3fd8afc2174ef9785c660f5028ae1a93b74d5b11
[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 #define CFQ_SLICE_SCALE         (5)
46 #define CFQ_HW_QUEUE_MIN        (5)
47 #define CFQ_SERVICE_SHIFT       12
48
49 #define CFQQ_SEEK_THR           (sector_t)(8 * 100)
50 #define CFQQ_SEEKY(cfqq)        (hweight32(cfqq->seek_history) > 32/8)
51
52 #define RQ_CIC(rq)              \
53         ((struct cfq_io_context *) (rq)->elevator_private)
54 #define RQ_CFQQ(rq)             (struct cfq_queue *) ((rq)->elevator_private2)
55
56 static struct kmem_cache *cfq_pool;
57 static struct kmem_cache *cfq_ioc_pool;
58
59 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
60 static struct completion *ioc_gone;
61 static DEFINE_SPINLOCK(ioc_gone_lock);
62
63 #define CFQ_PRIO_LISTS          IOPRIO_BE_NR
64 #define cfq_class_idle(cfqq)    ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
65 #define cfq_class_rt(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
66
67 #define sample_valid(samples)   ((samples) > 80)
68 #define rb_entry_cfqg(node)     rb_entry((node), struct cfq_group, rb_node)
69
70 /*
71  * Most of our rbtree usage is for sorting with min extraction, so
72  * if we cache the leftmost node we don't have to walk down the tree
73  * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
74  * move this into the elevator for the rq sorting as well.
75  */
76 struct cfq_rb_root {
77         struct rb_root rb;
78         struct rb_node *left;
79         unsigned count;
80         u64 min_vdisktime;
81         struct rb_node *active;
82         unsigned total_weight;
83 };
84 #define CFQ_RB_ROOT     (struct cfq_rb_root) { RB_ROOT, NULL, 0, 0, }
85
86 /*
87  * Per process-grouping structure
88  */
89 struct cfq_queue {
90         /* reference count */
91         atomic_t ref;
92         /* various state flags, see below */
93         unsigned int flags;
94         /* parent cfq_data */
95         struct cfq_data *cfqd;
96         /* service_tree member */
97         struct rb_node rb_node;
98         /* service_tree key */
99         unsigned long rb_key;
100         /* prio tree member */
101         struct rb_node p_node;
102         /* prio tree root we belong to, if any */
103         struct rb_root *p_root;
104         /* sorted list of pending requests */
105         struct rb_root sort_list;
106         /* if fifo isn't expired, next request to serve */
107         struct request *next_rq;
108         /* requests queued in sort_list */
109         int queued[2];
110         /* currently allocated requests */
111         int allocated[2];
112         /* fifo list of requests in sort_list */
113         struct list_head fifo;
114
115         /* time when queue got scheduled in to dispatch first request. */
116         unsigned long dispatch_start;
117         unsigned int allocated_slice;
118         unsigned int slice_dispatch;
119         /* time when first request from queue completed and slice started. */
120         unsigned long slice_start;
121         unsigned long slice_end;
122         long slice_resid;
123
124         /* pending metadata requests */
125         int meta_pending;
126         /* number of requests that are on the dispatch list or inside driver */
127         int dispatched;
128
129         /* io prio of this group */
130         unsigned short ioprio, org_ioprio;
131         unsigned short ioprio_class, org_ioprio_class;
132
133         pid_t pid;
134
135         u32 seek_history;
136         sector_t last_request_pos;
137
138         struct cfq_rb_root *service_tree;
139         struct cfq_queue *new_cfqq;
140         struct cfq_group *cfqg;
141         struct cfq_group *orig_cfqg;
142         /* Sectors dispatched in current dispatch round */
143         unsigned long nr_sectors;
144 };
145
146 /*
147  * First index in the service_trees.
148  * IDLE is handled separately, so it has negative index
149  */
150 enum wl_prio_t {
151         BE_WORKLOAD = 0,
152         RT_WORKLOAD = 1,
153         IDLE_WORKLOAD = 2,
154 };
155
156 /*
157  * Second index in the service_trees.
158  */
159 enum wl_type_t {
160         ASYNC_WORKLOAD = 0,
161         SYNC_NOIDLE_WORKLOAD = 1,
162         SYNC_WORKLOAD = 2
163 };
164
165 /* This is per cgroup per device grouping structure */
166 struct cfq_group {
167         /* group service_tree member */
168         struct rb_node rb_node;
169
170         /* group service_tree key */
171         u64 vdisktime;
172         unsigned int weight;
173         bool on_st;
174
175         /* number of cfqq currently on this group */
176         int nr_cfqq;
177
178         /* Per group busy queus average. Useful for workload slice calc. */
179         unsigned int busy_queues_avg[2];
180         /*
181          * rr lists of queues with requests, onle rr for each priority class.
182          * Counts are embedded in the cfq_rb_root
183          */
184         struct cfq_rb_root service_trees[2][3];
185         struct cfq_rb_root service_tree_idle;
186
187         unsigned long saved_workload_slice;
188         enum wl_type_t saved_workload;
189         enum wl_prio_t saved_serving_prio;
190         struct blkio_group blkg;
191 #ifdef CONFIG_CFQ_GROUP_IOSCHED
192         struct hlist_node cfqd_node;
193         atomic_t ref;
194 #endif
195 };
196
197 /*
198  * Per block device queue structure
199  */
200 struct cfq_data {
201         struct request_queue *queue;
202         /* Root service tree for cfq_groups */
203         struct cfq_rb_root grp_service_tree;
204         struct cfq_group root_group;
205
206         /*
207          * The priority currently being served
208          */
209         enum wl_prio_t serving_prio;
210         enum wl_type_t serving_type;
211         unsigned long workload_expires;
212         struct cfq_group *serving_group;
213         bool noidle_tree_requires_idle;
214
215         /*
216          * Each priority tree is sorted by next_request position.  These
217          * trees are used when determining if two or more queues are
218          * interleaving requests (see cfq_close_cooperator).
219          */
220         struct rb_root prio_trees[CFQ_PRIO_LISTS];
221
222         unsigned int busy_queues;
223
224         int rq_in_driver[2];
225         int sync_flight;
226
227         /*
228          * queue-depth detection
229          */
230         int rq_queued;
231         int hw_tag;
232         /*
233          * hw_tag can be
234          * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
235          *  1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
236          *  0 => no NCQ
237          */
238         int hw_tag_est_depth;
239         unsigned int hw_tag_samples;
240
241         /*
242          * idle window management
243          */
244         struct timer_list idle_slice_timer;
245         struct work_struct unplug_work;
246
247         struct cfq_queue *active_queue;
248         struct cfq_io_context *active_cic;
249
250         /*
251          * async queue for each priority case
252          */
253         struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
254         struct cfq_queue *async_idle_cfqq;
255
256         sector_t last_position;
257
258         /*
259          * tunables, see top of file
260          */
261         unsigned int cfq_quantum;
262         unsigned int cfq_fifo_expire[2];
263         unsigned int cfq_back_penalty;
264         unsigned int cfq_back_max;
265         unsigned int cfq_slice[2];
266         unsigned int cfq_slice_async_rq;
267         unsigned int cfq_slice_idle;
268         unsigned int cfq_latency;
269         unsigned int cfq_group_isolation;
270
271         struct list_head cic_list;
272
273         /*
274          * Fallback dummy cfqq for extreme OOM conditions
275          */
276         struct cfq_queue oom_cfqq;
277
278         unsigned long last_delayed_sync;
279
280         /* List of cfq groups being managed on this device*/
281         struct hlist_head cfqg_list;
282         struct rcu_head rcu;
283 };
284
285 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
286
287 static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
288                                             enum wl_prio_t prio,
289                                             enum wl_type_t type)
290 {
291         if (!cfqg)
292                 return NULL;
293
294         if (prio == IDLE_WORKLOAD)
295                 return &cfqg->service_tree_idle;
296
297         return &cfqg->service_trees[prio][type];
298 }
299
300 enum cfqq_state_flags {
301         CFQ_CFQQ_FLAG_on_rr = 0,        /* on round-robin busy list */
302         CFQ_CFQQ_FLAG_wait_request,     /* waiting for a request */
303         CFQ_CFQQ_FLAG_must_dispatch,    /* must be allowed a dispatch */
304         CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
305         CFQ_CFQQ_FLAG_fifo_expire,      /* FIFO checked in this slice */
306         CFQ_CFQQ_FLAG_idle_window,      /* slice idling enabled */
307         CFQ_CFQQ_FLAG_prio_changed,     /* task priority has changed */
308         CFQ_CFQQ_FLAG_slice_new,        /* no requests dispatched in slice */
309         CFQ_CFQQ_FLAG_sync,             /* synchronous queue */
310         CFQ_CFQQ_FLAG_coop,             /* cfqq is shared */
311         CFQ_CFQQ_FLAG_split_coop,       /* shared cfqq will be splitted */
312         CFQ_CFQQ_FLAG_deep,             /* sync cfqq experienced large depth */
313         CFQ_CFQQ_FLAG_wait_busy,        /* Waiting for next request */
314 };
315
316 #define CFQ_CFQQ_FNS(name)                                              \
317 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
318 {                                                                       \
319         (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name);                   \
320 }                                                                       \
321 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
322 {                                                                       \
323         (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                  \
324 }                                                                       \
325 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
326 {                                                                       \
327         return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;      \
328 }
329
330 CFQ_CFQQ_FNS(on_rr);
331 CFQ_CFQQ_FNS(wait_request);
332 CFQ_CFQQ_FNS(must_dispatch);
333 CFQ_CFQQ_FNS(must_alloc_slice);
334 CFQ_CFQQ_FNS(fifo_expire);
335 CFQ_CFQQ_FNS(idle_window);
336 CFQ_CFQQ_FNS(prio_changed);
337 CFQ_CFQQ_FNS(slice_new);
338 CFQ_CFQQ_FNS(sync);
339 CFQ_CFQQ_FNS(coop);
340 CFQ_CFQQ_FNS(split_coop);
341 CFQ_CFQQ_FNS(deep);
342 CFQ_CFQQ_FNS(wait_busy);
343 #undef CFQ_CFQQ_FNS
344
345 #ifdef CONFIG_DEBUG_CFQ_IOSCHED
346 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
347         blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
348                         cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
349                         blkg_path(&(cfqq)->cfqg->blkg), ##args);
350
351 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)                          \
352         blk_add_trace_msg((cfqd)->queue, "%s " fmt,                     \
353                                 blkg_path(&(cfqg)->blkg), ##args);      \
354
355 #else
356 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
357         blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
358 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)          do {} while (0);
359 #endif
360 #define cfq_log(cfqd, fmt, args...)     \
361         blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
362
363 /* Traverses through cfq group service trees */
364 #define for_each_cfqg_st(cfqg, i, j, st) \
365         for (i = 0; i <= IDLE_WORKLOAD; i++) \
366                 for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
367                         : &cfqg->service_tree_idle; \
368                         (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
369                         (i == IDLE_WORKLOAD && j == 0); \
370                         j++, st = i < IDLE_WORKLOAD ? \
371                         &cfqg->service_trees[i][j]: NULL) \
372
373
374 static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
375 {
376         if (cfq_class_idle(cfqq))
377                 return IDLE_WORKLOAD;
378         if (cfq_class_rt(cfqq))
379                 return RT_WORKLOAD;
380         return BE_WORKLOAD;
381 }
382
383
384 static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
385 {
386         if (!cfq_cfqq_sync(cfqq))
387                 return ASYNC_WORKLOAD;
388         if (!cfq_cfqq_idle_window(cfqq))
389                 return SYNC_NOIDLE_WORKLOAD;
390         return SYNC_WORKLOAD;
391 }
392
393 static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl,
394                                         struct cfq_data *cfqd,
395                                         struct cfq_group *cfqg)
396 {
397         if (wl == IDLE_WORKLOAD)
398                 return cfqg->service_tree_idle.count;
399
400         return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
401                 + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
402                 + cfqg->service_trees[wl][SYNC_WORKLOAD].count;
403 }
404
405 static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
406                                         struct cfq_group *cfqg)
407 {
408         return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count
409                 + cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
410 }
411
412 static void cfq_dispatch_insert(struct request_queue *, struct request *);
413 static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
414                                        struct io_context *, gfp_t);
415 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
416                                                 struct io_context *);
417
418 static inline int rq_in_driver(struct cfq_data *cfqd)
419 {
420         return cfqd->rq_in_driver[0] + cfqd->rq_in_driver[1];
421 }
422
423 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
424                                             bool is_sync)
425 {
426         return cic->cfqq[is_sync];
427 }
428
429 static inline void cic_set_cfqq(struct cfq_io_context *cic,
430                                 struct cfq_queue *cfqq, bool is_sync)
431 {
432         cic->cfqq[is_sync] = cfqq;
433 }
434
435 /*
436  * We regard a request as SYNC, if it's either a read or has the SYNC bit
437  * set (in which case it could also be direct WRITE).
438  */
439 static inline bool cfq_bio_sync(struct bio *bio)
440 {
441         return bio_data_dir(bio) == READ || bio_rw_flagged(bio, BIO_RW_SYNCIO);
442 }
443
444 /*
445  * scheduler run of queue, if there are requests pending and no one in the
446  * driver that will restart queueing
447  */
448 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
449 {
450         if (cfqd->busy_queues) {
451                 cfq_log(cfqd, "schedule dispatch");
452                 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
453         }
454 }
455
456 static int cfq_queue_empty(struct request_queue *q)
457 {
458         struct cfq_data *cfqd = q->elevator->elevator_data;
459
460         return !cfqd->rq_queued;
461 }
462
463 /*
464  * Scale schedule slice based on io priority. Use the sync time slice only
465  * if a queue is marked sync and has sync io queued. A sync queue with async
466  * io only, should not get full sync slice length.
467  */
468 static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
469                                  unsigned short prio)
470 {
471         const int base_slice = cfqd->cfq_slice[sync];
472
473         WARN_ON(prio >= IOPRIO_BE_NR);
474
475         return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
476 }
477
478 static inline int
479 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
480 {
481         return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
482 }
483
484 static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
485 {
486         u64 d = delta << CFQ_SERVICE_SHIFT;
487
488         d = d * BLKIO_WEIGHT_DEFAULT;
489         do_div(d, cfqg->weight);
490         return d;
491 }
492
493 static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
494 {
495         s64 delta = (s64)(vdisktime - min_vdisktime);
496         if (delta > 0)
497                 min_vdisktime = vdisktime;
498
499         return min_vdisktime;
500 }
501
502 static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
503 {
504         s64 delta = (s64)(vdisktime - min_vdisktime);
505         if (delta < 0)
506                 min_vdisktime = vdisktime;
507
508         return min_vdisktime;
509 }
510
511 static void update_min_vdisktime(struct cfq_rb_root *st)
512 {
513         u64 vdisktime = st->min_vdisktime;
514         struct cfq_group *cfqg;
515
516         if (st->active) {
517                 cfqg = rb_entry_cfqg(st->active);
518                 vdisktime = cfqg->vdisktime;
519         }
520
521         if (st->left) {
522                 cfqg = rb_entry_cfqg(st->left);
523                 vdisktime = min_vdisktime(vdisktime, cfqg->vdisktime);
524         }
525
526         st->min_vdisktime = max_vdisktime(st->min_vdisktime, vdisktime);
527 }
528
529 /*
530  * get averaged number of queues of RT/BE priority.
531  * average is updated, with a formula that gives more weight to higher numbers,
532  * to quickly follows sudden increases and decrease slowly
533  */
534
535 static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
536                                         struct cfq_group *cfqg, bool rt)
537 {
538         unsigned min_q, max_q;
539         unsigned mult  = cfq_hist_divisor - 1;
540         unsigned round = cfq_hist_divisor / 2;
541         unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
542
543         min_q = min(cfqg->busy_queues_avg[rt], busy);
544         max_q = max(cfqg->busy_queues_avg[rt], busy);
545         cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
546                 cfq_hist_divisor;
547         return cfqg->busy_queues_avg[rt];
548 }
549
550 static inline unsigned
551 cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
552 {
553         struct cfq_rb_root *st = &cfqd->grp_service_tree;
554
555         return cfq_target_latency * cfqg->weight / st->total_weight;
556 }
557
558 static inline void
559 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
560 {
561         unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
562         if (cfqd->cfq_latency) {
563                 /*
564                  * interested queues (we consider only the ones with the same
565                  * priority class in the cfq group)
566                  */
567                 unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
568                                                 cfq_class_rt(cfqq));
569                 unsigned sync_slice = cfqd->cfq_slice[1];
570                 unsigned expect_latency = sync_slice * iq;
571                 unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
572
573                 if (expect_latency > group_slice) {
574                         unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
575                         /* scale low_slice according to IO priority
576                          * and sync vs async */
577                         unsigned low_slice =
578                                 min(slice, base_low_slice * slice / sync_slice);
579                         /* the adapted slice value is scaled to fit all iqs
580                          * into the target latency */
581                         slice = max(slice * group_slice / expect_latency,
582                                     low_slice);
583                 }
584         }
585         cfqq->slice_start = jiffies;
586         cfqq->slice_end = jiffies + slice;
587         cfqq->allocated_slice = slice;
588         cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
589 }
590
591 /*
592  * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
593  * isn't valid until the first request from the dispatch is activated
594  * and the slice time set.
595  */
596 static inline bool cfq_slice_used(struct cfq_queue *cfqq)
597 {
598         if (cfq_cfqq_slice_new(cfqq))
599                 return 0;
600         if (time_before(jiffies, cfqq->slice_end))
601                 return 0;
602
603         return 1;
604 }
605
606 /*
607  * Lifted from AS - choose which of rq1 and rq2 that is best served now.
608  * We choose the request that is closest to the head right now. Distance
609  * behind the head is penalized and only allowed to a certain extent.
610  */
611 static struct request *
612 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
613 {
614         sector_t s1, s2, d1 = 0, d2 = 0;
615         unsigned long back_max;
616 #define CFQ_RQ1_WRAP    0x01 /* request 1 wraps */
617 #define CFQ_RQ2_WRAP    0x02 /* request 2 wraps */
618         unsigned wrap = 0; /* bit mask: requests behind the disk head? */
619
620         if (rq1 == NULL || rq1 == rq2)
621                 return rq2;
622         if (rq2 == NULL)
623                 return rq1;
624
625         if (rq_is_sync(rq1) && !rq_is_sync(rq2))
626                 return rq1;
627         else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
628                 return rq2;
629         if (rq_is_meta(rq1) && !rq_is_meta(rq2))
630                 return rq1;
631         else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
632                 return rq2;
633
634         s1 = blk_rq_pos(rq1);
635         s2 = blk_rq_pos(rq2);
636
637         /*
638          * by definition, 1KiB is 2 sectors
639          */
640         back_max = cfqd->cfq_back_max * 2;
641
642         /*
643          * Strict one way elevator _except_ in the case where we allow
644          * short backward seeks which are biased as twice the cost of a
645          * similar forward seek.
646          */
647         if (s1 >= last)
648                 d1 = s1 - last;
649         else if (s1 + back_max >= last)
650                 d1 = (last - s1) * cfqd->cfq_back_penalty;
651         else
652                 wrap |= CFQ_RQ1_WRAP;
653
654         if (s2 >= last)
655                 d2 = s2 - last;
656         else if (s2 + back_max >= last)
657                 d2 = (last - s2) * cfqd->cfq_back_penalty;
658         else
659                 wrap |= CFQ_RQ2_WRAP;
660
661         /* Found required data */
662
663         /*
664          * By doing switch() on the bit mask "wrap" we avoid having to
665          * check two variables for all permutations: --> faster!
666          */
667         switch (wrap) {
668         case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
669                 if (d1 < d2)
670                         return rq1;
671                 else if (d2 < d1)
672                         return rq2;
673                 else {
674                         if (s1 >= s2)
675                                 return rq1;
676                         else
677                                 return rq2;
678                 }
679
680         case CFQ_RQ2_WRAP:
681                 return rq1;
682         case CFQ_RQ1_WRAP:
683                 return rq2;
684         case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
685         default:
686                 /*
687                  * Since both rqs are wrapped,
688                  * start with the one that's further behind head
689                  * (--> only *one* back seek required),
690                  * since back seek takes more time than forward.
691                  */
692                 if (s1 <= s2)
693                         return rq1;
694                 else
695                         return rq2;
696         }
697 }
698
699 /*
700  * The below is leftmost cache rbtree addon
701  */
702 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
703 {
704         /* Service tree is empty */
705         if (!root->count)
706                 return NULL;
707
708         if (!root->left)
709                 root->left = rb_first(&root->rb);
710
711         if (root->left)
712                 return rb_entry(root->left, struct cfq_queue, rb_node);
713
714         return NULL;
715 }
716
717 static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
718 {
719         if (!root->left)
720                 root->left = rb_first(&root->rb);
721
722         if (root->left)
723                 return rb_entry_cfqg(root->left);
724
725         return NULL;
726 }
727
728 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
729 {
730         rb_erase(n, root);
731         RB_CLEAR_NODE(n);
732 }
733
734 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
735 {
736         if (root->left == n)
737                 root->left = NULL;
738         rb_erase_init(n, &root->rb);
739         --root->count;
740 }
741
742 /*
743  * would be nice to take fifo expire time into account as well
744  */
745 static struct request *
746 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
747                   struct request *last)
748 {
749         struct rb_node *rbnext = rb_next(&last->rb_node);
750         struct rb_node *rbprev = rb_prev(&last->rb_node);
751         struct request *next = NULL, *prev = NULL;
752
753         BUG_ON(RB_EMPTY_NODE(&last->rb_node));
754
755         if (rbprev)
756                 prev = rb_entry_rq(rbprev);
757
758         if (rbnext)
759                 next = rb_entry_rq(rbnext);
760         else {
761                 rbnext = rb_first(&cfqq->sort_list);
762                 if (rbnext && rbnext != &last->rb_node)
763                         next = rb_entry_rq(rbnext);
764         }
765
766         return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
767 }
768
769 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
770                                       struct cfq_queue *cfqq)
771 {
772         /*
773          * just an approximation, should be ok.
774          */
775         return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
776                        cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
777 }
778
779 static inline s64
780 cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
781 {
782         return cfqg->vdisktime - st->min_vdisktime;
783 }
784
785 static void
786 __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
787 {
788         struct rb_node **node = &st->rb.rb_node;
789         struct rb_node *parent = NULL;
790         struct cfq_group *__cfqg;
791         s64 key = cfqg_key(st, cfqg);
792         int left = 1;
793
794         while (*node != NULL) {
795                 parent = *node;
796                 __cfqg = rb_entry_cfqg(parent);
797
798                 if (key < cfqg_key(st, __cfqg))
799                         node = &parent->rb_left;
800                 else {
801                         node = &parent->rb_right;
802                         left = 0;
803                 }
804         }
805
806         if (left)
807                 st->left = &cfqg->rb_node;
808
809         rb_link_node(&cfqg->rb_node, parent, node);
810         rb_insert_color(&cfqg->rb_node, &st->rb);
811 }
812
813 static void
814 cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
815 {
816         struct cfq_rb_root *st = &cfqd->grp_service_tree;
817         struct cfq_group *__cfqg;
818         struct rb_node *n;
819
820         cfqg->nr_cfqq++;
821         if (cfqg->on_st)
822                 return;
823
824         /*
825          * Currently put the group at the end. Later implement something
826          * so that groups get lesser vtime based on their weights, so that
827          * if group does not loose all if it was not continously backlogged.
828          */
829         n = rb_last(&st->rb);
830         if (n) {
831                 __cfqg = rb_entry_cfqg(n);
832                 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
833         } else
834                 cfqg->vdisktime = st->min_vdisktime;
835
836         __cfq_group_service_tree_add(st, cfqg);
837         cfqg->on_st = true;
838         st->total_weight += cfqg->weight;
839 }
840
841 static void
842 cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
843 {
844         struct cfq_rb_root *st = &cfqd->grp_service_tree;
845
846         if (st->active == &cfqg->rb_node)
847                 st->active = NULL;
848
849         BUG_ON(cfqg->nr_cfqq < 1);
850         cfqg->nr_cfqq--;
851
852         /* If there are other cfq queues under this group, don't delete it */
853         if (cfqg->nr_cfqq)
854                 return;
855
856         cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
857         cfqg->on_st = false;
858         st->total_weight -= cfqg->weight;
859         if (!RB_EMPTY_NODE(&cfqg->rb_node))
860                 cfq_rb_erase(&cfqg->rb_node, st);
861         cfqg->saved_workload_slice = 0;
862         blkiocg_update_blkio_group_dequeue_stats(&cfqg->blkg, 1);
863 }
864
865 static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
866 {
867         unsigned int slice_used;
868
869         /*
870          * Queue got expired before even a single request completed or
871          * got expired immediately after first request completion.
872          */
873         if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
874                 /*
875                  * Also charge the seek time incurred to the group, otherwise
876                  * if there are mutiple queues in the group, each can dispatch
877                  * a single request on seeky media and cause lots of seek time
878                  * and group will never know it.
879                  */
880                 slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
881                                         1);
882         } else {
883                 slice_used = jiffies - cfqq->slice_start;
884                 if (slice_used > cfqq->allocated_slice)
885                         slice_used = cfqq->allocated_slice;
886         }
887
888         cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u sect=%lu", slice_used,
889                                 cfqq->nr_sectors);
890         return slice_used;
891 }
892
893 static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
894                                 struct cfq_queue *cfqq)
895 {
896         struct cfq_rb_root *st = &cfqd->grp_service_tree;
897         unsigned int used_sl, charge_sl;
898         int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
899                         - cfqg->service_tree_idle.count;
900
901         BUG_ON(nr_sync < 0);
902         used_sl = charge_sl = cfq_cfqq_slice_usage(cfqq);
903
904         if (!cfq_cfqq_sync(cfqq) && !nr_sync)
905                 charge_sl = cfqq->allocated_slice;
906
907         /* Can't update vdisktime while group is on service tree */
908         cfq_rb_erase(&cfqg->rb_node, st);
909         cfqg->vdisktime += cfq_scale_slice(charge_sl, cfqg);
910         __cfq_group_service_tree_add(st, cfqg);
911
912         /* This group is being expired. Save the context */
913         if (time_after(cfqd->workload_expires, jiffies)) {
914                 cfqg->saved_workload_slice = cfqd->workload_expires
915                                                 - jiffies;
916                 cfqg->saved_workload = cfqd->serving_type;
917                 cfqg->saved_serving_prio = cfqd->serving_prio;
918         } else
919                 cfqg->saved_workload_slice = 0;
920
921         cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
922                                         st->min_vdisktime);
923         blkiocg_update_blkio_group_stats(&cfqg->blkg, used_sl,
924                                                 cfqq->nr_sectors);
925 }
926
927 #ifdef CONFIG_CFQ_GROUP_IOSCHED
928 static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
929 {
930         if (blkg)
931                 return container_of(blkg, struct cfq_group, blkg);
932         return NULL;
933 }
934
935 void
936 cfq_update_blkio_group_weight(struct blkio_group *blkg, unsigned int weight)
937 {
938         cfqg_of_blkg(blkg)->weight = weight;
939 }
940
941 static struct cfq_group *
942 cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
943 {
944         struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
945         struct cfq_group *cfqg = NULL;
946         void *key = cfqd;
947         int i, j;
948         struct cfq_rb_root *st;
949         struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
950         unsigned int major, minor;
951
952         cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
953         if (cfqg || !create)
954                 goto done;
955
956         cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
957         if (!cfqg)
958                 goto done;
959
960         cfqg->weight = blkcg->weight;
961         for_each_cfqg_st(cfqg, i, j, st)
962                 *st = CFQ_RB_ROOT;
963         RB_CLEAR_NODE(&cfqg->rb_node);
964
965         /*
966          * Take the initial reference that will be released on destroy
967          * This can be thought of a joint reference by cgroup and
968          * elevator which will be dropped by either elevator exit
969          * or cgroup deletion path depending on who is exiting first.
970          */
971         atomic_set(&cfqg->ref, 1);
972
973         /* Add group onto cgroup list */
974         sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
975         blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
976                                         MKDEV(major, minor));
977
978         /* Add group on cfqd list */
979         hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
980
981 done:
982         return cfqg;
983 }
984
985 /*
986  * Search for the cfq group current task belongs to. If create = 1, then also
987  * create the cfq group if it does not exist. request_queue lock must be held.
988  */
989 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
990 {
991         struct cgroup *cgroup;
992         struct cfq_group *cfqg = NULL;
993
994         rcu_read_lock();
995         cgroup = task_cgroup(current, blkio_subsys_id);
996         cfqg = cfq_find_alloc_cfqg(cfqd, cgroup, create);
997         if (!cfqg && create)
998                 cfqg = &cfqd->root_group;
999         rcu_read_unlock();
1000         return cfqg;
1001 }
1002
1003 static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
1004 {
1005         /* Currently, all async queues are mapped to root group */
1006         if (!cfq_cfqq_sync(cfqq))
1007                 cfqg = &cfqq->cfqd->root_group;
1008
1009         cfqq->cfqg = cfqg;
1010         /* cfqq reference on cfqg */
1011         atomic_inc(&cfqq->cfqg->ref);
1012 }
1013
1014 static void cfq_put_cfqg(struct cfq_group *cfqg)
1015 {
1016         struct cfq_rb_root *st;
1017         int i, j;
1018
1019         BUG_ON(atomic_read(&cfqg->ref) <= 0);
1020         if (!atomic_dec_and_test(&cfqg->ref))
1021                 return;
1022         for_each_cfqg_st(cfqg, i, j, st)
1023                 BUG_ON(!RB_EMPTY_ROOT(&st->rb) || st->active != NULL);
1024         kfree(cfqg);
1025 }
1026
1027 static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
1028 {
1029         /* Something wrong if we are trying to remove same group twice */
1030         BUG_ON(hlist_unhashed(&cfqg->cfqd_node));
1031
1032         hlist_del_init(&cfqg->cfqd_node);
1033
1034         /*
1035          * Put the reference taken at the time of creation so that when all
1036          * queues are gone, group can be destroyed.
1037          */
1038         cfq_put_cfqg(cfqg);
1039 }
1040
1041 static void cfq_release_cfq_groups(struct cfq_data *cfqd)
1042 {
1043         struct hlist_node *pos, *n;
1044         struct cfq_group *cfqg;
1045
1046         hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) {
1047                 /*
1048                  * If cgroup removal path got to blk_group first and removed
1049                  * it from cgroup list, then it will take care of destroying
1050                  * cfqg also.
1051                  */
1052                 if (!blkiocg_del_blkio_group(&cfqg->blkg))
1053                         cfq_destroy_cfqg(cfqd, cfqg);
1054         }
1055 }
1056
1057 /*
1058  * Blk cgroup controller notification saying that blkio_group object is being
1059  * delinked as associated cgroup object is going away. That also means that
1060  * no new IO will come in this group. So get rid of this group as soon as
1061  * any pending IO in the group is finished.
1062  *
1063  * This function is called under rcu_read_lock(). key is the rcu protected
1064  * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu
1065  * read lock.
1066  *
1067  * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
1068  * it should not be NULL as even if elevator was exiting, cgroup deltion
1069  * path got to it first.
1070  */
1071 void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
1072 {
1073         unsigned long  flags;
1074         struct cfq_data *cfqd = key;
1075
1076         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1077         cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg));
1078         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1079 }
1080
1081 #else /* GROUP_IOSCHED */
1082 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
1083 {
1084         return &cfqd->root_group;
1085 }
1086 static inline void
1087 cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
1088         cfqq->cfqg = cfqg;
1089 }
1090
1091 static void cfq_release_cfq_groups(struct cfq_data *cfqd) {}
1092 static inline void cfq_put_cfqg(struct cfq_group *cfqg) {}
1093
1094 #endif /* GROUP_IOSCHED */
1095
1096 /*
1097  * The cfqd->service_trees holds all pending cfq_queue's that have
1098  * requests waiting to be processed. It is sorted in the order that
1099  * we will service the queues.
1100  */
1101 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1102                                  bool add_front)
1103 {
1104         struct rb_node **p, *parent;
1105         struct cfq_queue *__cfqq;
1106         unsigned long rb_key;
1107         struct cfq_rb_root *service_tree;
1108         int left;
1109         int new_cfqq = 1;
1110         int group_changed = 0;
1111
1112 #ifdef CONFIG_CFQ_GROUP_IOSCHED
1113         if (!cfqd->cfq_group_isolation
1114             && cfqq_type(cfqq) == SYNC_NOIDLE_WORKLOAD
1115             && cfqq->cfqg && cfqq->cfqg != &cfqd->root_group) {
1116                 /* Move this cfq to root group */
1117                 cfq_log_cfqq(cfqd, cfqq, "moving to root group");
1118                 if (!RB_EMPTY_NODE(&cfqq->rb_node))
1119                         cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1120                 cfqq->orig_cfqg = cfqq->cfqg;
1121                 cfqq->cfqg = &cfqd->root_group;
1122                 atomic_inc(&cfqd->root_group.ref);
1123                 group_changed = 1;
1124         } else if (!cfqd->cfq_group_isolation
1125                    && cfqq_type(cfqq) == SYNC_WORKLOAD && cfqq->orig_cfqg) {
1126                 /* cfqq is sequential now needs to go to its original group */
1127                 BUG_ON(cfqq->cfqg != &cfqd->root_group);
1128                 if (!RB_EMPTY_NODE(&cfqq->rb_node))
1129                         cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1130                 cfq_put_cfqg(cfqq->cfqg);
1131                 cfqq->cfqg = cfqq->orig_cfqg;
1132                 cfqq->orig_cfqg = NULL;
1133                 group_changed = 1;
1134                 cfq_log_cfqq(cfqd, cfqq, "moved to origin group");
1135         }
1136 #endif
1137
1138         service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
1139                                                 cfqq_type(cfqq));
1140         if (cfq_class_idle(cfqq)) {
1141                 rb_key = CFQ_IDLE_DELAY;
1142                 parent = rb_last(&service_tree->rb);
1143                 if (parent && parent != &cfqq->rb_node) {
1144                         __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1145                         rb_key += __cfqq->rb_key;
1146                 } else
1147                         rb_key += jiffies;
1148         } else if (!add_front) {
1149                 /*
1150                  * Get our rb key offset. Subtract any residual slice
1151                  * value carried from last service. A negative resid
1152                  * count indicates slice overrun, and this should position
1153                  * the next service time further away in the tree.
1154                  */
1155                 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
1156                 rb_key -= cfqq->slice_resid;
1157                 cfqq->slice_resid = 0;
1158         } else {
1159                 rb_key = -HZ;
1160                 __cfqq = cfq_rb_first(service_tree);
1161                 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
1162         }
1163
1164         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1165                 new_cfqq = 0;
1166                 /*
1167                  * same position, nothing more to do
1168                  */
1169                 if (rb_key == cfqq->rb_key &&
1170                     cfqq->service_tree == service_tree)
1171                         return;
1172
1173                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1174                 cfqq->service_tree = NULL;
1175         }
1176
1177         left = 1;
1178         parent = NULL;
1179         cfqq->service_tree = service_tree;
1180         p = &service_tree->rb.rb_node;
1181         while (*p) {
1182                 struct rb_node **n;
1183
1184                 parent = *p;
1185                 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1186
1187                 /*
1188                  * sort by key, that represents service time.
1189                  */
1190                 if (time_before(rb_key, __cfqq->rb_key))
1191                         n = &(*p)->rb_left;
1192                 else {
1193                         n = &(*p)->rb_right;
1194                         left = 0;
1195                 }
1196
1197                 p = n;
1198         }
1199
1200         if (left)
1201                 service_tree->left = &cfqq->rb_node;
1202
1203         cfqq->rb_key = rb_key;
1204         rb_link_node(&cfqq->rb_node, parent, p);
1205         rb_insert_color(&cfqq->rb_node, &service_tree->rb);
1206         service_tree->count++;
1207         if ((add_front || !new_cfqq) && !group_changed)
1208                 return;
1209         cfq_group_service_tree_add(cfqd, cfqq->cfqg);
1210 }
1211
1212 static struct cfq_queue *
1213 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
1214                      sector_t sector, struct rb_node **ret_parent,
1215                      struct rb_node ***rb_link)
1216 {
1217         struct rb_node **p, *parent;
1218         struct cfq_queue *cfqq = NULL;
1219
1220         parent = NULL;
1221         p = &root->rb_node;
1222         while (*p) {
1223                 struct rb_node **n;
1224
1225                 parent = *p;
1226                 cfqq = rb_entry(parent, struct cfq_queue, p_node);
1227
1228                 /*
1229                  * Sort strictly based on sector.  Smallest to the left,
1230                  * largest to the right.
1231                  */
1232                 if (sector > blk_rq_pos(cfqq->next_rq))
1233                         n = &(*p)->rb_right;
1234                 else if (sector < blk_rq_pos(cfqq->next_rq))
1235                         n = &(*p)->rb_left;
1236                 else
1237                         break;
1238                 p = n;
1239                 cfqq = NULL;
1240         }
1241
1242         *ret_parent = parent;
1243         if (rb_link)
1244                 *rb_link = p;
1245         return cfqq;
1246 }
1247
1248 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1249 {
1250         struct rb_node **p, *parent;
1251         struct cfq_queue *__cfqq;
1252
1253         if (cfqq->p_root) {
1254                 rb_erase(&cfqq->p_node, cfqq->p_root);
1255                 cfqq->p_root = NULL;
1256         }
1257
1258         if (cfq_class_idle(cfqq))
1259                 return;
1260         if (!cfqq->next_rq)
1261                 return;
1262
1263         cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
1264         __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
1265                                       blk_rq_pos(cfqq->next_rq), &parent, &p);
1266         if (!__cfqq) {
1267                 rb_link_node(&cfqq->p_node, parent, p);
1268                 rb_insert_color(&cfqq->p_node, cfqq->p_root);
1269         } else
1270                 cfqq->p_root = NULL;
1271 }
1272
1273 /*
1274  * Update cfqq's position in the service tree.
1275  */
1276 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1277 {
1278         /*
1279          * Resorting requires the cfqq to be on the RR list already.
1280          */
1281         if (cfq_cfqq_on_rr(cfqq)) {
1282                 cfq_service_tree_add(cfqd, cfqq, 0);
1283                 cfq_prio_tree_add(cfqd, cfqq);
1284         }
1285 }
1286
1287 /*
1288  * add to busy list of queues for service, trying to be fair in ordering
1289  * the pending list according to last request service
1290  */
1291 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1292 {
1293         cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
1294         BUG_ON(cfq_cfqq_on_rr(cfqq));
1295         cfq_mark_cfqq_on_rr(cfqq);
1296         cfqd->busy_queues++;
1297
1298         cfq_resort_rr_list(cfqd, cfqq);
1299 }
1300
1301 /*
1302  * Called when the cfqq no longer has requests pending, remove it from
1303  * the service tree.
1304  */
1305 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1306 {
1307         cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
1308         BUG_ON(!cfq_cfqq_on_rr(cfqq));
1309         cfq_clear_cfqq_on_rr(cfqq);
1310
1311         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1312                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1313                 cfqq->service_tree = NULL;
1314         }
1315         if (cfqq->p_root) {
1316                 rb_erase(&cfqq->p_node, cfqq->p_root);
1317                 cfqq->p_root = NULL;
1318         }
1319
1320         cfq_group_service_tree_del(cfqd, cfqq->cfqg);
1321         BUG_ON(!cfqd->busy_queues);
1322         cfqd->busy_queues--;
1323 }
1324
1325 /*
1326  * rb tree support functions
1327  */
1328 static void cfq_del_rq_rb(struct request *rq)
1329 {
1330         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1331         const int sync = rq_is_sync(rq);
1332
1333         BUG_ON(!cfqq->queued[sync]);
1334         cfqq->queued[sync]--;
1335
1336         elv_rb_del(&cfqq->sort_list, rq);
1337
1338         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1339                 /*
1340                  * Queue will be deleted from service tree when we actually
1341                  * expire it later. Right now just remove it from prio tree
1342                  * as it is empty.
1343                  */
1344                 if (cfqq->p_root) {
1345                         rb_erase(&cfqq->p_node, cfqq->p_root);
1346                         cfqq->p_root = NULL;
1347                 }
1348         }
1349 }
1350
1351 static void cfq_add_rq_rb(struct request *rq)
1352 {
1353         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1354         struct cfq_data *cfqd = cfqq->cfqd;
1355         struct request *__alias, *prev;
1356
1357         cfqq->queued[rq_is_sync(rq)]++;
1358
1359         /*
1360          * looks a little odd, but the first insert might return an alias.
1361          * if that happens, put the alias on the dispatch list
1362          */
1363         while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
1364                 cfq_dispatch_insert(cfqd->queue, __alias);
1365
1366         if (!cfq_cfqq_on_rr(cfqq))
1367                 cfq_add_cfqq_rr(cfqd, cfqq);
1368
1369         /*
1370          * check if this request is a better next-serve candidate
1371          */
1372         prev = cfqq->next_rq;
1373         cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
1374
1375         /*
1376          * adjust priority tree position, if ->next_rq changes
1377          */
1378         if (prev != cfqq->next_rq)
1379                 cfq_prio_tree_add(cfqd, cfqq);
1380
1381         BUG_ON(!cfqq->next_rq);
1382 }
1383
1384 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
1385 {
1386         elv_rb_del(&cfqq->sort_list, rq);
1387         cfqq->queued[rq_is_sync(rq)]--;
1388         cfq_add_rq_rb(rq);
1389 }
1390
1391 static struct request *
1392 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
1393 {
1394         struct task_struct *tsk = current;
1395         struct cfq_io_context *cic;
1396         struct cfq_queue *cfqq;
1397
1398         cic = cfq_cic_lookup(cfqd, tsk->io_context);
1399         if (!cic)
1400                 return NULL;
1401
1402         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1403         if (cfqq) {
1404                 sector_t sector = bio->bi_sector + bio_sectors(bio);
1405
1406                 return elv_rb_find(&cfqq->sort_list, sector);
1407         }
1408
1409         return NULL;
1410 }
1411
1412 static void cfq_activate_request(struct request_queue *q, struct request *rq)
1413 {
1414         struct cfq_data *cfqd = q->elevator->elevator_data;
1415
1416         cfqd->rq_in_driver[rq_is_sync(rq)]++;
1417         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
1418                                                 rq_in_driver(cfqd));
1419
1420         cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
1421 }
1422
1423 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
1424 {
1425         struct cfq_data *cfqd = q->elevator->elevator_data;
1426         const int sync = rq_is_sync(rq);
1427
1428         WARN_ON(!cfqd->rq_in_driver[sync]);
1429         cfqd->rq_in_driver[sync]--;
1430         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
1431                                                 rq_in_driver(cfqd));
1432 }
1433
1434 static void cfq_remove_request(struct request *rq)
1435 {
1436         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1437
1438         if (cfqq->next_rq == rq)
1439                 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
1440
1441         list_del_init(&rq->queuelist);
1442         cfq_del_rq_rb(rq);
1443
1444         cfqq->cfqd->rq_queued--;
1445         if (rq_is_meta(rq)) {
1446                 WARN_ON(!cfqq->meta_pending);
1447                 cfqq->meta_pending--;
1448         }
1449 }
1450
1451 static int cfq_merge(struct request_queue *q, struct request **req,
1452                      struct bio *bio)
1453 {
1454         struct cfq_data *cfqd = q->elevator->elevator_data;
1455         struct request *__rq;
1456
1457         __rq = cfq_find_rq_fmerge(cfqd, bio);
1458         if (__rq && elv_rq_merge_ok(__rq, bio)) {
1459                 *req = __rq;
1460                 return ELEVATOR_FRONT_MERGE;
1461         }
1462
1463         return ELEVATOR_NO_MERGE;
1464 }
1465
1466 static void cfq_merged_request(struct request_queue *q, struct request *req,
1467                                int type)
1468 {
1469         if (type == ELEVATOR_FRONT_MERGE) {
1470                 struct cfq_queue *cfqq = RQ_CFQQ(req);
1471
1472                 cfq_reposition_rq_rb(cfqq, req);
1473         }
1474 }
1475
1476 static void
1477 cfq_merged_requests(struct request_queue *q, struct request *rq,
1478                     struct request *next)
1479 {
1480         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1481         /*
1482          * reposition in fifo if next is older than rq
1483          */
1484         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
1485             time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
1486                 list_move(&rq->queuelist, &next->queuelist);
1487                 rq_set_fifo_time(rq, rq_fifo_time(next));
1488         }
1489
1490         if (cfqq->next_rq == next)
1491                 cfqq->next_rq = rq;
1492         cfq_remove_request(next);
1493 }
1494
1495 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
1496                            struct bio *bio)
1497 {
1498         struct cfq_data *cfqd = q->elevator->elevator_data;
1499         struct cfq_io_context *cic;
1500         struct cfq_queue *cfqq;
1501
1502         /*
1503          * Disallow merge of a sync bio into an async request.
1504          */
1505         if (cfq_bio_sync(bio) && !rq_is_sync(rq))
1506                 return false;
1507
1508         /*
1509          * Lookup the cfqq that this bio will be queued with. Allow
1510          * merge only if rq is queued there.
1511          */
1512         cic = cfq_cic_lookup(cfqd, current->io_context);
1513         if (!cic)
1514                 return false;
1515
1516         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1517         return cfqq == RQ_CFQQ(rq);
1518 }
1519
1520 static void __cfq_set_active_queue(struct cfq_data *cfqd,
1521                                    struct cfq_queue *cfqq)
1522 {
1523         if (cfqq) {
1524                 cfq_log_cfqq(cfqd, cfqq, "set_active");
1525                 cfqq->slice_start = 0;
1526                 cfqq->dispatch_start = jiffies;
1527                 cfqq->allocated_slice = 0;
1528                 cfqq->slice_end = 0;
1529                 cfqq->slice_dispatch = 0;
1530                 cfqq->nr_sectors = 0;
1531
1532                 cfq_clear_cfqq_wait_request(cfqq);
1533                 cfq_clear_cfqq_must_dispatch(cfqq);
1534                 cfq_clear_cfqq_must_alloc_slice(cfqq);
1535                 cfq_clear_cfqq_fifo_expire(cfqq);
1536                 cfq_mark_cfqq_slice_new(cfqq);
1537
1538                 del_timer(&cfqd->idle_slice_timer);
1539         }
1540
1541         cfqd->active_queue = cfqq;
1542 }
1543
1544 /*
1545  * current cfqq expired its slice (or was too idle), select new one
1546  */
1547 static void
1548 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1549                     bool timed_out)
1550 {
1551         cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
1552
1553         if (cfq_cfqq_wait_request(cfqq))
1554                 del_timer(&cfqd->idle_slice_timer);
1555
1556         cfq_clear_cfqq_wait_request(cfqq);
1557         cfq_clear_cfqq_wait_busy(cfqq);
1558
1559         /*
1560          * If this cfqq is shared between multiple processes, check to
1561          * make sure that those processes are still issuing I/Os within
1562          * the mean seek distance.  If not, it may be time to break the
1563          * queues apart again.
1564          */
1565         if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq))
1566                 cfq_mark_cfqq_split_coop(cfqq);
1567
1568         /*
1569          * store what was left of this slice, if the queue idled/timed out
1570          */
1571         if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
1572                 cfqq->slice_resid = cfqq->slice_end - jiffies;
1573                 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
1574         }
1575
1576         cfq_group_served(cfqd, cfqq->cfqg, cfqq);
1577
1578         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
1579                 cfq_del_cfqq_rr(cfqd, cfqq);
1580
1581         cfq_resort_rr_list(cfqd, cfqq);
1582
1583         if (cfqq == cfqd->active_queue)
1584                 cfqd->active_queue = NULL;
1585
1586         if (&cfqq->cfqg->rb_node == cfqd->grp_service_tree.active)
1587                 cfqd->grp_service_tree.active = NULL;
1588
1589         if (cfqd->active_cic) {
1590                 put_io_context(cfqd->active_cic->ioc);
1591                 cfqd->active_cic = NULL;
1592         }
1593 }
1594
1595 static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
1596 {
1597         struct cfq_queue *cfqq = cfqd->active_queue;
1598
1599         if (cfqq)
1600                 __cfq_slice_expired(cfqd, cfqq, timed_out);
1601 }
1602
1603 /*
1604  * Get next queue for service. Unless we have a queue preemption,
1605  * we'll simply select the first cfqq in the service tree.
1606  */
1607 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
1608 {
1609         struct cfq_rb_root *service_tree =
1610                 service_tree_for(cfqd->serving_group, cfqd->serving_prio,
1611                                         cfqd->serving_type);
1612
1613         if (!cfqd->rq_queued)
1614                 return NULL;
1615
1616         /* There is nothing to dispatch */
1617         if (!service_tree)
1618                 return NULL;
1619         if (RB_EMPTY_ROOT(&service_tree->rb))
1620                 return NULL;
1621         return cfq_rb_first(service_tree);
1622 }
1623
1624 static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
1625 {
1626         struct cfq_group *cfqg;
1627         struct cfq_queue *cfqq;
1628         int i, j;
1629         struct cfq_rb_root *st;
1630
1631         if (!cfqd->rq_queued)
1632                 return NULL;
1633
1634         cfqg = cfq_get_next_cfqg(cfqd);
1635         if (!cfqg)
1636                 return NULL;
1637
1638         for_each_cfqg_st(cfqg, i, j, st)
1639                 if ((cfqq = cfq_rb_first(st)) != NULL)
1640                         return cfqq;
1641         return NULL;
1642 }
1643
1644 /*
1645  * Get and set a new active queue for service.
1646  */
1647 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
1648                                               struct cfq_queue *cfqq)
1649 {
1650         if (!cfqq)
1651                 cfqq = cfq_get_next_queue(cfqd);
1652
1653         __cfq_set_active_queue(cfqd, cfqq);
1654         return cfqq;
1655 }
1656
1657 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
1658                                           struct request *rq)
1659 {
1660         if (blk_rq_pos(rq) >= cfqd->last_position)
1661                 return blk_rq_pos(rq) - cfqd->last_position;
1662         else
1663                 return cfqd->last_position - blk_rq_pos(rq);
1664 }
1665
1666 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1667                                struct request *rq, bool for_preempt)
1668 {
1669         return cfq_dist_from_last(cfqd, rq) <= CFQQ_SEEK_THR;
1670 }
1671
1672 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
1673                                     struct cfq_queue *cur_cfqq)
1674 {
1675         struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
1676         struct rb_node *parent, *node;
1677         struct cfq_queue *__cfqq;
1678         sector_t sector = cfqd->last_position;
1679
1680         if (RB_EMPTY_ROOT(root))
1681                 return NULL;
1682
1683         /*
1684          * First, if we find a request starting at the end of the last
1685          * request, choose it.
1686          */
1687         __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
1688         if (__cfqq)
1689                 return __cfqq;
1690
1691         /*
1692          * If the exact sector wasn't found, the parent of the NULL leaf
1693          * will contain the closest sector.
1694          */
1695         __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1696         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq, false))
1697                 return __cfqq;
1698
1699         if (blk_rq_pos(__cfqq->next_rq) < sector)
1700                 node = rb_next(&__cfqq->p_node);
1701         else
1702                 node = rb_prev(&__cfqq->p_node);
1703         if (!node)
1704                 return NULL;
1705
1706         __cfqq = rb_entry(node, struct cfq_queue, p_node);
1707         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq, false))
1708                 return __cfqq;
1709
1710         return NULL;
1711 }
1712
1713 /*
1714  * cfqd - obvious
1715  * cur_cfqq - passed in so that we don't decide that the current queue is
1716  *            closely cooperating with itself.
1717  *
1718  * So, basically we're assuming that that cur_cfqq has dispatched at least
1719  * one request, and that cfqd->last_position reflects a position on the disk
1720  * associated with the I/O issued by cur_cfqq.  I'm not sure this is a valid
1721  * assumption.
1722  */
1723 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1724                                               struct cfq_queue *cur_cfqq)
1725 {
1726         struct cfq_queue *cfqq;
1727
1728         if (!cfq_cfqq_sync(cur_cfqq))
1729                 return NULL;
1730         if (CFQQ_SEEKY(cur_cfqq))
1731                 return NULL;
1732
1733         /*
1734          * Don't search priority tree if it's the only queue in the group.
1735          */
1736         if (cur_cfqq->cfqg->nr_cfqq == 1)
1737                 return NULL;
1738
1739         /*
1740          * We should notice if some of the queues are cooperating, eg
1741          * working closely on the same area of the disk. In that case,
1742          * we can group them together and don't waste time idling.
1743          */
1744         cfqq = cfqq_close(cfqd, cur_cfqq);
1745         if (!cfqq)
1746                 return NULL;
1747
1748         /* If new queue belongs to different cfq_group, don't choose it */
1749         if (cur_cfqq->cfqg != cfqq->cfqg)
1750                 return NULL;
1751
1752         /*
1753          * It only makes sense to merge sync queues.
1754          */
1755         if (!cfq_cfqq_sync(cfqq))
1756                 return NULL;
1757         if (CFQQ_SEEKY(cfqq))
1758                 return NULL;
1759
1760         /*
1761          * Do not merge queues of different priority classes
1762          */
1763         if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
1764                 return NULL;
1765
1766         return cfqq;
1767 }
1768
1769 /*
1770  * Determine whether we should enforce idle window for this queue.
1771  */
1772
1773 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1774 {
1775         enum wl_prio_t prio = cfqq_prio(cfqq);
1776         struct cfq_rb_root *service_tree = cfqq->service_tree;
1777
1778         BUG_ON(!service_tree);
1779         BUG_ON(!service_tree->count);
1780
1781         /* We never do for idle class queues. */
1782         if (prio == IDLE_WORKLOAD)
1783                 return false;
1784
1785         /* We do for queues that were marked with idle window flag. */
1786         if (cfq_cfqq_idle_window(cfqq) &&
1787            !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag))
1788                 return true;
1789
1790         /*
1791          * Otherwise, we do only if they are the last ones
1792          * in their service tree.
1793          */
1794         return service_tree->count == 1 && cfq_cfqq_sync(cfqq);
1795 }
1796
1797 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
1798 {
1799         struct cfq_queue *cfqq = cfqd->active_queue;
1800         struct cfq_io_context *cic;
1801         unsigned long sl;
1802
1803         /*
1804          * SSD device without seek penalty, disable idling. But only do so
1805          * for devices that support queuing, otherwise we still have a problem
1806          * with sync vs async workloads.
1807          */
1808         if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
1809                 return;
1810
1811         WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
1812         WARN_ON(cfq_cfqq_slice_new(cfqq));
1813
1814         /*
1815          * idle is disabled, either manually or by past process history
1816          */
1817         if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq))
1818                 return;
1819
1820         /*
1821          * still active requests from this queue, don't idle
1822          */
1823         if (cfqq->dispatched)
1824                 return;
1825
1826         /*
1827          * task has exited, don't wait
1828          */
1829         cic = cfqd->active_cic;
1830         if (!cic || !atomic_read(&cic->ioc->nr_tasks))
1831                 return;
1832
1833         /*
1834          * If our average think time is larger than the remaining time
1835          * slice, then don't idle. This avoids overrunning the allotted
1836          * time slice.
1837          */
1838         if (sample_valid(cic->ttime_samples) &&
1839             (cfqq->slice_end - jiffies < cic->ttime_mean))
1840                 return;
1841
1842         cfq_mark_cfqq_wait_request(cfqq);
1843
1844         sl = cfqd->cfq_slice_idle;
1845
1846         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
1847         cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
1848 }
1849
1850 /*
1851  * Move request from internal lists to the request queue dispatch list.
1852  */
1853 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
1854 {
1855         struct cfq_data *cfqd = q->elevator->elevator_data;
1856         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1857
1858         cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
1859
1860         cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
1861         cfq_remove_request(rq);
1862         cfqq->dispatched++;
1863         elv_dispatch_sort(q, rq);
1864
1865         if (cfq_cfqq_sync(cfqq))
1866                 cfqd->sync_flight++;
1867         cfqq->nr_sectors += blk_rq_sectors(rq);
1868 }
1869
1870 /*
1871  * return expired entry, or NULL to just start from scratch in rbtree
1872  */
1873 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
1874 {
1875         struct request *rq = NULL;
1876
1877         if (cfq_cfqq_fifo_expire(cfqq))
1878                 return NULL;
1879
1880         cfq_mark_cfqq_fifo_expire(cfqq);
1881
1882         if (list_empty(&cfqq->fifo))
1883                 return NULL;
1884
1885         rq = rq_entry_fifo(cfqq->fifo.next);
1886         if (time_before(jiffies, rq_fifo_time(rq)))
1887                 rq = NULL;
1888
1889         cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
1890         return rq;
1891 }
1892
1893 static inline int
1894 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1895 {
1896         const int base_rq = cfqd->cfq_slice_async_rq;
1897
1898         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
1899
1900         return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
1901 }
1902
1903 /*
1904  * Must be called with the queue_lock held.
1905  */
1906 static int cfqq_process_refs(struct cfq_queue *cfqq)
1907 {
1908         int process_refs, io_refs;
1909
1910         io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
1911         process_refs = atomic_read(&cfqq->ref) - io_refs;
1912         BUG_ON(process_refs < 0);
1913         return process_refs;
1914 }
1915
1916 static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
1917 {
1918         int process_refs, new_process_refs;
1919         struct cfq_queue *__cfqq;
1920
1921         /* Avoid a circular list and skip interim queue merges */
1922         while ((__cfqq = new_cfqq->new_cfqq)) {
1923                 if (__cfqq == cfqq)
1924                         return;
1925                 new_cfqq = __cfqq;
1926         }
1927
1928         process_refs = cfqq_process_refs(cfqq);
1929         /*
1930          * If the process for the cfqq has gone away, there is no
1931          * sense in merging the queues.
1932          */
1933         if (process_refs == 0)
1934                 return;
1935
1936         /*
1937          * Merge in the direction of the lesser amount of work.
1938          */
1939         new_process_refs = cfqq_process_refs(new_cfqq);
1940         if (new_process_refs >= process_refs) {
1941                 cfqq->new_cfqq = new_cfqq;
1942                 atomic_add(process_refs, &new_cfqq->ref);
1943         } else {
1944                 new_cfqq->new_cfqq = cfqq;
1945                 atomic_add(new_process_refs, &cfqq->ref);
1946         }
1947 }
1948
1949 static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
1950                                 struct cfq_group *cfqg, enum wl_prio_t prio)
1951 {
1952         struct cfq_queue *queue;
1953         int i;
1954         bool key_valid = false;
1955         unsigned long lowest_key = 0;
1956         enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
1957
1958         for (i = 0; i <= SYNC_WORKLOAD; ++i) {
1959                 /* select the one with lowest rb_key */
1960                 queue = cfq_rb_first(service_tree_for(cfqg, prio, i));
1961                 if (queue &&
1962                     (!key_valid || time_before(queue->rb_key, lowest_key))) {
1963                         lowest_key = queue->rb_key;
1964                         cur_best = i;
1965                         key_valid = true;
1966                 }
1967         }
1968
1969         return cur_best;
1970 }
1971
1972 static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
1973 {
1974         unsigned slice;
1975         unsigned count;
1976         struct cfq_rb_root *st;
1977         unsigned group_slice;
1978
1979         if (!cfqg) {
1980                 cfqd->serving_prio = IDLE_WORKLOAD;
1981                 cfqd->workload_expires = jiffies + 1;
1982                 return;
1983         }
1984
1985         /* Choose next priority. RT > BE > IDLE */
1986         if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
1987                 cfqd->serving_prio = RT_WORKLOAD;
1988         else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
1989                 cfqd->serving_prio = BE_WORKLOAD;
1990         else {
1991                 cfqd->serving_prio = IDLE_WORKLOAD;
1992                 cfqd->workload_expires = jiffies + 1;
1993                 return;
1994         }
1995
1996         /*
1997          * For RT and BE, we have to choose also the type
1998          * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
1999          * expiration time
2000          */
2001         st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
2002         count = st->count;
2003
2004         /*
2005          * check workload expiration, and that we still have other queues ready
2006          */
2007         if (count && !time_after(jiffies, cfqd->workload_expires))
2008                 return;
2009
2010         /* otherwise select new workload type */
2011         cfqd->serving_type =
2012                 cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio);
2013         st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
2014         count = st->count;
2015
2016         /*
2017          * the workload slice is computed as a fraction of target latency
2018          * proportional to the number of queues in that workload, over
2019          * all the queues in the same priority class
2020          */
2021         group_slice = cfq_group_slice(cfqd, cfqg);
2022
2023         slice = group_slice * count /
2024                 max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio],
2025                       cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg));
2026
2027         if (cfqd->serving_type == ASYNC_WORKLOAD) {
2028                 unsigned int tmp;
2029
2030                 /*
2031                  * Async queues are currently system wide. Just taking
2032                  * proportion of queues with-in same group will lead to higher
2033                  * async ratio system wide as generally root group is going
2034                  * to have higher weight. A more accurate thing would be to
2035                  * calculate system wide asnc/sync ratio.
2036                  */
2037                 tmp = cfq_target_latency * cfqg_busy_async_queues(cfqd, cfqg);
2038                 tmp = tmp/cfqd->busy_queues;
2039                 slice = min_t(unsigned, slice, tmp);
2040
2041                 /* async workload slice is scaled down according to
2042                  * the sync/async slice ratio. */
2043                 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
2044         } else
2045                 /* sync workload slice is at least 2 * cfq_slice_idle */
2046                 slice = max(slice, 2 * cfqd->cfq_slice_idle);
2047
2048         slice = max_t(unsigned, slice, CFQ_MIN_TT);
2049         cfqd->workload_expires = jiffies + slice;
2050         cfqd->noidle_tree_requires_idle = false;
2051 }
2052
2053 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
2054 {
2055         struct cfq_rb_root *st = &cfqd->grp_service_tree;
2056         struct cfq_group *cfqg;
2057
2058         if (RB_EMPTY_ROOT(&st->rb))
2059                 return NULL;
2060         cfqg = cfq_rb_first_group(st);
2061         st->active = &cfqg->rb_node;
2062         update_min_vdisktime(st);
2063         return cfqg;
2064 }
2065
2066 static void cfq_choose_cfqg(struct cfq_data *cfqd)
2067 {
2068         struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
2069
2070         cfqd->serving_group = cfqg;
2071
2072         /* Restore the workload type data */
2073         if (cfqg->saved_workload_slice) {
2074                 cfqd->workload_expires = jiffies + cfqg->saved_workload_slice;
2075                 cfqd->serving_type = cfqg->saved_workload;
2076                 cfqd->serving_prio = cfqg->saved_serving_prio;
2077         } else
2078                 cfqd->workload_expires = jiffies - 1;
2079
2080         choose_service_tree(cfqd, cfqg);
2081 }
2082
2083 /*
2084  * Select a queue for service. If we have a current active queue,
2085  * check whether to continue servicing it, or retrieve and set a new one.
2086  */
2087 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
2088 {
2089         struct cfq_queue *cfqq, *new_cfqq = NULL;
2090
2091         cfqq = cfqd->active_queue;
2092         if (!cfqq)
2093                 goto new_queue;
2094
2095         if (!cfqd->rq_queued)
2096                 return NULL;
2097
2098         /*
2099          * We were waiting for group to get backlogged. Expire the queue
2100          */
2101         if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list))
2102                 goto expire;
2103
2104         /*
2105          * The active queue has run out of time, expire it and select new.
2106          */
2107         if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) {
2108                 /*
2109                  * If slice had not expired at the completion of last request
2110                  * we might not have turned on wait_busy flag. Don't expire
2111                  * the queue yet. Allow the group to get backlogged.
2112                  *
2113                  * The very fact that we have used the slice, that means we
2114                  * have been idling all along on this queue and it should be
2115                  * ok to wait for this request to complete.
2116                  */
2117                 if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list)
2118                     && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
2119                         cfqq = NULL;
2120                         goto keep_queue;
2121                 } else
2122                         goto expire;
2123         }
2124
2125         /*
2126          * The active queue has requests and isn't expired, allow it to
2127          * dispatch.
2128          */
2129         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2130                 goto keep_queue;
2131
2132         /*
2133          * If another queue has a request waiting within our mean seek
2134          * distance, let it run.  The expire code will check for close
2135          * cooperators and put the close queue at the front of the service
2136          * tree.  If possible, merge the expiring queue with the new cfqq.
2137          */
2138         new_cfqq = cfq_close_cooperator(cfqd, cfqq);
2139         if (new_cfqq) {
2140                 if (!cfqq->new_cfqq)
2141                         cfq_setup_merge(cfqq, new_cfqq);
2142                 goto expire;
2143         }
2144
2145         /*
2146          * No requests pending. If the active queue still has requests in
2147          * flight or is idling for a new request, allow either of these
2148          * conditions to happen (or time out) before selecting a new queue.
2149          */
2150         if (timer_pending(&cfqd->idle_slice_timer) ||
2151             (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) {
2152                 cfqq = NULL;
2153                 goto keep_queue;
2154         }
2155
2156 expire:
2157         cfq_slice_expired(cfqd, 0);
2158 new_queue:
2159         /*
2160          * Current queue expired. Check if we have to switch to a new
2161          * service tree
2162          */
2163         if (!new_cfqq)
2164                 cfq_choose_cfqg(cfqd);
2165
2166         cfqq = cfq_set_active_queue(cfqd, new_cfqq);
2167 keep_queue:
2168         return cfqq;
2169 }
2170
2171 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
2172 {
2173         int dispatched = 0;
2174
2175         while (cfqq->next_rq) {
2176                 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
2177                 dispatched++;
2178         }
2179
2180         BUG_ON(!list_empty(&cfqq->fifo));
2181
2182         /* By default cfqq is not expired if it is empty. Do it explicitly */
2183         __cfq_slice_expired(cfqq->cfqd, cfqq, 0);
2184         return dispatched;
2185 }
2186
2187 /*
2188  * Drain our current requests. Used for barriers and when switching
2189  * io schedulers on-the-fly.
2190  */
2191 static int cfq_forced_dispatch(struct cfq_data *cfqd)
2192 {
2193         struct cfq_queue *cfqq;
2194         int dispatched = 0;
2195
2196         while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL)
2197                 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
2198
2199         cfq_slice_expired(cfqd, 0);
2200         BUG_ON(cfqd->busy_queues);
2201
2202         cfq_log(cfqd, "forced_dispatch=%d", dispatched);
2203         return dispatched;
2204 }
2205
2206 static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2207 {
2208         unsigned int max_dispatch;
2209
2210         /*
2211          * Drain async requests before we start sync IO
2212          */
2213         if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
2214                 return false;
2215
2216         /*
2217          * If this is an async queue and we have sync IO in flight, let it wait
2218          */
2219         if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
2220                 return false;
2221
2222         max_dispatch = cfqd->cfq_quantum;
2223         if (cfq_class_idle(cfqq))
2224                 max_dispatch = 1;
2225
2226         /*
2227          * Does this cfqq already have too much IO in flight?
2228          */
2229         if (cfqq->dispatched >= max_dispatch) {
2230                 /*
2231                  * idle queue must always only have a single IO in flight
2232                  */
2233                 if (cfq_class_idle(cfqq))
2234                         return false;
2235
2236                 /*
2237                  * We have other queues, don't allow more IO from this one
2238                  */
2239                 if (cfqd->busy_queues > 1)
2240                         return false;
2241
2242                 /*
2243                  * Sole queue user, no limit
2244                  */
2245                 max_dispatch = -1;
2246         }
2247
2248         /*
2249          * Async queues must wait a bit before being allowed dispatch.
2250          * We also ramp up the dispatch depth gradually for async IO,
2251          * based on the last sync IO we serviced
2252          */
2253         if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
2254                 unsigned long last_sync = jiffies - cfqd->last_delayed_sync;
2255                 unsigned int depth;
2256
2257                 depth = last_sync / cfqd->cfq_slice[1];
2258                 if (!depth && !cfqq->dispatched)
2259                         depth = 1;
2260                 if (depth < max_dispatch)
2261                         max_dispatch = depth;
2262         }
2263
2264         /*
2265          * If we're below the current max, allow a dispatch
2266          */
2267         return cfqq->dispatched < max_dispatch;
2268 }
2269
2270 /*
2271  * Dispatch a request from cfqq, moving them to the request queue
2272  * dispatch list.
2273  */
2274 static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2275 {
2276         struct request *rq;
2277
2278         BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
2279
2280         if (!cfq_may_dispatch(cfqd, cfqq))
2281                 return false;
2282
2283         /*
2284          * follow expired path, else get first next available
2285          */
2286         rq = cfq_check_fifo(cfqq);
2287         if (!rq)
2288                 rq = cfqq->next_rq;
2289
2290         /*
2291          * insert request into driver dispatch list
2292          */
2293         cfq_dispatch_insert(cfqd->queue, rq);
2294
2295         if (!cfqd->active_cic) {
2296                 struct cfq_io_context *cic = RQ_CIC(rq);
2297
2298                 atomic_long_inc(&cic->ioc->refcount);
2299                 cfqd->active_cic = cic;
2300         }
2301
2302         return true;
2303 }
2304
2305 /*
2306  * Find the cfqq that we need to service and move a request from that to the
2307  * dispatch list
2308  */
2309 static int cfq_dispatch_requests(struct request_queue *q, int force)
2310 {
2311         struct cfq_data *cfqd = q->elevator->elevator_data;
2312         struct cfq_queue *cfqq;
2313
2314         if (!cfqd->busy_queues)
2315                 return 0;
2316
2317         if (unlikely(force))
2318                 return cfq_forced_dispatch(cfqd);
2319
2320         cfqq = cfq_select_queue(cfqd);
2321         if (!cfqq)
2322                 return 0;
2323
2324         /*
2325          * Dispatch a request from this cfqq, if it is allowed
2326          */
2327         if (!cfq_dispatch_request(cfqd, cfqq))
2328                 return 0;
2329
2330         cfqq->slice_dispatch++;
2331         cfq_clear_cfqq_must_dispatch(cfqq);
2332
2333         /*
2334          * expire an async queue immediately if it has used up its slice. idle
2335          * queue always expire after 1 dispatch round.
2336          */
2337         if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
2338             cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
2339             cfq_class_idle(cfqq))) {
2340                 cfqq->slice_end = jiffies + 1;
2341                 cfq_slice_expired(cfqd, 0);
2342         }
2343
2344         cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
2345         return 1;
2346 }
2347
2348 /*
2349  * task holds one reference to the queue, dropped when task exits. each rq
2350  * in-flight on this queue also holds a reference, dropped when rq is freed.
2351  *
2352  * Each cfq queue took a reference on the parent group. Drop it now.
2353  * queue lock must be held here.
2354  */
2355 static void cfq_put_queue(struct cfq_queue *cfqq)
2356 {
2357         struct cfq_data *cfqd = cfqq->cfqd;
2358         struct cfq_group *cfqg, *orig_cfqg;
2359
2360         BUG_ON(atomic_read(&cfqq->ref) <= 0);
2361
2362         if (!atomic_dec_and_test(&cfqq->ref))
2363                 return;
2364
2365         cfq_log_cfqq(cfqd, cfqq, "put_queue");
2366         BUG_ON(rb_first(&cfqq->sort_list));
2367         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
2368         cfqg = cfqq->cfqg;
2369         orig_cfqg = cfqq->orig_cfqg;
2370
2371         if (unlikely(cfqd->active_queue == cfqq)) {
2372                 __cfq_slice_expired(cfqd, cfqq, 0);
2373                 cfq_schedule_dispatch(cfqd);
2374         }
2375
2376         BUG_ON(cfq_cfqq_on_rr(cfqq));
2377         kmem_cache_free(cfq_pool, cfqq);
2378         cfq_put_cfqg(cfqg);
2379         if (orig_cfqg)
2380                 cfq_put_cfqg(orig_cfqg);
2381 }
2382
2383 /*
2384  * Must always be called with the rcu_read_lock() held
2385  */
2386 static void
2387 __call_for_each_cic(struct io_context *ioc,
2388                     void (*func)(struct io_context *, struct cfq_io_context *))
2389 {
2390         struct cfq_io_context *cic;
2391         struct hlist_node *n;
2392
2393         hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
2394                 func(ioc, cic);
2395 }
2396
2397 /*
2398  * Call func for each cic attached to this ioc.
2399  */
2400 static void
2401 call_for_each_cic(struct io_context *ioc,
2402                   void (*func)(struct io_context *, struct cfq_io_context *))
2403 {
2404         rcu_read_lock();
2405         __call_for_each_cic(ioc, func);
2406         rcu_read_unlock();
2407 }
2408
2409 static void cfq_cic_free_rcu(struct rcu_head *head)
2410 {
2411         struct cfq_io_context *cic;
2412
2413         cic = container_of(head, struct cfq_io_context, rcu_head);
2414
2415         kmem_cache_free(cfq_ioc_pool, cic);
2416         elv_ioc_count_dec(cfq_ioc_count);
2417
2418         if (ioc_gone) {
2419                 /*
2420                  * CFQ scheduler is exiting, grab exit lock and check
2421                  * the pending io context count. If it hits zero,
2422                  * complete ioc_gone and set it back to NULL
2423                  */
2424                 spin_lock(&ioc_gone_lock);
2425                 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
2426                         complete(ioc_gone);
2427                         ioc_gone = NULL;
2428                 }
2429                 spin_unlock(&ioc_gone_lock);
2430         }
2431 }
2432
2433 static void cfq_cic_free(struct cfq_io_context *cic)
2434 {
2435         call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
2436 }
2437
2438 static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
2439 {
2440         unsigned long flags;
2441
2442         BUG_ON(!cic->dead_key);
2443
2444         spin_lock_irqsave(&ioc->lock, flags);
2445         radix_tree_delete(&ioc->radix_root, cic->dead_key);
2446         hlist_del_rcu(&cic->cic_list);
2447         spin_unlock_irqrestore(&ioc->lock, flags);
2448
2449         cfq_cic_free(cic);
2450 }
2451
2452 /*
2453  * Must be called with rcu_read_lock() held or preemption otherwise disabled.
2454  * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
2455  * and ->trim() which is called with the task lock held
2456  */
2457 static void cfq_free_io_context(struct io_context *ioc)
2458 {
2459         /*
2460          * ioc->refcount is zero here, or we are called from elv_unregister(),
2461          * so no more cic's are allowed to be linked into this ioc.  So it
2462          * should be ok to iterate over the known list, we will see all cic's
2463          * since no new ones are added.
2464          */
2465         __call_for_each_cic(ioc, cic_free_func);
2466 }
2467
2468 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2469 {
2470         struct cfq_queue *__cfqq, *next;
2471
2472         if (unlikely(cfqq == cfqd->active_queue)) {
2473                 __cfq_slice_expired(cfqd, cfqq, 0);
2474                 cfq_schedule_dispatch(cfqd);
2475         }
2476
2477         /*
2478          * If this queue was scheduled to merge with another queue, be
2479          * sure to drop the reference taken on that queue (and others in
2480          * the merge chain).  See cfq_setup_merge and cfq_merge_cfqqs.
2481          */
2482         __cfqq = cfqq->new_cfqq;
2483         while (__cfqq) {
2484                 if (__cfqq == cfqq) {
2485                         WARN(1, "cfqq->new_cfqq loop detected\n");
2486                         break;
2487                 }
2488                 next = __cfqq->new_cfqq;
2489                 cfq_put_queue(__cfqq);
2490                 __cfqq = next;
2491         }
2492
2493         cfq_put_queue(cfqq);
2494 }
2495
2496 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
2497                                          struct cfq_io_context *cic)
2498 {
2499         struct io_context *ioc = cic->ioc;
2500
2501         list_del_init(&cic->queue_list);
2502
2503         /*
2504          * Make sure key == NULL is seen for dead queues
2505          */
2506         smp_wmb();
2507         cic->dead_key = (unsigned long) cic->key;
2508         cic->key = NULL;
2509
2510         if (ioc->ioc_data == cic)
2511                 rcu_assign_pointer(ioc->ioc_data, NULL);
2512
2513         if (cic->cfqq[BLK_RW_ASYNC]) {
2514                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
2515                 cic->cfqq[BLK_RW_ASYNC] = NULL;
2516         }
2517
2518         if (cic->cfqq[BLK_RW_SYNC]) {
2519                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
2520                 cic->cfqq[BLK_RW_SYNC] = NULL;
2521         }
2522 }
2523
2524 static void cfq_exit_single_io_context(struct io_context *ioc,
2525                                        struct cfq_io_context *cic)
2526 {
2527         struct cfq_data *cfqd = cic->key;
2528
2529         if (cfqd) {
2530                 struct request_queue *q = cfqd->queue;
2531                 unsigned long flags;
2532
2533                 spin_lock_irqsave(q->queue_lock, flags);
2534
2535                 /*
2536                  * Ensure we get a fresh copy of the ->key to prevent
2537                  * race between exiting task and queue
2538                  */
2539                 smp_read_barrier_depends();
2540                 if (cic->key)
2541                         __cfq_exit_single_io_context(cfqd, cic);
2542
2543                 spin_unlock_irqrestore(q->queue_lock, flags);
2544         }
2545 }
2546
2547 /*
2548  * The process that ioc belongs to has exited, we need to clean up
2549  * and put the internal structures we have that belongs to that process.
2550  */
2551 static void cfq_exit_io_context(struct io_context *ioc)
2552 {
2553         call_for_each_cic(ioc, cfq_exit_single_io_context);
2554 }
2555
2556 static struct cfq_io_context *
2557 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2558 {
2559         struct cfq_io_context *cic;
2560
2561         cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
2562                                                         cfqd->queue->node);
2563         if (cic) {
2564                 cic->last_end_request = jiffies;
2565                 INIT_LIST_HEAD(&cic->queue_list);
2566                 INIT_HLIST_NODE(&cic->cic_list);
2567                 cic->dtor = cfq_free_io_context;
2568                 cic->exit = cfq_exit_io_context;
2569                 elv_ioc_count_inc(cfq_ioc_count);
2570         }
2571
2572         return cic;
2573 }
2574
2575 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
2576 {
2577         struct task_struct *tsk = current;
2578         int ioprio_class;
2579
2580         if (!cfq_cfqq_prio_changed(cfqq))
2581                 return;
2582
2583         ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
2584         switch (ioprio_class) {
2585         default:
2586                 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
2587         case IOPRIO_CLASS_NONE:
2588                 /*
2589                  * no prio set, inherit CPU scheduling settings
2590                  */
2591                 cfqq->ioprio = task_nice_ioprio(tsk);
2592                 cfqq->ioprio_class = task_nice_ioclass(tsk);
2593                 break;
2594         case IOPRIO_CLASS_RT:
2595                 cfqq->ioprio = task_ioprio(ioc);
2596                 cfqq->ioprio_class = IOPRIO_CLASS_RT;
2597                 break;
2598         case IOPRIO_CLASS_BE:
2599                 cfqq->ioprio = task_ioprio(ioc);
2600                 cfqq->ioprio_class = IOPRIO_CLASS_BE;
2601                 break;
2602         case IOPRIO_CLASS_IDLE:
2603                 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
2604                 cfqq->ioprio = 7;
2605                 cfq_clear_cfqq_idle_window(cfqq);
2606                 break;
2607         }
2608
2609         /*
2610          * keep track of original prio settings in case we have to temporarily
2611          * elevate the priority of this queue
2612          */
2613         cfqq->org_ioprio = cfqq->ioprio;
2614         cfqq->org_ioprio_class = cfqq->ioprio_class;
2615         cfq_clear_cfqq_prio_changed(cfqq);
2616 }
2617
2618 static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
2619 {
2620         struct cfq_data *cfqd = cic->key;
2621         struct cfq_queue *cfqq;
2622         unsigned long flags;
2623
2624         if (unlikely(!cfqd))
2625                 return;
2626
2627         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2628
2629         cfqq = cic->cfqq[BLK_RW_ASYNC];
2630         if (cfqq) {
2631                 struct cfq_queue *new_cfqq;
2632                 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
2633                                                 GFP_ATOMIC);
2634                 if (new_cfqq) {
2635                         cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
2636                         cfq_put_queue(cfqq);
2637                 }
2638         }
2639
2640         cfqq = cic->cfqq[BLK_RW_SYNC];
2641         if (cfqq)
2642                 cfq_mark_cfqq_prio_changed(cfqq);
2643
2644         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2645 }
2646
2647 static void cfq_ioc_set_ioprio(struct io_context *ioc)
2648 {
2649         call_for_each_cic(ioc, changed_ioprio);
2650         ioc->ioprio_changed = 0;
2651 }
2652
2653 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2654                           pid_t pid, bool is_sync)
2655 {
2656         RB_CLEAR_NODE(&cfqq->rb_node);
2657         RB_CLEAR_NODE(&cfqq->p_node);
2658         INIT_LIST_HEAD(&cfqq->fifo);
2659
2660         atomic_set(&cfqq->ref, 0);
2661         cfqq->cfqd = cfqd;
2662
2663         cfq_mark_cfqq_prio_changed(cfqq);
2664
2665         if (is_sync) {
2666                 if (!cfq_class_idle(cfqq))
2667                         cfq_mark_cfqq_idle_window(cfqq);
2668                 cfq_mark_cfqq_sync(cfqq);
2669         }
2670         cfqq->pid = pid;
2671 }
2672
2673 #ifdef CONFIG_CFQ_GROUP_IOSCHED
2674 static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
2675 {
2676         struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1);
2677         struct cfq_data *cfqd = cic->key;
2678         unsigned long flags;
2679         struct request_queue *q;
2680
2681         if (unlikely(!cfqd))
2682                 return;
2683
2684         q = cfqd->queue;
2685
2686         spin_lock_irqsave(q->queue_lock, flags);
2687
2688         if (sync_cfqq) {
2689                 /*
2690                  * Drop reference to sync queue. A new sync queue will be
2691                  * assigned in new group upon arrival of a fresh request.
2692                  */
2693                 cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
2694                 cic_set_cfqq(cic, NULL, 1);
2695                 cfq_put_queue(sync_cfqq);
2696         }
2697
2698         spin_unlock_irqrestore(q->queue_lock, flags);
2699 }
2700
2701 static void cfq_ioc_set_cgroup(struct io_context *ioc)
2702 {
2703         call_for_each_cic(ioc, changed_cgroup);
2704         ioc->cgroup_changed = 0;
2705 }
2706 #endif  /* CONFIG_CFQ_GROUP_IOSCHED */
2707
2708 static struct cfq_queue *
2709 cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
2710                      struct io_context *ioc, gfp_t gfp_mask)
2711 {
2712         struct cfq_queue *cfqq, *new_cfqq = NULL;
2713         struct cfq_io_context *cic;
2714         struct cfq_group *cfqg;
2715
2716 retry:
2717         cfqg = cfq_get_cfqg(cfqd, 1);
2718         cic = cfq_cic_lookup(cfqd, ioc);
2719         /* cic always exists here */
2720         cfqq = cic_to_cfqq(cic, is_sync);
2721
2722         /*
2723          * Always try a new alloc if we fell back to the OOM cfqq
2724          * originally, since it should just be a temporary situation.
2725          */
2726         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2727                 cfqq = NULL;
2728                 if (new_cfqq) {
2729                         cfqq = new_cfqq;
2730                         new_cfqq = NULL;
2731                 } else if (gfp_mask & __GFP_WAIT) {
2732                         spin_unlock_irq(cfqd->queue->queue_lock);
2733                         new_cfqq = kmem_cache_alloc_node(cfq_pool,
2734                                         gfp_mask | __GFP_ZERO,
2735                                         cfqd->queue->node);
2736                         spin_lock_irq(cfqd->queue->queue_lock);
2737                         if (new_cfqq)
2738                                 goto retry;
2739                 } else {
2740                         cfqq = kmem_cache_alloc_node(cfq_pool,
2741                                         gfp_mask | __GFP_ZERO,
2742                                         cfqd->queue->node);
2743                 }
2744
2745                 if (cfqq) {
2746                         cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
2747                         cfq_init_prio_data(cfqq, ioc);
2748                         cfq_link_cfqq_cfqg(cfqq, cfqg);
2749                         cfq_log_cfqq(cfqd, cfqq, "alloced");
2750                 } else
2751                         cfqq = &cfqd->oom_cfqq;
2752         }
2753
2754         if (new_cfqq)
2755                 kmem_cache_free(cfq_pool, new_cfqq);
2756
2757         return cfqq;
2758 }
2759
2760 static struct cfq_queue **
2761 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
2762 {
2763         switch (ioprio_class) {
2764         case IOPRIO_CLASS_RT:
2765                 return &cfqd->async_cfqq[0][ioprio];
2766         case IOPRIO_CLASS_BE:
2767                 return &cfqd->async_cfqq[1][ioprio];
2768         case IOPRIO_CLASS_IDLE:
2769                 return &cfqd->async_idle_cfqq;
2770         default:
2771                 BUG();
2772         }
2773 }
2774
2775 static struct cfq_queue *
2776 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
2777               gfp_t gfp_mask)
2778 {
2779         const int ioprio = task_ioprio(ioc);
2780         const int ioprio_class = task_ioprio_class(ioc);
2781         struct cfq_queue **async_cfqq = NULL;
2782         struct cfq_queue *cfqq = NULL;
2783
2784         if (!is_sync) {
2785                 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
2786                 cfqq = *async_cfqq;
2787         }
2788
2789         if (!cfqq)
2790                 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
2791
2792         /*
2793          * pin the queue now that it's allocated, scheduler exit will prune it
2794          */
2795         if (!is_sync && !(*async_cfqq)) {
2796                 atomic_inc(&cfqq->ref);
2797                 *async_cfqq = cfqq;
2798         }
2799
2800         atomic_inc(&cfqq->ref);
2801         return cfqq;
2802 }
2803
2804 /*
2805  * We drop cfq io contexts lazily, so we may find a dead one.
2806  */
2807 static void
2808 cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
2809                   struct cfq_io_context *cic)
2810 {
2811         unsigned long flags;
2812
2813         WARN_ON(!list_empty(&cic->queue_list));
2814
2815         spin_lock_irqsave(&ioc->lock, flags);
2816
2817         BUG_ON(ioc->ioc_data == cic);
2818
2819         radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
2820         hlist_del_rcu(&cic->cic_list);
2821         spin_unlock_irqrestore(&ioc->lock, flags);
2822
2823         cfq_cic_free(cic);
2824 }
2825
2826 static struct cfq_io_context *
2827 cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
2828 {
2829         struct cfq_io_context *cic;
2830         unsigned long flags;
2831         void *k;
2832
2833         if (unlikely(!ioc))
2834                 return NULL;
2835
2836         rcu_read_lock();
2837
2838         /*
2839          * we maintain a last-hit cache, to avoid browsing over the tree
2840          */
2841         cic = rcu_dereference(ioc->ioc_data);
2842         if (cic && cic->key == cfqd) {
2843                 rcu_read_unlock();
2844                 return cic;
2845         }
2846
2847         do {
2848                 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
2849                 rcu_read_unlock();
2850                 if (!cic)
2851                         break;
2852                 /* ->key must be copied to avoid race with cfq_exit_queue() */
2853                 k = cic->key;
2854                 if (unlikely(!k)) {
2855                         cfq_drop_dead_cic(cfqd, ioc, cic);
2856                         rcu_read_lock();
2857                         continue;
2858                 }
2859
2860                 spin_lock_irqsave(&ioc->lock, flags);
2861                 rcu_assign_pointer(ioc->ioc_data, cic);
2862                 spin_unlock_irqrestore(&ioc->lock, flags);
2863                 break;
2864         } while (1);
2865
2866         return cic;
2867 }
2868
2869 /*
2870  * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2871  * the process specific cfq io context when entered from the block layer.
2872  * Also adds the cic to a per-cfqd list, used when this queue is removed.
2873  */
2874 static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
2875                         struct cfq_io_context *cic, gfp_t gfp_mask)
2876 {
2877         unsigned long flags;
2878         int ret;
2879
2880         ret = radix_tree_preload(gfp_mask);
2881         if (!ret) {
2882                 cic->ioc = ioc;
2883                 cic->key = cfqd;
2884
2885                 spin_lock_irqsave(&ioc->lock, flags);
2886                 ret = radix_tree_insert(&ioc->radix_root,
2887                                                 (unsigned long) cfqd, cic);
2888                 if (!ret)
2889                         hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
2890                 spin_unlock_irqrestore(&ioc->lock, flags);
2891
2892                 radix_tree_preload_end();
2893
2894                 if (!ret) {
2895                         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2896                         list_add(&cic->queue_list, &cfqd->cic_list);
2897                         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2898                 }
2899         }
2900
2901         if (ret)
2902                 printk(KERN_ERR "cfq: cic link failed!\n");
2903
2904         return ret;
2905 }
2906
2907 /*
2908  * Setup general io context and cfq io context. There can be several cfq
2909  * io contexts per general io context, if this process is doing io to more
2910  * than one device managed by cfq.
2911  */
2912 static struct cfq_io_context *
2913 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2914 {
2915         struct io_context *ioc = NULL;
2916         struct cfq_io_context *cic;
2917
2918         might_sleep_if(gfp_mask & __GFP_WAIT);
2919
2920         ioc = get_io_context(gfp_mask, cfqd->queue->node);
2921         if (!ioc)
2922                 return NULL;
2923
2924         cic = cfq_cic_lookup(cfqd, ioc);
2925         if (cic)
2926                 goto out;
2927
2928         cic = cfq_alloc_io_context(cfqd, gfp_mask);
2929         if (cic == NULL)
2930                 goto err;
2931
2932         if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
2933                 goto err_free;
2934
2935 out:
2936         smp_read_barrier_depends();
2937         if (unlikely(ioc->ioprio_changed))
2938                 cfq_ioc_set_ioprio(ioc);
2939
2940 #ifdef CONFIG_CFQ_GROUP_IOSCHED
2941         if (unlikely(ioc->cgroup_changed))
2942                 cfq_ioc_set_cgroup(ioc);
2943 #endif
2944         return cic;
2945 err_free:
2946         cfq_cic_free(cic);
2947 err:
2948         put_io_context(ioc);
2949         return NULL;
2950 }
2951
2952 static void
2953 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
2954 {
2955         unsigned long elapsed = jiffies - cic->last_end_request;
2956         unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
2957
2958         cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
2959         cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
2960         cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
2961 }
2962
2963 static void
2964 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2965                        struct request *rq)
2966 {
2967         sector_t sdist = 0;
2968         if (cfqq->last_request_pos) {
2969                 if (cfqq->last_request_pos < blk_rq_pos(rq))
2970                         sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
2971                 else
2972                         sdist = cfqq->last_request_pos - blk_rq_pos(rq);
2973         }
2974
2975         cfqq->seek_history <<= 1;
2976         cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
2977 }
2978
2979 /*
2980  * Disable idle window if the process thinks too long or seeks so much that
2981  * it doesn't matter
2982  */
2983 static void
2984 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2985                        struct cfq_io_context *cic)
2986 {
2987         int old_idle, enable_idle;
2988
2989         /*
2990          * Don't idle for async or idle io prio class
2991          */
2992         if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
2993                 return;
2994
2995         enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
2996
2997         if (cfqq->queued[0] + cfqq->queued[1] >= 4)
2998                 cfq_mark_cfqq_deep(cfqq);
2999
3000         if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
3001             (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
3002                 enable_idle = 0;
3003         else if (sample_valid(cic->ttime_samples)) {
3004                 if (cic->ttime_mean > cfqd->cfq_slice_idle)
3005                         enable_idle = 0;
3006                 else
3007                         enable_idle = 1;
3008         }
3009
3010         if (old_idle != enable_idle) {
3011                 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
3012                 if (enable_idle)
3013                         cfq_mark_cfqq_idle_window(cfqq);
3014                 else
3015                         cfq_clear_cfqq_idle_window(cfqq);
3016         }
3017 }
3018
3019 /*
3020  * Check if new_cfqq should preempt the currently active queue. Return 0 for
3021  * no or if we aren't sure, a 1 will cause a preempt.
3022  */
3023 static bool
3024 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
3025                    struct request *rq)
3026 {
3027         struct cfq_queue *cfqq;
3028
3029         cfqq = cfqd->active_queue;
3030         if (!cfqq)
3031                 return false;
3032
3033         if (cfq_class_idle(new_cfqq))
3034                 return false;
3035
3036         if (cfq_class_idle(cfqq))
3037                 return true;
3038
3039         /*
3040          * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice.
3041          */
3042         if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq))
3043                 return false;
3044
3045         /*
3046          * if the new request is sync, but the currently running queue is
3047          * not, let the sync request have priority.
3048          */
3049         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
3050                 return true;
3051
3052         if (new_cfqq->cfqg != cfqq->cfqg)
3053                 return false;
3054
3055         if (cfq_slice_used(cfqq))
3056                 return true;
3057
3058         /* Allow preemption only if we are idling on sync-noidle tree */
3059         if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
3060             cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
3061             new_cfqq->service_tree->count == 2 &&
3062             RB_EMPTY_ROOT(&cfqq->sort_list))
3063                 return true;
3064
3065         /*
3066          * So both queues are sync. Let the new request get disk time if
3067          * it's a metadata request and the current queue is doing regular IO.
3068          */
3069         if (rq_is_meta(rq) && !cfqq->meta_pending)
3070                 return true;
3071
3072         /*
3073          * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
3074          */
3075         if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
3076                 return true;
3077
3078         if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
3079                 return false;
3080
3081         /*
3082          * if this request is as-good as one we would expect from the
3083          * current cfqq, let it preempt
3084          */
3085         if (cfq_rq_close(cfqd, cfqq, rq, true))
3086                 return true;
3087
3088         return false;
3089 }
3090
3091 /*
3092  * cfqq preempts the active queue. if we allowed preempt with no slice left,
3093  * let it have half of its nominal slice.
3094  */
3095 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3096 {
3097         cfq_log_cfqq(cfqd, cfqq, "preempt");
3098         cfq_slice_expired(cfqd, 1);
3099
3100         /*
3101          * Put the new queue at the front of the of the current list,
3102          * so we know that it will be selected next.
3103          */
3104         BUG_ON(!cfq_cfqq_on_rr(cfqq));
3105
3106         cfq_service_tree_add(cfqd, cfqq, 1);
3107
3108         cfqq->slice_end = 0;
3109         cfq_mark_cfqq_slice_new(cfqq);
3110 }
3111
3112 /*
3113  * Called when a new fs request (rq) is added (to cfqq). Check if there's
3114  * something we should do about it
3115  */
3116 static void
3117 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3118                 struct request *rq)
3119 {
3120         struct cfq_io_context *cic = RQ_CIC(rq);
3121
3122         cfqd->rq_queued++;
3123         if (rq_is_meta(rq))
3124                 cfqq->meta_pending++;
3125
3126         cfq_update_io_thinktime(cfqd, cic);
3127         cfq_update_io_seektime(cfqd, cfqq, rq);
3128         cfq_update_idle_window(cfqd, cfqq, cic);
3129
3130         cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
3131
3132         if (cfqq == cfqd->active_queue) {
3133                 /*
3134                  * Remember that we saw a request from this process, but
3135                  * don't start queuing just yet. Otherwise we risk seeing lots
3136                  * of tiny requests, because we disrupt the normal plugging
3137                  * and merging. If the request is already larger than a single
3138                  * page, let it rip immediately. For that case we assume that
3139                  * merging is already done. Ditto for a busy system that
3140                  * has other work pending, don't risk delaying until the
3141                  * idle timer unplug to continue working.
3142                  */
3143                 if (cfq_cfqq_wait_request(cfqq)) {
3144                         if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
3145                             cfqd->busy_queues > 1) {
3146                                 del_timer(&cfqd->idle_slice_timer);
3147                                 cfq_clear_cfqq_wait_request(cfqq);
3148                                 __blk_run_queue(cfqd->queue);
3149                         } else
3150                                 cfq_mark_cfqq_must_dispatch(cfqq);
3151                 }
3152         } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
3153                 /*
3154                  * not the active queue - expire current slice if it is
3155                  * idle and has expired it's mean thinktime or this new queue
3156                  * has some old slice time left and is of higher priority or
3157                  * this new queue is RT and the current one is BE
3158                  */
3159                 cfq_preempt_queue(cfqd, cfqq);
3160                 __blk_run_queue(cfqd->queue);
3161         }
3162 }
3163
3164 static void cfq_insert_request(struct request_queue *q, struct request *rq)
3165 {
3166         struct cfq_data *cfqd = q->elevator->elevator_data;
3167         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3168
3169         cfq_log_cfqq(cfqd, cfqq, "insert_request");
3170         cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
3171
3172         rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
3173         list_add_tail(&rq->queuelist, &cfqq->fifo);
3174         cfq_add_rq_rb(rq);
3175
3176         cfq_rq_enqueued(cfqd, cfqq, rq);
3177 }
3178
3179 /*
3180  * Update hw_tag based on peak queue depth over 50 samples under
3181  * sufficient load.
3182  */
3183 static void cfq_update_hw_tag(struct cfq_data *cfqd)
3184 {
3185         struct cfq_queue *cfqq = cfqd->active_queue;
3186
3187         if (rq_in_driver(cfqd) > cfqd->hw_tag_est_depth)
3188                 cfqd->hw_tag_est_depth = rq_in_driver(cfqd);
3189
3190         if (cfqd->hw_tag == 1)
3191                 return;
3192
3193         if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
3194             rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)
3195                 return;
3196
3197         /*
3198          * If active queue hasn't enough requests and can idle, cfq might not
3199          * dispatch sufficient requests to hardware. Don't zero hw_tag in this
3200          * case
3201          */
3202         if (cfqq && cfq_cfqq_idle_window(cfqq) &&
3203             cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
3204             CFQ_HW_QUEUE_MIN && rq_in_driver(cfqd) < CFQ_HW_QUEUE_MIN)
3205                 return;
3206
3207         if (cfqd->hw_tag_samples++ < 50)
3208                 return;
3209
3210         if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
3211                 cfqd->hw_tag = 1;
3212         else
3213                 cfqd->hw_tag = 0;
3214 }
3215
3216 static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3217 {
3218         struct cfq_io_context *cic = cfqd->active_cic;
3219
3220         /* If there are other queues in the group, don't wait */
3221         if (cfqq->cfqg->nr_cfqq > 1)
3222                 return false;
3223
3224         if (cfq_slice_used(cfqq))
3225                 return true;
3226
3227         /* if slice left is less than think time, wait busy */
3228         if (cic && sample_valid(cic->ttime_samples)
3229             && (cfqq->slice_end - jiffies < cic->ttime_mean))
3230                 return true;
3231
3232         /*
3233          * If think times is less than a jiffy than ttime_mean=0 and above
3234          * will not be true. It might happen that slice has not expired yet
3235          * but will expire soon (4-5 ns) during select_queue(). To cover the
3236          * case where think time is less than a jiffy, mark the queue wait
3237          * busy if only 1 jiffy is left in the slice.
3238          */
3239         if (cfqq->slice_end - jiffies == 1)
3240                 return true;
3241
3242         return false;
3243 }
3244
3245 static void cfq_completed_request(struct request_queue *q, struct request *rq)
3246 {
3247         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3248         struct cfq_data *cfqd = cfqq->cfqd;
3249         const int sync = rq_is_sync(rq);
3250         unsigned long now;
3251
3252         now = jiffies;
3253         cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d", !!rq_noidle(rq));
3254
3255         cfq_update_hw_tag(cfqd);
3256
3257         WARN_ON(!cfqd->rq_in_driver[sync]);
3258         WARN_ON(!cfqq->dispatched);
3259         cfqd->rq_in_driver[sync]--;
3260         cfqq->dispatched--;
3261
3262         if (cfq_cfqq_sync(cfqq))
3263                 cfqd->sync_flight--;
3264
3265         if (sync) {
3266                 RQ_CIC(rq)->last_end_request = now;
3267                 if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
3268                         cfqd->last_delayed_sync = now;
3269         }
3270
3271         /*
3272          * If this is the active queue, check if it needs to be expired,
3273          * or if we want to idle in case it has no pending requests.
3274          */
3275         if (cfqd->active_queue == cfqq) {
3276                 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
3277
3278                 if (cfq_cfqq_slice_new(cfqq)) {
3279                         cfq_set_prio_slice(cfqd, cfqq);
3280                         cfq_clear_cfqq_slice_new(cfqq);
3281                 }
3282
3283                 /*
3284                  * Should we wait for next request to come in before we expire
3285                  * the queue.
3286                  */
3287                 if (cfq_should_wait_busy(cfqd, cfqq)) {
3288                         cfqq->slice_end = jiffies + cfqd->cfq_slice_idle;
3289                         cfq_mark_cfqq_wait_busy(cfqq);
3290                 }
3291
3292                 /*
3293                  * Idling is not enabled on:
3294                  * - expired queues
3295                  * - idle-priority queues
3296                  * - async queues
3297                  * - queues with still some requests queued
3298                  * - when there is a close cooperator
3299                  */
3300                 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
3301                         cfq_slice_expired(cfqd, 1);
3302                 else if (sync && cfqq_empty &&
3303                          !cfq_close_cooperator(cfqd, cfqq)) {
3304                         cfqd->noidle_tree_requires_idle |= !rq_noidle(rq);
3305                         /*
3306                          * Idling is enabled for SYNC_WORKLOAD.
3307                          * SYNC_NOIDLE_WORKLOAD idles at the end of the tree
3308                          * only if we processed at least one !rq_noidle request
3309                          */
3310                         if (cfqd->serving_type == SYNC_WORKLOAD
3311                             || cfqd->noidle_tree_requires_idle
3312                             || cfqq->cfqg->nr_cfqq == 1)
3313                                 cfq_arm_slice_timer(cfqd);
3314                 }
3315         }
3316
3317         if (!rq_in_driver(cfqd))
3318                 cfq_schedule_dispatch(cfqd);
3319 }
3320
3321 /*
3322  * we temporarily boost lower priority queues if they are holding fs exclusive
3323  * resources. they are boosted to normal prio (CLASS_BE/4)
3324  */
3325 static void cfq_prio_boost(struct cfq_queue *cfqq)
3326 {
3327         if (has_fs_excl()) {
3328                 /*
3329                  * boost idle prio on transactions that would lock out other
3330                  * users of the filesystem
3331                  */
3332                 if (cfq_class_idle(cfqq))
3333                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
3334                 if (cfqq->ioprio > IOPRIO_NORM)
3335                         cfqq->ioprio = IOPRIO_NORM;
3336         } else {
3337                 /*
3338                  * unboost the queue (if needed)
3339                  */
3340                 cfqq->ioprio_class = cfqq->org_ioprio_class;
3341                 cfqq->ioprio = cfqq->org_ioprio;
3342         }
3343 }
3344
3345 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
3346 {
3347         if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
3348                 cfq_mark_cfqq_must_alloc_slice(cfqq);
3349                 return ELV_MQUEUE_MUST;
3350         }
3351
3352         return ELV_MQUEUE_MAY;
3353 }
3354
3355 static int cfq_may_queue(struct request_queue *q, int rw)
3356 {
3357         struct cfq_data *cfqd = q->elevator->elevator_data;
3358         struct task_struct *tsk = current;
3359         struct cfq_io_context *cic;
3360         struct cfq_queue *cfqq;
3361
3362         /*
3363          * don't force setup of a queue from here, as a call to may_queue
3364          * does not necessarily imply that a request actually will be queued.
3365          * so just lookup a possibly existing queue, or return 'may queue'
3366          * if that fails
3367          */
3368         cic = cfq_cic_lookup(cfqd, tsk->io_context);
3369         if (!cic)
3370                 return ELV_MQUEUE_MAY;
3371
3372         cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
3373         if (cfqq) {
3374                 cfq_init_prio_data(cfqq, cic->ioc);
3375                 cfq_prio_boost(cfqq);
3376
3377                 return __cfq_may_queue(cfqq);
3378         }
3379
3380         return ELV_MQUEUE_MAY;
3381 }
3382
3383 /*
3384  * queue lock held here
3385  */
3386 static void cfq_put_request(struct request *rq)
3387 {
3388         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3389
3390         if (cfqq) {
3391                 const int rw = rq_data_dir(rq);
3392
3393                 BUG_ON(!cfqq->allocated[rw]);
3394                 cfqq->allocated[rw]--;
3395
3396                 put_io_context(RQ_CIC(rq)->ioc);
3397
3398                 rq->elevator_private = NULL;
3399                 rq->elevator_private2 = NULL;
3400
3401                 cfq_put_queue(cfqq);
3402         }
3403 }
3404
3405 static struct cfq_queue *
3406 cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
3407                 struct cfq_queue *cfqq)
3408 {
3409         cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
3410         cic_set_cfqq(cic, cfqq->new_cfqq, 1);
3411         cfq_mark_cfqq_coop(cfqq->new_cfqq);
3412         cfq_put_queue(cfqq);
3413         return cic_to_cfqq(cic, 1);
3414 }
3415
3416 /*
3417  * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
3418  * was the last process referring to said cfqq.
3419  */
3420 static struct cfq_queue *
3421 split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
3422 {
3423         if (cfqq_process_refs(cfqq) == 1) {
3424                 cfqq->pid = current->pid;
3425                 cfq_clear_cfqq_coop(cfqq);
3426                 cfq_clear_cfqq_split_coop(cfqq);
3427                 return cfqq;
3428         }
3429
3430         cic_set_cfqq(cic, NULL, 1);
3431         cfq_put_queue(cfqq);
3432         return NULL;
3433 }
3434 /*
3435  * Allocate cfq data structures associated with this request.
3436  */
3437 static int
3438 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
3439 {
3440         struct cfq_data *cfqd = q->elevator->elevator_data;
3441         struct cfq_io_context *cic;
3442         const int rw = rq_data_dir(rq);
3443         const bool is_sync = rq_is_sync(rq);
3444         struct cfq_queue *cfqq;
3445         unsigned long flags;
3446
3447         might_sleep_if(gfp_mask & __GFP_WAIT);
3448
3449         cic = cfq_get_io_context(cfqd, gfp_mask);
3450
3451         spin_lock_irqsave(q->queue_lock, flags);
3452
3453         if (!cic)
3454                 goto queue_fail;
3455
3456 new_queue:
3457         cfqq = cic_to_cfqq(cic, is_sync);
3458         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3459                 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
3460                 cic_set_cfqq(cic, cfqq, is_sync);
3461         } else {
3462                 /*
3463                  * If the queue was seeky for too long, break it apart.
3464                  */
3465                 if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) {
3466                         cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
3467                         cfqq = split_cfqq(cic, cfqq);
3468                         if (!cfqq)
3469                                 goto new_queue;
3470                 }
3471
3472                 /*
3473                  * Check to see if this queue is scheduled to merge with
3474                  * another, closely cooperating queue.  The merging of
3475                  * queues happens here as it must be done in process context.
3476                  * The reference on new_cfqq was taken in merge_cfqqs.
3477                  */
3478                 if (cfqq->new_cfqq)
3479                         cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
3480         }
3481
3482         cfqq->allocated[rw]++;
3483         atomic_inc(&cfqq->ref);
3484
3485         spin_unlock_irqrestore(q->queue_lock, flags);
3486
3487         rq->elevator_private = cic;
3488         rq->elevator_private2 = cfqq;
3489         return 0;
3490
3491 queue_fail:
3492         if (cic)
3493                 put_io_context(cic->ioc);
3494
3495         cfq_schedule_dispatch(cfqd);
3496         spin_unlock_irqrestore(q->queue_lock, flags);
3497         cfq_log(cfqd, "set_request fail");
3498         return 1;
3499 }
3500
3501 static void cfq_kick_queue(struct work_struct *work)
3502 {
3503         struct cfq_data *cfqd =
3504                 container_of(work, struct cfq_data, unplug_work);
3505         struct request_queue *q = cfqd->queue;
3506
3507         spin_lock_irq(q->queue_lock);
3508         __blk_run_queue(cfqd->queue);
3509         spin_unlock_irq(q->queue_lock);
3510 }
3511
3512 /*
3513  * Timer running if the active_queue is currently idling inside its time slice
3514  */
3515 static void cfq_idle_slice_timer(unsigned long data)
3516 {
3517         struct cfq_data *cfqd = (struct cfq_data *) data;
3518         struct cfq_queue *cfqq;
3519         unsigned long flags;
3520         int timed_out = 1;
3521
3522         cfq_log(cfqd, "idle timer fired");
3523
3524         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
3525
3526         cfqq = cfqd->active_queue;
3527         if (cfqq) {
3528                 timed_out = 0;
3529
3530                 /*
3531                  * We saw a request before the queue expired, let it through
3532                  */
3533                 if (cfq_cfqq_must_dispatch(cfqq))
3534                         goto out_kick;
3535
3536                 /*
3537                  * expired
3538                  */
3539                 if (cfq_slice_used(cfqq))
3540                         goto expire;
3541
3542                 /*
3543                  * only expire and reinvoke request handler, if there are
3544                  * other queues with pending requests
3545                  */
3546                 if (!cfqd->busy_queues)
3547                         goto out_cont;
3548
3549                 /*
3550                  * not expired and it has a request pending, let it dispatch
3551                  */
3552                 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3553                         goto out_kick;
3554
3555                 /*
3556                  * Queue depth flag is reset only when the idle didn't succeed
3557                  */
3558                 cfq_clear_cfqq_deep(cfqq);
3559         }
3560 expire:
3561         cfq_slice_expired(cfqd, timed_out);
3562 out_kick:
3563         cfq_schedule_dispatch(cfqd);
3564 out_cont:
3565         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
3566 }
3567
3568 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
3569 {
3570         del_timer_sync(&cfqd->idle_slice_timer);
3571         cancel_work_sync(&cfqd->unplug_work);
3572 }
3573
3574 static void cfq_put_async_queues(struct cfq_data *cfqd)
3575 {
3576         int i;
3577
3578         for (i = 0; i < IOPRIO_BE_NR; i++) {
3579                 if (cfqd->async_cfqq[0][i])
3580                         cfq_put_queue(cfqd->async_cfqq[0][i]);
3581                 if (cfqd->async_cfqq[1][i])
3582                         cfq_put_queue(cfqd->async_cfqq[1][i]);
3583         }
3584
3585         if (cfqd->async_idle_cfqq)
3586                 cfq_put_queue(cfqd->async_idle_cfqq);
3587 }
3588
3589 static void cfq_cfqd_free(struct rcu_head *head)
3590 {
3591         kfree(container_of(head, struct cfq_data, rcu));
3592 }
3593
3594 static void cfq_exit_queue(struct elevator_queue *e)
3595 {
3596         struct cfq_data *cfqd = e->elevator_data;
3597         struct request_queue *q = cfqd->queue;
3598
3599         cfq_shutdown_timer_wq(cfqd);
3600
3601         spin_lock_irq(q->queue_lock);
3602
3603         if (cfqd->active_queue)
3604                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
3605
3606         while (!list_empty(&cfqd->cic_list)) {
3607                 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
3608                                                         struct cfq_io_context,
3609                                                         queue_list);
3610
3611                 __cfq_exit_single_io_context(cfqd, cic);
3612         }
3613
3614         cfq_put_async_queues(cfqd);
3615         cfq_release_cfq_groups(cfqd);
3616         blkiocg_del_blkio_group(&cfqd->root_group.blkg);
3617
3618         spin_unlock_irq(q->queue_lock);
3619
3620         cfq_shutdown_timer_wq(cfqd);
3621
3622         /* Wait for cfqg->blkg->key accessors to exit their grace periods. */
3623         call_rcu(&cfqd->rcu, cfq_cfqd_free);
3624 }
3625
3626 static void *cfq_init_queue(struct request_queue *q)
3627 {
3628         struct cfq_data *cfqd;
3629         int i, j;
3630         struct cfq_group *cfqg;
3631         struct cfq_rb_root *st;
3632
3633         cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
3634         if (!cfqd)
3635                 return NULL;
3636
3637         /* Init root service tree */
3638         cfqd->grp_service_tree = CFQ_RB_ROOT;
3639
3640         /* Init root group */
3641         cfqg = &cfqd->root_group;
3642         for_each_cfqg_st(cfqg, i, j, st)
3643                 *st = CFQ_RB_ROOT;
3644         RB_CLEAR_NODE(&cfqg->rb_node);
3645
3646         /* Give preference to root group over other groups */
3647         cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
3648
3649 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3650         /*
3651          * Take a reference to root group which we never drop. This is just
3652          * to make sure that cfq_put_cfqg() does not try to kfree root group
3653          */
3654         atomic_set(&cfqg->ref, 1);
3655         blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd,
3656                                         0);
3657 #endif
3658         /*
3659          * Not strictly needed (since RB_ROOT just clears the node and we
3660          * zeroed cfqd on alloc), but better be safe in case someone decides
3661          * to add magic to the rb code
3662          */
3663         for (i = 0; i < CFQ_PRIO_LISTS; i++)
3664                 cfqd->prio_trees[i] = RB_ROOT;
3665
3666         /*
3667          * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
3668          * Grab a permanent reference to it, so that the normal code flow
3669          * will not attempt to free it.
3670          */
3671         cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
3672         atomic_inc(&cfqd->oom_cfqq.ref);
3673         cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
3674
3675         INIT_LIST_HEAD(&cfqd->cic_list);
3676
3677         cfqd->queue = q;
3678
3679         init_timer(&cfqd->idle_slice_timer);
3680         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
3681         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
3682
3683         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
3684
3685         cfqd->cfq_quantum = cfq_quantum;
3686         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
3687         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
3688         cfqd->cfq_back_max = cfq_back_max;
3689         cfqd->cfq_back_penalty = cfq_back_penalty;
3690         cfqd->cfq_slice[0] = cfq_slice_async;
3691         cfqd->cfq_slice[1] = cfq_slice_sync;
3692         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
3693         cfqd->cfq_slice_idle = cfq_slice_idle;
3694         cfqd->cfq_latency = 1;
3695         cfqd->cfq_group_isolation = 0;
3696         cfqd->hw_tag = -1;
3697         /*
3698          * we optimistically start assuming sync ops weren't delayed in last
3699          * second, in order to have larger depth for async operations.
3700          */
3701         cfqd->last_delayed_sync = jiffies - HZ;
3702         INIT_RCU_HEAD(&cfqd->rcu);
3703         return cfqd;
3704 }
3705
3706 static void cfq_slab_kill(void)
3707 {
3708         /*
3709          * Caller already ensured that pending RCU callbacks are completed,
3710          * so we should have no busy allocations at this point.
3711          */
3712         if (cfq_pool)
3713                 kmem_cache_destroy(cfq_pool);
3714         if (cfq_ioc_pool)
3715                 kmem_cache_destroy(cfq_ioc_pool);
3716 }
3717
3718 static int __init cfq_slab_setup(void)
3719 {
3720         cfq_pool = KMEM_CACHE(cfq_queue, 0);
3721         if (!cfq_pool)
3722                 goto fail;
3723
3724         cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
3725         if (!cfq_ioc_pool)
3726                 goto fail;
3727
3728         return 0;
3729 fail:
3730         cfq_slab_kill();
3731         return -ENOMEM;
3732 }
3733
3734 /*
3735  * sysfs parts below -->
3736  */
3737 static ssize_t
3738 cfq_var_show(unsigned int var, char *page)
3739 {
3740         return sprintf(page, "%d\n", var);
3741 }
3742
3743 static ssize_t
3744 cfq_var_store(unsigned int *var, const char *page, size_t count)
3745 {
3746         char *p = (char *) page;
3747
3748         *var = simple_strtoul(p, &p, 10);
3749         return count;
3750 }
3751
3752 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
3753 static ssize_t __FUNC(struct elevator_queue *e, char *page)             \
3754 {                                                                       \
3755         struct cfq_data *cfqd = e->elevator_data;                       \
3756         unsigned int __data = __VAR;                                    \
3757         if (__CONV)                                                     \
3758                 __data = jiffies_to_msecs(__data);                      \
3759         return cfq_var_show(__data, (page));                            \
3760 }
3761 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
3762 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
3763 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
3764 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
3765 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
3766 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
3767 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
3768 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
3769 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
3770 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
3771 SHOW_FUNCTION(cfq_group_isolation_show, cfqd->cfq_group_isolation, 0);
3772 #undef SHOW_FUNCTION
3773
3774 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
3775 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3776 {                                                                       \
3777         struct cfq_data *cfqd = e->elevator_data;                       \
3778         unsigned int __data;                                            \
3779         int ret = cfq_var_store(&__data, (page), count);                \
3780         if (__data < (MIN))                                             \
3781                 __data = (MIN);                                         \
3782         else if (__data > (MAX))                                        \
3783                 __data = (MAX);                                         \
3784         if (__CONV)                                                     \
3785                 *(__PTR) = msecs_to_jiffies(__data);                    \
3786         else                                                            \
3787                 *(__PTR) = __data;                                      \
3788         return ret;                                                     \
3789 }
3790 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
3791 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
3792                 UINT_MAX, 1);
3793 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
3794                 UINT_MAX, 1);
3795 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
3796 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
3797                 UINT_MAX, 0);
3798 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
3799 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
3800 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
3801 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
3802                 UINT_MAX, 0);
3803 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
3804 STORE_FUNCTION(cfq_group_isolation_store, &cfqd->cfq_group_isolation, 0, 1, 0);
3805 #undef STORE_FUNCTION
3806
3807 #define CFQ_ATTR(name) \
3808         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3809
3810 static struct elv_fs_entry cfq_attrs[] = {
3811         CFQ_ATTR(quantum),
3812         CFQ_ATTR(fifo_expire_sync),
3813         CFQ_ATTR(fifo_expire_async),
3814         CFQ_ATTR(back_seek_max),
3815         CFQ_ATTR(back_seek_penalty),
3816         CFQ_ATTR(slice_sync),
3817         CFQ_ATTR(slice_async),
3818         CFQ_ATTR(slice_async_rq),
3819         CFQ_ATTR(slice_idle),
3820         CFQ_ATTR(low_latency),
3821         CFQ_ATTR(group_isolation),
3822         __ATTR_NULL
3823 };
3824
3825 static struct elevator_type iosched_cfq = {
3826         .ops = {
3827                 .elevator_merge_fn =            cfq_merge,
3828                 .elevator_merged_fn =           cfq_merged_request,
3829                 .elevator_merge_req_fn =        cfq_merged_requests,
3830                 .elevator_allow_merge_fn =      cfq_allow_merge,
3831                 .elevator_dispatch_fn =         cfq_dispatch_requests,
3832                 .elevator_add_req_fn =          cfq_insert_request,
3833                 .elevator_activate_req_fn =     cfq_activate_request,
3834                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
3835                 .elevator_queue_empty_fn =      cfq_queue_empty,
3836                 .elevator_completed_req_fn =    cfq_completed_request,
3837                 .elevator_former_req_fn =       elv_rb_former_request,
3838                 .elevator_latter_req_fn =       elv_rb_latter_request,
3839                 .elevator_set_req_fn =          cfq_set_request,
3840                 .elevator_put_req_fn =          cfq_put_request,
3841                 .elevator_may_queue_fn =        cfq_may_queue,
3842                 .elevator_init_fn =             cfq_init_queue,
3843                 .elevator_exit_fn =             cfq_exit_queue,
3844                 .trim =                         cfq_free_io_context,
3845         },
3846         .elevator_attrs =       cfq_attrs,
3847         .elevator_name =        "cfq",
3848         .elevator_owner =       THIS_MODULE,
3849 };
3850
3851 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3852 static struct blkio_policy_type blkio_policy_cfq = {
3853         .ops = {
3854                 .blkio_unlink_group_fn =        cfq_unlink_blkio_group,
3855                 .blkio_update_group_weight_fn = cfq_update_blkio_group_weight,
3856         },
3857 };
3858 #else
3859 static struct blkio_policy_type blkio_policy_cfq;
3860 #endif
3861
3862 static int __init cfq_init(void)
3863 {
3864         /*
3865          * could be 0 on HZ < 1000 setups
3866          */
3867         if (!cfq_slice_async)
3868                 cfq_slice_async = 1;
3869         if (!cfq_slice_idle)
3870                 cfq_slice_idle = 1;
3871
3872         if (cfq_slab_setup())
3873                 return -ENOMEM;
3874
3875         elv_register(&iosched_cfq);
3876         blkio_policy_register(&blkio_policy_cfq);
3877
3878         return 0;
3879 }
3880
3881 static void __exit cfq_exit(void)
3882 {
3883         DECLARE_COMPLETION_ONSTACK(all_gone);
3884         blkio_policy_unregister(&blkio_policy_cfq);
3885         elv_unregister(&iosched_cfq);
3886         ioc_gone = &all_gone;
3887         /* ioc_gone's update must be visible before reading ioc_count */
3888         smp_wmb();
3889
3890         /*
3891          * this also protects us from entering cfq_slab_kill() with
3892          * pending RCU callbacks
3893          */
3894         if (elv_ioc_count_read(cfq_ioc_count))
3895                 wait_for_completion(&all_gone);
3896         cfq_slab_kill();
3897 }
3898
3899 module_init(cfq_init);
3900 module_exit(cfq_exit);
3901
3902 MODULE_AUTHOR("Jens Axboe");
3903 MODULE_LICENSE("GPL");
3904 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");