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>
37 #include <linux/uaccess.h>
39 #include <trace/events/block.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
->ops
->elevator_allow_merge_fn
)
66 return e
->ops
->elevator_allow_merge_fn(q
, rq
, bio
);
72 * can we safely merge with this request?
74 int elv_rq_merge_ok(struct request
*rq
, struct bio
*bio
)
76 if (!rq_mergeable(rq
))
80 * Don't merge file system requests and discard requests
82 if ((bio
->bi_rw
& REQ_DISCARD
) != (rq
->bio
->bi_rw
& REQ_DISCARD
))
86 * different data direction or already started, don't merge
88 if (bio_data_dir(bio
) != rq_data_dir(rq
))
92 * must be same device and not a special request
94 if (rq
->rq_disk
!= bio
->bi_bdev
->bd_disk
|| rq
->special
)
98 * only merge integrity protected bio into ditto rq
100 if (bio_integrity(bio
) != blk_integrity_rq(rq
))
103 if (!elv_iosched_allow_merge(rq
, bio
))
108 EXPORT_SYMBOL(elv_rq_merge_ok
);
110 static inline int elv_try_merge(struct request
*__rq
, struct bio
*bio
)
112 int ret
= ELEVATOR_NO_MERGE
;
115 * we can merge and sequence is ok, check if it's possible
117 if (elv_rq_merge_ok(__rq
, bio
)) {
118 if (blk_rq_pos(__rq
) + blk_rq_sectors(__rq
) == bio
->bi_sector
)
119 ret
= ELEVATOR_BACK_MERGE
;
120 else if (blk_rq_pos(__rq
) - bio_sectors(bio
) == bio
->bi_sector
)
121 ret
= ELEVATOR_FRONT_MERGE
;
127 static struct elevator_type
*elevator_find(const char *name
)
129 struct elevator_type
*e
;
131 list_for_each_entry(e
, &elv_list
, list
) {
132 if (!strcmp(e
->elevator_name
, name
))
139 static void elevator_put(struct elevator_type
*e
)
141 module_put(e
->elevator_owner
);
144 static struct elevator_type
*elevator_get(const char *name
)
146 struct elevator_type
*e
;
148 spin_lock(&elv_list_lock
);
150 e
= elevator_find(name
);
152 char elv
[ELV_NAME_MAX
+ strlen("-iosched")];
154 spin_unlock(&elv_list_lock
);
156 snprintf(elv
, sizeof(elv
), "%s-iosched", name
);
158 request_module("%s", elv
);
159 spin_lock(&elv_list_lock
);
160 e
= elevator_find(name
);
163 if (e
&& !try_module_get(e
->elevator_owner
))
166 spin_unlock(&elv_list_lock
);
171 static void *elevator_init_queue(struct request_queue
*q
,
172 struct elevator_queue
*eq
)
174 return eq
->ops
->elevator_init_fn(q
);
177 static void elevator_attach(struct request_queue
*q
, struct elevator_queue
*eq
,
181 eq
->elevator_data
= data
;
184 static char chosen_elevator
[16];
186 static int __init
elevator_setup(char *str
)
189 * Be backwards-compatible with previous kernels, so users
190 * won't get the wrong elevator.
192 strncpy(chosen_elevator
, str
, sizeof(chosen_elevator
) - 1);
196 __setup("elevator=", elevator_setup
);
198 static struct kobj_type elv_ktype
;
200 static struct elevator_queue
*elevator_alloc(struct request_queue
*q
,
201 struct elevator_type
*e
)
203 struct elevator_queue
*eq
;
206 eq
= kmalloc_node(sizeof(*eq
), GFP_KERNEL
| __GFP_ZERO
, q
->node
);
211 eq
->elevator_type
= e
;
212 kobject_init(&eq
->kobj
, &elv_ktype
);
213 mutex_init(&eq
->sysfs_lock
);
215 eq
->hash
= kmalloc_node(sizeof(struct hlist_head
) * ELV_HASH_ENTRIES
,
216 GFP_KERNEL
, q
->node
);
220 for (i
= 0; i
< ELV_HASH_ENTRIES
; i
++)
221 INIT_HLIST_HEAD(&eq
->hash
[i
]);
230 static void elevator_release(struct kobject
*kobj
)
232 struct elevator_queue
*e
;
234 e
= container_of(kobj
, struct elevator_queue
, kobj
);
235 elevator_put(e
->elevator_type
);
240 int elevator_init(struct request_queue
*q
, char *name
)
242 struct elevator_type
*e
= NULL
;
243 struct elevator_queue
*eq
;
246 if (unlikely(q
->elevator
))
249 INIT_LIST_HEAD(&q
->queue_head
);
250 q
->last_merge
= NULL
;
252 q
->boundary_rq
= NULL
;
255 e
= elevator_get(name
);
260 if (!e
&& *chosen_elevator
) {
261 e
= elevator_get(chosen_elevator
);
263 printk(KERN_ERR
"I/O scheduler %s not found\n",
268 e
= elevator_get(CONFIG_DEFAULT_IOSCHED
);
271 "Default I/O scheduler not found. " \
273 e
= elevator_get("noop");
277 eq
= elevator_alloc(q
, e
);
281 data
= elevator_init_queue(q
, eq
);
283 kobject_put(&eq
->kobj
);
287 elevator_attach(q
, eq
, data
);
290 EXPORT_SYMBOL(elevator_init
);
292 void elevator_exit(struct elevator_queue
*e
)
294 mutex_lock(&e
->sysfs_lock
);
295 if (e
->ops
->elevator_exit_fn
)
296 e
->ops
->elevator_exit_fn(e
);
298 mutex_unlock(&e
->sysfs_lock
);
300 kobject_put(&e
->kobj
);
302 EXPORT_SYMBOL(elevator_exit
);
304 static inline void __elv_rqhash_del(struct request
*rq
)
306 hlist_del_init(&rq
->hash
);
309 static void elv_rqhash_del(struct request_queue
*q
, struct request
*rq
)
312 __elv_rqhash_del(rq
);
315 static void elv_rqhash_add(struct request_queue
*q
, struct request
*rq
)
317 struct elevator_queue
*e
= q
->elevator
;
319 BUG_ON(ELV_ON_HASH(rq
));
320 hlist_add_head(&rq
->hash
, &e
->hash
[ELV_HASH_FN(rq_hash_key(rq
))]);
323 static void elv_rqhash_reposition(struct request_queue
*q
, struct request
*rq
)
325 __elv_rqhash_del(rq
);
326 elv_rqhash_add(q
, rq
);
329 static struct request
*elv_rqhash_find(struct request_queue
*q
, sector_t offset
)
331 struct elevator_queue
*e
= q
->elevator
;
332 struct hlist_head
*hash_list
= &e
->hash
[ELV_HASH_FN(offset
)];
333 struct hlist_node
*entry
, *next
;
336 hlist_for_each_entry_safe(rq
, entry
, next
, hash_list
, hash
) {
337 BUG_ON(!ELV_ON_HASH(rq
));
339 if (unlikely(!rq_mergeable(rq
))) {
340 __elv_rqhash_del(rq
);
344 if (rq_hash_key(rq
) == offset
)
352 * RB-tree support functions for inserting/lookup/removal of requests
353 * in a sorted RB tree.
355 struct request
*elv_rb_add(struct rb_root
*root
, struct request
*rq
)
357 struct rb_node
**p
= &root
->rb_node
;
358 struct rb_node
*parent
= NULL
;
359 struct request
*__rq
;
363 __rq
= rb_entry(parent
, struct request
, rb_node
);
365 if (blk_rq_pos(rq
) < blk_rq_pos(__rq
))
367 else if (blk_rq_pos(rq
) > blk_rq_pos(__rq
))
373 rb_link_node(&rq
->rb_node
, parent
, p
);
374 rb_insert_color(&rq
->rb_node
, root
);
377 EXPORT_SYMBOL(elv_rb_add
);
379 void elv_rb_del(struct rb_root
*root
, struct request
*rq
)
381 BUG_ON(RB_EMPTY_NODE(&rq
->rb_node
));
382 rb_erase(&rq
->rb_node
, root
);
383 RB_CLEAR_NODE(&rq
->rb_node
);
385 EXPORT_SYMBOL(elv_rb_del
);
387 struct request
*elv_rb_find(struct rb_root
*root
, sector_t sector
)
389 struct rb_node
*n
= root
->rb_node
;
393 rq
= rb_entry(n
, struct request
, rb_node
);
395 if (sector
< blk_rq_pos(rq
))
397 else if (sector
> blk_rq_pos(rq
))
405 EXPORT_SYMBOL(elv_rb_find
);
408 * Insert rq into dispatch queue of q. Queue lock must be held on
409 * entry. rq is sort instead into the dispatch queue. To be used by
410 * specific elevators.
412 void elv_dispatch_sort(struct request_queue
*q
, struct request
*rq
)
415 struct list_head
*entry
;
418 if (q
->last_merge
== rq
)
419 q
->last_merge
= NULL
;
421 elv_rqhash_del(q
, rq
);
425 boundary
= q
->end_sector
;
426 stop_flags
= REQ_SOFTBARRIER
| REQ_HARDBARRIER
| REQ_STARTED
;
427 list_for_each_prev(entry
, &q
->queue_head
) {
428 struct request
*pos
= list_entry_rq(entry
);
430 if ((rq
->cmd_flags
& REQ_DISCARD
) !=
431 (pos
->cmd_flags
& REQ_DISCARD
))
433 if (rq_data_dir(rq
) != rq_data_dir(pos
))
435 if (pos
->cmd_flags
& stop_flags
)
437 if (blk_rq_pos(rq
) >= boundary
) {
438 if (blk_rq_pos(pos
) < boundary
)
441 if (blk_rq_pos(pos
) >= boundary
)
444 if (blk_rq_pos(rq
) >= blk_rq_pos(pos
))
448 list_add(&rq
->queuelist
, entry
);
450 EXPORT_SYMBOL(elv_dispatch_sort
);
453 * Insert rq into dispatch queue of q. Queue lock must be held on
454 * entry. rq is added to the back of the dispatch queue. To be used by
455 * specific elevators.
457 void elv_dispatch_add_tail(struct request_queue
*q
, struct request
*rq
)
459 if (q
->last_merge
== rq
)
460 q
->last_merge
= NULL
;
462 elv_rqhash_del(q
, rq
);
466 q
->end_sector
= rq_end_sector(rq
);
468 list_add_tail(&rq
->queuelist
, &q
->queue_head
);
470 EXPORT_SYMBOL(elv_dispatch_add_tail
);
472 int elv_merge(struct request_queue
*q
, struct request
**req
, struct bio
*bio
)
474 struct elevator_queue
*e
= q
->elevator
;
475 struct request
*__rq
;
480 * nomerges: No merges at all attempted
481 * noxmerges: Only simple one-hit cache try
482 * merges: All merge tries attempted
484 if (blk_queue_nomerges(q
))
485 return ELEVATOR_NO_MERGE
;
488 * First try one-hit cache.
491 ret
= elv_try_merge(q
->last_merge
, bio
);
492 if (ret
!= ELEVATOR_NO_MERGE
) {
493 *req
= q
->last_merge
;
498 if (blk_queue_noxmerges(q
))
499 return ELEVATOR_NO_MERGE
;
502 * See if our hash lookup can find a potential backmerge.
504 __rq
= elv_rqhash_find(q
, bio
->bi_sector
);
505 if (__rq
&& elv_rq_merge_ok(__rq
, bio
)) {
507 return ELEVATOR_BACK_MERGE
;
510 if (e
->ops
->elevator_merge_fn
)
511 return e
->ops
->elevator_merge_fn(q
, req
, bio
);
513 return ELEVATOR_NO_MERGE
;
516 void elv_merged_request(struct request_queue
*q
, struct request
*rq
, int type
)
518 struct elevator_queue
*e
= q
->elevator
;
520 if (e
->ops
->elevator_merged_fn
)
521 e
->ops
->elevator_merged_fn(q
, rq
, type
);
523 if (type
== ELEVATOR_BACK_MERGE
)
524 elv_rqhash_reposition(q
, rq
);
529 void elv_merge_requests(struct request_queue
*q
, struct request
*rq
,
530 struct request
*next
)
532 struct elevator_queue
*e
= q
->elevator
;
534 if (e
->ops
->elevator_merge_req_fn
)
535 e
->ops
->elevator_merge_req_fn(q
, rq
, next
);
537 elv_rqhash_reposition(q
, rq
);
538 elv_rqhash_del(q
, next
);
544 void elv_bio_merged(struct request_queue
*q
, struct request
*rq
,
547 struct elevator_queue
*e
= q
->elevator
;
549 if (e
->ops
->elevator_bio_merged_fn
)
550 e
->ops
->elevator_bio_merged_fn(q
, rq
, bio
);
553 void elv_requeue_request(struct request_queue
*q
, struct request
*rq
)
556 * it already went through dequeue, we need to decrement the
557 * in_flight count again
559 if (blk_account_rq(rq
)) {
560 q
->in_flight
[rq_is_sync(rq
)]--;
561 if (rq
->cmd_flags
& REQ_SORTED
)
562 elv_deactivate_rq(q
, rq
);
565 rq
->cmd_flags
&= ~REQ_STARTED
;
567 elv_insert(q
, rq
, ELEVATOR_INSERT_REQUEUE
);
570 void elv_drain_elevator(struct request_queue
*q
)
573 while (q
->elevator
->ops
->elevator_dispatch_fn(q
, 1))
575 if (q
->nr_sorted
== 0)
577 if (printed
++ < 10) {
578 printk(KERN_ERR
"%s: forced dispatching is broken "
579 "(nr_sorted=%u), please report this\n",
580 q
->elevator
->elevator_type
->elevator_name
, q
->nr_sorted
);
585 * Call with queue lock held, interrupts disabled
587 void elv_quiesce_start(struct request_queue
*q
)
592 queue_flag_set(QUEUE_FLAG_ELVSWITCH
, q
);
595 * make sure we don't have any requests in flight
597 elv_drain_elevator(q
);
598 while (q
->rq
.elvpriv
) {
600 spin_unlock_irq(q
->queue_lock
);
602 spin_lock_irq(q
->queue_lock
);
603 elv_drain_elevator(q
);
607 void elv_quiesce_end(struct request_queue
*q
)
609 queue_flag_clear(QUEUE_FLAG_ELVSWITCH
, q
);
612 void elv_insert(struct request_queue
*q
, struct request
*rq
, int where
)
614 struct list_head
*pos
;
618 trace_block_rq_insert(q
, rq
);
623 case ELEVATOR_INSERT_FRONT
:
624 rq
->cmd_flags
|= REQ_SOFTBARRIER
;
626 list_add(&rq
->queuelist
, &q
->queue_head
);
629 case ELEVATOR_INSERT_BACK
:
630 rq
->cmd_flags
|= REQ_SOFTBARRIER
;
631 elv_drain_elevator(q
);
632 list_add_tail(&rq
->queuelist
, &q
->queue_head
);
634 * We kick the queue here for the following reasons.
635 * - The elevator might have returned NULL previously
636 * to delay requests and returned them now. As the
637 * queue wasn't empty before this request, ll_rw_blk
638 * won't run the queue on return, resulting in hang.
639 * - Usually, back inserted requests won't be merged
640 * with anything. There's no point in delaying queue
646 case ELEVATOR_INSERT_SORT
:
647 BUG_ON(rq
->cmd_type
!= REQ_TYPE_FS
&&
648 !(rq
->cmd_flags
& REQ_DISCARD
));
649 rq
->cmd_flags
|= REQ_SORTED
;
651 if (rq_mergeable(rq
)) {
652 elv_rqhash_add(q
, rq
);
658 * Some ioscheds (cfq) run q->request_fn directly, so
659 * rq cannot be accessed after calling
660 * elevator_add_req_fn.
662 q
->elevator
->ops
->elevator_add_req_fn(q
, rq
);
665 case ELEVATOR_INSERT_REQUEUE
:
667 * If ordered flush isn't in progress, we do front
668 * insertion; otherwise, requests should be requeued
671 rq
->cmd_flags
|= REQ_SOFTBARRIER
;
674 * Most requeues happen because of a busy condition,
675 * don't force unplug of the queue for that case.
679 if (q
->ordseq
== 0) {
680 list_add(&rq
->queuelist
, &q
->queue_head
);
684 ordseq
= blk_ordered_req_seq(rq
);
686 list_for_each(pos
, &q
->queue_head
) {
687 struct request
*pos_rq
= list_entry_rq(pos
);
688 if (ordseq
<= blk_ordered_req_seq(pos_rq
))
692 list_add_tail(&rq
->queuelist
, pos
);
696 printk(KERN_ERR
"%s: bad insertion point %d\n",
701 if (unplug_it
&& blk_queue_plugged(q
)) {
702 int nrq
= q
->rq
.count
[BLK_RW_SYNC
] + q
->rq
.count
[BLK_RW_ASYNC
]
703 - queue_in_flight(q
);
705 if (nrq
>= q
->unplug_thresh
)
706 __generic_unplug_device(q
);
710 void __elv_add_request(struct request_queue
*q
, struct request
*rq
, int where
,
714 rq
->cmd_flags
|= REQ_ORDERED_COLOR
;
716 if (rq
->cmd_flags
& (REQ_SOFTBARRIER
| REQ_HARDBARRIER
)) {
718 * toggle ordered color
720 if (rq
->cmd_flags
& REQ_HARDBARRIER
)
724 * barriers implicitly indicate back insertion
726 if (where
== ELEVATOR_INSERT_SORT
)
727 where
= ELEVATOR_INSERT_BACK
;
730 * this request is scheduling boundary, update
733 if (rq
->cmd_type
== REQ_TYPE_FS
||
734 (rq
->cmd_flags
& REQ_DISCARD
)) {
735 q
->end_sector
= rq_end_sector(rq
);
738 } else if (!(rq
->cmd_flags
& REQ_ELVPRIV
) &&
739 where
== ELEVATOR_INSERT_SORT
)
740 where
= ELEVATOR_INSERT_BACK
;
745 elv_insert(q
, rq
, where
);
747 EXPORT_SYMBOL(__elv_add_request
);
749 void elv_add_request(struct request_queue
*q
, struct request
*rq
, int where
,
754 spin_lock_irqsave(q
->queue_lock
, flags
);
755 __elv_add_request(q
, rq
, where
, plug
);
756 spin_unlock_irqrestore(q
->queue_lock
, flags
);
758 EXPORT_SYMBOL(elv_add_request
);
760 int elv_queue_empty(struct request_queue
*q
)
762 struct elevator_queue
*e
= q
->elevator
;
764 if (!list_empty(&q
->queue_head
))
767 if (e
->ops
->elevator_queue_empty_fn
)
768 return e
->ops
->elevator_queue_empty_fn(q
);
772 EXPORT_SYMBOL(elv_queue_empty
);
774 struct request
*elv_latter_request(struct request_queue
*q
, struct request
*rq
)
776 struct elevator_queue
*e
= q
->elevator
;
778 if (e
->ops
->elevator_latter_req_fn
)
779 return e
->ops
->elevator_latter_req_fn(q
, rq
);
783 struct request
*elv_former_request(struct request_queue
*q
, struct request
*rq
)
785 struct elevator_queue
*e
= q
->elevator
;
787 if (e
->ops
->elevator_former_req_fn
)
788 return e
->ops
->elevator_former_req_fn(q
, rq
);
792 int elv_set_request(struct request_queue
*q
, struct request
*rq
, gfp_t gfp_mask
)
794 struct elevator_queue
*e
= q
->elevator
;
796 if (e
->ops
->elevator_set_req_fn
)
797 return e
->ops
->elevator_set_req_fn(q
, rq
, gfp_mask
);
799 rq
->elevator_private
= NULL
;
803 void elv_put_request(struct request_queue
*q
, struct request
*rq
)
805 struct elevator_queue
*e
= q
->elevator
;
807 if (e
->ops
->elevator_put_req_fn
)
808 e
->ops
->elevator_put_req_fn(rq
);
811 int elv_may_queue(struct request_queue
*q
, int rw
)
813 struct elevator_queue
*e
= q
->elevator
;
815 if (e
->ops
->elevator_may_queue_fn
)
816 return e
->ops
->elevator_may_queue_fn(q
, rw
);
818 return ELV_MQUEUE_MAY
;
821 void elv_abort_queue(struct request_queue
*q
)
825 while (!list_empty(&q
->queue_head
)) {
826 rq
= list_entry_rq(q
->queue_head
.next
);
827 rq
->cmd_flags
|= REQ_QUIET
;
828 trace_block_rq_abort(q
, rq
);
830 * Mark this request as started so we don't trigger
831 * any debug logic in the end I/O path.
833 blk_start_request(rq
);
834 __blk_end_request_all(rq
, -EIO
);
837 EXPORT_SYMBOL(elv_abort_queue
);
839 void elv_completed_request(struct request_queue
*q
, struct request
*rq
)
841 struct elevator_queue
*e
= q
->elevator
;
844 * request is released from the driver, io must be done
846 if (blk_account_rq(rq
)) {
847 q
->in_flight
[rq_is_sync(rq
)]--;
848 if ((rq
->cmd_flags
& REQ_SORTED
) &&
849 e
->ops
->elevator_completed_req_fn
)
850 e
->ops
->elevator_completed_req_fn(q
, rq
);
854 * Check if the queue is waiting for fs requests to be
855 * drained for flush sequence.
857 if (unlikely(q
->ordseq
)) {
858 struct request
*next
= NULL
;
860 if (!list_empty(&q
->queue_head
))
861 next
= list_entry_rq(q
->queue_head
.next
);
863 if (!queue_in_flight(q
) &&
864 blk_ordered_cur_seq(q
) == QUEUE_ORDSEQ_DRAIN
&&
865 (!next
|| blk_ordered_req_seq(next
) > QUEUE_ORDSEQ_DRAIN
)) {
866 blk_ordered_complete_seq(q
, QUEUE_ORDSEQ_DRAIN
, 0);
872 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
875 elv_attr_show(struct kobject
*kobj
, struct attribute
*attr
, char *page
)
877 struct elv_fs_entry
*entry
= to_elv(attr
);
878 struct elevator_queue
*e
;
884 e
= container_of(kobj
, struct elevator_queue
, kobj
);
885 mutex_lock(&e
->sysfs_lock
);
886 error
= e
->ops
? entry
->show(e
, page
) : -ENOENT
;
887 mutex_unlock(&e
->sysfs_lock
);
892 elv_attr_store(struct kobject
*kobj
, struct attribute
*attr
,
893 const char *page
, size_t length
)
895 struct elv_fs_entry
*entry
= to_elv(attr
);
896 struct elevator_queue
*e
;
902 e
= container_of(kobj
, struct elevator_queue
, kobj
);
903 mutex_lock(&e
->sysfs_lock
);
904 error
= e
->ops
? entry
->store(e
, page
, length
) : -ENOENT
;
905 mutex_unlock(&e
->sysfs_lock
);
909 static const struct sysfs_ops elv_sysfs_ops
= {
910 .show
= elv_attr_show
,
911 .store
= elv_attr_store
,
914 static struct kobj_type elv_ktype
= {
915 .sysfs_ops
= &elv_sysfs_ops
,
916 .release
= elevator_release
,
919 int elv_register_queue(struct request_queue
*q
)
921 struct elevator_queue
*e
= q
->elevator
;
924 error
= kobject_add(&e
->kobj
, &q
->kobj
, "%s", "iosched");
926 struct elv_fs_entry
*attr
= e
->elevator_type
->elevator_attrs
;
928 while (attr
->attr
.name
) {
929 if (sysfs_create_file(&e
->kobj
, &attr
->attr
))
934 kobject_uevent(&e
->kobj
, KOBJ_ADD
);
938 EXPORT_SYMBOL(elv_register_queue
);
940 static void __elv_unregister_queue(struct elevator_queue
*e
)
942 kobject_uevent(&e
->kobj
, KOBJ_REMOVE
);
943 kobject_del(&e
->kobj
);
946 void elv_unregister_queue(struct request_queue
*q
)
949 __elv_unregister_queue(q
->elevator
);
951 EXPORT_SYMBOL(elv_unregister_queue
);
953 void elv_register(struct elevator_type
*e
)
957 spin_lock(&elv_list_lock
);
958 BUG_ON(elevator_find(e
->elevator_name
));
959 list_add_tail(&e
->list
, &elv_list
);
960 spin_unlock(&elv_list_lock
);
962 if (!strcmp(e
->elevator_name
, chosen_elevator
) ||
963 (!*chosen_elevator
&&
964 !strcmp(e
->elevator_name
, CONFIG_DEFAULT_IOSCHED
)))
967 printk(KERN_INFO
"io scheduler %s registered%s\n", e
->elevator_name
,
970 EXPORT_SYMBOL_GPL(elv_register
);
972 void elv_unregister(struct elevator_type
*e
)
974 struct task_struct
*g
, *p
;
977 * Iterate every thread in the process to remove the io contexts.
980 read_lock(&tasklist_lock
);
981 do_each_thread(g
, p
) {
984 e
->ops
.trim(p
->io_context
);
986 } while_each_thread(g
, p
);
987 read_unlock(&tasklist_lock
);
990 spin_lock(&elv_list_lock
);
991 list_del_init(&e
->list
);
992 spin_unlock(&elv_list_lock
);
994 EXPORT_SYMBOL_GPL(elv_unregister
);
997 * switch to new_e io scheduler. be careful not to introduce deadlocks -
998 * we don't free the old io scheduler, before we have allocated what we
999 * need for the new one. this way we have a chance of going back to the old
1000 * one, if the new one fails init for some reason.
1002 static int elevator_switch(struct request_queue
*q
, struct elevator_type
*new_e
)
1004 struct elevator_queue
*old_elevator
, *e
;
1008 * Allocate new elevator
1010 e
= elevator_alloc(q
, new_e
);
1014 data
= elevator_init_queue(q
, e
);
1016 kobject_put(&e
->kobj
);
1021 * Turn on BYPASS and drain all requests w/ elevator private data
1023 spin_lock_irq(q
->queue_lock
);
1024 elv_quiesce_start(q
);
1027 * Remember old elevator.
1029 old_elevator
= q
->elevator
;
1032 * attach and start new elevator
1034 elevator_attach(q
, e
, data
);
1036 spin_unlock_irq(q
->queue_lock
);
1038 __elv_unregister_queue(old_elevator
);
1040 if (elv_register_queue(q
))
1044 * finally exit old elevator and turn off BYPASS.
1046 elevator_exit(old_elevator
);
1047 spin_lock_irq(q
->queue_lock
);
1049 spin_unlock_irq(q
->queue_lock
);
1051 blk_add_trace_msg(q
, "elv switch: %s", e
->elevator_type
->elevator_name
);
1057 * switch failed, exit the new io scheduler and reattach the old
1058 * one again (along with re-adding the sysfs dir)
1061 q
->elevator
= old_elevator
;
1062 elv_register_queue(q
);
1064 spin_lock_irq(q
->queue_lock
);
1065 queue_flag_clear(QUEUE_FLAG_ELVSWITCH
, q
);
1066 spin_unlock_irq(q
->queue_lock
);
1071 ssize_t
elv_iosched_store(struct request_queue
*q
, const char *name
,
1074 char elevator_name
[ELV_NAME_MAX
];
1075 struct elevator_type
*e
;
1080 strlcpy(elevator_name
, name
, sizeof(elevator_name
));
1081 e
= elevator_get(strstrip(elevator_name
));
1083 printk(KERN_ERR
"elevator: type %s not found\n", elevator_name
);
1087 if (!strcmp(elevator_name
, q
->elevator
->elevator_type
->elevator_name
)) {
1092 if (!elevator_switch(q
, e
))
1093 printk(KERN_ERR
"elevator: switch to %s failed\n",
1098 ssize_t
elv_iosched_show(struct request_queue
*q
, char *name
)
1100 struct elevator_queue
*e
= q
->elevator
;
1101 struct elevator_type
*elv
;
1102 struct elevator_type
*__e
;
1105 if (!q
->elevator
|| !blk_queue_stackable(q
))
1106 return sprintf(name
, "none\n");
1108 elv
= e
->elevator_type
;
1110 spin_lock(&elv_list_lock
);
1111 list_for_each_entry(__e
, &elv_list
, list
) {
1112 if (!strcmp(elv
->elevator_name
, __e
->elevator_name
))
1113 len
+= sprintf(name
+len
, "[%s] ", elv
->elevator_name
);
1115 len
+= sprintf(name
+len
, "%s ", __e
->elevator_name
);
1117 spin_unlock(&elv_list_lock
);
1119 len
+= sprintf(len
+name
, "\n");
1123 struct request
*elv_rb_former_request(struct request_queue
*q
,
1126 struct rb_node
*rbprev
= rb_prev(&rq
->rb_node
);
1129 return rb_entry_rq(rbprev
);
1133 EXPORT_SYMBOL(elv_rb_former_request
);
1135 struct request
*elv_rb_latter_request(struct request_queue
*q
,
1138 struct rb_node
*rbnext
= rb_next(&rq
->rb_node
);
1141 return rb_entry_rq(rbnext
);
1145 EXPORT_SYMBOL(elv_rb_latter_request
);