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>
37 #include <linux/pm_runtime.h>
38 #include <linux/blk-cgroup.h>
40 #include <trace/events/block.h>
43 #include "blk-mq-sched.h"
45 static DEFINE_SPINLOCK(elv_list_lock
);
46 static LIST_HEAD(elv_list
);
51 #define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq))
54 * Query io scheduler to see if the current process issuing bio may be
57 static int elv_iosched_allow_bio_merge(struct request
*rq
, struct bio
*bio
)
59 struct request_queue
*q
= rq
->q
;
60 struct elevator_queue
*e
= q
->elevator
;
62 if (e
->uses_mq
&& e
->type
->ops
.mq
.allow_merge
)
63 return e
->type
->ops
.mq
.allow_merge(q
, rq
, bio
);
64 else if (!e
->uses_mq
&& e
->type
->ops
.sq
.elevator_allow_bio_merge_fn
)
65 return e
->type
->ops
.sq
.elevator_allow_bio_merge_fn(q
, rq
, bio
);
71 * can we safely merge with this request?
73 bool elv_bio_merge_ok(struct request
*rq
, struct bio
*bio
)
75 if (!blk_rq_merge_ok(rq
, bio
))
78 if (!elv_iosched_allow_bio_merge(rq
, bio
))
83 EXPORT_SYMBOL(elv_bio_merge_ok
);
85 static struct elevator_type
*elevator_find(const char *name
)
87 struct elevator_type
*e
;
89 list_for_each_entry(e
, &elv_list
, list
) {
90 if (!strcmp(e
->elevator_name
, name
))
97 static void elevator_put(struct elevator_type
*e
)
99 module_put(e
->elevator_owner
);
102 static struct elevator_type
*elevator_get(const char *name
, bool try_loading
)
104 struct elevator_type
*e
;
106 spin_lock(&elv_list_lock
);
108 e
= elevator_find(name
);
109 if (!e
&& try_loading
) {
110 spin_unlock(&elv_list_lock
);
111 request_module("%s-iosched", name
);
112 spin_lock(&elv_list_lock
);
113 e
= elevator_find(name
);
116 if (e
&& !try_module_get(e
->elevator_owner
))
119 spin_unlock(&elv_list_lock
);
124 static char chosen_elevator
[ELV_NAME_MAX
];
126 static int __init
elevator_setup(char *str
)
129 * Be backwards-compatible with previous kernels, so users
130 * won't get the wrong elevator.
132 strncpy(chosen_elevator
, str
, sizeof(chosen_elevator
) - 1);
136 __setup("elevator=", elevator_setup
);
138 /* called during boot to load the elevator chosen by the elevator param */
139 void __init
load_default_elevator_module(void)
141 struct elevator_type
*e
;
143 if (!chosen_elevator
[0])
146 spin_lock(&elv_list_lock
);
147 e
= elevator_find(chosen_elevator
);
148 spin_unlock(&elv_list_lock
);
151 request_module("%s-iosched", chosen_elevator
);
154 static struct kobj_type elv_ktype
;
156 struct elevator_queue
*elevator_alloc(struct request_queue
*q
,
157 struct elevator_type
*e
)
159 struct elevator_queue
*eq
;
161 eq
= kzalloc_node(sizeof(*eq
), GFP_KERNEL
, q
->node
);
166 kobject_init(&eq
->kobj
, &elv_ktype
);
167 mutex_init(&eq
->sysfs_lock
);
169 eq
->uses_mq
= e
->uses_mq
;
173 EXPORT_SYMBOL(elevator_alloc
);
175 static void elevator_release(struct kobject
*kobj
)
177 struct elevator_queue
*e
;
179 e
= container_of(kobj
, struct elevator_queue
, kobj
);
180 elevator_put(e
->type
);
184 int elevator_init(struct request_queue
*q
, char *name
)
186 struct elevator_type
*e
= NULL
;
190 * q->sysfs_lock must be held to provide mutual exclusion between
191 * elevator_switch() and here.
193 lockdep_assert_held(&q
->sysfs_lock
);
195 if (unlikely(q
->elevator
))
198 INIT_LIST_HEAD(&q
->queue_head
);
199 q
->last_merge
= NULL
;
201 q
->boundary_rq
= NULL
;
204 e
= elevator_get(name
, true);
210 * Use the default elevator specified by config boot param or
211 * config option. Don't try to load modules as we could be running
212 * off async and request_module() isn't allowed from async.
214 if (!e
&& *chosen_elevator
) {
215 e
= elevator_get(chosen_elevator
, false);
217 printk(KERN_ERR
"I/O scheduler %s not found\n",
222 if (q
->mq_ops
&& q
->nr_hw_queues
== 1)
223 e
= elevator_get(CONFIG_DEFAULT_SQ_IOSCHED
, false);
225 e
= elevator_get(CONFIG_DEFAULT_MQ_IOSCHED
, false);
227 e
= elevator_get(CONFIG_DEFAULT_IOSCHED
, false);
231 "Default I/O scheduler not found. " \
232 "Using noop/none.\n");
233 e
= elevator_get("noop", false);
238 err
= blk_mq_sched_setup(q
);
240 err
= e
->ops
.mq
.init_sched(q
, e
);
242 err
= e
->ops
.sq
.elevator_init_fn(q
, e
);
245 blk_mq_sched_teardown(q
);
250 EXPORT_SYMBOL(elevator_init
);
252 void elevator_exit(struct elevator_queue
*e
)
254 mutex_lock(&e
->sysfs_lock
);
255 if (e
->uses_mq
&& e
->type
->ops
.mq
.exit_sched
)
256 e
->type
->ops
.mq
.exit_sched(e
);
257 else if (!e
->uses_mq
&& e
->type
->ops
.sq
.elevator_exit_fn
)
258 e
->type
->ops
.sq
.elevator_exit_fn(e
);
259 mutex_unlock(&e
->sysfs_lock
);
261 kobject_put(&e
->kobj
);
263 EXPORT_SYMBOL(elevator_exit
);
265 static inline void __elv_rqhash_del(struct request
*rq
)
268 rq
->rq_flags
&= ~RQF_HASHED
;
271 void elv_rqhash_del(struct request_queue
*q
, struct request
*rq
)
274 __elv_rqhash_del(rq
);
276 EXPORT_SYMBOL_GPL(elv_rqhash_del
);
278 void elv_rqhash_add(struct request_queue
*q
, struct request
*rq
)
280 struct elevator_queue
*e
= q
->elevator
;
282 BUG_ON(ELV_ON_HASH(rq
));
283 hash_add(e
->hash
, &rq
->hash
, rq_hash_key(rq
));
284 rq
->rq_flags
|= RQF_HASHED
;
286 EXPORT_SYMBOL_GPL(elv_rqhash_add
);
288 void elv_rqhash_reposition(struct request_queue
*q
, struct request
*rq
)
290 __elv_rqhash_del(rq
);
291 elv_rqhash_add(q
, rq
);
294 struct request
*elv_rqhash_find(struct request_queue
*q
, sector_t offset
)
296 struct elevator_queue
*e
= q
->elevator
;
297 struct hlist_node
*next
;
300 hash_for_each_possible_safe(e
->hash
, rq
, next
, hash
, offset
) {
301 BUG_ON(!ELV_ON_HASH(rq
));
303 if (unlikely(!rq_mergeable(rq
))) {
304 __elv_rqhash_del(rq
);
308 if (rq_hash_key(rq
) == offset
)
316 * RB-tree support functions for inserting/lookup/removal of requests
317 * in a sorted RB tree.
319 void elv_rb_add(struct rb_root
*root
, struct request
*rq
)
321 struct rb_node
**p
= &root
->rb_node
;
322 struct rb_node
*parent
= NULL
;
323 struct request
*__rq
;
327 __rq
= rb_entry(parent
, struct request
, rb_node
);
329 if (blk_rq_pos(rq
) < blk_rq_pos(__rq
))
331 else if (blk_rq_pos(rq
) >= blk_rq_pos(__rq
))
335 rb_link_node(&rq
->rb_node
, parent
, p
);
336 rb_insert_color(&rq
->rb_node
, root
);
338 EXPORT_SYMBOL(elv_rb_add
);
340 void elv_rb_del(struct rb_root
*root
, struct request
*rq
)
342 BUG_ON(RB_EMPTY_NODE(&rq
->rb_node
));
343 rb_erase(&rq
->rb_node
, root
);
344 RB_CLEAR_NODE(&rq
->rb_node
);
346 EXPORT_SYMBOL(elv_rb_del
);
348 struct request
*elv_rb_find(struct rb_root
*root
, sector_t sector
)
350 struct rb_node
*n
= root
->rb_node
;
354 rq
= rb_entry(n
, struct request
, rb_node
);
356 if (sector
< blk_rq_pos(rq
))
358 else if (sector
> blk_rq_pos(rq
))
366 EXPORT_SYMBOL(elv_rb_find
);
369 * Insert rq into dispatch queue of q. Queue lock must be held on
370 * entry. rq is sort instead into the dispatch queue. To be used by
371 * specific elevators.
373 void elv_dispatch_sort(struct request_queue
*q
, struct request
*rq
)
376 struct list_head
*entry
;
378 if (q
->last_merge
== rq
)
379 q
->last_merge
= NULL
;
381 elv_rqhash_del(q
, rq
);
385 boundary
= q
->end_sector
;
386 list_for_each_prev(entry
, &q
->queue_head
) {
387 struct request
*pos
= list_entry_rq(entry
);
389 if (req_op(rq
) != req_op(pos
))
391 if (rq_data_dir(rq
) != rq_data_dir(pos
))
393 if (pos
->rq_flags
& (RQF_STARTED
| RQF_SOFTBARRIER
))
395 if (blk_rq_pos(rq
) >= boundary
) {
396 if (blk_rq_pos(pos
) < boundary
)
399 if (blk_rq_pos(pos
) >= boundary
)
402 if (blk_rq_pos(rq
) >= blk_rq_pos(pos
))
406 list_add(&rq
->queuelist
, entry
);
408 EXPORT_SYMBOL(elv_dispatch_sort
);
411 * Insert rq into dispatch queue of q. Queue lock must be held on
412 * entry. rq is added to the back of the dispatch queue. To be used by
413 * specific elevators.
415 void elv_dispatch_add_tail(struct request_queue
*q
, struct request
*rq
)
417 if (q
->last_merge
== rq
)
418 q
->last_merge
= NULL
;
420 elv_rqhash_del(q
, rq
);
424 q
->end_sector
= rq_end_sector(rq
);
426 list_add_tail(&rq
->queuelist
, &q
->queue_head
);
428 EXPORT_SYMBOL(elv_dispatch_add_tail
);
430 int elv_merge(struct request_queue
*q
, struct request
**req
, struct bio
*bio
)
432 struct elevator_queue
*e
= q
->elevator
;
433 struct request
*__rq
;
438 * nomerges: No merges at all attempted
439 * noxmerges: Only simple one-hit cache try
440 * merges: All merge tries attempted
442 if (blk_queue_nomerges(q
) || !bio_mergeable(bio
))
443 return ELEVATOR_NO_MERGE
;
446 * First try one-hit cache.
448 if (q
->last_merge
&& elv_bio_merge_ok(q
->last_merge
, bio
)) {
449 ret
= blk_try_merge(q
->last_merge
, bio
);
450 if (ret
!= ELEVATOR_NO_MERGE
) {
451 *req
= q
->last_merge
;
456 if (blk_queue_noxmerges(q
))
457 return ELEVATOR_NO_MERGE
;
460 * See if our hash lookup can find a potential backmerge.
462 __rq
= elv_rqhash_find(q
, bio
->bi_iter
.bi_sector
);
463 if (__rq
&& elv_bio_merge_ok(__rq
, bio
)) {
465 return ELEVATOR_BACK_MERGE
;
468 if (e
->uses_mq
&& e
->type
->ops
.mq
.request_merge
)
469 return e
->type
->ops
.mq
.request_merge(q
, req
, bio
);
470 else if (!e
->uses_mq
&& e
->type
->ops
.sq
.elevator_merge_fn
)
471 return e
->type
->ops
.sq
.elevator_merge_fn(q
, req
, bio
);
473 return ELEVATOR_NO_MERGE
;
477 * Attempt to do an insertion back merge. Only check for the case where
478 * we can append 'rq' to an existing request, so we can throw 'rq' away
481 * Returns true if we merged, false otherwise
483 bool elv_attempt_insert_merge(struct request_queue
*q
, struct request
*rq
)
485 struct request
*__rq
;
488 if (blk_queue_nomerges(q
))
492 * First try one-hit cache.
494 if (q
->last_merge
&& blk_attempt_req_merge(q
, q
->last_merge
, rq
))
497 if (blk_queue_noxmerges(q
))
502 * See if our hash lookup can find a potential backmerge.
505 __rq
= elv_rqhash_find(q
, blk_rq_pos(rq
));
506 if (!__rq
|| !blk_attempt_req_merge(q
, __rq
, rq
))
509 /* The merged request could be merged with others, try again */
517 void elv_merged_request(struct request_queue
*q
, struct request
*rq
, int type
)
519 struct elevator_queue
*e
= q
->elevator
;
521 if (e
->uses_mq
&& e
->type
->ops
.mq
.request_merged
)
522 e
->type
->ops
.mq
.request_merged(q
, rq
, type
);
523 else if (!e
->uses_mq
&& e
->type
->ops
.sq
.elevator_merged_fn
)
524 e
->type
->ops
.sq
.elevator_merged_fn(q
, rq
, type
);
526 if (type
== ELEVATOR_BACK_MERGE
)
527 elv_rqhash_reposition(q
, rq
);
532 void elv_merge_requests(struct request_queue
*q
, struct request
*rq
,
533 struct request
*next
)
535 struct elevator_queue
*e
= q
->elevator
;
536 bool next_sorted
= false;
538 if (e
->uses_mq
&& e
->type
->ops
.mq
.requests_merged
)
539 e
->type
->ops
.mq
.requests_merged(q
, rq
, next
);
540 else if (e
->type
->ops
.sq
.elevator_merge_req_fn
) {
541 next_sorted
= next
->rq_flags
& RQF_SORTED
;
543 e
->type
->ops
.sq
.elevator_merge_req_fn(q
, rq
, next
);
546 elv_rqhash_reposition(q
, rq
);
549 elv_rqhash_del(q
, next
);
556 void elv_bio_merged(struct request_queue
*q
, struct request
*rq
,
559 struct elevator_queue
*e
= q
->elevator
;
561 if (WARN_ON_ONCE(e
->uses_mq
))
564 if (e
->type
->ops
.sq
.elevator_bio_merged_fn
)
565 e
->type
->ops
.sq
.elevator_bio_merged_fn(q
, rq
, bio
);
569 static void blk_pm_requeue_request(struct request
*rq
)
571 if (rq
->q
->dev
&& !(rq
->rq_flags
& RQF_PM
))
575 static void blk_pm_add_request(struct request_queue
*q
, struct request
*rq
)
577 if (q
->dev
&& !(rq
->rq_flags
& RQF_PM
) && q
->nr_pending
++ == 0 &&
578 (q
->rpm_status
== RPM_SUSPENDED
|| q
->rpm_status
== RPM_SUSPENDING
))
579 pm_request_resume(q
->dev
);
582 static inline void blk_pm_requeue_request(struct request
*rq
) {}
583 static inline void blk_pm_add_request(struct request_queue
*q
,
589 void elv_requeue_request(struct request_queue
*q
, struct request
*rq
)
592 * it already went through dequeue, we need to decrement the
593 * in_flight count again
595 if (blk_account_rq(rq
)) {
596 q
->in_flight
[rq_is_sync(rq
)]--;
597 if (rq
->rq_flags
& RQF_SORTED
)
598 elv_deactivate_rq(q
, rq
);
601 rq
->rq_flags
&= ~RQF_STARTED
;
603 blk_pm_requeue_request(rq
);
605 __elv_add_request(q
, rq
, ELEVATOR_INSERT_REQUEUE
);
608 void elv_drain_elevator(struct request_queue
*q
)
610 struct elevator_queue
*e
= q
->elevator
;
613 if (WARN_ON_ONCE(e
->uses_mq
))
616 lockdep_assert_held(q
->queue_lock
);
618 while (e
->type
->ops
.sq
.elevator_dispatch_fn(q
, 1))
620 if (q
->nr_sorted
&& printed
++ < 10) {
621 printk(KERN_ERR
"%s: forced dispatching is broken "
622 "(nr_sorted=%u), please report this\n",
623 q
->elevator
->type
->elevator_name
, q
->nr_sorted
);
627 void __elv_add_request(struct request_queue
*q
, struct request
*rq
, int where
)
629 trace_block_rq_insert(q
, rq
);
631 blk_pm_add_request(q
, rq
);
635 if (rq
->rq_flags
& RQF_SOFTBARRIER
) {
636 /* barriers are scheduling boundary, update end_sector */
637 if (rq
->cmd_type
== REQ_TYPE_FS
) {
638 q
->end_sector
= rq_end_sector(rq
);
641 } else if (!(rq
->rq_flags
& RQF_ELVPRIV
) &&
642 (where
== ELEVATOR_INSERT_SORT
||
643 where
== ELEVATOR_INSERT_SORT_MERGE
))
644 where
= ELEVATOR_INSERT_BACK
;
647 case ELEVATOR_INSERT_REQUEUE
:
648 case ELEVATOR_INSERT_FRONT
:
649 rq
->rq_flags
|= RQF_SOFTBARRIER
;
650 list_add(&rq
->queuelist
, &q
->queue_head
);
653 case ELEVATOR_INSERT_BACK
:
654 rq
->rq_flags
|= RQF_SOFTBARRIER
;
655 elv_drain_elevator(q
);
656 list_add_tail(&rq
->queuelist
, &q
->queue_head
);
658 * We kick the queue here for the following reasons.
659 * - The elevator might have returned NULL previously
660 * to delay requests and returned them now. As the
661 * queue wasn't empty before this request, ll_rw_blk
662 * won't run the queue on return, resulting in hang.
663 * - Usually, back inserted requests won't be merged
664 * with anything. There's no point in delaying queue
670 case ELEVATOR_INSERT_SORT_MERGE
:
672 * If we succeed in merging this request with one in the
673 * queue already, we are done - rq has now been freed,
674 * so no need to do anything further.
676 if (elv_attempt_insert_merge(q
, rq
))
678 case ELEVATOR_INSERT_SORT
:
679 BUG_ON(rq
->cmd_type
!= REQ_TYPE_FS
);
680 rq
->rq_flags
|= RQF_SORTED
;
682 if (rq_mergeable(rq
)) {
683 elv_rqhash_add(q
, rq
);
689 * Some ioscheds (cfq) run q->request_fn directly, so
690 * rq cannot be accessed after calling
691 * elevator_add_req_fn.
693 q
->elevator
->type
->ops
.sq
.elevator_add_req_fn(q
, rq
);
696 case ELEVATOR_INSERT_FLUSH
:
697 rq
->rq_flags
|= RQF_SOFTBARRIER
;
698 blk_insert_flush(rq
);
701 printk(KERN_ERR
"%s: bad insertion point %d\n",
706 EXPORT_SYMBOL(__elv_add_request
);
708 void elv_add_request(struct request_queue
*q
, struct request
*rq
, int where
)
712 spin_lock_irqsave(q
->queue_lock
, flags
);
713 __elv_add_request(q
, rq
, where
);
714 spin_unlock_irqrestore(q
->queue_lock
, flags
);
716 EXPORT_SYMBOL(elv_add_request
);
718 struct request
*elv_latter_request(struct request_queue
*q
, struct request
*rq
)
720 struct elevator_queue
*e
= q
->elevator
;
722 if (e
->uses_mq
&& e
->type
->ops
.mq
.next_request
)
723 return e
->type
->ops
.mq
.next_request(q
, rq
);
724 else if (!e
->uses_mq
&& e
->type
->ops
.sq
.elevator_latter_req_fn
)
725 return e
->type
->ops
.sq
.elevator_latter_req_fn(q
, rq
);
730 struct request
*elv_former_request(struct request_queue
*q
, struct request
*rq
)
732 struct elevator_queue
*e
= q
->elevator
;
734 if (e
->uses_mq
&& e
->type
->ops
.mq
.former_request
)
735 return e
->type
->ops
.mq
.former_request(q
, rq
);
736 if (!e
->uses_mq
&& e
->type
->ops
.sq
.elevator_former_req_fn
)
737 return e
->type
->ops
.sq
.elevator_former_req_fn(q
, rq
);
741 int elv_set_request(struct request_queue
*q
, struct request
*rq
,
742 struct bio
*bio
, gfp_t gfp_mask
)
744 struct elevator_queue
*e
= q
->elevator
;
746 if (WARN_ON_ONCE(e
->uses_mq
))
749 if (e
->type
->ops
.sq
.elevator_set_req_fn
)
750 return e
->type
->ops
.sq
.elevator_set_req_fn(q
, rq
, bio
, gfp_mask
);
754 void elv_put_request(struct request_queue
*q
, struct request
*rq
)
756 struct elevator_queue
*e
= q
->elevator
;
758 if (WARN_ON_ONCE(e
->uses_mq
))
761 if (e
->type
->ops
.sq
.elevator_put_req_fn
)
762 e
->type
->ops
.sq
.elevator_put_req_fn(rq
);
765 int elv_may_queue(struct request_queue
*q
, unsigned int op
)
767 struct elevator_queue
*e
= q
->elevator
;
769 if (WARN_ON_ONCE(e
->uses_mq
))
772 if (e
->type
->ops
.sq
.elevator_may_queue_fn
)
773 return e
->type
->ops
.sq
.elevator_may_queue_fn(q
, op
);
775 return ELV_MQUEUE_MAY
;
778 void elv_completed_request(struct request_queue
*q
, struct request
*rq
)
780 struct elevator_queue
*e
= q
->elevator
;
782 if (WARN_ON_ONCE(e
->uses_mq
))
786 * request is released from the driver, io must be done
788 if (blk_account_rq(rq
)) {
789 q
->in_flight
[rq_is_sync(rq
)]--;
790 if ((rq
->rq_flags
& RQF_SORTED
) &&
791 e
->type
->ops
.sq
.elevator_completed_req_fn
)
792 e
->type
->ops
.sq
.elevator_completed_req_fn(q
, rq
);
796 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
799 elv_attr_show(struct kobject
*kobj
, struct attribute
*attr
, char *page
)
801 struct elv_fs_entry
*entry
= to_elv(attr
);
802 struct elevator_queue
*e
;
808 e
= container_of(kobj
, struct elevator_queue
, kobj
);
809 mutex_lock(&e
->sysfs_lock
);
810 error
= e
->type
? entry
->show(e
, page
) : -ENOENT
;
811 mutex_unlock(&e
->sysfs_lock
);
816 elv_attr_store(struct kobject
*kobj
, struct attribute
*attr
,
817 const char *page
, size_t length
)
819 struct elv_fs_entry
*entry
= to_elv(attr
);
820 struct elevator_queue
*e
;
826 e
= container_of(kobj
, struct elevator_queue
, kobj
);
827 mutex_lock(&e
->sysfs_lock
);
828 error
= e
->type
? entry
->store(e
, page
, length
) : -ENOENT
;
829 mutex_unlock(&e
->sysfs_lock
);
833 static const struct sysfs_ops elv_sysfs_ops
= {
834 .show
= elv_attr_show
,
835 .store
= elv_attr_store
,
838 static struct kobj_type elv_ktype
= {
839 .sysfs_ops
= &elv_sysfs_ops
,
840 .release
= elevator_release
,
843 int elv_register_queue(struct request_queue
*q
)
845 struct elevator_queue
*e
= q
->elevator
;
848 error
= kobject_add(&e
->kobj
, &q
->kobj
, "%s", "iosched");
850 struct elv_fs_entry
*attr
= e
->type
->elevator_attrs
;
852 while (attr
->attr
.name
) {
853 if (sysfs_create_file(&e
->kobj
, &attr
->attr
))
858 kobject_uevent(&e
->kobj
, KOBJ_ADD
);
860 if (!e
->uses_mq
&& e
->type
->ops
.sq
.elevator_registered_fn
)
861 e
->type
->ops
.sq
.elevator_registered_fn(q
);
865 EXPORT_SYMBOL(elv_register_queue
);
867 void elv_unregister_queue(struct request_queue
*q
)
870 struct elevator_queue
*e
= q
->elevator
;
872 kobject_uevent(&e
->kobj
, KOBJ_REMOVE
);
873 kobject_del(&e
->kobj
);
877 EXPORT_SYMBOL(elv_unregister_queue
);
879 int elv_register(struct elevator_type
*e
)
883 /* create icq_cache if requested */
885 if (WARN_ON(e
->icq_size
< sizeof(struct io_cq
)) ||
886 WARN_ON(e
->icq_align
< __alignof__(struct io_cq
)))
889 snprintf(e
->icq_cache_name
, sizeof(e
->icq_cache_name
),
890 "%s_io_cq", e
->elevator_name
);
891 e
->icq_cache
= kmem_cache_create(e
->icq_cache_name
, e
->icq_size
,
892 e
->icq_align
, 0, NULL
);
897 /* register, don't allow duplicate names */
898 spin_lock(&elv_list_lock
);
899 if (elevator_find(e
->elevator_name
)) {
900 spin_unlock(&elv_list_lock
);
902 kmem_cache_destroy(e
->icq_cache
);
905 list_add_tail(&e
->list
, &elv_list
);
906 spin_unlock(&elv_list_lock
);
908 /* print pretty message */
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
,
918 EXPORT_SYMBOL_GPL(elv_register
);
920 void elv_unregister(struct elevator_type
*e
)
923 spin_lock(&elv_list_lock
);
924 list_del_init(&e
->list
);
925 spin_unlock(&elv_list_lock
);
928 * Destroy icq_cache if it exists. icq's are RCU managed. Make
929 * sure all RCU operations are complete before proceeding.
933 kmem_cache_destroy(e
->icq_cache
);
937 EXPORT_SYMBOL_GPL(elv_unregister
);
940 * switch to new_e io scheduler. be careful not to introduce deadlocks -
941 * we don't free the old io scheduler, before we have allocated what we
942 * need for the new one. this way we have a chance of going back to the old
943 * one, if the new one fails init for some reason.
945 static int elevator_switch(struct request_queue
*q
, struct elevator_type
*new_e
)
947 struct elevator_queue
*old
= q
->elevator
;
948 bool old_registered
= false;
952 blk_mq_freeze_queue(q
);
953 blk_mq_quiesce_queue(q
);
957 * Turn on BYPASS and drain all requests w/ elevator private data.
958 * Block layer doesn't call into a quiesced elevator - all requests
959 * are directly put on the dispatch list without elevator data
960 * using INSERT_BACK. All requests have SOFTBARRIER set and no
961 * merge happens either.
964 old_registered
= old
->registered
;
967 blk_mq_sched_teardown(q
);
970 blk_queue_bypass_start(q
);
972 /* unregister and clear all auxiliary data of the old elevator */
974 elv_unregister_queue(q
);
976 spin_lock_irq(q
->queue_lock
);
978 spin_unlock_irq(q
->queue_lock
);
981 /* allocate, init and register new elevator */
983 if (new_e
->uses_mq
) {
984 err
= blk_mq_sched_setup(q
);
986 err
= new_e
->ops
.mq
.init_sched(q
, new_e
);
988 err
= new_e
->ops
.sq
.elevator_init_fn(q
, new_e
);
992 err
= elv_register_queue(q
);
998 /* done, kill the old one and finish */
1002 blk_queue_bypass_end(q
);
1006 blk_mq_unfreeze_queue(q
);
1007 blk_mq_start_stopped_hw_queues(q
, true);
1011 blk_add_trace_msg(q
, "elv switch: %s", new_e
->elevator_name
);
1013 blk_add_trace_msg(q
, "elv switch: none");
1019 blk_mq_sched_teardown(q
);
1020 elevator_exit(q
->elevator
);
1022 /* switch failed, restore and re-register old elevator */
1025 elv_register_queue(q
);
1027 blk_queue_bypass_end(q
);
1030 blk_mq_unfreeze_queue(q
);
1031 blk_mq_start_stopped_hw_queues(q
, true);
1038 * Switch this queue to the given IO scheduler.
1040 static int __elevator_change(struct request_queue
*q
, const char *name
)
1042 char elevator_name
[ELV_NAME_MAX
];
1043 struct elevator_type
*e
;
1046 * Special case for mq, turn off scheduling
1048 if (q
->mq_ops
&& !strncmp(name
, "none", 4))
1049 return elevator_switch(q
, NULL
);
1051 strlcpy(elevator_name
, name
, sizeof(elevator_name
));
1052 e
= elevator_get(strstrip(elevator_name
), true);
1054 printk(KERN_ERR
"elevator: type %s not found\n", elevator_name
);
1059 !strcmp(elevator_name
, q
->elevator
->type
->elevator_name
)) {
1064 if (!e
->uses_mq
&& q
->mq_ops
) {
1068 if (e
->uses_mq
&& !q
->mq_ops
) {
1073 return elevator_switch(q
, e
);
1076 int elevator_change(struct request_queue
*q
, const char *name
)
1080 /* Protect q->elevator from elevator_init() */
1081 mutex_lock(&q
->sysfs_lock
);
1082 ret
= __elevator_change(q
, name
);
1083 mutex_unlock(&q
->sysfs_lock
);
1087 EXPORT_SYMBOL(elevator_change
);
1089 ssize_t
elv_iosched_store(struct request_queue
*q
, const char *name
,
1094 if (!(q
->mq_ops
|| q
->request_fn
))
1097 ret
= __elevator_change(q
, name
);
1101 printk(KERN_ERR
"elevator: switch to %s failed\n", name
);
1105 ssize_t
elv_iosched_show(struct request_queue
*q
, char *name
)
1107 struct elevator_queue
*e
= q
->elevator
;
1108 struct elevator_type
*elv
= NULL
;
1109 struct elevator_type
*__e
;
1112 if (!blk_queue_stackable(q
))
1113 return sprintf(name
, "none\n");
1116 len
+= sprintf(name
+len
, "[none] ");
1120 spin_lock(&elv_list_lock
);
1121 list_for_each_entry(__e
, &elv_list
, list
) {
1122 if (elv
&& !strcmp(elv
->elevator_name
, __e
->elevator_name
)) {
1123 len
+= sprintf(name
+len
, "[%s] ", elv
->elevator_name
);
1126 if (__e
->uses_mq
&& q
->mq_ops
)
1127 len
+= sprintf(name
+len
, "%s ", __e
->elevator_name
);
1128 else if (!__e
->uses_mq
&& !q
->mq_ops
)
1129 len
+= sprintf(name
+len
, "%s ", __e
->elevator_name
);
1131 spin_unlock(&elv_list_lock
);
1133 if (q
->mq_ops
&& q
->elevator
)
1134 len
+= sprintf(name
+len
, "none");
1136 len
+= sprintf(len
+name
, "\n");
1140 struct request
*elv_rb_former_request(struct request_queue
*q
,
1143 struct rb_node
*rbprev
= rb_prev(&rq
->rb_node
);
1146 return rb_entry_rq(rbprev
);
1150 EXPORT_SYMBOL(elv_rb_former_request
);
1152 struct request
*elv_rb_latter_request(struct request_queue
*q
,
1155 struct rb_node
*rbnext
= rb_next(&rq
->rb_node
);
1158 return rb_entry_rq(rbnext
);
1162 EXPORT_SYMBOL(elv_rb_latter_request
);