projects/linux·blob assoc-array-fixes · refs

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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Block device elevator/IO-scheduler.
4 *
5 * Copyright (C) 2000 Andrea Arcangeli <[email protected]> SuSE
6 *
7 * 30042000 Jens Axboe <[email protected]> :
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 <[email protected]> :
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/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 "elevator.h"
42#include "blk.h"
43#include "blk-mq-sched.h"
44#include "blk-pm.h"
45#include "blk-wbt.h"
46#include "blk-cgroup.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 bool 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 true;
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
86/**
87 * elevator_match - Check whether @e's name or alias matches @name
88 * @e: Scheduler to test
89 * @name: Elevator name to test
90 *
91 * Return true if the elevator @e's name or alias matches @name.
92 */
93static bool elevator_match(const struct elevator_type *e, const char *name)
94{
95 return !strcmp(e->elevator_name, name) ||
96 (e->elevator_alias && !strcmp(e->elevator_alias, name));
97}
98
99static struct elevator_type *__elevator_find(const char *name)
100{
101 struct elevator_type *e;
102
103 list_for_each_entry(e, &elv_list, list)
104 if (elevator_match(e, name))
105 return e;
106 return NULL;
107}
108
109static struct elevator_type *elevator_find_get(const char *name)
110{
111 struct elevator_type *e;
112
113 spin_lock(&elv_list_lock);
114 e = __elevator_find(name);
115 if (e && (!elevator_tryget(e)))
116 e = NULL;
117 spin_unlock(&elv_list_lock);
118 return e;
119}
120
121static const struct kobj_type elv_ktype;
122
123struct elevator_queue *elevator_alloc(struct request_queue *q,
124 struct elevator_type *e, struct elevator_resources *res)
125{
126 struct elevator_queue *eq;
127
128 eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node);
129 if (unlikely(!eq))
130 return NULL;
131
132 __elevator_get(e);
133 eq->type = e;
134 kobject_init(&eq->kobj, &elv_ktype);
135 mutex_init(&eq->sysfs_lock);
136 hash_init(eq->hash);
137 eq->et = res->et;
138 eq->elevator_data = res->data;
139
140 return eq;
141}
142
143static void elevator_release(struct kobject *kobj)
144{
145 struct elevator_queue *e;
146
147 e = container_of(kobj, struct elevator_queue, kobj);
148 elevator_put(e->type);
149 kfree(e);
150}
151
152static void elevator_exit(struct request_queue *q)
153{
154 struct elevator_queue *e = q->elevator;
155
156 lockdep_assert_held(&q->elevator_lock);
157
158 ioc_clear_queue(q);
159
160 mutex_lock(&e->sysfs_lock);
161 blk_mq_exit_sched(q, e);
162 mutex_unlock(&e->sysfs_lock);
163}
164
165static inline void __elv_rqhash_del(struct request *rq)
166{
167 hash_del(&rq->hash);
168 rq->rq_flags &= ~RQF_HASHED;
169}
170
171void elv_rqhash_del(struct request_queue *q, struct request *rq)
172{
173 if (ELV_ON_HASH(rq))
174 __elv_rqhash_del(rq);
175}
176EXPORT_SYMBOL_GPL(elv_rqhash_del);
177
178void elv_rqhash_add(struct request_queue *q, struct request *rq)
179{
180 struct elevator_queue *e = q->elevator;
181
182 BUG_ON(ELV_ON_HASH(rq));
183 hash_add(e->hash, &rq->hash, rq_hash_key(rq));
184 rq->rq_flags |= RQF_HASHED;
185}
186EXPORT_SYMBOL_GPL(elv_rqhash_add);
187
188void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
189{
190 __elv_rqhash_del(rq);
191 elv_rqhash_add(q, rq);
192}
193
194struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
195{
196 struct elevator_queue *e = q->elevator;
197 struct hlist_node *next;
198 struct request *rq;
199
200 hash_for_each_possible_safe(e->hash, rq, next, hash, offset) {
201 BUG_ON(!ELV_ON_HASH(rq));
202
203 if (unlikely(!rq_mergeable(rq))) {
204 __elv_rqhash_del(rq);
205 continue;
206 }
207
208 if (rq_hash_key(rq) == offset)
209 return rq;
210 }
211
212 return NULL;
213}
214
215/*
216 * RB-tree support functions for inserting/lookup/removal of requests
217 * in a sorted RB tree.
218 */
219void elv_rb_add(struct rb_root *root, struct request *rq)
220{
221 struct rb_node **p = &root->rb_node;
222 struct rb_node *parent = NULL;
223 struct request *__rq;
224
225 while (*p) {
226 parent = *p;
227 __rq = rb_entry(parent, struct request, rb_node);
228
229 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
230 p = &(*p)->rb_left;
231 else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
232 p = &(*p)->rb_right;
233 }
234
235 rb_link_node(&rq->rb_node, parent, p);
236 rb_insert_color(&rq->rb_node, root);
237}
238EXPORT_SYMBOL(elv_rb_add);
239
240void elv_rb_del(struct rb_root *root, struct request *rq)
241{
242 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
243 rb_erase(&rq->rb_node, root);
244 RB_CLEAR_NODE(&rq->rb_node);
245}
246EXPORT_SYMBOL(elv_rb_del);
247
248struct request *elv_rb_find(struct rb_root *root, sector_t sector)
249{
250 struct rb_node *n = root->rb_node;
251 struct request *rq;
252
253 while (n) {
254 rq = rb_entry(n, struct request, rb_node);
255
256 if (sector < blk_rq_pos(rq))
257 n = n->rb_left;
258 else if (sector > blk_rq_pos(rq))
259 n = n->rb_right;
260 else
261 return rq;
262 }
263
264 return NULL;
265}
266EXPORT_SYMBOL(elv_rb_find);
267
268enum elv_merge elv_merge(struct request_queue *q, struct request **req,
269 struct bio *bio)
270{
271 struct elevator_queue *e = q->elevator;
272 struct request *__rq;
273
274 /*
275 * Levels of merges:
276 * nomerges: No merges at all attempted
277 * noxmerges: Only simple one-hit cache try
278 * merges: All merge tries attempted
279 */
280 if (blk_queue_nomerges(q) || !bio_mergeable(bio))
281 return ELEVATOR_NO_MERGE;
282
283 /*
284 * First try one-hit cache.
285 */
286 if (q->last_merge && elv_bio_merge_ok(q->last_merge, bio)) {
287 enum elv_merge ret = blk_try_merge(q->last_merge, bio);
288
289 if (ret != ELEVATOR_NO_MERGE) {
290 *req = q->last_merge;
291 return ret;
292 }
293 }
294
295 if (blk_queue_noxmerges(q))
296 return ELEVATOR_NO_MERGE;
297
298 /*
299 * See if our hash lookup can find a potential backmerge.
300 */
301 __rq = elv_rqhash_find(q, bio->bi_iter.bi_sector);
302 if (__rq && elv_bio_merge_ok(__rq, bio)) {
303 *req = __rq;
304
305 if (blk_discard_mergable(__rq))
306 return ELEVATOR_DISCARD_MERGE;
307 return ELEVATOR_BACK_MERGE;
308 }
309
310 if (e->type->ops.request_merge)
311 return e->type->ops.request_merge(q, req, bio);
312
313 return ELEVATOR_NO_MERGE;
314}
315
316/*
317 * Attempt to do an insertion back merge. Only check for the case where
318 * we can append 'rq' to an existing request, so we can throw 'rq' away
319 * afterwards.
320 *
321 * Returns true if we merged, false otherwise. 'free' will contain all
322 * requests that need to be freed.
323 */
324bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq,
325 struct list_head *free)
326{
327 struct request *__rq;
328 bool ret;
329
330 if (blk_queue_nomerges(q))
331 return false;
332
333 /*
334 * First try one-hit cache.
335 */
336 if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq)) {
337 list_add(&rq->queuelist, free);
338 return true;
339 }
340
341 if (blk_queue_noxmerges(q))
342 return false;
343
344 ret = false;
345 /*
346 * See if our hash lookup can find a potential backmerge.
347 */
348 while (1) {
349 __rq = elv_rqhash_find(q, blk_rq_pos(rq));
350 if (!__rq || !blk_attempt_req_merge(q, __rq, rq))
351 break;
352
353 list_add(&rq->queuelist, free);
354 /* The merged request could be merged with others, try again */
355 ret = true;
356 rq = __rq;
357 }
358
359 return ret;
360}
361
362void elv_merged_request(struct request_queue *q, struct request *rq,
363 enum elv_merge type)
364{
365 struct elevator_queue *e = q->elevator;
366
367 if (e->type->ops.request_merged)
368 e->type->ops.request_merged(q, rq, type);
369
370 if (type == ELEVATOR_BACK_MERGE)
371 elv_rqhash_reposition(q, rq);
372
373 q->last_merge = rq;
374}
375
376void elv_merge_requests(struct request_queue *q, struct request *rq,
377 struct request *next)
378{
379 struct elevator_queue *e = q->elevator;
380
381 if (e->type->ops.requests_merged)
382 e->type->ops.requests_merged(q, rq, next);
383
384 elv_rqhash_reposition(q, rq);
385 q->last_merge = rq;
386}
387
388struct request *elv_latter_request(struct request_queue *q, struct request *rq)
389{
390 struct elevator_queue *e = q->elevator;
391
392 if (e->type->ops.next_request)
393 return e->type->ops.next_request(q, rq);
394
395 return NULL;
396}
397
398struct request *elv_former_request(struct request_queue *q, struct request *rq)
399{
400 struct elevator_queue *e = q->elevator;
401
402 if (e->type->ops.former_request)
403 return e->type->ops.former_request(q, rq);
404
405 return NULL;
406}
407
408#define to_elv(atr) container_of_const((atr), struct elv_fs_entry, attr)
409
410static ssize_t
411elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
412{
413 const struct elv_fs_entry *entry = to_elv(attr);
414 struct elevator_queue *e;
415 ssize_t error = -ENODEV;
416
417 if (!entry->show)
418 return -EIO;
419
420 e = container_of(kobj, struct elevator_queue, kobj);
421 mutex_lock(&e->sysfs_lock);
422 if (!test_bit(ELEVATOR_FLAG_DYING, &e->flags))
423 error = entry->show(e, page);
424 mutex_unlock(&e->sysfs_lock);
425 return error;
426}
427
428static ssize_t
429elv_attr_store(struct kobject *kobj, struct attribute *attr,
430 const char *page, size_t length)
431{
432 const struct elv_fs_entry *entry = to_elv(attr);
433 struct elevator_queue *e;
434 ssize_t error = -ENODEV;
435
436 if (!entry->store)
437 return -EIO;
438
439 e = container_of(kobj, struct elevator_queue, kobj);
440 mutex_lock(&e->sysfs_lock);
441 if (!test_bit(ELEVATOR_FLAG_DYING, &e->flags))
442 error = entry->store(e, page, length);
443 mutex_unlock(&e->sysfs_lock);
444 return error;
445}
446
447static const struct sysfs_ops elv_sysfs_ops = {
448 .show = elv_attr_show,
449 .store = elv_attr_store,
450};
451
452static const struct kobj_type elv_ktype = {
453 .sysfs_ops = &elv_sysfs_ops,
454 .release = elevator_release,
455};
456
457static int elv_register_queue(struct request_queue *q,
458 struct elevator_queue *e,
459 bool uevent)
460{
461 int error;
462
463 error = kobject_add(&e->kobj, &q->disk->queue_kobj, "iosched");
464 if (!error) {
465 const struct elv_fs_entry *attr = e->type->elevator_attrs;
466 if (attr) {
467 while (attr->attr.name) {
468 if (sysfs_create_file(&e->kobj, &attr->attr))
469 break;
470 attr++;
471 }
472 }
473 if (uevent)
474 kobject_uevent(&e->kobj, KOBJ_ADD);
475
476 /*
477 * Sched is initialized, it is ready to export it via
478 * debugfs
479 */
480 blk_mq_sched_reg_debugfs(q);
481 set_bit(ELEVATOR_FLAG_REGISTERED, &e->flags);
482 }
483 return error;
484}
485
486static void elv_unregister_queue(struct request_queue *q,
487 struct elevator_queue *e)
488{
489 if (e && test_and_clear_bit(ELEVATOR_FLAG_REGISTERED, &e->flags)) {
490 kobject_uevent(&e->kobj, KOBJ_REMOVE);
491 kobject_del(&e->kobj);
492
493 /* unexport via debugfs before exiting sched */
494 blk_mq_sched_unreg_debugfs(q);
495 }
496}
497
498int elv_register(struct elevator_type *e)
499{
500 /* finish request is mandatory */
501 if (WARN_ON_ONCE(!e->ops.finish_request))
502 return -EINVAL;
503 /* insert_requests and dispatch_request are mandatory */
504 if (WARN_ON_ONCE(!e->ops.insert_requests || !e->ops.dispatch_request))
505 return -EINVAL;
506
507 /* create icq_cache if requested */
508 if (e->icq_size) {
509 if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
510 WARN_ON(e->icq_align < __alignof__(struct io_cq)))
511 return -EINVAL;
512
513 snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
514 "%s_io_cq", e->elevator_name);
515 e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
516 e->icq_align, 0, NULL);
517 if (!e->icq_cache)
518 return -ENOMEM;
519 }
520
521 /* register, don't allow duplicate names */
522 spin_lock(&elv_list_lock);
523 if (__elevator_find(e->elevator_name)) {
524 spin_unlock(&elv_list_lock);
525 kmem_cache_destroy(e->icq_cache);
526 return -EBUSY;
527 }
528 list_add_tail(&e->list, &elv_list);
529 spin_unlock(&elv_list_lock);
530
531 printk(KERN_INFO "io scheduler %s registered\n", e->elevator_name);
532
533 return 0;
534}
535EXPORT_SYMBOL_GPL(elv_register);
536
537void elv_unregister(struct elevator_type *e)
538{
539 /* unregister */
540 spin_lock(&elv_list_lock);
541 list_del_init(&e->list);
542 spin_unlock(&elv_list_lock);
543
544 /*
545 * Destroy icq_cache if it exists. icq's are RCU managed. Make
546 * sure all RCU operations are complete before proceeding.
547 */
548 if (e->icq_cache) {
549 rcu_barrier();
550 kmem_cache_destroy(e->icq_cache);
551 e->icq_cache = NULL;
552 }
553}
554EXPORT_SYMBOL_GPL(elv_unregister);
555
556/*
557 * Switch to new_e io scheduler.
558 *
559 * If switching fails, we are most likely running out of memory and not able
560 * to restore the old io scheduler, so leaving the io scheduler being none.
561 */
562static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)
563{
564 struct elevator_type *new_e = NULL;
565 int ret = 0;
566
567 WARN_ON_ONCE(q->mq_freeze_depth == 0);
568 lockdep_assert_held(&q->elevator_lock);
569
570 if (strncmp(ctx->name, "none", 4)) {
571 new_e = elevator_find_get(ctx->name);
572 if (!new_e)
573 return -EINVAL;
574 }
575
576 blk_mq_quiesce_queue(q);
577
578 if (q->elevator) {
579 ctx->old = q->elevator;
580 elevator_exit(q);
581 }
582
583 if (new_e) {
584 ret = blk_mq_init_sched(q, new_e, &ctx->res);
585 if (ret)
586 goto out_unfreeze;
587 ctx->new = q->elevator;
588 } else {
589 blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q);
590 q->elevator = NULL;
591 q->nr_requests = q->tag_set->queue_depth;
592 q->async_depth = q->tag_set->queue_depth;
593 }
594 blk_add_trace_msg(q, "elv switch: %s", ctx->name);
595
596out_unfreeze:
597 blk_mq_unquiesce_queue(q);
598
599 if (ret) {
600 pr_warn("elv: switch to \"%s\" failed, falling back to \"none\"\n",
601 new_e->elevator_name);
602 }
603
604 if (new_e)
605 elevator_put(new_e);
606 return ret;
607}
608
609static void elv_exit_and_release(struct elv_change_ctx *ctx,
610 struct request_queue *q)
611{
612 struct elevator_queue *e;
613 unsigned memflags;
614
615 memflags = blk_mq_freeze_queue(q);
616 mutex_lock(&q->elevator_lock);
617 e = q->elevator;
618 elevator_exit(q);
619 mutex_unlock(&q->elevator_lock);
620 blk_mq_unfreeze_queue(q, memflags);
621 if (e) {
622 blk_mq_free_sched_res(&ctx->res, ctx->type, q->tag_set);
623 kobject_put(&e->kobj);
624 }
625}
626
627static int elevator_change_done(struct request_queue *q,
628 struct elv_change_ctx *ctx)
629{
630 int ret = 0;
631
632 if (ctx->old) {
633 struct elevator_resources res = {
634 .et = ctx->old->et,
635 .data = ctx->old->elevator_data
636 };
637
638 elv_unregister_queue(q, ctx->old);
639 blk_mq_free_sched_res(&res, ctx->old->type, q->tag_set);
640 kobject_put(&ctx->old->kobj);
641 }
642 if (ctx->new) {
643 ret = elv_register_queue(q, ctx->new, !ctx->no_uevent);
644 if (ret)
645 elv_exit_and_release(ctx, q);
646 }
647 return ret;
648}
649
650/*
651 * Switch this queue to the given IO scheduler.
652 */
653static int elevator_change(struct request_queue *q, struct elv_change_ctx *ctx)
654{
655 unsigned int memflags;
656 struct blk_mq_tag_set *set = q->tag_set;
657 int ret = 0;
658
659 lockdep_assert_held(&set->update_nr_hwq_lock);
660
661 if (strncmp(ctx->name, "none", 4)) {
662 ret = blk_mq_alloc_sched_res(q, ctx->type, &ctx->res,
663 set->nr_hw_queues);
664 if (ret)
665 return ret;
666 }
667
668 memflags = blk_mq_freeze_queue(q);
669 /*
670 * May be called before adding disk, when there isn't any FS I/O,
671 * so freezing queue plus canceling dispatch work is enough to
672 * drain any dispatch activities originated from passthrough
673 * requests, then no need to quiesce queue which may add long boot
674 * latency, especially when lots of disks are involved.
675 *
676 * Disk isn't added yet, so verifying queue lock only manually.
677 */
678 blk_mq_cancel_work_sync(q);
679 mutex_lock(&q->elevator_lock);
680 if (!(q->elevator && elevator_match(q->elevator->type, ctx->name)))
681 ret = elevator_switch(q, ctx);
682 mutex_unlock(&q->elevator_lock);
683 blk_mq_unfreeze_queue(q, memflags);
684 if (!ret)
685 ret = elevator_change_done(q, ctx);
686
687 /*
688 * Free sched resource if it's allocated but we couldn't switch elevator.
689 */
690 if (!ctx->new)
691 blk_mq_free_sched_res(&ctx->res, ctx->type, set);
692
693 return ret;
694}
695
696/*
697 * The I/O scheduler depends on the number of hardware queues, this forces a
698 * reattachment when nr_hw_queues changes.
699 */
700void elv_update_nr_hw_queues(struct request_queue *q,
701 struct elv_change_ctx *ctx)
702{
703 struct blk_mq_tag_set *set = q->tag_set;
704 int ret = -ENODEV;
705
706 WARN_ON_ONCE(q->mq_freeze_depth == 0);
707
708 if (ctx->type && !blk_queue_dying(q) && blk_queue_registered(q)) {
709 mutex_lock(&q->elevator_lock);
710 /* force to reattach elevator after nr_hw_queue is updated */
711 ret = elevator_switch(q, ctx);
712 mutex_unlock(&q->elevator_lock);
713 }
714 blk_mq_unfreeze_queue_nomemrestore(q);
715 if (!ret)
716 WARN_ON_ONCE(elevator_change_done(q, ctx));
717
718 /*
719 * Free sched resource if it's allocated but we couldn't switch elevator.
720 */
721 if (!ctx->new)
722 blk_mq_free_sched_res(&ctx->res, ctx->type, set);
723}
724
725/*
726 * Use the default elevator settings. If the chosen elevator initialization
727 * fails, fall back to the "none" elevator (no elevator).
728 */
729void elevator_set_default(struct request_queue *q)
730{
731 struct elv_change_ctx ctx = {
732 .name = "mq-deadline",
733 .no_uevent = true,
734 };
735 int err;
736
737 /* now we allow to switch elevator */
738 blk_queue_flag_clear(QUEUE_FLAG_NO_ELV_SWITCH, q);
739
740 if (q->tag_set->flags & BLK_MQ_F_NO_SCHED_BY_DEFAULT)
741 return;
742
743 /*
744 * For single queue devices, default to using mq-deadline. If we
745 * have multiple queues or mq-deadline is not available, default
746 * to "none".
747 */
748 ctx.type = elevator_find_get(ctx.name);
749 if (!ctx.type)
750 return;
751
752 if ((q->nr_hw_queues == 1 ||
753 blk_mq_is_shared_tags(q->tag_set->flags))) {
754 err = elevator_change(q, &ctx);
755 if (err < 0)
756 pr_warn("\"%s\" elevator initialization, failed %d, falling back to \"none\"\n",
757 ctx.name, err);
758 }
759 elevator_put(ctx.type);
760}
761
762void elevator_set_none(struct request_queue *q)
763{
764 struct elv_change_ctx ctx = {
765 .name = "none",
766 };
767 int err;
768
769 err = elevator_change(q, &ctx);
770 if (err < 0)
771 pr_warn("%s: set none elevator failed %d\n", __func__, err);
772}
773
774static void elv_iosched_load_module(const char *elevator_name)
775{
776 struct elevator_type *found;
777
778 spin_lock(&elv_list_lock);
779 found = __elevator_find(elevator_name);
780 spin_unlock(&elv_list_lock);
781
782 if (!found)
783 request_module("%s-iosched", elevator_name);
784}
785
786ssize_t elv_iosched_store(struct gendisk *disk, const char *buf,
787 size_t count)
788{
789 char elevator_name[ELV_NAME_MAX];
790 struct elv_change_ctx ctx = {};
791 int ret;
792 struct request_queue *q = disk->queue;
793 struct blk_mq_tag_set *set = q->tag_set;
794
795 /* Make sure queue is not in the middle of being removed */
796 if (!blk_queue_registered(q))
797 return -ENOENT;
798
799 /*
800 * If the attribute needs to load a module, do it before freezing the
801 * queue to ensure that the module file can be read when the request
802 * queue is the one for the device storing the module file.
803 */
804 strscpy(elevator_name, buf, sizeof(elevator_name));
805 ctx.name = strstrip(elevator_name);
806
807 elv_iosched_load_module(ctx.name);
808 ctx.type = elevator_find_get(ctx.name);
809
810 /*
811 * Use trylock to avoid circular lock dependency with kernfs active
812 * reference during concurrent disk deletion:
813 * update_nr_hwq_lock -> kn->active (via del_gendisk -> kobject_del)
814 * kn->active -> update_nr_hwq_lock (via this sysfs write path)
815 *
816 * Use the writer lock instead of the reader lock of update_nr_hwq_lock
817 * to serialize the two-stage elevator switch steps in
818 * elevator_change(): the core switch step under the elevator lock and
819 * the elevator_change_done() step outside the elevator lock.
820 */
821 if (!down_write_trylock(&set->update_nr_hwq_lock)) {
822 ret = -EBUSY;
823 goto out;
824 }
825 if (!blk_queue_no_elv_switch(q)) {
826 ret = elevator_change(q, &ctx);
827 if (!ret)
828 ret = count;
829 } else {
830 ret = -ENOENT;
831 }
832 up_write(&set->update_nr_hwq_lock);
833
834out:
835 if (ctx.type)
836 elevator_put(ctx.type);
837 return ret;
838}
839
840ssize_t elv_iosched_show(struct gendisk *disk, char *name)
841{
842 struct request_queue *q = disk->queue;
843 struct elevator_type *cur = NULL, *e;
844 int len = 0;
845
846 mutex_lock(&q->elevator_lock);
847 if (!q->elevator) {
848 len += sprintf(name+len, "[none] ");
849 } else {
850 len += sprintf(name+len, "none ");
851 cur = q->elevator->type;
852 }
853
854 spin_lock(&elv_list_lock);
855 list_for_each_entry(e, &elv_list, list) {
856 if (e == cur)
857 len += sprintf(name+len, "[%s] ", e->elevator_name);
858 else
859 len += sprintf(name+len, "%s ", e->elevator_name);
860 }
861 spin_unlock(&elv_list_lock);
862
863 len += sprintf(name+len, "\n");
864 mutex_unlock(&q->elevator_lock);
865
866 return len;
867}
868
869struct request *elv_rb_former_request(struct request_queue *q,
870 struct request *rq)
871{
872 struct rb_node *rbprev = rb_prev(&rq->rb_node);
873
874 if (rbprev)
875 return rb_entry_rq(rbprev);
876
877 return NULL;
878}
879EXPORT_SYMBOL(elv_rb_former_request);
880
881struct request *elv_rb_latter_request(struct request_queue *q,
882 struct request *rq)
883{
884 struct rb_node *rbnext = rb_next(&rq->rb_node);
885
886 if (rbnext)
887 return rb_entry_rq(rbnext);
888
889 return NULL;
890}
891EXPORT_SYMBOL(elv_rb_latter_request);
892
893static int __init elevator_setup(char *str)
894{
895 pr_warn("Kernel parameter elevator= does not have any effect anymore.\n"
896 "Please use sysfs to set IO scheduler for individual devices.\n");
897 return 1;
898}
899
900__setup("elevator=", elevator_setup);