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