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TOMOYO Linux Cross Reference
Linux/block/cfq-iosched.c

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  1 /*
  2  *  CFQ, or complete fairness queueing, disk scheduler.
  3  *
  4  *  Based on ideas from a previously unfinished io
  5  *  scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
  6  *
  7  *  Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
  8  */
  9 #include <linux/module.h>
 10 #include <linux/slab.h>
 11 #include <linux/blkdev.h>
 12 #include <linux/elevator.h>
 13 #include <linux/jiffies.h>
 14 #include <linux/rbtree.h>
 15 #include <linux/ioprio.h>
 16 #include <linux/blktrace_api.h>
 17 #include "blk.h"
 18 #include "blk-cgroup.h"
 19 
 20 /*
 21  * tunables
 22  */
 23 /* max queue in one round of service */
 24 static const int cfq_quantum = 8;
 25 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
 26 /* maximum backwards seek, in KiB */
 27 static const int cfq_back_max = 16 * 1024;
 28 /* penalty of a backwards seek */
 29 static const int cfq_back_penalty = 2;
 30 static const int cfq_slice_sync = HZ / 10;
 31 static int cfq_slice_async = HZ / 25;
 32 static const int cfq_slice_async_rq = 2;
 33 static int cfq_slice_idle = HZ / 125;
 34 static int cfq_group_idle = HZ / 125;
 35 static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
 36 static const int cfq_hist_divisor = 4;
 37 
 38 /*
 39  * offset from end of service tree
 40  */
 41 #define CFQ_IDLE_DELAY          (HZ / 5)
 42 
 43 /*
 44  * below this threshold, we consider thinktime immediate
 45  */
 46 #define CFQ_MIN_TT              (2)
 47 
 48 #define CFQ_SLICE_SCALE         (5)
 49 #define CFQ_HW_QUEUE_MIN        (5)
 50 #define CFQ_SERVICE_SHIFT       12
 51 
 52 #define CFQQ_SEEK_THR           (sector_t)(8 * 100)
 53 #define CFQQ_CLOSE_THR          (sector_t)(8 * 1024)
 54 #define CFQQ_SECT_THR_NONROT    (sector_t)(2 * 32)
 55 #define CFQQ_SEEKY(cfqq)        (hweight32(cfqq->seek_history) > 32/8)
 56 
 57 #define RQ_CIC(rq)              icq_to_cic((rq)->elv.icq)
 58 #define RQ_CFQQ(rq)             (struct cfq_queue *) ((rq)->elv.priv[0])
 59 #define RQ_CFQG(rq)             (struct cfq_group *) ((rq)->elv.priv[1])
 60 
 61 static struct kmem_cache *cfq_pool;
 62 
 63 #define CFQ_PRIO_LISTS          IOPRIO_BE_NR
 64 #define cfq_class_idle(cfqq)    ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
 65 #define cfq_class_rt(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
 66 
 67 #define sample_valid(samples)   ((samples) > 80)
 68 #define rb_entry_cfqg(node)     rb_entry((node), struct cfq_group, rb_node)
 69 
 70 struct cfq_ttime {
 71         unsigned long last_end_request;
 72 
 73         unsigned long ttime_total;
 74         unsigned long ttime_samples;
 75         unsigned long ttime_mean;
 76 };
 77 
 78 /*
 79  * Most of our rbtree usage is for sorting with min extraction, so
 80  * if we cache the leftmost node we don't have to walk down the tree
 81  * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
 82  * move this into the elevator for the rq sorting as well.
 83  */
 84 struct cfq_rb_root {
 85         struct rb_root rb;
 86         struct rb_node *left;
 87         unsigned count;
 88         u64 min_vdisktime;
 89         struct cfq_ttime ttime;
 90 };
 91 #define CFQ_RB_ROOT     (struct cfq_rb_root) { .rb = RB_ROOT, \
 92                         .ttime = {.last_end_request = jiffies,},}
 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 priority requests */
133         int prio_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;
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_class_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 struct cfqg_stats {
174 #ifdef CONFIG_CFQ_GROUP_IOSCHED
175         /* total bytes transferred */
176         struct blkg_rwstat              service_bytes;
177         /* total IOs serviced, post merge */
178         struct blkg_rwstat              serviced;
179         /* number of ios merged */
180         struct blkg_rwstat              merged;
181         /* total time spent on device in ns, may not be accurate w/ queueing */
182         struct blkg_rwstat              service_time;
183         /* total time spent waiting in scheduler queue in ns */
184         struct blkg_rwstat              wait_time;
185         /* number of IOs queued up */
186         struct blkg_rwstat              queued;
187         /* total sectors transferred */
188         struct blkg_stat                sectors;
189         /* total disk time and nr sectors dispatched by this group */
190         struct blkg_stat                time;
191 #ifdef CONFIG_DEBUG_BLK_CGROUP
192         /* time not charged to this cgroup */
193         struct blkg_stat                unaccounted_time;
194         /* sum of number of ios queued across all samples */
195         struct blkg_stat                avg_queue_size_sum;
196         /* count of samples taken for average */
197         struct blkg_stat                avg_queue_size_samples;
198         /* how many times this group has been removed from service tree */
199         struct blkg_stat                dequeue;
200         /* total time spent waiting for it to be assigned a timeslice. */
201         struct blkg_stat                group_wait_time;
202         /* time spent idling for this blkcg_gq */
203         struct blkg_stat                idle_time;
204         /* total time with empty current active q with other requests queued */
205         struct blkg_stat                empty_time;
206         /* fields after this shouldn't be cleared on stat reset */
207         uint64_t                        start_group_wait_time;
208         uint64_t                        start_idle_time;
209         uint64_t                        start_empty_time;
210         uint16_t                        flags;
211 #endif  /* CONFIG_DEBUG_BLK_CGROUP */
212 #endif  /* CONFIG_CFQ_GROUP_IOSCHED */
213 };
214 
215 /* This is per cgroup per device grouping structure */
216 struct cfq_group {
217         /* must be the first member */
218         struct blkg_policy_data pd;
219 
220         /* group service_tree member */
221         struct rb_node rb_node;
222 
223         /* group service_tree key */
224         u64 vdisktime;
225 
226         /*
227          * The number of active cfqgs and sum of their weights under this
228          * cfqg.  This covers this cfqg's leaf_weight and all children's
229          * weights, but does not cover weights of further descendants.
230          *
231          * If a cfqg is on the service tree, it's active.  An active cfqg
232          * also activates its parent and contributes to the children_weight
233          * of the parent.
234          */
235         int nr_active;
236         unsigned int children_weight;
237 
238         /*
239          * vfraction is the fraction of vdisktime that the tasks in this
240          * cfqg are entitled to.  This is determined by compounding the
241          * ratios walking up from this cfqg to the root.
242          *
243          * It is in fixed point w/ CFQ_SERVICE_SHIFT and the sum of all
244          * vfractions on a service tree is approximately 1.  The sum may
245          * deviate a bit due to rounding errors and fluctuations caused by
246          * cfqgs entering and leaving the service tree.
247          */
248         unsigned int vfraction;
249 
250         /*
251          * There are two weights - (internal) weight is the weight of this
252          * cfqg against the sibling cfqgs.  leaf_weight is the wight of
253          * this cfqg against the child cfqgs.  For the root cfqg, both
254          * weights are kept in sync for backward compatibility.
255          */
256         unsigned int weight;
257         unsigned int new_weight;
258         unsigned int dev_weight;
259 
260         unsigned int leaf_weight;
261         unsigned int new_leaf_weight;
262         unsigned int dev_leaf_weight;
263 
264         /* number of cfqq currently on this group */
265         int nr_cfqq;
266 
267         /*
268          * Per group busy queues average. Useful for workload slice calc. We
269          * create the array for each prio class but at run time it is used
270          * only for RT and BE class and slot for IDLE class remains unused.
271          * This is primarily done to avoid confusion and a gcc warning.
272          */
273         unsigned int busy_queues_avg[CFQ_PRIO_NR];
274         /*
275          * rr lists of queues with requests. We maintain service trees for
276          * RT and BE classes. These trees are subdivided in subclasses
277          * of SYNC, SYNC_NOIDLE and ASYNC based on workload type. For IDLE
278          * class there is no subclassification and all the cfq queues go on
279          * a single tree service_tree_idle.
280          * Counts are embedded in the cfq_rb_root
281          */
282         struct cfq_rb_root service_trees[2][3];
283         struct cfq_rb_root service_tree_idle;
284 
285         unsigned long saved_wl_slice;
286         enum wl_type_t saved_wl_type;
287         enum wl_class_t saved_wl_class;
288 
289         /* number of requests that are on the dispatch list or inside driver */
290         int dispatched;
291         struct cfq_ttime ttime;
292         struct cfqg_stats stats;        /* stats for this cfqg */
293         struct cfqg_stats dead_stats;   /* stats pushed from dead children */
294 };
295 
296 struct cfq_io_cq {
297         struct io_cq            icq;            /* must be the first member */
298         struct cfq_queue        *cfqq[2];
299         struct cfq_ttime        ttime;
300         int                     ioprio;         /* the current ioprio */
301 #ifdef CONFIG_CFQ_GROUP_IOSCHED
302         uint64_t                blkcg_id;       /* the current blkcg ID */
303 #endif
304 };
305 
306 /*
307  * Per block device queue structure
308  */
309 struct cfq_data {
310         struct request_queue *queue;
311         /* Root service tree for cfq_groups */
312         struct cfq_rb_root grp_service_tree;
313         struct cfq_group *root_group;
314 
315         /*
316          * The priority currently being served
317          */
318         enum wl_class_t serving_wl_class;
319         enum wl_type_t serving_wl_type;
320         unsigned long workload_expires;
321         struct cfq_group *serving_group;
322 
323         /*
324          * Each priority tree is sorted by next_request position.  These
325          * trees are used when determining if two or more queues are
326          * interleaving requests (see cfq_close_cooperator).
327          */
328         struct rb_root prio_trees[CFQ_PRIO_LISTS];
329 
330         unsigned int busy_queues;
331         unsigned int busy_sync_queues;
332 
333         int rq_in_driver;
334         int rq_in_flight[2];
335 
336         /*
337          * queue-depth detection
338          */
339         int rq_queued;
340         int hw_tag;
341         /*
342          * hw_tag can be
343          * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
344          *  1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
345          *  0 => no NCQ
346          */
347         int hw_tag_est_depth;
348         unsigned int hw_tag_samples;
349 
350         /*
351          * idle window management
352          */
353         struct timer_list idle_slice_timer;
354         struct work_struct unplug_work;
355 
356         struct cfq_queue *active_queue;
357         struct cfq_io_cq *active_cic;
358 
359         /*
360          * async queue for each priority case
361          */
362         struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
363         struct cfq_queue *async_idle_cfqq;
364 
365         sector_t last_position;
366 
367         /*
368          * tunables, see top of file
369          */
370         unsigned int cfq_quantum;
371         unsigned int cfq_fifo_expire[2];
372         unsigned int cfq_back_penalty;
373         unsigned int cfq_back_max;
374         unsigned int cfq_slice[2];
375         unsigned int cfq_slice_async_rq;
376         unsigned int cfq_slice_idle;
377         unsigned int cfq_group_idle;
378         unsigned int cfq_latency;
379         unsigned int cfq_target_latency;
380 
381         /*
382          * Fallback dummy cfqq for extreme OOM conditions
383          */
384         struct cfq_queue oom_cfqq;
385 
386         unsigned long last_delayed_sync;
387 };
388 
389 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
390 
391 static struct cfq_rb_root *st_for(struct cfq_group *cfqg,
392                                             enum wl_class_t class,
393                                             enum wl_type_t type)
394 {
395         if (!cfqg)
396                 return NULL;
397 
398         if (class == IDLE_WORKLOAD)
399                 return &cfqg->service_tree_idle;
400 
401         return &cfqg->service_trees[class][type];
402 }
403 
404 enum cfqq_state_flags {
405         CFQ_CFQQ_FLAG_on_rr = 0,        /* on round-robin busy list */
406         CFQ_CFQQ_FLAG_wait_request,     /* waiting for a request */
407         CFQ_CFQQ_FLAG_must_dispatch,    /* must be allowed a dispatch */
408         CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
409         CFQ_CFQQ_FLAG_fifo_expire,      /* FIFO checked in this slice */
410         CFQ_CFQQ_FLAG_idle_window,      /* slice idling enabled */
411         CFQ_CFQQ_FLAG_prio_changed,     /* task priority has changed */
412         CFQ_CFQQ_FLAG_slice_new,        /* no requests dispatched in slice */
413         CFQ_CFQQ_FLAG_sync,             /* synchronous queue */
414         CFQ_CFQQ_FLAG_coop,             /* cfqq is shared */
415         CFQ_CFQQ_FLAG_split_coop,       /* shared cfqq will be splitted */
416         CFQ_CFQQ_FLAG_deep,             /* sync cfqq experienced large depth */
417         CFQ_CFQQ_FLAG_wait_busy,        /* Waiting for next request */
418 };
419 
420 #define CFQ_CFQQ_FNS(name)                                              \
421 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
422 {                                                                       \
423         (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name);                   \
424 }                                                                       \
425 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
426 {                                                                       \
427         (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                  \
428 }                                                                       \
429 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
430 {                                                                       \
431         return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;      \
432 }
433 
434 CFQ_CFQQ_FNS(on_rr);
435 CFQ_CFQQ_FNS(wait_request);
436 CFQ_CFQQ_FNS(must_dispatch);
437 CFQ_CFQQ_FNS(must_alloc_slice);
438 CFQ_CFQQ_FNS(fifo_expire);
439 CFQ_CFQQ_FNS(idle_window);
440 CFQ_CFQQ_FNS(prio_changed);
441 CFQ_CFQQ_FNS(slice_new);
442 CFQ_CFQQ_FNS(sync);
443 CFQ_CFQQ_FNS(coop);
444 CFQ_CFQQ_FNS(split_coop);
445 CFQ_CFQQ_FNS(deep);
446 CFQ_CFQQ_FNS(wait_busy);
447 #undef CFQ_CFQQ_FNS
448 
449 static inline struct cfq_group *pd_to_cfqg(struct blkg_policy_data *pd)
450 {
451         return pd ? container_of(pd, struct cfq_group, pd) : NULL;
452 }
453 
454 static inline struct blkcg_gq *cfqg_to_blkg(struct cfq_group *cfqg)
455 {
456         return pd_to_blkg(&cfqg->pd);
457 }
458 
459 #if defined(CONFIG_CFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
460 
461 /* cfqg stats flags */
462 enum cfqg_stats_flags {
463         CFQG_stats_waiting = 0,
464         CFQG_stats_idling,
465         CFQG_stats_empty,
466 };
467 
468 #define CFQG_FLAG_FNS(name)                                             \
469 static inline void cfqg_stats_mark_##name(struct cfqg_stats *stats)     \
470 {                                                                       \
471         stats->flags |= (1 << CFQG_stats_##name);                       \
472 }                                                                       \
473 static inline void cfqg_stats_clear_##name(struct cfqg_stats *stats)    \
474 {                                                                       \
475         stats->flags &= ~(1 << CFQG_stats_##name);                      \
476 }                                                                       \
477 static inline int cfqg_stats_##name(struct cfqg_stats *stats)           \
478 {                                                                       \
479         return (stats->flags & (1 << CFQG_stats_##name)) != 0;          \
480 }                                                                       \
481 
482 CFQG_FLAG_FNS(waiting)
483 CFQG_FLAG_FNS(idling)
484 CFQG_FLAG_FNS(empty)
485 #undef CFQG_FLAG_FNS
486 
487 /* This should be called with the queue_lock held. */
488 static void cfqg_stats_update_group_wait_time(struct cfqg_stats *stats)
489 {
490         unsigned long long now;
491 
492         if (!cfqg_stats_waiting(stats))
493                 return;
494 
495         now = sched_clock();
496         if (time_after64(now, stats->start_group_wait_time))
497                 blkg_stat_add(&stats->group_wait_time,
498                               now - stats->start_group_wait_time);
499         cfqg_stats_clear_waiting(stats);
500 }
501 
502 /* This should be called with the queue_lock held. */
503 static void cfqg_stats_set_start_group_wait_time(struct cfq_group *cfqg,
504                                                  struct cfq_group *curr_cfqg)
505 {
506         struct cfqg_stats *stats = &cfqg->stats;
507 
508         if (cfqg_stats_waiting(stats))
509                 return;
510         if (cfqg == curr_cfqg)
511                 return;
512         stats->start_group_wait_time = sched_clock();
513         cfqg_stats_mark_waiting(stats);
514 }
515 
516 /* This should be called with the queue_lock held. */
517 static void cfqg_stats_end_empty_time(struct cfqg_stats *stats)
518 {
519         unsigned long long now;
520 
521         if (!cfqg_stats_empty(stats))
522                 return;
523 
524         now = sched_clock();
525         if (time_after64(now, stats->start_empty_time))
526                 blkg_stat_add(&stats->empty_time,
527                               now - stats->start_empty_time);
528         cfqg_stats_clear_empty(stats);
529 }
530 
531 static void cfqg_stats_update_dequeue(struct cfq_group *cfqg)
532 {
533         blkg_stat_add(&cfqg->stats.dequeue, 1);
534 }
535 
536 static void cfqg_stats_set_start_empty_time(struct cfq_group *cfqg)
537 {
538         struct cfqg_stats *stats = &cfqg->stats;
539 
540         if (blkg_rwstat_total(&stats->queued))
541                 return;
542 
543         /*
544          * group is already marked empty. This can happen if cfqq got new
545          * request in parent group and moved to this group while being added
546          * to service tree. Just ignore the event and move on.
547          */
548         if (cfqg_stats_empty(stats))
549                 return;
550 
551         stats->start_empty_time = sched_clock();
552         cfqg_stats_mark_empty(stats);
553 }
554 
555 static void cfqg_stats_update_idle_time(struct cfq_group *cfqg)
556 {
557         struct cfqg_stats *stats = &cfqg->stats;
558 
559         if (cfqg_stats_idling(stats)) {
560                 unsigned long long now = sched_clock();
561 
562                 if (time_after64(now, stats->start_idle_time))
563                         blkg_stat_add(&stats->idle_time,
564                                       now - stats->start_idle_time);
565                 cfqg_stats_clear_idling(stats);
566         }
567 }
568 
569 static void cfqg_stats_set_start_idle_time(struct cfq_group *cfqg)
570 {
571         struct cfqg_stats *stats = &cfqg->stats;
572 
573         BUG_ON(cfqg_stats_idling(stats));
574 
575         stats->start_idle_time = sched_clock();
576         cfqg_stats_mark_idling(stats);
577 }
578 
579 static void cfqg_stats_update_avg_queue_size(struct cfq_group *cfqg)
580 {
581         struct cfqg_stats *stats = &cfqg->stats;
582 
583         blkg_stat_add(&stats->avg_queue_size_sum,
584                       blkg_rwstat_total(&stats->queued));
585         blkg_stat_add(&stats->avg_queue_size_samples, 1);
586         cfqg_stats_update_group_wait_time(stats);
587 }
588 
589 #else   /* CONFIG_CFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
590 
591 static inline void cfqg_stats_set_start_group_wait_time(struct cfq_group *cfqg, struct cfq_group *curr_cfqg) { }
592 static inline void cfqg_stats_end_empty_time(struct cfqg_stats *stats) { }
593 static inline void cfqg_stats_update_dequeue(struct cfq_group *cfqg) { }
594 static inline void cfqg_stats_set_start_empty_time(struct cfq_group *cfqg) { }
595 static inline void cfqg_stats_update_idle_time(struct cfq_group *cfqg) { }
596 static inline void cfqg_stats_set_start_idle_time(struct cfq_group *cfqg) { }
597 static inline void cfqg_stats_update_avg_queue_size(struct cfq_group *cfqg) { }
598 
599 #endif  /* CONFIG_CFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
600 
601 #ifdef CONFIG_CFQ_GROUP_IOSCHED
602 
603 static struct blkcg_policy blkcg_policy_cfq;
604 
605 static inline struct cfq_group *blkg_to_cfqg(struct blkcg_gq *blkg)
606 {
607         return pd_to_cfqg(blkg_to_pd(blkg, &blkcg_policy_cfq));
608 }
609 
610 static inline struct cfq_group *cfqg_parent(struct cfq_group *cfqg)
611 {
612         struct blkcg_gq *pblkg = cfqg_to_blkg(cfqg)->parent;
613 
614         return pblkg ? blkg_to_cfqg(pblkg) : NULL;
615 }
616 
617 static inline void cfqg_get(struct cfq_group *cfqg)
618 {
619         return blkg_get(cfqg_to_blkg(cfqg));
620 }
621 
622 static inline void cfqg_put(struct cfq_group *cfqg)
623 {
624         return blkg_put(cfqg_to_blkg(cfqg));
625 }
626 
627 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  do {                    \
628         char __pbuf[128];                                               \
629                                                                         \
630         blkg_path(cfqg_to_blkg((cfqq)->cfqg), __pbuf, sizeof(__pbuf));  \
631         blk_add_trace_msg((cfqd)->queue, "cfq%d%c%c %s " fmt, (cfqq)->pid, \
632                         cfq_cfqq_sync((cfqq)) ? 'S' : 'A',              \
633                         cfqq_type((cfqq)) == SYNC_NOIDLE_WORKLOAD ? 'N' : ' ',\
634                           __pbuf, ##args);                              \
635 } while (0)
636 
637 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)  do {                    \
638         char __pbuf[128];                                               \
639                                                                         \
640         blkg_path(cfqg_to_blkg(cfqg), __pbuf, sizeof(__pbuf));          \
641         blk_add_trace_msg((cfqd)->queue, "%s " fmt, __pbuf, ##args);    \
642 } while (0)
643 
644 static inline void cfqg_stats_update_io_add(struct cfq_group *cfqg,
645                                             struct cfq_group *curr_cfqg, int rw)
646 {
647         blkg_rwstat_add(&cfqg->stats.queued, rw, 1);
648         cfqg_stats_end_empty_time(&cfqg->stats);
649         cfqg_stats_set_start_group_wait_time(cfqg, curr_cfqg);
650 }
651 
652 static inline void cfqg_stats_update_timeslice_used(struct cfq_group *cfqg,
653                         unsigned long time, unsigned long unaccounted_time)
654 {
655         blkg_stat_add(&cfqg->stats.time, time);
656 #ifdef CONFIG_DEBUG_BLK_CGROUP
657         blkg_stat_add(&cfqg->stats.unaccounted_time, unaccounted_time);
658 #endif
659 }
660 
661 static inline void cfqg_stats_update_io_remove(struct cfq_group *cfqg, int rw)
662 {
663         blkg_rwstat_add(&cfqg->stats.queued, rw, -1);
664 }
665 
666 static inline void cfqg_stats_update_io_merged(struct cfq_group *cfqg, int rw)
667 {
668         blkg_rwstat_add(&cfqg->stats.merged, rw, 1);
669 }
670 
671 static inline void cfqg_stats_update_dispatch(struct cfq_group *cfqg,
672                                               uint64_t bytes, int rw)
673 {
674         blkg_stat_add(&cfqg->stats.sectors, bytes >> 9);
675         blkg_rwstat_add(&cfqg->stats.serviced, rw, 1);
676         blkg_rwstat_add(&cfqg->stats.service_bytes, rw, bytes);
677 }
678 
679 static inline void cfqg_stats_update_completion(struct cfq_group *cfqg,
680                         uint64_t start_time, uint64_t io_start_time, int rw)
681 {
682         struct cfqg_stats *stats = &cfqg->stats;
683         unsigned long long now = sched_clock();
684 
685         if (time_after64(now, io_start_time))
686                 blkg_rwstat_add(&stats->service_time, rw, now - io_start_time);
687         if (time_after64(io_start_time, start_time))
688                 blkg_rwstat_add(&stats->wait_time, rw,
689                                 io_start_time - start_time);
690 }
691 
692 /* @stats = 0 */
693 static void cfqg_stats_reset(struct cfqg_stats *stats)
694 {
695         /* queued stats shouldn't be cleared */
696         blkg_rwstat_reset(&stats->service_bytes);
697         blkg_rwstat_reset(&stats->serviced);
698         blkg_rwstat_reset(&stats->merged);
699         blkg_rwstat_reset(&stats->service_time);
700         blkg_rwstat_reset(&stats->wait_time);
701         blkg_stat_reset(&stats->time);
702 #ifdef CONFIG_DEBUG_BLK_CGROUP
703         blkg_stat_reset(&stats->unaccounted_time);
704         blkg_stat_reset(&stats->avg_queue_size_sum);
705         blkg_stat_reset(&stats->avg_queue_size_samples);
706         blkg_stat_reset(&stats->dequeue);
707         blkg_stat_reset(&stats->group_wait_time);
708         blkg_stat_reset(&stats->idle_time);
709         blkg_stat_reset(&stats->empty_time);
710 #endif
711 }
712 
713 /* @to += @from */
714 static void cfqg_stats_merge(struct cfqg_stats *to, struct cfqg_stats *from)
715 {
716         /* queued stats shouldn't be cleared */
717         blkg_rwstat_merge(&to->service_bytes, &from->service_bytes);
718         blkg_rwstat_merge(&to->serviced, &from->serviced);
719         blkg_rwstat_merge(&to->merged, &from->merged);
720         blkg_rwstat_merge(&to->service_time, &from->service_time);
721         blkg_rwstat_merge(&to->wait_time, &from->wait_time);
722         blkg_stat_merge(&from->time, &from->time);
723 #ifdef CONFIG_DEBUG_BLK_CGROUP
724         blkg_stat_merge(&to->unaccounted_time, &from->unaccounted_time);
725         blkg_stat_merge(&to->avg_queue_size_sum, &from->avg_queue_size_sum);
726         blkg_stat_merge(&to->avg_queue_size_samples, &from->avg_queue_size_samples);
727         blkg_stat_merge(&to->dequeue, &from->dequeue);
728         blkg_stat_merge(&to->group_wait_time, &from->group_wait_time);
729         blkg_stat_merge(&to->idle_time, &from->idle_time);
730         blkg_stat_merge(&to->empty_time, &from->empty_time);
731 #endif
732 }
733 
734 /*
735  * Transfer @cfqg's stats to its parent's dead_stats so that the ancestors'
736  * recursive stats can still account for the amount used by this cfqg after
737  * it's gone.
738  */
739 static void cfqg_stats_xfer_dead(struct cfq_group *cfqg)
740 {
741         struct cfq_group *parent = cfqg_parent(cfqg);
742 
743         lockdep_assert_held(cfqg_to_blkg(cfqg)->q->queue_lock);
744 
745         if (unlikely(!parent))
746                 return;
747 
748         cfqg_stats_merge(&parent->dead_stats, &cfqg->stats);
749         cfqg_stats_merge(&parent->dead_stats, &cfqg->dead_stats);
750         cfqg_stats_reset(&cfqg->stats);
751         cfqg_stats_reset(&cfqg->dead_stats);
752 }
753 
754 #else   /* CONFIG_CFQ_GROUP_IOSCHED */
755 
756 static inline struct cfq_group *cfqg_parent(struct cfq_group *cfqg) { return NULL; }
757 static inline void cfqg_get(struct cfq_group *cfqg) { }
758 static inline void cfqg_put(struct cfq_group *cfqg) { }
759 
760 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
761         blk_add_trace_msg((cfqd)->queue, "cfq%d%c%c " fmt, (cfqq)->pid, \
762                         cfq_cfqq_sync((cfqq)) ? 'S' : 'A',              \
763                         cfqq_type((cfqq)) == SYNC_NOIDLE_WORKLOAD ? 'N' : ' ',\
764                                 ##args)
765 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)          do {} while (0)
766 
767 static inline void cfqg_stats_update_io_add(struct cfq_group *cfqg,
768                         struct cfq_group *curr_cfqg, int rw) { }
769 static inline void cfqg_stats_update_timeslice_used(struct cfq_group *cfqg,
770                         unsigned long time, unsigned long unaccounted_time) { }
771 static inline void cfqg_stats_update_io_remove(struct cfq_group *cfqg, int rw) { }
772 static inline void cfqg_stats_update_io_merged(struct cfq_group *cfqg, int rw) { }
773 static inline void cfqg_stats_update_dispatch(struct cfq_group *cfqg,
774                                               uint64_t bytes, int rw) { }
775 static inline void cfqg_stats_update_completion(struct cfq_group *cfqg,
776                         uint64_t start_time, uint64_t io_start_time, int rw) { }
777 
778 #endif  /* CONFIG_CFQ_GROUP_IOSCHED */
779 
780 #define cfq_log(cfqd, fmt, args...)     \
781         blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
782 
783 /* Traverses through cfq group service trees */
784 #define for_each_cfqg_st(cfqg, i, j, st) \
785         for (i = 0; i <= IDLE_WORKLOAD; i++) \
786                 for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
787                         : &cfqg->service_tree_idle; \
788                         (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
789                         (i == IDLE_WORKLOAD && j == 0); \
790                         j++, st = i < IDLE_WORKLOAD ? \
791                         &cfqg->service_trees[i][j]: NULL) \
792 
793 static inline bool cfq_io_thinktime_big(struct cfq_data *cfqd,
794         struct cfq_ttime *ttime, bool group_idle)
795 {
796         unsigned long slice;
797         if (!sample_valid(ttime->ttime_samples))
798                 return false;
799         if (group_idle)
800                 slice = cfqd->cfq_group_idle;
801         else
802                 slice = cfqd->cfq_slice_idle;
803         return ttime->ttime_mean > slice;
804 }
805 
806 static inline bool iops_mode(struct cfq_data *cfqd)
807 {
808         /*
809          * If we are not idling on queues and it is a NCQ drive, parallel
810          * execution of requests is on and measuring time is not possible
811          * in most of the cases until and unless we drive shallower queue
812          * depths and that becomes a performance bottleneck. In such cases
813          * switch to start providing fairness in terms of number of IOs.
814          */
815         if (!cfqd->cfq_slice_idle && cfqd->hw_tag)
816                 return true;
817         else
818                 return false;
819 }
820 
821 static inline enum wl_class_t cfqq_class(struct cfq_queue *cfqq)
822 {
823         if (cfq_class_idle(cfqq))
824                 return IDLE_WORKLOAD;
825         if (cfq_class_rt(cfqq))
826                 return RT_WORKLOAD;
827         return BE_WORKLOAD;
828 }
829 
830 
831 static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
832 {
833         if (!cfq_cfqq_sync(cfqq))
834                 return ASYNC_WORKLOAD;
835         if (!cfq_cfqq_idle_window(cfqq))
836                 return SYNC_NOIDLE_WORKLOAD;
837         return SYNC_WORKLOAD;
838 }
839 
840 static inline int cfq_group_busy_queues_wl(enum wl_class_t wl_class,
841                                         struct cfq_data *cfqd,
842                                         struct cfq_group *cfqg)
843 {
844         if (wl_class == IDLE_WORKLOAD)
845                 return cfqg->service_tree_idle.count;
846 
847         return cfqg->service_trees[wl_class][ASYNC_WORKLOAD].count +
848                 cfqg->service_trees[wl_class][SYNC_NOIDLE_WORKLOAD].count +
849                 cfqg->service_trees[wl_class][SYNC_WORKLOAD].count;
850 }
851 
852 static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
853                                         struct cfq_group *cfqg)
854 {
855         return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count +
856                 cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
857 }
858 
859 static void cfq_dispatch_insert(struct request_queue *, struct request *);
860 static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, bool is_sync,
861                                        struct cfq_io_cq *cic, struct bio *bio,
862                                        gfp_t gfp_mask);
863 
864 static inline struct cfq_io_cq *icq_to_cic(struct io_cq *icq)
865 {
866         /* cic->icq is the first member, %NULL will convert to %NULL */
867         return container_of(icq, struct cfq_io_cq, icq);
868 }
869 
870 static inline struct cfq_io_cq *cfq_cic_lookup(struct cfq_data *cfqd,
871                                                struct io_context *ioc)
872 {
873         if (ioc)
874                 return icq_to_cic(ioc_lookup_icq(ioc, cfqd->queue));
875         return NULL;
876 }
877 
878 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_cq *cic, bool is_sync)
879 {
880         return cic->cfqq[is_sync];
881 }
882 
883 static inline void cic_set_cfqq(struct cfq_io_cq *cic, struct cfq_queue *cfqq,
884                                 bool is_sync)
885 {
886         cic->cfqq[is_sync] = cfqq;
887 }
888 
889 static inline struct cfq_data *cic_to_cfqd(struct cfq_io_cq *cic)
890 {
891         return cic->icq.q->elevator->elevator_data;
892 }
893 
894 /*
895  * We regard a request as SYNC, if it's either a read or has the SYNC bit
896  * set (in which case it could also be direct WRITE).
897  */
898 static inline bool cfq_bio_sync(struct bio *bio)
899 {
900         return bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC);
901 }
902 
903 /*
904  * scheduler run of queue, if there are requests pending and no one in the
905  * driver that will restart queueing
906  */
907 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
908 {
909         if (cfqd->busy_queues) {
910                 cfq_log(cfqd, "schedule dispatch");
911                 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
912         }
913 }
914 
915 /*
916  * Scale schedule slice based on io priority. Use the sync time slice only
917  * if a queue is marked sync and has sync io queued. A sync queue with async
918  * io only, should not get full sync slice length.
919  */
920 static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
921                                  unsigned short prio)
922 {
923         const int base_slice = cfqd->cfq_slice[sync];
924 
925         WARN_ON(prio >= IOPRIO_BE_NR);
926 
927         return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
928 }
929 
930 static inline int
931 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
932 {
933         return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
934 }
935 
936 /**
937  * cfqg_scale_charge - scale disk time charge according to cfqg weight
938  * @charge: disk time being charged
939  * @vfraction: vfraction of the cfqg, fixed point w/ CFQ_SERVICE_SHIFT
940  *
941  * Scale @charge according to @vfraction, which is in range (0, 1].  The
942  * scaling is inversely proportional.
943  *
944  * scaled = charge / vfraction
945  *
946  * The result is also in fixed point w/ CFQ_SERVICE_SHIFT.
947  */
948 static inline u64 cfqg_scale_charge(unsigned long charge,
949                                     unsigned int vfraction)
950 {
951         u64 c = charge << CFQ_SERVICE_SHIFT;    /* make it fixed point */
952 
953         /* charge / vfraction */
954         c <<= CFQ_SERVICE_SHIFT;
955         do_div(c, vfraction);
956         return c;
957 }
958 
959 static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
960 {
961         s64 delta = (s64)(vdisktime - min_vdisktime);
962         if (delta > 0)
963                 min_vdisktime = vdisktime;
964 
965         return min_vdisktime;
966 }
967 
968 static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
969 {
970         s64 delta = (s64)(vdisktime - min_vdisktime);
971         if (delta < 0)
972                 min_vdisktime = vdisktime;
973 
974         return min_vdisktime;
975 }
976 
977 static void update_min_vdisktime(struct cfq_rb_root *st)
978 {
979         struct cfq_group *cfqg;
980 
981         if (st->left) {
982                 cfqg = rb_entry_cfqg(st->left);
983                 st->min_vdisktime = max_vdisktime(st->min_vdisktime,
984                                                   cfqg->vdisktime);
985         }
986 }
987 
988 /*
989  * get averaged number of queues of RT/BE priority.
990  * average is updated, with a formula that gives more weight to higher numbers,
991  * to quickly follows sudden increases and decrease slowly
992  */
993 
994 static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
995                                         struct cfq_group *cfqg, bool rt)
996 {
997         unsigned min_q, max_q;
998         unsigned mult  = cfq_hist_divisor - 1;
999         unsigned round = cfq_hist_divisor / 2;
1000         unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
1001 
1002         min_q = min(cfqg->busy_queues_avg[rt], busy);
1003         max_q = max(cfqg->busy_queues_avg[rt], busy);
1004         cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
1005                 cfq_hist_divisor;
1006         return cfqg->busy_queues_avg[rt];
1007 }
1008 
1009 static inline unsigned
1010 cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
1011 {
1012         return cfqd->cfq_target_latency * cfqg->vfraction >> CFQ_SERVICE_SHIFT;
1013 }
1014 
1015 static inline unsigned
1016 cfq_scaled_cfqq_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1017 {
1018         unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
1019         if (cfqd->cfq_latency) {
1020                 /*
1021                  * interested queues (we consider only the ones with the same
1022                  * priority class in the cfq group)
1023                  */
1024                 unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
1025                                                 cfq_class_rt(cfqq));
1026                 unsigned sync_slice = cfqd->cfq_slice[1];
1027                 unsigned expect_latency = sync_slice * iq;
1028                 unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
1029 
1030                 if (expect_latency > group_slice) {
1031                         unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
1032                         /* scale low_slice according to IO priority
1033                          * and sync vs async */
1034                         unsigned low_slice =
1035                                 min(slice, base_low_slice * slice / sync_slice);
1036                         /* the adapted slice value is scaled to fit all iqs
1037                          * into the target latency */
1038                         slice = max(slice * group_slice / expect_latency,
1039                                     low_slice);
1040                 }
1041         }
1042         return slice;
1043 }
1044 
1045 static inline void
1046 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1047 {
1048         unsigned slice = cfq_scaled_cfqq_slice(cfqd, cfqq);
1049 
1050         cfqq->slice_start = jiffies;
1051         cfqq->slice_end = jiffies + slice;
1052         cfqq->allocated_slice = slice;
1053         cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
1054 }
1055 
1056 /*
1057  * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
1058  * isn't valid until the first request from the dispatch is activated
1059  * and the slice time set.
1060  */
1061 static inline bool cfq_slice_used(struct cfq_queue *cfqq)
1062 {
1063         if (cfq_cfqq_slice_new(cfqq))
1064                 return false;
1065         if (time_before(jiffies, cfqq->slice_end))
1066                 return false;
1067 
1068         return true;
1069 }
1070 
1071 /*
1072  * Lifted from AS - choose which of rq1 and rq2 that is best served now.
1073  * We choose the request that is closest to the head right now. Distance
1074  * behind the head is penalized and only allowed to a certain extent.
1075  */
1076 static struct request *
1077 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
1078 {
1079         sector_t s1, s2, d1 = 0, d2 = 0;
1080         unsigned long back_max;
1081 #define CFQ_RQ1_WRAP    0x01 /* request 1 wraps */
1082 #define CFQ_RQ2_WRAP    0x02 /* request 2 wraps */
1083         unsigned wrap = 0; /* bit mask: requests behind the disk head? */
1084 
1085         if (rq1 == NULL || rq1 == rq2)
1086                 return rq2;
1087         if (rq2 == NULL)
1088                 return rq1;
1089 
1090         if (rq_is_sync(rq1) != rq_is_sync(rq2))
1091                 return rq_is_sync(rq1) ? rq1 : rq2;
1092 
1093         if ((rq1->cmd_flags ^ rq2->cmd_flags) & REQ_PRIO)
1094                 return rq1->cmd_flags & REQ_PRIO ? rq1 : rq2;
1095 
1096         s1 = blk_rq_pos(rq1);
1097         s2 = blk_rq_pos(rq2);
1098 
1099         /*
1100          * by definition, 1KiB is 2 sectors
1101          */
1102         back_max = cfqd->cfq_back_max * 2;
1103 
1104         /*
1105          * Strict one way elevator _except_ in the case where we allow
1106          * short backward seeks which are biased as twice the cost of a
1107          * similar forward seek.
1108          */
1109         if (s1 >= last)
1110                 d1 = s1 - last;
1111         else if (s1 + back_max >= last)
1112                 d1 = (last - s1) * cfqd->cfq_back_penalty;
1113         else
1114                 wrap |= CFQ_RQ1_WRAP;
1115 
1116         if (s2 >= last)
1117                 d2 = s2 - last;
1118         else if (s2 + back_max >= last)
1119                 d2 = (last - s2) * cfqd->cfq_back_penalty;
1120         else
1121                 wrap |= CFQ_RQ2_WRAP;
1122 
1123         /* Found required data */
1124 
1125         /*
1126          * By doing switch() on the bit mask "wrap" we avoid having to
1127          * check two variables for all permutations: --> faster!
1128          */
1129         switch (wrap) {
1130         case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
1131                 if (d1 < d2)
1132                         return rq1;
1133                 else if (d2 < d1)
1134                         return rq2;
1135                 else {
1136                         if (s1 >= s2)
1137                                 return rq1;
1138                         else
1139                                 return rq2;
1140                 }
1141 
1142         case CFQ_RQ2_WRAP:
1143                 return rq1;
1144         case CFQ_RQ1_WRAP:
1145                 return rq2;
1146         case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
1147         default:
1148                 /*
1149                  * Since both rqs are wrapped,
1150                  * start with the one that's further behind head
1151                  * (--> only *one* back seek required),
1152                  * since back seek takes more time than forward.
1153                  */
1154                 if (s1 <= s2)
1155                         return rq1;
1156                 else
1157                         return rq2;
1158         }
1159 }
1160 
1161 /*
1162  * The below is leftmost cache rbtree addon
1163  */
1164 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
1165 {
1166         /* Service tree is empty */
1167         if (!root->count)
1168                 return NULL;
1169 
1170         if (!root->left)
1171                 root->left = rb_first(&root->rb);
1172 
1173         if (root->left)
1174                 return rb_entry(root->left, struct cfq_queue, rb_node);
1175 
1176         return NULL;
1177 }
1178 
1179 static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
1180 {
1181         if (!root->left)
1182                 root->left = rb_first(&root->rb);
1183 
1184         if (root->left)
1185                 return rb_entry_cfqg(root->left);
1186 
1187         return NULL;
1188 }
1189 
1190 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
1191 {
1192         rb_erase(n, root);
1193         RB_CLEAR_NODE(n);
1194 }
1195 
1196 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
1197 {
1198         if (root->left == n)
1199                 root->left = NULL;
1200         rb_erase_init(n, &root->rb);
1201         --root->count;
1202 }
1203 
1204 /*
1205  * would be nice to take fifo expire time into account as well
1206  */
1207 static struct request *
1208 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1209                   struct request *last)
1210 {
1211         struct rb_node *rbnext = rb_next(&last->rb_node);
1212         struct rb_node *rbprev = rb_prev(&last->rb_node);
1213         struct request *next = NULL, *prev = NULL;
1214 
1215         BUG_ON(RB_EMPTY_NODE(&last->rb_node));
1216 
1217         if (rbprev)
1218                 prev = rb_entry_rq(rbprev);
1219 
1220         if (rbnext)
1221                 next = rb_entry_rq(rbnext);
1222         else {
1223                 rbnext = rb_first(&cfqq->sort_list);
1224                 if (rbnext && rbnext != &last->rb_node)
1225                         next = rb_entry_rq(rbnext);
1226         }
1227 
1228         return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
1229 }
1230 
1231 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
1232                                       struct cfq_queue *cfqq)
1233 {
1234         /*
1235          * just an approximation, should be ok.
1236          */
1237         return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
1238                        cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
1239 }
1240 
1241 static inline s64
1242 cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
1243 {
1244         return cfqg->vdisktime - st->min_vdisktime;
1245 }
1246 
1247 static void
1248 __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
1249 {
1250         struct rb_node **node = &st->rb.rb_node;
1251         struct rb_node *parent = NULL;
1252         struct cfq_group *__cfqg;
1253         s64 key = cfqg_key(st, cfqg);
1254         int left = 1;
1255 
1256         while (*node != NULL) {
1257                 parent = *node;
1258                 __cfqg = rb_entry_cfqg(parent);
1259 
1260                 if (key < cfqg_key(st, __cfqg))
1261                         node = &parent->rb_left;
1262                 else {
1263                         node = &parent->rb_right;
1264                         left = 0;
1265                 }
1266         }
1267 
1268         if (left)
1269                 st->left = &cfqg->rb_node;
1270 
1271         rb_link_node(&cfqg->rb_node, parent, node);
1272         rb_insert_color(&cfqg->rb_node, &st->rb);
1273 }
1274 
1275 static void
1276 cfq_update_group_weight(struct cfq_group *cfqg)
1277 {
1278         if (cfqg->new_weight) {
1279                 cfqg->weight = cfqg->new_weight;
1280                 cfqg->new_weight = 0;
1281         }
1282 }
1283 
1284 static void
1285 cfq_update_group_leaf_weight(struct cfq_group *cfqg)
1286 {
1287         BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
1288 
1289         if (cfqg->new_leaf_weight) {
1290                 cfqg->leaf_weight = cfqg->new_leaf_weight;
1291                 cfqg->new_leaf_weight = 0;
1292         }
1293 }
1294 
1295 static void
1296 cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
1297 {
1298         unsigned int vfr = 1 << CFQ_SERVICE_SHIFT;      /* start with 1 */
1299         struct cfq_group *pos = cfqg;
1300         struct cfq_group *parent;
1301         bool propagate;
1302 
1303         /* add to the service tree */
1304         BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
1305 
1306         cfq_update_group_leaf_weight(cfqg);
1307         __cfq_group_service_tree_add(st, cfqg);
1308 
1309         /*
1310          * Activate @cfqg and calculate the portion of vfraction @cfqg is
1311          * entitled to.  vfraction is calculated by walking the tree
1312          * towards the root calculating the fraction it has at each level.
1313          * The compounded ratio is how much vfraction @cfqg owns.
1314          *
1315          * Start with the proportion tasks in this cfqg has against active
1316          * children cfqgs - its leaf_weight against children_weight.
1317          */
1318         propagate = !pos->nr_active++;
1319         pos->children_weight += pos->leaf_weight;
1320         vfr = vfr * pos->leaf_weight / pos->children_weight;
1321 
1322         /*
1323          * Compound ->weight walking up the tree.  Both activation and
1324          * vfraction calculation are done in the same loop.  Propagation
1325          * stops once an already activated node is met.  vfraction
1326          * calculation should always continue to the root.
1327          */
1328         while ((parent = cfqg_parent(pos))) {
1329                 if (propagate) {
1330                         cfq_update_group_weight(pos);
1331                         propagate = !parent->nr_active++;
1332                         parent->children_weight += pos->weight;
1333                 }
1334                 vfr = vfr * pos->weight / parent->children_weight;
1335                 pos = parent;
1336         }
1337 
1338         cfqg->vfraction = max_t(unsigned, vfr, 1);
1339 }
1340 
1341 static void
1342 cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
1343 {
1344         struct cfq_rb_root *st = &cfqd->grp_service_tree;
1345         struct cfq_group *__cfqg;
1346         struct rb_node *n;
1347 
1348         cfqg->nr_cfqq++;
1349         if (!RB_EMPTY_NODE(&cfqg->rb_node))
1350                 return;
1351 
1352         /*
1353          * Currently put the group at the end. Later implement something
1354          * so that groups get lesser vtime based on their weights, so that
1355          * if group does not loose all if it was not continuously backlogged.
1356          */
1357         n = rb_last(&st->rb);
1358         if (n) {
1359                 __cfqg = rb_entry_cfqg(n);
1360                 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
1361         } else
1362                 cfqg->vdisktime = st->min_vdisktime;
1363         cfq_group_service_tree_add(st, cfqg);
1364 }
1365 
1366 static void
1367 cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg)
1368 {
1369         struct cfq_group *pos = cfqg;
1370         bool propagate;
1371 
1372         /*
1373          * Undo activation from cfq_group_service_tree_add().  Deactivate
1374          * @cfqg and propagate deactivation upwards.
1375          */
1376         propagate = !--pos->nr_active;
1377         pos->children_weight -= pos->leaf_weight;
1378 
1379         while (propagate) {
1380                 struct cfq_group *parent = cfqg_parent(pos);
1381 
1382                 /* @pos has 0 nr_active at this point */
1383                 WARN_ON_ONCE(pos->children_weight);
1384                 pos->vfraction = 0;
1385 
1386                 if (!parent)
1387                         break;
1388 
1389                 propagate = !--parent->nr_active;
1390                 parent->children_weight -= pos->weight;
1391                 pos = parent;
1392         }
1393 
1394         /* remove from the service tree */
1395         if (!RB_EMPTY_NODE(&cfqg->rb_node))
1396                 cfq_rb_erase(&cfqg->rb_node, st);
1397 }
1398 
1399 static void
1400 cfq_group_notify_queue_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
1401 {
1402         struct cfq_rb_root *st = &cfqd->grp_service_tree;
1403 
1404         BUG_ON(cfqg->nr_cfqq < 1);
1405         cfqg->nr_cfqq--;
1406 
1407         /* If there are other cfq queues under this group, don't delete it */
1408         if (cfqg->nr_cfqq)
1409                 return;
1410 
1411         cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
1412         cfq_group_service_tree_del(st, cfqg);
1413         cfqg->saved_wl_slice = 0;
1414         cfqg_stats_update_dequeue(cfqg);
1415 }
1416 
1417 static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq,
1418                                                 unsigned int *unaccounted_time)
1419 {
1420         unsigned int slice_used;
1421 
1422         /*
1423          * Queue got expired before even a single request completed or
1424          * got expired immediately after first request completion.
1425          */
1426         if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
1427                 /*
1428                  * Also charge the seek time incurred to the group, otherwise
1429                  * if there are mutiple queues in the group, each can dispatch
1430                  * a single request on seeky media and cause lots of seek time
1431                  * and group will never know it.
1432                  */
1433                 slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
1434                                         1);
1435         } else {
1436                 slice_used = jiffies - cfqq->slice_start;
1437                 if (slice_used > cfqq->allocated_slice) {
1438                         *unaccounted_time = slice_used - cfqq->allocated_slice;
1439                         slice_used = cfqq->allocated_slice;
1440                 }
1441                 if (time_after(cfqq->slice_start, cfqq->dispatch_start))
1442                         *unaccounted_time += cfqq->slice_start -
1443                                         cfqq->dispatch_start;
1444         }
1445 
1446         return slice_used;
1447 }
1448 
1449 static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
1450                                 struct cfq_queue *cfqq)
1451 {
1452         struct cfq_rb_root *st = &cfqd->grp_service_tree;
1453         unsigned int used_sl, charge, unaccounted_sl = 0;
1454         int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
1455                         - cfqg->service_tree_idle.count;
1456         unsigned int vfr;
1457 
1458         BUG_ON(nr_sync < 0);
1459         used_sl = charge = cfq_cfqq_slice_usage(cfqq, &unaccounted_sl);
1460 
1461         if (iops_mode(cfqd))
1462                 charge = cfqq->slice_dispatch;
1463         else if (!cfq_cfqq_sync(cfqq) && !nr_sync)
1464                 charge = cfqq->allocated_slice;
1465 
1466         /*
1467          * Can't update vdisktime while on service tree and cfqg->vfraction
1468          * is valid only while on it.  Cache vfr, leave the service tree,
1469          * update vdisktime and go back on.  The re-addition to the tree
1470          * will also update the weights as necessary.
1471          */
1472         vfr = cfqg->vfraction;
1473         cfq_group_service_tree_del(st, cfqg);
1474         cfqg->vdisktime += cfqg_scale_charge(charge, vfr);
1475         cfq_group_service_tree_add(st, cfqg);
1476 
1477         /* This group is being expired. Save the context */
1478         if (time_after(cfqd->workload_expires, jiffies)) {
1479                 cfqg->saved_wl_slice = cfqd->workload_expires
1480                                                 - jiffies;
1481                 cfqg->saved_wl_type = cfqd->serving_wl_type;
1482                 cfqg->saved_wl_class = cfqd->serving_wl_class;
1483         } else
1484                 cfqg->saved_wl_slice = 0;
1485 
1486         cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
1487                                         st->min_vdisktime);
1488         cfq_log_cfqq(cfqq->cfqd, cfqq,
1489                      "sl_used=%u disp=%u charge=%u iops=%u sect=%lu",
1490                      used_sl, cfqq->slice_dispatch, charge,
1491                      iops_mode(cfqd), cfqq->nr_sectors);
1492         cfqg_stats_update_timeslice_used(cfqg, used_sl, unaccounted_sl);
1493         cfqg_stats_set_start_empty_time(cfqg);
1494 }
1495 
1496 /**
1497  * cfq_init_cfqg_base - initialize base part of a cfq_group
1498  * @cfqg: cfq_group to initialize
1499  *
1500  * Initialize the base part which is used whether %CONFIG_CFQ_GROUP_IOSCHED
1501  * is enabled or not.
1502  */
1503 static void cfq_init_cfqg_base(struct cfq_group *cfqg)
1504 {
1505         struct cfq_rb_root *st;
1506         int i, j;
1507 
1508         for_each_cfqg_st(cfqg, i, j, st)
1509                 *st = CFQ_RB_ROOT;
1510         RB_CLEAR_NODE(&cfqg->rb_node);
1511 
1512         cfqg->ttime.last_end_request = jiffies;
1513 }
1514 
1515 #ifdef CONFIG_CFQ_GROUP_IOSCHED
1516 static void cfq_pd_init(struct blkcg_gq *blkg)
1517 {
1518         struct cfq_group *cfqg = blkg_to_cfqg(blkg);
1519 
1520         cfq_init_cfqg_base(cfqg);
1521         cfqg->weight = blkg->blkcg->cfq_weight;
1522         cfqg->leaf_weight = blkg->blkcg->cfq_leaf_weight;
1523 }
1524 
1525 static void cfq_pd_offline(struct blkcg_gq *blkg)
1526 {
1527         /*
1528          * @blkg is going offline and will be ignored by
1529          * blkg_[rw]stat_recursive_sum().  Transfer stats to the parent so
1530          * that they don't get lost.  If IOs complete after this point, the
1531          * stats for them will be lost.  Oh well...
1532          */
1533         cfqg_stats_xfer_dead(blkg_to_cfqg(blkg));
1534 }
1535 
1536 /* offset delta from cfqg->stats to cfqg->dead_stats */
1537 static const int dead_stats_off_delta = offsetof(struct cfq_group, dead_stats) -
1538                                         offsetof(struct cfq_group, stats);
1539 
1540 /* to be used by recursive prfill, sums live and dead stats recursively */
1541 static u64 cfqg_stat_pd_recursive_sum(struct blkg_policy_data *pd, int off)
1542 {
1543         u64 sum = 0;
1544 
1545         sum += blkg_stat_recursive_sum(pd, off);
1546         sum += blkg_stat_recursive_sum(pd, off + dead_stats_off_delta);
1547         return sum;
1548 }
1549 
1550 /* to be used by recursive prfill, sums live and dead rwstats recursively */
1551 static struct blkg_rwstat cfqg_rwstat_pd_recursive_sum(struct blkg_policy_data *pd,
1552                                                        int off)
1553 {
1554         struct blkg_rwstat a, b;
1555 
1556         a = blkg_rwstat_recursive_sum(pd, off);
1557         b = blkg_rwstat_recursive_sum(pd, off + dead_stats_off_delta);
1558         blkg_rwstat_merge(&a, &b);
1559         return a;
1560 }
1561 
1562 static void cfq_pd_reset_stats(struct blkcg_gq *blkg)
1563 {
1564         struct cfq_group *cfqg = blkg_to_cfqg(blkg);
1565 
1566         cfqg_stats_reset(&cfqg->stats);
1567         cfqg_stats_reset(&cfqg->dead_stats);
1568 }
1569 
1570 /*
1571  * Search for the cfq group current task belongs to. request_queue lock must
1572  * be held.
1573  */
1574 static struct cfq_group *cfq_lookup_create_cfqg(struct cfq_data *cfqd,
1575                                                 struct blkcg *blkcg)
1576 {
1577         struct request_queue *q = cfqd->queue;
1578         struct cfq_group *cfqg = NULL;
1579 
1580         /* avoid lookup for the common case where there's no blkcg */
1581         if (blkcg == &blkcg_root) {
1582                 cfqg = cfqd->root_group;
1583         } else {
1584                 struct blkcg_gq *blkg;
1585 
1586                 blkg = blkg_lookup_create(blkcg, q);
1587                 if (!IS_ERR(blkg))
1588                         cfqg = blkg_to_cfqg(blkg);
1589         }
1590 
1591         return cfqg;
1592 }
1593 
1594 static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
1595 {
1596         /* Currently, all async queues are mapped to root group */
1597         if (!cfq_cfqq_sync(cfqq))
1598                 cfqg = cfqq->cfqd->root_group;
1599 
1600         cfqq->cfqg = cfqg;
1601         /* cfqq reference on cfqg */
1602         cfqg_get(cfqg);
1603 }
1604 
1605 static u64 cfqg_prfill_weight_device(struct seq_file *sf,
1606                                      struct blkg_policy_data *pd, int off)
1607 {
1608         struct cfq_group *cfqg = pd_to_cfqg(pd);
1609 
1610         if (!cfqg->dev_weight)
1611                 return 0;
1612         return __blkg_prfill_u64(sf, pd, cfqg->dev_weight);
1613 }
1614 
1615 static int cfqg_print_weight_device(struct cgroup_subsys_state *css,
1616                                     struct cftype *cft, struct seq_file *sf)
1617 {
1618         blkcg_print_blkgs(sf, css_to_blkcg(css), cfqg_prfill_weight_device,
1619                           &blkcg_policy_cfq, 0, false);
1620         return 0;
1621 }
1622 
1623 static u64 cfqg_prfill_leaf_weight_device(struct seq_file *sf,
1624                                           struct blkg_policy_data *pd, int off)
1625 {
1626         struct cfq_group *cfqg = pd_to_cfqg(pd);
1627 
1628         if (!cfqg->dev_leaf_weight)
1629                 return 0;
1630         return __blkg_prfill_u64(sf, pd, cfqg->dev_leaf_weight);
1631 }
1632 
1633 static int cfqg_print_leaf_weight_device(struct cgroup_subsys_state *css,
1634                                          struct cftype *cft,
1635                                          struct seq_file *sf)
1636 {
1637         blkcg_print_blkgs(sf, css_to_blkcg(css), cfqg_prfill_leaf_weight_device,
1638                           &blkcg_policy_cfq, 0, false);
1639         return 0;
1640 }
1641 
1642 static int cfq_print_weight(struct cgroup_subsys_state *css, struct cftype *cft,
1643                             struct seq_file *sf)
1644 {
1645         seq_printf(sf, "%u\n", css_to_blkcg(css)->cfq_weight);
1646         return 0;
1647 }
1648 
1649 static int cfq_print_leaf_weight(struct cgroup_subsys_state *css,
1650                                  struct cftype *cft, struct seq_file *sf)
1651 {
1652         seq_printf(sf, "%u\n", css_to_blkcg(css)->cfq_leaf_weight);
1653         return 0;
1654 }
1655 
1656 static int __cfqg_set_weight_device(struct cgroup_subsys_state *css,
1657                                     struct cftype *cft, const char *buf,
1658                                     bool is_leaf_weight)
1659 {
1660         struct blkcg *blkcg = css_to_blkcg(css);
1661         struct blkg_conf_ctx ctx;
1662         struct cfq_group *cfqg;
1663         int ret;
1664 
1665         ret = blkg_conf_prep(blkcg, &blkcg_policy_cfq, buf, &ctx);
1666         if (ret)
1667                 return ret;
1668 
1669         ret = -EINVAL;
1670         cfqg = blkg_to_cfqg(ctx.blkg);
1671         if (!ctx.v || (ctx.v >= CFQ_WEIGHT_MIN && ctx.v <= CFQ_WEIGHT_MAX)) {
1672                 if (!is_leaf_weight) {
1673                         cfqg->dev_weight = ctx.v;
1674                         cfqg->new_weight = ctx.v ?: blkcg->cfq_weight;
1675                 } else {
1676                         cfqg->dev_leaf_weight = ctx.v;
1677                         cfqg->new_leaf_weight = ctx.v ?: blkcg->cfq_leaf_weight;
1678                 }
1679                 ret = 0;
1680         }
1681 
1682         blkg_conf_finish(&ctx);
1683         return ret;
1684 }
1685 
1686 static int cfqg_set_weight_device(struct cgroup_subsys_state *css,
1687                                   struct cftype *cft, const char *buf)
1688 {
1689         return __cfqg_set_weight_device(css, cft, buf, false);
1690 }
1691 
1692 static int cfqg_set_leaf_weight_device(struct cgroup_subsys_state *css,
1693                                        struct cftype *cft, const char *buf)
1694 {
1695         return __cfqg_set_weight_device(css, cft, buf, true);
1696 }
1697 
1698 static int __cfq_set_weight(struct cgroup_subsys_state *css, struct cftype *cft,
1699                             u64 val, bool is_leaf_weight)
1700 {
1701         struct blkcg *blkcg = css_to_blkcg(css);
1702         struct blkcg_gq *blkg;
1703 
1704         if (val < CFQ_WEIGHT_MIN || val > CFQ_WEIGHT_MAX)
1705                 return -EINVAL;
1706 
1707         spin_lock_irq(&blkcg->lock);
1708 
1709         if (!is_leaf_weight)
1710                 blkcg->cfq_weight = val;
1711         else
1712                 blkcg->cfq_leaf_weight = val;
1713 
1714         hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
1715                 struct cfq_group *cfqg = blkg_to_cfqg(blkg);
1716 
1717                 if (!cfqg)
1718                         continue;
1719 
1720                 if (!is_leaf_weight) {
1721                         if (!cfqg->dev_weight)
1722                                 cfqg->new_weight = blkcg->cfq_weight;
1723                 } else {
1724                         if (!cfqg->dev_leaf_weight)
1725                                 cfqg->new_leaf_weight = blkcg->cfq_leaf_weight;
1726                 }
1727         }
1728 
1729         spin_unlock_irq(&blkcg->lock);
1730         return 0;
1731 }
1732 
1733 static int cfq_set_weight(struct cgroup_subsys_state *css, struct cftype *cft,
1734                           u64 val)
1735 {
1736         return __cfq_set_weight(css, cft, val, false);
1737 }
1738 
1739 static int cfq_set_leaf_weight(struct cgroup_subsys_state *css,
1740                                struct cftype *cft, u64 val)
1741 {
1742         return __cfq_set_weight(css, cft, val, true);
1743 }
1744 
1745 static int cfqg_print_stat(struct cgroup_subsys_state *css, struct cftype *cft,
1746                            struct seq_file *sf)
1747 {
1748         struct blkcg *blkcg = css_to_blkcg(css);
1749 
1750         blkcg_print_blkgs(sf, blkcg, blkg_prfill_stat, &blkcg_policy_cfq,
1751                           cft->private, false);
1752         return 0;
1753 }
1754 
1755 static int cfqg_print_rwstat(struct cgroup_subsys_state *css,
1756                              struct cftype *cft, struct seq_file *sf)
1757 {
1758         struct blkcg *blkcg = css_to_blkcg(css);
1759 
1760         blkcg_print_blkgs(sf, blkcg, blkg_prfill_rwstat, &blkcg_policy_cfq,
1761                           cft->private, true);
1762         return 0;
1763 }
1764 
1765 static u64 cfqg_prfill_stat_recursive(struct seq_file *sf,
1766                                       struct blkg_policy_data *pd, int off)
1767 {
1768         u64 sum = cfqg_stat_pd_recursive_sum(pd, off);
1769 
1770         return __blkg_prfill_u64(sf, pd, sum);
1771 }
1772 
1773 static u64 cfqg_prfill_rwstat_recursive(struct seq_file *sf,
1774                                         struct blkg_policy_data *pd, int off)
1775 {
1776         struct blkg_rwstat sum = cfqg_rwstat_pd_recursive_sum(pd, off);
1777 
1778         return __blkg_prfill_rwstat(sf, pd, &sum);
1779 }
1780 
1781 static int cfqg_print_stat_recursive(struct cgroup_subsys_state *css,
1782                                      struct cftype *cft, struct seq_file *sf)
1783 {
1784         struct blkcg *blkcg = css_to_blkcg(css);
1785 
1786         blkcg_print_blkgs(sf, blkcg, cfqg_prfill_stat_recursive,
1787                           &blkcg_policy_cfq, cft->private, false);
1788         return 0;
1789 }
1790 
1791 static int cfqg_print_rwstat_recursive(struct cgroup_subsys_state *css,
1792                                        struct cftype *cft, struct seq_file *sf)
1793 {
1794         struct blkcg *blkcg = css_to_blkcg(css);
1795 
1796         blkcg_print_blkgs(sf, blkcg, cfqg_prfill_rwstat_recursive,
1797                           &blkcg_policy_cfq, cft->private, true);
1798         return 0;
1799 }
1800 
1801 #ifdef CONFIG_DEBUG_BLK_CGROUP
1802 static u64 cfqg_prfill_avg_queue_size(struct seq_file *sf,
1803                                       struct blkg_policy_data *pd, int off)
1804 {
1805         struct cfq_group *cfqg = pd_to_cfqg(pd);
1806         u64 samples = blkg_stat_read(&cfqg->stats.avg_queue_size_samples);
1807         u64 v = 0;
1808 
1809         if (samples) {
1810                 v = blkg_stat_read(&cfqg->stats.avg_queue_size_sum);
1811                 v = div64_u64(v, samples);
1812         }
1813         __blkg_prfill_u64(sf, pd, v);
1814         return 0;
1815 }
1816 
1817 /* print avg_queue_size */
1818 static int cfqg_print_avg_queue_size(struct cgroup_subsys_state *css,
1819                                      struct cftype *cft, struct seq_file *sf)
1820 {
1821         struct blkcg *blkcg = css_to_blkcg(css);
1822 
1823         blkcg_print_blkgs(sf, blkcg, cfqg_prfill_avg_queue_size,
1824                           &blkcg_policy_cfq, 0, false);
1825         return 0;
1826 }
1827 #endif  /* CONFIG_DEBUG_BLK_CGROUP */
1828 
1829 static struct cftype cfq_blkcg_files[] = {
1830         /* on root, weight is mapped to leaf_weight */
1831         {
1832                 .name = "weight_device",
1833                 .flags = CFTYPE_ONLY_ON_ROOT,
1834                 .read_seq_string = cfqg_print_leaf_weight_device,
1835                 .write_string = cfqg_set_leaf_weight_device,
1836                 .max_write_len = 256,
1837         },
1838         {
1839                 .name = "weight",
1840                 .flags = CFTYPE_ONLY_ON_ROOT,
1841                 .read_seq_string = cfq_print_leaf_weight,
1842                 .write_u64 = cfq_set_leaf_weight,
1843         },
1844 
1845         /* no such mapping necessary for !roots */
1846         {
1847                 .name = "weight_device",
1848                 .flags = CFTYPE_NOT_ON_ROOT,
1849                 .read_seq_string = cfqg_print_weight_device,
1850                 .write_string = cfqg_set_weight_device,
1851                 .max_write_len = 256,
1852         },
1853         {
1854                 .name = "weight",
1855                 .flags = CFTYPE_NOT_ON_ROOT,
1856                 .read_seq_string = cfq_print_weight,
1857                 .write_u64 = cfq_set_weight,
1858         },
1859 
1860         {
1861                 .name = "leaf_weight_device",
1862                 .read_seq_string = cfqg_print_leaf_weight_device,
1863                 .write_string = cfqg_set_leaf_weight_device,
1864                 .max_write_len = 256,
1865         },
1866         {
1867                 .name = "leaf_weight",
1868                 .read_seq_string = cfq_print_leaf_weight,
1869                 .write_u64 = cfq_set_leaf_weight,
1870         },
1871 
1872         /* statistics, covers only the tasks in the cfqg */
1873         {
1874                 .name = "time",
1875                 .private = offsetof(struct cfq_group, stats.time),
1876                 .read_seq_string = cfqg_print_stat,
1877         },
1878         {
1879                 .name = "sectors",
1880                 .private = offsetof(struct cfq_group, stats.sectors),
1881                 .read_seq_string = cfqg_print_stat,
1882         },
1883         {
1884                 .name = "io_service_bytes",
1885                 .private = offsetof(struct cfq_group, stats.service_bytes),
1886                 .read_seq_string = cfqg_print_rwstat,
1887         },
1888         {
1889                 .name = "io_serviced",
1890                 .private = offsetof(struct cfq_group, stats.serviced),
1891                 .read_seq_string = cfqg_print_rwstat,
1892         },
1893         {
1894                 .name = "io_service_time",
1895                 .private = offsetof(struct cfq_group, stats.service_time),
1896                 .read_seq_string = cfqg_print_rwstat,
1897         },
1898         {
1899                 .name = "io_wait_time",
1900                 .private = offsetof(struct cfq_group, stats.wait_time),
1901                 .read_seq_string = cfqg_print_rwstat,
1902         },
1903         {
1904                 .name = "io_merged",
1905                 .private = offsetof(struct cfq_group, stats.merged),
1906                 .read_seq_string = cfqg_print_rwstat,
1907         },
1908         {
1909                 .name = "io_queued",
1910                 .private = offsetof(struct cfq_group, stats.queued),
1911                 .read_seq_string = cfqg_print_rwstat,
1912         },
1913 
1914         /* the same statictics which cover the cfqg and its descendants */
1915         {
1916                 .name = "time_recursive",
1917                 .private = offsetof(struct cfq_group, stats.time),
1918                 .read_seq_string = cfqg_print_stat_recursive,
1919         },
1920         {
1921                 .name = "sectors_recursive",
1922                 .private = offsetof(struct cfq_group, stats.sectors),
1923                 .read_seq_string = cfqg_print_stat_recursive,
1924         },
1925         {
1926                 .name = "io_service_bytes_recursive",
1927                 .private = offsetof(struct cfq_group, stats.service_bytes),
1928                 .read_seq_string = cfqg_print_rwstat_recursive,
1929         },
1930         {
1931                 .name = "io_serviced_recursive",
1932                 .private = offsetof(struct cfq_group, stats.serviced),
1933                 .read_seq_string = cfqg_print_rwstat_recursive,
1934         },
1935         {
1936                 .name = "io_service_time_recursive",
1937                 .private = offsetof(struct cfq_group, stats.service_time),
1938                 .read_seq_string = cfqg_print_rwstat_recursive,
1939         },
1940         {
1941                 .name = "io_wait_time_recursive",
1942                 .private = offsetof(struct cfq_group, stats.wait_time),
1943                 .read_seq_string = cfqg_print_rwstat_recursive,
1944         },
1945         {
1946                 .name = "io_merged_recursive",
1947                 .private = offsetof(struct cfq_group, stats.merged),
1948                 .read_seq_string = cfqg_print_rwstat_recursive,
1949         },
1950         {
1951                 .name = "io_queued_recursive",
1952                 .private = offsetof(struct cfq_group, stats.queued),
1953                 .read_seq_string = cfqg_print_rwstat_recursive,
1954         },
1955 #ifdef CONFIG_DEBUG_BLK_CGROUP
1956         {
1957                 .name = "avg_queue_size",
1958                 .read_seq_string = cfqg_print_avg_queue_size,
1959         },
1960         {
1961                 .name = "group_wait_time",
1962                 .private = offsetof(struct cfq_group, stats.group_wait_time),
1963                 .read_seq_string = cfqg_print_stat,
1964         },
1965         {
1966                 .name = "idle_time",
1967                 .private = offsetof(struct cfq_group, stats.idle_time),
1968                 .read_seq_string = cfqg_print_stat,
1969         },
1970         {
1971                 .name = "empty_time",
1972                 .private = offsetof(struct cfq_group, stats.empty_time),
1973                 .read_seq_string = cfqg_print_stat,
1974         },
1975         {
1976                 .name = "dequeue",
1977                 .private = offsetof(struct cfq_group, stats.dequeue),
1978                 .read_seq_string = cfqg_print_stat,
1979         },
1980         {
1981                 .name = "unaccounted_time",
1982                 .private = offsetof(struct cfq_group, stats.unaccounted_time),
1983                 .read_seq_string = cfqg_print_stat,
1984         },
1985 #endif  /* CONFIG_DEBUG_BLK_CGROUP */
1986         { }     /* terminate */
1987 };
1988 #else /* GROUP_IOSCHED */
1989 static struct cfq_group *cfq_lookup_create_cfqg(struct cfq_data *cfqd,
1990                                                 struct blkcg *blkcg)
1991 {
1992         return cfqd->root_group;
1993 }
1994 
1995 static inline void
1996 cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
1997         cfqq->cfqg = cfqg;
1998 }
1999 
2000 #endif /* GROUP_IOSCHED */
2001 
2002 /*
2003  * The cfqd->service_trees holds all pending cfq_queue's that have
2004  * requests waiting to be processed. It is sorted in the order that
2005  * we will service the queues.
2006  */
2007 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2008                                  bool add_front)
2009 {
2010         struct rb_node **p, *parent;
2011         struct cfq_queue *__cfqq;
2012         unsigned long rb_key;
2013         struct cfq_rb_root *st;
2014         int left;
2015         int new_cfqq = 1;
2016 
2017         st = st_for(cfqq->cfqg, cfqq_class(cfqq), cfqq_type(cfqq));
2018         if (cfq_class_idle(cfqq)) {
2019                 rb_key = CFQ_IDLE_DELAY;
2020                 parent = rb_last(&st->rb);
2021                 if (parent && parent != &cfqq->rb_node) {
2022                         __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
2023                         rb_key += __cfqq->rb_key;
2024                 } else
2025                         rb_key += jiffies;
2026         } else if (!add_front) {
2027                 /*
2028                  * Get our rb key offset. Subtract any residual slice
2029                  * value carried from last service. A negative resid
2030                  * count indicates slice overrun, and this should position
2031                  * the next service time further away in the tree.
2032                  */
2033                 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
2034                 rb_key -= cfqq->slice_resid;
2035                 cfqq->slice_resid = 0;
2036         } else {
2037                 rb_key = -HZ;
2038                 __cfqq = cfq_rb_first(st);
2039                 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
2040         }
2041 
2042         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
2043                 new_cfqq = 0;
2044                 /*
2045                  * same position, nothing more to do
2046                  */
2047                 if (rb_key == cfqq->rb_key && cfqq->service_tree == st)
2048                         return;
2049 
2050                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
2051                 cfqq->service_tree = NULL;
2052         }
2053 
2054         left = 1;
2055         parent = NULL;
2056         cfqq->service_tree = st;
2057         p = &st->rb.rb_node;
2058         while (*p) {
2059                 parent = *p;
2060                 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
2061 
2062                 /*
2063                  * sort by key, that represents service time.
2064                  */
2065                 if (time_before(rb_key, __cfqq->rb_key))
2066                         p = &parent->rb_left;
2067                 else {
2068                         p = &parent->rb_right;
2069                         left = 0;
2070                 }
2071         }
2072 
2073         if (left)
2074                 st->left = &cfqq->rb_node;
2075 
2076         cfqq->rb_key = rb_key;
2077         rb_link_node(&cfqq->rb_node, parent, p);
2078         rb_insert_color(&cfqq->rb_node, &st->rb);
2079         st->count++;
2080         if (add_front || !new_cfqq)
2081                 return;
2082         cfq_group_notify_queue_add(cfqd, cfqq->cfqg);
2083 }
2084 
2085 static struct cfq_queue *
2086 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
2087                      sector_t sector, struct rb_node **ret_parent,
2088                      struct rb_node ***rb_link)
2089 {
2090         struct rb_node **p, *parent;
2091         struct cfq_queue *cfqq = NULL;
2092 
2093         parent = NULL;
2094         p = &root->rb_node;
2095         while (*p) {
2096                 struct rb_node **n;
2097 
2098                 parent = *p;
2099                 cfqq = rb_entry(parent, struct cfq_queue, p_node);
2100 
2101                 /*
2102                  * Sort strictly based on sector.  Smallest to the left,
2103                  * largest to the right.
2104                  */
2105                 if (sector > blk_rq_pos(cfqq->next_rq))
2106                         n = &(*p)->rb_right;
2107                 else if (sector < blk_rq_pos(cfqq->next_rq))
2108                         n = &(*p)->rb_left;
2109                 else
2110                         break;
2111                 p = n;
2112                 cfqq = NULL;
2113         }
2114 
2115         *ret_parent = parent;
2116         if (rb_link)
2117                 *rb_link = p;
2118         return cfqq;
2119 }
2120 
2121 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2122 {
2123         struct rb_node **p, *parent;
2124         struct cfq_queue *__cfqq;
2125 
2126         if (cfqq->p_root) {
2127                 rb_erase(&cfqq->p_node, cfqq->p_root);
2128                 cfqq->p_root = NULL;
2129         }
2130 
2131         if (cfq_class_idle(cfqq))
2132                 return;
2133         if (!cfqq->next_rq)
2134                 return;
2135 
2136         cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
2137         __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
2138                                       blk_rq_pos(cfqq->next_rq), &parent, &p);
2139         if (!__cfqq) {
2140                 rb_link_node(&cfqq->p_node, parent, p);
2141                 rb_insert_color(&cfqq->p_node, cfqq->p_root);
2142         } else
2143                 cfqq->p_root = NULL;
2144 }
2145 
2146 /*
2147  * Update cfqq's position in the service tree.
2148  */
2149 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2150 {
2151         /*
2152          * Resorting requires the cfqq to be on the RR list already.
2153          */
2154         if (cfq_cfqq_on_rr(cfqq)) {
2155                 cfq_service_tree_add(cfqd, cfqq, 0);
2156                 cfq_prio_tree_add(cfqd, cfqq);
2157         }
2158 }
2159 
2160 /*
2161  * add to busy list of queues for service, trying to be fair in ordering
2162  * the pending list according to last request service
2163  */
2164 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2165 {
2166         cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
2167         BUG_ON(cfq_cfqq_on_rr(cfqq));
2168         cfq_mark_cfqq_on_rr(cfqq);
2169         cfqd->busy_queues++;
2170         if (cfq_cfqq_sync(cfqq))
2171                 cfqd->busy_sync_queues++;
2172 
2173         cfq_resort_rr_list(cfqd, cfqq);
2174 }
2175 
2176 /*
2177  * Called when the cfqq no longer has requests pending, remove it from
2178  * the service tree.
2179  */
2180 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2181 {
2182         cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
2183         BUG_ON(!cfq_cfqq_on_rr(cfqq));
2184         cfq_clear_cfqq_on_rr(cfqq);
2185 
2186         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
2187                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
2188                 cfqq->service_tree = NULL;
2189         }
2190         if (cfqq->p_root) {
2191                 rb_erase(&cfqq->p_node, cfqq->p_root);
2192                 cfqq->p_root = NULL;
2193         }
2194 
2195         cfq_group_notify_queue_del(cfqd, cfqq->cfqg);
2196         BUG_ON(!cfqd->busy_queues);
2197         cfqd->busy_queues--;
2198         if (cfq_cfqq_sync(cfqq))
2199                 cfqd->busy_sync_queues--;
2200 }
2201 
2202 /*
2203  * rb tree support functions
2204  */
2205 static void cfq_del_rq_rb(struct request *rq)
2206 {
2207         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2208         const int sync = rq_is_sync(rq);
2209 
2210         BUG_ON(!cfqq->queued[sync]);
2211         cfqq->queued[sync]--;
2212 
2213         elv_rb_del(&cfqq->sort_list, rq);
2214 
2215         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
2216                 /*
2217                  * Queue will be deleted from service tree when we actually
2218                  * expire it later. Right now just remove it from prio tree
2219                  * as it is empty.
2220                  */
2221                 if (cfqq->p_root) {
2222                         rb_erase(&cfqq->p_node, cfqq->p_root);
2223                         cfqq->p_root = NULL;
2224                 }
2225         }
2226 }
2227 
2228 static void cfq_add_rq_rb(struct request *rq)
2229 {
2230         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2231         struct cfq_data *cfqd = cfqq->cfqd;
2232         struct request *prev;
2233 
2234         cfqq->queued[rq_is_sync(rq)]++;
2235 
2236         elv_rb_add(&cfqq->sort_list, rq);
2237 
2238         if (!cfq_cfqq_on_rr(cfqq))
2239                 cfq_add_cfqq_rr(cfqd, cfqq);
2240 
2241         /*
2242          * check if this request is a better next-serve candidate
2243          */
2244         prev = cfqq->next_rq;
2245         cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
2246 
2247         /*
2248          * adjust priority tree position, if ->next_rq changes
2249          */
2250         if (prev != cfqq->next_rq)
2251                 cfq_prio_tree_add(cfqd, cfqq);
2252 
2253         BUG_ON(!cfqq->next_rq);
2254 }
2255 
2256 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
2257 {
2258         elv_rb_del(&cfqq->sort_list, rq);
2259         cfqq->queued[rq_is_sync(rq)]--;
2260         cfqg_stats_update_io_remove(RQ_CFQG(rq), rq->cmd_flags);
2261         cfq_add_rq_rb(rq);
2262         cfqg_stats_update_io_add(RQ_CFQG(rq), cfqq->cfqd->serving_group,
2263                                  rq->cmd_flags);
2264 }
2265 
2266 static struct request *
2267 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
2268 {
2269         struct task_struct *tsk = current;
2270         struct cfq_io_cq *cic;
2271         struct cfq_queue *cfqq;
2272 
2273         cic = cfq_cic_lookup(cfqd, tsk->io_context);
2274         if (!cic)
2275                 return NULL;
2276 
2277         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
2278         if (cfqq)
2279                 return elv_rb_find(&cfqq->sort_list, bio_end_sector(bio));
2280 
2281         return NULL;
2282 }
2283 
2284 static void cfq_activate_request(struct request_queue *q, struct request *rq)
2285 {
2286         struct cfq_data *cfqd = q->elevator->elevator_data;
2287 
2288         cfqd->rq_in_driver++;
2289         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
2290                                                 cfqd->rq_in_driver);
2291 
2292         cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
2293 }
2294 
2295 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
2296 {
2297         struct cfq_data *cfqd = q->elevator->elevator_data;
2298 
2299         WARN_ON(!cfqd->rq_in_driver);
2300         cfqd->rq_in_driver--;
2301         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
2302                                                 cfqd->rq_in_driver);
2303 }
2304 
2305 static void cfq_remove_request(struct request *rq)
2306 {
2307         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2308 
2309         if (cfqq->next_rq == rq)
2310                 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
2311 
2312         list_del_init(&rq->queuelist);
2313         cfq_del_rq_rb(rq);
2314 
2315         cfqq->cfqd->rq_queued--;
2316         cfqg_stats_update_io_remove(RQ_CFQG(rq), rq->cmd_flags);
2317         if (rq->cmd_flags & REQ_PRIO) {
2318                 WARN_ON(!cfqq->prio_pending);
2319                 cfqq->prio_pending--;
2320         }
2321 }
2322 
2323 static int cfq_merge(struct request_queue *q, struct request **req,
2324                      struct bio *bio)
2325 {
2326         struct cfq_data *cfqd = q->elevator->elevator_data;
2327         struct request *__rq;
2328 
2329         __rq = cfq_find_rq_fmerge(cfqd, bio);
2330         if (__rq && elv_rq_merge_ok(__rq, bio)) {
2331                 *req = __rq;
2332                 return ELEVATOR_FRONT_MERGE;
2333         }
2334 
2335         return ELEVATOR_NO_MERGE;
2336 }
2337 
2338 static void cfq_merged_request(struct request_queue *q, struct request *req,
2339                                int type)
2340 {
2341         if (type == ELEVATOR_FRONT_MERGE) {
2342                 struct cfq_queue *cfqq = RQ_CFQQ(req);
2343 
2344                 cfq_reposition_rq_rb(cfqq, req);
2345         }
2346 }
2347 
2348 static void cfq_bio_merged(struct request_queue *q, struct request *req,
2349                                 struct bio *bio)
2350 {
2351         cfqg_stats_update_io_merged(RQ_CFQG(req), bio->bi_rw);
2352 }
2353 
2354 static void
2355 cfq_merged_requests(struct request_queue *q, struct request *rq,
2356                     struct request *next)
2357 {
2358         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2359         struct cfq_data *cfqd = q->elevator->elevator_data;
2360 
2361         /*
2362          * reposition in fifo if next is older than rq
2363          */
2364         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
2365             time_before(rq_fifo_time(next), rq_fifo_time(rq)) &&
2366             cfqq == RQ_CFQQ(next)) {
2367                 list_move(&rq->queuelist, &next->queuelist);
2368                 rq_set_fifo_time(rq, rq_fifo_time(next));
2369         }
2370 
2371         if (cfqq->next_rq == next)
2372                 cfqq->next_rq = rq;
2373         cfq_remove_request(next);
2374         cfqg_stats_update_io_merged(RQ_CFQG(rq), next->cmd_flags);
2375 
2376         cfqq = RQ_CFQQ(next);
2377         /*
2378          * all requests of this queue are merged to other queues, delete it
2379          * from the service tree. If it's the active_queue,
2380          * cfq_dispatch_requests() will choose to expire it or do idle
2381          */
2382         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list) &&
2383             cfqq != cfqd->active_queue)
2384                 cfq_del_cfqq_rr(cfqd, cfqq);
2385 }
2386 
2387 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
2388                            struct bio *bio)
2389 {
2390         struct cfq_data *cfqd = q->elevator->elevator_data;
2391         struct cfq_io_cq *cic;
2392         struct cfq_queue *cfqq;
2393 
2394         /*
2395          * Disallow merge of a sync bio into an async request.
2396          */
2397         if (cfq_bio_sync(bio) && !rq_is_sync(rq))
2398                 return false;
2399 
2400         /*
2401          * Lookup the cfqq that this bio will be queued with and allow
2402          * merge only if rq is queued there.
2403          */
2404         cic = cfq_cic_lookup(cfqd, current->io_context);
2405         if (!cic)
2406                 return false;
2407 
2408         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
2409         return cfqq == RQ_CFQQ(rq);
2410 }
2411 
2412 static inline void cfq_del_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2413 {
2414         del_timer(&cfqd->idle_slice_timer);
2415         cfqg_stats_update_idle_time(cfqq->cfqg);
2416 }
2417 
2418 static void __cfq_set_active_queue(struct cfq_data *cfqd,
2419                                    struct cfq_queue *cfqq)
2420 {
2421         if (cfqq) {
2422                 cfq_log_cfqq(cfqd, cfqq, "set_active wl_class:%d wl_type:%d",
2423                                 cfqd->serving_wl_class, cfqd->serving_wl_type);
2424                 cfqg_stats_update_avg_queue_size(cfqq->cfqg);
2425                 cfqq->slice_start = 0;
2426                 cfqq->dispatch_start = jiffies;
2427                 cfqq->allocated_slice = 0;
2428                 cfqq->slice_end = 0;
2429                 cfqq->slice_dispatch = 0;
2430                 cfqq->nr_sectors = 0;
2431 
2432                 cfq_clear_cfqq_wait_request(cfqq);
2433                 cfq_clear_cfqq_must_dispatch(cfqq);
2434                 cfq_clear_cfqq_must_alloc_slice(cfqq);
2435                 cfq_clear_cfqq_fifo_expire(cfqq);
2436                 cfq_mark_cfqq_slice_new(cfqq);
2437 
2438                 cfq_del_timer(cfqd, cfqq);
2439         }
2440 
2441         cfqd->active_queue = cfqq;
2442 }
2443 
2444 /*
2445  * current cfqq expired its slice (or was too idle), select new one
2446  */
2447 static void
2448 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2449                     bool timed_out)
2450 {
2451         cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
2452 
2453         if (cfq_cfqq_wait_request(cfqq))
2454                 cfq_del_timer(cfqd, cfqq);
2455 
2456         cfq_clear_cfqq_wait_request(cfqq);
2457         cfq_clear_cfqq_wait_busy(cfqq);
2458 
2459         /*
2460          * If this cfqq is shared between multiple processes, check to
2461          * make sure that those processes are still issuing I/Os within
2462          * the mean seek distance.  If not, it may be time to break the
2463          * queues apart again.
2464          */
2465         if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq))
2466                 cfq_mark_cfqq_split_coop(cfqq);
2467 
2468         /*
2469          * store what was left of this slice, if the queue idled/timed out
2470          */
2471         if (timed_out) {
2472                 if (cfq_cfqq_slice_new(cfqq))
2473                         cfqq->slice_resid = cfq_scaled_cfqq_slice(cfqd, cfqq);
2474                 else
2475                         cfqq->slice_resid = cfqq->slice_end - jiffies;
2476                 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
2477         }
2478 
2479         cfq_group_served(cfqd, cfqq->cfqg, cfqq);
2480 
2481         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
2482                 cfq_del_cfqq_rr(cfqd, cfqq);
2483 
2484         cfq_resort_rr_list(cfqd, cfqq);
2485 
2486         if (cfqq == cfqd->active_queue)
2487                 cfqd->active_queue = NULL;
2488 
2489         if (cfqd->active_cic) {
2490                 put_io_context(cfqd->active_cic->icq.ioc);
2491                 cfqd->active_cic = NULL;
2492         }
2493 }
2494 
2495 static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
2496 {
2497         struct cfq_queue *cfqq = cfqd->active_queue;
2498 
2499         if (cfqq)
2500                 __cfq_slice_expired(cfqd, cfqq, timed_out);
2501 }
2502 
2503 /*
2504  * Get next queue for service. Unless we have a queue preemption,
2505  * we'll simply select the first cfqq in the service tree.
2506  */
2507 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
2508 {
2509         struct cfq_rb_root *st = st_for(cfqd->serving_group,
2510                         cfqd->serving_wl_class, cfqd->serving_wl_type);
2511 
2512         if (!cfqd->rq_queued)
2513                 return NULL;
2514 
2515         /* There is nothing to dispatch */
2516         if (!st)
2517                 return NULL;
2518         if (RB_EMPTY_ROOT(&st->rb))
2519                 return NULL;
2520         return cfq_rb_first(st);
2521 }
2522 
2523 static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
2524 {
2525         struct cfq_group *cfqg;
2526         struct cfq_queue *cfqq;
2527         int i, j;
2528         struct cfq_rb_root *st;
2529 
2530         if (!cfqd->rq_queued)
2531                 return NULL;
2532 
2533         cfqg = cfq_get_next_cfqg(cfqd);
2534         if (!cfqg)
2535                 return NULL;
2536 
2537         for_each_cfqg_st(cfqg, i, j, st)
2538                 if ((cfqq = cfq_rb_first(st)) != NULL)
2539                         return cfqq;
2540         return NULL;
2541 }
2542 
2543 /*
2544  * Get and set a new active queue for service.
2545  */
2546 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
2547                                               struct cfq_queue *cfqq)
2548 {
2549         if (!cfqq)
2550                 cfqq = cfq_get_next_queue(cfqd);
2551 
2552         __cfq_set_active_queue(cfqd, cfqq);
2553         return cfqq;
2554 }
2555 
2556 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
2557                                           struct request *rq)
2558 {
2559         if (blk_rq_pos(rq) >= cfqd->last_position)
2560                 return blk_rq_pos(rq) - cfqd->last_position;
2561         else
2562                 return cfqd->last_position - blk_rq_pos(rq);
2563 }
2564 
2565 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2566                                struct request *rq)
2567 {
2568         return cfq_dist_from_last(cfqd, rq) <= CFQQ_CLOSE_THR;
2569 }
2570 
2571 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
2572                                     struct cfq_queue *cur_cfqq)
2573 {
2574         struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
2575         struct rb_node *parent, *node;
2576         struct cfq_queue *__cfqq;
2577         sector_t sector = cfqd->last_position;
2578 
2579         if (RB_EMPTY_ROOT(root))
2580                 return NULL;
2581 
2582         /*
2583          * First, if we find a request starting at the end of the last
2584          * request, choose it.
2585          */
2586         __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
2587         if (__cfqq)
2588                 return __cfqq;
2589 
2590         /*
2591          * If the exact sector wasn't found, the parent of the NULL leaf
2592          * will contain the closest sector.
2593          */
2594         __cfqq = rb_entry(parent, struct cfq_queue, p_node);
2595         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
2596                 return __cfqq;
2597 
2598         if (blk_rq_pos(__cfqq->next_rq) < sector)
2599                 node = rb_next(&__cfqq->p_node);
2600         else
2601                 node = rb_prev(&__cfqq->p_node);
2602         if (!node)
2603                 return NULL;
2604 
2605         __cfqq = rb_entry(node, struct cfq_queue, p_node);
2606         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
2607                 return __cfqq;
2608 
2609         return NULL;
2610 }
2611 
2612 /*
2613  * cfqd - obvious
2614  * cur_cfqq - passed in so that we don't decide that the current queue is
2615  *            closely cooperating with itself.
2616  *
2617  * So, basically we're assuming that that cur_cfqq has dispatched at least
2618  * one request, and that cfqd->last_position reflects a position on the disk
2619  * associated with the I/O issued by cur_cfqq.  I'm not sure this is a valid
2620  * assumption.
2621  */
2622 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
2623                                               struct cfq_queue *cur_cfqq)
2624 {
2625         struct cfq_queue *cfqq;
2626 
2627         if (cfq_class_idle(cur_cfqq))
2628                 return NULL;
2629         if (!cfq_cfqq_sync(cur_cfqq))
2630                 return NULL;
2631         if (CFQQ_SEEKY(cur_cfqq))
2632                 return NULL;
2633 
2634         /*
2635          * Don't search priority tree if it's the only queue in the group.
2636          */
2637         if (cur_cfqq->cfqg->nr_cfqq == 1)
2638                 return NULL;
2639 
2640         /*
2641          * We should notice if some of the queues are cooperating, eg
2642          * working closely on the same area of the disk. In that case,
2643          * we can group them together and don't waste time idling.
2644          */
2645         cfqq = cfqq_close(cfqd, cur_cfqq);
2646         if (!cfqq)
2647                 return NULL;
2648 
2649         /* If new queue belongs to different cfq_group, don't choose it */
2650         if (cur_cfqq->cfqg != cfqq->cfqg)
2651                 return NULL;
2652 
2653         /*
2654          * It only makes sense to merge sync queues.
2655          */
2656         if (!cfq_cfqq_sync(cfqq))
2657                 return NULL;
2658         if (CFQQ_SEEKY(cfqq))
2659                 return NULL;
2660 
2661         /*
2662          * Do not merge queues of different priority classes
2663          */
2664         if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
2665                 return NULL;
2666 
2667         return cfqq;
2668 }
2669 
2670 /*
2671  * Determine whether we should enforce idle window for this queue.
2672  */
2673 
2674 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2675 {
2676         enum wl_class_t wl_class = cfqq_class(cfqq);
2677         struct cfq_rb_root *st = cfqq->service_tree;
2678 
2679         BUG_ON(!st);
2680         BUG_ON(!st->count);
2681 
2682         if (!cfqd->cfq_slice_idle)
2683                 return false;
2684 
2685         /* We never do for idle class queues. */
2686         if (wl_class == IDLE_WORKLOAD)
2687                 return false;
2688 
2689         /* We do for queues that were marked with idle window flag. */
2690         if (cfq_cfqq_idle_window(cfqq) &&
2691            !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag))
2692                 return true;
2693 
2694         /*
2695          * Otherwise, we do only if they are the last ones
2696          * in their service tree.
2697          */
2698         if (st->count == 1 && cfq_cfqq_sync(cfqq) &&
2699            !cfq_io_thinktime_big(cfqd, &st->ttime, false))
2700                 return true;
2701         cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d", st->count);
2702         return false;
2703 }
2704 
2705 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
2706 {
2707         struct cfq_queue *cfqq = cfqd->active_queue;
2708         struct cfq_io_cq *cic;
2709         unsigned long sl, group_idle = 0;
2710 
2711         /*
2712          * SSD device without seek penalty, disable idling. But only do so
2713          * for devices that support queuing, otherwise we still have a problem
2714          * with sync vs async workloads.
2715          */
2716         if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
2717                 return;
2718 
2719         WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
2720         WARN_ON(cfq_cfqq_slice_new(cfqq));
2721 
2722         /*
2723          * idle is disabled, either manually or by past process history
2724          */
2725         if (!cfq_should_idle(cfqd, cfqq)) {
2726                 /* no queue idling. Check for group idling */
2727                 if (cfqd->cfq_group_idle)
2728                         group_idle = cfqd->cfq_group_idle;
2729                 else
2730                         return;
2731         }
2732 
2733         /*
2734          * still active requests from this queue, don't idle
2735          */
2736         if (cfqq->dispatched)
2737                 return;
2738 
2739         /*
2740          * task has exited, don't wait
2741          */
2742         cic = cfqd->active_cic;
2743         if (!cic || !atomic_read(&cic->icq.ioc->active_ref))
2744                 return;
2745 
2746         /*
2747          * If our average think time is larger than the remaining time
2748          * slice, then don't idle. This avoids overrunning the allotted
2749          * time slice.
2750          */
2751         if (sample_valid(cic->ttime.ttime_samples) &&
2752             (cfqq->slice_end - jiffies < cic->ttime.ttime_mean)) {
2753                 cfq_log_cfqq(cfqd, cfqq, "Not idling. think_time:%lu",
2754                              cic->ttime.ttime_mean);
2755                 return;
2756         }
2757 
2758         /* There are other queues in the group, don't do group idle */
2759         if (group_idle && cfqq->cfqg->nr_cfqq > 1)
2760                 return;
2761 
2762         cfq_mark_cfqq_wait_request(cfqq);
2763 
2764         if (group_idle)
2765                 sl = cfqd->cfq_group_idle;
2766         else
2767                 sl = cfqd->cfq_slice_idle;
2768 
2769         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
2770         cfqg_stats_set_start_idle_time(cfqq->cfqg);
2771         cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu group_idle: %d", sl,
2772                         group_idle ? 1 : 0);
2773 }
2774 
2775 /*
2776  * Move request from internal lists to the request queue dispatch list.
2777  */
2778 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
2779 {
2780         struct cfq_data *cfqd = q->elevator->elevator_data;
2781         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2782 
2783         cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
2784 
2785         cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
2786         cfq_remove_request(rq);
2787         cfqq->dispatched++;
2788         (RQ_CFQG(rq))->dispatched++;
2789         elv_dispatch_sort(q, rq);
2790 
2791         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
2792         cfqq->nr_sectors += blk_rq_sectors(rq);
2793         cfqg_stats_update_dispatch(cfqq->cfqg, blk_rq_bytes(rq), rq->cmd_flags);
2794 }
2795 
2796 /*
2797  * return expired entry, or NULL to just start from scratch in rbtree
2798  */
2799 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
2800 {
2801         struct request *rq = NULL;
2802 
2803         if (cfq_cfqq_fifo_expire(cfqq))
2804                 return NULL;
2805 
2806         cfq_mark_cfqq_fifo_expire(cfqq);
2807 
2808         if (list_empty(&cfqq->fifo))
2809                 return NULL;
2810 
2811         rq = rq_entry_fifo(cfqq->fifo.next);
2812         if (time_before(jiffies, rq_fifo_time(rq)))
2813                 rq = NULL;
2814 
2815         return rq;
2816 }
2817 
2818 static inline int
2819 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2820 {
2821         const int base_rq = cfqd->cfq_slice_async_rq;
2822 
2823         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
2824 
2825         return 2 * base_rq * (IOPRIO_BE_NR - cfqq->ioprio);
2826 }
2827 
2828 /*
2829  * Must be called with the queue_lock held.
2830  */
2831 static int cfqq_process_refs(struct cfq_queue *cfqq)
2832 {
2833         int process_refs, io_refs;
2834 
2835         io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
2836         process_refs = cfqq->ref - io_refs;
2837         BUG_ON(process_refs < 0);
2838         return process_refs;
2839 }
2840 
2841 static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
2842 {
2843         int process_refs, new_process_refs;
2844         struct cfq_queue *__cfqq;
2845 
2846         /*
2847          * If there are no process references on the new_cfqq, then it is
2848          * unsafe to follow the ->new_cfqq chain as other cfqq's in the
2849          * chain may have dropped their last reference (not just their
2850          * last process reference).
2851          */
2852         if (!cfqq_process_refs(new_cfqq))
2853                 return;
2854 
2855         /* Avoid a circular list and skip interim queue merges */
2856         while ((__cfqq = new_cfqq->new_cfqq)) {
2857                 if (__cfqq == cfqq)
2858                         return;
2859                 new_cfqq = __cfqq;
2860         }
2861 
2862         process_refs = cfqq_process_refs(cfqq);
2863         new_process_refs = cfqq_process_refs(new_cfqq);
2864         /*
2865          * If the process for the cfqq has gone away, there is no
2866          * sense in merging the queues.
2867          */
2868         if (process_refs == 0 || new_process_refs == 0)
2869                 return;
2870 
2871         /*
2872          * Merge in the direction of the lesser amount of work.
2873          */
2874         if (new_process_refs >= process_refs) {
2875                 cfqq->new_cfqq = new_cfqq;
2876                 new_cfqq->ref += process_refs;
2877         } else {
2878                 new_cfqq->new_cfqq = cfqq;
2879                 cfqq->ref += new_process_refs;
2880         }
2881 }
2882 
2883 static enum wl_type_t cfq_choose_wl_type(struct cfq_data *cfqd,
2884                         struct cfq_group *cfqg, enum wl_class_t wl_class)
2885 {
2886         struct cfq_queue *queue;
2887         int i;
2888         bool key_valid = false;
2889         unsigned long lowest_key = 0;
2890         enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
2891 
2892         for (i = 0; i <= SYNC_WORKLOAD; ++i) {
2893                 /* select the one with lowest rb_key */
2894                 queue = cfq_rb_first(st_for(cfqg, wl_class, i));
2895                 if (queue &&
2896                     (!key_valid || time_before(queue->rb_key, lowest_key))) {
2897                         lowest_key = queue->rb_key;
2898                         cur_best = i;
2899                         key_valid = true;
2900                 }
2901         }
2902 
2903         return cur_best;
2904 }
2905 
2906 static void
2907 choose_wl_class_and_type(struct cfq_data *cfqd, struct cfq_group *cfqg)
2908 {
2909         unsigned slice;
2910         unsigned count;
2911         struct cfq_rb_root *st;
2912         unsigned group_slice;
2913         enum wl_class_t original_class = cfqd->serving_wl_class;
2914 
2915         /* Choose next priority. RT > BE > IDLE */
2916         if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
2917                 cfqd->serving_wl_class = RT_WORKLOAD;
2918         else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
2919                 cfqd->serving_wl_class = BE_WORKLOAD;
2920         else {
2921                 cfqd->serving_wl_class = IDLE_WORKLOAD;
2922                 cfqd->workload_expires = jiffies + 1;
2923                 return;
2924         }
2925 
2926         if (original_class != cfqd->serving_wl_class)
2927                 goto new_workload;
2928 
2929         /*
2930          * For RT and BE, we have to choose also the type
2931          * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
2932          * expiration time
2933          */
2934         st = st_for(cfqg, cfqd->serving_wl_class, cfqd->serving_wl_type);
2935         count = st->count;
2936 
2937         /*
2938          * check workload expiration, and that we still have other queues ready
2939          */
2940         if (count && !time_after(jiffies, cfqd->workload_expires))
2941                 return;
2942 
2943 new_workload:
2944         /* otherwise select new workload type */
2945         cfqd->serving_wl_type = cfq_choose_wl_type(cfqd, cfqg,
2946                                         cfqd->serving_wl_class);
2947         st = st_for(cfqg, cfqd->serving_wl_class, cfqd->serving_wl_type);
2948         count = st->count;
2949 
2950         /*
2951          * the workload slice is computed as a fraction of target latency
2952          * proportional to the number of queues in that workload, over
2953          * all the queues in the same priority class
2954          */
2955         group_slice = cfq_group_slice(cfqd, cfqg);
2956 
2957         slice = group_slice * count /
2958                 max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_wl_class],
2959                       cfq_group_busy_queues_wl(cfqd->serving_wl_class, cfqd,
2960                                         cfqg));
2961 
2962         if (cfqd->serving_wl_type == ASYNC_WORKLOAD) {
2963                 unsigned int tmp;
2964 
2965                 /*
2966                  * Async queues are currently system wide. Just taking
2967                  * proportion of queues with-in same group will lead to higher
2968                  * async ratio system wide as generally root group is going
2969                  * to have higher weight. A more accurate thing would be to
2970                  * calculate system wide asnc/sync ratio.
2971                  */
2972                 tmp = cfqd->cfq_target_latency *
2973                         cfqg_busy_async_queues(cfqd, cfqg);
2974                 tmp = tmp/cfqd->busy_queues;
2975                 slice = min_t(unsigned, slice, tmp);
2976 
2977                 /* async workload slice is scaled down according to
2978                  * the sync/async slice ratio. */
2979                 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
2980         } else
2981                 /* sync workload slice is at least 2 * cfq_slice_idle */
2982                 slice = max(slice, 2 * cfqd->cfq_slice_idle);
2983 
2984         slice = max_t(unsigned, slice, CFQ_MIN_TT);
2985         cfq_log(cfqd, "workload slice:%d", slice);
2986         cfqd->workload_expires = jiffies + slice;
2987 }
2988 
2989 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
2990 {
2991         struct cfq_rb_root *st = &cfqd->grp_service_tree;
2992         struct cfq_group *cfqg;
2993 
2994         if (RB_EMPTY_ROOT(&st->rb))
2995                 return NULL;
2996         cfqg = cfq_rb_first_group(st);
2997         update_min_vdisktime(st);
2998         return cfqg;
2999 }
3000 
3001 static void cfq_choose_cfqg(struct cfq_data *cfqd)
3002 {
3003         struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
3004 
3005         cfqd->serving_group = cfqg;
3006 
3007         /* Restore the workload type data */
3008         if (cfqg->saved_wl_slice) {
3009                 cfqd->workload_expires = jiffies + cfqg->saved_wl_slice;
3010                 cfqd->serving_wl_type = cfqg->saved_wl_type;
3011                 cfqd->serving_wl_class = cfqg->saved_wl_class;
3012         } else
3013                 cfqd->workload_expires = jiffies - 1;
3014 
3015         choose_wl_class_and_type(cfqd, cfqg);
3016 }
3017 
3018 /*
3019  * Select a queue for service. If we have a current active queue,
3020  * check whether to continue servicing it, or retrieve and set a new one.
3021  */
3022 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
3023 {
3024         struct cfq_queue *cfqq, *new_cfqq = NULL;
3025 
3026         cfqq = cfqd->active_queue;
3027         if (!cfqq)
3028                 goto new_queue;
3029 
3030         if (!cfqd->rq_queued)
3031                 return NULL;
3032 
3033         /*
3034          * We were waiting for group to get backlogged. Expire the queue
3035          */
3036         if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list))
3037                 goto expire;
3038 
3039         /*
3040          * The active queue has run out of time, expire it and select new.
3041          */
3042         if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) {
3043                 /*
3044                  * If slice had not expired at the completion of last request
3045                  * we might not have turned on wait_busy flag. Don't expire
3046                  * the queue yet. Allow the group to get backlogged.
3047                  *
3048                  * The very fact that we have used the slice, that means we
3049                  * have been idling all along on this queue and it should be
3050                  * ok to wait for this request to complete.
3051                  */
3052                 if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list)
3053                     && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
3054                         cfqq = NULL;
3055                         goto keep_queue;
3056                 } else
3057                         goto check_group_idle;
3058         }
3059 
3060         /*
3061          * The active queue has requests and isn't expired, allow it to
3062          * dispatch.
3063          */
3064         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3065                 goto keep_queue;
3066 
3067         /*
3068          * If another queue has a request waiting within our mean seek
3069          * distance, let it run.  The expire code will check for close
3070          * cooperators and put the close queue at the front of the service
3071          * tree.  If possible, merge the expiring queue with the new cfqq.
3072          */
3073         new_cfqq = cfq_close_cooperator(cfqd, cfqq);
3074         if (new_cfqq) {
3075                 if (!cfqq->new_cfqq)
3076                         cfq_setup_merge(cfqq, new_cfqq);
3077                 goto expire;
3078         }
3079 
3080         /*
3081          * No requests pending. If the active queue still has requests in
3082          * flight or is idling for a new request, allow either of these
3083          * conditions to happen (or time out) before selecting a new queue.
3084          */
3085         if (timer_pending(&cfqd->idle_slice_timer)) {
3086                 cfqq = NULL;
3087                 goto keep_queue;
3088         }
3089 
3090         /*
3091          * This is a deep seek queue, but the device is much faster than
3092          * the queue can deliver, don't idle
3093          **/
3094         if (CFQQ_SEEKY(cfqq) && cfq_cfqq_idle_window(cfqq) &&
3095             (cfq_cfqq_slice_new(cfqq) ||
3096             (cfqq->slice_end - jiffies > jiffies - cfqq->slice_start))) {
3097                 cfq_clear_cfqq_deep(cfqq);
3098                 cfq_clear_cfqq_idle_window(cfqq);
3099         }
3100 
3101         if (cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
3102                 cfqq = NULL;
3103                 goto keep_queue;
3104         }
3105 
3106         /*
3107          * If group idle is enabled and there are requests dispatched from
3108          * this group, wait for requests to complete.
3109          */
3110 check_group_idle:
3111         if (cfqd->cfq_group_idle && cfqq->cfqg->nr_cfqq == 1 &&
3112             cfqq->cfqg->dispatched &&
3113             !cfq_io_thinktime_big(cfqd, &cfqq->cfqg->ttime, true)) {
3114                 cfqq = NULL;
3115                 goto keep_queue;
3116         }
3117 
3118 expire:
3119         cfq_slice_expired(cfqd, 0);
3120 new_queue:
3121         /*
3122          * Current queue expired. Check if we have to switch to a new
3123          * service tree
3124          */
3125         if (!new_cfqq)
3126                 cfq_choose_cfqg(cfqd);
3127 
3128         cfqq = cfq_set_active_queue(cfqd, new_cfqq);
3129 keep_queue:
3130         return cfqq;
3131 }
3132 
3133 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
3134 {
3135         int dispatched = 0;
3136 
3137         while (cfqq->next_rq) {
3138                 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
3139                 dispatched++;
3140         }
3141 
3142         BUG_ON(!list_empty(&cfqq->fifo));
3143 
3144         /* By default cfqq is not expired if it is empty. Do it explicitly */
3145         __cfq_slice_expired(cfqq->cfqd, cfqq, 0);
3146         return dispatched;
3147 }
3148 
3149 /*
3150  * Drain our current requests. Used for barriers and when switching
3151  * io schedulers on-the-fly.
3152  */
3153 static int cfq_forced_dispatch(struct cfq_data *cfqd)
3154 {
3155         struct cfq_queue *cfqq;
3156         int dispatched = 0;
3157 
3158         /* Expire the timeslice of the current active queue first */
3159         cfq_slice_expired(cfqd, 0);
3160         while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) {
3161                 __cfq_set_active_queue(cfqd, cfqq);
3162                 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
3163         }
3164 
3165         BUG_ON(cfqd->busy_queues);
3166 
3167         cfq_log(cfqd, "forced_dispatch=%d", dispatched);
3168         return dispatched;
3169 }
3170 
3171 static inline bool cfq_slice_used_soon(struct cfq_data *cfqd,
3172         struct cfq_queue *cfqq)
3173 {
3174         /* the queue hasn't finished any request, can't estimate */
3175         if (cfq_cfqq_slice_new(cfqq))
3176                 return true;
3177         if (time_after(jiffies + cfqd->cfq_slice_idle * cfqq->dispatched,
3178                 cfqq->slice_end))
3179                 return true;
3180 
3181         return false;
3182 }
3183 
3184 static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3185 {
3186         unsigned int max_dispatch;
3187 
3188         if (cfq_cfqq_must_dispatch(cfqq))
3189                 return true;
3190 
3191         /*
3192          * Drain async requests before we start sync IO
3193          */
3194         if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_flight[BLK_RW_ASYNC])
3195                 return false;
3196 
3197         /*
3198          * If this is an async queue and we have sync IO in flight, let it wait
3199          */
3200         if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq))
3201                 return false;
3202 
3203         max_dispatch = max_t(unsigned int, cfqd->cfq_quantum / 2, 1);
3204         if (cfq_class_idle(cfqq))
3205                 max_dispatch = 1;
3206 
3207         /*
3208          * Does this cfqq already have too much IO in flight?
3209          */
3210         if (cfqq->dispatched >= max_dispatch) {
3211                 bool promote_sync = false;
3212                 /*
3213                  * idle queue must always only have a single IO in flight
3214                  */
3215                 if (cfq_class_idle(cfqq))
3216                         return false;
3217 
3218                 /*
3219                  * If there is only one sync queue
3220                  * we can ignore async queue here and give the sync
3221                  * queue no dispatch limit. The reason is a sync queue can
3222                  * preempt async queue, limiting the sync queue doesn't make
3223                  * sense. This is useful for aiostress test.
3224                  */
3225                 if (cfq_cfqq_sync(cfqq) && cfqd->busy_sync_queues == 1)
3226                         promote_sync = true;
3227 
3228                 /*
3229                  * We have other queues, don't allow more IO from this one
3230                  */
3231                 if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq) &&
3232                                 !promote_sync)
3233                         return false;
3234 
3235                 /*
3236                  * Sole queue user, no limit
3237                  */
3238                 if (cfqd->busy_queues == 1 || promote_sync)
3239                         max_dispatch = -1;
3240                 else
3241                         /*
3242                          * Normally we start throttling cfqq when cfq_quantum/2
3243                          * requests have been dispatched. But we can drive
3244                          * deeper queue depths at the beginning of slice
3245                          * subjected to upper limit of cfq_quantum.
3246                          * */
3247                         max_dispatch = cfqd->cfq_quantum;
3248         }
3249 
3250         /*
3251          * Async queues must wait a bit before being allowed dispatch.
3252          * We also ramp up the dispatch depth gradually for async IO,
3253          * based on the last sync IO we serviced
3254          */
3255         if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
3256                 unsigned long last_sync = jiffies - cfqd->last_delayed_sync;
3257                 unsigned int depth;
3258 
3259                 depth = last_sync / cfqd->cfq_slice[1];
3260                 if (!depth && !cfqq->dispatched)
3261                         depth = 1;
3262                 if (depth < max_dispatch)
3263                         max_dispatch = depth;
3264         }
3265 
3266         /*
3267          * If we're below the current max, allow a dispatch
3268          */
3269         return cfqq->dispatched < max_dispatch;
3270 }
3271 
3272 /*
3273  * Dispatch a request from cfqq, moving them to the request queue
3274  * dispatch list.
3275  */
3276 static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3277 {
3278         struct request *rq;
3279 
3280         BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
3281 
3282         rq = cfq_check_fifo(cfqq);
3283         if (rq)
3284                 cfq_mark_cfqq_must_dispatch(cfqq);
3285 
3286         if (!cfq_may_dispatch(cfqd, cfqq))
3287                 return false;
3288 
3289         /*
3290          * follow expired path, else get first next available
3291          */
3292         if (!rq)
3293                 rq = cfqq->next_rq;
3294         else
3295                 cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
3296 
3297         /*
3298          * insert request into driver dispatch list
3299          */
3300         cfq_dispatch_insert(cfqd->queue, rq);
3301 
3302         if (!cfqd->active_cic) {
3303                 struct cfq_io_cq *cic = RQ_CIC(rq);
3304 
3305                 atomic_long_inc(&cic->icq.ioc->refcount);
3306                 cfqd->active_cic = cic;
3307         }
3308 
3309         return true;
3310 }
3311 
3312 /*
3313  * Find the cfqq that we need to service and move a request from that to the
3314  * dispatch list
3315  */
3316 static int cfq_dispatch_requests(struct request_queue *q, int force)
3317 {
3318         struct cfq_data *cfqd = q->elevator->elevator_data;
3319         struct cfq_queue *cfqq;
3320 
3321         if (!cfqd->busy_queues)
3322                 return 0;
3323 
3324         if (unlikely(force))
3325                 return cfq_forced_dispatch(cfqd);
3326 
3327         cfqq = cfq_select_queue(cfqd);
3328         if (!cfqq)
3329                 return 0;
3330 
3331         /*
3332          * Dispatch a request from this cfqq, if it is allowed
3333          */
3334         if (!cfq_dispatch_request(cfqd, cfqq))
3335                 return 0;
3336 
3337         cfqq->slice_dispatch++;
3338         cfq_clear_cfqq_must_dispatch(cfqq);
3339 
3340         /*
3341          * expire an async queue immediately if it has used up its slice. idle
3342          * queue always expire after 1 dispatch round.
3343          */
3344         if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
3345             cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
3346             cfq_class_idle(cfqq))) {
3347                 cfqq->slice_end = jiffies + 1;
3348                 cfq_slice_expired(cfqd, 0);
3349         }
3350 
3351         cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
3352         return 1;
3353 }
3354 
3355 /*
3356  * task holds one reference to the queue, dropped when task exits. each rq
3357  * in-flight on this queue also holds a reference, dropped when rq is freed.
3358  *
3359  * Each cfq queue took a reference on the parent group. Drop it now.
3360  * queue lock must be held here.
3361  */
3362 static void cfq_put_queue(struct cfq_queue *cfqq)
3363 {
3364         struct cfq_data *cfqd = cfqq->cfqd;
3365         struct cfq_group *cfqg;
3366 
3367         BUG_ON(cfqq->ref <= 0);
3368 
3369         cfqq->ref--;
3370         if (cfqq->ref)
3371                 return;
3372 
3373         cfq_log_cfqq(cfqd, cfqq, "put_queue");
3374         BUG_ON(rb_first(&cfqq->sort_list));
3375         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
3376         cfqg = cfqq->cfqg;
3377 
3378         if (unlikely(cfqd->active_queue == cfqq)) {
3379                 __cfq_slice_expired(cfqd, cfqq, 0);
3380                 cfq_schedule_dispatch(cfqd);
3381         }
3382 
3383         BUG_ON(cfq_cfqq_on_rr(cfqq));
3384         kmem_cache_free(cfq_pool, cfqq);
3385         cfqg_put(cfqg);
3386 }
3387 
3388 static void cfq_put_cooperator(struct cfq_queue *cfqq)
3389 {
3390         struct cfq_queue *__cfqq, *next;
3391 
3392         /*
3393          * If this queue was scheduled to merge with another queue, be
3394          * sure to drop the reference taken on that queue (and others in
3395          * the merge chain).  See cfq_setup_merge and cfq_merge_cfqqs.
3396          */
3397         __cfqq = cfqq->new_cfqq;
3398         while (__cfqq) {
3399                 if (__cfqq == cfqq) {
3400                         WARN(1, "cfqq->new_cfqq loop detected\n");
3401                         break;
3402                 }
3403                 next = __cfqq->new_cfqq;
3404                 cfq_put_queue(__cfqq);
3405                 __cfqq = next;
3406         }
3407 }
3408 
3409 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3410 {
3411         if (unlikely(cfqq == cfqd->active_queue)) {
3412                 __cfq_slice_expired(cfqd, cfqq, 0);
3413                 cfq_schedule_dispatch(cfqd);
3414         }
3415 
3416         cfq_put_cooperator(cfqq);
3417 
3418         cfq_put_queue(cfqq);
3419 }
3420 
3421 static void cfq_init_icq(struct io_cq *icq)
3422 {
3423         struct cfq_io_cq *cic = icq_to_cic(icq);
3424 
3425         cic->ttime.last_end_request = jiffies;
3426 }
3427 
3428 static void cfq_exit_icq(struct io_cq *icq)
3429 {
3430         struct cfq_io_cq *cic = icq_to_cic(icq);
3431         struct cfq_data *cfqd = cic_to_cfqd(cic);
3432 
3433         if (cic->cfqq[BLK_RW_ASYNC]) {
3434                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
3435                 cic->cfqq[BLK_RW_ASYNC] = NULL;
3436         }
3437 
3438         if (cic->cfqq[BLK_RW_SYNC]) {
3439                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
3440                 cic->cfqq[BLK_RW_SYNC] = NULL;
3441         }
3442 }
3443 
3444 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct cfq_io_cq *cic)
3445 {
3446         struct task_struct *tsk = current;
3447         int ioprio_class;
3448 
3449         if (!cfq_cfqq_prio_changed(cfqq))
3450                 return;
3451 
3452         ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
3453         switch (ioprio_class) {
3454         default:
3455                 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
3456         case IOPRIO_CLASS_NONE:
3457                 /*
3458                  * no prio set, inherit CPU scheduling settings
3459                  */
3460                 cfqq->ioprio = task_nice_ioprio(tsk);
3461                 cfqq->ioprio_class = task_nice_ioclass(tsk);
3462                 break;
3463         case IOPRIO_CLASS_RT:
3464                 cfqq->ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
3465                 cfqq->ioprio_class = IOPRIO_CLASS_RT;
3466                 break;
3467         case IOPRIO_CLASS_BE:
3468                 cfqq->ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
3469                 cfqq->ioprio_class = IOPRIO_CLASS_BE;
3470                 break;
3471         case IOPRIO_CLASS_IDLE:
3472                 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
3473                 cfqq->ioprio = 7;
3474                 cfq_clear_cfqq_idle_window(cfqq);
3475                 break;
3476         }
3477 
3478         /*
3479          * keep track of original prio settings in case we have to temporarily
3480          * elevate the priority of this queue
3481          */
3482         cfqq->org_ioprio = cfqq->ioprio;
3483         cfq_clear_cfqq_prio_changed(cfqq);
3484 }
3485 
3486 static void check_ioprio_changed(struct cfq_io_cq *cic, struct bio *bio)
3487 {
3488         int ioprio = cic->icq.ioc->ioprio;
3489         struct cfq_data *cfqd = cic_to_cfqd(cic);
3490         struct cfq_queue *cfqq;
3491 
3492         /*
3493          * Check whether ioprio has changed.  The condition may trigger
3494          * spuriously on a newly created cic but there's no harm.
3495          */
3496         if (unlikely(!cfqd) || likely(cic->ioprio == ioprio))
3497                 return;
3498 
3499         cfqq = cic->cfqq[BLK_RW_ASYNC];
3500         if (cfqq) {
3501                 struct cfq_queue *new_cfqq;
3502                 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic, bio,
3503                                          GFP_ATOMIC);
3504                 if (new_cfqq) {
3505                         cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
3506                         cfq_put_queue(cfqq);
3507                 }
3508         }
3509 
3510         cfqq = cic->cfqq[BLK_RW_SYNC];
3511         if (cfqq)
3512                 cfq_mark_cfqq_prio_changed(cfqq);
3513 
3514         cic->ioprio = ioprio;
3515 }
3516 
3517 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3518                           pid_t pid, bool is_sync)
3519 {
3520         RB_CLEAR_NODE(&cfqq->rb_node);
3521         RB_CLEAR_NODE(&cfqq->p_node);
3522         INIT_LIST_HEAD(&cfqq->fifo);
3523 
3524         cfqq->ref = 0;
3525         cfqq->cfqd = cfqd;
3526 
3527         cfq_mark_cfqq_prio_changed(cfqq);
3528 
3529         if (is_sync) {
3530                 if (!cfq_class_idle(cfqq))
3531                         cfq_mark_cfqq_idle_window(cfqq);
3532                 cfq_mark_cfqq_sync(cfqq);
3533         }
3534         cfqq->pid = pid;
3535 }
3536 
3537 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3538 static void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
3539 {
3540         struct cfq_data *cfqd = cic_to_cfqd(cic);
3541         struct cfq_queue *sync_cfqq;
3542         uint64_t id;
3543 
3544         rcu_read_lock();
3545         id = bio_blkcg(bio)->id;
3546         rcu_read_unlock();
3547 
3548         /*
3549          * Check whether blkcg has changed.  The condition may trigger
3550          * spuriously on a newly created cic but there's no harm.
3551          */
3552         if (unlikely(!cfqd) || likely(cic->blkcg_id == id))
3553                 return;
3554 
3555         sync_cfqq = cic_to_cfqq(cic, 1);
3556         if (sync_cfqq) {
3557                 /*
3558                  * Drop reference to sync queue. A new sync queue will be
3559                  * assigned in new group upon arrival of a fresh request.
3560                  */
3561                 cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
3562                 cic_set_cfqq(cic, NULL, 1);
3563                 cfq_put_queue(sync_cfqq);
3564         }
3565 
3566         cic->blkcg_id = id;
3567 }
3568 #else
3569 static inline void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio) { }
3570 #endif  /* CONFIG_CFQ_GROUP_IOSCHED */
3571 
3572 static struct cfq_queue *
3573 cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
3574                      struct bio *bio, gfp_t gfp_mask)
3575 {
3576         struct blkcg *blkcg;
3577         struct cfq_queue *cfqq, *new_cfqq = NULL;
3578         struct cfq_group *cfqg;
3579 
3580 retry:
3581         rcu_read_lock();
3582 
3583         blkcg = bio_blkcg(bio);
3584         cfqg = cfq_lookup_create_cfqg(cfqd, blkcg);
3585         if (!cfqg) {
3586                 cfqq = &cfqd->oom_cfqq;
3587                 goto out;
3588         }
3589 
3590         cfqq = cic_to_cfqq(cic, is_sync);
3591 
3592         /*
3593          * Always try a new alloc if we fell back to the OOM cfqq
3594          * originally, since it should just be a temporary situation.
3595          */
3596         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3597                 cfqq = NULL;
3598                 if (new_cfqq) {
3599                         cfqq = new_cfqq;
3600                         new_cfqq = NULL;
3601                 } else if (gfp_mask & __GFP_WAIT) {
3602                         rcu_read_unlock();
3603                         spin_unlock_irq(cfqd->queue->queue_lock);
3604                         new_cfqq = kmem_cache_alloc_node(cfq_pool,
3605                                         gfp_mask | __GFP_ZERO,
3606                                         cfqd->queue->node);
3607                         spin_lock_irq(cfqd->queue->queue_lock);
3608                         if (new_cfqq)
3609                                 goto retry;
3610                         else
3611                                 return &cfqd->oom_cfqq;
3612                 } else {
3613                         cfqq = kmem_cache_alloc_node(cfq_pool,
3614                                         gfp_mask | __GFP_ZERO,
3615                                         cfqd->queue->node);
3616                 }
3617 
3618                 if (cfqq) {
3619                         cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
3620                         cfq_init_prio_data(cfqq, cic);
3621                         cfq_link_cfqq_cfqg(cfqq, cfqg);
3622                         cfq_log_cfqq(cfqd, cfqq, "alloced");
3623                 } else
3624                         cfqq = &cfqd->oom_cfqq;
3625         }
3626 out:
3627         if (new_cfqq)
3628                 kmem_cache_free(cfq_pool, new_cfqq);
3629 
3630         rcu_read_unlock();
3631         return cfqq;
3632 }
3633 
3634 static struct cfq_queue **
3635 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
3636 {
3637         switch (ioprio_class) {
3638         case IOPRIO_CLASS_RT:
3639                 return &cfqd->async_cfqq[0][ioprio];
3640         case IOPRIO_CLASS_NONE:
3641                 ioprio = IOPRIO_NORM;
3642                 /* fall through */
3643         case IOPRIO_CLASS_BE:
3644                 return &cfqd->async_cfqq[1][ioprio];
3645         case IOPRIO_CLASS_IDLE:
3646                 return &cfqd->async_idle_cfqq;
3647         default:
3648                 BUG();
3649         }
3650 }
3651 
3652 static struct cfq_queue *
3653 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
3654               struct bio *bio, gfp_t gfp_mask)
3655 {
3656         int ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
3657         int ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
3658         struct cfq_queue **async_cfqq = NULL;
3659         struct cfq_queue *cfqq = NULL;
3660 
3661         if (!is_sync) {
3662                 if (!ioprio_valid(cic->ioprio)) {
3663                         struct task_struct *tsk = current;
3664                         ioprio = task_nice_ioprio(tsk);
3665                         ioprio_class = task_nice_ioclass(tsk);
3666                 }
3667                 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
3668                 cfqq = *async_cfqq;
3669         }
3670 
3671         if (!cfqq)
3672                 cfqq = cfq_find_alloc_queue(cfqd, is_sync, cic, bio, gfp_mask);
3673 
3674         /*
3675          * pin the queue now that it's allocated, scheduler exit will prune it
3676          */
3677         if (!is_sync && !(*async_cfqq)) {
3678                 cfqq->ref++;
3679                 *async_cfqq = cfqq;
3680         }
3681 
3682         cfqq->ref++;
3683         return cfqq;
3684 }
3685 
3686 static void
3687 __cfq_update_io_thinktime(struct cfq_ttime *ttime, unsigned long slice_idle)
3688 {
3689         unsigned long elapsed = jiffies - ttime->last_end_request;
3690         elapsed = min(elapsed, 2UL * slice_idle);
3691 
3692         ttime->ttime_samples = (7*ttime->ttime_samples + 256) / 8;
3693         ttime->ttime_total = (7*ttime->ttime_total + 256*elapsed) / 8;
3694         ttime->ttime_mean = (ttime->ttime_total + 128) / ttime->ttime_samples;
3695 }
3696 
3697 static void
3698 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3699                         struct cfq_io_cq *cic)
3700 {
3701         if (cfq_cfqq_sync(cfqq)) {
3702                 __cfq_update_io_thinktime(&cic->ttime, cfqd->cfq_slice_idle);
3703                 __cfq_update_io_thinktime(&cfqq->service_tree->ttime,
3704                         cfqd->cfq_slice_idle);
3705         }
3706 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3707         __cfq_update_io_thinktime(&cfqq->cfqg->ttime, cfqd->cfq_group_idle);
3708 #endif
3709 }
3710 
3711 static void
3712 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3713                        struct request *rq)
3714 {
3715         sector_t sdist = 0;
3716         sector_t n_sec = blk_rq_sectors(rq);
3717         if (cfqq->last_request_pos) {
3718                 if (cfqq->last_request_pos < blk_rq_pos(rq))
3719                         sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
3720                 else
3721                         sdist = cfqq->last_request_pos - blk_rq_pos(rq);
3722         }
3723 
3724         cfqq->seek_history <<= 1;
3725         if (blk_queue_nonrot(cfqd->queue))
3726                 cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT);
3727         else
3728                 cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
3729 }
3730 
3731 /*
3732  * Disable idle window if the process thinks too long or seeks so much that
3733  * it doesn't matter
3734  */
3735 static void
3736 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3737                        struct cfq_io_cq *cic)
3738 {
3739         int old_idle, enable_idle;
3740 
3741         /*
3742          * Don't idle for async or idle io prio class
3743          */
3744         if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
3745                 return;
3746 
3747         enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
3748 
3749         if (cfqq->queued[0] + cfqq->queued[1] >= 4)
3750                 cfq_mark_cfqq_deep(cfqq);
3751 
3752         if (cfqq->next_rq && (cfqq->next_rq->cmd_flags & REQ_NOIDLE))
3753                 enable_idle = 0;
3754         else if (!atomic_read(&cic->icq.ioc->active_ref) ||
3755                  !cfqd->cfq_slice_idle ||
3756                  (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
3757                 enable_idle = 0;
3758         else if (sample_valid(cic->ttime.ttime_samples)) {
3759                 if (cic->ttime.ttime_mean > cfqd->cfq_slice_idle)
3760                         enable_idle = 0;
3761                 else
3762                         enable_idle = 1;
3763         }
3764 
3765         if (old_idle != enable_idle) {
3766                 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
3767                 if (enable_idle)
3768                         cfq_mark_cfqq_idle_window(cfqq);
3769                 else
3770                         cfq_clear_cfqq_idle_window(cfqq);
3771         }
3772 }
3773 
3774 /*
3775  * Check if new_cfqq should preempt the currently active queue. Return 0 for
3776  * no or if we aren't sure, a 1 will cause a preempt.
3777  */
3778 static bool
3779 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
3780                    struct request *rq)
3781 {
3782         struct cfq_queue *cfqq;
3783 
3784         cfqq = cfqd->active_queue;
3785         if (!cfqq)
3786                 return false;
3787 
3788         if (cfq_class_idle(new_cfqq))
3789                 return false;
3790 
3791         if (cfq_class_idle(cfqq))
3792                 return true;
3793 
3794         /*
3795          * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice.
3796          */
3797         if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq))
3798                 return false;
3799 
3800         /*
3801          * if the new request is sync, but the currently running queue is
3802          * not, let the sync request have priority.
3803          */
3804         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq) && !cfq_cfqq_must_dispatch(cfqq))
3805                 return true;
3806 
3807         if (new_cfqq->cfqg != cfqq->cfqg)
3808                 return false;
3809 
3810         if (cfq_slice_used(cfqq))
3811                 return true;
3812 
3813         /* Allow preemption only if we are idling on sync-noidle tree */
3814         if (cfqd->serving_wl_type == SYNC_NOIDLE_WORKLOAD &&
3815             cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
3816             new_cfqq->service_tree->count == 2 &&
3817             RB_EMPTY_ROOT(&cfqq->sort_list))
3818                 return true;
3819 
3820         /*
3821          * So both queues are sync. Let the new request get disk time if
3822          * it's a metadata request and the current queue is doing regular IO.
3823          */
3824         if ((rq->cmd_flags & REQ_PRIO) && !cfqq->prio_pending)
3825                 return true;
3826 
3827         /*
3828          * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
3829          */
3830         if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
3831                 return true;
3832 
3833         /* An idle queue should not be idle now for some reason */
3834         if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq))
3835                 return true;
3836 
3837         if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
3838                 return false;
3839 
3840         /*
3841          * if this request is as-good as one we would expect from the
3842          * current cfqq, let it preempt
3843          */
3844         if (cfq_rq_close(cfqd, cfqq, rq))
3845                 return true;
3846 
3847         return false;
3848 }
3849 
3850 /*
3851  * cfqq preempts the active queue. if we allowed preempt with no slice left,
3852  * let it have half of its nominal slice.
3853  */
3854 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3855 {
3856         enum wl_type_t old_type = cfqq_type(cfqd->active_queue);
3857 
3858         cfq_log_cfqq(cfqd, cfqq, "preempt");
3859         cfq_slice_expired(cfqd, 1);
3860 
3861         /*
3862          * workload type is changed, don't save slice, otherwise preempt
3863          * doesn't happen
3864          */
3865         if (old_type != cfqq_type(cfqq))
3866                 cfqq->cfqg->saved_wl_slice = 0;
3867 
3868         /*
3869          * Put the new queue at the front of the of the current list,
3870          * so we know that it will be selected next.
3871          */
3872         BUG_ON(!cfq_cfqq_on_rr(cfqq));
3873 
3874         cfq_service_tree_add(cfqd, cfqq, 1);
3875 
3876         cfqq->slice_end = 0;
3877         cfq_mark_cfqq_slice_new(cfqq);
3878 }
3879 
3880 /*
3881  * Called when a new fs request (rq) is added (to cfqq). Check if there's
3882  * something we should do about it
3883  */
3884 static void
3885 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3886                 struct request *rq)
3887 {
3888         struct cfq_io_cq *cic = RQ_CIC(rq);
3889 
3890         cfqd->rq_queued++;
3891         if (rq->cmd_flags & REQ_PRIO)
3892                 cfqq->prio_pending++;
3893 
3894         cfq_update_io_thinktime(cfqd, cfqq, cic);
3895         cfq_update_io_seektime(cfqd, cfqq, rq);
3896         cfq_update_idle_window(cfqd, cfqq, cic);
3897 
3898         cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
3899 
3900         if (cfqq == cfqd->active_queue) {
3901                 /*
3902                  * Remember that we saw a request from this process, but
3903                  * don't start queuing just yet. Otherwise we risk seeing lots
3904                  * of tiny requests, because we disrupt the normal plugging
3905                  * and merging. If the request is already larger than a single
3906                  * page, let it rip immediately. For that case we assume that
3907                  * merging is already done. Ditto for a busy system that
3908                  * has other work pending, don't risk delaying until the
3909                  * idle timer unplug to continue working.
3910                  */
3911                 if (cfq_cfqq_wait_request(cfqq)) {
3912                         if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
3913                             cfqd->busy_queues > 1) {
3914                                 cfq_del_timer(cfqd, cfqq);
3915                                 cfq_clear_cfqq_wait_request(cfqq);
3916                                 __blk_run_queue(cfqd->queue);
3917                         } else {
3918                                 cfqg_stats_update_idle_time(cfqq->cfqg);
3919                                 cfq_mark_cfqq_must_dispatch(cfqq);
3920                         }
3921                 }
3922         } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
3923                 /*
3924                  * not the active queue - expire current slice if it is
3925                  * idle and has expired it's mean thinktime or this new queue
3926                  * has some old slice time left and is of higher priority or
3927                  * this new queue is RT and the current one is BE
3928                  */
3929                 cfq_preempt_queue(cfqd, cfqq);
3930                 __blk_run_queue(cfqd->queue);
3931         }
3932 }
3933 
3934 static void cfq_insert_request(struct request_queue *q, struct request *rq)
3935 {
3936         struct cfq_data *cfqd = q->elevator->elevator_data;
3937         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3938 
3939         cfq_log_cfqq(cfqd, cfqq, "insert_request");
3940         cfq_init_prio_data(cfqq, RQ_CIC(rq));
3941 
3942         rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
3943         list_add_tail(&rq->queuelist, &cfqq->fifo);
3944         cfq_add_rq_rb(rq);
3945         cfqg_stats_update_io_add(RQ_CFQG(rq), cfqd->serving_group,
3946                                  rq->cmd_flags);
3947         cfq_rq_enqueued(cfqd, cfqq, rq);
3948 }
3949 
3950 /*
3951  * Update hw_tag based on peak queue depth over 50 samples under
3952  * sufficient load.
3953  */
3954 static void cfq_update_hw_tag(struct cfq_data *cfqd)
3955 {
3956         struct cfq_queue *cfqq = cfqd->active_queue;
3957 
3958         if (cfqd->rq_in_driver > cfqd->hw_tag_est_depth)
3959                 cfqd->hw_tag_est_depth = cfqd->rq_in_driver;
3960 
3961         if (cfqd->hw_tag == 1)
3962                 return;
3963 
3964         if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
3965             cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
3966                 return;
3967 
3968         /*
3969          * If active queue hasn't enough requests and can idle, cfq might not
3970          * dispatch sufficient requests to hardware. Don't zero hw_tag in this
3971          * case
3972          */
3973         if (cfqq && cfq_cfqq_idle_window(cfqq) &&
3974             cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
3975             CFQ_HW_QUEUE_MIN && cfqd->rq_in_driver < CFQ_HW_QUEUE_MIN)
3976                 return;
3977 
3978         if (cfqd->hw_tag_samples++ < 50)
3979                 return;
3980 
3981         if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
3982                 cfqd->hw_tag = 1;
3983         else
3984                 cfqd->hw_tag = 0;
3985 }
3986 
3987 static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3988 {
3989         struct cfq_io_cq *cic = cfqd->active_cic;
3990 
3991         /* If the queue already has requests, don't wait */
3992         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3993                 return false;
3994 
3995         /* If there are other queues in the group, don't wait */
3996         if (cfqq->cfqg->nr_cfqq > 1)
3997                 return false;
3998 
3999         /* the only queue in the group, but think time is big */
4000         if (cfq_io_thinktime_big(cfqd, &cfqq->cfqg->ttime, true))
4001                 return false;
4002 
4003         if (cfq_slice_used(cfqq))
4004                 return true;
4005 
4006         /* if slice left is less than think time, wait busy */
4007         if (cic && sample_valid(cic->ttime.ttime_samples)
4008             && (cfqq->slice_end - jiffies < cic->ttime.ttime_mean))
4009                 return true;
4010 
4011         /*
4012          * If think times is less than a jiffy than ttime_mean=0 and above
4013          * will not be true. It might happen that slice has not expired yet
4014          * but will expire soon (4-5 ns) during select_queue(). To cover the
4015          * case where think time is less than a jiffy, mark the queue wait
4016          * busy if only 1 jiffy is left in the slice.
4017          */
4018         if (cfqq->slice_end - jiffies == 1)
4019                 return true;
4020 
4021         return false;
4022 }
4023 
4024 static void cfq_completed_request(struct request_queue *q, struct request *rq)
4025 {
4026         struct cfq_queue *cfqq = RQ_CFQQ(rq);
4027         struct cfq_data *cfqd = cfqq->cfqd;
4028         const int sync = rq_is_sync(rq);
4029         unsigned long now;
4030 
4031         now = jiffies;
4032         cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d",
4033                      !!(rq->cmd_flags & REQ_NOIDLE));
4034 
4035         cfq_update_hw_tag(cfqd);
4036 
4037         WARN_ON(!cfqd->rq_in_driver);
4038         WARN_ON(!cfqq->dispatched);
4039         cfqd->rq_in_driver--;
4040         cfqq->dispatched--;
4041         (RQ_CFQG(rq))->dispatched--;
4042         cfqg_stats_update_completion(cfqq->cfqg, rq_start_time_ns(rq),
4043                                      rq_io_start_time_ns(rq), rq->cmd_flags);
4044 
4045         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
4046 
4047         if (sync) {
4048                 struct cfq_rb_root *st;
4049 
4050                 RQ_CIC(rq)->ttime.last_end_request = now;
4051 
4052                 if (cfq_cfqq_on_rr(cfqq))
4053                         st = cfqq->service_tree;
4054                 else
4055                         st = st_for(cfqq->cfqg, cfqq_class(cfqq),
4056                                         cfqq_type(cfqq));
4057 
4058                 st->ttime.last_end_request = now;
4059                 if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
4060                         cfqd->last_delayed_sync = now;
4061         }
4062 
4063 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4064         cfqq->cfqg->ttime.last_end_request = now;
4065 #endif
4066 
4067         /*
4068          * If this is the active queue, check if it needs to be expired,
4069          * or if we want to idle in case it has no pending requests.
4070          */
4071         if (cfqd->active_queue == cfqq) {
4072                 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
4073 
4074                 if (cfq_cfqq_slice_new(cfqq)) {
4075                         cfq_set_prio_slice(cfqd, cfqq);
4076                         cfq_clear_cfqq_slice_new(cfqq);
4077                 }
4078 
4079                 /*
4080                  * Should we wait for next request to come in before we expire
4081                  * the queue.
4082                  */
4083                 if (cfq_should_wait_busy(cfqd, cfqq)) {
4084                         unsigned long extend_sl = cfqd->cfq_slice_idle;
4085                         if (!cfqd->cfq_slice_idle)
4086                                 extend_sl = cfqd->cfq_group_idle;
4087                         cfqq->slice_end = jiffies + extend_sl;
4088                         cfq_mark_cfqq_wait_busy(cfqq);
4089                         cfq_log_cfqq(cfqd, cfqq, "will busy wait");
4090                 }
4091 
4092                 /*
4093                  * Idling is not enabled on:
4094                  * - expired queues
4095                  * - idle-priority queues
4096                  * - async queues
4097                  * - queues with still some requests queued
4098                  * - when there is a close cooperator
4099                  */
4100                 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
4101                         cfq_slice_expired(cfqd, 1);
4102                 else if (sync && cfqq_empty &&
4103                          !cfq_close_cooperator(cfqd, cfqq)) {
4104                         cfq_arm_slice_timer(cfqd);
4105                 }
4106         }
4107 
4108         if (!cfqd->rq_in_driver)
4109                 cfq_schedule_dispatch(cfqd);
4110 }
4111 
4112 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
4113 {
4114         if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
4115                 cfq_mark_cfqq_must_alloc_slice(cfqq);
4116                 return ELV_MQUEUE_MUST;
4117         }
4118 
4119         return ELV_MQUEUE_MAY;
4120 }
4121 
4122 static int cfq_may_queue(struct request_queue *q, int rw)
4123 {
4124         struct cfq_data *cfqd = q->elevator->elevator_data;
4125         struct task_struct *tsk = current;
4126         struct cfq_io_cq *cic;
4127         struct cfq_queue *cfqq;
4128 
4129         /*
4130          * don't force setup of a queue from here, as a call to may_queue
4131          * does not necessarily imply that a request actually will be queued.
4132          * so just lookup a possibly existing queue, or return 'may queue'
4133          * if that fails
4134          */
4135         cic = cfq_cic_lookup(cfqd, tsk->io_context);
4136         if (!cic)
4137                 return ELV_MQUEUE_MAY;
4138 
4139         cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
4140         if (cfqq) {
4141                 cfq_init_prio_data(cfqq, cic);
4142 
4143                 return __cfq_may_queue(cfqq);
4144         }
4145 
4146         return ELV_MQUEUE_MAY;
4147 }
4148 
4149 /*
4150  * queue lock held here
4151  */
4152 static void cfq_put_request(struct request *rq)
4153 {
4154         struct cfq_queue *cfqq = RQ_CFQQ(rq);
4155 
4156         if (cfqq) {
4157                 const int rw = rq_data_dir(rq);
4158 
4159                 BUG_ON(!cfqq->allocated[rw]);
4160                 cfqq->allocated[rw]--;
4161 
4162                 /* Put down rq reference on cfqg */
4163                 cfqg_put(RQ_CFQG(rq));
4164                 rq->elv.priv[0] = NULL;
4165                 rq->elv.priv[1] = NULL;
4166 
4167                 cfq_put_queue(cfqq);
4168         }
4169 }
4170 
4171 static struct cfq_queue *
4172 cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_cq *cic,
4173                 struct cfq_queue *cfqq)
4174 {
4175         cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
4176         cic_set_cfqq(cic, cfqq->new_cfqq, 1);
4177         cfq_mark_cfqq_coop(cfqq->new_cfqq);
4178         cfq_put_queue(cfqq);
4179         return cic_to_cfqq(cic, 1);
4180 }
4181 
4182 /*
4183  * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
4184  * was the last process referring to said cfqq.
4185  */
4186 static struct cfq_queue *
4187 split_cfqq(struct cfq_io_cq *cic, struct cfq_queue *cfqq)
4188 {
4189         if (cfqq_process_refs(cfqq) == 1) {
4190                 cfqq->pid = current->pid;
4191                 cfq_clear_cfqq_coop(cfqq);
4192                 cfq_clear_cfqq_split_coop(cfqq);
4193                 return cfqq;
4194         }
4195 
4196         cic_set_cfqq(cic, NULL, 1);
4197 
4198         cfq_put_cooperator(cfqq);
4199 
4200         cfq_put_queue(cfqq);
4201         return NULL;
4202 }
4203 /*
4204  * Allocate cfq data structures associated with this request.
4205  */
4206 static int
4207 cfq_set_request(struct request_queue *q, struct request *rq, struct bio *bio,
4208                 gfp_t gfp_mask)
4209 {
4210         struct cfq_data *cfqd = q->elevator->elevator_data;
4211         struct cfq_io_cq *cic = icq_to_cic(rq->elv.icq);
4212         const int rw = rq_data_dir(rq);
4213         const bool is_sync = rq_is_sync(rq);
4214         struct cfq_queue *cfqq;
4215 
4216         might_sleep_if(gfp_mask & __GFP_WAIT);
4217 
4218         spin_lock_irq(q->queue_lock);
4219 
4220         check_ioprio_changed(cic, bio);
4221         check_blkcg_changed(cic, bio);
4222 new_queue:
4223         cfqq = cic_to_cfqq(cic, is_sync);
4224         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
4225                 cfqq = cfq_get_queue(cfqd, is_sync, cic, bio, gfp_mask);
4226                 cic_set_cfqq(cic, cfqq, is_sync);
4227         } else {
4228                 /*
4229                  * If the queue was seeky for too long, break it apart.
4230                  */
4231                 if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) {
4232                         cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
4233                         cfqq = split_cfqq(cic, cfqq);
4234                         if (!cfqq)
4235                                 goto new_queue;
4236                 }
4237 
4238                 /*
4239                  * Check to see if this queue is scheduled to merge with
4240                  * another, closely cooperating queue.  The merging of
4241                  * queues happens here as it must be done in process context.
4242                  * The reference on new_cfqq was taken in merge_cfqqs.
4243                  */
4244                 if (cfqq->new_cfqq)
4245                         cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
4246         }
4247 
4248         cfqq->allocated[rw]++;
4249 
4250         cfqq->ref++;
4251         cfqg_get(cfqq->cfqg);
4252         rq->elv.priv[0] = cfqq;
4253         rq->elv.priv[1] = cfqq->cfqg;
4254         spin_unlock_irq(q->queue_lock);
4255         return 0;
4256 }
4257 
4258 static void cfq_kick_queue(struct work_struct *work)
4259 {
4260         struct cfq_data *cfqd =
4261                 container_of(work, struct cfq_data, unplug_work);
4262         struct request_queue *q = cfqd->queue;
4263 
4264         spin_lock_irq(q->queue_lock);
4265         __blk_run_queue(cfqd->queue);
4266         spin_unlock_irq(q->queue_lock);
4267 }
4268 
4269 /*
4270  * Timer running if the active_queue is currently idling inside its time slice
4271  */
4272 static void cfq_idle_slice_timer(unsigned long data)
4273 {
4274         struct cfq_data *cfqd = (struct cfq_data *) data;
4275         struct cfq_queue *cfqq;
4276         unsigned long flags;
4277         int timed_out = 1;
4278 
4279         cfq_log(cfqd, "idle timer fired");
4280 
4281         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
4282 
4283         cfqq = cfqd->active_queue;
4284         if (cfqq) {
4285                 timed_out = 0;
4286 
4287                 /*
4288                  * We saw a request before the queue expired, let it through
4289                  */
4290                 if (cfq_cfqq_must_dispatch(cfqq))
4291                         goto out_kick;
4292 
4293                 /*
4294                  * expired
4295                  */
4296                 if (cfq_slice_used(cfqq))
4297                         goto expire;
4298 
4299                 /*
4300                  * only expire and reinvoke request handler, if there are
4301                  * other queues with pending requests
4302                  */
4303                 if (!cfqd->busy_queues)
4304                         goto out_cont;
4305 
4306                 /*
4307                  * not expired and it has a request pending, let it dispatch
4308                  */
4309                 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
4310                         goto out_kick;
4311 
4312                 /*
4313                  * Queue depth flag is reset only when the idle didn't succeed
4314                  */
4315                 cfq_clear_cfqq_deep(cfqq);
4316         }
4317 expire:
4318         cfq_slice_expired(cfqd, timed_out);
4319 out_kick:
4320         cfq_schedule_dispatch(cfqd);
4321 out_cont:
4322         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
4323 }
4324 
4325 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
4326 {
4327         del_timer_sync(&cfqd->idle_slice_timer);
4328         cancel_work_sync(&cfqd->unplug_work);
4329 }
4330 
4331 static void cfq_put_async_queues(struct cfq_data *cfqd)
4332 {
4333         int i;
4334 
4335         for (i = 0; i < IOPRIO_BE_NR; i++) {
4336                 if (cfqd->async_cfqq[0][i])
4337                         cfq_put_queue(cfqd->async_cfqq[0][i]);
4338                 if (cfqd->async_cfqq[1][i])
4339                         cfq_put_queue(cfqd->async_cfqq[1][i]);
4340         }
4341 
4342         if (cfqd->async_idle_cfqq)
4343                 cfq_put_queue(cfqd->async_idle_cfqq);
4344 }
4345 
4346 static void cfq_exit_queue(struct elevator_queue *e)
4347 {
4348         struct cfq_data *cfqd = e->elevator_data;
4349         struct request_queue *q = cfqd->queue;
4350 
4351         cfq_shutdown_timer_wq(cfqd);
4352 
4353         spin_lock_irq(q->queue_lock);
4354 
4355         if (cfqd->active_queue)
4356                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
4357 
4358         cfq_put_async_queues(cfqd);
4359 
4360         spin_unlock_irq(q->queue_lock);
4361 
4362         cfq_shutdown_timer_wq(cfqd);
4363 
4364 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4365         blkcg_deactivate_policy(q, &blkcg_policy_cfq);
4366 #else
4367         kfree(cfqd->root_group);
4368 #endif
4369         kfree(cfqd);
4370 }
4371 
4372 static int cfq_init_queue(struct request_queue *q, struct elevator_type *e)
4373 {
4374         struct cfq_data *cfqd;
4375         struct blkcg_gq *blkg __maybe_unused;
4376         int i, ret;
4377         struct elevator_queue *eq;
4378 
4379         eq = elevator_alloc(q, e);
4380         if (!eq)
4381                 return -ENOMEM;
4382 
4383         cfqd = kzalloc_node(sizeof(*cfqd), GFP_KERNEL, q->node);
4384         if (!cfqd) {
4385                 kobject_put(&eq->kobj);
4386                 return -ENOMEM;
4387         }
4388         eq->elevator_data = cfqd;
4389 
4390         cfqd->queue = q;
4391         spin_lock_irq(q->queue_lock);
4392         q->elevator = eq;
4393         spin_unlock_irq(q->queue_lock);
4394 
4395         /* Init root service tree */
4396         cfqd->grp_service_tree = CFQ_RB_ROOT;
4397 
4398         /* Init root group and prefer root group over other groups by default */
4399 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4400         ret = blkcg_activate_policy(q, &blkcg_policy_cfq);
4401         if (ret)
4402                 goto out_free;
4403 
4404         cfqd->root_group = blkg_to_cfqg(q->root_blkg);
4405 #else
4406         ret = -ENOMEM;
4407         cfqd->root_group = kzalloc_node(sizeof(*cfqd->root_group),
4408                                         GFP_KERNEL, cfqd->queue->node);
4409         if (!cfqd->root_group)
4410                 goto out_free;
4411 
4412         cfq_init_cfqg_base(cfqd->root_group);
4413 #endif
4414         cfqd->root_group->weight = 2 * CFQ_WEIGHT_DEFAULT;
4415         cfqd->root_group->leaf_weight = 2 * CFQ_WEIGHT_DEFAULT;
4416 
4417         /*
4418          * Not strictly needed (since RB_ROOT just clears the node and we
4419          * zeroed cfqd on alloc), but better be safe in case someone decides
4420          * to add magic to the rb code
4421          */
4422         for (i = 0; i < CFQ_PRIO_LISTS; i++)
4423                 cfqd->prio_trees[i] = RB_ROOT;
4424 
4425         /*
4426          * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
4427          * Grab a permanent reference to it, so that the normal code flow
4428          * will not attempt to free it.  oom_cfqq is linked to root_group
4429          * but shouldn't hold a reference as it'll never be unlinked.  Lose
4430          * the reference from linking right away.
4431          */
4432         cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
4433         cfqd->oom_cfqq.ref++;
4434 
4435         spin_lock_irq(q->queue_lock);
4436         cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, cfqd->root_group);
4437         cfqg_put(cfqd->root_group);
4438         spin_unlock_irq(q->queue_lock);
4439 
4440         init_timer(&cfqd->idle_slice_timer);
4441         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
4442         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
4443 
4444         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
4445 
4446         cfqd->cfq_quantum = cfq_quantum;
4447         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
4448         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
4449         cfqd->cfq_back_max = cfq_back_max;
4450         cfqd->cfq_back_penalty = cfq_back_penalty;
4451         cfqd->cfq_slice[0] = cfq_slice_async;
4452         cfqd->cfq_slice[1] = cfq_slice_sync;
4453         cfqd->cfq_target_latency = cfq_target_latency;
4454         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
4455         cfqd->cfq_slice_idle = cfq_slice_idle;
4456         cfqd->cfq_group_idle = cfq_group_idle;
4457         cfqd->cfq_latency = 1;
4458         cfqd->hw_tag = -1;
4459         /*
4460          * we optimistically start assuming sync ops weren't delayed in last
4461          * second, in order to have larger depth for async operations.
4462          */
4463         cfqd->last_delayed_sync = jiffies - HZ;
4464         return 0;
4465 
4466 out_free:
4467         kfree(cfqd);
4468         kobject_put(&eq->kobj);
4469         return ret;
4470 }
4471 
4472 /*
4473  * sysfs parts below -->
4474  */
4475 static ssize_t
4476 cfq_var_show(unsigned int var, char *page)
4477 {
4478         return sprintf(page, "%d\n", var);
4479 }
4480 
4481 static ssize_t
4482 cfq_var_store(unsigned int *var, const char *page, size_t count)
4483 {
4484         char *p = (char *) page;
4485 
4486         *var = simple_strtoul(p, &p, 10);
4487         return count;
4488 }
4489 
4490 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
4491 static ssize_t __FUNC(struct elevator_queue *e, char *page)             \
4492 {                                                                       \
4493         struct cfq_data *cfqd = e->elevator_data;                       \
4494         unsigned int __data = __VAR;                                    \
4495         if (__CONV)                                                     \
4496                 __data = jiffies_to_msecs(__data);                      \
4497         return cfq_var_show(__data, (page));                            \
4498 }
4499 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
4500 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
4501 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
4502 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
4503 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
4504 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
4505 SHOW_FUNCTION(cfq_group_idle_show, cfqd->cfq_group_idle, 1);
4506 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
4507 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
4508 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
4509 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
4510 SHOW_FUNCTION(cfq_target_latency_show, cfqd->cfq_target_latency, 1);
4511 #undef SHOW_FUNCTION
4512 
4513 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
4514 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
4515 {                                                                       \
4516         struct cfq_data *cfqd = e->elevator_data;                       \
4517         unsigned int __data;                                            \
4518         int ret = cfq_var_store(&__data, (page), count);                \
4519         if (__data < (MIN))                                             \
4520                 __data = (MIN);                                         \
4521         else if (__data > (MAX))                                        \
4522                 __data = (MAX);                                         \
4523         if (__CONV)                                                     \
4524                 *(__PTR) = msecs_to_jiffies(__data);                    \
4525         else                                                            \
4526                 *(__PTR) = __data;                                      \
4527         return ret;                                                     \
4528 }
4529 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
4530 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
4531                 UINT_MAX, 1);
4532 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
4533                 UINT_MAX, 1);
4534 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
4535 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
4536                 UINT_MAX, 0);
4537 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
4538 STORE_FUNCTION(cfq_group_idle_store, &cfqd->cfq_group_idle, 0, UINT_MAX, 1);
4539 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
4540 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
4541 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
4542                 UINT_MAX, 0);
4543 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
4544 STORE_FUNCTION(cfq_target_latency_store, &cfqd->cfq_target_latency, 1, UINT_MAX, 1);
4545 #undef STORE_FUNCTION
4546 
4547 #define CFQ_ATTR(name) \
4548         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
4549 
4550 static struct elv_fs_entry cfq_attrs[] = {
4551         CFQ_ATTR(quantum),
4552         CFQ_ATTR(fifo_expire_sync),
4553         CFQ_ATTR(fifo_expire_async),
4554         CFQ_ATTR(back_seek_max),
4555         CFQ_ATTR(back_seek_penalty),
4556         CFQ_ATTR(slice_sync),
4557         CFQ_ATTR(slice_async),
4558         CFQ_ATTR(slice_async_rq),
4559         CFQ_ATTR(slice_idle),
4560         CFQ_ATTR(group_idle),
4561         CFQ_ATTR(low_latency),
4562         CFQ_ATTR(target_latency),
4563         __ATTR_NULL
4564 };
4565 
4566 static struct elevator_type iosched_cfq = {
4567         .ops = {
4568                 .elevator_merge_fn =            cfq_merge,
4569                 .elevator_merged_fn =           cfq_merged_request,
4570                 .elevator_merge_req_fn =        cfq_merged_requests,
4571                 .elevator_allow_merge_fn =      cfq_allow_merge,
4572                 .elevator_bio_merged_fn =       cfq_bio_merged,
4573                 .elevator_dispatch_fn =         cfq_dispatch_requests,
4574                 .elevator_add_req_fn =          cfq_insert_request,
4575                 .elevator_activate_req_fn =     cfq_activate_request,
4576                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
4577                 .elevator_completed_req_fn =    cfq_completed_request,
4578                 .elevator_former_req_fn =       elv_rb_former_request,
4579                 .elevator_latter_req_fn =       elv_rb_latter_request,
4580                 .elevator_init_icq_fn =         cfq_init_icq,
4581                 .elevator_exit_icq_fn =         cfq_exit_icq,
4582                 .elevator_set_req_fn =          cfq_set_request,
4583                 .elevator_put_req_fn =          cfq_put_request,
4584                 .elevator_may_queue_fn =        cfq_may_queue,
4585                 .elevator_init_fn =             cfq_init_queue,
4586                 .elevator_exit_fn =             cfq_exit_queue,
4587         },
4588         .icq_size       =       sizeof(struct cfq_io_cq),
4589         .icq_align      =       __alignof__(struct cfq_io_cq),
4590         .elevator_attrs =       cfq_attrs,
4591         .elevator_name  =       "cfq",
4592         .elevator_owner =       THIS_MODULE,
4593 };
4594 
4595 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4596 static struct blkcg_policy blkcg_policy_cfq = {
4597         .pd_size                = sizeof(struct cfq_group),
4598         .cftypes                = cfq_blkcg_files,
4599 
4600         .pd_init_fn             = cfq_pd_init,
4601         .pd_offline_fn          = cfq_pd_offline,
4602         .pd_reset_stats_fn      = cfq_pd_reset_stats,
4603 };
4604 #endif
4605 
4606 static int __init cfq_init(void)
4607 {
4608         int ret;
4609 
4610         /*
4611          * could be 0 on HZ < 1000 setups
4612          */
4613         if (!cfq_slice_async)
4614                 cfq_slice_async = 1;
4615         if (!cfq_slice_idle)
4616                 cfq_slice_idle = 1;
4617 
4618 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4619         if (!cfq_group_idle)
4620                 cfq_group_idle = 1;
4621 
4622         ret = blkcg_policy_register(&blkcg_policy_cfq);
4623         if (ret)
4624                 return ret;
4625 #else
4626         cfq_group_idle = 0;
4627 #endif
4628 
4629         ret = -ENOMEM;
4630         cfq_pool = KMEM_CACHE(cfq_queue, 0);
4631         if (!cfq_pool)
4632                 goto err_pol_unreg;
4633 
4634         ret = elv_register(&iosched_cfq);
4635         if (ret)
4636                 goto err_free_pool;
4637 
4638         return 0;
4639 
4640 err_free_pool:
4641         kmem_cache_destroy(cfq_pool);
4642 err_pol_unreg:
4643 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4644         blkcg_policy_unregister(&blkcg_policy_cfq);
4645 #endif
4646         return ret;
4647 }
4648 
4649 static void __exit cfq_exit(void)
4650 {
4651 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4652         blkcg_policy_unregister(&blkcg_policy_cfq);
4653 #endif
4654         elv_unregister(&iosched_cfq);
4655         kmem_cache_destroy(cfq_pool);
4656 }
4657 
4658 module_init(cfq_init);
4659 module_exit(cfq_exit);
4660 
4661 MODULE_AUTHOR("Jens Axboe");
4662 MODULE_LICENSE("GPL");
4663 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");
4664 

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