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1/*
2 * Block device elevator/IO-scheduler.
3 *
4 * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
5 *
6 * 30042000 Jens Axboe <axboe@kernel.dk> :
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 <davej@suse.de> :
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/blktrace_api.h>
35#include <linux/hash.h>
36#include <linux/uaccess.h>
37#include <linux/pm_runtime.h>
38#include <linux/blk-cgroup.h>
39
40#include <trace/events/block.h>
41
42#include "blk.h"
43
44static DEFINE_SPINLOCK(elv_list_lock);
45static LIST_HEAD(elv_list);
46
47/*
48 * Merge hash stuff.
49 */
50#define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq))
51
52/*
53 * Query io scheduler to see if the current process issuing bio may be
54 * merged with rq.
55 */
56static int elv_iosched_allow_bio_merge(struct request *rq, struct bio *bio)
57{
58 struct request_queue *q = rq->q;
59 struct elevator_queue *e = q->elevator;
60
61 if (e->type->ops.elevator_allow_bio_merge_fn)
62 return e->type->ops.elevator_allow_bio_merge_fn(q, rq, bio);
63
64 return 1;
65}
66
67/*
68 * can we safely merge with this request?
69 */
70bool elv_bio_merge_ok(struct request *rq, struct bio *bio)
71{
72 if (!blk_rq_merge_ok(rq, bio))
73 return false;
74
75 if (!elv_iosched_allow_bio_merge(rq, bio))
76 return false;
77
78 return true;
79}
80EXPORT_SYMBOL(elv_bio_merge_ok);
81
82static struct elevator_type *elevator_find(const char *name)
83{
84 struct elevator_type *e;
85
86 list_for_each_entry(e, &elv_list, list) {
87 if (!strcmp(e->elevator_name, name))
88 return e;
89 }
90
91 return NULL;
92}
93
94static void elevator_put(struct elevator_type *e)
95{
96 module_put(e->elevator_owner);
97}
98
99static struct elevator_type *elevator_get(const char *name, bool try_loading)
100{
101 struct elevator_type *e;
102
103 spin_lock(&elv_list_lock);
104
105 e = elevator_find(name);
106 if (!e && try_loading) {
107 spin_unlock(&elv_list_lock);
108 request_module("%s-iosched", name);
109 spin_lock(&elv_list_lock);
110 e = elevator_find(name);
111 }
112
113 if (e && !try_module_get(e->elevator_owner))
114 e = NULL;
115
116 spin_unlock(&elv_list_lock);
117
118 return e;
119}
120
121static char chosen_elevator[ELV_NAME_MAX];
122
123static int __init elevator_setup(char *str)
124{
125 /*
126 * Be backwards-compatible with previous kernels, so users
127 * won't get the wrong elevator.
128 */
129 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
130 return 1;
131}
132
133__setup("elevator=", elevator_setup);
134
135/* called during boot to load the elevator chosen by the elevator param */
136void __init load_default_elevator_module(void)
137{
138 struct elevator_type *e;
139
140 if (!chosen_elevator[0])
141 return;
142
143 spin_lock(&elv_list_lock);
144 e = elevator_find(chosen_elevator);
145 spin_unlock(&elv_list_lock);
146
147 if (!e)
148 request_module("%s-iosched", chosen_elevator);
149}
150
151static struct kobj_type elv_ktype;
152
153struct elevator_queue *elevator_alloc(struct request_queue *q,
154 struct elevator_type *e)
155{
156 struct elevator_queue *eq;
157
158 eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node);
159 if (unlikely(!eq))
160 return NULL;
161
162 eq->type = e;
163 kobject_init(&eq->kobj, &elv_ktype);
164 mutex_init(&eq->sysfs_lock);
165 hash_init(eq->hash);
166
167 return eq;
168}
169EXPORT_SYMBOL(elevator_alloc);
170
171static void elevator_release(struct kobject *kobj)
172{
173 struct elevator_queue *e;
174
175 e = container_of(kobj, struct elevator_queue, kobj);
176 elevator_put(e->type);
177 kfree(e);
178}
179
180int elevator_init(struct request_queue *q, char *name)
181{
182 struct elevator_type *e = NULL;
183 int err;
184
185 /*
186 * q->sysfs_lock must be held to provide mutual exclusion between
187 * elevator_switch() and here.
188 */
189 lockdep_assert_held(&q->sysfs_lock);
190
191 if (unlikely(q->elevator))
192 return 0;
193
194 INIT_LIST_HEAD(&q->queue_head);
195 q->last_merge = NULL;
196 q->end_sector = 0;
197 q->boundary_rq = NULL;
198
199 if (name) {
200 e = elevator_get(name, true);
201 if (!e)
202 return -EINVAL;
203 }
204
205 /*
206 * Use the default elevator specified by config boot param or
207 * config option. Don't try to load modules as we could be running
208 * off async and request_module() isn't allowed from async.
209 */
210 if (!e && *chosen_elevator) {
211 e = elevator_get(chosen_elevator, false);
212 if (!e)
213 printk(KERN_ERR "I/O scheduler %s not found\n",
214 chosen_elevator);
215 }
216
217 if (!e) {
218 e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);
219 if (!e) {
220 printk(KERN_ERR
221 "Default I/O scheduler not found. " \
222 "Using noop.\n");
223 e = elevator_get("noop", false);
224 }
225 }
226
227 err = e->ops.elevator_init_fn(q, e);
228 if (err)
229 elevator_put(e);
230 return err;
231}
232EXPORT_SYMBOL(elevator_init);
233
234void elevator_exit(struct elevator_queue *e)
235{
236 mutex_lock(&e->sysfs_lock);
237 if (e->type->ops.elevator_exit_fn)
238 e->type->ops.elevator_exit_fn(e);
239 mutex_unlock(&e->sysfs_lock);
240
241 kobject_put(&e->kobj);
242}
243EXPORT_SYMBOL(elevator_exit);
244
245static inline void __elv_rqhash_del(struct request *rq)
246{
247 hash_del(&rq->hash);
248 rq->cmd_flags &= ~REQ_HASHED;
249}
250
251static void elv_rqhash_del(struct request_queue *q, struct request *rq)
252{
253 if (ELV_ON_HASH(rq))
254 __elv_rqhash_del(rq);
255}
256
257static void elv_rqhash_add(struct request_queue *q, struct request *rq)
258{
259 struct elevator_queue *e = q->elevator;
260
261 BUG_ON(ELV_ON_HASH(rq));
262 hash_add(e->hash, &rq->hash, rq_hash_key(rq));
263 rq->cmd_flags |= REQ_HASHED;
264}
265
266static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
267{
268 __elv_rqhash_del(rq);
269 elv_rqhash_add(q, rq);
270}
271
272static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
273{
274 struct elevator_queue *e = q->elevator;
275 struct hlist_node *next;
276 struct request *rq;
277
278 hash_for_each_possible_safe(e->hash, rq, next, hash, offset) {
279 BUG_ON(!ELV_ON_HASH(rq));
280
281 if (unlikely(!rq_mergeable(rq))) {
282 __elv_rqhash_del(rq);
283 continue;
284 }
285
286 if (rq_hash_key(rq) == offset)
287 return rq;
288 }
289
290 return NULL;
291}
292
293/*
294 * RB-tree support functions for inserting/lookup/removal of requests
295 * in a sorted RB tree.
296 */
297void elv_rb_add(struct rb_root *root, struct request *rq)
298{
299 struct rb_node **p = &root->rb_node;
300 struct rb_node *parent = NULL;
301 struct request *__rq;
302
303 while (*p) {
304 parent = *p;
305 __rq = rb_entry(parent, struct request, rb_node);
306
307 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
308 p = &(*p)->rb_left;
309 else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
310 p = &(*p)->rb_right;
311 }
312
313 rb_link_node(&rq->rb_node, parent, p);
314 rb_insert_color(&rq->rb_node, root);
315}
316EXPORT_SYMBOL(elv_rb_add);
317
318void elv_rb_del(struct rb_root *root, struct request *rq)
319{
320 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
321 rb_erase(&rq->rb_node, root);
322 RB_CLEAR_NODE(&rq->rb_node);
323}
324EXPORT_SYMBOL(elv_rb_del);
325
326struct request *elv_rb_find(struct rb_root *root, sector_t sector)
327{
328 struct rb_node *n = root->rb_node;
329 struct request *rq;
330
331 while (n) {
332 rq = rb_entry(n, struct request, rb_node);
333
334 if (sector < blk_rq_pos(rq))
335 n = n->rb_left;
336 else if (sector > blk_rq_pos(rq))
337 n = n->rb_right;
338 else
339 return rq;
340 }
341
342 return NULL;
343}
344EXPORT_SYMBOL(elv_rb_find);
345
346/*
347 * Insert rq into dispatch queue of q. Queue lock must be held on
348 * entry. rq is sort instead into the dispatch queue. To be used by
349 * specific elevators.
350 */
351void elv_dispatch_sort(struct request_queue *q, struct request *rq)
352{
353 sector_t boundary;
354 struct list_head *entry;
355 int stop_flags;
356
357 if (q->last_merge == rq)
358 q->last_merge = NULL;
359
360 elv_rqhash_del(q, rq);
361
362 q->nr_sorted--;
363
364 boundary = q->end_sector;
365 stop_flags = REQ_SOFTBARRIER | REQ_STARTED;
366 list_for_each_prev(entry, &q->queue_head) {
367 struct request *pos = list_entry_rq(entry);
368
369 if (req_op(rq) != req_op(pos))
370 break;
371 if (rq_data_dir(rq) != rq_data_dir(pos))
372 break;
373 if (pos->cmd_flags & stop_flags)
374 break;
375 if (blk_rq_pos(rq) >= boundary) {
376 if (blk_rq_pos(pos) < boundary)
377 continue;
378 } else {
379 if (blk_rq_pos(pos) >= boundary)
380 break;
381 }
382 if (blk_rq_pos(rq) >= blk_rq_pos(pos))
383 break;
384 }
385
386 list_add(&rq->queuelist, entry);
387}
388EXPORT_SYMBOL(elv_dispatch_sort);
389
390/*
391 * Insert rq into dispatch queue of q. Queue lock must be held on
392 * entry. rq is added to the back of the dispatch queue. To be used by
393 * specific elevators.
394 */
395void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
396{
397 if (q->last_merge == rq)
398 q->last_merge = NULL;
399
400 elv_rqhash_del(q, rq);
401
402 q->nr_sorted--;
403
404 q->end_sector = rq_end_sector(rq);
405 q->boundary_rq = rq;
406 list_add_tail(&rq->queuelist, &q->queue_head);
407}
408EXPORT_SYMBOL(elv_dispatch_add_tail);
409
410int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
411{
412 struct elevator_queue *e = q->elevator;
413 struct request *__rq;
414 int ret;
415
416 /*
417 * Levels of merges:
418 * nomerges: No merges at all attempted
419 * noxmerges: Only simple one-hit cache try
420 * merges: All merge tries attempted
421 */
422 if (blk_queue_nomerges(q) || !bio_mergeable(bio))
423 return ELEVATOR_NO_MERGE;
424
425 /*
426 * First try one-hit cache.
427 */
428 if (q->last_merge && elv_bio_merge_ok(q->last_merge, bio)) {
429 ret = blk_try_merge(q->last_merge, bio);
430 if (ret != ELEVATOR_NO_MERGE) {
431 *req = q->last_merge;
432 return ret;
433 }
434 }
435
436 if (blk_queue_noxmerges(q))
437 return ELEVATOR_NO_MERGE;
438
439 /*
440 * See if our hash lookup can find a potential backmerge.
441 */
442 __rq = elv_rqhash_find(q, bio->bi_iter.bi_sector);
443 if (__rq && elv_bio_merge_ok(__rq, bio)) {
444 *req = __rq;
445 return ELEVATOR_BACK_MERGE;
446 }
447
448 if (e->type->ops.elevator_merge_fn)
449 return e->type->ops.elevator_merge_fn(q, req, bio);
450
451 return ELEVATOR_NO_MERGE;
452}
453
454/*
455 * Attempt to do an insertion back merge. Only check for the case where
456 * we can append 'rq' to an existing request, so we can throw 'rq' away
457 * afterwards.
458 *
459 * Returns true if we merged, false otherwise
460 */
461static bool elv_attempt_insert_merge(struct request_queue *q,
462 struct request *rq)
463{
464 struct request *__rq;
465 bool ret;
466
467 if (blk_queue_nomerges(q))
468 return false;
469
470 /*
471 * First try one-hit cache.
472 */
473 if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq))
474 return true;
475
476 if (blk_queue_noxmerges(q))
477 return false;
478
479 ret = false;
480 /*
481 * See if our hash lookup can find a potential backmerge.
482 */
483 while (1) {
484 __rq = elv_rqhash_find(q, blk_rq_pos(rq));
485 if (!__rq || !blk_attempt_req_merge(q, __rq, rq))
486 break;
487
488 /* The merged request could be merged with others, try again */
489 ret = true;
490 rq = __rq;
491 }
492
493 return ret;
494}
495
496void elv_merged_request(struct request_queue *q, struct request *rq, int type)
497{
498 struct elevator_queue *e = q->elevator;
499
500 if (e->type->ops.elevator_merged_fn)
501 e->type->ops.elevator_merged_fn(q, rq, type);
502
503 if (type == ELEVATOR_BACK_MERGE)
504 elv_rqhash_reposition(q, rq);
505
506 q->last_merge = rq;
507}
508
509void elv_merge_requests(struct request_queue *q, struct request *rq,
510 struct request *next)
511{
512 struct elevator_queue *e = q->elevator;
513 const int next_sorted = next->cmd_flags & REQ_SORTED;
514
515 if (next_sorted && e->type->ops.elevator_merge_req_fn)
516 e->type->ops.elevator_merge_req_fn(q, rq, next);
517
518 elv_rqhash_reposition(q, rq);
519
520 if (next_sorted) {
521 elv_rqhash_del(q, next);
522 q->nr_sorted--;
523 }
524
525 q->last_merge = rq;
526}
527
528void elv_bio_merged(struct request_queue *q, struct request *rq,
529 struct bio *bio)
530{
531 struct elevator_queue *e = q->elevator;
532
533 if (e->type->ops.elevator_bio_merged_fn)
534 e->type->ops.elevator_bio_merged_fn(q, rq, bio);
535}
536
537#ifdef CONFIG_PM
538static void blk_pm_requeue_request(struct request *rq)
539{
540 if (rq->q->dev && !(rq->cmd_flags & REQ_PM))
541 rq->q->nr_pending--;
542}
543
544static void blk_pm_add_request(struct request_queue *q, struct request *rq)
545{
546 if (q->dev && !(rq->cmd_flags & REQ_PM) && q->nr_pending++ == 0 &&
547 (q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING))
548 pm_request_resume(q->dev);
549}
550#else
551static inline void blk_pm_requeue_request(struct request *rq) {}
552static inline void blk_pm_add_request(struct request_queue *q,
553 struct request *rq)
554{
555}
556#endif
557
558void elv_requeue_request(struct request_queue *q, struct request *rq)
559{
560 /*
561 * it already went through dequeue, we need to decrement the
562 * in_flight count again
563 */
564 if (blk_account_rq(rq)) {
565 q->in_flight[rq_is_sync(rq)]--;
566 if (rq->cmd_flags & REQ_SORTED)
567 elv_deactivate_rq(q, rq);
568 }
569
570 rq->cmd_flags &= ~REQ_STARTED;
571
572 blk_pm_requeue_request(rq);
573
574 __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
575}
576
577void elv_drain_elevator(struct request_queue *q)
578{
579 static int printed;
580
581 lockdep_assert_held(q->queue_lock);
582
583 while (q->elevator->type->ops.elevator_dispatch_fn(q, 1))
584 ;
585 if (q->nr_sorted && printed++ < 10) {
586 printk(KERN_ERR "%s: forced dispatching is broken "
587 "(nr_sorted=%u), please report this\n",
588 q->elevator->type->elevator_name, q->nr_sorted);
589 }
590}
591
592void __elv_add_request(struct request_queue *q, struct request *rq, int where)
593{
594 trace_block_rq_insert(q, rq);
595
596 blk_pm_add_request(q, rq);
597
598 rq->q = q;
599
600 if (rq->cmd_flags & REQ_SOFTBARRIER) {
601 /* barriers are scheduling boundary, update end_sector */
602 if (rq->cmd_type == REQ_TYPE_FS) {
603 q->end_sector = rq_end_sector(rq);
604 q->boundary_rq = rq;
605 }
606 } else if (!(rq->cmd_flags & REQ_ELVPRIV) &&
607 (where == ELEVATOR_INSERT_SORT ||
608 where == ELEVATOR_INSERT_SORT_MERGE))
609 where = ELEVATOR_INSERT_BACK;
610
611 switch (where) {
612 case ELEVATOR_INSERT_REQUEUE:
613 case ELEVATOR_INSERT_FRONT:
614 rq->cmd_flags |= REQ_SOFTBARRIER;
615 list_add(&rq->queuelist, &q->queue_head);
616 break;
617
618 case ELEVATOR_INSERT_BACK:
619 rq->cmd_flags |= REQ_SOFTBARRIER;
620 elv_drain_elevator(q);
621 list_add_tail(&rq->queuelist, &q->queue_head);
622 /*
623 * We kick the queue here for the following reasons.
624 * - The elevator might have returned NULL previously
625 * to delay requests and returned them now. As the
626 * queue wasn't empty before this request, ll_rw_blk
627 * won't run the queue on return, resulting in hang.
628 * - Usually, back inserted requests won't be merged
629 * with anything. There's no point in delaying queue
630 * processing.
631 */
632 __blk_run_queue(q);
633 break;
634
635 case ELEVATOR_INSERT_SORT_MERGE:
636 /*
637 * If we succeed in merging this request with one in the
638 * queue already, we are done - rq has now been freed,
639 * so no need to do anything further.
640 */
641 if (elv_attempt_insert_merge(q, rq))
642 break;
643 case ELEVATOR_INSERT_SORT:
644 BUG_ON(rq->cmd_type != REQ_TYPE_FS);
645 rq->cmd_flags |= REQ_SORTED;
646 q->nr_sorted++;
647 if (rq_mergeable(rq)) {
648 elv_rqhash_add(q, rq);
649 if (!q->last_merge)
650 q->last_merge = rq;
651 }
652
653 /*
654 * Some ioscheds (cfq) run q->request_fn directly, so
655 * rq cannot be accessed after calling
656 * elevator_add_req_fn.
657 */
658 q->elevator->type->ops.elevator_add_req_fn(q, rq);
659 break;
660
661 case ELEVATOR_INSERT_FLUSH:
662 rq->cmd_flags |= REQ_SOFTBARRIER;
663 blk_insert_flush(rq);
664 break;
665 default:
666 printk(KERN_ERR "%s: bad insertion point %d\n",
667 __func__, where);
668 BUG();
669 }
670}
671EXPORT_SYMBOL(__elv_add_request);
672
673void elv_add_request(struct request_queue *q, struct request *rq, int where)
674{
675 unsigned long flags;
676
677 spin_lock_irqsave(q->queue_lock, flags);
678 __elv_add_request(q, rq, where);
679 spin_unlock_irqrestore(q->queue_lock, flags);
680}
681EXPORT_SYMBOL(elv_add_request);
682
683struct request *elv_latter_request(struct request_queue *q, struct request *rq)
684{
685 struct elevator_queue *e = q->elevator;
686
687 if (e->type->ops.elevator_latter_req_fn)
688 return e->type->ops.elevator_latter_req_fn(q, rq);
689 return NULL;
690}
691
692struct request *elv_former_request(struct request_queue *q, struct request *rq)
693{
694 struct elevator_queue *e = q->elevator;
695
696 if (e->type->ops.elevator_former_req_fn)
697 return e->type->ops.elevator_former_req_fn(q, rq);
698 return NULL;
699}
700
701int elv_set_request(struct request_queue *q, struct request *rq,
702 struct bio *bio, gfp_t gfp_mask)
703{
704 struct elevator_queue *e = q->elevator;
705
706 if (e->type->ops.elevator_set_req_fn)
707 return e->type->ops.elevator_set_req_fn(q, rq, bio, gfp_mask);
708 return 0;
709}
710
711void elv_put_request(struct request_queue *q, struct request *rq)
712{
713 struct elevator_queue *e = q->elevator;
714
715 if (e->type->ops.elevator_put_req_fn)
716 e->type->ops.elevator_put_req_fn(rq);
717}
718
719int elv_may_queue(struct request_queue *q, int op, int op_flags)
720{
721 struct elevator_queue *e = q->elevator;
722
723 if (e->type->ops.elevator_may_queue_fn)
724 return e->type->ops.elevator_may_queue_fn(q, op, op_flags);
725
726 return ELV_MQUEUE_MAY;
727}
728
729void elv_completed_request(struct request_queue *q, struct request *rq)
730{
731 struct elevator_queue *e = q->elevator;
732
733 /*
734 * request is released from the driver, io must be done
735 */
736 if (blk_account_rq(rq)) {
737 q->in_flight[rq_is_sync(rq)]--;
738 if ((rq->cmd_flags & REQ_SORTED) &&
739 e->type->ops.elevator_completed_req_fn)
740 e->type->ops.elevator_completed_req_fn(q, rq);
741 }
742}
743
744#define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
745
746static ssize_t
747elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
748{
749 struct elv_fs_entry *entry = to_elv(attr);
750 struct elevator_queue *e;
751 ssize_t error;
752
753 if (!entry->show)
754 return -EIO;
755
756 e = container_of(kobj, struct elevator_queue, kobj);
757 mutex_lock(&e->sysfs_lock);
758 error = e->type ? entry->show(e, page) : -ENOENT;
759 mutex_unlock(&e->sysfs_lock);
760 return error;
761}
762
763static ssize_t
764elv_attr_store(struct kobject *kobj, struct attribute *attr,
765 const char *page, size_t length)
766{
767 struct elv_fs_entry *entry = to_elv(attr);
768 struct elevator_queue *e;
769 ssize_t error;
770
771 if (!entry->store)
772 return -EIO;
773
774 e = container_of(kobj, struct elevator_queue, kobj);
775 mutex_lock(&e->sysfs_lock);
776 error = e->type ? entry->store(e, page, length) : -ENOENT;
777 mutex_unlock(&e->sysfs_lock);
778 return error;
779}
780
781static const struct sysfs_ops elv_sysfs_ops = {
782 .show = elv_attr_show,
783 .store = elv_attr_store,
784};
785
786static struct kobj_type elv_ktype = {
787 .sysfs_ops = &elv_sysfs_ops,
788 .release = elevator_release,
789};
790
791int elv_register_queue(struct request_queue *q)
792{
793 struct elevator_queue *e = q->elevator;
794 int error;
795
796 error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
797 if (!error) {
798 struct elv_fs_entry *attr = e->type->elevator_attrs;
799 if (attr) {
800 while (attr->attr.name) {
801 if (sysfs_create_file(&e->kobj, &attr->attr))
802 break;
803 attr++;
804 }
805 }
806 kobject_uevent(&e->kobj, KOBJ_ADD);
807 e->registered = 1;
808 if (e->type->ops.elevator_registered_fn)
809 e->type->ops.elevator_registered_fn(q);
810 }
811 return error;
812}
813EXPORT_SYMBOL(elv_register_queue);
814
815void elv_unregister_queue(struct request_queue *q)
816{
817 if (q) {
818 struct elevator_queue *e = q->elevator;
819
820 kobject_uevent(&e->kobj, KOBJ_REMOVE);
821 kobject_del(&e->kobj);
822 e->registered = 0;
823 }
824}
825EXPORT_SYMBOL(elv_unregister_queue);
826
827int elv_register(struct elevator_type *e)
828{
829 char *def = "";
830
831 /* create icq_cache if requested */
832 if (e->icq_size) {
833 if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
834 WARN_ON(e->icq_align < __alignof__(struct io_cq)))
835 return -EINVAL;
836
837 snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
838 "%s_io_cq", e->elevator_name);
839 e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
840 e->icq_align, 0, NULL);
841 if (!e->icq_cache)
842 return -ENOMEM;
843 }
844
845 /* register, don't allow duplicate names */
846 spin_lock(&elv_list_lock);
847 if (elevator_find(e->elevator_name)) {
848 spin_unlock(&elv_list_lock);
849 if (e->icq_cache)
850 kmem_cache_destroy(e->icq_cache);
851 return -EBUSY;
852 }
853 list_add_tail(&e->list, &elv_list);
854 spin_unlock(&elv_list_lock);
855
856 /* print pretty message */
857 if (!strcmp(e->elevator_name, chosen_elevator) ||
858 (!*chosen_elevator &&
859 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
860 def = " (default)";
861
862 printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
863 def);
864 return 0;
865}
866EXPORT_SYMBOL_GPL(elv_register);
867
868void elv_unregister(struct elevator_type *e)
869{
870 /* unregister */
871 spin_lock(&elv_list_lock);
872 list_del_init(&e->list);
873 spin_unlock(&elv_list_lock);
874
875 /*
876 * Destroy icq_cache if it exists. icq's are RCU managed. Make
877 * sure all RCU operations are complete before proceeding.
878 */
879 if (e->icq_cache) {
880 rcu_barrier();
881 kmem_cache_destroy(e->icq_cache);
882 e->icq_cache = NULL;
883 }
884}
885EXPORT_SYMBOL_GPL(elv_unregister);
886
887/*
888 * switch to new_e io scheduler. be careful not to introduce deadlocks -
889 * we don't free the old io scheduler, before we have allocated what we
890 * need for the new one. this way we have a chance of going back to the old
891 * one, if the new one fails init for some reason.
892 */
893static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
894{
895 struct elevator_queue *old = q->elevator;
896 bool registered = old->registered;
897 int err;
898
899 /*
900 * Turn on BYPASS and drain all requests w/ elevator private data.
901 * Block layer doesn't call into a quiesced elevator - all requests
902 * are directly put on the dispatch list without elevator data
903 * using INSERT_BACK. All requests have SOFTBARRIER set and no
904 * merge happens either.
905 */
906 blk_queue_bypass_start(q);
907
908 /* unregister and clear all auxiliary data of the old elevator */
909 if (registered)
910 elv_unregister_queue(q);
911
912 spin_lock_irq(q->queue_lock);
913 ioc_clear_queue(q);
914 spin_unlock_irq(q->queue_lock);
915
916 /* allocate, init and register new elevator */
917 err = new_e->ops.elevator_init_fn(q, new_e);
918 if (err)
919 goto fail_init;
920
921 if (registered) {
922 err = elv_register_queue(q);
923 if (err)
924 goto fail_register;
925 }
926
927 /* done, kill the old one and finish */
928 elevator_exit(old);
929 blk_queue_bypass_end(q);
930
931 blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
932
933 return 0;
934
935fail_register:
936 elevator_exit(q->elevator);
937fail_init:
938 /* switch failed, restore and re-register old elevator */
939 q->elevator = old;
940 elv_register_queue(q);
941 blk_queue_bypass_end(q);
942
943 return err;
944}
945
946/*
947 * Switch this queue to the given IO scheduler.
948 */
949static int __elevator_change(struct request_queue *q, const char *name)
950{
951 char elevator_name[ELV_NAME_MAX];
952 struct elevator_type *e;
953
954 if (!q->elevator)
955 return -ENXIO;
956
957 strlcpy(elevator_name, name, sizeof(elevator_name));
958 e = elevator_get(strstrip(elevator_name), true);
959 if (!e) {
960 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
961 return -EINVAL;
962 }
963
964 if (!strcmp(elevator_name, q->elevator->type->elevator_name)) {
965 elevator_put(e);
966 return 0;
967 }
968
969 return elevator_switch(q, e);
970}
971
972int elevator_change(struct request_queue *q, const char *name)
973{
974 int ret;
975
976 /* Protect q->elevator from elevator_init() */
977 mutex_lock(&q->sysfs_lock);
978 ret = __elevator_change(q, name);
979 mutex_unlock(&q->sysfs_lock);
980
981 return ret;
982}
983EXPORT_SYMBOL(elevator_change);
984
985ssize_t elv_iosched_store(struct request_queue *q, const char *name,
986 size_t count)
987{
988 int ret;
989
990 if (!q->elevator)
991 return count;
992
993 ret = __elevator_change(q, name);
994 if (!ret)
995 return count;
996
997 printk(KERN_ERR "elevator: switch to %s failed\n", name);
998 return ret;
999}
1000
1001ssize_t elv_iosched_show(struct request_queue *q, char *name)
1002{
1003 struct elevator_queue *e = q->elevator;
1004 struct elevator_type *elv;
1005 struct elevator_type *__e;
1006 int len = 0;
1007
1008 if (!q->elevator || !blk_queue_stackable(q))
1009 return sprintf(name, "none\n");
1010
1011 elv = e->type;
1012
1013 spin_lock(&elv_list_lock);
1014 list_for_each_entry(__e, &elv_list, list) {
1015 if (!strcmp(elv->elevator_name, __e->elevator_name))
1016 len += sprintf(name+len, "[%s] ", elv->elevator_name);
1017 else
1018 len += sprintf(name+len, "%s ", __e->elevator_name);
1019 }
1020 spin_unlock(&elv_list_lock);
1021
1022 len += sprintf(len+name, "\n");
1023 return len;
1024}
1025
1026struct request *elv_rb_former_request(struct request_queue *q,
1027 struct request *rq)
1028{
1029 struct rb_node *rbprev = rb_prev(&rq->rb_node);
1030
1031 if (rbprev)
1032 return rb_entry_rq(rbprev);
1033
1034 return NULL;
1035}
1036EXPORT_SYMBOL(elv_rb_former_request);
1037
1038struct request *elv_rb_latter_request(struct request_queue *q,
1039 struct request *rq)
1040{
1041 struct rb_node *rbnext = rb_next(&rq->rb_node);
1042
1043 if (rbnext)
1044 return rb_entry_rq(rbnext);
1045
1046 return NULL;
1047}
1048EXPORT_SYMBOL(elv_rb_latter_request);
1049
generated by cgit at 2024-05-18 13:49:16 (GMT)