docbook: rapidio: fix fatal filename error
[sfrench/cifs-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@kernel.dk> :
7  *
8  * Split the elevator a bit so that it is possible to choose a different
9  * one or even write a new "plug in". There are three pieces:
10  * - elevator_fn, inserts a new request in the queue list
11  * - elevator_merge_fn, decides whether a new buffer can be merged with
12  *   an existing request
13  * - elevator_dequeue_fn, called when a request is taken off the active list
14  *
15  * 20082000 Dave Jones <davej@suse.de> :
16  * Removed tests for max-bomb-segments, which was breaking elvtune
17  *  when run without -bN
18  *
19  * Jens:
20  * - Rework again to work with bio instead of buffer_heads
21  * - loose bi_dev comparisons, partition handling is right now
22  * - completely modularize elevator setup and teardown
23  *
24  */
25 #include <linux/kernel.h>
26 #include <linux/fs.h>
27 #include <linux/blkdev.h>
28 #include <linux/elevator.h>
29 #include <linux/bio.h>
30 #include <linux/module.h>
31 #include <linux/slab.h>
32 #include <linux/init.h>
33 #include <linux/compiler.h>
34 #include <linux/delay.h>
35 #include <linux/blktrace_api.h>
36 #include <linux/hash.h>
37
38 #include <asm/uaccess.h>
39
40 static DEFINE_SPINLOCK(elv_list_lock);
41 static LIST_HEAD(elv_list);
42
43 /*
44  * Merge hash stuff.
45  */
46 static const int elv_hash_shift = 6;
47 #define ELV_HASH_BLOCK(sec)     ((sec) >> 3)
48 #define ELV_HASH_FN(sec)        (hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift))
49 #define ELV_HASH_ENTRIES        (1 << elv_hash_shift)
50 #define rq_hash_key(rq)         ((rq)->sector + (rq)->nr_sectors)
51 #define ELV_ON_HASH(rq)         (!hlist_unhashed(&(rq)->hash))
52
53 /*
54  * Query io scheduler to see if the current process issuing bio may be
55  * merged with rq.
56  */
57 static int elv_iosched_allow_merge(struct request *rq, struct bio *bio)
58 {
59         struct request_queue *q = rq->q;
60         elevator_t *e = q->elevator;
61
62         if (e->ops->elevator_allow_merge_fn)
63                 return e->ops->elevator_allow_merge_fn(q, rq, bio);
64
65         return 1;
66 }
67
68 /*
69  * can we safely merge with this request?
70  */
71 inline int elv_rq_merge_ok(struct request *rq, struct bio *bio)
72 {
73         if (!rq_mergeable(rq))
74                 return 0;
75
76         /*
77          * different data direction or already started, don't merge
78          */
79         if (bio_data_dir(bio) != rq_data_dir(rq))
80                 return 0;
81
82         /*
83          * must be same device and not a special request
84          */
85         if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)
86                 return 0;
87
88         if (!elv_iosched_allow_merge(rq, bio))
89                 return 0;
90
91         return 1;
92 }
93 EXPORT_SYMBOL(elv_rq_merge_ok);
94
95 static inline int elv_try_merge(struct request *__rq, struct bio *bio)
96 {
97         int ret = ELEVATOR_NO_MERGE;
98
99         /*
100          * we can merge and sequence is ok, check if it's possible
101          */
102         if (elv_rq_merge_ok(__rq, bio)) {
103                 if (__rq->sector + __rq->nr_sectors == bio->bi_sector)
104                         ret = ELEVATOR_BACK_MERGE;
105                 else if (__rq->sector - bio_sectors(bio) == bio->bi_sector)
106                         ret = ELEVATOR_FRONT_MERGE;
107         }
108
109         return ret;
110 }
111
112 static struct elevator_type *elevator_find(const char *name)
113 {
114         struct elevator_type *e;
115
116         list_for_each_entry(e, &elv_list, list) {
117                 if (!strcmp(e->elevator_name, name))
118                         return e;
119         }
120
121         return NULL;
122 }
123
124 static void elevator_put(struct elevator_type *e)
125 {
126         module_put(e->elevator_owner);
127 }
128
129 static struct elevator_type *elevator_get(const char *name)
130 {
131         struct elevator_type *e;
132
133         spin_lock(&elv_list_lock);
134
135         e = elevator_find(name);
136         if (e && !try_module_get(e->elevator_owner))
137                 e = NULL;
138
139         spin_unlock(&elv_list_lock);
140
141         return e;
142 }
143
144 static void *elevator_init_queue(struct request_queue *q,
145                                  struct elevator_queue *eq)
146 {
147         return eq->ops->elevator_init_fn(q);
148 }
149
150 static void elevator_attach(struct request_queue *q, struct elevator_queue *eq,
151                            void *data)
152 {
153         q->elevator = eq;
154         eq->elevator_data = data;
155 }
156
157 static char chosen_elevator[16];
158
159 static int __init elevator_setup(char *str)
160 {
161         /*
162          * Be backwards-compatible with previous kernels, so users
163          * won't get the wrong elevator.
164          */
165         if (!strcmp(str, "as"))
166                 strcpy(chosen_elevator, "anticipatory");
167         else
168                 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
169         return 1;
170 }
171
172 __setup("elevator=", elevator_setup);
173
174 static struct kobj_type elv_ktype;
175
176 static elevator_t *elevator_alloc(struct request_queue *q,
177                                   struct elevator_type *e)
178 {
179         elevator_t *eq;
180         int i;
181
182         eq = kmalloc_node(sizeof(elevator_t), GFP_KERNEL | __GFP_ZERO, q->node);
183         if (unlikely(!eq))
184                 goto err;
185
186         eq->ops = &e->ops;
187         eq->elevator_type = e;
188         kobject_init(&eq->kobj, &elv_ktype);
189         mutex_init(&eq->sysfs_lock);
190
191         eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES,
192                                         GFP_KERNEL, q->node);
193         if (!eq->hash)
194                 goto err;
195
196         for (i = 0; i < ELV_HASH_ENTRIES; i++)
197                 INIT_HLIST_HEAD(&eq->hash[i]);
198
199         return eq;
200 err:
201         kfree(eq);
202         elevator_put(e);
203         return NULL;
204 }
205
206 static void elevator_release(struct kobject *kobj)
207 {
208         elevator_t *e = container_of(kobj, elevator_t, kobj);
209
210         elevator_put(e->elevator_type);
211         kfree(e->hash);
212         kfree(e);
213 }
214
215 int elevator_init(struct request_queue *q, char *name)
216 {
217         struct elevator_type *e = NULL;
218         struct elevator_queue *eq;
219         int ret = 0;
220         void *data;
221
222         INIT_LIST_HEAD(&q->queue_head);
223         q->last_merge = NULL;
224         q->end_sector = 0;
225         q->boundary_rq = NULL;
226
227         if (name && !(e = elevator_get(name)))
228                 return -EINVAL;
229
230         if (!e && *chosen_elevator && !(e = elevator_get(chosen_elevator)))
231                 printk("I/O scheduler %s not found\n", chosen_elevator);
232
233         if (!e && !(e = elevator_get(CONFIG_DEFAULT_IOSCHED))) {
234                 printk("Default I/O scheduler not found, using no-op\n");
235                 e = elevator_get("noop");
236         }
237
238         eq = elevator_alloc(q, e);
239         if (!eq)
240                 return -ENOMEM;
241
242         data = elevator_init_queue(q, eq);
243         if (!data) {
244                 kobject_put(&eq->kobj);
245                 return -ENOMEM;
246         }
247
248         elevator_attach(q, eq, data);
249         return ret;
250 }
251
252 EXPORT_SYMBOL(elevator_init);
253
254 void elevator_exit(elevator_t *e)
255 {
256         mutex_lock(&e->sysfs_lock);
257         if (e->ops->elevator_exit_fn)
258                 e->ops->elevator_exit_fn(e);
259         e->ops = NULL;
260         mutex_unlock(&e->sysfs_lock);
261
262         kobject_put(&e->kobj);
263 }
264
265 EXPORT_SYMBOL(elevator_exit);
266
267 static void elv_activate_rq(struct request_queue *q, struct request *rq)
268 {
269         elevator_t *e = q->elevator;
270
271         if (e->ops->elevator_activate_req_fn)
272                 e->ops->elevator_activate_req_fn(q, rq);
273 }
274
275 static void elv_deactivate_rq(struct request_queue *q, struct request *rq)
276 {
277         elevator_t *e = q->elevator;
278
279         if (e->ops->elevator_deactivate_req_fn)
280                 e->ops->elevator_deactivate_req_fn(q, rq);
281 }
282
283 static inline void __elv_rqhash_del(struct request *rq)
284 {
285         hlist_del_init(&rq->hash);
286 }
287
288 static void elv_rqhash_del(struct request_queue *q, struct request *rq)
289 {
290         if (ELV_ON_HASH(rq))
291                 __elv_rqhash_del(rq);
292 }
293
294 static void elv_rqhash_add(struct request_queue *q, struct request *rq)
295 {
296         elevator_t *e = q->elevator;
297
298         BUG_ON(ELV_ON_HASH(rq));
299         hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
300 }
301
302 static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
303 {
304         __elv_rqhash_del(rq);
305         elv_rqhash_add(q, rq);
306 }
307
308 static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
309 {
310         elevator_t *e = q->elevator;
311         struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
312         struct hlist_node *entry, *next;
313         struct request *rq;
314
315         hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
316                 BUG_ON(!ELV_ON_HASH(rq));
317
318                 if (unlikely(!rq_mergeable(rq))) {
319                         __elv_rqhash_del(rq);
320                         continue;
321                 }
322
323                 if (rq_hash_key(rq) == offset)
324                         return rq;
325         }
326
327         return NULL;
328 }
329
330 /*
331  * RB-tree support functions for inserting/lookup/removal of requests
332  * in a sorted RB tree.
333  */
334 struct request *elv_rb_add(struct rb_root *root, struct request *rq)
335 {
336         struct rb_node **p = &root->rb_node;
337         struct rb_node *parent = NULL;
338         struct request *__rq;
339
340         while (*p) {
341                 parent = *p;
342                 __rq = rb_entry(parent, struct request, rb_node);
343
344                 if (rq->sector < __rq->sector)
345                         p = &(*p)->rb_left;
346                 else if (rq->sector > __rq->sector)
347                         p = &(*p)->rb_right;
348                 else
349                         return __rq;
350         }
351
352         rb_link_node(&rq->rb_node, parent, p);
353         rb_insert_color(&rq->rb_node, root);
354         return NULL;
355 }
356
357 EXPORT_SYMBOL(elv_rb_add);
358
359 void elv_rb_del(struct rb_root *root, struct request *rq)
360 {
361         BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
362         rb_erase(&rq->rb_node, root);
363         RB_CLEAR_NODE(&rq->rb_node);
364 }
365
366 EXPORT_SYMBOL(elv_rb_del);
367
368 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
369 {
370         struct rb_node *n = root->rb_node;
371         struct request *rq;
372
373         while (n) {
374                 rq = rb_entry(n, struct request, rb_node);
375
376                 if (sector < rq->sector)
377                         n = n->rb_left;
378                 else if (sector > rq->sector)
379                         n = n->rb_right;
380                 else
381                         return rq;
382         }
383
384         return NULL;
385 }
386
387 EXPORT_SYMBOL(elv_rb_find);
388
389 /*
390  * Insert rq into dispatch queue of q.  Queue lock must be held on
391  * entry.  rq is sort instead into the dispatch queue. To be used by
392  * specific elevators.
393  */
394 void elv_dispatch_sort(struct request_queue *q, struct request *rq)
395 {
396         sector_t boundary;
397         struct list_head *entry;
398
399         if (q->last_merge == rq)
400                 q->last_merge = NULL;
401
402         elv_rqhash_del(q, rq);
403
404         q->nr_sorted--;
405
406         boundary = q->end_sector;
407
408         list_for_each_prev(entry, &q->queue_head) {
409                 struct request *pos = list_entry_rq(entry);
410
411                 if (rq_data_dir(rq) != rq_data_dir(pos))
412                         break;
413                 if (pos->cmd_flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED))
414                         break;
415                 if (rq->sector >= boundary) {
416                         if (pos->sector < boundary)
417                                 continue;
418                 } else {
419                         if (pos->sector >= boundary)
420                                 break;
421                 }
422                 if (rq->sector >= pos->sector)
423                         break;
424         }
425
426         list_add(&rq->queuelist, entry);
427 }
428
429 EXPORT_SYMBOL(elv_dispatch_sort);
430
431 /*
432  * Insert rq into dispatch queue of q.  Queue lock must be held on
433  * entry.  rq is added to the back of the dispatch queue. To be used by
434  * specific elevators.
435  */
436 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
437 {
438         if (q->last_merge == rq)
439                 q->last_merge = NULL;
440
441         elv_rqhash_del(q, rq);
442
443         q->nr_sorted--;
444
445         q->end_sector = rq_end_sector(rq);
446         q->boundary_rq = rq;
447         list_add_tail(&rq->queuelist, &q->queue_head);
448 }
449
450 EXPORT_SYMBOL(elv_dispatch_add_tail);
451
452 int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
453 {
454         elevator_t *e = q->elevator;
455         struct request *__rq;
456         int ret;
457
458         /*
459          * First try one-hit cache.
460          */
461         if (q->last_merge) {
462                 ret = elv_try_merge(q->last_merge, bio);
463                 if (ret != ELEVATOR_NO_MERGE) {
464                         *req = q->last_merge;
465                         return ret;
466                 }
467         }
468
469         /*
470          * See if our hash lookup can find a potential backmerge.
471          */
472         __rq = elv_rqhash_find(q, bio->bi_sector);
473         if (__rq && elv_rq_merge_ok(__rq, bio)) {
474                 *req = __rq;
475                 return ELEVATOR_BACK_MERGE;
476         }
477
478         if (e->ops->elevator_merge_fn)
479                 return e->ops->elevator_merge_fn(q, req, bio);
480
481         return ELEVATOR_NO_MERGE;
482 }
483
484 void elv_merged_request(struct request_queue *q, struct request *rq, int type)
485 {
486         elevator_t *e = q->elevator;
487
488         if (e->ops->elevator_merged_fn)
489                 e->ops->elevator_merged_fn(q, rq, type);
490
491         if (type == ELEVATOR_BACK_MERGE)
492                 elv_rqhash_reposition(q, rq);
493
494         q->last_merge = rq;
495 }
496
497 void elv_merge_requests(struct request_queue *q, struct request *rq,
498                              struct request *next)
499 {
500         elevator_t *e = q->elevator;
501
502         if (e->ops->elevator_merge_req_fn)
503                 e->ops->elevator_merge_req_fn(q, rq, next);
504
505         elv_rqhash_reposition(q, rq);
506         elv_rqhash_del(q, next);
507
508         q->nr_sorted--;
509         q->last_merge = rq;
510 }
511
512 void elv_requeue_request(struct request_queue *q, struct request *rq)
513 {
514         /*
515          * it already went through dequeue, we need to decrement the
516          * in_flight count again
517          */
518         if (blk_account_rq(rq)) {
519                 q->in_flight--;
520                 if (blk_sorted_rq(rq))
521                         elv_deactivate_rq(q, rq);
522         }
523
524         rq->cmd_flags &= ~REQ_STARTED;
525
526         elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
527 }
528
529 static void elv_drain_elevator(struct request_queue *q)
530 {
531         static int printed;
532         while (q->elevator->ops->elevator_dispatch_fn(q, 1))
533                 ;
534         if (q->nr_sorted == 0)
535                 return;
536         if (printed++ < 10) {
537                 printk(KERN_ERR "%s: forced dispatching is broken "
538                        "(nr_sorted=%u), please report this\n",
539                        q->elevator->elevator_type->elevator_name, q->nr_sorted);
540         }
541 }
542
543 void elv_insert(struct request_queue *q, struct request *rq, int where)
544 {
545         struct list_head *pos;
546         unsigned ordseq;
547         int unplug_it = 1;
548
549         blk_add_trace_rq(q, rq, BLK_TA_INSERT);
550
551         rq->q = q;
552
553         switch (where) {
554         case ELEVATOR_INSERT_FRONT:
555                 rq->cmd_flags |= REQ_SOFTBARRIER;
556
557                 list_add(&rq->queuelist, &q->queue_head);
558                 break;
559
560         case ELEVATOR_INSERT_BACK:
561                 rq->cmd_flags |= REQ_SOFTBARRIER;
562                 elv_drain_elevator(q);
563                 list_add_tail(&rq->queuelist, &q->queue_head);
564                 /*
565                  * We kick the queue here for the following reasons.
566                  * - The elevator might have returned NULL previously
567                  *   to delay requests and returned them now.  As the
568                  *   queue wasn't empty before this request, ll_rw_blk
569                  *   won't run the queue on return, resulting in hang.
570                  * - Usually, back inserted requests won't be merged
571                  *   with anything.  There's no point in delaying queue
572                  *   processing.
573                  */
574                 blk_remove_plug(q);
575                 q->request_fn(q);
576                 break;
577
578         case ELEVATOR_INSERT_SORT:
579                 BUG_ON(!blk_fs_request(rq));
580                 rq->cmd_flags |= REQ_SORTED;
581                 q->nr_sorted++;
582                 if (rq_mergeable(rq)) {
583                         elv_rqhash_add(q, rq);
584                         if (!q->last_merge)
585                                 q->last_merge = rq;
586                 }
587
588                 /*
589                  * Some ioscheds (cfq) run q->request_fn directly, so
590                  * rq cannot be accessed after calling
591                  * elevator_add_req_fn.
592                  */
593                 q->elevator->ops->elevator_add_req_fn(q, rq);
594                 break;
595
596         case ELEVATOR_INSERT_REQUEUE:
597                 /*
598                  * If ordered flush isn't in progress, we do front
599                  * insertion; otherwise, requests should be requeued
600                  * in ordseq order.
601                  */
602                 rq->cmd_flags |= REQ_SOFTBARRIER;
603
604                 /*
605                  * Most requeues happen because of a busy condition,
606                  * don't force unplug of the queue for that case.
607                  */
608                 unplug_it = 0;
609
610                 if (q->ordseq == 0) {
611                         list_add(&rq->queuelist, &q->queue_head);
612                         break;
613                 }
614
615                 ordseq = blk_ordered_req_seq(rq);
616
617                 list_for_each(pos, &q->queue_head) {
618                         struct request *pos_rq = list_entry_rq(pos);
619                         if (ordseq <= blk_ordered_req_seq(pos_rq))
620                                 break;
621                 }
622
623                 list_add_tail(&rq->queuelist, pos);
624                 break;
625
626         default:
627                 printk(KERN_ERR "%s: bad insertion point %d\n",
628                        __FUNCTION__, where);
629                 BUG();
630         }
631
632         if (unplug_it && blk_queue_plugged(q)) {
633                 int nrq = q->rq.count[READ] + q->rq.count[WRITE]
634                         - q->in_flight;
635
636                 if (nrq >= q->unplug_thresh)
637                         __generic_unplug_device(q);
638         }
639 }
640
641 void __elv_add_request(struct request_queue *q, struct request *rq, int where,
642                        int plug)
643 {
644         if (q->ordcolor)
645                 rq->cmd_flags |= REQ_ORDERED_COLOR;
646
647         if (rq->cmd_flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
648                 /*
649                  * toggle ordered color
650                  */
651                 if (blk_barrier_rq(rq))
652                         q->ordcolor ^= 1;
653
654                 /*
655                  * barriers implicitly indicate back insertion
656                  */
657                 if (where == ELEVATOR_INSERT_SORT)
658                         where = ELEVATOR_INSERT_BACK;
659
660                 /*
661                  * this request is scheduling boundary, update
662                  * end_sector
663                  */
664                 if (blk_fs_request(rq)) {
665                         q->end_sector = rq_end_sector(rq);
666                         q->boundary_rq = rq;
667                 }
668         } else if (!(rq->cmd_flags & REQ_ELVPRIV) && where == ELEVATOR_INSERT_SORT)
669                 where = ELEVATOR_INSERT_BACK;
670
671         if (plug)
672                 blk_plug_device(q);
673
674         elv_insert(q, rq, where);
675 }
676
677 EXPORT_SYMBOL(__elv_add_request);
678
679 void elv_add_request(struct request_queue *q, struct request *rq, int where,
680                      int plug)
681 {
682         unsigned long flags;
683
684         spin_lock_irqsave(q->queue_lock, flags);
685         __elv_add_request(q, rq, where, plug);
686         spin_unlock_irqrestore(q->queue_lock, flags);
687 }
688
689 EXPORT_SYMBOL(elv_add_request);
690
691 static inline struct request *__elv_next_request(struct request_queue *q)
692 {
693         struct request *rq;
694
695         while (1) {
696                 while (!list_empty(&q->queue_head)) {
697                         rq = list_entry_rq(q->queue_head.next);
698                         if (blk_do_ordered(q, &rq))
699                                 return rq;
700                 }
701
702                 if (!q->elevator->ops->elevator_dispatch_fn(q, 0))
703                         return NULL;
704         }
705 }
706
707 struct request *elv_next_request(struct request_queue *q)
708 {
709         struct request *rq;
710         int ret;
711
712         while ((rq = __elv_next_request(q)) != NULL) {
713                 /*
714                  * Kill the empty barrier place holder, the driver must
715                  * not ever see it.
716                  */
717                 if (blk_empty_barrier(rq)) {
718                         end_queued_request(rq, 1);
719                         continue;
720                 }
721                 if (!(rq->cmd_flags & REQ_STARTED)) {
722                         /*
723                          * This is the first time the device driver
724                          * sees this request (possibly after
725                          * requeueing).  Notify IO scheduler.
726                          */
727                         if (blk_sorted_rq(rq))
728                                 elv_activate_rq(q, rq);
729
730                         /*
731                          * just mark as started even if we don't start
732                          * it, a request that has been delayed should
733                          * not be passed by new incoming requests
734                          */
735                         rq->cmd_flags |= REQ_STARTED;
736                         blk_add_trace_rq(q, rq, BLK_TA_ISSUE);
737                 }
738
739                 if (!q->boundary_rq || q->boundary_rq == rq) {
740                         q->end_sector = rq_end_sector(rq);
741                         q->boundary_rq = NULL;
742                 }
743
744                 if (rq->cmd_flags & REQ_DONTPREP)
745                         break;
746
747                 if (q->dma_drain_size && rq->data_len) {
748                         /*
749                          * make sure space for the drain appears we
750                          * know we can do this because max_hw_segments
751                          * has been adjusted to be one fewer than the
752                          * device can handle
753                          */
754                         rq->nr_phys_segments++;
755                         rq->nr_hw_segments++;
756                 }
757
758                 if (!q->prep_rq_fn)
759                         break;
760
761                 ret = q->prep_rq_fn(q, rq);
762                 if (ret == BLKPREP_OK) {
763                         break;
764                 } else if (ret == BLKPREP_DEFER) {
765                         /*
766                          * the request may have been (partially) prepped.
767                          * we need to keep this request in the front to
768                          * avoid resource deadlock.  REQ_STARTED will
769                          * prevent other fs requests from passing this one.
770                          */
771                         if (q->dma_drain_size && rq->data_len &&
772                             !(rq->cmd_flags & REQ_DONTPREP)) {
773                                 /*
774                                  * remove the space for the drain we added
775                                  * so that we don't add it again
776                                  */
777                                 --rq->nr_phys_segments;
778                                 --rq->nr_hw_segments;
779                         }
780
781                         rq = NULL;
782                         break;
783                 } else if (ret == BLKPREP_KILL) {
784                         rq->cmd_flags |= REQ_QUIET;
785                         end_queued_request(rq, 0);
786                 } else {
787                         printk(KERN_ERR "%s: bad return=%d\n", __FUNCTION__,
788                                                                 ret);
789                         break;
790                 }
791         }
792
793         return rq;
794 }
795
796 EXPORT_SYMBOL(elv_next_request);
797
798 void elv_dequeue_request(struct request_queue *q, struct request *rq)
799 {
800         BUG_ON(list_empty(&rq->queuelist));
801         BUG_ON(ELV_ON_HASH(rq));
802
803         list_del_init(&rq->queuelist);
804
805         /*
806          * the time frame between a request being removed from the lists
807          * and to it is freed is accounted as io that is in progress at
808          * the driver side.
809          */
810         if (blk_account_rq(rq))
811                 q->in_flight++;
812 }
813
814 EXPORT_SYMBOL(elv_dequeue_request);
815
816 int elv_queue_empty(struct request_queue *q)
817 {
818         elevator_t *e = q->elevator;
819
820         if (!list_empty(&q->queue_head))
821                 return 0;
822
823         if (e->ops->elevator_queue_empty_fn)
824                 return e->ops->elevator_queue_empty_fn(q);
825
826         return 1;
827 }
828
829 EXPORT_SYMBOL(elv_queue_empty);
830
831 struct request *elv_latter_request(struct request_queue *q, struct request *rq)
832 {
833         elevator_t *e = q->elevator;
834
835         if (e->ops->elevator_latter_req_fn)
836                 return e->ops->elevator_latter_req_fn(q, rq);
837         return NULL;
838 }
839
840 struct request *elv_former_request(struct request_queue *q, struct request *rq)
841 {
842         elevator_t *e = q->elevator;
843
844         if (e->ops->elevator_former_req_fn)
845                 return e->ops->elevator_former_req_fn(q, rq);
846         return NULL;
847 }
848
849 int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
850 {
851         elevator_t *e = q->elevator;
852
853         if (e->ops->elevator_set_req_fn)
854                 return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
855
856         rq->elevator_private = NULL;
857         return 0;
858 }
859
860 void elv_put_request(struct request_queue *q, struct request *rq)
861 {
862         elevator_t *e = q->elevator;
863
864         if (e->ops->elevator_put_req_fn)
865                 e->ops->elevator_put_req_fn(rq);
866 }
867
868 int elv_may_queue(struct request_queue *q, int rw)
869 {
870         elevator_t *e = q->elevator;
871
872         if (e->ops->elevator_may_queue_fn)
873                 return e->ops->elevator_may_queue_fn(q, rw);
874
875         return ELV_MQUEUE_MAY;
876 }
877
878 void elv_completed_request(struct request_queue *q, struct request *rq)
879 {
880         elevator_t *e = q->elevator;
881
882         /*
883          * request is released from the driver, io must be done
884          */
885         if (blk_account_rq(rq)) {
886                 q->in_flight--;
887                 if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
888                         e->ops->elevator_completed_req_fn(q, rq);
889         }
890
891         /*
892          * Check if the queue is waiting for fs requests to be
893          * drained for flush sequence.
894          */
895         if (unlikely(q->ordseq)) {
896                 struct request *first_rq = list_entry_rq(q->queue_head.next);
897                 if (q->in_flight == 0 &&
898                     blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
899                     blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
900                         blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
901                         q->request_fn(q);
902                 }
903         }
904 }
905
906 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
907
908 static ssize_t
909 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
910 {
911         elevator_t *e = container_of(kobj, elevator_t, kobj);
912         struct elv_fs_entry *entry = to_elv(attr);
913         ssize_t error;
914
915         if (!entry->show)
916                 return -EIO;
917
918         mutex_lock(&e->sysfs_lock);
919         error = e->ops ? entry->show(e, page) : -ENOENT;
920         mutex_unlock(&e->sysfs_lock);
921         return error;
922 }
923
924 static ssize_t
925 elv_attr_store(struct kobject *kobj, struct attribute *attr,
926                const char *page, size_t length)
927 {
928         elevator_t *e = container_of(kobj, elevator_t, kobj);
929         struct elv_fs_entry *entry = to_elv(attr);
930         ssize_t error;
931
932         if (!entry->store)
933                 return -EIO;
934
935         mutex_lock(&e->sysfs_lock);
936         error = e->ops ? entry->store(e, page, length) : -ENOENT;
937         mutex_unlock(&e->sysfs_lock);
938         return error;
939 }
940
941 static struct sysfs_ops elv_sysfs_ops = {
942         .show   = elv_attr_show,
943         .store  = elv_attr_store,
944 };
945
946 static struct kobj_type elv_ktype = {
947         .sysfs_ops      = &elv_sysfs_ops,
948         .release        = elevator_release,
949 };
950
951 int elv_register_queue(struct request_queue *q)
952 {
953         elevator_t *e = q->elevator;
954         int error;
955
956         error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
957         if (!error) {
958                 struct elv_fs_entry *attr = e->elevator_type->elevator_attrs;
959                 if (attr) {
960                         while (attr->attr.name) {
961                                 if (sysfs_create_file(&e->kobj, &attr->attr))
962                                         break;
963                                 attr++;
964                         }
965                 }
966                 kobject_uevent(&e->kobj, KOBJ_ADD);
967         }
968         return error;
969 }
970
971 static void __elv_unregister_queue(elevator_t *e)
972 {
973         kobject_uevent(&e->kobj, KOBJ_REMOVE);
974         kobject_del(&e->kobj);
975 }
976
977 void elv_unregister_queue(struct request_queue *q)
978 {
979         if (q)
980                 __elv_unregister_queue(q->elevator);
981 }
982
983 void elv_register(struct elevator_type *e)
984 {
985         char *def = "";
986
987         spin_lock(&elv_list_lock);
988         BUG_ON(elevator_find(e->elevator_name));
989         list_add_tail(&e->list, &elv_list);
990         spin_unlock(&elv_list_lock);
991
992         if (!strcmp(e->elevator_name, chosen_elevator) ||
993                         (!*chosen_elevator &&
994                          !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
995                                 def = " (default)";
996
997         printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name, def);
998 }
999 EXPORT_SYMBOL_GPL(elv_register);
1000
1001 void elv_unregister(struct elevator_type *e)
1002 {
1003         struct task_struct *g, *p;
1004
1005         /*
1006          * Iterate every thread in the process to remove the io contexts.
1007          */
1008         if (e->ops.trim) {
1009                 read_lock(&tasklist_lock);
1010                 do_each_thread(g, p) {
1011                         task_lock(p);
1012                         if (p->io_context)
1013                                 e->ops.trim(p->io_context);
1014                         task_unlock(p);
1015                 } while_each_thread(g, p);
1016                 read_unlock(&tasklist_lock);
1017         }
1018
1019         spin_lock(&elv_list_lock);
1020         list_del_init(&e->list);
1021         spin_unlock(&elv_list_lock);
1022 }
1023 EXPORT_SYMBOL_GPL(elv_unregister);
1024
1025 /*
1026  * switch to new_e io scheduler. be careful not to introduce deadlocks -
1027  * we don't free the old io scheduler, before we have allocated what we
1028  * need for the new one. this way we have a chance of going back to the old
1029  * one, if the new one fails init for some reason.
1030  */
1031 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
1032 {
1033         elevator_t *old_elevator, *e;
1034         void *data;
1035
1036         /*
1037          * Allocate new elevator
1038          */
1039         e = elevator_alloc(q, new_e);
1040         if (!e)
1041                 return 0;
1042
1043         data = elevator_init_queue(q, e);
1044         if (!data) {
1045                 kobject_put(&e->kobj);
1046                 return 0;
1047         }
1048
1049         /*
1050          * Turn on BYPASS and drain all requests w/ elevator private data
1051          */
1052         spin_lock_irq(q->queue_lock);
1053
1054         set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1055
1056         elv_drain_elevator(q);
1057
1058         while (q->rq.elvpriv) {
1059                 blk_remove_plug(q);
1060                 q->request_fn(q);
1061                 spin_unlock_irq(q->queue_lock);
1062                 msleep(10);
1063                 spin_lock_irq(q->queue_lock);
1064                 elv_drain_elevator(q);
1065         }
1066
1067         /*
1068          * Remember old elevator.
1069          */
1070         old_elevator = q->elevator;
1071
1072         /*
1073          * attach and start new elevator
1074          */
1075         elevator_attach(q, e, data);
1076
1077         spin_unlock_irq(q->queue_lock);
1078
1079         __elv_unregister_queue(old_elevator);
1080
1081         if (elv_register_queue(q))
1082                 goto fail_register;
1083
1084         /*
1085          * finally exit old elevator and turn off BYPASS.
1086          */
1087         elevator_exit(old_elevator);
1088         clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1089         return 1;
1090
1091 fail_register:
1092         /*
1093          * switch failed, exit the new io scheduler and reattach the old
1094          * one again (along with re-adding the sysfs dir)
1095          */
1096         elevator_exit(e);
1097         q->elevator = old_elevator;
1098         elv_register_queue(q);
1099         clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1100         return 0;
1101 }
1102
1103 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
1104                           size_t count)
1105 {
1106         char elevator_name[ELV_NAME_MAX];
1107         size_t len;
1108         struct elevator_type *e;
1109
1110         elevator_name[sizeof(elevator_name) - 1] = '\0';
1111         strncpy(elevator_name, name, sizeof(elevator_name) - 1);
1112         len = strlen(elevator_name);
1113
1114         if (len && elevator_name[len - 1] == '\n')
1115                 elevator_name[len - 1] = '\0';
1116
1117         e = elevator_get(elevator_name);
1118         if (!e) {
1119                 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
1120                 return -EINVAL;
1121         }
1122
1123         if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
1124                 elevator_put(e);
1125                 return count;
1126         }
1127
1128         if (!elevator_switch(q, e))
1129                 printk(KERN_ERR "elevator: switch to %s failed\n",elevator_name);
1130         return count;
1131 }
1132
1133 ssize_t elv_iosched_show(struct request_queue *q, char *name)
1134 {
1135         elevator_t *e = q->elevator;
1136         struct elevator_type *elv = e->elevator_type;
1137         struct elevator_type *__e;
1138         int len = 0;
1139
1140         spin_lock(&elv_list_lock);
1141         list_for_each_entry(__e, &elv_list, list) {
1142                 if (!strcmp(elv->elevator_name, __e->elevator_name))
1143                         len += sprintf(name+len, "[%s] ", elv->elevator_name);
1144                 else
1145                         len += sprintf(name+len, "%s ", __e->elevator_name);
1146         }
1147         spin_unlock(&elv_list_lock);
1148
1149         len += sprintf(len+name, "\n");
1150         return len;
1151 }
1152
1153 struct request *elv_rb_former_request(struct request_queue *q,
1154                                       struct request *rq)
1155 {
1156         struct rb_node *rbprev = rb_prev(&rq->rb_node);
1157
1158         if (rbprev)
1159                 return rb_entry_rq(rbprev);
1160
1161         return NULL;
1162 }
1163
1164 EXPORT_SYMBOL(elv_rb_former_request);
1165
1166 struct request *elv_rb_latter_request(struct request_queue *q,
1167                                       struct request *rq)
1168 {
1169         struct rb_node *rbnext = rb_next(&rq->rb_node);
1170
1171         if (rbnext)
1172                 return rb_entry_rq(rbnext);
1173
1174         return NULL;
1175 }
1176
1177 EXPORT_SYMBOL(elv_rb_latter_request);