[PATCH] elevator: elv_list_lock does not need irq disabling
[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(&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(&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 (rq_data_dir(rq) != rq_data_dir(pos))
417                         break;
418                 if (pos->cmd_flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED))
419                         break;
420                 if (rq->sector >= boundary) {
421                         if (pos->sector < boundary)
422                                 continue;
423                 } else {
424                         if (pos->sector >= boundary)
425                                 break;
426                 }
427                 if (rq->sector >= pos->sector)
428                         break;
429         }
430
431         list_add(&rq->queuelist, entry);
432 }
433
434 EXPORT_SYMBOL(elv_dispatch_sort);
435
436 /*
437  * Insert rq into dispatch queue of q.  Queue lock must be held on
438  * entry.  rq is added to the back of the dispatch queue. To be used by
439  * specific elevators.
440  */
441 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
442 {
443         if (q->last_merge == rq)
444                 q->last_merge = NULL;
445
446         elv_rqhash_del(q, rq);
447
448         q->nr_sorted--;
449
450         q->end_sector = rq_end_sector(rq);
451         q->boundary_rq = rq;
452         list_add_tail(&rq->queuelist, &q->queue_head);
453 }
454
455 EXPORT_SYMBOL(elv_dispatch_add_tail);
456
457 int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
458 {
459         elevator_t *e = q->elevator;
460         struct request *__rq;
461         int ret;
462
463         /*
464          * First try one-hit cache.
465          */
466         if (q->last_merge) {
467                 ret = elv_try_merge(q->last_merge, bio);
468                 if (ret != ELEVATOR_NO_MERGE) {
469                         *req = q->last_merge;
470                         return ret;
471                 }
472         }
473
474         /*
475          * See if our hash lookup can find a potential backmerge.
476          */
477         __rq = elv_rqhash_find(q, bio->bi_sector);
478         if (__rq && elv_rq_merge_ok(__rq, bio)) {
479                 *req = __rq;
480                 return ELEVATOR_BACK_MERGE;
481         }
482
483         if (e->ops->elevator_merge_fn)
484                 return e->ops->elevator_merge_fn(q, req, bio);
485
486         return ELEVATOR_NO_MERGE;
487 }
488
489 void elv_merged_request(request_queue_t *q, struct request *rq, int type)
490 {
491         elevator_t *e = q->elevator;
492
493         if (e->ops->elevator_merged_fn)
494                 e->ops->elevator_merged_fn(q, rq, type);
495
496         if (type == ELEVATOR_BACK_MERGE)
497                 elv_rqhash_reposition(q, rq);
498
499         q->last_merge = rq;
500 }
501
502 void elv_merge_requests(request_queue_t *q, struct request *rq,
503                              struct request *next)
504 {
505         elevator_t *e = q->elevator;
506
507         if (e->ops->elevator_merge_req_fn)
508                 e->ops->elevator_merge_req_fn(q, rq, next);
509
510         elv_rqhash_reposition(q, rq);
511         elv_rqhash_del(q, next);
512
513         q->nr_sorted--;
514         q->last_merge = rq;
515 }
516
517 void elv_requeue_request(request_queue_t *q, struct request *rq)
518 {
519         /*
520          * it already went through dequeue, we need to decrement the
521          * in_flight count again
522          */
523         if (blk_account_rq(rq)) {
524                 q->in_flight--;
525                 if (blk_sorted_rq(rq))
526                         elv_deactivate_rq(q, rq);
527         }
528
529         rq->cmd_flags &= ~REQ_STARTED;
530
531         elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
532 }
533
534 static void elv_drain_elevator(request_queue_t *q)
535 {
536         static int printed;
537         while (q->elevator->ops->elevator_dispatch_fn(q, 1))
538                 ;
539         if (q->nr_sorted == 0)
540                 return;
541         if (printed++ < 10) {
542                 printk(KERN_ERR "%s: forced dispatching is broken "
543                        "(nr_sorted=%u), please report this\n",
544                        q->elevator->elevator_type->elevator_name, q->nr_sorted);
545         }
546 }
547
548 void elv_insert(request_queue_t *q, struct request *rq, int where)
549 {
550         struct list_head *pos;
551         unsigned ordseq;
552         int unplug_it = 1;
553
554         blk_add_trace_rq(q, rq, BLK_TA_INSERT);
555
556         rq->q = q;
557
558         switch (where) {
559         case ELEVATOR_INSERT_FRONT:
560                 rq->cmd_flags |= REQ_SOFTBARRIER;
561
562                 list_add(&rq->queuelist, &q->queue_head);
563                 break;
564
565         case ELEVATOR_INSERT_BACK:
566                 rq->cmd_flags |= REQ_SOFTBARRIER;
567                 elv_drain_elevator(q);
568                 list_add_tail(&rq->queuelist, &q->queue_head);
569                 /*
570                  * We kick the queue here for the following reasons.
571                  * - The elevator might have returned NULL previously
572                  *   to delay requests and returned them now.  As the
573                  *   queue wasn't empty before this request, ll_rw_blk
574                  *   won't run the queue on return, resulting in hang.
575                  * - Usually, back inserted requests won't be merged
576                  *   with anything.  There's no point in delaying queue
577                  *   processing.
578                  */
579                 blk_remove_plug(q);
580                 q->request_fn(q);
581                 break;
582
583         case ELEVATOR_INSERT_SORT:
584                 BUG_ON(!blk_fs_request(rq));
585                 rq->cmd_flags |= REQ_SORTED;
586                 q->nr_sorted++;
587                 if (rq_mergeable(rq)) {
588                         elv_rqhash_add(q, rq);
589                         if (!q->last_merge)
590                                 q->last_merge = rq;
591                 }
592
593                 /*
594                  * Some ioscheds (cfq) run q->request_fn directly, so
595                  * rq cannot be accessed after calling
596                  * elevator_add_req_fn.
597                  */
598                 q->elevator->ops->elevator_add_req_fn(q, rq);
599                 break;
600
601         case ELEVATOR_INSERT_REQUEUE:
602                 /*
603                  * If ordered flush isn't in progress, we do front
604                  * insertion; otherwise, requests should be requeued
605                  * in ordseq order.
606                  */
607                 rq->cmd_flags |= REQ_SOFTBARRIER;
608
609                 /*
610                  * Most requeues happen because of a busy condition,
611                  * don't force unplug of the queue for that case.
612                  */
613                 unplug_it = 0;
614
615                 if (q->ordseq == 0) {
616                         list_add(&rq->queuelist, &q->queue_head);
617                         break;
618                 }
619
620                 ordseq = blk_ordered_req_seq(rq);
621
622                 list_for_each(pos, &q->queue_head) {
623                         struct request *pos_rq = list_entry_rq(pos);
624                         if (ordseq <= blk_ordered_req_seq(pos_rq))
625                                 break;
626                 }
627
628                 list_add_tail(&rq->queuelist, pos);
629                 break;
630
631         default:
632                 printk(KERN_ERR "%s: bad insertion point %d\n",
633                        __FUNCTION__, where);
634                 BUG();
635         }
636
637         if (unplug_it && blk_queue_plugged(q)) {
638                 int nrq = q->rq.count[READ] + q->rq.count[WRITE]
639                         - q->in_flight;
640
641                 if (nrq >= q->unplug_thresh)
642                         __generic_unplug_device(q);
643         }
644 }
645
646 void __elv_add_request(request_queue_t *q, struct request *rq, int where,
647                        int plug)
648 {
649         if (q->ordcolor)
650                 rq->cmd_flags |= REQ_ORDERED_COLOR;
651
652         if (rq->cmd_flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
653                 /*
654                  * toggle ordered color
655                  */
656                 if (blk_barrier_rq(rq))
657                         q->ordcolor ^= 1;
658
659                 /*
660                  * barriers implicitly indicate back insertion
661                  */
662                 if (where == ELEVATOR_INSERT_SORT)
663                         where = ELEVATOR_INSERT_BACK;
664
665                 /*
666                  * this request is scheduling boundary, update
667                  * end_sector
668                  */
669                 if (blk_fs_request(rq)) {
670                         q->end_sector = rq_end_sector(rq);
671                         q->boundary_rq = rq;
672                 }
673         } else if (!(rq->cmd_flags & REQ_ELVPRIV) && where == ELEVATOR_INSERT_SORT)
674                 where = ELEVATOR_INSERT_BACK;
675
676         if (plug)
677                 blk_plug_device(q);
678
679         elv_insert(q, rq, where);
680 }
681
682 EXPORT_SYMBOL(__elv_add_request);
683
684 void elv_add_request(request_queue_t *q, struct request *rq, int where,
685                      int plug)
686 {
687         unsigned long flags;
688
689         spin_lock_irqsave(q->queue_lock, flags);
690         __elv_add_request(q, rq, where, plug);
691         spin_unlock_irqrestore(q->queue_lock, flags);
692 }
693
694 EXPORT_SYMBOL(elv_add_request);
695
696 static inline struct request *__elv_next_request(request_queue_t *q)
697 {
698         struct request *rq;
699
700         while (1) {
701                 while (!list_empty(&q->queue_head)) {
702                         rq = list_entry_rq(q->queue_head.next);
703                         if (blk_do_ordered(q, &rq))
704                                 return rq;
705                 }
706
707                 if (!q->elevator->ops->elevator_dispatch_fn(q, 0))
708                         return NULL;
709         }
710 }
711
712 struct request *elv_next_request(request_queue_t *q)
713 {
714         struct request *rq;
715         int ret;
716
717         while ((rq = __elv_next_request(q)) != NULL) {
718                 if (!(rq->cmd_flags & REQ_STARTED)) {
719                         /*
720                          * This is the first time the device driver
721                          * sees this request (possibly after
722                          * requeueing).  Notify IO scheduler.
723                          */
724                         if (blk_sorted_rq(rq))
725                                 elv_activate_rq(q, rq);
726
727                         /*
728                          * just mark as started even if we don't start
729                          * it, a request that has been delayed should
730                          * not be passed by new incoming requests
731                          */
732                         rq->cmd_flags |= REQ_STARTED;
733                         blk_add_trace_rq(q, rq, BLK_TA_ISSUE);
734                 }
735
736                 if (!q->boundary_rq || q->boundary_rq == rq) {
737                         q->end_sector = rq_end_sector(rq);
738                         q->boundary_rq = NULL;
739                 }
740
741                 if ((rq->cmd_flags & REQ_DONTPREP) || !q->prep_rq_fn)
742                         break;
743
744                 ret = q->prep_rq_fn(q, rq);
745                 if (ret == BLKPREP_OK) {
746                         break;
747                 } else if (ret == BLKPREP_DEFER) {
748                         /*
749                          * the request may have been (partially) prepped.
750                          * we need to keep this request in the front to
751                          * avoid resource deadlock.  REQ_STARTED will
752                          * prevent other fs requests from passing this one.
753                          */
754                         rq = NULL;
755                         break;
756                 } else if (ret == BLKPREP_KILL) {
757                         int nr_bytes = rq->hard_nr_sectors << 9;
758
759                         if (!nr_bytes)
760                                 nr_bytes = rq->data_len;
761
762                         blkdev_dequeue_request(rq);
763                         rq->cmd_flags |= REQ_QUIET;
764                         end_that_request_chunk(rq, 0, nr_bytes);
765                         end_that_request_last(rq, 0);
766                 } else {
767                         printk(KERN_ERR "%s: bad return=%d\n", __FUNCTION__,
768                                                                 ret);
769                         break;
770                 }
771         }
772
773         return rq;
774 }
775
776 EXPORT_SYMBOL(elv_next_request);
777
778 void elv_dequeue_request(request_queue_t *q, struct request *rq)
779 {
780         BUG_ON(list_empty(&rq->queuelist));
781         BUG_ON(ELV_ON_HASH(rq));
782
783         list_del_init(&rq->queuelist);
784
785         /*
786          * the time frame between a request being removed from the lists
787          * and to it is freed is accounted as io that is in progress at
788          * the driver side.
789          */
790         if (blk_account_rq(rq))
791                 q->in_flight++;
792 }
793
794 EXPORT_SYMBOL(elv_dequeue_request);
795
796 int elv_queue_empty(request_queue_t *q)
797 {
798         elevator_t *e = q->elevator;
799
800         if (!list_empty(&q->queue_head))
801                 return 0;
802
803         if (e->ops->elevator_queue_empty_fn)
804                 return e->ops->elevator_queue_empty_fn(q);
805
806         return 1;
807 }
808
809 EXPORT_SYMBOL(elv_queue_empty);
810
811 struct request *elv_latter_request(request_queue_t *q, struct request *rq)
812 {
813         elevator_t *e = q->elevator;
814
815         if (e->ops->elevator_latter_req_fn)
816                 return e->ops->elevator_latter_req_fn(q, rq);
817         return NULL;
818 }
819
820 struct request *elv_former_request(request_queue_t *q, struct request *rq)
821 {
822         elevator_t *e = q->elevator;
823
824         if (e->ops->elevator_former_req_fn)
825                 return e->ops->elevator_former_req_fn(q, rq);
826         return NULL;
827 }
828
829 int elv_set_request(request_queue_t *q, struct request *rq, gfp_t gfp_mask)
830 {
831         elevator_t *e = q->elevator;
832
833         if (e->ops->elevator_set_req_fn)
834                 return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
835
836         rq->elevator_private = NULL;
837         return 0;
838 }
839
840 void elv_put_request(request_queue_t *q, struct request *rq)
841 {
842         elevator_t *e = q->elevator;
843
844         if (e->ops->elevator_put_req_fn)
845                 e->ops->elevator_put_req_fn(rq);
846 }
847
848 int elv_may_queue(request_queue_t *q, int rw)
849 {
850         elevator_t *e = q->elevator;
851
852         if (e->ops->elevator_may_queue_fn)
853                 return e->ops->elevator_may_queue_fn(q, rw);
854
855         return ELV_MQUEUE_MAY;
856 }
857
858 void elv_completed_request(request_queue_t *q, struct request *rq)
859 {
860         elevator_t *e = q->elevator;
861
862         /*
863          * request is released from the driver, io must be done
864          */
865         if (blk_account_rq(rq)) {
866                 q->in_flight--;
867                 if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
868                         e->ops->elevator_completed_req_fn(q, rq);
869         }
870
871         /*
872          * Check if the queue is waiting for fs requests to be
873          * drained for flush sequence.
874          */
875         if (unlikely(q->ordseq)) {
876                 struct request *first_rq = list_entry_rq(q->queue_head.next);
877                 if (q->in_flight == 0 &&
878                     blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
879                     blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
880                         blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
881                         q->request_fn(q);
882                 }
883         }
884 }
885
886 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
887
888 static ssize_t
889 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
890 {
891         elevator_t *e = container_of(kobj, elevator_t, kobj);
892         struct elv_fs_entry *entry = to_elv(attr);
893         ssize_t error;
894
895         if (!entry->show)
896                 return -EIO;
897
898         mutex_lock(&e->sysfs_lock);
899         error = e->ops ? entry->show(e, page) : -ENOENT;
900         mutex_unlock(&e->sysfs_lock);
901         return error;
902 }
903
904 static ssize_t
905 elv_attr_store(struct kobject *kobj, struct attribute *attr,
906                const char *page, size_t length)
907 {
908         elevator_t *e = container_of(kobj, elevator_t, kobj);
909         struct elv_fs_entry *entry = to_elv(attr);
910         ssize_t error;
911
912         if (!entry->store)
913                 return -EIO;
914
915         mutex_lock(&e->sysfs_lock);
916         error = e->ops ? entry->store(e, page, length) : -ENOENT;
917         mutex_unlock(&e->sysfs_lock);
918         return error;
919 }
920
921 static struct sysfs_ops elv_sysfs_ops = {
922         .show   = elv_attr_show,
923         .store  = elv_attr_store,
924 };
925
926 static struct kobj_type elv_ktype = {
927         .sysfs_ops      = &elv_sysfs_ops,
928         .release        = elevator_release,
929 };
930
931 int elv_register_queue(struct request_queue *q)
932 {
933         elevator_t *e = q->elevator;
934         int error;
935
936         e->kobj.parent = &q->kobj;
937
938         error = kobject_add(&e->kobj);
939         if (!error) {
940                 struct elv_fs_entry *attr = e->elevator_type->elevator_attrs;
941                 if (attr) {
942                         while (attr->attr.name) {
943                                 if (sysfs_create_file(&e->kobj, &attr->attr))
944                                         break;
945                                 attr++;
946                         }
947                 }
948                 kobject_uevent(&e->kobj, KOBJ_ADD);
949         }
950         return error;
951 }
952
953 static void __elv_unregister_queue(elevator_t *e)
954 {
955         kobject_uevent(&e->kobj, KOBJ_REMOVE);
956         kobject_del(&e->kobj);
957 }
958
959 void elv_unregister_queue(struct request_queue *q)
960 {
961         if (q)
962                 __elv_unregister_queue(q->elevator);
963 }
964
965 int elv_register(struct elevator_type *e)
966 {
967         char *def = "";
968
969         spin_lock(&elv_list_lock);
970         BUG_ON(elevator_find(e->elevator_name));
971         list_add_tail(&e->list, &elv_list);
972         spin_unlock(&elv_list_lock);
973
974         if (!strcmp(e->elevator_name, chosen_elevator) ||
975                         (!*chosen_elevator &&
976                          !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
977                                 def = " (default)";
978
979         printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name, def);
980         return 0;
981 }
982 EXPORT_SYMBOL_GPL(elv_register);
983
984 void elv_unregister(struct elevator_type *e)
985 {
986         struct task_struct *g, *p;
987
988         /*
989          * Iterate every thread in the process to remove the io contexts.
990          */
991         if (e->ops.trim) {
992                 read_lock(&tasklist_lock);
993                 do_each_thread(g, p) {
994                         task_lock(p);
995                         if (p->io_context)
996                                 e->ops.trim(p->io_context);
997                         task_unlock(p);
998                 } while_each_thread(g, p);
999                 read_unlock(&tasklist_lock);
1000         }
1001
1002         spin_lock(&elv_list_lock);
1003         list_del_init(&e->list);
1004         spin_unlock(&elv_list_lock);
1005 }
1006 EXPORT_SYMBOL_GPL(elv_unregister);
1007
1008 /*
1009  * switch to new_e io scheduler. be careful not to introduce deadlocks -
1010  * we don't free the old io scheduler, before we have allocated what we
1011  * need for the new one. this way we have a chance of going back to the old
1012  * one, if the new one fails init for some reason.
1013  */
1014 static int elevator_switch(request_queue_t *q, struct elevator_type *new_e)
1015 {
1016         elevator_t *old_elevator, *e;
1017         void *data;
1018
1019         /*
1020          * Allocate new elevator
1021          */
1022         e = elevator_alloc(q, new_e);
1023         if (!e)
1024                 return 0;
1025
1026         data = elevator_init_queue(q, e);
1027         if (!data) {
1028                 kobject_put(&e->kobj);
1029                 return 0;
1030         }
1031
1032         /*
1033          * Turn on BYPASS and drain all requests w/ elevator private data
1034          */
1035         spin_lock_irq(q->queue_lock);
1036
1037         set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1038
1039         elv_drain_elevator(q);
1040
1041         while (q->rq.elvpriv) {
1042                 blk_remove_plug(q);
1043                 q->request_fn(q);
1044                 spin_unlock_irq(q->queue_lock);
1045                 msleep(10);
1046                 spin_lock_irq(q->queue_lock);
1047                 elv_drain_elevator(q);
1048         }
1049
1050         /*
1051          * Remember old elevator.
1052          */
1053         old_elevator = q->elevator;
1054
1055         /*
1056          * attach and start new elevator
1057          */
1058         elevator_attach(q, e, data);
1059
1060         spin_unlock_irq(q->queue_lock);
1061
1062         __elv_unregister_queue(old_elevator);
1063
1064         if (elv_register_queue(q))
1065                 goto fail_register;
1066
1067         /*
1068          * finally exit old elevator and turn off BYPASS.
1069          */
1070         elevator_exit(old_elevator);
1071         clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1072         return 1;
1073
1074 fail_register:
1075         /*
1076          * switch failed, exit the new io scheduler and reattach the old
1077          * one again (along with re-adding the sysfs dir)
1078          */
1079         elevator_exit(e);
1080         q->elevator = old_elevator;
1081         elv_register_queue(q);
1082         clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1083         return 0;
1084 }
1085
1086 ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
1087 {
1088         char elevator_name[ELV_NAME_MAX];
1089         size_t len;
1090         struct elevator_type *e;
1091
1092         elevator_name[sizeof(elevator_name) - 1] = '\0';
1093         strncpy(elevator_name, name, sizeof(elevator_name) - 1);
1094         len = strlen(elevator_name);
1095
1096         if (len && elevator_name[len - 1] == '\n')
1097                 elevator_name[len - 1] = '\0';
1098
1099         e = elevator_get(elevator_name);
1100         if (!e) {
1101                 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
1102                 return -EINVAL;
1103         }
1104
1105         if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
1106                 elevator_put(e);
1107                 return count;
1108         }
1109
1110         if (!elevator_switch(q, e))
1111                 printk(KERN_ERR "elevator: switch to %s failed\n",elevator_name);
1112         return count;
1113 }
1114
1115 ssize_t elv_iosched_show(request_queue_t *q, char *name)
1116 {
1117         elevator_t *e = q->elevator;
1118         struct elevator_type *elv = e->elevator_type;
1119         struct list_head *entry;
1120         int len = 0;
1121
1122         spin_lock(&elv_list_lock);
1123         list_for_each(entry, &elv_list) {
1124                 struct elevator_type *__e;
1125
1126                 __e = list_entry(entry, struct elevator_type, list);
1127                 if (!strcmp(elv->elevator_name, __e->elevator_name))
1128                         len += sprintf(name+len, "[%s] ", elv->elevator_name);
1129                 else
1130                         len += sprintf(name+len, "%s ", __e->elevator_name);
1131         }
1132         spin_unlock(&elv_list_lock);
1133
1134         len += sprintf(len+name, "\n");
1135         return len;
1136 }
1137
1138 struct request *elv_rb_former_request(request_queue_t *q, struct request *rq)
1139 {
1140         struct rb_node *rbprev = rb_prev(&rq->rb_node);
1141
1142         if (rbprev)
1143                 return rb_entry_rq(rbprev);
1144
1145         return NULL;
1146 }
1147
1148 EXPORT_SYMBOL(elv_rb_former_request);
1149
1150 struct request *elv_rb_latter_request(request_queue_t *q, struct request *rq)
1151 {
1152         struct rb_node *rbnext = rb_next(&rq->rb_node);
1153
1154         if (rbnext)
1155                 return rb_entry_rq(rbnext);
1156
1157         return NULL;
1158 }
1159
1160 EXPORT_SYMBOL(elv_rb_latter_request);