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",
224 * For blk-mq devices, we default to using mq-deadline,
225 * if available, for single queue devices. If deadline
226 * isn't available OR we have multiple queues, default
230 if (q->nr_hw_queues == 1)
231 e = elevator_get("mq-deadline", false);
235 e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);
239 "Default I/O scheduler not found. " \
241 e = elevator_get("noop", false);
246 err = blk_mq_init_sched(q, e);
248 err = e->ops.sq.elevator_init_fn(q, e);
253 EXPORT_SYMBOL(elevator_init);
255 void elevator_exit(struct request_queue *q, struct elevator_queue *e)
257 mutex_lock(&e->sysfs_lock);
258 if (e->uses_mq && e->type->ops.mq.exit_sched)
259 blk_mq_exit_sched(q, e);
260 else if (!e->uses_mq && e->type->ops.sq.elevator_exit_fn)
261 e->type->ops.sq.elevator_exit_fn(e);
262 mutex_unlock(&e->sysfs_lock);
264 kobject_put(&e->kobj);
266 EXPORT_SYMBOL(elevator_exit);
268 static inline void __elv_rqhash_del(struct request *rq)
271 rq->rq_flags &= ~RQF_HASHED;
274 void elv_rqhash_del(struct request_queue *q, struct request *rq)
277 __elv_rqhash_del(rq);
279 EXPORT_SYMBOL_GPL(elv_rqhash_del);
281 void elv_rqhash_add(struct request_queue *q, struct request *rq)
283 struct elevator_queue *e = q->elevator;
285 BUG_ON(ELV_ON_HASH(rq));
286 hash_add(e->hash, &rq->hash, rq_hash_key(rq));
287 rq->rq_flags |= RQF_HASHED;
289 EXPORT_SYMBOL_GPL(elv_rqhash_add);
291 void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
293 __elv_rqhash_del(rq);
294 elv_rqhash_add(q, rq);
297 struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
299 struct elevator_queue *e = q->elevator;
300 struct hlist_node *next;
303 hash_for_each_possible_safe(e->hash, rq, next, hash, offset) {
304 BUG_ON(!ELV_ON_HASH(rq));
306 if (unlikely(!rq_mergeable(rq))) {
307 __elv_rqhash_del(rq);
311 if (rq_hash_key(rq) == offset)
319 * RB-tree support functions for inserting/lookup/removal of requests
320 * in a sorted RB tree.
322 void elv_rb_add(struct rb_root *root, struct request *rq)
324 struct rb_node **p = &root->rb_node;
325 struct rb_node *parent = NULL;
326 struct request *__rq;
330 __rq = rb_entry(parent, struct request, rb_node);
332 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
334 else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
338 rb_link_node(&rq->rb_node, parent, p);
339 rb_insert_color(&rq->rb_node, root);
341 EXPORT_SYMBOL(elv_rb_add);
343 void elv_rb_del(struct rb_root *root, struct request *rq)
345 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
346 rb_erase(&rq->rb_node, root);
347 RB_CLEAR_NODE(&rq->rb_node);
349 EXPORT_SYMBOL(elv_rb_del);
351 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
353 struct rb_node *n = root->rb_node;
357 rq = rb_entry(n, struct request, rb_node);
359 if (sector < blk_rq_pos(rq))
361 else if (sector > blk_rq_pos(rq))
369 EXPORT_SYMBOL(elv_rb_find);
372 * Insert rq into dispatch queue of q. Queue lock must be held on
373 * entry. rq is sort instead into the dispatch queue. To be used by
374 * specific elevators.
376 void elv_dispatch_sort(struct request_queue *q, struct request *rq)
379 struct list_head *entry;
381 if (q->last_merge == rq)
382 q->last_merge = NULL;
384 elv_rqhash_del(q, rq);
388 boundary = q->end_sector;
389 list_for_each_prev(entry, &q->queue_head) {
390 struct request *pos = list_entry_rq(entry);
392 if (req_op(rq) != req_op(pos))
394 if (rq_data_dir(rq) != rq_data_dir(pos))
396 if (pos->rq_flags & (RQF_STARTED | RQF_SOFTBARRIER))
398 if (blk_rq_pos(rq) >= boundary) {
399 if (blk_rq_pos(pos) < boundary)
402 if (blk_rq_pos(pos) >= boundary)
405 if (blk_rq_pos(rq) >= blk_rq_pos(pos))
409 list_add(&rq->queuelist, entry);
411 EXPORT_SYMBOL(elv_dispatch_sort);
414 * Insert rq into dispatch queue of q. Queue lock must be held on
415 * entry. rq is added to the back of the dispatch queue. To be used by
416 * specific elevators.
418 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
420 if (q->last_merge == rq)
421 q->last_merge = NULL;
423 elv_rqhash_del(q, rq);
427 q->end_sector = rq_end_sector(rq);
429 list_add_tail(&rq->queuelist, &q->queue_head);
431 EXPORT_SYMBOL(elv_dispatch_add_tail);
433 enum elv_merge elv_merge(struct request_queue *q, struct request **req,
436 struct elevator_queue *e = q->elevator;
437 struct request *__rq;
441 * nomerges: No merges at all attempted
442 * noxmerges: Only simple one-hit cache try
443 * merges: All merge tries attempted
445 if (blk_queue_nomerges(q) || !bio_mergeable(bio))
446 return ELEVATOR_NO_MERGE;
449 * First try one-hit cache.
451 if (q->last_merge && elv_bio_merge_ok(q->last_merge, bio)) {
452 enum elv_merge ret = blk_try_merge(q->last_merge, bio);
454 if (ret != ELEVATOR_NO_MERGE) {
455 *req = q->last_merge;
460 if (blk_queue_noxmerges(q))
461 return ELEVATOR_NO_MERGE;
464 * See if our hash lookup can find a potential backmerge.
466 __rq = elv_rqhash_find(q, bio->bi_iter.bi_sector);
467 if (__rq && elv_bio_merge_ok(__rq, bio)) {
469 return ELEVATOR_BACK_MERGE;
472 if (e->uses_mq && e->type->ops.mq.request_merge)
473 return e->type->ops.mq.request_merge(q, req, bio);
474 else if (!e->uses_mq && e->type->ops.sq.elevator_merge_fn)
475 return e->type->ops.sq.elevator_merge_fn(q, req, bio);
477 return ELEVATOR_NO_MERGE;
481 * Attempt to do an insertion back merge. Only check for the case where
482 * we can append 'rq' to an existing request, so we can throw 'rq' away
485 * Returns true if we merged, false otherwise
487 bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq)
489 struct request *__rq;
492 if (blk_queue_nomerges(q))
496 * First try one-hit cache.
498 if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq))
501 if (blk_queue_noxmerges(q))
506 * See if our hash lookup can find a potential backmerge.
509 __rq = elv_rqhash_find(q, blk_rq_pos(rq));
510 if (!__rq || !blk_attempt_req_merge(q, __rq, rq))
513 /* The merged request could be merged with others, try again */
521 void elv_merged_request(struct request_queue *q, struct request *rq,
524 struct elevator_queue *e = q->elevator;
526 if (e->uses_mq && e->type->ops.mq.request_merged)
527 e->type->ops.mq.request_merged(q, rq, type);
528 else if (!e->uses_mq && e->type->ops.sq.elevator_merged_fn)
529 e->type->ops.sq.elevator_merged_fn(q, rq, type);
531 if (type == ELEVATOR_BACK_MERGE)
532 elv_rqhash_reposition(q, rq);
537 void elv_merge_requests(struct request_queue *q, struct request *rq,
538 struct request *next)
540 struct elevator_queue *e = q->elevator;
541 bool next_sorted = false;
543 if (e->uses_mq && e->type->ops.mq.requests_merged)
544 e->type->ops.mq.requests_merged(q, rq, next);
545 else if (e->type->ops.sq.elevator_merge_req_fn) {
546 next_sorted = (__force bool)(next->rq_flags & RQF_SORTED);
548 e->type->ops.sq.elevator_merge_req_fn(q, rq, next);
551 elv_rqhash_reposition(q, rq);
554 elv_rqhash_del(q, next);
561 void elv_bio_merged(struct request_queue *q, struct request *rq,
564 struct elevator_queue *e = q->elevator;
566 if (WARN_ON_ONCE(e->uses_mq))
569 if (e->type->ops.sq.elevator_bio_merged_fn)
570 e->type->ops.sq.elevator_bio_merged_fn(q, rq, bio);
574 static void blk_pm_requeue_request(struct request *rq)
576 if (rq->q->dev && !(rq->rq_flags & RQF_PM))
580 static void blk_pm_add_request(struct request_queue *q, struct request *rq)
582 if (q->dev && !(rq->rq_flags & RQF_PM) && q->nr_pending++ == 0 &&
583 (q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING))
584 pm_request_resume(q->dev);
587 static inline void blk_pm_requeue_request(struct request *rq) {}
588 static inline void blk_pm_add_request(struct request_queue *q,
594 void elv_requeue_request(struct request_queue *q, struct request *rq)
597 * it already went through dequeue, we need to decrement the
598 * in_flight count again
600 if (blk_account_rq(rq)) {
601 q->in_flight[rq_is_sync(rq)]--;
602 if (rq->rq_flags & RQF_SORTED)
603 elv_deactivate_rq(q, rq);
606 rq->rq_flags &= ~RQF_STARTED;
608 blk_pm_requeue_request(rq);
610 __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
613 void elv_drain_elevator(struct request_queue *q)
615 struct elevator_queue *e = q->elevator;
618 if (WARN_ON_ONCE(e->uses_mq))
621 lockdep_assert_held(q->queue_lock);
623 while (e->type->ops.sq.elevator_dispatch_fn(q, 1))
625 if (q->nr_sorted && printed++ < 10) {
626 printk(KERN_ERR "%s: forced dispatching is broken "
627 "(nr_sorted=%u), please report this\n",
628 q->elevator->type->elevator_name, q->nr_sorted);
632 void __elv_add_request(struct request_queue *q, struct request *rq, int where)
634 trace_block_rq_insert(q, rq);
636 blk_pm_add_request(q, rq);
640 if (rq->rq_flags & RQF_SOFTBARRIER) {
641 /* barriers are scheduling boundary, update end_sector */
642 if (!blk_rq_is_passthrough(rq)) {
643 q->end_sector = rq_end_sector(rq);
646 } else if (!(rq->rq_flags & RQF_ELVPRIV) &&
647 (where == ELEVATOR_INSERT_SORT ||
648 where == ELEVATOR_INSERT_SORT_MERGE))
649 where = ELEVATOR_INSERT_BACK;
652 case ELEVATOR_INSERT_REQUEUE:
653 case ELEVATOR_INSERT_FRONT:
654 rq->rq_flags |= RQF_SOFTBARRIER;
655 list_add(&rq->queuelist, &q->queue_head);
658 case ELEVATOR_INSERT_BACK:
659 rq->rq_flags |= RQF_SOFTBARRIER;
660 elv_drain_elevator(q);
661 list_add_tail(&rq->queuelist, &q->queue_head);
663 * We kick the queue here for the following reasons.
664 * - The elevator might have returned NULL previously
665 * to delay requests and returned them now. As the
666 * queue wasn't empty before this request, ll_rw_blk
667 * won't run the queue on return, resulting in hang.
668 * - Usually, back inserted requests won't be merged
669 * with anything. There's no point in delaying queue
675 case ELEVATOR_INSERT_SORT_MERGE:
677 * If we succeed in merging this request with one in the
678 * queue already, we are done - rq has now been freed,
679 * so no need to do anything further.
681 if (elv_attempt_insert_merge(q, rq))
683 case ELEVATOR_INSERT_SORT:
684 BUG_ON(blk_rq_is_passthrough(rq));
685 rq->rq_flags |= RQF_SORTED;
687 if (rq_mergeable(rq)) {
688 elv_rqhash_add(q, rq);
694 * Some ioscheds (cfq) run q->request_fn directly, so
695 * rq cannot be accessed after calling
696 * elevator_add_req_fn.
698 q->elevator->type->ops.sq.elevator_add_req_fn(q, rq);
701 case ELEVATOR_INSERT_FLUSH:
702 rq->rq_flags |= RQF_SOFTBARRIER;
703 blk_insert_flush(rq);
706 printk(KERN_ERR "%s: bad insertion point %d\n",
711 EXPORT_SYMBOL(__elv_add_request);
713 void elv_add_request(struct request_queue *q, struct request *rq, int where)
717 spin_lock_irqsave(q->queue_lock, flags);
718 __elv_add_request(q, rq, where);
719 spin_unlock_irqrestore(q->queue_lock, flags);
721 EXPORT_SYMBOL(elv_add_request);
723 struct request *elv_latter_request(struct request_queue *q, struct request *rq)
725 struct elevator_queue *e = q->elevator;
727 if (e->uses_mq && e->type->ops.mq.next_request)
728 return e->type->ops.mq.next_request(q, rq);
729 else if (!e->uses_mq && e->type->ops.sq.elevator_latter_req_fn)
730 return e->type->ops.sq.elevator_latter_req_fn(q, rq);
735 struct request *elv_former_request(struct request_queue *q, struct request *rq)
737 struct elevator_queue *e = q->elevator;
739 if (e->uses_mq && e->type->ops.mq.former_request)
740 return e->type->ops.mq.former_request(q, rq);
741 if (!e->uses_mq && e->type->ops.sq.elevator_former_req_fn)
742 return e->type->ops.sq.elevator_former_req_fn(q, rq);
746 int elv_set_request(struct request_queue *q, struct request *rq,
747 struct bio *bio, gfp_t gfp_mask)
749 struct elevator_queue *e = q->elevator;
751 if (WARN_ON_ONCE(e->uses_mq))
754 if (e->type->ops.sq.elevator_set_req_fn)
755 return e->type->ops.sq.elevator_set_req_fn(q, rq, bio, gfp_mask);
759 void elv_put_request(struct request_queue *q, struct request *rq)
761 struct elevator_queue *e = q->elevator;
763 if (WARN_ON_ONCE(e->uses_mq))
766 if (e->type->ops.sq.elevator_put_req_fn)
767 e->type->ops.sq.elevator_put_req_fn(rq);
770 int elv_may_queue(struct request_queue *q, unsigned int op)
772 struct elevator_queue *e = q->elevator;
774 if (WARN_ON_ONCE(e->uses_mq))
777 if (e->type->ops.sq.elevator_may_queue_fn)
778 return e->type->ops.sq.elevator_may_queue_fn(q, op);
780 return ELV_MQUEUE_MAY;
783 void elv_completed_request(struct request_queue *q, struct request *rq)
785 struct elevator_queue *e = q->elevator;
787 if (WARN_ON_ONCE(e->uses_mq))
791 * request is released from the driver, io must be done
793 if (blk_account_rq(rq)) {
794 q->in_flight[rq_is_sync(rq)]--;
795 if ((rq->rq_flags & RQF_SORTED) &&
796 e->type->ops.sq.elevator_completed_req_fn)
797 e->type->ops.sq.elevator_completed_req_fn(q, rq);
801 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
804 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
806 struct elv_fs_entry *entry = to_elv(attr);
807 struct elevator_queue *e;
813 e = container_of(kobj, struct elevator_queue, kobj);
814 mutex_lock(&e->sysfs_lock);
815 error = e->type ? entry->show(e, page) : -ENOENT;
816 mutex_unlock(&e->sysfs_lock);
821 elv_attr_store(struct kobject *kobj, struct attribute *attr,
822 const char *page, size_t length)
824 struct elv_fs_entry *entry = to_elv(attr);
825 struct elevator_queue *e;
831 e = container_of(kobj, struct elevator_queue, kobj);
832 mutex_lock(&e->sysfs_lock);
833 error = e->type ? entry->store(e, page, length) : -ENOENT;
834 mutex_unlock(&e->sysfs_lock);
838 static const struct sysfs_ops elv_sysfs_ops = {
839 .show = elv_attr_show,
840 .store = elv_attr_store,
843 static struct kobj_type elv_ktype = {
844 .sysfs_ops = &elv_sysfs_ops,
845 .release = elevator_release,
848 int elv_register_queue(struct request_queue *q)
850 struct elevator_queue *e = q->elevator;
853 error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
855 struct elv_fs_entry *attr = e->type->elevator_attrs;
857 while (attr->attr.name) {
858 if (sysfs_create_file(&e->kobj, &attr->attr))
863 kobject_uevent(&e->kobj, KOBJ_ADD);
865 if (!e->uses_mq && e->type->ops.sq.elevator_registered_fn)
866 e->type->ops.sq.elevator_registered_fn(q);
870 EXPORT_SYMBOL(elv_register_queue);
872 void elv_unregister_queue(struct request_queue *q)
875 struct elevator_queue *e = q->elevator;
877 kobject_uevent(&e->kobj, KOBJ_REMOVE);
878 kobject_del(&e->kobj);
882 EXPORT_SYMBOL(elv_unregister_queue);
884 int elv_register(struct elevator_type *e)
888 /* create icq_cache if requested */
890 if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
891 WARN_ON(e->icq_align < __alignof__(struct io_cq)))
894 snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
895 "%s_io_cq", e->elevator_name);
896 e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
897 e->icq_align, 0, NULL);
902 /* register, don't allow duplicate names */
903 spin_lock(&elv_list_lock);
904 if (elevator_find(e->elevator_name)) {
905 spin_unlock(&elv_list_lock);
907 kmem_cache_destroy(e->icq_cache);
910 list_add_tail(&e->list, &elv_list);
911 spin_unlock(&elv_list_lock);
913 /* print pretty message */
914 if (!strcmp(e->elevator_name, chosen_elevator) ||
915 (!*chosen_elevator &&
916 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
919 printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
923 EXPORT_SYMBOL_GPL(elv_register);
925 void elv_unregister(struct elevator_type *e)
928 spin_lock(&elv_list_lock);
929 list_del_init(&e->list);
930 spin_unlock(&elv_list_lock);
933 * Destroy icq_cache if it exists. icq's are RCU managed. Make
934 * sure all RCU operations are complete before proceeding.
938 kmem_cache_destroy(e->icq_cache);
942 EXPORT_SYMBOL_GPL(elv_unregister);
944 static int elevator_switch_mq(struct request_queue *q,
945 struct elevator_type *new_e)
949 blk_mq_freeze_queue(q);
950 blk_mq_quiesce_queue(q);
953 if (q->elevator->registered)
954 elv_unregister_queue(q);
956 elevator_exit(q, q->elevator);
959 ret = blk_mq_init_sched(q, new_e);
964 ret = elv_register_queue(q);
966 elevator_exit(q, q->elevator);
972 blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
974 blk_add_trace_msg(q, "elv switch: none");
977 blk_mq_unfreeze_queue(q);
978 blk_mq_start_stopped_hw_queues(q, true);
984 * switch to new_e io scheduler. be careful not to introduce deadlocks -
985 * we don't free the old io scheduler, before we have allocated what we
986 * need for the new one. this way we have a chance of going back to the old
987 * one, if the new one fails init for some reason.
989 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
991 struct elevator_queue *old = q->elevator;
992 bool old_registered = false;
996 return elevator_switch_mq(q, new_e);
999 * Turn on BYPASS and drain all requests w/ elevator private data.
1000 * Block layer doesn't call into a quiesced elevator - all requests
1001 * are directly put on the dispatch list without elevator data
1002 * using INSERT_BACK. All requests have SOFTBARRIER set and no
1003 * merge happens either.
1006 old_registered = old->registered;
1008 blk_queue_bypass_start(q);
1010 /* unregister and clear all auxiliary data of the old elevator */
1012 elv_unregister_queue(q);
1017 /* allocate, init and register new elevator */
1018 err = new_e->ops.sq.elevator_init_fn(q, new_e);
1022 err = elv_register_queue(q);
1026 /* done, kill the old one and finish */
1028 elevator_exit(q, old);
1029 blk_queue_bypass_end(q);
1032 blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
1037 elevator_exit(q, q->elevator);
1039 /* switch failed, restore and re-register old elevator */
1042 elv_register_queue(q);
1043 blk_queue_bypass_end(q);
1050 * Switch this queue to the given IO scheduler.
1052 static int __elevator_change(struct request_queue *q, const char *name)
1054 char elevator_name[ELV_NAME_MAX];
1055 struct elevator_type *e;
1058 * Special case for mq, turn off scheduling
1060 if (q->mq_ops && !strncmp(name, "none", 4))
1061 return elevator_switch(q, NULL);
1063 strlcpy(elevator_name, name, sizeof(elevator_name));
1064 e = elevator_get(strstrip(elevator_name), true);
1066 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
1071 !strcmp(elevator_name, q->elevator->type->elevator_name)) {
1076 if (!e->uses_mq && q->mq_ops) {
1080 if (e->uses_mq && !q->mq_ops) {
1085 return elevator_switch(q, e);
1088 int elevator_change(struct request_queue *q, const char *name)
1092 /* Protect q->elevator from elevator_init() */
1093 mutex_lock(&q->sysfs_lock);
1094 ret = __elevator_change(q, name);
1095 mutex_unlock(&q->sysfs_lock);
1099 EXPORT_SYMBOL(elevator_change);
1101 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
1106 if (!(q->mq_ops || q->request_fn))
1109 ret = __elevator_change(q, name);
1113 printk(KERN_ERR "elevator: switch to %s failed\n", name);
1117 ssize_t elv_iosched_show(struct request_queue *q, char *name)
1119 struct elevator_queue *e = q->elevator;
1120 struct elevator_type *elv = NULL;
1121 struct elevator_type *__e;
1124 if (!blk_queue_stackable(q))
1125 return sprintf(name, "none\n");
1128 len += sprintf(name+len, "[none] ");
1132 spin_lock(&elv_list_lock);
1133 list_for_each_entry(__e, &elv_list, list) {
1134 if (elv && !strcmp(elv->elevator_name, __e->elevator_name)) {
1135 len += sprintf(name+len, "[%s] ", elv->elevator_name);
1138 if (__e->uses_mq && q->mq_ops)
1139 len += sprintf(name+len, "%s ", __e->elevator_name);
1140 else if (!__e->uses_mq && !q->mq_ops)
1141 len += sprintf(name+len, "%s ", __e->elevator_name);
1143 spin_unlock(&elv_list_lock);
1145 if (q->mq_ops && q->elevator)
1146 len += sprintf(name+len, "none");
1148 len += sprintf(len+name, "\n");
1152 struct request *elv_rb_former_request(struct request_queue *q,
1155 struct rb_node *rbprev = rb_prev(&rq->rb_node);
1158 return rb_entry_rq(rbprev);
1162 EXPORT_SYMBOL(elv_rb_former_request);
1164 struct request *elv_rb_latter_request(struct request_queue *q,
1167 struct rb_node *rbnext = rb_next(&rq->rb_node);
1170 return rb_entry_rq(rbnext);
1174 EXPORT_SYMBOL(elv_rb_latter_request);