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[PATCH] Update cfq io scheduler to time sliced design
[linux-2.6/x86.git] / drivers / block / cfq-iosched.c
blob35f6e569d5e5373636d40a0103db513a9a6d63c6
1 /*
2 * linux/drivers/block/cfq-iosched.c
3 *
4 * CFQ, or complete fairness queueing, disk scheduler.
5 *
6 * Based on ideas from a previously unfinished io
7 * scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
8 *
9 * Copyright (C) 2003 Jens Axboe <axboe@suse.de>
10 */
11 #include <linux/kernel.h>
12 #include <linux/fs.h>
13 #include <linux/blkdev.h>
14 #include <linux/elevator.h>
15 #include <linux/bio.h>
16 #include <linux/config.h>
17 #include <linux/module.h>
18 #include <linux/slab.h>
19 #include <linux/init.h>
20 #include <linux/compiler.h>
21 #include <linux/hash.h>
22 #include <linux/rbtree.h>
23 #include <linux/mempool.h>
24 #include <linux/ioprio.h>
25 #include <linux/writeback.h>
26
27 /*
28 * tunables
29 */
30 static int cfq_quantum = 4; /* max queue in one round of service */
31 static int cfq_queued = 8; /* minimum rq allocate limit per-queue*/
32 static int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
33 static int cfq_back_max = 16 * 1024; /* maximum backwards seek, in KiB */
34 static int cfq_back_penalty = 2; /* penalty of a backwards seek */
35
36 static int cfq_slice_sync = HZ / 10;
37 static int cfq_slice_async = HZ / 50;
38 static int cfq_slice_async_rq = 2;
39 static int cfq_slice_idle = HZ / 50;
40
41 #define CFQ_IDLE_GRACE (HZ / 10)
42 #define CFQ_SLICE_SCALE (5)
43
44 #define CFQ_KEY_ASYNC (0)
45
46 /*
47 * disable queueing at the driver/hardware level
48 */
49 static int cfq_max_depth = 1;
50
51 /*
52 * for the hash of cfqq inside the cfqd
53 */
54 #define CFQ_QHASH_SHIFT 6
55 #define CFQ_QHASH_ENTRIES (1 << CFQ_QHASH_SHIFT)
56 #define list_entry_qhash(entry) hlist_entry((entry), struct cfq_queue, cfq_hash)
57
58 /*
59 * for the hash of crq inside the cfqq
60 */
61 #define CFQ_MHASH_SHIFT 6
62 #define CFQ_MHASH_BLOCK(sec) ((sec) >> 3)
63 #define CFQ_MHASH_ENTRIES (1 << CFQ_MHASH_SHIFT)
64 #define CFQ_MHASH_FN(sec) hash_long(CFQ_MHASH_BLOCK(sec), CFQ_MHASH_SHIFT)
65 #define rq_hash_key(rq) ((rq)->sector + (rq)->nr_sectors)
66 #define list_entry_hash(ptr) hlist_entry((ptr), struct cfq_rq, hash)
67
68 #define list_entry_cfqq(ptr) list_entry((ptr), struct cfq_queue, cfq_list)
69 #define list_entry_fifo(ptr) list_entry((ptr), struct request, queuelist)
70
71 #define RQ_DATA(rq) (rq)->elevator_private
72
73 /*
74 * rb-tree defines
75 */
76 #define RB_NONE (2)
77 #define RB_EMPTY(node) ((node)->rb_node == NULL)
78 #define RB_CLEAR_COLOR(node) (node)->rb_color = RB_NONE
79 #define RB_CLEAR(node) do { \
80 (node)->rb_parent = NULL; \
81 RB_CLEAR_COLOR((node)); \
82 (node)->rb_right = NULL; \
83 (node)->rb_left = NULL; \
84 } while (0)
85 #define RB_CLEAR_ROOT(root) ((root)->rb_node = NULL)
86 #define ON_RB(node) ((node)->rb_color != RB_NONE)
87 #define rb_entry_crq(node) rb_entry((node), struct cfq_rq, rb_node)
88 #define rq_rb_key(rq) (rq)->sector
89
90 static kmem_cache_t *crq_pool;
91 static kmem_cache_t *cfq_pool;
92 static kmem_cache_t *cfq_ioc_pool;
93
94 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
95 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
96 #define cfq_class_be(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_BE)
97 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
98
99 #define cfq_cfqq_sync(cfqq) ((cfqq)->key != CFQ_KEY_ASYNC)
100
101 /*
102 * Per block device queue structure
103 */
104 struct cfq_data {
105 atomic_t ref;
106 request_queue_t *queue;
107
108 /*
109 * rr list of queues with requests and the count of them
110 */
111 struct list_head rr_list[CFQ_PRIO_LISTS];
112 struct list_head busy_rr;
113 struct list_head cur_rr;
114 struct list_head idle_rr;
115 unsigned int busy_queues;
116
117 /*
118 * non-ordered list of empty cfqq's
119 */
120 struct list_head empty_list;
121
122 /*
123 * cfqq lookup hash
124 */
125 struct hlist_head *cfq_hash;
126
127 /*
128 * global crq hash for all queues
129 */
130 struct hlist_head *crq_hash;
131
132 unsigned int max_queued;
133
134 mempool_t *crq_pool;
135
136 int rq_in_driver;
137
138 /*
139 * schedule slice state info
140 */
141 /*
142 * idle window management
143 */
144 struct timer_list idle_slice_timer;
145 struct work_struct unplug_work;
146
147 struct cfq_queue *active_queue;
148 struct cfq_io_context *active_cic;
149 int cur_prio, cur_end_prio;
150 unsigned int dispatch_slice;
151
152 struct timer_list idle_class_timer;
153
154 sector_t last_sector;
155 unsigned long last_end_request;
156
157 unsigned int rq_starved;
158
159 /*
160 * tunables, see top of file
161 */
162 unsigned int cfq_quantum;
163 unsigned int cfq_queued;
164 unsigned int cfq_fifo_expire[2];
165 unsigned int cfq_back_penalty;
166 unsigned int cfq_back_max;
167 unsigned int cfq_slice[2];
168 unsigned int cfq_slice_async_rq;
169 unsigned int cfq_slice_idle;
170 unsigned int cfq_max_depth;
171 };
172
173 /*
174 * Per process-grouping structure
175 */
176 struct cfq_queue {
177 /* reference count */
178 atomic_t ref;
179 /* parent cfq_data */
180 struct cfq_data *cfqd;
181 /* cfqq lookup hash */
182 struct hlist_node cfq_hash;
183 /* hash key */
184 unsigned int key;
185 /* on either rr or empty list of cfqd */
186 struct list_head cfq_list;
187 /* sorted list of pending requests */
188 struct rb_root sort_list;
189 /* if fifo isn't expired, next request to serve */
190 struct cfq_rq *next_crq;
191 /* requests queued in sort_list */
192 int queued[2];
193 /* currently allocated requests */
194 int allocated[2];
195 /* fifo list of requests in sort_list */
196 struct list_head fifo;
197
198 unsigned long slice_start;
199 unsigned long slice_end;
200 unsigned long slice_left;
201 unsigned long service_last;
202
203 /* number of requests that have been handed to the driver */
204 int in_flight;
205
206 /* io prio of this group */
207 unsigned short ioprio, org_ioprio;
208 unsigned short ioprio_class, org_ioprio_class;
209
210 /* whether queue is on rr (or empty) list */
211 unsigned on_rr : 1;
212 /* idle slice, waiting for new request submission */
213 unsigned wait_request : 1;
214 /* set when wait_request gets set, reset on first rq alloc */
215 unsigned must_alloc : 1;
216 /* only gets one must_alloc per slice */
217 unsigned must_alloc_slice : 1;
218 /* idle slice, request added, now waiting to dispatch it */
219 unsigned must_dispatch : 1;
220 /* fifo expire per-slice */
221 unsigned fifo_expire : 1;
222
223 unsigned idle_window : 1;
224 unsigned prio_changed : 1;
225 };
226
227 struct cfq_rq {
228 struct rb_node rb_node;
229 sector_t rb_key;
230 struct request *request;
231 struct hlist_node hash;
232
233 struct cfq_queue *cfq_queue;
234 struct cfq_io_context *io_context;
235
236 unsigned in_flight : 1;
237 unsigned accounted : 1;
238 unsigned is_sync : 1;
239 unsigned requeued : 1;
240 };
241
242 static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int);
243 static void cfq_dispatch_sort(request_queue_t *, struct cfq_rq *);
244 static void cfq_put_cfqd(struct cfq_data *cfqd);
245
246 #define process_sync(tsk) ((tsk)->flags & PF_SYNCWRITE)
247
248 /*
249 * lots of deadline iosched dupes, can be abstracted later...
250 */
251 static inline void cfq_del_crq_hash(struct cfq_rq *crq)
252 {
253 hlist_del_init(&crq->hash);
254 }
255
256 static void cfq_remove_merge_hints(request_queue_t *q, struct cfq_rq *crq)
257 {
258 cfq_del_crq_hash(crq);
259
260 if (q->last_merge == crq->request)
261 q->last_merge = NULL;
262 }
263
264 static inline void cfq_add_crq_hash(struct cfq_data *cfqd, struct cfq_rq *crq)
265 {
266 const int hash_idx = CFQ_MHASH_FN(rq_hash_key(crq->request));
267
268 hlist_add_head(&crq->hash, &cfqd->crq_hash[hash_idx]);
269 }
270
271 static struct request *cfq_find_rq_hash(struct cfq_data *cfqd, sector_t offset)
272 {
273 struct hlist_head *hash_list = &cfqd->crq_hash[CFQ_MHASH_FN(offset)];
274 struct hlist_node *entry, *next;
275
276 hlist_for_each_safe(entry, next, hash_list) {
277 struct cfq_rq *crq = list_entry_hash(entry);
278 struct request *__rq = crq->request;
279
280 if (!rq_mergeable(__rq)) {
281 cfq_del_crq_hash(crq);
282 continue;
283 }
284
285 if (rq_hash_key(__rq) == offset)
286 return __rq;
287 }
288
289 return NULL;
290 }
291
292 /*
293 * Lifted from AS - choose which of crq1 and crq2 that is best served now.
294 * We choose the request that is closest to the head right now. Distance
295 * behind the head are penalized and only allowed to a certain extent.
296 */
297 static struct cfq_rq *
298 cfq_choose_req(struct cfq_data *cfqd, struct cfq_rq *crq1, struct cfq_rq *crq2)
299 {
300 sector_t last, s1, s2, d1 = 0, d2 = 0;
301 int r1_wrap = 0, r2_wrap = 0; /* requests are behind the disk head */
302 unsigned long back_max;
303
304 if (crq1 == NULL || crq1 == crq2)
305 return crq2;
306 if (crq2 == NULL)
307 return crq1;
308 if (crq1->requeued)
309 return crq1;
310 if (crq2->requeued)
311 return crq2;
312
313 s1 = crq1->request->sector;
314 s2 = crq2->request->sector;
315
316 last = cfqd->last_sector;
317
318 /*
319 * by definition, 1KiB is 2 sectors
320 */
321 back_max = cfqd->cfq_back_max * 2;
322
323 /*
324 * Strict one way elevator _except_ in the case where we allow
325 * short backward seeks which are biased as twice the cost of a
326 * similar forward seek.
327 */
328 if (s1 >= last)
329 d1 = s1 - last;
330 else if (s1 + back_max >= last)
331 d1 = (last - s1) * cfqd->cfq_back_penalty;
332 else
333 r1_wrap = 1;
334
335 if (s2 >= last)
336 d2 = s2 - last;
337 else if (s2 + back_max >= last)
338 d2 = (last - s2) * cfqd->cfq_back_penalty;
339 else
340 r2_wrap = 1;
341
342 /* Found required data */
343 if (!r1_wrap && r2_wrap)
344 return crq1;
345 else if (!r2_wrap && r1_wrap)
346 return crq2;
347 else if (r1_wrap && r2_wrap) {
348 /* both behind the head */
349 if (s1 <= s2)
350 return crq1;
351 else
352 return crq2;
353 }
354
355 /* Both requests in front of the head */
356 if (d1 < d2)
357 return crq1;
358 else if (d2 < d1)
359 return crq2;
360 else {
361 if (s1 >= s2)
362 return crq1;
363 else
364 return crq2;
365 }
366 }
367
368 /*
369 * would be nice to take fifo expire time into account as well
370 */
371 static struct cfq_rq *
372 cfq_find_next_crq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
373 struct cfq_rq *last)
374 {
375 struct cfq_rq *crq_next = NULL, *crq_prev = NULL;
376 struct rb_node *rbnext, *rbprev;
377
378 if (ON_RB(&last->rb_node))
379 rbnext = rb_next(&last->rb_node);
380 else {
381 rbnext = rb_first(&cfqq->sort_list);
382 if (rbnext == &last->rb_node)
383 rbnext = NULL;
384 }
385
386 rbprev = rb_prev(&last->rb_node);
387
388 if (rbprev)
389 crq_prev = rb_entry_crq(rbprev);
390 if (rbnext)
391 crq_next = rb_entry_crq(rbnext);
392
393 return cfq_choose_req(cfqd, crq_next, crq_prev);
394 }
395
396 static void cfq_update_next_crq(struct cfq_rq *crq)
397 {
398 struct cfq_queue *cfqq = crq->cfq_queue;
399
400 if (cfqq->next_crq == crq)
401 cfqq->next_crq = cfq_find_next_crq(cfqq->cfqd, cfqq, crq);
402 }
403
404 static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
405 {
406 struct cfq_data *cfqd = cfqq->cfqd;
407 struct list_head *list, *entry;
408
409 BUG_ON(!cfqq->on_rr);
410
411 list_del(&cfqq->cfq_list);
412
413 if (cfq_class_rt(cfqq))
414 list = &cfqd->cur_rr;
415 else if (cfq_class_idle(cfqq))
416 list = &cfqd->idle_rr;
417 else {
418 /*
419 * if cfqq has requests in flight, don't allow it to be
420 * found in cfq_set_active_queue before it has finished them.
421 * this is done to increase fairness between a process that
422 * has lots of io pending vs one that only generates one
423 * sporadically or synchronously
424 */
425 if (cfqq->in_flight)
426 list = &cfqd->busy_rr;
427 else
428 list = &cfqd->rr_list[cfqq->ioprio];
429 }
430
431 /*
432 * if queue was preempted, just add to front to be fair. busy_rr
433 * isn't sorted.
434 */
435 if (preempted || list == &cfqd->busy_rr) {
436 list_add(&cfqq->cfq_list, list);
437 return;
438 }
439
440 /*
441 * sort by when queue was last serviced
442 */
443 entry = list;
444 while ((entry = entry->prev) != list) {
445 struct cfq_queue *__cfqq = list_entry_cfqq(entry);
446
447 if (!__cfqq->service_last)
448 break;
449 if (time_before(__cfqq->service_last, cfqq->service_last))
450 break;
451 }
452
453 list_add(&cfqq->cfq_list, entry);
454 }
455
456 /*
457 * add to busy list of queues for service, trying to be fair in ordering
458 * the pending list according to last request service
459 */
460 static inline void
461 cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq, int requeue)
462 {
463 BUG_ON(cfqq->on_rr);
464 cfqq->on_rr = 1;
465 cfqd->busy_queues++;
466
467 cfq_resort_rr_list(cfqq, requeue);
468 }
469
470 static inline void
471 cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
472 {
473 BUG_ON(!cfqq->on_rr);
474 cfqq->on_rr = 0;
475 list_move(&cfqq->cfq_list, &cfqd->empty_list);
476
477 BUG_ON(!cfqd->busy_queues);
478 cfqd->busy_queues--;
479 }
480
481 /*
482 * rb tree support functions
483 */
484 static inline void cfq_del_crq_rb(struct cfq_rq *crq)
485 {
486 struct cfq_queue *cfqq = crq->cfq_queue;
487
488 if (ON_RB(&crq->rb_node)) {
489 struct cfq_data *cfqd = cfqq->cfqd;
490 const int sync = crq->is_sync;
491
492 BUG_ON(!cfqq->queued[sync]);
493 cfqq->queued[sync]--;
494
495 cfq_update_next_crq(crq);
496
497 rb_erase(&crq->rb_node, &cfqq->sort_list);
498 RB_CLEAR_COLOR(&crq->rb_node);
499
500 if (cfqq->on_rr && RB_EMPTY(&cfqq->sort_list))
501 cfq_del_cfqq_rr(cfqd, cfqq);
502 }
503 }
504
505 static struct cfq_rq *
506 __cfq_add_crq_rb(struct cfq_rq *crq)
507 {
508 struct rb_node **p = &crq->cfq_queue->sort_list.rb_node;
509 struct rb_node *parent = NULL;
510 struct cfq_rq *__crq;
511
512 while (*p) {
513 parent = *p;
514 __crq = rb_entry_crq(parent);
515
516 if (crq->rb_key < __crq->rb_key)
517 p = &(*p)->rb_left;
518 else if (crq->rb_key > __crq->rb_key)
519 p = &(*p)->rb_right;
520 else
521 return __crq;
522 }
523
524 rb_link_node(&crq->rb_node, parent, p);
525 return NULL;
526 }
527
528 static void cfq_add_crq_rb(struct cfq_rq *crq)
529 {
530 struct cfq_queue *cfqq = crq->cfq_queue;
531 struct cfq_data *cfqd = cfqq->cfqd;
532 struct request *rq = crq->request;
533 struct cfq_rq *__alias;
534
535 crq->rb_key = rq_rb_key(rq);
536 cfqq->queued[crq->is_sync]++;
537
538 /*
539 * looks a little odd, but the first insert might return an alias.
540 * if that happens, put the alias on the dispatch list
541 */
542 while ((__alias = __cfq_add_crq_rb(crq)) != NULL)
543 cfq_dispatch_sort(cfqd->queue, __alias);
544
545 rb_insert_color(&crq->rb_node, &cfqq->sort_list);
546
547 if (!cfqq->on_rr)
548 cfq_add_cfqq_rr(cfqd, cfqq, crq->requeued);
549
550 /*
551 * check if this request is a better next-serve candidate
552 */
553 cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
554 }
555
556 static inline void
557 cfq_reposition_crq_rb(struct cfq_queue *cfqq, struct cfq_rq *crq)
558 {
559 if (ON_RB(&crq->rb_node)) {
560 rb_erase(&crq->rb_node, &cfqq->sort_list);
561 cfqq->queued[crq->is_sync]--;
562 }
563
564 cfq_add_crq_rb(crq);
565 }
566
567 static struct request *cfq_find_rq_rb(struct cfq_data *cfqd, sector_t sector)
568
569 {
570 struct cfq_queue *cfqq = cfq_find_cfq_hash(cfqd, current->pid);
571 struct rb_node *n;
572
573 if (!cfqq)
574 goto out;
575
576 n = cfqq->sort_list.rb_node;
577 while (n) {
578 struct cfq_rq *crq = rb_entry_crq(n);
579
580 if (sector < crq->rb_key)
581 n = n->rb_left;
582 else if (sector > crq->rb_key)
583 n = n->rb_right;
584 else
585 return crq->request;
586 }
587
588 out:
589 return NULL;
590 }
591
592 static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
593 {
594 struct cfq_data *cfqd = q->elevator->elevator_data;
595 struct cfq_rq *crq = RQ_DATA(rq);
596
597 if (crq) {
598 struct cfq_queue *cfqq = crq->cfq_queue;
599
600 if (crq->accounted) {
601 crq->accounted = 0;
602 WARN_ON(!cfqd->rq_in_driver);
603 cfqd->rq_in_driver--;
604 }
605 if (crq->in_flight) {
606 crq->in_flight = 0;
607 WARN_ON(!cfqq->in_flight);
608 cfqq->in_flight--;
609 }
610 crq->requeued = 1;
611 }
612 }
613
614 /*
615 * make sure the service time gets corrected on reissue of this request
616 */
617 static void cfq_requeue_request(request_queue_t *q, struct request *rq)
618 {
619 cfq_deactivate_request(q, rq);
620 list_add(&rq->queuelist, &q->queue_head);
621 }
622
623 static void cfq_remove_request(request_queue_t *q, struct request *rq)
624 {
625 struct cfq_rq *crq = RQ_DATA(rq);
626
627 if (crq) {
628 list_del_init(&rq->queuelist);
629 cfq_del_crq_rb(crq);
630 cfq_remove_merge_hints(q, crq);
631
632 }
633 }
634
635 static int
636 cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
637 {
638 struct cfq_data *cfqd = q->elevator->elevator_data;
639 struct request *__rq;
640 int ret;
641
642 ret = elv_try_last_merge(q, bio);
643 if (ret != ELEVATOR_NO_MERGE) {
644 __rq = q->last_merge;
645 goto out_insert;
646 }
647
648 __rq = cfq_find_rq_hash(cfqd, bio->bi_sector);
649 if (__rq && elv_rq_merge_ok(__rq, bio)) {
650 ret = ELEVATOR_BACK_MERGE;
651 goto out;
652 }
653
654 __rq = cfq_find_rq_rb(cfqd, bio->bi_sector + bio_sectors(bio));
655 if (__rq && elv_rq_merge_ok(__rq, bio)) {
656 ret = ELEVATOR_FRONT_MERGE;
657 goto out;
658 }
659
660 return ELEVATOR_NO_MERGE;
661 out:
662 q->last_merge = __rq;
663 out_insert:
664 *req = __rq;
665 return ret;
666 }
667
668 static void cfq_merged_request(request_queue_t *q, struct request *req)
669 {
670 struct cfq_data *cfqd = q->elevator->elevator_data;
671 struct cfq_rq *crq = RQ_DATA(req);
672
673 cfq_del_crq_hash(crq);
674 cfq_add_crq_hash(cfqd, crq);
675
676 if (ON_RB(&crq->rb_node) && (rq_rb_key(req) != crq->rb_key)) {
677 struct cfq_queue *cfqq = crq->cfq_queue;
678
679 cfq_update_next_crq(crq);
680 cfq_reposition_crq_rb(cfqq, crq);
681 }
682
683 q->last_merge = req;
684 }
685
686 static void
687 cfq_merged_requests(request_queue_t *q, struct request *rq,
688 struct request *next)
689 {
690 cfq_merged_request(q, rq);
691
692 /*
693 * reposition in fifo if next is older than rq
694 */
695 if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
696 time_before(next->start_time, rq->start_time))
697 list_move(&rq->queuelist, &next->queuelist);
698
699 cfq_remove_request(q, next);
700 }
701
702 static inline void
703 __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
704 {
705 if (cfqq) {
706 /*
707 * stop potential idle class queues waiting service
708 */
709 del_timer(&cfqd->idle_class_timer);
710
711 cfqq->slice_start = jiffies;
712 cfqq->slice_end = 0;
713 cfqq->slice_left = 0;
714 cfqq->must_alloc_slice = 0;
715 cfqq->fifo_expire = 0;
716 }
717
718 cfqd->active_queue = cfqq;
719 }
720
721 /*
722 * 0
723 * 0,1
724 * 0,1,2
725 * 0,1,2,3
726 * 0,1,2,3,4
727 * 0,1,2,3,4,5
728 * 0,1,2,3,4,5,6
729 * 0,1,2,3,4,5,6,7
730 */
731 static int cfq_get_next_prio_level(struct cfq_data *cfqd)
732 {
733 int prio, wrap;
734
735 prio = -1;
736 wrap = 0;
737 do {
738 int p;
739
740 for (p = cfqd->cur_prio; p <= cfqd->cur_end_prio; p++) {
741 if (!list_empty(&cfqd->rr_list[p])) {
742 prio = p;
743 break;
744 }
745 }
746
747 if (prio != -1)
748 break;
749 cfqd->cur_prio = 0;
750 if (++cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
751 cfqd->cur_end_prio = 0;
752 if (wrap)
753 break;
754 wrap = 1;
755 }
756 } while (1);
757
758 if (unlikely(prio == -1))
759 return -1;
760
761 BUG_ON(prio >= CFQ_PRIO_LISTS);
762
763 list_splice_init(&cfqd->rr_list[prio], &cfqd->cur_rr);
764
765 cfqd->cur_prio = prio + 1;
766 if (cfqd->cur_prio > cfqd->cur_end_prio) {
767 cfqd->cur_end_prio = cfqd->cur_prio;
768 cfqd->cur_prio = 0;
769 }
770 if (cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
771 cfqd->cur_prio = 0;
772 cfqd->cur_end_prio = 0;
773 }
774
775 return prio;
776 }
777
778 static void cfq_set_active_queue(struct cfq_data *cfqd)
779 {
780 struct cfq_queue *cfqq = NULL;
781
782 /*
783 * if current list is non-empty, grab first entry. if it is empty,
784 * get next prio level and grab first entry then if any are spliced
785 */
786 if (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1)
787 cfqq = list_entry_cfqq(cfqd->cur_rr.next);
788
789 /*
790 * if we have idle queues and no rt or be queues had pending
791 * requests, either allow immediate service if the grace period
792 * has passed or arm the idle grace timer
793 */
794 if (!cfqq && !list_empty(&cfqd->idle_rr)) {
795 unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE;
796
797 if (time_after_eq(jiffies, end))
798 cfqq = list_entry_cfqq(cfqd->idle_rr.next);
799 else
800 mod_timer(&cfqd->idle_class_timer, end);
801 }
802
803 __cfq_set_active_queue(cfqd, cfqq);
804 }
805
806 /*
807 * current cfqq expired its slice (or was too idle), select new one
808 */
809 static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted)
810 {
811 struct cfq_queue *cfqq = cfqd->active_queue;
812
813 if (cfqq) {
814 unsigned long now = jiffies;
815
816 if (cfqq->wait_request)
817 del_timer(&cfqd->idle_slice_timer);
818
819 if (!preempted && !cfqq->in_flight)
820 cfqq->service_last = now;
821
822 cfqq->must_dispatch = 0;
823 cfqq->wait_request = 0;
824
825 /*
826 * store what was left of this slice, if the queue idled out
827 * or was preempted
828 */
829 if (time_after(now, cfqq->slice_end))
830 cfqq->slice_left = now - cfqq->slice_end;
831 else
832 cfqq->slice_left = 0;
833
834 if (cfqq->on_rr)
835 cfq_resort_rr_list(cfqq, preempted);
836
837 cfqd->active_queue = NULL;
838
839 if (cfqd->active_cic) {
840 put_io_context(cfqd->active_cic->ioc);
841 cfqd->active_cic = NULL;
842 }
843 }
844
845 cfqd->dispatch_slice = 0;
846 }
847
848 static int cfq_arm_slice_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
849
850 {
851 WARN_ON(!RB_EMPTY(&cfqq->sort_list));
852 WARN_ON(cfqq != cfqd->active_queue);
853
854 /*
855 * idle is disabled, either manually or by past process history
856 */
857 if (!cfqd->cfq_slice_idle)
858 return 0;
859 if (!cfqq->idle_window)
860 return 0;
861 /*
862 * task has exited, don't wait
863 */
864 if (cfqd->active_cic && !cfqd->active_cic->ioc->task)
865 return 0;
866
867 cfqq->wait_request = 1;
868 cfqq->must_alloc = 1;
869
870 if (!timer_pending(&cfqd->idle_slice_timer)) {
871 unsigned long slice_left = cfqq->slice_end - 1;
872
873 cfqd->idle_slice_timer.expires = min(jiffies + cfqd->cfq_slice_idle, slice_left);
874 add_timer(&cfqd->idle_slice_timer);
875 }
876
877 return 1;
878 }
879
880 /*
881 * we dispatch cfqd->cfq_quantum requests in total from the rr_list queues,
882 * this function sector sorts the selected request to minimize seeks. we start
883 * at cfqd->last_sector, not 0.
884 */
885 static void cfq_dispatch_sort(request_queue_t *q, struct cfq_rq *crq)
886 {
887 struct cfq_data *cfqd = q->elevator->elevator_data;
888 struct cfq_queue *cfqq = crq->cfq_queue;
889 struct list_head *head = &q->queue_head, *entry = head;
890 struct request *__rq;
891 sector_t last;
892
893 list_del(&crq->request->queuelist);
894
895 last = cfqd->last_sector;
896 list_for_each_entry_reverse(__rq, head, queuelist) {
897 struct cfq_rq *__crq = RQ_DATA(__rq);
898
899 if (blk_barrier_rq(__rq))
900 break;
901 if (!blk_fs_request(__rq))
902 break;
903 if (__crq->requeued)
904 break;
905
906 if (__rq->sector <= crq->request->sector)
907 break;
908 if (__rq->sector > last && crq->request->sector < last) {
909 last = crq->request->sector + crq->request->nr_sectors;
910 break;
911 }
912 entry = &__rq->queuelist;
913 }
914
915 cfqd->last_sector = last;
916
917 cfqq->next_crq = cfq_find_next_crq(cfqd, cfqq, crq);
918
919 cfq_del_crq_rb(crq);
920 cfq_remove_merge_hints(q, crq);
921
922 crq->in_flight = 1;
923 crq->requeued = 0;
924 cfqq->in_flight++;
925 list_add_tail(&crq->request->queuelist, entry);
926 }
927
928 /*
929 * return expired entry, or NULL to just start from scratch in rbtree
930 */
931 static inline struct cfq_rq *cfq_check_fifo(struct cfq_queue *cfqq)
932 {
933 struct cfq_data *cfqd = cfqq->cfqd;
934 struct request *rq;
935 struct cfq_rq *crq;
936
937 if (cfqq->fifo_expire)
938 return NULL;
939
940 if (!list_empty(&cfqq->fifo)) {
941 int fifo = cfq_cfqq_sync(cfqq);
942
943 crq = RQ_DATA(list_entry_fifo(cfqq->fifo.next));
944 rq = crq->request;
945 if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) {
946 cfqq->fifo_expire = 1;
947 return crq;
948 }
949 }
950
951 return NULL;
952 }
953
954 /*
955 * Scale schedule slice based on io priority
956 */
957 static inline int
958 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
959 {
960 const int base_slice = cfqd->cfq_slice[cfq_cfqq_sync(cfqq)];
961
962 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
963
964 return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - cfqq->ioprio));
965 }
966
967 static inline void
968 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
969 {
970 cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
971 }
972
973 static inline int
974 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
975 {
976 const int base_rq = cfqd->cfq_slice_async_rq;
977
978 WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
979
980 return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
981 }
982
983 /*
984 * get next queue for service
985 */
986 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd, int force)
987 {
988 unsigned long now = jiffies;
989 struct cfq_queue *cfqq;
990
991 cfqq = cfqd->active_queue;
992 if (!cfqq)
993 goto new_queue;
994
995 /*
996 * slice has expired
997 */
998 if (!cfqq->must_dispatch && time_after(jiffies, cfqq->slice_end))
999 goto new_queue;
1000
1001 /*
1002 * if queue has requests, dispatch one. if not, check if
1003 * enough slice is left to wait for one
1004 */
1005 if (!RB_EMPTY(&cfqq->sort_list))
1006 goto keep_queue;
1007 else if (!force && cfq_cfqq_sync(cfqq) &&
1008 time_before(now, cfqq->slice_end)) {
1009 if (cfq_arm_slice_timer(cfqd, cfqq))
1010 return NULL;
1011 }
1012
1013 new_queue:
1014 cfq_slice_expired(cfqd, 0);
1015 cfq_set_active_queue(cfqd);
1016 keep_queue:
1017 return cfqd->active_queue;
1018 }
1019
1020 static int
1021 __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1022 int max_dispatch)
1023 {
1024 int dispatched = 0;
1025
1026 BUG_ON(RB_EMPTY(&cfqq->sort_list));
1027
1028 do {
1029 struct cfq_rq *crq;
1030
1031 /*
1032 * follow expired path, else get first next available
1033 */
1034 if ((crq = cfq_check_fifo(cfqq)) == NULL)
1035 crq = cfqq->next_crq;
1036
1037 /*
1038 * finally, insert request into driver dispatch list
1039 */
1040 cfq_dispatch_sort(cfqd->queue, crq);
1041
1042 cfqd->dispatch_slice++;
1043 dispatched++;
1044
1045 if (!cfqd->active_cic) {
1046 atomic_inc(&crq->io_context->ioc->refcount);
1047 cfqd->active_cic = crq->io_context;
1048 }
1049
1050 if (RB_EMPTY(&cfqq->sort_list))
1051 break;
1052
1053 } while (dispatched < max_dispatch);
1054
1055 /*
1056 * if slice end isn't set yet, set it. if at least one request was
1057 * sync, use the sync time slice value
1058 */
1059 if (!cfqq->slice_end)
1060 cfq_set_prio_slice(cfqd, cfqq);
1061
1062 /*
1063 * expire an async queue immediately if it has used up its slice. idle
1064 * queue always expire after 1 dispatch round.
1065 */
1066 if ((!cfq_cfqq_sync(cfqq) &&
1067 cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1068 cfq_class_idle(cfqq))
1069 cfq_slice_expired(cfqd, 0);
1070
1071 return dispatched;
1072 }
1073
1074 static int
1075 cfq_dispatch_requests(request_queue_t *q, int max_dispatch, int force)
1076 {
1077 struct cfq_data *cfqd = q->elevator->elevator_data;
1078 struct cfq_queue *cfqq;
1079
1080 if (!cfqd->busy_queues)
1081 return 0;
1082
1083 cfqq = cfq_select_queue(cfqd, force);
1084 if (cfqq) {
1085 cfqq->wait_request = 0;
1086 cfqq->must_dispatch = 0;
1087 del_timer(&cfqd->idle_slice_timer);
1088
1089 if (cfq_class_idle(cfqq))
1090 max_dispatch = 1;
1091
1092 return __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
1093 }
1094
1095 return 0;
1096 }
1097
1098 static inline void cfq_account_dispatch(struct cfq_rq *crq)
1099 {
1100 struct cfq_queue *cfqq = crq->cfq_queue;
1101 struct cfq_data *cfqd = cfqq->cfqd;
1102
1103 if (unlikely(!blk_fs_request(crq->request)))
1104 return;
1105
1106 /*
1107 * accounted bit is necessary since some drivers will call
1108 * elv_next_request() many times for the same request (eg ide)
1109 */
1110 if (crq->accounted)
1111 return;
1112
1113 crq->accounted = 1;
1114 cfqd->rq_in_driver++;
1115 }
1116
1117 static inline void
1118 cfq_account_completion(struct cfq_queue *cfqq, struct cfq_rq *crq)
1119 {
1120 struct cfq_data *cfqd = cfqq->cfqd;
1121 unsigned long now;
1122
1123 if (!crq->accounted)
1124 return;
1125
1126 now = jiffies;
1127
1128 WARN_ON(!cfqd->rq_in_driver);
1129 cfqd->rq_in_driver--;
1130
1131 if (!cfq_class_idle(cfqq))
1132 cfqd->last_end_request = now;
1133
1134 if (!cfqq->in_flight && cfqq->on_rr) {
1135 cfqq->service_last = now;
1136 cfq_resort_rr_list(cfqq, 0);
1137 }
1138
1139 if (crq->is_sync)
1140 crq->io_context->last_end_request = now;
1141 }
1142
1143 static struct request *cfq_next_request(request_queue_t *q)
1144 {
1145 struct cfq_data *cfqd = q->elevator->elevator_data;
1146 struct request *rq;
1147
1148 if (!list_empty(&q->queue_head)) {
1149 struct cfq_rq *crq;
1150 dispatch:
1151 rq = list_entry_rq(q->queue_head.next);
1152
1153 crq = RQ_DATA(rq);
1154 if (crq) {
1155 /*
1156 * if idle window is disabled, allow queue buildup
1157 */
1158 if (!crq->in_flight && !crq->cfq_queue->idle_window &&
1159 cfqd->rq_in_driver >= cfqd->cfq_max_depth)
1160 return NULL;
1161
1162 cfq_remove_merge_hints(q, crq);
1163 cfq_account_dispatch(crq);
1164 }
1165
1166 return rq;
1167 }
1168
1169 if (cfq_dispatch_requests(q, cfqd->cfq_quantum, 0))
1170 goto dispatch;
1171
1172 return NULL;
1173 }
1174
1175 /*
1176 * task holds one reference to the queue, dropped when task exits. each crq
1177 * in-flight on this queue also holds a reference, dropped when crq is freed.
1178 *
1179 * queue lock must be held here.
1180 */
1181 static void cfq_put_queue(struct cfq_queue *cfqq)
1182 {
1183 struct cfq_data *cfqd = cfqq->cfqd;
1184
1185 BUG_ON(atomic_read(&cfqq->ref) <= 0);
1186
1187 if (!atomic_dec_and_test(&cfqq->ref))
1188 return;
1189
1190 BUG_ON(rb_first(&cfqq->sort_list));
1191 BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1192 BUG_ON(cfqq->on_rr);
1193
1194 if (unlikely(cfqd->active_queue == cfqq)) {
1195 cfq_slice_expired(cfqd, 0);
1196 kblockd_schedule_work(&cfqd->unplug_work);
1197 }
1198
1199 cfq_put_cfqd(cfqq->cfqd);
1200
1201 /*
1202 * it's on the empty list and still hashed
1203 */
1204 list_del(&cfqq->cfq_list);
1205 hlist_del(&cfqq->cfq_hash);
1206 kmem_cache_free(cfq_pool, cfqq);
1207 }
1208
1209 static inline struct cfq_queue *
1210 __cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, const int hashval)
1211 {
1212 struct hlist_head *hash_list = &cfqd->cfq_hash[hashval];
1213 struct hlist_node *entry, *next;
1214
1215 hlist_for_each_safe(entry, next, hash_list) {
1216 struct cfq_queue *__cfqq = list_entry_qhash(entry);
1217
1218 if (__cfqq->key == key)
1219 return __cfqq;
1220 }
1221
1222 return NULL;
1223 }
1224
1225 static struct cfq_queue *
1226 cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key)
1227 {
1228 return __cfq_find_cfq_hash(cfqd, key, hash_long(key, CFQ_QHASH_SHIFT));
1229 }
1230
1231 static void cfq_free_io_context(struct cfq_io_context *cic)
1232 {
1233 struct cfq_io_context *__cic;
1234 struct list_head *entry, *next;
1235
1236 list_for_each_safe(entry, next, &cic->list) {
1237 __cic = list_entry(entry, struct cfq_io_context, list);
1238 kmem_cache_free(cfq_ioc_pool, __cic);
1239 }
1240
1241 kmem_cache_free(cfq_ioc_pool, cic);
1242 }
1243
1244 /*
1245 * Called with interrupts disabled
1246 */
1247 static void cfq_exit_single_io_context(struct cfq_io_context *cic)
1248 {
1249 struct cfq_data *cfqd = cic->cfqq->cfqd;
1250 request_queue_t *q = cfqd->queue;
1251
1252 WARN_ON(!irqs_disabled());
1253
1254 spin_lock(q->queue_lock);
1255
1256 if (unlikely(cic->cfqq == cfqd->active_queue)) {
1257 cfq_slice_expired(cfqd, 0);
1258 kblockd_schedule_work(&cfqd->unplug_work);
1259 }
1260
1261 cfq_put_queue(cic->cfqq);
1262 cic->cfqq = NULL;
1263 spin_unlock(q->queue_lock);
1264 }
1265
1266 /*
1267 * Another task may update the task cic list, if it is doing a queue lookup
1268 * on its behalf. cfq_cic_lock excludes such concurrent updates
1269 */
1270 static void cfq_exit_io_context(struct cfq_io_context *cic)
1271 {
1272 struct cfq_io_context *__cic;
1273 struct list_head *entry;
1274 unsigned long flags;
1275
1276 local_irq_save(flags);
1277
1278 /*
1279 * put the reference this task is holding to the various queues
1280 */
1281 list_for_each(entry, &cic->list) {
1282 __cic = list_entry(entry, struct cfq_io_context, list);
1283 cfq_exit_single_io_context(__cic);
1284 }
1285
1286 cfq_exit_single_io_context(cic);
1287 local_irq_restore(flags);
1288 }
1289
1290 static struct cfq_io_context *
1291 cfq_alloc_io_context(struct cfq_data *cfqd, int gfp_mask)
1292 {
1293 struct cfq_io_context *cic = kmem_cache_alloc(cfq_ioc_pool, gfp_mask);
1294
1295 if (cic) {
1296 INIT_LIST_HEAD(&cic->list);
1297 cic->cfqq = NULL;
1298 cic->key = NULL;
1299 cic->last_end_request = jiffies;
1300 cic->ttime_total = 0;
1301 cic->ttime_samples = 0;
1302 cic->ttime_mean = 0;
1303 cic->dtor = cfq_free_io_context;
1304 cic->exit = cfq_exit_io_context;
1305 }
1306
1307 return cic;
1308 }
1309
1310 static void cfq_init_prio_data(struct cfq_queue *cfqq)
1311 {
1312 struct task_struct *tsk = current;
1313 int ioprio_class;
1314
1315 if (!cfqq->prio_changed)
1316 return;
1317
1318 ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
1319 switch (ioprio_class) {
1320 default:
1321 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1322 case IOPRIO_CLASS_NONE:
1323 /*
1324 * no prio set, place us in the middle of the BE classes
1325 */
1326 cfqq->ioprio = task_nice_ioprio(tsk);
1327 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1328 break;
1329 case IOPRIO_CLASS_RT:
1330 cfqq->ioprio = task_ioprio(tsk);
1331 cfqq->ioprio_class = IOPRIO_CLASS_RT;
1332 break;
1333 case IOPRIO_CLASS_BE:
1334 cfqq->ioprio = task_ioprio(tsk);
1335 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1336 break;
1337 case IOPRIO_CLASS_IDLE:
1338 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1339 cfqq->ioprio = 7;
1340 cfqq->idle_window = 0;
1341 break;
1342 }
1343
1344 /*
1345 * keep track of original prio settings in case we have to temporarily
1346 * elevate the priority of this queue
1347 */
1348 cfqq->org_ioprio = cfqq->ioprio;
1349 cfqq->org_ioprio_class = cfqq->ioprio_class;
1350
1351 if (cfqq->on_rr)
1352 cfq_resort_rr_list(cfqq, 0);
1353
1354 cfqq->prio_changed = 0;
1355 }
1356
1357 static inline void changed_ioprio(struct cfq_queue *cfqq)
1358 {
1359 if (cfqq) {
1360 struct cfq_data *cfqd = cfqq->cfqd;
1361
1362 spin_lock(cfqd->queue->queue_lock);
1363 cfqq->prio_changed = 1;
1364 cfq_init_prio_data(cfqq);
1365 spin_unlock(cfqd->queue->queue_lock);
1366 }
1367 }
1368
1369 /*
1370 * callback from sys_ioprio_set, irqs are disabled
1371 */
1372 static int cfq_ioc_set_ioprio(struct io_context *ioc, unsigned int ioprio)
1373 {
1374 struct cfq_io_context *cic = ioc->cic;
1375
1376 changed_ioprio(cic->cfqq);
1377
1378 list_for_each_entry(cic, &cic->list, list)
1379 changed_ioprio(cic->cfqq);
1380
1381 return 0;
1382 }
1383
1384 static struct cfq_queue *
1385 cfq_get_queue(struct cfq_data *cfqd, unsigned int key, int gfp_mask)
1386 {
1387 const int hashval = hash_long(key, CFQ_QHASH_SHIFT);
1388 struct cfq_queue *cfqq, *new_cfqq = NULL;
1389
1390 retry:
1391 cfqq = __cfq_find_cfq_hash(cfqd, key, hashval);
1392
1393 if (!cfqq) {
1394 if (new_cfqq) {
1395 cfqq = new_cfqq;
1396 new_cfqq = NULL;
1397 } else if (gfp_mask & __GFP_WAIT) {
1398 spin_unlock_irq(cfqd->queue->queue_lock);
1399 new_cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
1400 spin_lock_irq(cfqd->queue->queue_lock);
1401 goto retry;
1402 } else {
1403 cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
1404 if (!cfqq)
1405 goto out;
1406 }
1407
1408 memset(cfqq, 0, sizeof(*cfqq));
1409
1410 INIT_HLIST_NODE(&cfqq->cfq_hash);
1411 INIT_LIST_HEAD(&cfqq->cfq_list);
1412 RB_CLEAR_ROOT(&cfqq->sort_list);
1413 INIT_LIST_HEAD(&cfqq->fifo);
1414
1415 cfqq->key = key;
1416 hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
1417 atomic_set(&cfqq->ref, 0);
1418 cfqq->cfqd = cfqd;
1419 atomic_inc(&cfqd->ref);
1420 cfqq->service_last = 0;
1421 /*
1422 * set ->slice_left to allow preemption for a new process
1423 */
1424 cfqq->slice_left = 2 * cfqd->cfq_slice_idle;
1425 cfqq->idle_window = 1;
1426 cfqq->ioprio = -1;
1427 cfqq->ioprio_class = -1;
1428 cfqq->prio_changed = 1;
1429 }
1430
1431 if (new_cfqq)
1432 kmem_cache_free(cfq_pool, new_cfqq);
1433
1434 atomic_inc(&cfqq->ref);
1435 out:
1436 WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
1437 return cfqq;
1438 }
1439
1440 /*
1441 * Setup general io context and cfq io context. There can be several cfq
1442 * io contexts per general io context, if this process is doing io to more
1443 * than one device managed by cfq. Note that caller is holding a reference to
1444 * cfqq, so we don't need to worry about it disappearing
1445 */
1446 static struct cfq_io_context *
1447 cfq_get_io_context(struct cfq_data *cfqd, pid_t pid, int gfp_mask)
1448 {
1449 struct io_context *ioc = NULL;
1450 struct cfq_io_context *cic;
1451
1452 might_sleep_if(gfp_mask & __GFP_WAIT);
1453
1454 ioc = get_io_context(gfp_mask);
1455 if (!ioc)
1456 return NULL;
1457
1458 if ((cic = ioc->cic) == NULL) {
1459 cic = cfq_alloc_io_context(cfqd, gfp_mask);
1460
1461 if (cic == NULL)
1462 goto err;
1463
1464 /*
1465 * manually increment generic io_context usage count, it
1466 * cannot go away since we are already holding one ref to it
1467 */
1468 ioc->cic = cic;
1469 ioc->set_ioprio = cfq_ioc_set_ioprio;
1470 cic->ioc = ioc;
1471 cic->key = cfqd;
1472 atomic_inc(&cfqd->ref);
1473 } else {
1474 struct cfq_io_context *__cic;
1475
1476 /*
1477 * the first cic on the list is actually the head itself
1478 */
1479 if (cic->key == cfqd)
1480 goto out;
1481
1482 /*
1483 * cic exists, check if we already are there. linear search
1484 * should be ok here, the list will usually not be more than
1485 * 1 or a few entries long
1486 */
1487 list_for_each_entry(__cic, &cic->list, list) {
1488 /*
1489 * this process is already holding a reference to
1490 * this queue, so no need to get one more
1491 */
1492 if (__cic->key == cfqd) {
1493 cic = __cic;
1494 goto out;
1495 }
1496 }
1497
1498 /*
1499 * nope, process doesn't have a cic assoicated with this
1500 * cfqq yet. get a new one and add to list
1501 */
1502 __cic = cfq_alloc_io_context(cfqd, gfp_mask);
1503 if (__cic == NULL)
1504 goto err;
1505
1506 __cic->ioc = ioc;
1507 __cic->key = cfqd;
1508 atomic_inc(&cfqd->ref);
1509 list_add(&__cic->list, &cic->list);
1510 cic = __cic;
1511 }
1512
1513 out:
1514 return cic;
1515 err:
1516 put_io_context(ioc);
1517 return NULL;
1518 }
1519
1520 static void
1521 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1522 {
1523 unsigned long elapsed, ttime;
1524
1525 /*
1526 * if this context already has stuff queued, thinktime is from
1527 * last queue not last end
1528 */
1529 #if 0
1530 if (time_after(cic->last_end_request, cic->last_queue))
1531 elapsed = jiffies - cic->last_end_request;
1532 else
1533 elapsed = jiffies - cic->last_queue;
1534 #else
1535 elapsed = jiffies - cic->last_end_request;
1536 #endif
1537
1538 ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1539
1540 cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1541 cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1542 cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1543 }
1544
1545 #define sample_valid(samples) ((samples) > 80)
1546
1547 /*
1548 * Disable idle window if the process thinks too long or seeks so much that
1549 * it doesn't matter
1550 */
1551 static void
1552 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1553 struct cfq_io_context *cic)
1554 {
1555 int enable_idle = cfqq->idle_window;
1556
1557 if (!cic->ioc->task || !cfqd->cfq_slice_idle)
1558 enable_idle = 0;
1559 else if (sample_valid(cic->ttime_samples)) {
1560 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1561 enable_idle = 0;
1562 else
1563 enable_idle = 1;
1564 }
1565
1566 cfqq->idle_window = enable_idle;
1567 }
1568
1569
1570 /*
1571 * Check if new_cfqq should preempt the currently active queue. Return 0 for
1572 * no or if we aren't sure, a 1 will cause a preempt.
1573 */
1574 static int
1575 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1576 struct cfq_rq *crq)
1577 {
1578 struct cfq_queue *cfqq = cfqd->active_queue;
1579
1580 if (cfq_class_idle(new_cfqq))
1581 return 0;
1582
1583 if (!cfqq)
1584 return 1;
1585
1586 if (cfq_class_idle(cfqq))
1587 return 1;
1588 if (!new_cfqq->wait_request)
1589 return 0;
1590 /*
1591 * if it doesn't have slice left, forget it
1592 */
1593 if (new_cfqq->slice_left < cfqd->cfq_slice_idle)
1594 return 0;
1595 if (crq->is_sync && !cfq_cfqq_sync(cfqq))
1596 return 1;
1597
1598 return 0;
1599 }
1600
1601 /*
1602 * cfqq preempts the active queue. if we allowed preempt with no slice left,
1603 * let it have half of its nominal slice.
1604 */
1605 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1606 {
1607 struct cfq_queue *__cfqq, *next;
1608
1609 list_for_each_entry_safe(__cfqq, next, &cfqd->cur_rr, cfq_list)
1610 cfq_resort_rr_list(__cfqq, 1);
1611
1612 if (!cfqq->slice_left)
1613 cfqq->slice_left = cfq_prio_to_slice(cfqd, cfqq) / 2;
1614
1615 cfqq->slice_end = cfqq->slice_left + jiffies;
1616 cfq_slice_expired(cfqd, 1);
1617 __cfq_set_active_queue(cfqd, cfqq);
1618 }
1619
1620 /*
1621 * should really be a ll_rw_blk.c helper
1622 */
1623 static void cfq_start_queueing(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1624 {
1625 request_queue_t *q = cfqd->queue;
1626
1627 if (!blk_queue_plugged(q))
1628 q->request_fn(q);
1629 else
1630 __generic_unplug_device(q);
1631 }
1632
1633 /*
1634 * Called when a new fs request (crq) is added (to cfqq). Check if there's
1635 * something we should do about it
1636 */
1637 static void
1638 cfq_crq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1639 struct cfq_rq *crq)
1640 {
1641 const int sync = crq->is_sync;
1642
1643 cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
1644
1645 if (sync) {
1646 struct cfq_io_context *cic = crq->io_context;
1647
1648 cfq_update_io_thinktime(cfqd, cic);
1649 cfq_update_idle_window(cfqd, cfqq, cic);
1650
1651 cic->last_queue = jiffies;
1652 }
1653
1654 if (cfqq == cfqd->active_queue) {
1655 /*
1656 * if we are waiting for a request for this queue, let it rip
1657 * immediately and flag that we must not expire this queue
1658 * just now
1659 */
1660 if (cfqq->wait_request) {
1661 cfqq->must_dispatch = 1;
1662 del_timer(&cfqd->idle_slice_timer);
1663 cfq_start_queueing(cfqd, cfqq);
1664 }
1665 } else if (cfq_should_preempt(cfqd, cfqq, crq)) {
1666 /*
1667 * not the active queue - expire current slice if it is
1668 * idle and has expired it's mean thinktime or this new queue
1669 * has some old slice time left and is of higher priority
1670 */
1671 cfq_preempt_queue(cfqd, cfqq);
1672 cfqq->must_dispatch = 1;
1673 cfq_start_queueing(cfqd, cfqq);
1674 }
1675 }
1676
1677 static void cfq_enqueue(struct cfq_data *cfqd, struct request *rq)
1678 {
1679 struct cfq_rq *crq = RQ_DATA(rq);
1680 struct cfq_queue *cfqq = crq->cfq_queue;
1681
1682 cfq_init_prio_data(cfqq);
1683
1684 cfq_add_crq_rb(crq);
1685
1686 list_add_tail(&rq->queuelist, &cfqq->fifo);
1687
1688 if (rq_mergeable(rq)) {
1689 cfq_add_crq_hash(cfqd, crq);
1690
1691 if (!cfqd->queue->last_merge)
1692 cfqd->queue->last_merge = rq;
1693 }
1694
1695 cfq_crq_enqueued(cfqd, cfqq, crq);
1696 }
1697
1698 static void
1699 cfq_insert_request(request_queue_t *q, struct request *rq, int where)
1700 {
1701 struct cfq_data *cfqd = q->elevator->elevator_data;
1702
1703 switch (where) {
1704 case ELEVATOR_INSERT_BACK:
1705 while (cfq_dispatch_requests(q, INT_MAX, 1))
1706 ;
1707 list_add_tail(&rq->queuelist, &q->queue_head);
1708 /*
1709 * If we were idling with pending requests on
1710 * inactive cfqqs, force dispatching will
1711 * remove the idle timer and the queue won't
1712 * be kicked by __make_request() afterward.
1713 * Kick it here.
1714 */
1715 kblockd_schedule_work(&cfqd->unplug_work);
1716 break;
1717 case ELEVATOR_INSERT_FRONT:
1718 list_add(&rq->queuelist, &q->queue_head);
1719 break;
1720 case ELEVATOR_INSERT_SORT:
1721 BUG_ON(!blk_fs_request(rq));
1722 cfq_enqueue(cfqd, rq);
1723 break;
1724 default:
1725 printk("%s: bad insert point %d\n", __FUNCTION__,where);
1726 return;
1727 }
1728 }
1729
1730 static inline int cfq_pending_requests(struct cfq_data *cfqd)
1731 {
1732 return !list_empty(&cfqd->queue->queue_head) || cfqd->busy_queues;
1733 }
1734
1735 static int cfq_queue_empty(request_queue_t *q)
1736 {
1737 struct cfq_data *cfqd = q->elevator->elevator_data;
1738
1739 return !cfq_pending_requests(cfqd);
1740 }
1741
1742 static void cfq_completed_request(request_queue_t *q, struct request *rq)
1743 {
1744 struct cfq_rq *crq = RQ_DATA(rq);
1745 struct cfq_queue *cfqq;
1746
1747 if (unlikely(!blk_fs_request(rq)))
1748 return;
1749
1750 cfqq = crq->cfq_queue;
1751
1752 if (crq->in_flight) {
1753 WARN_ON(!cfqq->in_flight);
1754 cfqq->in_flight--;
1755 }
1756
1757 cfq_account_completion(cfqq, crq);
1758 }
1759
1760 static struct request *
1761 cfq_former_request(request_queue_t *q, struct request *rq)
1762 {
1763 struct cfq_rq *crq = RQ_DATA(rq);
1764 struct rb_node *rbprev = rb_prev(&crq->rb_node);
1765
1766 if (rbprev)
1767 return rb_entry_crq(rbprev)->request;
1768
1769 return NULL;
1770 }
1771
1772 static struct request *
1773 cfq_latter_request(request_queue_t *q, struct request *rq)
1774 {
1775 struct cfq_rq *crq = RQ_DATA(rq);
1776 struct rb_node *rbnext = rb_next(&crq->rb_node);
1777
1778 if (rbnext)
1779 return rb_entry_crq(rbnext)->request;
1780
1781 return NULL;
1782 }
1783
1784 /*
1785 * we temporarily boost lower priority queues if they are holding fs exclusive
1786 * resources. they are boosted to normal prio (CLASS_BE/4)
1787 */
1788 static void cfq_prio_boost(struct cfq_queue *cfqq)
1789 {
1790 const int ioprio_class = cfqq->ioprio_class;
1791 const int ioprio = cfqq->ioprio;
1792
1793 if (has_fs_excl()) {
1794 /*
1795 * boost idle prio on transactions that would lock out other
1796 * users of the filesystem
1797 */
1798 if (cfq_class_idle(cfqq))
1799 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1800 if (cfqq->ioprio > IOPRIO_NORM)
1801 cfqq->ioprio = IOPRIO_NORM;
1802 } else {
1803 /*
1804 * check if we need to unboost the queue
1805 */
1806 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
1807 cfqq->ioprio_class = cfqq->org_ioprio_class;
1808 if (cfqq->ioprio != cfqq->org_ioprio)
1809 cfqq->ioprio = cfqq->org_ioprio;
1810 }
1811
1812 /*
1813 * refile between round-robin lists if we moved the priority class
1814 */
1815 if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio) &&
1816 cfqq->on_rr)
1817 cfq_resort_rr_list(cfqq, 0);
1818 }
1819
1820 static inline pid_t cfq_queue_pid(struct task_struct *task, int rw)
1821 {
1822 if (rw == READ || process_sync(task))
1823 return task->pid;
1824
1825 return CFQ_KEY_ASYNC;
1826 }
1827
1828 static inline int
1829 __cfq_may_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1830 struct task_struct *task, int rw)
1831 {
1832 if (cfqq->wait_request && cfqq->must_alloc)
1833 return ELV_MQUEUE_MUST;
1834
1835 return ELV_MQUEUE_MAY;
1836 #if 0
1837 if (!cfqq || task->flags & PF_MEMALLOC)
1838 return ELV_MQUEUE_MAY;
1839 if (!cfqq->allocated[rw] || cfqq->must_alloc) {
1840 if (cfqq->wait_request)
1841 return ELV_MQUEUE_MUST;
1842
1843 /*
1844 * only allow 1 ELV_MQUEUE_MUST per slice, otherwise we
1845 * can quickly flood the queue with writes from a single task
1846 */
1847 if (rw == READ || !cfqq->must_alloc_slice) {
1848 cfqq->must_alloc_slice = 1;
1849 return ELV_MQUEUE_MUST;
1850 }
1851
1852 return ELV_MQUEUE_MAY;
1853 }
1854 if (cfq_class_idle(cfqq))
1855 return ELV_MQUEUE_NO;
1856 if (cfqq->allocated[rw] >= cfqd->max_queued) {
1857 struct io_context *ioc = get_io_context(GFP_ATOMIC);
1858 int ret = ELV_MQUEUE_NO;
1859
1860 if (ioc && ioc->nr_batch_requests)
1861 ret = ELV_MQUEUE_MAY;
1862
1863 put_io_context(ioc);
1864 return ret;
1865 }
1866
1867 return ELV_MQUEUE_MAY;
1868 #endif
1869 }
1870
1871 static int cfq_may_queue(request_queue_t *q, int rw, struct bio *bio)
1872 {
1873 struct cfq_data *cfqd = q->elevator->elevator_data;
1874 struct task_struct *tsk = current;
1875 struct cfq_queue *cfqq;
1876
1877 /*
1878 * don't force setup of a queue from here, as a call to may_queue
1879 * does not necessarily imply that a request actually will be queued.
1880 * so just lookup a possibly existing queue, or return 'may queue'
1881 * if that fails
1882 */
1883 cfqq = cfq_find_cfq_hash(cfqd, cfq_queue_pid(tsk, rw));
1884 if (cfqq) {
1885 cfq_init_prio_data(cfqq);
1886 cfq_prio_boost(cfqq);
1887
1888 return __cfq_may_queue(cfqd, cfqq, tsk, rw);
1889 }
1890
1891 return ELV_MQUEUE_MAY;
1892 }
1893
1894 static void cfq_check_waiters(request_queue_t *q, struct cfq_queue *cfqq)
1895 {
1896 struct cfq_data *cfqd = q->elevator->elevator_data;
1897 struct request_list *rl = &q->rq;
1898
1899 if (cfqq->allocated[READ] <= cfqd->max_queued || cfqd->rq_starved) {
1900 smp_mb();
1901 if (waitqueue_active(&rl->wait[READ]))
1902 wake_up(&rl->wait[READ]);
1903 }
1904
1905 if (cfqq->allocated[WRITE] <= cfqd->max_queued || cfqd->rq_starved) {
1906 smp_mb();
1907 if (waitqueue_active(&rl->wait[WRITE]))
1908 wake_up(&rl->wait[WRITE]);
1909 }
1910 }
1911
1912 /*
1913 * queue lock held here
1914 */
1915 static void cfq_put_request(request_queue_t *q, struct request *rq)
1916 {
1917 struct cfq_data *cfqd = q->elevator->elevator_data;
1918 struct cfq_rq *crq = RQ_DATA(rq);
1919
1920 if (crq) {
1921 struct cfq_queue *cfqq = crq->cfq_queue;
1922 const int rw = rq_data_dir(rq);
1923
1924 BUG_ON(!cfqq->allocated[rw]);
1925 cfqq->allocated[rw]--;
1926
1927 put_io_context(crq->io_context->ioc);
1928
1929 mempool_free(crq, cfqd->crq_pool);
1930 rq->elevator_private = NULL;
1931
1932 cfq_check_waiters(q, cfqq);
1933 cfq_put_queue(cfqq);
1934 }
1935 }
1936
1937 /*
1938 * Allocate cfq data structures associated with this request.
1939 */
1940 static int
1941 cfq_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
1942 int gfp_mask)
1943 {
1944 struct cfq_data *cfqd = q->elevator->elevator_data;
1945 struct cfq_io_context *cic;
1946 const int rw = rq_data_dir(rq);
1947 struct cfq_queue *cfqq;
1948 struct cfq_rq *crq;
1949 unsigned long flags;
1950
1951 might_sleep_if(gfp_mask & __GFP_WAIT);
1952
1953 cic = cfq_get_io_context(cfqd, cfq_queue_pid(current, rw), gfp_mask);
1954
1955 spin_lock_irqsave(q->queue_lock, flags);
1956
1957 if (!cic)
1958 goto queue_fail;
1959
1960 if (!cic->cfqq) {
1961 cfqq = cfq_get_queue(cfqd, current->pid, gfp_mask);
1962 if (!cfqq)
1963 goto queue_fail;
1964
1965 cic->cfqq = cfqq;
1966 } else
1967 cfqq = cic->cfqq;
1968
1969 cfqq->allocated[rw]++;
1970 cfqq->must_alloc = 0;
1971 cfqd->rq_starved = 0;
1972 atomic_inc(&cfqq->ref);
1973 spin_unlock_irqrestore(q->queue_lock, flags);
1974
1975 crq = mempool_alloc(cfqd->crq_pool, gfp_mask);
1976 if (crq) {
1977 RB_CLEAR(&crq->rb_node);
1978 crq->rb_key = 0;
1979 crq->request = rq;
1980 INIT_HLIST_NODE(&crq->hash);
1981 crq->cfq_queue = cfqq;
1982 crq->io_context = cic;
1983 crq->in_flight = crq->accounted = 0;
1984 crq->is_sync = (rw == READ || process_sync(current));
1985 crq->requeued = 0;
1986 rq->elevator_private = crq;
1987 return 0;
1988 }
1989
1990 spin_lock_irqsave(q->queue_lock, flags);
1991 cfqq->allocated[rw]--;
1992 if (!(cfqq->allocated[0] + cfqq->allocated[1]))
1993 cfqq->must_alloc = 1;
1994 cfq_put_queue(cfqq);
1995 queue_fail:
1996 if (cic)
1997 put_io_context(cic->ioc);
1998 /*
1999 * mark us rq allocation starved. we need to kickstart the process
2000 * ourselves if there are no pending requests that can do it for us.
2001 * that would be an extremely rare OOM situation
2002 */
2003 cfqd->rq_starved = 1;
2004 kblockd_schedule_work(&cfqd->unplug_work);
2005 spin_unlock_irqrestore(q->queue_lock, flags);
2006 return 1;
2007 }
2008
2009 static void cfq_kick_queue(void *data)
2010 {
2011 request_queue_t *q = data;
2012 struct cfq_data *cfqd = q->elevator->elevator_data;
2013 unsigned long flags;
2014
2015 spin_lock_irqsave(q->queue_lock, flags);
2016
2017 if (cfqd->rq_starved) {
2018 struct request_list *rl = &q->rq;
2019
2020 /*
2021 * we aren't guaranteed to get a request after this, but we
2022 * have to be opportunistic
2023 */
2024 smp_mb();
2025 if (waitqueue_active(&rl->wait[READ]))
2026 wake_up(&rl->wait[READ]);
2027 if (waitqueue_active(&rl->wait[WRITE]))
2028 wake_up(&rl->wait[WRITE]);
2029 }
2030
2031 blk_remove_plug(q);
2032 q->request_fn(q);
2033 spin_unlock_irqrestore(q->queue_lock, flags);
2034 }
2035
2036 /*
2037 * Timer running if the active_queue is currently idling inside its time slice
2038 */
2039 static void cfq_idle_slice_timer(unsigned long data)
2040 {
2041 struct cfq_data *cfqd = (struct cfq_data *) data;
2042 struct cfq_queue *cfqq;
2043 unsigned long flags;
2044
2045 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2046
2047 if ((cfqq = cfqd->active_queue) != NULL) {
2048 unsigned long now = jiffies;
2049
2050 /*
2051 * expired
2052 */
2053 if (time_after(now, cfqq->slice_end))
2054 goto expire;
2055
2056 /*
2057 * only expire and reinvoke request handler, if there are
2058 * other queues with pending requests
2059 */
2060 if (!cfq_pending_requests(cfqd)) {
2061 cfqd->idle_slice_timer.expires = min(now + cfqd->cfq_slice_idle, cfqq->slice_end);
2062 add_timer(&cfqd->idle_slice_timer);
2063 goto out_cont;
2064 }
2065
2066 /*
2067 * not expired and it has a request pending, let it dispatch
2068 */
2069 if (!RB_EMPTY(&cfqq->sort_list)) {
2070 cfqq->must_dispatch = 1;
2071 goto out_kick;
2072 }
2073 }
2074 expire:
2075 cfq_slice_expired(cfqd, 0);
2076 out_kick:
2077 if (cfq_pending_requests(cfqd))
2078 kblockd_schedule_work(&cfqd->unplug_work);
2079 out_cont:
2080 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2081 }
2082
2083 /*
2084 * Timer running if an idle class queue is waiting for service
2085 */
2086 static void cfq_idle_class_timer(unsigned long data)
2087 {
2088 struct cfq_data *cfqd = (struct cfq_data *) data;
2089 unsigned long flags, end;
2090
2091 spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2092
2093 /*
2094 * race with a non-idle queue, reset timer
2095 */
2096 end = cfqd->last_end_request + CFQ_IDLE_GRACE;
2097 if (!time_after_eq(jiffies, end)) {
2098 cfqd->idle_class_timer.expires = end;
2099 add_timer(&cfqd->idle_class_timer);
2100 } else
2101 kblockd_schedule_work(&cfqd->unplug_work);
2102
2103 spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2104 }
2105
2106
2107 static void cfq_put_cfqd(struct cfq_data *cfqd)
2108 {
2109 request_queue_t *q = cfqd->queue;
2110
2111 if (!atomic_dec_and_test(&cfqd->ref))
2112 return;
2113
2114 blk_sync_queue(q);
2115
2116 blk_put_queue(q);
2117
2118 mempool_destroy(cfqd->crq_pool);
2119 kfree(cfqd->crq_hash);
2120 kfree(cfqd->cfq_hash);
2121 kfree(cfqd);
2122 }
2123
2124 static void cfq_exit_queue(elevator_t *e)
2125 {
2126 struct cfq_data *cfqd = e->elevator_data;
2127
2128 del_timer_sync(&cfqd->idle_slice_timer);
2129 del_timer_sync(&cfqd->idle_class_timer);
2130 cfq_put_cfqd(cfqd);
2131 }
2132
2133 static int cfq_init_queue(request_queue_t *q, elevator_t *e)
2134 {
2135 struct cfq_data *cfqd;
2136 int i;
2137
2138 cfqd = kmalloc(sizeof(*cfqd), GFP_KERNEL);
2139 if (!cfqd)
2140 return -ENOMEM;
2141
2142 memset(cfqd, 0, sizeof(*cfqd));
2143
2144 for (i = 0; i < CFQ_PRIO_LISTS; i++)
2145 INIT_LIST_HEAD(&cfqd->rr_list[i]);
2146
2147 INIT_LIST_HEAD(&cfqd->busy_rr);
2148 INIT_LIST_HEAD(&cfqd->cur_rr);
2149 INIT_LIST_HEAD(&cfqd->idle_rr);
2150 INIT_LIST_HEAD(&cfqd->empty_list);
2151
2152 cfqd->crq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_MHASH_ENTRIES, GFP_KERNEL);
2153 if (!cfqd->crq_hash)
2154 goto out_crqhash;
2155
2156 cfqd->cfq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL);
2157 if (!cfqd->cfq_hash)
2158 goto out_cfqhash;
2159
2160 cfqd->crq_pool = mempool_create(BLKDEV_MIN_RQ, mempool_alloc_slab, mempool_free_slab, crq_pool);
2161 if (!cfqd->crq_pool)
2162 goto out_crqpool;
2163
2164 for (i = 0; i < CFQ_MHASH_ENTRIES; i++)
2165 INIT_HLIST_HEAD(&cfqd->crq_hash[i]);
2166 for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
2167 INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
2168
2169 e->elevator_data = cfqd;
2170
2171 cfqd->queue = q;
2172 atomic_inc(&q->refcnt);
2173
2174 cfqd->max_queued = q->nr_requests / 4;
2175 q->nr_batching = cfq_queued;
2176
2177 init_timer(&cfqd->idle_slice_timer);
2178 cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2179 cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2180
2181 init_timer(&cfqd->idle_class_timer);
2182 cfqd->idle_class_timer.function = cfq_idle_class_timer;
2183 cfqd->idle_class_timer.data = (unsigned long) cfqd;
2184
2185 INIT_WORK(&cfqd->unplug_work, cfq_kick_queue, q);
2186
2187 atomic_set(&cfqd->ref, 1);
2188
2189 cfqd->cfq_queued = cfq_queued;
2190 cfqd->cfq_quantum = cfq_quantum;
2191 cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2192 cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2193 cfqd->cfq_back_max = cfq_back_max;
2194 cfqd->cfq_back_penalty = cfq_back_penalty;
2195 cfqd->cfq_slice[0] = cfq_slice_async;
2196 cfqd->cfq_slice[1] = cfq_slice_sync;
2197 cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2198 cfqd->cfq_slice_idle = cfq_slice_idle;
2199 cfqd->cfq_max_depth = cfq_max_depth;
2200 return 0;
2201 out_crqpool:
2202 kfree(cfqd->cfq_hash);
2203 out_cfqhash:
2204 kfree(cfqd->crq_hash);
2205 out_crqhash:
2206 kfree(cfqd);
2207 return -ENOMEM;
2208 }
2209
2210 static void cfq_slab_kill(void)
2211 {
2212 if (crq_pool)
2213 kmem_cache_destroy(crq_pool);
2214 if (cfq_pool)
2215 kmem_cache_destroy(cfq_pool);
2216 if (cfq_ioc_pool)
2217 kmem_cache_destroy(cfq_ioc_pool);
2218 }
2219
2220 static int __init cfq_slab_setup(void)
2221 {
2222 crq_pool = kmem_cache_create("crq_pool", sizeof(struct cfq_rq), 0, 0,
2223 NULL, NULL);
2224 if (!crq_pool)
2225 goto fail;
2226
2227 cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0,
2228 NULL, NULL);
2229 if (!cfq_pool)
2230 goto fail;
2231
2232 cfq_ioc_pool = kmem_cache_create("cfq_ioc_pool",
2233 sizeof(struct cfq_io_context), 0, 0, NULL, NULL);
2234 if (!cfq_ioc_pool)
2235 goto fail;
2236
2237 return 0;
2238 fail:
2239 cfq_slab_kill();
2240 return -ENOMEM;
2241 }
2242
2243 /*
2244 * sysfs parts below -->
2245 */
2246 struct cfq_fs_entry {
2247 struct attribute attr;
2248 ssize_t (*show)(struct cfq_data *, char *);
2249 ssize_t (*store)(struct cfq_data *, const char *, size_t);
2250 };
2251
2252 static ssize_t
2253 cfq_var_show(unsigned int var, char *page)
2254 {
2255 return sprintf(page, "%d\n", var);
2256 }
2257
2258 static ssize_t
2259 cfq_var_store(unsigned int *var, const char *page, size_t count)
2260 {
2261 char *p = (char *) page;
2262
2263 *var = simple_strtoul(p, &p, 10);
2264 return count;
2265 }
2266
2267 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
2268 static ssize_t __FUNC(struct cfq_data *cfqd, char *page) \
2269 { \
2270 unsigned int __data = __VAR; \
2271 if (__CONV) \
2272 __data = jiffies_to_msecs(__data); \
2273 return cfq_var_show(__data, (page)); \
2274 }
2275 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2276 SHOW_FUNCTION(cfq_queued_show, cfqd->cfq_queued, 0);
2277 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2278 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2279 SHOW_FUNCTION(cfq_back_max_show, cfqd->cfq_back_max, 0);
2280 SHOW_FUNCTION(cfq_back_penalty_show, cfqd->cfq_back_penalty, 0);
2281 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2282 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2283 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2284 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2285 SHOW_FUNCTION(cfq_max_depth_show, cfqd->cfq_max_depth, 0);
2286 #undef SHOW_FUNCTION
2287
2288 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
2289 static ssize_t __FUNC(struct cfq_data *cfqd, const char *page, size_t count) \
2290 { \
2291 unsigned int __data; \
2292 int ret = cfq_var_store(&__data, (page), count); \
2293 if (__data < (MIN)) \
2294 __data = (MIN); \
2295 else if (__data > (MAX)) \
2296 __data = (MAX); \
2297 if (__CONV) \
2298 *(__PTR) = msecs_to_jiffies(__data); \
2299 else \
2300 *(__PTR) = __data; \
2301 return ret; \
2302 }
2303 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2304 STORE_FUNCTION(cfq_queued_store, &cfqd->cfq_queued, 1, UINT_MAX, 0);
2305 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1);
2306 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1);
2307 STORE_FUNCTION(cfq_back_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2308 STORE_FUNCTION(cfq_back_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0);
2309 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2310 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2311 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2312 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0);
2313 STORE_FUNCTION(cfq_max_depth_store, &cfqd->cfq_max_depth, 1, UINT_MAX, 0);
2314 #undef STORE_FUNCTION
2315
2316 static struct cfq_fs_entry cfq_quantum_entry = {
2317 .attr = {.name = "quantum", .mode = S_IRUGO | S_IWUSR },
2318 .show = cfq_quantum_show,
2319 .store = cfq_quantum_store,
2320 };
2321 static struct cfq_fs_entry cfq_queued_entry = {
2322 .attr = {.name = "queued", .mode = S_IRUGO | S_IWUSR },
2323 .show = cfq_queued_show,
2324 .store = cfq_queued_store,
2325 };
2326 static struct cfq_fs_entry cfq_fifo_expire_sync_entry = {
2327 .attr = {.name = "fifo_expire_sync", .mode = S_IRUGO | S_IWUSR },
2328 .show = cfq_fifo_expire_sync_show,
2329 .store = cfq_fifo_expire_sync_store,
2330 };
2331 static struct cfq_fs_entry cfq_fifo_expire_async_entry = {
2332 .attr = {.name = "fifo_expire_async", .mode = S_IRUGO | S_IWUSR },
2333 .show = cfq_fifo_expire_async_show,
2334 .store = cfq_fifo_expire_async_store,
2335 };
2336 static struct cfq_fs_entry cfq_back_max_entry = {
2337 .attr = {.name = "back_seek_max", .mode = S_IRUGO | S_IWUSR },
2338 .show = cfq_back_max_show,
2339 .store = cfq_back_max_store,
2340 };
2341 static struct cfq_fs_entry cfq_back_penalty_entry = {
2342 .attr = {.name = "back_seek_penalty", .mode = S_IRUGO | S_IWUSR },
2343 .show = cfq_back_penalty_show,
2344 .store = cfq_back_penalty_store,
2345 };
2346 static struct cfq_fs_entry cfq_slice_sync_entry = {
2347 .attr = {.name = "slice_sync", .mode = S_IRUGO | S_IWUSR },
2348 .show = cfq_slice_sync_show,
2349 .store = cfq_slice_sync_store,
2350 };
2351 static struct cfq_fs_entry cfq_slice_async_entry = {
2352 .attr = {.name = "slice_async", .mode = S_IRUGO | S_IWUSR },
2353 .show = cfq_slice_async_show,
2354 .store = cfq_slice_async_store,
2355 };
2356 static struct cfq_fs_entry cfq_slice_async_rq_entry = {
2357 .attr = {.name = "slice_async_rq", .mode = S_IRUGO | S_IWUSR },
2358 .show = cfq_slice_async_rq_show,
2359 .store = cfq_slice_async_rq_store,
2360 };
2361 static struct cfq_fs_entry cfq_slice_idle_entry = {
2362 .attr = {.name = "slice_idle", .mode = S_IRUGO | S_IWUSR },
2363 .show = cfq_slice_idle_show,
2364 .store = cfq_slice_idle_store,
2365 };
2366 static struct cfq_fs_entry cfq_max_depth_entry = {
2367 .attr = {.name = "max_depth", .mode = S_IRUGO | S_IWUSR },
2368 .show = cfq_max_depth_show,
2369 .store = cfq_max_depth_store,
2370 };
2371 static struct attribute *default_attrs[] = {
2372 &cfq_quantum_entry.attr,
2373 &cfq_queued_entry.attr,
2374 &cfq_fifo_expire_sync_entry.attr,
2375 &cfq_fifo_expire_async_entry.attr,
2376 &cfq_back_max_entry.attr,
2377 &cfq_back_penalty_entry.attr,
2378 &cfq_slice_sync_entry.attr,
2379 &cfq_slice_async_entry.attr,
2380 &cfq_slice_async_rq_entry.attr,
2381 &cfq_slice_idle_entry.attr,
2382 &cfq_max_depth_entry.attr,
2383 NULL,
2384 };
2385
2386 #define to_cfq(atr) container_of((atr), struct cfq_fs_entry, attr)
2387
2388 static ssize_t
2389 cfq_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
2390 {
2391 elevator_t *e = container_of(kobj, elevator_t, kobj);
2392 struct cfq_fs_entry *entry = to_cfq(attr);
2393
2394 if (!entry->show)
2395 return -EIO;
2396
2397 return entry->show(e->elevator_data, page);
2398 }
2399
2400 static ssize_t
2401 cfq_attr_store(struct kobject *kobj, struct attribute *attr,
2402 const char *page, size_t length)
2403 {
2404 elevator_t *e = container_of(kobj, elevator_t, kobj);
2405 struct cfq_fs_entry *entry = to_cfq(attr);
2406
2407 if (!entry->store)
2408 return -EIO;
2409
2410 return entry->store(e->elevator_data, page, length);
2411 }
2412
2413 static struct sysfs_ops cfq_sysfs_ops = {
2414 .show = cfq_attr_show,
2415 .store = cfq_attr_store,
2416 };
2417
2418 static struct kobj_type cfq_ktype = {
2419 .sysfs_ops = &cfq_sysfs_ops,
2420 .default_attrs = default_attrs,
2421 };
2422
2423 static struct elevator_type iosched_cfq = {
2424 .ops = {
2425 .elevator_merge_fn = cfq_merge,
2426 .elevator_merged_fn = cfq_merged_request,
2427 .elevator_merge_req_fn = cfq_merged_requests,
2428 .elevator_next_req_fn = cfq_next_request,
2429 .elevator_add_req_fn = cfq_insert_request,
2430 .elevator_remove_req_fn = cfq_remove_request,
2431 .elevator_requeue_req_fn = cfq_requeue_request,
2432 .elevator_deactivate_req_fn = cfq_deactivate_request,
2433 .elevator_queue_empty_fn = cfq_queue_empty,
2434 .elevator_completed_req_fn = cfq_completed_request,
2435 .elevator_former_req_fn = cfq_former_request,
2436 .elevator_latter_req_fn = cfq_latter_request,
2437 .elevator_set_req_fn = cfq_set_request,
2438 .elevator_put_req_fn = cfq_put_request,
2439 .elevator_may_queue_fn = cfq_may_queue,
2440 .elevator_init_fn = cfq_init_queue,
2441 .elevator_exit_fn = cfq_exit_queue,
2442 },
2443 .elevator_ktype = &cfq_ktype,
2444 .elevator_name = "cfq",
2445 .elevator_owner = THIS_MODULE,
2446 };
2447
2448 static int __init cfq_init(void)
2449 {
2450 int ret;
2451
2452 /*
2453 * could be 0 on HZ < 1000 setups
2454 */
2455 if (!cfq_slice_async)
2456 cfq_slice_async = 1;
2457 if (!cfq_slice_idle)
2458 cfq_slice_idle = 1;
2459
2460 if (cfq_slab_setup())
2461 return -ENOMEM;
2462
2463 ret = elv_register(&iosched_cfq);
2464 if (ret)
2465 cfq_slab_kill();
2466
2467 return ret;
2468 }
2469
2470 static void __exit cfq_exit(void)
2471 {
2472 struct task_struct *g, *p;
2473 unsigned long flags;
2474
2475 read_lock_irqsave(&tasklist_lock, flags);
2476
2477 /*
2478 * iterate each process in the system, removing our io_context
2479 */
2480 do_each_thread(g, p) {
2481 struct io_context *ioc = p->io_context;
2482
2483 if (ioc && ioc->cic) {
2484 ioc->cic->exit(ioc->cic);
2485 cfq_free_io_context(ioc->cic);
2486 ioc->cic = NULL;
2487 }
2488 } while_each_thread(g, p);
2489
2490 read_unlock_irqrestore(&tasklist_lock, flags);
2491
2492 cfq_slab_kill();
2493 elv_unregister(&iosched_cfq);
2494 }
2495
2496 module_init(cfq_init);
2497 module_exit(cfq_exit);
2498
2499 MODULE_AUTHOR("Jens Axboe");
2500 MODULE_LICENSE("GPL");
2501 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");
x86 "subsystem" repository