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/delay.h>
35 #include <linux/blktrace_api.h>
36 #include <linux/hash.h>
37 #include <linux/uaccess.h>
39 #include <trace/events/block.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->ops->elevator_allow_merge_fn)
66 return e->ops->elevator_allow_merge_fn(q, rq, bio);
72 * can we safely merge with this request?
74 int elv_rq_merge_ok(struct request *rq, struct bio *bio)
76 if (!rq_mergeable(rq))
80 * Don't merge file system requests and discard requests
82 if ((bio->bi_rw & REQ_DISCARD) != (rq->bio->bi_rw & REQ_DISCARD))
86 * Don't merge discard requests and secure discard requests
88 if ((bio->bi_rw & REQ_SECURE) != (rq->bio->bi_rw & REQ_SECURE))
92 * different data direction or already started, don't merge
94 if (bio_data_dir(bio) != rq_data_dir(rq))
98 * must be same device and not a special request
100 if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)
104 * only merge integrity protected bio into ditto rq
106 if (bio_integrity(bio) != blk_integrity_rq(rq))
109 if (!elv_iosched_allow_merge(rq, bio))
114 EXPORT_SYMBOL(elv_rq_merge_ok);
116 static inline int elv_try_merge(struct request *__rq, struct bio *bio)
118 int ret = ELEVATOR_NO_MERGE;
121 * we can merge and sequence is ok, check if it's possible
123 if (elv_rq_merge_ok(__rq, bio)) {
124 if (blk_rq_pos(__rq) + blk_rq_sectors(__rq) == bio->bi_sector)
125 ret = ELEVATOR_BACK_MERGE;
126 else if (blk_rq_pos(__rq) - bio_sectors(bio) == bio->bi_sector)
127 ret = ELEVATOR_FRONT_MERGE;
133 static struct elevator_type *elevator_find(const char *name)
135 struct elevator_type *e;
137 list_for_each_entry(e, &elv_list, list) {
138 if (!strcmp(e->elevator_name, name))
145 static void elevator_put(struct elevator_type *e)
147 module_put(e->elevator_owner);
150 static struct elevator_type *elevator_get(const char *name)
152 struct elevator_type *e;
154 spin_lock(&elv_list_lock);
156 e = elevator_find(name);
158 char elv[ELV_NAME_MAX + strlen("-iosched")];
160 spin_unlock(&elv_list_lock);
162 snprintf(elv, sizeof(elv), "%s-iosched", name);
164 request_module("%s", elv);
165 spin_lock(&elv_list_lock);
166 e = elevator_find(name);
169 if (e && !try_module_get(e->elevator_owner))
172 spin_unlock(&elv_list_lock);
177 static void *elevator_init_queue(struct request_queue *q,
178 struct elevator_queue *eq)
180 return eq->ops->elevator_init_fn(q);
183 static void elevator_attach(struct request_queue *q, struct elevator_queue *eq,
187 eq->elevator_data = data;
190 static char chosen_elevator[16];
192 static int __init elevator_setup(char *str)
195 * Be backwards-compatible with previous kernels, so users
196 * won't get the wrong elevator.
198 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
202 __setup("elevator=", elevator_setup);
204 static struct kobj_type elv_ktype;
206 static struct elevator_queue *elevator_alloc(struct request_queue *q,
207 struct elevator_type *e)
209 struct elevator_queue *eq;
212 eq = kmalloc_node(sizeof(*eq), GFP_KERNEL | __GFP_ZERO, q->node);
217 eq->elevator_type = e;
218 kobject_init(&eq->kobj, &elv_ktype);
219 mutex_init(&eq->sysfs_lock);
221 eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES,
222 GFP_KERNEL, q->node);
226 for (i = 0; i < ELV_HASH_ENTRIES; i++)
227 INIT_HLIST_HEAD(&eq->hash[i]);
236 static void elevator_release(struct kobject *kobj)
238 struct elevator_queue *e;
240 e = container_of(kobj, struct elevator_queue, kobj);
241 elevator_put(e->elevator_type);
246 int elevator_init(struct request_queue *q, char *name)
248 struct elevator_type *e = NULL;
249 struct elevator_queue *eq;
252 if (unlikely(q->elevator))
255 INIT_LIST_HEAD(&q->queue_head);
256 q->last_merge = NULL;
258 q->boundary_rq = NULL;
261 e = elevator_get(name);
266 if (!e && *chosen_elevator) {
267 e = elevator_get(chosen_elevator);
269 printk(KERN_ERR "I/O scheduler %s not found\n",
274 e = elevator_get(CONFIG_DEFAULT_IOSCHED);
277 "Default I/O scheduler not found. " \
279 e = elevator_get("noop");
283 eq = elevator_alloc(q, e);
287 data = elevator_init_queue(q, eq);
289 kobject_put(&eq->kobj);
293 elevator_attach(q, eq, data);
296 EXPORT_SYMBOL(elevator_init);
298 void elevator_exit(struct elevator_queue *e)
300 mutex_lock(&e->sysfs_lock);
301 if (e->ops->elevator_exit_fn)
302 e->ops->elevator_exit_fn(e);
304 mutex_unlock(&e->sysfs_lock);
306 kobject_put(&e->kobj);
308 EXPORT_SYMBOL(elevator_exit);
310 static inline void __elv_rqhash_del(struct request *rq)
312 hlist_del_init(&rq->hash);
315 static void elv_rqhash_del(struct request_queue *q, struct request *rq)
318 __elv_rqhash_del(rq);
321 static void elv_rqhash_add(struct request_queue *q, struct request *rq)
323 struct elevator_queue *e = q->elevator;
325 BUG_ON(ELV_ON_HASH(rq));
326 hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
329 static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
331 __elv_rqhash_del(rq);
332 elv_rqhash_add(q, rq);
335 static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
337 struct elevator_queue *e = q->elevator;
338 struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
339 struct hlist_node *entry, *next;
342 hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
343 BUG_ON(!ELV_ON_HASH(rq));
345 if (unlikely(!rq_mergeable(rq))) {
346 __elv_rqhash_del(rq);
350 if (rq_hash_key(rq) == offset)
358 * RB-tree support functions for inserting/lookup/removal of requests
359 * in a sorted RB tree.
361 struct request *elv_rb_add(struct rb_root *root, struct request *rq)
363 struct rb_node **p = &root->rb_node;
364 struct rb_node *parent = NULL;
365 struct request *__rq;
369 __rq = rb_entry(parent, struct request, rb_node);
371 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
373 else if (blk_rq_pos(rq) > blk_rq_pos(__rq))
379 rb_link_node(&rq->rb_node, parent, p);
380 rb_insert_color(&rq->rb_node, root);
383 EXPORT_SYMBOL(elv_rb_add);
385 void elv_rb_del(struct rb_root *root, struct request *rq)
387 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
388 rb_erase(&rq->rb_node, root);
389 RB_CLEAR_NODE(&rq->rb_node);
391 EXPORT_SYMBOL(elv_rb_del);
393 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
395 struct rb_node *n = root->rb_node;
399 rq = rb_entry(n, struct request, rb_node);
401 if (sector < blk_rq_pos(rq))
403 else if (sector > blk_rq_pos(rq))
411 EXPORT_SYMBOL(elv_rb_find);
414 * Insert rq into dispatch queue of q. Queue lock must be held on
415 * entry. rq is sort instead into the dispatch queue. To be used by
416 * specific elevators.
418 void elv_dispatch_sort(struct request_queue *q, struct request *rq)
421 struct list_head *entry;
424 if (q->last_merge == rq)
425 q->last_merge = NULL;
427 elv_rqhash_del(q, rq);
431 boundary = q->end_sector;
432 stop_flags = REQ_SOFTBARRIER | REQ_STARTED;
433 list_for_each_prev(entry, &q->queue_head) {
434 struct request *pos = list_entry_rq(entry);
436 if ((rq->cmd_flags & REQ_DISCARD) !=
437 (pos->cmd_flags & REQ_DISCARD))
439 if (rq_data_dir(rq) != rq_data_dir(pos))
441 if (pos->cmd_flags & stop_flags)
443 if (blk_rq_pos(rq) >= boundary) {
444 if (blk_rq_pos(pos) < boundary)
447 if (blk_rq_pos(pos) >= boundary)
450 if (blk_rq_pos(rq) >= blk_rq_pos(pos))
454 list_add(&rq->queuelist, entry);
456 EXPORT_SYMBOL(elv_dispatch_sort);
459 * Insert rq into dispatch queue of q. Queue lock must be held on
460 * entry. rq is added to the back of the dispatch queue. To be used by
461 * specific elevators.
463 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
465 if (q->last_merge == rq)
466 q->last_merge = NULL;
468 elv_rqhash_del(q, rq);
472 q->end_sector = rq_end_sector(rq);
474 list_add_tail(&rq->queuelist, &q->queue_head);
476 EXPORT_SYMBOL(elv_dispatch_add_tail);
478 int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
480 struct elevator_queue *e = q->elevator;
481 struct request *__rq;
486 * nomerges: No merges at all attempted
487 * noxmerges: Only simple one-hit cache try
488 * merges: All merge tries attempted
490 if (blk_queue_nomerges(q))
491 return ELEVATOR_NO_MERGE;
494 * First try one-hit cache.
497 ret = elv_try_merge(q->last_merge, bio);
498 if (ret != ELEVATOR_NO_MERGE) {
499 *req = q->last_merge;
504 if (blk_queue_noxmerges(q))
505 return ELEVATOR_NO_MERGE;
508 * See if our hash lookup can find a potential backmerge.
510 __rq = elv_rqhash_find(q, bio->bi_sector);
511 if (__rq && elv_rq_merge_ok(__rq, bio)) {
513 return ELEVATOR_BACK_MERGE;
516 if (e->ops->elevator_merge_fn)
517 return e->ops->elevator_merge_fn(q, req, bio);
519 return ELEVATOR_NO_MERGE;
522 void elv_merged_request(struct request_queue *q, struct request *rq, int type)
524 struct elevator_queue *e = q->elevator;
526 if (e->ops->elevator_merged_fn)
527 e->ops->elevator_merged_fn(q, rq, type);
529 if (type == ELEVATOR_BACK_MERGE)
530 elv_rqhash_reposition(q, rq);
535 void elv_merge_requests(struct request_queue *q, struct request *rq,
536 struct request *next)
538 struct elevator_queue *e = q->elevator;
540 if (e->ops->elevator_merge_req_fn)
541 e->ops->elevator_merge_req_fn(q, rq, next);
543 elv_rqhash_reposition(q, rq);
544 elv_rqhash_del(q, next);
550 void elv_bio_merged(struct request_queue *q, struct request *rq,
553 struct elevator_queue *e = q->elevator;
555 if (e->ops->elevator_bio_merged_fn)
556 e->ops->elevator_bio_merged_fn(q, rq, bio);
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 elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
576 void elv_drain_elevator(struct request_queue *q)
579 while (q->elevator->ops->elevator_dispatch_fn(q, 1))
581 if (q->nr_sorted == 0)
583 if (printed++ < 10) {
584 printk(KERN_ERR "%s: forced dispatching is broken "
585 "(nr_sorted=%u), please report this\n",
586 q->elevator->elevator_type->elevator_name, q->nr_sorted);
591 * Call with queue lock held, interrupts disabled
593 void elv_quiesce_start(struct request_queue *q)
598 queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
601 * make sure we don't have any requests in flight
603 elv_drain_elevator(q);
604 while (q->rq.elvpriv) {
606 spin_unlock_irq(q->queue_lock);
608 spin_lock_irq(q->queue_lock);
609 elv_drain_elevator(q);
613 void elv_quiesce_end(struct request_queue *q)
615 queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
618 void elv_insert(struct request_queue *q, struct request *rq, int where)
622 trace_block_rq_insert(q, rq);
627 case ELEVATOR_INSERT_REQUEUE:
629 * Most requeues happen because of a busy condition,
630 * don't force unplug of the queue for that case.
631 * Clear unplug_it and fall through.
635 case ELEVATOR_INSERT_FRONT:
636 rq->cmd_flags |= REQ_SOFTBARRIER;
637 list_add(&rq->queuelist, &q->queue_head);
640 case ELEVATOR_INSERT_BACK:
641 rq->cmd_flags |= REQ_SOFTBARRIER;
642 elv_drain_elevator(q);
643 list_add_tail(&rq->queuelist, &q->queue_head);
645 * We kick the queue here for the following reasons.
646 * - The elevator might have returned NULL previously
647 * to delay requests and returned them now. As the
648 * queue wasn't empty before this request, ll_rw_blk
649 * won't run the queue on return, resulting in hang.
650 * - Usually, back inserted requests won't be merged
651 * with anything. There's no point in delaying queue
657 case ELEVATOR_INSERT_SORT:
658 BUG_ON(rq->cmd_type != REQ_TYPE_FS &&
659 !(rq->cmd_flags & REQ_DISCARD));
660 rq->cmd_flags |= REQ_SORTED;
662 if (rq_mergeable(rq)) {
663 elv_rqhash_add(q, rq);
669 * Some ioscheds (cfq) run q->request_fn directly, so
670 * rq cannot be accessed after calling
671 * elevator_add_req_fn.
673 q->elevator->ops->elevator_add_req_fn(q, rq);
677 printk(KERN_ERR "%s: bad insertion point %d\n",
682 if (unplug_it && blk_queue_plugged(q)) {
683 int nrq = q->rq.count[BLK_RW_SYNC] + q->rq.count[BLK_RW_ASYNC]
684 - queue_in_flight(q);
686 if (nrq >= q->unplug_thresh)
687 __generic_unplug_device(q);
691 void __elv_add_request(struct request_queue *q, struct request *rq, int where,
694 if (rq->cmd_flags & REQ_SOFTBARRIER) {
695 /* barriers are scheduling boundary, update end_sector */
696 if (rq->cmd_type == REQ_TYPE_FS ||
697 (rq->cmd_flags & REQ_DISCARD)) {
698 q->end_sector = rq_end_sector(rq);
701 } else if (!(rq->cmd_flags & REQ_ELVPRIV) &&
702 where == ELEVATOR_INSERT_SORT)
703 where = ELEVATOR_INSERT_BACK;
708 elv_insert(q, rq, where);
710 EXPORT_SYMBOL(__elv_add_request);
712 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, plug);
719 spin_unlock_irqrestore(q->queue_lock, flags);
721 EXPORT_SYMBOL(elv_add_request);
723 int elv_queue_empty(struct request_queue *q)
725 struct elevator_queue *e = q->elevator;
727 if (!list_empty(&q->queue_head))
730 if (e->ops->elevator_queue_empty_fn)
731 return e->ops->elevator_queue_empty_fn(q);
735 EXPORT_SYMBOL(elv_queue_empty);
737 struct request *elv_latter_request(struct request_queue *q, struct request *rq)
739 struct elevator_queue *e = q->elevator;
741 if (e->ops->elevator_latter_req_fn)
742 return e->ops->elevator_latter_req_fn(q, rq);
746 struct request *elv_former_request(struct request_queue *q, struct request *rq)
748 struct elevator_queue *e = q->elevator;
750 if (e->ops->elevator_former_req_fn)
751 return e->ops->elevator_former_req_fn(q, rq);
755 int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
757 struct elevator_queue *e = q->elevator;
759 if (e->ops->elevator_set_req_fn)
760 return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
762 rq->elevator_private = NULL;
766 void elv_put_request(struct request_queue *q, struct request *rq)
768 struct elevator_queue *e = q->elevator;
770 if (e->ops->elevator_put_req_fn)
771 e->ops->elevator_put_req_fn(rq);
774 int elv_may_queue(struct request_queue *q, int rw)
776 struct elevator_queue *e = q->elevator;
778 if (e->ops->elevator_may_queue_fn)
779 return e->ops->elevator_may_queue_fn(q, rw);
781 return ELV_MQUEUE_MAY;
784 void elv_abort_queue(struct request_queue *q)
788 while (!list_empty(&q->queue_head)) {
789 rq = list_entry_rq(q->queue_head.next);
790 rq->cmd_flags |= REQ_QUIET;
791 trace_block_rq_abort(q, rq);
793 * Mark this request as started so we don't trigger
794 * any debug logic in the end I/O path.
796 blk_start_request(rq);
797 __blk_end_request_all(rq, -EIO);
800 EXPORT_SYMBOL(elv_abort_queue);
802 void elv_completed_request(struct request_queue *q, struct request *rq)
804 struct elevator_queue *e = q->elevator;
807 * request is released from the driver, io must be done
809 if (blk_account_rq(rq)) {
810 q->in_flight[rq_is_sync(rq)]--;
811 if ((rq->cmd_flags & REQ_SORTED) &&
812 e->ops->elevator_completed_req_fn)
813 e->ops->elevator_completed_req_fn(q, rq);
817 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
820 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
822 struct elv_fs_entry *entry = to_elv(attr);
823 struct elevator_queue *e;
829 e = container_of(kobj, struct elevator_queue, kobj);
830 mutex_lock(&e->sysfs_lock);
831 error = e->ops ? entry->show(e, page) : -ENOENT;
832 mutex_unlock(&e->sysfs_lock);
837 elv_attr_store(struct kobject *kobj, struct attribute *attr,
838 const char *page, size_t length)
840 struct elv_fs_entry *entry = to_elv(attr);
841 struct elevator_queue *e;
847 e = container_of(kobj, struct elevator_queue, kobj);
848 mutex_lock(&e->sysfs_lock);
849 error = e->ops ? entry->store(e, page, length) : -ENOENT;
850 mutex_unlock(&e->sysfs_lock);
854 static const struct sysfs_ops elv_sysfs_ops = {
855 .show = elv_attr_show,
856 .store = elv_attr_store,
859 static struct kobj_type elv_ktype = {
860 .sysfs_ops = &elv_sysfs_ops,
861 .release = elevator_release,
864 int elv_register_queue(struct request_queue *q)
866 struct elevator_queue *e = q->elevator;
869 error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
871 struct elv_fs_entry *attr = e->elevator_type->elevator_attrs;
873 while (attr->attr.name) {
874 if (sysfs_create_file(&e->kobj, &attr->attr))
879 kobject_uevent(&e->kobj, KOBJ_ADD);
884 EXPORT_SYMBOL(elv_register_queue);
886 static void __elv_unregister_queue(struct elevator_queue *e)
888 kobject_uevent(&e->kobj, KOBJ_REMOVE);
889 kobject_del(&e->kobj);
893 void elv_unregister_queue(struct request_queue *q)
896 __elv_unregister_queue(q->elevator);
898 EXPORT_SYMBOL(elv_unregister_queue);
900 void elv_register(struct elevator_type *e)
904 spin_lock(&elv_list_lock);
905 BUG_ON(elevator_find(e->elevator_name));
906 list_add_tail(&e->list, &elv_list);
907 spin_unlock(&elv_list_lock);
909 if (!strcmp(e->elevator_name, chosen_elevator) ||
910 (!*chosen_elevator &&
911 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
914 printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
917 EXPORT_SYMBOL_GPL(elv_register);
919 void elv_unregister(struct elevator_type *e)
921 struct task_struct *g, *p;
924 * Iterate every thread in the process to remove the io contexts.
927 read_lock(&tasklist_lock);
928 do_each_thread(g, p) {
931 e->ops.trim(p->io_context);
933 } while_each_thread(g, p);
934 read_unlock(&tasklist_lock);
937 spin_lock(&elv_list_lock);
938 list_del_init(&e->list);
939 spin_unlock(&elv_list_lock);
941 EXPORT_SYMBOL_GPL(elv_unregister);
944 * switch to new_e io scheduler. be careful not to introduce deadlocks -
945 * we don't free the old io scheduler, before we have allocated what we
946 * need for the new one. this way we have a chance of going back to the old
947 * one, if the new one fails init for some reason.
949 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
951 struct elevator_queue *old_elevator, *e;
956 * Allocate new elevator
958 e = elevator_alloc(q, new_e);
962 data = elevator_init_queue(q, e);
964 kobject_put(&e->kobj);
969 * Turn on BYPASS and drain all requests w/ elevator private data
971 spin_lock_irq(q->queue_lock);
972 elv_quiesce_start(q);
975 * Remember old elevator.
977 old_elevator = q->elevator;
980 * attach and start new elevator
982 elevator_attach(q, e, data);
984 spin_unlock_irq(q->queue_lock);
986 if (old_elevator->registered) {
987 __elv_unregister_queue(old_elevator);
989 err = elv_register_queue(q);
995 * finally exit old elevator and turn off BYPASS.
997 elevator_exit(old_elevator);
998 spin_lock_irq(q->queue_lock);
1000 spin_unlock_irq(q->queue_lock);
1002 blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name);
1008 * switch failed, exit the new io scheduler and reattach the old
1009 * one again (along with re-adding the sysfs dir)
1012 q->elevator = old_elevator;
1013 elv_register_queue(q);
1015 spin_lock_irq(q->queue_lock);
1016 queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
1017 spin_unlock_irq(q->queue_lock);
1023 * Switch this queue to the given IO scheduler.
1025 int elevator_change(struct request_queue *q, const char *name)
1027 char elevator_name[ELV_NAME_MAX];
1028 struct elevator_type *e;
1033 strlcpy(elevator_name, name, sizeof(elevator_name));
1034 e = elevator_get(strstrip(elevator_name));
1036 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
1040 if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
1045 return elevator_switch(q, e);
1047 EXPORT_SYMBOL(elevator_change);
1049 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
1057 ret = elevator_change(q, name);
1061 printk(KERN_ERR "elevator: switch to %s failed\n", name);
1065 ssize_t elv_iosched_show(struct request_queue *q, char *name)
1067 struct elevator_queue *e = q->elevator;
1068 struct elevator_type *elv;
1069 struct elevator_type *__e;
1072 if (!q->elevator || !blk_queue_stackable(q))
1073 return sprintf(name, "none\n");
1075 elv = e->elevator_type;
1077 spin_lock(&elv_list_lock);
1078 list_for_each_entry(__e, &elv_list, list) {
1079 if (!strcmp(elv->elevator_name, __e->elevator_name))
1080 len += sprintf(name+len, "[%s] ", elv->elevator_name);
1082 len += sprintf(name+len, "%s ", __e->elevator_name);
1084 spin_unlock(&elv_list_lock);
1086 len += sprintf(len+name, "\n");
1090 struct request *elv_rb_former_request(struct request_queue *q,
1093 struct rb_node *rbprev = rb_prev(&rq->rb_node);
1096 return rb_entry_rq(rbprev);
1100 EXPORT_SYMBOL(elv_rb_former_request);
1102 struct request *elv_rb_latter_request(struct request_queue *q,
1105 struct rb_node *rbnext = rb_next(&rq->rb_node);
1108 return rb_entry_rq(rbnext);
1112 EXPORT_SYMBOL(elv_rb_latter_request);