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>
31 #include <linux/delay.h>
33 #define CREATE_TRACE_POINTS
34 #include <trace/events/block.h>
38 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
39 EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
40 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
42 DEFINE_IDA(blk_queue_ida);
45 * For the allocated request tables
47 static struct kmem_cache *request_cachep;
50 * For queue allocation
52 struct kmem_cache *blk_requestq_cachep;
55 * Controlling structure to kblockd
57 static struct workqueue_struct *kblockd_workqueue;
59 static void drive_stat_acct(struct request *rq, int new_io)
61 struct hd_struct *part;
62 int rw = rq_data_dir(rq);
65 if (!blk_do_io_stat(rq))
68 cpu = part_stat_lock();
72 part_stat_inc(cpu, part, merges[rw]);
74 part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq));
75 if (!hd_struct_try_get(part)) {
77 * The partition is already being removed,
78 * the request will be accounted on the disk only
80 * We take a reference on disk->part0 although that
81 * partition will never be deleted, so we can treat
82 * it as any other partition.
84 part = &rq->rq_disk->part0;
87 part_round_stats(cpu, part);
88 part_inc_in_flight(part, rw);
95 void blk_queue_congestion_threshold(struct request_queue *q)
99 nr = q->nr_requests - (q->nr_requests / 8) + 1;
100 if (nr > q->nr_requests)
102 q->nr_congestion_on = nr;
104 nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
107 q->nr_congestion_off = nr;
111 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
114 * Locates the passed device's request queue and returns the address of its
117 * Will return NULL if the request queue cannot be located.
119 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
121 struct backing_dev_info *ret = NULL;
122 struct request_queue *q = bdev_get_queue(bdev);
125 ret = &q->backing_dev_info;
128 EXPORT_SYMBOL(blk_get_backing_dev_info);
130 void blk_rq_init(struct request_queue *q, struct request *rq)
132 memset(rq, 0, sizeof(*rq));
134 INIT_LIST_HEAD(&rq->queuelist);
135 INIT_LIST_HEAD(&rq->timeout_list);
138 rq->__sector = (sector_t) -1;
139 INIT_HLIST_NODE(&rq->hash);
140 RB_CLEAR_NODE(&rq->rb_node);
142 rq->cmd_len = BLK_MAX_CDB;
145 rq->start_time = jiffies;
146 set_start_time_ns(rq);
149 EXPORT_SYMBOL(blk_rq_init);
151 static void req_bio_endio(struct request *rq, struct bio *bio,
152 unsigned int nbytes, int error)
155 clear_bit(BIO_UPTODATE, &bio->bi_flags);
156 else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
159 if (unlikely(nbytes > bio->bi_size)) {
160 printk(KERN_ERR "%s: want %u bytes done, %u left\n",
161 __func__, nbytes, bio->bi_size);
162 nbytes = bio->bi_size;
165 if (unlikely(rq->cmd_flags & REQ_QUIET))
166 set_bit(BIO_QUIET, &bio->bi_flags);
168 bio->bi_size -= nbytes;
169 bio->bi_sector += (nbytes >> 9);
171 if (bio_integrity(bio))
172 bio_integrity_advance(bio, nbytes);
174 /* don't actually finish bio if it's part of flush sequence */
175 if (bio->bi_size == 0 && !(rq->cmd_flags & REQ_FLUSH_SEQ))
176 bio_endio(bio, error);
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 %u/%u\n",
188 (unsigned long long)blk_rq_pos(rq),
189 blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
190 printk(KERN_INFO " bio %p, biotail %p, buffer %p, len %u\n",
191 rq->bio, rq->biotail, rq->buffer, blk_rq_bytes(rq));
193 if (rq->cmd_type == REQ_TYPE_BLOCK_PC) {
194 printk(KERN_INFO " cdb: ");
195 for (bit = 0; bit < BLK_MAX_CDB; bit++)
196 printk("%02x ", rq->cmd[bit]);
200 EXPORT_SYMBOL(blk_dump_rq_flags);
202 static void blk_delay_work(struct work_struct *work)
204 struct request_queue *q;
206 q = container_of(work, struct request_queue, delay_work.work);
207 spin_lock_irq(q->queue_lock);
209 spin_unlock_irq(q->queue_lock);
213 * blk_delay_queue - restart queueing after defined interval
214 * @q: The &struct request_queue in question
215 * @msecs: Delay in msecs
218 * Sometimes queueing needs to be postponed for a little while, to allow
219 * resources to come back. This function will make sure that queueing is
220 * restarted around the specified time.
222 void blk_delay_queue(struct request_queue *q, unsigned long msecs)
224 queue_delayed_work(kblockd_workqueue, &q->delay_work,
225 msecs_to_jiffies(msecs));
227 EXPORT_SYMBOL(blk_delay_queue);
230 * blk_start_queue - restart a previously stopped queue
231 * @q: The &struct request_queue in question
234 * blk_start_queue() will clear the stop flag on the queue, and call
235 * the request_fn for the queue if it was in a stopped state when
236 * entered. Also see blk_stop_queue(). Queue lock must be held.
238 void blk_start_queue(struct request_queue *q)
240 WARN_ON(!irqs_disabled());
242 queue_flag_clear(QUEUE_FLAG_STOPPED, q);
245 EXPORT_SYMBOL(blk_start_queue);
248 * blk_stop_queue - stop a queue
249 * @q: The &struct request_queue in question
252 * The Linux block layer assumes that a block driver will consume all
253 * entries on the request queue when the request_fn strategy is called.
254 * Often this will not happen, because of hardware limitations (queue
255 * depth settings). If a device driver gets a 'queue full' response,
256 * or if it simply chooses not to queue more I/O at one point, it can
257 * call this function to prevent the request_fn from being called until
258 * the driver has signalled it's ready to go again. This happens by calling
259 * blk_start_queue() to restart queue operations. Queue lock must be held.
261 void blk_stop_queue(struct request_queue *q)
263 __cancel_delayed_work(&q->delay_work);
264 queue_flag_set(QUEUE_FLAG_STOPPED, q);
266 EXPORT_SYMBOL(blk_stop_queue);
269 * blk_sync_queue - cancel any pending callbacks on a queue
273 * The block layer may perform asynchronous callback activity
274 * on a queue, such as calling the unplug function after a timeout.
275 * A block device may call blk_sync_queue to ensure that any
276 * such activity is cancelled, thus allowing it to release resources
277 * that the callbacks might use. The caller must already have made sure
278 * that its ->make_request_fn will not re-add plugging prior to calling
281 * This function does not cancel any asynchronous activity arising
282 * out of elevator or throttling code. That would require elevaotor_exit()
283 * and blk_throtl_exit() to be called with queue lock initialized.
286 void blk_sync_queue(struct request_queue *q)
288 del_timer_sync(&q->timeout);
289 cancel_delayed_work_sync(&q->delay_work);
291 EXPORT_SYMBOL(blk_sync_queue);
294 * __blk_run_queue - run a single device queue
295 * @q: The queue to run
298 * See @blk_run_queue. This variant must be called with the queue lock
299 * held and interrupts disabled.
301 void __blk_run_queue(struct request_queue *q)
303 if (unlikely(blk_queue_stopped(q)))
308 EXPORT_SYMBOL(__blk_run_queue);
311 * blk_run_queue_async - run a single device queue in workqueue context
312 * @q: The queue to run
315 * Tells kblockd to perform the equivalent of @blk_run_queue on behalf
318 void blk_run_queue_async(struct request_queue *q)
320 if (likely(!blk_queue_stopped(q))) {
321 __cancel_delayed_work(&q->delay_work);
322 queue_delayed_work(kblockd_workqueue, &q->delay_work, 0);
325 EXPORT_SYMBOL(blk_run_queue_async);
328 * blk_run_queue - run a single device queue
329 * @q: The queue to run
332 * Invoke request handling on this queue, if it has pending work to do.
333 * May be used to restart queueing when a request has completed.
335 void blk_run_queue(struct request_queue *q)
339 spin_lock_irqsave(q->queue_lock, flags);
341 spin_unlock_irqrestore(q->queue_lock, flags);
343 EXPORT_SYMBOL(blk_run_queue);
345 void blk_put_queue(struct request_queue *q)
347 kobject_put(&q->kobj);
349 EXPORT_SYMBOL(blk_put_queue);
352 * blk_drain_queue - drain requests from request_queue
354 * @drain_all: whether to drain all requests or only the ones w/ ELVPRIV
356 * Drain requests from @q. If @drain_all is set, all requests are drained.
357 * If not, only ELVPRIV requests are drained. The caller is responsible
358 * for ensuring that no new requests which need to be drained are queued.
360 void blk_drain_queue(struct request_queue *q, bool drain_all)
366 spin_lock_irq(q->queue_lock);
369 * The caller might be trying to drain @q before its
370 * elevator is initialized.
373 elv_drain_elevator(q);
379 * This function might be called on a queue which failed
380 * driver init after queue creation or is not yet fully
381 * active yet. Some drivers (e.g. fd and loop) get unhappy
382 * in such cases. Kick queue iff dispatch queue has
383 * something on it and @q has request_fn set.
385 if (!list_empty(&q->queue_head) && q->request_fn)
388 drain |= q->rq.elvpriv;
391 * Unfortunately, requests are queued at and tracked from
392 * multiple places and there's no single counter which can
393 * be drained. Check all the queues and counters.
396 drain |= !list_empty(&q->queue_head);
397 for (i = 0; i < 2; i++) {
398 drain |= q->rq.count[i];
399 drain |= q->in_flight[i];
400 drain |= !list_empty(&q->flush_queue[i]);
404 spin_unlock_irq(q->queue_lock);
413 * blk_queue_bypass_start - enter queue bypass mode
414 * @q: queue of interest
416 * In bypass mode, only the dispatch FIFO queue of @q is used. This
417 * function makes @q enter bypass mode and drains all requests which were
418 * issued before. On return, it's guaranteed that no request has ELVPRIV
421 void blk_queue_bypass_start(struct request_queue *q)
423 spin_lock_irq(q->queue_lock);
425 queue_flag_set(QUEUE_FLAG_BYPASS, q);
426 spin_unlock_irq(q->queue_lock);
428 blk_drain_queue(q, false);
430 EXPORT_SYMBOL_GPL(blk_queue_bypass_start);
433 * blk_queue_bypass_end - leave queue bypass mode
434 * @q: queue of interest
436 * Leave bypass mode and restore the normal queueing behavior.
438 void blk_queue_bypass_end(struct request_queue *q)
440 spin_lock_irq(q->queue_lock);
441 if (!--q->bypass_depth)
442 queue_flag_clear(QUEUE_FLAG_BYPASS, q);
443 WARN_ON_ONCE(q->bypass_depth < 0);
444 spin_unlock_irq(q->queue_lock);
446 EXPORT_SYMBOL_GPL(blk_queue_bypass_end);
449 * blk_cleanup_queue - shutdown a request queue
450 * @q: request queue to shutdown
452 * Mark @q DEAD, drain all pending requests, destroy and put it. All
453 * future requests will be failed immediately with -ENODEV.
455 void blk_cleanup_queue(struct request_queue *q)
457 spinlock_t *lock = q->queue_lock;
459 /* mark @q DEAD, no new request or merges will be allowed afterwards */
460 mutex_lock(&q->sysfs_lock);
461 queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
464 queue_flag_set(QUEUE_FLAG_NOMERGES, q);
465 queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
466 queue_flag_set(QUEUE_FLAG_DEAD, q);
468 if (q->queue_lock != &q->__queue_lock)
469 q->queue_lock = &q->__queue_lock;
471 spin_unlock_irq(lock);
472 mutex_unlock(&q->sysfs_lock);
474 /* drain all requests queued before DEAD marking */
475 blk_drain_queue(q, true);
477 /* @q won't process any more request, flush async actions */
478 del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);
481 /* @q is and will stay empty, shutdown and put */
484 EXPORT_SYMBOL(blk_cleanup_queue);
486 static int blk_init_free_list(struct request_queue *q)
488 struct request_list *rl = &q->rq;
490 if (unlikely(rl->rq_pool))
493 rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
494 rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
496 init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
497 init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
499 rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
500 mempool_free_slab, request_cachep, q->node);
508 struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
510 return blk_alloc_queue_node(gfp_mask, -1);
512 EXPORT_SYMBOL(blk_alloc_queue);
514 struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
516 struct request_queue *q;
519 q = kmem_cache_alloc_node(blk_requestq_cachep,
520 gfp_mask | __GFP_ZERO, node_id);
524 q->id = ida_simple_get(&blk_queue_ida, 0, 0, GFP_KERNEL);
528 q->backing_dev_info.ra_pages =
529 (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
530 q->backing_dev_info.state = 0;
531 q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
532 q->backing_dev_info.name = "block";
535 err = bdi_init(&q->backing_dev_info);
539 if (blk_throtl_init(q))
542 setup_timer(&q->backing_dev_info.laptop_mode_wb_timer,
543 laptop_mode_timer_fn, (unsigned long) q);
544 setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
545 INIT_LIST_HEAD(&q->queue_head);
546 INIT_LIST_HEAD(&q->timeout_list);
547 INIT_LIST_HEAD(&q->icq_list);
548 INIT_LIST_HEAD(&q->flush_queue[0]);
549 INIT_LIST_HEAD(&q->flush_queue[1]);
550 INIT_LIST_HEAD(&q->flush_data_in_flight);
551 INIT_DELAYED_WORK(&q->delay_work, blk_delay_work);
553 kobject_init(&q->kobj, &blk_queue_ktype);
555 mutex_init(&q->sysfs_lock);
556 spin_lock_init(&q->__queue_lock);
559 * By default initialize queue_lock to internal lock and driver can
560 * override it later if need be.
562 q->queue_lock = &q->__queue_lock;
567 ida_simple_remove(&blk_queue_ida, q->id);
569 kmem_cache_free(blk_requestq_cachep, q);
572 EXPORT_SYMBOL(blk_alloc_queue_node);
575 * blk_init_queue - prepare a request queue for use with a block device
576 * @rfn: The function to be called to process requests that have been
577 * placed on the queue.
578 * @lock: Request queue spin lock
581 * If a block device wishes to use the standard request handling procedures,
582 * which sorts requests and coalesces adjacent requests, then it must
583 * call blk_init_queue(). The function @rfn will be called when there
584 * are requests on the queue that need to be processed. If the device
585 * supports plugging, then @rfn may not be called immediately when requests
586 * are available on the queue, but may be called at some time later instead.
587 * Plugged queues are generally unplugged when a buffer belonging to one
588 * of the requests on the queue is needed, or due to memory pressure.
590 * @rfn is not required, or even expected, to remove all requests off the
591 * queue, but only as many as it can handle at a time. If it does leave
592 * requests on the queue, it is responsible for arranging that the requests
593 * get dealt with eventually.
595 * The queue spin lock must be held while manipulating the requests on the
596 * request queue; this lock will be taken also from interrupt context, so irq
597 * disabling is needed for it.
599 * Function returns a pointer to the initialized request queue, or %NULL if
603 * blk_init_queue() must be paired with a blk_cleanup_queue() call
604 * when the block device is deactivated (such as at module unload).
607 struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
609 return blk_init_queue_node(rfn, lock, -1);
611 EXPORT_SYMBOL(blk_init_queue);
613 struct request_queue *
614 blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
616 struct request_queue *uninit_q, *q;
618 uninit_q = blk_alloc_queue_node(GFP_KERNEL, node_id);
622 q = blk_init_allocated_queue(uninit_q, rfn, lock);
624 blk_cleanup_queue(uninit_q);
628 EXPORT_SYMBOL(blk_init_queue_node);
630 struct request_queue *
631 blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
637 if (blk_init_free_list(q))
641 q->prep_rq_fn = NULL;
642 q->unprep_rq_fn = NULL;
643 q->queue_flags = QUEUE_FLAG_DEFAULT;
645 /* Override internal queue lock with supplied lock pointer */
647 q->queue_lock = lock;
650 * This also sets hw/phys segments, boundary and size
652 blk_queue_make_request(q, blk_queue_bio);
654 q->sg_reserved_size = INT_MAX;
659 if (!elevator_init(q, NULL)) {
660 blk_queue_congestion_threshold(q);
666 EXPORT_SYMBOL(blk_init_allocated_queue);
668 bool blk_get_queue(struct request_queue *q)
670 if (likely(!blk_queue_dead(q))) {
677 EXPORT_SYMBOL(blk_get_queue);
679 static inline void blk_free_request(struct request_queue *q, struct request *rq)
681 if (rq->cmd_flags & REQ_ELVPRIV) {
682 elv_put_request(q, rq);
684 put_io_context(rq->elv.icq->ioc);
687 mempool_free(rq, q->rq.rq_pool);
690 static struct request *
691 blk_alloc_request(struct request_queue *q, struct io_cq *icq,
692 unsigned int flags, gfp_t gfp_mask)
694 struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
701 rq->cmd_flags = flags | REQ_ALLOCED;
703 if (flags & REQ_ELVPRIV) {
705 if (unlikely(elv_set_request(q, rq, gfp_mask))) {
706 mempool_free(rq, q->rq.rq_pool);
709 /* @rq->elv.icq holds on to io_context until @rq is freed */
711 get_io_context(icq->ioc);
718 * ioc_batching returns true if the ioc is a valid batching request and
719 * should be given priority access to a request.
721 static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
727 * Make sure the process is able to allocate at least 1 request
728 * even if the batch times out, otherwise we could theoretically
731 return ioc->nr_batch_requests == q->nr_batching ||
732 (ioc->nr_batch_requests > 0
733 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
737 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
738 * will cause the process to be a "batcher" on all queues in the system. This
739 * is the behaviour we want though - once it gets a wakeup it should be given
742 static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
744 if (!ioc || ioc_batching(q, ioc))
747 ioc->nr_batch_requests = q->nr_batching;
748 ioc->last_waited = jiffies;
751 static void __freed_request(struct request_queue *q, int sync)
753 struct request_list *rl = &q->rq;
755 if (rl->count[sync] < queue_congestion_off_threshold(q))
756 blk_clear_queue_congested(q, sync);
758 if (rl->count[sync] + 1 <= q->nr_requests) {
759 if (waitqueue_active(&rl->wait[sync]))
760 wake_up(&rl->wait[sync]);
762 blk_clear_queue_full(q, sync);
767 * A request has just been released. Account for it, update the full and
768 * congestion status, wake up any waiters. Called under q->queue_lock.
770 static void freed_request(struct request_queue *q, unsigned int flags)
772 struct request_list *rl = &q->rq;
773 int sync = rw_is_sync(flags);
776 if (flags & REQ_ELVPRIV)
779 __freed_request(q, sync);
781 if (unlikely(rl->starved[sync ^ 1]))
782 __freed_request(q, sync ^ 1);
786 * Determine if elevator data should be initialized when allocating the
787 * request associated with @bio.
789 static bool blk_rq_should_init_elevator(struct bio *bio)
795 * Flush requests do not use the elevator so skip initialization.
796 * This allows a request to share the flush and elevator data.
798 if (bio->bi_rw & (REQ_FLUSH | REQ_FUA))
805 * get_request - get a free request
806 * @q: request_queue to allocate request from
807 * @rw_flags: RW and SYNC flags
808 * @bio: bio to allocate request for (can be %NULL)
809 * @gfp_mask: allocation mask
811 * Get a free request from @q. This function may fail under memory
812 * pressure or if @q is dead.
814 * Must be callled with @q->queue_lock held and,
815 * Returns %NULL on failure, with @q->queue_lock held.
816 * Returns !%NULL on success, with @q->queue_lock *not held*.
818 static struct request *get_request(struct request_queue *q, int rw_flags,
819 struct bio *bio, gfp_t gfp_mask)
821 struct request *rq = NULL;
822 struct request_list *rl = &q->rq;
823 struct elevator_type *et;
824 struct io_context *ioc;
825 struct io_cq *icq = NULL;
826 const bool is_sync = rw_is_sync(rw_flags) != 0;
827 bool retried = false;
830 et = q->elevator->type;
831 ioc = current->io_context;
833 if (unlikely(blk_queue_dead(q)))
836 may_queue = elv_may_queue(q, rw_flags);
837 if (may_queue == ELV_MQUEUE_NO)
840 if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
841 if (rl->count[is_sync]+1 >= q->nr_requests) {
843 * We want ioc to record batching state. If it's
844 * not already there, creating a new one requires
845 * dropping queue_lock, which in turn requires
846 * retesting conditions to avoid queue hang.
848 if (!ioc && !retried) {
849 spin_unlock_irq(q->queue_lock);
850 create_io_context(current, gfp_mask, q->node);
851 spin_lock_irq(q->queue_lock);
857 * The queue will fill after this allocation, so set
858 * it as full, and mark this process as "batching".
859 * This process will be allowed to complete a batch of
860 * requests, others will be blocked.
862 if (!blk_queue_full(q, is_sync)) {
863 ioc_set_batching(q, ioc);
864 blk_set_queue_full(q, is_sync);
866 if (may_queue != ELV_MQUEUE_MUST
867 && !ioc_batching(q, ioc)) {
869 * The queue is full and the allocating
870 * process is not a "batcher", and not
871 * exempted by the IO scheduler
877 blk_set_queue_congested(q, is_sync);
881 * Only allow batching queuers to allocate up to 50% over the defined
882 * limit of requests, otherwise we could have thousands of requests
883 * allocated with any setting of ->nr_requests
885 if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
888 rl->count[is_sync]++;
889 rl->starved[is_sync] = 0;
892 * Decide whether the new request will be managed by elevator. If
893 * so, mark @rw_flags and increment elvpriv. Non-zero elvpriv will
894 * prevent the current elevator from being destroyed until the new
895 * request is freed. This guarantees icq's won't be destroyed and
896 * makes creating new ones safe.
898 * Also, lookup icq while holding queue_lock. If it doesn't exist,
899 * it will be created after releasing queue_lock.
901 if (blk_rq_should_init_elevator(bio) && !blk_queue_bypass(q)) {
902 rw_flags |= REQ_ELVPRIV;
904 if (et->icq_cache && ioc)
905 icq = ioc_lookup_icq(ioc, q);
908 if (blk_queue_io_stat(q))
909 rw_flags |= REQ_IO_STAT;
910 spin_unlock_irq(q->queue_lock);
912 /* create icq if missing */
913 if ((rw_flags & REQ_ELVPRIV) && unlikely(et->icq_cache && !icq)) {
914 icq = ioc_create_icq(q, gfp_mask);
919 rq = blk_alloc_request(q, icq, rw_flags, gfp_mask);
924 * Allocation failed presumably due to memory. Undo anything
925 * we might have messed up.
927 * Allocating task should really be put onto the front of the
928 * wait queue, but this is pretty rare.
930 spin_lock_irq(q->queue_lock);
931 freed_request(q, rw_flags);
934 * in the very unlikely event that allocation failed and no
935 * requests for this direction was pending, mark us starved
936 * so that freeing of a request in the other direction will
937 * notice us. another possible fix would be to split the
938 * rq mempool into READ and WRITE
941 if (unlikely(rl->count[is_sync] == 0))
942 rl->starved[is_sync] = 1;
948 * ioc may be NULL here, and ioc_batching will be false. That's
949 * OK, if the queue is under the request limit then requests need
950 * not count toward the nr_batch_requests limit. There will always
951 * be some limit enforced by BLK_BATCH_TIME.
953 if (ioc_batching(q, ioc))
954 ioc->nr_batch_requests--;
956 trace_block_getrq(q, bio, rw_flags & 1);
962 * get_request_wait - get a free request with retry
963 * @q: request_queue to allocate request from
964 * @rw_flags: RW and SYNC flags
965 * @bio: bio to allocate request for (can be %NULL)
967 * Get a free request from @q. This function keeps retrying under memory
968 * pressure and fails iff @q is dead.
970 * Must be callled with @q->queue_lock held and,
971 * Returns %NULL on failure, with @q->queue_lock held.
972 * Returns !%NULL on success, with @q->queue_lock *not held*.
974 static struct request *get_request_wait(struct request_queue *q, int rw_flags,
977 const bool is_sync = rw_is_sync(rw_flags) != 0;
980 rq = get_request(q, rw_flags, bio, GFP_NOIO);
983 struct request_list *rl = &q->rq;
985 if (unlikely(blk_queue_dead(q)))
988 prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
989 TASK_UNINTERRUPTIBLE);
991 trace_block_sleeprq(q, bio, rw_flags & 1);
993 spin_unlock_irq(q->queue_lock);
997 * After sleeping, we become a "batching" process and
998 * will be able to allocate at least one request, and
999 * up to a big batch of them for a small period time.
1000 * See ioc_batching, ioc_set_batching
1002 create_io_context(current, GFP_NOIO, q->node);
1003 ioc_set_batching(q, current->io_context);
1005 spin_lock_irq(q->queue_lock);
1006 finish_wait(&rl->wait[is_sync], &wait);
1008 rq = get_request(q, rw_flags, bio, GFP_NOIO);
1014 struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
1018 BUG_ON(rw != READ && rw != WRITE);
1020 spin_lock_irq(q->queue_lock);
1021 if (gfp_mask & __GFP_WAIT)
1022 rq = get_request_wait(q, rw, NULL);
1024 rq = get_request(q, rw, NULL, gfp_mask);
1026 spin_unlock_irq(q->queue_lock);
1027 /* q->queue_lock is unlocked at this point */
1031 EXPORT_SYMBOL(blk_get_request);
1034 * blk_make_request - given a bio, allocate a corresponding struct request.
1035 * @q: target request queue
1036 * @bio: The bio describing the memory mappings that will be submitted for IO.
1037 * It may be a chained-bio properly constructed by block/bio layer.
1038 * @gfp_mask: gfp flags to be used for memory allocation
1040 * blk_make_request is the parallel of generic_make_request for BLOCK_PC
1041 * type commands. Where the struct request needs to be farther initialized by
1042 * the caller. It is passed a &struct bio, which describes the memory info of
1045 * The caller of blk_make_request must make sure that bi_io_vec
1046 * are set to describe the memory buffers. That bio_data_dir() will return
1047 * the needed direction of the request. (And all bio's in the passed bio-chain
1048 * are properly set accordingly)
1050 * If called under none-sleepable conditions, mapped bio buffers must not
1051 * need bouncing, by calling the appropriate masked or flagged allocator,
1052 * suitable for the target device. Otherwise the call to blk_queue_bounce will
1055 * WARNING: When allocating/cloning a bio-chain, careful consideration should be
1056 * given to how you allocate bios. In particular, you cannot use __GFP_WAIT for
1057 * anything but the first bio in the chain. Otherwise you risk waiting for IO
1058 * completion of a bio that hasn't been submitted yet, thus resulting in a
1059 * deadlock. Alternatively bios should be allocated using bio_kmalloc() instead
1060 * of bio_alloc(), as that avoids the mempool deadlock.
1061 * If possible a big IO should be split into smaller parts when allocation
1062 * fails. Partial allocation should not be an error, or you risk a live-lock.
1064 struct request *blk_make_request(struct request_queue *q, struct bio *bio,
1067 struct request *rq = blk_get_request(q, bio_data_dir(bio), gfp_mask);
1070 return ERR_PTR(-ENOMEM);
1073 struct bio *bounce_bio = bio;
1076 blk_queue_bounce(q, &bounce_bio);
1077 ret = blk_rq_append_bio(q, rq, bounce_bio);
1078 if (unlikely(ret)) {
1079 blk_put_request(rq);
1080 return ERR_PTR(ret);
1086 EXPORT_SYMBOL(blk_make_request);
1089 * blk_requeue_request - put a request back on queue
1090 * @q: request queue where request should be inserted
1091 * @rq: request to be inserted
1094 * Drivers often keep queueing requests until the hardware cannot accept
1095 * more, when that condition happens we need to put the request back
1096 * on the queue. Must be called with queue lock held.
1098 void blk_requeue_request(struct request_queue *q, struct request *rq)
1100 blk_delete_timer(rq);
1101 blk_clear_rq_complete(rq);
1102 trace_block_rq_requeue(q, rq);
1104 if (blk_rq_tagged(rq))
1105 blk_queue_end_tag(q, rq);
1107 BUG_ON(blk_queued_rq(rq));
1109 elv_requeue_request(q, rq);
1111 EXPORT_SYMBOL(blk_requeue_request);
1113 static void add_acct_request(struct request_queue *q, struct request *rq,
1116 drive_stat_acct(rq, 1);
1117 __elv_add_request(q, rq, where);
1120 static void part_round_stats_single(int cpu, struct hd_struct *part,
1123 if (now == part->stamp)
1126 if (part_in_flight(part)) {
1127 __part_stat_add(cpu, part, time_in_queue,
1128 part_in_flight(part) * (now - part->stamp));
1129 __part_stat_add(cpu, part, io_ticks, (now - part->stamp));
1135 * part_round_stats() - Round off the performance stats on a struct disk_stats.
1136 * @cpu: cpu number for stats access
1137 * @part: target partition
1139 * The average IO queue length and utilisation statistics are maintained
1140 * by observing the current state of the queue length and the amount of
1141 * time it has been in this state for.
1143 * Normally, that accounting is done on IO completion, but that can result
1144 * in more than a second's worth of IO being accounted for within any one
1145 * second, leading to >100% utilisation. To deal with that, we call this
1146 * function to do a round-off before returning the results when reading
1147 * /proc/diskstats. This accounts immediately for all queue usage up to
1148 * the current jiffies and restarts the counters again.
1150 void part_round_stats(int cpu, struct hd_struct *part)
1152 unsigned long now = jiffies;
1155 part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1156 part_round_stats_single(cpu, part, now);
1158 EXPORT_SYMBOL_GPL(part_round_stats);
1161 * queue lock must be held
1163 void __blk_put_request(struct request_queue *q, struct request *req)
1167 if (unlikely(--req->ref_count))
1170 elv_completed_request(q, req);
1172 /* this is a bio leak */
1173 WARN_ON(req->bio != NULL);
1176 * Request may not have originated from ll_rw_blk. if not,
1177 * it didn't come out of our reserved rq pools
1179 if (req->cmd_flags & REQ_ALLOCED) {
1180 unsigned int flags = req->cmd_flags;
1182 BUG_ON(!list_empty(&req->queuelist));
1183 BUG_ON(!hlist_unhashed(&req->hash));
1185 blk_free_request(q, req);
1186 freed_request(q, flags);
1189 EXPORT_SYMBOL_GPL(__blk_put_request);
1191 void blk_put_request(struct request *req)
1193 unsigned long flags;
1194 struct request_queue *q = req->q;
1196 spin_lock_irqsave(q->queue_lock, flags);
1197 __blk_put_request(q, req);
1198 spin_unlock_irqrestore(q->queue_lock, flags);
1200 EXPORT_SYMBOL(blk_put_request);
1203 * blk_add_request_payload - add a payload to a request
1204 * @rq: request to update
1205 * @page: page backing the payload
1206 * @len: length of the payload.
1208 * This allows to later add a payload to an already submitted request by
1209 * a block driver. The driver needs to take care of freeing the payload
1212 * Note that this is a quite horrible hack and nothing but handling of
1213 * discard requests should ever use it.
1215 void blk_add_request_payload(struct request *rq, struct page *page,
1218 struct bio *bio = rq->bio;
1220 bio->bi_io_vec->bv_page = page;
1221 bio->bi_io_vec->bv_offset = 0;
1222 bio->bi_io_vec->bv_len = len;
1226 bio->bi_phys_segments = 1;
1228 rq->__data_len = rq->resid_len = len;
1229 rq->nr_phys_segments = 1;
1230 rq->buffer = bio_data(bio);
1232 EXPORT_SYMBOL_GPL(blk_add_request_payload);
1234 static bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
1237 const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1239 if (!ll_back_merge_fn(q, req, bio))
1242 trace_block_bio_backmerge(q, bio);
1244 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1245 blk_rq_set_mixed_merge(req);
1247 req->biotail->bi_next = bio;
1249 req->__data_len += bio->bi_size;
1250 req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1252 drive_stat_acct(req, 0);
1256 static bool bio_attempt_front_merge(struct request_queue *q,
1257 struct request *req, struct bio *bio)
1259 const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1261 if (!ll_front_merge_fn(q, req, bio))
1264 trace_block_bio_frontmerge(q, bio);
1266 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1267 blk_rq_set_mixed_merge(req);
1269 bio->bi_next = req->bio;
1273 * may not be valid. if the low level driver said
1274 * it didn't need a bounce buffer then it better
1275 * not touch req->buffer either...
1277 req->buffer = bio_data(bio);
1278 req->__sector = bio->bi_sector;
1279 req->__data_len += bio->bi_size;
1280 req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1282 drive_stat_acct(req, 0);
1287 * attempt_plug_merge - try to merge with %current's plugged list
1288 * @q: request_queue new bio is being queued at
1289 * @bio: new bio being queued
1290 * @request_count: out parameter for number of traversed plugged requests
1292 * Determine whether @bio being queued on @q can be merged with a request
1293 * on %current's plugged list. Returns %true if merge was successful,
1296 * Plugging coalesces IOs from the same issuer for the same purpose without
1297 * going through @q->queue_lock. As such it's more of an issuing mechanism
1298 * than scheduling, and the request, while may have elvpriv data, is not
1299 * added on the elevator at this point. In addition, we don't have
1300 * reliable access to the elevator outside queue lock. Only check basic
1301 * merging parameters without querying the elevator.
1303 static bool attempt_plug_merge(struct request_queue *q, struct bio *bio,
1304 unsigned int *request_count)
1306 struct blk_plug *plug;
1310 plug = current->plug;
1315 list_for_each_entry_reverse(rq, &plug->list, queuelist) {
1320 if (rq->q != q || !blk_rq_merge_ok(rq, bio))
1323 el_ret = blk_try_merge(rq, bio);
1324 if (el_ret == ELEVATOR_BACK_MERGE) {
1325 ret = bio_attempt_back_merge(q, rq, bio);
1328 } else if (el_ret == ELEVATOR_FRONT_MERGE) {
1329 ret = bio_attempt_front_merge(q, rq, bio);
1338 void init_request_from_bio(struct request *req, struct bio *bio)
1340 req->cmd_type = REQ_TYPE_FS;
1342 req->cmd_flags |= bio->bi_rw & REQ_COMMON_MASK;
1343 if (bio->bi_rw & REQ_RAHEAD)
1344 req->cmd_flags |= REQ_FAILFAST_MASK;
1347 req->__sector = bio->bi_sector;
1348 req->ioprio = bio_prio(bio);
1349 blk_rq_bio_prep(req->q, req, bio);
1352 void blk_queue_bio(struct request_queue *q, struct bio *bio)
1354 const bool sync = !!(bio->bi_rw & REQ_SYNC);
1355 struct blk_plug *plug;
1356 int el_ret, rw_flags, where = ELEVATOR_INSERT_SORT;
1357 struct request *req;
1358 unsigned int request_count = 0;
1361 * low level driver can indicate that it wants pages above a
1362 * certain limit bounced to low memory (ie for highmem, or even
1363 * ISA dma in theory)
1365 blk_queue_bounce(q, &bio);
1367 if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) {
1368 spin_lock_irq(q->queue_lock);
1369 where = ELEVATOR_INSERT_FLUSH;
1374 * Check if we can merge with the plugged list before grabbing
1377 if (attempt_plug_merge(q, bio, &request_count))
1380 spin_lock_irq(q->queue_lock);
1382 el_ret = elv_merge(q, &req, bio);
1383 if (el_ret == ELEVATOR_BACK_MERGE) {
1384 if (bio_attempt_back_merge(q, req, bio)) {
1385 elv_bio_merged(q, req, bio);
1386 if (!attempt_back_merge(q, req))
1387 elv_merged_request(q, req, el_ret);
1390 } else if (el_ret == ELEVATOR_FRONT_MERGE) {
1391 if (bio_attempt_front_merge(q, req, bio)) {
1392 elv_bio_merged(q, req, bio);
1393 if (!attempt_front_merge(q, req))
1394 elv_merged_request(q, req, el_ret);
1401 * This sync check and mask will be re-done in init_request_from_bio(),
1402 * but we need to set it earlier to expose the sync flag to the
1403 * rq allocator and io schedulers.
1405 rw_flags = bio_data_dir(bio);
1407 rw_flags |= REQ_SYNC;
1410 * Grab a free request. This is might sleep but can not fail.
1411 * Returns with the queue unlocked.
1413 req = get_request_wait(q, rw_flags, bio);
1414 if (unlikely(!req)) {
1415 bio_endio(bio, -ENODEV); /* @q is dead */
1420 * After dropping the lock and possibly sleeping here, our request
1421 * may now be mergeable after it had proven unmergeable (above).
1422 * We don't worry about that case for efficiency. It won't happen
1423 * often, and the elevators are able to handle it.
1425 init_request_from_bio(req, bio);
1427 if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags))
1428 req->cpu = raw_smp_processor_id();
1430 plug = current->plug;
1433 * If this is the first request added after a plug, fire
1434 * of a plug trace. If others have been added before, check
1435 * if we have multiple devices in this plug. If so, make a
1436 * note to sort the list before dispatch.
1438 if (list_empty(&plug->list))
1439 trace_block_plug(q);
1441 if (!plug->should_sort) {
1442 struct request *__rq;
1444 __rq = list_entry_rq(plug->list.prev);
1446 plug->should_sort = 1;
1448 if (request_count >= BLK_MAX_REQUEST_COUNT) {
1449 blk_flush_plug_list(plug, false);
1450 trace_block_plug(q);
1453 list_add_tail(&req->queuelist, &plug->list);
1454 drive_stat_acct(req, 1);
1456 spin_lock_irq(q->queue_lock);
1457 add_acct_request(q, req, where);
1460 spin_unlock_irq(q->queue_lock);
1463 EXPORT_SYMBOL_GPL(blk_queue_bio); /* for device mapper only */
1466 * If bio->bi_dev is a partition, remap the location
1468 static inline void blk_partition_remap(struct bio *bio)
1470 struct block_device *bdev = bio->bi_bdev;
1472 if (bio_sectors(bio) && bdev != bdev->bd_contains) {
1473 struct hd_struct *p = bdev->bd_part;
1475 bio->bi_sector += p->start_sect;
1476 bio->bi_bdev = bdev->bd_contains;
1478 trace_block_bio_remap(bdev_get_queue(bio->bi_bdev), bio,
1480 bio->bi_sector - p->start_sect);
1484 static void handle_bad_sector(struct bio *bio)
1486 char b[BDEVNAME_SIZE];
1488 printk(KERN_INFO "attempt to access beyond end of device\n");
1489 printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
1490 bdevname(bio->bi_bdev, b),
1492 (unsigned long long)bio->bi_sector + bio_sectors(bio),
1493 (long long)(i_size_read(bio->bi_bdev->bd_inode) >> 9));
1495 set_bit(BIO_EOF, &bio->bi_flags);
1498 #ifdef CONFIG_FAIL_MAKE_REQUEST
1500 static DECLARE_FAULT_ATTR(fail_make_request);
1502 static int __init setup_fail_make_request(char *str)
1504 return setup_fault_attr(&fail_make_request, str);
1506 __setup("fail_make_request=", setup_fail_make_request);
1508 static bool should_fail_request(struct hd_struct *part, unsigned int bytes)
1510 return part->make_it_fail && should_fail(&fail_make_request, bytes);
1513 static int __init fail_make_request_debugfs(void)
1515 struct dentry *dir = fault_create_debugfs_attr("fail_make_request",
1516 NULL, &fail_make_request);
1518 return IS_ERR(dir) ? PTR_ERR(dir) : 0;
1521 late_initcall(fail_make_request_debugfs);
1523 #else /* CONFIG_FAIL_MAKE_REQUEST */
1525 static inline bool should_fail_request(struct hd_struct *part,
1531 #endif /* CONFIG_FAIL_MAKE_REQUEST */
1534 * Check whether this bio extends beyond the end of the device.
1536 static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1543 /* Test device or partition size, when known. */
1544 maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
1546 sector_t sector = bio->bi_sector;
1548 if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1550 * This may well happen - the kernel calls bread()
1551 * without checking the size of the device, e.g., when
1552 * mounting a device.
1554 handle_bad_sector(bio);
1562 static noinline_for_stack bool
1563 generic_make_request_checks(struct bio *bio)
1565 struct request_queue *q;
1566 int nr_sectors = bio_sectors(bio);
1568 char b[BDEVNAME_SIZE];
1569 struct hd_struct *part;
1573 if (bio_check_eod(bio, nr_sectors))
1576 q = bdev_get_queue(bio->bi_bdev);
1579 "generic_make_request: Trying to access "
1580 "nonexistent block-device %s (%Lu)\n",
1581 bdevname(bio->bi_bdev, b),
1582 (long long) bio->bi_sector);
1586 if (unlikely(!(bio->bi_rw & REQ_DISCARD) &&
1587 nr_sectors > queue_max_hw_sectors(q))) {
1588 printk(KERN_ERR "bio too big device %s (%u > %u)\n",
1589 bdevname(bio->bi_bdev, b),
1591 queue_max_hw_sectors(q));
1595 part = bio->bi_bdev->bd_part;
1596 if (should_fail_request(part, bio->bi_size) ||
1597 should_fail_request(&part_to_disk(part)->part0,
1602 * If this device has partitions, remap block n
1603 * of partition p to block n+start(p) of the disk.
1605 blk_partition_remap(bio);
1607 if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
1610 if (bio_check_eod(bio, nr_sectors))
1614 * Filter flush bio's early so that make_request based
1615 * drivers without flush support don't have to worry
1618 if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
1619 bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
1626 if ((bio->bi_rw & REQ_DISCARD) &&
1627 (!blk_queue_discard(q) ||
1628 ((bio->bi_rw & REQ_SECURE) &&
1629 !blk_queue_secdiscard(q)))) {
1634 if (blk_throtl_bio(q, bio))
1635 return false; /* throttled, will be resubmitted later */
1637 trace_block_bio_queue(q, bio);
1641 bio_endio(bio, err);
1646 * generic_make_request - hand a buffer to its device driver for I/O
1647 * @bio: The bio describing the location in memory and on the device.
1649 * generic_make_request() is used to make I/O requests of block
1650 * devices. It is passed a &struct bio, which describes the I/O that needs
1653 * generic_make_request() does not return any status. The
1654 * success/failure status of the request, along with notification of
1655 * completion, is delivered asynchronously through the bio->bi_end_io
1656 * function described (one day) else where.
1658 * The caller of generic_make_request must make sure that bi_io_vec
1659 * are set to describe the memory buffer, and that bi_dev and bi_sector are
1660 * set to describe the device address, and the
1661 * bi_end_io and optionally bi_private are set to describe how
1662 * completion notification should be signaled.
1664 * generic_make_request and the drivers it calls may use bi_next if this
1665 * bio happens to be merged with someone else, and may resubmit the bio to
1666 * a lower device by calling into generic_make_request recursively, which
1667 * means the bio should NOT be touched after the call to ->make_request_fn.
1669 void generic_make_request(struct bio *bio)
1671 struct bio_list bio_list_on_stack;
1673 if (!generic_make_request_checks(bio))
1677 * We only want one ->make_request_fn to be active at a time, else
1678 * stack usage with stacked devices could be a problem. So use
1679 * current->bio_list to keep a list of requests submited by a
1680 * make_request_fn function. current->bio_list is also used as a
1681 * flag to say if generic_make_request is currently active in this
1682 * task or not. If it is NULL, then no make_request is active. If
1683 * it is non-NULL, then a make_request is active, and new requests
1684 * should be added at the tail
1686 if (current->bio_list) {
1687 bio_list_add(current->bio_list, bio);
1691 /* following loop may be a bit non-obvious, and so deserves some
1693 * Before entering the loop, bio->bi_next is NULL (as all callers
1694 * ensure that) so we have a list with a single bio.
1695 * We pretend that we have just taken it off a longer list, so
1696 * we assign bio_list to a pointer to the bio_list_on_stack,
1697 * thus initialising the bio_list of new bios to be
1698 * added. ->make_request() may indeed add some more bios
1699 * through a recursive call to generic_make_request. If it
1700 * did, we find a non-NULL value in bio_list and re-enter the loop
1701 * from the top. In this case we really did just take the bio
1702 * of the top of the list (no pretending) and so remove it from
1703 * bio_list, and call into ->make_request() again.
1705 BUG_ON(bio->bi_next);
1706 bio_list_init(&bio_list_on_stack);
1707 current->bio_list = &bio_list_on_stack;
1709 struct request_queue *q = bdev_get_queue(bio->bi_bdev);
1711 q->make_request_fn(q, bio);
1713 bio = bio_list_pop(current->bio_list);
1715 current->bio_list = NULL; /* deactivate */
1717 EXPORT_SYMBOL(generic_make_request);
1720 * submit_bio - submit a bio to the block device layer for I/O
1721 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1722 * @bio: The &struct bio which describes the I/O
1724 * submit_bio() is very similar in purpose to generic_make_request(), and
1725 * uses that function to do most of the work. Both are fairly rough
1726 * interfaces; @bio must be presetup and ready for I/O.
1729 void submit_bio(int rw, struct bio *bio)
1731 int count = bio_sectors(bio);
1736 * If it's a regular read/write or a barrier with data attached,
1737 * go through the normal accounting stuff before submission.
1739 if (bio_has_data(bio) && !(rw & REQ_DISCARD)) {
1741 count_vm_events(PGPGOUT, count);
1743 task_io_account_read(bio->bi_size);
1744 count_vm_events(PGPGIN, count);
1747 if (unlikely(block_dump)) {
1748 char b[BDEVNAME_SIZE];
1749 printk(KERN_DEBUG "%s(%d): %s block %Lu on %s (%u sectors)\n",
1750 current->comm, task_pid_nr(current),
1751 (rw & WRITE) ? "WRITE" : "READ",
1752 (unsigned long long)bio->bi_sector,
1753 bdevname(bio->bi_bdev, b),
1758 generic_make_request(bio);
1760 EXPORT_SYMBOL(submit_bio);
1763 * blk_rq_check_limits - Helper function to check a request for the queue limit
1765 * @rq: the request being checked
1768 * @rq may have been made based on weaker limitations of upper-level queues
1769 * in request stacking drivers, and it may violate the limitation of @q.
1770 * Since the block layer and the underlying device driver trust @rq
1771 * after it is inserted to @q, it should be checked against @q before
1772 * the insertion using this generic function.
1774 * This function should also be useful for request stacking drivers
1775 * in some cases below, so export this function.
1776 * Request stacking drivers like request-based dm may change the queue
1777 * limits while requests are in the queue (e.g. dm's table swapping).
1778 * Such request stacking drivers should check those requests agaist
1779 * the new queue limits again when they dispatch those requests,
1780 * although such checkings are also done against the old queue limits
1781 * when submitting requests.
1783 int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1785 if (rq->cmd_flags & REQ_DISCARD)
1788 if (blk_rq_sectors(rq) > queue_max_sectors(q) ||
1789 blk_rq_bytes(rq) > queue_max_hw_sectors(q) << 9) {
1790 printk(KERN_ERR "%s: over max size limit.\n", __func__);
1795 * queue's settings related to segment counting like q->bounce_pfn
1796 * may differ from that of other stacking queues.
1797 * Recalculate it to check the request correctly on this queue's
1800 blk_recalc_rq_segments(rq);
1801 if (rq->nr_phys_segments > queue_max_segments(q)) {
1802 printk(KERN_ERR "%s: over max segments limit.\n", __func__);
1808 EXPORT_SYMBOL_GPL(blk_rq_check_limits);
1811 * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1812 * @q: the queue to submit the request
1813 * @rq: the request being queued
1815 int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1817 unsigned long flags;
1818 int where = ELEVATOR_INSERT_BACK;
1820 if (blk_rq_check_limits(q, rq))
1824 should_fail_request(&rq->rq_disk->part0, blk_rq_bytes(rq)))
1827 spin_lock_irqsave(q->queue_lock, flags);
1828 if (unlikely(blk_queue_dead(q))) {
1829 spin_unlock_irqrestore(q->queue_lock, flags);
1834 * Submitting request must be dequeued before calling this function
1835 * because it will be linked to another request_queue
1837 BUG_ON(blk_queued_rq(rq));
1839 if (rq->cmd_flags & (REQ_FLUSH|REQ_FUA))
1840 where = ELEVATOR_INSERT_FLUSH;
1842 add_acct_request(q, rq, where);
1843 if (where == ELEVATOR_INSERT_FLUSH)
1845 spin_unlock_irqrestore(q->queue_lock, flags);
1849 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
1852 * blk_rq_err_bytes - determine number of bytes till the next failure boundary
1853 * @rq: request to examine
1856 * A request could be merge of IOs which require different failure
1857 * handling. This function determines the number of bytes which
1858 * can be failed from the beginning of the request without
1859 * crossing into area which need to be retried further.
1862 * The number of bytes to fail.
1865 * queue_lock must be held.
1867 unsigned int blk_rq_err_bytes(const struct request *rq)
1869 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
1870 unsigned int bytes = 0;
1873 if (!(rq->cmd_flags & REQ_MIXED_MERGE))
1874 return blk_rq_bytes(rq);
1877 * Currently the only 'mixing' which can happen is between
1878 * different fastfail types. We can safely fail portions
1879 * which have all the failfast bits that the first one has -
1880 * the ones which are at least as eager to fail as the first
1883 for (bio = rq->bio; bio; bio = bio->bi_next) {
1884 if ((bio->bi_rw & ff) != ff)
1886 bytes += bio->bi_size;
1889 /* this could lead to infinite loop */
1890 BUG_ON(blk_rq_bytes(rq) && !bytes);
1893 EXPORT_SYMBOL_GPL(blk_rq_err_bytes);
1895 static void blk_account_io_completion(struct request *req, unsigned int bytes)
1897 if (blk_do_io_stat(req)) {
1898 const int rw = rq_data_dir(req);
1899 struct hd_struct *part;
1902 cpu = part_stat_lock();
1904 part_stat_add(cpu, part, sectors[rw], bytes >> 9);
1909 static void blk_account_io_done(struct request *req)
1912 * Account IO completion. flush_rq isn't accounted as a
1913 * normal IO on queueing nor completion. Accounting the
1914 * containing request is enough.
1916 if (blk_do_io_stat(req) && !(req->cmd_flags & REQ_FLUSH_SEQ)) {
1917 unsigned long duration = jiffies - req->start_time;
1918 const int rw = rq_data_dir(req);
1919 struct hd_struct *part;
1922 cpu = part_stat_lock();
1925 part_stat_inc(cpu, part, ios[rw]);
1926 part_stat_add(cpu, part, ticks[rw], duration);
1927 part_round_stats(cpu, part);
1928 part_dec_in_flight(part, rw);
1930 hd_struct_put(part);
1936 * blk_peek_request - peek at the top of a request queue
1937 * @q: request queue to peek at
1940 * Return the request at the top of @q. The returned request
1941 * should be started using blk_start_request() before LLD starts
1945 * Pointer to the request at the top of @q if available. Null
1949 * queue_lock must be held.
1951 struct request *blk_peek_request(struct request_queue *q)
1956 while ((rq = __elv_next_request(q)) != NULL) {
1957 if (!(rq->cmd_flags & REQ_STARTED)) {
1959 * This is the first time the device driver
1960 * sees this request (possibly after
1961 * requeueing). Notify IO scheduler.
1963 if (rq->cmd_flags & REQ_SORTED)
1964 elv_activate_rq(q, rq);
1967 * just mark as started even if we don't start
1968 * it, a request that has been delayed should
1969 * not be passed by new incoming requests
1971 rq->cmd_flags |= REQ_STARTED;
1972 trace_block_rq_issue(q, rq);
1975 if (!q->boundary_rq || q->boundary_rq == rq) {
1976 q->end_sector = rq_end_sector(rq);
1977 q->boundary_rq = NULL;
1980 if (rq->cmd_flags & REQ_DONTPREP)
1983 if (q->dma_drain_size && blk_rq_bytes(rq)) {
1985 * make sure space for the drain appears we
1986 * know we can do this because max_hw_segments
1987 * has been adjusted to be one fewer than the
1990 rq->nr_phys_segments++;
1996 ret = q->prep_rq_fn(q, rq);
1997 if (ret == BLKPREP_OK) {
1999 } else if (ret == BLKPREP_DEFER) {
2001 * the request may have been (partially) prepped.
2002 * we need to keep this request in the front to
2003 * avoid resource deadlock. REQ_STARTED will
2004 * prevent other fs requests from passing this one.
2006 if (q->dma_drain_size && blk_rq_bytes(rq) &&
2007 !(rq->cmd_flags & REQ_DONTPREP)) {
2009 * remove the space for the drain we added
2010 * so that we don't add it again
2012 --rq->nr_phys_segments;
2017 } else if (ret == BLKPREP_KILL) {
2018 rq->cmd_flags |= REQ_QUIET;
2020 * Mark this request as started so we don't trigger
2021 * any debug logic in the end I/O path.
2023 blk_start_request(rq);
2024 __blk_end_request_all(rq, -EIO);
2026 printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
2033 EXPORT_SYMBOL(blk_peek_request);
2035 void blk_dequeue_request(struct request *rq)
2037 struct request_queue *q = rq->q;
2039 BUG_ON(list_empty(&rq->queuelist));
2040 BUG_ON(ELV_ON_HASH(rq));
2042 list_del_init(&rq->queuelist);
2045 * the time frame between a request being removed from the lists
2046 * and to it is freed is accounted as io that is in progress at
2049 if (blk_account_rq(rq)) {
2050 q->in_flight[rq_is_sync(rq)]++;
2051 set_io_start_time_ns(rq);
2056 * blk_start_request - start request processing on the driver
2057 * @req: request to dequeue
2060 * Dequeue @req and start timeout timer on it. This hands off the
2061 * request to the driver.
2063 * Block internal functions which don't want to start timer should
2064 * call blk_dequeue_request().
2067 * queue_lock must be held.
2069 void blk_start_request(struct request *req)
2071 blk_dequeue_request(req);
2074 * We are now handing the request to the hardware, initialize
2075 * resid_len to full count and add the timeout handler.
2077 req->resid_len = blk_rq_bytes(req);
2078 if (unlikely(blk_bidi_rq(req)))
2079 req->next_rq->resid_len = blk_rq_bytes(req->next_rq);
2083 EXPORT_SYMBOL(blk_start_request);
2086 * blk_fetch_request - fetch a request from a request queue
2087 * @q: request queue to fetch a request from
2090 * Return the request at the top of @q. The request is started on
2091 * return and LLD can start processing it immediately.
2094 * Pointer to the request at the top of @q if available. Null
2098 * queue_lock must be held.
2100 struct request *blk_fetch_request(struct request_queue *q)
2104 rq = blk_peek_request(q);
2106 blk_start_request(rq);
2109 EXPORT_SYMBOL(blk_fetch_request);
2112 * blk_update_request - Special helper function for request stacking drivers
2113 * @req: the request being processed
2114 * @error: %0 for success, < %0 for error
2115 * @nr_bytes: number of bytes to complete @req
2118 * Ends I/O on a number of bytes attached to @req, but doesn't complete
2119 * the request structure even if @req doesn't have leftover.
2120 * If @req has leftover, sets it up for the next range of segments.
2122 * This special helper function is only for request stacking drivers
2123 * (e.g. request-based dm) so that they can handle partial completion.
2124 * Actual device drivers should use blk_end_request instead.
2126 * Passing the result of blk_rq_bytes() as @nr_bytes guarantees
2127 * %false return from this function.
2130 * %false - this request doesn't have any more data
2131 * %true - this request has more data
2133 bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
2135 int total_bytes, bio_nbytes, next_idx = 0;
2141 trace_block_rq_complete(req->q, req);
2144 * For fs requests, rq is just carrier of independent bio's
2145 * and each partial completion should be handled separately.
2146 * Reset per-request error on each partial completion.
2148 * TODO: tj: This is too subtle. It would be better to let
2149 * low level drivers do what they see fit.
2151 if (req->cmd_type == REQ_TYPE_FS)
2154 if (error && req->cmd_type == REQ_TYPE_FS &&
2155 !(req->cmd_flags & REQ_QUIET)) {
2160 error_type = "recoverable transport";
2163 error_type = "critical target";
2166 error_type = "critical nexus";
2173 printk(KERN_ERR "end_request: %s error, dev %s, sector %llu\n",
2174 error_type, req->rq_disk ? req->rq_disk->disk_name : "?",
2175 (unsigned long long)blk_rq_pos(req));
2178 blk_account_io_completion(req, nr_bytes);
2180 total_bytes = bio_nbytes = 0;
2181 while ((bio = req->bio) != NULL) {
2184 if (nr_bytes >= bio->bi_size) {
2185 req->bio = bio->bi_next;
2186 nbytes = bio->bi_size;
2187 req_bio_endio(req, bio, nbytes, error);
2191 int idx = bio->bi_idx + next_idx;
2193 if (unlikely(idx >= bio->bi_vcnt)) {
2194 blk_dump_rq_flags(req, "__end_that");
2195 printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
2196 __func__, idx, bio->bi_vcnt);
2200 nbytes = bio_iovec_idx(bio, idx)->bv_len;
2201 BIO_BUG_ON(nbytes > bio->bi_size);
2204 * not a complete bvec done
2206 if (unlikely(nbytes > nr_bytes)) {
2207 bio_nbytes += nr_bytes;
2208 total_bytes += nr_bytes;
2213 * advance to the next vector
2216 bio_nbytes += nbytes;
2219 total_bytes += nbytes;
2225 * end more in this run, or just return 'not-done'
2227 if (unlikely(nr_bytes <= 0))
2237 * Reset counters so that the request stacking driver
2238 * can find how many bytes remain in the request
2241 req->__data_len = 0;
2246 * if the request wasn't completed, update state
2249 req_bio_endio(req, bio, bio_nbytes, error);
2250 bio->bi_idx += next_idx;
2251 bio_iovec(bio)->bv_offset += nr_bytes;
2252 bio_iovec(bio)->bv_len -= nr_bytes;
2255 req->__data_len -= total_bytes;
2256 req->buffer = bio_data(req->bio);
2258 /* update sector only for requests with clear definition of sector */
2259 if (req->cmd_type == REQ_TYPE_FS || (req->cmd_flags & REQ_DISCARD))
2260 req->__sector += total_bytes >> 9;
2262 /* mixed attributes always follow the first bio */
2263 if (req->cmd_flags & REQ_MIXED_MERGE) {
2264 req->cmd_flags &= ~REQ_FAILFAST_MASK;
2265 req->cmd_flags |= req->bio->bi_rw & REQ_FAILFAST_MASK;
2269 * If total number of sectors is less than the first segment
2270 * size, something has gone terribly wrong.
2272 if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
2273 blk_dump_rq_flags(req, "request botched");
2274 req->__data_len = blk_rq_cur_bytes(req);
2277 /* recalculate the number of segments */
2278 blk_recalc_rq_segments(req);
2282 EXPORT_SYMBOL_GPL(blk_update_request);
2284 static bool blk_update_bidi_request(struct request *rq, int error,
2285 unsigned int nr_bytes,
2286 unsigned int bidi_bytes)
2288 if (blk_update_request(rq, error, nr_bytes))
2291 /* Bidi request must be completed as a whole */
2292 if (unlikely(blk_bidi_rq(rq)) &&
2293 blk_update_request(rq->next_rq, error, bidi_bytes))
2296 if (blk_queue_add_random(rq->q))
2297 add_disk_randomness(rq->rq_disk);
2303 * blk_unprep_request - unprepare a request
2306 * This function makes a request ready for complete resubmission (or
2307 * completion). It happens only after all error handling is complete,
2308 * so represents the appropriate moment to deallocate any resources
2309 * that were allocated to the request in the prep_rq_fn. The queue
2310 * lock is held when calling this.
2312 void blk_unprep_request(struct request *req)
2314 struct request_queue *q = req->q;
2316 req->cmd_flags &= ~REQ_DONTPREP;
2317 if (q->unprep_rq_fn)
2318 q->unprep_rq_fn(q, req);
2320 EXPORT_SYMBOL_GPL(blk_unprep_request);
2323 * queue lock must be held
2325 static void blk_finish_request(struct request *req, int error)
2327 if (blk_rq_tagged(req))
2328 blk_queue_end_tag(req->q, req);
2330 BUG_ON(blk_queued_rq(req));
2332 if (unlikely(laptop_mode) && req->cmd_type == REQ_TYPE_FS)
2333 laptop_io_completion(&req->q->backing_dev_info);
2335 blk_delete_timer(req);
2337 if (req->cmd_flags & REQ_DONTPREP)
2338 blk_unprep_request(req);
2341 blk_account_io_done(req);
2344 req->end_io(req, error);
2346 if (blk_bidi_rq(req))
2347 __blk_put_request(req->next_rq->q, req->next_rq);
2349 __blk_put_request(req->q, req);
2354 * blk_end_bidi_request - Complete a bidi request
2355 * @rq: the request to complete
2356 * @error: %0 for success, < %0 for error
2357 * @nr_bytes: number of bytes to complete @rq
2358 * @bidi_bytes: number of bytes to complete @rq->next_rq
2361 * Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2362 * Drivers that supports bidi can safely call this member for any
2363 * type of request, bidi or uni. In the later case @bidi_bytes is
2367 * %false - we are done with this request
2368 * %true - still buffers pending for this request
2370 static bool blk_end_bidi_request(struct request *rq, int error,
2371 unsigned int nr_bytes, unsigned int bidi_bytes)
2373 struct request_queue *q = rq->q;
2374 unsigned long flags;
2376 if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2379 spin_lock_irqsave(q->queue_lock, flags);
2380 blk_finish_request(rq, error);
2381 spin_unlock_irqrestore(q->queue_lock, flags);
2387 * __blk_end_bidi_request - Complete a bidi request with queue lock held
2388 * @rq: the request to complete
2389 * @error: %0 for success, < %0 for error
2390 * @nr_bytes: number of bytes to complete @rq
2391 * @bidi_bytes: number of bytes to complete @rq->next_rq
2394 * Identical to blk_end_bidi_request() except that queue lock is
2395 * assumed to be locked on entry and remains so on return.
2398 * %false - we are done with this request
2399 * %true - still buffers pending for this request
2401 bool __blk_end_bidi_request(struct request *rq, int error,
2402 unsigned int nr_bytes, unsigned int bidi_bytes)
2404 if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2407 blk_finish_request(rq, error);
2413 * blk_end_request - Helper function for drivers to complete the request.
2414 * @rq: the request being processed
2415 * @error: %0 for success, < %0 for error
2416 * @nr_bytes: number of bytes to complete
2419 * Ends I/O on a number of bytes attached to @rq.
2420 * If @rq has leftover, sets it up for the next range of segments.
2423 * %false - we are done with this request
2424 * %true - still buffers pending for this request
2426 bool blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2428 return blk_end_bidi_request(rq, error, nr_bytes, 0);
2430 EXPORT_SYMBOL(blk_end_request);
2433 * blk_end_request_all - Helper function for drives to finish the request.
2434 * @rq: the request to finish
2435 * @error: %0 for success, < %0 for error
2438 * Completely finish @rq.
2440 void blk_end_request_all(struct request *rq, int error)
2443 unsigned int bidi_bytes = 0;
2445 if (unlikely(blk_bidi_rq(rq)))
2446 bidi_bytes = blk_rq_bytes(rq->next_rq);
2448 pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2451 EXPORT_SYMBOL(blk_end_request_all);
2454 * blk_end_request_cur - Helper function to finish the current request chunk.
2455 * @rq: the request to finish the current chunk for
2456 * @error: %0 for success, < %0 for error
2459 * Complete the current consecutively mapped chunk from @rq.
2462 * %false - we are done with this request
2463 * %true - still buffers pending for this request
2465 bool blk_end_request_cur(struct request *rq, int error)
2467 return blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2469 EXPORT_SYMBOL(blk_end_request_cur);
2472 * blk_end_request_err - Finish a request till the next failure boundary.
2473 * @rq: the request to finish till the next failure boundary for
2474 * @error: must be negative errno
2477 * Complete @rq till the next failure boundary.
2480 * %false - we are done with this request
2481 * %true - still buffers pending for this request
2483 bool blk_end_request_err(struct request *rq, int error)
2485 WARN_ON(error >= 0);
2486 return blk_end_request(rq, error, blk_rq_err_bytes(rq));
2488 EXPORT_SYMBOL_GPL(blk_end_request_err);
2491 * __blk_end_request - Helper function for drivers to complete the request.
2492 * @rq: the request being processed
2493 * @error: %0 for success, < %0 for error
2494 * @nr_bytes: number of bytes to complete
2497 * Must be called with queue lock held unlike blk_end_request().
2500 * %false - we are done with this request
2501 * %true - still buffers pending for this request
2503 bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2505 return __blk_end_bidi_request(rq, error, nr_bytes, 0);
2507 EXPORT_SYMBOL(__blk_end_request);
2510 * __blk_end_request_all - Helper function for drives to finish the request.
2511 * @rq: the request to finish
2512 * @error: %0 for success, < %0 for error
2515 * Completely finish @rq. Must be called with queue lock held.
2517 void __blk_end_request_all(struct request *rq, int error)
2520 unsigned int bidi_bytes = 0;
2522 if (unlikely(blk_bidi_rq(rq)))
2523 bidi_bytes = blk_rq_bytes(rq->next_rq);
2525 pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2528 EXPORT_SYMBOL(__blk_end_request_all);
2531 * __blk_end_request_cur - Helper function to finish the current request chunk.
2532 * @rq: the request to finish the current chunk for
2533 * @error: %0 for success, < %0 for error
2536 * Complete the current consecutively mapped chunk from @rq. Must
2537 * be called with queue lock held.
2540 * %false - we are done with this request
2541 * %true - still buffers pending for this request
2543 bool __blk_end_request_cur(struct request *rq, int error)
2545 return __blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2547 EXPORT_SYMBOL(__blk_end_request_cur);
2550 * __blk_end_request_err - Finish a request till the next failure boundary.
2551 * @rq: the request to finish till the next failure boundary for
2552 * @error: must be negative errno
2555 * Complete @rq till the next failure boundary. Must be called
2556 * with queue lock held.
2559 * %false - we are done with this request
2560 * %true - still buffers pending for this request
2562 bool __blk_end_request_err(struct request *rq, int error)
2564 WARN_ON(error >= 0);
2565 return __blk_end_request(rq, error, blk_rq_err_bytes(rq));
2567 EXPORT_SYMBOL_GPL(__blk_end_request_err);
2569 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2572 /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */
2573 rq->cmd_flags |= bio->bi_rw & REQ_WRITE;
2575 if (bio_has_data(bio)) {
2576 rq->nr_phys_segments = bio_phys_segments(q, bio);
2577 rq->buffer = bio_data(bio);
2579 rq->__data_len = bio->bi_size;
2580 rq->bio = rq->biotail = bio;
2583 rq->rq_disk = bio->bi_bdev->bd_disk;
2586 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
2588 * rq_flush_dcache_pages - Helper function to flush all pages in a request
2589 * @rq: the request to be flushed
2592 * Flush all pages in @rq.
2594 void rq_flush_dcache_pages(struct request *rq)
2596 struct req_iterator iter;
2597 struct bio_vec *bvec;
2599 rq_for_each_segment(bvec, rq, iter)
2600 flush_dcache_page(bvec->bv_page);
2602 EXPORT_SYMBOL_GPL(rq_flush_dcache_pages);
2606 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2607 * @q : the queue of the device being checked
2610 * Check if underlying low-level drivers of a device are busy.
2611 * If the drivers want to export their busy state, they must set own
2612 * exporting function using blk_queue_lld_busy() first.
2614 * Basically, this function is used only by request stacking drivers
2615 * to stop dispatching requests to underlying devices when underlying
2616 * devices are busy. This behavior helps more I/O merging on the queue
2617 * of the request stacking driver and prevents I/O throughput regression
2618 * on burst I/O load.
2621 * 0 - Not busy (The request stacking driver should dispatch request)
2622 * 1 - Busy (The request stacking driver should stop dispatching request)
2624 int blk_lld_busy(struct request_queue *q)
2627 return q->lld_busy_fn(q);
2631 EXPORT_SYMBOL_GPL(blk_lld_busy);
2634 * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
2635 * @rq: the clone request to be cleaned up
2638 * Free all bios in @rq for a cloned request.
2640 void blk_rq_unprep_clone(struct request *rq)
2644 while ((bio = rq->bio) != NULL) {
2645 rq->bio = bio->bi_next;
2650 EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
2653 * Copy attributes of the original request to the clone request.
2654 * The actual data parts (e.g. ->cmd, ->buffer, ->sense) are not copied.
2656 static void __blk_rq_prep_clone(struct request *dst, struct request *src)
2658 dst->cpu = src->cpu;
2659 dst->cmd_flags = (src->cmd_flags & REQ_CLONE_MASK) | REQ_NOMERGE;
2660 dst->cmd_type = src->cmd_type;
2661 dst->__sector = blk_rq_pos(src);
2662 dst->__data_len = blk_rq_bytes(src);
2663 dst->nr_phys_segments = src->nr_phys_segments;
2664 dst->ioprio = src->ioprio;
2665 dst->extra_len = src->extra_len;
2669 * blk_rq_prep_clone - Helper function to setup clone request
2670 * @rq: the request to be setup
2671 * @rq_src: original request to be cloned
2672 * @bs: bio_set that bios for clone are allocated from
2673 * @gfp_mask: memory allocation mask for bio
2674 * @bio_ctr: setup function to be called for each clone bio.
2675 * Returns %0 for success, non %0 for failure.
2676 * @data: private data to be passed to @bio_ctr
2679 * Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
2680 * The actual data parts of @rq_src (e.g. ->cmd, ->buffer, ->sense)
2681 * are not copied, and copying such parts is the caller's responsibility.
2682 * Also, pages which the original bios are pointing to are not copied
2683 * and the cloned bios just point same pages.
2684 * So cloned bios must be completed before original bios, which means
2685 * the caller must complete @rq before @rq_src.
2687 int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
2688 struct bio_set *bs, gfp_t gfp_mask,
2689 int (*bio_ctr)(struct bio *, struct bio *, void *),
2692 struct bio *bio, *bio_src;
2697 blk_rq_init(NULL, rq);
2699 __rq_for_each_bio(bio_src, rq_src) {
2700 bio = bio_alloc_bioset(gfp_mask, bio_src->bi_max_vecs, bs);
2704 __bio_clone(bio, bio_src);
2706 if (bio_integrity(bio_src) &&
2707 bio_integrity_clone(bio, bio_src, gfp_mask, bs))
2710 if (bio_ctr && bio_ctr(bio, bio_src, data))
2714 rq->biotail->bi_next = bio;
2717 rq->bio = rq->biotail = bio;
2720 __blk_rq_prep_clone(rq, rq_src);
2727 blk_rq_unprep_clone(rq);
2731 EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
2733 int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
2735 return queue_work(kblockd_workqueue, work);
2737 EXPORT_SYMBOL(kblockd_schedule_work);
2739 int kblockd_schedule_delayed_work(struct request_queue *q,
2740 struct delayed_work *dwork, unsigned long delay)
2742 return queue_delayed_work(kblockd_workqueue, dwork, delay);
2744 EXPORT_SYMBOL(kblockd_schedule_delayed_work);
2746 #define PLUG_MAGIC 0x91827364
2749 * blk_start_plug - initialize blk_plug and track it inside the task_struct
2750 * @plug: The &struct blk_plug that needs to be initialized
2753 * Tracking blk_plug inside the task_struct will help with auto-flushing the
2754 * pending I/O should the task end up blocking between blk_start_plug() and
2755 * blk_finish_plug(). This is important from a performance perspective, but
2756 * also ensures that we don't deadlock. For instance, if the task is blocking
2757 * for a memory allocation, memory reclaim could end up wanting to free a
2758 * page belonging to that request that is currently residing in our private
2759 * plug. By flushing the pending I/O when the process goes to sleep, we avoid
2760 * this kind of deadlock.
2762 void blk_start_plug(struct blk_plug *plug)
2764 struct task_struct *tsk = current;
2766 plug->magic = PLUG_MAGIC;
2767 INIT_LIST_HEAD(&plug->list);
2768 INIT_LIST_HEAD(&plug->cb_list);
2769 plug->should_sort = 0;
2772 * If this is a nested plug, don't actually assign it. It will be
2773 * flushed on its own.
2777 * Store ordering should not be needed here, since a potential
2778 * preempt will imply a full memory barrier
2783 EXPORT_SYMBOL(blk_start_plug);
2785 static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
2787 struct request *rqa = container_of(a, struct request, queuelist);
2788 struct request *rqb = container_of(b, struct request, queuelist);
2790 return !(rqa->q <= rqb->q);
2794 * If 'from_schedule' is true, then postpone the dispatch of requests
2795 * until a safe kblockd context. We due this to avoid accidental big
2796 * additional stack usage in driver dispatch, in places where the originally
2797 * plugger did not intend it.
2799 static void queue_unplugged(struct request_queue *q, unsigned int depth,
2801 __releases(q->queue_lock)
2803 trace_block_unplug(q, depth, !from_schedule);
2806 * Don't mess with dead queue.
2808 if (unlikely(blk_queue_dead(q))) {
2809 spin_unlock(q->queue_lock);
2814 * If we are punting this to kblockd, then we can safely drop
2815 * the queue_lock before waking kblockd (which needs to take
2818 if (from_schedule) {
2819 spin_unlock(q->queue_lock);
2820 blk_run_queue_async(q);
2823 spin_unlock(q->queue_lock);
2828 static void flush_plug_callbacks(struct blk_plug *plug)
2830 LIST_HEAD(callbacks);
2832 if (list_empty(&plug->cb_list))
2835 list_splice_init(&plug->cb_list, &callbacks);
2837 while (!list_empty(&callbacks)) {
2838 struct blk_plug_cb *cb = list_first_entry(&callbacks,
2841 list_del(&cb->list);
2846 void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
2848 struct request_queue *q;
2849 unsigned long flags;
2854 BUG_ON(plug->magic != PLUG_MAGIC);
2856 flush_plug_callbacks(plug);
2857 if (list_empty(&plug->list))
2860 list_splice_init(&plug->list, &list);
2862 if (plug->should_sort) {
2863 list_sort(NULL, &list, plug_rq_cmp);
2864 plug->should_sort = 0;
2871 * Save and disable interrupts here, to avoid doing it for every
2872 * queue lock we have to take.
2874 local_irq_save(flags);
2875 while (!list_empty(&list)) {
2876 rq = list_entry_rq(list.next);
2877 list_del_init(&rq->queuelist);
2881 * This drops the queue lock
2884 queue_unplugged(q, depth, from_schedule);
2887 spin_lock(q->queue_lock);
2891 * Short-circuit if @q is dead
2893 if (unlikely(blk_queue_dead(q))) {
2894 __blk_end_request_all(rq, -ENODEV);
2899 * rq is already accounted, so use raw insert
2901 if (rq->cmd_flags & (REQ_FLUSH | REQ_FUA))
2902 __elv_add_request(q, rq, ELEVATOR_INSERT_FLUSH);
2904 __elv_add_request(q, rq, ELEVATOR_INSERT_SORT_MERGE);
2910 * This drops the queue lock
2913 queue_unplugged(q, depth, from_schedule);
2915 local_irq_restore(flags);
2918 void blk_finish_plug(struct blk_plug *plug)
2920 blk_flush_plug_list(plug, false);
2922 if (plug == current->plug)
2923 current->plug = NULL;
2925 EXPORT_SYMBOL(blk_finish_plug);
2927 int __init blk_dev_init(void)
2929 BUILD_BUG_ON(__REQ_NR_BITS > 8 *
2930 sizeof(((struct request *)0)->cmd_flags));
2932 /* used for unplugging and affects IO latency/throughput - HIGHPRI */
2933 kblockd_workqueue = alloc_workqueue("kblockd",
2934 WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
2935 if (!kblockd_workqueue)
2936 panic("Failed to create kblockd\n");
2938 request_cachep = kmem_cache_create("blkdev_requests",
2939 sizeof(struct request), 0, SLAB_PANIC, NULL);
2941 blk_requestq_cachep = kmem_cache_create("blkdev_queue",
2942 sizeof(struct request_queue), 0, SLAB_PANIC, NULL);