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>
38 #include <trace/events/block.h>
42 static DEFINE_SPINLOCK(elv_list_lock);
43 static LIST_HEAD(elv_list);
48 static const int elv_hash_shift = 6;
49 #define ELV_HASH_BLOCK(sec) ((sec) >> 3)
50 #define ELV_HASH_FN(sec) \
51 (hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift))
52 #define ELV_HASH_ENTRIES (1 << elv_hash_shift)
53 #define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq))
56 * Query io scheduler to see if the current process issuing bio may be
59 static int elv_iosched_allow_merge(struct request *rq, struct bio *bio)
61 struct request_queue *q = rq->q;
62 struct elevator_queue *e = q->elevator;
64 if (e->type->ops.elevator_allow_merge_fn)
65 return e->type->ops.elevator_allow_merge_fn(q, rq, bio);
71 * can we safely merge with this request?
73 bool elv_rq_merge_ok(struct request *rq, struct bio *bio)
75 if (!blk_rq_merge_ok(rq, bio))
78 if (!elv_iosched_allow_merge(rq, bio))
83 EXPORT_SYMBOL(elv_rq_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)
104 struct elevator_type *e;
106 spin_lock(&elv_list_lock);
108 e = elevator_find(name);
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 static struct kobj_type elv_ktype;
140 static struct elevator_queue *elevator_alloc(struct request_queue *q,
141 struct elevator_type *e)
143 struct elevator_queue *eq;
146 eq = kmalloc_node(sizeof(*eq), GFP_KERNEL | __GFP_ZERO, q->node);
151 kobject_init(&eq->kobj, &elv_ktype);
152 mutex_init(&eq->sysfs_lock);
154 eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES,
155 GFP_KERNEL, q->node);
159 for (i = 0; i < ELV_HASH_ENTRIES; i++)
160 INIT_HLIST_HEAD(&eq->hash[i]);
169 static void elevator_release(struct kobject *kobj)
171 struct elevator_queue *e;
173 e = container_of(kobj, struct elevator_queue, kobj);
174 elevator_put(e->type);
179 int elevator_init(struct request_queue *q, char *name)
181 struct elevator_type *e = NULL;
184 if (unlikely(q->elevator))
187 INIT_LIST_HEAD(&q->queue_head);
188 q->last_merge = NULL;
190 q->boundary_rq = NULL;
193 e = elevator_get(name);
198 if (!e && *chosen_elevator) {
199 e = elevator_get(chosen_elevator);
201 printk(KERN_ERR "I/O scheduler %s not found\n",
206 e = elevator_get(CONFIG_DEFAULT_IOSCHED);
209 "Default I/O scheduler not found. " \
211 e = elevator_get("noop");
215 q->elevator = elevator_alloc(q, e);
219 err = e->ops.elevator_init_fn(q);
221 kobject_put(&q->elevator->kobj);
227 EXPORT_SYMBOL(elevator_init);
229 void elevator_exit(struct elevator_queue *e)
231 mutex_lock(&e->sysfs_lock);
232 if (e->type->ops.elevator_exit_fn)
233 e->type->ops.elevator_exit_fn(e);
234 mutex_unlock(&e->sysfs_lock);
236 kobject_put(&e->kobj);
238 EXPORT_SYMBOL(elevator_exit);
240 static inline void __elv_rqhash_del(struct request *rq)
242 hlist_del_init(&rq->hash);
245 static void elv_rqhash_del(struct request_queue *q, struct request *rq)
248 __elv_rqhash_del(rq);
251 static void elv_rqhash_add(struct request_queue *q, struct request *rq)
253 struct elevator_queue *e = q->elevator;
255 BUG_ON(ELV_ON_HASH(rq));
256 hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
259 static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
261 __elv_rqhash_del(rq);
262 elv_rqhash_add(q, rq);
265 static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
267 struct elevator_queue *e = q->elevator;
268 struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
269 struct hlist_node *entry, *next;
272 hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
273 BUG_ON(!ELV_ON_HASH(rq));
275 if (unlikely(!rq_mergeable(rq))) {
276 __elv_rqhash_del(rq);
280 if (rq_hash_key(rq) == offset)
288 * RB-tree support functions for inserting/lookup/removal of requests
289 * in a sorted RB tree.
291 void elv_rb_add(struct rb_root *root, struct request *rq)
293 struct rb_node **p = &root->rb_node;
294 struct rb_node *parent = NULL;
295 struct request *__rq;
299 __rq = rb_entry(parent, struct request, rb_node);
301 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
303 else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
307 rb_link_node(&rq->rb_node, parent, p);
308 rb_insert_color(&rq->rb_node, root);
310 EXPORT_SYMBOL(elv_rb_add);
312 void elv_rb_del(struct rb_root *root, struct request *rq)
314 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
315 rb_erase(&rq->rb_node, root);
316 RB_CLEAR_NODE(&rq->rb_node);
318 EXPORT_SYMBOL(elv_rb_del);
320 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
322 struct rb_node *n = root->rb_node;
326 rq = rb_entry(n, struct request, rb_node);
328 if (sector < blk_rq_pos(rq))
330 else if (sector > blk_rq_pos(rq))
338 EXPORT_SYMBOL(elv_rb_find);
341 * Insert rq into dispatch queue of q. Queue lock must be held on
342 * entry. rq is sort instead into the dispatch queue. To be used by
343 * specific elevators.
345 void elv_dispatch_sort(struct request_queue *q, struct request *rq)
348 struct list_head *entry;
351 if (q->last_merge == rq)
352 q->last_merge = NULL;
354 elv_rqhash_del(q, rq);
358 boundary = q->end_sector;
359 stop_flags = REQ_SOFTBARRIER | REQ_STARTED;
360 list_for_each_prev(entry, &q->queue_head) {
361 struct request *pos = list_entry_rq(entry);
363 if ((rq->cmd_flags & REQ_DISCARD) !=
364 (pos->cmd_flags & REQ_DISCARD))
366 if (rq_data_dir(rq) != rq_data_dir(pos))
368 if (pos->cmd_flags & stop_flags)
370 if (blk_rq_pos(rq) >= boundary) {
371 if (blk_rq_pos(pos) < boundary)
374 if (blk_rq_pos(pos) >= boundary)
377 if (blk_rq_pos(rq) >= blk_rq_pos(pos))
381 list_add(&rq->queuelist, entry);
383 EXPORT_SYMBOL(elv_dispatch_sort);
386 * Insert rq into dispatch queue of q. Queue lock must be held on
387 * entry. rq is added to the back of the dispatch queue. To be used by
388 * specific elevators.
390 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
392 if (q->last_merge == rq)
393 q->last_merge = NULL;
395 elv_rqhash_del(q, rq);
399 q->end_sector = rq_end_sector(rq);
401 list_add_tail(&rq->queuelist, &q->queue_head);
403 EXPORT_SYMBOL(elv_dispatch_add_tail);
405 int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
407 struct elevator_queue *e = q->elevator;
408 struct request *__rq;
413 * nomerges: No merges at all attempted
414 * noxmerges: Only simple one-hit cache try
415 * merges: All merge tries attempted
417 if (blk_queue_nomerges(q))
418 return ELEVATOR_NO_MERGE;
421 * First try one-hit cache.
423 if (q->last_merge && elv_rq_merge_ok(q->last_merge, bio)) {
424 ret = blk_try_merge(q->last_merge, bio);
425 if (ret != ELEVATOR_NO_MERGE) {
426 *req = q->last_merge;
431 if (blk_queue_noxmerges(q))
432 return ELEVATOR_NO_MERGE;
435 * See if our hash lookup can find a potential backmerge.
437 __rq = elv_rqhash_find(q, bio->bi_sector);
438 if (__rq && elv_rq_merge_ok(__rq, bio)) {
440 return ELEVATOR_BACK_MERGE;
443 if (e->type->ops.elevator_merge_fn)
444 return e->type->ops.elevator_merge_fn(q, req, bio);
446 return ELEVATOR_NO_MERGE;
450 * Attempt to do an insertion back merge. Only check for the case where
451 * we can append 'rq' to an existing request, so we can throw 'rq' away
454 * Returns true if we merged, false otherwise
456 static bool elv_attempt_insert_merge(struct request_queue *q,
459 struct request *__rq;
461 if (blk_queue_nomerges(q))
465 * First try one-hit cache.
467 if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq))
470 if (blk_queue_noxmerges(q))
474 * See if our hash lookup can find a potential backmerge.
476 __rq = elv_rqhash_find(q, blk_rq_pos(rq));
477 if (__rq && blk_attempt_req_merge(q, __rq, rq))
483 void elv_merged_request(struct request_queue *q, struct request *rq, int type)
485 struct elevator_queue *e = q->elevator;
487 if (e->type->ops.elevator_merged_fn)
488 e->type->ops.elevator_merged_fn(q, rq, type);
490 if (type == ELEVATOR_BACK_MERGE)
491 elv_rqhash_reposition(q, rq);
496 void elv_merge_requests(struct request_queue *q, struct request *rq,
497 struct request *next)
499 struct elevator_queue *e = q->elevator;
500 const int next_sorted = next->cmd_flags & REQ_SORTED;
502 if (next_sorted && e->type->ops.elevator_merge_req_fn)
503 e->type->ops.elevator_merge_req_fn(q, rq, next);
505 elv_rqhash_reposition(q, rq);
508 elv_rqhash_del(q, next);
515 void elv_bio_merged(struct request_queue *q, struct request *rq,
518 struct elevator_queue *e = q->elevator;
520 if (e->type->ops.elevator_bio_merged_fn)
521 e->type->ops.elevator_bio_merged_fn(q, rq, bio);
524 void elv_requeue_request(struct request_queue *q, struct request *rq)
527 * it already went through dequeue, we need to decrement the
528 * in_flight count again
530 if (blk_account_rq(rq)) {
531 q->in_flight[rq_is_sync(rq)]--;
532 if (rq->cmd_flags & REQ_SORTED)
533 elv_deactivate_rq(q, rq);
536 rq->cmd_flags &= ~REQ_STARTED;
538 __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
541 void elv_drain_elevator(struct request_queue *q)
545 lockdep_assert_held(q->queue_lock);
547 while (q->elevator->type->ops.elevator_dispatch_fn(q, 1))
549 if (q->nr_sorted && printed++ < 10) {
550 printk(KERN_ERR "%s: forced dispatching is broken "
551 "(nr_sorted=%u), please report this\n",
552 q->elevator->type->elevator_name, q->nr_sorted);
556 void elv_quiesce_start(struct request_queue *q)
561 spin_lock_irq(q->queue_lock);
562 queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
563 spin_unlock_irq(q->queue_lock);
565 blk_drain_queue(q, false);
568 void elv_quiesce_end(struct request_queue *q)
570 spin_lock_irq(q->queue_lock);
571 queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
572 spin_unlock_irq(q->queue_lock);
575 void __elv_add_request(struct request_queue *q, struct request *rq, int where)
577 trace_block_rq_insert(q, rq);
581 if (rq->cmd_flags & REQ_SOFTBARRIER) {
582 /* barriers are scheduling boundary, update end_sector */
583 if (rq->cmd_type == REQ_TYPE_FS ||
584 (rq->cmd_flags & REQ_DISCARD)) {
585 q->end_sector = rq_end_sector(rq);
588 } else if (!(rq->cmd_flags & REQ_ELVPRIV) &&
589 (where == ELEVATOR_INSERT_SORT ||
590 where == ELEVATOR_INSERT_SORT_MERGE))
591 where = ELEVATOR_INSERT_BACK;
594 case ELEVATOR_INSERT_REQUEUE:
595 case ELEVATOR_INSERT_FRONT:
596 rq->cmd_flags |= REQ_SOFTBARRIER;
597 list_add(&rq->queuelist, &q->queue_head);
600 case ELEVATOR_INSERT_BACK:
601 rq->cmd_flags |= REQ_SOFTBARRIER;
602 elv_drain_elevator(q);
603 list_add_tail(&rq->queuelist, &q->queue_head);
605 * We kick the queue here for the following reasons.
606 * - The elevator might have returned NULL previously
607 * to delay requests and returned them now. As the
608 * queue wasn't empty before this request, ll_rw_blk
609 * won't run the queue on return, resulting in hang.
610 * - Usually, back inserted requests won't be merged
611 * with anything. There's no point in delaying queue
617 case ELEVATOR_INSERT_SORT_MERGE:
619 * If we succeed in merging this request with one in the
620 * queue already, we are done - rq has now been freed,
621 * so no need to do anything further.
623 if (elv_attempt_insert_merge(q, rq))
625 case ELEVATOR_INSERT_SORT:
626 BUG_ON(rq->cmd_type != REQ_TYPE_FS &&
627 !(rq->cmd_flags & REQ_DISCARD));
628 rq->cmd_flags |= REQ_SORTED;
630 if (rq_mergeable(rq)) {
631 elv_rqhash_add(q, rq);
637 * Some ioscheds (cfq) run q->request_fn directly, so
638 * rq cannot be accessed after calling
639 * elevator_add_req_fn.
641 q->elevator->type->ops.elevator_add_req_fn(q, rq);
644 case ELEVATOR_INSERT_FLUSH:
645 rq->cmd_flags |= REQ_SOFTBARRIER;
646 blk_insert_flush(rq);
649 printk(KERN_ERR "%s: bad insertion point %d\n",
654 EXPORT_SYMBOL(__elv_add_request);
656 void elv_add_request(struct request_queue *q, struct request *rq, int where)
660 spin_lock_irqsave(q->queue_lock, flags);
661 __elv_add_request(q, rq, where);
662 spin_unlock_irqrestore(q->queue_lock, flags);
664 EXPORT_SYMBOL(elv_add_request);
666 struct request *elv_latter_request(struct request_queue *q, struct request *rq)
668 struct elevator_queue *e = q->elevator;
670 if (e->type->ops.elevator_latter_req_fn)
671 return e->type->ops.elevator_latter_req_fn(q, rq);
675 struct request *elv_former_request(struct request_queue *q, struct request *rq)
677 struct elevator_queue *e = q->elevator;
679 if (e->type->ops.elevator_former_req_fn)
680 return e->type->ops.elevator_former_req_fn(q, rq);
684 int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
686 struct elevator_queue *e = q->elevator;
688 if (e->type->ops.elevator_set_req_fn)
689 return e->type->ops.elevator_set_req_fn(q, rq, gfp_mask);
693 void elv_put_request(struct request_queue *q, struct request *rq)
695 struct elevator_queue *e = q->elevator;
697 if (e->type->ops.elevator_put_req_fn)
698 e->type->ops.elevator_put_req_fn(rq);
701 int elv_may_queue(struct request_queue *q, int rw)
703 struct elevator_queue *e = q->elevator;
705 if (e->type->ops.elevator_may_queue_fn)
706 return e->type->ops.elevator_may_queue_fn(q, rw);
708 return ELV_MQUEUE_MAY;
711 void elv_abort_queue(struct request_queue *q)
715 blk_abort_flushes(q);
717 while (!list_empty(&q->queue_head)) {
718 rq = list_entry_rq(q->queue_head.next);
719 rq->cmd_flags |= REQ_QUIET;
720 trace_block_rq_abort(q, rq);
722 * Mark this request as started so we don't trigger
723 * any debug logic in the end I/O path.
725 blk_start_request(rq);
726 __blk_end_request_all(rq, -EIO);
729 EXPORT_SYMBOL(elv_abort_queue);
731 void elv_completed_request(struct request_queue *q, struct request *rq)
733 struct elevator_queue *e = q->elevator;
736 * request is released from the driver, io must be done
738 if (blk_account_rq(rq)) {
739 q->in_flight[rq_is_sync(rq)]--;
740 if ((rq->cmd_flags & REQ_SORTED) &&
741 e->type->ops.elevator_completed_req_fn)
742 e->type->ops.elevator_completed_req_fn(q, rq);
746 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
749 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
751 struct elv_fs_entry *entry = to_elv(attr);
752 struct elevator_queue *e;
758 e = container_of(kobj, struct elevator_queue, kobj);
759 mutex_lock(&e->sysfs_lock);
760 error = e->type ? entry->show(e, page) : -ENOENT;
761 mutex_unlock(&e->sysfs_lock);
766 elv_attr_store(struct kobject *kobj, struct attribute *attr,
767 const char *page, size_t length)
769 struct elv_fs_entry *entry = to_elv(attr);
770 struct elevator_queue *e;
776 e = container_of(kobj, struct elevator_queue, kobj);
777 mutex_lock(&e->sysfs_lock);
778 error = e->type ? entry->store(e, page, length) : -ENOENT;
779 mutex_unlock(&e->sysfs_lock);
783 static const struct sysfs_ops elv_sysfs_ops = {
784 .show = elv_attr_show,
785 .store = elv_attr_store,
788 static struct kobj_type elv_ktype = {
789 .sysfs_ops = &elv_sysfs_ops,
790 .release = elevator_release,
793 int elv_register_queue(struct request_queue *q)
795 struct elevator_queue *e = q->elevator;
798 error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
800 struct elv_fs_entry *attr = e->type->elevator_attrs;
802 while (attr->attr.name) {
803 if (sysfs_create_file(&e->kobj, &attr->attr))
808 kobject_uevent(&e->kobj, KOBJ_ADD);
813 EXPORT_SYMBOL(elv_register_queue);
815 void elv_unregister_queue(struct request_queue *q)
818 struct elevator_queue *e = q->elevator;
820 kobject_uevent(&e->kobj, KOBJ_REMOVE);
821 kobject_del(&e->kobj);
825 EXPORT_SYMBOL(elv_unregister_queue);
827 int elv_register(struct elevator_type *e)
831 /* create icq_cache if requested */
833 if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
834 WARN_ON(e->icq_align < __alignof__(struct io_cq)))
837 snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
838 "%s_io_cq", e->elevator_name);
839 e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
840 e->icq_align, 0, NULL);
845 /* register, don't allow duplicate names */
846 spin_lock(&elv_list_lock);
847 if (elevator_find(e->elevator_name)) {
848 spin_unlock(&elv_list_lock);
850 kmem_cache_destroy(e->icq_cache);
853 list_add_tail(&e->list, &elv_list);
854 spin_unlock(&elv_list_lock);
856 /* print pretty message */
857 if (!strcmp(e->elevator_name, chosen_elevator) ||
858 (!*chosen_elevator &&
859 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
862 printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
866 EXPORT_SYMBOL_GPL(elv_register);
868 void elv_unregister(struct elevator_type *e)
871 spin_lock(&elv_list_lock);
872 list_del_init(&e->list);
873 spin_unlock(&elv_list_lock);
876 * Destroy icq_cache if it exists. icq's are RCU managed. Make
877 * sure all RCU operations are complete before proceeding.
881 kmem_cache_destroy(e->icq_cache);
885 EXPORT_SYMBOL_GPL(elv_unregister);
888 * switch to new_e io scheduler. be careful not to introduce deadlocks -
889 * we don't free the old io scheduler, before we have allocated what we
890 * need for the new one. this way we have a chance of going back to the old
891 * one, if the new one fails init for some reason.
893 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
895 struct elevator_queue *old = q->elevator;
896 bool registered = old->registered;
900 * Turn on BYPASS and drain all requests w/ elevator private data.
901 * Block layer doesn't call into a quiesced elevator - all requests
902 * are directly put on the dispatch list without elevator data
903 * using INSERT_BACK. All requests have SOFTBARRIER set and no
904 * merge happens either.
906 elv_quiesce_start(q);
908 /* unregister and clear all auxiliary data of the old elevator */
910 elv_unregister_queue(q);
912 spin_lock_irq(q->queue_lock);
914 spin_unlock_irq(q->queue_lock);
916 /* allocate, init and register new elevator */
918 q->elevator = elevator_alloc(q, new_e);
922 err = new_e->ops.elevator_init_fn(q);
924 kobject_put(&q->elevator->kobj);
929 err = elv_register_queue(q);
934 /* done, kill the old one and finish */
938 blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
943 elevator_exit(q->elevator);
945 /* switch failed, restore and re-register old elevator */
947 elv_register_queue(q);
954 * Switch this queue to the given IO scheduler.
956 int elevator_change(struct request_queue *q, const char *name)
958 char elevator_name[ELV_NAME_MAX];
959 struct elevator_type *e;
964 strlcpy(elevator_name, name, sizeof(elevator_name));
965 e = elevator_get(strstrip(elevator_name));
967 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
971 if (!strcmp(elevator_name, q->elevator->type->elevator_name)) {
976 return elevator_switch(q, e);
978 EXPORT_SYMBOL(elevator_change);
980 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
988 ret = elevator_change(q, name);
992 printk(KERN_ERR "elevator: switch to %s failed\n", name);
996 ssize_t elv_iosched_show(struct request_queue *q, char *name)
998 struct elevator_queue *e = q->elevator;
999 struct elevator_type *elv;
1000 struct elevator_type *__e;
1003 if (!q->elevator || !blk_queue_stackable(q))
1004 return sprintf(name, "none\n");
1008 spin_lock(&elv_list_lock);
1009 list_for_each_entry(__e, &elv_list, list) {
1010 if (!strcmp(elv->elevator_name, __e->elevator_name))
1011 len += sprintf(name+len, "[%s] ", elv->elevator_name);
1013 len += sprintf(name+len, "%s ", __e->elevator_name);
1015 spin_unlock(&elv_list_lock);
1017 len += sprintf(len+name, "\n");
1021 struct request *elv_rb_former_request(struct request_queue *q,
1024 struct rb_node *rbprev = rb_prev(&rq->rb_node);
1027 return rb_entry_rq(rbprev);
1031 EXPORT_SYMBOL(elv_rb_former_request);
1033 struct request *elv_rb_latter_request(struct request_queue *q,
1036 struct rb_node *rbnext = rb_next(&rq->rb_node);
1039 return rb_entry_rq(rbnext);
1043 EXPORT_SYMBOL(elv_rb_latter_request);