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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 "blk.h" | |
40 | ||
41 | static DEFINE_SPINLOCK(elv_list_lock); | |
42 | static LIST_HEAD(elv_list); | |
43 | ||
44 | /* | |
45 | * Merge hash stuff. | |
46 | */ | |
47 | static const int elv_hash_shift = 6; | |
48 | #define ELV_HASH_BLOCK(sec) ((sec) >> 3) | |
49 | #define ELV_HASH_FN(sec) \ | |
50 | (hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift)) | |
51 | #define ELV_HASH_ENTRIES (1 << elv_hash_shift) | |
52 | #define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors) | |
53 | #define ELV_ON_HASH(rq) (!hlist_unhashed(&(rq)->hash)) | |
54 | ||
55 | /* | |
56 | * Query io scheduler to see if the current process issuing bio may be | |
57 | * merged with rq. | |
58 | */ | |
59 | static int elv_iosched_allow_merge(struct request *rq, struct bio *bio) | |
60 | { | |
61 | struct request_queue *q = rq->q; | |
62 | elevator_t *e = q->elevator; | |
63 | ||
64 | if (e->ops->elevator_allow_merge_fn) | |
65 | return e->ops->elevator_allow_merge_fn(q, rq, bio); | |
66 | ||
67 | return 1; | |
68 | } | |
69 | ||
70 | /* | |
71 | * can we safely merge with this request? | |
72 | */ | |
73 | int elv_rq_merge_ok(struct request *rq, struct bio *bio) | |
74 | { | |
75 | if (!rq_mergeable(rq)) | |
76 | return 0; | |
77 | ||
78 | /* | |
79 | * Don't merge file system requests and discard requests | |
80 | */ | |
81 | if (bio_discard(bio) != bio_discard(rq->bio)) | |
82 | return 0; | |
83 | ||
84 | /* | |
85 | * different data direction or already started, don't merge | |
86 | */ | |
87 | if (bio_data_dir(bio) != rq_data_dir(rq)) | |
88 | return 0; | |
89 | ||
90 | /* | |
91 | * must be same device and not a special request | |
92 | */ | |
93 | if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special) | |
94 | return 0; | |
95 | ||
96 | /* | |
97 | * only merge integrity protected bio into ditto rq | |
98 | */ | |
99 | if (bio_integrity(bio) != blk_integrity_rq(rq)) | |
100 | return 0; | |
101 | ||
102 | if (!elv_iosched_allow_merge(rq, bio)) | |
103 | return 0; | |
104 | ||
105 | return 1; | |
106 | } | |
107 | EXPORT_SYMBOL(elv_rq_merge_ok); | |
108 | ||
109 | static inline int elv_try_merge(struct request *__rq, struct bio *bio) | |
110 | { | |
111 | int ret = ELEVATOR_NO_MERGE; | |
112 | ||
113 | /* | |
114 | * we can merge and sequence is ok, check if it's possible | |
115 | */ | |
116 | if (elv_rq_merge_ok(__rq, bio)) { | |
117 | if (__rq->sector + __rq->nr_sectors == bio->bi_sector) | |
118 | ret = ELEVATOR_BACK_MERGE; | |
119 | else if (__rq->sector - bio_sectors(bio) == bio->bi_sector) | |
120 | ret = ELEVATOR_FRONT_MERGE; | |
121 | } | |
122 | ||
123 | return ret; | |
124 | } | |
125 | ||
126 | static struct elevator_type *elevator_find(const char *name) | |
127 | { | |
128 | struct elevator_type *e; | |
129 | ||
130 | list_for_each_entry(e, &elv_list, list) { | |
131 | if (!strcmp(e->elevator_name, name)) | |
132 | return e; | |
133 | } | |
134 | ||
135 | return NULL; | |
136 | } | |
137 | ||
138 | static void elevator_put(struct elevator_type *e) | |
139 | { | |
140 | module_put(e->elevator_owner); | |
141 | } | |
142 | ||
143 | static struct elevator_type *elevator_get(const char *name) | |
144 | { | |
145 | struct elevator_type *e; | |
146 | ||
147 | spin_lock(&elv_list_lock); | |
148 | ||
149 | e = elevator_find(name); | |
150 | if (!e) { | |
151 | char elv[ELV_NAME_MAX + strlen("-iosched")]; | |
152 | ||
153 | spin_unlock(&elv_list_lock); | |
154 | ||
155 | if (!strcmp(name, "anticipatory")) | |
156 | sprintf(elv, "as-iosched"); | |
157 | else | |
158 | sprintf(elv, "%s-iosched", name); | |
159 | ||
160 | request_module("%s", elv); | |
161 | spin_lock(&elv_list_lock); | |
162 | e = elevator_find(name); | |
163 | } | |
164 | ||
165 | if (e && !try_module_get(e->elevator_owner)) | |
166 | e = NULL; | |
167 | ||
168 | spin_unlock(&elv_list_lock); | |
169 | ||
170 | return e; | |
171 | } | |
172 | ||
173 | static void *elevator_init_queue(struct request_queue *q, | |
174 | struct elevator_queue *eq) | |
175 | { | |
176 | return eq->ops->elevator_init_fn(q); | |
177 | } | |
178 | ||
179 | static void elevator_attach(struct request_queue *q, struct elevator_queue *eq, | |
180 | void *data) | |
181 | { | |
182 | q->elevator = eq; | |
183 | eq->elevator_data = data; | |
184 | } | |
185 | ||
186 | static char chosen_elevator[16]; | |
187 | ||
188 | static int __init elevator_setup(char *str) | |
189 | { | |
190 | /* | |
191 | * Be backwards-compatible with previous kernels, so users | |
192 | * won't get the wrong elevator. | |
193 | */ | |
194 | if (!strcmp(str, "as")) | |
195 | strcpy(chosen_elevator, "anticipatory"); | |
196 | else | |
197 | strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1); | |
198 | return 1; | |
199 | } | |
200 | ||
201 | __setup("elevator=", elevator_setup); | |
202 | ||
203 | static struct kobj_type elv_ktype; | |
204 | ||
205 | static elevator_t *elevator_alloc(struct request_queue *q, | |
206 | struct elevator_type *e) | |
207 | { | |
208 | elevator_t *eq; | |
209 | int i; | |
210 | ||
211 | eq = kmalloc_node(sizeof(elevator_t), GFP_KERNEL | __GFP_ZERO, q->node); | |
212 | if (unlikely(!eq)) | |
213 | goto err; | |
214 | ||
215 | eq->ops = &e->ops; | |
216 | eq->elevator_type = e; | |
217 | kobject_init(&eq->kobj, &elv_ktype); | |
218 | mutex_init(&eq->sysfs_lock); | |
219 | ||
220 | eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES, | |
221 | GFP_KERNEL, q->node); | |
222 | if (!eq->hash) | |
223 | goto err; | |
224 | ||
225 | for (i = 0; i < ELV_HASH_ENTRIES; i++) | |
226 | INIT_HLIST_HEAD(&eq->hash[i]); | |
227 | ||
228 | return eq; | |
229 | err: | |
230 | kfree(eq); | |
231 | elevator_put(e); | |
232 | return NULL; | |
233 | } | |
234 | ||
235 | static void elevator_release(struct kobject *kobj) | |
236 | { | |
237 | elevator_t *e = container_of(kobj, elevator_t, kobj); | |
238 | ||
239 | elevator_put(e->elevator_type); | |
240 | kfree(e->hash); | |
241 | kfree(e); | |
242 | } | |
243 | ||
244 | int elevator_init(struct request_queue *q, char *name) | |
245 | { | |
246 | struct elevator_type *e = NULL; | |
247 | struct elevator_queue *eq; | |
248 | int ret = 0; | |
249 | void *data; | |
250 | ||
251 | INIT_LIST_HEAD(&q->queue_head); | |
252 | q->last_merge = NULL; | |
253 | q->end_sector = 0; | |
254 | q->boundary_rq = NULL; | |
255 | ||
256 | if (name) { | |
257 | e = elevator_get(name); | |
258 | if (!e) | |
259 | return -EINVAL; | |
260 | } | |
261 | ||
262 | if (!e && *chosen_elevator) { | |
263 | e = elevator_get(chosen_elevator); | |
264 | if (!e) | |
265 | printk(KERN_ERR "I/O scheduler %s not found\n", | |
266 | chosen_elevator); | |
267 | } | |
268 | ||
269 | if (!e) { | |
270 | e = elevator_get(CONFIG_DEFAULT_IOSCHED); | |
271 | if (!e) { | |
272 | printk(KERN_ERR | |
273 | "Default I/O scheduler not found. " \ | |
274 | "Using noop.\n"); | |
275 | e = elevator_get("noop"); | |
276 | } | |
277 | } | |
278 | ||
279 | eq = elevator_alloc(q, e); | |
280 | if (!eq) | |
281 | return -ENOMEM; | |
282 | ||
283 | data = elevator_init_queue(q, eq); | |
284 | if (!data) { | |
285 | kobject_put(&eq->kobj); | |
286 | return -ENOMEM; | |
287 | } | |
288 | ||
289 | elevator_attach(q, eq, data); | |
290 | return ret; | |
291 | } | |
292 | EXPORT_SYMBOL(elevator_init); | |
293 | ||
294 | void elevator_exit(elevator_t *e) | |
295 | { | |
296 | mutex_lock(&e->sysfs_lock); | |
297 | if (e->ops->elevator_exit_fn) | |
298 | e->ops->elevator_exit_fn(e); | |
299 | e->ops = NULL; | |
300 | mutex_unlock(&e->sysfs_lock); | |
301 | ||
302 | kobject_put(&e->kobj); | |
303 | } | |
304 | EXPORT_SYMBOL(elevator_exit); | |
305 | ||
306 | static void elv_activate_rq(struct request_queue *q, struct request *rq) | |
307 | { | |
308 | elevator_t *e = q->elevator; | |
309 | ||
310 | if (e->ops->elevator_activate_req_fn) | |
311 | e->ops->elevator_activate_req_fn(q, rq); | |
312 | } | |
313 | ||
314 | static void elv_deactivate_rq(struct request_queue *q, struct request *rq) | |
315 | { | |
316 | elevator_t *e = q->elevator; | |
317 | ||
318 | if (e->ops->elevator_deactivate_req_fn) | |
319 | e->ops->elevator_deactivate_req_fn(q, rq); | |
320 | } | |
321 | ||
322 | static inline void __elv_rqhash_del(struct request *rq) | |
323 | { | |
324 | hlist_del_init(&rq->hash); | |
325 | } | |
326 | ||
327 | static void elv_rqhash_del(struct request_queue *q, struct request *rq) | |
328 | { | |
329 | if (ELV_ON_HASH(rq)) | |
330 | __elv_rqhash_del(rq); | |
331 | } | |
332 | ||
333 | static void elv_rqhash_add(struct request_queue *q, struct request *rq) | |
334 | { | |
335 | elevator_t *e = q->elevator; | |
336 | ||
337 | BUG_ON(ELV_ON_HASH(rq)); | |
338 | hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]); | |
339 | } | |
340 | ||
341 | static void elv_rqhash_reposition(struct request_queue *q, struct request *rq) | |
342 | { | |
343 | __elv_rqhash_del(rq); | |
344 | elv_rqhash_add(q, rq); | |
345 | } | |
346 | ||
347 | static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset) | |
348 | { | |
349 | elevator_t *e = q->elevator; | |
350 | struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)]; | |
351 | struct hlist_node *entry, *next; | |
352 | struct request *rq; | |
353 | ||
354 | hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) { | |
355 | BUG_ON(!ELV_ON_HASH(rq)); | |
356 | ||
357 | if (unlikely(!rq_mergeable(rq))) { | |
358 | __elv_rqhash_del(rq); | |
359 | continue; | |
360 | } | |
361 | ||
362 | if (rq_hash_key(rq) == offset) | |
363 | return rq; | |
364 | } | |
365 | ||
366 | return NULL; | |
367 | } | |
368 | ||
369 | /* | |
370 | * RB-tree support functions for inserting/lookup/removal of requests | |
371 | * in a sorted RB tree. | |
372 | */ | |
373 | struct request *elv_rb_add(struct rb_root *root, struct request *rq) | |
374 | { | |
375 | struct rb_node **p = &root->rb_node; | |
376 | struct rb_node *parent = NULL; | |
377 | struct request *__rq; | |
378 | ||
379 | while (*p) { | |
380 | parent = *p; | |
381 | __rq = rb_entry(parent, struct request, rb_node); | |
382 | ||
383 | if (rq->sector < __rq->sector) | |
384 | p = &(*p)->rb_left; | |
385 | else if (rq->sector > __rq->sector) | |
386 | p = &(*p)->rb_right; | |
387 | else | |
388 | return __rq; | |
389 | } | |
390 | ||
391 | rb_link_node(&rq->rb_node, parent, p); | |
392 | rb_insert_color(&rq->rb_node, root); | |
393 | return NULL; | |
394 | } | |
395 | EXPORT_SYMBOL(elv_rb_add); | |
396 | ||
397 | void elv_rb_del(struct rb_root *root, struct request *rq) | |
398 | { | |
399 | BUG_ON(RB_EMPTY_NODE(&rq->rb_node)); | |
400 | rb_erase(&rq->rb_node, root); | |
401 | RB_CLEAR_NODE(&rq->rb_node); | |
402 | } | |
403 | EXPORT_SYMBOL(elv_rb_del); | |
404 | ||
405 | struct request *elv_rb_find(struct rb_root *root, sector_t sector) | |
406 | { | |
407 | struct rb_node *n = root->rb_node; | |
408 | struct request *rq; | |
409 | ||
410 | while (n) { | |
411 | rq = rb_entry(n, struct request, rb_node); | |
412 | ||
413 | if (sector < rq->sector) | |
414 | n = n->rb_left; | |
415 | else if (sector > rq->sector) | |
416 | n = n->rb_right; | |
417 | else | |
418 | return rq; | |
419 | } | |
420 | ||
421 | return NULL; | |
422 | } | |
423 | EXPORT_SYMBOL(elv_rb_find); | |
424 | ||
425 | /* | |
426 | * Insert rq into dispatch queue of q. Queue lock must be held on | |
427 | * entry. rq is sort instead into the dispatch queue. To be used by | |
428 | * specific elevators. | |
429 | */ | |
430 | void elv_dispatch_sort(struct request_queue *q, struct request *rq) | |
431 | { | |
432 | sector_t boundary; | |
433 | struct list_head *entry; | |
434 | int stop_flags; | |
435 | ||
436 | if (q->last_merge == rq) | |
437 | q->last_merge = NULL; | |
438 | ||
439 | elv_rqhash_del(q, rq); | |
440 | ||
441 | q->nr_sorted--; | |
442 | ||
443 | boundary = q->end_sector; | |
444 | stop_flags = REQ_SOFTBARRIER | REQ_HARDBARRIER | REQ_STARTED; | |
445 | list_for_each_prev(entry, &q->queue_head) { | |
446 | struct request *pos = list_entry_rq(entry); | |
447 | ||
448 | if (blk_discard_rq(rq) != blk_discard_rq(pos)) | |
449 | break; | |
450 | if (rq_data_dir(rq) != rq_data_dir(pos)) | |
451 | break; | |
452 | if (pos->cmd_flags & stop_flags) | |
453 | break; | |
454 | if (rq->sector >= boundary) { | |
455 | if (pos->sector < boundary) | |
456 | continue; | |
457 | } else { | |
458 | if (pos->sector >= boundary) | |
459 | break; | |
460 | } | |
461 | if (rq->sector >= pos->sector) | |
462 | break; | |
463 | } | |
464 | ||
465 | list_add(&rq->queuelist, entry); | |
466 | } | |
467 | EXPORT_SYMBOL(elv_dispatch_sort); | |
468 | ||
469 | /* | |
470 | * Insert rq into dispatch queue of q. Queue lock must be held on | |
471 | * entry. rq is added to the back of the dispatch queue. To be used by | |
472 | * specific elevators. | |
473 | */ | |
474 | void elv_dispatch_add_tail(struct request_queue *q, struct request *rq) | |
475 | { | |
476 | if (q->last_merge == rq) | |
477 | q->last_merge = NULL; | |
478 | ||
479 | elv_rqhash_del(q, rq); | |
480 | ||
481 | q->nr_sorted--; | |
482 | ||
483 | q->end_sector = rq_end_sector(rq); | |
484 | q->boundary_rq = rq; | |
485 | list_add_tail(&rq->queuelist, &q->queue_head); | |
486 | } | |
487 | EXPORT_SYMBOL(elv_dispatch_add_tail); | |
488 | ||
489 | int elv_merge(struct request_queue *q, struct request **req, struct bio *bio) | |
490 | { | |
491 | elevator_t *e = q->elevator; | |
492 | struct request *__rq; | |
493 | int ret; | |
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_nomerges(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 | void elv_merged_request(struct request_queue *q, struct request *rq, int type) | |
525 | { | |
526 | elevator_t *e = q->elevator; | |
527 | ||
528 | if (e->ops->elevator_merged_fn) | |
529 | e->ops->elevator_merged_fn(q, rq, type); | |
530 | ||
531 | if (type == ELEVATOR_BACK_MERGE) | |
532 | elv_rqhash_reposition(q, rq); | |
533 | ||
534 | q->last_merge = rq; | |
535 | } | |
536 | ||
537 | void elv_merge_requests(struct request_queue *q, struct request *rq, | |
538 | struct request *next) | |
539 | { | |
540 | elevator_t *e = q->elevator; | |
541 | ||
542 | if (e->ops->elevator_merge_req_fn) | |
543 | e->ops->elevator_merge_req_fn(q, rq, next); | |
544 | ||
545 | elv_rqhash_reposition(q, rq); | |
546 | elv_rqhash_del(q, next); | |
547 | ||
548 | q->nr_sorted--; | |
549 | q->last_merge = rq; | |
550 | } | |
551 | ||
552 | void elv_requeue_request(struct request_queue *q, struct request *rq) | |
553 | { | |
554 | /* | |
555 | * it already went through dequeue, we need to decrement the | |
556 | * in_flight count again | |
557 | */ | |
558 | if (blk_account_rq(rq)) { | |
559 | q->in_flight--; | |
560 | if (blk_sorted_rq(rq)) | |
561 | elv_deactivate_rq(q, rq); | |
562 | } | |
563 | ||
564 | rq->cmd_flags &= ~REQ_STARTED; | |
565 | ||
566 | elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE); | |
567 | } | |
568 | ||
569 | static void elv_drain_elevator(struct request_queue *q) | |
570 | { | |
571 | static int printed; | |
572 | while (q->elevator->ops->elevator_dispatch_fn(q, 1)) | |
573 | ; | |
574 | if (q->nr_sorted == 0) | |
575 | return; | |
576 | if (printed++ < 10) { | |
577 | printk(KERN_ERR "%s: forced dispatching is broken " | |
578 | "(nr_sorted=%u), please report this\n", | |
579 | q->elevator->elevator_type->elevator_name, q->nr_sorted); | |
580 | } | |
581 | } | |
582 | ||
583 | void elv_insert(struct request_queue *q, struct request *rq, int where) | |
584 | { | |
585 | struct list_head *pos; | |
586 | unsigned ordseq; | |
587 | int unplug_it = 1; | |
588 | ||
589 | blk_add_trace_rq(q, rq, BLK_TA_INSERT); | |
590 | ||
591 | rq->q = q; | |
592 | ||
593 | switch (where) { | |
594 | case ELEVATOR_INSERT_FRONT: | |
595 | rq->cmd_flags |= REQ_SOFTBARRIER; | |
596 | ||
597 | list_add(&rq->queuelist, &q->queue_head); | |
598 | break; | |
599 | ||
600 | case ELEVATOR_INSERT_BACK: | |
601 | rq->cmd_flags |= REQ_SOFTBARRIER; | |
602 | elv_drain_elevator(q); | |
603 | list_add_tail(&rq->queuelist, &q->queue_head); | |
604 | /* | |
605 | * We kick the queue here for the following reasons. | |
606 | * - The elevator might have returned NULL previously | |
607 | * to delay requests and returned them now. As the | |
608 | * queue wasn't empty before this request, ll_rw_blk | |
609 | * won't run the queue on return, resulting in hang. | |
610 | * - Usually, back inserted requests won't be merged | |
611 | * with anything. There's no point in delaying queue | |
612 | * processing. | |
613 | */ | |
614 | blk_remove_plug(q); | |
615 | q->request_fn(q); | |
616 | break; | |
617 | ||
618 | case ELEVATOR_INSERT_SORT: | |
619 | BUG_ON(!blk_fs_request(rq) && !blk_discard_rq(rq)); | |
620 | rq->cmd_flags |= REQ_SORTED; | |
621 | q->nr_sorted++; | |
622 | if (rq_mergeable(rq)) { | |
623 | elv_rqhash_add(q, rq); | |
624 | if (!q->last_merge) | |
625 | q->last_merge = rq; | |
626 | } | |
627 | ||
628 | /* | |
629 | * Some ioscheds (cfq) run q->request_fn directly, so | |
630 | * rq cannot be accessed after calling | |
631 | * elevator_add_req_fn. | |
632 | */ | |
633 | q->elevator->ops->elevator_add_req_fn(q, rq); | |
634 | break; | |
635 | ||
636 | case ELEVATOR_INSERT_REQUEUE: | |
637 | /* | |
638 | * If ordered flush isn't in progress, we do front | |
639 | * insertion; otherwise, requests should be requeued | |
640 | * in ordseq order. | |
641 | */ | |
642 | rq->cmd_flags |= REQ_SOFTBARRIER; | |
643 | ||
644 | /* | |
645 | * Most requeues happen because of a busy condition, | |
646 | * don't force unplug of the queue for that case. | |
647 | */ | |
648 | unplug_it = 0; | |
649 | ||
650 | if (q->ordseq == 0) { | |
651 | list_add(&rq->queuelist, &q->queue_head); | |
652 | break; | |
653 | } | |
654 | ||
655 | ordseq = blk_ordered_req_seq(rq); | |
656 | ||
657 | list_for_each(pos, &q->queue_head) { | |
658 | struct request *pos_rq = list_entry_rq(pos); | |
659 | if (ordseq <= blk_ordered_req_seq(pos_rq)) | |
660 | break; | |
661 | } | |
662 | ||
663 | list_add_tail(&rq->queuelist, pos); | |
664 | break; | |
665 | ||
666 | default: | |
667 | printk(KERN_ERR "%s: bad insertion point %d\n", | |
668 | __func__, where); | |
669 | BUG(); | |
670 | } | |
671 | ||
672 | if (unplug_it && blk_queue_plugged(q)) { | |
673 | int nrq = q->rq.count[READ] + q->rq.count[WRITE] | |
674 | - q->in_flight; | |
675 | ||
676 | if (nrq >= q->unplug_thresh) | |
677 | __generic_unplug_device(q); | |
678 | } | |
679 | } | |
680 | ||
681 | void __elv_add_request(struct request_queue *q, struct request *rq, int where, | |
682 | int plug) | |
683 | { | |
684 | if (q->ordcolor) | |
685 | rq->cmd_flags |= REQ_ORDERED_COLOR; | |
686 | ||
687 | if (rq->cmd_flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) { | |
688 | /* | |
689 | * toggle ordered color | |
690 | */ | |
691 | if (blk_barrier_rq(rq)) | |
692 | q->ordcolor ^= 1; | |
693 | ||
694 | /* | |
695 | * barriers implicitly indicate back insertion | |
696 | */ | |
697 | if (where == ELEVATOR_INSERT_SORT) | |
698 | where = ELEVATOR_INSERT_BACK; | |
699 | ||
700 | /* | |
701 | * this request is scheduling boundary, update | |
702 | * end_sector | |
703 | */ | |
704 | if (blk_fs_request(rq) || blk_discard_rq(rq)) { | |
705 | q->end_sector = rq_end_sector(rq); | |
706 | q->boundary_rq = rq; | |
707 | } | |
708 | } else if (!(rq->cmd_flags & REQ_ELVPRIV) && | |
709 | where == ELEVATOR_INSERT_SORT) | |
710 | where = ELEVATOR_INSERT_BACK; | |
711 | ||
712 | if (plug) | |
713 | blk_plug_device(q); | |
714 | ||
715 | elv_insert(q, rq, where); | |
716 | } | |
717 | EXPORT_SYMBOL(__elv_add_request); | |
718 | ||
719 | void elv_add_request(struct request_queue *q, struct request *rq, int where, | |
720 | int plug) | |
721 | { | |
722 | unsigned long flags; | |
723 | ||
724 | spin_lock_irqsave(q->queue_lock, flags); | |
725 | __elv_add_request(q, rq, where, plug); | |
726 | spin_unlock_irqrestore(q->queue_lock, flags); | |
727 | } | |
728 | EXPORT_SYMBOL(elv_add_request); | |
729 | ||
730 | static inline struct request *__elv_next_request(struct request_queue *q) | |
731 | { | |
732 | struct request *rq; | |
733 | ||
734 | while (1) { | |
735 | while (!list_empty(&q->queue_head)) { | |
736 | rq = list_entry_rq(q->queue_head.next); | |
737 | if (blk_do_ordered(q, &rq)) | |
738 | return rq; | |
739 | } | |
740 | ||
741 | if (!q->elevator->ops->elevator_dispatch_fn(q, 0)) | |
742 | return NULL; | |
743 | } | |
744 | } | |
745 | ||
746 | struct request *elv_next_request(struct request_queue *q) | |
747 | { | |
748 | struct request *rq; | |
749 | int ret; | |
750 | ||
751 | while ((rq = __elv_next_request(q)) != NULL) { | |
752 | /* | |
753 | * Kill the empty barrier place holder, the driver must | |
754 | * not ever see it. | |
755 | */ | |
756 | if (blk_empty_barrier(rq)) { | |
757 | end_queued_request(rq, 1); | |
758 | continue; | |
759 | } | |
760 | if (!(rq->cmd_flags & REQ_STARTED)) { | |
761 | /* | |
762 | * This is the first time the device driver | |
763 | * sees this request (possibly after | |
764 | * requeueing). Notify IO scheduler. | |
765 | */ | |
766 | if (blk_sorted_rq(rq)) | |
767 | elv_activate_rq(q, rq); | |
768 | ||
769 | /* | |
770 | * just mark as started even if we don't start | |
771 | * it, a request that has been delayed should | |
772 | * not be passed by new incoming requests | |
773 | */ | |
774 | rq->cmd_flags |= REQ_STARTED; | |
775 | blk_add_trace_rq(q, rq, BLK_TA_ISSUE); | |
776 | ||
777 | /* | |
778 | * We are now handing the request to the hardware, | |
779 | * add the timeout handler | |
780 | */ | |
781 | blk_add_timer(rq); | |
782 | } | |
783 | ||
784 | if (!q->boundary_rq || q->boundary_rq == rq) { | |
785 | q->end_sector = rq_end_sector(rq); | |
786 | q->boundary_rq = NULL; | |
787 | } | |
788 | ||
789 | if (rq->cmd_flags & REQ_DONTPREP) | |
790 | break; | |
791 | ||
792 | if (q->dma_drain_size && rq->data_len) { | |
793 | /* | |
794 | * make sure space for the drain appears we | |
795 | * know we can do this because max_hw_segments | |
796 | * has been adjusted to be one fewer than the | |
797 | * device can handle | |
798 | */ | |
799 | rq->nr_phys_segments++; | |
800 | } | |
801 | ||
802 | if (!q->prep_rq_fn) | |
803 | break; | |
804 | ||
805 | ret = q->prep_rq_fn(q, rq); | |
806 | if (ret == BLKPREP_OK) { | |
807 | break; | |
808 | } else if (ret == BLKPREP_DEFER) { | |
809 | /* | |
810 | * the request may have been (partially) prepped. | |
811 | * we need to keep this request in the front to | |
812 | * avoid resource deadlock. REQ_STARTED will | |
813 | * prevent other fs requests from passing this one. | |
814 | */ | |
815 | if (q->dma_drain_size && rq->data_len && | |
816 | !(rq->cmd_flags & REQ_DONTPREP)) { | |
817 | /* | |
818 | * remove the space for the drain we added | |
819 | * so that we don't add it again | |
820 | */ | |
821 | --rq->nr_phys_segments; | |
822 | } | |
823 | ||
824 | rq = NULL; | |
825 | break; | |
826 | } else if (ret == BLKPREP_KILL) { | |
827 | rq->cmd_flags |= REQ_QUIET; | |
828 | end_queued_request(rq, 0); | |
829 | } else { | |
830 | printk(KERN_ERR "%s: bad return=%d\n", __func__, ret); | |
831 | break; | |
832 | } | |
833 | } | |
834 | ||
835 | return rq; | |
836 | } | |
837 | EXPORT_SYMBOL(elv_next_request); | |
838 | ||
839 | void elv_dequeue_request(struct request_queue *q, struct request *rq) | |
840 | { | |
841 | BUG_ON(list_empty(&rq->queuelist)); | |
842 | BUG_ON(ELV_ON_HASH(rq)); | |
843 | ||
844 | list_del_init(&rq->queuelist); | |
845 | ||
846 | /* | |
847 | * the time frame between a request being removed from the lists | |
848 | * and to it is freed is accounted as io that is in progress at | |
849 | * the driver side. | |
850 | */ | |
851 | if (blk_account_rq(rq)) | |
852 | q->in_flight++; | |
853 | } | |
854 | EXPORT_SYMBOL(elv_dequeue_request); | |
855 | ||
856 | int elv_queue_empty(struct request_queue *q) | |
857 | { | |
858 | elevator_t *e = q->elevator; | |
859 | ||
860 | if (!list_empty(&q->queue_head)) | |
861 | return 0; | |
862 | ||
863 | if (e->ops->elevator_queue_empty_fn) | |
864 | return e->ops->elevator_queue_empty_fn(q); | |
865 | ||
866 | return 1; | |
867 | } | |
868 | EXPORT_SYMBOL(elv_queue_empty); | |
869 | ||
870 | struct request *elv_latter_request(struct request_queue *q, struct request *rq) | |
871 | { | |
872 | elevator_t *e = q->elevator; | |
873 | ||
874 | if (e->ops->elevator_latter_req_fn) | |
875 | return e->ops->elevator_latter_req_fn(q, rq); | |
876 | return NULL; | |
877 | } | |
878 | ||
879 | struct request *elv_former_request(struct request_queue *q, struct request *rq) | |
880 | { | |
881 | elevator_t *e = q->elevator; | |
882 | ||
883 | if (e->ops->elevator_former_req_fn) | |
884 | return e->ops->elevator_former_req_fn(q, rq); | |
885 | return NULL; | |
886 | } | |
887 | ||
888 | int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) | |
889 | { | |
890 | elevator_t *e = q->elevator; | |
891 | ||
892 | if (e->ops->elevator_set_req_fn) | |
893 | return e->ops->elevator_set_req_fn(q, rq, gfp_mask); | |
894 | ||
895 | rq->elevator_private = NULL; | |
896 | return 0; | |
897 | } | |
898 | ||
899 | void elv_put_request(struct request_queue *q, struct request *rq) | |
900 | { | |
901 | elevator_t *e = q->elevator; | |
902 | ||
903 | if (e->ops->elevator_put_req_fn) | |
904 | e->ops->elevator_put_req_fn(rq); | |
905 | } | |
906 | ||
907 | int elv_may_queue(struct request_queue *q, int rw) | |
908 | { | |
909 | elevator_t *e = q->elevator; | |
910 | ||
911 | if (e->ops->elevator_may_queue_fn) | |
912 | return e->ops->elevator_may_queue_fn(q, rw); | |
913 | ||
914 | return ELV_MQUEUE_MAY; | |
915 | } | |
916 | ||
917 | void elv_abort_queue(struct request_queue *q) | |
918 | { | |
919 | struct request *rq; | |
920 | ||
921 | while (!list_empty(&q->queue_head)) { | |
922 | rq = list_entry_rq(q->queue_head.next); | |
923 | rq->cmd_flags |= REQ_QUIET; | |
924 | blk_add_trace_rq(q, rq, BLK_TA_ABORT); | |
925 | end_queued_request(rq, 0); | |
926 | } | |
927 | } | |
928 | EXPORT_SYMBOL(elv_abort_queue); | |
929 | ||
930 | void elv_completed_request(struct request_queue *q, struct request *rq) | |
931 | { | |
932 | elevator_t *e = q->elevator; | |
933 | ||
934 | /* | |
935 | * request is released from the driver, io must be done | |
936 | */ | |
937 | if (blk_account_rq(rq)) { | |
938 | q->in_flight--; | |
939 | if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn) | |
940 | e->ops->elevator_completed_req_fn(q, rq); | |
941 | } | |
942 | ||
943 | /* | |
944 | * Check if the queue is waiting for fs requests to be | |
945 | * drained for flush sequence. | |
946 | */ | |
947 | if (unlikely(q->ordseq)) { | |
948 | struct request *first_rq = list_entry_rq(q->queue_head.next); | |
949 | if (q->in_flight == 0 && | |
950 | blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN && | |
951 | blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) { | |
952 | blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0); | |
953 | q->request_fn(q); | |
954 | } | |
955 | } | |
956 | } | |
957 | ||
958 | #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr) | |
959 | ||
960 | static ssize_t | |
961 | elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page) | |
962 | { | |
963 | elevator_t *e = container_of(kobj, elevator_t, kobj); | |
964 | struct elv_fs_entry *entry = to_elv(attr); | |
965 | ssize_t error; | |
966 | ||
967 | if (!entry->show) | |
968 | return -EIO; | |
969 | ||
970 | mutex_lock(&e->sysfs_lock); | |
971 | error = e->ops ? entry->show(e, page) : -ENOENT; | |
972 | mutex_unlock(&e->sysfs_lock); | |
973 | return error; | |
974 | } | |
975 | ||
976 | static ssize_t | |
977 | elv_attr_store(struct kobject *kobj, struct attribute *attr, | |
978 | const char *page, size_t length) | |
979 | { | |
980 | elevator_t *e = container_of(kobj, elevator_t, kobj); | |
981 | struct elv_fs_entry *entry = to_elv(attr); | |
982 | ssize_t error; | |
983 | ||
984 | if (!entry->store) | |
985 | return -EIO; | |
986 | ||
987 | mutex_lock(&e->sysfs_lock); | |
988 | error = e->ops ? entry->store(e, page, length) : -ENOENT; | |
989 | mutex_unlock(&e->sysfs_lock); | |
990 | return error; | |
991 | } | |
992 | ||
993 | static struct sysfs_ops elv_sysfs_ops = { | |
994 | .show = elv_attr_show, | |
995 | .store = elv_attr_store, | |
996 | }; | |
997 | ||
998 | static struct kobj_type elv_ktype = { | |
999 | .sysfs_ops = &elv_sysfs_ops, | |
1000 | .release = elevator_release, | |
1001 | }; | |
1002 | ||
1003 | int elv_register_queue(struct request_queue *q) | |
1004 | { | |
1005 | elevator_t *e = q->elevator; | |
1006 | int error; | |
1007 | ||
1008 | error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched"); | |
1009 | if (!error) { | |
1010 | struct elv_fs_entry *attr = e->elevator_type->elevator_attrs; | |
1011 | if (attr) { | |
1012 | while (attr->attr.name) { | |
1013 | if (sysfs_create_file(&e->kobj, &attr->attr)) | |
1014 | break; | |
1015 | attr++; | |
1016 | } | |
1017 | } | |
1018 | kobject_uevent(&e->kobj, KOBJ_ADD); | |
1019 | } | |
1020 | return error; | |
1021 | } | |
1022 | ||
1023 | static void __elv_unregister_queue(elevator_t *e) | |
1024 | { | |
1025 | kobject_uevent(&e->kobj, KOBJ_REMOVE); | |
1026 | kobject_del(&e->kobj); | |
1027 | } | |
1028 | ||
1029 | void elv_unregister_queue(struct request_queue *q) | |
1030 | { | |
1031 | if (q) | |
1032 | __elv_unregister_queue(q->elevator); | |
1033 | } | |
1034 | ||
1035 | void elv_register(struct elevator_type *e) | |
1036 | { | |
1037 | char *def = ""; | |
1038 | ||
1039 | spin_lock(&elv_list_lock); | |
1040 | BUG_ON(elevator_find(e->elevator_name)); | |
1041 | list_add_tail(&e->list, &elv_list); | |
1042 | spin_unlock(&elv_list_lock); | |
1043 | ||
1044 | if (!strcmp(e->elevator_name, chosen_elevator) || | |
1045 | (!*chosen_elevator && | |
1046 | !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED))) | |
1047 | def = " (default)"; | |
1048 | ||
1049 | printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name, | |
1050 | def); | |
1051 | } | |
1052 | EXPORT_SYMBOL_GPL(elv_register); | |
1053 | ||
1054 | void elv_unregister(struct elevator_type *e) | |
1055 | { | |
1056 | struct task_struct *g, *p; | |
1057 | ||
1058 | /* | |
1059 | * Iterate every thread in the process to remove the io contexts. | |
1060 | */ | |
1061 | if (e->ops.trim) { | |
1062 | read_lock(&tasklist_lock); | |
1063 | do_each_thread(g, p) { | |
1064 | task_lock(p); | |
1065 | if (p->io_context) | |
1066 | e->ops.trim(p->io_context); | |
1067 | task_unlock(p); | |
1068 | } while_each_thread(g, p); | |
1069 | read_unlock(&tasklist_lock); | |
1070 | } | |
1071 | ||
1072 | spin_lock(&elv_list_lock); | |
1073 | list_del_init(&e->list); | |
1074 | spin_unlock(&elv_list_lock); | |
1075 | } | |
1076 | EXPORT_SYMBOL_GPL(elv_unregister); | |
1077 | ||
1078 | /* | |
1079 | * switch to new_e io scheduler. be careful not to introduce deadlocks - | |
1080 | * we don't free the old io scheduler, before we have allocated what we | |
1081 | * need for the new one. this way we have a chance of going back to the old | |
1082 | * one, if the new one fails init for some reason. | |
1083 | */ | |
1084 | static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) | |
1085 | { | |
1086 | elevator_t *old_elevator, *e; | |
1087 | void *data; | |
1088 | ||
1089 | /* | |
1090 | * Allocate new elevator | |
1091 | */ | |
1092 | e = elevator_alloc(q, new_e); | |
1093 | if (!e) | |
1094 | return 0; | |
1095 | ||
1096 | data = elevator_init_queue(q, e); | |
1097 | if (!data) { | |
1098 | kobject_put(&e->kobj); | |
1099 | return 0; | |
1100 | } | |
1101 | ||
1102 | /* | |
1103 | * Turn on BYPASS and drain all requests w/ elevator private data | |
1104 | */ | |
1105 | spin_lock_irq(q->queue_lock); | |
1106 | ||
1107 | queue_flag_set(QUEUE_FLAG_ELVSWITCH, q); | |
1108 | ||
1109 | elv_drain_elevator(q); | |
1110 | ||
1111 | while (q->rq.elvpriv) { | |
1112 | blk_remove_plug(q); | |
1113 | q->request_fn(q); | |
1114 | spin_unlock_irq(q->queue_lock); | |
1115 | msleep(10); | |
1116 | spin_lock_irq(q->queue_lock); | |
1117 | elv_drain_elevator(q); | |
1118 | } | |
1119 | ||
1120 | /* | |
1121 | * Remember old elevator. | |
1122 | */ | |
1123 | old_elevator = q->elevator; | |
1124 | ||
1125 | /* | |
1126 | * attach and start new elevator | |
1127 | */ | |
1128 | elevator_attach(q, e, data); | |
1129 | ||
1130 | spin_unlock_irq(q->queue_lock); | |
1131 | ||
1132 | __elv_unregister_queue(old_elevator); | |
1133 | ||
1134 | if (elv_register_queue(q)) | |
1135 | goto fail_register; | |
1136 | ||
1137 | /* | |
1138 | * finally exit old elevator and turn off BYPASS. | |
1139 | */ | |
1140 | elevator_exit(old_elevator); | |
1141 | spin_lock_irq(q->queue_lock); | |
1142 | queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q); | |
1143 | spin_unlock_irq(q->queue_lock); | |
1144 | ||
1145 | blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name); | |
1146 | ||
1147 | return 1; | |
1148 | ||
1149 | fail_register: | |
1150 | /* | |
1151 | * switch failed, exit the new io scheduler and reattach the old | |
1152 | * one again (along with re-adding the sysfs dir) | |
1153 | */ | |
1154 | elevator_exit(e); | |
1155 | q->elevator = old_elevator; | |
1156 | elv_register_queue(q); | |
1157 | ||
1158 | spin_lock_irq(q->queue_lock); | |
1159 | queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q); | |
1160 | spin_unlock_irq(q->queue_lock); | |
1161 | ||
1162 | return 0; | |
1163 | } | |
1164 | ||
1165 | ssize_t elv_iosched_store(struct request_queue *q, const char *name, | |
1166 | size_t count) | |
1167 | { | |
1168 | char elevator_name[ELV_NAME_MAX]; | |
1169 | size_t len; | |
1170 | struct elevator_type *e; | |
1171 | ||
1172 | elevator_name[sizeof(elevator_name) - 1] = '\0'; | |
1173 | strncpy(elevator_name, name, sizeof(elevator_name) - 1); | |
1174 | len = strlen(elevator_name); | |
1175 | ||
1176 | if (len && elevator_name[len - 1] == '\n') | |
1177 | elevator_name[len - 1] = '\0'; | |
1178 | ||
1179 | e = elevator_get(elevator_name); | |
1180 | if (!e) { | |
1181 | printk(KERN_ERR "elevator: type %s not found\n", elevator_name); | |
1182 | return -EINVAL; | |
1183 | } | |
1184 | ||
1185 | if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) { | |
1186 | elevator_put(e); | |
1187 | return count; | |
1188 | } | |
1189 | ||
1190 | if (!elevator_switch(q, e)) | |
1191 | printk(KERN_ERR "elevator: switch to %s failed\n", | |
1192 | elevator_name); | |
1193 | return count; | |
1194 | } | |
1195 | ||
1196 | ssize_t elv_iosched_show(struct request_queue *q, char *name) | |
1197 | { | |
1198 | elevator_t *e = q->elevator; | |
1199 | struct elevator_type *elv = e->elevator_type; | |
1200 | struct elevator_type *__e; | |
1201 | int len = 0; | |
1202 | ||
1203 | spin_lock(&elv_list_lock); | |
1204 | list_for_each_entry(__e, &elv_list, list) { | |
1205 | if (!strcmp(elv->elevator_name, __e->elevator_name)) | |
1206 | len += sprintf(name+len, "[%s] ", elv->elevator_name); | |
1207 | else | |
1208 | len += sprintf(name+len, "%s ", __e->elevator_name); | |
1209 | } | |
1210 | spin_unlock(&elv_list_lock); | |
1211 | ||
1212 | len += sprintf(len+name, "\n"); | |
1213 | return len; | |
1214 | } | |
1215 | ||
1216 | struct request *elv_rb_former_request(struct request_queue *q, | |
1217 | struct request *rq) | |
1218 | { | |
1219 | struct rb_node *rbprev = rb_prev(&rq->rb_node); | |
1220 | ||
1221 | if (rbprev) | |
1222 | return rb_entry_rq(rbprev); | |
1223 | ||
1224 | return NULL; | |
1225 | } | |
1226 | EXPORT_SYMBOL(elv_rb_former_request); | |
1227 | ||
1228 | struct request *elv_rb_latter_request(struct request_queue *q, | |
1229 | struct request *rq) | |
1230 | { | |
1231 | struct rb_node *rbnext = rb_next(&rq->rb_node); | |
1232 | ||
1233 | if (rbnext) | |
1234 | return rb_entry_rq(rbnext); | |
1235 | ||
1236 | return NULL; | |
1237 | } | |
1238 | EXPORT_SYMBOL(elv_rb_latter_request); |