ_TYPE_FS)
2206 laptop_io_completion(&req->q->backing_dev_info);
2208 blk_delete_timer(req);
2210 if (req->cmd_flags & REQ_DONTPREP)
2211 blk_unprep_request(req);
2214 blk_account_io_done(req);
2217 req->end_io(req, error);
2219 if (blk_bidi_rq(req))
2220 __blk_put_request(req->next_rq->q, req->next_rq);
2222 __blk_put_request(req->q, req);
2227 * blk_end_bidi_request - Complete a bidi request
2228 * @rq: the request to complete
2229 * @error: %0 for success, < %0 for error
2230 * @nr_bytes: number of bytes to complete @rq
2231 * @bidi_bytes: number of bytes to complete @rq->next_rq
2234 * Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2235 * Drivers that supports bidi can safely call this member for any
2236 * type of request, bidi or uni. In the later case @bidi_bytes is
2240 * %false - we are done with this request
2241 * %true - still buffers pending for this request
2243 static bool blk_end_bidi_request(struct request *rq, int error,
2244 unsigned int nr_bytes, unsigned int bidi_bytes)
2246 struct request_queue *q = rq->q;
2247 unsigned long flags;
2249 if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2252 spin_lock_irqsave(q->queue_lock, flags);
2253 blk_finish_request(rq, error);
2254 spin_unlock_irqrestore(q->queue_lock, flags);
2260 * __blk_end_bidi_request - Complete a bidi request with queue lock held
2261 * @rq: the request to complete
2262 * @error: %0 for success, < %0 for error
2263 * @nr_bytes: number of bytes to complete @rq
2264 * @bidi_bytes: number of bytes to complete @rq->next_rq
2267 * Identical to blk_end_bidi_request() except that queue lock is
2268 * assumed to be locked on entry and remains so on return.
2271 * %false - we are done with this request
2272 * %true - still buffers pending for this request
2274 static bool __blk_end_bidi_request(struct request *rq, int error,
2275 unsigned int nr_bytes, unsigned int bidi_bytes)
2277 if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2280 blk_finish_request(rq, error);
2286 * blk_end_request - Helper function for drivers to complete the request.
2287 * @rq: the request being processed
2288 * @error: %0 for success, < %0 for error
2289 * @nr_bytes: number of bytes to complete
2292 * Ends I/O on a number of bytes attached to @rq.
2293 * If @rq has leftover, sets it up for the next range of segments.
2296 * %false - we are done with this request
2297 * %true - still buffers pending for this request
2299 bool blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2301 return blk_end_bidi_request(rq, error, nr_bytes, 0);
2303 EXPORT_SYMBOL(blk_end_request);
2306 * blk_end_request_all - Helper function for drives to finish the request.
2307 * @rq: the request to finish
2308 * @error: %0 for success, < %0 for error
2311 * Completely finish @rq.
2313 void blk_end_request_all(struct request *rq, int error)
2316 unsigned int bidi_bytes = 0;
2318 if (unlikely(blk_bidi_rq(rq)))
2319 bidi_bytes = blk_rq_bytes(rq->next_rq);
2321 pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2324 EXPORT_SYMBOL(blk_end_request_all);
2327 * blk_end_request_cur - Helper function to finish the current request chunk.
2328 * @rq: the request to finish the current chunk for
2329 * @error: %0 for success, < %0 for error
2332 * Complete the current consecutively mapped chunk from @rq.
2335 * %false - we are done with this request
2336 * %true - still buffers pending for this request
2338 bool blk_end_request_cur(struct request *rq, int error)
2340 return blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2342 EXPORT_SYMBOL(blk_end_request_cur);
2345 * blk_end_request_err - Finish a request till the next failure boundary.
2346 * @rq: the request to finish till the next failure boundary for
2347 * @error: must be negative errno
2350 * Complete @rq till the next failure boundary.
2353 * %false - we are done with this request
2354 * %true - still buffers pending for this request
2356 bool blk_end_request_err(struct request *rq, int error)
2358 WARN_ON(error >= 0);
2359 return blk_end_request(rq, error, blk_rq_err_bytes(rq));
2361 EXPORT_SYMBOL_GPL(blk_end_request_err);
2364 * __blk_end_request - Helper function for drivers to complete the request.
2365 * @rq: the request being processed
2366 * @error: %0 for success, < %0 for error
2367 * @nr_bytes: number of bytes to complete
2370 * Must be called with queue lock held unlike blk_end_request().
2373 * %false - we are done with this request
2374 * %true - still buffers pending for this request
2376 bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2378 return __blk_end_bidi_request(rq, error, nr_bytes, 0);
2380 EXPORT_SYMBOL(__blk_end_request);
2383 * __blk_end_request_all - Helper function for drives to finish the request.
2384 * @rq: the request to finish
2385 * @error: %0 for success, < %0 for error
2388 * Completely finish @rq. Must be called with queue lock held.
2390 void __blk_end_request_all(struct request *rq, int error)
2393 unsigned int bidi_bytes = 0;
2395 if (unlikely(blk_bidi_rq(rq)))
2396 bidi_bytes = blk_rq_bytes(rq->next_rq);
2398 pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2401 EXPORT_SYMBOL(__blk_end_request_all);
2404 * __blk_end_request_cur - Helper function to finish the current request chunk.
2405 * @rq: the request to finish the current chunk for
2406 * @error: %0 for success, < %0 for error
2409 * Complete the current consecutively mapped chunk from @rq. Must
2410 * be called with queue lock held.
2413 * %false - we are done with this request
2414 * %true - still buffers pending for this request
2416 bool __blk_end_request_cur(struct request *rq, int error)
2418 return __blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2420 EXPORT_SYMBOL(__blk_end_request_cur);
2423 * __blk_end_request_err - Finish a request till the next failure boundary.
2424 * @rq: the request to finish till the next failure boundary for
2425 * @error: must be negative errno
2428 * Complete @rq till the next failure boundary. Must be called
2429 * with queue lock held.
2432 * %false - we are done with this request
2433 * %true - still buffers pending for this request
2435 bool __blk_end_request_err(struct request *rq, int error)
2437 WARN_ON(error >= 0);
2438 return __blk_end_request(rq, error, blk_rq_err_bytes(rq));
2440 EXPORT_SYMBOL_GPL(__blk_end_request_err);
2442 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2445 /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */
2446 rq->cmd_flags |= bio->bi_rw & REQ_WRITE;
2448 if (bio_has_data(bio)) {
2449 rq->nr_phys_segments = bio_phys_segments(q, bio);
2450 rq->buffer = bio_data(bio);
2452 rq->__data_len = bio->bi_size;
2453 rq->bio = rq->biotail = bio;
2456 rq->rq_disk = bio->bi_bdev->bd_disk;
2459 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
2461 * rq_flush_dcache_pages - Helper function to flush all pages in a request
2462 * @rq: the request to be flushed
2465 * Flush all pages in @rq.
2467 void rq_flush_dcache_pages(struct request *rq)
2469 struct req_iterator iter;
2470 struct bio_vec *bvec;
2472 rq_for_each_segment(bvec, rq, iter)
2473 flush_dcache_page(bvec->bv_page);
2475 EXPORT_SYMBOL_GPL(rq_flush_dcache_pages);
2479 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2480 * @q : the queue of the device being checked
2483 * Check if underlying low-level drivers of a device are busy.
2484 * If the drivers want to export their busy state, they must set own
2485 * exporting function using blk_queue_lld_busy() first.
2487 * Basically, this function is used only by request stacking drivers
2488 * to stop dispatching requests to underlying devices when underlying
2489 * devices are busy. This behavior helps more I/O merging on the queue
2490 * of the request stacking driver and prevents I/O throughput regression
2491 * on burst I/O load.
2494 * 0 - Not busy (The request stacking driver should dispatch request)
2495 * 1 - Busy (The request stacking driver should stop dispatching request)
2497 int blk_lld_busy(struct request_queue *q)
2500 return q->lld_busy_fn(q);
2504 EXPORT_SYMBOL_GPL(blk_lld_busy);
2507 * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
2508 * @rq: the clone request to be cleaned up
2511 * Free all bios in @rq for a cloned request.
2513 void blk_rq_unprep_clone(struct request *rq)
2517 while ((bio = rq->bio) != NULL) {
2518 rq->bio = bio->bi_next;
2523 EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
2526 * Copy attributes of the original request to the clone request.
2527 * The actual data parts (e.g. ->cmd, ->buffer, ->sense) are not copied.
2529 static void __blk_rq_prep_clone(struct request *dst, struct request *src)
2531 dst->cpu = src->cpu;
2532 dst->cmd_flags = (src->cmd_flags & REQ_CLONE_MASK) | REQ_NOMERGE;
2533 dst->cmd_type = src->cmd_type;
2534 dst->__sector = blk_rq_pos(src);
2535 dst->__data_len = blk_rq_bytes(src);
2536 dst->nr_phys_segments = src->nr_phys_segments;
2537 dst->ioprio = src->ioprio;
2538 dst->extra_len = src->extra_len;
2542 * blk_rq_prep_clone - Helper function to setup clone request
2543 * @rq: the request to be setup
2544 * @rq_src: original request to be cloned
2545 * @bs: bio_set that bios for clone are allocated from
2546 * @gfp_mask: memory allocation mask for bio
2547 * @bio_ctr: setup function to be called for each clone bio.
2548 * Returns %0 for success, non %0 for failure.
2549 * @data: private data to be passed to @bio_ctr
2552 * Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
2553 * The actual data parts of @rq_src (e.g. ->cmd, ->buffer, ->sense)
2554 * are not copied, and copying such parts is the caller's responsibility.
2555 * Also, pages which the original bios are pointing to are not copied
2556 * and the cloned bios just point same pages.
2557 * So cloned bios must be completed before original bios, which means
2558 * the caller must complete @rq before @rq_src.
2560 int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
2561 struct bio_set *bs, gfp_t gfp_mask,
2562 int (*bio_ctr)(struct bio *, struct bio *, void *),
2565 struct bio *bio, *bio_src;
2570 blk_rq_init(NULL, rq);
2572 __rq_for_each_bio(bio_src, rq_src) {
2573 bio = bio_alloc_bioset(gfp_mask, bio_src->bi_max_vecs, bs);
2577 __bio_clone(bio, bio_src);
2579 if (bio_integrity(bio_src) &&
2580 bio_integrity_clone(bio, bio_src, gfp_mask, bs))
2583 if (bio_ctr && bio_ctr(bio, bio_src, data))
2587 rq->biotail->bi_next = bio;
2590 rq->bio = rq->biotail = bio;
2593 __blk_rq_prep_clone(rq, rq_src);
2600 blk_rq_unprep_clone(rq);
2604 EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
2606 int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
2608 return queue_work(kblockd_workqueue, work);
2610 EXPORT_SYMBOL(kblockd_schedule_work);
2612 int kblockd_schedule_delayed_work(struct request_queue *q,
2613 struct delayed_work *dwork, unsigned long delay)
2615 return queue_delayed_work(kblockd_workqueue, dwork, delay);
2617 EXPORT_SYMBOL(kblockd_schedule_delayed_work);
2619 #define PLUG_MAGIC 0x91827364
2621 void blk_start_plug(struct blk_plug *plug)
2623 struct task_struct *tsk = current;
2625 plug->magic = PLUG_MAGIC;
2626 INIT_LIST_HEAD(&plug->list);
2627 INIT_LIST_HEAD(&plug->cb_list);
2628 plug->should_sort = 0;
2631 * If this is a nested plug, don't actually assign it. It will be
2632 * flushed on its own.
2636 * Store ordering should not be needed here, since a potential
2637 * preempt will imply a full memory barrier
2642 EXPORT_SYMBOL(blk_start_plug);
2644 static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
2646 struct request *rqa = container_of(a, struct request, queuelist);
2647 struct request *rqb = container_of(b, struct request, queuelist);
2649 return !(rqa->q <= rqb->q);
2653 * If 'from_schedule' is true, then postpone the dispatch of requests
2654 * until a safe kblockd context. We due this to avoid accidental big
2655 * additional stack usage in driver dispatch, in places where the originally
2656 * plugger did not intend it.
2658 static void queue_unplugged(struct request_queue *q, unsigned int depth,
2660 __releases(q->queue_lock)
2662 trace_block_unplug(q, depth, !from_schedule);
2665 * If we are punting this to kblockd, then we can safely drop
2666 * the queue_lock before waking kblockd (which needs to take
2669 if (from_schedule) {
2670 spin_unlock(q->queue_lock);
2671 blk_run_queue_async(q);
2674 spin_unlock(q->queue_lock);
2679 static void flush_plug_callbacks(struct blk_plug *plug)
2681 LIST_HEAD(callbacks);
2683 if (list_empty(&plug->cb_list))
2686 list_splice_init(&plug->cb_list, &callbacks);
2688 while (!list_empty(&callbacks)) {
2689 struct blk_plug_cb *cb = list_first_entry(&callbacks,
2692 list_del(&cb->list);
2697 void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
2699 struct request_queue *q;
2700 unsigned long flags;
2705 BUG_ON(plug->magic != PLUG_MAGIC);
2707 flush_plug_callbacks(plug);
2708 if (list_empty(&plug->list))
2711 list_splice_init(&plug->list, &list);
2713 if (plug->should_sort) {
2714 list_sort(NULL, &list, plug_rq_cmp);
2715 plug->should_sort = 0;
2722 * Save and disable interrupts here, to avoid doing it for every
2723 * queue lock we have to take.
2725 local_irq_save(flags);
2726 while (!list_empty(&list)) {
2727 rq = list_entry_rq(list.next);
2728 list_del_init(&rq->queuelist);
2732 * This drops the queue lock
2735 queue_unplugged(q, depth, from_schedule);
2738 spin_lock(q->queue_lock);
2741 * rq is already accounted, so use raw insert
2743 if (rq->cmd_flags & (REQ_FLUSH | REQ_FUA))
2744 __elv_add_request(q, rq, ELEVATOR_INSERT_FLUSH);
2746 __elv_add_request(q, rq, ELEVATOR_INSERT_SORT_MERGE);
2752 * This drops the queue lock
2755 queue_unplugged(q, depth, from_schedule);
2757 local_irq_restore(flags);
2760 void blk_finish_plug(struct blk_plug *plug)
2762 blk_flush_plug_list(plug, false);
2764 if (plug == current->plug)
2765 current->plug = NULL;
2767 EXPORT_SYMBOL(blk_finish_plug);
2769 int __init blk_dev_init(void)
2771 BUILD_BUG_ON(__REQ_NR_BITS > 8 *
2772 sizeof(((struct request *)0)->cmd_flags));
2774 /* used for unplugging and affects IO latency/throughput - HIGHPRI */
2775 kblockd_workqueue = alloc_workqueue("kblockd",
2776 WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
2777 if (!kblockd_workqueue)
2778 panic("Failed to create kblockd\n");
2780 request_cachep = kmem_cache_create("blkdev_requests",
2781 sizeof(struct request), 0, SLAB_PANIC, NULL);
2783 blk_requestq_cachep = kmem_cache_create("blkdev_queue",
2784 sizeof(struct request_queue), 0, SLAB_PANIC, NULL);