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/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 
48 static DEFINE_SPINLOCK(elv_list_lock);
49 static 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  */
elv_iosched_allow_bio_merge(struct request * rq,struct bio * bio)60 static 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  */
elv_bio_merge_ok(struct request * rq,struct bio * bio)74 bool 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 }
84 EXPORT_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  */
elevator_match(const struct elevator_type * e,const char * name)93 static 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 
__elevator_find(const char * name)99 static 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 
elevator_find_get(const char * name)109 static 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 
121 static const struct kobj_type elv_ktype;
122 
elevator_alloc(struct request_queue * q,struct elevator_type * e)123 struct elevator_queue *elevator_alloc(struct request_queue *q,
124 				  struct elevator_type *e)
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 
138 	return eq;
139 }
140 EXPORT_SYMBOL(elevator_alloc);
141 
elevator_release(struct kobject * kobj)142 static void elevator_release(struct kobject *kobj)
143 {
144 	struct elevator_queue *e;
145 
146 	e = container_of(kobj, struct elevator_queue, kobj);
147 	elevator_put(e->type);
148 	kfree(e);
149 }
150 
elevator_exit(struct request_queue * q)151 void elevator_exit(struct request_queue *q)
152 {
153 	struct elevator_queue *e = q->elevator;
154 
155 	ioc_clear_queue(q);
156 	blk_mq_sched_free_rqs(q);
157 
158 	mutex_lock(&e->sysfs_lock);
159 	blk_mq_exit_sched(q, e);
160 	mutex_unlock(&e->sysfs_lock);
161 
162 	kobject_put(&e->kobj);
163 }
164 
__elv_rqhash_del(struct request * rq)165 static inline void __elv_rqhash_del(struct request *rq)
166 {
167 	hash_del(&rq->hash);
168 	rq->rq_flags &= ~RQF_HASHED;
169 }
170 
elv_rqhash_del(struct request_queue * q,struct request * rq)171 void elv_rqhash_del(struct request_queue *q, struct request *rq)
172 {
173 	if (ELV_ON_HASH(rq))
174 		__elv_rqhash_del(rq);
175 }
176 EXPORT_SYMBOL_GPL(elv_rqhash_del);
177 
elv_rqhash_add(struct request_queue * q,struct request * rq)178 void 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 }
186 EXPORT_SYMBOL_GPL(elv_rqhash_add);
187 
elv_rqhash_reposition(struct request_queue * q,struct request * rq)188 void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
189 {
190 	__elv_rqhash_del(rq);
191 	elv_rqhash_add(q, rq);
192 }
193 
elv_rqhash_find(struct request_queue * q,sector_t offset)194 struct 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  */
elv_rb_add(struct rb_root * root,struct request * rq)219 void 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 }
238 EXPORT_SYMBOL(elv_rb_add);
239 
elv_rb_del(struct rb_root * root,struct request * rq)240 void 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 }
246 EXPORT_SYMBOL(elv_rb_del);
247 
elv_rb_find(struct rb_root * root,sector_t sector)248 struct 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 }
266 EXPORT_SYMBOL(elv_rb_find);
267 
elv_merge(struct request_queue * q,struct request ** req,struct bio * bio)268 enum 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  */
elv_attempt_insert_merge(struct request_queue * q,struct request * rq,struct list_head * free)324 bool 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 
elv_merged_request(struct request_queue * q,struct request * rq,enum elv_merge type)362 void 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 
elv_merge_requests(struct request_queue * q,struct request * rq,struct request * next)376 void 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 
elv_latter_request(struct request_queue * q,struct request * rq)388 struct 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 
elv_former_request(struct request_queue * q,struct request * rq)398 struct 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((atr), struct elv_fs_entry, attr)
409 
410 static ssize_t
elv_attr_show(struct kobject * kobj,struct attribute * attr,char * page)411 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
412 {
413 	struct elv_fs_entry *entry = to_elv(attr);
414 	struct elevator_queue *e;
415 	ssize_t error;
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 	error = e->type ? entry->show(e, page) : -ENOENT;
423 	mutex_unlock(&e->sysfs_lock);
424 	return error;
425 }
426 
427 static ssize_t
elv_attr_store(struct kobject * kobj,struct attribute * attr,const char * page,size_t length)428 elv_attr_store(struct kobject *kobj, struct attribute *attr,
429 	       const char *page, size_t length)
430 {
431 	struct elv_fs_entry *entry = to_elv(attr);
432 	struct elevator_queue *e;
433 	ssize_t error;
434 
435 	if (!entry->store)
436 		return -EIO;
437 
438 	e = container_of(kobj, struct elevator_queue, kobj);
439 	mutex_lock(&e->sysfs_lock);
440 	error = e->type ? entry->store(e, page, length) : -ENOENT;
441 	mutex_unlock(&e->sysfs_lock);
442 	return error;
443 }
444 
445 static const struct sysfs_ops elv_sysfs_ops = {
446 	.show	= elv_attr_show,
447 	.store	= elv_attr_store,
448 };
449 
450 static const struct kobj_type elv_ktype = {
451 	.sysfs_ops	= &elv_sysfs_ops,
452 	.release	= elevator_release,
453 };
454 
elv_register_queue(struct request_queue * q,bool uevent)455 int elv_register_queue(struct request_queue *q, bool uevent)
456 {
457 	struct elevator_queue *e = q->elevator;
458 	int error;
459 
460 	lockdep_assert_held(&q->sysfs_lock);
461 
462 	error = kobject_add(&e->kobj, &q->disk->queue_kobj, "iosched");
463 	if (!error) {
464 		struct elv_fs_entry *attr = e->type->elevator_attrs;
465 		if (attr) {
466 			while (attr->attr.name) {
467 				if (sysfs_create_file(&e->kobj, &attr->attr))
468 					break;
469 				attr++;
470 			}
471 		}
472 		if (uevent)
473 			kobject_uevent(&e->kobj, KOBJ_ADD);
474 
475 		set_bit(ELEVATOR_FLAG_REGISTERED, &e->flags);
476 	}
477 	return error;
478 }
479 
elv_unregister_queue(struct request_queue * q)480 void elv_unregister_queue(struct request_queue *q)
481 {
482 	struct elevator_queue *e = q->elevator;
483 
484 	lockdep_assert_held(&q->sysfs_lock);
485 
486 	if (e && test_and_clear_bit(ELEVATOR_FLAG_REGISTERED, &e->flags)) {
487 		kobject_uevent(&e->kobj, KOBJ_REMOVE);
488 		kobject_del(&e->kobj);
489 	}
490 }
491 
elv_register(struct elevator_type * e)492 int elv_register(struct elevator_type *e)
493 {
494 	/* finish request is mandatory */
495 	if (WARN_ON_ONCE(!e->ops.finish_request))
496 		return -EINVAL;
497 	/* insert_requests and dispatch_request are mandatory */
498 	if (WARN_ON_ONCE(!e->ops.insert_requests || !e->ops.dispatch_request))
499 		return -EINVAL;
500 
501 	/* create icq_cache if requested */
502 	if (e->icq_size) {
503 		if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
504 		    WARN_ON(e->icq_align < __alignof__(struct io_cq)))
505 			return -EINVAL;
506 
507 		snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
508 			 "%s_io_cq", e->elevator_name);
509 		e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
510 						 e->icq_align, 0, NULL);
511 		if (!e->icq_cache)
512 			return -ENOMEM;
513 	}
514 
515 	/* register, don't allow duplicate names */
516 	spin_lock(&elv_list_lock);
517 	if (__elevator_find(e->elevator_name)) {
518 		spin_unlock(&elv_list_lock);
519 		kmem_cache_destroy(e->icq_cache);
520 		return -EBUSY;
521 	}
522 	list_add_tail(&e->list, &elv_list);
523 	spin_unlock(&elv_list_lock);
524 
525 	printk(KERN_INFO "io scheduler %s registered\n", e->elevator_name);
526 
527 	return 0;
528 }
529 EXPORT_SYMBOL_GPL(elv_register);
530 
elv_unregister(struct elevator_type * e)531 void elv_unregister(struct elevator_type *e)
532 {
533 	/* unregister */
534 	spin_lock(&elv_list_lock);
535 	list_del_init(&e->list);
536 	spin_unlock(&elv_list_lock);
537 
538 	/*
539 	 * Destroy icq_cache if it exists.  icq's are RCU managed.  Make
540 	 * sure all RCU operations are complete before proceeding.
541 	 */
542 	if (e->icq_cache) {
543 		rcu_barrier();
544 		kmem_cache_destroy(e->icq_cache);
545 		e->icq_cache = NULL;
546 	}
547 }
548 EXPORT_SYMBOL_GPL(elv_unregister);
549 
elv_support_iosched(struct request_queue * q)550 static inline bool elv_support_iosched(struct request_queue *q)
551 {
552 	if (!queue_is_mq(q) ||
553 	    (q->tag_set->flags & BLK_MQ_F_NO_SCHED))
554 		return false;
555 	return true;
556 }
557 
558 /*
559  * For single queue devices, default to using mq-deadline. If we have multiple
560  * queues or mq-deadline is not available, default to "none".
561  */
elevator_get_default(struct request_queue * q)562 static struct elevator_type *elevator_get_default(struct request_queue *q)
563 {
564 	if (q->tag_set->flags & BLK_MQ_F_NO_SCHED_BY_DEFAULT)
565 		return NULL;
566 
567 	if (q->nr_hw_queues != 1 &&
568 	    !blk_mq_is_shared_tags(q->tag_set->flags))
569 		return NULL;
570 
571 	return elevator_find_get("mq-deadline");
572 }
573 
574 /*
575  * Use the default elevator settings. If the chosen elevator initialization
576  * fails, fall back to the "none" elevator (no elevator).
577  */
elevator_init_mq(struct request_queue * q)578 void elevator_init_mq(struct request_queue *q)
579 {
580 	struct elevator_type *e;
581 	int err;
582 
583 	if (!elv_support_iosched(q))
584 		return;
585 
586 	WARN_ON_ONCE(blk_queue_registered(q));
587 
588 	if (unlikely(q->elevator))
589 		return;
590 
591 	e = elevator_get_default(q);
592 	if (!e)
593 		return;
594 
595 	/*
596 	 * We are called before adding disk, when there isn't any FS I/O,
597 	 * so freezing queue plus canceling dispatch work is enough to
598 	 * drain any dispatch activities originated from passthrough
599 	 * requests, then no need to quiesce queue which may add long boot
600 	 * latency, especially when lots of disks are involved.
601 	 */
602 	blk_mq_freeze_queue(q);
603 	blk_mq_cancel_work_sync(q);
604 
605 	err = blk_mq_init_sched(q, e);
606 
607 	blk_mq_unfreeze_queue(q);
608 
609 	if (err) {
610 		pr_warn("\"%s\" elevator initialization failed, "
611 			"falling back to \"none\"\n", e->elevator_name);
612 	}
613 
614 	elevator_put(e);
615 }
616 
617 /*
618  * Switch to new_e io scheduler.
619  *
620  * If switching fails, we are most likely running out of memory and not able
621  * to restore the old io scheduler, so leaving the io scheduler being none.
622  */
elevator_switch(struct request_queue * q,struct elevator_type * new_e)623 int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
624 {
625 	int ret;
626 
627 	lockdep_assert_held(&q->sysfs_lock);
628 
629 	blk_mq_freeze_queue(q);
630 	blk_mq_quiesce_queue(q);
631 
632 	if (q->elevator) {
633 		elv_unregister_queue(q);
634 		elevator_exit(q);
635 	}
636 
637 	ret = blk_mq_init_sched(q, new_e);
638 	if (ret)
639 		goto out_unfreeze;
640 
641 	ret = elv_register_queue(q, true);
642 	if (ret) {
643 		elevator_exit(q);
644 		goto out_unfreeze;
645 	}
646 	blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
647 
648 out_unfreeze:
649 	blk_mq_unquiesce_queue(q);
650 	blk_mq_unfreeze_queue(q);
651 
652 	if (ret) {
653 		pr_warn("elv: switch to \"%s\" failed, falling back to \"none\"\n",
654 			new_e->elevator_name);
655 	}
656 
657 	return ret;
658 }
659 
elevator_disable(struct request_queue * q)660 void elevator_disable(struct request_queue *q)
661 {
662 	lockdep_assert_held(&q->sysfs_lock);
663 
664 	blk_mq_freeze_queue(q);
665 	blk_mq_quiesce_queue(q);
666 
667 	elv_unregister_queue(q);
668 	elevator_exit(q);
669 	blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q);
670 	q->elevator = NULL;
671 	q->nr_requests = q->tag_set->queue_depth;
672 	blk_add_trace_msg(q, "elv switch: none");
673 
674 	blk_mq_unquiesce_queue(q);
675 	blk_mq_unfreeze_queue(q);
676 }
677 
678 /*
679  * Switch this queue to the given IO scheduler.
680  */
elevator_change(struct request_queue * q,const char * elevator_name)681 static int elevator_change(struct request_queue *q, const char *elevator_name)
682 {
683 	struct elevator_type *e;
684 	int ret;
685 
686 	/* Make sure queue is not in the middle of being removed */
687 	if (!blk_queue_registered(q))
688 		return -ENOENT;
689 
690 	if (!strncmp(elevator_name, "none", 4)) {
691 		if (q->elevator)
692 			elevator_disable(q);
693 		return 0;
694 	}
695 
696 	if (q->elevator && elevator_match(q->elevator->type, elevator_name))
697 		return 0;
698 
699 	e = elevator_find_get(elevator_name);
700 	if (!e)
701 		return -EINVAL;
702 	ret = elevator_switch(q, e);
703 	elevator_put(e);
704 	return ret;
705 }
706 
elv_iosched_load_module(struct gendisk * disk,const char * buf,size_t count)707 int elv_iosched_load_module(struct gendisk *disk, const char *buf,
708 			    size_t count)
709 {
710 	char elevator_name[ELV_NAME_MAX];
711 	struct elevator_type *found;
712 	const char *name;
713 
714 	if (!elv_support_iosched(disk->queue))
715 		return -EOPNOTSUPP;
716 
717 	strscpy(elevator_name, buf, sizeof(elevator_name));
718 	name = strstrip(elevator_name);
719 
720 	spin_lock(&elv_list_lock);
721 	found = __elevator_find(name);
722 	spin_unlock(&elv_list_lock);
723 
724 	if (!found)
725 		request_module("%s-iosched", name);
726 
727 	return 0;
728 }
729 
elv_iosched_store(struct gendisk * disk,const char * buf,size_t count)730 ssize_t elv_iosched_store(struct gendisk *disk, const char *buf,
731 			  size_t count)
732 {
733 	char elevator_name[ELV_NAME_MAX];
734 	int ret;
735 
736 	if (!elv_support_iosched(disk->queue))
737 		return count;
738 
739 	strscpy(elevator_name, buf, sizeof(elevator_name));
740 	ret = elevator_change(disk->queue, strstrip(elevator_name));
741 	if (!ret)
742 		return count;
743 	return ret;
744 }
745 
elv_iosched_show(struct gendisk * disk,char * name)746 ssize_t elv_iosched_show(struct gendisk *disk, char *name)
747 {
748 	struct request_queue *q = disk->queue;
749 	struct elevator_queue *eq = q->elevator;
750 	struct elevator_type *cur = NULL, *e;
751 	int len = 0;
752 
753 	if (!elv_support_iosched(q))
754 		return sprintf(name, "none\n");
755 
756 	if (!q->elevator) {
757 		len += sprintf(name+len, "[none] ");
758 	} else {
759 		len += sprintf(name+len, "none ");
760 		cur = eq->type;
761 	}
762 
763 	spin_lock(&elv_list_lock);
764 	list_for_each_entry(e, &elv_list, list) {
765 		if (e == cur)
766 			len += sprintf(name+len, "[%s] ", e->elevator_name);
767 		else
768 			len += sprintf(name+len, "%s ", e->elevator_name);
769 	}
770 	spin_unlock(&elv_list_lock);
771 
772 	len += sprintf(name+len, "\n");
773 	return len;
774 }
775 
elv_rb_former_request(struct request_queue * q,struct request * rq)776 struct request *elv_rb_former_request(struct request_queue *q,
777 				      struct request *rq)
778 {
779 	struct rb_node *rbprev = rb_prev(&rq->rb_node);
780 
781 	if (rbprev)
782 		return rb_entry_rq(rbprev);
783 
784 	return NULL;
785 }
786 EXPORT_SYMBOL(elv_rb_former_request);
787 
elv_rb_latter_request(struct request_queue * q,struct request * rq)788 struct request *elv_rb_latter_request(struct request_queue *q,
789 				      struct request *rq)
790 {
791 	struct rb_node *rbnext = rb_next(&rq->rb_node);
792 
793 	if (rbnext)
794 		return rb_entry_rq(rbnext);
795 
796 	return NULL;
797 }
798 EXPORT_SYMBOL(elv_rb_latter_request);
799 
elevator_setup(char * str)800 static int __init elevator_setup(char *str)
801 {
802 	pr_warn("Kernel parameter elevator= does not have any effect anymore.\n"
803 		"Please use sysfs to set IO scheduler for individual devices.\n");
804 	return 1;
805 }
806 
807 __setup("elevator=", elevator_setup);
808