[PATCH] elevator: move clearing of unplug flag earlier
[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 inline void __elv_rqhash_del(struct request *rq)
273 {
274         hlist_del_init(&rq->hash);
275 }
276
277 static void elv_rqhash_del(request_queue_t *q, struct request *rq)
278 {
279         if (ELV_ON_HASH(rq))
280                 __elv_rqhash_del(rq);
281 }
282
283 static void elv_rqhash_add(request_queue_t *q, struct request *rq)
284 {
285         elevator_t *e = q->elevator;
286
287         BUG_ON(ELV_ON_HASH(rq));
288         hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
289 }
290
291 static void elv_rqhash_reposition(request_queue_t *q, struct request *rq)
292 {
293         __elv_rqhash_del(rq);
294         elv_rqhash_add(q, rq);
295 }
296
297 static struct request *elv_rqhash_find(request_queue_t *q, sector_t offset)
298 {
299         elevator_t *e = q->elevator;
300         struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
301         struct hlist_node *entry, *next;
302         struct request *rq;
303
304         hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
305                 BUG_ON(!ELV_ON_HASH(rq));
306
307                 if (unlikely(!rq_mergeable(rq))) {
308                         __elv_rqhash_del(rq);
309                         continue;
310                 }
311
312                 if (rq_hash_key(rq) == offset)
313                         return rq;
314         }
315
316         return NULL;
317 }
318
319 /*
320  * RB-tree support functions for inserting/lookup/removal of requests
321  * in a sorted RB tree.
322  */
323 struct request *elv_rb_add(struct rb_root *root, struct request *rq)
324 {
325         struct rb_node **p = &root->rb_node;
326         struct rb_node *parent = NULL;
327         struct request *__rq;
328
329         while (*p) {
330                 parent = *p;
331                 __rq = rb_entry(parent, struct request, rb_node);
332
333                 if (rq->sector < __rq->sector)
334                         p = &(*p)->rb_left;
335                 else if (rq->sector > __rq->sector)
336                         p = &(*p)->rb_right;
337                 else
338                         return __rq;
339         }
340
341         rb_link_node(&rq->rb_node, parent, p);
342         rb_insert_color(&rq->rb_node, root);
343         return NULL;
344 }
345
346 EXPORT_SYMBOL(elv_rb_add);
347
348 void elv_rb_del(struct rb_root *root, struct request *rq)
349 {
350         BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
351         rb_erase(&rq->rb_node, root);
352         RB_CLEAR_NODE(&rq->rb_node);
353 }
354
355 EXPORT_SYMBOL(elv_rb_del);
356
357 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
358 {
359         struct rb_node *n = root->rb_node;
360         struct request *rq;
361
362         while (n) {
363                 rq = rb_entry(n, struct request, rb_node);
364
365                 if (sector < rq->sector)
366                         n = n->rb_left;
367                 else if (sector > rq->sector)
368                         n = n->rb_right;
369                 else
370                         return rq;
371         }
372
373         return NULL;
374 }
375
376 EXPORT_SYMBOL(elv_rb_find);
377
378 /*
379  * Insert rq into dispatch queue of q.  Queue lock must be held on
380  * entry.  rq is sort insted into the dispatch queue. To be used by
381  * specific elevators.
382  */
383 void elv_dispatch_sort(request_queue_t *q, struct request *rq)
384 {
385         sector_t boundary;
386         struct list_head *entry;
387
388         if (q->last_merge == rq)
389                 q->last_merge = NULL;
390
391         elv_rqhash_del(q, rq);
392
393         q->nr_sorted--;
394
395         boundary = q->end_sector;
396
397         list_for_each_prev(entry, &q->queue_head) {
398                 struct request *pos = list_entry_rq(entry);
399
400                 if (pos->cmd_flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED))
401                         break;
402                 if (rq->sector >= boundary) {
403                         if (pos->sector < boundary)
404                                 continue;
405                 } else {
406                         if (pos->sector >= boundary)
407                                 break;
408                 }
409                 if (rq->sector >= pos->sector)
410                         break;
411         }
412
413         list_add(&rq->queuelist, entry);
414 }
415
416 EXPORT_SYMBOL(elv_dispatch_sort);
417
418 /*
419  * Insert rq into dispatch queue of q.  Queue lock must be held on
420  * entry.  rq is added to the back of the dispatch queue. To be used by
421  * specific elevators.
422  */
423 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
424 {
425         if (q->last_merge == rq)
426                 q->last_merge = NULL;
427
428         elv_rqhash_del(q, rq);
429
430         q->nr_sorted--;
431
432         q->end_sector = rq_end_sector(rq);
433         q->boundary_rq = rq;
434         list_add_tail(&rq->queuelist, &q->queue_head);
435 }
436
437 EXPORT_SYMBOL(elv_dispatch_add_tail);
438
439 int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
440 {
441         elevator_t *e = q->elevator;
442         struct request *__rq;
443         int ret;
444
445         /*
446          * First try one-hit cache.
447          */
448         if (q->last_merge) {
449                 ret = elv_try_merge(q->last_merge, bio);
450                 if (ret != ELEVATOR_NO_MERGE) {
451                         *req = q->last_merge;
452                         return ret;
453                 }
454         }
455
456         /*
457          * See if our hash lookup can find a potential backmerge.
458          */
459         __rq = elv_rqhash_find(q, bio->bi_sector);
460         if (__rq && elv_rq_merge_ok(__rq, bio)) {
461                 *req = __rq;
462                 return ELEVATOR_BACK_MERGE;
463         }
464
465         if (e->ops->elevator_merge_fn)
466                 return e->ops->elevator_merge_fn(q, req, bio);
467
468         return ELEVATOR_NO_MERGE;
469 }
470
471 void elv_merged_request(request_queue_t *q, struct request *rq, int type)
472 {
473         elevator_t *e = q->elevator;
474
475         if (e->ops->elevator_merged_fn)
476                 e->ops->elevator_merged_fn(q, rq, type);
477
478         if (type == ELEVATOR_BACK_MERGE)
479                 elv_rqhash_reposition(q, rq);
480
481         q->last_merge = rq;
482 }
483
484 void elv_merge_requests(request_queue_t *q, struct request *rq,
485                              struct request *next)
486 {
487         elevator_t *e = q->elevator;
488
489         if (e->ops->elevator_merge_req_fn)
490                 e->ops->elevator_merge_req_fn(q, rq, next);
491
492         elv_rqhash_reposition(q, rq);
493         elv_rqhash_del(q, next);
494
495         q->nr_sorted--;
496         q->last_merge = rq;
497 }
498
499 void elv_requeue_request(request_queue_t *q, struct request *rq)
500 {
501         elevator_t *e = q->elevator;
502
503         /*
504          * it already went through dequeue, we need to decrement the
505          * in_flight count again
506          */
507         if (blk_account_rq(rq)) {
508                 q->in_flight--;
509                 if (blk_sorted_rq(rq) && e->ops->elevator_deactivate_req_fn)
510                         e->ops->elevator_deactivate_req_fn(q, rq);
511         }
512
513         rq->cmd_flags &= ~REQ_STARTED;
514
515         elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
516 }
517
518 static void elv_drain_elevator(request_queue_t *q)
519 {
520         static int printed;
521         while (q->elevator->ops->elevator_dispatch_fn(q, 1))
522                 ;
523         if (q->nr_sorted == 0)
524                 return;
525         if (printed++ < 10) {
526                 printk(KERN_ERR "%s: forced dispatching is broken "
527                        "(nr_sorted=%u), please report this\n",
528                        q->elevator->elevator_type->elevator_name, q->nr_sorted);
529         }
530 }
531
532 void elv_insert(request_queue_t *q, struct request *rq, int where)
533 {
534         struct list_head *pos;
535         unsigned ordseq;
536         int unplug_it = 1;
537
538         blk_add_trace_rq(q, rq, BLK_TA_INSERT);
539
540         rq->q = q;
541
542         switch (where) {
543         case ELEVATOR_INSERT_FRONT:
544                 rq->cmd_flags |= REQ_SOFTBARRIER;
545
546                 list_add(&rq->queuelist, &q->queue_head);
547                 break;
548
549         case ELEVATOR_INSERT_BACK:
550                 rq->cmd_flags |= REQ_SOFTBARRIER;
551                 elv_drain_elevator(q);
552                 list_add_tail(&rq->queuelist, &q->queue_head);
553                 /*
554                  * We kick the queue here for the following reasons.
555                  * - The elevator might have returned NULL previously
556                  *   to delay requests and returned them now.  As the
557                  *   queue wasn't empty before this request, ll_rw_blk
558                  *   won't run the queue on return, resulting in hang.
559                  * - Usually, back inserted requests won't be merged
560                  *   with anything.  There's no point in delaying queue
561                  *   processing.
562                  */
563                 blk_remove_plug(q);
564                 q->request_fn(q);
565                 break;
566
567         case ELEVATOR_INSERT_SORT:
568                 BUG_ON(!blk_fs_request(rq));
569                 rq->cmd_flags |= REQ_SORTED;
570                 q->nr_sorted++;
571                 if (rq_mergeable(rq)) {
572                         elv_rqhash_add(q, rq);
573                         if (!q->last_merge)
574                                 q->last_merge = rq;
575                 }
576
577                 /*
578                  * Some ioscheds (cfq) run q->request_fn directly, so
579                  * rq cannot be accessed after calling
580                  * elevator_add_req_fn.
581                  */
582                 q->elevator->ops->elevator_add_req_fn(q, rq);
583                 break;
584
585         case ELEVATOR_INSERT_REQUEUE:
586                 /*
587                  * If ordered flush isn't in progress, we do front
588                  * insertion; otherwise, requests should be requeued
589                  * in ordseq order.
590                  */
591                 rq->cmd_flags |= REQ_SOFTBARRIER;
592
593                 /*
594                  * Most requeues happen because of a busy condition,
595                  * don't force unplug of the queue for that case.
596                  */
597                 unplug_it = 0;
598
599                 if (q->ordseq == 0) {
600                         list_add(&rq->queuelist, &q->queue_head);
601                         break;
602                 }
603
604                 ordseq = blk_ordered_req_seq(rq);
605
606                 list_for_each(pos, &q->queue_head) {
607                         struct request *pos_rq = list_entry_rq(pos);
608                         if (ordseq <= blk_ordered_req_seq(pos_rq))
609                                 break;
610                 }
611
612                 list_add_tail(&rq->queuelist, pos);
613                 break;
614
615         default:
616                 printk(KERN_ERR "%s: bad insertion point %d\n",
617                        __FUNCTION__, where);
618                 BUG();
619         }
620
621         if (unplug_it && blk_queue_plugged(q)) {
622                 int nrq = q->rq.count[READ] + q->rq.count[WRITE]
623                         - q->in_flight;
624
625                 if (nrq >= q->unplug_thresh)
626                         __generic_unplug_device(q);
627         }
628 }
629
630 void __elv_add_request(request_queue_t *q, struct request *rq, int where,
631                        int plug)
632 {
633         if (q->ordcolor)
634                 rq->cmd_flags |= REQ_ORDERED_COLOR;
635
636         if (rq->cmd_flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
637                 /*
638                  * toggle ordered color
639                  */
640                 if (blk_barrier_rq(rq))
641                         q->ordcolor ^= 1;
642
643                 /*
644                  * barriers implicitly indicate back insertion
645                  */
646                 if (where == ELEVATOR_INSERT_SORT)
647                         where = ELEVATOR_INSERT_BACK;
648
649                 /*
650                  * this request is scheduling boundary, update
651                  * end_sector
652                  */
653                 if (blk_fs_request(rq)) {
654                         q->end_sector = rq_end_sector(rq);
655                         q->boundary_rq = rq;
656                 }
657         } else if (!(rq->cmd_flags & REQ_ELVPRIV) && where == ELEVATOR_INSERT_SORT)
658                 where = ELEVATOR_INSERT_BACK;
659
660         if (plug)
661                 blk_plug_device(q);
662
663         elv_insert(q, rq, where);
664 }
665
666 EXPORT_SYMBOL(__elv_add_request);
667
668 void elv_add_request(request_queue_t *q, struct request *rq, int where,
669                      int plug)
670 {
671         unsigned long flags;
672
673         spin_lock_irqsave(q->queue_lock, flags);
674         __elv_add_request(q, rq, where, plug);
675         spin_unlock_irqrestore(q->queue_lock, flags);
676 }
677
678 EXPORT_SYMBOL(elv_add_request);
679
680 static inline struct request *__elv_next_request(request_queue_t *q)
681 {
682         struct request *rq;
683
684         while (1) {
685                 while (!list_empty(&q->queue_head)) {
686                         rq = list_entry_rq(q->queue_head.next);
687                         if (blk_do_ordered(q, &rq))
688                                 return rq;
689                 }
690
691                 if (!q->elevator->ops->elevator_dispatch_fn(q, 0))
692                         return NULL;
693         }
694 }
695
696 struct request *elv_next_request(request_queue_t *q)
697 {
698         struct request *rq;
699         int ret;
700
701         while ((rq = __elv_next_request(q)) != NULL) {
702                 if (!(rq->cmd_flags & REQ_STARTED)) {
703                         elevator_t *e = q->elevator;
704
705                         /*
706                          * This is the first time the device driver
707                          * sees this request (possibly after
708                          * requeueing).  Notify IO scheduler.
709                          */
710                         if (blk_sorted_rq(rq) &&
711                             e->ops->elevator_activate_req_fn)
712                                 e->ops->elevator_activate_req_fn(q, rq);
713
714                         /*
715                          * just mark as started even if we don't start
716                          * it, a request that has been delayed should
717                          * not be passed by new incoming requests
718                          */
719                         rq->cmd_flags |= REQ_STARTED;
720                         blk_add_trace_rq(q, rq, BLK_TA_ISSUE);
721                 }
722
723                 if (!q->boundary_rq || q->boundary_rq == rq) {
724                         q->end_sector = rq_end_sector(rq);
725                         q->boundary_rq = NULL;
726                 }
727
728                 if ((rq->cmd_flags & REQ_DONTPREP) || !q->prep_rq_fn)
729                         break;
730
731                 ret = q->prep_rq_fn(q, rq);
732                 if (ret == BLKPREP_OK) {
733                         break;
734                 } else if (ret == BLKPREP_DEFER) {
735                         /*
736                          * the request may have been (partially) prepped.
737                          * we need to keep this request in the front to
738                          * avoid resource deadlock.  REQ_STARTED will
739                          * prevent other fs requests from passing this one.
740                          */
741                         rq = NULL;
742                         break;
743                 } else if (ret == BLKPREP_KILL) {
744                         int nr_bytes = rq->hard_nr_sectors << 9;
745
746                         if (!nr_bytes)
747                                 nr_bytes = rq->data_len;
748
749                         blkdev_dequeue_request(rq);
750                         rq->cmd_flags |= REQ_QUIET;
751                         end_that_request_chunk(rq, 0, nr_bytes);
752                         end_that_request_last(rq, 0);
753                 } else {
754                         printk(KERN_ERR "%s: bad return=%d\n", __FUNCTION__,
755                                                                 ret);
756                         break;
757                 }
758         }
759
760         return rq;
761 }
762
763 EXPORT_SYMBOL(elv_next_request);
764
765 void elv_dequeue_request(request_queue_t *q, struct request *rq)
766 {
767         BUG_ON(list_empty(&rq->queuelist));
768         BUG_ON(ELV_ON_HASH(rq));
769
770         list_del_init(&rq->queuelist);
771
772         /*
773          * the time frame between a request being removed from the lists
774          * and to it is freed is accounted as io that is in progress at
775          * the driver side.
776          */
777         if (blk_account_rq(rq))
778                 q->in_flight++;
779 }
780
781 EXPORT_SYMBOL(elv_dequeue_request);
782
783 int elv_queue_empty(request_queue_t *q)
784 {
785         elevator_t *e = q->elevator;
786
787         if (!list_empty(&q->queue_head))
788                 return 0;
789
790         if (e->ops->elevator_queue_empty_fn)
791                 return e->ops->elevator_queue_empty_fn(q);
792
793         return 1;
794 }
795
796 EXPORT_SYMBOL(elv_queue_empty);
797
798 struct request *elv_latter_request(request_queue_t *q, struct request *rq)
799 {
800         elevator_t *e = q->elevator;
801
802         if (e->ops->elevator_latter_req_fn)
803                 return e->ops->elevator_latter_req_fn(q, rq);
804         return NULL;
805 }
806
807 struct request *elv_former_request(request_queue_t *q, struct request *rq)
808 {
809         elevator_t *e = q->elevator;
810
811         if (e->ops->elevator_former_req_fn)
812                 return e->ops->elevator_former_req_fn(q, rq);
813         return NULL;
814 }
815
816 int elv_set_request(request_queue_t *q, struct request *rq, gfp_t gfp_mask)
817 {
818         elevator_t *e = q->elevator;
819
820         if (e->ops->elevator_set_req_fn)
821                 return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
822
823         rq->elevator_private = NULL;
824         return 0;
825 }
826
827 void elv_put_request(request_queue_t *q, struct request *rq)
828 {
829         elevator_t *e = q->elevator;
830
831         if (e->ops->elevator_put_req_fn)
832                 e->ops->elevator_put_req_fn(rq);
833 }
834
835 int elv_may_queue(request_queue_t *q, int rw)
836 {
837         elevator_t *e = q->elevator;
838
839         if (e->ops->elevator_may_queue_fn)
840                 return e->ops->elevator_may_queue_fn(q, rw);
841
842         return ELV_MQUEUE_MAY;
843 }
844
845 void elv_completed_request(request_queue_t *q, struct request *rq)
846 {
847         elevator_t *e = q->elevator;
848
849         /*
850          * request is released from the driver, io must be done
851          */
852         if (blk_account_rq(rq)) {
853                 q->in_flight--;
854                 if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
855                         e->ops->elevator_completed_req_fn(q, rq);
856         }
857
858         /*
859          * Check if the queue is waiting for fs requests to be
860          * drained for flush sequence.
861          */
862         if (unlikely(q->ordseq)) {
863                 struct request *first_rq = list_entry_rq(q->queue_head.next);
864                 if (q->in_flight == 0 &&
865                     blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
866                     blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
867                         blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
868                         q->request_fn(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         elevator_t *e = container_of(kobj, elevator_t, kobj);
879         struct elv_fs_entry *entry = to_elv(attr);
880         ssize_t error;
881
882         if (!entry->show)
883                 return -EIO;
884
885         mutex_lock(&e->sysfs_lock);
886         error = e->ops ? entry->show(e, page) : -ENOENT;
887         mutex_unlock(&e->sysfs_lock);
888         return error;
889 }
890
891 static ssize_t
892 elv_attr_store(struct kobject *kobj, struct attribute *attr,
893                const char *page, size_t length)
894 {
895         elevator_t *e = container_of(kobj, elevator_t, kobj);
896         struct elv_fs_entry *entry = to_elv(attr);
897         ssize_t error;
898
899         if (!entry->store)
900                 return -EIO;
901
902         mutex_lock(&e->sysfs_lock);
903         error = e->ops ? entry->store(e, page, length) : -ENOENT;
904         mutex_unlock(&e->sysfs_lock);
905         return error;
906 }
907
908 static struct sysfs_ops elv_sysfs_ops = {
909         .show   = elv_attr_show,
910         .store  = elv_attr_store,
911 };
912
913 static struct kobj_type elv_ktype = {
914         .sysfs_ops      = &elv_sysfs_ops,
915         .release        = elevator_release,
916 };
917
918 int elv_register_queue(struct request_queue *q)
919 {
920         elevator_t *e = q->elevator;
921         int error;
922
923         e->kobj.parent = &q->kobj;
924
925         error = kobject_add(&e->kobj);
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
940 static void __elv_unregister_queue(elevator_t *e)
941 {
942         kobject_uevent(&e->kobj, KOBJ_REMOVE);
943         kobject_del(&e->kobj);
944 }
945
946 void elv_unregister_queue(struct request_queue *q)
947 {
948         if (q)
949                 __elv_unregister_queue(q->elevator);
950 }
951
952 int elv_register(struct elevator_type *e)
953 {
954         spin_lock_irq(&elv_list_lock);
955         BUG_ON(elevator_find(e->elevator_name));
956         list_add_tail(&e->list, &elv_list);
957         spin_unlock_irq(&elv_list_lock);
958
959         printk(KERN_INFO "io scheduler %s registered", e->elevator_name);
960         if (!strcmp(e->elevator_name, chosen_elevator) ||
961                         (!*chosen_elevator &&
962                          !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
963                                 printk(" (default)");
964         printk("\n");
965         return 0;
966 }
967 EXPORT_SYMBOL_GPL(elv_register);
968
969 void elv_unregister(struct elevator_type *e)
970 {
971         struct task_struct *g, *p;
972
973         /*
974          * Iterate every thread in the process to remove the io contexts.
975          */
976         if (e->ops.trim) {
977                 read_lock(&tasklist_lock);
978                 do_each_thread(g, p) {
979                         task_lock(p);
980                         if (p->io_context)
981                                 e->ops.trim(p->io_context);
982                         task_unlock(p);
983                 } while_each_thread(g, p);
984                 read_unlock(&tasklist_lock);
985         }
986
987         spin_lock_irq(&elv_list_lock);
988         list_del_init(&e->list);
989         spin_unlock_irq(&elv_list_lock);
990 }
991 EXPORT_SYMBOL_GPL(elv_unregister);
992
993 /*
994  * switch to new_e io scheduler. be careful not to introduce deadlocks -
995  * we don't free the old io scheduler, before we have allocated what we
996  * need for the new one. this way we have a chance of going back to the old
997  * one, if the new one fails init for some reason.
998  */
999 static int elevator_switch(request_queue_t *q, struct elevator_type *new_e)
1000 {
1001         elevator_t *old_elevator, *e;
1002         void *data;
1003
1004         /*
1005          * Allocate new elevator
1006          */
1007         e = elevator_alloc(q, new_e);
1008         if (!e)
1009                 return 0;
1010
1011         data = elevator_init_queue(q, e);
1012         if (!data) {
1013                 kobject_put(&e->kobj);
1014                 return 0;
1015         }
1016
1017         /*
1018          * Turn on BYPASS and drain all requests w/ elevator private data
1019          */
1020         spin_lock_irq(q->queue_lock);
1021
1022         set_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1023
1024         elv_drain_elevator(q);
1025
1026         while (q->rq.elvpriv) {
1027                 blk_remove_plug(q);
1028                 q->request_fn(q);
1029                 spin_unlock_irq(q->queue_lock);
1030                 msleep(10);
1031                 spin_lock_irq(q->queue_lock);
1032                 elv_drain_elevator(q);
1033         }
1034
1035         /*
1036          * Remember old elevator.
1037          */
1038         old_elevator = q->elevator;
1039
1040         /*
1041          * attach and start new elevator
1042          */
1043         elevator_attach(q, e, data);
1044
1045         spin_unlock_irq(q->queue_lock);
1046
1047         __elv_unregister_queue(old_elevator);
1048
1049         if (elv_register_queue(q))
1050                 goto fail_register;
1051
1052         /*
1053          * finally exit old elevator and turn off BYPASS.
1054          */
1055         elevator_exit(old_elevator);
1056         clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1057         return 1;
1058
1059 fail_register:
1060         /*
1061          * switch failed, exit the new io scheduler and reattach the old
1062          * one again (along with re-adding the sysfs dir)
1063          */
1064         elevator_exit(e);
1065         q->elevator = old_elevator;
1066         elv_register_queue(q);
1067         clear_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
1068         return 0;
1069 }
1070
1071 ssize_t elv_iosched_store(request_queue_t *q, const char *name, size_t count)
1072 {
1073         char elevator_name[ELV_NAME_MAX];
1074         size_t len;
1075         struct elevator_type *e;
1076
1077         elevator_name[sizeof(elevator_name) - 1] = '\0';
1078         strncpy(elevator_name, name, sizeof(elevator_name) - 1);
1079         len = strlen(elevator_name);
1080
1081         if (len && elevator_name[len - 1] == '\n')
1082                 elevator_name[len - 1] = '\0';
1083
1084         e = elevator_get(elevator_name);
1085         if (!e) {
1086                 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
1087                 return -EINVAL;
1088         }
1089
1090         if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
1091                 elevator_put(e);
1092                 return count;
1093         }
1094
1095         if (!elevator_switch(q, e))
1096                 printk(KERN_ERR "elevator: switch to %s failed\n",elevator_name);
1097         return count;
1098 }
1099
1100 ssize_t elv_iosched_show(request_queue_t *q, char *name)
1101 {
1102         elevator_t *e = q->elevator;
1103         struct elevator_type *elv = e->elevator_type;
1104         struct list_head *entry;
1105         int len = 0;
1106
1107         spin_lock_irq(&elv_list_lock);
1108         list_for_each(entry, &elv_list) {
1109                 struct elevator_type *__e;
1110
1111                 __e = list_entry(entry, struct elevator_type, list);
1112                 if (!strcmp(elv->elevator_name, __e->elevator_name))
1113                         len += sprintf(name+len, "[%s] ", elv->elevator_name);
1114                 else
1115                         len += sprintf(name+len, "%s ", __e->elevator_name);
1116         }
1117         spin_unlock_irq(&elv_list_lock);
1118
1119         len += sprintf(len+name, "\n");
1120         return len;
1121 }
1122
1123 struct request *elv_rb_former_request(request_queue_t *q, struct request *rq)
1124 {
1125         struct rb_node *rbprev = rb_prev(&rq->rb_node);
1126
1127         if (rbprev)
1128                 return rb_entry_rq(rbprev);
1129
1130         return NULL;
1131 }
1132
1133 EXPORT_SYMBOL(elv_rb_former_request);
1134
1135 struct request *elv_rb_latter_request(request_queue_t *q, struct request *rq)
1136 {
1137         struct rb_node *rbnext = rb_next(&rq->rb_node);
1138
1139         if (rbnext)
1140                 return rb_entry_rq(rbnext);
1141
1142         return NULL;
1143 }
1144
1145 EXPORT_SYMBOL(elv_rb_latter_request);