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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 bool elevator_match(const struct elevator_type *e, const char *name) | |
87 | { | |
88 | if (!strcmp(e->elevator_name, name)) | |
89 | return true; | |
90 | if (e->elevator_alias && !strcmp(e->elevator_alias, name)) | |
91 | return true; | |
92 | ||
93 | return false; | |
94 | } | |
95 | ||
96 | /* | |
97 | * Return scheduler with name 'name' and with matching 'mq capability | |
98 | */ | |
99 | static struct elevator_type *elevator_find(const char *name, bool mq) | |
100 | { | |
101 | struct elevator_type *e; | |
102 | ||
103 | list_for_each_entry(e, &elv_list, list) { | |
104 | if (elevator_match(e, name) && (mq == e->uses_mq)) | |
105 | return e; | |
106 | } | |
107 | ||
108 | return NULL; | |
109 | } | |
110 | ||
111 | static void elevator_put(struct elevator_type *e) | |
112 | { | |
113 | module_put(e->elevator_owner); | |
114 | } | |
115 | ||
116 | static struct elevator_type *elevator_get(struct request_queue *q, | |
117 | const char *name, bool try_loading) | |
118 | { | |
119 | struct elevator_type *e; | |
120 | ||
121 | spin_lock(&elv_list_lock); | |
122 | ||
123 | e = elevator_find(name, q->mq_ops != NULL); | |
124 | if (!e && try_loading) { | |
125 | spin_unlock(&elv_list_lock); | |
126 | request_module("%s-iosched", name); | |
127 | spin_lock(&elv_list_lock); | |
128 | e = elevator_find(name, q->mq_ops != NULL); | |
129 | } | |
130 | ||
131 | if (e && !try_module_get(e->elevator_owner)) | |
132 | e = NULL; | |
133 | ||
134 | spin_unlock(&elv_list_lock); | |
135 | return e; | |
136 | } | |
137 | ||
138 | static char chosen_elevator[ELV_NAME_MAX]; | |
139 | ||
140 | static int __init elevator_setup(char *str) | |
141 | { | |
142 | /* | |
143 | * Be backwards-compatible with previous kernels, so users | |
144 | * won't get the wrong elevator. | |
145 | */ | |
146 | strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1); | |
147 | return 1; | |
148 | } | |
149 | ||
150 | __setup("elevator=", elevator_setup); | |
151 | ||
152 | /* called during boot to load the elevator chosen by the elevator param */ | |
153 | void __init load_default_elevator_module(void) | |
154 | { | |
155 | struct elevator_type *e; | |
156 | ||
157 | if (!chosen_elevator[0]) | |
158 | return; | |
159 | ||
160 | /* | |
161 | * Boot parameter is deprecated, we haven't supported that for MQ. | |
162 | * Only look for non-mq schedulers from here. | |
163 | */ | |
164 | spin_lock(&elv_list_lock); | |
165 | e = elevator_find(chosen_elevator, false); | |
166 | spin_unlock(&elv_list_lock); | |
167 | ||
168 | if (!e) | |
169 | request_module("%s-iosched", chosen_elevator); | |
170 | } | |
171 | ||
172 | static struct kobj_type elv_ktype; | |
173 | ||
174 | struct elevator_queue *elevator_alloc(struct request_queue *q, | |
175 | struct elevator_type *e) | |
176 | { | |
177 | struct elevator_queue *eq; | |
178 | ||
179 | eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node); | |
180 | if (unlikely(!eq)) | |
181 | return NULL; | |
182 | ||
183 | eq->type = e; | |
184 | kobject_init(&eq->kobj, &elv_ktype); | |
185 | mutex_init(&eq->sysfs_lock); | |
186 | hash_init(eq->hash); | |
187 | eq->uses_mq = e->uses_mq; | |
188 | ||
189 | return eq; | |
190 | } | |
191 | EXPORT_SYMBOL(elevator_alloc); | |
192 | ||
193 | static void elevator_release(struct kobject *kobj) | |
194 | { | |
195 | struct elevator_queue *e; | |
196 | ||
197 | e = container_of(kobj, struct elevator_queue, kobj); | |
198 | elevator_put(e->type); | |
199 | kfree(e); | |
200 | } | |
201 | ||
202 | int elevator_init(struct request_queue *q, char *name) | |
203 | { | |
204 | struct elevator_type *e = NULL; | |
205 | int err; | |
206 | ||
207 | /* | |
208 | * q->sysfs_lock must be held to provide mutual exclusion between | |
209 | * elevator_switch() and here. | |
210 | */ | |
211 | lockdep_assert_held(&q->sysfs_lock); | |
212 | ||
213 | if (unlikely(q->elevator)) | |
214 | return 0; | |
215 | ||
216 | INIT_LIST_HEAD(&q->queue_head); | |
217 | q->last_merge = NULL; | |
218 | q->end_sector = 0; | |
219 | q->boundary_rq = NULL; | |
220 | ||
221 | if (name) { | |
222 | e = elevator_get(q, name, true); | |
223 | if (!e) | |
224 | return -EINVAL; | |
225 | } | |
226 | ||
227 | /* | |
228 | * Use the default elevator specified by config boot param for | |
229 | * non-mq devices, or by config option. Don't try to load modules | |
230 | * as we could be running off async and request_module() isn't | |
231 | * allowed from async. | |
232 | */ | |
233 | if (!e && !q->mq_ops && *chosen_elevator) { | |
234 | e = elevator_get(q, chosen_elevator, false); | |
235 | if (!e) | |
236 | printk(KERN_ERR "I/O scheduler %s not found\n", | |
237 | chosen_elevator); | |
238 | } | |
239 | ||
240 | if (!e) { | |
241 | /* | |
242 | * For blk-mq devices, we default to using mq-deadline, | |
243 | * if available, for single queue devices. If deadline | |
244 | * isn't available OR we have multiple queues, default | |
245 | * to "none". | |
246 | */ | |
247 | if (q->mq_ops) { | |
248 | if (q->nr_hw_queues == 1) | |
249 | e = elevator_get(q, "mq-deadline", false); | |
250 | if (!e) | |
251 | return 0; | |
252 | } else | |
253 | e = elevator_get(q, CONFIG_DEFAULT_IOSCHED, false); | |
254 | ||
255 | if (!e) { | |
256 | printk(KERN_ERR | |
257 | "Default I/O scheduler not found. " \ | |
258 | "Using noop.\n"); | |
259 | e = elevator_get(q, "noop", false); | |
260 | } | |
261 | } | |
262 | ||
263 | if (e->uses_mq) | |
264 | err = blk_mq_init_sched(q, e); | |
265 | else | |
266 | err = e->ops.sq.elevator_init_fn(q, e); | |
267 | if (err) | |
268 | elevator_put(e); | |
269 | return err; | |
270 | } | |
271 | EXPORT_SYMBOL(elevator_init); | |
272 | ||
273 | void elevator_exit(struct request_queue *q, struct elevator_queue *e) | |
274 | { | |
275 | mutex_lock(&e->sysfs_lock); | |
276 | if (e->uses_mq && e->type->ops.mq.exit_sched) | |
277 | blk_mq_exit_sched(q, e); | |
278 | else if (!e->uses_mq && e->type->ops.sq.elevator_exit_fn) | |
279 | e->type->ops.sq.elevator_exit_fn(e); | |
280 | mutex_unlock(&e->sysfs_lock); | |
281 | ||
282 | kobject_put(&e->kobj); | |
283 | } | |
284 | EXPORT_SYMBOL(elevator_exit); | |
285 | ||
286 | static inline void __elv_rqhash_del(struct request *rq) | |
287 | { | |
288 | hash_del(&rq->hash); | |
289 | rq->rq_flags &= ~RQF_HASHED; | |
290 | } | |
291 | ||
292 | void elv_rqhash_del(struct request_queue *q, struct request *rq) | |
293 | { | |
294 | if (ELV_ON_HASH(rq)) | |
295 | __elv_rqhash_del(rq); | |
296 | } | |
297 | EXPORT_SYMBOL_GPL(elv_rqhash_del); | |
298 | ||
299 | void elv_rqhash_add(struct request_queue *q, struct request *rq) | |
300 | { | |
301 | struct elevator_queue *e = q->elevator; | |
302 | ||
303 | BUG_ON(ELV_ON_HASH(rq)); | |
304 | hash_add(e->hash, &rq->hash, rq_hash_key(rq)); | |
305 | rq->rq_flags |= RQF_HASHED; | |
306 | } | |
307 | EXPORT_SYMBOL_GPL(elv_rqhash_add); | |
308 | ||
309 | void elv_rqhash_reposition(struct request_queue *q, struct request *rq) | |
310 | { | |
311 | __elv_rqhash_del(rq); | |
312 | elv_rqhash_add(q, rq); | |
313 | } | |
314 | ||
315 | struct request *elv_rqhash_find(struct request_queue *q, sector_t offset) | |
316 | { | |
317 | struct elevator_queue *e = q->elevator; | |
318 | struct hlist_node *next; | |
319 | struct request *rq; | |
320 | ||
321 | hash_for_each_possible_safe(e->hash, rq, next, hash, offset) { | |
322 | BUG_ON(!ELV_ON_HASH(rq)); | |
323 | ||
324 | if (unlikely(!rq_mergeable(rq))) { | |
325 | __elv_rqhash_del(rq); | |
326 | continue; | |
327 | } | |
328 | ||
329 | if (rq_hash_key(rq) == offset) | |
330 | return rq; | |
331 | } | |
332 | ||
333 | return NULL; | |
334 | } | |
335 | ||
336 | /* | |
337 | * RB-tree support functions for inserting/lookup/removal of requests | |
338 | * in a sorted RB tree. | |
339 | */ | |
340 | void elv_rb_add(struct rb_root *root, struct request *rq) | |
341 | { | |
342 | struct rb_node **p = &root->rb_node; | |
343 | struct rb_node *parent = NULL; | |
344 | struct request *__rq; | |
345 | ||
346 | while (*p) { | |
347 | parent = *p; | |
348 | __rq = rb_entry(parent, struct request, rb_node); | |
349 | ||
350 | if (blk_rq_pos(rq) < blk_rq_pos(__rq)) | |
351 | p = &(*p)->rb_left; | |
352 | else if (blk_rq_pos(rq) >= blk_rq_pos(__rq)) | |
353 | p = &(*p)->rb_right; | |
354 | } | |
355 | ||
356 | rb_link_node(&rq->rb_node, parent, p); | |
357 | rb_insert_color(&rq->rb_node, root); | |
358 | } | |
359 | EXPORT_SYMBOL(elv_rb_add); | |
360 | ||
361 | void elv_rb_del(struct rb_root *root, struct request *rq) | |
362 | { | |
363 | BUG_ON(RB_EMPTY_NODE(&rq->rb_node)); | |
364 | rb_erase(&rq->rb_node, root); | |
365 | RB_CLEAR_NODE(&rq->rb_node); | |
366 | } | |
367 | EXPORT_SYMBOL(elv_rb_del); | |
368 | ||
369 | struct request *elv_rb_find(struct rb_root *root, sector_t sector) | |
370 | { | |
371 | struct rb_node *n = root->rb_node; | |
372 | struct request *rq; | |
373 | ||
374 | while (n) { | |
375 | rq = rb_entry(n, struct request, rb_node); | |
376 | ||
377 | if (sector < blk_rq_pos(rq)) | |
378 | n = n->rb_left; | |
379 | else if (sector > blk_rq_pos(rq)) | |
380 | n = n->rb_right; | |
381 | else | |
382 | return rq; | |
383 | } | |
384 | ||
385 | return NULL; | |
386 | } | |
387 | EXPORT_SYMBOL(elv_rb_find); | |
388 | ||
389 | /* | |
390 | * Insert rq into dispatch queue of q. Queue lock must be held on | |
391 | * entry. rq is sort instead into the dispatch queue. To be used by | |
392 | * specific elevators. | |
393 | */ | |
394 | void elv_dispatch_sort(struct request_queue *q, struct request *rq) | |
395 | { | |
396 | sector_t boundary; | |
397 | struct list_head *entry; | |
398 | ||
399 | if (q->last_merge == rq) | |
400 | q->last_merge = NULL; | |
401 | ||
402 | elv_rqhash_del(q, rq); | |
403 | ||
404 | q->nr_sorted--; | |
405 | ||
406 | boundary = q->end_sector; | |
407 | list_for_each_prev(entry, &q->queue_head) { | |
408 | struct request *pos = list_entry_rq(entry); | |
409 | ||
410 | if (req_op(rq) != req_op(pos)) | |
411 | break; | |
412 | if (rq_data_dir(rq) != rq_data_dir(pos)) | |
413 | break; | |
414 | if (pos->rq_flags & (RQF_STARTED | RQF_SOFTBARRIER)) | |
415 | break; | |
416 | if (blk_rq_pos(rq) >= boundary) { | |
417 | if (blk_rq_pos(pos) < boundary) | |
418 | continue; | |
419 | } else { | |
420 | if (blk_rq_pos(pos) >= boundary) | |
421 | break; | |
422 | } | |
423 | if (blk_rq_pos(rq) >= blk_rq_pos(pos)) | |
424 | break; | |
425 | } | |
426 | ||
427 | list_add(&rq->queuelist, entry); | |
428 | } | |
429 | EXPORT_SYMBOL(elv_dispatch_sort); | |
430 | ||
431 | /* | |
432 | * Insert rq into dispatch queue of q. Queue lock must be held on | |
433 | * entry. rq is added to the back of the dispatch queue. To be used by | |
434 | * specific elevators. | |
435 | */ | |
436 | void elv_dispatch_add_tail(struct request_queue *q, struct request *rq) | |
437 | { | |
438 | if (q->last_merge == rq) | |
439 | q->last_merge = NULL; | |
440 | ||
441 | elv_rqhash_del(q, rq); | |
442 | ||
443 | q->nr_sorted--; | |
444 | ||
445 | q->end_sector = rq_end_sector(rq); | |
446 | q->boundary_rq = rq; | |
447 | list_add_tail(&rq->queuelist, &q->queue_head); | |
448 | } | |
449 | EXPORT_SYMBOL(elv_dispatch_add_tail); | |
450 | ||
451 | enum elv_merge elv_merge(struct request_queue *q, struct request **req, | |
452 | struct bio *bio) | |
453 | { | |
454 | struct elevator_queue *e = q->elevator; | |
455 | struct request *__rq; | |
456 | ||
457 | /* | |
458 | * Levels of merges: | |
459 | * nomerges: No merges at all attempted | |
460 | * noxmerges: Only simple one-hit cache try | |
461 | * merges: All merge tries attempted | |
462 | */ | |
463 | if (blk_queue_nomerges(q) || !bio_mergeable(bio)) | |
464 | return ELEVATOR_NO_MERGE; | |
465 | ||
466 | /* | |
467 | * First try one-hit cache. | |
468 | */ | |
469 | if (q->last_merge && elv_bio_merge_ok(q->last_merge, bio)) { | |
470 | enum elv_merge ret = blk_try_merge(q->last_merge, bio); | |
471 | ||
472 | if (ret != ELEVATOR_NO_MERGE) { | |
473 | *req = q->last_merge; | |
474 | return ret; | |
475 | } | |
476 | } | |
477 | ||
478 | if (blk_queue_noxmerges(q)) | |
479 | return ELEVATOR_NO_MERGE; | |
480 | ||
481 | /* | |
482 | * See if our hash lookup can find a potential backmerge. | |
483 | */ | |
484 | __rq = elv_rqhash_find(q, bio->bi_iter.bi_sector); | |
485 | if (__rq && elv_bio_merge_ok(__rq, bio)) { | |
486 | *req = __rq; | |
487 | return ELEVATOR_BACK_MERGE; | |
488 | } | |
489 | ||
490 | if (e->uses_mq && e->type->ops.mq.request_merge) | |
491 | return e->type->ops.mq.request_merge(q, req, bio); | |
492 | else if (!e->uses_mq && e->type->ops.sq.elevator_merge_fn) | |
493 | return e->type->ops.sq.elevator_merge_fn(q, req, bio); | |
494 | ||
495 | return ELEVATOR_NO_MERGE; | |
496 | } | |
497 | ||
498 | /* | |
499 | * Attempt to do an insertion back merge. Only check for the case where | |
500 | * we can append 'rq' to an existing request, so we can throw 'rq' away | |
501 | * afterwards. | |
502 | * | |
503 | * Returns true if we merged, false otherwise | |
504 | */ | |
505 | bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq) | |
506 | { | |
507 | struct request *__rq; | |
508 | bool ret; | |
509 | ||
510 | if (blk_queue_nomerges(q)) | |
511 | return false; | |
512 | ||
513 | /* | |
514 | * First try one-hit cache. | |
515 | */ | |
516 | if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq)) | |
517 | return true; | |
518 | ||
519 | if (blk_queue_noxmerges(q)) | |
520 | return false; | |
521 | ||
522 | ret = false; | |
523 | /* | |
524 | * See if our hash lookup can find a potential backmerge. | |
525 | */ | |
526 | while (1) { | |
527 | __rq = elv_rqhash_find(q, blk_rq_pos(rq)); | |
528 | if (!__rq || !blk_attempt_req_merge(q, __rq, rq)) | |
529 | break; | |
530 | ||
531 | /* The merged request could be merged with others, try again */ | |
532 | ret = true; | |
533 | rq = __rq; | |
534 | } | |
535 | ||
536 | return ret; | |
537 | } | |
538 | ||
539 | void elv_merged_request(struct request_queue *q, struct request *rq, | |
540 | enum elv_merge type) | |
541 | { | |
542 | struct elevator_queue *e = q->elevator; | |
543 | ||
544 | if (e->uses_mq && e->type->ops.mq.request_merged) | |
545 | e->type->ops.mq.request_merged(q, rq, type); | |
546 | else if (!e->uses_mq && e->type->ops.sq.elevator_merged_fn) | |
547 | e->type->ops.sq.elevator_merged_fn(q, rq, type); | |
548 | ||
549 | if (type == ELEVATOR_BACK_MERGE) | |
550 | elv_rqhash_reposition(q, rq); | |
551 | ||
552 | q->last_merge = rq; | |
553 | } | |
554 | ||
555 | void elv_merge_requests(struct request_queue *q, struct request *rq, | |
556 | struct request *next) | |
557 | { | |
558 | struct elevator_queue *e = q->elevator; | |
559 | bool next_sorted = false; | |
560 | ||
561 | if (e->uses_mq && e->type->ops.mq.requests_merged) | |
562 | e->type->ops.mq.requests_merged(q, rq, next); | |
563 | else if (e->type->ops.sq.elevator_merge_req_fn) { | |
564 | next_sorted = (__force bool)(next->rq_flags & RQF_SORTED); | |
565 | if (next_sorted) | |
566 | e->type->ops.sq.elevator_merge_req_fn(q, rq, next); | |
567 | } | |
568 | ||
569 | elv_rqhash_reposition(q, rq); | |
570 | ||
571 | if (next_sorted) { | |
572 | elv_rqhash_del(q, next); | |
573 | q->nr_sorted--; | |
574 | } | |
575 | ||
576 | q->last_merge = rq; | |
577 | } | |
578 | ||
579 | void elv_bio_merged(struct request_queue *q, struct request *rq, | |
580 | struct bio *bio) | |
581 | { | |
582 | struct elevator_queue *e = q->elevator; | |
583 | ||
584 | if (WARN_ON_ONCE(e->uses_mq)) | |
585 | return; | |
586 | ||
587 | if (e->type->ops.sq.elevator_bio_merged_fn) | |
588 | e->type->ops.sq.elevator_bio_merged_fn(q, rq, bio); | |
589 | } | |
590 | ||
591 | #ifdef CONFIG_PM | |
592 | static void blk_pm_requeue_request(struct request *rq) | |
593 | { | |
594 | if (rq->q->dev && !(rq->rq_flags & RQF_PM)) | |
595 | rq->q->nr_pending--; | |
596 | } | |
597 | ||
598 | static void blk_pm_add_request(struct request_queue *q, struct request *rq) | |
599 | { | |
600 | if (q->dev && !(rq->rq_flags & RQF_PM) && q->nr_pending++ == 0 && | |
601 | (q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING)) | |
602 | pm_request_resume(q->dev); | |
603 | } | |
604 | #else | |
605 | static inline void blk_pm_requeue_request(struct request *rq) {} | |
606 | static inline void blk_pm_add_request(struct request_queue *q, | |
607 | struct request *rq) | |
608 | { | |
609 | } | |
610 | #endif | |
611 | ||
612 | void elv_requeue_request(struct request_queue *q, struct request *rq) | |
613 | { | |
614 | /* | |
615 | * it already went through dequeue, we need to decrement the | |
616 | * in_flight count again | |
617 | */ | |
618 | if (blk_account_rq(rq)) { | |
619 | q->in_flight[rq_is_sync(rq)]--; | |
620 | if (rq->rq_flags & RQF_SORTED) | |
621 | elv_deactivate_rq(q, rq); | |
622 | } | |
623 | ||
624 | rq->rq_flags &= ~RQF_STARTED; | |
625 | ||
626 | blk_pm_requeue_request(rq); | |
627 | ||
628 | __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE); | |
629 | } | |
630 | ||
631 | void elv_drain_elevator(struct request_queue *q) | |
632 | { | |
633 | struct elevator_queue *e = q->elevator; | |
634 | static int printed; | |
635 | ||
636 | if (WARN_ON_ONCE(e->uses_mq)) | |
637 | return; | |
638 | ||
639 | lockdep_assert_held(q->queue_lock); | |
640 | ||
641 | while (e->type->ops.sq.elevator_dispatch_fn(q, 1)) | |
642 | ; | |
643 | if (q->nr_sorted && !blk_queue_is_zoned(q) && printed++ < 10 ) { | |
644 | printk(KERN_ERR "%s: forced dispatching is broken " | |
645 | "(nr_sorted=%u), please report this\n", | |
646 | q->elevator->type->elevator_name, q->nr_sorted); | |
647 | } | |
648 | } | |
649 | ||
650 | void __elv_add_request(struct request_queue *q, struct request *rq, int where) | |
651 | { | |
652 | trace_block_rq_insert(q, rq); | |
653 | ||
654 | blk_pm_add_request(q, rq); | |
655 | ||
656 | rq->q = q; | |
657 | ||
658 | if (rq->rq_flags & RQF_SOFTBARRIER) { | |
659 | /* barriers are scheduling boundary, update end_sector */ | |
660 | if (!blk_rq_is_passthrough(rq)) { | |
661 | q->end_sector = rq_end_sector(rq); | |
662 | q->boundary_rq = rq; | |
663 | } | |
664 | } else if (!(rq->rq_flags & RQF_ELVPRIV) && | |
665 | (where == ELEVATOR_INSERT_SORT || | |
666 | where == ELEVATOR_INSERT_SORT_MERGE)) | |
667 | where = ELEVATOR_INSERT_BACK; | |
668 | ||
669 | switch (where) { | |
670 | case ELEVATOR_INSERT_REQUEUE: | |
671 | case ELEVATOR_INSERT_FRONT: | |
672 | rq->rq_flags |= RQF_SOFTBARRIER; | |
673 | list_add(&rq->queuelist, &q->queue_head); | |
674 | break; | |
675 | ||
676 | case ELEVATOR_INSERT_BACK: | |
677 | rq->rq_flags |= RQF_SOFTBARRIER; | |
678 | elv_drain_elevator(q); | |
679 | list_add_tail(&rq->queuelist, &q->queue_head); | |
680 | /* | |
681 | * We kick the queue here for the following reasons. | |
682 | * - The elevator might have returned NULL previously | |
683 | * to delay requests and returned them now. As the | |
684 | * queue wasn't empty before this request, ll_rw_blk | |
685 | * won't run the queue on return, resulting in hang. | |
686 | * - Usually, back inserted requests won't be merged | |
687 | * with anything. There's no point in delaying queue | |
688 | * processing. | |
689 | */ | |
690 | __blk_run_queue(q); | |
691 | break; | |
692 | ||
693 | case ELEVATOR_INSERT_SORT_MERGE: | |
694 | /* | |
695 | * If we succeed in merging this request with one in the | |
696 | * queue already, we are done - rq has now been freed, | |
697 | * so no need to do anything further. | |
698 | */ | |
699 | if (elv_attempt_insert_merge(q, rq)) | |
700 | break; | |
701 | /* fall through */ | |
702 | case ELEVATOR_INSERT_SORT: | |
703 | BUG_ON(blk_rq_is_passthrough(rq)); | |
704 | rq->rq_flags |= RQF_SORTED; | |
705 | q->nr_sorted++; | |
706 | if (rq_mergeable(rq)) { | |
707 | elv_rqhash_add(q, rq); | |
708 | if (!q->last_merge) | |
709 | q->last_merge = rq; | |
710 | } | |
711 | ||
712 | /* | |
713 | * Some ioscheds (cfq) run q->request_fn directly, so | |
714 | * rq cannot be accessed after calling | |
715 | * elevator_add_req_fn. | |
716 | */ | |
717 | q->elevator->type->ops.sq.elevator_add_req_fn(q, rq); | |
718 | break; | |
719 | ||
720 | case ELEVATOR_INSERT_FLUSH: | |
721 | rq->rq_flags |= RQF_SOFTBARRIER; | |
722 | blk_insert_flush(rq); | |
723 | break; | |
724 | default: | |
725 | printk(KERN_ERR "%s: bad insertion point %d\n", | |
726 | __func__, where); | |
727 | BUG(); | |
728 | } | |
729 | } | |
730 | EXPORT_SYMBOL(__elv_add_request); | |
731 | ||
732 | void elv_add_request(struct request_queue *q, struct request *rq, int where) | |
733 | { | |
734 | unsigned long flags; | |
735 | ||
736 | spin_lock_irqsave(q->queue_lock, flags); | |
737 | __elv_add_request(q, rq, where); | |
738 | spin_unlock_irqrestore(q->queue_lock, flags); | |
739 | } | |
740 | EXPORT_SYMBOL(elv_add_request); | |
741 | ||
742 | struct request *elv_latter_request(struct request_queue *q, struct request *rq) | |
743 | { | |
744 | struct elevator_queue *e = q->elevator; | |
745 | ||
746 | if (e->uses_mq && e->type->ops.mq.next_request) | |
747 | return e->type->ops.mq.next_request(q, rq); | |
748 | else if (!e->uses_mq && e->type->ops.sq.elevator_latter_req_fn) | |
749 | return e->type->ops.sq.elevator_latter_req_fn(q, rq); | |
750 | ||
751 | return NULL; | |
752 | } | |
753 | ||
754 | struct request *elv_former_request(struct request_queue *q, struct request *rq) | |
755 | { | |
756 | struct elevator_queue *e = q->elevator; | |
757 | ||
758 | if (e->uses_mq && e->type->ops.mq.former_request) | |
759 | return e->type->ops.mq.former_request(q, rq); | |
760 | if (!e->uses_mq && e->type->ops.sq.elevator_former_req_fn) | |
761 | return e->type->ops.sq.elevator_former_req_fn(q, rq); | |
762 | return NULL; | |
763 | } | |
764 | ||
765 | int elv_set_request(struct request_queue *q, struct request *rq, | |
766 | struct bio *bio, gfp_t gfp_mask) | |
767 | { | |
768 | struct elevator_queue *e = q->elevator; | |
769 | ||
770 | if (WARN_ON_ONCE(e->uses_mq)) | |
771 | return 0; | |
772 | ||
773 | if (e->type->ops.sq.elevator_set_req_fn) | |
774 | return e->type->ops.sq.elevator_set_req_fn(q, rq, bio, gfp_mask); | |
775 | return 0; | |
776 | } | |
777 | ||
778 | void elv_put_request(struct request_queue *q, struct request *rq) | |
779 | { | |
780 | struct elevator_queue *e = q->elevator; | |
781 | ||
782 | if (WARN_ON_ONCE(e->uses_mq)) | |
783 | return; | |
784 | ||
785 | if (e->type->ops.sq.elevator_put_req_fn) | |
786 | e->type->ops.sq.elevator_put_req_fn(rq); | |
787 | } | |
788 | ||
789 | int elv_may_queue(struct request_queue *q, unsigned int op) | |
790 | { | |
791 | struct elevator_queue *e = q->elevator; | |
792 | ||
793 | if (WARN_ON_ONCE(e->uses_mq)) | |
794 | return 0; | |
795 | ||
796 | if (e->type->ops.sq.elevator_may_queue_fn) | |
797 | return e->type->ops.sq.elevator_may_queue_fn(q, op); | |
798 | ||
799 | return ELV_MQUEUE_MAY; | |
800 | } | |
801 | ||
802 | void elv_completed_request(struct request_queue *q, struct request *rq) | |
803 | { | |
804 | struct elevator_queue *e = q->elevator; | |
805 | ||
806 | if (WARN_ON_ONCE(e->uses_mq)) | |
807 | return; | |
808 | ||
809 | /* | |
810 | * request is released from the driver, io must be done | |
811 | */ | |
812 | if (blk_account_rq(rq)) { | |
813 | q->in_flight[rq_is_sync(rq)]--; | |
814 | if ((rq->rq_flags & RQF_SORTED) && | |
815 | e->type->ops.sq.elevator_completed_req_fn) | |
816 | e->type->ops.sq.elevator_completed_req_fn(q, rq); | |
817 | } | |
818 | } | |
819 | ||
820 | #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr) | |
821 | ||
822 | static ssize_t | |
823 | elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page) | |
824 | { | |
825 | struct elv_fs_entry *entry = to_elv(attr); | |
826 | struct elevator_queue *e; | |
827 | ssize_t error; | |
828 | ||
829 | if (!entry->show) | |
830 | return -EIO; | |
831 | ||
832 | e = container_of(kobj, struct elevator_queue, kobj); | |
833 | mutex_lock(&e->sysfs_lock); | |
834 | error = e->type ? entry->show(e, page) : -ENOENT; | |
835 | mutex_unlock(&e->sysfs_lock); | |
836 | return error; | |
837 | } | |
838 | ||
839 | static ssize_t | |
840 | elv_attr_store(struct kobject *kobj, struct attribute *attr, | |
841 | const char *page, size_t length) | |
842 | { | |
843 | struct elv_fs_entry *entry = to_elv(attr); | |
844 | struct elevator_queue *e; | |
845 | ssize_t error; | |
846 | ||
847 | if (!entry->store) | |
848 | return -EIO; | |
849 | ||
850 | e = container_of(kobj, struct elevator_queue, kobj); | |
851 | mutex_lock(&e->sysfs_lock); | |
852 | error = e->type ? entry->store(e, page, length) : -ENOENT; | |
853 | mutex_unlock(&e->sysfs_lock); | |
854 | return error; | |
855 | } | |
856 | ||
857 | static const struct sysfs_ops elv_sysfs_ops = { | |
858 | .show = elv_attr_show, | |
859 | .store = elv_attr_store, | |
860 | }; | |
861 | ||
862 | static struct kobj_type elv_ktype = { | |
863 | .sysfs_ops = &elv_sysfs_ops, | |
864 | .release = elevator_release, | |
865 | }; | |
866 | ||
867 | int elv_register_queue(struct request_queue *q) | |
868 | { | |
869 | struct elevator_queue *e = q->elevator; | |
870 | int error; | |
871 | ||
872 | error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched"); | |
873 | if (!error) { | |
874 | struct elv_fs_entry *attr = e->type->elevator_attrs; | |
875 | if (attr) { | |
876 | while (attr->attr.name) { | |
877 | if (sysfs_create_file(&e->kobj, &attr->attr)) | |
878 | break; | |
879 | attr++; | |
880 | } | |
881 | } | |
882 | kobject_uevent(&e->kobj, KOBJ_ADD); | |
883 | e->registered = 1; | |
884 | if (!e->uses_mq && e->type->ops.sq.elevator_registered_fn) | |
885 | e->type->ops.sq.elevator_registered_fn(q); | |
886 | } | |
887 | return error; | |
888 | } | |
889 | EXPORT_SYMBOL(elv_register_queue); | |
890 | ||
891 | void elv_unregister_queue(struct request_queue *q) | |
892 | { | |
893 | if (q) { | |
894 | struct elevator_queue *e = q->elevator; | |
895 | ||
896 | kobject_uevent(&e->kobj, KOBJ_REMOVE); | |
897 | kobject_del(&e->kobj); | |
898 | e->registered = 0; | |
899 | /* Re-enable throttling in case elevator disabled it */ | |
900 | wbt_enable_default(q); | |
901 | } | |
902 | } | |
903 | EXPORT_SYMBOL(elv_unregister_queue); | |
904 | ||
905 | int elv_register(struct elevator_type *e) | |
906 | { | |
907 | char *def = ""; | |
908 | ||
909 | /* create icq_cache if requested */ | |
910 | if (e->icq_size) { | |
911 | if (WARN_ON(e->icq_size < sizeof(struct io_cq)) || | |
912 | WARN_ON(e->icq_align < __alignof__(struct io_cq))) | |
913 | return -EINVAL; | |
914 | ||
915 | snprintf(e->icq_cache_name, sizeof(e->icq_cache_name), | |
916 | "%s_io_cq", e->elevator_name); | |
917 | e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size, | |
918 | e->icq_align, 0, NULL); | |
919 | if (!e->icq_cache) | |
920 | return -ENOMEM; | |
921 | } | |
922 | ||
923 | /* register, don't allow duplicate names */ | |
924 | spin_lock(&elv_list_lock); | |
925 | if (elevator_find(e->elevator_name, e->uses_mq)) { | |
926 | spin_unlock(&elv_list_lock); | |
927 | if (e->icq_cache) | |
928 | kmem_cache_destroy(e->icq_cache); | |
929 | return -EBUSY; | |
930 | } | |
931 | list_add_tail(&e->list, &elv_list); | |
932 | spin_unlock(&elv_list_lock); | |
933 | ||
934 | /* print pretty message */ | |
935 | if (elevator_match(e, chosen_elevator) || | |
936 | (!*chosen_elevator && | |
937 | elevator_match(e, CONFIG_DEFAULT_IOSCHED))) | |
938 | def = " (default)"; | |
939 | ||
940 | printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name, | |
941 | def); | |
942 | return 0; | |
943 | } | |
944 | EXPORT_SYMBOL_GPL(elv_register); | |
945 | ||
946 | void elv_unregister(struct elevator_type *e) | |
947 | { | |
948 | /* unregister */ | |
949 | spin_lock(&elv_list_lock); | |
950 | list_del_init(&e->list); | |
951 | spin_unlock(&elv_list_lock); | |
952 | ||
953 | /* | |
954 | * Destroy icq_cache if it exists. icq's are RCU managed. Make | |
955 | * sure all RCU operations are complete before proceeding. | |
956 | */ | |
957 | if (e->icq_cache) { | |
958 | rcu_barrier(); | |
959 | kmem_cache_destroy(e->icq_cache); | |
960 | e->icq_cache = NULL; | |
961 | } | |
962 | } | |
963 | EXPORT_SYMBOL_GPL(elv_unregister); | |
964 | ||
965 | static int elevator_switch_mq(struct request_queue *q, | |
966 | struct elevator_type *new_e) | |
967 | { | |
968 | int ret; | |
969 | ||
970 | blk_mq_freeze_queue(q); | |
971 | blk_mq_quiesce_queue(q); | |
972 | ||
973 | if (q->elevator) { | |
974 | if (q->elevator->registered) | |
975 | elv_unregister_queue(q); | |
976 | ioc_clear_queue(q); | |
977 | elevator_exit(q, q->elevator); | |
978 | } | |
979 | ||
980 | ret = blk_mq_init_sched(q, new_e); | |
981 | if (ret) | |
982 | goto out; | |
983 | ||
984 | if (new_e) { | |
985 | ret = elv_register_queue(q); | |
986 | if (ret) { | |
987 | elevator_exit(q, q->elevator); | |
988 | goto out; | |
989 | } | |
990 | } | |
991 | ||
992 | if (new_e) | |
993 | blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name); | |
994 | else | |
995 | blk_add_trace_msg(q, "elv switch: none"); | |
996 | ||
997 | out: | |
998 | blk_mq_unquiesce_queue(q); | |
999 | blk_mq_unfreeze_queue(q); | |
1000 | return ret; | |
1001 | } | |
1002 | ||
1003 | /* | |
1004 | * switch to new_e io scheduler. be careful not to introduce deadlocks - | |
1005 | * we don't free the old io scheduler, before we have allocated what we | |
1006 | * need for the new one. this way we have a chance of going back to the old | |
1007 | * one, if the new one fails init for some reason. | |
1008 | */ | |
1009 | static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) | |
1010 | { | |
1011 | struct elevator_queue *old = q->elevator; | |
1012 | bool old_registered = false; | |
1013 | int err; | |
1014 | ||
1015 | if (q->mq_ops) | |
1016 | return elevator_switch_mq(q, new_e); | |
1017 | ||
1018 | /* | |
1019 | * Turn on BYPASS and drain all requests w/ elevator private data. | |
1020 | * Block layer doesn't call into a quiesced elevator - all requests | |
1021 | * are directly put on the dispatch list without elevator data | |
1022 | * using INSERT_BACK. All requests have SOFTBARRIER set and no | |
1023 | * merge happens either. | |
1024 | */ | |
1025 | if (old) { | |
1026 | old_registered = old->registered; | |
1027 | ||
1028 | blk_queue_bypass_start(q); | |
1029 | ||
1030 | /* unregister and clear all auxiliary data of the old elevator */ | |
1031 | if (old_registered) | |
1032 | elv_unregister_queue(q); | |
1033 | ||
1034 | ioc_clear_queue(q); | |
1035 | } | |
1036 | ||
1037 | /* allocate, init and register new elevator */ | |
1038 | err = new_e->ops.sq.elevator_init_fn(q, new_e); | |
1039 | if (err) | |
1040 | goto fail_init; | |
1041 | ||
1042 | err = elv_register_queue(q); | |
1043 | if (err) | |
1044 | goto fail_register; | |
1045 | ||
1046 | /* done, kill the old one and finish */ | |
1047 | if (old) { | |
1048 | elevator_exit(q, old); | |
1049 | blk_queue_bypass_end(q); | |
1050 | } | |
1051 | ||
1052 | blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name); | |
1053 | ||
1054 | return 0; | |
1055 | ||
1056 | fail_register: | |
1057 | elevator_exit(q, q->elevator); | |
1058 | fail_init: | |
1059 | /* switch failed, restore and re-register old elevator */ | |
1060 | if (old) { | |
1061 | q->elevator = old; | |
1062 | elv_register_queue(q); | |
1063 | blk_queue_bypass_end(q); | |
1064 | } | |
1065 | ||
1066 | return err; | |
1067 | } | |
1068 | ||
1069 | /* | |
1070 | * Switch this queue to the given IO scheduler. | |
1071 | */ | |
1072 | static int __elevator_change(struct request_queue *q, const char *name) | |
1073 | { | |
1074 | char elevator_name[ELV_NAME_MAX]; | |
1075 | struct elevator_type *e; | |
1076 | ||
1077 | /* Make sure queue is not in the middle of being removed */ | |
1078 | if (!test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags)) | |
1079 | return -ENOENT; | |
1080 | ||
1081 | /* | |
1082 | * Special case for mq, turn off scheduling | |
1083 | */ | |
1084 | if (q->mq_ops && !strncmp(name, "none", 4)) { | |
1085 | if (!q->elevator) | |
1086 | return 0; | |
1087 | return elevator_switch(q, NULL); | |
1088 | } | |
1089 | ||
1090 | strlcpy(elevator_name, name, sizeof(elevator_name)); | |
1091 | e = elevator_get(q, strstrip(elevator_name), true); | |
1092 | if (!e) | |
1093 | return -EINVAL; | |
1094 | ||
1095 | if (q->elevator && elevator_match(q->elevator->type, elevator_name)) { | |
1096 | elevator_put(e); | |
1097 | return 0; | |
1098 | } | |
1099 | ||
1100 | return elevator_switch(q, e); | |
1101 | } | |
1102 | ||
1103 | static inline bool elv_support_iosched(struct request_queue *q) | |
1104 | { | |
1105 | if (q->mq_ops && q->tag_set && (q->tag_set->flags & | |
1106 | BLK_MQ_F_NO_SCHED)) | |
1107 | return false; | |
1108 | return true; | |
1109 | } | |
1110 | ||
1111 | ssize_t elv_iosched_store(struct request_queue *q, const char *name, | |
1112 | size_t count) | |
1113 | { | |
1114 | int ret; | |
1115 | ||
1116 | if (!(q->mq_ops || q->request_fn) || !elv_support_iosched(q)) | |
1117 | return count; | |
1118 | ||
1119 | ret = __elevator_change(q, name); | |
1120 | if (!ret) | |
1121 | return count; | |
1122 | ||
1123 | return ret; | |
1124 | } | |
1125 | ||
1126 | ssize_t elv_iosched_show(struct request_queue *q, char *name) | |
1127 | { | |
1128 | struct elevator_queue *e = q->elevator; | |
1129 | struct elevator_type *elv = NULL; | |
1130 | struct elevator_type *__e; | |
1131 | bool uses_mq = q->mq_ops != NULL; | |
1132 | int len = 0; | |
1133 | ||
1134 | if (!queue_is_rq_based(q)) | |
1135 | return sprintf(name, "none\n"); | |
1136 | ||
1137 | if (!q->elevator) | |
1138 | len += sprintf(name+len, "[none] "); | |
1139 | else | |
1140 | elv = e->type; | |
1141 | ||
1142 | spin_lock(&elv_list_lock); | |
1143 | list_for_each_entry(__e, &elv_list, list) { | |
1144 | if (elv && elevator_match(elv, __e->elevator_name) && | |
1145 | (__e->uses_mq == uses_mq)) { | |
1146 | len += sprintf(name+len, "[%s] ", elv->elevator_name); | |
1147 | continue; | |
1148 | } | |
1149 | if (__e->uses_mq && q->mq_ops && elv_support_iosched(q)) | |
1150 | len += sprintf(name+len, "%s ", __e->elevator_name); | |
1151 | else if (!__e->uses_mq && !q->mq_ops) | |
1152 | len += sprintf(name+len, "%s ", __e->elevator_name); | |
1153 | } | |
1154 | spin_unlock(&elv_list_lock); | |
1155 | ||
1156 | if (q->mq_ops && q->elevator) | |
1157 | len += sprintf(name+len, "none"); | |
1158 | ||
1159 | len += sprintf(len+name, "\n"); | |
1160 | return len; | |
1161 | } | |
1162 | ||
1163 | struct request *elv_rb_former_request(struct request_queue *q, | |
1164 | struct request *rq) | |
1165 | { | |
1166 | struct rb_node *rbprev = rb_prev(&rq->rb_node); | |
1167 | ||
1168 | if (rbprev) | |
1169 | return rb_entry_rq(rbprev); | |
1170 | ||
1171 | return NULL; | |
1172 | } | |
1173 | EXPORT_SYMBOL(elv_rb_former_request); | |
1174 | ||
1175 | struct request *elv_rb_latter_request(struct request_queue *q, | |
1176 | struct request *rq) | |
1177 | { | |
1178 | struct rb_node *rbnext = rb_next(&rq->rb_node); | |
1179 | ||
1180 | if (rbnext) | |
1181 | return rb_entry_rq(rbnext); | |
1182 | ||
1183 | return NULL; | |
1184 | } | |
1185 | EXPORT_SYMBOL(elv_rb_latter_request); |