scsi,block: update SCSI to handle mixed merge failures
[linux-2.6.git] / block / elevator.c
1 /*
2  *  Block device elevator/IO-scheduler.
3  *
4  *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
5  *
6  * 30042000 Jens Axboe <axboe@kernel.dk> :
7  *
8  * Split the elevator a bit so that it is possible to choose a different
9  * one or even write a new "plug in". There are three pieces:
10  * - elevator_fn, inserts a new request in the queue list
11  * - elevator_merge_fn, decides whether a new buffer can be merged with
12  *   an existing request
13  * - elevator_dequeue_fn, called when a request is taken off the active list
14  *
15  * 20082000 Dave Jones <davej@suse.de> :
16  * Removed tests for max-bomb-segments, which was breaking elvtune
17  *  when run without -bN
18  *
19  * Jens:
20  * - Rework again to work with bio instead of buffer_heads
21  * - loose bi_dev comparisons, partition handling is right now
22  * - completely modularize elevator setup and teardown
23  *
24  */
25 #include <linux/kernel.h>
26 #include <linux/fs.h>
27 #include <linux/blkdev.h>
28 #include <linux/elevator.h>
29 #include <linux/bio.h>
30 #include <linux/module.h>
31 #include <linux/slab.h>
32 #include <linux/init.h>
33 #include <linux/compiler.h>
34 #include <linux/delay.h>
35 #include <linux/blktrace_api.h>
36 #include <linux/hash.h>
37 #include <linux/uaccess.h>
38
39 #include <trace/events/block.h>
40
41 #include "blk.h"
42
43 static DEFINE_SPINLOCK(elv_list_lock);
44 static LIST_HEAD(elv_list);
45
46 /*
47  * Merge hash stuff.
48  */
49 static const int elv_hash_shift = 6;
50 #define ELV_HASH_BLOCK(sec)     ((sec) >> 3)
51 #define ELV_HASH_FN(sec)        \
52                 (hash_long(ELV_HASH_BLOCK((sec)), elv_hash_shift))
53 #define ELV_HASH_ENTRIES        (1 << elv_hash_shift)
54 #define rq_hash_key(rq)         (blk_rq_pos(rq) + blk_rq_sectors(rq))
55
56 /*
57  * Query io scheduler to see if the current process issuing bio may be
58  * merged with rq.
59  */
60 static int elv_iosched_allow_merge(struct request *rq, struct bio *bio)
61 {
62         struct request_queue *q = rq->q;
63         struct elevator_queue *e = q->elevator;
64
65         if (e->ops->elevator_allow_merge_fn)
66                 return e->ops->elevator_allow_merge_fn(q, rq, bio);
67
68         return 1;
69 }
70
71 /*
72  * can we safely merge with this request?
73  */
74 int elv_rq_merge_ok(struct request *rq, struct bio *bio)
75 {
76         if (!rq_mergeable(rq))
77                 return 0;
78
79         /*
80          * Don't merge file system requests and discard requests
81          */
82         if (bio_discard(bio) != bio_discard(rq->bio))
83                 return 0;
84
85         /*
86          * different data direction or already started, don't merge
87          */
88         if (bio_data_dir(bio) != rq_data_dir(rq))
89                 return 0;
90
91         /*
92          * must be same device and not a special request
93          */
94         if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)
95                 return 0;
96
97         /*
98          * only merge integrity protected bio into ditto rq
99          */
100         if (bio_integrity(bio) != blk_integrity_rq(rq))
101                 return 0;
102
103         if (!elv_iosched_allow_merge(rq, bio))
104                 return 0;
105
106         return 1;
107 }
108 EXPORT_SYMBOL(elv_rq_merge_ok);
109
110 static inline int elv_try_merge(struct request *__rq, struct bio *bio)
111 {
112         int ret = ELEVATOR_NO_MERGE;
113
114         /*
115          * we can merge and sequence is ok, check if it's possible
116          */
117         if (elv_rq_merge_ok(__rq, bio)) {
118                 if (blk_rq_pos(__rq) + blk_rq_sectors(__rq) == bio->bi_sector)
119                         ret = ELEVATOR_BACK_MERGE;
120                 else if (blk_rq_pos(__rq) - bio_sectors(bio) == bio->bi_sector)
121                         ret = ELEVATOR_FRONT_MERGE;
122         }
123
124         return ret;
125 }
126
127 static struct elevator_type *elevator_find(const char *name)
128 {
129         struct elevator_type *e;
130
131         list_for_each_entry(e, &elv_list, list) {
132                 if (!strcmp(e->elevator_name, name))
133                         return e;
134         }
135
136         return NULL;
137 }
138
139 static void elevator_put(struct elevator_type *e)
140 {
141         module_put(e->elevator_owner);
142 }
143
144 static struct elevator_type *elevator_get(const char *name)
145 {
146         struct elevator_type *e;
147
148         spin_lock(&elv_list_lock);
149
150         e = elevator_find(name);
151         if (!e) {
152                 char elv[ELV_NAME_MAX + strlen("-iosched")];
153
154                 spin_unlock(&elv_list_lock);
155
156                 if (!strcmp(name, "anticipatory"))
157                         sprintf(elv, "as-iosched");
158                 else
159                         sprintf(elv, "%s-iosched", name);
160
161                 request_module("%s", elv);
162                 spin_lock(&elv_list_lock);
163                 e = elevator_find(name);
164         }
165
166         if (e && !try_module_get(e->elevator_owner))
167                 e = NULL;
168
169         spin_unlock(&elv_list_lock);
170
171         return e;
172 }
173
174 static void *elevator_init_queue(struct request_queue *q,
175                                  struct elevator_queue *eq)
176 {
177         return eq->ops->elevator_init_fn(q);
178 }
179
180 static void elevator_attach(struct request_queue *q, struct elevator_queue *eq,
181                            void *data)
182 {
183         q->elevator = eq;
184         eq->elevator_data = data;
185 }
186
187 static char chosen_elevator[16];
188
189 static int __init elevator_setup(char *str)
190 {
191         /*
192          * Be backwards-compatible with previous kernels, so users
193          * won't get the wrong elevator.
194          */
195         if (!strcmp(str, "as"))
196                 strcpy(chosen_elevator, "anticipatory");
197         else
198                 strncpy(chosen_elevator, str, sizeof(chosen_elevator) - 1);
199         return 1;
200 }
201
202 __setup("elevator=", elevator_setup);
203
204 static struct kobj_type elv_ktype;
205
206 static struct elevator_queue *elevator_alloc(struct request_queue *q,
207                                   struct elevator_type *e)
208 {
209         struct elevator_queue *eq;
210         int i;
211
212         eq = kmalloc_node(sizeof(*eq), GFP_KERNEL | __GFP_ZERO, q->node);
213         if (unlikely(!eq))
214                 goto err;
215
216         eq->ops = &e->ops;
217         eq->elevator_type = e;
218         kobject_init(&eq->kobj, &elv_ktype);
219         mutex_init(&eq->sysfs_lock);
220
221         eq->hash = kmalloc_node(sizeof(struct hlist_head) * ELV_HASH_ENTRIES,
222                                         GFP_KERNEL, q->node);
223         if (!eq->hash)
224                 goto err;
225
226         for (i = 0; i < ELV_HASH_ENTRIES; i++)
227                 INIT_HLIST_HEAD(&eq->hash[i]);
228
229         return eq;
230 err:
231         kfree(eq);
232         elevator_put(e);
233         return NULL;
234 }
235
236 static void elevator_release(struct kobject *kobj)
237 {
238         struct elevator_queue *e;
239
240         e = container_of(kobj, struct elevator_queue, kobj);
241         elevator_put(e->elevator_type);
242         kfree(e->hash);
243         kfree(e);
244 }
245
246 int elevator_init(struct request_queue *q, char *name)
247 {
248         struct elevator_type *e = NULL;
249         struct elevator_queue *eq;
250         int ret = 0;
251         void *data;
252
253         INIT_LIST_HEAD(&q->queue_head);
254         q->last_merge = NULL;
255         q->end_sector = 0;
256         q->boundary_rq = NULL;
257
258         if (name) {
259                 e = elevator_get(name);
260                 if (!e)
261                         return -EINVAL;
262         }
263
264         if (!e && *chosen_elevator) {
265                 e = elevator_get(chosen_elevator);
266                 if (!e)
267                         printk(KERN_ERR "I/O scheduler %s not found\n",
268                                                         chosen_elevator);
269         }
270
271         if (!e) {
272                 e = elevator_get(CONFIG_DEFAULT_IOSCHED);
273                 if (!e) {
274                         printk(KERN_ERR
275                                 "Default I/O scheduler not found. " \
276                                 "Using noop.\n");
277                         e = elevator_get("noop");
278                 }
279         }
280
281         eq = elevator_alloc(q, e);
282         if (!eq)
283                 return -ENOMEM;
284
285         data = elevator_init_queue(q, eq);
286         if (!data) {
287                 kobject_put(&eq->kobj);
288                 return -ENOMEM;
289         }
290
291         elevator_attach(q, eq, data);
292         return ret;
293 }
294 EXPORT_SYMBOL(elevator_init);
295
296 void elevator_exit(struct elevator_queue *e)
297 {
298         mutex_lock(&e->sysfs_lock);
299         if (e->ops->elevator_exit_fn)
300                 e->ops->elevator_exit_fn(e);
301         e->ops = NULL;
302         mutex_unlock(&e->sysfs_lock);
303
304         kobject_put(&e->kobj);
305 }
306 EXPORT_SYMBOL(elevator_exit);
307
308 static inline void __elv_rqhash_del(struct request *rq)
309 {
310         hlist_del_init(&rq->hash);
311 }
312
313 static void elv_rqhash_del(struct request_queue *q, struct request *rq)
314 {
315         if (ELV_ON_HASH(rq))
316                 __elv_rqhash_del(rq);
317 }
318
319 static void elv_rqhash_add(struct request_queue *q, struct request *rq)
320 {
321         struct elevator_queue *e = q->elevator;
322
323         BUG_ON(ELV_ON_HASH(rq));
324         hlist_add_head(&rq->hash, &e->hash[ELV_HASH_FN(rq_hash_key(rq))]);
325 }
326
327 static void elv_rqhash_reposition(struct request_queue *q, struct request *rq)
328 {
329         __elv_rqhash_del(rq);
330         elv_rqhash_add(q, rq);
331 }
332
333 static struct request *elv_rqhash_find(struct request_queue *q, sector_t offset)
334 {
335         struct elevator_queue *e = q->elevator;
336         struct hlist_head *hash_list = &e->hash[ELV_HASH_FN(offset)];
337         struct hlist_node *entry, *next;
338         struct request *rq;
339
340         hlist_for_each_entry_safe(rq, entry, next, hash_list, hash) {
341                 BUG_ON(!ELV_ON_HASH(rq));
342
343                 if (unlikely(!rq_mergeable(rq))) {
344                         __elv_rqhash_del(rq);
345                         continue;
346                 }
347
348                 if (rq_hash_key(rq) == offset)
349                         return rq;
350         }
351
352         return NULL;
353 }
354
355 /*
356  * RB-tree support functions for inserting/lookup/removal of requests
357  * in a sorted RB tree.
358  */
359 struct request *elv_rb_add(struct rb_root *root, struct request *rq)
360 {
361         struct rb_node **p = &root->rb_node;
362         struct rb_node *parent = NULL;
363         struct request *__rq;
364
365         while (*p) {
366                 parent = *p;
367                 __rq = rb_entry(parent, struct request, rb_node);
368
369                 if (blk_rq_pos(rq) < blk_rq_pos(__rq))
370                         p = &(*p)->rb_left;
371                 else if (blk_rq_pos(rq) > blk_rq_pos(__rq))
372                         p = &(*p)->rb_right;
373                 else
374                         return __rq;
375         }
376
377         rb_link_node(&rq->rb_node, parent, p);
378         rb_insert_color(&rq->rb_node, root);
379         return NULL;
380 }
381 EXPORT_SYMBOL(elv_rb_add);
382
383 void elv_rb_del(struct rb_root *root, struct request *rq)
384 {
385         BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
386         rb_erase(&rq->rb_node, root);
387         RB_CLEAR_NODE(&rq->rb_node);
388 }
389 EXPORT_SYMBOL(elv_rb_del);
390
391 struct request *elv_rb_find(struct rb_root *root, sector_t sector)
392 {
393         struct rb_node *n = root->rb_node;
394         struct request *rq;
395
396         while (n) {
397                 rq = rb_entry(n, struct request, rb_node);
398
399                 if (sector < blk_rq_pos(rq))
400                         n = n->rb_left;
401                 else if (sector > blk_rq_pos(rq))
402                         n = n->rb_right;
403                 else
404                         return rq;
405         }
406
407         return NULL;
408 }
409 EXPORT_SYMBOL(elv_rb_find);
410
411 /*
412  * Insert rq into dispatch queue of q.  Queue lock must be held on
413  * entry.  rq is sort instead into the dispatch queue. To be used by
414  * specific elevators.
415  */
416 void elv_dispatch_sort(struct request_queue *q, struct request *rq)
417 {
418         sector_t boundary;
419         struct list_head *entry;
420         int stop_flags;
421
422         if (q->last_merge == rq)
423                 q->last_merge = NULL;
424
425         elv_rqhash_del(q, rq);
426
427         q->nr_sorted--;
428
429         boundary = q->end_sector;
430         stop_flags = REQ_SOFTBARRIER | REQ_HARDBARRIER | REQ_STARTED;
431         list_for_each_prev(entry, &q->queue_head) {
432                 struct request *pos = list_entry_rq(entry);
433
434                 if (blk_discard_rq(rq) != blk_discard_rq(pos))
435                         break;
436                 if (rq_data_dir(rq) != rq_data_dir(pos))
437                         break;
438                 if (pos->cmd_flags & stop_flags)
439                         break;
440                 if (blk_rq_pos(rq) >= boundary) {
441                         if (blk_rq_pos(pos) < boundary)
442                                 continue;
443                 } else {
444                         if (blk_rq_pos(pos) >= boundary)
445                                 break;
446                 }
447                 if (blk_rq_pos(rq) >= blk_rq_pos(pos))
448                         break;
449         }
450
451         list_add(&rq->queuelist, entry);
452 }
453 EXPORT_SYMBOL(elv_dispatch_sort);
454
455 /*
456  * Insert rq into dispatch queue of q.  Queue lock must be held on
457  * entry.  rq is added to the back of the dispatch queue. To be used by
458  * specific elevators.
459  */
460 void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
461 {
462         if (q->last_merge == rq)
463                 q->last_merge = NULL;
464
465         elv_rqhash_del(q, rq);
466
467         q->nr_sorted--;
468
469         q->end_sector = rq_end_sector(rq);
470         q->boundary_rq = rq;
471         list_add_tail(&rq->queuelist, &q->queue_head);
472 }
473 EXPORT_SYMBOL(elv_dispatch_add_tail);
474
475 int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
476 {
477         struct elevator_queue *e = q->elevator;
478         struct request *__rq;
479         int ret;
480
481         /*
482          * First try one-hit cache.
483          */
484         if (q->last_merge) {
485                 ret = elv_try_merge(q->last_merge, bio);
486                 if (ret != ELEVATOR_NO_MERGE) {
487                         *req = q->last_merge;
488                         return ret;
489                 }
490         }
491
492         if (blk_queue_nomerges(q))
493                 return ELEVATOR_NO_MERGE;
494
495         /*
496          * See if our hash lookup can find a potential backmerge.
497          */
498         __rq = elv_rqhash_find(q, bio->bi_sector);
499         if (__rq && elv_rq_merge_ok(__rq, bio)) {
500                 *req = __rq;
501                 return ELEVATOR_BACK_MERGE;
502         }
503
504         if (e->ops->elevator_merge_fn)
505                 return e->ops->elevator_merge_fn(q, req, bio);
506
507         return ELEVATOR_NO_MERGE;
508 }
509
510 void elv_merged_request(struct request_queue *q, struct request *rq, int type)
511 {
512         struct elevator_queue *e = q->elevator;
513
514         if (e->ops->elevator_merged_fn)
515                 e->ops->elevator_merged_fn(q, rq, type);
516
517         if (type == ELEVATOR_BACK_MERGE)
518                 elv_rqhash_reposition(q, rq);
519
520         q->last_merge = rq;
521 }
522
523 void elv_merge_requests(struct request_queue *q, struct request *rq,
524                              struct request *next)
525 {
526         struct elevator_queue *e = q->elevator;
527
528         if (e->ops->elevator_merge_req_fn)
529                 e->ops->elevator_merge_req_fn(q, rq, next);
530
531         elv_rqhash_reposition(q, rq);
532         elv_rqhash_del(q, next);
533
534         q->nr_sorted--;
535         q->last_merge = rq;
536 }
537
538 void elv_requeue_request(struct request_queue *q, struct request *rq)
539 {
540         /*
541          * it already went through dequeue, we need to decrement the
542          * in_flight count again
543          */
544         if (blk_account_rq(rq)) {
545                 q->in_flight[rq_is_sync(rq)]--;
546                 if (blk_sorted_rq(rq))
547                         elv_deactivate_rq(q, rq);
548         }
549
550         rq->cmd_flags &= ~REQ_STARTED;
551
552         elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
553 }
554
555 void elv_drain_elevator(struct request_queue *q)
556 {
557         static int printed;
558         while (q->elevator->ops->elevator_dispatch_fn(q, 1))
559                 ;
560         if (q->nr_sorted == 0)
561                 return;
562         if (printed++ < 10) {
563                 printk(KERN_ERR "%s: forced dispatching is broken "
564                        "(nr_sorted=%u), please report this\n",
565                        q->elevator->elevator_type->elevator_name, q->nr_sorted);
566         }
567 }
568
569 /*
570  * Call with queue lock held, interrupts disabled
571  */
572 void elv_quiesce_start(struct request_queue *q)
573 {
574         if (!q->elevator)
575                 return;
576
577         queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
578
579         /*
580          * make sure we don't have any requests in flight
581          */
582         elv_drain_elevator(q);
583         while (q->rq.elvpriv) {
584                 __blk_run_queue(q);
585                 spin_unlock_irq(q->queue_lock);
586                 msleep(10);
587                 spin_lock_irq(q->queue_lock);
588                 elv_drain_elevator(q);
589         }
590 }
591
592 void elv_quiesce_end(struct request_queue *q)
593 {
594         queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
595 }
596
597 void elv_insert(struct request_queue *q, struct request *rq, int where)
598 {
599         struct list_head *pos;
600         unsigned ordseq;
601         int unplug_it = 1;
602
603         trace_block_rq_insert(q, rq);
604
605         rq->q = q;
606
607         switch (where) {
608         case ELEVATOR_INSERT_FRONT:
609                 rq->cmd_flags |= REQ_SOFTBARRIER;
610
611                 list_add(&rq->queuelist, &q->queue_head);
612                 break;
613
614         case ELEVATOR_INSERT_BACK:
615                 rq->cmd_flags |= REQ_SOFTBARRIER;
616                 elv_drain_elevator(q);
617                 list_add_tail(&rq->queuelist, &q->queue_head);
618                 /*
619                  * We kick the queue here for the following reasons.
620                  * - The elevator might have returned NULL previously
621                  *   to delay requests and returned them now.  As the
622                  *   queue wasn't empty before this request, ll_rw_blk
623                  *   won't run the queue on return, resulting in hang.
624                  * - Usually, back inserted requests won't be merged
625                  *   with anything.  There's no point in delaying queue
626                  *   processing.
627                  */
628                 __blk_run_queue(q);
629                 break;
630
631         case ELEVATOR_INSERT_SORT:
632                 BUG_ON(!blk_fs_request(rq) && !blk_discard_rq(rq));
633                 rq->cmd_flags |= REQ_SORTED;
634                 q->nr_sorted++;
635                 if (rq_mergeable(rq)) {
636                         elv_rqhash_add(q, rq);
637                         if (!q->last_merge)
638                                 q->last_merge = rq;
639                 }
640
641                 /*
642                  * Some ioscheds (cfq) run q->request_fn directly, so
643                  * rq cannot be accessed after calling
644                  * elevator_add_req_fn.
645                  */
646                 q->elevator->ops->elevator_add_req_fn(q, rq);
647                 break;
648
649         case ELEVATOR_INSERT_REQUEUE:
650                 /*
651                  * If ordered flush isn't in progress, we do front
652                  * insertion; otherwise, requests should be requeued
653                  * in ordseq order.
654                  */
655                 rq->cmd_flags |= REQ_SOFTBARRIER;
656
657                 /*
658                  * Most requeues happen because of a busy condition,
659                  * don't force unplug of the queue for that case.
660                  */
661                 unplug_it = 0;
662
663                 if (q->ordseq == 0) {
664                         list_add(&rq->queuelist, &q->queue_head);
665                         break;
666                 }
667
668                 ordseq = blk_ordered_req_seq(rq);
669
670                 list_for_each(pos, &q->queue_head) {
671                         struct request *pos_rq = list_entry_rq(pos);
672                         if (ordseq <= blk_ordered_req_seq(pos_rq))
673                                 break;
674                 }
675
676                 list_add_tail(&rq->queuelist, pos);
677                 break;
678
679         default:
680                 printk(KERN_ERR "%s: bad insertion point %d\n",
681                        __func__, where);
682                 BUG();
683         }
684
685         if (unplug_it && blk_queue_plugged(q)) {
686                 int nrq = q->rq.count[BLK_RW_SYNC] + q->rq.count[BLK_RW_ASYNC]
687                                 - queue_in_flight(q);
688
689                 if (nrq >= q->unplug_thresh)
690                         __generic_unplug_device(q);
691         }
692 }
693
694 void __elv_add_request(struct request_queue *q, struct request *rq, int where,
695                        int plug)
696 {
697         if (q->ordcolor)
698                 rq->cmd_flags |= REQ_ORDERED_COLOR;
699
700         if (rq->cmd_flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
701                 /*
702                  * toggle ordered color
703                  */
704                 if (blk_barrier_rq(rq))
705                         q->ordcolor ^= 1;
706
707                 /*
708                  * barriers implicitly indicate back insertion
709                  */
710                 if (where == ELEVATOR_INSERT_SORT)
711                         where = ELEVATOR_INSERT_BACK;
712
713                 /*
714                  * this request is scheduling boundary, update
715                  * end_sector
716                  */
717                 if (blk_fs_request(rq) || blk_discard_rq(rq)) {
718                         q->end_sector = rq_end_sector(rq);
719                         q->boundary_rq = rq;
720                 }
721         } else if (!(rq->cmd_flags & REQ_ELVPRIV) &&
722                     where == ELEVATOR_INSERT_SORT)
723                 where = ELEVATOR_INSERT_BACK;
724
725         if (plug)
726                 blk_plug_device(q);
727
728         elv_insert(q, rq, where);
729 }
730 EXPORT_SYMBOL(__elv_add_request);
731
732 void elv_add_request(struct request_queue *q, struct request *rq, int where,
733                      int plug)
734 {
735         unsigned long flags;
736
737         spin_lock_irqsave(q->queue_lock, flags);
738         __elv_add_request(q, rq, where, plug);
739         spin_unlock_irqrestore(q->queue_lock, flags);
740 }
741 EXPORT_SYMBOL(elv_add_request);
742
743 int elv_queue_empty(struct request_queue *q)
744 {
745         struct elevator_queue *e = q->elevator;
746
747         if (!list_empty(&q->queue_head))
748                 return 0;
749
750         if (e->ops->elevator_queue_empty_fn)
751                 return e->ops->elevator_queue_empty_fn(q);
752
753         return 1;
754 }
755 EXPORT_SYMBOL(elv_queue_empty);
756
757 struct request *elv_latter_request(struct request_queue *q, struct request *rq)
758 {
759         struct elevator_queue *e = q->elevator;
760
761         if (e->ops->elevator_latter_req_fn)
762                 return e->ops->elevator_latter_req_fn(q, rq);
763         return NULL;
764 }
765
766 struct request *elv_former_request(struct request_queue *q, struct request *rq)
767 {
768         struct elevator_queue *e = q->elevator;
769
770         if (e->ops->elevator_former_req_fn)
771                 return e->ops->elevator_former_req_fn(q, rq);
772         return NULL;
773 }
774
775 int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
776 {
777         struct elevator_queue *e = q->elevator;
778
779         if (e->ops->elevator_set_req_fn)
780                 return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
781
782         rq->elevator_private = NULL;
783         return 0;
784 }
785
786 void elv_put_request(struct request_queue *q, struct request *rq)
787 {
788         struct elevator_queue *e = q->elevator;
789
790         if (e->ops->elevator_put_req_fn)
791                 e->ops->elevator_put_req_fn(rq);
792 }
793
794 int elv_may_queue(struct request_queue *q, int rw)
795 {
796         struct elevator_queue *e = q->elevator;
797
798         if (e->ops->elevator_may_queue_fn)
799                 return e->ops->elevator_may_queue_fn(q, rw);
800
801         return ELV_MQUEUE_MAY;
802 }
803
804 void elv_abort_queue(struct request_queue *q)
805 {
806         struct request *rq;
807
808         while (!list_empty(&q->queue_head)) {
809                 rq = list_entry_rq(q->queue_head.next);
810                 rq->cmd_flags |= REQ_QUIET;
811                 trace_block_rq_abort(q, rq);
812                 /*
813                  * Mark this request as started so we don't trigger
814                  * any debug logic in the end I/O path.
815                  */
816                 blk_start_request(rq);
817                 __blk_end_request_all(rq, -EIO);
818         }
819 }
820 EXPORT_SYMBOL(elv_abort_queue);
821
822 void elv_completed_request(struct request_queue *q, struct request *rq)
823 {
824         struct elevator_queue *e = q->elevator;
825
826         /*
827          * request is released from the driver, io must be done
828          */
829         if (blk_account_rq(rq)) {
830                 q->in_flight[rq_is_sync(rq)]--;
831                 if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
832                         e->ops->elevator_completed_req_fn(q, rq);
833         }
834
835         /*
836          * Check if the queue is waiting for fs requests to be
837          * drained for flush sequence.
838          */
839         if (unlikely(q->ordseq)) {
840                 struct request *next = NULL;
841
842                 if (!list_empty(&q->queue_head))
843                         next = list_entry_rq(q->queue_head.next);
844
845                 if (!queue_in_flight(q) &&
846                     blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
847                     (!next || blk_ordered_req_seq(next) > QUEUE_ORDSEQ_DRAIN)) {
848                         blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
849                         __blk_run_queue(q);
850                 }
851         }
852 }
853
854 #define to_elv(atr) container_of((atr), struct elv_fs_entry, attr)
855
856 static ssize_t
857 elv_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
858 {
859         struct elv_fs_entry *entry = to_elv(attr);
860         struct elevator_queue *e;
861         ssize_t error;
862
863         if (!entry->show)
864                 return -EIO;
865
866         e = container_of(kobj, struct elevator_queue, kobj);
867         mutex_lock(&e->sysfs_lock);
868         error = e->ops ? entry->show(e, page) : -ENOENT;
869         mutex_unlock(&e->sysfs_lock);
870         return error;
871 }
872
873 static ssize_t
874 elv_attr_store(struct kobject *kobj, struct attribute *attr,
875                const char *page, size_t length)
876 {
877         struct elv_fs_entry *entry = to_elv(attr);
878         struct elevator_queue *e;
879         ssize_t error;
880
881         if (!entry->store)
882                 return -EIO;
883
884         e = container_of(kobj, struct elevator_queue, kobj);
885         mutex_lock(&e->sysfs_lock);
886         error = e->ops ? entry->store(e, page, length) : -ENOENT;
887         mutex_unlock(&e->sysfs_lock);
888         return error;
889 }
890
891 static struct sysfs_ops elv_sysfs_ops = {
892         .show   = elv_attr_show,
893         .store  = elv_attr_store,
894 };
895
896 static struct kobj_type elv_ktype = {
897         .sysfs_ops      = &elv_sysfs_ops,
898         .release        = elevator_release,
899 };
900
901 int elv_register_queue(struct request_queue *q)
902 {
903         struct elevator_queue *e = q->elevator;
904         int error;
905
906         error = kobject_add(&e->kobj, &q->kobj, "%s", "iosched");
907         if (!error) {
908                 struct elv_fs_entry *attr = e->elevator_type->elevator_attrs;
909                 if (attr) {
910                         while (attr->attr.name) {
911                                 if (sysfs_create_file(&e->kobj, &attr->attr))
912                                         break;
913                                 attr++;
914                         }
915                 }
916                 kobject_uevent(&e->kobj, KOBJ_ADD);
917         }
918         return error;
919 }
920
921 static void __elv_unregister_queue(struct elevator_queue *e)
922 {
923         kobject_uevent(&e->kobj, KOBJ_REMOVE);
924         kobject_del(&e->kobj);
925 }
926
927 void elv_unregister_queue(struct request_queue *q)
928 {
929         if (q)
930                 __elv_unregister_queue(q->elevator);
931 }
932
933 void elv_register(struct elevator_type *e)
934 {
935         char *def = "";
936
937         spin_lock(&elv_list_lock);
938         BUG_ON(elevator_find(e->elevator_name));
939         list_add_tail(&e->list, &elv_list);
940         spin_unlock(&elv_list_lock);
941
942         if (!strcmp(e->elevator_name, chosen_elevator) ||
943                         (!*chosen_elevator &&
944                          !strcmp(e->elevator_name, CONFIG_DEFAULT_IOSCHED)))
945                                 def = " (default)";
946
947         printk(KERN_INFO "io scheduler %s registered%s\n", e->elevator_name,
948                                                                 def);
949 }
950 EXPORT_SYMBOL_GPL(elv_register);
951
952 void elv_unregister(struct elevator_type *e)
953 {
954         struct task_struct *g, *p;
955
956         /*
957          * Iterate every thread in the process to remove the io contexts.
958          */
959         if (e->ops.trim) {
960                 read_lock(&tasklist_lock);
961                 do_each_thread(g, p) {
962                         task_lock(p);
963                         if (p->io_context)
964                                 e->ops.trim(p->io_context);
965                         task_unlock(p);
966                 } while_each_thread(g, p);
967                 read_unlock(&tasklist_lock);
968         }
969
970         spin_lock(&elv_list_lock);
971         list_del_init(&e->list);
972         spin_unlock(&elv_list_lock);
973 }
974 EXPORT_SYMBOL_GPL(elv_unregister);
975
976 /*
977  * switch to new_e io scheduler. be careful not to introduce deadlocks -
978  * we don't free the old io scheduler, before we have allocated what we
979  * need for the new one. this way we have a chance of going back to the old
980  * one, if the new one fails init for some reason.
981  */
982 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
983 {
984         struct elevator_queue *old_elevator, *e;
985         void *data;
986
987         /*
988          * Allocate new elevator
989          */
990         e = elevator_alloc(q, new_e);
991         if (!e)
992                 return 0;
993
994         data = elevator_init_queue(q, e);
995         if (!data) {
996                 kobject_put(&e->kobj);
997                 return 0;
998         }
999
1000         /*
1001          * Turn on BYPASS and drain all requests w/ elevator private data
1002          */
1003         spin_lock_irq(q->queue_lock);
1004         elv_quiesce_start(q);
1005
1006         /*
1007          * Remember old elevator.
1008          */
1009         old_elevator = q->elevator;
1010
1011         /*
1012          * attach and start new elevator
1013          */
1014         elevator_attach(q, e, data);
1015
1016         spin_unlock_irq(q->queue_lock);
1017
1018         __elv_unregister_queue(old_elevator);
1019
1020         if (elv_register_queue(q))
1021                 goto fail_register;
1022
1023         /*
1024          * finally exit old elevator and turn off BYPASS.
1025          */
1026         elevator_exit(old_elevator);
1027         spin_lock_irq(q->queue_lock);
1028         elv_quiesce_end(q);
1029         spin_unlock_irq(q->queue_lock);
1030
1031         blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name);
1032
1033         return 1;
1034
1035 fail_register:
1036         /*
1037          * switch failed, exit the new io scheduler and reattach the old
1038          * one again (along with re-adding the sysfs dir)
1039          */
1040         elevator_exit(e);
1041         q->elevator = old_elevator;
1042         elv_register_queue(q);
1043
1044         spin_lock_irq(q->queue_lock);
1045         queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
1046         spin_unlock_irq(q->queue_lock);
1047
1048         return 0;
1049 }
1050
1051 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
1052                           size_t count)
1053 {
1054         char elevator_name[ELV_NAME_MAX];
1055         struct elevator_type *e;
1056
1057         if (!q->elevator)
1058                 return count;
1059
1060         strlcpy(elevator_name, name, sizeof(elevator_name));
1061         strstrip(elevator_name);
1062
1063         e = elevator_get(elevator_name);
1064         if (!e) {
1065                 printk(KERN_ERR "elevator: type %s not found\n", elevator_name);
1066                 return -EINVAL;
1067         }
1068
1069         if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) {
1070                 elevator_put(e);
1071                 return count;
1072         }
1073
1074         if (!elevator_switch(q, e))
1075                 printk(KERN_ERR "elevator: switch to %s failed\n",
1076                                                         elevator_name);
1077         return count;
1078 }
1079
1080 ssize_t elv_iosched_show(struct request_queue *q, char *name)
1081 {
1082         struct elevator_queue *e = q->elevator;
1083         struct elevator_type *elv;
1084         struct elevator_type *__e;
1085         int len = 0;
1086
1087         if (!q->elevator)
1088                 return sprintf(name, "none\n");
1089
1090         elv = e->elevator_type;
1091
1092         spin_lock(&elv_list_lock);
1093         list_for_each_entry(__e, &elv_list, list) {
1094                 if (!strcmp(elv->elevator_name, __e->elevator_name))
1095                         len += sprintf(name+len, "[%s] ", elv->elevator_name);
1096                 else
1097                         len += sprintf(name+len, "%s ", __e->elevator_name);
1098         }
1099         spin_unlock(&elv_list_lock);
1100
1101         len += sprintf(len+name, "\n");
1102         return len;
1103 }
1104
1105 struct request *elv_rb_former_request(struct request_queue *q,
1106                                       struct request *rq)
1107 {
1108         struct rb_node *rbprev = rb_prev(&rq->rb_node);
1109
1110         if (rbprev)
1111                 return rb_entry_rq(rbprev);
1112
1113         return NULL;
1114 }
1115 EXPORT_SYMBOL(elv_rb_former_request);
1116
1117 struct request *elv_rb_latter_request(struct request_queue *q,
1118                                       struct request *rq)
1119 {
1120         struct rb_node *rbnext = rb_next(&rq->rb_node);
1121
1122         if (rbnext)
1123                 return rb_entry_rq(rbnext);
1124
1125         return NULL;
1126 }
1127 EXPORT_SYMBOL(elv_rb_latter_request);