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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 <linux/blk-cgroup.h>
 18 #include "blk.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 /* blkio-related constants */
 71 #define CFQ_WEIGHT_LEGACY_MIN   10
 72 #define CFQ_WEIGHT_LEGACY_DFL   500
 73 #define CFQ_WEIGHT_LEGACY_MAX   1000
 74 
 75 struct cfq_ttime {
 76         unsigned long last_end_request;
 77 
 78         unsigned long ttime_total;
 79         unsigned long ttime_samples;
 80         unsigned long ttime_mean;
 81 };
 82 
 83 /*
 84  * Most of our rbtree usage is for sorting with min extraction, so
 85  * if we cache the leftmost node we don't have to walk down the tree
 86  * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
 87  * move this into the elevator for the rq sorting as well.
 88  */
 89 struct cfq_rb_root {
 90         struct rb_root rb;
 91         struct rb_node *left;
 92         unsigned count;
 93         u64 min_vdisktime;
 94         struct cfq_ttime ttime;
 95 };
 96 #define CFQ_RB_ROOT     (struct cfq_rb_root) { .rb = RB_ROOT, \
 97                         .ttime = {.last_end_request = jiffies,},}
 98 
 99 /*
100  * Per process-grouping structure
101  */
102 struct cfq_queue {
103         /* reference count */
104         int ref;
105         /* various state flags, see below */
106         unsigned int flags;
107         /* parent cfq_data */
108         struct cfq_data *cfqd;
109         /* service_tree member */
110         struct rb_node rb_node;
111         /* service_tree key */
112         unsigned long rb_key;
113         /* prio tree member */
114         struct rb_node p_node;
115         /* prio tree root we belong to, if any */
116         struct rb_root *p_root;
117         /* sorted list of pending requests */
118         struct rb_root sort_list;
119         /* if fifo isn't expired, next request to serve */
120         struct request *next_rq;
121         /* requests queued in sort_list */
122         int queued[2];
123         /* currently allocated requests */
124         int allocated[2];
125         /* fifo list of requests in sort_list */
126         struct list_head fifo;
127 
128         /* time when queue got scheduled in to dispatch first request. */
129         unsigned long dispatch_start;
130         unsigned int allocated_slice;
131         unsigned int slice_dispatch;
132         /* time when first request from queue completed and slice started. */
133         unsigned long slice_start;
134         unsigned long slice_end;
135         long slice_resid;
136 
137         /* pending priority requests */
138         int prio_pending;
139         /* number of requests that are on the dispatch list or inside driver */
140         int dispatched;
141 
142         /* io prio of this group */
143         unsigned short ioprio, org_ioprio;
144         unsigned short ioprio_class;
145 
146         pid_t pid;
147 
148         u32 seek_history;
149         sector_t last_request_pos;
150 
151         struct cfq_rb_root *service_tree;
152         struct cfq_queue *new_cfqq;
153         struct cfq_group *cfqg;
154         /* Number of sectors dispatched from queue in single dispatch round */
155         unsigned long nr_sectors;
156 };
157 
158 /*
159  * First index in the service_trees.
160  * IDLE is handled separately, so it has negative index
161  */
162 enum wl_class_t {
163         BE_WORKLOAD = 0,
164         RT_WORKLOAD = 1,
165         IDLE_WORKLOAD = 2,
166         CFQ_PRIO_NR,
167 };
168 
169 /*
170  * Second index in the service_trees.
171  */
172 enum wl_type_t {
173         ASYNC_WORKLOAD = 0,
174         SYNC_NOIDLE_WORKLOAD = 1,
175         SYNC_WORKLOAD = 2
176 };
177 
178 struct cfqg_stats {
179 #ifdef CONFIG_CFQ_GROUP_IOSCHED
180         /* number of ios merged */
181         struct blkg_rwstat              merged;
182         /* total time spent on device in ns, may not be accurate w/ queueing */
183         struct blkg_rwstat              service_time;
184         /* total time spent waiting in scheduler queue in ns */
185         struct blkg_rwstat              wait_time;
186         /* number of IOs queued up */
187         struct blkg_rwstat              queued;
188         /* total disk time and nr sectors dispatched by this group */
189         struct blkg_stat                time;
190 #ifdef CONFIG_DEBUG_BLK_CGROUP
191         /* time not charged to this cgroup */
192         struct blkg_stat                unaccounted_time;
193         /* sum of number of ios queued across all samples */
194         struct blkg_stat                avg_queue_size_sum;
195         /* count of samples taken for average */
196         struct blkg_stat                avg_queue_size_samples;
197         /* how many times this group has been removed from service tree */
198         struct blkg_stat                dequeue;
199         /* total time spent waiting for it to be assigned a timeslice. */
200         struct blkg_stat                group_wait_time;
201         /* time spent idling for this blkcg_gq */
202         struct blkg_stat                idle_time;
203         /* total time with empty current active q with other requests queued */
204         struct blkg_stat                empty_time;
205         /* fields after this shouldn't be cleared on stat reset */
206         uint64_t                        start_group_wait_time;
207         uint64_t                        start_idle_time;
208         uint64_t                        start_empty_time;
209         uint16_t                        flags;
210 #endif  /* CONFIG_DEBUG_BLK_CGROUP */
211 #endif  /* CONFIG_CFQ_GROUP_IOSCHED */
212 };
213 
214 /* Per-cgroup data */
215 struct cfq_group_data {
216         /* must be the first member */
217         struct blkcg_policy_data cpd;
218 
219         unsigned int weight;
220         unsigned int leaf_weight;
221 };
222 
223 /* This is per cgroup per device grouping structure */
224 struct cfq_group {
225         /* must be the first member */
226         struct blkg_policy_data pd;
227 
228         /* group service_tree member */
229         struct rb_node rb_node;
230 
231         /* group service_tree key */
232         u64 vdisktime;
233 
234         /*
235          * The number of active cfqgs and sum of their weights under this
236          * cfqg.  This covers this cfqg's leaf_weight and all children's
237          * weights, but does not cover weights of further descendants.
238          *
239          * If a cfqg is on the service tree, it's active.  An active cfqg
240          * also activates its parent and contributes to the children_weight
241          * of the parent.
242          */
243         int nr_active;
244         unsigned int children_weight;
245 
246         /*
247          * vfraction is the fraction of vdisktime that the tasks in this
248          * cfqg are entitled to.  This is determined by compounding the
249          * ratios walking up from this cfqg to the root.
250          *
251          * It is in fixed point w/ CFQ_SERVICE_SHIFT and the sum of all
252          * vfractions on a service tree is approximately 1.  The sum may
253          * deviate a bit due to rounding errors and fluctuations caused by
254          * cfqgs entering and leaving the service tree.
255          */
256         unsigned int vfraction;
257 
258         /*
259          * There are two weights - (internal) weight is the weight of this
260          * cfqg against the sibling cfqgs.  leaf_weight is the wight of
261          * this cfqg against the child cfqgs.  For the root cfqg, both
262          * weights are kept in sync for backward compatibility.
263          */
264         unsigned int weight;
265         unsigned int new_weight;
266         unsigned int dev_weight;
267 
268         unsigned int leaf_weight;
269         unsigned int new_leaf_weight;
270         unsigned int dev_leaf_weight;
271 
272         /* number of cfqq currently on this group */
273         int nr_cfqq;
274 
275         /*
276          * Per group busy queues average. Useful for workload slice calc. We
277          * create the array for each prio class but at run time it is used
278          * only for RT and BE class and slot for IDLE class remains unused.
279          * This is primarily done to avoid confusion and a gcc warning.
280          */
281         unsigned int busy_queues_avg[CFQ_PRIO_NR];
282         /*
283          * rr lists of queues with requests. We maintain service trees for
284          * RT and BE classes. These trees are subdivided in subclasses
285          * of SYNC, SYNC_NOIDLE and ASYNC based on workload type. For IDLE
286          * class there is no subclassification and all the cfq queues go on
287          * a single tree service_tree_idle.
288          * Counts are embedded in the cfq_rb_root
289          */
290         struct cfq_rb_root service_trees[2][3];
291         struct cfq_rb_root service_tree_idle;
292 
293         unsigned long saved_wl_slice;
294         enum wl_type_t saved_wl_type;
295         enum wl_class_t saved_wl_class;
296 
297         /* number of requests that are on the dispatch list or inside driver */
298         int dispatched;
299         struct cfq_ttime ttime;
300         struct cfqg_stats stats;        /* stats for this cfqg */
301 
302         /* async queue for each priority case */
303         struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
304         struct cfq_queue *async_idle_cfqq;
305 
306 };
307 
308 struct cfq_io_cq {
309         struct io_cq            icq;            /* must be the first member */
310         struct cfq_queue        *cfqq[2];
311         struct cfq_ttime        ttime;
312         int                     ioprio;         /* the current ioprio */
313 #ifdef CONFIG_CFQ_GROUP_IOSCHED
314         uint64_t                blkcg_serial_nr; /* the current blkcg serial */
315 #endif
316 };
317 
318 /*
319  * Per block device queue structure
320  */
321 struct cfq_data {
322         struct request_queue *queue;
323         /* Root service tree for cfq_groups */
324         struct cfq_rb_root grp_service_tree;
325         struct cfq_group *root_group;
326 
327         /*
328          * The priority currently being served
329          */
330         enum wl_class_t serving_wl_class;
331         enum wl_type_t serving_wl_type;
332         unsigned long workload_expires;
333         struct cfq_group *serving_group;
334 
335         /*
336          * Each priority tree is sorted by next_request position.  These
337          * trees are used when determining if two or more queues are
338          * interleaving requests (see cfq_close_cooperator).
339          */
340         struct rb_root prio_trees[CFQ_PRIO_LISTS];
341 
342         unsigned int busy_queues;
343         unsigned int busy_sync_queues;
344 
345         int rq_in_driver;
346         int rq_in_flight[2];
347 
348         /*
349          * queue-depth detection
350          */
351         int rq_queued;
352         int hw_tag;
353         /*
354          * hw_tag can be
355          * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
356          *  1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
357          *  0 => no NCQ
358          */
359         int hw_tag_est_depth;
360         unsigned int hw_tag_samples;
361 
362         /*
363          * idle window management
364          */
365         struct timer_list idle_slice_timer;
366         struct work_struct unplug_work;
367 
368         struct cfq_queue *active_queue;
369         struct cfq_io_cq *active_cic;
370 
371         sector_t last_position;
372 
373         /*
374          * tunables, see top of file
375          */
376         unsigned int cfq_quantum;
377         unsigned int cfq_fifo_expire[2];
378         unsigned int cfq_back_penalty;
379         unsigned int cfq_back_max;
380         unsigned int cfq_slice[2];
381         unsigned int cfq_slice_async_rq;
382         unsigned int cfq_slice_idle;
383         unsigned int cfq_group_idle;
384         unsigned int cfq_latency;
385         unsigned int cfq_target_latency;
386 
387         /*
388          * Fallback dummy cfqq for extreme OOM conditions
389          */
390         struct cfq_queue oom_cfqq;
391 
392         unsigned long last_delayed_sync;
393 };
394 
395 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
396 static void cfq_put_queue(struct cfq_queue *cfqq);
397 
398 static struct cfq_rb_root *st_for(struct cfq_group *cfqg,
399                                             enum wl_class_t class,
400                                             enum wl_type_t type)
401 {
402         if (!cfqg)
403                 return NULL;
404 
405         if (class == IDLE_WORKLOAD)
406                 return &cfqg->service_tree_idle;
407 
408         return &cfqg->service_trees[class][type];
409 }
410 
411 enum cfqq_state_flags {
412         CFQ_CFQQ_FLAG_on_rr = 0,        /* on round-robin busy list */
413         CFQ_CFQQ_FLAG_wait_request,     /* waiting for a request */
414         CFQ_CFQQ_FLAG_must_dispatch,    /* must be allowed a dispatch */
415         CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
416         CFQ_CFQQ_FLAG_fifo_expire,      /* FIFO checked in this slice */
417         CFQ_CFQQ_FLAG_idle_window,      /* slice idling enabled */
418         CFQ_CFQQ_FLAG_prio_changed,     /* task priority has changed */
419         CFQ_CFQQ_FLAG_slice_new,        /* no requests dispatched in slice */
420         CFQ_CFQQ_FLAG_sync,             /* synchronous queue */
421         CFQ_CFQQ_FLAG_coop,             /* cfqq is shared */
422         CFQ_CFQQ_FLAG_split_coop,       /* shared cfqq will be splitted */
423         CFQ_CFQQ_FLAG_deep,             /* sync cfqq experienced large depth */
424         CFQ_CFQQ_FLAG_wait_busy,        /* Waiting for next request */
425 };
426 
427 #define CFQ_CFQQ_FNS(name)                                              \
428 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
429 {                                                                       \
430         (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name);                   \
431 }                                                                       \
432 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
433 {                                                                       \
434         (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                  \
435 }                                                                       \
436 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
437 {                                                                       \
438         return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;      \
439 }
440 
441 CFQ_CFQQ_FNS(on_rr);
442 CFQ_CFQQ_FNS(wait_request);
443 CFQ_CFQQ_FNS(must_dispatch);
444 CFQ_CFQQ_FNS(must_alloc_slice);
445 CFQ_CFQQ_FNS(fifo_expire);
446 CFQ_CFQQ_FNS(idle_window);
447 CFQ_CFQQ_FNS(prio_changed);
448 CFQ_CFQQ_FNS(slice_new);
449 CFQ_CFQQ_FNS(sync);
450 CFQ_CFQQ_FNS(coop);
451 CFQ_CFQQ_FNS(split_coop);
452 CFQ_CFQQ_FNS(deep);
453 CFQ_CFQQ_FNS(wait_busy);
454 #undef CFQ_CFQQ_FNS
455 
456 #if defined(CONFIG_CFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
457 
458 /* cfqg stats flags */
459 enum cfqg_stats_flags {
460         CFQG_stats_waiting = 0,
461         CFQG_stats_idling,
462         CFQG_stats_empty,
463 };
464 
465 #define CFQG_FLAG_FNS(name)                                             \
466 static inline void cfqg_stats_mark_##name(struct cfqg_stats *stats)     \
467 {                                                                       \
468         stats->flags |= (1 << CFQG_stats_##name);                       \
469 }                                                                       \
470 static inline void cfqg_stats_clear_##name(struct cfqg_stats *stats)    \
471 {                                                                       \
472         stats->flags &= ~(1 << CFQG_stats_##name);                      \
473 }                                                                       \
474 static inline int cfqg_stats_##name(struct cfqg_stats *stats)           \
475 {                                                                       \
476         return (stats->flags & (1 << CFQG_stats_##name)) != 0;          \
477 }                                                                       \
478 
479 CFQG_FLAG_FNS(waiting)
480 CFQG_FLAG_FNS(idling)
481 CFQG_FLAG_FNS(empty)
482 #undef CFQG_FLAG_FNS
483 
484 /* This should be called with the queue_lock held. */
485 static void cfqg_stats_update_group_wait_time(struct cfqg_stats *stats)
486 {
487         unsigned long long now;
488 
489         if (!cfqg_stats_waiting(stats))
490                 return;
491 
492         now = sched_clock();
493         if (time_after64(now, stats->start_group_wait_time))
494                 blkg_stat_add(&stats->group_wait_time,
495                               now - stats->start_group_wait_time);
496         cfqg_stats_clear_waiting(stats);
497 }
498 
499 /* This should be called with the queue_lock held. */
500 static void cfqg_stats_set_start_group_wait_time(struct cfq_group *cfqg,
501                                                  struct cfq_group *curr_cfqg)
502 {
503         struct cfqg_stats *stats = &cfqg->stats;
504 
505         if (cfqg_stats_waiting(stats))
506                 return;
507         if (cfqg == curr_cfqg)
508                 return;
509         stats->start_group_wait_time = sched_clock();
510         cfqg_stats_mark_waiting(stats);
511 }
512 
513 /* This should be called with the queue_lock held. */
514 static void cfqg_stats_end_empty_time(struct cfqg_stats *stats)
515 {
516         unsigned long long now;
517 
518         if (!cfqg_stats_empty(stats))
519                 return;
520 
521         now = sched_clock();
522         if (time_after64(now, stats->start_empty_time))
523                 blkg_stat_add(&stats->empty_time,
524                               now - stats->start_empty_time);
525         cfqg_stats_clear_empty(stats);
526 }
527 
528 static void cfqg_stats_update_dequeue(struct cfq_group *cfqg)
529 {
530         blkg_stat_add(&cfqg->stats.dequeue, 1);
531 }
532 
533 static void cfqg_stats_set_start_empty_time(struct cfq_group *cfqg)
534 {
535         struct cfqg_stats *stats = &cfqg->stats;
536 
537         if (blkg_rwstat_total(&stats->queued))
538                 return;
539 
540         /*
541          * group is already marked empty. This can happen if cfqq got new
542          * request in parent group and moved to this group while being added
543          * to service tree. Just ignore the event and move on.
544          */
545         if (cfqg_stats_empty(stats))
546                 return;
547 
548         stats->start_empty_time = sched_clock();
549         cfqg_stats_mark_empty(stats);
550 }
551 
552 static void cfqg_stats_update_idle_time(struct cfq_group *cfqg)
553 {
554         struct cfqg_stats *stats = &cfqg->stats;
555 
556         if (cfqg_stats_idling(stats)) {
557                 unsigned long long now = sched_clock();
558 
559                 if (time_after64(now, stats->start_idle_time))
560                         blkg_stat_add(&stats->idle_time,
561                                       now - stats->start_idle_time);
562                 cfqg_stats_clear_idling(stats);
563         }
564 }
565 
566 static void cfqg_stats_set_start_idle_time(struct cfq_group *cfqg)
567 {
568         struct cfqg_stats *stats = &cfqg->stats;
569 
570         BUG_ON(cfqg_stats_idling(stats));
571 
572         stats->start_idle_time = sched_clock();
573         cfqg_stats_mark_idling(stats);
574 }
575 
576 static void cfqg_stats_update_avg_queue_size(struct cfq_group *cfqg)
577 {
578         struct cfqg_stats *stats = &cfqg->stats;
579 
580         blkg_stat_add(&stats->avg_queue_size_sum,
581                       blkg_rwstat_total(&stats->queued));
582         blkg_stat_add(&stats->avg_queue_size_samples, 1);
583         cfqg_stats_update_group_wait_time(stats);
584 }
585 
586 #else   /* CONFIG_CFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
587 
588 static inline void cfqg_stats_set_start_group_wait_time(struct cfq_group *cfqg, struct cfq_group *curr_cfqg) { }
589 static inline void cfqg_stats_end_empty_time(struct cfqg_stats *stats) { }
590 static inline void cfqg_stats_update_dequeue(struct cfq_group *cfqg) { }
591 static inline void cfqg_stats_set_start_empty_time(struct cfq_group *cfqg) { }
592 static inline void cfqg_stats_update_idle_time(struct cfq_group *cfqg) { }
593 static inline void cfqg_stats_set_start_idle_time(struct cfq_group *cfqg) { }
594 static inline void cfqg_stats_update_avg_queue_size(struct cfq_group *cfqg) { }
595 
596 #endif  /* CONFIG_CFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
597 
598 #ifdef CONFIG_CFQ_GROUP_IOSCHED
599 
600 static inline struct cfq_group *pd_to_cfqg(struct blkg_policy_data *pd)
601 {
602         return pd ? container_of(pd, struct cfq_group, pd) : NULL;
603 }
604 
605 static struct cfq_group_data
606 *cpd_to_cfqgd(struct blkcg_policy_data *cpd)
607 {
608         return cpd ? container_of(cpd, struct cfq_group_data, cpd) : NULL;
609 }
610 
611 static inline struct blkcg_gq *cfqg_to_blkg(struct cfq_group *cfqg)
612 {
613         return pd_to_blkg(&cfqg->pd);
614 }
615 
616 static struct blkcg_policy blkcg_policy_cfq;
617 
618 static inline struct cfq_group *blkg_to_cfqg(struct blkcg_gq *blkg)
619 {
620         return pd_to_cfqg(blkg_to_pd(blkg, &blkcg_policy_cfq));
621 }
622 
623 static struct cfq_group_data *blkcg_to_cfqgd(struct blkcg *blkcg)
624 {
625         return cpd_to_cfqgd(blkcg_to_cpd(blkcg, &blkcg_policy_cfq));
626 }
627 
628 static inline struct cfq_group *cfqg_parent(struct cfq_group *cfqg)
629 {
630         struct blkcg_gq *pblkg = cfqg_to_blkg(cfqg)->parent;
631 
632         return pblkg ? blkg_to_cfqg(pblkg) : NULL;
633 }
634 
635 static inline void cfqg_get(struct cfq_group *cfqg)
636 {
637         return blkg_get(cfqg_to_blkg(cfqg));
638 }
639 
640 static inline void cfqg_put(struct cfq_group *cfqg)
641 {
642         return blkg_put(cfqg_to_blkg(cfqg));
643 }
644 
645 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  do {                    \
646         char __pbuf[128];                                               \
647                                                                         \
648         blkg_path(cfqg_to_blkg((cfqq)->cfqg), __pbuf, sizeof(__pbuf));  \
649         blk_add_trace_msg((cfqd)->queue, "cfq%d%c%c %s " fmt, (cfqq)->pid, \
650                         cfq_cfqq_sync((cfqq)) ? 'S' : 'A',              \
651                         cfqq_type((cfqq)) == SYNC_NOIDLE_WORKLOAD ? 'N' : ' ',\
652                           __pbuf, ##args);                              \
653 } while (0)
654 
655 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)  do {                    \
656         char __pbuf[128];                                               \
657                                                                         \
658         blkg_path(cfqg_to_blkg(cfqg), __pbuf, sizeof(__pbuf));          \
659         blk_add_trace_msg((cfqd)->queue, "%s " fmt, __pbuf, ##args);    \
660 } while (0)
661 
662 static inline void cfqg_stats_update_io_add(struct cfq_group *cfqg,
663                                             struct cfq_group *curr_cfqg, int rw)
664 {
665         blkg_rwstat_add(&cfqg->stats.queued, rw, 1);
666         cfqg_stats_end_empty_time(&cfqg->stats);
667         cfqg_stats_set_start_group_wait_time(cfqg, curr_cfqg);
668 }
669 
670 static inline void cfqg_stats_update_timeslice_used(struct cfq_group *cfqg,
671                         unsigned long time, unsigned long unaccounted_time)
672 {
673         blkg_stat_add(&cfqg->stats.time, time);
674 #ifdef CONFIG_DEBUG_BLK_CGROUP
675         blkg_stat_add(&cfqg->stats.unaccounted_time, unaccounted_time);
676 #endif
677 }
678 
679 static inline void cfqg_stats_update_io_remove(struct cfq_group *cfqg, int rw)
680 {
681         blkg_rwstat_add(&cfqg->stats.queued, rw, -1);
682 }
683 
684 static inline void cfqg_stats_update_io_merged(struct cfq_group *cfqg, int rw)
685 {
686         blkg_rwstat_add(&cfqg->stats.merged, rw, 1);
687 }
688 
689 static inline void cfqg_stats_update_completion(struct cfq_group *cfqg,
690                         uint64_t start_time, uint64_t io_start_time, int rw)
691 {
692         struct cfqg_stats *stats = &cfqg->stats;
693         unsigned long long now = sched_clock();
694 
695         if (time_after64(now, io_start_time))
696                 blkg_rwstat_add(&stats->service_time, rw, now - io_start_time);
697         if (time_after64(io_start_time, start_time))
698                 blkg_rwstat_add(&stats->wait_time, rw,
699                                 io_start_time - start_time);
700 }
701 
702 /* @stats = 0 */
703 static void cfqg_stats_reset(struct cfqg_stats *stats)
704 {
705         /* queued stats shouldn't be cleared */
706         blkg_rwstat_reset(&stats->merged);
707         blkg_rwstat_reset(&stats->service_time);
708         blkg_rwstat_reset(&stats->wait_time);
709         blkg_stat_reset(&stats->time);
710 #ifdef CONFIG_DEBUG_BLK_CGROUP
711         blkg_stat_reset(&stats->unaccounted_time);
712         blkg_stat_reset(&stats->avg_queue_size_sum);
713         blkg_stat_reset(&stats->avg_queue_size_samples);
714         blkg_stat_reset(&stats->dequeue);
715         blkg_stat_reset(&stats->group_wait_time);
716         blkg_stat_reset(&stats->idle_time);
717         blkg_stat_reset(&stats->empty_time);
718 #endif
719 }
720 
721 /* @to += @from */
722 static void cfqg_stats_add_aux(struct cfqg_stats *to, struct cfqg_stats *from)
723 {
724         /* queued stats shouldn't be cleared */
725         blkg_rwstat_add_aux(&to->merged, &from->merged);
726         blkg_rwstat_add_aux(&to->service_time, &from->service_time);
727         blkg_rwstat_add_aux(&to->wait_time, &from->wait_time);
728         blkg_stat_add_aux(&from->time, &from->time);
729 #ifdef CONFIG_DEBUG_BLK_CGROUP
730         blkg_stat_add_aux(&to->unaccounted_time, &from->unaccounted_time);
731         blkg_stat_add_aux(&to->avg_queue_size_sum, &from->avg_queue_size_sum);
732         blkg_stat_add_aux(&to->avg_queue_size_samples, &from->avg_queue_size_samples);
733         blkg_stat_add_aux(&to->dequeue, &from->dequeue);
734         blkg_stat_add_aux(&to->group_wait_time, &from->group_wait_time);
735         blkg_stat_add_aux(&to->idle_time, &from->idle_time);
736         blkg_stat_add_aux(&to->empty_time, &from->empty_time);
737 #endif
738 }
739 
740 /*
741  * Transfer @cfqg's stats to its parent's aux counts so that the ancestors'
742  * recursive stats can still account for the amount used by this cfqg after
743  * it's gone.
744  */
745 static void cfqg_stats_xfer_dead(struct cfq_group *cfqg)
746 {
747         struct cfq_group *parent = cfqg_parent(cfqg);
748 
749         lockdep_assert_held(cfqg_to_blkg(cfqg)->q->queue_lock);
750 
751         if (unlikely(!parent))
752                 return;
753 
754         cfqg_stats_add_aux(&parent->stats, &cfqg->stats);
755         cfqg_stats_reset(&cfqg->stats);
756 }
757 
758 #else   /* CONFIG_CFQ_GROUP_IOSCHED */
759 
760 static inline struct cfq_group *cfqg_parent(struct cfq_group *cfqg) { return NULL; }
761 static inline void cfqg_get(struct cfq_group *cfqg) { }
762 static inline void cfqg_put(struct cfq_group *cfqg) { }
763 
764 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
765         blk_add_trace_msg((cfqd)->queue, "cfq%d%c%c " fmt, (cfqq)->pid, \
766                         cfq_cfqq_sync((cfqq)) ? 'S' : 'A',              \
767                         cfqq_type((cfqq)) == SYNC_NOIDLE_WORKLOAD ? 'N' : ' ',\
768                                 ##args)
769 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)          do {} while (0)
770 
771 static inline void cfqg_stats_update_io_add(struct cfq_group *cfqg,
772                         struct cfq_group *curr_cfqg, int rw) { }
773 static inline void cfqg_stats_update_timeslice_used(struct cfq_group *cfqg,
774                         unsigned long time, unsigned long unaccounted_time) { }
775 static inline void cfqg_stats_update_io_remove(struct cfq_group *cfqg, int rw) { }
776 static inline void cfqg_stats_update_io_merged(struct cfq_group *cfqg, int rw) { }
777 static inline void cfqg_stats_update_completion(struct cfq_group *cfqg,
778                         uint64_t start_time, uint64_t io_start_time, int rw) { }
779 
780 #endif  /* CONFIG_CFQ_GROUP_IOSCHED */
781 
782 #define cfq_log(cfqd, fmt, args...)     \
783         blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
784 
785 /* Traverses through cfq group service trees */
786 #define for_each_cfqg_st(cfqg, i, j, st) \
787         for (i = 0; i <= IDLE_WORKLOAD; i++) \
788                 for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
789                         : &cfqg->service_tree_idle; \
790                         (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
791                         (i == IDLE_WORKLOAD && j == 0); \
792                         j++, st = i < IDLE_WORKLOAD ? \
793                         &cfqg->service_trees[i][j]: NULL) \
794 
795 static inline bool cfq_io_thinktime_big(struct cfq_data *cfqd,
796         struct cfq_ttime *ttime, bool group_idle)
797 {
798         unsigned long slice;
799         if (!sample_valid(ttime->ttime_samples))
800                 return false;
801         if (group_idle)
802                 slice = cfqd->cfq_group_idle;
803         else
804                 slice = cfqd->cfq_slice_idle;
805         return ttime->ttime_mean > slice;
806 }
807 
808 static inline bool iops_mode(struct cfq_data *cfqd)
809 {
810         /*
811          * If we are not idling on queues and it is a NCQ drive, parallel
812          * execution of requests is on and measuring time is not possible
813          * in most of the cases until and unless we drive shallower queue
814          * depths and that becomes a performance bottleneck. In such cases
815          * switch to start providing fairness in terms of number of IOs.
816          */
817         if (!cfqd->cfq_slice_idle && cfqd->hw_tag)
818                 return true;
819         else
820                 return false;
821 }
822 
823 static inline enum wl_class_t cfqq_class(struct cfq_queue *cfqq)
824 {
825         if (cfq_class_idle(cfqq))
826                 return IDLE_WORKLOAD;
827         if (cfq_class_rt(cfqq))
828                 return RT_WORKLOAD;
829         return BE_WORKLOAD;
830 }
831 
832 
833 static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
834 {
835         if (!cfq_cfqq_sync(cfqq))
836                 return ASYNC_WORKLOAD;
837         if (!cfq_cfqq_idle_window(cfqq))
838                 return SYNC_NOIDLE_WORKLOAD;
839         return SYNC_WORKLOAD;
840 }
841 
842 static inline int cfq_group_busy_queues_wl(enum wl_class_t wl_class,
843                                         struct cfq_data *cfqd,
844                                         struct cfq_group *cfqg)
845 {
846         if (wl_class == IDLE_WORKLOAD)
847                 return cfqg->service_tree_idle.count;
848 
849         return cfqg->service_trees[wl_class][ASYNC_WORKLOAD].count +
850                 cfqg->service_trees[wl_class][SYNC_NOIDLE_WORKLOAD].count +
851                 cfqg->service_trees[wl_class][SYNC_WORKLOAD].count;
852 }
853 
854 static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
855                                         struct cfq_group *cfqg)
856 {
857         return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count +
858                 cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
859 }
860 
861 static void cfq_dispatch_insert(struct request_queue *, struct request *);
862 static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, bool is_sync,
863                                        struct cfq_io_cq *cic, struct bio *bio);
864 
865 static inline struct cfq_io_cq *icq_to_cic(struct io_cq *icq)
866 {
867         /* cic->icq is the first member, %NULL will convert to %NULL */
868         return container_of(icq, struct cfq_io_cq, icq);
869 }
870 
871 static inline struct cfq_io_cq *cfq_cic_lookup(struct cfq_data *cfqd,
872                                                struct io_context *ioc)
873 {
874         if (ioc)
875                 return icq_to_cic(ioc_lookup_icq(ioc, cfqd->queue));
876         return NULL;
877 }
878 
879 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_cq *cic, bool is_sync)
880 {
881         return cic->cfqq[is_sync];
882 }
883 
884 static inline void cic_set_cfqq(struct cfq_io_cq *cic, struct cfq_queue *cfqq,
885                                 bool is_sync)
886 {
887         cic->cfqq[is_sync] = cfqq;
888 }
889 
890 static inline struct cfq_data *cic_to_cfqd(struct cfq_io_cq *cic)
891 {
892         return cic->icq.q->elevator->elevator_data;
893 }
894 
895 /*
896  * We regard a request as SYNC, if it's either a read or has the SYNC bit
897  * set (in which case it could also be direct WRITE).
898  */
899 static inline bool cfq_bio_sync(struct bio *bio)
900 {
901         return bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC);
902 }
903 
904 /*
905  * scheduler run of queue, if there are requests pending and no one in the
906  * driver that will restart queueing
907  */
908 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
909 {
910         if (cfqd->busy_queues) {
911                 cfq_log(cfqd, "schedule dispatch");
912                 kblockd_schedule_work(&cfqd->unplug_work);
913         }
914 }
915 
916 /*
917  * Scale schedule slice based on io priority. Use the sync time slice only
918  * if a queue is marked sync and has sync io queued. A sync queue with async
919  * io only, should not get full sync slice length.
920  */
921 static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
922                                  unsigned short prio)
923 {
924         const int base_slice = cfqd->cfq_slice[sync];
925 
926         WARN_ON(prio >= IOPRIO_BE_NR);
927 
928         return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
929 }
930 
931 static inline int
932 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
933 {
934         return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
935 }
936 
937 /**
938  * cfqg_scale_charge - scale disk time charge according to cfqg weight
939  * @charge: disk time being charged
940  * @vfraction: vfraction of the cfqg, fixed point w/ CFQ_SERVICE_SHIFT
941  *
942  * Scale @charge according to @vfraction, which is in range (0, 1].  The
943  * scaling is inversely proportional.
944  *
945  * scaled = charge / vfraction
946  *
947  * The result is also in fixed point w/ CFQ_SERVICE_SHIFT.
948  */
949 static inline u64 cfqg_scale_charge(unsigned long charge,
950                                     unsigned int vfraction)
951 {
952         u64 c = charge << CFQ_SERVICE_SHIFT;    /* make it fixed point */
953 
954         /* charge / vfraction */
955         c <<= CFQ_SERVICE_SHIFT;
956         do_div(c, vfraction);
957         return c;
958 }
959 
960 static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
961 {
962         s64 delta = (s64)(vdisktime - min_vdisktime);
963         if (delta > 0)
964                 min_vdisktime = vdisktime;
965 
966         return min_vdisktime;
967 }
968 
969 static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
970 {
971         s64 delta = (s64)(vdisktime - min_vdisktime);
972         if (delta < 0)
973                 min_vdisktime = vdisktime;
974 
975         return min_vdisktime;
976 }
977 
978 static void update_min_vdisktime(struct cfq_rb_root *st)
979 {
980         struct cfq_group *cfqg;
981 
982         if (st->left) {
983                 cfqg = rb_entry_cfqg(st->left);
984                 st->min_vdisktime = max_vdisktime(st->min_vdisktime,
985                                                   cfqg->vdisktime);
986         }
987 }
988 
989 /*
990  * get averaged number of queues of RT/BE priority.
991  * average is updated, with a formula that gives more weight to higher numbers,
992  * to quickly follows sudden increases and decrease slowly
993  */
994 
995 static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
996                                         struct cfq_group *cfqg, bool rt)
997 {
998         unsigned min_q, max_q;
999         unsigned mult  = cfq_hist_divisor - 1;
1000         unsigned round = cfq_hist_divisor / 2;
1001         unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
1002 
1003         min_q = min(cfqg->busy_queues_avg[rt], busy);
1004         max_q = max(cfqg->busy_queues_avg[rt], busy);
1005         cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
1006                 cfq_hist_divisor;
1007         return cfqg->busy_queues_avg[rt];
1008 }
1009 
1010 static inline unsigned
1011 cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
1012 {
1013         return cfqd->cfq_target_latency * cfqg->vfraction >> CFQ_SERVICE_SHIFT;
1014 }
1015 
1016 static inline unsigned
1017 cfq_scaled_cfqq_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1018 {
1019         unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
1020         if (cfqd->cfq_latency) {
1021                 /*
1022                  * interested queues (we consider only the ones with the same
1023                  * priority class in the cfq group)
1024                  */
1025                 unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
1026                                                 cfq_class_rt(cfqq));
1027                 unsigned sync_slice = cfqd->cfq_slice[1];
1028                 unsigned expect_latency = sync_slice * iq;
1029                 unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
1030 
1031                 if (expect_latency > group_slice) {
1032                         unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
1033                         /* scale low_slice according to IO priority
1034                          * and sync vs async */
1035                         unsigned low_slice =
1036                                 min(slice, base_low_slice * slice / sync_slice);
1037                         /* the adapted slice value is scaled to fit all iqs
1038                          * into the target latency */
1039                         slice = max(slice * group_slice / expect_latency,
1040                                     low_slice);
1041                 }
1042         }
1043         return slice;
1044 }
1045 
1046 static inline void
1047 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1048 {
1049         unsigned slice = cfq_scaled_cfqq_slice(cfqd, cfqq);
1050 
1051         cfqq->slice_start = jiffies;
1052         cfqq->slice_end = jiffies + slice;
1053         cfqq->allocated_slice = slice;
1054         cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
1055 }
1056 
1057 /*
1058  * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
1059  * isn't valid until the first request from the dispatch is activated
1060  * and the slice time set.
1061  */
1062 static inline bool cfq_slice_used(struct cfq_queue *cfqq)
1063 {
1064         if (cfq_cfqq_slice_new(cfqq))
1065                 return false;
1066         if (time_before(jiffies, cfqq->slice_end))
1067                 return false;
1068 
1069         return true;
1070 }
1071 
1072 /*
1073  * Lifted from AS - choose which of rq1 and rq2 that is best served now.
1074  * We choose the request that is closest to the head right now. Distance
1075  * behind the head is penalized and only allowed to a certain extent.
1076  */
1077 static struct request *
1078 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
1079 {
1080         sector_t s1, s2, d1 = 0, d2 = 0;
1081         unsigned long back_max;
1082 #define CFQ_RQ1_WRAP    0x01 /* request 1 wraps */
1083 #define CFQ_RQ2_WRAP    0x02 /* request 2 wraps */
1084         unsigned wrap = 0; /* bit mask: requests behind the disk head? */
1085 
1086         if (rq1 == NULL || rq1 == rq2)
1087                 return rq2;
1088         if (rq2 == NULL)
1089                 return rq1;
1090 
1091         if (rq_is_sync(rq1) != rq_is_sync(rq2))
1092                 return rq_is_sync(rq1) ? rq1 : rq2;
1093 
1094         if ((rq1->cmd_flags ^ rq2->cmd_flags) & REQ_PRIO)
1095                 return rq1->cmd_flags & REQ_PRIO ? rq1 : rq2;
1096 
1097         s1 = blk_rq_pos(rq1);
1098         s2 = blk_rq_pos(rq2);
1099 
1100         /*
1101          * by definition, 1KiB is 2 sectors
1102          */
1103         back_max = cfqd->cfq_back_max * 2;
1104 
1105         /*
1106          * Strict one way elevator _except_ in the case where we allow
1107          * short backward seeks which are biased as twice the cost of a
1108          * similar forward seek.
1109          */
1110         if (s1 >= last)
1111                 d1 = s1 - last;
1112         else if (s1 + back_max >= last)
1113                 d1 = (last - s1) * cfqd->cfq_back_penalty;
1114         else
1115                 wrap |= CFQ_RQ1_WRAP;
1116 
1117         if (s2 >= last)
1118                 d2 = s2 - last;
1119         else if (s2 + back_max >= last)
1120                 d2 = (last - s2) * cfqd->cfq_back_penalty;
1121         else
1122                 wrap |= CFQ_RQ2_WRAP;
1123 
1124         /* Found required data */
1125 
1126         /*
1127          * By doing switch() on the bit mask "wrap" we avoid having to
1128          * check two variables for all permutations: --> faster!
1129          */
1130         switch (wrap) {
1131         case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
1132                 if (d1 < d2)
1133                         return rq1;
1134                 else if (d2 < d1)
1135                         return rq2;
1136                 else {
1137                         if (s1 >= s2)
1138                                 return rq1;
1139                         else
1140                                 return rq2;
1141                 }
1142 
1143         case CFQ_RQ2_WRAP:
1144                 return rq1;
1145         case CFQ_RQ1_WRAP:
1146                 return rq2;
1147         case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
1148         default:
1149                 /*
1150                  * Since both rqs are wrapped,
1151                  * start with the one that's further behind head
1152                  * (--> only *one* back seek required),
1153                  * since back seek takes more time than forward.
1154                  */
1155                 if (s1 <= s2)
1156                         return rq1;
1157                 else
1158                         return rq2;
1159         }
1160 }
1161 
1162 /*
1163  * The below is leftmost cache rbtree addon
1164  */
1165 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
1166 {
1167         /* Service tree is empty */
1168         if (!root->count)
1169                 return NULL;
1170 
1171         if (!root->left)
1172                 root->left = rb_first(&root->rb);
1173 
1174         if (root->left)
1175                 return rb_entry(root->left, struct cfq_queue, rb_node);
1176 
1177         return NULL;
1178 }
1179 
1180 static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
1181 {
1182         if (!root->left)
1183                 root->left = rb_first(&root->rb);
1184 
1185         if (root->left)
1186                 return rb_entry_cfqg(root->left);
1187 
1188         return NULL;
1189 }
1190 
1191 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
1192 {
1193         rb_erase(n, root);
1194         RB_CLEAR_NODE(n);
1195 }
1196 
1197 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
1198 {
1199         if (root->left == n)
1200                 root->left = NULL;
1201         rb_erase_init(n, &root->rb);
1202         --root->count;
1203 }
1204 
1205 /*
1206  * would be nice to take fifo expire time into account as well
1207  */
1208 static struct request *
1209 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1210                   struct request *last)
1211 {
1212         struct rb_node *rbnext = rb_next(&last->rb_node);
1213         struct rb_node *rbprev = rb_prev(&last->rb_node);
1214         struct request *next = NULL, *prev = NULL;
1215 
1216         BUG_ON(RB_EMPTY_NODE(&last->rb_node));
1217 
1218         if (rbprev)
1219                 prev = rb_entry_rq(rbprev);
1220 
1221         if (rbnext)
1222                 next = rb_entry_rq(rbnext);
1223         else {
1224                 rbnext = rb_first(&cfqq->sort_list);
1225                 if (rbnext && rbnext != &last->rb_node)
1226                         next = rb_entry_rq(rbnext);
1227         }
1228 
1229         return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
1230 }
1231 
1232 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
1233                                       struct cfq_queue *cfqq)
1234 {
1235         /*
1236          * just an approximation, should be ok.
1237          */
1238         return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
1239                        cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
1240 }
1241 
1242 static inline s64
1243 cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
1244 {
1245         return cfqg->vdisktime - st->min_vdisktime;
1246 }
1247 
1248 static void
1249 __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
1250 {
1251         struct rb_node **node = &st->rb.rb_node;
1252         struct rb_node *parent = NULL;
1253         struct cfq_group *__cfqg;
1254         s64 key = cfqg_key(st, cfqg);
1255         int left = 1;
1256 
1257         while (*node != NULL) {
1258                 parent = *node;
1259                 __cfqg = rb_entry_cfqg(parent);
1260 
1261                 if (key < cfqg_key(st, __cfqg))
1262                         node = &parent->rb_left;
1263                 else {
1264                         node = &parent->rb_right;
1265                         left = 0;
1266                 }
1267         }
1268 
1269         if (left)
1270                 st->left = &cfqg->rb_node;
1271 
1272         rb_link_node(&cfqg->rb_node, parent, node);
1273         rb_insert_color(&cfqg->rb_node, &st->rb);
1274 }
1275 
1276 /*
1277  * This has to be called only on activation of cfqg
1278  */
1279 static void
1280 cfq_update_group_weight(struct cfq_group *cfqg)
1281 {
1282         if (cfqg->new_weight) {
1283                 cfqg->weight = cfqg->new_weight;
1284                 cfqg->new_weight = 0;
1285         }
1286 }
1287 
1288 static void
1289 cfq_update_group_leaf_weight(struct cfq_group *cfqg)
1290 {
1291         BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
1292 
1293         if (cfqg->new_leaf_weight) {
1294                 cfqg->leaf_weight = cfqg->new_leaf_weight;
1295                 cfqg->new_leaf_weight = 0;
1296         }
1297 }
1298 
1299 static void
1300 cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
1301 {
1302         unsigned int vfr = 1 << CFQ_SERVICE_SHIFT;      /* start with 1 */
1303         struct cfq_group *pos = cfqg;
1304         struct cfq_group *parent;
1305         bool propagate;
1306 
1307         /* add to the service tree */
1308         BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
1309 
1310         /*
1311          * Update leaf_weight.  We cannot update weight at this point
1312          * because cfqg might already have been activated and is
1313          * contributing its current weight to the parent's child_weight.
1314          */
1315         cfq_update_group_leaf_weight(cfqg);
1316         __cfq_group_service_tree_add(st, cfqg);
1317 
1318         /*
1319          * Activate @cfqg and calculate the portion of vfraction @cfqg is
1320          * entitled to.  vfraction is calculated by walking the tree
1321          * towards the root calculating the fraction it has at each level.
1322          * The compounded ratio is how much vfraction @cfqg owns.
1323          *
1324          * Start with the proportion tasks in this cfqg has against active
1325          * children cfqgs - its leaf_weight against children_weight.
1326          */
1327         propagate = !pos->nr_active++;
1328         pos->children_weight += pos->leaf_weight;
1329         vfr = vfr * pos->leaf_weight / pos->children_weight;
1330 
1331         /*
1332          * Compound ->weight walking up the tree.  Both activation and
1333          * vfraction calculation are done in the same loop.  Propagation
1334          * stops once an already activated node is met.  vfraction
1335          * calculation should always continue to the root.
1336          */
1337         while ((parent = cfqg_parent(pos))) {
1338                 if (propagate) {
1339                         cfq_update_group_weight(pos);
1340                         propagate = !parent->nr_active++;
1341                         parent->children_weight += pos->weight;
1342                 }
1343                 vfr = vfr * pos->weight / parent->children_weight;
1344                 pos = parent;
1345         }
1346 
1347         cfqg->vfraction = max_t(unsigned, vfr, 1);
1348 }
1349 
1350 static void
1351 cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
1352 {
1353         struct cfq_rb_root *st = &cfqd->grp_service_tree;
1354         struct cfq_group *__cfqg;
1355         struct rb_node *n;
1356 
1357         cfqg->nr_cfqq++;
1358         if (!RB_EMPTY_NODE(&cfqg->rb_node))
1359                 return;
1360 
1361         /*
1362          * Currently put the group at the end. Later implement something
1363          * so that groups get lesser vtime based on their weights, so that
1364          * if group does not loose all if it was not continuously backlogged.
1365          */
1366         n = rb_last(&st->rb);
1367         if (n) {
1368                 __cfqg = rb_entry_cfqg(n);
1369                 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
1370         } else
1371                 cfqg->vdisktime = st->min_vdisktime;
1372         cfq_group_service_tree_add(st, cfqg);
1373 }
1374 
1375 static void
1376 cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg)
1377 {
1378         struct cfq_group *pos = cfqg;
1379         bool propagate;
1380 
1381         /*
1382          * Undo activation from cfq_group_service_tree_add().  Deactivate
1383          * @cfqg and propagate deactivation upwards.
1384          */
1385         propagate = !--pos->nr_active;
1386         pos->children_weight -= pos->leaf_weight;
1387 
1388         while (propagate) {
1389                 struct cfq_group *parent = cfqg_parent(pos);
1390 
1391                 /* @pos has 0 nr_active at this point */
1392                 WARN_ON_ONCE(pos->children_weight);
1393                 pos->vfraction = 0;
1394 
1395                 if (!parent)
1396                         break;
1397 
1398                 propagate = !--parent->nr_active;
1399                 parent->children_weight -= pos->weight;
1400                 pos = parent;
1401         }
1402 
1403         /* remove from the service tree */
1404         if (!RB_EMPTY_NODE(&cfqg->rb_node))
1405                 cfq_rb_erase(&cfqg->rb_node, st);
1406 }
1407 
1408 static void
1409 cfq_group_notify_queue_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
1410 {
1411         struct cfq_rb_root *st = &cfqd->grp_service_tree;
1412 
1413         BUG_ON(cfqg->nr_cfqq < 1);
1414         cfqg->nr_cfqq--;
1415 
1416         /* If there are other cfq queues under this group, don't delete it */
1417         if (cfqg->nr_cfqq)
1418                 return;
1419 
1420         cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
1421         cfq_group_service_tree_del(st, cfqg);
1422         cfqg->saved_wl_slice = 0;
1423         cfqg_stats_update_dequeue(cfqg);
1424 }
1425 
1426 static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq,
1427                                                 unsigned int *unaccounted_time)
1428 {
1429         unsigned int slice_used;
1430 
1431         /*
1432          * Queue got expired before even a single request completed or
1433          * got expired immediately after first request completion.
1434          */
1435         if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
1436                 /*
1437                  * Also charge the seek time incurred to the group, otherwise
1438                  * if there are mutiple queues in the group, each can dispatch
1439                  * a single request on seeky media and cause lots of seek time
1440                  * and group will never know it.
1441                  */
1442                 slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
1443                                         1);
1444         } else {
1445                 slice_used = jiffies - cfqq->slice_start;
1446                 if (slice_used > cfqq->allocated_slice) {
1447                         *unaccounted_time = slice_used - cfqq->allocated_slice;
1448                         slice_used = cfqq->allocated_slice;
1449                 }
1450                 if (time_after(cfqq->slice_start, cfqq->dispatch_start))
1451                         *unaccounted_time += cfqq->slice_start -
1452                                         cfqq->dispatch_start;
1453         }
1454 
1455         return slice_used;
1456 }
1457 
1458 static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
1459                                 struct cfq_queue *cfqq)
1460 {
1461         struct cfq_rb_root *st = &cfqd->grp_service_tree;
1462         unsigned int used_sl, charge, unaccounted_sl = 0;
1463         int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
1464                         - cfqg->service_tree_idle.count;
1465         unsigned int vfr;
1466 
1467         BUG_ON(nr_sync < 0);
1468         used_sl = charge = cfq_cfqq_slice_usage(cfqq, &unaccounted_sl);
1469 
1470         if (iops_mode(cfqd))
1471                 charge = cfqq->slice_dispatch;
1472         else if (!cfq_cfqq_sync(cfqq) && !nr_sync)
1473                 charge = cfqq->allocated_slice;
1474 
1475         /*
1476          * Can't update vdisktime while on service tree and cfqg->vfraction
1477          * is valid only while on it.  Cache vfr, leave the service tree,
1478          * update vdisktime and go back on.  The re-addition to the tree
1479          * will also update the weights as necessary.
1480          */
1481         vfr = cfqg->vfraction;
1482         cfq_group_service_tree_del(st, cfqg);
1483         cfqg->vdisktime += cfqg_scale_charge(charge, vfr);
1484         cfq_group_service_tree_add(st, cfqg);
1485 
1486         /* This group is being expired. Save the context */
1487         if (time_after(cfqd->workload_expires, jiffies)) {
1488                 cfqg->saved_wl_slice = cfqd->workload_expires
1489                                                 - jiffies;
1490                 cfqg->saved_wl_type = cfqd->serving_wl_type;
1491                 cfqg->saved_wl_class = cfqd->serving_wl_class;
1492         } else
1493                 cfqg->saved_wl_slice = 0;
1494 
1495         cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
1496                                         st->min_vdisktime);
1497         cfq_log_cfqq(cfqq->cfqd, cfqq,
1498                      "sl_used=%u disp=%u charge=%u iops=%u sect=%lu",
1499                      used_sl, cfqq->slice_dispatch, charge,
1500                      iops_mode(cfqd), cfqq->nr_sectors);
1501         cfqg_stats_update_timeslice_used(cfqg, used_sl, unaccounted_sl);
1502         cfqg_stats_set_start_empty_time(cfqg);
1503 }
1504 
1505 /**
1506  * cfq_init_cfqg_base - initialize base part of a cfq_group
1507  * @cfqg: cfq_group to initialize
1508  *
1509  * Initialize the base part which is used whether %CONFIG_CFQ_GROUP_IOSCHED
1510  * is enabled or not.
1511  */
1512 static void cfq_init_cfqg_base(struct cfq_group *cfqg)
1513 {
1514         struct cfq_rb_root *st;
1515         int i, j;
1516 
1517         for_each_cfqg_st(cfqg, i, j, st)
1518                 *st = CFQ_RB_ROOT;
1519         RB_CLEAR_NODE(&cfqg->rb_node);
1520 
1521         cfqg->ttime.last_end_request = jiffies;
1522 }
1523 
1524 #ifdef CONFIG_CFQ_GROUP_IOSCHED
1525 static int __cfq_set_weight(struct cgroup_subsys_state *css, u64 val,
1526                             bool on_dfl, bool reset_dev, bool is_leaf_weight);
1527 
1528 static void cfqg_stats_exit(struct cfqg_stats *stats)
1529 {
1530         blkg_rwstat_exit(&stats->merged);
1531         blkg_rwstat_exit(&stats->service_time);
1532         blkg_rwstat_exit(&stats->wait_time);
1533         blkg_rwstat_exit(&stats->queued);
1534         blkg_stat_exit(&stats->time);
1535 #ifdef CONFIG_DEBUG_BLK_CGROUP
1536         blkg_stat_exit(&stats->unaccounted_time);
1537         blkg_stat_exit(&stats->avg_queue_size_sum);
1538         blkg_stat_exit(&stats->avg_queue_size_samples);
1539         blkg_stat_exit(&stats->dequeue);
1540         blkg_stat_exit(&stats->group_wait_time);
1541         blkg_stat_exit(&stats->idle_time);
1542         blkg_stat_exit(&stats->empty_time);
1543 #endif
1544 }
1545 
1546 static int cfqg_stats_init(struct cfqg_stats *stats, gfp_t gfp)
1547 {
1548         if (blkg_rwstat_init(&stats->merged, gfp) ||
1549             blkg_rwstat_init(&stats->service_time, gfp) ||
1550             blkg_rwstat_init(&stats->wait_time, gfp) ||
1551             blkg_rwstat_init(&stats->queued, gfp) ||
1552             blkg_stat_init(&stats->time, gfp))
1553                 goto err;
1554 
1555 #ifdef CONFIG_DEBUG_BLK_CGROUP
1556         if (blkg_stat_init(&stats->unaccounted_time, gfp) ||
1557             blkg_stat_init(&stats->avg_queue_size_sum, gfp) ||
1558             blkg_stat_init(&stats->avg_queue_size_samples, gfp) ||
1559             blkg_stat_init(&stats->dequeue, gfp) ||
1560             blkg_stat_init(&stats->group_wait_time, gfp) ||
1561             blkg_stat_init(&stats->idle_time, gfp) ||
1562             blkg_stat_init(&stats->empty_time, gfp))
1563                 goto err;
1564 #endif
1565         return 0;
1566 err:
1567         cfqg_stats_exit(stats);
1568         return -ENOMEM;
1569 }
1570 
1571 static struct blkcg_policy_data *cfq_cpd_alloc(gfp_t gfp)
1572 {
1573         struct cfq_group_data *cgd;
1574 
1575         cgd = kzalloc(sizeof(*cgd), gfp);
1576         if (!cgd)
1577                 return NULL;
1578         return &cgd->cpd;
1579 }
1580 
1581 static void cfq_cpd_init(struct blkcg_policy_data *cpd)
1582 {
1583         struct cfq_group_data *cgd = cpd_to_cfqgd(cpd);
1584         unsigned int weight = cgroup_subsys_on_dfl(io_cgrp_subsys) ?
1585                               CGROUP_WEIGHT_DFL : CFQ_WEIGHT_LEGACY_DFL;
1586 
1587         if (cpd_to_blkcg(cpd) == &blkcg_root)
1588                 weight *= 2;
1589 
1590         cgd->weight = weight;
1591         cgd->leaf_weight = weight;
1592 }
1593 
1594 static void cfq_cpd_free(struct blkcg_policy_data *cpd)
1595 {
1596         kfree(cpd_to_cfqgd(cpd));
1597 }
1598 
1599 static void cfq_cpd_bind(struct blkcg_policy_data *cpd)
1600 {
1601         struct blkcg *blkcg = cpd_to_blkcg(cpd);
1602         bool on_dfl = cgroup_subsys_on_dfl(io_cgrp_subsys);
1603         unsigned int weight = on_dfl ? CGROUP_WEIGHT_DFL : CFQ_WEIGHT_LEGACY_DFL;
1604 
1605         if (blkcg == &blkcg_root)
1606                 weight *= 2;
1607 
1608         WARN_ON_ONCE(__cfq_set_weight(&blkcg->css, weight, on_dfl, true, false));
1609         WARN_ON_ONCE(__cfq_set_weight(&blkcg->css, weight, on_dfl, true, true));
1610 }
1611 
1612 static struct blkg_policy_data *cfq_pd_alloc(gfp_t gfp, int node)
1613 {
1614         struct cfq_group *cfqg;
1615 
1616         cfqg = kzalloc_node(sizeof(*cfqg), gfp, node);
1617         if (!cfqg)
1618                 return NULL;
1619 
1620         cfq_init_cfqg_base(cfqg);
1621         if (cfqg_stats_init(&cfqg->stats, gfp)) {
1622                 kfree(cfqg);
1623                 return NULL;
1624         }
1625 
1626         return &cfqg->pd;
1627 }
1628 
1629 static void cfq_pd_init(struct blkg_policy_data *pd)
1630 {
1631         struct cfq_group *cfqg = pd_to_cfqg(pd);
1632         struct cfq_group_data *cgd = blkcg_to_cfqgd(pd->blkg->blkcg);
1633 
1634         cfqg->weight = cgd->weight;
1635         cfqg->leaf_weight = cgd->leaf_weight;
1636 }
1637 
1638 static void cfq_pd_offline(struct blkg_policy_data *pd)
1639 {
1640         struct cfq_group *cfqg = pd_to_cfqg(pd);
1641         int i;
1642 
1643         for (i = 0; i < IOPRIO_BE_NR; i++) {
1644                 if (cfqg->async_cfqq[0][i])
1645                         cfq_put_queue(cfqg->async_cfqq[0][i]);
1646                 if (cfqg->async_cfqq[1][i])
1647                         cfq_put_queue(cfqg->async_cfqq[1][i]);
1648         }
1649 
1650         if (cfqg->async_idle_cfqq)
1651                 cfq_put_queue(cfqg->async_idle_cfqq);
1652 
1653         /*
1654          * @blkg is going offline and will be ignored by
1655          * blkg_[rw]stat_recursive_sum().  Transfer stats to the parent so
1656          * that they don't get lost.  If IOs complete after this point, the
1657          * stats for them will be lost.  Oh well...
1658          */
1659         cfqg_stats_xfer_dead(cfqg);
1660 }
1661 
1662 static void cfq_pd_free(struct blkg_policy_data *pd)
1663 {
1664         struct cfq_group *cfqg = pd_to_cfqg(pd);
1665 
1666         cfqg_stats_exit(&cfqg->stats);
1667         return kfree(cfqg);
1668 }
1669 
1670 static void cfq_pd_reset_stats(struct blkg_policy_data *pd)
1671 {
1672         struct cfq_group *cfqg = pd_to_cfqg(pd);
1673 
1674         cfqg_stats_reset(&cfqg->stats);
1675 }
1676 
1677 static struct cfq_group *cfq_lookup_cfqg(struct cfq_data *cfqd,
1678                                          struct blkcg *blkcg)
1679 {
1680         struct blkcg_gq *blkg;
1681 
1682         blkg = blkg_lookup(blkcg, cfqd->queue);
1683         if (likely(blkg))
1684                 return blkg_to_cfqg(blkg);
1685         return NULL;
1686 }
1687 
1688 static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
1689 {
1690         cfqq->cfqg = cfqg;
1691         /* cfqq reference on cfqg */
1692         cfqg_get(cfqg);
1693 }
1694 
1695 static u64 cfqg_prfill_weight_device(struct seq_file *sf,
1696                                      struct blkg_policy_data *pd, int off)
1697 {
1698         struct cfq_group *cfqg = pd_to_cfqg(pd);
1699 
1700         if (!cfqg->dev_weight)
1701                 return 0;
1702         return __blkg_prfill_u64(sf, pd, cfqg->dev_weight);
1703 }
1704 
1705 static int cfqg_print_weight_device(struct seq_file *sf, void *v)
1706 {
1707         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1708                           cfqg_prfill_weight_device, &blkcg_policy_cfq,
1709                           0, false);
1710         return 0;
1711 }
1712 
1713 static u64 cfqg_prfill_leaf_weight_device(struct seq_file *sf,
1714                                           struct blkg_policy_data *pd, int off)
1715 {
1716         struct cfq_group *cfqg = pd_to_cfqg(pd);
1717 
1718         if (!cfqg->dev_leaf_weight)
1719                 return 0;
1720         return __blkg_prfill_u64(sf, pd, cfqg->dev_leaf_weight);
1721 }
1722 
1723 static int cfqg_print_leaf_weight_device(struct seq_file *sf, void *v)
1724 {
1725         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1726                           cfqg_prfill_leaf_weight_device, &blkcg_policy_cfq,
1727                           0, false);
1728         return 0;
1729 }
1730 
1731 static int cfq_print_weight(struct seq_file *sf, void *v)
1732 {
1733         struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
1734         struct cfq_group_data *cgd = blkcg_to_cfqgd(blkcg);
1735         unsigned int val = 0;
1736 
1737         if (cgd)
1738                 val = cgd->weight;
1739 
1740         seq_printf(sf, "%u\n", val);
1741         return 0;
1742 }
1743 
1744 static int cfq_print_leaf_weight(struct seq_file *sf, void *v)
1745 {
1746         struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
1747         struct cfq_group_data *cgd = blkcg_to_cfqgd(blkcg);
1748         unsigned int val = 0;
1749 
1750         if (cgd)
1751                 val = cgd->leaf_weight;
1752 
1753         seq_printf(sf, "%u\n", val);
1754         return 0;
1755 }
1756 
1757 static ssize_t __cfqg_set_weight_device(struct kernfs_open_file *of,
1758                                         char *buf, size_t nbytes, loff_t off,
1759                                         bool on_dfl, bool is_leaf_weight)
1760 {
1761         unsigned int min = on_dfl ? CGROUP_WEIGHT_MIN : CFQ_WEIGHT_LEGACY_MIN;
1762         unsigned int max = on_dfl ? CGROUP_WEIGHT_MAX : CFQ_WEIGHT_LEGACY_MAX;
1763         struct blkcg *blkcg = css_to_blkcg(of_css(of));
1764         struct blkg_conf_ctx ctx;
1765         struct cfq_group *cfqg;
1766         struct cfq_group_data *cfqgd;
1767         int ret;
1768         u64 v;
1769 
1770         ret = blkg_conf_prep(blkcg, &blkcg_policy_cfq, buf, &ctx);
1771         if (ret)
1772                 return ret;
1773 
1774         if (sscanf(ctx.body, "%llu", &v) == 1) {
1775                 /* require "default" on dfl */
1776                 ret = -ERANGE;
1777                 if (!v && on_dfl)
1778                         goto out_finish;
1779         } else if (!strcmp(strim(ctx.body), "default")) {
1780                 v = 0;
1781         } else {
1782                 ret = -EINVAL;
1783                 goto out_finish;
1784         }
1785 
1786         cfqg = blkg_to_cfqg(ctx.blkg);
1787         cfqgd = blkcg_to_cfqgd(blkcg);
1788 
1789         ret = -ERANGE;
1790         if (!v || (v >= min && v <= max)) {
1791                 if (!is_leaf_weight) {
1792                         cfqg->dev_weight = v;
1793                         cfqg->new_weight = v ?: cfqgd->weight;
1794                 } else {
1795                         cfqg->dev_leaf_weight = v;
1796                         cfqg->new_leaf_weight = v ?: cfqgd->leaf_weight;
1797                 }
1798                 ret = 0;
1799         }
1800 out_finish:
1801         blkg_conf_finish(&ctx);
1802         return ret ?: nbytes;
1803 }
1804 
1805 static ssize_t cfqg_set_weight_device(struct kernfs_open_file *of,
1806                                       char *buf, size_t nbytes, loff_t off)
1807 {
1808         return __cfqg_set_weight_device(of, buf, nbytes, off, false, false);
1809 }
1810 
1811 static ssize_t cfqg_set_leaf_weight_device(struct kernfs_open_file *of,
1812                                            char *buf, size_t nbytes, loff_t off)
1813 {
1814         return __cfqg_set_weight_device(of, buf, nbytes, off, false, true);
1815 }
1816 
1817 static int __cfq_set_weight(struct cgroup_subsys_state *css, u64 val,
1818                             bool on_dfl, bool reset_dev, bool is_leaf_weight)
1819 {
1820         unsigned int min = on_dfl ? CGROUP_WEIGHT_MIN : CFQ_WEIGHT_LEGACY_MIN;
1821         unsigned int max = on_dfl ? CGROUP_WEIGHT_MAX : CFQ_WEIGHT_LEGACY_MAX;
1822         struct blkcg *blkcg = css_to_blkcg(css);
1823         struct blkcg_gq *blkg;
1824         struct cfq_group_data *cfqgd;
1825         int ret = 0;
1826 
1827         if (val < min || val > max)
1828                 return -ERANGE;
1829 
1830         spin_lock_irq(&blkcg->lock);
1831         cfqgd = blkcg_to_cfqgd(blkcg);
1832         if (!cfqgd) {
1833                 ret = -EINVAL;
1834                 goto out;
1835         }
1836 
1837         if (!is_leaf_weight)
1838                 cfqgd->weight = val;
1839         else
1840                 cfqgd->leaf_weight = val;
1841 
1842         hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
1843                 struct cfq_group *cfqg = blkg_to_cfqg(blkg);
1844 
1845                 if (!cfqg)
1846                         continue;
1847 
1848                 if (!is_leaf_weight) {
1849                         if (reset_dev)
1850                                 cfqg->dev_weight = 0;
1851                         if (!cfqg->dev_weight)
1852                                 cfqg->new_weight = cfqgd->weight;
1853                 } else {
1854                         if (reset_dev)
1855                                 cfqg->dev_leaf_weight = 0;
1856                         if (!cfqg->dev_leaf_weight)
1857                                 cfqg->new_leaf_weight = cfqgd->leaf_weight;
1858                 }
1859         }
1860 
1861 out:
1862         spin_unlock_irq(&blkcg->lock);
1863         return ret;
1864 }
1865 
1866 static int cfq_set_weight(struct cgroup_subsys_state *css, struct cftype *cft,
1867                           u64 val)
1868 {
1869         return __cfq_set_weight(css, val, false, false, false);
1870 }
1871 
1872 static int cfq_set_leaf_weight(struct cgroup_subsys_state *css,
1873                                struct cftype *cft, u64 val)
1874 {
1875         return __cfq_set_weight(css, val, false, false, true);
1876 }
1877 
1878 static int cfqg_print_stat(struct seq_file *sf, void *v)
1879 {
1880         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_stat,
1881                           &blkcg_policy_cfq, seq_cft(sf)->private, false);
1882         return 0;
1883 }
1884 
1885 static int cfqg_print_rwstat(struct seq_file *sf, void *v)
1886 {
1887         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_rwstat,
1888                           &blkcg_policy_cfq, seq_cft(sf)->private, true);
1889         return 0;
1890 }
1891 
1892 static u64 cfqg_prfill_stat_recursive(struct seq_file *sf,
1893                                       struct blkg_policy_data *pd, int off)
1894 {
1895         u64 sum = blkg_stat_recursive_sum(pd_to_blkg(pd),
1896                                           &blkcg_policy_cfq, off);
1897         return __blkg_prfill_u64(sf, pd, sum);
1898 }
1899 
1900 static u64 cfqg_prfill_rwstat_recursive(struct seq_file *sf,
1901                                         struct blkg_policy_data *pd, int off)
1902 {
1903         struct blkg_rwstat sum = blkg_rwstat_recursive_sum(pd_to_blkg(pd),
1904                                                         &blkcg_policy_cfq, off);
1905         return __blkg_prfill_rwstat(sf, pd, &sum);
1906 }
1907 
1908 static int cfqg_print_stat_recursive(struct seq_file *sf, void *v)
1909 {
1910         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1911                           cfqg_prfill_stat_recursive, &blkcg_policy_cfq,
1912                           seq_cft(sf)->private, false);
1913         return 0;
1914 }
1915 
1916 static int cfqg_print_rwstat_recursive(struct seq_file *sf, void *v)
1917 {
1918         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1919                           cfqg_prfill_rwstat_recursive, &blkcg_policy_cfq,
1920                           seq_cft(sf)->private, true);
1921         return 0;
1922 }
1923 
1924 static u64 cfqg_prfill_sectors(struct seq_file *sf, struct blkg_policy_data *pd,
1925                                int off)
1926 {
1927         u64 sum = blkg_rwstat_total(&pd->blkg->stat_bytes);
1928 
1929         return __blkg_prfill_u64(sf, pd, sum >> 9);
1930 }
1931 
1932 static int cfqg_print_stat_sectors(struct seq_file *sf, void *v)
1933 {
1934         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1935                           cfqg_prfill_sectors, &blkcg_policy_cfq, 0, false);
1936         return 0;
1937 }
1938 
1939 static u64 cfqg_prfill_sectors_recursive(struct seq_file *sf,
1940                                          struct blkg_policy_data *pd, int off)
1941 {
1942         struct blkg_rwstat tmp = blkg_rwstat_recursive_sum(pd->blkg, NULL,
1943                                         offsetof(struct blkcg_gq, stat_bytes));
1944         u64 sum = atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_READ]) +
1945                 atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_WRITE]);
1946 
1947         return __blkg_prfill_u64(sf, pd, sum >> 9);
1948 }
1949 
1950 static int cfqg_print_stat_sectors_recursive(struct seq_file *sf, void *v)
1951 {
1952         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1953                           cfqg_prfill_sectors_recursive, &blkcg_policy_cfq, 0,
1954                           false);
1955         return 0;
1956 }
1957 
1958 #ifdef CONFIG_DEBUG_BLK_CGROUP
1959 static u64 cfqg_prfill_avg_queue_size(struct seq_file *sf,
1960                                       struct blkg_policy_data *pd, int off)
1961 {
1962         struct cfq_group *cfqg = pd_to_cfqg(pd);
1963         u64 samples = blkg_stat_read(&cfqg->stats.avg_queue_size_samples);
1964         u64 v = 0;
1965 
1966         if (samples) {
1967                 v = blkg_stat_read(&cfqg->stats.avg_queue_size_sum);
1968                 v = div64_u64(v, samples);
1969         }
1970         __blkg_prfill_u64(sf, pd, v);
1971         return 0;
1972 }
1973 
1974 /* print avg_queue_size */
1975 static int cfqg_print_avg_queue_size(struct seq_file *sf, void *v)
1976 {
1977         blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
1978                           cfqg_prfill_avg_queue_size, &blkcg_policy_cfq,
1979                           0, false);
1980         return 0;
1981 }
1982 #endif  /* CONFIG_DEBUG_BLK_CGROUP */
1983 
1984 static struct cftype cfq_blkcg_legacy_files[] = {
1985         /* on root, weight is mapped to leaf_weight */
1986         {
1987                 .name = "weight_device",
1988                 .flags = CFTYPE_ONLY_ON_ROOT,
1989                 .seq_show = cfqg_print_leaf_weight_device,
1990                 .write = cfqg_set_leaf_weight_device,
1991         },
1992         {
1993                 .name = "weight",
1994                 .flags = CFTYPE_ONLY_ON_ROOT,
1995                 .seq_show = cfq_print_leaf_weight,
1996                 .write_u64 = cfq_set_leaf_weight,
1997         },
1998 
1999         /* no such mapping necessary for !roots */
2000         {
2001                 .name = "weight_device",
2002                 .flags = CFTYPE_NOT_ON_ROOT,
2003                 .seq_show = cfqg_print_weight_device,
2004                 .write = cfqg_set_weight_device,
2005         },
2006         {
2007                 .name = "weight",
2008                 .flags = CFTYPE_NOT_ON_ROOT,
2009                 .seq_show = cfq_print_weight,
2010                 .write_u64 = cfq_set_weight,
2011         },
2012 
2013         {
2014                 .name = "leaf_weight_device",
2015                 .seq_show = cfqg_print_leaf_weight_device,
2016                 .write = cfqg_set_leaf_weight_device,
2017         },
2018         {
2019                 .name = "leaf_weight",
2020                 .seq_show = cfq_print_leaf_weight,
2021                 .write_u64 = cfq_set_leaf_weight,
2022         },
2023 
2024         /* statistics, covers only the tasks in the cfqg */
2025         {
2026                 .name = "time",
2027                 .private = offsetof(struct cfq_group, stats.time),
2028                 .seq_show = cfqg_print_stat,
2029         },
2030         {
2031                 .name = "sectors",
2032                 .seq_show = cfqg_print_stat_sectors,
2033         },
2034         {
2035                 .name = "io_service_bytes",
2036                 .private = (unsigned long)&blkcg_policy_cfq,
2037                 .seq_show = blkg_print_stat_bytes,
2038         },
2039         {
2040                 .name = "io_serviced",
2041                 .private = (unsigned long)&blkcg_policy_cfq,
2042                 .seq_show = blkg_print_stat_ios,
2043         },
2044         {
2045                 .name = "io_service_time",
2046                 .private = offsetof(struct cfq_group, stats.service_time),
2047                 .seq_show = cfqg_print_rwstat,
2048         },
2049         {
2050                 .name = "io_wait_time",
2051                 .private = offsetof(struct cfq_group, stats.wait_time),
2052                 .seq_show = cfqg_print_rwstat,
2053         },
2054         {
2055                 .name = "io_merged",
2056                 .private = offsetof(struct cfq_group, stats.merged),
2057                 .seq_show = cfqg_print_rwstat,
2058         },
2059         {
2060                 .name = "io_queued",
2061                 .private = offsetof(struct cfq_group, stats.queued),
2062                 .seq_show = cfqg_print_rwstat,
2063         },
2064 
2065         /* the same statictics which cover the cfqg and its descendants */
2066         {
2067                 .name = "time_recursive",
2068                 .private = offsetof(struct cfq_group, stats.time),
2069                 .seq_show = cfqg_print_stat_recursive,
2070         },
2071         {
2072                 .name = "sectors_recursive",
2073                 .seq_show = cfqg_print_stat_sectors_recursive,
2074         },
2075         {
2076                 .name = "io_service_bytes_recursive",
2077                 .private = (unsigned long)&blkcg_policy_cfq,
2078                 .seq_show = blkg_print_stat_bytes_recursive,
2079         },
2080         {
2081                 .name = "io_serviced_recursive",
2082                 .private = (unsigned long)&blkcg_policy_cfq,
2083                 .seq_show = blkg_print_stat_ios_recursive,
2084         },
2085         {
2086                 .name = "io_service_time_recursive",
2087                 .private = offsetof(struct cfq_group, stats.service_time),
2088                 .seq_show = cfqg_print_rwstat_recursive,
2089         },
2090         {
2091                 .name = "io_wait_time_recursive",
2092                 .private = offsetof(struct cfq_group, stats.wait_time),
2093                 .seq_show = cfqg_print_rwstat_recursive,
2094         },
2095         {
2096                 .name = "io_merged_recursive",
2097                 .private = offsetof(struct cfq_group, stats.merged),
2098                 .seq_show = cfqg_print_rwstat_recursive,
2099         },
2100         {
2101                 .name = "io_queued_recursive",
2102                 .private = offsetof(struct cfq_group, stats.queued),
2103                 .seq_show = cfqg_print_rwstat_recursive,
2104         },
2105 #ifdef CONFIG_DEBUG_BLK_CGROUP
2106         {
2107                 .name = "avg_queue_size",
2108                 .seq_show = cfqg_print_avg_queue_size,
2109         },
2110         {
2111                 .name = "group_wait_time",
2112                 .private = offsetof(struct cfq_group, stats.group_wait_time),
2113                 .seq_show = cfqg_print_stat,
2114         },
2115         {
2116                 .name = "idle_time",
2117                 .private = offsetof(struct cfq_group, stats.idle_time),
2118                 .seq_show = cfqg_print_stat,
2119         },
2120         {
2121                 .name = "empty_time",
2122                 .private = offsetof(struct cfq_group, stats.empty_time),
2123                 .seq_show = cfqg_print_stat,
2124         },
2125         {
2126                 .name = "dequeue",
2127                 .private = offsetof(struct cfq_group, stats.dequeue),
2128                 .seq_show = cfqg_print_stat,
2129         },
2130         {
2131                 .name = "unaccounted_time",
2132                 .private = offsetof(struct cfq_group, stats.unaccounted_time),
2133                 .seq_show = cfqg_print_stat,
2134         },
2135 #endif  /* CONFIG_DEBUG_BLK_CGROUP */
2136         { }     /* terminate */
2137 };
2138 
2139 static int cfq_print_weight_on_dfl(struct seq_file *sf, void *v)
2140 {
2141         struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
2142         struct cfq_group_data *cgd = blkcg_to_cfqgd(blkcg);
2143 
2144         seq_printf(sf, "default %u\n", cgd->weight);
2145         blkcg_print_blkgs(sf, blkcg, cfqg_prfill_weight_device,
2146                           &blkcg_policy_cfq, 0, false);
2147         return 0;
2148 }
2149 
2150 static ssize_t cfq_set_weight_on_dfl(struct kernfs_open_file *of,
2151                                      char *buf, size_t nbytes, loff_t off)
2152 {
2153         char *endp;
2154         int ret;
2155         u64 v;
2156 
2157         buf = strim(buf);
2158 
2159         /* "WEIGHT" or "default WEIGHT" sets the default weight */
2160         v = simple_strtoull(buf, &endp, 0);
2161         if (*endp == '\0' || sscanf(buf, "default %llu", &v) == 1) {
2162                 ret = __cfq_set_weight(of_css(of), v, true, false, false);
2163                 return ret ?: nbytes;
2164         }
2165 
2166         /* "MAJ:MIN WEIGHT" */
2167         return __cfqg_set_weight_device(of, buf, nbytes, off, true, false);
2168 }
2169 
2170 static struct cftype cfq_blkcg_files[] = {
2171         {
2172                 .name = "weight",
2173                 .flags = CFTYPE_NOT_ON_ROOT,
2174                 .seq_show = cfq_print_weight_on_dfl,
2175                 .write = cfq_set_weight_on_dfl,
2176         },
2177         { }     /* terminate */
2178 };
2179 
2180 #else /* GROUP_IOSCHED */
2181 static struct cfq_group *cfq_lookup_cfqg(struct cfq_data *cfqd,
2182                                          struct blkcg *blkcg)
2183 {
2184         return cfqd->root_group;
2185 }
2186 
2187 static inline void
2188 cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
2189         cfqq->cfqg = cfqg;
2190 }
2191 
2192 #endif /* GROUP_IOSCHED */
2193 
2194 /*
2195  * The cfqd->service_trees holds all pending cfq_queue's that have
2196  * requests waiting to be processed. It is sorted in the order that
2197  * we will service the queues.
2198  */
2199 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2200                                  bool add_front)
2201 {
2202         struct rb_node **p, *parent;
2203         struct cfq_queue *__cfqq;
2204         unsigned long rb_key;
2205         struct cfq_rb_root *st;
2206         int left;
2207         int new_cfqq = 1;
2208 
2209         st = st_for(cfqq->cfqg, cfqq_class(cfqq), cfqq_type(cfqq));
2210         if (cfq_class_idle(cfqq)) {
2211                 rb_key = CFQ_IDLE_DELAY;
2212                 parent = rb_last(&st->rb);
2213                 if (parent && parent != &cfqq->rb_node) {
2214                         __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
2215                         rb_key += __cfqq->rb_key;
2216                 } else
2217                         rb_key += jiffies;
2218         } else if (!add_front) {
2219                 /*
2220                  * Get our rb key offset. Subtract any residual slice
2221                  * value carried from last service. A negative resid
2222                  * count indicates slice overrun, and this should position
2223                  * the next service time further away in the tree.
2224                  */
2225                 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
2226                 rb_key -= cfqq->slice_resid;
2227                 cfqq->slice_resid = 0;
2228         } else {
2229                 rb_key = -HZ;
2230                 __cfqq = cfq_rb_first(st);
2231                 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
2232         }
2233 
2234         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
2235                 new_cfqq = 0;
2236                 /*
2237                  * same position, nothing more to do
2238                  */
2239                 if (rb_key == cfqq->rb_key && cfqq->service_tree == st)
2240                         return;
2241 
2242                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
2243                 cfqq->service_tree = NULL;
2244         }
2245 
2246         left = 1;
2247         parent = NULL;
2248         cfqq->service_tree = st;
2249         p = &st->rb.rb_node;
2250         while (*p) {
2251                 parent = *p;
2252                 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
2253 
2254                 /*
2255                  * sort by key, that represents service time.
2256                  */
2257                 if (time_before(rb_key, __cfqq->rb_key))
2258                         p = &parent->rb_left;
2259                 else {
2260                         p = &parent->rb_right;
2261                         left = 0;
2262                 }
2263         }
2264 
2265         if (left)
2266                 st->left = &cfqq->rb_node;
2267 
2268         cfqq->rb_key = rb_key;
2269         rb_link_node(&cfqq->rb_node, parent, p);
2270         rb_insert_color(&cfqq->rb_node, &st->rb);
2271         st->count++;
2272         if (add_front || !new_cfqq)
2273                 return;
2274         cfq_group_notify_queue_add(cfqd, cfqq->cfqg);
2275 }
2276 
2277 static struct cfq_queue *
2278 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
2279                      sector_t sector, struct rb_node **ret_parent,
2280                      struct rb_node ***rb_link)
2281 {
2282         struct rb_node **p, *parent;
2283         struct cfq_queue *cfqq = NULL;
2284 
2285         parent = NULL;
2286         p = &root->rb_node;
2287         while (*p) {
2288                 struct rb_node **n;
2289 
2290                 parent = *p;
2291                 cfqq = rb_entry(parent, struct cfq_queue, p_node);
2292 
2293                 /*
2294                  * Sort strictly based on sector.  Smallest to the left,
2295                  * largest to the right.
2296                  */
2297                 if (sector > blk_rq_pos(cfqq->next_rq))
2298                         n = &(*p)->rb_right;
2299                 else if (sector < blk_rq_pos(cfqq->next_rq))
2300                         n = &(*p)->rb_left;
2301                 else
2302                         break;
2303                 p = n;
2304                 cfqq = NULL;
2305         }
2306 
2307         *ret_parent = parent;
2308         if (rb_link)
2309                 *rb_link = p;
2310         return cfqq;
2311 }
2312 
2313 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2314 {
2315         struct rb_node **p, *parent;
2316         struct cfq_queue *__cfqq;
2317 
2318         if (cfqq->p_root) {
2319                 rb_erase(&cfqq->p_node, cfqq->p_root);
2320                 cfqq->p_root = NULL;
2321         }
2322 
2323         if (cfq_class_idle(cfqq))
2324                 return;
2325         if (!cfqq->next_rq)
2326                 return;
2327 
2328         cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
2329         __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
2330                                       blk_rq_pos(cfqq->next_rq), &parent, &p);
2331         if (!__cfqq) {
2332                 rb_link_node(&cfqq->p_node, parent, p);
2333                 rb_insert_color(&cfqq->p_node, cfqq->p_root);
2334         } else
2335                 cfqq->p_root = NULL;
2336 }
2337 
2338 /*
2339  * Update cfqq's position in the service tree.
2340  */
2341 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2342 {
2343         /*
2344          * Resorting requires the cfqq to be on the RR list already.
2345          */
2346         if (cfq_cfqq_on_rr(cfqq)) {
2347                 cfq_service_tree_add(cfqd, cfqq, 0);
2348                 cfq_prio_tree_add(cfqd, cfqq);
2349         }
2350 }
2351 
2352 /*
2353  * add to busy list of queues for service, trying to be fair in ordering
2354  * the pending list according to last request service
2355  */
2356 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2357 {
2358         cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
2359         BUG_ON(cfq_cfqq_on_rr(cfqq));
2360         cfq_mark_cfqq_on_rr(cfqq);
2361         cfqd->busy_queues++;
2362         if (cfq_cfqq_sync(cfqq))
2363                 cfqd->busy_sync_queues++;
2364 
2365         cfq_resort_rr_list(cfqd, cfqq);
2366 }
2367 
2368 /*
2369  * Called when the cfqq no longer has requests pending, remove it from
2370  * the service tree.
2371  */
2372 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2373 {
2374         cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
2375         BUG_ON(!cfq_cfqq_on_rr(cfqq));
2376         cfq_clear_cfqq_on_rr(cfqq);
2377 
2378         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
2379                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
2380                 cfqq->service_tree = NULL;
2381         }
2382         if (cfqq->p_root) {
2383                 rb_erase(&cfqq->p_node, cfqq->p_root);
2384                 cfqq->p_root = NULL;
2385         }
2386 
2387         cfq_group_notify_queue_del(cfqd, cfqq->cfqg);
2388         BUG_ON(!cfqd->busy_queues);
2389         cfqd->busy_queues--;
2390         if (cfq_cfqq_sync(cfqq))
2391                 cfqd->busy_sync_queues--;
2392 }
2393 
2394 /*
2395  * rb tree support functions
2396  */
2397 static void cfq_del_rq_rb(struct request *rq)
2398 {
2399         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2400         const int sync = rq_is_sync(rq);
2401 
2402         BUG_ON(!cfqq->queued[sync]);
2403         cfqq->queued[sync]--;
2404 
2405         elv_rb_del(&cfqq->sort_list, rq);
2406 
2407         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
2408                 /*
2409                  * Queue will be deleted from service tree when we actually
2410                  * expire it later. Right now just remove it from prio tree
2411                  * as it is empty.
2412                  */
2413                 if (cfqq->p_root) {
2414                         rb_erase(&cfqq->p_node, cfqq->p_root);
2415                         cfqq->p_root = NULL;
2416                 }
2417         }
2418 }
2419 
2420 static void cfq_add_rq_rb(struct request *rq)
2421 {
2422         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2423         struct cfq_data *cfqd = cfqq->cfqd;
2424         struct request *prev;
2425 
2426         cfqq->queued[rq_is_sync(rq)]++;
2427 
2428         elv_rb_add(&cfqq->sort_list, rq);
2429 
2430         if (!cfq_cfqq_on_rr(cfqq))
2431                 cfq_add_cfqq_rr(cfqd, cfqq);
2432 
2433         /*
2434          * check if this request is a better next-serve candidate
2435          */
2436         prev = cfqq->next_rq;
2437         cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
2438 
2439         /*
2440          * adjust priority tree position, if ->next_rq changes
2441          */
2442         if (prev != cfqq->next_rq)
2443                 cfq_prio_tree_add(cfqd, cfqq);
2444 
2445         BUG_ON(!cfqq->next_rq);
2446 }
2447 
2448 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
2449 {
2450         elv_rb_del(&cfqq->sort_list, rq);
2451         cfqq->queued[rq_is_sync(rq)]--;
2452         cfqg_stats_update_io_remove(RQ_CFQG(rq), rq->cmd_flags);
2453         cfq_add_rq_rb(rq);
2454         cfqg_stats_update_io_add(RQ_CFQG(rq), cfqq->cfqd->serving_group,
2455                                  rq->cmd_flags);
2456 }
2457 
2458 static struct request *
2459 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
2460 {
2461         struct task_struct *tsk = current;
2462         struct cfq_io_cq *cic;
2463         struct cfq_queue *cfqq;
2464 
2465         cic = cfq_cic_lookup(cfqd, tsk->io_context);
2466         if (!cic)
2467                 return NULL;
2468 
2469         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
2470         if (cfqq)
2471                 return elv_rb_find(&cfqq->sort_list, bio_end_sector(bio));
2472 
2473         return NULL;
2474 }
2475 
2476 static void cfq_activate_request(struct request_queue *q, struct request *rq)
2477 {
2478         struct cfq_data *cfqd = q->elevator->elevator_data;
2479 
2480         cfqd->rq_in_driver++;
2481         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
2482                                                 cfqd->rq_in_driver);
2483 
2484         cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
2485 }
2486 
2487 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
2488 {
2489         struct cfq_data *cfqd = q->elevator->elevator_data;
2490 
2491         WARN_ON(!cfqd->rq_in_driver);
2492         cfqd->rq_in_driver--;
2493         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
2494                                                 cfqd->rq_in_driver);
2495 }
2496 
2497 static void cfq_remove_request(struct request *rq)
2498 {
2499         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2500 
2501         if (cfqq->next_rq == rq)
2502                 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
2503 
2504         list_del_init(&rq->queuelist);
2505         cfq_del_rq_rb(rq);
2506 
2507         cfqq->cfqd->rq_queued--;
2508         cfqg_stats_update_io_remove(RQ_CFQG(rq), rq->cmd_flags);
2509         if (rq->cmd_flags & REQ_PRIO) {
2510                 WARN_ON(!cfqq->prio_pending);
2511                 cfqq->prio_pending--;
2512         }
2513 }
2514 
2515 static int cfq_merge(struct request_queue *q, struct request **req,
2516                      struct bio *bio)
2517 {
2518         struct cfq_data *cfqd = q->elevator->elevator_data;
2519         struct request *__rq;
2520 
2521         __rq = cfq_find_rq_fmerge(cfqd, bio);
2522         if (__rq && elv_rq_merge_ok(__rq, bio)) {
2523                 *req = __rq;
2524                 return ELEVATOR_FRONT_MERGE;
2525         }
2526 
2527         return ELEVATOR_NO_MERGE;
2528 }
2529 
2530 static void cfq_merged_request(struct request_queue *q, struct request *req,
2531                                int type)
2532 {
2533         if (type == ELEVATOR_FRONT_MERGE) {
2534                 struct cfq_queue *cfqq = RQ_CFQQ(req);
2535 
2536                 cfq_reposition_rq_rb(cfqq, req);
2537         }
2538 }
2539 
2540 static void cfq_bio_merged(struct request_queue *q, struct request *req,
2541                                 struct bio *bio)
2542 {
2543         cfqg_stats_update_io_merged(RQ_CFQG(req), bio->bi_rw);
2544 }
2545 
2546 static void
2547 cfq_merged_requests(struct request_queue *q, struct request *rq,
2548                     struct request *next)
2549 {
2550         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2551         struct cfq_data *cfqd = q->elevator->elevator_data;
2552 
2553         /*
2554          * reposition in fifo if next is older than rq
2555          */
2556         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
2557             time_before(next->fifo_time, rq->fifo_time) &&
2558             cfqq == RQ_CFQQ(next)) {
2559                 list_move(&rq->queuelist, &next->queuelist);
2560                 rq->fifo_time = next->fifo_time;
2561         }
2562 
2563         if (cfqq->next_rq == next)
2564                 cfqq->next_rq = rq;
2565         cfq_remove_request(next);
2566         cfqg_stats_update_io_merged(RQ_CFQG(rq), next->cmd_flags);
2567 
2568         cfqq = RQ_CFQQ(next);
2569         /*
2570          * all requests of this queue are merged to other queues, delete it
2571          * from the service tree. If it's the active_queue,
2572          * cfq_dispatch_requests() will choose to expire it or do idle
2573          */
2574         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list) &&
2575             cfqq != cfqd->active_queue)
2576                 cfq_del_cfqq_rr(cfqd, cfqq);
2577 }
2578 
2579 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
2580                            struct bio *bio)
2581 {
2582         struct cfq_data *cfqd = q->elevator->elevator_data;
2583         struct cfq_io_cq *cic;
2584         struct cfq_queue *cfqq;
2585 
2586         /*
2587          * Disallow merge of a sync bio into an async request.
2588          */
2589         if (cfq_bio_sync(bio) && !rq_is_sync(rq))
2590                 return false;
2591 
2592         /*
2593          * Lookup the cfqq that this bio will be queued with and allow
2594          * merge only if rq is queued there.
2595          */
2596         cic = cfq_cic_lookup(cfqd, current->io_context);
2597         if (!cic)
2598                 return false;
2599 
2600         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
2601         return cfqq == RQ_CFQQ(rq);
2602 }
2603 
2604 static inline void cfq_del_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2605 {
2606         del_timer(&cfqd->idle_slice_timer);
2607         cfqg_stats_update_idle_time(cfqq->cfqg);
2608 }
2609 
2610 static void __cfq_set_active_queue(struct cfq_data *cfqd,
2611                                    struct cfq_queue *cfqq)
2612 {
2613         if (cfqq) {
2614                 cfq_log_cfqq(cfqd, cfqq, "set_active wl_class:%d wl_type:%d",
2615                                 cfqd->serving_wl_class, cfqd->serving_wl_type);
2616                 cfqg_stats_update_avg_queue_size(cfqq->cfqg);
2617                 cfqq->slice_start = 0;
2618                 cfqq->dispatch_start = jiffies;
2619                 cfqq->allocated_slice = 0;
2620                 cfqq->slice_end = 0;
2621                 cfqq->slice_dispatch = 0;
2622                 cfqq->nr_sectors = 0;
2623 
2624                 cfq_clear_cfqq_wait_request(cfqq);
2625                 cfq_clear_cfqq_must_dispatch(cfqq);
2626                 cfq_clear_cfqq_must_alloc_slice(cfqq);
2627                 cfq_clear_cfqq_fifo_expire(cfqq);
2628                 cfq_mark_cfqq_slice_new(cfqq);
2629 
2630                 cfq_del_timer(cfqd, cfqq);
2631         }
2632 
2633         cfqd->active_queue = cfqq;
2634 }
2635 
2636 /*
2637  * current cfqq expired its slice (or was too idle), select new one
2638  */
2639 static void
2640 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2641                     bool timed_out)
2642 {
2643         cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
2644 
2645         if (cfq_cfqq_wait_request(cfqq))
2646                 cfq_del_timer(cfqd, cfqq);
2647 
2648         cfq_clear_cfqq_wait_request(cfqq);
2649         cfq_clear_cfqq_wait_busy(cfqq);
2650 
2651         /*
2652          * If this cfqq is shared between multiple processes, check to
2653          * make sure that those processes are still issuing I/Os within
2654          * the mean seek distance.  If not, it may be time to break the
2655          * queues apart again.
2656          */
2657         if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq))
2658                 cfq_mark_cfqq_split_coop(cfqq);
2659 
2660         /*
2661          * store what was left of this slice, if the queue idled/timed out
2662          */
2663         if (timed_out) {
2664                 if (cfq_cfqq_slice_new(cfqq))
2665                         cfqq->slice_resid = cfq_scaled_cfqq_slice(cfqd, cfqq);
2666                 else
2667                         cfqq->slice_resid = cfqq->slice_end - jiffies;
2668                 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
2669         }
2670 
2671         cfq_group_served(cfqd, cfqq->cfqg, cfqq);
2672 
2673         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
2674                 cfq_del_cfqq_rr(cfqd, cfqq);
2675 
2676         cfq_resort_rr_list(cfqd, cfqq);
2677 
2678         if (cfqq == cfqd->active_queue)
2679                 cfqd->active_queue = NULL;
2680 
2681         if (cfqd->active_cic) {
2682                 put_io_context(cfqd->active_cic->icq.ioc);
2683                 cfqd->active_cic = NULL;
2684         }
2685 }
2686 
2687 static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
2688 {
2689         struct cfq_queue *cfqq = cfqd->active_queue;
2690 
2691         if (cfqq)
2692                 __cfq_slice_expired(cfqd, cfqq, timed_out);
2693 }
2694 
2695 /*
2696  * Get next queue for service. Unless we have a queue preemption,
2697  * we'll simply select the first cfqq in the service tree.
2698  */
2699 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
2700 {
2701         struct cfq_rb_root *st = st_for(cfqd->serving_group,
2702                         cfqd->serving_wl_class, cfqd->serving_wl_type);
2703 
2704         if (!cfqd->rq_queued)
2705                 return NULL;
2706 
2707         /* There is nothing to dispatch */
2708         if (!st)
2709                 return NULL;
2710         if (RB_EMPTY_ROOT(&st->rb))
2711                 return NULL;
2712         return cfq_rb_first(st);
2713 }
2714 
2715 static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
2716 {
2717         struct cfq_group *cfqg;
2718         struct cfq_queue *cfqq;
2719         int i, j;
2720         struct cfq_rb_root *st;
2721 
2722         if (!cfqd->rq_queued)
2723                 return NULL;
2724 
2725         cfqg = cfq_get_next_cfqg(cfqd);
2726         if (!cfqg)
2727                 return NULL;
2728 
2729         for_each_cfqg_st(cfqg, i, j, st)
2730                 if ((cfqq = cfq_rb_first(st)) != NULL)
2731                         return cfqq;
2732         return NULL;
2733 }
2734 
2735 /*
2736  * Get and set a new active queue for service.
2737  */
2738 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
2739                                               struct cfq_queue *cfqq)
2740 {
2741         if (!cfqq)
2742                 cfqq = cfq_get_next_queue(cfqd);
2743 
2744         __cfq_set_active_queue(cfqd, cfqq);
2745         return cfqq;
2746 }
2747 
2748 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
2749                                           struct request *rq)
2750 {
2751         if (blk_rq_pos(rq) >= cfqd->last_position)
2752                 return blk_rq_pos(rq) - cfqd->last_position;
2753         else
2754                 return cfqd->last_position - blk_rq_pos(rq);
2755 }
2756 
2757 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2758                                struct request *rq)
2759 {
2760         return cfq_dist_from_last(cfqd, rq) <= CFQQ_CLOSE_THR;
2761 }
2762 
2763 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
2764                                     struct cfq_queue *cur_cfqq)
2765 {
2766         struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
2767         struct rb_node *parent, *node;
2768         struct cfq_queue *__cfqq;
2769         sector_t sector = cfqd->last_position;
2770 
2771         if (RB_EMPTY_ROOT(root))
2772                 return NULL;
2773 
2774         /*
2775          * First, if we find a request starting at the end of the last
2776          * request, choose it.
2777          */
2778         __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
2779         if (__cfqq)
2780                 return __cfqq;
2781 
2782         /*
2783          * If the exact sector wasn't found, the parent of the NULL leaf
2784          * will contain the closest sector.
2785          */
2786         __cfqq = rb_entry(parent, struct cfq_queue, p_node);
2787         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
2788                 return __cfqq;
2789 
2790         if (blk_rq_pos(__cfqq->next_rq) < sector)
2791                 node = rb_next(&__cfqq->p_node);
2792         else
2793                 node = rb_prev(&__cfqq->p_node);
2794         if (!node)
2795                 return NULL;
2796 
2797         __cfqq = rb_entry(node, struct cfq_queue, p_node);
2798         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
2799                 return __cfqq;
2800 
2801         return NULL;
2802 }
2803 
2804 /*
2805  * cfqd - obvious
2806  * cur_cfqq - passed in so that we don't decide that the current queue is
2807  *            closely cooperating with itself.
2808  *
2809  * So, basically we're assuming that that cur_cfqq has dispatched at least
2810  * one request, and that cfqd->last_position reflects a position on the disk
2811  * associated with the I/O issued by cur_cfqq.  I'm not sure this is a valid
2812  * assumption.
2813  */
2814 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
2815                                               struct cfq_queue *cur_cfqq)
2816 {
2817         struct cfq_queue *cfqq;
2818 
2819         if (cfq_class_idle(cur_cfqq))
2820                 return NULL;
2821         if (!cfq_cfqq_sync(cur_cfqq))
2822                 return NULL;
2823         if (CFQQ_SEEKY(cur_cfqq))
2824                 return NULL;
2825 
2826         /*
2827          * Don't search priority tree if it's the only queue in the group.
2828          */
2829         if (cur_cfqq->cfqg->nr_cfqq == 1)
2830                 return NULL;
2831 
2832         /*
2833          * We should notice if some of the queues are cooperating, eg
2834          * working closely on the same area of the disk. In that case,
2835          * we can group them together and don't waste time idling.
2836          */
2837         cfqq = cfqq_close(cfqd, cur_cfqq);
2838         if (!cfqq)
2839                 return NULL;
2840 
2841         /* If new queue belongs to different cfq_group, don't choose it */
2842         if (cur_cfqq->cfqg != cfqq->cfqg)
2843                 return NULL;
2844 
2845         /*
2846          * It only makes sense to merge sync queues.
2847          */
2848         if (!cfq_cfqq_sync(cfqq))
2849                 return NULL;
2850         if (CFQQ_SEEKY(cfqq))
2851                 return NULL;
2852 
2853         /*
2854          * Do not merge queues of different priority classes
2855          */
2856         if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
2857                 return NULL;
2858 
2859         return cfqq;
2860 }
2861 
2862 /*
2863  * Determine whether we should enforce idle window for this queue.
2864  */
2865 
2866 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2867 {
2868         enum wl_class_t wl_class = cfqq_class(cfqq);
2869         struct cfq_rb_root *st = cfqq->service_tree;
2870 
2871         BUG_ON(!st);
2872         BUG_ON(!st->count);
2873 
2874         if (!cfqd->cfq_slice_idle)
2875                 return false;
2876 
2877         /* We never do for idle class queues. */
2878         if (wl_class == IDLE_WORKLOAD)
2879                 return false;
2880 
2881         /* We do for queues that were marked with idle window flag. */
2882         if (cfq_cfqq_idle_window(cfqq) &&
2883            !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag))
2884                 return true;
2885 
2886         /*
2887          * Otherwise, we do only if they are the last ones
2888          * in their service tree.
2889          */
2890         if (st->count == 1 && cfq_cfqq_sync(cfqq) &&
2891            !cfq_io_thinktime_big(cfqd, &st->ttime, false))
2892                 return true;
2893         cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d", st->count);
2894         return false;
2895 }
2896 
2897 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
2898 {
2899         struct cfq_queue *cfqq = cfqd->active_queue;
2900         struct cfq_io_cq *cic;
2901         unsigned long sl, group_idle = 0;
2902 
2903         /*
2904          * SSD device without seek penalty, disable idling. But only do so
2905          * for devices that support queuing, otherwise we still have a problem
2906          * with sync vs async workloads.
2907          */
2908         if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag &&
2909                 !cfqd->cfq_group_idle)
2910                 return;
2911 
2912         WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
2913         WARN_ON(cfq_cfqq_slice_new(cfqq));
2914 
2915         /*
2916          * idle is disabled, either manually or by past process history
2917          */
2918         if (!cfq_should_idle(cfqd, cfqq)) {
2919                 /* no queue idling. Check for group idling */
2920                 if (cfqd->cfq_group_idle)
2921                         group_idle = cfqd->cfq_group_idle;
2922                 else
2923                         return;
2924         }
2925 
2926         /*
2927          * still active requests from this queue, don't idle
2928          */
2929         if (cfqq->dispatched)
2930                 return;
2931 
2932         /*
2933          * task has exited, don't wait
2934          */
2935         cic = cfqd->active_cic;
2936         if (!cic || !atomic_read(&cic->icq.ioc->active_ref))
2937                 return;
2938 
2939         /*
2940          * If our average think time is larger than the remaining time
2941          * slice, then don't idle. This avoids overrunning the allotted
2942          * time slice.
2943          */
2944         if (sample_valid(cic->ttime.ttime_samples) &&
2945             (cfqq->slice_end - jiffies < cic->ttime.ttime_mean)) {
2946                 cfq_log_cfqq(cfqd, cfqq, "Not idling. think_time:%lu",
2947                              cic->ttime.ttime_mean);
2948                 return;
2949         }
2950 
2951         /* There are other queues in the group, don't do group idle */
2952         if (group_idle && cfqq->cfqg->nr_cfqq > 1)
2953                 return;
2954 
2955         cfq_mark_cfqq_wait_request(cfqq);
2956 
2957         if (group_idle)
2958                 sl = cfqd->cfq_group_idle;
2959         else
2960                 sl = cfqd->cfq_slice_idle;
2961 
2962         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
2963         cfqg_stats_set_start_idle_time(cfqq->cfqg);
2964         cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu group_idle: %d", sl,
2965                         group_idle ? 1 : 0);
2966 }
2967 
2968 /*
2969  * Move request from internal lists to the request queue dispatch list.
2970  */
2971 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
2972 {
2973         struct cfq_data *cfqd = q->elevator->elevator_data;
2974         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2975 
2976         cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
2977 
2978         cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
2979         cfq_remove_request(rq);
2980         cfqq->dispatched++;
2981         (RQ_CFQG(rq))->dispatched++;
2982         elv_dispatch_sort(q, rq);
2983 
2984         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
2985         cfqq->nr_sectors += blk_rq_sectors(rq);
2986 }
2987 
2988 /*
2989  * return expired entry, or NULL to just start from scratch in rbtree
2990  */
2991 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
2992 {
2993         struct request *rq = NULL;
2994 
2995         if (cfq_cfqq_fifo_expire(cfqq))
2996                 return NULL;
2997 
2998         cfq_mark_cfqq_fifo_expire(cfqq);
2999 
3000         if (list_empty(&cfqq->fifo))
3001                 return NULL;
3002 
3003         rq = rq_entry_fifo(cfqq->fifo.next);
3004         if (time_before(jiffies, rq->fifo_time))
3005                 rq = NULL;
3006 
3007         return rq;
3008 }
3009 
3010 static inline int
3011 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3012 {
3013         const int base_rq = cfqd->cfq_slice_async_rq;
3014 
3015         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
3016 
3017         return 2 * base_rq * (IOPRIO_BE_NR - cfqq->ioprio);
3018 }
3019 
3020 /*
3021  * Must be called with the queue_lock held.
3022  */
3023 static int cfqq_process_refs(struct cfq_queue *cfqq)
3024 {
3025         int process_refs, io_refs;
3026 
3027         io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
3028         process_refs = cfqq->ref - io_refs;
3029         BUG_ON(process_refs < 0);
3030         return process_refs;
3031 }
3032 
3033 static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
3034 {
3035         int process_refs, new_process_refs;
3036         struct cfq_queue *__cfqq;
3037 
3038         /*
3039          * If there are no process references on the new_cfqq, then it is
3040          * unsafe to follow the ->new_cfqq chain as other cfqq's in the
3041          * chain may have dropped their last reference (not just their
3042          * last process reference).
3043          */
3044         if (!cfqq_process_refs(new_cfqq))
3045                 return;
3046 
3047         /* Avoid a circular list and skip interim queue merges */
3048         while ((__cfqq = new_cfqq->new_cfqq)) {
3049                 if (__cfqq == cfqq)
3050                         return;
3051                 new_cfqq = __cfqq;
3052         }
3053 
3054         process_refs = cfqq_process_refs(cfqq);
3055         new_process_refs = cfqq_process_refs(new_cfqq);
3056         /*
3057          * If the process for the cfqq has gone away, there is no
3058          * sense in merging the queues.
3059          */
3060         if (process_refs == 0 || new_process_refs == 0)
3061                 return;
3062 
3063         /*
3064          * Merge in the direction of the lesser amount of work.
3065          */
3066         if (new_process_refs >= process_refs) {
3067                 cfqq->new_cfqq = new_cfqq;
3068                 new_cfqq->ref += process_refs;
3069         } else {
3070                 new_cfqq->new_cfqq = cfqq;
3071                 cfqq->ref += new_process_refs;
3072         }
3073 }
3074 
3075 static enum wl_type_t cfq_choose_wl_type(struct cfq_data *cfqd,
3076                         struct cfq_group *cfqg, enum wl_class_t wl_class)
3077 {
3078         struct cfq_queue *queue;
3079         int i;
3080         bool key_valid = false;
3081         unsigned long lowest_key = 0;
3082         enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
3083 
3084         for (i = 0; i <= SYNC_WORKLOAD; ++i) {
3085                 /* select the one with lowest rb_key */
3086                 queue = cfq_rb_first(st_for(cfqg, wl_class, i));
3087                 if (queue &&
3088                     (!key_valid || time_before(queue->rb_key, lowest_key))) {
3089                         lowest_key = queue->rb_key;
3090                         cur_best = i;
3091                         key_valid = true;
3092                 }
3093         }
3094 
3095         return cur_best;
3096 }
3097 
3098 static void
3099 choose_wl_class_and_type(struct cfq_data *cfqd, struct cfq_group *cfqg)
3100 {
3101         unsigned slice;
3102         unsigned count;
3103         struct cfq_rb_root *st;
3104         unsigned group_slice;
3105         enum wl_class_t original_class = cfqd->serving_wl_class;
3106 
3107         /* Choose next priority. RT > BE > IDLE */
3108         if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
3109                 cfqd->serving_wl_class = RT_WORKLOAD;
3110         else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
3111                 cfqd->serving_wl_class = BE_WORKLOAD;
3112         else {
3113                 cfqd->serving_wl_class = IDLE_WORKLOAD;
3114                 cfqd->workload_expires = jiffies + 1;
3115                 return;
3116         }
3117 
3118         if (original_class != cfqd->serving_wl_class)
3119                 goto new_workload;
3120 
3121         /*
3122          * For RT and BE, we have to choose also the type
3123          * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
3124          * expiration time
3125          */
3126         st = st_for(cfqg, cfqd->serving_wl_class, cfqd->serving_wl_type);
3127         count = st->count;
3128 
3129         /*
3130          * check workload expiration, and that we still have other queues ready
3131          */
3132         if (count && !time_after(jiffies, cfqd->workload_expires))
3133                 return;
3134 
3135 new_workload:
3136         /* otherwise select new workload type */
3137         cfqd->serving_wl_type = cfq_choose_wl_type(cfqd, cfqg,
3138                                         cfqd->serving_wl_class);
3139         st = st_for(cfqg, cfqd->serving_wl_class, cfqd->serving_wl_type);
3140         count = st->count;
3141 
3142         /*
3143          * the workload slice is computed as a fraction of target latency
3144          * proportional to the number of queues in that workload, over
3145          * all the queues in the same priority class
3146          */
3147         group_slice = cfq_group_slice(cfqd, cfqg);
3148 
3149         slice = group_slice * count /
3150                 max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_wl_class],
3151                       cfq_group_busy_queues_wl(cfqd->serving_wl_class, cfqd,
3152                                         cfqg));
3153 
3154         if (cfqd->serving_wl_type == ASYNC_WORKLOAD) {
3155                 unsigned int tmp;
3156 
3157                 /*
3158                  * Async queues are currently system wide. Just taking
3159                  * proportion of queues with-in same group will lead to higher
3160                  * async ratio system wide as generally root group is going
3161                  * to have higher weight. A more accurate thing would be to
3162                  * calculate system wide asnc/sync ratio.
3163                  */
3164                 tmp = cfqd->cfq_target_latency *
3165                         cfqg_busy_async_queues(cfqd, cfqg);
3166                 tmp = tmp/cfqd->busy_queues;
3167                 slice = min_t(unsigned, slice, tmp);
3168 
3169                 /* async workload slice is scaled down according to
3170                  * the sync/async slice ratio. */
3171                 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
3172         } else
3173                 /* sync workload slice is at least 2 * cfq_slice_idle */
3174                 slice = max(slice, 2 * cfqd->cfq_slice_idle);
3175 
3176         slice = max_t(unsigned, slice, CFQ_MIN_TT);
3177         cfq_log(cfqd, "workload slice:%d", slice);
3178         cfqd->workload_expires = jiffies + slice;
3179 }
3180 
3181 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
3182 {
3183         struct cfq_rb_root *st = &cfqd->grp_service_tree;
3184         struct cfq_group *cfqg;
3185 
3186         if (RB_EMPTY_ROOT(&st->rb))
3187                 return NULL;
3188         cfqg = cfq_rb_first_group(st);
3189         update_min_vdisktime(st);
3190         return cfqg;
3191 }
3192 
3193 static void cfq_choose_cfqg(struct cfq_data *cfqd)
3194 {
3195         struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
3196 
3197         cfqd->serving_group = cfqg;
3198 
3199         /* Restore the workload type data */
3200         if (cfqg->saved_wl_slice) {
3201                 cfqd->workload_expires = jiffies + cfqg->saved_wl_slice;
3202                 cfqd->serving_wl_type = cfqg->saved_wl_type;
3203                 cfqd->serving_wl_class = cfqg->saved_wl_class;
3204         } else
3205                 cfqd->workload_expires = jiffies - 1;
3206 
3207         choose_wl_class_and_type(cfqd, cfqg);
3208 }
3209 
3210 /*
3211  * Select a queue for service. If we have a current active queue,
3212  * check whether to continue servicing it, or retrieve and set a new one.
3213  */
3214 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
3215 {
3216         struct cfq_queue *cfqq, *new_cfqq = NULL;
3217 
3218         cfqq = cfqd->active_queue;
3219         if (!cfqq)
3220                 goto new_queue;
3221 
3222         if (!cfqd->rq_queued)
3223                 return NULL;
3224 
3225         /*
3226          * We were waiting for group to get backlogged. Expire the queue
3227          */
3228         if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list))
3229                 goto expire;
3230 
3231         /*
3232          * The active queue has run out of time, expire it and select new.
3233          */
3234         if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) {
3235                 /*
3236                  * If slice had not expired at the completion of last request
3237                  * we might not have turned on wait_busy flag. Don't expire
3238                  * the queue yet. Allow the group to get backlogged.
3239                  *
3240                  * The very fact that we have used the slice, that means we
3241                  * have been idling all along on this queue and it should be
3242                  * ok to wait for this request to complete.
3243                  */
3244                 if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list)
3245                     && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
3246                         cfqq = NULL;
3247                         goto keep_queue;
3248                 } else
3249                         goto check_group_idle;
3250         }
3251 
3252         /*
3253          * The active queue has requests and isn't expired, allow it to
3254          * dispatch.
3255          */
3256         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3257                 goto keep_queue;
3258 
3259         /*
3260          * If another queue has a request waiting within our mean seek
3261          * distance, let it run.  The expire code will check for close
3262          * cooperators and put the close queue at the front of the service
3263          * tree.  If possible, merge the expiring queue with the new cfqq.
3264          */
3265         new_cfqq = cfq_close_cooperator(cfqd, cfqq);
3266         if (new_cfqq) {
3267                 if (!cfqq->new_cfqq)
3268                         cfq_setup_merge(cfqq, new_cfqq);
3269                 goto expire;
3270         }
3271 
3272         /*
3273          * No requests pending. If the active queue still has requests in
3274          * flight or is idling for a new request, allow either of these
3275          * conditions to happen (or time out) before selecting a new queue.
3276          */
3277         if (timer_pending(&cfqd->idle_slice_timer)) {
3278                 cfqq = NULL;
3279                 goto keep_queue;
3280         }
3281 
3282         /*
3283          * This is a deep seek queue, but the device is much faster than
3284          * the queue can deliver, don't idle
3285          **/
3286         if (CFQQ_SEEKY(cfqq) && cfq_cfqq_idle_window(cfqq) &&
3287             (cfq_cfqq_slice_new(cfqq) ||
3288             (cfqq->slice_end - jiffies > jiffies - cfqq->slice_start))) {
3289                 cfq_clear_cfqq_deep(cfqq);
3290                 cfq_clear_cfqq_idle_window(cfqq);
3291         }
3292 
3293         if (cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
3294                 cfqq = NULL;
3295                 goto keep_queue;
3296         }
3297 
3298         /*
3299          * If group idle is enabled and there are requests dispatched from
3300          * this group, wait for requests to complete.
3301          */
3302 check_group_idle:
3303         if (cfqd->cfq_group_idle && cfqq->cfqg->nr_cfqq == 1 &&
3304             cfqq->cfqg->dispatched &&
3305             !cfq_io_thinktime_big(cfqd, &cfqq->cfqg->ttime, true)) {
3306                 cfqq = NULL;
3307                 goto keep_queue;
3308         }
3309 
3310 expire:
3311         cfq_slice_expired(cfqd, 0);
3312 new_queue:
3313         /*
3314          * Current queue expired. Check if we have to switch to a new
3315          * service tree
3316          */
3317         if (!new_cfqq)
3318                 cfq_choose_cfqg(cfqd);
3319 
3320         cfqq = cfq_set_active_queue(cfqd, new_cfqq);
3321 keep_queue:
3322         return cfqq;
3323 }
3324 
3325 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
3326 {
3327         int dispatched = 0;
3328 
3329         while (cfqq->next_rq) {
3330                 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
3331                 dispatched++;
3332         }
3333 
3334         BUG_ON(!list_empty(&cfqq->fifo));
3335 
3336         /* By default cfqq is not expired if it is empty. Do it explicitly */
3337         __cfq_slice_expired(cfqq->cfqd, cfqq, 0);
3338         return dispatched;
3339 }
3340 
3341 /*
3342  * Drain our current requests. Used for barriers and when switching
3343  * io schedulers on-the-fly.
3344  */
3345 static int cfq_forced_dispatch(struct cfq_data *cfqd)
3346 {
3347         struct cfq_queue *cfqq;
3348         int dispatched = 0;
3349 
3350         /* Expire the timeslice of the current active queue first */
3351         cfq_slice_expired(cfqd, 0);
3352         while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) {
3353                 __cfq_set_active_queue(cfqd, cfqq);
3354                 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
3355         }
3356 
3357         BUG_ON(cfqd->busy_queues);
3358 
3359         cfq_log(cfqd, "forced_dispatch=%d", dispatched);
3360         return dispatched;
3361 }
3362 
3363 static inline bool cfq_slice_used_soon(struct cfq_data *cfqd,
3364         struct cfq_queue *cfqq)
3365 {
3366         /* the queue hasn't finished any request, can't estimate */
3367         if (cfq_cfqq_slice_new(cfqq))
3368                 return true;
3369         if (time_after(jiffies + cfqd->cfq_slice_idle * cfqq->dispatched,
3370                 cfqq->slice_end))
3371                 return true;
3372 
3373         return false;
3374 }
3375 
3376 static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3377 {
3378         unsigned int max_dispatch;
3379 
3380         if (cfq_cfqq_must_dispatch(cfqq))
3381                 return true;
3382 
3383         /*
3384          * Drain async requests before we start sync IO
3385          */
3386         if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_flight[BLK_RW_ASYNC])
3387                 return false;
3388 
3389         /*
3390          * If this is an async queue and we have sync IO in flight, let it wait
3391          */
3392         if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq))
3393                 return false;
3394 
3395         max_dispatch = max_t(unsigned int, cfqd->cfq_quantum / 2, 1);
3396         if (cfq_class_idle(cfqq))
3397                 max_dispatch = 1;
3398 
3399         /*
3400          * Does this cfqq already have too much IO in flight?
3401          */
3402         if (cfqq->dispatched >= max_dispatch) {
3403                 bool promote_sync = false;
3404                 /*
3405                  * idle queue must always only have a single IO in flight
3406                  */
3407                 if (cfq_class_idle(cfqq))
3408                         return false;
3409 
3410                 /*
3411                  * If there is only one sync queue
3412                  * we can ignore async queue here and give the sync
3413                  * queue no dispatch limit. The reason is a sync queue can
3414                  * preempt async queue, limiting the sync queue doesn't make
3415                  * sense. This is useful for aiostress test.
3416                  */
3417                 if (cfq_cfqq_sync(cfqq) && cfqd->busy_sync_queues == 1)
3418                         promote_sync = true;
3419 
3420                 /*
3421                  * We have other queues, don't allow more IO from this one
3422                  */
3423                 if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq) &&
3424                                 !promote_sync)
3425                         return false;
3426 
3427                 /*
3428                  * Sole queue user, no limit
3429                  */
3430                 if (cfqd->busy_queues == 1 || promote_sync)
3431                         max_dispatch = -1;
3432                 else
3433                         /*
3434                          * Normally we start throttling cfqq when cfq_quantum/2
3435                          * requests have been dispatched. But we can drive
3436                          * deeper queue depths at the beginning of slice
3437                          * subjected to upper limit of cfq_quantum.
3438                          * */
3439                         max_dispatch = cfqd->cfq_quantum;
3440         }
3441 
3442         /*
3443          * Async queues must wait a bit before being allowed dispatch.
3444          * We also ramp up the dispatch depth gradually for async IO,
3445          * based on the last sync IO we serviced
3446          */
3447         if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
3448                 unsigned long last_sync = jiffies - cfqd->last_delayed_sync;
3449                 unsigned int depth;
3450 
3451                 depth = last_sync / cfqd->cfq_slice[1];
3452                 if (!depth && !cfqq->dispatched)
3453                         depth = 1;
3454                 if (depth < max_dispatch)
3455                         max_dispatch = depth;
3456         }
3457 
3458         /*
3459          * If we're below the current max, allow a dispatch
3460          */
3461         return cfqq->dispatched < max_dispatch;
3462 }
3463 
3464 /*
3465  * Dispatch a request from cfqq, moving them to the request queue
3466  * dispatch list.
3467  */
3468 static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3469 {
3470         struct request *rq;
3471 
3472         BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
3473 
3474         rq = cfq_check_fifo(cfqq);
3475         if (rq)
3476                 cfq_mark_cfqq_must_dispatch(cfqq);
3477 
3478         if (!cfq_may_dispatch(cfqd, cfqq))
3479                 return false;
3480 
3481         /*
3482          * follow expired path, else get first next available
3483          */
3484         if (!rq)
3485                 rq = cfqq->next_rq;
3486         else
3487                 cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
3488 
3489         /*
3490          * insert request into driver dispatch list
3491          */
3492         cfq_dispatch_insert(cfqd->queue, rq);
3493 
3494         if (!cfqd->active_cic) {
3495                 struct cfq_io_cq *cic = RQ_CIC(rq);
3496 
3497                 atomic_long_inc(&cic->icq.ioc->refcount);
3498                 cfqd->active_cic = cic;
3499         }
3500 
3501         return true;
3502 }
3503 
3504 /*
3505  * Find the cfqq that we need to service and move a request from that to the
3506  * dispatch list
3507  */
3508 static int cfq_dispatch_requests(struct request_queue *q, int force)
3509 {
3510         struct cfq_data *cfqd = q->elevator->elevator_data;
3511         struct cfq_queue *cfqq;
3512 
3513         if (!cfqd->busy_queues)
3514                 return 0;
3515 
3516         if (unlikely(force))
3517                 return cfq_forced_dispatch(cfqd);
3518 
3519         cfqq = cfq_select_queue(cfqd);
3520         if (!cfqq)
3521                 return 0;
3522 
3523         /*
3524          * Dispatch a request from this cfqq, if it is allowed
3525          */
3526         if (!cfq_dispatch_request(cfqd, cfqq))
3527                 return 0;
3528 
3529         cfqq->slice_dispatch++;
3530         cfq_clear_cfqq_must_dispatch(cfqq);
3531 
3532         /*
3533          * expire an async queue immediately if it has used up its slice. idle
3534          * queue always expire after 1 dispatch round.
3535          */
3536         if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
3537             cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
3538             cfq_class_idle(cfqq))) {
3539                 cfqq->slice_end = jiffies + 1;
3540                 cfq_slice_expired(cfqd, 0);
3541         }
3542 
3543         cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
3544         return 1;
3545 }
3546 
3547 /*
3548  * task holds one reference to the queue, dropped when task exits. each rq
3549  * in-flight on this queue also holds a reference, dropped when rq is freed.
3550  *
3551  * Each cfq queue took a reference on the parent group. Drop it now.
3552  * queue lock must be held here.
3553  */
3554 static void cfq_put_queue(struct cfq_queue *cfqq)
3555 {
3556         struct cfq_data *cfqd = cfqq->cfqd;
3557         struct cfq_group *cfqg;
3558 
3559         BUG_ON(cfqq->ref <= 0);
3560 
3561         cfqq->ref--;
3562         if (cfqq->ref)
3563                 return;
3564 
3565         cfq_log_cfqq(cfqd, cfqq, "put_queue");
3566         BUG_ON(rb_first(&cfqq->sort_list));
3567         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
3568         cfqg = cfqq->cfqg;
3569 
3570         if (unlikely(cfqd->active_queue == cfqq)) {
3571                 __cfq_slice_expired(cfqd, cfqq, 0);
3572                 cfq_schedule_dispatch(cfqd);
3573         }
3574 
3575         BUG_ON(cfq_cfqq_on_rr(cfqq));
3576         kmem_cache_free(cfq_pool, cfqq);
3577         cfqg_put(cfqg);
3578 }
3579 
3580 static void cfq_put_cooperator(struct cfq_queue *cfqq)
3581 {
3582         struct cfq_queue *__cfqq, *next;
3583 
3584         /*
3585          * If this queue was scheduled to merge with another queue, be
3586          * sure to drop the reference taken on that queue (and others in
3587          * the merge chain).  See cfq_setup_merge and cfq_merge_cfqqs.
3588          */
3589         __cfqq = cfqq->new_cfqq;
3590         while (__cfqq) {
3591                 if (__cfqq == cfqq) {
3592                         WARN(1, "cfqq->new_cfqq loop detected\n");
3593                         break;
3594                 }
3595                 next = __cfqq->new_cfqq;
3596                 cfq_put_queue(__cfqq);
3597                 __cfqq = next;
3598         }
3599 }
3600 
3601 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3602 {
3603         if (unlikely(cfqq == cfqd->active_queue)) {
3604                 __cfq_slice_expired(cfqd, cfqq, 0);
3605                 cfq_schedule_dispatch(cfqd);
3606         }
3607 
3608         cfq_put_cooperator(cfqq);
3609 
3610         cfq_put_queue(cfqq);
3611 }
3612 
3613 static void cfq_init_icq(struct io_cq *icq)
3614 {
3615         struct cfq_io_cq *cic = icq_to_cic(icq);
3616 
3617         cic->ttime.last_end_request = jiffies;
3618 }
3619 
3620 static void cfq_exit_icq(struct io_cq *icq)
3621 {
3622         struct cfq_io_cq *cic = icq_to_cic(icq);
3623         struct cfq_data *cfqd = cic_to_cfqd(cic);
3624 
3625         if (cic_to_cfqq(cic, false)) {
3626                 cfq_exit_cfqq(cfqd, cic_to_cfqq(cic, false));
3627                 cic_set_cfqq(cic, NULL, false);
3628         }
3629 
3630         if (cic_to_cfqq(cic, true)) {
3631                 cfq_exit_cfqq(cfqd, cic_to_cfqq(cic, true));
3632                 cic_set_cfqq(cic, NULL, true);
3633         }
3634 }
3635 
3636 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct cfq_io_cq *cic)
3637 {
3638         struct task_struct *tsk = current;
3639         int ioprio_class;
3640 
3641         if (!cfq_cfqq_prio_changed(cfqq))
3642                 return;
3643 
3644         ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
3645         switch (ioprio_class) {
3646         default:
3647                 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
3648         case IOPRIO_CLASS_NONE:
3649                 /*
3650                  * no prio set, inherit CPU scheduling settings
3651                  */
3652                 cfqq->ioprio = task_nice_ioprio(tsk);
3653                 cfqq->ioprio_class = task_nice_ioclass(tsk);
3654                 break;
3655         case IOPRIO_CLASS_RT:
3656                 cfqq->ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
3657                 cfqq->ioprio_class = IOPRIO_CLASS_RT;
3658                 break;
3659         case IOPRIO_CLASS_BE:
3660                 cfqq->ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
3661                 cfqq->ioprio_class = IOPRIO_CLASS_BE;
3662                 break;
3663         case IOPRIO_CLASS_IDLE:
3664                 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
3665                 cfqq->ioprio = 7;
3666                 cfq_clear_cfqq_idle_window(cfqq);
3667                 break;
3668         }
3669 
3670         /*
3671          * keep track of original prio settings in case we have to temporarily
3672          * elevate the priority of this queue
3673          */
3674         cfqq->org_ioprio = cfqq->ioprio;
3675         cfq_clear_cfqq_prio_changed(cfqq);
3676 }
3677 
3678 static void check_ioprio_changed(struct cfq_io_cq *cic, struct bio *bio)
3679 {
3680         int ioprio = cic->icq.ioc->ioprio;
3681         struct cfq_data *cfqd = cic_to_cfqd(cic);
3682         struct cfq_queue *cfqq;
3683 
3684         /*
3685          * Check whether ioprio has changed.  The condition may trigger
3686          * spuriously on a newly created cic but there's no harm.
3687          */
3688         if (unlikely(!cfqd) || likely(cic->ioprio == ioprio))
3689                 return;
3690 
3691         cfqq = cic_to_cfqq(cic, false);
3692         if (cfqq) {
3693                 cfq_put_queue(cfqq);
3694                 cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic, bio);
3695                 cic_set_cfqq(cic, cfqq, false);
3696         }
3697 
3698         cfqq = cic_to_cfqq(cic, true);
3699         if (cfqq)
3700                 cfq_mark_cfqq_prio_changed(cfqq);
3701 
3702         cic->ioprio = ioprio;
3703 }
3704 
3705 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3706                           pid_t pid, bool is_sync)
3707 {
3708         RB_CLEAR_NODE(&cfqq->rb_node);
3709         RB_CLEAR_NODE(&cfqq->p_node);
3710         INIT_LIST_HEAD(&cfqq->fifo);
3711 
3712         cfqq->ref = 0;
3713         cfqq->cfqd = cfqd;
3714 
3715         cfq_mark_cfqq_prio_changed(cfqq);
3716 
3717         if (is_sync) {
3718                 if (!cfq_class_idle(cfqq))
3719                         cfq_mark_cfqq_idle_window(cfqq);
3720                 cfq_mark_cfqq_sync(cfqq);
3721         }
3722         cfqq->pid = pid;
3723 }
3724 
3725 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3726 static void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
3727 {
3728         struct cfq_data *cfqd = cic_to_cfqd(cic);
3729         struct cfq_queue *cfqq;
3730         uint64_t serial_nr;
3731 
3732         rcu_read_lock();
3733         serial_nr = bio_blkcg(bio)->css.serial_nr;
3734         rcu_read_unlock();
3735 
3736         /*
3737          * Check whether blkcg has changed.  The condition may trigger
3738          * spuriously on a newly created cic but there's no harm.
3739          */
3740         if (unlikely(!cfqd) || likely(cic->blkcg_serial_nr == serial_nr))
3741                 return;
3742 
3743         /*
3744          * Drop reference to queues.  New queues will be assigned in new
3745          * group upon arrival of fresh requests.
3746          */
3747         cfqq = cic_to_cfqq(cic, false);
3748         if (cfqq) {
3749                 cfq_log_cfqq(cfqd, cfqq, "changed cgroup");
3750                 cic_set_cfqq(cic, NULL, false);
3751                 cfq_put_queue(cfqq);
3752         }
3753 
3754         cfqq = cic_to_cfqq(cic, true);
3755         if (cfqq) {
3756                 cfq_log_cfqq(cfqd, cfqq, "changed cgroup");
3757                 cic_set_cfqq(cic, NULL, true);
3758                 cfq_put_queue(cfqq);
3759         }
3760 
3761         cic->blkcg_serial_nr = serial_nr;
3762 }
3763 #else
3764 static inline void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio) { }
3765 #endif  /* CONFIG_CFQ_GROUP_IOSCHED */
3766 
3767 static struct cfq_queue **
3768 cfq_async_queue_prio(struct cfq_group *cfqg, int ioprio_class, int ioprio)
3769 {
3770         switch (ioprio_class) {
3771         case IOPRIO_CLASS_RT:
3772                 return &cfqg->async_cfqq[0][ioprio];
3773         case IOPRIO_CLASS_NONE:
3774                 ioprio = IOPRIO_NORM;
3775                 /* fall through */
3776         case IOPRIO_CLASS_BE:
3777                 return &cfqg->async_cfqq[1][ioprio];
3778         case IOPRIO_CLASS_IDLE:
3779                 return &cfqg->async_idle_cfqq;
3780         default:
3781                 BUG();
3782         }
3783 }
3784 
3785 static struct cfq_queue *
3786 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
3787               struct bio *bio)
3788 {
3789         int ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
3790         int ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
3791         struct cfq_queue **async_cfqq = NULL;
3792         struct cfq_queue *cfqq;
3793         struct cfq_group *cfqg;
3794 
3795         rcu_read_lock();
3796         cfqg = cfq_lookup_cfqg(cfqd, bio_blkcg(bio));
3797         if (!cfqg) {
3798                 cfqq = &cfqd->oom_cfqq;
3799                 goto out;
3800         }
3801 
3802         if (!is_sync) {
3803                 if (!ioprio_valid(cic->ioprio)) {
3804                         struct task_struct *tsk = current;
3805                         ioprio = task_nice_ioprio(tsk);
3806                         ioprio_class = task_nice_ioclass(tsk);
3807                 }
3808                 async_cfqq = cfq_async_queue_prio(cfqg, ioprio_class, ioprio);
3809                 cfqq = *async_cfqq;
3810                 if (cfqq)
3811                         goto out;
3812         }
3813 
3814         cfqq = kmem_cache_alloc_node(cfq_pool,
3815                                      GFP_NOWAIT | __GFP_ZERO | __GFP_NOWARN,
3816                                      cfqd->queue->node);
3817         if (!cfqq) {
3818                 cfqq = &cfqd->oom_cfqq;
3819                 goto out;
3820         }
3821 
3822         cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
3823         cfq_init_prio_data(cfqq, cic);
3824         cfq_link_cfqq_cfqg(cfqq, cfqg);
3825         cfq_log_cfqq(cfqd, cfqq, "alloced");
3826 
3827         if (async_cfqq) {
3828                 /* a new async queue is created, pin and remember */
3829                 cfqq->ref++;
3830                 *async_cfqq = cfqq;
3831         }
3832 out:
3833         cfqq->ref++;
3834         rcu_read_unlock();
3835         return cfqq;
3836 }
3837 
3838 static void
3839 __cfq_update_io_thinktime(struct cfq_ttime *ttime, unsigned long slice_idle)
3840 {
3841         unsigned long elapsed = jiffies - ttime->last_end_request;
3842         elapsed = min(elapsed, 2UL * slice_idle);
3843 
3844         ttime->ttime_samples = (7*ttime->ttime_samples + 256) / 8;
3845         ttime->ttime_total = (7*ttime->ttime_total + 256*elapsed) / 8;
3846         ttime->ttime_mean = (ttime->ttime_total + 128) / ttime->ttime_samples;
3847 }
3848 
3849 static void
3850 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3851                         struct cfq_io_cq *cic)
3852 {
3853         if (cfq_cfqq_sync(cfqq)) {
3854                 __cfq_update_io_thinktime(&cic->ttime, cfqd->cfq_slice_idle);
3855                 __cfq_update_io_thinktime(&cfqq->service_tree->ttime,
3856                         cfqd->cfq_slice_idle);
3857         }
3858 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3859         __cfq_update_io_thinktime(&cfqq->cfqg->ttime, cfqd->cfq_group_idle);
3860 #endif
3861 }
3862 
3863 static void
3864 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3865                        struct request *rq)
3866 {
3867         sector_t sdist = 0;
3868         sector_t n_sec = blk_rq_sectors(rq);
3869         if (cfqq->last_request_pos) {
3870                 if (cfqq->last_request_pos < blk_rq_pos(rq))
3871                         sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
3872                 else
3873                         sdist = cfqq->last_request_pos - blk_rq_pos(rq);
3874         }
3875 
3876         cfqq->seek_history <<= 1;
3877         if (blk_queue_nonrot(cfqd->queue))
3878                 cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT);
3879         else
3880                 cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
3881 }
3882 
3883 /*
3884  * Disable idle window if the process thinks too long or seeks so much that
3885  * it doesn't matter
3886  */
3887 static void
3888 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3889                        struct cfq_io_cq *cic)
3890 {
3891         int old_idle, enable_idle;
3892 
3893         /*
3894          * Don't idle for async or idle io prio class
3895          */
3896         if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
3897                 return;
3898 
3899         enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
3900 
3901         if (cfqq->queued[0] + cfqq->queued[1] >= 4)
3902                 cfq_mark_cfqq_deep(cfqq);
3903 
3904         if (cfqq->next_rq && (cfqq->next_rq->cmd_flags & REQ_NOIDLE))
3905                 enable_idle = 0;
3906         else if (!atomic_read(&cic->icq.ioc->active_ref) ||
3907                  !cfqd->cfq_slice_idle ||
3908                  (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
3909                 enable_idle = 0;
3910         else if (sample_valid(cic->ttime.ttime_samples)) {
3911                 if (cic->ttime.ttime_mean > cfqd->cfq_slice_idle)
3912                         enable_idle = 0;
3913                 else
3914                         enable_idle = 1;
3915         }
3916 
3917         if (old_idle != enable_idle) {
3918                 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
3919                 if (enable_idle)
3920                         cfq_mark_cfqq_idle_window(cfqq);
3921                 else
3922                         cfq_clear_cfqq_idle_window(cfqq);
3923         }
3924 }
3925 
3926 /*
3927  * Check if new_cfqq should preempt the currently active queue. Return 0 for
3928  * no or if we aren't sure, a 1 will cause a preempt.
3929  */
3930 static bool
3931 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
3932                    struct request *rq)
3933 {
3934         struct cfq_queue *cfqq;
3935 
3936         cfqq = cfqd->active_queue;
3937         if (!cfqq)
3938                 return false;
3939 
3940         if (cfq_class_idle(new_cfqq))
3941                 return false;
3942 
3943         if (cfq_class_idle(cfqq))
3944                 return true;
3945 
3946         /*
3947          * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice.
3948          */
3949         if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq))
3950                 return false;
3951 
3952         /*
3953          * if the new request is sync, but the currently running queue is
3954          * not, let the sync request have priority.
3955          */
3956         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq) && !cfq_cfqq_must_dispatch(cfqq))
3957                 return true;
3958 
3959         if (new_cfqq->cfqg != cfqq->cfqg)
3960                 return false;
3961 
3962         if (cfq_slice_used(cfqq))
3963                 return true;
3964 
3965         /* Allow preemption only if we are idling on sync-noidle tree */
3966         if (cfqd->serving_wl_type == SYNC_NOIDLE_WORKLOAD &&
3967             cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
3968             new_cfqq->service_tree->count == 2 &&
3969             RB_EMPTY_ROOT(&cfqq->sort_list))
3970                 return true;
3971 
3972         /*
3973          * So both queues are sync. Let the new request get disk time if
3974          * it's a metadata request and the current queue is doing regular IO.
3975          */
3976         if ((rq->cmd_flags & REQ_PRIO) && !cfqq->prio_pending)
3977                 return true;
3978 
3979         /*
3980          * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
3981          */
3982         if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
3983                 return true;
3984 
3985         /* An idle queue should not be idle now for some reason */
3986         if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq))
3987                 return true;
3988 
3989         if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
3990                 return false;
3991 
3992         /*
3993          * if this request is as-good as one we would expect from the
3994          * current cfqq, let it preempt
3995          */
3996         if (cfq_rq_close(cfqd, cfqq, rq))
3997                 return true;
3998 
3999         return false;
4000 }
4001 
4002 /*
4003  * cfqq preempts the active queue. if we allowed preempt with no slice left,
4004  * let it have half of its nominal slice.
4005  */
4006 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
4007 {
4008         enum wl_type_t old_type = cfqq_type(cfqd->active_queue);
4009 
4010         cfq_log_cfqq(cfqd, cfqq, "preempt");
4011         cfq_slice_expired(cfqd, 1);
4012 
4013         /*
4014          * workload type is changed, don't save slice, otherwise preempt
4015          * doesn't happen
4016          */
4017         if (old_type != cfqq_type(cfqq))
4018                 cfqq->cfqg->saved_wl_slice = 0;
4019 
4020         /*
4021          * Put the new queue at the front of the of the current list,
4022          * so we know that it will be selected next.
4023          */
4024         BUG_ON(!cfq_cfqq_on_rr(cfqq));
4025 
4026         cfq_service_tree_add(cfqd, cfqq, 1);
4027 
4028         cfqq->slice_end = 0;
4029         cfq_mark_cfqq_slice_new(cfqq);
4030 }
4031 
4032 /*
4033  * Called when a new fs request (rq) is added (to cfqq). Check if there's
4034  * something we should do about it
4035  */
4036 static void
4037 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
4038                 struct request *rq)
4039 {
4040         struct cfq_io_cq *cic = RQ_CIC(rq);
4041 
4042         cfqd->rq_queued++;
4043         if (rq->cmd_flags & REQ_PRIO)
4044                 cfqq->prio_pending++;
4045 
4046         cfq_update_io_thinktime(cfqd, cfqq, cic);
4047         cfq_update_io_seektime(cfqd, cfqq, rq);
4048         cfq_update_idle_window(cfqd, cfqq, cic);
4049 
4050         cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
4051 
4052         if (cfqq == cfqd->active_queue) {
4053                 /*
4054                  * Remember that we saw a request from this process, but
4055                  * don't start queuing just yet. Otherwise we risk seeing lots
4056                  * of tiny requests, because we disrupt the normal plugging
4057                  * and merging. If the request is already larger than a single
4058                  * page, let it rip immediately. For that case we assume that
4059                  * merging is already done. Ditto for a busy system that
4060                  * has other work pending, don't risk delaying until the
4061                  * idle timer unplug to continue working.
4062                  */
4063                 if (cfq_cfqq_wait_request(cfqq)) {
4064                         if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
4065                             cfqd->busy_queues > 1) {
4066                                 cfq_del_timer(cfqd, cfqq);
4067                                 cfq_clear_cfqq_wait_request(cfqq);
4068                                 __blk_run_queue(cfqd->queue);
4069                         } else {
4070                                 cfqg_stats_update_idle_time(cfqq->cfqg);
4071                                 cfq_mark_cfqq_must_dispatch(cfqq);
4072                         }
4073                 }
4074         } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
4075                 /*
4076                  * not the active queue - expire current slice if it is
4077                  * idle and has expired it's mean thinktime or this new queue
4078                  * has some old slice time left and is of higher priority or
4079                  * this new queue is RT and the current one is BE
4080                  */
4081                 cfq_preempt_queue(cfqd, cfqq);
4082                 __blk_run_queue(cfqd->queue);
4083         }
4084 }
4085 
4086 static void cfq_insert_request(struct request_queue *q, struct request *rq)
4087 {
4088         struct cfq_data *cfqd = q->elevator->elevator_data;
4089         struct cfq_queue *cfqq = RQ_CFQQ(rq);
4090 
4091         cfq_log_cfqq(cfqd, cfqq, "insert_request");
4092         cfq_init_prio_data(cfqq, RQ_CIC(rq));
4093 
4094         rq->fifo_time = jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)];
4095         list_add_tail(&rq->queuelist, &cfqq->fifo);
4096         cfq_add_rq_rb(rq);
4097         cfqg_stats_update_io_add(RQ_CFQG(rq), cfqd->serving_group,
4098                                  rq->cmd_flags);
4099         cfq_rq_enqueued(cfqd, cfqq, rq);
4100 }
4101 
4102 /*
4103  * Update hw_tag based on peak queue depth over 50 samples under
4104  * sufficient load.
4105  */
4106 static void cfq_update_hw_tag(struct cfq_data *cfqd)
4107 {
4108         struct cfq_queue *cfqq = cfqd->active_queue;
4109 
4110         if (cfqd->rq_in_driver > cfqd->hw_tag_est_depth)
4111                 cfqd->hw_tag_est_depth = cfqd->rq_in_driver;
4112 
4113         if (cfqd->hw_tag == 1)
4114                 return;
4115 
4116         if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
4117             cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
4118                 return;
4119 
4120         /*
4121          * If active queue hasn't enough requests and can idle, cfq might not
4122          * dispatch sufficient requests to hardware. Don't zero hw_tag in this
4123          * case
4124          */
4125         if (cfqq && cfq_cfqq_idle_window(cfqq) &&
4126             cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
4127             CFQ_HW_QUEUE_MIN && cfqd->rq_in_driver < CFQ_HW_QUEUE_MIN)
4128                 return;
4129 
4130         if (cfqd->hw_tag_samples++ < 50)
4131                 return;
4132 
4133         if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
4134                 cfqd->hw_tag = 1;
4135         else
4136                 cfqd->hw_tag = 0;
4137 }
4138 
4139 static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq)
4140 {
4141         struct cfq_io_cq *cic = cfqd->active_cic;
4142 
4143         /* If the queue already has requests, don't wait */
4144         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
4145                 return false;
4146 
4147         /* If there are other queues in the group, don't wait */
4148         if (cfqq->cfqg->nr_cfqq > 1)
4149                 return false;
4150 
4151         /* the only queue in the group, but think time is big */
4152         if (cfq_io_thinktime_big(cfqd, &cfqq->cfqg->ttime, true))
4153                 return false;
4154 
4155         if (cfq_slice_used(cfqq))
4156                 return true;
4157 
4158         /* if slice left is less than think time, wait busy */
4159         if (cic && sample_valid(cic->ttime.ttime_samples)
4160             && (cfqq->slice_end - jiffies < cic->ttime.ttime_mean))
4161                 return true;
4162 
4163         /*
4164          * If think times is less than a jiffy than ttime_mean=0 and above
4165          * will not be true. It might happen that slice has not expired yet
4166          * but will expire soon (4-5 ns) during select_queue(). To cover the
4167          * case where think time is less than a jiffy, mark the queue wait
4168          * busy if only 1 jiffy is left in the slice.
4169          */
4170         if (cfqq->slice_end - jiffies == 1)
4171                 return true;
4172 
4173         return false;
4174 }
4175 
4176 static void cfq_completed_request(struct request_queue *q, struct request *rq)
4177 {
4178         struct cfq_queue *cfqq = RQ_CFQQ(rq);
4179         struct cfq_data *cfqd = cfqq->cfqd;
4180         const int sync = rq_is_sync(rq);
4181         unsigned long now;
4182 
4183         now = jiffies;
4184         cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d",
4185                      !!(rq->cmd_flags & REQ_NOIDLE));
4186 
4187         cfq_update_hw_tag(cfqd);
4188 
4189         WARN_ON(!cfqd->rq_in_driver);
4190         WARN_ON(!cfqq->dispatched);
4191         cfqd->rq_in_driver--;
4192         cfqq->dispatched--;
4193         (RQ_CFQG(rq))->dispatched--;
4194         cfqg_stats_update_completion(cfqq->cfqg, rq_start_time_ns(rq),
4195                                      rq_io_start_time_ns(rq), rq->cmd_flags);
4196 
4197         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
4198 
4199         if (sync) {
4200                 struct cfq_rb_root *st;
4201 
4202                 RQ_CIC(rq)->ttime.last_end_request = now;
4203 
4204                 if (cfq_cfqq_on_rr(cfqq))
4205                         st = cfqq->service_tree;
4206                 else
4207                         st = st_for(cfqq->cfqg, cfqq_class(cfqq),
4208                                         cfqq_type(cfqq));
4209 
4210                 st->ttime.last_end_request = now;
4211                 if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
4212                         cfqd->last_delayed_sync = now;
4213         }
4214 
4215 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4216         cfqq->cfqg->ttime.last_end_request = now;
4217 #endif
4218 
4219         /*
4220          * If this is the active queue, check if it needs to be expired,
4221          * or if we want to idle in case it has no pending requests.
4222          */
4223         if (cfqd->active_queue == cfqq) {
4224                 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
4225 
4226                 if (cfq_cfqq_slice_new(cfqq)) {
4227                         cfq_set_prio_slice(cfqd, cfqq);
4228                         cfq_clear_cfqq_slice_new(cfqq);
4229                 }
4230 
4231                 /*
4232                  * Should we wait for next request to come in before we expire
4233                  * the queue.
4234                  */
4235                 if (cfq_should_wait_busy(cfqd, cfqq)) {
4236                         unsigned long extend_sl = cfqd->cfq_slice_idle;
4237                         if (!cfqd->cfq_slice_idle)
4238                                 extend_sl = cfqd->cfq_group_idle;
4239                         cfqq->slice_end = jiffies + extend_sl;
4240                         cfq_mark_cfqq_wait_busy(cfqq);
4241                         cfq_log_cfqq(cfqd, cfqq, "will busy wait");
4242                 }
4243 
4244                 /*
4245                  * Idling is not enabled on:
4246                  * - expired queues
4247                  * - idle-priority queues
4248                  * - async queues
4249                  * - queues with still some requests queued
4250                  * - when there is a close cooperator
4251                  */
4252                 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
4253                         cfq_slice_expired(cfqd, 1);
4254                 else if (sync && cfqq_empty &&
4255                          !cfq_close_cooperator(cfqd, cfqq)) {
4256                         cfq_arm_slice_timer(cfqd);
4257                 }
4258         }
4259 
4260         if (!cfqd->rq_in_driver)
4261                 cfq_schedule_dispatch(cfqd);
4262 }
4263 
4264 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
4265 {
4266         if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
4267                 cfq_mark_cfqq_must_alloc_slice(cfqq);
4268                 return ELV_MQUEUE_MUST;
4269         }
4270 
4271         return ELV_MQUEUE_MAY;
4272 }
4273 
4274 static int cfq_may_queue(struct request_queue *q, int rw)
4275 {
4276         struct cfq_data *cfqd = q->elevator->elevator_data;
4277         struct task_struct *tsk = current;
4278         struct cfq_io_cq *cic;
4279         struct cfq_queue *cfqq;
4280 
4281         /*
4282          * don't force setup of a queue from here, as a call to may_queue
4283          * does not necessarily imply that a request actually will be queued.
4284          * so just lookup a possibly existing queue, or return 'may queue'
4285          * if that fails
4286          */
4287         cic = cfq_cic_lookup(cfqd, tsk->io_context);
4288         if (!cic)
4289                 return ELV_MQUEUE_MAY;
4290 
4291         cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
4292         if (cfqq) {
4293                 cfq_init_prio_data(cfqq, cic);
4294 
4295                 return __cfq_may_queue(cfqq);
4296         }
4297 
4298         return ELV_MQUEUE_MAY;
4299 }
4300 
4301 /*
4302  * queue lock held here
4303  */
4304 static void cfq_put_request(struct request *rq)
4305 {
4306         struct cfq_queue *cfqq = RQ_CFQQ(rq);
4307 
4308         if (cfqq) {
4309                 const int rw = rq_data_dir(rq);
4310 
4311                 BUG_ON(!cfqq->allocated[rw]);
4312                 cfqq->allocated[rw]--;
4313 
4314                 /* Put down rq reference on cfqg */
4315                 cfqg_put(RQ_CFQG(rq));
4316                 rq->elv.priv[0] = NULL;
4317                 rq->elv.priv[1] = NULL;
4318 
4319                 cfq_put_queue(cfqq);
4320         }
4321 }
4322 
4323 static struct cfq_queue *
4324 cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_cq *cic,
4325                 struct cfq_queue *cfqq)
4326 {
4327         cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
4328         cic_set_cfqq(cic, cfqq->new_cfqq, 1);
4329         cfq_mark_cfqq_coop(cfqq->new_cfqq);
4330         cfq_put_queue(cfqq);
4331         return cic_to_cfqq(cic, 1);
4332 }
4333 
4334 /*
4335  * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
4336  * was the last process referring to said cfqq.
4337  */
4338 static struct cfq_queue *
4339 split_cfqq(struct cfq_io_cq *cic, struct cfq_queue *cfqq)
4340 {
4341         if (cfqq_process_refs(cfqq) == 1) {
4342                 cfqq->pid = current->pid;
4343                 cfq_clear_cfqq_coop(cfqq);
4344                 cfq_clear_cfqq_split_coop(cfqq);
4345                 return cfqq;
4346         }
4347 
4348         cic_set_cfqq(cic, NULL, 1);
4349 
4350         cfq_put_cooperator(cfqq);
4351 
4352         cfq_put_queue(cfqq);
4353         return NULL;
4354 }
4355 /*
4356  * Allocate cfq data structures associated with this request.
4357  */
4358 static int
4359 cfq_set_request(struct request_queue *q, struct request *rq, struct bio *bio,
4360                 gfp_t gfp_mask)
4361 {
4362         struct cfq_data *cfqd = q->elevator->elevator_data;
4363         struct cfq_io_cq *cic = icq_to_cic(rq->elv.icq);
4364         const int rw = rq_data_dir(rq);
4365         const bool is_sync = rq_is_sync(rq);
4366         struct cfq_queue *cfqq;
4367 
4368         spin_lock_irq(q->queue_lock);
4369 
4370         check_ioprio_changed(cic, bio);
4371         check_blkcg_changed(cic, bio);
4372 new_queue:
4373         cfqq = cic_to_cfqq(cic, is_sync);
4374         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
4375                 if (cfqq)
4376                         cfq_put_queue(cfqq);
4377                 cfqq = cfq_get_queue(cfqd, is_sync, cic, bio);
4378                 cic_set_cfqq(cic, cfqq, is_sync);
4379         } else {
4380                 /*
4381                  * If the queue was seeky for too long, break it apart.
4382                  */
4383                 if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) {
4384                         cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
4385                         cfqq = split_cfqq(cic, cfqq);
4386                         if (!cfqq)
4387                                 goto new_queue;
4388                 }
4389 
4390                 /*
4391                  * Check to see if this queue is scheduled to merge with
4392                  * another, closely cooperating queue.  The merging of
4393                  * queues happens here as it must be done in process context.
4394                  * The reference on new_cfqq was taken in merge_cfqqs.
4395                  */
4396                 if (cfqq->new_cfqq)
4397                         cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
4398         }
4399 
4400         cfqq->allocated[rw]++;
4401 
4402         cfqq->ref++;
4403         cfqg_get(cfqq->cfqg);
4404         rq->elv.priv[0] = cfqq;
4405         rq->elv.priv[1] = cfqq->cfqg;
4406         spin_unlock_irq(q->queue_lock);
4407         return 0;
4408 }
4409 
4410 static void cfq_kick_queue(struct work_struct *work)
4411 {
4412         struct cfq_data *cfqd =
4413                 container_of(work, struct cfq_data, unplug_work);
4414         struct request_queue *q = cfqd->queue;
4415 
4416         spin_lock_irq(q->queue_lock);
4417         __blk_run_queue(cfqd->queue);
4418         spin_unlock_irq(q->queue_lock);
4419 }
4420 
4421 /*
4422  * Timer running if the active_queue is currently idling inside its time slice
4423  */
4424 static void cfq_idle_slice_timer(unsigned long data)
4425 {
4426         struct cfq_data *cfqd = (struct cfq_data *) data;
4427         struct cfq_queue *cfqq;
4428         unsigned long flags;
4429         int timed_out = 1;
4430 
4431         cfq_log(cfqd, "idle timer fired");
4432 
4433         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
4434 
4435         cfqq = cfqd->active_queue;
4436         if (cfqq) {
4437                 timed_out = 0;
4438 
4439                 /*
4440                  * We saw a request before the queue expired, let it through
4441                  */
4442                 if (cfq_cfqq_must_dispatch(cfqq))
4443                         goto out_kick;
4444 
4445                 /*
4446                  * expired
4447                  */
4448                 if (cfq_slice_used(cfqq))
4449                         goto expire;
4450 
4451                 /*
4452                  * only expire and reinvoke request handler, if there are
4453                  * other queues with pending requests
4454                  */
4455                 if (!cfqd->busy_queues)
4456                         goto out_cont;
4457 
4458                 /*
4459                  * not expired and it has a request pending, let it dispatch
4460                  */
4461                 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
4462                         goto out_kick;
4463 
4464                 /*
4465                  * Queue depth flag is reset only when the idle didn't succeed
4466                  */
4467                 cfq_clear_cfqq_deep(cfqq);
4468         }
4469 expire:
4470         cfq_slice_expired(cfqd, timed_out);
4471 out_kick:
4472         cfq_schedule_dispatch(cfqd);
4473 out_cont:
4474         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
4475 }
4476 
4477 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
4478 {
4479         del_timer_sync(&cfqd->idle_slice_timer);
4480         cancel_work_sync(&cfqd->unplug_work);
4481 }
4482 
4483 static void cfq_exit_queue(struct elevator_queue *e)
4484 {
4485         struct cfq_data *cfqd = e->elevator_data;
4486         struct request_queue *q = cfqd->queue;
4487 
4488         cfq_shutdown_timer_wq(cfqd);
4489 
4490         spin_lock_irq(q->queue_lock);
4491 
4492         if (cfqd->active_queue)
4493                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
4494 
4495         spin_unlock_irq(q->queue_lock);
4496 
4497         cfq_shutdown_timer_wq(cfqd);
4498 
4499 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4500         blkcg_deactivate_policy(q, &blkcg_policy_cfq);
4501 #else
4502         kfree(cfqd->root_group);
4503 #endif
4504         kfree(cfqd);
4505 }
4506 
4507 static int cfq_init_queue(struct request_queue *q, struct elevator_type *e)
4508 {
4509         struct cfq_data *cfqd;
4510         struct blkcg_gq *blkg __maybe_unused;
4511         int i, ret;
4512         struct elevator_queue *eq;
4513 
4514         eq = elevator_alloc(q, e);
4515         if (!eq)
4516                 return -ENOMEM;
4517 
4518         cfqd = kzalloc_node(sizeof(*cfqd), GFP_KERNEL, q->node);
4519         if (!cfqd) {
4520                 kobject_put(&eq->kobj);
4521                 return -ENOMEM;
4522         }
4523         eq->elevator_data = cfqd;
4524 
4525         cfqd->queue = q;
4526         spin_lock_irq(q->queue_lock);
4527         q->elevator = eq;
4528         spin_unlock_irq(q->queue_lock);
4529 
4530         /* Init root service tree */
4531         cfqd->grp_service_tree = CFQ_RB_ROOT;
4532 
4533         /* Init root group and prefer root group over other groups by default */
4534 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4535         ret = blkcg_activate_policy(q, &blkcg_policy_cfq);
4536         if (ret)
4537                 goto out_free;
4538 
4539         cfqd->root_group = blkg_to_cfqg(q->root_blkg);
4540 #else
4541         ret = -ENOMEM;
4542         cfqd->root_group = kzalloc_node(sizeof(*cfqd->root_group),
4543                                         GFP_KERNEL, cfqd->queue->node);
4544         if (!cfqd->root_group)
4545                 goto out_free;
4546 
4547         cfq_init_cfqg_base(cfqd->root_group);
4548         cfqd->root_group->weight = 2 * CFQ_WEIGHT_LEGACY_DFL;
4549         cfqd->root_group->leaf_weight = 2 * CFQ_WEIGHT_LEGACY_DFL;
4550 #endif
4551 
4552         /*
4553          * Not strictly needed (since RB_ROOT just clears the node and we
4554          * zeroed cfqd on alloc), but better be safe in case someone decides
4555          * to add magic to the rb code
4556          */
4557         for (i = 0; i < CFQ_PRIO_LISTS; i++)
4558                 cfqd->prio_trees[i] = RB_ROOT;
4559 
4560         /*
4561          * Our fallback cfqq if cfq_get_queue() runs into OOM issues.
4562          * Grab a permanent reference to it, so that the normal code flow
4563          * will not attempt to free it.  oom_cfqq is linked to root_group
4564          * but shouldn't hold a reference as it'll never be unlinked.  Lose
4565          * the reference from linking right away.
4566          */
4567         cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
4568         cfqd->oom_cfqq.ref++;
4569 
4570         spin_lock_irq(q->queue_lock);
4571         cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, cfqd->root_group);
4572         cfqg_put(cfqd->root_group);
4573         spin_unlock_irq(q->queue_lock);
4574 
4575         init_timer(&cfqd->idle_slice_timer);
4576         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
4577         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
4578 
4579         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
4580 
4581         cfqd->cfq_quantum = cfq_quantum;
4582         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
4583         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
4584         cfqd->cfq_back_max = cfq_back_max;
4585         cfqd->cfq_back_penalty = cfq_back_penalty;
4586         cfqd->cfq_slice[0] = cfq_slice_async;
4587         cfqd->cfq_slice[1] = cfq_slice_sync;
4588         cfqd->cfq_target_latency = cfq_target_latency;
4589         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
4590         cfqd->cfq_slice_idle = cfq_slice_idle;
4591         cfqd->cfq_group_idle = cfq_group_idle;
4592         cfqd->cfq_latency = 1;
4593         cfqd->hw_tag = -1;
4594         /*
4595          * we optimistically start assuming sync ops weren't delayed in last
4596          * second, in order to have larger depth for async operations.
4597          */
4598         cfqd->last_delayed_sync = jiffies - HZ;
4599         return 0;
4600 
4601 out_free:
4602         kfree(cfqd);
4603         kobject_put(&eq->kobj);
4604         return ret;
4605 }
4606 
4607 static void cfq_registered_queue(struct request_queue *q)
4608 {
4609         struct elevator_queue *e = q->elevator;
4610         struct cfq_data *cfqd = e->elevator_data;
4611 
4612         /*
4613          * Default to IOPS mode with no idling for SSDs
4614          */
4615         if (blk_queue_nonrot(q))
4616                 cfqd->cfq_slice_idle = 0;
4617 }
4618 
4619 /*
4620  * sysfs parts below -->
4621  */
4622 static ssize_t
4623 cfq_var_show(unsigned int var, char *page)
4624 {
4625         return sprintf(page, "%u\n", var);
4626 }
4627 
4628 static ssize_t
4629 cfq_var_store(unsigned int *var, const char *page, size_t count)
4630 {
4631         char *p = (char *) page;
4632 
4633         *var = simple_strtoul(p, &p, 10);
4634         return count;
4635 }
4636 
4637 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
4638 static ssize_t __FUNC(struct elevator_queue *e, char *page)             \
4639 {                                                                       \
4640         struct cfq_data *cfqd = e->elevator_data;                       \
4641         unsigned int __data = __VAR;                                    \
4642         if (__CONV)                                                     \
4643                 __data = jiffies_to_msecs(__data);                      \
4644         return cfq_var_show(__data, (page));                            \
4645 }
4646 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
4647 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
4648 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
4649 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
4650 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
4651 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
4652 SHOW_FUNCTION(cfq_group_idle_show, cfqd->cfq_group_idle, 1);
4653 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
4654 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
4655 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
4656 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
4657 SHOW_FUNCTION(cfq_target_latency_show, cfqd->cfq_target_latency, 1);
4658 #undef SHOW_FUNCTION
4659 
4660 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
4661 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
4662 {                                                                       \
4663         struct cfq_data *cfqd = e->elevator_data;                       \
4664         unsigned int __data;                                            \
4665         int ret = cfq_var_store(&__data, (page), count);                \
4666         if (__data < (MIN))                                             \
4667                 __data = (MIN);                                         \
4668         else if (__data > (MAX))                                        \
4669                 __data = (MAX);                                         \
4670         if (__CONV)                                                     \
4671                 *(__PTR) = msecs_to_jiffies(__data);                    \
4672         else                                                            \
4673                 *(__PTR) = __data;                                      \
4674         return ret;                                                     \
4675 }
4676 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
4677 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
4678                 UINT_MAX, 1);
4679 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
4680                 UINT_MAX, 1);
4681 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
4682 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
4683                 UINT_MAX, 0);
4684 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
4685 STORE_FUNCTION(cfq_group_idle_store, &cfqd->cfq_group_idle, 0, UINT_MAX, 1);
4686 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
4687 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
4688 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
4689                 UINT_MAX, 0);
4690 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
4691 STORE_FUNCTION(cfq_target_latency_store, &cfqd->cfq_target_latency, 1, UINT_MAX, 1);
4692 #undef STORE_FUNCTION
4693 
4694 #define CFQ_ATTR(name) \
4695         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
4696 
4697 static struct elv_fs_entry cfq_attrs[] = {
4698         CFQ_ATTR(quantum),
4699         CFQ_ATTR(fifo_expire_sync),
4700         CFQ_ATTR(fifo_expire_async),
4701         CFQ_ATTR(back_seek_max),
4702         CFQ_ATTR(back_seek_penalty),
4703         CFQ_ATTR(slice_sync),
4704         CFQ_ATTR(slice_async),
4705         CFQ_ATTR(slice_async_rq),
4706         CFQ_ATTR(slice_idle),
4707         CFQ_ATTR(group_idle),
4708         CFQ_ATTR(low_latency),
4709         CFQ_ATTR(target_latency),
4710         __ATTR_NULL
4711 };
4712 
4713 static struct elevator_type iosched_cfq = {
4714         .ops = {
4715                 .elevator_merge_fn =            cfq_merge,
4716                 .elevator_merged_fn =           cfq_merged_request,
4717                 .elevator_merge_req_fn =        cfq_merged_requests,
4718                 .elevator_allow_merge_fn =      cfq_allow_merge,
4719                 .elevator_bio_merged_fn =       cfq_bio_merged,
4720                 .elevator_dispatch_fn =         cfq_dispatch_requests,
4721                 .elevator_add_req_fn =          cfq_insert_request,
4722                 .elevator_activate_req_fn =     cfq_activate_request,
4723                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
4724                 .elevator_completed_req_fn =    cfq_completed_request,
4725                 .elevator_former_req_fn =       elv_rb_former_request,
4726                 .elevator_latter_req_fn =       elv_rb_latter_request,
4727                 .elevator_init_icq_fn =         cfq_init_icq,
4728                 .elevator_exit_icq_fn =         cfq_exit_icq,
4729                 .elevator_set_req_fn =          cfq_set_request,
4730                 .elevator_put_req_fn =          cfq_put_request,
4731                 .elevator_may_queue_fn =        cfq_may_queue,
4732                 .elevator_init_fn =             cfq_init_queue,
4733                 .elevator_exit_fn =             cfq_exit_queue,
4734                 .elevator_registered_fn =       cfq_registered_queue,
4735         },
4736         .icq_size       =       sizeof(struct cfq_io_cq),
4737         .icq_align      =       __alignof__(struct cfq_io_cq),
4738         .elevator_attrs =       cfq_attrs,
4739         .elevator_name  =       "cfq",
4740         .elevator_owner =       THIS_MODULE,
4741 };
4742 
4743 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4744 static struct blkcg_policy blkcg_policy_cfq = {
4745         .dfl_cftypes            = cfq_blkcg_files,
4746         .legacy_cftypes         = cfq_blkcg_legacy_files,
4747 
4748         .cpd_alloc_fn           = cfq_cpd_alloc,
4749         .cpd_init_fn            = cfq_cpd_init,
4750         .cpd_free_fn            = cfq_cpd_free,
4751         .cpd_bind_fn            = cfq_cpd_bind,
4752 
4753         .pd_alloc_fn            = cfq_pd_alloc,
4754         .pd_init_fn             = cfq_pd_init,
4755         .pd_offline_fn          = cfq_pd_offline,
4756         .pd_free_fn             = cfq_pd_free,
4757         .pd_reset_stats_fn      = cfq_pd_reset_stats,
4758 };
4759 #endif
4760 
4761 static int __init cfq_init(void)
4762 {
4763         int ret;
4764 
4765         /*
4766          * could be 0 on HZ < 1000 setups
4767          */
4768         if (!cfq_slice_async)
4769                 cfq_slice_async = 1;
4770         if (!cfq_slice_idle)
4771                 cfq_slice_idle = 1;
4772 
4773 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4774         if (!cfq_group_idle)
4775                 cfq_group_idle = 1;
4776 
4777         ret = blkcg_policy_register(&blkcg_policy_cfq);
4778         if (ret)
4779                 return ret;
4780 #else
4781         cfq_group_idle = 0;
4782 #endif
4783 
4784         ret = -ENOMEM;
4785         cfq_pool = KMEM_CACHE(cfq_queue, 0);
4786         if (!cfq_pool)
4787                 goto err_pol_unreg;
4788 
4789         ret = elv_register(&iosched_cfq);
4790         if (ret)
4791                 goto err_free_pool;
4792 
4793         return 0;
4794 
4795 err_free_pool:
4796         kmem_cache_destroy(cfq_pool);
4797 err_pol_unreg:
4798 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4799         blkcg_policy_unregister(&blkcg_policy_cfq);
4800 #endif
4801         return ret;
4802 }
4803 
4804 static void __exit cfq_exit(void)
4805 {
4806 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4807         blkcg_policy_unregister(&blkcg_policy_cfq);
4808 #endif
4809         elv_unregister(&iosched_cfq);
4810         kmem_cache_destroy(cfq_pool);
4811 }
4812 
4813 module_init(cfq_init);
4814 module_exit(cfq_exit);
4815 
4816 MODULE_AUTHOR("Jens Axboe");
4817 MODULE_LICENSE("GPL");
4818 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");
4819 

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