[Bluetooth] Fix firmware loading problem of BT3C driver
[linux-2.6.git] / block / elevator.c
1 /*
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>
35 #include <linux/delay.h>
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
67 static inline int elv_try_merge(struct request *__rq, struct bio *bio)
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 }
83
84 static struct elevator_type *elevator_find(const char *name)
85 {
86         struct elevator_type *e = NULL;
87         struct list_head *entry;
88
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         }
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 {
110         struct elevator_type *e;
111
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);
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
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 int __init elevator_setup(char *str)
143 {
144         /*
145          * Be backwards-compatible with previous kernels, so users
146          * won't get the wrong elevator.
147          */
148         if (!strcmp(str, "as"))
149                 strcpy(chosen_elevator, "anticipatory");
150         else
151                 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
152         return 0;
153 }
154
155 __setup("elevator=", elevator_setup);
156
157 int elevator_init(request_queue_t *q, char *name)
158 {
159         struct elevator_type *e = NULL;
160         struct elevator_queue *eq;
161         int ret = 0;
162
163         INIT_LIST_HEAD(&q->queue_head);
164         q->last_merge = NULL;
165         q->end_sector = 0;
166         q->boundary_rq = NULL;
167
168         if (name && !(e = elevator_get(name)))
169                 return -EINVAL;
170
171         if (!e && *chosen_elevator && !(e = elevator_get(chosen_elevator)))
172                 printk("I/O scheduler %s not found\n", chosen_elevator);
173
174         if (!e && !(e = elevator_get(CONFIG_DEFAULT_IOSCHED))) {
175                 printk("Default I/O scheduler not found, using no-op\n");
176                 e = elevator_get("noop");
177         }
178
179         eq = kmalloc(sizeof(struct elevator_queue), GFP_KERNEL);
180         if (!eq) {
181                 elevator_put(e);
182                 return -ENOMEM;
183         }
184
185         ret = elevator_attach(q, e, eq);
186         if (ret) {
187                 kfree(eq);
188                 elevator_put(e);
189         }
190
191         return ret;
192 }
193
194 void elevator_exit(elevator_t *e)
195 {
196         if (e->ops->elevator_exit_fn)
197                 e->ops->elevator_exit_fn(e);
198
199         elevator_put(e->elevator_type);
200         e->elevator_type = NULL;
201         kfree(e);
202 }
203
204 /*
205  * Insert rq into dispatch queue of q.  Queue lock must be held on
206  * entry.  If sort != 0, rq is sort-inserted; otherwise, rq will be
207  * appended to the dispatch queue.  To be used by specific elevators.
208  */
209 void elv_dispatch_sort(request_queue_t *q, struct request *rq)
210 {
211         sector_t boundary;
212         struct list_head *entry;
213
214         if (q->last_merge == rq)
215                 q->last_merge = NULL;
216         q->nr_sorted--;
217
218         boundary = q->end_sector;
219
220         list_for_each_prev(entry, &q->queue_head) {
221                 struct request *pos = list_entry_rq(entry);
222
223                 if (pos->flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED))
224                         break;
225                 if (rq->sector >= boundary) {
226                         if (pos->sector < boundary)
227                                 continue;
228                 } else {
229                         if (pos->sector >= boundary)
230                                 break;
231                 }
232                 if (rq->sector >= pos->sector)
233                         break;
234         }
235
236         list_add(&rq->queuelist, entry);
237 }
238
239 int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
240 {
241         elevator_t *e = q->elevator;
242         int ret;
243
244         if (q->last_merge) {
245                 ret = elv_try_merge(q->last_merge, bio);
246                 if (ret != ELEVATOR_NO_MERGE) {
247                         *req = q->last_merge;
248                         return ret;
249                 }
250         }
251
252         if (e->ops->elevator_merge_fn)
253                 return e->ops->elevator_merge_fn(q, req, bio);
254
255         return ELEVATOR_NO_MERGE;
256 }
257
258 void elv_merged_request(request_queue_t *q, struct request *rq)
259 {
260         elevator_t *e = q->elevator;
261
262         if (e->ops->elevator_merged_fn)
263                 e->ops->elevator_merged_fn(q, rq);
264
265         q->last_merge = rq;
266 }
267
268 void elv_merge_requests(request_queue_t *q, struct request *rq,
269                              struct request *next)
270 {
271         elevator_t *e = q->elevator;
272
273         if (e->ops->elevator_merge_req_fn)
274                 e->ops->elevator_merge_req_fn(q, rq, next);
275         q->nr_sorted--;
276
277         q->last_merge = rq;
278 }
279
280 void elv_requeue_request(request_queue_t *q, struct request *rq)
281 {
282         elevator_t *e = q->elevator;
283
284         /*
285          * it already went through dequeue, we need to decrement the
286          * in_flight count again
287          */
288         if (blk_account_rq(rq)) {
289                 q->in_flight--;
290                 if (blk_sorted_rq(rq) && e->ops->elevator_deactivate_req_fn)
291                         e->ops->elevator_deactivate_req_fn(q, rq);
292         }
293
294         rq->flags &= ~REQ_STARTED;
295
296         elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
297 }
298
299 static void elv_drain_elevator(request_queue_t *q)
300 {
301         static int printed;
302         while (q->elevator->ops->elevator_dispatch_fn(q, 1))
303                 ;
304         if (q->nr_sorted == 0)
305                 return;
306         if (printed++ < 10) {
307                 printk(KERN_ERR "%s: forced dispatching is broken "
308                        "(nr_sorted=%u), please report this\n",
309                        q->elevator->elevator_type->elevator_name, q->nr_sorted);
310         }
311 }
312
313 void elv_insert(request_queue_t *q, struct request *rq, int where)
314 {
315         struct list_head *pos;
316         unsigned ordseq;
317
318         rq->q = q;
319
320         switch (where) {
321         case ELEVATOR_INSERT_FRONT:
322                 rq->flags |= REQ_SOFTBARRIER;
323
324                 list_add(&rq->queuelist, &q->queue_head);
325                 break;
326
327         case ELEVATOR_INSERT_BACK:
328                 rq->flags |= REQ_SOFTBARRIER;
329                 elv_drain_elevator(q);
330                 list_add_tail(&rq->queuelist, &q->queue_head);
331                 /*
332                  * We kick the queue here for the following reasons.
333                  * - The elevator might have returned NULL previously
334                  *   to delay requests and returned them now.  As the
335                  *   queue wasn't empty before this request, ll_rw_blk
336                  *   won't run the queue on return, resulting in hang.
337                  * - Usually, back inserted requests won't be merged
338                  *   with anything.  There's no point in delaying queue
339                  *   processing.
340                  */
341                 blk_remove_plug(q);
342                 q->request_fn(q);
343                 break;
344
345         case ELEVATOR_INSERT_SORT:
346                 BUG_ON(!blk_fs_request(rq));
347                 rq->flags |= REQ_SORTED;
348                 q->nr_sorted++;
349                 if (q->last_merge == NULL && rq_mergeable(rq))
350                         q->last_merge = rq;
351                 /*
352                  * Some ioscheds (cfq) run q->request_fn directly, so
353                  * rq cannot be accessed after calling
354                  * elevator_add_req_fn.
355                  */
356                 q->elevator->ops->elevator_add_req_fn(q, rq);
357                 break;
358
359         case ELEVATOR_INSERT_REQUEUE:
360                 /*
361                  * If ordered flush isn't in progress, we do front
362                  * insertion; otherwise, requests should be requeued
363                  * in ordseq order.
364                  */
365                 rq->flags |= REQ_SOFTBARRIER;
366
367                 if (q->ordseq == 0) {
368                         list_add(&rq->queuelist, &q->queue_head);
369                         break;
370                 }
371
372                 ordseq = blk_ordered_req_seq(rq);
373
374                 list_for_each(pos, &q->queue_head) {
375                         struct request *pos_rq = list_entry_rq(pos);
376                         if (ordseq <= blk_ordered_req_seq(pos_rq))
377                                 break;
378                 }
379
380                 list_add_tail(&rq->queuelist, pos);
381                 break;
382
383         default:
384                 printk(KERN_ERR "%s: bad insertion point %d\n",
385                        __FUNCTION__, where);
386                 BUG();
387         }
388
389         if (blk_queue_plugged(q)) {
390                 int nrq = q->rq.count[READ] + q->rq.count[WRITE]
391                         - q->in_flight;
392
393                 if (nrq >= q->unplug_thresh)
394                         __generic_unplug_device(q);
395         }
396 }
397
398 void __elv_add_request(request_queue_t *q, struct request *rq, int where,
399                        int plug)
400 {
401         if (q->ordcolor)
402                 rq->flags |= REQ_ORDERED_COLOR;
403
404         if (rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
405                 /*
406                  * toggle ordered color
407                  */
408                 if (blk_barrier_rq(rq))
409                         q->ordcolor ^= 1;
410
411                 /*
412                  * barriers implicitly indicate back insertion
413                  */
414                 if (where == ELEVATOR_INSERT_SORT)
415                         where = ELEVATOR_INSERT_BACK;
416
417                 /*
418                  * this request is scheduling boundary, update
419                  * end_sector
420                  */
421                 if (blk_fs_request(rq)) {
422                         q->end_sector = rq_end_sector(rq);
423                         q->boundary_rq = rq;
424                 }
425         } else if (!(rq->flags & REQ_ELVPRIV) && where == ELEVATOR_INSERT_SORT)
426                 where = ELEVATOR_INSERT_BACK;
427
428         if (plug)
429                 blk_plug_device(q);
430
431         elv_insert(q, rq, where);
432 }
433
434 void elv_add_request(request_queue_t *q, struct request *rq, int where,
435                      int plug)
436 {
437         unsigned long flags;
438
439         spin_lock_irqsave(q->queue_lock, flags);
440         __elv_add_request(q, rq, where, plug);
441         spin_unlock_irqrestore(q->queue_lock, flags);
442 }
443
444 static inline struct request *__elv_next_request(request_queue_t *q)
445 {
446         struct request *rq;
447
448         while (1) {
449                 while (!list_empty(&q->queue_head)) {
450                         rq = list_entry_rq(q->queue_head.next);
451                         if (blk_do_ordered(q, &rq))
452                                 return rq;
453                 }
454
455                 if (!q->elevator->ops->elevator_dispatch_fn(q, 0))
456                         return NULL;
457         }
458 }
459
460 struct request *elv_next_request(request_queue_t *q)
461 {
462         struct request *rq;
463         int ret;
464
465         while ((rq = __elv_next_request(q)) != NULL) {
466                 if (!(rq->flags & REQ_STARTED)) {
467                         elevator_t *e = q->elevator;
468
469                         /*
470                          * This is the first time the device driver
471                          * sees this request (possibly after
472                          * requeueing).  Notify IO scheduler.
473                          */
474                         if (blk_sorted_rq(rq) &&
475                             e->ops->elevator_activate_req_fn)
476                                 e->ops->elevator_activate_req_fn(q, rq);
477
478                         /*
479                          * just mark as started even if we don't start
480                          * it, a request that has been delayed should
481                          * not be passed by new incoming requests
482                          */
483                         rq->flags |= REQ_STARTED;
484                 }
485
486                 if (!q->boundary_rq || q->boundary_rq == rq) {
487                         q->end_sector = rq_end_sector(rq);
488                         q->boundary_rq = NULL;
489                 }
490
491                 if ((rq->flags & REQ_DONTPREP) || !q->prep_rq_fn)
492                         break;
493
494                 ret = q->prep_rq_fn(q, rq);
495                 if (ret == BLKPREP_OK) {
496                         break;
497                 } else if (ret == BLKPREP_DEFER) {
498                         /*
499                          * the request may have been (partially) prepped.
500                          * we need to keep this request in the front to
501                          * avoid resource deadlock.  REQ_STARTED will
502                          * prevent other fs requests from passing this one.
503                          */
504                         rq = NULL;
505                         break;
506                 } else if (ret == BLKPREP_KILL) {
507                         int nr_bytes = rq->hard_nr_sectors << 9;
508
509                         if (!nr_bytes)
510                                 nr_bytes = rq->data_len;
511
512                         blkdev_dequeue_request(rq);
513                         rq->flags |= REQ_QUIET;
514                         end_that_request_chunk(rq, 0, nr_bytes);
515                         end_that_request_last(rq, 0);
516                 } else {
517                         printk(KERN_ERR "%s: bad return=%d\n", __FUNCTION__,
518                                                                 ret);
519                         break;
520                 }
521         }
522
523         return rq;
524 }
525
526 void elv_dequeue_request(request_queue_t *q, struct request *rq)
527 {
528         BUG_ON(list_empty(&rq->queuelist));
529
530         list_del_init(&rq->queuelist);
531
532         /*
533          * the time frame between a request being removed from the lists
534          * and to it is freed is accounted as io that is in progress at
535          * the driver side.
536          */
537         if (blk_account_rq(rq))
538                 q->in_flight++;
539 }
540
541 int elv_queue_empty(request_queue_t *q)
542 {
543         elevator_t *e = q->elevator;
544
545         if (!list_empty(&q->queue_head))
546                 return 0;
547
548         if (e->ops->elevator_queue_empty_fn)
549                 return e->ops->elevator_queue_empty_fn(q);
550
551         return 1;
552 }
553
554 struct request *elv_latter_request(request_queue_t *q, struct request *rq)
555 {
556         elevator_t *e = q->elevator;
557
558         if (e->ops->elevator_latter_req_fn)
559                 return e->ops->elevator_latter_req_fn(q, rq);
560         return NULL;
561 }
562
563 struct request *elv_former_request(request_queue_t *q, struct request *rq)
564 {
565         elevator_t *e = q->elevator;
566
567         if (e->ops->elevator_former_req_fn)
568                 return e->ops->elevator_former_req_fn(q, rq);
569         return NULL;
570 }
571
572 int elv_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
573                     gfp_t gfp_mask)
574 {
575         elevator_t *e = q->elevator;
576
577         if (e->ops->elevator_set_req_fn)
578                 return e->ops->elevator_set_req_fn(q, rq, bio, gfp_mask);
579
580         rq->elevator_private = NULL;
581         return 0;
582 }
583
584 void elv_put_request(request_queue_t *q, struct request *rq)
585 {
586         elevator_t *e = q->elevator;
587
588         if (e->ops->elevator_put_req_fn)
589                 e->ops->elevator_put_req_fn(q, rq);
590 }
591
592 int elv_may_queue(request_queue_t *q, int rw, struct bio *bio)
593 {
594         elevator_t *e = q->elevator;
595
596         if (e->ops->elevator_may_queue_fn)
597                 return e->ops->elevator_may_queue_fn(q, rw, bio);
598
599         return ELV_MQUEUE_MAY;
600 }
601
602 void elv_completed_request(request_queue_t *q, struct request *rq)
603 {
604         elevator_t *e = q->elevator;
605
606         /*
607          * request is released from the driver, io must be done
608          */
609         if (blk_account_rq(rq)) {
610                 q->in_flight--;
611                 if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
612                         e->ops->elevator_completed_req_fn(q, rq);
613         }
614
615         /*
616          * Check if the queue is waiting for fs requests to be
617          * drained for flush sequence.
618          */
619         if (unlikely(q->ordseq)) {
620                 struct request *first_rq = list_entry_rq(q->queue_head.next);
621                 if (q->in_flight == 0 &&
622                     blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
623                     blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
624                         blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
625                         q->request_fn(q);
626                 }
627         }
628 }
629
630 int elv_register_queue(struct request_queue *q)
631 {
632         elevator_t *e = q->elevator;
633
634         e->kobj.parent = kobject_get(&q->kobj);
635         if (!e->kobj.parent)
636                 return -EBUSY;
637
638         snprintf(e->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
639         e->kobj.ktype = e->elevator_type->elevator_ktype;
640
641         return kobject_register(&e->kobj);
642 }
643
644 void elv_unregister_queue(struct request_queue *q)
645 {
646         if (q) {
647                 elevator_t *e = q->elevator;
648                 kobject_unregister(&e->kobj);
649                 kobject_put(&q->kobj);
650         }
651 }
652
653 int elv_register(struct elevator_type *e)
654 {
655         spin_lock_irq(&elv_list_lock);
656         if (elevator_find(e->elevator_name))
657                 BUG();
658         list_add_tail(&e->list, &elv_list);
659         spin_unlock_irq(&elv_list_lock);
660
661         printk(KERN_INFO "io scheduler %s registered", e->elevator_name);
662         if (!strcmp(e->elevator_name, chosen_elevator) ||
663                         (!*chosen_elevator &&
664                          !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
665                                 printk(" (default)");
666         printk("\n");
667         return 0;
668 }
669 EXPORT_SYMBOL_GPL(elv_register);
670
671 void elv_unregister(struct elevator_type *e)
672 {
673         struct task_struct *g, *p;
674
675         /*
676          * Iterate every thread in the process to remove the io contexts.
677          */
678         read_lock(&tasklist_lock);
679         do_each_thread(g, p) {
680                 struct io_context *ioc = p->io_context;
681                 if (ioc && ioc->cic) {
682                         ioc->cic->exit(ioc->cic);
683                         ioc->cic->dtor(ioc->cic);
684                         ioc->cic = NULL;
685                 }
686                 if (ioc && ioc->aic) {
687                         ioc->aic->exit(ioc->aic);
688                         ioc->aic->dtor(ioc->aic);
689                         ioc->aic = NULL;
690                 }
691         } while_each_thread(g, p);
692         read_unlock(&tasklist_lock);
693
694         spin_lock_irq(&elv_list_lock);
695         list_del_init(&e->list);
696         spin_unlock_irq(&elv_list_lock);
697 }
698 EXPORT_SYMBOL_GPL(elv_unregister);
699
700 /*
701  * switch to new_e io scheduler. be careful not to introduce deadlocks -
702  * we don't free the old io scheduler, before we have allocated what we
703  * need for the new one. this way we have a chance of going back to the old
704  * one, if the new one fails init for some reason.
705  */
706 static void elevator_switch(request_queue_t *q, struct elevator_type *new_e)
707 {
708         elevator_t *old_elevator, *e;
709
710         /*
711          * Allocate new elevator
712          */
713         e = kmalloc(sizeof(elevator_t), GFP_KERNEL);
714         if (!e)
715                 goto error;
716
717         /*
718          * Turn on BYPASS and drain all requests w/ elevator private data
719          */
720         spin_lock_irq(q->queue_lock);
721
722         set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
723
724         elv_drain_elevator(q);
725
726         while (q->rq.elvpriv) {
727                 blk_remove_plug(q);
728                 q->request_fn(q);
729                 spin_unlock_irq(q->queue_lock);
730                 msleep(10);
731                 spin_lock_irq(q->queue_lock);
732                 elv_drain_elevator(q);
733         }
734
735         spin_unlock_irq(q->queue_lock);
736
737         /*
738          * unregister old elevator data
739          */
740         elv_unregister_queue(q);
741         old_elevator = q->elevator;
742
743         /*
744          * attach and start new elevator
745          */
746         if (elevator_attach(q, new_e, e))
747                 goto fail;
748
749         if (elv_register_queue(q))
750                 goto fail_register;
751
752         /*
753          * finally exit old elevator and turn off BYPASS.
754          */
755         elevator_exit(old_elevator);
756         clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
757         return;
758
759 fail_register:
760         /*
761          * switch failed, exit the new io scheduler and reattach the old
762          * one again (along with re-adding the sysfs dir)
763          */
764         elevator_exit(e);
765         e = NULL;
766 fail:
767         q->elevator = old_elevator;
768         elv_register_queue(q);
769         clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
770         kfree(e);
771 error:
772         elevator_put(new_e);
773         printk(KERN_ERR "elevator: switch to %s failed\n",new_e->elevator_name);
774 }
775
776 ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
777 {
778         char elevator_name[ELV_NAME_MAX];
779         size_t len;
780         struct elevator_type *e;
781
782         elevator_name[sizeof(elevator_name) - 1] = '\0';
783         strncpy(elevator_name, name, sizeof(elevator_name) - 1);
784         len = strlen(elevator_name);
785
786         if (len && elevator_name[len - 1] == '\n')
787                 elevator_name[len - 1] = '\0';
788
789         e = elevator_get(elevator_name);
790         if (!e) {
791                 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
792                 return -EINVAL;
793         }
794
795         if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
796                 elevator_put(e);
797                 return count;
798         }
799
800         elevator_switch(q, e);
801         return count;
802 }
803
804 ssize_t elv_iosched_show(request_queue_t *q, char *name)
805 {
806         elevator_t *e = q->elevator;
807         struct elevator_type *elv = e->elevator_type;
808         struct list_head *entry;
809         int len = 0;
810
811         spin_lock_irq(q->queue_lock);
812         list_for_each(entry, &elv_list) {
813                 struct elevator_type *__e;
814
815                 __e = list_entry(entry, struct elevator_type, list);
816                 if (!strcmp(elv->elevator_name, __e->elevator_name))
817                         len += sprintf(name+len, "[%s] ", elv->elevator_name);
818                 else
819                         len += sprintf(name+len, "%s ", __e->elevator_name);
820         }
821         spin_unlock_irq(q->queue_lock);
822
823         len += sprintf(len+name, "\n");
824         return len;
825 }
826
827 EXPORT_SYMBOL(elv_dispatch_sort);
828 EXPORT_SYMBOL(elv_add_request);
829 EXPORT_SYMBOL(__elv_add_request);
830 EXPORT_SYMBOL(elv_requeue_request);
831 EXPORT_SYMBOL(elv_next_request);
832 EXPORT_SYMBOL(elv_dequeue_request);
833 EXPORT_SYMBOL(elv_queue_empty);
834 EXPORT_SYMBOL(elv_completed_request);
835 EXPORT_SYMBOL(elevator_exit);
836 EXPORT_SYMBOL(elevator_init);