Root/
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/delay.h> |
35 | #include <linux/blktrace_api.h> |
36 | #include <linux/hash.h> |
37 | #include <linux/uaccess.h> |
38 | |
39 | #include <trace/events/block.h> |
40 | |
41 | #include "blk.h" |
42 | |
43 | static DEFINE_SPINLOCK(elv_list_lock); |
44 | static LIST_HEAD(elv_list); |
45 | |
46 | /* |
47 | * Merge hash stuff. |
48 | */ |
49 | static const int elv_hash_shift = 6; |
50 | #define ELV_HASH_BLOCK(sec) ((sec) >> 3) |
51 | #define ELV_HASH_FN(sec) \ |
52 | (hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift)) |
53 | #define ELV_HASH_ENTRIES (1 << elv_hash_shift) |
54 | #define rq_hash_key(rq) (blk_rq_pos(rq) + blk_rq_sectors(rq)) |
55 | |
56 | /* |
57 | * Query io scheduler to see if the current process issuing bio may be |
58 | * merged with rq. |
59 | */ |
60 | static int elv_iosched_allow_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->ops->elevator_allow_merge_fn) |
66 | return e->ops->elevator_allow_merge_fn(q, rq, bio); |
67 | |
68 | return 1; |
69 | } |
70 | |
71 | /* |
72 | * can we safely merge with this request? |
73 | */ |
74 | int elv_rq_merge_ok(struct request *rq, struct bio *bio) |
75 | { |
76 | if (!rq_mergeable(rq)) |
77 | return 0; |
78 | |
79 | /* |
80 | * Don't merge file system requests and discard requests |
81 | */ |
82 | if ((bio->bi_rw & REQ_DISCARD) != (rq->bio->bi_rw & REQ_DISCARD)) |
83 | return 0; |
84 | |
85 | /* |
86 | * Don't merge discard requests and secure discard requests |
87 | */ |
88 | if ((bio->bi_rw & REQ_SECURE) != (rq->bio->bi_rw & REQ_SECURE)) |
89 | return 0; |
90 | |
91 | /* |
92 | * different data direction or already started, don't merge |
93 | */ |
94 | if (bio_data_dir(bio) != rq_data_dir(rq)) |
95 | return 0; |
96 | |
97 | /* |
98 | * must be same device and not a special request |
99 | */ |
100 | if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special) |
101 | return 0; |
102 | |
103 | /* |
104 | * only merge integrity protected bio into ditto rq |
105 | */ |
106 | if (bio_integrity(bio) != blk_integrity_rq(rq)) |
107 | return 0; |
108 | |
109 | if (!elv_iosched_allow_merge(rq, bio)) |
110 | return 0; |
111 | |
112 | return 1; |
113 | } |
114 | EXPORT_SYMBOL(elv_rq_merge_ok); |
115 | |
116 | int elv_try_merge(struct request *__rq, struct bio *bio) |
117 | { |
118 | int ret = ELEVATOR_NO_MERGE; |
119 | |
120 | /* |
121 | * we can merge and sequence is ok, check if it's possible |
122 | */ |
123 | if (elv_rq_merge_ok(__rq, bio)) { |
124 | if (blk_rq_pos(__rq) + blk_rq_sectors(__rq) == bio->bi_sector) |
125 | ret = ELEVATOR_BACK_MERGE; |
126 | else if (blk_rq_pos(__rq) - bio_sectors(bio) == bio->bi_sector) |
127 | ret = ELEVATOR_FRONT_MERGE; |
128 | } |
129 | |
130 | return ret; |
131 | } |
132 | |
133 | static struct elevator_type *elevator_find(const char *name) |
134 | { |
135 | struct elevator_type *e; |
136 | |
137 | list_for_each_entry(e, &elv_list, list) { |
138 | if (!strcmp(e->elevator_name, name)) |
139 | return e; |
140 | } |
141 | |
142 | return NULL; |
143 | } |
144 | |
145 | static void elevator_put(struct elevator_type *e) |
146 | { |
147 | module_put(e->elevator_owner); |
148 | } |
149 | |
150 | static struct elevator_type *elevator_get(const char *name) |
151 | { |
152 | struct elevator_type *e; |
153 | |
154 | spin_lock(&elv_list_lock); |
155 | |
156 | e = elevator_find(name); |
157 | if (!e) { |
158 | char elv[ELV_NAME_MAX + strlen("-iosched")]; |
159 | |
160 | spin_unlock(&elv_list_lock); |
161 | |
162 | snprintf(elv, sizeof(elv), "%s-iosched", name); |
163 | |
164 | request_module("%s", elv); |
165 | spin_lock(&elv_list_lock); |
166 | e = elevator_find(name); |
167 | } |
168 | |
169 | if (e && !try_module_get(e->elevator_owner)) |
170 | e = NULL; |
171 | |
172 | spin_unlock(&elv_list_lock); |
173 | |
174 | return e; |
175 | } |
176 | |
177 | static void *elevator_init_queue(struct request_queue *q, |
178 | struct elevator_queue *eq) |
179 | { |
180 | return eq->ops->elevator_init_fn(q); |
181 | } |
182 | |
183 | static void elevator_attach(struct request_queue *q, struct elevator_queue *eq, |
184 | void *data) |
185 | { |
186 | q->elevator = eq; |
187 | eq->elevator_data = data; |
188 | } |
189 | |
190 | static char chosen_elevator[16]; |
191 | |
192 | static int __init elevator_setup(char *str) |
193 | { |
194 | /* |
195 | * Be backwards-compatible with previous kernels, so users |
196 | * won't get the wrong elevator. |
197 | */ |
198 | strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1); |
199 | return 1; |
200 | } |
201 | |
202 | __setup("elevator=", elevator_setup); |
203 | |
204 | static struct kobj_type elv_ktype; |
205 | |
206 | static struct elevator_queue *elevator_alloc(struct request_queue *q, |
207 | struct elevator_type *e) |
208 | { |
209 | struct elevator_queue *eq; |
210 | int i; |
211 | |
212 | eq = kmalloc_node(sizeof(*eq), GFP_KERNEL | __GFP_ZERO, q->node); |
213 | if (unlikely(!eq)) |
214 | goto err; |
215 | |
216 | eq->ops = &e->ops; |
217 | eq->elevator_type = e; |
218 | kobject_init(&eq->kobj, &elv_ktype); |
219 | mutex_init(&eq->sysfs_lock); |
220 | |
221 | eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES, |
222 | GFP_KERNEL, q->node); |
223 | if (!eq->hash) |
224 | goto err; |
225 | |
226 | for (i = 0; i < ELV_HASH_ENTRIES; i++) |
227 | INIT_HLIST_HEAD(&eq->hash[i]); |
228 | |
229 | return eq; |
230 | err: |
231 | kfree(eq); |
232 | elevator_put(e); |
233 | return NULL; |
234 | } |
235 | |
236 | static void elevator_release(struct kobject *kobj) |
237 | { |
238 | struct elevator_queue *e; |
239 | |
240 | e = container_of(kobj, struct elevator_queue, kobj); |
241 | elevator_put(e->elevator_type); |
242 | kfree(e->hash); |
243 | kfree(e); |
244 | } |
245 | |
246 | int elevator_init(struct request_queue *q, char *name) |
247 | { |
248 | struct elevator_type *e = NULL; |
249 | struct elevator_queue *eq; |
250 | void *data; |
251 | |
252 | if (unlikely(q->elevator)) |
253 | return 0; |
254 | |
255 | INIT_LIST_HEAD(&q->queue_head); |
256 | q->last_merge = NULL; |
257 | q->end_sector = 0; |
258 | q->boundary_rq = NULL; |
259 | |
260 | if (name) { |
261 | e = elevator_get(name); |
262 | if (!e) |
263 | return -EINVAL; |
264 | } |
265 | |
266 | if (!e && *chosen_elevator) { |
267 | e = elevator_get(chosen_elevator); |
268 | if (!e) |
269 | printk(KERN_ERR "I/O scheduler %s not found\n", |
270 | chosen_elevator); |
271 | } |
272 | |
273 | if (!e) { |
274 | e = elevator_get(CONFIG_DEFAULT_IOSCHED); |
275 | if (!e) { |
276 | printk(KERN_ERR |
277 | "Default I/O scheduler not found. " \ |
278 | "Using noop.\n"); |
279 | e = elevator_get("noop"); |
280 | } |
281 | } |
282 | |
283 | eq = elevator_alloc(q, e); |
284 | if (!eq) |
285 | return -ENOMEM; |
286 | |
287 | data = elevator_init_queue(q, eq); |
288 | if (!data) { |
289 | kobject_put(&eq->kobj); |
290 | return -ENOMEM; |
291 | } |
292 | |
293 | elevator_attach(q, eq, data); |
294 | return 0; |
295 | } |
296 | EXPORT_SYMBOL(elevator_init); |
297 | |
298 | void elevator_exit(struct elevator_queue *e) |
299 | { |
300 | mutex_lock(&e->sysfs_lock); |
301 | if (e->ops->elevator_exit_fn) |
302 | e->ops->elevator_exit_fn(e); |
303 | e->ops = NULL; |
304 | mutex_unlock(&e->sysfs_lock); |
305 | |
306 | kobject_put(&e->kobj); |
307 | } |
308 | EXPORT_SYMBOL(elevator_exit); |
309 | |
310 | static inline void __elv_rqhash_del(struct request *rq) |
311 | { |
312 | hlist_del_init(&rq->hash); |
313 | } |
314 | |
315 | static void elv_rqhash_del(struct request_queue *q, struct request *rq) |
316 | { |
317 | if (ELV_ON_HASH(rq)) |
318 | __elv_rqhash_del(rq); |
319 | } |
320 | |
321 | static void elv_rqhash_add(struct request_queue *q, struct request *rq) |
322 | { |
323 | struct elevator_queue *e = q->elevator; |
324 | |
325 | BUG_ON(ELV_ON_HASH(rq)); |
326 | hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]); |
327 | } |
328 | |
329 | static void elv_rqhash_reposition(struct request_queue *q, struct request *rq) |
330 | { |
331 | __elv_rqhash_del(rq); |
332 | elv_rqhash_add(q, rq); |
333 | } |
334 | |
335 | static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset) |
336 | { |
337 | struct elevator_queue *e = q->elevator; |
338 | struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)]; |
339 | struct hlist_node *entry, *next; |
340 | struct request *rq; |
341 | |
342 | hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) { |
343 | BUG_ON(!ELV_ON_HASH(rq)); |
344 | |
345 | if (unlikely(!rq_mergeable(rq))) { |
346 | __elv_rqhash_del(rq); |
347 | continue; |
348 | } |
349 | |
350 | if (rq_hash_key(rq) == offset) |
351 | return rq; |
352 | } |
353 | |
354 | return NULL; |
355 | } |
356 | |
357 | /* |
358 | * RB-tree support functions for inserting/lookup/removal of requests |
359 | * in a sorted RB tree. |
360 | */ |
361 | struct request *elv_rb_add(struct rb_root *root, struct request *rq) |
362 | { |
363 | struct rb_node **p = &root->rb_node; |
364 | struct rb_node *parent = NULL; |
365 | struct request *__rq; |
366 | |
367 | while (*p) { |
368 | parent = *p; |
369 | __rq = rb_entry(parent, struct request, rb_node); |
370 | |
371 | if (blk_rq_pos(rq) < blk_rq_pos(__rq)) |
372 | p = &(*p)->rb_left; |
373 | else if (blk_rq_pos(rq) > blk_rq_pos(__rq)) |
374 | p = &(*p)->rb_right; |
375 | else |
376 | return __rq; |
377 | } |
378 | |
379 | rb_link_node(&rq->rb_node, parent, p); |
380 | rb_insert_color(&rq->rb_node, root); |
381 | return NULL; |
382 | } |
383 | EXPORT_SYMBOL(elv_rb_add); |
384 | |
385 | void elv_rb_del(struct rb_root *root, struct request *rq) |
386 | { |
387 | BUG_ON(RB_EMPTY_NODE(&rq->rb_node)); |
388 | rb_erase(&rq->rb_node, root); |
389 | RB_CLEAR_NODE(&rq->rb_node); |
390 | } |
391 | EXPORT_SYMBOL(elv_rb_del); |
392 | |
393 | struct request *elv_rb_find(struct rb_root *root, sector_t sector) |
394 | { |
395 | struct rb_node *n = root->rb_node; |
396 | struct request *rq; |
397 | |
398 | while (n) { |
399 | rq = rb_entry(n, struct request, rb_node); |
400 | |
401 | if (sector < blk_rq_pos(rq)) |
402 | n = n->rb_left; |
403 | else if (sector > blk_rq_pos(rq)) |
404 | n = n->rb_right; |
405 | else |
406 | return rq; |
407 | } |
408 | |
409 | return NULL; |
410 | } |
411 | EXPORT_SYMBOL(elv_rb_find); |
412 | |
413 | /* |
414 | * Insert rq into dispatch queue of q. Queue lock must be held on |
415 | * entry. rq is sort instead into the dispatch queue. To be used by |
416 | * specific elevators. |
417 | */ |
418 | void elv_dispatch_sort(struct request_queue *q, struct request *rq) |
419 | { |
420 | sector_t boundary; |
421 | struct list_head *entry; |
422 | int stop_flags; |
423 | |
424 | BUG_ON(rq->cmd_flags & REQ_ON_PLUG); |
425 | |
426 | if (q->last_merge == rq) |
427 | q->last_merge = NULL; |
428 | |
429 | elv_rqhash_del(q, rq); |
430 | |
431 | q->nr_sorted--; |
432 | |
433 | boundary = q->end_sector; |
434 | stop_flags = REQ_SOFTBARRIER | REQ_STARTED; |
435 | list_for_each_prev(entry, &q->queue_head) { |
436 | struct request *pos = list_entry_rq(entry); |
437 | |
438 | if ((rq->cmd_flags & REQ_DISCARD) != |
439 | (pos->cmd_flags & REQ_DISCARD)) |
440 | break; |
441 | if (rq_data_dir(rq) != rq_data_dir(pos)) |
442 | break; |
443 | if (pos->cmd_flags & stop_flags) |
444 | break; |
445 | if (blk_rq_pos(rq) >= boundary) { |
446 | if (blk_rq_pos(pos) < boundary) |
447 | continue; |
448 | } else { |
449 | if (blk_rq_pos(pos) >= boundary) |
450 | break; |
451 | } |
452 | if (blk_rq_pos(rq) >= blk_rq_pos(pos)) |
453 | break; |
454 | } |
455 | |
456 | list_add(&rq->queuelist, entry); |
457 | } |
458 | EXPORT_SYMBOL(elv_dispatch_sort); |
459 | |
460 | /* |
461 | * Insert rq into dispatch queue of q. Queue lock must be held on |
462 | * entry. rq is added to the back of the dispatch queue. To be used by |
463 | * specific elevators. |
464 | */ |
465 | void elv_dispatch_add_tail(struct request_queue *q, struct request *rq) |
466 | { |
467 | if (q->last_merge == rq) |
468 | q->last_merge = NULL; |
469 | |
470 | elv_rqhash_del(q, rq); |
471 | |
472 | q->nr_sorted--; |
473 | |
474 | q->end_sector = rq_end_sector(rq); |
475 | q->boundary_rq = rq; |
476 | list_add_tail(&rq->queuelist, &q->queue_head); |
477 | } |
478 | EXPORT_SYMBOL(elv_dispatch_add_tail); |
479 | |
480 | int elv_merge(struct request_queue *q, struct request **req, struct bio *bio) |
481 | { |
482 | struct elevator_queue *e = q->elevator; |
483 | struct request *__rq; |
484 | int ret; |
485 | |
486 | /* |
487 | * Levels of merges: |
488 | * nomerges: No merges at all attempted |
489 | * noxmerges: Only simple one-hit cache try |
490 | * merges: All merge tries attempted |
491 | */ |
492 | if (blk_queue_nomerges(q)) |
493 | return ELEVATOR_NO_MERGE; |
494 | |
495 | /* |
496 | * First try one-hit cache. |
497 | */ |
498 | if (q->last_merge) { |
499 | ret = elv_try_merge(q->last_merge, bio); |
500 | if (ret != ELEVATOR_NO_MERGE) { |
501 | *req = q->last_merge; |
502 | return ret; |
503 | } |
504 | } |
505 | |
506 | if (blk_queue_noxmerges(q)) |
507 | return ELEVATOR_NO_MERGE; |
508 | |
509 | /* |
510 | * See if our hash lookup can find a potential backmerge. |
511 | */ |
512 | __rq = elv_rqhash_find(q, bio->bi_sector); |
513 | if (__rq && elv_rq_merge_ok(__rq, bio)) { |
514 | *req = __rq; |
515 | return ELEVATOR_BACK_MERGE; |
516 | } |
517 | |
518 | if (e->ops->elevator_merge_fn) |
519 | return e->ops->elevator_merge_fn(q, req, bio); |
520 | |
521 | return ELEVATOR_NO_MERGE; |
522 | } |
523 | |
524 | /* |
525 | * Attempt to do an insertion back merge. Only check for the case where |
526 | * we can append 'rq' to an existing request, so we can throw 'rq' away |
527 | * afterwards. |
528 | * |
529 | * Returns true if we merged, false otherwise |
530 | */ |
531 | static bool elv_attempt_insert_merge(struct request_queue *q, |
532 | struct request *rq) |
533 | { |
534 | struct request *__rq; |
535 | |
536 | if (blk_queue_nomerges(q)) |
537 | return false; |
538 | |
539 | /* |
540 | * First try one-hit cache. |
541 | */ |
542 | if (q->last_merge && blk_attempt_req_merge(q, q->last_merge, rq)) |
543 | return true; |
544 | |
545 | if (blk_queue_noxmerges(q)) |
546 | return false; |
547 | |
548 | /* |
549 | * See if our hash lookup can find a potential backmerge. |
550 | */ |
551 | __rq = elv_rqhash_find(q, blk_rq_pos(rq)); |
552 | if (__rq && blk_attempt_req_merge(q, __rq, rq)) |
553 | return true; |
554 | |
555 | return false; |
556 | } |
557 | |
558 | void elv_merged_request(struct request_queue *q, struct request *rq, int type) |
559 | { |
560 | struct elevator_queue *e = q->elevator; |
561 | |
562 | if (e->ops->elevator_merged_fn) |
563 | e->ops->elevator_merged_fn(q, rq, type); |
564 | |
565 | if (type == ELEVATOR_BACK_MERGE) |
566 | elv_rqhash_reposition(q, rq); |
567 | |
568 | q->last_merge = rq; |
569 | } |
570 | |
571 | void elv_merge_requests(struct request_queue *q, struct request *rq, |
572 | struct request *next) |
573 | { |
574 | struct elevator_queue *e = q->elevator; |
575 | const int next_sorted = next->cmd_flags & REQ_SORTED; |
576 | |
577 | if (next_sorted && e->ops->elevator_merge_req_fn) |
578 | e->ops->elevator_merge_req_fn(q, rq, next); |
579 | |
580 | elv_rqhash_reposition(q, rq); |
581 | |
582 | if (next_sorted) { |
583 | elv_rqhash_del(q, next); |
584 | q->nr_sorted--; |
585 | } |
586 | |
587 | q->last_merge = rq; |
588 | } |
589 | |
590 | void elv_bio_merged(struct request_queue *q, struct request *rq, |
591 | struct bio *bio) |
592 | { |
593 | struct elevator_queue *e = q->elevator; |
594 | |
595 | if (e->ops->elevator_bio_merged_fn) |
596 | e->ops->elevator_bio_merged_fn(q, rq, bio); |
597 | } |
598 | |
599 | void elv_requeue_request(struct request_queue *q, struct request *rq) |
600 | { |
601 | /* |
602 | * it already went through dequeue, we need to decrement the |
603 | * in_flight count again |
604 | */ |
605 | if (blk_account_rq(rq)) { |
606 | q->in_flight[rq_is_sync(rq)]--; |
607 | if (rq->cmd_flags & REQ_SORTED) |
608 | elv_deactivate_rq(q, rq); |
609 | } |
610 | |
611 | rq->cmd_flags &= ~REQ_STARTED; |
612 | |
613 | __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE); |
614 | } |
615 | |
616 | void elv_drain_elevator(struct request_queue *q) |
617 | { |
618 | static int printed; |
619 | while (q->elevator->ops->elevator_dispatch_fn(q, 1)) |
620 | ; |
621 | if (q->nr_sorted == 0) |
622 | return; |
623 | if (printed++ < 10) { |
624 | printk(KERN_ERR "%s: forced dispatching is broken " |
625 | "(nr_sorted=%u), please report this\n", |
626 | q->elevator->elevator_type->elevator_name, q->nr_sorted); |
627 | } |
628 | } |
629 | |
630 | /* |
631 | * Call with queue lock held, interrupts disabled |
632 | */ |
633 | void elv_quiesce_start(struct request_queue *q) |
634 | { |
635 | if (!q->elevator) |
636 | return; |
637 | |
638 | queue_flag_set(QUEUE_FLAG_ELVSWITCH, q); |
639 | |
640 | /* |
641 | * make sure we don't have any requests in flight |
642 | */ |
643 | elv_drain_elevator(q); |
644 | while (q->rq.elvpriv) { |
645 | __blk_run_queue(q); |
646 | spin_unlock_irq(q->queue_lock); |
647 | msleep(10); |
648 | spin_lock_irq(q->queue_lock); |
649 | elv_drain_elevator(q); |
650 | } |
651 | } |
652 | |
653 | void elv_quiesce_end(struct request_queue *q) |
654 | { |
655 | queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q); |
656 | } |
657 | |
658 | void __elv_add_request(struct request_queue *q, struct request *rq, int where) |
659 | { |
660 | trace_block_rq_insert(q, rq); |
661 | |
662 | rq->q = q; |
663 | |
664 | BUG_ON(rq->cmd_flags & REQ_ON_PLUG); |
665 | |
666 | if (rq->cmd_flags & REQ_SOFTBARRIER) { |
667 | /* barriers are scheduling boundary, update end_sector */ |
668 | if (rq->cmd_type == REQ_TYPE_FS || |
669 | (rq->cmd_flags & REQ_DISCARD)) { |
670 | q->end_sector = rq_end_sector(rq); |
671 | q->boundary_rq = rq; |
672 | } |
673 | } else if (!(rq->cmd_flags & REQ_ELVPRIV) && |
674 | (where == ELEVATOR_INSERT_SORT || |
675 | where == ELEVATOR_INSERT_SORT_MERGE)) |
676 | where = ELEVATOR_INSERT_BACK; |
677 | |
678 | switch (where) { |
679 | case ELEVATOR_INSERT_REQUEUE: |
680 | case ELEVATOR_INSERT_FRONT: |
681 | rq->cmd_flags |= REQ_SOFTBARRIER; |
682 | list_add(&rq->queuelist, &q->queue_head); |
683 | break; |
684 | |
685 | case ELEVATOR_INSERT_BACK: |
686 | rq->cmd_flags |= REQ_SOFTBARRIER; |
687 | elv_drain_elevator(q); |
688 | list_add_tail(&rq->queuelist, &q->queue_head); |
689 | /* |
690 | * We kick the queue here for the following reasons. |
691 | * - The elevator might have returned NULL previously |
692 | * to delay requests and returned them now. As the |
693 | * queue wasn't empty before this request, ll_rw_blk |
694 | * won't run the queue on return, resulting in hang. |
695 | * - Usually, back inserted requests won't be merged |
696 | * with anything. There's no point in delaying queue |
697 | * processing. |
698 | */ |
699 | __blk_run_queue(q); |
700 | break; |
701 | |
702 | case ELEVATOR_INSERT_SORT_MERGE: |
703 | /* |
704 | * If we succeed in merging this request with one in the |
705 | * queue already, we are done - rq has now been freed, |
706 | * so no need to do anything further. |
707 | */ |
708 | if (elv_attempt_insert_merge(q, rq)) |
709 | break; |
710 | case ELEVATOR_INSERT_SORT: |
711 | BUG_ON(rq->cmd_type != REQ_TYPE_FS && |
712 | !(rq->cmd_flags & REQ_DISCARD)); |
713 | rq->cmd_flags |= REQ_SORTED; |
714 | q->nr_sorted++; |
715 | if (rq_mergeable(rq)) { |
716 | elv_rqhash_add(q, rq); |
717 | if (!q->last_merge) |
718 | q->last_merge = rq; |
719 | } |
720 | |
721 | /* |
722 | * Some ioscheds (cfq) run q->request_fn directly, so |
723 | * rq cannot be accessed after calling |
724 | * elevator_add_req_fn. |
725 | */ |
726 | q->elevator->ops->elevator_add_req_fn(q, rq); |
727 | break; |
728 | |
729 | case ELEVATOR_INSERT_FLUSH: |
730 | rq->cmd_flags |= REQ_SOFTBARRIER; |
731 | blk_insert_flush(rq); |
732 | break; |
733 | default: |
734 | printk(KERN_ERR "%s: bad insertion point %d\n", |
735 | __func__, where); |
736 | BUG(); |
737 | } |
738 | } |
739 | EXPORT_SYMBOL(__elv_add_request); |
740 | |
741 | void elv_add_request(struct request_queue *q, struct request *rq, int where) |
742 | { |
743 | unsigned long flags; |
744 | |
745 | spin_lock_irqsave(q->queue_lock, flags); |
746 | __elv_add_request(q, rq, where); |
747 | spin_unlock_irqrestore(q->queue_lock, flags); |
748 | } |
749 | EXPORT_SYMBOL(elv_add_request); |
750 | |
751 | struct request *elv_latter_request(struct request_queue *q, struct request *rq) |
752 | { |
753 | struct elevator_queue *e = q->elevator; |
754 | |
755 | if (e->ops->elevator_latter_req_fn) |
756 | return e->ops->elevator_latter_req_fn(q, rq); |
757 | return NULL; |
758 | } |
759 | |
760 | struct request *elv_former_request(struct request_queue *q, struct request *rq) |
761 | { |
762 | struct elevator_queue *e = q->elevator; |
763 | |
764 | if (e->ops->elevator_former_req_fn) |
765 | return e->ops->elevator_former_req_fn(q, rq); |
766 | return NULL; |
767 | } |
768 | |
769 | int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) |
770 | { |
771 | struct elevator_queue *e = q->elevator; |
772 | |
773 | if (e->ops->elevator_set_req_fn) |
774 | return e->ops->elevator_set_req_fn(q, rq, gfp_mask); |
775 | |
776 | rq->elevator_private[0] = NULL; |
777 | return 0; |
778 | } |
779 | |
780 | void elv_put_request(struct request_queue *q, struct request *rq) |
781 | { |
782 | struct elevator_queue *e = q->elevator; |
783 | |
784 | if (e->ops->elevator_put_req_fn) |
785 | e->ops->elevator_put_req_fn(rq); |
786 | } |
787 | |
788 | int elv_may_queue(struct request_queue *q, int rw) |
789 | { |
790 | struct elevator_queue *e = q->elevator; |
791 | |
792 | if (e->ops->elevator_may_queue_fn) |
793 | return e->ops->elevator_may_queue_fn(q, rw); |
794 | |
795 | return ELV_MQUEUE_MAY; |
796 | } |
797 | |
798 | void elv_abort_queue(struct request_queue *q) |
799 | { |
800 | struct request *rq; |
801 | |
802 | blk_abort_flushes(q); |
803 | |
804 | while (!list_empty(&q->queue_head)) { |
805 | rq = list_entry_rq(q->queue_head.next); |
806 | rq->cmd_flags |= REQ_QUIET; |
807 | trace_block_rq_abort(q, rq); |
808 | /* |
809 | * Mark this request as started so we don't trigger |
810 | * any debug logic in the end I/O path. |
811 | */ |
812 | blk_start_request(rq); |
813 | __blk_end_request_all(rq, -EIO); |
814 | } |
815 | } |
816 | EXPORT_SYMBOL(elv_abort_queue); |
817 | |
818 | void elv_completed_request(struct request_queue *q, struct request *rq) |
819 | { |
820 | struct elevator_queue *e = q->elevator; |
821 | |
822 | /* |
823 | * request is released from the driver, io must be done |
824 | */ |
825 | if (blk_account_rq(rq)) { |
826 | q->in_flight[rq_is_sync(rq)]--; |
827 | if ((rq->cmd_flags & REQ_SORTED) && |
828 | e->ops->elevator_completed_req_fn) |
829 | e->ops->elevator_completed_req_fn(q, rq); |
830 | } |
831 | } |
832 | |
833 | #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr) |
834 | |
835 | static ssize_t |
836 | elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page) |
837 | { |
838 | struct elv_fs_entry *entry = to_elv(attr); |
839 | struct elevator_queue *e; |
840 | ssize_t error; |
841 | |
842 | if (!entry->show) |
843 | return -EIO; |
844 | |
845 | e = container_of(kobj, struct elevator_queue, kobj); |
846 | mutex_lock(&e->sysfs_lock); |
847 | error = e->ops ? entry->show(e, page) : -ENOENT; |
848 | mutex_unlock(&e->sysfs_lock); |
849 | return error; |
850 | } |
851 | |
852 | static ssize_t |
853 | elv_attr_store(struct kobject *kobj, struct attribute *attr, |
854 | const char *page, size_t length) |
855 | { |
856 | struct elv_fs_entry *entry = to_elv(attr); |
857 | struct elevator_queue *e; |
858 | ssize_t error; |
859 | |
860 | if (!entry->store) |
861 | return -EIO; |
862 | |
863 | e = container_of(kobj, struct elevator_queue, kobj); |
864 | mutex_lock(&e->sysfs_lock); |
865 | error = e->ops ? entry->store(e, page, length) : -ENOENT; |
866 | mutex_unlock(&e->sysfs_lock); |
867 | return error; |
868 | } |
869 | |
870 | static const struct sysfs_ops elv_sysfs_ops = { |
871 | .show = elv_attr_show, |
872 | .store = elv_attr_store, |
873 | }; |
874 | |
875 | static struct kobj_type elv_ktype = { |
876 | .sysfs_ops = &elv_sysfs_ops, |
877 | .release = elevator_release, |
878 | }; |
879 | |
880 | int elv_register_queue(struct request_queue *q) |
881 | { |
882 | struct elevator_queue *e = q->elevator; |
883 | int error; |
884 | |
885 | error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched"); |
886 | if (!error) { |
887 | struct elv_fs_entry *attr = e->elevator_type->elevator_attrs; |
888 | if (attr) { |
889 | while (attr->attr.name) { |
890 | if (sysfs_create_file(&e->kobj, &attr->attr)) |
891 | break; |
892 | attr++; |
893 | } |
894 | } |
895 | kobject_uevent(&e->kobj, KOBJ_ADD); |
896 | e->registered = 1; |
897 | } |
898 | return error; |
899 | } |
900 | EXPORT_SYMBOL(elv_register_queue); |
901 | |
902 | static void __elv_unregister_queue(struct elevator_queue *e) |
903 | { |
904 | kobject_uevent(&e->kobj, KOBJ_REMOVE); |
905 | kobject_del(&e->kobj); |
906 | e->registered = 0; |
907 | } |
908 | |
909 | void elv_unregister_queue(struct request_queue *q) |
910 | { |
911 | if (q) |
912 | __elv_unregister_queue(q->elevator); |
913 | } |
914 | EXPORT_SYMBOL(elv_unregister_queue); |
915 | |
916 | void elv_register(struct elevator_type *e) |
917 | { |
918 | char *def = ""; |
919 | |
920 | spin_lock(&elv_list_lock); |
921 | BUG_ON(elevator_find(e->elevator_name)); |
922 | list_add_tail(&e->list, &elv_list); |
923 | spin_unlock(&elv_list_lock); |
924 | |
925 | if (!strcmp(e->elevator_name, chosen_elevator) || |
926 | (!*chosen_elevator && |
927 | !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED))) |
928 | def = " (default)"; |
929 | |
930 | printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name, |
931 | def); |
932 | } |
933 | EXPORT_SYMBOL_GPL(elv_register); |
934 | |
935 | void elv_unregister(struct elevator_type *e) |
936 | { |
937 | struct task_struct *g, *p; |
938 | |
939 | /* |
940 | * Iterate every thread in the process to remove the io contexts. |
941 | */ |
942 | if (e->ops.trim) { |
943 | read_lock(&tasklist_lock); |
944 | do_each_thread(g, p) { |
945 | task_lock(p); |
946 | if (p->io_context) |
947 | e->ops.trim(p->io_context); |
948 | task_unlock(p); |
949 | } while_each_thread(g, p); |
950 | read_unlock(&tasklist_lock); |
951 | } |
952 | |
953 | spin_lock(&elv_list_lock); |
954 | list_del_init(&e->list); |
955 | spin_unlock(&elv_list_lock); |
956 | } |
957 | EXPORT_SYMBOL_GPL(elv_unregister); |
958 | |
959 | /* |
960 | * switch to new_e io scheduler. be careful not to introduce deadlocks - |
961 | * we don't free the old io scheduler, before we have allocated what we |
962 | * need for the new one. this way we have a chance of going back to the old |
963 | * one, if the new one fails init for some reason. |
964 | */ |
965 | static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) |
966 | { |
967 | struct elevator_queue *old_elevator, *e; |
968 | void *data; |
969 | int err; |
970 | |
971 | /* |
972 | * Allocate new elevator |
973 | */ |
974 | e = elevator_alloc(q, new_e); |
975 | if (!e) |
976 | return -ENOMEM; |
977 | |
978 | data = elevator_init_queue(q, e); |
979 | if (!data) { |
980 | kobject_put(&e->kobj); |
981 | return -ENOMEM; |
982 | } |
983 | |
984 | /* |
985 | * Turn on BYPASS and drain all requests w/ elevator private data |
986 | */ |
987 | spin_lock_irq(q->queue_lock); |
988 | elv_quiesce_start(q); |
989 | |
990 | /* |
991 | * Remember old elevator. |
992 | */ |
993 | old_elevator = q->elevator; |
994 | |
995 | /* |
996 | * attach and start new elevator |
997 | */ |
998 | elevator_attach(q, e, data); |
999 | |
1000 | spin_unlock_irq(q->queue_lock); |
1001 | |
1002 | if (old_elevator->registered) { |
1003 | __elv_unregister_queue(old_elevator); |
1004 | |
1005 | err = elv_register_queue(q); |
1006 | if (err) |
1007 | goto fail_register; |
1008 | } |
1009 | |
1010 | /* |
1011 | * finally exit old elevator and turn off BYPASS. |
1012 | */ |
1013 | elevator_exit(old_elevator); |
1014 | spin_lock_irq(q->queue_lock); |
1015 | elv_quiesce_end(q); |
1016 | spin_unlock_irq(q->queue_lock); |
1017 | |
1018 | blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name); |
1019 | |
1020 | return 0; |
1021 | |
1022 | fail_register: |
1023 | /* |
1024 | * switch failed, exit the new io scheduler and reattach the old |
1025 | * one again (along with re-adding the sysfs dir) |
1026 | */ |
1027 | elevator_exit(e); |
1028 | q->elevator = old_elevator; |
1029 | elv_register_queue(q); |
1030 | |
1031 | spin_lock_irq(q->queue_lock); |
1032 | queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q); |
1033 | spin_unlock_irq(q->queue_lock); |
1034 | |
1035 | return err; |
1036 | } |
1037 | |
1038 | /* |
1039 | * Switch this queue to the given IO scheduler. |
1040 | */ |
1041 | int elevator_change(struct request_queue *q, const char *name) |
1042 | { |
1043 | char elevator_name[ELV_NAME_MAX]; |
1044 | struct elevator_type *e; |
1045 | |
1046 | if (!q->elevator) |
1047 | return -ENXIO; |
1048 | |
1049 | strlcpy(elevator_name, name, sizeof(elevator_name)); |
1050 | e = elevator_get(strstrip(elevator_name)); |
1051 | if (!e) { |
1052 | printk(KERN_ERR "elevator: type %s not found\n", elevator_name); |
1053 | return -EINVAL; |
1054 | } |
1055 | |
1056 | if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) { |
1057 | elevator_put(e); |
1058 | return 0; |
1059 | } |
1060 | |
1061 | return elevator_switch(q, e); |
1062 | } |
1063 | EXPORT_SYMBOL(elevator_change); |
1064 | |
1065 | ssize_t elv_iosched_store(struct request_queue *q, const char *name, |
1066 | size_t count) |
1067 | { |
1068 | int ret; |
1069 | |
1070 | if (!q->elevator) |
1071 | return count; |
1072 | |
1073 | ret = elevator_change(q, name); |
1074 | if (!ret) |
1075 | return count; |
1076 | |
1077 | printk(KERN_ERR "elevator: switch to %s failed\n", name); |
1078 | return ret; |
1079 | } |
1080 | |
1081 | ssize_t elv_iosched_show(struct request_queue *q, char *name) |
1082 | { |
1083 | struct elevator_queue *e = q->elevator; |
1084 | struct elevator_type *elv; |
1085 | struct elevator_type *__e; |
1086 | int len = 0; |
1087 | |
1088 | if (!q->elevator || !blk_queue_stackable(q)) |
1089 | return sprintf(name, "none\n"); |
1090 | |
1091 | elv = e->elevator_type; |
1092 | |
1093 | spin_lock(&elv_list_lock); |
1094 | list_for_each_entry(__e, &elv_list, list) { |
1095 | if (!strcmp(elv->elevator_name, __e->elevator_name)) |
1096 | len += sprintf(name+len, "[%s] ", elv->elevator_name); |
1097 | else |
1098 | len += sprintf(name+len, "%s ", __e->elevator_name); |
1099 | } |
1100 | spin_unlock(&elv_list_lock); |
1101 | |
1102 | len += sprintf(len+name, "\n"); |
1103 | return len; |
1104 | } |
1105 | |
1106 | struct request *elv_rb_former_request(struct request_queue *q, |
1107 | struct request *rq) |
1108 | { |
1109 | struct rb_node *rbprev = rb_prev(&rq->rb_node); |
1110 | |
1111 | if (rbprev) |
1112 | return rb_entry_rq(rbprev); |
1113 | |
1114 | return NULL; |
1115 | } |
1116 | EXPORT_SYMBOL(elv_rb_former_request); |
1117 | |
1118 | struct request *elv_rb_latter_request(struct request_queue *q, |
1119 | struct request *rq) |
1120 | { |
1121 | struct rb_node *rbnext = rb_next(&rq->rb_node); |
1122 | |
1123 | if (rbnext) |
1124 | return rb_entry_rq(rbnext); |
1125 | |
1126 | return NULL; |
1127 | } |
1128 | EXPORT_SYMBOL(elv_rb_latter_request); |
1129 |
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