[PATCH] [BLOCK] cfq-iosched: change cfq io context linking from list to tree
[linux-3.10.git] / block / cfq-iosched.c
1 /*
2  *  CFQ, or complete fairness queueing, disk scheduler.
3  *
4  *  Based on ideas from a previously unfinished io
5  *  scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
6  *
7  *  Copyright (C) 2003 Jens Axboe <axboe@suse.de>
8  */
9 #include <linux/config.h>
10 #include <linux/module.h>
11 #include <linux/blkdev.h>
12 #include <linux/elevator.h>
13 #include <linux/hash.h>
14 #include <linux/rbtree.h>
15 #include <linux/ioprio.h>
16
17 /*
18  * tunables
19  */
20 static const int cfq_quantum = 4;               /* max queue in one round of service */
21 static const int cfq_queued = 8;                /* minimum rq allocate limit per-queue*/
22 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
23 static const int cfq_back_max = 16 * 1024;      /* maximum backwards seek, in KiB */
24 static const int cfq_back_penalty = 2;          /* penalty of a backwards seek */
25
26 static const int cfq_slice_sync = HZ / 10;
27 static int cfq_slice_async = HZ / 25;
28 static const int cfq_slice_async_rq = 2;
29 static int cfq_slice_idle = HZ / 100;
30
31 #define CFQ_IDLE_GRACE          (HZ / 10)
32 #define CFQ_SLICE_SCALE         (5)
33
34 #define CFQ_KEY_ASYNC           (0)
35 #define CFQ_KEY_ANY             (0xffff)
36
37 /*
38  * disable queueing at the driver/hardware level
39  */
40 static const int cfq_max_depth = 2;
41
42 static DEFINE_RWLOCK(cfq_exit_lock);
43
44 /*
45  * for the hash of cfqq inside the cfqd
46  */
47 #define CFQ_QHASH_SHIFT         6
48 #define CFQ_QHASH_ENTRIES       (1 << CFQ_QHASH_SHIFT)
49 #define list_entry_qhash(entry) hlist_entry((entry), struct cfq_queue, cfq_hash)
50
51 /*
52  * for the hash of crq inside the cfqq
53  */
54 #define CFQ_MHASH_SHIFT         6
55 #define CFQ_MHASH_BLOCK(sec)    ((sec) >> 3)
56 #define CFQ_MHASH_ENTRIES       (1 << CFQ_MHASH_SHIFT)
57 #define CFQ_MHASH_FN(sec)       hash_long(CFQ_MHASH_BLOCK(sec), CFQ_MHASH_SHIFT)
58 #define rq_hash_key(rq)         ((rq)->sector + (rq)->nr_sectors)
59 #define list_entry_hash(ptr)    hlist_entry((ptr), struct cfq_rq, hash)
60
61 #define list_entry_cfqq(ptr)    list_entry((ptr), struct cfq_queue, cfq_list)
62 #define list_entry_fifo(ptr)    list_entry((ptr), struct request, queuelist)
63
64 #define RQ_DATA(rq)             (rq)->elevator_private
65
66 /*
67  * rb-tree defines
68  */
69 #define RB_NONE                 (2)
70 #define RB_EMPTY(node)          ((node)->rb_node == NULL)
71 #define RB_CLEAR_COLOR(node)    (node)->rb_color = RB_NONE
72 #define RB_CLEAR(node)          do {    \
73         (node)->rb_parent = NULL;       \
74         RB_CLEAR_COLOR((node));         \
75         (node)->rb_right = NULL;        \
76         (node)->rb_left = NULL;         \
77 } while (0)
78 #define RB_CLEAR_ROOT(root)     ((root)->rb_node = NULL)
79 #define rb_entry_crq(node)      rb_entry((node), struct cfq_rq, rb_node)
80 #define rq_rb_key(rq)           (rq)->sector
81
82 static kmem_cache_t *crq_pool;
83 static kmem_cache_t *cfq_pool;
84 static kmem_cache_t *cfq_ioc_pool;
85
86 static atomic_t ioc_count = ATOMIC_INIT(0);
87 static struct completion *ioc_gone;
88
89 #define CFQ_PRIO_LISTS          IOPRIO_BE_NR
90 #define cfq_class_idle(cfqq)    ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
91 #define cfq_class_be(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_BE)
92 #define cfq_class_rt(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
93
94 #define ASYNC                   (0)
95 #define SYNC                    (1)
96
97 #define cfq_cfqq_dispatched(cfqq)       \
98         ((cfqq)->on_dispatch[ASYNC] + (cfqq)->on_dispatch[SYNC])
99
100 #define cfq_cfqq_class_sync(cfqq)       ((cfqq)->key != CFQ_KEY_ASYNC)
101
102 #define cfq_cfqq_sync(cfqq)             \
103         (cfq_cfqq_class_sync(cfqq) || (cfqq)->on_dispatch[SYNC])
104
105 /*
106  * Per block device queue structure
107  */
108 struct cfq_data {
109         request_queue_t *queue;
110
111         /*
112          * rr list of queues with requests and the count of them
113          */
114         struct list_head rr_list[CFQ_PRIO_LISTS];
115         struct list_head busy_rr;
116         struct list_head cur_rr;
117         struct list_head idle_rr;
118         unsigned int busy_queues;
119
120         /*
121          * non-ordered list of empty cfqq's
122          */
123         struct list_head empty_list;
124
125         /*
126          * cfqq lookup hash
127          */
128         struct hlist_head *cfq_hash;
129
130         /*
131          * global crq hash for all queues
132          */
133         struct hlist_head *crq_hash;
134
135         unsigned int max_queued;
136
137         mempool_t *crq_pool;
138
139         int rq_in_driver;
140
141         /*
142          * schedule slice state info
143          */
144         /*
145          * idle window management
146          */
147         struct timer_list idle_slice_timer;
148         struct work_struct unplug_work;
149
150         struct cfq_queue *active_queue;
151         struct cfq_io_context *active_cic;
152         int cur_prio, cur_end_prio;
153         unsigned int dispatch_slice;
154
155         struct timer_list idle_class_timer;
156
157         sector_t last_sector;
158         unsigned long last_end_request;
159
160         unsigned int rq_starved;
161
162         /*
163          * tunables, see top of file
164          */
165         unsigned int cfq_quantum;
166         unsigned int cfq_queued;
167         unsigned int cfq_fifo_expire[2];
168         unsigned int cfq_back_penalty;
169         unsigned int cfq_back_max;
170         unsigned int cfq_slice[2];
171         unsigned int cfq_slice_async_rq;
172         unsigned int cfq_slice_idle;
173         unsigned int cfq_max_depth;
174
175         struct list_head cic_list;
176 };
177
178 /*
179  * Per process-grouping structure
180  */
181 struct cfq_queue {
182         /* reference count */
183         atomic_t ref;
184         /* parent cfq_data */
185         struct cfq_data *cfqd;
186         /* cfqq lookup hash */
187         struct hlist_node cfq_hash;
188         /* hash key */
189         unsigned int key;
190         /* on either rr or empty list of cfqd */
191         struct list_head cfq_list;
192         /* sorted list of pending requests */
193         struct rb_root sort_list;
194         /* if fifo isn't expired, next request to serve */
195         struct cfq_rq *next_crq;
196         /* requests queued in sort_list */
197         int queued[2];
198         /* currently allocated requests */
199         int allocated[2];
200         /* fifo list of requests in sort_list */
201         struct list_head fifo;
202
203         unsigned long slice_start;
204         unsigned long slice_end;
205         unsigned long slice_left;
206         unsigned long service_last;
207
208         /* number of requests that are on the dispatch list */
209         int on_dispatch[2];
210
211         /* io prio of this group */
212         unsigned short ioprio, org_ioprio;
213         unsigned short ioprio_class, org_ioprio_class;
214
215         /* various state flags, see below */
216         unsigned int flags;
217 };
218
219 struct cfq_rq {
220         struct rb_node rb_node;
221         sector_t rb_key;
222         struct request *request;
223         struct hlist_node hash;
224
225         struct cfq_queue *cfq_queue;
226         struct cfq_io_context *io_context;
227
228         unsigned int crq_flags;
229 };
230
231 enum cfqq_state_flags {
232         CFQ_CFQQ_FLAG_on_rr = 0,
233         CFQ_CFQQ_FLAG_wait_request,
234         CFQ_CFQQ_FLAG_must_alloc,
235         CFQ_CFQQ_FLAG_must_alloc_slice,
236         CFQ_CFQQ_FLAG_must_dispatch,
237         CFQ_CFQQ_FLAG_fifo_expire,
238         CFQ_CFQQ_FLAG_idle_window,
239         CFQ_CFQQ_FLAG_prio_changed,
240 };
241
242 #define CFQ_CFQQ_FNS(name)                                              \
243 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
244 {                                                                       \
245         cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name);                     \
246 }                                                                       \
247 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
248 {                                                                       \
249         cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                    \
250 }                                                                       \
251 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
252 {                                                                       \
253         return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;        \
254 }
255
256 CFQ_CFQQ_FNS(on_rr);
257 CFQ_CFQQ_FNS(wait_request);
258 CFQ_CFQQ_FNS(must_alloc);
259 CFQ_CFQQ_FNS(must_alloc_slice);
260 CFQ_CFQQ_FNS(must_dispatch);
261 CFQ_CFQQ_FNS(fifo_expire);
262 CFQ_CFQQ_FNS(idle_window);
263 CFQ_CFQQ_FNS(prio_changed);
264 #undef CFQ_CFQQ_FNS
265
266 enum cfq_rq_state_flags {
267         CFQ_CRQ_FLAG_is_sync = 0,
268 };
269
270 #define CFQ_CRQ_FNS(name)                                               \
271 static inline void cfq_mark_crq_##name(struct cfq_rq *crq)              \
272 {                                                                       \
273         crq->crq_flags |= (1 << CFQ_CRQ_FLAG_##name);                   \
274 }                                                                       \
275 static inline void cfq_clear_crq_##name(struct cfq_rq *crq)             \
276 {                                                                       \
277         crq->crq_flags &= ~(1 << CFQ_CRQ_FLAG_##name);                  \
278 }                                                                       \
279 static inline int cfq_crq_##name(const struct cfq_rq *crq)              \
280 {                                                                       \
281         return (crq->crq_flags & (1 << CFQ_CRQ_FLAG_##name)) != 0;      \
282 }
283
284 CFQ_CRQ_FNS(is_sync);
285 #undef CFQ_CRQ_FNS
286
287 static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short);
288 static void cfq_dispatch_insert(request_queue_t *, struct cfq_rq *);
289 static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask);
290
291 #define process_sync(tsk)       ((tsk)->flags & PF_SYNCWRITE)
292
293 /*
294  * lots of deadline iosched dupes, can be abstracted later...
295  */
296 static inline void cfq_del_crq_hash(struct cfq_rq *crq)
297 {
298         hlist_del_init(&crq->hash);
299 }
300
301 static inline void cfq_add_crq_hash(struct cfq_data *cfqd, struct cfq_rq *crq)
302 {
303         const int hash_idx = CFQ_MHASH_FN(rq_hash_key(crq->request));
304
305         hlist_add_head(&crq->hash, &cfqd->crq_hash[hash_idx]);
306 }
307
308 static struct request *cfq_find_rq_hash(struct cfq_data *cfqd, sector_t offset)
309 {
310         struct hlist_head *hash_list = &cfqd->crq_hash[CFQ_MHASH_FN(offset)];
311         struct hlist_node *entry, *next;
312
313         hlist_for_each_safe(entry, next, hash_list) {
314                 struct cfq_rq *crq = list_entry_hash(entry);
315                 struct request *__rq = crq->request;
316
317                 if (!rq_mergeable(__rq)) {
318                         cfq_del_crq_hash(crq);
319                         continue;
320                 }
321
322                 if (rq_hash_key(__rq) == offset)
323                         return __rq;
324         }
325
326         return NULL;
327 }
328
329 /*
330  * scheduler run of queue, if there are requests pending and no one in the
331  * driver that will restart queueing
332  */
333 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
334 {
335         if (cfqd->busy_queues)
336                 kblockd_schedule_work(&cfqd->unplug_work);
337 }
338
339 static int cfq_queue_empty(request_queue_t *q)
340 {
341         struct cfq_data *cfqd = q->elevator->elevator_data;
342
343         return !cfqd->busy_queues;
344 }
345
346 /*
347  * Lifted from AS - choose which of crq1 and crq2 that is best served now.
348  * We choose the request that is closest to the head right now. Distance
349  * behind the head are penalized and only allowed to a certain extent.
350  */
351 static struct cfq_rq *
352 cfq_choose_req(struct cfq_data *cfqd, struct cfq_rq *crq1, struct cfq_rq *crq2)
353 {
354         sector_t last, s1, s2, d1 = 0, d2 = 0;
355         int r1_wrap = 0, r2_wrap = 0;   /* requests are behind the disk head */
356         unsigned long back_max;
357
358         if (crq1 == NULL || crq1 == crq2)
359                 return crq2;
360         if (crq2 == NULL)
361                 return crq1;
362
363         if (cfq_crq_is_sync(crq1) && !cfq_crq_is_sync(crq2))
364                 return crq1;
365         else if (cfq_crq_is_sync(crq2) && !cfq_crq_is_sync(crq1))
366                 return crq2;
367
368         s1 = crq1->request->sector;
369         s2 = crq2->request->sector;
370
371         last = cfqd->last_sector;
372
373         /*
374          * by definition, 1KiB is 2 sectors
375          */
376         back_max = cfqd->cfq_back_max * 2;
377
378         /*
379          * Strict one way elevator _except_ in the case where we allow
380          * short backward seeks which are biased as twice the cost of a
381          * similar forward seek.
382          */
383         if (s1 >= last)
384                 d1 = s1 - last;
385         else if (s1 + back_max >= last)
386                 d1 = (last - s1) * cfqd->cfq_back_penalty;
387         else
388                 r1_wrap = 1;
389
390         if (s2 >= last)
391                 d2 = s2 - last;
392         else if (s2 + back_max >= last)
393                 d2 = (last - s2) * cfqd->cfq_back_penalty;
394         else
395                 r2_wrap = 1;
396
397         /* Found required data */
398         if (!r1_wrap && r2_wrap)
399                 return crq1;
400         else if (!r2_wrap && r1_wrap)
401                 return crq2;
402         else if (r1_wrap && r2_wrap) {
403                 /* both behind the head */
404                 if (s1 <= s2)
405                         return crq1;
406                 else
407                         return crq2;
408         }
409
410         /* Both requests in front of the head */
411         if (d1 < d2)
412                 return crq1;
413         else if (d2 < d1)
414                 return crq2;
415         else {
416                 if (s1 >= s2)
417                         return crq1;
418                 else
419                         return crq2;
420         }
421 }
422
423 /*
424  * would be nice to take fifo expire time into account as well
425  */
426 static struct cfq_rq *
427 cfq_find_next_crq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
428                   struct cfq_rq *last)
429 {
430         struct cfq_rq *crq_next = NULL, *crq_prev = NULL;
431         struct rb_node *rbnext, *rbprev;
432
433         if (!(rbnext = rb_next(&last->rb_node))) {
434                 rbnext = rb_first(&cfqq->sort_list);
435                 if (rbnext == &last->rb_node)
436                         rbnext = NULL;
437         }
438
439         rbprev = rb_prev(&last->rb_node);
440
441         if (rbprev)
442                 crq_prev = rb_entry_crq(rbprev);
443         if (rbnext)
444                 crq_next = rb_entry_crq(rbnext);
445
446         return cfq_choose_req(cfqd, crq_next, crq_prev);
447 }
448
449 static void cfq_update_next_crq(struct cfq_rq *crq)
450 {
451         struct cfq_queue *cfqq = crq->cfq_queue;
452
453         if (cfqq->next_crq == crq)
454                 cfqq->next_crq = cfq_find_next_crq(cfqq->cfqd, cfqq, crq);
455 }
456
457 static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
458 {
459         struct cfq_data *cfqd = cfqq->cfqd;
460         struct list_head *list, *entry;
461
462         BUG_ON(!cfq_cfqq_on_rr(cfqq));
463
464         list_del(&cfqq->cfq_list);
465
466         if (cfq_class_rt(cfqq))
467                 list = &cfqd->cur_rr;
468         else if (cfq_class_idle(cfqq))
469                 list = &cfqd->idle_rr;
470         else {
471                 /*
472                  * if cfqq has requests in flight, don't allow it to be
473                  * found in cfq_set_active_queue before it has finished them.
474                  * this is done to increase fairness between a process that
475                  * has lots of io pending vs one that only generates one
476                  * sporadically or synchronously
477                  */
478                 if (cfq_cfqq_dispatched(cfqq))
479                         list = &cfqd->busy_rr;
480                 else
481                         list = &cfqd->rr_list[cfqq->ioprio];
482         }
483
484         /*
485          * if queue was preempted, just add to front to be fair. busy_rr
486          * isn't sorted.
487          */
488         if (preempted || list == &cfqd->busy_rr) {
489                 list_add(&cfqq->cfq_list, list);
490                 return;
491         }
492
493         /*
494          * sort by when queue was last serviced
495          */
496         entry = list;
497         while ((entry = entry->prev) != list) {
498                 struct cfq_queue *__cfqq = list_entry_cfqq(entry);
499
500                 if (!__cfqq->service_last)
501                         break;
502                 if (time_before(__cfqq->service_last, cfqq->service_last))
503                         break;
504         }
505
506         list_add(&cfqq->cfq_list, entry);
507 }
508
509 /*
510  * add to busy list of queues for service, trying to be fair in ordering
511  * the pending list according to last request service
512  */
513 static inline void
514 cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
515 {
516         BUG_ON(cfq_cfqq_on_rr(cfqq));
517         cfq_mark_cfqq_on_rr(cfqq);
518         cfqd->busy_queues++;
519
520         cfq_resort_rr_list(cfqq, 0);
521 }
522
523 static inline void
524 cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
525 {
526         BUG_ON(!cfq_cfqq_on_rr(cfqq));
527         cfq_clear_cfqq_on_rr(cfqq);
528         list_move(&cfqq->cfq_list, &cfqd->empty_list);
529
530         BUG_ON(!cfqd->busy_queues);
531         cfqd->busy_queues--;
532 }
533
534 /*
535  * rb tree support functions
536  */
537 static inline void cfq_del_crq_rb(struct cfq_rq *crq)
538 {
539         struct cfq_queue *cfqq = crq->cfq_queue;
540         struct cfq_data *cfqd = cfqq->cfqd;
541         const int sync = cfq_crq_is_sync(crq);
542
543         BUG_ON(!cfqq->queued[sync]);
544         cfqq->queued[sync]--;
545
546         cfq_update_next_crq(crq);
547
548         rb_erase(&crq->rb_node, &cfqq->sort_list);
549         RB_CLEAR_COLOR(&crq->rb_node);
550
551         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY(&cfqq->sort_list))
552                 cfq_del_cfqq_rr(cfqd, cfqq);
553 }
554
555 static struct cfq_rq *
556 __cfq_add_crq_rb(struct cfq_rq *crq)
557 {
558         struct rb_node **p = &crq->cfq_queue->sort_list.rb_node;
559         struct rb_node *parent = NULL;
560         struct cfq_rq *__crq;
561
562         while (*p) {
563                 parent = *p;
564                 __crq = rb_entry_crq(parent);
565
566                 if (crq->rb_key < __crq->rb_key)
567                         p = &(*p)->rb_left;
568                 else if (crq->rb_key > __crq->rb_key)
569                         p = &(*p)->rb_right;
570                 else
571                         return __crq;
572         }
573
574         rb_link_node(&crq->rb_node, parent, p);
575         return NULL;
576 }
577
578 static void cfq_add_crq_rb(struct cfq_rq *crq)
579 {
580         struct cfq_queue *cfqq = crq->cfq_queue;
581         struct cfq_data *cfqd = cfqq->cfqd;
582         struct request *rq = crq->request;
583         struct cfq_rq *__alias;
584
585         crq->rb_key = rq_rb_key(rq);
586         cfqq->queued[cfq_crq_is_sync(crq)]++;
587
588         /*
589          * looks a little odd, but the first insert might return an alias.
590          * if that happens, put the alias on the dispatch list
591          */
592         while ((__alias = __cfq_add_crq_rb(crq)) != NULL)
593                 cfq_dispatch_insert(cfqd->queue, __alias);
594
595         rb_insert_color(&crq->rb_node, &cfqq->sort_list);
596
597         if (!cfq_cfqq_on_rr(cfqq))
598                 cfq_add_cfqq_rr(cfqd, cfqq);
599
600         /*
601          * check if this request is a better next-serve candidate
602          */
603         cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
604 }
605
606 static inline void
607 cfq_reposition_crq_rb(struct cfq_queue *cfqq, struct cfq_rq *crq)
608 {
609         rb_erase(&crq->rb_node, &cfqq->sort_list);
610         cfqq->queued[cfq_crq_is_sync(crq)]--;
611
612         cfq_add_crq_rb(crq);
613 }
614
615 static struct request *cfq_find_rq_rb(struct cfq_data *cfqd, sector_t sector)
616
617 {
618         struct cfq_queue *cfqq = cfq_find_cfq_hash(cfqd, current->pid, CFQ_KEY_ANY);
619         struct rb_node *n;
620
621         if (!cfqq)
622                 goto out;
623
624         n = cfqq->sort_list.rb_node;
625         while (n) {
626                 struct cfq_rq *crq = rb_entry_crq(n);
627
628                 if (sector < crq->rb_key)
629                         n = n->rb_left;
630                 else if (sector > crq->rb_key)
631                         n = n->rb_right;
632                 else
633                         return crq->request;
634         }
635
636 out:
637         return NULL;
638 }
639
640 static void cfq_activate_request(request_queue_t *q, struct request *rq)
641 {
642         struct cfq_data *cfqd = q->elevator->elevator_data;
643
644         cfqd->rq_in_driver++;
645 }
646
647 static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
648 {
649         struct cfq_data *cfqd = q->elevator->elevator_data;
650
651         WARN_ON(!cfqd->rq_in_driver);
652         cfqd->rq_in_driver--;
653 }
654
655 static void cfq_remove_request(struct request *rq)
656 {
657         struct cfq_rq *crq = RQ_DATA(rq);
658
659         list_del_init(&rq->queuelist);
660         cfq_del_crq_rb(crq);
661         cfq_del_crq_hash(crq);
662 }
663
664 static int
665 cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
666 {
667         struct cfq_data *cfqd = q->elevator->elevator_data;
668         struct request *__rq;
669         int ret;
670
671         __rq = cfq_find_rq_hash(cfqd, bio->bi_sector);
672         if (__rq && elv_rq_merge_ok(__rq, bio)) {
673                 ret = ELEVATOR_BACK_MERGE;
674                 goto out;
675         }
676
677         __rq = cfq_find_rq_rb(cfqd, bio->bi_sector + bio_sectors(bio));
678         if (__rq && elv_rq_merge_ok(__rq, bio)) {
679                 ret = ELEVATOR_FRONT_MERGE;
680                 goto out;
681         }
682
683         return ELEVATOR_NO_MERGE;
684 out:
685         *req = __rq;
686         return ret;
687 }
688
689 static void cfq_merged_request(request_queue_t *q, struct request *req)
690 {
691         struct cfq_data *cfqd = q->elevator->elevator_data;
692         struct cfq_rq *crq = RQ_DATA(req);
693
694         cfq_del_crq_hash(crq);
695         cfq_add_crq_hash(cfqd, crq);
696
697         if (rq_rb_key(req) != crq->rb_key) {
698                 struct cfq_queue *cfqq = crq->cfq_queue;
699
700                 cfq_update_next_crq(crq);
701                 cfq_reposition_crq_rb(cfqq, crq);
702         }
703 }
704
705 static void
706 cfq_merged_requests(request_queue_t *q, struct request *rq,
707                     struct request *next)
708 {
709         cfq_merged_request(q, rq);
710
711         /*
712          * reposition in fifo if next is older than rq
713          */
714         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
715             time_before(next->start_time, rq->start_time))
716                 list_move(&rq->queuelist, &next->queuelist);
717
718         cfq_remove_request(next);
719 }
720
721 static inline void
722 __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
723 {
724         if (cfqq) {
725                 /*
726                  * stop potential idle class queues waiting service
727                  */
728                 del_timer(&cfqd->idle_class_timer);
729
730                 cfqq->slice_start = jiffies;
731                 cfqq->slice_end = 0;
732                 cfqq->slice_left = 0;
733                 cfq_clear_cfqq_must_alloc_slice(cfqq);
734                 cfq_clear_cfqq_fifo_expire(cfqq);
735         }
736
737         cfqd->active_queue = cfqq;
738 }
739
740 /*
741  * current cfqq expired its slice (or was too idle), select new one
742  */
743 static void
744 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
745                     int preempted)
746 {
747         unsigned long now = jiffies;
748
749         if (cfq_cfqq_wait_request(cfqq))
750                 del_timer(&cfqd->idle_slice_timer);
751
752         if (!preempted && !cfq_cfqq_dispatched(cfqq)) {
753                 cfqq->service_last = now;
754                 cfq_schedule_dispatch(cfqd);
755         }
756
757         cfq_clear_cfqq_must_dispatch(cfqq);
758         cfq_clear_cfqq_wait_request(cfqq);
759
760         /*
761          * store what was left of this slice, if the queue idled out
762          * or was preempted
763          */
764         if (time_after(cfqq->slice_end, now))
765                 cfqq->slice_left = cfqq->slice_end - now;
766         else
767                 cfqq->slice_left = 0;
768
769         if (cfq_cfqq_on_rr(cfqq))
770                 cfq_resort_rr_list(cfqq, preempted);
771
772         if (cfqq == cfqd->active_queue)
773                 cfqd->active_queue = NULL;
774
775         if (cfqd->active_cic) {
776                 put_io_context(cfqd->active_cic->ioc);
777                 cfqd->active_cic = NULL;
778         }
779
780         cfqd->dispatch_slice = 0;
781 }
782
783 static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted)
784 {
785         struct cfq_queue *cfqq = cfqd->active_queue;
786
787         if (cfqq)
788                 __cfq_slice_expired(cfqd, cfqq, preempted);
789 }
790
791 /*
792  * 0
793  * 0,1
794  * 0,1,2
795  * 0,1,2,3
796  * 0,1,2,3,4
797  * 0,1,2,3,4,5
798  * 0,1,2,3,4,5,6
799  * 0,1,2,3,4,5,6,7
800  */
801 static int cfq_get_next_prio_level(struct cfq_data *cfqd)
802 {
803         int prio, wrap;
804
805         prio = -1;
806         wrap = 0;
807         do {
808                 int p;
809
810                 for (p = cfqd->cur_prio; p <= cfqd->cur_end_prio; p++) {
811                         if (!list_empty(&cfqd->rr_list[p])) {
812                                 prio = p;
813                                 break;
814                         }
815                 }
816
817                 if (prio != -1)
818                         break;
819                 cfqd->cur_prio = 0;
820                 if (++cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
821                         cfqd->cur_end_prio = 0;
822                         if (wrap)
823                                 break;
824                         wrap = 1;
825                 }
826         } while (1);
827
828         if (unlikely(prio == -1))
829                 return -1;
830
831         BUG_ON(prio >= CFQ_PRIO_LISTS);
832
833         list_splice_init(&cfqd->rr_list[prio], &cfqd->cur_rr);
834
835         cfqd->cur_prio = prio + 1;
836         if (cfqd->cur_prio > cfqd->cur_end_prio) {
837                 cfqd->cur_end_prio = cfqd->cur_prio;
838                 cfqd->cur_prio = 0;
839         }
840         if (cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
841                 cfqd->cur_prio = 0;
842                 cfqd->cur_end_prio = 0;
843         }
844
845         return prio;
846 }
847
848 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
849 {
850         struct cfq_queue *cfqq = NULL;
851
852         /*
853          * if current list is non-empty, grab first entry. if it is empty,
854          * get next prio level and grab first entry then if any are spliced
855          */
856         if (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1)
857                 cfqq = list_entry_cfqq(cfqd->cur_rr.next);
858
859         /*
860          * if we have idle queues and no rt or be queues had pending
861          * requests, either allow immediate service if the grace period
862          * has passed or arm the idle grace timer
863          */
864         if (!cfqq && !list_empty(&cfqd->idle_rr)) {
865                 unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE;
866
867                 if (time_after_eq(jiffies, end))
868                         cfqq = list_entry_cfqq(cfqd->idle_rr.next);
869                 else
870                         mod_timer(&cfqd->idle_class_timer, end);
871         }
872
873         __cfq_set_active_queue(cfqd, cfqq);
874         return cfqq;
875 }
876
877 static int cfq_arm_slice_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
878
879 {
880         unsigned long sl;
881
882         WARN_ON(!RB_EMPTY(&cfqq->sort_list));
883         WARN_ON(cfqq != cfqd->active_queue);
884
885         /*
886          * idle is disabled, either manually or by past process history
887          */
888         if (!cfqd->cfq_slice_idle)
889                 return 0;
890         if (!cfq_cfqq_idle_window(cfqq))
891                 return 0;
892         /*
893          * task has exited, don't wait
894          */
895         if (cfqd->active_cic && !cfqd->active_cic->ioc->task)
896                 return 0;
897
898         cfq_mark_cfqq_must_dispatch(cfqq);
899         cfq_mark_cfqq_wait_request(cfqq);
900
901         sl = min(cfqq->slice_end - 1, (unsigned long) cfqd->cfq_slice_idle);
902         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
903         return 1;
904 }
905
906 static void cfq_dispatch_insert(request_queue_t *q, struct cfq_rq *crq)
907 {
908         struct cfq_data *cfqd = q->elevator->elevator_data;
909         struct cfq_queue *cfqq = crq->cfq_queue;
910
911         cfqq->next_crq = cfq_find_next_crq(cfqd, cfqq, crq);
912         cfq_remove_request(crq->request);
913         cfqq->on_dispatch[cfq_crq_is_sync(crq)]++;
914         elv_dispatch_sort(q, crq->request);
915 }
916
917 /*
918  * return expired entry, or NULL to just start from scratch in rbtree
919  */
920 static inline struct cfq_rq *cfq_check_fifo(struct cfq_queue *cfqq)
921 {
922         struct cfq_data *cfqd = cfqq->cfqd;
923         struct request *rq;
924         struct cfq_rq *crq;
925
926         if (cfq_cfqq_fifo_expire(cfqq))
927                 return NULL;
928
929         if (!list_empty(&cfqq->fifo)) {
930                 int fifo = cfq_cfqq_class_sync(cfqq);
931
932                 crq = RQ_DATA(list_entry_fifo(cfqq->fifo.next));
933                 rq = crq->request;
934                 if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) {
935                         cfq_mark_cfqq_fifo_expire(cfqq);
936                         return crq;
937                 }
938         }
939
940         return NULL;
941 }
942
943 /*
944  * Scale schedule slice based on io priority. Use the sync time slice only
945  * if a queue is marked sync and has sync io queued. A sync queue with async
946  * io only, should not get full sync slice length.
947  */
948 static inline int
949 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
950 {
951         const int base_slice = cfqd->cfq_slice[cfq_cfqq_sync(cfqq)];
952
953         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
954
955         return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - cfqq->ioprio));
956 }
957
958 static inline void
959 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
960 {
961         cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
962 }
963
964 static inline int
965 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
966 {
967         const int base_rq = cfqd->cfq_slice_async_rq;
968
969         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
970
971         return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
972 }
973
974 /*
975  * get next queue for service
976  */
977 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
978 {
979         unsigned long now = jiffies;
980         struct cfq_queue *cfqq;
981
982         cfqq = cfqd->active_queue;
983         if (!cfqq)
984                 goto new_queue;
985
986         /*
987          * slice has expired
988          */
989         if (!cfq_cfqq_must_dispatch(cfqq) && time_after(now, cfqq->slice_end))
990                 goto expire;
991
992         /*
993          * if queue has requests, dispatch one. if not, check if
994          * enough slice is left to wait for one
995          */
996         if (!RB_EMPTY(&cfqq->sort_list))
997                 goto keep_queue;
998         else if (cfq_cfqq_class_sync(cfqq) &&
999                  time_before(now, cfqq->slice_end)) {
1000                 if (cfq_arm_slice_timer(cfqd, cfqq))
1001                         return NULL;
1002         }
1003
1004 expire:
1005         cfq_slice_expired(cfqd, 0);
1006 new_queue:
1007         cfqq = cfq_set_active_queue(cfqd);
1008 keep_queue:
1009         return cfqq;
1010 }
1011
1012 static int
1013 __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1014                         int max_dispatch)
1015 {
1016         int dispatched = 0;
1017
1018         BUG_ON(RB_EMPTY(&cfqq->sort_list));
1019
1020         do {
1021                 struct cfq_rq *crq;
1022
1023                 /*
1024                  * follow expired path, else get first next available
1025                  */
1026                 if ((crq = cfq_check_fifo(cfqq)) == NULL)
1027                         crq = cfqq->next_crq;
1028
1029                 /*
1030                  * finally, insert request into driver dispatch list
1031                  */
1032                 cfq_dispatch_insert(cfqd->queue, crq);
1033
1034                 cfqd->dispatch_slice++;
1035                 dispatched++;
1036
1037                 if (!cfqd->active_cic) {
1038                         atomic_inc(&crq->io_context->ioc->refcount);
1039                         cfqd->active_cic = crq->io_context;
1040                 }
1041
1042                 if (RB_EMPTY(&cfqq->sort_list))
1043                         break;
1044
1045         } while (dispatched < max_dispatch);
1046
1047         /*
1048          * if slice end isn't set yet, set it. if at least one request was
1049          * sync, use the sync time slice value
1050          */
1051         if (!cfqq->slice_end)
1052                 cfq_set_prio_slice(cfqd, cfqq);
1053
1054         /*
1055          * expire an async queue immediately if it has used up its slice. idle
1056          * queue always expire after 1 dispatch round.
1057          */
1058         if ((!cfq_cfqq_sync(cfqq) &&
1059             cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1060             cfq_class_idle(cfqq))
1061                 cfq_slice_expired(cfqd, 0);
1062
1063         return dispatched;
1064 }
1065
1066 static int
1067 cfq_forced_dispatch_cfqqs(struct list_head *list)
1068 {
1069         int dispatched = 0;
1070         struct cfq_queue *cfqq, *next;
1071         struct cfq_rq *crq;
1072
1073         list_for_each_entry_safe(cfqq, next, list, cfq_list) {
1074                 while ((crq = cfqq->next_crq)) {
1075                         cfq_dispatch_insert(cfqq->cfqd->queue, crq);
1076                         dispatched++;
1077                 }
1078                 BUG_ON(!list_empty(&cfqq->fifo));
1079         }
1080         return dispatched;
1081 }
1082
1083 static int
1084 cfq_forced_dispatch(struct cfq_data *cfqd)
1085 {
1086         int i, dispatched = 0;
1087
1088         for (i = 0; i < CFQ_PRIO_LISTS; i++)
1089                 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]);
1090
1091         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->busy_rr);
1092         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr);
1093         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr);
1094
1095         cfq_slice_expired(cfqd, 0);
1096
1097         BUG_ON(cfqd->busy_queues);
1098
1099         return dispatched;
1100 }
1101
1102 static int
1103 cfq_dispatch_requests(request_queue_t *q, int force)
1104 {
1105         struct cfq_data *cfqd = q->elevator->elevator_data;
1106         struct cfq_queue *cfqq;
1107
1108         if (!cfqd->busy_queues)
1109                 return 0;
1110
1111         if (unlikely(force))
1112                 return cfq_forced_dispatch(cfqd);
1113
1114         cfqq = cfq_select_queue(cfqd);
1115         if (cfqq) {
1116                 int max_dispatch;
1117
1118                 /*
1119                  * if idle window is disabled, allow queue buildup
1120                  */
1121                 if (!cfq_cfqq_idle_window(cfqq) &&
1122                     cfqd->rq_in_driver >= cfqd->cfq_max_depth)
1123                         return 0;
1124
1125                 cfq_clear_cfqq_must_dispatch(cfqq);
1126                 cfq_clear_cfqq_wait_request(cfqq);
1127                 del_timer(&cfqd->idle_slice_timer);
1128
1129                 max_dispatch = cfqd->cfq_quantum;
1130                 if (cfq_class_idle(cfqq))
1131                         max_dispatch = 1;
1132
1133                 return __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
1134         }
1135
1136         return 0;
1137 }
1138
1139 /*
1140  * task holds one reference to the queue, dropped when task exits. each crq
1141  * in-flight on this queue also holds a reference, dropped when crq is freed.
1142  *
1143  * queue lock must be held here.
1144  */
1145 static void cfq_put_queue(struct cfq_queue *cfqq)
1146 {
1147         struct cfq_data *cfqd = cfqq->cfqd;
1148
1149         BUG_ON(atomic_read(&cfqq->ref) <= 0);
1150
1151         if (!atomic_dec_and_test(&cfqq->ref))
1152                 return;
1153
1154         BUG_ON(rb_first(&cfqq->sort_list));
1155         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1156         BUG_ON(cfq_cfqq_on_rr(cfqq));
1157
1158         if (unlikely(cfqd->active_queue == cfqq))
1159                 __cfq_slice_expired(cfqd, cfqq, 0);
1160
1161         /*
1162          * it's on the empty list and still hashed
1163          */
1164         list_del(&cfqq->cfq_list);
1165         hlist_del(&cfqq->cfq_hash);
1166         kmem_cache_free(cfq_pool, cfqq);
1167 }
1168
1169 static inline struct cfq_queue *
1170 __cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned int prio,
1171                     const int hashval)
1172 {
1173         struct hlist_head *hash_list = &cfqd->cfq_hash[hashval];
1174         struct hlist_node *entry, *next;
1175
1176         hlist_for_each_safe(entry, next, hash_list) {
1177                 struct cfq_queue *__cfqq = list_entry_qhash(entry);
1178                 const unsigned short __p = IOPRIO_PRIO_VALUE(__cfqq->org_ioprio_class, __cfqq->org_ioprio);
1179
1180                 if (__cfqq->key == key && (__p == prio || prio == CFQ_KEY_ANY))
1181                         return __cfqq;
1182         }
1183
1184         return NULL;
1185 }
1186
1187 static struct cfq_queue *
1188 cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned short prio)
1189 {
1190         return __cfq_find_cfq_hash(cfqd, key, prio, hash_long(key, CFQ_QHASH_SHIFT));
1191 }
1192
1193 static void cfq_free_io_context(struct io_context *ioc)
1194 {
1195         struct cfq_io_context *__cic;
1196         struct rb_node *n;
1197         int freed = 0;
1198
1199         while ((n = rb_first(&ioc->cic_root)) != NULL) {
1200                 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1201                 rb_erase(&__cic->rb_node, &ioc->cic_root);
1202                 kmem_cache_free(cfq_ioc_pool, __cic);
1203                 freed++;
1204         }
1205
1206         if (atomic_sub_and_test(freed, &ioc_count) && ioc_gone)
1207                 complete(ioc_gone);
1208 }
1209
1210 static void cfq_trim(struct io_context *ioc)
1211 {
1212         ioc->set_ioprio = NULL;
1213         cfq_free_io_context(ioc);
1214 }
1215
1216 /*
1217  * Called with interrupts disabled
1218  */
1219 static void cfq_exit_single_io_context(struct cfq_io_context *cic)
1220 {
1221         struct cfq_data *cfqd = cic->key;
1222         request_queue_t *q;
1223
1224         if (!cfqd)
1225                 return;
1226
1227         q = cfqd->queue;
1228
1229         WARN_ON(!irqs_disabled());
1230
1231         spin_lock(q->queue_lock);
1232
1233         if (cic->cfqq[ASYNC]) {
1234                 if (unlikely(cic->cfqq[ASYNC] == cfqd->active_queue))
1235                         __cfq_slice_expired(cfqd, cic->cfqq[ASYNC], 0);
1236                 cfq_put_queue(cic->cfqq[ASYNC]);
1237                 cic->cfqq[ASYNC] = NULL;
1238         }
1239
1240         if (cic->cfqq[SYNC]) {
1241                 if (unlikely(cic->cfqq[SYNC] == cfqd->active_queue))
1242                         __cfq_slice_expired(cfqd, cic->cfqq[SYNC], 0);
1243                 cfq_put_queue(cic->cfqq[SYNC]);
1244                 cic->cfqq[SYNC] = NULL;
1245         }
1246
1247         cic->key = NULL;
1248         list_del_init(&cic->queue_list);
1249         spin_unlock(q->queue_lock);
1250 }
1251
1252 static void cfq_exit_io_context(struct io_context *ioc)
1253 {
1254         struct cfq_io_context *__cic;
1255         unsigned long flags;
1256         struct rb_node *n;
1257
1258         /*
1259          * put the reference this task is holding to the various queues
1260          */
1261         read_lock_irqsave(&cfq_exit_lock, flags);
1262
1263         n = rb_first(&ioc->cic_root);
1264         while (n != NULL) {
1265                 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1266
1267                 cfq_exit_single_io_context(__cic);
1268                 n = rb_next(n);
1269         }
1270
1271         read_unlock_irqrestore(&cfq_exit_lock, flags);
1272 }
1273
1274 static struct cfq_io_context *
1275 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1276 {
1277         struct cfq_io_context *cic = kmem_cache_alloc(cfq_ioc_pool, gfp_mask);
1278
1279         if (cic) {
1280                 RB_CLEAR(&cic->rb_node);
1281                 cic->key = NULL;
1282                 cic->cfqq[ASYNC] = NULL;
1283                 cic->cfqq[SYNC] = NULL;
1284                 cic->last_end_request = jiffies;
1285                 cic->ttime_total = 0;
1286                 cic->ttime_samples = 0;
1287                 cic->ttime_mean = 0;
1288                 cic->dtor = cfq_free_io_context;
1289                 cic->exit = cfq_exit_io_context;
1290                 INIT_LIST_HEAD(&cic->queue_list);
1291                 atomic_inc(&ioc_count);
1292         }
1293
1294         return cic;
1295 }
1296
1297 static void cfq_init_prio_data(struct cfq_queue *cfqq)
1298 {
1299         struct task_struct *tsk = current;
1300         int ioprio_class;
1301
1302         if (!cfq_cfqq_prio_changed(cfqq))
1303                 return;
1304
1305         ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
1306         switch (ioprio_class) {
1307                 default:
1308                         printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1309                 case IOPRIO_CLASS_NONE:
1310                         /*
1311                          * no prio set, place us in the middle of the BE classes
1312                          */
1313                         cfqq->ioprio = task_nice_ioprio(tsk);
1314                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1315                         break;
1316                 case IOPRIO_CLASS_RT:
1317                         cfqq->ioprio = task_ioprio(tsk);
1318                         cfqq->ioprio_class = IOPRIO_CLASS_RT;
1319                         break;
1320                 case IOPRIO_CLASS_BE:
1321                         cfqq->ioprio = task_ioprio(tsk);
1322                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1323                         break;
1324                 case IOPRIO_CLASS_IDLE:
1325                         cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1326                         cfqq->ioprio = 7;
1327                         cfq_clear_cfqq_idle_window(cfqq);
1328                         break;
1329         }
1330
1331         /*
1332          * keep track of original prio settings in case we have to temporarily
1333          * elevate the priority of this queue
1334          */
1335         cfqq->org_ioprio = cfqq->ioprio;
1336         cfqq->org_ioprio_class = cfqq->ioprio_class;
1337
1338         if (cfq_cfqq_on_rr(cfqq))
1339                 cfq_resort_rr_list(cfqq, 0);
1340
1341         cfq_clear_cfqq_prio_changed(cfqq);
1342 }
1343
1344 static inline void changed_ioprio(struct cfq_io_context *cic)
1345 {
1346         struct cfq_data *cfqd = cic->key;
1347         struct cfq_queue *cfqq;
1348         if (cfqd) {
1349                 spin_lock(cfqd->queue->queue_lock);
1350                 cfqq = cic->cfqq[ASYNC];
1351                 if (cfqq) {
1352                         struct cfq_queue *new_cfqq;
1353                         new_cfqq = cfq_get_queue(cfqd, CFQ_KEY_ASYNC,
1354                                                 cic->ioc->task, GFP_ATOMIC);
1355                         if (new_cfqq) {
1356                                 cic->cfqq[ASYNC] = new_cfqq;
1357                                 cfq_put_queue(cfqq);
1358                         }
1359                 }
1360                 cfqq = cic->cfqq[SYNC];
1361                 if (cfqq) {
1362                         cfq_mark_cfqq_prio_changed(cfqq);
1363                         cfq_init_prio_data(cfqq);
1364                 }
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;
1375         struct rb_node *n;
1376
1377         write_lock(&cfq_exit_lock);
1378
1379         n = rb_first(&ioc->cic_root);
1380         while (n != NULL) {
1381                 cic = rb_entry(n, struct cfq_io_context, rb_node);
1382  
1383                 changed_ioprio(cic);
1384                 n = rb_next(n);
1385         }
1386
1387         write_unlock(&cfq_exit_lock);
1388
1389         return 0;
1390 }
1391
1392 static struct cfq_queue *
1393 cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk,
1394               gfp_t gfp_mask)
1395 {
1396         const int hashval = hash_long(key, CFQ_QHASH_SHIFT);
1397         struct cfq_queue *cfqq, *new_cfqq = NULL;
1398         unsigned short ioprio;
1399
1400 retry:
1401         ioprio = tsk->ioprio;
1402         cfqq = __cfq_find_cfq_hash(cfqd, key, ioprio, hashval);
1403
1404         if (!cfqq) {
1405                 if (new_cfqq) {
1406                         cfqq = new_cfqq;
1407                         new_cfqq = NULL;
1408                 } else if (gfp_mask & __GFP_WAIT) {
1409                         spin_unlock_irq(cfqd->queue->queue_lock);
1410                         new_cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
1411                         spin_lock_irq(cfqd->queue->queue_lock);
1412                         goto retry;
1413                 } else {
1414                         cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
1415                         if (!cfqq)
1416                                 goto out;
1417                 }
1418
1419                 memset(cfqq, 0, sizeof(*cfqq));
1420
1421                 INIT_HLIST_NODE(&cfqq->cfq_hash);
1422                 INIT_LIST_HEAD(&cfqq->cfq_list);
1423                 RB_CLEAR_ROOT(&cfqq->sort_list);
1424                 INIT_LIST_HEAD(&cfqq->fifo);
1425
1426                 cfqq->key = key;
1427                 hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
1428                 atomic_set(&cfqq->ref, 0);
1429                 cfqq->cfqd = cfqd;
1430                 cfqq->service_last = 0;
1431                 /*
1432                  * set ->slice_left to allow preemption for a new process
1433                  */
1434                 cfqq->slice_left = 2 * cfqd->cfq_slice_idle;
1435                 cfq_mark_cfqq_idle_window(cfqq);
1436                 cfq_mark_cfqq_prio_changed(cfqq);
1437                 cfq_init_prio_data(cfqq);
1438         }
1439
1440         if (new_cfqq)
1441                 kmem_cache_free(cfq_pool, new_cfqq);
1442
1443         atomic_inc(&cfqq->ref);
1444 out:
1445         WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
1446         return cfqq;
1447 }
1448
1449 static struct cfq_io_context *
1450 cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
1451 {
1452         struct rb_node *n = ioc->cic_root.rb_node;
1453         struct cfq_io_context *cic;
1454         void *key = cfqd;
1455
1456         while (n) {
1457                 cic = rb_entry(n, struct cfq_io_context, rb_node);
1458
1459                 if (key < cic->key)
1460                         n = n->rb_left;
1461                 else if (key > cic->key)
1462                         n = n->rb_right;
1463                 else
1464                         return cic;
1465         }
1466
1467         return NULL;
1468 }
1469
1470 static inline void
1471 cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
1472              struct cfq_io_context *cic)
1473 {
1474         struct rb_node **p = &ioc->cic_root.rb_node;
1475         struct rb_node *parent = NULL;
1476         struct cfq_io_context *__cic;
1477
1478         read_lock(&cfq_exit_lock);
1479
1480         cic->ioc = ioc;
1481         cic->key = cfqd;
1482
1483         ioc->set_ioprio = cfq_ioc_set_ioprio;
1484
1485         while (*p) {
1486                 parent = *p;
1487                 __cic = rb_entry(parent, struct cfq_io_context, rb_node);
1488
1489                 if (cic->key < __cic->key)
1490                         p = &(*p)->rb_left;
1491                 else if (cic->key > __cic->key)
1492                         p = &(*p)->rb_right;
1493                 else
1494                         BUG();
1495         }
1496
1497         rb_link_node(&cic->rb_node, parent, p);
1498         rb_insert_color(&cic->rb_node, &ioc->cic_root);
1499         list_add(&cic->queue_list, &cfqd->cic_list);
1500         read_unlock(&cfq_exit_lock);
1501 }
1502
1503 /*
1504  * Setup general io context and cfq io context. There can be several cfq
1505  * io contexts per general io context, if this process is doing io to more
1506  * than one device managed by cfq.
1507  */
1508 static struct cfq_io_context *
1509 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1510 {
1511         struct io_context *ioc = NULL;
1512         struct cfq_io_context *cic;
1513
1514         might_sleep_if(gfp_mask & __GFP_WAIT);
1515
1516         ioc = get_io_context(gfp_mask);
1517         if (!ioc)
1518                 return NULL;
1519
1520         cic = cfq_cic_rb_lookup(cfqd, ioc);
1521         if (cic)
1522                 goto out;
1523
1524         cic = cfq_alloc_io_context(cfqd, gfp_mask);
1525         if (cic == NULL)
1526                 goto err;
1527
1528         cfq_cic_link(cfqd, ioc, cic);
1529 out:
1530         return cic;
1531 err:
1532         put_io_context(ioc);
1533         return NULL;
1534 }
1535
1536 static void
1537 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1538 {
1539         unsigned long elapsed, ttime;
1540
1541         /*
1542          * if this context already has stuff queued, thinktime is from
1543          * last queue not last end
1544          */
1545 #if 0
1546         if (time_after(cic->last_end_request, cic->last_queue))
1547                 elapsed = jiffies - cic->last_end_request;
1548         else
1549                 elapsed = jiffies - cic->last_queue;
1550 #else
1551                 elapsed = jiffies - cic->last_end_request;
1552 #endif
1553
1554         ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1555
1556         cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1557         cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1558         cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1559 }
1560
1561 #define sample_valid(samples)   ((samples) > 80)
1562
1563 /*
1564  * Disable idle window if the process thinks too long or seeks so much that
1565  * it doesn't matter
1566  */
1567 static void
1568 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1569                        struct cfq_io_context *cic)
1570 {
1571         int enable_idle = cfq_cfqq_idle_window(cfqq);
1572
1573         if (!cic->ioc->task || !cfqd->cfq_slice_idle)
1574                 enable_idle = 0;
1575         else if (sample_valid(cic->ttime_samples)) {
1576                 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1577                         enable_idle = 0;
1578                 else
1579                         enable_idle = 1;
1580         }
1581
1582         if (enable_idle)
1583                 cfq_mark_cfqq_idle_window(cfqq);
1584         else
1585                 cfq_clear_cfqq_idle_window(cfqq);
1586 }
1587
1588
1589 /*
1590  * Check if new_cfqq should preempt the currently active queue. Return 0 for
1591  * no or if we aren't sure, a 1 will cause a preempt.
1592  */
1593 static int
1594 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1595                    struct cfq_rq *crq)
1596 {
1597         struct cfq_queue *cfqq = cfqd->active_queue;
1598
1599         if (cfq_class_idle(new_cfqq))
1600                 return 0;
1601
1602         if (!cfqq)
1603                 return 1;
1604
1605         if (cfq_class_idle(cfqq))
1606                 return 1;
1607         if (!cfq_cfqq_wait_request(new_cfqq))
1608                 return 0;
1609         /*
1610          * if it doesn't have slice left, forget it
1611          */
1612         if (new_cfqq->slice_left < cfqd->cfq_slice_idle)
1613                 return 0;
1614         if (cfq_crq_is_sync(crq) && !cfq_cfqq_sync(cfqq))
1615                 return 1;
1616
1617         return 0;
1618 }
1619
1620 /*
1621  * cfqq preempts the active queue. if we allowed preempt with no slice left,
1622  * let it have half of its nominal slice.
1623  */
1624 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1625 {
1626         struct cfq_queue *__cfqq, *next;
1627
1628         list_for_each_entry_safe(__cfqq, next, &cfqd->cur_rr, cfq_list)
1629                 cfq_resort_rr_list(__cfqq, 1);
1630
1631         if (!cfqq->slice_left)
1632                 cfqq->slice_left = cfq_prio_to_slice(cfqd, cfqq) / 2;
1633
1634         cfqq->slice_end = cfqq->slice_left + jiffies;
1635         __cfq_slice_expired(cfqd, cfqq, 1);
1636         __cfq_set_active_queue(cfqd, cfqq);
1637 }
1638
1639 /*
1640  * should really be a ll_rw_blk.c helper
1641  */
1642 static void cfq_start_queueing(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1643 {
1644         request_queue_t *q = cfqd->queue;
1645
1646         if (!blk_queue_plugged(q))
1647                 q->request_fn(q);
1648         else
1649                 __generic_unplug_device(q);
1650 }
1651
1652 /*
1653  * Called when a new fs request (crq) is added (to cfqq). Check if there's
1654  * something we should do about it
1655  */
1656 static void
1657 cfq_crq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1658                  struct cfq_rq *crq)
1659 {
1660         struct cfq_io_context *cic;
1661
1662         cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
1663
1664         /*
1665          * we never wait for an async request and we don't allow preemption
1666          * of an async request. so just return early
1667          */
1668         if (!cfq_crq_is_sync(crq))
1669                 return;
1670
1671         cic = crq->io_context;
1672
1673         cfq_update_io_thinktime(cfqd, cic);
1674         cfq_update_idle_window(cfqd, cfqq, cic);
1675
1676         cic->last_queue = jiffies;
1677
1678         if (cfqq == cfqd->active_queue) {
1679                 /*
1680                  * if we are waiting for a request for this queue, let it rip
1681                  * immediately and flag that we must not expire this queue
1682                  * just now
1683                  */
1684                 if (cfq_cfqq_wait_request(cfqq)) {
1685                         cfq_mark_cfqq_must_dispatch(cfqq);
1686                         del_timer(&cfqd->idle_slice_timer);
1687                         cfq_start_queueing(cfqd, cfqq);
1688                 }
1689         } else if (cfq_should_preempt(cfqd, cfqq, crq)) {
1690                 /*
1691                  * not the active queue - expire current slice if it is
1692                  * idle and has expired it's mean thinktime or this new queue
1693                  * has some old slice time left and is of higher priority
1694                  */
1695                 cfq_preempt_queue(cfqd, cfqq);
1696                 cfq_mark_cfqq_must_dispatch(cfqq);
1697                 cfq_start_queueing(cfqd, cfqq);
1698         }
1699 }
1700
1701 static void cfq_insert_request(request_queue_t *q, struct request *rq)
1702 {
1703         struct cfq_data *cfqd = q->elevator->elevator_data;
1704         struct cfq_rq *crq = RQ_DATA(rq);
1705         struct cfq_queue *cfqq = crq->cfq_queue;
1706
1707         cfq_init_prio_data(cfqq);
1708
1709         cfq_add_crq_rb(crq);
1710
1711         list_add_tail(&rq->queuelist, &cfqq->fifo);
1712
1713         if (rq_mergeable(rq))
1714                 cfq_add_crq_hash(cfqd, crq);
1715
1716         cfq_crq_enqueued(cfqd, cfqq, crq);
1717 }
1718
1719 static void cfq_completed_request(request_queue_t *q, struct request *rq)
1720 {
1721         struct cfq_rq *crq = RQ_DATA(rq);
1722         struct cfq_queue *cfqq = crq->cfq_queue;
1723         struct cfq_data *cfqd = cfqq->cfqd;
1724         const int sync = cfq_crq_is_sync(crq);
1725         unsigned long now;
1726
1727         now = jiffies;
1728
1729         WARN_ON(!cfqd->rq_in_driver);
1730         WARN_ON(!cfqq->on_dispatch[sync]);
1731         cfqd->rq_in_driver--;
1732         cfqq->on_dispatch[sync]--;
1733
1734         if (!cfq_class_idle(cfqq))
1735                 cfqd->last_end_request = now;
1736
1737         if (!cfq_cfqq_dispatched(cfqq)) {
1738                 if (cfq_cfqq_on_rr(cfqq)) {
1739                         cfqq->service_last = now;
1740                         cfq_resort_rr_list(cfqq, 0);
1741                 }
1742                 cfq_schedule_dispatch(cfqd);
1743         }
1744
1745         if (cfq_crq_is_sync(crq))
1746                 crq->io_context->last_end_request = now;
1747 }
1748
1749 static struct request *
1750 cfq_former_request(request_queue_t *q, struct request *rq)
1751 {
1752         struct cfq_rq *crq = RQ_DATA(rq);
1753         struct rb_node *rbprev = rb_prev(&crq->rb_node);
1754
1755         if (rbprev)
1756                 return rb_entry_crq(rbprev)->request;
1757
1758         return NULL;
1759 }
1760
1761 static struct request *
1762 cfq_latter_request(request_queue_t *q, struct request *rq)
1763 {
1764         struct cfq_rq *crq = RQ_DATA(rq);
1765         struct rb_node *rbnext = rb_next(&crq->rb_node);
1766
1767         if (rbnext)
1768                 return rb_entry_crq(rbnext)->request;
1769
1770         return NULL;
1771 }
1772
1773 /*
1774  * we temporarily boost lower priority queues if they are holding fs exclusive
1775  * resources. they are boosted to normal prio (CLASS_BE/4)
1776  */
1777 static void cfq_prio_boost(struct cfq_queue *cfqq)
1778 {
1779         const int ioprio_class = cfqq->ioprio_class;
1780         const int ioprio = cfqq->ioprio;
1781
1782         if (has_fs_excl()) {
1783                 /*
1784                  * boost idle prio on transactions that would lock out other
1785                  * users of the filesystem
1786                  */
1787                 if (cfq_class_idle(cfqq))
1788                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1789                 if (cfqq->ioprio > IOPRIO_NORM)
1790                         cfqq->ioprio = IOPRIO_NORM;
1791         } else {
1792                 /*
1793                  * check if we need to unboost the queue
1794                  */
1795                 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
1796                         cfqq->ioprio_class = cfqq->org_ioprio_class;
1797                 if (cfqq->ioprio != cfqq->org_ioprio)
1798                         cfqq->ioprio = cfqq->org_ioprio;
1799         }
1800
1801         /*
1802          * refile between round-robin lists if we moved the priority class
1803          */
1804         if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio) &&
1805             cfq_cfqq_on_rr(cfqq))
1806                 cfq_resort_rr_list(cfqq, 0);
1807 }
1808
1809 static inline pid_t cfq_queue_pid(struct task_struct *task, int rw)
1810 {
1811         if (rw == READ || process_sync(task))
1812                 return task->pid;
1813
1814         return CFQ_KEY_ASYNC;
1815 }
1816
1817 static inline int
1818 __cfq_may_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1819                 struct task_struct *task, int rw)
1820 {
1821 #if 1
1822         if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
1823             !cfq_cfqq_must_alloc_slice(cfqq)) {
1824                 cfq_mark_cfqq_must_alloc_slice(cfqq);
1825                 return ELV_MQUEUE_MUST;
1826         }
1827
1828         return ELV_MQUEUE_MAY;
1829 #else
1830         if (!cfqq || task->flags & PF_MEMALLOC)
1831                 return ELV_MQUEUE_MAY;
1832         if (!cfqq->allocated[rw] || cfq_cfqq_must_alloc(cfqq)) {
1833                 if (cfq_cfqq_wait_request(cfqq))
1834                         return ELV_MQUEUE_MUST;
1835
1836                 /*
1837                  * only allow 1 ELV_MQUEUE_MUST per slice, otherwise we
1838                  * can quickly flood the queue with writes from a single task
1839                  */
1840                 if (rw == READ || !cfq_cfqq_must_alloc_slice(cfqq)) {
1841                         cfq_mark_cfqq_must_alloc_slice(cfqq);
1842                         return ELV_MQUEUE_MUST;
1843                 }
1844
1845                 return ELV_MQUEUE_MAY;
1846         }
1847         if (cfq_class_idle(cfqq))
1848                 return ELV_MQUEUE_NO;
1849         if (cfqq->allocated[rw] >= cfqd->max_queued) {
1850                 struct io_context *ioc = get_io_context(GFP_ATOMIC);
1851                 int ret = ELV_MQUEUE_NO;
1852
1853                 if (ioc && ioc->nr_batch_requests)
1854                         ret = ELV_MQUEUE_MAY;
1855
1856                 put_io_context(ioc);
1857                 return ret;
1858         }
1859
1860         return ELV_MQUEUE_MAY;
1861 #endif
1862 }
1863
1864 static int cfq_may_queue(request_queue_t *q, int rw, struct bio *bio)
1865 {
1866         struct cfq_data *cfqd = q->elevator->elevator_data;
1867         struct task_struct *tsk = current;
1868         struct cfq_queue *cfqq;
1869
1870         /*
1871          * don't force setup of a queue from here, as a call to may_queue
1872          * does not necessarily imply that a request actually will be queued.
1873          * so just lookup a possibly existing queue, or return 'may queue'
1874          * if that fails
1875          */
1876         cfqq = cfq_find_cfq_hash(cfqd, cfq_queue_pid(tsk, rw), tsk->ioprio);
1877         if (cfqq) {
1878                 cfq_init_prio_data(cfqq);
1879                 cfq_prio_boost(cfqq);
1880
1881                 return __cfq_may_queue(cfqd, cfqq, tsk, rw);
1882         }
1883
1884         return ELV_MQUEUE_MAY;
1885 }
1886
1887 static void cfq_check_waiters(request_queue_t *q, struct cfq_queue *cfqq)
1888 {
1889         struct cfq_data *cfqd = q->elevator->elevator_data;
1890         struct request_list *rl = &q->rq;
1891
1892         if (cfqq->allocated[READ] <= cfqd->max_queued || cfqd->rq_starved) {
1893                 smp_mb();
1894                 if (waitqueue_active(&rl->wait[READ]))
1895                         wake_up(&rl->wait[READ]);
1896         }
1897
1898         if (cfqq->allocated[WRITE] <= cfqd->max_queued || cfqd->rq_starved) {
1899                 smp_mb();
1900                 if (waitqueue_active(&rl->wait[WRITE]))
1901                         wake_up(&rl->wait[WRITE]);
1902         }
1903 }
1904
1905 /*
1906  * queue lock held here
1907  */
1908 static void cfq_put_request(request_queue_t *q, struct request *rq)
1909 {
1910         struct cfq_data *cfqd = q->elevator->elevator_data;
1911         struct cfq_rq *crq = RQ_DATA(rq);
1912
1913         if (crq) {
1914                 struct cfq_queue *cfqq = crq->cfq_queue;
1915                 const int rw = rq_data_dir(rq);
1916
1917                 BUG_ON(!cfqq->allocated[rw]);
1918                 cfqq->allocated[rw]--;
1919
1920                 put_io_context(crq->io_context->ioc);
1921
1922                 mempool_free(crq, cfqd->crq_pool);
1923                 rq->elevator_private = NULL;
1924
1925                 cfq_check_waiters(q, cfqq);
1926                 cfq_put_queue(cfqq);
1927         }
1928 }
1929
1930 /*
1931  * Allocate cfq data structures associated with this request.
1932  */
1933 static int
1934 cfq_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
1935                 gfp_t gfp_mask)
1936 {
1937         struct cfq_data *cfqd = q->elevator->elevator_data;
1938         struct task_struct *tsk = current;
1939         struct cfq_io_context *cic;
1940         const int rw = rq_data_dir(rq);
1941         pid_t key = cfq_queue_pid(tsk, rw);
1942         struct cfq_queue *cfqq;
1943         struct cfq_rq *crq;
1944         unsigned long flags;
1945         int is_sync = key != CFQ_KEY_ASYNC;
1946
1947         might_sleep_if(gfp_mask & __GFP_WAIT);
1948
1949         cic = cfq_get_io_context(cfqd, gfp_mask);
1950
1951         spin_lock_irqsave(q->queue_lock, flags);
1952
1953         if (!cic)
1954                 goto queue_fail;
1955
1956         if (!cic->cfqq[is_sync]) {
1957                 cfqq = cfq_get_queue(cfqd, key, tsk, gfp_mask);
1958                 if (!cfqq)
1959                         goto queue_fail;
1960
1961                 cic->cfqq[is_sync] = cfqq;
1962         } else
1963                 cfqq = cic->cfqq[is_sync];
1964
1965         cfqq->allocated[rw]++;
1966         cfq_clear_cfqq_must_alloc(cfqq);
1967         cfqd->rq_starved = 0;
1968         atomic_inc(&cfqq->ref);
1969         spin_unlock_irqrestore(q->queue_lock, flags);
1970
1971         crq = mempool_alloc(cfqd->crq_pool, gfp_mask);
1972         if (crq) {
1973                 RB_CLEAR(&crq->rb_node);
1974                 crq->rb_key = 0;
1975                 crq->request = rq;
1976                 INIT_HLIST_NODE(&crq->hash);
1977                 crq->cfq_queue = cfqq;
1978                 crq->io_context = cic;
1979
1980                 if (is_sync)
1981                         cfq_mark_crq_is_sync(crq);
1982                 else
1983                         cfq_clear_crq_is_sync(crq);
1984
1985                 rq->elevator_private = crq;
1986                 return 0;
1987         }
1988
1989         spin_lock_irqsave(q->queue_lock, flags);
1990         cfqq->allocated[rw]--;
1991         if (!(cfqq->allocated[0] + cfqq->allocated[1]))
1992                 cfq_mark_cfqq_must_alloc(cfqq);
1993         cfq_put_queue(cfqq);
1994 queue_fail:
1995         if (cic)
1996                 put_io_context(cic->ioc);
1997         /*
1998          * mark us rq allocation starved. we need to kickstart the process
1999          * ourselves if there are no pending requests that can do it for us.
2000          * that would be an extremely rare OOM situation
2001          */
2002         cfqd->rq_starved = 1;
2003         cfq_schedule_dispatch(cfqd);
2004         spin_unlock_irqrestore(q->queue_lock, flags);
2005         return 1;
2006 }
2007
2008 static void cfq_kick_queue(void *data)
2009 {
2010         request_queue_t *q = data;
2011         struct cfq_data *cfqd = q->elevator->elevator_data;
2012         unsigned long flags;
2013
2014         spin_lock_irqsave(q->queue_lock, flags);
2015
2016         if (cfqd->rq_starved) {
2017                 struct request_list *rl = &q->rq;
2018
2019                 /*
2020                  * we aren't guaranteed to get a request after this, but we
2021                  * have to be opportunistic
2022                  */
2023                 smp_mb();
2024                 if (waitqueue_active(&rl->wait[READ]))
2025                         wake_up(&rl->wait[READ]);
2026                 if (waitqueue_active(&rl->wait[WRITE]))
2027                         wake_up(&rl->wait[WRITE]);
2028         }
2029
2030         blk_remove_plug(q);
2031         q->request_fn(q);
2032         spin_unlock_irqrestore(q->queue_lock, flags);
2033 }
2034
2035 /*
2036  * Timer running if the active_queue is currently idling inside its time slice
2037  */
2038 static void cfq_idle_slice_timer(unsigned long data)
2039 {
2040         struct cfq_data *cfqd = (struct cfq_data *) data;
2041         struct cfq_queue *cfqq;
2042         unsigned long flags;
2043
2044         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2045
2046         if ((cfqq = cfqd->active_queue) != NULL) {
2047                 unsigned long now = jiffies;
2048
2049                 /*
2050                  * expired
2051                  */
2052                 if (time_after(now, cfqq->slice_end))
2053                         goto expire;
2054
2055                 /*
2056                  * only expire and reinvoke request handler, if there are
2057                  * other queues with pending requests
2058                  */
2059                 if (!cfqd->busy_queues) {
2060                         cfqd->idle_slice_timer.expires = min(now + cfqd->cfq_slice_idle, cfqq->slice_end);
2061                         add_timer(&cfqd->idle_slice_timer);
2062                         goto out_cont;
2063                 }
2064
2065                 /*
2066                  * not expired and it has a request pending, let it dispatch
2067                  */
2068                 if (!RB_EMPTY(&cfqq->sort_list)) {
2069                         cfq_mark_cfqq_must_dispatch(cfqq);
2070                         goto out_kick;
2071                 }
2072         }
2073 expire:
2074         cfq_slice_expired(cfqd, 0);
2075 out_kick:
2076         cfq_schedule_dispatch(cfqd);
2077 out_cont:
2078         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2079 }
2080
2081 /*
2082  * Timer running if an idle class queue is waiting for service
2083  */
2084 static void cfq_idle_class_timer(unsigned long data)
2085 {
2086         struct cfq_data *cfqd = (struct cfq_data *) data;
2087         unsigned long flags, end;
2088
2089         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2090
2091         /*
2092          * race with a non-idle queue, reset timer
2093          */
2094         end = cfqd->last_end_request + CFQ_IDLE_GRACE;
2095         if (!time_after_eq(jiffies, end)) {
2096                 cfqd->idle_class_timer.expires = end;
2097                 add_timer(&cfqd->idle_class_timer);
2098         } else
2099                 cfq_schedule_dispatch(cfqd);
2100
2101         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2102 }
2103
2104 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2105 {
2106         del_timer_sync(&cfqd->idle_slice_timer);
2107         del_timer_sync(&cfqd->idle_class_timer);
2108         blk_sync_queue(cfqd->queue);
2109 }
2110
2111 static void cfq_exit_queue(elevator_t *e)
2112 {
2113         struct cfq_data *cfqd = e->elevator_data;
2114         request_queue_t *q = cfqd->queue;
2115
2116         cfq_shutdown_timer_wq(cfqd);
2117
2118         write_lock(&cfq_exit_lock);
2119         spin_lock_irq(q->queue_lock);
2120
2121         if (cfqd->active_queue)
2122                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
2123
2124         while (!list_empty(&cfqd->cic_list)) {
2125                 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2126                                                         struct cfq_io_context,
2127                                                         queue_list);
2128                 if (cic->cfqq[ASYNC]) {
2129                         cfq_put_queue(cic->cfqq[ASYNC]);
2130                         cic->cfqq[ASYNC] = NULL;
2131                 }
2132                 if (cic->cfqq[SYNC]) {
2133                         cfq_put_queue(cic->cfqq[SYNC]);
2134                         cic->cfqq[SYNC] = NULL;
2135                 }
2136                 cic->key = NULL;
2137                 list_del_init(&cic->queue_list);
2138         }
2139
2140         spin_unlock_irq(q->queue_lock);
2141         write_unlock(&cfq_exit_lock);
2142
2143         cfq_shutdown_timer_wq(cfqd);
2144
2145         mempool_destroy(cfqd->crq_pool);
2146         kfree(cfqd->crq_hash);
2147         kfree(cfqd->cfq_hash);
2148         kfree(cfqd);
2149 }
2150
2151 static int cfq_init_queue(request_queue_t *q, elevator_t *e)
2152 {
2153         struct cfq_data *cfqd;
2154         int i;
2155
2156         cfqd = kmalloc(sizeof(*cfqd), GFP_KERNEL);
2157         if (!cfqd)
2158                 return -ENOMEM;
2159
2160         memset(cfqd, 0, sizeof(*cfqd));
2161
2162         for (i = 0; i < CFQ_PRIO_LISTS; i++)
2163                 INIT_LIST_HEAD(&cfqd->rr_list[i]);
2164
2165         INIT_LIST_HEAD(&cfqd->busy_rr);
2166         INIT_LIST_HEAD(&cfqd->cur_rr);
2167         INIT_LIST_HEAD(&cfqd->idle_rr);
2168         INIT_LIST_HEAD(&cfqd->empty_list);
2169         INIT_LIST_HEAD(&cfqd->cic_list);
2170
2171         cfqd->crq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_MHASH_ENTRIES, GFP_KERNEL);
2172         if (!cfqd->crq_hash)
2173                 goto out_crqhash;
2174
2175         cfqd->cfq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL);
2176         if (!cfqd->cfq_hash)
2177                 goto out_cfqhash;
2178
2179         cfqd->crq_pool = mempool_create_slab_pool(BLKDEV_MIN_RQ, crq_pool);
2180         if (!cfqd->crq_pool)
2181                 goto out_crqpool;
2182
2183         for (i = 0; i < CFQ_MHASH_ENTRIES; i++)
2184                 INIT_HLIST_HEAD(&cfqd->crq_hash[i]);
2185         for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
2186                 INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
2187
2188         e->elevator_data = cfqd;
2189
2190         cfqd->queue = q;
2191
2192         cfqd->max_queued = q->nr_requests / 4;
2193         q->nr_batching = cfq_queued;
2194
2195         init_timer(&cfqd->idle_slice_timer);
2196         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2197         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2198
2199         init_timer(&cfqd->idle_class_timer);
2200         cfqd->idle_class_timer.function = cfq_idle_class_timer;
2201         cfqd->idle_class_timer.data = (unsigned long) cfqd;
2202
2203         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue, q);
2204
2205         cfqd->cfq_queued = cfq_queued;
2206         cfqd->cfq_quantum = cfq_quantum;
2207         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2208         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2209         cfqd->cfq_back_max = cfq_back_max;
2210         cfqd->cfq_back_penalty = cfq_back_penalty;
2211         cfqd->cfq_slice[0] = cfq_slice_async;
2212         cfqd->cfq_slice[1] = cfq_slice_sync;
2213         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2214         cfqd->cfq_slice_idle = cfq_slice_idle;
2215         cfqd->cfq_max_depth = cfq_max_depth;
2216
2217         return 0;
2218 out_crqpool:
2219         kfree(cfqd->cfq_hash);
2220 out_cfqhash:
2221         kfree(cfqd->crq_hash);
2222 out_crqhash:
2223         kfree(cfqd);
2224         return -ENOMEM;
2225 }
2226
2227 static void cfq_slab_kill(void)
2228 {
2229         if (crq_pool)
2230                 kmem_cache_destroy(crq_pool);
2231         if (cfq_pool)
2232                 kmem_cache_destroy(cfq_pool);
2233         if (cfq_ioc_pool)
2234                 kmem_cache_destroy(cfq_ioc_pool);
2235 }
2236
2237 static int __init cfq_slab_setup(void)
2238 {
2239         crq_pool = kmem_cache_create("crq_pool", sizeof(struct cfq_rq), 0, 0,
2240                                         NULL, NULL);
2241         if (!crq_pool)
2242                 goto fail;
2243
2244         cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0,
2245                                         NULL, NULL);
2246         if (!cfq_pool)
2247                 goto fail;
2248
2249         cfq_ioc_pool = kmem_cache_create("cfq_ioc_pool",
2250                         sizeof(struct cfq_io_context), 0, 0, NULL, NULL);
2251         if (!cfq_ioc_pool)
2252                 goto fail;
2253
2254         return 0;
2255 fail:
2256         cfq_slab_kill();
2257         return -ENOMEM;
2258 }
2259
2260 /*
2261  * sysfs parts below -->
2262  */
2263
2264 static ssize_t
2265 cfq_var_show(unsigned int var, char *page)
2266 {
2267         return sprintf(page, "%d\n", var);
2268 }
2269
2270 static ssize_t
2271 cfq_var_store(unsigned int *var, const char *page, size_t count)
2272 {
2273         char *p = (char *) page;
2274
2275         *var = simple_strtoul(p, &p, 10);
2276         return count;
2277 }
2278
2279 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
2280 static ssize_t __FUNC(elevator_t *e, char *page)                        \
2281 {                                                                       \
2282         struct cfq_data *cfqd = e->elevator_data;                       \
2283         unsigned int __data = __VAR;                                    \
2284         if (__CONV)                                                     \
2285                 __data = jiffies_to_msecs(__data);                      \
2286         return cfq_var_show(__data, (page));                            \
2287 }
2288 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2289 SHOW_FUNCTION(cfq_queued_show, cfqd->cfq_queued, 0);
2290 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2291 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2292 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
2293 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
2294 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2295 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2296 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2297 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2298 SHOW_FUNCTION(cfq_max_depth_show, cfqd->cfq_max_depth, 0);
2299 #undef SHOW_FUNCTION
2300
2301 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
2302 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count)    \
2303 {                                                                       \
2304         struct cfq_data *cfqd = e->elevator_data;                       \
2305         unsigned int __data;                                            \
2306         int ret = cfq_var_store(&__data, (page), count);                \
2307         if (__data < (MIN))                                             \
2308                 __data = (MIN);                                         \
2309         else if (__data > (MAX))                                        \
2310                 __data = (MAX);                                         \
2311         if (__CONV)                                                     \
2312                 *(__PTR) = msecs_to_jiffies(__data);                    \
2313         else                                                            \
2314                 *(__PTR) = __data;                                      \
2315         return ret;                                                     \
2316 }
2317 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2318 STORE_FUNCTION(cfq_queued_store, &cfqd->cfq_queued, 1, UINT_MAX, 0);
2319 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1);
2320 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1);
2321 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2322 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0);
2323 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2324 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2325 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2326 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0);
2327 STORE_FUNCTION(cfq_max_depth_store, &cfqd->cfq_max_depth, 1, UINT_MAX, 0);
2328 #undef STORE_FUNCTION
2329
2330 #define CFQ_ATTR(name) \
2331         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2332
2333 static struct elv_fs_entry cfq_attrs[] = {
2334         CFQ_ATTR(quantum),
2335         CFQ_ATTR(queued),
2336         CFQ_ATTR(fifo_expire_sync),
2337         CFQ_ATTR(fifo_expire_async),
2338         CFQ_ATTR(back_seek_max),
2339         CFQ_ATTR(back_seek_penalty),
2340         CFQ_ATTR(slice_sync),
2341         CFQ_ATTR(slice_async),
2342         CFQ_ATTR(slice_async_rq),
2343         CFQ_ATTR(slice_idle),
2344         CFQ_ATTR(max_depth),
2345         __ATTR_NULL
2346 };
2347
2348 static struct elevator_type iosched_cfq = {
2349         .ops = {
2350                 .elevator_merge_fn =            cfq_merge,
2351                 .elevator_merged_fn =           cfq_merged_request,
2352                 .elevator_merge_req_fn =        cfq_merged_requests,
2353                 .elevator_dispatch_fn =         cfq_dispatch_requests,
2354                 .elevator_add_req_fn =          cfq_insert_request,
2355                 .elevator_activate_req_fn =     cfq_activate_request,
2356                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
2357                 .elevator_queue_empty_fn =      cfq_queue_empty,
2358                 .elevator_completed_req_fn =    cfq_completed_request,
2359                 .elevator_former_req_fn =       cfq_former_request,
2360                 .elevator_latter_req_fn =       cfq_latter_request,
2361                 .elevator_set_req_fn =          cfq_set_request,
2362                 .elevator_put_req_fn =          cfq_put_request,
2363                 .elevator_may_queue_fn =        cfq_may_queue,
2364                 .elevator_init_fn =             cfq_init_queue,
2365                 .elevator_exit_fn =             cfq_exit_queue,
2366                 .trim =                         cfq_trim,
2367         },
2368         .elevator_attrs =       cfq_attrs,
2369         .elevator_name =        "cfq",
2370         .elevator_owner =       THIS_MODULE,
2371 };
2372
2373 static int __init cfq_init(void)
2374 {
2375         int ret;
2376
2377         /*
2378          * could be 0 on HZ < 1000 setups
2379          */
2380         if (!cfq_slice_async)
2381                 cfq_slice_async = 1;
2382         if (!cfq_slice_idle)
2383                 cfq_slice_idle = 1;
2384
2385         if (cfq_slab_setup())
2386                 return -ENOMEM;
2387
2388         ret = elv_register(&iosched_cfq);
2389         if (ret)
2390                 cfq_slab_kill();
2391
2392         return ret;
2393 }
2394
2395 static void __exit cfq_exit(void)
2396 {
2397         DECLARE_COMPLETION(all_gone);
2398         elv_unregister(&iosched_cfq);
2399         ioc_gone = &all_gone;
2400         barrier();
2401         if (atomic_read(&ioc_count))
2402                 complete(ioc_gone);
2403         synchronize_rcu();
2404         cfq_slab_kill();
2405 }
2406
2407 module_init(cfq_init);
2408 module_exit(cfq_exit);
2409
2410 MODULE_AUTHOR("Jens Axboe");
2411 MODULE_LICENSE("GPL");
2412 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");