projects/linux·blob v2.6.32 · refs

1126 lines · 24.4 KiB

1/*
2 * Block device elevator/IO-scheduler.
3 *
4 * Copyright (C) 2000 Andrea Arcangeli <[email protected]> SuSE
5 *
6 * 30042000 Jens Axboe <[email protected]> :
7 *
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
14 *
15 * 20082000 Dave Jones <[email protected]> :
16 * Removed tests for max-bomb-segments, which was breaking elvtune
17 * when run without -bN
18 *
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
23 *
24 */
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>
37#include <linux/uaccess.h>
38
39#include <trace/events/block.h>
40
41#include "blk.h"
42
43static DEFINE_SPINLOCK(elv_list_lock);
44static LIST_HEAD(elv_list);
45
46/*
47 * Merge hash stuff.
48 */
49static 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))
55
56/*
57 * Query io scheduler to see if the current process issuing bio may be
58 * merged with rq.
59 */
60static int elv_iosched_allow_merge(struct request *rq, struct bio *bio)
61{
62 struct request_queue *q = rq->q;
63 struct elevator_queue *e = q->elevator;
64
65 if (e->ops->elevator_allow_merge_fn)
66 return e->ops->elevator_allow_merge_fn(q, rq, bio);
67
68 return 1;
69}
70
71/*
72 * can we safely merge with this request?
73 */
74int elv_rq_merge_ok(struct request *rq, struct bio *bio)
75{
76 if (!rq_mergeable(rq))
77 return 0;
78
79 /*
80 * Don't merge file system requests and discard requests
81 */
82 if (bio_rw_flagged(bio, BIO_RW_DISCARD) !=
83 bio_rw_flagged(rq->bio, BIO_RW_DISCARD))
84 return 0;
85
86 /*
87 * different data direction or already started, don't merge
88 */
89 if (bio_data_dir(bio) != rq_data_dir(rq))
90 return 0;
91
92 /*
93 * must be same device and not a special request
94 */
95 if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)
96 return 0;
97
98 /*
99 * only merge integrity protected bio into ditto rq
100 */
101 if (bio_integrity(bio) != blk_integrity_rq(rq))
102 return 0;
103
104 if (!elv_iosched_allow_merge(rq, bio))
105 return 0;
106
107 return 1;
108}
109EXPORT_SYMBOL(elv_rq_merge_ok);
110
111static inline int elv_try_merge(struct request *__rq, struct bio *bio)
112{
113 int ret = ELEVATOR_NO_MERGE;
114
115 /*
116 * we can merge and sequence is ok, check if it's possible
117 */
118 if (elv_rq_merge_ok(__rq, bio)) {
119 if (blk_rq_pos(__rq) + blk_rq_sectors(__rq) == bio->bi_sector)
120 ret = ELEVATOR_BACK_MERGE;
121 else if (blk_rq_pos(__rq) - bio_sectors(bio) == bio->bi_sector)
122 ret = ELEVATOR_FRONT_MERGE;
123 }
124
125 return ret;
126}
127
128static struct elevator_type *elevator_find(const char *name)
129{
130 struct elevator_type *e;
131
132 list_for_each_entry(e, &elv_list, list) {
133 if (!strcmp(e->elevator_name, name))
134 return e;
135 }
136
137 return NULL;
138}
139
140static void elevator_put(struct elevator_type *e)
141{
142 module_put(e->elevator_owner);
143}
144
145static struct elevator_type *elevator_get(const char *name)
146{
147 struct elevator_type *e;
148
149 spin_lock(&elv_list_lock);
150
151 e = elevator_find(name);
152 if (!e) {
153 char elv[ELV_NAME_MAX + strlen("-iosched")];
154
155 spin_unlock(&elv_list_lock);
156
157 if (!strcmp(name, "anticipatory"))
158 sprintf(elv, "as-iosched");
159 else
160 sprintf(elv, "%s-iosched", name);
161
162 request_module("%s", elv);
163 spin_lock(&elv_list_lock);
164 e = elevator_find(name);
165 }
166
167 if (e && !try_module_get(e->elevator_owner))
168 e = NULL;
169
170 spin_unlock(&elv_list_lock);
171
172 return e;
173}
174
175static void *elevator_init_queue(struct request_queue *q,
176 struct elevator_queue *eq)
177{
178 return eq->ops->elevator_init_fn(q);
179}
180
181static void elevator_attach(struct request_queue *q, struct elevator_queue *eq,
182 void *data)
183{
184 q->elevator = eq;
185 eq->elevator_data = data;
186}
187
188static char chosen_elevator[16];
189
190static int __init elevator_setup(char *str)
191{
192 /*
193 * Be backwards-compatible with previous kernels, so users
194 * won't get the wrong elevator.
195 */
196 if (!strcmp(str, "as"))
197 strcpy(chosen_elevator, "anticipatory");
198 else
199 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
200 return 1;
201}
202
203__setup("elevator=", elevator_setup);
204
205static struct kobj_type elv_ktype;
206
207static struct elevator_queue *elevator_alloc(struct request_queue *q,
208 struct elevator_type *e)
209{
210 struct elevator_queue *eq;
211 int i;
212
213 eq = kmalloc_node(sizeof(*eq), GFP_KERNEL | __GFP_ZERO, q->node);
214 if (unlikely(!eq))
215 goto err;
216
217 eq->ops = &e->ops;
218 eq->elevator_type = e;
219 kobject_init(&eq->kobj, &elv_ktype);
220 mutex_init(&eq->sysfs_lock);
221
222 eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES,
223 GFP_KERNEL, q->node);
224 if (!eq->hash)
225 goto err;
226
227 for (i = 0; i < ELV_HASH_ENTRIES; i++)
228 INIT_HLIST_HEAD(&eq->hash[i]);
229
230 return eq;
231err:
232 kfree(eq);
233 elevator_put(e);
234 return NULL;
235}
236
237static void elevator_release(struct kobject *kobj)
238{
239 struct elevator_queue *e;
240
241 e = container_of(kobj, struct elevator_queue, kobj);
242 elevator_put(e->elevator_type);
243 kfree(e->hash);
244 kfree(e);
245}
246
247int elevator_init(struct request_queue *q, char *name)
248{
249 struct elevator_type *e = NULL;
250 struct elevator_queue *eq;
251 int ret = 0;
252 void *data;
253
254 INIT_LIST_HEAD(&q->queue_head);
255 q->last_merge = NULL;
256 q->end_sector = 0;
257 q->boundary_rq = NULL;
258
259 if (name) {
260 e = elevator_get(name);
261 if (!e)
262 return -EINVAL;
263 }
264
265 if (!e && *chosen_elevator) {
266 e = elevator_get(chosen_elevator);
267 if (!e)
268 printk(KERN_ERR "I/O scheduler %s not found\n",
269 chosen_elevator);
270 }
271
272 if (!e) {
273 e = elevator_get(CONFIG_DEFAULT_IOSCHED);
274 if (!e) {
275 printk(KERN_ERR
276 "Default I/O scheduler not found. " \
277 "Using noop.\n");
278 e = elevator_get("noop");
279 }
280 }
281
282 eq = elevator_alloc(q, e);
283 if (!eq)
284 return -ENOMEM;
285
286 data = elevator_init_queue(q, eq);
287 if (!data) {
288 kobject_put(&eq->kobj);
289 return -ENOMEM;
290 }
291
292 elevator_attach(q, eq, data);
293 return ret;
294}
295EXPORT_SYMBOL(elevator_init);
296
297void elevator_exit(struct elevator_queue *e)
298{
299 mutex_lock(&e->sysfs_lock);
300 if (e->ops->elevator_exit_fn)
301 e->ops->elevator_exit_fn(e);
302 e->ops = NULL;
303 mutex_unlock(&e->sysfs_lock);
304
305 kobject_put(&e->kobj);
306}
307EXPORT_SYMBOL(elevator_exit);
308
309static inline void __elv_rqhash_del(struct request *rq)
310{
311 hlist_del_init(&rq->hash);
312}
313
314static void elv_rqhash_del(struct request_queue *q, struct request *rq)
315{
316 if (ELV_ON_HASH(rq))
317 __elv_rqhash_del(rq);
318}
319
320static void elv_rqhash_add(struct request_queue *q, struct request *rq)
321{
322 struct elevator_queue *e = q->elevator;
323
324 BUG_ON(ELV_ON_HASH(rq));
325 hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
326}
327
328static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
329{
330 __elv_rqhash_del(rq);
331 elv_rqhash_add(q, rq);
332}
333
334static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
335{
336 struct elevator_queue *e = q->elevator;
337 struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
338 struct hlist_node *entry, *next;
339 struct request *rq;
340
341 hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
342 BUG_ON(!ELV_ON_HASH(rq));
343
344 if (unlikely(!rq_mergeable(rq))) {
345 __elv_rqhash_del(rq);
346 continue;
347 }
348
349 if (rq_hash_key(rq) == offset)
350 return rq;
351 }
352
353 return NULL;
354}
355
356/*
357 * RB-tree support functions for inserting/lookup/removal of requests
358 * in a sorted RB tree.
359 */
360struct request *elv_rb_add(struct rb_root *root, struct request *rq)
361{
362 struct rb_node **p = &root->rb_node;
363 struct rb_node *parent = NULL;
364 struct request *__rq;
365
366 while (*p) {
367 parent = *p;
368 __rq = rb_entry(parent, struct request, rb_node);
369
370 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
371 p = &(*p)->rb_left;
372 else if (blk_rq_pos(rq) > blk_rq_pos(__rq))
373 p = &(*p)->rb_right;
374 else
375 return __rq;
376 }
377
378 rb_link_node(&rq->rb_node, parent, p);
379 rb_insert_color(&rq->rb_node, root);
380 return NULL;
381}
382EXPORT_SYMBOL(elv_rb_add);
383
384void elv_rb_del(struct rb_root *root, struct request *rq)
385{
386 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
387 rb_erase(&rq->rb_node, root);
388 RB_CLEAR_NODE(&rq->rb_node);
389}
390EXPORT_SYMBOL(elv_rb_del);
391
392struct request *elv_rb_find(struct rb_root *root, sector_t sector)
393{
394 struct rb_node *n = root->rb_node;
395 struct request *rq;
396
397 while (n) {
398 rq = rb_entry(n, struct request, rb_node);
399
400 if (sector < blk_rq_pos(rq))
401 n = n->rb_left;
402 else if (sector > blk_rq_pos(rq))
403 n = n->rb_right;
404 else
405 return rq;
406 }
407
408 return NULL;
409}
410EXPORT_SYMBOL(elv_rb_find);
411
412/*
413 * Insert rq into dispatch queue of q. Queue lock must be held on
414 * entry. rq is sort instead into the dispatch queue. To be used by
415 * specific elevators.
416 */
417void elv_dispatch_sort(struct request_queue *q, struct request *rq)
418{
419 sector_t boundary;
420 struct list_head *entry;
421 int stop_flags;
422
423 if (q->last_merge == rq)
424 q->last_merge = NULL;
425
426 elv_rqhash_del(q, rq);
427
428 q->nr_sorted--;
429
430 boundary = q->end_sector;
431 stop_flags = REQ_SOFTBARRIER | REQ_HARDBARRIER | REQ_STARTED;
432 list_for_each_prev(entry, &q->queue_head) {
433 struct request *pos = list_entry_rq(entry);
434
435 if (blk_discard_rq(rq) != blk_discard_rq(pos))
436 break;
437 if (rq_data_dir(rq) != rq_data_dir(pos))
438 break;
439 if (pos->cmd_flags & stop_flags)
440 break;
441 if (blk_rq_pos(rq) >= boundary) {
442 if (blk_rq_pos(pos) < boundary)
443 continue;
444 } else {
445 if (blk_rq_pos(pos) >= boundary)
446 break;
447 }
448 if (blk_rq_pos(rq) >= blk_rq_pos(pos))
449 break;
450 }
451
452 list_add(&rq->queuelist, entry);
453}
454EXPORT_SYMBOL(elv_dispatch_sort);
455
456/*
457 * Insert rq into dispatch queue of q. Queue lock must be held on
458 * entry. rq is added to the back of the dispatch queue. To be used by
459 * specific elevators.
460 */
461void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
462{
463 if (q->last_merge == rq)
464 q->last_merge = NULL;
465
466 elv_rqhash_del(q, rq);
467
468 q->nr_sorted--;
469
470 q->end_sector = rq_end_sector(rq);
471 q->boundary_rq = rq;
472 list_add_tail(&rq->queuelist, &q->queue_head);
473}
474EXPORT_SYMBOL(elv_dispatch_add_tail);
475
476int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
477{
478 struct elevator_queue *e = q->elevator;
479 struct request *__rq;
480 int ret;
481
482 /*
483 * First try one-hit cache.
484 */
485 if (q->last_merge) {
486 ret = elv_try_merge(q->last_merge, bio);
487 if (ret != ELEVATOR_NO_MERGE) {
488 *req = q->last_merge;
489 return ret;
490 }
491 }
492
493 if (blk_queue_nomerges(q))
494 return ELEVATOR_NO_MERGE;
495
496 /*
497 * See if our hash lookup can find a potential backmerge.
498 */
499 __rq = elv_rqhash_find(q, bio->bi_sector);
500 if (__rq && elv_rq_merge_ok(__rq, bio)) {
501 *req = __rq;
502 return ELEVATOR_BACK_MERGE;
503 }
504
505 if (e->ops->elevator_merge_fn)
506 return e->ops->elevator_merge_fn(q, req, bio);
507
508 return ELEVATOR_NO_MERGE;
509}
510
511void elv_merged_request(struct request_queue *q, struct request *rq, int type)
512{
513 struct elevator_queue *e = q->elevator;
514
515 if (e->ops->elevator_merged_fn)
516 e->ops->elevator_merged_fn(q, rq, type);
517
518 if (type == ELEVATOR_BACK_MERGE)
519 elv_rqhash_reposition(q, rq);
520
521 q->last_merge = rq;
522}
523
524void elv_merge_requests(struct request_queue *q, struct request *rq,
525 struct request *next)
526{
527 struct elevator_queue *e = q->elevator;
528
529 if (e->ops->elevator_merge_req_fn)
530 e->ops->elevator_merge_req_fn(q, rq, next);
531
532 elv_rqhash_reposition(q, rq);
533 elv_rqhash_del(q, next);
534
535 q->nr_sorted--;
536 q->last_merge = rq;
537}
538
539void elv_requeue_request(struct request_queue *q, struct request *rq)
540{
541 /*
542 * it already went through dequeue, we need to decrement the
543 * in_flight count again
544 */
545 if (blk_account_rq(rq)) {
546 q->in_flight[rq_is_sync(rq)]--;
547 if (blk_sorted_rq(rq))
548 elv_deactivate_rq(q, rq);
549 }
550
551 rq->cmd_flags &= ~REQ_STARTED;
552
553 elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
554}
555
556void elv_drain_elevator(struct request_queue *q)
557{
558 static int printed;
559 while (q->elevator->ops->elevator_dispatch_fn(q, 1))
560 ;
561 if (q->nr_sorted == 0)
562 return;
563 if (printed++ < 10) {
564 printk(KERN_ERR "%s: forced dispatching is broken "
565 "(nr_sorted=%u), please report this\n",
566 q->elevator->elevator_type->elevator_name, q->nr_sorted);
567 }
568}
569
570/*
571 * Call with queue lock held, interrupts disabled
572 */
573void elv_quiesce_start(struct request_queue *q)
574{
575 if (!q->elevator)
576 return;
577
578 queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
579
580 /*
581 * make sure we don't have any requests in flight
582 */
583 elv_drain_elevator(q);
584 while (q->rq.elvpriv) {
585 __blk_run_queue(q);
586 spin_unlock_irq(q->queue_lock);
587 msleep(10);
588 spin_lock_irq(q->queue_lock);
589 elv_drain_elevator(q);
590 }
591}
592
593void elv_quiesce_end(struct request_queue *q)
594{
595 queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
596}
597
598void elv_insert(struct request_queue *q, struct request *rq, int where)
599{
600 struct list_head *pos;
601 unsigned ordseq;
602 int unplug_it = 1;
603
604 trace_block_rq_insert(q, rq);
605
606 rq->q = q;
607
608 switch (where) {
609 case ELEVATOR_INSERT_FRONT:
610 rq->cmd_flags |= REQ_SOFTBARRIER;
611
612 list_add(&rq->queuelist, &q->queue_head);
613 break;
614
615 case ELEVATOR_INSERT_BACK:
616 rq->cmd_flags |= REQ_SOFTBARRIER;
617 elv_drain_elevator(q);
618 list_add_tail(&rq->queuelist, &q->queue_head);
619 /*
620 * We kick the queue here for the following reasons.
621 * - The elevator might have returned NULL previously
622 * to delay requests and returned them now. As the
623 * queue wasn't empty before this request, ll_rw_blk
624 * won't run the queue on return, resulting in hang.
625 * - Usually, back inserted requests won't be merged
626 * with anything. There's no point in delaying queue
627 * processing.
628 */
629 __blk_run_queue(q);
630 break;
631
632 case ELEVATOR_INSERT_SORT:
633 BUG_ON(!blk_fs_request(rq) && !blk_discard_rq(rq));
634 rq->cmd_flags |= REQ_SORTED;
635 q->nr_sorted++;
636 if (rq_mergeable(rq)) {
637 elv_rqhash_add(q, rq);
638 if (!q->last_merge)
639 q->last_merge = rq;
640 }
641
642 /*
643 * Some ioscheds (cfq) run q->request_fn directly, so
644 * rq cannot be accessed after calling
645 * elevator_add_req_fn.
646 */
647 q->elevator->ops->elevator_add_req_fn(q, rq);
648 break;
649
650 case ELEVATOR_INSERT_REQUEUE:
651 /*
652 * If ordered flush isn't in progress, we do front
653 * insertion; otherwise, requests should be requeued
654 * in ordseq order.
655 */
656 rq->cmd_flags |= REQ_SOFTBARRIER;
657
658 /*
659 * Most requeues happen because of a busy condition,
660 * don't force unplug of the queue for that case.
661 */
662 unplug_it = 0;
663
664 if (q->ordseq == 0) {
665 list_add(&rq->queuelist, &q->queue_head);
666 break;
667 }
668
669 ordseq = blk_ordered_req_seq(rq);
670
671 list_for_each(pos, &q->queue_head) {
672 struct request *pos_rq = list_entry_rq(pos);
673 if (ordseq <= blk_ordered_req_seq(pos_rq))
674 break;
675 }
676
677 list_add_tail(&rq->queuelist, pos);
678 break;
679
680 default:
681 printk(KERN_ERR "%s: bad insertion point %d\n",
682 __func__, where);
683 BUG();
684 }
685
686 if (unplug_it && blk_queue_plugged(q)) {
687 int nrq = q->rq.count[BLK_RW_SYNC] + q->rq.count[BLK_RW_ASYNC]
688 - queue_in_flight(q);
689
690 if (nrq >= q->unplug_thresh)
691 __generic_unplug_device(q);
692 }
693}
694
695void __elv_add_request(struct request_queue *q, struct request *rq, int where,
696 int plug)
697{
698 if (q->ordcolor)
699 rq->cmd_flags |= REQ_ORDERED_COLOR;
700
701 if (rq->cmd_flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
702 /*
703 * toggle ordered color
704 */
705 if (blk_barrier_rq(rq))
706 q->ordcolor ^= 1;
707
708 /*
709 * barriers implicitly indicate back insertion
710 */
711 if (where == ELEVATOR_INSERT_SORT)
712 where = ELEVATOR_INSERT_BACK;
713
714 /*
715 * this request is scheduling boundary, update
716 * end_sector
717 */
718 if (blk_fs_request(rq) || blk_discard_rq(rq)) {
719 q->end_sector = rq_end_sector(rq);
720 q->boundary_rq = rq;
721 }
722 } else if (!(rq->cmd_flags & REQ_ELVPRIV) &&
723 where == ELEVATOR_INSERT_SORT)
724 where = ELEVATOR_INSERT_BACK;
725
726 if (plug)
727 blk_plug_device(q);
728
729 elv_insert(q, rq, where);
730}
731EXPORT_SYMBOL(__elv_add_request);
732
733void elv_add_request(struct request_queue *q, struct request *rq, int where,
734 int plug)
735{
736 unsigned long flags;
737
738 spin_lock_irqsave(q->queue_lock, flags);
739 __elv_add_request(q, rq, where, plug);
740 spin_unlock_irqrestore(q->queue_lock, flags);
741}
742EXPORT_SYMBOL(elv_add_request);
743
744int elv_queue_empty(struct request_queue *q)
745{
746 struct elevator_queue *e = q->elevator;
747
748 if (!list_empty(&q->queue_head))
749 return 0;
750
751 if (e->ops->elevator_queue_empty_fn)
752 return e->ops->elevator_queue_empty_fn(q);
753
754 return 1;
755}
756EXPORT_SYMBOL(elv_queue_empty);
757
758struct request *elv_latter_request(struct request_queue *q, struct request *rq)
759{
760 struct elevator_queue *e = q->elevator;
761
762 if (e->ops->elevator_latter_req_fn)
763 return e->ops->elevator_latter_req_fn(q, rq);
764 return NULL;
765}
766
767struct request *elv_former_request(struct request_queue *q, struct request *rq)
768{
769 struct elevator_queue *e = q->elevator;
770
771 if (e->ops->elevator_former_req_fn)
772 return e->ops->elevator_former_req_fn(q, rq);
773 return NULL;
774}
775
776int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
777{
778 struct elevator_queue *e = q->elevator;
779
780 if (e->ops->elevator_set_req_fn)
781 return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
782
783 rq->elevator_private = NULL;
784 return 0;
785}
786
787void elv_put_request(struct request_queue *q, struct request *rq)
788{
789 struct elevator_queue *e = q->elevator;
790
791 if (e->ops->elevator_put_req_fn)
792 e->ops->elevator_put_req_fn(rq);
793}
794
795int elv_may_queue(struct request_queue *q, int rw)
796{
797 struct elevator_queue *e = q->elevator;
798
799 if (e->ops->elevator_may_queue_fn)
800 return e->ops->elevator_may_queue_fn(q, rw);
801
802 return ELV_MQUEUE_MAY;
803}
804
805void elv_abort_queue(struct request_queue *q)
806{
807 struct request *rq;
808
809 while (!list_empty(&q->queue_head)) {
810 rq = list_entry_rq(q->queue_head.next);
811 rq->cmd_flags |= REQ_QUIET;
812 trace_block_rq_abort(q, rq);
813 /*
814 * Mark this request as started so we don't trigger
815 * any debug logic in the end I/O path.
816 */
817 blk_start_request(rq);
818 __blk_end_request_all(rq, -EIO);
819 }
820}
821EXPORT_SYMBOL(elv_abort_queue);
822
823void elv_completed_request(struct request_queue *q, struct request *rq)
824{
825 struct elevator_queue *e = q->elevator;
826
827 /*
828 * request is released from the driver, io must be done
829 */
830 if (blk_account_rq(rq)) {
831 q->in_flight[rq_is_sync(rq)]--;
832 if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
833 e->ops->elevator_completed_req_fn(q, rq);
834 }
835
836 /*
837 * Check if the queue is waiting for fs requests to be
838 * drained for flush sequence.
839 */
840 if (unlikely(q->ordseq)) {
841 struct request *next = NULL;
842
843 if (!list_empty(&q->queue_head))
844 next = list_entry_rq(q->queue_head.next);
845
846 if (!queue_in_flight(q) &&
847 blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
848 (!next || blk_ordered_req_seq(next) > QUEUE_ORDSEQ_DRAIN)) {
849 blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
850 __blk_run_queue(q);
851 }
852 }
853}
854
855#define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
856
857static ssize_t
858elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
859{
860 struct elv_fs_entry *entry = to_elv(attr);
861 struct elevator_queue *e;
862 ssize_t error;
863
864 if (!entry->show)
865 return -EIO;
866
867 e = container_of(kobj, struct elevator_queue, kobj);
868 mutex_lock(&e->sysfs_lock);
869 error = e->ops ? entry->show(e, page) : -ENOENT;
870 mutex_unlock(&e->sysfs_lock);
871 return error;
872}
873
874static ssize_t
875elv_attr_store(struct kobject *kobj, struct attribute *attr,
876 const char *page, size_t length)
877{
878 struct elv_fs_entry *entry = to_elv(attr);
879 struct elevator_queue *e;
880 ssize_t error;
881
882 if (!entry->store)
883 return -EIO;
884
885 e = container_of(kobj, struct elevator_queue, kobj);
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;
890}
891
892static struct sysfs_ops elv_sysfs_ops = {
893 .show = elv_attr_show,
894 .store = elv_attr_store,
895};
896
897static struct kobj_type elv_ktype = {
898 .sysfs_ops = &elv_sysfs_ops,
899 .release = elevator_release,
900};
901
902int elv_register_queue(struct request_queue *q)
903{
904 struct elevator_queue *e = q->elevator;
905 int error;
906
907 error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
908 if (!error) {
909 struct elv_fs_entry *attr = e->elevator_type->elevator_attrs;
910 if (attr) {
911 while (attr->attr.name) {
912 if (sysfs_create_file(&e->kobj, &attr->attr))
913 break;
914 attr++;
915 }
916 }
917 kobject_uevent(&e->kobj, KOBJ_ADD);
918 }
919 return error;
920}
921
922static void __elv_unregister_queue(struct elevator_queue *e)
923{
924 kobject_uevent(&e->kobj, KOBJ_REMOVE);
925 kobject_del(&e->kobj);
926}
927
928void elv_unregister_queue(struct request_queue *q)
929{
930 if (q)
931 __elv_unregister_queue(q->elevator);
932}
933
934void elv_register(struct elevator_type *e)
935{
936 char *def = "";
937
938 spin_lock(&elv_list_lock);
939 BUG_ON(elevator_find(e->elevator_name));
940 list_add_tail(&e->list, &elv_list);
941 spin_unlock(&elv_list_lock);
942
943 if (!strcmp(e->elevator_name, chosen_elevator) ||
944 (!*chosen_elevator &&
945 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
946 def = " (default)";
947
948 printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
949 def);
950}
951EXPORT_SYMBOL_GPL(elv_register);
952
953void elv_unregister(struct elevator_type *e)
954{
955 struct task_struct *g, *p;
956
957 /*
958 * Iterate every thread in the process to remove the io contexts.
959 */
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);
969 }
970
971 spin_lock(&elv_list_lock);
972 list_del_init(&e->list);
973 spin_unlock(&elv_list_lock);
974}
975EXPORT_SYMBOL_GPL(elv_unregister);
976
977/*
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.
982 */
983static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
984{
985 struct elevator_queue *old_elevator, *e;
986 void *data;
987
988 /*
989 * Allocate new elevator
990 */
991 e = elevator_alloc(q, new_e);
992 if (!e)
993 return 0;
994
995 data = elevator_init_queue(q, e);
996 if (!data) {
997 kobject_put(&e->kobj);
998 return 0;
999 }
1000
1001 /*
1002 * Turn on BYPASS and drain all requests w/ elevator private data
1003 */
1004 spin_lock_irq(q->queue_lock);
1005 elv_quiesce_start(q);
1006
1007 /*
1008 * Remember old elevator.
1009 */
1010 old_elevator = q->elevator;
1011
1012 /*
1013 * attach and start new elevator
1014 */
1015 elevator_attach(q, e, data);
1016
1017 spin_unlock_irq(q->queue_lock);
1018
1019 __elv_unregister_queue(old_elevator);
1020
1021 if (elv_register_queue(q))
1022 goto fail_register;
1023
1024 /*
1025 * finally exit old elevator and turn off BYPASS.
1026 */
1027 elevator_exit(old_elevator);
1028 spin_lock_irq(q->queue_lock);
1029 elv_quiesce_end(q);
1030 spin_unlock_irq(q->queue_lock);
1031
1032 blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name);
1033
1034 return 1;
1035
1036fail_register:
1037 /*
1038 * switch failed, exit the new io scheduler and reattach the old
1039 * one again (along with re-adding the sysfs dir)
1040 */
1041 elevator_exit(e);
1042 q->elevator = old_elevator;
1043 elv_register_queue(q);
1044
1045 spin_lock_irq(q->queue_lock);
1046 queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
1047 spin_unlock_irq(q->queue_lock);
1048
1049 return 0;
1050}
1051
1052ssize_t elv_iosched_store(struct request_queue *q, const char *name,
1053 size_t count)
1054{
1055 char elevator_name[ELV_NAME_MAX];
1056 struct elevator_type *e;
1057
1058 if (!q->elevator)
1059 return count;
1060
1061 strlcpy(elevator_name, name, sizeof(elevator_name));
1062 e = elevator_get(strstrip(elevator_name));
1063 if (!e) {
1064 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
1065 return -EINVAL;
1066 }
1067
1068 if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
1069 elevator_put(e);
1070 return count;
1071 }
1072
1073 if (!elevator_switch(q, e))
1074 printk(KERN_ERR "elevator: switch to %s failed\n",
1075 elevator_name);
1076 return count;
1077}
1078
1079ssize_t elv_iosched_show(struct request_queue *q, char *name)
1080{
1081 struct elevator_queue *e = q->elevator;
1082 struct elevator_type *elv;
1083 struct elevator_type *__e;
1084 int len = 0;
1085
1086 if (!q->elevator)
1087 return sprintf(name, "none\n");
1088
1089 elv = e->elevator_type;
1090
1091 spin_lock(&elv_list_lock);
1092 list_for_each_entry(__e, &elv_list, list) {
1093 if (!strcmp(elv->elevator_name, __e->elevator_name))
1094 len += sprintf(name+len, "[%s] ", elv->elevator_name);
1095 else
1096 len += sprintf(name+len, "%s ", __e->elevator_name);
1097 }
1098 spin_unlock(&elv_list_lock);
1099
1100 len += sprintf(len+name, "\n");
1101 return len;
1102}
1103
1104struct request *elv_rb_former_request(struct request_queue *q,
1105 struct request *rq)
1106{
1107 struct rb_node *rbprev = rb_prev(&rq->rb_node);
1108
1109 if (rbprev)
1110 return rb_entry_rq(rbprev);
1111
1112 return NULL;
1113}
1114EXPORT_SYMBOL(elv_rb_former_request);
1115
1116struct request *elv_rb_latter_request(struct request_queue *q,
1117 struct request *rq)
1118{
1119 struct rb_node *rbnext = rb_next(&rq->rb_node);
1120
1121 if (rbnext)
1122 return rb_entry_rq(rbnext);
1123
1124 return NULL;
1125}
1126EXPORT_SYMBOL(elv_rb_latter_request);