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