[BLOCK] kill generic max_back_kb handling
[linux-2.6.git] / drivers / block / elevator.c
1 /*
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
40 static DEFINE_SPINLOCK(elv_list_lock);
41 static LIST_HEAD(elv_list);
42
43 /*
44  * can we safely merge with this request?
45  */
46 inline 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 }
66 EXPORT_SYMBOL(elv_rq_merge_ok);
67
68 inline 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 }
84 EXPORT_SYMBOL(elv_try_merge);
85
86 static struct elevator_type *elevator_find(const char *name)
87 {
88         struct elevator_type *e = NULL;
89         struct list_head *entry;
90
91         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         }
101
102         return e;
103 }
104
105 static void elevator_put(struct elevator_type *e)
106 {
107         module_put(e->elevator_owner);
108 }
109
110 static struct elevator_type *elevator_get(const char *name)
111 {
112         struct elevator_type *e;
113
114         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);
121
122         return e;
123 }
124
125 static 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;
137         q->end_sector = 0;
138         q->boundary_rq = NULL;
139
140         if (eq->ops->elevator_init_fn)
141                 ret = eq->ops->elevator_init_fn(q, eq);
142
143         return ret;
144 }
145
146 static char chosen_elevator[16];
147
148 static void elevator_setup_default(void)
149 {
150         struct elevator_type *e;
151
152         /*
153          * check if default is set and exists
154          */
155         if (chosen_elevator[0] && (e = elevator_get(chosen_elevator))) {
156                 elevator_put(e);
157                 return;
158         }
159
160 #if defined(CONFIG_IOSCHED_AS)
161         strcpy(chosen_elevator, "anticipatory");
162 #elif defined(CONFIG_IOSCHED_DEADLINE)
163         strcpy(chosen_elevator, "deadline");
164 #elif defined(CONFIG_IOSCHED_CFQ)
165         strcpy(chosen_elevator, "cfq");
166 #elif defined(CONFIG_IOSCHED_NOOP)
167         strcpy(chosen_elevator, "noop");
168 #else
169 #error "You must build at least 1 IO scheduler into the kernel"
170 #endif
171 }
172
173 static int __init elevator_setup(char *str)
174 {
175         strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
176         return 0;
177 }
178
179 __setup("elevator=", elevator_setup);
180
181 int elevator_init(request_queue_t *q, char *name)
182 {
183         struct elevator_type *e = NULL;
184         struct elevator_queue *eq;
185         int ret = 0;
186
187         elevator_setup_default();
188
189         if (!name)
190                 name = chosen_elevator;
191
192         e = elevator_get(name);
193         if (!e)
194                 return -EINVAL;
195
196         eq = kmalloc(sizeof(struct elevator_queue), GFP_KERNEL);
197         if (!eq) {
198                 elevator_put(e->elevator_type);
199                 return -ENOMEM;
200         }
201
202         ret = elevator_attach(q, e, eq);
203         if (ret) {
204                 kfree(eq);
205                 elevator_put(e->elevator_type);
206         }
207
208         return ret;
209 }
210
211 void elevator_exit(elevator_t *e)
212 {
213         if (e->ops->elevator_exit_fn)
214                 e->ops->elevator_exit_fn(e);
215
216         elevator_put(e->elevator_type);
217         e->elevator_type = NULL;
218         kfree(e);
219 }
220
221 /*
222  * Insert rq into dispatch queue of q.  Queue lock must be held on
223  * entry.  If sort != 0, rq is sort-inserted; otherwise, rq will be
224  * appended to the dispatch queue.  To be used by specific elevators.
225  */
226 void elv_dispatch_sort(request_queue_t *q, struct request *rq)
227 {
228         sector_t boundary;
229         struct list_head *entry;
230
231         if (q->last_merge == rq)
232                 q->last_merge = NULL;
233
234         boundary = q->end_sector;
235
236         list_for_each_prev(entry, &q->queue_head) {
237                 struct request *pos = list_entry_rq(entry);
238
239                 if (pos->flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED))
240                         break;
241                 if (rq->sector >= boundary) {
242                         if (pos->sector < boundary)
243                                 continue;
244                 } else {
245                         if (pos->sector >= boundary)
246                                 break;
247                 }
248                 if (rq->sector >= pos->sector)
249                         break;
250         }
251
252         list_add(&rq->queuelist, entry);
253 }
254
255 int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
256 {
257         elevator_t *e = q->elevator;
258         int ret;
259
260         if (q->last_merge) {
261                 ret = elv_try_merge(q->last_merge, bio);
262                 if (ret != ELEVATOR_NO_MERGE) {
263                         *req = q->last_merge;
264                         return ret;
265                 }
266         }
267
268         if (e->ops->elevator_merge_fn)
269                 return e->ops->elevator_merge_fn(q, req, bio);
270
271         return ELEVATOR_NO_MERGE;
272 }
273
274 void elv_merged_request(request_queue_t *q, struct request *rq)
275 {
276         elevator_t *e = q->elevator;
277
278         if (e->ops->elevator_merged_fn)
279                 e->ops->elevator_merged_fn(q, rq);
280
281         q->last_merge = rq;
282 }
283
284 void elv_merge_requests(request_queue_t *q, struct request *rq,
285                              struct request *next)
286 {
287         elevator_t *e = q->elevator;
288
289         if (e->ops->elevator_merge_req_fn)
290                 e->ops->elevator_merge_req_fn(q, rq, next);
291
292         q->last_merge = rq;
293 }
294
295 void elv_requeue_request(request_queue_t *q, struct request *rq)
296 {
297         elevator_t *e = q->elevator;
298
299         /*
300          * it already went through dequeue, we need to decrement the
301          * in_flight count again
302          */
303         if (blk_account_rq(rq)) {
304                 q->in_flight--;
305                 if (blk_sorted_rq(rq) && e->ops->elevator_deactivate_req_fn)
306                         e->ops->elevator_deactivate_req_fn(q, rq);
307         }
308
309         rq->flags &= ~REQ_STARTED;
310
311         /*
312          * if this is the flush, requeue the original instead and drop the flush
313          */
314         if (rq->flags & REQ_BAR_FLUSH) {
315                 clear_bit(QUEUE_FLAG_FLUSH, &q->queue_flags);
316                 rq = rq->end_io_data;
317         }
318
319         __elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 0);
320 }
321
322 void __elv_add_request(request_queue_t *q, struct request *rq, int where,
323                        int plug)
324 {
325         if (rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
326                 /*
327                  * barriers implicitly indicate back insertion
328                  */
329                 if (where == ELEVATOR_INSERT_SORT)
330                         where = ELEVATOR_INSERT_BACK;
331
332                 /*
333                  * this request is scheduling boundary, update end_sector
334                  */
335                 if (blk_fs_request(rq)) {
336                         q->end_sector = rq_end_sector(rq);
337                         q->boundary_rq = rq;
338                 }
339         }
340
341         if (plug)
342                 blk_plug_device(q);
343
344         rq->q = q;
345
346         if (unlikely(test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags))) {
347                 /*
348                  * if drain is set, store the request "locally". when the drain
349                  * is finished, the requests will be handed ordered to the io
350                  * scheduler
351                  */
352                 list_add_tail(&rq->queuelist, &q->drain_list);
353                 return;
354         }
355
356         switch (where) {
357         case ELEVATOR_INSERT_FRONT:
358                 rq->flags |= REQ_SOFTBARRIER;
359
360                 list_add(&rq->queuelist, &q->queue_head);
361                 break;
362
363         case ELEVATOR_INSERT_BACK:
364                 rq->flags |= REQ_SOFTBARRIER;
365
366                 while (q->elevator->ops->elevator_dispatch_fn(q, 1))
367                         ;
368                 list_add_tail(&rq->queuelist, &q->queue_head);
369                 /*
370                  * We kick the queue here for the following reasons.
371                  * - The elevator might have returned NULL previously
372                  *   to delay requests and returned them now.  As the
373                  *   queue wasn't empty before this request, ll_rw_blk
374                  *   won't run the queue on return, resulting in hang.
375                  * - Usually, back inserted requests won't be merged
376                  *   with anything.  There's no point in delaying queue
377                  *   processing.
378                  */
379                 blk_remove_plug(q);
380                 q->request_fn(q);
381                 break;
382
383         case ELEVATOR_INSERT_SORT:
384                 BUG_ON(!blk_fs_request(rq));
385                 rq->flags |= REQ_SORTED;
386                 q->elevator->ops->elevator_add_req_fn(q, rq);
387                 if (q->last_merge == NULL && rq_mergeable(rq))
388                         q->last_merge = rq;
389                 break;
390
391         default:
392                 printk(KERN_ERR "%s: bad insertion point %d\n",
393                        __FUNCTION__, where);
394                 BUG();
395         }
396
397         if (blk_queue_plugged(q)) {
398                 int nrq = q->rq.count[READ] + q->rq.count[WRITE]
399                         - q->in_flight;
400
401                 if (nrq >= q->unplug_thresh)
402                         __generic_unplug_device(q);
403         }
404 }
405
406 void elv_add_request(request_queue_t *q, struct request *rq, int where,
407                      int plug)
408 {
409         unsigned long flags;
410
411         spin_lock_irqsave(q->queue_lock, flags);
412         __elv_add_request(q, rq, where, plug);
413         spin_unlock_irqrestore(q->queue_lock, flags);
414 }
415
416 static inline struct request *__elv_next_request(request_queue_t *q)
417 {
418         struct request *rq;
419
420         if (unlikely(list_empty(&q->queue_head) &&
421                      !q->elevator->ops->elevator_dispatch_fn(q, 0)))
422                 return NULL;
423
424         rq = list_entry_rq(q->queue_head.next);
425
426         /*
427          * if this is a barrier write and the device has to issue a
428          * flush sequence to support it, check how far we are
429          */
430         if (blk_fs_request(rq) && blk_barrier_rq(rq)) {
431                 BUG_ON(q->ordered == QUEUE_ORDERED_NONE);
432
433                 if (q->ordered == QUEUE_ORDERED_FLUSH &&
434                     !blk_barrier_preflush(rq))
435                         rq = blk_start_pre_flush(q, rq);
436         }
437
438         return rq;
439 }
440
441 struct request *elv_next_request(request_queue_t *q)
442 {
443         struct request *rq;
444         int ret;
445
446         while ((rq = __elv_next_request(q)) != NULL) {
447                 if (!(rq->flags & REQ_STARTED)) {
448                         elevator_t *e = q->elevator;
449
450                         /*
451                          * This is the first time the device driver
452                          * sees this request (possibly after
453                          * requeueing).  Notify IO scheduler.
454                          */
455                         if (blk_sorted_rq(rq) &&
456                             e->ops->elevator_activate_req_fn)
457                                 e->ops->elevator_activate_req_fn(q, rq);
458
459                         /*
460                          * just mark as started even if we don't start
461                          * it, a request that has been delayed should
462                          * not be passed by new incoming requests
463                          */
464                         rq->flags |= REQ_STARTED;
465                 }
466
467                 if (!q->boundary_rq || q->boundary_rq == rq) {
468                         q->end_sector = rq_end_sector(rq);
469                         q->boundary_rq = NULL;
470                 }
471
472                 if ((rq->flags & REQ_DONTPREP) || !q->prep_rq_fn)
473                         break;
474
475                 ret = q->prep_rq_fn(q, rq);
476                 if (ret == BLKPREP_OK) {
477                         break;
478                 } else if (ret == BLKPREP_DEFER) {
479                         /*
480                          * the request may have been (partially) prepped.
481                          * we need to keep this request in the front to
482                          * avoid resource deadlock.  REQ_STARTED will
483                          * prevent other fs requests from passing this one.
484                          */
485                         rq = NULL;
486                         break;
487                 } else if (ret == BLKPREP_KILL) {
488                         int nr_bytes = rq->hard_nr_sectors << 9;
489
490                         if (!nr_bytes)
491                                 nr_bytes = rq->data_len;
492
493                         blkdev_dequeue_request(rq);
494                         rq->flags |= REQ_QUIET;
495                         end_that_request_chunk(rq, 0, nr_bytes);
496                         end_that_request_last(rq);
497                 } else {
498                         printk(KERN_ERR "%s: bad return=%d\n", __FUNCTION__,
499                                                                 ret);
500                         break;
501                 }
502         }
503
504         return rq;
505 }
506
507 void elv_dequeue_request(request_queue_t *q, struct request *rq)
508 {
509         BUG_ON(list_empty(&rq->queuelist));
510
511         list_del_init(&rq->queuelist);
512
513         /*
514          * the time frame between a request being removed from the lists
515          * and to it is freed is accounted as io that is in progress at
516          * the driver side.
517          */
518         if (blk_account_rq(rq))
519                 q->in_flight++;
520 }
521
522 int elv_queue_empty(request_queue_t *q)
523 {
524         elevator_t *e = q->elevator;
525
526         if (!list_empty(&q->queue_head))
527                 return 0;
528
529         if (e->ops->elevator_queue_empty_fn)
530                 return e->ops->elevator_queue_empty_fn(q);
531
532         return 1;
533 }
534
535 struct request *elv_latter_request(request_queue_t *q, struct request *rq)
536 {
537         struct list_head *next;
538
539         elevator_t *e = q->elevator;
540
541         if (e->ops->elevator_latter_req_fn)
542                 return e->ops->elevator_latter_req_fn(q, rq);
543
544         next = rq->queuelist.next;
545         if (next != &q->queue_head && next != &rq->queuelist)
546                 return list_entry_rq(next);
547
548         return NULL;
549 }
550
551 struct request *elv_former_request(request_queue_t *q, struct request *rq)
552 {
553         struct list_head *prev;
554
555         elevator_t *e = q->elevator;
556
557         if (e->ops->elevator_former_req_fn)
558                 return e->ops->elevator_former_req_fn(q, rq);
559
560         prev = rq->queuelist.prev;
561         if (prev != &q->queue_head && prev != &rq->queuelist)
562                 return list_entry_rq(prev);
563
564         return NULL;
565 }
566
567 int elv_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
568                     int gfp_mask)
569 {
570         elevator_t *e = q->elevator;
571
572         if (e->ops->elevator_set_req_fn)
573                 return e->ops->elevator_set_req_fn(q, rq, bio, gfp_mask);
574
575         rq->elevator_private = NULL;
576         return 0;
577 }
578
579 void elv_put_request(request_queue_t *q, struct request *rq)
580 {
581         elevator_t *e = q->elevator;
582
583         if (e->ops->elevator_put_req_fn)
584                 e->ops->elevator_put_req_fn(q, rq);
585 }
586
587 int elv_may_queue(request_queue_t *q, int rw, struct bio *bio)
588 {
589         elevator_t *e = q->elevator;
590
591         if (e->ops->elevator_may_queue_fn)
592                 return e->ops->elevator_may_queue_fn(q, rw, bio);
593
594         return ELV_MQUEUE_MAY;
595 }
596
597 void elv_completed_request(request_queue_t *q, struct request *rq)
598 {
599         elevator_t *e = q->elevator;
600
601         /*
602          * request is released from the driver, io must be done
603          */
604         if (blk_account_rq(rq)) {
605                 q->in_flight--;
606                 if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
607                         e->ops->elevator_completed_req_fn(q, rq);
608         }
609 }
610
611 int elv_register_queue(struct request_queue *q)
612 {
613         elevator_t *e = q->elevator;
614
615         e->kobj.parent = kobject_get(&q->kobj);
616         if (!e->kobj.parent)
617                 return -EBUSY;
618
619         snprintf(e->kobj.name, KOBJ_NAME_LEN, "%s", "iosched");
620         e->kobj.ktype = e->elevator_type->elevator_ktype;
621
622         return kobject_register(&e->kobj);
623 }
624
625 void elv_unregister_queue(struct request_queue *q)
626 {
627         if (q) {
628                 elevator_t *e = q->elevator;
629                 kobject_unregister(&e->kobj);
630                 kobject_put(&q->kobj);
631         }
632 }
633
634 int elv_register(struct elevator_type *e)
635 {
636         spin_lock_irq(&elv_list_lock);
637         if (elevator_find(e->elevator_name))
638                 BUG();
639         list_add_tail(&e->list, &elv_list);
640         spin_unlock_irq(&elv_list_lock);
641
642         printk(KERN_INFO "io scheduler %s registered", e->elevator_name);
643         if (!strcmp(e->elevator_name, chosen_elevator))
644                 printk(" (default)");
645         printk("\n");
646         return 0;
647 }
648 EXPORT_SYMBOL_GPL(elv_register);
649
650 void elv_unregister(struct elevator_type *e)
651 {
652         spin_lock_irq(&elv_list_lock);
653         list_del_init(&e->list);
654         spin_unlock_irq(&elv_list_lock);
655 }
656 EXPORT_SYMBOL_GPL(elv_unregister);
657
658 /*
659  * switch to new_e io scheduler. be careful not to introduce deadlocks -
660  * we don't free the old io scheduler, before we have allocated what we
661  * need for the new one. this way we have a chance of going back to the old
662  * one, if the new one fails init for some reason. we also do an intermediate
663  * switch to noop to ensure safety with stack-allocated requests, since they
664  * don't originate from the block layer allocator. noop is safe here, because
665  * it never needs to touch the elevator itself for completion events. DRAIN
666  * flags will make sure we don't touch it for additions either.
667  */
668 static void elevator_switch(request_queue_t *q, struct elevator_type *new_e)
669 {
670         elevator_t *e = kmalloc(sizeof(elevator_t), GFP_KERNEL);
671         struct elevator_type *noop_elevator = NULL;
672         elevator_t *old_elevator;
673
674         if (!e)
675                 goto error;
676
677         /*
678          * first step, drain requests from the block freelist
679          */
680         blk_wait_queue_drained(q, 0);
681
682         /*
683          * unregister old elevator data
684          */
685         elv_unregister_queue(q);
686         old_elevator = q->elevator;
687
688         /*
689          * next step, switch to noop since it uses no private rq structures
690          * and doesn't allocate any memory for anything. then wait for any
691          * non-fs requests in-flight
692          */
693         noop_elevator = elevator_get("noop");
694         spin_lock_irq(q->queue_lock);
695         elevator_attach(q, noop_elevator, e);
696         spin_unlock_irq(q->queue_lock);
697
698         blk_wait_queue_drained(q, 1);
699
700         /*
701          * attach and start new elevator
702          */
703         if (elevator_attach(q, new_e, e))
704                 goto fail;
705
706         if (elv_register_queue(q))
707                 goto fail_register;
708
709         /*
710          * finally exit old elevator and start queue again
711          */
712         elevator_exit(old_elevator);
713         blk_finish_queue_drain(q);
714         elevator_put(noop_elevator);
715         return;
716
717 fail_register:
718         /*
719          * switch failed, exit the new io scheduler and reattach the old
720          * one again (along with re-adding the sysfs dir)
721          */
722         elevator_exit(e);
723 fail:
724         q->elevator = old_elevator;
725         elv_register_queue(q);
726         blk_finish_queue_drain(q);
727 error:
728         if (noop_elevator)
729                 elevator_put(noop_elevator);
730         elevator_put(new_e);
731         printk(KERN_ERR "elevator: switch to %s failed\n",new_e->elevator_name);
732 }
733
734 ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
735 {
736         char elevator_name[ELV_NAME_MAX];
737         struct elevator_type *e;
738
739         memset(elevator_name, 0, sizeof(elevator_name));
740         strncpy(elevator_name, name, sizeof(elevator_name));
741
742         if (elevator_name[strlen(elevator_name) - 1] == '\n')
743                 elevator_name[strlen(elevator_name) - 1] = '\0';
744
745         e = elevator_get(elevator_name);
746         if (!e) {
747                 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
748                 return -EINVAL;
749         }
750
751         if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name))
752                 return count;
753
754         elevator_switch(q, e);
755         return count;
756 }
757
758 ssize_t elv_iosched_show(request_queue_t *q, char *name)
759 {
760         elevator_t *e = q->elevator;
761         struct elevator_type *elv = e->elevator_type;
762         struct list_head *entry;
763         int len = 0;
764
765         spin_lock_irq(q->queue_lock);
766         list_for_each(entry, &elv_list) {
767                 struct elevator_type *__e;
768
769                 __e = list_entry(entry, struct elevator_type, list);
770                 if (!strcmp(elv->elevator_name, __e->elevator_name))
771                         len += sprintf(name+len, "[%s] ", elv->elevator_name);
772                 else
773                         len += sprintf(name+len, "%s ", __e->elevator_name);
774         }
775         spin_unlock_irq(q->queue_lock);
776
777         len += sprintf(len+name, "\n");
778         return len;
779 }
780
781 EXPORT_SYMBOL(elv_dispatch_sort);
782 EXPORT_SYMBOL(elv_add_request);
783 EXPORT_SYMBOL(__elv_add_request);
784 EXPORT_SYMBOL(elv_requeue_request);
785 EXPORT_SYMBOL(elv_next_request);
786 EXPORT_SYMBOL(elv_dequeue_request);
787 EXPORT_SYMBOL(elv_queue_empty);
788 EXPORT_SYMBOL(elv_completed_request);
789 EXPORT_SYMBOL(elevator_exit);
790 EXPORT_SYMBOL(elevator_init);