[MIPS] Stacktrace build-fix and improvement
[linux-2.6/linux-mips.git] / block / elevator.c
blob487dd3da8853971d9bcb77cf6ecf51eb39faedf3
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 * can we safely merge with this request?
56 inline int elv_rq_merge_ok(struct request *rq, struct bio *bio)
58 if (!rq_mergeable(rq))
59 return 0;
62 * different data direction or already started, don't merge
64 if (bio_data_dir(bio) != rq_data_dir(rq))
65 return 0;
68 * same device and no special stuff set, merge is ok
70 if (rq->rq_disk == bio->bi_bdev->bd_disk && !rq->special)
71 return 1;
73 return 0;
75 EXPORT_SYMBOL(elv_rq_merge_ok);
77 static inline int elv_try_merge(struct request *__rq, struct bio *bio)
79 int ret = ELEVATOR_NO_MERGE;
82 * we can merge and sequence is ok, check if it's possible
84 if (elv_rq_merge_ok(__rq, bio)) {
85 if (__rq->sector + __rq->nr_sectors == bio->bi_sector)
86 ret = ELEVATOR_BACK_MERGE;
87 else if (__rq->sector - bio_sectors(bio) == bio->bi_sector)
88 ret = ELEVATOR_FRONT_MERGE;
91 return ret;
94 static struct elevator_type *elevator_find(const char *name)
96 struct elevator_type *e = NULL;
97 struct list_head *entry;
99 list_for_each(entry, &elv_list) {
100 struct elevator_type *__e;
102 __e = list_entry(entry, struct elevator_type, list);
104 if (!strcmp(__e->elevator_name, name)) {
105 e = __e;
106 break;
110 return e;
113 static void elevator_put(struct elevator_type *e)
115 module_put(e->elevator_owner);
118 static struct elevator_type *elevator_get(const char *name)
120 struct elevator_type *e;
122 spin_lock_irq(&elv_list_lock);
124 e = elevator_find(name);
125 if (e && !try_module_get(e->elevator_owner))
126 e = NULL;
128 spin_unlock_irq(&elv_list_lock);
130 return e;
133 static void *elevator_init_queue(request_queue_t *q, struct elevator_queue *eq)
135 return eq->ops->elevator_init_fn(q, eq);
138 static void elevator_attach(request_queue_t *q, struct elevator_queue *eq,
139 void *data)
141 q->elevator = eq;
142 eq->elevator_data = data;
145 static char chosen_elevator[16];
147 static int __init elevator_setup(char *str)
150 * Be backwards-compatible with previous kernels, so users
151 * won't get the wrong elevator.
153 if (!strcmp(str, "as"))
154 strcpy(chosen_elevator, "anticipatory");
155 else
156 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
157 return 1;
160 __setup("elevator=", elevator_setup);
162 static struct kobj_type elv_ktype;
164 static elevator_t *elevator_alloc(request_queue_t *q, struct elevator_type *e)
166 elevator_t *eq;
167 int i;
169 eq = kmalloc_node(sizeof(elevator_t), GFP_KERNEL, q->node);
170 if (unlikely(!eq))
171 goto err;
173 memset(eq, 0, sizeof(*eq));
174 eq->ops = &e->ops;
175 eq->elevator_type = e;
176 kobject_init(&eq->kobj);
177 snprintf(eq->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
178 eq->kobj.ktype = &elv_ktype;
179 mutex_init(&eq->sysfs_lock);
181 eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES,
182 GFP_KERNEL, q->node);
183 if (!eq->hash)
184 goto err;
186 for (i = 0; i < ELV_HASH_ENTRIES; i++)
187 INIT_HLIST_HEAD(&eq->hash[i]);
189 return eq;
190 err:
191 kfree(eq);
192 elevator_put(e);
193 return NULL;
196 static void elevator_release(struct kobject *kobj)
198 elevator_t *e = container_of(kobj, elevator_t, kobj);
200 elevator_put(e->elevator_type);
201 kfree(e->hash);
202 kfree(e);
205 int elevator_init(request_queue_t *q, char *name)
207 struct elevator_type *e = NULL;
208 struct elevator_queue *eq;
209 int ret = 0;
210 void *data;
212 INIT_LIST_HEAD(&q->queue_head);
213 q->last_merge = NULL;
214 q->end_sector = 0;
215 q->boundary_rq = NULL;
217 if (name && !(e = elevator_get(name)))
218 return -EINVAL;
220 if (!e && *chosen_elevator && !(e = elevator_get(chosen_elevator)))
221 printk("I/O scheduler %s not found\n", chosen_elevator);
223 if (!e && !(e = elevator_get(CONFIG_DEFAULT_IOSCHED))) {
224 printk("Default I/O scheduler not found, using no-op\n");
225 e = elevator_get("noop");
228 eq = elevator_alloc(q, e);
229 if (!eq)
230 return -ENOMEM;
232 data = elevator_init_queue(q, eq);
233 if (!data) {
234 kobject_put(&eq->kobj);
235 return -ENOMEM;
238 elevator_attach(q, eq, data);
239 return ret;
242 EXPORT_SYMBOL(elevator_init);
244 void elevator_exit(elevator_t *e)
246 mutex_lock(&e->sysfs_lock);
247 if (e->ops->elevator_exit_fn)
248 e->ops->elevator_exit_fn(e);
249 e->ops = NULL;
250 mutex_unlock(&e->sysfs_lock);
252 kobject_put(&e->kobj);
255 EXPORT_SYMBOL(elevator_exit);
257 static inline void __elv_rqhash_del(struct request *rq)
259 hlist_del_init(&rq->hash);
262 static void elv_rqhash_del(request_queue_t *q, struct request *rq)
264 if (ELV_ON_HASH(rq))
265 __elv_rqhash_del(rq);
268 static void elv_rqhash_add(request_queue_t *q, struct request *rq)
270 elevator_t *e = q->elevator;
272 BUG_ON(ELV_ON_HASH(rq));
273 hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
276 static void elv_rqhash_reposition(request_queue_t *q, struct request *rq)
278 __elv_rqhash_del(rq);
279 elv_rqhash_add(q, rq);
282 static struct request *elv_rqhash_find(request_queue_t *q, sector_t offset)
284 elevator_t *e = q->elevator;
285 struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
286 struct hlist_node *entry, *next;
287 struct request *rq;
289 hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
290 BUG_ON(!ELV_ON_HASH(rq));
292 if (unlikely(!rq_mergeable(rq))) {
293 __elv_rqhash_del(rq);
294 continue;
297 if (rq_hash_key(rq) == offset)
298 return rq;
301 return NULL;
305 * RB-tree support functions for inserting/lookup/removal of requests
306 * in a sorted RB tree.
308 struct request *elv_rb_add(struct rb_root *root, struct request *rq)
310 struct rb_node **p = &root->rb_node;
311 struct rb_node *parent = NULL;
312 struct request *__rq;
314 while (*p) {
315 parent = *p;
316 __rq = rb_entry(parent, struct request, rb_node);
318 if (rq->sector < __rq->sector)
319 p = &(*p)->rb_left;
320 else if (rq->sector > __rq->sector)
321 p = &(*p)->rb_right;
322 else
323 return __rq;
326 rb_link_node(&rq->rb_node, parent, p);
327 rb_insert_color(&rq->rb_node, root);
328 return NULL;
331 EXPORT_SYMBOL(elv_rb_add);
333 void elv_rb_del(struct rb_root *root, struct request *rq)
335 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
336 rb_erase(&rq->rb_node, root);
337 RB_CLEAR_NODE(&rq->rb_node);
340 EXPORT_SYMBOL(elv_rb_del);
342 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
344 struct rb_node *n = root->rb_node;
345 struct request *rq;
347 while (n) {
348 rq = rb_entry(n, struct request, rb_node);
350 if (sector < rq->sector)
351 n = n->rb_left;
352 else if (sector > rq->sector)
353 n = n->rb_right;
354 else
355 return rq;
358 return NULL;
361 EXPORT_SYMBOL(elv_rb_find);
364 * Insert rq into dispatch queue of q. Queue lock must be held on
365 * entry. rq is sort insted into the dispatch queue. To be used by
366 * specific elevators.
368 void elv_dispatch_sort(request_queue_t *q, struct request *rq)
370 sector_t boundary;
371 struct list_head *entry;
373 if (q->last_merge == rq)
374 q->last_merge = NULL;
376 elv_rqhash_del(q, rq);
378 q->nr_sorted--;
380 boundary = q->end_sector;
382 list_for_each_prev(entry, &q->queue_head) {
383 struct request *pos = list_entry_rq(entry);
385 if (pos->cmd_flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED))
386 break;
387 if (rq->sector >= boundary) {
388 if (pos->sector < boundary)
389 continue;
390 } else {
391 if (pos->sector >= boundary)
392 break;
394 if (rq->sector >= pos->sector)
395 break;
398 list_add(&rq->queuelist, entry);
401 EXPORT_SYMBOL(elv_dispatch_sort);
404 * Insert rq into dispatch queue of q. Queue lock must be held on
405 * entry. rq is added to the back of the dispatch queue. To be used by
406 * specific elevators.
408 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
410 if (q->last_merge == rq)
411 q->last_merge = NULL;
413 elv_rqhash_del(q, rq);
415 q->nr_sorted--;
417 q->end_sector = rq_end_sector(rq);
418 q->boundary_rq = rq;
419 list_add_tail(&rq->queuelist, &q->queue_head);
422 EXPORT_SYMBOL(elv_dispatch_add_tail);
424 int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
426 elevator_t *e = q->elevator;
427 struct request *__rq;
428 int ret;
431 * First try one-hit cache.
433 if (q->last_merge) {
434 ret = elv_try_merge(q->last_merge, bio);
435 if (ret != ELEVATOR_NO_MERGE) {
436 *req = q->last_merge;
437 return ret;
442 * See if our hash lookup can find a potential backmerge.
444 __rq = elv_rqhash_find(q, bio->bi_sector);
445 if (__rq && elv_rq_merge_ok(__rq, bio)) {
446 *req = __rq;
447 return ELEVATOR_BACK_MERGE;
450 if (e->ops->elevator_merge_fn)
451 return e->ops->elevator_merge_fn(q, req, bio);
453 return ELEVATOR_NO_MERGE;
456 void elv_merged_request(request_queue_t *q, struct request *rq, int type)
458 elevator_t *e = q->elevator;
460 if (e->ops->elevator_merged_fn)
461 e->ops->elevator_merged_fn(q, rq, type);
463 if (type == ELEVATOR_BACK_MERGE)
464 elv_rqhash_reposition(q, rq);
466 q->last_merge = rq;
469 void elv_merge_requests(request_queue_t *q, struct request *rq,
470 struct request *next)
472 elevator_t *e = q->elevator;
474 if (e->ops->elevator_merge_req_fn)
475 e->ops->elevator_merge_req_fn(q, rq, next);
477 elv_rqhash_reposition(q, rq);
478 elv_rqhash_del(q, next);
480 q->nr_sorted--;
481 q->last_merge = rq;
484 void elv_requeue_request(request_queue_t *q, struct request *rq)
486 elevator_t *e = q->elevator;
489 * it already went through dequeue, we need to decrement the
490 * in_flight count again
492 if (blk_account_rq(rq)) {
493 q->in_flight--;
494 if (blk_sorted_rq(rq) && e->ops->elevator_deactivate_req_fn)
495 e->ops->elevator_deactivate_req_fn(q, rq);
498 rq->cmd_flags &= ~REQ_STARTED;
500 elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
503 static void elv_drain_elevator(request_queue_t *q)
505 static int printed;
506 while (q->elevator->ops->elevator_dispatch_fn(q, 1))
508 if (q->nr_sorted == 0)
509 return;
510 if (printed++ < 10) {
511 printk(KERN_ERR "%s: forced dispatching is broken "
512 "(nr_sorted=%u), please report this\n",
513 q->elevator->elevator_type->elevator_name, q->nr_sorted);
517 void elv_insert(request_queue_t *q, struct request *rq, int where)
519 struct list_head *pos;
520 unsigned ordseq;
521 int unplug_it = 1;
523 blk_add_trace_rq(q, rq, BLK_TA_INSERT);
525 rq->q = q;
527 switch (where) {
528 case ELEVATOR_INSERT_FRONT:
529 rq->cmd_flags |= REQ_SOFTBARRIER;
531 list_add(&rq->queuelist, &q->queue_head);
532 break;
534 case ELEVATOR_INSERT_BACK:
535 rq->cmd_flags |= REQ_SOFTBARRIER;
536 elv_drain_elevator(q);
537 list_add_tail(&rq->queuelist, &q->queue_head);
539 * We kick the queue here for the following reasons.
540 * - The elevator might have returned NULL previously
541 * to delay requests and returned them now. As the
542 * queue wasn't empty before this request, ll_rw_blk
543 * won't run the queue on return, resulting in hang.
544 * - Usually, back inserted requests won't be merged
545 * with anything. There's no point in delaying queue
546 * processing.
548 blk_remove_plug(q);
549 q->request_fn(q);
550 break;
552 case ELEVATOR_INSERT_SORT:
553 BUG_ON(!blk_fs_request(rq));
554 rq->cmd_flags |= REQ_SORTED;
555 q->nr_sorted++;
556 if (rq_mergeable(rq)) {
557 elv_rqhash_add(q, rq);
558 if (!q->last_merge)
559 q->last_merge = rq;
563 * Some ioscheds (cfq) run q->request_fn directly, so
564 * rq cannot be accessed after calling
565 * elevator_add_req_fn.
567 q->elevator->ops->elevator_add_req_fn(q, rq);
568 break;
570 case ELEVATOR_INSERT_REQUEUE:
572 * If ordered flush isn't in progress, we do front
573 * insertion; otherwise, requests should be requeued
574 * in ordseq order.
576 rq->cmd_flags |= REQ_SOFTBARRIER;
578 if (q->ordseq == 0) {
579 list_add(&rq->queuelist, &q->queue_head);
580 break;
583 ordseq = blk_ordered_req_seq(rq);
585 list_for_each(pos, &q->queue_head) {
586 struct request *pos_rq = list_entry_rq(pos);
587 if (ordseq <= blk_ordered_req_seq(pos_rq))
588 break;
591 list_add_tail(&rq->queuelist, pos);
593 * most requeues happen because of a busy condition, don't
594 * force unplug of the queue for that case.
596 unplug_it = 0;
597 break;
599 default:
600 printk(KERN_ERR "%s: bad insertion point %d\n",
601 __FUNCTION__, where);
602 BUG();
605 if (unplug_it && blk_queue_plugged(q)) {
606 int nrq = q->rq.count[READ] + q->rq.count[WRITE]
607 - q->in_flight;
609 if (nrq >= q->unplug_thresh)
610 __generic_unplug_device(q);
614 void __elv_add_request(request_queue_t *q, struct request *rq, int where,
615 int plug)
617 if (q->ordcolor)
618 rq->cmd_flags |= REQ_ORDERED_COLOR;
620 if (rq->cmd_flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
622 * toggle ordered color
624 if (blk_barrier_rq(rq))
625 q->ordcolor ^= 1;
628 * barriers implicitly indicate back insertion
630 if (where == ELEVATOR_INSERT_SORT)
631 where = ELEVATOR_INSERT_BACK;
634 * this request is scheduling boundary, update
635 * end_sector
637 if (blk_fs_request(rq)) {
638 q->end_sector = rq_end_sector(rq);
639 q->boundary_rq = rq;
641 } else if (!(rq->cmd_flags & REQ_ELVPRIV) && where == ELEVATOR_INSERT_SORT)
642 where = ELEVATOR_INSERT_BACK;
644 if (plug)
645 blk_plug_device(q);
647 elv_insert(q, rq, where);
650 EXPORT_SYMBOL(__elv_add_request);
652 void elv_add_request(request_queue_t *q, struct request *rq, int where,
653 int plug)
655 unsigned long flags;
657 spin_lock_irqsave(q->queue_lock, flags);
658 __elv_add_request(q, rq, where, plug);
659 spin_unlock_irqrestore(q->queue_lock, flags);
662 EXPORT_SYMBOL(elv_add_request);
664 static inline struct request *__elv_next_request(request_queue_t *q)
666 struct request *rq;
668 while (1) {
669 while (!list_empty(&q->queue_head)) {
670 rq = list_entry_rq(q->queue_head.next);
671 if (blk_do_ordered(q, &rq))
672 return rq;
675 if (!q->elevator->ops->elevator_dispatch_fn(q, 0))
676 return NULL;
680 struct request *elv_next_request(request_queue_t *q)
682 struct request *rq;
683 int ret;
685 while ((rq = __elv_next_request(q)) != NULL) {
686 if (!(rq->cmd_flags & REQ_STARTED)) {
687 elevator_t *e = q->elevator;
690 * This is the first time the device driver
691 * sees this request (possibly after
692 * requeueing). Notify IO scheduler.
694 if (blk_sorted_rq(rq) &&
695 e->ops->elevator_activate_req_fn)
696 e->ops->elevator_activate_req_fn(q, rq);
699 * just mark as started even if we don't start
700 * it, a request that has been delayed should
701 * not be passed by new incoming requests
703 rq->cmd_flags |= REQ_STARTED;
704 blk_add_trace_rq(q, rq, BLK_TA_ISSUE);
707 if (!q->boundary_rq || q->boundary_rq == rq) {
708 q->end_sector = rq_end_sector(rq);
709 q->boundary_rq = NULL;
712 if ((rq->cmd_flags & REQ_DONTPREP) || !q->prep_rq_fn)
713 break;
715 ret = q->prep_rq_fn(q, rq);
716 if (ret == BLKPREP_OK) {
717 break;
718 } else if (ret == BLKPREP_DEFER) {
720 * the request may have been (partially) prepped.
721 * we need to keep this request in the front to
722 * avoid resource deadlock. REQ_STARTED will
723 * prevent other fs requests from passing this one.
725 rq = NULL;
726 break;
727 } else if (ret == BLKPREP_KILL) {
728 int nr_bytes = rq->hard_nr_sectors << 9;
730 if (!nr_bytes)
731 nr_bytes = rq->data_len;
733 blkdev_dequeue_request(rq);
734 rq->cmd_flags |= REQ_QUIET;
735 end_that_request_chunk(rq, 0, nr_bytes);
736 end_that_request_last(rq, 0);
737 } else {
738 printk(KERN_ERR "%s: bad return=%d\n", __FUNCTION__,
739 ret);
740 break;
744 return rq;
747 EXPORT_SYMBOL(elv_next_request);
749 void elv_dequeue_request(request_queue_t *q, struct request *rq)
751 BUG_ON(list_empty(&rq->queuelist));
752 BUG_ON(ELV_ON_HASH(rq));
754 list_del_init(&rq->queuelist);
757 * the time frame between a request being removed from the lists
758 * and to it is freed is accounted as io that is in progress at
759 * the driver side.
761 if (blk_account_rq(rq))
762 q->in_flight++;
765 EXPORT_SYMBOL(elv_dequeue_request);
767 int elv_queue_empty(request_queue_t *q)
769 elevator_t *e = q->elevator;
771 if (!list_empty(&q->queue_head))
772 return 0;
774 if (e->ops->elevator_queue_empty_fn)
775 return e->ops->elevator_queue_empty_fn(q);
777 return 1;
780 EXPORT_SYMBOL(elv_queue_empty);
782 struct request *elv_latter_request(request_queue_t *q, struct request *rq)
784 elevator_t *e = q->elevator;
786 if (e->ops->elevator_latter_req_fn)
787 return e->ops->elevator_latter_req_fn(q, rq);
788 return NULL;
791 struct request *elv_former_request(request_queue_t *q, struct request *rq)
793 elevator_t *e = q->elevator;
795 if (e->ops->elevator_former_req_fn)
796 return e->ops->elevator_former_req_fn(q, rq);
797 return NULL;
800 int elv_set_request(request_queue_t *q, struct request *rq, gfp_t gfp_mask)
802 elevator_t *e = q->elevator;
804 if (e->ops->elevator_set_req_fn)
805 return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
807 rq->elevator_private = NULL;
808 return 0;
811 void elv_put_request(request_queue_t *q, struct request *rq)
813 elevator_t *e = q->elevator;
815 if (e->ops->elevator_put_req_fn)
816 e->ops->elevator_put_req_fn(q, rq);
819 int elv_may_queue(request_queue_t *q, int rw)
821 elevator_t *e = q->elevator;
823 if (e->ops->elevator_may_queue_fn)
824 return e->ops->elevator_may_queue_fn(q, rw);
826 return ELV_MQUEUE_MAY;
829 void elv_completed_request(request_queue_t *q, struct request *rq)
831 elevator_t *e = q->elevator;
834 * request is released from the driver, io must be done
836 if (blk_account_rq(rq)) {
837 q->in_flight--;
838 if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
839 e->ops->elevator_completed_req_fn(q, rq);
843 * Check if the queue is waiting for fs requests to be
844 * drained for flush sequence.
846 if (unlikely(q->ordseq)) {
847 struct request *first_rq = list_entry_rq(q->queue_head.next);
848 if (q->in_flight == 0 &&
849 blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
850 blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
851 blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
852 q->request_fn(q);
857 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
859 static ssize_t
860 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
862 elevator_t *e = container_of(kobj, elevator_t, kobj);
863 struct elv_fs_entry *entry = to_elv(attr);
864 ssize_t error;
866 if (!entry->show)
867 return -EIO;
869 mutex_lock(&e->sysfs_lock);
870 error = e->ops ? entry->show(e, page) : -ENOENT;
871 mutex_unlock(&e->sysfs_lock);
872 return error;
875 static ssize_t
876 elv_attr_store(struct kobject *kobj, struct attribute *attr,
877 const char *page, size_t length)
879 elevator_t *e = container_of(kobj, elevator_t, kobj);
880 struct elv_fs_entry *entry = to_elv(attr);
881 ssize_t error;
883 if (!entry->store)
884 return -EIO;
886 mutex_lock(&e->sysfs_lock);
887 error = e->ops ? entry->store(e, page, length) : -ENOENT;
888 mutex_unlock(&e->sysfs_lock);
889 return error;
892 static struct sysfs_ops elv_sysfs_ops = {
893 .show = elv_attr_show,
894 .store = elv_attr_store,
897 static struct kobj_type elv_ktype = {
898 .sysfs_ops = &elv_sysfs_ops,
899 .release = elevator_release,
902 int elv_register_queue(struct request_queue *q)
904 elevator_t *e = q->elevator;
905 int error;
907 e->kobj.parent = &q->kobj;
909 error = kobject_add(&e->kobj);
910 if (!error) {
911 struct elv_fs_entry *attr = e->elevator_type->elevator_attrs;
912 if (attr) {
913 while (attr->attr.name) {
914 if (sysfs_create_file(&e->kobj, &attr->attr))
915 break;
916 attr++;
919 kobject_uevent(&e->kobj, KOBJ_ADD);
921 return error;
924 static void __elv_unregister_queue(elevator_t *e)
926 kobject_uevent(&e->kobj, KOBJ_REMOVE);
927 kobject_del(&e->kobj);
930 void elv_unregister_queue(struct request_queue *q)
932 if (q)
933 __elv_unregister_queue(q->elevator);
936 int elv_register(struct elevator_type *e)
938 spin_lock_irq(&elv_list_lock);
939 BUG_ON(elevator_find(e->elevator_name));
940 list_add_tail(&e->list, &elv_list);
941 spin_unlock_irq(&elv_list_lock);
943 printk(KERN_INFO "io scheduler %s registered", e->elevator_name);
944 if (!strcmp(e->elevator_name, chosen_elevator) ||
945 (!*chosen_elevator &&
946 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
947 printk(" (default)");
948 printk("\n");
949 return 0;
951 EXPORT_SYMBOL_GPL(elv_register);
953 void elv_unregister(struct elevator_type *e)
955 struct task_struct *g, *p;
958 * Iterate every thread in the process to remove the io contexts.
960 if (e->ops.trim) {
961 read_lock(&tasklist_lock);
962 do_each_thread(g, p) {
963 task_lock(p);
964 if (p->io_context)
965 e->ops.trim(p->io_context);
966 task_unlock(p);
967 } while_each_thread(g, p);
968 read_unlock(&tasklist_lock);
971 spin_lock_irq(&elv_list_lock);
972 list_del_init(&e->list);
973 spin_unlock_irq(&elv_list_lock);
975 EXPORT_SYMBOL_GPL(elv_unregister);
978 * switch to new_e io scheduler. be careful not to introduce deadlocks -
979 * we don't free the old io scheduler, before we have allocated what we
980 * need for the new one. this way we have a chance of going back to the old
981 * one, if the new one fails init for some reason.
983 static int elevator_switch(request_queue_t *q, struct elevator_type *new_e)
985 elevator_t *old_elevator, *e;
986 void *data;
989 * Allocate new elevator
991 e = elevator_alloc(q, new_e);
992 if (!e)
993 return 0;
995 data = elevator_init_queue(q, e);
996 if (!data) {
997 kobject_put(&e->kobj);
998 return 0;
1002 * Turn on BYPASS and drain all requests w/ elevator private data
1004 spin_lock_irq(q->queue_lock);
1006 set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1008 elv_drain_elevator(q);
1010 while (q->rq.elvpriv) {
1011 blk_remove_plug(q);
1012 q->request_fn(q);
1013 spin_unlock_irq(q->queue_lock);
1014 msleep(10);
1015 spin_lock_irq(q->queue_lock);
1016 elv_drain_elevator(q);
1020 * Remember old elevator.
1022 old_elevator = q->elevator;
1025 * attach and start new elevator
1027 elevator_attach(q, e, data);
1029 spin_unlock_irq(q->queue_lock);
1031 __elv_unregister_queue(old_elevator);
1033 if (elv_register_queue(q))
1034 goto fail_register;
1037 * finally exit old elevator and turn off BYPASS.
1039 elevator_exit(old_elevator);
1040 clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1041 return 1;
1043 fail_register:
1045 * switch failed, exit the new io scheduler and reattach the old
1046 * one again (along with re-adding the sysfs dir)
1048 elevator_exit(e);
1049 q->elevator = old_elevator;
1050 elv_register_queue(q);
1051 clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1052 return 0;
1055 ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
1057 char elevator_name[ELV_NAME_MAX];
1058 size_t len;
1059 struct elevator_type *e;
1061 elevator_name[sizeof(elevator_name) - 1] = '\0';
1062 strncpy(elevator_name, name, sizeof(elevator_name) - 1);
1063 len = strlen(elevator_name);
1065 if (len && elevator_name[len - 1] == '\n')
1066 elevator_name[len - 1] = '\0';
1068 e = elevator_get(elevator_name);
1069 if (!e) {
1070 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
1071 return -EINVAL;
1074 if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
1075 elevator_put(e);
1076 return count;
1079 if (!elevator_switch(q, e))
1080 printk(KERN_ERR "elevator: switch to %s failed\n",elevator_name);
1081 return count;
1084 ssize_t elv_iosched_show(request_queue_t *q, char *name)
1086 elevator_t *e = q->elevator;
1087 struct elevator_type *elv = e->elevator_type;
1088 struct list_head *entry;
1089 int len = 0;
1091 spin_lock_irq(q->queue_lock);
1092 list_for_each(entry, &elv_list) {
1093 struct elevator_type *__e;
1095 __e = list_entry(entry, struct elevator_type, list);
1096 if (!strcmp(elv->elevator_name, __e->elevator_name))
1097 len += sprintf(name+len, "[%s] ", elv->elevator_name);
1098 else
1099 len += sprintf(name+len, "%s ", __e->elevator_name);
1101 spin_unlock_irq(q->queue_lock);
1103 len += sprintf(len+name, "\n");
1104 return len;
1107 struct request *elv_rb_former_request(request_queue_t *q, struct request *rq)
1109 struct rb_node *rbprev = rb_prev(&rq->rb_node);
1111 if (rbprev)
1112 return rb_entry_rq(rbprev);
1114 return NULL;
1117 EXPORT_SYMBOL(elv_rb_former_request);
1119 struct request *elv_rb_latter_request(request_queue_t *q, struct request *rq)
1121 struct rb_node *rbnext = rb_next(&rq->rb_node);
1123 if (rbnext)
1124 return rb_entry_rq(rbnext);
1126 return NULL;
1129 EXPORT_SYMBOL(elv_rb_latter_request);