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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 | ||
38 | #include <asm/uaccess.h> | |
39 | ||
40 | static DEFINE_SPINLOCK(elv_list_lock); | |
41 | static LIST_HEAD(elv_list); | |
42 | ||
43 | /* | |
44 | * Merge hash stuff. | |
45 | */ | |
46 | static const int elv_hash_shift = 6; | |
47 | #define ELV_HASH_BLOCK(sec) ((sec) >> 3) | |
48 | #define ELV_HASH_FN(sec) \ | |
49 | (hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift)) | |
50 | #define ELV_HASH_ENTRIES (1 << elv_hash_shift) | |
51 | #define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors) | |
52 | #define ELV_ON_HASH(rq) (!hlist_unhashed(&(rq)->hash)) | |
53 | ||
54 | /* | |
55 | * Query io scheduler to see if the current process issuing bio may be | |
56 | * merged with rq. | |
57 | */ | |
58 | static int elv_iosched_allow_merge(struct request *rq, struct bio *bio) | |
59 | { | |
60 | struct request_queue *q = rq->q; | |
61 | elevator_t *e = q->elevator; | |
62 | ||
63 | if (e->ops->elevator_allow_merge_fn) | |
64 | return e->ops->elevator_allow_merge_fn(q, rq, bio); | |
65 | ||
66 | return 1; | |
67 | } | |
68 | ||
69 | /* | |
70 | * can we safely merge with this request? | |
71 | */ | |
72 | int elv_rq_merge_ok(struct request *rq, struct bio *bio) | |
73 | { | |
74 | if (!rq_mergeable(rq)) | |
75 | return 0; | |
76 | ||
77 | /* | |
78 | * Don't merge file system requests and discard requests | |
79 | */ | |
80 | if (bio_discard(bio) != bio_discard(rq->bio)) | |
81 | return 0; | |
82 | ||
83 | /* | |
84 | * different data direction or already started, don't merge | |
85 | */ | |
86 | if (bio_data_dir(bio) != rq_data_dir(rq)) | |
87 | return 0; | |
88 | ||
89 | /* | |
90 | * must be same device and not a special request | |
91 | */ | |
92 | if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special) | |
93 | return 0; | |
94 | ||
95 | /* | |
96 | * only merge integrity protected bio into ditto rq | |
97 | */ | |
98 | if (bio_integrity(bio) != blk_integrity_rq(rq)) | |
99 | return 0; | |
100 | ||
101 | if (!elv_iosched_allow_merge(rq, bio)) | |
102 | return 0; | |
103 | ||
104 | return 1; | |
105 | } | |
106 | EXPORT_SYMBOL(elv_rq_merge_ok); | |
107 | ||
108 | static inline int elv_try_merge(struct request *__rq, struct bio *bio) | |
109 | { | |
110 | int ret = ELEVATOR_NO_MERGE; | |
111 | ||
112 | /* | |
113 | * we can merge and sequence is ok, check if it's possible | |
114 | */ | |
115 | if (elv_rq_merge_ok(__rq, bio)) { | |
116 | if (__rq->sector + __rq->nr_sectors == bio->bi_sector) | |
117 | ret = ELEVATOR_BACK_MERGE; | |
118 | else if (__rq->sector - bio_sectors(bio) == bio->bi_sector) | |
119 | ret = ELEVATOR_FRONT_MERGE; | |
120 | } | |
121 | ||
122 | return ret; | |
123 | } | |
124 | ||
125 | static struct elevator_type *elevator_find(const char *name) | |
126 | { | |
127 | struct elevator_type *e; | |
128 | ||
129 | list_for_each_entry(e, &elv_list, list) { | |
130 | if (!strcmp(e->elevator_name, name)) | |
131 | return e; | |
132 | } | |
133 | ||
134 | return NULL; | |
135 | } | |
136 | ||
137 | static void elevator_put(struct elevator_type *e) | |
138 | { | |
139 | module_put(e->elevator_owner); | |
140 | } | |
141 | ||
142 | static struct elevator_type *elevator_get(const char *name) | |
143 | { | |
144 | struct elevator_type *e; | |
145 | ||
146 | spin_lock(&elv_list_lock); | |
147 | ||
148 | e = elevator_find(name); | |
149 | if (!e) { | |
150 | char elv[ELV_NAME_MAX + strlen("-iosched")]; | |
151 | ||
152 | spin_unlock(&elv_list_lock); | |
153 | ||
154 | if (!strcmp(name, "anticipatory")) | |
155 | sprintf(elv, "as-iosched"); | |
156 | else | |
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 | if (!strcmp(str, "as")) | |
194 | strcpy(chosen_elevator, "anticipatory"); | |
195 | else | |
196 | strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1); | |
197 | return 1; | |
198 | } | |
199 | ||
200 | __setup("elevator=", elevator_setup); | |
201 | ||
202 | static struct kobj_type elv_ktype; | |
203 | ||
204 | static elevator_t *elevator_alloc(struct request_queue *q, | |
205 | struct elevator_type *e) | |
206 | { | |
207 | elevator_t *eq; | |
208 | int i; | |
209 | ||
210 | eq = kmalloc_node(sizeof(elevator_t), GFP_KERNEL | __GFP_ZERO, q->node); | |
211 | if (unlikely(!eq)) | |
212 | goto err; | |
213 | ||
214 | eq->ops = &e->ops; | |
215 | eq->elevator_type = e; | |
216 | kobject_init(&eq->kobj, &elv_ktype); | |
217 | mutex_init(&eq->sysfs_lock); | |
218 | ||
219 | eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES, | |
220 | GFP_KERNEL, q->node); | |
221 | if (!eq->hash) | |
222 | goto err; | |
223 | ||
224 | for (i = 0; i < ELV_HASH_ENTRIES; i++) | |
225 | INIT_HLIST_HEAD(&eq->hash[i]); | |
226 | ||
227 | return eq; | |
228 | err: | |
229 | kfree(eq); | |
230 | elevator_put(e); | |
231 | return NULL; | |
232 | } | |
233 | ||
234 | static void elevator_release(struct kobject *kobj) | |
235 | { | |
236 | elevator_t *e = container_of(kobj, elevator_t, kobj); | |
237 | ||
238 | elevator_put(e->elevator_type); | |
239 | kfree(e->hash); | |
240 | kfree(e); | |
241 | } | |
242 | ||
243 | int elevator_init(struct request_queue *q, char *name) | |
244 | { | |
245 | struct elevator_type *e = NULL; | |
246 | struct elevator_queue *eq; | |
247 | int ret = 0; | |
248 | void *data; | |
249 | ||
250 | INIT_LIST_HEAD(&q->queue_head); | |
251 | q->last_merge = NULL; | |
252 | q->end_sector = 0; | |
253 | q->boundary_rq = NULL; | |
254 | ||
255 | if (name) { | |
256 | e = elevator_get(name); | |
257 | if (!e) | |
258 | return -EINVAL; | |
259 | } | |
260 | ||
261 | if (!e && *chosen_elevator) { | |
262 | e = elevator_get(chosen_elevator); | |
263 | if (!e) | |
264 | printk(KERN_ERR "I/O scheduler %s not found\n", | |
265 | chosen_elevator); | |
266 | } | |
267 | ||
268 | if (!e) { | |
269 | e = elevator_get(CONFIG_DEFAULT_IOSCHED); | |
270 | if (!e) { | |
271 | printk(KERN_ERR | |
272 | "Default I/O scheduler not found. " \ | |
273 | "Using noop.\n"); | |
274 | e = elevator_get("noop"); | |
275 | } | |
276 | } | |
277 | ||
278 | eq = elevator_alloc(q, e); | |
279 | if (!eq) | |
280 | return -ENOMEM; | |
281 | ||
282 | data = elevator_init_queue(q, eq); | |
283 | if (!data) { | |
284 | kobject_put(&eq->kobj); | |
285 | return -ENOMEM; | |
286 | } | |
287 | ||
288 | elevator_attach(q, eq, data); | |
289 | return ret; | |
290 | } | |
291 | EXPORT_SYMBOL(elevator_init); | |
292 | ||
293 | void elevator_exit(elevator_t *e) | |
294 | { | |
295 | mutex_lock(&e->sysfs_lock); | |
296 | if (e->ops->elevator_exit_fn) | |
297 | e->ops->elevator_exit_fn(e); | |
298 | e->ops = NULL; | |
299 | mutex_unlock(&e->sysfs_lock); | |
300 | ||
301 | kobject_put(&e->kobj); | |
302 | } | |
303 | EXPORT_SYMBOL(elevator_exit); | |
304 | ||
305 | static void elv_activate_rq(struct request_queue *q, struct request *rq) | |
306 | { | |
307 | elevator_t *e = q->elevator; | |
308 | ||
309 | if (e->ops->elevator_activate_req_fn) | |
310 | e->ops->elevator_activate_req_fn(q, rq); | |
311 | } | |
312 | ||
313 | static void elv_deactivate_rq(struct request_queue *q, struct request *rq) | |
314 | { | |
315 | elevator_t *e = q->elevator; | |
316 | ||
317 | if (e->ops->elevator_deactivate_req_fn) | |
318 | e->ops->elevator_deactivate_req_fn(q, rq); | |
319 | } | |
320 | ||
321 | static inline void __elv_rqhash_del(struct request *rq) | |
322 | { | |
323 | hlist_del_init(&rq->hash); | |
324 | } | |
325 | ||
326 | static void elv_rqhash_del(struct request_queue *q, struct request *rq) | |
327 | { | |
328 | if (ELV_ON_HASH(rq)) | |
329 | __elv_rqhash_del(rq); | |
330 | } | |
331 | ||
332 | static void elv_rqhash_add(struct request_queue *q, struct request *rq) | |
333 | { | |
334 | elevator_t *e = q->elevator; | |
335 | ||
336 | BUG_ON(ELV_ON_HASH(rq)); | |
337 | hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]); | |
338 | } | |
339 | ||
340 | static void elv_rqhash_reposition(struct request_queue *q, struct request *rq) | |
341 | { | |
342 | __elv_rqhash_del(rq); | |
343 | elv_rqhash_add(q, rq); | |
344 | } | |
345 | ||
346 | static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset) | |
347 | { | |
348 | elevator_t *e = q->elevator; | |
349 | struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)]; | |
350 | struct hlist_node *entry, *next; | |
351 | struct request *rq; | |
352 | ||
353 | hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) { | |
354 | BUG_ON(!ELV_ON_HASH(rq)); | |
355 | ||
356 | if (unlikely(!rq_mergeable(rq))) { | |
357 | __elv_rqhash_del(rq); | |
358 | continue; | |
359 | } | |
360 | ||
361 | if (rq_hash_key(rq) == offset) | |
362 | return rq; | |
363 | } | |
364 | ||
365 | return NULL; | |
366 | } | |
367 | ||
368 | /* | |
369 | * RB-tree support functions for inserting/lookup/removal of requests | |
370 | * in a sorted RB tree. | |
371 | */ | |
372 | struct request *elv_rb_add(struct rb_root *root, struct request *rq) | |
373 | { | |
374 | struct rb_node **p = &root->rb_node; | |
375 | struct rb_node *parent = NULL; | |
376 | struct request *__rq; | |
377 | ||
378 | while (*p) { | |
379 | parent = *p; | |
380 | __rq = rb_entry(parent, struct request, rb_node); | |
381 | ||
382 | if (rq->sector < __rq->sector) | |
383 | p = &(*p)->rb_left; | |
384 | else if (rq->sector > __rq->sector) | |
385 | p = &(*p)->rb_right; | |
386 | else | |
387 | return __rq; | |
388 | } | |
389 | ||
390 | rb_link_node(&rq->rb_node, parent, p); | |
391 | rb_insert_color(&rq->rb_node, root); | |
392 | return NULL; | |
393 | } | |
394 | EXPORT_SYMBOL(elv_rb_add); | |
395 | ||
396 | void elv_rb_del(struct rb_root *root, struct request *rq) | |
397 | { | |
398 | BUG_ON(RB_EMPTY_NODE(&rq->rb_node)); | |
399 | rb_erase(&rq->rb_node, root); | |
400 | RB_CLEAR_NODE(&rq->rb_node); | |
401 | } | |
402 | EXPORT_SYMBOL(elv_rb_del); | |
403 | ||
404 | struct request *elv_rb_find(struct rb_root *root, sector_t sector) | |
405 | { | |
406 | struct rb_node *n = root->rb_node; | |
407 | struct request *rq; | |
408 | ||
409 | while (n) { | |
410 | rq = rb_entry(n, struct request, rb_node); | |
411 | ||
412 | if (sector < rq->sector) | |
413 | n = n->rb_left; | |
414 | else if (sector > rq->sector) | |
415 | n = n->rb_right; | |
416 | else | |
417 | return rq; | |
418 | } | |
419 | ||
420 | return NULL; | |
421 | } | |
422 | EXPORT_SYMBOL(elv_rb_find); | |
423 | ||
424 | /* | |
425 | * Insert rq into dispatch queue of q. Queue lock must be held on | |
426 | * entry. rq is sort instead into the dispatch queue. To be used by | |
427 | * specific elevators. | |
428 | */ | |
429 | void elv_dispatch_sort(struct request_queue *q, struct request *rq) | |
430 | { | |
431 | sector_t boundary; | |
432 | struct list_head *entry; | |
433 | int stop_flags; | |
434 | ||
435 | if (q->last_merge == rq) | |
436 | q->last_merge = NULL; | |
437 | ||
438 | elv_rqhash_del(q, rq); | |
439 | ||
440 | q->nr_sorted--; | |
441 | ||
442 | boundary = q->end_sector; | |
443 | stop_flags = REQ_SOFTBARRIER | REQ_HARDBARRIER | REQ_STARTED; | |
444 | list_for_each_prev(entry, &q->queue_head) { | |
445 | struct request *pos = list_entry_rq(entry); | |
446 | ||
447 | if (blk_discard_rq(rq) != blk_discard_rq(pos)) | |
448 | break; | |
449 | if (rq_data_dir(rq) != rq_data_dir(pos)) | |
450 | break; | |
451 | if (pos->cmd_flags & stop_flags) | |
452 | break; | |
453 | if (rq->sector >= boundary) { | |
454 | if (pos->sector < boundary) | |
455 | continue; | |
456 | } else { | |
457 | if (pos->sector >= boundary) | |
458 | break; | |
459 | } | |
460 | if (rq->sector >= pos->sector) | |
461 | break; | |
462 | } | |
463 | ||
464 | list_add(&rq->queuelist, entry); | |
465 | } | |
466 | EXPORT_SYMBOL(elv_dispatch_sort); | |
467 | ||
468 | /* | |
469 | * Insert rq into dispatch queue of q. Queue lock must be held on | |
470 | * entry. rq is added to the back of the dispatch queue. To be used by | |
471 | * specific elevators. | |
472 | */ | |
473 | void elv_dispatch_add_tail(struct request_queue *q, struct request *rq) | |
474 | { | |
475 | if (q->last_merge == rq) | |
476 | q->last_merge = NULL; | |
477 | ||
478 | elv_rqhash_del(q, rq); | |
479 | ||
480 | q->nr_sorted--; | |
481 | ||
482 | q->end_sector = rq_end_sector(rq); | |
483 | q->boundary_rq = rq; | |
484 | list_add_tail(&rq->queuelist, &q->queue_head); | |
485 | } | |
486 | EXPORT_SYMBOL(elv_dispatch_add_tail); | |
487 | ||
488 | int elv_merge(struct request_queue *q, struct request **req, struct bio *bio) | |
489 | { | |
490 | elevator_t *e = q->elevator; | |
491 | struct request *__rq; | |
492 | int ret; | |
493 | ||
494 | /* | |
495 | * First try one-hit cache. | |
496 | */ | |
497 | if (q->last_merge) { | |
498 | ret = elv_try_merge(q->last_merge, bio); | |
499 | if (ret != ELEVATOR_NO_MERGE) { | |
500 | *req = q->last_merge; | |
501 | return ret; | |
502 | } | |
503 | } | |
504 | ||
505 | if (blk_queue_nomerges(q)) | |
506 | return ELEVATOR_NO_MERGE; | |
507 | ||
508 | /* | |
509 | * See if our hash lookup can find a potential backmerge. | |
510 | */ | |
511 | __rq = elv_rqhash_find(q, bio->bi_sector); | |
512 | if (__rq && elv_rq_merge_ok(__rq, bio)) { | |
513 | *req = __rq; | |
514 | return ELEVATOR_BACK_MERGE; | |
515 | } | |
516 | ||
517 | if (e->ops->elevator_merge_fn) | |
518 | return e->ops->elevator_merge_fn(q, req, bio); | |
519 | ||
520 | return ELEVATOR_NO_MERGE; | |
521 | } | |
522 | ||
523 | void elv_merged_request(struct request_queue *q, struct request *rq, int type) | |
524 | { | |
525 | elevator_t *e = q->elevator; | |
526 | ||
527 | if (e->ops->elevator_merged_fn) | |
528 | e->ops->elevator_merged_fn(q, rq, type); | |
529 | ||
530 | if (type == ELEVATOR_BACK_MERGE) | |
531 | elv_rqhash_reposition(q, rq); | |
532 | ||
533 | q->last_merge = rq; | |
534 | } | |
535 | ||
536 | void elv_merge_requests(struct request_queue *q, struct request *rq, | |
537 | struct request *next) | |
538 | { | |
539 | elevator_t *e = q->elevator; | |
540 | ||
541 | if (e->ops->elevator_merge_req_fn) | |
542 | e->ops->elevator_merge_req_fn(q, rq, next); | |
543 | ||
544 | elv_rqhash_reposition(q, rq); | |
545 | elv_rqhash_del(q, next); | |
546 | ||
547 | q->nr_sorted--; | |
548 | q->last_merge = rq; | |
549 | } | |
550 | ||
551 | void elv_requeue_request(struct request_queue *q, struct request *rq) | |
552 | { | |
553 | /* | |
554 | * it already went through dequeue, we need to decrement the | |
555 | * in_flight count again | |
556 | */ | |
557 | if (blk_account_rq(rq)) { | |
558 | q->in_flight--; | |
559 | if (blk_sorted_rq(rq)) | |
560 | elv_deactivate_rq(q, rq); | |
561 | } | |
562 | ||
563 | rq->cmd_flags &= ~REQ_STARTED; | |
564 | ||
565 | elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE); | |
566 | } | |
567 | ||
568 | static void elv_drain_elevator(struct request_queue *q) | |
569 | { | |
570 | static int printed; | |
571 | while (q->elevator->ops->elevator_dispatch_fn(q, 1)) | |
572 | ; | |
573 | if (q->nr_sorted == 0) | |
574 | return; | |
575 | if (printed++ < 10) { | |
576 | printk(KERN_ERR "%s: forced dispatching is broken " | |
577 | "(nr_sorted=%u), please report this\n", | |
578 | q->elevator->elevator_type->elevator_name, q->nr_sorted); | |
579 | } | |
580 | } | |
581 | ||
582 | void elv_insert(struct request_queue *q, struct request *rq, int where) | |
583 | { | |
584 | struct list_head *pos; | |
585 | unsigned ordseq; | |
586 | int unplug_it = 1; | |
587 | ||
588 | blk_add_trace_rq(q, rq, BLK_TA_INSERT); | |
589 | ||
590 | rq->q = q; | |
591 | ||
592 | switch (where) { | |
593 | case ELEVATOR_INSERT_FRONT: | |
594 | rq->cmd_flags |= REQ_SOFTBARRIER; | |
595 | ||
596 | list_add(&rq->queuelist, &q->queue_head); | |
597 | break; | |
598 | ||
599 | case ELEVATOR_INSERT_BACK: | |
600 | rq->cmd_flags |= REQ_SOFTBARRIER; | |
601 | elv_drain_elevator(q); | |
602 | list_add_tail(&rq->queuelist, &q->queue_head); | |
603 | /* | |
604 | * We kick the queue here for the following reasons. | |
605 | * - The elevator might have returned NULL previously | |
606 | * to delay requests and returned them now. As the | |
607 | * queue wasn't empty before this request, ll_rw_blk | |
608 | * won't run the queue on return, resulting in hang. | |
609 | * - Usually, back inserted requests won't be merged | |
610 | * with anything. There's no point in delaying queue | |
611 | * processing. | |
612 | */ | |
613 | blk_remove_plug(q); | |
614 | q->request_fn(q); | |
615 | break; | |
616 | ||
617 | case ELEVATOR_INSERT_SORT: | |
618 | BUG_ON(!blk_fs_request(rq) && !blk_discard_rq(rq)); | |
619 | rq->cmd_flags |= REQ_SORTED; | |
620 | q->nr_sorted++; | |
621 | if (rq_mergeable(rq)) { | |
622 | elv_rqhash_add(q, rq); | |
623 | if (!q->last_merge) | |
624 | q->last_merge = rq; | |
625 | } | |
626 | ||
627 | /* | |
628 | * Some ioscheds (cfq) run q->request_fn directly, so | |
629 | * rq cannot be accessed after calling | |
630 | * elevator_add_req_fn. | |
631 | */ | |
632 | q->elevator->ops->elevator_add_req_fn(q, rq); | |
633 | break; | |
634 | ||
635 | case ELEVATOR_INSERT_REQUEUE: | |
636 | /* | |
637 | * If ordered flush isn't in progress, we do front | |
638 | * insertion; otherwise, requests should be requeued | |
639 | * in ordseq order. | |
640 | */ | |
641 | rq->cmd_flags |= REQ_SOFTBARRIER; | |
642 | ||
643 | /* | |
644 | * Most requeues happen because of a busy condition, | |
645 | * don't force unplug of the queue for that case. | |
646 | */ | |
647 | unplug_it = 0; | |
648 | ||
649 | if (q->ordseq == 0) { | |
650 | list_add(&rq->queuelist, &q->queue_head); | |
651 | break; | |
652 | } | |
653 | ||
654 | ordseq = blk_ordered_req_seq(rq); | |
655 | ||
656 | list_for_each(pos, &q->queue_head) { | |
657 | struct request *pos_rq = list_entry_rq(pos); | |
658 | if (ordseq <= blk_ordered_req_seq(pos_rq)) | |
659 | break; | |
660 | } | |
661 | ||
662 | list_add_tail(&rq->queuelist, pos); | |
663 | break; | |
664 | ||
665 | default: | |
666 | printk(KERN_ERR "%s: bad insertion point %d\n", | |
667 | __func__, where); | |
668 | BUG(); | |
669 | } | |
670 | ||
671 | if (unplug_it && blk_queue_plugged(q)) { | |
672 | int nrq = q->rq.count[READ] + q->rq.count[WRITE] | |
673 | - q->in_flight; | |
674 | ||
675 | if (nrq >= q->unplug_thresh) | |
676 | __generic_unplug_device(q); | |
677 | } | |
678 | } | |
679 | ||
680 | void __elv_add_request(struct request_queue *q, struct request *rq, int where, | |
681 | int plug) | |
682 | { | |
683 | if (q->ordcolor) | |
684 | rq->cmd_flags |= REQ_ORDERED_COLOR; | |
685 | ||
686 | if (rq->cmd_flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) { | |
687 | /* | |
688 | * toggle ordered color | |
689 | */ | |
690 | if (blk_barrier_rq(rq)) | |
691 | q->ordcolor ^= 1; | |
692 | ||
693 | /* | |
694 | * barriers implicitly indicate back insertion | |
695 | */ | |
696 | if (where == ELEVATOR_INSERT_SORT) | |
697 | where = ELEVATOR_INSERT_BACK; | |
698 | ||
699 | /* | |
700 | * this request is scheduling boundary, update | |
701 | * end_sector | |
702 | */ | |
703 | if (blk_fs_request(rq) || blk_discard_rq(rq)) { | |
704 | q->end_sector = rq_end_sector(rq); | |
705 | q->boundary_rq = rq; | |
706 | } | |
707 | } else if (!(rq->cmd_flags & REQ_ELVPRIV) && | |
708 | where == ELEVATOR_INSERT_SORT) | |
709 | where = ELEVATOR_INSERT_BACK; | |
710 | ||
711 | if (plug) | |
712 | blk_plug_device(q); | |
713 | ||
714 | elv_insert(q, rq, where); | |
715 | } | |
716 | EXPORT_SYMBOL(__elv_add_request); | |
717 | ||
718 | void elv_add_request(struct request_queue *q, struct request *rq, int where, | |
719 | int plug) | |
720 | { | |
721 | unsigned long flags; | |
722 | ||
723 | spin_lock_irqsave(q->queue_lock, flags); | |
724 | __elv_add_request(q, rq, where, plug); | |
725 | spin_unlock_irqrestore(q->queue_lock, flags); | |
726 | } | |
727 | EXPORT_SYMBOL(elv_add_request); | |
728 | ||
729 | static inline struct request *__elv_next_request(struct request_queue *q) | |
730 | { | |
731 | struct request *rq; | |
732 | ||
733 | while (1) { | |
734 | while (!list_empty(&q->queue_head)) { | |
735 | rq = list_entry_rq(q->queue_head.next); | |
736 | if (blk_do_ordered(q, &rq)) | |
737 | return rq; | |
738 | } | |
739 | ||
740 | if (!q->elevator->ops->elevator_dispatch_fn(q, 0)) | |
741 | return NULL; | |
742 | } | |
743 | } | |
744 | ||
745 | struct request *elv_next_request(struct request_queue *q) | |
746 | { | |
747 | struct request *rq; | |
748 | int ret; | |
749 | ||
750 | while ((rq = __elv_next_request(q)) != NULL) { | |
751 | /* | |
752 | * Kill the empty barrier place holder, the driver must | |
753 | * not ever see it. | |
754 | */ | |
755 | if (blk_empty_barrier(rq)) { | |
756 | end_queued_request(rq, 1); | |
757 | continue; | |
758 | } | |
759 | if (!(rq->cmd_flags & REQ_STARTED)) { | |
760 | /* | |
761 | * This is the first time the device driver | |
762 | * sees this request (possibly after | |
763 | * requeueing). Notify IO scheduler. | |
764 | */ | |
765 | if (blk_sorted_rq(rq)) | |
766 | elv_activate_rq(q, rq); | |
767 | ||
768 | /* | |
769 | * just mark as started even if we don't start | |
770 | * it, a request that has been delayed should | |
771 | * not be passed by new incoming requests | |
772 | */ | |
773 | rq->cmd_flags |= REQ_STARTED; | |
774 | blk_add_trace_rq(q, rq, BLK_TA_ISSUE); | |
775 | } | |
776 | ||
777 | if (!q->boundary_rq || q->boundary_rq == rq) { | |
778 | q->end_sector = rq_end_sector(rq); | |
779 | q->boundary_rq = NULL; | |
780 | } | |
781 | ||
782 | if (rq->cmd_flags & REQ_DONTPREP) | |
783 | break; | |
784 | ||
785 | if (q->dma_drain_size && rq->data_len) { | |
786 | /* | |
787 | * make sure space for the drain appears we | |
788 | * know we can do this because max_hw_segments | |
789 | * has been adjusted to be one fewer than the | |
790 | * device can handle | |
791 | */ | |
792 | rq->nr_phys_segments++; | |
793 | } | |
794 | ||
795 | if (!q->prep_rq_fn) | |
796 | break; | |
797 | ||
798 | ret = q->prep_rq_fn(q, rq); | |
799 | if (ret == BLKPREP_OK) { | |
800 | break; | |
801 | } else if (ret == BLKPREP_DEFER) { | |
802 | /* | |
803 | * the request may have been (partially) prepped. | |
804 | * we need to keep this request in the front to | |
805 | * avoid resource deadlock. REQ_STARTED will | |
806 | * prevent other fs requests from passing this one. | |
807 | */ | |
808 | if (q->dma_drain_size && rq->data_len && | |
809 | !(rq->cmd_flags & REQ_DONTPREP)) { | |
810 | /* | |
811 | * remove the space for the drain we added | |
812 | * so that we don't add it again | |
813 | */ | |
814 | --rq->nr_phys_segments; | |
815 | } | |
816 | ||
817 | rq = NULL; | |
818 | break; | |
819 | } else if (ret == BLKPREP_KILL) { | |
820 | rq->cmd_flags |= REQ_QUIET; | |
821 | end_queued_request(rq, 0); | |
822 | } else { | |
823 | printk(KERN_ERR "%s: bad return=%d\n", __func__, ret); | |
824 | break; | |
825 | } | |
826 | } | |
827 | ||
828 | return rq; | |
829 | } | |
830 | EXPORT_SYMBOL(elv_next_request); | |
831 | ||
832 | void elv_dequeue_request(struct request_queue *q, struct request *rq) | |
833 | { | |
834 | BUG_ON(list_empty(&rq->queuelist)); | |
835 | BUG_ON(ELV_ON_HASH(rq)); | |
836 | ||
837 | list_del_init(&rq->queuelist); | |
838 | ||
839 | /* | |
840 | * the time frame between a request being removed from the lists | |
841 | * and to it is freed is accounted as io that is in progress at | |
842 | * the driver side. | |
843 | */ | |
844 | if (blk_account_rq(rq)) | |
845 | q->in_flight++; | |
846 | } | |
847 | EXPORT_SYMBOL(elv_dequeue_request); | |
848 | ||
849 | int elv_queue_empty(struct request_queue *q) | |
850 | { | |
851 | elevator_t *e = q->elevator; | |
852 | ||
853 | if (!list_empty(&q->queue_head)) | |
854 | return 0; | |
855 | ||
856 | if (e->ops->elevator_queue_empty_fn) | |
857 | return e->ops->elevator_queue_empty_fn(q); | |
858 | ||
859 | return 1; | |
860 | } | |
861 | EXPORT_SYMBOL(elv_queue_empty); | |
862 | ||
863 | struct request *elv_latter_request(struct request_queue *q, struct request *rq) | |
864 | { | |
865 | elevator_t *e = q->elevator; | |
866 | ||
867 | if (e->ops->elevator_latter_req_fn) | |
868 | return e->ops->elevator_latter_req_fn(q, rq); | |
869 | return NULL; | |
870 | } | |
871 | ||
872 | struct request *elv_former_request(struct request_queue *q, struct request *rq) | |
873 | { | |
874 | elevator_t *e = q->elevator; | |
875 | ||
876 | if (e->ops->elevator_former_req_fn) | |
877 | return e->ops->elevator_former_req_fn(q, rq); | |
878 | return NULL; | |
879 | } | |
880 | ||
881 | int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) | |
882 | { | |
883 | elevator_t *e = q->elevator; | |
884 | ||
885 | if (e->ops->elevator_set_req_fn) | |
886 | return e->ops->elevator_set_req_fn(q, rq, gfp_mask); | |
887 | ||
888 | rq->elevator_private = NULL; | |
889 | return 0; | |
890 | } | |
891 | ||
892 | void elv_put_request(struct request_queue *q, struct request *rq) | |
893 | { | |
894 | elevator_t *e = q->elevator; | |
895 | ||
896 | if (e->ops->elevator_put_req_fn) | |
897 | e->ops->elevator_put_req_fn(rq); | |
898 | } | |
899 | ||
900 | int elv_may_queue(struct request_queue *q, int rw) | |
901 | { | |
902 | elevator_t *e = q->elevator; | |
903 | ||
904 | if (e->ops->elevator_may_queue_fn) | |
905 | return e->ops->elevator_may_queue_fn(q, rw); | |
906 | ||
907 | return ELV_MQUEUE_MAY; | |
908 | } | |
909 | ||
910 | void elv_completed_request(struct request_queue *q, struct request *rq) | |
911 | { | |
912 | elevator_t *e = q->elevator; | |
913 | ||
914 | /* | |
915 | * request is released from the driver, io must be done | |
916 | */ | |
917 | if (blk_account_rq(rq)) { | |
918 | q->in_flight--; | |
919 | if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn) | |
920 | e->ops->elevator_completed_req_fn(q, rq); | |
921 | } | |
922 | ||
923 | /* | |
924 | * Check if the queue is waiting for fs requests to be | |
925 | * drained for flush sequence. | |
926 | */ | |
927 | if (unlikely(q->ordseq)) { | |
928 | struct request *first_rq = list_entry_rq(q->queue_head.next); | |
929 | if (q->in_flight == 0 && | |
930 | blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN && | |
931 | blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) { | |
932 | blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0); | |
933 | q->request_fn(q); | |
934 | } | |
935 | } | |
936 | } | |
937 | ||
938 | #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr) | |
939 | ||
940 | static ssize_t | |
941 | elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page) | |
942 | { | |
943 | elevator_t *e = container_of(kobj, elevator_t, kobj); | |
944 | struct elv_fs_entry *entry = to_elv(attr); | |
945 | ssize_t error; | |
946 | ||
947 | if (!entry->show) | |
948 | return -EIO; | |
949 | ||
950 | mutex_lock(&e->sysfs_lock); | |
951 | error = e->ops ? entry->show(e, page) : -ENOENT; | |
952 | mutex_unlock(&e->sysfs_lock); | |
953 | return error; | |
954 | } | |
955 | ||
956 | static ssize_t | |
957 | elv_attr_store(struct kobject *kobj, struct attribute *attr, | |
958 | const char *page, size_t length) | |
959 | { | |
960 | elevator_t *e = container_of(kobj, elevator_t, kobj); | |
961 | struct elv_fs_entry *entry = to_elv(attr); | |
962 | ssize_t error; | |
963 | ||
964 | if (!entry->store) | |
965 | return -EIO; | |
966 | ||
967 | mutex_lock(&e->sysfs_lock); | |
968 | error = e->ops ? entry->store(e, page, length) : -ENOENT; | |
969 | mutex_unlock(&e->sysfs_lock); | |
970 | return error; | |
971 | } | |
972 | ||
973 | static struct sysfs_ops elv_sysfs_ops = { | |
974 | .show = elv_attr_show, | |
975 | .store = elv_attr_store, | |
976 | }; | |
977 | ||
978 | static struct kobj_type elv_ktype = { | |
979 | .sysfs_ops = &elv_sysfs_ops, | |
980 | .release = elevator_release, | |
981 | }; | |
982 | ||
983 | int elv_register_queue(struct request_queue *q) | |
984 | { | |
985 | elevator_t *e = q->elevator; | |
986 | int error; | |
987 | ||
988 | error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched"); | |
989 | if (!error) { | |
990 | struct elv_fs_entry *attr = e->elevator_type->elevator_attrs; | |
991 | if (attr) { | |
992 | while (attr->attr.name) { | |
993 | if (sysfs_create_file(&e->kobj, &attr->attr)) | |
994 | break; | |
995 | attr++; | |
996 | } | |
997 | } | |
998 | kobject_uevent(&e->kobj, KOBJ_ADD); | |
999 | } | |
1000 | return error; | |
1001 | } | |
1002 | ||
1003 | static void __elv_unregister_queue(elevator_t *e) | |
1004 | { | |
1005 | kobject_uevent(&e->kobj, KOBJ_REMOVE); | |
1006 | kobject_del(&e->kobj); | |
1007 | } | |
1008 | ||
1009 | void elv_unregister_queue(struct request_queue *q) | |
1010 | { | |
1011 | if (q) | |
1012 | __elv_unregister_queue(q->elevator); | |
1013 | } | |
1014 | ||
1015 | void elv_register(struct elevator_type *e) | |
1016 | { | |
1017 | char *def = ""; | |
1018 | ||
1019 | spin_lock(&elv_list_lock); | |
1020 | BUG_ON(elevator_find(e->elevator_name)); | |
1021 | list_add_tail(&e->list, &elv_list); | |
1022 | spin_unlock(&elv_list_lock); | |
1023 | ||
1024 | if (!strcmp(e->elevator_name, chosen_elevator) || | |
1025 | (!*chosen_elevator && | |
1026 | !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED))) | |
1027 | def = " (default)"; | |
1028 | ||
1029 | printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name, | |
1030 | def); | |
1031 | } | |
1032 | EXPORT_SYMBOL_GPL(elv_register); | |
1033 | ||
1034 | void elv_unregister(struct elevator_type *e) | |
1035 | { | |
1036 | struct task_struct *g, *p; | |
1037 | ||
1038 | /* | |
1039 | * Iterate every thread in the process to remove the io contexts. | |
1040 | */ | |
1041 | if (e->ops.trim) { | |
1042 | read_lock(&tasklist_lock); | |
1043 | do_each_thread(g, p) { | |
1044 | task_lock(p); | |
1045 | if (p->io_context) | |
1046 | e->ops.trim(p->io_context); | |
1047 | task_unlock(p); | |
1048 | } while_each_thread(g, p); | |
1049 | read_unlock(&tasklist_lock); | |
1050 | } | |
1051 | ||
1052 | spin_lock(&elv_list_lock); | |
1053 | list_del_init(&e->list); | |
1054 | spin_unlock(&elv_list_lock); | |
1055 | } | |
1056 | EXPORT_SYMBOL_GPL(elv_unregister); | |
1057 | ||
1058 | /* | |
1059 | * switch to new_e io scheduler. be careful not to introduce deadlocks - | |
1060 | * we don't free the old io scheduler, before we have allocated what we | |
1061 | * need for the new one. this way we have a chance of going back to the old | |
1062 | * one, if the new one fails init for some reason. | |
1063 | */ | |
1064 | static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) | |
1065 | { | |
1066 | elevator_t *old_elevator, *e; | |
1067 | void *data; | |
1068 | ||
1069 | /* | |
1070 | * Allocate new elevator | |
1071 | */ | |
1072 | e = elevator_alloc(q, new_e); | |
1073 | if (!e) | |
1074 | return 0; | |
1075 | ||
1076 | data = elevator_init_queue(q, e); | |
1077 | if (!data) { | |
1078 | kobject_put(&e->kobj); | |
1079 | return 0; | |
1080 | } | |
1081 | ||
1082 | /* | |
1083 | * Turn on BYPASS and drain all requests w/ elevator private data | |
1084 | */ | |
1085 | spin_lock_irq(q->queue_lock); | |
1086 | ||
1087 | queue_flag_set(QUEUE_FLAG_ELVSWITCH, q); | |
1088 | ||
1089 | elv_drain_elevator(q); | |
1090 | ||
1091 | while (q->rq.elvpriv) { | |
1092 | blk_remove_plug(q); | |
1093 | q->request_fn(q); | |
1094 | spin_unlock_irq(q->queue_lock); | |
1095 | msleep(10); | |
1096 | spin_lock_irq(q->queue_lock); | |
1097 | elv_drain_elevator(q); | |
1098 | } | |
1099 | ||
1100 | /* | |
1101 | * Remember old elevator. | |
1102 | */ | |
1103 | old_elevator = q->elevator; | |
1104 | ||
1105 | /* | |
1106 | * attach and start new elevator | |
1107 | */ | |
1108 | elevator_attach(q, e, data); | |
1109 | ||
1110 | spin_unlock_irq(q->queue_lock); | |
1111 | ||
1112 | __elv_unregister_queue(old_elevator); | |
1113 | ||
1114 | if (elv_register_queue(q)) | |
1115 | goto fail_register; | |
1116 | ||
1117 | /* | |
1118 | * finally exit old elevator and turn off BYPASS. | |
1119 | */ | |
1120 | elevator_exit(old_elevator); | |
1121 | spin_lock_irq(q->queue_lock); | |
1122 | queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q); | |
1123 | spin_unlock_irq(q->queue_lock); | |
1124 | ||
1125 | blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name); | |
1126 | ||
1127 | return 1; | |
1128 | ||
1129 | fail_register: | |
1130 | /* | |
1131 | * switch failed, exit the new io scheduler and reattach the old | |
1132 | * one again (along with re-adding the sysfs dir) | |
1133 | */ | |
1134 | elevator_exit(e); | |
1135 | q->elevator = old_elevator; | |
1136 | elv_register_queue(q); | |
1137 | ||
1138 | spin_lock_irq(q->queue_lock); | |
1139 | queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q); | |
1140 | spin_unlock_irq(q->queue_lock); | |
1141 | ||
1142 | return 0; | |
1143 | } | |
1144 | ||
1145 | ssize_t elv_iosched_store(struct request_queue *q, const char *name, | |
1146 | size_t count) | |
1147 | { | |
1148 | char elevator_name[ELV_NAME_MAX]; | |
1149 | size_t len; | |
1150 | struct elevator_type *e; | |
1151 | ||
1152 | elevator_name[sizeof(elevator_name) - 1] = '\0'; | |
1153 | strncpy(elevator_name, name, sizeof(elevator_name) - 1); | |
1154 | len = strlen(elevator_name); | |
1155 | ||
1156 | if (len && elevator_name[len - 1] == '\n') | |
1157 | elevator_name[len - 1] = '\0'; | |
1158 | ||
1159 | e = elevator_get(elevator_name); | |
1160 | if (!e) { | |
1161 | printk(KERN_ERR "elevator: type %s not found\n", elevator_name); | |
1162 | return -EINVAL; | |
1163 | } | |
1164 | ||
1165 | if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) { | |
1166 | elevator_put(e); | |
1167 | return count; | |
1168 | } | |
1169 | ||
1170 | if (!elevator_switch(q, e)) | |
1171 | printk(KERN_ERR "elevator: switch to %s failed\n", | |
1172 | elevator_name); | |
1173 | return count; | |
1174 | } | |
1175 | ||
1176 | ssize_t elv_iosched_show(struct request_queue *q, char *name) | |
1177 | { | |
1178 | elevator_t *e = q->elevator; | |
1179 | struct elevator_type *elv = e->elevator_type; | |
1180 | struct elevator_type *__e; | |
1181 | int len = 0; | |
1182 | ||
1183 | spin_lock(&elv_list_lock); | |
1184 | list_for_each_entry(__e, &elv_list, list) { | |
1185 | if (!strcmp(elv->elevator_name, __e->elevator_name)) | |
1186 | len += sprintf(name+len, "[%s] ", elv->elevator_name); | |
1187 | else | |
1188 | len += sprintf(name+len, "%s ", __e->elevator_name); | |
1189 | } | |
1190 | spin_unlock(&elv_list_lock); | |
1191 | ||
1192 | len += sprintf(len+name, "\n"); | |
1193 | return len; | |
1194 | } | |
1195 | ||
1196 | struct request *elv_rb_former_request(struct request_queue *q, | |
1197 | struct request *rq) | |
1198 | { | |
1199 | struct rb_node *rbprev = rb_prev(&rq->rb_node); | |
1200 | ||
1201 | if (rbprev) | |
1202 | return rb_entry_rq(rbprev); | |
1203 | ||
1204 | return NULL; | |
1205 | } | |
1206 | EXPORT_SYMBOL(elv_rb_former_request); | |
1207 | ||
1208 | struct request *elv_rb_latter_request(struct request_queue *q, | |
1209 | struct request *rq) | |
1210 | { | |
1211 | struct rb_node *rbnext = rb_next(&rq->rb_node); | |
1212 | ||
1213 | if (rbnext) | |
1214 | return rb_entry_rq(rbnext); | |
1215 | ||
1216 | return NULL; | |
1217 | } | |
1218 | EXPORT_SYMBOL(elv_rb_latter_request); |