[PATCH] elevator switching race
[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 / 70;
30
31 #define CFQ_IDLE_GRACE          (HZ / 10)
32 #define CFQ_SLICE_SCALE         (5)
33
34 #define CFQ_KEY_ASYNC           (0)
35
36 static DEFINE_SPINLOCK(cfq_exit_lock);
37
38 /*
39  * for the hash of cfqq inside the cfqd
40  */
41 #define CFQ_QHASH_SHIFT         6
42 #define CFQ_QHASH_ENTRIES       (1 << CFQ_QHASH_SHIFT)
43 #define list_entry_qhash(entry) hlist_entry((entry), struct cfq_queue, cfq_hash)
44
45 /*
46  * for the hash of crq inside the cfqq
47  */
48 #define CFQ_MHASH_SHIFT         6
49 #define CFQ_MHASH_BLOCK(sec)    ((sec) >> 3)
50 #define CFQ_MHASH_ENTRIES       (1 << CFQ_MHASH_SHIFT)
51 #define CFQ_MHASH_FN(sec)       hash_long(CFQ_MHASH_BLOCK(sec), CFQ_MHASH_SHIFT)
52 #define rq_hash_key(rq)         ((rq)->sector + (rq)->nr_sectors)
53 #define list_entry_hash(ptr)    hlist_entry((ptr), struct cfq_rq, hash)
54
55 #define list_entry_cfqq(ptr)    list_entry((ptr), struct cfq_queue, cfq_list)
56 #define list_entry_fifo(ptr)    list_entry((ptr), struct request, queuelist)
57
58 #define RQ_DATA(rq)             (rq)->elevator_private
59
60 /*
61  * rb-tree defines
62  */
63 #define RB_NONE                 (2)
64 #define RB_EMPTY(node)          ((node)->rb_node == NULL)
65 #define RB_CLEAR_COLOR(node)    (node)->rb_color = RB_NONE
66 #define RB_CLEAR(node)          do {    \
67         (node)->rb_parent = NULL;       \
68         RB_CLEAR_COLOR((node));         \
69         (node)->rb_right = NULL;        \
70         (node)->rb_left = NULL;         \
71 } while (0)
72 #define RB_CLEAR_ROOT(root)     ((root)->rb_node = NULL)
73 #define rb_entry_crq(node)      rb_entry((node), struct cfq_rq, rb_node)
74 #define rq_rb_key(rq)           (rq)->sector
75
76 static kmem_cache_t *crq_pool;
77 static kmem_cache_t *cfq_pool;
78 static kmem_cache_t *cfq_ioc_pool;
79
80 static atomic_t ioc_count = ATOMIC_INIT(0);
81 static struct completion *ioc_gone;
82
83 #define CFQ_PRIO_LISTS          IOPRIO_BE_NR
84 #define cfq_class_idle(cfqq)    ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
85 #define cfq_class_be(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_BE)
86 #define cfq_class_rt(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
87
88 #define ASYNC                   (0)
89 #define SYNC                    (1)
90
91 #define cfq_cfqq_dispatched(cfqq)       \
92         ((cfqq)->on_dispatch[ASYNC] + (cfqq)->on_dispatch[SYNC])
93
94 #define cfq_cfqq_class_sync(cfqq)       ((cfqq)->key != CFQ_KEY_ASYNC)
95
96 #define cfq_cfqq_sync(cfqq)             \
97         (cfq_cfqq_class_sync(cfqq) || (cfqq)->on_dispatch[SYNC])
98
99 #define sample_valid(samples)   ((samples) > 80)
100
101 /*
102  * Per block device queue structure
103  */
104 struct cfq_data {
105         request_queue_t *queue;
106
107         /*
108          * rr list of queues with requests and the count of them
109          */
110         struct list_head rr_list[CFQ_PRIO_LISTS];
111         struct list_head busy_rr;
112         struct list_head cur_rr;
113         struct list_head idle_rr;
114         unsigned int busy_queues;
115
116         /*
117          * non-ordered list of empty cfqq's
118          */
119         struct list_head empty_list;
120
121         /*
122          * cfqq lookup hash
123          */
124         struct hlist_head *cfq_hash;
125
126         /*
127          * global crq hash for all queues
128          */
129         struct hlist_head *crq_hash;
130
131         unsigned int max_queued;
132
133         mempool_t *crq_pool;
134
135         int rq_in_driver;
136         int hw_tag;
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
171         struct list_head cic_list;
172 };
173
174 /*
175  * Per process-grouping structure
176  */
177 struct cfq_queue {
178         /* reference count */
179         atomic_t ref;
180         /* parent cfq_data */
181         struct cfq_data *cfqd;
182         /* cfqq lookup hash */
183         struct hlist_node cfq_hash;
184         /* hash key */
185         unsigned int key;
186         /* on either rr or empty list of cfqd */
187         struct list_head cfq_list;
188         /* sorted list of pending requests */
189         struct rb_root sort_list;
190         /* if fifo isn't expired, next request to serve */
191         struct cfq_rq *next_crq;
192         /* requests queued in sort_list */
193         int queued[2];
194         /* currently allocated requests */
195         int allocated[2];
196         /* fifo list of requests in sort_list */
197         struct list_head fifo;
198
199         unsigned long slice_start;
200         unsigned long slice_end;
201         unsigned long slice_left;
202         unsigned long service_last;
203
204         /* number of requests that are on the dispatch list */
205         int on_dispatch[2];
206
207         /* io prio of this group */
208         unsigned short ioprio, org_ioprio;
209         unsigned short ioprio_class, org_ioprio_class;
210
211         /* various state flags, see below */
212         unsigned int flags;
213 };
214
215 struct cfq_rq {
216         struct rb_node rb_node;
217         sector_t rb_key;
218         struct request *request;
219         struct hlist_node hash;
220
221         struct cfq_queue *cfq_queue;
222         struct cfq_io_context *io_context;
223
224         unsigned int crq_flags;
225 };
226
227 enum cfqq_state_flags {
228         CFQ_CFQQ_FLAG_on_rr = 0,
229         CFQ_CFQQ_FLAG_wait_request,
230         CFQ_CFQQ_FLAG_must_alloc,
231         CFQ_CFQQ_FLAG_must_alloc_slice,
232         CFQ_CFQQ_FLAG_must_dispatch,
233         CFQ_CFQQ_FLAG_fifo_expire,
234         CFQ_CFQQ_FLAG_idle_window,
235         CFQ_CFQQ_FLAG_prio_changed,
236 };
237
238 #define CFQ_CFQQ_FNS(name)                                              \
239 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
240 {                                                                       \
241         cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name);                     \
242 }                                                                       \
243 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
244 {                                                                       \
245         cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                    \
246 }                                                                       \
247 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
248 {                                                                       \
249         return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;        \
250 }
251
252 CFQ_CFQQ_FNS(on_rr);
253 CFQ_CFQQ_FNS(wait_request);
254 CFQ_CFQQ_FNS(must_alloc);
255 CFQ_CFQQ_FNS(must_alloc_slice);
256 CFQ_CFQQ_FNS(must_dispatch);
257 CFQ_CFQQ_FNS(fifo_expire);
258 CFQ_CFQQ_FNS(idle_window);
259 CFQ_CFQQ_FNS(prio_changed);
260 #undef CFQ_CFQQ_FNS
261
262 enum cfq_rq_state_flags {
263         CFQ_CRQ_FLAG_is_sync = 0,
264 };
265
266 #define CFQ_CRQ_FNS(name)                                               \
267 static inline void cfq_mark_crq_##name(struct cfq_rq *crq)              \
268 {                                                                       \
269         crq->crq_flags |= (1 << CFQ_CRQ_FLAG_##name);                   \
270 }                                                                       \
271 static inline void cfq_clear_crq_##name(struct cfq_rq *crq)             \
272 {                                                                       \
273         crq->crq_flags &= ~(1 << CFQ_CRQ_FLAG_##name);                  \
274 }                                                                       \
275 static inline int cfq_crq_##name(const struct cfq_rq *crq)              \
276 {                                                                       \
277         return (crq->crq_flags & (1 << CFQ_CRQ_FLAG_##name)) != 0;      \
278 }
279
280 CFQ_CRQ_FNS(is_sync);
281 #undef CFQ_CRQ_FNS
282
283 static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short);
284 static void cfq_dispatch_insert(request_queue_t *, struct cfq_rq *);
285 static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask);
286
287 #define process_sync(tsk)       ((tsk)->flags & PF_SYNCWRITE)
288
289 /*
290  * lots of deadline iosched dupes, can be abstracted later...
291  */
292 static inline void cfq_del_crq_hash(struct cfq_rq *crq)
293 {
294         hlist_del_init(&crq->hash);
295 }
296
297 static inline void cfq_add_crq_hash(struct cfq_data *cfqd, struct cfq_rq *crq)
298 {
299         const int hash_idx = CFQ_MHASH_FN(rq_hash_key(crq->request));
300
301         hlist_add_head(&crq->hash, &cfqd->crq_hash[hash_idx]);
302 }
303
304 static struct request *cfq_find_rq_hash(struct cfq_data *cfqd, sector_t offset)
305 {
306         struct hlist_head *hash_list = &cfqd->crq_hash[CFQ_MHASH_FN(offset)];
307         struct hlist_node *entry, *next;
308
309         hlist_for_each_safe(entry, next, hash_list) {
310                 struct cfq_rq *crq = list_entry_hash(entry);
311                 struct request *__rq = crq->request;
312
313                 if (!rq_mergeable(__rq)) {
314                         cfq_del_crq_hash(crq);
315                         continue;
316                 }
317
318                 if (rq_hash_key(__rq) == offset)
319                         return __rq;
320         }
321
322         return NULL;
323 }
324
325 /*
326  * scheduler run of queue, if there are requests pending and no one in the
327  * driver that will restart queueing
328  */
329 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
330 {
331         if (cfqd->busy_queues)
332                 kblockd_schedule_work(&cfqd->unplug_work);
333 }
334
335 static int cfq_queue_empty(request_queue_t *q)
336 {
337         struct cfq_data *cfqd = q->elevator->elevator_data;
338
339         return !cfqd->busy_queues;
340 }
341
342 static inline pid_t cfq_queue_pid(struct task_struct *task, int rw)
343 {
344         if (rw == READ || process_sync(task))
345                 return task->pid;
346
347         return CFQ_KEY_ASYNC;
348 }
349
350 /*
351  * Lifted from AS - choose which of crq1 and crq2 that is best served now.
352  * We choose the request that is closest to the head right now. Distance
353  * behind the head is penalized and only allowed to a certain extent.
354  */
355 static struct cfq_rq *
356 cfq_choose_req(struct cfq_data *cfqd, struct cfq_rq *crq1, struct cfq_rq *crq2)
357 {
358         sector_t last, s1, s2, d1 = 0, d2 = 0;
359         unsigned long back_max;
360 #define CFQ_RQ1_WRAP    0x01 /* request 1 wraps */
361 #define CFQ_RQ2_WRAP    0x02 /* request 2 wraps */
362         unsigned wrap = 0; /* bit mask: requests behind the disk head? */
363
364         if (crq1 == NULL || crq1 == crq2)
365                 return crq2;
366         if (crq2 == NULL)
367                 return crq1;
368
369         if (cfq_crq_is_sync(crq1) && !cfq_crq_is_sync(crq2))
370                 return crq1;
371         else if (cfq_crq_is_sync(crq2) && !cfq_crq_is_sync(crq1))
372                 return crq2;
373
374         s1 = crq1->request->sector;
375         s2 = crq2->request->sector;
376
377         last = cfqd->last_sector;
378
379         /*
380          * by definition, 1KiB is 2 sectors
381          */
382         back_max = cfqd->cfq_back_max * 2;
383
384         /*
385          * Strict one way elevator _except_ in the case where we allow
386          * short backward seeks which are biased as twice the cost of a
387          * similar forward seek.
388          */
389         if (s1 >= last)
390                 d1 = s1 - last;
391         else if (s1 + back_max >= last)
392                 d1 = (last - s1) * cfqd->cfq_back_penalty;
393         else
394                 wrap |= CFQ_RQ1_WRAP;
395
396         if (s2 >= last)
397                 d2 = s2 - last;
398         else if (s2 + back_max >= last)
399                 d2 = (last - s2) * cfqd->cfq_back_penalty;
400         else
401                 wrap |= CFQ_RQ2_WRAP;
402
403         /* Found required data */
404
405         /*
406          * By doing switch() on the bit mask "wrap" we avoid having to
407          * check two variables for all permutations: --> faster!
408          */
409         switch (wrap) {
410         case 0: /* common case for CFQ: crq1 and crq2 not wrapped */
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         case CFQ_RQ2_WRAP:
423                 return crq1;
424         case CFQ_RQ1_WRAP:
425                 return crq2;
426         case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both crqs wrapped */
427         default:
428                 /*
429                  * Since both rqs are wrapped,
430                  * start with the one that's further behind head
431                  * (--> only *one* back seek required),
432                  * since back seek takes more time than forward.
433                  */
434                 if (s1 <= s2)
435                         return crq1;
436                 else
437                         return crq2;
438         }
439 }
440
441 /*
442  * would be nice to take fifo expire time into account as well
443  */
444 static struct cfq_rq *
445 cfq_find_next_crq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
446                   struct cfq_rq *last)
447 {
448         struct cfq_rq *crq_next = NULL, *crq_prev = NULL;
449         struct rb_node *rbnext, *rbprev;
450
451         if (!(rbnext = rb_next(&last->rb_node))) {
452                 rbnext = rb_first(&cfqq->sort_list);
453                 if (rbnext == &last->rb_node)
454                         rbnext = NULL;
455         }
456
457         rbprev = rb_prev(&last->rb_node);
458
459         if (rbprev)
460                 crq_prev = rb_entry_crq(rbprev);
461         if (rbnext)
462                 crq_next = rb_entry_crq(rbnext);
463
464         return cfq_choose_req(cfqd, crq_next, crq_prev);
465 }
466
467 static void cfq_update_next_crq(struct cfq_rq *crq)
468 {
469         struct cfq_queue *cfqq = crq->cfq_queue;
470
471         if (cfqq->next_crq == crq)
472                 cfqq->next_crq = cfq_find_next_crq(cfqq->cfqd, cfqq, crq);
473 }
474
475 static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
476 {
477         struct cfq_data *cfqd = cfqq->cfqd;
478         struct list_head *list, *entry;
479
480         BUG_ON(!cfq_cfqq_on_rr(cfqq));
481
482         list_del(&cfqq->cfq_list);
483
484         if (cfq_class_rt(cfqq))
485                 list = &cfqd->cur_rr;
486         else if (cfq_class_idle(cfqq))
487                 list = &cfqd->idle_rr;
488         else {
489                 /*
490                  * if cfqq has requests in flight, don't allow it to be
491                  * found in cfq_set_active_queue before it has finished them.
492                  * this is done to increase fairness between a process that
493                  * has lots of io pending vs one that only generates one
494                  * sporadically or synchronously
495                  */
496                 if (cfq_cfqq_dispatched(cfqq))
497                         list = &cfqd->busy_rr;
498                 else
499                         list = &cfqd->rr_list[cfqq->ioprio];
500         }
501
502         /*
503          * if queue was preempted, just add to front to be fair. busy_rr
504          * isn't sorted, but insert at the back for fairness.
505          */
506         if (preempted || list == &cfqd->busy_rr) {
507                 if (preempted)
508                         list = list->prev;
509
510                 list_add_tail(&cfqq->cfq_list, list);
511                 return;
512         }
513
514         /*
515          * sort by when queue was last serviced
516          */
517         entry = list;
518         while ((entry = entry->prev) != list) {
519                 struct cfq_queue *__cfqq = list_entry_cfqq(entry);
520
521                 if (!__cfqq->service_last)
522                         break;
523                 if (time_before(__cfqq->service_last, cfqq->service_last))
524                         break;
525         }
526
527         list_add(&cfqq->cfq_list, entry);
528 }
529
530 /*
531  * add to busy list of queues for service, trying to be fair in ordering
532  * the pending list according to last request service
533  */
534 static inline void
535 cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
536 {
537         BUG_ON(cfq_cfqq_on_rr(cfqq));
538         cfq_mark_cfqq_on_rr(cfqq);
539         cfqd->busy_queues++;
540
541         cfq_resort_rr_list(cfqq, 0);
542 }
543
544 static inline void
545 cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
546 {
547         BUG_ON(!cfq_cfqq_on_rr(cfqq));
548         cfq_clear_cfqq_on_rr(cfqq);
549         list_move(&cfqq->cfq_list, &cfqd->empty_list);
550
551         BUG_ON(!cfqd->busy_queues);
552         cfqd->busy_queues--;
553 }
554
555 /*
556  * rb tree support functions
557  */
558 static inline void cfq_del_crq_rb(struct cfq_rq *crq)
559 {
560         struct cfq_queue *cfqq = crq->cfq_queue;
561         struct cfq_data *cfqd = cfqq->cfqd;
562         const int sync = cfq_crq_is_sync(crq);
563
564         BUG_ON(!cfqq->queued[sync]);
565         cfqq->queued[sync]--;
566
567         cfq_update_next_crq(crq);
568
569         rb_erase(&crq->rb_node, &cfqq->sort_list);
570         RB_CLEAR_COLOR(&crq->rb_node);
571
572         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY(&cfqq->sort_list))
573                 cfq_del_cfqq_rr(cfqd, cfqq);
574 }
575
576 static struct cfq_rq *
577 __cfq_add_crq_rb(struct cfq_rq *crq)
578 {
579         struct rb_node **p = &crq->cfq_queue->sort_list.rb_node;
580         struct rb_node *parent = NULL;
581         struct cfq_rq *__crq;
582
583         while (*p) {
584                 parent = *p;
585                 __crq = rb_entry_crq(parent);
586
587                 if (crq->rb_key < __crq->rb_key)
588                         p = &(*p)->rb_left;
589                 else if (crq->rb_key > __crq->rb_key)
590                         p = &(*p)->rb_right;
591                 else
592                         return __crq;
593         }
594
595         rb_link_node(&crq->rb_node, parent, p);
596         return NULL;
597 }
598
599 static void cfq_add_crq_rb(struct cfq_rq *crq)
600 {
601         struct cfq_queue *cfqq = crq->cfq_queue;
602         struct cfq_data *cfqd = cfqq->cfqd;
603         struct request *rq = crq->request;
604         struct cfq_rq *__alias;
605
606         crq->rb_key = rq_rb_key(rq);
607         cfqq->queued[cfq_crq_is_sync(crq)]++;
608
609         /*
610          * looks a little odd, but the first insert might return an alias.
611          * if that happens, put the alias on the dispatch list
612          */
613         while ((__alias = __cfq_add_crq_rb(crq)) != NULL)
614                 cfq_dispatch_insert(cfqd->queue, __alias);
615
616         rb_insert_color(&crq->rb_node, &cfqq->sort_list);
617
618         if (!cfq_cfqq_on_rr(cfqq))
619                 cfq_add_cfqq_rr(cfqd, cfqq);
620
621         /*
622          * check if this request is a better next-serve candidate
623          */
624         cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
625 }
626
627 static inline void
628 cfq_reposition_crq_rb(struct cfq_queue *cfqq, struct cfq_rq *crq)
629 {
630         rb_erase(&crq->rb_node, &cfqq->sort_list);
631         cfqq->queued[cfq_crq_is_sync(crq)]--;
632
633         cfq_add_crq_rb(crq);
634 }
635
636 static struct request *
637 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
638 {
639         struct task_struct *tsk = current;
640         pid_t key = cfq_queue_pid(tsk, bio_data_dir(bio));
641         struct cfq_queue *cfqq;
642         struct rb_node *n;
643         sector_t sector;
644
645         cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
646         if (!cfqq)
647                 goto out;
648
649         sector = bio->bi_sector + bio_sectors(bio);
650         n = cfqq->sort_list.rb_node;
651         while (n) {
652                 struct cfq_rq *crq = rb_entry_crq(n);
653
654                 if (sector < crq->rb_key)
655                         n = n->rb_left;
656                 else if (sector > crq->rb_key)
657                         n = n->rb_right;
658                 else
659                         return crq->request;
660         }
661
662 out:
663         return NULL;
664 }
665
666 static void cfq_activate_request(request_queue_t *q, struct request *rq)
667 {
668         struct cfq_data *cfqd = q->elevator->elevator_data;
669
670         cfqd->rq_in_driver++;
671
672         /*
673          * If the depth is larger 1, it really could be queueing. But lets
674          * make the mark a little higher - idling could still be good for
675          * low queueing, and a low queueing number could also just indicate
676          * a SCSI mid layer like behaviour where limit+1 is often seen.
677          */
678         if (!cfqd->hw_tag && cfqd->rq_in_driver > 4)
679                 cfqd->hw_tag = 1;
680 }
681
682 static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
683 {
684         struct cfq_data *cfqd = q->elevator->elevator_data;
685
686         WARN_ON(!cfqd->rq_in_driver);
687         cfqd->rq_in_driver--;
688 }
689
690 static void cfq_remove_request(struct request *rq)
691 {
692         struct cfq_rq *crq = RQ_DATA(rq);
693
694         list_del_init(&rq->queuelist);
695         cfq_del_crq_rb(crq);
696         cfq_del_crq_hash(crq);
697 }
698
699 static int
700 cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
701 {
702         struct cfq_data *cfqd = q->elevator->elevator_data;
703         struct request *__rq;
704         int ret;
705
706         __rq = cfq_find_rq_hash(cfqd, bio->bi_sector);
707         if (__rq && elv_rq_merge_ok(__rq, bio)) {
708                 ret = ELEVATOR_BACK_MERGE;
709                 goto out;
710         }
711
712         __rq = cfq_find_rq_fmerge(cfqd, bio);
713         if (__rq && elv_rq_merge_ok(__rq, bio)) {
714                 ret = ELEVATOR_FRONT_MERGE;
715                 goto out;
716         }
717
718         return ELEVATOR_NO_MERGE;
719 out:
720         *req = __rq;
721         return ret;
722 }
723
724 static void cfq_merged_request(request_queue_t *q, struct request *req)
725 {
726         struct cfq_data *cfqd = q->elevator->elevator_data;
727         struct cfq_rq *crq = RQ_DATA(req);
728
729         cfq_del_crq_hash(crq);
730         cfq_add_crq_hash(cfqd, crq);
731
732         if (rq_rb_key(req) != crq->rb_key) {
733                 struct cfq_queue *cfqq = crq->cfq_queue;
734
735                 cfq_update_next_crq(crq);
736                 cfq_reposition_crq_rb(cfqq, crq);
737         }
738 }
739
740 static void
741 cfq_merged_requests(request_queue_t *q, struct request *rq,
742                     struct request *next)
743 {
744         cfq_merged_request(q, rq);
745
746         /*
747          * reposition in fifo if next is older than rq
748          */
749         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
750             time_before(next->start_time, rq->start_time))
751                 list_move(&rq->queuelist, &next->queuelist);
752
753         cfq_remove_request(next);
754 }
755
756 static inline void
757 __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
758 {
759         if (cfqq) {
760                 /*
761                  * stop potential idle class queues waiting service
762                  */
763                 del_timer(&cfqd->idle_class_timer);
764
765                 cfqq->slice_start = jiffies;
766                 cfqq->slice_end = 0;
767                 cfqq->slice_left = 0;
768                 cfq_clear_cfqq_must_alloc_slice(cfqq);
769                 cfq_clear_cfqq_fifo_expire(cfqq);
770         }
771
772         cfqd->active_queue = cfqq;
773 }
774
775 /*
776  * current cfqq expired its slice (or was too idle), select new one
777  */
778 static void
779 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
780                     int preempted)
781 {
782         unsigned long now = jiffies;
783
784         if (cfq_cfqq_wait_request(cfqq))
785                 del_timer(&cfqd->idle_slice_timer);
786
787         if (!preempted && !cfq_cfqq_dispatched(cfqq)) {
788                 cfqq->service_last = now;
789                 cfq_schedule_dispatch(cfqd);
790         }
791
792         cfq_clear_cfqq_must_dispatch(cfqq);
793         cfq_clear_cfqq_wait_request(cfqq);
794
795         /*
796          * store what was left of this slice, if the queue idled out
797          * or was preempted
798          */
799         if (time_after(cfqq->slice_end, now))
800                 cfqq->slice_left = cfqq->slice_end - now;
801         else
802                 cfqq->slice_left = 0;
803
804         if (cfq_cfqq_on_rr(cfqq))
805                 cfq_resort_rr_list(cfqq, preempted);
806
807         if (cfqq == cfqd->active_queue)
808                 cfqd->active_queue = NULL;
809
810         if (cfqd->active_cic) {
811                 put_io_context(cfqd->active_cic->ioc);
812                 cfqd->active_cic = NULL;
813         }
814
815         cfqd->dispatch_slice = 0;
816 }
817
818 static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted)
819 {
820         struct cfq_queue *cfqq = cfqd->active_queue;
821
822         if (cfqq)
823                 __cfq_slice_expired(cfqd, cfqq, preempted);
824 }
825
826 /*
827  * 0
828  * 0,1
829  * 0,1,2
830  * 0,1,2,3
831  * 0,1,2,3,4
832  * 0,1,2,3,4,5
833  * 0,1,2,3,4,5,6
834  * 0,1,2,3,4,5,6,7
835  */
836 static int cfq_get_next_prio_level(struct cfq_data *cfqd)
837 {
838         int prio, wrap;
839
840         prio = -1;
841         wrap = 0;
842         do {
843                 int p;
844
845                 for (p = cfqd->cur_prio; p <= cfqd->cur_end_prio; p++) {
846                         if (!list_empty(&cfqd->rr_list[p])) {
847                                 prio = p;
848                                 break;
849                         }
850                 }
851
852                 if (prio != -1)
853                         break;
854                 cfqd->cur_prio = 0;
855                 if (++cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
856                         cfqd->cur_end_prio = 0;
857                         if (wrap)
858                                 break;
859                         wrap = 1;
860                 }
861         } while (1);
862
863         if (unlikely(prio == -1))
864                 return -1;
865
866         BUG_ON(prio >= CFQ_PRIO_LISTS);
867
868         list_splice_init(&cfqd->rr_list[prio], &cfqd->cur_rr);
869
870         cfqd->cur_prio = prio + 1;
871         if (cfqd->cur_prio > cfqd->cur_end_prio) {
872                 cfqd->cur_end_prio = cfqd->cur_prio;
873                 cfqd->cur_prio = 0;
874         }
875         if (cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
876                 cfqd->cur_prio = 0;
877                 cfqd->cur_end_prio = 0;
878         }
879
880         return prio;
881 }
882
883 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
884 {
885         struct cfq_queue *cfqq = NULL;
886
887         /*
888          * if current list is non-empty, grab first entry. if it is empty,
889          * get next prio level and grab first entry then if any are spliced
890          */
891         if (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1)
892                 cfqq = list_entry_cfqq(cfqd->cur_rr.next);
893
894         /*
895          * If no new queues are available, check if the busy list has some
896          * before falling back to idle io.
897          */
898         if (!cfqq && !list_empty(&cfqd->busy_rr))
899                 cfqq = list_entry_cfqq(cfqd->busy_rr.next);
900
901         /*
902          * if we have idle queues and no rt or be queues had pending
903          * requests, either allow immediate service if the grace period
904          * has passed or arm the idle grace timer
905          */
906         if (!cfqq && !list_empty(&cfqd->idle_rr)) {
907                 unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE;
908
909                 if (time_after_eq(jiffies, end))
910                         cfqq = list_entry_cfqq(cfqd->idle_rr.next);
911                 else
912                         mod_timer(&cfqd->idle_class_timer, end);
913         }
914
915         __cfq_set_active_queue(cfqd, cfqq);
916         return cfqq;
917 }
918
919 static int cfq_arm_slice_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
920
921 {
922         struct cfq_io_context *cic;
923         unsigned long sl;
924
925         WARN_ON(!RB_EMPTY(&cfqq->sort_list));
926         WARN_ON(cfqq != cfqd->active_queue);
927
928         /*
929          * idle is disabled, either manually or by past process history
930          */
931         if (!cfqd->cfq_slice_idle)
932                 return 0;
933         if (!cfq_cfqq_idle_window(cfqq))
934                 return 0;
935         /*
936          * task has exited, don't wait
937          */
938         cic = cfqd->active_cic;
939         if (!cic || !cic->ioc->task)
940                 return 0;
941
942         cfq_mark_cfqq_must_dispatch(cfqq);
943         cfq_mark_cfqq_wait_request(cfqq);
944
945         sl = min(cfqq->slice_end - 1, (unsigned long) cfqd->cfq_slice_idle);
946
947         /*
948          * we don't want to idle for seeks, but we do want to allow
949          * fair distribution of slice time for a process doing back-to-back
950          * seeks. so allow a little bit of time for him to submit a new rq
951          */
952         if (sample_valid(cic->seek_samples) && cic->seek_mean > 131072)
953                 sl = 2;
954
955         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
956         return 1;
957 }
958
959 static void cfq_dispatch_insert(request_queue_t *q, struct cfq_rq *crq)
960 {
961         struct cfq_data *cfqd = q->elevator->elevator_data;
962         struct cfq_queue *cfqq = crq->cfq_queue;
963
964         cfqq->next_crq = cfq_find_next_crq(cfqd, cfqq, crq);
965         cfq_remove_request(crq->request);
966         cfqq->on_dispatch[cfq_crq_is_sync(crq)]++;
967         elv_dispatch_sort(q, crq->request);
968 }
969
970 /*
971  * return expired entry, or NULL to just start from scratch in rbtree
972  */
973 static inline struct cfq_rq *cfq_check_fifo(struct cfq_queue *cfqq)
974 {
975         struct cfq_data *cfqd = cfqq->cfqd;
976         struct request *rq;
977         struct cfq_rq *crq;
978
979         if (cfq_cfqq_fifo_expire(cfqq))
980                 return NULL;
981
982         if (!list_empty(&cfqq->fifo)) {
983                 int fifo = cfq_cfqq_class_sync(cfqq);
984
985                 crq = RQ_DATA(list_entry_fifo(cfqq->fifo.next));
986                 rq = crq->request;
987                 if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) {
988                         cfq_mark_cfqq_fifo_expire(cfqq);
989                         return crq;
990                 }
991         }
992
993         return NULL;
994 }
995
996 /*
997  * Scale schedule slice based on io priority. Use the sync time slice only
998  * if a queue is marked sync and has sync io queued. A sync queue with async
999  * io only, should not get full sync slice length.
1000  */
1001 static inline int
1002 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1003 {
1004         const int base_slice = cfqd->cfq_slice[cfq_cfqq_sync(cfqq)];
1005
1006         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1007
1008         return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - cfqq->ioprio));
1009 }
1010
1011 static inline void
1012 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1013 {
1014         cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
1015 }
1016
1017 static inline int
1018 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1019 {
1020         const int base_rq = cfqd->cfq_slice_async_rq;
1021
1022         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1023
1024         return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1025 }
1026
1027 /*
1028  * get next queue for service
1029  */
1030 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
1031 {
1032         unsigned long now = jiffies;
1033         struct cfq_queue *cfqq;
1034
1035         cfqq = cfqd->active_queue;
1036         if (!cfqq)
1037                 goto new_queue;
1038
1039         /*
1040          * slice has expired
1041          */
1042         if (!cfq_cfqq_must_dispatch(cfqq) && time_after(now, cfqq->slice_end))
1043                 goto expire;
1044
1045         /*
1046          * if queue has requests, dispatch one. if not, check if
1047          * enough slice is left to wait for one
1048          */
1049         if (!RB_EMPTY(&cfqq->sort_list))
1050                 goto keep_queue;
1051         else if (cfq_cfqq_class_sync(cfqq) &&
1052                  time_before(now, cfqq->slice_end)) {
1053                 if (cfq_arm_slice_timer(cfqd, cfqq))
1054                         return NULL;
1055         }
1056
1057 expire:
1058         cfq_slice_expired(cfqd, 0);
1059 new_queue:
1060         cfqq = cfq_set_active_queue(cfqd);
1061 keep_queue:
1062         return cfqq;
1063 }
1064
1065 static int
1066 __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1067                         int max_dispatch)
1068 {
1069         int dispatched = 0;
1070
1071         BUG_ON(RB_EMPTY(&cfqq->sort_list));
1072
1073         do {
1074                 struct cfq_rq *crq;
1075
1076                 /*
1077                  * follow expired path, else get first next available
1078                  */
1079                 if ((crq = cfq_check_fifo(cfqq)) == NULL)
1080                         crq = cfqq->next_crq;
1081
1082                 /*
1083                  * finally, insert request into driver dispatch list
1084                  */
1085                 cfq_dispatch_insert(cfqd->queue, crq);
1086
1087                 cfqd->dispatch_slice++;
1088                 dispatched++;
1089
1090                 if (!cfqd->active_cic) {
1091                         atomic_inc(&crq->io_context->ioc->refcount);
1092                         cfqd->active_cic = crq->io_context;
1093                 }
1094
1095                 if (RB_EMPTY(&cfqq->sort_list))
1096                         break;
1097
1098         } while (dispatched < max_dispatch);
1099
1100         /*
1101          * if slice end isn't set yet, set it. if at least one request was
1102          * sync, use the sync time slice value
1103          */
1104         if (!cfqq->slice_end)
1105                 cfq_set_prio_slice(cfqd, cfqq);
1106
1107         /*
1108          * expire an async queue immediately if it has used up its slice. idle
1109          * queue always expire after 1 dispatch round.
1110          */
1111         if ((!cfq_cfqq_sync(cfqq) &&
1112             cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1113             cfq_class_idle(cfqq))
1114                 cfq_slice_expired(cfqd, 0);
1115
1116         return dispatched;
1117 }
1118
1119 static int
1120 cfq_forced_dispatch_cfqqs(struct list_head *list)
1121 {
1122         int dispatched = 0;
1123         struct cfq_queue *cfqq, *next;
1124         struct cfq_rq *crq;
1125
1126         list_for_each_entry_safe(cfqq, next, list, cfq_list) {
1127                 while ((crq = cfqq->next_crq)) {
1128                         cfq_dispatch_insert(cfqq->cfqd->queue, crq);
1129                         dispatched++;
1130                 }
1131                 BUG_ON(!list_empty(&cfqq->fifo));
1132         }
1133         return dispatched;
1134 }
1135
1136 static int
1137 cfq_forced_dispatch(struct cfq_data *cfqd)
1138 {
1139         int i, dispatched = 0;
1140
1141         for (i = 0; i < CFQ_PRIO_LISTS; i++)
1142                 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]);
1143
1144         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->busy_rr);
1145         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr);
1146         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr);
1147
1148         cfq_slice_expired(cfqd, 0);
1149
1150         BUG_ON(cfqd->busy_queues);
1151
1152         return dispatched;
1153 }
1154
1155 static int
1156 cfq_dispatch_requests(request_queue_t *q, int force)
1157 {
1158         struct cfq_data *cfqd = q->elevator->elevator_data;
1159         struct cfq_queue *cfqq;
1160
1161         if (!cfqd->busy_queues)
1162                 return 0;
1163
1164         if (unlikely(force))
1165                 return cfq_forced_dispatch(cfqd);
1166
1167         cfqq = cfq_select_queue(cfqd);
1168         if (cfqq) {
1169                 int max_dispatch;
1170
1171                 cfq_clear_cfqq_must_dispatch(cfqq);
1172                 cfq_clear_cfqq_wait_request(cfqq);
1173                 del_timer(&cfqd->idle_slice_timer);
1174
1175                 max_dispatch = cfqd->cfq_quantum;
1176                 if (cfq_class_idle(cfqq))
1177                         max_dispatch = 1;
1178
1179                 return __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
1180         }
1181
1182         return 0;
1183 }
1184
1185 /*
1186  * task holds one reference to the queue, dropped when task exits. each crq
1187  * in-flight on this queue also holds a reference, dropped when crq is freed.
1188  *
1189  * queue lock must be held here.
1190  */
1191 static void cfq_put_queue(struct cfq_queue *cfqq)
1192 {
1193         struct cfq_data *cfqd = cfqq->cfqd;
1194
1195         BUG_ON(atomic_read(&cfqq->ref) <= 0);
1196
1197         if (!atomic_dec_and_test(&cfqq->ref))
1198                 return;
1199
1200         BUG_ON(rb_first(&cfqq->sort_list));
1201         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1202         BUG_ON(cfq_cfqq_on_rr(cfqq));
1203
1204         if (unlikely(cfqd->active_queue == cfqq))
1205                 __cfq_slice_expired(cfqd, cfqq, 0);
1206
1207         /*
1208          * it's on the empty list and still hashed
1209          */
1210         list_del(&cfqq->cfq_list);
1211         hlist_del(&cfqq->cfq_hash);
1212         kmem_cache_free(cfq_pool, cfqq);
1213 }
1214
1215 static inline struct cfq_queue *
1216 __cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned int prio,
1217                     const int hashval)
1218 {
1219         struct hlist_head *hash_list = &cfqd->cfq_hash[hashval];
1220         struct hlist_node *entry;
1221         struct cfq_queue *__cfqq;
1222
1223         hlist_for_each_entry(__cfqq, entry, hash_list, cfq_hash) {
1224                 const unsigned short __p = IOPRIO_PRIO_VALUE(__cfqq->org_ioprio_class, __cfqq->org_ioprio);
1225
1226                 if (__cfqq->key == key && (__p == prio || !prio))
1227                         return __cfqq;
1228         }
1229
1230         return NULL;
1231 }
1232
1233 static struct cfq_queue *
1234 cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned short prio)
1235 {
1236         return __cfq_find_cfq_hash(cfqd, key, prio, hash_long(key, CFQ_QHASH_SHIFT));
1237 }
1238
1239 static void cfq_free_io_context(struct io_context *ioc)
1240 {
1241         struct cfq_io_context *__cic;
1242         struct rb_node *n;
1243         int freed = 0;
1244
1245         while ((n = rb_first(&ioc->cic_root)) != NULL) {
1246                 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1247                 rb_erase(&__cic->rb_node, &ioc->cic_root);
1248                 kmem_cache_free(cfq_ioc_pool, __cic);
1249                 freed++;
1250         }
1251
1252         if (atomic_sub_and_test(freed, &ioc_count) && ioc_gone)
1253                 complete(ioc_gone);
1254 }
1255
1256 static void cfq_trim(struct io_context *ioc)
1257 {
1258         ioc->set_ioprio = NULL;
1259         cfq_free_io_context(ioc);
1260 }
1261
1262 /*
1263  * Called with interrupts disabled
1264  */
1265 static void cfq_exit_single_io_context(struct cfq_io_context *cic)
1266 {
1267         struct cfq_data *cfqd = cic->key;
1268         request_queue_t *q;
1269
1270         if (!cfqd)
1271                 return;
1272
1273         q = cfqd->queue;
1274
1275         WARN_ON(!irqs_disabled());
1276
1277         spin_lock(q->queue_lock);
1278
1279         if (cic->cfqq[ASYNC]) {
1280                 if (unlikely(cic->cfqq[ASYNC] == cfqd->active_queue))
1281                         __cfq_slice_expired(cfqd, cic->cfqq[ASYNC], 0);
1282                 cfq_put_queue(cic->cfqq[ASYNC]);
1283                 cic->cfqq[ASYNC] = NULL;
1284         }
1285
1286         if (cic->cfqq[SYNC]) {
1287                 if (unlikely(cic->cfqq[SYNC] == cfqd->active_queue))
1288                         __cfq_slice_expired(cfqd, cic->cfqq[SYNC], 0);
1289                 cfq_put_queue(cic->cfqq[SYNC]);
1290                 cic->cfqq[SYNC] = NULL;
1291         }
1292
1293         cic->key = NULL;
1294         list_del_init(&cic->queue_list);
1295         spin_unlock(q->queue_lock);
1296 }
1297
1298 static void cfq_exit_io_context(struct io_context *ioc)
1299 {
1300         struct cfq_io_context *__cic;
1301         unsigned long flags;
1302         struct rb_node *n;
1303
1304         /*
1305          * put the reference this task is holding to the various queues
1306          */
1307         spin_lock_irqsave(&cfq_exit_lock, flags);
1308
1309         n = rb_first(&ioc->cic_root);
1310         while (n != NULL) {
1311                 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1312
1313                 cfq_exit_single_io_context(__cic);
1314                 n = rb_next(n);
1315         }
1316
1317         spin_unlock_irqrestore(&cfq_exit_lock, flags);
1318 }
1319
1320 static struct cfq_io_context *
1321 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1322 {
1323         struct cfq_io_context *cic = kmem_cache_alloc(cfq_ioc_pool, gfp_mask);
1324
1325         if (cic) {
1326                 RB_CLEAR(&cic->rb_node);
1327                 cic->key = NULL;
1328                 cic->cfqq[ASYNC] = NULL;
1329                 cic->cfqq[SYNC] = NULL;
1330                 cic->last_end_request = jiffies;
1331                 cic->ttime_total = 0;
1332                 cic->ttime_samples = 0;
1333                 cic->ttime_mean = 0;
1334                 cic->dtor = cfq_free_io_context;
1335                 cic->exit = cfq_exit_io_context;
1336                 INIT_LIST_HEAD(&cic->queue_list);
1337                 atomic_inc(&ioc_count);
1338         }
1339
1340         return cic;
1341 }
1342
1343 static void cfq_init_prio_data(struct cfq_queue *cfqq)
1344 {
1345         struct task_struct *tsk = current;
1346         int ioprio_class;
1347
1348         if (!cfq_cfqq_prio_changed(cfqq))
1349                 return;
1350
1351         ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
1352         switch (ioprio_class) {
1353                 default:
1354                         printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1355                 case IOPRIO_CLASS_NONE:
1356                         /*
1357                          * no prio set, place us in the middle of the BE classes
1358                          */
1359                         cfqq->ioprio = task_nice_ioprio(tsk);
1360                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1361                         break;
1362                 case IOPRIO_CLASS_RT:
1363                         cfqq->ioprio = task_ioprio(tsk);
1364                         cfqq->ioprio_class = IOPRIO_CLASS_RT;
1365                         break;
1366                 case IOPRIO_CLASS_BE:
1367                         cfqq->ioprio = task_ioprio(tsk);
1368                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1369                         break;
1370                 case IOPRIO_CLASS_IDLE:
1371                         cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1372                         cfqq->ioprio = 7;
1373                         cfq_clear_cfqq_idle_window(cfqq);
1374                         break;
1375         }
1376
1377         /*
1378          * keep track of original prio settings in case we have to temporarily
1379          * elevate the priority of this queue
1380          */
1381         cfqq->org_ioprio = cfqq->ioprio;
1382         cfqq->org_ioprio_class = cfqq->ioprio_class;
1383
1384         if (cfq_cfqq_on_rr(cfqq))
1385                 cfq_resort_rr_list(cfqq, 0);
1386
1387         cfq_clear_cfqq_prio_changed(cfqq);
1388 }
1389
1390 static inline void changed_ioprio(struct cfq_io_context *cic)
1391 {
1392         struct cfq_data *cfqd = cic->key;
1393         struct cfq_queue *cfqq;
1394         if (cfqd) {
1395                 spin_lock(cfqd->queue->queue_lock);
1396                 cfqq = cic->cfqq[ASYNC];
1397                 if (cfqq) {
1398                         struct cfq_queue *new_cfqq;
1399                         new_cfqq = cfq_get_queue(cfqd, CFQ_KEY_ASYNC,
1400                                                 cic->ioc->task, GFP_ATOMIC);
1401                         if (new_cfqq) {
1402                                 cic->cfqq[ASYNC] = new_cfqq;
1403                                 cfq_put_queue(cfqq);
1404                         }
1405                 }
1406                 cfqq = cic->cfqq[SYNC];
1407                 if (cfqq) {
1408                         cfq_mark_cfqq_prio_changed(cfqq);
1409                         cfq_init_prio_data(cfqq);
1410                 }
1411                 spin_unlock(cfqd->queue->queue_lock);
1412         }
1413 }
1414
1415 /*
1416  * callback from sys_ioprio_set, irqs are disabled
1417  */
1418 static int cfq_ioc_set_ioprio(struct io_context *ioc, unsigned int ioprio)
1419 {
1420         struct cfq_io_context *cic;
1421         struct rb_node *n;
1422
1423         spin_lock(&cfq_exit_lock);
1424
1425         n = rb_first(&ioc->cic_root);
1426         while (n != NULL) {
1427                 cic = rb_entry(n, struct cfq_io_context, rb_node);
1428
1429                 changed_ioprio(cic);
1430                 n = rb_next(n);
1431         }
1432
1433         spin_unlock(&cfq_exit_lock);
1434
1435         return 0;
1436 }
1437
1438 static struct cfq_queue *
1439 cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk,
1440               gfp_t gfp_mask)
1441 {
1442         const int hashval = hash_long(key, CFQ_QHASH_SHIFT);
1443         struct cfq_queue *cfqq, *new_cfqq = NULL;
1444         unsigned short ioprio;
1445
1446 retry:
1447         ioprio = tsk->ioprio;
1448         cfqq = __cfq_find_cfq_hash(cfqd, key, ioprio, hashval);
1449
1450         if (!cfqq) {
1451                 if (new_cfqq) {
1452                         cfqq = new_cfqq;
1453                         new_cfqq = NULL;
1454                 } else if (gfp_mask & __GFP_WAIT) {
1455                         spin_unlock_irq(cfqd->queue->queue_lock);
1456                         new_cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
1457                         spin_lock_irq(cfqd->queue->queue_lock);
1458                         goto retry;
1459                 } else {
1460                         cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
1461                         if (!cfqq)
1462                                 goto out;
1463                 }
1464
1465                 memset(cfqq, 0, sizeof(*cfqq));
1466
1467                 INIT_HLIST_NODE(&cfqq->cfq_hash);
1468                 INIT_LIST_HEAD(&cfqq->cfq_list);
1469                 RB_CLEAR_ROOT(&cfqq->sort_list);
1470                 INIT_LIST_HEAD(&cfqq->fifo);
1471
1472                 cfqq->key = key;
1473                 hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
1474                 atomic_set(&cfqq->ref, 0);
1475                 cfqq->cfqd = cfqd;
1476                 cfqq->service_last = 0;
1477                 /*
1478                  * set ->slice_left to allow preemption for a new process
1479                  */
1480                 cfqq->slice_left = 2 * cfqd->cfq_slice_idle;
1481                 if (!cfqd->hw_tag)
1482                         cfq_mark_cfqq_idle_window(cfqq);
1483                 cfq_mark_cfqq_prio_changed(cfqq);
1484                 cfq_init_prio_data(cfqq);
1485         }
1486
1487         if (new_cfqq)
1488                 kmem_cache_free(cfq_pool, new_cfqq);
1489
1490         atomic_inc(&cfqq->ref);
1491 out:
1492         WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
1493         return cfqq;
1494 }
1495
1496 static void
1497 cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)
1498 {
1499         spin_lock(&cfq_exit_lock);
1500         rb_erase(&cic->rb_node, &ioc->cic_root);
1501         list_del_init(&cic->queue_list);
1502         spin_unlock(&cfq_exit_lock);
1503         kmem_cache_free(cfq_ioc_pool, cic);
1504         atomic_dec(&ioc_count);
1505 }
1506
1507 static struct cfq_io_context *
1508 cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
1509 {
1510         struct rb_node *n;
1511         struct cfq_io_context *cic;
1512         void *k, *key = cfqd;
1513
1514 restart:
1515         n = ioc->cic_root.rb_node;
1516         while (n) {
1517                 cic = rb_entry(n, struct cfq_io_context, rb_node);
1518                 /* ->key must be copied to avoid race with cfq_exit_queue() */
1519                 k = cic->key;
1520                 if (unlikely(!k)) {
1521                         cfq_drop_dead_cic(ioc, cic);
1522                         goto restart;
1523                 }
1524
1525                 if (key < k)
1526                         n = n->rb_left;
1527                 else if (key > k)
1528                         n = n->rb_right;
1529                 else
1530                         return cic;
1531         }
1532
1533         return NULL;
1534 }
1535
1536 static inline void
1537 cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
1538              struct cfq_io_context *cic)
1539 {
1540         struct rb_node **p;
1541         struct rb_node *parent;
1542         struct cfq_io_context *__cic;
1543         void *k;
1544
1545         cic->ioc = ioc;
1546         cic->key = cfqd;
1547
1548         ioc->set_ioprio = cfq_ioc_set_ioprio;
1549 restart:
1550         parent = NULL;
1551         p = &ioc->cic_root.rb_node;
1552         while (*p) {
1553                 parent = *p;
1554                 __cic = rb_entry(parent, struct cfq_io_context, rb_node);
1555                 /* ->key must be copied to avoid race with cfq_exit_queue() */
1556                 k = __cic->key;
1557                 if (unlikely(!k)) {
1558                         cfq_drop_dead_cic(ioc, cic);
1559                         goto restart;
1560                 }
1561
1562                 if (cic->key < k)
1563                         p = &(*p)->rb_left;
1564                 else if (cic->key > k)
1565                         p = &(*p)->rb_right;
1566                 else
1567                         BUG();
1568         }
1569
1570         spin_lock(&cfq_exit_lock);
1571         rb_link_node(&cic->rb_node, parent, p);
1572         rb_insert_color(&cic->rb_node, &ioc->cic_root);
1573         list_add(&cic->queue_list, &cfqd->cic_list);
1574         spin_unlock(&cfq_exit_lock);
1575 }
1576
1577 /*
1578  * Setup general io context and cfq io context. There can be several cfq
1579  * io contexts per general io context, if this process is doing io to more
1580  * than one device managed by cfq.
1581  */
1582 static struct cfq_io_context *
1583 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1584 {
1585         struct io_context *ioc = NULL;
1586         struct cfq_io_context *cic;
1587
1588         might_sleep_if(gfp_mask & __GFP_WAIT);
1589
1590         ioc = get_io_context(gfp_mask);
1591         if (!ioc)
1592                 return NULL;
1593
1594         cic = cfq_cic_rb_lookup(cfqd, ioc);
1595         if (cic)
1596                 goto out;
1597
1598         cic = cfq_alloc_io_context(cfqd, gfp_mask);
1599         if (cic == NULL)
1600                 goto err;
1601
1602         cfq_cic_link(cfqd, ioc, cic);
1603 out:
1604         return cic;
1605 err:
1606         put_io_context(ioc);
1607         return NULL;
1608 }
1609
1610 static void
1611 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1612 {
1613         unsigned long elapsed, ttime;
1614
1615         /*
1616          * if this context already has stuff queued, thinktime is from
1617          * last queue not last end
1618          */
1619 #if 0
1620         if (time_after(cic->last_end_request, cic->last_queue))
1621                 elapsed = jiffies - cic->last_end_request;
1622         else
1623                 elapsed = jiffies - cic->last_queue;
1624 #else
1625                 elapsed = jiffies - cic->last_end_request;
1626 #endif
1627
1628         ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1629
1630         cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1631         cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1632         cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1633 }
1634
1635 static void
1636 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
1637                        struct cfq_rq *crq)
1638 {
1639         sector_t sdist;
1640         u64 total;
1641
1642         if (cic->last_request_pos < crq->request->sector)
1643                 sdist = crq->request->sector - cic->last_request_pos;
1644         else
1645                 sdist = cic->last_request_pos - crq->request->sector;
1646
1647         /*
1648          * Don't allow the seek distance to get too large from the
1649          * odd fragment, pagein, etc
1650          */
1651         if (cic->seek_samples <= 60) /* second&third seek */
1652                 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
1653         else
1654                 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
1655
1656         cic->seek_samples = (7*cic->seek_samples + 256) / 8;
1657         cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
1658         total = cic->seek_total + (cic->seek_samples/2);
1659         do_div(total, cic->seek_samples);
1660         cic->seek_mean = (sector_t)total;
1661 }
1662
1663 /*
1664  * Disable idle window if the process thinks too long or seeks so much that
1665  * it doesn't matter
1666  */
1667 static void
1668 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1669                        struct cfq_io_context *cic)
1670 {
1671         int enable_idle = cfq_cfqq_idle_window(cfqq);
1672
1673         if (!cic->ioc->task || !cfqd->cfq_slice_idle || cfqd->hw_tag)
1674                 enable_idle = 0;
1675         else if (sample_valid(cic->ttime_samples)) {
1676                 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1677                         enable_idle = 0;
1678                 else
1679                         enable_idle = 1;
1680         }
1681
1682         if (enable_idle)
1683                 cfq_mark_cfqq_idle_window(cfqq);
1684         else
1685                 cfq_clear_cfqq_idle_window(cfqq);
1686 }
1687
1688
1689 /*
1690  * Check if new_cfqq should preempt the currently active queue. Return 0 for
1691  * no or if we aren't sure, a 1 will cause a preempt.
1692  */
1693 static int
1694 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1695                    struct cfq_rq *crq)
1696 {
1697         struct cfq_queue *cfqq = cfqd->active_queue;
1698
1699         if (cfq_class_idle(new_cfqq))
1700                 return 0;
1701
1702         if (!cfqq)
1703                 return 1;
1704
1705         if (cfq_class_idle(cfqq))
1706                 return 1;
1707         if (!cfq_cfqq_wait_request(new_cfqq))
1708                 return 0;
1709         /*
1710          * if it doesn't have slice left, forget it
1711          */
1712         if (new_cfqq->slice_left < cfqd->cfq_slice_idle)
1713                 return 0;
1714         if (cfq_crq_is_sync(crq) && !cfq_cfqq_sync(cfqq))
1715                 return 1;
1716
1717         return 0;
1718 }
1719
1720 /*
1721  * cfqq preempts the active queue. if we allowed preempt with no slice left,
1722  * let it have half of its nominal slice.
1723  */
1724 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1725 {
1726         struct cfq_queue *__cfqq, *next;
1727
1728         list_for_each_entry_safe(__cfqq, next, &cfqd->cur_rr, cfq_list)
1729                 cfq_resort_rr_list(__cfqq, 1);
1730
1731         if (!cfqq->slice_left)
1732                 cfqq->slice_left = cfq_prio_to_slice(cfqd, cfqq) / 2;
1733
1734         cfqq->slice_end = cfqq->slice_left + jiffies;
1735         __cfq_slice_expired(cfqd, cfqq, 1);
1736         __cfq_set_active_queue(cfqd, cfqq);
1737 }
1738
1739 /*
1740  * should really be a ll_rw_blk.c helper
1741  */
1742 static void cfq_start_queueing(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1743 {
1744         request_queue_t *q = cfqd->queue;
1745
1746         if (!blk_queue_plugged(q))
1747                 q->request_fn(q);
1748         else
1749                 __generic_unplug_device(q);
1750 }
1751
1752 /*
1753  * Called when a new fs request (crq) is added (to cfqq). Check if there's
1754  * something we should do about it
1755  */
1756 static void
1757 cfq_crq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1758                  struct cfq_rq *crq)
1759 {
1760         struct cfq_io_context *cic;
1761
1762         cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
1763
1764         cic = crq->io_context;
1765
1766         /*
1767          * we never wait for an async request and we don't allow preemption
1768          * of an async request. so just return early
1769          */
1770         if (!cfq_crq_is_sync(crq)) {
1771                 /*
1772                  * sync process issued an async request, if it's waiting
1773                  * then expire it and kick rq handling.
1774                  */
1775                 if (cic == cfqd->active_cic &&
1776                     del_timer(&cfqd->idle_slice_timer)) {
1777                         cfq_slice_expired(cfqd, 0);
1778                         cfq_start_queueing(cfqd, cfqq);
1779                 }
1780                 return;
1781         }
1782
1783         cfq_update_io_thinktime(cfqd, cic);
1784         cfq_update_io_seektime(cfqd, cic, crq);
1785         cfq_update_idle_window(cfqd, cfqq, cic);
1786
1787         cic->last_queue = jiffies;
1788         cic->last_request_pos = crq->request->sector + crq->request->nr_sectors;
1789
1790         if (cfqq == cfqd->active_queue) {
1791                 /*
1792                  * if we are waiting for a request for this queue, let it rip
1793                  * immediately and flag that we must not expire this queue
1794                  * just now
1795                  */
1796                 if (cfq_cfqq_wait_request(cfqq)) {
1797                         cfq_mark_cfqq_must_dispatch(cfqq);
1798                         del_timer(&cfqd->idle_slice_timer);
1799                         cfq_start_queueing(cfqd, cfqq);
1800                 }
1801         } else if (cfq_should_preempt(cfqd, cfqq, crq)) {
1802                 /*
1803                  * not the active queue - expire current slice if it is
1804                  * idle and has expired it's mean thinktime or this new queue
1805                  * has some old slice time left and is of higher priority
1806                  */
1807                 cfq_preempt_queue(cfqd, cfqq);
1808                 cfq_mark_cfqq_must_dispatch(cfqq);
1809                 cfq_start_queueing(cfqd, cfqq);
1810         }
1811 }
1812
1813 static void cfq_insert_request(request_queue_t *q, struct request *rq)
1814 {
1815         struct cfq_data *cfqd = q->elevator->elevator_data;
1816         struct cfq_rq *crq = RQ_DATA(rq);
1817         struct cfq_queue *cfqq = crq->cfq_queue;
1818
1819         cfq_init_prio_data(cfqq);
1820
1821         cfq_add_crq_rb(crq);
1822
1823         list_add_tail(&rq->queuelist, &cfqq->fifo);
1824
1825         if (rq_mergeable(rq))
1826                 cfq_add_crq_hash(cfqd, crq);
1827
1828         cfq_crq_enqueued(cfqd, cfqq, crq);
1829 }
1830
1831 static void cfq_completed_request(request_queue_t *q, struct request *rq)
1832 {
1833         struct cfq_rq *crq = RQ_DATA(rq);
1834         struct cfq_queue *cfqq = crq->cfq_queue;
1835         struct cfq_data *cfqd = cfqq->cfqd;
1836         const int sync = cfq_crq_is_sync(crq);
1837         unsigned long now;
1838
1839         now = jiffies;
1840
1841         WARN_ON(!cfqd->rq_in_driver);
1842         WARN_ON(!cfqq->on_dispatch[sync]);
1843         cfqd->rq_in_driver--;
1844         cfqq->on_dispatch[sync]--;
1845
1846         if (!cfq_class_idle(cfqq))
1847                 cfqd->last_end_request = now;
1848
1849         if (!cfq_cfqq_dispatched(cfqq)) {
1850                 if (cfq_cfqq_on_rr(cfqq)) {
1851                         cfqq->service_last = now;
1852                         cfq_resort_rr_list(cfqq, 0);
1853                 }
1854                 cfq_schedule_dispatch(cfqd);
1855         }
1856
1857         if (cfq_crq_is_sync(crq))
1858                 crq->io_context->last_end_request = now;
1859 }
1860
1861 static struct request *
1862 cfq_former_request(request_queue_t *q, struct request *rq)
1863 {
1864         struct cfq_rq *crq = RQ_DATA(rq);
1865         struct rb_node *rbprev = rb_prev(&crq->rb_node);
1866
1867         if (rbprev)
1868                 return rb_entry_crq(rbprev)->request;
1869
1870         return NULL;
1871 }
1872
1873 static struct request *
1874 cfq_latter_request(request_queue_t *q, struct request *rq)
1875 {
1876         struct cfq_rq *crq = RQ_DATA(rq);
1877         struct rb_node *rbnext = rb_next(&crq->rb_node);
1878
1879         if (rbnext)
1880                 return rb_entry_crq(rbnext)->request;
1881
1882         return NULL;
1883 }
1884
1885 /*
1886  * we temporarily boost lower priority queues if they are holding fs exclusive
1887  * resources. they are boosted to normal prio (CLASS_BE/4)
1888  */
1889 static void cfq_prio_boost(struct cfq_queue *cfqq)
1890 {
1891         const int ioprio_class = cfqq->ioprio_class;
1892         const int ioprio = cfqq->ioprio;
1893
1894         if (has_fs_excl()) {
1895                 /*
1896                  * boost idle prio on transactions that would lock out other
1897                  * users of the filesystem
1898                  */
1899                 if (cfq_class_idle(cfqq))
1900                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1901                 if (cfqq->ioprio > IOPRIO_NORM)
1902                         cfqq->ioprio = IOPRIO_NORM;
1903         } else {
1904                 /*
1905                  * check if we need to unboost the queue
1906                  */
1907                 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
1908                         cfqq->ioprio_class = cfqq->org_ioprio_class;
1909                 if (cfqq->ioprio != cfqq->org_ioprio)
1910                         cfqq->ioprio = cfqq->org_ioprio;
1911         }
1912
1913         /*
1914          * refile between round-robin lists if we moved the priority class
1915          */
1916         if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio) &&
1917             cfq_cfqq_on_rr(cfqq))
1918                 cfq_resort_rr_list(cfqq, 0);
1919 }
1920
1921 static inline int
1922 __cfq_may_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1923                 struct task_struct *task, int rw)
1924 {
1925 #if 1
1926         if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
1927             !cfq_cfqq_must_alloc_slice(cfqq)) {
1928                 cfq_mark_cfqq_must_alloc_slice(cfqq);
1929                 return ELV_MQUEUE_MUST;
1930         }
1931
1932         return ELV_MQUEUE_MAY;
1933 #else
1934         if (!cfqq || task->flags & PF_MEMALLOC)
1935                 return ELV_MQUEUE_MAY;
1936         if (!cfqq->allocated[rw] || cfq_cfqq_must_alloc(cfqq)) {
1937                 if (cfq_cfqq_wait_request(cfqq))
1938                         return ELV_MQUEUE_MUST;
1939
1940                 /*
1941                  * only allow 1 ELV_MQUEUE_MUST per slice, otherwise we
1942                  * can quickly flood the queue with writes from a single task
1943                  */
1944                 if (rw == READ || !cfq_cfqq_must_alloc_slice(cfqq)) {
1945                         cfq_mark_cfqq_must_alloc_slice(cfqq);
1946                         return ELV_MQUEUE_MUST;
1947                 }
1948
1949                 return ELV_MQUEUE_MAY;
1950         }
1951         if (cfq_class_idle(cfqq))
1952                 return ELV_MQUEUE_NO;
1953         if (cfqq->allocated[rw] >= cfqd->max_queued) {
1954                 struct io_context *ioc = get_io_context(GFP_ATOMIC);
1955                 int ret = ELV_MQUEUE_NO;
1956
1957                 if (ioc && ioc->nr_batch_requests)
1958                         ret = ELV_MQUEUE_MAY;
1959
1960                 put_io_context(ioc);
1961                 return ret;
1962         }
1963
1964         return ELV_MQUEUE_MAY;
1965 #endif
1966 }
1967
1968 static int cfq_may_queue(request_queue_t *q, int rw, struct bio *bio)
1969 {
1970         struct cfq_data *cfqd = q->elevator->elevator_data;
1971         struct task_struct *tsk = current;
1972         struct cfq_queue *cfqq;
1973
1974         /*
1975          * don't force setup of a queue from here, as a call to may_queue
1976          * does not necessarily imply that a request actually will be queued.
1977          * so just lookup a possibly existing queue, or return 'may queue'
1978          * if that fails
1979          */
1980         cfqq = cfq_find_cfq_hash(cfqd, cfq_queue_pid(tsk, rw), tsk->ioprio);
1981         if (cfqq) {
1982                 cfq_init_prio_data(cfqq);
1983                 cfq_prio_boost(cfqq);
1984
1985                 return __cfq_may_queue(cfqd, cfqq, tsk, rw);
1986         }
1987
1988         return ELV_MQUEUE_MAY;
1989 }
1990
1991 static void cfq_check_waiters(request_queue_t *q, struct cfq_queue *cfqq)
1992 {
1993         struct cfq_data *cfqd = q->elevator->elevator_data;
1994         struct request_list *rl = &q->rq;
1995
1996         if (cfqq->allocated[READ] <= cfqd->max_queued || cfqd->rq_starved) {
1997                 smp_mb();
1998                 if (waitqueue_active(&rl->wait[READ]))
1999                         wake_up(&rl->wait[READ]);
2000         }
2001
2002         if (cfqq->allocated[WRITE] <= cfqd->max_queued || cfqd->rq_starved) {
2003                 smp_mb();
2004                 if (waitqueue_active(&rl->wait[WRITE]))
2005                         wake_up(&rl->wait[WRITE]);
2006         }
2007 }
2008
2009 /*
2010  * queue lock held here
2011  */
2012 static void cfq_put_request(request_queue_t *q, struct request *rq)
2013 {
2014         struct cfq_data *cfqd = q->elevator->elevator_data;
2015         struct cfq_rq *crq = RQ_DATA(rq);
2016
2017         if (crq) {
2018                 struct cfq_queue *cfqq = crq->cfq_queue;
2019                 const int rw = rq_data_dir(rq);
2020
2021                 BUG_ON(!cfqq->allocated[rw]);
2022                 cfqq->allocated[rw]--;
2023
2024                 put_io_context(crq->io_context->ioc);
2025
2026                 mempool_free(crq, cfqd->crq_pool);
2027                 rq->elevator_private = NULL;
2028
2029                 cfq_check_waiters(q, cfqq);
2030                 cfq_put_queue(cfqq);
2031         }
2032 }
2033
2034 /*
2035  * Allocate cfq data structures associated with this request.
2036  */
2037 static int
2038 cfq_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
2039                 gfp_t gfp_mask)
2040 {
2041         struct cfq_data *cfqd = q->elevator->elevator_data;
2042         struct task_struct *tsk = current;
2043         struct cfq_io_context *cic;
2044         const int rw = rq_data_dir(rq);
2045         pid_t key = cfq_queue_pid(tsk, rw);
2046         struct cfq_queue *cfqq;
2047         struct cfq_rq *crq;
2048         unsigned long flags;
2049         int is_sync = key != CFQ_KEY_ASYNC;
2050
2051         might_sleep_if(gfp_mask & __GFP_WAIT);
2052
2053         cic = cfq_get_io_context(cfqd, gfp_mask);
2054
2055         spin_lock_irqsave(q->queue_lock, flags);
2056
2057         if (!cic)
2058                 goto queue_fail;
2059
2060         if (!cic->cfqq[is_sync]) {
2061                 cfqq = cfq_get_queue(cfqd, key, tsk, gfp_mask);
2062                 if (!cfqq)
2063                         goto queue_fail;
2064
2065                 cic->cfqq[is_sync] = cfqq;
2066         } else
2067                 cfqq = cic->cfqq[is_sync];
2068
2069         cfqq->allocated[rw]++;
2070         cfq_clear_cfqq_must_alloc(cfqq);
2071         cfqd->rq_starved = 0;
2072         atomic_inc(&cfqq->ref);
2073         spin_unlock_irqrestore(q->queue_lock, flags);
2074
2075         crq = mempool_alloc(cfqd->crq_pool, gfp_mask);
2076         if (crq) {
2077                 RB_CLEAR(&crq->rb_node);
2078                 crq->rb_key = 0;
2079                 crq->request = rq;
2080                 INIT_HLIST_NODE(&crq->hash);
2081                 crq->cfq_queue = cfqq;
2082                 crq->io_context = cic;
2083
2084                 if (is_sync)
2085                         cfq_mark_crq_is_sync(crq);
2086                 else
2087                         cfq_clear_crq_is_sync(crq);
2088
2089                 rq->elevator_private = crq;
2090                 return 0;
2091         }
2092
2093         spin_lock_irqsave(q->queue_lock, flags);
2094         cfqq->allocated[rw]--;
2095         if (!(cfqq->allocated[0] + cfqq->allocated[1]))
2096                 cfq_mark_cfqq_must_alloc(cfqq);
2097         cfq_put_queue(cfqq);
2098 queue_fail:
2099         if (cic)
2100                 put_io_context(cic->ioc);
2101         /*
2102          * mark us rq allocation starved. we need to kickstart the process
2103          * ourselves if there are no pending requests that can do it for us.
2104          * that would be an extremely rare OOM situation
2105          */
2106         cfqd->rq_starved = 1;
2107         cfq_schedule_dispatch(cfqd);
2108         spin_unlock_irqrestore(q->queue_lock, flags);
2109         return 1;
2110 }
2111
2112 static void cfq_kick_queue(void *data)
2113 {
2114         request_queue_t *q = data;
2115         struct cfq_data *cfqd = q->elevator->elevator_data;
2116         unsigned long flags;
2117
2118         spin_lock_irqsave(q->queue_lock, flags);
2119
2120         if (cfqd->rq_starved) {
2121                 struct request_list *rl = &q->rq;
2122
2123                 /*
2124                  * we aren't guaranteed to get a request after this, but we
2125                  * have to be opportunistic
2126                  */
2127                 smp_mb();
2128                 if (waitqueue_active(&rl->wait[READ]))
2129                         wake_up(&rl->wait[READ]);
2130                 if (waitqueue_active(&rl->wait[WRITE]))
2131                         wake_up(&rl->wait[WRITE]);
2132         }
2133
2134         blk_remove_plug(q);
2135         q->request_fn(q);
2136         spin_unlock_irqrestore(q->queue_lock, flags);
2137 }
2138
2139 /*
2140  * Timer running if the active_queue is currently idling inside its time slice
2141  */
2142 static void cfq_idle_slice_timer(unsigned long data)
2143 {
2144         struct cfq_data *cfqd = (struct cfq_data *) data;
2145         struct cfq_queue *cfqq;
2146         unsigned long flags;
2147
2148         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2149
2150         if ((cfqq = cfqd->active_queue) != NULL) {
2151                 unsigned long now = jiffies;
2152
2153                 /*
2154                  * expired
2155                  */
2156                 if (time_after(now, cfqq->slice_end))
2157                         goto expire;
2158
2159                 /*
2160                  * only expire and reinvoke request handler, if there are
2161                  * other queues with pending requests
2162                  */
2163                 if (!cfqd->busy_queues) {
2164                         cfqd->idle_slice_timer.expires = min(now + cfqd->cfq_slice_idle, cfqq->slice_end);
2165                         add_timer(&cfqd->idle_slice_timer);
2166                         goto out_cont;
2167                 }
2168
2169                 /*
2170                  * not expired and it has a request pending, let it dispatch
2171                  */
2172                 if (!RB_EMPTY(&cfqq->sort_list)) {
2173                         cfq_mark_cfqq_must_dispatch(cfqq);
2174                         goto out_kick;
2175                 }
2176         }
2177 expire:
2178         cfq_slice_expired(cfqd, 0);
2179 out_kick:
2180         cfq_schedule_dispatch(cfqd);
2181 out_cont:
2182         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2183 }
2184
2185 /*
2186  * Timer running if an idle class queue is waiting for service
2187  */
2188 static void cfq_idle_class_timer(unsigned long data)
2189 {
2190         struct cfq_data *cfqd = (struct cfq_data *) data;
2191         unsigned long flags, end;
2192
2193         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2194
2195         /*
2196          * race with a non-idle queue, reset timer
2197          */
2198         end = cfqd->last_end_request + CFQ_IDLE_GRACE;
2199         if (!time_after_eq(jiffies, end))
2200                 mod_timer(&cfqd->idle_class_timer, end);
2201         else
2202                 cfq_schedule_dispatch(cfqd);
2203
2204         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2205 }
2206
2207 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2208 {
2209         del_timer_sync(&cfqd->idle_slice_timer);
2210         del_timer_sync(&cfqd->idle_class_timer);
2211         blk_sync_queue(cfqd->queue);
2212 }
2213
2214 static void cfq_exit_queue(elevator_t *e)
2215 {
2216         struct cfq_data *cfqd = e->elevator_data;
2217         request_queue_t *q = cfqd->queue;
2218
2219         cfq_shutdown_timer_wq(cfqd);
2220
2221         spin_lock(&cfq_exit_lock);
2222         spin_lock_irq(q->queue_lock);
2223
2224         if (cfqd->active_queue)
2225                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
2226
2227         while (!list_empty(&cfqd->cic_list)) {
2228                 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2229                                                         struct cfq_io_context,
2230                                                         queue_list);
2231                 if (cic->cfqq[ASYNC]) {
2232                         cfq_put_queue(cic->cfqq[ASYNC]);
2233                         cic->cfqq[ASYNC] = NULL;
2234                 }
2235                 if (cic->cfqq[SYNC]) {
2236                         cfq_put_queue(cic->cfqq[SYNC]);
2237                         cic->cfqq[SYNC] = NULL;
2238                 }
2239                 cic->key = NULL;
2240                 list_del_init(&cic->queue_list);
2241         }
2242
2243         spin_unlock_irq(q->queue_lock);
2244         spin_unlock(&cfq_exit_lock);
2245
2246         cfq_shutdown_timer_wq(cfqd);
2247
2248         mempool_destroy(cfqd->crq_pool);
2249         kfree(cfqd->crq_hash);
2250         kfree(cfqd->cfq_hash);
2251         kfree(cfqd);
2252 }
2253
2254 static void *cfq_init_queue(request_queue_t *q, elevator_t *e)
2255 {
2256         struct cfq_data *cfqd;
2257         int i;
2258
2259         cfqd = kmalloc(sizeof(*cfqd), GFP_KERNEL);
2260         if (!cfqd)
2261                 return NULL;
2262
2263         memset(cfqd, 0, sizeof(*cfqd));
2264
2265         for (i = 0; i < CFQ_PRIO_LISTS; i++)
2266                 INIT_LIST_HEAD(&cfqd->rr_list[i]);
2267
2268         INIT_LIST_HEAD(&cfqd->busy_rr);
2269         INIT_LIST_HEAD(&cfqd->cur_rr);
2270         INIT_LIST_HEAD(&cfqd->idle_rr);
2271         INIT_LIST_HEAD(&cfqd->empty_list);
2272         INIT_LIST_HEAD(&cfqd->cic_list);
2273
2274         cfqd->crq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_MHASH_ENTRIES, GFP_KERNEL);
2275         if (!cfqd->crq_hash)
2276                 goto out_crqhash;
2277
2278         cfqd->cfq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL);
2279         if (!cfqd->cfq_hash)
2280                 goto out_cfqhash;
2281
2282         cfqd->crq_pool = mempool_create_slab_pool(BLKDEV_MIN_RQ, crq_pool);
2283         if (!cfqd->crq_pool)
2284                 goto out_crqpool;
2285
2286         for (i = 0; i < CFQ_MHASH_ENTRIES; i++)
2287                 INIT_HLIST_HEAD(&cfqd->crq_hash[i]);
2288         for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
2289                 INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
2290
2291         cfqd->queue = q;
2292
2293         cfqd->max_queued = q->nr_requests / 4;
2294         q->nr_batching = cfq_queued;
2295
2296         init_timer(&cfqd->idle_slice_timer);
2297         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2298         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2299
2300         init_timer(&cfqd->idle_class_timer);
2301         cfqd->idle_class_timer.function = cfq_idle_class_timer;
2302         cfqd->idle_class_timer.data = (unsigned long) cfqd;
2303
2304         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue, q);
2305
2306         cfqd->cfq_queued = cfq_queued;
2307         cfqd->cfq_quantum = cfq_quantum;
2308         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2309         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2310         cfqd->cfq_back_max = cfq_back_max;
2311         cfqd->cfq_back_penalty = cfq_back_penalty;
2312         cfqd->cfq_slice[0] = cfq_slice_async;
2313         cfqd->cfq_slice[1] = cfq_slice_sync;
2314         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2315         cfqd->cfq_slice_idle = cfq_slice_idle;
2316
2317         return cfqd;
2318 out_crqpool:
2319         kfree(cfqd->cfq_hash);
2320 out_cfqhash:
2321         kfree(cfqd->crq_hash);
2322 out_crqhash:
2323         kfree(cfqd);
2324         return NULL;
2325 }
2326
2327 static void cfq_slab_kill(void)
2328 {
2329         if (crq_pool)
2330                 kmem_cache_destroy(crq_pool);
2331         if (cfq_pool)
2332                 kmem_cache_destroy(cfq_pool);
2333         if (cfq_ioc_pool)
2334                 kmem_cache_destroy(cfq_ioc_pool);
2335 }
2336
2337 static int __init cfq_slab_setup(void)
2338 {
2339         crq_pool = kmem_cache_create("crq_pool", sizeof(struct cfq_rq), 0, 0,
2340                                         NULL, NULL);
2341         if (!crq_pool)
2342                 goto fail;
2343
2344         cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0,
2345                                         NULL, NULL);
2346         if (!cfq_pool)
2347                 goto fail;
2348
2349         cfq_ioc_pool = kmem_cache_create("cfq_ioc_pool",
2350                         sizeof(struct cfq_io_context), 0, 0, NULL, NULL);
2351         if (!cfq_ioc_pool)
2352                 goto fail;
2353
2354         return 0;
2355 fail:
2356         cfq_slab_kill();
2357         return -ENOMEM;
2358 }
2359
2360 /*
2361  * sysfs parts below -->
2362  */
2363
2364 static ssize_t
2365 cfq_var_show(unsigned int var, char *page)
2366 {
2367         return sprintf(page, "%d\n", var);
2368 }
2369
2370 static ssize_t
2371 cfq_var_store(unsigned int *var, const char *page, size_t count)
2372 {
2373         char *p = (char *) page;
2374
2375         *var = simple_strtoul(p, &p, 10);
2376         return count;
2377 }
2378
2379 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
2380 static ssize_t __FUNC(elevator_t *e, char *page)                        \
2381 {                                                                       \
2382         struct cfq_data *cfqd = e->elevator_data;                       \
2383         unsigned int __data = __VAR;                                    \
2384         if (__CONV)                                                     \
2385                 __data = jiffies_to_msecs(__data);                      \
2386         return cfq_var_show(__data, (page));                            \
2387 }
2388 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2389 SHOW_FUNCTION(cfq_queued_show, cfqd->cfq_queued, 0);
2390 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2391 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2392 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
2393 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
2394 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2395 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2396 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2397 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2398 #undef SHOW_FUNCTION
2399
2400 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
2401 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count)    \
2402 {                                                                       \
2403         struct cfq_data *cfqd = e->elevator_data;                       \
2404         unsigned int __data;                                            \
2405         int ret = cfq_var_store(&__data, (page), count);                \
2406         if (__data < (MIN))                                             \
2407                 __data = (MIN);                                         \
2408         else if (__data > (MAX))                                        \
2409                 __data = (MAX);                                         \
2410         if (__CONV)                                                     \
2411                 *(__PTR) = msecs_to_jiffies(__data);                    \
2412         else                                                            \
2413                 *(__PTR) = __data;                                      \
2414         return ret;                                                     \
2415 }
2416 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2417 STORE_FUNCTION(cfq_queued_store, &cfqd->cfq_queued, 1, UINT_MAX, 0);
2418 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1);
2419 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1);
2420 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2421 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0);
2422 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2423 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2424 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2425 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0);
2426 #undef STORE_FUNCTION
2427
2428 #define CFQ_ATTR(name) \
2429         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2430
2431 static struct elv_fs_entry cfq_attrs[] = {
2432         CFQ_ATTR(quantum),
2433         CFQ_ATTR(queued),
2434         CFQ_ATTR(fifo_expire_sync),
2435         CFQ_ATTR(fifo_expire_async),
2436         CFQ_ATTR(back_seek_max),
2437         CFQ_ATTR(back_seek_penalty),
2438         CFQ_ATTR(slice_sync),
2439         CFQ_ATTR(slice_async),
2440         CFQ_ATTR(slice_async_rq),
2441         CFQ_ATTR(slice_idle),
2442         __ATTR_NULL
2443 };
2444
2445 static struct elevator_type iosched_cfq = {
2446         .ops = {
2447                 .elevator_merge_fn =            cfq_merge,
2448                 .elevator_merged_fn =           cfq_merged_request,
2449                 .elevator_merge_req_fn =        cfq_merged_requests,
2450                 .elevator_dispatch_fn =         cfq_dispatch_requests,
2451                 .elevator_add_req_fn =          cfq_insert_request,
2452                 .elevator_activate_req_fn =     cfq_activate_request,
2453                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
2454                 .elevator_queue_empty_fn =      cfq_queue_empty,
2455                 .elevator_completed_req_fn =    cfq_completed_request,
2456                 .elevator_former_req_fn =       cfq_former_request,
2457                 .elevator_latter_req_fn =       cfq_latter_request,
2458                 .elevator_set_req_fn =          cfq_set_request,
2459                 .elevator_put_req_fn =          cfq_put_request,
2460                 .elevator_may_queue_fn =        cfq_may_queue,
2461                 .elevator_init_fn =             cfq_init_queue,
2462                 .elevator_exit_fn =             cfq_exit_queue,
2463                 .trim =                         cfq_trim,
2464         },
2465         .elevator_attrs =       cfq_attrs,
2466         .elevator_name =        "cfq",
2467         .elevator_owner =       THIS_MODULE,
2468 };
2469
2470 static int __init cfq_init(void)
2471 {
2472         int ret;
2473
2474         /*
2475          * could be 0 on HZ < 1000 setups
2476          */
2477         if (!cfq_slice_async)
2478                 cfq_slice_async = 1;
2479         if (!cfq_slice_idle)
2480                 cfq_slice_idle = 1;
2481
2482         if (cfq_slab_setup())
2483                 return -ENOMEM;
2484
2485         ret = elv_register(&iosched_cfq);
2486         if (ret)
2487                 cfq_slab_kill();
2488
2489         return ret;
2490 }
2491
2492 static void __exit cfq_exit(void)
2493 {
2494         DECLARE_COMPLETION(all_gone);
2495         elv_unregister(&iosched_cfq);
2496         ioc_gone = &all_gone;
2497         /* ioc_gone's update must be visible before reading ioc_count */
2498         smp_wmb();
2499         if (atomic_read(&ioc_count))
2500                 wait_for_completion(ioc_gone);
2501         synchronize_rcu();
2502         cfq_slab_kill();
2503 }
2504
2505 module_init(cfq_init);
2506 module_exit(cfq_exit);
2507
2508 MODULE_AUTHOR("Jens Axboe");
2509 MODULE_LICENSE("GPL");
2510 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");