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1da177e4 | 1 | /* |
1da177e4 LT |
2 | * Block device elevator/IO-scheduler. |
3 | * | |
4 | * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE | |
5 | * | |
6 | * 30042000 Jens Axboe <axboe@suse.de> : | |
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/config.h> | |
31 | #include <linux/module.h> | |
32 | #include <linux/slab.h> | |
33 | #include <linux/init.h> | |
34 | #include <linux/compiler.h> | |
cb98fc8b | 35 | #include <linux/delay.h> |
1da177e4 LT |
36 | |
37 | #include <asm/uaccess.h> | |
38 | ||
39 | static DEFINE_SPINLOCK(elv_list_lock); | |
40 | static LIST_HEAD(elv_list); | |
41 | ||
42 | /* | |
43 | * can we safely merge with this request? | |
44 | */ | |
45 | inline int elv_rq_merge_ok(struct request *rq, struct bio *bio) | |
46 | { | |
47 | if (!rq_mergeable(rq)) | |
48 | return 0; | |
49 | ||
50 | /* | |
51 | * different data direction or already started, don't merge | |
52 | */ | |
53 | if (bio_data_dir(bio) != rq_data_dir(rq)) | |
54 | return 0; | |
55 | ||
56 | /* | |
57 | * same device and no special stuff set, merge is ok | |
58 | */ | |
59 | if (rq->rq_disk == bio->bi_bdev->bd_disk && | |
60 | !rq->waiting && !rq->special) | |
61 | return 1; | |
62 | ||
63 | return 0; | |
64 | } | |
65 | EXPORT_SYMBOL(elv_rq_merge_ok); | |
66 | ||
769db45b | 67 | static inline int elv_try_merge(struct request *__rq, struct bio *bio) |
1da177e4 LT |
68 | { |
69 | int ret = ELEVATOR_NO_MERGE; | |
70 | ||
71 | /* | |
72 | * we can merge and sequence is ok, check if it's possible | |
73 | */ | |
74 | if (elv_rq_merge_ok(__rq, bio)) { | |
75 | if (__rq->sector + __rq->nr_sectors == bio->bi_sector) | |
76 | ret = ELEVATOR_BACK_MERGE; | |
77 | else if (__rq->sector - bio_sectors(bio) == bio->bi_sector) | |
78 | ret = ELEVATOR_FRONT_MERGE; | |
79 | } | |
80 | ||
81 | return ret; | |
82 | } | |
1da177e4 | 83 | |
1da177e4 LT |
84 | static struct elevator_type *elevator_find(const char *name) |
85 | { | |
86 | struct elevator_type *e = NULL; | |
87 | struct list_head *entry; | |
88 | ||
1da177e4 LT |
89 | list_for_each(entry, &elv_list) { |
90 | struct elevator_type *__e; | |
91 | ||
92 | __e = list_entry(entry, struct elevator_type, list); | |
93 | ||
94 | if (!strcmp(__e->elevator_name, name)) { | |
95 | e = __e; | |
96 | break; | |
97 | } | |
98 | } | |
1da177e4 LT |
99 | |
100 | return e; | |
101 | } | |
102 | ||
103 | static void elevator_put(struct elevator_type *e) | |
104 | { | |
105 | module_put(e->elevator_owner); | |
106 | } | |
107 | ||
108 | static struct elevator_type *elevator_get(const char *name) | |
109 | { | |
2824bc93 | 110 | struct elevator_type *e; |
1da177e4 | 111 | |
2824bc93 TH |
112 | spin_lock_irq(&elv_list_lock); |
113 | ||
114 | e = elevator_find(name); | |
115 | if (e && !try_module_get(e->elevator_owner)) | |
116 | e = NULL; | |
117 | ||
118 | spin_unlock_irq(&elv_list_lock); | |
1da177e4 LT |
119 | |
120 | return e; | |
121 | } | |
122 | ||
123 | static int elevator_attach(request_queue_t *q, struct elevator_type *e, | |
124 | struct elevator_queue *eq) | |
125 | { | |
126 | int ret = 0; | |
127 | ||
128 | memset(eq, 0, sizeof(*eq)); | |
129 | eq->ops = &e->ops; | |
130 | eq->elevator_type = e; | |
131 | ||
1da177e4 LT |
132 | q->elevator = eq; |
133 | ||
134 | if (eq->ops->elevator_init_fn) | |
135 | ret = eq->ops->elevator_init_fn(q, eq); | |
136 | ||
137 | return ret; | |
138 | } | |
139 | ||
140 | static char chosen_elevator[16]; | |
141 | ||
142 | static void elevator_setup_default(void) | |
143 | { | |
2824bc93 TH |
144 | struct elevator_type *e; |
145 | ||
1da177e4 | 146 | /* |
131dda7f | 147 | * If default has not been set, use the compiled-in selection. |
1da177e4 | 148 | */ |
131dda7f ND |
149 | if (!chosen_elevator[0]) |
150 | strcpy(chosen_elevator, CONFIG_DEFAULT_IOSCHED); | |
151 | ||
152 | /* | |
153 | * If the given scheduler is not available, fall back to no-op. | |
154 | */ | |
cff3ba22 ZA |
155 | if ((e = elevator_find(chosen_elevator))) |
156 | elevator_put(e); | |
157 | else | |
131dda7f | 158 | strcpy(chosen_elevator, "noop"); |
1da177e4 LT |
159 | } |
160 | ||
161 | static int __init elevator_setup(char *str) | |
162 | { | |
163 | strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1); | |
164 | return 0; | |
165 | } | |
166 | ||
167 | __setup("elevator=", elevator_setup); | |
168 | ||
169 | int elevator_init(request_queue_t *q, char *name) | |
170 | { | |
171 | struct elevator_type *e = NULL; | |
172 | struct elevator_queue *eq; | |
173 | int ret = 0; | |
174 | ||
cb98fc8b TH |
175 | INIT_LIST_HEAD(&q->queue_head); |
176 | q->last_merge = NULL; | |
177 | q->end_sector = 0; | |
178 | q->boundary_rq = NULL; | |
cb98fc8b | 179 | |
1da177e4 LT |
180 | elevator_setup_default(); |
181 | ||
182 | if (!name) | |
183 | name = chosen_elevator; | |
184 | ||
185 | e = elevator_get(name); | |
186 | if (!e) | |
187 | return -EINVAL; | |
188 | ||
189 | eq = kmalloc(sizeof(struct elevator_queue), GFP_KERNEL); | |
190 | if (!eq) { | |
b8ea2cb5 | 191 | elevator_put(e); |
1da177e4 LT |
192 | return -ENOMEM; |
193 | } | |
194 | ||
195 | ret = elevator_attach(q, e, eq); | |
196 | if (ret) { | |
197 | kfree(eq); | |
b8ea2cb5 | 198 | elevator_put(e); |
1da177e4 LT |
199 | } |
200 | ||
201 | return ret; | |
202 | } | |
203 | ||
204 | void elevator_exit(elevator_t *e) | |
205 | { | |
206 | if (e->ops->elevator_exit_fn) | |
207 | e->ops->elevator_exit_fn(e); | |
208 | ||
209 | elevator_put(e->elevator_type); | |
210 | e->elevator_type = NULL; | |
211 | kfree(e); | |
212 | } | |
213 | ||
8922e16c TH |
214 | /* |
215 | * Insert rq into dispatch queue of q. Queue lock must be held on | |
216 | * entry. If sort != 0, rq is sort-inserted; otherwise, rq will be | |
217 | * appended to the dispatch queue. To be used by specific elevators. | |
218 | */ | |
1b47f531 | 219 | void elv_dispatch_sort(request_queue_t *q, struct request *rq) |
8922e16c TH |
220 | { |
221 | sector_t boundary; | |
8922e16c TH |
222 | struct list_head *entry; |
223 | ||
06b86245 TH |
224 | if (q->last_merge == rq) |
225 | q->last_merge = NULL; | |
15853af9 | 226 | q->nr_sorted--; |
06b86245 | 227 | |
1b47f531 | 228 | boundary = q->end_sector; |
cb19833d | 229 | |
8922e16c TH |
230 | list_for_each_prev(entry, &q->queue_head) { |
231 | struct request *pos = list_entry_rq(entry); | |
232 | ||
233 | if (pos->flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED)) | |
234 | break; | |
235 | if (rq->sector >= boundary) { | |
236 | if (pos->sector < boundary) | |
237 | continue; | |
238 | } else { | |
239 | if (pos->sector >= boundary) | |
240 | break; | |
241 | } | |
242 | if (rq->sector >= pos->sector) | |
243 | break; | |
244 | } | |
245 | ||
246 | list_add(&rq->queuelist, entry); | |
247 | } | |
248 | ||
1da177e4 LT |
249 | int elv_merge(request_queue_t *q, struct request **req, struct bio *bio) |
250 | { | |
251 | elevator_t *e = q->elevator; | |
06b86245 TH |
252 | int ret; |
253 | ||
254 | if (q->last_merge) { | |
255 | ret = elv_try_merge(q->last_merge, bio); | |
256 | if (ret != ELEVATOR_NO_MERGE) { | |
257 | *req = q->last_merge; | |
258 | return ret; | |
259 | } | |
260 | } | |
1da177e4 LT |
261 | |
262 | if (e->ops->elevator_merge_fn) | |
263 | return e->ops->elevator_merge_fn(q, req, bio); | |
264 | ||
265 | return ELEVATOR_NO_MERGE; | |
266 | } | |
267 | ||
268 | void elv_merged_request(request_queue_t *q, struct request *rq) | |
269 | { | |
270 | elevator_t *e = q->elevator; | |
271 | ||
272 | if (e->ops->elevator_merged_fn) | |
273 | e->ops->elevator_merged_fn(q, rq); | |
06b86245 TH |
274 | |
275 | q->last_merge = rq; | |
1da177e4 LT |
276 | } |
277 | ||
278 | void elv_merge_requests(request_queue_t *q, struct request *rq, | |
279 | struct request *next) | |
280 | { | |
281 | elevator_t *e = q->elevator; | |
282 | ||
1da177e4 LT |
283 | if (e->ops->elevator_merge_req_fn) |
284 | e->ops->elevator_merge_req_fn(q, rq, next); | |
15853af9 | 285 | q->nr_sorted--; |
06b86245 TH |
286 | |
287 | q->last_merge = rq; | |
1da177e4 LT |
288 | } |
289 | ||
8922e16c | 290 | void elv_requeue_request(request_queue_t *q, struct request *rq) |
1da177e4 LT |
291 | { |
292 | elevator_t *e = q->elevator; | |
293 | ||
294 | /* | |
295 | * it already went through dequeue, we need to decrement the | |
296 | * in_flight count again | |
297 | */ | |
8922e16c | 298 | if (blk_account_rq(rq)) { |
1da177e4 | 299 | q->in_flight--; |
8922e16c TH |
300 | if (blk_sorted_rq(rq) && e->ops->elevator_deactivate_req_fn) |
301 | e->ops->elevator_deactivate_req_fn(q, rq); | |
302 | } | |
1da177e4 LT |
303 | |
304 | rq->flags &= ~REQ_STARTED; | |
305 | ||
797e7dbb | 306 | __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE, 0); |
1da177e4 LT |
307 | } |
308 | ||
15853af9 TH |
309 | static void elv_drain_elevator(request_queue_t *q) |
310 | { | |
311 | static int printed; | |
312 | while (q->elevator->ops->elevator_dispatch_fn(q, 1)) | |
313 | ; | |
314 | if (q->nr_sorted == 0) | |
315 | return; | |
316 | if (printed++ < 10) { | |
317 | printk(KERN_ERR "%s: forced dispatching is broken " | |
318 | "(nr_sorted=%u), please report this\n", | |
319 | q->elevator->elevator_type->elevator_name, q->nr_sorted); | |
320 | } | |
321 | } | |
322 | ||
1da177e4 LT |
323 | void __elv_add_request(request_queue_t *q, struct request *rq, int where, |
324 | int plug) | |
325 | { | |
797e7dbb TH |
326 | struct list_head *pos; |
327 | unsigned ordseq; | |
328 | ||
329 | if (q->ordcolor) | |
330 | rq->flags |= REQ_ORDERED_COLOR; | |
331 | ||
8922e16c | 332 | if (rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) { |
797e7dbb TH |
333 | /* |
334 | * toggle ordered color | |
335 | */ | |
336 | q->ordcolor ^= 1; | |
337 | ||
8922e16c TH |
338 | /* |
339 | * barriers implicitly indicate back insertion | |
340 | */ | |
341 | if (where == ELEVATOR_INSERT_SORT) | |
342 | where = ELEVATOR_INSERT_BACK; | |
343 | ||
344 | /* | |
1b47f531 | 345 | * this request is scheduling boundary, update end_sector |
8922e16c TH |
346 | */ |
347 | if (blk_fs_request(rq)) { | |
1b47f531 | 348 | q->end_sector = rq_end_sector(rq); |
8922e16c TH |
349 | q->boundary_rq = rq; |
350 | } | |
cb98fc8b TH |
351 | } else if (!(rq->flags & REQ_ELVPRIV) && where == ELEVATOR_INSERT_SORT) |
352 | where = ELEVATOR_INSERT_BACK; | |
1da177e4 LT |
353 | |
354 | if (plug) | |
355 | blk_plug_device(q); | |
356 | ||
357 | rq->q = q; | |
358 | ||
8922e16c TH |
359 | switch (where) { |
360 | case ELEVATOR_INSERT_FRONT: | |
361 | rq->flags |= REQ_SOFTBARRIER; | |
362 | ||
363 | list_add(&rq->queuelist, &q->queue_head); | |
364 | break; | |
365 | ||
366 | case ELEVATOR_INSERT_BACK: | |
367 | rq->flags |= REQ_SOFTBARRIER; | |
15853af9 | 368 | elv_drain_elevator(q); |
8922e16c TH |
369 | list_add_tail(&rq->queuelist, &q->queue_head); |
370 | /* | |
371 | * We kick the queue here for the following reasons. | |
372 | * - The elevator might have returned NULL previously | |
373 | * to delay requests and returned them now. As the | |
374 | * queue wasn't empty before this request, ll_rw_blk | |
375 | * won't run the queue on return, resulting in hang. | |
376 | * - Usually, back inserted requests won't be merged | |
377 | * with anything. There's no point in delaying queue | |
378 | * processing. | |
379 | */ | |
380 | blk_remove_plug(q); | |
381 | q->request_fn(q); | |
382 | break; | |
383 | ||
384 | case ELEVATOR_INSERT_SORT: | |
385 | BUG_ON(!blk_fs_request(rq)); | |
386 | rq->flags |= REQ_SORTED; | |
15853af9 | 387 | q->nr_sorted++; |
06b86245 TH |
388 | if (q->last_merge == NULL && rq_mergeable(rq)) |
389 | q->last_merge = rq; | |
ca23509f TH |
390 | /* |
391 | * Some ioscheds (cfq) run q->request_fn directly, so | |
392 | * rq cannot be accessed after calling | |
393 | * elevator_add_req_fn. | |
394 | */ | |
395 | q->elevator->ops->elevator_add_req_fn(q, rq); | |
8922e16c TH |
396 | break; |
397 | ||
797e7dbb TH |
398 | case ELEVATOR_INSERT_REQUEUE: |
399 | /* | |
400 | * If ordered flush isn't in progress, we do front | |
401 | * insertion; otherwise, requests should be requeued | |
402 | * in ordseq order. | |
403 | */ | |
404 | rq->flags |= REQ_SOFTBARRIER; | |
405 | ||
406 | if (q->ordseq == 0) { | |
407 | list_add(&rq->queuelist, &q->queue_head); | |
408 | break; | |
409 | } | |
410 | ||
411 | ordseq = blk_ordered_req_seq(rq); | |
412 | ||
413 | list_for_each(pos, &q->queue_head) { | |
414 | struct request *pos_rq = list_entry_rq(pos); | |
415 | if (ordseq <= blk_ordered_req_seq(pos_rq)) | |
416 | break; | |
417 | } | |
418 | ||
419 | list_add_tail(&rq->queuelist, pos); | |
420 | break; | |
421 | ||
8922e16c TH |
422 | default: |
423 | printk(KERN_ERR "%s: bad insertion point %d\n", | |
424 | __FUNCTION__, where); | |
425 | BUG(); | |
426 | } | |
427 | ||
428 | if (blk_queue_plugged(q)) { | |
429 | int nrq = q->rq.count[READ] + q->rq.count[WRITE] | |
430 | - q->in_flight; | |
431 | ||
432 | if (nrq >= q->unplug_thresh) | |
433 | __generic_unplug_device(q); | |
434 | } | |
1da177e4 LT |
435 | } |
436 | ||
437 | void elv_add_request(request_queue_t *q, struct request *rq, int where, | |
438 | int plug) | |
439 | { | |
440 | unsigned long flags; | |
441 | ||
442 | spin_lock_irqsave(q->queue_lock, flags); | |
443 | __elv_add_request(q, rq, where, plug); | |
444 | spin_unlock_irqrestore(q->queue_lock, flags); | |
445 | } | |
446 | ||
447 | static inline struct request *__elv_next_request(request_queue_t *q) | |
448 | { | |
8922e16c TH |
449 | struct request *rq; |
450 | ||
797e7dbb TH |
451 | while (1) { |
452 | while (!list_empty(&q->queue_head)) { | |
453 | rq = list_entry_rq(q->queue_head.next); | |
454 | if (blk_do_ordered(q, &rq)) | |
455 | return rq; | |
456 | } | |
1da177e4 | 457 | |
797e7dbb TH |
458 | if (!q->elevator->ops->elevator_dispatch_fn(q, 0)) |
459 | return NULL; | |
1da177e4 | 460 | } |
1da177e4 LT |
461 | } |
462 | ||
463 | struct request *elv_next_request(request_queue_t *q) | |
464 | { | |
465 | struct request *rq; | |
466 | int ret; | |
467 | ||
468 | while ((rq = __elv_next_request(q)) != NULL) { | |
8922e16c TH |
469 | if (!(rq->flags & REQ_STARTED)) { |
470 | elevator_t *e = q->elevator; | |
471 | ||
472 | /* | |
473 | * This is the first time the device driver | |
474 | * sees this request (possibly after | |
475 | * requeueing). Notify IO scheduler. | |
476 | */ | |
477 | if (blk_sorted_rq(rq) && | |
478 | e->ops->elevator_activate_req_fn) | |
479 | e->ops->elevator_activate_req_fn(q, rq); | |
1da177e4 | 480 | |
8922e16c TH |
481 | /* |
482 | * just mark as started even if we don't start | |
483 | * it, a request that has been delayed should | |
484 | * not be passed by new incoming requests | |
485 | */ | |
486 | rq->flags |= REQ_STARTED; | |
487 | } | |
1da177e4 | 488 | |
8922e16c | 489 | if (!q->boundary_rq || q->boundary_rq == rq) { |
1b47f531 | 490 | q->end_sector = rq_end_sector(rq); |
8922e16c TH |
491 | q->boundary_rq = NULL; |
492 | } | |
1da177e4 LT |
493 | |
494 | if ((rq->flags & REQ_DONTPREP) || !q->prep_rq_fn) | |
495 | break; | |
496 | ||
497 | ret = q->prep_rq_fn(q, rq); | |
498 | if (ret == BLKPREP_OK) { | |
499 | break; | |
500 | } else if (ret == BLKPREP_DEFER) { | |
2e759cd4 TH |
501 | /* |
502 | * the request may have been (partially) prepped. | |
503 | * we need to keep this request in the front to | |
8922e16c TH |
504 | * avoid resource deadlock. REQ_STARTED will |
505 | * prevent other fs requests from passing this one. | |
2e759cd4 | 506 | */ |
1da177e4 LT |
507 | rq = NULL; |
508 | break; | |
509 | } else if (ret == BLKPREP_KILL) { | |
510 | int nr_bytes = rq->hard_nr_sectors << 9; | |
511 | ||
512 | if (!nr_bytes) | |
513 | nr_bytes = rq->data_len; | |
514 | ||
515 | blkdev_dequeue_request(rq); | |
516 | rq->flags |= REQ_QUIET; | |
517 | end_that_request_chunk(rq, 0, nr_bytes); | |
8ffdc655 | 518 | end_that_request_last(rq, 0); |
1da177e4 LT |
519 | } else { |
520 | printk(KERN_ERR "%s: bad return=%d\n", __FUNCTION__, | |
521 | ret); | |
522 | break; | |
523 | } | |
524 | } | |
525 | ||
526 | return rq; | |
527 | } | |
528 | ||
8922e16c | 529 | void elv_dequeue_request(request_queue_t *q, struct request *rq) |
1da177e4 | 530 | { |
8922e16c TH |
531 | BUG_ON(list_empty(&rq->queuelist)); |
532 | ||
533 | list_del_init(&rq->queuelist); | |
1da177e4 LT |
534 | |
535 | /* | |
536 | * the time frame between a request being removed from the lists | |
537 | * and to it is freed is accounted as io that is in progress at | |
8922e16c | 538 | * the driver side. |
1da177e4 LT |
539 | */ |
540 | if (blk_account_rq(rq)) | |
541 | q->in_flight++; | |
1da177e4 LT |
542 | } |
543 | ||
544 | int elv_queue_empty(request_queue_t *q) | |
545 | { | |
546 | elevator_t *e = q->elevator; | |
547 | ||
8922e16c TH |
548 | if (!list_empty(&q->queue_head)) |
549 | return 0; | |
550 | ||
1da177e4 LT |
551 | if (e->ops->elevator_queue_empty_fn) |
552 | return e->ops->elevator_queue_empty_fn(q); | |
553 | ||
8922e16c | 554 | return 1; |
1da177e4 LT |
555 | } |
556 | ||
557 | struct request *elv_latter_request(request_queue_t *q, struct request *rq) | |
558 | { | |
1da177e4 LT |
559 | elevator_t *e = q->elevator; |
560 | ||
561 | if (e->ops->elevator_latter_req_fn) | |
562 | return e->ops->elevator_latter_req_fn(q, rq); | |
1da177e4 LT |
563 | return NULL; |
564 | } | |
565 | ||
566 | struct request *elv_former_request(request_queue_t *q, struct request *rq) | |
567 | { | |
1da177e4 LT |
568 | elevator_t *e = q->elevator; |
569 | ||
570 | if (e->ops->elevator_former_req_fn) | |
571 | return e->ops->elevator_former_req_fn(q, rq); | |
1da177e4 LT |
572 | return NULL; |
573 | } | |
574 | ||
22e2c507 | 575 | int elv_set_request(request_queue_t *q, struct request *rq, struct bio *bio, |
8267e268 | 576 | gfp_t gfp_mask) |
1da177e4 LT |
577 | { |
578 | elevator_t *e = q->elevator; | |
579 | ||
580 | if (e->ops->elevator_set_req_fn) | |
22e2c507 | 581 | return e->ops->elevator_set_req_fn(q, rq, bio, gfp_mask); |
1da177e4 LT |
582 | |
583 | rq->elevator_private = NULL; | |
584 | return 0; | |
585 | } | |
586 | ||
587 | void elv_put_request(request_queue_t *q, struct request *rq) | |
588 | { | |
589 | elevator_t *e = q->elevator; | |
590 | ||
591 | if (e->ops->elevator_put_req_fn) | |
592 | e->ops->elevator_put_req_fn(q, rq); | |
593 | } | |
594 | ||
22e2c507 | 595 | int elv_may_queue(request_queue_t *q, int rw, struct bio *bio) |
1da177e4 LT |
596 | { |
597 | elevator_t *e = q->elevator; | |
598 | ||
599 | if (e->ops->elevator_may_queue_fn) | |
22e2c507 | 600 | return e->ops->elevator_may_queue_fn(q, rw, bio); |
1da177e4 LT |
601 | |
602 | return ELV_MQUEUE_MAY; | |
603 | } | |
604 | ||
605 | void elv_completed_request(request_queue_t *q, struct request *rq) | |
606 | { | |
607 | elevator_t *e = q->elevator; | |
608 | ||
609 | /* | |
610 | * request is released from the driver, io must be done | |
611 | */ | |
8922e16c | 612 | if (blk_account_rq(rq)) { |
1da177e4 | 613 | q->in_flight--; |
1bc691d3 TH |
614 | if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn) |
615 | e->ops->elevator_completed_req_fn(q, rq); | |
616 | } | |
797e7dbb | 617 | |
1bc691d3 TH |
618 | /* |
619 | * Check if the queue is waiting for fs requests to be | |
620 | * drained for flush sequence. | |
621 | */ | |
622 | if (unlikely(q->ordseq)) { | |
623 | struct request *first_rq = list_entry_rq(q->queue_head.next); | |
624 | if (q->in_flight == 0 && | |
797e7dbb TH |
625 | blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN && |
626 | blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) { | |
627 | blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0); | |
628 | q->request_fn(q); | |
629 | } | |
8922e16c | 630 | } |
1da177e4 LT |
631 | } |
632 | ||
633 | int elv_register_queue(struct request_queue *q) | |
634 | { | |
635 | elevator_t *e = q->elevator; | |
636 | ||
637 | e->kobj.parent = kobject_get(&q->kobj); | |
638 | if (!e->kobj.parent) | |
639 | return -EBUSY; | |
640 | ||
641 | snprintf(e->kobj.name, KOBJ_NAME_LEN, "%s", "iosched"); | |
642 | e->kobj.ktype = e->elevator_type->elevator_ktype; | |
643 | ||
644 | return kobject_register(&e->kobj); | |
645 | } | |
646 | ||
647 | void elv_unregister_queue(struct request_queue *q) | |
648 | { | |
649 | if (q) { | |
650 | elevator_t *e = q->elevator; | |
651 | kobject_unregister(&e->kobj); | |
652 | kobject_put(&q->kobj); | |
653 | } | |
654 | } | |
655 | ||
656 | int elv_register(struct elevator_type *e) | |
657 | { | |
2824bc93 | 658 | spin_lock_irq(&elv_list_lock); |
1da177e4 LT |
659 | if (elevator_find(e->elevator_name)) |
660 | BUG(); | |
1da177e4 LT |
661 | list_add_tail(&e->list, &elv_list); |
662 | spin_unlock_irq(&elv_list_lock); | |
663 | ||
664 | printk(KERN_INFO "io scheduler %s registered", e->elevator_name); | |
665 | if (!strcmp(e->elevator_name, chosen_elevator)) | |
666 | printk(" (default)"); | |
667 | printk("\n"); | |
668 | return 0; | |
669 | } | |
670 | EXPORT_SYMBOL_GPL(elv_register); | |
671 | ||
672 | void elv_unregister(struct elevator_type *e) | |
673 | { | |
83521d3e CH |
674 | struct task_struct *g, *p; |
675 | ||
676 | /* | |
677 | * Iterate every thread in the process to remove the io contexts. | |
678 | */ | |
679 | read_lock(&tasklist_lock); | |
680 | do_each_thread(g, p) { | |
681 | struct io_context *ioc = p->io_context; | |
682 | if (ioc && ioc->cic) { | |
683 | ioc->cic->exit(ioc->cic); | |
684 | ioc->cic->dtor(ioc->cic); | |
685 | ioc->cic = NULL; | |
686 | } | |
687 | if (ioc && ioc->aic) { | |
688 | ioc->aic->exit(ioc->aic); | |
689 | ioc->aic->dtor(ioc->aic); | |
690 | ioc->aic = NULL; | |
691 | } | |
692 | } while_each_thread(g, p); | |
693 | read_unlock(&tasklist_lock); | |
694 | ||
1da177e4 LT |
695 | spin_lock_irq(&elv_list_lock); |
696 | list_del_init(&e->list); | |
697 | spin_unlock_irq(&elv_list_lock); | |
698 | } | |
699 | EXPORT_SYMBOL_GPL(elv_unregister); | |
700 | ||
701 | /* | |
702 | * switch to new_e io scheduler. be careful not to introduce deadlocks - | |
703 | * we don't free the old io scheduler, before we have allocated what we | |
704 | * need for the new one. this way we have a chance of going back to the old | |
cb98fc8b | 705 | * one, if the new one fails init for some reason. |
1da177e4 LT |
706 | */ |
707 | static void elevator_switch(request_queue_t *q, struct elevator_type *new_e) | |
708 | { | |
cb98fc8b | 709 | elevator_t *old_elevator, *e; |
1da177e4 | 710 | |
cb98fc8b TH |
711 | /* |
712 | * Allocate new elevator | |
713 | */ | |
714 | e = kmalloc(sizeof(elevator_t), GFP_KERNEL); | |
1da177e4 LT |
715 | if (!e) |
716 | goto error; | |
717 | ||
718 | /* | |
cb98fc8b | 719 | * Turn on BYPASS and drain all requests w/ elevator private data |
1da177e4 | 720 | */ |
cb98fc8b TH |
721 | spin_lock_irq(q->queue_lock); |
722 | ||
64521d1a | 723 | set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags); |
cb98fc8b | 724 | |
15853af9 | 725 | elv_drain_elevator(q); |
cb98fc8b TH |
726 | |
727 | while (q->rq.elvpriv) { | |
407df2aa TH |
728 | blk_remove_plug(q); |
729 | q->request_fn(q); | |
cb98fc8b | 730 | spin_unlock_irq(q->queue_lock); |
64521d1a | 731 | msleep(10); |
cb98fc8b | 732 | spin_lock_irq(q->queue_lock); |
15853af9 | 733 | elv_drain_elevator(q); |
cb98fc8b TH |
734 | } |
735 | ||
736 | spin_unlock_irq(q->queue_lock); | |
1da177e4 LT |
737 | |
738 | /* | |
739 | * unregister old elevator data | |
740 | */ | |
741 | elv_unregister_queue(q); | |
742 | old_elevator = q->elevator; | |
743 | ||
1da177e4 LT |
744 | /* |
745 | * attach and start new elevator | |
746 | */ | |
747 | if (elevator_attach(q, new_e, e)) | |
748 | goto fail; | |
749 | ||
750 | if (elv_register_queue(q)) | |
751 | goto fail_register; | |
752 | ||
753 | /* | |
cb98fc8b | 754 | * finally exit old elevator and turn off BYPASS. |
1da177e4 LT |
755 | */ |
756 | elevator_exit(old_elevator); | |
64521d1a | 757 | clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags); |
1da177e4 LT |
758 | return; |
759 | ||
760 | fail_register: | |
761 | /* | |
762 | * switch failed, exit the new io scheduler and reattach the old | |
763 | * one again (along with re-adding the sysfs dir) | |
764 | */ | |
765 | elevator_exit(e); | |
cb98fc8b | 766 | e = NULL; |
1da177e4 LT |
767 | fail: |
768 | q->elevator = old_elevator; | |
769 | elv_register_queue(q); | |
64521d1a | 770 | clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags); |
cb98fc8b | 771 | kfree(e); |
1da177e4 | 772 | error: |
1da177e4 LT |
773 | elevator_put(new_e); |
774 | printk(KERN_ERR "elevator: switch to %s failed\n",new_e->elevator_name); | |
775 | } | |
776 | ||
777 | ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count) | |
778 | { | |
779 | char elevator_name[ELV_NAME_MAX]; | |
be561235 | 780 | size_t len; |
1da177e4 LT |
781 | struct elevator_type *e; |
782 | ||
be561235 TH |
783 | elevator_name[sizeof(elevator_name) - 1] = '\0'; |
784 | strncpy(elevator_name, name, sizeof(elevator_name) - 1); | |
785 | len = strlen(elevator_name); | |
1da177e4 | 786 | |
be561235 TH |
787 | if (len && elevator_name[len - 1] == '\n') |
788 | elevator_name[len - 1] = '\0'; | |
1da177e4 LT |
789 | |
790 | e = elevator_get(elevator_name); | |
791 | if (!e) { | |
792 | printk(KERN_ERR "elevator: type %s not found\n", elevator_name); | |
793 | return -EINVAL; | |
794 | } | |
795 | ||
2ca7d93b ND |
796 | if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) { |
797 | elevator_put(e); | |
1da177e4 | 798 | return count; |
2ca7d93b | 799 | } |
1da177e4 LT |
800 | |
801 | elevator_switch(q, e); | |
802 | return count; | |
803 | } | |
804 | ||
805 | ssize_t elv_iosched_show(request_queue_t *q, char *name) | |
806 | { | |
807 | elevator_t *e = q->elevator; | |
808 | struct elevator_type *elv = e->elevator_type; | |
809 | struct list_head *entry; | |
810 | int len = 0; | |
811 | ||
812 | spin_lock_irq(q->queue_lock); | |
813 | list_for_each(entry, &elv_list) { | |
814 | struct elevator_type *__e; | |
815 | ||
816 | __e = list_entry(entry, struct elevator_type, list); | |
817 | if (!strcmp(elv->elevator_name, __e->elevator_name)) | |
818 | len += sprintf(name+len, "[%s] ", elv->elevator_name); | |
819 | else | |
820 | len += sprintf(name+len, "%s ", __e->elevator_name); | |
821 | } | |
822 | spin_unlock_irq(q->queue_lock); | |
823 | ||
824 | len += sprintf(len+name, "\n"); | |
825 | return len; | |
826 | } | |
827 | ||
1b47f531 | 828 | EXPORT_SYMBOL(elv_dispatch_sort); |
1da177e4 LT |
829 | EXPORT_SYMBOL(elv_add_request); |
830 | EXPORT_SYMBOL(__elv_add_request); | |
831 | EXPORT_SYMBOL(elv_requeue_request); | |
832 | EXPORT_SYMBOL(elv_next_request); | |
8922e16c | 833 | EXPORT_SYMBOL(elv_dequeue_request); |
1da177e4 LT |
834 | EXPORT_SYMBOL(elv_queue_empty); |
835 | EXPORT_SYMBOL(elv_completed_request); | |
836 | EXPORT_SYMBOL(elevator_exit); | |
837 | EXPORT_SYMBOL(elevator_init); |