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