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>
44 static DEFINE_SPINLOCK(elv_list_lock);
45 static LIST_HEAD(elv_list);
50 #define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq))
53 * Query io scheduler to see if the current process issuing bio may be
56 static int elv_iosched_allow_merge(struct request *rq, struct bio *bio)
58 struct request_queue *q = rq->q;
59 struct elevator_queue *e = q->elevator;
61 if (e->type->ops.elevator_allow_merge_fn)
62 return e->type->ops.elevator_allow_merge_fn(q, rq, bio);
68 * can we safely merge with this request?
70 bool elv_rq_merge_ok(struct request *rq, struct bio *bio)
72 if (!blk_rq_merge_ok(rq, bio))
75 if (!elv_iosched_allow_merge(rq, bio))
80 EXPORT_SYMBOL(elv_rq_merge_ok);
82 static struct elevator_type *elevator_find(const char *name)
84 struct elevator_type *e;
86 list_for_each_entry(e, &elv_list, list) {
87 if (!strcmp(e->elevator_name, name))
94 static void elevator_put(struct elevator_type *e)
96 module_put(e->elevator_owner);
99 static struct elevator_type *elevator_get(const char *name, bool try_loading)
101 struct elevator_type *e;
103 spin_lock(&elv_list_lock);
105 e = elevator_find(name);
106 if (!e && try_loading) {
107 spin_unlock(&elv_list_lock);
108 request_module("%s-iosched", name);
109 spin_lock(&elv_list_lock);
110 e = elevator_find(name);
113 if (e && !try_module_get(e->elevator_owner))
116 spin_unlock(&elv_list_lock);
121 static char chosen_elevator[ELV_NAME_MAX];
123 static int __init elevator_setup(char *str)
126 * Be backwards-compatible with previous kernels, so users
127 * won't get the wrong elevator.
129 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
133 __setup("elevator=", elevator_setup);
135 /* called during boot to load the elevator chosen by the elevator param */
136 void __init load_default_elevator_module(void)
138 struct elevator_type *e;
140 if (!chosen_elevator[0])
143 spin_lock(&elv_list_lock);
144 e = elevator_find(chosen_elevator);
145 spin_unlock(&elv_list_lock);
148 request_module("%s-iosched", chosen_elevator);
151 static struct kobj_type elv_ktype;
153 struct elevator_queue *elevator_alloc(struct request_queue *q,
154 struct elevator_type *e)
156 struct elevator_queue *eq;
158 eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node);
163 kobject_init(&eq->kobj, &elv_ktype);
164 mutex_init(&eq->sysfs_lock);
169 EXPORT_SYMBOL(elevator_alloc);
171 static void elevator_release(struct kobject *kobj)
173 struct elevator_queue *e;
175 e = container_of(kobj, struct elevator_queue, kobj);
176 elevator_put(e->type);
180 int elevator_init(struct request_queue *q, char *name)
182 struct elevator_type *e = NULL;
186 * q->sysfs_lock must be held to provide mutual exclusion between
187 * elevator_switch() and here.
189 lockdep_assert_held(&q->sysfs_lock);
191 if (unlikely(q->elevator))
194 INIT_LIST_HEAD(&q->queue_head);
195 q->last_merge = NULL;
197 q->boundary_rq = NULL;
200 e = elevator_get(name, true);
206 * Use the default elevator specified by config boot param or
207 * config option. Don't try to load modules as we could be running
208 * off async and request_module() isn't allowed from async.
210 if (!e && *chosen_elevator) {
211 e = elevator_get(chosen_elevator, false);
213 printk(KERN_ERR "I/O scheduler %s not found\n",
218 e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);
221 "Default I/O scheduler not found. " \
223 e = elevator_get("noop", false);
227 err = e->ops.elevator_init_fn(q, e);
232 EXPORT_SYMBOL(elevator_init);
234 void elevator_exit(struct elevator_queue *e)
236 mutex_lock(&e->sysfs_lock);
237 if (e->type->ops.elevator_exit_fn)
238 e->type->ops.elevator_exit_fn(e);
239 mutex_unlock(&e->sysfs_lock);
241 kobject_put(&e->kobj);
243 EXPORT_SYMBOL(elevator_exit);
245 static inline void __elv_rqhash_del(struct request *rq)
248 rq->cmd_flags &= ~REQ_HASHED;
251 static void elv_rqhash_del(struct request_queue *q, struct request *rq)
254 __elv_rqhash_del(rq);
257 static void elv_rqhash_add(struct request_queue *q, struct request *rq)
259 struct elevator_queue *e = q->elevator;
261 BUG_ON(ELV_ON_HASH(rq));
262 hash_add(e->hash, &rq->hash, rq_hash_key(rq));
263 rq->cmd_flags |= REQ_HASHED;
266 static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
268 __elv_rqhash_del(rq);
269 elv_rqhash_add(q, rq);
272 static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
274 struct elevator_queue *e = q->elevator;
275 struct hlist_node *next;
278 hash_for_each_possible_safe(e->hash, rq, next, hash, offset) {
279 BUG_ON(!ELV_ON_HASH(rq));
281 if (unlikely(!rq_mergeable(rq))) {
282 __elv_rqhash_del(rq);
286 if (rq_hash_key(rq) == offset)
294 * RB-tree support functions for inserting/lookup/removal of requests
295 * in a sorted RB tree.
297 void elv_rb_add(struct rb_root *root, struct request *rq)
299 struct rb_node **p = &root->rb_node;
300 struct rb_node *parent = NULL;
301 struct request *__rq;
305 __rq = rb_entry(parent, struct request, rb_node);
307 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
309 else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
313 rb_link_node(&rq->rb_node, parent, p);
314 rb_insert_color(&rq->rb_node, root);
316 EXPORT_SYMBOL(elv_rb_add);
318 void elv_rb_del(struct rb_root *root, struct request *rq)
320 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
321 rb_erase(&rq->rb_node, root);
322 RB_CLEAR_NODE(&rq->rb_node);
324 EXPORT_SYMBOL(elv_rb_del);
326 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
328 struct rb_node *n = root->rb_node;
332 rq = rb_entry(n, struct request, rb_node);
334 if (sector < blk_rq_pos(rq))
336 else if (sector > blk_rq_pos(rq))
344 EXPORT_SYMBOL(elv_rb_find);
347 * Insert rq into dispatch queue of q. Queue lock must be held on
348 * entry. rq is sort instead into the dispatch queue. To be used by
349 * specific elevators.
351 void elv_dispatch_sort(struct request_queue *q, struct request *rq)
354 struct list_head *entry;
357 if (q->last_merge == rq)
358 q->last_merge = NULL;
360 elv_rqhash_del(q, rq);
364 boundary = q->end_sector;
365 stop_flags = REQ_SOFTBARRIER | REQ_STARTED;
366 list_for_each_prev(entry, &q->queue_head) {
367 struct request *pos = list_entry_rq(entry);
369 if ((rq->cmd_flags & REQ_DISCARD) !=
370 (pos->cmd_flags & REQ_DISCARD))
372 if (rq_data_dir(rq) != rq_data_dir(pos))
374 if (pos->cmd_flags & stop_flags)
376 if (blk_rq_pos(rq) >= boundary) {
377 if (blk_rq_pos(pos) < boundary)
380 if (blk_rq_pos(pos) >= boundary)
383 if (blk_rq_pos(rq) >= blk_rq_pos(pos))
387 list_add(&rq->queuelist, entry);
389 EXPORT_SYMBOL(elv_dispatch_sort);
392 * Insert rq into dispatch queue of q. Queue lock must be held on
393 * entry. rq is added to the back of the dispatch queue. To be used by
394 * specific elevators.
396 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
398 if (q->last_merge == rq)
399 q->last_merge = NULL;
401 elv_rqhash_del(q, rq);
405 q->end_sector = rq_end_sector(rq);
407 list_add_tail(&rq->queuelist, &q->queue_head);
409 EXPORT_SYMBOL(elv_dispatch_add_tail);
411 int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
413 struct elevator_queue *e = q->elevator;
414 struct request *__rq;
419 * nomerges: No merges at all attempted
420 * noxmerges: Only simple one-hit cache try
421 * merges: All merge tries attempted
423 if (blk_queue_nomerges(q) || !bio_mergeable(bio))
424 return ELEVATOR_NO_MERGE;
427 * First try one-hit cache.
429 if (q->last_merge && elv_rq_merge_ok(q->last_merge, bio)) {
430 ret = blk_try_merge(q->last_merge, bio);
431 if (ret != ELEVATOR_NO_MERGE) {
432 *req = q->last_merge;
437 if (blk_queue_noxmerges(q))
438 return ELEVATOR_NO_MERGE;
441 * See if our hash lookup can find a potential backmerge.
443 __rq = elv_rqhash_find(q, bio->bi_iter.bi_sector);
444 if (__rq && elv_rq_merge_ok(__rq, bio)) {
446 return ELEVATOR_BACK_MERGE;
449 if (e->type->ops.elevator_merge_fn)
450 return e->type->ops.elevator_merge_fn(q, req, bio);
452 return ELEVATOR_NO_MERGE;
456 * Attempt to do an insertion back merge. Only check for the case where
457 * we can append 'rq' to an existing request, so we can throw 'rq' away
460 * Returns true if we merged, false otherwise
462 static bool elv_attempt_insert_merge(struct request_queue *q,
465 struct request *__rq;
468 if (blk_queue_nomerges(q))
472 * First try one-hit cache.
474 if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq))
477 if (blk_queue_noxmerges(q))
482 * See if our hash lookup can find a potential backmerge.
485 __rq = elv_rqhash_find(q, blk_rq_pos(rq));
486 if (!__rq || !blk_attempt_req_merge(q, __rq, rq))
489 /* The merged request could be merged with others, try again */
497 void elv_merged_request(struct request_queue *q, struct request *rq, int type)
499 struct elevator_queue *e = q->elevator;
501 if (e->type->ops.elevator_merged_fn)
502 e->type->ops.elevator_merged_fn(q, rq, type);
504 if (type == ELEVATOR_BACK_MERGE)
505 elv_rqhash_reposition(q, rq);
510 void elv_merge_requests(struct request_queue *q, struct request *rq,
511 struct request *next)
513 struct elevator_queue *e = q->elevator;
514 const int next_sorted = next->cmd_flags & REQ_SORTED;
516 if (next_sorted && e->type->ops.elevator_merge_req_fn)
517 e->type->ops.elevator_merge_req_fn(q, rq, next);
519 elv_rqhash_reposition(q, rq);
522 elv_rqhash_del(q, next);
529 void elv_bio_merged(struct request_queue *q, struct request *rq,
532 struct elevator_queue *e = q->elevator;
534 if (e->type->ops.elevator_bio_merged_fn)
535 e->type->ops.elevator_bio_merged_fn(q, rq, bio);
539 static void blk_pm_requeue_request(struct request *rq)
541 if (rq->q->dev && !(rq->cmd_flags & REQ_PM))
545 static void blk_pm_add_request(struct request_queue *q, struct request *rq)
547 if (q->dev && !(rq->cmd_flags & REQ_PM) && q->nr_pending++ == 0 &&
548 (q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING))
549 pm_request_resume(q->dev);
552 static inline void blk_pm_requeue_request(struct request *rq) {}
553 static inline void blk_pm_add_request(struct request_queue *q,
559 void elv_requeue_request(struct request_queue *q, struct request *rq)
562 * it already went through dequeue, we need to decrement the
563 * in_flight count again
565 if (blk_account_rq(rq)) {
566 q->in_flight[rq_is_sync(rq)]--;
567 if (rq->cmd_flags & REQ_SORTED)
568 elv_deactivate_rq(q, rq);
571 rq->cmd_flags &= ~REQ_STARTED;
573 blk_pm_requeue_request(rq);
575 __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
578 void elv_drain_elevator(struct request_queue *q)
582 lockdep_assert_held(q->queue_lock);
584 while (q->elevator->type->ops.elevator_dispatch_fn(q, 1))
586 if (q->nr_sorted && printed++ < 10) {
587 printk(KERN_ERR "%s: forced dispatching is broken "
588 "(nr_sorted=%u), please report this\n",
589 q->elevator->type->elevator_name, q->nr_sorted);
593 void __elv_add_request(struct request_queue *q, struct request *rq, int where)
595 trace_block_rq_insert(q, rq);
597 blk_pm_add_request(q, rq);
601 if (rq->cmd_flags & REQ_SOFTBARRIER) {
602 /* barriers are scheduling boundary, update end_sector */
603 if (rq->cmd_type == REQ_TYPE_FS) {
604 q->end_sector = rq_end_sector(rq);
607 } else if (!(rq->cmd_flags & REQ_ELVPRIV) &&
608 (where == ELEVATOR_INSERT_SORT ||
609 where == ELEVATOR_INSERT_SORT_MERGE))
610 where = ELEVATOR_INSERT_BACK;
613 case ELEVATOR_INSERT_REQUEUE:
614 case ELEVATOR_INSERT_FRONT:
615 rq->cmd_flags |= REQ_SOFTBARRIER;
616 list_add(&rq->queuelist, &q->queue_head);
619 case ELEVATOR_INSERT_BACK:
620 rq->cmd_flags |= REQ_SOFTBARRIER;
621 elv_drain_elevator(q);
622 list_add_tail(&rq->queuelist, &q->queue_head);
624 * We kick the queue here for the following reasons.
625 * - The elevator might have returned NULL previously
626 * to delay requests and returned them now. As the
627 * queue wasn't empty before this request, ll_rw_blk
628 * won't run the queue on return, resulting in hang.
629 * - Usually, back inserted requests won't be merged
630 * with anything. There's no point in delaying queue
636 case ELEVATOR_INSERT_SORT_MERGE:
638 * If we succeed in merging this request with one in the
639 * queue already, we are done - rq has now been freed,
640 * so no need to do anything further.
642 if (elv_attempt_insert_merge(q, rq))
644 case ELEVATOR_INSERT_SORT:
645 BUG_ON(rq->cmd_type != REQ_TYPE_FS);
646 rq->cmd_flags |= REQ_SORTED;
648 if (rq_mergeable(rq)) {
649 elv_rqhash_add(q, rq);
655 * Some ioscheds (cfq) run q->request_fn directly, so
656 * rq cannot be accessed after calling
657 * elevator_add_req_fn.
659 q->elevator->type->ops.elevator_add_req_fn(q, rq);
662 case ELEVATOR_INSERT_FLUSH:
663 rq->cmd_flags |= REQ_SOFTBARRIER;
664 blk_insert_flush(rq);
667 printk(KERN_ERR "%s: bad insertion point %d\n",
672 EXPORT_SYMBOL(__elv_add_request);
674 void elv_add_request(struct request_queue *q, struct request *rq, int where)
678 spin_lock_irqsave(q->queue_lock, flags);
679 __elv_add_request(q, rq, where);
680 spin_unlock_irqrestore(q->queue_lock, flags);
682 EXPORT_SYMBOL(elv_add_request);
684 struct request *elv_latter_request(struct request_queue *q, struct request *rq)
686 struct elevator_queue *e = q->elevator;
688 if (e->type->ops.elevator_latter_req_fn)
689 return e->type->ops.elevator_latter_req_fn(q, rq);
693 struct request *elv_former_request(struct request_queue *q, struct request *rq)
695 struct elevator_queue *e = q->elevator;
697 if (e->type->ops.elevator_former_req_fn)
698 return e->type->ops.elevator_former_req_fn(q, rq);
702 int elv_set_request(struct request_queue *q, struct request *rq,
703 struct bio *bio, gfp_t gfp_mask)
705 struct elevator_queue *e = q->elevator;
707 if (e->type->ops.elevator_set_req_fn)
708 return e->type->ops.elevator_set_req_fn(q, rq, bio, gfp_mask);
712 void elv_put_request(struct request_queue *q, struct request *rq)
714 struct elevator_queue *e = q->elevator;
716 if (e->type->ops.elevator_put_req_fn)
717 e->type->ops.elevator_put_req_fn(rq);
720 int elv_may_queue(struct request_queue *q, int rw)
722 struct elevator_queue *e = q->elevator;
724 if (e->type->ops.elevator_may_queue_fn)
725 return e->type->ops.elevator_may_queue_fn(q, rw);
727 return ELV_MQUEUE_MAY;
730 void elv_completed_request(struct request_queue *q, struct request *rq)
732 struct elevator_queue *e = q->elevator;
735 * request is released from the driver, io must be done
737 if (blk_account_rq(rq)) {
738 q->in_flight[rq_is_sync(rq)]--;
739 if ((rq->cmd_flags & REQ_SORTED) &&
740 e->type->ops.elevator_completed_req_fn)
741 e->type->ops.elevator_completed_req_fn(q, rq);
745 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
748 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
750 struct elv_fs_entry *entry = to_elv(attr);
751 struct elevator_queue *e;
757 e = container_of(kobj, struct elevator_queue, kobj);
758 mutex_lock(&e->sysfs_lock);
759 error = e->type ? entry->show(e, page) : -ENOENT;
760 mutex_unlock(&e->sysfs_lock);
765 elv_attr_store(struct kobject *kobj, struct attribute *attr,
766 const char *page, size_t length)
768 struct elv_fs_entry *entry = to_elv(attr);
769 struct elevator_queue *e;
775 e = container_of(kobj, struct elevator_queue, kobj);
776 mutex_lock(&e->sysfs_lock);
777 error = e->type ? entry->store(e, page, length) : -ENOENT;
778 mutex_unlock(&e->sysfs_lock);
782 static const struct sysfs_ops elv_sysfs_ops = {
783 .show = elv_attr_show,
784 .store = elv_attr_store,
787 static struct kobj_type elv_ktype = {
788 .sysfs_ops = &elv_sysfs_ops,
789 .release = elevator_release,
792 int elv_register_queue(struct request_queue *q)
794 struct elevator_queue *e = q->elevator;
797 error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
799 struct elv_fs_entry *attr = e->type->elevator_attrs;
801 while (attr->attr.name) {
802 if (sysfs_create_file(&e->kobj, &attr->attr))
807 kobject_uevent(&e->kobj, KOBJ_ADD);
809 if (e->type->ops.elevator_registered_fn)
810 e->type->ops.elevator_registered_fn(q);
814 EXPORT_SYMBOL(elv_register_queue);
816 void elv_unregister_queue(struct request_queue *q)
819 struct elevator_queue *e = q->elevator;
821 kobject_uevent(&e->kobj, KOBJ_REMOVE);
822 kobject_del(&e->kobj);
826 EXPORT_SYMBOL(elv_unregister_queue);
828 int elv_register(struct elevator_type *e)
832 /* create icq_cache if requested */
834 if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
835 WARN_ON(e->icq_align < __alignof__(struct io_cq)))
838 snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
839 "%s_io_cq", e->elevator_name);
840 e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
841 e->icq_align, 0, NULL);
846 /* register, don't allow duplicate names */
847 spin_lock(&elv_list_lock);
848 if (elevator_find(e->elevator_name)) {
849 spin_unlock(&elv_list_lock);
851 kmem_cache_destroy(e->icq_cache);
854 list_add_tail(&e->list, &elv_list);
855 spin_unlock(&elv_list_lock);
857 /* print pretty message */
858 if (!strcmp(e->elevator_name, chosen_elevator) ||
859 (!*chosen_elevator &&
860 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
863 printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
867 EXPORT_SYMBOL_GPL(elv_register);
869 void elv_unregister(struct elevator_type *e)
872 spin_lock(&elv_list_lock);
873 list_del_init(&e->list);
874 spin_unlock(&elv_list_lock);
877 * Destroy icq_cache if it exists. icq's are RCU managed. Make
878 * sure all RCU operations are complete before proceeding.
882 kmem_cache_destroy(e->icq_cache);
886 EXPORT_SYMBOL_GPL(elv_unregister);
889 * switch to new_e io scheduler. be careful not to introduce deadlocks -
890 * we don't free the old io scheduler, before we have allocated what we
891 * need for the new one. this way we have a chance of going back to the old
892 * one, if the new one fails init for some reason.
894 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
896 struct elevator_queue *old = q->elevator;
897 bool registered = old->registered;
901 * Turn on BYPASS and drain all requests w/ elevator private data.
902 * Block layer doesn't call into a quiesced elevator - all requests
903 * are directly put on the dispatch list without elevator data
904 * using INSERT_BACK. All requests have SOFTBARRIER set and no
905 * merge happens either.
907 blk_queue_bypass_start(q);
909 /* unregister and clear all auxiliary data of the old elevator */
911 elv_unregister_queue(q);
913 spin_lock_irq(q->queue_lock);
915 spin_unlock_irq(q->queue_lock);
917 /* allocate, init and register new elevator */
918 err = new_e->ops.elevator_init_fn(q, new_e);
923 err = elv_register_queue(q);
928 /* done, kill the old one and finish */
930 blk_queue_bypass_end(q);
932 blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
937 elevator_exit(q->elevator);
939 /* switch failed, restore and re-register old elevator */
941 elv_register_queue(q);
942 blk_queue_bypass_end(q);
948 * Switch this queue to the given IO scheduler.
950 static int __elevator_change(struct request_queue *q, const char *name)
952 char elevator_name[ELV_NAME_MAX];
953 struct elevator_type *e;
958 strlcpy(elevator_name, name, sizeof(elevator_name));
959 e = elevator_get(strstrip(elevator_name), true);
961 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
965 if (!strcmp(elevator_name, q->elevator->type->elevator_name)) {
970 return elevator_switch(q, e);
973 int elevator_change(struct request_queue *q, const char *name)
977 /* Protect q->elevator from elevator_init() */
978 mutex_lock(&q->sysfs_lock);
979 ret = __elevator_change(q, name);
980 mutex_unlock(&q->sysfs_lock);
984 EXPORT_SYMBOL(elevator_change);
986 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
994 ret = __elevator_change(q, name);
998 printk(KERN_ERR "elevator: switch to %s failed\n", name);
1002 ssize_t elv_iosched_show(struct request_queue *q, char *name)
1004 struct elevator_queue *e = q->elevator;
1005 struct elevator_type *elv;
1006 struct elevator_type *__e;
1009 if (!q->elevator || !blk_queue_stackable(q))
1010 return sprintf(name, "none\n");
1014 spin_lock(&elv_list_lock);
1015 list_for_each_entry(__e, &elv_list, list) {
1016 if (!strcmp(elv->elevator_name, __e->elevator_name))
1017 len += sprintf(name+len, "[%s] ", elv->elevator_name);
1019 len += sprintf(name+len, "%s ", __e->elevator_name);
1021 spin_unlock(&elv_list_lock);
1023 len += sprintf(len+name, "\n");
1027 struct request *elv_rb_former_request(struct request_queue *q,
1030 struct rb_node *rbprev = rb_prev(&rq->rb_node);
1033 return rb_entry_rq(rbprev);
1037 EXPORT_SYMBOL(elv_rb_former_request);
1039 struct request *elv_rb_latter_request(struct request_queue *q,
1042 struct rb_node *rbnext = rb_next(&rq->rb_node);
1045 return rb_entry_rq(rbnext);
1049 EXPORT_SYMBOL(elv_rb_latter_request);