7f5646ac9f5daeb475ab598b5fc5fe74e60b7285
[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@kernel.dk>
8  */
9 #include <linux/module.h>
10 #include <linux/blkdev.h>
11 #include <linux/elevator.h>
12 #include <linux/jiffies.h>
13 #include <linux/rbtree.h>
14 #include <linux/ioprio.h>
15 #include <linux/blktrace_api.h>
16
17 /*
18  * tunables
19  */
20 /* max queue in one round of service */
21 static const int cfq_quantum = 4;
22 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
23 /* maximum backwards seek, in KiB */
24 static const int cfq_back_max = 16 * 1024;
25 /* penalty of a backwards seek */
26 static const int cfq_back_penalty = 2;
27 static const int cfq_slice_sync = HZ / 10;
28 static int cfq_slice_async = HZ / 25;
29 static const int cfq_slice_async_rq = 2;
30 static int cfq_slice_idle = HZ / 125;
31 static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
32 static const int cfq_hist_divisor = 4;
33
34 /*
35  * offset from end of service tree
36  */
37 #define CFQ_IDLE_DELAY          (HZ / 5)
38
39 /*
40  * below this threshold, we consider thinktime immediate
41  */
42 #define CFQ_MIN_TT              (2)
43
44 /*
45  * Allow merged cfqqs to perform this amount of seeky I/O before
46  * deciding to break the queues up again.
47  */
48 #define CFQQ_COOP_TOUT          (HZ)
49
50 #define CFQ_SLICE_SCALE         (5)
51 #define CFQ_HW_QUEUE_MIN        (5)
52
53 #define RQ_CIC(rq)              \
54         ((struct cfq_io_context *) (rq)->elevator_private)
55 #define RQ_CFQQ(rq)             (struct cfq_queue *) ((rq)->elevator_private2)
56
57 static struct kmem_cache *cfq_pool;
58 static struct kmem_cache *cfq_ioc_pool;
59
60 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
61 static struct completion *ioc_gone;
62 static DEFINE_SPINLOCK(ioc_gone_lock);
63
64 #define CFQ_PRIO_LISTS          IOPRIO_BE_NR
65 #define cfq_class_idle(cfqq)    ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
66 #define cfq_class_rt(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
67
68 #define sample_valid(samples)   ((samples) > 80)
69
70 /*
71  * Most of our rbtree usage is for sorting with min extraction, so
72  * if we cache the leftmost node we don't have to walk down the tree
73  * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
74  * move this into the elevator for the rq sorting as well.
75  */
76 struct cfq_rb_root {
77         struct rb_root rb;
78         struct rb_node *left;
79         unsigned count;
80 };
81 #define CFQ_RB_ROOT     (struct cfq_rb_root) { RB_ROOT, NULL, 0, }
82
83 /*
84  * Per process-grouping structure
85  */
86 struct cfq_queue {
87         /* reference count */
88         atomic_t ref;
89         /* various state flags, see below */
90         unsigned int flags;
91         /* parent cfq_data */
92         struct cfq_data *cfqd;
93         /* service_tree member */
94         struct rb_node rb_node;
95         /* service_tree key */
96         unsigned long rb_key;
97         /* prio tree member */
98         struct rb_node p_node;
99         /* prio tree root we belong to, if any */
100         struct rb_root *p_root;
101         /* sorted list of pending requests */
102         struct rb_root sort_list;
103         /* if fifo isn't expired, next request to serve */
104         struct request *next_rq;
105         /* requests queued in sort_list */
106         int queued[2];
107         /* currently allocated requests */
108         int allocated[2];
109         /* fifo list of requests in sort_list */
110         struct list_head fifo;
111
112         unsigned long slice_end;
113         long slice_resid;
114         unsigned int slice_dispatch;
115
116         /* pending metadata requests */
117         int meta_pending;
118         /* number of requests that are on the dispatch list or inside driver */
119         int dispatched;
120
121         /* io prio of this group */
122         unsigned short ioprio, org_ioprio;
123         unsigned short ioprio_class, org_ioprio_class;
124
125         unsigned int seek_samples;
126         u64 seek_total;
127         sector_t seek_mean;
128         sector_t last_request_pos;
129         unsigned long seeky_start;
130
131         pid_t pid;
132
133         struct cfq_rb_root *service_tree;
134         struct cfq_queue *new_cfqq;
135         struct cfq_group *cfqg;
136 };
137
138 /*
139  * First index in the service_trees.
140  * IDLE is handled separately, so it has negative index
141  */
142 enum wl_prio_t {
143         BE_WORKLOAD = 0,
144         RT_WORKLOAD = 1,
145         IDLE_WORKLOAD = 2,
146 };
147
148 /*
149  * Second index in the service_trees.
150  */
151 enum wl_type_t {
152         ASYNC_WORKLOAD = 0,
153         SYNC_NOIDLE_WORKLOAD = 1,
154         SYNC_WORKLOAD = 2
155 };
156
157 /* This is per cgroup per device grouping structure */
158 struct cfq_group {
159         /*
160          * rr lists of queues with requests, onle rr for each priority class.
161          * Counts are embedded in the cfq_rb_root
162          */
163         struct cfq_rb_root service_trees[2][3];
164         struct cfq_rb_root service_tree_idle;
165 };
166
167 /*
168  * Per block device queue structure
169  */
170 struct cfq_data {
171         struct request_queue *queue;
172         struct cfq_group root_group;
173
174         /*
175          * The priority currently being served
176          */
177         enum wl_prio_t serving_prio;
178         enum wl_type_t serving_type;
179         unsigned long workload_expires;
180         struct cfq_group *serving_group;
181         bool noidle_tree_requires_idle;
182
183         /*
184          * Each priority tree is sorted by next_request position.  These
185          * trees are used when determining if two or more queues are
186          * interleaving requests (see cfq_close_cooperator).
187          */
188         struct rb_root prio_trees[CFQ_PRIO_LISTS];
189
190         unsigned int busy_queues;
191         unsigned int busy_queues_avg[2];
192
193         int rq_in_driver[2];
194         int sync_flight;
195
196         /*
197          * queue-depth detection
198          */
199         int rq_queued;
200         int hw_tag;
201         /*
202          * hw_tag can be
203          * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
204          *  1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
205          *  0 => no NCQ
206          */
207         int hw_tag_est_depth;
208         unsigned int hw_tag_samples;
209
210         /*
211          * idle window management
212          */
213         struct timer_list idle_slice_timer;
214         struct work_struct unplug_work;
215
216         struct cfq_queue *active_queue;
217         struct cfq_io_context *active_cic;
218
219         /*
220          * async queue for each priority case
221          */
222         struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
223         struct cfq_queue *async_idle_cfqq;
224
225         sector_t last_position;
226
227         /*
228          * tunables, see top of file
229          */
230         unsigned int cfq_quantum;
231         unsigned int cfq_fifo_expire[2];
232         unsigned int cfq_back_penalty;
233         unsigned int cfq_back_max;
234         unsigned int cfq_slice[2];
235         unsigned int cfq_slice_async_rq;
236         unsigned int cfq_slice_idle;
237         unsigned int cfq_latency;
238
239         struct list_head cic_list;
240
241         /*
242          * Fallback dummy cfqq for extreme OOM conditions
243          */
244         struct cfq_queue oom_cfqq;
245
246         unsigned long last_end_sync_rq;
247 };
248
249 static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
250                                             enum wl_prio_t prio,
251                                             enum wl_type_t type,
252                                             struct cfq_data *cfqd)
253 {
254         if (prio == IDLE_WORKLOAD)
255                 return &cfqg->service_tree_idle;
256
257         return &cfqg->service_trees[prio][type];
258 }
259
260 enum cfqq_state_flags {
261         CFQ_CFQQ_FLAG_on_rr = 0,        /* on round-robin busy list */
262         CFQ_CFQQ_FLAG_wait_request,     /* waiting for a request */
263         CFQ_CFQQ_FLAG_must_dispatch,    /* must be allowed a dispatch */
264         CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
265         CFQ_CFQQ_FLAG_fifo_expire,      /* FIFO checked in this slice */
266         CFQ_CFQQ_FLAG_idle_window,      /* slice idling enabled */
267         CFQ_CFQQ_FLAG_prio_changed,     /* task priority has changed */
268         CFQ_CFQQ_FLAG_slice_new,        /* no requests dispatched in slice */
269         CFQ_CFQQ_FLAG_sync,             /* synchronous queue */
270         CFQ_CFQQ_FLAG_coop,             /* cfqq is shared */
271         CFQ_CFQQ_FLAG_deep,             /* sync cfqq experienced large depth */
272 };
273
274 #define CFQ_CFQQ_FNS(name)                                              \
275 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
276 {                                                                       \
277         (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name);                   \
278 }                                                                       \
279 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
280 {                                                                       \
281         (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                  \
282 }                                                                       \
283 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
284 {                                                                       \
285         return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;      \
286 }
287
288 CFQ_CFQQ_FNS(on_rr);
289 CFQ_CFQQ_FNS(wait_request);
290 CFQ_CFQQ_FNS(must_dispatch);
291 CFQ_CFQQ_FNS(must_alloc_slice);
292 CFQ_CFQQ_FNS(fifo_expire);
293 CFQ_CFQQ_FNS(idle_window);
294 CFQ_CFQQ_FNS(prio_changed);
295 CFQ_CFQQ_FNS(slice_new);
296 CFQ_CFQQ_FNS(sync);
297 CFQ_CFQQ_FNS(coop);
298 CFQ_CFQQ_FNS(deep);
299 #undef CFQ_CFQQ_FNS
300
301 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
302         blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
303 #define cfq_log(cfqd, fmt, args...)     \
304         blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
305
306 /* Traverses through cfq group service trees */
307 #define for_each_cfqg_st(cfqg, i, j, st) \
308         for (i = 0; i <= IDLE_WORKLOAD; i++) \
309                 for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
310                         : &cfqg->service_tree_idle; \
311                         (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
312                         (i == IDLE_WORKLOAD && j == 0); \
313                         j++, st = i < IDLE_WORKLOAD ? \
314                         &cfqg->service_trees[i][j]: NULL) \
315
316
317 static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
318 {
319         if (cfq_class_idle(cfqq))
320                 return IDLE_WORKLOAD;
321         if (cfq_class_rt(cfqq))
322                 return RT_WORKLOAD;
323         return BE_WORKLOAD;
324 }
325
326
327 static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
328 {
329         if (!cfq_cfqq_sync(cfqq))
330                 return ASYNC_WORKLOAD;
331         if (!cfq_cfqq_idle_window(cfqq))
332                 return SYNC_NOIDLE_WORKLOAD;
333         return SYNC_WORKLOAD;
334 }
335
336 static inline int cfq_busy_queues_wl(enum wl_prio_t wl, struct cfq_data *cfqd)
337 {
338         struct cfq_group *cfqg = &cfqd->root_group;
339
340         if (wl == IDLE_WORKLOAD)
341                 return cfqg->service_tree_idle.count;
342
343         return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
344                 + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
345                 + cfqg->service_trees[wl][SYNC_WORKLOAD].count;
346 }
347
348 static void cfq_dispatch_insert(struct request_queue *, struct request *);
349 static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
350                                        struct io_context *, gfp_t);
351 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
352                                                 struct io_context *);
353
354 static inline int rq_in_driver(struct cfq_data *cfqd)
355 {
356         return cfqd->rq_in_driver[0] + cfqd->rq_in_driver[1];
357 }
358
359 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
360                                             bool is_sync)
361 {
362         return cic->cfqq[is_sync];
363 }
364
365 static inline void cic_set_cfqq(struct cfq_io_context *cic,
366                                 struct cfq_queue *cfqq, bool is_sync)
367 {
368         cic->cfqq[is_sync] = cfqq;
369 }
370
371 /*
372  * We regard a request as SYNC, if it's either a read or has the SYNC bit
373  * set (in which case it could also be direct WRITE).
374  */
375 static inline bool cfq_bio_sync(struct bio *bio)
376 {
377         return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO);
378 }
379
380 /*
381  * scheduler run of queue, if there are requests pending and no one in the
382  * driver that will restart queueing
383  */
384 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
385 {
386         if (cfqd->busy_queues) {
387                 cfq_log(cfqd, "schedule dispatch");
388                 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
389         }
390 }
391
392 static int cfq_queue_empty(struct request_queue *q)
393 {
394         struct cfq_data *cfqd = q->elevator->elevator_data;
395
396         return !cfqd->rq_queued;
397 }
398
399 /*
400  * Scale schedule slice based on io priority. Use the sync time slice only
401  * if a queue is marked sync and has sync io queued. A sync queue with async
402  * io only, should not get full sync slice length.
403  */
404 static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
405                                  unsigned short prio)
406 {
407         const int base_slice = cfqd->cfq_slice[sync];
408
409         WARN_ON(prio >= IOPRIO_BE_NR);
410
411         return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
412 }
413
414 static inline int
415 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
416 {
417         return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
418 }
419
420 /*
421  * get averaged number of queues of RT/BE priority.
422  * average is updated, with a formula that gives more weight to higher numbers,
423  * to quickly follows sudden increases and decrease slowly
424  */
425
426 static inline unsigned cfq_get_avg_queues(struct cfq_data *cfqd, bool rt)
427 {
428         unsigned min_q, max_q;
429         unsigned mult  = cfq_hist_divisor - 1;
430         unsigned round = cfq_hist_divisor / 2;
431         unsigned busy = cfq_busy_queues_wl(rt, cfqd);
432
433         min_q = min(cfqd->busy_queues_avg[rt], busy);
434         max_q = max(cfqd->busy_queues_avg[rt], busy);
435         cfqd->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
436                 cfq_hist_divisor;
437         return cfqd->busy_queues_avg[rt];
438 }
439
440 static inline void
441 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
442 {
443         unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
444         if (cfqd->cfq_latency) {
445                 /* interested queues (we consider only the ones with the same
446                  * priority class) */
447                 unsigned iq = cfq_get_avg_queues(cfqd, cfq_class_rt(cfqq));
448                 unsigned sync_slice = cfqd->cfq_slice[1];
449                 unsigned expect_latency = sync_slice * iq;
450                 if (expect_latency > cfq_target_latency) {
451                         unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
452                         /* scale low_slice according to IO priority
453                          * and sync vs async */
454                         unsigned low_slice =
455                                 min(slice, base_low_slice * slice / sync_slice);
456                         /* the adapted slice value is scaled to fit all iqs
457                          * into the target latency */
458                         slice = max(slice * cfq_target_latency / expect_latency,
459                                     low_slice);
460                 }
461         }
462         cfqq->slice_end = jiffies + slice;
463         cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
464 }
465
466 /*
467  * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
468  * isn't valid until the first request from the dispatch is activated
469  * and the slice time set.
470  */
471 static inline bool cfq_slice_used(struct cfq_queue *cfqq)
472 {
473         if (cfq_cfqq_slice_new(cfqq))
474                 return 0;
475         if (time_before(jiffies, cfqq->slice_end))
476                 return 0;
477
478         return 1;
479 }
480
481 /*
482  * Lifted from AS - choose which of rq1 and rq2 that is best served now.
483  * We choose the request that is closest to the head right now. Distance
484  * behind the head is penalized and only allowed to a certain extent.
485  */
486 static struct request *
487 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
488 {
489         sector_t s1, s2, d1 = 0, d2 = 0;
490         unsigned long back_max;
491 #define CFQ_RQ1_WRAP    0x01 /* request 1 wraps */
492 #define CFQ_RQ2_WRAP    0x02 /* request 2 wraps */
493         unsigned wrap = 0; /* bit mask: requests behind the disk head? */
494
495         if (rq1 == NULL || rq1 == rq2)
496                 return rq2;
497         if (rq2 == NULL)
498                 return rq1;
499
500         if (rq_is_sync(rq1) && !rq_is_sync(rq2))
501                 return rq1;
502         else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
503                 return rq2;
504         if (rq_is_meta(rq1) && !rq_is_meta(rq2))
505                 return rq1;
506         else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
507                 return rq2;
508
509         s1 = blk_rq_pos(rq1);
510         s2 = blk_rq_pos(rq2);
511
512         /*
513          * by definition, 1KiB is 2 sectors
514          */
515         back_max = cfqd->cfq_back_max * 2;
516
517         /*
518          * Strict one way elevator _except_ in the case where we allow
519          * short backward seeks which are biased as twice the cost of a
520          * similar forward seek.
521          */
522         if (s1 >= last)
523                 d1 = s1 - last;
524         else if (s1 + back_max >= last)
525                 d1 = (last - s1) * cfqd->cfq_back_penalty;
526         else
527                 wrap |= CFQ_RQ1_WRAP;
528
529         if (s2 >= last)
530                 d2 = s2 - last;
531         else if (s2 + back_max >= last)
532                 d2 = (last - s2) * cfqd->cfq_back_penalty;
533         else
534                 wrap |= CFQ_RQ2_WRAP;
535
536         /* Found required data */
537
538         /*
539          * By doing switch() on the bit mask "wrap" we avoid having to
540          * check two variables for all permutations: --> faster!
541          */
542         switch (wrap) {
543         case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
544                 if (d1 < d2)
545                         return rq1;
546                 else if (d2 < d1)
547                         return rq2;
548                 else {
549                         if (s1 >= s2)
550                                 return rq1;
551                         else
552                                 return rq2;
553                 }
554
555         case CFQ_RQ2_WRAP:
556                 return rq1;
557         case CFQ_RQ1_WRAP:
558                 return rq2;
559         case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
560         default:
561                 /*
562                  * Since both rqs are wrapped,
563                  * start with the one that's further behind head
564                  * (--> only *one* back seek required),
565                  * since back seek takes more time than forward.
566                  */
567                 if (s1 <= s2)
568                         return rq1;
569                 else
570                         return rq2;
571         }
572 }
573
574 /*
575  * The below is leftmost cache rbtree addon
576  */
577 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
578 {
579         /* Service tree is empty */
580         if (!root->count)
581                 return NULL;
582
583         if (!root->left)
584                 root->left = rb_first(&root->rb);
585
586         if (root->left)
587                 return rb_entry(root->left, struct cfq_queue, rb_node);
588
589         return NULL;
590 }
591
592 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
593 {
594         rb_erase(n, root);
595         RB_CLEAR_NODE(n);
596 }
597
598 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
599 {
600         if (root->left == n)
601                 root->left = NULL;
602         rb_erase_init(n, &root->rb);
603         --root->count;
604 }
605
606 /*
607  * would be nice to take fifo expire time into account as well
608  */
609 static struct request *
610 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
611                   struct request *last)
612 {
613         struct rb_node *rbnext = rb_next(&last->rb_node);
614         struct rb_node *rbprev = rb_prev(&last->rb_node);
615         struct request *next = NULL, *prev = NULL;
616
617         BUG_ON(RB_EMPTY_NODE(&last->rb_node));
618
619         if (rbprev)
620                 prev = rb_entry_rq(rbprev);
621
622         if (rbnext)
623                 next = rb_entry_rq(rbnext);
624         else {
625                 rbnext = rb_first(&cfqq->sort_list);
626                 if (rbnext && rbnext != &last->rb_node)
627                         next = rb_entry_rq(rbnext);
628         }
629
630         return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
631 }
632
633 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
634                                       struct cfq_queue *cfqq)
635 {
636         /*
637          * just an approximation, should be ok.
638          */
639         return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
640                        cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
641 }
642
643 /*
644  * The cfqd->service_trees holds all pending cfq_queue's that have
645  * requests waiting to be processed. It is sorted in the order that
646  * we will service the queues.
647  */
648 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
649                                  bool add_front)
650 {
651         struct rb_node **p, *parent;
652         struct cfq_queue *__cfqq;
653         unsigned long rb_key;
654         struct cfq_rb_root *service_tree;
655         int left;
656
657         service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
658                                                 cfqq_type(cfqq), cfqd);
659         if (cfq_class_idle(cfqq)) {
660                 rb_key = CFQ_IDLE_DELAY;
661                 parent = rb_last(&service_tree->rb);
662                 if (parent && parent != &cfqq->rb_node) {
663                         __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
664                         rb_key += __cfqq->rb_key;
665                 } else
666                         rb_key += jiffies;
667         } else if (!add_front) {
668                 /*
669                  * Get our rb key offset. Subtract any residual slice
670                  * value carried from last service. A negative resid
671                  * count indicates slice overrun, and this should position
672                  * the next service time further away in the tree.
673                  */
674                 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
675                 rb_key -= cfqq->slice_resid;
676                 cfqq->slice_resid = 0;
677         } else {
678                 rb_key = -HZ;
679                 __cfqq = cfq_rb_first(service_tree);
680                 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
681         }
682
683         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
684                 /*
685                  * same position, nothing more to do
686                  */
687                 if (rb_key == cfqq->rb_key &&
688                     cfqq->service_tree == service_tree)
689                         return;
690
691                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
692                 cfqq->service_tree = NULL;
693         }
694
695         left = 1;
696         parent = NULL;
697         cfqq->service_tree = service_tree;
698         p = &service_tree->rb.rb_node;
699         while (*p) {
700                 struct rb_node **n;
701
702                 parent = *p;
703                 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
704
705                 /*
706                  * sort by key, that represents service time.
707                  */
708                 if (time_before(rb_key, __cfqq->rb_key))
709                         n = &(*p)->rb_left;
710                 else {
711                         n = &(*p)->rb_right;
712                         left = 0;
713                 }
714
715                 p = n;
716         }
717
718         if (left)
719                 service_tree->left = &cfqq->rb_node;
720
721         cfqq->rb_key = rb_key;
722         rb_link_node(&cfqq->rb_node, parent, p);
723         rb_insert_color(&cfqq->rb_node, &service_tree->rb);
724         service_tree->count++;
725 }
726
727 static struct cfq_queue *
728 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
729                      sector_t sector, struct rb_node **ret_parent,
730                      struct rb_node ***rb_link)
731 {
732         struct rb_node **p, *parent;
733         struct cfq_queue *cfqq = NULL;
734
735         parent = NULL;
736         p = &root->rb_node;
737         while (*p) {
738                 struct rb_node **n;
739
740                 parent = *p;
741                 cfqq = rb_entry(parent, struct cfq_queue, p_node);
742
743                 /*
744                  * Sort strictly based on sector.  Smallest to the left,
745                  * largest to the right.
746                  */
747                 if (sector > blk_rq_pos(cfqq->next_rq))
748                         n = &(*p)->rb_right;
749                 else if (sector < blk_rq_pos(cfqq->next_rq))
750                         n = &(*p)->rb_left;
751                 else
752                         break;
753                 p = n;
754                 cfqq = NULL;
755         }
756
757         *ret_parent = parent;
758         if (rb_link)
759                 *rb_link = p;
760         return cfqq;
761 }
762
763 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
764 {
765         struct rb_node **p, *parent;
766         struct cfq_queue *__cfqq;
767
768         if (cfqq->p_root) {
769                 rb_erase(&cfqq->p_node, cfqq->p_root);
770                 cfqq->p_root = NULL;
771         }
772
773         if (cfq_class_idle(cfqq))
774                 return;
775         if (!cfqq->next_rq)
776                 return;
777
778         cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
779         __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
780                                       blk_rq_pos(cfqq->next_rq), &parent, &p);
781         if (!__cfqq) {
782                 rb_link_node(&cfqq->p_node, parent, p);
783                 rb_insert_color(&cfqq->p_node, cfqq->p_root);
784         } else
785                 cfqq->p_root = NULL;
786 }
787
788 /*
789  * Update cfqq's position in the service tree.
790  */
791 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
792 {
793         /*
794          * Resorting requires the cfqq to be on the RR list already.
795          */
796         if (cfq_cfqq_on_rr(cfqq)) {
797                 cfq_service_tree_add(cfqd, cfqq, 0);
798                 cfq_prio_tree_add(cfqd, cfqq);
799         }
800 }
801
802 /*
803  * add to busy list of queues for service, trying to be fair in ordering
804  * the pending list according to last request service
805  */
806 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
807 {
808         cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
809         BUG_ON(cfq_cfqq_on_rr(cfqq));
810         cfq_mark_cfqq_on_rr(cfqq);
811         cfqd->busy_queues++;
812
813         cfq_resort_rr_list(cfqd, cfqq);
814 }
815
816 /*
817  * Called when the cfqq no longer has requests pending, remove it from
818  * the service tree.
819  */
820 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
821 {
822         cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
823         BUG_ON(!cfq_cfqq_on_rr(cfqq));
824         cfq_clear_cfqq_on_rr(cfqq);
825
826         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
827                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
828                 cfqq->service_tree = NULL;
829         }
830         if (cfqq->p_root) {
831                 rb_erase(&cfqq->p_node, cfqq->p_root);
832                 cfqq->p_root = NULL;
833         }
834
835         BUG_ON(!cfqd->busy_queues);
836         cfqd->busy_queues--;
837 }
838
839 /*
840  * rb tree support functions
841  */
842 static void cfq_del_rq_rb(struct request *rq)
843 {
844         struct cfq_queue *cfqq = RQ_CFQQ(rq);
845         const int sync = rq_is_sync(rq);
846
847         BUG_ON(!cfqq->queued[sync]);
848         cfqq->queued[sync]--;
849
850         elv_rb_del(&cfqq->sort_list, rq);
851
852         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
853                 /*
854                  * Queue will be deleted from service tree when we actually
855                  * expire it later. Right now just remove it from prio tree
856                  * as it is empty.
857                  */
858                 if (cfqq->p_root) {
859                         rb_erase(&cfqq->p_node, cfqq->p_root);
860                         cfqq->p_root = NULL;
861                 }
862         }
863 }
864
865 static void cfq_add_rq_rb(struct request *rq)
866 {
867         struct cfq_queue *cfqq = RQ_CFQQ(rq);
868         struct cfq_data *cfqd = cfqq->cfqd;
869         struct request *__alias, *prev;
870
871         cfqq->queued[rq_is_sync(rq)]++;
872
873         /*
874          * looks a little odd, but the first insert might return an alias.
875          * if that happens, put the alias on the dispatch list
876          */
877         while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
878                 cfq_dispatch_insert(cfqd->queue, __alias);
879
880         if (!cfq_cfqq_on_rr(cfqq))
881                 cfq_add_cfqq_rr(cfqd, cfqq);
882
883         /*
884          * check if this request is a better next-serve candidate
885          */
886         prev = cfqq->next_rq;
887         cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
888
889         /*
890          * adjust priority tree position, if ->next_rq changes
891          */
892         if (prev != cfqq->next_rq)
893                 cfq_prio_tree_add(cfqd, cfqq);
894
895         BUG_ON(!cfqq->next_rq);
896 }
897
898 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
899 {
900         elv_rb_del(&cfqq->sort_list, rq);
901         cfqq->queued[rq_is_sync(rq)]--;
902         cfq_add_rq_rb(rq);
903 }
904
905 static struct request *
906 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
907 {
908         struct task_struct *tsk = current;
909         struct cfq_io_context *cic;
910         struct cfq_queue *cfqq;
911
912         cic = cfq_cic_lookup(cfqd, tsk->io_context);
913         if (!cic)
914                 return NULL;
915
916         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
917         if (cfqq) {
918                 sector_t sector = bio->bi_sector + bio_sectors(bio);
919
920                 return elv_rb_find(&cfqq->sort_list, sector);
921         }
922
923         return NULL;
924 }
925
926 static void cfq_activate_request(struct request_queue *q, struct request *rq)
927 {
928         struct cfq_data *cfqd = q->elevator->elevator_data;
929
930         cfqd->rq_in_driver[rq_is_sync(rq)]++;
931         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
932                                                 rq_in_driver(cfqd));
933
934         cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
935 }
936
937 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
938 {
939         struct cfq_data *cfqd = q->elevator->elevator_data;
940         const int sync = rq_is_sync(rq);
941
942         WARN_ON(!cfqd->rq_in_driver[sync]);
943         cfqd->rq_in_driver[sync]--;
944         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
945                                                 rq_in_driver(cfqd));
946 }
947
948 static void cfq_remove_request(struct request *rq)
949 {
950         struct cfq_queue *cfqq = RQ_CFQQ(rq);
951
952         if (cfqq->next_rq == rq)
953                 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
954
955         list_del_init(&rq->queuelist);
956         cfq_del_rq_rb(rq);
957
958         cfqq->cfqd->rq_queued--;
959         if (rq_is_meta(rq)) {
960                 WARN_ON(!cfqq->meta_pending);
961                 cfqq->meta_pending--;
962         }
963 }
964
965 static int cfq_merge(struct request_queue *q, struct request **req,
966                      struct bio *bio)
967 {
968         struct cfq_data *cfqd = q->elevator->elevator_data;
969         struct request *__rq;
970
971         __rq = cfq_find_rq_fmerge(cfqd, bio);
972         if (__rq && elv_rq_merge_ok(__rq, bio)) {
973                 *req = __rq;
974                 return ELEVATOR_FRONT_MERGE;
975         }
976
977         return ELEVATOR_NO_MERGE;
978 }
979
980 static void cfq_merged_request(struct request_queue *q, struct request *req,
981                                int type)
982 {
983         if (type == ELEVATOR_FRONT_MERGE) {
984                 struct cfq_queue *cfqq = RQ_CFQQ(req);
985
986                 cfq_reposition_rq_rb(cfqq, req);
987         }
988 }
989
990 static void
991 cfq_merged_requests(struct request_queue *q, struct request *rq,
992                     struct request *next)
993 {
994         struct cfq_queue *cfqq = RQ_CFQQ(rq);
995         /*
996          * reposition in fifo if next is older than rq
997          */
998         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
999             time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
1000                 list_move(&rq->queuelist, &next->queuelist);
1001                 rq_set_fifo_time(rq, rq_fifo_time(next));
1002         }
1003
1004         if (cfqq->next_rq == next)
1005                 cfqq->next_rq = rq;
1006         cfq_remove_request(next);
1007 }
1008
1009 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
1010                            struct bio *bio)
1011 {
1012         struct cfq_data *cfqd = q->elevator->elevator_data;
1013         struct cfq_io_context *cic;
1014         struct cfq_queue *cfqq;
1015
1016         /*
1017          * Disallow merge of a sync bio into an async request.
1018          */
1019         if (cfq_bio_sync(bio) && !rq_is_sync(rq))
1020                 return false;
1021
1022         /*
1023          * Lookup the cfqq that this bio will be queued with. Allow
1024          * merge only if rq is queued there.
1025          */
1026         cic = cfq_cic_lookup(cfqd, current->io_context);
1027         if (!cic)
1028                 return false;
1029
1030         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1031         return cfqq == RQ_CFQQ(rq);
1032 }
1033
1034 static void __cfq_set_active_queue(struct cfq_data *cfqd,
1035                                    struct cfq_queue *cfqq)
1036 {
1037         if (cfqq) {
1038                 cfq_log_cfqq(cfqd, cfqq, "set_active");
1039                 cfqq->slice_end = 0;
1040                 cfqq->slice_dispatch = 0;
1041
1042                 cfq_clear_cfqq_wait_request(cfqq);
1043                 cfq_clear_cfqq_must_dispatch(cfqq);
1044                 cfq_clear_cfqq_must_alloc_slice(cfqq);
1045                 cfq_clear_cfqq_fifo_expire(cfqq);
1046                 cfq_mark_cfqq_slice_new(cfqq);
1047
1048                 del_timer(&cfqd->idle_slice_timer);
1049         }
1050
1051         cfqd->active_queue = cfqq;
1052 }
1053
1054 /*
1055  * current cfqq expired its slice (or was too idle), select new one
1056  */
1057 static void
1058 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1059                     bool timed_out)
1060 {
1061         cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
1062
1063         if (cfq_cfqq_wait_request(cfqq))
1064                 del_timer(&cfqd->idle_slice_timer);
1065
1066         cfq_clear_cfqq_wait_request(cfqq);
1067
1068         /*
1069          * store what was left of this slice, if the queue idled/timed out
1070          */
1071         if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
1072                 cfqq->slice_resid = cfqq->slice_end - jiffies;
1073                 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
1074         }
1075
1076         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
1077                 cfq_del_cfqq_rr(cfqd, cfqq);
1078
1079         cfq_resort_rr_list(cfqd, cfqq);
1080
1081         if (cfqq == cfqd->active_queue)
1082                 cfqd->active_queue = NULL;
1083
1084         if (cfqd->active_cic) {
1085                 put_io_context(cfqd->active_cic->ioc);
1086                 cfqd->active_cic = NULL;
1087         }
1088 }
1089
1090 static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
1091 {
1092         struct cfq_queue *cfqq = cfqd->active_queue;
1093
1094         if (cfqq)
1095                 __cfq_slice_expired(cfqd, cfqq, timed_out);
1096 }
1097
1098 /*
1099  * Get next queue for service. Unless we have a queue preemption,
1100  * we'll simply select the first cfqq in the service tree.
1101  */
1102 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
1103 {
1104         struct cfq_rb_root *service_tree =
1105                 service_tree_for(cfqd->serving_group, cfqd->serving_prio,
1106                                         cfqd->serving_type, cfqd);
1107
1108         if (!cfqd->rq_queued)
1109                 return NULL;
1110
1111         if (RB_EMPTY_ROOT(&service_tree->rb))
1112                 return NULL;
1113         return cfq_rb_first(service_tree);
1114 }
1115
1116 static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
1117 {
1118         struct cfq_group *cfqg = &cfqd->root_group;
1119         struct cfq_queue *cfqq;
1120         int i, j;
1121         struct cfq_rb_root *st;
1122
1123         if (!cfqd->rq_queued)
1124                 return NULL;
1125
1126         for_each_cfqg_st(cfqg, i, j, st)
1127                 if ((cfqq = cfq_rb_first(st)) != NULL)
1128                         return cfqq;
1129         return NULL;
1130 }
1131
1132 /*
1133  * Get and set a new active queue for service.
1134  */
1135 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
1136                                               struct cfq_queue *cfqq)
1137 {
1138         if (!cfqq)
1139                 cfqq = cfq_get_next_queue(cfqd);
1140
1141         __cfq_set_active_queue(cfqd, cfqq);
1142         return cfqq;
1143 }
1144
1145 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
1146                                           struct request *rq)
1147 {
1148         if (blk_rq_pos(rq) >= cfqd->last_position)
1149                 return blk_rq_pos(rq) - cfqd->last_position;
1150         else
1151                 return cfqd->last_position - blk_rq_pos(rq);
1152 }
1153
1154 #define CFQQ_SEEK_THR           8 * 1024
1155 #define CFQQ_SEEKY(cfqq)        ((cfqq)->seek_mean > CFQQ_SEEK_THR)
1156
1157 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1158                                struct request *rq)
1159 {
1160         sector_t sdist = cfqq->seek_mean;
1161
1162         if (!sample_valid(cfqq->seek_samples))
1163                 sdist = CFQQ_SEEK_THR;
1164
1165         return cfq_dist_from_last(cfqd, rq) <= sdist;
1166 }
1167
1168 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
1169                                     struct cfq_queue *cur_cfqq)
1170 {
1171         struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
1172         struct rb_node *parent, *node;
1173         struct cfq_queue *__cfqq;
1174         sector_t sector = cfqd->last_position;
1175
1176         if (RB_EMPTY_ROOT(root))
1177                 return NULL;
1178
1179         /*
1180          * First, if we find a request starting at the end of the last
1181          * request, choose it.
1182          */
1183         __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
1184         if (__cfqq)
1185                 return __cfqq;
1186
1187         /*
1188          * If the exact sector wasn't found, the parent of the NULL leaf
1189          * will contain the closest sector.
1190          */
1191         __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1192         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1193                 return __cfqq;
1194
1195         if (blk_rq_pos(__cfqq->next_rq) < sector)
1196                 node = rb_next(&__cfqq->p_node);
1197         else
1198                 node = rb_prev(&__cfqq->p_node);
1199         if (!node)
1200                 return NULL;
1201
1202         __cfqq = rb_entry(node, struct cfq_queue, p_node);
1203         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1204                 return __cfqq;
1205
1206         return NULL;
1207 }
1208
1209 /*
1210  * cfqd - obvious
1211  * cur_cfqq - passed in so that we don't decide that the current queue is
1212  *            closely cooperating with itself.
1213  *
1214  * So, basically we're assuming that that cur_cfqq has dispatched at least
1215  * one request, and that cfqd->last_position reflects a position on the disk
1216  * associated with the I/O issued by cur_cfqq.  I'm not sure this is a valid
1217  * assumption.
1218  */
1219 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1220                                               struct cfq_queue *cur_cfqq)
1221 {
1222         struct cfq_queue *cfqq;
1223
1224         if (!cfq_cfqq_sync(cur_cfqq))
1225                 return NULL;
1226         if (CFQQ_SEEKY(cur_cfqq))
1227                 return NULL;
1228
1229         /*
1230          * We should notice if some of the queues are cooperating, eg
1231          * working closely on the same area of the disk. In that case,
1232          * we can group them together and don't waste time idling.
1233          */
1234         cfqq = cfqq_close(cfqd, cur_cfqq);
1235         if (!cfqq)
1236                 return NULL;
1237
1238         /*
1239          * It only makes sense to merge sync queues.
1240          */
1241         if (!cfq_cfqq_sync(cfqq))
1242                 return NULL;
1243         if (CFQQ_SEEKY(cfqq))
1244                 return NULL;
1245
1246         /*
1247          * Do not merge queues of different priority classes
1248          */
1249         if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
1250                 return NULL;
1251
1252         return cfqq;
1253 }
1254
1255 /*
1256  * Determine whether we should enforce idle window for this queue.
1257  */
1258
1259 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1260 {
1261         enum wl_prio_t prio = cfqq_prio(cfqq);
1262         struct cfq_rb_root *service_tree = cfqq->service_tree;
1263
1264         BUG_ON(!service_tree);
1265         BUG_ON(!service_tree->count);
1266
1267         /* We never do for idle class queues. */
1268         if (prio == IDLE_WORKLOAD)
1269                 return false;
1270
1271         /* We do for queues that were marked with idle window flag. */
1272         if (cfq_cfqq_idle_window(cfqq))
1273                 return true;
1274
1275         /*
1276          * Otherwise, we do only if they are the last ones
1277          * in their service tree.
1278          */
1279         return service_tree->count == 1;
1280 }
1281
1282 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
1283 {
1284         struct cfq_queue *cfqq = cfqd->active_queue;
1285         struct cfq_io_context *cic;
1286         unsigned long sl;
1287
1288         /*
1289          * SSD device without seek penalty, disable idling. But only do so
1290          * for devices that support queuing, otherwise we still have a problem
1291          * with sync vs async workloads.
1292          */
1293         if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
1294                 return;
1295
1296         WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
1297         WARN_ON(cfq_cfqq_slice_new(cfqq));
1298
1299         /*
1300          * idle is disabled, either manually or by past process history
1301          */
1302         if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq))
1303                 return;
1304
1305         /*
1306          * still active requests from this queue, don't idle
1307          */
1308         if (cfqq->dispatched)
1309                 return;
1310
1311         /*
1312          * task has exited, don't wait
1313          */
1314         cic = cfqd->active_cic;
1315         if (!cic || !atomic_read(&cic->ioc->nr_tasks))
1316                 return;
1317
1318         /*
1319          * If our average think time is larger than the remaining time
1320          * slice, then don't idle. This avoids overrunning the allotted
1321          * time slice.
1322          */
1323         if (sample_valid(cic->ttime_samples) &&
1324             (cfqq->slice_end - jiffies < cic->ttime_mean))
1325                 return;
1326
1327         cfq_mark_cfqq_wait_request(cfqq);
1328
1329         sl = cfqd->cfq_slice_idle;
1330
1331         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
1332         cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
1333 }
1334
1335 /*
1336  * Move request from internal lists to the request queue dispatch list.
1337  */
1338 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
1339 {
1340         struct cfq_data *cfqd = q->elevator->elevator_data;
1341         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1342
1343         cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
1344
1345         cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
1346         cfq_remove_request(rq);
1347         cfqq->dispatched++;
1348         elv_dispatch_sort(q, rq);
1349
1350         if (cfq_cfqq_sync(cfqq))
1351                 cfqd->sync_flight++;
1352 }
1353
1354 /*
1355  * return expired entry, or NULL to just start from scratch in rbtree
1356  */
1357 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
1358 {
1359         struct request *rq = NULL;
1360
1361         if (cfq_cfqq_fifo_expire(cfqq))
1362                 return NULL;
1363
1364         cfq_mark_cfqq_fifo_expire(cfqq);
1365
1366         if (list_empty(&cfqq->fifo))
1367                 return NULL;
1368
1369         rq = rq_entry_fifo(cfqq->fifo.next);
1370         if (time_before(jiffies, rq_fifo_time(rq)))
1371                 rq = NULL;
1372
1373         cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
1374         return rq;
1375 }
1376
1377 static inline int
1378 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1379 {
1380         const int base_rq = cfqd->cfq_slice_async_rq;
1381
1382         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1383
1384         return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1385 }
1386
1387 /*
1388  * Must be called with the queue_lock held.
1389  */
1390 static int cfqq_process_refs(struct cfq_queue *cfqq)
1391 {
1392         int process_refs, io_refs;
1393
1394         io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
1395         process_refs = atomic_read(&cfqq->ref) - io_refs;
1396         BUG_ON(process_refs < 0);
1397         return process_refs;
1398 }
1399
1400 static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
1401 {
1402         int process_refs, new_process_refs;
1403         struct cfq_queue *__cfqq;
1404
1405         /* Avoid a circular list and skip interim queue merges */
1406         while ((__cfqq = new_cfqq->new_cfqq)) {
1407                 if (__cfqq == cfqq)
1408                         return;
1409                 new_cfqq = __cfqq;
1410         }
1411
1412         process_refs = cfqq_process_refs(cfqq);
1413         /*
1414          * If the process for the cfqq has gone away, there is no
1415          * sense in merging the queues.
1416          */
1417         if (process_refs == 0)
1418                 return;
1419
1420         /*
1421          * Merge in the direction of the lesser amount of work.
1422          */
1423         new_process_refs = cfqq_process_refs(new_cfqq);
1424         if (new_process_refs >= process_refs) {
1425                 cfqq->new_cfqq = new_cfqq;
1426                 atomic_add(process_refs, &new_cfqq->ref);
1427         } else {
1428                 new_cfqq->new_cfqq = cfqq;
1429                 atomic_add(new_process_refs, &cfqq->ref);
1430         }
1431 }
1432
1433 static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
1434                                 struct cfq_group *cfqg, enum wl_prio_t prio,
1435                                 bool prio_changed)
1436 {
1437         struct cfq_queue *queue;
1438         int i;
1439         bool key_valid = false;
1440         unsigned long lowest_key = 0;
1441         enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
1442
1443         if (prio_changed) {
1444                 /*
1445                  * When priorities switched, we prefer starting
1446                  * from SYNC_NOIDLE (first choice), or just SYNC
1447                  * over ASYNC
1448                  */
1449                 if (service_tree_for(cfqg, prio, cur_best, cfqd)->count)
1450                         return cur_best;
1451                 cur_best = SYNC_WORKLOAD;
1452                 if (service_tree_for(cfqg, prio, cur_best, cfqd)->count)
1453                         return cur_best;
1454
1455                 return ASYNC_WORKLOAD;
1456         }
1457
1458         for (i = 0; i < 3; ++i) {
1459                 /* otherwise, select the one with lowest rb_key */
1460                 queue = cfq_rb_first(service_tree_for(cfqg, prio, i, cfqd));
1461                 if (queue &&
1462                     (!key_valid || time_before(queue->rb_key, lowest_key))) {
1463                         lowest_key = queue->rb_key;
1464                         cur_best = i;
1465                         key_valid = true;
1466                 }
1467         }
1468
1469         return cur_best;
1470 }
1471
1472 static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
1473 {
1474         enum wl_prio_t previous_prio = cfqd->serving_prio;
1475         bool prio_changed;
1476         unsigned slice;
1477         unsigned count;
1478         struct cfq_rb_root *st;
1479
1480         /* Choose next priority. RT > BE > IDLE */
1481         if (cfq_busy_queues_wl(RT_WORKLOAD, cfqd))
1482                 cfqd->serving_prio = RT_WORKLOAD;
1483         else if (cfq_busy_queues_wl(BE_WORKLOAD, cfqd))
1484                 cfqd->serving_prio = BE_WORKLOAD;
1485         else {
1486                 cfqd->serving_prio = IDLE_WORKLOAD;
1487                 cfqd->workload_expires = jiffies + 1;
1488                 return;
1489         }
1490
1491         /*
1492          * For RT and BE, we have to choose also the type
1493          * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
1494          * expiration time
1495          */
1496         prio_changed = (cfqd->serving_prio != previous_prio);
1497         st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type,
1498                                 cfqd);
1499         count = st->count;
1500
1501         /*
1502          * If priority didn't change, check workload expiration,
1503          * and that we still have other queues ready
1504          */
1505         if (!prio_changed && count &&
1506             !time_after(jiffies, cfqd->workload_expires))
1507                 return;
1508
1509         /* otherwise select new workload type */
1510         cfqd->serving_type =
1511                 cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio, prio_changed);
1512         st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type,
1513                                 cfqd);
1514         count = st->count;
1515
1516         /*
1517          * the workload slice is computed as a fraction of target latency
1518          * proportional to the number of queues in that workload, over
1519          * all the queues in the same priority class
1520          */
1521         slice = cfq_target_latency * count /
1522                 max_t(unsigned, cfqd->busy_queues_avg[cfqd->serving_prio],
1523                       cfq_busy_queues_wl(cfqd->serving_prio, cfqd));
1524
1525         if (cfqd->serving_type == ASYNC_WORKLOAD)
1526                 /* async workload slice is scaled down according to
1527                  * the sync/async slice ratio. */
1528                 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
1529         else
1530                 /* sync workload slice is at least 2 * cfq_slice_idle */
1531                 slice = max(slice, 2 * cfqd->cfq_slice_idle);
1532
1533         slice = max_t(unsigned, slice, CFQ_MIN_TT);
1534         cfqd->workload_expires = jiffies + slice;
1535         cfqd->noidle_tree_requires_idle = false;
1536 }
1537
1538 static void cfq_choose_cfqg(struct cfq_data *cfqd)
1539 {
1540         cfqd->serving_group = &cfqd->root_group;
1541         choose_service_tree(cfqd, &cfqd->root_group);
1542 }
1543
1544 /*
1545  * Select a queue for service. If we have a current active queue,
1546  * check whether to continue servicing it, or retrieve and set a new one.
1547  */
1548 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
1549 {
1550         struct cfq_queue *cfqq, *new_cfqq = NULL;
1551
1552         cfqq = cfqd->active_queue;
1553         if (!cfqq)
1554                 goto new_queue;
1555
1556         if (!cfqd->rq_queued)
1557                 return NULL;
1558         /*
1559          * The active queue has run out of time, expire it and select new.
1560          */
1561         if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq))
1562                 goto expire;
1563
1564         /*
1565          * The active queue has requests and isn't expired, allow it to
1566          * dispatch.
1567          */
1568         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
1569                 goto keep_queue;
1570
1571         /*
1572          * If another queue has a request waiting within our mean seek
1573          * distance, let it run.  The expire code will check for close
1574          * cooperators and put the close queue at the front of the service
1575          * tree.  If possible, merge the expiring queue with the new cfqq.
1576          */
1577         new_cfqq = cfq_close_cooperator(cfqd, cfqq);
1578         if (new_cfqq) {
1579                 if (!cfqq->new_cfqq)
1580                         cfq_setup_merge(cfqq, new_cfqq);
1581                 goto expire;
1582         }
1583
1584         /*
1585          * No requests pending. If the active queue still has requests in
1586          * flight or is idling for a new request, allow either of these
1587          * conditions to happen (or time out) before selecting a new queue.
1588          */
1589         if (timer_pending(&cfqd->idle_slice_timer) ||
1590             (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) {
1591                 cfqq = NULL;
1592                 goto keep_queue;
1593         }
1594
1595 expire:
1596         cfq_slice_expired(cfqd, 0);
1597 new_queue:
1598         /*
1599          * Current queue expired. Check if we have to switch to a new
1600          * service tree
1601          */
1602         if (!new_cfqq)
1603                 cfq_choose_cfqg(cfqd);
1604
1605         cfqq = cfq_set_active_queue(cfqd, new_cfqq);
1606 keep_queue:
1607         return cfqq;
1608 }
1609
1610 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
1611 {
1612         int dispatched = 0;
1613
1614         while (cfqq->next_rq) {
1615                 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
1616                 dispatched++;
1617         }
1618
1619         BUG_ON(!list_empty(&cfqq->fifo));
1620
1621         /* By default cfqq is not expired if it is empty. Do it explicitly */
1622         __cfq_slice_expired(cfqq->cfqd, cfqq, 0);
1623         return dispatched;
1624 }
1625
1626 /*
1627  * Drain our current requests. Used for barriers and when switching
1628  * io schedulers on-the-fly.
1629  */
1630 static int cfq_forced_dispatch(struct cfq_data *cfqd)
1631 {
1632         struct cfq_queue *cfqq;
1633         int dispatched = 0;
1634
1635         while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL)
1636                 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
1637
1638         cfq_slice_expired(cfqd, 0);
1639         BUG_ON(cfqd->busy_queues);
1640
1641         cfq_log(cfqd, "forced_dispatch=%d", dispatched);
1642         return dispatched;
1643 }
1644
1645 static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1646 {
1647         unsigned int max_dispatch;
1648
1649         /*
1650          * Drain async requests before we start sync IO
1651          */
1652         if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
1653                 return false;
1654
1655         /*
1656          * If this is an async queue and we have sync IO in flight, let it wait
1657          */
1658         if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
1659                 return false;
1660
1661         max_dispatch = cfqd->cfq_quantum;
1662         if (cfq_class_idle(cfqq))
1663                 max_dispatch = 1;
1664
1665         /*
1666          * Does this cfqq already have too much IO in flight?
1667          */
1668         if (cfqq->dispatched >= max_dispatch) {
1669                 /*
1670                  * idle queue must always only have a single IO in flight
1671                  */
1672                 if (cfq_class_idle(cfqq))
1673                         return false;
1674
1675                 /*
1676                  * We have other queues, don't allow more IO from this one
1677                  */
1678                 if (cfqd->busy_queues > 1)
1679                         return false;
1680
1681                 /*
1682                  * Sole queue user, no limit
1683                  */
1684                 max_dispatch = -1;
1685         }
1686
1687         /*
1688          * Async queues must wait a bit before being allowed dispatch.
1689          * We also ramp up the dispatch depth gradually for async IO,
1690          * based on the last sync IO we serviced
1691          */
1692         if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
1693                 unsigned long last_sync = jiffies - cfqd->last_end_sync_rq;
1694                 unsigned int depth;
1695
1696                 depth = last_sync / cfqd->cfq_slice[1];
1697                 if (!depth && !cfqq->dispatched)
1698                         depth = 1;
1699                 if (depth < max_dispatch)
1700                         max_dispatch = depth;
1701         }
1702
1703         /*
1704          * If we're below the current max, allow a dispatch
1705          */
1706         return cfqq->dispatched < max_dispatch;
1707 }
1708
1709 /*
1710  * Dispatch a request from cfqq, moving them to the request queue
1711  * dispatch list.
1712  */
1713 static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1714 {
1715         struct request *rq;
1716
1717         BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
1718
1719         if (!cfq_may_dispatch(cfqd, cfqq))
1720                 return false;
1721
1722         /*
1723          * follow expired path, else get first next available
1724          */
1725         rq = cfq_check_fifo(cfqq);
1726         if (!rq)
1727                 rq = cfqq->next_rq;
1728
1729         /*
1730          * insert request into driver dispatch list
1731          */
1732         cfq_dispatch_insert(cfqd->queue, rq);
1733
1734         if (!cfqd->active_cic) {
1735                 struct cfq_io_context *cic = RQ_CIC(rq);
1736
1737                 atomic_long_inc(&cic->ioc->refcount);
1738                 cfqd->active_cic = cic;
1739         }
1740
1741         return true;
1742 }
1743
1744 /*
1745  * Find the cfqq that we need to service and move a request from that to the
1746  * dispatch list
1747  */
1748 static int cfq_dispatch_requests(struct request_queue *q, int force)
1749 {
1750         struct cfq_data *cfqd = q->elevator->elevator_data;
1751         struct cfq_queue *cfqq;
1752
1753         if (!cfqd->busy_queues)
1754                 return 0;
1755
1756         if (unlikely(force))
1757                 return cfq_forced_dispatch(cfqd);
1758
1759         cfqq = cfq_select_queue(cfqd);
1760         if (!cfqq)
1761                 return 0;
1762
1763         /*
1764          * Dispatch a request from this cfqq, if it is allowed
1765          */
1766         if (!cfq_dispatch_request(cfqd, cfqq))
1767                 return 0;
1768
1769         cfqq->slice_dispatch++;
1770         cfq_clear_cfqq_must_dispatch(cfqq);
1771
1772         /*
1773          * expire an async queue immediately if it has used up its slice. idle
1774          * queue always expire after 1 dispatch round.
1775          */
1776         if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
1777             cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1778             cfq_class_idle(cfqq))) {
1779                 cfqq->slice_end = jiffies + 1;
1780                 cfq_slice_expired(cfqd, 0);
1781         }
1782
1783         cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
1784         return 1;
1785 }
1786
1787 /*
1788  * task holds one reference to the queue, dropped when task exits. each rq
1789  * in-flight on this queue also holds a reference, dropped when rq is freed.
1790  *
1791  * queue lock must be held here.
1792  */
1793 static void cfq_put_queue(struct cfq_queue *cfqq)
1794 {
1795         struct cfq_data *cfqd = cfqq->cfqd;
1796
1797         BUG_ON(atomic_read(&cfqq->ref) <= 0);
1798
1799         if (!atomic_dec_and_test(&cfqq->ref))
1800                 return;
1801
1802         cfq_log_cfqq(cfqd, cfqq, "put_queue");
1803         BUG_ON(rb_first(&cfqq->sort_list));
1804         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1805
1806         if (unlikely(cfqd->active_queue == cfqq)) {
1807                 __cfq_slice_expired(cfqd, cfqq, 0);
1808                 cfq_schedule_dispatch(cfqd);
1809         }
1810
1811         BUG_ON(cfq_cfqq_on_rr(cfqq));
1812         kmem_cache_free(cfq_pool, cfqq);
1813 }
1814
1815 /*
1816  * Must always be called with the rcu_read_lock() held
1817  */
1818 static void
1819 __call_for_each_cic(struct io_context *ioc,
1820                     void (*func)(struct io_context *, struct cfq_io_context *))
1821 {
1822         struct cfq_io_context *cic;
1823         struct hlist_node *n;
1824
1825         hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
1826                 func(ioc, cic);
1827 }
1828
1829 /*
1830  * Call func for each cic attached to this ioc.
1831  */
1832 static void
1833 call_for_each_cic(struct io_context *ioc,
1834                   void (*func)(struct io_context *, struct cfq_io_context *))
1835 {
1836         rcu_read_lock();
1837         __call_for_each_cic(ioc, func);
1838         rcu_read_unlock();
1839 }
1840
1841 static void cfq_cic_free_rcu(struct rcu_head *head)
1842 {
1843         struct cfq_io_context *cic;
1844
1845         cic = container_of(head, struct cfq_io_context, rcu_head);
1846
1847         kmem_cache_free(cfq_ioc_pool, cic);
1848         elv_ioc_count_dec(cfq_ioc_count);
1849
1850         if (ioc_gone) {
1851                 /*
1852                  * CFQ scheduler is exiting, grab exit lock and check
1853                  * the pending io context count. If it hits zero,
1854                  * complete ioc_gone and set it back to NULL
1855                  */
1856                 spin_lock(&ioc_gone_lock);
1857                 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
1858                         complete(ioc_gone);
1859                         ioc_gone = NULL;
1860                 }
1861                 spin_unlock(&ioc_gone_lock);
1862         }
1863 }
1864
1865 static void cfq_cic_free(struct cfq_io_context *cic)
1866 {
1867         call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
1868 }
1869
1870 static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
1871 {
1872         unsigned long flags;
1873
1874         BUG_ON(!cic->dead_key);
1875
1876         spin_lock_irqsave(&ioc->lock, flags);
1877         radix_tree_delete(&ioc->radix_root, cic->dead_key);
1878         hlist_del_rcu(&cic->cic_list);
1879         spin_unlock_irqrestore(&ioc->lock, flags);
1880
1881         cfq_cic_free(cic);
1882 }
1883
1884 /*
1885  * Must be called with rcu_read_lock() held or preemption otherwise disabled.
1886  * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
1887  * and ->trim() which is called with the task lock held
1888  */
1889 static void cfq_free_io_context(struct io_context *ioc)
1890 {
1891         /*
1892          * ioc->refcount is zero here, or we are called from elv_unregister(),
1893          * so no more cic's are allowed to be linked into this ioc.  So it
1894          * should be ok to iterate over the known list, we will see all cic's
1895          * since no new ones are added.
1896          */
1897         __call_for_each_cic(ioc, cic_free_func);
1898 }
1899
1900 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1901 {
1902         struct cfq_queue *__cfqq, *next;
1903
1904         if (unlikely(cfqq == cfqd->active_queue)) {
1905                 __cfq_slice_expired(cfqd, cfqq, 0);
1906                 cfq_schedule_dispatch(cfqd);
1907         }
1908
1909         /*
1910          * If this queue was scheduled to merge with another queue, be
1911          * sure to drop the reference taken on that queue (and others in
1912          * the merge chain).  See cfq_setup_merge and cfq_merge_cfqqs.
1913          */
1914         __cfqq = cfqq->new_cfqq;
1915         while (__cfqq) {
1916                 if (__cfqq == cfqq) {
1917                         WARN(1, "cfqq->new_cfqq loop detected\n");
1918                         break;
1919                 }
1920                 next = __cfqq->new_cfqq;
1921                 cfq_put_queue(__cfqq);
1922                 __cfqq = next;
1923         }
1924
1925         cfq_put_queue(cfqq);
1926 }
1927
1928 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
1929                                          struct cfq_io_context *cic)
1930 {
1931         struct io_context *ioc = cic->ioc;
1932
1933         list_del_init(&cic->queue_list);
1934
1935         /*
1936          * Make sure key == NULL is seen for dead queues
1937          */
1938         smp_wmb();
1939         cic->dead_key = (unsigned long) cic->key;
1940         cic->key = NULL;
1941
1942         if (ioc->ioc_data == cic)
1943                 rcu_assign_pointer(ioc->ioc_data, NULL);
1944
1945         if (cic->cfqq[BLK_RW_ASYNC]) {
1946                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
1947                 cic->cfqq[BLK_RW_ASYNC] = NULL;
1948         }
1949
1950         if (cic->cfqq[BLK_RW_SYNC]) {
1951                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
1952                 cic->cfqq[BLK_RW_SYNC] = NULL;
1953         }
1954 }
1955
1956 static void cfq_exit_single_io_context(struct io_context *ioc,
1957                                        struct cfq_io_context *cic)
1958 {
1959         struct cfq_data *cfqd = cic->key;
1960
1961         if (cfqd) {
1962                 struct request_queue *q = cfqd->queue;
1963                 unsigned long flags;
1964
1965                 spin_lock_irqsave(q->queue_lock, flags);
1966
1967                 /*
1968                  * Ensure we get a fresh copy of the ->key to prevent
1969                  * race between exiting task and queue
1970                  */
1971                 smp_read_barrier_depends();
1972                 if (cic->key)
1973                         __cfq_exit_single_io_context(cfqd, cic);
1974
1975                 spin_unlock_irqrestore(q->queue_lock, flags);
1976         }
1977 }
1978
1979 /*
1980  * The process that ioc belongs to has exited, we need to clean up
1981  * and put the internal structures we have that belongs to that process.
1982  */
1983 static void cfq_exit_io_context(struct io_context *ioc)
1984 {
1985         call_for_each_cic(ioc, cfq_exit_single_io_context);
1986 }
1987
1988 static struct cfq_io_context *
1989 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1990 {
1991         struct cfq_io_context *cic;
1992
1993         cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
1994                                                         cfqd->queue->node);
1995         if (cic) {
1996                 cic->last_end_request = jiffies;
1997                 INIT_LIST_HEAD(&cic->queue_list);
1998                 INIT_HLIST_NODE(&cic->cic_list);
1999                 cic->dtor = cfq_free_io_context;
2000                 cic->exit = cfq_exit_io_context;
2001                 elv_ioc_count_inc(cfq_ioc_count);
2002         }
2003
2004         return cic;
2005 }
2006
2007 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
2008 {
2009         struct task_struct *tsk = current;
2010         int ioprio_class;
2011
2012         if (!cfq_cfqq_prio_changed(cfqq))
2013                 return;
2014
2015         ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
2016         switch (ioprio_class) {
2017         default:
2018                 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
2019         case IOPRIO_CLASS_NONE:
2020                 /*
2021                  * no prio set, inherit CPU scheduling settings
2022                  */
2023                 cfqq->ioprio = task_nice_ioprio(tsk);
2024                 cfqq->ioprio_class = task_nice_ioclass(tsk);
2025                 break;
2026         case IOPRIO_CLASS_RT:
2027                 cfqq->ioprio = task_ioprio(ioc);
2028                 cfqq->ioprio_class = IOPRIO_CLASS_RT;
2029                 break;
2030         case IOPRIO_CLASS_BE:
2031                 cfqq->ioprio = task_ioprio(ioc);
2032                 cfqq->ioprio_class = IOPRIO_CLASS_BE;
2033                 break;
2034         case IOPRIO_CLASS_IDLE:
2035                 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
2036                 cfqq->ioprio = 7;
2037                 cfq_clear_cfqq_idle_window(cfqq);
2038                 break;
2039         }
2040
2041         /*
2042          * keep track of original prio settings in case we have to temporarily
2043          * elevate the priority of this queue
2044          */
2045         cfqq->org_ioprio = cfqq->ioprio;
2046         cfqq->org_ioprio_class = cfqq->ioprio_class;
2047         cfq_clear_cfqq_prio_changed(cfqq);
2048 }
2049
2050 static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
2051 {
2052         struct cfq_data *cfqd = cic->key;
2053         struct cfq_queue *cfqq;
2054         unsigned long flags;
2055
2056         if (unlikely(!cfqd))
2057                 return;
2058
2059         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2060
2061         cfqq = cic->cfqq[BLK_RW_ASYNC];
2062         if (cfqq) {
2063                 struct cfq_queue *new_cfqq;
2064                 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
2065                                                 GFP_ATOMIC);
2066                 if (new_cfqq) {
2067                         cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
2068                         cfq_put_queue(cfqq);
2069                 }
2070         }
2071
2072         cfqq = cic->cfqq[BLK_RW_SYNC];
2073         if (cfqq)
2074                 cfq_mark_cfqq_prio_changed(cfqq);
2075
2076         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2077 }
2078
2079 static void cfq_ioc_set_ioprio(struct io_context *ioc)
2080 {
2081         call_for_each_cic(ioc, changed_ioprio);
2082         ioc->ioprio_changed = 0;
2083 }
2084
2085 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2086                           pid_t pid, bool is_sync)
2087 {
2088         RB_CLEAR_NODE(&cfqq->rb_node);
2089         RB_CLEAR_NODE(&cfqq->p_node);
2090         INIT_LIST_HEAD(&cfqq->fifo);
2091
2092         atomic_set(&cfqq->ref, 0);
2093         cfqq->cfqd = cfqd;
2094
2095         cfq_mark_cfqq_prio_changed(cfqq);
2096
2097         if (is_sync) {
2098                 if (!cfq_class_idle(cfqq))
2099                         cfq_mark_cfqq_idle_window(cfqq);
2100                 cfq_mark_cfqq_sync(cfqq);
2101         }
2102         cfqq->pid = pid;
2103 }
2104
2105 static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
2106 {
2107         cfqq->cfqg = cfqg;
2108 }
2109
2110 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
2111 {
2112         return &cfqd->root_group;
2113 }
2114
2115 static struct cfq_queue *
2116 cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
2117                      struct io_context *ioc, gfp_t gfp_mask)
2118 {
2119         struct cfq_queue *cfqq, *new_cfqq = NULL;
2120         struct cfq_io_context *cic;
2121         struct cfq_group *cfqg;
2122
2123 retry:
2124         cfqg = cfq_get_cfqg(cfqd, 1);
2125         cic = cfq_cic_lookup(cfqd, ioc);
2126         /* cic always exists here */
2127         cfqq = cic_to_cfqq(cic, is_sync);
2128
2129         /*
2130          * Always try a new alloc if we fell back to the OOM cfqq
2131          * originally, since it should just be a temporary situation.
2132          */
2133         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2134                 cfqq = NULL;
2135                 if (new_cfqq) {
2136                         cfqq = new_cfqq;
2137                         new_cfqq = NULL;
2138                 } else if (gfp_mask & __GFP_WAIT) {
2139                         spin_unlock_irq(cfqd->queue->queue_lock);
2140                         new_cfqq = kmem_cache_alloc_node(cfq_pool,
2141                                         gfp_mask | __GFP_ZERO,
2142                                         cfqd->queue->node);
2143                         spin_lock_irq(cfqd->queue->queue_lock);
2144                         if (new_cfqq)
2145                                 goto retry;
2146                 } else {
2147                         cfqq = kmem_cache_alloc_node(cfq_pool,
2148                                         gfp_mask | __GFP_ZERO,
2149                                         cfqd->queue->node);
2150                 }
2151
2152                 if (cfqq) {
2153                         cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
2154                         cfq_init_prio_data(cfqq, ioc);
2155                         cfq_link_cfqq_cfqg(cfqq, cfqg);
2156                         cfq_log_cfqq(cfqd, cfqq, "alloced");
2157                 } else
2158                         cfqq = &cfqd->oom_cfqq;
2159         }
2160
2161         if (new_cfqq)
2162                 kmem_cache_free(cfq_pool, new_cfqq);
2163
2164         return cfqq;
2165 }
2166
2167 static struct cfq_queue **
2168 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
2169 {
2170         switch (ioprio_class) {
2171         case IOPRIO_CLASS_RT:
2172                 return &cfqd->async_cfqq[0][ioprio];
2173         case IOPRIO_CLASS_BE:
2174                 return &cfqd->async_cfqq[1][ioprio];
2175         case IOPRIO_CLASS_IDLE:
2176                 return &cfqd->async_idle_cfqq;
2177         default:
2178                 BUG();
2179         }
2180 }
2181
2182 static struct cfq_queue *
2183 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
2184               gfp_t gfp_mask)
2185 {
2186         const int ioprio = task_ioprio(ioc);
2187         const int ioprio_class = task_ioprio_class(ioc);
2188         struct cfq_queue **async_cfqq = NULL;
2189         struct cfq_queue *cfqq = NULL;
2190
2191         if (!is_sync) {
2192                 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
2193                 cfqq = *async_cfqq;
2194         }
2195
2196         if (!cfqq)
2197                 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
2198
2199         /*
2200          * pin the queue now that it's allocated, scheduler exit will prune it
2201          */
2202         if (!is_sync && !(*async_cfqq)) {
2203                 atomic_inc(&cfqq->ref);
2204                 *async_cfqq = cfqq;
2205         }
2206
2207         atomic_inc(&cfqq->ref);
2208         return cfqq;
2209 }
2210
2211 /*
2212  * We drop cfq io contexts lazily, so we may find a dead one.
2213  */
2214 static void
2215 cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
2216                   struct cfq_io_context *cic)
2217 {
2218         unsigned long flags;
2219
2220         WARN_ON(!list_empty(&cic->queue_list));
2221
2222         spin_lock_irqsave(&ioc->lock, flags);
2223
2224         BUG_ON(ioc->ioc_data == cic);
2225
2226         radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
2227         hlist_del_rcu(&cic->cic_list);
2228         spin_unlock_irqrestore(&ioc->lock, flags);
2229
2230         cfq_cic_free(cic);
2231 }
2232
2233 static struct cfq_io_context *
2234 cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
2235 {
2236         struct cfq_io_context *cic;
2237         unsigned long flags;
2238         void *k;
2239
2240         if (unlikely(!ioc))
2241                 return NULL;
2242
2243         rcu_read_lock();
2244
2245         /*
2246          * we maintain a last-hit cache, to avoid browsing over the tree
2247          */
2248         cic = rcu_dereference(ioc->ioc_data);
2249         if (cic && cic->key == cfqd) {
2250                 rcu_read_unlock();
2251                 return cic;
2252         }
2253
2254         do {
2255                 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
2256                 rcu_read_unlock();
2257                 if (!cic)
2258                         break;
2259                 /* ->key must be copied to avoid race with cfq_exit_queue() */
2260                 k = cic->key;
2261                 if (unlikely(!k)) {
2262                         cfq_drop_dead_cic(cfqd, ioc, cic);
2263                         rcu_read_lock();
2264                         continue;
2265                 }
2266
2267                 spin_lock_irqsave(&ioc->lock, flags);
2268                 rcu_assign_pointer(ioc->ioc_data, cic);
2269                 spin_unlock_irqrestore(&ioc->lock, flags);
2270                 break;
2271         } while (1);
2272
2273         return cic;
2274 }
2275
2276 /*
2277  * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2278  * the process specific cfq io context when entered from the block layer.
2279  * Also adds the cic to a per-cfqd list, used when this queue is removed.
2280  */
2281 static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
2282                         struct cfq_io_context *cic, gfp_t gfp_mask)
2283 {
2284         unsigned long flags;
2285         int ret;
2286
2287         ret = radix_tree_preload(gfp_mask);
2288         if (!ret) {
2289                 cic->ioc = ioc;
2290                 cic->key = cfqd;
2291
2292                 spin_lock_irqsave(&ioc->lock, flags);
2293                 ret = radix_tree_insert(&ioc->radix_root,
2294                                                 (unsigned long) cfqd, cic);
2295                 if (!ret)
2296                         hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
2297                 spin_unlock_irqrestore(&ioc->lock, flags);
2298
2299                 radix_tree_preload_end();
2300
2301                 if (!ret) {
2302                         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2303                         list_add(&cic->queue_list, &cfqd->cic_list);
2304                         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2305                 }
2306         }
2307
2308         if (ret)
2309                 printk(KERN_ERR "cfq: cic link failed!\n");
2310
2311         return ret;
2312 }
2313
2314 /*
2315  * Setup general io context and cfq io context. There can be several cfq
2316  * io contexts per general io context, if this process is doing io to more
2317  * than one device managed by cfq.
2318  */
2319 static struct cfq_io_context *
2320 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2321 {
2322         struct io_context *ioc = NULL;
2323         struct cfq_io_context *cic;
2324
2325         might_sleep_if(gfp_mask & __GFP_WAIT);
2326
2327         ioc = get_io_context(gfp_mask, cfqd->queue->node);
2328         if (!ioc)
2329                 return NULL;
2330
2331         cic = cfq_cic_lookup(cfqd, ioc);
2332         if (cic)
2333                 goto out;
2334
2335         cic = cfq_alloc_io_context(cfqd, gfp_mask);
2336         if (cic == NULL)
2337                 goto err;
2338
2339         if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
2340                 goto err_free;
2341
2342 out:
2343         smp_read_barrier_depends();
2344         if (unlikely(ioc->ioprio_changed))
2345                 cfq_ioc_set_ioprio(ioc);
2346
2347         return cic;
2348 err_free:
2349         cfq_cic_free(cic);
2350 err:
2351         put_io_context(ioc);
2352         return NULL;
2353 }
2354
2355 static void
2356 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
2357 {
2358         unsigned long elapsed = jiffies - cic->last_end_request;
2359         unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
2360
2361         cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
2362         cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
2363         cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
2364 }
2365
2366 static void
2367 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2368                        struct request *rq)
2369 {
2370         sector_t sdist;
2371         u64 total;
2372
2373         if (!cfqq->last_request_pos)
2374                 sdist = 0;
2375         else if (cfqq->last_request_pos < blk_rq_pos(rq))
2376                 sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
2377         else
2378                 sdist = cfqq->last_request_pos - blk_rq_pos(rq);
2379
2380         /*
2381          * Don't allow the seek distance to get too large from the
2382          * odd fragment, pagein, etc
2383          */
2384         if (cfqq->seek_samples <= 60) /* second&third seek */
2385                 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*1024);
2386         else
2387                 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*64);
2388
2389         cfqq->seek_samples = (7*cfqq->seek_samples + 256) / 8;
2390         cfqq->seek_total = (7*cfqq->seek_total + (u64)256*sdist) / 8;
2391         total = cfqq->seek_total + (cfqq->seek_samples/2);
2392         do_div(total, cfqq->seek_samples);
2393         cfqq->seek_mean = (sector_t)total;
2394
2395         /*
2396          * If this cfqq is shared between multiple processes, check to
2397          * make sure that those processes are still issuing I/Os within
2398          * the mean seek distance.  If not, it may be time to break the
2399          * queues apart again.
2400          */
2401         if (cfq_cfqq_coop(cfqq)) {
2402                 if (CFQQ_SEEKY(cfqq) && !cfqq->seeky_start)
2403                         cfqq->seeky_start = jiffies;
2404                 else if (!CFQQ_SEEKY(cfqq))
2405                         cfqq->seeky_start = 0;
2406         }
2407 }
2408
2409 /*
2410  * Disable idle window if the process thinks too long or seeks so much that
2411  * it doesn't matter
2412  */
2413 static void
2414 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2415                        struct cfq_io_context *cic)
2416 {
2417         int old_idle, enable_idle;
2418
2419         /*
2420          * Don't idle for async or idle io prio class
2421          */
2422         if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
2423                 return;
2424
2425         enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
2426
2427         if (cfqq->queued[0] + cfqq->queued[1] >= 4)
2428                 cfq_mark_cfqq_deep(cfqq);
2429
2430         if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
2431             (!cfq_cfqq_deep(cfqq) && sample_valid(cfqq->seek_samples)
2432              && CFQQ_SEEKY(cfqq)))
2433                 enable_idle = 0;
2434         else if (sample_valid(cic->ttime_samples)) {
2435                 if (cic->ttime_mean > cfqd->cfq_slice_idle)
2436                         enable_idle = 0;
2437                 else
2438                         enable_idle = 1;
2439         }
2440
2441         if (old_idle != enable_idle) {
2442                 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
2443                 if (enable_idle)
2444                         cfq_mark_cfqq_idle_window(cfqq);
2445                 else
2446                         cfq_clear_cfqq_idle_window(cfqq);
2447         }
2448 }
2449
2450 /*
2451  * Check if new_cfqq should preempt the currently active queue. Return 0 for
2452  * no or if we aren't sure, a 1 will cause a preempt.
2453  */
2454 static bool
2455 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
2456                    struct request *rq)
2457 {
2458         struct cfq_queue *cfqq;
2459
2460         cfqq = cfqd->active_queue;
2461         if (!cfqq)
2462                 return false;
2463
2464         if (cfq_slice_used(cfqq))
2465                 return true;
2466
2467         if (cfq_class_idle(new_cfqq))
2468                 return false;
2469
2470         if (cfq_class_idle(cfqq))
2471                 return true;
2472
2473         /* Allow preemption only if we are idling on sync-noidle tree */
2474         if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
2475             cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
2476             new_cfqq->service_tree->count == 2 &&
2477             RB_EMPTY_ROOT(&cfqq->sort_list))
2478                 return true;
2479
2480         /*
2481          * if the new request is sync, but the currently running queue is
2482          * not, let the sync request have priority.
2483          */
2484         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
2485                 return true;
2486
2487         /*
2488          * So both queues are sync. Let the new request get disk time if
2489          * it's a metadata request and the current queue is doing regular IO.
2490          */
2491         if (rq_is_meta(rq) && !cfqq->meta_pending)
2492                 return true;
2493
2494         /*
2495          * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
2496          */
2497         if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
2498                 return true;
2499
2500         if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
2501                 return false;
2502
2503         /*
2504          * if this request is as-good as one we would expect from the
2505          * current cfqq, let it preempt
2506          */
2507         if (cfq_rq_close(cfqd, cfqq, rq))
2508                 return true;
2509
2510         return false;
2511 }
2512
2513 /*
2514  * cfqq preempts the active queue. if we allowed preempt with no slice left,
2515  * let it have half of its nominal slice.
2516  */
2517 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2518 {
2519         cfq_log_cfqq(cfqd, cfqq, "preempt");
2520         cfq_slice_expired(cfqd, 1);
2521
2522         /*
2523          * Put the new queue at the front of the of the current list,
2524          * so we know that it will be selected next.
2525          */
2526         BUG_ON(!cfq_cfqq_on_rr(cfqq));
2527
2528         cfq_service_tree_add(cfqd, cfqq, 1);
2529
2530         cfqq->slice_end = 0;
2531         cfq_mark_cfqq_slice_new(cfqq);
2532 }
2533
2534 /*
2535  * Called when a new fs request (rq) is added (to cfqq). Check if there's
2536  * something we should do about it
2537  */
2538 static void
2539 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2540                 struct request *rq)
2541 {
2542         struct cfq_io_context *cic = RQ_CIC(rq);
2543
2544         cfqd->rq_queued++;
2545         if (rq_is_meta(rq))
2546                 cfqq->meta_pending++;
2547
2548         cfq_update_io_thinktime(cfqd, cic);
2549         cfq_update_io_seektime(cfqd, cfqq, rq);
2550         cfq_update_idle_window(cfqd, cfqq, cic);
2551
2552         cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
2553
2554         if (cfqq == cfqd->active_queue) {
2555                 /*
2556                  * Remember that we saw a request from this process, but
2557                  * don't start queuing just yet. Otherwise we risk seeing lots
2558                  * of tiny requests, because we disrupt the normal plugging
2559                  * and merging. If the request is already larger than a single
2560                  * page, let it rip immediately. For that case we assume that
2561                  * merging is already done. Ditto for a busy system that
2562                  * has other work pending, don't risk delaying until the
2563                  * idle timer unplug to continue working.
2564                  */
2565                 if (cfq_cfqq_wait_request(cfqq)) {
2566                         if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
2567                             cfqd->busy_queues > 1) {
2568                                 del_timer(&cfqd->idle_slice_timer);
2569                                 __blk_run_queue(cfqd->queue);
2570                         } else
2571                                 cfq_mark_cfqq_must_dispatch(cfqq);
2572                 }
2573         } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
2574                 /*
2575                  * not the active queue - expire current slice if it is
2576                  * idle and has expired it's mean thinktime or this new queue
2577                  * has some old slice time left and is of higher priority or
2578                  * this new queue is RT and the current one is BE
2579                  */
2580                 cfq_preempt_queue(cfqd, cfqq);
2581                 __blk_run_queue(cfqd->queue);
2582         }
2583 }
2584
2585 static void cfq_insert_request(struct request_queue *q, struct request *rq)
2586 {
2587         struct cfq_data *cfqd = q->elevator->elevator_data;
2588         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2589
2590         cfq_log_cfqq(cfqd, cfqq, "insert_request");
2591         cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
2592
2593         rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
2594         list_add_tail(&rq->queuelist, &cfqq->fifo);
2595         cfq_add_rq_rb(rq);
2596
2597         cfq_rq_enqueued(cfqd, cfqq, rq);
2598 }
2599
2600 /*
2601  * Update hw_tag based on peak queue depth over 50 samples under
2602  * sufficient load.
2603  */
2604 static void cfq_update_hw_tag(struct cfq_data *cfqd)
2605 {
2606         struct cfq_queue *cfqq = cfqd->active_queue;
2607
2608         if (rq_in_driver(cfqd) > cfqd->hw_tag_est_depth)
2609                 cfqd->hw_tag_est_depth = rq_in_driver(cfqd);
2610
2611         if (cfqd->hw_tag == 1)
2612                 return;
2613
2614         if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
2615             rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)
2616                 return;
2617
2618         /*
2619          * If active queue hasn't enough requests and can idle, cfq might not
2620          * dispatch sufficient requests to hardware. Don't zero hw_tag in this
2621          * case
2622          */
2623         if (cfqq && cfq_cfqq_idle_window(cfqq) &&
2624             cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
2625             CFQ_HW_QUEUE_MIN && rq_in_driver(cfqd) < CFQ_HW_QUEUE_MIN)
2626                 return;
2627
2628         if (cfqd->hw_tag_samples++ < 50)
2629                 return;
2630
2631         if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
2632                 cfqd->hw_tag = 1;
2633         else
2634                 cfqd->hw_tag = 0;
2635 }
2636
2637 static void cfq_completed_request(struct request_queue *q, struct request *rq)
2638 {
2639         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2640         struct cfq_data *cfqd = cfqq->cfqd;
2641         const int sync = rq_is_sync(rq);
2642         unsigned long now;
2643
2644         now = jiffies;
2645         cfq_log_cfqq(cfqd, cfqq, "complete");
2646
2647         cfq_update_hw_tag(cfqd);
2648
2649         WARN_ON(!cfqd->rq_in_driver[sync]);
2650         WARN_ON(!cfqq->dispatched);
2651         cfqd->rq_in_driver[sync]--;
2652         cfqq->dispatched--;
2653
2654         if (cfq_cfqq_sync(cfqq))
2655                 cfqd->sync_flight--;
2656
2657         if (sync) {
2658                 RQ_CIC(rq)->last_end_request = now;
2659                 cfqd->last_end_sync_rq = now;
2660         }
2661
2662         /*
2663          * If this is the active queue, check if it needs to be expired,
2664          * or if we want to idle in case it has no pending requests.
2665          */
2666         if (cfqd->active_queue == cfqq) {
2667                 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
2668
2669                 if (cfq_cfqq_slice_new(cfqq)) {
2670                         cfq_set_prio_slice(cfqd, cfqq);
2671                         cfq_clear_cfqq_slice_new(cfqq);
2672                 }
2673                 /*
2674                  * Idling is not enabled on:
2675                  * - expired queues
2676                  * - idle-priority queues
2677                  * - async queues
2678                  * - queues with still some requests queued
2679                  * - when there is a close cooperator
2680                  */
2681                 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
2682                         cfq_slice_expired(cfqd, 1);
2683                 else if (sync && cfqq_empty &&
2684                          !cfq_close_cooperator(cfqd, cfqq)) {
2685                         cfqd->noidle_tree_requires_idle |= !rq_noidle(rq);
2686                         /*
2687                          * Idling is enabled for SYNC_WORKLOAD.
2688                          * SYNC_NOIDLE_WORKLOAD idles at the end of the tree
2689                          * only if we processed at least one !rq_noidle request
2690                          */
2691                         if (cfqd->serving_type == SYNC_WORKLOAD
2692                             || cfqd->noidle_tree_requires_idle)
2693                                 cfq_arm_slice_timer(cfqd);
2694                 }
2695         }
2696
2697         if (!rq_in_driver(cfqd))
2698                 cfq_schedule_dispatch(cfqd);
2699 }
2700
2701 /*
2702  * we temporarily boost lower priority queues if they are holding fs exclusive
2703  * resources. they are boosted to normal prio (CLASS_BE/4)
2704  */
2705 static void cfq_prio_boost(struct cfq_queue *cfqq)
2706 {
2707         if (has_fs_excl()) {
2708                 /*
2709                  * boost idle prio on transactions that would lock out other
2710                  * users of the filesystem
2711                  */
2712                 if (cfq_class_idle(cfqq))
2713                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
2714                 if (cfqq->ioprio > IOPRIO_NORM)
2715                         cfqq->ioprio = IOPRIO_NORM;
2716         } else {
2717                 /*
2718                  * unboost the queue (if needed)
2719                  */
2720                 cfqq->ioprio_class = cfqq->org_ioprio_class;
2721                 cfqq->ioprio = cfqq->org_ioprio;
2722         }
2723 }
2724
2725 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
2726 {
2727         if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
2728                 cfq_mark_cfqq_must_alloc_slice(cfqq);
2729                 return ELV_MQUEUE_MUST;
2730         }
2731
2732         return ELV_MQUEUE_MAY;
2733 }
2734
2735 static int cfq_may_queue(struct request_queue *q, int rw)
2736 {
2737         struct cfq_data *cfqd = q->elevator->elevator_data;
2738         struct task_struct *tsk = current;
2739         struct cfq_io_context *cic;
2740         struct cfq_queue *cfqq;
2741
2742         /*
2743          * don't force setup of a queue from here, as a call to may_queue
2744          * does not necessarily imply that a request actually will be queued.
2745          * so just lookup a possibly existing queue, or return 'may queue'
2746          * if that fails
2747          */
2748         cic = cfq_cic_lookup(cfqd, tsk->io_context);
2749         if (!cic)
2750                 return ELV_MQUEUE_MAY;
2751
2752         cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
2753         if (cfqq) {
2754                 cfq_init_prio_data(cfqq, cic->ioc);
2755                 cfq_prio_boost(cfqq);
2756
2757                 return __cfq_may_queue(cfqq);
2758         }
2759
2760         return ELV_MQUEUE_MAY;
2761 }
2762
2763 /*
2764  * queue lock held here
2765  */
2766 static void cfq_put_request(struct request *rq)
2767 {
2768         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2769
2770         if (cfqq) {
2771                 const int rw = rq_data_dir(rq);
2772
2773                 BUG_ON(!cfqq->allocated[rw]);
2774                 cfqq->allocated[rw]--;
2775
2776                 put_io_context(RQ_CIC(rq)->ioc);
2777
2778                 rq->elevator_private = NULL;
2779                 rq->elevator_private2 = NULL;
2780
2781                 cfq_put_queue(cfqq);
2782         }
2783 }
2784
2785 static struct cfq_queue *
2786 cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
2787                 struct cfq_queue *cfqq)
2788 {
2789         cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
2790         cic_set_cfqq(cic, cfqq->new_cfqq, 1);
2791         cfq_mark_cfqq_coop(cfqq->new_cfqq);
2792         cfq_put_queue(cfqq);
2793         return cic_to_cfqq(cic, 1);
2794 }
2795
2796 static int should_split_cfqq(struct cfq_queue *cfqq)
2797 {
2798         if (cfqq->seeky_start &&
2799             time_after(jiffies, cfqq->seeky_start + CFQQ_COOP_TOUT))
2800                 return 1;
2801         return 0;
2802 }
2803
2804 /*
2805  * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
2806  * was the last process referring to said cfqq.
2807  */
2808 static struct cfq_queue *
2809 split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
2810 {
2811         if (cfqq_process_refs(cfqq) == 1) {
2812                 cfqq->seeky_start = 0;
2813                 cfqq->pid = current->pid;
2814                 cfq_clear_cfqq_coop(cfqq);
2815                 return cfqq;
2816         }
2817
2818         cic_set_cfqq(cic, NULL, 1);
2819         cfq_put_queue(cfqq);
2820         return NULL;
2821 }
2822 /*
2823  * Allocate cfq data structures associated with this request.
2824  */
2825 static int
2826 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
2827 {
2828         struct cfq_data *cfqd = q->elevator->elevator_data;
2829         struct cfq_io_context *cic;
2830         const int rw = rq_data_dir(rq);
2831         const bool is_sync = rq_is_sync(rq);
2832         struct cfq_queue *cfqq;
2833         unsigned long flags;
2834
2835         might_sleep_if(gfp_mask & __GFP_WAIT);
2836
2837         cic = cfq_get_io_context(cfqd, gfp_mask);
2838
2839         spin_lock_irqsave(q->queue_lock, flags);
2840
2841         if (!cic)
2842                 goto queue_fail;
2843
2844 new_queue:
2845         cfqq = cic_to_cfqq(cic, is_sync);
2846         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2847                 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
2848                 cic_set_cfqq(cic, cfqq, is_sync);
2849         } else {
2850                 /*
2851                  * If the queue was seeky for too long, break it apart.
2852                  */
2853                 if (cfq_cfqq_coop(cfqq) && should_split_cfqq(cfqq)) {
2854                         cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
2855                         cfqq = split_cfqq(cic, cfqq);
2856                         if (!cfqq)
2857                                 goto new_queue;
2858                 }
2859
2860                 /*
2861                  * Check to see if this queue is scheduled to merge with
2862                  * another, closely cooperating queue.  The merging of
2863                  * queues happens here as it must be done in process context.
2864                  * The reference on new_cfqq was taken in merge_cfqqs.
2865                  */
2866                 if (cfqq->new_cfqq)
2867                         cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
2868         }
2869
2870         cfqq->allocated[rw]++;
2871         atomic_inc(&cfqq->ref);
2872
2873         spin_unlock_irqrestore(q->queue_lock, flags);
2874
2875         rq->elevator_private = cic;
2876         rq->elevator_private2 = cfqq;
2877         return 0;
2878
2879 queue_fail:
2880         if (cic)
2881                 put_io_context(cic->ioc);
2882
2883         cfq_schedule_dispatch(cfqd);
2884         spin_unlock_irqrestore(q->queue_lock, flags);
2885         cfq_log(cfqd, "set_request fail");
2886         return 1;
2887 }
2888
2889 static void cfq_kick_queue(struct work_struct *work)
2890 {
2891         struct cfq_data *cfqd =
2892                 container_of(work, struct cfq_data, unplug_work);
2893         struct request_queue *q = cfqd->queue;
2894
2895         spin_lock_irq(q->queue_lock);
2896         __blk_run_queue(cfqd->queue);
2897         spin_unlock_irq(q->queue_lock);
2898 }
2899
2900 /*
2901  * Timer running if the active_queue is currently idling inside its time slice
2902  */
2903 static void cfq_idle_slice_timer(unsigned long data)
2904 {
2905         struct cfq_data *cfqd = (struct cfq_data *) data;
2906         struct cfq_queue *cfqq;
2907         unsigned long flags;
2908         int timed_out = 1;
2909
2910         cfq_log(cfqd, "idle timer fired");
2911
2912         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2913
2914         cfqq = cfqd->active_queue;
2915         if (cfqq) {
2916                 timed_out = 0;
2917
2918                 /*
2919                  * We saw a request before the queue expired, let it through
2920                  */
2921                 if (cfq_cfqq_must_dispatch(cfqq))
2922                         goto out_kick;
2923
2924                 /*
2925                  * expired
2926                  */
2927                 if (cfq_slice_used(cfqq))
2928                         goto expire;
2929
2930                 /*
2931                  * only expire and reinvoke request handler, if there are
2932                  * other queues with pending requests
2933                  */
2934                 if (!cfqd->busy_queues)
2935                         goto out_cont;
2936
2937                 /*
2938                  * not expired and it has a request pending, let it dispatch
2939                  */
2940                 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2941                         goto out_kick;
2942
2943                 /*
2944                  * Queue depth flag is reset only when the idle didn't succeed
2945                  */
2946                 cfq_clear_cfqq_deep(cfqq);
2947         }
2948 expire:
2949         cfq_slice_expired(cfqd, timed_out);
2950 out_kick:
2951         cfq_schedule_dispatch(cfqd);
2952 out_cont:
2953         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2954 }
2955
2956 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2957 {
2958         del_timer_sync(&cfqd->idle_slice_timer);
2959         cancel_work_sync(&cfqd->unplug_work);
2960 }
2961
2962 static void cfq_put_async_queues(struct cfq_data *cfqd)
2963 {
2964         int i;
2965
2966         for (i = 0; i < IOPRIO_BE_NR; i++) {
2967                 if (cfqd->async_cfqq[0][i])
2968                         cfq_put_queue(cfqd->async_cfqq[0][i]);
2969                 if (cfqd->async_cfqq[1][i])
2970                         cfq_put_queue(cfqd->async_cfqq[1][i]);
2971         }
2972
2973         if (cfqd->async_idle_cfqq)
2974                 cfq_put_queue(cfqd->async_idle_cfqq);
2975 }
2976
2977 static void cfq_exit_queue(struct elevator_queue *e)
2978 {
2979         struct cfq_data *cfqd = e->elevator_data;
2980         struct request_queue *q = cfqd->queue;
2981
2982         cfq_shutdown_timer_wq(cfqd);
2983
2984         spin_lock_irq(q->queue_lock);
2985
2986         if (cfqd->active_queue)
2987                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
2988
2989         while (!list_empty(&cfqd->cic_list)) {
2990                 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2991                                                         struct cfq_io_context,
2992                                                         queue_list);
2993
2994                 __cfq_exit_single_io_context(cfqd, cic);
2995         }
2996
2997         cfq_put_async_queues(cfqd);
2998
2999         spin_unlock_irq(q->queue_lock);
3000
3001         cfq_shutdown_timer_wq(cfqd);
3002
3003         kfree(cfqd);
3004 }
3005
3006 static void *cfq_init_queue(struct request_queue *q)
3007 {
3008         struct cfq_data *cfqd;
3009         int i, j;
3010         struct cfq_group *cfqg;
3011         struct cfq_rb_root *st;
3012
3013         cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
3014         if (!cfqd)
3015                 return NULL;
3016
3017         /* Init root group */
3018         cfqg = &cfqd->root_group;
3019         for_each_cfqg_st(cfqg, i, j, st)
3020                 *st = CFQ_RB_ROOT;
3021
3022         /*
3023          * Not strictly needed (since RB_ROOT just clears the node and we
3024          * zeroed cfqd on alloc), but better be safe in case someone decides
3025          * to add magic to the rb code
3026          */
3027         for (i = 0; i < CFQ_PRIO_LISTS; i++)
3028                 cfqd->prio_trees[i] = RB_ROOT;
3029
3030         /*
3031          * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
3032          * Grab a permanent reference to it, so that the normal code flow
3033          * will not attempt to free it.
3034          */
3035         cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
3036         atomic_inc(&cfqd->oom_cfqq.ref);
3037         cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
3038
3039         INIT_LIST_HEAD(&cfqd->cic_list);
3040
3041         cfqd->queue = q;
3042
3043         init_timer(&cfqd->idle_slice_timer);
3044         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
3045         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
3046
3047         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
3048
3049         cfqd->cfq_quantum = cfq_quantum;
3050         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
3051         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
3052         cfqd->cfq_back_max = cfq_back_max;
3053         cfqd->cfq_back_penalty = cfq_back_penalty;
3054         cfqd->cfq_slice[0] = cfq_slice_async;
3055         cfqd->cfq_slice[1] = cfq_slice_sync;
3056         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
3057         cfqd->cfq_slice_idle = cfq_slice_idle;
3058         cfqd->cfq_latency = 1;
3059         cfqd->hw_tag = -1;
3060         cfqd->last_end_sync_rq = jiffies;
3061         return cfqd;
3062 }
3063
3064 static void cfq_slab_kill(void)
3065 {
3066         /*
3067          * Caller already ensured that pending RCU callbacks are completed,
3068          * so we should have no busy allocations at this point.
3069          */
3070         if (cfq_pool)
3071                 kmem_cache_destroy(cfq_pool);
3072         if (cfq_ioc_pool)
3073                 kmem_cache_destroy(cfq_ioc_pool);
3074 }
3075
3076 static int __init cfq_slab_setup(void)
3077 {
3078         cfq_pool = KMEM_CACHE(cfq_queue, 0);
3079         if (!cfq_pool)
3080                 goto fail;
3081
3082         cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
3083         if (!cfq_ioc_pool)
3084                 goto fail;
3085
3086         return 0;
3087 fail:
3088         cfq_slab_kill();
3089         return -ENOMEM;
3090 }
3091
3092 /*
3093  * sysfs parts below -->
3094  */
3095 static ssize_t
3096 cfq_var_show(unsigned int var, char *page)
3097 {
3098         return sprintf(page, "%d\n", var);
3099 }
3100
3101 static ssize_t
3102 cfq_var_store(unsigned int *var, const char *page, size_t count)
3103 {
3104         char *p = (char *) page;
3105
3106         *var = simple_strtoul(p, &p, 10);
3107         return count;
3108 }
3109
3110 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
3111 static ssize_t __FUNC(struct elevator_queue *e, char *page)             \
3112 {                                                                       \
3113         struct cfq_data *cfqd = e->elevator_data;                       \
3114         unsigned int __data = __VAR;                                    \
3115         if (__CONV)                                                     \
3116                 __data = jiffies_to_msecs(__data);                      \
3117         return cfq_var_show(__data, (page));                            \
3118 }
3119 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
3120 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
3121 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
3122 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
3123 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
3124 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
3125 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
3126 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
3127 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
3128 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
3129 #undef SHOW_FUNCTION
3130
3131 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
3132 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3133 {                                                                       \
3134         struct cfq_data *cfqd = e->elevator_data;                       \
3135         unsigned int __data;                                            \
3136         int ret = cfq_var_store(&__data, (page), count);                \
3137         if (__data < (MIN))                                             \
3138                 __data = (MIN);                                         \
3139         else if (__data > (MAX))                                        \
3140                 __data = (MAX);                                         \
3141         if (__CONV)                                                     \
3142                 *(__PTR) = msecs_to_jiffies(__data);                    \
3143         else                                                            \
3144                 *(__PTR) = __data;                                      \
3145         return ret;                                                     \
3146 }
3147 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
3148 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
3149                 UINT_MAX, 1);
3150 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
3151                 UINT_MAX, 1);
3152 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
3153 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
3154                 UINT_MAX, 0);
3155 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
3156 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
3157 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
3158 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
3159                 UINT_MAX, 0);
3160 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
3161 #undef STORE_FUNCTION
3162
3163 #define CFQ_ATTR(name) \
3164         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3165
3166 static struct elv_fs_entry cfq_attrs[] = {
3167         CFQ_ATTR(quantum),
3168         CFQ_ATTR(fifo_expire_sync),
3169         CFQ_ATTR(fifo_expire_async),
3170         CFQ_ATTR(back_seek_max),
3171         CFQ_ATTR(back_seek_penalty),
3172         CFQ_ATTR(slice_sync),
3173         CFQ_ATTR(slice_async),
3174         CFQ_ATTR(slice_async_rq),
3175         CFQ_ATTR(slice_idle),
3176         CFQ_ATTR(low_latency),
3177         __ATTR_NULL
3178 };
3179
3180 static struct elevator_type iosched_cfq = {
3181         .ops = {
3182                 .elevator_merge_fn =            cfq_merge,
3183                 .elevator_merged_fn =           cfq_merged_request,
3184                 .elevator_merge_req_fn =        cfq_merged_requests,
3185                 .elevator_allow_merge_fn =      cfq_allow_merge,
3186                 .elevator_dispatch_fn =         cfq_dispatch_requests,
3187                 .elevator_add_req_fn =          cfq_insert_request,
3188                 .elevator_activate_req_fn =     cfq_activate_request,
3189                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
3190                 .elevator_queue_empty_fn =      cfq_queue_empty,
3191                 .elevator_completed_req_fn =    cfq_completed_request,
3192                 .elevator_former_req_fn =       elv_rb_former_request,
3193                 .elevator_latter_req_fn =       elv_rb_latter_request,
3194                 .elevator_set_req_fn =          cfq_set_request,
3195                 .elevator_put_req_fn =          cfq_put_request,
3196                 .elevator_may_queue_fn =        cfq_may_queue,
3197                 .elevator_init_fn =             cfq_init_queue,
3198                 .elevator_exit_fn =             cfq_exit_queue,
3199                 .trim =                         cfq_free_io_context,
3200         },
3201         .elevator_attrs =       cfq_attrs,
3202         .elevator_name =        "cfq",
3203         .elevator_owner =       THIS_MODULE,
3204 };
3205
3206 static int __init cfq_init(void)
3207 {
3208         /*
3209          * could be 0 on HZ < 1000 setups
3210          */
3211         if (!cfq_slice_async)
3212                 cfq_slice_async = 1;
3213         if (!cfq_slice_idle)
3214                 cfq_slice_idle = 1;
3215
3216         if (cfq_slab_setup())
3217                 return -ENOMEM;
3218
3219         elv_register(&iosched_cfq);
3220
3221         return 0;
3222 }
3223
3224 static void __exit cfq_exit(void)
3225 {
3226         DECLARE_COMPLETION_ONSTACK(all_gone);
3227         elv_unregister(&iosched_cfq);
3228         ioc_gone = &all_gone;
3229         /* ioc_gone's update must be visible before reading ioc_count */
3230         smp_wmb();
3231
3232         /*
3233          * this also protects us from entering cfq_slab_kill() with
3234          * pending RCU callbacks
3235          */
3236         if (elv_ioc_count_read(cfq_ioc_count))
3237                 wait_for_completion(&all_gone);
3238         cfq_slab_kill();
3239 }
3240
3241 module_init(cfq_init);
3242 module_exit(cfq_exit);
3243
3244 MODULE_AUTHOR("Jens Axboe");
3245 MODULE_LICENSE("GPL");
3246 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");