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>
39 #include <trace/events/block.h>
42 #include "blk-cgroup.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);
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 or
211 * config option. Don't try to load modules as we could be running
212 * off async and request_module() isn't allowed from async.
214 if (!e && *chosen_elevator) {
215 e = elevator_get(chosen_elevator, false);
217 printk(KERN_ERR "I/O scheduler %s not found\n",
222 e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);
225 "Default I/O scheduler not found. " \
227 e = elevator_get("noop", false);
231 err = e->ops.elevator_init_fn(q, e);
236 EXPORT_SYMBOL(elevator_init);
238 void elevator_exit(struct elevator_queue *e)
240 mutex_lock(&e->sysfs_lock);
241 if (e->type->ops.elevator_exit_fn)
242 e->type->ops.elevator_exit_fn(e);
243 mutex_unlock(&e->sysfs_lock);
245 kobject_put(&e->kobj);
247 EXPORT_SYMBOL(elevator_exit);
249 static inline void __elv_rqhash_del(struct request *rq)
252 rq->cmd_flags &= ~REQ_HASHED;
255 static void elv_rqhash_del(struct request_queue *q, struct request *rq)
258 __elv_rqhash_del(rq);
261 static void elv_rqhash_add(struct request_queue *q, struct request *rq)
263 struct elevator_queue *e = q->elevator;
265 BUG_ON(ELV_ON_HASH(rq));
266 hash_add(e->hash, &rq->hash, rq_hash_key(rq));
267 rq->cmd_flags |= REQ_HASHED;
270 static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
272 __elv_rqhash_del(rq);
273 elv_rqhash_add(q, rq);
276 static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
278 struct elevator_queue *e = q->elevator;
279 struct hlist_node *next;
282 hash_for_each_possible_safe(e->hash, rq, next, hash, offset) {
283 BUG_ON(!ELV_ON_HASH(rq));
285 if (unlikely(!rq_mergeable(rq))) {
286 __elv_rqhash_del(rq);
290 if (rq_hash_key(rq) == offset)
298 * RB-tree support functions for inserting/lookup/removal of requests
299 * in a sorted RB tree.
301 void elv_rb_add(struct rb_root *root, struct request *rq)
303 struct rb_node **p = &root->rb_node;
304 struct rb_node *parent = NULL;
305 struct request *__rq;
309 __rq = rb_entry(parent, struct request, rb_node);
311 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
313 else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
317 rb_link_node(&rq->rb_node, parent, p);
318 rb_insert_color(&rq->rb_node, root);
320 EXPORT_SYMBOL(elv_rb_add);
322 void elv_rb_del(struct rb_root *root, struct request *rq)
324 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
325 rb_erase(&rq->rb_node, root);
326 RB_CLEAR_NODE(&rq->rb_node);
328 EXPORT_SYMBOL(elv_rb_del);
330 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
332 struct rb_node *n = root->rb_node;
336 rq = rb_entry(n, struct request, rb_node);
338 if (sector < blk_rq_pos(rq))
340 else if (sector > blk_rq_pos(rq))
348 EXPORT_SYMBOL(elv_rb_find);
351 * Insert rq into dispatch queue of q. Queue lock must be held on
352 * entry. rq is sort instead into the dispatch queue. To be used by
353 * specific elevators.
355 void elv_dispatch_sort(struct request_queue *q, struct request *rq)
358 struct list_head *entry;
361 if (q->last_merge == rq)
362 q->last_merge = NULL;
364 elv_rqhash_del(q, rq);
368 boundary = q->end_sector;
369 stop_flags = REQ_SOFTBARRIER | REQ_STARTED;
370 list_for_each_prev(entry, &q->queue_head) {
371 struct request *pos = list_entry_rq(entry);
373 if ((rq->cmd_flags & REQ_DISCARD) !=
374 (pos->cmd_flags & REQ_DISCARD))
376 if (rq_data_dir(rq) != rq_data_dir(pos))
378 if (pos->cmd_flags & stop_flags)
380 if (blk_rq_pos(rq) >= boundary) {
381 if (blk_rq_pos(pos) < boundary)
384 if (blk_rq_pos(pos) >= boundary)
387 if (blk_rq_pos(rq) >= blk_rq_pos(pos))
391 list_add(&rq->queuelist, entry);
393 EXPORT_SYMBOL(elv_dispatch_sort);
396 * Insert rq into dispatch queue of q. Queue lock must be held on
397 * entry. rq is added to the back of the dispatch queue. To be used by
398 * specific elevators.
400 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
402 if (q->last_merge == rq)
403 q->last_merge = NULL;
405 elv_rqhash_del(q, rq);
409 q->end_sector = rq_end_sector(rq);
411 list_add_tail(&rq->queuelist, &q->queue_head);
413 EXPORT_SYMBOL(elv_dispatch_add_tail);
415 int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
417 struct elevator_queue *e = q->elevator;
418 struct request *__rq;
423 * nomerges: No merges at all attempted
424 * noxmerges: Only simple one-hit cache try
425 * merges: All merge tries attempted
427 if (blk_queue_nomerges(q))
428 return ELEVATOR_NO_MERGE;
431 * First try one-hit cache.
433 if (q->last_merge && elv_rq_merge_ok(q->last_merge, bio)) {
434 ret = blk_try_merge(q->last_merge, bio);
435 if (ret != ELEVATOR_NO_MERGE) {
436 *req = q->last_merge;
441 if (blk_queue_noxmerges(q))
442 return ELEVATOR_NO_MERGE;
445 * See if our hash lookup can find a potential backmerge.
447 __rq = elv_rqhash_find(q, bio->bi_iter.bi_sector);
448 if (__rq && elv_rq_merge_ok(__rq, bio)) {
450 return ELEVATOR_BACK_MERGE;
453 if (e->type->ops.elevator_merge_fn)
454 return e->type->ops.elevator_merge_fn(q, req, bio);
456 return ELEVATOR_NO_MERGE;
460 * Attempt to do an insertion back merge. Only check for the case where
461 * we can append 'rq' to an existing request, so we can throw 'rq' away
464 * Returns true if we merged, false otherwise
466 static bool elv_attempt_insert_merge(struct request_queue *q,
469 struct request *__rq;
472 if (blk_queue_nomerges(q))
476 * First try one-hit cache.
478 if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq))
481 if (blk_queue_noxmerges(q))
486 * See if our hash lookup can find a potential backmerge.
489 __rq = elv_rqhash_find(q, blk_rq_pos(rq));
490 if (!__rq || !blk_attempt_req_merge(q, __rq, rq))
493 /* The merged request could be merged with others, try again */
501 void elv_merged_request(struct request_queue *q, struct request *rq, int type)
503 struct elevator_queue *e = q->elevator;
505 if (e->type->ops.elevator_merged_fn)
506 e->type->ops.elevator_merged_fn(q, rq, type);
508 if (type == ELEVATOR_BACK_MERGE)
509 elv_rqhash_reposition(q, rq);
514 void elv_merge_requests(struct request_queue *q, struct request *rq,
515 struct request *next)
517 struct elevator_queue *e = q->elevator;
518 const int next_sorted = next->cmd_flags & REQ_SORTED;
520 if (next_sorted && e->type->ops.elevator_merge_req_fn)
521 e->type->ops.elevator_merge_req_fn(q, rq, next);
523 elv_rqhash_reposition(q, rq);
526 elv_rqhash_del(q, next);
533 void elv_bio_merged(struct request_queue *q, struct request *rq,
536 struct elevator_queue *e = q->elevator;
538 if (e->type->ops.elevator_bio_merged_fn)
539 e->type->ops.elevator_bio_merged_fn(q, rq, bio);
543 static void blk_pm_requeue_request(struct request *rq)
545 if (rq->q->dev && !(rq->cmd_flags & REQ_PM))
549 static void blk_pm_add_request(struct request_queue *q, struct request *rq)
551 if (q->dev && !(rq->cmd_flags & REQ_PM) && q->nr_pending++ == 0 &&
552 (q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING))
553 pm_request_resume(q->dev);
556 static inline void blk_pm_requeue_request(struct request *rq) {}
557 static inline void blk_pm_add_request(struct request_queue *q,
563 void elv_requeue_request(struct request_queue *q, struct request *rq)
566 * it already went through dequeue, we need to decrement the
567 * in_flight count again
569 if (blk_account_rq(rq)) {
570 q->in_flight[rq_is_sync(rq)]--;
571 if (rq->cmd_flags & REQ_SORTED)
572 elv_deactivate_rq(q, rq);
575 rq->cmd_flags &= ~REQ_STARTED;
577 blk_pm_requeue_request(rq);
579 __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
582 void elv_drain_elevator(struct request_queue *q)
586 lockdep_assert_held(q->queue_lock);
588 while (q->elevator->type->ops.elevator_dispatch_fn(q, 1))
590 if (q->nr_sorted && printed++ < 10) {
591 printk(KERN_ERR "%s: forced dispatching is broken "
592 "(nr_sorted=%u), please report this\n",
593 q->elevator->type->elevator_name, q->nr_sorted);
597 void __elv_add_request(struct request_queue *q, struct request *rq, int where)
599 trace_block_rq_insert(q, rq);
601 blk_pm_add_request(q, rq);
605 if (rq->cmd_flags & REQ_SOFTBARRIER) {
606 /* barriers are scheduling boundary, update end_sector */
607 if (rq->cmd_type == REQ_TYPE_FS) {
608 q->end_sector = rq_end_sector(rq);
611 } else if (!(rq->cmd_flags & REQ_ELVPRIV) &&
612 (where == ELEVATOR_INSERT_SORT ||
613 where == ELEVATOR_INSERT_SORT_MERGE))
614 where = ELEVATOR_INSERT_BACK;
617 case ELEVATOR_INSERT_REQUEUE:
618 case ELEVATOR_INSERT_FRONT:
619 rq->cmd_flags |= REQ_SOFTBARRIER;
620 list_add(&rq->queuelist, &q->queue_head);
623 case ELEVATOR_INSERT_BACK:
624 rq->cmd_flags |= REQ_SOFTBARRIER;
625 elv_drain_elevator(q);
626 list_add_tail(&rq->queuelist, &q->queue_head);
628 * We kick the queue here for the following reasons.
629 * - The elevator might have returned NULL previously
630 * to delay requests and returned them now. As the
631 * queue wasn't empty before this request, ll_rw_blk
632 * won't run the queue on return, resulting in hang.
633 * - Usually, back inserted requests won't be merged
634 * with anything. There's no point in delaying queue
640 case ELEVATOR_INSERT_SORT_MERGE:
642 * If we succeed in merging this request with one in the
643 * queue already, we are done - rq has now been freed,
644 * so no need to do anything further.
646 if (elv_attempt_insert_merge(q, rq))
648 case ELEVATOR_INSERT_SORT:
649 BUG_ON(rq->cmd_type != REQ_TYPE_FS);
650 rq->cmd_flags |= REQ_SORTED;
652 if (rq_mergeable(rq)) {
653 elv_rqhash_add(q, rq);
659 * Some ioscheds (cfq) run q->request_fn directly, so
660 * rq cannot be accessed after calling
661 * elevator_add_req_fn.
663 q->elevator->type->ops.elevator_add_req_fn(q, rq);
666 case ELEVATOR_INSERT_FLUSH:
667 rq->cmd_flags |= REQ_SOFTBARRIER;
668 blk_insert_flush(rq);
671 printk(KERN_ERR "%s: bad insertion point %d\n",
676 EXPORT_SYMBOL(__elv_add_request);
678 void elv_add_request(struct request_queue *q, struct request *rq, int where)
682 spin_lock_irqsave(q->queue_lock, flags);
683 __elv_add_request(q, rq, where);
684 spin_unlock_irqrestore(q->queue_lock, flags);
686 EXPORT_SYMBOL(elv_add_request);
688 struct request *elv_latter_request(struct request_queue *q, struct request *rq)
690 struct elevator_queue *e = q->elevator;
692 if (e->type->ops.elevator_latter_req_fn)
693 return e->type->ops.elevator_latter_req_fn(q, rq);
697 struct request *elv_former_request(struct request_queue *q, struct request *rq)
699 struct elevator_queue *e = q->elevator;
701 if (e->type->ops.elevator_former_req_fn)
702 return e->type->ops.elevator_former_req_fn(q, rq);
706 int elv_set_request(struct request_queue *q, struct request *rq,
707 struct bio *bio, gfp_t gfp_mask)
709 struct elevator_queue *e = q->elevator;
711 if (e->type->ops.elevator_set_req_fn)
712 return e->type->ops.elevator_set_req_fn(q, rq, bio, gfp_mask);
716 void elv_put_request(struct request_queue *q, struct request *rq)
718 struct elevator_queue *e = q->elevator;
720 if (e->type->ops.elevator_put_req_fn)
721 e->type->ops.elevator_put_req_fn(rq);
724 int elv_may_queue(struct request_queue *q, int rw)
726 struct elevator_queue *e = q->elevator;
728 if (e->type->ops.elevator_may_queue_fn)
729 return e->type->ops.elevator_may_queue_fn(q, rw);
731 return ELV_MQUEUE_MAY;
734 void elv_completed_request(struct request_queue *q, struct request *rq)
736 struct elevator_queue *e = q->elevator;
739 * request is released from the driver, io must be done
741 if (blk_account_rq(rq)) {
742 q->in_flight[rq_is_sync(rq)]--;
743 if ((rq->cmd_flags & REQ_SORTED) &&
744 e->type->ops.elevator_completed_req_fn)
745 e->type->ops.elevator_completed_req_fn(q, rq);
749 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
752 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
754 struct elv_fs_entry *entry = to_elv(attr);
755 struct elevator_queue *e;
761 e = container_of(kobj, struct elevator_queue, kobj);
762 mutex_lock(&e->sysfs_lock);
763 error = e->type ? entry->show(e, page) : -ENOENT;
764 mutex_unlock(&e->sysfs_lock);
769 elv_attr_store(struct kobject *kobj, struct attribute *attr,
770 const char *page, size_t length)
772 struct elv_fs_entry *entry = to_elv(attr);
773 struct elevator_queue *e;
779 e = container_of(kobj, struct elevator_queue, kobj);
780 mutex_lock(&e->sysfs_lock);
781 error = e->type ? entry->store(e, page, length) : -ENOENT;
782 mutex_unlock(&e->sysfs_lock);
786 static const struct sysfs_ops elv_sysfs_ops = {
787 .show = elv_attr_show,
788 .store = elv_attr_store,
791 static struct kobj_type elv_ktype = {
792 .sysfs_ops = &elv_sysfs_ops,
793 .release = elevator_release,
796 int elv_register_queue(struct request_queue *q)
798 struct elevator_queue *e = q->elevator;
801 error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
803 struct elv_fs_entry *attr = e->type->elevator_attrs;
805 while (attr->attr.name) {
806 if (sysfs_create_file(&e->kobj, &attr->attr))
811 kobject_uevent(&e->kobj, KOBJ_ADD);
816 EXPORT_SYMBOL(elv_register_queue);
818 void elv_unregister_queue(struct request_queue *q)
821 struct elevator_queue *e = q->elevator;
823 kobject_uevent(&e->kobj, KOBJ_REMOVE);
824 kobject_del(&e->kobj);
828 EXPORT_SYMBOL(elv_unregister_queue);
830 int elv_register(struct elevator_type *e)
834 /* create icq_cache if requested */
836 if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
837 WARN_ON(e->icq_align < __alignof__(struct io_cq)))
840 snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
841 "%s_io_cq", e->elevator_name);
842 e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
843 e->icq_align, 0, NULL);
848 /* register, don't allow duplicate names */
849 spin_lock(&elv_list_lock);
850 if (elevator_find(e->elevator_name)) {
851 spin_unlock(&elv_list_lock);
853 kmem_cache_destroy(e->icq_cache);
856 list_add_tail(&e->list, &elv_list);
857 spin_unlock(&elv_list_lock);
859 /* print pretty message */
860 if (!strcmp(e->elevator_name, chosen_elevator) ||
861 (!*chosen_elevator &&
862 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
865 printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
869 EXPORT_SYMBOL_GPL(elv_register);
871 void elv_unregister(struct elevator_type *e)
874 spin_lock(&elv_list_lock);
875 list_del_init(&e->list);
876 spin_unlock(&elv_list_lock);
879 * Destroy icq_cache if it exists. icq's are RCU managed. Make
880 * sure all RCU operations are complete before proceeding.
884 kmem_cache_destroy(e->icq_cache);
888 EXPORT_SYMBOL_GPL(elv_unregister);
891 * switch to new_e io scheduler. be careful not to introduce deadlocks -
892 * we don't free the old io scheduler, before we have allocated what we
893 * need for the new one. this way we have a chance of going back to the old
894 * one, if the new one fails init for some reason.
896 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
898 struct elevator_queue *old = q->elevator;
899 bool registered = old->registered;
903 * Turn on BYPASS and drain all requests w/ elevator private data.
904 * Block layer doesn't call into a quiesced elevator - all requests
905 * are directly put on the dispatch list without elevator data
906 * using INSERT_BACK. All requests have SOFTBARRIER set and no
907 * merge happens either.
909 blk_queue_bypass_start(q);
911 /* unregister and clear all auxiliary data of the old elevator */
913 elv_unregister_queue(q);
915 spin_lock_irq(q->queue_lock);
917 spin_unlock_irq(q->queue_lock);
919 /* allocate, init and register new elevator */
920 err = new_e->ops.elevator_init_fn(q, new_e);
925 err = elv_register_queue(q);
930 /* done, kill the old one and finish */
932 blk_queue_bypass_end(q);
934 blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
939 elevator_exit(q->elevator);
941 /* switch failed, restore and re-register old elevator */
943 elv_register_queue(q);
944 blk_queue_bypass_end(q);
950 * Switch this queue to the given IO scheduler.
952 static int __elevator_change(struct request_queue *q, const char *name)
954 char elevator_name[ELV_NAME_MAX];
955 struct elevator_type *e;
960 strlcpy(elevator_name, name, sizeof(elevator_name));
961 e = elevator_get(strstrip(elevator_name), true);
963 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
967 if (!strcmp(elevator_name, q->elevator->type->elevator_name)) {
972 return elevator_switch(q, e);
975 int elevator_change(struct request_queue *q, const char *name)
979 /* Protect q->elevator from elevator_init() */
980 mutex_lock(&q->sysfs_lock);
981 ret = __elevator_change(q, name);
982 mutex_unlock(&q->sysfs_lock);
986 EXPORT_SYMBOL(elevator_change);
988 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
996 ret = __elevator_change(q, name);
1000 printk(KERN_ERR "elevator: switch to %s failed\n", name);
1004 ssize_t elv_iosched_show(struct request_queue *q, char *name)
1006 struct elevator_queue *e = q->elevator;
1007 struct elevator_type *elv;
1008 struct elevator_type *__e;
1011 if (!q->elevator || !blk_queue_stackable(q))
1012 return sprintf(name, "none\n");
1016 spin_lock(&elv_list_lock);
1017 list_for_each_entry(__e, &elv_list, list) {
1018 if (!strcmp(elv->elevator_name, __e->elevator_name))
1019 len += sprintf(name+len, "[%s] ", elv->elevator_name);
1021 len += sprintf(name+len, "%s ", __e->elevator_name);
1023 spin_unlock(&elv_list_lock);
1025 len += sprintf(len+name, "\n");
1029 struct request *elv_rb_former_request(struct request_queue *q,
1032 struct rb_node *rbprev = rb_prev(&rq->rb_node);
1035 return rb_entry_rq(rbprev);
1039 EXPORT_SYMBOL(elv_rb_former_request);
1041 struct request *elv_rb_latter_request(struct request_queue *q,
1044 struct rb_node *rbnext = rb_next(&rq->rb_node);
1047 return rb_entry_rq(rbnext);
1051 EXPORT_SYMBOL(elv_rb_latter_request);