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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
39#include <trace/events/block.h>
40
41#include "blk.h"
42#include "blk-cgroup.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_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_merge_fn)
62 return e->type->ops.elevator_allow_merge_fn(q, rq, bio);
63
64 return 1;
65}
66
67/*
68 * can we safely merge with this request?
69 */
70bool elv_rq_merge_ok(struct request *rq, struct bio *bio)
71{
72 if (!blk_rq_merge_ok(rq, bio))
73 return 0;
74
75 if (!elv_iosched_allow_merge(rq, bio))
76 return 0;
77
78 return 1;
79}
80EXPORT_SYMBOL(elv_rq_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 goto err;
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;
168err:
169 kfree(eq);
170 elevator_put(e);
171 return NULL;
172}
173EXPORT_SYMBOL(elevator_alloc);
174
175static void elevator_release(struct kobject *kobj)
176{
177 struct elevator_queue *e;
178
179 e = container_of(kobj, struct elevator_queue, kobj);
180 elevator_put(e->type);
181 kfree(e);
182}
183
184int elevator_init(struct request_queue *q, char *name)
185{
186 struct elevator_type *e = NULL;
187 int err;
188
189 /*
190 * q->sysfs_lock must be held to provide mutual exclusion between
191 * elevator_switch() and here.
192 */
193 lockdep_assert_held(&q->sysfs_lock);
194
195 if (unlikely(q->elevator))
196 return 0;
197
198 INIT_LIST_HEAD(&q->queue_head);
199 q->last_merge = NULL;
200 q->end_sector = 0;
201 q->boundary_rq = NULL;
202
203 if (name) {
204 e = elevator_get(name, true);
205 if (!e)
206 return -EINVAL;
207 }
208
209 /*
210 * Use the default elevator specified by config boot param or
211 * config option. Don't try to load modules as we could be running
212 * off async and request_module() isn't allowed from async.
213 */
214 if (!e && *chosen_elevator) {
215 e = elevator_get(chosen_elevator, false);
216 if (!e)
217 printk(KERN_ERR "I/O scheduler %s not found\n",
218 chosen_elevator);
219 }
220
221 if (!e) {
222 e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);
223 if (!e) {
224 printk(KERN_ERR
225 "Default I/O scheduler not found. " \
226 "Using noop.\n");
227 e = elevator_get("noop", false);
228 }
229 }
230
231 err = e->ops.elevator_init_fn(q, e);
232 return 0;
233}
234EXPORT_SYMBOL(elevator_init);
235
236void elevator_exit(struct elevator_queue *e)
237{
238 mutex_lock(&e->sysfs_lock);
239 if (e->type->ops.elevator_exit_fn)
240 e->type->ops.elevator_exit_fn(e);
241 mutex_unlock(&e->sysfs_lock);
242
243 kobject_put(&e->kobj);
244}
245EXPORT_SYMBOL(elevator_exit);
246
247static inline void __elv_rqhash_del(struct request *rq)
248{
249 hash_del(&rq->hash);
250 rq->cmd_flags &= ~REQ_HASHED;
251}
252
253static void elv_rqhash_del(struct request_queue *q, struct request *rq)
254{
255 if (ELV_ON_HASH(rq))
256 __elv_rqhash_del(rq);
257}
258
259static void elv_rqhash_add(struct request_queue *q, struct request *rq)
260{
261 struct elevator_queue *e = q->elevator;
262
263 BUG_ON(ELV_ON_HASH(rq));
264 hash_add(e->hash, &rq->hash, rq_hash_key(rq));
265 rq->cmd_flags |= REQ_HASHED;
266}
267
268static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
269{
270 __elv_rqhash_del(rq);
271 elv_rqhash_add(q, rq);
272}
273
274static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
275{
276 struct elevator_queue *e = q->elevator;
277 struct hlist_node *next;
278 struct request *rq;
279
280 hash_for_each_possible_safe(e->hash, rq, next, hash, offset) {
281 BUG_ON(!ELV_ON_HASH(rq));
282
283 if (unlikely(!rq_mergeable(rq))) {
284 __elv_rqhash_del(rq);
285 continue;
286 }
287
288 if (rq_hash_key(rq) == offset)
289 return rq;
290 }
291
292 return NULL;
293}
294
295/*
296 * RB-tree support functions for inserting/lookup/removal of requests
297 * in a sorted RB tree.
298 */
299void elv_rb_add(struct rb_root *root, struct request *rq)
300{
301 struct rb_node **p = &root->rb_node;
302 struct rb_node *parent = NULL;
303 struct request *__rq;
304
305 while (*p) {
306 parent = *p;
307 __rq = rb_entry(parent, struct request, rb_node);
308
309 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
310 p = &(*p)->rb_left;
311 else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
312 p = &(*p)->rb_right;
313 }
314
315 rb_link_node(&rq->rb_node, parent, p);
316 rb_insert_color(&rq->rb_node, root);
317}
318EXPORT_SYMBOL(elv_rb_add);
319
320void elv_rb_del(struct rb_root *root, struct request *rq)
321{
322 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
323 rb_erase(&rq->rb_node, root);
324 RB_CLEAR_NODE(&rq->rb_node);
325}
326EXPORT_SYMBOL(elv_rb_del);
327
328struct request *elv_rb_find(struct rb_root *root, sector_t sector)
329{
330 struct rb_node *n = root->rb_node;
331 struct request *rq;
332
333 while (n) {
334 rq = rb_entry(n, struct request, rb_node);
335
336 if (sector < blk_rq_pos(rq))
337 n = n->rb_left;
338 else if (sector > blk_rq_pos(rq))
339 n = n->rb_right;
340 else
341 return rq;
342 }
343
344 return NULL;
345}
346EXPORT_SYMBOL(elv_rb_find);
347
348/*
349 * Insert rq into dispatch queue of q. Queue lock must be held on
350 * entry. rq is sort instead into the dispatch queue. To be used by
351 * specific elevators.
352 */
353void elv_dispatch_sort(struct request_queue *q, struct request *rq)
354{
355 sector_t boundary;
356 struct list_head *entry;
357 int stop_flags;
358
359 if (q->last_merge == rq)
360 q->last_merge = NULL;
361
362 elv_rqhash_del(q, rq);
363
364 q->nr_sorted--;
365
366 boundary = q->end_sector;
367 stop_flags = REQ_SOFTBARRIER | REQ_STARTED;
368 list_for_each_prev(entry, &q->queue_head) {
369 struct request *pos = list_entry_rq(entry);
370
371 if ((rq->cmd_flags & REQ_DISCARD) !=
372 (pos->cmd_flags & REQ_DISCARD))
373 break;
374 if (rq_data_dir(rq) != rq_data_dir(pos))
375 break;
376 if (pos->cmd_flags & stop_flags)
377 break;
378 if (blk_rq_pos(rq) >= boundary) {
379 if (blk_rq_pos(pos) < boundary)
380 continue;
381 } else {
382 if (blk_rq_pos(pos) >= boundary)
383 break;
384 }
385 if (blk_rq_pos(rq) >= blk_rq_pos(pos))
386 break;
387 }
388
389 list_add(&rq->queuelist, entry);
390}
391EXPORT_SYMBOL(elv_dispatch_sort);
392
393/*
394 * Insert rq into dispatch queue of q. Queue lock must be held on
395 * entry. rq is added to the back of the dispatch queue. To be used by
396 * specific elevators.
397 */
398void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
399{
400 if (q->last_merge == rq)
401 q->last_merge = NULL;
402
403 elv_rqhash_del(q, rq);
404
405 q->nr_sorted--;
406
407 q->end_sector = rq_end_sector(rq);
408 q->boundary_rq = rq;
409 list_add_tail(&rq->queuelist, &q->queue_head);
410}
411EXPORT_SYMBOL(elv_dispatch_add_tail);
412
413int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
414{
415 struct elevator_queue *e = q->elevator;
416 struct request *__rq;
417 int ret;
418
419 /*
420 * Levels of merges:
421 * nomerges: No merges at all attempted
422 * noxmerges: Only simple one-hit cache try
423 * merges: All merge tries attempted
424 */
425 if (blk_queue_nomerges(q))
426 return ELEVATOR_NO_MERGE;
427
428 /*
429 * First try one-hit cache.
430 */
431 if (q->last_merge && elv_rq_merge_ok(q->last_merge, bio)) {
432 ret = blk_try_merge(q->last_merge, bio);
433 if (ret != ELEVATOR_NO_MERGE) {
434 *req = q->last_merge;
435 return ret;
436 }
437 }
438
439 if (blk_queue_noxmerges(q))
440 return ELEVATOR_NO_MERGE;
441
442 /*
443 * See if our hash lookup can find a potential backmerge.
444 */
445 __rq = elv_rqhash_find(q, bio->bi_iter.bi_sector);
446 if (__rq && elv_rq_merge_ok(__rq, bio)) {
447 *req = __rq;
448 return ELEVATOR_BACK_MERGE;
449 }
450
451 if (e->type->ops.elevator_merge_fn)
452 return e->type->ops.elevator_merge_fn(q, req, bio);
453
454 return ELEVATOR_NO_MERGE;
455}
456
457/*
458 * Attempt to do an insertion back merge. Only check for the case where
459 * we can append 'rq' to an existing request, so we can throw 'rq' away
460 * afterwards.
461 *
462 * Returns true if we merged, false otherwise
463 */
464static bool elv_attempt_insert_merge(struct request_queue *q,
465 struct request *rq)
466{
467 struct request *__rq;
468 bool ret;
469
470 if (blk_queue_nomerges(q))
471 return false;
472
473 /*
474 * First try one-hit cache.
475 */
476 if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq))
477 return true;
478
479 if (blk_queue_noxmerges(q))
480 return false;
481
482 ret = false;
483 /*
484 * See if our hash lookup can find a potential backmerge.
485 */
486 while (1) {
487 __rq = elv_rqhash_find(q, blk_rq_pos(rq));
488 if (!__rq || !blk_attempt_req_merge(q, __rq, rq))
489 break;
490
491 /* The merged request could be merged with others, try again */
492 ret = true;
493 rq = __rq;
494 }
495
496 return ret;
497}
498
499void elv_merged_request(struct request_queue *q, struct request *rq, int type)
500{
501 struct elevator_queue *e = q->elevator;
502
503 if (e->type->ops.elevator_merged_fn)
504 e->type->ops.elevator_merged_fn(q, rq, type);
505
506 if (type == ELEVATOR_BACK_MERGE)
507 elv_rqhash_reposition(q, rq);
508
509 q->last_merge = rq;
510}
511
512void elv_merge_requests(struct request_queue *q, struct request *rq,
513 struct request *next)
514{
515 struct elevator_queue *e = q->elevator;
516 const int next_sorted = next->cmd_flags & REQ_SORTED;
517
518 if (next_sorted && e->type->ops.elevator_merge_req_fn)
519 e->type->ops.elevator_merge_req_fn(q, rq, next);
520
521 elv_rqhash_reposition(q, rq);
522
523 if (next_sorted) {
524 elv_rqhash_del(q, next);
525 q->nr_sorted--;
526 }
527
528 q->last_merge = rq;
529}
530
531void elv_bio_merged(struct request_queue *q, struct request *rq,
532 struct bio *bio)
533{
534 struct elevator_queue *e = q->elevator;
535
536 if (e->type->ops.elevator_bio_merged_fn)
537 e->type->ops.elevator_bio_merged_fn(q, rq, bio);
538}
539
540#ifdef CONFIG_PM_RUNTIME
541static void blk_pm_requeue_request(struct request *rq)
542{
543 if (rq->q->dev && !(rq->cmd_flags & REQ_PM))
544 rq->q->nr_pending--;
545}
546
547static void blk_pm_add_request(struct request_queue *q, struct request *rq)
548{
549 if (q->dev && !(rq->cmd_flags & REQ_PM) && q->nr_pending++ == 0 &&
550 (q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING))
551 pm_request_resume(q->dev);
552}
553#else
554static inline void blk_pm_requeue_request(struct request *rq) {}
555static inline void blk_pm_add_request(struct request_queue *q,
556 struct request *rq)
557{
558}
559#endif
560
561void elv_requeue_request(struct request_queue *q, struct request *rq)
562{
563 /*
564 * it already went through dequeue, we need to decrement the
565 * in_flight count again
566 */
567 if (blk_account_rq(rq)) {
568 q->in_flight[rq_is_sync(rq)]--;
569 if (rq->cmd_flags & REQ_SORTED)
570 elv_deactivate_rq(q, rq);
571 }
572
573 rq->cmd_flags &= ~REQ_STARTED;
574
575 blk_pm_requeue_request(rq);
576
577 __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
578}
579
580void elv_drain_elevator(struct request_queue *q)
581{
582 static int printed;
583
584 lockdep_assert_held(q->queue_lock);
585
586 while (q->elevator->type->ops.elevator_dispatch_fn(q, 1))
587 ;
588 if (q->nr_sorted && printed++ < 10) {
589 printk(KERN_ERR "%s: forced dispatching is broken "
590 "(nr_sorted=%u), please report this\n",
591 q->elevator->type->elevator_name, q->nr_sorted);
592 }
593}
594
595void __elv_add_request(struct request_queue *q, struct request *rq, int where)
596{
597 trace_block_rq_insert(q, rq);
598
599 blk_pm_add_request(q, rq);
600
601 rq->q = q;
602
603 if (rq->cmd_flags & REQ_SOFTBARRIER) {
604 /* barriers are scheduling boundary, update end_sector */
605 if (rq->cmd_type == REQ_TYPE_FS) {
606 q->end_sector = rq_end_sector(rq);
607 q->boundary_rq = rq;
608 }
609 } else if (!(rq->cmd_flags & REQ_ELVPRIV) &&
610 (where == ELEVATOR_INSERT_SORT ||
611 where == ELEVATOR_INSERT_SORT_MERGE))
612 where = ELEVATOR_INSERT_BACK;
613
614 switch (where) {
615 case ELEVATOR_INSERT_REQUEUE:
616 case ELEVATOR_INSERT_FRONT:
617 rq->cmd_flags |= REQ_SOFTBARRIER;
618 list_add(&rq->queuelist, &q->queue_head);
619 break;
620
621 case ELEVATOR_INSERT_BACK:
622 rq->cmd_flags |= REQ_SOFTBARRIER;
623 elv_drain_elevator(q);
624 list_add_tail(&rq->queuelist, &q->queue_head);
625 /*
626 * We kick the queue here for the following reasons.
627 * - The elevator might have returned NULL previously
628 * to delay requests and returned them now. As the
629 * queue wasn't empty before this request, ll_rw_blk
630 * won't run the queue on return, resulting in hang.
631 * - Usually, back inserted requests won't be merged
632 * with anything. There's no point in delaying queue
633 * processing.
634 */
635 __blk_run_queue(q);
636 break;
637
638 case ELEVATOR_INSERT_SORT_MERGE:
639 /*
640 * If we succeed in merging this request with one in the
641 * queue already, we are done - rq has now been freed,
642 * so no need to do anything further.
643 */
644 if (elv_attempt_insert_merge(q, rq))
645 break;
646 case ELEVATOR_INSERT_SORT:
647 BUG_ON(rq->cmd_type != REQ_TYPE_FS);
648 rq->cmd_flags |= REQ_SORTED;
649 q->nr_sorted++;
650 if (rq_mergeable(rq)) {
651 elv_rqhash_add(q, rq);
652 if (!q->last_merge)
653 q->last_merge = rq;
654 }
655
656 /*
657 * Some ioscheds (cfq) run q->request_fn directly, so
658 * rq cannot be accessed after calling
659 * elevator_add_req_fn.
660 */
661 q->elevator->type->ops.elevator_add_req_fn(q, rq);
662 break;
663
664 case ELEVATOR_INSERT_FLUSH:
665 rq->cmd_flags |= REQ_SOFTBARRIER;
666 blk_insert_flush(rq);
667 break;
668 default:
669 printk(KERN_ERR "%s: bad insertion point %d\n",
670 __func__, where);
671 BUG();
672 }
673}
674EXPORT_SYMBOL(__elv_add_request);
675
676void elv_add_request(struct request_queue *q, struct request *rq, int where)
677{
678 unsigned long flags;
679
680 spin_lock_irqsave(q->queue_lock, flags);
681 __elv_add_request(q, rq, where);
682 spin_unlock_irqrestore(q->queue_lock, flags);
683}
684EXPORT_SYMBOL(elv_add_request);
685
686struct request *elv_latter_request(struct request_queue *q, struct request *rq)
687{
688 struct elevator_queue *e = q->elevator;
689
690 if (e->type->ops.elevator_latter_req_fn)
691 return e->type->ops.elevator_latter_req_fn(q, rq);
692 return NULL;
693}
694
695struct request *elv_former_request(struct request_queue *q, struct request *rq)
696{
697 struct elevator_queue *e = q->elevator;
698
699 if (e->type->ops.elevator_former_req_fn)
700 return e->type->ops.elevator_former_req_fn(q, rq);
701 return NULL;
702}
703
704int elv_set_request(struct request_queue *q, struct request *rq,
705 struct bio *bio, gfp_t gfp_mask)
706{
707 struct elevator_queue *e = q->elevator;
708
709 if (e->type->ops.elevator_set_req_fn)
710 return e->type->ops.elevator_set_req_fn(q, rq, bio, gfp_mask);
711 return 0;
712}
713
714void elv_put_request(struct request_queue *q, struct request *rq)
715{
716 struct elevator_queue *e = q->elevator;
717
718 if (e->type->ops.elevator_put_req_fn)
719 e->type->ops.elevator_put_req_fn(rq);
720}
721
722int elv_may_queue(struct request_queue *q, int rw)
723{
724 struct elevator_queue *e = q->elevator;
725
726 if (e->type->ops.elevator_may_queue_fn)
727 return e->type->ops.elevator_may_queue_fn(q, rw);
728
729 return ELV_MQUEUE_MAY;
730}
731
732void elv_abort_queue(struct request_queue *q)
733{
734 struct request *rq;
735
736 blk_abort_flushes(q);
737
738 while (!list_empty(&q->queue_head)) {
739 rq = list_entry_rq(q->queue_head.next);
740 rq->cmd_flags |= REQ_QUIET;
741 trace_block_rq_abort(q, rq);
742 /*
743 * Mark this request as started so we don't trigger
744 * any debug logic in the end I/O path.
745 */
746 blk_start_request(rq);
747 __blk_end_request_all(rq, -EIO);
748 }
749}
750EXPORT_SYMBOL(elv_abort_queue);
751
752void elv_completed_request(struct request_queue *q, struct request *rq)
753{
754 struct elevator_queue *e = q->elevator;
755
756 /*
757 * request is released from the driver, io must be done
758 */
759 if (blk_account_rq(rq)) {
760 q->in_flight[rq_is_sync(rq)]--;
761 if ((rq->cmd_flags & REQ_SORTED) &&
762 e->type->ops.elevator_completed_req_fn)
763 e->type->ops.elevator_completed_req_fn(q, rq);
764 }
765}
766
767#define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
768
769static ssize_t
770elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
771{
772 struct elv_fs_entry *entry = to_elv(attr);
773 struct elevator_queue *e;
774 ssize_t error;
775
776 if (!entry->show)
777 return -EIO;
778
779 e = container_of(kobj, struct elevator_queue, kobj);
780 mutex_lock(&e->sysfs_lock);
781 error = e->type ? entry->show(e, page) : -ENOENT;
782 mutex_unlock(&e->sysfs_lock);
783 return error;
784}
785
786static ssize_t
787elv_attr_store(struct kobject *kobj, struct attribute *attr,
788 const char *page, size_t length)
789{
790 struct elv_fs_entry *entry = to_elv(attr);
791 struct elevator_queue *e;
792 ssize_t error;
793
794 if (!entry->store)
795 return -EIO;
796
797 e = container_of(kobj, struct elevator_queue, kobj);
798 mutex_lock(&e->sysfs_lock);
799 error = e->type ? entry->store(e, page, length) : -ENOENT;
800 mutex_unlock(&e->sysfs_lock);
801 return error;
802}
803
804static const struct sysfs_ops elv_sysfs_ops = {
805 .show = elv_attr_show,
806 .store = elv_attr_store,
807};
808
809static struct kobj_type elv_ktype = {
810 .sysfs_ops = &elv_sysfs_ops,
811 .release = elevator_release,
812};
813
814int elv_register_queue(struct request_queue *q)
815{
816 struct elevator_queue *e = q->elevator;
817 int error;
818
819 error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
820 if (!error) {
821 struct elv_fs_entry *attr = e->type->elevator_attrs;
822 if (attr) {
823 while (attr->attr.name) {
824 if (sysfs_create_file(&e->kobj, &attr->attr))
825 break;
826 attr++;
827 }
828 }
829 kobject_uevent(&e->kobj, KOBJ_ADD);
830 e->registered = 1;
831 }
832 return error;
833}
834EXPORT_SYMBOL(elv_register_queue);
835
836void elv_unregister_queue(struct request_queue *q)
837{
838 if (q) {
839 struct elevator_queue *e = q->elevator;
840
841 kobject_uevent(&e->kobj, KOBJ_REMOVE);
842 kobject_del(&e->kobj);
843 e->registered = 0;
844 }
845}
846EXPORT_SYMBOL(elv_unregister_queue);
847
848int elv_register(struct elevator_type *e)
849{
850 char *def = "";
851
852 /* create icq_cache if requested */
853 if (e->icq_size) {
854 if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
855 WARN_ON(e->icq_align < __alignof__(struct io_cq)))
856 return -EINVAL;
857
858 snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
859 "%s_io_cq", e->elevator_name);
860 e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
861 e->icq_align, 0, NULL);
862 if (!e->icq_cache)
863 return -ENOMEM;
864 }
865
866 /* register, don't allow duplicate names */
867 spin_lock(&elv_list_lock);
868 if (elevator_find(e->elevator_name)) {
869 spin_unlock(&elv_list_lock);
870 if (e->icq_cache)
871 kmem_cache_destroy(e->icq_cache);
872 return -EBUSY;
873 }
874 list_add_tail(&e->list, &elv_list);
875 spin_unlock(&elv_list_lock);
876
877 /* print pretty message */
878 if (!strcmp(e->elevator_name, chosen_elevator) ||
879 (!*chosen_elevator &&
880 !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
881 def = " (default)";
882
883 printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
884 def);
885 return 0;
886}
887EXPORT_SYMBOL_GPL(elv_register);
888
889void elv_unregister(struct elevator_type *e)
890{
891 /* unregister */
892 spin_lock(&elv_list_lock);
893 list_del_init(&e->list);
894 spin_unlock(&elv_list_lock);
895
896 /*
897 * Destroy icq_cache if it exists. icq's are RCU managed. Make
898 * sure all RCU operations are complete before proceeding.
899 */
900 if (e->icq_cache) {
901 rcu_barrier();
902 kmem_cache_destroy(e->icq_cache);
903 e->icq_cache = NULL;
904 }
905}
906EXPORT_SYMBOL_GPL(elv_unregister);
907
908/*
909 * switch to new_e io scheduler. be careful not to introduce deadlocks -
910 * we don't free the old io scheduler, before we have allocated what we
911 * need for the new one. this way we have a chance of going back to the old
912 * one, if the new one fails init for some reason.
913 */
914static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
915{
916 struct elevator_queue *old = q->elevator;
917 bool registered = old->registered;
918 int err;
919
920 /*
921 * Turn on BYPASS and drain all requests w/ elevator private data.
922 * Block layer doesn't call into a quiesced elevator - all requests
923 * are directly put on the dispatch list without elevator data
924 * using INSERT_BACK. All requests have SOFTBARRIER set and no
925 * merge happens either.
926 */
927 blk_queue_bypass_start(q);
928
929 /* unregister and clear all auxiliary data of the old elevator */
930 if (registered)
931 elv_unregister_queue(q);
932
933 spin_lock_irq(q->queue_lock);
934 ioc_clear_queue(q);
935 spin_unlock_irq(q->queue_lock);
936
937 /* allocate, init and register new elevator */
938 err = new_e->ops.elevator_init_fn(q, new_e);
939 if (err)
940 goto fail_init;
941
942 if (registered) {
943 err = elv_register_queue(q);
944 if (err)
945 goto fail_register;
946 }
947
948 /* done, kill the old one and finish */
949 elevator_exit(old);
950 blk_queue_bypass_end(q);
951
952 blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
953
954 return 0;
955
956fail_register:
957 elevator_exit(q->elevator);
958fail_init:
959 /* switch failed, restore and re-register old elevator */
960 q->elevator = old;
961 elv_register_queue(q);
962 blk_queue_bypass_end(q);
963
964 return err;
965}
966
967/*
968 * Switch this queue to the given IO scheduler.
969 */
970static int __elevator_change(struct request_queue *q, const char *name)
971{
972 char elevator_name[ELV_NAME_MAX];
973 struct elevator_type *e;
974
975 if (!q->elevator)
976 return -ENXIO;
977
978 strlcpy(elevator_name, name, sizeof(elevator_name));
979 e = elevator_get(strstrip(elevator_name), true);
980 if (!e) {
981 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
982 return -EINVAL;
983 }
984
985 if (!strcmp(elevator_name, q->elevator->type->elevator_name)) {
986 elevator_put(e);
987 return 0;
988 }
989
990 return elevator_switch(q, e);
991}
992
993int elevator_change(struct request_queue *q, const char *name)
994{
995 int ret;
996
997 /* Protect q->elevator from elevator_init() */
998 mutex_lock(&q->sysfs_lock);
999 ret = __elevator_change(q, name);
1000 mutex_unlock(&q->sysfs_lock);
1001
1002 return ret;
1003}
1004EXPORT_SYMBOL(elevator_change);
1005
1006ssize_t elv_iosched_store(struct request_queue *q, const char *name,
1007 size_t count)
1008{
1009 int ret;
1010
1011 if (!q->elevator)
1012 return count;
1013
1014 ret = __elevator_change(q, name);
1015 if (!ret)
1016 return count;
1017
1018 printk(KERN_ERR "elevator: switch to %s failed\n", name);
1019 return ret;
1020}
1021
1022ssize_t elv_iosched_show(struct request_queue *q, char *name)
1023{
1024 struct elevator_queue *e = q->elevator;
1025 struct elevator_type *elv;
1026 struct elevator_type *__e;
1027 int len = 0;
1028
1029 if (!q->elevator || !blk_queue_stackable(q))
1030 return sprintf(name, "none\n");
1031
1032 elv = e->type;
1033
1034 spin_lock(&elv_list_lock);
1035 list_for_each_entry(__e, &elv_list, list) {
1036 if (!strcmp(elv->elevator_name, __e->elevator_name))
1037 len += sprintf(name+len, "[%s] ", elv->elevator_name);
1038 else
1039 len += sprintf(name+len, "%s ", __e->elevator_name);
1040 }
1041 spin_unlock(&elv_list_lock);
1042
1043 len += sprintf(len+name, "\n");
1044 return len;
1045}
1046
1047struct request *elv_rb_former_request(struct request_queue *q,
1048 struct request *rq)
1049{
1050 struct rb_node *rbprev = rb_prev(&rq->rb_node);
1051
1052 if (rbprev)
1053 return rb_entry_rq(rbprev);
1054
1055 return NULL;
1056}
1057EXPORT_SYMBOL(elv_rb_former_request);
1058
1059struct request *elv_rb_latter_request(struct request_queue *q,
1060 struct request *rq)
1061{
1062 struct rb_node *rbnext = rb_next(&rq->rb_node);
1063
1064 if (rbnext)
1065 return rb_entry_rq(rbnext);
1066
1067 return NULL;
1068}
1069EXPORT_SYMBOL(elv_rb_latter_request);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Block device elevator/IO-scheduler.
4 *
5 * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
6 *
7 * 30042000 Jens Axboe <axboe@kernel.dk> :
8 *
9 * Split the elevator a bit so that it is possible to choose a different
10 * one or even write a new "plug in". There are three pieces:
11 * - elevator_fn, inserts a new request in the queue list
12 * - elevator_merge_fn, decides whether a new buffer can be merged with
13 * an existing request
14 * - elevator_dequeue_fn, called when a request is taken off the active list
15 *
16 * 20082000 Dave Jones <davej@suse.de> :
17 * Removed tests for max-bomb-segments, which was breaking elvtune
18 * when run without -bN
19 *
20 * Jens:
21 * - Rework again to work with bio instead of buffer_heads
22 * - loose bi_dev comparisons, partition handling is right now
23 * - completely modularize elevator setup and teardown
24 *
25 */
26#include <linux/kernel.h>
27#include <linux/fs.h>
28#include <linux/blkdev.h>
29#include <linux/elevator.h>
30#include <linux/bio.h>
31#include <linux/module.h>
32#include <linux/slab.h>
33#include <linux/init.h>
34#include <linux/compiler.h>
35#include <linux/blktrace_api.h>
36#include <linux/hash.h>
37#include <linux/uaccess.h>
38#include <linux/pm_runtime.h>
39#include <linux/blk-cgroup.h>
40
41#include <trace/events/block.h>
42
43#include "blk.h"
44#include "blk-mq-sched.h"
45#include "blk-pm.h"
46#include "blk-wbt.h"
47
48static DEFINE_SPINLOCK(elv_list_lock);
49static LIST_HEAD(elv_list);
50
51/*
52 * Merge hash stuff.
53 */
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_bio_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->type->ops.allow_merge)
66 return e->type->ops.allow_merge(q, rq, bio);
67
68 return 1;
69}
70
71/*
72 * can we safely merge with this request?
73 */
74bool elv_bio_merge_ok(struct request *rq, struct bio *bio)
75{
76 if (!blk_rq_merge_ok(rq, bio))
77 return false;
78
79 if (!elv_iosched_allow_bio_merge(rq, bio))
80 return false;
81
82 return true;
83}
84EXPORT_SYMBOL(elv_bio_merge_ok);
85
86static inline bool elv_support_features(unsigned int elv_features,
87 unsigned int required_features)
88{
89 return (required_features & elv_features) == required_features;
90}
91
92/**
93 * elevator_match - Test an elevator name and features
94 * @e: Scheduler to test
95 * @name: Elevator name to test
96 * @required_features: Features that the elevator must provide
97 *
98 * Return true if the elevator @e name matches @name and if @e provides all
99 * the features specified by @required_features.
100 */
101static bool elevator_match(const struct elevator_type *e, const char *name,
102 unsigned int required_features)
103{
104 if (!elv_support_features(e->elevator_features, required_features))
105 return false;
106 if (!strcmp(e->elevator_name, name))
107 return true;
108 if (e->elevator_alias && !strcmp(e->elevator_alias, name))
109 return true;
110
111 return false;
112}
113
114/**
115 * elevator_find - Find an elevator
116 * @name: Name of the elevator to find
117 * @required_features: Features that the elevator must provide
118 *
119 * Return the first registered scheduler with name @name and supporting the
120 * features @required_features and NULL otherwise.
121 */
122static struct elevator_type *elevator_find(const char *name,
123 unsigned int required_features)
124{
125 struct elevator_type *e;
126
127 list_for_each_entry(e, &elv_list, list) {
128 if (elevator_match(e, name, required_features))
129 return e;
130 }
131
132 return NULL;
133}
134
135static void elevator_put(struct elevator_type *e)
136{
137 module_put(e->elevator_owner);
138}
139
140static struct elevator_type *elevator_get(struct request_queue *q,
141 const char *name, bool try_loading)
142{
143 struct elevator_type *e;
144
145 spin_lock(&elv_list_lock);
146
147 e = elevator_find(name, q->required_elevator_features);
148 if (!e && try_loading) {
149 spin_unlock(&elv_list_lock);
150 request_module("%s-iosched", name);
151 spin_lock(&elv_list_lock);
152 e = elevator_find(name, q->required_elevator_features);
153 }
154
155 if (e && !try_module_get(e->elevator_owner))
156 e = NULL;
157
158 spin_unlock(&elv_list_lock);
159 return e;
160}
161
162static struct kobj_type elv_ktype;
163
164struct elevator_queue *elevator_alloc(struct request_queue *q,
165 struct elevator_type *e)
166{
167 struct elevator_queue *eq;
168
169 eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node);
170 if (unlikely(!eq))
171 return NULL;
172
173 eq->type = e;
174 kobject_init(&eq->kobj, &elv_ktype);
175 mutex_init(&eq->sysfs_lock);
176 hash_init(eq->hash);
177
178 return eq;
179}
180EXPORT_SYMBOL(elevator_alloc);
181
182static void elevator_release(struct kobject *kobj)
183{
184 struct elevator_queue *e;
185
186 e = container_of(kobj, struct elevator_queue, kobj);
187 elevator_put(e->type);
188 kfree(e);
189}
190
191void __elevator_exit(struct request_queue *q, struct elevator_queue *e)
192{
193 mutex_lock(&e->sysfs_lock);
194 if (e->type->ops.exit_sched)
195 blk_mq_exit_sched(q, e);
196 mutex_unlock(&e->sysfs_lock);
197
198 kobject_put(&e->kobj);
199}
200
201static inline void __elv_rqhash_del(struct request *rq)
202{
203 hash_del(&rq->hash);
204 rq->rq_flags &= ~RQF_HASHED;
205}
206
207void elv_rqhash_del(struct request_queue *q, struct request *rq)
208{
209 if (ELV_ON_HASH(rq))
210 __elv_rqhash_del(rq);
211}
212EXPORT_SYMBOL_GPL(elv_rqhash_del);
213
214void elv_rqhash_add(struct request_queue *q, struct request *rq)
215{
216 struct elevator_queue *e = q->elevator;
217
218 BUG_ON(ELV_ON_HASH(rq));
219 hash_add(e->hash, &rq->hash, rq_hash_key(rq));
220 rq->rq_flags |= RQF_HASHED;
221}
222EXPORT_SYMBOL_GPL(elv_rqhash_add);
223
224void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
225{
226 __elv_rqhash_del(rq);
227 elv_rqhash_add(q, rq);
228}
229
230struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
231{
232 struct elevator_queue *e = q->elevator;
233 struct hlist_node *next;
234 struct request *rq;
235
236 hash_for_each_possible_safe(e->hash, rq, next, hash, offset) {
237 BUG_ON(!ELV_ON_HASH(rq));
238
239 if (unlikely(!rq_mergeable(rq))) {
240 __elv_rqhash_del(rq);
241 continue;
242 }
243
244 if (rq_hash_key(rq) == offset)
245 return rq;
246 }
247
248 return NULL;
249}
250
251/*
252 * RB-tree support functions for inserting/lookup/removal of requests
253 * in a sorted RB tree.
254 */
255void elv_rb_add(struct rb_root *root, struct request *rq)
256{
257 struct rb_node **p = &root->rb_node;
258 struct rb_node *parent = NULL;
259 struct request *__rq;
260
261 while (*p) {
262 parent = *p;
263 __rq = rb_entry(parent, struct request, rb_node);
264
265 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
266 p = &(*p)->rb_left;
267 else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
268 p = &(*p)->rb_right;
269 }
270
271 rb_link_node(&rq->rb_node, parent, p);
272 rb_insert_color(&rq->rb_node, root);
273}
274EXPORT_SYMBOL(elv_rb_add);
275
276void elv_rb_del(struct rb_root *root, struct request *rq)
277{
278 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
279 rb_erase(&rq->rb_node, root);
280 RB_CLEAR_NODE(&rq->rb_node);
281}
282EXPORT_SYMBOL(elv_rb_del);
283
284struct request *elv_rb_find(struct rb_root *root, sector_t sector)
285{
286 struct rb_node *n = root->rb_node;
287 struct request *rq;
288
289 while (n) {
290 rq = rb_entry(n, struct request, rb_node);
291
292 if (sector < blk_rq_pos(rq))
293 n = n->rb_left;
294 else if (sector > blk_rq_pos(rq))
295 n = n->rb_right;
296 else
297 return rq;
298 }
299
300 return NULL;
301}
302EXPORT_SYMBOL(elv_rb_find);
303
304enum elv_merge elv_merge(struct request_queue *q, struct request **req,
305 struct bio *bio)
306{
307 struct elevator_queue *e = q->elevator;
308 struct request *__rq;
309
310 /*
311 * Levels of merges:
312 * nomerges: No merges at all attempted
313 * noxmerges: Only simple one-hit cache try
314 * merges: All merge tries attempted
315 */
316 if (blk_queue_nomerges(q) || !bio_mergeable(bio))
317 return ELEVATOR_NO_MERGE;
318
319 /*
320 * First try one-hit cache.
321 */
322 if (q->last_merge && elv_bio_merge_ok(q->last_merge, bio)) {
323 enum elv_merge ret = blk_try_merge(q->last_merge, bio);
324
325 if (ret != ELEVATOR_NO_MERGE) {
326 *req = q->last_merge;
327 return ret;
328 }
329 }
330
331 if (blk_queue_noxmerges(q))
332 return ELEVATOR_NO_MERGE;
333
334 /*
335 * See if our hash lookup can find a potential backmerge.
336 */
337 __rq = elv_rqhash_find(q, bio->bi_iter.bi_sector);
338 if (__rq && elv_bio_merge_ok(__rq, bio)) {
339 *req = __rq;
340 return ELEVATOR_BACK_MERGE;
341 }
342
343 if (e->type->ops.request_merge)
344 return e->type->ops.request_merge(q, req, bio);
345
346 return ELEVATOR_NO_MERGE;
347}
348
349/*
350 * Attempt to do an insertion back merge. Only check for the case where
351 * we can append 'rq' to an existing request, so we can throw 'rq' away
352 * afterwards.
353 *
354 * Returns true if we merged, false otherwise
355 */
356bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq)
357{
358 struct request *__rq;
359 bool ret;
360
361 if (blk_queue_nomerges(q))
362 return false;
363
364 /*
365 * First try one-hit cache.
366 */
367 if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq))
368 return true;
369
370 if (blk_queue_noxmerges(q))
371 return false;
372
373 ret = false;
374 /*
375 * See if our hash lookup can find a potential backmerge.
376 */
377 while (1) {
378 __rq = elv_rqhash_find(q, blk_rq_pos(rq));
379 if (!__rq || !blk_attempt_req_merge(q, __rq, rq))
380 break;
381
382 /* The merged request could be merged with others, try again */
383 ret = true;
384 rq = __rq;
385 }
386
387 return ret;
388}
389
390void elv_merged_request(struct request_queue *q, struct request *rq,
391 enum elv_merge type)
392{
393 struct elevator_queue *e = q->elevator;
394
395 if (e->type->ops.request_merged)
396 e->type->ops.request_merged(q, rq, type);
397
398 if (type == ELEVATOR_BACK_MERGE)
399 elv_rqhash_reposition(q, rq);
400
401 q->last_merge = rq;
402}
403
404void elv_merge_requests(struct request_queue *q, struct request *rq,
405 struct request *next)
406{
407 struct elevator_queue *e = q->elevator;
408
409 if (e->type->ops.requests_merged)
410 e->type->ops.requests_merged(q, rq, next);
411
412 elv_rqhash_reposition(q, rq);
413 q->last_merge = rq;
414}
415
416struct request *elv_latter_request(struct request_queue *q, struct request *rq)
417{
418 struct elevator_queue *e = q->elevator;
419
420 if (e->type->ops.next_request)
421 return e->type->ops.next_request(q, rq);
422
423 return NULL;
424}
425
426struct request *elv_former_request(struct request_queue *q, struct request *rq)
427{
428 struct elevator_queue *e = q->elevator;
429
430 if (e->type->ops.former_request)
431 return e->type->ops.former_request(q, rq);
432
433 return NULL;
434}
435
436#define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
437
438static ssize_t
439elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
440{
441 struct elv_fs_entry *entry = to_elv(attr);
442 struct elevator_queue *e;
443 ssize_t error;
444
445 if (!entry->show)
446 return -EIO;
447
448 e = container_of(kobj, struct elevator_queue, kobj);
449 mutex_lock(&e->sysfs_lock);
450 error = e->type ? entry->show(e, page) : -ENOENT;
451 mutex_unlock(&e->sysfs_lock);
452 return error;
453}
454
455static ssize_t
456elv_attr_store(struct kobject *kobj, struct attribute *attr,
457 const char *page, size_t length)
458{
459 struct elv_fs_entry *entry = to_elv(attr);
460 struct elevator_queue *e;
461 ssize_t error;
462
463 if (!entry->store)
464 return -EIO;
465
466 e = container_of(kobj, struct elevator_queue, kobj);
467 mutex_lock(&e->sysfs_lock);
468 error = e->type ? entry->store(e, page, length) : -ENOENT;
469 mutex_unlock(&e->sysfs_lock);
470 return error;
471}
472
473static const struct sysfs_ops elv_sysfs_ops = {
474 .show = elv_attr_show,
475 .store = elv_attr_store,
476};
477
478static struct kobj_type elv_ktype = {
479 .sysfs_ops = &elv_sysfs_ops,
480 .release = elevator_release,
481};
482
483/*
484 * elv_register_queue is called from either blk_register_queue or
485 * elevator_switch, elevator switch is prevented from being happen
486 * in the two paths, so it is safe to not hold q->sysfs_lock.
487 */
488int elv_register_queue(struct request_queue *q, bool uevent)
489{
490 struct elevator_queue *e = q->elevator;
491 int error;
492
493 error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
494 if (!error) {
495 struct elv_fs_entry *attr = e->type->elevator_attrs;
496 if (attr) {
497 while (attr->attr.name) {
498 if (sysfs_create_file(&e->kobj, &attr->attr))
499 break;
500 attr++;
501 }
502 }
503 if (uevent)
504 kobject_uevent(&e->kobj, KOBJ_ADD);
505
506 e->registered = 1;
507 }
508 return error;
509}
510
511/*
512 * elv_unregister_queue is called from either blk_unregister_queue or
513 * elevator_switch, elevator switch is prevented from being happen
514 * in the two paths, so it is safe to not hold q->sysfs_lock.
515 */
516void elv_unregister_queue(struct request_queue *q)
517{
518 if (q) {
519 struct elevator_queue *e = q->elevator;
520
521 kobject_uevent(&e->kobj, KOBJ_REMOVE);
522 kobject_del(&e->kobj);
523
524 e->registered = 0;
525 /* Re-enable throttling in case elevator disabled it */
526 wbt_enable_default(q);
527 }
528}
529
530int elv_register(struct elevator_type *e)
531{
532 /* create icq_cache if requested */
533 if (e->icq_size) {
534 if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
535 WARN_ON(e->icq_align < __alignof__(struct io_cq)))
536 return -EINVAL;
537
538 snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
539 "%s_io_cq", e->elevator_name);
540 e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
541 e->icq_align, 0, NULL);
542 if (!e->icq_cache)
543 return -ENOMEM;
544 }
545
546 /* register, don't allow duplicate names */
547 spin_lock(&elv_list_lock);
548 if (elevator_find(e->elevator_name, 0)) {
549 spin_unlock(&elv_list_lock);
550 kmem_cache_destroy(e->icq_cache);
551 return -EBUSY;
552 }
553 list_add_tail(&e->list, &elv_list);
554 spin_unlock(&elv_list_lock);
555
556 printk(KERN_INFO "io scheduler %s registered\n", e->elevator_name);
557
558 return 0;
559}
560EXPORT_SYMBOL_GPL(elv_register);
561
562void elv_unregister(struct elevator_type *e)
563{
564 /* unregister */
565 spin_lock(&elv_list_lock);
566 list_del_init(&e->list);
567 spin_unlock(&elv_list_lock);
568
569 /*
570 * Destroy icq_cache if it exists. icq's are RCU managed. Make
571 * sure all RCU operations are complete before proceeding.
572 */
573 if (e->icq_cache) {
574 rcu_barrier();
575 kmem_cache_destroy(e->icq_cache);
576 e->icq_cache = NULL;
577 }
578}
579EXPORT_SYMBOL_GPL(elv_unregister);
580
581int elevator_switch_mq(struct request_queue *q,
582 struct elevator_type *new_e)
583{
584 int ret;
585
586 lockdep_assert_held(&q->sysfs_lock);
587
588 if (q->elevator) {
589 if (q->elevator->registered)
590 elv_unregister_queue(q);
591
592 ioc_clear_queue(q);
593 elevator_exit(q, q->elevator);
594 }
595
596 ret = blk_mq_init_sched(q, new_e);
597 if (ret)
598 goto out;
599
600 if (new_e) {
601 ret = elv_register_queue(q, true);
602 if (ret) {
603 elevator_exit(q, q->elevator);
604 goto out;
605 }
606 }
607
608 if (new_e)
609 blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
610 else
611 blk_add_trace_msg(q, "elv switch: none");
612
613out:
614 return ret;
615}
616
617static inline bool elv_support_iosched(struct request_queue *q)
618{
619 if (!q->mq_ops ||
620 (q->tag_set && (q->tag_set->flags & BLK_MQ_F_NO_SCHED)))
621 return false;
622 return true;
623}
624
625/*
626 * For single queue devices, default to using mq-deadline. If we have multiple
627 * queues or mq-deadline is not available, default to "none".
628 */
629static struct elevator_type *elevator_get_default(struct request_queue *q)
630{
631 if (q->nr_hw_queues != 1)
632 return NULL;
633
634 return elevator_get(q, "mq-deadline", false);
635}
636
637/*
638 * Get the first elevator providing the features required by the request queue.
639 * Default to "none" if no matching elevator is found.
640 */
641static struct elevator_type *elevator_get_by_features(struct request_queue *q)
642{
643 struct elevator_type *e, *found = NULL;
644
645 spin_lock(&elv_list_lock);
646
647 list_for_each_entry(e, &elv_list, list) {
648 if (elv_support_features(e->elevator_features,
649 q->required_elevator_features)) {
650 found = e;
651 break;
652 }
653 }
654
655 if (found && !try_module_get(found->elevator_owner))
656 found = NULL;
657
658 spin_unlock(&elv_list_lock);
659 return found;
660}
661
662/*
663 * For a device queue that has no required features, use the default elevator
664 * settings. Otherwise, use the first elevator available matching the required
665 * features. If no suitable elevator is find or if the chosen elevator
666 * initialization fails, fall back to the "none" elevator (no elevator).
667 */
668void elevator_init_mq(struct request_queue *q)
669{
670 struct elevator_type *e;
671 int err;
672
673 if (!elv_support_iosched(q))
674 return;
675
676 WARN_ON_ONCE(test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags));
677
678 if (unlikely(q->elevator))
679 return;
680
681 if (!q->required_elevator_features)
682 e = elevator_get_default(q);
683 else
684 e = elevator_get_by_features(q);
685 if (!e)
686 return;
687
688 blk_mq_freeze_queue(q);
689 blk_mq_quiesce_queue(q);
690
691 err = blk_mq_init_sched(q, e);
692
693 blk_mq_unquiesce_queue(q);
694 blk_mq_unfreeze_queue(q);
695
696 if (err) {
697 pr_warn("\"%s\" elevator initialization failed, "
698 "falling back to \"none\"\n", e->elevator_name);
699 elevator_put(e);
700 }
701}
702
703
704/*
705 * switch to new_e io scheduler. be careful not to introduce deadlocks -
706 * we don't free the old io scheduler, before we have allocated what we
707 * need for the new one. this way we have a chance of going back to the old
708 * one, if the new one fails init for some reason.
709 */
710static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
711{
712 int err;
713
714 lockdep_assert_held(&q->sysfs_lock);
715
716 blk_mq_freeze_queue(q);
717 blk_mq_quiesce_queue(q);
718
719 err = elevator_switch_mq(q, new_e);
720
721 blk_mq_unquiesce_queue(q);
722 blk_mq_unfreeze_queue(q);
723
724 return err;
725}
726
727/*
728 * Switch this queue to the given IO scheduler.
729 */
730static int __elevator_change(struct request_queue *q, const char *name)
731{
732 char elevator_name[ELV_NAME_MAX];
733 struct elevator_type *e;
734
735 /* Make sure queue is not in the middle of being removed */
736 if (!blk_queue_registered(q))
737 return -ENOENT;
738
739 /*
740 * Special case for mq, turn off scheduling
741 */
742 if (!strncmp(name, "none", 4)) {
743 if (!q->elevator)
744 return 0;
745 return elevator_switch(q, NULL);
746 }
747
748 strlcpy(elevator_name, name, sizeof(elevator_name));
749 e = elevator_get(q, strstrip(elevator_name), true);
750 if (!e)
751 return -EINVAL;
752
753 if (q->elevator &&
754 elevator_match(q->elevator->type, elevator_name, 0)) {
755 elevator_put(e);
756 return 0;
757 }
758
759 return elevator_switch(q, e);
760}
761
762ssize_t elv_iosched_store(struct request_queue *q, const char *name,
763 size_t count)
764{
765 int ret;
766
767 if (!queue_is_mq(q) || !elv_support_iosched(q))
768 return count;
769
770 ret = __elevator_change(q, name);
771 if (!ret)
772 return count;
773
774 return ret;
775}
776
777ssize_t elv_iosched_show(struct request_queue *q, char *name)
778{
779 struct elevator_queue *e = q->elevator;
780 struct elevator_type *elv = NULL;
781 struct elevator_type *__e;
782 int len = 0;
783
784 if (!queue_is_mq(q))
785 return sprintf(name, "none\n");
786
787 if (!q->elevator)
788 len += sprintf(name+len, "[none] ");
789 else
790 elv = e->type;
791
792 spin_lock(&elv_list_lock);
793 list_for_each_entry(__e, &elv_list, list) {
794 if (elv && elevator_match(elv, __e->elevator_name, 0)) {
795 len += sprintf(name+len, "[%s] ", elv->elevator_name);
796 continue;
797 }
798 if (elv_support_iosched(q) &&
799 elevator_match(__e, __e->elevator_name,
800 q->required_elevator_features))
801 len += sprintf(name+len, "%s ", __e->elevator_name);
802 }
803 spin_unlock(&elv_list_lock);
804
805 if (q->elevator)
806 len += sprintf(name+len, "none");
807
808 len += sprintf(len+name, "\n");
809 return len;
810}
811
812struct request *elv_rb_former_request(struct request_queue *q,
813 struct request *rq)
814{
815 struct rb_node *rbprev = rb_prev(&rq->rb_node);
816
817 if (rbprev)
818 return rb_entry_rq(rbprev);
819
820 return NULL;
821}
822EXPORT_SYMBOL(elv_rb_former_request);
823
824struct request *elv_rb_latter_request(struct request_queue *q,
825 struct request *rq)
826{
827 struct rb_node *rbnext = rb_next(&rq->rb_node);
828
829 if (rbnext)
830 return rb_entry_rq(rbnext);
831
832 return NULL;
833}
834EXPORT_SYMBOL(elv_rb_latter_request);
835
836static int __init elevator_setup(char *str)
837{
838 pr_warn("Kernel parameter elevator= does not have any effect anymore.\n"
839 "Please use sysfs to set IO scheduler for individual devices.\n");
840 return 1;
841}
842
843__setup("elevator=", elevator_setup);