Fix a CFQ crash in "for-2.6.33" branch of block tree
[linux-2.6.git] / block / cfq-iosched.c
1 /*
2  *  CFQ, or complete fairness queueing, disk scheduler.
3  *
4  *  Based on ideas from a previously unfinished io
5  *  scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
6  *
7  *  Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
8  */
9 #include <linux/module.h>
10 #include <linux/blkdev.h>
11 #include <linux/elevator.h>
12 #include <linux/jiffies.h>
13 #include <linux/rbtree.h>
14 #include <linux/ioprio.h>
15 #include <linux/blktrace_api.h>
16 #include "blk-cgroup.h"
17
18 /*
19  * tunables
20  */
21 /* max queue in one round of service */
22 static const int cfq_quantum = 4;
23 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
24 /* maximum backwards seek, in KiB */
25 static const int cfq_back_max = 16 * 1024;
26 /* penalty of a backwards seek */
27 static const int cfq_back_penalty = 2;
28 static const int cfq_slice_sync = HZ / 10;
29 static int cfq_slice_async = HZ / 25;
30 static const int cfq_slice_async_rq = 2;
31 static int cfq_slice_idle = HZ / 125;
32 static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
33 static const int cfq_hist_divisor = 4;
34
35 /*
36  * offset from end of service tree
37  */
38 #define CFQ_IDLE_DELAY          (HZ / 5)
39
40 /*
41  * below this threshold, we consider thinktime immediate
42  */
43 #define CFQ_MIN_TT              (2)
44
45 /*
46  * Allow merged cfqqs to perform this amount of seeky I/O before
47  * deciding to break the queues up again.
48  */
49 #define CFQQ_COOP_TOUT          (HZ)
50
51 #define CFQ_SLICE_SCALE         (5)
52 #define CFQ_HW_QUEUE_MIN        (5)
53 #define CFQ_SERVICE_SHIFT       12
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
59 static struct kmem_cache *cfq_pool;
60 static struct kmem_cache *cfq_ioc_pool;
61
62 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
63 static struct completion *ioc_gone;
64 static DEFINE_SPINLOCK(ioc_gone_lock);
65
66 #define CFQ_PRIO_LISTS          IOPRIO_BE_NR
67 #define cfq_class_idle(cfqq)    ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
68 #define cfq_class_rt(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
69
70 #define sample_valid(samples)   ((samples) > 80)
71 #define rb_entry_cfqg(node)     rb_entry((node), struct cfq_group, rb_node)
72
73 /*
74  * Most of our rbtree usage is for sorting with min extraction, so
75  * if we cache the leftmost node we don't have to walk down the tree
76  * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
77  * move this into the elevator for the rq sorting as well.
78  */
79 struct cfq_rb_root {
80         struct rb_root rb;
81         struct rb_node *left;
82         unsigned count;
83         u64 min_vdisktime;
84         struct rb_node *active;
85         unsigned total_weight;
86 };
87 #define CFQ_RB_ROOT     (struct cfq_rb_root) { RB_ROOT, NULL, 0, 0, }
88
89 /*
90  * Per process-grouping structure
91  */
92 struct cfq_queue {
93         /* reference count */
94         atomic_t ref;
95         /* various state flags, see below */
96         unsigned int flags;
97         /* parent cfq_data */
98         struct cfq_data *cfqd;
99         /* service_tree member */
100         struct rb_node rb_node;
101         /* service_tree key */
102         unsigned long rb_key;
103         /* prio tree member */
104         struct rb_node p_node;
105         /* prio tree root we belong to, if any */
106         struct rb_root *p_root;
107         /* sorted list of pending requests */
108         struct rb_root sort_list;
109         /* if fifo isn't expired, next request to serve */
110         struct request *next_rq;
111         /* requests queued in sort_list */
112         int queued[2];
113         /* currently allocated requests */
114         int allocated[2];
115         /* fifo list of requests in sort_list */
116         struct list_head fifo;
117
118         /* time when queue got scheduled in to dispatch first request. */
119         unsigned long dispatch_start;
120         unsigned int allocated_slice;
121         /* time when first request from queue completed and slice started. */
122         unsigned long slice_start;
123         unsigned long slice_end;
124         long slice_resid;
125         unsigned int slice_dispatch;
126
127         /* pending metadata requests */
128         int meta_pending;
129         /* number of requests that are on the dispatch list or inside driver */
130         int dispatched;
131
132         /* io prio of this group */
133         unsigned short ioprio, org_ioprio;
134         unsigned short ioprio_class, org_ioprio_class;
135
136         unsigned int seek_samples;
137         u64 seek_total;
138         sector_t seek_mean;
139         sector_t last_request_pos;
140         unsigned long seeky_start;
141
142         pid_t pid;
143
144         struct cfq_rb_root *service_tree;
145         struct cfq_queue *new_cfqq;
146         struct cfq_group *cfqg;
147         struct cfq_group *orig_cfqg;
148         /* Sectors dispatched in current dispatch round */
149         unsigned long nr_sectors;
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         /* Number of active cfq groups on group service tree */
212         int nr_groups;
213
214         /*
215          * The priority currently being served
216          */
217         enum wl_prio_t serving_prio;
218         enum wl_type_t serving_type;
219         unsigned long workload_expires;
220         struct cfq_group *serving_group;
221         bool noidle_tree_requires_idle;
222
223         /*
224          * Each priority tree is sorted by next_request position.  These
225          * trees are used when determining if two or more queues are
226          * interleaving requests (see cfq_close_cooperator).
227          */
228         struct rb_root prio_trees[CFQ_PRIO_LISTS];
229
230         unsigned int busy_queues;
231
232         int rq_in_driver[2];
233         int sync_flight;
234
235         /*
236          * queue-depth detection
237          */
238         int rq_queued;
239         int hw_tag;
240         /*
241          * hw_tag can be
242          * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
243          *  1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
244          *  0 => no NCQ
245          */
246         int hw_tag_est_depth;
247         unsigned int hw_tag_samples;
248
249         /*
250          * idle window management
251          */
252         struct timer_list idle_slice_timer;
253         struct work_struct unplug_work;
254
255         struct cfq_queue *active_queue;
256         struct cfq_io_context *active_cic;
257
258         /*
259          * async queue for each priority case
260          */
261         struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
262         struct cfq_queue *async_idle_cfqq;
263
264         sector_t last_position;
265
266         /*
267          * tunables, see top of file
268          */
269         unsigned int cfq_quantum;
270         unsigned int cfq_fifo_expire[2];
271         unsigned int cfq_back_penalty;
272         unsigned int cfq_back_max;
273         unsigned int cfq_slice[2];
274         unsigned int cfq_slice_async_rq;
275         unsigned int cfq_slice_idle;
276         unsigned int cfq_latency;
277         unsigned int cfq_group_isolation;
278
279         struct list_head cic_list;
280
281         /*
282          * Fallback dummy cfqq for extreme OOM conditions
283          */
284         struct cfq_queue oom_cfqq;
285
286         unsigned long last_delayed_sync;
287
288         /* List of cfq groups being managed on this device*/
289         struct hlist_head cfqg_list;
290         struct rcu_head rcu;
291 };
292
293 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
294
295 static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
296                                             enum wl_prio_t prio,
297                                             enum wl_type_t type,
298                                             struct cfq_data *cfqd)
299 {
300         if (!cfqg)
301                 return NULL;
302
303         if (prio == IDLE_WORKLOAD)
304                 return &cfqg->service_tree_idle;
305
306         return &cfqg->service_trees[prio][type];
307 }
308
309 enum cfqq_state_flags {
310         CFQ_CFQQ_FLAG_on_rr = 0,        /* on round-robin busy list */
311         CFQ_CFQQ_FLAG_wait_request,     /* waiting for a request */
312         CFQ_CFQQ_FLAG_must_dispatch,    /* must be allowed a dispatch */
313         CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
314         CFQ_CFQQ_FLAG_fifo_expire,      /* FIFO checked in this slice */
315         CFQ_CFQQ_FLAG_idle_window,      /* slice idling enabled */
316         CFQ_CFQQ_FLAG_prio_changed,     /* task priority has changed */
317         CFQ_CFQQ_FLAG_slice_new,        /* no requests dispatched in slice */
318         CFQ_CFQQ_FLAG_sync,             /* synchronous queue */
319         CFQ_CFQQ_FLAG_coop,             /* cfqq is shared */
320         CFQ_CFQQ_FLAG_deep,             /* sync cfqq experienced large depth */
321         CFQ_CFQQ_FLAG_wait_busy,        /* Waiting for next request */
322 };
323
324 #define CFQ_CFQQ_FNS(name)                                              \
325 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
326 {                                                                       \
327         (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name);                   \
328 }                                                                       \
329 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
330 {                                                                       \
331         (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                  \
332 }                                                                       \
333 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
334 {                                                                       \
335         return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;      \
336 }
337
338 CFQ_CFQQ_FNS(on_rr);
339 CFQ_CFQQ_FNS(wait_request);
340 CFQ_CFQQ_FNS(must_dispatch);
341 CFQ_CFQQ_FNS(must_alloc_slice);
342 CFQ_CFQQ_FNS(fifo_expire);
343 CFQ_CFQQ_FNS(idle_window);
344 CFQ_CFQQ_FNS(prio_changed);
345 CFQ_CFQQ_FNS(slice_new);
346 CFQ_CFQQ_FNS(sync);
347 CFQ_CFQQ_FNS(coop);
348 CFQ_CFQQ_FNS(deep);
349 CFQ_CFQQ_FNS(wait_busy);
350 #undef CFQ_CFQQ_FNS
351
352 #ifdef CONFIG_DEBUG_CFQ_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 int rq_in_driver(struct cfq_data *cfqd)
426 {
427         return cfqd->rq_in_driver[0] + cfqd->rq_in_driver[1];
428 }
429
430 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
431                                             bool is_sync)
432 {
433         return cic->cfqq[is_sync];
434 }
435
436 static inline void cic_set_cfqq(struct cfq_io_context *cic,
437                                 struct cfq_queue *cfqq, bool is_sync)
438 {
439         cic->cfqq[is_sync] = cfqq;
440 }
441
442 /*
443  * We regard a request as SYNC, if it's either a read or has the SYNC bit
444  * set (in which case it could also be direct WRITE).
445  */
446 static inline bool cfq_bio_sync(struct bio *bio)
447 {
448         return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO);
449 }
450
451 /*
452  * scheduler run of queue, if there are requests pending and no one in the
453  * driver that will restart queueing
454  */
455 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
456 {
457         if (cfqd->busy_queues) {
458                 cfq_log(cfqd, "schedule dispatch");
459                 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
460         }
461 }
462
463 static int cfq_queue_empty(struct request_queue *q)
464 {
465         struct cfq_data *cfqd = q->elevator->elevator_data;
466
467         return !cfqd->rq_queued;
468 }
469
470 /*
471  * Scale schedule slice based on io priority. Use the sync time slice only
472  * if a queue is marked sync and has sync io queued. A sync queue with async
473  * io only, should not get full sync slice length.
474  */
475 static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
476                                  unsigned short prio)
477 {
478         const int base_slice = cfqd->cfq_slice[sync];
479
480         WARN_ON(prio >= IOPRIO_BE_NR);
481
482         return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
483 }
484
485 static inline int
486 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
487 {
488         return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
489 }
490
491 static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
492 {
493         u64 d = delta << CFQ_SERVICE_SHIFT;
494
495         d = d * BLKIO_WEIGHT_DEFAULT;
496         do_div(d, cfqg->weight);
497         return d;
498 }
499
500 static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
501 {
502         s64 delta = (s64)(vdisktime - min_vdisktime);
503         if (delta > 0)
504                 min_vdisktime = vdisktime;
505
506         return min_vdisktime;
507 }
508
509 static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
510 {
511         s64 delta = (s64)(vdisktime - min_vdisktime);
512         if (delta < 0)
513                 min_vdisktime = vdisktime;
514
515         return min_vdisktime;
516 }
517
518 static void update_min_vdisktime(struct cfq_rb_root *st)
519 {
520         u64 vdisktime = st->min_vdisktime;
521         struct cfq_group *cfqg;
522
523         if (st->active) {
524                 cfqg = rb_entry_cfqg(st->active);
525                 vdisktime = cfqg->vdisktime;
526         }
527
528         if (st->left) {
529                 cfqg = rb_entry_cfqg(st->left);
530                 vdisktime = min_vdisktime(vdisktime, cfqg->vdisktime);
531         }
532
533         st->min_vdisktime = max_vdisktime(st->min_vdisktime, vdisktime);
534 }
535
536 /*
537  * get averaged number of queues of RT/BE priority.
538  * average is updated, with a formula that gives more weight to higher numbers,
539  * to quickly follows sudden increases and decrease slowly
540  */
541
542 static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
543                                         struct cfq_group *cfqg, bool rt)
544 {
545         unsigned min_q, max_q;
546         unsigned mult  = cfq_hist_divisor - 1;
547         unsigned round = cfq_hist_divisor / 2;
548         unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
549
550         min_q = min(cfqg->busy_queues_avg[rt], busy);
551         max_q = max(cfqg->busy_queues_avg[rt], busy);
552         cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
553                 cfq_hist_divisor;
554         return cfqg->busy_queues_avg[rt];
555 }
556
557 static inline unsigned
558 cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
559 {
560         struct cfq_rb_root *st = &cfqd->grp_service_tree;
561
562         return cfq_target_latency * cfqg->weight / st->total_weight;
563 }
564
565 static inline void
566 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
567 {
568         unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
569         if (cfqd->cfq_latency) {
570                 /*
571                  * interested queues (we consider only the ones with the same
572                  * priority class in the cfq group)
573                  */
574                 unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
575                                                 cfq_class_rt(cfqq));
576                 unsigned sync_slice = cfqd->cfq_slice[1];
577                 unsigned expect_latency = sync_slice * iq;
578                 unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
579
580                 if (expect_latency > group_slice) {
581                         unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
582                         /* scale low_slice according to IO priority
583                          * and sync vs async */
584                         unsigned low_slice =
585                                 min(slice, base_low_slice * slice / sync_slice);
586                         /* the adapted slice value is scaled to fit all iqs
587                          * into the target latency */
588                         slice = max(slice * group_slice / expect_latency,
589                                     low_slice);
590                 }
591         }
592         cfqq->slice_start = jiffies;
593         cfqq->slice_end = jiffies + slice;
594         cfqq->allocated_slice = slice;
595         cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
596 }
597
598 /*
599  * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
600  * isn't valid until the first request from the dispatch is activated
601  * and the slice time set.
602  */
603 static inline bool cfq_slice_used(struct cfq_queue *cfqq)
604 {
605         if (cfq_cfqq_slice_new(cfqq))
606                 return 0;
607         if (time_before(jiffies, cfqq->slice_end))
608                 return 0;
609
610         return 1;
611 }
612
613 /*
614  * Lifted from AS - choose which of rq1 and rq2 that is best served now.
615  * We choose the request that is closest to the head right now. Distance
616  * behind the head is penalized and only allowed to a certain extent.
617  */
618 static struct request *
619 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
620 {
621         sector_t s1, s2, d1 = 0, d2 = 0;
622         unsigned long back_max;
623 #define CFQ_RQ1_WRAP    0x01 /* request 1 wraps */
624 #define CFQ_RQ2_WRAP    0x02 /* request 2 wraps */
625         unsigned wrap = 0; /* bit mask: requests behind the disk head? */
626
627         if (rq1 == NULL || rq1 == rq2)
628                 return rq2;
629         if (rq2 == NULL)
630                 return rq1;
631
632         if (rq_is_sync(rq1) && !rq_is_sync(rq2))
633                 return rq1;
634         else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
635                 return rq2;
636         if (rq_is_meta(rq1) && !rq_is_meta(rq2))
637                 return rq1;
638         else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
639                 return rq2;
640
641         s1 = blk_rq_pos(rq1);
642         s2 = blk_rq_pos(rq2);
643
644         /*
645          * by definition, 1KiB is 2 sectors
646          */
647         back_max = cfqd->cfq_back_max * 2;
648
649         /*
650          * Strict one way elevator _except_ in the case where we allow
651          * short backward seeks which are biased as twice the cost of a
652          * similar forward seek.
653          */
654         if (s1 >= last)
655                 d1 = s1 - last;
656         else if (s1 + back_max >= last)
657                 d1 = (last - s1) * cfqd->cfq_back_penalty;
658         else
659                 wrap |= CFQ_RQ1_WRAP;
660
661         if (s2 >= last)
662                 d2 = s2 - last;
663         else if (s2 + back_max >= last)
664                 d2 = (last - s2) * cfqd->cfq_back_penalty;
665         else
666                 wrap |= CFQ_RQ2_WRAP;
667
668         /* Found required data */
669
670         /*
671          * By doing switch() on the bit mask "wrap" we avoid having to
672          * check two variables for all permutations: --> faster!
673          */
674         switch (wrap) {
675         case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
676                 if (d1 < d2)
677                         return rq1;
678                 else if (d2 < d1)
679                         return rq2;
680                 else {
681                         if (s1 >= s2)
682                                 return rq1;
683                         else
684                                 return rq2;
685                 }
686
687         case CFQ_RQ2_WRAP:
688                 return rq1;
689         case CFQ_RQ1_WRAP:
690                 return rq2;
691         case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
692         default:
693                 /*
694                  * Since both rqs are wrapped,
695                  * start with the one that's further behind head
696                  * (--> only *one* back seek required),
697                  * since back seek takes more time than forward.
698                  */
699                 if (s1 <= s2)
700                         return rq1;
701                 else
702                         return rq2;
703         }
704 }
705
706 /*
707  * The below is leftmost cache rbtree addon
708  */
709 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
710 {
711         /* Service tree is empty */
712         if (!root->count)
713                 return NULL;
714
715         if (!root->left)
716                 root->left = rb_first(&root->rb);
717
718         if (root->left)
719                 return rb_entry(root->left, struct cfq_queue, rb_node);
720
721         return NULL;
722 }
723
724 static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
725 {
726         if (!root->left)
727                 root->left = rb_first(&root->rb);
728
729         if (root->left)
730                 return rb_entry_cfqg(root->left);
731
732         return NULL;
733 }
734
735 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
736 {
737         rb_erase(n, root);
738         RB_CLEAR_NODE(n);
739 }
740
741 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
742 {
743         if (root->left == n)
744                 root->left = NULL;
745         rb_erase_init(n, &root->rb);
746         --root->count;
747 }
748
749 /*
750  * would be nice to take fifo expire time into account as well
751  */
752 static struct request *
753 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
754                   struct request *last)
755 {
756         struct rb_node *rbnext = rb_next(&last->rb_node);
757         struct rb_node *rbprev = rb_prev(&last->rb_node);
758         struct request *next = NULL, *prev = NULL;
759
760         BUG_ON(RB_EMPTY_NODE(&last->rb_node));
761
762         if (rbprev)
763                 prev = rb_entry_rq(rbprev);
764
765         if (rbnext)
766                 next = rb_entry_rq(rbnext);
767         else {
768                 rbnext = rb_first(&cfqq->sort_list);
769                 if (rbnext && rbnext != &last->rb_node)
770                         next = rb_entry_rq(rbnext);
771         }
772
773         return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
774 }
775
776 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
777                                       struct cfq_queue *cfqq)
778 {
779         /*
780          * just an approximation, should be ok.
781          */
782         return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
783                        cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
784 }
785
786 static inline s64
787 cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
788 {
789         return cfqg->vdisktime - st->min_vdisktime;
790 }
791
792 static void
793 __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
794 {
795         struct rb_node **node = &st->rb.rb_node;
796         struct rb_node *parent = NULL;
797         struct cfq_group *__cfqg;
798         s64 key = cfqg_key(st, cfqg);
799         int left = 1;
800
801         while (*node != NULL) {
802                 parent = *node;
803                 __cfqg = rb_entry_cfqg(parent);
804
805                 if (key < cfqg_key(st, __cfqg))
806                         node = &parent->rb_left;
807                 else {
808                         node = &parent->rb_right;
809                         left = 0;
810                 }
811         }
812
813         if (left)
814                 st->left = &cfqg->rb_node;
815
816         rb_link_node(&cfqg->rb_node, parent, node);
817         rb_insert_color(&cfqg->rb_node, &st->rb);
818 }
819
820 static void
821 cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
822 {
823         struct cfq_rb_root *st = &cfqd->grp_service_tree;
824         struct cfq_group *__cfqg;
825         struct rb_node *n;
826
827         cfqg->nr_cfqq++;
828         if (cfqg->on_st)
829                 return;
830
831         /*
832          * Currently put the group at the end. Later implement something
833          * so that groups get lesser vtime based on their weights, so that
834          * if group does not loose all if it was not continously backlogged.
835          */
836         n = rb_last(&st->rb);
837         if (n) {
838                 __cfqg = rb_entry_cfqg(n);
839                 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
840         } else
841                 cfqg->vdisktime = st->min_vdisktime;
842
843         __cfq_group_service_tree_add(st, cfqg);
844         cfqg->on_st = true;
845         cfqd->nr_groups++;
846         st->total_weight += cfqg->weight;
847 }
848
849 static void
850 cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
851 {
852         struct cfq_rb_root *st = &cfqd->grp_service_tree;
853
854         if (st->active == &cfqg->rb_node)
855                 st->active = NULL;
856
857         BUG_ON(cfqg->nr_cfqq < 1);
858         cfqg->nr_cfqq--;
859
860         /* If there are other cfq queues under this group, don't delete it */
861         if (cfqg->nr_cfqq)
862                 return;
863
864         cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
865         cfqg->on_st = false;
866         cfqd->nr_groups--;
867         st->total_weight -= cfqg->weight;
868         if (!RB_EMPTY_NODE(&cfqg->rb_node))
869                 cfq_rb_erase(&cfqg->rb_node, st);
870         cfqg->saved_workload_slice = 0;
871         blkiocg_update_blkio_group_dequeue_stats(&cfqg->blkg, 1);
872 }
873
874 static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
875 {
876         unsigned int slice_used;
877
878         /*
879          * Queue got expired before even a single request completed or
880          * got expired immediately after first request completion.
881          */
882         if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
883                 /*
884                  * Also charge the seek time incurred to the group, otherwise
885                  * if there are mutiple queues in the group, each can dispatch
886                  * a single request on seeky media and cause lots of seek time
887                  * and group will never know it.
888                  */
889                 slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
890                                         1);
891         } else {
892                 slice_used = jiffies - cfqq->slice_start;
893                 if (slice_used > cfqq->allocated_slice)
894                         slice_used = cfqq->allocated_slice;
895         }
896
897         cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u sect=%lu", slice_used,
898                                 cfqq->nr_sectors);
899         return slice_used;
900 }
901
902 static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
903                                 struct cfq_queue *cfqq)
904 {
905         struct cfq_rb_root *st = &cfqd->grp_service_tree;
906         unsigned int used_sl, charge_sl;
907         int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
908                         - cfqg->service_tree_idle.count;
909
910         BUG_ON(nr_sync < 0);
911         used_sl = charge_sl = cfq_cfqq_slice_usage(cfqq);
912
913         if (!cfq_cfqq_sync(cfqq) && !nr_sync)
914                 charge_sl = cfqq->allocated_slice;
915
916         /* Can't update vdisktime while group is on service tree */
917         cfq_rb_erase(&cfqg->rb_node, st);
918         cfqg->vdisktime += cfq_scale_slice(charge_sl, cfqg);
919         __cfq_group_service_tree_add(st, cfqg);
920
921         /* This group is being expired. Save the context */
922         if (time_after(cfqd->workload_expires, jiffies)) {
923                 cfqg->saved_workload_slice = cfqd->workload_expires
924                                                 - jiffies;
925                 cfqg->saved_workload = cfqd->serving_type;
926                 cfqg->saved_serving_prio = cfqd->serving_prio;
927         } else
928                 cfqg->saved_workload_slice = 0;
929
930         cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
931                                         st->min_vdisktime);
932         blkiocg_update_blkio_group_stats(&cfqg->blkg, used_sl,
933                                                 cfqq->nr_sectors);
934 }
935
936 #ifdef CONFIG_CFQ_GROUP_IOSCHED
937 static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
938 {
939         if (blkg)
940                 return container_of(blkg, struct cfq_group, blkg);
941         return NULL;
942 }
943
944 void
945 cfq_update_blkio_group_weight(struct blkio_group *blkg, unsigned int weight)
946 {
947         cfqg_of_blkg(blkg)->weight = weight;
948 }
949
950 static struct cfq_group *
951 cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
952 {
953         struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
954         struct cfq_group *cfqg = NULL;
955         void *key = cfqd;
956         int i, j;
957         struct cfq_rb_root *st;
958         struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
959         unsigned int major, minor;
960
961         /* Do we need to take this reference */
962         if (!blkiocg_css_tryget(blkcg))
963                 return NULL;;
964
965         cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
966         if (cfqg || !create)
967                 goto done;
968
969         cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
970         if (!cfqg)
971                 goto done;
972
973         cfqg->weight = blkcg->weight;
974         for_each_cfqg_st(cfqg, i, j, st)
975                 *st = CFQ_RB_ROOT;
976         RB_CLEAR_NODE(&cfqg->rb_node);
977
978         /*
979          * Take the initial reference that will be released on destroy
980          * This can be thought of a joint reference by cgroup and
981          * elevator which will be dropped by either elevator exit
982          * or cgroup deletion path depending on who is exiting first.
983          */
984         atomic_set(&cfqg->ref, 1);
985
986         /* Add group onto cgroup list */
987         sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
988         blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
989                                         MKDEV(major, minor));
990
991         /* Add group on cfqd list */
992         hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
993
994 done:
995         blkiocg_css_put(blkcg);
996         return cfqg;
997 }
998
999 /*
1000  * Search for the cfq group current task belongs to. If create = 1, then also
1001  * create the cfq group if it does not exist. request_queue lock must be held.
1002  */
1003 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
1004 {
1005         struct cgroup *cgroup;
1006         struct cfq_group *cfqg = NULL;
1007
1008         rcu_read_lock();
1009         cgroup = task_cgroup(current, blkio_subsys_id);
1010         cfqg = cfq_find_alloc_cfqg(cfqd, cgroup, create);
1011         if (!cfqg && create)
1012                 cfqg = &cfqd->root_group;
1013         rcu_read_unlock();
1014         return cfqg;
1015 }
1016
1017 static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
1018 {
1019         /* Currently, all async queues are mapped to root group */
1020         if (!cfq_cfqq_sync(cfqq))
1021                 cfqg = &cfqq->cfqd->root_group;
1022
1023         cfqq->cfqg = cfqg;
1024         /* cfqq reference on cfqg */
1025         atomic_inc(&cfqq->cfqg->ref);
1026 }
1027
1028 static void cfq_put_cfqg(struct cfq_group *cfqg)
1029 {
1030         struct cfq_rb_root *st;
1031         int i, j;
1032
1033         BUG_ON(atomic_read(&cfqg->ref) <= 0);
1034         if (!atomic_dec_and_test(&cfqg->ref))
1035                 return;
1036         for_each_cfqg_st(cfqg, i, j, st)
1037                 BUG_ON(!RB_EMPTY_ROOT(&st->rb) || st->active != NULL);
1038         kfree(cfqg);
1039 }
1040
1041 static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
1042 {
1043         /* Something wrong if we are trying to remove same group twice */
1044         BUG_ON(hlist_unhashed(&cfqg->cfqd_node));
1045
1046         hlist_del_init(&cfqg->cfqd_node);
1047
1048         /*
1049          * Put the reference taken at the time of creation so that when all
1050          * queues are gone, group can be destroyed.
1051          */
1052         cfq_put_cfqg(cfqg);
1053 }
1054
1055 static void cfq_release_cfq_groups(struct cfq_data *cfqd)
1056 {
1057         struct hlist_node *pos, *n;
1058         struct cfq_group *cfqg;
1059
1060         hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) {
1061                 /*
1062                  * If cgroup removal path got to blk_group first and removed
1063                  * it from cgroup list, then it will take care of destroying
1064                  * cfqg also.
1065                  */
1066                 if (!blkiocg_del_blkio_group(&cfqg->blkg))
1067                         cfq_destroy_cfqg(cfqd, cfqg);
1068         }
1069 }
1070
1071 /*
1072  * Blk cgroup controller notification saying that blkio_group object is being
1073  * delinked as associated cgroup object is going away. That also means that
1074  * no new IO will come in this group. So get rid of this group as soon as
1075  * any pending IO in the group is finished.
1076  *
1077  * This function is called under rcu_read_lock(). key is the rcu protected
1078  * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu
1079  * read lock.
1080  *
1081  * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
1082  * it should not be NULL as even if elevator was exiting, cgroup deltion
1083  * path got to it first.
1084  */
1085 void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
1086 {
1087         unsigned long  flags;
1088         struct cfq_data *cfqd = key;
1089
1090         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1091         cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg));
1092         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1093 }
1094
1095 #else /* GROUP_IOSCHED */
1096 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
1097 {
1098         return &cfqd->root_group;
1099 }
1100 static inline void
1101 cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
1102         cfqq->cfqg = cfqg;
1103 }
1104
1105 static void cfq_release_cfq_groups(struct cfq_data *cfqd) {}
1106 static inline void cfq_put_cfqg(struct cfq_group *cfqg) {}
1107
1108 #endif /* GROUP_IOSCHED */
1109
1110 /*
1111  * The cfqd->service_trees holds all pending cfq_queue's that have
1112  * requests waiting to be processed. It is sorted in the order that
1113  * we will service the queues.
1114  */
1115 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1116                                  bool add_front)
1117 {
1118         struct rb_node **p, *parent;
1119         struct cfq_queue *__cfqq;
1120         unsigned long rb_key;
1121         struct cfq_rb_root *service_tree;
1122         int left;
1123         int new_cfqq = 1;
1124         int group_changed = 0;
1125
1126 #ifdef CONFIG_CFQ_GROUP_IOSCHED
1127         if (!cfqd->cfq_group_isolation
1128             && cfqq_type(cfqq) == SYNC_NOIDLE_WORKLOAD
1129             && cfqq->cfqg && cfqq->cfqg != &cfqd->root_group) {
1130                 /* Move this cfq to root group */
1131                 cfq_log_cfqq(cfqd, cfqq, "moving to root group");
1132                 if (!RB_EMPTY_NODE(&cfqq->rb_node))
1133                         cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1134                 cfqq->orig_cfqg = cfqq->cfqg;
1135                 cfqq->cfqg = &cfqd->root_group;
1136                 atomic_inc(&cfqd->root_group.ref);
1137                 group_changed = 1;
1138         } else if (!cfqd->cfq_group_isolation
1139                    && cfqq_type(cfqq) == SYNC_WORKLOAD && cfqq->orig_cfqg) {
1140                 /* cfqq is sequential now needs to go to its original group */
1141                 BUG_ON(cfqq->cfqg != &cfqd->root_group);
1142                 if (!RB_EMPTY_NODE(&cfqq->rb_node))
1143                         cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1144                 cfq_put_cfqg(cfqq->cfqg);
1145                 cfqq->cfqg = cfqq->orig_cfqg;
1146                 cfqq->orig_cfqg = NULL;
1147                 group_changed = 1;
1148                 cfq_log_cfqq(cfqd, cfqq, "moved to origin group");
1149         }
1150 #endif
1151
1152         service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
1153                                                 cfqq_type(cfqq), cfqd);
1154         if (cfq_class_idle(cfqq)) {
1155                 rb_key = CFQ_IDLE_DELAY;
1156                 parent = rb_last(&service_tree->rb);
1157                 if (parent && parent != &cfqq->rb_node) {
1158                         __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1159                         rb_key += __cfqq->rb_key;
1160                 } else
1161                         rb_key += jiffies;
1162         } else if (!add_front) {
1163                 /*
1164                  * Get our rb key offset. Subtract any residual slice
1165                  * value carried from last service. A negative resid
1166                  * count indicates slice overrun, and this should position
1167                  * the next service time further away in the tree.
1168                  */
1169                 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
1170                 rb_key -= cfqq->slice_resid;
1171                 cfqq->slice_resid = 0;
1172         } else {
1173                 rb_key = -HZ;
1174                 __cfqq = cfq_rb_first(service_tree);
1175                 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
1176         }
1177
1178         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1179                 new_cfqq = 0;
1180                 /*
1181                  * same position, nothing more to do
1182                  */
1183                 if (rb_key == cfqq->rb_key &&
1184                     cfqq->service_tree == service_tree)
1185                         return;
1186
1187                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1188                 cfqq->service_tree = NULL;
1189         }
1190
1191         left = 1;
1192         parent = NULL;
1193         cfqq->service_tree = service_tree;
1194         p = &service_tree->rb.rb_node;
1195         while (*p) {
1196                 struct rb_node **n;
1197
1198                 parent = *p;
1199                 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1200
1201                 /*
1202                  * sort by key, that represents service time.
1203                  */
1204                 if (time_before(rb_key, __cfqq->rb_key))
1205                         n = &(*p)->rb_left;
1206                 else {
1207                         n = &(*p)->rb_right;
1208                         left = 0;
1209                 }
1210
1211                 p = n;
1212         }
1213
1214         if (left)
1215                 service_tree->left = &cfqq->rb_node;
1216
1217         cfqq->rb_key = rb_key;
1218         rb_link_node(&cfqq->rb_node, parent, p);
1219         rb_insert_color(&cfqq->rb_node, &service_tree->rb);
1220         service_tree->count++;
1221         if ((add_front || !new_cfqq) && !group_changed)
1222                 return;
1223         cfq_group_service_tree_add(cfqd, cfqq->cfqg);
1224 }
1225
1226 static struct cfq_queue *
1227 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
1228                      sector_t sector, struct rb_node **ret_parent,
1229                      struct rb_node ***rb_link)
1230 {
1231         struct rb_node **p, *parent;
1232         struct cfq_queue *cfqq = NULL;
1233
1234         parent = NULL;
1235         p = &root->rb_node;
1236         while (*p) {
1237                 struct rb_node **n;
1238
1239                 parent = *p;
1240                 cfqq = rb_entry(parent, struct cfq_queue, p_node);
1241
1242                 /*
1243                  * Sort strictly based on sector.  Smallest to the left,
1244                  * largest to the right.
1245                  */
1246                 if (sector > blk_rq_pos(cfqq->next_rq))
1247                         n = &(*p)->rb_right;
1248                 else if (sector < blk_rq_pos(cfqq->next_rq))
1249                         n = &(*p)->rb_left;
1250                 else
1251                         break;
1252                 p = n;
1253                 cfqq = NULL;
1254         }
1255
1256         *ret_parent = parent;
1257         if (rb_link)
1258                 *rb_link = p;
1259         return cfqq;
1260 }
1261
1262 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1263 {
1264         struct rb_node **p, *parent;
1265         struct cfq_queue *__cfqq;
1266
1267         if (cfqq->p_root) {
1268                 rb_erase(&cfqq->p_node, cfqq->p_root);
1269                 cfqq->p_root = NULL;
1270         }
1271
1272         if (cfq_class_idle(cfqq))
1273                 return;
1274         if (!cfqq->next_rq)
1275                 return;
1276
1277         cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
1278         __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
1279                                       blk_rq_pos(cfqq->next_rq), &parent, &p);
1280         if (!__cfqq) {
1281                 rb_link_node(&cfqq->p_node, parent, p);
1282                 rb_insert_color(&cfqq->p_node, cfqq->p_root);
1283         } else
1284                 cfqq->p_root = NULL;
1285 }
1286
1287 /*
1288  * Update cfqq's position in the service tree.
1289  */
1290 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1291 {
1292         /*
1293          * Resorting requires the cfqq to be on the RR list already.
1294          */
1295         if (cfq_cfqq_on_rr(cfqq)) {
1296                 cfq_service_tree_add(cfqd, cfqq, 0);
1297                 cfq_prio_tree_add(cfqd, cfqq);
1298         }
1299 }
1300
1301 /*
1302  * add to busy list of queues for service, trying to be fair in ordering
1303  * the pending list according to last request service
1304  */
1305 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1306 {
1307         cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
1308         BUG_ON(cfq_cfqq_on_rr(cfqq));
1309         cfq_mark_cfqq_on_rr(cfqq);
1310         cfqd->busy_queues++;
1311
1312         cfq_resort_rr_list(cfqd, cfqq);
1313 }
1314
1315 /*
1316  * Called when the cfqq no longer has requests pending, remove it from
1317  * the service tree.
1318  */
1319 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1320 {
1321         cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
1322         BUG_ON(!cfq_cfqq_on_rr(cfqq));
1323         cfq_clear_cfqq_on_rr(cfqq);
1324
1325         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1326                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1327                 cfqq->service_tree = NULL;
1328         }
1329         if (cfqq->p_root) {
1330                 rb_erase(&cfqq->p_node, cfqq->p_root);
1331                 cfqq->p_root = NULL;
1332         }
1333
1334         cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1335         BUG_ON(!cfqd->busy_queues);
1336         cfqd->busy_queues--;
1337 }
1338
1339 /*
1340  * rb tree support functions
1341  */
1342 static void cfq_del_rq_rb(struct request *rq)
1343 {
1344         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1345         const int sync = rq_is_sync(rq);
1346
1347         BUG_ON(!cfqq->queued[sync]);
1348         cfqq->queued[sync]--;
1349
1350         elv_rb_del(&cfqq->sort_list, rq);
1351
1352         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1353                 /*
1354                  * Queue will be deleted from service tree when we actually
1355                  * expire it later. Right now just remove it from prio tree
1356                  * as it is empty.
1357                  */
1358                 if (cfqq->p_root) {
1359                         rb_erase(&cfqq->p_node, cfqq->p_root);
1360                         cfqq->p_root = NULL;
1361                 }
1362         }
1363 }
1364
1365 static void cfq_add_rq_rb(struct request *rq)
1366 {
1367         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1368         struct cfq_data *cfqd = cfqq->cfqd;
1369         struct request *__alias, *prev;
1370
1371         cfqq->queued[rq_is_sync(rq)]++;
1372
1373         /*
1374          * looks a little odd, but the first insert might return an alias.
1375          * if that happens, put the alias on the dispatch list
1376          */
1377         while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
1378                 cfq_dispatch_insert(cfqd->queue, __alias);
1379
1380         if (!cfq_cfqq_on_rr(cfqq))
1381                 cfq_add_cfqq_rr(cfqd, cfqq);
1382
1383         /*
1384          * check if this request is a better next-serve candidate
1385          */
1386         prev = cfqq->next_rq;
1387         cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
1388
1389         /*
1390          * adjust priority tree position, if ->next_rq changes
1391          */
1392         if (prev != cfqq->next_rq)
1393                 cfq_prio_tree_add(cfqd, cfqq);
1394
1395         BUG_ON(!cfqq->next_rq);
1396 }
1397
1398 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
1399 {
1400         elv_rb_del(&cfqq->sort_list, rq);
1401         cfqq->queued[rq_is_sync(rq)]--;
1402         cfq_add_rq_rb(rq);
1403 }
1404
1405 static struct request *
1406 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
1407 {
1408         struct task_struct *tsk = current;
1409         struct cfq_io_context *cic;
1410         struct cfq_queue *cfqq;
1411
1412         cic = cfq_cic_lookup(cfqd, tsk->io_context);
1413         if (!cic)
1414                 return NULL;
1415
1416         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1417         if (cfqq) {
1418                 sector_t sector = bio->bi_sector + bio_sectors(bio);
1419
1420                 return elv_rb_find(&cfqq->sort_list, sector);
1421         }
1422
1423         return NULL;
1424 }
1425
1426 static void cfq_activate_request(struct request_queue *q, struct request *rq)
1427 {
1428         struct cfq_data *cfqd = q->elevator->elevator_data;
1429
1430         cfqd->rq_in_driver[rq_is_sync(rq)]++;
1431         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
1432                                                 rq_in_driver(cfqd));
1433
1434         cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
1435 }
1436
1437 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
1438 {
1439         struct cfq_data *cfqd = q->elevator->elevator_data;
1440         const int sync = rq_is_sync(rq);
1441
1442         WARN_ON(!cfqd->rq_in_driver[sync]);
1443         cfqd->rq_in_driver[sync]--;
1444         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
1445                                                 rq_in_driver(cfqd));
1446 }
1447
1448 static void cfq_remove_request(struct request *rq)
1449 {
1450         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1451
1452         if (cfqq->next_rq == rq)
1453                 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
1454
1455         list_del_init(&rq->queuelist);
1456         cfq_del_rq_rb(rq);
1457
1458         cfqq->cfqd->rq_queued--;
1459         if (rq_is_meta(rq)) {
1460                 WARN_ON(!cfqq->meta_pending);
1461                 cfqq->meta_pending--;
1462         }
1463 }
1464
1465 static int cfq_merge(struct request_queue *q, struct request **req,
1466                      struct bio *bio)
1467 {
1468         struct cfq_data *cfqd = q->elevator->elevator_data;
1469         struct request *__rq;
1470
1471         __rq = cfq_find_rq_fmerge(cfqd, bio);
1472         if (__rq && elv_rq_merge_ok(__rq, bio)) {
1473                 *req = __rq;
1474                 return ELEVATOR_FRONT_MERGE;
1475         }
1476
1477         return ELEVATOR_NO_MERGE;
1478 }
1479
1480 static void cfq_merged_request(struct request_queue *q, struct request *req,
1481                                int type)
1482 {
1483         if (type == ELEVATOR_FRONT_MERGE) {
1484                 struct cfq_queue *cfqq = RQ_CFQQ(req);
1485
1486                 cfq_reposition_rq_rb(cfqq, req);
1487         }
1488 }
1489
1490 static void
1491 cfq_merged_requests(struct request_queue *q, struct request *rq,
1492                     struct request *next)
1493 {
1494         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1495         /*
1496          * reposition in fifo if next is older than rq
1497          */
1498         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
1499             time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
1500                 list_move(&rq->queuelist, &next->queuelist);
1501                 rq_set_fifo_time(rq, rq_fifo_time(next));
1502         }
1503
1504         if (cfqq->next_rq == next)
1505                 cfqq->next_rq = rq;
1506         cfq_remove_request(next);
1507 }
1508
1509 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
1510                            struct bio *bio)
1511 {
1512         struct cfq_data *cfqd = q->elevator->elevator_data;
1513         struct cfq_io_context *cic;
1514         struct cfq_queue *cfqq;
1515
1516         /* Deny merge if bio and rq don't belong to same cfq group */
1517         if ((RQ_CFQQ(rq))->cfqg != cfq_get_cfqg(cfqd, 0))
1518                 return false;
1519         /*
1520          * Disallow merge of a sync bio into an async request.
1521          */
1522         if (cfq_bio_sync(bio) && !rq_is_sync(rq))
1523                 return false;
1524
1525         /*
1526          * Lookup the cfqq that this bio will be queued with. Allow
1527          * merge only if rq is queued there.
1528          */
1529         cic = cfq_cic_lookup(cfqd, current->io_context);
1530         if (!cic)
1531                 return false;
1532
1533         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1534         return cfqq == RQ_CFQQ(rq);
1535 }
1536
1537 static void __cfq_set_active_queue(struct cfq_data *cfqd,
1538                                    struct cfq_queue *cfqq)
1539 {
1540         if (cfqq) {
1541                 cfq_log_cfqq(cfqd, cfqq, "set_active");
1542                 cfqq->slice_start = 0;
1543                 cfqq->dispatch_start = jiffies;
1544                 cfqq->allocated_slice = 0;
1545                 cfqq->slice_end = 0;
1546                 cfqq->slice_dispatch = 0;
1547                 cfqq->nr_sectors = 0;
1548
1549                 cfq_clear_cfqq_wait_request(cfqq);
1550                 cfq_clear_cfqq_must_dispatch(cfqq);
1551                 cfq_clear_cfqq_must_alloc_slice(cfqq);
1552                 cfq_clear_cfqq_fifo_expire(cfqq);
1553                 cfq_mark_cfqq_slice_new(cfqq);
1554
1555                 del_timer(&cfqd->idle_slice_timer);
1556         }
1557
1558         cfqd->active_queue = cfqq;
1559 }
1560
1561 /*
1562  * current cfqq expired its slice (or was too idle), select new one
1563  */
1564 static void
1565 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1566                     bool timed_out)
1567 {
1568         cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
1569
1570         if (cfq_cfqq_wait_request(cfqq))
1571                 del_timer(&cfqd->idle_slice_timer);
1572
1573         cfq_clear_cfqq_wait_request(cfqq);
1574         cfq_clear_cfqq_wait_busy(cfqq);
1575
1576         /*
1577          * store what was left of this slice, if the queue idled/timed out
1578          */
1579         if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
1580                 cfqq->slice_resid = cfqq->slice_end - jiffies;
1581                 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
1582         }
1583
1584         cfq_group_served(cfqd, cfqq->cfqg, cfqq);
1585
1586         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
1587                 cfq_del_cfqq_rr(cfqd, cfqq);
1588
1589         cfq_resort_rr_list(cfqd, cfqq);
1590
1591         if (cfqq == cfqd->active_queue)
1592                 cfqd->active_queue = NULL;
1593
1594         if (&cfqq->cfqg->rb_node == cfqd->grp_service_tree.active)
1595                 cfqd->grp_service_tree.active = NULL;
1596
1597         if (cfqd->active_cic) {
1598                 put_io_context(cfqd->active_cic->ioc);
1599                 cfqd->active_cic = NULL;
1600         }
1601 }
1602
1603 static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
1604 {
1605         struct cfq_queue *cfqq = cfqd->active_queue;
1606
1607         if (cfqq)
1608                 __cfq_slice_expired(cfqd, cfqq, timed_out);
1609 }
1610
1611 /*
1612  * Get next queue for service. Unless we have a queue preemption,
1613  * we'll simply select the first cfqq in the service tree.
1614  */
1615 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
1616 {
1617         struct cfq_rb_root *service_tree =
1618                 service_tree_for(cfqd->serving_group, cfqd->serving_prio,
1619                                         cfqd->serving_type, cfqd);
1620
1621         if (!cfqd->rq_queued)
1622                 return NULL;
1623
1624         /* There is nothing to dispatch */
1625         if (!service_tree)
1626                 return NULL;
1627         if (RB_EMPTY_ROOT(&service_tree->rb))
1628                 return NULL;
1629         return cfq_rb_first(service_tree);
1630 }
1631
1632 static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
1633 {
1634         struct cfq_group *cfqg;
1635         struct cfq_queue *cfqq;
1636         int i, j;
1637         struct cfq_rb_root *st;
1638
1639         if (!cfqd->rq_queued)
1640                 return NULL;
1641
1642         cfqg = cfq_get_next_cfqg(cfqd);
1643         if (!cfqg)
1644                 return NULL;
1645
1646         for_each_cfqg_st(cfqg, i, j, st)
1647                 if ((cfqq = cfq_rb_first(st)) != NULL)
1648                         return cfqq;
1649         return NULL;
1650 }
1651
1652 /*
1653  * Get and set a new active queue for service.
1654  */
1655 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
1656                                               struct cfq_queue *cfqq)
1657 {
1658         if (!cfqq)
1659                 cfqq = cfq_get_next_queue(cfqd);
1660
1661         __cfq_set_active_queue(cfqd, cfqq);
1662         return cfqq;
1663 }
1664
1665 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
1666                                           struct request *rq)
1667 {
1668         if (blk_rq_pos(rq) >= cfqd->last_position)
1669                 return blk_rq_pos(rq) - cfqd->last_position;
1670         else
1671                 return cfqd->last_position - blk_rq_pos(rq);
1672 }
1673
1674 #define CFQQ_SEEK_THR           8 * 1024
1675 #define CFQQ_SEEKY(cfqq)        ((cfqq)->seek_mean > CFQQ_SEEK_THR)
1676
1677 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1678                                struct request *rq)
1679 {
1680         sector_t sdist = cfqq->seek_mean;
1681
1682         if (!sample_valid(cfqq->seek_samples))
1683                 sdist = CFQQ_SEEK_THR;
1684
1685         return cfq_dist_from_last(cfqd, rq) <= sdist;
1686 }
1687
1688 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
1689                                     struct cfq_queue *cur_cfqq)
1690 {
1691         struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
1692         struct rb_node *parent, *node;
1693         struct cfq_queue *__cfqq;
1694         sector_t sector = cfqd->last_position;
1695
1696         if (RB_EMPTY_ROOT(root))
1697                 return NULL;
1698
1699         /*
1700          * First, if we find a request starting at the end of the last
1701          * request, choose it.
1702          */
1703         __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
1704         if (__cfqq)
1705                 return __cfqq;
1706
1707         /*
1708          * If the exact sector wasn't found, the parent of the NULL leaf
1709          * will contain the closest sector.
1710          */
1711         __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1712         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1713                 return __cfqq;
1714
1715         if (blk_rq_pos(__cfqq->next_rq) < sector)
1716                 node = rb_next(&__cfqq->p_node);
1717         else
1718                 node = rb_prev(&__cfqq->p_node);
1719         if (!node)
1720                 return NULL;
1721
1722         __cfqq = rb_entry(node, struct cfq_queue, p_node);
1723         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1724                 return __cfqq;
1725
1726         return NULL;
1727 }
1728
1729 /*
1730  * cfqd - obvious
1731  * cur_cfqq - passed in so that we don't decide that the current queue is
1732  *            closely cooperating with itself.
1733  *
1734  * So, basically we're assuming that that cur_cfqq has dispatched at least
1735  * one request, and that cfqd->last_position reflects a position on the disk
1736  * associated with the I/O issued by cur_cfqq.  I'm not sure this is a valid
1737  * assumption.
1738  */
1739 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1740                                               struct cfq_queue *cur_cfqq)
1741 {
1742         struct cfq_queue *cfqq;
1743
1744         if (!cfq_cfqq_sync(cur_cfqq))
1745                 return NULL;
1746         if (CFQQ_SEEKY(cur_cfqq))
1747                 return NULL;
1748
1749         /*
1750          * Don't search priority tree if it's the only queue in the group.
1751          */
1752         if (cur_cfqq->cfqg->nr_cfqq == 1)
1753                 return NULL;
1754
1755         /*
1756          * We should notice if some of the queues are cooperating, eg
1757          * working closely on the same area of the disk. In that case,
1758          * we can group them together and don't waste time idling.
1759          */
1760         cfqq = cfqq_close(cfqd, cur_cfqq);
1761         if (!cfqq)
1762                 return NULL;
1763
1764         /* If new queue belongs to different cfq_group, don't choose it */
1765         if (cur_cfqq->cfqg != cfqq->cfqg)
1766                 return NULL;
1767
1768         /*
1769          * It only makes sense to merge sync queues.
1770          */
1771         if (!cfq_cfqq_sync(cfqq))
1772                 return NULL;
1773         if (CFQQ_SEEKY(cfqq))
1774                 return NULL;
1775
1776         /*
1777          * Do not merge queues of different priority classes
1778          */
1779         if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
1780                 return NULL;
1781
1782         return cfqq;
1783 }
1784
1785 /*
1786  * Determine whether we should enforce idle window for this queue.
1787  */
1788
1789 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1790 {
1791         enum wl_prio_t prio = cfqq_prio(cfqq);
1792         struct cfq_rb_root *service_tree = cfqq->service_tree;
1793
1794         BUG_ON(!service_tree);
1795         BUG_ON(!service_tree->count);
1796
1797         /* We never do for idle class queues. */
1798         if (prio == IDLE_WORKLOAD)
1799                 return false;
1800
1801         /* We do for queues that were marked with idle window flag. */
1802         if (cfq_cfqq_idle_window(cfqq) &&
1803            !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag))
1804                 return true;
1805
1806         /*
1807          * Otherwise, we do only if they are the last ones
1808          * in their service tree.
1809          */
1810         return service_tree->count == 1;
1811 }
1812
1813 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
1814 {
1815         struct cfq_queue *cfqq = cfqd->active_queue;
1816         struct cfq_io_context *cic;
1817         unsigned long sl;
1818
1819         /*
1820          * SSD device without seek penalty, disable idling. But only do so
1821          * for devices that support queuing, otherwise we still have a problem
1822          * with sync vs async workloads.
1823          */
1824         if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
1825                 return;
1826
1827         WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
1828         WARN_ON(cfq_cfqq_slice_new(cfqq));
1829
1830         /*
1831          * idle is disabled, either manually or by past process history
1832          */
1833         if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq))
1834                 return;
1835
1836         /*
1837          * still active requests from this queue, don't idle
1838          */
1839         if (cfqq->dispatched)
1840                 return;
1841
1842         /*
1843          * task has exited, don't wait
1844          */
1845         cic = cfqd->active_cic;
1846         if (!cic || !atomic_read(&cic->ioc->nr_tasks))
1847                 return;
1848
1849         /*
1850          * If our average think time is larger than the remaining time
1851          * slice, then don't idle. This avoids overrunning the allotted
1852          * time slice.
1853          */
1854         if (sample_valid(cic->ttime_samples) &&
1855             (cfqq->slice_end - jiffies < cic->ttime_mean))
1856                 return;
1857
1858         cfq_mark_cfqq_wait_request(cfqq);
1859
1860         sl = cfqd->cfq_slice_idle;
1861
1862         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
1863         cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
1864 }
1865
1866 /*
1867  * Move request from internal lists to the request queue dispatch list.
1868  */
1869 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
1870 {
1871         struct cfq_data *cfqd = q->elevator->elevator_data;
1872         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1873
1874         cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
1875
1876         cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
1877         cfq_remove_request(rq);
1878         cfqq->dispatched++;
1879         elv_dispatch_sort(q, rq);
1880
1881         if (cfq_cfqq_sync(cfqq))
1882                 cfqd->sync_flight++;
1883         cfqq->nr_sectors += blk_rq_sectors(rq);
1884 }
1885
1886 /*
1887  * return expired entry, or NULL to just start from scratch in rbtree
1888  */
1889 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
1890 {
1891         struct request *rq = NULL;
1892
1893         if (cfq_cfqq_fifo_expire(cfqq))
1894                 return NULL;
1895
1896         cfq_mark_cfqq_fifo_expire(cfqq);
1897
1898         if (list_empty(&cfqq->fifo))
1899                 return NULL;
1900
1901         rq = rq_entry_fifo(cfqq->fifo.next);
1902         if (time_before(jiffies, rq_fifo_time(rq)))
1903                 rq = NULL;
1904
1905         cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
1906         return rq;
1907 }
1908
1909 static inline int
1910 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1911 {
1912         const int base_rq = cfqd->cfq_slice_async_rq;
1913
1914         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1915
1916         return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1917 }
1918
1919 /*
1920  * Must be called with the queue_lock held.
1921  */
1922 static int cfqq_process_refs(struct cfq_queue *cfqq)
1923 {
1924         int process_refs, io_refs;
1925
1926         io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
1927         process_refs = atomic_read(&cfqq->ref) - io_refs;
1928         BUG_ON(process_refs < 0);
1929         return process_refs;
1930 }
1931
1932 static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
1933 {
1934         int process_refs, new_process_refs;
1935         struct cfq_queue *__cfqq;
1936
1937         /* Avoid a circular list and skip interim queue merges */
1938         while ((__cfqq = new_cfqq->new_cfqq)) {
1939                 if (__cfqq == cfqq)
1940                         return;
1941                 new_cfqq = __cfqq;
1942         }
1943
1944         process_refs = cfqq_process_refs(cfqq);
1945         /*
1946          * If the process for the cfqq has gone away, there is no
1947          * sense in merging the queues.
1948          */
1949         if (process_refs == 0)
1950                 return;
1951
1952         /*
1953          * Merge in the direction of the lesser amount of work.
1954          */
1955         new_process_refs = cfqq_process_refs(new_cfqq);
1956         if (new_process_refs >= process_refs) {
1957                 cfqq->new_cfqq = new_cfqq;
1958                 atomic_add(process_refs, &new_cfqq->ref);
1959         } else {
1960                 new_cfqq->new_cfqq = cfqq;
1961                 atomic_add(new_process_refs, &cfqq->ref);
1962         }
1963 }
1964
1965 static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
1966                                 struct cfq_group *cfqg, enum wl_prio_t prio,
1967                                 bool prio_changed)
1968 {
1969         struct cfq_queue *queue;
1970         int i;
1971         bool key_valid = false;
1972         unsigned long lowest_key = 0;
1973         enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
1974
1975         if (prio_changed) {
1976                 /*
1977                  * When priorities switched, we prefer starting
1978                  * from SYNC_NOIDLE (first choice), or just SYNC
1979                  * over ASYNC
1980                  */
1981                 if (service_tree_for(cfqg, prio, cur_best, cfqd)->count)
1982                         return cur_best;
1983                 cur_best = SYNC_WORKLOAD;
1984                 if (service_tree_for(cfqg, prio, cur_best, cfqd)->count)
1985                         return cur_best;
1986
1987                 return ASYNC_WORKLOAD;
1988         }
1989
1990         for (i = 0; i < 3; ++i) {
1991                 /* otherwise, select the one with lowest rb_key */
1992                 queue = cfq_rb_first(service_tree_for(cfqg, prio, i, cfqd));
1993                 if (queue &&
1994                     (!key_valid || time_before(queue->rb_key, lowest_key))) {
1995                         lowest_key = queue->rb_key;
1996                         cur_best = i;
1997                         key_valid = true;
1998                 }
1999         }
2000
2001         return cur_best;
2002 }
2003
2004 static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
2005 {
2006         enum wl_prio_t previous_prio = cfqd->serving_prio;
2007         bool prio_changed;
2008         unsigned slice;
2009         unsigned count;
2010         struct cfq_rb_root *st;
2011         unsigned group_slice;
2012
2013         if (!cfqg) {
2014                 cfqd->serving_prio = IDLE_WORKLOAD;
2015                 cfqd->workload_expires = jiffies + 1;
2016                 return;
2017         }
2018
2019         /* Choose next priority. RT > BE > IDLE */
2020         if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
2021                 cfqd->serving_prio = RT_WORKLOAD;
2022         else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
2023                 cfqd->serving_prio = BE_WORKLOAD;
2024         else {
2025                 cfqd->serving_prio = IDLE_WORKLOAD;
2026                 cfqd->workload_expires = jiffies + 1;
2027                 return;
2028         }
2029
2030         /*
2031          * For RT and BE, we have to choose also the type
2032          * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
2033          * expiration time
2034          */
2035         prio_changed = (cfqd->serving_prio != previous_prio);
2036         st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type,
2037                                 cfqd);
2038         count = st->count;
2039
2040         /*
2041          * If priority didn't change, check workload expiration,
2042          * and that we still have other queues ready
2043          */
2044         if (!prio_changed && count &&
2045             !time_after(jiffies, cfqd->workload_expires))
2046                 return;
2047
2048         /* otherwise select new workload type */
2049         cfqd->serving_type =
2050                 cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio, prio_changed);
2051         st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type,
2052                                 cfqd);
2053         count = st->count;
2054
2055         /*
2056          * the workload slice is computed as a fraction of target latency
2057          * proportional to the number of queues in that workload, over
2058          * all the queues in the same priority class
2059          */
2060         group_slice = cfq_group_slice(cfqd, cfqg);
2061
2062         slice = group_slice * count /
2063                 max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio],
2064                       cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg));
2065
2066         if (cfqd->serving_type == ASYNC_WORKLOAD) {
2067                 unsigned int tmp;
2068
2069                 /*
2070                  * Async queues are currently system wide. Just taking
2071                  * proportion of queues with-in same group will lead to higher
2072                  * async ratio system wide as generally root group is going
2073                  * to have higher weight. A more accurate thing would be to
2074                  * calculate system wide asnc/sync ratio.
2075                  */
2076                 tmp = cfq_target_latency * cfqg_busy_async_queues(cfqd, cfqg);
2077                 tmp = tmp/cfqd->busy_queues;
2078                 slice = min_t(unsigned, slice, tmp);
2079
2080                 /* async workload slice is scaled down according to
2081                  * the sync/async slice ratio. */
2082                 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
2083         } else
2084                 /* sync workload slice is at least 2 * cfq_slice_idle */
2085                 slice = max(slice, 2 * cfqd->cfq_slice_idle);
2086
2087         slice = max_t(unsigned, slice, CFQ_MIN_TT);
2088         cfqd->workload_expires = jiffies + slice;
2089         cfqd->noidle_tree_requires_idle = false;
2090 }
2091
2092 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
2093 {
2094         struct cfq_rb_root *st = &cfqd->grp_service_tree;
2095         struct cfq_group *cfqg;
2096
2097         if (RB_EMPTY_ROOT(&st->rb))
2098                 return NULL;
2099         cfqg = cfq_rb_first_group(st);
2100         st->active = &cfqg->rb_node;
2101         update_min_vdisktime(st);
2102         return cfqg;
2103 }
2104
2105 static void cfq_choose_cfqg(struct cfq_data *cfqd)
2106 {
2107         struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
2108
2109         cfqd->serving_group = cfqg;
2110
2111         /* Restore the workload type data */
2112         if (cfqg->saved_workload_slice) {
2113                 cfqd->workload_expires = jiffies + cfqg->saved_workload_slice;
2114                 cfqd->serving_type = cfqg->saved_workload;
2115                 cfqd->serving_prio = cfqg->saved_serving_prio;
2116         }
2117         choose_service_tree(cfqd, cfqg);
2118 }
2119
2120 /*
2121  * Select a queue for service. If we have a current active queue,
2122  * check whether to continue servicing it, or retrieve and set a new one.
2123  */
2124 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
2125 {
2126         struct cfq_queue *cfqq, *new_cfqq = NULL;
2127
2128         cfqq = cfqd->active_queue;
2129         if (!cfqq)
2130                 goto new_queue;
2131
2132         if (!cfqd->rq_queued)
2133                 return NULL;
2134
2135         /*
2136          * We were waiting for group to get backlogged. Expire the queue
2137          */
2138         if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list))
2139                 goto expire;
2140
2141         /*
2142          * The active queue has run out of time, expire it and select new.
2143          */
2144         if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) {
2145                 /*
2146                  * If slice had not expired at the completion of last request
2147                  * we might not have turned on wait_busy flag. Don't expire
2148                  * the queue yet. Allow the group to get backlogged.
2149                  *
2150                  * The very fact that we have used the slice, that means we
2151                  * have been idling all along on this queue and it should be
2152                  * ok to wait for this request to complete.
2153                  */
2154                 if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list)
2155                     && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
2156                         cfqq = NULL;
2157                         goto keep_queue;
2158                 } else
2159                         goto expire;
2160         }
2161
2162         /*
2163          * The active queue has requests and isn't expired, allow it to
2164          * dispatch.
2165          */
2166         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2167                 goto keep_queue;
2168
2169         /*
2170          * If another queue has a request waiting within our mean seek
2171          * distance, let it run.  The expire code will check for close
2172          * cooperators and put the close queue at the front of the service
2173          * tree.  If possible, merge the expiring queue with the new cfqq.
2174          */
2175         new_cfqq = cfq_close_cooperator(cfqd, cfqq);
2176         if (new_cfqq) {
2177                 if (!cfqq->new_cfqq)
2178                         cfq_setup_merge(cfqq, new_cfqq);
2179                 goto expire;
2180         }
2181
2182         /*
2183          * No requests pending. If the active queue still has requests in
2184          * flight or is idling for a new request, allow either of these
2185          * conditions to happen (or time out) before selecting a new queue.
2186          */
2187         if (timer_pending(&cfqd->idle_slice_timer) ||
2188             (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) {
2189                 cfqq = NULL;
2190                 goto keep_queue;
2191         }
2192
2193 expire:
2194         cfq_slice_expired(cfqd, 0);
2195 new_queue:
2196         /*
2197          * Current queue expired. Check if we have to switch to a new
2198          * service tree
2199          */
2200         if (!new_cfqq)
2201                 cfq_choose_cfqg(cfqd);
2202
2203         cfqq = cfq_set_active_queue(cfqd, new_cfqq);
2204 keep_queue:
2205         return cfqq;
2206 }
2207
2208 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
2209 {
2210         int dispatched = 0;
2211
2212         while (cfqq->next_rq) {
2213                 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
2214                 dispatched++;
2215         }
2216
2217         BUG_ON(!list_empty(&cfqq->fifo));
2218
2219         /* By default cfqq is not expired if it is empty. Do it explicitly */
2220         __cfq_slice_expired(cfqq->cfqd, cfqq, 0);
2221         return dispatched;
2222 }
2223
2224 /*
2225  * Drain our current requests. Used for barriers and when switching
2226  * io schedulers on-the-fly.
2227  */
2228 static int cfq_forced_dispatch(struct cfq_data *cfqd)
2229 {
2230         struct cfq_queue *cfqq;
2231         int dispatched = 0;
2232
2233         while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL)
2234                 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
2235
2236         cfq_slice_expired(cfqd, 0);
2237         BUG_ON(cfqd->busy_queues);
2238
2239         cfq_log(cfqd, "forced_dispatch=%d", dispatched);
2240         return dispatched;
2241 }
2242
2243 static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2244 {
2245         unsigned int max_dispatch;
2246
2247         /*
2248          * Drain async requests before we start sync IO
2249          */
2250         if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
2251                 return false;
2252
2253         /*
2254          * If this is an async queue and we have sync IO in flight, let it wait
2255          */
2256         if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
2257                 return false;
2258
2259         max_dispatch = cfqd->cfq_quantum;
2260         if (cfq_class_idle(cfqq))
2261                 max_dispatch = 1;
2262
2263         /*
2264          * Does this cfqq already have too much IO in flight?
2265          */
2266         if (cfqq->dispatched >= max_dispatch) {
2267                 /*
2268                  * idle queue must always only have a single IO in flight
2269                  */
2270                 if (cfq_class_idle(cfqq))
2271                         return false;
2272
2273                 /*
2274                  * We have other queues, don't allow more IO from this one
2275                  */
2276                 if (cfqd->busy_queues > 1)
2277                         return false;
2278
2279                 /*
2280                  * Sole queue user, no limit
2281                  */
2282                 max_dispatch = -1;
2283         }
2284
2285         /*
2286          * Async queues must wait a bit before being allowed dispatch.
2287          * We also ramp up the dispatch depth gradually for async IO,
2288          * based on the last sync IO we serviced
2289          */
2290         if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
2291                 unsigned long last_sync = jiffies - cfqd->last_delayed_sync;
2292                 unsigned int depth;
2293
2294                 depth = last_sync / cfqd->cfq_slice[1];
2295                 if (!depth && !cfqq->dispatched)
2296                         depth = 1;
2297                 if (depth < max_dispatch)
2298                         max_dispatch = depth;
2299         }
2300
2301         /*
2302          * If we're below the current max, allow a dispatch
2303          */
2304         return cfqq->dispatched < max_dispatch;
2305 }
2306
2307 /*
2308  * Dispatch a request from cfqq, moving them to the request queue
2309  * dispatch list.
2310  */
2311 static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2312 {
2313         struct request *rq;
2314
2315         BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
2316
2317         if (!cfq_may_dispatch(cfqd, cfqq))
2318                 return false;
2319
2320         /*
2321          * follow expired path, else get first next available
2322          */
2323         rq = cfq_check_fifo(cfqq);
2324         if (!rq)
2325                 rq = cfqq->next_rq;
2326
2327         /*
2328          * insert request into driver dispatch list
2329          */
2330         cfq_dispatch_insert(cfqd->queue, rq);
2331
2332         if (!cfqd->active_cic) {
2333                 struct cfq_io_context *cic = RQ_CIC(rq);
2334
2335                 atomic_long_inc(&cic->ioc->refcount);
2336                 cfqd->active_cic = cic;
2337         }
2338
2339         return true;
2340 }
2341
2342 /*
2343  * Find the cfqq that we need to service and move a request from that to the
2344  * dispatch list
2345  */
2346 static int cfq_dispatch_requests(struct request_queue *q, int force)
2347 {
2348         struct cfq_data *cfqd = q->elevator->elevator_data;
2349         struct cfq_queue *cfqq;
2350
2351         if (!cfqd->busy_queues)
2352                 return 0;
2353
2354         if (unlikely(force))
2355                 return cfq_forced_dispatch(cfqd);
2356
2357         cfqq = cfq_select_queue(cfqd);
2358         if (!cfqq)
2359                 return 0;
2360
2361         /*
2362          * Dispatch a request from this cfqq, if it is allowed
2363          */
2364         if (!cfq_dispatch_request(cfqd, cfqq))
2365                 return 0;
2366
2367         cfqq->slice_dispatch++;
2368         cfq_clear_cfqq_must_dispatch(cfqq);
2369
2370         /*
2371          * expire an async queue immediately if it has used up its slice. idle
2372          * queue always expire after 1 dispatch round.
2373          */
2374         if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
2375             cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
2376             cfq_class_idle(cfqq))) {
2377                 cfqq->slice_end = jiffies + 1;
2378                 cfq_slice_expired(cfqd, 0);
2379         }
2380
2381         cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
2382         return 1;
2383 }
2384
2385 /*
2386  * task holds one reference to the queue, dropped when task exits. each rq
2387  * in-flight on this queue also holds a reference, dropped when rq is freed.
2388  *
2389  * Each cfq queue took a reference on the parent group. Drop it now.
2390  * queue lock must be held here.
2391  */
2392 static void cfq_put_queue(struct cfq_queue *cfqq)
2393 {
2394         struct cfq_data *cfqd = cfqq->cfqd;
2395         struct cfq_group *cfqg, *orig_cfqg;
2396
2397         BUG_ON(atomic_read(&cfqq->ref) <= 0);
2398
2399         if (!atomic_dec_and_test(&cfqq->ref))
2400                 return;
2401
2402         cfq_log_cfqq(cfqd, cfqq, "put_queue");
2403         BUG_ON(rb_first(&cfqq->sort_list));
2404         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
2405         cfqg = cfqq->cfqg;
2406         orig_cfqg = cfqq->orig_cfqg;
2407
2408         if (unlikely(cfqd->active_queue == cfqq)) {
2409                 __cfq_slice_expired(cfqd, cfqq, 0);
2410                 cfq_schedule_dispatch(cfqd);
2411         }
2412
2413         BUG_ON(cfq_cfqq_on_rr(cfqq));
2414         kmem_cache_free(cfq_pool, cfqq);
2415         cfq_put_cfqg(cfqg);
2416         if (orig_cfqg)
2417                 cfq_put_cfqg(orig_cfqg);
2418 }
2419
2420 /*
2421  * Must always be called with the rcu_read_lock() held
2422  */
2423 static void
2424 __call_for_each_cic(struct io_context *ioc,
2425                     void (*func)(struct io_context *, struct cfq_io_context *))
2426 {
2427         struct cfq_io_context *cic;
2428         struct hlist_node *n;
2429
2430         hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
2431                 func(ioc, cic);
2432 }
2433
2434 /*
2435  * Call func for each cic attached to this ioc.
2436  */
2437 static void
2438 call_for_each_cic(struct io_context *ioc,
2439                   void (*func)(struct io_context *, struct cfq_io_context *))
2440 {
2441         rcu_read_lock();
2442         __call_for_each_cic(ioc, func);
2443         rcu_read_unlock();
2444 }
2445
2446 static void cfq_cic_free_rcu(struct rcu_head *head)
2447 {
2448         struct cfq_io_context *cic;
2449
2450         cic = container_of(head, struct cfq_io_context, rcu_head);
2451
2452         kmem_cache_free(cfq_ioc_pool, cic);
2453         elv_ioc_count_dec(cfq_ioc_count);
2454
2455         if (ioc_gone) {
2456                 /*
2457                  * CFQ scheduler is exiting, grab exit lock and check
2458                  * the pending io context count. If it hits zero,
2459                  * complete ioc_gone and set it back to NULL
2460                  */
2461                 spin_lock(&ioc_gone_lock);
2462                 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
2463                         complete(ioc_gone);
2464                         ioc_gone = NULL;
2465                 }
2466                 spin_unlock(&ioc_gone_lock);
2467         }
2468 }
2469
2470 static void cfq_cic_free(struct cfq_io_context *cic)
2471 {
2472         call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
2473 }
2474
2475 static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
2476 {
2477         unsigned long flags;
2478
2479         BUG_ON(!cic->dead_key);
2480
2481         spin_lock_irqsave(&ioc->lock, flags);
2482         radix_tree_delete(&ioc->radix_root, cic->dead_key);
2483         hlist_del_rcu(&cic->cic_list);
2484         spin_unlock_irqrestore(&ioc->lock, flags);
2485
2486         cfq_cic_free(cic);
2487 }
2488
2489 /*
2490  * Must be called with rcu_read_lock() held or preemption otherwise disabled.
2491  * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
2492  * and ->trim() which is called with the task lock held
2493  */
2494 static void cfq_free_io_context(struct io_context *ioc)
2495 {
2496         /*
2497          * ioc->refcount is zero here, or we are called from elv_unregister(),
2498          * so no more cic's are allowed to be linked into this ioc.  So it
2499          * should be ok to iterate over the known list, we will see all cic's
2500          * since no new ones are added.
2501          */
2502         __call_for_each_cic(ioc, cic_free_func);
2503 }
2504
2505 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2506 {
2507         struct cfq_queue *__cfqq, *next;
2508
2509         if (unlikely(cfqq == cfqd->active_queue)) {
2510                 __cfq_slice_expired(cfqd, cfqq, 0);
2511                 cfq_schedule_dispatch(cfqd);
2512         }
2513
2514         /*
2515          * If this queue was scheduled to merge with another queue, be
2516          * sure to drop the reference taken on that queue (and others in
2517          * the merge chain).  See cfq_setup_merge and cfq_merge_cfqqs.
2518          */
2519         __cfqq = cfqq->new_cfqq;
2520         while (__cfqq) {
2521                 if (__cfqq == cfqq) {
2522                         WARN(1, "cfqq->new_cfqq loop detected\n");
2523                         break;
2524                 }
2525                 next = __cfqq->new_cfqq;
2526                 cfq_put_queue(__cfqq);
2527                 __cfqq = next;
2528         }
2529
2530         cfq_put_queue(cfqq);
2531 }
2532
2533 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
2534                                          struct cfq_io_context *cic)
2535 {
2536         struct io_context *ioc = cic->ioc;
2537
2538         list_del_init(&cic->queue_list);
2539
2540         /*
2541          * Make sure key == NULL is seen for dead queues
2542          */
2543         smp_wmb();
2544         cic->dead_key = (unsigned long) cic->key;
2545         cic->key = NULL;
2546
2547         if (ioc->ioc_data == cic)
2548                 rcu_assign_pointer(ioc->ioc_data, NULL);
2549
2550         if (cic->cfqq[BLK_RW_ASYNC]) {
2551                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
2552                 cic->cfqq[BLK_RW_ASYNC] = NULL;
2553         }
2554
2555         if (cic->cfqq[BLK_RW_SYNC]) {
2556                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
2557                 cic->cfqq[BLK_RW_SYNC] = NULL;
2558         }
2559 }
2560
2561 static void cfq_exit_single_io_context(struct io_context *ioc,
2562                                        struct cfq_io_context *cic)
2563 {
2564         struct cfq_data *cfqd = cic->key;
2565
2566         if (cfqd) {
2567                 struct request_queue *q = cfqd->queue;
2568                 unsigned long flags;
2569
2570                 spin_lock_irqsave(q->queue_lock, flags);
2571
2572                 /*
2573                  * Ensure we get a fresh copy of the ->key to prevent
2574                  * race between exiting task and queue
2575                  */
2576                 smp_read_barrier_depends();
2577                 if (cic->key)
2578                         __cfq_exit_single_io_context(cfqd, cic);
2579
2580                 spin_unlock_irqrestore(q->queue_lock, flags);
2581         }
2582 }
2583
2584 /*
2585  * The process that ioc belongs to has exited, we need to clean up
2586  * and put the internal structures we have that belongs to that process.
2587  */
2588 static void cfq_exit_io_context(struct io_context *ioc)
2589 {
2590         call_for_each_cic(ioc, cfq_exit_single_io_context);
2591 }
2592
2593 static struct cfq_io_context *
2594 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2595 {
2596         struct cfq_io_context *cic;
2597
2598         cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
2599                                                         cfqd->queue->node);
2600         if (cic) {
2601                 cic->last_end_request = jiffies;
2602                 INIT_LIST_HEAD(&cic->queue_list);
2603                 INIT_HLIST_NODE(&cic->cic_list);
2604                 cic->dtor = cfq_free_io_context;
2605                 cic->exit = cfq_exit_io_context;
2606                 elv_ioc_count_inc(cfq_ioc_count);
2607         }
2608
2609         return cic;
2610 }
2611
2612 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
2613 {
2614         struct task_struct *tsk = current;
2615         int ioprio_class;
2616
2617         if (!cfq_cfqq_prio_changed(cfqq))
2618                 return;
2619
2620         ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
2621         switch (ioprio_class) {
2622         default:
2623                 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
2624         case IOPRIO_CLASS_NONE:
2625                 /*
2626                  * no prio set, inherit CPU scheduling settings
2627                  */
2628                 cfqq->ioprio = task_nice_ioprio(tsk);
2629                 cfqq->ioprio_class = task_nice_ioclass(tsk);
2630                 break;
2631         case IOPRIO_CLASS_RT:
2632                 cfqq->ioprio = task_ioprio(ioc);
2633                 cfqq->ioprio_class = IOPRIO_CLASS_RT;
2634                 break;
2635         case IOPRIO_CLASS_BE:
2636                 cfqq->ioprio = task_ioprio(ioc);
2637                 cfqq->ioprio_class = IOPRIO_CLASS_BE;
2638                 break;
2639         case IOPRIO_CLASS_IDLE:
2640                 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
2641                 cfqq->ioprio = 7;
2642                 cfq_clear_cfqq_idle_window(cfqq);
2643                 break;
2644         }
2645
2646         /*
2647          * keep track of original prio settings in case we have to temporarily
2648          * elevate the priority of this queue
2649          */
2650         cfqq->org_ioprio = cfqq->ioprio;
2651         cfqq->org_ioprio_class = cfqq->ioprio_class;
2652         cfq_clear_cfqq_prio_changed(cfqq);
2653 }
2654
2655 static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
2656 {
2657         struct cfq_data *cfqd = cic->key;
2658         struct cfq_queue *cfqq;
2659         unsigned long flags;
2660
2661         if (unlikely(!cfqd))
2662                 return;
2663
2664         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2665
2666         cfqq = cic->cfqq[BLK_RW_ASYNC];
2667         if (cfqq) {
2668                 struct cfq_queue *new_cfqq;
2669                 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
2670                                                 GFP_ATOMIC);
2671                 if (new_cfqq) {
2672                         cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
2673                         cfq_put_queue(cfqq);
2674                 }
2675         }
2676
2677         cfqq = cic->cfqq[BLK_RW_SYNC];
2678         if (cfqq)
2679                 cfq_mark_cfqq_prio_changed(cfqq);
2680
2681         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2682 }
2683
2684 static void cfq_ioc_set_ioprio(struct io_context *ioc)
2685 {
2686         call_for_each_cic(ioc, changed_ioprio);
2687         ioc->ioprio_changed = 0;
2688 }
2689
2690 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2691                           pid_t pid, bool is_sync)
2692 {
2693         RB_CLEAR_NODE(&cfqq->rb_node);
2694         RB_CLEAR_NODE(&cfqq->p_node);
2695         INIT_LIST_HEAD(&cfqq->fifo);
2696
2697         atomic_set(&cfqq->ref, 0);
2698         cfqq->cfqd = cfqd;
2699
2700         cfq_mark_cfqq_prio_changed(cfqq);
2701
2702         if (is_sync) {
2703                 if (!cfq_class_idle(cfqq))
2704                         cfq_mark_cfqq_idle_window(cfqq);
2705                 cfq_mark_cfqq_sync(cfqq);
2706         }
2707         cfqq->pid = pid;
2708 }
2709
2710 #ifdef CONFIG_CFQ_GROUP_IOSCHED
2711 static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
2712 {
2713         struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1);
2714         struct cfq_data *cfqd = cic->key;
2715         unsigned long flags;
2716         struct request_queue *q;
2717
2718         if (unlikely(!cfqd))
2719                 return;
2720
2721         q = cfqd->queue;
2722
2723         spin_lock_irqsave(q->queue_lock, flags);
2724
2725         if (sync_cfqq) {
2726                 /*
2727                  * Drop reference to sync queue. A new sync queue will be
2728                  * assigned in new group upon arrival of a fresh request.
2729                  */
2730                 cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
2731                 cic_set_cfqq(cic, NULL, 1);
2732                 cfq_put_queue(sync_cfqq);
2733         }
2734
2735         spin_unlock_irqrestore(q->queue_lock, flags);
2736 }
2737
2738 static void cfq_ioc_set_cgroup(struct io_context *ioc)
2739 {
2740         call_for_each_cic(ioc, changed_cgroup);
2741         ioc->cgroup_changed = 0;
2742 }
2743 #endif  /* CONFIG_CFQ_GROUP_IOSCHED */
2744
2745 static struct cfq_queue *
2746 cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
2747                      struct io_context *ioc, gfp_t gfp_mask)
2748 {
2749         struct cfq_queue *cfqq, *new_cfqq = NULL;
2750         struct cfq_io_context *cic;
2751         struct cfq_group *cfqg;
2752
2753 retry:
2754         cfqg = cfq_get_cfqg(cfqd, 1);
2755         cic = cfq_cic_lookup(cfqd, ioc);
2756         /* cic always exists here */
2757         cfqq = cic_to_cfqq(cic, is_sync);
2758
2759         /*
2760          * Always try a new alloc if we fell back to the OOM cfqq
2761          * originally, since it should just be a temporary situation.
2762          */
2763         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2764                 cfqq = NULL;
2765                 if (new_cfqq) {
2766                         cfqq = new_cfqq;
2767                         new_cfqq = NULL;
2768                 } else if (gfp_mask & __GFP_WAIT) {
2769                         spin_unlock_irq(cfqd->queue->queue_lock);
2770                         new_cfqq = kmem_cache_alloc_node(cfq_pool,
2771                                         gfp_mask | __GFP_ZERO,
2772                                         cfqd->queue->node);
2773                         spin_lock_irq(cfqd->queue->queue_lock);
2774                         if (new_cfqq)
2775                                 goto retry;
2776                 } else {
2777                         cfqq = kmem_cache_alloc_node(cfq_pool,
2778                                         gfp_mask | __GFP_ZERO,
2779                                         cfqd->queue->node);
2780                 }
2781
2782                 if (cfqq) {
2783                         cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
2784                         cfq_init_prio_data(cfqq, ioc);
2785                         cfq_link_cfqq_cfqg(cfqq, cfqg);
2786                         cfq_log_cfqq(cfqd, cfqq, "alloced");
2787                 } else
2788                         cfqq = &cfqd->oom_cfqq;
2789         }
2790
2791         if (new_cfqq)
2792                 kmem_cache_free(cfq_pool, new_cfqq);
2793
2794         return cfqq;
2795 }
2796
2797 static struct cfq_queue **
2798 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
2799 {
2800         switch (ioprio_class) {
2801         case IOPRIO_CLASS_RT:
2802                 return &cfqd->async_cfqq[0][ioprio];
2803         case IOPRIO_CLASS_BE:
2804                 return &cfqd->async_cfqq[1][ioprio];
2805         case IOPRIO_CLASS_IDLE:
2806                 return &cfqd->async_idle_cfqq;
2807         default:
2808                 BUG();
2809         }
2810 }
2811
2812 static struct cfq_queue *
2813 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
2814               gfp_t gfp_mask)
2815 {
2816         const int ioprio = task_ioprio(ioc);
2817         const int ioprio_class = task_ioprio_class(ioc);
2818         struct cfq_queue **async_cfqq = NULL;
2819         struct cfq_queue *cfqq = NULL;
2820
2821         if (!is_sync) {
2822                 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
2823                 cfqq = *async_cfqq;
2824         }
2825
2826         if (!cfqq)
2827                 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
2828
2829         /*
2830          * pin the queue now that it's allocated, scheduler exit will prune it
2831          */
2832         if (!is_sync && !(*async_cfqq)) {
2833                 atomic_inc(&cfqq->ref);
2834                 *async_cfqq = cfqq;
2835         }
2836
2837         atomic_inc(&cfqq->ref);
2838         return cfqq;
2839 }
2840
2841 /*
2842  * We drop cfq io contexts lazily, so we may find a dead one.
2843  */
2844 static void
2845 cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
2846                   struct cfq_io_context *cic)
2847 {
2848         unsigned long flags;
2849
2850         WARN_ON(!list_empty(&cic->queue_list));
2851
2852         spin_lock_irqsave(&ioc->lock, flags);
2853
2854         BUG_ON(ioc->ioc_data == cic);
2855
2856         radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
2857         hlist_del_rcu(&cic->cic_list);
2858         spin_unlock_irqrestore(&ioc->lock, flags);
2859
2860         cfq_cic_free(cic);
2861 }
2862
2863 static struct cfq_io_context *
2864 cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
2865 {
2866         struct cfq_io_context *cic;
2867         unsigned long flags;
2868         void *k;
2869
2870         if (unlikely(!ioc))
2871                 return NULL;
2872
2873         rcu_read_lock();
2874
2875         /*
2876          * we maintain a last-hit cache, to avoid browsing over the tree
2877          */
2878         cic = rcu_dereference(ioc->ioc_data);
2879         if (cic && cic->key == cfqd) {
2880                 rcu_read_unlock();
2881                 return cic;
2882         }
2883
2884         do {
2885                 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
2886                 rcu_read_unlock();
2887                 if (!cic)
2888                         break;
2889                 /* ->key must be copied to avoid race with cfq_exit_queue() */
2890                 k = cic->key;
2891                 if (unlikely(!k)) {
2892                         cfq_drop_dead_cic(cfqd, ioc, cic);
2893                         rcu_read_lock();
2894                         continue;
2895                 }
2896
2897                 spin_lock_irqsave(&ioc->lock, flags);
2898                 rcu_assign_pointer(ioc->ioc_data, cic);
2899                 spin_unlock_irqrestore(&ioc->lock, flags);
2900                 break;
2901         } while (1);
2902
2903         return cic;
2904 }
2905
2906 /*
2907  * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2908  * the process specific cfq io context when entered from the block layer.
2909  * Also adds the cic to a per-cfqd list, used when this queue is removed.
2910  */
2911 static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
2912                         struct cfq_io_context *cic, gfp_t gfp_mask)
2913 {
2914         unsigned long flags;
2915         int ret;
2916
2917         ret = radix_tree_preload(gfp_mask);
2918         if (!ret) {
2919                 cic->ioc = ioc;
2920                 cic->key = cfqd;
2921
2922                 spin_lock_irqsave(&ioc->lock, flags);
2923                 ret = radix_tree_insert(&ioc->radix_root,
2924                                                 (unsigned long) cfqd, cic);
2925                 if (!ret)
2926                         hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
2927                 spin_unlock_irqrestore(&ioc->lock, flags);
2928
2929                 radix_tree_preload_end();
2930
2931                 if (!ret) {
2932                         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2933                         list_add(&cic->queue_list, &cfqd->cic_list);
2934                         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2935                 }
2936         }
2937
2938         if (ret)
2939                 printk(KERN_ERR "cfq: cic link failed!\n");
2940
2941         return ret;
2942 }
2943
2944 /*
2945  * Setup general io context and cfq io context. There can be several cfq
2946  * io contexts per general io context, if this process is doing io to more
2947  * than one device managed by cfq.
2948  */
2949 static struct cfq_io_context *
2950 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2951 {
2952         struct io_context *ioc = NULL;
2953         struct cfq_io_context *cic;
2954
2955         might_sleep_if(gfp_mask & __GFP_WAIT);
2956
2957         ioc = get_io_context(gfp_mask, cfqd->queue->node);
2958         if (!ioc)
2959                 return NULL;
2960
2961         cic = cfq_cic_lookup(cfqd, ioc);
2962         if (cic)
2963                 goto out;
2964
2965         cic = cfq_alloc_io_context(cfqd, gfp_mask);
2966         if (cic == NULL)
2967                 goto err;
2968
2969         if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
2970                 goto err_free;
2971
2972 out:
2973         smp_read_barrier_depends();
2974         if (unlikely(ioc->ioprio_changed))
2975                 cfq_ioc_set_ioprio(ioc);
2976
2977 #ifdef CONFIG_CFQ_GROUP_IOSCHED
2978         if (unlikely(ioc->cgroup_changed))
2979                 cfq_ioc_set_cgroup(ioc);
2980 #endif
2981         return cic;
2982 err_free:
2983         cfq_cic_free(cic);
2984 err:
2985         put_io_context(ioc);
2986         return NULL;
2987 }
2988
2989 static void
2990 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
2991 {
2992         unsigned long elapsed = jiffies - cic->last_end_request;
2993         unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
2994
2995         cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
2996         cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
2997         cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
2998 }
2999
3000 static void
3001 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3002                        struct request *rq)
3003 {
3004         sector_t sdist;
3005         u64 total;
3006
3007         if (!cfqq->last_request_pos)
3008                 sdist = 0;
3009         else if (cfqq->last_request_pos < blk_rq_pos(rq))
3010                 sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
3011         else
3012                 sdist = cfqq->last_request_pos - blk_rq_pos(rq);
3013
3014         /*
3015          * Don't allow the seek distance to get too large from the
3016          * odd fragment, pagein, etc
3017          */
3018         if (cfqq->seek_samples <= 60) /* second&third seek */
3019                 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*1024);
3020         else
3021                 sdist = min(sdist, (cfqq->seek_mean * 4) + 2*1024*64);
3022
3023         cfqq->seek_samples = (7*cfqq->seek_samples + 256) / 8;
3024         cfqq->seek_total = (7*cfqq->seek_total + (u64)256*sdist) / 8;
3025         total = cfqq->seek_total + (cfqq->seek_samples/2);
3026         do_div(total, cfqq->seek_samples);
3027         cfqq->seek_mean = (sector_t)total;
3028
3029         /*
3030          * If this cfqq is shared between multiple processes, check to
3031          * make sure that those processes are still issuing I/Os within
3032          * the mean seek distance.  If not, it may be time to break the
3033          * queues apart again.
3034          */
3035         if (cfq_cfqq_coop(cfqq)) {
3036                 if (CFQQ_SEEKY(cfqq) && !cfqq->seeky_start)
3037                         cfqq->seeky_start = jiffies;
3038                 else if (!CFQQ_SEEKY(cfqq))
3039                         cfqq->seeky_start = 0;
3040         }
3041 }
3042
3043 /*
3044  * Disable idle window if the process thinks too long or seeks so much that
3045  * it doesn't matter
3046  */
3047 static void
3048 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3049                        struct cfq_io_context *cic)
3050 {
3051         int old_idle, enable_idle;
3052
3053         /*
3054          * Don't idle for async or idle io prio class
3055          */
3056         if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
3057                 return;
3058
3059         enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
3060
3061         if (cfqq->queued[0] + cfqq->queued[1] >= 4)
3062                 cfq_mark_cfqq_deep(cfqq);
3063
3064         if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
3065             (!cfq_cfqq_deep(cfqq) && sample_valid(cfqq->seek_samples)
3066              && CFQQ_SEEKY(cfqq)))
3067                 enable_idle = 0;
3068         else if (sample_valid(cic->ttime_samples)) {
3069                 if (cic->ttime_mean > cfqd->cfq_slice_idle)
3070                         enable_idle = 0;
3071                 else
3072                         enable_idle = 1;
3073         }
3074
3075         if (old_idle != enable_idle) {
3076                 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
3077                 if (enable_idle)
3078                         cfq_mark_cfqq_idle_window(cfqq);
3079                 else
3080                         cfq_clear_cfqq_idle_window(cfqq);
3081         }
3082 }
3083
3084 /*
3085  * Check if new_cfqq should preempt the currently active queue. Return 0 for
3086  * no or if we aren't sure, a 1 will cause a preempt.
3087  */
3088 static bool
3089 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
3090                    struct request *rq)
3091 {
3092         struct cfq_queue *cfqq;
3093
3094         cfqq = cfqd->active_queue;
3095         if (!cfqq)
3096                 return false;
3097
3098         if (cfq_class_idle(new_cfqq))
3099                 return false;
3100
3101         if (cfq_class_idle(cfqq))
3102                 return true;
3103
3104         /*
3105          * if the new request is sync, but the currently running queue is
3106          * not, let the sync request have priority.
3107          */
3108         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
3109                 return true;
3110
3111         if (new_cfqq->cfqg != cfqq->cfqg)
3112                 return false;
3113
3114         if (cfq_slice_used(cfqq))
3115                 return true;
3116
3117         /* Allow preemption only if we are idling on sync-noidle tree */
3118         if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
3119             cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
3120             new_cfqq->service_tree->count == 2 &&
3121             RB_EMPTY_ROOT(&cfqq->sort_list))
3122                 return true;
3123
3124         /*
3125          * So both queues are sync. Let the new request get disk time if
3126          * it's a metadata request and the current queue is doing regular IO.
3127          */
3128         if (rq_is_meta(rq) && !cfqq->meta_pending)
3129                 return true;
3130
3131         /*
3132          * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
3133          */
3134         if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
3135                 return true;
3136
3137         if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
3138                 return false;
3139
3140         /*
3141          * if this request is as-good as one we would expect from the
3142          * current cfqq, let it preempt
3143          */
3144         if (cfq_rq_close(cfqd, cfqq, rq))
3145                 return true;
3146
3147         return false;
3148 }
3149
3150 /*
3151  * cfqq preempts the active queue. if we allowed preempt with no slice left,
3152  * let it have half of its nominal slice.
3153  */
3154 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3155 {
3156         cfq_log_cfqq(cfqd, cfqq, "preempt");
3157         cfq_slice_expired(cfqd, 1);
3158
3159         /*
3160          * Put the new queue at the front of the of the current list,
3161          * so we know that it will be selected next.
3162          */
3163         BUG_ON(!cfq_cfqq_on_rr(cfqq));
3164
3165         cfq_service_tree_add(cfqd, cfqq, 1);
3166
3167         cfqq->slice_end = 0;
3168         cfq_mark_cfqq_slice_new(cfqq);
3169 }
3170
3171 /*
3172  * Called when a new fs request (rq) is added (to cfqq). Check if there's
3173  * something we should do about it
3174  */
3175 static void
3176 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3177                 struct request *rq)
3178 {
3179         struct cfq_io_context *cic = RQ_CIC(rq);
3180
3181         cfqd->rq_queued++;
3182         if (rq_is_meta(rq))
3183                 cfqq->meta_pending++;
3184
3185         cfq_update_io_thinktime(cfqd, cic);
3186         cfq_update_io_seektime(cfqd, cfqq, rq);
3187         cfq_update_idle_window(cfqd, cfqq, cic);
3188
3189         cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
3190
3191         if (cfqq == cfqd->active_queue) {
3192                 /*
3193                  * Remember that we saw a request from this process, but
3194                  * don't start queuing just yet. Otherwise we risk seeing lots
3195                  * of tiny requests, because we disrupt the normal plugging
3196                  * and merging. If the request is already larger than a single
3197                  * page, let it rip immediately. For that case we assume that
3198                  * merging is already done. Ditto for a busy system that
3199                  * has other work pending, don't risk delaying until the
3200                  * idle timer unplug to continue working.
3201                  */
3202                 if (cfq_cfqq_wait_request(cfqq)) {
3203                         if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
3204                             cfqd->busy_queues > 1) {
3205                                 del_timer(&cfqd->idle_slice_timer);
3206                                 cfq_clear_cfqq_wait_request(cfqq);
3207                                 __blk_run_queue(cfqd->queue);
3208                         } else
3209                                 cfq_mark_cfqq_must_dispatch(cfqq);
3210                 }
3211         } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
3212                 /*
3213                  * not the active queue - expire current slice if it is
3214                  * idle and has expired it's mean thinktime or this new queue
3215                  * has some old slice time left and is of higher priority or
3216                  * this new queue is RT and the current one is BE
3217                  */
3218                 cfq_preempt_queue(cfqd, cfqq);
3219                 __blk_run_queue(cfqd->queue);
3220         }
3221 }
3222
3223 static void cfq_insert_request(struct request_queue *q, struct request *rq)
3224 {
3225         struct cfq_data *cfqd = q->elevator->elevator_data;
3226         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3227
3228         cfq_log_cfqq(cfqd, cfqq, "insert_request");
3229         cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
3230
3231         rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
3232         list_add_tail(&rq->queuelist, &cfqq->fifo);
3233         cfq_add_rq_rb(rq);
3234
3235         cfq_rq_enqueued(cfqd, cfqq, rq);
3236 }
3237
3238 /*
3239  * Update hw_tag based on peak queue depth over 50 samples under
3240  * sufficient load.
3241  */
3242 static void cfq_update_hw_tag(struct cfq_data *cfqd)
3243 {
3244         struct cfq_queue *cfqq = cfqd->active_queue;
3245
3246         if (rq_in_driver(cfqd) > cfqd->hw_tag_est_depth)
3247                 cfqd->hw_tag_est_depth = rq_in_driver(cfqd);
3248
3249         if (cfqd->hw_tag == 1)
3250                 return;
3251
3252         if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
3253             rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)
3254                 return;
3255
3256         /*
3257          * If active queue hasn't enough requests and can idle, cfq might not
3258          * dispatch sufficient requests to hardware. Don't zero hw_tag in this
3259          * case
3260          */
3261         if (cfqq && cfq_cfqq_idle_window(cfqq) &&
3262             cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
3263             CFQ_HW_QUEUE_MIN && rq_in_driver(cfqd) < CFQ_HW_QUEUE_MIN)
3264                 return;
3265
3266         if (cfqd->hw_tag_samples++ < 50)
3267                 return;
3268
3269         if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
3270                 cfqd->hw_tag = 1;
3271         else
3272                 cfqd->hw_tag = 0;
3273 }
3274
3275 static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3276 {
3277         struct cfq_io_context *cic = cfqd->active_cic;
3278
3279         /* If there are other queues in the group, don't wait */
3280         if (cfqq->cfqg->nr_cfqq > 1)
3281                 return false;
3282
3283         if (cfq_slice_used(cfqq))
3284                 return true;
3285
3286         /* if slice left is less than think time, wait busy */
3287         if (cic && sample_valid(cic->ttime_samples)
3288             && (cfqq->slice_end - jiffies < cic->ttime_mean))
3289                 return true;
3290
3291         /*
3292          * If think times is less than a jiffy than ttime_mean=0 and above
3293          * will not be true. It might happen that slice has not expired yet
3294          * but will expire soon (4-5 ns) during select_queue(). To cover the
3295          * case where think time is less than a jiffy, mark the queue wait
3296          * busy if only 1 jiffy is left in the slice.
3297          */
3298         if (cfqq->slice_end - jiffies == 1)
3299                 return true;
3300
3301         return false;
3302 }
3303
3304 static void cfq_completed_request(struct request_queue *q, struct request *rq)
3305 {
3306         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3307         struct cfq_data *cfqd = cfqq->cfqd;
3308         const int sync = rq_is_sync(rq);
3309         unsigned long now;
3310
3311         now = jiffies;
3312         cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d", !!rq_noidle(rq));
3313
3314         cfq_update_hw_tag(cfqd);
3315
3316         WARN_ON(!cfqd->rq_in_driver[sync]);
3317         WARN_ON(!cfqq->dispatched);
3318         cfqd->rq_in_driver[sync]--;
3319         cfqq->dispatched--;
3320
3321         if (cfq_cfqq_sync(cfqq))
3322                 cfqd->sync_flight--;
3323
3324         if (sync) {
3325                 RQ_CIC(rq)->last_end_request = now;
3326                 if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
3327                         cfqd->last_delayed_sync = now;
3328         }
3329
3330         /*
3331          * If this is the active queue, check if it needs to be expired,
3332          * or if we want to idle in case it has no pending requests.
3333          */
3334         if (cfqd->active_queue == cfqq) {
3335                 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
3336
3337                 if (cfq_cfqq_slice_new(cfqq)) {
3338                         cfq_set_prio_slice(cfqd, cfqq);
3339                         cfq_clear_cfqq_slice_new(cfqq);
3340                 }
3341
3342                 /*
3343                  * Should we wait for next request to come in before we expire
3344                  * the queue.
3345                  */
3346                 if (cfq_should_wait_busy(cfqd, cfqq)) {
3347                         cfqq->slice_end = jiffies + cfqd->cfq_slice_idle;
3348                         cfq_mark_cfqq_wait_busy(cfqq);
3349                 }
3350
3351                 /*
3352                  * Idling is not enabled on:
3353                  * - expired queues
3354                  * - idle-priority queues
3355                  * - async queues
3356                  * - queues with still some requests queued
3357                  * - when there is a close cooperator
3358                  */
3359                 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
3360                         cfq_slice_expired(cfqd, 1);
3361                 else if (sync && cfqq_empty &&
3362                          !cfq_close_cooperator(cfqd, cfqq)) {
3363                         cfqd->noidle_tree_requires_idle |= !rq_noidle(rq);
3364                         /*
3365                          * Idling is enabled for SYNC_WORKLOAD.
3366                          * SYNC_NOIDLE_WORKLOAD idles at the end of the tree
3367                          * only if we processed at least one !rq_noidle request
3368                          */
3369                         if (cfqd->serving_type == SYNC_WORKLOAD
3370                             || cfqd->noidle_tree_requires_idle
3371                             || cfqq->cfqg->nr_cfqq == 1)
3372                                 cfq_arm_slice_timer(cfqd);
3373                 }
3374         }
3375
3376         if (!rq_in_driver(cfqd))
3377                 cfq_schedule_dispatch(cfqd);
3378 }
3379
3380 /*
3381  * we temporarily boost lower priority queues if they are holding fs exclusive
3382  * resources. they are boosted to normal prio (CLASS_BE/4)
3383  */
3384 static void cfq_prio_boost(struct cfq_queue *cfqq)
3385 {
3386         if (has_fs_excl()) {
3387                 /*
3388                  * boost idle prio on transactions that would lock out other
3389                  * users of the filesystem
3390                  */
3391                 if (cfq_class_idle(cfqq))
3392                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
3393                 if (cfqq->ioprio > IOPRIO_NORM)
3394                         cfqq->ioprio = IOPRIO_NORM;
3395         } else {
3396                 /*
3397                  * unboost the queue (if needed)
3398                  */
3399                 cfqq->ioprio_class = cfqq->org_ioprio_class;
3400                 cfqq->ioprio = cfqq->org_ioprio;
3401         }
3402 }
3403
3404 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
3405 {
3406         if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
3407                 cfq_mark_cfqq_must_alloc_slice(cfqq);
3408                 return ELV_MQUEUE_MUST;
3409         }
3410
3411         return ELV_MQUEUE_MAY;
3412 }
3413
3414 static int cfq_may_queue(struct request_queue *q, int rw)
3415 {
3416         struct cfq_data *cfqd = q->elevator->elevator_data;
3417         struct task_struct *tsk = current;
3418         struct cfq_io_context *cic;
3419         struct cfq_queue *cfqq;
3420
3421         /*
3422          * don't force setup of a queue from here, as a call to may_queue
3423          * does not necessarily imply that a request actually will be queued.
3424          * so just lookup a possibly existing queue, or return 'may queue'
3425          * if that fails
3426          */
3427         cic = cfq_cic_lookup(cfqd, tsk->io_context);
3428         if (!cic)
3429                 return ELV_MQUEUE_MAY;
3430
3431         cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
3432         if (cfqq) {
3433                 cfq_init_prio_data(cfqq, cic->ioc);
3434                 cfq_prio_boost(cfqq);
3435
3436                 return __cfq_may_queue(cfqq);
3437         }
3438
3439         return ELV_MQUEUE_MAY;
3440 }
3441
3442 /*
3443  * queue lock held here
3444  */
3445 static void cfq_put_request(struct request *rq)
3446 {
3447         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3448
3449         if (cfqq) {
3450                 const int rw = rq_data_dir(rq);
3451
3452                 BUG_ON(!cfqq->allocated[rw]);
3453                 cfqq->allocated[rw]--;
3454
3455                 put_io_context(RQ_CIC(rq)->ioc);
3456
3457                 rq->elevator_private = NULL;
3458                 rq->elevator_private2 = NULL;
3459
3460                 cfq_put_queue(cfqq);
3461         }
3462 }
3463
3464 static struct cfq_queue *
3465 cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
3466                 struct cfq_queue *cfqq)
3467 {
3468         cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
3469         cic_set_cfqq(cic, cfqq->new_cfqq, 1);
3470         cfq_mark_cfqq_coop(cfqq->new_cfqq);
3471         cfq_put_queue(cfqq);
3472         return cic_to_cfqq(cic, 1);
3473 }
3474
3475 static int should_split_cfqq(struct cfq_queue *cfqq)
3476 {
3477         if (cfqq->seeky_start &&
3478             time_after(jiffies, cfqq->seeky_start + CFQQ_COOP_TOUT))
3479                 return 1;
3480         return 0;
3481 }
3482
3483 /*
3484  * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
3485  * was the last process referring to said cfqq.
3486  */
3487 static struct cfq_queue *
3488 split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
3489 {
3490         if (cfqq_process_refs(cfqq) == 1) {
3491                 cfqq->seeky_start = 0;
3492                 cfqq->pid = current->pid;
3493                 cfq_clear_cfqq_coop(cfqq);
3494                 return cfqq;
3495         }
3496
3497         cic_set_cfqq(cic, NULL, 1);
3498         cfq_put_queue(cfqq);
3499         return NULL;
3500 }
3501 /*
3502  * Allocate cfq data structures associated with this request.
3503  */
3504 static int
3505 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
3506 {
3507         struct cfq_data *cfqd = q->elevator->elevator_data;
3508         struct cfq_io_context *cic;
3509         const int rw = rq_data_dir(rq);
3510         const bool is_sync = rq_is_sync(rq);
3511         struct cfq_queue *cfqq;
3512         unsigned long flags;
3513
3514         might_sleep_if(gfp_mask & __GFP_WAIT);
3515
3516         cic = cfq_get_io_context(cfqd, gfp_mask);
3517
3518         spin_lock_irqsave(q->queue_lock, flags);
3519
3520         if (!cic)
3521                 goto queue_fail;
3522
3523 new_queue:
3524         cfqq = cic_to_cfqq(cic, is_sync);
3525         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3526                 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
3527                 cic_set_cfqq(cic, cfqq, is_sync);
3528         } else {
3529                 /*
3530                  * If the queue was seeky for too long, break it apart.
3531                  */
3532                 if (cfq_cfqq_coop(cfqq) && should_split_cfqq(cfqq)) {
3533                         cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
3534                         cfqq = split_cfqq(cic, cfqq);
3535                         if (!cfqq)
3536                                 goto new_queue;
3537                 }
3538
3539                 /*
3540                  * Check to see if this queue is scheduled to merge with
3541                  * another, closely cooperating queue.  The merging of
3542                  * queues happens here as it must be done in process context.
3543                  * The reference on new_cfqq was taken in merge_cfqqs.
3544                  */
3545                 if (cfqq->new_cfqq)
3546                         cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
3547         }
3548
3549         cfqq->allocated[rw]++;
3550         atomic_inc(&cfqq->ref);
3551
3552         spin_unlock_irqrestore(q->queue_lock, flags);
3553
3554         rq->elevator_private = cic;
3555         rq->elevator_private2 = cfqq;
3556         return 0;
3557
3558 queue_fail:
3559         if (cic)
3560                 put_io_context(cic->ioc);
3561
3562         cfq_schedule_dispatch(cfqd);
3563         spin_unlock_irqrestore(q->queue_lock, flags);
3564         cfq_log(cfqd, "set_request fail");
3565         return 1;
3566 }
3567
3568 static void cfq_kick_queue(struct work_struct *work)
3569 {
3570         struct cfq_data *cfqd =
3571                 container_of(work, struct cfq_data, unplug_work);
3572         struct request_queue *q = cfqd->queue;
3573
3574         spin_lock_irq(q->queue_lock);
3575         __blk_run_queue(cfqd->queue);
3576         spin_unlock_irq(q->queue_lock);
3577 }
3578
3579 /*
3580  * Timer running if the active_queue is currently idling inside its time slice
3581  */
3582 static void cfq_idle_slice_timer(unsigned long data)
3583 {
3584         struct cfq_data *cfqd = (struct cfq_data *) data;
3585         struct cfq_queue *cfqq;
3586         unsigned long flags;
3587         int timed_out = 1;
3588
3589         cfq_log(cfqd, "idle timer fired");
3590
3591         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
3592
3593         cfqq = cfqd->active_queue;
3594         if (cfqq) {
3595                 timed_out = 0;
3596
3597                 /*
3598                  * We saw a request before the queue expired, let it through
3599                  */
3600                 if (cfq_cfqq_must_dispatch(cfqq))
3601                         goto out_kick;
3602
3603                 /*
3604                  * expired
3605                  */
3606                 if (cfq_slice_used(cfqq))
3607                         goto expire;
3608
3609                 /*
3610                  * only expire and reinvoke request handler, if there are
3611                  * other queues with pending requests
3612                  */
3613                 if (!cfqd->busy_queues)
3614                         goto out_cont;
3615
3616                 /*
3617                  * not expired and it has a request pending, let it dispatch
3618                  */
3619                 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3620                         goto out_kick;
3621
3622                 /*
3623                  * Queue depth flag is reset only when the idle didn't succeed
3624                  */
3625                 cfq_clear_cfqq_deep(cfqq);
3626         }
3627 expire:
3628         cfq_slice_expired(cfqd, timed_out);
3629 out_kick:
3630         cfq_schedule_dispatch(cfqd);
3631 out_cont:
3632         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
3633 }
3634
3635 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
3636 {
3637         del_timer_sync(&cfqd->idle_slice_timer);
3638         cancel_work_sync(&cfqd->unplug_work);
3639 }
3640
3641 static void cfq_put_async_queues(struct cfq_data *cfqd)
3642 {
3643         int i;
3644
3645         for (i = 0; i < IOPRIO_BE_NR; i++) {
3646                 if (cfqd->async_cfqq[0][i])
3647                         cfq_put_queue(cfqd->async_cfqq[0][i]);
3648                 if (cfqd->async_cfqq[1][i])
3649                         cfq_put_queue(cfqd->async_cfqq[1][i]);
3650         }
3651
3652         if (cfqd->async_idle_cfqq)
3653                 cfq_put_queue(cfqd->async_idle_cfqq);
3654 }
3655
3656 static void cfq_cfqd_free(struct rcu_head *head)
3657 {
3658         kfree(container_of(head, struct cfq_data, rcu));
3659 }
3660
3661 static void cfq_exit_queue(struct elevator_queue *e)
3662 {
3663         struct cfq_data *cfqd = e->elevator_data;
3664         struct request_queue *q = cfqd->queue;
3665
3666         cfq_shutdown_timer_wq(cfqd);
3667
3668         spin_lock_irq(q->queue_lock);
3669
3670         if (cfqd->active_queue)
3671                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
3672
3673         while (!list_empty(&cfqd->cic_list)) {
3674                 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
3675                                                         struct cfq_io_context,
3676                                                         queue_list);
3677
3678                 __cfq_exit_single_io_context(cfqd, cic);
3679         }
3680
3681         cfq_put_async_queues(cfqd);
3682         cfq_release_cfq_groups(cfqd);
3683         blkiocg_del_blkio_group(&cfqd->root_group.blkg);
3684
3685         spin_unlock_irq(q->queue_lock);
3686
3687         cfq_shutdown_timer_wq(cfqd);
3688
3689         /* Wait for cfqg->blkg->key accessors to exit their grace periods. */
3690         call_rcu(&cfqd->rcu, cfq_cfqd_free);
3691 }
3692
3693 static void *cfq_init_queue(struct request_queue *q)
3694 {
3695         struct cfq_data *cfqd;
3696         int i, j;
3697         struct cfq_group *cfqg;
3698         struct cfq_rb_root *st;
3699
3700         cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
3701         if (!cfqd)
3702                 return NULL;
3703
3704         /* Init root service tree */
3705         cfqd->grp_service_tree = CFQ_RB_ROOT;
3706
3707         /* Init root group */
3708         cfqg = &cfqd->root_group;
3709         for_each_cfqg_st(cfqg, i, j, st)
3710                 *st = CFQ_RB_ROOT;
3711         RB_CLEAR_NODE(&cfqg->rb_node);
3712
3713         /* Give preference to root group over other groups */
3714         cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
3715
3716 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3717         /*
3718          * Take a reference to root group which we never drop. This is just
3719          * to make sure that cfq_put_cfqg() does not try to kfree root group
3720          */
3721         atomic_set(&cfqg->ref, 1);
3722         blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd,
3723                                         0);
3724 #endif
3725         /*
3726          * Not strictly needed (since RB_ROOT just clears the node and we
3727          * zeroed cfqd on alloc), but better be safe in case someone decides
3728          * to add magic to the rb code
3729          */
3730         for (i = 0; i < CFQ_PRIO_LISTS; i++)
3731                 cfqd->prio_trees[i] = RB_ROOT;
3732
3733         /*
3734          * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
3735          * Grab a permanent reference to it, so that the normal code flow
3736          * will not attempt to free it.
3737          */
3738         cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
3739         atomic_inc(&cfqd->oom_cfqq.ref);
3740         cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
3741
3742         INIT_LIST_HEAD(&cfqd->cic_list);
3743
3744         cfqd->queue = q;
3745
3746         init_timer(&cfqd->idle_slice_timer);
3747         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
3748         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
3749
3750         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
3751
3752         cfqd->cfq_quantum = cfq_quantum;
3753         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
3754         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
3755         cfqd->cfq_back_max = cfq_back_max;
3756         cfqd->cfq_back_penalty = cfq_back_penalty;
3757         cfqd->cfq_slice[0] = cfq_slice_async;
3758         cfqd->cfq_slice[1] = cfq_slice_sync;
3759         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
3760         cfqd->cfq_slice_idle = cfq_slice_idle;
3761         cfqd->cfq_latency = 1;
3762         cfqd->cfq_group_isolation = 0;
3763         cfqd->hw_tag = -1;
3764         /*
3765          * we optimistically start assuming sync ops weren't delayed in last
3766          * second, in order to have larger depth for async operations.
3767          */
3768         cfqd->last_delayed_sync = jiffies - HZ;
3769         INIT_RCU_HEAD(&cfqd->rcu);
3770         return cfqd;
3771 }
3772
3773 static void cfq_slab_kill(void)
3774 {
3775         /*
3776          * Caller already ensured that pending RCU callbacks are completed,
3777          * so we should have no busy allocations at this point.
3778          */
3779         if (cfq_pool)
3780                 kmem_cache_destroy(cfq_pool);
3781         if (cfq_ioc_pool)
3782                 kmem_cache_destroy(cfq_ioc_pool);
3783 }
3784
3785 static int __init cfq_slab_setup(void)
3786 {
3787         cfq_pool = KMEM_CACHE(cfq_queue, 0);
3788         if (!cfq_pool)
3789                 goto fail;
3790
3791         cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
3792         if (!cfq_ioc_pool)
3793                 goto fail;
3794
3795         return 0;
3796 fail:
3797         cfq_slab_kill();
3798         return -ENOMEM;
3799 }
3800
3801 /*
3802  * sysfs parts below -->
3803  */
3804 static ssize_t
3805 cfq_var_show(unsigned int var, char *page)
3806 {
3807         return sprintf(page, "%d\n", var);
3808 }
3809
3810 static ssize_t
3811 cfq_var_store(unsigned int *var, const char *page, size_t count)
3812 {
3813         char *p = (char *) page;
3814
3815         *var = simple_strtoul(p, &p, 10);
3816         return count;
3817 }
3818
3819 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
3820 static ssize_t __FUNC(struct elevator_queue *e, char *page)             \
3821 {                                                                       \
3822         struct cfq_data *cfqd = e->elevator_data;                       \
3823         unsigned int __data = __VAR;                                    \
3824         if (__CONV)                                                     \
3825                 __data = jiffies_to_msecs(__data);                      \
3826         return cfq_var_show(__data, (page));                            \
3827 }
3828 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
3829 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
3830 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
3831 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
3832 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
3833 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
3834 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
3835 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
3836 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
3837 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
3838 SHOW_FUNCTION(cfq_group_isolation_show, cfqd->cfq_group_isolation, 0);
3839 #undef SHOW_FUNCTION
3840
3841 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
3842 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3843 {                                                                       \
3844         struct cfq_data *cfqd = e->elevator_data;                       \
3845         unsigned int __data;                                            \
3846         int ret = cfq_var_store(&__data, (page), count);                \
3847         if (__data < (MIN))                                             \
3848                 __data = (MIN);                                         \
3849         else if (__data > (MAX))                                        \
3850                 __data = (MAX);                                         \
3851         if (__CONV)                                                     \
3852                 *(__PTR) = msecs_to_jiffies(__data);                    \
3853         else                                                            \
3854                 *(__PTR) = __data;                                      \
3855         return ret;                                                     \
3856 }
3857 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
3858 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
3859                 UINT_MAX, 1);
3860 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
3861                 UINT_MAX, 1);
3862 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
3863 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
3864                 UINT_MAX, 0);
3865 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
3866 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
3867 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
3868 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
3869                 UINT_MAX, 0);
3870 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
3871 STORE_FUNCTION(cfq_group_isolation_store, &cfqd->cfq_group_isolation, 0, 1, 0);
3872 #undef STORE_FUNCTION
3873
3874 #define CFQ_ATTR(name) \
3875         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3876
3877 static struct elv_fs_entry cfq_attrs[] = {
3878         CFQ_ATTR(quantum),
3879         CFQ_ATTR(fifo_expire_sync),
3880         CFQ_ATTR(fifo_expire_async),
3881         CFQ_ATTR(back_seek_max),
3882         CFQ_ATTR(back_seek_penalty),
3883         CFQ_ATTR(slice_sync),
3884         CFQ_ATTR(slice_async),
3885         CFQ_ATTR(slice_async_rq),
3886         CFQ_ATTR(slice_idle),
3887         CFQ_ATTR(low_latency),
3888         CFQ_ATTR(group_isolation),
3889         __ATTR_NULL
3890 };
3891
3892 static struct elevator_type iosched_cfq = {
3893         .ops = {
3894                 .elevator_merge_fn =            cfq_merge,
3895                 .elevator_merged_fn =           cfq_merged_request,
3896                 .elevator_merge_req_fn =        cfq_merged_requests,
3897                 .elevator_allow_merge_fn =      cfq_allow_merge,
3898                 .elevator_dispatch_fn =         cfq_dispatch_requests,
3899                 .elevator_add_req_fn =          cfq_insert_request,
3900                 .elevator_activate_req_fn =     cfq_activate_request,
3901                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
3902                 .elevator_queue_empty_fn =      cfq_queue_empty,
3903                 .elevator_completed_req_fn =    cfq_completed_request,
3904                 .elevator_former_req_fn =       elv_rb_former_request,
3905                 .elevator_latter_req_fn =       elv_rb_latter_request,
3906                 .elevator_set_req_fn =          cfq_set_request,
3907                 .elevator_put_req_fn =          cfq_put_request,
3908                 .elevator_may_queue_fn =        cfq_may_queue,
3909                 .elevator_init_fn =             cfq_init_queue,
3910                 .elevator_exit_fn =             cfq_exit_queue,
3911                 .trim =                         cfq_free_io_context,
3912         },
3913         .elevator_attrs =       cfq_attrs,
3914         .elevator_name =        "cfq",
3915         .elevator_owner =       THIS_MODULE,
3916 };
3917
3918 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3919 static struct blkio_policy_type blkio_policy_cfq = {
3920         .ops = {
3921                 .blkio_unlink_group_fn =        cfq_unlink_blkio_group,
3922                 .blkio_update_group_weight_fn = cfq_update_blkio_group_weight,
3923         },
3924 };
3925 #else
3926 static struct blkio_policy_type blkio_policy_cfq;
3927 #endif
3928
3929 static int __init cfq_init(void)
3930 {
3931         /*
3932          * could be 0 on HZ < 1000 setups
3933          */
3934         if (!cfq_slice_async)
3935                 cfq_slice_async = 1;
3936         if (!cfq_slice_idle)
3937                 cfq_slice_idle = 1;
3938
3939         if (cfq_slab_setup())
3940                 return -ENOMEM;
3941
3942         elv_register(&iosched_cfq);
3943         blkio_policy_register(&blkio_policy_cfq);
3944
3945         return 0;
3946 }
3947
3948 static void __exit cfq_exit(void)
3949 {
3950         DECLARE_COMPLETION_ONSTACK(all_gone);
3951         blkio_policy_unregister(&blkio_policy_cfq);
3952         elv_unregister(&iosched_cfq);
3953         ioc_gone = &all_gone;
3954         /* ioc_gone's update must be visible before reading ioc_count */
3955         smp_wmb();
3956
3957         /*
3958          * this also protects us from entering cfq_slab_kill() with
3959          * pending RCU callbacks
3960          */
3961         if (elv_ioc_count_read(cfq_ioc_count))
3962                 wait_for_completion(&all_gone);
3963         cfq_slab_kill();
3964 }
3965
3966 module_init(cfq_init);
3967 module_exit(cfq_exit);
3968
3969 MODULE_AUTHOR("Jens Axboe");
3970 MODULE_LICENSE("GPL");
3971 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");