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