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1 /*
2  *  Block device elevator/IO-scheduler.
3  *
4  *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
5  *
6  * 30042000 Jens Axboe <axboe@kernel.dk> :
7  *
8  * Split the elevator a bit so that it is possible to choose a different
9  * one or even write a new "plug in". There are three pieces:
10  * - elevator_fn, inserts a new request in the queue list
11  * - elevator_merge_fn, decides whether a new buffer can be merged with
12  *   an existing request
13  * - elevator_dequeue_fn, called when a request is taken off the active list
14  *
15  * 20082000 Dave Jones <davej@suse.de> :
16  * Removed tests for max-bomb-segments, which was breaking elvtune
17  *  when run without -bN
18  *
19  * Jens:
20  * - Rework again to work with bio instead of buffer_heads
21  * - loose bi_dev comparisons, partition handling is right now
22  * - completely modularize elevator setup and teardown
23  *
24  */
25 #include <linux/kernel.h>
26 #include <linux/fs.h>
27 #include <linux/blkdev.h>
28 #include <linux/elevator.h>
29 #include <linux/bio.h>
30 #include <linux/module.h>
31 #include <linux/slab.h>
32 #include <linux/init.h>
33 #include <linux/compiler.h>
34 #include <linux/blktrace_api.h>
35 #include <linux/hash.h>
36 #include <linux/uaccess.h>
37 #include <linux/pm_runtime.h>
38 #include <linux/blk-cgroup.h>
39
40 #include <trace/events/block.h>
41
42 #include "blk.h"
43 #include "blk-mq-sched.h"
44 #include "blk-wbt.h"
45
46 static DEFINE_SPINLOCK(elv_list_lock);
47 static LIST_HEAD(elv_list);
48
49 /*
50  * Merge hash stuff.
51  */
52 #define rq_hash_key(rq)         (blk_rq_pos(rq) + blk_rq_sectors(rq))
53
54 /*
55  * Query io scheduler to see if the current process issuing bio may be
56  * merged with rq.
57  */
58 static int elv_iosched_allow_bio_merge(struct request *rq, struct bio *bio)
59 {
60         struct request_queue *q = rq->q;
61         struct elevator_queue *e = q->elevator;
62
63         if (e->uses_mq && e->type->ops.mq.allow_merge)
64                 return e->type->ops.mq.allow_merge(q, rq, bio);
65         else if (!e->uses_mq && e->type->ops.sq.elevator_allow_bio_merge_fn)
66                 return e->type->ops.sq.elevator_allow_bio_merge_fn(q, rq, bio);
67
68         return 1;
69 }
70
71 /*
72  * can we safely merge with this request?
73  */
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 static 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
98 static void elevator_put(struct elevator_type *e)
99 {
100         module_put(e->elevator_owner);
101 }
102
103 static struct elevator_type *elevator_get(const char *name, bool try_loading)
104 {
105         struct elevator_type *e;
106
107         spin_lock(&elv_list_lock);
108
109         e = elevator_find(name);
110         if (!e && try_loading) {
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
125 static char chosen_elevator[ELV_NAME_MAX];
126
127 static 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
139 /* called during boot to load the elevator chosen by the elevator param */
140 void __init load_default_elevator_module(void)
141 {
142         struct elevator_type *e;
143
144         if (!chosen_elevator[0])
145                 return;
146
147         spin_lock(&elv_list_lock);
148         e = elevator_find(chosen_elevator);
149         spin_unlock(&elv_list_lock);
150
151         if (!e)
152                 request_module("%s-iosched", chosen_elevator);
153 }
154
155 static struct kobj_type elv_ktype;
156
157 struct elevator_queue *elevator_alloc(struct request_queue *q,
158                                   struct elevator_type *e)
159 {
160         struct elevator_queue *eq;
161
162         eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node);
163         if (unlikely(!eq))
164                 return NULL;
165
166         eq->type = e;
167         kobject_init(&eq->kobj, &elv_ktype);
168         mutex_init(&eq->sysfs_lock);
169         hash_init(eq->hash);
170         eq->uses_mq = e->uses_mq;
171
172         return eq;
173 }
174 EXPORT_SYMBOL(elevator_alloc);
175
176 static void elevator_release(struct kobject *kobj)
177 {
178         struct elevator_queue *e;
179
180         e = container_of(kobj, struct elevator_queue, kobj);
181         elevator_put(e->type);
182         kfree(e);
183 }
184
185 int elevator_init(struct request_queue *q, char *name)
186 {
187         struct elevator_type *e = NULL;
188         int err;
189
190         /*
191          * q->sysfs_lock must be held to provide mutual exclusion between
192          * elevator_switch() and here.
193          */
194         lockdep_assert_held(&q->sysfs_lock);
195
196         if (unlikely(q->elevator))
197                 return 0;
198
199         INIT_LIST_HEAD(&q->queue_head);
200         q->last_merge = NULL;
201         q->end_sector = 0;
202         q->boundary_rq = NULL;
203
204         if (name) {
205                 e = elevator_get(name, true);
206                 if (!e)
207                         return -EINVAL;
208         }
209
210         /*
211          * Use the default elevator specified by config boot param for
212          * non-mq devices, or by config option. Don't try to load modules
213          * as we could be running off async and request_module() isn't
214          * allowed from async.
215          */
216         if (!e && !q->mq_ops && *chosen_elevator) {
217                 e = elevator_get(chosen_elevator, false);
218                 if (!e)
219                         printk(KERN_ERR "I/O scheduler %s not found\n",
220                                                         chosen_elevator);
221         }
222
223         if (!e) {
224                 /*
225                  * For blk-mq devices, we default to using mq-deadline,
226                  * if available, for single queue devices. If deadline
227                  * isn't available OR we have multiple queues, default
228                  * to "none".
229                  */
230                 if (q->mq_ops) {
231                         if (q->nr_hw_queues == 1)
232                                 e = elevator_get("mq-deadline", false);
233                         if (!e)
234                                 return 0;
235                 } else
236                         e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);
237
238                 if (!e) {
239                         printk(KERN_ERR
240                                 "Default I/O scheduler not found. " \
241                                 "Using noop.\n");
242                         e = elevator_get("noop", false);
243                 }
244         }
245
246         if (e->uses_mq)
247                 err = blk_mq_init_sched(q, e);
248         else
249                 err = e->ops.sq.elevator_init_fn(q, e);
250         if (err)
251                 elevator_put(e);
252         return err;
253 }
254 EXPORT_SYMBOL(elevator_init);
255
256 void elevator_exit(struct request_queue *q, struct elevator_queue *e)
257 {
258         mutex_lock(&e->sysfs_lock);
259         if (e->uses_mq && e->type->ops.mq.exit_sched)
260                 blk_mq_exit_sched(q, e);
261         else if (!e->uses_mq && e->type->ops.sq.elevator_exit_fn)
262                 e->type->ops.sq.elevator_exit_fn(e);
263         mutex_unlock(&e->sysfs_lock);
264
265         kobject_put(&e->kobj);
266 }
267 EXPORT_SYMBOL(elevator_exit);
268
269 static inline void __elv_rqhash_del(struct request *rq)
270 {
271         hash_del(&rq->hash);
272         rq->rq_flags &= ~RQF_HASHED;
273 }
274
275 void elv_rqhash_del(struct request_queue *q, struct request *rq)
276 {
277         if (ELV_ON_HASH(rq))
278                 __elv_rqhash_del(rq);
279 }
280 EXPORT_SYMBOL_GPL(elv_rqhash_del);
281
282 void elv_rqhash_add(struct request_queue *q, struct request *rq)
283 {
284         struct elevator_queue *e = q->elevator;
285
286         BUG_ON(ELV_ON_HASH(rq));
287         hash_add(e->hash, &rq->hash, rq_hash_key(rq));
288         rq->rq_flags |= RQF_HASHED;
289 }
290 EXPORT_SYMBOL_GPL(elv_rqhash_add);
291
292 void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
293 {
294         __elv_rqhash_del(rq);
295         elv_rqhash_add(q, rq);
296 }
297
298 struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
299 {
300         struct elevator_queue *e = q->elevator;
301         struct hlist_node *next;
302         struct request *rq;
303
304         hash_for_each_possible_safe(e->hash, rq, next, hash, offset) {
305                 BUG_ON(!ELV_ON_HASH(rq));
306
307                 if (unlikely(!rq_mergeable(rq))) {
308                         __elv_rqhash_del(rq);
309                         continue;
310                 }
311
312                 if (rq_hash_key(rq) == offset)
313                         return rq;
314         }
315
316         return NULL;
317 }
318
319 /*
320  * RB-tree support functions for inserting/lookup/removal of requests
321  * in a sorted RB tree.
322  */
323 void elv_rb_add(struct rb_root *root, struct request *rq)
324 {
325         struct rb_node **p = &root->rb_node;
326         struct rb_node *parent = NULL;
327         struct request *__rq;
328
329         while (*p) {
330                 parent = *p;
331                 __rq = rb_entry(parent, struct request, rb_node);
332
333                 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
334                         p = &(*p)->rb_left;
335                 else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
336                         p = &(*p)->rb_right;
337         }
338
339         rb_link_node(&rq->rb_node, parent, p);
340         rb_insert_color(&rq->rb_node, root);
341 }
342 EXPORT_SYMBOL(elv_rb_add);
343
344 void elv_rb_del(struct rb_root *root, struct request *rq)
345 {
346         BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
347         rb_erase(&rq->rb_node, root);
348         RB_CLEAR_NODE(&rq->rb_node);
349 }
350 EXPORT_SYMBOL(elv_rb_del);
351
352 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
353 {
354         struct rb_node *n = root->rb_node;
355         struct request *rq;
356
357         while (n) {
358                 rq = rb_entry(n, struct request, rb_node);
359
360                 if (sector < blk_rq_pos(rq))
361                         n = n->rb_left;
362                 else if (sector > blk_rq_pos(rq))
363                         n = n->rb_right;
364                 else
365                         return rq;
366         }
367
368         return NULL;
369 }
370 EXPORT_SYMBOL(elv_rb_find);
371
372 /*
373  * Insert rq into dispatch queue of q.  Queue lock must be held on
374  * entry.  rq is sort instead into the dispatch queue. To be used by
375  * specific elevators.
376  */
377 void elv_dispatch_sort(struct request_queue *q, struct request *rq)
378 {
379         sector_t boundary;
380         struct list_head *entry;
381
382         if (q->last_merge == rq)
383                 q->last_merge = NULL;
384
385         elv_rqhash_del(q, rq);
386
387         q->nr_sorted--;
388
389         boundary = q->end_sector;
390         list_for_each_prev(entry, &q->queue_head) {
391                 struct request *pos = list_entry_rq(entry);
392
393                 if (req_op(rq) != req_op(pos))
394                         break;
395                 if (rq_data_dir(rq) != rq_data_dir(pos))
396                         break;
397                 if (pos->rq_flags & (RQF_STARTED | RQF_SOFTBARRIER))
398                         break;
399                 if (blk_rq_pos(rq) >= boundary) {
400                         if (blk_rq_pos(pos) < boundary)
401                                 continue;
402                 } else {
403                         if (blk_rq_pos(pos) >= boundary)
404                                 break;
405                 }
406                 if (blk_rq_pos(rq) >= blk_rq_pos(pos))
407                         break;
408         }
409
410         list_add(&rq->queuelist, entry);
411 }
412 EXPORT_SYMBOL(elv_dispatch_sort);
413
414 /*
415  * Insert rq into dispatch queue of q.  Queue lock must be held on
416  * entry.  rq is added to the back of the dispatch queue. To be used by
417  * specific elevators.
418  */
419 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
420 {
421         if (q->last_merge == rq)
422                 q->last_merge = NULL;
423
424         elv_rqhash_del(q, rq);
425
426         q->nr_sorted--;
427
428         q->end_sector = rq_end_sector(rq);
429         q->boundary_rq = rq;
430         list_add_tail(&rq->queuelist, &q->queue_head);
431 }
432 EXPORT_SYMBOL(elv_dispatch_add_tail);
433
434 enum elv_merge elv_merge(struct request_queue *q, struct request **req,
435                 struct bio *bio)
436 {
437         struct elevator_queue *e = q->elevator;
438         struct request *__rq;
439
440         /*
441          * Levels of merges:
442          *      nomerges:  No merges at all attempted
443          *      noxmerges: Only simple one-hit cache try
444          *      merges:    All merge tries attempted
445          */
446         if (blk_queue_nomerges(q) || !bio_mergeable(bio))
447                 return ELEVATOR_NO_MERGE;
448
449         /*
450          * First try one-hit cache.
451          */
452         if (q->last_merge && elv_bio_merge_ok(q->last_merge, bio)) {
453                 enum elv_merge ret = blk_try_merge(q->last_merge, bio);
454
455                 if (ret != ELEVATOR_NO_MERGE) {
456                         *req = q->last_merge;
457                         return ret;
458                 }
459         }
460
461         if (blk_queue_noxmerges(q))
462                 return ELEVATOR_NO_MERGE;
463
464         /*
465          * See if our hash lookup can find a potential backmerge.
466          */
467         __rq = elv_rqhash_find(q, bio->bi_iter.bi_sector);
468         if (__rq && elv_bio_merge_ok(__rq, bio)) {
469                 *req = __rq;
470                 return ELEVATOR_BACK_MERGE;
471         }
472
473         if (e->uses_mq && e->type->ops.mq.request_merge)
474                 return e->type->ops.mq.request_merge(q, req, bio);
475         else if (!e->uses_mq && e->type->ops.sq.elevator_merge_fn)
476                 return e->type->ops.sq.elevator_merge_fn(q, req, bio);
477
478         return ELEVATOR_NO_MERGE;
479 }
480
481 /*
482  * Attempt to do an insertion back merge. Only check for the case where
483  * we can append 'rq' to an existing request, so we can throw 'rq' away
484  * afterwards.
485  *
486  * Returns true if we merged, false otherwise
487  */
488 bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq)
489 {
490         struct request *__rq;
491         bool ret;
492
493         if (blk_queue_nomerges(q))
494                 return false;
495
496         /*
497          * First try one-hit cache.
498          */
499         if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq))
500                 return true;
501
502         if (blk_queue_noxmerges(q))
503                 return false;
504
505         ret = false;
506         /*
507          * See if our hash lookup can find a potential backmerge.
508          */
509         while (1) {
510                 __rq = elv_rqhash_find(q, blk_rq_pos(rq));
511                 if (!__rq || !blk_attempt_req_merge(q, __rq, rq))
512                         break;
513
514                 /* The merged request could be merged with others, try again */
515                 ret = true;
516                 rq = __rq;
517         }
518
519         return ret;
520 }
521
522 void elv_merged_request(struct request_queue *q, struct request *rq,
523                 enum elv_merge type)
524 {
525         struct elevator_queue *e = q->elevator;
526
527         if (e->uses_mq && e->type->ops.mq.request_merged)
528                 e->type->ops.mq.request_merged(q, rq, type);
529         else if (!e->uses_mq && e->type->ops.sq.elevator_merged_fn)
530                 e->type->ops.sq.elevator_merged_fn(q, rq, type);
531
532         if (type == ELEVATOR_BACK_MERGE)
533                 elv_rqhash_reposition(q, rq);
534
535         q->last_merge = rq;
536 }
537
538 void elv_merge_requests(struct request_queue *q, struct request *rq,
539                              struct request *next)
540 {
541         struct elevator_queue *e = q->elevator;
542         bool next_sorted = false;
543
544         if (e->uses_mq && e->type->ops.mq.requests_merged)
545                 e->type->ops.mq.requests_merged(q, rq, next);
546         else if (e->type->ops.sq.elevator_merge_req_fn) {
547                 next_sorted = (__force bool)(next->rq_flags & RQF_SORTED);
548                 if (next_sorted)
549                         e->type->ops.sq.elevator_merge_req_fn(q, rq, next);
550         }
551
552         elv_rqhash_reposition(q, rq);
553
554         if (next_sorted) {
555                 elv_rqhash_del(q, next);
556                 q->nr_sorted--;
557         }
558
559         q->last_merge = rq;
560 }
561
562 void elv_bio_merged(struct request_queue *q, struct request *rq,
563                         struct bio *bio)
564 {
565         struct elevator_queue *e = q->elevator;
566
567         if (WARN_ON_ONCE(e->uses_mq))
568                 return;
569
570         if (e->type->ops.sq.elevator_bio_merged_fn)
571                 e->type->ops.sq.elevator_bio_merged_fn(q, rq, bio);
572 }
573
574 #ifdef CONFIG_PM
575 static void blk_pm_requeue_request(struct request *rq)
576 {
577         if (rq->q->dev && !(rq->rq_flags & RQF_PM))
578                 rq->q->nr_pending--;
579 }
580
581 static void blk_pm_add_request(struct request_queue *q, struct request *rq)
582 {
583         if (q->dev && !(rq->rq_flags & RQF_PM) && q->nr_pending++ == 0 &&
584             (q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING))
585                 pm_request_resume(q->dev);
586 }
587 #else
588 static inline void blk_pm_requeue_request(struct request *rq) {}
589 static inline void blk_pm_add_request(struct request_queue *q,
590                                       struct request *rq)
591 {
592 }
593 #endif
594
595 void elv_requeue_request(struct request_queue *q, struct request *rq)
596 {
597         /*
598          * it already went through dequeue, we need to decrement the
599          * in_flight count again
600          */
601         if (blk_account_rq(rq)) {
602                 q->in_flight[rq_is_sync(rq)]--;
603                 if (rq->rq_flags & RQF_SORTED)
604                         elv_deactivate_rq(q, rq);
605         }
606
607         rq->rq_flags &= ~RQF_STARTED;
608
609         blk_pm_requeue_request(rq);
610
611         __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
612 }
613
614 void elv_drain_elevator(struct request_queue *q)
615 {
616         struct elevator_queue *e = q->elevator;
617         static int printed;
618
619         if (WARN_ON_ONCE(e->uses_mq))
620                 return;
621
622         lockdep_assert_held(q->queue_lock);
623
624         while (e->type->ops.sq.elevator_dispatch_fn(q, 1))
625                 ;
626         if (q->nr_sorted && printed++ < 10) {
627                 printk(KERN_ERR "%s: forced dispatching is broken "
628                        "(nr_sorted=%u), please report this\n",
629                        q->elevator->type->elevator_name, q->nr_sorted);
630         }
631 }
632
633 void __elv_add_request(struct request_queue *q, struct request *rq, int where)
634 {
635         trace_block_rq_insert(q, rq);
636
637         blk_pm_add_request(q, rq);
638
639         rq->q = q;
640
641         if (rq->rq_flags & RQF_SOFTBARRIER) {
642                 /* barriers are scheduling boundary, update end_sector */
643                 if (!blk_rq_is_passthrough(rq)) {
644                         q->end_sector = rq_end_sector(rq);
645                         q->boundary_rq = rq;
646                 }
647         } else if (!(rq->rq_flags & RQF_ELVPRIV) &&
648                     (where == ELEVATOR_INSERT_SORT ||
649                      where == ELEVATOR_INSERT_SORT_MERGE))
650                 where = ELEVATOR_INSERT_BACK;
651
652         switch (where) {
653         case ELEVATOR_INSERT_REQUEUE:
654         case ELEVATOR_INSERT_FRONT:
655                 rq->rq_flags |= RQF_SOFTBARRIER;
656                 list_add(&rq->queuelist, &q->queue_head);
657                 break;
658
659         case ELEVATOR_INSERT_BACK:
660                 rq->rq_flags |= RQF_SOFTBARRIER;
661                 elv_drain_elevator(q);
662                 list_add_tail(&rq->queuelist, &q->queue_head);
663                 /*
664                  * We kick the queue here for the following reasons.
665                  * - The elevator might have returned NULL previously
666                  *   to delay requests and returned them now.  As the
667                  *   queue wasn't empty before this request, ll_rw_blk
668                  *   won't run the queue on return, resulting in hang.
669                  * - Usually, back inserted requests won't be merged
670                  *   with anything.  There's no point in delaying queue
671                  *   processing.
672                  */
673                 __blk_run_queue(q);
674                 break;
675
676         case ELEVATOR_INSERT_SORT_MERGE:
677                 /*
678                  * If we succeed in merging this request with one in the
679                  * queue already, we are done - rq has now been freed,
680                  * so no need to do anything further.
681                  */
682                 if (elv_attempt_insert_merge(q, rq))
683                         break;
684                 /* fall through */
685         case ELEVATOR_INSERT_SORT:
686                 BUG_ON(blk_rq_is_passthrough(rq));
687                 rq->rq_flags |= RQF_SORTED;
688                 q->nr_sorted++;
689                 if (rq_mergeable(rq)) {
690                         elv_rqhash_add(q, rq);
691                         if (!q->last_merge)
692                                 q->last_merge = rq;
693                 }
694
695                 /*
696                  * Some ioscheds (cfq) run q->request_fn directly, so
697                  * rq cannot be accessed after calling
698                  * elevator_add_req_fn.
699                  */
700                 q->elevator->type->ops.sq.elevator_add_req_fn(q, rq);
701                 break;
702
703         case ELEVATOR_INSERT_FLUSH:
704                 rq->rq_flags |= RQF_SOFTBARRIER;
705                 blk_insert_flush(rq);
706                 break;
707         default:
708                 printk(KERN_ERR "%s: bad insertion point %d\n",
709                        __func__, where);
710                 BUG();
711         }
712 }
713 EXPORT_SYMBOL(__elv_add_request);
714
715 void elv_add_request(struct request_queue *q, struct request *rq, int where)
716 {
717         unsigned long flags;
718
719         spin_lock_irqsave(q->queue_lock, flags);
720         __elv_add_request(q, rq, where);
721         spin_unlock_irqrestore(q->queue_lock, flags);
722 }
723 EXPORT_SYMBOL(elv_add_request);
724
725 struct request *elv_latter_request(struct request_queue *q, struct request *rq)
726 {
727         struct elevator_queue *e = q->elevator;
728
729         if (e->uses_mq && e->type->ops.mq.next_request)
730                 return e->type->ops.mq.next_request(q, rq);
731         else if (!e->uses_mq && e->type->ops.sq.elevator_latter_req_fn)
732                 return e->type->ops.sq.elevator_latter_req_fn(q, rq);
733
734         return NULL;
735 }
736
737 struct request *elv_former_request(struct request_queue *q, struct request *rq)
738 {
739         struct elevator_queue *e = q->elevator;
740
741         if (e->uses_mq && e->type->ops.mq.former_request)
742                 return e->type->ops.mq.former_request(q, rq);
743         if (!e->uses_mq && e->type->ops.sq.elevator_former_req_fn)
744                 return e->type->ops.sq.elevator_former_req_fn(q, rq);
745         return NULL;
746 }
747
748 int elv_set_request(struct request_queue *q, struct request *rq,
749                     struct bio *bio, gfp_t gfp_mask)
750 {
751         struct elevator_queue *e = q->elevator;
752
753         if (WARN_ON_ONCE(e->uses_mq))
754                 return 0;
755
756         if (e->type->ops.sq.elevator_set_req_fn)
757                 return e->type->ops.sq.elevator_set_req_fn(q, rq, bio, gfp_mask);
758         return 0;
759 }
760
761 void elv_put_request(struct request_queue *q, struct request *rq)
762 {
763         struct elevator_queue *e = q->elevator;
764
765         if (WARN_ON_ONCE(e->uses_mq))
766                 return;
767
768         if (e->type->ops.sq.elevator_put_req_fn)
769                 e->type->ops.sq.elevator_put_req_fn(rq);
770 }
771
772 int elv_may_queue(struct request_queue *q, unsigned int op)
773 {
774         struct elevator_queue *e = q->elevator;
775
776         if (WARN_ON_ONCE(e->uses_mq))
777                 return 0;
778
779         if (e->type->ops.sq.elevator_may_queue_fn)
780                 return e->type->ops.sq.elevator_may_queue_fn(q, op);
781
782         return ELV_MQUEUE_MAY;
783 }
784
785 void elv_completed_request(struct request_queue *q, struct request *rq)
786 {
787         struct elevator_queue *e = q->elevator;
788
789         if (WARN_ON_ONCE(e->uses_mq))
790                 return;
791
792         /*
793          * request is released from the driver, io must be done
794          */
795         if (blk_account_rq(rq)) {
796                 q->in_flight[rq_is_sync(rq)]--;
797                 if ((rq->rq_flags & RQF_SORTED) &&
798                     e->type->ops.sq.elevator_completed_req_fn)
799                         e->type->ops.sq.elevator_completed_req_fn(q, rq);
800         }
801 }
802
803 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
804
805 static ssize_t
806 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
807 {
808         struct elv_fs_entry *entry = to_elv(attr);
809         struct elevator_queue *e;
810         ssize_t error;
811
812         if (!entry->show)
813                 return -EIO;
814
815         e = container_of(kobj, struct elevator_queue, kobj);
816         mutex_lock(&e->sysfs_lock);
817         error = e->type ? entry->show(e, page) : -ENOENT;
818         mutex_unlock(&e->sysfs_lock);
819         return error;
820 }
821
822 static ssize_t
823 elv_attr_store(struct kobject *kobj, struct attribute *attr,
824                const char *page, size_t length)
825 {
826         struct elv_fs_entry *entry = to_elv(attr);
827         struct elevator_queue *e;
828         ssize_t error;
829
830         if (!entry->store)
831                 return -EIO;
832
833         e = container_of(kobj, struct elevator_queue, kobj);
834         mutex_lock(&e->sysfs_lock);
835         error = e->type ? entry->store(e, page, length) : -ENOENT;
836         mutex_unlock(&e->sysfs_lock);
837         return error;
838 }
839
840 static const struct sysfs_ops elv_sysfs_ops = {
841         .show   = elv_attr_show,
842         .store  = elv_attr_store,
843 };
844
845 static struct kobj_type elv_ktype = {
846         .sysfs_ops      = &elv_sysfs_ops,
847         .release        = elevator_release,
848 };
849
850 int elv_register_queue(struct request_queue *q)
851 {
852         struct elevator_queue *e = q->elevator;
853         int error;
854
855         error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
856         if (!error) {
857                 struct elv_fs_entry *attr = e->type->elevator_attrs;
858                 if (attr) {
859                         while (attr->attr.name) {
860                                 if (sysfs_create_file(&e->kobj, &attr->attr))
861                                         break;
862                                 attr++;
863                         }
864                 }
865                 kobject_uevent(&e->kobj, KOBJ_ADD);
866                 e->registered = 1;
867                 if (!e->uses_mq && e->type->ops.sq.elevator_registered_fn)
868                         e->type->ops.sq.elevator_registered_fn(q);
869         }
870         return error;
871 }
872 EXPORT_SYMBOL(elv_register_queue);
873
874 void elv_unregister_queue(struct request_queue *q)
875 {
876         if (q) {
877                 struct elevator_queue *e = q->elevator;
878
879                 kobject_uevent(&e->kobj, KOBJ_REMOVE);
880                 kobject_del(&e->kobj);
881                 e->registered = 0;
882                 /* Re-enable throttling in case elevator disabled it */
883                 wbt_enable_default(q);
884         }
885 }
886 EXPORT_SYMBOL(elv_unregister_queue);
887
888 int elv_register(struct elevator_type *e)
889 {
890         char *def = "";
891
892         /* create icq_cache if requested */
893         if (e->icq_size) {
894                 if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
895                     WARN_ON(e->icq_align < __alignof__(struct io_cq)))
896                         return -EINVAL;
897
898                 snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
899                          "%s_io_cq", e->elevator_name);
900                 e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
901                                                  e->icq_align, 0, NULL);
902                 if (!e->icq_cache)
903                         return -ENOMEM;
904         }
905
906         /* register, don't allow duplicate names */
907         spin_lock(&elv_list_lock);
908         if (elevator_find(e->elevator_name)) {
909                 spin_unlock(&elv_list_lock);
910                 if (e->icq_cache)
911                         kmem_cache_destroy(e->icq_cache);
912                 return -EBUSY;
913         }
914         list_add_tail(&e->list, &elv_list);
915         spin_unlock(&elv_list_lock);
916
917         /* print pretty message */
918         if (!strcmp(e->elevator_name, chosen_elevator) ||
919                         (!*chosen_elevator &&
920                          !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
921                                 def = " (default)";
922
923         printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
924                                                                 def);
925         return 0;
926 }
927 EXPORT_SYMBOL_GPL(elv_register);
928
929 void elv_unregister(struct elevator_type *e)
930 {
931         /* unregister */
932         spin_lock(&elv_list_lock);
933         list_del_init(&e->list);
934         spin_unlock(&elv_list_lock);
935
936         /*
937          * Destroy icq_cache if it exists.  icq's are RCU managed.  Make
938          * sure all RCU operations are complete before proceeding.
939          */
940         if (e->icq_cache) {
941                 rcu_barrier();
942                 kmem_cache_destroy(e->icq_cache);
943                 e->icq_cache = NULL;
944         }
945 }
946 EXPORT_SYMBOL_GPL(elv_unregister);
947
948 static int elevator_switch_mq(struct request_queue *q,
949                               struct elevator_type *new_e)
950 {
951         int ret;
952
953         blk_mq_freeze_queue(q);
954
955         if (q->elevator) {
956                 if (q->elevator->registered)
957                         elv_unregister_queue(q);
958                 ioc_clear_queue(q);
959                 elevator_exit(q, q->elevator);
960         }
961
962         ret = blk_mq_init_sched(q, new_e);
963         if (ret)
964                 goto out;
965
966         if (new_e) {
967                 ret = elv_register_queue(q);
968                 if (ret) {
969                         elevator_exit(q, q->elevator);
970                         goto out;
971                 }
972         }
973
974         if (new_e)
975                 blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
976         else
977                 blk_add_trace_msg(q, "elv switch: none");
978
979 out:
980         blk_mq_unfreeze_queue(q);
981         return ret;
982 }
983
984 /*
985  * switch to new_e io scheduler. be careful not to introduce deadlocks -
986  * we don't free the old io scheduler, before we have allocated what we
987  * need for the new one. this way we have a chance of going back to the old
988  * one, if the new one fails init for some reason.
989  */
990 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
991 {
992         struct elevator_queue *old = q->elevator;
993         bool old_registered = false;
994         int err;
995
996         if (q->mq_ops)
997                 return elevator_switch_mq(q, new_e);
998
999         /*
1000          * Turn on BYPASS and drain all requests w/ elevator private data.
1001          * Block layer doesn't call into a quiesced elevator - all requests
1002          * are directly put on the dispatch list without elevator data
1003          * using INSERT_BACK.  All requests have SOFTBARRIER set and no
1004          * merge happens either.
1005          */
1006         if (old) {
1007                 old_registered = old->registered;
1008
1009                 blk_queue_bypass_start(q);
1010
1011                 /* unregister and clear all auxiliary data of the old elevator */
1012                 if (old_registered)
1013                         elv_unregister_queue(q);
1014
1015                 ioc_clear_queue(q);
1016         }
1017
1018         /* allocate, init and register new elevator */
1019         err = new_e->ops.sq.elevator_init_fn(q, new_e);
1020         if (err)
1021                 goto fail_init;
1022
1023         err = elv_register_queue(q);
1024         if (err)
1025                 goto fail_register;
1026
1027         /* done, kill the old one and finish */
1028         if (old) {
1029                 elevator_exit(q, old);
1030                 blk_queue_bypass_end(q);
1031         }
1032
1033         blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
1034
1035         return 0;
1036
1037 fail_register:
1038         elevator_exit(q, q->elevator);
1039 fail_init:
1040         /* switch failed, restore and re-register old elevator */
1041         if (old) {
1042                 q->elevator = old;
1043                 elv_register_queue(q);
1044                 blk_queue_bypass_end(q);
1045         }
1046
1047         return err;
1048 }
1049
1050 /*
1051  * Switch this queue to the given IO scheduler.
1052  */
1053 static int __elevator_change(struct request_queue *q, const char *name)
1054 {
1055         char elevator_name[ELV_NAME_MAX];
1056         struct elevator_type *e;
1057
1058         /*
1059          * Special case for mq, turn off scheduling
1060          */
1061         if (q->mq_ops && !strncmp(name, "none", 4))
1062                 return elevator_switch(q, NULL);
1063
1064         strlcpy(elevator_name, name, sizeof(elevator_name));
1065         e = elevator_get(strstrip(elevator_name), true);
1066         if (!e)
1067                 return -EINVAL;
1068
1069         if (q->elevator &&
1070             !strcmp(elevator_name, q->elevator->type->elevator_name)) {
1071                 elevator_put(e);
1072                 return 0;
1073         }
1074
1075         if (!e->uses_mq && q->mq_ops) {
1076                 elevator_put(e);
1077                 return -EINVAL;
1078         }
1079         if (e->uses_mq && !q->mq_ops) {
1080                 elevator_put(e);
1081                 return -EINVAL;
1082         }
1083
1084         return elevator_switch(q, e);
1085 }
1086
1087 static inline bool elv_support_iosched(struct request_queue *q)
1088 {
1089         if (q->mq_ops && q->tag_set && (q->tag_set->flags &
1090                                 BLK_MQ_F_NO_SCHED))
1091                 return false;
1092         return true;
1093 }
1094
1095 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
1096                           size_t count)
1097 {
1098         int ret;
1099
1100         if (!(q->mq_ops || q->request_fn) || !elv_support_iosched(q))
1101                 return count;
1102
1103         ret = __elevator_change(q, name);
1104         if (!ret)
1105                 return count;
1106
1107         return ret;
1108 }
1109
1110 ssize_t elv_iosched_show(struct request_queue *q, char *name)
1111 {
1112         struct elevator_queue *e = q->elevator;
1113         struct elevator_type *elv = NULL;
1114         struct elevator_type *__e;
1115         int len = 0;
1116
1117         if (!blk_queue_stackable(q))
1118                 return sprintf(name, "none\n");
1119
1120         if (!q->elevator)
1121                 len += sprintf(name+len, "[none] ");
1122         else
1123                 elv = e->type;
1124
1125         spin_lock(&elv_list_lock);
1126         list_for_each_entry(__e, &elv_list, list) {
1127                 if (elv && !strcmp(elv->elevator_name, __e->elevator_name)) {
1128                         len += sprintf(name+len, "[%s] ", elv->elevator_name);
1129                         continue;
1130                 }
1131                 if (__e->uses_mq && q->mq_ops && elv_support_iosched(q))
1132                         len += sprintf(name+len, "%s ", __e->elevator_name);
1133                 else if (!__e->uses_mq && !q->mq_ops)
1134                         len += sprintf(name+len, "%s ", __e->elevator_name);
1135         }
1136         spin_unlock(&elv_list_lock);
1137
1138         if (q->mq_ops && q->elevator)
1139                 len += sprintf(name+len, "none");
1140
1141         len += sprintf(len+name, "\n");
1142         return len;
1143 }
1144
1145 struct request *elv_rb_former_request(struct request_queue *q,
1146                                       struct request *rq)
1147 {
1148         struct rb_node *rbprev = rb_prev(&rq->rb_node);
1149
1150         if (rbprev)
1151                 return rb_entry_rq(rbprev);
1152
1153         return NULL;
1154 }
1155 EXPORT_SYMBOL(elv_rb_former_request);
1156
1157 struct request *elv_rb_latter_request(struct request_queue *q,
1158                                       struct request *rq)
1159 {
1160         struct rb_node *rbnext = rb_next(&rq->rb_node);
1161
1162         if (rbnext)
1163                 return rb_entry_rq(rbnext);
1164
1165         return NULL;
1166 }
1167 EXPORT_SYMBOL(elv_rb_latter_request);