d63d34c671f7a7fcbc9007ca009a04f125303cd1
[linux-2.6.git] / drivers / block / deadline-iosched.c
1 /*
2  *  linux/drivers/block/deadline-iosched.c
3  *
4  *  Deadline i/o scheduler.
5  *
6  *  Copyright (C) 2002 Jens Axboe <axboe@suse.de>
7  */
8 #include <linux/kernel.h>
9 #include <linux/fs.h>
10 #include <linux/blkdev.h>
11 #include <linux/elevator.h>
12 #include <linux/bio.h>
13 #include <linux/config.h>
14 #include <linux/module.h>
15 #include <linux/slab.h>
16 #include <linux/init.h>
17 #include <linux/compiler.h>
18 #include <linux/hash.h>
19 #include <linux/rbtree.h>
20
21 /*
22  * See Documentation/block/deadline-iosched.txt
23  */
24 static int read_expire = HZ / 2;  /* max time before a read is submitted. */
25 static int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */
26 static int writes_starved = 2;    /* max times reads can starve a write */
27 static int fifo_batch = 16;       /* # of sequential requests treated as one
28                                      by the above parameters. For throughput. */
29
30 static const int deadline_hash_shift = 5;
31 #define DL_HASH_BLOCK(sec)      ((sec) >> 3)
32 #define DL_HASH_FN(sec)         (hash_long(DL_HASH_BLOCK((sec)), deadline_hash_shift))
33 #define DL_HASH_ENTRIES         (1 << deadline_hash_shift)
34 #define rq_hash_key(rq)         ((rq)->sector + (rq)->nr_sectors)
35 #define list_entry_hash(ptr)    list_entry((ptr), struct deadline_rq, hash)
36 #define ON_HASH(drq)            (drq)->on_hash
37
38 struct deadline_data {
39         /*
40          * run time data
41          */
42
43         /*
44          * requests (deadline_rq s) are present on both sort_list and fifo_list
45          */
46         struct rb_root sort_list[2];    
47         struct list_head fifo_list[2];
48         
49         /*
50          * next in sort order. read, write or both are NULL
51          */
52         struct deadline_rq *next_drq[2];
53         struct list_head *dispatch;     /* driver dispatch queue */
54         struct list_head *hash;         /* request hash */
55         unsigned int batching;          /* number of sequential requests made */
56         sector_t last_sector;           /* head position */
57         unsigned int starved;           /* times reads have starved writes */
58
59         /*
60          * settings that change how the i/o scheduler behaves
61          */
62         int fifo_expire[2];
63         int fifo_batch;
64         int writes_starved;
65         int front_merges;
66
67         mempool_t *drq_pool;
68 };
69
70 /*
71  * pre-request data.
72  */
73 struct deadline_rq {
74         /*
75          * rbtree index, key is the starting offset
76          */
77         struct rb_node rb_node;
78         sector_t rb_key;
79
80         struct request *request;
81
82         /*
83          * request hash, key is the ending offset (for back merge lookup)
84          */
85         struct list_head hash;
86         char on_hash;
87
88         /*
89          * expire fifo
90          */
91         struct list_head fifo;
92         unsigned long expires;
93 };
94
95 static void deadline_move_request(struct deadline_data *dd, struct deadline_rq *drq);
96
97 static kmem_cache_t *drq_pool;
98
99 #define RQ_DATA(rq)     ((struct deadline_rq *) (rq)->elevator_private)
100
101 /*
102  * the back merge hash support functions
103  */
104 static inline void __deadline_del_drq_hash(struct deadline_rq *drq)
105 {
106         drq->on_hash = 0;
107         list_del_init(&drq->hash);
108 }
109
110 static inline void deadline_del_drq_hash(struct deadline_rq *drq)
111 {
112         if (ON_HASH(drq))
113                 __deadline_del_drq_hash(drq);
114 }
115
116 static void
117 deadline_remove_merge_hints(request_queue_t *q, struct deadline_rq *drq)
118 {
119         deadline_del_drq_hash(drq);
120
121         if (q->last_merge == drq->request)
122                 q->last_merge = NULL;
123 }
124
125 static inline void
126 deadline_add_drq_hash(struct deadline_data *dd, struct deadline_rq *drq)
127 {
128         struct request *rq = drq->request;
129
130         BUG_ON(ON_HASH(drq));
131
132         drq->on_hash = 1;
133         list_add(&drq->hash, &dd->hash[DL_HASH_FN(rq_hash_key(rq))]);
134 }
135
136 /*
137  * move hot entry to front of chain
138  */
139 static inline void
140 deadline_hot_drq_hash(struct deadline_data *dd, struct deadline_rq *drq)
141 {
142         struct request *rq = drq->request;
143         struct list_head *head = &dd->hash[DL_HASH_FN(rq_hash_key(rq))];
144
145         if (ON_HASH(drq) && drq->hash.prev != head) {
146                 list_del(&drq->hash);
147                 list_add(&drq->hash, head);
148         }
149 }
150
151 static struct request *
152 deadline_find_drq_hash(struct deadline_data *dd, sector_t offset)
153 {
154         struct list_head *hash_list = &dd->hash[DL_HASH_FN(offset)];
155         struct list_head *entry, *next = hash_list->next;
156
157         while ((entry = next) != hash_list) {
158                 struct deadline_rq *drq = list_entry_hash(entry);
159                 struct request *__rq = drq->request;
160
161                 next = entry->next;
162                 
163                 BUG_ON(!ON_HASH(drq));
164
165                 if (!rq_mergeable(__rq)) {
166                         __deadline_del_drq_hash(drq);
167                         continue;
168                 }
169
170                 if (rq_hash_key(__rq) == offset)
171                         return __rq;
172         }
173
174         return NULL;
175 }
176
177 /*
178  * rb tree support functions
179  */
180 #define RB_NONE         (2)
181 #define RB_EMPTY(root)  ((root)->rb_node == NULL)
182 #define ON_RB(node)     ((node)->rb_color != RB_NONE)
183 #define RB_CLEAR(node)  ((node)->rb_color = RB_NONE)
184 #define rb_entry_drq(node)      rb_entry((node), struct deadline_rq, rb_node)
185 #define DRQ_RB_ROOT(dd, drq)    (&(dd)->sort_list[rq_data_dir((drq)->request)])
186 #define rq_rb_key(rq)           (rq)->sector
187
188 static struct deadline_rq *
189 __deadline_add_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
190 {
191         struct rb_node **p = &DRQ_RB_ROOT(dd, drq)->rb_node;
192         struct rb_node *parent = NULL;
193         struct deadline_rq *__drq;
194
195         while (*p) {
196                 parent = *p;
197                 __drq = rb_entry_drq(parent);
198
199                 if (drq->rb_key < __drq->rb_key)
200                         p = &(*p)->rb_left;
201                 else if (drq->rb_key > __drq->rb_key)
202                         p = &(*p)->rb_right;
203                 else
204                         return __drq;
205         }
206
207         rb_link_node(&drq->rb_node, parent, p);
208         return NULL;
209 }
210
211 static void
212 deadline_add_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
213 {
214         struct deadline_rq *__alias;
215
216         drq->rb_key = rq_rb_key(drq->request);
217
218 retry:
219         __alias = __deadline_add_drq_rb(dd, drq);
220         if (!__alias) {
221                 rb_insert_color(&drq->rb_node, DRQ_RB_ROOT(dd, drq));
222                 return;
223         }
224
225         deadline_move_request(dd, __alias);
226         goto retry;
227 }
228
229 static inline void
230 deadline_del_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
231 {
232         const int data_dir = rq_data_dir(drq->request);
233
234         if (dd->next_drq[data_dir] == drq) {
235                 struct rb_node *rbnext = rb_next(&drq->rb_node);
236
237                 dd->next_drq[data_dir] = NULL;
238                 if (rbnext)
239                         dd->next_drq[data_dir] = rb_entry_drq(rbnext);
240         }
241
242         if (ON_RB(&drq->rb_node)) {
243                 rb_erase(&drq->rb_node, DRQ_RB_ROOT(dd, drq));
244                 RB_CLEAR(&drq->rb_node);
245         }
246 }
247
248 static struct request *
249 deadline_find_drq_rb(struct deadline_data *dd, sector_t sector, int data_dir)
250 {
251         struct rb_node *n = dd->sort_list[data_dir].rb_node;
252         struct deadline_rq *drq;
253
254         while (n) {
255                 drq = rb_entry_drq(n);
256
257                 if (sector < drq->rb_key)
258                         n = n->rb_left;
259                 else if (sector > drq->rb_key)
260                         n = n->rb_right;
261                 else
262                         return drq->request;
263         }
264
265         return NULL;
266 }
267
268 /*
269  * deadline_find_first_drq finds the first (lowest sector numbered) request
270  * for the specified data_dir. Used to sweep back to the start of the disk
271  * (1-way elevator) after we process the last (highest sector) request.
272  */
273 static struct deadline_rq *
274 deadline_find_first_drq(struct deadline_data *dd, int data_dir)
275 {
276         struct rb_node *n = dd->sort_list[data_dir].rb_node;
277
278         for (;;) {
279                 if (n->rb_left == NULL)
280                         return rb_entry_drq(n);
281                 
282                 n = n->rb_left;
283         }
284 }
285
286 /*
287  * add drq to rbtree and fifo
288  */
289 static inline void
290 deadline_add_request(struct request_queue *q, struct request *rq)
291 {
292         struct deadline_data *dd = q->elevator->elevator_data;
293         struct deadline_rq *drq = RQ_DATA(rq);
294
295         const int data_dir = rq_data_dir(drq->request);
296
297         deadline_add_drq_rb(dd, drq);
298         /*
299          * set expire time (only used for reads) and add to fifo list
300          */
301         drq->expires = jiffies + dd->fifo_expire[data_dir];
302         list_add_tail(&drq->fifo, &dd->fifo_list[data_dir]);
303
304         if (rq_mergeable(rq)) {
305                 deadline_add_drq_hash(dd, drq);
306
307                 if (!q->last_merge)
308                         q->last_merge = rq;
309         }
310 }
311
312 /*
313  * remove rq from rbtree, fifo, and hash
314  */
315 static void deadline_remove_request(request_queue_t *q, struct request *rq)
316 {
317         struct deadline_rq *drq = RQ_DATA(rq);
318
319         if (drq) {
320                 struct deadline_data *dd = q->elevator->elevator_data;
321
322                 list_del_init(&drq->fifo);
323                 deadline_remove_merge_hints(q, drq);
324                 deadline_del_drq_rb(dd, drq);
325         }
326 }
327
328 static int
329 deadline_merge(request_queue_t *q, struct request **req, struct bio *bio)
330 {
331         struct deadline_data *dd = q->elevator->elevator_data;
332         struct request *__rq;
333         int ret;
334
335         /*
336          * try last_merge to avoid going to hash
337          */
338         ret = elv_try_last_merge(q, bio);
339         if (ret != ELEVATOR_NO_MERGE) {
340                 __rq = q->last_merge;
341                 goto out_insert;
342         }
343
344         /*
345          * see if the merge hash can satisfy a back merge
346          */
347         __rq = deadline_find_drq_hash(dd, bio->bi_sector);
348         if (__rq) {
349                 BUG_ON(__rq->sector + __rq->nr_sectors != bio->bi_sector);
350
351                 if (elv_rq_merge_ok(__rq, bio)) {
352                         ret = ELEVATOR_BACK_MERGE;
353                         goto out;
354                 }
355         }
356
357         /*
358          * check for front merge
359          */
360         if (dd->front_merges) {
361                 sector_t rb_key = bio->bi_sector + bio_sectors(bio);
362
363                 __rq = deadline_find_drq_rb(dd, rb_key, bio_data_dir(bio));
364                 if (__rq) {
365                         BUG_ON(rb_key != rq_rb_key(__rq));
366
367                         if (elv_rq_merge_ok(__rq, bio)) {
368                                 ret = ELEVATOR_FRONT_MERGE;
369                                 goto out;
370                         }
371                 }
372         }
373
374         return ELEVATOR_NO_MERGE;
375 out:
376         q->last_merge = __rq;
377 out_insert:
378         if (ret)
379                 deadline_hot_drq_hash(dd, RQ_DATA(__rq));
380         *req = __rq;
381         return ret;
382 }
383
384 static void deadline_merged_request(request_queue_t *q, struct request *req)
385 {
386         struct deadline_data *dd = q->elevator->elevator_data;
387         struct deadline_rq *drq = RQ_DATA(req);
388
389         /*
390          * hash always needs to be repositioned, key is end sector
391          */
392         deadline_del_drq_hash(drq);
393         deadline_add_drq_hash(dd, drq);
394
395         /*
396          * if the merge was a front merge, we need to reposition request
397          */
398         if (rq_rb_key(req) != drq->rb_key) {
399                 deadline_del_drq_rb(dd, drq);
400                 deadline_add_drq_rb(dd, drq);
401         }
402
403         q->last_merge = req;
404 }
405
406 static void
407 deadline_merged_requests(request_queue_t *q, struct request *req,
408                          struct request *next)
409 {
410         struct deadline_data *dd = q->elevator->elevator_data;
411         struct deadline_rq *drq = RQ_DATA(req);
412         struct deadline_rq *dnext = RQ_DATA(next);
413
414         BUG_ON(!drq);
415         BUG_ON(!dnext);
416
417         /*
418          * reposition drq (this is the merged request) in hash, and in rbtree
419          * in case of a front merge
420          */
421         deadline_del_drq_hash(drq);
422         deadline_add_drq_hash(dd, drq);
423
424         if (rq_rb_key(req) != drq->rb_key) {
425                 deadline_del_drq_rb(dd, drq);
426                 deadline_add_drq_rb(dd, drq);
427         }
428
429         /*
430          * if dnext expires before drq, assign its expire time to drq
431          * and move into dnext position (dnext will be deleted) in fifo
432          */
433         if (!list_empty(&drq->fifo) && !list_empty(&dnext->fifo)) {
434                 if (time_before(dnext->expires, drq->expires)) {
435                         list_move(&drq->fifo, &dnext->fifo);
436                         drq->expires = dnext->expires;
437                 }
438         }
439
440         /*
441          * kill knowledge of next, this one is a goner
442          */
443         deadline_remove_request(q, next);
444 }
445
446 /*
447  * move request from sort list to dispatch queue.
448  */
449 static inline void
450 deadline_move_to_dispatch(struct deadline_data *dd, struct deadline_rq *drq)
451 {
452         request_queue_t *q = drq->request->q;
453
454         deadline_remove_request(q, drq->request);
455         list_add_tail(&drq->request->queuelist, dd->dispatch);
456 }
457
458 /*
459  * move an entry to dispatch queue
460  */
461 static void
462 deadline_move_request(struct deadline_data *dd, struct deadline_rq *drq)
463 {
464         const int data_dir = rq_data_dir(drq->request);
465         struct rb_node *rbnext = rb_next(&drq->rb_node);
466
467         dd->next_drq[READ] = NULL;
468         dd->next_drq[WRITE] = NULL;
469
470         if (rbnext)
471                 dd->next_drq[data_dir] = rb_entry_drq(rbnext);
472         
473         dd->last_sector = drq->request->sector + drq->request->nr_sectors;
474
475         /*
476          * take it off the sort and fifo list, move
477          * to dispatch queue
478          */
479         deadline_move_to_dispatch(dd, drq);
480 }
481
482 #define list_entry_fifo(ptr)    list_entry((ptr), struct deadline_rq, fifo)
483
484 /*
485  * deadline_check_fifo returns 0 if there are no expired reads on the fifo,
486  * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
487  */
488 static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
489 {
490         struct deadline_rq *drq = list_entry_fifo(dd->fifo_list[ddir].next);
491
492         /*
493          * drq is expired!
494          */
495         if (time_after(jiffies, drq->expires))
496                 return 1;
497
498         return 0;
499 }
500
501 /*
502  * deadline_dispatch_requests selects the best request according to
503  * read/write expire, fifo_batch, etc
504  */
505 static int deadline_dispatch_requests(struct deadline_data *dd)
506 {
507         const int reads = !list_empty(&dd->fifo_list[READ]);
508         const int writes = !list_empty(&dd->fifo_list[WRITE]);
509         struct deadline_rq *drq;
510         int data_dir, other_dir;
511
512         /*
513          * batches are currently reads XOR writes
514          */
515         drq = NULL;
516
517         if (dd->next_drq[READ])
518                 drq = dd->next_drq[READ];
519
520         if (dd->next_drq[WRITE])
521                 drq = dd->next_drq[WRITE];
522
523         if (drq) {
524                 /* we have a "next request" */
525                 
526                 if (dd->last_sector != drq->request->sector)
527                         /* end the batch on a non sequential request */
528                         dd->batching += dd->fifo_batch;
529                 
530                 if (dd->batching < dd->fifo_batch)
531                         /* we are still entitled to batch */
532                         goto dispatch_request;
533         }
534
535         /*
536          * at this point we are not running a batch. select the appropriate
537          * data direction (read / write)
538          */
539
540         if (reads) {
541                 BUG_ON(RB_EMPTY(&dd->sort_list[READ]));
542
543                 if (writes && (dd->starved++ >= dd->writes_starved))
544                         goto dispatch_writes;
545
546                 data_dir = READ;
547                 other_dir = WRITE;
548
549                 goto dispatch_find_request;
550         }
551
552         /*
553          * there are either no reads or writes have been starved
554          */
555
556         if (writes) {
557 dispatch_writes:
558                 BUG_ON(RB_EMPTY(&dd->sort_list[WRITE]));
559
560                 dd->starved = 0;
561
562                 data_dir = WRITE;
563                 other_dir = READ;
564
565                 goto dispatch_find_request;
566         }
567
568         return 0;
569
570 dispatch_find_request:
571         /*
572          * we are not running a batch, find best request for selected data_dir
573          */
574         if (deadline_check_fifo(dd, data_dir)) {
575                 /* An expired request exists - satisfy it */
576                 dd->batching = 0;
577                 drq = list_entry_fifo(dd->fifo_list[data_dir].next);
578                 
579         } else if (dd->next_drq[data_dir]) {
580                 /*
581                  * The last req was the same dir and we have a next request in
582                  * sort order. No expired requests so continue on from here.
583                  */
584                 drq = dd->next_drq[data_dir];
585         } else {
586                 /*
587                  * The last req was the other direction or we have run out of
588                  * higher-sectored requests. Go back to the lowest sectored
589                  * request (1 way elevator) and start a new batch.
590                  */
591                 dd->batching = 0;
592                 drq = deadline_find_first_drq(dd, data_dir);
593         }
594
595 dispatch_request:
596         /*
597          * drq is the selected appropriate request.
598          */
599         dd->batching++;
600         deadline_move_request(dd, drq);
601
602         return 1;
603 }
604
605 static struct request *deadline_next_request(request_queue_t *q)
606 {
607         struct deadline_data *dd = q->elevator->elevator_data;
608         struct request *rq;
609
610         /*
611          * if there are still requests on the dispatch queue, grab the first one
612          */
613         if (!list_empty(dd->dispatch)) {
614 dispatch:
615                 rq = list_entry_rq(dd->dispatch->next);
616                 return rq;
617         }
618
619         if (deadline_dispatch_requests(dd))
620                 goto dispatch;
621
622         return NULL;
623 }
624
625 static void
626 deadline_insert_request(request_queue_t *q, struct request *rq, int where)
627 {
628         struct deadline_data *dd = q->elevator->elevator_data;
629
630         /* barriers must flush the reorder queue */
631         if (unlikely(rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)
632                         && where == ELEVATOR_INSERT_SORT))
633                 where = ELEVATOR_INSERT_BACK;
634
635         switch (where) {
636                 case ELEVATOR_INSERT_BACK:
637                         while (deadline_dispatch_requests(dd))
638                                 ;
639                         list_add_tail(&rq->queuelist, dd->dispatch);
640                         break;
641                 case ELEVATOR_INSERT_FRONT:
642                         list_add(&rq->queuelist, dd->dispatch);
643                         break;
644                 case ELEVATOR_INSERT_SORT:
645                         BUG_ON(!blk_fs_request(rq));
646                         deadline_add_request(q, rq);
647                         break;
648                 default:
649                         printk("%s: bad insert point %d\n", __FUNCTION__,where);
650                         return;
651         }
652 }
653
654 static int deadline_queue_empty(request_queue_t *q)
655 {
656         struct deadline_data *dd = q->elevator->elevator_data;
657
658         if (!list_empty(&dd->fifo_list[WRITE])
659             || !list_empty(&dd->fifo_list[READ])
660             || !list_empty(dd->dispatch))
661                 return 0;
662
663         return 1;
664 }
665
666 static struct request *
667 deadline_former_request(request_queue_t *q, struct request *rq)
668 {
669         struct deadline_rq *drq = RQ_DATA(rq);
670         struct rb_node *rbprev = rb_prev(&drq->rb_node);
671
672         if (rbprev)
673                 return rb_entry_drq(rbprev)->request;
674
675         return NULL;
676 }
677
678 static struct request *
679 deadline_latter_request(request_queue_t *q, struct request *rq)
680 {
681         struct deadline_rq *drq = RQ_DATA(rq);
682         struct rb_node *rbnext = rb_next(&drq->rb_node);
683
684         if (rbnext)
685                 return rb_entry_drq(rbnext)->request;
686
687         return NULL;
688 }
689
690 static void deadline_exit_queue(elevator_t *e)
691 {
692         struct deadline_data *dd = e->elevator_data;
693
694         BUG_ON(!list_empty(&dd->fifo_list[READ]));
695         BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
696
697         mempool_destroy(dd->drq_pool);
698         kfree(dd->hash);
699         kfree(dd);
700 }
701
702 /*
703  * initialize elevator private data (deadline_data), and alloc a drq for
704  * each request on the free lists
705  */
706 static int deadline_init_queue(request_queue_t *q, elevator_t *e)
707 {
708         struct deadline_data *dd;
709         int i;
710
711         if (!drq_pool)
712                 return -ENOMEM;
713
714         dd = kmalloc(sizeof(*dd), GFP_KERNEL);
715         if (!dd)
716                 return -ENOMEM;
717         memset(dd, 0, sizeof(*dd));
718
719         dd->hash = kmalloc(sizeof(struct list_head)*DL_HASH_ENTRIES,GFP_KERNEL);
720         if (!dd->hash) {
721                 kfree(dd);
722                 return -ENOMEM;
723         }
724
725         dd->drq_pool = mempool_create(BLKDEV_MIN_RQ, mempool_alloc_slab, mempool_free_slab, drq_pool);
726         if (!dd->drq_pool) {
727                 kfree(dd->hash);
728                 kfree(dd);
729                 return -ENOMEM;
730         }
731
732         for (i = 0; i < DL_HASH_ENTRIES; i++)
733                 INIT_LIST_HEAD(&dd->hash[i]);
734
735         INIT_LIST_HEAD(&dd->fifo_list[READ]);
736         INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
737         dd->sort_list[READ] = RB_ROOT;
738         dd->sort_list[WRITE] = RB_ROOT;
739         dd->dispatch = &q->queue_head;
740         dd->fifo_expire[READ] = read_expire;
741         dd->fifo_expire[WRITE] = write_expire;
742         dd->writes_starved = writes_starved;
743         dd->front_merges = 1;
744         dd->fifo_batch = fifo_batch;
745         e->elevator_data = dd;
746         return 0;
747 }
748
749 static void deadline_put_request(request_queue_t *q, struct request *rq)
750 {
751         struct deadline_data *dd = q->elevator->elevator_data;
752         struct deadline_rq *drq = RQ_DATA(rq);
753
754         if (drq) {
755                 mempool_free(drq, dd->drq_pool);
756                 rq->elevator_private = NULL;
757         }
758 }
759
760 static int
761 deadline_set_request(request_queue_t *q, struct request *rq, int gfp_mask)
762 {
763         struct deadline_data *dd = q->elevator->elevator_data;
764         struct deadline_rq *drq;
765
766         drq = mempool_alloc(dd->drq_pool, gfp_mask);
767         if (drq) {
768                 memset(drq, 0, sizeof(*drq));
769                 RB_CLEAR(&drq->rb_node);
770                 drq->request = rq;
771
772                 INIT_LIST_HEAD(&drq->hash);
773                 drq->on_hash = 0;
774
775                 INIT_LIST_HEAD(&drq->fifo);
776
777                 rq->elevator_private = drq;
778                 return 0;
779         }
780
781         return 1;
782 }
783
784 /*
785  * sysfs parts below
786  */
787 struct deadline_fs_entry {
788         struct attribute attr;
789         ssize_t (*show)(struct deadline_data *, char *);
790         ssize_t (*store)(struct deadline_data *, const char *, size_t);
791 };
792
793 static ssize_t
794 deadline_var_show(int var, char *page)
795 {
796         return sprintf(page, "%d\n", var);
797 }
798
799 static ssize_t
800 deadline_var_store(int *var, const char *page, size_t count)
801 {
802         char *p = (char *) page;
803
804         *var = simple_strtol(p, &p, 10);
805         return count;
806 }
807
808 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
809 static ssize_t __FUNC(struct deadline_data *dd, char *page)             \
810 {                                                                       \
811         int __data = __VAR;                                     \
812         if (__CONV)                                                     \
813                 __data = jiffies_to_msecs(__data);                      \
814         return deadline_var_show(__data, (page));                       \
815 }
816 SHOW_FUNCTION(deadline_readexpire_show, dd->fifo_expire[READ], 1);
817 SHOW_FUNCTION(deadline_writeexpire_show, dd->fifo_expire[WRITE], 1);
818 SHOW_FUNCTION(deadline_writesstarved_show, dd->writes_starved, 0);
819 SHOW_FUNCTION(deadline_frontmerges_show, dd->front_merges, 0);
820 SHOW_FUNCTION(deadline_fifobatch_show, dd->fifo_batch, 0);
821 #undef SHOW_FUNCTION
822
823 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
824 static ssize_t __FUNC(struct deadline_data *dd, const char *page, size_t count) \
825 {                                                                       \
826         int __data;                                                     \
827         int ret = deadline_var_store(&__data, (page), count);           \
828         if (__data < (MIN))                                             \
829                 __data = (MIN);                                         \
830         else if (__data > (MAX))                                        \
831                 __data = (MAX);                                         \
832         if (__CONV)                                                     \
833                 *(__PTR) = msecs_to_jiffies(__data);                    \
834         else                                                            \
835                 *(__PTR) = __data;                                      \
836         return ret;                                                     \
837 }
838 STORE_FUNCTION(deadline_readexpire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
839 STORE_FUNCTION(deadline_writeexpire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
840 STORE_FUNCTION(deadline_writesstarved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
841 STORE_FUNCTION(deadline_frontmerges_store, &dd->front_merges, 0, 1, 0);
842 STORE_FUNCTION(deadline_fifobatch_store, &dd->fifo_batch, 0, INT_MAX, 0);
843 #undef STORE_FUNCTION
844
845 static struct deadline_fs_entry deadline_readexpire_entry = {
846         .attr = {.name = "read_expire", .mode = S_IRUGO | S_IWUSR },
847         .show = deadline_readexpire_show,
848         .store = deadline_readexpire_store,
849 };
850 static struct deadline_fs_entry deadline_writeexpire_entry = {
851         .attr = {.name = "write_expire", .mode = S_IRUGO | S_IWUSR },
852         .show = deadline_writeexpire_show,
853         .store = deadline_writeexpire_store,
854 };
855 static struct deadline_fs_entry deadline_writesstarved_entry = {
856         .attr = {.name = "writes_starved", .mode = S_IRUGO | S_IWUSR },
857         .show = deadline_writesstarved_show,
858         .store = deadline_writesstarved_store,
859 };
860 static struct deadline_fs_entry deadline_frontmerges_entry = {
861         .attr = {.name = "front_merges", .mode = S_IRUGO | S_IWUSR },
862         .show = deadline_frontmerges_show,
863         .store = deadline_frontmerges_store,
864 };
865 static struct deadline_fs_entry deadline_fifobatch_entry = {
866         .attr = {.name = "fifo_batch", .mode = S_IRUGO | S_IWUSR },
867         .show = deadline_fifobatch_show,
868         .store = deadline_fifobatch_store,
869 };
870
871 static struct attribute *default_attrs[] = {
872         &deadline_readexpire_entry.attr,
873         &deadline_writeexpire_entry.attr,
874         &deadline_writesstarved_entry.attr,
875         &deadline_frontmerges_entry.attr,
876         &deadline_fifobatch_entry.attr,
877         NULL,
878 };
879
880 #define to_deadline(atr) container_of((atr), struct deadline_fs_entry, attr)
881
882 static ssize_t
883 deadline_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
884 {
885         elevator_t *e = container_of(kobj, elevator_t, kobj);
886         struct deadline_fs_entry *entry = to_deadline(attr);
887
888         if (!entry->show)
889                 return 0;
890
891         return entry->show(e->elevator_data, page);
892 }
893
894 static ssize_t
895 deadline_attr_store(struct kobject *kobj, struct attribute *attr,
896                     const char *page, size_t length)
897 {
898         elevator_t *e = container_of(kobj, elevator_t, kobj);
899         struct deadline_fs_entry *entry = to_deadline(attr);
900
901         if (!entry->store)
902                 return -EINVAL;
903
904         return entry->store(e->elevator_data, page, length);
905 }
906
907 static struct sysfs_ops deadline_sysfs_ops = {
908         .show   = deadline_attr_show,
909         .store  = deadline_attr_store,
910 };
911
912 static struct kobj_type deadline_ktype = {
913         .sysfs_ops      = &deadline_sysfs_ops,
914         .default_attrs  = default_attrs,
915 };
916
917 static struct elevator_type iosched_deadline = {
918         .ops = {
919                 .elevator_merge_fn =            deadline_merge,
920                 .elevator_merged_fn =           deadline_merged_request,
921                 .elevator_merge_req_fn =        deadline_merged_requests,
922                 .elevator_next_req_fn =         deadline_next_request,
923                 .elevator_add_req_fn =          deadline_insert_request,
924                 .elevator_remove_req_fn =       deadline_remove_request,
925                 .elevator_queue_empty_fn =      deadline_queue_empty,
926                 .elevator_former_req_fn =       deadline_former_request,
927                 .elevator_latter_req_fn =       deadline_latter_request,
928                 .elevator_set_req_fn =          deadline_set_request,
929                 .elevator_put_req_fn =          deadline_put_request,
930                 .elevator_init_fn =             deadline_init_queue,
931                 .elevator_exit_fn =             deadline_exit_queue,
932         },
933
934         .elevator_ktype = &deadline_ktype,
935         .elevator_name = "deadline",
936         .elevator_owner = THIS_MODULE,
937 };
938
939 static int __init deadline_init(void)
940 {
941         int ret;
942
943         drq_pool = kmem_cache_create("deadline_drq", sizeof(struct deadline_rq),
944                                      0, 0, NULL, NULL);
945
946         if (!drq_pool)
947                 return -ENOMEM;
948
949         ret = elv_register(&iosched_deadline);
950         if (ret)
951                 kmem_cache_destroy(drq_pool);
952
953         return ret;
954 }
955
956 static void __exit deadline_exit(void)
957 {
958         kmem_cache_destroy(drq_pool);
959         elv_unregister(&iosched_deadline);
960 }
961
962 module_init(deadline_init);
963 module_exit(deadline_exit);
964
965 MODULE_AUTHOR("Jens Axboe");
966 MODULE_LICENSE("GPL");
967 MODULE_DESCRIPTION("deadline IO scheduler");