blob: 415144372c75e6ca8ad1f632da9b2c18213f92c0 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/drivers/block/elevator.c
3 *
4 * Block device elevator/IO-scheduler.
5 *
6 * Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
7 *
8 * 30042000 Jens Axboe <axboe@suse.de> :
9 *
10 * Split the elevator a bit so that it is possible to choose a different
11 * one or even write a new "plug in". There are three pieces:
12 * - elevator_fn, inserts a new request in the queue list
13 * - elevator_merge_fn, decides whether a new buffer can be merged with
14 * an existing request
15 * - elevator_dequeue_fn, called when a request is taken off the active list
16 *
17 * 20082000 Dave Jones <davej@suse.de> :
18 * Removed tests for max-bomb-segments, which was breaking elvtune
19 * when run without -bN
20 *
21 * Jens:
22 * - Rework again to work with bio instead of buffer_heads
23 * - loose bi_dev comparisons, partition handling is right now
24 * - completely modularize elevator setup and teardown
25 *
26 */
27#include <linux/kernel.h>
28#include <linux/fs.h>
29#include <linux/blkdev.h>
30#include <linux/elevator.h>
31#include <linux/bio.h>
32#include <linux/config.h>
33#include <linux/module.h>
34#include <linux/slab.h>
35#include <linux/init.h>
36#include <linux/compiler.h>
37
38#include <asm/uaccess.h>
39
40static DEFINE_SPINLOCK(elv_list_lock);
41static LIST_HEAD(elv_list);
42
43/*
44 * can we safely merge with this request?
45 */
46inline int elv_rq_merge_ok(struct request *rq, struct bio *bio)
47{
48 if (!rq_mergeable(rq))
49 return 0;
50
51 /*
52 * different data direction or already started, don't merge
53 */
54 if (bio_data_dir(bio) != rq_data_dir(rq))
55 return 0;
56
57 /*
58 * same device and no special stuff set, merge is ok
59 */
60 if (rq->rq_disk == bio->bi_bdev->bd_disk &&
61 !rq->waiting && !rq->special)
62 return 1;
63
64 return 0;
65}
66EXPORT_SYMBOL(elv_rq_merge_ok);
67
68inline int elv_try_merge(struct request *__rq, struct bio *bio)
69{
70 int ret = ELEVATOR_NO_MERGE;
71
72 /*
73 * we can merge and sequence is ok, check if it's possible
74 */
75 if (elv_rq_merge_ok(__rq, bio)) {
76 if (__rq->sector + __rq->nr_sectors == bio->bi_sector)
77 ret = ELEVATOR_BACK_MERGE;
78 else if (__rq->sector - bio_sectors(bio) == bio->bi_sector)
79 ret = ELEVATOR_FRONT_MERGE;
80 }
81
82 return ret;
83}
84EXPORT_SYMBOL(elv_try_merge);
85
Linus Torvalds1da177e2005-04-16 15:20:36 -070086static struct elevator_type *elevator_find(const char *name)
87{
88 struct elevator_type *e = NULL;
89 struct list_head *entry;
90
Linus Torvalds1da177e2005-04-16 15:20:36 -070091 list_for_each(entry, &elv_list) {
92 struct elevator_type *__e;
93
94 __e = list_entry(entry, struct elevator_type, list);
95
96 if (!strcmp(__e->elevator_name, name)) {
97 e = __e;
98 break;
99 }
100 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101
102 return e;
103}
104
105static void elevator_put(struct elevator_type *e)
106{
107 module_put(e->elevator_owner);
108}
109
110static struct elevator_type *elevator_get(const char *name)
111{
Tejun Heo2824bc932005-10-20 10:56:41 +0200112 struct elevator_type *e;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113
Tejun Heo2824bc932005-10-20 10:56:41 +0200114 spin_lock_irq(&elv_list_lock);
115
116 e = elevator_find(name);
117 if (e && !try_module_get(e->elevator_owner))
118 e = NULL;
119
120 spin_unlock_irq(&elv_list_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121
122 return e;
123}
124
125static int elevator_attach(request_queue_t *q, struct elevator_type *e,
126 struct elevator_queue *eq)
127{
128 int ret = 0;
129
130 memset(eq, 0, sizeof(*eq));
131 eq->ops = &e->ops;
132 eq->elevator_type = e;
133
134 INIT_LIST_HEAD(&q->queue_head);
135 q->last_merge = NULL;
136 q->elevator = eq;
Jens Axboe1b47f532005-10-20 16:37:00 +0200137 q->end_sector = 0;
Tejun Heo8922e162005-10-20 16:23:44 +0200138 q->boundary_rq = NULL;
139 q->max_back_kb = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140
141 if (eq->ops->elevator_init_fn)
142 ret = eq->ops->elevator_init_fn(q, eq);
143
144 return ret;
145}
146
147static char chosen_elevator[16];
148
149static void elevator_setup_default(void)
150{
Tejun Heo2824bc932005-10-20 10:56:41 +0200151 struct elevator_type *e;
152
Linus Torvalds1da177e2005-04-16 15:20:36 -0700153 /*
154 * check if default is set and exists
155 */
Tejun Heo2824bc932005-10-20 10:56:41 +0200156 if (chosen_elevator[0] && (e = elevator_get(chosen_elevator))) {
157 elevator_put(e);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700158 return;
Tejun Heo2824bc932005-10-20 10:56:41 +0200159 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160
161#if defined(CONFIG_IOSCHED_AS)
162 strcpy(chosen_elevator, "anticipatory");
163#elif defined(CONFIG_IOSCHED_DEADLINE)
164 strcpy(chosen_elevator, "deadline");
165#elif defined(CONFIG_IOSCHED_CFQ)
166 strcpy(chosen_elevator, "cfq");
167#elif defined(CONFIG_IOSCHED_NOOP)
168 strcpy(chosen_elevator, "noop");
169#else
170#error "You must build at least 1 IO scheduler into the kernel"
171#endif
172}
173
174static int __init elevator_setup(char *str)
175{
176 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
177 return 0;
178}
179
180__setup("elevator=", elevator_setup);
181
182int elevator_init(request_queue_t *q, char *name)
183{
184 struct elevator_type *e = NULL;
185 struct elevator_queue *eq;
186 int ret = 0;
187
188 elevator_setup_default();
189
190 if (!name)
191 name = chosen_elevator;
192
193 e = elevator_get(name);
194 if (!e)
195 return -EINVAL;
196
197 eq = kmalloc(sizeof(struct elevator_queue), GFP_KERNEL);
198 if (!eq) {
199 elevator_put(e->elevator_type);
200 return -ENOMEM;
201 }
202
203 ret = elevator_attach(q, e, eq);
204 if (ret) {
205 kfree(eq);
206 elevator_put(e->elevator_type);
207 }
208
209 return ret;
210}
211
212void elevator_exit(elevator_t *e)
213{
214 if (e->ops->elevator_exit_fn)
215 e->ops->elevator_exit_fn(e);
216
217 elevator_put(e->elevator_type);
218 e->elevator_type = NULL;
219 kfree(e);
220}
221
Tejun Heo8922e162005-10-20 16:23:44 +0200222/*
223 * Insert rq into dispatch queue of q. Queue lock must be held on
224 * entry. If sort != 0, rq is sort-inserted; otherwise, rq will be
225 * appended to the dispatch queue. To be used by specific elevators.
226 */
Jens Axboe1b47f532005-10-20 16:37:00 +0200227void elv_dispatch_sort(request_queue_t *q, struct request *rq)
Tejun Heo8922e162005-10-20 16:23:44 +0200228{
229 sector_t boundary;
230 unsigned max_back;
231 struct list_head *entry;
232
Tejun Heo06b86242005-10-20 16:46:23 +0200233 if (q->last_merge == rq)
234 q->last_merge = NULL;
235
Jens Axboe1b47f532005-10-20 16:37:00 +0200236 boundary = q->end_sector;
Tejun Heo8922e162005-10-20 16:23:44 +0200237 max_back = q->max_back_kb * 2;
238 boundary = boundary > max_back ? boundary - max_back : 0;
Jens Axboe1b47f532005-10-20 16:37:00 +0200239
Tejun Heo8922e162005-10-20 16:23:44 +0200240 list_for_each_prev(entry, &q->queue_head) {
241 struct request *pos = list_entry_rq(entry);
242
243 if (pos->flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED))
244 break;
245 if (rq->sector >= boundary) {
246 if (pos->sector < boundary)
247 continue;
248 } else {
249 if (pos->sector >= boundary)
250 break;
251 }
252 if (rq->sector >= pos->sector)
253 break;
254 }
255
256 list_add(&rq->queuelist, entry);
257}
258
Linus Torvalds1da177e2005-04-16 15:20:36 -0700259int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
260{
261 elevator_t *e = q->elevator;
Tejun Heo06b86242005-10-20 16:46:23 +0200262 int ret;
263
264 if (q->last_merge) {
265 ret = elv_try_merge(q->last_merge, bio);
266 if (ret != ELEVATOR_NO_MERGE) {
267 *req = q->last_merge;
268 return ret;
269 }
270 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700271
272 if (e->ops->elevator_merge_fn)
273 return e->ops->elevator_merge_fn(q, req, bio);
274
275 return ELEVATOR_NO_MERGE;
276}
277
278void elv_merged_request(request_queue_t *q, struct request *rq)
279{
280 elevator_t *e = q->elevator;
281
282 if (e->ops->elevator_merged_fn)
283 e->ops->elevator_merged_fn(q, rq);
Tejun Heo06b86242005-10-20 16:46:23 +0200284
285 q->last_merge = rq;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700286}
287
288void elv_merge_requests(request_queue_t *q, struct request *rq,
289 struct request *next)
290{
291 elevator_t *e = q->elevator;
292
Linus Torvalds1da177e2005-04-16 15:20:36 -0700293 if (e->ops->elevator_merge_req_fn)
294 e->ops->elevator_merge_req_fn(q, rq, next);
Tejun Heo06b86242005-10-20 16:46:23 +0200295
296 q->last_merge = rq;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700297}
298
Tejun Heo8922e162005-10-20 16:23:44 +0200299void elv_requeue_request(request_queue_t *q, struct request *rq)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700300{
301 elevator_t *e = q->elevator;
302
303 /*
304 * it already went through dequeue, we need to decrement the
305 * in_flight count again
306 */
Tejun Heo8922e162005-10-20 16:23:44 +0200307 if (blk_account_rq(rq)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700308 q->in_flight--;
Tejun Heo8922e162005-10-20 16:23:44 +0200309 if (blk_sorted_rq(rq) && e->ops->elevator_deactivate_req_fn)
310 e->ops->elevator_deactivate_req_fn(q, rq);
311 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700312
313 rq->flags &= ~REQ_STARTED;
314
Linus Torvalds1da177e2005-04-16 15:20:36 -0700315 /*
316 * if this is the flush, requeue the original instead and drop the flush
317 */
318 if (rq->flags & REQ_BAR_FLUSH) {
319 clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
320 rq = rq->end_io_data;
321 }
322
Tejun Heo8922e162005-10-20 16:23:44 +0200323 __elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700324}
325
326void __elv_add_request(request_queue_t *q, struct request *rq, int where,
327 int plug)
328{
Tejun Heo8922e162005-10-20 16:23:44 +0200329 if (rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
330 /*
331 * barriers implicitly indicate back insertion
332 */
333 if (where == ELEVATOR_INSERT_SORT)
334 where = ELEVATOR_INSERT_BACK;
335
336 /*
Jens Axboe1b47f532005-10-20 16:37:00 +0200337 * this request is scheduling boundary, update end_sector
Tejun Heo8922e162005-10-20 16:23:44 +0200338 */
339 if (blk_fs_request(rq)) {
Jens Axboe1b47f532005-10-20 16:37:00 +0200340 q->end_sector = rq_end_sector(rq);
Tejun Heo8922e162005-10-20 16:23:44 +0200341 q->boundary_rq = rq;
342 }
343 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700344
345 if (plug)
346 blk_plug_device(q);
347
348 rq->q = q;
349
Tejun Heo8922e162005-10-20 16:23:44 +0200350 if (unlikely(test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags))) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700351 /*
352 * if drain is set, store the request "locally". when the drain
353 * is finished, the requests will be handed ordered to the io
354 * scheduler
355 */
356 list_add_tail(&rq->queuelist, &q->drain_list);
Tejun Heo8922e162005-10-20 16:23:44 +0200357 return;
358 }
359
360 switch (where) {
361 case ELEVATOR_INSERT_FRONT:
362 rq->flags |= REQ_SOFTBARRIER;
363
364 list_add(&rq->queuelist, &q->queue_head);
365 break;
366
367 case ELEVATOR_INSERT_BACK:
368 rq->flags |= REQ_SOFTBARRIER;
369
370 while (q->elevator->ops->elevator_dispatch_fn(q, 1))
371 ;
372 list_add_tail(&rq->queuelist, &q->queue_head);
373 /*
374 * We kick the queue here for the following reasons.
375 * - The elevator might have returned NULL previously
376 * to delay requests and returned them now. As the
377 * queue wasn't empty before this request, ll_rw_blk
378 * won't run the queue on return, resulting in hang.
379 * - Usually, back inserted requests won't be merged
380 * with anything. There's no point in delaying queue
381 * processing.
382 */
383 blk_remove_plug(q);
384 q->request_fn(q);
385 break;
386
387 case ELEVATOR_INSERT_SORT:
388 BUG_ON(!blk_fs_request(rq));
389 rq->flags |= REQ_SORTED;
390 q->elevator->ops->elevator_add_req_fn(q, rq);
Tejun Heo06b86242005-10-20 16:46:23 +0200391 if (q->last_merge == NULL && rq_mergeable(rq))
392 q->last_merge = rq;
Tejun Heo8922e162005-10-20 16:23:44 +0200393 break;
394
395 default:
396 printk(KERN_ERR "%s: bad insertion point %d\n",
397 __FUNCTION__, where);
398 BUG();
399 }
400
401 if (blk_queue_plugged(q)) {
402 int nrq = q->rq.count[READ] + q->rq.count[WRITE]
403 - q->in_flight;
404
405 if (nrq >= q->unplug_thresh)
406 __generic_unplug_device(q);
407 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700408}
409
410void elv_add_request(request_queue_t *q, struct request *rq, int where,
411 int plug)
412{
413 unsigned long flags;
414
415 spin_lock_irqsave(q->queue_lock, flags);
416 __elv_add_request(q, rq, where, plug);
417 spin_unlock_irqrestore(q->queue_lock, flags);
418}
419
420static inline struct request *__elv_next_request(request_queue_t *q)
421{
Tejun Heo8922e162005-10-20 16:23:44 +0200422 struct request *rq;
423
424 if (unlikely(list_empty(&q->queue_head) &&
425 !q->elevator->ops->elevator_dispatch_fn(q, 0)))
426 return NULL;
427
428 rq = list_entry_rq(q->queue_head.next);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700429
430 /*
431 * if this is a barrier write and the device has to issue a
432 * flush sequence to support it, check how far we are
433 */
Tejun Heo8922e162005-10-20 16:23:44 +0200434 if (blk_fs_request(rq) && blk_barrier_rq(rq)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700435 BUG_ON(q->ordered == QUEUE_ORDERED_NONE);
436
437 if (q->ordered == QUEUE_ORDERED_FLUSH &&
438 !blk_barrier_preflush(rq))
439 rq = blk_start_pre_flush(q, rq);
440 }
441
442 return rq;
443}
444
445struct request *elv_next_request(request_queue_t *q)
446{
447 struct request *rq;
448 int ret;
449
450 while ((rq = __elv_next_request(q)) != NULL) {
Tejun Heo8922e162005-10-20 16:23:44 +0200451 if (!(rq->flags & REQ_STARTED)) {
452 elevator_t *e = q->elevator;
453
454 /*
455 * This is the first time the device driver
456 * sees this request (possibly after
457 * requeueing). Notify IO scheduler.
458 */
459 if (blk_sorted_rq(rq) &&
460 e->ops->elevator_activate_req_fn)
461 e->ops->elevator_activate_req_fn(q, rq);
462
463 /*
464 * just mark as started even if we don't start
465 * it, a request that has been delayed should
466 * not be passed by new incoming requests
467 */
468 rq->flags |= REQ_STARTED;
469 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700470
Tejun Heo8922e162005-10-20 16:23:44 +0200471 if (!q->boundary_rq || q->boundary_rq == rq) {
Jens Axboe1b47f532005-10-20 16:37:00 +0200472 q->end_sector = rq_end_sector(rq);
Tejun Heo8922e162005-10-20 16:23:44 +0200473 q->boundary_rq = NULL;
474 }
475
Linus Torvalds1da177e2005-04-16 15:20:36 -0700476 if ((rq->flags & REQ_DONTPREP) || !q->prep_rq_fn)
477 break;
478
479 ret = q->prep_rq_fn(q, rq);
480 if (ret == BLKPREP_OK) {
481 break;
482 } else if (ret == BLKPREP_DEFER) {
Tejun Heo 2e759cd2005-04-24 02:04:21 -0500483 /*
484 * the request may have been (partially) prepped.
485 * we need to keep this request in the front to
Tejun Heo8922e162005-10-20 16:23:44 +0200486 * avoid resource deadlock. REQ_STARTED will
487 * prevent other fs requests from passing this one.
Tejun Heo 2e759cd2005-04-24 02:04:21 -0500488 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700489 rq = NULL;
490 break;
491 } else if (ret == BLKPREP_KILL) {
492 int nr_bytes = rq->hard_nr_sectors << 9;
493
494 if (!nr_bytes)
495 nr_bytes = rq->data_len;
496
497 blkdev_dequeue_request(rq);
498 rq->flags |= REQ_QUIET;
499 end_that_request_chunk(rq, 0, nr_bytes);
500 end_that_request_last(rq);
501 } else {
502 printk(KERN_ERR "%s: bad return=%d\n", __FUNCTION__,
503 ret);
504 break;
505 }
506 }
507
508 return rq;
509}
510
Tejun Heo8922e162005-10-20 16:23:44 +0200511void elv_dequeue_request(request_queue_t *q, struct request *rq)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700512{
Tejun Heo8922e162005-10-20 16:23:44 +0200513 BUG_ON(list_empty(&rq->queuelist));
514
515 list_del_init(&rq->queuelist);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700516
517 /*
518 * the time frame between a request being removed from the lists
519 * and to it is freed is accounted as io that is in progress at
Tejun Heo8922e162005-10-20 16:23:44 +0200520 * the driver side.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700521 */
522 if (blk_account_rq(rq))
523 q->in_flight++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700524}
525
526int elv_queue_empty(request_queue_t *q)
527{
528 elevator_t *e = q->elevator;
529
Tejun Heo8922e162005-10-20 16:23:44 +0200530 if (!list_empty(&q->queue_head))
531 return 0;
532
Linus Torvalds1da177e2005-04-16 15:20:36 -0700533 if (e->ops->elevator_queue_empty_fn)
534 return e->ops->elevator_queue_empty_fn(q);
535
Tejun Heo8922e162005-10-20 16:23:44 +0200536 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700537}
538
539struct request *elv_latter_request(request_queue_t *q, struct request *rq)
540{
541 struct list_head *next;
542
543 elevator_t *e = q->elevator;
544
545 if (e->ops->elevator_latter_req_fn)
546 return e->ops->elevator_latter_req_fn(q, rq);
547
548 next = rq->queuelist.next;
549 if (next != &q->queue_head && next != &rq->queuelist)
550 return list_entry_rq(next);
551
552 return NULL;
553}
554
555struct request *elv_former_request(request_queue_t *q, struct request *rq)
556{
557 struct list_head *prev;
558
559 elevator_t *e = q->elevator;
560
561 if (e->ops->elevator_former_req_fn)
562 return e->ops->elevator_former_req_fn(q, rq);
563
564 prev = rq->queuelist.prev;
565 if (prev != &q->queue_head && prev != &rq->queuelist)
566 return list_entry_rq(prev);
567
568 return NULL;
569}
570
Jens Axboe22e2c502005-06-27 10:55:12 +0200571int elv_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
572 int gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700573{
574 elevator_t *e = q->elevator;
575
576 if (e->ops->elevator_set_req_fn)
Jens Axboe22e2c502005-06-27 10:55:12 +0200577 return e->ops->elevator_set_req_fn(q, rq, bio, gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700578
579 rq->elevator_private = NULL;
580 return 0;
581}
582
583void elv_put_request(request_queue_t *q, struct request *rq)
584{
585 elevator_t *e = q->elevator;
586
587 if (e->ops->elevator_put_req_fn)
588 e->ops->elevator_put_req_fn(q, rq);
589}
590
Jens Axboe22e2c502005-06-27 10:55:12 +0200591int elv_may_queue(request_queue_t *q, int rw, struct bio *bio)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700592{
593 elevator_t *e = q->elevator;
594
595 if (e->ops->elevator_may_queue_fn)
Jens Axboe22e2c502005-06-27 10:55:12 +0200596 return e->ops->elevator_may_queue_fn(q, rw, bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700597
598 return ELV_MQUEUE_MAY;
599}
600
601void elv_completed_request(request_queue_t *q, struct request *rq)
602{
603 elevator_t *e = q->elevator;
604
605 /*
606 * request is released from the driver, io must be done
607 */
Tejun Heo8922e162005-10-20 16:23:44 +0200608 if (blk_account_rq(rq)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700609 q->in_flight--;
Tejun Heo8922e162005-10-20 16:23:44 +0200610 if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
611 e->ops->elevator_completed_req_fn(q, rq);
612 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700613}
614
615int elv_register_queue(struct request_queue *q)
616{
617 elevator_t *e = q->elevator;
618
619 e->kobj.parent = kobject_get(&q->kobj);
620 if (!e->kobj.parent)
621 return -EBUSY;
622
623 snprintf(e->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
624 e->kobj.ktype = e->elevator_type->elevator_ktype;
625
626 return kobject_register(&e->kobj);
627}
628
629void elv_unregister_queue(struct request_queue *q)
630{
631 if (q) {
632 elevator_t *e = q->elevator;
633 kobject_unregister(&e->kobj);
634 kobject_put(&q->kobj);
635 }
636}
637
638int elv_register(struct elevator_type *e)
639{
Tejun Heo2824bc932005-10-20 10:56:41 +0200640 spin_lock_irq(&elv_list_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700641 if (elevator_find(e->elevator_name))
642 BUG();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700643 list_add_tail(&e->list, &elv_list);
644 spin_unlock_irq(&elv_list_lock);
645
646 printk(KERN_INFO "io scheduler %s registered", e->elevator_name);
647 if (!strcmp(e->elevator_name, chosen_elevator))
648 printk(" (default)");
649 printk("\n");
650 return 0;
651}
652EXPORT_SYMBOL_GPL(elv_register);
653
654void elv_unregister(struct elevator_type *e)
655{
656 spin_lock_irq(&elv_list_lock);
657 list_del_init(&e->list);
658 spin_unlock_irq(&elv_list_lock);
659}
660EXPORT_SYMBOL_GPL(elv_unregister);
661
662/*
663 * switch to new_e io scheduler. be careful not to introduce deadlocks -
664 * we don't free the old io scheduler, before we have allocated what we
665 * need for the new one. this way we have a chance of going back to the old
666 * one, if the new one fails init for some reason. we also do an intermediate
667 * switch to noop to ensure safety with stack-allocated requests, since they
668 * don't originate from the block layer allocator. noop is safe here, because
669 * it never needs to touch the elevator itself for completion events. DRAIN
670 * flags will make sure we don't touch it for additions either.
671 */
672static void elevator_switch(request_queue_t *q, struct elevator_type *new_e)
673{
674 elevator_t *e = kmalloc(sizeof(elevator_t), GFP_KERNEL);
675 struct elevator_type *noop_elevator = NULL;
676 elevator_t *old_elevator;
677
678 if (!e)
679 goto error;
680
681 /*
682 * first step, drain requests from the block freelist
683 */
684 blk_wait_queue_drained(q, 0);
685
686 /*
687 * unregister old elevator data
688 */
689 elv_unregister_queue(q);
690 old_elevator = q->elevator;
691
692 /*
693 * next step, switch to noop since it uses no private rq structures
694 * and doesn't allocate any memory for anything. then wait for any
695 * non-fs requests in-flight
696 */
697 noop_elevator = elevator_get("noop");
698 spin_lock_irq(q->queue_lock);
699 elevator_attach(q, noop_elevator, e);
700 spin_unlock_irq(q->queue_lock);
701
702 blk_wait_queue_drained(q, 1);
703
704 /*
705 * attach and start new elevator
706 */
707 if (elevator_attach(q, new_e, e))
708 goto fail;
709
710 if (elv_register_queue(q))
711 goto fail_register;
712
713 /*
714 * finally exit old elevator and start queue again
715 */
716 elevator_exit(old_elevator);
717 blk_finish_queue_drain(q);
718 elevator_put(noop_elevator);
719 return;
720
721fail_register:
722 /*
723 * switch failed, exit the new io scheduler and reattach the old
724 * one again (along with re-adding the sysfs dir)
725 */
726 elevator_exit(e);
727fail:
728 q->elevator = old_elevator;
729 elv_register_queue(q);
730 blk_finish_queue_drain(q);
731error:
732 if (noop_elevator)
733 elevator_put(noop_elevator);
734 elevator_put(new_e);
735 printk(KERN_ERR "elevator: switch to %s failed\n",new_e->elevator_name);
736}
737
738ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
739{
740 char elevator_name[ELV_NAME_MAX];
741 struct elevator_type *e;
742
743 memset(elevator_name, 0, sizeof(elevator_name));
744 strncpy(elevator_name, name, sizeof(elevator_name));
745
746 if (elevator_name[strlen(elevator_name) - 1] == '\n')
747 elevator_name[strlen(elevator_name) - 1] = '\0';
748
749 e = elevator_get(elevator_name);
750 if (!e) {
751 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
752 return -EINVAL;
753 }
754
755 if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name))
756 return count;
757
758 elevator_switch(q, e);
759 return count;
760}
761
762ssize_t elv_iosched_show(request_queue_t *q, char *name)
763{
764 elevator_t *e = q->elevator;
765 struct elevator_type *elv = e->elevator_type;
766 struct list_head *entry;
767 int len = 0;
768
769 spin_lock_irq(q->queue_lock);
770 list_for_each(entry, &elv_list) {
771 struct elevator_type *__e;
772
773 __e = list_entry(entry, struct elevator_type, list);
774 if (!strcmp(elv->elevator_name, __e->elevator_name))
775 len += sprintf(name+len, "[%s] ", elv->elevator_name);
776 else
777 len += sprintf(name+len, "%s ", __e->elevator_name);
778 }
779 spin_unlock_irq(q->queue_lock);
780
781 len += sprintf(len+name, "\n");
782 return len;
783}
784
Jens Axboe1b47f532005-10-20 16:37:00 +0200785EXPORT_SYMBOL(elv_dispatch_sort);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700786EXPORT_SYMBOL(elv_add_request);
787EXPORT_SYMBOL(__elv_add_request);
788EXPORT_SYMBOL(elv_requeue_request);
789EXPORT_SYMBOL(elv_next_request);
Tejun Heo8922e162005-10-20 16:23:44 +0200790EXPORT_SYMBOL(elv_dequeue_request);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700791EXPORT_SYMBOL(elv_queue_empty);
792EXPORT_SYMBOL(elv_completed_request);
793EXPORT_SYMBOL(elevator_exit);
794EXPORT_SYMBOL(elevator_init);