pid namespaces: make alloc_pid(), free_pid() and put_pid() work with struct upid
[linux-2.6/pdupreez.git] / block / elevator.c
blob952aee04a68ad7cc240b8ecb7a8a0e1590b9a33f
1 /*
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
12 * an existing request
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
19 * Jens:
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>
26 #include <linux/fs.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);
44 * Merge hash stuff.
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
55 * merged with rq.
57 static int elv_iosched_allow_merge(struct request *rq, struct bio *bio)
59 struct request_queue *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);
65 return 1;
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))
74 return 0;
77 * different data direction or already started, don't merge
79 if (bio_data_dir(bio) != rq_data_dir(rq))
80 return 0;
83 * must be same device and not a special request
85 if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)
86 return 0;
88 if (!elv_iosched_allow_merge(rq, bio))
89 return 0;
91 return 1;
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;
109 return ret;
112 static struct elevator_type *elevator_find(const char *name)
114 struct elevator_type *e;
116 list_for_each_entry(e, &elv_list, list) {
117 if (!strcmp(e->elevator_name, name))
118 return e;
121 return NULL;
124 static void elevator_put(struct elevator_type *e)
126 module_put(e->elevator_owner);
129 static struct elevator_type *elevator_get(const char *name)
131 struct elevator_type *e;
133 spin_lock(&elv_list_lock);
135 e = elevator_find(name);
136 if (e && !try_module_get(e->elevator_owner))
137 e = NULL;
139 spin_unlock(&elv_list_lock);
141 return e;
144 static void *elevator_init_queue(struct request_queue *q,
145 struct elevator_queue *eq)
147 return eq->ops->elevator_init_fn(q);
150 static void elevator_attach(struct request_queue *q, struct elevator_queue *eq,
151 void *data)
153 q->elevator = eq;
154 eq->elevator_data = data;
157 static char chosen_elevator[16];
159 static int __init elevator_setup(char *str)
162 * Be backwards-compatible with previous kernels, so users
163 * won't get the wrong elevator.
165 if (!strcmp(str, "as"))
166 strcpy(chosen_elevator, "anticipatory");
167 else
168 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
169 return 1;
172 __setup("elevator=", elevator_setup);
174 static struct kobj_type elv_ktype;
176 static elevator_t *elevator_alloc(struct request_queue *q,
177 struct elevator_type *e)
179 elevator_t *eq;
180 int i;
182 eq = kmalloc_node(sizeof(elevator_t), GFP_KERNEL | __GFP_ZERO, q->node);
183 if (unlikely(!eq))
184 goto err;
186 eq->ops = &e->ops;
187 eq->elevator_type = e;
188 kobject_init(&eq->kobj);
189 kobject_set_name(&eq->kobj, "%s", "iosched");
190 eq->kobj.ktype = &elv_ktype;
191 mutex_init(&eq->sysfs_lock);
193 eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES,
194 GFP_KERNEL, q->node);
195 if (!eq->hash)
196 goto err;
198 for (i = 0; i < ELV_HASH_ENTRIES; i++)
199 INIT_HLIST_HEAD(&eq->hash[i]);
201 return eq;
202 err:
203 kfree(eq);
204 elevator_put(e);
205 return NULL;
208 static void elevator_release(struct kobject *kobj)
210 elevator_t *e = container_of(kobj, elevator_t, kobj);
212 elevator_put(e->elevator_type);
213 kfree(e->hash);
214 kfree(e);
217 int elevator_init(struct request_queue *q, char *name)
219 struct elevator_type *e = NULL;
220 struct elevator_queue *eq;
221 int ret = 0;
222 void *data;
224 INIT_LIST_HEAD(&q->queue_head);
225 q->last_merge = NULL;
226 q->end_sector = 0;
227 q->boundary_rq = NULL;
229 if (name && !(e = elevator_get(name)))
230 return -EINVAL;
232 if (!e && *chosen_elevator && !(e = elevator_get(chosen_elevator)))
233 printk("I/O scheduler %s not found\n", chosen_elevator);
235 if (!e && !(e = elevator_get(CONFIG_DEFAULT_IOSCHED))) {
236 printk("Default I/O scheduler not found, using no-op\n");
237 e = elevator_get("noop");
240 eq = elevator_alloc(q, e);
241 if (!eq)
242 return -ENOMEM;
244 data = elevator_init_queue(q, eq);
245 if (!data) {
246 kobject_put(&eq->kobj);
247 return -ENOMEM;
250 elevator_attach(q, eq, data);
251 return ret;
254 EXPORT_SYMBOL(elevator_init);
256 void elevator_exit(elevator_t *e)
258 mutex_lock(&e->sysfs_lock);
259 if (e->ops->elevator_exit_fn)
260 e->ops->elevator_exit_fn(e);
261 e->ops = NULL;
262 mutex_unlock(&e->sysfs_lock);
264 kobject_put(&e->kobj);
267 EXPORT_SYMBOL(elevator_exit);
269 static void elv_activate_rq(struct request_queue *q, struct request *rq)
271 elevator_t *e = q->elevator;
273 if (e->ops->elevator_activate_req_fn)
274 e->ops->elevator_activate_req_fn(q, rq);
277 static void elv_deactivate_rq(struct request_queue *q, struct request *rq)
279 elevator_t *e = q->elevator;
281 if (e->ops->elevator_deactivate_req_fn)
282 e->ops->elevator_deactivate_req_fn(q, rq);
285 static inline void __elv_rqhash_del(struct request *rq)
287 hlist_del_init(&rq->hash);
290 static void elv_rqhash_del(struct request_queue *q, struct request *rq)
292 if (ELV_ON_HASH(rq))
293 __elv_rqhash_del(rq);
296 static void elv_rqhash_add(struct request_queue *q, struct request *rq)
298 elevator_t *e = q->elevator;
300 BUG_ON(ELV_ON_HASH(rq));
301 hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
304 static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
306 __elv_rqhash_del(rq);
307 elv_rqhash_add(q, rq);
310 static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
312 elevator_t *e = q->elevator;
313 struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
314 struct hlist_node *entry, *next;
315 struct request *rq;
317 hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
318 BUG_ON(!ELV_ON_HASH(rq));
320 if (unlikely(!rq_mergeable(rq))) {
321 __elv_rqhash_del(rq);
322 continue;
325 if (rq_hash_key(rq) == offset)
326 return rq;
329 return NULL;
333 * RB-tree support functions for inserting/lookup/removal of requests
334 * in a sorted RB tree.
336 struct request *elv_rb_add(struct rb_root *root, struct request *rq)
338 struct rb_node **p = &root->rb_node;
339 struct rb_node *parent = NULL;
340 struct request *__rq;
342 while (*p) {
343 parent = *p;
344 __rq = rb_entry(parent, struct request, rb_node);
346 if (rq->sector < __rq->sector)
347 p = &(*p)->rb_left;
348 else if (rq->sector > __rq->sector)
349 p = &(*p)->rb_right;
350 else
351 return __rq;
354 rb_link_node(&rq->rb_node, parent, p);
355 rb_insert_color(&rq->rb_node, root);
356 return NULL;
359 EXPORT_SYMBOL(elv_rb_add);
361 void elv_rb_del(struct rb_root *root, struct request *rq)
363 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
364 rb_erase(&rq->rb_node, root);
365 RB_CLEAR_NODE(&rq->rb_node);
368 EXPORT_SYMBOL(elv_rb_del);
370 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
372 struct rb_node *n = root->rb_node;
373 struct request *rq;
375 while (n) {
376 rq = rb_entry(n, struct request, rb_node);
378 if (sector < rq->sector)
379 n = n->rb_left;
380 else if (sector > rq->sector)
381 n = n->rb_right;
382 else
383 return rq;
386 return NULL;
389 EXPORT_SYMBOL(elv_rb_find);
392 * Insert rq into dispatch queue of q. Queue lock must be held on
393 * entry. rq is sort insted into the dispatch queue. To be used by
394 * specific elevators.
396 void elv_dispatch_sort(struct request_queue *q, struct request *rq)
398 sector_t boundary;
399 struct list_head *entry;
401 if (q->last_merge == rq)
402 q->last_merge = NULL;
404 elv_rqhash_del(q, rq);
406 q->nr_sorted--;
408 boundary = q->end_sector;
410 list_for_each_prev(entry, &q->queue_head) {
411 struct request *pos = list_entry_rq(entry);
413 if (rq_data_dir(rq) != rq_data_dir(pos))
414 break;
415 if (pos->cmd_flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED))
416 break;
417 if (rq->sector >= boundary) {
418 if (pos->sector < boundary)
419 continue;
420 } else {
421 if (pos->sector >= boundary)
422 break;
424 if (rq->sector >= pos->sector)
425 break;
428 list_add(&rq->queuelist, entry);
431 EXPORT_SYMBOL(elv_dispatch_sort);
434 * Insert rq into dispatch queue of q. Queue lock must be held on
435 * entry. rq is added to the back of the dispatch queue. To be used by
436 * specific elevators.
438 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
440 if (q->last_merge == rq)
441 q->last_merge = NULL;
443 elv_rqhash_del(q, rq);
445 q->nr_sorted--;
447 q->end_sector = rq_end_sector(rq);
448 q->boundary_rq = rq;
449 list_add_tail(&rq->queuelist, &q->queue_head);
452 EXPORT_SYMBOL(elv_dispatch_add_tail);
454 int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
456 elevator_t *e = q->elevator;
457 struct request *__rq;
458 int ret;
461 * First try one-hit cache.
463 if (q->last_merge) {
464 ret = elv_try_merge(q->last_merge, bio);
465 if (ret != ELEVATOR_NO_MERGE) {
466 *req = q->last_merge;
467 return ret;
472 * See if our hash lookup can find a potential backmerge.
474 __rq = elv_rqhash_find(q, bio->bi_sector);
475 if (__rq && elv_rq_merge_ok(__rq, bio)) {
476 *req = __rq;
477 return ELEVATOR_BACK_MERGE;
480 if (e->ops->elevator_merge_fn)
481 return e->ops->elevator_merge_fn(q, req, bio);
483 return ELEVATOR_NO_MERGE;
486 void elv_merged_request(struct request_queue *q, struct request *rq, int type)
488 elevator_t *e = q->elevator;
490 if (e->ops->elevator_merged_fn)
491 e->ops->elevator_merged_fn(q, rq, type);
493 if (type == ELEVATOR_BACK_MERGE)
494 elv_rqhash_reposition(q, rq);
496 q->last_merge = rq;
499 void elv_merge_requests(struct request_queue *q, struct request *rq,
500 struct request *next)
502 elevator_t *e = q->elevator;
504 if (e->ops->elevator_merge_req_fn)
505 e->ops->elevator_merge_req_fn(q, rq, next);
507 elv_rqhash_reposition(q, rq);
508 elv_rqhash_del(q, next);
510 q->nr_sorted--;
511 q->last_merge = rq;
514 void elv_requeue_request(struct request_queue *q, struct request *rq)
517 * it already went through dequeue, we need to decrement the
518 * in_flight count again
520 if (blk_account_rq(rq)) {
521 q->in_flight--;
522 if (blk_sorted_rq(rq))
523 elv_deactivate_rq(q, rq);
526 rq->cmd_flags &= ~REQ_STARTED;
528 elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
531 static void elv_drain_elevator(struct request_queue *q)
533 static int printed;
534 while (q->elevator->ops->elevator_dispatch_fn(q, 1))
536 if (q->nr_sorted == 0)
537 return;
538 if (printed++ < 10) {
539 printk(KERN_ERR "%s: forced dispatching is broken "
540 "(nr_sorted=%u), please report this\n",
541 q->elevator->elevator_type->elevator_name, q->nr_sorted);
545 void elv_insert(struct request_queue *q, struct request *rq, int where)
547 struct list_head *pos;
548 unsigned ordseq;
549 int unplug_it = 1;
551 blk_add_trace_rq(q, rq, BLK_TA_INSERT);
553 rq->q = q;
555 switch (where) {
556 case ELEVATOR_INSERT_FRONT:
557 rq->cmd_flags |= REQ_SOFTBARRIER;
559 list_add(&rq->queuelist, &q->queue_head);
560 break;
562 case ELEVATOR_INSERT_BACK:
563 rq->cmd_flags |= REQ_SOFTBARRIER;
564 elv_drain_elevator(q);
565 list_add_tail(&rq->queuelist, &q->queue_head);
567 * We kick the queue here for the following reasons.
568 * - The elevator might have returned NULL previously
569 * to delay requests and returned them now. As the
570 * queue wasn't empty before this request, ll_rw_blk
571 * won't run the queue on return, resulting in hang.
572 * - Usually, back inserted requests won't be merged
573 * with anything. There's no point in delaying queue
574 * processing.
576 blk_remove_plug(q);
577 q->request_fn(q);
578 break;
580 case ELEVATOR_INSERT_SORT:
581 BUG_ON(!blk_fs_request(rq));
582 rq->cmd_flags |= REQ_SORTED;
583 q->nr_sorted++;
584 if (rq_mergeable(rq)) {
585 elv_rqhash_add(q, rq);
586 if (!q->last_merge)
587 q->last_merge = rq;
591 * Some ioscheds (cfq) run q->request_fn directly, so
592 * rq cannot be accessed after calling
593 * elevator_add_req_fn.
595 q->elevator->ops->elevator_add_req_fn(q, rq);
596 break;
598 case ELEVATOR_INSERT_REQUEUE:
600 * If ordered flush isn't in progress, we do front
601 * insertion; otherwise, requests should be requeued
602 * in ordseq order.
604 rq->cmd_flags |= REQ_SOFTBARRIER;
607 * Most requeues happen because of a busy condition,
608 * don't force unplug of the queue for that case.
610 unplug_it = 0;
612 if (q->ordseq == 0) {
613 list_add(&rq->queuelist, &q->queue_head);
614 break;
617 ordseq = blk_ordered_req_seq(rq);
619 list_for_each(pos, &q->queue_head) {
620 struct request *pos_rq = list_entry_rq(pos);
621 if (ordseq <= blk_ordered_req_seq(pos_rq))
622 break;
625 list_add_tail(&rq->queuelist, pos);
626 break;
628 default:
629 printk(KERN_ERR "%s: bad insertion point %d\n",
630 __FUNCTION__, where);
631 BUG();
634 if (unplug_it && blk_queue_plugged(q)) {
635 int nrq = q->rq.count[READ] + q->rq.count[WRITE]
636 - q->in_flight;
638 if (nrq >= q->unplug_thresh)
639 __generic_unplug_device(q);
643 void __elv_add_request(struct request_queue *q, struct request *rq, int where,
644 int plug)
646 if (q->ordcolor)
647 rq->cmd_flags |= REQ_ORDERED_COLOR;
649 if (rq->cmd_flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
651 * toggle ordered color
653 if (blk_barrier_rq(rq))
654 q->ordcolor ^= 1;
657 * barriers implicitly indicate back insertion
659 if (where == ELEVATOR_INSERT_SORT)
660 where = ELEVATOR_INSERT_BACK;
663 * this request is scheduling boundary, update
664 * end_sector
666 if (blk_fs_request(rq)) {
667 q->end_sector = rq_end_sector(rq);
668 q->boundary_rq = rq;
670 } else if (!(rq->cmd_flags & REQ_ELVPRIV) && where == ELEVATOR_INSERT_SORT)
671 where = ELEVATOR_INSERT_BACK;
673 if (plug)
674 blk_plug_device(q);
676 elv_insert(q, rq, where);
679 EXPORT_SYMBOL(__elv_add_request);
681 void elv_add_request(struct request_queue *q, struct request *rq, int where,
682 int plug)
684 unsigned long flags;
686 spin_lock_irqsave(q->queue_lock, flags);
687 __elv_add_request(q, rq, where, plug);
688 spin_unlock_irqrestore(q->queue_lock, flags);
691 EXPORT_SYMBOL(elv_add_request);
693 static inline struct request *__elv_next_request(struct request_queue *q)
695 struct request *rq;
697 while (1) {
698 while (!list_empty(&q->queue_head)) {
699 rq = list_entry_rq(q->queue_head.next);
700 if (blk_do_ordered(q, &rq))
701 return rq;
704 if (!q->elevator->ops->elevator_dispatch_fn(q, 0))
705 return NULL;
709 struct request *elv_next_request(struct request_queue *q)
711 struct request *rq;
712 int ret;
714 while ((rq = __elv_next_request(q)) != NULL) {
716 * Kill the empty barrier place holder, the driver must
717 * not ever see it.
719 if (blk_empty_barrier(rq)) {
720 end_queued_request(rq, 1);
721 continue;
723 if (!(rq->cmd_flags & REQ_STARTED)) {
725 * This is the first time the device driver
726 * sees this request (possibly after
727 * requeueing). Notify IO scheduler.
729 if (blk_sorted_rq(rq))
730 elv_activate_rq(q, rq);
733 * just mark as started even if we don't start
734 * it, a request that has been delayed should
735 * not be passed by new incoming requests
737 rq->cmd_flags |= REQ_STARTED;
738 blk_add_trace_rq(q, rq, BLK_TA_ISSUE);
741 if (!q->boundary_rq || q->boundary_rq == rq) {
742 q->end_sector = rq_end_sector(rq);
743 q->boundary_rq = NULL;
746 if ((rq->cmd_flags & REQ_DONTPREP) || !q->prep_rq_fn)
747 break;
749 ret = q->prep_rq_fn(q, rq);
750 if (ret == BLKPREP_OK) {
751 break;
752 } else if (ret == BLKPREP_DEFER) {
754 * the request may have been (partially) prepped.
755 * we need to keep this request in the front to
756 * avoid resource deadlock. REQ_STARTED will
757 * prevent other fs requests from passing this one.
759 rq = NULL;
760 break;
761 } else if (ret == BLKPREP_KILL) {
762 rq->cmd_flags |= REQ_QUIET;
763 end_queued_request(rq, 0);
764 } else {
765 printk(KERN_ERR "%s: bad return=%d\n", __FUNCTION__,
766 ret);
767 break;
771 return rq;
774 EXPORT_SYMBOL(elv_next_request);
776 void elv_dequeue_request(struct request_queue *q, struct request *rq)
778 BUG_ON(list_empty(&rq->queuelist));
779 BUG_ON(ELV_ON_HASH(rq));
781 list_del_init(&rq->queuelist);
784 * the time frame between a request being removed from the lists
785 * and to it is freed is accounted as io that is in progress at
786 * the driver side.
788 if (blk_account_rq(rq))
789 q->in_flight++;
792 EXPORT_SYMBOL(elv_dequeue_request);
794 int elv_queue_empty(struct request_queue *q)
796 elevator_t *e = q->elevator;
798 if (!list_empty(&q->queue_head))
799 return 0;
801 if (e->ops->elevator_queue_empty_fn)
802 return e->ops->elevator_queue_empty_fn(q);
804 return 1;
807 EXPORT_SYMBOL(elv_queue_empty);
809 struct request *elv_latter_request(struct request_queue *q, struct request *rq)
811 elevator_t *e = q->elevator;
813 if (e->ops->elevator_latter_req_fn)
814 return e->ops->elevator_latter_req_fn(q, rq);
815 return NULL;
818 struct request *elv_former_request(struct request_queue *q, struct request *rq)
820 elevator_t *e = q->elevator;
822 if (e->ops->elevator_former_req_fn)
823 return e->ops->elevator_former_req_fn(q, rq);
824 return NULL;
827 int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
829 elevator_t *e = q->elevator;
831 if (e->ops->elevator_set_req_fn)
832 return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
834 rq->elevator_private = NULL;
835 return 0;
838 void elv_put_request(struct request_queue *q, struct request *rq)
840 elevator_t *e = q->elevator;
842 if (e->ops->elevator_put_req_fn)
843 e->ops->elevator_put_req_fn(rq);
846 int elv_may_queue(struct request_queue *q, int rw)
848 elevator_t *e = q->elevator;
850 if (e->ops->elevator_may_queue_fn)
851 return e->ops->elevator_may_queue_fn(q, rw);
853 return ELV_MQUEUE_MAY;
856 void elv_completed_request(struct request_queue *q, struct request *rq)
858 elevator_t *e = q->elevator;
861 * request is released from the driver, io must be done
863 if (blk_account_rq(rq)) {
864 q->in_flight--;
865 if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
866 e->ops->elevator_completed_req_fn(q, rq);
870 * Check if the queue is waiting for fs requests to be
871 * drained for flush sequence.
873 if (unlikely(q->ordseq)) {
874 struct request *first_rq = list_entry_rq(q->queue_head.next);
875 if (q->in_flight == 0 &&
876 blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
877 blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
878 blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
879 q->request_fn(q);
884 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
886 static ssize_t
887 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
889 elevator_t *e = container_of(kobj, elevator_t, kobj);
890 struct elv_fs_entry *entry = to_elv(attr);
891 ssize_t error;
893 if (!entry->show)
894 return -EIO;
896 mutex_lock(&e->sysfs_lock);
897 error = e->ops ? entry->show(e, page) : -ENOENT;
898 mutex_unlock(&e->sysfs_lock);
899 return error;
902 static ssize_t
903 elv_attr_store(struct kobject *kobj, struct attribute *attr,
904 const char *page, size_t length)
906 elevator_t *e = container_of(kobj, elevator_t, kobj);
907 struct elv_fs_entry *entry = to_elv(attr);
908 ssize_t error;
910 if (!entry->store)
911 return -EIO;
913 mutex_lock(&e->sysfs_lock);
914 error = e->ops ? entry->store(e, page, length) : -ENOENT;
915 mutex_unlock(&e->sysfs_lock);
916 return error;
919 static struct sysfs_ops elv_sysfs_ops = {
920 .show = elv_attr_show,
921 .store = elv_attr_store,
924 static struct kobj_type elv_ktype = {
925 .sysfs_ops = &elv_sysfs_ops,
926 .release = elevator_release,
929 int elv_register_queue(struct request_queue *q)
931 elevator_t *e = q->elevator;
932 int error;
934 e->kobj.parent = &q->kobj;
936 error = kobject_add(&e->kobj);
937 if (!error) {
938 struct elv_fs_entry *attr = e->elevator_type->elevator_attrs;
939 if (attr) {
940 while (attr->attr.name) {
941 if (sysfs_create_file(&e->kobj, &attr->attr))
942 break;
943 attr++;
946 kobject_uevent(&e->kobj, KOBJ_ADD);
948 return error;
951 static void __elv_unregister_queue(elevator_t *e)
953 kobject_uevent(&e->kobj, KOBJ_REMOVE);
954 kobject_del(&e->kobj);
957 void elv_unregister_queue(struct request_queue *q)
959 if (q)
960 __elv_unregister_queue(q->elevator);
963 int elv_register(struct elevator_type *e)
965 char *def = "";
967 spin_lock(&elv_list_lock);
968 BUG_ON(elevator_find(e->elevator_name));
969 list_add_tail(&e->list, &elv_list);
970 spin_unlock(&elv_list_lock);
972 if (!strcmp(e->elevator_name, chosen_elevator) ||
973 (!*chosen_elevator &&
974 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
975 def = " (default)";
977 printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name, def);
978 return 0;
980 EXPORT_SYMBOL_GPL(elv_register);
982 void elv_unregister(struct elevator_type *e)
984 struct task_struct *g, *p;
987 * Iterate every thread in the process to remove the io contexts.
989 if (e->ops.trim) {
990 read_lock(&tasklist_lock);
991 do_each_thread(g, p) {
992 task_lock(p);
993 if (p->io_context)
994 e->ops.trim(p->io_context);
995 task_unlock(p);
996 } while_each_thread(g, p);
997 read_unlock(&tasklist_lock);
1000 spin_lock(&elv_list_lock);
1001 list_del_init(&e->list);
1002 spin_unlock(&elv_list_lock);
1004 EXPORT_SYMBOL_GPL(elv_unregister);
1007 * switch to new_e io scheduler. be careful not to introduce deadlocks -
1008 * we don't free the old io scheduler, before we have allocated what we
1009 * need for the new one. this way we have a chance of going back to the old
1010 * one, if the new one fails init for some reason.
1012 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
1014 elevator_t *old_elevator, *e;
1015 void *data;
1018 * Allocate new elevator
1020 e = elevator_alloc(q, new_e);
1021 if (!e)
1022 return 0;
1024 data = elevator_init_queue(q, e);
1025 if (!data) {
1026 kobject_put(&e->kobj);
1027 return 0;
1031 * Turn on BYPASS and drain all requests w/ elevator private data
1033 spin_lock_irq(q->queue_lock);
1035 set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1037 elv_drain_elevator(q);
1039 while (q->rq.elvpriv) {
1040 blk_remove_plug(q);
1041 q->request_fn(q);
1042 spin_unlock_irq(q->queue_lock);
1043 msleep(10);
1044 spin_lock_irq(q->queue_lock);
1045 elv_drain_elevator(q);
1049 * Remember old elevator.
1051 old_elevator = q->elevator;
1054 * attach and start new elevator
1056 elevator_attach(q, e, data);
1058 spin_unlock_irq(q->queue_lock);
1060 __elv_unregister_queue(old_elevator);
1062 if (elv_register_queue(q))
1063 goto fail_register;
1066 * finally exit old elevator and turn off BYPASS.
1068 elevator_exit(old_elevator);
1069 clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1070 return 1;
1072 fail_register:
1074 * switch failed, exit the new io scheduler and reattach the old
1075 * one again (along with re-adding the sysfs dir)
1077 elevator_exit(e);
1078 q->elevator = old_elevator;
1079 elv_register_queue(q);
1080 clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1081 return 0;
1084 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
1085 size_t count)
1087 char elevator_name[ELV_NAME_MAX];
1088 size_t len;
1089 struct elevator_type *e;
1091 elevator_name[sizeof(elevator_name) - 1] = '\0';
1092 strncpy(elevator_name, name, sizeof(elevator_name) - 1);
1093 len = strlen(elevator_name);
1095 if (len && elevator_name[len - 1] == '\n')
1096 elevator_name[len - 1] = '\0';
1098 e = elevator_get(elevator_name);
1099 if (!e) {
1100 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
1101 return -EINVAL;
1104 if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
1105 elevator_put(e);
1106 return count;
1109 if (!elevator_switch(q, e))
1110 printk(KERN_ERR "elevator: switch to %s failed\n",elevator_name);
1111 return count;
1114 ssize_t elv_iosched_show(struct request_queue *q, char *name)
1116 elevator_t *e = q->elevator;
1117 struct elevator_type *elv = e->elevator_type;
1118 struct elevator_type *__e;
1119 int len = 0;
1121 spin_lock(&elv_list_lock);
1122 list_for_each_entry(__e, &elv_list, list) {
1123 if (!strcmp(elv->elevator_name, __e->elevator_name))
1124 len += sprintf(name+len, "[%s] ", elv->elevator_name);
1125 else
1126 len += sprintf(name+len, "%s ", __e->elevator_name);
1128 spin_unlock(&elv_list_lock);
1130 len += sprintf(len+name, "\n");
1131 return len;
1134 struct request *elv_rb_former_request(struct request_queue *q,
1135 struct request *rq)
1137 struct rb_node *rbprev = rb_prev(&rq->rb_node);
1139 if (rbprev)
1140 return rb_entry_rq(rbprev);
1142 return NULL;
1145 EXPORT_SYMBOL(elv_rb_former_request);
1147 struct request *elv_rb_latter_request(struct request_queue *q,
1148 struct request *rq)
1150 struct rb_node *rbnext = rb_next(&rq->rb_node);
1152 if (rbnext)
1153 return rb_entry_rq(rbnext);
1155 return NULL;
1158 EXPORT_SYMBOL(elv_rb_latter_request);