388fe01de18e845b6be4b27aa36827dd0a15de15
[sfrench/cifs-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/slab.h>
11 #include <linux/blkdev.h>
12 #include <linux/elevator.h>
13 #include <linux/jiffies.h>
14 #include <linux/rbtree.h>
15 #include <linux/ioprio.h>
16 #include <linux/blktrace_api.h>
17 #include "blk.h"
18 #include "cfq.h"
19
20 /*
21  * tunables
22  */
23 /* max queue in one round of service */
24 static const int cfq_quantum = 8;
25 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
26 /* maximum backwards seek, in KiB */
27 static const int cfq_back_max = 16 * 1024;
28 /* penalty of a backwards seek */
29 static const int cfq_back_penalty = 2;
30 static const int cfq_slice_sync = HZ / 10;
31 static int cfq_slice_async = HZ / 25;
32 static const int cfq_slice_async_rq = 2;
33 static int cfq_slice_idle = HZ / 125;
34 static int cfq_group_idle = HZ / 125;
35 static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
36 static const int cfq_hist_divisor = 4;
37
38 /*
39  * offset from end of service tree
40  */
41 #define CFQ_IDLE_DELAY          (HZ / 5)
42
43 /*
44  * below this threshold, we consider thinktime immediate
45  */
46 #define CFQ_MIN_TT              (2)
47
48 #define CFQ_SLICE_SCALE         (5)
49 #define CFQ_HW_QUEUE_MIN        (5)
50 #define CFQ_SERVICE_SHIFT       12
51
52 #define CFQQ_SEEK_THR           (sector_t)(8 * 100)
53 #define CFQQ_CLOSE_THR          (sector_t)(8 * 1024)
54 #define CFQQ_SECT_THR_NONROT    (sector_t)(2 * 32)
55 #define CFQQ_SEEKY(cfqq)        (hweight32(cfqq->seek_history) > 32/8)
56
57 #define RQ_CIC(rq)              icq_to_cic((rq)->elv.icq)
58 #define RQ_CFQQ(rq)             (struct cfq_queue *) ((rq)->elv.priv[0])
59 #define RQ_CFQG(rq)             (struct cfq_group *) ((rq)->elv.priv[1])
60
61 static struct kmem_cache *cfq_pool;
62
63 #define CFQ_PRIO_LISTS          IOPRIO_BE_NR
64 #define cfq_class_idle(cfqq)    ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
65 #define cfq_class_rt(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
66
67 #define sample_valid(samples)   ((samples) > 80)
68 #define rb_entry_cfqg(node)     rb_entry((node), struct cfq_group, rb_node)
69
70 struct cfq_ttime {
71         unsigned long last_end_request;
72
73         unsigned long ttime_total;
74         unsigned long ttime_samples;
75         unsigned long ttime_mean;
76 };
77
78 /*
79  * Most of our rbtree usage is for sorting with min extraction, so
80  * if we cache the leftmost node we don't have to walk down the tree
81  * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
82  * move this into the elevator for the rq sorting as well.
83  */
84 struct cfq_rb_root {
85         struct rb_root rb;
86         struct rb_node *left;
87         unsigned count;
88         unsigned total_weight;
89         u64 min_vdisktime;
90         struct cfq_ttime ttime;
91 };
92 #define CFQ_RB_ROOT     (struct cfq_rb_root) { .rb = RB_ROOT, \
93                         .ttime = {.last_end_request = jiffies,},}
94
95 /*
96  * Per process-grouping structure
97  */
98 struct cfq_queue {
99         /* reference count */
100         int ref;
101         /* various state flags, see below */
102         unsigned int flags;
103         /* parent cfq_data */
104         struct cfq_data *cfqd;
105         /* service_tree member */
106         struct rb_node rb_node;
107         /* service_tree key */
108         unsigned long rb_key;
109         /* prio tree member */
110         struct rb_node p_node;
111         /* prio tree root we belong to, if any */
112         struct rb_root *p_root;
113         /* sorted list of pending requests */
114         struct rb_root sort_list;
115         /* if fifo isn't expired, next request to serve */
116         struct request *next_rq;
117         /* requests queued in sort_list */
118         int queued[2];
119         /* currently allocated requests */
120         int allocated[2];
121         /* fifo list of requests in sort_list */
122         struct list_head fifo;
123
124         /* time when queue got scheduled in to dispatch first request. */
125         unsigned long dispatch_start;
126         unsigned int allocated_slice;
127         unsigned int slice_dispatch;
128         /* time when first request from queue completed and slice started. */
129         unsigned long slice_start;
130         unsigned long slice_end;
131         long slice_resid;
132
133         /* pending priority requests */
134         int prio_pending;
135         /* number of requests that are on the dispatch list or inside driver */
136         int dispatched;
137
138         /* io prio of this group */
139         unsigned short ioprio, org_ioprio;
140         unsigned short ioprio_class;
141
142         pid_t pid;
143
144         u32 seek_history;
145         sector_t last_request_pos;
146
147         struct cfq_rb_root *service_tree;
148         struct cfq_queue *new_cfqq;
149         struct cfq_group *cfqg;
150         /* Number of sectors dispatched from queue in single dispatch round */
151         unsigned long nr_sectors;
152 };
153
154 /*
155  * First index in the service_trees.
156  * IDLE is handled separately, so it has negative index
157  */
158 enum wl_prio_t {
159         BE_WORKLOAD = 0,
160         RT_WORKLOAD = 1,
161         IDLE_WORKLOAD = 2,
162         CFQ_PRIO_NR,
163 };
164
165 /*
166  * Second index in the service_trees.
167  */
168 enum wl_type_t {
169         ASYNC_WORKLOAD = 0,
170         SYNC_NOIDLE_WORKLOAD = 1,
171         SYNC_WORKLOAD = 2
172 };
173
174 /* This is per cgroup per device grouping structure */
175 struct cfq_group {
176         /* group service_tree member */
177         struct rb_node rb_node;
178
179         /* group service_tree key */
180         u64 vdisktime;
181         unsigned int weight;
182         unsigned int new_weight;
183         bool needs_update;
184
185         /* number of cfqq currently on this group */
186         int nr_cfqq;
187
188         /*
189          * Per group busy queues average. Useful for workload slice calc. We
190          * create the array for each prio class but at run time it is used
191          * only for RT and BE class and slot for IDLE class remains unused.
192          * This is primarily done to avoid confusion and a gcc warning.
193          */
194         unsigned int busy_queues_avg[CFQ_PRIO_NR];
195         /*
196          * rr lists of queues with requests. We maintain service trees for
197          * RT and BE classes. These trees are subdivided in subclasses
198          * of SYNC, SYNC_NOIDLE and ASYNC based on workload type. For IDLE
199          * class there is no subclassification and all the cfq queues go on
200          * a single tree service_tree_idle.
201          * Counts are embedded in the cfq_rb_root
202          */
203         struct cfq_rb_root service_trees[2][3];
204         struct cfq_rb_root service_tree_idle;
205
206         unsigned long saved_workload_slice;
207         enum wl_type_t saved_workload;
208         enum wl_prio_t saved_serving_prio;
209         struct blkio_group blkg;
210 #ifdef CONFIG_CFQ_GROUP_IOSCHED
211         struct hlist_node cfqd_node;
212         int ref;
213 #endif
214         /* number of requests that are on the dispatch list or inside driver */
215         int dispatched;
216         struct cfq_ttime ttime;
217 };
218
219 struct cfq_io_cq {
220         struct io_cq            icq;            /* must be the first member */
221         struct cfq_queue        *cfqq[2];
222         struct cfq_ttime        ttime;
223 };
224
225 /*
226  * Per block device queue structure
227  */
228 struct cfq_data {
229         struct request_queue *queue;
230         /* Root service tree for cfq_groups */
231         struct cfq_rb_root grp_service_tree;
232         struct cfq_group root_group;
233
234         /*
235          * The priority currently being served
236          */
237         enum wl_prio_t serving_prio;
238         enum wl_type_t serving_type;
239         unsigned long workload_expires;
240         struct cfq_group *serving_group;
241
242         /*
243          * Each priority tree is sorted by next_request position.  These
244          * trees are used when determining if two or more queues are
245          * interleaving requests (see cfq_close_cooperator).
246          */
247         struct rb_root prio_trees[CFQ_PRIO_LISTS];
248
249         unsigned int busy_queues;
250         unsigned int busy_sync_queues;
251
252         int rq_in_driver;
253         int rq_in_flight[2];
254
255         /*
256          * queue-depth detection
257          */
258         int rq_queued;
259         int hw_tag;
260         /*
261          * hw_tag can be
262          * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
263          *  1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
264          *  0 => no NCQ
265          */
266         int hw_tag_est_depth;
267         unsigned int hw_tag_samples;
268
269         /*
270          * idle window management
271          */
272         struct timer_list idle_slice_timer;
273         struct work_struct unplug_work;
274
275         struct cfq_queue *active_queue;
276         struct cfq_io_cq *active_cic;
277
278         /*
279          * async queue for each priority case
280          */
281         struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
282         struct cfq_queue *async_idle_cfqq;
283
284         sector_t last_position;
285
286         /*
287          * tunables, see top of file
288          */
289         unsigned int cfq_quantum;
290         unsigned int cfq_fifo_expire[2];
291         unsigned int cfq_back_penalty;
292         unsigned int cfq_back_max;
293         unsigned int cfq_slice[2];
294         unsigned int cfq_slice_async_rq;
295         unsigned int cfq_slice_idle;
296         unsigned int cfq_group_idle;
297         unsigned int cfq_latency;
298
299         /*
300          * Fallback dummy cfqq for extreme OOM conditions
301          */
302         struct cfq_queue oom_cfqq;
303
304         unsigned long last_delayed_sync;
305
306         /* List of cfq groups being managed on this device*/
307         struct hlist_head cfqg_list;
308
309         /* Number of groups which are on blkcg->blkg_list */
310         unsigned int nr_blkcg_linked_grps;
311 };
312
313 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
314
315 static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
316                                             enum wl_prio_t prio,
317                                             enum wl_type_t type)
318 {
319         if (!cfqg)
320                 return NULL;
321
322         if (prio == IDLE_WORKLOAD)
323                 return &cfqg->service_tree_idle;
324
325         return &cfqg->service_trees[prio][type];
326 }
327
328 enum cfqq_state_flags {
329         CFQ_CFQQ_FLAG_on_rr = 0,        /* on round-robin busy list */
330         CFQ_CFQQ_FLAG_wait_request,     /* waiting for a request */
331         CFQ_CFQQ_FLAG_must_dispatch,    /* must be allowed a dispatch */
332         CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
333         CFQ_CFQQ_FLAG_fifo_expire,      /* FIFO checked in this slice */
334         CFQ_CFQQ_FLAG_idle_window,      /* slice idling enabled */
335         CFQ_CFQQ_FLAG_prio_changed,     /* task priority has changed */
336         CFQ_CFQQ_FLAG_slice_new,        /* no requests dispatched in slice */
337         CFQ_CFQQ_FLAG_sync,             /* synchronous queue */
338         CFQ_CFQQ_FLAG_coop,             /* cfqq is shared */
339         CFQ_CFQQ_FLAG_split_coop,       /* shared cfqq will be splitted */
340         CFQ_CFQQ_FLAG_deep,             /* sync cfqq experienced large depth */
341         CFQ_CFQQ_FLAG_wait_busy,        /* Waiting for next request */
342 };
343
344 #define CFQ_CFQQ_FNS(name)                                              \
345 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
346 {                                                                       \
347         (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name);                   \
348 }                                                                       \
349 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
350 {                                                                       \
351         (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                  \
352 }                                                                       \
353 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
354 {                                                                       \
355         return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;      \
356 }
357
358 CFQ_CFQQ_FNS(on_rr);
359 CFQ_CFQQ_FNS(wait_request);
360 CFQ_CFQQ_FNS(must_dispatch);
361 CFQ_CFQQ_FNS(must_alloc_slice);
362 CFQ_CFQQ_FNS(fifo_expire);
363 CFQ_CFQQ_FNS(idle_window);
364 CFQ_CFQQ_FNS(prio_changed);
365 CFQ_CFQQ_FNS(slice_new);
366 CFQ_CFQQ_FNS(sync);
367 CFQ_CFQQ_FNS(coop);
368 CFQ_CFQQ_FNS(split_coop);
369 CFQ_CFQQ_FNS(deep);
370 CFQ_CFQQ_FNS(wait_busy);
371 #undef CFQ_CFQQ_FNS
372
373 #ifdef CONFIG_CFQ_GROUP_IOSCHED
374 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
375         blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
376                         cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
377                         blkg_path(&(cfqq)->cfqg->blkg), ##args)
378
379 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)                          \
380         blk_add_trace_msg((cfqd)->queue, "%s " fmt,                     \
381                                 blkg_path(&(cfqg)->blkg), ##args)       \
382
383 #else
384 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
385         blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
386 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)          do {} while (0)
387 #endif
388 #define cfq_log(cfqd, fmt, args...)     \
389         blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
390
391 /* Traverses through cfq group service trees */
392 #define for_each_cfqg_st(cfqg, i, j, st) \
393         for (i = 0; i <= IDLE_WORKLOAD; i++) \
394                 for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
395                         : &cfqg->service_tree_idle; \
396                         (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
397                         (i == IDLE_WORKLOAD && j == 0); \
398                         j++, st = i < IDLE_WORKLOAD ? \
399                         &cfqg->service_trees[i][j]: NULL) \
400
401 static inline bool cfq_io_thinktime_big(struct cfq_data *cfqd,
402         struct cfq_ttime *ttime, bool group_idle)
403 {
404         unsigned long slice;
405         if (!sample_valid(ttime->ttime_samples))
406                 return false;
407         if (group_idle)
408                 slice = cfqd->cfq_group_idle;
409         else
410                 slice = cfqd->cfq_slice_idle;
411         return ttime->ttime_mean > slice;
412 }
413
414 static inline bool iops_mode(struct cfq_data *cfqd)
415 {
416         /*
417          * If we are not idling on queues and it is a NCQ drive, parallel
418          * execution of requests is on and measuring time is not possible
419          * in most of the cases until and unless we drive shallower queue
420          * depths and that becomes a performance bottleneck. In such cases
421          * switch to start providing fairness in terms of number of IOs.
422          */
423         if (!cfqd->cfq_slice_idle && cfqd->hw_tag)
424                 return true;
425         else
426                 return false;
427 }
428
429 static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
430 {
431         if (cfq_class_idle(cfqq))
432                 return IDLE_WORKLOAD;
433         if (cfq_class_rt(cfqq))
434                 return RT_WORKLOAD;
435         return BE_WORKLOAD;
436 }
437
438
439 static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
440 {
441         if (!cfq_cfqq_sync(cfqq))
442                 return ASYNC_WORKLOAD;
443         if (!cfq_cfqq_idle_window(cfqq))
444                 return SYNC_NOIDLE_WORKLOAD;
445         return SYNC_WORKLOAD;
446 }
447
448 static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl,
449                                         struct cfq_data *cfqd,
450                                         struct cfq_group *cfqg)
451 {
452         if (wl == IDLE_WORKLOAD)
453                 return cfqg->service_tree_idle.count;
454
455         return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
456                 + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
457                 + cfqg->service_trees[wl][SYNC_WORKLOAD].count;
458 }
459
460 static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
461                                         struct cfq_group *cfqg)
462 {
463         return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count
464                 + cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
465 }
466
467 static void cfq_dispatch_insert(struct request_queue *, struct request *);
468 static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
469                                        struct io_context *, gfp_t);
470
471 static inline struct cfq_io_cq *icq_to_cic(struct io_cq *icq)
472 {
473         /* cic->icq is the first member, %NULL will convert to %NULL */
474         return container_of(icq, struct cfq_io_cq, icq);
475 }
476
477 static inline struct cfq_io_cq *cfq_cic_lookup(struct cfq_data *cfqd,
478                                                struct io_context *ioc)
479 {
480         if (ioc)
481                 return icq_to_cic(ioc_lookup_icq(ioc, cfqd->queue));
482         return NULL;
483 }
484
485 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_cq *cic, bool is_sync)
486 {
487         return cic->cfqq[is_sync];
488 }
489
490 static inline void cic_set_cfqq(struct cfq_io_cq *cic, struct cfq_queue *cfqq,
491                                 bool is_sync)
492 {
493         cic->cfqq[is_sync] = cfqq;
494 }
495
496 static inline struct cfq_data *cic_to_cfqd(struct cfq_io_cq *cic)
497 {
498         return cic->icq.q->elevator->elevator_data;
499 }
500
501 /*
502  * We regard a request as SYNC, if it's either a read or has the SYNC bit
503  * set (in which case it could also be direct WRITE).
504  */
505 static inline bool cfq_bio_sync(struct bio *bio)
506 {
507         return bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC);
508 }
509
510 /*
511  * scheduler run of queue, if there are requests pending and no one in the
512  * driver that will restart queueing
513  */
514 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
515 {
516         if (cfqd->busy_queues) {
517                 cfq_log(cfqd, "schedule dispatch");
518                 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
519         }
520 }
521
522 /*
523  * Scale schedule slice based on io priority. Use the sync time slice only
524  * if a queue is marked sync and has sync io queued. A sync queue with async
525  * io only, should not get full sync slice length.
526  */
527 static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
528                                  unsigned short prio)
529 {
530         const int base_slice = cfqd->cfq_slice[sync];
531
532         WARN_ON(prio >= IOPRIO_BE_NR);
533
534         return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
535 }
536
537 static inline int
538 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
539 {
540         return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
541 }
542
543 static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
544 {
545         u64 d = delta << CFQ_SERVICE_SHIFT;
546
547         d = d * BLKIO_WEIGHT_DEFAULT;
548         do_div(d, cfqg->weight);
549         return d;
550 }
551
552 static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
553 {
554         s64 delta = (s64)(vdisktime - min_vdisktime);
555         if (delta > 0)
556                 min_vdisktime = vdisktime;
557
558         return min_vdisktime;
559 }
560
561 static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
562 {
563         s64 delta = (s64)(vdisktime - min_vdisktime);
564         if (delta < 0)
565                 min_vdisktime = vdisktime;
566
567         return min_vdisktime;
568 }
569
570 static void update_min_vdisktime(struct cfq_rb_root *st)
571 {
572         struct cfq_group *cfqg;
573
574         if (st->left) {
575                 cfqg = rb_entry_cfqg(st->left);
576                 st->min_vdisktime = max_vdisktime(st->min_vdisktime,
577                                                   cfqg->vdisktime);
578         }
579 }
580
581 /*
582  * get averaged number of queues of RT/BE priority.
583  * average is updated, with a formula that gives more weight to higher numbers,
584  * to quickly follows sudden increases and decrease slowly
585  */
586
587 static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
588                                         struct cfq_group *cfqg, bool rt)
589 {
590         unsigned min_q, max_q;
591         unsigned mult  = cfq_hist_divisor - 1;
592         unsigned round = cfq_hist_divisor / 2;
593         unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
594
595         min_q = min(cfqg->busy_queues_avg[rt], busy);
596         max_q = max(cfqg->busy_queues_avg[rt], busy);
597         cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
598                 cfq_hist_divisor;
599         return cfqg->busy_queues_avg[rt];
600 }
601
602 static inline unsigned
603 cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
604 {
605         struct cfq_rb_root *st = &cfqd->grp_service_tree;
606
607         return cfq_target_latency * cfqg->weight / st->total_weight;
608 }
609
610 static inline unsigned
611 cfq_scaled_cfqq_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
612 {
613         unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
614         if (cfqd->cfq_latency) {
615                 /*
616                  * interested queues (we consider only the ones with the same
617                  * priority class in the cfq group)
618                  */
619                 unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
620                                                 cfq_class_rt(cfqq));
621                 unsigned sync_slice = cfqd->cfq_slice[1];
622                 unsigned expect_latency = sync_slice * iq;
623                 unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
624
625                 if (expect_latency > group_slice) {
626                         unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
627                         /* scale low_slice according to IO priority
628                          * and sync vs async */
629                         unsigned low_slice =
630                                 min(slice, base_low_slice * slice / sync_slice);
631                         /* the adapted slice value is scaled to fit all iqs
632                          * into the target latency */
633                         slice = max(slice * group_slice / expect_latency,
634                                     low_slice);
635                 }
636         }
637         return slice;
638 }
639
640 static inline void
641 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
642 {
643         unsigned slice = cfq_scaled_cfqq_slice(cfqd, cfqq);
644
645         cfqq->slice_start = jiffies;
646         cfqq->slice_end = jiffies + slice;
647         cfqq->allocated_slice = slice;
648         cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
649 }
650
651 /*
652  * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
653  * isn't valid until the first request from the dispatch is activated
654  * and the slice time set.
655  */
656 static inline bool cfq_slice_used(struct cfq_queue *cfqq)
657 {
658         if (cfq_cfqq_slice_new(cfqq))
659                 return false;
660         if (time_before(jiffies, cfqq->slice_end))
661                 return false;
662
663         return true;
664 }
665
666 /*
667  * Lifted from AS - choose which of rq1 and rq2 that is best served now.
668  * We choose the request that is closest to the head right now. Distance
669  * behind the head is penalized and only allowed to a certain extent.
670  */
671 static struct request *
672 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
673 {
674         sector_t s1, s2, d1 = 0, d2 = 0;
675         unsigned long back_max;
676 #define CFQ_RQ1_WRAP    0x01 /* request 1 wraps */
677 #define CFQ_RQ2_WRAP    0x02 /* request 2 wraps */
678         unsigned wrap = 0; /* bit mask: requests behind the disk head? */
679
680         if (rq1 == NULL || rq1 == rq2)
681                 return rq2;
682         if (rq2 == NULL)
683                 return rq1;
684
685         if (rq_is_sync(rq1) != rq_is_sync(rq2))
686                 return rq_is_sync(rq1) ? rq1 : rq2;
687
688         if ((rq1->cmd_flags ^ rq2->cmd_flags) & REQ_PRIO)
689                 return rq1->cmd_flags & REQ_PRIO ? rq1 : rq2;
690
691         s1 = blk_rq_pos(rq1);
692         s2 = blk_rq_pos(rq2);
693
694         /*
695          * by definition, 1KiB is 2 sectors
696          */
697         back_max = cfqd->cfq_back_max * 2;
698
699         /*
700          * Strict one way elevator _except_ in the case where we allow
701          * short backward seeks which are biased as twice the cost of a
702          * similar forward seek.
703          */
704         if (s1 >= last)
705                 d1 = s1 - last;
706         else if (s1 + back_max >= last)
707                 d1 = (last - s1) * cfqd->cfq_back_penalty;
708         else
709                 wrap |= CFQ_RQ1_WRAP;
710
711         if (s2 >= last)
712                 d2 = s2 - last;
713         else if (s2 + back_max >= last)
714                 d2 = (last - s2) * cfqd->cfq_back_penalty;
715         else
716                 wrap |= CFQ_RQ2_WRAP;
717
718         /* Found required data */
719
720         /*
721          * By doing switch() on the bit mask "wrap" we avoid having to
722          * check two variables for all permutations: --> faster!
723          */
724         switch (wrap) {
725         case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
726                 if (d1 < d2)
727                         return rq1;
728                 else if (d2 < d1)
729                         return rq2;
730                 else {
731                         if (s1 >= s2)
732                                 return rq1;
733                         else
734                                 return rq2;
735                 }
736
737         case CFQ_RQ2_WRAP:
738                 return rq1;
739         case CFQ_RQ1_WRAP:
740                 return rq2;
741         case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
742         default:
743                 /*
744                  * Since both rqs are wrapped,
745                  * start with the one that's further behind head
746                  * (--> only *one* back seek required),
747                  * since back seek takes more time than forward.
748                  */
749                 if (s1 <= s2)
750                         return rq1;
751                 else
752                         return rq2;
753         }
754 }
755
756 /*
757  * The below is leftmost cache rbtree addon
758  */
759 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
760 {
761         /* Service tree is empty */
762         if (!root->count)
763                 return NULL;
764
765         if (!root->left)
766                 root->left = rb_first(&root->rb);
767
768         if (root->left)
769                 return rb_entry(root->left, struct cfq_queue, rb_node);
770
771         return NULL;
772 }
773
774 static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
775 {
776         if (!root->left)
777                 root->left = rb_first(&root->rb);
778
779         if (root->left)
780                 return rb_entry_cfqg(root->left);
781
782         return NULL;
783 }
784
785 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
786 {
787         rb_erase(n, root);
788         RB_CLEAR_NODE(n);
789 }
790
791 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
792 {
793         if (root->left == n)
794                 root->left = NULL;
795         rb_erase_init(n, &root->rb);
796         --root->count;
797 }
798
799 /*
800  * would be nice to take fifo expire time into account as well
801  */
802 static struct request *
803 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
804                   struct request *last)
805 {
806         struct rb_node *rbnext = rb_next(&last->rb_node);
807         struct rb_node *rbprev = rb_prev(&last->rb_node);
808         struct request *next = NULL, *prev = NULL;
809
810         BUG_ON(RB_EMPTY_NODE(&last->rb_node));
811
812         if (rbprev)
813                 prev = rb_entry_rq(rbprev);
814
815         if (rbnext)
816                 next = rb_entry_rq(rbnext);
817         else {
818                 rbnext = rb_first(&cfqq->sort_list);
819                 if (rbnext && rbnext != &last->rb_node)
820                         next = rb_entry_rq(rbnext);
821         }
822
823         return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
824 }
825
826 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
827                                       struct cfq_queue *cfqq)
828 {
829         /*
830          * just an approximation, should be ok.
831          */
832         return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
833                        cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
834 }
835
836 static inline s64
837 cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
838 {
839         return cfqg->vdisktime - st->min_vdisktime;
840 }
841
842 static void
843 __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
844 {
845         struct rb_node **node = &st->rb.rb_node;
846         struct rb_node *parent = NULL;
847         struct cfq_group *__cfqg;
848         s64 key = cfqg_key(st, cfqg);
849         int left = 1;
850
851         while (*node != NULL) {
852                 parent = *node;
853                 __cfqg = rb_entry_cfqg(parent);
854
855                 if (key < cfqg_key(st, __cfqg))
856                         node = &parent->rb_left;
857                 else {
858                         node = &parent->rb_right;
859                         left = 0;
860                 }
861         }
862
863         if (left)
864                 st->left = &cfqg->rb_node;
865
866         rb_link_node(&cfqg->rb_node, parent, node);
867         rb_insert_color(&cfqg->rb_node, &st->rb);
868 }
869
870 static void
871 cfq_update_group_weight(struct cfq_group *cfqg)
872 {
873         BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
874         if (cfqg->needs_update) {
875                 cfqg->weight = cfqg->new_weight;
876                 cfqg->needs_update = false;
877         }
878 }
879
880 static void
881 cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
882 {
883         BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
884
885         cfq_update_group_weight(cfqg);
886         __cfq_group_service_tree_add(st, cfqg);
887         st->total_weight += cfqg->weight;
888 }
889
890 static void
891 cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
892 {
893         struct cfq_rb_root *st = &cfqd->grp_service_tree;
894         struct cfq_group *__cfqg;
895         struct rb_node *n;
896
897         cfqg->nr_cfqq++;
898         if (!RB_EMPTY_NODE(&cfqg->rb_node))
899                 return;
900
901         /*
902          * Currently put the group at the end. Later implement something
903          * so that groups get lesser vtime based on their weights, so that
904          * if group does not loose all if it was not continuously backlogged.
905          */
906         n = rb_last(&st->rb);
907         if (n) {
908                 __cfqg = rb_entry_cfqg(n);
909                 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
910         } else
911                 cfqg->vdisktime = st->min_vdisktime;
912         cfq_group_service_tree_add(st, cfqg);
913 }
914
915 static void
916 cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg)
917 {
918         st->total_weight -= cfqg->weight;
919         if (!RB_EMPTY_NODE(&cfqg->rb_node))
920                 cfq_rb_erase(&cfqg->rb_node, st);
921 }
922
923 static void
924 cfq_group_notify_queue_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
925 {
926         struct cfq_rb_root *st = &cfqd->grp_service_tree;
927
928         BUG_ON(cfqg->nr_cfqq < 1);
929         cfqg->nr_cfqq--;
930
931         /* If there are other cfq queues under this group, don't delete it */
932         if (cfqg->nr_cfqq)
933                 return;
934
935         cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
936         cfq_group_service_tree_del(st, cfqg);
937         cfqg->saved_workload_slice = 0;
938         cfq_blkiocg_update_dequeue_stats(&cfqg->blkg, 1);
939 }
940
941 static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq,
942                                                 unsigned int *unaccounted_time)
943 {
944         unsigned int slice_used;
945
946         /*
947          * Queue got expired before even a single request completed or
948          * got expired immediately after first request completion.
949          */
950         if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
951                 /*
952                  * Also charge the seek time incurred to the group, otherwise
953                  * if there are mutiple queues in the group, each can dispatch
954                  * a single request on seeky media and cause lots of seek time
955                  * and group will never know it.
956                  */
957                 slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
958                                         1);
959         } else {
960                 slice_used = jiffies - cfqq->slice_start;
961                 if (slice_used > cfqq->allocated_slice) {
962                         *unaccounted_time = slice_used - cfqq->allocated_slice;
963                         slice_used = cfqq->allocated_slice;
964                 }
965                 if (time_after(cfqq->slice_start, cfqq->dispatch_start))
966                         *unaccounted_time += cfqq->slice_start -
967                                         cfqq->dispatch_start;
968         }
969
970         return slice_used;
971 }
972
973 static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
974                                 struct cfq_queue *cfqq)
975 {
976         struct cfq_rb_root *st = &cfqd->grp_service_tree;
977         unsigned int used_sl, charge, unaccounted_sl = 0;
978         int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
979                         - cfqg->service_tree_idle.count;
980
981         BUG_ON(nr_sync < 0);
982         used_sl = charge = cfq_cfqq_slice_usage(cfqq, &unaccounted_sl);
983
984         if (iops_mode(cfqd))
985                 charge = cfqq->slice_dispatch;
986         else if (!cfq_cfqq_sync(cfqq) && !nr_sync)
987                 charge = cfqq->allocated_slice;
988
989         /* Can't update vdisktime while group is on service tree */
990         cfq_group_service_tree_del(st, cfqg);
991         cfqg->vdisktime += cfq_scale_slice(charge, cfqg);
992         /* If a new weight was requested, update now, off tree */
993         cfq_group_service_tree_add(st, cfqg);
994
995         /* This group is being expired. Save the context */
996         if (time_after(cfqd->workload_expires, jiffies)) {
997                 cfqg->saved_workload_slice = cfqd->workload_expires
998                                                 - jiffies;
999                 cfqg->saved_workload = cfqd->serving_type;
1000                 cfqg->saved_serving_prio = cfqd->serving_prio;
1001         } else
1002                 cfqg->saved_workload_slice = 0;
1003
1004         cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
1005                                         st->min_vdisktime);
1006         cfq_log_cfqq(cfqq->cfqd, cfqq,
1007                      "sl_used=%u disp=%u charge=%u iops=%u sect=%lu",
1008                      used_sl, cfqq->slice_dispatch, charge,
1009                      iops_mode(cfqd), cfqq->nr_sectors);
1010         cfq_blkiocg_update_timeslice_used(&cfqg->blkg, used_sl,
1011                                           unaccounted_sl);
1012         cfq_blkiocg_set_start_empty_time(&cfqg->blkg);
1013 }
1014
1015 #ifdef CONFIG_CFQ_GROUP_IOSCHED
1016 static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
1017 {
1018         if (blkg)
1019                 return container_of(blkg, struct cfq_group, blkg);
1020         return NULL;
1021 }
1022
1023 static void cfq_update_blkio_group_weight(void *key, struct blkio_group *blkg,
1024                                           unsigned int weight)
1025 {
1026         struct cfq_group *cfqg = cfqg_of_blkg(blkg);
1027         cfqg->new_weight = weight;
1028         cfqg->needs_update = true;
1029 }
1030
1031 static void cfq_init_add_cfqg_lists(struct cfq_data *cfqd,
1032                         struct cfq_group *cfqg, struct blkio_cgroup *blkcg)
1033 {
1034         struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
1035         unsigned int major, minor;
1036
1037         /*
1038          * Add group onto cgroup list. It might happen that bdi->dev is
1039          * not initialized yet. Initialize this new group without major
1040          * and minor info and this info will be filled in once a new thread
1041          * comes for IO.
1042          */
1043         if (bdi->dev) {
1044                 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
1045                 cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg,
1046                                         (void *)cfqd, MKDEV(major, minor));
1047         } else
1048                 cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg,
1049                                         (void *)cfqd, 0);
1050
1051         cfqd->nr_blkcg_linked_grps++;
1052         cfqg->weight = blkcg_get_weight(blkcg, cfqg->blkg.dev);
1053
1054         /* Add group on cfqd list */
1055         hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
1056 }
1057
1058 /*
1059  * Should be called from sleepable context. No request queue lock as per
1060  * cpu stats are allocated dynamically and alloc_percpu needs to be called
1061  * from sleepable context.
1062  */
1063 static struct cfq_group * cfq_alloc_cfqg(struct cfq_data *cfqd)
1064 {
1065         struct cfq_group *cfqg = NULL;
1066         int i, j, ret;
1067         struct cfq_rb_root *st;
1068
1069         cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
1070         if (!cfqg)
1071                 return NULL;
1072
1073         for_each_cfqg_st(cfqg, i, j, st)
1074                 *st = CFQ_RB_ROOT;
1075         RB_CLEAR_NODE(&cfqg->rb_node);
1076
1077         cfqg->ttime.last_end_request = jiffies;
1078
1079         /*
1080          * Take the initial reference that will be released on destroy
1081          * This can be thought of a joint reference by cgroup and
1082          * elevator which will be dropped by either elevator exit
1083          * or cgroup deletion path depending on who is exiting first.
1084          */
1085         cfqg->ref = 1;
1086
1087         ret = blkio_alloc_blkg_stats(&cfqg->blkg);
1088         if (ret) {
1089                 kfree(cfqg);
1090                 return NULL;
1091         }
1092
1093         return cfqg;
1094 }
1095
1096 static struct cfq_group *
1097 cfq_find_cfqg(struct cfq_data *cfqd, struct blkio_cgroup *blkcg)
1098 {
1099         struct cfq_group *cfqg = NULL;
1100         void *key = cfqd;
1101         struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
1102         unsigned int major, minor;
1103
1104         /*
1105          * This is the common case when there are no blkio cgroups.
1106          * Avoid lookup in this case
1107          */
1108         if (blkcg == &blkio_root_cgroup)
1109                 cfqg = &cfqd->root_group;
1110         else
1111                 cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
1112
1113         if (cfqg && !cfqg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
1114                 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
1115                 cfqg->blkg.dev = MKDEV(major, minor);
1116         }
1117
1118         return cfqg;
1119 }
1120
1121 /*
1122  * Search for the cfq group current task belongs to. request_queue lock must
1123  * be held.
1124  */
1125 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd)
1126 {
1127         struct blkio_cgroup *blkcg;
1128         struct cfq_group *cfqg = NULL, *__cfqg = NULL;
1129         struct request_queue *q = cfqd->queue;
1130
1131         rcu_read_lock();
1132         blkcg = task_blkio_cgroup(current);
1133         cfqg = cfq_find_cfqg(cfqd, blkcg);
1134         if (cfqg) {
1135                 rcu_read_unlock();
1136                 return cfqg;
1137         }
1138
1139         /*
1140          * Need to allocate a group. Allocation of group also needs allocation
1141          * of per cpu stats which in-turn takes a mutex() and can block. Hence
1142          * we need to drop rcu lock and queue_lock before we call alloc.
1143          *
1144          * Not taking any queue reference here and assuming that queue is
1145          * around by the time we return. CFQ queue allocation code does
1146          * the same. It might be racy though.
1147          */
1148
1149         rcu_read_unlock();
1150         spin_unlock_irq(q->queue_lock);
1151
1152         cfqg = cfq_alloc_cfqg(cfqd);
1153
1154         spin_lock_irq(q->queue_lock);
1155
1156         rcu_read_lock();
1157         blkcg = task_blkio_cgroup(current);
1158
1159         /*
1160          * If some other thread already allocated the group while we were
1161          * not holding queue lock, free up the group
1162          */
1163         __cfqg = cfq_find_cfqg(cfqd, blkcg);
1164
1165         if (__cfqg) {
1166                 kfree(cfqg);
1167                 rcu_read_unlock();
1168                 return __cfqg;
1169         }
1170
1171         if (!cfqg)
1172                 cfqg = &cfqd->root_group;
1173
1174         cfq_init_add_cfqg_lists(cfqd, cfqg, blkcg);
1175         rcu_read_unlock();
1176         return cfqg;
1177 }
1178
1179 static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
1180 {
1181         cfqg->ref++;
1182         return cfqg;
1183 }
1184
1185 static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
1186 {
1187         /* Currently, all async queues are mapped to root group */
1188         if (!cfq_cfqq_sync(cfqq))
1189                 cfqg = &cfqq->cfqd->root_group;
1190
1191         cfqq->cfqg = cfqg;
1192         /* cfqq reference on cfqg */
1193         cfqq->cfqg->ref++;
1194 }
1195
1196 static void cfq_put_cfqg(struct cfq_group *cfqg)
1197 {
1198         struct cfq_rb_root *st;
1199         int i, j;
1200
1201         BUG_ON(cfqg->ref <= 0);
1202         cfqg->ref--;
1203         if (cfqg->ref)
1204                 return;
1205         for_each_cfqg_st(cfqg, i, j, st)
1206                 BUG_ON(!RB_EMPTY_ROOT(&st->rb));
1207         free_percpu(cfqg->blkg.stats_cpu);
1208         kfree(cfqg);
1209 }
1210
1211 static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
1212 {
1213         /* Something wrong if we are trying to remove same group twice */
1214         BUG_ON(hlist_unhashed(&cfqg->cfqd_node));
1215
1216         hlist_del_init(&cfqg->cfqd_node);
1217
1218         BUG_ON(cfqd->nr_blkcg_linked_grps <= 0);
1219         cfqd->nr_blkcg_linked_grps--;
1220
1221         /*
1222          * Put the reference taken at the time of creation so that when all
1223          * queues are gone, group can be destroyed.
1224          */
1225         cfq_put_cfqg(cfqg);
1226 }
1227
1228 static void cfq_release_cfq_groups(struct cfq_data *cfqd)
1229 {
1230         struct hlist_node *pos, *n;
1231         struct cfq_group *cfqg;
1232
1233         hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) {
1234                 /*
1235                  * If cgroup removal path got to blk_group first and removed
1236                  * it from cgroup list, then it will take care of destroying
1237                  * cfqg also.
1238                  */
1239                 if (!cfq_blkiocg_del_blkio_group(&cfqg->blkg))
1240                         cfq_destroy_cfqg(cfqd, cfqg);
1241         }
1242 }
1243
1244 /*
1245  * Blk cgroup controller notification saying that blkio_group object is being
1246  * delinked as associated cgroup object is going away. That also means that
1247  * no new IO will come in this group. So get rid of this group as soon as
1248  * any pending IO in the group is finished.
1249  *
1250  * This function is called under rcu_read_lock(). key is the rcu protected
1251  * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu
1252  * read lock.
1253  *
1254  * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
1255  * it should not be NULL as even if elevator was exiting, cgroup deltion
1256  * path got to it first.
1257  */
1258 static void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
1259 {
1260         unsigned long  flags;
1261         struct cfq_data *cfqd = key;
1262
1263         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1264         cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg));
1265         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1266 }
1267
1268 #else /* GROUP_IOSCHED */
1269 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd)
1270 {
1271         return &cfqd->root_group;
1272 }
1273
1274 static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
1275 {
1276         return cfqg;
1277 }
1278
1279 static inline void
1280 cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
1281         cfqq->cfqg = cfqg;
1282 }
1283
1284 static void cfq_release_cfq_groups(struct cfq_data *cfqd) {}
1285 static inline void cfq_put_cfqg(struct cfq_group *cfqg) {}
1286
1287 #endif /* GROUP_IOSCHED */
1288
1289 /*
1290  * The cfqd->service_trees holds all pending cfq_queue's that have
1291  * requests waiting to be processed. It is sorted in the order that
1292  * we will service the queues.
1293  */
1294 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1295                                  bool add_front)
1296 {
1297         struct rb_node **p, *parent;
1298         struct cfq_queue *__cfqq;
1299         unsigned long rb_key;
1300         struct cfq_rb_root *service_tree;
1301         int left;
1302         int new_cfqq = 1;
1303
1304         service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
1305                                                 cfqq_type(cfqq));
1306         if (cfq_class_idle(cfqq)) {
1307                 rb_key = CFQ_IDLE_DELAY;
1308                 parent = rb_last(&service_tree->rb);
1309                 if (parent && parent != &cfqq->rb_node) {
1310                         __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1311                         rb_key += __cfqq->rb_key;
1312                 } else
1313                         rb_key += jiffies;
1314         } else if (!add_front) {
1315                 /*
1316                  * Get our rb key offset. Subtract any residual slice
1317                  * value carried from last service. A negative resid
1318                  * count indicates slice overrun, and this should position
1319                  * the next service time further away in the tree.
1320                  */
1321                 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
1322                 rb_key -= cfqq->slice_resid;
1323                 cfqq->slice_resid = 0;
1324         } else {
1325                 rb_key = -HZ;
1326                 __cfqq = cfq_rb_first(service_tree);
1327                 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
1328         }
1329
1330         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1331                 new_cfqq = 0;
1332                 /*
1333                  * same position, nothing more to do
1334                  */
1335                 if (rb_key == cfqq->rb_key &&
1336                     cfqq->service_tree == service_tree)
1337                         return;
1338
1339                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1340                 cfqq->service_tree = NULL;
1341         }
1342
1343         left = 1;
1344         parent = NULL;
1345         cfqq->service_tree = service_tree;
1346         p = &service_tree->rb.rb_node;
1347         while (*p) {
1348                 struct rb_node **n;
1349
1350                 parent = *p;
1351                 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1352
1353                 /*
1354                  * sort by key, that represents service time.
1355                  */
1356                 if (time_before(rb_key, __cfqq->rb_key))
1357                         n = &(*p)->rb_left;
1358                 else {
1359                         n = &(*p)->rb_right;
1360                         left = 0;
1361                 }
1362
1363                 p = n;
1364         }
1365
1366         if (left)
1367                 service_tree->left = &cfqq->rb_node;
1368
1369         cfqq->rb_key = rb_key;
1370         rb_link_node(&cfqq->rb_node, parent, p);
1371         rb_insert_color(&cfqq->rb_node, &service_tree->rb);
1372         service_tree->count++;
1373         if (add_front || !new_cfqq)
1374                 return;
1375         cfq_group_notify_queue_add(cfqd, cfqq->cfqg);
1376 }
1377
1378 static struct cfq_queue *
1379 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
1380                      sector_t sector, struct rb_node **ret_parent,
1381                      struct rb_node ***rb_link)
1382 {
1383         struct rb_node **p, *parent;
1384         struct cfq_queue *cfqq = NULL;
1385
1386         parent = NULL;
1387         p = &root->rb_node;
1388         while (*p) {
1389                 struct rb_node **n;
1390
1391                 parent = *p;
1392                 cfqq = rb_entry(parent, struct cfq_queue, p_node);
1393
1394                 /*
1395                  * Sort strictly based on sector.  Smallest to the left,
1396                  * largest to the right.
1397                  */
1398                 if (sector > blk_rq_pos(cfqq->next_rq))
1399                         n = &(*p)->rb_right;
1400                 else if (sector < blk_rq_pos(cfqq->next_rq))
1401                         n = &(*p)->rb_left;
1402                 else
1403                         break;
1404                 p = n;
1405                 cfqq = NULL;
1406         }
1407
1408         *ret_parent = parent;
1409         if (rb_link)
1410                 *rb_link = p;
1411         return cfqq;
1412 }
1413
1414 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1415 {
1416         struct rb_node **p, *parent;
1417         struct cfq_queue *__cfqq;
1418
1419         if (cfqq->p_root) {
1420                 rb_erase(&cfqq->p_node, cfqq->p_root);
1421                 cfqq->p_root = NULL;
1422         }
1423
1424         if (cfq_class_idle(cfqq))
1425                 return;
1426         if (!cfqq->next_rq)
1427                 return;
1428
1429         cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
1430         __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
1431                                       blk_rq_pos(cfqq->next_rq), &parent, &p);
1432         if (!__cfqq) {
1433                 rb_link_node(&cfqq->p_node, parent, p);
1434                 rb_insert_color(&cfqq->p_node, cfqq->p_root);
1435         } else
1436                 cfqq->p_root = NULL;
1437 }
1438
1439 /*
1440  * Update cfqq's position in the service tree.
1441  */
1442 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1443 {
1444         /*
1445          * Resorting requires the cfqq to be on the RR list already.
1446          */
1447         if (cfq_cfqq_on_rr(cfqq)) {
1448                 cfq_service_tree_add(cfqd, cfqq, 0);
1449                 cfq_prio_tree_add(cfqd, cfqq);
1450         }
1451 }
1452
1453 /*
1454  * add to busy list of queues for service, trying to be fair in ordering
1455  * the pending list according to last request service
1456  */
1457 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1458 {
1459         cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
1460         BUG_ON(cfq_cfqq_on_rr(cfqq));
1461         cfq_mark_cfqq_on_rr(cfqq);
1462         cfqd->busy_queues++;
1463         if (cfq_cfqq_sync(cfqq))
1464                 cfqd->busy_sync_queues++;
1465
1466         cfq_resort_rr_list(cfqd, cfqq);
1467 }
1468
1469 /*
1470  * Called when the cfqq no longer has requests pending, remove it from
1471  * the service tree.
1472  */
1473 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1474 {
1475         cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
1476         BUG_ON(!cfq_cfqq_on_rr(cfqq));
1477         cfq_clear_cfqq_on_rr(cfqq);
1478
1479         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1480                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1481                 cfqq->service_tree = NULL;
1482         }
1483         if (cfqq->p_root) {
1484                 rb_erase(&cfqq->p_node, cfqq->p_root);
1485                 cfqq->p_root = NULL;
1486         }
1487
1488         cfq_group_notify_queue_del(cfqd, cfqq->cfqg);
1489         BUG_ON(!cfqd->busy_queues);
1490         cfqd->busy_queues--;
1491         if (cfq_cfqq_sync(cfqq))
1492                 cfqd->busy_sync_queues--;
1493 }
1494
1495 /*
1496  * rb tree support functions
1497  */
1498 static void cfq_del_rq_rb(struct request *rq)
1499 {
1500         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1501         const int sync = rq_is_sync(rq);
1502
1503         BUG_ON(!cfqq->queued[sync]);
1504         cfqq->queued[sync]--;
1505
1506         elv_rb_del(&cfqq->sort_list, rq);
1507
1508         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1509                 /*
1510                  * Queue will be deleted from service tree when we actually
1511                  * expire it later. Right now just remove it from prio tree
1512                  * as it is empty.
1513                  */
1514                 if (cfqq->p_root) {
1515                         rb_erase(&cfqq->p_node, cfqq->p_root);
1516                         cfqq->p_root = NULL;
1517                 }
1518         }
1519 }
1520
1521 static void cfq_add_rq_rb(struct request *rq)
1522 {
1523         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1524         struct cfq_data *cfqd = cfqq->cfqd;
1525         struct request *prev;
1526
1527         cfqq->queued[rq_is_sync(rq)]++;
1528
1529         elv_rb_add(&cfqq->sort_list, rq);
1530
1531         if (!cfq_cfqq_on_rr(cfqq))
1532                 cfq_add_cfqq_rr(cfqd, cfqq);
1533
1534         /*
1535          * check if this request is a better next-serve candidate
1536          */
1537         prev = cfqq->next_rq;
1538         cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
1539
1540         /*
1541          * adjust priority tree position, if ->next_rq changes
1542          */
1543         if (prev != cfqq->next_rq)
1544                 cfq_prio_tree_add(cfqd, cfqq);
1545
1546         BUG_ON(!cfqq->next_rq);
1547 }
1548
1549 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
1550 {
1551         elv_rb_del(&cfqq->sort_list, rq);
1552         cfqq->queued[rq_is_sync(rq)]--;
1553         cfq_blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg,
1554                                         rq_data_dir(rq), rq_is_sync(rq));
1555         cfq_add_rq_rb(rq);
1556         cfq_blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg,
1557                         &cfqq->cfqd->serving_group->blkg, rq_data_dir(rq),
1558                         rq_is_sync(rq));
1559 }
1560
1561 static struct request *
1562 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
1563 {
1564         struct task_struct *tsk = current;
1565         struct cfq_io_cq *cic;
1566         struct cfq_queue *cfqq;
1567
1568         cic = cfq_cic_lookup(cfqd, tsk->io_context);
1569         if (!cic)
1570                 return NULL;
1571
1572         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1573         if (cfqq) {
1574                 sector_t sector = bio->bi_sector + bio_sectors(bio);
1575
1576                 return elv_rb_find(&cfqq->sort_list, sector);
1577         }
1578
1579         return NULL;
1580 }
1581
1582 static void cfq_activate_request(struct request_queue *q, struct request *rq)
1583 {
1584         struct cfq_data *cfqd = q->elevator->elevator_data;
1585
1586         cfqd->rq_in_driver++;
1587         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
1588                                                 cfqd->rq_in_driver);
1589
1590         cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
1591 }
1592
1593 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
1594 {
1595         struct cfq_data *cfqd = q->elevator->elevator_data;
1596
1597         WARN_ON(!cfqd->rq_in_driver);
1598         cfqd->rq_in_driver--;
1599         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
1600                                                 cfqd->rq_in_driver);
1601 }
1602
1603 static void cfq_remove_request(struct request *rq)
1604 {
1605         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1606
1607         if (cfqq->next_rq == rq)
1608                 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
1609
1610         list_del_init(&rq->queuelist);
1611         cfq_del_rq_rb(rq);
1612
1613         cfqq->cfqd->rq_queued--;
1614         cfq_blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg,
1615                                         rq_data_dir(rq), rq_is_sync(rq));
1616         if (rq->cmd_flags & REQ_PRIO) {
1617                 WARN_ON(!cfqq->prio_pending);
1618                 cfqq->prio_pending--;
1619         }
1620 }
1621
1622 static int cfq_merge(struct request_queue *q, struct request **req,
1623                      struct bio *bio)
1624 {
1625         struct cfq_data *cfqd = q->elevator->elevator_data;
1626         struct request *__rq;
1627
1628         __rq = cfq_find_rq_fmerge(cfqd, bio);
1629         if (__rq && elv_rq_merge_ok(__rq, bio)) {
1630                 *req = __rq;
1631                 return ELEVATOR_FRONT_MERGE;
1632         }
1633
1634         return ELEVATOR_NO_MERGE;
1635 }
1636
1637 static void cfq_merged_request(struct request_queue *q, struct request *req,
1638                                int type)
1639 {
1640         if (type == ELEVATOR_FRONT_MERGE) {
1641                 struct cfq_queue *cfqq = RQ_CFQQ(req);
1642
1643                 cfq_reposition_rq_rb(cfqq, req);
1644         }
1645 }
1646
1647 static void cfq_bio_merged(struct request_queue *q, struct request *req,
1648                                 struct bio *bio)
1649 {
1650         cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(req))->blkg,
1651                                         bio_data_dir(bio), cfq_bio_sync(bio));
1652 }
1653
1654 static void
1655 cfq_merged_requests(struct request_queue *q, struct request *rq,
1656                     struct request *next)
1657 {
1658         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1659         struct cfq_data *cfqd = q->elevator->elevator_data;
1660
1661         /*
1662          * reposition in fifo if next is older than rq
1663          */
1664         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
1665             time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
1666                 list_move(&rq->queuelist, &next->queuelist);
1667                 rq_set_fifo_time(rq, rq_fifo_time(next));
1668         }
1669
1670         if (cfqq->next_rq == next)
1671                 cfqq->next_rq = rq;
1672         cfq_remove_request(next);
1673         cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(rq))->blkg,
1674                                         rq_data_dir(next), rq_is_sync(next));
1675
1676         cfqq = RQ_CFQQ(next);
1677         /*
1678          * all requests of this queue are merged to other queues, delete it
1679          * from the service tree. If it's the active_queue,
1680          * cfq_dispatch_requests() will choose to expire it or do idle
1681          */
1682         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list) &&
1683             cfqq != cfqd->active_queue)
1684                 cfq_del_cfqq_rr(cfqd, cfqq);
1685 }
1686
1687 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
1688                            struct bio *bio)
1689 {
1690         struct cfq_data *cfqd = q->elevator->elevator_data;
1691         struct cfq_io_cq *cic;
1692         struct cfq_queue *cfqq;
1693
1694         /*
1695          * Disallow merge of a sync bio into an async request.
1696          */
1697         if (cfq_bio_sync(bio) && !rq_is_sync(rq))
1698                 return false;
1699
1700         /*
1701          * Lookup the cfqq that this bio will be queued with and allow
1702          * merge only if rq is queued there.
1703          */
1704         cic = cfq_cic_lookup(cfqd, current->io_context);
1705         if (!cic)
1706                 return false;
1707
1708         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1709         return cfqq == RQ_CFQQ(rq);
1710 }
1711
1712 static inline void cfq_del_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1713 {
1714         del_timer(&cfqd->idle_slice_timer);
1715         cfq_blkiocg_update_idle_time_stats(&cfqq->cfqg->blkg);
1716 }
1717
1718 static void __cfq_set_active_queue(struct cfq_data *cfqd,
1719                                    struct cfq_queue *cfqq)
1720 {
1721         if (cfqq) {
1722                 cfq_log_cfqq(cfqd, cfqq, "set_active wl_prio:%d wl_type:%d",
1723                                 cfqd->serving_prio, cfqd->serving_type);
1724                 cfq_blkiocg_update_avg_queue_size_stats(&cfqq->cfqg->blkg);
1725                 cfqq->slice_start = 0;
1726                 cfqq->dispatch_start = jiffies;
1727                 cfqq->allocated_slice = 0;
1728                 cfqq->slice_end = 0;
1729                 cfqq->slice_dispatch = 0;
1730                 cfqq->nr_sectors = 0;
1731
1732                 cfq_clear_cfqq_wait_request(cfqq);
1733                 cfq_clear_cfqq_must_dispatch(cfqq);
1734                 cfq_clear_cfqq_must_alloc_slice(cfqq);
1735                 cfq_clear_cfqq_fifo_expire(cfqq);
1736                 cfq_mark_cfqq_slice_new(cfqq);
1737
1738                 cfq_del_timer(cfqd, cfqq);
1739         }
1740
1741         cfqd->active_queue = cfqq;
1742 }
1743
1744 /*
1745  * current cfqq expired its slice (or was too idle), select new one
1746  */
1747 static void
1748 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1749                     bool timed_out)
1750 {
1751         cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
1752
1753         if (cfq_cfqq_wait_request(cfqq))
1754                 cfq_del_timer(cfqd, cfqq);
1755
1756         cfq_clear_cfqq_wait_request(cfqq);
1757         cfq_clear_cfqq_wait_busy(cfqq);
1758
1759         /*
1760          * If this cfqq is shared between multiple processes, check to
1761          * make sure that those processes are still issuing I/Os within
1762          * the mean seek distance.  If not, it may be time to break the
1763          * queues apart again.
1764          */
1765         if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq))
1766                 cfq_mark_cfqq_split_coop(cfqq);
1767
1768         /*
1769          * store what was left of this slice, if the queue idled/timed out
1770          */
1771         if (timed_out) {
1772                 if (cfq_cfqq_slice_new(cfqq))
1773                         cfqq->slice_resid = cfq_scaled_cfqq_slice(cfqd, cfqq);
1774                 else
1775                         cfqq->slice_resid = cfqq->slice_end - jiffies;
1776                 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
1777         }
1778
1779         cfq_group_served(cfqd, cfqq->cfqg, cfqq);
1780
1781         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
1782                 cfq_del_cfqq_rr(cfqd, cfqq);
1783
1784         cfq_resort_rr_list(cfqd, cfqq);
1785
1786         if (cfqq == cfqd->active_queue)
1787                 cfqd->active_queue = NULL;
1788
1789         if (cfqd->active_cic) {
1790                 put_io_context(cfqd->active_cic->icq.ioc);
1791                 cfqd->active_cic = NULL;
1792         }
1793 }
1794
1795 static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
1796 {
1797         struct cfq_queue *cfqq = cfqd->active_queue;
1798
1799         if (cfqq)
1800                 __cfq_slice_expired(cfqd, cfqq, timed_out);
1801 }
1802
1803 /*
1804  * Get next queue for service. Unless we have a queue preemption,
1805  * we'll simply select the first cfqq in the service tree.
1806  */
1807 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
1808 {
1809         struct cfq_rb_root *service_tree =
1810                 service_tree_for(cfqd->serving_group, cfqd->serving_prio,
1811                                         cfqd->serving_type);
1812
1813         if (!cfqd->rq_queued)
1814                 return NULL;
1815
1816         /* There is nothing to dispatch */
1817         if (!service_tree)
1818                 return NULL;
1819         if (RB_EMPTY_ROOT(&service_tree->rb))
1820                 return NULL;
1821         return cfq_rb_first(service_tree);
1822 }
1823
1824 static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
1825 {
1826         struct cfq_group *cfqg;
1827         struct cfq_queue *cfqq;
1828         int i, j;
1829         struct cfq_rb_root *st;
1830
1831         if (!cfqd->rq_queued)
1832                 return NULL;
1833
1834         cfqg = cfq_get_next_cfqg(cfqd);
1835         if (!cfqg)
1836                 return NULL;
1837
1838         for_each_cfqg_st(cfqg, i, j, st)
1839                 if ((cfqq = cfq_rb_first(st)) != NULL)
1840                         return cfqq;
1841         return NULL;
1842 }
1843
1844 /*
1845  * Get and set a new active queue for service.
1846  */
1847 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
1848                                               struct cfq_queue *cfqq)
1849 {
1850         if (!cfqq)
1851                 cfqq = cfq_get_next_queue(cfqd);
1852
1853         __cfq_set_active_queue(cfqd, cfqq);
1854         return cfqq;
1855 }
1856
1857 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
1858                                           struct request *rq)
1859 {
1860         if (blk_rq_pos(rq) >= cfqd->last_position)
1861                 return blk_rq_pos(rq) - cfqd->last_position;
1862         else
1863                 return cfqd->last_position - blk_rq_pos(rq);
1864 }
1865
1866 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1867                                struct request *rq)
1868 {
1869         return cfq_dist_from_last(cfqd, rq) <= CFQQ_CLOSE_THR;
1870 }
1871
1872 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
1873                                     struct cfq_queue *cur_cfqq)
1874 {
1875         struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
1876         struct rb_node *parent, *node;
1877         struct cfq_queue *__cfqq;
1878         sector_t sector = cfqd->last_position;
1879
1880         if (RB_EMPTY_ROOT(root))
1881                 return NULL;
1882
1883         /*
1884          * First, if we find a request starting at the end of the last
1885          * request, choose it.
1886          */
1887         __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
1888         if (__cfqq)
1889                 return __cfqq;
1890
1891         /*
1892          * If the exact sector wasn't found, the parent of the NULL leaf
1893          * will contain the closest sector.
1894          */
1895         __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1896         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1897                 return __cfqq;
1898
1899         if (blk_rq_pos(__cfqq->next_rq) < sector)
1900                 node = rb_next(&__cfqq->p_node);
1901         else
1902                 node = rb_prev(&__cfqq->p_node);
1903         if (!node)
1904                 return NULL;
1905
1906         __cfqq = rb_entry(node, struct cfq_queue, p_node);
1907         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1908                 return __cfqq;
1909
1910         return NULL;
1911 }
1912
1913 /*
1914  * cfqd - obvious
1915  * cur_cfqq - passed in so that we don't decide that the current queue is
1916  *            closely cooperating with itself.
1917  *
1918  * So, basically we're assuming that that cur_cfqq has dispatched at least
1919  * one request, and that cfqd->last_position reflects a position on the disk
1920  * associated with the I/O issued by cur_cfqq.  I'm not sure this is a valid
1921  * assumption.
1922  */
1923 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1924                                               struct cfq_queue *cur_cfqq)
1925 {
1926         struct cfq_queue *cfqq;
1927
1928         if (cfq_class_idle(cur_cfqq))
1929                 return NULL;
1930         if (!cfq_cfqq_sync(cur_cfqq))
1931                 return NULL;
1932         if (CFQQ_SEEKY(cur_cfqq))
1933                 return NULL;
1934
1935         /*
1936          * Don't search priority tree if it's the only queue in the group.
1937          */
1938         if (cur_cfqq->cfqg->nr_cfqq == 1)
1939                 return NULL;
1940
1941         /*
1942          * We should notice if some of the queues are cooperating, eg
1943          * working closely on the same area of the disk. In that case,
1944          * we can group them together and don't waste time idling.
1945          */
1946         cfqq = cfqq_close(cfqd, cur_cfqq);
1947         if (!cfqq)
1948                 return NULL;
1949
1950         /* If new queue belongs to different cfq_group, don't choose it */
1951         if (cur_cfqq->cfqg != cfqq->cfqg)
1952                 return NULL;
1953
1954         /*
1955          * It only makes sense to merge sync queues.
1956          */
1957         if (!cfq_cfqq_sync(cfqq))
1958                 return NULL;
1959         if (CFQQ_SEEKY(cfqq))
1960                 return NULL;
1961
1962         /*
1963          * Do not merge queues of different priority classes
1964          */
1965         if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
1966                 return NULL;
1967
1968         return cfqq;
1969 }
1970
1971 /*
1972  * Determine whether we should enforce idle window for this queue.
1973  */
1974
1975 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1976 {
1977         enum wl_prio_t prio = cfqq_prio(cfqq);
1978         struct cfq_rb_root *service_tree = cfqq->service_tree;
1979
1980         BUG_ON(!service_tree);
1981         BUG_ON(!service_tree->count);
1982
1983         if (!cfqd->cfq_slice_idle)
1984                 return false;
1985
1986         /* We never do for idle class queues. */
1987         if (prio == IDLE_WORKLOAD)
1988                 return false;
1989
1990         /* We do for queues that were marked with idle window flag. */
1991         if (cfq_cfqq_idle_window(cfqq) &&
1992            !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag))
1993                 return true;
1994
1995         /*
1996          * Otherwise, we do only if they are the last ones
1997          * in their service tree.
1998          */
1999         if (service_tree->count == 1 && cfq_cfqq_sync(cfqq) &&
2000            !cfq_io_thinktime_big(cfqd, &service_tree->ttime, false))
2001                 return true;
2002         cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d",
2003                         service_tree->count);
2004         return false;
2005 }
2006
2007 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
2008 {
2009         struct cfq_queue *cfqq = cfqd->active_queue;
2010         struct cfq_io_cq *cic;
2011         unsigned long sl, group_idle = 0;
2012
2013         /*
2014          * SSD device without seek penalty, disable idling. But only do so
2015          * for devices that support queuing, otherwise we still have a problem
2016          * with sync vs async workloads.
2017          */
2018         if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
2019                 return;
2020
2021         WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
2022         WARN_ON(cfq_cfqq_slice_new(cfqq));
2023
2024         /*
2025          * idle is disabled, either manually or by past process history
2026          */
2027         if (!cfq_should_idle(cfqd, cfqq)) {
2028                 /* no queue idling. Check for group idling */
2029                 if (cfqd->cfq_group_idle)
2030                         group_idle = cfqd->cfq_group_idle;
2031                 else
2032                         return;
2033         }
2034
2035         /*
2036          * still active requests from this queue, don't idle
2037          */
2038         if (cfqq->dispatched)
2039                 return;
2040
2041         /*
2042          * task has exited, don't wait
2043          */
2044         cic = cfqd->active_cic;
2045         if (!cic || !atomic_read(&cic->icq.ioc->nr_tasks))
2046                 return;
2047
2048         /*
2049          * If our average think time is larger than the remaining time
2050          * slice, then don't idle. This avoids overrunning the allotted
2051          * time slice.
2052          */
2053         if (sample_valid(cic->ttime.ttime_samples) &&
2054             (cfqq->slice_end - jiffies < cic->ttime.ttime_mean)) {
2055                 cfq_log_cfqq(cfqd, cfqq, "Not idling. think_time:%lu",
2056                              cic->ttime.ttime_mean);
2057                 return;
2058         }
2059
2060         /* There are other queues in the group, don't do group idle */
2061         if (group_idle && cfqq->cfqg->nr_cfqq > 1)
2062                 return;
2063
2064         cfq_mark_cfqq_wait_request(cfqq);
2065
2066         if (group_idle)
2067                 sl = cfqd->cfq_group_idle;
2068         else
2069                 sl = cfqd->cfq_slice_idle;
2070
2071         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
2072         cfq_blkiocg_update_set_idle_time_stats(&cfqq->cfqg->blkg);
2073         cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu group_idle: %d", sl,
2074                         group_idle ? 1 : 0);
2075 }
2076
2077 /*
2078  * Move request from internal lists to the request queue dispatch list.
2079  */
2080 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
2081 {
2082         struct cfq_data *cfqd = q->elevator->elevator_data;
2083         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2084
2085         cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
2086
2087         cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
2088         cfq_remove_request(rq);
2089         cfqq->dispatched++;
2090         (RQ_CFQG(rq))->dispatched++;
2091         elv_dispatch_sort(q, rq);
2092
2093         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
2094         cfqq->nr_sectors += blk_rq_sectors(rq);
2095         cfq_blkiocg_update_dispatch_stats(&cfqq->cfqg->blkg, blk_rq_bytes(rq),
2096                                         rq_data_dir(rq), rq_is_sync(rq));
2097 }
2098
2099 /*
2100  * return expired entry, or NULL to just start from scratch in rbtree
2101  */
2102 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
2103 {
2104         struct request *rq = NULL;
2105
2106         if (cfq_cfqq_fifo_expire(cfqq))
2107                 return NULL;
2108
2109         cfq_mark_cfqq_fifo_expire(cfqq);
2110
2111         if (list_empty(&cfqq->fifo))
2112                 return NULL;
2113
2114         rq = rq_entry_fifo(cfqq->fifo.next);
2115         if (time_before(jiffies, rq_fifo_time(rq)))
2116                 rq = NULL;
2117
2118         cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
2119         return rq;
2120 }
2121
2122 static inline int
2123 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2124 {
2125         const int base_rq = cfqd->cfq_slice_async_rq;
2126
2127         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
2128
2129         return 2 * base_rq * (IOPRIO_BE_NR - cfqq->ioprio);
2130 }
2131
2132 /*
2133  * Must be called with the queue_lock held.
2134  */
2135 static int cfqq_process_refs(struct cfq_queue *cfqq)
2136 {
2137         int process_refs, io_refs;
2138
2139         io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
2140         process_refs = cfqq->ref - io_refs;
2141         BUG_ON(process_refs < 0);
2142         return process_refs;
2143 }
2144
2145 static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
2146 {
2147         int process_refs, new_process_refs;
2148         struct cfq_queue *__cfqq;
2149
2150         /*
2151          * If there are no process references on the new_cfqq, then it is
2152          * unsafe to follow the ->new_cfqq chain as other cfqq's in the
2153          * chain may have dropped their last reference (not just their
2154          * last process reference).
2155          */
2156         if (!cfqq_process_refs(new_cfqq))
2157                 return;
2158
2159         /* Avoid a circular list and skip interim queue merges */
2160         while ((__cfqq = new_cfqq->new_cfqq)) {
2161                 if (__cfqq == cfqq)
2162                         return;
2163                 new_cfqq = __cfqq;
2164         }
2165
2166         process_refs = cfqq_process_refs(cfqq);
2167         new_process_refs = cfqq_process_refs(new_cfqq);
2168         /*
2169          * If the process for the cfqq has gone away, there is no
2170          * sense in merging the queues.
2171          */
2172         if (process_refs == 0 || new_process_refs == 0)
2173                 return;
2174
2175         /*
2176          * Merge in the direction of the lesser amount of work.
2177          */
2178         if (new_process_refs >= process_refs) {
2179                 cfqq->new_cfqq = new_cfqq;
2180                 new_cfqq->ref += process_refs;
2181         } else {
2182                 new_cfqq->new_cfqq = cfqq;
2183                 cfqq->ref += new_process_refs;
2184         }
2185 }
2186
2187 static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
2188                                 struct cfq_group *cfqg, enum wl_prio_t prio)
2189 {
2190         struct cfq_queue *queue;
2191         int i;
2192         bool key_valid = false;
2193         unsigned long lowest_key = 0;
2194         enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
2195
2196         for (i = 0; i <= SYNC_WORKLOAD; ++i) {
2197                 /* select the one with lowest rb_key */
2198                 queue = cfq_rb_first(service_tree_for(cfqg, prio, i));
2199                 if (queue &&
2200                     (!key_valid || time_before(queue->rb_key, lowest_key))) {
2201                         lowest_key = queue->rb_key;
2202                         cur_best = i;
2203                         key_valid = true;
2204                 }
2205         }
2206
2207         return cur_best;
2208 }
2209
2210 static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
2211 {
2212         unsigned slice;
2213         unsigned count;
2214         struct cfq_rb_root *st;
2215         unsigned group_slice;
2216         enum wl_prio_t original_prio = cfqd->serving_prio;
2217
2218         /* Choose next priority. RT > BE > IDLE */
2219         if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
2220                 cfqd->serving_prio = RT_WORKLOAD;
2221         else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
2222                 cfqd->serving_prio = BE_WORKLOAD;
2223         else {
2224                 cfqd->serving_prio = IDLE_WORKLOAD;
2225                 cfqd->workload_expires = jiffies + 1;
2226                 return;
2227         }
2228
2229         if (original_prio != cfqd->serving_prio)
2230                 goto new_workload;
2231
2232         /*
2233          * For RT and BE, we have to choose also the type
2234          * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
2235          * expiration time
2236          */
2237         st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
2238         count = st->count;
2239
2240         /*
2241          * check workload expiration, and that we still have other queues ready
2242          */
2243         if (count && !time_after(jiffies, cfqd->workload_expires))
2244                 return;
2245
2246 new_workload:
2247         /* otherwise select new workload type */
2248         cfqd->serving_type =
2249                 cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio);
2250         st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
2251         count = st->count;
2252
2253         /*
2254          * the workload slice is computed as a fraction of target latency
2255          * proportional to the number of queues in that workload, over
2256          * all the queues in the same priority class
2257          */
2258         group_slice = cfq_group_slice(cfqd, cfqg);
2259
2260         slice = group_slice * count /
2261                 max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio],
2262                       cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg));
2263
2264         if (cfqd->serving_type == ASYNC_WORKLOAD) {
2265                 unsigned int tmp;
2266
2267                 /*
2268                  * Async queues are currently system wide. Just taking
2269                  * proportion of queues with-in same group will lead to higher
2270                  * async ratio system wide as generally root group is going
2271                  * to have higher weight. A more accurate thing would be to
2272                  * calculate system wide asnc/sync ratio.
2273                  */
2274                 tmp = cfq_target_latency * cfqg_busy_async_queues(cfqd, cfqg);
2275                 tmp = tmp/cfqd->busy_queues;
2276                 slice = min_t(unsigned, slice, tmp);
2277
2278                 /* async workload slice is scaled down according to
2279                  * the sync/async slice ratio. */
2280                 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
2281         } else
2282                 /* sync workload slice is at least 2 * cfq_slice_idle */
2283                 slice = max(slice, 2 * cfqd->cfq_slice_idle);
2284
2285         slice = max_t(unsigned, slice, CFQ_MIN_TT);
2286         cfq_log(cfqd, "workload slice:%d", slice);
2287         cfqd->workload_expires = jiffies + slice;
2288 }
2289
2290 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
2291 {
2292         struct cfq_rb_root *st = &cfqd->grp_service_tree;
2293         struct cfq_group *cfqg;
2294
2295         if (RB_EMPTY_ROOT(&st->rb))
2296                 return NULL;
2297         cfqg = cfq_rb_first_group(st);
2298         update_min_vdisktime(st);
2299         return cfqg;
2300 }
2301
2302 static void cfq_choose_cfqg(struct cfq_data *cfqd)
2303 {
2304         struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
2305
2306         cfqd->serving_group = cfqg;
2307
2308         /* Restore the workload type data */
2309         if (cfqg->saved_workload_slice) {
2310                 cfqd->workload_expires = jiffies + cfqg->saved_workload_slice;
2311                 cfqd->serving_type = cfqg->saved_workload;
2312                 cfqd->serving_prio = cfqg->saved_serving_prio;
2313         } else
2314                 cfqd->workload_expires = jiffies - 1;
2315
2316         choose_service_tree(cfqd, cfqg);
2317 }
2318
2319 /*
2320  * Select a queue for service. If we have a current active queue,
2321  * check whether to continue servicing it, or retrieve and set a new one.
2322  */
2323 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
2324 {
2325         struct cfq_queue *cfqq, *new_cfqq = NULL;
2326
2327         cfqq = cfqd->active_queue;
2328         if (!cfqq)
2329                 goto new_queue;
2330
2331         if (!cfqd->rq_queued)
2332                 return NULL;
2333
2334         /*
2335          * We were waiting for group to get backlogged. Expire the queue
2336          */
2337         if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list))
2338                 goto expire;
2339
2340         /*
2341          * The active queue has run out of time, expire it and select new.
2342          */
2343         if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) {
2344                 /*
2345                  * If slice had not expired at the completion of last request
2346                  * we might not have turned on wait_busy flag. Don't expire
2347                  * the queue yet. Allow the group to get backlogged.
2348                  *
2349                  * The very fact that we have used the slice, that means we
2350                  * have been idling all along on this queue and it should be
2351                  * ok to wait for this request to complete.
2352                  */
2353                 if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list)
2354                     && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
2355                         cfqq = NULL;
2356                         goto keep_queue;
2357                 } else
2358                         goto check_group_idle;
2359         }
2360
2361         /*
2362          * The active queue has requests and isn't expired, allow it to
2363          * dispatch.
2364          */
2365         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2366                 goto keep_queue;
2367
2368         /*
2369          * If another queue has a request waiting within our mean seek
2370          * distance, let it run.  The expire code will check for close
2371          * cooperators and put the close queue at the front of the service
2372          * tree.  If possible, merge the expiring queue with the new cfqq.
2373          */
2374         new_cfqq = cfq_close_cooperator(cfqd, cfqq);
2375         if (new_cfqq) {
2376                 if (!cfqq->new_cfqq)
2377                         cfq_setup_merge(cfqq, new_cfqq);
2378                 goto expire;
2379         }
2380
2381         /*
2382          * No requests pending. If the active queue still has requests in
2383          * flight or is idling for a new request, allow either of these
2384          * conditions to happen (or time out) before selecting a new queue.
2385          */
2386         if (timer_pending(&cfqd->idle_slice_timer)) {
2387                 cfqq = NULL;
2388                 goto keep_queue;
2389         }
2390
2391         /*
2392          * This is a deep seek queue, but the device is much faster than
2393          * the queue can deliver, don't idle
2394          **/
2395         if (CFQQ_SEEKY(cfqq) && cfq_cfqq_idle_window(cfqq) &&
2396             (cfq_cfqq_slice_new(cfqq) ||
2397             (cfqq->slice_end - jiffies > jiffies - cfqq->slice_start))) {
2398                 cfq_clear_cfqq_deep(cfqq);
2399                 cfq_clear_cfqq_idle_window(cfqq);
2400         }
2401
2402         if (cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
2403                 cfqq = NULL;
2404                 goto keep_queue;
2405         }
2406
2407         /*
2408          * If group idle is enabled and there are requests dispatched from
2409          * this group, wait for requests to complete.
2410          */
2411 check_group_idle:
2412         if (cfqd->cfq_group_idle && cfqq->cfqg->nr_cfqq == 1 &&
2413             cfqq->cfqg->dispatched &&
2414             !cfq_io_thinktime_big(cfqd, &cfqq->cfqg->ttime, true)) {
2415                 cfqq = NULL;
2416                 goto keep_queue;
2417         }
2418
2419 expire:
2420         cfq_slice_expired(cfqd, 0);
2421 new_queue:
2422         /*
2423          * Current queue expired. Check if we have to switch to a new
2424          * service tree
2425          */
2426         if (!new_cfqq)
2427                 cfq_choose_cfqg(cfqd);
2428
2429         cfqq = cfq_set_active_queue(cfqd, new_cfqq);
2430 keep_queue:
2431         return cfqq;
2432 }
2433
2434 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
2435 {
2436         int dispatched = 0;
2437
2438         while (cfqq->next_rq) {
2439                 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
2440                 dispatched++;
2441         }
2442
2443         BUG_ON(!list_empty(&cfqq->fifo));
2444
2445         /* By default cfqq is not expired if it is empty. Do it explicitly */
2446         __cfq_slice_expired(cfqq->cfqd, cfqq, 0);
2447         return dispatched;
2448 }
2449
2450 /*
2451  * Drain our current requests. Used for barriers and when switching
2452  * io schedulers on-the-fly.
2453  */
2454 static int cfq_forced_dispatch(struct cfq_data *cfqd)
2455 {
2456         struct cfq_queue *cfqq;
2457         int dispatched = 0;
2458
2459         /* Expire the timeslice of the current active queue first */
2460         cfq_slice_expired(cfqd, 0);
2461         while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) {
2462                 __cfq_set_active_queue(cfqd, cfqq);
2463                 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
2464         }
2465
2466         BUG_ON(cfqd->busy_queues);
2467
2468         cfq_log(cfqd, "forced_dispatch=%d", dispatched);
2469         return dispatched;
2470 }
2471
2472 static inline bool cfq_slice_used_soon(struct cfq_data *cfqd,
2473         struct cfq_queue *cfqq)
2474 {
2475         /* the queue hasn't finished any request, can't estimate */
2476         if (cfq_cfqq_slice_new(cfqq))
2477                 return true;
2478         if (time_after(jiffies + cfqd->cfq_slice_idle * cfqq->dispatched,
2479                 cfqq->slice_end))
2480                 return true;
2481
2482         return false;
2483 }
2484
2485 static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2486 {
2487         unsigned int max_dispatch;
2488
2489         /*
2490          * Drain async requests before we start sync IO
2491          */
2492         if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_flight[BLK_RW_ASYNC])
2493                 return false;
2494
2495         /*
2496          * If this is an async queue and we have sync IO in flight, let it wait
2497          */
2498         if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq))
2499                 return false;
2500
2501         max_dispatch = max_t(unsigned int, cfqd->cfq_quantum / 2, 1);
2502         if (cfq_class_idle(cfqq))
2503                 max_dispatch = 1;
2504
2505         /*
2506          * Does this cfqq already have too much IO in flight?
2507          */
2508         if (cfqq->dispatched >= max_dispatch) {
2509                 bool promote_sync = false;
2510                 /*
2511                  * idle queue must always only have a single IO in flight
2512                  */
2513                 if (cfq_class_idle(cfqq))
2514                         return false;
2515
2516                 /*
2517                  * If there is only one sync queue
2518                  * we can ignore async queue here and give the sync
2519                  * queue no dispatch limit. The reason is a sync queue can
2520                  * preempt async queue, limiting the sync queue doesn't make
2521                  * sense. This is useful for aiostress test.
2522                  */
2523                 if (cfq_cfqq_sync(cfqq) && cfqd->busy_sync_queues == 1)
2524                         promote_sync = true;
2525
2526                 /*
2527                  * We have other queues, don't allow more IO from this one
2528                  */
2529                 if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq) &&
2530                                 !promote_sync)
2531                         return false;
2532
2533                 /*
2534                  * Sole queue user, no limit
2535                  */
2536                 if (cfqd->busy_queues == 1 || promote_sync)
2537                         max_dispatch = -1;
2538                 else
2539                         /*
2540                          * Normally we start throttling cfqq when cfq_quantum/2
2541                          * requests have been dispatched. But we can drive
2542                          * deeper queue depths at the beginning of slice
2543                          * subjected to upper limit of cfq_quantum.
2544                          * */
2545                         max_dispatch = cfqd->cfq_quantum;
2546         }
2547
2548         /*
2549          * Async queues must wait a bit before being allowed dispatch.
2550          * We also ramp up the dispatch depth gradually for async IO,
2551          * based on the last sync IO we serviced
2552          */
2553         if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
2554                 unsigned long last_sync = jiffies - cfqd->last_delayed_sync;
2555                 unsigned int depth;
2556
2557                 depth = last_sync / cfqd->cfq_slice[1];
2558                 if (!depth && !cfqq->dispatched)
2559                         depth = 1;
2560                 if (depth < max_dispatch)
2561                         max_dispatch = depth;
2562         }
2563
2564         /*
2565          * If we're below the current max, allow a dispatch
2566          */
2567         return cfqq->dispatched < max_dispatch;
2568 }
2569
2570 /*
2571  * Dispatch a request from cfqq, moving them to the request queue
2572  * dispatch list.
2573  */
2574 static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2575 {
2576         struct request *rq;
2577
2578         BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
2579
2580         if (!cfq_may_dispatch(cfqd, cfqq))
2581                 return false;
2582
2583         /*
2584          * follow expired path, else get first next available
2585          */
2586         rq = cfq_check_fifo(cfqq);
2587         if (!rq)
2588                 rq = cfqq->next_rq;
2589
2590         /*
2591          * insert request into driver dispatch list
2592          */
2593         cfq_dispatch_insert(cfqd->queue, rq);
2594
2595         if (!cfqd->active_cic) {
2596                 struct cfq_io_cq *cic = RQ_CIC(rq);
2597
2598                 atomic_long_inc(&cic->icq.ioc->refcount);
2599                 cfqd->active_cic = cic;
2600         }
2601
2602         return true;
2603 }
2604
2605 /*
2606  * Find the cfqq that we need to service and move a request from that to the
2607  * dispatch list
2608  */
2609 static int cfq_dispatch_requests(struct request_queue *q, int force)
2610 {
2611         struct cfq_data *cfqd = q->elevator->elevator_data;
2612         struct cfq_queue *cfqq;
2613
2614         if (!cfqd->busy_queues)
2615                 return 0;
2616
2617         if (unlikely(force))
2618                 return cfq_forced_dispatch(cfqd);
2619
2620         cfqq = cfq_select_queue(cfqd);
2621         if (!cfqq)
2622                 return 0;
2623
2624         /*
2625          * Dispatch a request from this cfqq, if it is allowed
2626          */
2627         if (!cfq_dispatch_request(cfqd, cfqq))
2628                 return 0;
2629
2630         cfqq->slice_dispatch++;
2631         cfq_clear_cfqq_must_dispatch(cfqq);
2632
2633         /*
2634          * expire an async queue immediately if it has used up its slice. idle
2635          * queue always expire after 1 dispatch round.
2636          */
2637         if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
2638             cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
2639             cfq_class_idle(cfqq))) {
2640                 cfqq->slice_end = jiffies + 1;
2641                 cfq_slice_expired(cfqd, 0);
2642         }
2643
2644         cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
2645         return 1;
2646 }
2647
2648 /*
2649  * task holds one reference to the queue, dropped when task exits. each rq
2650  * in-flight on this queue also holds a reference, dropped when rq is freed.
2651  *
2652  * Each cfq queue took a reference on the parent group. Drop it now.
2653  * queue lock must be held here.
2654  */
2655 static void cfq_put_queue(struct cfq_queue *cfqq)
2656 {
2657         struct cfq_data *cfqd = cfqq->cfqd;
2658         struct cfq_group *cfqg;
2659
2660         BUG_ON(cfqq->ref <= 0);
2661
2662         cfqq->ref--;
2663         if (cfqq->ref)
2664                 return;
2665
2666         cfq_log_cfqq(cfqd, cfqq, "put_queue");
2667         BUG_ON(rb_first(&cfqq->sort_list));
2668         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
2669         cfqg = cfqq->cfqg;
2670
2671         if (unlikely(cfqd->active_queue == cfqq)) {
2672                 __cfq_slice_expired(cfqd, cfqq, 0);
2673                 cfq_schedule_dispatch(cfqd);
2674         }
2675
2676         BUG_ON(cfq_cfqq_on_rr(cfqq));
2677         kmem_cache_free(cfq_pool, cfqq);
2678         cfq_put_cfqg(cfqg);
2679 }
2680
2681 static void cfq_put_cooperator(struct cfq_queue *cfqq)
2682 {
2683         struct cfq_queue *__cfqq, *next;
2684
2685         /*
2686          * If this queue was scheduled to merge with another queue, be
2687          * sure to drop the reference taken on that queue (and others in
2688          * the merge chain).  See cfq_setup_merge and cfq_merge_cfqqs.
2689          */
2690         __cfqq = cfqq->new_cfqq;
2691         while (__cfqq) {
2692                 if (__cfqq == cfqq) {
2693                         WARN(1, "cfqq->new_cfqq loop detected\n");
2694                         break;
2695                 }
2696                 next = __cfqq->new_cfqq;
2697                 cfq_put_queue(__cfqq);
2698                 __cfqq = next;
2699         }
2700 }
2701
2702 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2703 {
2704         if (unlikely(cfqq == cfqd->active_queue)) {
2705                 __cfq_slice_expired(cfqd, cfqq, 0);
2706                 cfq_schedule_dispatch(cfqd);
2707         }
2708
2709         cfq_put_cooperator(cfqq);
2710
2711         cfq_put_queue(cfqq);
2712 }
2713
2714 static void cfq_init_icq(struct io_cq *icq)
2715 {
2716         struct cfq_io_cq *cic = icq_to_cic(icq);
2717
2718         cic->ttime.last_end_request = jiffies;
2719 }
2720
2721 static void cfq_exit_icq(struct io_cq *icq)
2722 {
2723         struct cfq_io_cq *cic = icq_to_cic(icq);
2724         struct cfq_data *cfqd = cic_to_cfqd(cic);
2725
2726         if (cic->cfqq[BLK_RW_ASYNC]) {
2727                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
2728                 cic->cfqq[BLK_RW_ASYNC] = NULL;
2729         }
2730
2731         if (cic->cfqq[BLK_RW_SYNC]) {
2732                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
2733                 cic->cfqq[BLK_RW_SYNC] = NULL;
2734         }
2735 }
2736
2737 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
2738 {
2739         struct task_struct *tsk = current;
2740         int ioprio_class;
2741
2742         if (!cfq_cfqq_prio_changed(cfqq))
2743                 return;
2744
2745         ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
2746         switch (ioprio_class) {
2747         default:
2748                 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
2749         case IOPRIO_CLASS_NONE:
2750                 /*
2751                  * no prio set, inherit CPU scheduling settings
2752                  */
2753                 cfqq->ioprio = task_nice_ioprio(tsk);
2754                 cfqq->ioprio_class = task_nice_ioclass(tsk);
2755                 break;
2756         case IOPRIO_CLASS_RT:
2757                 cfqq->ioprio = task_ioprio(ioc);
2758                 cfqq->ioprio_class = IOPRIO_CLASS_RT;
2759                 break;
2760         case IOPRIO_CLASS_BE:
2761                 cfqq->ioprio = task_ioprio(ioc);
2762                 cfqq->ioprio_class = IOPRIO_CLASS_BE;
2763                 break;
2764         case IOPRIO_CLASS_IDLE:
2765                 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
2766                 cfqq->ioprio = 7;
2767                 cfq_clear_cfqq_idle_window(cfqq);
2768                 break;
2769         }
2770
2771         /*
2772          * keep track of original prio settings in case we have to temporarily
2773          * elevate the priority of this queue
2774          */
2775         cfqq->org_ioprio = cfqq->ioprio;
2776         cfq_clear_cfqq_prio_changed(cfqq);
2777 }
2778
2779 static void changed_ioprio(struct cfq_io_cq *cic)
2780 {
2781         struct cfq_data *cfqd = cic_to_cfqd(cic);
2782         struct cfq_queue *cfqq;
2783
2784         if (unlikely(!cfqd))
2785                 return;
2786
2787         cfqq = cic->cfqq[BLK_RW_ASYNC];
2788         if (cfqq) {
2789                 struct cfq_queue *new_cfqq;
2790                 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->icq.ioc,
2791                                                 GFP_ATOMIC);
2792                 if (new_cfqq) {
2793                         cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
2794                         cfq_put_queue(cfqq);
2795                 }
2796         }
2797
2798         cfqq = cic->cfqq[BLK_RW_SYNC];
2799         if (cfqq)
2800                 cfq_mark_cfqq_prio_changed(cfqq);
2801 }
2802
2803 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2804                           pid_t pid, bool is_sync)
2805 {
2806         RB_CLEAR_NODE(&cfqq->rb_node);
2807         RB_CLEAR_NODE(&cfqq->p_node);
2808         INIT_LIST_HEAD(&cfqq->fifo);
2809
2810         cfqq->ref = 0;
2811         cfqq->cfqd = cfqd;
2812
2813         cfq_mark_cfqq_prio_changed(cfqq);
2814
2815         if (is_sync) {
2816                 if (!cfq_class_idle(cfqq))
2817                         cfq_mark_cfqq_idle_window(cfqq);
2818                 cfq_mark_cfqq_sync(cfqq);
2819         }
2820         cfqq->pid = pid;
2821 }
2822
2823 #ifdef CONFIG_CFQ_GROUP_IOSCHED
2824 static void changed_cgroup(struct cfq_io_cq *cic)
2825 {
2826         struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1);
2827         struct cfq_data *cfqd = cic_to_cfqd(cic);
2828         struct request_queue *q;
2829
2830         if (unlikely(!cfqd))
2831                 return;
2832
2833         q = cfqd->queue;
2834
2835         if (sync_cfqq) {
2836                 /*
2837                  * Drop reference to sync queue. A new sync queue will be
2838                  * assigned in new group upon arrival of a fresh request.
2839                  */
2840                 cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
2841                 cic_set_cfqq(cic, NULL, 1);
2842                 cfq_put_queue(sync_cfqq);
2843         }
2844 }
2845 #endif  /* CONFIG_CFQ_GROUP_IOSCHED */
2846
2847 static struct cfq_queue *
2848 cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
2849                      struct io_context *ioc, gfp_t gfp_mask)
2850 {
2851         struct cfq_queue *cfqq, *new_cfqq = NULL;
2852         struct cfq_io_cq *cic;
2853         struct cfq_group *cfqg;
2854
2855 retry:
2856         cfqg = cfq_get_cfqg(cfqd);
2857         cic = cfq_cic_lookup(cfqd, ioc);
2858         /* cic always exists here */
2859         cfqq = cic_to_cfqq(cic, is_sync);
2860
2861         /*
2862          * Always try a new alloc if we fell back to the OOM cfqq
2863          * originally, since it should just be a temporary situation.
2864          */
2865         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2866                 cfqq = NULL;
2867                 if (new_cfqq) {
2868                         cfqq = new_cfqq;
2869                         new_cfqq = NULL;
2870                 } else if (gfp_mask & __GFP_WAIT) {
2871                         spin_unlock_irq(cfqd->queue->queue_lock);
2872                         new_cfqq = kmem_cache_alloc_node(cfq_pool,
2873                                         gfp_mask | __GFP_ZERO,
2874                                         cfqd->queue->node);
2875                         spin_lock_irq(cfqd->queue->queue_lock);
2876                         if (new_cfqq)
2877                                 goto retry;
2878                 } else {
2879                         cfqq = kmem_cache_alloc_node(cfq_pool,
2880                                         gfp_mask | __GFP_ZERO,
2881                                         cfqd->queue->node);
2882                 }
2883
2884                 if (cfqq) {
2885                         cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
2886                         cfq_init_prio_data(cfqq, ioc);
2887                         cfq_link_cfqq_cfqg(cfqq, cfqg);
2888                         cfq_log_cfqq(cfqd, cfqq, "alloced");
2889                 } else
2890                         cfqq = &cfqd->oom_cfqq;
2891         }
2892
2893         if (new_cfqq)
2894                 kmem_cache_free(cfq_pool, new_cfqq);
2895
2896         return cfqq;
2897 }
2898
2899 static struct cfq_queue **
2900 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
2901 {
2902         switch (ioprio_class) {
2903         case IOPRIO_CLASS_RT:
2904                 return &cfqd->async_cfqq[0][ioprio];
2905         case IOPRIO_CLASS_BE:
2906                 return &cfqd->async_cfqq[1][ioprio];
2907         case IOPRIO_CLASS_IDLE:
2908                 return &cfqd->async_idle_cfqq;
2909         default:
2910                 BUG();
2911         }
2912 }
2913
2914 static struct cfq_queue *
2915 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
2916               gfp_t gfp_mask)
2917 {
2918         const int ioprio = task_ioprio(ioc);
2919         const int ioprio_class = task_ioprio_class(ioc);
2920         struct cfq_queue **async_cfqq = NULL;
2921         struct cfq_queue *cfqq = NULL;
2922
2923         if (!is_sync) {
2924                 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
2925                 cfqq = *async_cfqq;
2926         }
2927
2928         if (!cfqq)
2929                 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
2930
2931         /*
2932          * pin the queue now that it's allocated, scheduler exit will prune it
2933          */
2934         if (!is_sync && !(*async_cfqq)) {
2935                 cfqq->ref++;
2936                 *async_cfqq = cfqq;
2937         }
2938
2939         cfqq->ref++;
2940         return cfqq;
2941 }
2942
2943 static void
2944 __cfq_update_io_thinktime(struct cfq_ttime *ttime, unsigned long slice_idle)
2945 {
2946         unsigned long elapsed = jiffies - ttime->last_end_request;
2947         elapsed = min(elapsed, 2UL * slice_idle);
2948
2949         ttime->ttime_samples = (7*ttime->ttime_samples + 256) / 8;
2950         ttime->ttime_total = (7*ttime->ttime_total + 256*elapsed) / 8;
2951         ttime->ttime_mean = (ttime->ttime_total + 128) / ttime->ttime_samples;
2952 }
2953
2954 static void
2955 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2956                         struct cfq_io_cq *cic)
2957 {
2958         if (cfq_cfqq_sync(cfqq)) {
2959                 __cfq_update_io_thinktime(&cic->ttime, cfqd->cfq_slice_idle);
2960                 __cfq_update_io_thinktime(&cfqq->service_tree->ttime,
2961                         cfqd->cfq_slice_idle);
2962         }
2963 #ifdef CONFIG_CFQ_GROUP_IOSCHED
2964         __cfq_update_io_thinktime(&cfqq->cfqg->ttime, cfqd->cfq_group_idle);
2965 #endif
2966 }
2967
2968 static void
2969 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2970                        struct request *rq)
2971 {
2972         sector_t sdist = 0;
2973         sector_t n_sec = blk_rq_sectors(rq);
2974         if (cfqq->last_request_pos) {
2975                 if (cfqq->last_request_pos < blk_rq_pos(rq))
2976                         sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
2977                 else
2978                         sdist = cfqq->last_request_pos - blk_rq_pos(rq);
2979         }
2980
2981         cfqq->seek_history <<= 1;
2982         if (blk_queue_nonrot(cfqd->queue))
2983                 cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT);
2984         else
2985                 cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
2986 }
2987
2988 /*
2989  * Disable idle window if the process thinks too long or seeks so much that
2990  * it doesn't matter
2991  */
2992 static void
2993 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2994                        struct cfq_io_cq *cic)
2995 {
2996         int old_idle, enable_idle;
2997
2998         /*
2999          * Don't idle for async or idle io prio class
3000          */
3001         if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
3002                 return;
3003
3004         enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
3005
3006         if (cfqq->queued[0] + cfqq->queued[1] >= 4)
3007                 cfq_mark_cfqq_deep(cfqq);
3008
3009         if (cfqq->next_rq && (cfqq->next_rq->cmd_flags & REQ_NOIDLE))
3010                 enable_idle = 0;
3011         else if (!atomic_read(&cic->icq.ioc->nr_tasks) ||
3012                  !cfqd->cfq_slice_idle ||
3013                  (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
3014                 enable_idle = 0;
3015         else if (sample_valid(cic->ttime.ttime_samples)) {
3016                 if (cic->ttime.ttime_mean > cfqd->cfq_slice_idle)
3017                         enable_idle = 0;
3018                 else
3019                         enable_idle = 1;
3020         }
3021
3022         if (old_idle != enable_idle) {
3023                 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
3024                 if (enable_idle)
3025                         cfq_mark_cfqq_idle_window(cfqq);
3026                 else
3027                         cfq_clear_cfqq_idle_window(cfqq);
3028         }
3029 }
3030
3031 /*
3032  * Check if new_cfqq should preempt the currently active queue. Return 0 for
3033  * no or if we aren't sure, a 1 will cause a preempt.
3034  */
3035 static bool
3036 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
3037                    struct request *rq)
3038 {
3039         struct cfq_queue *cfqq;
3040
3041         cfqq = cfqd->active_queue;
3042         if (!cfqq)
3043                 return false;
3044
3045         if (cfq_class_idle(new_cfqq))
3046                 return false;
3047
3048         if (cfq_class_idle(cfqq))
3049                 return true;
3050
3051         /*
3052          * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice.
3053          */
3054         if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq))
3055                 return false;
3056
3057         /*
3058          * if the new request is sync, but the currently running queue is
3059          * not, let the sync request have priority.
3060          */
3061         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
3062                 return true;
3063
3064         if (new_cfqq->cfqg != cfqq->cfqg)
3065                 return false;
3066
3067         if (cfq_slice_used(cfqq))
3068                 return true;
3069
3070         /* Allow preemption only if we are idling on sync-noidle tree */
3071         if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
3072             cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
3073             new_cfqq->service_tree->count == 2 &&
3074             RB_EMPTY_ROOT(&cfqq->sort_list))
3075                 return true;
3076
3077         /*
3078          * So both queues are sync. Let the new request get disk time if
3079          * it's a metadata request and the current queue is doing regular IO.
3080          */
3081         if ((rq->cmd_flags & REQ_PRIO) && !cfqq->prio_pending)
3082                 return true;
3083
3084         /*
3085          * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
3086          */
3087         if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
3088                 return true;
3089
3090         /* An idle queue should not be idle now for some reason */
3091         if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq))
3092                 return true;
3093
3094         if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
3095                 return false;
3096
3097         /*
3098          * if this request is as-good as one we would expect from the
3099          * current cfqq, let it preempt
3100          */
3101         if (cfq_rq_close(cfqd, cfqq, rq))
3102                 return true;
3103
3104         return false;
3105 }
3106
3107 /*
3108  * cfqq preempts the active queue. if we allowed preempt with no slice left,
3109  * let it have half of its nominal slice.
3110  */
3111 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3112 {
3113         enum wl_type_t old_type = cfqq_type(cfqd->active_queue);
3114
3115         cfq_log_cfqq(cfqd, cfqq, "preempt");
3116         cfq_slice_expired(cfqd, 1);
3117
3118         /*
3119          * workload type is changed, don't save slice, otherwise preempt
3120          * doesn't happen
3121          */
3122         if (old_type != cfqq_type(cfqq))
3123                 cfqq->cfqg->saved_workload_slice = 0;
3124
3125         /*
3126          * Put the new queue at the front of the of the current list,
3127          * so we know that it will be selected next.
3128          */
3129         BUG_ON(!cfq_cfqq_on_rr(cfqq));
3130
3131         cfq_service_tree_add(cfqd, cfqq, 1);
3132
3133         cfqq->slice_end = 0;
3134         cfq_mark_cfqq_slice_new(cfqq);
3135 }
3136
3137 /*
3138  * Called when a new fs request (rq) is added (to cfqq). Check if there's
3139  * something we should do about it
3140  */
3141 static void
3142 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3143                 struct request *rq)
3144 {
3145         struct cfq_io_cq *cic = RQ_CIC(rq);
3146
3147         cfqd->rq_queued++;
3148         if (rq->cmd_flags & REQ_PRIO)
3149                 cfqq->prio_pending++;
3150
3151         cfq_update_io_thinktime(cfqd, cfqq, cic);
3152         cfq_update_io_seektime(cfqd, cfqq, rq);
3153         cfq_update_idle_window(cfqd, cfqq, cic);
3154
3155         cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
3156
3157         if (cfqq == cfqd->active_queue) {
3158                 /*
3159                  * Remember that we saw a request from this process, but
3160                  * don't start queuing just yet. Otherwise we risk seeing lots
3161                  * of tiny requests, because we disrupt the normal plugging
3162                  * and merging. If the request is already larger than a single
3163                  * page, let it rip immediately. For that case we assume that
3164                  * merging is already done. Ditto for a busy system that
3165                  * has other work pending, don't risk delaying until the
3166                  * idle timer unplug to continue working.
3167                  */
3168                 if (cfq_cfqq_wait_request(cfqq)) {
3169                         if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
3170                             cfqd->busy_queues > 1) {
3171                                 cfq_del_timer(cfqd, cfqq);
3172                                 cfq_clear_cfqq_wait_request(cfqq);
3173                                 __blk_run_queue(cfqd->queue);
3174                         } else {
3175                                 cfq_blkiocg_update_idle_time_stats(
3176                                                 &cfqq->cfqg->blkg);
3177                                 cfq_mark_cfqq_must_dispatch(cfqq);
3178                         }
3179                 }
3180         } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
3181                 /*
3182                  * not the active queue - expire current slice if it is
3183                  * idle and has expired it's mean thinktime or this new queue
3184                  * has some old slice time left and is of higher priority or
3185                  * this new queue is RT and the current one is BE
3186                  */
3187                 cfq_preempt_queue(cfqd, cfqq);
3188                 __blk_run_queue(cfqd->queue);
3189         }
3190 }
3191
3192 static void cfq_insert_request(struct request_queue *q, struct request *rq)
3193 {
3194         struct cfq_data *cfqd = q->elevator->elevator_data;
3195         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3196
3197         cfq_log_cfqq(cfqd, cfqq, "insert_request");
3198         cfq_init_prio_data(cfqq, RQ_CIC(rq)->icq.ioc);
3199
3200         rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
3201         list_add_tail(&rq->queuelist, &cfqq->fifo);
3202         cfq_add_rq_rb(rq);
3203         cfq_blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg,
3204                         &cfqd->serving_group->blkg, rq_data_dir(rq),
3205                         rq_is_sync(rq));
3206         cfq_rq_enqueued(cfqd, cfqq, rq);
3207 }
3208
3209 /*
3210  * Update hw_tag based on peak queue depth over 50 samples under
3211  * sufficient load.
3212  */
3213 static void cfq_update_hw_tag(struct cfq_data *cfqd)
3214 {
3215         struct cfq_queue *cfqq = cfqd->active_queue;
3216
3217         if (cfqd->rq_in_driver > cfqd->hw_tag_est_depth)
3218                 cfqd->hw_tag_est_depth = cfqd->rq_in_driver;
3219
3220         if (cfqd->hw_tag == 1)
3221                 return;
3222
3223         if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
3224             cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
3225                 return;
3226
3227         /*
3228          * If active queue hasn't enough requests and can idle, cfq might not
3229          * dispatch sufficient requests to hardware. Don't zero hw_tag in this
3230          * case
3231          */
3232         if (cfqq && cfq_cfqq_idle_window(cfqq) &&
3233             cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
3234             CFQ_HW_QUEUE_MIN && cfqd->rq_in_driver < CFQ_HW_QUEUE_MIN)
3235                 return;
3236
3237         if (cfqd->hw_tag_samples++ < 50)
3238                 return;
3239
3240         if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
3241                 cfqd->hw_tag = 1;
3242         else
3243                 cfqd->hw_tag = 0;
3244 }
3245
3246 static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3247 {
3248         struct cfq_io_cq *cic = cfqd->active_cic;
3249
3250         /* If the queue already has requests, don't wait */
3251         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3252                 return false;
3253
3254         /* If there are other queues in the group, don't wait */
3255         if (cfqq->cfqg->nr_cfqq > 1)
3256                 return false;
3257
3258         /* the only queue in the group, but think time is big */
3259         if (cfq_io_thinktime_big(cfqd, &cfqq->cfqg->ttime, true))
3260                 return false;
3261
3262         if (cfq_slice_used(cfqq))
3263                 return true;
3264
3265         /* if slice left is less than think time, wait busy */
3266         if (cic && sample_valid(cic->ttime.ttime_samples)
3267             && (cfqq->slice_end - jiffies < cic->ttime.ttime_mean))
3268                 return true;
3269
3270         /*
3271          * If think times is less than a jiffy than ttime_mean=0 and above
3272          * will not be true. It might happen that slice has not expired yet
3273          * but will expire soon (4-5 ns) during select_queue(). To cover the
3274          * case where think time is less than a jiffy, mark the queue wait
3275          * busy if only 1 jiffy is left in the slice.
3276          */
3277         if (cfqq->slice_end - jiffies == 1)
3278                 return true;
3279
3280         return false;
3281 }
3282
3283 static void cfq_completed_request(struct request_queue *q, struct request *rq)
3284 {
3285         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3286         struct cfq_data *cfqd = cfqq->cfqd;
3287         const int sync = rq_is_sync(rq);
3288         unsigned long now;
3289
3290         now = jiffies;
3291         cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d",
3292                      !!(rq->cmd_flags & REQ_NOIDLE));
3293
3294         cfq_update_hw_tag(cfqd);
3295
3296         WARN_ON(!cfqd->rq_in_driver);
3297         WARN_ON(!cfqq->dispatched);
3298         cfqd->rq_in_driver--;
3299         cfqq->dispatched--;
3300         (RQ_CFQG(rq))->dispatched--;
3301         cfq_blkiocg_update_completion_stats(&cfqq->cfqg->blkg,
3302                         rq_start_time_ns(rq), rq_io_start_time_ns(rq),
3303                         rq_data_dir(rq), rq_is_sync(rq));
3304
3305         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
3306
3307         if (sync) {
3308                 struct cfq_rb_root *service_tree;
3309
3310                 RQ_CIC(rq)->ttime.last_end_request = now;
3311
3312                 if (cfq_cfqq_on_rr(cfqq))
3313                         service_tree = cfqq->service_tree;
3314                 else
3315                         service_tree = service_tree_for(cfqq->cfqg,
3316                                 cfqq_prio(cfqq), cfqq_type(cfqq));
3317                 service_tree->ttime.last_end_request = now;
3318                 if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
3319                         cfqd->last_delayed_sync = now;
3320         }
3321
3322 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3323         cfqq->cfqg->ttime.last_end_request = now;
3324 #endif
3325
3326         /*
3327          * If this is the active queue, check if it needs to be expired,
3328          * or if we want to idle in case it has no pending requests.
3329          */
3330         if (cfqd->active_queue == cfqq) {
3331                 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
3332
3333                 if (cfq_cfqq_slice_new(cfqq)) {
3334                         cfq_set_prio_slice(cfqd, cfqq);
3335                         cfq_clear_cfqq_slice_new(cfqq);
3336                 }
3337
3338                 /*
3339                  * Should we wait for next request to come in before we expire
3340                  * the queue.
3341                  */
3342                 if (cfq_should_wait_busy(cfqd, cfqq)) {
3343                         unsigned long extend_sl = cfqd->cfq_slice_idle;
3344                         if (!cfqd->cfq_slice_idle)
3345                                 extend_sl = cfqd->cfq_group_idle;
3346                         cfqq->slice_end = jiffies + extend_sl;
3347                         cfq_mark_cfqq_wait_busy(cfqq);
3348                         cfq_log_cfqq(cfqd, cfqq, "will busy wait");
3349                 }
3350
3351                 /*
3352                  * Idling is not enabled on:
3353                  * - expired queues
3354                  * - idle-priority queues
3355                  * - async queues
3356                  * - queues with still some requests queued
3357                  * - when there is a close cooperator
3358                  */
3359                 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
3360                         cfq_slice_expired(cfqd, 1);
3361                 else if (sync && cfqq_empty &&
3362                          !cfq_close_cooperator(cfqd, cfqq)) {
3363                         cfq_arm_slice_timer(cfqd);
3364                 }
3365         }
3366
3367         if (!cfqd->rq_in_driver)
3368                 cfq_schedule_dispatch(cfqd);
3369 }
3370
3371 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
3372 {
3373         if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
3374                 cfq_mark_cfqq_must_alloc_slice(cfqq);
3375                 return ELV_MQUEUE_MUST;
3376         }
3377
3378         return ELV_MQUEUE_MAY;
3379 }
3380
3381 static int cfq_may_queue(struct request_queue *q, int rw)
3382 {
3383         struct cfq_data *cfqd = q->elevator->elevator_data;
3384         struct task_struct *tsk = current;
3385         struct cfq_io_cq *cic;
3386         struct cfq_queue *cfqq;
3387
3388         /*
3389          * don't force setup of a queue from here, as a call to may_queue
3390          * does not necessarily imply that a request actually will be queued.
3391          * so just lookup a possibly existing queue, or return 'may queue'
3392          * if that fails
3393          */
3394         cic = cfq_cic_lookup(cfqd, tsk->io_context);
3395         if (!cic)
3396                 return ELV_MQUEUE_MAY;
3397
3398         cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
3399         if (cfqq) {
3400                 cfq_init_prio_data(cfqq, cic->icq.ioc);
3401
3402                 return __cfq_may_queue(cfqq);
3403         }
3404
3405         return ELV_MQUEUE_MAY;
3406 }
3407
3408 /*
3409  * queue lock held here
3410  */
3411 static void cfq_put_request(struct request *rq)
3412 {
3413         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3414
3415         if (cfqq) {
3416                 const int rw = rq_data_dir(rq);
3417
3418                 BUG_ON(!cfqq->allocated[rw]);
3419                 cfqq->allocated[rw]--;
3420
3421                 /* Put down rq reference on cfqg */
3422                 cfq_put_cfqg(RQ_CFQG(rq));
3423                 rq->elv.priv[0] = NULL;
3424                 rq->elv.priv[1] = NULL;
3425
3426                 cfq_put_queue(cfqq);
3427         }
3428 }
3429
3430 static struct cfq_queue *
3431 cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_cq *cic,
3432                 struct cfq_queue *cfqq)
3433 {
3434         cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
3435         cic_set_cfqq(cic, cfqq->new_cfqq, 1);
3436         cfq_mark_cfqq_coop(cfqq->new_cfqq);
3437         cfq_put_queue(cfqq);
3438         return cic_to_cfqq(cic, 1);
3439 }
3440
3441 /*
3442  * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
3443  * was the last process referring to said cfqq.
3444  */
3445 static struct cfq_queue *
3446 split_cfqq(struct cfq_io_cq *cic, struct cfq_queue *cfqq)
3447 {
3448         if (cfqq_process_refs(cfqq) == 1) {
3449                 cfqq->pid = current->pid;
3450                 cfq_clear_cfqq_coop(cfqq);
3451                 cfq_clear_cfqq_split_coop(cfqq);
3452                 return cfqq;
3453         }
3454
3455         cic_set_cfqq(cic, NULL, 1);
3456
3457         cfq_put_cooperator(cfqq);
3458
3459         cfq_put_queue(cfqq);
3460         return NULL;
3461 }
3462 /*
3463  * Allocate cfq data structures associated with this request.
3464  */
3465 static int
3466 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
3467 {
3468         struct cfq_data *cfqd = q->elevator->elevator_data;
3469         struct cfq_io_cq *cic = icq_to_cic(rq->elv.icq);
3470         const int rw = rq_data_dir(rq);
3471         const bool is_sync = rq_is_sync(rq);
3472         struct cfq_queue *cfqq;
3473         unsigned int changed;
3474
3475         might_sleep_if(gfp_mask & __GFP_WAIT);
3476
3477         spin_lock_irq(q->queue_lock);
3478
3479         /* handle changed notifications */
3480         changed = icq_get_changed(&cic->icq);
3481         if (unlikely(changed & ICQ_IOPRIO_CHANGED))
3482                 changed_ioprio(cic);
3483 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3484         if (unlikely(changed & ICQ_CGROUP_CHANGED))
3485                 changed_cgroup(cic);
3486 #endif
3487
3488 new_queue:
3489         cfqq = cic_to_cfqq(cic, is_sync);
3490         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3491                 cfqq = cfq_get_queue(cfqd, is_sync, cic->icq.ioc, gfp_mask);
3492                 cic_set_cfqq(cic, cfqq, is_sync);
3493         } else {
3494                 /*
3495                  * If the queue was seeky for too long, break it apart.
3496                  */
3497                 if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) {
3498                         cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
3499                         cfqq = split_cfqq(cic, cfqq);
3500                         if (!cfqq)
3501                                 goto new_queue;
3502                 }
3503
3504                 /*
3505                  * Check to see if this queue is scheduled to merge with
3506                  * another, closely cooperating queue.  The merging of
3507                  * queues happens here as it must be done in process context.
3508                  * The reference on new_cfqq was taken in merge_cfqqs.
3509                  */
3510                 if (cfqq->new_cfqq)
3511                         cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
3512         }
3513
3514         cfqq->allocated[rw]++;
3515
3516         cfqq->ref++;
3517         rq->elv.priv[0] = cfqq;
3518         rq->elv.priv[1] = cfq_ref_get_cfqg(cfqq->cfqg);
3519         spin_unlock_irq(q->queue_lock);
3520         return 0;
3521 }
3522
3523 static void cfq_kick_queue(struct work_struct *work)
3524 {
3525         struct cfq_data *cfqd =
3526                 container_of(work, struct cfq_data, unplug_work);
3527         struct request_queue *q = cfqd->queue;
3528
3529         spin_lock_irq(q->queue_lock);
3530         __blk_run_queue(cfqd->queue);
3531         spin_unlock_irq(q->queue_lock);
3532 }
3533
3534 /*
3535  * Timer running if the active_queue is currently idling inside its time slice
3536  */
3537 static void cfq_idle_slice_timer(unsigned long data)
3538 {
3539         struct cfq_data *cfqd = (struct cfq_data *) data;
3540         struct cfq_queue *cfqq;
3541         unsigned long flags;
3542         int timed_out = 1;
3543
3544         cfq_log(cfqd, "idle timer fired");
3545
3546         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
3547
3548         cfqq = cfqd->active_queue;
3549         if (cfqq) {
3550                 timed_out = 0;
3551
3552                 /*
3553                  * We saw a request before the queue expired, let it through
3554                  */
3555                 if (cfq_cfqq_must_dispatch(cfqq))
3556                         goto out_kick;
3557
3558                 /*
3559                  * expired
3560                  */
3561                 if (cfq_slice_used(cfqq))
3562                         goto expire;
3563
3564                 /*
3565                  * only expire and reinvoke request handler, if there are
3566                  * other queues with pending requests
3567                  */
3568                 if (!cfqd->busy_queues)
3569                         goto out_cont;
3570
3571                 /*
3572                  * not expired and it has a request pending, let it dispatch
3573                  */
3574                 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3575                         goto out_kick;
3576
3577                 /*
3578                  * Queue depth flag is reset only when the idle didn't succeed
3579                  */
3580                 cfq_clear_cfqq_deep(cfqq);
3581         }
3582 expire:
3583         cfq_slice_expired(cfqd, timed_out);
3584 out_kick:
3585         cfq_schedule_dispatch(cfqd);
3586 out_cont:
3587         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
3588 }
3589
3590 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
3591 {
3592         del_timer_sync(&cfqd->idle_slice_timer);
3593         cancel_work_sync(&cfqd->unplug_work);
3594 }
3595
3596 static void cfq_put_async_queues(struct cfq_data *cfqd)
3597 {
3598         int i;
3599
3600         for (i = 0; i < IOPRIO_BE_NR; i++) {
3601                 if (cfqd->async_cfqq[0][i])
3602                         cfq_put_queue(cfqd->async_cfqq[0][i]);
3603                 if (cfqd->async_cfqq[1][i])
3604                         cfq_put_queue(cfqd->async_cfqq[1][i]);
3605         }
3606
3607         if (cfqd->async_idle_cfqq)
3608                 cfq_put_queue(cfqd->async_idle_cfqq);
3609 }
3610
3611 static void cfq_exit_queue(struct elevator_queue *e)
3612 {
3613         struct cfq_data *cfqd = e->elevator_data;
3614         struct request_queue *q = cfqd->queue;
3615         bool wait = false;
3616
3617         cfq_shutdown_timer_wq(cfqd);
3618
3619         spin_lock_irq(q->queue_lock);
3620
3621         if (cfqd->active_queue)
3622                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
3623
3624         cfq_put_async_queues(cfqd);
3625         cfq_release_cfq_groups(cfqd);
3626
3627         /*
3628          * If there are groups which we could not unlink from blkcg list,
3629          * wait for a rcu period for them to be freed.
3630          */
3631         if (cfqd->nr_blkcg_linked_grps)
3632                 wait = true;
3633
3634         spin_unlock_irq(q->queue_lock);
3635
3636         cfq_shutdown_timer_wq(cfqd);
3637
3638         /*
3639          * Wait for cfqg->blkg->key accessors to exit their grace periods.
3640          * Do this wait only if there are other unlinked groups out
3641          * there. This can happen if cgroup deletion path claimed the
3642          * responsibility of cleaning up a group before queue cleanup code
3643          * get to the group.
3644          *
3645          * Do not call synchronize_rcu() unconditionally as there are drivers
3646          * which create/delete request queue hundreds of times during scan/boot
3647          * and synchronize_rcu() can take significant time and slow down boot.
3648          */
3649         if (wait)
3650                 synchronize_rcu();
3651
3652 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3653         /* Free up per cpu stats for root group */
3654         free_percpu(cfqd->root_group.blkg.stats_cpu);
3655 #endif
3656         kfree(cfqd);
3657 }
3658
3659 static void *cfq_init_queue(struct request_queue *q)
3660 {
3661         struct cfq_data *cfqd;
3662         int i, j;
3663         struct cfq_group *cfqg;
3664         struct cfq_rb_root *st;
3665
3666         cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
3667         if (!cfqd)
3668                 return NULL;
3669
3670         /* Init root service tree */
3671         cfqd->grp_service_tree = CFQ_RB_ROOT;
3672
3673         /* Init root group */
3674         cfqg = &cfqd->root_group;
3675         for_each_cfqg_st(cfqg, i, j, st)
3676                 *st = CFQ_RB_ROOT;
3677         RB_CLEAR_NODE(&cfqg->rb_node);
3678
3679         /* Give preference to root group over other groups */
3680         cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
3681
3682 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3683         /*
3684          * Set root group reference to 2. One reference will be dropped when
3685          * all groups on cfqd->cfqg_list are being deleted during queue exit.
3686          * Other reference will remain there as we don't want to delete this
3687          * group as it is statically allocated and gets destroyed when
3688          * throtl_data goes away.
3689          */
3690         cfqg->ref = 2;
3691
3692         if (blkio_alloc_blkg_stats(&cfqg->blkg)) {
3693                 kfree(cfqg);
3694                 kfree(cfqd);
3695                 return NULL;
3696         }
3697
3698         rcu_read_lock();
3699
3700         cfq_blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg,
3701                                         (void *)cfqd, 0);
3702         rcu_read_unlock();
3703         cfqd->nr_blkcg_linked_grps++;
3704
3705         /* Add group on cfqd->cfqg_list */
3706         hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
3707 #endif
3708         /*
3709          * Not strictly needed (since RB_ROOT just clears the node and we
3710          * zeroed cfqd on alloc), but better be safe in case someone decides
3711          * to add magic to the rb code
3712          */
3713         for (i = 0; i < CFQ_PRIO_LISTS; i++)
3714                 cfqd->prio_trees[i] = RB_ROOT;
3715
3716         /*
3717          * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
3718          * Grab a permanent reference to it, so that the normal code flow
3719          * will not attempt to free it.
3720          */
3721         cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
3722         cfqd->oom_cfqq.ref++;
3723         cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
3724
3725         cfqd->queue = q;
3726
3727         init_timer(&cfqd->idle_slice_timer);
3728         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
3729         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
3730
3731         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
3732
3733         cfqd->cfq_quantum = cfq_quantum;
3734         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
3735         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
3736         cfqd->cfq_back_max = cfq_back_max;
3737         cfqd->cfq_back_penalty = cfq_back_penalty;
3738         cfqd->cfq_slice[0] = cfq_slice_async;
3739         cfqd->cfq_slice[1] = cfq_slice_sync;
3740         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
3741         cfqd->cfq_slice_idle = cfq_slice_idle;
3742         cfqd->cfq_group_idle = cfq_group_idle;
3743         cfqd->cfq_latency = 1;
3744         cfqd->hw_tag = -1;
3745         /*
3746          * we optimistically start assuming sync ops weren't delayed in last
3747          * second, in order to have larger depth for async operations.
3748          */
3749         cfqd->last_delayed_sync = jiffies - HZ;
3750         return cfqd;
3751 }
3752
3753 /*
3754  * sysfs parts below -->
3755  */
3756 static ssize_t
3757 cfq_var_show(unsigned int var, char *page)
3758 {
3759         return sprintf(page, "%d\n", var);
3760 }
3761
3762 static ssize_t
3763 cfq_var_store(unsigned int *var, const char *page, size_t count)
3764 {
3765         char *p = (char *) page;
3766
3767         *var = simple_strtoul(p, &p, 10);
3768         return count;
3769 }
3770
3771 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
3772 static ssize_t __FUNC(struct elevator_queue *e, char *page)             \
3773 {                                                                       \
3774         struct cfq_data *cfqd = e->elevator_data;                       \
3775         unsigned int __data = __VAR;                                    \
3776         if (__CONV)                                                     \
3777                 __data = jiffies_to_msecs(__data);                      \
3778         return cfq_var_show(__data, (page));                            \
3779 }
3780 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
3781 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
3782 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
3783 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
3784 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
3785 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
3786 SHOW_FUNCTION(cfq_group_idle_show, cfqd->cfq_group_idle, 1);
3787 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
3788 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
3789 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
3790 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
3791 #undef SHOW_FUNCTION
3792
3793 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
3794 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3795 {                                                                       \
3796         struct cfq_data *cfqd = e->elevator_data;                       \
3797         unsigned int __data;                                            \
3798         int ret = cfq_var_store(&__data, (page), count);                \
3799         if (__data < (MIN))                                             \
3800                 __data = (MIN);                                         \
3801         else if (__data > (MAX))                                        \
3802                 __data = (MAX);                                         \
3803         if (__CONV)                                                     \
3804                 *(__PTR) = msecs_to_jiffies(__data);                    \
3805         else                                                            \
3806                 *(__PTR) = __data;                                      \
3807         return ret;                                                     \
3808 }
3809 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
3810 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
3811                 UINT_MAX, 1);
3812 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
3813                 UINT_MAX, 1);
3814 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
3815 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
3816                 UINT_MAX, 0);
3817 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
3818 STORE_FUNCTION(cfq_group_idle_store, &cfqd->cfq_group_idle, 0, UINT_MAX, 1);
3819 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
3820 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
3821 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
3822                 UINT_MAX, 0);
3823 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
3824 #undef STORE_FUNCTION
3825
3826 #define CFQ_ATTR(name) \
3827         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3828
3829 static struct elv_fs_entry cfq_attrs[] = {
3830         CFQ_ATTR(quantum),
3831         CFQ_ATTR(fifo_expire_sync),
3832         CFQ_ATTR(fifo_expire_async),
3833         CFQ_ATTR(back_seek_max),
3834         CFQ_ATTR(back_seek_penalty),
3835         CFQ_ATTR(slice_sync),
3836         CFQ_ATTR(slice_async),
3837         CFQ_ATTR(slice_async_rq),
3838         CFQ_ATTR(slice_idle),
3839         CFQ_ATTR(group_idle),
3840         CFQ_ATTR(low_latency),
3841         __ATTR_NULL
3842 };
3843
3844 static struct elevator_type iosched_cfq = {
3845         .ops = {
3846                 .elevator_merge_fn =            cfq_merge,
3847                 .elevator_merged_fn =           cfq_merged_request,
3848                 .elevator_merge_req_fn =        cfq_merged_requests,
3849                 .elevator_allow_merge_fn =      cfq_allow_merge,
3850                 .elevator_bio_merged_fn =       cfq_bio_merged,
3851                 .elevator_dispatch_fn =         cfq_dispatch_requests,
3852                 .elevator_add_req_fn =          cfq_insert_request,
3853                 .elevator_activate_req_fn =     cfq_activate_request,
3854                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
3855                 .elevator_completed_req_fn =    cfq_completed_request,
3856                 .elevator_former_req_fn =       elv_rb_former_request,
3857                 .elevator_latter_req_fn =       elv_rb_latter_request,
3858                 .elevator_init_icq_fn =         cfq_init_icq,
3859                 .elevator_exit_icq_fn =         cfq_exit_icq,
3860                 .elevator_set_req_fn =          cfq_set_request,
3861                 .elevator_put_req_fn =          cfq_put_request,
3862                 .elevator_may_queue_fn =        cfq_may_queue,
3863                 .elevator_init_fn =             cfq_init_queue,
3864                 .elevator_exit_fn =             cfq_exit_queue,
3865         },
3866         .icq_size       =       sizeof(struct cfq_io_cq),
3867         .icq_align      =       __alignof__(struct cfq_io_cq),
3868         .elevator_attrs =       cfq_attrs,
3869         .elevator_name  =       "cfq",
3870         .elevator_owner =       THIS_MODULE,
3871 };
3872
3873 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3874 static struct blkio_policy_type blkio_policy_cfq = {
3875         .ops = {
3876                 .blkio_unlink_group_fn =        cfq_unlink_blkio_group,
3877                 .blkio_update_group_weight_fn = cfq_update_blkio_group_weight,
3878         },
3879         .plid = BLKIO_POLICY_PROP,
3880 };
3881 #endif
3882
3883 static int __init cfq_init(void)
3884 {
3885         int ret;
3886
3887         /*
3888          * could be 0 on HZ < 1000 setups
3889          */
3890         if (!cfq_slice_async)
3891                 cfq_slice_async = 1;
3892         if (!cfq_slice_idle)
3893                 cfq_slice_idle = 1;
3894
3895 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3896         if (!cfq_group_idle)
3897                 cfq_group_idle = 1;
3898 #else
3899                 cfq_group_idle = 0;
3900 #endif
3901         cfq_pool = KMEM_CACHE(cfq_queue, 0);
3902         if (!cfq_pool)
3903                 return -ENOMEM;
3904
3905         ret = elv_register(&iosched_cfq);
3906         if (ret) {
3907                 kmem_cache_destroy(cfq_pool);
3908                 return ret;
3909         }
3910
3911 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3912         blkio_policy_register(&blkio_policy_cfq);
3913 #endif
3914         return 0;
3915 }
3916