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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
53
54#define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq))
55
56
57
58
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
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
94
95
96
97
98
99
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
116
117
118
119
120
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 blk_mq_exit_sched(q, e);
195 mutex_unlock(&e->sysfs_lock);
196
197 kobject_put(&e->kobj);
198}
199
200static inline void __elv_rqhash_del(struct request *rq)
201{
202 hash_del(&rq->hash);
203 rq->rq_flags &= ~RQF_HASHED;
204}
205
206void elv_rqhash_del(struct request_queue *q, struct request *rq)
207{
208 if (ELV_ON_HASH(rq))
209 __elv_rqhash_del(rq);
210}
211EXPORT_SYMBOL_GPL(elv_rqhash_del);
212
213void elv_rqhash_add(struct request_queue *q, struct request *rq)
214{
215 struct elevator_queue *e = q->elevator;
216
217 BUG_ON(ELV_ON_HASH(rq));
218 hash_add(e->hash, &rq->hash, rq_hash_key(rq));
219 rq->rq_flags |= RQF_HASHED;
220}
221EXPORT_SYMBOL_GPL(elv_rqhash_add);
222
223void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
224{
225 __elv_rqhash_del(rq);
226 elv_rqhash_add(q, rq);
227}
228
229struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
230{
231 struct elevator_queue *e = q->elevator;
232 struct hlist_node *next;
233 struct request *rq;
234
235 hash_for_each_possible_safe(e->hash, rq, next, hash, offset) {
236 BUG_ON(!ELV_ON_HASH(rq));
237
238 if (unlikely(!rq_mergeable(rq))) {
239 __elv_rqhash_del(rq);
240 continue;
241 }
242
243 if (rq_hash_key(rq) == offset)
244 return rq;
245 }
246
247 return NULL;
248}
249
250
251
252
253
254void elv_rb_add(struct rb_root *root, struct request *rq)
255{
256 struct rb_node **p = &root->rb_node;
257 struct rb_node *parent = NULL;
258 struct request *__rq;
259
260 while (*p) {
261 parent = *p;
262 __rq = rb_entry(parent, struct request, rb_node);
263
264 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
265 p = &(*p)->rb_left;
266 else if (blk_rq_pos(rq) >= blk_rq_pos(__rq))
267 p = &(*p)->rb_right;
268 }
269
270 rb_link_node(&rq->rb_node, parent, p);
271 rb_insert_color(&rq->rb_node, root);
272}
273EXPORT_SYMBOL(elv_rb_add);
274
275void elv_rb_del(struct rb_root *root, struct request *rq)
276{
277 BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
278 rb_erase(&rq->rb_node, root);
279 RB_CLEAR_NODE(&rq->rb_node);
280}
281EXPORT_SYMBOL(elv_rb_del);
282
283struct request *elv_rb_find(struct rb_root *root, sector_t sector)
284{
285 struct rb_node *n = root->rb_node;
286 struct request *rq;
287
288 while (n) {
289 rq = rb_entry(n, struct request, rb_node);
290
291 if (sector < blk_rq_pos(rq))
292 n = n->rb_left;
293 else if (sector > blk_rq_pos(rq))
294 n = n->rb_right;
295 else
296 return rq;
297 }
298
299 return NULL;
300}
301EXPORT_SYMBOL(elv_rb_find);
302
303enum elv_merge elv_merge(struct request_queue *q, struct request **req,
304 struct bio *bio)
305{
306 struct elevator_queue *e = q->elevator;
307 struct request *__rq;
308
309
310
311
312
313
314
315 if (blk_queue_nomerges(q) || !bio_mergeable(bio))
316 return ELEVATOR_NO_MERGE;
317
318
319
320
321 if (q->last_merge && elv_bio_merge_ok(q->last_merge, bio)) {
322 enum elv_merge ret = blk_try_merge(q->last_merge, bio);
323
324 if (ret != ELEVATOR_NO_MERGE) {
325 *req = q->last_merge;
326 return ret;
327 }
328 }
329
330 if (blk_queue_noxmerges(q))
331 return ELEVATOR_NO_MERGE;
332
333
334
335
336 __rq = elv_rqhash_find(q, bio->bi_iter.bi_sector);
337 if (__rq && elv_bio_merge_ok(__rq, bio)) {
338 *req = __rq;
339
340 if (blk_discard_mergable(__rq))
341 return ELEVATOR_DISCARD_MERGE;
342 return ELEVATOR_BACK_MERGE;
343 }
344
345 if (e->type->ops.request_merge)
346 return e->type->ops.request_merge(q, req, bio);
347
348 return ELEVATOR_NO_MERGE;
349}
350
351
352
353
354
355
356
357
358
359bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq,
360 struct list_head *free)
361{
362 struct request *__rq;
363 bool ret;
364
365 if (blk_queue_nomerges(q))
366 return false;
367
368
369
370
371 if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq)) {
372 list_add(&rq->queuelist, free);
373 return true;
374 }
375
376 if (blk_queue_noxmerges(q))
377 return false;
378
379 ret = false;
380
381
382
383 while (1) {
384 __rq = elv_rqhash_find(q, blk_rq_pos(rq));
385 if (!__rq || !blk_attempt_req_merge(q, __rq, rq))
386 break;
387
388 list_add(&rq->queuelist, free);
389
390 ret = true;
391 rq = __rq;
392 }
393
394 return ret;
395}
396
397void elv_merged_request(struct request_queue *q, struct request *rq,
398 enum elv_merge type)
399{
400 struct elevator_queue *e = q->elevator;
401
402 if (e->type->ops.request_merged)
403 e->type->ops.request_merged(q, rq, type);
404
405 if (type == ELEVATOR_BACK_MERGE)
406 elv_rqhash_reposition(q, rq);
407
408 q->last_merge = rq;
409}
410
411void elv_merge_requests(struct request_queue *q, struct request *rq,
412 struct request *next)
413{
414 struct elevator_queue *e = q->elevator;
415
416 if (e->type->ops.requests_merged)
417 e->type->ops.requests_merged(q, rq, next);
418
419 elv_rqhash_reposition(q, rq);
420 q->last_merge = rq;
421}
422
423struct request *elv_latter_request(struct request_queue *q, struct request *rq)
424{
425 struct elevator_queue *e = q->elevator;
426
427 if (e->type->ops.next_request)
428 return e->type->ops.next_request(q, rq);
429
430 return NULL;
431}
432
433struct request *elv_former_request(struct request_queue *q, struct request *rq)
434{
435 struct elevator_queue *e = q->elevator;
436
437 if (e->type->ops.former_request)
438 return e->type->ops.former_request(q, rq);
439
440 return NULL;
441}
442
443#define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
444
445static ssize_t
446elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
447{
448 struct elv_fs_entry *entry = to_elv(attr);
449 struct elevator_queue *e;
450 ssize_t error;
451
452 if (!entry->show)
453 return -EIO;
454
455 e = container_of(kobj, struct elevator_queue, kobj);
456 mutex_lock(&e->sysfs_lock);
457 error = e->type ? entry->show(e, page) : -ENOENT;
458 mutex_unlock(&e->sysfs_lock);
459 return error;
460}
461
462static ssize_t
463elv_attr_store(struct kobject *kobj, struct attribute *attr,
464 const char *page, size_t length)
465{
466 struct elv_fs_entry *entry = to_elv(attr);
467 struct elevator_queue *e;
468 ssize_t error;
469
470 if (!entry->store)
471 return -EIO;
472
473 e = container_of(kobj, struct elevator_queue, kobj);
474 mutex_lock(&e->sysfs_lock);
475 error = e->type ? entry->store(e, page, length) : -ENOENT;
476 mutex_unlock(&e->sysfs_lock);
477 return error;
478}
479
480static const struct sysfs_ops elv_sysfs_ops = {
481 .show = elv_attr_show,
482 .store = elv_attr_store,
483};
484
485static struct kobj_type elv_ktype = {
486 .sysfs_ops = &elv_sysfs_ops,
487 .release = elevator_release,
488};
489
490int elv_register_queue(struct request_queue *q, bool uevent)
491{
492 struct elevator_queue *e = q->elevator;
493 int error;
494
495 lockdep_assert_held(&q->sysfs_lock);
496
497 error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
498 if (!error) {
499 struct elv_fs_entry *attr = e->type->elevator_attrs;
500 if (attr) {
501 while (attr->attr.name) {
502 if (sysfs_create_file(&e->kobj, &attr->attr))
503 break;
504 attr++;
505 }
506 }
507 if (uevent)
508 kobject_uevent(&e->kobj, KOBJ_ADD);
509
510 e->registered = 1;
511 }
512 return error;
513}
514
515void elv_unregister_queue(struct request_queue *q)
516{
517 lockdep_assert_held(&q->sysfs_lock);
518
519 if (q) {
520 struct elevator_queue *e = q->elevator;
521
522 kobject_uevent(&e->kobj, KOBJ_REMOVE);
523 kobject_del(&e->kobj);
524
525 e->registered = 0;
526
527 wbt_enable_default(q);
528 }
529}
530
531int elv_register(struct elevator_type *e)
532{
533
534 if (WARN_ON_ONCE(!e->ops.insert_requests || !e->ops.dispatch_request))
535 return -EINVAL;
536
537
538 if (e->icq_size) {
539 if (WARN_ON(e->icq_size < sizeof(struct io_cq)) ||
540 WARN_ON(e->icq_align < __alignof__(struct io_cq)))
541 return -EINVAL;
542
543 snprintf(e->icq_cache_name, sizeof(e->icq_cache_name),
544 "%s_io_cq", e->elevator_name);
545 e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size,
546 e->icq_align, 0, NULL);
547 if (!e->icq_cache)
548 return -ENOMEM;
549 }
550
551
552 spin_lock(&elv_list_lock);
553 if (elevator_find(e->elevator_name, 0)) {
554 spin_unlock(&elv_list_lock);
555 kmem_cache_destroy(e->icq_cache);
556 return -EBUSY;
557 }
558 list_add_tail(&e->list, &elv_list);
559 spin_unlock(&elv_list_lock);
560
561 printk(KERN_INFO "io scheduler %s registered\n", e->elevator_name);
562
563 return 0;
564}
565EXPORT_SYMBOL_GPL(elv_register);
566
567void elv_unregister(struct elevator_type *e)
568{
569
570 spin_lock(&elv_list_lock);
571 list_del_init(&e->list);
572 spin_unlock(&elv_list_lock);
573
574
575
576
577
578 if (e->icq_cache) {
579 rcu_barrier();
580 kmem_cache_destroy(e->icq_cache);
581 e->icq_cache = NULL;
582 }
583}
584EXPORT_SYMBOL_GPL(elv_unregister);
585
586int elevator_switch_mq(struct request_queue *q,
587 struct elevator_type *new_e)
588{
589 int ret;
590
591 lockdep_assert_held(&q->sysfs_lock);
592
593 if (q->elevator) {
594 if (q->elevator->registered)
595 elv_unregister_queue(q);
596
597 ioc_clear_queue(q);
598 elevator_exit(q, q->elevator);
599 }
600
601 ret = blk_mq_init_sched(q, new_e);
602 if (ret)
603 goto out;
604
605 if (new_e) {
606 ret = elv_register_queue(q, true);
607 if (ret) {
608 elevator_exit(q, q->elevator);
609 goto out;
610 }
611 }
612
613 if (new_e)
614 blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name);
615 else
616 blk_add_trace_msg(q, "elv switch: none");
617
618out:
619 return ret;
620}
621
622static inline bool elv_support_iosched(struct request_queue *q)
623{
624 if (!queue_is_mq(q) ||
625 (q->tag_set && (q->tag_set->flags & BLK_MQ_F_NO_SCHED)))
626 return false;
627 return true;
628}
629
630
631
632
633
634static struct elevator_type *elevator_get_default(struct request_queue *q)
635{
636 if (q->tag_set && q->tag_set->flags & BLK_MQ_F_NO_SCHED_BY_DEFAULT)
637 return NULL;
638
639 if (q->nr_hw_queues != 1 &&
640 !blk_mq_is_sbitmap_shared(q->tag_set->flags))
641 return NULL;
642
643 return elevator_get(q, "mq-deadline", false);
644}
645
646
647
648
649
650static struct elevator_type *elevator_get_by_features(struct request_queue *q)
651{
652 struct elevator_type *e, *found = NULL;
653
654 spin_lock(&elv_list_lock);
655
656 list_for_each_entry(e, &elv_list, list) {
657 if (elv_support_features(e->elevator_features,
658 q->required_elevator_features)) {
659 found = e;
660 break;
661 }
662 }
663
664 if (found && !try_module_get(found->elevator_owner))
665 found = NULL;
666
667 spin_unlock(&elv_list_lock);
668 return found;
669}
670
671
672
673
674
675
676
677void elevator_init_mq(struct request_queue *q)
678{
679 struct elevator_type *e;
680 int err;
681
682 if (!elv_support_iosched(q))
683 return;
684
685 WARN_ON_ONCE(blk_queue_registered(q));
686
687 if (unlikely(q->elevator))
688 return;
689
690 if (!q->required_elevator_features)
691 e = elevator_get_default(q);
692 else
693 e = elevator_get_by_features(q);
694 if (!e)
695 return;
696
697 blk_mq_freeze_queue(q);
698 blk_mq_quiesce_queue(q);
699
700 err = blk_mq_init_sched(q, e);
701
702 blk_mq_unquiesce_queue(q);
703 blk_mq_unfreeze_queue(q);
704
705 if (err) {
706 pr_warn("\"%s\" elevator initialization failed, "
707 "falling back to \"none\"\n", e->elevator_name);
708 elevator_put(e);
709 }
710}
711
712
713
714
715
716
717
718static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
719{
720 int err;
721
722 lockdep_assert_held(&q->sysfs_lock);
723
724 blk_mq_freeze_queue(q);
725 blk_mq_quiesce_queue(q);
726
727 err = elevator_switch_mq(q, new_e);
728
729 blk_mq_unquiesce_queue(q);
730 blk_mq_unfreeze_queue(q);
731
732 return err;
733}
734
735
736
737
738static int __elevator_change(struct request_queue *q, const char *name)
739{
740 char elevator_name[ELV_NAME_MAX];
741 struct elevator_type *e;
742
743
744 if (!blk_queue_registered(q))
745 return -ENOENT;
746
747
748
749
750 if (!strncmp(name, "none", 4)) {
751 if (!q->elevator)
752 return 0;
753 return elevator_switch(q, NULL);
754 }
755
756 strlcpy(elevator_name, name, sizeof(elevator_name));
757 e = elevator_get(q, strstrip(elevator_name), true);
758 if (!e)
759 return -EINVAL;
760
761 if (q->elevator &&
762 elevator_match(q->elevator->type, elevator_name, 0)) {
763 elevator_put(e);
764 return 0;
765 }
766
767 return elevator_switch(q, e);
768}
769
770ssize_t elv_iosched_store(struct request_queue *q, const char *name,
771 size_t count)
772{
773 int ret;
774
775 if (!elv_support_iosched(q))
776 return count;
777
778 ret = __elevator_change(q, name);
779 if (!ret)
780 return count;
781
782 return ret;
783}
784
785ssize_t elv_iosched_show(struct request_queue *q, char *name)
786{
787 struct elevator_queue *e = q->elevator;
788 struct elevator_type *elv = NULL;
789 struct elevator_type *__e;
790 int len = 0;
791
792 if (!queue_is_mq(q))
793 return sprintf(name, "none\n");
794
795 if (!q->elevator)
796 len += sprintf(name+len, "[none] ");
797 else
798 elv = e->type;
799
800 spin_lock(&elv_list_lock);
801 list_for_each_entry(__e, &elv_list, list) {
802 if (elv && elevator_match(elv, __e->elevator_name, 0)) {
803 len += sprintf(name+len, "[%s] ", elv->elevator_name);
804 continue;
805 }
806 if (elv_support_iosched(q) &&
807 elevator_match(__e, __e->elevator_name,
808 q->required_elevator_features))
809 len += sprintf(name+len, "%s ", __e->elevator_name);
810 }
811 spin_unlock(&elv_list_lock);
812
813 if (q->elevator)
814 len += sprintf(name+len, "none");
815
816 len += sprintf(len+name, "\n");
817 return len;
818}
819
820struct request *elv_rb_former_request(struct request_queue *q,
821 struct request *rq)
822{
823 struct rb_node *rbprev = rb_prev(&rq->rb_node);
824
825 if (rbprev)
826 return rb_entry_rq(rbprev);
827
828 return NULL;
829}
830EXPORT_SYMBOL(elv_rb_former_request);
831
832struct request *elv_rb_latter_request(struct request_queue *q,
833 struct request *rq)
834{
835 struct rb_node *rbnext = rb_next(&rq->rb_node);
836
837 if (rbnext)
838 return rb_entry_rq(rbnext);
839
840 return NULL;
841}
842EXPORT_SYMBOL(elv_rb_latter_request);
843
844static int __init elevator_setup(char *str)
845{
846 pr_warn("Kernel parameter elevator= does not have any effect anymore.\n"
847 "Please use sysfs to set IO scheduler for individual devices.\n");
848 return 1;
849}
850
851__setup("elevator=", elevator_setup);
852