drivers/base/node.c: reduce stack usage of node_read_meminfo()
[linux-2.6.git] / block / cfq-iosched.c
1 /*
2  *  CFQ, or complete fairness queueing, disk scheduler.
3  *
4  *  Based on ideas from a previously unfinished io
5  *  scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
6  *
7  *  Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
8  */
9 #include <linux/module.h>
10 #include <linux/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 "cfq.h"
18
19 /*
20  * tunables
21  */
22 /* max queue in one round of service */
23 static const int cfq_quantum = 8;
24 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
25 /* maximum backwards seek, in KiB */
26 static const int cfq_back_max = 16 * 1024;
27 /* penalty of a backwards seek */
28 static const int cfq_back_penalty = 2;
29 static const int cfq_slice_sync = HZ / 10;
30 static int cfq_slice_async = HZ / 25;
31 static const int cfq_slice_async_rq = 2;
32 static int cfq_slice_idle = HZ / 125;
33 static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
34 static const int cfq_hist_divisor = 4;
35
36 /*
37  * offset from end of service tree
38  */
39 #define CFQ_IDLE_DELAY          (HZ / 5)
40
41 /*
42  * below this threshold, we consider thinktime immediate
43  */
44 #define CFQ_MIN_TT              (2)
45
46 #define CFQ_SLICE_SCALE         (5)
47 #define CFQ_HW_QUEUE_MIN        (5)
48 #define CFQ_SERVICE_SHIFT       12
49
50 #define CFQQ_SEEK_THR           (sector_t)(8 * 100)
51 #define CFQQ_CLOSE_THR          (sector_t)(8 * 1024)
52 #define CFQQ_SECT_THR_NONROT    (sector_t)(2 * 32)
53 #define CFQQ_SEEKY(cfqq)        (hweight32(cfqq->seek_history) > 32/8)
54
55 #define RQ_CIC(rq)              \
56         ((struct cfq_io_context *) (rq)->elevator_private)
57 #define RQ_CFQQ(rq)             (struct cfq_queue *) ((rq)->elevator_private2)
58 #define RQ_CFQG(rq)             (struct cfq_group *) ((rq)->elevator_private3)
59
60 static struct kmem_cache *cfq_pool;
61 static struct kmem_cache *cfq_ioc_pool;
62
63 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
64 static struct completion *ioc_gone;
65 static DEFINE_SPINLOCK(ioc_gone_lock);
66
67 static DEFINE_SPINLOCK(cic_index_lock);
68 static DEFINE_IDA(cic_index_ida);
69
70 #define CFQ_PRIO_LISTS          IOPRIO_BE_NR
71 #define cfq_class_idle(cfqq)    ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
72 #define cfq_class_rt(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
73
74 #define sample_valid(samples)   ((samples) > 80)
75 #define rb_entry_cfqg(node)     rb_entry((node), struct cfq_group, rb_node)
76
77 /*
78  * Most of our rbtree usage is for sorting with min extraction, so
79  * if we cache the leftmost node we don't have to walk down the tree
80  * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
81  * move this into the elevator for the rq sorting as well.
82  */
83 struct cfq_rb_root {
84         struct rb_root rb;
85         struct rb_node *left;
86         unsigned count;
87         unsigned total_weight;
88         u64 min_vdisktime;
89         struct rb_node *active;
90 };
91 #define CFQ_RB_ROOT     (struct cfq_rb_root) { .rb = RB_ROOT, .left = NULL, \
92                         .count = 0, .min_vdisktime = 0, }
93
94 /*
95  * Per process-grouping structure
96  */
97 struct cfq_queue {
98         /* reference count */
99         atomic_t ref;
100         /* various state flags, see below */
101         unsigned int flags;
102         /* parent cfq_data */
103         struct cfq_data *cfqd;
104         /* service_tree member */
105         struct rb_node rb_node;
106         /* service_tree key */
107         unsigned long rb_key;
108         /* prio tree member */
109         struct rb_node p_node;
110         /* prio tree root we belong to, if any */
111         struct rb_root *p_root;
112         /* sorted list of pending requests */
113         struct rb_root sort_list;
114         /* if fifo isn't expired, next request to serve */
115         struct request *next_rq;
116         /* requests queued in sort_list */
117         int queued[2];
118         /* currently allocated requests */
119         int allocated[2];
120         /* fifo list of requests in sort_list */
121         struct list_head fifo;
122
123         /* time when queue got scheduled in to dispatch first request. */
124         unsigned long dispatch_start;
125         unsigned int allocated_slice;
126         unsigned int slice_dispatch;
127         /* time when first request from queue completed and slice started. */
128         unsigned long slice_start;
129         unsigned long slice_end;
130         long slice_resid;
131
132         /* pending metadata requests */
133         int meta_pending;
134         /* number of requests that are on the dispatch list or inside driver */
135         int dispatched;
136
137         /* io prio of this group */
138         unsigned short ioprio, org_ioprio;
139         unsigned short ioprio_class, org_ioprio_class;
140
141         pid_t pid;
142
143         u32 seek_history;
144         sector_t last_request_pos;
145
146         struct cfq_rb_root *service_tree;
147         struct cfq_queue *new_cfqq;
148         struct cfq_group *cfqg;
149         struct cfq_group *orig_cfqg;
150 };
151
152 /*
153  * First index in the service_trees.
154  * IDLE is handled separately, so it has negative index
155  */
156 enum wl_prio_t {
157         BE_WORKLOAD = 0,
158         RT_WORKLOAD = 1,
159         IDLE_WORKLOAD = 2,
160 };
161
162 /*
163  * Second index in the service_trees.
164  */
165 enum wl_type_t {
166         ASYNC_WORKLOAD = 0,
167         SYNC_NOIDLE_WORKLOAD = 1,
168         SYNC_WORKLOAD = 2
169 };
170
171 /* This is per cgroup per device grouping structure */
172 struct cfq_group {
173         /* group service_tree member */
174         struct rb_node rb_node;
175
176         /* group service_tree key */
177         u64 vdisktime;
178         unsigned int weight;
179         bool on_st;
180
181         /* number of cfqq currently on this group */
182         int nr_cfqq;
183
184         /* Per group busy queus average. Useful for workload slice calc. */
185         unsigned int busy_queues_avg[2];
186         /*
187          * rr lists of queues with requests, onle rr for each priority class.
188          * Counts are embedded in the cfq_rb_root
189          */
190         struct cfq_rb_root service_trees[2][3];
191         struct cfq_rb_root service_tree_idle;
192
193         unsigned long saved_workload_slice;
194         enum wl_type_t saved_workload;
195         enum wl_prio_t saved_serving_prio;
196         struct blkio_group blkg;
197 #ifdef CONFIG_CFQ_GROUP_IOSCHED
198         struct hlist_node cfqd_node;
199         atomic_t ref;
200 #endif
201 };
202
203 /*
204  * Per block device queue structure
205  */
206 struct cfq_data {
207         struct request_queue *queue;
208         /* Root service tree for cfq_groups */
209         struct cfq_rb_root grp_service_tree;
210         struct cfq_group root_group;
211
212         /*
213          * The priority currently being served
214          */
215         enum wl_prio_t serving_prio;
216         enum wl_type_t serving_type;
217         unsigned long workload_expires;
218         struct cfq_group *serving_group;
219         bool noidle_tree_requires_idle;
220
221         /*
222          * Each priority tree is sorted by next_request position.  These
223          * trees are used when determining if two or more queues are
224          * interleaving requests (see cfq_close_cooperator).
225          */
226         struct rb_root prio_trees[CFQ_PRIO_LISTS];
227
228         unsigned int busy_queues;
229
230         int rq_in_driver;
231         int rq_in_flight[2];
232
233         /*
234          * queue-depth detection
235          */
236         int rq_queued;
237         int hw_tag;
238         /*
239          * hw_tag can be
240          * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
241          *  1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
242          *  0 => no NCQ
243          */
244         int hw_tag_est_depth;
245         unsigned int hw_tag_samples;
246
247         /*
248          * idle window management
249          */
250         struct timer_list idle_slice_timer;
251         struct work_struct unplug_work;
252
253         struct cfq_queue *active_queue;
254         struct cfq_io_context *active_cic;
255
256         /*
257          * async queue for each priority case
258          */
259         struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
260         struct cfq_queue *async_idle_cfqq;
261
262         sector_t last_position;
263
264         /*
265          * tunables, see top of file
266          */
267         unsigned int cfq_quantum;
268         unsigned int cfq_fifo_expire[2];
269         unsigned int cfq_back_penalty;
270         unsigned int cfq_back_max;
271         unsigned int cfq_slice[2];
272         unsigned int cfq_slice_async_rq;
273         unsigned int cfq_slice_idle;
274         unsigned int cfq_latency;
275         unsigned int cfq_group_isolation;
276
277         unsigned int cic_index;
278         struct list_head cic_list;
279
280         /*
281          * Fallback dummy cfqq for extreme OOM conditions
282          */
283         struct cfq_queue oom_cfqq;
284
285         unsigned long last_delayed_sync;
286
287         /* List of cfq groups being managed on this device*/
288         struct hlist_head cfqg_list;
289         struct rcu_head rcu;
290 };
291
292 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
293
294 static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
295                                             enum wl_prio_t prio,
296                                             enum wl_type_t type)
297 {
298         if (!cfqg)
299                 return NULL;
300
301         if (prio == IDLE_WORKLOAD)
302                 return &cfqg->service_tree_idle;
303
304         return &cfqg->service_trees[prio][type];
305 }
306
307 enum cfqq_state_flags {
308         CFQ_CFQQ_FLAG_on_rr = 0,        /* on round-robin busy list */
309         CFQ_CFQQ_FLAG_wait_request,     /* waiting for a request */
310         CFQ_CFQQ_FLAG_must_dispatch,    /* must be allowed a dispatch */
311         CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
312         CFQ_CFQQ_FLAG_fifo_expire,      /* FIFO checked in this slice */
313         CFQ_CFQQ_FLAG_idle_window,      /* slice idling enabled */
314         CFQ_CFQQ_FLAG_prio_changed,     /* task priority has changed */
315         CFQ_CFQQ_FLAG_slice_new,        /* no requests dispatched in slice */
316         CFQ_CFQQ_FLAG_sync,             /* synchronous queue */
317         CFQ_CFQQ_FLAG_coop,             /* cfqq is shared */
318         CFQ_CFQQ_FLAG_split_coop,       /* shared cfqq will be splitted */
319         CFQ_CFQQ_FLAG_deep,             /* sync cfqq experienced large depth */
320         CFQ_CFQQ_FLAG_wait_busy,        /* Waiting for next request */
321 };
322
323 #define CFQ_CFQQ_FNS(name)                                              \
324 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
325 {                                                                       \
326         (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name);                   \
327 }                                                                       \
328 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
329 {                                                                       \
330         (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                  \
331 }                                                                       \
332 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
333 {                                                                       \
334         return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;      \
335 }
336
337 CFQ_CFQQ_FNS(on_rr);
338 CFQ_CFQQ_FNS(wait_request);
339 CFQ_CFQQ_FNS(must_dispatch);
340 CFQ_CFQQ_FNS(must_alloc_slice);
341 CFQ_CFQQ_FNS(fifo_expire);
342 CFQ_CFQQ_FNS(idle_window);
343 CFQ_CFQQ_FNS(prio_changed);
344 CFQ_CFQQ_FNS(slice_new);
345 CFQ_CFQQ_FNS(sync);
346 CFQ_CFQQ_FNS(coop);
347 CFQ_CFQQ_FNS(split_coop);
348 CFQ_CFQQ_FNS(deep);
349 CFQ_CFQQ_FNS(wait_busy);
350 #undef CFQ_CFQQ_FNS
351
352 #ifdef CONFIG_CFQ_GROUP_IOSCHED
353 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
354         blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
355                         cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
356                         blkg_path(&(cfqq)->cfqg->blkg), ##args);
357
358 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)                          \
359         blk_add_trace_msg((cfqd)->queue, "%s " fmt,                     \
360                                 blkg_path(&(cfqg)->blkg), ##args);      \
361
362 #else
363 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
364         blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
365 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)          do {} while (0);
366 #endif
367 #define cfq_log(cfqd, fmt, args...)     \
368         blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
369
370 /* Traverses through cfq group service trees */
371 #define for_each_cfqg_st(cfqg, i, j, st) \
372         for (i = 0; i <= IDLE_WORKLOAD; i++) \
373                 for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
374                         : &cfqg->service_tree_idle; \
375                         (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
376                         (i == IDLE_WORKLOAD && j == 0); \
377                         j++, st = i < IDLE_WORKLOAD ? \
378                         &cfqg->service_trees[i][j]: NULL) \
379
380
381 static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
382 {
383         if (cfq_class_idle(cfqq))
384                 return IDLE_WORKLOAD;
385         if (cfq_class_rt(cfqq))
386                 return RT_WORKLOAD;
387         return BE_WORKLOAD;
388 }
389
390
391 static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
392 {
393         if (!cfq_cfqq_sync(cfqq))
394                 return ASYNC_WORKLOAD;
395         if (!cfq_cfqq_idle_window(cfqq))
396                 return SYNC_NOIDLE_WORKLOAD;
397         return SYNC_WORKLOAD;
398 }
399
400 static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl,
401                                         struct cfq_data *cfqd,
402                                         struct cfq_group *cfqg)
403 {
404         if (wl == IDLE_WORKLOAD)
405                 return cfqg->service_tree_idle.count;
406
407         return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
408                 + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
409                 + cfqg->service_trees[wl][SYNC_WORKLOAD].count;
410 }
411
412 static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
413                                         struct cfq_group *cfqg)
414 {
415         return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count
416                 + cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
417 }
418
419 static void cfq_dispatch_insert(struct request_queue *, struct request *);
420 static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
421                                        struct io_context *, gfp_t);
422 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
423                                                 struct io_context *);
424
425 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
426                                             bool is_sync)
427 {
428         return cic->cfqq[is_sync];
429 }
430
431 static inline void cic_set_cfqq(struct cfq_io_context *cic,
432                                 struct cfq_queue *cfqq, bool is_sync)
433 {
434         cic->cfqq[is_sync] = cfqq;
435 }
436
437 #define CIC_DEAD_KEY    1ul
438 #define CIC_DEAD_INDEX_SHIFT    1
439
440 static inline void *cfqd_dead_key(struct cfq_data *cfqd)
441 {
442         return (void *)(cfqd->cic_index << CIC_DEAD_INDEX_SHIFT | CIC_DEAD_KEY);
443 }
444
445 static inline struct cfq_data *cic_to_cfqd(struct cfq_io_context *cic)
446 {
447         struct cfq_data *cfqd = cic->key;
448
449         if (unlikely((unsigned long) cfqd & CIC_DEAD_KEY))
450                 return NULL;
451
452         return cfqd;
453 }
454
455 /*
456  * We regard a request as SYNC, if it's either a read or has the SYNC bit
457  * set (in which case it could also be direct WRITE).
458  */
459 static inline bool cfq_bio_sync(struct bio *bio)
460 {
461         return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO);
462 }
463
464 /*
465  * scheduler run of queue, if there are requests pending and no one in the
466  * driver that will restart queueing
467  */
468 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
469 {
470         if (cfqd->busy_queues) {
471                 cfq_log(cfqd, "schedule dispatch");
472                 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
473         }
474 }
475
476 static int cfq_queue_empty(struct request_queue *q)
477 {
478         struct cfq_data *cfqd = q->elevator->elevator_data;
479
480         return !cfqd->rq_queued;
481 }
482
483 /*
484  * Scale schedule slice based on io priority. Use the sync time slice only
485  * if a queue is marked sync and has sync io queued. A sync queue with async
486  * io only, should not get full sync slice length.
487  */
488 static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
489                                  unsigned short prio)
490 {
491         const int base_slice = cfqd->cfq_slice[sync];
492
493         WARN_ON(prio >= IOPRIO_BE_NR);
494
495         return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
496 }
497
498 static inline int
499 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
500 {
501         return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
502 }
503
504 static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
505 {
506         u64 d = delta << CFQ_SERVICE_SHIFT;
507
508         d = d * BLKIO_WEIGHT_DEFAULT;
509         do_div(d, cfqg->weight);
510         return d;
511 }
512
513 static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
514 {
515         s64 delta = (s64)(vdisktime - min_vdisktime);
516         if (delta > 0)
517                 min_vdisktime = vdisktime;
518
519         return min_vdisktime;
520 }
521
522 static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
523 {
524         s64 delta = (s64)(vdisktime - min_vdisktime);
525         if (delta < 0)
526                 min_vdisktime = vdisktime;
527
528         return min_vdisktime;
529 }
530
531 static void update_min_vdisktime(struct cfq_rb_root *st)
532 {
533         u64 vdisktime = st->min_vdisktime;
534         struct cfq_group *cfqg;
535
536         if (st->active) {
537                 cfqg = rb_entry_cfqg(st->active);
538                 vdisktime = cfqg->vdisktime;
539         }
540
541         if (st->left) {
542                 cfqg = rb_entry_cfqg(st->left);
543                 vdisktime = min_vdisktime(vdisktime, cfqg->vdisktime);
544         }
545
546         st->min_vdisktime = max_vdisktime(st->min_vdisktime, vdisktime);
547 }
548
549 /*
550  * get averaged number of queues of RT/BE priority.
551  * average is updated, with a formula that gives more weight to higher numbers,
552  * to quickly follows sudden increases and decrease slowly
553  */
554
555 static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
556                                         struct cfq_group *cfqg, bool rt)
557 {
558         unsigned min_q, max_q;
559         unsigned mult  = cfq_hist_divisor - 1;
560         unsigned round = cfq_hist_divisor / 2;
561         unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
562
563         min_q = min(cfqg->busy_queues_avg[rt], busy);
564         max_q = max(cfqg->busy_queues_avg[rt], busy);
565         cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
566                 cfq_hist_divisor;
567         return cfqg->busy_queues_avg[rt];
568 }
569
570 static inline unsigned
571 cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
572 {
573         struct cfq_rb_root *st = &cfqd->grp_service_tree;
574
575         return cfq_target_latency * cfqg->weight / st->total_weight;
576 }
577
578 static inline void
579 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
580 {
581         unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
582         if (cfqd->cfq_latency) {
583                 /*
584                  * interested queues (we consider only the ones with the same
585                  * priority class in the cfq group)
586                  */
587                 unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
588                                                 cfq_class_rt(cfqq));
589                 unsigned sync_slice = cfqd->cfq_slice[1];
590                 unsigned expect_latency = sync_slice * iq;
591                 unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
592
593                 if (expect_latency > group_slice) {
594                         unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
595                         /* scale low_slice according to IO priority
596                          * and sync vs async */
597                         unsigned low_slice =
598                                 min(slice, base_low_slice * slice / sync_slice);
599                         /* the adapted slice value is scaled to fit all iqs
600                          * into the target latency */
601                         slice = max(slice * group_slice / expect_latency,
602                                     low_slice);
603                 }
604         }
605         cfqq->slice_start = jiffies;
606         cfqq->slice_end = jiffies + slice;
607         cfqq->allocated_slice = slice;
608         cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
609 }
610
611 /*
612  * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
613  * isn't valid until the first request from the dispatch is activated
614  * and the slice time set.
615  */
616 static inline bool cfq_slice_used(struct cfq_queue *cfqq)
617 {
618         if (cfq_cfqq_slice_new(cfqq))
619                 return 0;
620         if (time_before(jiffies, cfqq->slice_end))
621                 return 0;
622
623         return 1;
624 }
625
626 /*
627  * Lifted from AS - choose which of rq1 and rq2 that is best served now.
628  * We choose the request that is closest to the head right now. Distance
629  * behind the head is penalized and only allowed to a certain extent.
630  */
631 static struct request *
632 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
633 {
634         sector_t s1, s2, d1 = 0, d2 = 0;
635         unsigned long back_max;
636 #define CFQ_RQ1_WRAP    0x01 /* request 1 wraps */
637 #define CFQ_RQ2_WRAP    0x02 /* request 2 wraps */
638         unsigned wrap = 0; /* bit mask: requests behind the disk head? */
639
640         if (rq1 == NULL || rq1 == rq2)
641                 return rq2;
642         if (rq2 == NULL)
643                 return rq1;
644
645         if (rq_is_sync(rq1) && !rq_is_sync(rq2))
646                 return rq1;
647         else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
648                 return rq2;
649         if (rq_is_meta(rq1) && !rq_is_meta(rq2))
650                 return rq1;
651         else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
652                 return rq2;
653
654         s1 = blk_rq_pos(rq1);
655         s2 = blk_rq_pos(rq2);
656
657         /*
658          * by definition, 1KiB is 2 sectors
659          */
660         back_max = cfqd->cfq_back_max * 2;
661
662         /*
663          * Strict one way elevator _except_ in the case where we allow
664          * short backward seeks which are biased as twice the cost of a
665          * similar forward seek.
666          */
667         if (s1 >= last)
668                 d1 = s1 - last;
669         else if (s1 + back_max >= last)
670                 d1 = (last - s1) * cfqd->cfq_back_penalty;
671         else
672                 wrap |= CFQ_RQ1_WRAP;
673
674         if (s2 >= last)
675                 d2 = s2 - last;
676         else if (s2 + back_max >= last)
677                 d2 = (last - s2) * cfqd->cfq_back_penalty;
678         else
679                 wrap |= CFQ_RQ2_WRAP;
680
681         /* Found required data */
682
683         /*
684          * By doing switch() on the bit mask "wrap" we avoid having to
685          * check two variables for all permutations: --> faster!
686          */
687         switch (wrap) {
688         case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
689                 if (d1 < d2)
690                         return rq1;
691                 else if (d2 < d1)
692                         return rq2;
693                 else {
694                         if (s1 >= s2)
695                                 return rq1;
696                         else
697                                 return rq2;
698                 }
699
700         case CFQ_RQ2_WRAP:
701                 return rq1;
702         case CFQ_RQ1_WRAP:
703                 return rq2;
704         case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
705         default:
706                 /*
707                  * Since both rqs are wrapped,
708                  * start with the one that's further behind head
709                  * (--> only *one* back seek required),
710                  * since back seek takes more time than forward.
711                  */
712                 if (s1 <= s2)
713                         return rq1;
714                 else
715                         return rq2;
716         }
717 }
718
719 /*
720  * The below is leftmost cache rbtree addon
721  */
722 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
723 {
724         /* Service tree is empty */
725         if (!root->count)
726                 return NULL;
727
728         if (!root->left)
729                 root->left = rb_first(&root->rb);
730
731         if (root->left)
732                 return rb_entry(root->left, struct cfq_queue, rb_node);
733
734         return NULL;
735 }
736
737 static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
738 {
739         if (!root->left)
740                 root->left = rb_first(&root->rb);
741
742         if (root->left)
743                 return rb_entry_cfqg(root->left);
744
745         return NULL;
746 }
747
748 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
749 {
750         rb_erase(n, root);
751         RB_CLEAR_NODE(n);
752 }
753
754 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
755 {
756         if (root->left == n)
757                 root->left = NULL;
758         rb_erase_init(n, &root->rb);
759         --root->count;
760 }
761
762 /*
763  * would be nice to take fifo expire time into account as well
764  */
765 static struct request *
766 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
767                   struct request *last)
768 {
769         struct rb_node *rbnext = rb_next(&last->rb_node);
770         struct rb_node *rbprev = rb_prev(&last->rb_node);
771         struct request *next = NULL, *prev = NULL;
772
773         BUG_ON(RB_EMPTY_NODE(&last->rb_node));
774
775         if (rbprev)
776                 prev = rb_entry_rq(rbprev);
777
778         if (rbnext)
779                 next = rb_entry_rq(rbnext);
780         else {
781                 rbnext = rb_first(&cfqq->sort_list);
782                 if (rbnext && rbnext != &last->rb_node)
783                         next = rb_entry_rq(rbnext);
784         }
785
786         return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
787 }
788
789 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
790                                       struct cfq_queue *cfqq)
791 {
792         /*
793          * just an approximation, should be ok.
794          */
795         return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
796                        cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
797 }
798
799 static inline s64
800 cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
801 {
802         return cfqg->vdisktime - st->min_vdisktime;
803 }
804
805 static void
806 __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
807 {
808         struct rb_node **node = &st->rb.rb_node;
809         struct rb_node *parent = NULL;
810         struct cfq_group *__cfqg;
811         s64 key = cfqg_key(st, cfqg);
812         int left = 1;
813
814         while (*node != NULL) {
815                 parent = *node;
816                 __cfqg = rb_entry_cfqg(parent);
817
818                 if (key < cfqg_key(st, __cfqg))
819                         node = &parent->rb_left;
820                 else {
821                         node = &parent->rb_right;
822                         left = 0;
823                 }
824         }
825
826         if (left)
827                 st->left = &cfqg->rb_node;
828
829         rb_link_node(&cfqg->rb_node, parent, node);
830         rb_insert_color(&cfqg->rb_node, &st->rb);
831 }
832
833 static void
834 cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
835 {
836         struct cfq_rb_root *st = &cfqd->grp_service_tree;
837         struct cfq_group *__cfqg;
838         struct rb_node *n;
839
840         cfqg->nr_cfqq++;
841         if (cfqg->on_st)
842                 return;
843
844         /*
845          * Currently put the group at the end. Later implement something
846          * so that groups get lesser vtime based on their weights, so that
847          * if group does not loose all if it was not continously backlogged.
848          */
849         n = rb_last(&st->rb);
850         if (n) {
851                 __cfqg = rb_entry_cfqg(n);
852                 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
853         } else
854                 cfqg->vdisktime = st->min_vdisktime;
855
856         __cfq_group_service_tree_add(st, cfqg);
857         cfqg->on_st = true;
858         st->total_weight += cfqg->weight;
859 }
860
861 static void
862 cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
863 {
864         struct cfq_rb_root *st = &cfqd->grp_service_tree;
865
866         if (st->active == &cfqg->rb_node)
867                 st->active = NULL;
868
869         BUG_ON(cfqg->nr_cfqq < 1);
870         cfqg->nr_cfqq--;
871
872         /* If there are other cfq queues under this group, don't delete it */
873         if (cfqg->nr_cfqq)
874                 return;
875
876         cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
877         cfqg->on_st = false;
878         st->total_weight -= cfqg->weight;
879         if (!RB_EMPTY_NODE(&cfqg->rb_node))
880                 cfq_rb_erase(&cfqg->rb_node, st);
881         cfqg->saved_workload_slice = 0;
882         cfq_blkiocg_update_dequeue_stats(&cfqg->blkg, 1);
883 }
884
885 static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
886 {
887         unsigned int slice_used;
888
889         /*
890          * Queue got expired before even a single request completed or
891          * got expired immediately after first request completion.
892          */
893         if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
894                 /*
895                  * Also charge the seek time incurred to the group, otherwise
896                  * if there are mutiple queues in the group, each can dispatch
897                  * a single request on seeky media and cause lots of seek time
898                  * and group will never know it.
899                  */
900                 slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
901                                         1);
902         } else {
903                 slice_used = jiffies - cfqq->slice_start;
904                 if (slice_used > cfqq->allocated_slice)
905                         slice_used = cfqq->allocated_slice;
906         }
907
908         cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u", slice_used);
909         return slice_used;
910 }
911
912 static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
913                                 struct cfq_queue *cfqq)
914 {
915         struct cfq_rb_root *st = &cfqd->grp_service_tree;
916         unsigned int used_sl, charge_sl;
917         int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
918                         - cfqg->service_tree_idle.count;
919
920         BUG_ON(nr_sync < 0);
921         used_sl = charge_sl = cfq_cfqq_slice_usage(cfqq);
922
923         if (!cfq_cfqq_sync(cfqq) && !nr_sync)
924                 charge_sl = cfqq->allocated_slice;
925
926         /* Can't update vdisktime while group is on service tree */
927         cfq_rb_erase(&cfqg->rb_node, st);
928         cfqg->vdisktime += cfq_scale_slice(charge_sl, cfqg);
929         __cfq_group_service_tree_add(st, cfqg);
930
931         /* This group is being expired. Save the context */
932         if (time_after(cfqd->workload_expires, jiffies)) {
933                 cfqg->saved_workload_slice = cfqd->workload_expires
934                                                 - jiffies;
935                 cfqg->saved_workload = cfqd->serving_type;
936                 cfqg->saved_serving_prio = cfqd->serving_prio;
937         } else
938                 cfqg->saved_workload_slice = 0;
939
940         cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
941                                         st->min_vdisktime);
942         cfq_blkiocg_update_timeslice_used(&cfqg->blkg, used_sl);
943         cfq_blkiocg_set_start_empty_time(&cfqg->blkg);
944 }
945
946 #ifdef CONFIG_CFQ_GROUP_IOSCHED
947 static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
948 {
949         if (blkg)
950                 return container_of(blkg, struct cfq_group, blkg);
951         return NULL;
952 }
953
954 void
955 cfq_update_blkio_group_weight(struct blkio_group *blkg, unsigned int weight)
956 {
957         cfqg_of_blkg(blkg)->weight = weight;
958 }
959
960 static struct cfq_group *
961 cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
962 {
963         struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
964         struct cfq_group *cfqg = NULL;
965         void *key = cfqd;
966         int i, j;
967         struct cfq_rb_root *st;
968         struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
969         unsigned int major, minor;
970
971         cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
972         if (cfqg && !cfqg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
973                 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
974                 cfqg->blkg.dev = MKDEV(major, minor);
975                 goto done;
976         }
977         if (cfqg || !create)
978                 goto done;
979
980         cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
981         if (!cfqg)
982                 goto done;
983
984         for_each_cfqg_st(cfqg, i, j, st)
985                 *st = CFQ_RB_ROOT;
986         RB_CLEAR_NODE(&cfqg->rb_node);
987
988         /*
989          * Take the initial reference that will be released on destroy
990          * This can be thought of a joint reference by cgroup and
991          * elevator which will be dropped by either elevator exit
992          * or cgroup deletion path depending on who is exiting first.
993          */
994         atomic_set(&cfqg->ref, 1);
995
996         /* Add group onto cgroup list */
997         sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
998         cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
999                                         MKDEV(major, minor));
1000         cfqg->weight = blkcg_get_weight(blkcg, cfqg->blkg.dev);
1001
1002         /* Add group on cfqd list */
1003         hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
1004
1005 done:
1006         return cfqg;
1007 }
1008
1009 /*
1010  * Search for the cfq group current task belongs to. If create = 1, then also
1011  * create the cfq group if it does not exist. request_queue lock must be held.
1012  */
1013 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
1014 {
1015         struct cgroup *cgroup;
1016         struct cfq_group *cfqg = NULL;
1017
1018         rcu_read_lock();
1019         cgroup = task_cgroup(current, blkio_subsys_id);
1020         cfqg = cfq_find_alloc_cfqg(cfqd, cgroup, create);
1021         if (!cfqg && create)
1022                 cfqg = &cfqd->root_group;
1023         rcu_read_unlock();
1024         return cfqg;
1025 }
1026
1027 static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
1028 {
1029         atomic_inc(&cfqg->ref);
1030         return cfqg;
1031 }
1032
1033 static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
1034 {
1035         /* Currently, all async queues are mapped to root group */
1036         if (!cfq_cfqq_sync(cfqq))
1037                 cfqg = &cfqq->cfqd->root_group;
1038
1039         cfqq->cfqg = cfqg;
1040         /* cfqq reference on cfqg */
1041         atomic_inc(&cfqq->cfqg->ref);
1042 }
1043
1044 static void cfq_put_cfqg(struct cfq_group *cfqg)
1045 {
1046         struct cfq_rb_root *st;
1047         int i, j;
1048
1049         BUG_ON(atomic_read(&cfqg->ref) <= 0);
1050         if (!atomic_dec_and_test(&cfqg->ref))
1051                 return;
1052         for_each_cfqg_st(cfqg, i, j, st)
1053                 BUG_ON(!RB_EMPTY_ROOT(&st->rb) || st->active != NULL);
1054         kfree(cfqg);
1055 }
1056
1057 static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
1058 {
1059         /* Something wrong if we are trying to remove same group twice */
1060         BUG_ON(hlist_unhashed(&cfqg->cfqd_node));
1061
1062         hlist_del_init(&cfqg->cfqd_node);
1063
1064         /*
1065          * Put the reference taken at the time of creation so that when all
1066          * queues are gone, group can be destroyed.
1067          */
1068         cfq_put_cfqg(cfqg);
1069 }
1070
1071 static void cfq_release_cfq_groups(struct cfq_data *cfqd)
1072 {
1073         struct hlist_node *pos, *n;
1074         struct cfq_group *cfqg;
1075
1076         hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) {
1077                 /*
1078                  * If cgroup removal path got to blk_group first and removed
1079                  * it from cgroup list, then it will take care of destroying
1080                  * cfqg also.
1081                  */
1082                 if (!cfq_blkiocg_del_blkio_group(&cfqg->blkg))
1083                         cfq_destroy_cfqg(cfqd, cfqg);
1084         }
1085 }
1086
1087 /*
1088  * Blk cgroup controller notification saying that blkio_group object is being
1089  * delinked as associated cgroup object is going away. That also means that
1090  * no new IO will come in this group. So get rid of this group as soon as
1091  * any pending IO in the group is finished.
1092  *
1093  * This function is called under rcu_read_lock(). key is the rcu protected
1094  * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu
1095  * read lock.
1096  *
1097  * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
1098  * it should not be NULL as even if elevator was exiting, cgroup deltion
1099  * path got to it first.
1100  */
1101 void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
1102 {
1103         unsigned long  flags;
1104         struct cfq_data *cfqd = key;
1105
1106         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1107         cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg));
1108         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1109 }
1110
1111 #else /* GROUP_IOSCHED */
1112 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
1113 {
1114         return &cfqd->root_group;
1115 }
1116
1117 static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
1118 {
1119         return cfqg;
1120 }
1121
1122 static inline void
1123 cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
1124         cfqq->cfqg = cfqg;
1125 }
1126
1127 static void cfq_release_cfq_groups(struct cfq_data *cfqd) {}
1128 static inline void cfq_put_cfqg(struct cfq_group *cfqg) {}
1129
1130 #endif /* GROUP_IOSCHED */
1131
1132 /*
1133  * The cfqd->service_trees holds all pending cfq_queue's that have
1134  * requests waiting to be processed. It is sorted in the order that
1135  * we will service the queues.
1136  */
1137 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1138                                  bool add_front)
1139 {
1140         struct rb_node **p, *parent;
1141         struct cfq_queue *__cfqq;
1142         unsigned long rb_key;
1143         struct cfq_rb_root *service_tree;
1144         int left;
1145         int new_cfqq = 1;
1146         int group_changed = 0;
1147
1148 #ifdef CONFIG_CFQ_GROUP_IOSCHED
1149         if (!cfqd->cfq_group_isolation
1150             && cfqq_type(cfqq) == SYNC_NOIDLE_WORKLOAD
1151             && cfqq->cfqg && cfqq->cfqg != &cfqd->root_group) {
1152                 /* Move this cfq to root group */
1153                 cfq_log_cfqq(cfqd, cfqq, "moving to root group");
1154                 if (!RB_EMPTY_NODE(&cfqq->rb_node))
1155                         cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1156                 cfqq->orig_cfqg = cfqq->cfqg;
1157                 cfqq->cfqg = &cfqd->root_group;
1158                 atomic_inc(&cfqd->root_group.ref);
1159                 group_changed = 1;
1160         } else if (!cfqd->cfq_group_isolation
1161                    && cfqq_type(cfqq) == SYNC_WORKLOAD && cfqq->orig_cfqg) {
1162                 /* cfqq is sequential now needs to go to its original group */
1163                 BUG_ON(cfqq->cfqg != &cfqd->root_group);
1164                 if (!RB_EMPTY_NODE(&cfqq->rb_node))
1165                         cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1166                 cfq_put_cfqg(cfqq->cfqg);
1167                 cfqq->cfqg = cfqq->orig_cfqg;
1168                 cfqq->orig_cfqg = NULL;
1169                 group_changed = 1;
1170                 cfq_log_cfqq(cfqd, cfqq, "moved to origin group");
1171         }
1172 #endif
1173
1174         service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
1175                                                 cfqq_type(cfqq));
1176         if (cfq_class_idle(cfqq)) {
1177                 rb_key = CFQ_IDLE_DELAY;
1178                 parent = rb_last(&service_tree->rb);
1179                 if (parent && parent != &cfqq->rb_node) {
1180                         __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1181                         rb_key += __cfqq->rb_key;
1182                 } else
1183                         rb_key += jiffies;
1184         } else if (!add_front) {
1185                 /*
1186                  * Get our rb key offset. Subtract any residual slice
1187                  * value carried from last service. A negative resid
1188                  * count indicates slice overrun, and this should position
1189                  * the next service time further away in the tree.
1190                  */
1191                 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
1192                 rb_key -= cfqq->slice_resid;
1193                 cfqq->slice_resid = 0;
1194         } else {
1195                 rb_key = -HZ;
1196                 __cfqq = cfq_rb_first(service_tree);
1197                 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
1198         }
1199
1200         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1201                 new_cfqq = 0;
1202                 /*
1203                  * same position, nothing more to do
1204                  */
1205                 if (rb_key == cfqq->rb_key &&
1206                     cfqq->service_tree == service_tree)
1207                         return;
1208
1209                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1210                 cfqq->service_tree = NULL;
1211         }
1212
1213         left = 1;
1214         parent = NULL;
1215         cfqq->service_tree = service_tree;
1216         p = &service_tree->rb.rb_node;
1217         while (*p) {
1218                 struct rb_node **n;
1219
1220                 parent = *p;
1221                 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1222
1223                 /*
1224                  * sort by key, that represents service time.
1225                  */
1226                 if (time_before(rb_key, __cfqq->rb_key))
1227                         n = &(*p)->rb_left;
1228                 else {
1229                         n = &(*p)->rb_right;
1230                         left = 0;
1231                 }
1232
1233                 p = n;
1234         }
1235
1236         if (left)
1237                 service_tree->left = &cfqq->rb_node;
1238
1239         cfqq->rb_key = rb_key;
1240         rb_link_node(&cfqq->rb_node, parent, p);
1241         rb_insert_color(&cfqq->rb_node, &service_tree->rb);
1242         service_tree->count++;
1243         if ((add_front || !new_cfqq) && !group_changed)
1244                 return;
1245         cfq_group_service_tree_add(cfqd, cfqq->cfqg);
1246 }
1247
1248 static struct cfq_queue *
1249 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
1250                      sector_t sector, struct rb_node **ret_parent,
1251                      struct rb_node ***rb_link)
1252 {
1253         struct rb_node **p, *parent;
1254         struct cfq_queue *cfqq = NULL;
1255
1256         parent = NULL;
1257         p = &root->rb_node;
1258         while (*p) {
1259                 struct rb_node **n;
1260
1261                 parent = *p;
1262                 cfqq = rb_entry(parent, struct cfq_queue, p_node);
1263
1264                 /*
1265                  * Sort strictly based on sector.  Smallest to the left,
1266                  * largest to the right.
1267                  */
1268                 if (sector > blk_rq_pos(cfqq->next_rq))
1269                         n = &(*p)->rb_right;
1270                 else if (sector < blk_rq_pos(cfqq->next_rq))
1271                         n = &(*p)->rb_left;
1272                 else
1273                         break;
1274                 p = n;
1275                 cfqq = NULL;
1276         }
1277
1278         *ret_parent = parent;
1279         if (rb_link)
1280                 *rb_link = p;
1281         return cfqq;
1282 }
1283
1284 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1285 {
1286         struct rb_node **p, *parent;
1287         struct cfq_queue *__cfqq;
1288
1289         if (cfqq->p_root) {
1290                 rb_erase(&cfqq->p_node, cfqq->p_root);
1291                 cfqq->p_root = NULL;
1292         }
1293
1294         if (cfq_class_idle(cfqq))
1295                 return;
1296         if (!cfqq->next_rq)
1297                 return;
1298
1299         cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
1300         __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
1301                                       blk_rq_pos(cfqq->next_rq), &parent, &p);
1302         if (!__cfqq) {
1303                 rb_link_node(&cfqq->p_node, parent, p);
1304                 rb_insert_color(&cfqq->p_node, cfqq->p_root);
1305         } else
1306                 cfqq->p_root = NULL;
1307 }
1308
1309 /*
1310  * Update cfqq's position in the service tree.
1311  */
1312 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1313 {
1314         /*
1315          * Resorting requires the cfqq to be on the RR list already.
1316          */
1317         if (cfq_cfqq_on_rr(cfqq)) {
1318                 cfq_service_tree_add(cfqd, cfqq, 0);
1319                 cfq_prio_tree_add(cfqd, cfqq);
1320         }
1321 }
1322
1323 /*
1324  * add to busy list of queues for service, trying to be fair in ordering
1325  * the pending list according to last request service
1326  */
1327 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1328 {
1329         cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
1330         BUG_ON(cfq_cfqq_on_rr(cfqq));
1331         cfq_mark_cfqq_on_rr(cfqq);
1332         cfqd->busy_queues++;
1333
1334         cfq_resort_rr_list(cfqd, cfqq);
1335 }
1336
1337 /*
1338  * Called when the cfqq no longer has requests pending, remove it from
1339  * the service tree.
1340  */
1341 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1342 {
1343         cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
1344         BUG_ON(!cfq_cfqq_on_rr(cfqq));
1345         cfq_clear_cfqq_on_rr(cfqq);
1346
1347         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1348                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1349                 cfqq->service_tree = NULL;
1350         }
1351         if (cfqq->p_root) {
1352                 rb_erase(&cfqq->p_node, cfqq->p_root);
1353                 cfqq->p_root = NULL;
1354         }
1355
1356         cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1357         BUG_ON(!cfqd->busy_queues);
1358         cfqd->busy_queues--;
1359 }
1360
1361 /*
1362  * rb tree support functions
1363  */
1364 static void cfq_del_rq_rb(struct request *rq)
1365 {
1366         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1367         const int sync = rq_is_sync(rq);
1368
1369         BUG_ON(!cfqq->queued[sync]);
1370         cfqq->queued[sync]--;
1371
1372         elv_rb_del(&cfqq->sort_list, rq);
1373
1374         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1375                 /*
1376                  * Queue will be deleted from service tree when we actually
1377                  * expire it later. Right now just remove it from prio tree
1378                  * as it is empty.
1379                  */
1380                 if (cfqq->p_root) {
1381                         rb_erase(&cfqq->p_node, cfqq->p_root);
1382                         cfqq->p_root = NULL;
1383                 }
1384         }
1385 }
1386
1387 static void cfq_add_rq_rb(struct request *rq)
1388 {
1389         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1390         struct cfq_data *cfqd = cfqq->cfqd;
1391         struct request *__alias, *prev;
1392
1393         cfqq->queued[rq_is_sync(rq)]++;
1394
1395         /*
1396          * looks a little odd, but the first insert might return an alias.
1397          * if that happens, put the alias on the dispatch list
1398          */
1399         while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
1400                 cfq_dispatch_insert(cfqd->queue, __alias);
1401
1402         if (!cfq_cfqq_on_rr(cfqq))
1403                 cfq_add_cfqq_rr(cfqd, cfqq);
1404
1405         /*
1406          * check if this request is a better next-serve candidate
1407          */
1408         prev = cfqq->next_rq;
1409         cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
1410
1411         /*
1412          * adjust priority tree position, if ->next_rq changes
1413          */
1414         if (prev != cfqq->next_rq)
1415                 cfq_prio_tree_add(cfqd, cfqq);
1416
1417         BUG_ON(!cfqq->next_rq);
1418 }
1419
1420 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
1421 {
1422         elv_rb_del(&cfqq->sort_list, rq);
1423         cfqq->queued[rq_is_sync(rq)]--;
1424         cfq_blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg,
1425                                         rq_data_dir(rq), rq_is_sync(rq));
1426         cfq_add_rq_rb(rq);
1427         cfq_blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg,
1428                         &cfqq->cfqd->serving_group->blkg, rq_data_dir(rq),
1429                         rq_is_sync(rq));
1430 }
1431
1432 static struct request *
1433 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
1434 {
1435         struct task_struct *tsk = current;
1436         struct cfq_io_context *cic;
1437         struct cfq_queue *cfqq;
1438
1439         cic = cfq_cic_lookup(cfqd, tsk->io_context);
1440         if (!cic)
1441                 return NULL;
1442
1443         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1444         if (cfqq) {
1445                 sector_t sector = bio->bi_sector + bio_sectors(bio);
1446
1447                 return elv_rb_find(&cfqq->sort_list, sector);
1448         }
1449
1450         return NULL;
1451 }
1452
1453 static void cfq_activate_request(struct request_queue *q, struct request *rq)
1454 {
1455         struct cfq_data *cfqd = q->elevator->elevator_data;
1456
1457         cfqd->rq_in_driver++;
1458         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
1459                                                 cfqd->rq_in_driver);
1460
1461         cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
1462 }
1463
1464 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
1465 {
1466         struct cfq_data *cfqd = q->elevator->elevator_data;
1467
1468         WARN_ON(!cfqd->rq_in_driver);
1469         cfqd->rq_in_driver--;
1470         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
1471                                                 cfqd->rq_in_driver);
1472 }
1473
1474 static void cfq_remove_request(struct request *rq)
1475 {
1476         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1477
1478         if (cfqq->next_rq == rq)
1479                 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
1480
1481         list_del_init(&rq->queuelist);
1482         cfq_del_rq_rb(rq);
1483
1484         cfqq->cfqd->rq_queued--;
1485         cfq_blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg,
1486                                         rq_data_dir(rq), rq_is_sync(rq));
1487         if (rq_is_meta(rq)) {
1488                 WARN_ON(!cfqq->meta_pending);
1489                 cfqq->meta_pending--;
1490         }
1491 }
1492
1493 static int cfq_merge(struct request_queue *q, struct request **req,
1494                      struct bio *bio)
1495 {
1496         struct cfq_data *cfqd = q->elevator->elevator_data;
1497         struct request *__rq;
1498
1499         __rq = cfq_find_rq_fmerge(cfqd, bio);
1500         if (__rq && elv_rq_merge_ok(__rq, bio)) {
1501                 *req = __rq;
1502                 return ELEVATOR_FRONT_MERGE;
1503         }
1504
1505         return ELEVATOR_NO_MERGE;
1506 }
1507
1508 static void cfq_merged_request(struct request_queue *q, struct request *req,
1509                                int type)
1510 {
1511         if (type == ELEVATOR_FRONT_MERGE) {
1512                 struct cfq_queue *cfqq = RQ_CFQQ(req);
1513
1514                 cfq_reposition_rq_rb(cfqq, req);
1515         }
1516 }
1517
1518 static void cfq_bio_merged(struct request_queue *q, struct request *req,
1519                                 struct bio *bio)
1520 {
1521         cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(req))->blkg,
1522                                         bio_data_dir(bio), cfq_bio_sync(bio));
1523 }
1524
1525 static void
1526 cfq_merged_requests(struct request_queue *q, struct request *rq,
1527                     struct request *next)
1528 {
1529         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1530         /*
1531          * reposition in fifo if next is older than rq
1532          */
1533         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
1534             time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
1535                 list_move(&rq->queuelist, &next->queuelist);
1536                 rq_set_fifo_time(rq, rq_fifo_time(next));
1537         }
1538
1539         if (cfqq->next_rq == next)
1540                 cfqq->next_rq = rq;
1541         cfq_remove_request(next);
1542         cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(rq))->blkg,
1543                                         rq_data_dir(next), rq_is_sync(next));
1544 }
1545
1546 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
1547                            struct bio *bio)
1548 {
1549         struct cfq_data *cfqd = q->elevator->elevator_data;
1550         struct cfq_io_context *cic;
1551         struct cfq_queue *cfqq;
1552
1553         /*
1554          * Disallow merge of a sync bio into an async request.
1555          */
1556         if (cfq_bio_sync(bio) && !rq_is_sync(rq))
1557                 return false;
1558
1559         /*
1560          * Lookup the cfqq that this bio will be queued with. Allow
1561          * merge only if rq is queued there.
1562          */
1563         cic = cfq_cic_lookup(cfqd, current->io_context);
1564         if (!cic)
1565                 return false;
1566
1567         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1568         return cfqq == RQ_CFQQ(rq);
1569 }
1570
1571 static inline void cfq_del_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1572 {
1573         del_timer(&cfqd->idle_slice_timer);
1574         cfq_blkiocg_update_idle_time_stats(&cfqq->cfqg->blkg);
1575 }
1576
1577 static void __cfq_set_active_queue(struct cfq_data *cfqd,
1578                                    struct cfq_queue *cfqq)
1579 {
1580         if (cfqq) {
1581                 cfq_log_cfqq(cfqd, cfqq, "set_active wl_prio:%d wl_type:%d",
1582                                 cfqd->serving_prio, cfqd->serving_type);
1583                 cfq_blkiocg_update_avg_queue_size_stats(&cfqq->cfqg->blkg);
1584                 cfqq->slice_start = 0;
1585                 cfqq->dispatch_start = jiffies;
1586                 cfqq->allocated_slice = 0;
1587                 cfqq->slice_end = 0;
1588                 cfqq->slice_dispatch = 0;
1589
1590                 cfq_clear_cfqq_wait_request(cfqq);
1591                 cfq_clear_cfqq_must_dispatch(cfqq);
1592                 cfq_clear_cfqq_must_alloc_slice(cfqq);
1593                 cfq_clear_cfqq_fifo_expire(cfqq);
1594                 cfq_mark_cfqq_slice_new(cfqq);
1595
1596                 cfq_del_timer(cfqd, cfqq);
1597         }
1598
1599         cfqd->active_queue = cfqq;
1600 }
1601
1602 /*
1603  * current cfqq expired its slice (or was too idle), select new one
1604  */
1605 static void
1606 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1607                     bool timed_out)
1608 {
1609         cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
1610
1611         if (cfq_cfqq_wait_request(cfqq))
1612                 cfq_del_timer(cfqd, cfqq);
1613
1614         cfq_clear_cfqq_wait_request(cfqq);
1615         cfq_clear_cfqq_wait_busy(cfqq);
1616
1617         /*
1618          * If this cfqq is shared between multiple processes, check to
1619          * make sure that those processes are still issuing I/Os within
1620          * the mean seek distance.  If not, it may be time to break the
1621          * queues apart again.
1622          */
1623         if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq))
1624                 cfq_mark_cfqq_split_coop(cfqq);
1625
1626         /*
1627          * store what was left of this slice, if the queue idled/timed out
1628          */
1629         if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
1630                 cfqq->slice_resid = cfqq->slice_end - jiffies;
1631                 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
1632         }
1633
1634         cfq_group_served(cfqd, cfqq->cfqg, cfqq);
1635
1636         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
1637                 cfq_del_cfqq_rr(cfqd, cfqq);
1638
1639         cfq_resort_rr_list(cfqd, cfqq);
1640
1641         if (cfqq == cfqd->active_queue)
1642                 cfqd->active_queue = NULL;
1643
1644         if (&cfqq->cfqg->rb_node == cfqd->grp_service_tree.active)
1645                 cfqd->grp_service_tree.active = NULL;
1646
1647         if (cfqd->active_cic) {
1648                 put_io_context(cfqd->active_cic->ioc);
1649                 cfqd->active_cic = NULL;
1650         }
1651 }
1652
1653 static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
1654 {
1655         struct cfq_queue *cfqq = cfqd->active_queue;
1656
1657         if (cfqq)
1658                 __cfq_slice_expired(cfqd, cfqq, timed_out);
1659 }
1660
1661 /*
1662  * Get next queue for service. Unless we have a queue preemption,
1663  * we'll simply select the first cfqq in the service tree.
1664  */
1665 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
1666 {
1667         struct cfq_rb_root *service_tree =
1668                 service_tree_for(cfqd->serving_group, cfqd->serving_prio,
1669                                         cfqd->serving_type);
1670
1671         if (!cfqd->rq_queued)
1672                 return NULL;
1673
1674         /* There is nothing to dispatch */
1675         if (!service_tree)
1676                 return NULL;
1677         if (RB_EMPTY_ROOT(&service_tree->rb))
1678                 return NULL;
1679         return cfq_rb_first(service_tree);
1680 }
1681
1682 static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
1683 {
1684         struct cfq_group *cfqg;
1685         struct cfq_queue *cfqq;
1686         int i, j;
1687         struct cfq_rb_root *st;
1688
1689         if (!cfqd->rq_queued)
1690                 return NULL;
1691
1692         cfqg = cfq_get_next_cfqg(cfqd);
1693         if (!cfqg)
1694                 return NULL;
1695
1696         for_each_cfqg_st(cfqg, i, j, st)
1697                 if ((cfqq = cfq_rb_first(st)) != NULL)
1698                         return cfqq;
1699         return NULL;
1700 }
1701
1702 /*
1703  * Get and set a new active queue for service.
1704  */
1705 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
1706                                               struct cfq_queue *cfqq)
1707 {
1708         if (!cfqq)
1709                 cfqq = cfq_get_next_queue(cfqd);
1710
1711         __cfq_set_active_queue(cfqd, cfqq);
1712         return cfqq;
1713 }
1714
1715 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
1716                                           struct request *rq)
1717 {
1718         if (blk_rq_pos(rq) >= cfqd->last_position)
1719                 return blk_rq_pos(rq) - cfqd->last_position;
1720         else
1721                 return cfqd->last_position - blk_rq_pos(rq);
1722 }
1723
1724 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1725                                struct request *rq)
1726 {
1727         return cfq_dist_from_last(cfqd, rq) <= CFQQ_CLOSE_THR;
1728 }
1729
1730 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
1731                                     struct cfq_queue *cur_cfqq)
1732 {
1733         struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
1734         struct rb_node *parent, *node;
1735         struct cfq_queue *__cfqq;
1736         sector_t sector = cfqd->last_position;
1737
1738         if (RB_EMPTY_ROOT(root))
1739                 return NULL;
1740
1741         /*
1742          * First, if we find a request starting at the end of the last
1743          * request, choose it.
1744          */
1745         __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
1746         if (__cfqq)
1747                 return __cfqq;
1748
1749         /*
1750          * If the exact sector wasn't found, the parent of the NULL leaf
1751          * will contain the closest sector.
1752          */
1753         __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1754         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1755                 return __cfqq;
1756
1757         if (blk_rq_pos(__cfqq->next_rq) < sector)
1758                 node = rb_next(&__cfqq->p_node);
1759         else
1760                 node = rb_prev(&__cfqq->p_node);
1761         if (!node)
1762                 return NULL;
1763
1764         __cfqq = rb_entry(node, struct cfq_queue, p_node);
1765         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1766                 return __cfqq;
1767
1768         return NULL;
1769 }
1770
1771 /*
1772  * cfqd - obvious
1773  * cur_cfqq - passed in so that we don't decide that the current queue is
1774  *            closely cooperating with itself.
1775  *
1776  * So, basically we're assuming that that cur_cfqq has dispatched at least
1777  * one request, and that cfqd->last_position reflects a position on the disk
1778  * associated with the I/O issued by cur_cfqq.  I'm not sure this is a valid
1779  * assumption.
1780  */
1781 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1782                                               struct cfq_queue *cur_cfqq)
1783 {
1784         struct cfq_queue *cfqq;
1785
1786         if (cfq_class_idle(cur_cfqq))
1787                 return NULL;
1788         if (!cfq_cfqq_sync(cur_cfqq))
1789                 return NULL;
1790         if (CFQQ_SEEKY(cur_cfqq))
1791                 return NULL;
1792
1793         /*
1794          * Don't search priority tree if it's the only queue in the group.
1795          */
1796         if (cur_cfqq->cfqg->nr_cfqq == 1)
1797                 return NULL;
1798
1799         /*
1800          * We should notice if some of the queues are cooperating, eg
1801          * working closely on the same area of the disk. In that case,
1802          * we can group them together and don't waste time idling.
1803          */
1804         cfqq = cfqq_close(cfqd, cur_cfqq);
1805         if (!cfqq)
1806                 return NULL;
1807
1808         /* If new queue belongs to different cfq_group, don't choose it */
1809         if (cur_cfqq->cfqg != cfqq->cfqg)
1810                 return NULL;
1811
1812         /*
1813          * It only makes sense to merge sync queues.
1814          */
1815         if (!cfq_cfqq_sync(cfqq))
1816                 return NULL;
1817         if (CFQQ_SEEKY(cfqq))
1818                 return NULL;
1819
1820         /*
1821          * Do not merge queues of different priority classes
1822          */
1823         if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
1824                 return NULL;
1825
1826         return cfqq;
1827 }
1828
1829 /*
1830  * Determine whether we should enforce idle window for this queue.
1831  */
1832
1833 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1834 {
1835         enum wl_prio_t prio = cfqq_prio(cfqq);
1836         struct cfq_rb_root *service_tree = cfqq->service_tree;
1837
1838         BUG_ON(!service_tree);
1839         BUG_ON(!service_tree->count);
1840
1841         /* We never do for idle class queues. */
1842         if (prio == IDLE_WORKLOAD)
1843                 return false;
1844
1845         /* We do for queues that were marked with idle window flag. */
1846         if (cfq_cfqq_idle_window(cfqq) &&
1847            !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag))
1848                 return true;
1849
1850         /*
1851          * Otherwise, we do only if they are the last ones
1852          * in their service tree.
1853          */
1854         if (service_tree->count == 1 && cfq_cfqq_sync(cfqq))
1855                 return 1;
1856         cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d",
1857                         service_tree->count);
1858         return 0;
1859 }
1860
1861 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
1862 {
1863         struct cfq_queue *cfqq = cfqd->active_queue;
1864         struct cfq_io_context *cic;
1865         unsigned long sl;
1866
1867         /*
1868          * SSD device without seek penalty, disable idling. But only do so
1869          * for devices that support queuing, otherwise we still have a problem
1870          * with sync vs async workloads.
1871          */
1872         if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
1873                 return;
1874
1875         WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
1876         WARN_ON(cfq_cfqq_slice_new(cfqq));
1877
1878         /*
1879          * idle is disabled, either manually or by past process history
1880          */
1881         if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq))
1882                 return;
1883
1884         /*
1885          * still active requests from this queue, don't idle
1886          */
1887         if (cfqq->dispatched)
1888                 return;
1889
1890         /*
1891          * task has exited, don't wait
1892          */
1893         cic = cfqd->active_cic;
1894         if (!cic || !atomic_read(&cic->ioc->nr_tasks))
1895                 return;
1896
1897         /*
1898          * If our average think time is larger than the remaining time
1899          * slice, then don't idle. This avoids overrunning the allotted
1900          * time slice.
1901          */
1902         if (sample_valid(cic->ttime_samples) &&
1903             (cfqq->slice_end - jiffies < cic->ttime_mean)) {
1904                 cfq_log_cfqq(cfqd, cfqq, "Not idling. think_time:%d",
1905                                 cic->ttime_mean);
1906                 return;
1907         }
1908
1909         cfq_mark_cfqq_wait_request(cfqq);
1910
1911         sl = cfqd->cfq_slice_idle;
1912
1913         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
1914         cfq_blkiocg_update_set_idle_time_stats(&cfqq->cfqg->blkg);
1915         cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
1916 }
1917
1918 /*
1919  * Move request from internal lists to the request queue dispatch list.
1920  */
1921 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
1922 {
1923         struct cfq_data *cfqd = q->elevator->elevator_data;
1924         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1925
1926         cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
1927
1928         cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
1929         cfq_remove_request(rq);
1930         cfqq->dispatched++;
1931         elv_dispatch_sort(q, rq);
1932
1933         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
1934         cfq_blkiocg_update_dispatch_stats(&cfqq->cfqg->blkg, blk_rq_bytes(rq),
1935                                         rq_data_dir(rq), rq_is_sync(rq));
1936 }
1937
1938 /*
1939  * return expired entry, or NULL to just start from scratch in rbtree
1940  */
1941 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
1942 {
1943         struct request *rq = NULL;
1944
1945         if (cfq_cfqq_fifo_expire(cfqq))
1946                 return NULL;
1947
1948         cfq_mark_cfqq_fifo_expire(cfqq);
1949
1950         if (list_empty(&cfqq->fifo))
1951                 return NULL;
1952
1953         rq = rq_entry_fifo(cfqq->fifo.next);
1954         if (time_before(jiffies, rq_fifo_time(rq)))
1955                 rq = NULL;
1956
1957         cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
1958         return rq;
1959 }
1960
1961 static inline int
1962 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1963 {
1964         const int base_rq = cfqd->cfq_slice_async_rq;
1965
1966         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1967
1968         return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1969 }
1970
1971 /*
1972  * Must be called with the queue_lock held.
1973  */
1974 static int cfqq_process_refs(struct cfq_queue *cfqq)
1975 {
1976         int process_refs, io_refs;
1977
1978         io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
1979         process_refs = atomic_read(&cfqq->ref) - io_refs;
1980         BUG_ON(process_refs < 0);
1981         return process_refs;
1982 }
1983
1984 static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
1985 {
1986         int process_refs, new_process_refs;
1987         struct cfq_queue *__cfqq;
1988
1989         /*
1990          * If there are no process references on the new_cfqq, then it is
1991          * unsafe to follow the ->new_cfqq chain as other cfqq's in the
1992          * chain may have dropped their last reference (not just their
1993          * last process reference).
1994          */
1995         if (!cfqq_process_refs(new_cfqq))
1996                 return;
1997
1998         /* Avoid a circular list and skip interim queue merges */
1999         while ((__cfqq = new_cfqq->new_cfqq)) {
2000                 if (__cfqq == cfqq)
2001                         return;
2002                 new_cfqq = __cfqq;
2003         }
2004
2005         process_refs = cfqq_process_refs(cfqq);
2006         new_process_refs = cfqq_process_refs(new_cfqq);
2007         /*
2008          * If the process for the cfqq has gone away, there is no
2009          * sense in merging the queues.
2010          */
2011         if (process_refs == 0 || new_process_refs == 0)
2012                 return;
2013
2014         /*
2015          * Merge in the direction of the lesser amount of work.
2016          */
2017         if (new_process_refs >= process_refs) {
2018                 cfqq->new_cfqq = new_cfqq;
2019                 atomic_add(process_refs, &new_cfqq->ref);
2020         } else {
2021                 new_cfqq->new_cfqq = cfqq;
2022                 atomic_add(new_process_refs, &cfqq->ref);
2023         }
2024 }
2025
2026 static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
2027                                 struct cfq_group *cfqg, enum wl_prio_t prio)
2028 {
2029         struct cfq_queue *queue;
2030         int i;
2031         bool key_valid = false;
2032         unsigned long lowest_key = 0;
2033         enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
2034
2035         for (i = 0; i <= SYNC_WORKLOAD; ++i) {
2036                 /* select the one with lowest rb_key */
2037                 queue = cfq_rb_first(service_tree_for(cfqg, prio, i));
2038                 if (queue &&
2039                     (!key_valid || time_before(queue->rb_key, lowest_key))) {
2040                         lowest_key = queue->rb_key;
2041                         cur_best = i;
2042                         key_valid = true;
2043                 }
2044         }
2045
2046         return cur_best;
2047 }
2048
2049 static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
2050 {
2051         unsigned slice;
2052         unsigned count;
2053         struct cfq_rb_root *st;
2054         unsigned group_slice;
2055
2056         if (!cfqg) {
2057                 cfqd->serving_prio = IDLE_WORKLOAD;
2058                 cfqd->workload_expires = jiffies + 1;
2059                 return;
2060         }
2061
2062         /* Choose next priority. RT > BE > IDLE */
2063         if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
2064                 cfqd->serving_prio = RT_WORKLOAD;
2065         else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
2066                 cfqd->serving_prio = BE_WORKLOAD;
2067         else {
2068                 cfqd->serving_prio = IDLE_WORKLOAD;
2069                 cfqd->workload_expires = jiffies + 1;
2070                 return;
2071         }
2072
2073         /*
2074          * For RT and BE, we have to choose also the type
2075          * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
2076          * expiration time
2077          */
2078         st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
2079         count = st->count;
2080
2081         /*
2082          * check workload expiration, and that we still have other queues ready
2083          */
2084         if (count && !time_after(jiffies, cfqd->workload_expires))
2085                 return;
2086
2087         /* otherwise select new workload type */
2088         cfqd->serving_type =
2089                 cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio);
2090         st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
2091         count = st->count;
2092
2093         /*
2094          * the workload slice is computed as a fraction of target latency
2095          * proportional to the number of queues in that workload, over
2096          * all the queues in the same priority class
2097          */
2098         group_slice = cfq_group_slice(cfqd, cfqg);
2099
2100         slice = group_slice * count /
2101                 max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio],
2102                       cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg));
2103
2104         if (cfqd->serving_type == ASYNC_WORKLOAD) {
2105                 unsigned int tmp;
2106
2107                 /*
2108                  * Async queues are currently system wide. Just taking
2109                  * proportion of queues with-in same group will lead to higher
2110                  * async ratio system wide as generally root group is going
2111                  * to have higher weight. A more accurate thing would be to
2112                  * calculate system wide asnc/sync ratio.
2113                  */
2114                 tmp = cfq_target_latency * cfqg_busy_async_queues(cfqd, cfqg);
2115                 tmp = tmp/cfqd->busy_queues;
2116                 slice = min_t(unsigned, slice, tmp);
2117
2118                 /* async workload slice is scaled down according to
2119                  * the sync/async slice ratio. */
2120                 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
2121         } else
2122                 /* sync workload slice is at least 2 * cfq_slice_idle */
2123                 slice = max(slice, 2 * cfqd->cfq_slice_idle);
2124
2125         slice = max_t(unsigned, slice, CFQ_MIN_TT);
2126         cfq_log(cfqd, "workload slice:%d", slice);
2127         cfqd->workload_expires = jiffies + slice;
2128         cfqd->noidle_tree_requires_idle = false;
2129 }
2130
2131 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
2132 {
2133         struct cfq_rb_root *st = &cfqd->grp_service_tree;
2134         struct cfq_group *cfqg;
2135
2136         if (RB_EMPTY_ROOT(&st->rb))
2137                 return NULL;
2138         cfqg = cfq_rb_first_group(st);
2139         st->active = &cfqg->rb_node;
2140         update_min_vdisktime(st);
2141         return cfqg;
2142 }
2143
2144 static void cfq_choose_cfqg(struct cfq_data *cfqd)
2145 {
2146         struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
2147
2148         cfqd->serving_group = cfqg;
2149
2150         /* Restore the workload type data */
2151         if (cfqg->saved_workload_slice) {
2152                 cfqd->workload_expires = jiffies + cfqg->saved_workload_slice;
2153                 cfqd->serving_type = cfqg->saved_workload;
2154                 cfqd->serving_prio = cfqg->saved_serving_prio;
2155         } else
2156                 cfqd->workload_expires = jiffies - 1;
2157
2158         choose_service_tree(cfqd, cfqg);
2159 }
2160
2161 /*
2162  * Select a queue for service. If we have a current active queue,
2163  * check whether to continue servicing it, or retrieve and set a new one.
2164  */
2165 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
2166 {
2167         struct cfq_queue *cfqq, *new_cfqq = NULL;
2168
2169         cfqq = cfqd->active_queue;
2170         if (!cfqq)
2171                 goto new_queue;
2172
2173         if (!cfqd->rq_queued)
2174                 return NULL;
2175
2176         /*
2177          * We were waiting for group to get backlogged. Expire the queue
2178          */
2179         if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list))
2180                 goto expire;
2181
2182         /*
2183          * The active queue has run out of time, expire it and select new.
2184          */
2185         if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) {
2186                 /*
2187                  * If slice had not expired at the completion of last request
2188                  * we might not have turned on wait_busy flag. Don't expire
2189                  * the queue yet. Allow the group to get backlogged.
2190                  *
2191                  * The very fact that we have used the slice, that means we
2192                  * have been idling all along on this queue and it should be
2193                  * ok to wait for this request to complete.
2194                  */
2195                 if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list)
2196                     && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
2197                         cfqq = NULL;
2198                         goto keep_queue;
2199                 } else
2200                         goto expire;
2201         }
2202
2203         /*
2204          * The active queue has requests and isn't expired, allow it to
2205          * dispatch.
2206          */
2207         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2208                 goto keep_queue;
2209
2210         /*
2211          * If another queue has a request waiting within our mean seek
2212          * distance, let it run.  The expire code will check for close
2213          * cooperators and put the close queue at the front of the service
2214          * tree.  If possible, merge the expiring queue with the new cfqq.
2215          */
2216         new_cfqq = cfq_close_cooperator(cfqd, cfqq);
2217         if (new_cfqq) {
2218                 if (!cfqq->new_cfqq)
2219                         cfq_setup_merge(cfqq, new_cfqq);
2220                 goto expire;
2221         }
2222
2223         /*
2224          * No requests pending. If the active queue still has requests in
2225          * flight or is idling for a new request, allow either of these
2226          * conditions to happen (or time out) before selecting a new queue.
2227          */
2228         if (timer_pending(&cfqd->idle_slice_timer) ||
2229             (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) {
2230                 cfqq = NULL;
2231                 goto keep_queue;
2232         }
2233
2234 expire:
2235         cfq_slice_expired(cfqd, 0);
2236 new_queue:
2237         /*
2238          * Current queue expired. Check if we have to switch to a new
2239          * service tree
2240          */
2241         if (!new_cfqq)
2242                 cfq_choose_cfqg(cfqd);
2243
2244         cfqq = cfq_set_active_queue(cfqd, new_cfqq);
2245 keep_queue:
2246         return cfqq;
2247 }
2248
2249 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
2250 {
2251         int dispatched = 0;
2252
2253         while (cfqq->next_rq) {
2254                 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
2255                 dispatched++;
2256         }
2257
2258         BUG_ON(!list_empty(&cfqq->fifo));
2259
2260         /* By default cfqq is not expired if it is empty. Do it explicitly */
2261         __cfq_slice_expired(cfqq->cfqd, cfqq, 0);
2262         return dispatched;
2263 }
2264
2265 /*
2266  * Drain our current requests. Used for barriers and when switching
2267  * io schedulers on-the-fly.
2268  */
2269 static int cfq_forced_dispatch(struct cfq_data *cfqd)
2270 {
2271         struct cfq_queue *cfqq;
2272         int dispatched = 0;
2273
2274         /* Expire the timeslice of the current active queue first */
2275         cfq_slice_expired(cfqd, 0);
2276         while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) {
2277                 __cfq_set_active_queue(cfqd, cfqq);
2278                 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
2279         }
2280
2281         BUG_ON(cfqd->busy_queues);
2282
2283         cfq_log(cfqd, "forced_dispatch=%d", dispatched);
2284         return dispatched;
2285 }
2286
2287 static inline bool cfq_slice_used_soon(struct cfq_data *cfqd,
2288         struct cfq_queue *cfqq)
2289 {
2290         /* the queue hasn't finished any request, can't estimate */
2291         if (cfq_cfqq_slice_new(cfqq))
2292                 return 1;
2293         if (time_after(jiffies + cfqd->cfq_slice_idle * cfqq->dispatched,
2294                 cfqq->slice_end))
2295                 return 1;
2296
2297         return 0;
2298 }
2299
2300 static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2301 {
2302         unsigned int max_dispatch;
2303
2304         /*
2305          * Drain async requests before we start sync IO
2306          */
2307         if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_flight[BLK_RW_ASYNC])
2308                 return false;
2309
2310         /*
2311          * If this is an async queue and we have sync IO in flight, let it wait
2312          */
2313         if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq))
2314                 return false;
2315
2316         max_dispatch = max_t(unsigned int, cfqd->cfq_quantum / 2, 1);
2317         if (cfq_class_idle(cfqq))
2318                 max_dispatch = 1;
2319
2320         /*
2321          * Does this cfqq already have too much IO in flight?
2322          */
2323         if (cfqq->dispatched >= max_dispatch) {
2324                 /*
2325                  * idle queue must always only have a single IO in flight
2326                  */
2327                 if (cfq_class_idle(cfqq))
2328                         return false;
2329
2330                 /*
2331                  * We have other queues, don't allow more IO from this one
2332                  */
2333                 if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq))
2334                         return false;
2335
2336                 /*
2337                  * Sole queue user, no limit
2338                  */
2339                 if (cfqd->busy_queues == 1)
2340                         max_dispatch = -1;
2341                 else
2342                         /*
2343                          * Normally we start throttling cfqq when cfq_quantum/2
2344                          * requests have been dispatched. But we can drive
2345                          * deeper queue depths at the beginning of slice
2346                          * subjected to upper limit of cfq_quantum.
2347                          * */
2348                         max_dispatch = cfqd->cfq_quantum;
2349         }
2350
2351         /*
2352          * Async queues must wait a bit before being allowed dispatch.
2353          * We also ramp up the dispatch depth gradually for async IO,
2354          * based on the last sync IO we serviced
2355          */
2356         if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
2357                 unsigned long last_sync = jiffies - cfqd->last_delayed_sync;
2358                 unsigned int depth;
2359
2360                 depth = last_sync / cfqd->cfq_slice[1];
2361                 if (!depth && !cfqq->dispatched)
2362                         depth = 1;
2363                 if (depth < max_dispatch)
2364                         max_dispatch = depth;
2365         }
2366
2367         /*
2368          * If we're below the current max, allow a dispatch
2369          */
2370         return cfqq->dispatched < max_dispatch;
2371 }
2372
2373 /*
2374  * Dispatch a request from cfqq, moving them to the request queue
2375  * dispatch list.
2376  */
2377 static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2378 {
2379         struct request *rq;
2380
2381         BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
2382
2383         if (!cfq_may_dispatch(cfqd, cfqq))
2384                 return false;
2385
2386         /*
2387          * follow expired path, else get first next available
2388          */
2389         rq = cfq_check_fifo(cfqq);
2390         if (!rq)
2391                 rq = cfqq->next_rq;
2392
2393         /*
2394          * insert request into driver dispatch list
2395          */
2396         cfq_dispatch_insert(cfqd->queue, rq);
2397
2398         if (!cfqd->active_cic) {
2399                 struct cfq_io_context *cic = RQ_CIC(rq);
2400
2401                 atomic_long_inc(&cic->ioc->refcount);
2402                 cfqd->active_cic = cic;
2403         }
2404
2405         return true;
2406 }
2407
2408 /*
2409  * Find the cfqq that we need to service and move a request from that to the
2410  * dispatch list
2411  */
2412 static int cfq_dispatch_requests(struct request_queue *q, int force)
2413 {
2414         struct cfq_data *cfqd = q->elevator->elevator_data;
2415         struct cfq_queue *cfqq;
2416
2417         if (!cfqd->busy_queues)
2418                 return 0;
2419
2420         if (unlikely(force))
2421                 return cfq_forced_dispatch(cfqd);
2422
2423         cfqq = cfq_select_queue(cfqd);
2424         if (!cfqq)
2425                 return 0;
2426
2427         /*
2428          * Dispatch a request from this cfqq, if it is allowed
2429          */
2430         if (!cfq_dispatch_request(cfqd, cfqq))
2431                 return 0;
2432
2433         cfqq->slice_dispatch++;
2434         cfq_clear_cfqq_must_dispatch(cfqq);
2435
2436         /*
2437          * expire an async queue immediately if it has used up its slice. idle
2438          * queue always expire after 1 dispatch round.
2439          */
2440         if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
2441             cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
2442             cfq_class_idle(cfqq))) {
2443                 cfqq->slice_end = jiffies + 1;
2444                 cfq_slice_expired(cfqd, 0);
2445         }
2446
2447         cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
2448         return 1;
2449 }
2450
2451 /*
2452  * task holds one reference to the queue, dropped when task exits. each rq
2453  * in-flight on this queue also holds a reference, dropped when rq is freed.
2454  *
2455  * Each cfq queue took a reference on the parent group. Drop it now.
2456  * queue lock must be held here.
2457  */
2458 static void cfq_put_queue(struct cfq_queue *cfqq)
2459 {
2460         struct cfq_data *cfqd = cfqq->cfqd;
2461         struct cfq_group *cfqg, *orig_cfqg;
2462
2463         BUG_ON(atomic_read(&cfqq->ref) <= 0);
2464
2465         if (!atomic_dec_and_test(&cfqq->ref))
2466                 return;
2467
2468         cfq_log_cfqq(cfqd, cfqq, "put_queue");
2469         BUG_ON(rb_first(&cfqq->sort_list));
2470         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
2471         cfqg = cfqq->cfqg;
2472         orig_cfqg = cfqq->orig_cfqg;
2473
2474         if (unlikely(cfqd->active_queue == cfqq)) {
2475                 __cfq_slice_expired(cfqd, cfqq, 0);
2476                 cfq_schedule_dispatch(cfqd);
2477         }
2478
2479         BUG_ON(cfq_cfqq_on_rr(cfqq));
2480         kmem_cache_free(cfq_pool, cfqq);
2481         cfq_put_cfqg(cfqg);
2482         if (orig_cfqg)
2483                 cfq_put_cfqg(orig_cfqg);
2484 }
2485
2486 /*
2487  * Must always be called with the rcu_read_lock() held
2488  */
2489 static void
2490 __call_for_each_cic(struct io_context *ioc,
2491                     void (*func)(struct io_context *, struct cfq_io_context *))
2492 {
2493         struct cfq_io_context *cic;
2494         struct hlist_node *n;
2495
2496         hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
2497                 func(ioc, cic);
2498 }
2499
2500 /*
2501  * Call func for each cic attached to this ioc.
2502  */
2503 static void
2504 call_for_each_cic(struct io_context *ioc,
2505                   void (*func)(struct io_context *, struct cfq_io_context *))
2506 {
2507         rcu_read_lock();
2508         __call_for_each_cic(ioc, func);
2509         rcu_read_unlock();
2510 }
2511
2512 static void cfq_cic_free_rcu(struct rcu_head *head)
2513 {
2514         struct cfq_io_context *cic;
2515
2516         cic = container_of(head, struct cfq_io_context, rcu_head);
2517
2518         kmem_cache_free(cfq_ioc_pool, cic);
2519         elv_ioc_count_dec(cfq_ioc_count);
2520
2521         if (ioc_gone) {
2522                 /*
2523                  * CFQ scheduler is exiting, grab exit lock and check
2524                  * the pending io context count. If it hits zero,
2525                  * complete ioc_gone and set it back to NULL
2526                  */
2527                 spin_lock(&ioc_gone_lock);
2528                 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
2529                         complete(ioc_gone);
2530                         ioc_gone = NULL;
2531                 }
2532                 spin_unlock(&ioc_gone_lock);
2533         }
2534 }
2535
2536 static void cfq_cic_free(struct cfq_io_context *cic)
2537 {
2538         call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
2539 }
2540
2541 static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
2542 {
2543         unsigned long flags;
2544         unsigned long dead_key = (unsigned long) cic->key;
2545
2546         BUG_ON(!(dead_key & CIC_DEAD_KEY));
2547
2548         spin_lock_irqsave(&ioc->lock, flags);
2549         radix_tree_delete(&ioc->radix_root, dead_key >> CIC_DEAD_INDEX_SHIFT);
2550         hlist_del_rcu(&cic->cic_list);
2551         spin_unlock_irqrestore(&ioc->lock, flags);
2552
2553         cfq_cic_free(cic);
2554 }
2555
2556 /*
2557  * Must be called with rcu_read_lock() held or preemption otherwise disabled.
2558  * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
2559  * and ->trim() which is called with the task lock held
2560  */
2561 static void cfq_free_io_context(struct io_context *ioc)
2562 {
2563         /*
2564          * ioc->refcount is zero here, or we are called from elv_unregister(),
2565          * so no more cic's are allowed to be linked into this ioc.  So it
2566          * should be ok to iterate over the known list, we will see all cic's
2567          * since no new ones are added.
2568          */
2569         __call_for_each_cic(ioc, cic_free_func);
2570 }
2571
2572 static void cfq_put_cooperator(struct cfq_queue *cfqq)
2573 {
2574         struct cfq_queue *__cfqq, *next;
2575
2576         /*
2577          * If this queue was scheduled to merge with another queue, be
2578          * sure to drop the reference taken on that queue (and others in
2579          * the merge chain).  See cfq_setup_merge and cfq_merge_cfqqs.
2580          */
2581         __cfqq = cfqq->new_cfqq;
2582         while (__cfqq) {
2583                 if (__cfqq == cfqq) {
2584                         WARN(1, "cfqq->new_cfqq loop detected\n");
2585                         break;
2586                 }
2587                 next = __cfqq->new_cfqq;
2588                 cfq_put_queue(__cfqq);
2589                 __cfqq = next;
2590         }
2591 }
2592
2593 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2594 {
2595         if (unlikely(cfqq == cfqd->active_queue)) {
2596                 __cfq_slice_expired(cfqd, cfqq, 0);
2597                 cfq_schedule_dispatch(cfqd);
2598         }
2599
2600         cfq_put_cooperator(cfqq);
2601
2602         cfq_put_queue(cfqq);
2603 }
2604
2605 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
2606                                          struct cfq_io_context *cic)
2607 {
2608         struct io_context *ioc = cic->ioc;
2609
2610         list_del_init(&cic->queue_list);
2611
2612         /*
2613          * Make sure dead mark is seen for dead queues
2614          */
2615         smp_wmb();
2616         cic->key = cfqd_dead_key(cfqd);
2617
2618         if (ioc->ioc_data == cic)
2619                 rcu_assign_pointer(ioc->ioc_data, NULL);
2620
2621         if (cic->cfqq[BLK_RW_ASYNC]) {
2622                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
2623                 cic->cfqq[BLK_RW_ASYNC] = NULL;
2624         }
2625
2626         if (cic->cfqq[BLK_RW_SYNC]) {
2627                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
2628                 cic->cfqq[BLK_RW_SYNC] = NULL;
2629         }
2630 }
2631
2632 static void cfq_exit_single_io_context(struct io_context *ioc,
2633                                        struct cfq_io_context *cic)
2634 {
2635         struct cfq_data *cfqd = cic_to_cfqd(cic);
2636
2637         if (cfqd) {
2638                 struct request_queue *q = cfqd->queue;
2639                 unsigned long flags;
2640
2641                 spin_lock_irqsave(q->queue_lock, flags);
2642
2643                 /*
2644                  * Ensure we get a fresh copy of the ->key to prevent
2645                  * race between exiting task and queue
2646                  */
2647                 smp_read_barrier_depends();
2648                 if (cic->key == cfqd)
2649                         __cfq_exit_single_io_context(cfqd, cic);
2650
2651                 spin_unlock_irqrestore(q->queue_lock, flags);
2652         }
2653 }
2654
2655 /*
2656  * The process that ioc belongs to has exited, we need to clean up
2657  * and put the internal structures we have that belongs to that process.
2658  */
2659 static void cfq_exit_io_context(struct io_context *ioc)
2660 {
2661         call_for_each_cic(ioc, cfq_exit_single_io_context);
2662 }
2663
2664 static struct cfq_io_context *
2665 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2666 {
2667         struct cfq_io_context *cic;
2668
2669         cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
2670                                                         cfqd->queue->node);
2671         if (cic) {
2672                 cic->last_end_request = jiffies;
2673                 INIT_LIST_HEAD(&cic->queue_list);
2674                 INIT_HLIST_NODE(&cic->cic_list);
2675                 cic->dtor = cfq_free_io_context;
2676                 cic->exit = cfq_exit_io_context;
2677                 elv_ioc_count_inc(cfq_ioc_count);
2678         }
2679
2680         return cic;
2681 }
2682
2683 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
2684 {
2685         struct task_struct *tsk = current;
2686         int ioprio_class;
2687
2688         if (!cfq_cfqq_prio_changed(cfqq))
2689                 return;
2690
2691         ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
2692         switch (ioprio_class) {
2693         default:
2694                 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
2695         case IOPRIO_CLASS_NONE:
2696                 /*
2697                  * no prio set, inherit CPU scheduling settings
2698                  */
2699                 cfqq->ioprio = task_nice_ioprio(tsk);
2700                 cfqq->ioprio_class = task_nice_ioclass(tsk);
2701                 break;
2702         case IOPRIO_CLASS_RT:
2703                 cfqq->ioprio = task_ioprio(ioc);
2704                 cfqq->ioprio_class = IOPRIO_CLASS_RT;
2705                 break;
2706         case IOPRIO_CLASS_BE:
2707                 cfqq->ioprio = task_ioprio(ioc);
2708                 cfqq->ioprio_class = IOPRIO_CLASS_BE;
2709                 break;
2710         case IOPRIO_CLASS_IDLE:
2711                 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
2712                 cfqq->ioprio = 7;
2713                 cfq_clear_cfqq_idle_window(cfqq);
2714                 break;
2715         }
2716
2717         /*
2718          * keep track of original prio settings in case we have to temporarily
2719          * elevate the priority of this queue
2720          */
2721         cfqq->org_ioprio = cfqq->ioprio;
2722         cfqq->org_ioprio_class = cfqq->ioprio_class;
2723         cfq_clear_cfqq_prio_changed(cfqq);
2724 }
2725
2726 static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
2727 {
2728         struct cfq_data *cfqd = cic_to_cfqd(cic);
2729         struct cfq_queue *cfqq;
2730         unsigned long flags;
2731
2732         if (unlikely(!cfqd))
2733                 return;
2734
2735         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2736
2737         cfqq = cic->cfqq[BLK_RW_ASYNC];
2738         if (cfqq) {
2739                 struct cfq_queue *new_cfqq;
2740                 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
2741                                                 GFP_ATOMIC);
2742                 if (new_cfqq) {
2743                         cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
2744                         cfq_put_queue(cfqq);
2745                 }
2746         }
2747
2748         cfqq = cic->cfqq[BLK_RW_SYNC];
2749         if (cfqq)
2750                 cfq_mark_cfqq_prio_changed(cfqq);
2751
2752         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2753 }
2754
2755 static void cfq_ioc_set_ioprio(struct io_context *ioc)
2756 {
2757         call_for_each_cic(ioc, changed_ioprio);
2758         ioc->ioprio_changed = 0;
2759 }
2760
2761 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2762                           pid_t pid, bool is_sync)
2763 {
2764         RB_CLEAR_NODE(&cfqq->rb_node);
2765         RB_CLEAR_NODE(&cfqq->p_node);
2766         INIT_LIST_HEAD(&cfqq->fifo);
2767
2768         atomic_set(&cfqq->ref, 0);
2769         cfqq->cfqd = cfqd;
2770
2771         cfq_mark_cfqq_prio_changed(cfqq);
2772
2773         if (is_sync) {
2774                 if (!cfq_class_idle(cfqq))
2775                         cfq_mark_cfqq_idle_window(cfqq);
2776                 cfq_mark_cfqq_sync(cfqq);
2777         }
2778         cfqq->pid = pid;
2779 }
2780
2781 #ifdef CONFIG_CFQ_GROUP_IOSCHED
2782 static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
2783 {
2784         struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1);
2785         struct cfq_data *cfqd = cic_to_cfqd(cic);
2786         unsigned long flags;
2787         struct request_queue *q;
2788
2789         if (unlikely(!cfqd))
2790                 return;
2791
2792         q = cfqd->queue;
2793
2794         spin_lock_irqsave(q->queue_lock, flags);
2795
2796         if (sync_cfqq) {
2797                 /*
2798                  * Drop reference to sync queue. A new sync queue will be
2799                  * assigned in new group upon arrival of a fresh request.
2800                  */
2801                 cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
2802                 cic_set_cfqq(cic, NULL, 1);
2803                 cfq_put_queue(sync_cfqq);
2804         }
2805
2806         spin_unlock_irqrestore(q->queue_lock, flags);
2807 }
2808
2809 static void cfq_ioc_set_cgroup(struct io_context *ioc)
2810 {
2811         call_for_each_cic(ioc, changed_cgroup);
2812         ioc->cgroup_changed = 0;
2813 }
2814 #endif  /* CONFIG_CFQ_GROUP_IOSCHED */
2815
2816 static struct cfq_queue *
2817 cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
2818                      struct io_context *ioc, gfp_t gfp_mask)
2819 {
2820         struct cfq_queue *cfqq, *new_cfqq = NULL;
2821         struct cfq_io_context *cic;
2822         struct cfq_group *cfqg;
2823
2824 retry:
2825         cfqg = cfq_get_cfqg(cfqd, 1);
2826         cic = cfq_cic_lookup(cfqd, ioc);
2827         /* cic always exists here */
2828         cfqq = cic_to_cfqq(cic, is_sync);
2829
2830         /*
2831          * Always try a new alloc if we fell back to the OOM cfqq
2832          * originally, since it should just be a temporary situation.
2833          */
2834         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2835                 cfqq = NULL;
2836                 if (new_cfqq) {
2837                         cfqq = new_cfqq;
2838                         new_cfqq = NULL;
2839                 } else if (gfp_mask & __GFP_WAIT) {
2840                         spin_unlock_irq(cfqd->queue->queue_lock);
2841                         new_cfqq = kmem_cache_alloc_node(cfq_pool,
2842                                         gfp_mask | __GFP_ZERO,
2843                                         cfqd->queue->node);
2844                         spin_lock_irq(cfqd->queue->queue_lock);
2845                         if (new_cfqq)
2846                                 goto retry;
2847                 } else {
2848                         cfqq = kmem_cache_alloc_node(cfq_pool,
2849                                         gfp_mask | __GFP_ZERO,
2850                                         cfqd->queue->node);
2851                 }
2852
2853                 if (cfqq) {
2854                         cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
2855                         cfq_init_prio_data(cfqq, ioc);
2856                         cfq_link_cfqq_cfqg(cfqq, cfqg);
2857                         cfq_log_cfqq(cfqd, cfqq, "alloced");
2858                 } else
2859                         cfqq = &cfqd->oom_cfqq;
2860         }
2861
2862         if (new_cfqq)
2863                 kmem_cache_free(cfq_pool, new_cfqq);
2864
2865         return cfqq;
2866 }
2867
2868 static struct cfq_queue **
2869 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
2870 {
2871         switch (ioprio_class) {
2872         case IOPRIO_CLASS_RT:
2873                 return &cfqd->async_cfqq[0][ioprio];
2874         case IOPRIO_CLASS_BE:
2875                 return &cfqd->async_cfqq[1][ioprio];
2876         case IOPRIO_CLASS_IDLE:
2877                 return &cfqd->async_idle_cfqq;
2878         default:
2879                 BUG();
2880         }
2881 }
2882
2883 static struct cfq_queue *
2884 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
2885               gfp_t gfp_mask)
2886 {
2887         const int ioprio = task_ioprio(ioc);
2888         const int ioprio_class = task_ioprio_class(ioc);
2889         struct cfq_queue **async_cfqq = NULL;
2890         struct cfq_queue *cfqq = NULL;
2891
2892         if (!is_sync) {
2893                 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
2894                 cfqq = *async_cfqq;
2895         }
2896
2897         if (!cfqq)
2898                 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
2899
2900         /*
2901          * pin the queue now that it's allocated, scheduler exit will prune it
2902          */
2903         if (!is_sync && !(*async_cfqq)) {
2904                 atomic_inc(&cfqq->ref);
2905                 *async_cfqq = cfqq;
2906         }
2907
2908         atomic_inc(&cfqq->ref);
2909         return cfqq;
2910 }
2911
2912 /*
2913  * We drop cfq io contexts lazily, so we may find a dead one.
2914  */
2915 static void
2916 cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
2917                   struct cfq_io_context *cic)
2918 {
2919         unsigned long flags;
2920
2921         WARN_ON(!list_empty(&cic->queue_list));
2922         BUG_ON(cic->key != cfqd_dead_key(cfqd));
2923
2924         spin_lock_irqsave(&ioc->lock, flags);
2925
2926         BUG_ON(ioc->ioc_data == cic);
2927
2928         radix_tree_delete(&ioc->radix_root, cfqd->cic_index);
2929         hlist_del_rcu(&cic->cic_list);
2930         spin_unlock_irqrestore(&ioc->lock, flags);
2931
2932         cfq_cic_free(cic);
2933 }
2934
2935 static struct cfq_io_context *
2936 cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
2937 {
2938         struct cfq_io_context *cic;
2939         unsigned long flags;
2940
2941         if (unlikely(!ioc))
2942                 return NULL;
2943
2944         rcu_read_lock();
2945
2946         /*
2947          * we maintain a last-hit cache, to avoid browsing over the tree
2948          */
2949         cic = rcu_dereference(ioc->ioc_data);
2950         if (cic && cic->key == cfqd) {
2951                 rcu_read_unlock();
2952                 return cic;
2953         }
2954
2955         do {
2956                 cic = radix_tree_lookup(&ioc->radix_root, cfqd->cic_index);
2957                 rcu_read_unlock();
2958                 if (!cic)
2959                         break;
2960                 if (unlikely(cic->key != cfqd)) {
2961                         cfq_drop_dead_cic(cfqd, ioc, cic);
2962                         rcu_read_lock();
2963                         continue;
2964                 }
2965
2966                 spin_lock_irqsave(&ioc->lock, flags);
2967                 rcu_assign_pointer(ioc->ioc_data, cic);
2968                 spin_unlock_irqrestore(&ioc->lock, flags);
2969                 break;
2970         } while (1);
2971
2972         return cic;
2973 }
2974
2975 /*
2976  * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2977  * the process specific cfq io context when entered from the block layer.
2978  * Also adds the cic to a per-cfqd list, used when this queue is removed.
2979  */
2980 static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
2981                         struct cfq_io_context *cic, gfp_t gfp_mask)
2982 {
2983         unsigned long flags;
2984         int ret;
2985
2986         ret = radix_tree_preload(gfp_mask);
2987         if (!ret) {
2988                 cic->ioc = ioc;
2989                 cic->key = cfqd;
2990
2991                 spin_lock_irqsave(&ioc->lock, flags);
2992                 ret = radix_tree_insert(&ioc->radix_root,
2993                                                 cfqd->cic_index, cic);
2994                 if (!ret)
2995                         hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
2996                 spin_unlock_irqrestore(&ioc->lock, flags);
2997
2998                 radix_tree_preload_end();
2999
3000                 if (!ret) {
3001                         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
3002                         list_add(&cic->queue_list, &cfqd->cic_list);
3003                         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
3004                 }
3005         }
3006
3007         if (ret)
3008                 printk(KERN_ERR "cfq: cic link failed!\n");
3009
3010         return ret;
3011 }
3012
3013 /*
3014  * Setup general io context and cfq io context. There can be several cfq
3015  * io contexts per general io context, if this process is doing io to more
3016  * than one device managed by cfq.
3017  */
3018 static struct cfq_io_context *
3019 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
3020 {
3021         struct io_context *ioc = NULL;
3022         struct cfq_io_context *cic;
3023
3024         might_sleep_if(gfp_mask & __GFP_WAIT);
3025
3026         ioc = get_io_context(gfp_mask, cfqd->queue->node);
3027         if (!ioc)
3028                 return NULL;
3029
3030         cic = cfq_cic_lookup(cfqd, ioc);
3031         if (cic)
3032                 goto out;
3033
3034         cic = cfq_alloc_io_context(cfqd, gfp_mask);
3035         if (cic == NULL)
3036                 goto err;
3037
3038         if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
3039                 goto err_free;
3040
3041 out:
3042         smp_read_barrier_depends();
3043         if (unlikely(ioc->ioprio_changed))
3044                 cfq_ioc_set_ioprio(ioc);
3045
3046 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3047         if (unlikely(ioc->cgroup_changed))
3048                 cfq_ioc_set_cgroup(ioc);
3049 #endif
3050         return cic;
3051 err_free:
3052         cfq_cic_free(cic);
3053 err:
3054         put_io_context(ioc);
3055         return NULL;
3056 }
3057
3058 static void
3059 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
3060 {
3061         unsigned long elapsed = jiffies - cic->last_end_request;
3062         unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
3063
3064         cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
3065         cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
3066         cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
3067 }
3068
3069 static void
3070 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3071                        struct request *rq)
3072 {
3073         sector_t sdist = 0;
3074         sector_t n_sec = blk_rq_sectors(rq);
3075         if (cfqq->last_request_pos) {
3076                 if (cfqq->last_request_pos < blk_rq_pos(rq))
3077                         sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
3078                 else
3079                         sdist = cfqq->last_request_pos - blk_rq_pos(rq);
3080         }
3081
3082         cfqq->seek_history <<= 1;
3083         if (blk_queue_nonrot(cfqd->queue))
3084                 cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT);
3085         else
3086                 cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
3087 }
3088
3089 /*
3090  * Disable idle window if the process thinks too long or seeks so much that
3091  * it doesn't matter
3092  */
3093 static void
3094 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3095                        struct cfq_io_context *cic)
3096 {
3097         int old_idle, enable_idle;
3098
3099         /*
3100          * Don't idle for async or idle io prio class
3101          */
3102         if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
3103                 return;
3104
3105         enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
3106
3107         if (cfqq->queued[0] + cfqq->queued[1] >= 4)
3108                 cfq_mark_cfqq_deep(cfqq);
3109
3110         if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
3111             (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
3112                 enable_idle = 0;
3113         else if (sample_valid(cic->ttime_samples)) {
3114                 if (cic->ttime_mean > cfqd->cfq_slice_idle)
3115                         enable_idle = 0;
3116                 else
3117                         enable_idle = 1;
3118         }
3119
3120         if (old_idle != enable_idle) {
3121                 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
3122                 if (enable_idle)
3123                         cfq_mark_cfqq_idle_window(cfqq);
3124                 else
3125                         cfq_clear_cfqq_idle_window(cfqq);
3126         }
3127 }
3128
3129 /*
3130  * Check if new_cfqq should preempt the currently active queue. Return 0 for
3131  * no or if we aren't sure, a 1 will cause a preempt.
3132  */
3133 static bool
3134 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
3135                    struct request *rq)
3136 {
3137         struct cfq_queue *cfqq;
3138
3139         cfqq = cfqd->active_queue;
3140         if (!cfqq)
3141                 return false;
3142
3143         if (cfq_class_idle(new_cfqq))
3144                 return false;
3145
3146         if (cfq_class_idle(cfqq))
3147                 return true;
3148
3149         /*
3150          * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice.
3151          */
3152         if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq))
3153                 return false;
3154
3155         /*
3156          * if the new request is sync, but the currently running queue is
3157          * not, let the sync request have priority.
3158          */
3159         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
3160                 return true;
3161
3162         if (new_cfqq->cfqg != cfqq->cfqg)
3163                 return false;
3164
3165         if (cfq_slice_used(cfqq))
3166                 return true;
3167
3168         /* Allow preemption only if we are idling on sync-noidle tree */
3169         if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
3170             cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
3171             new_cfqq->service_tree->count == 2 &&
3172             RB_EMPTY_ROOT(&cfqq->sort_list))
3173                 return true;
3174
3175         /*
3176          * So both queues are sync. Let the new request get disk time if
3177          * it's a metadata request and the current queue is doing regular IO.
3178          */
3179         if (rq_is_meta(rq) && !cfqq->meta_pending)
3180                 return true;
3181
3182         /*
3183          * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
3184          */
3185         if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
3186                 return true;
3187
3188         if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
3189                 return false;
3190
3191         /*
3192          * if this request is as-good as one we would expect from the
3193          * current cfqq, let it preempt
3194          */
3195         if (cfq_rq_close(cfqd, cfqq, rq))
3196                 return true;
3197
3198         return false;
3199 }
3200
3201 /*
3202  * cfqq preempts the active queue. if we allowed preempt with no slice left,
3203  * let it have half of its nominal slice.
3204  */
3205 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3206 {
3207         cfq_log_cfqq(cfqd, cfqq, "preempt");
3208         cfq_slice_expired(cfqd, 1);
3209
3210         /*
3211          * Put the new queue at the front of the of the current list,
3212          * so we know that it will be selected next.
3213          */
3214         BUG_ON(!cfq_cfqq_on_rr(cfqq));
3215
3216         cfq_service_tree_add(cfqd, cfqq, 1);
3217
3218         cfqq->slice_end = 0;
3219         cfq_mark_cfqq_slice_new(cfqq);
3220 }
3221
3222 /*
3223  * Called when a new fs request (rq) is added (to cfqq). Check if there's
3224  * something we should do about it
3225  */
3226 static void
3227 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3228                 struct request *rq)
3229 {
3230         struct cfq_io_context *cic = RQ_CIC(rq);
3231
3232         cfqd->rq_queued++;
3233         if (rq_is_meta(rq))
3234                 cfqq->meta_pending++;
3235
3236         cfq_update_io_thinktime(cfqd, cic);
3237         cfq_update_io_seektime(cfqd, cfqq, rq);
3238         cfq_update_idle_window(cfqd, cfqq, cic);
3239
3240         cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
3241
3242         if (cfqq == cfqd->active_queue) {
3243                 /*
3244                  * Remember that we saw a request from this process, but
3245                  * don't start queuing just yet. Otherwise we risk seeing lots
3246                  * of tiny requests, because we disrupt the normal plugging
3247                  * and merging. If the request is already larger than a single
3248                  * page, let it rip immediately. For that case we assume that
3249                  * merging is already done. Ditto for a busy system that
3250                  * has other work pending, don't risk delaying until the
3251                  * idle timer unplug to continue working.
3252                  */
3253                 if (cfq_cfqq_wait_request(cfqq)) {
3254                         if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
3255                             cfqd->busy_queues > 1) {
3256                                 cfq_del_timer(cfqd, cfqq);
3257                                 cfq_clear_cfqq_wait_request(cfqq);
3258                                 __blk_run_queue(cfqd->queue);
3259                         } else {
3260                                 cfq_blkiocg_update_idle_time_stats(
3261                                                 &cfqq->cfqg->blkg);
3262                                 cfq_mark_cfqq_must_dispatch(cfqq);
3263                         }
3264                 }
3265         } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
3266                 /*
3267                  * not the active queue - expire current slice if it is
3268                  * idle and has expired it's mean thinktime or this new queue
3269                  * has some old slice time left and is of higher priority or
3270                  * this new queue is RT and the current one is BE
3271                  */
3272                 cfq_preempt_queue(cfqd, cfqq);
3273                 __blk_run_queue(cfqd->queue);
3274         }
3275 }
3276
3277 static void cfq_insert_request(struct request_queue *q, struct request *rq)
3278 {
3279         struct cfq_data *cfqd = q->elevator->elevator_data;
3280         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3281
3282         cfq_log_cfqq(cfqd, cfqq, "insert_request");
3283         cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
3284
3285         rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
3286         list_add_tail(&rq->queuelist, &cfqq->fifo);
3287         cfq_add_rq_rb(rq);
3288         cfq_blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg,
3289                         &cfqd->serving_group->blkg, rq_data_dir(rq),
3290                         rq_is_sync(rq));
3291         cfq_rq_enqueued(cfqd, cfqq, rq);
3292 }
3293
3294 /*
3295  * Update hw_tag based on peak queue depth over 50 samples under
3296  * sufficient load.
3297  */
3298 static void cfq_update_hw_tag(struct cfq_data *cfqd)
3299 {
3300         struct cfq_queue *cfqq = cfqd->active_queue;
3301
3302         if (cfqd->rq_in_driver > cfqd->hw_tag_est_depth)
3303                 cfqd->hw_tag_est_depth = cfqd->rq_in_driver;
3304
3305         if (cfqd->hw_tag == 1)
3306                 return;
3307
3308         if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
3309             cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
3310                 return;
3311
3312         /*
3313          * If active queue hasn't enough requests and can idle, cfq might not
3314          * dispatch sufficient requests to hardware. Don't zero hw_tag in this
3315          * case
3316          */
3317         if (cfqq && cfq_cfqq_idle_window(cfqq) &&
3318             cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
3319             CFQ_HW_QUEUE_MIN && cfqd->rq_in_driver < CFQ_HW_QUEUE_MIN)
3320                 return;
3321
3322         if (cfqd->hw_tag_samples++ < 50)
3323                 return;
3324
3325         if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
3326                 cfqd->hw_tag = 1;
3327         else
3328                 cfqd->hw_tag = 0;
3329 }
3330
3331 static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3332 {
3333         struct cfq_io_context *cic = cfqd->active_cic;
3334
3335         /* If there are other queues in the group, don't wait */
3336         if (cfqq->cfqg->nr_cfqq > 1)
3337                 return false;
3338
3339         if (cfq_slice_used(cfqq))
3340                 return true;
3341
3342         /* if slice left is less than think time, wait busy */
3343         if (cic && sample_valid(cic->ttime_samples)
3344             && (cfqq->slice_end - jiffies < cic->ttime_mean))
3345                 return true;
3346
3347         /*
3348          * If think times is less than a jiffy than ttime_mean=0 and above
3349          * will not be true. It might happen that slice has not expired yet
3350          * but will expire soon (4-5 ns) during select_queue(). To cover the
3351          * case where think time is less than a jiffy, mark the queue wait
3352          * busy if only 1 jiffy is left in the slice.
3353          */
3354         if (cfqq->slice_end - jiffies == 1)
3355                 return true;
3356
3357         return false;
3358 }
3359
3360 static void cfq_completed_request(struct request_queue *q, struct request *rq)
3361 {
3362         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3363         struct cfq_data *cfqd = cfqq->cfqd;
3364         const int sync = rq_is_sync(rq);
3365         unsigned long now;
3366
3367         now = jiffies;
3368         cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d", !!rq_noidle(rq));
3369
3370         cfq_update_hw_tag(cfqd);
3371
3372         WARN_ON(!cfqd->rq_in_driver);
3373         WARN_ON(!cfqq->dispatched);
3374         cfqd->rq_in_driver--;
3375         cfqq->dispatched--;
3376         cfq_blkiocg_update_completion_stats(&cfqq->cfqg->blkg,
3377                         rq_start_time_ns(rq), rq_io_start_time_ns(rq),
3378                         rq_data_dir(rq), rq_is_sync(rq));
3379
3380         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
3381
3382         if (sync) {
3383                 RQ_CIC(rq)->last_end_request = now;
3384                 if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
3385                         cfqd->last_delayed_sync = now;
3386         }
3387
3388         /*
3389          * If this is the active queue, check if it needs to be expired,
3390          * or if we want to idle in case it has no pending requests.
3391          */
3392         if (cfqd->active_queue == cfqq) {
3393                 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
3394
3395                 if (cfq_cfqq_slice_new(cfqq)) {
3396                         cfq_set_prio_slice(cfqd, cfqq);
3397                         cfq_clear_cfqq_slice_new(cfqq);
3398                 }
3399
3400                 /*
3401                  * Should we wait for next request to come in before we expire
3402                  * the queue.
3403                  */
3404                 if (cfq_should_wait_busy(cfqd, cfqq)) {
3405                         cfqq->slice_end = jiffies + cfqd->cfq_slice_idle;
3406                         cfq_mark_cfqq_wait_busy(cfqq);
3407                         cfq_log_cfqq(cfqd, cfqq, "will busy wait");
3408                 }
3409
3410                 /*
3411                  * Idling is not enabled on:
3412                  * - expired queues
3413                  * - idle-priority queues
3414                  * - async queues
3415                  * - queues with still some requests queued
3416                  * - when there is a close cooperator
3417                  */
3418                 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
3419                         cfq_slice_expired(cfqd, 1);
3420                 else if (sync && cfqq_empty &&
3421                          !cfq_close_cooperator(cfqd, cfqq)) {
3422                         cfqd->noidle_tree_requires_idle |= !rq_noidle(rq);
3423                         /*
3424                          * Idling is enabled for SYNC_WORKLOAD.
3425                          * SYNC_NOIDLE_WORKLOAD idles at the end of the tree
3426                          * only if we processed at least one !rq_noidle request
3427                          */
3428                         if (cfqd->serving_type == SYNC_WORKLOAD
3429                             || cfqd->noidle_tree_requires_idle
3430                             || cfqq->cfqg->nr_cfqq == 1)
3431                                 cfq_arm_slice_timer(cfqd);
3432                 }
3433         }
3434
3435         if (!cfqd->rq_in_driver)
3436                 cfq_schedule_dispatch(cfqd);
3437 }
3438
3439 /*
3440  * we temporarily boost lower priority queues if they are holding fs exclusive
3441  * resources. they are boosted to normal prio (CLASS_BE/4)
3442  */
3443 static void cfq_prio_boost(struct cfq_queue *cfqq)
3444 {
3445         if (has_fs_excl()) {
3446                 /*
3447                  * boost idle prio on transactions that would lock out other
3448                  * users of the filesystem
3449                  */
3450                 if (cfq_class_idle(cfqq))
3451                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
3452                 if (cfqq->ioprio > IOPRIO_NORM)
3453                         cfqq->ioprio = IOPRIO_NORM;
3454         } else {
3455                 /*
3456                  * unboost the queue (if needed)
3457                  */
3458                 cfqq->ioprio_class = cfqq->org_ioprio_class;
3459                 cfqq->ioprio = cfqq->org_ioprio;
3460         }
3461 }
3462
3463 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
3464 {
3465         if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
3466                 cfq_mark_cfqq_must_alloc_slice(cfqq);
3467                 return ELV_MQUEUE_MUST;
3468         }
3469
3470         return ELV_MQUEUE_MAY;
3471 }
3472
3473 static int cfq_may_queue(struct request_queue *q, int rw)
3474 {
3475         struct cfq_data *cfqd = q->elevator->elevator_data;
3476         struct task_struct *tsk = current;
3477         struct cfq_io_context *cic;
3478         struct cfq_queue *cfqq;
3479
3480         /*
3481          * don't force setup of a queue from here, as a call to may_queue
3482          * does not necessarily imply that a request actually will be queued.
3483          * so just lookup a possibly existing queue, or return 'may queue'
3484          * if that fails
3485          */
3486         cic = cfq_cic_lookup(cfqd, tsk->io_context);
3487         if (!cic)
3488                 return ELV_MQUEUE_MAY;
3489
3490         cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
3491         if (cfqq) {
3492                 cfq_init_prio_data(cfqq, cic->ioc);
3493                 cfq_prio_boost(cfqq);
3494
3495                 return __cfq_may_queue(cfqq);
3496         }
3497
3498         return ELV_MQUEUE_MAY;
3499 }
3500
3501 /*
3502  * queue lock held here
3503  */
3504 static void cfq_put_request(struct request *rq)
3505 {
3506         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3507
3508         if (cfqq) {
3509                 const int rw = rq_data_dir(rq);
3510
3511                 BUG_ON(!cfqq->allocated[rw]);
3512                 cfqq->allocated[rw]--;
3513
3514                 put_io_context(RQ_CIC(rq)->ioc);
3515
3516                 rq->elevator_private = NULL;
3517                 rq->elevator_private2 = NULL;
3518
3519                 /* Put down rq reference on cfqg */
3520                 cfq_put_cfqg(RQ_CFQG(rq));
3521                 rq->elevator_private3 = NULL;
3522
3523                 cfq_put_queue(cfqq);
3524         }
3525 }
3526
3527 static struct cfq_queue *
3528 cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
3529                 struct cfq_queue *cfqq)
3530 {
3531         cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
3532         cic_set_cfqq(cic, cfqq->new_cfqq, 1);
3533         cfq_mark_cfqq_coop(cfqq->new_cfqq);
3534         cfq_put_queue(cfqq);
3535         return cic_to_cfqq(cic, 1);
3536 }
3537
3538 /*
3539  * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
3540  * was the last process referring to said cfqq.
3541  */
3542 static struct cfq_queue *
3543 split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
3544 {
3545         if (cfqq_process_refs(cfqq) == 1) {
3546                 cfqq->pid = current->pid;
3547                 cfq_clear_cfqq_coop(cfqq);
3548                 cfq_clear_cfqq_split_coop(cfqq);
3549                 return cfqq;
3550         }
3551
3552         cic_set_cfqq(cic, NULL, 1);
3553
3554         cfq_put_cooperator(cfqq);
3555
3556         cfq_put_queue(cfqq);
3557         return NULL;
3558 }
3559 /*
3560  * Allocate cfq data structures associated with this request.
3561  */
3562 static int
3563 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
3564 {
3565         struct cfq_data *cfqd = q->elevator->elevator_data;
3566         struct cfq_io_context *cic;
3567         const int rw = rq_data_dir(rq);
3568         const bool is_sync = rq_is_sync(rq);
3569         struct cfq_queue *cfqq;
3570         unsigned long flags;
3571
3572         might_sleep_if(gfp_mask & __GFP_WAIT);
3573
3574         cic = cfq_get_io_context(cfqd, gfp_mask);
3575
3576         spin_lock_irqsave(q->queue_lock, flags);
3577
3578         if (!cic)
3579                 goto queue_fail;
3580
3581 new_queue:
3582         cfqq = cic_to_cfqq(cic, is_sync);
3583         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3584                 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
3585                 cic_set_cfqq(cic, cfqq, is_sync);
3586         } else {
3587                 /*
3588                  * If the queue was seeky for too long, break it apart.
3589                  */
3590                 if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) {
3591                         cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
3592                         cfqq = split_cfqq(cic, cfqq);
3593                         if (!cfqq)
3594                                 goto new_queue;
3595                 }
3596
3597                 /*
3598                  * Check to see if this queue is scheduled to merge with
3599                  * another, closely cooperating queue.  The merging of
3600                  * queues happens here as it must be done in process context.
3601                  * The reference on new_cfqq was taken in merge_cfqqs.
3602                  */
3603                 if (cfqq->new_cfqq)
3604                         cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
3605         }
3606
3607         cfqq->allocated[rw]++;
3608         atomic_inc(&cfqq->ref);
3609
3610         spin_unlock_irqrestore(q->queue_lock, flags);
3611
3612         rq->elevator_private = cic;
3613         rq->elevator_private2 = cfqq;
3614         rq->elevator_private3 = cfq_ref_get_cfqg(cfqq->cfqg);
3615         return 0;
3616
3617 queue_fail:
3618         if (cic)
3619                 put_io_context(cic->ioc);
3620
3621         cfq_schedule_dispatch(cfqd);
3622         spin_unlock_irqrestore(q->queue_lock, flags);
3623         cfq_log(cfqd, "set_request fail");
3624         return 1;
3625 }
3626
3627 static void cfq_kick_queue(struct work_struct *work)
3628 {
3629         struct cfq_data *cfqd =
3630                 container_of(work, struct cfq_data, unplug_work);
3631         struct request_queue *q = cfqd->queue;
3632
3633         spin_lock_irq(q->queue_lock);
3634         __blk_run_queue(cfqd->queue);
3635         spin_unlock_irq(q->queue_lock);
3636 }
3637
3638 /*
3639  * Timer running if the active_queue is currently idling inside its time slice
3640  */
3641 static void cfq_idle_slice_timer(unsigned long data)
3642 {
3643         struct cfq_data *cfqd = (struct cfq_data *) data;
3644         struct cfq_queue *cfqq;
3645         unsigned long flags;
3646         int timed_out = 1;
3647
3648         cfq_log(cfqd, "idle timer fired");
3649
3650         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
3651
3652         cfqq = cfqd->active_queue;
3653         if (cfqq) {
3654                 timed_out = 0;
3655
3656                 /*
3657                  * We saw a request before the queue expired, let it through
3658                  */
3659                 if (cfq_cfqq_must_dispatch(cfqq))
3660                         goto out_kick;
3661
3662                 /*
3663                  * expired
3664                  */
3665                 if (cfq_slice_used(cfqq))
3666                         goto expire;
3667
3668                 /*
3669                  * only expire and reinvoke request handler, if there are
3670                  * other queues with pending requests
3671                  */
3672                 if (!cfqd->busy_queues)
3673                         goto out_cont;
3674
3675                 /*
3676                  * not expired and it has a request pending, let it dispatch
3677                  */
3678                 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3679                         goto out_kick;
3680
3681                 /*
3682                  * Queue depth flag is reset only when the idle didn't succeed
3683                  */
3684                 cfq_clear_cfqq_deep(cfqq);
3685         }
3686 expire:
3687         cfq_slice_expired(cfqd, timed_out);
3688 out_kick:
3689         cfq_schedule_dispatch(cfqd);
3690 out_cont:
3691         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
3692 }
3693
3694 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
3695 {
3696         del_timer_sync(&cfqd->idle_slice_timer);
3697         cancel_work_sync(&cfqd->unplug_work);
3698 }
3699
3700 static void cfq_put_async_queues(struct cfq_data *cfqd)
3701 {
3702         int i;
3703
3704         for (i = 0; i < IOPRIO_BE_NR; i++) {
3705                 if (cfqd->async_cfqq[0][i])
3706                         cfq_put_queue(cfqd->async_cfqq[0][i]);
3707                 if (cfqd->async_cfqq[1][i])
3708                         cfq_put_queue(cfqd->async_cfqq[1][i]);
3709         }
3710
3711         if (cfqd->async_idle_cfqq)
3712                 cfq_put_queue(cfqd->async_idle_cfqq);
3713 }
3714
3715 static void cfq_cfqd_free(struct rcu_head *head)
3716 {
3717         kfree(container_of(head, struct cfq_data, rcu));
3718 }
3719
3720 static void cfq_exit_queue(struct elevator_queue *e)
3721 {
3722         struct cfq_data *cfqd = e->elevator_data;
3723         struct request_queue *q = cfqd->queue;
3724
3725         cfq_shutdown_timer_wq(cfqd);
3726
3727         spin_lock_irq(q->queue_lock);
3728
3729         if (cfqd->active_queue)
3730                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
3731
3732         while (!list_empty(&cfqd->cic_list)) {
3733                 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
3734                                                         struct cfq_io_context,
3735                                                         queue_list);
3736
3737                 __cfq_exit_single_io_context(cfqd, cic);
3738         }
3739
3740         cfq_put_async_queues(cfqd);
3741         cfq_release_cfq_groups(cfqd);
3742         cfq_blkiocg_del_blkio_group(&cfqd->root_group.blkg);
3743
3744         spin_unlock_irq(q->queue_lock);
3745
3746         cfq_shutdown_timer_wq(cfqd);
3747
3748         spin_lock(&cic_index_lock);
3749         ida_remove(&cic_index_ida, cfqd->cic_index);
3750         spin_unlock(&cic_index_lock);
3751
3752         /* Wait for cfqg->blkg->key accessors to exit their grace periods. */
3753         call_rcu(&cfqd->rcu, cfq_cfqd_free);
3754 }
3755
3756 static int cfq_alloc_cic_index(void)
3757 {
3758         int index, error;
3759
3760         do {
3761                 if (!ida_pre_get(&cic_index_ida, GFP_KERNEL))
3762                         return -ENOMEM;
3763
3764                 spin_lock(&cic_index_lock);
3765                 error = ida_get_new(&cic_index_ida, &index);
3766                 spin_unlock(&cic_index_lock);
3767                 if (error && error != -EAGAIN)
3768                         return error;
3769         } while (error);
3770
3771         return index;
3772 }
3773
3774 static void *cfq_init_queue(struct request_queue *q)
3775 {
3776         struct cfq_data *cfqd;
3777         int i, j;
3778         struct cfq_group *cfqg;
3779         struct cfq_rb_root *st;
3780
3781         i = cfq_alloc_cic_index();
3782         if (i < 0)
3783                 return NULL;
3784
3785         cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
3786         if (!cfqd)
3787                 return NULL;
3788
3789         cfqd->cic_index = i;
3790
3791         /* Init root service tree */
3792         cfqd->grp_service_tree = CFQ_RB_ROOT;
3793
3794         /* Init root group */
3795         cfqg = &cfqd->root_group;
3796         for_each_cfqg_st(cfqg, i, j, st)
3797                 *st = CFQ_RB_ROOT;
3798         RB_CLEAR_NODE(&cfqg->rb_node);
3799
3800         /* Give preference to root group over other groups */
3801         cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
3802
3803 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3804         /*
3805          * Take a reference to root group which we never drop. This is just
3806          * to make sure that cfq_put_cfqg() does not try to kfree root group
3807          */
3808         atomic_set(&cfqg->ref, 1);
3809         rcu_read_lock();
3810         cfq_blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg,
3811                                         (void *)cfqd, 0);
3812         rcu_read_unlock();
3813 #endif
3814         /*
3815          * Not strictly needed (since RB_ROOT just clears the node and we
3816          * zeroed cfqd on alloc), but better be safe in case someone decides
3817          * to add magic to the rb code
3818          */
3819         for (i = 0; i < CFQ_PRIO_LISTS; i++)
3820                 cfqd->prio_trees[i] = RB_ROOT;
3821
3822         /*
3823          * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
3824          * Grab a permanent reference to it, so that the normal code flow
3825          * will not attempt to free it.
3826          */
3827         cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
3828         atomic_inc(&cfqd->oom_cfqq.ref);
3829         cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
3830
3831         INIT_LIST_HEAD(&cfqd->cic_list);
3832
3833         cfqd->queue = q;
3834
3835         init_timer(&cfqd->idle_slice_timer);
3836         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
3837         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
3838
3839         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
3840
3841         cfqd->cfq_quantum = cfq_quantum;
3842         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
3843         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
3844         cfqd->cfq_back_max = cfq_back_max;
3845         cfqd->cfq_back_penalty = cfq_back_penalty;
3846         cfqd->cfq_slice[0] = cfq_slice_async;
3847         cfqd->cfq_slice[1] = cfq_slice_sync;
3848         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
3849         cfqd->cfq_slice_idle = cfq_slice_idle;
3850         cfqd->cfq_latency = 1;
3851         cfqd->cfq_group_isolation = 0;
3852         cfqd->hw_tag = -1;
3853         /*
3854          * we optimistically start assuming sync ops weren't delayed in last
3855          * second, in order to have larger depth for async operations.
3856          */
3857         cfqd->last_delayed_sync = jiffies - HZ;
3858         return cfqd;
3859 }
3860
3861 static void cfq_slab_kill(void)
3862 {
3863         /*
3864          * Caller already ensured that pending RCU callbacks are completed,
3865          * so we should have no busy allocations at this point.
3866          */
3867         if (cfq_pool)
3868                 kmem_cache_destroy(cfq_pool);
3869         if (cfq_ioc_pool)
3870                 kmem_cache_destroy(cfq_ioc_pool);
3871 }
3872
3873 static int __init cfq_slab_setup(void)
3874 {
3875         cfq_pool = KMEM_CACHE(cfq_queue, 0);
3876         if (!cfq_pool)
3877                 goto fail;
3878
3879         cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
3880         if (!cfq_ioc_pool)
3881                 goto fail;
3882
3883         return 0;
3884 fail:
3885         cfq_slab_kill();
3886         return -ENOMEM;
3887 }
3888
3889 /*
3890  * sysfs parts below -->
3891  */
3892 static ssize_t
3893 cfq_var_show(unsigned int var, char *page)
3894 {
3895         return sprintf(page, "%d\n", var);
3896 }
3897
3898 static ssize_t
3899 cfq_var_store(unsigned int *var, const char *page, size_t count)
3900 {
3901         char *p = (char *) page;
3902
3903         *var = simple_strtoul(p, &p, 10);
3904         return count;
3905 }
3906
3907 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
3908 static ssize_t __FUNC(struct elevator_queue *e, char *page)             \
3909 {                                                                       \
3910         struct cfq_data *cfqd = e->elevator_data;                       \
3911         unsigned int __data = __VAR;                                    \
3912         if (__CONV)                                                     \
3913                 __data = jiffies_to_msecs(__data);                      \
3914         return cfq_var_show(__data, (page));                            \
3915 }
3916 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
3917 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
3918 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
3919 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
3920 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
3921 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
3922 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
3923 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
3924 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
3925 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
3926 SHOW_FUNCTION(cfq_group_isolation_show, cfqd->cfq_group_isolation, 0);
3927 #undef SHOW_FUNCTION
3928
3929 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
3930 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3931 {                                                                       \
3932         struct cfq_data *cfqd = e->elevator_data;                       \
3933         unsigned int __data;                                            \
3934         int ret = cfq_var_store(&__data, (page), count);                \
3935         if (__data < (MIN))                                             \
3936                 __data = (MIN);                                         \
3937         else if (__data > (MAX))                                        \
3938                 __data = (MAX);                                         \
3939         if (__CONV)                                                     \
3940                 *(__PTR) = msecs_to_jiffies(__data);                    \
3941         else                                                            \
3942                 *(__PTR) = __data;                                      \
3943         return ret;                                                     \
3944 }
3945 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
3946 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
3947                 UINT_MAX, 1);
3948 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
3949                 UINT_MAX, 1);
3950 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
3951 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
3952                 UINT_MAX, 0);
3953 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
3954 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
3955 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
3956 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
3957                 UINT_MAX, 0);
3958 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
3959 STORE_FUNCTION(cfq_group_isolation_store, &cfqd->cfq_group_isolation, 0, 1, 0);
3960 #undef STORE_FUNCTION
3961
3962 #define CFQ_ATTR(name) \
3963         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3964
3965 static struct elv_fs_entry cfq_attrs[] = {
3966         CFQ_ATTR(quantum),
3967         CFQ_ATTR(fifo_expire_sync),
3968         CFQ_ATTR(fifo_expire_async),
3969         CFQ_ATTR(back_seek_max),
3970         CFQ_ATTR(back_seek_penalty),
3971         CFQ_ATTR(slice_sync),
3972         CFQ_ATTR(slice_async),
3973         CFQ_ATTR(slice_async_rq),
3974         CFQ_ATTR(slice_idle),
3975         CFQ_ATTR(low_latency),
3976         CFQ_ATTR(group_isolation),
3977         __ATTR_NULL
3978 };
3979
3980 static struct elevator_type iosched_cfq = {
3981         .ops = {
3982                 .elevator_merge_fn =            cfq_merge,
3983                 .elevator_merged_fn =           cfq_merged_request,
3984                 .elevator_merge_req_fn =        cfq_merged_requests,
3985                 .elevator_allow_merge_fn =      cfq_allow_merge,
3986                 .elevator_bio_merged_fn =       cfq_bio_merged,
3987                 .elevator_dispatch_fn =         cfq_dispatch_requests,
3988                 .elevator_add_req_fn =          cfq_insert_request,
3989                 .elevator_activate_req_fn =     cfq_activate_request,
3990                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
3991                 .elevator_queue_empty_fn =      cfq_queue_empty,
3992                 .elevator_completed_req_fn =    cfq_completed_request,
3993                 .elevator_former_req_fn =       elv_rb_former_request,
3994                 .elevator_latter_req_fn =       elv_rb_latter_request,
3995                 .elevator_set_req_fn =          cfq_set_request,
3996                 .elevator_put_req_fn =          cfq_put_request,
3997                 .elevator_may_queue_fn =        cfq_may_queue,
3998                 .elevator_init_fn =             cfq_init_queue,
3999                 .elevator_exit_fn =             cfq_exit_queue,
4000                 .trim =                         cfq_free_io_context,
4001         },
4002         .elevator_attrs =       cfq_attrs,
4003         .elevator_name =        "cfq",
4004         .elevator_owner =       THIS_MODULE,
4005 };
4006
4007 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4008 static struct blkio_policy_type blkio_policy_cfq = {
4009         .ops = {
4010                 .blkio_unlink_group_fn =        cfq_unlink_blkio_group,
4011                 .blkio_update_group_weight_fn = cfq_update_blkio_group_weight,
4012         },
4013 };
4014 #else
4015 static struct blkio_policy_type blkio_policy_cfq;
4016 #endif
4017
4018 static int __init cfq_init(void)
4019 {
4020         /*
4021          * could be 0 on HZ < 1000 setups
4022          */
4023         if (!cfq_slice_async)
4024                 cfq_slice_async = 1;
4025         if (!cfq_slice_idle)
4026                 cfq_slice_idle = 1;
4027
4028         if (cfq_slab_setup())
4029                 return -ENOMEM;
4030
4031         elv_register(&iosched_cfq);
4032         blkio_policy_register(&blkio_policy_cfq);
4033
4034         return 0;
4035 }
4036
4037 static void __exit cfq_exit(void)
4038 {
4039         DECLARE_COMPLETION_ONSTACK(all_gone);
4040         blkio_policy_unregister(&blkio_policy_cfq);
4041         elv_unregister(&iosched_cfq);
4042         ioc_gone = &all_gone;
4043         /* ioc_gone's update must be visible before reading ioc_count */
4044         smp_wmb();
4045
4046         /*
4047          * this also protects us from entering cfq_slab_kill() with
4048          * pending RCU callbacks
4049          */
4050         if (elv_ioc_count_read(cfq_ioc_count))
4051                 wait_for_completion(&all_gone);
4052         ida_destroy(&cic_index_ida);
4053         cfq_slab_kill();
4054 }
4055
4056 module_init(cfq_init);
4057 module_exit(cfq_exit);
4058
4059 MODULE_AUTHOR("Jens Axboe");
4060 MODULE_LICENSE("GPL");
4061 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");