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