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
, bool try_loading
)
105 struct elevator_type
*e
;
107 spin_lock(&elv_list_lock
);
109 e
= elevator_find(name
);
110 if (!e
&& try_loading
) {
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 /* called during boot to load the elevator chosen by the elevator param */
140 void __init
load_default_elevator_module(void)
142 struct elevator_type
*e
;
144 if (!chosen_elevator
[0])
147 spin_lock(&elv_list_lock
);
148 e
= elevator_find(chosen_elevator
);
149 spin_unlock(&elv_list_lock
);
152 request_module("%s-iosched", chosen_elevator
);
155 static struct kobj_type elv_ktype
;
157 static struct elevator_queue
*elevator_alloc(struct request_queue
*q
,
158 struct elevator_type
*e
)
160 struct elevator_queue
*eq
;
163 eq
= kmalloc_node(sizeof(*eq
), GFP_KERNEL
| __GFP_ZERO
, q
->node
);
168 kobject_init(&eq
->kobj
, &elv_ktype
);
169 mutex_init(&eq
->sysfs_lock
);
171 eq
->hash
= kmalloc_node(sizeof(struct hlist_head
) * ELV_HASH_ENTRIES
,
172 GFP_KERNEL
, q
->node
);
176 for (i
= 0; i
< ELV_HASH_ENTRIES
; i
++)
177 INIT_HLIST_HEAD(&eq
->hash
[i
]);
186 static void elevator_release(struct kobject
*kobj
)
188 struct elevator_queue
*e
;
190 e
= container_of(kobj
, struct elevator_queue
, kobj
);
191 elevator_put(e
->type
);
196 int elevator_init(struct request_queue
*q
, char *name
)
198 struct elevator_type
*e
= NULL
;
201 if (unlikely(q
->elevator
))
204 INIT_LIST_HEAD(&q
->queue_head
);
205 q
->last_merge
= NULL
;
207 q
->boundary_rq
= NULL
;
210 e
= elevator_get(name
, true);
216 * Use the default elevator specified by config boot param or
217 * config option. Don't try to load modules as we could be running
218 * off async and request_module() isn't allowed from async.
220 if (!e
&& *chosen_elevator
) {
221 e
= elevator_get(chosen_elevator
, false);
223 printk(KERN_ERR
"I/O scheduler %s not found\n",
228 e
= elevator_get(CONFIG_DEFAULT_IOSCHED
, false);
231 "Default I/O scheduler not found. " \
233 e
= elevator_get("noop", false);
237 q
->elevator
= elevator_alloc(q
, e
);
241 err
= e
->ops
.elevator_init_fn(q
);
243 kobject_put(&q
->elevator
->kobj
);
249 EXPORT_SYMBOL(elevator_init
);
251 void elevator_exit(struct elevator_queue
*e
)
253 mutex_lock(&e
->sysfs_lock
);
254 if (e
->type
->ops
.elevator_exit_fn
)
255 e
->type
->ops
.elevator_exit_fn(e
);
256 mutex_unlock(&e
->sysfs_lock
);
258 kobject_put(&e
->kobj
);
260 EXPORT_SYMBOL(elevator_exit
);
262 static inline void __elv_rqhash_del(struct request
*rq
)
264 hlist_del_init(&rq
->hash
);
267 static void elv_rqhash_del(struct request_queue
*q
, struct request
*rq
)
270 __elv_rqhash_del(rq
);
273 static void elv_rqhash_add(struct request_queue
*q
, struct request
*rq
)
275 struct elevator_queue
*e
= q
->elevator
;
277 BUG_ON(ELV_ON_HASH(rq
));
278 hlist_add_head(&rq
->hash
, &e
->hash
[ELV_HASH_FN(rq_hash_key(rq
))]);
281 static void elv_rqhash_reposition(struct request_queue
*q
, struct request
*rq
)
283 __elv_rqhash_del(rq
);
284 elv_rqhash_add(q
, rq
);
287 static struct request
*elv_rqhash_find(struct request_queue
*q
, sector_t offset
)
289 struct elevator_queue
*e
= q
->elevator
;
290 struct hlist_head
*hash_list
= &e
->hash
[ELV_HASH_FN(offset
)];
291 struct hlist_node
*entry
, *next
;
294 hlist_for_each_entry_safe(rq
, entry
, next
, hash_list
, hash
) {
295 BUG_ON(!ELV_ON_HASH(rq
));
297 if (unlikely(!rq_mergeable(rq
))) {
298 __elv_rqhash_del(rq
);
302 if (rq_hash_key(rq
) == offset
)
310 * RB-tree support functions for inserting/lookup/removal of requests
311 * in a sorted RB tree.
313 void elv_rb_add(struct rb_root
*root
, struct request
*rq
)
315 struct rb_node
**p
= &root
->rb_node
;
316 struct rb_node
*parent
= NULL
;
317 struct request
*__rq
;
321 __rq
= rb_entry(parent
, struct request
, rb_node
);
323 if (blk_rq_pos(rq
) < blk_rq_pos(__rq
))
325 else if (blk_rq_pos(rq
) >= blk_rq_pos(__rq
))
329 rb_link_node(&rq
->rb_node
, parent
, p
);
330 rb_insert_color(&rq
->rb_node
, root
);
332 EXPORT_SYMBOL(elv_rb_add
);
334 void elv_rb_del(struct rb_root
*root
, struct request
*rq
)
336 BUG_ON(RB_EMPTY_NODE(&rq
->rb_node
));
337 rb_erase(&rq
->rb_node
, root
);
338 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
< blk_rq_pos(rq
))
352 else if (sector
> blk_rq_pos(rq
))
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 instead into the dispatch queue. To be used by
365 * specific elevators.
367 void elv_dispatch_sort(struct request_queue
*q
, struct request
*rq
)
370 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
;
381 stop_flags
= REQ_SOFTBARRIER
| REQ_STARTED
;
382 list_for_each_prev(entry
, &q
->queue_head
) {
383 struct request
*pos
= list_entry_rq(entry
);
385 if ((rq
->cmd_flags
& REQ_DISCARD
) !=
386 (pos
->cmd_flags
& REQ_DISCARD
))
388 if (rq_data_dir(rq
) != rq_data_dir(pos
))
390 if (pos
->cmd_flags
& stop_flags
)
392 if (blk_rq_pos(rq
) >= boundary
) {
393 if (blk_rq_pos(pos
) < boundary
)
396 if (blk_rq_pos(pos
) >= boundary
)
399 if (blk_rq_pos(rq
) >= blk_rq_pos(pos
))
403 list_add(&rq
->queuelist
, entry
);
405 EXPORT_SYMBOL(elv_dispatch_sort
);
408 * Insert rq into dispatch queue of q. Queue lock must be held on
409 * entry. rq is added to the back of the dispatch queue. To be used by
410 * specific elevators.
412 void elv_dispatch_add_tail(struct request_queue
*q
, struct request
*rq
)
414 if (q
->last_merge
== rq
)
415 q
->last_merge
= NULL
;
417 elv_rqhash_del(q
, rq
);
421 q
->end_sector
= rq_end_sector(rq
);
423 list_add_tail(&rq
->queuelist
, &q
->queue_head
);
425 EXPORT_SYMBOL(elv_dispatch_add_tail
);
427 int elv_merge(struct request_queue
*q
, struct request
**req
, struct bio
*bio
)
429 struct elevator_queue
*e
= q
->elevator
;
430 struct request
*__rq
;
435 * nomerges: No merges at all attempted
436 * noxmerges: Only simple one-hit cache try
437 * merges: All merge tries attempted
439 if (blk_queue_nomerges(q
))
440 return ELEVATOR_NO_MERGE
;
443 * First try one-hit cache.
445 if (q
->last_merge
&& elv_rq_merge_ok(q
->last_merge
, bio
)) {
446 ret
= blk_try_merge(q
->last_merge
, bio
);
447 if (ret
!= ELEVATOR_NO_MERGE
) {
448 *req
= q
->last_merge
;
453 if (blk_queue_noxmerges(q
))
454 return ELEVATOR_NO_MERGE
;
457 * See if our hash lookup can find a potential backmerge.
459 __rq
= elv_rqhash_find(q
, bio
->bi_sector
);
460 if (__rq
&& elv_rq_merge_ok(__rq
, bio
)) {
462 return ELEVATOR_BACK_MERGE
;
465 if (e
->type
->ops
.elevator_merge_fn
)
466 return e
->type
->ops
.elevator_merge_fn(q
, req
, bio
);
468 return ELEVATOR_NO_MERGE
;
472 * Attempt to do an insertion back merge. Only check for the case where
473 * we can append 'rq' to an existing request, so we can throw 'rq' away
476 * Returns true if we merged, false otherwise
478 static bool elv_attempt_insert_merge(struct request_queue
*q
,
481 struct request
*__rq
;
484 if (blk_queue_nomerges(q
))
488 * First try one-hit cache.
490 if (q
->last_merge
&& blk_attempt_req_merge(q
, q
->last_merge
, rq
))
493 if (blk_queue_noxmerges(q
))
498 * See if our hash lookup can find a potential backmerge.
501 __rq
= elv_rqhash_find(q
, blk_rq_pos(rq
));
502 if (!__rq
|| !blk_attempt_req_merge(q
, __rq
, rq
))
505 /* The merged request could be merged with others, try again */
513 void elv_merged_request(struct request_queue
*q
, struct request
*rq
, int type
)
515 struct elevator_queue
*e
= q
->elevator
;
517 if (e
->type
->ops
.elevator_merged_fn
)
518 e
->type
->ops
.elevator_merged_fn(q
, rq
, type
);
520 if (type
== ELEVATOR_BACK_MERGE
)
521 elv_rqhash_reposition(q
, rq
);
526 void elv_merge_requests(struct request_queue
*q
, struct request
*rq
,
527 struct request
*next
)
529 struct elevator_queue
*e
= q
->elevator
;
530 const int next_sorted
= next
->cmd_flags
& REQ_SORTED
;
532 if (next_sorted
&& e
->type
->ops
.elevator_merge_req_fn
)
533 e
->type
->ops
.elevator_merge_req_fn(q
, rq
, next
);
535 elv_rqhash_reposition(q
, rq
);
538 elv_rqhash_del(q
, next
);
545 void elv_bio_merged(struct request_queue
*q
, struct request
*rq
,
548 struct elevator_queue
*e
= q
->elevator
;
550 if (e
->type
->ops
.elevator_bio_merged_fn
)
551 e
->type
->ops
.elevator_bio_merged_fn(q
, rq
, bio
);
554 void elv_requeue_request(struct request_queue
*q
, struct request
*rq
)
557 * it already went through dequeue, we need to decrement the
558 * in_flight count again
560 if (blk_account_rq(rq
)) {
561 q
->in_flight
[rq_is_sync(rq
)]--;
562 if (rq
->cmd_flags
& REQ_SORTED
)
563 elv_deactivate_rq(q
, rq
);
566 rq
->cmd_flags
&= ~REQ_STARTED
;
568 __elv_add_request(q
, rq
, ELEVATOR_INSERT_REQUEUE
);
571 void elv_drain_elevator(struct request_queue
*q
)
575 lockdep_assert_held(q
->queue_lock
);
577 while (q
->elevator
->type
->ops
.elevator_dispatch_fn(q
, 1))
579 if (q
->nr_sorted
&& printed
++ < 10) {
580 printk(KERN_ERR
"%s: forced dispatching is broken "
581 "(nr_sorted=%u), please report this\n",
582 q
->elevator
->type
->elevator_name
, q
->nr_sorted
);
586 void __elv_add_request(struct request_queue
*q
, struct request
*rq
, int where
)
588 trace_block_rq_insert(q
, rq
);
592 if (rq
->cmd_flags
& REQ_SOFTBARRIER
) {
593 /* barriers are scheduling boundary, update end_sector */
594 if (rq
->cmd_type
== REQ_TYPE_FS
) {
595 q
->end_sector
= rq_end_sector(rq
);
598 } else if (!(rq
->cmd_flags
& REQ_ELVPRIV
) &&
599 (where
== ELEVATOR_INSERT_SORT
||
600 where
== ELEVATOR_INSERT_SORT_MERGE
))
601 where
= ELEVATOR_INSERT_BACK
;
604 case ELEVATOR_INSERT_REQUEUE
:
605 case ELEVATOR_INSERT_FRONT
:
606 rq
->cmd_flags
|= REQ_SOFTBARRIER
;
607 list_add(&rq
->queuelist
, &q
->queue_head
);
610 case ELEVATOR_INSERT_BACK
:
611 rq
->cmd_flags
|= REQ_SOFTBARRIER
;
612 elv_drain_elevator(q
);
613 list_add_tail(&rq
->queuelist
, &q
->queue_head
);
615 * We kick the queue here for the following reasons.
616 * - The elevator might have returned NULL previously
617 * to delay requests and returned them now. As the
618 * queue wasn't empty before this request, ll_rw_blk
619 * won't run the queue on return, resulting in hang.
620 * - Usually, back inserted requests won't be merged
621 * with anything. There's no point in delaying queue
627 case ELEVATOR_INSERT_SORT_MERGE
:
629 * If we succeed in merging this request with one in the
630 * queue already, we are done - rq has now been freed,
631 * so no need to do anything further.
633 if (elv_attempt_insert_merge(q
, rq
))
635 case ELEVATOR_INSERT_SORT
:
636 BUG_ON(rq
->cmd_type
!= REQ_TYPE_FS
);
637 rq
->cmd_flags
|= REQ_SORTED
;
639 if (rq_mergeable(rq
)) {
640 elv_rqhash_add(q
, rq
);
646 * Some ioscheds (cfq) run q->request_fn directly, so
647 * rq cannot be accessed after calling
648 * elevator_add_req_fn.
650 q
->elevator
->type
->ops
.elevator_add_req_fn(q
, rq
);
653 case ELEVATOR_INSERT_FLUSH
:
654 rq
->cmd_flags
|= REQ_SOFTBARRIER
;
655 blk_insert_flush(rq
);
658 printk(KERN_ERR
"%s: bad insertion point %d\n",
663 EXPORT_SYMBOL(__elv_add_request
);
665 void elv_add_request(struct request_queue
*q
, struct request
*rq
, int where
)
669 spin_lock_irqsave(q
->queue_lock
, flags
);
670 __elv_add_request(q
, rq
, where
);
671 spin_unlock_irqrestore(q
->queue_lock
, flags
);
673 EXPORT_SYMBOL(elv_add_request
);
675 struct request
*elv_latter_request(struct request_queue
*q
, struct request
*rq
)
677 struct elevator_queue
*e
= q
->elevator
;
679 if (e
->type
->ops
.elevator_latter_req_fn
)
680 return e
->type
->ops
.elevator_latter_req_fn(q
, rq
);
684 struct request
*elv_former_request(struct request_queue
*q
, struct request
*rq
)
686 struct elevator_queue
*e
= q
->elevator
;
688 if (e
->type
->ops
.elevator_former_req_fn
)
689 return e
->type
->ops
.elevator_former_req_fn(q
, rq
);
693 int elv_set_request(struct request_queue
*q
, struct request
*rq
,
694 struct bio
*bio
, gfp_t gfp_mask
)
696 struct elevator_queue
*e
= q
->elevator
;
698 if (e
->type
->ops
.elevator_set_req_fn
)
699 return e
->type
->ops
.elevator_set_req_fn(q
, rq
, bio
, gfp_mask
);
703 void elv_put_request(struct request_queue
*q
, struct request
*rq
)
705 struct elevator_queue
*e
= q
->elevator
;
707 if (e
->type
->ops
.elevator_put_req_fn
)
708 e
->type
->ops
.elevator_put_req_fn(rq
);
711 int elv_may_queue(struct request_queue
*q
, int rw
)
713 struct elevator_queue
*e
= q
->elevator
;
715 if (e
->type
->ops
.elevator_may_queue_fn
)
716 return e
->type
->ops
.elevator_may_queue_fn(q
, rw
);
718 return ELV_MQUEUE_MAY
;
721 void elv_abort_queue(struct request_queue
*q
)
725 blk_abort_flushes(q
);
727 while (!list_empty(&q
->queue_head
)) {
728 rq
= list_entry_rq(q
->queue_head
.next
);
729 rq
->cmd_flags
|= REQ_QUIET
;
730 trace_block_rq_abort(q
, rq
);
732 * Mark this request as started so we don't trigger
733 * any debug logic in the end I/O path.
735 blk_start_request(rq
);
736 __blk_end_request_all(rq
, -EIO
);
739 EXPORT_SYMBOL(elv_abort_queue
);
741 void elv_completed_request(struct request_queue
*q
, struct request
*rq
)
743 struct elevator_queue
*e
= q
->elevator
;
746 * request is released from the driver, io must be done
748 if (blk_account_rq(rq
)) {
749 q
->in_flight
[rq_is_sync(rq
)]--;
750 if ((rq
->cmd_flags
& REQ_SORTED
) &&
751 e
->type
->ops
.elevator_completed_req_fn
)
752 e
->type
->ops
.elevator_completed_req_fn(q
, rq
);
756 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
759 elv_attr_show(struct kobject
*kobj
, struct attribute
*attr
, char *page
)
761 struct elv_fs_entry
*entry
= to_elv(attr
);
762 struct elevator_queue
*e
;
768 e
= container_of(kobj
, struct elevator_queue
, kobj
);
769 mutex_lock(&e
->sysfs_lock
);
770 error
= e
->type
? entry
->show(e
, page
) : -ENOENT
;
771 mutex_unlock(&e
->sysfs_lock
);
776 elv_attr_store(struct kobject
*kobj
, struct attribute
*attr
,
777 const char *page
, size_t length
)
779 struct elv_fs_entry
*entry
= to_elv(attr
);
780 struct elevator_queue
*e
;
786 e
= container_of(kobj
, struct elevator_queue
, kobj
);
787 mutex_lock(&e
->sysfs_lock
);
788 error
= e
->type
? entry
->store(e
, page
, length
) : -ENOENT
;
789 mutex_unlock(&e
->sysfs_lock
);
793 static const struct sysfs_ops elv_sysfs_ops
= {
794 .show
= elv_attr_show
,
795 .store
= elv_attr_store
,
798 static struct kobj_type elv_ktype
= {
799 .sysfs_ops
= &elv_sysfs_ops
,
800 .release
= elevator_release
,
803 int elv_register_queue(struct request_queue
*q
)
805 struct elevator_queue
*e
= q
->elevator
;
808 error
= kobject_add(&e
->kobj
, &q
->kobj
, "%s", "iosched");
810 struct elv_fs_entry
*attr
= e
->type
->elevator_attrs
;
812 while (attr
->attr
.name
) {
813 if (sysfs_create_file(&e
->kobj
, &attr
->attr
))
818 kobject_uevent(&e
->kobj
, KOBJ_ADD
);
823 EXPORT_SYMBOL(elv_register_queue
);
825 void elv_unregister_queue(struct request_queue
*q
)
828 struct elevator_queue
*e
= q
->elevator
;
830 kobject_uevent(&e
->kobj
, KOBJ_REMOVE
);
831 kobject_del(&e
->kobj
);
835 EXPORT_SYMBOL(elv_unregister_queue
);
837 int elv_register(struct elevator_type
*e
)
841 /* create icq_cache if requested */
843 if (WARN_ON(e
->icq_size
< sizeof(struct io_cq
)) ||
844 WARN_ON(e
->icq_align
< __alignof__(struct io_cq
)))
847 snprintf(e
->icq_cache_name
, sizeof(e
->icq_cache_name
),
848 "%s_io_cq", e
->elevator_name
);
849 e
->icq_cache
= kmem_cache_create(e
->icq_cache_name
, e
->icq_size
,
850 e
->icq_align
, 0, NULL
);
855 /* register, don't allow duplicate names */
856 spin_lock(&elv_list_lock
);
857 if (elevator_find(e
->elevator_name
)) {
858 spin_unlock(&elv_list_lock
);
860 kmem_cache_destroy(e
->icq_cache
);
863 list_add_tail(&e
->list
, &elv_list
);
864 spin_unlock(&elv_list_lock
);
866 /* print pretty message */
867 if (!strcmp(e
->elevator_name
, chosen_elevator
) ||
868 (!*chosen_elevator
&&
869 !strcmp(e
->elevator_name
, CONFIG_DEFAULT_IOSCHED
)))
872 printk(KERN_INFO
"io scheduler %s registered%s\n", e
->elevator_name
,
876 EXPORT_SYMBOL_GPL(elv_register
);
878 void elv_unregister(struct elevator_type
*e
)
881 spin_lock(&elv_list_lock
);
882 list_del_init(&e
->list
);
883 spin_unlock(&elv_list_lock
);
886 * Destroy icq_cache if it exists. icq's are RCU managed. Make
887 * sure all RCU operations are complete before proceeding.
891 kmem_cache_destroy(e
->icq_cache
);
895 EXPORT_SYMBOL_GPL(elv_unregister
);
898 * switch to new_e io scheduler. be careful not to introduce deadlocks -
899 * we don't free the old io scheduler, before we have allocated what we
900 * need for the new one. this way we have a chance of going back to the old
901 * one, if the new one fails init for some reason.
903 static int elevator_switch(struct request_queue
*q
, struct elevator_type
*new_e
)
905 struct elevator_queue
*old
= q
->elevator
;
906 bool registered
= old
->registered
;
910 * Turn on BYPASS and drain all requests w/ elevator private data.
911 * Block layer doesn't call into a quiesced elevator - all requests
912 * are directly put on the dispatch list without elevator data
913 * using INSERT_BACK. All requests have SOFTBARRIER set and no
914 * merge happens either.
916 blk_queue_bypass_start(q
);
918 /* unregister and clear all auxiliary data of the old elevator */
920 elv_unregister_queue(q
);
922 spin_lock_irq(q
->queue_lock
);
924 spin_unlock_irq(q
->queue_lock
);
926 /* allocate, init and register new elevator */
928 q
->elevator
= elevator_alloc(q
, new_e
);
932 err
= new_e
->ops
.elevator_init_fn(q
);
934 kobject_put(&q
->elevator
->kobj
);
939 err
= elv_register_queue(q
);
944 /* done, kill the old one and finish */
946 blk_queue_bypass_end(q
);
948 blk_add_trace_msg(q
, "elv switch: %s", new_e
->elevator_name
);
953 elevator_exit(q
->elevator
);
955 /* switch failed, restore and re-register old elevator */
957 elv_register_queue(q
);
958 blk_queue_bypass_end(q
);
964 * Switch this queue to the given IO scheduler.
966 int elevator_change(struct request_queue
*q
, const char *name
)
968 char elevator_name
[ELV_NAME_MAX
];
969 struct elevator_type
*e
;
974 strlcpy(elevator_name
, name
, sizeof(elevator_name
));
975 e
= elevator_get(strstrip(elevator_name
), true);
977 printk(KERN_ERR
"elevator: type %s not found\n", elevator_name
);
981 if (!strcmp(elevator_name
, q
->elevator
->type
->elevator_name
)) {
986 return elevator_switch(q
, e
);
988 EXPORT_SYMBOL(elevator_change
);
990 ssize_t
elv_iosched_store(struct request_queue
*q
, const char *name
,
998 ret
= elevator_change(q
, name
);
1002 printk(KERN_ERR
"elevator: switch to %s failed\n", name
);
1006 ssize_t
elv_iosched_show(struct request_queue
*q
, char *name
)
1008 struct elevator_queue
*e
= q
->elevator
;
1009 struct elevator_type
*elv
;
1010 struct elevator_type
*__e
;
1013 if (!q
->elevator
|| !blk_queue_stackable(q
))
1014 return sprintf(name
, "none\n");
1018 spin_lock(&elv_list_lock
);
1019 list_for_each_entry(__e
, &elv_list
, list
) {
1020 if (!strcmp(elv
->elevator_name
, __e
->elevator_name
))
1021 len
+= sprintf(name
+len
, "[%s] ", elv
->elevator_name
);
1023 len
+= sprintf(name
+len
, "%s ", __e
->elevator_name
);
1025 spin_unlock(&elv_list_lock
);
1027 len
+= sprintf(len
+name
, "\n");
1031 struct request
*elv_rb_former_request(struct request_queue
*q
,
1034 struct rb_node
*rbprev
= rb_prev(&rq
->rb_node
);
1037 return rb_entry_rq(rbprev
);
1041 EXPORT_SYMBOL(elv_rb_former_request
);
1043 struct request
*elv_rb_latter_request(struct request_queue
*q
,
1046 struct rb_node
*rbnext
= rb_next(&rq
->rb_node
);
1049 return rb_entry_rq(rbnext
);
1053 EXPORT_SYMBOL(elv_rb_latter_request
);