2 * Block device elevator/IO-scheduler.
4 * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
6 * 30042000 Jens Axboe <axboe@kernel.dk> :
8 * Split the elevator a bit so that it is possible to choose a different
9 * one or even write a new "plug in". There are three pieces:
10 * - elevator_fn, inserts a new request in the queue list
11 * - elevator_merge_fn, decides whether a new buffer can be merged with
13 * - elevator_dequeue_fn, called when a request is taken off the active list
15 * 20082000 Dave Jones <davej@suse.de> :
16 * Removed tests for max-bomb-segments, which was breaking elvtune
17 * when run without -bN
20 * - Rework again to work with bio instead of buffer_heads
21 * - loose bi_dev comparisons, partition handling is right now
22 * - completely modularize elevator setup and teardown
25 #include <linux/kernel.h>
27 #include <linux/blkdev.h>
28 #include <linux/elevator.h>
29 #include <linux/bio.h>
30 #include <linux/module.h>
31 #include <linux/slab.h>
32 #include <linux/init.h>
33 #include <linux/compiler.h>
34 #include <linux/delay.h>
35 #include <linux/blktrace_api.h>
36 #include <linux/hash.h>
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 * Query io scheduler to see if the current process issuing bio may be
57 static int elv_iosched_allow_merge(struct request
*rq
, struct bio
*bio
)
59 request_queue_t
*q
= rq
->q
;
60 elevator_t
*e
= q
->elevator
;
62 if (e
->ops
->elevator_allow_merge_fn
)
63 return e
->ops
->elevator_allow_merge_fn(q
, rq
, bio
);
69 * can we safely merge with this request?
71 inline int elv_rq_merge_ok(struct request
*rq
, struct bio
*bio
)
73 if (!rq_mergeable(rq
))
77 * different data direction or already started, don't merge
79 if (bio_data_dir(bio
) != rq_data_dir(rq
))
83 * must be same device and not a special request
85 if (rq
->rq_disk
!= bio
->bi_bdev
->bd_disk
|| rq
->special
)
88 if (!elv_iosched_allow_merge(rq
, bio
))
93 EXPORT_SYMBOL(elv_rq_merge_ok
);
95 static inline int elv_try_merge(struct request
*__rq
, struct bio
*bio
)
97 int ret
= ELEVATOR_NO_MERGE
;
100 * we can merge and sequence is ok, check if it's possible
102 if (elv_rq_merge_ok(__rq
, bio
)) {
103 if (__rq
->sector
+ __rq
->nr_sectors
== bio
->bi_sector
)
104 ret
= ELEVATOR_BACK_MERGE
;
105 else if (__rq
->sector
- bio_sectors(bio
) == bio
->bi_sector
)
106 ret
= ELEVATOR_FRONT_MERGE
;
112 static struct elevator_type
*elevator_find(const char *name
)
114 struct elevator_type
*e
;
115 struct list_head
*entry
;
117 list_for_each(entry
, &elv_list
) {
119 e
= list_entry(entry
, struct elevator_type
, list
);
121 if (!strcmp(e
->elevator_name
, name
))
128 static void elevator_put(struct elevator_type
*e
)
130 module_put(e
->elevator_owner
);
133 static struct elevator_type
*elevator_get(const char *name
)
135 struct elevator_type
*e
;
137 spin_lock(&elv_list_lock
);
139 e
= elevator_find(name
);
140 if (e
&& !try_module_get(e
->elevator_owner
))
143 spin_unlock(&elv_list_lock
);
148 static void *elevator_init_queue(request_queue_t
*q
, struct elevator_queue
*eq
)
150 return eq
->ops
->elevator_init_fn(q
);
153 static void elevator_attach(request_queue_t
*q
, struct elevator_queue
*eq
,
157 eq
->elevator_data
= data
;
160 static char chosen_elevator
[16];
162 static int __init
elevator_setup(char *str
)
165 * Be backwards-compatible with previous kernels, so users
166 * won't get the wrong elevator.
168 if (!strcmp(str
, "as"))
169 strcpy(chosen_elevator
, "anticipatory");
171 strncpy(chosen_elevator
, str
, sizeof(chosen_elevator
) - 1);
175 __setup("elevator=", elevator_setup
);
177 static struct kobj_type elv_ktype
;
179 static elevator_t
*elevator_alloc(request_queue_t
*q
, struct elevator_type
*e
)
184 eq
= kmalloc_node(sizeof(elevator_t
), GFP_KERNEL
| __GFP_ZERO
, q
->node
);
189 eq
->elevator_type
= e
;
190 kobject_init(&eq
->kobj
);
191 snprintf(eq
->kobj
.name
, KOBJ_NAME_LEN
, "%s", "iosched");
192 eq
->kobj
.ktype
= &elv_ktype
;
193 mutex_init(&eq
->sysfs_lock
);
195 eq
->hash
= kmalloc_node(sizeof(struct hlist_head
) * ELV_HASH_ENTRIES
,
196 GFP_KERNEL
, q
->node
);
200 for (i
= 0; i
< ELV_HASH_ENTRIES
; i
++)
201 INIT_HLIST_HEAD(&eq
->hash
[i
]);
210 static void elevator_release(struct kobject
*kobj
)
212 elevator_t
*e
= container_of(kobj
, elevator_t
, kobj
);
214 elevator_put(e
->elevator_type
);
219 int elevator_init(request_queue_t
*q
, char *name
)
221 struct elevator_type
*e
= NULL
;
222 struct elevator_queue
*eq
;
226 INIT_LIST_HEAD(&q
->queue_head
);
227 q
->last_merge
= NULL
;
229 q
->boundary_rq
= NULL
;
231 if (name
&& !(e
= elevator_get(name
)))
234 if (!e
&& *chosen_elevator
&& !(e
= elevator_get(chosen_elevator
)))
235 printk("I/O scheduler %s not found\n", chosen_elevator
);
237 if (!e
&& !(e
= elevator_get(CONFIG_DEFAULT_IOSCHED
))) {
238 printk("Default I/O scheduler not found, using no-op\n");
239 e
= elevator_get("noop");
242 eq
= elevator_alloc(q
, e
);
246 data
= elevator_init_queue(q
, eq
);
248 kobject_put(&eq
->kobj
);
252 elevator_attach(q
, eq
, data
);
256 EXPORT_SYMBOL(elevator_init
);
258 void elevator_exit(elevator_t
*e
)
260 mutex_lock(&e
->sysfs_lock
);
261 if (e
->ops
->elevator_exit_fn
)
262 e
->ops
->elevator_exit_fn(e
);
264 mutex_unlock(&e
->sysfs_lock
);
266 kobject_put(&e
->kobj
);
269 EXPORT_SYMBOL(elevator_exit
);
271 static void elv_activate_rq(request_queue_t
*q
, struct request
*rq
)
273 elevator_t
*e
= q
->elevator
;
275 if (e
->ops
->elevator_activate_req_fn
)
276 e
->ops
->elevator_activate_req_fn(q
, rq
);
279 static void elv_deactivate_rq(request_queue_t
*q
, struct request
*rq
)
281 elevator_t
*e
= q
->elevator
;
283 if (e
->ops
->elevator_deactivate_req_fn
)
284 e
->ops
->elevator_deactivate_req_fn(q
, rq
);
287 static inline void __elv_rqhash_del(struct request
*rq
)
289 hlist_del_init(&rq
->hash
);
292 static void elv_rqhash_del(request_queue_t
*q
, struct request
*rq
)
295 __elv_rqhash_del(rq
);
298 static void elv_rqhash_add(request_queue_t
*q
, struct request
*rq
)
300 elevator_t
*e
= q
->elevator
;
302 BUG_ON(ELV_ON_HASH(rq
));
303 hlist_add_head(&rq
->hash
, &e
->hash
[ELV_HASH_FN(rq_hash_key(rq
))]);
306 static void elv_rqhash_reposition(request_queue_t
*q
, struct request
*rq
)
308 __elv_rqhash_del(rq
);
309 elv_rqhash_add(q
, rq
);
312 static struct request
*elv_rqhash_find(request_queue_t
*q
, sector_t offset
)
314 elevator_t
*e
= q
->elevator
;
315 struct hlist_head
*hash_list
= &e
->hash
[ELV_HASH_FN(offset
)];
316 struct hlist_node
*entry
, *next
;
319 hlist_for_each_entry_safe(rq
, entry
, next
, hash_list
, hash
) {
320 BUG_ON(!ELV_ON_HASH(rq
));
322 if (unlikely(!rq_mergeable(rq
))) {
323 __elv_rqhash_del(rq
);
327 if (rq_hash_key(rq
) == offset
)
335 * RB-tree support functions for inserting/lookup/removal of requests
336 * in a sorted RB tree.
338 struct request
*elv_rb_add(struct rb_root
*root
, struct request
*rq
)
340 struct rb_node
**p
= &root
->rb_node
;
341 struct rb_node
*parent
= NULL
;
342 struct request
*__rq
;
346 __rq
= rb_entry(parent
, struct request
, rb_node
);
348 if (rq
->sector
< __rq
->sector
)
350 else if (rq
->sector
> __rq
->sector
)
356 rb_link_node(&rq
->rb_node
, parent
, p
);
357 rb_insert_color(&rq
->rb_node
, root
);
361 EXPORT_SYMBOL(elv_rb_add
);
363 void elv_rb_del(struct rb_root
*root
, struct request
*rq
)
365 BUG_ON(RB_EMPTY_NODE(&rq
->rb_node
));
366 rb_erase(&rq
->rb_node
, root
);
367 RB_CLEAR_NODE(&rq
->rb_node
);
370 EXPORT_SYMBOL(elv_rb_del
);
372 struct request
*elv_rb_find(struct rb_root
*root
, sector_t sector
)
374 struct rb_node
*n
= root
->rb_node
;
378 rq
= rb_entry(n
, struct request
, rb_node
);
380 if (sector
< rq
->sector
)
382 else if (sector
> rq
->sector
)
391 EXPORT_SYMBOL(elv_rb_find
);
394 * Insert rq into dispatch queue of q. Queue lock must be held on
395 * entry. rq is sort insted into the dispatch queue. To be used by
396 * specific elevators.
398 void elv_dispatch_sort(request_queue_t
*q
, struct request
*rq
)
401 struct list_head
*entry
;
403 if (q
->last_merge
== rq
)
404 q
->last_merge
= NULL
;
406 elv_rqhash_del(q
, rq
);
410 boundary
= q
->end_sector
;
412 list_for_each_prev(entry
, &q
->queue_head
) {
413 struct request
*pos
= list_entry_rq(entry
);
415 if (rq_data_dir(rq
) != rq_data_dir(pos
))
417 if (pos
->cmd_flags
& (REQ_SOFTBARRIER
|REQ_HARDBARRIER
|REQ_STARTED
))
419 if (rq
->sector
>= boundary
) {
420 if (pos
->sector
< boundary
)
423 if (pos
->sector
>= boundary
)
426 if (rq
->sector
>= pos
->sector
)
430 list_add(&rq
->queuelist
, entry
);
433 EXPORT_SYMBOL(elv_dispatch_sort
);
436 * Insert rq into dispatch queue of q. Queue lock must be held on
437 * entry. rq is added to the back of the dispatch queue. To be used by
438 * specific elevators.
440 void elv_dispatch_add_tail(struct request_queue
*q
, struct request
*rq
)
442 if (q
->last_merge
== rq
)
443 q
->last_merge
= NULL
;
445 elv_rqhash_del(q
, rq
);
449 q
->end_sector
= rq_end_sector(rq
);
451 list_add_tail(&rq
->queuelist
, &q
->queue_head
);
454 EXPORT_SYMBOL(elv_dispatch_add_tail
);
456 int elv_merge(request_queue_t
*q
, struct request
**req
, struct bio
*bio
)
458 elevator_t
*e
= q
->elevator
;
459 struct request
*__rq
;
463 * First try one-hit cache.
466 ret
= elv_try_merge(q
->last_merge
, bio
);
467 if (ret
!= ELEVATOR_NO_MERGE
) {
468 *req
= q
->last_merge
;
474 * See if our hash lookup can find a potential backmerge.
476 __rq
= elv_rqhash_find(q
, bio
->bi_sector
);
477 if (__rq
&& elv_rq_merge_ok(__rq
, bio
)) {
479 return ELEVATOR_BACK_MERGE
;
482 if (e
->ops
->elevator_merge_fn
)
483 return e
->ops
->elevator_merge_fn(q
, req
, bio
);
485 return ELEVATOR_NO_MERGE
;
488 void elv_merged_request(request_queue_t
*q
, struct request
*rq
, int type
)
490 elevator_t
*e
= q
->elevator
;
492 if (e
->ops
->elevator_merged_fn
)
493 e
->ops
->elevator_merged_fn(q
, rq
, type
);
495 if (type
== ELEVATOR_BACK_MERGE
)
496 elv_rqhash_reposition(q
, rq
);
501 void elv_merge_requests(request_queue_t
*q
, struct request
*rq
,
502 struct request
*next
)
504 elevator_t
*e
= q
->elevator
;
506 if (e
->ops
->elevator_merge_req_fn
)
507 e
->ops
->elevator_merge_req_fn(q
, rq
, next
);
509 elv_rqhash_reposition(q
, rq
);
510 elv_rqhash_del(q
, next
);
516 void elv_requeue_request(request_queue_t
*q
, struct request
*rq
)
519 * it already went through dequeue, we need to decrement the
520 * in_flight count again
522 if (blk_account_rq(rq
)) {
524 if (blk_sorted_rq(rq
))
525 elv_deactivate_rq(q
, rq
);
528 rq
->cmd_flags
&= ~REQ_STARTED
;
530 elv_insert(q
, rq
, ELEVATOR_INSERT_REQUEUE
);
533 static void elv_drain_elevator(request_queue_t
*q
)
536 while (q
->elevator
->ops
->elevator_dispatch_fn(q
, 1))
538 if (q
->nr_sorted
== 0)
540 if (printed
++ < 10) {
541 printk(KERN_ERR
"%s: forced dispatching is broken "
542 "(nr_sorted=%u), please report this\n",
543 q
->elevator
->elevator_type
->elevator_name
, q
->nr_sorted
);
547 void elv_insert(request_queue_t
*q
, struct request
*rq
, int where
)
549 struct list_head
*pos
;
553 blk_add_trace_rq(q
, rq
, BLK_TA_INSERT
);
558 case ELEVATOR_INSERT_FRONT
:
559 rq
->cmd_flags
|= REQ_SOFTBARRIER
;
561 list_add(&rq
->queuelist
, &q
->queue_head
);
564 case ELEVATOR_INSERT_BACK
:
565 rq
->cmd_flags
|= REQ_SOFTBARRIER
;
566 elv_drain_elevator(q
);
567 list_add_tail(&rq
->queuelist
, &q
->queue_head
);
569 * We kick the queue here for the following reasons.
570 * - The elevator might have returned NULL previously
571 * to delay requests and returned them now. As the
572 * queue wasn't empty before this request, ll_rw_blk
573 * won't run the queue on return, resulting in hang.
574 * - Usually, back inserted requests won't be merged
575 * with anything. There's no point in delaying queue
582 case ELEVATOR_INSERT_SORT
:
583 BUG_ON(!blk_fs_request(rq
));
584 rq
->cmd_flags
|= REQ_SORTED
;
586 if (rq_mergeable(rq
)) {
587 elv_rqhash_add(q
, rq
);
593 * Some ioscheds (cfq) run q->request_fn directly, so
594 * rq cannot be accessed after calling
595 * elevator_add_req_fn.
597 q
->elevator
->ops
->elevator_add_req_fn(q
, rq
);
600 case ELEVATOR_INSERT_REQUEUE
:
602 * If ordered flush isn't in progress, we do front
603 * insertion; otherwise, requests should be requeued
606 rq
->cmd_flags
|= REQ_SOFTBARRIER
;
609 * Most requeues happen because of a busy condition,
610 * don't force unplug of the queue for that case.
614 if (q
->ordseq
== 0) {
615 list_add(&rq
->queuelist
, &q
->queue_head
);
619 ordseq
= blk_ordered_req_seq(rq
);
621 list_for_each(pos
, &q
->queue_head
) {
622 struct request
*pos_rq
= list_entry_rq(pos
);
623 if (ordseq
<= blk_ordered_req_seq(pos_rq
))
627 list_add_tail(&rq
->queuelist
, pos
);
631 printk(KERN_ERR
"%s: bad insertion point %d\n",
632 __FUNCTION__
, where
);
636 if (unplug_it
&& blk_queue_plugged(q
)) {
637 int nrq
= q
->rq
.count
[READ
] + q
->rq
.count
[WRITE
]
640 if (nrq
>= q
->unplug_thresh
)
641 __generic_unplug_device(q
);
645 void __elv_add_request(request_queue_t
*q
, struct request
*rq
, int where
,
649 rq
->cmd_flags
|= REQ_ORDERED_COLOR
;
651 if (rq
->cmd_flags
& (REQ_SOFTBARRIER
| REQ_HARDBARRIER
)) {
653 * toggle ordered color
655 if (blk_barrier_rq(rq
))
659 * barriers implicitly indicate back insertion
661 if (where
== ELEVATOR_INSERT_SORT
)
662 where
= ELEVATOR_INSERT_BACK
;
665 * this request is scheduling boundary, update
668 if (blk_fs_request(rq
)) {
669 q
->end_sector
= rq_end_sector(rq
);
672 } else if (!(rq
->cmd_flags
& REQ_ELVPRIV
) && where
== ELEVATOR_INSERT_SORT
)
673 where
= ELEVATOR_INSERT_BACK
;
678 elv_insert(q
, rq
, where
);
681 EXPORT_SYMBOL(__elv_add_request
);
683 void elv_add_request(request_queue_t
*q
, struct request
*rq
, int where
,
688 spin_lock_irqsave(q
->queue_lock
, flags
);
689 __elv_add_request(q
, rq
, where
, plug
);
690 spin_unlock_irqrestore(q
->queue_lock
, flags
);
693 EXPORT_SYMBOL(elv_add_request
);
695 static inline struct request
*__elv_next_request(request_queue_t
*q
)
700 while (!list_empty(&q
->queue_head
)) {
701 rq
= list_entry_rq(q
->queue_head
.next
);
702 if (blk_do_ordered(q
, &rq
))
706 if (!q
->elevator
->ops
->elevator_dispatch_fn(q
, 0))
711 struct request
*elv_next_request(request_queue_t
*q
)
716 while ((rq
= __elv_next_request(q
)) != NULL
) {
717 if (!(rq
->cmd_flags
& REQ_STARTED
)) {
719 * This is the first time the device driver
720 * sees this request (possibly after
721 * requeueing). Notify IO scheduler.
723 if (blk_sorted_rq(rq
))
724 elv_activate_rq(q
, rq
);
727 * just mark as started even if we don't start
728 * it, a request that has been delayed should
729 * not be passed by new incoming requests
731 rq
->cmd_flags
|= REQ_STARTED
;
732 blk_add_trace_rq(q
, rq
, BLK_TA_ISSUE
);
735 if (!q
->boundary_rq
|| q
->boundary_rq
== rq
) {
736 q
->end_sector
= rq_end_sector(rq
);
737 q
->boundary_rq
= NULL
;
740 if ((rq
->cmd_flags
& REQ_DONTPREP
) || !q
->prep_rq_fn
)
743 ret
= q
->prep_rq_fn(q
, rq
);
744 if (ret
== BLKPREP_OK
) {
746 } else if (ret
== BLKPREP_DEFER
) {
748 * the request may have been (partially) prepped.
749 * we need to keep this request in the front to
750 * avoid resource deadlock. REQ_STARTED will
751 * prevent other fs requests from passing this one.
755 } else if (ret
== BLKPREP_KILL
) {
756 rq
->cmd_flags
|= REQ_QUIET
;
757 end_queued_request(rq
, 0);
759 printk(KERN_ERR
"%s: bad return=%d\n", __FUNCTION__
,
768 EXPORT_SYMBOL(elv_next_request
);
770 void elv_dequeue_request(request_queue_t
*q
, struct request
*rq
)
772 BUG_ON(list_empty(&rq
->queuelist
));
773 BUG_ON(ELV_ON_HASH(rq
));
775 list_del_init(&rq
->queuelist
);
778 * the time frame between a request being removed from the lists
779 * and to it is freed is accounted as io that is in progress at
782 if (blk_account_rq(rq
))
786 EXPORT_SYMBOL(elv_dequeue_request
);
788 int elv_queue_empty(request_queue_t
*q
)
790 elevator_t
*e
= q
->elevator
;
792 if (!list_empty(&q
->queue_head
))
795 if (e
->ops
->elevator_queue_empty_fn
)
796 return e
->ops
->elevator_queue_empty_fn(q
);
801 EXPORT_SYMBOL(elv_queue_empty
);
803 struct request
*elv_latter_request(request_queue_t
*q
, struct request
*rq
)
805 elevator_t
*e
= q
->elevator
;
807 if (e
->ops
->elevator_latter_req_fn
)
808 return e
->ops
->elevator_latter_req_fn(q
, rq
);
812 struct request
*elv_former_request(request_queue_t
*q
, struct request
*rq
)
814 elevator_t
*e
= q
->elevator
;
816 if (e
->ops
->elevator_former_req_fn
)
817 return e
->ops
->elevator_former_req_fn(q
, rq
);
821 int elv_set_request(request_queue_t
*q
, struct request
*rq
, gfp_t gfp_mask
)
823 elevator_t
*e
= q
->elevator
;
825 if (e
->ops
->elevator_set_req_fn
)
826 return e
->ops
->elevator_set_req_fn(q
, rq
, gfp_mask
);
828 rq
->elevator_private
= NULL
;
832 void elv_put_request(request_queue_t
*q
, struct request
*rq
)
834 elevator_t
*e
= q
->elevator
;
836 if (e
->ops
->elevator_put_req_fn
)
837 e
->ops
->elevator_put_req_fn(rq
);
840 int elv_may_queue(request_queue_t
*q
, int rw
)
842 elevator_t
*e
= q
->elevator
;
844 if (e
->ops
->elevator_may_queue_fn
)
845 return e
->ops
->elevator_may_queue_fn(q
, rw
);
847 return ELV_MQUEUE_MAY
;
850 void elv_completed_request(request_queue_t
*q
, struct request
*rq
)
852 elevator_t
*e
= q
->elevator
;
855 * request is released from the driver, io must be done
857 if (blk_account_rq(rq
)) {
859 if (blk_sorted_rq(rq
) && e
->ops
->elevator_completed_req_fn
)
860 e
->ops
->elevator_completed_req_fn(q
, rq
);
864 * Check if the queue is waiting for fs requests to be
865 * drained for flush sequence.
867 if (unlikely(q
->ordseq
)) {
868 struct request
*first_rq
= list_entry_rq(q
->queue_head
.next
);
869 if (q
->in_flight
== 0 &&
870 blk_ordered_cur_seq(q
) == QUEUE_ORDSEQ_DRAIN
&&
871 blk_ordered_req_seq(first_rq
) > QUEUE_ORDSEQ_DRAIN
) {
872 blk_ordered_complete_seq(q
, QUEUE_ORDSEQ_DRAIN
, 0);
878 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
881 elv_attr_show(struct kobject
*kobj
, struct attribute
*attr
, char *page
)
883 elevator_t
*e
= container_of(kobj
, elevator_t
, kobj
);
884 struct elv_fs_entry
*entry
= to_elv(attr
);
890 mutex_lock(&e
->sysfs_lock
);
891 error
= e
->ops
? entry
->show(e
, page
) : -ENOENT
;
892 mutex_unlock(&e
->sysfs_lock
);
897 elv_attr_store(struct kobject
*kobj
, struct attribute
*attr
,
898 const char *page
, size_t length
)
900 elevator_t
*e
= container_of(kobj
, elevator_t
, kobj
);
901 struct elv_fs_entry
*entry
= to_elv(attr
);
907 mutex_lock(&e
->sysfs_lock
);
908 error
= e
->ops
? entry
->store(e
, page
, length
) : -ENOENT
;
909 mutex_unlock(&e
->sysfs_lock
);
913 static struct sysfs_ops elv_sysfs_ops
= {
914 .show
= elv_attr_show
,
915 .store
= elv_attr_store
,
918 static struct kobj_type elv_ktype
= {
919 .sysfs_ops
= &elv_sysfs_ops
,
920 .release
= elevator_release
,
923 int elv_register_queue(struct request_queue
*q
)
925 elevator_t
*e
= q
->elevator
;
928 e
->kobj
.parent
= &q
->kobj
;
930 error
= kobject_add(&e
->kobj
);
932 struct elv_fs_entry
*attr
= e
->elevator_type
->elevator_attrs
;
934 while (attr
->attr
.name
) {
935 if (sysfs_create_file(&e
->kobj
, &attr
->attr
))
940 kobject_uevent(&e
->kobj
, KOBJ_ADD
);
945 static void __elv_unregister_queue(elevator_t
*e
)
947 kobject_uevent(&e
->kobj
, KOBJ_REMOVE
);
948 kobject_del(&e
->kobj
);
951 void elv_unregister_queue(struct request_queue
*q
)
954 __elv_unregister_queue(q
->elevator
);
957 int elv_register(struct elevator_type
*e
)
961 spin_lock(&elv_list_lock
);
962 BUG_ON(elevator_find(e
->elevator_name
));
963 list_add_tail(&e
->list
, &elv_list
);
964 spin_unlock(&elv_list_lock
);
966 if (!strcmp(e
->elevator_name
, chosen_elevator
) ||
967 (!*chosen_elevator
&&
968 !strcmp(e
->elevator_name
, CONFIG_DEFAULT_IOSCHED
)))
971 printk(KERN_INFO
"io scheduler %s registered%s\n", e
->elevator_name
, def
);
974 EXPORT_SYMBOL_GPL(elv_register
);
976 void elv_unregister(struct elevator_type
*e
)
978 struct task_struct
*g
, *p
;
981 * Iterate every thread in the process to remove the io contexts.
984 read_lock(&tasklist_lock
);
985 do_each_thread(g
, p
) {
988 e
->ops
.trim(p
->io_context
);
990 } while_each_thread(g
, p
);
991 read_unlock(&tasklist_lock
);
994 spin_lock(&elv_list_lock
);
995 list_del_init(&e
->list
);
996 spin_unlock(&elv_list_lock
);
998 EXPORT_SYMBOL_GPL(elv_unregister
);
1001 * switch to new_e io scheduler. be careful not to introduce deadlocks -
1002 * we don't free the old io scheduler, before we have allocated what we
1003 * need for the new one. this way we have a chance of going back to the old
1004 * one, if the new one fails init for some reason.
1006 static int elevator_switch(request_queue_t
*q
, struct elevator_type
*new_e
)
1008 elevator_t
*old_elevator
, *e
;
1012 * Allocate new elevator
1014 e
= elevator_alloc(q
, new_e
);
1018 data
= elevator_init_queue(q
, e
);
1020 kobject_put(&e
->kobj
);
1025 * Turn on BYPASS and drain all requests w/ elevator private data
1027 spin_lock_irq(q
->queue_lock
);
1029 set_bit(QUEUE_FLAG_ELVSWITCH
, &q
->queue_flags
);
1031 elv_drain_elevator(q
);
1033 while (q
->rq
.elvpriv
) {
1036 spin_unlock_irq(q
->queue_lock
);
1038 spin_lock_irq(q
->queue_lock
);
1039 elv_drain_elevator(q
);
1043 * Remember old elevator.
1045 old_elevator
= q
->elevator
;
1048 * attach and start new elevator
1050 elevator_attach(q
, e
, data
);
1052 spin_unlock_irq(q
->queue_lock
);
1054 __elv_unregister_queue(old_elevator
);
1056 if (elv_register_queue(q
))
1060 * finally exit old elevator and turn off BYPASS.
1062 elevator_exit(old_elevator
);
1063 clear_bit(QUEUE_FLAG_ELVSWITCH
, &q
->queue_flags
);
1068 * switch failed, exit the new io scheduler and reattach the old
1069 * one again (along with re-adding the sysfs dir)
1072 q
->elevator
= old_elevator
;
1073 elv_register_queue(q
);
1074 clear_bit(QUEUE_FLAG_ELVSWITCH
, &q
->queue_flags
);
1078 ssize_t
elv_iosched_store(request_queue_t
*q
, const char *name
, size_t count
)
1080 char elevator_name
[ELV_NAME_MAX
];
1082 struct elevator_type
*e
;
1084 elevator_name
[sizeof(elevator_name
) - 1] = '\0';
1085 strncpy(elevator_name
, name
, sizeof(elevator_name
) - 1);
1086 len
= strlen(elevator_name
);
1088 if (len
&& elevator_name
[len
- 1] == '\n')
1089 elevator_name
[len
- 1] = '\0';
1091 e
= elevator_get(elevator_name
);
1093 printk(KERN_ERR
"elevator: type %s not found\n", elevator_name
);
1097 if (!strcmp(elevator_name
, q
->elevator
->elevator_type
->elevator_name
)) {
1102 if (!elevator_switch(q
, e
))
1103 printk(KERN_ERR
"elevator: switch to %s failed\n",elevator_name
);
1107 ssize_t
elv_iosched_show(request_queue_t
*q
, char *name
)
1109 elevator_t
*e
= q
->elevator
;
1110 struct elevator_type
*elv
= e
->elevator_type
;
1111 struct list_head
*entry
;
1114 spin_lock(&elv_list_lock
);
1115 list_for_each(entry
, &elv_list
) {
1116 struct elevator_type
*__e
;
1118 __e
= list_entry(entry
, struct elevator_type
, list
);
1119 if (!strcmp(elv
->elevator_name
, __e
->elevator_name
))
1120 len
+= sprintf(name
+len
, "[%s] ", elv
->elevator_name
);
1122 len
+= sprintf(name
+len
, "%s ", __e
->elevator_name
);
1124 spin_unlock(&elv_list_lock
);
1126 len
+= sprintf(len
+name
, "\n");
1130 struct request
*elv_rb_former_request(request_queue_t
*q
, struct request
*rq
)
1132 struct rb_node
*rbprev
= rb_prev(&rq
->rb_node
);
1135 return rb_entry_rq(rbprev
);
1140 EXPORT_SYMBOL(elv_rb_former_request
);
1142 struct request
*elv_rb_latter_request(request_queue_t
*q
, struct request
*rq
)
1144 struct rb_node
*rbnext
= rb_next(&rq
->rb_node
);
1147 return rb_entry_rq(rbnext
);
1152 EXPORT_SYMBOL(elv_rb_latter_request
);