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[linux-2.6.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_RWLOCK(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
137         /*
138          * schedule slice state info
139          */
140         /*
141          * idle window management
142          */
143         struct timer_list idle_slice_timer;
144         struct work_struct unplug_work;
145
146         struct cfq_queue *active_queue;
147         struct cfq_io_context *active_cic;
148         int cur_prio, cur_end_prio;
149         unsigned int dispatch_slice;
150
151         struct timer_list idle_class_timer;
152
153         sector_t last_sector;
154         unsigned long last_end_request;
155
156         unsigned int rq_starved;
157
158         /*
159          * tunables, see top of file
160          */
161         unsigned int cfq_quantum;
162         unsigned int cfq_queued;
163         unsigned int cfq_fifo_expire[2];
164         unsigned int cfq_back_penalty;
165         unsigned int cfq_back_max;
166         unsigned int cfq_slice[2];
167         unsigned int cfq_slice_async_rq;
168         unsigned int cfq_slice_idle;
169
170         struct list_head cic_list;
171 };
172
173 /*
174  * Per process-grouping structure
175  */
176 struct cfq_queue {
177         /* reference count */
178         atomic_t ref;
179         /* parent cfq_data */
180         struct cfq_data *cfqd;
181         /* cfqq lookup hash */
182         struct hlist_node cfq_hash;
183         /* hash key */
184         unsigned int key;
185         /* on either rr or empty list of cfqd */
186         struct list_head cfq_list;
187         /* sorted list of pending requests */
188         struct rb_root sort_list;
189         /* if fifo isn't expired, next request to serve */
190         struct cfq_rq *next_crq;
191         /* requests queued in sort_list */
192         int queued[2];
193         /* currently allocated requests */
194         int allocated[2];
195         /* fifo list of requests in sort_list */
196         struct list_head fifo;
197
198         unsigned long slice_start;
199         unsigned long slice_end;
200         unsigned long slice_left;
201         unsigned long service_last;
202
203         /* number of requests that are on the dispatch list */
204         int on_dispatch[2];
205
206         /* io prio of this group */
207         unsigned short ioprio, org_ioprio;
208         unsigned short ioprio_class, org_ioprio_class;
209
210         /* various state flags, see below */
211         unsigned int flags;
212 };
213
214 struct cfq_rq {
215         struct rb_node rb_node;
216         sector_t rb_key;
217         struct request *request;
218         struct hlist_node hash;
219
220         struct cfq_queue *cfq_queue;
221         struct cfq_io_context *io_context;
222
223         unsigned int crq_flags;
224 };
225
226 enum cfqq_state_flags {
227         CFQ_CFQQ_FLAG_on_rr = 0,
228         CFQ_CFQQ_FLAG_wait_request,
229         CFQ_CFQQ_FLAG_must_alloc,
230         CFQ_CFQQ_FLAG_must_alloc_slice,
231         CFQ_CFQQ_FLAG_must_dispatch,
232         CFQ_CFQQ_FLAG_fifo_expire,
233         CFQ_CFQQ_FLAG_idle_window,
234         CFQ_CFQQ_FLAG_prio_changed,
235 };
236
237 #define CFQ_CFQQ_FNS(name)                                              \
238 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
239 {                                                                       \
240         cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name);                     \
241 }                                                                       \
242 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
243 {                                                                       \
244         cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                    \
245 }                                                                       \
246 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
247 {                                                                       \
248         return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;        \
249 }
250
251 CFQ_CFQQ_FNS(on_rr);
252 CFQ_CFQQ_FNS(wait_request);
253 CFQ_CFQQ_FNS(must_alloc);
254 CFQ_CFQQ_FNS(must_alloc_slice);
255 CFQ_CFQQ_FNS(must_dispatch);
256 CFQ_CFQQ_FNS(fifo_expire);
257 CFQ_CFQQ_FNS(idle_window);
258 CFQ_CFQQ_FNS(prio_changed);
259 #undef CFQ_CFQQ_FNS
260
261 enum cfq_rq_state_flags {
262         CFQ_CRQ_FLAG_is_sync = 0,
263 };
264
265 #define CFQ_CRQ_FNS(name)                                               \
266 static inline void cfq_mark_crq_##name(struct cfq_rq *crq)              \
267 {                                                                       \
268         crq->crq_flags |= (1 << CFQ_CRQ_FLAG_##name);                   \
269 }                                                                       \
270 static inline void cfq_clear_crq_##name(struct cfq_rq *crq)             \
271 {                                                                       \
272         crq->crq_flags &= ~(1 << CFQ_CRQ_FLAG_##name);                  \
273 }                                                                       \
274 static inline int cfq_crq_##name(const struct cfq_rq *crq)              \
275 {                                                                       \
276         return (crq->crq_flags & (1 << CFQ_CRQ_FLAG_##name)) != 0;      \
277 }
278
279 CFQ_CRQ_FNS(is_sync);
280 #undef CFQ_CRQ_FNS
281
282 static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short);
283 static void cfq_dispatch_insert(request_queue_t *, struct cfq_rq *);
284 static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask);
285
286 #define process_sync(tsk)       ((tsk)->flags & PF_SYNCWRITE)
287
288 /*
289  * lots of deadline iosched dupes, can be abstracted later...
290  */
291 static inline void cfq_del_crq_hash(struct cfq_rq *crq)
292 {
293         hlist_del_init(&crq->hash);
294 }
295
296 static inline void cfq_add_crq_hash(struct cfq_data *cfqd, struct cfq_rq *crq)
297 {
298         const int hash_idx = CFQ_MHASH_FN(rq_hash_key(crq->request));
299
300         hlist_add_head(&crq->hash, &cfqd->crq_hash[hash_idx]);
301 }
302
303 static struct request *cfq_find_rq_hash(struct cfq_data *cfqd, sector_t offset)
304 {
305         struct hlist_head *hash_list = &cfqd->crq_hash[CFQ_MHASH_FN(offset)];
306         struct hlist_node *entry, *next;
307
308         hlist_for_each_safe(entry, next, hash_list) {
309                 struct cfq_rq *crq = list_entry_hash(entry);
310                 struct request *__rq = crq->request;
311
312                 if (!rq_mergeable(__rq)) {
313                         cfq_del_crq_hash(crq);
314                         continue;
315                 }
316
317                 if (rq_hash_key(__rq) == offset)
318                         return __rq;
319         }
320
321         return NULL;
322 }
323
324 /*
325  * scheduler run of queue, if there are requests pending and no one in the
326  * driver that will restart queueing
327  */
328 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
329 {
330         if (cfqd->busy_queues)
331                 kblockd_schedule_work(&cfqd->unplug_work);
332 }
333
334 static int cfq_queue_empty(request_queue_t *q)
335 {
336         struct cfq_data *cfqd = q->elevator->elevator_data;
337
338         return !cfqd->busy_queues;
339 }
340
341 static inline pid_t cfq_queue_pid(struct task_struct *task, int rw)
342 {
343         if (rw == READ || process_sync(task))
344                 return task->pid;
345
346         return CFQ_KEY_ASYNC;
347 }
348
349 /*
350  * Lifted from AS - choose which of crq1 and crq2 that is best served now.
351  * We choose the request that is closest to the head right now. Distance
352  * behind the head is penalized and only allowed to a certain extent.
353  */
354 static struct cfq_rq *
355 cfq_choose_req(struct cfq_data *cfqd, struct cfq_rq *crq1, struct cfq_rq *crq2)
356 {
357         sector_t last, s1, s2, d1 = 0, d2 = 0;
358         unsigned long back_max;
359 #define CFQ_RQ1_WRAP    0x01 /* request 1 wraps */
360 #define CFQ_RQ2_WRAP    0x02 /* request 2 wraps */
361         unsigned wrap = 0; /* bit mask: requests behind the disk head? */
362
363         if (crq1 == NULL || crq1 == crq2)
364                 return crq2;
365         if (crq2 == NULL)
366                 return crq1;
367
368         if (cfq_crq_is_sync(crq1) && !cfq_crq_is_sync(crq2))
369                 return crq1;
370         else if (cfq_crq_is_sync(crq2) && !cfq_crq_is_sync(crq1))
371                 return crq2;
372
373         s1 = crq1->request->sector;
374         s2 = crq2->request->sector;
375
376         last = cfqd->last_sector;
377
378         /*
379          * by definition, 1KiB is 2 sectors
380          */
381         back_max = cfqd->cfq_back_max * 2;
382
383         /*
384          * Strict one way elevator _except_ in the case where we allow
385          * short backward seeks which are biased as twice the cost of a
386          * similar forward seek.
387          */
388         if (s1 >= last)
389                 d1 = s1 - last;
390         else if (s1 + back_max >= last)
391                 d1 = (last - s1) * cfqd->cfq_back_penalty;
392         else
393                 wrap |= CFQ_RQ1_WRAP;
394
395         if (s2 >= last)
396                 d2 = s2 - last;
397         else if (s2 + back_max >= last)
398                 d2 = (last - s2) * cfqd->cfq_back_penalty;
399         else
400                 wrap |= CFQ_RQ2_WRAP;
401
402         /* Found required data */
403
404         /*
405          * By doing switch() on the bit mask "wrap" we avoid having to
406          * check two variables for all permutations: --> faster!
407          */
408         switch (wrap) {
409         case 0: /* common case for CFQ: crq1 and crq2 not wrapped */
410                 if (d1 < d2)
411                         return crq1;
412                 else if (d2 < d1)
413                         return crq2;
414                 else {
415                         if (s1 >= s2)
416                                 return crq1;
417                         else
418                                 return crq2;
419                 }
420
421         case CFQ_RQ2_WRAP:
422                 return crq1;
423         case CFQ_RQ1_WRAP:
424                 return crq2;
425         case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both crqs wrapped */
426         default:
427                 /*
428                  * Since both rqs are wrapped,
429                  * start with the one that's further behind head
430                  * (--> only *one* back seek required),
431                  * since back seek takes more time than forward.
432                  */
433                 if (s1 <= s2)
434                         return crq1;
435                 else
436                         return crq2;
437         }
438 }
439
440 /*
441  * would be nice to take fifo expire time into account as well
442  */
443 static struct cfq_rq *
444 cfq_find_next_crq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
445                   struct cfq_rq *last)
446 {
447         struct cfq_rq *crq_next = NULL, *crq_prev = NULL;
448         struct rb_node *rbnext, *rbprev;
449
450         if (!(rbnext = rb_next(&last->rb_node))) {
451                 rbnext = rb_first(&cfqq->sort_list);
452                 if (rbnext == &last->rb_node)
453                         rbnext = NULL;
454         }
455
456         rbprev = rb_prev(&last->rb_node);
457
458         if (rbprev)
459                 crq_prev = rb_entry_crq(rbprev);
460         if (rbnext)
461                 crq_next = rb_entry_crq(rbnext);
462
463         return cfq_choose_req(cfqd, crq_next, crq_prev);
464 }
465
466 static void cfq_update_next_crq(struct cfq_rq *crq)
467 {
468         struct cfq_queue *cfqq = crq->cfq_queue;
469
470         if (cfqq->next_crq == crq)
471                 cfqq->next_crq = cfq_find_next_crq(cfqq->cfqd, cfqq, crq);
472 }
473
474 static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
475 {
476         struct cfq_data *cfqd = cfqq->cfqd;
477         struct list_head *list, *entry;
478
479         BUG_ON(!cfq_cfqq_on_rr(cfqq));
480
481         list_del(&cfqq->cfq_list);
482
483         if (cfq_class_rt(cfqq))
484                 list = &cfqd->cur_rr;
485         else if (cfq_class_idle(cfqq))
486                 list = &cfqd->idle_rr;
487         else {
488                 /*
489                  * if cfqq has requests in flight, don't allow it to be
490                  * found in cfq_set_active_queue before it has finished them.
491                  * this is done to increase fairness between a process that
492                  * has lots of io pending vs one that only generates one
493                  * sporadically or synchronously
494                  */
495                 if (cfq_cfqq_dispatched(cfqq))
496                         list = &cfqd->busy_rr;
497                 else
498                         list = &cfqd->rr_list[cfqq->ioprio];
499         }
500
501         /*
502          * if queue was preempted, just add to front to be fair. busy_rr
503          * isn't sorted.
504          */
505         if (preempted || list == &cfqd->busy_rr) {
506                 list_add(&cfqq->cfq_list, list);
507                 return;
508         }
509
510         /*
511          * sort by when queue was last serviced
512          */
513         entry = list;
514         while ((entry = entry->prev) != list) {
515                 struct cfq_queue *__cfqq = list_entry_cfqq(entry);
516
517                 if (!__cfqq->service_last)
518                         break;
519                 if (time_before(__cfqq->service_last, cfqq->service_last))
520                         break;
521         }
522
523         list_add(&cfqq->cfq_list, entry);
524 }
525
526 /*
527  * add to busy list of queues for service, trying to be fair in ordering
528  * the pending list according to last request service
529  */
530 static inline void
531 cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
532 {
533         BUG_ON(cfq_cfqq_on_rr(cfqq));
534         cfq_mark_cfqq_on_rr(cfqq);
535         cfqd->busy_queues++;
536
537         cfq_resort_rr_list(cfqq, 0);
538 }
539
540 static inline void
541 cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
542 {
543         BUG_ON(!cfq_cfqq_on_rr(cfqq));
544         cfq_clear_cfqq_on_rr(cfqq);
545         list_move(&cfqq->cfq_list, &cfqd->empty_list);
546
547         BUG_ON(!cfqd->busy_queues);
548         cfqd->busy_queues--;
549 }
550
551 /*
552  * rb tree support functions
553  */
554 static inline void cfq_del_crq_rb(struct cfq_rq *crq)
555 {
556         struct cfq_queue *cfqq = crq->cfq_queue;
557         struct cfq_data *cfqd = cfqq->cfqd;
558         const int sync = cfq_crq_is_sync(crq);
559
560         BUG_ON(!cfqq->queued[sync]);
561         cfqq->queued[sync]--;
562
563         cfq_update_next_crq(crq);
564
565         rb_erase(&crq->rb_node, &cfqq->sort_list);
566         RB_CLEAR_COLOR(&crq->rb_node);
567
568         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY(&cfqq->sort_list))
569                 cfq_del_cfqq_rr(cfqd, cfqq);
570 }
571
572 static struct cfq_rq *
573 __cfq_add_crq_rb(struct cfq_rq *crq)
574 {
575         struct rb_node **p = &crq->cfq_queue->sort_list.rb_node;
576         struct rb_node *parent = NULL;
577         struct cfq_rq *__crq;
578
579         while (*p) {
580                 parent = *p;
581                 __crq = rb_entry_crq(parent);
582
583                 if (crq->rb_key < __crq->rb_key)
584                         p = &(*p)->rb_left;
585                 else if (crq->rb_key > __crq->rb_key)
586                         p = &(*p)->rb_right;
587                 else
588                         return __crq;
589         }
590
591         rb_link_node(&crq->rb_node, parent, p);
592         return NULL;
593 }
594
595 static void cfq_add_crq_rb(struct cfq_rq *crq)
596 {
597         struct cfq_queue *cfqq = crq->cfq_queue;
598         struct cfq_data *cfqd = cfqq->cfqd;
599         struct request *rq = crq->request;
600         struct cfq_rq *__alias;
601
602         crq->rb_key = rq_rb_key(rq);
603         cfqq->queued[cfq_crq_is_sync(crq)]++;
604
605         /*
606          * looks a little odd, but the first insert might return an alias.
607          * if that happens, put the alias on the dispatch list
608          */
609         while ((__alias = __cfq_add_crq_rb(crq)) != NULL)
610                 cfq_dispatch_insert(cfqd->queue, __alias);
611
612         rb_insert_color(&crq->rb_node, &cfqq->sort_list);
613
614         if (!cfq_cfqq_on_rr(cfqq))
615                 cfq_add_cfqq_rr(cfqd, cfqq);
616
617         /*
618          * check if this request is a better next-serve candidate
619          */
620         cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
621 }
622
623 static inline void
624 cfq_reposition_crq_rb(struct cfq_queue *cfqq, struct cfq_rq *crq)
625 {
626         rb_erase(&crq->rb_node, &cfqq->sort_list);
627         cfqq->queued[cfq_crq_is_sync(crq)]--;
628
629         cfq_add_crq_rb(crq);
630 }
631
632 static struct request *
633 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
634 {
635         struct task_struct *tsk = current;
636         pid_t key = cfq_queue_pid(tsk, bio_data_dir(bio));
637         struct cfq_queue *cfqq;
638         struct rb_node *n;
639         sector_t sector;
640
641         cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
642         if (!cfqq)
643                 goto out;
644
645         sector = bio->bi_sector + bio_sectors(bio);
646         n = cfqq->sort_list.rb_node;
647         while (n) {
648                 struct cfq_rq *crq = rb_entry_crq(n);
649
650                 if (sector < crq->rb_key)
651                         n = n->rb_left;
652                 else if (sector > crq->rb_key)
653                         n = n->rb_right;
654                 else
655                         return crq->request;
656         }
657
658 out:
659         return NULL;
660 }
661
662 static void cfq_activate_request(request_queue_t *q, struct request *rq)
663 {
664         struct cfq_data *cfqd = q->elevator->elevator_data;
665
666         cfqd->rq_in_driver++;
667 }
668
669 static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
670 {
671         struct cfq_data *cfqd = q->elevator->elevator_data;
672
673         WARN_ON(!cfqd->rq_in_driver);
674         cfqd->rq_in_driver--;
675 }
676
677 static void cfq_remove_request(struct request *rq)
678 {
679         struct cfq_rq *crq = RQ_DATA(rq);
680
681         list_del_init(&rq->queuelist);
682         cfq_del_crq_rb(crq);
683         cfq_del_crq_hash(crq);
684 }
685
686 static int
687 cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
688 {
689         struct cfq_data *cfqd = q->elevator->elevator_data;
690         struct request *__rq;
691         int ret;
692
693         __rq = cfq_find_rq_hash(cfqd, bio->bi_sector);
694         if (__rq && elv_rq_merge_ok(__rq, bio)) {
695                 ret = ELEVATOR_BACK_MERGE;
696                 goto out;
697         }
698
699         __rq = cfq_find_rq_fmerge(cfqd, bio);
700         if (__rq && elv_rq_merge_ok(__rq, bio)) {
701                 ret = ELEVATOR_FRONT_MERGE;
702                 goto out;
703         }
704
705         return ELEVATOR_NO_MERGE;
706 out:
707         *req = __rq;
708         return ret;
709 }
710
711 static void cfq_merged_request(request_queue_t *q, struct request *req)
712 {
713         struct cfq_data *cfqd = q->elevator->elevator_data;
714         struct cfq_rq *crq = RQ_DATA(req);
715
716         cfq_del_crq_hash(crq);
717         cfq_add_crq_hash(cfqd, crq);
718
719         if (rq_rb_key(req) != crq->rb_key) {
720                 struct cfq_queue *cfqq = crq->cfq_queue;
721
722                 cfq_update_next_crq(crq);
723                 cfq_reposition_crq_rb(cfqq, crq);
724         }
725 }
726
727 static void
728 cfq_merged_requests(request_queue_t *q, struct request *rq,
729                     struct request *next)
730 {
731         cfq_merged_request(q, rq);
732
733         /*
734          * reposition in fifo if next is older than rq
735          */
736         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
737             time_before(next->start_time, rq->start_time))
738                 list_move(&rq->queuelist, &next->queuelist);
739
740         cfq_remove_request(next);
741 }
742
743 static inline void
744 __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
745 {
746         if (cfqq) {
747                 /*
748                  * stop potential idle class queues waiting service
749                  */
750                 del_timer(&cfqd->idle_class_timer);
751
752                 cfqq->slice_start = jiffies;
753                 cfqq->slice_end = 0;
754                 cfqq->slice_left = 0;
755                 cfq_clear_cfqq_must_alloc_slice(cfqq);
756                 cfq_clear_cfqq_fifo_expire(cfqq);
757         }
758
759         cfqd->active_queue = cfqq;
760 }
761
762 /*
763  * current cfqq expired its slice (or was too idle), select new one
764  */
765 static void
766 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
767                     int preempted)
768 {
769         unsigned long now = jiffies;
770
771         if (cfq_cfqq_wait_request(cfqq))
772                 del_timer(&cfqd->idle_slice_timer);
773
774         if (!preempted && !cfq_cfqq_dispatched(cfqq)) {
775                 cfqq->service_last = now;
776                 cfq_schedule_dispatch(cfqd);
777         }
778
779         cfq_clear_cfqq_must_dispatch(cfqq);
780         cfq_clear_cfqq_wait_request(cfqq);
781
782         /*
783          * store what was left of this slice, if the queue idled out
784          * or was preempted
785          */
786         if (time_after(cfqq->slice_end, now))
787                 cfqq->slice_left = cfqq->slice_end - now;
788         else
789                 cfqq->slice_left = 0;
790
791         if (cfq_cfqq_on_rr(cfqq))
792                 cfq_resort_rr_list(cfqq, preempted);
793
794         if (cfqq == cfqd->active_queue)
795                 cfqd->active_queue = NULL;
796
797         if (cfqd->active_cic) {
798                 put_io_context(cfqd->active_cic->ioc);
799                 cfqd->active_cic = NULL;
800         }
801
802         cfqd->dispatch_slice = 0;
803 }
804
805 static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted)
806 {
807         struct cfq_queue *cfqq = cfqd->active_queue;
808
809         if (cfqq)
810                 __cfq_slice_expired(cfqd, cfqq, preempted);
811 }
812
813 /*
814  * 0
815  * 0,1
816  * 0,1,2
817  * 0,1,2,3
818  * 0,1,2,3,4
819  * 0,1,2,3,4,5
820  * 0,1,2,3,4,5,6
821  * 0,1,2,3,4,5,6,7
822  */
823 static int cfq_get_next_prio_level(struct cfq_data *cfqd)
824 {
825         int prio, wrap;
826
827         prio = -1;
828         wrap = 0;
829         do {
830                 int p;
831
832                 for (p = cfqd->cur_prio; p <= cfqd->cur_end_prio; p++) {
833                         if (!list_empty(&cfqd->rr_list[p])) {
834                                 prio = p;
835                                 break;
836                         }
837                 }
838
839                 if (prio != -1)
840                         break;
841                 cfqd->cur_prio = 0;
842                 if (++cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
843                         cfqd->cur_end_prio = 0;
844                         if (wrap)
845                                 break;
846                         wrap = 1;
847                 }
848         } while (1);
849
850         if (unlikely(prio == -1))
851                 return -1;
852
853         BUG_ON(prio >= CFQ_PRIO_LISTS);
854
855         list_splice_init(&cfqd->rr_list[prio], &cfqd->cur_rr);
856
857         cfqd->cur_prio = prio + 1;
858         if (cfqd->cur_prio > cfqd->cur_end_prio) {
859                 cfqd->cur_end_prio = cfqd->cur_prio;
860                 cfqd->cur_prio = 0;
861         }
862         if (cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
863                 cfqd->cur_prio = 0;
864                 cfqd->cur_end_prio = 0;
865         }
866
867         return prio;
868 }
869
870 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
871 {
872         struct cfq_queue *cfqq = NULL;
873
874         /*
875          * if current list is non-empty, grab first entry. if it is empty,
876          * get next prio level and grab first entry then if any are spliced
877          */
878         if (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1)
879                 cfqq = list_entry_cfqq(cfqd->cur_rr.next);
880
881         /*
882          * if we have idle queues and no rt or be queues had pending
883          * requests, either allow immediate service if the grace period
884          * has passed or arm the idle grace timer
885          */
886         if (!cfqq && !list_empty(&cfqd->idle_rr)) {
887                 unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE;
888
889                 if (time_after_eq(jiffies, end))
890                         cfqq = list_entry_cfqq(cfqd->idle_rr.next);
891                 else
892                         mod_timer(&cfqd->idle_class_timer, end);
893         }
894
895         __cfq_set_active_queue(cfqd, cfqq);
896         return cfqq;
897 }
898
899 static int cfq_arm_slice_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
900
901 {
902         struct cfq_io_context *cic;
903         unsigned long sl;
904
905         WARN_ON(!RB_EMPTY(&cfqq->sort_list));
906         WARN_ON(cfqq != cfqd->active_queue);
907
908         /*
909          * idle is disabled, either manually or by past process history
910          */
911         if (!cfqd->cfq_slice_idle)
912                 return 0;
913         if (!cfq_cfqq_idle_window(cfqq))
914                 return 0;
915         /*
916          * task has exited, don't wait
917          */
918         cic = cfqd->active_cic;
919         if (!cic || !cic->ioc->task)
920                 return 0;
921
922         cfq_mark_cfqq_must_dispatch(cfqq);
923         cfq_mark_cfqq_wait_request(cfqq);
924
925         sl = min(cfqq->slice_end - 1, (unsigned long) cfqd->cfq_slice_idle);
926
927         /*
928          * we don't want to idle for seeks, but we do want to allow
929          * fair distribution of slice time for a process doing back-to-back
930          * seeks. so allow a little bit of time for him to submit a new rq
931          */
932         if (sample_valid(cic->seek_samples) && cic->seek_mean > 131072)
933                 sl = 2;
934
935         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
936         return 1;
937 }
938
939 static void cfq_dispatch_insert(request_queue_t *q, struct cfq_rq *crq)
940 {
941         struct cfq_data *cfqd = q->elevator->elevator_data;
942         struct cfq_queue *cfqq = crq->cfq_queue;
943
944         cfqq->next_crq = cfq_find_next_crq(cfqd, cfqq, crq);
945         cfq_remove_request(crq->request);
946         cfqq->on_dispatch[cfq_crq_is_sync(crq)]++;
947         elv_dispatch_sort(q, crq->request);
948 }
949
950 /*
951  * return expired entry, or NULL to just start from scratch in rbtree
952  */
953 static inline struct cfq_rq *cfq_check_fifo(struct cfq_queue *cfqq)
954 {
955         struct cfq_data *cfqd = cfqq->cfqd;
956         struct request *rq;
957         struct cfq_rq *crq;
958
959         if (cfq_cfqq_fifo_expire(cfqq))
960                 return NULL;
961
962         if (!list_empty(&cfqq->fifo)) {
963                 int fifo = cfq_cfqq_class_sync(cfqq);
964
965                 crq = RQ_DATA(list_entry_fifo(cfqq->fifo.next));
966                 rq = crq->request;
967                 if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) {
968                         cfq_mark_cfqq_fifo_expire(cfqq);
969                         return crq;
970                 }
971         }
972
973         return NULL;
974 }
975
976 /*
977  * Scale schedule slice based on io priority. Use the sync time slice only
978  * if a queue is marked sync and has sync io queued. A sync queue with async
979  * io only, should not get full sync slice length.
980  */
981 static inline int
982 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
983 {
984         const int base_slice = cfqd->cfq_slice[cfq_cfqq_sync(cfqq)];
985
986         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
987
988         return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - cfqq->ioprio));
989 }
990
991 static inline void
992 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
993 {
994         cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
995 }
996
997 static inline int
998 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
999 {
1000         const int base_rq = cfqd->cfq_slice_async_rq;
1001
1002         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1003
1004         return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1005 }
1006
1007 /*
1008  * get next queue for service
1009  */
1010 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
1011 {
1012         unsigned long now = jiffies;
1013         struct cfq_queue *cfqq;
1014
1015         cfqq = cfqd->active_queue;
1016         if (!cfqq)
1017                 goto new_queue;
1018
1019         /*
1020          * slice has expired
1021          */
1022         if (!cfq_cfqq_must_dispatch(cfqq) && time_after(now, cfqq->slice_end))
1023                 goto expire;
1024
1025         /*
1026          * if queue has requests, dispatch one. if not, check if
1027          * enough slice is left to wait for one
1028          */
1029         if (!RB_EMPTY(&cfqq->sort_list))
1030                 goto keep_queue;
1031         else if (cfq_cfqq_class_sync(cfqq) &&
1032                  time_before(now, cfqq->slice_end)) {
1033                 if (cfq_arm_slice_timer(cfqd, cfqq))
1034                         return NULL;
1035         }
1036
1037 expire:
1038         cfq_slice_expired(cfqd, 0);
1039 new_queue:
1040         cfqq = cfq_set_active_queue(cfqd);
1041 keep_queue:
1042         return cfqq;
1043 }
1044
1045 static int
1046 __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1047                         int max_dispatch)
1048 {
1049         int dispatched = 0;
1050
1051         BUG_ON(RB_EMPTY(&cfqq->sort_list));
1052
1053         do {
1054                 struct cfq_rq *crq;
1055
1056                 /*
1057                  * follow expired path, else get first next available
1058                  */
1059                 if ((crq = cfq_check_fifo(cfqq)) == NULL)
1060                         crq = cfqq->next_crq;
1061
1062                 /*
1063                  * finally, insert request into driver dispatch list
1064                  */
1065                 cfq_dispatch_insert(cfqd->queue, crq);
1066
1067                 cfqd->dispatch_slice++;
1068                 dispatched++;
1069
1070                 if (!cfqd->active_cic) {
1071                         atomic_inc(&crq->io_context->ioc->refcount);
1072                         cfqd->active_cic = crq->io_context;
1073                 }
1074
1075                 if (RB_EMPTY(&cfqq->sort_list))
1076                         break;
1077
1078         } while (dispatched < max_dispatch);
1079
1080         /*
1081          * if slice end isn't set yet, set it. if at least one request was
1082          * sync, use the sync time slice value
1083          */
1084         if (!cfqq->slice_end)
1085                 cfq_set_prio_slice(cfqd, cfqq);
1086
1087         /*
1088          * expire an async queue immediately if it has used up its slice. idle
1089          * queue always expire after 1 dispatch round.
1090          */
1091         if ((!cfq_cfqq_sync(cfqq) &&
1092             cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1093             cfq_class_idle(cfqq))
1094                 cfq_slice_expired(cfqd, 0);
1095
1096         return dispatched;
1097 }
1098
1099 static int
1100 cfq_forced_dispatch_cfqqs(struct list_head *list)
1101 {
1102         int dispatched = 0;
1103         struct cfq_queue *cfqq, *next;
1104         struct cfq_rq *crq;
1105
1106         list_for_each_entry_safe(cfqq, next, list, cfq_list) {
1107                 while ((crq = cfqq->next_crq)) {
1108                         cfq_dispatch_insert(cfqq->cfqd->queue, crq);
1109                         dispatched++;
1110                 }
1111                 BUG_ON(!list_empty(&cfqq->fifo));
1112         }
1113         return dispatched;
1114 }
1115
1116 static int
1117 cfq_forced_dispatch(struct cfq_data *cfqd)
1118 {
1119         int i, dispatched = 0;
1120
1121         for (i = 0; i < CFQ_PRIO_LISTS; i++)
1122                 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]);
1123
1124         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->busy_rr);
1125         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr);
1126         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr);
1127
1128         cfq_slice_expired(cfqd, 0);
1129
1130         BUG_ON(cfqd->busy_queues);
1131
1132         return dispatched;
1133 }
1134
1135 static int
1136 cfq_dispatch_requests(request_queue_t *q, int force)
1137 {
1138         struct cfq_data *cfqd = q->elevator->elevator_data;
1139         struct cfq_queue *cfqq;
1140
1141         if (!cfqd->busy_queues)
1142                 return 0;
1143
1144         if (unlikely(force))
1145                 return cfq_forced_dispatch(cfqd);
1146
1147         cfqq = cfq_select_queue(cfqd);
1148         if (cfqq) {
1149                 int max_dispatch;
1150
1151                 cfq_clear_cfqq_must_dispatch(cfqq);
1152                 cfq_clear_cfqq_wait_request(cfqq);
1153                 del_timer(&cfqd->idle_slice_timer);
1154
1155                 max_dispatch = cfqd->cfq_quantum;
1156                 if (cfq_class_idle(cfqq))
1157                         max_dispatch = 1;
1158
1159                 return __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
1160         }
1161
1162         return 0;
1163 }
1164
1165 /*
1166  * task holds one reference to the queue, dropped when task exits. each crq
1167  * in-flight on this queue also holds a reference, dropped when crq is freed.
1168  *
1169  * queue lock must be held here.
1170  */
1171 static void cfq_put_queue(struct cfq_queue *cfqq)
1172 {
1173         struct cfq_data *cfqd = cfqq->cfqd;
1174
1175         BUG_ON(atomic_read(&cfqq->ref) <= 0);
1176
1177         if (!atomic_dec_and_test(&cfqq->ref))
1178                 return;
1179
1180         BUG_ON(rb_first(&cfqq->sort_list));
1181         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1182         BUG_ON(cfq_cfqq_on_rr(cfqq));
1183
1184         if (unlikely(cfqd->active_queue == cfqq))
1185                 __cfq_slice_expired(cfqd, cfqq, 0);
1186
1187         /*
1188          * it's on the empty list and still hashed
1189          */
1190         list_del(&cfqq->cfq_list);
1191         hlist_del(&cfqq->cfq_hash);
1192         kmem_cache_free(cfq_pool, cfqq);
1193 }
1194
1195 static inline struct cfq_queue *
1196 __cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned int prio,
1197                     const int hashval)
1198 {
1199         struct hlist_head *hash_list = &cfqd->cfq_hash[hashval];
1200         struct hlist_node *entry;
1201         struct cfq_queue *__cfqq;
1202
1203         hlist_for_each_entry(__cfqq, entry, hash_list, cfq_hash) {
1204                 const unsigned short __p = IOPRIO_PRIO_VALUE(__cfqq->org_ioprio_class, __cfqq->org_ioprio);
1205
1206                 if (__cfqq->key == key && (__p == prio || !prio))
1207                         return __cfqq;
1208         }
1209
1210         return NULL;
1211 }
1212
1213 static struct cfq_queue *
1214 cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned short prio)
1215 {
1216         return __cfq_find_cfq_hash(cfqd, key, prio, hash_long(key, CFQ_QHASH_SHIFT));
1217 }
1218
1219 static void cfq_free_io_context(struct io_context *ioc)
1220 {
1221         struct cfq_io_context *__cic;
1222         struct rb_node *n;
1223         int freed = 0;
1224
1225         while ((n = rb_first(&ioc->cic_root)) != NULL) {
1226                 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1227                 rb_erase(&__cic->rb_node, &ioc->cic_root);
1228                 kmem_cache_free(cfq_ioc_pool, __cic);
1229                 freed++;
1230         }
1231
1232         if (atomic_sub_and_test(freed, &ioc_count) && ioc_gone)
1233                 complete(ioc_gone);
1234 }
1235
1236 static void cfq_trim(struct io_context *ioc)
1237 {
1238         ioc->set_ioprio = NULL;
1239         cfq_free_io_context(ioc);
1240 }
1241
1242 /*
1243  * Called with interrupts disabled
1244  */
1245 static void cfq_exit_single_io_context(struct cfq_io_context *cic)
1246 {
1247         struct cfq_data *cfqd = cic->key;
1248         request_queue_t *q;
1249
1250         if (!cfqd)
1251                 return;
1252
1253         q = cfqd->queue;
1254
1255         WARN_ON(!irqs_disabled());
1256
1257         spin_lock(q->queue_lock);
1258
1259         if (cic->cfqq[ASYNC]) {
1260                 if (unlikely(cic->cfqq[ASYNC] == cfqd->active_queue))
1261                         __cfq_slice_expired(cfqd, cic->cfqq[ASYNC], 0);
1262                 cfq_put_queue(cic->cfqq[ASYNC]);
1263                 cic->cfqq[ASYNC] = NULL;
1264         }
1265
1266         if (cic->cfqq[SYNC]) {
1267                 if (unlikely(cic->cfqq[SYNC] == cfqd->active_queue))
1268                         __cfq_slice_expired(cfqd, cic->cfqq[SYNC], 0);
1269                 cfq_put_queue(cic->cfqq[SYNC]);
1270                 cic->cfqq[SYNC] = NULL;
1271         }
1272
1273         cic->key = NULL;
1274         list_del_init(&cic->queue_list);
1275         spin_unlock(q->queue_lock);
1276 }
1277
1278 static void cfq_exit_io_context(struct io_context *ioc)
1279 {
1280         struct cfq_io_context *__cic;
1281         unsigned long flags;
1282         struct rb_node *n;
1283
1284         /*
1285          * put the reference this task is holding to the various queues
1286          */
1287         read_lock_irqsave(&cfq_exit_lock, flags);
1288
1289         n = rb_first(&ioc->cic_root);
1290         while (n != NULL) {
1291                 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1292
1293                 cfq_exit_single_io_context(__cic);
1294                 n = rb_next(n);
1295         }
1296
1297         read_unlock_irqrestore(&cfq_exit_lock, flags);
1298 }
1299
1300 static struct cfq_io_context *
1301 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1302 {
1303         struct cfq_io_context *cic = kmem_cache_alloc(cfq_ioc_pool, gfp_mask);
1304
1305         if (cic) {
1306                 RB_CLEAR(&cic->rb_node);
1307                 cic->key = NULL;
1308                 cic->cfqq[ASYNC] = NULL;
1309                 cic->cfqq[SYNC] = NULL;
1310                 cic->last_end_request = jiffies;
1311                 cic->ttime_total = 0;
1312                 cic->ttime_samples = 0;
1313                 cic->ttime_mean = 0;
1314                 cic->dtor = cfq_free_io_context;
1315                 cic->exit = cfq_exit_io_context;
1316                 INIT_LIST_HEAD(&cic->queue_list);
1317                 atomic_inc(&ioc_count);
1318         }
1319
1320         return cic;
1321 }
1322
1323 static void cfq_init_prio_data(struct cfq_queue *cfqq)
1324 {
1325         struct task_struct *tsk = current;
1326         int ioprio_class;
1327
1328         if (!cfq_cfqq_prio_changed(cfqq))
1329                 return;
1330
1331         ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
1332         switch (ioprio_class) {
1333                 default:
1334                         printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1335                 case IOPRIO_CLASS_NONE:
1336                         /*
1337                          * no prio set, place us in the middle of the BE classes
1338                          */
1339                         cfqq->ioprio = task_nice_ioprio(tsk);
1340                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1341                         break;
1342                 case IOPRIO_CLASS_RT:
1343                         cfqq->ioprio = task_ioprio(tsk);
1344                         cfqq->ioprio_class = IOPRIO_CLASS_RT;
1345                         break;
1346                 case IOPRIO_CLASS_BE:
1347                         cfqq->ioprio = task_ioprio(tsk);
1348                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1349                         break;
1350                 case IOPRIO_CLASS_IDLE:
1351                         cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1352                         cfqq->ioprio = 7;
1353                         cfq_clear_cfqq_idle_window(cfqq);
1354                         break;
1355         }
1356
1357         /*
1358          * keep track of original prio settings in case we have to temporarily
1359          * elevate the priority of this queue
1360          */
1361         cfqq->org_ioprio = cfqq->ioprio;
1362         cfqq->org_ioprio_class = cfqq->ioprio_class;
1363
1364         if (cfq_cfqq_on_rr(cfqq))
1365                 cfq_resort_rr_list(cfqq, 0);
1366
1367         cfq_clear_cfqq_prio_changed(cfqq);
1368 }
1369
1370 static inline void changed_ioprio(struct cfq_io_context *cic)
1371 {
1372         struct cfq_data *cfqd = cic->key;
1373         struct cfq_queue *cfqq;
1374         if (cfqd) {
1375                 spin_lock(cfqd->queue->queue_lock);
1376                 cfqq = cic->cfqq[ASYNC];
1377                 if (cfqq) {
1378                         struct cfq_queue *new_cfqq;
1379                         new_cfqq = cfq_get_queue(cfqd, CFQ_KEY_ASYNC,
1380                                                 cic->ioc->task, GFP_ATOMIC);
1381                         if (new_cfqq) {
1382                                 cic->cfqq[ASYNC] = new_cfqq;
1383                                 cfq_put_queue(cfqq);
1384                         }
1385                 }
1386                 cfqq = cic->cfqq[SYNC];
1387                 if (cfqq) {
1388                         cfq_mark_cfqq_prio_changed(cfqq);
1389                         cfq_init_prio_data(cfqq);
1390                 }
1391                 spin_unlock(cfqd->queue->queue_lock);
1392         }
1393 }
1394
1395 /*
1396  * callback from sys_ioprio_set, irqs are disabled
1397  */
1398 static int cfq_ioc_set_ioprio(struct io_context *ioc, unsigned int ioprio)
1399 {
1400         struct cfq_io_context *cic;
1401         struct rb_node *n;
1402
1403         write_lock(&cfq_exit_lock);
1404
1405         n = rb_first(&ioc->cic_root);
1406         while (n != NULL) {
1407                 cic = rb_entry(n, struct cfq_io_context, rb_node);
1408  
1409                 changed_ioprio(cic);
1410                 n = rb_next(n);
1411         }
1412
1413         write_unlock(&cfq_exit_lock);
1414
1415         return 0;
1416 }
1417
1418 static struct cfq_queue *
1419 cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk,
1420               gfp_t gfp_mask)
1421 {
1422         const int hashval = hash_long(key, CFQ_QHASH_SHIFT);
1423         struct cfq_queue *cfqq, *new_cfqq = NULL;
1424         unsigned short ioprio;
1425
1426 retry:
1427         ioprio = tsk->ioprio;
1428         cfqq = __cfq_find_cfq_hash(cfqd, key, ioprio, hashval);
1429
1430         if (!cfqq) {
1431                 if (new_cfqq) {
1432                         cfqq = new_cfqq;
1433                         new_cfqq = NULL;
1434                 } else if (gfp_mask & __GFP_WAIT) {
1435                         spin_unlock_irq(cfqd->queue->queue_lock);
1436                         new_cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
1437                         spin_lock_irq(cfqd->queue->queue_lock);
1438                         goto retry;
1439                 } else {
1440                         cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
1441                         if (!cfqq)
1442                                 goto out;
1443                 }
1444
1445                 memset(cfqq, 0, sizeof(*cfqq));
1446
1447                 INIT_HLIST_NODE(&cfqq->cfq_hash);
1448                 INIT_LIST_HEAD(&cfqq->cfq_list);
1449                 RB_CLEAR_ROOT(&cfqq->sort_list);
1450                 INIT_LIST_HEAD(&cfqq->fifo);
1451
1452                 cfqq->key = key;
1453                 hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
1454                 atomic_set(&cfqq->ref, 0);
1455                 cfqq->cfqd = cfqd;
1456                 cfqq->service_last = 0;
1457                 /*
1458                  * set ->slice_left to allow preemption for a new process
1459                  */
1460                 cfqq->slice_left = 2 * cfqd->cfq_slice_idle;
1461                 cfq_mark_cfqq_idle_window(cfqq);
1462                 cfq_mark_cfqq_prio_changed(cfqq);
1463                 cfq_init_prio_data(cfqq);
1464         }
1465
1466         if (new_cfqq)
1467                 kmem_cache_free(cfq_pool, new_cfqq);
1468
1469         atomic_inc(&cfqq->ref);
1470 out:
1471         WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
1472         return cfqq;
1473 }
1474
1475 static void
1476 cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)
1477 {
1478         read_lock(&cfq_exit_lock);
1479         rb_erase(&cic->rb_node, &ioc->cic_root);
1480         read_unlock(&cfq_exit_lock);
1481         kmem_cache_free(cfq_ioc_pool, cic);
1482         atomic_dec(&ioc_count);
1483 }
1484
1485 static struct cfq_io_context *
1486 cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
1487 {
1488         struct rb_node *n;
1489         struct cfq_io_context *cic;
1490         void *k, *key = cfqd;
1491
1492 restart:
1493         n = ioc->cic_root.rb_node;
1494         while (n) {
1495                 cic = rb_entry(n, struct cfq_io_context, rb_node);
1496                 /* ->key must be copied to avoid race with cfq_exit_queue() */
1497                 k = cic->key;
1498                 if (unlikely(!k)) {
1499                         cfq_drop_dead_cic(ioc, cic);
1500                         goto restart;
1501                 }
1502
1503                 if (key < k)
1504                         n = n->rb_left;
1505                 else if (key > k)
1506                         n = n->rb_right;
1507                 else
1508                         return cic;
1509         }
1510
1511         return NULL;
1512 }
1513
1514 static inline void
1515 cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
1516              struct cfq_io_context *cic)
1517 {
1518         struct rb_node **p;
1519         struct rb_node *parent;
1520         struct cfq_io_context *__cic;
1521         void *k;
1522
1523         cic->ioc = ioc;
1524         cic->key = cfqd;
1525
1526         ioc->set_ioprio = cfq_ioc_set_ioprio;
1527 restart:
1528         parent = NULL;
1529         p = &ioc->cic_root.rb_node;
1530         while (*p) {
1531                 parent = *p;
1532                 __cic = rb_entry(parent, struct cfq_io_context, rb_node);
1533                 /* ->key must be copied to avoid race with cfq_exit_queue() */
1534                 k = __cic->key;
1535                 if (unlikely(!k)) {
1536                         cfq_drop_dead_cic(ioc, cic);
1537                         goto restart;
1538                 }
1539
1540                 if (cic->key < k)
1541                         p = &(*p)->rb_left;
1542                 else if (cic->key > k)
1543                         p = &(*p)->rb_right;
1544                 else
1545                         BUG();
1546         }
1547
1548         read_lock(&cfq_exit_lock);
1549         rb_link_node(&cic->rb_node, parent, p);
1550         rb_insert_color(&cic->rb_node, &ioc->cic_root);
1551         list_add(&cic->queue_list, &cfqd->cic_list);
1552         read_unlock(&cfq_exit_lock);
1553 }
1554
1555 /*
1556  * Setup general io context and cfq io context. There can be several cfq
1557  * io contexts per general io context, if this process is doing io to more
1558  * than one device managed by cfq.
1559  */
1560 static struct cfq_io_context *
1561 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1562 {
1563         struct io_context *ioc = NULL;
1564         struct cfq_io_context *cic;
1565
1566         might_sleep_if(gfp_mask & __GFP_WAIT);
1567
1568         ioc = get_io_context(gfp_mask);
1569         if (!ioc)
1570                 return NULL;
1571
1572         cic = cfq_cic_rb_lookup(cfqd, ioc);
1573         if (cic)
1574                 goto out;
1575
1576         cic = cfq_alloc_io_context(cfqd, gfp_mask);
1577         if (cic == NULL)
1578                 goto err;
1579
1580         cfq_cic_link(cfqd, ioc, cic);
1581 out:
1582         return cic;
1583 err:
1584         put_io_context(ioc);
1585         return NULL;
1586 }
1587
1588 static void
1589 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1590 {
1591         unsigned long elapsed, ttime;
1592
1593         /*
1594          * if this context already has stuff queued, thinktime is from
1595          * last queue not last end
1596          */
1597 #if 0
1598         if (time_after(cic->last_end_request, cic->last_queue))
1599                 elapsed = jiffies - cic->last_end_request;
1600         else
1601                 elapsed = jiffies - cic->last_queue;
1602 #else
1603                 elapsed = jiffies - cic->last_end_request;
1604 #endif
1605
1606         ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1607
1608         cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1609         cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1610         cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1611 }
1612
1613 static void
1614 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
1615                        struct cfq_rq *crq)
1616 {
1617         sector_t sdist;
1618         u64 total;
1619
1620         if (cic->last_request_pos < crq->request->sector)
1621                 sdist = crq->request->sector - cic->last_request_pos;
1622         else
1623                 sdist = cic->last_request_pos - crq->request->sector;
1624
1625         /*
1626          * Don't allow the seek distance to get too large from the
1627          * odd fragment, pagein, etc
1628          */
1629         if (cic->seek_samples <= 60) /* second&third seek */
1630                 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
1631         else
1632                 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
1633
1634         cic->seek_samples = (7*cic->seek_samples + 256) / 8;
1635         cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
1636         total = cic->seek_total + (cic->seek_samples/2);
1637         do_div(total, cic->seek_samples);
1638         cic->seek_mean = (sector_t)total;
1639 }
1640
1641 /*
1642  * Disable idle window if the process thinks too long or seeks so much that
1643  * it doesn't matter
1644  */
1645 static void
1646 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1647                        struct cfq_io_context *cic)
1648 {
1649         int enable_idle = cfq_cfqq_idle_window(cfqq);
1650
1651         if (!cic->ioc->task || !cfqd->cfq_slice_idle)
1652                 enable_idle = 0;
1653         else if (sample_valid(cic->ttime_samples)) {
1654                 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1655                         enable_idle = 0;
1656                 else
1657                         enable_idle = 1;
1658         }
1659
1660         if (enable_idle)
1661                 cfq_mark_cfqq_idle_window(cfqq);
1662         else
1663                 cfq_clear_cfqq_idle_window(cfqq);
1664 }
1665
1666
1667 /*
1668  * Check if new_cfqq should preempt the currently active queue. Return 0 for
1669  * no or if we aren't sure, a 1 will cause a preempt.
1670  */
1671 static int
1672 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1673                    struct cfq_rq *crq)
1674 {
1675         struct cfq_queue *cfqq = cfqd->active_queue;
1676
1677         if (cfq_class_idle(new_cfqq))
1678                 return 0;
1679
1680         if (!cfqq)
1681                 return 1;
1682
1683         if (cfq_class_idle(cfqq))
1684                 return 1;
1685         if (!cfq_cfqq_wait_request(new_cfqq))
1686                 return 0;
1687         /*
1688          * if it doesn't have slice left, forget it
1689          */
1690         if (new_cfqq->slice_left < cfqd->cfq_slice_idle)
1691                 return 0;
1692         if (cfq_crq_is_sync(crq) && !cfq_cfqq_sync(cfqq))
1693                 return 1;
1694
1695         return 0;
1696 }
1697
1698 /*
1699  * cfqq preempts the active queue. if we allowed preempt with no slice left,
1700  * let it have half of its nominal slice.
1701  */
1702 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1703 {
1704         struct cfq_queue *__cfqq, *next;
1705
1706         list_for_each_entry_safe(__cfqq, next, &cfqd->cur_rr, cfq_list)
1707                 cfq_resort_rr_list(__cfqq, 1);
1708
1709         if (!cfqq->slice_left)
1710                 cfqq->slice_left = cfq_prio_to_slice(cfqd, cfqq) / 2;
1711
1712         cfqq->slice_end = cfqq->slice_left + jiffies;
1713         __cfq_slice_expired(cfqd, cfqq, 1);
1714         __cfq_set_active_queue(cfqd, cfqq);
1715 }
1716
1717 /*
1718  * should really be a ll_rw_blk.c helper
1719  */
1720 static void cfq_start_queueing(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1721 {
1722         request_queue_t *q = cfqd->queue;
1723
1724         if (!blk_queue_plugged(q))
1725                 q->request_fn(q);
1726         else
1727                 __generic_unplug_device(q);
1728 }
1729
1730 /*
1731  * Called when a new fs request (crq) is added (to cfqq). Check if there's
1732  * something we should do about it
1733  */
1734 static void
1735 cfq_crq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1736                  struct cfq_rq *crq)
1737 {
1738         struct cfq_io_context *cic;
1739
1740         cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
1741
1742         /*
1743          * we never wait for an async request and we don't allow preemption
1744          * of an async request. so just return early
1745          */
1746         if (!cfq_crq_is_sync(crq))
1747                 return;
1748
1749         cic = crq->io_context;
1750
1751         cfq_update_io_thinktime(cfqd, cic);
1752         cfq_update_io_seektime(cfqd, cic, crq);
1753         cfq_update_idle_window(cfqd, cfqq, cic);
1754
1755         cic->last_queue = jiffies;
1756         cic->last_request_pos = crq->request->sector + crq->request->nr_sectors;
1757
1758         if (cfqq == cfqd->active_queue) {
1759                 /*
1760                  * if we are waiting for a request for this queue, let it rip
1761                  * immediately and flag that we must not expire this queue
1762                  * just now
1763                  */
1764                 if (cfq_cfqq_wait_request(cfqq)) {
1765                         cfq_mark_cfqq_must_dispatch(cfqq);
1766                         del_timer(&cfqd->idle_slice_timer);
1767                         cfq_start_queueing(cfqd, cfqq);
1768                 }
1769         } else if (cfq_should_preempt(cfqd, cfqq, crq)) {
1770                 /*
1771                  * not the active queue - expire current slice if it is
1772                  * idle and has expired it's mean thinktime or this new queue
1773                  * has some old slice time left and is of higher priority
1774                  */
1775                 cfq_preempt_queue(cfqd, cfqq);
1776                 cfq_mark_cfqq_must_dispatch(cfqq);
1777                 cfq_start_queueing(cfqd, cfqq);
1778         }
1779 }
1780
1781 static void cfq_insert_request(request_queue_t *q, struct request *rq)
1782 {
1783         struct cfq_data *cfqd = q->elevator->elevator_data;
1784         struct cfq_rq *crq = RQ_DATA(rq);
1785         struct cfq_queue *cfqq = crq->cfq_queue;
1786
1787         cfq_init_prio_data(cfqq);
1788
1789         cfq_add_crq_rb(crq);
1790
1791         list_add_tail(&rq->queuelist, &cfqq->fifo);
1792
1793         if (rq_mergeable(rq))
1794                 cfq_add_crq_hash(cfqd, crq);
1795
1796         cfq_crq_enqueued(cfqd, cfqq, crq);
1797 }
1798
1799 static void cfq_completed_request(request_queue_t *q, struct request *rq)
1800 {
1801         struct cfq_rq *crq = RQ_DATA(rq);
1802         struct cfq_queue *cfqq = crq->cfq_queue;
1803         struct cfq_data *cfqd = cfqq->cfqd;
1804         const int sync = cfq_crq_is_sync(crq);
1805         unsigned long now;
1806
1807         now = jiffies;
1808
1809         WARN_ON(!cfqd->rq_in_driver);
1810         WARN_ON(!cfqq->on_dispatch[sync]);
1811         cfqd->rq_in_driver--;
1812         cfqq->on_dispatch[sync]--;
1813
1814         if (!cfq_class_idle(cfqq))
1815                 cfqd->last_end_request = now;
1816
1817         if (!cfq_cfqq_dispatched(cfqq)) {
1818                 if (cfq_cfqq_on_rr(cfqq)) {
1819                         cfqq->service_last = now;
1820                         cfq_resort_rr_list(cfqq, 0);
1821                 }
1822                 cfq_schedule_dispatch(cfqd);
1823         }
1824
1825         if (cfq_crq_is_sync(crq))
1826                 crq->io_context->last_end_request = now;
1827 }
1828
1829 static struct request *
1830 cfq_former_request(request_queue_t *q, struct request *rq)
1831 {
1832         struct cfq_rq *crq = RQ_DATA(rq);
1833         struct rb_node *rbprev = rb_prev(&crq->rb_node);
1834
1835         if (rbprev)
1836                 return rb_entry_crq(rbprev)->request;
1837
1838         return NULL;
1839 }
1840
1841 static struct request *
1842 cfq_latter_request(request_queue_t *q, struct request *rq)
1843 {
1844         struct cfq_rq *crq = RQ_DATA(rq);
1845         struct rb_node *rbnext = rb_next(&crq->rb_node);
1846
1847         if (rbnext)
1848                 return rb_entry_crq(rbnext)->request;
1849
1850         return NULL;
1851 }
1852
1853 /*
1854  * we temporarily boost lower priority queues if they are holding fs exclusive
1855  * resources. they are boosted to normal prio (CLASS_BE/4)
1856  */
1857 static void cfq_prio_boost(struct cfq_queue *cfqq)
1858 {
1859         const int ioprio_class = cfqq->ioprio_class;
1860         const int ioprio = cfqq->ioprio;
1861
1862         if (has_fs_excl()) {
1863                 /*
1864                  * boost idle prio on transactions that would lock out other
1865                  * users of the filesystem
1866                  */
1867                 if (cfq_class_idle(cfqq))
1868                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1869                 if (cfqq->ioprio > IOPRIO_NORM)
1870                         cfqq->ioprio = IOPRIO_NORM;
1871         } else {
1872                 /*
1873                  * check if we need to unboost the queue
1874                  */
1875                 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
1876                         cfqq->ioprio_class = cfqq->org_ioprio_class;
1877                 if (cfqq->ioprio != cfqq->org_ioprio)
1878                         cfqq->ioprio = cfqq->org_ioprio;
1879         }
1880
1881         /*
1882          * refile between round-robin lists if we moved the priority class
1883          */
1884         if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio) &&
1885             cfq_cfqq_on_rr(cfqq))
1886                 cfq_resort_rr_list(cfqq, 0);
1887 }
1888
1889 static inline int
1890 __cfq_may_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1891                 struct task_struct *task, int rw)
1892 {
1893 #if 1
1894         if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
1895             !cfq_cfqq_must_alloc_slice(cfqq)) {
1896                 cfq_mark_cfqq_must_alloc_slice(cfqq);
1897                 return ELV_MQUEUE_MUST;
1898         }
1899
1900         return ELV_MQUEUE_MAY;
1901 #else
1902         if (!cfqq || task->flags & PF_MEMALLOC)
1903                 return ELV_MQUEUE_MAY;
1904         if (!cfqq->allocated[rw] || cfq_cfqq_must_alloc(cfqq)) {
1905                 if (cfq_cfqq_wait_request(cfqq))
1906                         return ELV_MQUEUE_MUST;
1907
1908                 /*
1909                  * only allow 1 ELV_MQUEUE_MUST per slice, otherwise we
1910                  * can quickly flood the queue with writes from a single task
1911                  */
1912                 if (rw == READ || !cfq_cfqq_must_alloc_slice(cfqq)) {
1913                         cfq_mark_cfqq_must_alloc_slice(cfqq);
1914                         return ELV_MQUEUE_MUST;
1915                 }
1916
1917                 return ELV_MQUEUE_MAY;
1918         }
1919         if (cfq_class_idle(cfqq))
1920                 return ELV_MQUEUE_NO;
1921         if (cfqq->allocated[rw] >= cfqd->max_queued) {
1922                 struct io_context *ioc = get_io_context(GFP_ATOMIC);
1923                 int ret = ELV_MQUEUE_NO;
1924
1925                 if (ioc && ioc->nr_batch_requests)
1926                         ret = ELV_MQUEUE_MAY;
1927
1928                 put_io_context(ioc);
1929                 return ret;
1930         }
1931
1932         return ELV_MQUEUE_MAY;
1933 #endif
1934 }
1935
1936 static int cfq_may_queue(request_queue_t *q, int rw, struct bio *bio)
1937 {
1938         struct cfq_data *cfqd = q->elevator->elevator_data;
1939         struct task_struct *tsk = current;
1940         struct cfq_queue *cfqq;
1941
1942         /*
1943          * don't force setup of a queue from here, as a call to may_queue
1944          * does not necessarily imply that a request actually will be queued.
1945          * so just lookup a possibly existing queue, or return 'may queue'
1946          * if that fails
1947          */
1948         cfqq = cfq_find_cfq_hash(cfqd, cfq_queue_pid(tsk, rw), tsk->ioprio);
1949         if (cfqq) {
1950                 cfq_init_prio_data(cfqq);
1951                 cfq_prio_boost(cfqq);
1952
1953                 return __cfq_may_queue(cfqd, cfqq, tsk, rw);
1954         }
1955
1956         return ELV_MQUEUE_MAY;
1957 }
1958
1959 static void cfq_check_waiters(request_queue_t *q, struct cfq_queue *cfqq)
1960 {
1961         struct cfq_data *cfqd = q->elevator->elevator_data;
1962         struct request_list *rl = &q->rq;
1963
1964         if (cfqq->allocated[READ] <= cfqd->max_queued || cfqd->rq_starved) {
1965                 smp_mb();
1966                 if (waitqueue_active(&rl->wait[READ]))
1967                         wake_up(&rl->wait[READ]);
1968         }
1969
1970         if (cfqq->allocated[WRITE] <= cfqd->max_queued || cfqd->rq_starved) {
1971                 smp_mb();
1972                 if (waitqueue_active(&rl->wait[WRITE]))
1973                         wake_up(&rl->wait[WRITE]);
1974         }
1975 }
1976
1977 /*
1978  * queue lock held here
1979  */
1980 static void cfq_put_request(request_queue_t *q, struct request *rq)
1981 {
1982         struct cfq_data *cfqd = q->elevator->elevator_data;
1983         struct cfq_rq *crq = RQ_DATA(rq);
1984
1985         if (crq) {
1986                 struct cfq_queue *cfqq = crq->cfq_queue;
1987                 const int rw = rq_data_dir(rq);
1988
1989                 BUG_ON(!cfqq->allocated[rw]);
1990                 cfqq->allocated[rw]--;
1991
1992                 put_io_context(crq->io_context->ioc);
1993
1994                 mempool_free(crq, cfqd->crq_pool);
1995                 rq->elevator_private = NULL;
1996
1997                 cfq_check_waiters(q, cfqq);
1998                 cfq_put_queue(cfqq);
1999         }
2000 }
2001
2002 /*
2003  * Allocate cfq data structures associated with this request.
2004  */
2005 static int
2006 cfq_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
2007                 gfp_t gfp_mask)
2008 {
2009         struct cfq_data *cfqd = q->elevator->elevator_data;
2010         struct task_struct *tsk = current;
2011         struct cfq_io_context *cic;
2012         const int rw = rq_data_dir(rq);
2013         pid_t key = cfq_queue_pid(tsk, rw);
2014         struct cfq_queue *cfqq;
2015         struct cfq_rq *crq;
2016         unsigned long flags;
2017         int is_sync = key != CFQ_KEY_ASYNC;
2018
2019         might_sleep_if(gfp_mask & __GFP_WAIT);
2020
2021         cic = cfq_get_io_context(cfqd, gfp_mask);
2022
2023         spin_lock_irqsave(q->queue_lock, flags);
2024
2025         if (!cic)
2026                 goto queue_fail;
2027
2028         if (!cic->cfqq[is_sync]) {
2029                 cfqq = cfq_get_queue(cfqd, key, tsk, gfp_mask);
2030                 if (!cfqq)
2031                         goto queue_fail;
2032
2033                 cic->cfqq[is_sync] = cfqq;
2034         } else
2035                 cfqq = cic->cfqq[is_sync];
2036
2037         cfqq->allocated[rw]++;
2038         cfq_clear_cfqq_must_alloc(cfqq);
2039         cfqd->rq_starved = 0;
2040         atomic_inc(&cfqq->ref);
2041         spin_unlock_irqrestore(q->queue_lock, flags);
2042
2043         crq = mempool_alloc(cfqd->crq_pool, gfp_mask);
2044         if (crq) {
2045                 RB_CLEAR(&crq->rb_node);
2046                 crq->rb_key = 0;
2047                 crq->request = rq;
2048                 INIT_HLIST_NODE(&crq->hash);
2049                 crq->cfq_queue = cfqq;
2050                 crq->io_context = cic;
2051
2052                 if (is_sync)
2053                         cfq_mark_crq_is_sync(crq);
2054                 else
2055                         cfq_clear_crq_is_sync(crq);
2056
2057                 rq->elevator_private = crq;
2058                 return 0;
2059         }
2060
2061         spin_lock_irqsave(q->queue_lock, flags);
2062         cfqq->allocated[rw]--;
2063         if (!(cfqq->allocated[0] + cfqq->allocated[1]))
2064                 cfq_mark_cfqq_must_alloc(cfqq);
2065         cfq_put_queue(cfqq);
2066 queue_fail:
2067         if (cic)
2068                 put_io_context(cic->ioc);
2069         /*
2070          * mark us rq allocation starved. we need to kickstart the process
2071          * ourselves if there are no pending requests that can do it for us.
2072          * that would be an extremely rare OOM situation
2073          */
2074         cfqd->rq_starved = 1;
2075         cfq_schedule_dispatch(cfqd);
2076         spin_unlock_irqrestore(q->queue_lock, flags);
2077         return 1;
2078 }
2079
2080 static void cfq_kick_queue(void *data)
2081 {
2082         request_queue_t *q = data;
2083         struct cfq_data *cfqd = q->elevator->elevator_data;
2084         unsigned long flags;
2085
2086         spin_lock_irqsave(q->queue_lock, flags);
2087
2088         if (cfqd->rq_starved) {
2089                 struct request_list *rl = &q->rq;
2090
2091                 /*
2092                  * we aren't guaranteed to get a request after this, but we
2093                  * have to be opportunistic
2094                  */
2095                 smp_mb();
2096                 if (waitqueue_active(&rl->wait[READ]))
2097                         wake_up(&rl->wait[READ]);
2098                 if (waitqueue_active(&rl->wait[WRITE]))
2099                         wake_up(&rl->wait[WRITE]);
2100         }
2101
2102         blk_remove_plug(q);
2103         q->request_fn(q);
2104         spin_unlock_irqrestore(q->queue_lock, flags);
2105 }
2106
2107 /*
2108  * Timer running if the active_queue is currently idling inside its time slice
2109  */
2110 static void cfq_idle_slice_timer(unsigned long data)
2111 {
2112         struct cfq_data *cfqd = (struct cfq_data *) data;
2113         struct cfq_queue *cfqq;
2114         unsigned long flags;
2115
2116         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2117
2118         if ((cfqq = cfqd->active_queue) != NULL) {
2119                 unsigned long now = jiffies;
2120
2121                 /*
2122                  * expired
2123                  */
2124                 if (time_after(now, cfqq->slice_end))
2125                         goto expire;
2126
2127                 /*
2128                  * only expire and reinvoke request handler, if there are
2129                  * other queues with pending requests
2130                  */
2131                 if (!cfqd->busy_queues) {
2132                         cfqd->idle_slice_timer.expires = min(now + cfqd->cfq_slice_idle, cfqq->slice_end);
2133                         add_timer(&cfqd->idle_slice_timer);
2134                         goto out_cont;
2135                 }
2136
2137                 /*
2138                  * not expired and it has a request pending, let it dispatch
2139                  */
2140                 if (!RB_EMPTY(&cfqq->sort_list)) {
2141                         cfq_mark_cfqq_must_dispatch(cfqq);
2142                         goto out_kick;
2143                 }
2144         }
2145 expire:
2146         cfq_slice_expired(cfqd, 0);
2147 out_kick:
2148         cfq_schedule_dispatch(cfqd);
2149 out_cont:
2150         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2151 }
2152
2153 /*
2154  * Timer running if an idle class queue is waiting for service
2155  */
2156 static void cfq_idle_class_timer(unsigned long data)
2157 {
2158         struct cfq_data *cfqd = (struct cfq_data *) data;
2159         unsigned long flags, end;
2160
2161         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2162
2163         /*
2164          * race with a non-idle queue, reset timer
2165          */
2166         end = cfqd->last_end_request + CFQ_IDLE_GRACE;
2167         if (!time_after_eq(jiffies, end)) {
2168                 cfqd->idle_class_timer.expires = end;
2169                 add_timer(&cfqd->idle_class_timer);
2170         } else
2171                 cfq_schedule_dispatch(cfqd);
2172
2173         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2174 }
2175
2176 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2177 {
2178         del_timer_sync(&cfqd->idle_slice_timer);
2179         del_timer_sync(&cfqd->idle_class_timer);
2180         blk_sync_queue(cfqd->queue);
2181 }
2182
2183 static void cfq_exit_queue(elevator_t *e)
2184 {
2185         struct cfq_data *cfqd = e->elevator_data;
2186         request_queue_t *q = cfqd->queue;
2187
2188         cfq_shutdown_timer_wq(cfqd);
2189
2190         write_lock(&cfq_exit_lock);
2191         spin_lock_irq(q->queue_lock);
2192
2193         if (cfqd->active_queue)
2194                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
2195
2196         while (!list_empty(&cfqd->cic_list)) {
2197                 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2198                                                         struct cfq_io_context,
2199                                                         queue_list);
2200                 if (cic->cfqq[ASYNC]) {
2201                         cfq_put_queue(cic->cfqq[ASYNC]);
2202                         cic->cfqq[ASYNC] = NULL;
2203                 }
2204                 if (cic->cfqq[SYNC]) {
2205                         cfq_put_queue(cic->cfqq[SYNC]);
2206                         cic->cfqq[SYNC] = NULL;
2207                 }
2208                 cic->key = NULL;
2209                 list_del_init(&cic->queue_list);
2210         }
2211
2212         spin_unlock_irq(q->queue_lock);
2213         write_unlock(&cfq_exit_lock);
2214
2215         cfq_shutdown_timer_wq(cfqd);
2216
2217         mempool_destroy(cfqd->crq_pool);
2218         kfree(cfqd->crq_hash);
2219         kfree(cfqd->cfq_hash);
2220         kfree(cfqd);
2221 }
2222
2223 static int cfq_init_queue(request_queue_t *q, elevator_t *e)
2224 {
2225         struct cfq_data *cfqd;
2226         int i;
2227
2228         cfqd = kmalloc(sizeof(*cfqd), GFP_KERNEL);
2229         if (!cfqd)
2230                 return -ENOMEM;
2231
2232         memset(cfqd, 0, sizeof(*cfqd));
2233
2234         for (i = 0; i < CFQ_PRIO_LISTS; i++)
2235                 INIT_LIST_HEAD(&cfqd->rr_list[i]);
2236
2237         INIT_LIST_HEAD(&cfqd->busy_rr);
2238         INIT_LIST_HEAD(&cfqd->cur_rr);
2239         INIT_LIST_HEAD(&cfqd->idle_rr);
2240         INIT_LIST_HEAD(&cfqd->empty_list);
2241         INIT_LIST_HEAD(&cfqd->cic_list);
2242
2243         cfqd->crq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_MHASH_ENTRIES, GFP_KERNEL);
2244         if (!cfqd->crq_hash)
2245                 goto out_crqhash;
2246
2247         cfqd->cfq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL);
2248         if (!cfqd->cfq_hash)
2249                 goto out_cfqhash;
2250
2251         cfqd->crq_pool = mempool_create_slab_pool(BLKDEV_MIN_RQ, crq_pool);
2252         if (!cfqd->crq_pool)
2253                 goto out_crqpool;
2254
2255         for (i = 0; i < CFQ_MHASH_ENTRIES; i++)
2256                 INIT_HLIST_HEAD(&cfqd->crq_hash[i]);
2257         for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
2258                 INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
2259
2260         e->elevator_data = cfqd;
2261
2262         cfqd->queue = q;
2263
2264         cfqd->max_queued = q->nr_requests / 4;
2265         q->nr_batching = cfq_queued;
2266
2267         init_timer(&cfqd->idle_slice_timer);
2268         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2269         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2270
2271         init_timer(&cfqd->idle_class_timer);
2272         cfqd->idle_class_timer.function = cfq_idle_class_timer;
2273         cfqd->idle_class_timer.data = (unsigned long) cfqd;
2274
2275         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue, q);
2276
2277         cfqd->cfq_queued = cfq_queued;
2278         cfqd->cfq_quantum = cfq_quantum;
2279         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2280         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2281         cfqd->cfq_back_max = cfq_back_max;
2282         cfqd->cfq_back_penalty = cfq_back_penalty;
2283         cfqd->cfq_slice[0] = cfq_slice_async;
2284         cfqd->cfq_slice[1] = cfq_slice_sync;
2285         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2286         cfqd->cfq_slice_idle = cfq_slice_idle;
2287
2288         return 0;
2289 out_crqpool:
2290         kfree(cfqd->cfq_hash);
2291 out_cfqhash:
2292         kfree(cfqd->crq_hash);
2293 out_crqhash:
2294         kfree(cfqd);
2295         return -ENOMEM;
2296 }
2297
2298 static void cfq_slab_kill(void)
2299 {
2300         if (crq_pool)
2301                 kmem_cache_destroy(crq_pool);
2302         if (cfq_pool)
2303                 kmem_cache_destroy(cfq_pool);
2304         if (cfq_ioc_pool)
2305                 kmem_cache_destroy(cfq_ioc_pool);
2306 }
2307
2308 static int __init cfq_slab_setup(void)
2309 {
2310         crq_pool = kmem_cache_create("crq_pool", sizeof(struct cfq_rq), 0, 0,
2311                                         NULL, NULL);
2312         if (!crq_pool)
2313                 goto fail;
2314
2315         cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0,
2316                                         NULL, NULL);
2317         if (!cfq_pool)
2318                 goto fail;
2319
2320         cfq_ioc_pool = kmem_cache_create("cfq_ioc_pool",
2321                         sizeof(struct cfq_io_context), 0, 0, NULL, NULL);
2322         if (!cfq_ioc_pool)
2323                 goto fail;
2324
2325         return 0;
2326 fail:
2327         cfq_slab_kill();
2328         return -ENOMEM;
2329 }
2330
2331 /*
2332  * sysfs parts below -->
2333  */
2334
2335 static ssize_t
2336 cfq_var_show(unsigned int var, char *page)
2337 {
2338         return sprintf(page, "%d\n", var);
2339 }
2340
2341 static ssize_t
2342 cfq_var_store(unsigned int *var, const char *page, size_t count)
2343 {
2344         char *p = (char *) page;
2345
2346         *var = simple_strtoul(p, &p, 10);
2347         return count;
2348 }
2349
2350 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
2351 static ssize_t __FUNC(elevator_t *e, char *page)                        \
2352 {                                                                       \
2353         struct cfq_data *cfqd = e->elevator_data;                       \
2354         unsigned int __data = __VAR;                                    \
2355         if (__CONV)                                                     \
2356                 __data = jiffies_to_msecs(__data);                      \
2357         return cfq_var_show(__data, (page));                            \
2358 }
2359 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2360 SHOW_FUNCTION(cfq_queued_show, cfqd->cfq_queued, 0);
2361 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2362 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2363 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
2364 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
2365 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2366 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2367 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2368 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2369 #undef SHOW_FUNCTION
2370
2371 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
2372 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count)    \
2373 {                                                                       \
2374         struct cfq_data *cfqd = e->elevator_data;                       \
2375         unsigned int __data;                                            \
2376         int ret = cfq_var_store(&__data, (page), count);                \
2377         if (__data < (MIN))                                             \
2378                 __data = (MIN);                                         \
2379         else if (__data > (MAX))                                        \
2380                 __data = (MAX);                                         \
2381         if (__CONV)                                                     \
2382                 *(__PTR) = msecs_to_jiffies(__data);                    \
2383         else                                                            \
2384                 *(__PTR) = __data;                                      \
2385         return ret;                                                     \
2386 }
2387 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2388 STORE_FUNCTION(cfq_queued_store, &cfqd->cfq_queued, 1, UINT_MAX, 0);
2389 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1);
2390 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1);
2391 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2392 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0);
2393 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2394 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2395 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2396 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0);
2397 #undef STORE_FUNCTION
2398
2399 #define CFQ_ATTR(name) \
2400         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2401
2402 static struct elv_fs_entry cfq_attrs[] = {
2403         CFQ_ATTR(quantum),
2404         CFQ_ATTR(queued),
2405         CFQ_ATTR(fifo_expire_sync),
2406         CFQ_ATTR(fifo_expire_async),
2407         CFQ_ATTR(back_seek_max),
2408         CFQ_ATTR(back_seek_penalty),
2409         CFQ_ATTR(slice_sync),
2410         CFQ_ATTR(slice_async),
2411         CFQ_ATTR(slice_async_rq),
2412         CFQ_ATTR(slice_idle),
2413         __ATTR_NULL
2414 };
2415
2416 static struct elevator_type iosched_cfq = {
2417         .ops = {
2418                 .elevator_merge_fn =            cfq_merge,
2419                 .elevator_merged_fn =           cfq_merged_request,
2420                 .elevator_merge_req_fn =        cfq_merged_requests,
2421                 .elevator_dispatch_fn =         cfq_dispatch_requests,
2422                 .elevator_add_req_fn =          cfq_insert_request,
2423                 .elevator_activate_req_fn =     cfq_activate_request,
2424                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
2425                 .elevator_queue_empty_fn =      cfq_queue_empty,
2426                 .elevator_completed_req_fn =    cfq_completed_request,
2427                 .elevator_former_req_fn =       cfq_former_request,
2428                 .elevator_latter_req_fn =       cfq_latter_request,
2429                 .elevator_set_req_fn =          cfq_set_request,
2430                 .elevator_put_req_fn =          cfq_put_request,
2431                 .elevator_may_queue_fn =        cfq_may_queue,
2432                 .elevator_init_fn =             cfq_init_queue,
2433                 .elevator_exit_fn =             cfq_exit_queue,
2434                 .trim =                         cfq_trim,
2435         },
2436         .elevator_attrs =       cfq_attrs,
2437         .elevator_name =        "cfq",
2438         .elevator_owner =       THIS_MODULE,
2439 };
2440
2441 static int __init cfq_init(void)
2442 {
2443         int ret;
2444
2445         /*
2446          * could be 0 on HZ < 1000 setups
2447          */
2448         if (!cfq_slice_async)
2449                 cfq_slice_async = 1;
2450         if (!cfq_slice_idle)
2451                 cfq_slice_idle = 1;
2452
2453         if (cfq_slab_setup())
2454                 return -ENOMEM;
2455
2456         ret = elv_register(&iosched_cfq);
2457         if (ret)
2458                 cfq_slab_kill();
2459
2460         return ret;
2461 }
2462
2463 static void __exit cfq_exit(void)
2464 {
2465         DECLARE_COMPLETION(all_gone);
2466         elv_unregister(&iosched_cfq);
2467         ioc_gone = &all_gone;
2468         /* ioc_gone's update must be visible before reading ioc_count */
2469         smp_wmb();
2470         if (atomic_read(&ioc_count))
2471                 wait_for_completion(ioc_gone);
2472         synchronize_rcu();
2473         cfq_slab_kill();
2474 }
2475
2476 module_init(cfq_init);
2477 module_exit(cfq_exit);
2478
2479 MODULE_AUTHOR("Jens Axboe");
2480 MODULE_LICENSE("GPL");
2481 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");