block: remove wrappers for request type/flags
[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 ((rq->cmd_flags & REQ_DISCARD) !=
432                     (pos->cmd_flags & REQ_DISCARD))
433                         break;
434                 if (rq_data_dir(rq) != rq_data_dir(pos))
435                         break;
436                 if (pos->cmd_flags & stop_flags)
437                         break;
438                 if (blk_rq_pos(rq) >= boundary) {
439                         if (blk_rq_pos(pos) < boundary)
440                                 continue;
441                 } else {
442                         if (blk_rq_pos(pos) >= boundary)
443                                 break;
444                 }
445                 if (blk_rq_pos(rq) >= blk_rq_pos(pos))
446                         break;
447         }
448
449         list_add(&rq->queuelist, entry);
450 }
451 EXPORT_SYMBOL(elv_dispatch_sort);
452
453 /*
454  * Insert rq into dispatch queue of q.  Queue lock must be held on
455  * entry.  rq is added to the back of the dispatch queue. To be used by
456  * specific elevators.
457  */
458 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
459 {
460         if (q->last_merge == rq)
461                 q->last_merge = NULL;
462
463         elv_rqhash_del(q, rq);
464
465         q->nr_sorted--;
466
467         q->end_sector = rq_end_sector(rq);
468         q->boundary_rq = rq;
469         list_add_tail(&rq->queuelist, &q->queue_head);
470 }
471 EXPORT_SYMBOL(elv_dispatch_add_tail);
472
473 int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
474 {
475         struct elevator_queue *e = q->elevator;
476         struct request *__rq;
477         int ret;
478
479         /*
480          * Levels of merges:
481          *      nomerges:  No merges at all attempted
482          *      noxmerges: Only simple one-hit cache try
483          *      merges:    All merge tries attempted
484          */
485         if (blk_queue_nomerges(q))
486                 return ELEVATOR_NO_MERGE;
487
488         /*
489          * First try one-hit cache.
490          */
491         if (q->last_merge) {
492                 ret = elv_try_merge(q->last_merge, bio);
493                 if (ret != ELEVATOR_NO_MERGE) {
494                         *req = q->last_merge;
495                         return ret;
496                 }
497         }
498
499         if (blk_queue_noxmerges(q))
500                 return ELEVATOR_NO_MERGE;
501
502         /*
503          * See if our hash lookup can find a potential backmerge.
504          */
505         __rq = elv_rqhash_find(q, bio->bi_sector);
506         if (__rq && elv_rq_merge_ok(__rq, bio)) {
507                 *req = __rq;
508                 return ELEVATOR_BACK_MERGE;
509         }
510
511         if (e->ops->elevator_merge_fn)
512                 return e->ops->elevator_merge_fn(q, req, bio);
513
514         return ELEVATOR_NO_MERGE;
515 }
516
517 void elv_merged_request(struct request_queue *q, struct request *rq, int type)
518 {
519         struct elevator_queue *e = q->elevator;
520
521         if (e->ops->elevator_merged_fn)
522                 e->ops->elevator_merged_fn(q, rq, type);
523
524         if (type == ELEVATOR_BACK_MERGE)
525                 elv_rqhash_reposition(q, rq);
526
527         q->last_merge = rq;
528 }
529
530 void elv_merge_requests(struct request_queue *q, struct request *rq,
531                              struct request *next)
532 {
533         struct elevator_queue *e = q->elevator;
534
535         if (e->ops->elevator_merge_req_fn)
536                 e->ops->elevator_merge_req_fn(q, rq, next);
537
538         elv_rqhash_reposition(q, rq);
539         elv_rqhash_del(q, next);
540
541         q->nr_sorted--;
542         q->last_merge = rq;
543 }
544
545 void elv_bio_merged(struct request_queue *q, struct request *rq,
546                         struct bio *bio)
547 {
548         struct elevator_queue *e = q->elevator;
549
550         if (e->ops->elevator_bio_merged_fn)
551                 e->ops->elevator_bio_merged_fn(q, rq, bio);
552 }
553
554 void elv_requeue_request(struct request_queue *q, struct request *rq)
555 {
556         /*
557          * it already went through dequeue, we need to decrement the
558          * in_flight count again
559          */
560         if (blk_account_rq(rq)) {
561                 q->in_flight[rq_is_sync(rq)]--;
562                 if (rq->cmd_flags & REQ_SORTED)
563                         elv_deactivate_rq(q, rq);
564         }
565
566         rq->cmd_flags &= ~REQ_STARTED;
567
568         elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
569 }
570
571 void elv_drain_elevator(struct request_queue *q)
572 {
573         static int printed;
574         while (q->elevator->ops->elevator_dispatch_fn(q, 1))
575                 ;
576         if (q->nr_sorted == 0)
577                 return;
578         if (printed++ < 10) {
579                 printk(KERN_ERR "%s: forced dispatching is broken "
580                        "(nr_sorted=%u), please report this\n",
581                        q->elevator->elevator_type->elevator_name, q->nr_sorted);
582         }
583 }
584
585 /*
586  * Call with queue lock held, interrupts disabled
587  */
588 void elv_quiesce_start(struct request_queue *q)
589 {
590         if (!q->elevator)
591                 return;
592
593         queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
594
595         /*
596          * make sure we don't have any requests in flight
597          */
598         elv_drain_elevator(q);
599         while (q->rq.elvpriv) {
600                 __blk_run_queue(q);
601                 spin_unlock_irq(q->queue_lock);
602                 msleep(10);
603                 spin_lock_irq(q->queue_lock);
604                 elv_drain_elevator(q);
605         }
606 }
607
608 void elv_quiesce_end(struct request_queue *q)
609 {
610         queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
611 }
612
613 void elv_insert(struct request_queue *q, struct request *rq, int where)
614 {
615         struct list_head *pos;
616         unsigned ordseq;
617         int unplug_it = 1;
618
619         trace_block_rq_insert(q, rq);
620
621         rq->q = q;
622
623         switch (where) {
624         case ELEVATOR_INSERT_FRONT:
625                 rq->cmd_flags |= REQ_SOFTBARRIER;
626
627                 list_add(&rq->queuelist, &q->queue_head);
628                 break;
629
630         case ELEVATOR_INSERT_BACK:
631                 rq->cmd_flags |= REQ_SOFTBARRIER;
632                 elv_drain_elevator(q);
633                 list_add_tail(&rq->queuelist, &q->queue_head);
634                 /*
635                  * We kick the queue here for the following reasons.
636                  * - The elevator might have returned NULL previously
637                  *   to delay requests and returned them now.  As the
638                  *   queue wasn't empty before this request, ll_rw_blk
639                  *   won't run the queue on return, resulting in hang.
640                  * - Usually, back inserted requests won't be merged
641                  *   with anything.  There's no point in delaying queue
642                  *   processing.
643                  */
644                 __blk_run_queue(q);
645                 break;
646
647         case ELEVATOR_INSERT_SORT:
648                 BUG_ON(rq->cmd_type != REQ_TYPE_FS &&
649                        !(rq->cmd_flags & REQ_DISCARD));
650                 rq->cmd_flags |= REQ_SORTED;
651                 q->nr_sorted++;
652                 if (rq_mergeable(rq)) {
653                         elv_rqhash_add(q, rq);
654                         if (!q->last_merge)
655                                 q->last_merge = rq;
656                 }
657
658                 /*
659                  * Some ioscheds (cfq) run q->request_fn directly, so
660                  * rq cannot be accessed after calling
661                  * elevator_add_req_fn.
662                  */
663                 q->elevator->ops->elevator_add_req_fn(q, rq);
664                 break;
665
666         case ELEVATOR_INSERT_REQUEUE:
667                 /*
668                  * If ordered flush isn't in progress, we do front
669                  * insertion; otherwise, requests should be requeued
670                  * in ordseq order.
671                  */
672                 rq->cmd_flags |= REQ_SOFTBARRIER;
673
674                 /*
675                  * Most requeues happen because of a busy condition,
676                  * don't force unplug of the queue for that case.
677                  */
678                 unplug_it = 0;
679
680                 if (q->ordseq == 0) {
681                         list_add(&rq->queuelist, &q->queue_head);
682                         break;
683                 }
684
685                 ordseq = blk_ordered_req_seq(rq);
686
687                 list_for_each(pos, &q->queue_head) {
688                         struct request *pos_rq = list_entry_rq(pos);
689                         if (ordseq <= blk_ordered_req_seq(pos_rq))
690                                 break;
691                 }
692
693                 list_add_tail(&rq->queuelist, pos);
694                 break;
695
696         default:
697                 printk(KERN_ERR "%s: bad insertion point %d\n",
698                        __func__, where);
699                 BUG();
700         }
701
702         if (unplug_it && blk_queue_plugged(q)) {
703                 int nrq = q->rq.count[BLK_RW_SYNC] + q->rq.count[BLK_RW_ASYNC]
704                                 - queue_in_flight(q);
705
706                 if (nrq >= q->unplug_thresh)
707                         __generic_unplug_device(q);
708         }
709 }
710
711 void __elv_add_request(struct request_queue *q, struct request *rq, int where,
712                        int plug)
713 {
714         if (q->ordcolor)
715                 rq->cmd_flags |= REQ_ORDERED_COLOR;
716
717         if (rq->cmd_flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
718                 /*
719                  * toggle ordered color
720                  */
721                 if (rq->cmd_flags & REQ_HARDBARRIER)
722                         q->ordcolor ^= 1;
723
724                 /*
725                  * barriers implicitly indicate back insertion
726                  */
727                 if (where == ELEVATOR_INSERT_SORT)
728                         where = ELEVATOR_INSERT_BACK;
729
730                 /*
731                  * this request is scheduling boundary, update
732                  * end_sector
733                  */
734                 if (rq->cmd_type == REQ_TYPE_FS ||
735                     (rq->cmd_flags & REQ_DISCARD)) {
736                         q->end_sector = rq_end_sector(rq);
737                         q->boundary_rq = rq;
738                 }
739         } else if (!(rq->cmd_flags & REQ_ELVPRIV) &&
740                     where == ELEVATOR_INSERT_SORT)
741                 where = ELEVATOR_INSERT_BACK;
742
743         if (plug)
744                 blk_plug_device(q);
745
746         elv_insert(q, rq, where);
747 }
748 EXPORT_SYMBOL(__elv_add_request);
749
750 void elv_add_request(struct request_queue *q, struct request *rq, int where,
751                      int plug)
752 {
753         unsigned long flags;
754
755         spin_lock_irqsave(q->queue_lock, flags);
756         __elv_add_request(q, rq, where, plug);
757         spin_unlock_irqrestore(q->queue_lock, flags);
758 }
759 EXPORT_SYMBOL(elv_add_request);
760
761 int elv_queue_empty(struct request_queue *q)
762 {
763         struct elevator_queue *e = q->elevator;
764
765         if (!list_empty(&q->queue_head))
766                 return 0;
767
768         if (e->ops->elevator_queue_empty_fn)
769                 return e->ops->elevator_queue_empty_fn(q);
770
771         return 1;
772 }
773 EXPORT_SYMBOL(elv_queue_empty);
774
775 struct request *elv_latter_request(struct request_queue *q, struct request *rq)
776 {
777         struct elevator_queue *e = q->elevator;
778
779         if (e->ops->elevator_latter_req_fn)
780                 return e->ops->elevator_latter_req_fn(q, rq);
781         return NULL;
782 }
783
784 struct request *elv_former_request(struct request_queue *q, struct request *rq)
785 {
786         struct elevator_queue *e = q->elevator;
787
788         if (e->ops->elevator_former_req_fn)
789                 return e->ops->elevator_former_req_fn(q, rq);
790         return NULL;
791 }
792
793 int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
794 {
795         struct elevator_queue *e = q->elevator;
796
797         if (e->ops->elevator_set_req_fn)
798                 return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
799
800         rq->elevator_private = NULL;
801         return 0;
802 }
803
804 void elv_put_request(struct request_queue *q, struct request *rq)
805 {
806         struct elevator_queue *e = q->elevator;
807
808         if (e->ops->elevator_put_req_fn)
809                 e->ops->elevator_put_req_fn(rq);
810 }
811
812 int elv_may_queue(struct request_queue *q, int rw)
813 {
814         struct elevator_queue *e = q->elevator;
815
816         if (e->ops->elevator_may_queue_fn)
817                 return e->ops->elevator_may_queue_fn(q, rw);
818
819         return ELV_MQUEUE_MAY;
820 }
821
822 void elv_abort_queue(struct request_queue *q)
823 {
824         struct request *rq;
825
826         while (!list_empty(&q->queue_head)) {
827                 rq = list_entry_rq(q->queue_head.next);
828                 rq->cmd_flags |= REQ_QUIET;
829                 trace_block_rq_abort(q, rq);
830                 /*
831                  * Mark this request as started so we don't trigger
832                  * any debug logic in the end I/O path.
833                  */
834                 blk_start_request(rq);
835                 __blk_end_request_all(rq, -EIO);
836         }
837 }
838 EXPORT_SYMBOL(elv_abort_queue);
839
840 void elv_completed_request(struct request_queue *q, struct request *rq)
841 {
842         struct elevator_queue *e = q->elevator;
843
844         /*
845          * request is released from the driver, io must be done
846          */
847         if (blk_account_rq(rq)) {
848                 q->in_flight[rq_is_sync(rq)]--;
849                 if ((rq->cmd_flags & REQ_SORTED) &&
850                     e->ops->elevator_completed_req_fn)
851                         e->ops->elevator_completed_req_fn(q, rq);
852         }
853
854         /*
855          * Check if the queue is waiting for fs requests to be
856          * drained for flush sequence.
857          */
858         if (unlikely(q->ordseq)) {
859                 struct request *next = NULL;
860
861                 if (!list_empty(&q->queue_head))
862                         next = list_entry_rq(q->queue_head.next);
863
864                 if (!queue_in_flight(q) &&
865                     blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
866                     (!next || blk_ordered_req_seq(next) > QUEUE_ORDSEQ_DRAIN)) {
867                         blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
868                         __blk_run_queue(q);
869                 }
870         }
871 }
872
873 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
874
875 static ssize_t
876 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
877 {
878         struct elv_fs_entry *entry = to_elv(attr);
879         struct elevator_queue *e;
880         ssize_t error;
881
882         if (!entry->show)
883                 return -EIO;
884
885         e = container_of(kobj, struct elevator_queue, kobj);
886         mutex_lock(&e->sysfs_lock);
887         error = e->ops ? entry->show(e, page) : -ENOENT;
888         mutex_unlock(&e->sysfs_lock);
889         return error;
890 }
891
892 static ssize_t
893 elv_attr_store(struct kobject *kobj, struct attribute *attr,
894                const char *page, size_t length)
895 {
896         struct elv_fs_entry *entry = to_elv(attr);
897         struct elevator_queue *e;
898         ssize_t error;
899
900         if (!entry->store)
901                 return -EIO;
902
903         e = container_of(kobj, struct elevator_queue, kobj);
904         mutex_lock(&e->sysfs_lock);
905         error = e->ops ? entry->store(e, page, length) : -ENOENT;
906         mutex_unlock(&e->sysfs_lock);
907         return error;
908 }
909
910 static const struct sysfs_ops elv_sysfs_ops = {
911         .show   = elv_attr_show,
912         .store  = elv_attr_store,
913 };
914
915 static struct kobj_type elv_ktype = {
916         .sysfs_ops      = &elv_sysfs_ops,
917         .release        = elevator_release,
918 };
919
920 int elv_register_queue(struct request_queue *q)
921 {
922         struct elevator_queue *e = q->elevator;
923         int error;
924
925         error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
926         if (!error) {
927                 struct elv_fs_entry *attr = e->elevator_type->elevator_attrs;
928                 if (attr) {
929                         while (attr->attr.name) {
930                                 if (sysfs_create_file(&e->kobj, &attr->attr))
931                                         break;
932                                 attr++;
933                         }
934                 }
935                 kobject_uevent(&e->kobj, KOBJ_ADD);
936         }
937         return error;
938 }
939 EXPORT_SYMBOL(elv_register_queue);
940
941 static void __elv_unregister_queue(struct elevator_queue *e)
942 {
943         kobject_uevent(&e->kobj, KOBJ_REMOVE);
944         kobject_del(&e->kobj);
945 }
946
947 void elv_unregister_queue(struct request_queue *q)
948 {
949         if (q)
950                 __elv_unregister_queue(q->elevator);
951 }
952 EXPORT_SYMBOL(elv_unregister_queue);
953
954 void elv_register(struct elevator_type *e)
955 {
956         char *def = "";
957
958         spin_lock(&elv_list_lock);
959         BUG_ON(elevator_find(e->elevator_name));
960         list_add_tail(&e->list, &elv_list);
961         spin_unlock(&elv_list_lock);
962
963         if (!strcmp(e->elevator_name, chosen_elevator) ||
964                         (!*chosen_elevator &&
965                          !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
966                                 def = " (default)";
967
968         printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
969                                                                 def);
970 }
971 EXPORT_SYMBOL_GPL(elv_register);
972
973 void elv_unregister(struct elevator_type *e)
974 {
975         struct task_struct *g, *p;
976
977         /*
978          * Iterate every thread in the process to remove the io contexts.
979          */
980         if (e->ops.trim) {
981                 read_lock(&tasklist_lock);
982                 do_each_thread(g, p) {
983                         task_lock(p);
984                         if (p->io_context)
985                                 e->ops.trim(p->io_context);
986                         task_unlock(p);
987                 } while_each_thread(g, p);
988                 read_unlock(&tasklist_lock);
989         }
990
991         spin_lock(&elv_list_lock);
992         list_del_init(&e->list);
993         spin_unlock(&elv_list_lock);
994 }
995 EXPORT_SYMBOL_GPL(elv_unregister);
996
997 /*
998  * switch to new_e io scheduler. be careful not to introduce deadlocks -
999  * we don't free the old io scheduler, before we have allocated what we
1000  * need for the new one. this way we have a chance of going back to the old
1001  * one, if the new one fails init for some reason.
1002  */
1003 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
1004 {
1005         struct elevator_queue *old_elevator, *e;
1006         void *data;
1007
1008         /*
1009          * Allocate new elevator
1010          */
1011         e = elevator_alloc(q, new_e);
1012         if (!e)
1013                 return 0;
1014
1015         data = elevator_init_queue(q, e);
1016         if (!data) {
1017                 kobject_put(&e->kobj);
1018                 return 0;
1019         }
1020
1021         /*
1022          * Turn on BYPASS and drain all requests w/ elevator private data
1023          */
1024         spin_lock_irq(q->queue_lock);
1025         elv_quiesce_start(q);
1026
1027         /*
1028          * Remember old elevator.
1029          */
1030         old_elevator = q->elevator;
1031
1032         /*
1033          * attach and start new elevator
1034          */
1035         elevator_attach(q, e, data);
1036
1037         spin_unlock_irq(q->queue_lock);
1038
1039         __elv_unregister_queue(old_elevator);
1040
1041         if (elv_register_queue(q))
1042                 goto fail_register;
1043
1044         /*
1045          * finally exit old elevator and turn off BYPASS.
1046          */
1047         elevator_exit(old_elevator);
1048         spin_lock_irq(q->queue_lock);
1049         elv_quiesce_end(q);
1050         spin_unlock_irq(q->queue_lock);
1051
1052         blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name);
1053
1054         return 1;
1055
1056 fail_register:
1057         /*
1058          * switch failed, exit the new io scheduler and reattach the old
1059          * one again (along with re-adding the sysfs dir)
1060          */
1061         elevator_exit(e);
1062         q->elevator = old_elevator;
1063         elv_register_queue(q);
1064
1065         spin_lock_irq(q->queue_lock);
1066         queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
1067         spin_unlock_irq(q->queue_lock);
1068
1069         return 0;
1070 }
1071
1072 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
1073                           size_t count)
1074 {
1075         char elevator_name[ELV_NAME_MAX];
1076         struct elevator_type *e;
1077
1078         if (!q->elevator)
1079                 return count;
1080
1081         strlcpy(elevator_name, name, sizeof(elevator_name));
1082         e = elevator_get(strstrip(elevator_name));
1083         if (!e) {
1084                 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
1085                 return -EINVAL;
1086         }
1087
1088         if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
1089                 elevator_put(e);
1090                 return count;
1091         }
1092
1093         if (!elevator_switch(q, e))
1094                 printk(KERN_ERR "elevator: switch to %s failed\n",
1095                                                         elevator_name);
1096         return count;
1097 }
1098
1099 ssize_t elv_iosched_show(struct request_queue *q, char *name)
1100 {
1101         struct elevator_queue *e = q->elevator;
1102         struct elevator_type *elv;
1103         struct elevator_type *__e;
1104         int len = 0;
1105
1106         if (!q->elevator || !blk_queue_stackable(q))
1107                 return sprintf(name, "none\n");
1108
1109         elv = e->elevator_type;
1110
1111         spin_lock(&elv_list_lock);
1112         list_for_each_entry(__e, &elv_list, list) {
1113                 if (!strcmp(elv->elevator_name, __e->elevator_name))
1114                         len += sprintf(name+len, "[%s] ", elv->elevator_name);
1115                 else
1116                         len += sprintf(name+len, "%s ", __e->elevator_name);
1117         }
1118         spin_unlock(&elv_list_lock);
1119
1120         len += sprintf(len+name, "\n");
1121         return len;
1122 }
1123
1124 struct request *elv_rb_former_request(struct request_queue *q,
1125                                       struct request *rq)
1126 {
1127         struct rb_node *rbprev = rb_prev(&rq->rb_node);
1128
1129         if (rbprev)
1130                 return rb_entry_rq(rbprev);
1131
1132         return NULL;
1133 }
1134 EXPORT_SYMBOL(elv_rb_former_request);
1135
1136 struct request *elv_rb_latter_request(struct request_queue *q,
1137                                       struct request *rq)
1138 {
1139         struct rb_node *rbnext = rb_next(&rq->rb_node);
1140
1141         if (rbnext)
1142                 return rb_entry_rq(rbnext);
1143
1144         return NULL;
1145 }
1146 EXPORT_SYMBOL(elv_rb_latter_request);