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>
41 #include "blk-cgroup.h"
43 static DEFINE_SPINLOCK(elv_list_lock);
44 static LIST_HEAD(elv_list);
49 static const int elv_hash_shift = 6;
50 #define ELV_HASH_BLOCK(sec) ((sec) >> 3)
51 #define ELV_HASH_FN(sec) \
52 (hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift))
53 #define ELV_HASH_ENTRIES (1 << elv_hash_shift)
54 #define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq))
57 * Query io scheduler to see if the current process issuing bio may be
60 static int elv_iosched_allow_merge(struct request *rq, struct bio *bio)
62 struct request_queue *q = rq->q;
63 struct elevator_queue *e = q->elevator;
65 if (e->type->ops.elevator_allow_merge_fn)
66 return e->type->ops.elevator_allow_merge_fn(q, rq, bio);
72 * can we safely merge with this request?
74 bool elv_rq_merge_ok(struct request *rq, struct bio *bio)
76 if (!blk_rq_merge_ok(rq, bio))
79 if (!elv_iosched_allow_merge(rq, bio))
84 EXPORT_SYMBOL(elv_rq_merge_ok);
86 static struct elevator_type *elevator_find(const char *name)
88 struct elevator_type *e;
90 list_for_each_entry(e, &elv_list, list) {
91 if (!strcmp(e->elevator_name, name))
98 static void elevator_put(struct elevator_type *e)
100 module_put(e->elevator_owner);
103 static struct elevator_type *elevator_get(const char *name)
105 struct elevator_type *e;
107 spin_lock(&elv_list_lock);
109 e = elevator_find(name);
111 spin_unlock(&elv_list_lock);
112 request_module("%s-iosched", name);
113 spin_lock(&elv_list_lock);
114 e = elevator_find(name);
117 if (e && !try_module_get(e->elevator_owner))
120 spin_unlock(&elv_list_lock);
125 static char chosen_elevator[ELV_NAME_MAX];
127 static int __init elevator_setup(char *str)
130 * Be backwards-compatible with previous kernels, so users
131 * won't get the wrong elevator.
133 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
137 __setup("elevator=", elevator_setup);
139 static struct kobj_type elv_ktype;
141 static struct elevator_queue *elevator_alloc(struct request_queue *q,
142 struct elevator_type *e)
144 struct elevator_queue *eq;
147 eq = kmalloc_node(sizeof(*eq), GFP_KERNEL | __GFP_ZERO, q->node);
152 kobject_init(&eq->kobj, &elv_ktype);
153 mutex_init(&eq->sysfs_lock);
155 eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES,
156 GFP_KERNEL, q->node);
160 for (i = 0; i < ELV_HASH_ENTRIES; i++)
161 INIT_HLIST_HEAD(&eq->hash[i]);
170 static void elevator_release(struct kobject *kobj)
172 struct elevator_queue *e;
174 e = container_of(kobj, struct elevator_queue, kobj);
175 elevator_put(e->type);
180 int elevator_init(struct request_queue *q, char *name)
182 struct elevator_type *e = NULL;
185 if (unlikely(q->elevator))
188 INIT_LIST_HEAD(&q->queue_head);
189 q->last_merge = NULL;
191 q->boundary_rq = NULL;
194 e = elevator_get(name);
199 if (!e && *chosen_elevator) {
200 e = elevator_get(chosen_elevator);
202 printk(KERN_ERR "I/O scheduler %s not found\n",
207 e = elevator_get(CONFIG_DEFAULT_IOSCHED);
210 "Default I/O scheduler not found. " \
212 e = elevator_get("noop");
216 q->elevator = elevator_alloc(q, e);
220 err = e->ops.elevator_init_fn(q);
222 kobject_put(&q->elevator->kobj);
228 EXPORT_SYMBOL(elevator_init);
230 void elevator_exit(struct elevator_queue *e)
232 mutex_lock(&e->sysfs_lock);
233 if (e->type->ops.elevator_exit_fn)
234 e->type->ops.elevator_exit_fn(e);
235 mutex_unlock(&e->sysfs_lock);
237 kobject_put(&e->kobj);
239 EXPORT_SYMBOL(elevator_exit);
241 static inline void __elv_rqhash_del(struct request *rq)
243 hlist_del_init(&rq->hash);
246 static void elv_rqhash_del(struct request_queue *q, struct request *rq)
249 __elv_rqhash_del(rq);
252 static void elv_rqhash_add(struct request_queue *q, struct request *rq)
254 struct elevator_queue *e = q->elevator;
256 BUG_ON(ELV_ON_HASH(rq));
257 hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
260 static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
262 __elv_rqhash_del(rq);
263 elv_rqhash_add(q, rq);
266 static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
268 struct elevator_queue *e = q->elevator;
269 struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
270 struct hlist_node *entry, *next;
273 hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
274 BUG_ON(!ELV_ON_HASH(rq));
276 if (unlikely(!rq_mergeable(rq))) {
277 __elv_rqhash_del(rq);
281 if (rq_hash_key(rq) == offset)
289 * RB-tree support functions for inserting/lookup/removal of requests
290 * in a sorted RB tree.
292 void elv_rb_add(struct rb_root *root, struct request *rq)
294 struct rb_node **p = &root->rb_node;
295 struct rb_node *parent = NULL;
296 struct request *__rq;
300 __rq = rb_entry(parent, struct request, rb_node);
302 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
304 else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
308 rb_link_node(&rq->rb_node, parent, p);
309 rb_insert_color(&rq->rb_node, root);
311 EXPORT_SYMBOL(elv_rb_add);
313 void elv_rb_del(struct rb_root *root, struct request *rq)
315 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
316 rb_erase(&rq->rb_node, root);
317 RB_CLEAR_NODE(&rq->rb_node);
319 EXPORT_SYMBOL(elv_rb_del);
321 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
323 struct rb_node *n = root->rb_node;
327 rq = rb_entry(n, struct request, rb_node);
329 if (sector < blk_rq_pos(rq))
331 else if (sector > blk_rq_pos(rq))
339 EXPORT_SYMBOL(elv_rb_find);
342 * Insert rq into dispatch queue of q. Queue lock must be held on
343 * entry. rq is sort instead into the dispatch queue. To be used by
344 * specific elevators.
346 void elv_dispatch_sort(struct request_queue *q, struct request *rq)
349 struct list_head *entry;
352 if (q->last_merge == rq)
353 q->last_merge = NULL;
355 elv_rqhash_del(q, rq);
359 boundary = q->end_sector;
360 stop_flags = REQ_SOFTBARRIER | REQ_STARTED;
361 list_for_each_prev(entry, &q->queue_head) {
362 struct request *pos = list_entry_rq(entry);
364 if ((rq->cmd_flags & REQ_DISCARD) !=
365 (pos->cmd_flags & REQ_DISCARD))
367 if (rq_data_dir(rq) != rq_data_dir(pos))
369 if (pos->cmd_flags & stop_flags)
371 if (blk_rq_pos(rq) >= boundary) {
372 if (blk_rq_pos(pos) < boundary)
375 if (blk_rq_pos(pos) >= boundary)
378 if (blk_rq_pos(rq) >= blk_rq_pos(pos))
382 list_add(&rq->queuelist, entry);
384 EXPORT_SYMBOL(elv_dispatch_sort);
387 * Insert rq into dispatch queue of q. Queue lock must be held on
388 * entry. rq is added to the back of the dispatch queue. To be used by
389 * specific elevators.
391 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
393 if (q->last_merge == rq)
394 q->last_merge = NULL;
396 elv_rqhash_del(q, rq);
400 q->end_sector = rq_end_sector(rq);
402 list_add_tail(&rq->queuelist, &q->queue_head);
404 EXPORT_SYMBOL(elv_dispatch_add_tail);
406 int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
408 struct elevator_queue *e = q->elevator;
409 struct request *__rq;
414 * nomerges: No merges at all attempted
415 * noxmerges: Only simple one-hit cache try
416 * merges: All merge tries attempted
418 if (blk_queue_nomerges(q))
419 return ELEVATOR_NO_MERGE;
422 * First try one-hit cache.
424 if (q->last_merge && elv_rq_merge_ok(q->last_merge, bio)) {
425 ret = blk_try_merge(q->last_merge, bio);
426 if (ret != ELEVATOR_NO_MERGE) {
427 *req = q->last_merge;
432 if (blk_queue_noxmerges(q))
433 return ELEVATOR_NO_MERGE;
436 * See if our hash lookup can find a potential backmerge.
438 __rq = elv_rqhash_find(q, bio->bi_sector);
439 if (__rq && elv_rq_merge_ok(__rq, bio)) {
441 return ELEVATOR_BACK_MERGE;
444 if (e->type->ops.elevator_merge_fn)
445 return e->type->ops.elevator_merge_fn(q, req, bio);
447 return ELEVATOR_NO_MERGE;
451 * Attempt to do an insertion back merge. Only check for the case where
452 * we can append 'rq' to an existing request, so we can throw 'rq' away
455 * Returns true if we merged, false otherwise
457 static bool elv_attempt_insert_merge(struct request_queue *q,
460 struct request *__rq;
462 if (blk_queue_nomerges(q))
466 * First try one-hit cache.
468 if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq))
471 if (blk_queue_noxmerges(q))
475 * See if our hash lookup can find a potential backmerge.
477 __rq = elv_rqhash_find(q, blk_rq_pos(rq));
478 if (__rq && blk_attempt_req_merge(q, __rq, rq))
484 void elv_merged_request(struct request_queue *q, struct request *rq, int type)
486 struct elevator_queue *e = q->elevator;
488 if (e->type->ops.elevator_merged_fn)
489 e->type->ops.elevator_merged_fn(q, rq, type);
491 if (type == ELEVATOR_BACK_MERGE)
492 elv_rqhash_reposition(q, rq);
497 void elv_merge_requests(struct request_queue *q, struct request *rq,
498 struct request *next)
500 struct elevator_queue *e = q->elevator;
501 const int next_sorted = next->cmd_flags & REQ_SORTED;
503 if (next_sorted && e->type->ops.elevator_merge_req_fn)
504 e->type->ops.elevator_merge_req_fn(q, rq, next);
506 elv_rqhash_reposition(q, rq);
509 elv_rqhash_del(q, next);
516 void elv_bio_merged(struct request_queue *q, struct request *rq,
519 struct elevator_queue *e = q->elevator;
521 if (e->type->ops.elevator_bio_merged_fn)
522 e->type->ops.elevator_bio_merged_fn(q, rq, bio);
525 void elv_requeue_request(struct request_queue *q, struct request *rq)
528 * it already went through dequeue, we need to decrement the
529 * in_flight count again
531 if (blk_account_rq(rq)) {
532 q->in_flight[rq_is_sync(rq)]--;
533 if (rq->cmd_flags & REQ_SORTED)
534 elv_deactivate_rq(q, rq);
537 rq->cmd_flags &= ~REQ_STARTED;
539 __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
542 void elv_drain_elevator(struct request_queue *q)
546 lockdep_assert_held(q->queue_lock);
548 while (q->elevator->type->ops.elevator_dispatch_fn(q, 1))
550 if (q->nr_sorted && printed++ < 10) {
551 printk(KERN_ERR "%s: forced dispatching is broken "
552 "(nr_sorted=%u), please report this\n",
553 q->elevator->type->elevator_name, q->nr_sorted);
557 void __elv_add_request(struct request_queue *q, struct request *rq, int where)
559 trace_block_rq_insert(q, rq);
563 if (rq->cmd_flags & REQ_SOFTBARRIER) {
564 /* barriers are scheduling boundary, update end_sector */
565 if (rq->cmd_type == REQ_TYPE_FS ||
566 (rq->cmd_flags & REQ_DISCARD)) {
567 q->end_sector = rq_end_sector(rq);
570 } else if (!(rq->cmd_flags & REQ_ELVPRIV) &&
571 (where == ELEVATOR_INSERT_SORT ||
572 where == ELEVATOR_INSERT_SORT_MERGE))
573 where = ELEVATOR_INSERT_BACK;
576 case ELEVATOR_INSERT_REQUEUE:
577 case ELEVATOR_INSERT_FRONT:
578 rq->cmd_flags |= REQ_SOFTBARRIER;
579 list_add(&rq->queuelist, &q->queue_head);
582 case ELEVATOR_INSERT_BACK:
583 rq->cmd_flags |= REQ_SOFTBARRIER;
584 elv_drain_elevator(q);
585 list_add_tail(&rq->queuelist, &q->queue_head);
587 * We kick the queue here for the following reasons.
588 * - The elevator might have returned NULL previously
589 * to delay requests and returned them now. As the
590 * queue wasn't empty before this request, ll_rw_blk
591 * won't run the queue on return, resulting in hang.
592 * - Usually, back inserted requests won't be merged
593 * with anything. There's no point in delaying queue
599 case ELEVATOR_INSERT_SORT_MERGE:
601 * If we succeed in merging this request with one in the
602 * queue already, we are done - rq has now been freed,
603 * so no need to do anything further.
605 if (elv_attempt_insert_merge(q, rq))
607 case ELEVATOR_INSERT_SORT:
608 BUG_ON(rq->cmd_type != REQ_TYPE_FS &&
609 !(rq->cmd_flags & REQ_DISCARD));
610 rq->cmd_flags |= REQ_SORTED;
612 if (rq_mergeable(rq)) {
613 elv_rqhash_add(q, rq);
619 * Some ioscheds (cfq) run q->request_fn directly, so
620 * rq cannot be accessed after calling
621 * elevator_add_req_fn.
623 q->elevator->type->ops.elevator_add_req_fn(q, rq);
626 case ELEVATOR_INSERT_FLUSH:
627 rq->cmd_flags |= REQ_SOFTBARRIER;
628 blk_insert_flush(rq);
631 printk(KERN_ERR "%s: bad insertion point %d\n",
636 EXPORT_SYMBOL(__elv_add_request);
638 void elv_add_request(struct request_queue *q, struct request *rq, int where)
642 spin_lock_irqsave(q->queue_lock, flags);
643 __elv_add_request(q, rq, where);
644 spin_unlock_irqrestore(q->queue_lock, flags);
646 EXPORT_SYMBOL(elv_add_request);
648 struct request *elv_latter_request(struct request_queue *q, struct request *rq)
650 struct elevator_queue *e = q->elevator;
652 if (e->type->ops.elevator_latter_req_fn)
653 return e->type->ops.elevator_latter_req_fn(q, rq);
657 struct request *elv_former_request(struct request_queue *q, struct request *rq)
659 struct elevator_queue *e = q->elevator;
661 if (e->type->ops.elevator_former_req_fn)
662 return e->type->ops.elevator_former_req_fn(q, rq);
666 int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
668 struct elevator_queue *e = q->elevator;
670 if (e->type->ops.elevator_set_req_fn)
671 return e->type->ops.elevator_set_req_fn(q, rq, gfp_mask);
675 void elv_put_request(struct request_queue *q, struct request *rq)
677 struct elevator_queue *e = q->elevator;
679 if (e->type->ops.elevator_put_req_fn)
680 e->type->ops.elevator_put_req_fn(rq);
683 int elv_may_queue(struct request_queue *q, int rw)
685 struct elevator_queue *e = q->elevator;
687 if (e->type->ops.elevator_may_queue_fn)
688 return e->type->ops.elevator_may_queue_fn(q, rw);
690 return ELV_MQUEUE_MAY;
693 void elv_abort_queue(struct request_queue *q)
697 blk_abort_flushes(q);
699 while (!list_empty(&q->queue_head)) {
700 rq = list_entry_rq(q->queue_head.next);
701 rq->cmd_flags |= REQ_QUIET;
702 trace_block_rq_abort(q, rq);
704 * Mark this request as started so we don't trigger
705 * any debug logic in the end I/O path.
707 blk_start_request(rq);
708 __blk_end_request_all(rq, -EIO);
711 EXPORT_SYMBOL(elv_abort_queue);
713 void elv_completed_request(struct request_queue *q, struct request *rq)
715 struct elevator_queue *e = q->elevator;
718 * request is released from the driver, io must be done
720 if (blk_account_rq(rq)) {
721 q->in_flight[rq_is_sync(rq)]--;
722 if ((rq->cmd_flags & REQ_SORTED) &&
723 e->type->ops.elevator_completed_req_fn)
724 e->type->ops.elevator_completed_req_fn(q, rq);
728 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
731 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
733 struct elv_fs_entry *entry = to_elv(attr);
734 struct elevator_queue *e;
740 e = container_of(kobj, struct elevator_queue, kobj);
741 mutex_lock(&e->sysfs_lock);
742 error = e->type ? entry->show(e, page) : -ENOENT;
743 mutex_unlock(&e->sysfs_lock);
748 elv_attr_store(struct kobject *kobj, struct attribute *attr,
749 const char *page, size_t length)
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->store(e, page, length) : -ENOENT;
761 mutex_unlock(&e->sysfs_lock);
765 static const struct sysfs_ops elv_sysfs_ops = {
766 .show = elv_attr_show,
767 .store = elv_attr_store,
770 static struct kobj_type elv_ktype = {
771 .sysfs_ops = &elv_sysfs_ops,
772 .release = elevator_release,
775 int elv_register_queue(struct request_queue *q)
777 struct elevator_queue *e = q->elevator;
780 error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
782 struct elv_fs_entry *attr = e->type->elevator_attrs;
784 while (attr->attr.name) {
785 if (sysfs_create_file(&e->kobj, &attr->attr))
790 kobject_uevent(&e->kobj, KOBJ_ADD);
795 EXPORT_SYMBOL(elv_register_queue);
797 void elv_unregister_queue(struct request_queue *q)
800 struct elevator_queue *e = q->elevator;
802 kobject_uevent(&e->kobj, KOBJ_REMOVE);
803 kobject_del(&e->kobj);
807 EXPORT_SYMBOL(elv_unregister_queue);
809 int elv_register(struct elevator_type *e)
813 /* create icq_cache if requested */
815 if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
816 WARN_ON(e->icq_align < __alignof__(struct io_cq)))
819 snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
820 "%s_io_cq", e->elevator_name);
821 e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
822 e->icq_align, 0, NULL);
827 /* register, don't allow duplicate names */
828 spin_lock(&elv_list_lock);
829 if (elevator_find(e->elevator_name)) {
830 spin_unlock(&elv_list_lock);
832 kmem_cache_destroy(e->icq_cache);
835 list_add_tail(&e->list, &elv_list);
836 spin_unlock(&elv_list_lock);
838 /* print pretty message */
839 if (!strcmp(e->elevator_name, chosen_elevator) ||
840 (!*chosen_elevator &&
841 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
844 printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
848 EXPORT_SYMBOL_GPL(elv_register);
850 void elv_unregister(struct elevator_type *e)
853 spin_lock(&elv_list_lock);
854 list_del_init(&e->list);
855 spin_unlock(&elv_list_lock);
858 * Destroy icq_cache if it exists. icq's are RCU managed. Make
859 * sure all RCU operations are complete before proceeding.
863 kmem_cache_destroy(e->icq_cache);
867 EXPORT_SYMBOL_GPL(elv_unregister);
870 * switch to new_e io scheduler. be careful not to introduce deadlocks -
871 * we don't free the old io scheduler, before we have allocated what we
872 * need for the new one. this way we have a chance of going back to the old
873 * one, if the new one fails init for some reason.
875 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
877 struct elevator_queue *old = q->elevator;
878 bool registered = old->registered;
882 * Turn on BYPASS and drain all requests w/ elevator private data.
883 * Block layer doesn't call into a quiesced elevator - all requests
884 * are directly put on the dispatch list without elevator data
885 * using INSERT_BACK. All requests have SOFTBARRIER set and no
886 * merge happens either.
888 blk_queue_bypass_start(q);
890 /* unregister and clear all auxiliary data of the old elevator */
892 elv_unregister_queue(q);
894 spin_lock_irq(q->queue_lock);
896 spin_unlock_irq(q->queue_lock);
898 blkg_destroy_all(q, false);
900 /* allocate, init and register new elevator */
902 q->elevator = elevator_alloc(q, new_e);
906 err = new_e->ops.elevator_init_fn(q);
908 kobject_put(&q->elevator->kobj);
913 err = elv_register_queue(q);
918 /* done, kill the old one and finish */
920 blk_queue_bypass_end(q);
922 blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
927 elevator_exit(q->elevator);
929 /* switch failed, restore and re-register old elevator */
931 elv_register_queue(q);
932 blk_queue_bypass_end(q);
938 * Switch this queue to the given IO scheduler.
940 int elevator_change(struct request_queue *q, const char *name)
942 char elevator_name[ELV_NAME_MAX];
943 struct elevator_type *e;
948 strlcpy(elevator_name, name, sizeof(elevator_name));
949 e = elevator_get(strstrip(elevator_name));
951 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
955 if (!strcmp(elevator_name, q->elevator->type->elevator_name)) {
960 return elevator_switch(q, e);
962 EXPORT_SYMBOL(elevator_change);
964 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
972 ret = elevator_change(q, name);
976 printk(KERN_ERR "elevator: switch to %s failed\n", name);
980 ssize_t elv_iosched_show(struct request_queue *q, char *name)
982 struct elevator_queue *e = q->elevator;
983 struct elevator_type *elv;
984 struct elevator_type *__e;
987 if (!q->elevator || !blk_queue_stackable(q))
988 return sprintf(name, "none\n");
992 spin_lock(&elv_list_lock);
993 list_for_each_entry(__e, &elv_list, list) {
994 if (!strcmp(elv->elevator_name, __e->elevator_name))
995 len += sprintf(name+len, "[%s] ", elv->elevator_name);
997 len += sprintf(name+len, "%s ", __e->elevator_name);
999 spin_unlock(&elv_list_lock);
1001 len += sprintf(len+name, "\n");
1005 struct request *elv_rb_former_request(struct request_queue *q,
1008 struct rb_node *rbprev = rb_prev(&rq->rb_node);
1011 return rb_entry_rq(rbprev);
1015 EXPORT_SYMBOL(elv_rb_former_request);
1017 struct request *elv_rb_latter_request(struct request_queue *q,
1020 struct rb_node *rbnext = rb_next(&rq->rb_node);
1023 return rb_entry_rq(rbnext);
1027 EXPORT_SYMBOL(elv_rb_latter_request);