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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 | ||
44 | static DEFINE_SPINLOCK(elv_list_lock); | |
45 | static LIST_HEAD(elv_list); | |
46 | ||
47 | /* | |
48 | * Merge hash stuff. | |
49 | */ | |
50 | #define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq)) | |
51 | ||
52 | /* | |
53 | * Query io scheduler to see if the current process issuing bio may be | |
54 | * merged with rq. | |
55 | */ | |
56 | static int elv_iosched_allow_merge(struct request *rq, struct bio *bio) | |
57 | { | |
58 | struct request_queue *q = rq->q; | |
59 | struct elevator_queue *e = q->elevator; | |
60 | ||
61 | if (e->type->ops.elevator_allow_merge_fn) | |
62 | return e->type->ops.elevator_allow_merge_fn(q, rq, bio); | |
63 | ||
64 | return 1; | |
65 | } | |
66 | ||
67 | /* | |
68 | * can we safely merge with this request? | |
69 | */ | |
70 | bool elv_rq_merge_ok(struct request *rq, struct bio *bio) | |
71 | { | |
72 | if (!blk_rq_merge_ok(rq, bio)) | |
73 | return 0; | |
74 | ||
75 | if (!elv_iosched_allow_merge(rq, bio)) | |
76 | return 0; | |
77 | ||
78 | return 1; | |
79 | } | |
80 | EXPORT_SYMBOL(elv_rq_merge_ok); | |
81 | ||
82 | static struct elevator_type *elevator_find(const char *name) | |
83 | { | |
84 | struct elevator_type *e; | |
85 | ||
86 | list_for_each_entry(e, &elv_list, list) { | |
87 | if (!strcmp(e->elevator_name, name)) | |
88 | return e; | |
89 | } | |
90 | ||
91 | return NULL; | |
92 | } | |
93 | ||
94 | static void elevator_put(struct elevator_type *e) | |
95 | { | |
96 | module_put(e->elevator_owner); | |
97 | } | |
98 | ||
99 | static struct elevator_type *elevator_get(const char *name, bool try_loading) | |
100 | { | |
101 | struct elevator_type *e; | |
102 | ||
103 | spin_lock(&elv_list_lock); | |
104 | ||
105 | e = elevator_find(name); | |
106 | if (!e && try_loading) { | |
107 | spin_unlock(&elv_list_lock); | |
108 | request_module("%s-iosched", name); | |
109 | spin_lock(&elv_list_lock); | |
110 | e = elevator_find(name); | |
111 | } | |
112 | ||
113 | if (e && !try_module_get(e->elevator_owner)) | |
114 | e = NULL; | |
115 | ||
116 | spin_unlock(&elv_list_lock); | |
117 | ||
118 | return e; | |
119 | } | |
120 | ||
121 | static char chosen_elevator[ELV_NAME_MAX]; | |
122 | ||
123 | static int __init elevator_setup(char *str) | |
124 | { | |
125 | /* | |
126 | * Be backwards-compatible with previous kernels, so users | |
127 | * won't get the wrong elevator. | |
128 | */ | |
129 | strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1); | |
130 | return 1; | |
131 | } | |
132 | ||
133 | __setup("elevator=", elevator_setup); | |
134 | ||
135 | /* called during boot to load the elevator chosen by the elevator param */ | |
136 | void __init load_default_elevator_module(void) | |
137 | { | |
138 | struct elevator_type *e; | |
139 | ||
140 | if (!chosen_elevator[0]) | |
141 | return; | |
142 | ||
143 | spin_lock(&elv_list_lock); | |
144 | e = elevator_find(chosen_elevator); | |
145 | spin_unlock(&elv_list_lock); | |
146 | ||
147 | if (!e) | |
148 | request_module("%s-iosched", chosen_elevator); | |
149 | } | |
150 | ||
151 | static struct kobj_type elv_ktype; | |
152 | ||
153 | struct elevator_queue *elevator_alloc(struct request_queue *q, | |
154 | struct elevator_type *e) | |
155 | { | |
156 | struct elevator_queue *eq; | |
157 | ||
158 | eq = kzalloc_node(sizeof(*eq), GFP_KERNEL, q->node); | |
159 | if (unlikely(!eq)) | |
160 | return NULL; | |
161 | ||
162 | eq->type = e; | |
163 | kobject_init(&eq->kobj, &elv_ktype); | |
164 | mutex_init(&eq->sysfs_lock); | |
165 | hash_init(eq->hash); | |
166 | ||
167 | return eq; | |
168 | } | |
169 | EXPORT_SYMBOL(elevator_alloc); | |
170 | ||
171 | static void elevator_release(struct kobject *kobj) | |
172 | { | |
173 | struct elevator_queue *e; | |
174 | ||
175 | e = container_of(kobj, struct elevator_queue, kobj); | |
176 | elevator_put(e->type); | |
177 | kfree(e); | |
178 | } | |
179 | ||
180 | int elevator_init(struct request_queue *q, char *name) | |
181 | { | |
182 | struct elevator_type *e = NULL; | |
183 | int err; | |
184 | ||
185 | /* | |
186 | * q->sysfs_lock must be held to provide mutual exclusion between | |
187 | * elevator_switch() and here. | |
188 | */ | |
189 | lockdep_assert_held(&q->sysfs_lock); | |
190 | ||
191 | if (unlikely(q->elevator)) | |
192 | return 0; | |
193 | ||
194 | INIT_LIST_HEAD(&q->queue_head); | |
195 | q->last_merge = NULL; | |
196 | q->end_sector = 0; | |
197 | q->boundary_rq = NULL; | |
198 | ||
199 | if (name) { | |
200 | e = elevator_get(name, true); | |
201 | if (!e) | |
202 | return -EINVAL; | |
203 | } | |
204 | ||
205 | /* | |
206 | * Use the default elevator specified by config boot param or | |
207 | * config option. Don't try to load modules as we could be running | |
208 | * off async and request_module() isn't allowed from async. | |
209 | */ | |
210 | if (!e && *chosen_elevator) { | |
211 | e = elevator_get(chosen_elevator, false); | |
212 | if (!e) | |
213 | printk(KERN_ERR "I/O scheduler %s not found\n", | |
214 | chosen_elevator); | |
215 | } | |
216 | ||
217 | if (!e) { | |
218 | e = elevator_get(CONFIG_DEFAULT_IOSCHED, false); | |
219 | if (!e) { | |
220 | printk(KERN_ERR | |
221 | "Default I/O scheduler not found. " \ | |
222 | "Using noop.\n"); | |
223 | e = elevator_get("noop", false); | |
224 | } | |
225 | } | |
226 | ||
227 | err = e->ops.elevator_init_fn(q, e); | |
228 | if (err) | |
229 | elevator_put(e); | |
230 | return err; | |
231 | } | |
232 | EXPORT_SYMBOL(elevator_init); | |
233 | ||
234 | void elevator_exit(struct elevator_queue *e) | |
235 | { | |
236 | mutex_lock(&e->sysfs_lock); | |
237 | if (e->type->ops.elevator_exit_fn) | |
238 | e->type->ops.elevator_exit_fn(e); | |
239 | mutex_unlock(&e->sysfs_lock); | |
240 | ||
241 | kobject_put(&e->kobj); | |
242 | } | |
243 | EXPORT_SYMBOL(elevator_exit); | |
244 | ||
245 | static inline void __elv_rqhash_del(struct request *rq) | |
246 | { | |
247 | hash_del(&rq->hash); | |
248 | rq->cmd_flags &= ~REQ_HASHED; | |
249 | } | |
250 | ||
251 | static void elv_rqhash_del(struct request_queue *q, struct request *rq) | |
252 | { | |
253 | if (ELV_ON_HASH(rq)) | |
254 | __elv_rqhash_del(rq); | |
255 | } | |
256 | ||
257 | static void elv_rqhash_add(struct request_queue *q, struct request *rq) | |
258 | { | |
259 | struct elevator_queue *e = q->elevator; | |
260 | ||
261 | BUG_ON(ELV_ON_HASH(rq)); | |
262 | hash_add(e->hash, &rq->hash, rq_hash_key(rq)); | |
263 | rq->cmd_flags |= REQ_HASHED; | |
264 | } | |
265 | ||
266 | static void elv_rqhash_reposition(struct request_queue *q, struct request *rq) | |
267 | { | |
268 | __elv_rqhash_del(rq); | |
269 | elv_rqhash_add(q, rq); | |
270 | } | |
271 | ||
272 | static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset) | |
273 | { | |
274 | struct elevator_queue *e = q->elevator; | |
275 | struct hlist_node *next; | |
276 | struct request *rq; | |
277 | ||
278 | hash_for_each_possible_safe(e->hash, rq, next, hash, offset) { | |
279 | BUG_ON(!ELV_ON_HASH(rq)); | |
280 | ||
281 | if (unlikely(!rq_mergeable(rq))) { | |
282 | __elv_rqhash_del(rq); | |
283 | continue; | |
284 | } | |
285 | ||
286 | if (rq_hash_key(rq) == offset) | |
287 | return rq; | |
288 | } | |
289 | ||
290 | return NULL; | |
291 | } | |
292 | ||
293 | /* | |
294 | * RB-tree support functions for inserting/lookup/removal of requests | |
295 | * in a sorted RB tree. | |
296 | */ | |
297 | void elv_rb_add(struct rb_root *root, struct request *rq) | |
298 | { | |
299 | struct rb_node **p = &root->rb_node; | |
300 | struct rb_node *parent = NULL; | |
301 | struct request *__rq; | |
302 | ||
303 | while (*p) { | |
304 | parent = *p; | |
305 | __rq = rb_entry(parent, struct request, rb_node); | |
306 | ||
307 | if (blk_rq_pos(rq) < blk_rq_pos(__rq)) | |
308 | p = &(*p)->rb_left; | |
309 | else if (blk_rq_pos(rq) >= blk_rq_pos(__rq)) | |
310 | p = &(*p)->rb_right; | |
311 | } | |
312 | ||
313 | rb_link_node(&rq->rb_node, parent, p); | |
314 | rb_insert_color(&rq->rb_node, root); | |
315 | } | |
316 | EXPORT_SYMBOL(elv_rb_add); | |
317 | ||
318 | void elv_rb_del(struct rb_root *root, struct request *rq) | |
319 | { | |
320 | BUG_ON(RB_EMPTY_NODE(&rq->rb_node)); | |
321 | rb_erase(&rq->rb_node, root); | |
322 | RB_CLEAR_NODE(&rq->rb_node); | |
323 | } | |
324 | EXPORT_SYMBOL(elv_rb_del); | |
325 | ||
326 | struct request *elv_rb_find(struct rb_root *root, sector_t sector) | |
327 | { | |
328 | struct rb_node *n = root->rb_node; | |
329 | struct request *rq; | |
330 | ||
331 | while (n) { | |
332 | rq = rb_entry(n, struct request, rb_node); | |
333 | ||
334 | if (sector < blk_rq_pos(rq)) | |
335 | n = n->rb_left; | |
336 | else if (sector > blk_rq_pos(rq)) | |
337 | n = n->rb_right; | |
338 | else | |
339 | return rq; | |
340 | } | |
341 | ||
342 | return NULL; | |
343 | } | |
344 | EXPORT_SYMBOL(elv_rb_find); | |
345 | ||
346 | /* | |
347 | * Insert rq into dispatch queue of q. Queue lock must be held on | |
348 | * entry. rq is sort instead into the dispatch queue. To be used by | |
349 | * specific elevators. | |
350 | */ | |
351 | void elv_dispatch_sort(struct request_queue *q, struct request *rq) | |
352 | { | |
353 | sector_t boundary; | |
354 | struct list_head *entry; | |
355 | int stop_flags; | |
356 | ||
357 | if (q->last_merge == rq) | |
358 | q->last_merge = NULL; | |
359 | ||
360 | elv_rqhash_del(q, rq); | |
361 | ||
362 | q->nr_sorted--; | |
363 | ||
364 | boundary = q->end_sector; | |
365 | stop_flags = REQ_SOFTBARRIER | REQ_STARTED; | |
366 | list_for_each_prev(entry, &q->queue_head) { | |
367 | struct request *pos = list_entry_rq(entry); | |
368 | ||
369 | if ((rq->cmd_flags & REQ_DISCARD) != | |
370 | (pos->cmd_flags & REQ_DISCARD)) | |
371 | break; | |
372 | if (rq_data_dir(rq) != rq_data_dir(pos)) | |
373 | break; | |
374 | if (pos->cmd_flags & stop_flags) | |
375 | break; | |
376 | if (blk_rq_pos(rq) >= boundary) { | |
377 | if (blk_rq_pos(pos) < boundary) | |
378 | continue; | |
379 | } else { | |
380 | if (blk_rq_pos(pos) >= boundary) | |
381 | break; | |
382 | } | |
383 | if (blk_rq_pos(rq) >= blk_rq_pos(pos)) | |
384 | break; | |
385 | } | |
386 | ||
387 | list_add(&rq->queuelist, entry); | |
388 | } | |
389 | EXPORT_SYMBOL(elv_dispatch_sort); | |
390 | ||
391 | /* | |
392 | * Insert rq into dispatch queue of q. Queue lock must be held on | |
393 | * entry. rq is added to the back of the dispatch queue. To be used by | |
394 | * specific elevators. | |
395 | */ | |
396 | void elv_dispatch_add_tail(struct request_queue *q, struct request *rq) | |
397 | { | |
398 | if (q->last_merge == rq) | |
399 | q->last_merge = NULL; | |
400 | ||
401 | elv_rqhash_del(q, rq); | |
402 | ||
403 | q->nr_sorted--; | |
404 | ||
405 | q->end_sector = rq_end_sector(rq); | |
406 | q->boundary_rq = rq; | |
407 | list_add_tail(&rq->queuelist, &q->queue_head); | |
408 | } | |
409 | EXPORT_SYMBOL(elv_dispatch_add_tail); | |
410 | ||
411 | int elv_merge(struct request_queue *q, struct request **req, struct bio *bio) | |
412 | { | |
413 | struct elevator_queue *e = q->elevator; | |
414 | struct request *__rq; | |
415 | int ret; | |
416 | ||
417 | /* | |
418 | * Levels of merges: | |
419 | * nomerges: No merges at all attempted | |
420 | * noxmerges: Only simple one-hit cache try | |
421 | * merges: All merge tries attempted | |
422 | */ | |
423 | if (blk_queue_nomerges(q) || !bio_mergeable(bio)) | |
424 | return ELEVATOR_NO_MERGE; | |
425 | ||
426 | /* | |
427 | * First try one-hit cache. | |
428 | */ | |
429 | if (q->last_merge && elv_rq_merge_ok(q->last_merge, bio)) { | |
430 | ret = blk_try_merge(q->last_merge, bio); | |
431 | if (ret != ELEVATOR_NO_MERGE) { | |
432 | *req = q->last_merge; | |
433 | return ret; | |
434 | } | |
435 | } | |
436 | ||
437 | if (blk_queue_noxmerges(q)) | |
438 | return ELEVATOR_NO_MERGE; | |
439 | ||
440 | /* | |
441 | * See if our hash lookup can find a potential backmerge. | |
442 | */ | |
443 | __rq = elv_rqhash_find(q, bio->bi_iter.bi_sector); | |
444 | if (__rq && elv_rq_merge_ok(__rq, bio)) { | |
445 | *req = __rq; | |
446 | return ELEVATOR_BACK_MERGE; | |
447 | } | |
448 | ||
449 | if (e->type->ops.elevator_merge_fn) | |
450 | return e->type->ops.elevator_merge_fn(q, req, bio); | |
451 | ||
452 | return ELEVATOR_NO_MERGE; | |
453 | } | |
454 | ||
455 | /* | |
456 | * Attempt to do an insertion back merge. Only check for the case where | |
457 | * we can append 'rq' to an existing request, so we can throw 'rq' away | |
458 | * afterwards. | |
459 | * | |
460 | * Returns true if we merged, false otherwise | |
461 | */ | |
462 | static bool elv_attempt_insert_merge(struct request_queue *q, | |
463 | struct request *rq) | |
464 | { | |
465 | struct request *__rq; | |
466 | bool ret; | |
467 | ||
468 | if (blk_queue_nomerges(q)) | |
469 | return false; | |
470 | ||
471 | /* | |
472 | * First try one-hit cache. | |
473 | */ | |
474 | if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq)) | |
475 | return true; | |
476 | ||
477 | if (blk_queue_noxmerges(q)) | |
478 | return false; | |
479 | ||
480 | ret = false; | |
481 | /* | |
482 | * See if our hash lookup can find a potential backmerge. | |
483 | */ | |
484 | while (1) { | |
485 | __rq = elv_rqhash_find(q, blk_rq_pos(rq)); | |
486 | if (!__rq || !blk_attempt_req_merge(q, __rq, rq)) | |
487 | break; | |
488 | ||
489 | /* The merged request could be merged with others, try again */ | |
490 | ret = true; | |
491 | rq = __rq; | |
492 | } | |
493 | ||
494 | return ret; | |
495 | } | |
496 | ||
497 | void elv_merged_request(struct request_queue *q, struct request *rq, int type) | |
498 | { | |
499 | struct elevator_queue *e = q->elevator; | |
500 | ||
501 | if (e->type->ops.elevator_merged_fn) | |
502 | e->type->ops.elevator_merged_fn(q, rq, type); | |
503 | ||
504 | if (type == ELEVATOR_BACK_MERGE) | |
505 | elv_rqhash_reposition(q, rq); | |
506 | ||
507 | q->last_merge = rq; | |
508 | } | |
509 | ||
510 | void elv_merge_requests(struct request_queue *q, struct request *rq, | |
511 | struct request *next) | |
512 | { | |
513 | struct elevator_queue *e = q->elevator; | |
514 | const int next_sorted = next->cmd_flags & REQ_SORTED; | |
515 | ||
516 | if (next_sorted && e->type->ops.elevator_merge_req_fn) | |
517 | e->type->ops.elevator_merge_req_fn(q, rq, next); | |
518 | ||
519 | elv_rqhash_reposition(q, rq); | |
520 | ||
521 | if (next_sorted) { | |
522 | elv_rqhash_del(q, next); | |
523 | q->nr_sorted--; | |
524 | } | |
525 | ||
526 | q->last_merge = rq; | |
527 | } | |
528 | ||
529 | void elv_bio_merged(struct request_queue *q, struct request *rq, | |
530 | struct bio *bio) | |
531 | { | |
532 | struct elevator_queue *e = q->elevator; | |
533 | ||
534 | if (e->type->ops.elevator_bio_merged_fn) | |
535 | e->type->ops.elevator_bio_merged_fn(q, rq, bio); | |
536 | } | |
537 | ||
538 | #ifdef CONFIG_PM | |
539 | static void blk_pm_requeue_request(struct request *rq) | |
540 | { | |
541 | if (rq->q->dev && !(rq->cmd_flags & REQ_PM)) | |
542 | rq->q->nr_pending--; | |
543 | } | |
544 | ||
545 | static void blk_pm_add_request(struct request_queue *q, struct request *rq) | |
546 | { | |
547 | if (q->dev && !(rq->cmd_flags & REQ_PM) && q->nr_pending++ == 0 && | |
548 | (q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING)) | |
549 | pm_request_resume(q->dev); | |
550 | } | |
551 | #else | |
552 | static inline void blk_pm_requeue_request(struct request *rq) {} | |
553 | static inline void blk_pm_add_request(struct request_queue *q, | |
554 | struct request *rq) | |
555 | { | |
556 | } | |
557 | #endif | |
558 | ||
559 | void elv_requeue_request(struct request_queue *q, struct request *rq) | |
560 | { | |
561 | /* | |
562 | * it already went through dequeue, we need to decrement the | |
563 | * in_flight count again | |
564 | */ | |
565 | if (blk_account_rq(rq)) { | |
566 | q->in_flight[rq_is_sync(rq)]--; | |
567 | if (rq->cmd_flags & REQ_SORTED) | |
568 | elv_deactivate_rq(q, rq); | |
569 | } | |
570 | ||
571 | rq->cmd_flags &= ~REQ_STARTED; | |
572 | ||
573 | blk_pm_requeue_request(rq); | |
574 | ||
575 | __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE); | |
576 | } | |
577 | ||
578 | void elv_drain_elevator(struct request_queue *q) | |
579 | { | |
580 | static int printed; | |
581 | ||
582 | lockdep_assert_held(q->queue_lock); | |
583 | ||
584 | while (q->elevator->type->ops.elevator_dispatch_fn(q, 1)) | |
585 | ; | |
586 | if (q->nr_sorted && printed++ < 10) { | |
587 | printk(KERN_ERR "%s: forced dispatching is broken " | |
588 | "(nr_sorted=%u), please report this\n", | |
589 | q->elevator->type->elevator_name, q->nr_sorted); | |
590 | } | |
591 | } | |
592 | ||
593 | void __elv_add_request(struct request_queue *q, struct request *rq, int where) | |
594 | { | |
595 | trace_block_rq_insert(q, rq); | |
596 | ||
597 | blk_pm_add_request(q, rq); | |
598 | ||
599 | rq->q = q; | |
600 | ||
601 | if (rq->cmd_flags & REQ_SOFTBARRIER) { | |
602 | /* barriers are scheduling boundary, update end_sector */ | |
603 | if (rq->cmd_type == REQ_TYPE_FS) { | |
604 | q->end_sector = rq_end_sector(rq); | |
605 | q->boundary_rq = rq; | |
606 | } | |
607 | } else if (!(rq->cmd_flags & REQ_ELVPRIV) && | |
608 | (where == ELEVATOR_INSERT_SORT || | |
609 | where == ELEVATOR_INSERT_SORT_MERGE)) | |
610 | where = ELEVATOR_INSERT_BACK; | |
611 | ||
612 | switch (where) { | |
613 | case ELEVATOR_INSERT_REQUEUE: | |
614 | case ELEVATOR_INSERT_FRONT: | |
615 | rq->cmd_flags |= REQ_SOFTBARRIER; | |
616 | list_add(&rq->queuelist, &q->queue_head); | |
617 | break; | |
618 | ||
619 | case ELEVATOR_INSERT_BACK: | |
620 | rq->cmd_flags |= REQ_SOFTBARRIER; | |
621 | elv_drain_elevator(q); | |
622 | list_add_tail(&rq->queuelist, &q->queue_head); | |
623 | /* | |
624 | * We kick the queue here for the following reasons. | |
625 | * - The elevator might have returned NULL previously | |
626 | * to delay requests and returned them now. As the | |
627 | * queue wasn't empty before this request, ll_rw_blk | |
628 | * won't run the queue on return, resulting in hang. | |
629 | * - Usually, back inserted requests won't be merged | |
630 | * with anything. There's no point in delaying queue | |
631 | * processing. | |
632 | */ | |
633 | __blk_run_queue(q); | |
634 | break; | |
635 | ||
636 | case ELEVATOR_INSERT_SORT_MERGE: | |
637 | /* | |
638 | * If we succeed in merging this request with one in the | |
639 | * queue already, we are done - rq has now been freed, | |
640 | * so no need to do anything further. | |
641 | */ | |
642 | if (elv_attempt_insert_merge(q, rq)) | |
643 | break; | |
644 | case ELEVATOR_INSERT_SORT: | |
645 | BUG_ON(rq->cmd_type != REQ_TYPE_FS); | |
646 | rq->cmd_flags |= REQ_SORTED; | |
647 | q->nr_sorted++; | |
648 | if (rq_mergeable(rq)) { | |
649 | elv_rqhash_add(q, rq); | |
650 | if (!q->last_merge) | |
651 | q->last_merge = rq; | |
652 | } | |
653 | ||
654 | /* | |
655 | * Some ioscheds (cfq) run q->request_fn directly, so | |
656 | * rq cannot be accessed after calling | |
657 | * elevator_add_req_fn. | |
658 | */ | |
659 | q->elevator->type->ops.elevator_add_req_fn(q, rq); | |
660 | break; | |
661 | ||
662 | case ELEVATOR_INSERT_FLUSH: | |
663 | rq->cmd_flags |= REQ_SOFTBARRIER; | |
664 | blk_insert_flush(rq); | |
665 | break; | |
666 | default: | |
667 | printk(KERN_ERR "%s: bad insertion point %d\n", | |
668 | __func__, where); | |
669 | BUG(); | |
670 | } | |
671 | } | |
672 | EXPORT_SYMBOL(__elv_add_request); | |
673 | ||
674 | void elv_add_request(struct request_queue *q, struct request *rq, int where) | |
675 | { | |
676 | unsigned long flags; | |
677 | ||
678 | spin_lock_irqsave(q->queue_lock, flags); | |
679 | __elv_add_request(q, rq, where); | |
680 | spin_unlock_irqrestore(q->queue_lock, flags); | |
681 | } | |
682 | EXPORT_SYMBOL(elv_add_request); | |
683 | ||
684 | struct request *elv_latter_request(struct request_queue *q, struct request *rq) | |
685 | { | |
686 | struct elevator_queue *e = q->elevator; | |
687 | ||
688 | if (e->type->ops.elevator_latter_req_fn) | |
689 | return e->type->ops.elevator_latter_req_fn(q, rq); | |
690 | return NULL; | |
691 | } | |
692 | ||
693 | struct request *elv_former_request(struct request_queue *q, struct request *rq) | |
694 | { | |
695 | struct elevator_queue *e = q->elevator; | |
696 | ||
697 | if (e->type->ops.elevator_former_req_fn) | |
698 | return e->type->ops.elevator_former_req_fn(q, rq); | |
699 | return NULL; | |
700 | } | |
701 | ||
702 | int elv_set_request(struct request_queue *q, struct request *rq, | |
703 | struct bio *bio, gfp_t gfp_mask) | |
704 | { | |
705 | struct elevator_queue *e = q->elevator; | |
706 | ||
707 | if (e->type->ops.elevator_set_req_fn) | |
708 | return e->type->ops.elevator_set_req_fn(q, rq, bio, gfp_mask); | |
709 | return 0; | |
710 | } | |
711 | ||
712 | void elv_put_request(struct request_queue *q, struct request *rq) | |
713 | { | |
714 | struct elevator_queue *e = q->elevator; | |
715 | ||
716 | if (e->type->ops.elevator_put_req_fn) | |
717 | e->type->ops.elevator_put_req_fn(rq); | |
718 | } | |
719 | ||
720 | int elv_may_queue(struct request_queue *q, int rw) | |
721 | { | |
722 | struct elevator_queue *e = q->elevator; | |
723 | ||
724 | if (e->type->ops.elevator_may_queue_fn) | |
725 | return e->type->ops.elevator_may_queue_fn(q, rw); | |
726 | ||
727 | return ELV_MQUEUE_MAY; | |
728 | } | |
729 | ||
730 | void elv_completed_request(struct request_queue *q, struct request *rq) | |
731 | { | |
732 | struct elevator_queue *e = q->elevator; | |
733 | ||
734 | /* | |
735 | * request is released from the driver, io must be done | |
736 | */ | |
737 | if (blk_account_rq(rq)) { | |
738 | q->in_flight[rq_is_sync(rq)]--; | |
739 | if ((rq->cmd_flags & REQ_SORTED) && | |
740 | e->type->ops.elevator_completed_req_fn) | |
741 | e->type->ops.elevator_completed_req_fn(q, rq); | |
742 | } | |
743 | } | |
744 | ||
745 | #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr) | |
746 | ||
747 | static ssize_t | |
748 | elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page) | |
749 | { | |
750 | struct elv_fs_entry *entry = to_elv(attr); | |
751 | struct elevator_queue *e; | |
752 | ssize_t error; | |
753 | ||
754 | if (!entry->show) | |
755 | return -EIO; | |
756 | ||
757 | e = container_of(kobj, struct elevator_queue, kobj); | |
758 | mutex_lock(&e->sysfs_lock); | |
759 | error = e->type ? entry->show(e, page) : -ENOENT; | |
760 | mutex_unlock(&e->sysfs_lock); | |
761 | return error; | |
762 | } | |
763 | ||
764 | static ssize_t | |
765 | elv_attr_store(struct kobject *kobj, struct attribute *attr, | |
766 | const char *page, size_t length) | |
767 | { | |
768 | struct elv_fs_entry *entry = to_elv(attr); | |
769 | struct elevator_queue *e; | |
770 | ssize_t error; | |
771 | ||
772 | if (!entry->store) | |
773 | return -EIO; | |
774 | ||
775 | e = container_of(kobj, struct elevator_queue, kobj); | |
776 | mutex_lock(&e->sysfs_lock); | |
777 | error = e->type ? entry->store(e, page, length) : -ENOENT; | |
778 | mutex_unlock(&e->sysfs_lock); | |
779 | return error; | |
780 | } | |
781 | ||
782 | static const struct sysfs_ops elv_sysfs_ops = { | |
783 | .show = elv_attr_show, | |
784 | .store = elv_attr_store, | |
785 | }; | |
786 | ||
787 | static struct kobj_type elv_ktype = { | |
788 | .sysfs_ops = &elv_sysfs_ops, | |
789 | .release = elevator_release, | |
790 | }; | |
791 | ||
792 | int elv_register_queue(struct request_queue *q) | |
793 | { | |
794 | struct elevator_queue *e = q->elevator; | |
795 | int error; | |
796 | ||
797 | error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched"); | |
798 | if (!error) { | |
799 | struct elv_fs_entry *attr = e->type->elevator_attrs; | |
800 | if (attr) { | |
801 | while (attr->attr.name) { | |
802 | if (sysfs_create_file(&e->kobj, &attr->attr)) | |
803 | break; | |
804 | attr++; | |
805 | } | |
806 | } | |
807 | kobject_uevent(&e->kobj, KOBJ_ADD); | |
808 | e->registered = 1; | |
809 | if (e->type->ops.elevator_registered_fn) | |
810 | e->type->ops.elevator_registered_fn(q); | |
811 | } | |
812 | return error; | |
813 | } | |
814 | EXPORT_SYMBOL(elv_register_queue); | |
815 | ||
816 | void elv_unregister_queue(struct request_queue *q) | |
817 | { | |
818 | if (q) { | |
819 | struct elevator_queue *e = q->elevator; | |
820 | ||
821 | kobject_uevent(&e->kobj, KOBJ_REMOVE); | |
822 | kobject_del(&e->kobj); | |
823 | e->registered = 0; | |
824 | } | |
825 | } | |
826 | EXPORT_SYMBOL(elv_unregister_queue); | |
827 | ||
828 | int elv_register(struct elevator_type *e) | |
829 | { | |
830 | char *def = ""; | |
831 | ||
832 | /* create icq_cache if requested */ | |
833 | if (e->icq_size) { | |
834 | if (WARN_ON(e->icq_size < sizeof(struct io_cq)) || | |
835 | WARN_ON(e->icq_align < __alignof__(struct io_cq))) | |
836 | return -EINVAL; | |
837 | ||
838 | snprintf(e->icq_cache_name, sizeof(e->icq_cache_name), | |
839 | "%s_io_cq", e->elevator_name); | |
840 | e->icq_cache = kmem_cache_create(e->icq_cache_name, e->icq_size, | |
841 | e->icq_align, 0, NULL); | |
842 | if (!e->icq_cache) | |
843 | return -ENOMEM; | |
844 | } | |
845 | ||
846 | /* register, don't allow duplicate names */ | |
847 | spin_lock(&elv_list_lock); | |
848 | if (elevator_find(e->elevator_name)) { | |
849 | spin_unlock(&elv_list_lock); | |
850 | if (e->icq_cache) | |
851 | kmem_cache_destroy(e->icq_cache); | |
852 | return -EBUSY; | |
853 | } | |
854 | list_add_tail(&e->list, &elv_list); | |
855 | spin_unlock(&elv_list_lock); | |
856 | ||
857 | /* print pretty message */ | |
858 | if (!strcmp(e->elevator_name, chosen_elevator) || | |
859 | (!*chosen_elevator && | |
860 | !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED))) | |
861 | def = " (default)"; | |
862 | ||
863 | printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name, | |
864 | def); | |
865 | return 0; | |
866 | } | |
867 | EXPORT_SYMBOL_GPL(elv_register); | |
868 | ||
869 | void elv_unregister(struct elevator_type *e) | |
870 | { | |
871 | /* unregister */ | |
872 | spin_lock(&elv_list_lock); | |
873 | list_del_init(&e->list); | |
874 | spin_unlock(&elv_list_lock); | |
875 | ||
876 | /* | |
877 | * Destroy icq_cache if it exists. icq's are RCU managed. Make | |
878 | * sure all RCU operations are complete before proceeding. | |
879 | */ | |
880 | if (e->icq_cache) { | |
881 | rcu_barrier(); | |
882 | kmem_cache_destroy(e->icq_cache); | |
883 | e->icq_cache = NULL; | |
884 | } | |
885 | } | |
886 | EXPORT_SYMBOL_GPL(elv_unregister); | |
887 | ||
888 | /* | |
889 | * switch to new_e io scheduler. be careful not to introduce deadlocks - | |
890 | * we don't free the old io scheduler, before we have allocated what we | |
891 | * need for the new one. this way we have a chance of going back to the old | |
892 | * one, if the new one fails init for some reason. | |
893 | */ | |
894 | static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) | |
895 | { | |
896 | struct elevator_queue *old = q->elevator; | |
897 | bool registered = old->registered; | |
898 | int err; | |
899 | ||
900 | /* | |
901 | * Turn on BYPASS and drain all requests w/ elevator private data. | |
902 | * Block layer doesn't call into a quiesced elevator - all requests | |
903 | * are directly put on the dispatch list without elevator data | |
904 | * using INSERT_BACK. All requests have SOFTBARRIER set and no | |
905 | * merge happens either. | |
906 | */ | |
907 | blk_queue_bypass_start(q); | |
908 | ||
909 | /* unregister and clear all auxiliary data of the old elevator */ | |
910 | if (registered) | |
911 | elv_unregister_queue(q); | |
912 | ||
913 | spin_lock_irq(q->queue_lock); | |
914 | ioc_clear_queue(q); | |
915 | spin_unlock_irq(q->queue_lock); | |
916 | ||
917 | /* allocate, init and register new elevator */ | |
918 | err = new_e->ops.elevator_init_fn(q, new_e); | |
919 | if (err) | |
920 | goto fail_init; | |
921 | ||
922 | if (registered) { | |
923 | err = elv_register_queue(q); | |
924 | if (err) | |
925 | goto fail_register; | |
926 | } | |
927 | ||
928 | /* done, kill the old one and finish */ | |
929 | elevator_exit(old); | |
930 | blk_queue_bypass_end(q); | |
931 | ||
932 | blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name); | |
933 | ||
934 | return 0; | |
935 | ||
936 | fail_register: | |
937 | elevator_exit(q->elevator); | |
938 | fail_init: | |
939 | /* switch failed, restore and re-register old elevator */ | |
940 | q->elevator = old; | |
941 | elv_register_queue(q); | |
942 | blk_queue_bypass_end(q); | |
943 | ||
944 | return err; | |
945 | } | |
946 | ||
947 | /* | |
948 | * Switch this queue to the given IO scheduler. | |
949 | */ | |
950 | static int __elevator_change(struct request_queue *q, const char *name) | |
951 | { | |
952 | char elevator_name[ELV_NAME_MAX]; | |
953 | struct elevator_type *e; | |
954 | ||
955 | if (!q->elevator) | |
956 | return -ENXIO; | |
957 | ||
958 | strlcpy(elevator_name, name, sizeof(elevator_name)); | |
959 | e = elevator_get(strstrip(elevator_name), true); | |
960 | if (!e) { | |
961 | printk(KERN_ERR "elevator: type %s not found\n", elevator_name); | |
962 | return -EINVAL; | |
963 | } | |
964 | ||
965 | if (!strcmp(elevator_name, q->elevator->type->elevator_name)) { | |
966 | elevator_put(e); | |
967 | return 0; | |
968 | } | |
969 | ||
970 | return elevator_switch(q, e); | |
971 | } | |
972 | ||
973 | int elevator_change(struct request_queue *q, const char *name) | |
974 | { | |
975 | int ret; | |
976 | ||
977 | /* Protect q->elevator from elevator_init() */ | |
978 | mutex_lock(&q->sysfs_lock); | |
979 | ret = __elevator_change(q, name); | |
980 | mutex_unlock(&q->sysfs_lock); | |
981 | ||
982 | return ret; | |
983 | } | |
984 | EXPORT_SYMBOL(elevator_change); | |
985 | ||
986 | ssize_t elv_iosched_store(struct request_queue *q, const char *name, | |
987 | size_t count) | |
988 | { | |
989 | int ret; | |
990 | ||
991 | if (!q->elevator) | |
992 | return count; | |
993 | ||
994 | ret = __elevator_change(q, name); | |
995 | if (!ret) | |
996 | return count; | |
997 | ||
998 | printk(KERN_ERR "elevator: switch to %s failed\n", name); | |
999 | return ret; | |
1000 | } | |
1001 | ||
1002 | ssize_t elv_iosched_show(struct request_queue *q, char *name) | |
1003 | { | |
1004 | struct elevator_queue *e = q->elevator; | |
1005 | struct elevator_type *elv; | |
1006 | struct elevator_type *__e; | |
1007 | int len = 0; | |
1008 | ||
1009 | if (!q->elevator || !blk_queue_stackable(q)) | |
1010 | return sprintf(name, "none\n"); | |
1011 | ||
1012 | elv = e->type; | |
1013 | ||
1014 | spin_lock(&elv_list_lock); | |
1015 | list_for_each_entry(__e, &elv_list, list) { | |
1016 | if (!strcmp(elv->elevator_name, __e->elevator_name)) | |
1017 | len += sprintf(name+len, "[%s] ", elv->elevator_name); | |
1018 | else | |
1019 | len += sprintf(name+len, "%s ", __e->elevator_name); | |
1020 | } | |
1021 | spin_unlock(&elv_list_lock); | |
1022 | ||
1023 | len += sprintf(len+name, "\n"); | |
1024 | return len; | |
1025 | } | |
1026 | ||
1027 | struct request *elv_rb_former_request(struct request_queue *q, | |
1028 | struct request *rq) | |
1029 | { | |
1030 | struct rb_node *rbprev = rb_prev(&rq->rb_node); | |
1031 | ||
1032 | if (rbprev) | |
1033 | return rb_entry_rq(rbprev); | |
1034 | ||
1035 | return NULL; | |
1036 | } | |
1037 | EXPORT_SYMBOL(elv_rb_former_request); | |
1038 | ||
1039 | struct request *elv_rb_latter_request(struct request_queue *q, | |
1040 | struct request *rq) | |
1041 | { | |
1042 | struct rb_node *rbnext = rb_next(&rq->rb_node); | |
1043 | ||
1044 | if (rbnext) | |
1045 | return rb_entry_rq(rbnext); | |
1046 | ||
1047 | return NULL; | |
1048 | } | |
1049 | EXPORT_SYMBOL(elv_rb_latter_request); |