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>
32 #include <linux/ratelimit.h>
34 #define CREATE_TRACE_POINTS
35 #include <trace/events/block.h>
38 #include "blk-cgroup.h"
40 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
41 EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
42 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
44 DEFINE_IDA(blk_queue_ida);
47 * For the allocated request tables
49 static struct kmem_cache *request_cachep;
52 * For queue allocation
54 struct kmem_cache *blk_requestq_cachep;
57 * Controlling structure to kblockd
59 static struct workqueue_struct *kblockd_workqueue;
61 static void drive_stat_acct(struct request *rq, int new_io)
63 struct hd_struct *part;
64 int rw = rq_data_dir(rq);
67 if (!blk_do_io_stat(rq))
70 cpu = part_stat_lock();
74 part_stat_inc(cpu, part, merges[rw]);
76 part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq));
77 if (!hd_struct_try_get(part)) {
79 * The partition is already being removed,
80 * the request will be accounted on the disk only
82 * We take a reference on disk->part0 although that
83 * partition will never be deleted, so we can treat
84 * it as any other partition.
86 part = &rq->rq_disk->part0;
89 part_round_stats(cpu, part);
90 part_inc_in_flight(part, rw);
97 void blk_queue_congestion_threshold(struct request_queue *q)
101 nr = q->nr_requests - (q->nr_requests / 8) + 1;
102 if (nr > q->nr_requests)
104 q->nr_congestion_on = nr;
106 nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
109 q->nr_congestion_off = nr;
113 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
116 * Locates the passed device's request queue and returns the address of its
119 * Will return NULL if the request queue cannot be located.
121 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
123 struct backing_dev_info *ret = NULL;
124 struct request_queue *q = bdev_get_queue(bdev);
127 ret = &q->backing_dev_info;
130 EXPORT_SYMBOL(blk_get_backing_dev_info);
132 void blk_rq_init(struct request_queue *q, struct request *rq)
134 memset(rq, 0, sizeof(*rq));
136 INIT_LIST_HEAD(&rq->queuelist);
137 INIT_LIST_HEAD(&rq->timeout_list);
140 rq->__sector = (sector_t) -1;
141 INIT_HLIST_NODE(&rq->hash);
142 RB_CLEAR_NODE(&rq->rb_node);
144 rq->cmd_len = BLK_MAX_CDB;
147 rq->start_time = jiffies;
148 set_start_time_ns(rq);
151 EXPORT_SYMBOL(blk_rq_init);
153 static void req_bio_endio(struct request *rq, struct bio *bio,
154 unsigned int nbytes, int error)
157 clear_bit(BIO_UPTODATE, &bio->bi_flags);
158 else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
161 if (unlikely(nbytes > bio->bi_size)) {
162 printk(KERN_ERR "%s: want %u bytes done, %u left\n",
163 __func__, nbytes, bio->bi_size);
164 nbytes = bio->bi_size;
167 if (unlikely(rq->cmd_flags & REQ_QUIET))
168 set_bit(BIO_QUIET, &bio->bi_flags);
170 bio->bi_size -= nbytes;
171 bio->bi_sector += (nbytes >> 9);
173 if (bio_integrity(bio))
174 bio_integrity_advance(bio, nbytes);
176 /* don't actually finish bio if it's part of flush sequence */
177 if (bio->bi_size == 0 && !(rq->cmd_flags & REQ_FLUSH_SEQ))
178 bio_endio(bio, error);
181 void blk_dump_rq_flags(struct request *rq, char *msg)
185 printk(KERN_INFO "%s: dev %s: type=%x, flags=%x\n", msg,
186 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type,
189 printk(KERN_INFO " sector %llu, nr/cnr %u/%u\n",
190 (unsigned long long)blk_rq_pos(rq),
191 blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
192 printk(KERN_INFO " bio %p, biotail %p, buffer %p, len %u\n",
193 rq->bio, rq->biotail, rq->buffer, blk_rq_bytes(rq));
195 if (rq->cmd_type == REQ_TYPE_BLOCK_PC) {
196 printk(KERN_INFO " cdb: ");
197 for (bit = 0; bit < BLK_MAX_CDB; bit++)
198 printk("%02x ", rq->cmd[bit]);
202 EXPORT_SYMBOL(blk_dump_rq_flags);
204 static void blk_delay_work(struct work_struct *work)
206 struct request_queue *q;
208 q = container_of(work, struct request_queue, delay_work.work);
209 spin_lock_irq(q->queue_lock);
211 spin_unlock_irq(q->queue_lock);
215 * blk_delay_queue - restart queueing after defined interval
216 * @q: The &struct request_queue in question
217 * @msecs: Delay in msecs
220 * Sometimes queueing needs to be postponed for a little while, to allow
221 * resources to come back. This function will make sure that queueing is
222 * restarted around the specified time.
224 void blk_delay_queue(struct request_queue *q, unsigned long msecs)
226 queue_delayed_work(kblockd_workqueue, &q->delay_work,
227 msecs_to_jiffies(msecs));
229 EXPORT_SYMBOL(blk_delay_queue);
232 * blk_start_queue - restart a previously stopped queue
233 * @q: The &struct request_queue in question
236 * blk_start_queue() will clear the stop flag on the queue, and call
237 * the request_fn for the queue if it was in a stopped state when
238 * entered. Also see blk_stop_queue(). Queue lock must be held.
240 void blk_start_queue(struct request_queue *q)
242 WARN_ON(!irqs_disabled());
244 queue_flag_clear(QUEUE_FLAG_STOPPED, q);
247 EXPORT_SYMBOL(blk_start_queue);
250 * blk_stop_queue - stop a queue
251 * @q: The &struct request_queue in question
254 * The Linux block layer assumes that a block driver will consume all
255 * entries on the request queue when the request_fn strategy is called.
256 * Often this will not happen, because of hardware limitations (queue
257 * depth settings). If a device driver gets a 'queue full' response,
258 * or if it simply chooses not to queue more I/O at one point, it can
259 * call this function to prevent the request_fn from being called until
260 * the driver has signalled it's ready to go again. This happens by calling
261 * blk_start_queue() to restart queue operations. Queue lock must be held.
263 void blk_stop_queue(struct request_queue *q)
265 __cancel_delayed_work(&q->delay_work);
266 queue_flag_set(QUEUE_FLAG_STOPPED, q);
268 EXPORT_SYMBOL(blk_stop_queue);
271 * blk_sync_queue - cancel any pending callbacks on a queue
275 * The block layer may perform asynchronous callback activity
276 * on a queue, such as calling the unplug function after a timeout.
277 * A block device may call blk_sync_queue to ensure that any
278 * such activity is cancelled, thus allowing it to release resources
279 * that the callbacks might use. The caller must already have made sure
280 * that its ->make_request_fn will not re-add plugging prior to calling
283 * This function does not cancel any asynchronous activity arising
284 * out of elevator or throttling code. That would require elevaotor_exit()
285 * and blkcg_exit_queue() to be called with queue lock initialized.
288 void blk_sync_queue(struct request_queue *q)
290 del_timer_sync(&q->timeout);
291 cancel_delayed_work_sync(&q->delay_work);
293 EXPORT_SYMBOL(blk_sync_queue);
296 * __blk_run_queue - run a single device queue
297 * @q: The queue to run
300 * See @blk_run_queue. This variant must be called with the queue lock
301 * held and interrupts disabled.
303 void __blk_run_queue(struct request_queue *q)
305 if (unlikely(blk_queue_stopped(q)))
310 EXPORT_SYMBOL(__blk_run_queue);
313 * blk_run_queue_async - run a single device queue in workqueue context
314 * @q: The queue to run
317 * Tells kblockd to perform the equivalent of @blk_run_queue on behalf
320 void blk_run_queue_async(struct request_queue *q)
322 if (likely(!blk_queue_stopped(q))) {
323 __cancel_delayed_work(&q->delay_work);
324 queue_delayed_work(kblockd_workqueue, &q->delay_work, 0);
327 EXPORT_SYMBOL(blk_run_queue_async);
330 * blk_run_queue - run a single device queue
331 * @q: The queue to run
334 * Invoke request handling on this queue, if it has pending work to do.
335 * May be used to restart queueing when a request has completed.
337 void blk_run_queue(struct request_queue *q)
341 spin_lock_irqsave(q->queue_lock, flags);
343 spin_unlock_irqrestore(q->queue_lock, flags);
345 EXPORT_SYMBOL(blk_run_queue);
347 void blk_put_queue(struct request_queue *q)
349 kobject_put(&q->kobj);
351 EXPORT_SYMBOL(blk_put_queue);
354 * blk_drain_queue - drain requests from request_queue
356 * @drain_all: whether to drain all requests or only the ones w/ ELVPRIV
358 * Drain requests from @q. If @drain_all is set, all requests are drained.
359 * If not, only ELVPRIV requests are drained. The caller is responsible
360 * for ensuring that no new requests which need to be drained are queued.
362 void blk_drain_queue(struct request_queue *q, bool drain_all)
369 spin_lock_irq(q->queue_lock);
372 * The caller might be trying to drain @q before its
373 * elevator is initialized.
376 elv_drain_elevator(q);
378 blkcg_drain_queue(q);
381 * This function might be called on a queue which failed
382 * driver init after queue creation or is not yet fully
383 * active yet. Some drivers (e.g. fd and loop) get unhappy
384 * in such cases. Kick queue iff dispatch queue has
385 * something on it and @q has request_fn set.
387 if (!list_empty(&q->queue_head) && q->request_fn)
390 drain |= q->nr_rqs_elvpriv;
393 * Unfortunately, requests are queued at and tracked from
394 * multiple places and there's no single counter which can
395 * be drained. Check all the queues and counters.
398 drain |= !list_empty(&q->queue_head);
399 for (i = 0; i < 2; i++) {
400 drain |= q->nr_rqs[i];
401 drain |= q->in_flight[i];
402 drain |= !list_empty(&q->flush_queue[i]);
406 spin_unlock_irq(q->queue_lock);
414 * With queue marked dead, any woken up waiter will fail the
415 * allocation path, so the wakeup chaining is lost and we're
416 * left with hung waiters. We need to wake up those waiters.
419 struct request_list *rl;
421 spin_lock_irq(q->queue_lock);
423 blk_queue_for_each_rl(rl, q)
424 for (i = 0; i < ARRAY_SIZE(rl->wait); i++)
425 wake_up_all(&rl->wait[i]);
427 spin_unlock_irq(q->queue_lock);
432 * blk_queue_bypass_start - enter queue bypass mode
433 * @q: queue of interest
435 * In bypass mode, only the dispatch FIFO queue of @q is used. This
436 * function makes @q enter bypass mode and drains all requests which were
437 * throttled or issued before. On return, it's guaranteed that no request
438 * is being throttled or has ELVPRIV set and blk_queue_bypass() %true
439 * inside queue or RCU read lock.
441 void blk_queue_bypass_start(struct request_queue *q)
445 spin_lock_irq(q->queue_lock);
446 drain = !q->bypass_depth++;
447 queue_flag_set(QUEUE_FLAG_BYPASS, q);
448 spin_unlock_irq(q->queue_lock);
451 blk_drain_queue(q, false);
452 /* ensure blk_queue_bypass() is %true inside RCU read lock */
456 EXPORT_SYMBOL_GPL(blk_queue_bypass_start);
459 * blk_queue_bypass_end - leave queue bypass mode
460 * @q: queue of interest
462 * Leave bypass mode and restore the normal queueing behavior.
464 void blk_queue_bypass_end(struct request_queue *q)
466 spin_lock_irq(q->queue_lock);
467 if (!--q->bypass_depth)
468 queue_flag_clear(QUEUE_FLAG_BYPASS, q);
469 WARN_ON_ONCE(q->bypass_depth < 0);
470 spin_unlock_irq(q->queue_lock);
472 EXPORT_SYMBOL_GPL(blk_queue_bypass_end);
475 * blk_cleanup_queue - shutdown a request queue
476 * @q: request queue to shutdown
478 * Mark @q DEAD, drain all pending requests, destroy and put it. All
479 * future requests will be failed immediately with -ENODEV.
481 void blk_cleanup_queue(struct request_queue *q)
483 spinlock_t *lock = q->queue_lock;
485 /* mark @q DEAD, no new request or merges will be allowed afterwards */
486 mutex_lock(&q->sysfs_lock);
487 queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
491 * Dead queue is permanently in bypass mode till released. Note
492 * that, unlike blk_queue_bypass_start(), we aren't performing
493 * synchronize_rcu() after entering bypass mode to avoid the delay
494 * as some drivers create and destroy a lot of queues while
495 * probing. This is still safe because blk_release_queue() will be
496 * called only after the queue refcnt drops to zero and nothing,
497 * RCU or not, would be traversing the queue by then.
500 queue_flag_set(QUEUE_FLAG_BYPASS, q);
502 queue_flag_set(QUEUE_FLAG_NOMERGES, q);
503 queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
504 queue_flag_set(QUEUE_FLAG_DEAD, q);
505 spin_unlock_irq(lock);
506 mutex_unlock(&q->sysfs_lock);
508 /* drain all requests queued before DEAD marking */
509 blk_drain_queue(q, true);
511 /* @q won't process any more request, flush async actions */
512 del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);
516 if (q->queue_lock != &q->__queue_lock)
517 q->queue_lock = &q->__queue_lock;
518 spin_unlock_irq(lock);
520 /* @q is and will stay empty, shutdown and put */
523 EXPORT_SYMBOL(blk_cleanup_queue);
525 int blk_init_rl(struct request_list *rl, struct request_queue *q,
528 if (unlikely(rl->rq_pool))
532 rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
533 rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
534 init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
535 init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
537 rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
538 mempool_free_slab, request_cachep,
546 void blk_exit_rl(struct request_list *rl)
549 mempool_destroy(rl->rq_pool);
552 struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
554 return blk_alloc_queue_node(gfp_mask, -1);
556 EXPORT_SYMBOL(blk_alloc_queue);
558 struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
560 struct request_queue *q;
563 q = kmem_cache_alloc_node(blk_requestq_cachep,
564 gfp_mask | __GFP_ZERO, node_id);
568 q->id = ida_simple_get(&blk_queue_ida, 0, 0, gfp_mask);
572 q->backing_dev_info.ra_pages =
573 (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
574 q->backing_dev_info.state = 0;
575 q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
576 q->backing_dev_info.name = "block";
579 err = bdi_init(&q->backing_dev_info);
583 setup_timer(&q->backing_dev_info.laptop_mode_wb_timer,
584 laptop_mode_timer_fn, (unsigned long) q);
585 setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
586 INIT_LIST_HEAD(&q->queue_head);
587 INIT_LIST_HEAD(&q->timeout_list);
588 INIT_LIST_HEAD(&q->icq_list);
589 #ifdef CONFIG_BLK_CGROUP
590 INIT_LIST_HEAD(&q->blkg_list);
592 INIT_LIST_HEAD(&q->flush_queue[0]);
593 INIT_LIST_HEAD(&q->flush_queue[1]);
594 INIT_LIST_HEAD(&q->flush_data_in_flight);
595 INIT_DELAYED_WORK(&q->delay_work, blk_delay_work);
597 kobject_init(&q->kobj, &blk_queue_ktype);
599 mutex_init(&q->sysfs_lock);
600 spin_lock_init(&q->__queue_lock);
603 * By default initialize queue_lock to internal lock and driver can
604 * override it later if need be.
606 q->queue_lock = &q->__queue_lock;
609 * A queue starts its life with bypass turned on to avoid
610 * unnecessary bypass on/off overhead and nasty surprises during
611 * init. The initial bypass will be finished at the end of
612 * blk_init_allocated_queue().
615 __set_bit(QUEUE_FLAG_BYPASS, &q->queue_flags);
617 if (blkcg_init_queue(q))
623 ida_simple_remove(&blk_queue_ida, q->id);
625 kmem_cache_free(blk_requestq_cachep, q);
628 EXPORT_SYMBOL(blk_alloc_queue_node);
631 * blk_init_queue - prepare a request queue for use with a block device
632 * @rfn: The function to be called to process requests that have been
633 * placed on the queue.
634 * @lock: Request queue spin lock
637 * If a block device wishes to use the standard request handling procedures,
638 * which sorts requests and coalesces adjacent requests, then it must
639 * call blk_init_queue(). The function @rfn will be called when there
640 * are requests on the queue that need to be processed. If the device
641 * supports plugging, then @rfn may not be called immediately when requests
642 * are available on the queue, but may be called at some time later instead.
643 * Plugged queues are generally unplugged when a buffer belonging to one
644 * of the requests on the queue is needed, or due to memory pressure.
646 * @rfn is not required, or even expected, to remove all requests off the
647 * queue, but only as many as it can handle at a time. If it does leave
648 * requests on the queue, it is responsible for arranging that the requests
649 * get dealt with eventually.
651 * The queue spin lock must be held while manipulating the requests on the
652 * request queue; this lock will be taken also from interrupt context, so irq
653 * disabling is needed for it.
655 * Function returns a pointer to the initialized request queue, or %NULL if
659 * blk_init_queue() must be paired with a blk_cleanup_queue() call
660 * when the block device is deactivated (such as at module unload).
663 struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
665 return blk_init_queue_node(rfn, lock, -1);
667 EXPORT_SYMBOL(blk_init_queue);
669 struct request_queue *
670 blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
672 struct request_queue *uninit_q, *q;
674 uninit_q = blk_alloc_queue_node(GFP_KERNEL, node_id);
678 q = blk_init_allocated_queue(uninit_q, rfn, lock);
680 blk_cleanup_queue(uninit_q);
684 EXPORT_SYMBOL(blk_init_queue_node);
686 struct request_queue *
687 blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
693 if (blk_init_rl(&q->root_rl, q, GFP_KERNEL))
697 q->prep_rq_fn = NULL;
698 q->unprep_rq_fn = NULL;
699 q->queue_flags = QUEUE_FLAG_DEFAULT;
701 /* Override internal queue lock with supplied lock pointer */
703 q->queue_lock = lock;
706 * This also sets hw/phys segments, boundary and size
708 blk_queue_make_request(q, blk_queue_bio);
710 q->sg_reserved_size = INT_MAX;
713 if (elevator_init(q, NULL))
716 blk_queue_congestion_threshold(q);
718 /* all done, end the initial bypass */
719 blk_queue_bypass_end(q);
722 EXPORT_SYMBOL(blk_init_allocated_queue);
724 bool blk_get_queue(struct request_queue *q)
726 if (likely(!blk_queue_dead(q))) {
733 EXPORT_SYMBOL(blk_get_queue);
735 static inline void blk_free_request(struct request_list *rl, struct request *rq)
737 if (rq->cmd_flags & REQ_ELVPRIV) {
738 elv_put_request(rl->q, rq);
740 put_io_context(rq->elv.icq->ioc);
743 mempool_free(rq, rl->rq_pool);
747 * ioc_batching returns true if the ioc is a valid batching request and
748 * should be given priority access to a request.
750 static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
756 * Make sure the process is able to allocate at least 1 request
757 * even if the batch times out, otherwise we could theoretically
760 return ioc->nr_batch_requests == q->nr_batching ||
761 (ioc->nr_batch_requests > 0
762 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
766 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
767 * will cause the process to be a "batcher" on all queues in the system. This
768 * is the behaviour we want though - once it gets a wakeup it should be given
771 static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
773 if (!ioc || ioc_batching(q, ioc))
776 ioc->nr_batch_requests = q->nr_batching;
777 ioc->last_waited = jiffies;
780 static void __freed_request(struct request_list *rl, int sync)
782 struct request_queue *q = rl->q;
785 * bdi isn't aware of blkcg yet. As all async IOs end up root
786 * blkcg anyway, just use root blkcg state.
788 if (rl == &q->root_rl &&
789 rl->count[sync] < queue_congestion_off_threshold(q))
790 blk_clear_queue_congested(q, sync);
792 if (rl->count[sync] + 1 <= q->nr_requests) {
793 if (waitqueue_active(&rl->wait[sync]))
794 wake_up(&rl->wait[sync]);
796 blk_clear_rl_full(rl, sync);
801 * A request has just been released. Account for it, update the full and
802 * congestion status, wake up any waiters. Called under q->queue_lock.
804 static void freed_request(struct request_list *rl, unsigned int flags)
806 struct request_queue *q = rl->q;
807 int sync = rw_is_sync(flags);
811 if (flags & REQ_ELVPRIV)
814 __freed_request(rl, sync);
816 if (unlikely(rl->starved[sync ^ 1]))
817 __freed_request(rl, sync ^ 1);
821 * Determine if elevator data should be initialized when allocating the
822 * request associated with @bio.
824 static bool blk_rq_should_init_elevator(struct bio *bio)
830 * Flush requests do not use the elevator so skip initialization.
831 * This allows a request to share the flush and elevator data.
833 if (bio->bi_rw & (REQ_FLUSH | REQ_FUA))
840 * rq_ioc - determine io_context for request allocation
841 * @bio: request being allocated is for this bio (can be %NULL)
843 * Determine io_context to use for request allocation for @bio. May return
844 * %NULL if %current->io_context doesn't exist.
846 static struct io_context *rq_ioc(struct bio *bio)
848 #ifdef CONFIG_BLK_CGROUP
849 if (bio && bio->bi_ioc)
852 return current->io_context;
856 * __get_request - get a free request
857 * @rl: request list to allocate from
858 * @rw_flags: RW and SYNC flags
859 * @bio: bio to allocate request for (can be %NULL)
860 * @gfp_mask: allocation mask
862 * Get a free request from @q. This function may fail under memory
863 * pressure or if @q is dead.
865 * Must be callled with @q->queue_lock held and,
866 * Returns %NULL on failure, with @q->queue_lock held.
867 * Returns !%NULL on success, with @q->queue_lock *not held*.
869 static struct request *__get_request(struct request_list *rl, int rw_flags,
870 struct bio *bio, gfp_t gfp_mask)
872 struct request_queue *q = rl->q;
874 struct elevator_type *et = q->elevator->type;
875 struct io_context *ioc = rq_ioc(bio);
876 struct io_cq *icq = NULL;
877 const bool is_sync = rw_is_sync(rw_flags) != 0;
880 if (unlikely(blk_queue_dead(q)))
883 may_queue = elv_may_queue(q, rw_flags);
884 if (may_queue == ELV_MQUEUE_NO)
887 if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
888 if (rl->count[is_sync]+1 >= q->nr_requests) {
890 * The queue will fill after this allocation, so set
891 * it as full, and mark this process as "batching".
892 * This process will be allowed to complete a batch of
893 * requests, others will be blocked.
895 if (!blk_rl_full(rl, is_sync)) {
896 ioc_set_batching(q, ioc);
897 blk_set_rl_full(rl, is_sync);
899 if (may_queue != ELV_MQUEUE_MUST
900 && !ioc_batching(q, ioc)) {
902 * The queue is full and the allocating
903 * process is not a "batcher", and not
904 * exempted by the IO scheduler
911 * bdi isn't aware of blkcg yet. As all async IOs end up
912 * root blkcg anyway, just use root blkcg state.
914 if (rl == &q->root_rl)
915 blk_set_queue_congested(q, is_sync);
919 * Only allow batching queuers to allocate up to 50% over the defined
920 * limit of requests, otherwise we could have thousands of requests
921 * allocated with any setting of ->nr_requests
923 if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
926 q->nr_rqs[is_sync]++;
927 rl->count[is_sync]++;
928 rl->starved[is_sync] = 0;
931 * Decide whether the new request will be managed by elevator. If
932 * so, mark @rw_flags and increment elvpriv. Non-zero elvpriv will
933 * prevent the current elevator from being destroyed until the new
934 * request is freed. This guarantees icq's won't be destroyed and
935 * makes creating new ones safe.
937 * Also, lookup icq while holding queue_lock. If it doesn't exist,
938 * it will be created after releasing queue_lock.
940 if (blk_rq_should_init_elevator(bio) && !blk_queue_bypass(q)) {
941 rw_flags |= REQ_ELVPRIV;
943 if (et->icq_cache && ioc)
944 icq = ioc_lookup_icq(ioc, q);
947 if (blk_queue_io_stat(q))
948 rw_flags |= REQ_IO_STAT;
949 spin_unlock_irq(q->queue_lock);
951 /* allocate and init request */
952 rq = mempool_alloc(rl->rq_pool, gfp_mask);
957 blk_rq_set_rl(rq, rl);
958 rq->cmd_flags = rw_flags | REQ_ALLOCED;
961 if (rw_flags & REQ_ELVPRIV) {
962 if (unlikely(et->icq_cache && !icq)) {
964 icq = ioc_create_icq(ioc, q, gfp_mask);
970 if (unlikely(elv_set_request(q, rq, bio, gfp_mask)))
973 /* @rq->elv.icq holds io_context until @rq is freed */
975 get_io_context(icq->ioc);
979 * ioc may be NULL here, and ioc_batching will be false. That's
980 * OK, if the queue is under the request limit then requests need
981 * not count toward the nr_batch_requests limit. There will always
982 * be some limit enforced by BLK_BATCH_TIME.
984 if (ioc_batching(q, ioc))
985 ioc->nr_batch_requests--;
987 trace_block_getrq(q, bio, rw_flags & 1);
992 * elvpriv init failed. ioc, icq and elvpriv aren't mempool backed
993 * and may fail indefinitely under memory pressure and thus
994 * shouldn't stall IO. Treat this request as !elvpriv. This will
995 * disturb iosched and blkcg but weird is bettern than dead.
997 printk_ratelimited(KERN_WARNING "%s: request aux data allocation failed, iosched may be disturbed\n",
998 dev_name(q->backing_dev_info.dev));
1000 rq->cmd_flags &= ~REQ_ELVPRIV;
1003 spin_lock_irq(q->queue_lock);
1004 q->nr_rqs_elvpriv--;
1005 spin_unlock_irq(q->queue_lock);
1010 * Allocation failed presumably due to memory. Undo anything we
1011 * might have messed up.
1013 * Allocating task should really be put onto the front of the wait
1014 * queue, but this is pretty rare.
1016 spin_lock_irq(q->queue_lock);
1017 freed_request(rl, rw_flags);
1020 * in the very unlikely event that allocation failed and no
1021 * requests for this direction was pending, mark us starved so that
1022 * freeing of a request in the other direction will notice
1023 * us. another possible fix would be to split the rq mempool into
1027 if (unlikely(rl->count[is_sync] == 0))
1028 rl->starved[is_sync] = 1;
1033 * get_request - get a free request
1034 * @q: request_queue to allocate request from
1035 * @rw_flags: RW and SYNC flags
1036 * @bio: bio to allocate request for (can be %NULL)
1037 * @gfp_mask: allocation mask
1039 * Get a free request from @q. If %__GFP_WAIT is set in @gfp_mask, this
1040 * function keeps retrying under memory pressure and fails iff @q is dead.
1042 * Must be callled with @q->queue_lock held and,
1043 * Returns %NULL on failure, with @q->queue_lock held.
1044 * Returns !%NULL on success, with @q->queue_lock *not held*.
1046 static struct request *get_request(struct request_queue *q, int rw_flags,
1047 struct bio *bio, gfp_t gfp_mask)
1049 const bool is_sync = rw_is_sync(rw_flags) != 0;
1051 struct request_list *rl;
1054 rl = blk_get_rl(q, bio); /* transferred to @rq on success */
1056 rq = __get_request(rl, rw_flags, bio, gfp_mask);
1060 if (!(gfp_mask & __GFP_WAIT) || unlikely(blk_queue_dead(q))) {
1065 /* wait on @rl and retry */
1066 prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
1067 TASK_UNINTERRUPTIBLE);
1069 trace_block_sleeprq(q, bio, rw_flags & 1);
1071 spin_unlock_irq(q->queue_lock);
1075 * After sleeping, we become a "batching" process and will be able
1076 * to allocate at least one request, and up to a big batch of them
1077 * for a small period time. See ioc_batching, ioc_set_batching
1079 ioc_set_batching(q, current->io_context);
1081 spin_lock_irq(q->queue_lock);
1082 finish_wait(&rl->wait[is_sync], &wait);
1087 struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
1091 BUG_ON(rw != READ && rw != WRITE);
1093 /* create ioc upfront */
1094 create_io_context(gfp_mask, q->node);
1096 spin_lock_irq(q->queue_lock);
1097 rq = get_request(q, rw, NULL, gfp_mask);
1099 spin_unlock_irq(q->queue_lock);
1100 /* q->queue_lock is unlocked at this point */
1104 EXPORT_SYMBOL(blk_get_request);
1107 * blk_make_request - given a bio, allocate a corresponding struct request.
1108 * @q: target request queue
1109 * @bio: The bio describing the memory mappings that will be submitted for IO.
1110 * It may be a chained-bio properly constructed by block/bio layer.
1111 * @gfp_mask: gfp flags to be used for memory allocation
1113 * blk_make_request is the parallel of generic_make_request for BLOCK_PC
1114 * type commands. Where the struct request needs to be farther initialized by
1115 * the caller. It is passed a &struct bio, which describes the memory info of
1118 * The caller of blk_make_request must make sure that bi_io_vec
1119 * are set to describe the memory buffers. That bio_data_dir() will return
1120 * the needed direction of the request. (And all bio's in the passed bio-chain
1121 * are properly set accordingly)
1123 * If called under none-sleepable conditions, mapped bio buffers must not
1124 * need bouncing, by calling the appropriate masked or flagged allocator,
1125 * suitable for the target device. Otherwise the call to blk_queue_bounce will
1128 * WARNING: When allocating/cloning a bio-chain, careful consideration should be
1129 * given to how you allocate bios. In particular, you cannot use __GFP_WAIT for
1130 * anything but the first bio in the chain. Otherwise you risk waiting for IO
1131 * completion of a bio that hasn't been submitted yet, thus resulting in a
1132 * deadlock. Alternatively bios should be allocated using bio_kmalloc() instead
1133 * of bio_alloc(), as that avoids the mempool deadlock.
1134 * If possible a big IO should be split into smaller parts when allocation
1135 * fails. Partial allocation should not be an error, or you risk a live-lock.
1137 struct request *blk_make_request(struct request_queue *q, struct bio *bio,
1140 struct request *rq = blk_get_request(q, bio_data_dir(bio), gfp_mask);
1143 return ERR_PTR(-ENOMEM);
1146 struct bio *bounce_bio = bio;
1149 blk_queue_bounce(q, &bounce_bio);
1150 ret = blk_rq_append_bio(q, rq, bounce_bio);
1151 if (unlikely(ret)) {
1152 blk_put_request(rq);
1153 return ERR_PTR(ret);
1159 EXPORT_SYMBOL(blk_make_request);
1162 * blk_requeue_request - put a request back on queue
1163 * @q: request queue where request should be inserted
1164 * @rq: request to be inserted
1167 * Drivers often keep queueing requests until the hardware cannot accept
1168 * more, when that condition happens we need to put the request back
1169 * on the queue. Must be called with queue lock held.
1171 void blk_requeue_request(struct request_queue *q, struct request *rq)
1173 blk_delete_timer(rq);
1174 blk_clear_rq_complete(rq);
1175 trace_block_rq_requeue(q, rq);
1177 if (blk_rq_tagged(rq))
1178 blk_queue_end_tag(q, rq);
1180 BUG_ON(blk_queued_rq(rq));
1182 elv_requeue_request(q, rq);
1184 EXPORT_SYMBOL(blk_requeue_request);
1186 static void add_acct_request(struct request_queue *q, struct request *rq,
1189 drive_stat_acct(rq, 1);
1190 __elv_add_request(q, rq, where);
1193 static void part_round_stats_single(int cpu, struct hd_struct *part,
1196 if (now == part->stamp)
1199 if (part_in_flight(part)) {
1200 __part_stat_add(cpu, part, time_in_queue,
1201 part_in_flight(part) * (now - part->stamp));
1202 __part_stat_add(cpu, part, io_ticks, (now - part->stamp));
1208 * part_round_stats() - Round off the performance stats on a struct disk_stats.
1209 * @cpu: cpu number for stats access
1210 * @part: target partition
1212 * The average IO queue length and utilisation statistics are maintained
1213 * by observing the current state of the queue length and the amount of
1214 * time it has been in this state for.
1216 * Normally, that accounting is done on IO completion, but that can result
1217 * in more than a second's worth of IO being accounted for within any one
1218 * second, leading to >100% utilisation. To deal with that, we call this
1219 * function to do a round-off before returning the results when reading
1220 * /proc/diskstats. This accounts immediately for all queue usage up to
1221 * the current jiffies and restarts the counters again.
1223 void part_round_stats(int cpu, struct hd_struct *part)
1225 unsigned long now = jiffies;
1228 part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1229 part_round_stats_single(cpu, part, now);
1231 EXPORT_SYMBOL_GPL(part_round_stats);
1234 * queue lock must be held
1236 void __blk_put_request(struct request_queue *q, struct request *req)
1240 if (unlikely(--req->ref_count))
1243 elv_completed_request(q, req);
1245 /* this is a bio leak */
1246 WARN_ON(req->bio != NULL);
1249 * Request may not have originated from ll_rw_blk. if not,
1250 * it didn't come out of our reserved rq pools
1252 if (req->cmd_flags & REQ_ALLOCED) {
1253 unsigned int flags = req->cmd_flags;
1254 struct request_list *rl = blk_rq_rl(req);
1256 BUG_ON(!list_empty(&req->queuelist));
1257 BUG_ON(!hlist_unhashed(&req->hash));
1259 blk_free_request(rl, req);
1260 freed_request(rl, flags);
1264 EXPORT_SYMBOL_GPL(__blk_put_request);
1266 void blk_put_request(struct request *req)
1268 unsigned long flags;
1269 struct request_queue *q = req->q;
1271 spin_lock_irqsave(q->queue_lock, flags);
1272 __blk_put_request(q, req);
1273 spin_unlock_irqrestore(q->queue_lock, flags);
1275 EXPORT_SYMBOL(blk_put_request);
1278 * blk_add_request_payload - add a payload to a request
1279 * @rq: request to update
1280 * @page: page backing the payload
1281 * @len: length of the payload.
1283 * This allows to later add a payload to an already submitted request by
1284 * a block driver. The driver needs to take care of freeing the payload
1287 * Note that this is a quite horrible hack and nothing but handling of
1288 * discard requests should ever use it.
1290 void blk_add_request_payload(struct request *rq, struct page *page,
1293 struct bio *bio = rq->bio;
1295 bio->bi_io_vec->bv_page = page;
1296 bio->bi_io_vec->bv_offset = 0;
1297 bio->bi_io_vec->bv_len = len;
1301 bio->bi_phys_segments = 1;
1303 rq->__data_len = rq->resid_len = len;
1304 rq->nr_phys_segments = 1;
1305 rq->buffer = bio_data(bio);
1307 EXPORT_SYMBOL_GPL(blk_add_request_payload);
1309 static bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
1312 const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1314 if (!ll_back_merge_fn(q, req, bio))
1317 trace_block_bio_backmerge(q, bio);
1319 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1320 blk_rq_set_mixed_merge(req);
1322 req->biotail->bi_next = bio;
1324 req->__data_len += bio->bi_size;
1325 req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1327 drive_stat_acct(req, 0);
1331 static bool bio_attempt_front_merge(struct request_queue *q,
1332 struct request *req, struct bio *bio)
1334 const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1336 if (!ll_front_merge_fn(q, req, bio))
1339 trace_block_bio_frontmerge(q, bio);
1341 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1342 blk_rq_set_mixed_merge(req);
1344 bio->bi_next = req->bio;
1348 * may not be valid. if the low level driver said
1349 * it didn't need a bounce buffer then it better
1350 * not touch req->buffer either...
1352 req->buffer = bio_data(bio);
1353 req->__sector = bio->bi_sector;
1354 req->__data_len += bio->bi_size;
1355 req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1357 drive_stat_acct(req, 0);
1362 * attempt_plug_merge - try to merge with %current's plugged list
1363 * @q: request_queue new bio is being queued at
1364 * @bio: new bio being queued
1365 * @request_count: out parameter for number of traversed plugged requests
1367 * Determine whether @bio being queued on @q can be merged with a request
1368 * on %current's plugged list. Returns %true if merge was successful,
1371 * Plugging coalesces IOs from the same issuer for the same purpose without
1372 * going through @q->queue_lock. As such it's more of an issuing mechanism
1373 * than scheduling, and the request, while may have elvpriv data, is not
1374 * added on the elevator at this point. In addition, we don't have
1375 * reliable access to the elevator outside queue lock. Only check basic
1376 * merging parameters without querying the elevator.
1378 static bool attempt_plug_merge(struct request_queue *q, struct bio *bio,
1379 unsigned int *request_count)
1381 struct blk_plug *plug;
1385 plug = current->plug;
1390 list_for_each_entry_reverse(rq, &plug->list, queuelist) {
1396 if (rq->q != q || !blk_rq_merge_ok(rq, bio))
1399 el_ret = blk_try_merge(rq, bio);
1400 if (el_ret == ELEVATOR_BACK_MERGE) {
1401 ret = bio_attempt_back_merge(q, rq, bio);
1404 } else if (el_ret == ELEVATOR_FRONT_MERGE) {
1405 ret = bio_attempt_front_merge(q, rq, bio);
1414 void init_request_from_bio(struct request *req, struct bio *bio)
1416 req->cmd_type = REQ_TYPE_FS;
1418 req->cmd_flags |= bio->bi_rw & REQ_COMMON_MASK;
1419 if (bio->bi_rw & REQ_RAHEAD)
1420 req->cmd_flags |= REQ_FAILFAST_MASK;
1423 req->__sector = bio->bi_sector;
1424 req->ioprio = bio_prio(bio);
1425 blk_rq_bio_prep(req->q, req, bio);
1428 void blk_queue_bio(struct request_queue *q, struct bio *bio)
1430 const bool sync = !!(bio->bi_rw & REQ_SYNC);
1431 struct blk_plug *plug;
1432 int el_ret, rw_flags, where = ELEVATOR_INSERT_SORT;
1433 struct request *req;
1434 unsigned int request_count = 0;
1437 * low level driver can indicate that it wants pages above a
1438 * certain limit bounced to low memory (ie for highmem, or even
1439 * ISA dma in theory)
1441 blk_queue_bounce(q, &bio);
1443 if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) {
1444 spin_lock_irq(q->queue_lock);
1445 where = ELEVATOR_INSERT_FLUSH;
1450 * Check if we can merge with the plugged list before grabbing
1453 if (attempt_plug_merge(q, bio, &request_count))
1456 spin_lock_irq(q->queue_lock);
1458 el_ret = elv_merge(q, &req, bio);
1459 if (el_ret == ELEVATOR_BACK_MERGE) {
1460 if (bio_attempt_back_merge(q, req, bio)) {
1461 elv_bio_merged(q, req, bio);
1462 if (!attempt_back_merge(q, req))
1463 elv_merged_request(q, req, el_ret);
1466 } else if (el_ret == ELEVATOR_FRONT_MERGE) {
1467 if (bio_attempt_front_merge(q, req, bio)) {
1468 elv_bio_merged(q, req, bio);
1469 if (!attempt_front_merge(q, req))
1470 elv_merged_request(q, req, el_ret);
1477 * This sync check and mask will be re-done in init_request_from_bio(),
1478 * but we need to set it earlier to expose the sync flag to the
1479 * rq allocator and io schedulers.
1481 rw_flags = bio_data_dir(bio);
1483 rw_flags |= REQ_SYNC;
1486 * Grab a free request. This is might sleep but can not fail.
1487 * Returns with the queue unlocked.
1489 req = get_request(q, rw_flags, bio, GFP_NOIO);
1490 if (unlikely(!req)) {
1491 bio_endio(bio, -ENODEV); /* @q is dead */
1496 * After dropping the lock and possibly sleeping here, our request
1497 * may now be mergeable after it had proven unmergeable (above).
1498 * We don't worry about that case for efficiency. It won't happen
1499 * often, and the elevators are able to handle it.
1501 init_request_from_bio(req, bio);
1503 if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags))
1504 req->cpu = raw_smp_processor_id();
1506 plug = current->plug;
1509 * If this is the first request added after a plug, fire
1510 * of a plug trace. If others have been added before, check
1511 * if we have multiple devices in this plug. If so, make a
1512 * note to sort the list before dispatch.
1514 if (list_empty(&plug->list))
1515 trace_block_plug(q);
1517 if (!plug->should_sort) {
1518 struct request *__rq;
1520 __rq = list_entry_rq(plug->list.prev);
1522 plug->should_sort = 1;
1524 if (request_count >= BLK_MAX_REQUEST_COUNT) {
1525 blk_flush_plug_list(plug, false);
1526 trace_block_plug(q);
1529 list_add_tail(&req->queuelist, &plug->list);
1530 drive_stat_acct(req, 1);
1532 spin_lock_irq(q->queue_lock);
1533 add_acct_request(q, req, where);
1536 spin_unlock_irq(q->queue_lock);
1539 EXPORT_SYMBOL_GPL(blk_queue_bio); /* for device mapper only */
1542 * If bio->bi_dev is a partition, remap the location
1544 static inline void blk_partition_remap(struct bio *bio)
1546 struct block_device *bdev = bio->bi_bdev;
1548 if (bio_sectors(bio) && bdev != bdev->bd_contains) {
1549 struct hd_struct *p = bdev->bd_part;
1551 bio->bi_sector += p->start_sect;
1552 bio->bi_bdev = bdev->bd_contains;
1554 trace_block_bio_remap(bdev_get_queue(bio->bi_bdev), bio,
1556 bio->bi_sector - p->start_sect);
1560 static void handle_bad_sector(struct bio *bio)
1562 char b[BDEVNAME_SIZE];
1564 printk(KERN_INFO "attempt to access beyond end of device\n");
1565 printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
1566 bdevname(bio->bi_bdev, b),
1568 (unsigned long long)bio->bi_sector + bio_sectors(bio),
1569 (long long)(i_size_read(bio->bi_bdev->bd_inode) >> 9));
1571 set_bit(BIO_EOF, &bio->bi_flags);
1574 #ifdef CONFIG_FAIL_MAKE_REQUEST
1576 static DECLARE_FAULT_ATTR(fail_make_request);
1578 static int __init setup_fail_make_request(char *str)
1580 return setup_fault_attr(&fail_make_request, str);
1582 __setup("fail_make_request=", setup_fail_make_request);
1584 static bool should_fail_request(struct hd_struct *part, unsigned int bytes)
1586 return part->make_it_fail && should_fail(&fail_make_request, bytes);
1589 static int __init fail_make_request_debugfs(void)
1591 struct dentry *dir = fault_create_debugfs_attr("fail_make_request",
1592 NULL, &fail_make_request);
1594 return IS_ERR(dir) ? PTR_ERR(dir) : 0;
1597 late_initcall(fail_make_request_debugfs);
1599 #else /* CONFIG_FAIL_MAKE_REQUEST */
1601 static inline bool should_fail_request(struct hd_struct *part,
1607 #endif /* CONFIG_FAIL_MAKE_REQUEST */
1610 * Check whether this bio extends beyond the end of the device.
1612 static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1619 /* Test device or partition size, when known. */
1620 maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
1622 sector_t sector = bio->bi_sector;
1624 if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1626 * This may well happen - the kernel calls bread()
1627 * without checking the size of the device, e.g., when
1628 * mounting a device.
1630 handle_bad_sector(bio);
1638 static noinline_for_stack bool
1639 generic_make_request_checks(struct bio *bio)
1641 struct request_queue *q;
1642 int nr_sectors = bio_sectors(bio);
1644 char b[BDEVNAME_SIZE];
1645 struct hd_struct *part;
1649 if (bio_check_eod(bio, nr_sectors))
1652 q = bdev_get_queue(bio->bi_bdev);
1655 "generic_make_request: Trying to access "
1656 "nonexistent block-device %s (%Lu)\n",
1657 bdevname(bio->bi_bdev, b),
1658 (long long) bio->bi_sector);
1662 if (unlikely(!(bio->bi_rw & REQ_DISCARD) &&
1663 nr_sectors > queue_max_hw_sectors(q))) {
1664 printk(KERN_ERR "bio too big device %s (%u > %u)\n",
1665 bdevname(bio->bi_bdev, b),
1667 queue_max_hw_sectors(q));
1671 part = bio->bi_bdev->bd_part;
1672 if (should_fail_request(part, bio->bi_size) ||
1673 should_fail_request(&part_to_disk(part)->part0,
1678 * If this device has partitions, remap block n
1679 * of partition p to block n+start(p) of the disk.
1681 blk_partition_remap(bio);
1683 if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
1686 if (bio_check_eod(bio, nr_sectors))
1690 * Filter flush bio's early so that make_request based
1691 * drivers without flush support don't have to worry
1694 if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
1695 bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
1702 if ((bio->bi_rw & REQ_DISCARD) &&
1703 (!blk_queue_discard(q) ||
1704 ((bio->bi_rw & REQ_SECURE) &&
1705 !blk_queue_secdiscard(q)))) {
1711 * Various block parts want %current->io_context and lazy ioc
1712 * allocation ends up trading a lot of pain for a small amount of
1713 * memory. Just allocate it upfront. This may fail and block
1714 * layer knows how to live with it.
1716 create_io_context(GFP_ATOMIC, q->node);
1718 if (blk_throtl_bio(q, bio))
1719 return false; /* throttled, will be resubmitted later */
1721 trace_block_bio_queue(q, bio);
1725 bio_endio(bio, err);
1730 * generic_make_request - hand a buffer to its device driver for I/O
1731 * @bio: The bio describing the location in memory and on the device.
1733 * generic_make_request() is used to make I/O requests of block
1734 * devices. It is passed a &struct bio, which describes the I/O that needs
1737 * generic_make_request() does not return any status. The
1738 * success/failure status of the request, along with notification of
1739 * completion, is delivered asynchronously through the bio->bi_end_io
1740 * function described (one day) else where.
1742 * The caller of generic_make_request must make sure that bi_io_vec
1743 * are set to describe the memory buffer, and that bi_dev and bi_sector are
1744 * set to describe the device address, and the
1745 * bi_end_io and optionally bi_private are set to describe how
1746 * completion notification should be signaled.
1748 * generic_make_request and the drivers it calls may use bi_next if this
1749 * bio happens to be merged with someone else, and may resubmit the bio to
1750 * a lower device by calling into generic_make_request recursively, which
1751 * means the bio should NOT be touched after the call to ->make_request_fn.
1753 void generic_make_request(struct bio *bio)
1755 struct bio_list bio_list_on_stack;
1757 if (!generic_make_request_checks(bio))
1761 * We only want one ->make_request_fn to be active at a time, else
1762 * stack usage with stacked devices could be a problem. So use
1763 * current->bio_list to keep a list of requests submited by a
1764 * make_request_fn function. current->bio_list is also used as a
1765 * flag to say if generic_make_request is currently active in this
1766 * task or not. If it is NULL, then no make_request is active. If
1767 * it is non-NULL, then a make_request is active, and new requests
1768 * should be added at the tail
1770 if (current->bio_list) {
1771 bio_list_add(current->bio_list, bio);
1775 /* following loop may be a bit non-obvious, and so deserves some
1777 * Before entering the loop, bio->bi_next is NULL (as all callers
1778 * ensure that) so we have a list with a single bio.
1779 * We pretend that we have just taken it off a longer list, so
1780 * we assign bio_list to a pointer to the bio_list_on_stack,
1781 * thus initialising the bio_list of new bios to be
1782 * added. ->make_request() may indeed add some more bios
1783 * through a recursive call to generic_make_request. If it
1784 * did, we find a non-NULL value in bio_list and re-enter the loop
1785 * from the top. In this case we really did just take the bio
1786 * of the top of the list (no pretending) and so remove it from
1787 * bio_list, and call into ->make_request() again.
1789 BUG_ON(bio->bi_next);
1790 bio_list_init(&bio_list_on_stack);
1791 current->bio_list = &bio_list_on_stack;
1793 struct request_queue *q = bdev_get_queue(bio->bi_bdev);
1795 q->make_request_fn(q, bio);
1797 bio = bio_list_pop(current->bio_list);
1799 current->bio_list = NULL; /* deactivate */
1801 EXPORT_SYMBOL(generic_make_request);
1804 * submit_bio - submit a bio to the block device layer for I/O
1805 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1806 * @bio: The &struct bio which describes the I/O
1808 * submit_bio() is very similar in purpose to generic_make_request(), and
1809 * uses that function to do most of the work. Both are fairly rough
1810 * interfaces; @bio must be presetup and ready for I/O.
1813 void submit_bio(int rw, struct bio *bio)
1815 int count = bio_sectors(bio);
1820 * If it's a regular read/write or a barrier with data attached,
1821 * go through the normal accounting stuff before submission.
1823 if (bio_has_data(bio) && !(rw & REQ_DISCARD)) {
1825 count_vm_events(PGPGOUT, count);
1827 task_io_account_read(bio->bi_size);
1828 count_vm_events(PGPGIN, count);
1831 if (unlikely(block_dump)) {
1832 char b[BDEVNAME_SIZE];
1833 printk(KERN_DEBUG "%s(%d): %s block %Lu on %s (%u sectors)\n",
1834 current->comm, task_pid_nr(current),
1835 (rw & WRITE) ? "WRITE" : "READ",
1836 (unsigned long long)bio->bi_sector,
1837 bdevname(bio->bi_bdev, b),
1842 generic_make_request(bio);
1844 EXPORT_SYMBOL(submit_bio);
1847 * blk_rq_check_limits - Helper function to check a request for the queue limit
1849 * @rq: the request being checked
1852 * @rq may have been made based on weaker limitations of upper-level queues
1853 * in request stacking drivers, and it may violate the limitation of @q.
1854 * Since the block layer and the underlying device driver trust @rq
1855 * after it is inserted to @q, it should be checked against @q before
1856 * the insertion using this generic function.
1858 * This function should also be useful for request stacking drivers
1859 * in some cases below, so export this function.
1860 * Request stacking drivers like request-based dm may change the queue
1861 * limits while requests are in the queue (e.g. dm's table swapping).
1862 * Such request stacking drivers should check those requests agaist
1863 * the new queue limits again when they dispatch those requests,
1864 * although such checkings are also done against the old queue limits
1865 * when submitting requests.
1867 int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1869 if (rq->cmd_flags & REQ_DISCARD)
1872 if (blk_rq_sectors(rq) > queue_max_sectors(q) ||
1873 blk_rq_bytes(rq) > queue_max_hw_sectors(q) << 9) {
1874 printk(KERN_ERR "%s: over max size limit.\n", __func__);
1879 * queue's settings related to segment counting like q->bounce_pfn
1880 * may differ from that of other stacking queues.
1881 * Recalculate it to check the request correctly on this queue's
1884 blk_recalc_rq_segments(rq);
1885 if (rq->nr_phys_segments > queue_max_segments(q)) {
1886 printk(KERN_ERR "%s: over max segments limit.\n", __func__);
1892 EXPORT_SYMBOL_GPL(blk_rq_check_limits);
1895 * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1896 * @q: the queue to submit the request
1897 * @rq: the request being queued
1899 int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1901 unsigned long flags;
1902 int where = ELEVATOR_INSERT_BACK;
1904 if (blk_rq_check_limits(q, rq))
1908 should_fail_request(&rq->rq_disk->part0, blk_rq_bytes(rq)))
1911 spin_lock_irqsave(q->queue_lock, flags);
1912 if (unlikely(blk_queue_dead(q))) {
1913 spin_unlock_irqrestore(q->queue_lock, flags);
1918 * Submitting request must be dequeued before calling this function
1919 * because it will be linked to another request_queue
1921 BUG_ON(blk_queued_rq(rq));
1923 if (rq->cmd_flags & (REQ_FLUSH|REQ_FUA))
1924 where = ELEVATOR_INSERT_FLUSH;
1926 add_acct_request(q, rq, where);
1927 if (where == ELEVATOR_INSERT_FLUSH)
1929 spin_unlock_irqrestore(q->queue_lock, flags);
1933 EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
1936 * blk_rq_err_bytes - determine number of bytes till the next failure boundary
1937 * @rq: request to examine
1940 * A request could be merge of IOs which require different failure
1941 * handling. This function determines the number of bytes which
1942 * can be failed from the beginning of the request without
1943 * crossing into area which need to be retried further.
1946 * The number of bytes to fail.
1949 * queue_lock must be held.
1951 unsigned int blk_rq_err_bytes(const struct request *rq)
1953 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
1954 unsigned int bytes = 0;
1957 if (!(rq->cmd_flags & REQ_MIXED_MERGE))
1958 return blk_rq_bytes(rq);
1961 * Currently the only 'mixing' which can happen is between
1962 * different fastfail types. We can safely fail portions
1963 * which have all the failfast bits that the first one has -
1964 * the ones which are at least as eager to fail as the first
1967 for (bio = rq->bio; bio; bio = bio->bi_next) {
1968 if ((bio->bi_rw & ff) != ff)
1970 bytes += bio->bi_size;
1973 /* this could lead to infinite loop */
1974 BUG_ON(blk_rq_bytes(rq) && !bytes);
1977 EXPORT_SYMBOL_GPL(blk_rq_err_bytes);
1979 static void blk_account_io_completion(struct request *req, unsigned int bytes)
1981 if (blk_do_io_stat(req)) {
1982 const int rw = rq_data_dir(req);
1983 struct hd_struct *part;
1986 cpu = part_stat_lock();
1988 part_stat_add(cpu, part, sectors[rw], bytes >> 9);
1993 static void blk_account_io_done(struct request *req)
1996 * Account IO completion. flush_rq isn't accounted as a
1997 * normal IO on queueing nor completion. Accounting the
1998 * containing request is enough.
2000 if (blk_do_io_stat(req) && !(req->cmd_flags & REQ_FLUSH_SEQ)) {
2001 unsigned long duration = jiffies - req->start_time;
2002 const int rw = rq_data_dir(req);
2003 struct hd_struct *part;
2006 cpu = part_stat_lock();
2009 part_stat_inc(cpu, part, ios[rw]);
2010 part_stat_add(cpu, part, ticks[rw], duration);
2011 part_round_stats(cpu, part);
2012 part_dec_in_flight(part, rw);
2014 hd_struct_put(part);
2020 * blk_peek_request - peek at the top of a request queue
2021 * @q: request queue to peek at
2024 * Return the request at the top of @q. The returned request
2025 * should be started using blk_start_request() before LLD starts
2029 * Pointer to the request at the top of @q if available. Null
2033 * queue_lock must be held.
2035 struct request *blk_peek_request(struct request_queue *q)
2040 while ((rq = __elv_next_request(q)) != NULL) {
2041 if (!(rq->cmd_flags & REQ_STARTED)) {
2043 * This is the first time the device driver
2044 * sees this request (possibly after
2045 * requeueing). Notify IO scheduler.
2047 if (rq->cmd_flags & REQ_SORTED)
2048 elv_activate_rq(q, rq);
2051 * just mark as started even if we don't start
2052 * it, a request that has been delayed should
2053 * not be passed by new incoming requests
2055 rq->cmd_flags |= REQ_STARTED;
2056 trace_block_rq_issue(q, rq);
2059 if (!q->boundary_rq || q->boundary_rq == rq) {
2060 q->end_sector = rq_end_sector(rq);
2061 q->boundary_rq = NULL;
2064 if (rq->cmd_flags & REQ_DONTPREP)
2067 if (q->dma_drain_size && blk_rq_bytes(rq)) {
2069 * make sure space for the drain appears we
2070 * know we can do this because max_hw_segments
2071 * has been adjusted to be one fewer than the
2074 rq->nr_phys_segments++;
2080 ret = q->prep_rq_fn(q, rq);
2081 if (ret == BLKPREP_OK) {
2083 } else if (ret == BLKPREP_DEFER) {
2085 * the request may have been (partially) prepped.
2086 * we need to keep this request in the front to
2087 * avoid resource deadlock. REQ_STARTED will
2088 * prevent other fs requests from passing this one.
2090 if (q->dma_drain_size && blk_rq_bytes(rq) &&
2091 !(rq->cmd_flags & REQ_DONTPREP)) {
2093 * remove the space for the drain we added
2094 * so that we don't add it again
2096 --rq->nr_phys_segments;
2101 } else if (ret == BLKPREP_KILL) {
2102 rq->cmd_flags |= REQ_QUIET;
2104 * Mark this request as started so we don't trigger
2105 * any debug logic in the end I/O path.
2107 blk_start_request(rq);
2108 __blk_end_request_all(rq, -EIO);
2110 printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
2117 EXPORT_SYMBOL(blk_peek_request);
2119 void blk_dequeue_request(struct request *rq)
2121 struct request_queue *q = rq->q;
2123 BUG_ON(list_empty(&rq->queuelist));
2124 BUG_ON(ELV_ON_HASH(rq));
2126 list_del_init(&rq->queuelist);
2129 * the time frame between a request being removed from the lists
2130 * and to it is freed is accounted as io that is in progress at
2133 if (blk_account_rq(rq)) {
2134 q->in_flight[rq_is_sync(rq)]++;
2135 set_io_start_time_ns(rq);
2140 * blk_start_request - start request processing on the driver
2141 * @req: request to dequeue
2144 * Dequeue @req and start timeout timer on it. This hands off the
2145 * request to the driver.
2147 * Block internal functions which don't want to start timer should
2148 * call blk_dequeue_request().
2151 * queue_lock must be held.
2153 void blk_start_request(struct request *req)
2155 blk_dequeue_request(req);
2158 * We are now handing the request to the hardware, initialize
2159 * resid_len to full count and add the timeout handler.
2161 req->resid_len = blk_rq_bytes(req);
2162 if (unlikely(blk_bidi_rq(req)))
2163 req->next_rq->resid_len = blk_rq_bytes(req->next_rq);
2167 EXPORT_SYMBOL(blk_start_request);
2170 * blk_fetch_request - fetch a request from a request queue
2171 * @q: request queue to fetch a request from
2174 * Return the request at the top of @q. The request is started on
2175 * return and LLD can start processing it immediately.
2178 * Pointer to the request at the top of @q if available. Null
2182 * queue_lock must be held.
2184 struct request *blk_fetch_request(struct request_queue *q)
2188 rq = blk_peek_request(q);
2190 blk_start_request(rq);
2193 EXPORT_SYMBOL(blk_fetch_request);
2196 * blk_update_request - Special helper function for request stacking drivers
2197 * @req: the request being processed
2198 * @error: %0 for success, < %0 for error
2199 * @nr_bytes: number of bytes to complete @req
2202 * Ends I/O on a number of bytes attached to @req, but doesn't complete
2203 * the request structure even if @req doesn't have leftover.
2204 * If @req has leftover, sets it up for the next range of segments.
2206 * This special helper function is only for request stacking drivers
2207 * (e.g. request-based dm) so that they can handle partial completion.
2208 * Actual device drivers should use blk_end_request instead.
2210 * Passing the result of blk_rq_bytes() as @nr_bytes guarantees
2211 * %false return from this function.
2214 * %false - this request doesn't have any more data
2215 * %true - this request has more data
2217 bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
2219 int total_bytes, bio_nbytes, next_idx = 0;
2225 trace_block_rq_complete(req->q, req);
2228 * For fs requests, rq is just carrier of independent bio's
2229 * and each partial completion should be handled separately.
2230 * Reset per-request error on each partial completion.
2232 * TODO: tj: This is too subtle. It would be better to let
2233 * low level drivers do what they see fit.
2235 if (req->cmd_type == REQ_TYPE_FS)
2238 if (error && req->cmd_type == REQ_TYPE_FS &&
2239 !(req->cmd_flags & REQ_QUIET)) {
2244 error_type = "recoverable transport";
2247 error_type = "critical target";
2250 error_type = "critical nexus";
2257 printk(KERN_ERR "end_request: %s error, dev %s, sector %llu\n",
2258 error_type, req->rq_disk ? req->rq_disk->disk_name : "?",
2259 (unsigned long long)blk_rq_pos(req));
2262 blk_account_io_completion(req, nr_bytes);
2264 total_bytes = bio_nbytes = 0;
2265 while ((bio = req->bio) != NULL) {
2268 if (nr_bytes >= bio->bi_size) {
2269 req->bio = bio->bi_next;
2270 nbytes = bio->bi_size;
2271 req_bio_endio(req, bio, nbytes, error);
2275 int idx = bio->bi_idx + next_idx;
2277 if (unlikely(idx >= bio->bi_vcnt)) {
2278 blk_dump_rq_flags(req, "__end_that");
2279 printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
2280 __func__, idx, bio->bi_vcnt);
2284 nbytes = bio_iovec_idx(bio, idx)->bv_len;
2285 BIO_BUG_ON(nbytes > bio->bi_size);
2288 * not a complete bvec done
2290 if (unlikely(nbytes > nr_bytes)) {
2291 bio_nbytes += nr_bytes;
2292 total_bytes += nr_bytes;
2297 * advance to the next vector
2300 bio_nbytes += nbytes;
2303 total_bytes += nbytes;
2309 * end more in this run, or just return 'not-done'
2311 if (unlikely(nr_bytes <= 0))
2321 * Reset counters so that the request stacking driver
2322 * can find how many bytes remain in the request
2325 req->__data_len = 0;
2330 * if the request wasn't completed, update state
2333 req_bio_endio(req, bio, bio_nbytes, error);
2334 bio->bi_idx += next_idx;
2335 bio_iovec(bio)->bv_offset += nr_bytes;
2336 bio_iovec(bio)->bv_len -= nr_bytes;
2339 req->__data_len -= total_bytes;
2340 req->buffer = bio_data(req->bio);
2342 /* update sector only for requests with clear definition of sector */
2343 if (req->cmd_type == REQ_TYPE_FS || (req->cmd_flags & REQ_DISCARD))
2344 req->__sector += total_bytes >> 9;
2346 /* mixed attributes always follow the first bio */
2347 if (req->cmd_flags & REQ_MIXED_MERGE) {
2348 req->cmd_flags &= ~REQ_FAILFAST_MASK;
2349 req->cmd_flags |= req->bio->bi_rw & REQ_FAILFAST_MASK;
2353 * If total number of sectors is less than the first segment
2354 * size, something has gone terribly wrong.
2356 if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
2357 blk_dump_rq_flags(req, "request botched");
2358 req->__data_len = blk_rq_cur_bytes(req);
2361 /* recalculate the number of segments */
2362 blk_recalc_rq_segments(req);
2366 EXPORT_SYMBOL_GPL(blk_update_request);
2368 static bool blk_update_bidi_request(struct request *rq, int error,
2369 unsigned int nr_bytes,
2370 unsigned int bidi_bytes)
2372 if (blk_update_request(rq, error, nr_bytes))
2375 /* Bidi request must be completed as a whole */
2376 if (unlikely(blk_bidi_rq(rq)) &&
2377 blk_update_request(rq->next_rq, error, bidi_bytes))
2380 if (blk_queue_add_random(rq->q))
2381 add_disk_randomness(rq->rq_disk);
2387 * blk_unprep_request - unprepare a request
2390 * This function makes a request ready for complete resubmission (or
2391 * completion). It happens only after all error handling is complete,
2392 * so represents the appropriate moment to deallocate any resources
2393 * that were allocated to the request in the prep_rq_fn. The queue
2394 * lock is held when calling this.
2396 void blk_unprep_request(struct request *req)
2398 struct request_queue *q = req->q;
2400 req->cmd_flags &= ~REQ_DONTPREP;
2401 if (q->unprep_rq_fn)
2402 q->unprep_rq_fn(q, req);
2404 EXPORT_SYMBOL_GPL(blk_unprep_request);
2407 * queue lock must be held
2409 static void blk_finish_request(struct request *req, int error)
2411 if (blk_rq_tagged(req))
2412 blk_queue_end_tag(req->q, req);
2414 BUG_ON(blk_queued_rq(req));
2416 if (unlikely(laptop_mode) && req->cmd_type == REQ_TYPE_FS)
2417 laptop_io_completion(&req->q->backing_dev_info);
2419 blk_delete_timer(req);
2421 if (req->cmd_flags & REQ_DONTPREP)
2422 blk_unprep_request(req);
2425 blk_account_io_done(req);
2428 req->end_io(req, error);
2430 if (blk_bidi_rq(req))
2431 __blk_put_request(req->next_rq->q, req->next_rq);
2433 __blk_put_request(req->q, req);
2438 * blk_end_bidi_request - Complete a bidi request
2439 * @rq: the request to complete
2440 * @error: %0 for success, < %0 for error
2441 * @nr_bytes: number of bytes to complete @rq
2442 * @bidi_bytes: number of bytes to complete @rq->next_rq
2445 * Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2446 * Drivers that supports bidi can safely call this member for any
2447 * type of request, bidi or uni. In the later case @bidi_bytes is
2451 * %false - we are done with this request
2452 * %true - still buffers pending for this request
2454 static bool blk_end_bidi_request(struct request *rq, int error,
2455 unsigned int nr_bytes, unsigned int bidi_bytes)
2457 struct request_queue *q = rq->q;
2458 unsigned long flags;
2460 if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2463 spin_lock_irqsave(q->queue_lock, flags);
2464 blk_finish_request(rq, error);
2465 spin_unlock_irqrestore(q->queue_lock, flags);
2471 * __blk_end_bidi_request - Complete a bidi request with queue lock held
2472 * @rq: the request to complete
2473 * @error: %0 for success, < %0 for error
2474 * @nr_bytes: number of bytes to complete @rq
2475 * @bidi_bytes: number of bytes to complete @rq->next_rq
2478 * Identical to blk_end_bidi_request() except that queue lock is
2479 * assumed to be locked on entry and remains so on return.
2482 * %false - we are done with this request
2483 * %true - still buffers pending for this request
2485 bool __blk_end_bidi_request(struct request *rq, int error,
2486 unsigned int nr_bytes, unsigned int bidi_bytes)
2488 if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2491 blk_finish_request(rq, error);
2497 * blk_end_request - Helper function for drivers to complete the request.
2498 * @rq: the request being processed
2499 * @error: %0 for success, < %0 for error
2500 * @nr_bytes: number of bytes to complete
2503 * Ends I/O on a number of bytes attached to @rq.
2504 * If @rq has leftover, sets it up for the next range of segments.
2507 * %false - we are done with this request
2508 * %true - still buffers pending for this request
2510 bool blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2512 return blk_end_bidi_request(rq, error, nr_bytes, 0);
2514 EXPORT_SYMBOL(blk_end_request);
2517 * blk_end_request_all - Helper function for drives to finish the request.
2518 * @rq: the request to finish
2519 * @error: %0 for success, < %0 for error
2522 * Completely finish @rq.
2524 void blk_end_request_all(struct request *rq, int error)
2527 unsigned int bidi_bytes = 0;
2529 if (unlikely(blk_bidi_rq(rq)))
2530 bidi_bytes = blk_rq_bytes(rq->next_rq);
2532 pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2535 EXPORT_SYMBOL(blk_end_request_all);
2538 * blk_end_request_cur - Helper function to finish the current request chunk.
2539 * @rq: the request to finish the current chunk for
2540 * @error: %0 for success, < %0 for error
2543 * Complete the current consecutively mapped chunk from @rq.
2546 * %false - we are done with this request
2547 * %true - still buffers pending for this request
2549 bool blk_end_request_cur(struct request *rq, int error)
2551 return blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2553 EXPORT_SYMBOL(blk_end_request_cur);
2556 * blk_end_request_err - Finish a request till the next failure boundary.
2557 * @rq: the request to finish till the next failure boundary for
2558 * @error: must be negative errno
2561 * Complete @rq till the next failure boundary.
2564 * %false - we are done with this request
2565 * %true - still buffers pending for this request
2567 bool blk_end_request_err(struct request *rq, int error)
2569 WARN_ON(error >= 0);
2570 return blk_end_request(rq, error, blk_rq_err_bytes(rq));
2572 EXPORT_SYMBOL_GPL(blk_end_request_err);
2575 * __blk_end_request - Helper function for drivers to complete the request.
2576 * @rq: the request being processed
2577 * @error: %0 for success, < %0 for error
2578 * @nr_bytes: number of bytes to complete
2581 * Must be called with queue lock held unlike blk_end_request().
2584 * %false - we are done with this request
2585 * %true - still buffers pending for this request
2587 bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2589 return __blk_end_bidi_request(rq, error, nr_bytes, 0);
2591 EXPORT_SYMBOL(__blk_end_request);
2594 * __blk_end_request_all - Helper function for drives to finish the request.
2595 * @rq: the request to finish
2596 * @error: %0 for success, < %0 for error
2599 * Completely finish @rq. Must be called with queue lock held.
2601 void __blk_end_request_all(struct request *rq, int error)
2604 unsigned int bidi_bytes = 0;
2606 if (unlikely(blk_bidi_rq(rq)))
2607 bidi_bytes = blk_rq_bytes(rq->next_rq);
2609 pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2612 EXPORT_SYMBOL(__blk_end_request_all);
2615 * __blk_end_request_cur - Helper function to finish the current request chunk.
2616 * @rq: the request to finish the current chunk for
2617 * @error: %0 for success, < %0 for error
2620 * Complete the current consecutively mapped chunk from @rq. Must
2621 * be called with queue lock held.
2624 * %false - we are done with this request
2625 * %true - still buffers pending for this request
2627 bool __blk_end_request_cur(struct request *rq, int error)
2629 return __blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2631 EXPORT_SYMBOL(__blk_end_request_cur);
2634 * __blk_end_request_err - Finish a request till the next failure boundary.
2635 * @rq: the request to finish till the next failure boundary for
2636 * @error: must be negative errno
2639 * Complete @rq till the next failure boundary. Must be called
2640 * with queue lock held.
2643 * %false - we are done with this request
2644 * %true - still buffers pending for this request
2646 bool __blk_end_request_err(struct request *rq, int error)
2648 WARN_ON(error >= 0);
2649 return __blk_end_request(rq, error, blk_rq_err_bytes(rq));
2651 EXPORT_SYMBOL_GPL(__blk_end_request_err);
2653 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2656 /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */
2657 rq->cmd_flags |= bio->bi_rw & REQ_WRITE;
2659 if (bio_has_data(bio)) {
2660 rq->nr_phys_segments = bio_phys_segments(q, bio);
2661 rq->buffer = bio_data(bio);
2663 rq->__data_len = bio->bi_size;
2664 rq->bio = rq->biotail = bio;
2667 rq->rq_disk = bio->bi_bdev->bd_disk;
2670 #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
2672 * rq_flush_dcache_pages - Helper function to flush all pages in a request
2673 * @rq: the request to be flushed
2676 * Flush all pages in @rq.
2678 void rq_flush_dcache_pages(struct request *rq)
2680 struct req_iterator iter;
2681 struct bio_vec *bvec;
2683 rq_for_each_segment(bvec, rq, iter)
2684 flush_dcache_page(bvec->bv_page);
2686 EXPORT_SYMBOL_GPL(rq_flush_dcache_pages);
2690 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2691 * @q : the queue of the device being checked
2694 * Check if underlying low-level drivers of a device are busy.
2695 * If the drivers want to export their busy state, they must set own
2696 * exporting function using blk_queue_lld_busy() first.
2698 * Basically, this function is used only by request stacking drivers
2699 * to stop dispatching requests to underlying devices when underlying
2700 * devices are busy. This behavior helps more I/O merging on the queue
2701 * of the request stacking driver and prevents I/O throughput regression
2702 * on burst I/O load.
2705 * 0 - Not busy (The request stacking driver should dispatch request)
2706 * 1 - Busy (The request stacking driver should stop dispatching request)
2708 int blk_lld_busy(struct request_queue *q)
2711 return q->lld_busy_fn(q);
2715 EXPORT_SYMBOL_GPL(blk_lld_busy);
2718 * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
2719 * @rq: the clone request to be cleaned up
2722 * Free all bios in @rq for a cloned request.
2724 void blk_rq_unprep_clone(struct request *rq)
2728 while ((bio = rq->bio) != NULL) {
2729 rq->bio = bio->bi_next;
2734 EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
2737 * Copy attributes of the original request to the clone request.
2738 * The actual data parts (e.g. ->cmd, ->buffer, ->sense) are not copied.
2740 static void __blk_rq_prep_clone(struct request *dst, struct request *src)
2742 dst->cpu = src->cpu;
2743 dst->cmd_flags = (src->cmd_flags & REQ_CLONE_MASK) | REQ_NOMERGE;
2744 dst->cmd_type = src->cmd_type;
2745 dst->__sector = blk_rq_pos(src);
2746 dst->__data_len = blk_rq_bytes(src);
2747 dst->nr_phys_segments = src->nr_phys_segments;
2748 dst->ioprio = src->ioprio;
2749 dst->extra_len = src->extra_len;
2753 * blk_rq_prep_clone - Helper function to setup clone request
2754 * @rq: the request to be setup
2755 * @rq_src: original request to be cloned
2756 * @bs: bio_set that bios for clone are allocated from
2757 * @gfp_mask: memory allocation mask for bio
2758 * @bio_ctr: setup function to be called for each clone bio.
2759 * Returns %0 for success, non %0 for failure.
2760 * @data: private data to be passed to @bio_ctr
2763 * Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
2764 * The actual data parts of @rq_src (e.g. ->cmd, ->buffer, ->sense)
2765 * are not copied, and copying such parts is the caller's responsibility.
2766 * Also, pages which the original bios are pointing to are not copied
2767 * and the cloned bios just point same pages.
2768 * So cloned bios must be completed before original bios, which means
2769 * the caller must complete @rq before @rq_src.
2771 int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
2772 struct bio_set *bs, gfp_t gfp_mask,
2773 int (*bio_ctr)(struct bio *, struct bio *, void *),
2776 struct bio *bio, *bio_src;
2781 blk_rq_init(NULL, rq);
2783 __rq_for_each_bio(bio_src, rq_src) {
2784 bio = bio_alloc_bioset(gfp_mask, bio_src->bi_max_vecs, bs);
2788 __bio_clone(bio, bio_src);
2790 if (bio_integrity(bio_src) &&
2791 bio_integrity_clone(bio, bio_src, gfp_mask, bs))
2794 if (bio_ctr && bio_ctr(bio, bio_src, data))
2798 rq->biotail->bi_next = bio;
2801 rq->bio = rq->biotail = bio;
2804 __blk_rq_prep_clone(rq, rq_src);
2811 blk_rq_unprep_clone(rq);
2815 EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
2817 int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
2819 return queue_work(kblockd_workqueue, work);
2821 EXPORT_SYMBOL(kblockd_schedule_work);
2823 int kblockd_schedule_delayed_work(struct request_queue *q,
2824 struct delayed_work *dwork, unsigned long delay)
2826 return queue_delayed_work(kblockd_workqueue, dwork, delay);
2828 EXPORT_SYMBOL(kblockd_schedule_delayed_work);
2830 #define PLUG_MAGIC 0x91827364
2833 * blk_start_plug - initialize blk_plug and track it inside the task_struct
2834 * @plug: The &struct blk_plug that needs to be initialized
2837 * Tracking blk_plug inside the task_struct will help with auto-flushing the
2838 * pending I/O should the task end up blocking between blk_start_plug() and
2839 * blk_finish_plug(). This is important from a performance perspective, but
2840 * also ensures that we don't deadlock. For instance, if the task is blocking
2841 * for a memory allocation, memory reclaim could end up wanting to free a
2842 * page belonging to that request that is currently residing in our private
2843 * plug. By flushing the pending I/O when the process goes to sleep, we avoid
2844 * this kind of deadlock.
2846 void blk_start_plug(struct blk_plug *plug)
2848 struct task_struct *tsk = current;
2850 plug->magic = PLUG_MAGIC;
2851 INIT_LIST_HEAD(&plug->list);
2852 INIT_LIST_HEAD(&plug->cb_list);
2853 plug->should_sort = 0;
2856 * If this is a nested plug, don't actually assign it. It will be
2857 * flushed on its own.
2861 * Store ordering should not be needed here, since a potential
2862 * preempt will imply a full memory barrier
2867 EXPORT_SYMBOL(blk_start_plug);
2869 static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
2871 struct request *rqa = container_of(a, struct request, queuelist);
2872 struct request *rqb = container_of(b, struct request, queuelist);
2874 return !(rqa->q <= rqb->q);
2878 * If 'from_schedule' is true, then postpone the dispatch of requests
2879 * until a safe kblockd context. We due this to avoid accidental big
2880 * additional stack usage in driver dispatch, in places where the originally
2881 * plugger did not intend it.
2883 static void queue_unplugged(struct request_queue *q, unsigned int depth,
2885 __releases(q->queue_lock)
2887 trace_block_unplug(q, depth, !from_schedule);
2890 * Don't mess with dead queue.
2892 if (unlikely(blk_queue_dead(q))) {
2893 spin_unlock(q->queue_lock);
2898 * If we are punting this to kblockd, then we can safely drop
2899 * the queue_lock before waking kblockd (which needs to take
2902 if (from_schedule) {
2903 spin_unlock(q->queue_lock);
2904 blk_run_queue_async(q);
2907 spin_unlock(q->queue_lock);
2912 static void flush_plug_callbacks(struct blk_plug *plug, bool from_schedule)
2914 LIST_HEAD(callbacks);
2916 while (!list_empty(&plug->cb_list)) {
2917 list_splice_init(&plug->cb_list, &callbacks);
2919 while (!list_empty(&callbacks)) {
2920 struct blk_plug_cb *cb = list_first_entry(&callbacks,
2923 list_del(&cb->list);
2924 cb->callback(cb, from_schedule);
2929 struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug, void *data,
2932 struct blk_plug *plug = current->plug;
2933 struct blk_plug_cb *cb;
2938 list_for_each_entry(cb, &plug->cb_list, list)
2939 if (cb->callback == unplug && cb->data == data)
2942 /* Not currently on the callback list */
2943 BUG_ON(size < sizeof(*cb));
2944 cb = kzalloc(size, GFP_ATOMIC);
2947 cb->callback = unplug;
2948 list_add(&cb->list, &plug->cb_list);
2952 EXPORT_SYMBOL(blk_check_plugged);
2954 void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
2956 struct request_queue *q;
2957 unsigned long flags;
2962 BUG_ON(plug->magic != PLUG_MAGIC);
2964 flush_plug_callbacks(plug, from_schedule);
2965 if (list_empty(&plug->list))
2968 list_splice_init(&plug->list, &list);
2970 if (plug->should_sort) {
2971 list_sort(NULL, &list, plug_rq_cmp);
2972 plug->should_sort = 0;
2979 * Save and disable interrupts here, to avoid doing it for every
2980 * queue lock we have to take.
2982 local_irq_save(flags);
2983 while (!list_empty(&list)) {
2984 rq = list_entry_rq(list.next);
2985 list_del_init(&rq->queuelist);
2989 * This drops the queue lock
2992 queue_unplugged(q, depth, from_schedule);
2995 spin_lock(q->queue_lock);
2999 * Short-circuit if @q is dead
3001 if (unlikely(blk_queue_dead(q))) {
3002 __blk_end_request_all(rq, -ENODEV);
3007 * rq is already accounted, so use raw insert
3009 if (rq->cmd_flags & (REQ_FLUSH | REQ_FUA))
3010 __elv_add_request(q, rq, ELEVATOR_INSERT_FLUSH);
3012 __elv_add_request(q, rq, ELEVATOR_INSERT_SORT_MERGE);
3018 * This drops the queue lock
3021 queue_unplugged(q, depth, from_schedule);
3023 local_irq_restore(flags);
3026 void blk_finish_plug(struct blk_plug *plug)
3028 blk_flush_plug_list(plug, false);
3030 if (plug == current->plug)
3031 current->plug = NULL;
3033 EXPORT_SYMBOL(blk_finish_plug);
3035 int __init blk_dev_init(void)
3037 BUILD_BUG_ON(__REQ_NR_BITS > 8 *
3038 sizeof(((struct request *)0)->cmd_flags));
3040 /* used for unplugging and affects IO latency/throughput - HIGHPRI */
3041 kblockd_workqueue = alloc_workqueue("kblockd",
3042 WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
3043 if (!kblockd_workqueue)
3044 panic("Failed to create kblockd\n");
3046 request_cachep = kmem_cache_create("blkdev_requests",
3047 sizeof(struct request), 0, SLAB_PANIC, NULL);
3049 blk_requestq_cachep = kmem_cache_create("blkdev_queue",
3050 sizeof(struct request_queue), 0, SLAB_PANIC, NULL);