2 * Block device elevator/IO-scheduler.
4 * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
6 * 30042000 Jens Axboe <axboe@suse.de> :
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>
38 #include <asm/uaccess.h>
40 static DEFINE_SPINLOCK(elv_list_lock);
41 static LIST_HEAD(elv_list);
46 static const int elv_hash_shift = 6;
47 #define ELV_HASH_BLOCK(sec) ((sec) >> 3)
48 #define ELV_HASH_FN(sec) (hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift))
49 #define ELV_HASH_ENTRIES (1 << elv_hash_shift)
50 #define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors)
51 #define ELV_ON_HASH(rq) (!hlist_unhashed(&(rq)->hash))
54 * can we safely merge with this request?
56 inline int elv_rq_merge_ok(struct request *rq, struct bio *bio)
58 if (!rq_mergeable(rq))
62 * different data direction or already started, don't merge
64 if (bio_data_dir(bio) != rq_data_dir(rq))
68 * same device and no special stuff set, merge is ok
70 if (rq->rq_disk == bio->bi_bdev->bd_disk && !rq->special)
75 EXPORT_SYMBOL(elv_rq_merge_ok);
77 static inline int elv_try_merge(struct request *__rq, struct bio *bio)
79 int ret = ELEVATOR_NO_MERGE;
82 * we can merge and sequence is ok, check if it's possible
84 if (elv_rq_merge_ok(__rq, bio)) {
85 if (__rq->sector + __rq->nr_sectors == bio->bi_sector)
86 ret = ELEVATOR_BACK_MERGE;
87 else if (__rq->sector - bio_sectors(bio) == bio->bi_sector)
88 ret = ELEVATOR_FRONT_MERGE;
94 static struct elevator_type *elevator_find(const char *name)
96 struct elevator_type *e = NULL;
97 struct list_head *entry;
99 list_for_each(entry, &elv_list) {
100 struct elevator_type *__e;
102 __e = list_entry(entry, struct elevator_type, list);
104 if (!strcmp(__e->elevator_name, name)) {
113 static void elevator_put(struct elevator_type *e)
115 module_put(e->elevator_owner);
118 static struct elevator_type *elevator_get(const char *name)
120 struct elevator_type *e;
122 spin_lock_irq(&elv_list_lock);
124 e = elevator_find(name);
125 if (e && !try_module_get(e->elevator_owner))
128 spin_unlock_irq(&elv_list_lock);
133 static void *elevator_init_queue(request_queue_t *q, struct elevator_queue *eq)
135 return eq->ops->elevator_init_fn(q, eq);
138 static void elevator_attach(request_queue_t *q, struct elevator_queue *eq,
142 eq->elevator_data = data;
145 static char chosen_elevator[16];
147 static int __init elevator_setup(char *str)
150 * Be backwards-compatible with previous kernels, so users
151 * won't get the wrong elevator.
153 if (!strcmp(str, "as"))
154 strcpy(chosen_elevator, "anticipatory");
156 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
160 __setup("elevator=", elevator_setup);
162 static struct kobj_type elv_ktype;
164 static elevator_t *elevator_alloc(struct elevator_type *e)
169 eq = kmalloc(sizeof(elevator_t), GFP_KERNEL);
173 memset(eq, 0, sizeof(*eq));
175 eq->elevator_type = e;
176 kobject_init(&eq->kobj);
177 snprintf(eq->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
178 eq->kobj.ktype = &elv_ktype;
179 mutex_init(&eq->sysfs_lock);
181 eq->hash = kmalloc(sizeof(struct hlist_head) * ELV_HASH_ENTRIES, GFP_KERNEL);
185 for (i = 0; i < ELV_HASH_ENTRIES; i++)
186 INIT_HLIST_HEAD(&eq->hash[i]);
195 static void elevator_release(struct kobject *kobj)
197 elevator_t *e = container_of(kobj, elevator_t, kobj);
199 elevator_put(e->elevator_type);
204 int elevator_init(request_queue_t *q, char *name)
206 struct elevator_type *e = NULL;
207 struct elevator_queue *eq;
211 INIT_LIST_HEAD(&q->queue_head);
212 q->last_merge = NULL;
214 q->boundary_rq = NULL;
216 if (name && !(e = elevator_get(name)))
219 if (!e && *chosen_elevator && !(e = elevator_get(chosen_elevator)))
220 printk("I/O scheduler %s not found\n", chosen_elevator);
222 if (!e && !(e = elevator_get(CONFIG_DEFAULT_IOSCHED))) {
223 printk("Default I/O scheduler not found, using no-op\n");
224 e = elevator_get("noop");
227 eq = elevator_alloc(e);
231 data = elevator_init_queue(q, eq);
233 kobject_put(&eq->kobj);
237 elevator_attach(q, eq, data);
241 EXPORT_SYMBOL(elevator_init);
243 void elevator_exit(elevator_t *e)
245 mutex_lock(&e->sysfs_lock);
246 if (e->ops->elevator_exit_fn)
247 e->ops->elevator_exit_fn(e);
249 mutex_unlock(&e->sysfs_lock);
251 kobject_put(&e->kobj);
254 EXPORT_SYMBOL(elevator_exit);
256 static inline void __elv_rqhash_del(struct request *rq)
258 hlist_del_init(&rq->hash);
261 static void elv_rqhash_del(request_queue_t *q, struct request *rq)
264 __elv_rqhash_del(rq);
267 static void elv_rqhash_add(request_queue_t *q, struct request *rq)
269 elevator_t *e = q->elevator;
271 BUG_ON(ELV_ON_HASH(rq));
272 hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
275 static void elv_rqhash_reposition(request_queue_t *q, struct request *rq)
277 __elv_rqhash_del(rq);
278 elv_rqhash_add(q, rq);
281 static struct request *elv_rqhash_find(request_queue_t *q, sector_t offset)
283 elevator_t *e = q->elevator;
284 struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
285 struct hlist_node *entry, *next;
288 hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
289 BUG_ON(!ELV_ON_HASH(rq));
291 if (unlikely(!rq_mergeable(rq))) {
292 __elv_rqhash_del(rq);
296 if (rq_hash_key(rq) == offset)
304 * RB-tree support functions for inserting/lookup/removal of requests
305 * in a sorted RB tree.
307 struct request *elv_rb_add(struct rb_root *root, struct request *rq)
309 struct rb_node **p = &root->rb_node;
310 struct rb_node *parent = NULL;
311 struct request *__rq;
315 __rq = rb_entry(parent, struct request, rb_node);
317 if (rq->sector < __rq->sector)
319 else if (rq->sector > __rq->sector)
325 rb_link_node(&rq->rb_node, parent, p);
326 rb_insert_color(&rq->rb_node, root);
330 EXPORT_SYMBOL(elv_rb_add);
332 void elv_rb_del(struct rb_root *root, struct request *rq)
334 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
335 rb_erase(&rq->rb_node, root);
336 RB_CLEAR_NODE(&rq->rb_node);
339 EXPORT_SYMBOL(elv_rb_del);
341 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
343 struct rb_node *n = root->rb_node;
347 rq = rb_entry(n, struct request, rb_node);
349 if (sector < rq->sector)
351 else if (sector > rq->sector)
360 EXPORT_SYMBOL(elv_rb_find);
363 * Insert rq into dispatch queue of q. Queue lock must be held on
364 * entry. rq is sort insted into the dispatch queue. To be used by
365 * specific elevators.
367 void elv_dispatch_sort(request_queue_t *q, struct request *rq)
370 struct list_head *entry;
372 if (q->last_merge == rq)
373 q->last_merge = NULL;
375 elv_rqhash_del(q, rq);
379 boundary = q->end_sector;
381 list_for_each_prev(entry, &q->queue_head) {
382 struct request *pos = list_entry_rq(entry);
384 if (pos->cmd_flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED))
386 if (rq->sector >= boundary) {
387 if (pos->sector < boundary)
390 if (pos->sector >= boundary)
393 if (rq->sector >= pos->sector)
397 list_add(&rq->queuelist, entry);
400 EXPORT_SYMBOL(elv_dispatch_sort);
403 * Insert rq into dispatch queue of q. Queue lock must be held on
404 * entry. rq is added to the back of the dispatch queue. To be used by
405 * specific elevators.
407 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
409 if (q->last_merge == rq)
410 q->last_merge = NULL;
412 elv_rqhash_del(q, rq);
416 q->end_sector = rq_end_sector(rq);
418 list_add_tail(&rq->queuelist, &q->queue_head);
421 EXPORT_SYMBOL(elv_dispatch_add_tail);
423 int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
425 elevator_t *e = q->elevator;
426 struct request *__rq;
430 * First try one-hit cache.
433 ret = elv_try_merge(q->last_merge, bio);
434 if (ret != ELEVATOR_NO_MERGE) {
435 *req = q->last_merge;
441 * See if our hash lookup can find a potential backmerge.
443 __rq = elv_rqhash_find(q, bio->bi_sector);
444 if (__rq && elv_rq_merge_ok(__rq, bio)) {
446 return ELEVATOR_BACK_MERGE;
449 if (e->ops->elevator_merge_fn)
450 return e->ops->elevator_merge_fn(q, req, bio);
452 return ELEVATOR_NO_MERGE;
455 void elv_merged_request(request_queue_t *q, struct request *rq, int type)
457 elevator_t *e = q->elevator;
459 if (e->ops->elevator_merged_fn)
460 e->ops->elevator_merged_fn(q, rq, type);
462 if (type == ELEVATOR_BACK_MERGE)
463 elv_rqhash_reposition(q, rq);
468 void elv_merge_requests(request_queue_t *q, struct request *rq,
469 struct request *next)
471 elevator_t *e = q->elevator;
473 if (e->ops->elevator_merge_req_fn)
474 e->ops->elevator_merge_req_fn(q, rq, next);
476 elv_rqhash_reposition(q, rq);
477 elv_rqhash_del(q, next);
483 void elv_requeue_request(request_queue_t *q, struct request *rq)
485 elevator_t *e = q->elevator;
488 * it already went through dequeue, we need to decrement the
489 * in_flight count again
491 if (blk_account_rq(rq)) {
493 if (blk_sorted_rq(rq) && e->ops->elevator_deactivate_req_fn)
494 e->ops->elevator_deactivate_req_fn(q, rq);
497 rq->cmd_flags &= ~REQ_STARTED;
499 elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
502 static void elv_drain_elevator(request_queue_t *q)
505 while (q->elevator->ops->elevator_dispatch_fn(q, 1))
507 if (q->nr_sorted == 0)
509 if (printed++ < 10) {
510 printk(KERN_ERR "%s: forced dispatching is broken "
511 "(nr_sorted=%u), please report this\n",
512 q->elevator->elevator_type->elevator_name, q->nr_sorted);
516 void elv_insert(request_queue_t *q, struct request *rq, int where)
518 struct list_head *pos;
522 blk_add_trace_rq(q, rq, BLK_TA_INSERT);
527 case ELEVATOR_INSERT_FRONT:
528 rq->cmd_flags |= REQ_SOFTBARRIER;
530 list_add(&rq->queuelist, &q->queue_head);
533 case ELEVATOR_INSERT_BACK:
534 rq->cmd_flags |= REQ_SOFTBARRIER;
535 elv_drain_elevator(q);
536 list_add_tail(&rq->queuelist, &q->queue_head);
538 * We kick the queue here for the following reasons.
539 * - The elevator might have returned NULL previously
540 * to delay requests and returned them now. As the
541 * queue wasn't empty before this request, ll_rw_blk
542 * won't run the queue on return, resulting in hang.
543 * - Usually, back inserted requests won't be merged
544 * with anything. There's no point in delaying queue
551 case ELEVATOR_INSERT_SORT:
552 BUG_ON(!blk_fs_request(rq));
553 rq->cmd_flags |= REQ_SORTED;
555 if (rq_mergeable(rq)) {
556 elv_rqhash_add(q, rq);
562 * Some ioscheds (cfq) run q->request_fn directly, so
563 * rq cannot be accessed after calling
564 * elevator_add_req_fn.
566 q->elevator->ops->elevator_add_req_fn(q, rq);
569 case ELEVATOR_INSERT_REQUEUE:
571 * If ordered flush isn't in progress, we do front
572 * insertion; otherwise, requests should be requeued
575 rq->cmd_flags |= REQ_SOFTBARRIER;
577 if (q->ordseq == 0) {
578 list_add(&rq->queuelist, &q->queue_head);
582 ordseq = blk_ordered_req_seq(rq);
584 list_for_each(pos, &q->queue_head) {
585 struct request *pos_rq = list_entry_rq(pos);
586 if (ordseq <= blk_ordered_req_seq(pos_rq))
590 list_add_tail(&rq->queuelist, pos);
592 * most requeues happen because of a busy condition, don't
593 * force unplug of the queue for that case.
599 printk(KERN_ERR "%s: bad insertion point %d\n",
600 __FUNCTION__, where);
604 if (unplug_it && blk_queue_plugged(q)) {
605 int nrq = q->rq.count[READ] + q->rq.count[WRITE]
608 if (nrq >= q->unplug_thresh)
609 __generic_unplug_device(q);
613 void __elv_add_request(request_queue_t *q, struct request *rq, int where,
617 rq->cmd_flags |= REQ_ORDERED_COLOR;
619 if (rq->cmd_flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
621 * toggle ordered color
623 if (blk_barrier_rq(rq))
627 * barriers implicitly indicate back insertion
629 if (where == ELEVATOR_INSERT_SORT)
630 where = ELEVATOR_INSERT_BACK;
633 * this request is scheduling boundary, update
636 if (blk_fs_request(rq)) {
637 q->end_sector = rq_end_sector(rq);
640 } else if (!(rq->cmd_flags & REQ_ELVPRIV) && where == ELEVATOR_INSERT_SORT)
641 where = ELEVATOR_INSERT_BACK;
646 elv_insert(q, rq, where);
649 EXPORT_SYMBOL(__elv_add_request);
651 void elv_add_request(request_queue_t *q, struct request *rq, int where,
656 spin_lock_irqsave(q->queue_lock, flags);
657 __elv_add_request(q, rq, where, plug);
658 spin_unlock_irqrestore(q->queue_lock, flags);
661 EXPORT_SYMBOL(elv_add_request);
663 static inline struct request *__elv_next_request(request_queue_t *q)
668 while (!list_empty(&q->queue_head)) {
669 rq = list_entry_rq(q->queue_head.next);
670 if (blk_do_ordered(q, &rq))
674 if (!q->elevator->ops->elevator_dispatch_fn(q, 0))
679 struct request *elv_next_request(request_queue_t *q)
684 while ((rq = __elv_next_request(q)) != NULL) {
685 if (!(rq->cmd_flags & REQ_STARTED)) {
686 elevator_t *e = q->elevator;
689 * This is the first time the device driver
690 * sees this request (possibly after
691 * requeueing). Notify IO scheduler.
693 if (blk_sorted_rq(rq) &&
694 e->ops->elevator_activate_req_fn)
695 e->ops->elevator_activate_req_fn(q, rq);
698 * just mark as started even if we don't start
699 * it, a request that has been delayed should
700 * not be passed by new incoming requests
702 rq->cmd_flags |= REQ_STARTED;
703 blk_add_trace_rq(q, rq, BLK_TA_ISSUE);
706 if (!q->boundary_rq || q->boundary_rq == rq) {
707 q->end_sector = rq_end_sector(rq);
708 q->boundary_rq = NULL;
711 if ((rq->cmd_flags & REQ_DONTPREP) || !q->prep_rq_fn)
714 ret = q->prep_rq_fn(q, rq);
715 if (ret == BLKPREP_OK) {
717 } else if (ret == BLKPREP_DEFER) {
719 * the request may have been (partially) prepped.
720 * we need to keep this request in the front to
721 * avoid resource deadlock. REQ_STARTED will
722 * prevent other fs requests from passing this one.
726 } else if (ret == BLKPREP_KILL) {
727 int nr_bytes = rq->hard_nr_sectors << 9;
730 nr_bytes = rq->data_len;
732 blkdev_dequeue_request(rq);
733 rq->cmd_flags |= REQ_QUIET;
734 end_that_request_chunk(rq, 0, nr_bytes);
735 end_that_request_last(rq, 0);
737 printk(KERN_ERR "%s: bad return=%d\n", __FUNCTION__,
746 EXPORT_SYMBOL(elv_next_request);
748 void elv_dequeue_request(request_queue_t *q, struct request *rq)
750 BUG_ON(list_empty(&rq->queuelist));
751 BUG_ON(ELV_ON_HASH(rq));
753 list_del_init(&rq->queuelist);
756 * the time frame between a request being removed from the lists
757 * and to it is freed is accounted as io that is in progress at
760 if (blk_account_rq(rq))
764 EXPORT_SYMBOL(elv_dequeue_request);
766 int elv_queue_empty(request_queue_t *q)
768 elevator_t *e = q->elevator;
770 if (!list_empty(&q->queue_head))
773 if (e->ops->elevator_queue_empty_fn)
774 return e->ops->elevator_queue_empty_fn(q);
779 EXPORT_SYMBOL(elv_queue_empty);
781 struct request *elv_latter_request(request_queue_t *q, struct request *rq)
783 elevator_t *e = q->elevator;
785 if (e->ops->elevator_latter_req_fn)
786 return e->ops->elevator_latter_req_fn(q, rq);
790 struct request *elv_former_request(request_queue_t *q, struct request *rq)
792 elevator_t *e = q->elevator;
794 if (e->ops->elevator_former_req_fn)
795 return e->ops->elevator_former_req_fn(q, rq);
799 int elv_set_request(request_queue_t *q, struct request *rq, gfp_t gfp_mask)
801 elevator_t *e = q->elevator;
803 if (e->ops->elevator_set_req_fn)
804 return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
806 rq->elevator_private = NULL;
810 void elv_put_request(request_queue_t *q, struct request *rq)
812 elevator_t *e = q->elevator;
814 if (e->ops->elevator_put_req_fn)
815 e->ops->elevator_put_req_fn(q, rq);
818 int elv_may_queue(request_queue_t *q, int rw)
820 elevator_t *e = q->elevator;
822 if (e->ops->elevator_may_queue_fn)
823 return e->ops->elevator_may_queue_fn(q, rw);
825 return ELV_MQUEUE_MAY;
828 void elv_completed_request(request_queue_t *q, struct request *rq)
830 elevator_t *e = q->elevator;
833 * request is released from the driver, io must be done
835 if (blk_account_rq(rq)) {
837 if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
838 e->ops->elevator_completed_req_fn(q, rq);
842 * Check if the queue is waiting for fs requests to be
843 * drained for flush sequence.
845 if (unlikely(q->ordseq)) {
846 struct request *first_rq = list_entry_rq(q->queue_head.next);
847 if (q->in_flight == 0 &&
848 blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
849 blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
850 blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
856 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
859 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
861 elevator_t *e = container_of(kobj, elevator_t, kobj);
862 struct elv_fs_entry *entry = to_elv(attr);
868 mutex_lock(&e->sysfs_lock);
869 error = e->ops ? entry->show(e, page) : -ENOENT;
870 mutex_unlock(&e->sysfs_lock);
875 elv_attr_store(struct kobject *kobj, struct attribute *attr,
876 const char *page, size_t length)
878 elevator_t *e = container_of(kobj, elevator_t, kobj);
879 struct elv_fs_entry *entry = to_elv(attr);
885 mutex_lock(&e->sysfs_lock);
886 error = e->ops ? entry->store(e, page, length) : -ENOENT;
887 mutex_unlock(&e->sysfs_lock);
891 static struct sysfs_ops elv_sysfs_ops = {
892 .show = elv_attr_show,
893 .store = elv_attr_store,
896 static struct kobj_type elv_ktype = {
897 .sysfs_ops = &elv_sysfs_ops,
898 .release = elevator_release,
901 int elv_register_queue(struct request_queue *q)
903 elevator_t *e = q->elevator;
906 e->kobj.parent = &q->kobj;
908 error = kobject_add(&e->kobj);
910 struct elv_fs_entry *attr = e->elevator_type->elevator_attrs;
912 while (attr->attr.name) {
913 if (sysfs_create_file(&e->kobj, &attr->attr))
918 kobject_uevent(&e->kobj, KOBJ_ADD);
923 static void __elv_unregister_queue(elevator_t *e)
925 kobject_uevent(&e->kobj, KOBJ_REMOVE);
926 kobject_del(&e->kobj);
929 void elv_unregister_queue(struct request_queue *q)
932 __elv_unregister_queue(q->elevator);
935 int elv_register(struct elevator_type *e)
937 spin_lock_irq(&elv_list_lock);
938 BUG_ON(elevator_find(e->elevator_name));
939 list_add_tail(&e->list, &elv_list);
940 spin_unlock_irq(&elv_list_lock);
942 printk(KERN_INFO "io scheduler %s registered", e->elevator_name);
943 if (!strcmp(e->elevator_name, chosen_elevator) ||
944 (!*chosen_elevator &&
945 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
946 printk(" (default)");
950 EXPORT_SYMBOL_GPL(elv_register);
952 void elv_unregister(struct elevator_type *e)
954 struct task_struct *g, *p;
957 * Iterate every thread in the process to remove the io contexts.
960 read_lock(&tasklist_lock);
961 do_each_thread(g, p) {
964 e->ops.trim(p->io_context);
966 } while_each_thread(g, p);
967 read_unlock(&tasklist_lock);
970 spin_lock_irq(&elv_list_lock);
971 list_del_init(&e->list);
972 spin_unlock_irq(&elv_list_lock);
974 EXPORT_SYMBOL_GPL(elv_unregister);
977 * switch to new_e io scheduler. be careful not to introduce deadlocks -
978 * we don't free the old io scheduler, before we have allocated what we
979 * need for the new one. this way we have a chance of going back to the old
980 * one, if the new one fails init for some reason.
982 static int elevator_switch(request_queue_t *q, struct elevator_type *new_e)
984 elevator_t *old_elevator, *e;
988 * Allocate new elevator
990 e = elevator_alloc(new_e);
994 data = elevator_init_queue(q, e);
996 kobject_put(&e->kobj);
1001 * Turn on BYPASS and drain all requests w/ elevator private data
1003 spin_lock_irq(q->queue_lock);
1005 set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1007 elv_drain_elevator(q);
1009 while (q->rq.elvpriv) {
1012 spin_unlock_irq(q->queue_lock);
1014 spin_lock_irq(q->queue_lock);
1015 elv_drain_elevator(q);
1019 * Remember old elevator.
1021 old_elevator = q->elevator;
1024 * attach and start new elevator
1026 elevator_attach(q, e, data);
1028 spin_unlock_irq(q->queue_lock);
1030 __elv_unregister_queue(old_elevator);
1032 if (elv_register_queue(q))
1036 * finally exit old elevator and turn off BYPASS.
1038 elevator_exit(old_elevator);
1039 clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1044 * switch failed, exit the new io scheduler and reattach the old
1045 * one again (along with re-adding the sysfs dir)
1048 q->elevator = old_elevator;
1049 elv_register_queue(q);
1050 clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1054 ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
1056 char elevator_name[ELV_NAME_MAX];
1058 struct elevator_type *e;
1060 elevator_name[sizeof(elevator_name) - 1] = '\0';
1061 strncpy(elevator_name, name, sizeof(elevator_name) - 1);
1062 len = strlen(elevator_name);
1064 if (len && elevator_name[len - 1] == '\n')
1065 elevator_name[len - 1] = '\0';
1067 e = elevator_get(elevator_name);
1069 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
1073 if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
1078 if (!elevator_switch(q, e))
1079 printk(KERN_ERR "elevator: switch to %s failed\n",elevator_name);
1083 ssize_t elv_iosched_show(request_queue_t *q, char *name)
1085 elevator_t *e = q->elevator;
1086 struct elevator_type *elv = e->elevator_type;
1087 struct list_head *entry;
1090 spin_lock_irq(q->queue_lock);
1091 list_for_each(entry, &elv_list) {
1092 struct elevator_type *__e;
1094 __e = list_entry(entry, struct elevator_type, list);
1095 if (!strcmp(elv->elevator_name, __e->elevator_name))
1096 len += sprintf(name+len, "[%s] ", elv->elevator_name);
1098 len += sprintf(name+len, "%s ", __e->elevator_name);
1100 spin_unlock_irq(q->queue_lock);
1102 len += sprintf(len+name, "\n");
1106 struct request *elv_rb_former_request(request_queue_t *q, struct request *rq)
1108 struct rb_node *rbprev = rb_prev(&rq->rb_node);
1111 return rb_entry_rq(rbprev);
1116 EXPORT_SYMBOL(elv_rb_former_request);
1118 struct request *elv_rb_latter_request(request_queue_t *q, struct request *rq)
1120 struct rb_node *rbnext = rb_next(&rq->rb_node);
1123 return rb_entry_rq(rbnext);
1128 EXPORT_SYMBOL(elv_rb_latter_request);