cfq-iosched: Don't set active queue in preempt
[linux-2.6.git] / block / cfq-iosched.c
1 /*
2  *  CFQ, or complete fairness queueing, disk scheduler.
3  *
4  *  Based on ideas from a previously unfinished io
5  *  scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
6  *
7  *  Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
8  */
9 #include <linux/module.h>
10 #include <linux/slab.h>
11 #include <linux/blkdev.h>
12 #include <linux/elevator.h>
13 #include <linux/jiffies.h>
14 #include <linux/rbtree.h>
15 #include <linux/ioprio.h>
16 #include <linux/blktrace_api.h>
17 #include "cfq.h"
18
19 /*
20  * tunables
21  */
22 /* max queue in one round of service */
23 static const int cfq_quantum = 8;
24 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
25 /* maximum backwards seek, in KiB */
26 static const int cfq_back_max = 16 * 1024;
27 /* penalty of a backwards seek */
28 static const int cfq_back_penalty = 2;
29 static const int cfq_slice_sync = HZ / 10;
30 static int cfq_slice_async = HZ / 25;
31 static const int cfq_slice_async_rq = 2;
32 static int cfq_slice_idle = HZ / 125;
33 static int cfq_group_idle = HZ / 125;
34 static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
35 static const int cfq_hist_divisor = 4;
36
37 /*
38  * offset from end of service tree
39  */
40 #define CFQ_IDLE_DELAY          (HZ / 5)
41
42 /*
43  * below this threshold, we consider thinktime immediate
44  */
45 #define CFQ_MIN_TT              (2)
46
47 #define CFQ_SLICE_SCALE         (5)
48 #define CFQ_HW_QUEUE_MIN        (5)
49 #define CFQ_SERVICE_SHIFT       12
50
51 #define CFQQ_SEEK_THR           (sector_t)(8 * 100)
52 #define CFQQ_CLOSE_THR          (sector_t)(8 * 1024)
53 #define CFQQ_SECT_THR_NONROT    (sector_t)(2 * 32)
54 #define CFQQ_SEEKY(cfqq)        (hweight32(cfqq->seek_history) > 32/8)
55
56 #define RQ_CIC(rq)              \
57         ((struct cfq_io_context *) (rq)->elevator_private[0])
58 #define RQ_CFQQ(rq)             (struct cfq_queue *) ((rq)->elevator_private[1])
59 #define RQ_CFQG(rq)             (struct cfq_group *) ((rq)->elevator_private[2])
60
61 static struct kmem_cache *cfq_pool;
62 static struct kmem_cache *cfq_ioc_pool;
63
64 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
65 static struct completion *ioc_gone;
66 static DEFINE_SPINLOCK(ioc_gone_lock);
67
68 static DEFINE_SPINLOCK(cic_index_lock);
69 static DEFINE_IDA(cic_index_ida);
70
71 #define CFQ_PRIO_LISTS          IOPRIO_BE_NR
72 #define cfq_class_idle(cfqq)    ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
73 #define cfq_class_rt(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
74
75 #define sample_valid(samples)   ((samples) > 80)
76 #define rb_entry_cfqg(node)     rb_entry((node), struct cfq_group, rb_node)
77
78 /*
79  * Most of our rbtree usage is for sorting with min extraction, so
80  * if we cache the leftmost node we don't have to walk down the tree
81  * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
82  * move this into the elevator for the rq sorting as well.
83  */
84 struct cfq_rb_root {
85         struct rb_root rb;
86         struct rb_node *left;
87         unsigned count;
88         unsigned total_weight;
89         u64 min_vdisktime;
90 };
91 #define CFQ_RB_ROOT     (struct cfq_rb_root) { .rb = RB_ROOT, .left = NULL, \
92                         .count = 0, .min_vdisktime = 0, }
93
94 /*
95  * Per process-grouping structure
96  */
97 struct cfq_queue {
98         /* reference count */
99         int ref;
100         /* various state flags, see below */
101         unsigned int flags;
102         /* parent cfq_data */
103         struct cfq_data *cfqd;
104         /* service_tree member */
105         struct rb_node rb_node;
106         /* service_tree key */
107         unsigned long rb_key;
108         /* prio tree member */
109         struct rb_node p_node;
110         /* prio tree root we belong to, if any */
111         struct rb_root *p_root;
112         /* sorted list of pending requests */
113         struct rb_root sort_list;
114         /* if fifo isn't expired, next request to serve */
115         struct request *next_rq;
116         /* requests queued in sort_list */
117         int queued[2];
118         /* currently allocated requests */
119         int allocated[2];
120         /* fifo list of requests in sort_list */
121         struct list_head fifo;
122
123         /* time when queue got scheduled in to dispatch first request. */
124         unsigned long dispatch_start;
125         unsigned int allocated_slice;
126         unsigned int slice_dispatch;
127         /* time when first request from queue completed and slice started. */
128         unsigned long slice_start;
129         unsigned long slice_end;
130         long slice_resid;
131
132         /* pending metadata requests */
133         int meta_pending;
134         /* number of requests that are on the dispatch list or inside driver */
135         int dispatched;
136
137         /* io prio of this group */
138         unsigned short ioprio, org_ioprio;
139         unsigned short ioprio_class, org_ioprio_class;
140
141         pid_t pid;
142
143         u32 seek_history;
144         sector_t last_request_pos;
145
146         struct cfq_rb_root *service_tree;
147         struct cfq_queue *new_cfqq;
148         struct cfq_group *cfqg;
149         /* Number of sectors dispatched from queue in single dispatch round */
150         unsigned long nr_sectors;
151 };
152
153 /*
154  * First index in the service_trees.
155  * IDLE is handled separately, so it has negative index
156  */
157 enum wl_prio_t {
158         BE_WORKLOAD = 0,
159         RT_WORKLOAD = 1,
160         IDLE_WORKLOAD = 2,
161         CFQ_PRIO_NR,
162 };
163
164 /*
165  * Second index in the service_trees.
166  */
167 enum wl_type_t {
168         ASYNC_WORKLOAD = 0,
169         SYNC_NOIDLE_WORKLOAD = 1,
170         SYNC_WORKLOAD = 2
171 };
172
173 /* This is per cgroup per device grouping structure */
174 struct cfq_group {
175         /* group service_tree member */
176         struct rb_node rb_node;
177
178         /* group service_tree key */
179         u64 vdisktime;
180         unsigned int weight;
181         unsigned int new_weight;
182         bool needs_update;
183
184         /* number of cfqq currently on this group */
185         int nr_cfqq;
186
187         /*
188          * Per group busy queus average. Useful for workload slice calc. We
189          * create the array for each prio class but at run time it is used
190          * only for RT and BE class and slot for IDLE class remains unused.
191          * This is primarily done to avoid confusion and a gcc warning.
192          */
193         unsigned int busy_queues_avg[CFQ_PRIO_NR];
194         /*
195          * rr lists of queues with requests. We maintain service trees for
196          * RT and BE classes. These trees are subdivided in subclasses
197          * of SYNC, SYNC_NOIDLE and ASYNC based on workload type. For IDLE
198          * class there is no subclassification and all the cfq queues go on
199          * a single tree service_tree_idle.
200          * Counts are embedded in the cfq_rb_root
201          */
202         struct cfq_rb_root service_trees[2][3];
203         struct cfq_rb_root service_tree_idle;
204
205         unsigned long saved_workload_slice;
206         enum wl_type_t saved_workload;
207         enum wl_prio_t saved_serving_prio;
208         struct blkio_group blkg;
209 #ifdef CONFIG_CFQ_GROUP_IOSCHED
210         struct hlist_node cfqd_node;
211         int ref;
212 #endif
213         /* number of requests that are on the dispatch list or inside driver */
214         int dispatched;
215 };
216
217 /*
218  * Per block device queue structure
219  */
220 struct cfq_data {
221         struct request_queue *queue;
222         /* Root service tree for cfq_groups */
223         struct cfq_rb_root grp_service_tree;
224         struct cfq_group root_group;
225
226         /*
227          * The priority currently being served
228          */
229         enum wl_prio_t serving_prio;
230         enum wl_type_t serving_type;
231         unsigned long workload_expires;
232         struct cfq_group *serving_group;
233
234         /*
235          * Each priority tree is sorted by next_request position.  These
236          * trees are used when determining if two or more queues are
237          * interleaving requests (see cfq_close_cooperator).
238          */
239         struct rb_root prio_trees[CFQ_PRIO_LISTS];
240
241         unsigned int busy_queues;
242         unsigned int busy_sync_queues;
243
244         int rq_in_driver;
245         int rq_in_flight[2];
246
247         /*
248          * queue-depth detection
249          */
250         int rq_queued;
251         int hw_tag;
252         /*
253          * hw_tag can be
254          * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
255          *  1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
256          *  0 => no NCQ
257          */
258         int hw_tag_est_depth;
259         unsigned int hw_tag_samples;
260
261         /*
262          * idle window management
263          */
264         struct timer_list idle_slice_timer;
265         struct work_struct unplug_work;
266
267         struct cfq_queue *active_queue;
268         struct cfq_io_context *active_cic;
269
270         /*
271          * async queue for each priority case
272          */
273         struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
274         struct cfq_queue *async_idle_cfqq;
275
276         sector_t last_position;
277
278         /*
279          * tunables, see top of file
280          */
281         unsigned int cfq_quantum;
282         unsigned int cfq_fifo_expire[2];
283         unsigned int cfq_back_penalty;
284         unsigned int cfq_back_max;
285         unsigned int cfq_slice[2];
286         unsigned int cfq_slice_async_rq;
287         unsigned int cfq_slice_idle;
288         unsigned int cfq_group_idle;
289         unsigned int cfq_latency;
290
291         unsigned int cic_index;
292         struct list_head cic_list;
293
294         /*
295          * Fallback dummy cfqq for extreme OOM conditions
296          */
297         struct cfq_queue oom_cfqq;
298
299         unsigned long last_delayed_sync;
300
301         /* List of cfq groups being managed on this device*/
302         struct hlist_head cfqg_list;
303         struct rcu_head rcu;
304 };
305
306 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
307
308 static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
309                                             enum wl_prio_t prio,
310                                             enum wl_type_t type)
311 {
312         if (!cfqg)
313                 return NULL;
314
315         if (prio == IDLE_WORKLOAD)
316                 return &cfqg->service_tree_idle;
317
318         return &cfqg->service_trees[prio][type];
319 }
320
321 enum cfqq_state_flags {
322         CFQ_CFQQ_FLAG_on_rr = 0,        /* on round-robin busy list */
323         CFQ_CFQQ_FLAG_wait_request,     /* waiting for a request */
324         CFQ_CFQQ_FLAG_must_dispatch,    /* must be allowed a dispatch */
325         CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
326         CFQ_CFQQ_FLAG_fifo_expire,      /* FIFO checked in this slice */
327         CFQ_CFQQ_FLAG_idle_window,      /* slice idling enabled */
328         CFQ_CFQQ_FLAG_prio_changed,     /* task priority has changed */
329         CFQ_CFQQ_FLAG_slice_new,        /* no requests dispatched in slice */
330         CFQ_CFQQ_FLAG_sync,             /* synchronous queue */
331         CFQ_CFQQ_FLAG_coop,             /* cfqq is shared */
332         CFQ_CFQQ_FLAG_split_coop,       /* shared cfqq will be splitted */
333         CFQ_CFQQ_FLAG_deep,             /* sync cfqq experienced large depth */
334         CFQ_CFQQ_FLAG_wait_busy,        /* Waiting for next request */
335 };
336
337 #define CFQ_CFQQ_FNS(name)                                              \
338 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
339 {                                                                       \
340         (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name);                   \
341 }                                                                       \
342 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
343 {                                                                       \
344         (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                  \
345 }                                                                       \
346 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
347 {                                                                       \
348         return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;      \
349 }
350
351 CFQ_CFQQ_FNS(on_rr);
352 CFQ_CFQQ_FNS(wait_request);
353 CFQ_CFQQ_FNS(must_dispatch);
354 CFQ_CFQQ_FNS(must_alloc_slice);
355 CFQ_CFQQ_FNS(fifo_expire);
356 CFQ_CFQQ_FNS(idle_window);
357 CFQ_CFQQ_FNS(prio_changed);
358 CFQ_CFQQ_FNS(slice_new);
359 CFQ_CFQQ_FNS(sync);
360 CFQ_CFQQ_FNS(coop);
361 CFQ_CFQQ_FNS(split_coop);
362 CFQ_CFQQ_FNS(deep);
363 CFQ_CFQQ_FNS(wait_busy);
364 #undef CFQ_CFQQ_FNS
365
366 #ifdef CONFIG_CFQ_GROUP_IOSCHED
367 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
368         blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
369                         cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
370                         blkg_path(&(cfqq)->cfqg->blkg), ##args);
371
372 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)                          \
373         blk_add_trace_msg((cfqd)->queue, "%s " fmt,                     \
374                                 blkg_path(&(cfqg)->blkg), ##args);      \
375
376 #else
377 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
378         blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
379 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)          do {} while (0);
380 #endif
381 #define cfq_log(cfqd, fmt, args...)     \
382         blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
383
384 /* Traverses through cfq group service trees */
385 #define for_each_cfqg_st(cfqg, i, j, st) \
386         for (i = 0; i <= IDLE_WORKLOAD; i++) \
387                 for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
388                         : &cfqg->service_tree_idle; \
389                         (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
390                         (i == IDLE_WORKLOAD && j == 0); \
391                         j++, st = i < IDLE_WORKLOAD ? \
392                         &cfqg->service_trees[i][j]: NULL) \
393
394
395 static inline bool iops_mode(struct cfq_data *cfqd)
396 {
397         /*
398          * If we are not idling on queues and it is a NCQ drive, parallel
399          * execution of requests is on and measuring time is not possible
400          * in most of the cases until and unless we drive shallower queue
401          * depths and that becomes a performance bottleneck. In such cases
402          * switch to start providing fairness in terms of number of IOs.
403          */
404         if (!cfqd->cfq_slice_idle && cfqd->hw_tag)
405                 return true;
406         else
407                 return false;
408 }
409
410 static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
411 {
412         if (cfq_class_idle(cfqq))
413                 return IDLE_WORKLOAD;
414         if (cfq_class_rt(cfqq))
415                 return RT_WORKLOAD;
416         return BE_WORKLOAD;
417 }
418
419
420 static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
421 {
422         if (!cfq_cfqq_sync(cfqq))
423                 return ASYNC_WORKLOAD;
424         if (!cfq_cfqq_idle_window(cfqq))
425                 return SYNC_NOIDLE_WORKLOAD;
426         return SYNC_WORKLOAD;
427 }
428
429 static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl,
430                                         struct cfq_data *cfqd,
431                                         struct cfq_group *cfqg)
432 {
433         if (wl == IDLE_WORKLOAD)
434                 return cfqg->service_tree_idle.count;
435
436         return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
437                 + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
438                 + cfqg->service_trees[wl][SYNC_WORKLOAD].count;
439 }
440
441 static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
442                                         struct cfq_group *cfqg)
443 {
444         return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count
445                 + cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
446 }
447
448 static void cfq_dispatch_insert(struct request_queue *, struct request *);
449 static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
450                                        struct io_context *, gfp_t);
451 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
452                                                 struct io_context *);
453
454 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
455                                             bool is_sync)
456 {
457         return cic->cfqq[is_sync];
458 }
459
460 static inline void cic_set_cfqq(struct cfq_io_context *cic,
461                                 struct cfq_queue *cfqq, bool is_sync)
462 {
463         cic->cfqq[is_sync] = cfqq;
464 }
465
466 #define CIC_DEAD_KEY    1ul
467 #define CIC_DEAD_INDEX_SHIFT    1
468
469 static inline void *cfqd_dead_key(struct cfq_data *cfqd)
470 {
471         return (void *)(cfqd->cic_index << CIC_DEAD_INDEX_SHIFT | CIC_DEAD_KEY);
472 }
473
474 static inline struct cfq_data *cic_to_cfqd(struct cfq_io_context *cic)
475 {
476         struct cfq_data *cfqd = cic->key;
477
478         if (unlikely((unsigned long) cfqd & CIC_DEAD_KEY))
479                 return NULL;
480
481         return cfqd;
482 }
483
484 /*
485  * We regard a request as SYNC, if it's either a read or has the SYNC bit
486  * set (in which case it could also be direct WRITE).
487  */
488 static inline bool cfq_bio_sync(struct bio *bio)
489 {
490         return bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC);
491 }
492
493 /*
494  * scheduler run of queue, if there are requests pending and no one in the
495  * driver that will restart queueing
496  */
497 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
498 {
499         if (cfqd->busy_queues) {
500                 cfq_log(cfqd, "schedule dispatch");
501                 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
502         }
503 }
504
505 /*
506  * Scale schedule slice based on io priority. Use the sync time slice only
507  * if a queue is marked sync and has sync io queued. A sync queue with async
508  * io only, should not get full sync slice length.
509  */
510 static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
511                                  unsigned short prio)
512 {
513         const int base_slice = cfqd->cfq_slice[sync];
514
515         WARN_ON(prio >= IOPRIO_BE_NR);
516
517         return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
518 }
519
520 static inline int
521 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
522 {
523         return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
524 }
525
526 static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
527 {
528         u64 d = delta << CFQ_SERVICE_SHIFT;
529
530         d = d * BLKIO_WEIGHT_DEFAULT;
531         do_div(d, cfqg->weight);
532         return d;
533 }
534
535 static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
536 {
537         s64 delta = (s64)(vdisktime - min_vdisktime);
538         if (delta > 0)
539                 min_vdisktime = vdisktime;
540
541         return min_vdisktime;
542 }
543
544 static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
545 {
546         s64 delta = (s64)(vdisktime - min_vdisktime);
547         if (delta < 0)
548                 min_vdisktime = vdisktime;
549
550         return min_vdisktime;
551 }
552
553 static void update_min_vdisktime(struct cfq_rb_root *st)
554 {
555         struct cfq_group *cfqg;
556
557         if (st->left) {
558                 cfqg = rb_entry_cfqg(st->left);
559                 st->min_vdisktime = max_vdisktime(st->min_vdisktime,
560                                                   cfqg->vdisktime);
561         }
562 }
563
564 /*
565  * get averaged number of queues of RT/BE priority.
566  * average is updated, with a formula that gives more weight to higher numbers,
567  * to quickly follows sudden increases and decrease slowly
568  */
569
570 static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
571                                         struct cfq_group *cfqg, bool rt)
572 {
573         unsigned min_q, max_q;
574         unsigned mult  = cfq_hist_divisor - 1;
575         unsigned round = cfq_hist_divisor / 2;
576         unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
577
578         min_q = min(cfqg->busy_queues_avg[rt], busy);
579         max_q = max(cfqg->busy_queues_avg[rt], busy);
580         cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
581                 cfq_hist_divisor;
582         return cfqg->busy_queues_avg[rt];
583 }
584
585 static inline unsigned
586 cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
587 {
588         struct cfq_rb_root *st = &cfqd->grp_service_tree;
589
590         return cfq_target_latency * cfqg->weight / st->total_weight;
591 }
592
593 static inline unsigned
594 cfq_scaled_cfqq_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
595 {
596         unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
597         if (cfqd->cfq_latency) {
598                 /*
599                  * interested queues (we consider only the ones with the same
600                  * priority class in the cfq group)
601                  */
602                 unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
603                                                 cfq_class_rt(cfqq));
604                 unsigned sync_slice = cfqd->cfq_slice[1];
605                 unsigned expect_latency = sync_slice * iq;
606                 unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
607
608                 if (expect_latency > group_slice) {
609                         unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
610                         /* scale low_slice according to IO priority
611                          * and sync vs async */
612                         unsigned low_slice =
613                                 min(slice, base_low_slice * slice / sync_slice);
614                         /* the adapted slice value is scaled to fit all iqs
615                          * into the target latency */
616                         slice = max(slice * group_slice / expect_latency,
617                                     low_slice);
618                 }
619         }
620         return slice;
621 }
622
623 static inline void
624 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
625 {
626         unsigned slice = cfq_scaled_cfqq_slice(cfqd, cfqq);
627
628         cfqq->slice_start = jiffies;
629         cfqq->slice_end = jiffies + slice;
630         cfqq->allocated_slice = slice;
631         cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
632 }
633
634 /*
635  * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
636  * isn't valid until the first request from the dispatch is activated
637  * and the slice time set.
638  */
639 static inline bool cfq_slice_used(struct cfq_queue *cfqq)
640 {
641         if (cfq_cfqq_slice_new(cfqq))
642                 return false;
643         if (time_before(jiffies, cfqq->slice_end))
644                 return false;
645
646         return true;
647 }
648
649 /*
650  * Lifted from AS - choose which of rq1 and rq2 that is best served now.
651  * We choose the request that is closest to the head right now. Distance
652  * behind the head is penalized and only allowed to a certain extent.
653  */
654 static struct request *
655 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
656 {
657         sector_t s1, s2, d1 = 0, d2 = 0;
658         unsigned long back_max;
659 #define CFQ_RQ1_WRAP    0x01 /* request 1 wraps */
660 #define CFQ_RQ2_WRAP    0x02 /* request 2 wraps */
661         unsigned wrap = 0; /* bit mask: requests behind the disk head? */
662
663         if (rq1 == NULL || rq1 == rq2)
664                 return rq2;
665         if (rq2 == NULL)
666                 return rq1;
667
668         if (rq_is_sync(rq1) && !rq_is_sync(rq2))
669                 return rq1;
670         else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
671                 return rq2;
672         if ((rq1->cmd_flags & REQ_META) && !(rq2->cmd_flags & REQ_META))
673                 return rq1;
674         else if ((rq2->cmd_flags & REQ_META) &&
675                  !(rq1->cmd_flags & REQ_META))
676                 return rq2;
677
678         s1 = blk_rq_pos(rq1);
679         s2 = blk_rq_pos(rq2);
680
681         /*
682          * by definition, 1KiB is 2 sectors
683          */
684         back_max = cfqd->cfq_back_max * 2;
685
686         /*
687          * Strict one way elevator _except_ in the case where we allow
688          * short backward seeks which are biased as twice the cost of a
689          * similar forward seek.
690          */
691         if (s1 >= last)
692                 d1 = s1 - last;
693         else if (s1 + back_max >= last)
694                 d1 = (last - s1) * cfqd->cfq_back_penalty;
695         else
696                 wrap |= CFQ_RQ1_WRAP;
697
698         if (s2 >= last)
699                 d2 = s2 - last;
700         else if (s2 + back_max >= last)
701                 d2 = (last - s2) * cfqd->cfq_back_penalty;
702         else
703                 wrap |= CFQ_RQ2_WRAP;
704
705         /* Found required data */
706
707         /*
708          * By doing switch() on the bit mask "wrap" we avoid having to
709          * check two variables for all permutations: --> faster!
710          */
711         switch (wrap) {
712         case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
713                 if (d1 < d2)
714                         return rq1;
715                 else if (d2 < d1)
716                         return rq2;
717                 else {
718                         if (s1 >= s2)
719                                 return rq1;
720                         else
721                                 return rq2;
722                 }
723
724         case CFQ_RQ2_WRAP:
725                 return rq1;
726         case CFQ_RQ1_WRAP:
727                 return rq2;
728         case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
729         default:
730                 /*
731                  * Since both rqs are wrapped,
732                  * start with the one that's further behind head
733                  * (--> only *one* back seek required),
734                  * since back seek takes more time than forward.
735                  */
736                 if (s1 <= s2)
737                         return rq1;
738                 else
739                         return rq2;
740         }
741 }
742
743 /*
744  * The below is leftmost cache rbtree addon
745  */
746 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
747 {
748         /* Service tree is empty */
749         if (!root->count)
750                 return NULL;
751
752         if (!root->left)
753                 root->left = rb_first(&root->rb);
754
755         if (root->left)
756                 return rb_entry(root->left, struct cfq_queue, rb_node);
757
758         return NULL;
759 }
760
761 static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
762 {
763         if (!root->left)
764                 root->left = rb_first(&root->rb);
765
766         if (root->left)
767                 return rb_entry_cfqg(root->left);
768
769         return NULL;
770 }
771
772 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
773 {
774         rb_erase(n, root);
775         RB_CLEAR_NODE(n);
776 }
777
778 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
779 {
780         if (root->left == n)
781                 root->left = NULL;
782         rb_erase_init(n, &root->rb);
783         --root->count;
784 }
785
786 /*
787  * would be nice to take fifo expire time into account as well
788  */
789 static struct request *
790 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
791                   struct request *last)
792 {
793         struct rb_node *rbnext = rb_next(&last->rb_node);
794         struct rb_node *rbprev = rb_prev(&last->rb_node);
795         struct request *next = NULL, *prev = NULL;
796
797         BUG_ON(RB_EMPTY_NODE(&last->rb_node));
798
799         if (rbprev)
800                 prev = rb_entry_rq(rbprev);
801
802         if (rbnext)
803                 next = rb_entry_rq(rbnext);
804         else {
805                 rbnext = rb_first(&cfqq->sort_list);
806                 if (rbnext && rbnext != &last->rb_node)
807                         next = rb_entry_rq(rbnext);
808         }
809
810         return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
811 }
812
813 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
814                                       struct cfq_queue *cfqq)
815 {
816         /*
817          * just an approximation, should be ok.
818          */
819         return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
820                        cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
821 }
822
823 static inline s64
824 cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
825 {
826         return cfqg->vdisktime - st->min_vdisktime;
827 }
828
829 static void
830 __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
831 {
832         struct rb_node **node = &st->rb.rb_node;
833         struct rb_node *parent = NULL;
834         struct cfq_group *__cfqg;
835         s64 key = cfqg_key(st, cfqg);
836         int left = 1;
837
838         while (*node != NULL) {
839                 parent = *node;
840                 __cfqg = rb_entry_cfqg(parent);
841
842                 if (key < cfqg_key(st, __cfqg))
843                         node = &parent->rb_left;
844                 else {
845                         node = &parent->rb_right;
846                         left = 0;
847                 }
848         }
849
850         if (left)
851                 st->left = &cfqg->rb_node;
852
853         rb_link_node(&cfqg->rb_node, parent, node);
854         rb_insert_color(&cfqg->rb_node, &st->rb);
855 }
856
857 static void
858 cfq_update_group_weight(struct cfq_group *cfqg)
859 {
860         BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
861         if (cfqg->needs_update) {
862                 cfqg->weight = cfqg->new_weight;
863                 cfqg->needs_update = false;
864         }
865 }
866
867 static void
868 cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
869 {
870         BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
871
872         cfq_update_group_weight(cfqg);
873         __cfq_group_service_tree_add(st, cfqg);
874         st->total_weight += cfqg->weight;
875 }
876
877 static void
878 cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
879 {
880         struct cfq_rb_root *st = &cfqd->grp_service_tree;
881         struct cfq_group *__cfqg;
882         struct rb_node *n;
883
884         cfqg->nr_cfqq++;
885         if (!RB_EMPTY_NODE(&cfqg->rb_node))
886                 return;
887
888         /*
889          * Currently put the group at the end. Later implement something
890          * so that groups get lesser vtime based on their weights, so that
891          * if group does not loose all if it was not continously backlogged.
892          */
893         n = rb_last(&st->rb);
894         if (n) {
895                 __cfqg = rb_entry_cfqg(n);
896                 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
897         } else
898                 cfqg->vdisktime = st->min_vdisktime;
899         cfq_group_service_tree_add(st, cfqg);
900 }
901
902 static void
903 cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg)
904 {
905         st->total_weight -= cfqg->weight;
906         if (!RB_EMPTY_NODE(&cfqg->rb_node))
907                 cfq_rb_erase(&cfqg->rb_node, st);
908 }
909
910 static void
911 cfq_group_notify_queue_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
912 {
913         struct cfq_rb_root *st = &cfqd->grp_service_tree;
914
915         BUG_ON(cfqg->nr_cfqq < 1);
916         cfqg->nr_cfqq--;
917
918         /* If there are other cfq queues under this group, don't delete it */
919         if (cfqg->nr_cfqq)
920                 return;
921
922         cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
923         cfq_group_service_tree_del(st, cfqg);
924         cfqg->saved_workload_slice = 0;
925         cfq_blkiocg_update_dequeue_stats(&cfqg->blkg, 1);
926 }
927
928 static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq,
929                                                 unsigned int *unaccounted_time)
930 {
931         unsigned int slice_used;
932
933         /*
934          * Queue got expired before even a single request completed or
935          * got expired immediately after first request completion.
936          */
937         if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
938                 /*
939                  * Also charge the seek time incurred to the group, otherwise
940                  * if there are mutiple queues in the group, each can dispatch
941                  * a single request on seeky media and cause lots of seek time
942                  * and group will never know it.
943                  */
944                 slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
945                                         1);
946         } else {
947                 slice_used = jiffies - cfqq->slice_start;
948                 if (slice_used > cfqq->allocated_slice) {
949                         *unaccounted_time = slice_used - cfqq->allocated_slice;
950                         slice_used = cfqq->allocated_slice;
951                 }
952                 if (time_after(cfqq->slice_start, cfqq->dispatch_start))
953                         *unaccounted_time += cfqq->slice_start -
954                                         cfqq->dispatch_start;
955         }
956
957         return slice_used;
958 }
959
960 static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
961                                 struct cfq_queue *cfqq)
962 {
963         struct cfq_rb_root *st = &cfqd->grp_service_tree;
964         unsigned int used_sl, charge, unaccounted_sl = 0;
965         int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
966                         - cfqg->service_tree_idle.count;
967
968         BUG_ON(nr_sync < 0);
969         used_sl = charge = cfq_cfqq_slice_usage(cfqq, &unaccounted_sl);
970
971         if (iops_mode(cfqd))
972                 charge = cfqq->slice_dispatch;
973         else if (!cfq_cfqq_sync(cfqq) && !nr_sync)
974                 charge = cfqq->allocated_slice;
975
976         /* Can't update vdisktime while group is on service tree */
977         cfq_group_service_tree_del(st, cfqg);
978         cfqg->vdisktime += cfq_scale_slice(charge, cfqg);
979         /* If a new weight was requested, update now, off tree */
980         cfq_group_service_tree_add(st, cfqg);
981
982         /* This group is being expired. Save the context */
983         if (time_after(cfqd->workload_expires, jiffies)) {
984                 cfqg->saved_workload_slice = cfqd->workload_expires
985                                                 - jiffies;
986                 cfqg->saved_workload = cfqd->serving_type;
987                 cfqg->saved_serving_prio = cfqd->serving_prio;
988         } else
989                 cfqg->saved_workload_slice = 0;
990
991         cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
992                                         st->min_vdisktime);
993         cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u disp=%u charge=%u iops=%u"
994                         " sect=%u", used_sl, cfqq->slice_dispatch, charge,
995                         iops_mode(cfqd), cfqq->nr_sectors);
996         cfq_blkiocg_update_timeslice_used(&cfqg->blkg, used_sl,
997                                           unaccounted_sl);
998         cfq_blkiocg_set_start_empty_time(&cfqg->blkg);
999 }
1000
1001 #ifdef CONFIG_CFQ_GROUP_IOSCHED
1002 static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
1003 {
1004         if (blkg)
1005                 return container_of(blkg, struct cfq_group, blkg);
1006         return NULL;
1007 }
1008
1009 void cfq_update_blkio_group_weight(void *key, struct blkio_group *blkg,
1010                                         unsigned int weight)
1011 {
1012         struct cfq_group *cfqg = cfqg_of_blkg(blkg);
1013         cfqg->new_weight = weight;
1014         cfqg->needs_update = true;
1015 }
1016
1017 static struct cfq_group *
1018 cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
1019 {
1020         struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
1021         struct cfq_group *cfqg = NULL;
1022         void *key = cfqd;
1023         int i, j;
1024         struct cfq_rb_root *st;
1025         struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
1026         unsigned int major, minor;
1027
1028         cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
1029         if (cfqg && !cfqg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
1030                 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
1031                 cfqg->blkg.dev = MKDEV(major, minor);
1032                 goto done;
1033         }
1034         if (cfqg || !create)
1035                 goto done;
1036
1037         cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
1038         if (!cfqg)
1039                 goto done;
1040
1041         for_each_cfqg_st(cfqg, i, j, st)
1042                 *st = CFQ_RB_ROOT;
1043         RB_CLEAR_NODE(&cfqg->rb_node);
1044
1045         /*
1046          * Take the initial reference that will be released on destroy
1047          * This can be thought of a joint reference by cgroup and
1048          * elevator which will be dropped by either elevator exit
1049          * or cgroup deletion path depending on who is exiting first.
1050          */
1051         cfqg->ref = 1;
1052
1053         /*
1054          * Add group onto cgroup list. It might happen that bdi->dev is
1055          * not initialized yet. Initialize this new group without major
1056          * and minor info and this info will be filled in once a new thread
1057          * comes for IO. See code above.
1058          */
1059         if (bdi->dev) {
1060                 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
1061                 cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
1062                                         MKDEV(major, minor));
1063         } else
1064                 cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
1065                                         0);
1066
1067         cfqg->weight = blkcg_get_weight(blkcg, cfqg->blkg.dev);
1068
1069         /* Add group on cfqd list */
1070         hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
1071
1072 done:
1073         return cfqg;
1074 }
1075
1076 /*
1077  * Search for the cfq group current task belongs to. If create = 1, then also
1078  * create the cfq group if it does not exist. request_queue lock must be held.
1079  */
1080 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
1081 {
1082         struct cgroup *cgroup;
1083         struct cfq_group *cfqg = NULL;
1084
1085         rcu_read_lock();
1086         cgroup = task_cgroup(current, blkio_subsys_id);
1087         cfqg = cfq_find_alloc_cfqg(cfqd, cgroup, create);
1088         if (!cfqg && create)
1089                 cfqg = &cfqd->root_group;
1090         rcu_read_unlock();
1091         return cfqg;
1092 }
1093
1094 static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
1095 {
1096         cfqg->ref++;
1097         return cfqg;
1098 }
1099
1100 static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
1101 {
1102         /* Currently, all async queues are mapped to root group */
1103         if (!cfq_cfqq_sync(cfqq))
1104                 cfqg = &cfqq->cfqd->root_group;
1105
1106         cfqq->cfqg = cfqg;
1107         /* cfqq reference on cfqg */
1108         cfqq->cfqg->ref++;
1109 }
1110
1111 static void cfq_put_cfqg(struct cfq_group *cfqg)
1112 {
1113         struct cfq_rb_root *st;
1114         int i, j;
1115
1116         BUG_ON(cfqg->ref <= 0);
1117         cfqg->ref--;
1118         if (cfqg->ref)
1119                 return;
1120         for_each_cfqg_st(cfqg, i, j, st)
1121                 BUG_ON(!RB_EMPTY_ROOT(&st->rb));
1122         kfree(cfqg);
1123 }
1124
1125 static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
1126 {
1127         /* Something wrong if we are trying to remove same group twice */
1128         BUG_ON(hlist_unhashed(&cfqg->cfqd_node));
1129
1130         hlist_del_init(&cfqg->cfqd_node);
1131
1132         /*
1133          * Put the reference taken at the time of creation so that when all
1134          * queues are gone, group can be destroyed.
1135          */
1136         cfq_put_cfqg(cfqg);
1137 }
1138
1139 static void cfq_release_cfq_groups(struct cfq_data *cfqd)
1140 {
1141         struct hlist_node *pos, *n;
1142         struct cfq_group *cfqg;
1143
1144         hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) {
1145                 /*
1146                  * If cgroup removal path got to blk_group first and removed
1147                  * it from cgroup list, then it will take care of destroying
1148                  * cfqg also.
1149                  */
1150                 if (!cfq_blkiocg_del_blkio_group(&cfqg->blkg))
1151                         cfq_destroy_cfqg(cfqd, cfqg);
1152         }
1153 }
1154
1155 /*
1156  * Blk cgroup controller notification saying that blkio_group object is being
1157  * delinked as associated cgroup object is going away. That also means that
1158  * no new IO will come in this group. So get rid of this group as soon as
1159  * any pending IO in the group is finished.
1160  *
1161  * This function is called under rcu_read_lock(). key is the rcu protected
1162  * pointer. That means "key" is a valid cfq_data pointer as long as we are rcu
1163  * read lock.
1164  *
1165  * "key" was fetched from blkio_group under blkio_cgroup->lock. That means
1166  * it should not be NULL as even if elevator was exiting, cgroup deltion
1167  * path got to it first.
1168  */
1169 void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
1170 {
1171         unsigned long  flags;
1172         struct cfq_data *cfqd = key;
1173
1174         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1175         cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg));
1176         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1177 }
1178
1179 #else /* GROUP_IOSCHED */
1180 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
1181 {
1182         return &cfqd->root_group;
1183 }
1184
1185 static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
1186 {
1187         return cfqg;
1188 }
1189
1190 static inline void
1191 cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
1192         cfqq->cfqg = cfqg;
1193 }
1194
1195 static void cfq_release_cfq_groups(struct cfq_data *cfqd) {}
1196 static inline void cfq_put_cfqg(struct cfq_group *cfqg) {}
1197
1198 #endif /* GROUP_IOSCHED */
1199
1200 /*
1201  * The cfqd->service_trees holds all pending cfq_queue's that have
1202  * requests waiting to be processed. It is sorted in the order that
1203  * we will service the queues.
1204  */
1205 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1206                                  bool add_front)
1207 {
1208         struct rb_node **p, *parent;
1209         struct cfq_queue *__cfqq;
1210         unsigned long rb_key;
1211         struct cfq_rb_root *service_tree;
1212         int left;
1213         int new_cfqq = 1;
1214         int group_changed = 0;
1215
1216         service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
1217                                                 cfqq_type(cfqq));
1218         if (cfq_class_idle(cfqq)) {
1219                 rb_key = CFQ_IDLE_DELAY;
1220                 parent = rb_last(&service_tree->rb);
1221                 if (parent && parent != &cfqq->rb_node) {
1222                         __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1223                         rb_key += __cfqq->rb_key;
1224                 } else
1225                         rb_key += jiffies;
1226         } else if (!add_front) {
1227                 /*
1228                  * Get our rb key offset. Subtract any residual slice
1229                  * value carried from last service. A negative resid
1230                  * count indicates slice overrun, and this should position
1231                  * the next service time further away in the tree.
1232                  */
1233                 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
1234                 rb_key -= cfqq->slice_resid;
1235                 cfqq->slice_resid = 0;
1236         } else {
1237                 rb_key = -HZ;
1238                 __cfqq = cfq_rb_first(service_tree);
1239                 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
1240         }
1241
1242         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1243                 new_cfqq = 0;
1244                 /*
1245                  * same position, nothing more to do
1246                  */
1247                 if (rb_key == cfqq->rb_key &&
1248                     cfqq->service_tree == service_tree)
1249                         return;
1250
1251                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1252                 cfqq->service_tree = NULL;
1253         }
1254
1255         left = 1;
1256         parent = NULL;
1257         cfqq->service_tree = service_tree;
1258         p = &service_tree->rb.rb_node;
1259         while (*p) {
1260                 struct rb_node **n;
1261
1262                 parent = *p;
1263                 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1264
1265                 /*
1266                  * sort by key, that represents service time.
1267                  */
1268                 if (time_before(rb_key, __cfqq->rb_key))
1269                         n = &(*p)->rb_left;
1270                 else {
1271                         n = &(*p)->rb_right;
1272                         left = 0;
1273                 }
1274
1275                 p = n;
1276         }
1277
1278         if (left)
1279                 service_tree->left = &cfqq->rb_node;
1280
1281         cfqq->rb_key = rb_key;
1282         rb_link_node(&cfqq->rb_node, parent, p);
1283         rb_insert_color(&cfqq->rb_node, &service_tree->rb);
1284         service_tree->count++;
1285         if ((add_front || !new_cfqq) && !group_changed)
1286                 return;
1287         cfq_group_notify_queue_add(cfqd, cfqq->cfqg);
1288 }
1289
1290 static struct cfq_queue *
1291 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
1292                      sector_t sector, struct rb_node **ret_parent,
1293                      struct rb_node ***rb_link)
1294 {
1295         struct rb_node **p, *parent;
1296         struct cfq_queue *cfqq = NULL;
1297
1298         parent = NULL;
1299         p = &root->rb_node;
1300         while (*p) {
1301                 struct rb_node **n;
1302
1303                 parent = *p;
1304                 cfqq = rb_entry(parent, struct cfq_queue, p_node);
1305
1306                 /*
1307                  * Sort strictly based on sector.  Smallest to the left,
1308                  * largest to the right.
1309                  */
1310                 if (sector > blk_rq_pos(cfqq->next_rq))
1311                         n = &(*p)->rb_right;
1312                 else if (sector < blk_rq_pos(cfqq->next_rq))
1313                         n = &(*p)->rb_left;
1314                 else
1315                         break;
1316                 p = n;
1317                 cfqq = NULL;
1318         }
1319
1320         *ret_parent = parent;
1321         if (rb_link)
1322                 *rb_link = p;
1323         return cfqq;
1324 }
1325
1326 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1327 {
1328         struct rb_node **p, *parent;
1329         struct cfq_queue *__cfqq;
1330
1331         if (cfqq->p_root) {
1332                 rb_erase(&cfqq->p_node, cfqq->p_root);
1333                 cfqq->p_root = NULL;
1334         }
1335
1336         if (cfq_class_idle(cfqq))
1337                 return;
1338         if (!cfqq->next_rq)
1339                 return;
1340
1341         cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
1342         __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
1343                                       blk_rq_pos(cfqq->next_rq), &parent, &p);
1344         if (!__cfqq) {
1345                 rb_link_node(&cfqq->p_node, parent, p);
1346                 rb_insert_color(&cfqq->p_node, cfqq->p_root);
1347         } else
1348                 cfqq->p_root = NULL;
1349 }
1350
1351 /*
1352  * Update cfqq's position in the service tree.
1353  */
1354 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1355 {
1356         /*
1357          * Resorting requires the cfqq to be on the RR list already.
1358          */
1359         if (cfq_cfqq_on_rr(cfqq)) {
1360                 cfq_service_tree_add(cfqd, cfqq, 0);
1361                 cfq_prio_tree_add(cfqd, cfqq);
1362         }
1363 }
1364
1365 /*
1366  * add to busy list of queues for service, trying to be fair in ordering
1367  * the pending list according to last request service
1368  */
1369 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1370 {
1371         cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
1372         BUG_ON(cfq_cfqq_on_rr(cfqq));
1373         cfq_mark_cfqq_on_rr(cfqq);
1374         cfqd->busy_queues++;
1375         if (cfq_cfqq_sync(cfqq))
1376                 cfqd->busy_sync_queues++;
1377
1378         cfq_resort_rr_list(cfqd, cfqq);
1379 }
1380
1381 /*
1382  * Called when the cfqq no longer has requests pending, remove it from
1383  * the service tree.
1384  */
1385 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1386 {
1387         cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
1388         BUG_ON(!cfq_cfqq_on_rr(cfqq));
1389         cfq_clear_cfqq_on_rr(cfqq);
1390
1391         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1392                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1393                 cfqq->service_tree = NULL;
1394         }
1395         if (cfqq->p_root) {
1396                 rb_erase(&cfqq->p_node, cfqq->p_root);
1397                 cfqq->p_root = NULL;
1398         }
1399
1400         cfq_group_notify_queue_del(cfqd, cfqq->cfqg);
1401         BUG_ON(!cfqd->busy_queues);
1402         cfqd->busy_queues--;
1403         if (cfq_cfqq_sync(cfqq))
1404                 cfqd->busy_sync_queues--;
1405 }
1406
1407 /*
1408  * rb tree support functions
1409  */
1410 static void cfq_del_rq_rb(struct request *rq)
1411 {
1412         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1413         const int sync = rq_is_sync(rq);
1414
1415         BUG_ON(!cfqq->queued[sync]);
1416         cfqq->queued[sync]--;
1417
1418         elv_rb_del(&cfqq->sort_list, rq);
1419
1420         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1421                 /*
1422                  * Queue will be deleted from service tree when we actually
1423                  * expire it later. Right now just remove it from prio tree
1424                  * as it is empty.
1425                  */
1426                 if (cfqq->p_root) {
1427                         rb_erase(&cfqq->p_node, cfqq->p_root);
1428                         cfqq->p_root = NULL;
1429                 }
1430         }
1431 }
1432
1433 static void cfq_add_rq_rb(struct request *rq)
1434 {
1435         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1436         struct cfq_data *cfqd = cfqq->cfqd;
1437         struct request *__alias, *prev;
1438
1439         cfqq->queued[rq_is_sync(rq)]++;
1440
1441         /*
1442          * looks a little odd, but the first insert might return an alias.
1443          * if that happens, put the alias on the dispatch list
1444          */
1445         while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
1446                 cfq_dispatch_insert(cfqd->queue, __alias);
1447
1448         if (!cfq_cfqq_on_rr(cfqq))
1449                 cfq_add_cfqq_rr(cfqd, cfqq);
1450
1451         /*
1452          * check if this request is a better next-serve candidate
1453          */
1454         prev = cfqq->next_rq;
1455         cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
1456
1457         /*
1458          * adjust priority tree position, if ->next_rq changes
1459          */
1460         if (prev != cfqq->next_rq)
1461                 cfq_prio_tree_add(cfqd, cfqq);
1462
1463         BUG_ON(!cfqq->next_rq);
1464 }
1465
1466 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
1467 {
1468         elv_rb_del(&cfqq->sort_list, rq);
1469         cfqq->queued[rq_is_sync(rq)]--;
1470         cfq_blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg,
1471                                         rq_data_dir(rq), rq_is_sync(rq));
1472         cfq_add_rq_rb(rq);
1473         cfq_blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg,
1474                         &cfqq->cfqd->serving_group->blkg, rq_data_dir(rq),
1475                         rq_is_sync(rq));
1476 }
1477
1478 static struct request *
1479 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
1480 {
1481         struct task_struct *tsk = current;
1482         struct cfq_io_context *cic;
1483         struct cfq_queue *cfqq;
1484
1485         cic = cfq_cic_lookup(cfqd, tsk->io_context);
1486         if (!cic)
1487                 return NULL;
1488
1489         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1490         if (cfqq) {
1491                 sector_t sector = bio->bi_sector + bio_sectors(bio);
1492
1493                 return elv_rb_find(&cfqq->sort_list, sector);
1494         }
1495
1496         return NULL;
1497 }
1498
1499 static void cfq_activate_request(struct request_queue *q, struct request *rq)
1500 {
1501         struct cfq_data *cfqd = q->elevator->elevator_data;
1502
1503         cfqd->rq_in_driver++;
1504         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
1505                                                 cfqd->rq_in_driver);
1506
1507         cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
1508 }
1509
1510 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
1511 {
1512         struct cfq_data *cfqd = q->elevator->elevator_data;
1513
1514         WARN_ON(!cfqd->rq_in_driver);
1515         cfqd->rq_in_driver--;
1516         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
1517                                                 cfqd->rq_in_driver);
1518 }
1519
1520 static void cfq_remove_request(struct request *rq)
1521 {
1522         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1523
1524         if (cfqq->next_rq == rq)
1525                 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
1526
1527         list_del_init(&rq->queuelist);
1528         cfq_del_rq_rb(rq);
1529
1530         cfqq->cfqd->rq_queued--;
1531         cfq_blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg,
1532                                         rq_data_dir(rq), rq_is_sync(rq));
1533         if (rq->cmd_flags & REQ_META) {
1534                 WARN_ON(!cfqq->meta_pending);
1535                 cfqq->meta_pending--;
1536         }
1537 }
1538
1539 static int cfq_merge(struct request_queue *q, struct request **req,
1540                      struct bio *bio)
1541 {
1542         struct cfq_data *cfqd = q->elevator->elevator_data;
1543         struct request *__rq;
1544
1545         __rq = cfq_find_rq_fmerge(cfqd, bio);
1546         if (__rq && elv_rq_merge_ok(__rq, bio)) {
1547                 *req = __rq;
1548                 return ELEVATOR_FRONT_MERGE;
1549         }
1550
1551         return ELEVATOR_NO_MERGE;
1552 }
1553
1554 static void cfq_merged_request(struct request_queue *q, struct request *req,
1555                                int type)
1556 {
1557         if (type == ELEVATOR_FRONT_MERGE) {
1558                 struct cfq_queue *cfqq = RQ_CFQQ(req);
1559
1560                 cfq_reposition_rq_rb(cfqq, req);
1561         }
1562 }
1563
1564 static void cfq_bio_merged(struct request_queue *q, struct request *req,
1565                                 struct bio *bio)
1566 {
1567         cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(req))->blkg,
1568                                         bio_data_dir(bio), cfq_bio_sync(bio));
1569 }
1570
1571 static void
1572 cfq_merged_requests(struct request_queue *q, struct request *rq,
1573                     struct request *next)
1574 {
1575         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1576         /*
1577          * reposition in fifo if next is older than rq
1578          */
1579         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
1580             time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
1581                 list_move(&rq->queuelist, &next->queuelist);
1582                 rq_set_fifo_time(rq, rq_fifo_time(next));
1583         }
1584
1585         if (cfqq->next_rq == next)
1586                 cfqq->next_rq = rq;
1587         cfq_remove_request(next);
1588         cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(rq))->blkg,
1589                                         rq_data_dir(next), rq_is_sync(next));
1590 }
1591
1592 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
1593                            struct bio *bio)
1594 {
1595         struct cfq_data *cfqd = q->elevator->elevator_data;
1596         struct cfq_io_context *cic;
1597         struct cfq_queue *cfqq;
1598
1599         /*
1600          * Disallow merge of a sync bio into an async request.
1601          */
1602         if (cfq_bio_sync(bio) && !rq_is_sync(rq))
1603                 return false;
1604
1605         /*
1606          * Lookup the cfqq that this bio will be queued with. Allow
1607          * merge only if rq is queued there.
1608          */
1609         cic = cfq_cic_lookup(cfqd, current->io_context);
1610         if (!cic)
1611                 return false;
1612
1613         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
1614         return cfqq == RQ_CFQQ(rq);
1615 }
1616
1617 static inline void cfq_del_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1618 {
1619         del_timer(&cfqd->idle_slice_timer);
1620         cfq_blkiocg_update_idle_time_stats(&cfqq->cfqg->blkg);
1621 }
1622
1623 static void cfq_clear_queue_stats(struct cfq_data *cfqd,
1624                                   struct cfq_queue *cfqq)
1625 {
1626         cfq_blkiocg_update_avg_queue_size_stats(&cfqq->cfqg->blkg);
1627         cfqq->slice_start = 0;
1628         cfqq->dispatch_start = jiffies;
1629         cfqq->allocated_slice = 0;
1630         cfqq->slice_end = 0;
1631         cfqq->slice_dispatch = 0;
1632         cfqq->nr_sectors = 0;
1633
1634         cfq_clear_cfqq_wait_request(cfqq);
1635         cfq_clear_cfqq_must_dispatch(cfqq);
1636         cfq_clear_cfqq_must_alloc_slice(cfqq);
1637         cfq_clear_cfqq_fifo_expire(cfqq);
1638         cfq_mark_cfqq_slice_new(cfqq);
1639
1640         cfq_del_timer(cfqd, cfqq);
1641 }
1642
1643 static void __cfq_set_active_queue(struct cfq_data *cfqd,
1644                                    struct cfq_queue *cfqq)
1645 {
1646         if (cfqq) {
1647                 cfq_log_cfqq(cfqd, cfqq, "set_active wl_prio:%d wl_type:%d",
1648                                 cfqd->serving_prio, cfqd->serving_type);
1649                 cfq_clear_queue_stats(cfqd, cfqq);
1650         }
1651
1652         cfqd->active_queue = cfqq;
1653 }
1654
1655 /*
1656  * current cfqq expired its slice (or was too idle), select new one
1657  */
1658 static void
1659 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1660                     bool timed_out)
1661 {
1662         cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
1663
1664         if (cfq_cfqq_wait_request(cfqq))
1665                 cfq_del_timer(cfqd, cfqq);
1666
1667         cfq_clear_cfqq_wait_request(cfqq);
1668         cfq_clear_cfqq_wait_busy(cfqq);
1669
1670         /*
1671          * If this cfqq is shared between multiple processes, check to
1672          * make sure that those processes are still issuing I/Os within
1673          * the mean seek distance.  If not, it may be time to break the
1674          * queues apart again.
1675          */
1676         if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq))
1677                 cfq_mark_cfqq_split_coop(cfqq);
1678
1679         /*
1680          * store what was left of this slice, if the queue idled/timed out
1681          */
1682         if (timed_out) {
1683                 if (cfq_cfqq_slice_new(cfqq))
1684                         cfqq->slice_resid = cfq_scaled_cfqq_slice(cfqd, cfqq);
1685                 else
1686                         cfqq->slice_resid = cfqq->slice_end - jiffies;
1687                 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
1688         }
1689
1690         cfq_group_served(cfqd, cfqq->cfqg, cfqq);
1691
1692         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
1693                 cfq_del_cfqq_rr(cfqd, cfqq);
1694
1695         cfq_resort_rr_list(cfqd, cfqq);
1696
1697         if (cfqq == cfqd->active_queue)
1698                 cfqd->active_queue = NULL;
1699
1700         if (cfqd->active_cic) {
1701                 put_io_context(cfqd->active_cic->ioc);
1702                 cfqd->active_cic = NULL;
1703         }
1704 }
1705
1706 static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
1707 {
1708         struct cfq_queue *cfqq = cfqd->active_queue;
1709
1710         if (cfqq)
1711                 __cfq_slice_expired(cfqd, cfqq, timed_out);
1712 }
1713
1714 /*
1715  * Get next queue for service. Unless we have a queue preemption,
1716  * we'll simply select the first cfqq in the service tree.
1717  */
1718 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
1719 {
1720         struct cfq_rb_root *service_tree =
1721                 service_tree_for(cfqd->serving_group, cfqd->serving_prio,
1722                                         cfqd->serving_type);
1723
1724         if (!cfqd->rq_queued)
1725                 return NULL;
1726
1727         /* There is nothing to dispatch */
1728         if (!service_tree)
1729                 return NULL;
1730         if (RB_EMPTY_ROOT(&service_tree->rb))
1731                 return NULL;
1732         return cfq_rb_first(service_tree);
1733 }
1734
1735 static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
1736 {
1737         struct cfq_group *cfqg;
1738         struct cfq_queue *cfqq;
1739         int i, j;
1740         struct cfq_rb_root *st;
1741
1742         if (!cfqd->rq_queued)
1743                 return NULL;
1744
1745         cfqg = cfq_get_next_cfqg(cfqd);
1746         if (!cfqg)
1747                 return NULL;
1748
1749         for_each_cfqg_st(cfqg, i, j, st)
1750                 if ((cfqq = cfq_rb_first(st)) != NULL)
1751                         return cfqq;
1752         return NULL;
1753 }
1754
1755 /*
1756  * Get and set a new active queue for service.
1757  */
1758 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
1759                                               struct cfq_queue *cfqq)
1760 {
1761         if (!cfqq)
1762                 cfqq = cfq_get_next_queue(cfqd);
1763
1764         __cfq_set_active_queue(cfqd, cfqq);
1765         return cfqq;
1766 }
1767
1768 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
1769                                           struct request *rq)
1770 {
1771         if (blk_rq_pos(rq) >= cfqd->last_position)
1772                 return blk_rq_pos(rq) - cfqd->last_position;
1773         else
1774                 return cfqd->last_position - blk_rq_pos(rq);
1775 }
1776
1777 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1778                                struct request *rq)
1779 {
1780         return cfq_dist_from_last(cfqd, rq) <= CFQQ_CLOSE_THR;
1781 }
1782
1783 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
1784                                     struct cfq_queue *cur_cfqq)
1785 {
1786         struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
1787         struct rb_node *parent, *node;
1788         struct cfq_queue *__cfqq;
1789         sector_t sector = cfqd->last_position;
1790
1791         if (RB_EMPTY_ROOT(root))
1792                 return NULL;
1793
1794         /*
1795          * First, if we find a request starting at the end of the last
1796          * request, choose it.
1797          */
1798         __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
1799         if (__cfqq)
1800                 return __cfqq;
1801
1802         /*
1803          * If the exact sector wasn't found, the parent of the NULL leaf
1804          * will contain the closest sector.
1805          */
1806         __cfqq = rb_entry(parent, struct cfq_queue, p_node);
1807         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1808                 return __cfqq;
1809
1810         if (blk_rq_pos(__cfqq->next_rq) < sector)
1811                 node = rb_next(&__cfqq->p_node);
1812         else
1813                 node = rb_prev(&__cfqq->p_node);
1814         if (!node)
1815                 return NULL;
1816
1817         __cfqq = rb_entry(node, struct cfq_queue, p_node);
1818         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
1819                 return __cfqq;
1820
1821         return NULL;
1822 }
1823
1824 /*
1825  * cfqd - obvious
1826  * cur_cfqq - passed in so that we don't decide that the current queue is
1827  *            closely cooperating with itself.
1828  *
1829  * So, basically we're assuming that that cur_cfqq has dispatched at least
1830  * one request, and that cfqd->last_position reflects a position on the disk
1831  * associated with the I/O issued by cur_cfqq.  I'm not sure this is a valid
1832  * assumption.
1833  */
1834 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
1835                                               struct cfq_queue *cur_cfqq)
1836 {
1837         struct cfq_queue *cfqq;
1838
1839         if (cfq_class_idle(cur_cfqq))
1840                 return NULL;
1841         if (!cfq_cfqq_sync(cur_cfqq))
1842                 return NULL;
1843         if (CFQQ_SEEKY(cur_cfqq))
1844                 return NULL;
1845
1846         /*
1847          * Don't search priority tree if it's the only queue in the group.
1848          */
1849         if (cur_cfqq->cfqg->nr_cfqq == 1)
1850                 return NULL;
1851
1852         /*
1853          * We should notice if some of the queues are cooperating, eg
1854          * working closely on the same area of the disk. In that case,
1855          * we can group them together and don't waste time idling.
1856          */
1857         cfqq = cfqq_close(cfqd, cur_cfqq);
1858         if (!cfqq)
1859                 return NULL;
1860
1861         /* If new queue belongs to different cfq_group, don't choose it */
1862         if (cur_cfqq->cfqg != cfqq->cfqg)
1863                 return NULL;
1864
1865         /*
1866          * It only makes sense to merge sync queues.
1867          */
1868         if (!cfq_cfqq_sync(cfqq))
1869                 return NULL;
1870         if (CFQQ_SEEKY(cfqq))
1871                 return NULL;
1872
1873         /*
1874          * Do not merge queues of different priority classes
1875          */
1876         if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
1877                 return NULL;
1878
1879         return cfqq;
1880 }
1881
1882 /*
1883  * Determine whether we should enforce idle window for this queue.
1884  */
1885
1886 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1887 {
1888         enum wl_prio_t prio = cfqq_prio(cfqq);
1889         struct cfq_rb_root *service_tree = cfqq->service_tree;
1890
1891         BUG_ON(!service_tree);
1892         BUG_ON(!service_tree->count);
1893
1894         if (!cfqd->cfq_slice_idle)
1895                 return false;
1896
1897         /* We never do for idle class queues. */
1898         if (prio == IDLE_WORKLOAD)
1899                 return false;
1900
1901         /* We do for queues that were marked with idle window flag. */
1902         if (cfq_cfqq_idle_window(cfqq) &&
1903            !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag))
1904                 return true;
1905
1906         /*
1907          * Otherwise, we do only if they are the last ones
1908          * in their service tree.
1909          */
1910         if (service_tree->count == 1 && cfq_cfqq_sync(cfqq))
1911                 return true;
1912         cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d",
1913                         service_tree->count);
1914         return false;
1915 }
1916
1917 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
1918 {
1919         struct cfq_queue *cfqq = cfqd->active_queue;
1920         struct cfq_io_context *cic;
1921         unsigned long sl, group_idle = 0;
1922
1923         /*
1924          * SSD device without seek penalty, disable idling. But only do so
1925          * for devices that support queuing, otherwise we still have a problem
1926          * with sync vs async workloads.
1927          */
1928         if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
1929                 return;
1930
1931         WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
1932         WARN_ON(cfq_cfqq_slice_new(cfqq));
1933
1934         /*
1935          * idle is disabled, either manually or by past process history
1936          */
1937         if (!cfq_should_idle(cfqd, cfqq)) {
1938                 /* no queue idling. Check for group idling */
1939                 if (cfqd->cfq_group_idle)
1940                         group_idle = cfqd->cfq_group_idle;
1941                 else
1942                         return;
1943         }
1944
1945         /*
1946          * still active requests from this queue, don't idle
1947          */
1948         if (cfqq->dispatched)
1949                 return;
1950
1951         /*
1952          * task has exited, don't wait
1953          */
1954         cic = cfqd->active_cic;
1955         if (!cic || !atomic_read(&cic->ioc->nr_tasks))
1956                 return;
1957
1958         /*
1959          * If our average think time is larger than the remaining time
1960          * slice, then don't idle. This avoids overrunning the allotted
1961          * time slice.
1962          */
1963         if (sample_valid(cic->ttime_samples) &&
1964             (cfqq->slice_end - jiffies < cic->ttime_mean)) {
1965                 cfq_log_cfqq(cfqd, cfqq, "Not idling. think_time:%d",
1966                                 cic->ttime_mean);
1967                 return;
1968         }
1969
1970         /* There are other queues in the group, don't do group idle */
1971         if (group_idle && cfqq->cfqg->nr_cfqq > 1)
1972                 return;
1973
1974         cfq_mark_cfqq_wait_request(cfqq);
1975
1976         if (group_idle)
1977                 sl = cfqd->cfq_group_idle;
1978         else
1979                 sl = cfqd->cfq_slice_idle;
1980
1981         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
1982         cfq_blkiocg_update_set_idle_time_stats(&cfqq->cfqg->blkg);
1983         cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu group_idle: %d", sl,
1984                         group_idle ? 1 : 0);
1985 }
1986
1987 /*
1988  * Move request from internal lists to the request queue dispatch list.
1989  */
1990 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
1991 {
1992         struct cfq_data *cfqd = q->elevator->elevator_data;
1993         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1994
1995         cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
1996
1997         cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
1998         cfq_remove_request(rq);
1999         cfqq->dispatched++;
2000         (RQ_CFQG(rq))->dispatched++;
2001         elv_dispatch_sort(q, rq);
2002
2003         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
2004         cfqq->nr_sectors += blk_rq_sectors(rq);
2005         cfq_blkiocg_update_dispatch_stats(&cfqq->cfqg->blkg, blk_rq_bytes(rq),
2006                                         rq_data_dir(rq), rq_is_sync(rq));
2007 }
2008
2009 /*
2010  * return expired entry, or NULL to just start from scratch in rbtree
2011  */
2012 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
2013 {
2014         struct request *rq = NULL;
2015
2016         if (cfq_cfqq_fifo_expire(cfqq))
2017                 return NULL;
2018
2019         cfq_mark_cfqq_fifo_expire(cfqq);
2020
2021         if (list_empty(&cfqq->fifo))
2022                 return NULL;
2023
2024         rq = rq_entry_fifo(cfqq->fifo.next);
2025         if (time_before(jiffies, rq_fifo_time(rq)))
2026                 rq = NULL;
2027
2028         cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
2029         return rq;
2030 }
2031
2032 static inline int
2033 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2034 {
2035         const int base_rq = cfqd->cfq_slice_async_rq;
2036
2037         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
2038
2039         return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
2040 }
2041
2042 /*
2043  * Must be called with the queue_lock held.
2044  */
2045 static int cfqq_process_refs(struct cfq_queue *cfqq)
2046 {
2047         int process_refs, io_refs;
2048
2049         io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
2050         process_refs = cfqq->ref - io_refs;
2051         BUG_ON(process_refs < 0);
2052         return process_refs;
2053 }
2054
2055 static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
2056 {
2057         int process_refs, new_process_refs;
2058         struct cfq_queue *__cfqq;
2059
2060         /*
2061          * If there are no process references on the new_cfqq, then it is
2062          * unsafe to follow the ->new_cfqq chain as other cfqq's in the
2063          * chain may have dropped their last reference (not just their
2064          * last process reference).
2065          */
2066         if (!cfqq_process_refs(new_cfqq))
2067                 return;
2068
2069         /* Avoid a circular list and skip interim queue merges */
2070         while ((__cfqq = new_cfqq->new_cfqq)) {
2071                 if (__cfqq == cfqq)
2072                         return;
2073                 new_cfqq = __cfqq;
2074         }
2075
2076         process_refs = cfqq_process_refs(cfqq);
2077         new_process_refs = cfqq_process_refs(new_cfqq);
2078         /*
2079          * If the process for the cfqq has gone away, there is no
2080          * sense in merging the queues.
2081          */
2082         if (process_refs == 0 || new_process_refs == 0)
2083                 return;
2084
2085         /*
2086          * Merge in the direction of the lesser amount of work.
2087          */
2088         if (new_process_refs >= process_refs) {
2089                 cfqq->new_cfqq = new_cfqq;
2090                 new_cfqq->ref += process_refs;
2091         } else {
2092                 new_cfqq->new_cfqq = cfqq;
2093                 cfqq->ref += new_process_refs;
2094         }
2095 }
2096
2097 static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
2098                                 struct cfq_group *cfqg, enum wl_prio_t prio)
2099 {
2100         struct cfq_queue *queue;
2101         int i;
2102         bool key_valid = false;
2103         unsigned long lowest_key = 0;
2104         enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
2105
2106         for (i = 0; i <= SYNC_WORKLOAD; ++i) {
2107                 /* select the one with lowest rb_key */
2108                 queue = cfq_rb_first(service_tree_for(cfqg, prio, i));
2109                 if (queue &&
2110                     (!key_valid || time_before(queue->rb_key, lowest_key))) {
2111                         lowest_key = queue->rb_key;
2112                         cur_best = i;
2113                         key_valid = true;
2114                 }
2115         }
2116
2117         return cur_best;
2118 }
2119
2120 static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
2121 {
2122         unsigned slice;
2123         unsigned count;
2124         struct cfq_rb_root *st;
2125         unsigned group_slice;
2126         enum wl_prio_t original_prio = cfqd->serving_prio;
2127
2128         /* Choose next priority. RT > BE > IDLE */
2129         if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
2130                 cfqd->serving_prio = RT_WORKLOAD;
2131         else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
2132                 cfqd->serving_prio = BE_WORKLOAD;
2133         else {
2134                 cfqd->serving_prio = IDLE_WORKLOAD;
2135                 cfqd->workload_expires = jiffies + 1;
2136                 return;
2137         }
2138
2139         if (original_prio != cfqd->serving_prio)
2140                 goto new_workload;
2141
2142         /*
2143          * For RT and BE, we have to choose also the type
2144          * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
2145          * expiration time
2146          */
2147         st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
2148         count = st->count;
2149
2150         /*
2151          * check workload expiration, and that we still have other queues ready
2152          */
2153         if (count && !time_after(jiffies, cfqd->workload_expires))
2154                 return;
2155
2156 new_workload:
2157         /* otherwise select new workload type */
2158         cfqd->serving_type =
2159                 cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio);
2160         st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
2161         count = st->count;
2162
2163         /*
2164          * the workload slice is computed as a fraction of target latency
2165          * proportional to the number of queues in that workload, over
2166          * all the queues in the same priority class
2167          */
2168         group_slice = cfq_group_slice(cfqd, cfqg);
2169
2170         slice = group_slice * count /
2171                 max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio],
2172                       cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg));
2173
2174         if (cfqd->serving_type == ASYNC_WORKLOAD) {
2175                 unsigned int tmp;
2176
2177                 /*
2178                  * Async queues are currently system wide. Just taking
2179                  * proportion of queues with-in same group will lead to higher
2180                  * async ratio system wide as generally root group is going
2181                  * to have higher weight. A more accurate thing would be to
2182                  * calculate system wide asnc/sync ratio.
2183                  */
2184                 tmp = cfq_target_latency * cfqg_busy_async_queues(cfqd, cfqg);
2185                 tmp = tmp/cfqd->busy_queues;
2186                 slice = min_t(unsigned, slice, tmp);
2187
2188                 /* async workload slice is scaled down according to
2189                  * the sync/async slice ratio. */
2190                 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
2191         } else
2192                 /* sync workload slice is at least 2 * cfq_slice_idle */
2193                 slice = max(slice, 2 * cfqd->cfq_slice_idle);
2194
2195         slice = max_t(unsigned, slice, CFQ_MIN_TT);
2196         cfq_log(cfqd, "workload slice:%d", slice);
2197         cfqd->workload_expires = jiffies + slice;
2198 }
2199
2200 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
2201 {
2202         struct cfq_rb_root *st = &cfqd->grp_service_tree;
2203         struct cfq_group *cfqg;
2204
2205         if (RB_EMPTY_ROOT(&st->rb))
2206                 return NULL;
2207         cfqg = cfq_rb_first_group(st);
2208         update_min_vdisktime(st);
2209         return cfqg;
2210 }
2211
2212 static void cfq_choose_cfqg(struct cfq_data *cfqd)
2213 {
2214         struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
2215
2216         cfqd->serving_group = cfqg;
2217
2218         /* Restore the workload type data */
2219         if (cfqg->saved_workload_slice) {
2220                 cfqd->workload_expires = jiffies + cfqg->saved_workload_slice;
2221                 cfqd->serving_type = cfqg->saved_workload;
2222                 cfqd->serving_prio = cfqg->saved_serving_prio;
2223         } else
2224                 cfqd->workload_expires = jiffies - 1;
2225
2226         choose_service_tree(cfqd, cfqg);
2227 }
2228
2229 /*
2230  * Select a queue for service. If we have a current active queue,
2231  * check whether to continue servicing it, or retrieve and set a new one.
2232  */
2233 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
2234 {
2235         struct cfq_queue *cfqq, *new_cfqq = NULL;
2236
2237         cfqq = cfqd->active_queue;
2238         if (!cfqq)
2239                 goto new_queue;
2240
2241         if (!cfqd->rq_queued)
2242                 return NULL;
2243
2244         /*
2245          * We were waiting for group to get backlogged. Expire the queue
2246          */
2247         if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list))
2248                 goto expire;
2249
2250         /*
2251          * The active queue has run out of time, expire it and select new.
2252          */
2253         if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) {
2254                 /*
2255                  * If slice had not expired at the completion of last request
2256                  * we might not have turned on wait_busy flag. Don't expire
2257                  * the queue yet. Allow the group to get backlogged.
2258                  *
2259                  * The very fact that we have used the slice, that means we
2260                  * have been idling all along on this queue and it should be
2261                  * ok to wait for this request to complete.
2262                  */
2263                 if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list)
2264                     && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
2265                         cfqq = NULL;
2266                         goto keep_queue;
2267                 } else
2268                         goto check_group_idle;
2269         }
2270
2271         /*
2272          * The active queue has requests and isn't expired, allow it to
2273          * dispatch.
2274          */
2275         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2276                 goto keep_queue;
2277
2278         /*
2279          * If another queue has a request waiting within our mean seek
2280          * distance, let it run.  The expire code will check for close
2281          * cooperators and put the close queue at the front of the service
2282          * tree.  If possible, merge the expiring queue with the new cfqq.
2283          */
2284         new_cfqq = cfq_close_cooperator(cfqd, cfqq);
2285         if (new_cfqq) {
2286                 if (!cfqq->new_cfqq)
2287                         cfq_setup_merge(cfqq, new_cfqq);
2288                 goto expire;
2289         }
2290
2291         /*
2292          * No requests pending. If the active queue still has requests in
2293          * flight or is idling for a new request, allow either of these
2294          * conditions to happen (or time out) before selecting a new queue.
2295          */
2296         if (timer_pending(&cfqd->idle_slice_timer)) {
2297                 cfqq = NULL;
2298                 goto keep_queue;
2299         }
2300
2301         /*
2302          * This is a deep seek queue, but the device is much faster than
2303          * the queue can deliver, don't idle
2304          **/
2305         if (CFQQ_SEEKY(cfqq) && cfq_cfqq_idle_window(cfqq) &&
2306             (cfq_cfqq_slice_new(cfqq) ||
2307             (cfqq->slice_end - jiffies > jiffies - cfqq->slice_start))) {
2308                 cfq_clear_cfqq_deep(cfqq);
2309                 cfq_clear_cfqq_idle_window(cfqq);
2310         }
2311
2312         if (cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
2313                 cfqq = NULL;
2314                 goto keep_queue;
2315         }
2316
2317         /*
2318          * If group idle is enabled and there are requests dispatched from
2319          * this group, wait for requests to complete.
2320          */
2321 check_group_idle:
2322         if (cfqd->cfq_group_idle && cfqq->cfqg->nr_cfqq == 1
2323             && cfqq->cfqg->dispatched) {
2324                 cfqq = NULL;
2325                 goto keep_queue;
2326         }
2327
2328 expire:
2329         cfq_slice_expired(cfqd, 0);
2330 new_queue:
2331         /*
2332          * Current queue expired. Check if we have to switch to a new
2333          * service tree
2334          */
2335         if (!new_cfqq)
2336                 cfq_choose_cfqg(cfqd);
2337
2338         cfqq = cfq_set_active_queue(cfqd, new_cfqq);
2339 keep_queue:
2340         return cfqq;
2341 }
2342
2343 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
2344 {
2345         int dispatched = 0;
2346
2347         while (cfqq->next_rq) {
2348                 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
2349                 dispatched++;
2350         }
2351
2352         BUG_ON(!list_empty(&cfqq->fifo));
2353
2354         /* By default cfqq is not expired if it is empty. Do it explicitly */
2355         __cfq_slice_expired(cfqq->cfqd, cfqq, 0);
2356         return dispatched;
2357 }
2358
2359 /*
2360  * Drain our current requests. Used for barriers and when switching
2361  * io schedulers on-the-fly.
2362  */
2363 static int cfq_forced_dispatch(struct cfq_data *cfqd)
2364 {
2365         struct cfq_queue *cfqq;
2366         int dispatched = 0;
2367
2368         /* Expire the timeslice of the current active queue first */
2369         cfq_slice_expired(cfqd, 0);
2370         while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) {
2371                 __cfq_set_active_queue(cfqd, cfqq);
2372                 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
2373         }
2374
2375         BUG_ON(cfqd->busy_queues);
2376
2377         cfq_log(cfqd, "forced_dispatch=%d", dispatched);
2378         return dispatched;
2379 }
2380
2381 static inline bool cfq_slice_used_soon(struct cfq_data *cfqd,
2382         struct cfq_queue *cfqq)
2383 {
2384         /* the queue hasn't finished any request, can't estimate */
2385         if (cfq_cfqq_slice_new(cfqq))
2386                 return true;
2387         if (time_after(jiffies + cfqd->cfq_slice_idle * cfqq->dispatched,
2388                 cfqq->slice_end))
2389                 return true;
2390
2391         return false;
2392 }
2393
2394 static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2395 {
2396         unsigned int max_dispatch;
2397
2398         /*
2399          * Drain async requests before we start sync IO
2400          */
2401         if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_flight[BLK_RW_ASYNC])
2402                 return false;
2403
2404         /*
2405          * If this is an async queue and we have sync IO in flight, let it wait
2406          */
2407         if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq))
2408                 return false;
2409
2410         max_dispatch = max_t(unsigned int, cfqd->cfq_quantum / 2, 1);
2411         if (cfq_class_idle(cfqq))
2412                 max_dispatch = 1;
2413
2414         /*
2415          * Does this cfqq already have too much IO in flight?
2416          */
2417         if (cfqq->dispatched >= max_dispatch) {
2418                 bool promote_sync = false;
2419                 /*
2420                  * idle queue must always only have a single IO in flight
2421                  */
2422                 if (cfq_class_idle(cfqq))
2423                         return false;
2424
2425                 /*
2426                  * If there is only one sync queue, and its think time is
2427                  * small, we can ignore async queue here and give the sync
2428                  * queue no dispatch limit. The reason is a sync queue can
2429                  * preempt async queue, limiting the sync queue doesn't make
2430                  * sense. This is useful for aiostress test.
2431                  */
2432                 if (cfq_cfqq_sync(cfqq) && cfqd->busy_sync_queues == 1) {
2433                         struct cfq_io_context *cic = RQ_CIC(cfqq->next_rq);
2434
2435                         if (sample_valid(cic->ttime_samples) &&
2436                                 cic->ttime_mean < cfqd->cfq_slice_idle)
2437                                 promote_sync = true;
2438                 }
2439
2440                 /*
2441                  * We have other queues, don't allow more IO from this one
2442                  */
2443                 if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq) &&
2444                                 !promote_sync)
2445                         return false;
2446
2447                 /*
2448                  * Sole queue user, no limit
2449                  */
2450                 if (cfqd->busy_queues == 1 || promote_sync)
2451                         max_dispatch = -1;
2452                 else
2453                         /*
2454                          * Normally we start throttling cfqq when cfq_quantum/2
2455                          * requests have been dispatched. But we can drive
2456                          * deeper queue depths at the beginning of slice
2457                          * subjected to upper limit of cfq_quantum.
2458                          * */
2459                         max_dispatch = cfqd->cfq_quantum;
2460         }
2461
2462         /*
2463          * Async queues must wait a bit before being allowed dispatch.
2464          * We also ramp up the dispatch depth gradually for async IO,
2465          * based on the last sync IO we serviced
2466          */
2467         if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
2468                 unsigned long last_sync = jiffies - cfqd->last_delayed_sync;
2469                 unsigned int depth;
2470
2471                 depth = last_sync / cfqd->cfq_slice[1];
2472                 if (!depth && !cfqq->dispatched)
2473                         depth = 1;
2474                 if (depth < max_dispatch)
2475                         max_dispatch = depth;
2476         }
2477
2478         /*
2479          * If we're below the current max, allow a dispatch
2480          */
2481         return cfqq->dispatched < max_dispatch;
2482 }
2483
2484 /*
2485  * Dispatch a request from cfqq, moving them to the request queue
2486  * dispatch list.
2487  */
2488 static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2489 {
2490         struct request *rq;
2491
2492         BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
2493
2494         if (!cfq_may_dispatch(cfqd, cfqq))
2495                 return false;
2496
2497         /*
2498          * follow expired path, else get first next available
2499          */
2500         rq = cfq_check_fifo(cfqq);
2501         if (!rq)
2502                 rq = cfqq->next_rq;
2503
2504         /*
2505          * insert request into driver dispatch list
2506          */
2507         cfq_dispatch_insert(cfqd->queue, rq);
2508
2509         if (!cfqd->active_cic) {
2510                 struct cfq_io_context *cic = RQ_CIC(rq);
2511
2512                 atomic_long_inc(&cic->ioc->refcount);
2513                 cfqd->active_cic = cic;
2514         }
2515
2516         return true;
2517 }
2518
2519 /*
2520  * Find the cfqq that we need to service and move a request from that to the
2521  * dispatch list
2522  */
2523 static int cfq_dispatch_requests(struct request_queue *q, int force)
2524 {
2525         struct cfq_data *cfqd = q->elevator->elevator_data;
2526         struct cfq_queue *cfqq;
2527
2528         if (!cfqd->busy_queues)
2529                 return 0;
2530
2531         if (unlikely(force))
2532                 return cfq_forced_dispatch(cfqd);
2533
2534         cfqq = cfq_select_queue(cfqd);
2535         if (!cfqq)
2536                 return 0;
2537
2538         /*
2539          * Dispatch a request from this cfqq, if it is allowed
2540          */
2541         if (!cfq_dispatch_request(cfqd, cfqq))
2542                 return 0;
2543
2544         cfqq->slice_dispatch++;
2545         cfq_clear_cfqq_must_dispatch(cfqq);
2546
2547         /*
2548          * expire an async queue immediately if it has used up its slice. idle
2549          * queue always expire after 1 dispatch round.
2550          */
2551         if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
2552             cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
2553             cfq_class_idle(cfqq))) {
2554                 cfqq->slice_end = jiffies + 1;
2555                 cfq_slice_expired(cfqd, 0);
2556         }
2557
2558         cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
2559         return 1;
2560 }
2561
2562 /*
2563  * task holds one reference to the queue, dropped when task exits. each rq
2564  * in-flight on this queue also holds a reference, dropped when rq is freed.
2565  *
2566  * Each cfq queue took a reference on the parent group. Drop it now.
2567  * queue lock must be held here.
2568  */
2569 static void cfq_put_queue(struct cfq_queue *cfqq)
2570 {
2571         struct cfq_data *cfqd = cfqq->cfqd;
2572         struct cfq_group *cfqg;
2573
2574         BUG_ON(cfqq->ref <= 0);
2575
2576         cfqq->ref--;
2577         if (cfqq->ref)
2578                 return;
2579
2580         cfq_log_cfqq(cfqd, cfqq, "put_queue");
2581         BUG_ON(rb_first(&cfqq->sort_list));
2582         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
2583         cfqg = cfqq->cfqg;
2584
2585         if (unlikely(cfqd->active_queue == cfqq)) {
2586                 __cfq_slice_expired(cfqd, cfqq, 0);
2587                 cfq_schedule_dispatch(cfqd);
2588         }
2589
2590         BUG_ON(cfq_cfqq_on_rr(cfqq));
2591         kmem_cache_free(cfq_pool, cfqq);
2592         cfq_put_cfqg(cfqg);
2593 }
2594
2595 /*
2596  * Must always be called with the rcu_read_lock() held
2597  */
2598 static void
2599 __call_for_each_cic(struct io_context *ioc,
2600                     void (*func)(struct io_context *, struct cfq_io_context *))
2601 {
2602         struct cfq_io_context *cic;
2603         struct hlist_node *n;
2604
2605         hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
2606                 func(ioc, cic);
2607 }
2608
2609 /*
2610  * Call func for each cic attached to this ioc.
2611  */
2612 static void
2613 call_for_each_cic(struct io_context *ioc,
2614                   void (*func)(struct io_context *, struct cfq_io_context *))
2615 {
2616         rcu_read_lock();
2617         __call_for_each_cic(ioc, func);
2618         rcu_read_unlock();
2619 }
2620
2621 static void cfq_cic_free_rcu(struct rcu_head *head)
2622 {
2623         struct cfq_io_context *cic;
2624
2625         cic = container_of(head, struct cfq_io_context, rcu_head);
2626
2627         kmem_cache_free(cfq_ioc_pool, cic);
2628         elv_ioc_count_dec(cfq_ioc_count);
2629
2630         if (ioc_gone) {
2631                 /*
2632                  * CFQ scheduler is exiting, grab exit lock and check
2633                  * the pending io context count. If it hits zero,
2634                  * complete ioc_gone and set it back to NULL
2635                  */
2636                 spin_lock(&ioc_gone_lock);
2637                 if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
2638                         complete(ioc_gone);
2639                         ioc_gone = NULL;
2640                 }
2641                 spin_unlock(&ioc_gone_lock);
2642         }
2643 }
2644
2645 static void cfq_cic_free(struct cfq_io_context *cic)
2646 {
2647         call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
2648 }
2649
2650 static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
2651 {
2652         unsigned long flags;
2653         unsigned long dead_key = (unsigned long) cic->key;
2654
2655         BUG_ON(!(dead_key & CIC_DEAD_KEY));
2656
2657         spin_lock_irqsave(&ioc->lock, flags);
2658         radix_tree_delete(&ioc->radix_root, dead_key >> CIC_DEAD_INDEX_SHIFT);
2659         hlist_del_rcu(&cic->cic_list);
2660         spin_unlock_irqrestore(&ioc->lock, flags);
2661
2662         cfq_cic_free(cic);
2663 }
2664
2665 /*
2666  * Must be called with rcu_read_lock() held or preemption otherwise disabled.
2667  * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
2668  * and ->trim() which is called with the task lock held
2669  */
2670 static void cfq_free_io_context(struct io_context *ioc)
2671 {
2672         /*
2673          * ioc->refcount is zero here, or we are called from elv_unregister(),
2674          * so no more cic's are allowed to be linked into this ioc.  So it
2675          * should be ok to iterate over the known list, we will see all cic's
2676          * since no new ones are added.
2677          */
2678         __call_for_each_cic(ioc, cic_free_func);
2679 }
2680
2681 static void cfq_put_cooperator(struct cfq_queue *cfqq)
2682 {
2683         struct cfq_queue *__cfqq, *next;
2684
2685         /*
2686          * If this queue was scheduled to merge with another queue, be
2687          * sure to drop the reference taken on that queue (and others in
2688          * the merge chain).  See cfq_setup_merge and cfq_merge_cfqqs.
2689          */
2690         __cfqq = cfqq->new_cfqq;
2691         while (__cfqq) {
2692                 if (__cfqq == cfqq) {
2693                         WARN(1, "cfqq->new_cfqq loop detected\n");
2694                         break;
2695                 }
2696                 next = __cfqq->new_cfqq;
2697                 cfq_put_queue(__cfqq);
2698                 __cfqq = next;
2699         }
2700 }
2701
2702 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2703 {
2704         if (unlikely(cfqq == cfqd->active_queue)) {
2705                 __cfq_slice_expired(cfqd, cfqq, 0);
2706                 cfq_schedule_dispatch(cfqd);
2707         }
2708
2709         cfq_put_cooperator(cfqq);
2710
2711         cfq_put_queue(cfqq);
2712 }
2713
2714 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
2715                                          struct cfq_io_context *cic)
2716 {
2717         struct io_context *ioc = cic->ioc;
2718
2719         list_del_init(&cic->queue_list);
2720
2721         /*
2722          * Make sure dead mark is seen for dead queues
2723          */
2724         smp_wmb();
2725         cic->key = cfqd_dead_key(cfqd);
2726
2727         if (ioc->ioc_data == cic)
2728                 rcu_assign_pointer(ioc->ioc_data, NULL);
2729
2730         if (cic->cfqq[BLK_RW_ASYNC]) {
2731                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
2732                 cic->cfqq[BLK_RW_ASYNC] = NULL;
2733         }
2734
2735         if (cic->cfqq[BLK_RW_SYNC]) {
2736                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
2737                 cic->cfqq[BLK_RW_SYNC] = NULL;
2738         }
2739 }
2740
2741 static void cfq_exit_single_io_context(struct io_context *ioc,
2742                                        struct cfq_io_context *cic)
2743 {
2744         struct cfq_data *cfqd = cic_to_cfqd(cic);
2745
2746         if (cfqd) {
2747                 struct request_queue *q = cfqd->queue;
2748                 unsigned long flags;
2749
2750                 spin_lock_irqsave(q->queue_lock, flags);
2751
2752                 /*
2753                  * Ensure we get a fresh copy of the ->key to prevent
2754                  * race between exiting task and queue
2755                  */
2756                 smp_read_barrier_depends();
2757                 if (cic->key == cfqd)
2758                         __cfq_exit_single_io_context(cfqd, cic);
2759
2760                 spin_unlock_irqrestore(q->queue_lock, flags);
2761         }
2762 }
2763
2764 /*
2765  * The process that ioc belongs to has exited, we need to clean up
2766  * and put the internal structures we have that belongs to that process.
2767  */
2768 static void cfq_exit_io_context(struct io_context *ioc)
2769 {
2770         call_for_each_cic(ioc, cfq_exit_single_io_context);
2771 }
2772
2773 static struct cfq_io_context *
2774 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
2775 {
2776         struct cfq_io_context *cic;
2777
2778         cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
2779                                                         cfqd->queue->node);
2780         if (cic) {
2781                 cic->last_end_request = jiffies;
2782                 INIT_LIST_HEAD(&cic->queue_list);
2783                 INIT_HLIST_NODE(&cic->cic_list);
2784                 cic->dtor = cfq_free_io_context;
2785                 cic->exit = cfq_exit_io_context;
2786                 elv_ioc_count_inc(cfq_ioc_count);
2787         }
2788
2789         return cic;
2790 }
2791
2792 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
2793 {
2794         struct task_struct *tsk = current;
2795         int ioprio_class;
2796
2797         if (!cfq_cfqq_prio_changed(cfqq))
2798                 return;
2799
2800         ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
2801         switch (ioprio_class) {
2802         default:
2803                 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
2804         case IOPRIO_CLASS_NONE:
2805                 /*
2806                  * no prio set, inherit CPU scheduling settings
2807                  */
2808                 cfqq->ioprio = task_nice_ioprio(tsk);
2809                 cfqq->ioprio_class = task_nice_ioclass(tsk);
2810                 break;
2811         case IOPRIO_CLASS_RT:
2812                 cfqq->ioprio = task_ioprio(ioc);
2813                 cfqq->ioprio_class = IOPRIO_CLASS_RT;
2814                 break;
2815         case IOPRIO_CLASS_BE:
2816                 cfqq->ioprio = task_ioprio(ioc);
2817                 cfqq->ioprio_class = IOPRIO_CLASS_BE;
2818                 break;
2819         case IOPRIO_CLASS_IDLE:
2820                 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
2821                 cfqq->ioprio = 7;
2822                 cfq_clear_cfqq_idle_window(cfqq);
2823                 break;
2824         }
2825
2826         /*
2827          * keep track of original prio settings in case we have to temporarily
2828          * elevate the priority of this queue
2829          */
2830         cfqq->org_ioprio = cfqq->ioprio;
2831         cfqq->org_ioprio_class = cfqq->ioprio_class;
2832         cfq_clear_cfqq_prio_changed(cfqq);
2833 }
2834
2835 static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
2836 {
2837         struct cfq_data *cfqd = cic_to_cfqd(cic);
2838         struct cfq_queue *cfqq;
2839         unsigned long flags;
2840
2841         if (unlikely(!cfqd))
2842                 return;
2843
2844         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2845
2846         cfqq = cic->cfqq[BLK_RW_ASYNC];
2847         if (cfqq) {
2848                 struct cfq_queue *new_cfqq;
2849                 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
2850                                                 GFP_ATOMIC);
2851                 if (new_cfqq) {
2852                         cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
2853                         cfq_put_queue(cfqq);
2854                 }
2855         }
2856
2857         cfqq = cic->cfqq[BLK_RW_SYNC];
2858         if (cfqq)
2859                 cfq_mark_cfqq_prio_changed(cfqq);
2860
2861         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2862 }
2863
2864 static void cfq_ioc_set_ioprio(struct io_context *ioc)
2865 {
2866         call_for_each_cic(ioc, changed_ioprio);
2867         ioc->ioprio_changed = 0;
2868 }
2869
2870 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2871                           pid_t pid, bool is_sync)
2872 {
2873         RB_CLEAR_NODE(&cfqq->rb_node);
2874         RB_CLEAR_NODE(&cfqq->p_node);
2875         INIT_LIST_HEAD(&cfqq->fifo);
2876
2877         cfqq->ref = 0;
2878         cfqq->cfqd = cfqd;
2879
2880         cfq_mark_cfqq_prio_changed(cfqq);
2881
2882         if (is_sync) {
2883                 if (!cfq_class_idle(cfqq))
2884                         cfq_mark_cfqq_idle_window(cfqq);
2885                 cfq_mark_cfqq_sync(cfqq);
2886         }
2887         cfqq->pid = pid;
2888 }
2889
2890 #ifdef CONFIG_CFQ_GROUP_IOSCHED
2891 static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
2892 {
2893         struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1);
2894         struct cfq_data *cfqd = cic_to_cfqd(cic);
2895         unsigned long flags;
2896         struct request_queue *q;
2897
2898         if (unlikely(!cfqd))
2899                 return;
2900
2901         q = cfqd->queue;
2902
2903         spin_lock_irqsave(q->queue_lock, flags);
2904
2905         if (sync_cfqq) {
2906                 /*
2907                  * Drop reference to sync queue. A new sync queue will be
2908                  * assigned in new group upon arrival of a fresh request.
2909                  */
2910                 cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
2911                 cic_set_cfqq(cic, NULL, 1);
2912                 cfq_put_queue(sync_cfqq);
2913         }
2914
2915         spin_unlock_irqrestore(q->queue_lock, flags);
2916 }
2917
2918 static void cfq_ioc_set_cgroup(struct io_context *ioc)
2919 {
2920         call_for_each_cic(ioc, changed_cgroup);
2921         ioc->cgroup_changed = 0;
2922 }
2923 #endif  /* CONFIG_CFQ_GROUP_IOSCHED */
2924
2925 static struct cfq_queue *
2926 cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
2927                      struct io_context *ioc, gfp_t gfp_mask)
2928 {
2929         struct cfq_queue *cfqq, *new_cfqq = NULL;
2930         struct cfq_io_context *cic;
2931         struct cfq_group *cfqg;
2932
2933 retry:
2934         cfqg = cfq_get_cfqg(cfqd, 1);
2935         cic = cfq_cic_lookup(cfqd, ioc);
2936         /* cic always exists here */
2937         cfqq = cic_to_cfqq(cic, is_sync);
2938
2939         /*
2940          * Always try a new alloc if we fell back to the OOM cfqq
2941          * originally, since it should just be a temporary situation.
2942          */
2943         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
2944                 cfqq = NULL;
2945                 if (new_cfqq) {
2946                         cfqq = new_cfqq;
2947                         new_cfqq = NULL;
2948                 } else if (gfp_mask & __GFP_WAIT) {
2949                         spin_unlock_irq(cfqd->queue->queue_lock);
2950                         new_cfqq = kmem_cache_alloc_node(cfq_pool,
2951                                         gfp_mask | __GFP_ZERO,
2952                                         cfqd->queue->node);
2953                         spin_lock_irq(cfqd->queue->queue_lock);
2954                         if (new_cfqq)
2955                                 goto retry;
2956                 } else {
2957                         cfqq = kmem_cache_alloc_node(cfq_pool,
2958                                         gfp_mask | __GFP_ZERO,
2959                                         cfqd->queue->node);
2960                 }
2961
2962                 if (cfqq) {
2963                         cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
2964                         cfq_init_prio_data(cfqq, ioc);
2965                         cfq_link_cfqq_cfqg(cfqq, cfqg);
2966                         cfq_log_cfqq(cfqd, cfqq, "alloced");
2967                 } else
2968                         cfqq = &cfqd->oom_cfqq;
2969         }
2970
2971         if (new_cfqq)
2972                 kmem_cache_free(cfq_pool, new_cfqq);
2973
2974         return cfqq;
2975 }
2976
2977 static struct cfq_queue **
2978 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
2979 {
2980         switch (ioprio_class) {
2981         case IOPRIO_CLASS_RT:
2982                 return &cfqd->async_cfqq[0][ioprio];
2983         case IOPRIO_CLASS_BE:
2984                 return &cfqd->async_cfqq[1][ioprio];
2985         case IOPRIO_CLASS_IDLE:
2986                 return &cfqd->async_idle_cfqq;
2987         default:
2988                 BUG();
2989         }
2990 }
2991
2992 static struct cfq_queue *
2993 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
2994               gfp_t gfp_mask)
2995 {
2996         const int ioprio = task_ioprio(ioc);
2997         const int ioprio_class = task_ioprio_class(ioc);
2998         struct cfq_queue **async_cfqq = NULL;
2999         struct cfq_queue *cfqq = NULL;
3000
3001         if (!is_sync) {
3002                 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
3003                 cfqq = *async_cfqq;
3004         }
3005
3006         if (!cfqq)
3007                 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
3008
3009         /*
3010          * pin the queue now that it's allocated, scheduler exit will prune it
3011          */
3012         if (!is_sync && !(*async_cfqq)) {
3013                 cfqq->ref++;
3014                 *async_cfqq = cfqq;
3015         }
3016
3017         cfqq->ref++;
3018         return cfqq;
3019 }
3020
3021 /*
3022  * We drop cfq io contexts lazily, so we may find a dead one.
3023  */
3024 static void
3025 cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
3026                   struct cfq_io_context *cic)
3027 {
3028         unsigned long flags;
3029
3030         WARN_ON(!list_empty(&cic->queue_list));
3031         BUG_ON(cic->key != cfqd_dead_key(cfqd));
3032
3033         spin_lock_irqsave(&ioc->lock, flags);
3034
3035         BUG_ON(ioc->ioc_data == cic);
3036
3037         radix_tree_delete(&ioc->radix_root, cfqd->cic_index);
3038         hlist_del_rcu(&cic->cic_list);
3039         spin_unlock_irqrestore(&ioc->lock, flags);
3040
3041         cfq_cic_free(cic);
3042 }
3043
3044 static struct cfq_io_context *
3045 cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
3046 {
3047         struct cfq_io_context *cic;
3048         unsigned long flags;
3049
3050         if (unlikely(!ioc))
3051                 return NULL;
3052
3053         rcu_read_lock();
3054
3055         /*
3056          * we maintain a last-hit cache, to avoid browsing over the tree
3057          */
3058         cic = rcu_dereference(ioc->ioc_data);
3059         if (cic && cic->key == cfqd) {
3060                 rcu_read_unlock();
3061                 return cic;
3062         }
3063
3064         do {
3065                 cic = radix_tree_lookup(&ioc->radix_root, cfqd->cic_index);
3066                 rcu_read_unlock();
3067                 if (!cic)
3068                         break;
3069                 if (unlikely(cic->key != cfqd)) {
3070                         cfq_drop_dead_cic(cfqd, ioc, cic);
3071                         rcu_read_lock();
3072                         continue;
3073                 }
3074
3075                 spin_lock_irqsave(&ioc->lock, flags);
3076                 rcu_assign_pointer(ioc->ioc_data, cic);
3077                 spin_unlock_irqrestore(&ioc->lock, flags);
3078                 break;
3079         } while (1);
3080
3081         return cic;
3082 }
3083
3084 /*
3085  * Add cic into ioc, using cfqd as the search key. This enables us to lookup
3086  * the process specific cfq io context when entered from the block layer.
3087  * Also adds the cic to a per-cfqd list, used when this queue is removed.
3088  */
3089 static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
3090                         struct cfq_io_context *cic, gfp_t gfp_mask)
3091 {
3092         unsigned long flags;
3093         int ret;
3094
3095         ret = radix_tree_preload(gfp_mask);
3096         if (!ret) {
3097                 cic->ioc = ioc;
3098                 cic->key = cfqd;
3099
3100                 spin_lock_irqsave(&ioc->lock, flags);
3101                 ret = radix_tree_insert(&ioc->radix_root,
3102                                                 cfqd->cic_index, cic);
3103                 if (!ret)
3104                         hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
3105                 spin_unlock_irqrestore(&ioc->lock, flags);
3106
3107                 radix_tree_preload_end();
3108
3109                 if (!ret) {
3110                         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
3111                         list_add(&cic->queue_list, &cfqd->cic_list);
3112                         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
3113                 }
3114         }
3115
3116         if (ret)
3117                 printk(KERN_ERR "cfq: cic link failed!\n");
3118
3119         return ret;
3120 }
3121
3122 /*
3123  * Setup general io context and cfq io context. There can be several cfq
3124  * io contexts per general io context, if this process is doing io to more
3125  * than one device managed by cfq.
3126  */
3127 static struct cfq_io_context *
3128 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
3129 {
3130         struct io_context *ioc = NULL;
3131         struct cfq_io_context *cic;
3132
3133         might_sleep_if(gfp_mask & __GFP_WAIT);
3134
3135         ioc = get_io_context(gfp_mask, cfqd->queue->node);
3136         if (!ioc)
3137                 return NULL;
3138
3139         cic = cfq_cic_lookup(cfqd, ioc);
3140         if (cic)
3141                 goto out;
3142
3143         cic = cfq_alloc_io_context(cfqd, gfp_mask);
3144         if (cic == NULL)
3145                 goto err;
3146
3147         if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
3148                 goto err_free;
3149
3150 out:
3151         smp_read_barrier_depends();
3152         if (unlikely(ioc->ioprio_changed))
3153                 cfq_ioc_set_ioprio(ioc);
3154
3155 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3156         if (unlikely(ioc->cgroup_changed))
3157                 cfq_ioc_set_cgroup(ioc);
3158 #endif
3159         return cic;
3160 err_free:
3161         cfq_cic_free(cic);
3162 err:
3163         put_io_context(ioc);
3164         return NULL;
3165 }
3166
3167 static void
3168 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
3169 {
3170         unsigned long elapsed = jiffies - cic->last_end_request;
3171         unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
3172
3173         cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
3174         cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
3175         cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
3176 }
3177
3178 static void
3179 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3180                        struct request *rq)
3181 {
3182         sector_t sdist = 0;
3183         sector_t n_sec = blk_rq_sectors(rq);
3184         if (cfqq->last_request_pos) {
3185                 if (cfqq->last_request_pos < blk_rq_pos(rq))
3186                         sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
3187                 else
3188                         sdist = cfqq->last_request_pos - blk_rq_pos(rq);
3189         }
3190
3191         cfqq->seek_history <<= 1;
3192         if (blk_queue_nonrot(cfqd->queue))
3193                 cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT);
3194         else
3195                 cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
3196 }
3197
3198 /*
3199  * Disable idle window if the process thinks too long or seeks so much that
3200  * it doesn't matter
3201  */
3202 static void
3203 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3204                        struct cfq_io_context *cic)
3205 {
3206         int old_idle, enable_idle;
3207
3208         /*
3209          * Don't idle for async or idle io prio class
3210          */
3211         if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
3212                 return;
3213
3214         enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
3215
3216         if (cfqq->queued[0] + cfqq->queued[1] >= 4)
3217                 cfq_mark_cfqq_deep(cfqq);
3218
3219         if (cfqq->next_rq && (cfqq->next_rq->cmd_flags & REQ_NOIDLE))
3220                 enable_idle = 0;
3221         else if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
3222             (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
3223                 enable_idle = 0;
3224         else if (sample_valid(cic->ttime_samples)) {
3225                 if (cic->ttime_mean > cfqd->cfq_slice_idle)
3226                         enable_idle = 0;
3227                 else
3228                         enable_idle = 1;
3229         }
3230
3231         if (old_idle != enable_idle) {
3232                 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
3233                 if (enable_idle)
3234                         cfq_mark_cfqq_idle_window(cfqq);
3235                 else
3236                         cfq_clear_cfqq_idle_window(cfqq);
3237         }
3238 }
3239
3240 /*
3241  * Check if new_cfqq should preempt the currently active queue. Return 0 for
3242  * no or if we aren't sure, a 1 will cause a preempt.
3243  */
3244 static bool
3245 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
3246                    struct request *rq)
3247 {
3248         struct cfq_queue *cfqq;
3249
3250         cfqq = cfqd->active_queue;
3251         if (!cfqq)
3252                 return false;
3253
3254         if (cfq_class_idle(new_cfqq))
3255                 return false;
3256
3257         if (cfq_class_idle(cfqq))
3258                 return true;
3259
3260         /*
3261          * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice.
3262          */
3263         if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq))
3264                 return false;
3265
3266         /*
3267          * if the new request is sync, but the currently running queue is
3268          * not, let the sync request have priority.
3269          */
3270         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
3271                 return true;
3272
3273         if (new_cfqq->cfqg != cfqq->cfqg)
3274                 return false;
3275
3276         if (cfq_slice_used(cfqq))
3277                 return true;
3278
3279         /* Allow preemption only if we are idling on sync-noidle tree */
3280         if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
3281             cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
3282             new_cfqq->service_tree->count == 2 &&
3283             RB_EMPTY_ROOT(&cfqq->sort_list))
3284                 return true;
3285
3286         /*
3287          * So both queues are sync. Let the new request get disk time if
3288          * it's a metadata request and the current queue is doing regular IO.
3289          */
3290         if ((rq->cmd_flags & REQ_META) && !cfqq->meta_pending)
3291                 return true;
3292
3293         /*
3294          * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
3295          */
3296         if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
3297                 return true;
3298
3299         /* An idle queue should not be idle now for some reason */
3300         if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq))
3301                 return true;
3302
3303         if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
3304                 return false;
3305
3306         /*
3307          * if this request is as-good as one we would expect from the
3308          * current cfqq, let it preempt
3309          */
3310         if (cfq_rq_close(cfqd, cfqq, rq))
3311                 return true;
3312
3313         return false;
3314 }
3315
3316 /*
3317  * cfqq preempts the active queue. if we allowed preempt with no slice left,
3318  * let it have half of its nominal slice.
3319  */
3320 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3321 {
3322         struct cfq_queue *old_cfqq = cfqd->active_queue;
3323
3324         cfq_log_cfqq(cfqd, cfqq, "preempt");
3325         cfq_slice_expired(cfqd, 1);
3326
3327         /*
3328          * workload type is changed, don't save slice, otherwise preempt
3329          * doesn't happen
3330          */
3331         if (cfqq_type(old_cfqq) != cfqq_type(cfqq))
3332                 cfqq->cfqg->saved_workload_slice = 0;
3333
3334         /*
3335          * Put the new queue at the front of the of the current list,
3336          * so we know that it will be selected next.
3337          */
3338         BUG_ON(!cfq_cfqq_on_rr(cfqq));
3339
3340         cfq_service_tree_add(cfqd, cfqq, 1);
3341
3342         cfq_clear_queue_stats(cfqd, cfqq);
3343 }
3344
3345 /*
3346  * Called when a new fs request (rq) is added (to cfqq). Check if there's
3347  * something we should do about it
3348  */
3349 static void
3350 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3351                 struct request *rq)
3352 {
3353         struct cfq_io_context *cic = RQ_CIC(rq);
3354
3355         cfqd->rq_queued++;
3356         if (rq->cmd_flags & REQ_META)
3357                 cfqq->meta_pending++;
3358
3359         cfq_update_io_thinktime(cfqd, cic);
3360         cfq_update_io_seektime(cfqd, cfqq, rq);
3361         cfq_update_idle_window(cfqd, cfqq, cic);
3362
3363         cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
3364
3365         if (cfqq == cfqd->active_queue) {
3366                 /*
3367                  * Remember that we saw a request from this process, but
3368                  * don't start queuing just yet. Otherwise we risk seeing lots
3369                  * of tiny requests, because we disrupt the normal plugging
3370                  * and merging. If the request is already larger than a single
3371                  * page, let it rip immediately. For that case we assume that
3372                  * merging is already done. Ditto for a busy system that
3373                  * has other work pending, don't risk delaying until the
3374                  * idle timer unplug to continue working.
3375                  */
3376                 if (cfq_cfqq_wait_request(cfqq)) {
3377                         if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
3378                             cfqd->busy_queues > 1) {
3379                                 cfq_del_timer(cfqd, cfqq);
3380                                 cfq_clear_cfqq_wait_request(cfqq);
3381                                 __blk_run_queue(cfqd->queue, false);
3382                         } else {
3383                                 cfq_blkiocg_update_idle_time_stats(
3384                                                 &cfqq->cfqg->blkg);
3385                                 cfq_mark_cfqq_must_dispatch(cfqq);
3386                         }
3387                 }
3388         } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
3389                 /*
3390                  * not the active queue - expire current slice if it is
3391                  * idle and has expired it's mean thinktime or this new queue
3392                  * has some old slice time left and is of higher priority or
3393                  * this new queue is RT and the current one is BE
3394                  */
3395                 cfq_preempt_queue(cfqd, cfqq);
3396                 __blk_run_queue(cfqd->queue, false);
3397         }
3398 }
3399
3400 static void cfq_insert_request(struct request_queue *q, struct request *rq)
3401 {
3402         struct cfq_data *cfqd = q->elevator->elevator_data;
3403         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3404
3405         cfq_log_cfqq(cfqd, cfqq, "insert_request");
3406         cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
3407
3408         rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
3409         list_add_tail(&rq->queuelist, &cfqq->fifo);
3410         cfq_add_rq_rb(rq);
3411         cfq_blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg,
3412                         &cfqd->serving_group->blkg, rq_data_dir(rq),
3413                         rq_is_sync(rq));
3414         cfq_rq_enqueued(cfqd, cfqq, rq);
3415 }
3416
3417 /*
3418  * Update hw_tag based on peak queue depth over 50 samples under
3419  * sufficient load.
3420  */
3421 static void cfq_update_hw_tag(struct cfq_data *cfqd)
3422 {
3423         struct cfq_queue *cfqq = cfqd->active_queue;
3424
3425         if (cfqd->rq_in_driver > cfqd->hw_tag_est_depth)
3426                 cfqd->hw_tag_est_depth = cfqd->rq_in_driver;
3427
3428         if (cfqd->hw_tag == 1)
3429                 return;
3430
3431         if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
3432             cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
3433                 return;
3434
3435         /*
3436          * If active queue hasn't enough requests and can idle, cfq might not
3437          * dispatch sufficient requests to hardware. Don't zero hw_tag in this
3438          * case
3439          */
3440         if (cfqq && cfq_cfqq_idle_window(cfqq) &&
3441             cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
3442             CFQ_HW_QUEUE_MIN && cfqd->rq_in_driver < CFQ_HW_QUEUE_MIN)
3443                 return;
3444
3445         if (cfqd->hw_tag_samples++ < 50)
3446                 return;
3447
3448         if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
3449                 cfqd->hw_tag = 1;
3450         else
3451                 cfqd->hw_tag = 0;
3452 }
3453
3454 static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3455 {
3456         struct cfq_io_context *cic = cfqd->active_cic;
3457
3458         /* If the queue already has requests, don't wait */
3459         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3460                 return false;
3461
3462         /* If there are other queues in the group, don't wait */
3463         if (cfqq->cfqg->nr_cfqq > 1)
3464                 return false;
3465
3466         if (cfq_slice_used(cfqq))
3467                 return true;
3468
3469         /* if slice left is less than think time, wait busy */
3470         if (cic && sample_valid(cic->ttime_samples)
3471             && (cfqq->slice_end - jiffies < cic->ttime_mean))
3472                 return true;
3473
3474         /*
3475          * If think times is less than a jiffy than ttime_mean=0 and above
3476          * will not be true. It might happen that slice has not expired yet
3477          * but will expire soon (4-5 ns) during select_queue(). To cover the
3478          * case where think time is less than a jiffy, mark the queue wait
3479          * busy if only 1 jiffy is left in the slice.
3480          */
3481         if (cfqq->slice_end - jiffies == 1)
3482                 return true;
3483
3484         return false;
3485 }
3486
3487 static void cfq_completed_request(struct request_queue *q, struct request *rq)
3488 {
3489         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3490         struct cfq_data *cfqd = cfqq->cfqd;
3491         const int sync = rq_is_sync(rq);
3492         unsigned long now;
3493
3494         now = jiffies;
3495         cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d",
3496                      !!(rq->cmd_flags & REQ_NOIDLE));
3497
3498         cfq_update_hw_tag(cfqd);
3499
3500         WARN_ON(!cfqd->rq_in_driver);
3501         WARN_ON(!cfqq->dispatched);
3502         cfqd->rq_in_driver--;
3503         cfqq->dispatched--;
3504         (RQ_CFQG(rq))->dispatched--;
3505         cfq_blkiocg_update_completion_stats(&cfqq->cfqg->blkg,
3506                         rq_start_time_ns(rq), rq_io_start_time_ns(rq),
3507                         rq_data_dir(rq), rq_is_sync(rq));
3508
3509         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
3510
3511         if (sync) {
3512                 RQ_CIC(rq)->last_end_request = now;
3513                 if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
3514                         cfqd->last_delayed_sync = now;
3515         }
3516
3517         /*
3518          * If this is the active queue, check if it needs to be expired,
3519          * or if we want to idle in case it has no pending requests.
3520          */
3521         if (cfqd->active_queue == cfqq) {
3522                 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
3523
3524                 if (cfq_cfqq_slice_new(cfqq)) {
3525                         cfq_set_prio_slice(cfqd, cfqq);
3526                         cfq_clear_cfqq_slice_new(cfqq);
3527                 }
3528
3529                 /*
3530                  * Should we wait for next request to come in before we expire
3531                  * the queue.
3532                  */
3533                 if (cfq_should_wait_busy(cfqd, cfqq)) {
3534                         unsigned long extend_sl = cfqd->cfq_slice_idle;
3535                         if (!cfqd->cfq_slice_idle)
3536                                 extend_sl = cfqd->cfq_group_idle;
3537                         cfqq->slice_end = jiffies + extend_sl;
3538                         cfq_mark_cfqq_wait_busy(cfqq);
3539                         cfq_log_cfqq(cfqd, cfqq, "will busy wait");
3540                 }
3541
3542                 /*
3543                  * Idling is not enabled on:
3544                  * - expired queues
3545                  * - idle-priority queues
3546                  * - async queues
3547                  * - queues with still some requests queued
3548                  * - when there is a close cooperator
3549                  */
3550                 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
3551                         cfq_slice_expired(cfqd, 1);
3552                 else if (sync && cfqq_empty &&
3553                          !cfq_close_cooperator(cfqd, cfqq)) {
3554                         cfq_arm_slice_timer(cfqd);
3555                 }
3556         }
3557
3558         if (!cfqd->rq_in_driver)
3559                 cfq_schedule_dispatch(cfqd);
3560 }
3561
3562 /*
3563  * we temporarily boost lower priority queues if they are holding fs exclusive
3564  * resources. they are boosted to normal prio (CLASS_BE/4)
3565  */
3566 static void cfq_prio_boost(struct cfq_queue *cfqq)
3567 {
3568         if (has_fs_excl()) {
3569                 /*
3570                  * boost idle prio on transactions that would lock out other
3571                  * users of the filesystem
3572                  */
3573                 if (cfq_class_idle(cfqq))
3574                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
3575                 if (cfqq->ioprio > IOPRIO_NORM)
3576                         cfqq->ioprio = IOPRIO_NORM;
3577         } else {
3578                 /*
3579                  * unboost the queue (if needed)
3580                  */
3581                 cfqq->ioprio_class = cfqq->org_ioprio_class;
3582                 cfqq->ioprio = cfqq->org_ioprio;
3583         }
3584 }
3585
3586 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
3587 {
3588         if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
3589                 cfq_mark_cfqq_must_alloc_slice(cfqq);
3590                 return ELV_MQUEUE_MUST;
3591         }
3592
3593         return ELV_MQUEUE_MAY;
3594 }
3595
3596 static int cfq_may_queue(struct request_queue *q, int rw)
3597 {
3598         struct cfq_data *cfqd = q->elevator->elevator_data;
3599         struct task_struct *tsk = current;
3600         struct cfq_io_context *cic;
3601         struct cfq_queue *cfqq;
3602
3603         /*
3604          * don't force setup of a queue from here, as a call to may_queue
3605          * does not necessarily imply that a request actually will be queued.
3606          * so just lookup a possibly existing queue, or return 'may queue'
3607          * if that fails
3608          */
3609         cic = cfq_cic_lookup(cfqd, tsk->io_context);
3610         if (!cic)
3611                 return ELV_MQUEUE_MAY;
3612
3613         cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
3614         if (cfqq) {
3615                 cfq_init_prio_data(cfqq, cic->ioc);
3616                 cfq_prio_boost(cfqq);
3617
3618                 return __cfq_may_queue(cfqq);
3619         }
3620
3621         return ELV_MQUEUE_MAY;
3622 }
3623
3624 /*
3625  * queue lock held here
3626  */
3627 static void cfq_put_request(struct request *rq)
3628 {
3629         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3630
3631         if (cfqq) {
3632                 const int rw = rq_data_dir(rq);
3633
3634                 BUG_ON(!cfqq->allocated[rw]);
3635                 cfqq->allocated[rw]--;
3636
3637                 put_io_context(RQ_CIC(rq)->ioc);
3638
3639                 rq->elevator_private[0] = NULL;
3640                 rq->elevator_private[1] = NULL;
3641
3642                 /* Put down rq reference on cfqg */
3643                 cfq_put_cfqg(RQ_CFQG(rq));
3644                 rq->elevator_private[2] = NULL;
3645
3646                 cfq_put_queue(cfqq);
3647         }
3648 }
3649
3650 static struct cfq_queue *
3651 cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
3652                 struct cfq_queue *cfqq)
3653 {
3654         cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
3655         cic_set_cfqq(cic, cfqq->new_cfqq, 1);
3656         cfq_mark_cfqq_coop(cfqq->new_cfqq);
3657         cfq_put_queue(cfqq);
3658         return cic_to_cfqq(cic, 1);
3659 }
3660
3661 /*
3662  * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
3663  * was the last process referring to said cfqq.
3664  */
3665 static struct cfq_queue *
3666 split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
3667 {
3668         if (cfqq_process_refs(cfqq) == 1) {
3669                 cfqq->pid = current->pid;
3670                 cfq_clear_cfqq_coop(cfqq);
3671                 cfq_clear_cfqq_split_coop(cfqq);
3672                 return cfqq;
3673         }
3674
3675         cic_set_cfqq(cic, NULL, 1);
3676
3677         cfq_put_cooperator(cfqq);
3678
3679         cfq_put_queue(cfqq);
3680         return NULL;
3681 }
3682 /*
3683  * Allocate cfq data structures associated with this request.
3684  */
3685 static int
3686 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
3687 {
3688         struct cfq_data *cfqd = q->elevator->elevator_data;
3689         struct cfq_io_context *cic;
3690         const int rw = rq_data_dir(rq);
3691         const bool is_sync = rq_is_sync(rq);
3692         struct cfq_queue *cfqq;
3693         unsigned long flags;
3694
3695         might_sleep_if(gfp_mask & __GFP_WAIT);
3696
3697         cic = cfq_get_io_context(cfqd, gfp_mask);
3698
3699         spin_lock_irqsave(q->queue_lock, flags);
3700
3701         if (!cic)
3702                 goto queue_fail;
3703
3704 new_queue:
3705         cfqq = cic_to_cfqq(cic, is_sync);
3706         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3707                 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
3708                 cic_set_cfqq(cic, cfqq, is_sync);
3709         } else {
3710                 /*
3711                  * If the queue was seeky for too long, break it apart.
3712                  */
3713                 if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) {
3714                         cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
3715                         cfqq = split_cfqq(cic, cfqq);
3716                         if (!cfqq)
3717                                 goto new_queue;
3718                 }
3719
3720                 /*
3721                  * Check to see if this queue is scheduled to merge with
3722                  * another, closely cooperating queue.  The merging of
3723                  * queues happens here as it must be done in process context.
3724                  * The reference on new_cfqq was taken in merge_cfqqs.
3725                  */
3726                 if (cfqq->new_cfqq)
3727                         cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
3728         }
3729
3730         cfqq->allocated[rw]++;
3731
3732         cfqq->ref++;
3733         rq->elevator_private[0] = cic;
3734         rq->elevator_private[1] = cfqq;
3735         rq->elevator_private[2] = cfq_ref_get_cfqg(cfqq->cfqg);
3736         spin_unlock_irqrestore(q->queue_lock, flags);
3737         return 0;
3738
3739 queue_fail:
3740         if (cic)
3741                 put_io_context(cic->ioc);
3742
3743         cfq_schedule_dispatch(cfqd);
3744         spin_unlock_irqrestore(q->queue_lock, flags);
3745         cfq_log(cfqd, "set_request fail");
3746         return 1;
3747 }
3748
3749 static void cfq_kick_queue(struct work_struct *work)
3750 {
3751         struct cfq_data *cfqd =
3752                 container_of(work, struct cfq_data, unplug_work);
3753         struct request_queue *q = cfqd->queue;
3754
3755         spin_lock_irq(q->queue_lock);
3756         __blk_run_queue(cfqd->queue, false);
3757         spin_unlock_irq(q->queue_lock);
3758 }
3759
3760 /*
3761  * Timer running if the active_queue is currently idling inside its time slice
3762  */
3763 static void cfq_idle_slice_timer(unsigned long data)
3764 {
3765         struct cfq_data *cfqd = (struct cfq_data *) data;
3766         struct cfq_queue *cfqq;
3767         unsigned long flags;
3768         int timed_out = 1;
3769
3770         cfq_log(cfqd, "idle timer fired");
3771
3772         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
3773
3774         cfqq = cfqd->active_queue;
3775         if (cfqq) {
3776                 timed_out = 0;
3777
3778                 /*
3779                  * We saw a request before the queue expired, let it through
3780                  */
3781                 if (cfq_cfqq_must_dispatch(cfqq))
3782                         goto out_kick;
3783
3784                 /*
3785                  * expired
3786                  */
3787                 if (cfq_slice_used(cfqq))
3788                         goto expire;
3789
3790                 /*
3791                  * only expire and reinvoke request handler, if there are
3792                  * other queues with pending requests
3793                  */
3794                 if (!cfqd->busy_queues)
3795                         goto out_cont;
3796
3797                 /*
3798                  * not expired and it has a request pending, let it dispatch
3799                  */
3800                 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3801                         goto out_kick;
3802
3803                 /*
3804                  * Queue depth flag is reset only when the idle didn't succeed
3805                  */
3806                 cfq_clear_cfqq_deep(cfqq);
3807         }
3808 expire:
3809         cfq_slice_expired(cfqd, timed_out);
3810 out_kick:
3811         cfq_schedule_dispatch(cfqd);
3812 out_cont:
3813         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
3814 }
3815
3816 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
3817 {
3818         del_timer_sync(&cfqd->idle_slice_timer);
3819         cancel_work_sync(&cfqd->unplug_work);
3820 }
3821
3822 static void cfq_put_async_queues(struct cfq_data *cfqd)
3823 {
3824         int i;
3825
3826         for (i = 0; i < IOPRIO_BE_NR; i++) {
3827                 if (cfqd->async_cfqq[0][i])
3828                         cfq_put_queue(cfqd->async_cfqq[0][i]);
3829                 if (cfqd->async_cfqq[1][i])
3830                         cfq_put_queue(cfqd->async_cfqq[1][i]);
3831         }
3832
3833         if (cfqd->async_idle_cfqq)
3834                 cfq_put_queue(cfqd->async_idle_cfqq);
3835 }
3836
3837 static void cfq_cfqd_free(struct rcu_head *head)
3838 {
3839         kfree(container_of(head, struct cfq_data, rcu));
3840 }
3841
3842 static void cfq_exit_queue(struct elevator_queue *e)
3843 {
3844         struct cfq_data *cfqd = e->elevator_data;
3845         struct request_queue *q = cfqd->queue;
3846
3847         cfq_shutdown_timer_wq(cfqd);
3848
3849         spin_lock_irq(q->queue_lock);
3850
3851         if (cfqd->active_queue)
3852                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
3853
3854         while (!list_empty(&cfqd->cic_list)) {
3855                 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
3856                                                         struct cfq_io_context,
3857                                                         queue_list);
3858
3859                 __cfq_exit_single_io_context(cfqd, cic);
3860         }
3861
3862         cfq_put_async_queues(cfqd);
3863         cfq_release_cfq_groups(cfqd);
3864         cfq_blkiocg_del_blkio_group(&cfqd->root_group.blkg);
3865
3866         spin_unlock_irq(q->queue_lock);
3867
3868         cfq_shutdown_timer_wq(cfqd);
3869
3870         spin_lock(&cic_index_lock);
3871         ida_remove(&cic_index_ida, cfqd->cic_index);
3872         spin_unlock(&cic_index_lock);
3873
3874         /* Wait for cfqg->blkg->key accessors to exit their grace periods. */
3875         call_rcu(&cfqd->rcu, cfq_cfqd_free);
3876 }
3877
3878 static int cfq_alloc_cic_index(void)
3879 {
3880         int index, error;
3881
3882         do {
3883                 if (!ida_pre_get(&cic_index_ida, GFP_KERNEL))
3884                         return -ENOMEM;
3885
3886                 spin_lock(&cic_index_lock);
3887                 error = ida_get_new(&cic_index_ida, &index);
3888                 spin_unlock(&cic_index_lock);
3889                 if (error && error != -EAGAIN)
3890                         return error;
3891         } while (error);
3892
3893         return index;
3894 }
3895
3896 static void *cfq_init_queue(struct request_queue *q)
3897 {
3898         struct cfq_data *cfqd;
3899         int i, j;
3900         struct cfq_group *cfqg;
3901         struct cfq_rb_root *st;
3902
3903         i = cfq_alloc_cic_index();
3904         if (i < 0)
3905                 return NULL;
3906
3907         cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
3908         if (!cfqd)
3909                 return NULL;
3910
3911         /*
3912          * Don't need take queue_lock in the routine, since we are
3913          * initializing the ioscheduler, and nobody is using cfqd
3914          */
3915         cfqd->cic_index = i;
3916
3917         /* Init root service tree */
3918         cfqd->grp_service_tree = CFQ_RB_ROOT;
3919
3920         /* Init root group */
3921         cfqg = &cfqd->root_group;
3922         for_each_cfqg_st(cfqg, i, j, st)
3923                 *st = CFQ_RB_ROOT;
3924         RB_CLEAR_NODE(&cfqg->rb_node);
3925
3926         /* Give preference to root group over other groups */
3927         cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
3928
3929 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3930         /*
3931          * Take a reference to root group which we never drop. This is just
3932          * to make sure that cfq_put_cfqg() does not try to kfree root group
3933          */
3934         cfqg->ref = 1;
3935         rcu_read_lock();
3936         cfq_blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg,
3937                                         (void *)cfqd, 0);
3938         rcu_read_unlock();
3939 #endif
3940         /*
3941          * Not strictly needed (since RB_ROOT just clears the node and we
3942          * zeroed cfqd on alloc), but better be safe in case someone decides
3943          * to add magic to the rb code
3944          */
3945         for (i = 0; i < CFQ_PRIO_LISTS; i++)
3946                 cfqd->prio_trees[i] = RB_ROOT;
3947
3948         /*
3949          * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
3950          * Grab a permanent reference to it, so that the normal code flow
3951          * will not attempt to free it.
3952          */
3953         cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
3954         cfqd->oom_cfqq.ref++;
3955         cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
3956
3957         INIT_LIST_HEAD(&cfqd->cic_list);
3958
3959         cfqd->queue = q;
3960
3961         init_timer(&cfqd->idle_slice_timer);
3962         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
3963         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
3964
3965         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
3966
3967         cfqd->cfq_quantum = cfq_quantum;
3968         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
3969         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
3970         cfqd->cfq_back_max = cfq_back_max;
3971         cfqd->cfq_back_penalty = cfq_back_penalty;
3972         cfqd->cfq_slice[0] = cfq_slice_async;
3973         cfqd->cfq_slice[1] = cfq_slice_sync;
3974         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
3975         cfqd->cfq_slice_idle = cfq_slice_idle;
3976         cfqd->cfq_group_idle = cfq_group_idle;
3977         cfqd->cfq_latency = 1;
3978         cfqd->hw_tag = -1;
3979         /*
3980          * we optimistically start assuming sync ops weren't delayed in last
3981          * second, in order to have larger depth for async operations.
3982          */
3983         cfqd->last_delayed_sync = jiffies - HZ;
3984         return cfqd;
3985 }
3986
3987 static void cfq_slab_kill(void)
3988 {
3989         /*
3990          * Caller already ensured that pending RCU callbacks are completed,
3991          * so we should have no busy allocations at this point.
3992          */
3993         if (cfq_pool)
3994                 kmem_cache_destroy(cfq_pool);
3995         if (cfq_ioc_pool)
3996                 kmem_cache_destroy(cfq_ioc_pool);
3997 }
3998
3999 static int __init cfq_slab_setup(void)
4000 {
4001         cfq_pool = KMEM_CACHE(cfq_queue, 0);
4002         if (!cfq_pool)
4003                 goto fail;
4004
4005         cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
4006         if (!cfq_ioc_pool)
4007                 goto fail;
4008
4009         return 0;
4010 fail:
4011         cfq_slab_kill();
4012         return -ENOMEM;
4013 }
4014
4015 /*
4016  * sysfs parts below -->
4017  */
4018 static ssize_t
4019 cfq_var_show(unsigned int var, char *page)
4020 {
4021         return sprintf(page, "%d\n", var);
4022 }
4023
4024 static ssize_t
4025 cfq_var_store(unsigned int *var, const char *page, size_t count)
4026 {
4027         char *p = (char *) page;
4028
4029         *var = simple_strtoul(p, &p, 10);
4030         return count;
4031 }
4032
4033 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
4034 static ssize_t __FUNC(struct elevator_queue *e, char *page)             \
4035 {                                                                       \
4036         struct cfq_data *cfqd = e->elevator_data;                       \
4037         unsigned int __data = __VAR;                                    \
4038         if (__CONV)                                                     \
4039                 __data = jiffies_to_msecs(__data);                      \
4040         return cfq_var_show(__data, (page));                            \
4041 }
4042 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
4043 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
4044 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
4045 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
4046 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
4047 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
4048 SHOW_FUNCTION(cfq_group_idle_show, cfqd->cfq_group_idle, 1);
4049 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
4050 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
4051 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
4052 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
4053 #undef SHOW_FUNCTION
4054
4055 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
4056 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
4057 {                                                                       \
4058         struct cfq_data *cfqd = e->elevator_data;                       \
4059         unsigned int __data;                                            \
4060         int ret = cfq_var_store(&__data, (page), count);                \
4061         if (__data < (MIN))                                             \
4062                 __data = (MIN);                                         \
4063         else if (__data > (MAX))                                        \
4064                 __data = (MAX);                                         \
4065         if (__CONV)                                                     \
4066                 *(__PTR) = msecs_to_jiffies(__data);                    \
4067         else                                                            \
4068                 *(__PTR) = __data;                                      \
4069         return ret;                                                     \
4070 }
4071 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
4072 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
4073                 UINT_MAX, 1);
4074 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
4075                 UINT_MAX, 1);
4076 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
4077 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
4078                 UINT_MAX, 0);
4079 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
4080 STORE_FUNCTION(cfq_group_idle_store, &cfqd->cfq_group_idle, 0, UINT_MAX, 1);
4081 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
4082 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
4083 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
4084                 UINT_MAX, 0);
4085 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
4086 #undef STORE_FUNCTION
4087
4088 #define CFQ_ATTR(name) \
4089         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
4090
4091 static struct elv_fs_entry cfq_attrs[] = {
4092         CFQ_ATTR(quantum),
4093         CFQ_ATTR(fifo_expire_sync),
4094         CFQ_ATTR(fifo_expire_async),
4095         CFQ_ATTR(back_seek_max),
4096         CFQ_ATTR(back_seek_penalty),
4097         CFQ_ATTR(slice_sync),
4098         CFQ_ATTR(slice_async),
4099         CFQ_ATTR(slice_async_rq),
4100         CFQ_ATTR(slice_idle),
4101         CFQ_ATTR(group_idle),
4102         CFQ_ATTR(low_latency),
4103         __ATTR_NULL
4104 };
4105
4106 static struct elevator_type iosched_cfq = {
4107         .ops = {
4108                 .elevator_merge_fn =            cfq_merge,
4109                 .elevator_merged_fn =           cfq_merged_request,
4110                 .elevator_merge_req_fn =        cfq_merged_requests,
4111                 .elevator_allow_merge_fn =      cfq_allow_merge,
4112                 .elevator_bio_merged_fn =       cfq_bio_merged,
4113                 .elevator_dispatch_fn =         cfq_dispatch_requests,
4114                 .elevator_add_req_fn =          cfq_insert_request,
4115                 .elevator_activate_req_fn =     cfq_activate_request,
4116                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
4117                 .elevator_completed_req_fn =    cfq_completed_request,
4118                 .elevator_former_req_fn =       elv_rb_former_request,
4119                 .elevator_latter_req_fn =       elv_rb_latter_request,
4120                 .elevator_set_req_fn =          cfq_set_request,
4121                 .elevator_put_req_fn =          cfq_put_request,
4122                 .elevator_may_queue_fn =        cfq_may_queue,
4123                 .elevator_init_fn =             cfq_init_queue,
4124                 .elevator_exit_fn =             cfq_exit_queue,
4125                 .trim =                         cfq_free_io_context,
4126         },
4127         .elevator_attrs =       cfq_attrs,
4128         .elevator_name =        "cfq",
4129         .elevator_owner =       THIS_MODULE,
4130 };
4131
4132 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4133 static struct blkio_policy_type blkio_policy_cfq = {
4134         .ops = {
4135                 .blkio_unlink_group_fn =        cfq_unlink_blkio_group,
4136                 .blkio_update_group_weight_fn = cfq_update_blkio_group_weight,
4137         },
4138         .plid = BLKIO_POLICY_PROP,
4139 };
4140 #else
4141 static struct blkio_policy_type blkio_policy_cfq;
4142 #endif
4143
4144 static int __init cfq_init(void)
4145 {
4146         /*
4147          * could be 0 on HZ < 1000 setups
4148          */
4149         if (!cfq_slice_async)
4150                 cfq_slice_async = 1;
4151         if (!cfq_slice_idle)
4152                 cfq_slice_idle = 1;
4153
4154 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4155         if (!cfq_group_idle)
4156                 cfq_group_idle = 1;
4157 #else
4158                 cfq_group_idle = 0;
4159 #endif
4160         if (cfq_slab_setup())
4161                 return -ENOMEM;
4162
4163         elv_register(&iosched_cfq);
4164         blkio_policy_register(&blkio_policy_cfq);
4165
4166         return 0;
4167 }
4168
4169 static void __exit cfq_exit(void)
4170 {
4171         DECLARE_COMPLETION_ONSTACK(all_gone);
4172         blkio_policy_unregister(&blkio_policy_cfq);
4173         elv_unregister(&iosched_cfq);
4174         ioc_gone = &all_gone;
4175         /* ioc_gone's update must be visible before reading ioc_count */
4176         smp_wmb();
4177
4178         /*
4179          * this also protects us from entering cfq_slab_kill() with
4180          * pending RCU callbacks
4181          */
4182         if (elv_ioc_count_read(cfq_ioc_count))
4183                 wait_for_completion(&all_gone);
4184         ida_destroy(&cic_index_ida);
4185         cfq_slab_kill();
4186 }
4187
4188 module_init(cfq_init);
4189 module_exit(cfq_exit);
4190
4191 MODULE_AUTHOR("Jens Axboe");
4192 MODULE_LICENSE("GPL");
4193 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");