Root/block/cfq-iosched.c

1/*
2 * CFQ, or complete fairness queueing, disk scheduler.
3 *
4 * Based on ideas from a previously unfinished io
5 * scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
6 *
7 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
8 */
9#include <linux/module.h>
10#include <linux/slab.h>
11#include <linux/blkdev.h>
12#include <linux/elevator.h>
13#include <linux/jiffies.h>
14#include <linux/rbtree.h>
15#include <linux/ioprio.h>
16#include <linux/blktrace_api.h>
17#include "blk.h"
18#include "blk-cgroup.h"
19
20/*
21 * tunables
22 */
23/* max queue in one round of service */
24static const int cfq_quantum = 8;
25static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
26/* maximum backwards seek, in KiB */
27static const int cfq_back_max = 16 * 1024;
28/* penalty of a backwards seek */
29static const int cfq_back_penalty = 2;
30static const int cfq_slice_sync = HZ / 10;
31static int cfq_slice_async = HZ / 25;
32static const int cfq_slice_async_rq = 2;
33static int cfq_slice_idle = HZ / 125;
34static int cfq_group_idle = HZ / 125;
35static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
36static 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
61static 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
70struct cfq_ttime {
71    unsigned long last_end_request;
72
73    unsigned long ttime_total;
74    unsigned long ttime_samples;
75    unsigned long ttime_mean;
76};
77
78/*
79 * Most of our rbtree usage is for sorting with min extraction, so
80 * if we cache the leftmost node we don't have to walk down the tree
81 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
82 * move this into the elevator for the rq sorting as well.
83 */
84struct cfq_rb_root {
85    struct rb_root rb;
86    struct rb_node *left;
87    unsigned count;
88    u64 min_vdisktime;
89    struct cfq_ttime ttime;
90};
91#define CFQ_RB_ROOT (struct cfq_rb_root) { .rb = RB_ROOT, \
92            .ttime = {.last_end_request = jiffies,},}
93
94/*
95 * Per process-grouping structure
96 */
97struct cfq_queue {
98    /* reference count */
99    int ref;
100    /* various state flags, see below */
101    unsigned int flags;
102    /* parent cfq_data */
103    struct cfq_data *cfqd;
104    /* service_tree member */
105    struct rb_node rb_node;
106    /* service_tree key */
107    unsigned long rb_key;
108    /* prio tree member */
109    struct rb_node p_node;
110    /* prio tree root we belong to, if any */
111    struct rb_root *p_root;
112    /* sorted list of pending requests */
113    struct rb_root sort_list;
114    /* if fifo isn't expired, next request to serve */
115    struct request *next_rq;
116    /* requests queued in sort_list */
117    int queued[2];
118    /* currently allocated requests */
119    int allocated[2];
120    /* fifo list of requests in sort_list */
121    struct list_head fifo;
122
123    /* time when queue got scheduled in to dispatch first request. */
124    unsigned long dispatch_start;
125    unsigned int allocated_slice;
126    unsigned int slice_dispatch;
127    /* time when first request from queue completed and slice started. */
128    unsigned long slice_start;
129    unsigned long slice_end;
130    long slice_resid;
131
132    /* pending priority requests */
133    int prio_pending;
134    /* number of requests that are on the dispatch list or inside driver */
135    int dispatched;
136
137    /* io prio of this group */
138    unsigned short ioprio, org_ioprio;
139    unsigned short ioprio_class;
140
141    pid_t pid;
142
143    u32 seek_history;
144    sector_t last_request_pos;
145
146    struct cfq_rb_root *service_tree;
147    struct cfq_queue *new_cfqq;
148    struct cfq_group *cfqg;
149    /* Number of sectors dispatched from queue in single dispatch round */
150    unsigned long nr_sectors;
151};
152
153/*
154 * First index in the service_trees.
155 * IDLE is handled separately, so it has negative index
156 */
157enum wl_class_t {
158    BE_WORKLOAD = 0,
159    RT_WORKLOAD = 1,
160    IDLE_WORKLOAD = 2,
161    CFQ_PRIO_NR,
162};
163
164/*
165 * Second index in the service_trees.
166 */
167enum wl_type_t {
168    ASYNC_WORKLOAD = 0,
169    SYNC_NOIDLE_WORKLOAD = 1,
170    SYNC_WORKLOAD = 2
171};
172
173struct cfqg_stats {
174#ifdef CONFIG_CFQ_GROUP_IOSCHED
175    /* total bytes transferred */
176    struct blkg_rwstat service_bytes;
177    /* total IOs serviced, post merge */
178    struct blkg_rwstat serviced;
179    /* number of ios merged */
180    struct blkg_rwstat merged;
181    /* total time spent on device in ns, may not be accurate w/ queueing */
182    struct blkg_rwstat service_time;
183    /* total time spent waiting in scheduler queue in ns */
184    struct blkg_rwstat wait_time;
185    /* number of IOs queued up */
186    struct blkg_rwstat queued;
187    /* total sectors transferred */
188    struct blkg_stat sectors;
189    /* total disk time and nr sectors dispatched by this group */
190    struct blkg_stat time;
191#ifdef CONFIG_DEBUG_BLK_CGROUP
192    /* time not charged to this cgroup */
193    struct blkg_stat unaccounted_time;
194    /* sum of number of ios queued across all samples */
195    struct blkg_stat avg_queue_size_sum;
196    /* count of samples taken for average */
197    struct blkg_stat avg_queue_size_samples;
198    /* how many times this group has been removed from service tree */
199    struct blkg_stat dequeue;
200    /* total time spent waiting for it to be assigned a timeslice. */
201    struct blkg_stat group_wait_time;
202    /* time spent idling for this blkcg_gq */
203    struct blkg_stat idle_time;
204    /* total time with empty current active q with other requests queued */
205    struct blkg_stat empty_time;
206    /* fields after this shouldn't be cleared on stat reset */
207    uint64_t start_group_wait_time;
208    uint64_t start_idle_time;
209    uint64_t start_empty_time;
210    uint16_t flags;
211#endif /* CONFIG_DEBUG_BLK_CGROUP */
212#endif /* CONFIG_CFQ_GROUP_IOSCHED */
213};
214
215/* This is per cgroup per device grouping structure */
216struct cfq_group {
217    /* must be the first member */
218    struct blkg_policy_data pd;
219
220    /* group service_tree member */
221    struct rb_node rb_node;
222
223    /* group service_tree key */
224    u64 vdisktime;
225
226    /*
227     * The number of active cfqgs and sum of their weights under this
228     * cfqg. This covers this cfqg's leaf_weight and all children's
229     * weights, but does not cover weights of further descendants.
230     *
231     * If a cfqg is on the service tree, it's active. An active cfqg
232     * also activates its parent and contributes to the children_weight
233     * of the parent.
234     */
235    int nr_active;
236    unsigned int children_weight;
237
238    /*
239     * vfraction is the fraction of vdisktime that the tasks in this
240     * cfqg are entitled to. This is determined by compounding the
241     * ratios walking up from this cfqg to the root.
242     *
243     * It is in fixed point w/ CFQ_SERVICE_SHIFT and the sum of all
244     * vfractions on a service tree is approximately 1. The sum may
245     * deviate a bit due to rounding errors and fluctuations caused by
246     * cfqgs entering and leaving the service tree.
247     */
248    unsigned int vfraction;
249
250    /*
251     * There are two weights - (internal) weight is the weight of this
252     * cfqg against the sibling cfqgs. leaf_weight is the wight of
253     * this cfqg against the child cfqgs. For the root cfqg, both
254     * weights are kept in sync for backward compatibility.
255     */
256    unsigned int weight;
257    unsigned int new_weight;
258    unsigned int dev_weight;
259
260    unsigned int leaf_weight;
261    unsigned int new_leaf_weight;
262    unsigned int dev_leaf_weight;
263
264    /* number of cfqq currently on this group */
265    int nr_cfqq;
266
267    /*
268     * Per group busy queues average. Useful for workload slice calc. We
269     * create the array for each prio class but at run time it is used
270     * only for RT and BE class and slot for IDLE class remains unused.
271     * This is primarily done to avoid confusion and a gcc warning.
272     */
273    unsigned int busy_queues_avg[CFQ_PRIO_NR];
274    /*
275     * rr lists of queues with requests. We maintain service trees for
276     * RT and BE classes. These trees are subdivided in subclasses
277     * of SYNC, SYNC_NOIDLE and ASYNC based on workload type. For IDLE
278     * class there is no subclassification and all the cfq queues go on
279     * a single tree service_tree_idle.
280     * Counts are embedded in the cfq_rb_root
281     */
282    struct cfq_rb_root service_trees[2][3];
283    struct cfq_rb_root service_tree_idle;
284
285    unsigned long saved_wl_slice;
286    enum wl_type_t saved_wl_type;
287    enum wl_class_t saved_wl_class;
288
289    /* number of requests that are on the dispatch list or inside driver */
290    int dispatched;
291    struct cfq_ttime ttime;
292    struct cfqg_stats stats; /* stats for this cfqg */
293    struct cfqg_stats dead_stats; /* stats pushed from dead children */
294};
295
296struct cfq_io_cq {
297    struct io_cq icq; /* must be the first member */
298    struct cfq_queue *cfqq[2];
299    struct cfq_ttime ttime;
300    int ioprio; /* the current ioprio */
301#ifdef CONFIG_CFQ_GROUP_IOSCHED
302    uint64_t blkcg_id; /* the current blkcg ID */
303#endif
304};
305
306/*
307 * Per block device queue structure
308 */
309struct cfq_data {
310    struct request_queue *queue;
311    /* Root service tree for cfq_groups */
312    struct cfq_rb_root grp_service_tree;
313    struct cfq_group *root_group;
314
315    /*
316     * The priority currently being served
317     */
318    enum wl_class_t serving_wl_class;
319    enum wl_type_t serving_wl_type;
320    unsigned long workload_expires;
321    struct cfq_group *serving_group;
322
323    /*
324     * Each priority tree is sorted by next_request position. These
325     * trees are used when determining if two or more queues are
326     * interleaving requests (see cfq_close_cooperator).
327     */
328    struct rb_root prio_trees[CFQ_PRIO_LISTS];
329
330    unsigned int busy_queues;
331    unsigned int busy_sync_queues;
332
333    int rq_in_driver;
334    int rq_in_flight[2];
335
336    /*
337     * queue-depth detection
338     */
339    int rq_queued;
340    int hw_tag;
341    /*
342     * hw_tag can be
343     * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
344     * 1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
345     * 0 => no NCQ
346     */
347    int hw_tag_est_depth;
348    unsigned int hw_tag_samples;
349
350    /*
351     * idle window management
352     */
353    struct timer_list idle_slice_timer;
354    struct work_struct unplug_work;
355
356    struct cfq_queue *active_queue;
357    struct cfq_io_cq *active_cic;
358
359    /*
360     * async queue for each priority case
361     */
362    struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
363    struct cfq_queue *async_idle_cfqq;
364
365    sector_t last_position;
366
367    /*
368     * tunables, see top of file
369     */
370    unsigned int cfq_quantum;
371    unsigned int cfq_fifo_expire[2];
372    unsigned int cfq_back_penalty;
373    unsigned int cfq_back_max;
374    unsigned int cfq_slice[2];
375    unsigned int cfq_slice_async_rq;
376    unsigned int cfq_slice_idle;
377    unsigned int cfq_group_idle;
378    unsigned int cfq_latency;
379    unsigned int cfq_target_latency;
380
381    /*
382     * Fallback dummy cfqq for extreme OOM conditions
383     */
384    struct cfq_queue oom_cfqq;
385
386    unsigned long last_delayed_sync;
387};
388
389static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
390
391static struct cfq_rb_root *st_for(struct cfq_group *cfqg,
392                        enum wl_class_t class,
393                        enum wl_type_t type)
394{
395    if (!cfqg)
396        return NULL;
397
398    if (class == IDLE_WORKLOAD)
399        return &cfqg->service_tree_idle;
400
401    return &cfqg->service_trees[class][type];
402}
403
404enum cfqq_state_flags {
405    CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
406    CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
407    CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */
408    CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
409    CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
410    CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
411    CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
412    CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
413    CFQ_CFQQ_FLAG_sync, /* synchronous queue */
414    CFQ_CFQQ_FLAG_coop, /* cfqq is shared */
415    CFQ_CFQQ_FLAG_split_coop, /* shared cfqq will be splitted */
416    CFQ_CFQQ_FLAG_deep, /* sync cfqq experienced large depth */
417    CFQ_CFQQ_FLAG_wait_busy, /* Waiting for next request */
418};
419
420#define CFQ_CFQQ_FNS(name) \
421static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
422{ \
423    (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
424} \
425static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
426{ \
427    (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
428} \
429static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
430{ \
431    return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
432}
433
434CFQ_CFQQ_FNS(on_rr);
435CFQ_CFQQ_FNS(wait_request);
436CFQ_CFQQ_FNS(must_dispatch);
437CFQ_CFQQ_FNS(must_alloc_slice);
438CFQ_CFQQ_FNS(fifo_expire);
439CFQ_CFQQ_FNS(idle_window);
440CFQ_CFQQ_FNS(prio_changed);
441CFQ_CFQQ_FNS(slice_new);
442CFQ_CFQQ_FNS(sync);
443CFQ_CFQQ_FNS(coop);
444CFQ_CFQQ_FNS(split_coop);
445CFQ_CFQQ_FNS(deep);
446CFQ_CFQQ_FNS(wait_busy);
447#undef CFQ_CFQQ_FNS
448
449static inline struct cfq_group *pd_to_cfqg(struct blkg_policy_data *pd)
450{
451    return pd ? container_of(pd, struct cfq_group, pd) : NULL;
452}
453
454static inline struct blkcg_gq *cfqg_to_blkg(struct cfq_group *cfqg)
455{
456    return pd_to_blkg(&cfqg->pd);
457}
458
459#if defined(CONFIG_CFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
460
461/* cfqg stats flags */
462enum cfqg_stats_flags {
463    CFQG_stats_waiting = 0,
464    CFQG_stats_idling,
465    CFQG_stats_empty,
466};
467
468#define CFQG_FLAG_FNS(name) \
469static inline void cfqg_stats_mark_##name(struct cfqg_stats *stats) \
470{ \
471    stats->flags |= (1 << CFQG_stats_##name); \
472} \
473static inline void cfqg_stats_clear_##name(struct cfqg_stats *stats) \
474{ \
475    stats->flags &= ~(1 << CFQG_stats_##name); \
476} \
477static inline int cfqg_stats_##name(struct cfqg_stats *stats) \
478{ \
479    return (stats->flags & (1 << CFQG_stats_##name)) != 0; \
480} \
481
482CFQG_FLAG_FNS(waiting)
483CFQG_FLAG_FNS(idling)
484CFQG_FLAG_FNS(empty)
485#undef CFQG_FLAG_FNS
486
487/* This should be called with the queue_lock held. */
488static void cfqg_stats_update_group_wait_time(struct cfqg_stats *stats)
489{
490    unsigned long long now;
491
492    if (!cfqg_stats_waiting(stats))
493        return;
494
495    now = sched_clock();
496    if (time_after64(now, stats->start_group_wait_time))
497        blkg_stat_add(&stats->group_wait_time,
498                  now - stats->start_group_wait_time);
499    cfqg_stats_clear_waiting(stats);
500}
501
502/* This should be called with the queue_lock held. */
503static void cfqg_stats_set_start_group_wait_time(struct cfq_group *cfqg,
504                         struct cfq_group *curr_cfqg)
505{
506    struct cfqg_stats *stats = &cfqg->stats;
507
508    if (cfqg_stats_waiting(stats))
509        return;
510    if (cfqg == curr_cfqg)
511        return;
512    stats->start_group_wait_time = sched_clock();
513    cfqg_stats_mark_waiting(stats);
514}
515
516/* This should be called with the queue_lock held. */
517static void cfqg_stats_end_empty_time(struct cfqg_stats *stats)
518{
519    unsigned long long now;
520
521    if (!cfqg_stats_empty(stats))
522        return;
523
524    now = sched_clock();
525    if (time_after64(now, stats->start_empty_time))
526        blkg_stat_add(&stats->empty_time,
527                  now - stats->start_empty_time);
528    cfqg_stats_clear_empty(stats);
529}
530
531static void cfqg_stats_update_dequeue(struct cfq_group *cfqg)
532{
533    blkg_stat_add(&cfqg->stats.dequeue, 1);
534}
535
536static void cfqg_stats_set_start_empty_time(struct cfq_group *cfqg)
537{
538    struct cfqg_stats *stats = &cfqg->stats;
539
540    if (blkg_rwstat_total(&stats->queued))
541        return;
542
543    /*
544     * group is already marked empty. This can happen if cfqq got new
545     * request in parent group and moved to this group while being added
546     * to service tree. Just ignore the event and move on.
547     */
548    if (cfqg_stats_empty(stats))
549        return;
550
551    stats->start_empty_time = sched_clock();
552    cfqg_stats_mark_empty(stats);
553}
554
555static void cfqg_stats_update_idle_time(struct cfq_group *cfqg)
556{
557    struct cfqg_stats *stats = &cfqg->stats;
558
559    if (cfqg_stats_idling(stats)) {
560        unsigned long long now = sched_clock();
561
562        if (time_after64(now, stats->start_idle_time))
563            blkg_stat_add(&stats->idle_time,
564                      now - stats->start_idle_time);
565        cfqg_stats_clear_idling(stats);
566    }
567}
568
569static void cfqg_stats_set_start_idle_time(struct cfq_group *cfqg)
570{
571    struct cfqg_stats *stats = &cfqg->stats;
572
573    BUG_ON(cfqg_stats_idling(stats));
574
575    stats->start_idle_time = sched_clock();
576    cfqg_stats_mark_idling(stats);
577}
578
579static void cfqg_stats_update_avg_queue_size(struct cfq_group *cfqg)
580{
581    struct cfqg_stats *stats = &cfqg->stats;
582
583    blkg_stat_add(&stats->avg_queue_size_sum,
584              blkg_rwstat_total(&stats->queued));
585    blkg_stat_add(&stats->avg_queue_size_samples, 1);
586    cfqg_stats_update_group_wait_time(stats);
587}
588
589#else /* CONFIG_CFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
590
591static inline void cfqg_stats_set_start_group_wait_time(struct cfq_group *cfqg, struct cfq_group *curr_cfqg) { }
592static inline void cfqg_stats_end_empty_time(struct cfqg_stats *stats) { }
593static inline void cfqg_stats_update_dequeue(struct cfq_group *cfqg) { }
594static inline void cfqg_stats_set_start_empty_time(struct cfq_group *cfqg) { }
595static inline void cfqg_stats_update_idle_time(struct cfq_group *cfqg) { }
596static inline void cfqg_stats_set_start_idle_time(struct cfq_group *cfqg) { }
597static inline void cfqg_stats_update_avg_queue_size(struct cfq_group *cfqg) { }
598
599#endif /* CONFIG_CFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
600
601#ifdef CONFIG_CFQ_GROUP_IOSCHED
602
603static struct blkcg_policy blkcg_policy_cfq;
604
605static inline struct cfq_group *blkg_to_cfqg(struct blkcg_gq *blkg)
606{
607    return pd_to_cfqg(blkg_to_pd(blkg, &blkcg_policy_cfq));
608}
609
610static inline struct cfq_group *cfqg_parent(struct cfq_group *cfqg)
611{
612    struct blkcg_gq *pblkg = cfqg_to_blkg(cfqg)->parent;
613
614    return pblkg ? blkg_to_cfqg(pblkg) : NULL;
615}
616
617static inline void cfqg_get(struct cfq_group *cfqg)
618{
619    return blkg_get(cfqg_to_blkg(cfqg));
620}
621
622static inline void cfqg_put(struct cfq_group *cfqg)
623{
624    return blkg_put(cfqg_to_blkg(cfqg));
625}
626
627#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) do { \
628    char __pbuf[128]; \
629                                    \
630    blkg_path(cfqg_to_blkg((cfqq)->cfqg), __pbuf, sizeof(__pbuf)); \
631    blk_add_trace_msg((cfqd)->queue, "cfq%d%c%c %s " fmt, (cfqq)->pid, \
632            cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
633            cfqq_type((cfqq)) == SYNC_NOIDLE_WORKLOAD ? 'N' : ' ',\
634              __pbuf, ##args); \
635} while (0)
636
637#define cfq_log_cfqg(cfqd, cfqg, fmt, args...) do { \
638    char __pbuf[128]; \
639                                    \
640    blkg_path(cfqg_to_blkg(cfqg), __pbuf, sizeof(__pbuf)); \
641    blk_add_trace_msg((cfqd)->queue, "%s " fmt, __pbuf, ##args); \
642} while (0)
643
644static inline void cfqg_stats_update_io_add(struct cfq_group *cfqg,
645                        struct cfq_group *curr_cfqg, int rw)
646{
647    blkg_rwstat_add(&cfqg->stats.queued, rw, 1);
648    cfqg_stats_end_empty_time(&cfqg->stats);
649    cfqg_stats_set_start_group_wait_time(cfqg, curr_cfqg);
650}
651
652static inline void cfqg_stats_update_timeslice_used(struct cfq_group *cfqg,
653            unsigned long time, unsigned long unaccounted_time)
654{
655    blkg_stat_add(&cfqg->stats.time, time);
656#ifdef CONFIG_DEBUG_BLK_CGROUP
657    blkg_stat_add(&cfqg->stats.unaccounted_time, unaccounted_time);
658#endif
659}
660
661static inline void cfqg_stats_update_io_remove(struct cfq_group *cfqg, int rw)
662{
663    blkg_rwstat_add(&cfqg->stats.queued, rw, -1);
664}
665
666static inline void cfqg_stats_update_io_merged(struct cfq_group *cfqg, int rw)
667{
668    blkg_rwstat_add(&cfqg->stats.merged, rw, 1);
669}
670
671static inline void cfqg_stats_update_dispatch(struct cfq_group *cfqg,
672                          uint64_t bytes, int rw)
673{
674    blkg_stat_add(&cfqg->stats.sectors, bytes >> 9);
675    blkg_rwstat_add(&cfqg->stats.serviced, rw, 1);
676    blkg_rwstat_add(&cfqg->stats.service_bytes, rw, bytes);
677}
678
679static inline void cfqg_stats_update_completion(struct cfq_group *cfqg,
680            uint64_t start_time, uint64_t io_start_time, int rw)
681{
682    struct cfqg_stats *stats = &cfqg->stats;
683    unsigned long long now = sched_clock();
684
685    if (time_after64(now, io_start_time))
686        blkg_rwstat_add(&stats->service_time, rw, now - io_start_time);
687    if (time_after64(io_start_time, start_time))
688        blkg_rwstat_add(&stats->wait_time, rw,
689                io_start_time - start_time);
690}
691
692/* @stats = 0 */
693static void cfqg_stats_reset(struct cfqg_stats *stats)
694{
695    /* queued stats shouldn't be cleared */
696    blkg_rwstat_reset(&stats->service_bytes);
697    blkg_rwstat_reset(&stats->serviced);
698    blkg_rwstat_reset(&stats->merged);
699    blkg_rwstat_reset(&stats->service_time);
700    blkg_rwstat_reset(&stats->wait_time);
701    blkg_stat_reset(&stats->time);
702#ifdef CONFIG_DEBUG_BLK_CGROUP
703    blkg_stat_reset(&stats->unaccounted_time);
704    blkg_stat_reset(&stats->avg_queue_size_sum);
705    blkg_stat_reset(&stats->avg_queue_size_samples);
706    blkg_stat_reset(&stats->dequeue);
707    blkg_stat_reset(&stats->group_wait_time);
708    blkg_stat_reset(&stats->idle_time);
709    blkg_stat_reset(&stats->empty_time);
710#endif
711}
712
713/* @to += @from */
714static void cfqg_stats_merge(struct cfqg_stats *to, struct cfqg_stats *from)
715{
716    /* queued stats shouldn't be cleared */
717    blkg_rwstat_merge(&to->service_bytes, &from->service_bytes);
718    blkg_rwstat_merge(&to->serviced, &from->serviced);
719    blkg_rwstat_merge(&to->merged, &from->merged);
720    blkg_rwstat_merge(&to->service_time, &from->service_time);
721    blkg_rwstat_merge(&to->wait_time, &from->wait_time);
722    blkg_stat_merge(&from->time, &from->time);
723#ifdef CONFIG_DEBUG_BLK_CGROUP
724    blkg_stat_merge(&to->unaccounted_time, &from->unaccounted_time);
725    blkg_stat_merge(&to->avg_queue_size_sum, &from->avg_queue_size_sum);
726    blkg_stat_merge(&to->avg_queue_size_samples, &from->avg_queue_size_samples);
727    blkg_stat_merge(&to->dequeue, &from->dequeue);
728    blkg_stat_merge(&to->group_wait_time, &from->group_wait_time);
729    blkg_stat_merge(&to->idle_time, &from->idle_time);
730    blkg_stat_merge(&to->empty_time, &from->empty_time);
731#endif
732}
733
734/*
735 * Transfer @cfqg's stats to its parent's dead_stats so that the ancestors'
736 * recursive stats can still account for the amount used by this cfqg after
737 * it's gone.
738 */
739static void cfqg_stats_xfer_dead(struct cfq_group *cfqg)
740{
741    struct cfq_group *parent = cfqg_parent(cfqg);
742
743    lockdep_assert_held(cfqg_to_blkg(cfqg)->q->queue_lock);
744
745    if (unlikely(!parent))
746        return;
747
748    cfqg_stats_merge(&parent->dead_stats, &cfqg->stats);
749    cfqg_stats_merge(&parent->dead_stats, &cfqg->dead_stats);
750    cfqg_stats_reset(&cfqg->stats);
751    cfqg_stats_reset(&cfqg->dead_stats);
752}
753
754#else /* CONFIG_CFQ_GROUP_IOSCHED */
755
756static inline struct cfq_group *cfqg_parent(struct cfq_group *cfqg) { return NULL; }
757static inline void cfqg_get(struct cfq_group *cfqg) { }
758static inline void cfqg_put(struct cfq_group *cfqg) { }
759
760#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
761    blk_add_trace_msg((cfqd)->queue, "cfq%d%c%c " fmt, (cfqq)->pid, \
762            cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
763            cfqq_type((cfqq)) == SYNC_NOIDLE_WORKLOAD ? 'N' : ' ',\
764                ##args)
765#define cfq_log_cfqg(cfqd, cfqg, fmt, args...) do {} while (0)
766
767static inline void cfqg_stats_update_io_add(struct cfq_group *cfqg,
768            struct cfq_group *curr_cfqg, int rw) { }
769static inline void cfqg_stats_update_timeslice_used(struct cfq_group *cfqg,
770            unsigned long time, unsigned long unaccounted_time) { }
771static inline void cfqg_stats_update_io_remove(struct cfq_group *cfqg, int rw) { }
772static inline void cfqg_stats_update_io_merged(struct cfq_group *cfqg, int rw) { }
773static inline void cfqg_stats_update_dispatch(struct cfq_group *cfqg,
774                          uint64_t bytes, int rw) { }
775static inline void cfqg_stats_update_completion(struct cfq_group *cfqg,
776            uint64_t start_time, uint64_t io_start_time, int rw) { }
777
778#endif /* CONFIG_CFQ_GROUP_IOSCHED */
779
780#define cfq_log(cfqd, fmt, args...) \
781    blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
782
783/* Traverses through cfq group service trees */
784#define for_each_cfqg_st(cfqg, i, j, st) \
785    for (i = 0; i <= IDLE_WORKLOAD; i++) \
786        for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
787            : &cfqg->service_tree_idle; \
788            (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
789            (i == IDLE_WORKLOAD && j == 0); \
790            j++, st = i < IDLE_WORKLOAD ? \
791            &cfqg->service_trees[i][j]: NULL) \
792
793static inline bool cfq_io_thinktime_big(struct cfq_data *cfqd,
794    struct cfq_ttime *ttime, bool group_idle)
795{
796    unsigned long slice;
797    if (!sample_valid(ttime->ttime_samples))
798        return false;
799    if (group_idle)
800        slice = cfqd->cfq_group_idle;
801    else
802        slice = cfqd->cfq_slice_idle;
803    return ttime->ttime_mean > slice;
804}
805
806static inline bool iops_mode(struct cfq_data *cfqd)
807{
808    /*
809     * If we are not idling on queues and it is a NCQ drive, parallel
810     * execution of requests is on and measuring time is not possible
811     * in most of the cases until and unless we drive shallower queue
812     * depths and that becomes a performance bottleneck. In such cases
813     * switch to start providing fairness in terms of number of IOs.
814     */
815    if (!cfqd->cfq_slice_idle && cfqd->hw_tag)
816        return true;
817    else
818        return false;
819}
820
821static inline enum wl_class_t cfqq_class(struct cfq_queue *cfqq)
822{
823    if (cfq_class_idle(cfqq))
824        return IDLE_WORKLOAD;
825    if (cfq_class_rt(cfqq))
826        return RT_WORKLOAD;
827    return BE_WORKLOAD;
828}
829
830
831static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
832{
833    if (!cfq_cfqq_sync(cfqq))
834        return ASYNC_WORKLOAD;
835    if (!cfq_cfqq_idle_window(cfqq))
836        return SYNC_NOIDLE_WORKLOAD;
837    return SYNC_WORKLOAD;
838}
839
840static inline int cfq_group_busy_queues_wl(enum wl_class_t wl_class,
841                    struct cfq_data *cfqd,
842                    struct cfq_group *cfqg)
843{
844    if (wl_class == IDLE_WORKLOAD)
845        return cfqg->service_tree_idle.count;
846
847    return cfqg->service_trees[wl_class][ASYNC_WORKLOAD].count +
848        cfqg->service_trees[wl_class][SYNC_NOIDLE_WORKLOAD].count +
849        cfqg->service_trees[wl_class][SYNC_WORKLOAD].count;
850}
851
852static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
853                    struct cfq_group *cfqg)
854{
855    return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count +
856        cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
857}
858
859static void cfq_dispatch_insert(struct request_queue *, struct request *);
860static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, bool is_sync,
861                       struct cfq_io_cq *cic, struct bio *bio,
862                       gfp_t gfp_mask);
863
864static inline struct cfq_io_cq *icq_to_cic(struct io_cq *icq)
865{
866    /* cic->icq is the first member, %NULL will convert to %NULL */
867    return container_of(icq, struct cfq_io_cq, icq);
868}
869
870static inline struct cfq_io_cq *cfq_cic_lookup(struct cfq_data *cfqd,
871                           struct io_context *ioc)
872{
873    if (ioc)
874        return icq_to_cic(ioc_lookup_icq(ioc, cfqd->queue));
875    return NULL;
876}
877
878static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_cq *cic, bool is_sync)
879{
880    return cic->cfqq[is_sync];
881}
882
883static inline void cic_set_cfqq(struct cfq_io_cq *cic, struct cfq_queue *cfqq,
884                bool is_sync)
885{
886    cic->cfqq[is_sync] = cfqq;
887}
888
889static inline struct cfq_data *cic_to_cfqd(struct cfq_io_cq *cic)
890{
891    return cic->icq.q->elevator->elevator_data;
892}
893
894/*
895 * We regard a request as SYNC, if it's either a read or has the SYNC bit
896 * set (in which case it could also be direct WRITE).
897 */
898static inline bool cfq_bio_sync(struct bio *bio)
899{
900    return bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC);
901}
902
903/*
904 * scheduler run of queue, if there are requests pending and no one in the
905 * driver that will restart queueing
906 */
907static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
908{
909    if (cfqd->busy_queues) {
910        cfq_log(cfqd, "schedule dispatch");
911        kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
912    }
913}
914
915/*
916 * Scale schedule slice based on io priority. Use the sync time slice only
917 * if a queue is marked sync and has sync io queued. A sync queue with async
918 * io only, should not get full sync slice length.
919 */
920static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
921                 unsigned short prio)
922{
923    const int base_slice = cfqd->cfq_slice[sync];
924
925    WARN_ON(prio >= IOPRIO_BE_NR);
926
927    return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
928}
929
930static inline int
931cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
932{
933    return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
934}
935
936/**
937 * cfqg_scale_charge - scale disk time charge according to cfqg weight
938 * @charge: disk time being charged
939 * @vfraction: vfraction of the cfqg, fixed point w/ CFQ_SERVICE_SHIFT
940 *
941 * Scale @charge according to @vfraction, which is in range (0, 1]. The
942 * scaling is inversely proportional.
943 *
944 * scaled = charge / vfraction
945 *
946 * The result is also in fixed point w/ CFQ_SERVICE_SHIFT.
947 */
948static inline u64 cfqg_scale_charge(unsigned long charge,
949                    unsigned int vfraction)
950{
951    u64 c = charge << CFQ_SERVICE_SHIFT; /* make it fixed point */
952
953    /* charge / vfraction */
954    c <<= CFQ_SERVICE_SHIFT;
955    do_div(c, vfraction);
956    return c;
957}
958
959static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
960{
961    s64 delta = (s64)(vdisktime - min_vdisktime);
962    if (delta > 0)
963        min_vdisktime = vdisktime;
964
965    return min_vdisktime;
966}
967
968static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
969{
970    s64 delta = (s64)(vdisktime - min_vdisktime);
971    if (delta < 0)
972        min_vdisktime = vdisktime;
973
974    return min_vdisktime;
975}
976
977static void update_min_vdisktime(struct cfq_rb_root *st)
978{
979    struct cfq_group *cfqg;
980
981    if (st->left) {
982        cfqg = rb_entry_cfqg(st->left);
983        st->min_vdisktime = max_vdisktime(st->min_vdisktime,
984                          cfqg->vdisktime);
985    }
986}
987
988/*
989 * get averaged number of queues of RT/BE priority.
990 * average is updated, with a formula that gives more weight to higher numbers,
991 * to quickly follows sudden increases and decrease slowly
992 */
993
994static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
995                    struct cfq_group *cfqg, bool rt)
996{
997    unsigned min_q, max_q;
998    unsigned mult = cfq_hist_divisor - 1;
999    unsigned round = cfq_hist_divisor / 2;
1000    unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
1001
1002    min_q = min(cfqg->busy_queues_avg[rt], busy);
1003    max_q = max(cfqg->busy_queues_avg[rt], busy);
1004    cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
1005        cfq_hist_divisor;
1006    return cfqg->busy_queues_avg[rt];
1007}
1008
1009static inline unsigned
1010cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
1011{
1012    return cfqd->cfq_target_latency * cfqg->vfraction >> CFQ_SERVICE_SHIFT;
1013}
1014
1015static inline unsigned
1016cfq_scaled_cfqq_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1017{
1018    unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
1019    if (cfqd->cfq_latency) {
1020        /*
1021         * interested queues (we consider only the ones with the same
1022         * priority class in the cfq group)
1023         */
1024        unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
1025                        cfq_class_rt(cfqq));
1026        unsigned sync_slice = cfqd->cfq_slice[1];
1027        unsigned expect_latency = sync_slice * iq;
1028        unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
1029
1030        if (expect_latency > group_slice) {
1031            unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
1032            /* scale low_slice according to IO priority
1033             * and sync vs async */
1034            unsigned low_slice =
1035                min(slice, base_low_slice * slice / sync_slice);
1036            /* the adapted slice value is scaled to fit all iqs
1037             * into the target latency */
1038            slice = max(slice * group_slice / expect_latency,
1039                    low_slice);
1040        }
1041    }
1042    return slice;
1043}
1044
1045static inline void
1046cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1047{
1048    unsigned slice = cfq_scaled_cfqq_slice(cfqd, cfqq);
1049
1050    cfqq->slice_start = jiffies;
1051    cfqq->slice_end = jiffies + slice;
1052    cfqq->allocated_slice = slice;
1053    cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
1054}
1055
1056/*
1057 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
1058 * isn't valid until the first request from the dispatch is activated
1059 * and the slice time set.
1060 */
1061static inline bool cfq_slice_used(struct cfq_queue *cfqq)
1062{
1063    if (cfq_cfqq_slice_new(cfqq))
1064        return false;
1065    if (time_before(jiffies, cfqq->slice_end))
1066        return false;
1067
1068    return true;
1069}
1070
1071/*
1072 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
1073 * We choose the request that is closest to the head right now. Distance
1074 * behind the head is penalized and only allowed to a certain extent.
1075 */
1076static struct request *
1077cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
1078{
1079    sector_t s1, s2, d1 = 0, d2 = 0;
1080    unsigned long back_max;
1081#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
1082#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
1083    unsigned wrap = 0; /* bit mask: requests behind the disk head? */
1084
1085    if (rq1 == NULL || rq1 == rq2)
1086        return rq2;
1087    if (rq2 == NULL)
1088        return rq1;
1089
1090    if (rq_is_sync(rq1) != rq_is_sync(rq2))
1091        return rq_is_sync(rq1) ? rq1 : rq2;
1092
1093    if ((rq1->cmd_flags ^ rq2->cmd_flags) & REQ_PRIO)
1094        return rq1->cmd_flags & REQ_PRIO ? rq1 : rq2;
1095
1096    s1 = blk_rq_pos(rq1);
1097    s2 = blk_rq_pos(rq2);
1098
1099    /*
1100     * by definition, 1KiB is 2 sectors
1101     */
1102    back_max = cfqd->cfq_back_max * 2;
1103
1104    /*
1105     * Strict one way elevator _except_ in the case where we allow
1106     * short backward seeks which are biased as twice the cost of a
1107     * similar forward seek.
1108     */
1109    if (s1 >= last)
1110        d1 = s1 - last;
1111    else if (s1 + back_max >= last)
1112        d1 = (last - s1) * cfqd->cfq_back_penalty;
1113    else
1114        wrap |= CFQ_RQ1_WRAP;
1115
1116    if (s2 >= last)
1117        d2 = s2 - last;
1118    else if (s2 + back_max >= last)
1119        d2 = (last - s2) * cfqd->cfq_back_penalty;
1120    else
1121        wrap |= CFQ_RQ2_WRAP;
1122
1123    /* Found required data */
1124
1125    /*
1126     * By doing switch() on the bit mask "wrap" we avoid having to
1127     * check two variables for all permutations: --> faster!
1128     */
1129    switch (wrap) {
1130    case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
1131        if (d1 < d2)
1132            return rq1;
1133        else if (d2 < d1)
1134            return rq2;
1135        else {
1136            if (s1 >= s2)
1137                return rq1;
1138            else
1139                return rq2;
1140        }
1141
1142    case CFQ_RQ2_WRAP:
1143        return rq1;
1144    case CFQ_RQ1_WRAP:
1145        return rq2;
1146    case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
1147    default:
1148        /*
1149         * Since both rqs are wrapped,
1150         * start with the one that's further behind head
1151         * (--> only *one* back seek required),
1152         * since back seek takes more time than forward.
1153         */
1154        if (s1 <= s2)
1155            return rq1;
1156        else
1157            return rq2;
1158    }
1159}
1160
1161/*
1162 * The below is leftmost cache rbtree addon
1163 */
1164static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
1165{
1166    /* Service tree is empty */
1167    if (!root->count)
1168        return NULL;
1169
1170    if (!root->left)
1171        root->left = rb_first(&root->rb);
1172
1173    if (root->left)
1174        return rb_entry(root->left, struct cfq_queue, rb_node);
1175
1176    return NULL;
1177}
1178
1179static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
1180{
1181    if (!root->left)
1182        root->left = rb_first(&root->rb);
1183
1184    if (root->left)
1185        return rb_entry_cfqg(root->left);
1186
1187    return NULL;
1188}
1189
1190static void rb_erase_init(struct rb_node *n, struct rb_root *root)
1191{
1192    rb_erase(n, root);
1193    RB_CLEAR_NODE(n);
1194}
1195
1196static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
1197{
1198    if (root->left == n)
1199        root->left = NULL;
1200    rb_erase_init(n, &root->rb);
1201    --root->count;
1202}
1203
1204/*
1205 * would be nice to take fifo expire time into account as well
1206 */
1207static struct request *
1208cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1209          struct request *last)
1210{
1211    struct rb_node *rbnext = rb_next(&last->rb_node);
1212    struct rb_node *rbprev = rb_prev(&last->rb_node);
1213    struct request *next = NULL, *prev = NULL;
1214
1215    BUG_ON(RB_EMPTY_NODE(&last->rb_node));
1216
1217    if (rbprev)
1218        prev = rb_entry_rq(rbprev);
1219
1220    if (rbnext)
1221        next = rb_entry_rq(rbnext);
1222    else {
1223        rbnext = rb_first(&cfqq->sort_list);
1224        if (rbnext && rbnext != &last->rb_node)
1225            next = rb_entry_rq(rbnext);
1226    }
1227
1228    return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
1229}
1230
1231static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
1232                      struct cfq_queue *cfqq)
1233{
1234    /*
1235     * just an approximation, should be ok.
1236     */
1237    return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
1238               cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
1239}
1240
1241static inline s64
1242cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
1243{
1244    return cfqg->vdisktime - st->min_vdisktime;
1245}
1246
1247static void
1248__cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
1249{
1250    struct rb_node **node = &st->rb.rb_node;
1251    struct rb_node *parent = NULL;
1252    struct cfq_group *__cfqg;
1253    s64 key = cfqg_key(st, cfqg);
1254    int left = 1;
1255
1256    while (*node != NULL) {
1257        parent = *node;
1258        __cfqg = rb_entry_cfqg(parent);
1259
1260        if (key < cfqg_key(st, __cfqg))
1261            node = &parent->rb_left;
1262        else {
1263            node = &parent->rb_right;
1264            left = 0;
1265        }
1266    }
1267
1268    if (left)
1269        st->left = &cfqg->rb_node;
1270
1271    rb_link_node(&cfqg->rb_node, parent, node);
1272    rb_insert_color(&cfqg->rb_node, &st->rb);
1273}
1274
1275static void
1276cfq_update_group_weight(struct cfq_group *cfqg)
1277{
1278    BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
1279
1280    if (cfqg->new_weight) {
1281        cfqg->weight = cfqg->new_weight;
1282        cfqg->new_weight = 0;
1283    }
1284
1285    if (cfqg->new_leaf_weight) {
1286        cfqg->leaf_weight = cfqg->new_leaf_weight;
1287        cfqg->new_leaf_weight = 0;
1288    }
1289}
1290
1291static void
1292cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
1293{
1294    unsigned int vfr = 1 << CFQ_SERVICE_SHIFT; /* start with 1 */
1295    struct cfq_group *pos = cfqg;
1296    struct cfq_group *parent;
1297    bool propagate;
1298
1299    /* add to the service tree */
1300    BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
1301
1302    cfq_update_group_weight(cfqg);
1303    __cfq_group_service_tree_add(st, cfqg);
1304
1305    /*
1306     * Activate @cfqg and calculate the portion of vfraction @cfqg is
1307     * entitled to. vfraction is calculated by walking the tree
1308     * towards the root calculating the fraction it has at each level.
1309     * The compounded ratio is how much vfraction @cfqg owns.
1310     *
1311     * Start with the proportion tasks in this cfqg has against active
1312     * children cfqgs - its leaf_weight against children_weight.
1313     */
1314    propagate = !pos->nr_active++;
1315    pos->children_weight += pos->leaf_weight;
1316    vfr = vfr * pos->leaf_weight / pos->children_weight;
1317
1318    /*
1319     * Compound ->weight walking up the tree. Both activation and
1320     * vfraction calculation are done in the same loop. Propagation
1321     * stops once an already activated node is met. vfraction
1322     * calculation should always continue to the root.
1323     */
1324    while ((parent = cfqg_parent(pos))) {
1325        if (propagate) {
1326            propagate = !parent->nr_active++;
1327            parent->children_weight += pos->weight;
1328        }
1329        vfr = vfr * pos->weight / parent->children_weight;
1330        pos = parent;
1331    }
1332
1333    cfqg->vfraction = max_t(unsigned, vfr, 1);
1334}
1335
1336static void
1337cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
1338{
1339    struct cfq_rb_root *st = &cfqd->grp_service_tree;
1340    struct cfq_group *__cfqg;
1341    struct rb_node *n;
1342
1343    cfqg->nr_cfqq++;
1344    if (!RB_EMPTY_NODE(&cfqg->rb_node))
1345        return;
1346
1347    /*
1348     * Currently put the group at the end. Later implement something
1349     * so that groups get lesser vtime based on their weights, so that
1350     * if group does not loose all if it was not continuously backlogged.
1351     */
1352    n = rb_last(&st->rb);
1353    if (n) {
1354        __cfqg = rb_entry_cfqg(n);
1355        cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
1356    } else
1357        cfqg->vdisktime = st->min_vdisktime;
1358    cfq_group_service_tree_add(st, cfqg);
1359}
1360
1361static void
1362cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg)
1363{
1364    struct cfq_group *pos = cfqg;
1365    bool propagate;
1366
1367    /*
1368     * Undo activation from cfq_group_service_tree_add(). Deactivate
1369     * @cfqg and propagate deactivation upwards.
1370     */
1371    propagate = !--pos->nr_active;
1372    pos->children_weight -= pos->leaf_weight;
1373
1374    while (propagate) {
1375        struct cfq_group *parent = cfqg_parent(pos);
1376
1377        /* @pos has 0 nr_active at this point */
1378        WARN_ON_ONCE(pos->children_weight);
1379        pos->vfraction = 0;
1380
1381        if (!parent)
1382            break;
1383
1384        propagate = !--parent->nr_active;
1385        parent->children_weight -= pos->weight;
1386        pos = parent;
1387    }
1388
1389    /* remove from the service tree */
1390    if (!RB_EMPTY_NODE(&cfqg->rb_node))
1391        cfq_rb_erase(&cfqg->rb_node, st);
1392}
1393
1394static void
1395cfq_group_notify_queue_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
1396{
1397    struct cfq_rb_root *st = &cfqd->grp_service_tree;
1398
1399    BUG_ON(cfqg->nr_cfqq < 1);
1400    cfqg->nr_cfqq--;
1401
1402    /* If there are other cfq queues under this group, don't delete it */
1403    if (cfqg->nr_cfqq)
1404        return;
1405
1406    cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
1407    cfq_group_service_tree_del(st, cfqg);
1408    cfqg->saved_wl_slice = 0;
1409    cfqg_stats_update_dequeue(cfqg);
1410}
1411
1412static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq,
1413                        unsigned int *unaccounted_time)
1414{
1415    unsigned int slice_used;
1416
1417    /*
1418     * Queue got expired before even a single request completed or
1419     * got expired immediately after first request completion.
1420     */
1421    if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
1422        /*
1423         * Also charge the seek time incurred to the group, otherwise
1424         * if there are mutiple queues in the group, each can dispatch
1425         * a single request on seeky media and cause lots of seek time
1426         * and group will never know it.
1427         */
1428        slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
1429                    1);
1430    } else {
1431        slice_used = jiffies - cfqq->slice_start;
1432        if (slice_used > cfqq->allocated_slice) {
1433            *unaccounted_time = slice_used - cfqq->allocated_slice;
1434            slice_used = cfqq->allocated_slice;
1435        }
1436        if (time_after(cfqq->slice_start, cfqq->dispatch_start))
1437            *unaccounted_time += cfqq->slice_start -
1438                    cfqq->dispatch_start;
1439    }
1440
1441    return slice_used;
1442}
1443
1444static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
1445                struct cfq_queue *cfqq)
1446{
1447    struct cfq_rb_root *st = &cfqd->grp_service_tree;
1448    unsigned int used_sl, charge, unaccounted_sl = 0;
1449    int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
1450            - cfqg->service_tree_idle.count;
1451    unsigned int vfr;
1452
1453    BUG_ON(nr_sync < 0);
1454    used_sl = charge = cfq_cfqq_slice_usage(cfqq, &unaccounted_sl);
1455
1456    if (iops_mode(cfqd))
1457        charge = cfqq->slice_dispatch;
1458    else if (!cfq_cfqq_sync(cfqq) && !nr_sync)
1459        charge = cfqq->allocated_slice;
1460
1461    /*
1462     * Can't update vdisktime while on service tree and cfqg->vfraction
1463     * is valid only while on it. Cache vfr, leave the service tree,
1464     * update vdisktime and go back on. The re-addition to the tree
1465     * will also update the weights as necessary.
1466     */
1467    vfr = cfqg->vfraction;
1468    cfq_group_service_tree_del(st, cfqg);
1469    cfqg->vdisktime += cfqg_scale_charge(charge, vfr);
1470    cfq_group_service_tree_add(st, cfqg);
1471
1472    /* This group is being expired. Save the context */
1473    if (time_after(cfqd->workload_expires, jiffies)) {
1474        cfqg->saved_wl_slice = cfqd->workload_expires
1475                        - jiffies;
1476        cfqg->saved_wl_type = cfqd->serving_wl_type;
1477        cfqg->saved_wl_class = cfqd->serving_wl_class;
1478    } else
1479        cfqg->saved_wl_slice = 0;
1480
1481    cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
1482                    st->min_vdisktime);
1483    cfq_log_cfqq(cfqq->cfqd, cfqq,
1484             "sl_used=%u disp=%u charge=%u iops=%u sect=%lu",
1485             used_sl, cfqq->slice_dispatch, charge,
1486             iops_mode(cfqd), cfqq->nr_sectors);
1487    cfqg_stats_update_timeslice_used(cfqg, used_sl, unaccounted_sl);
1488    cfqg_stats_set_start_empty_time(cfqg);
1489}
1490
1491/**
1492 * cfq_init_cfqg_base - initialize base part of a cfq_group
1493 * @cfqg: cfq_group to initialize
1494 *
1495 * Initialize the base part which is used whether %CONFIG_CFQ_GROUP_IOSCHED
1496 * is enabled or not.
1497 */
1498static void cfq_init_cfqg_base(struct cfq_group *cfqg)
1499{
1500    struct cfq_rb_root *st;
1501    int i, j;
1502
1503    for_each_cfqg_st(cfqg, i, j, st)
1504        *st = CFQ_RB_ROOT;
1505    RB_CLEAR_NODE(&cfqg->rb_node);
1506
1507    cfqg->ttime.last_end_request = jiffies;
1508}
1509
1510#ifdef CONFIG_CFQ_GROUP_IOSCHED
1511static void cfq_pd_init(struct blkcg_gq *blkg)
1512{
1513    struct cfq_group *cfqg = blkg_to_cfqg(blkg);
1514
1515    cfq_init_cfqg_base(cfqg);
1516    cfqg->weight = blkg->blkcg->cfq_weight;
1517    cfqg->leaf_weight = blkg->blkcg->cfq_leaf_weight;
1518}
1519
1520static void cfq_pd_offline(struct blkcg_gq *blkg)
1521{
1522    /*
1523     * @blkg is going offline and will be ignored by
1524     * blkg_[rw]stat_recursive_sum(). Transfer stats to the parent so
1525     * that they don't get lost. If IOs complete after this point, the
1526     * stats for them will be lost. Oh well...
1527     */
1528    cfqg_stats_xfer_dead(blkg_to_cfqg(blkg));
1529}
1530
1531/* offset delta from cfqg->stats to cfqg->dead_stats */
1532static const int dead_stats_off_delta = offsetof(struct cfq_group, dead_stats) -
1533                    offsetof(struct cfq_group, stats);
1534
1535/* to be used by recursive prfill, sums live and dead stats recursively */
1536static u64 cfqg_stat_pd_recursive_sum(struct blkg_policy_data *pd, int off)
1537{
1538    u64 sum = 0;
1539
1540    sum += blkg_stat_recursive_sum(pd, off);
1541    sum += blkg_stat_recursive_sum(pd, off + dead_stats_off_delta);
1542    return sum;
1543}
1544
1545/* to be used by recursive prfill, sums live and dead rwstats recursively */
1546static struct blkg_rwstat cfqg_rwstat_pd_recursive_sum(struct blkg_policy_data *pd,
1547                               int off)
1548{
1549    struct blkg_rwstat a, b;
1550
1551    a = blkg_rwstat_recursive_sum(pd, off);
1552    b = blkg_rwstat_recursive_sum(pd, off + dead_stats_off_delta);
1553    blkg_rwstat_merge(&a, &b);
1554    return a;
1555}
1556
1557static void cfq_pd_reset_stats(struct blkcg_gq *blkg)
1558{
1559    struct cfq_group *cfqg = blkg_to_cfqg(blkg);
1560
1561    cfqg_stats_reset(&cfqg->stats);
1562    cfqg_stats_reset(&cfqg->dead_stats);
1563}
1564
1565/*
1566 * Search for the cfq group current task belongs to. request_queue lock must
1567 * be held.
1568 */
1569static struct cfq_group *cfq_lookup_create_cfqg(struct cfq_data *cfqd,
1570                        struct blkcg *blkcg)
1571{
1572    struct request_queue *q = cfqd->queue;
1573    struct cfq_group *cfqg = NULL;
1574
1575    /* avoid lookup for the common case where there's no blkcg */
1576    if (blkcg == &blkcg_root) {
1577        cfqg = cfqd->root_group;
1578    } else {
1579        struct blkcg_gq *blkg;
1580
1581        blkg = blkg_lookup_create(blkcg, q);
1582        if (!IS_ERR(blkg))
1583            cfqg = blkg_to_cfqg(blkg);
1584    }
1585
1586    return cfqg;
1587}
1588
1589static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
1590{
1591    /* Currently, all async queues are mapped to root group */
1592    if (!cfq_cfqq_sync(cfqq))
1593        cfqg = cfqq->cfqd->root_group;
1594
1595    cfqq->cfqg = cfqg;
1596    /* cfqq reference on cfqg */
1597    cfqg_get(cfqg);
1598}
1599
1600static u64 cfqg_prfill_weight_device(struct seq_file *sf,
1601                     struct blkg_policy_data *pd, int off)
1602{
1603    struct cfq_group *cfqg = pd_to_cfqg(pd);
1604
1605    if (!cfqg->dev_weight)
1606        return 0;
1607    return __blkg_prfill_u64(sf, pd, cfqg->dev_weight);
1608}
1609
1610static int cfqg_print_weight_device(struct cgroup_subsys_state *css,
1611                    struct cftype *cft, struct seq_file *sf)
1612{
1613    blkcg_print_blkgs(sf, css_to_blkcg(css), cfqg_prfill_weight_device,
1614              &blkcg_policy_cfq, 0, false);
1615    return 0;
1616}
1617
1618static u64 cfqg_prfill_leaf_weight_device(struct seq_file *sf,
1619                      struct blkg_policy_data *pd, int off)
1620{
1621    struct cfq_group *cfqg = pd_to_cfqg(pd);
1622
1623    if (!cfqg->dev_leaf_weight)
1624        return 0;
1625    return __blkg_prfill_u64(sf, pd, cfqg->dev_leaf_weight);
1626}
1627
1628static int cfqg_print_leaf_weight_device(struct cgroup_subsys_state *css,
1629                     struct cftype *cft,
1630                     struct seq_file *sf)
1631{
1632    blkcg_print_blkgs(sf, css_to_blkcg(css), cfqg_prfill_leaf_weight_device,
1633              &blkcg_policy_cfq, 0, false);
1634    return 0;
1635}
1636
1637static int cfq_print_weight(struct cgroup_subsys_state *css, struct cftype *cft,
1638                struct seq_file *sf)
1639{
1640    seq_printf(sf, "%u\n", css_to_blkcg(css)->cfq_weight);
1641    return 0;
1642}
1643
1644static int cfq_print_leaf_weight(struct cgroup_subsys_state *css,
1645                 struct cftype *cft, struct seq_file *sf)
1646{
1647    seq_printf(sf, "%u\n", css_to_blkcg(css)->cfq_leaf_weight);
1648    return 0;
1649}
1650
1651static int __cfqg_set_weight_device(struct cgroup_subsys_state *css,
1652                    struct cftype *cft, const char *buf,
1653                    bool is_leaf_weight)
1654{
1655    struct blkcg *blkcg = css_to_blkcg(css);
1656    struct blkg_conf_ctx ctx;
1657    struct cfq_group *cfqg;
1658    int ret;
1659
1660    ret = blkg_conf_prep(blkcg, &blkcg_policy_cfq, buf, &ctx);
1661    if (ret)
1662        return ret;
1663
1664    ret = -EINVAL;
1665    cfqg = blkg_to_cfqg(ctx.blkg);
1666    if (!ctx.v || (ctx.v >= CFQ_WEIGHT_MIN && ctx.v <= CFQ_WEIGHT_MAX)) {
1667        if (!is_leaf_weight) {
1668            cfqg->dev_weight = ctx.v;
1669            cfqg->new_weight = ctx.v ?: blkcg->cfq_weight;
1670        } else {
1671            cfqg->dev_leaf_weight = ctx.v;
1672            cfqg->new_leaf_weight = ctx.v ?: blkcg->cfq_leaf_weight;
1673        }
1674        ret = 0;
1675    }
1676
1677    blkg_conf_finish(&ctx);
1678    return ret;
1679}
1680
1681static int cfqg_set_weight_device(struct cgroup_subsys_state *css,
1682                  struct cftype *cft, const char *buf)
1683{
1684    return __cfqg_set_weight_device(css, cft, buf, false);
1685}
1686
1687static int cfqg_set_leaf_weight_device(struct cgroup_subsys_state *css,
1688                       struct cftype *cft, const char *buf)
1689{
1690    return __cfqg_set_weight_device(css, cft, buf, true);
1691}
1692
1693static int __cfq_set_weight(struct cgroup_subsys_state *css, struct cftype *cft,
1694                u64 val, bool is_leaf_weight)
1695{
1696    struct blkcg *blkcg = css_to_blkcg(css);
1697    struct blkcg_gq *blkg;
1698
1699    if (val < CFQ_WEIGHT_MIN || val > CFQ_WEIGHT_MAX)
1700        return -EINVAL;
1701
1702    spin_lock_irq(&blkcg->lock);
1703
1704    if (!is_leaf_weight)
1705        blkcg->cfq_weight = val;
1706    else
1707        blkcg->cfq_leaf_weight = val;
1708
1709    hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
1710        struct cfq_group *cfqg = blkg_to_cfqg(blkg);
1711
1712        if (!cfqg)
1713            continue;
1714
1715        if (!is_leaf_weight) {
1716            if (!cfqg->dev_weight)
1717                cfqg->new_weight = blkcg->cfq_weight;
1718        } else {
1719            if (!cfqg->dev_leaf_weight)
1720                cfqg->new_leaf_weight = blkcg->cfq_leaf_weight;
1721        }
1722    }
1723
1724    spin_unlock_irq(&blkcg->lock);
1725    return 0;
1726}
1727
1728static int cfq_set_weight(struct cgroup_subsys_state *css, struct cftype *cft,
1729              u64 val)
1730{
1731    return __cfq_set_weight(css, cft, val, false);
1732}
1733
1734static int cfq_set_leaf_weight(struct cgroup_subsys_state *css,
1735                   struct cftype *cft, u64 val)
1736{
1737    return __cfq_set_weight(css, cft, val, true);
1738}
1739
1740static int cfqg_print_stat(struct cgroup_subsys_state *css, struct cftype *cft,
1741               struct seq_file *sf)
1742{
1743    struct blkcg *blkcg = css_to_blkcg(css);
1744
1745    blkcg_print_blkgs(sf, blkcg, blkg_prfill_stat, &blkcg_policy_cfq,
1746              cft->private, false);
1747    return 0;
1748}
1749
1750static int cfqg_print_rwstat(struct cgroup_subsys_state *css,
1751                 struct cftype *cft, struct seq_file *sf)
1752{
1753    struct blkcg *blkcg = css_to_blkcg(css);
1754
1755    blkcg_print_blkgs(sf, blkcg, blkg_prfill_rwstat, &blkcg_policy_cfq,
1756              cft->private, true);
1757    return 0;
1758}
1759
1760static u64 cfqg_prfill_stat_recursive(struct seq_file *sf,
1761                      struct blkg_policy_data *pd, int off)
1762{
1763    u64 sum = cfqg_stat_pd_recursive_sum(pd, off);
1764
1765    return __blkg_prfill_u64(sf, pd, sum);
1766}
1767
1768static u64 cfqg_prfill_rwstat_recursive(struct seq_file *sf,
1769                    struct blkg_policy_data *pd, int off)
1770{
1771    struct blkg_rwstat sum = cfqg_rwstat_pd_recursive_sum(pd, off);
1772
1773    return __blkg_prfill_rwstat(sf, pd, &sum);
1774}
1775
1776static int cfqg_print_stat_recursive(struct cgroup_subsys_state *css,
1777                     struct cftype *cft, struct seq_file *sf)
1778{
1779    struct blkcg *blkcg = css_to_blkcg(css);
1780
1781    blkcg_print_blkgs(sf, blkcg, cfqg_prfill_stat_recursive,
1782              &blkcg_policy_cfq, cft->private, false);
1783    return 0;
1784}
1785
1786static int cfqg_print_rwstat_recursive(struct cgroup_subsys_state *css,
1787                       struct cftype *cft, struct seq_file *sf)
1788{
1789    struct blkcg *blkcg = css_to_blkcg(css);
1790
1791    blkcg_print_blkgs(sf, blkcg, cfqg_prfill_rwstat_recursive,
1792              &blkcg_policy_cfq, cft->private, true);
1793    return 0;
1794}
1795
1796#ifdef CONFIG_DEBUG_BLK_CGROUP
1797static u64 cfqg_prfill_avg_queue_size(struct seq_file *sf,
1798                      struct blkg_policy_data *pd, int off)
1799{
1800    struct cfq_group *cfqg = pd_to_cfqg(pd);
1801    u64 samples = blkg_stat_read(&cfqg->stats.avg_queue_size_samples);
1802    u64 v = 0;
1803
1804    if (samples) {
1805        v = blkg_stat_read(&cfqg->stats.avg_queue_size_sum);
1806        v = div64_u64(v, samples);
1807    }
1808    __blkg_prfill_u64(sf, pd, v);
1809    return 0;
1810}
1811
1812/* print avg_queue_size */
1813static int cfqg_print_avg_queue_size(struct cgroup_subsys_state *css,
1814                     struct cftype *cft, struct seq_file *sf)
1815{
1816    struct blkcg *blkcg = css_to_blkcg(css);
1817
1818    blkcg_print_blkgs(sf, blkcg, cfqg_prfill_avg_queue_size,
1819              &blkcg_policy_cfq, 0, false);
1820    return 0;
1821}
1822#endif /* CONFIG_DEBUG_BLK_CGROUP */
1823
1824static struct cftype cfq_blkcg_files[] = {
1825    /* on root, weight is mapped to leaf_weight */
1826    {
1827        .name = "weight_device",
1828        .flags = CFTYPE_ONLY_ON_ROOT,
1829        .read_seq_string = cfqg_print_leaf_weight_device,
1830        .write_string = cfqg_set_leaf_weight_device,
1831        .max_write_len = 256,
1832    },
1833    {
1834        .name = "weight",
1835        .flags = CFTYPE_ONLY_ON_ROOT,
1836        .read_seq_string = cfq_print_leaf_weight,
1837        .write_u64 = cfq_set_leaf_weight,
1838    },
1839
1840    /* no such mapping necessary for !roots */
1841    {
1842        .name = "weight_device",
1843        .flags = CFTYPE_NOT_ON_ROOT,
1844        .read_seq_string = cfqg_print_weight_device,
1845        .write_string = cfqg_set_weight_device,
1846        .max_write_len = 256,
1847    },
1848    {
1849        .name = "weight",
1850        .flags = CFTYPE_NOT_ON_ROOT,
1851        .read_seq_string = cfq_print_weight,
1852        .write_u64 = cfq_set_weight,
1853    },
1854
1855    {
1856        .name = "leaf_weight_device",
1857        .read_seq_string = cfqg_print_leaf_weight_device,
1858        .write_string = cfqg_set_leaf_weight_device,
1859        .max_write_len = 256,
1860    },
1861    {
1862        .name = "leaf_weight",
1863        .read_seq_string = cfq_print_leaf_weight,
1864        .write_u64 = cfq_set_leaf_weight,
1865    },
1866
1867    /* statistics, covers only the tasks in the cfqg */
1868    {
1869        .name = "time",
1870        .private = offsetof(struct cfq_group, stats.time),
1871        .read_seq_string = cfqg_print_stat,
1872    },
1873    {
1874        .name = "sectors",
1875        .private = offsetof(struct cfq_group, stats.sectors),
1876        .read_seq_string = cfqg_print_stat,
1877    },
1878    {
1879        .name = "io_service_bytes",
1880        .private = offsetof(struct cfq_group, stats.service_bytes),
1881        .read_seq_string = cfqg_print_rwstat,
1882    },
1883    {
1884        .name = "io_serviced",
1885        .private = offsetof(struct cfq_group, stats.serviced),
1886        .read_seq_string = cfqg_print_rwstat,
1887    },
1888    {
1889        .name = "io_service_time",
1890        .private = offsetof(struct cfq_group, stats.service_time),
1891        .read_seq_string = cfqg_print_rwstat,
1892    },
1893    {
1894        .name = "io_wait_time",
1895        .private = offsetof(struct cfq_group, stats.wait_time),
1896        .read_seq_string = cfqg_print_rwstat,
1897    },
1898    {
1899        .name = "io_merged",
1900        .private = offsetof(struct cfq_group, stats.merged),
1901        .read_seq_string = cfqg_print_rwstat,
1902    },
1903    {
1904        .name = "io_queued",
1905        .private = offsetof(struct cfq_group, stats.queued),
1906        .read_seq_string = cfqg_print_rwstat,
1907    },
1908
1909    /* the same statictics which cover the cfqg and its descendants */
1910    {
1911        .name = "time_recursive",
1912        .private = offsetof(struct cfq_group, stats.time),
1913        .read_seq_string = cfqg_print_stat_recursive,
1914    },
1915    {
1916        .name = "sectors_recursive",
1917        .private = offsetof(struct cfq_group, stats.sectors),
1918        .read_seq_string = cfqg_print_stat_recursive,
1919    },
1920    {
1921        .name = "io_service_bytes_recursive",
1922        .private = offsetof(struct cfq_group, stats.service_bytes),
1923        .read_seq_string = cfqg_print_rwstat_recursive,
1924    },
1925    {
1926        .name = "io_serviced_recursive",
1927        .private = offsetof(struct cfq_group, stats.serviced),
1928        .read_seq_string = cfqg_print_rwstat_recursive,
1929    },
1930    {
1931        .name = "io_service_time_recursive",
1932        .private = offsetof(struct cfq_group, stats.service_time),
1933        .read_seq_string = cfqg_print_rwstat_recursive,
1934    },
1935    {
1936        .name = "io_wait_time_recursive",
1937        .private = offsetof(struct cfq_group, stats.wait_time),
1938        .read_seq_string = cfqg_print_rwstat_recursive,
1939    },
1940    {
1941        .name = "io_merged_recursive",
1942        .private = offsetof(struct cfq_group, stats.merged),
1943        .read_seq_string = cfqg_print_rwstat_recursive,
1944    },
1945    {
1946        .name = "io_queued_recursive",
1947        .private = offsetof(struct cfq_group, stats.queued),
1948        .read_seq_string = cfqg_print_rwstat_recursive,
1949    },
1950#ifdef CONFIG_DEBUG_BLK_CGROUP
1951    {
1952        .name = "avg_queue_size",
1953        .read_seq_string = cfqg_print_avg_queue_size,
1954    },
1955    {
1956        .name = "group_wait_time",
1957        .private = offsetof(struct cfq_group, stats.group_wait_time),
1958        .read_seq_string = cfqg_print_stat,
1959    },
1960    {
1961        .name = "idle_time",
1962        .private = offsetof(struct cfq_group, stats.idle_time),
1963        .read_seq_string = cfqg_print_stat,
1964    },
1965    {
1966        .name = "empty_time",
1967        .private = offsetof(struct cfq_group, stats.empty_time),
1968        .read_seq_string = cfqg_print_stat,
1969    },
1970    {
1971        .name = "dequeue",
1972        .private = offsetof(struct cfq_group, stats.dequeue),
1973        .read_seq_string = cfqg_print_stat,
1974    },
1975    {
1976        .name = "unaccounted_time",
1977        .private = offsetof(struct cfq_group, stats.unaccounted_time),
1978        .read_seq_string = cfqg_print_stat,
1979    },
1980#endif /* CONFIG_DEBUG_BLK_CGROUP */
1981    { } /* terminate */
1982};
1983#else /* GROUP_IOSCHED */
1984static struct cfq_group *cfq_lookup_create_cfqg(struct cfq_data *cfqd,
1985                        struct blkcg *blkcg)
1986{
1987    return cfqd->root_group;
1988}
1989
1990static inline void
1991cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
1992    cfqq->cfqg = cfqg;
1993}
1994
1995#endif /* GROUP_IOSCHED */
1996
1997/*
1998 * The cfqd->service_trees holds all pending cfq_queue's that have
1999 * requests waiting to be processed. It is sorted in the order that
2000 * we will service the queues.
2001 */
2002static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2003                 bool add_front)
2004{
2005    struct rb_node **p, *parent;
2006    struct cfq_queue *__cfqq;
2007    unsigned long rb_key;
2008    struct cfq_rb_root *st;
2009    int left;
2010    int new_cfqq = 1;
2011
2012    st = st_for(cfqq->cfqg, cfqq_class(cfqq), cfqq_type(cfqq));
2013    if (cfq_class_idle(cfqq)) {
2014        rb_key = CFQ_IDLE_DELAY;
2015        parent = rb_last(&st->rb);
2016        if (parent && parent != &cfqq->rb_node) {
2017            __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
2018            rb_key += __cfqq->rb_key;
2019        } else
2020            rb_key += jiffies;
2021    } else if (!add_front) {
2022        /*
2023         * Get our rb key offset. Subtract any residual slice
2024         * value carried from last service. A negative resid
2025         * count indicates slice overrun, and this should position
2026         * the next service time further away in the tree.
2027         */
2028        rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
2029        rb_key -= cfqq->slice_resid;
2030        cfqq->slice_resid = 0;
2031    } else {
2032        rb_key = -HZ;
2033        __cfqq = cfq_rb_first(st);
2034        rb_key += __cfqq ? __cfqq->rb_key : jiffies;
2035    }
2036
2037    if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
2038        new_cfqq = 0;
2039        /*
2040         * same position, nothing more to do
2041         */
2042        if (rb_key == cfqq->rb_key && cfqq->service_tree == st)
2043            return;
2044
2045        cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
2046        cfqq->service_tree = NULL;
2047    }
2048
2049    left = 1;
2050    parent = NULL;
2051    cfqq->service_tree = st;
2052    p = &st->rb.rb_node;
2053    while (*p) {
2054        parent = *p;
2055        __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
2056
2057        /*
2058         * sort by key, that represents service time.
2059         */
2060        if (time_before(rb_key, __cfqq->rb_key))
2061            p = &parent->rb_left;
2062        else {
2063            p = &parent->rb_right;
2064            left = 0;
2065        }
2066    }
2067
2068    if (left)
2069        st->left = &cfqq->rb_node;
2070
2071    cfqq->rb_key = rb_key;
2072    rb_link_node(&cfqq->rb_node, parent, p);
2073    rb_insert_color(&cfqq->rb_node, &st->rb);
2074    st->count++;
2075    if (add_front || !new_cfqq)
2076        return;
2077    cfq_group_notify_queue_add(cfqd, cfqq->cfqg);
2078}
2079
2080static struct cfq_queue *
2081cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
2082             sector_t sector, struct rb_node **ret_parent,
2083             struct rb_node ***rb_link)
2084{
2085    struct rb_node **p, *parent;
2086    struct cfq_queue *cfqq = NULL;
2087
2088    parent = NULL;
2089    p = &root->rb_node;
2090    while (*p) {
2091        struct rb_node **n;
2092
2093        parent = *p;
2094        cfqq = rb_entry(parent, struct cfq_queue, p_node);
2095
2096        /*
2097         * Sort strictly based on sector. Smallest to the left,
2098         * largest to the right.
2099         */
2100        if (sector > blk_rq_pos(cfqq->next_rq))
2101            n = &(*p)->rb_right;
2102        else if (sector < blk_rq_pos(cfqq->next_rq))
2103            n = &(*p)->rb_left;
2104        else
2105            break;
2106        p = n;
2107        cfqq = NULL;
2108    }
2109
2110    *ret_parent = parent;
2111    if (rb_link)
2112        *rb_link = p;
2113    return cfqq;
2114}
2115
2116static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2117{
2118    struct rb_node **p, *parent;
2119    struct cfq_queue *__cfqq;
2120
2121    if (cfqq->p_root) {
2122        rb_erase(&cfqq->p_node, cfqq->p_root);
2123        cfqq->p_root = NULL;
2124    }
2125
2126    if (cfq_class_idle(cfqq))
2127        return;
2128    if (!cfqq->next_rq)
2129        return;
2130
2131    cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
2132    __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
2133                      blk_rq_pos(cfqq->next_rq), &parent, &p);
2134    if (!__cfqq) {
2135        rb_link_node(&cfqq->p_node, parent, p);
2136        rb_insert_color(&cfqq->p_node, cfqq->p_root);
2137    } else
2138        cfqq->p_root = NULL;
2139}
2140
2141/*
2142 * Update cfqq's position in the service tree.
2143 */
2144static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2145{
2146    /*
2147     * Resorting requires the cfqq to be on the RR list already.
2148     */
2149    if (cfq_cfqq_on_rr(cfqq)) {
2150        cfq_service_tree_add(cfqd, cfqq, 0);
2151        cfq_prio_tree_add(cfqd, cfqq);
2152    }
2153}
2154
2155/*
2156 * add to busy list of queues for service, trying to be fair in ordering
2157 * the pending list according to last request service
2158 */
2159static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2160{
2161    cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
2162    BUG_ON(cfq_cfqq_on_rr(cfqq));
2163    cfq_mark_cfqq_on_rr(cfqq);
2164    cfqd->busy_queues++;
2165    if (cfq_cfqq_sync(cfqq))
2166        cfqd->busy_sync_queues++;
2167
2168    cfq_resort_rr_list(cfqd, cfqq);
2169}
2170
2171/*
2172 * Called when the cfqq no longer has requests pending, remove it from
2173 * the service tree.
2174 */
2175static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2176{
2177    cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
2178    BUG_ON(!cfq_cfqq_on_rr(cfqq));
2179    cfq_clear_cfqq_on_rr(cfqq);
2180
2181    if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
2182        cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
2183        cfqq->service_tree = NULL;
2184    }
2185    if (cfqq->p_root) {
2186        rb_erase(&cfqq->p_node, cfqq->p_root);
2187        cfqq->p_root = NULL;
2188    }
2189
2190    cfq_group_notify_queue_del(cfqd, cfqq->cfqg);
2191    BUG_ON(!cfqd->busy_queues);
2192    cfqd->busy_queues--;
2193    if (cfq_cfqq_sync(cfqq))
2194        cfqd->busy_sync_queues--;
2195}
2196
2197/*
2198 * rb tree support functions
2199 */
2200static void cfq_del_rq_rb(struct request *rq)
2201{
2202    struct cfq_queue *cfqq = RQ_CFQQ(rq);
2203    const int sync = rq_is_sync(rq);
2204
2205    BUG_ON(!cfqq->queued[sync]);
2206    cfqq->queued[sync]--;
2207
2208    elv_rb_del(&cfqq->sort_list, rq);
2209
2210    if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
2211        /*
2212         * Queue will be deleted from service tree when we actually
2213         * expire it later. Right now just remove it from prio tree
2214         * as it is empty.
2215         */
2216        if (cfqq->p_root) {
2217            rb_erase(&cfqq->p_node, cfqq->p_root);
2218            cfqq->p_root = NULL;
2219        }
2220    }
2221}
2222
2223static void cfq_add_rq_rb(struct request *rq)
2224{
2225    struct cfq_queue *cfqq = RQ_CFQQ(rq);
2226    struct cfq_data *cfqd = cfqq->cfqd;
2227    struct request *prev;
2228
2229    cfqq->queued[rq_is_sync(rq)]++;
2230
2231    elv_rb_add(&cfqq->sort_list, rq);
2232
2233    if (!cfq_cfqq_on_rr(cfqq))
2234        cfq_add_cfqq_rr(cfqd, cfqq);
2235
2236    /*
2237     * check if this request is a better next-serve candidate
2238     */
2239    prev = cfqq->next_rq;
2240    cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
2241
2242    /*
2243     * adjust priority tree position, if ->next_rq changes
2244     */
2245    if (prev != cfqq->next_rq)
2246        cfq_prio_tree_add(cfqd, cfqq);
2247
2248    BUG_ON(!cfqq->next_rq);
2249}
2250
2251static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
2252{
2253    elv_rb_del(&cfqq->sort_list, rq);
2254    cfqq->queued[rq_is_sync(rq)]--;
2255    cfqg_stats_update_io_remove(RQ_CFQG(rq), rq->cmd_flags);
2256    cfq_add_rq_rb(rq);
2257    cfqg_stats_update_io_add(RQ_CFQG(rq), cfqq->cfqd->serving_group,
2258                 rq->cmd_flags);
2259}
2260
2261static struct request *
2262cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
2263{
2264    struct task_struct *tsk = current;
2265    struct cfq_io_cq *cic;
2266    struct cfq_queue *cfqq;
2267
2268    cic = cfq_cic_lookup(cfqd, tsk->io_context);
2269    if (!cic)
2270        return NULL;
2271
2272    cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
2273    if (cfqq)
2274        return elv_rb_find(&cfqq->sort_list, bio_end_sector(bio));
2275
2276    return NULL;
2277}
2278
2279static void cfq_activate_request(struct request_queue *q, struct request *rq)
2280{
2281    struct cfq_data *cfqd = q->elevator->elevator_data;
2282
2283    cfqd->rq_in_driver++;
2284    cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
2285                        cfqd->rq_in_driver);
2286
2287    cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
2288}
2289
2290static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
2291{
2292    struct cfq_data *cfqd = q->elevator->elevator_data;
2293
2294    WARN_ON(!cfqd->rq_in_driver);
2295    cfqd->rq_in_driver--;
2296    cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
2297                        cfqd->rq_in_driver);
2298}
2299
2300static void cfq_remove_request(struct request *rq)
2301{
2302    struct cfq_queue *cfqq = RQ_CFQQ(rq);
2303
2304    if (cfqq->next_rq == rq)
2305        cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
2306
2307    list_del_init(&rq->queuelist);
2308    cfq_del_rq_rb(rq);
2309
2310    cfqq->cfqd->rq_queued--;
2311    cfqg_stats_update_io_remove(RQ_CFQG(rq), rq->cmd_flags);
2312    if (rq->cmd_flags & REQ_PRIO) {
2313        WARN_ON(!cfqq->prio_pending);
2314        cfqq->prio_pending--;
2315    }
2316}
2317
2318static int cfq_merge(struct request_queue *q, struct request **req,
2319             struct bio *bio)
2320{
2321    struct cfq_data *cfqd = q->elevator->elevator_data;
2322    struct request *__rq;
2323
2324    __rq = cfq_find_rq_fmerge(cfqd, bio);
2325    if (__rq && elv_rq_merge_ok(__rq, bio)) {
2326        *req = __rq;
2327        return ELEVATOR_FRONT_MERGE;
2328    }
2329
2330    return ELEVATOR_NO_MERGE;
2331}
2332
2333static void cfq_merged_request(struct request_queue *q, struct request *req,
2334                   int type)
2335{
2336    if (type == ELEVATOR_FRONT_MERGE) {
2337        struct cfq_queue *cfqq = RQ_CFQQ(req);
2338
2339        cfq_reposition_rq_rb(cfqq, req);
2340    }
2341}
2342
2343static void cfq_bio_merged(struct request_queue *q, struct request *req,
2344                struct bio *bio)
2345{
2346    cfqg_stats_update_io_merged(RQ_CFQG(req), bio->bi_rw);
2347}
2348
2349static void
2350cfq_merged_requests(struct request_queue *q, struct request *rq,
2351            struct request *next)
2352{
2353    struct cfq_queue *cfqq = RQ_CFQQ(rq);
2354    struct cfq_data *cfqd = q->elevator->elevator_data;
2355
2356    /*
2357     * reposition in fifo if next is older than rq
2358     */
2359    if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
2360        time_before(rq_fifo_time(next), rq_fifo_time(rq)) &&
2361        cfqq == RQ_CFQQ(next)) {
2362        list_move(&rq->queuelist, &next->queuelist);
2363        rq_set_fifo_time(rq, rq_fifo_time(next));
2364    }
2365
2366    if (cfqq->next_rq == next)
2367        cfqq->next_rq = rq;
2368    cfq_remove_request(next);
2369    cfqg_stats_update_io_merged(RQ_CFQG(rq), next->cmd_flags);
2370
2371    cfqq = RQ_CFQQ(next);
2372    /*
2373     * all requests of this queue are merged to other queues, delete it
2374     * from the service tree. If it's the active_queue,
2375     * cfq_dispatch_requests() will choose to expire it or do idle
2376     */
2377    if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list) &&
2378        cfqq != cfqd->active_queue)
2379        cfq_del_cfqq_rr(cfqd, cfqq);
2380}
2381
2382static int cfq_allow_merge(struct request_queue *q, struct request *rq,
2383               struct bio *bio)
2384{
2385    struct cfq_data *cfqd = q->elevator->elevator_data;
2386    struct cfq_io_cq *cic;
2387    struct cfq_queue *cfqq;
2388
2389    /*
2390     * Disallow merge of a sync bio into an async request.
2391     */
2392    if (cfq_bio_sync(bio) && !rq_is_sync(rq))
2393        return false;
2394
2395    /*
2396     * Lookup the cfqq that this bio will be queued with and allow
2397     * merge only if rq is queued there.
2398     */
2399    cic = cfq_cic_lookup(cfqd, current->io_context);
2400    if (!cic)
2401        return false;
2402
2403    cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
2404    return cfqq == RQ_CFQQ(rq);
2405}
2406
2407static inline void cfq_del_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2408{
2409    del_timer(&cfqd->idle_slice_timer);
2410    cfqg_stats_update_idle_time(cfqq->cfqg);
2411}
2412
2413static void __cfq_set_active_queue(struct cfq_data *cfqd,
2414                   struct cfq_queue *cfqq)
2415{
2416    if (cfqq) {
2417        cfq_log_cfqq(cfqd, cfqq, "set_active wl_class:%d wl_type:%d",
2418                cfqd->serving_wl_class, cfqd->serving_wl_type);
2419        cfqg_stats_update_avg_queue_size(cfqq->cfqg);
2420        cfqq->slice_start = 0;
2421        cfqq->dispatch_start = jiffies;
2422        cfqq->allocated_slice = 0;
2423        cfqq->slice_end = 0;
2424        cfqq->slice_dispatch = 0;
2425        cfqq->nr_sectors = 0;
2426
2427        cfq_clear_cfqq_wait_request(cfqq);
2428        cfq_clear_cfqq_must_dispatch(cfqq);
2429        cfq_clear_cfqq_must_alloc_slice(cfqq);
2430        cfq_clear_cfqq_fifo_expire(cfqq);
2431        cfq_mark_cfqq_slice_new(cfqq);
2432
2433        cfq_del_timer(cfqd, cfqq);
2434    }
2435
2436    cfqd->active_queue = cfqq;
2437}
2438
2439/*
2440 * current cfqq expired its slice (or was too idle), select new one
2441 */
2442static void
2443__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2444            bool timed_out)
2445{
2446    cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
2447
2448    if (cfq_cfqq_wait_request(cfqq))
2449        cfq_del_timer(cfqd, cfqq);
2450
2451    cfq_clear_cfqq_wait_request(cfqq);
2452    cfq_clear_cfqq_wait_busy(cfqq);
2453
2454    /*
2455     * If this cfqq is shared between multiple processes, check to
2456     * make sure that those processes are still issuing I/Os within
2457     * the mean seek distance. If not, it may be time to break the
2458     * queues apart again.
2459     */
2460    if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq))
2461        cfq_mark_cfqq_split_coop(cfqq);
2462
2463    /*
2464     * store what was left of this slice, if the queue idled/timed out
2465     */
2466    if (timed_out) {
2467        if (cfq_cfqq_slice_new(cfqq))
2468            cfqq->slice_resid = cfq_scaled_cfqq_slice(cfqd, cfqq);
2469        else
2470            cfqq->slice_resid = cfqq->slice_end - jiffies;
2471        cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
2472    }
2473
2474    cfq_group_served(cfqd, cfqq->cfqg, cfqq);
2475
2476    if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
2477        cfq_del_cfqq_rr(cfqd, cfqq);
2478
2479    cfq_resort_rr_list(cfqd, cfqq);
2480
2481    if (cfqq == cfqd->active_queue)
2482        cfqd->active_queue = NULL;
2483
2484    if (cfqd->active_cic) {
2485        put_io_context(cfqd->active_cic->icq.ioc);
2486        cfqd->active_cic = NULL;
2487    }
2488}
2489
2490static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
2491{
2492    struct cfq_queue *cfqq = cfqd->active_queue;
2493
2494    if (cfqq)
2495        __cfq_slice_expired(cfqd, cfqq, timed_out);
2496}
2497
2498/*
2499 * Get next queue for service. Unless we have a queue preemption,
2500 * we'll simply select the first cfqq in the service tree.
2501 */
2502static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
2503{
2504    struct cfq_rb_root *st = st_for(cfqd->serving_group,
2505            cfqd->serving_wl_class, cfqd->serving_wl_type);
2506
2507    if (!cfqd->rq_queued)
2508        return NULL;
2509
2510    /* There is nothing to dispatch */
2511    if (!st)
2512        return NULL;
2513    if (RB_EMPTY_ROOT(&st->rb))
2514        return NULL;
2515    return cfq_rb_first(st);
2516}
2517
2518static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
2519{
2520    struct cfq_group *cfqg;
2521    struct cfq_queue *cfqq;
2522    int i, j;
2523    struct cfq_rb_root *st;
2524
2525    if (!cfqd->rq_queued)
2526        return NULL;
2527
2528    cfqg = cfq_get_next_cfqg(cfqd);
2529    if (!cfqg)
2530        return NULL;
2531
2532    for_each_cfqg_st(cfqg, i, j, st)
2533        if ((cfqq = cfq_rb_first(st)) != NULL)
2534            return cfqq;
2535    return NULL;
2536}
2537
2538/*
2539 * Get and set a new active queue for service.
2540 */
2541static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
2542                          struct cfq_queue *cfqq)
2543{
2544    if (!cfqq)
2545        cfqq = cfq_get_next_queue(cfqd);
2546
2547    __cfq_set_active_queue(cfqd, cfqq);
2548    return cfqq;
2549}
2550
2551static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
2552                      struct request *rq)
2553{
2554    if (blk_rq_pos(rq) >= cfqd->last_position)
2555        return blk_rq_pos(rq) - cfqd->last_position;
2556    else
2557        return cfqd->last_position - blk_rq_pos(rq);
2558}
2559
2560static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2561                   struct request *rq)
2562{
2563    return cfq_dist_from_last(cfqd, rq) <= CFQQ_CLOSE_THR;
2564}
2565
2566static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
2567                    struct cfq_queue *cur_cfqq)
2568{
2569    struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
2570    struct rb_node *parent, *node;
2571    struct cfq_queue *__cfqq;
2572    sector_t sector = cfqd->last_position;
2573
2574    if (RB_EMPTY_ROOT(root))
2575        return NULL;
2576
2577    /*
2578     * First, if we find a request starting at the end of the last
2579     * request, choose it.
2580     */
2581    __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
2582    if (__cfqq)
2583        return __cfqq;
2584
2585    /*
2586     * If the exact sector wasn't found, the parent of the NULL leaf
2587     * will contain the closest sector.
2588     */
2589    __cfqq = rb_entry(parent, struct cfq_queue, p_node);
2590    if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
2591        return __cfqq;
2592
2593    if (blk_rq_pos(__cfqq->next_rq) < sector)
2594        node = rb_next(&__cfqq->p_node);
2595    else
2596        node = rb_prev(&__cfqq->p_node);
2597    if (!node)
2598        return NULL;
2599
2600    __cfqq = rb_entry(node, struct cfq_queue, p_node);
2601    if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
2602        return __cfqq;
2603
2604    return NULL;
2605}
2606
2607/*
2608 * cfqd - obvious
2609 * cur_cfqq - passed in so that we don't decide that the current queue is
2610 * closely cooperating with itself.
2611 *
2612 * So, basically we're assuming that that cur_cfqq has dispatched at least
2613 * one request, and that cfqd->last_position reflects a position on the disk
2614 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
2615 * assumption.
2616 */
2617static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
2618                          struct cfq_queue *cur_cfqq)
2619{
2620    struct cfq_queue *cfqq;
2621
2622    if (cfq_class_idle(cur_cfqq))
2623        return NULL;
2624    if (!cfq_cfqq_sync(cur_cfqq))
2625        return NULL;
2626    if (CFQQ_SEEKY(cur_cfqq))
2627        return NULL;
2628
2629    /*
2630     * Don't search priority tree if it's the only queue in the group.
2631     */
2632    if (cur_cfqq->cfqg->nr_cfqq == 1)
2633        return NULL;
2634
2635    /*
2636     * We should notice if some of the queues are cooperating, eg
2637     * working closely on the same area of the disk. In that case,
2638     * we can group them together and don't waste time idling.
2639     */
2640    cfqq = cfqq_close(cfqd, cur_cfqq);
2641    if (!cfqq)
2642        return NULL;
2643
2644    /* If new queue belongs to different cfq_group, don't choose it */
2645    if (cur_cfqq->cfqg != cfqq->cfqg)
2646        return NULL;
2647
2648    /*
2649     * It only makes sense to merge sync queues.
2650     */
2651    if (!cfq_cfqq_sync(cfqq))
2652        return NULL;
2653    if (CFQQ_SEEKY(cfqq))
2654        return NULL;
2655
2656    /*
2657     * Do not merge queues of different priority classes
2658     */
2659    if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
2660        return NULL;
2661
2662    return cfqq;
2663}
2664
2665/*
2666 * Determine whether we should enforce idle window for this queue.
2667 */
2668
2669static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2670{
2671    enum wl_class_t wl_class = cfqq_class(cfqq);
2672    struct cfq_rb_root *st = cfqq->service_tree;
2673
2674    BUG_ON(!st);
2675    BUG_ON(!st->count);
2676
2677    if (!cfqd->cfq_slice_idle)
2678        return false;
2679
2680    /* We never do for idle class queues. */
2681    if (wl_class == IDLE_WORKLOAD)
2682        return false;
2683
2684    /* We do for queues that were marked with idle window flag. */
2685    if (cfq_cfqq_idle_window(cfqq) &&
2686       !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag))
2687        return true;
2688
2689    /*
2690     * Otherwise, we do only if they are the last ones
2691     * in their service tree.
2692     */
2693    if (st->count == 1 && cfq_cfqq_sync(cfqq) &&
2694       !cfq_io_thinktime_big(cfqd, &st->ttime, false))
2695        return true;
2696    cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d", st->count);
2697    return false;
2698}
2699
2700static void cfq_arm_slice_timer(struct cfq_data *cfqd)
2701{
2702    struct cfq_queue *cfqq = cfqd->active_queue;
2703    struct cfq_io_cq *cic;
2704    unsigned long sl, group_idle = 0;
2705
2706    /*
2707     * SSD device without seek penalty, disable idling. But only do so
2708     * for devices that support queuing, otherwise we still have a problem
2709     * with sync vs async workloads.
2710     */
2711    if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
2712        return;
2713
2714    WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
2715    WARN_ON(cfq_cfqq_slice_new(cfqq));
2716
2717    /*
2718     * idle is disabled, either manually or by past process history
2719     */
2720    if (!cfq_should_idle(cfqd, cfqq)) {
2721        /* no queue idling. Check for group idling */
2722        if (cfqd->cfq_group_idle)
2723            group_idle = cfqd->cfq_group_idle;
2724        else
2725            return;
2726    }
2727
2728    /*
2729     * still active requests from this queue, don't idle
2730     */
2731    if (cfqq->dispatched)
2732        return;
2733
2734    /*
2735     * task has exited, don't wait
2736     */
2737    cic = cfqd->active_cic;
2738    if (!cic || !atomic_read(&cic->icq.ioc->active_ref))
2739        return;
2740
2741    /*
2742     * If our average think time is larger than the remaining time
2743     * slice, then don't idle. This avoids overrunning the allotted
2744     * time slice.
2745     */
2746    if (sample_valid(cic->ttime.ttime_samples) &&
2747        (cfqq->slice_end - jiffies < cic->ttime.ttime_mean)) {
2748        cfq_log_cfqq(cfqd, cfqq, "Not idling. think_time:%lu",
2749                 cic->ttime.ttime_mean);
2750        return;
2751    }
2752
2753    /* There are other queues in the group, don't do group idle */
2754    if (group_idle && cfqq->cfqg->nr_cfqq > 1)
2755        return;
2756
2757    cfq_mark_cfqq_wait_request(cfqq);
2758
2759    if (group_idle)
2760        sl = cfqd->cfq_group_idle;
2761    else
2762        sl = cfqd->cfq_slice_idle;
2763
2764    mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
2765    cfqg_stats_set_start_idle_time(cfqq->cfqg);
2766    cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu group_idle: %d", sl,
2767            group_idle ? 1 : 0);
2768}
2769
2770/*
2771 * Move request from internal lists to the request queue dispatch list.
2772 */
2773static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
2774{
2775    struct cfq_data *cfqd = q->elevator->elevator_data;
2776    struct cfq_queue *cfqq = RQ_CFQQ(rq);
2777
2778    cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
2779
2780    cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
2781    cfq_remove_request(rq);
2782    cfqq->dispatched++;
2783    (RQ_CFQG(rq))->dispatched++;
2784    elv_dispatch_sort(q, rq);
2785
2786    cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
2787    cfqq->nr_sectors += blk_rq_sectors(rq);
2788    cfqg_stats_update_dispatch(cfqq->cfqg, blk_rq_bytes(rq), rq->cmd_flags);
2789}
2790
2791/*
2792 * return expired entry, or NULL to just start from scratch in rbtree
2793 */
2794static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
2795{
2796    struct request *rq = NULL;
2797
2798    if (cfq_cfqq_fifo_expire(cfqq))
2799        return NULL;
2800
2801    cfq_mark_cfqq_fifo_expire(cfqq);
2802
2803    if (list_empty(&cfqq->fifo))
2804        return NULL;
2805
2806    rq = rq_entry_fifo(cfqq->fifo.next);
2807    if (time_before(jiffies, rq_fifo_time(rq)))
2808        rq = NULL;
2809
2810    cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
2811    return rq;
2812}
2813
2814static inline int
2815cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2816{
2817    const int base_rq = cfqd->cfq_slice_async_rq;
2818
2819    WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
2820
2821    return 2 * base_rq * (IOPRIO_BE_NR - cfqq->ioprio);
2822}
2823
2824/*
2825 * Must be called with the queue_lock held.
2826 */
2827static int cfqq_process_refs(struct cfq_queue *cfqq)
2828{
2829    int process_refs, io_refs;
2830
2831    io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
2832    process_refs = cfqq->ref - io_refs;
2833    BUG_ON(process_refs < 0);
2834    return process_refs;
2835}
2836
2837static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
2838{
2839    int process_refs, new_process_refs;
2840    struct cfq_queue *__cfqq;
2841
2842    /*
2843     * If there are no process references on the new_cfqq, then it is
2844     * unsafe to follow the ->new_cfqq chain as other cfqq's in the
2845     * chain may have dropped their last reference (not just their
2846     * last process reference).
2847     */
2848    if (!cfqq_process_refs(new_cfqq))
2849        return;
2850
2851    /* Avoid a circular list and skip interim queue merges */
2852    while ((__cfqq = new_cfqq->new_cfqq)) {
2853        if (__cfqq == cfqq)
2854            return;
2855        new_cfqq = __cfqq;
2856    }
2857
2858    process_refs = cfqq_process_refs(cfqq);
2859    new_process_refs = cfqq_process_refs(new_cfqq);
2860    /*
2861     * If the process for the cfqq has gone away, there is no
2862     * sense in merging the queues.
2863     */
2864    if (process_refs == 0 || new_process_refs == 0)
2865        return;
2866
2867    /*
2868     * Merge in the direction of the lesser amount of work.
2869     */
2870    if (new_process_refs >= process_refs) {
2871        cfqq->new_cfqq = new_cfqq;
2872        new_cfqq->ref += process_refs;
2873    } else {
2874        new_cfqq->new_cfqq = cfqq;
2875        cfqq->ref += new_process_refs;
2876    }
2877}
2878
2879static enum wl_type_t cfq_choose_wl_type(struct cfq_data *cfqd,
2880            struct cfq_group *cfqg, enum wl_class_t wl_class)
2881{
2882    struct cfq_queue *queue;
2883    int i;
2884    bool key_valid = false;
2885    unsigned long lowest_key = 0;
2886    enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
2887
2888    for (i = 0; i <= SYNC_WORKLOAD; ++i) {
2889        /* select the one with lowest rb_key */
2890        queue = cfq_rb_first(st_for(cfqg, wl_class, i));
2891        if (queue &&
2892            (!key_valid || time_before(queue->rb_key, lowest_key))) {
2893            lowest_key = queue->rb_key;
2894            cur_best = i;
2895            key_valid = true;
2896        }
2897    }
2898
2899    return cur_best;
2900}
2901
2902static void
2903choose_wl_class_and_type(struct cfq_data *cfqd, struct cfq_group *cfqg)
2904{
2905    unsigned slice;
2906    unsigned count;
2907    struct cfq_rb_root *st;
2908    unsigned group_slice;
2909    enum wl_class_t original_class = cfqd->serving_wl_class;
2910
2911    /* Choose next priority. RT > BE > IDLE */
2912    if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
2913        cfqd->serving_wl_class = RT_WORKLOAD;
2914    else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
2915        cfqd->serving_wl_class = BE_WORKLOAD;
2916    else {
2917        cfqd->serving_wl_class = IDLE_WORKLOAD;
2918        cfqd->workload_expires = jiffies + 1;
2919        return;
2920    }
2921
2922    if (original_class != cfqd->serving_wl_class)
2923        goto new_workload;
2924
2925    /*
2926     * For RT and BE, we have to choose also the type
2927     * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
2928     * expiration time
2929     */
2930    st = st_for(cfqg, cfqd->serving_wl_class, cfqd->serving_wl_type);
2931    count = st->count;
2932
2933    /*
2934     * check workload expiration, and that we still have other queues ready
2935     */
2936    if (count && !time_after(jiffies, cfqd->workload_expires))
2937        return;
2938
2939new_workload:
2940    /* otherwise select new workload type */
2941    cfqd->serving_wl_type = cfq_choose_wl_type(cfqd, cfqg,
2942                    cfqd->serving_wl_class);
2943    st = st_for(cfqg, cfqd->serving_wl_class, cfqd->serving_wl_type);
2944    count = st->count;
2945
2946    /*
2947     * the workload slice is computed as a fraction of target latency
2948     * proportional to the number of queues in that workload, over
2949     * all the queues in the same priority class
2950     */
2951    group_slice = cfq_group_slice(cfqd, cfqg);
2952
2953    slice = group_slice * count /
2954        max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_wl_class],
2955              cfq_group_busy_queues_wl(cfqd->serving_wl_class, cfqd,
2956                    cfqg));
2957
2958    if (cfqd->serving_wl_type == ASYNC_WORKLOAD) {
2959        unsigned int tmp;
2960
2961        /*
2962         * Async queues are currently system wide. Just taking
2963         * proportion of queues with-in same group will lead to higher
2964         * async ratio system wide as generally root group is going
2965         * to have higher weight. A more accurate thing would be to
2966         * calculate system wide asnc/sync ratio.
2967         */
2968        tmp = cfqd->cfq_target_latency *
2969            cfqg_busy_async_queues(cfqd, cfqg);
2970        tmp = tmp/cfqd->busy_queues;
2971        slice = min_t(unsigned, slice, tmp);
2972
2973        /* async workload slice is scaled down according to
2974         * the sync/async slice ratio. */
2975        slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
2976    } else
2977        /* sync workload slice is at least 2 * cfq_slice_idle */
2978        slice = max(slice, 2 * cfqd->cfq_slice_idle);
2979
2980    slice = max_t(unsigned, slice, CFQ_MIN_TT);
2981    cfq_log(cfqd, "workload slice:%d", slice);
2982    cfqd->workload_expires = jiffies + slice;
2983}
2984
2985static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
2986{
2987    struct cfq_rb_root *st = &cfqd->grp_service_tree;
2988    struct cfq_group *cfqg;
2989
2990    if (RB_EMPTY_ROOT(&st->rb))
2991        return NULL;
2992    cfqg = cfq_rb_first_group(st);
2993    update_min_vdisktime(st);
2994    return cfqg;
2995}
2996
2997static void cfq_choose_cfqg(struct cfq_data *cfqd)
2998{
2999    struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
3000
3001    cfqd->serving_group = cfqg;
3002
3003    /* Restore the workload type data */
3004    if (cfqg->saved_wl_slice) {
3005        cfqd->workload_expires = jiffies + cfqg->saved_wl_slice;
3006        cfqd->serving_wl_type = cfqg->saved_wl_type;
3007        cfqd->serving_wl_class = cfqg->saved_wl_class;
3008    } else
3009        cfqd->workload_expires = jiffies - 1;
3010
3011    choose_wl_class_and_type(cfqd, cfqg);
3012}
3013
3014/*
3015 * Select a queue for service. If we have a current active queue,
3016 * check whether to continue servicing it, or retrieve and set a new one.
3017 */
3018static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
3019{
3020    struct cfq_queue *cfqq, *new_cfqq = NULL;
3021
3022    cfqq = cfqd->active_queue;
3023    if (!cfqq)
3024        goto new_queue;
3025
3026    if (!cfqd->rq_queued)
3027        return NULL;
3028
3029    /*
3030     * We were waiting for group to get backlogged. Expire the queue
3031     */
3032    if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list))
3033        goto expire;
3034
3035    /*
3036     * The active queue has run out of time, expire it and select new.
3037     */
3038    if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) {
3039        /*
3040         * If slice had not expired at the completion of last request
3041         * we might not have turned on wait_busy flag. Don't expire
3042         * the queue yet. Allow the group to get backlogged.
3043         *
3044         * The very fact that we have used the slice, that means we
3045         * have been idling all along on this queue and it should be
3046         * ok to wait for this request to complete.
3047         */
3048        if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list)
3049            && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
3050            cfqq = NULL;
3051            goto keep_queue;
3052        } else
3053            goto check_group_idle;
3054    }
3055
3056    /*
3057     * The active queue has requests and isn't expired, allow it to
3058     * dispatch.
3059     */
3060    if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3061        goto keep_queue;
3062
3063    /*
3064     * If another queue has a request waiting within our mean seek
3065     * distance, let it run. The expire code will check for close
3066     * cooperators and put the close queue at the front of the service
3067     * tree. If possible, merge the expiring queue with the new cfqq.
3068     */
3069    new_cfqq = cfq_close_cooperator(cfqd, cfqq);
3070    if (new_cfqq) {
3071        if (!cfqq->new_cfqq)
3072            cfq_setup_merge(cfqq, new_cfqq);
3073        goto expire;
3074    }
3075
3076    /*
3077     * No requests pending. If the active queue still has requests in
3078     * flight or is idling for a new request, allow either of these
3079     * conditions to happen (or time out) before selecting a new queue.
3080     */
3081    if (timer_pending(&cfqd->idle_slice_timer)) {
3082        cfqq = NULL;
3083        goto keep_queue;
3084    }
3085
3086    /*
3087     * This is a deep seek queue, but the device is much faster than
3088     * the queue can deliver, don't idle
3089     **/
3090    if (CFQQ_SEEKY(cfqq) && cfq_cfqq_idle_window(cfqq) &&
3091        (cfq_cfqq_slice_new(cfqq) ||
3092        (cfqq->slice_end - jiffies > jiffies - cfqq->slice_start))) {
3093        cfq_clear_cfqq_deep(cfqq);
3094        cfq_clear_cfqq_idle_window(cfqq);
3095    }
3096
3097    if (cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
3098        cfqq = NULL;
3099        goto keep_queue;
3100    }
3101
3102    /*
3103     * If group idle is enabled and there are requests dispatched from
3104     * this group, wait for requests to complete.
3105     */
3106check_group_idle:
3107    if (cfqd->cfq_group_idle && cfqq->cfqg->nr_cfqq == 1 &&
3108        cfqq->cfqg->dispatched &&
3109        !cfq_io_thinktime_big(cfqd, &cfqq->cfqg->ttime, true)) {
3110        cfqq = NULL;
3111        goto keep_queue;
3112    }
3113
3114expire:
3115    cfq_slice_expired(cfqd, 0);
3116new_queue:
3117    /*
3118     * Current queue expired. Check if we have to switch to a new
3119     * service tree
3120     */
3121    if (!new_cfqq)
3122        cfq_choose_cfqg(cfqd);
3123
3124    cfqq = cfq_set_active_queue(cfqd, new_cfqq);
3125keep_queue:
3126    return cfqq;
3127}
3128
3129static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
3130{
3131    int dispatched = 0;
3132
3133    while (cfqq->next_rq) {
3134        cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
3135        dispatched++;
3136    }
3137
3138    BUG_ON(!list_empty(&cfqq->fifo));
3139
3140    /* By default cfqq is not expired if it is empty. Do it explicitly */
3141    __cfq_slice_expired(cfqq->cfqd, cfqq, 0);
3142    return dispatched;
3143}
3144
3145/*
3146 * Drain our current requests. Used for barriers and when switching
3147 * io schedulers on-the-fly.
3148 */
3149static int cfq_forced_dispatch(struct cfq_data *cfqd)
3150{
3151    struct cfq_queue *cfqq;
3152    int dispatched = 0;
3153
3154    /* Expire the timeslice of the current active queue first */
3155    cfq_slice_expired(cfqd, 0);
3156    while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) {
3157        __cfq_set_active_queue(cfqd, cfqq);
3158        dispatched += __cfq_forced_dispatch_cfqq(cfqq);
3159    }
3160
3161    BUG_ON(cfqd->busy_queues);
3162
3163    cfq_log(cfqd, "forced_dispatch=%d", dispatched);
3164    return dispatched;
3165}
3166
3167static inline bool cfq_slice_used_soon(struct cfq_data *cfqd,
3168    struct cfq_queue *cfqq)
3169{
3170    /* the queue hasn't finished any request, can't estimate */
3171    if (cfq_cfqq_slice_new(cfqq))
3172        return true;
3173    if (time_after(jiffies + cfqd->cfq_slice_idle * cfqq->dispatched,
3174        cfqq->slice_end))
3175        return true;
3176
3177    return false;
3178}
3179
3180static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3181{
3182    unsigned int max_dispatch;
3183
3184    /*
3185     * Drain async requests before we start sync IO
3186     */
3187    if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_flight[BLK_RW_ASYNC])
3188        return false;
3189
3190    /*
3191     * If this is an async queue and we have sync IO in flight, let it wait
3192     */
3193    if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq))
3194        return false;
3195
3196    max_dispatch = max_t(unsigned int, cfqd->cfq_quantum / 2, 1);
3197    if (cfq_class_idle(cfqq))
3198        max_dispatch = 1;
3199
3200    /*
3201     * Does this cfqq already have too much IO in flight?
3202     */
3203    if (cfqq->dispatched >= max_dispatch) {
3204        bool promote_sync = false;
3205        /*
3206         * idle queue must always only have a single IO in flight
3207         */
3208        if (cfq_class_idle(cfqq))
3209            return false;
3210
3211        /*
3212         * If there is only one sync queue
3213         * we can ignore async queue here and give the sync
3214         * queue no dispatch limit. The reason is a sync queue can
3215         * preempt async queue, limiting the sync queue doesn't make
3216         * sense. This is useful for aiostress test.
3217         */
3218        if (cfq_cfqq_sync(cfqq) && cfqd->busy_sync_queues == 1)
3219            promote_sync = true;
3220
3221        /*
3222         * We have other queues, don't allow more IO from this one
3223         */
3224        if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq) &&
3225                !promote_sync)
3226            return false;
3227
3228        /*
3229         * Sole queue user, no limit
3230         */
3231        if (cfqd->busy_queues == 1 || promote_sync)
3232            max_dispatch = -1;
3233        else
3234            /*
3235             * Normally we start throttling cfqq when cfq_quantum/2
3236             * requests have been dispatched. But we can drive
3237             * deeper queue depths at the beginning of slice
3238             * subjected to upper limit of cfq_quantum.
3239             * */
3240            max_dispatch = cfqd->cfq_quantum;
3241    }
3242
3243    /*
3244     * Async queues must wait a bit before being allowed dispatch.
3245     * We also ramp up the dispatch depth gradually for async IO,
3246     * based on the last sync IO we serviced
3247     */
3248    if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
3249        unsigned long last_sync = jiffies - cfqd->last_delayed_sync;
3250        unsigned int depth;
3251
3252        depth = last_sync / cfqd->cfq_slice[1];
3253        if (!depth && !cfqq->dispatched)
3254            depth = 1;
3255        if (depth < max_dispatch)
3256            max_dispatch = depth;
3257    }
3258
3259    /*
3260     * If we're below the current max, allow a dispatch
3261     */
3262    return cfqq->dispatched < max_dispatch;
3263}
3264
3265/*
3266 * Dispatch a request from cfqq, moving them to the request queue
3267 * dispatch list.
3268 */
3269static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3270{
3271    struct request *rq;
3272
3273    BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
3274
3275    if (!cfq_may_dispatch(cfqd, cfqq))
3276        return false;
3277
3278    /*
3279     * follow expired path, else get first next available
3280     */
3281    rq = cfq_check_fifo(cfqq);
3282    if (!rq)
3283        rq = cfqq->next_rq;
3284
3285    /*
3286     * insert request into driver dispatch list
3287     */
3288    cfq_dispatch_insert(cfqd->queue, rq);
3289
3290    if (!cfqd->active_cic) {
3291        struct cfq_io_cq *cic = RQ_CIC(rq);
3292
3293        atomic_long_inc(&cic->icq.ioc->refcount);
3294        cfqd->active_cic = cic;
3295    }
3296
3297    return true;
3298}
3299
3300/*
3301 * Find the cfqq that we need to service and move a request from that to the
3302 * dispatch list
3303 */
3304static int cfq_dispatch_requests(struct request_queue *q, int force)
3305{
3306    struct cfq_data *cfqd = q->elevator->elevator_data;
3307    struct cfq_queue *cfqq;
3308
3309    if (!cfqd->busy_queues)
3310        return 0;
3311
3312    if (unlikely(force))
3313        return cfq_forced_dispatch(cfqd);
3314
3315    cfqq = cfq_select_queue(cfqd);
3316    if (!cfqq)
3317        return 0;
3318
3319    /*
3320     * Dispatch a request from this cfqq, if it is allowed
3321     */
3322    if (!cfq_dispatch_request(cfqd, cfqq))
3323        return 0;
3324
3325    cfqq->slice_dispatch++;
3326    cfq_clear_cfqq_must_dispatch(cfqq);
3327
3328    /*
3329     * expire an async queue immediately if it has used up its slice. idle
3330     * queue always expire after 1 dispatch round.
3331     */
3332    if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
3333        cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
3334        cfq_class_idle(cfqq))) {
3335        cfqq->slice_end = jiffies + 1;
3336        cfq_slice_expired(cfqd, 0);
3337    }
3338
3339    cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
3340    return 1;
3341}
3342
3343/*
3344 * task holds one reference to the queue, dropped when task exits. each rq
3345 * in-flight on this queue also holds a reference, dropped when rq is freed.
3346 *
3347 * Each cfq queue took a reference on the parent group. Drop it now.
3348 * queue lock must be held here.
3349 */
3350static void cfq_put_queue(struct cfq_queue *cfqq)
3351{
3352    struct cfq_data *cfqd = cfqq->cfqd;
3353    struct cfq_group *cfqg;
3354
3355    BUG_ON(cfqq->ref <= 0);
3356
3357    cfqq->ref--;
3358    if (cfqq->ref)
3359        return;
3360
3361    cfq_log_cfqq(cfqd, cfqq, "put_queue");
3362    BUG_ON(rb_first(&cfqq->sort_list));
3363    BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
3364    cfqg = cfqq->cfqg;
3365
3366    if (unlikely(cfqd->active_queue == cfqq)) {
3367        __cfq_slice_expired(cfqd, cfqq, 0);
3368        cfq_schedule_dispatch(cfqd);
3369    }
3370
3371    BUG_ON(cfq_cfqq_on_rr(cfqq));
3372    kmem_cache_free(cfq_pool, cfqq);
3373    cfqg_put(cfqg);
3374}
3375
3376static void cfq_put_cooperator(struct cfq_queue *cfqq)
3377{
3378    struct cfq_queue *__cfqq, *next;
3379
3380    /*
3381     * If this queue was scheduled to merge with another queue, be
3382     * sure to drop the reference taken on that queue (and others in
3383     * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs.
3384     */
3385    __cfqq = cfqq->new_cfqq;
3386    while (__cfqq) {
3387        if (__cfqq == cfqq) {
3388            WARN(1, "cfqq->new_cfqq loop detected\n");
3389            break;
3390        }
3391        next = __cfqq->new_cfqq;
3392        cfq_put_queue(__cfqq);
3393        __cfqq = next;
3394    }
3395}
3396
3397static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3398{
3399    if (unlikely(cfqq == cfqd->active_queue)) {
3400        __cfq_slice_expired(cfqd, cfqq, 0);
3401        cfq_schedule_dispatch(cfqd);
3402    }
3403
3404    cfq_put_cooperator(cfqq);
3405
3406    cfq_put_queue(cfqq);
3407}
3408
3409static void cfq_init_icq(struct io_cq *icq)
3410{
3411    struct cfq_io_cq *cic = icq_to_cic(icq);
3412
3413    cic->ttime.last_end_request = jiffies;
3414}
3415
3416static void cfq_exit_icq(struct io_cq *icq)
3417{
3418    struct cfq_io_cq *cic = icq_to_cic(icq);
3419    struct cfq_data *cfqd = cic_to_cfqd(cic);
3420
3421    if (cic->cfqq[BLK_RW_ASYNC]) {
3422        cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
3423        cic->cfqq[BLK_RW_ASYNC] = NULL;
3424    }
3425
3426    if (cic->cfqq[BLK_RW_SYNC]) {
3427        cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
3428        cic->cfqq[BLK_RW_SYNC] = NULL;
3429    }
3430}
3431
3432static void cfq_init_prio_data(struct cfq_queue *cfqq, struct cfq_io_cq *cic)
3433{
3434    struct task_struct *tsk = current;
3435    int ioprio_class;
3436
3437    if (!cfq_cfqq_prio_changed(cfqq))
3438        return;
3439
3440    ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
3441    switch (ioprio_class) {
3442    default:
3443        printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
3444    case IOPRIO_CLASS_NONE:
3445        /*
3446         * no prio set, inherit CPU scheduling settings
3447         */
3448        cfqq->ioprio = task_nice_ioprio(tsk);
3449        cfqq->ioprio_class = task_nice_ioclass(tsk);
3450        break;
3451    case IOPRIO_CLASS_RT:
3452        cfqq->ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
3453        cfqq->ioprio_class = IOPRIO_CLASS_RT;
3454        break;
3455    case IOPRIO_CLASS_BE:
3456        cfqq->ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
3457        cfqq->ioprio_class = IOPRIO_CLASS_BE;
3458        break;
3459    case IOPRIO_CLASS_IDLE:
3460        cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
3461        cfqq->ioprio = 7;
3462        cfq_clear_cfqq_idle_window(cfqq);
3463        break;
3464    }
3465
3466    /*
3467     * keep track of original prio settings in case we have to temporarily
3468     * elevate the priority of this queue
3469     */
3470    cfqq->org_ioprio = cfqq->ioprio;
3471    cfq_clear_cfqq_prio_changed(cfqq);
3472}
3473
3474static void check_ioprio_changed(struct cfq_io_cq *cic, struct bio *bio)
3475{
3476    int ioprio = cic->icq.ioc->ioprio;
3477    struct cfq_data *cfqd = cic_to_cfqd(cic);
3478    struct cfq_queue *cfqq;
3479
3480    /*
3481     * Check whether ioprio has changed. The condition may trigger
3482     * spuriously on a newly created cic but there's no harm.
3483     */
3484    if (unlikely(!cfqd) || likely(cic->ioprio == ioprio))
3485        return;
3486
3487    cfqq = cic->cfqq[BLK_RW_ASYNC];
3488    if (cfqq) {
3489        struct cfq_queue *new_cfqq;
3490        new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic, bio,
3491                     GFP_ATOMIC);
3492        if (new_cfqq) {
3493            cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
3494            cfq_put_queue(cfqq);
3495        }
3496    }
3497
3498    cfqq = cic->cfqq[BLK_RW_SYNC];
3499    if (cfqq)
3500        cfq_mark_cfqq_prio_changed(cfqq);
3501
3502    cic->ioprio = ioprio;
3503}
3504
3505static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3506              pid_t pid, bool is_sync)
3507{
3508    RB_CLEAR_NODE(&cfqq->rb_node);
3509    RB_CLEAR_NODE(&cfqq->p_node);
3510    INIT_LIST_HEAD(&cfqq->fifo);
3511
3512    cfqq->ref = 0;
3513    cfqq->cfqd = cfqd;
3514
3515    cfq_mark_cfqq_prio_changed(cfqq);
3516
3517    if (is_sync) {
3518        if (!cfq_class_idle(cfqq))
3519            cfq_mark_cfqq_idle_window(cfqq);
3520        cfq_mark_cfqq_sync(cfqq);
3521    }
3522    cfqq->pid = pid;
3523}
3524
3525#ifdef CONFIG_CFQ_GROUP_IOSCHED
3526static void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
3527{
3528    struct cfq_data *cfqd = cic_to_cfqd(cic);
3529    struct cfq_queue *sync_cfqq;
3530    uint64_t id;
3531
3532    rcu_read_lock();
3533    id = bio_blkcg(bio)->id;
3534    rcu_read_unlock();
3535
3536    /*
3537     * Check whether blkcg has changed. The condition may trigger
3538     * spuriously on a newly created cic but there's no harm.
3539     */
3540    if (unlikely(!cfqd) || likely(cic->blkcg_id == id))
3541        return;
3542
3543    sync_cfqq = cic_to_cfqq(cic, 1);
3544    if (sync_cfqq) {
3545        /*
3546         * Drop reference to sync queue. A new sync queue will be
3547         * assigned in new group upon arrival of a fresh request.
3548         */
3549        cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
3550        cic_set_cfqq(cic, NULL, 1);
3551        cfq_put_queue(sync_cfqq);
3552    }
3553
3554    cic->blkcg_id = id;
3555}
3556#else
3557static inline void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio) { }
3558#endif /* CONFIG_CFQ_GROUP_IOSCHED */
3559
3560static struct cfq_queue *
3561cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
3562             struct bio *bio, gfp_t gfp_mask)
3563{
3564    struct blkcg *blkcg;
3565    struct cfq_queue *cfqq, *new_cfqq = NULL;
3566    struct cfq_group *cfqg;
3567
3568retry:
3569    rcu_read_lock();
3570
3571    blkcg = bio_blkcg(bio);
3572    cfqg = cfq_lookup_create_cfqg(cfqd, blkcg);
3573    cfqq = cic_to_cfqq(cic, is_sync);
3574
3575    /*
3576     * Always try a new alloc if we fell back to the OOM cfqq
3577     * originally, since it should just be a temporary situation.
3578     */
3579    if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3580        cfqq = NULL;
3581        if (new_cfqq) {
3582            cfqq = new_cfqq;
3583            new_cfqq = NULL;
3584        } else if (gfp_mask & __GFP_WAIT) {
3585            rcu_read_unlock();
3586            spin_unlock_irq(cfqd->queue->queue_lock);
3587            new_cfqq = kmem_cache_alloc_node(cfq_pool,
3588                    gfp_mask | __GFP_ZERO,
3589                    cfqd->queue->node);
3590            spin_lock_irq(cfqd->queue->queue_lock);
3591            if (new_cfqq)
3592                goto retry;
3593            else
3594                return &cfqd->oom_cfqq;
3595        } else {
3596            cfqq = kmem_cache_alloc_node(cfq_pool,
3597                    gfp_mask | __GFP_ZERO,
3598                    cfqd->queue->node);
3599        }
3600
3601        if (cfqq) {
3602            cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
3603            cfq_init_prio_data(cfqq, cic);
3604            cfq_link_cfqq_cfqg(cfqq, cfqg);
3605            cfq_log_cfqq(cfqd, cfqq, "alloced");
3606        } else
3607            cfqq = &cfqd->oom_cfqq;
3608    }
3609
3610    if (new_cfqq)
3611        kmem_cache_free(cfq_pool, new_cfqq);
3612
3613    rcu_read_unlock();
3614    return cfqq;
3615}
3616
3617static struct cfq_queue **
3618cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
3619{
3620    switch (ioprio_class) {
3621    case IOPRIO_CLASS_RT:
3622        return &cfqd->async_cfqq[0][ioprio];
3623    case IOPRIO_CLASS_NONE:
3624        ioprio = IOPRIO_NORM;
3625        /* fall through */
3626    case IOPRIO_CLASS_BE:
3627        return &cfqd->async_cfqq[1][ioprio];
3628    case IOPRIO_CLASS_IDLE:
3629        return &cfqd->async_idle_cfqq;
3630    default:
3631        BUG();
3632    }
3633}
3634
3635static struct cfq_queue *
3636cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
3637          struct bio *bio, gfp_t gfp_mask)
3638{
3639    const int ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
3640    const int ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
3641    struct cfq_queue **async_cfqq = NULL;
3642    struct cfq_queue *cfqq = NULL;
3643
3644    if (!is_sync) {
3645        async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
3646        cfqq = *async_cfqq;
3647    }
3648
3649    if (!cfqq)
3650        cfqq = cfq_find_alloc_queue(cfqd, is_sync, cic, bio, gfp_mask);
3651
3652    /*
3653     * pin the queue now that it's allocated, scheduler exit will prune it
3654     */
3655    if (!is_sync && !(*async_cfqq)) {
3656        cfqq->ref++;
3657        *async_cfqq = cfqq;
3658    }
3659
3660    cfqq->ref++;
3661    return cfqq;
3662}
3663
3664static void
3665__cfq_update_io_thinktime(struct cfq_ttime *ttime, unsigned long slice_idle)
3666{
3667    unsigned long elapsed = jiffies - ttime->last_end_request;
3668    elapsed = min(elapsed, 2UL * slice_idle);
3669
3670    ttime->ttime_samples = (7*ttime->ttime_samples + 256) / 8;
3671    ttime->ttime_total = (7*ttime->ttime_total + 256*elapsed) / 8;
3672    ttime->ttime_mean = (ttime->ttime_total + 128) / ttime->ttime_samples;
3673}
3674
3675static void
3676cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3677            struct cfq_io_cq *cic)
3678{
3679    if (cfq_cfqq_sync(cfqq)) {
3680        __cfq_update_io_thinktime(&cic->ttime, cfqd->cfq_slice_idle);
3681        __cfq_update_io_thinktime(&cfqq->service_tree->ttime,
3682            cfqd->cfq_slice_idle);
3683    }
3684#ifdef CONFIG_CFQ_GROUP_IOSCHED
3685    __cfq_update_io_thinktime(&cfqq->cfqg->ttime, cfqd->cfq_group_idle);
3686#endif
3687}
3688
3689static void
3690cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3691               struct request *rq)
3692{
3693    sector_t sdist = 0;
3694    sector_t n_sec = blk_rq_sectors(rq);
3695    if (cfqq->last_request_pos) {
3696        if (cfqq->last_request_pos < blk_rq_pos(rq))
3697            sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
3698        else
3699            sdist = cfqq->last_request_pos - blk_rq_pos(rq);
3700    }
3701
3702    cfqq->seek_history <<= 1;
3703    if (blk_queue_nonrot(cfqd->queue))
3704        cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT);
3705    else
3706        cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
3707}
3708
3709/*
3710 * Disable idle window if the process thinks too long or seeks so much that
3711 * it doesn't matter
3712 */
3713static void
3714cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3715               struct cfq_io_cq *cic)
3716{
3717    int old_idle, enable_idle;
3718
3719    /*
3720     * Don't idle for async or idle io prio class
3721     */
3722    if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
3723        return;
3724
3725    enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
3726
3727    if (cfqq->queued[0] + cfqq->queued[1] >= 4)
3728        cfq_mark_cfqq_deep(cfqq);
3729
3730    if (cfqq->next_rq && (cfqq->next_rq->cmd_flags & REQ_NOIDLE))
3731        enable_idle = 0;
3732    else if (!atomic_read(&cic->icq.ioc->active_ref) ||
3733         !cfqd->cfq_slice_idle ||
3734         (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
3735        enable_idle = 0;
3736    else if (sample_valid(cic->ttime.ttime_samples)) {
3737        if (cic->ttime.ttime_mean > cfqd->cfq_slice_idle)
3738            enable_idle = 0;
3739        else
3740            enable_idle = 1;
3741    }
3742
3743    if (old_idle != enable_idle) {
3744        cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
3745        if (enable_idle)
3746            cfq_mark_cfqq_idle_window(cfqq);
3747        else
3748            cfq_clear_cfqq_idle_window(cfqq);
3749    }
3750}
3751
3752/*
3753 * Check if new_cfqq should preempt the currently active queue. Return 0 for
3754 * no or if we aren't sure, a 1 will cause a preempt.
3755 */
3756static bool
3757cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
3758           struct request *rq)
3759{
3760    struct cfq_queue *cfqq;
3761
3762    cfqq = cfqd->active_queue;
3763    if (!cfqq)
3764        return false;
3765
3766    if (cfq_class_idle(new_cfqq))
3767        return false;
3768
3769    if (cfq_class_idle(cfqq))
3770        return true;
3771
3772    /*
3773     * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice.
3774     */
3775    if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq))
3776        return false;
3777
3778    /*
3779     * if the new request is sync, but the currently running queue is
3780     * not, let the sync request have priority.
3781     */
3782    if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
3783        return true;
3784
3785    if (new_cfqq->cfqg != cfqq->cfqg)
3786        return false;
3787
3788    if (cfq_slice_used(cfqq))
3789        return true;
3790
3791    /* Allow preemption only if we are idling on sync-noidle tree */
3792    if (cfqd->serving_wl_type == SYNC_NOIDLE_WORKLOAD &&
3793        cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
3794        new_cfqq->service_tree->count == 2 &&
3795        RB_EMPTY_ROOT(&cfqq->sort_list))
3796        return true;
3797
3798    /*
3799     * So both queues are sync. Let the new request get disk time if
3800     * it's a metadata request and the current queue is doing regular IO.
3801     */
3802    if ((rq->cmd_flags & REQ_PRIO) && !cfqq->prio_pending)
3803        return true;
3804
3805    /*
3806     * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
3807     */
3808    if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
3809        return true;
3810
3811    /* An idle queue should not be idle now for some reason */
3812    if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq))
3813        return true;
3814
3815    if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
3816        return false;
3817
3818    /*
3819     * if this request is as-good as one we would expect from the
3820     * current cfqq, let it preempt
3821     */
3822    if (cfq_rq_close(cfqd, cfqq, rq))
3823        return true;
3824
3825    return false;
3826}
3827
3828/*
3829 * cfqq preempts the active queue. if we allowed preempt with no slice left,
3830 * let it have half of its nominal slice.
3831 */
3832static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3833{
3834    enum wl_type_t old_type = cfqq_type(cfqd->active_queue);
3835
3836    cfq_log_cfqq(cfqd, cfqq, "preempt");
3837    cfq_slice_expired(cfqd, 1);
3838
3839    /*
3840     * workload type is changed, don't save slice, otherwise preempt
3841     * doesn't happen
3842     */
3843    if (old_type != cfqq_type(cfqq))
3844        cfqq->cfqg->saved_wl_slice = 0;
3845
3846    /*
3847     * Put the new queue at the front of the of the current list,
3848     * so we know that it will be selected next.
3849     */
3850    BUG_ON(!cfq_cfqq_on_rr(cfqq));
3851
3852    cfq_service_tree_add(cfqd, cfqq, 1);
3853
3854    cfqq->slice_end = 0;
3855    cfq_mark_cfqq_slice_new(cfqq);
3856}
3857
3858/*
3859 * Called when a new fs request (rq) is added (to cfqq). Check if there's
3860 * something we should do about it
3861 */
3862static void
3863cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3864        struct request *rq)
3865{
3866    struct cfq_io_cq *cic = RQ_CIC(rq);
3867
3868    cfqd->rq_queued++;
3869    if (rq->cmd_flags & REQ_PRIO)
3870        cfqq->prio_pending++;
3871
3872    cfq_update_io_thinktime(cfqd, cfqq, cic);
3873    cfq_update_io_seektime(cfqd, cfqq, rq);
3874    cfq_update_idle_window(cfqd, cfqq, cic);
3875
3876    cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
3877
3878    if (cfqq == cfqd->active_queue) {
3879        /*
3880         * Remember that we saw a request from this process, but
3881         * don't start queuing just yet. Otherwise we risk seeing lots
3882         * of tiny requests, because we disrupt the normal plugging
3883         * and merging. If the request is already larger than a single
3884         * page, let it rip immediately. For that case we assume that
3885         * merging is already done. Ditto for a busy system that
3886         * has other work pending, don't risk delaying until the
3887         * idle timer unplug to continue working.
3888         */
3889        if (cfq_cfqq_wait_request(cfqq)) {
3890            if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
3891                cfqd->busy_queues > 1) {
3892                cfq_del_timer(cfqd, cfqq);
3893                cfq_clear_cfqq_wait_request(cfqq);
3894                __blk_run_queue(cfqd->queue);
3895            } else {
3896                cfqg_stats_update_idle_time(cfqq->cfqg);
3897                cfq_mark_cfqq_must_dispatch(cfqq);
3898            }
3899        }
3900    } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
3901        /*
3902         * not the active queue - expire current slice if it is
3903         * idle and has expired it's mean thinktime or this new queue
3904         * has some old slice time left and is of higher priority or
3905         * this new queue is RT and the current one is BE
3906         */
3907        cfq_preempt_queue(cfqd, cfqq);
3908        __blk_run_queue(cfqd->queue);
3909    }
3910}
3911
3912static void cfq_insert_request(struct request_queue *q, struct request *rq)
3913{
3914    struct cfq_data *cfqd = q->elevator->elevator_data;
3915    struct cfq_queue *cfqq = RQ_CFQQ(rq);
3916
3917    cfq_log_cfqq(cfqd, cfqq, "insert_request");
3918    cfq_init_prio_data(cfqq, RQ_CIC(rq));
3919
3920    rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
3921    list_add_tail(&rq->queuelist, &cfqq->fifo);
3922    cfq_add_rq_rb(rq);
3923    cfqg_stats_update_io_add(RQ_CFQG(rq), cfqd->serving_group,
3924                 rq->cmd_flags);
3925    cfq_rq_enqueued(cfqd, cfqq, rq);
3926}
3927
3928/*
3929 * Update hw_tag based on peak queue depth over 50 samples under
3930 * sufficient load.
3931 */
3932static void cfq_update_hw_tag(struct cfq_data *cfqd)
3933{
3934    struct cfq_queue *cfqq = cfqd->active_queue;
3935
3936    if (cfqd->rq_in_driver > cfqd->hw_tag_est_depth)
3937        cfqd->hw_tag_est_depth = cfqd->rq_in_driver;
3938
3939    if (cfqd->hw_tag == 1)
3940        return;
3941
3942    if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
3943        cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
3944        return;
3945
3946    /*
3947     * If active queue hasn't enough requests and can idle, cfq might not
3948     * dispatch sufficient requests to hardware. Don't zero hw_tag in this
3949     * case
3950     */
3951    if (cfqq && cfq_cfqq_idle_window(cfqq) &&
3952        cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
3953        CFQ_HW_QUEUE_MIN && cfqd->rq_in_driver < CFQ_HW_QUEUE_MIN)
3954        return;
3955
3956    if (cfqd->hw_tag_samples++ < 50)
3957        return;
3958
3959    if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
3960        cfqd->hw_tag = 1;
3961    else
3962        cfqd->hw_tag = 0;
3963}
3964
3965static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3966{
3967    struct cfq_io_cq *cic = cfqd->active_cic;
3968
3969    /* If the queue already has requests, don't wait */
3970    if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3971        return false;
3972
3973    /* If there are other queues in the group, don't wait */
3974    if (cfqq->cfqg->nr_cfqq > 1)
3975        return false;
3976
3977    /* the only queue in the group, but think time is big */
3978    if (cfq_io_thinktime_big(cfqd, &cfqq->cfqg->ttime, true))
3979        return false;
3980
3981    if (cfq_slice_used(cfqq))
3982        return true;
3983
3984    /* if slice left is less than think time, wait busy */
3985    if (cic && sample_valid(cic->ttime.ttime_samples)
3986        && (cfqq->slice_end - jiffies < cic->ttime.ttime_mean))
3987        return true;
3988
3989    /*
3990     * If think times is less than a jiffy than ttime_mean=0 and above
3991     * will not be true. It might happen that slice has not expired yet
3992     * but will expire soon (4-5 ns) during select_queue(). To cover the
3993     * case where think time is less than a jiffy, mark the queue wait
3994     * busy if only 1 jiffy is left in the slice.
3995     */
3996    if (cfqq->slice_end - jiffies == 1)
3997        return true;
3998
3999    return false;
4000}
4001
4002static void cfq_completed_request(struct request_queue *q, struct request *rq)
4003{
4004    struct cfq_queue *cfqq = RQ_CFQQ(rq);
4005    struct cfq_data *cfqd = cfqq->cfqd;
4006    const int sync = rq_is_sync(rq);
4007    unsigned long now;
4008
4009    now = jiffies;
4010    cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d",
4011             !!(rq->cmd_flags & REQ_NOIDLE));
4012
4013    cfq_update_hw_tag(cfqd);
4014
4015    WARN_ON(!cfqd->rq_in_driver);
4016    WARN_ON(!cfqq->dispatched);
4017    cfqd->rq_in_driver--;
4018    cfqq->dispatched--;
4019    (RQ_CFQG(rq))->dispatched--;
4020    cfqg_stats_update_completion(cfqq->cfqg, rq_start_time_ns(rq),
4021                     rq_io_start_time_ns(rq), rq->cmd_flags);
4022
4023    cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
4024
4025    if (sync) {
4026        struct cfq_rb_root *st;
4027
4028        RQ_CIC(rq)->ttime.last_end_request = now;
4029
4030        if (cfq_cfqq_on_rr(cfqq))
4031            st = cfqq->service_tree;
4032        else
4033            st = st_for(cfqq->cfqg, cfqq_class(cfqq),
4034                    cfqq_type(cfqq));
4035
4036        st->ttime.last_end_request = now;
4037        if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
4038            cfqd->last_delayed_sync = now;
4039    }
4040
4041#ifdef CONFIG_CFQ_GROUP_IOSCHED
4042    cfqq->cfqg->ttime.last_end_request = now;
4043#endif
4044
4045    /*
4046     * If this is the active queue, check if it needs to be expired,
4047     * or if we want to idle in case it has no pending requests.
4048     */
4049    if (cfqd->active_queue == cfqq) {
4050        const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
4051
4052        if (cfq_cfqq_slice_new(cfqq)) {
4053            cfq_set_prio_slice(cfqd, cfqq);
4054            cfq_clear_cfqq_slice_new(cfqq);
4055        }
4056
4057        /*
4058         * Should we wait for next request to come in before we expire
4059         * the queue.
4060         */
4061        if (cfq_should_wait_busy(cfqd, cfqq)) {
4062            unsigned long extend_sl = cfqd->cfq_slice_idle;
4063            if (!cfqd->cfq_slice_idle)
4064                extend_sl = cfqd->cfq_group_idle;
4065            cfqq->slice_end = jiffies + extend_sl;
4066            cfq_mark_cfqq_wait_busy(cfqq);
4067            cfq_log_cfqq(cfqd, cfqq, "will busy wait");
4068        }
4069
4070        /*
4071         * Idling is not enabled on:
4072         * - expired queues
4073         * - idle-priority queues
4074         * - async queues
4075         * - queues with still some requests queued
4076         * - when there is a close cooperator
4077         */
4078        if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
4079            cfq_slice_expired(cfqd, 1);
4080        else if (sync && cfqq_empty &&
4081             !cfq_close_cooperator(cfqd, cfqq)) {
4082            cfq_arm_slice_timer(cfqd);
4083        }
4084    }
4085
4086    if (!cfqd->rq_in_driver)
4087        cfq_schedule_dispatch(cfqd);
4088}
4089
4090static inline int __cfq_may_queue(struct cfq_queue *cfqq)
4091{
4092    if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
4093        cfq_mark_cfqq_must_alloc_slice(cfqq);
4094        return ELV_MQUEUE_MUST;
4095    }
4096
4097    return ELV_MQUEUE_MAY;
4098}
4099
4100static int cfq_may_queue(struct request_queue *q, int rw)
4101{
4102    struct cfq_data *cfqd = q->elevator->elevator_data;
4103    struct task_struct *tsk = current;
4104    struct cfq_io_cq *cic;
4105    struct cfq_queue *cfqq;
4106
4107    /*
4108     * don't force setup of a queue from here, as a call to may_queue
4109     * does not necessarily imply that a request actually will be queued.
4110     * so just lookup a possibly existing queue, or return 'may queue'
4111     * if that fails
4112     */
4113    cic = cfq_cic_lookup(cfqd, tsk->io_context);
4114    if (!cic)
4115        return ELV_MQUEUE_MAY;
4116
4117    cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
4118    if (cfqq) {
4119        cfq_init_prio_data(cfqq, cic);
4120
4121        return __cfq_may_queue(cfqq);
4122    }
4123
4124    return ELV_MQUEUE_MAY;
4125}
4126
4127/*
4128 * queue lock held here
4129 */
4130static void cfq_put_request(struct request *rq)
4131{
4132    struct cfq_queue *cfqq = RQ_CFQQ(rq);
4133
4134    if (cfqq) {
4135        const int rw = rq_data_dir(rq);
4136
4137        BUG_ON(!cfqq->allocated[rw]);
4138        cfqq->allocated[rw]--;
4139
4140        /* Put down rq reference on cfqg */
4141        cfqg_put(RQ_CFQG(rq));
4142        rq->elv.priv[0] = NULL;
4143        rq->elv.priv[1] = NULL;
4144
4145        cfq_put_queue(cfqq);
4146    }
4147}
4148
4149static struct cfq_queue *
4150cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_cq *cic,
4151        struct cfq_queue *cfqq)
4152{
4153    cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
4154    cic_set_cfqq(cic, cfqq->new_cfqq, 1);
4155    cfq_mark_cfqq_coop(cfqq->new_cfqq);
4156    cfq_put_queue(cfqq);
4157    return cic_to_cfqq(cic, 1);
4158}
4159
4160/*
4161 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
4162 * was the last process referring to said cfqq.
4163 */
4164static struct cfq_queue *
4165split_cfqq(struct cfq_io_cq *cic, struct cfq_queue *cfqq)
4166{
4167    if (cfqq_process_refs(cfqq) == 1) {
4168        cfqq->pid = current->pid;
4169        cfq_clear_cfqq_coop(cfqq);
4170        cfq_clear_cfqq_split_coop(cfqq);
4171        return cfqq;
4172    }
4173
4174    cic_set_cfqq(cic, NULL, 1);
4175
4176    cfq_put_cooperator(cfqq);
4177
4178    cfq_put_queue(cfqq);
4179    return NULL;
4180}
4181/*
4182 * Allocate cfq data structures associated with this request.
4183 */
4184static int
4185cfq_set_request(struct request_queue *q, struct request *rq, struct bio *bio,
4186        gfp_t gfp_mask)
4187{
4188    struct cfq_data *cfqd = q->elevator->elevator_data;
4189    struct cfq_io_cq *cic = icq_to_cic(rq->elv.icq);
4190    const int rw = rq_data_dir(rq);
4191    const bool is_sync = rq_is_sync(rq);
4192    struct cfq_queue *cfqq;
4193
4194    might_sleep_if(gfp_mask & __GFP_WAIT);
4195
4196    spin_lock_irq(q->queue_lock);
4197
4198    check_ioprio_changed(cic, bio);
4199    check_blkcg_changed(cic, bio);
4200new_queue:
4201    cfqq = cic_to_cfqq(cic, is_sync);
4202    if (!cfqq || cfqq == &cfqd->oom_cfqq) {
4203        cfqq = cfq_get_queue(cfqd, is_sync, cic, bio, gfp_mask);
4204        cic_set_cfqq(cic, cfqq, is_sync);
4205    } else {
4206        /*
4207         * If the queue was seeky for too long, break it apart.
4208         */
4209        if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) {
4210            cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
4211            cfqq = split_cfqq(cic, cfqq);
4212            if (!cfqq)
4213                goto new_queue;
4214        }
4215
4216        /*
4217         * Check to see if this queue is scheduled to merge with
4218         * another, closely cooperating queue. The merging of
4219         * queues happens here as it must be done in process context.
4220         * The reference on new_cfqq was taken in merge_cfqqs.
4221         */
4222        if (cfqq->new_cfqq)
4223            cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
4224    }
4225
4226    cfqq->allocated[rw]++;
4227
4228    cfqq->ref++;
4229    cfqg_get(cfqq->cfqg);
4230    rq->elv.priv[0] = cfqq;
4231    rq->elv.priv[1] = cfqq->cfqg;
4232    spin_unlock_irq(q->queue_lock);
4233    return 0;
4234}
4235
4236static void cfq_kick_queue(struct work_struct *work)
4237{
4238    struct cfq_data *cfqd =
4239        container_of(work, struct cfq_data, unplug_work);
4240    struct request_queue *q = cfqd->queue;
4241
4242    spin_lock_irq(q->queue_lock);
4243    __blk_run_queue(cfqd->queue);
4244    spin_unlock_irq(q->queue_lock);
4245}
4246
4247/*
4248 * Timer running if the active_queue is currently idling inside its time slice
4249 */
4250static void cfq_idle_slice_timer(unsigned long data)
4251{
4252    struct cfq_data *cfqd = (struct cfq_data *) data;
4253    struct cfq_queue *cfqq;
4254    unsigned long flags;
4255    int timed_out = 1;
4256
4257    cfq_log(cfqd, "idle timer fired");
4258
4259    spin_lock_irqsave(cfqd->queue->queue_lock, flags);
4260
4261    cfqq = cfqd->active_queue;
4262    if (cfqq) {
4263        timed_out = 0;
4264
4265        /*
4266         * We saw a request before the queue expired, let it through
4267         */
4268        if (cfq_cfqq_must_dispatch(cfqq))
4269            goto out_kick;
4270
4271        /*
4272         * expired
4273         */
4274        if (cfq_slice_used(cfqq))
4275            goto expire;
4276
4277        /*
4278         * only expire and reinvoke request handler, if there are
4279         * other queues with pending requests
4280         */
4281        if (!cfqd->busy_queues)
4282            goto out_cont;
4283
4284        /*
4285         * not expired and it has a request pending, let it dispatch
4286         */
4287        if (!RB_EMPTY_ROOT(&cfqq->sort_list))
4288            goto out_kick;
4289
4290        /*
4291         * Queue depth flag is reset only when the idle didn't succeed
4292         */
4293        cfq_clear_cfqq_deep(cfqq);
4294    }
4295expire:
4296    cfq_slice_expired(cfqd, timed_out);
4297out_kick:
4298    cfq_schedule_dispatch(cfqd);
4299out_cont:
4300    spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
4301}
4302
4303static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
4304{
4305    del_timer_sync(&cfqd->idle_slice_timer);
4306    cancel_work_sync(&cfqd->unplug_work);
4307}
4308
4309static void cfq_put_async_queues(struct cfq_data *cfqd)
4310{
4311    int i;
4312
4313    for (i = 0; i < IOPRIO_BE_NR; i++) {
4314        if (cfqd->async_cfqq[0][i])
4315            cfq_put_queue(cfqd->async_cfqq[0][i]);
4316        if (cfqd->async_cfqq[1][i])
4317            cfq_put_queue(cfqd->async_cfqq[1][i]);
4318    }
4319
4320    if (cfqd->async_idle_cfqq)
4321        cfq_put_queue(cfqd->async_idle_cfqq);
4322}
4323
4324static void cfq_exit_queue(struct elevator_queue *e)
4325{
4326    struct cfq_data *cfqd = e->elevator_data;
4327    struct request_queue *q = cfqd->queue;
4328
4329    cfq_shutdown_timer_wq(cfqd);
4330
4331    spin_lock_irq(q->queue_lock);
4332
4333    if (cfqd->active_queue)
4334        __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
4335
4336    cfq_put_async_queues(cfqd);
4337
4338    spin_unlock_irq(q->queue_lock);
4339
4340    cfq_shutdown_timer_wq(cfqd);
4341
4342#ifdef CONFIG_CFQ_GROUP_IOSCHED
4343    blkcg_deactivate_policy(q, &blkcg_policy_cfq);
4344#else
4345    kfree(cfqd->root_group);
4346#endif
4347    kfree(cfqd);
4348}
4349
4350static int cfq_init_queue(struct request_queue *q, struct elevator_type *e)
4351{
4352    struct cfq_data *cfqd;
4353    struct blkcg_gq *blkg __maybe_unused;
4354    int i, ret;
4355    struct elevator_queue *eq;
4356
4357    eq = elevator_alloc(q, e);
4358    if (!eq)
4359        return -ENOMEM;
4360
4361    cfqd = kzalloc_node(sizeof(*cfqd), GFP_KERNEL, q->node);
4362    if (!cfqd) {
4363        kobject_put(&eq->kobj);
4364        return -ENOMEM;
4365    }
4366    eq->elevator_data = cfqd;
4367
4368    cfqd->queue = q;
4369    spin_lock_irq(q->queue_lock);
4370    q->elevator = eq;
4371    spin_unlock_irq(q->queue_lock);
4372
4373    /* Init root service tree */
4374    cfqd->grp_service_tree = CFQ_RB_ROOT;
4375
4376    /* Init root group and prefer root group over other groups by default */
4377#ifdef CONFIG_CFQ_GROUP_IOSCHED
4378    ret = blkcg_activate_policy(q, &blkcg_policy_cfq);
4379    if (ret)
4380        goto out_free;
4381
4382    cfqd->root_group = blkg_to_cfqg(q->root_blkg);
4383#else
4384    ret = -ENOMEM;
4385    cfqd->root_group = kzalloc_node(sizeof(*cfqd->root_group),
4386                    GFP_KERNEL, cfqd->queue->node);
4387    if (!cfqd->root_group)
4388        goto out_free;
4389
4390    cfq_init_cfqg_base(cfqd->root_group);
4391#endif
4392    cfqd->root_group->weight = 2 * CFQ_WEIGHT_DEFAULT;
4393    cfqd->root_group->leaf_weight = 2 * CFQ_WEIGHT_DEFAULT;
4394
4395    /*
4396     * Not strictly needed (since RB_ROOT just clears the node and we
4397     * zeroed cfqd on alloc), but better be safe in case someone decides
4398     * to add magic to the rb code
4399     */
4400    for (i = 0; i < CFQ_PRIO_LISTS; i++)
4401        cfqd->prio_trees[i] = RB_ROOT;
4402
4403    /*
4404     * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
4405     * Grab a permanent reference to it, so that the normal code flow
4406     * will not attempt to free it. oom_cfqq is linked to root_group
4407     * but shouldn't hold a reference as it'll never be unlinked. Lose
4408     * the reference from linking right away.
4409     */
4410    cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
4411    cfqd->oom_cfqq.ref++;
4412
4413    spin_lock_irq(q->queue_lock);
4414    cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, cfqd->root_group);
4415    cfqg_put(cfqd->root_group);
4416    spin_unlock_irq(q->queue_lock);
4417
4418    init_timer(&cfqd->idle_slice_timer);
4419    cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
4420    cfqd->idle_slice_timer.data = (unsigned long) cfqd;
4421
4422    INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
4423
4424    cfqd->cfq_quantum = cfq_quantum;
4425    cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
4426    cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
4427    cfqd->cfq_back_max = cfq_back_max;
4428    cfqd->cfq_back_penalty = cfq_back_penalty;
4429    cfqd->cfq_slice[0] = cfq_slice_async;
4430    cfqd->cfq_slice[1] = cfq_slice_sync;
4431    cfqd->cfq_target_latency = cfq_target_latency;
4432    cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
4433    cfqd->cfq_slice_idle = cfq_slice_idle;
4434    cfqd->cfq_group_idle = cfq_group_idle;
4435    cfqd->cfq_latency = 1;
4436    cfqd->hw_tag = -1;
4437    /*
4438     * we optimistically start assuming sync ops weren't delayed in last
4439     * second, in order to have larger depth for async operations.
4440     */
4441    cfqd->last_delayed_sync = jiffies - HZ;
4442    return 0;
4443
4444out_free:
4445    kfree(cfqd);
4446    kobject_put(&eq->kobj);
4447    return ret;
4448}
4449
4450/*
4451 * sysfs parts below -->
4452 */
4453static ssize_t
4454cfq_var_show(unsigned int var, char *page)
4455{
4456    return sprintf(page, "%d\n", var);
4457}
4458
4459static ssize_t
4460cfq_var_store(unsigned int *var, const char *page, size_t count)
4461{
4462    char *p = (char *) page;
4463
4464    *var = simple_strtoul(p, &p, 10);
4465    return count;
4466}
4467
4468#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
4469static ssize_t __FUNC(struct elevator_queue *e, char *page) \
4470{ \
4471    struct cfq_data *cfqd = e->elevator_data; \
4472    unsigned int __data = __VAR; \
4473    if (__CONV) \
4474        __data = jiffies_to_msecs(__data); \
4475    return cfq_var_show(__data, (page)); \
4476}
4477SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
4478SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
4479SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
4480SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
4481SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
4482SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
4483SHOW_FUNCTION(cfq_group_idle_show, cfqd->cfq_group_idle, 1);
4484SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
4485SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
4486SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
4487SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
4488SHOW_FUNCTION(cfq_target_latency_show, cfqd->cfq_target_latency, 1);
4489#undef SHOW_FUNCTION
4490
4491#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
4492static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
4493{ \
4494    struct cfq_data *cfqd = e->elevator_data; \
4495    unsigned int __data; \
4496    int ret = cfq_var_store(&__data, (page), count); \
4497    if (__data < (MIN)) \
4498        __data = (MIN); \
4499    else if (__data > (MAX)) \
4500        __data = (MAX); \
4501    if (__CONV) \
4502        *(__PTR) = msecs_to_jiffies(__data); \
4503    else \
4504        *(__PTR) = __data; \
4505    return ret; \
4506}
4507STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
4508STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
4509        UINT_MAX, 1);
4510STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
4511        UINT_MAX, 1);
4512STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
4513STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
4514        UINT_MAX, 0);
4515STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
4516STORE_FUNCTION(cfq_group_idle_store, &cfqd->cfq_group_idle, 0, UINT_MAX, 1);
4517STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
4518STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
4519STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
4520        UINT_MAX, 0);
4521STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
4522STORE_FUNCTION(cfq_target_latency_store, &cfqd->cfq_target_latency, 1, UINT_MAX, 1);
4523#undef STORE_FUNCTION
4524
4525#define CFQ_ATTR(name) \
4526    __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
4527
4528static struct elv_fs_entry cfq_attrs[] = {
4529    CFQ_ATTR(quantum),
4530    CFQ_ATTR(fifo_expire_sync),
4531    CFQ_ATTR(fifo_expire_async),
4532    CFQ_ATTR(back_seek_max),
4533    CFQ_ATTR(back_seek_penalty),
4534    CFQ_ATTR(slice_sync),
4535    CFQ_ATTR(slice_async),
4536    CFQ_ATTR(slice_async_rq),
4537    CFQ_ATTR(slice_idle),
4538    CFQ_ATTR(group_idle),
4539    CFQ_ATTR(low_latency),
4540    CFQ_ATTR(target_latency),
4541    __ATTR_NULL
4542};
4543
4544static struct elevator_type iosched_cfq = {
4545    .ops = {
4546        .elevator_merge_fn = cfq_merge,
4547        .elevator_merged_fn = cfq_merged_request,
4548        .elevator_merge_req_fn = cfq_merged_requests,
4549        .elevator_allow_merge_fn = cfq_allow_merge,
4550        .elevator_bio_merged_fn = cfq_bio_merged,
4551        .elevator_dispatch_fn = cfq_dispatch_requests,
4552        .elevator_add_req_fn = cfq_insert_request,
4553        .elevator_activate_req_fn = cfq_activate_request,
4554        .elevator_deactivate_req_fn = cfq_deactivate_request,
4555        .elevator_completed_req_fn = cfq_completed_request,
4556        .elevator_former_req_fn = elv_rb_former_request,
4557        .elevator_latter_req_fn = elv_rb_latter_request,
4558        .elevator_init_icq_fn = cfq_init_icq,
4559        .elevator_exit_icq_fn = cfq_exit_icq,
4560        .elevator_set_req_fn = cfq_set_request,
4561        .elevator_put_req_fn = cfq_put_request,
4562        .elevator_may_queue_fn = cfq_may_queue,
4563        .elevator_init_fn = cfq_init_queue,
4564        .elevator_exit_fn = cfq_exit_queue,
4565    },
4566    .icq_size = sizeof(struct cfq_io_cq),
4567    .icq_align = __alignof__(struct cfq_io_cq),
4568    .elevator_attrs = cfq_attrs,
4569    .elevator_name = "cfq",
4570    .elevator_owner = THIS_MODULE,
4571};
4572
4573#ifdef CONFIG_CFQ_GROUP_IOSCHED
4574static struct blkcg_policy blkcg_policy_cfq = {
4575    .pd_size = sizeof(struct cfq_group),
4576    .cftypes = cfq_blkcg_files,
4577
4578    .pd_init_fn = cfq_pd_init,
4579    .pd_offline_fn = cfq_pd_offline,
4580    .pd_reset_stats_fn = cfq_pd_reset_stats,
4581};
4582#endif
4583
4584static int __init cfq_init(void)
4585{
4586    int ret;
4587
4588    /*
4589     * could be 0 on HZ < 1000 setups
4590     */
4591    if (!cfq_slice_async)
4592        cfq_slice_async = 1;
4593    if (!cfq_slice_idle)
4594        cfq_slice_idle = 1;
4595
4596#ifdef CONFIG_CFQ_GROUP_IOSCHED
4597    if (!cfq_group_idle)
4598        cfq_group_idle = 1;
4599
4600    ret = blkcg_policy_register(&blkcg_policy_cfq);
4601    if (ret)
4602        return ret;
4603#else
4604    cfq_group_idle = 0;
4605#endif
4606
4607    ret = -ENOMEM;
4608    cfq_pool = KMEM_CACHE(cfq_queue, 0);
4609    if (!cfq_pool)
4610        goto err_pol_unreg;
4611
4612    ret = elv_register(&iosched_cfq);
4613    if (ret)
4614        goto err_free_pool;
4615
4616    return 0;
4617
4618err_free_pool:
4619    kmem_cache_destroy(cfq_pool);
4620err_pol_unreg:
4621#ifdef CONFIG_CFQ_GROUP_IOSCHED
4622    blkcg_policy_unregister(&blkcg_policy_cfq);
4623#endif
4624    return ret;
4625}
4626
4627static void __exit cfq_exit(void)
4628{
4629#ifdef CONFIG_CFQ_GROUP_IOSCHED
4630    blkcg_policy_unregister(&blkcg_policy_cfq);
4631#endif
4632    elv_unregister(&iosched_cfq);
4633    kmem_cache_destroy(cfq_pool);
4634}
4635
4636module_init(cfq_init);
4637module_exit(cfq_exit);
4638
4639MODULE_AUTHOR("Jens Axboe");
4640MODULE_LICENSE("GPL");
4641MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");
4642

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