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