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 &&
71 !rq->waiting && !rq->special)
76 EXPORT_SYMBOL(elv_rq_merge_ok);
78 static inline int elv_try_merge(struct request *__rq, struct bio *bio)
80 int ret = ELEVATOR_NO_MERGE;
83 * we can merge and sequence is ok, check if it's possible
85 if (elv_rq_merge_ok(__rq, bio)) {
86 if (__rq->sector + __rq->nr_sectors == bio->bi_sector)
87 ret = ELEVATOR_BACK_MERGE;
88 else if (__rq->sector - bio_sectors(bio) == bio->bi_sector)
89 ret = ELEVATOR_FRONT_MERGE;
95 static struct elevator_type *elevator_find(const char *name)
97 struct elevator_type *e = NULL;
98 struct list_head *entry;
100 list_for_each(entry, &elv_list) {
101 struct elevator_type *__e;
103 __e = list_entry(entry, struct elevator_type, list);
105 if (!strcmp(__e->elevator_name, name)) {
114 static void elevator_put(struct elevator_type *e)
116 module_put(e->elevator_owner);
119 static struct elevator_type *elevator_get(const char *name)
121 struct elevator_type *e;
123 spin_lock_irq(&elv_list_lock);
125 e = elevator_find(name);
126 if (e && !try_module_get(e->elevator_owner))
129 spin_unlock_irq(&elv_list_lock);
134 static void *elevator_init_queue(request_queue_t *q, struct elevator_queue *eq)
136 return eq->ops->elevator_init_fn(q, eq);
139 static void elevator_attach(request_queue_t *q, struct elevator_queue *eq,
143 eq->elevator_data = data;
146 static char chosen_elevator[16];
148 static int __init elevator_setup(char *str)
151 * Be backwards-compatible with previous kernels, so users
152 * won't get the wrong elevator.
154 if (!strcmp(str, "as"))
155 strcpy(chosen_elevator, "anticipatory");
157 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
161 __setup("elevator=", elevator_setup);
163 static struct kobj_type elv_ktype;
165 static elevator_t *elevator_alloc(struct elevator_type *e)
170 eq = kmalloc(sizeof(elevator_t), GFP_KERNEL);
174 memset(eq, 0, sizeof(*eq));
176 eq->elevator_type = e;
177 kobject_init(&eq->kobj);
178 snprintf(eq->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
179 eq->kobj.ktype = &elv_ktype;
180 mutex_init(&eq->sysfs_lock);
182 eq->hash = kmalloc(sizeof(struct hlist_head) * ELV_HASH_ENTRIES, GFP_KERNEL);
186 for (i = 0; i < ELV_HASH_ENTRIES; i++)
187 INIT_HLIST_HEAD(&eq->hash[i]);
196 static void elevator_release(struct kobject *kobj)
198 elevator_t *e = container_of(kobj, elevator_t, kobj);
200 elevator_put(e->elevator_type);
205 int elevator_init(request_queue_t *q, char *name)
207 struct elevator_type *e = NULL;
208 struct elevator_queue *eq;
212 INIT_LIST_HEAD(&q->queue_head);
213 q->last_merge = NULL;
215 q->boundary_rq = NULL;
217 if (name && !(e = elevator_get(name)))
220 if (!e && *chosen_elevator && !(e = elevator_get(chosen_elevator)))
221 printk("I/O scheduler %s not found\n", chosen_elevator);
223 if (!e && !(e = elevator_get(CONFIG_DEFAULT_IOSCHED))) {
224 printk("Default I/O scheduler not found, using no-op\n");
225 e = elevator_get("noop");
228 eq = elevator_alloc(e);
232 data = elevator_init_queue(q, eq);
234 kobject_put(&eq->kobj);
238 elevator_attach(q, eq, data);
242 EXPORT_SYMBOL(elevator_init);
244 void elevator_exit(elevator_t *e)
246 mutex_lock(&e->sysfs_lock);
247 if (e->ops->elevator_exit_fn)
248 e->ops->elevator_exit_fn(e);
250 mutex_unlock(&e->sysfs_lock);
252 kobject_put(&e->kobj);
255 EXPORT_SYMBOL(elevator_exit);
257 static inline void __elv_rqhash_del(struct request *rq)
259 hlist_del_init(&rq->hash);
262 static void elv_rqhash_del(request_queue_t *q, struct request *rq)
265 __elv_rqhash_del(rq);
268 static void elv_rqhash_add(request_queue_t *q, struct request *rq)
270 elevator_t *e = q->elevator;
272 BUG_ON(ELV_ON_HASH(rq));
273 hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
276 static void elv_rqhash_reposition(request_queue_t *q, struct request *rq)
278 __elv_rqhash_del(rq);
279 elv_rqhash_add(q, rq);
282 static struct request *elv_rqhash_find(request_queue_t *q, sector_t offset)
284 elevator_t *e = q->elevator;
285 struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
286 struct hlist_node *entry, *next;
289 hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
290 BUG_ON(!ELV_ON_HASH(rq));
292 if (unlikely(!rq_mergeable(rq))) {
293 __elv_rqhash_del(rq);
297 if (rq_hash_key(rq) == offset)
305 * RB-tree support functions for inserting/lookup/removal of requests
306 * in a sorted RB tree.
308 struct request *elv_rb_add(struct rb_root *root, struct request *rq)
310 struct rb_node **p = &root->rb_node;
311 struct rb_node *parent = NULL;
312 struct request *__rq;
316 __rq = rb_entry(parent, struct request, rb_node);
318 if (rq->sector < __rq->sector)
320 else if (rq->sector > __rq->sector)
326 rb_link_node(&rq->rb_node, parent, p);
327 rb_insert_color(&rq->rb_node, root);
331 EXPORT_SYMBOL(elv_rb_add);
333 void elv_rb_del(struct rb_root *root, struct request *rq)
335 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
336 rb_erase(&rq->rb_node, root);
337 RB_CLEAR_NODE(&rq->rb_node);
340 EXPORT_SYMBOL(elv_rb_del);
342 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
344 struct rb_node *n = root->rb_node;
348 rq = rb_entry(n, struct request, rb_node);
350 if (sector < rq->sector)
352 else if (sector > rq->sector)
361 EXPORT_SYMBOL(elv_rb_find);
364 * Insert rq into dispatch queue of q. Queue lock must be held on
365 * entry. rq is sort insted into the dispatch queue. To be used by
366 * specific elevators.
368 void elv_dispatch_sort(request_queue_t *q, struct request *rq)
371 struct list_head *entry;
373 if (q->last_merge == rq)
374 q->last_merge = NULL;
376 elv_rqhash_del(q, rq);
380 boundary = q->end_sector;
382 list_for_each_prev(entry, &q->queue_head) {
383 struct request *pos = list_entry_rq(entry);
385 if (pos->cmd_flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED))
387 if (rq->sector >= boundary) {
388 if (pos->sector < boundary)
391 if (pos->sector >= boundary)
394 if (rq->sector >= pos->sector)
398 list_add(&rq->queuelist, entry);
401 EXPORT_SYMBOL(elv_dispatch_sort);
404 * Insert rq into dispatch queue of q. Queue lock must be held on
405 * entry. rq is added to the back of the dispatch queue. To be used by
406 * specific elevators.
408 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
410 if (q->last_merge == rq)
411 q->last_merge = NULL;
413 elv_rqhash_del(q, rq);
417 q->end_sector = rq_end_sector(rq);
419 list_add_tail(&rq->queuelist, &q->queue_head);
422 EXPORT_SYMBOL(elv_dispatch_add_tail);
424 int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
426 elevator_t *e = q->elevator;
427 struct request *__rq;
431 * First try one-hit cache.
434 ret = elv_try_merge(q->last_merge, bio);
435 if (ret != ELEVATOR_NO_MERGE) {
436 *req = q->last_merge;
442 * See if our hash lookup can find a potential backmerge.
444 __rq = elv_rqhash_find(q, bio->bi_sector);
445 if (__rq && elv_rq_merge_ok(__rq, bio)) {
447 return ELEVATOR_BACK_MERGE;
450 if (e->ops->elevator_merge_fn)
451 return e->ops->elevator_merge_fn(q, req, bio);
453 return ELEVATOR_NO_MERGE;
456 void elv_merged_request(request_queue_t *q, struct request *rq, int type)
458 elevator_t *e = q->elevator;
460 if (e->ops->elevator_merged_fn)
461 e->ops->elevator_merged_fn(q, rq, type);
463 if (type == ELEVATOR_BACK_MERGE)
464 elv_rqhash_reposition(q, rq);
469 void elv_merge_requests(request_queue_t *q, struct request *rq,
470 struct request *next)
472 elevator_t *e = q->elevator;
474 if (e->ops->elevator_merge_req_fn)
475 e->ops->elevator_merge_req_fn(q, rq, next);
477 elv_rqhash_reposition(q, rq);
478 elv_rqhash_del(q, next);
484 void elv_requeue_request(request_queue_t *q, struct request *rq)
486 elevator_t *e = q->elevator;
489 * it already went through dequeue, we need to decrement the
490 * in_flight count again
492 if (blk_account_rq(rq)) {
494 if (blk_sorted_rq(rq) && e->ops->elevator_deactivate_req_fn)
495 e->ops->elevator_deactivate_req_fn(q, rq);
498 rq->cmd_flags &= ~REQ_STARTED;
500 elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
503 static void elv_drain_elevator(request_queue_t *q)
506 while (q->elevator->ops->elevator_dispatch_fn(q, 1))
508 if (q->nr_sorted == 0)
510 if (printed++ < 10) {
511 printk(KERN_ERR "%s: forced dispatching is broken "
512 "(nr_sorted=%u), please report this\n",
513 q->elevator->elevator_type->elevator_name, q->nr_sorted);
517 void elv_insert(request_queue_t *q, struct request *rq, int where)
519 struct list_head *pos;
523 blk_add_trace_rq(q, rq, BLK_TA_INSERT);
528 case ELEVATOR_INSERT_FRONT:
529 rq->cmd_flags |= REQ_SOFTBARRIER;
531 list_add(&rq->queuelist, &q->queue_head);
534 case ELEVATOR_INSERT_BACK:
535 rq->cmd_flags |= REQ_SOFTBARRIER;
536 elv_drain_elevator(q);
537 list_add_tail(&rq->queuelist, &q->queue_head);
539 * We kick the queue here for the following reasons.
540 * - The elevator might have returned NULL previously
541 * to delay requests and returned them now. As the
542 * queue wasn't empty before this request, ll_rw_blk
543 * won't run the queue on return, resulting in hang.
544 * - Usually, back inserted requests won't be merged
545 * with anything. There's no point in delaying queue
552 case ELEVATOR_INSERT_SORT:
553 BUG_ON(!blk_fs_request(rq));
554 rq->cmd_flags |= REQ_SORTED;
556 if (rq_mergeable(rq)) {
557 elv_rqhash_add(q, rq);
563 * Some ioscheds (cfq) run q->request_fn directly, so
564 * rq cannot be accessed after calling
565 * elevator_add_req_fn.
567 q->elevator->ops->elevator_add_req_fn(q, rq);
570 case ELEVATOR_INSERT_REQUEUE:
572 * If ordered flush isn't in progress, we do front
573 * insertion; otherwise, requests should be requeued
576 rq->cmd_flags |= REQ_SOFTBARRIER;
578 if (q->ordseq == 0) {
579 list_add(&rq->queuelist, &q->queue_head);
583 ordseq = blk_ordered_req_seq(rq);
585 list_for_each(pos, &q->queue_head) {
586 struct request *pos_rq = list_entry_rq(pos);
587 if (ordseq <= blk_ordered_req_seq(pos_rq))
591 list_add_tail(&rq->queuelist, pos);
593 * most requeues happen because of a busy condition, don't
594 * force unplug of the queue for that case.
600 printk(KERN_ERR "%s: bad insertion point %d\n",
601 __FUNCTION__, where);
605 if (unplug_it && blk_queue_plugged(q)) {
606 int nrq = q->rq.count[READ] + q->rq.count[WRITE]
609 if (nrq >= q->unplug_thresh)
610 __generic_unplug_device(q);
614 void __elv_add_request(request_queue_t *q, struct request *rq, int where,
618 rq->cmd_flags |= REQ_ORDERED_COLOR;
620 if (rq->cmd_flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
622 * toggle ordered color
624 if (blk_barrier_rq(rq))
628 * barriers implicitly indicate back insertion
630 if (where == ELEVATOR_INSERT_SORT)
631 where = ELEVATOR_INSERT_BACK;
634 * this request is scheduling boundary, update
637 if (blk_fs_request(rq)) {
638 q->end_sector = rq_end_sector(rq);
641 } else if (!(rq->cmd_flags & REQ_ELVPRIV) && where == ELEVATOR_INSERT_SORT)
642 where = ELEVATOR_INSERT_BACK;
647 elv_insert(q, rq, where);
650 EXPORT_SYMBOL(__elv_add_request);
652 void elv_add_request(request_queue_t *q, struct request *rq, int where,
657 spin_lock_irqsave(q->queue_lock, flags);
658 __elv_add_request(q, rq, where, plug);
659 spin_unlock_irqrestore(q->queue_lock, flags);
662 EXPORT_SYMBOL(elv_add_request);
664 static inline struct request *__elv_next_request(request_queue_t *q)
669 while (!list_empty(&q->queue_head)) {
670 rq = list_entry_rq(q->queue_head.next);
671 if (blk_do_ordered(q, &rq))
675 if (!q->elevator->ops->elevator_dispatch_fn(q, 0))
680 struct request *elv_next_request(request_queue_t *q)
685 while ((rq = __elv_next_request(q)) != NULL) {
686 if (!(rq->cmd_flags & REQ_STARTED)) {
687 elevator_t *e = q->elevator;
690 * This is the first time the device driver
691 * sees this request (possibly after
692 * requeueing). Notify IO scheduler.
694 if (blk_sorted_rq(rq) &&
695 e->ops->elevator_activate_req_fn)
696 e->ops->elevator_activate_req_fn(q, rq);
699 * just mark as started even if we don't start
700 * it, a request that has been delayed should
701 * not be passed by new incoming requests
703 rq->cmd_flags |= REQ_STARTED;
704 blk_add_trace_rq(q, rq, BLK_TA_ISSUE);
707 if (!q->boundary_rq || q->boundary_rq == rq) {
708 q->end_sector = rq_end_sector(rq);
709 q->boundary_rq = NULL;
712 if ((rq->cmd_flags & REQ_DONTPREP) || !q->prep_rq_fn)
715 ret = q->prep_rq_fn(q, rq);
716 if (ret == BLKPREP_OK) {
718 } else if (ret == BLKPREP_DEFER) {
720 * the request may have been (partially) prepped.
721 * we need to keep this request in the front to
722 * avoid resource deadlock. REQ_STARTED will
723 * prevent other fs requests from passing this one.
727 } else if (ret == BLKPREP_KILL) {
728 int nr_bytes = rq->hard_nr_sectors << 9;
731 nr_bytes = rq->data_len;
733 blkdev_dequeue_request(rq);
734 rq->cmd_flags |= REQ_QUIET;
735 end_that_request_chunk(rq, 0, nr_bytes);
736 end_that_request_last(rq, 0);
738 printk(KERN_ERR "%s: bad return=%d\n", __FUNCTION__,
747 EXPORT_SYMBOL(elv_next_request);
749 void elv_dequeue_request(request_queue_t *q, struct request *rq)
751 BUG_ON(list_empty(&rq->queuelist));
752 BUG_ON(ELV_ON_HASH(rq));
754 list_del_init(&rq->queuelist);
757 * the time frame between a request being removed from the lists
758 * and to it is freed is accounted as io that is in progress at
761 if (blk_account_rq(rq))
765 EXPORT_SYMBOL(elv_dequeue_request);
767 int elv_queue_empty(request_queue_t *q)
769 elevator_t *e = q->elevator;
771 if (!list_empty(&q->queue_head))
774 if (e->ops->elevator_queue_empty_fn)
775 return e->ops->elevator_queue_empty_fn(q);
780 EXPORT_SYMBOL(elv_queue_empty);
782 struct request *elv_latter_request(request_queue_t *q, struct request *rq)
784 elevator_t *e = q->elevator;
786 if (e->ops->elevator_latter_req_fn)
787 return e->ops->elevator_latter_req_fn(q, rq);
791 struct request *elv_former_request(request_queue_t *q, struct request *rq)
793 elevator_t *e = q->elevator;
795 if (e->ops->elevator_former_req_fn)
796 return e->ops->elevator_former_req_fn(q, rq);
800 int elv_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
803 elevator_t *e = q->elevator;
805 if (e->ops->elevator_set_req_fn)
806 return e->ops->elevator_set_req_fn(q, rq, bio, gfp_mask);
808 rq->elevator_private = NULL;
812 void elv_put_request(request_queue_t *q, struct request *rq)
814 elevator_t *e = q->elevator;
816 if (e->ops->elevator_put_req_fn)
817 e->ops->elevator_put_req_fn(q, rq);
820 int elv_may_queue(request_queue_t *q, int rw, struct bio *bio)
822 elevator_t *e = q->elevator;
824 if (e->ops->elevator_may_queue_fn)
825 return e->ops->elevator_may_queue_fn(q, rw, bio);
827 return ELV_MQUEUE_MAY;
830 void elv_completed_request(request_queue_t *q, struct request *rq)
832 elevator_t *e = q->elevator;
835 * request is released from the driver, io must be done
837 if (blk_account_rq(rq)) {
839 if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
840 e->ops->elevator_completed_req_fn(q, rq);
844 * Check if the queue is waiting for fs requests to be
845 * drained for flush sequence.
847 if (unlikely(q->ordseq)) {
848 struct request *first_rq = list_entry_rq(q->queue_head.next);
849 if (q->in_flight == 0 &&
850 blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
851 blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
852 blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
858 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
861 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
863 elevator_t *e = container_of(kobj, elevator_t, kobj);
864 struct elv_fs_entry *entry = to_elv(attr);
870 mutex_lock(&e->sysfs_lock);
871 error = e->ops ? entry->show(e, page) : -ENOENT;
872 mutex_unlock(&e->sysfs_lock);
877 elv_attr_store(struct kobject *kobj, struct attribute *attr,
878 const char *page, size_t length)
880 elevator_t *e = container_of(kobj, elevator_t, kobj);
881 struct elv_fs_entry *entry = to_elv(attr);
887 mutex_lock(&e->sysfs_lock);
888 error = e->ops ? entry->store(e, page, length) : -ENOENT;
889 mutex_unlock(&e->sysfs_lock);
893 static struct sysfs_ops elv_sysfs_ops = {
894 .show = elv_attr_show,
895 .store = elv_attr_store,
898 static struct kobj_type elv_ktype = {
899 .sysfs_ops = &elv_sysfs_ops,
900 .release = elevator_release,
903 int elv_register_queue(struct request_queue *q)
905 elevator_t *e = q->elevator;
908 e->kobj.parent = &q->kobj;
910 error = kobject_add(&e->kobj);
912 struct elv_fs_entry *attr = e->elevator_type->elevator_attrs;
914 while (attr->attr.name) {
915 if (sysfs_create_file(&e->kobj, &attr->attr))
920 kobject_uevent(&e->kobj, KOBJ_ADD);
925 static void __elv_unregister_queue(elevator_t *e)
927 kobject_uevent(&e->kobj, KOBJ_REMOVE);
928 kobject_del(&e->kobj);
931 void elv_unregister_queue(struct request_queue *q)
934 __elv_unregister_queue(q->elevator);
937 int elv_register(struct elevator_type *e)
939 spin_lock_irq(&elv_list_lock);
940 BUG_ON(elevator_find(e->elevator_name));
941 list_add_tail(&e->list, &elv_list);
942 spin_unlock_irq(&elv_list_lock);
944 printk(KERN_INFO "io scheduler %s registered", e->elevator_name);
945 if (!strcmp(e->elevator_name, chosen_elevator) ||
946 (!*chosen_elevator &&
947 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
948 printk(" (default)");
952 EXPORT_SYMBOL_GPL(elv_register);
954 void elv_unregister(struct elevator_type *e)
956 struct task_struct *g, *p;
959 * Iterate every thread in the process to remove the io contexts.
962 read_lock(&tasklist_lock);
963 do_each_thread(g, p) {
966 e->ops.trim(p->io_context);
968 } while_each_thread(g, p);
969 read_unlock(&tasklist_lock);
972 spin_lock_irq(&elv_list_lock);
973 list_del_init(&e->list);
974 spin_unlock_irq(&elv_list_lock);
976 EXPORT_SYMBOL_GPL(elv_unregister);
979 * switch to new_e io scheduler. be careful not to introduce deadlocks -
980 * we don't free the old io scheduler, before we have allocated what we
981 * need for the new one. this way we have a chance of going back to the old
982 * one, if the new one fails init for some reason.
984 static int elevator_switch(request_queue_t *q, struct elevator_type *new_e)
986 elevator_t *old_elevator, *e;
990 * Allocate new elevator
992 e = elevator_alloc(new_e);
996 data = elevator_init_queue(q, e);
998 kobject_put(&e->kobj);
1003 * Turn on BYPASS and drain all requests w/ elevator private data
1005 spin_lock_irq(q->queue_lock);
1007 set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1009 elv_drain_elevator(q);
1011 while (q->rq.elvpriv) {
1014 spin_unlock_irq(q->queue_lock);
1016 spin_lock_irq(q->queue_lock);
1017 elv_drain_elevator(q);
1021 * Remember old elevator.
1023 old_elevator = q->elevator;
1026 * attach and start new elevator
1028 elevator_attach(q, e, data);
1030 spin_unlock_irq(q->queue_lock);
1032 __elv_unregister_queue(old_elevator);
1034 if (elv_register_queue(q))
1038 * finally exit old elevator and turn off BYPASS.
1040 elevator_exit(old_elevator);
1041 clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1046 * switch failed, exit the new io scheduler and reattach the old
1047 * one again (along with re-adding the sysfs dir)
1050 q->elevator = old_elevator;
1051 elv_register_queue(q);
1052 clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1056 ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
1058 char elevator_name[ELV_NAME_MAX];
1060 struct elevator_type *e;
1062 elevator_name[sizeof(elevator_name) - 1] = '\0';
1063 strncpy(elevator_name, name, sizeof(elevator_name) - 1);
1064 len = strlen(elevator_name);
1066 if (len && elevator_name[len - 1] == '\n')
1067 elevator_name[len - 1] = '\0';
1069 e = elevator_get(elevator_name);
1071 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
1075 if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
1080 if (!elevator_switch(q, e))
1081 printk(KERN_ERR "elevator: switch to %s failed\n",elevator_name);
1085 ssize_t elv_iosched_show(request_queue_t *q, char *name)
1087 elevator_t *e = q->elevator;
1088 struct elevator_type *elv = e->elevator_type;
1089 struct list_head *entry;
1092 spin_lock_irq(q->queue_lock);
1093 list_for_each(entry, &elv_list) {
1094 struct elevator_type *__e;
1096 __e = list_entry(entry, struct elevator_type, list);
1097 if (!strcmp(elv->elevator_name, __e->elevator_name))
1098 len += sprintf(name+len, "[%s] ", elv->elevator_name);
1100 len += sprintf(name+len, "%s ", __e->elevator_name);
1102 spin_unlock_irq(q->queue_lock);
1104 len += sprintf(len+name, "\n");
1108 struct request *elv_rb_former_request(request_queue_t *q, struct request *rq)
1110 struct rb_node *rbprev = rb_prev(&rq->rb_node);
1113 return rb_entry_rq(rbprev);
1118 EXPORT_SYMBOL(elv_rb_former_request);
1120 struct request *elv_rb_latter_request(request_queue_t *q, struct request *rq)
1122 struct rb_node *rbnext = rb_next(&rq->rb_node);
1125 return rb_entry_rq(rbnext);
1130 EXPORT_SYMBOL(elv_rb_latter_request);