2 * Block device elevator/IO-scheduler.
4 * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
6 * 30042000 Jens Axboe <axboe@kernel.dk> :
8 * Split the elevator a bit so that it is possible to choose a different
9 * one or even write a new "plug in". There are three pieces:
10 * - elevator_fn, inserts a new request in the queue list
11 * - elevator_merge_fn, decides whether a new buffer can be merged with
13 * - elevator_dequeue_fn, called when a request is taken off the active list
15 * 20082000 Dave Jones <davej@suse.de> :
16 * Removed tests for max-bomb-segments, which was breaking elvtune
17 * when run without -bN
20 * - Rework again to work with bio instead of buffer_heads
21 * - loose bi_dev comparisons, partition handling is right now
22 * - completely modularize elevator setup and teardown
25 #include <linux/kernel.h>
27 #include <linux/blkdev.h>
28 #include <linux/elevator.h>
29 #include <linux/bio.h>
30 #include <linux/module.h>
31 #include <linux/slab.h>
32 #include <linux/init.h>
33 #include <linux/compiler.h>
34 #include <linux/blktrace_api.h>
35 #include <linux/hash.h>
36 #include <linux/uaccess.h>
37 #include <linux/pm_runtime.h>
38 #include <linux/blk-cgroup.h>
40 #include <trace/events/block.h>
43 #include "blk-mq-sched.h"
45 static DEFINE_SPINLOCK(elv_list_lock);
46 static LIST_HEAD(elv_list);
51 #define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq))
54 * Query io scheduler to see if the current process issuing bio may be
57 static int elv_iosched_allow_bio_merge(struct request *rq, struct bio *bio)
59 struct request_queue *q = rq->q;
60 struct elevator_queue *e = q->elevator;
62 if (e->uses_mq && e->type->ops.mq.allow_merge)
63 return e->type->ops.mq.allow_merge(q, rq, bio);
64 else if (!e->uses_mq && e->type->ops.sq.elevator_allow_bio_merge_fn)
65 return e->type->ops.sq.elevator_allow_bio_merge_fn(q, rq, bio);
71 * can we safely merge with this request?
73 bool elv_bio_merge_ok(struct request *rq, struct bio *bio)
75 if (!blk_rq_merge_ok(rq, bio))
78 if (!elv_iosched_allow_bio_merge(rq, bio))
83 EXPORT_SYMBOL(elv_bio_merge_ok);
85 static struct elevator_type *elevator_find(const char *name)
87 struct elevator_type *e;
89 list_for_each_entry(e, &elv_list, list) {
90 if (!strcmp(e->elevator_name, name))
97 static void elevator_put(struct elevator_type *e)
99 module_put(e->elevator_owner);
102 static struct elevator_type *elevator_get(const char *name, bool try_loading)
104 struct elevator_type *e;
106 spin_lock(&elv_list_lock);
108 e = elevator_find(name);
109 if (!e && try_loading) {
110 spin_unlock(&elv_list_lock);
111 request_module("%s-iosched", name);
112 spin_lock(&elv_list_lock);
113 e = elevator_find(name);
116 if (e && !try_module_get(e->elevator_owner))
119 spin_unlock(&elv_list_lock);
124 static char chosen_elevator[ELV_NAME_MAX];
126 static int __init elevator_setup(char *str)
129 * Be backwards-compatible with previous kernels, so users
130 * won't get the wrong elevator.
132 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
136 __setup("elevator=", elevator_setup);
138 /* called during boot to load the elevator chosen by the elevator param */
139 void __init load_default_elevator_module(void)
141 struct elevator_type *e;
143 if (!chosen_elevator[0])
146 spin_lock(&elv_list_lock);
147 e = elevator_find(chosen_elevator);
148 spin_unlock(&elv_list_lock);
151 request_module("%s-iosched", chosen_elevator);
154 static struct kobj_type elv_ktype;
156 struct elevator_queue *elevator_alloc(struct request_queue *q,
157 struct elevator_type *e)
159 struct elevator_queue *eq;
161 eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node);
166 kobject_init(&eq->kobj, &elv_ktype);
167 mutex_init(&eq->sysfs_lock);
169 eq->uses_mq = e->uses_mq;
173 EXPORT_SYMBOL(elevator_alloc);
175 static void elevator_release(struct kobject *kobj)
177 struct elevator_queue *e;
179 e = container_of(kobj, struct elevator_queue, kobj);
180 elevator_put(e->type);
184 int elevator_init(struct request_queue *q, char *name)
186 struct elevator_type *e = NULL;
190 * q->sysfs_lock must be held to provide mutual exclusion between
191 * elevator_switch() and here.
193 lockdep_assert_held(&q->sysfs_lock);
195 if (unlikely(q->elevator))
198 INIT_LIST_HEAD(&q->queue_head);
199 q->last_merge = NULL;
201 q->boundary_rq = NULL;
204 e = elevator_get(name, true);
210 * Use the default elevator specified by config boot param for
211 * non-mq devices, or by config option. Don't try to load modules
212 * as we could be running off async and request_module() isn't
213 * allowed from async.
215 if (!e && !q->mq_ops && *chosen_elevator) {
216 e = elevator_get(chosen_elevator, false);
218 printk(KERN_ERR "I/O scheduler %s not found\n",
223 if (q->mq_ops && q->nr_hw_queues == 1)
224 e = elevator_get(CONFIG_DEFAULT_SQ_IOSCHED, false);
226 e = elevator_get(CONFIG_DEFAULT_MQ_IOSCHED, false);
228 e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);
232 "Default I/O scheduler not found. " \
233 "Using noop/none.\n");
234 e = elevator_get("noop", false);
239 err = blk_mq_sched_setup(q);
241 err = e->ops.mq.init_sched(q, e);
243 err = e->ops.sq.elevator_init_fn(q, e);
246 blk_mq_sched_teardown(q);
251 EXPORT_SYMBOL(elevator_init);
253 void elevator_exit(struct elevator_queue *e)
255 mutex_lock(&e->sysfs_lock);
256 if (e->uses_mq && e->type->ops.mq.exit_sched)
257 e->type->ops.mq.exit_sched(e);
258 else if (!e->uses_mq && e->type->ops.sq.elevator_exit_fn)
259 e->type->ops.sq.elevator_exit_fn(e);
260 mutex_unlock(&e->sysfs_lock);
262 kobject_put(&e->kobj);
264 EXPORT_SYMBOL(elevator_exit);
266 static inline void __elv_rqhash_del(struct request *rq)
269 rq->rq_flags &= ~RQF_HASHED;
272 void elv_rqhash_del(struct request_queue *q, struct request *rq)
275 __elv_rqhash_del(rq);
277 EXPORT_SYMBOL_GPL(elv_rqhash_del);
279 void elv_rqhash_add(struct request_queue *q, struct request *rq)
281 struct elevator_queue *e = q->elevator;
283 BUG_ON(ELV_ON_HASH(rq));
284 hash_add(e->hash, &rq->hash, rq_hash_key(rq));
285 rq->rq_flags |= RQF_HASHED;
287 EXPORT_SYMBOL_GPL(elv_rqhash_add);
289 void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
291 __elv_rqhash_del(rq);
292 elv_rqhash_add(q, rq);
295 struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
297 struct elevator_queue *e = q->elevator;
298 struct hlist_node *next;
301 hash_for_each_possible_safe(e->hash, rq, next, hash, offset) {
302 BUG_ON(!ELV_ON_HASH(rq));
304 if (unlikely(!rq_mergeable(rq))) {
305 __elv_rqhash_del(rq);
309 if (rq_hash_key(rq) == offset)
317 * RB-tree support functions for inserting/lookup/removal of requests
318 * in a sorted RB tree.
320 void elv_rb_add(struct rb_root *root, struct request *rq)
322 struct rb_node **p = &root->rb_node;
323 struct rb_node *parent = NULL;
324 struct request *__rq;
328 __rq = rb_entry(parent, struct request, rb_node);
330 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
332 else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
336 rb_link_node(&rq->rb_node, parent, p);
337 rb_insert_color(&rq->rb_node, root);
339 EXPORT_SYMBOL(elv_rb_add);
341 void elv_rb_del(struct rb_root *root, struct request *rq)
343 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
344 rb_erase(&rq->rb_node, root);
345 RB_CLEAR_NODE(&rq->rb_node);
347 EXPORT_SYMBOL(elv_rb_del);
349 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
351 struct rb_node *n = root->rb_node;
355 rq = rb_entry(n, struct request, rb_node);
357 if (sector < blk_rq_pos(rq))
359 else if (sector > blk_rq_pos(rq))
367 EXPORT_SYMBOL(elv_rb_find);
370 * Insert rq into dispatch queue of q. Queue lock must be held on
371 * entry. rq is sort instead into the dispatch queue. To be used by
372 * specific elevators.
374 void elv_dispatch_sort(struct request_queue *q, struct request *rq)
377 struct list_head *entry;
379 if (q->last_merge == rq)
380 q->last_merge = NULL;
382 elv_rqhash_del(q, rq);
386 boundary = q->end_sector;
387 list_for_each_prev(entry, &q->queue_head) {
388 struct request *pos = list_entry_rq(entry);
390 if (req_op(rq) != req_op(pos))
392 if (rq_data_dir(rq) != rq_data_dir(pos))
394 if (pos->rq_flags & (RQF_STARTED | RQF_SOFTBARRIER))
396 if (blk_rq_pos(rq) >= boundary) {
397 if (blk_rq_pos(pos) < boundary)
400 if (blk_rq_pos(pos) >= boundary)
403 if (blk_rq_pos(rq) >= blk_rq_pos(pos))
407 list_add(&rq->queuelist, entry);
409 EXPORT_SYMBOL(elv_dispatch_sort);
412 * Insert rq into dispatch queue of q. Queue lock must be held on
413 * entry. rq is added to the back of the dispatch queue. To be used by
414 * specific elevators.
416 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
418 if (q->last_merge == rq)
419 q->last_merge = NULL;
421 elv_rqhash_del(q, rq);
425 q->end_sector = rq_end_sector(rq);
427 list_add_tail(&rq->queuelist, &q->queue_head);
429 EXPORT_SYMBOL(elv_dispatch_add_tail);
431 enum elv_merge elv_merge(struct request_queue *q, struct request **req,
434 struct elevator_queue *e = q->elevator;
435 struct request *__rq;
439 * nomerges: No merges at all attempted
440 * noxmerges: Only simple one-hit cache try
441 * merges: All merge tries attempted
443 if (blk_queue_nomerges(q) || !bio_mergeable(bio))
444 return ELEVATOR_NO_MERGE;
447 * First try one-hit cache.
449 if (q->last_merge && elv_bio_merge_ok(q->last_merge, bio)) {
450 enum elv_merge ret = blk_try_merge(q->last_merge, bio);
452 if (ret != ELEVATOR_NO_MERGE) {
453 *req = q->last_merge;
458 if (blk_queue_noxmerges(q))
459 return ELEVATOR_NO_MERGE;
462 * See if our hash lookup can find a potential backmerge.
464 __rq = elv_rqhash_find(q, bio->bi_iter.bi_sector);
465 if (__rq && elv_bio_merge_ok(__rq, bio)) {
467 return ELEVATOR_BACK_MERGE;
470 if (e->uses_mq && e->type->ops.mq.request_merge)
471 return e->type->ops.mq.request_merge(q, req, bio);
472 else if (!e->uses_mq && e->type->ops.sq.elevator_merge_fn)
473 return e->type->ops.sq.elevator_merge_fn(q, req, bio);
475 return ELEVATOR_NO_MERGE;
479 * Attempt to do an insertion back merge. Only check for the case where
480 * we can append 'rq' to an existing request, so we can throw 'rq' away
483 * Returns true if we merged, false otherwise
485 bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq)
487 struct request *__rq;
490 if (blk_queue_nomerges(q))
494 * First try one-hit cache.
496 if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq))
499 if (blk_queue_noxmerges(q))
504 * See if our hash lookup can find a potential backmerge.
507 __rq = elv_rqhash_find(q, blk_rq_pos(rq));
508 if (!__rq || !blk_attempt_req_merge(q, __rq, rq))
511 /* The merged request could be merged with others, try again */
519 void elv_merged_request(struct request_queue *q, struct request *rq,
522 struct elevator_queue *e = q->elevator;
524 if (e->uses_mq && e->type->ops.mq.request_merged)
525 e->type->ops.mq.request_merged(q, rq, type);
526 else if (!e->uses_mq && e->type->ops.sq.elevator_merged_fn)
527 e->type->ops.sq.elevator_merged_fn(q, rq, type);
529 if (type == ELEVATOR_BACK_MERGE)
530 elv_rqhash_reposition(q, rq);
535 void elv_merge_requests(struct request_queue *q, struct request *rq,
536 struct request *next)
538 struct elevator_queue *e = q->elevator;
539 bool next_sorted = false;
541 if (e->uses_mq && e->type->ops.mq.requests_merged)
542 e->type->ops.mq.requests_merged(q, rq, next);
543 else if (e->type->ops.sq.elevator_merge_req_fn) {
544 next_sorted = (__force bool)(next->rq_flags & RQF_SORTED);
546 e->type->ops.sq.elevator_merge_req_fn(q, rq, next);
549 elv_rqhash_reposition(q, rq);
552 elv_rqhash_del(q, next);
559 void elv_bio_merged(struct request_queue *q, struct request *rq,
562 struct elevator_queue *e = q->elevator;
564 if (WARN_ON_ONCE(e->uses_mq))
567 if (e->type->ops.sq.elevator_bio_merged_fn)
568 e->type->ops.sq.elevator_bio_merged_fn(q, rq, bio);
572 static void blk_pm_requeue_request(struct request *rq)
574 if (rq->q->dev && !(rq->rq_flags & RQF_PM))
578 static void blk_pm_add_request(struct request_queue *q, struct request *rq)
580 if (q->dev && !(rq->rq_flags & RQF_PM) && q->nr_pending++ == 0 &&
581 (q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING))
582 pm_request_resume(q->dev);
585 static inline void blk_pm_requeue_request(struct request *rq) {}
586 static inline void blk_pm_add_request(struct request_queue *q,
592 void elv_requeue_request(struct request_queue *q, struct request *rq)
595 * it already went through dequeue, we need to decrement the
596 * in_flight count again
598 if (blk_account_rq(rq)) {
599 q->in_flight[rq_is_sync(rq)]--;
600 if (rq->rq_flags & RQF_SORTED)
601 elv_deactivate_rq(q, rq);
604 rq->rq_flags &= ~RQF_STARTED;
606 blk_pm_requeue_request(rq);
608 __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
611 void elv_drain_elevator(struct request_queue *q)
613 struct elevator_queue *e = q->elevator;
616 if (WARN_ON_ONCE(e->uses_mq))
619 lockdep_assert_held(q->queue_lock);
621 while (e->type->ops.sq.elevator_dispatch_fn(q, 1))
623 if (q->nr_sorted && printed++ < 10) {
624 printk(KERN_ERR "%s: forced dispatching is broken "
625 "(nr_sorted=%u), please report this\n",
626 q->elevator->type->elevator_name, q->nr_sorted);
630 void __elv_add_request(struct request_queue *q, struct request *rq, int where)
632 trace_block_rq_insert(q, rq);
634 blk_pm_add_request(q, rq);
638 if (rq->rq_flags & RQF_SOFTBARRIER) {
639 /* barriers are scheduling boundary, update end_sector */
640 if (!blk_rq_is_passthrough(rq)) {
641 q->end_sector = rq_end_sector(rq);
644 } else if (!(rq->rq_flags & RQF_ELVPRIV) &&
645 (where == ELEVATOR_INSERT_SORT ||
646 where == ELEVATOR_INSERT_SORT_MERGE))
647 where = ELEVATOR_INSERT_BACK;
650 case ELEVATOR_INSERT_REQUEUE:
651 case ELEVATOR_INSERT_FRONT:
652 rq->rq_flags |= RQF_SOFTBARRIER;
653 list_add(&rq->queuelist, &q->queue_head);
656 case ELEVATOR_INSERT_BACK:
657 rq->rq_flags |= RQF_SOFTBARRIER;
658 elv_drain_elevator(q);
659 list_add_tail(&rq->queuelist, &q->queue_head);
661 * We kick the queue here for the following reasons.
662 * - The elevator might have returned NULL previously
663 * to delay requests and returned them now. As the
664 * queue wasn't empty before this request, ll_rw_blk
665 * won't run the queue on return, resulting in hang.
666 * - Usually, back inserted requests won't be merged
667 * with anything. There's no point in delaying queue
673 case ELEVATOR_INSERT_SORT_MERGE:
675 * If we succeed in merging this request with one in the
676 * queue already, we are done - rq has now been freed,
677 * so no need to do anything further.
679 if (elv_attempt_insert_merge(q, rq))
681 case ELEVATOR_INSERT_SORT:
682 BUG_ON(blk_rq_is_passthrough(rq));
683 rq->rq_flags |= RQF_SORTED;
685 if (rq_mergeable(rq)) {
686 elv_rqhash_add(q, rq);
692 * Some ioscheds (cfq) run q->request_fn directly, so
693 * rq cannot be accessed after calling
694 * elevator_add_req_fn.
696 q->elevator->type->ops.sq.elevator_add_req_fn(q, rq);
699 case ELEVATOR_INSERT_FLUSH:
700 rq->rq_flags |= RQF_SOFTBARRIER;
701 blk_insert_flush(rq);
704 printk(KERN_ERR "%s: bad insertion point %d\n",
709 EXPORT_SYMBOL(__elv_add_request);
711 void elv_add_request(struct request_queue *q, struct request *rq, int where)
715 spin_lock_irqsave(q->queue_lock, flags);
716 __elv_add_request(q, rq, where);
717 spin_unlock_irqrestore(q->queue_lock, flags);
719 EXPORT_SYMBOL(elv_add_request);
721 struct request *elv_latter_request(struct request_queue *q, struct request *rq)
723 struct elevator_queue *e = q->elevator;
725 if (e->uses_mq && e->type->ops.mq.next_request)
726 return e->type->ops.mq.next_request(q, rq);
727 else if (!e->uses_mq && e->type->ops.sq.elevator_latter_req_fn)
728 return e->type->ops.sq.elevator_latter_req_fn(q, rq);
733 struct request *elv_former_request(struct request_queue *q, struct request *rq)
735 struct elevator_queue *e = q->elevator;
737 if (e->uses_mq && e->type->ops.mq.former_request)
738 return e->type->ops.mq.former_request(q, rq);
739 if (!e->uses_mq && e->type->ops.sq.elevator_former_req_fn)
740 return e->type->ops.sq.elevator_former_req_fn(q, rq);
744 int elv_set_request(struct request_queue *q, struct request *rq,
745 struct bio *bio, gfp_t gfp_mask)
747 struct elevator_queue *e = q->elevator;
749 if (WARN_ON_ONCE(e->uses_mq))
752 if (e->type->ops.sq.elevator_set_req_fn)
753 return e->type->ops.sq.elevator_set_req_fn(q, rq, bio, gfp_mask);
757 void elv_put_request(struct request_queue *q, struct request *rq)
759 struct elevator_queue *e = q->elevator;
761 if (WARN_ON_ONCE(e->uses_mq))
764 if (e->type->ops.sq.elevator_put_req_fn)
765 e->type->ops.sq.elevator_put_req_fn(rq);
768 int elv_may_queue(struct request_queue *q, unsigned int op)
770 struct elevator_queue *e = q->elevator;
772 if (WARN_ON_ONCE(e->uses_mq))
775 if (e->type->ops.sq.elevator_may_queue_fn)
776 return e->type->ops.sq.elevator_may_queue_fn(q, op);
778 return ELV_MQUEUE_MAY;
781 void elv_completed_request(struct request_queue *q, struct request *rq)
783 struct elevator_queue *e = q->elevator;
785 if (WARN_ON_ONCE(e->uses_mq))
789 * request is released from the driver, io must be done
791 if (blk_account_rq(rq)) {
792 q->in_flight[rq_is_sync(rq)]--;
793 if ((rq->rq_flags & RQF_SORTED) &&
794 e->type->ops.sq.elevator_completed_req_fn)
795 e->type->ops.sq.elevator_completed_req_fn(q, rq);
799 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
802 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
804 struct elv_fs_entry *entry = to_elv(attr);
805 struct elevator_queue *e;
811 e = container_of(kobj, struct elevator_queue, kobj);
812 mutex_lock(&e->sysfs_lock);
813 error = e->type ? entry->show(e, page) : -ENOENT;
814 mutex_unlock(&e->sysfs_lock);
819 elv_attr_store(struct kobject *kobj, struct attribute *attr,
820 const char *page, size_t length)
822 struct elv_fs_entry *entry = to_elv(attr);
823 struct elevator_queue *e;
829 e = container_of(kobj, struct elevator_queue, kobj);
830 mutex_lock(&e->sysfs_lock);
831 error = e->type ? entry->store(e, page, length) : -ENOENT;
832 mutex_unlock(&e->sysfs_lock);
836 static const struct sysfs_ops elv_sysfs_ops = {
837 .show = elv_attr_show,
838 .store = elv_attr_store,
841 static struct kobj_type elv_ktype = {
842 .sysfs_ops = &elv_sysfs_ops,
843 .release = elevator_release,
846 int elv_register_queue(struct request_queue *q)
848 struct elevator_queue *e = q->elevator;
851 error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
853 struct elv_fs_entry *attr = e->type->elevator_attrs;
855 while (attr->attr.name) {
856 if (sysfs_create_file(&e->kobj, &attr->attr))
861 kobject_uevent(&e->kobj, KOBJ_ADD);
863 if (!e->uses_mq && e->type->ops.sq.elevator_registered_fn)
864 e->type->ops.sq.elevator_registered_fn(q);
868 EXPORT_SYMBOL(elv_register_queue);
870 void elv_unregister_queue(struct request_queue *q)
873 struct elevator_queue *e = q->elevator;
875 kobject_uevent(&e->kobj, KOBJ_REMOVE);
876 kobject_del(&e->kobj);
880 EXPORT_SYMBOL(elv_unregister_queue);
882 int elv_register(struct elevator_type *e)
886 /* create icq_cache if requested */
888 if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
889 WARN_ON(e->icq_align < __alignof__(struct io_cq)))
892 snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
893 "%s_io_cq", e->elevator_name);
894 e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
895 e->icq_align, 0, NULL);
900 /* register, don't allow duplicate names */
901 spin_lock(&elv_list_lock);
902 if (elevator_find(e->elevator_name)) {
903 spin_unlock(&elv_list_lock);
905 kmem_cache_destroy(e->icq_cache);
908 list_add_tail(&e->list, &elv_list);
909 spin_unlock(&elv_list_lock);
911 /* print pretty message */
912 if (!strcmp(e->elevator_name, chosen_elevator) ||
913 (!*chosen_elevator &&
914 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
917 printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
921 EXPORT_SYMBOL_GPL(elv_register);
923 void elv_unregister(struct elevator_type *e)
926 spin_lock(&elv_list_lock);
927 list_del_init(&e->list);
928 spin_unlock(&elv_list_lock);
931 * Destroy icq_cache if it exists. icq's are RCU managed. Make
932 * sure all RCU operations are complete before proceeding.
936 kmem_cache_destroy(e->icq_cache);
940 EXPORT_SYMBOL_GPL(elv_unregister);
943 * switch to new_e io scheduler. be careful not to introduce deadlocks -
944 * we don't free the old io scheduler, before we have allocated what we
945 * need for the new one. this way we have a chance of going back to the old
946 * one, if the new one fails init for some reason.
948 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
950 struct elevator_queue *old = q->elevator;
951 bool old_registered = false;
955 blk_mq_freeze_queue(q);
956 blk_mq_quiesce_queue(q);
960 * Turn on BYPASS and drain all requests w/ elevator private data.
961 * Block layer doesn't call into a quiesced elevator - all requests
962 * are directly put on the dispatch list without elevator data
963 * using INSERT_BACK. All requests have SOFTBARRIER set and no
964 * merge happens either.
967 old_registered = old->registered;
970 blk_mq_sched_teardown(q);
973 blk_queue_bypass_start(q);
975 /* unregister and clear all auxiliary data of the old elevator */
977 elv_unregister_queue(q);
979 spin_lock_irq(q->queue_lock);
981 spin_unlock_irq(q->queue_lock);
984 /* allocate, init and register new elevator */
986 if (new_e->uses_mq) {
987 err = blk_mq_sched_setup(q);
989 err = new_e->ops.mq.init_sched(q, new_e);
991 err = new_e->ops.sq.elevator_init_fn(q, new_e);
995 err = elv_register_queue(q);
1001 /* done, kill the old one and finish */
1005 blk_queue_bypass_end(q);
1009 blk_mq_unfreeze_queue(q);
1010 blk_mq_start_stopped_hw_queues(q, true);
1014 blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
1016 blk_add_trace_msg(q, "elv switch: none");
1022 blk_mq_sched_teardown(q);
1023 elevator_exit(q->elevator);
1025 /* switch failed, restore and re-register old elevator */
1028 elv_register_queue(q);
1030 blk_queue_bypass_end(q);
1033 blk_mq_unfreeze_queue(q);
1034 blk_mq_start_stopped_hw_queues(q, true);
1041 * Switch this queue to the given IO scheduler.
1043 static int __elevator_change(struct request_queue *q, const char *name)
1045 char elevator_name[ELV_NAME_MAX];
1046 struct elevator_type *e;
1049 * Special case for mq, turn off scheduling
1051 if (q->mq_ops && !strncmp(name, "none", 4))
1052 return elevator_switch(q, NULL);
1054 strlcpy(elevator_name, name, sizeof(elevator_name));
1055 e = elevator_get(strstrip(elevator_name), true);
1057 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
1062 !strcmp(elevator_name, q->elevator->type->elevator_name)) {
1067 if (!e->uses_mq && q->mq_ops) {
1071 if (e->uses_mq && !q->mq_ops) {
1076 return elevator_switch(q, e);
1079 int elevator_change(struct request_queue *q, const char *name)
1083 /* Protect q->elevator from elevator_init() */
1084 mutex_lock(&q->sysfs_lock);
1085 ret = __elevator_change(q, name);
1086 mutex_unlock(&q->sysfs_lock);
1090 EXPORT_SYMBOL(elevator_change);
1092 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
1097 if (!(q->mq_ops || q->request_fn))
1100 ret = __elevator_change(q, name);
1104 printk(KERN_ERR "elevator: switch to %s failed\n", name);
1108 ssize_t elv_iosched_show(struct request_queue *q, char *name)
1110 struct elevator_queue *e = q->elevator;
1111 struct elevator_type *elv = NULL;
1112 struct elevator_type *__e;
1115 if (!blk_queue_stackable(q))
1116 return sprintf(name, "none\n");
1119 len += sprintf(name+len, "[none] ");
1123 spin_lock(&elv_list_lock);
1124 list_for_each_entry(__e, &elv_list, list) {
1125 if (elv && !strcmp(elv->elevator_name, __e->elevator_name)) {
1126 len += sprintf(name+len, "[%s] ", elv->elevator_name);
1129 if (__e->uses_mq && q->mq_ops)
1130 len += sprintf(name+len, "%s ", __e->elevator_name);
1131 else if (!__e->uses_mq && !q->mq_ops)
1132 len += sprintf(name+len, "%s ", __e->elevator_name);
1134 spin_unlock(&elv_list_lock);
1136 if (q->mq_ops && q->elevator)
1137 len += sprintf(name+len, "none");
1139 len += sprintf(len+name, "\n");
1143 struct request *elv_rb_former_request(struct request_queue *q,
1146 struct rb_node *rbprev = rb_prev(&rq->rb_node);
1149 return rb_entry_rq(rbprev);
1153 EXPORT_SYMBOL(elv_rb_former_request);
1155 struct request *elv_rb_latter_request(struct request_queue *q,
1158 struct rb_node *rbnext = rb_next(&rq->rb_node);
1161 return rb_entry_rq(rbnext);
1165 EXPORT_SYMBOL(elv_rb_latter_request);