block/cfq-iosched.c

   1 /*
   2  *  CFQ, or complete fairness queueing, disk scheduler.
   3  *
   4  *  Based on ideas from a previously unfinished io
   5  *  scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
   6  *
   7  *  Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
   8  */
   9 #include <linux/module.h>
  10 #include <linux/slab.h>
  11 #include <linux/blkdev.h>
  12 #include <linux/elevator.h>
  13 #include <linux/jiffies.h>
  14 #include <linux/rbtree.h>
  15 #include <linux/ioprio.h>
  16 #include <linux/blktrace_api.h>
  17 #include "blk.h"
  18 #include "blk-cgroup.h"
  19
  20 /*
  21  * tunables
  22  */
  23 /* max queue in one round of service */
  24 static const int cfq_quantum = 8;
  25 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
  26 /* maximum backwards seek, in KiB */
  27 static const int cfq_back_max = 16 * 1024;
  28 /* penalty of a backwards seek */
  29 static const int cfq_back_penalty = 2;
  30 static const int cfq_slice_sync = HZ / 10;
  31 static int cfq_slice_async = HZ / 25;
  32 static const int cfq_slice_async_rq = 2;
  33 static int cfq_slice_idle = HZ / 125;
  34 static int cfq_group_idle = HZ / 125;
  35 static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
  36 static const int cfq_hist_divisor = 4;
  37
  38 /*
  39  * offset from end of service tree
  40  */
  41 #define CFQ_IDLE_DELAY          (HZ / 5)
  42
  43 /*
  44  * below this threshold, we consider thinktime immediate
  45  */
  46 #define CFQ_MIN_TT              (2)
  47
  48 #define CFQ_SLICE_SCALE         (5)
  49 #define CFQ_HW_QUEUE_MIN        (5)
  50 #define CFQ_SERVICE_SHIFT       12
  51
  52 #define CFQQ_SEEK_THR           (sector_t)(8 * 100)
  53 #define CFQQ_CLOSE_THR          (sector_t)(8 * 1024)
  54 #define CFQQ_SECT_THR_NONROT    (sector_t)(2 * 32)
  55 #define CFQQ_SEEKY(cfqq)        (hweight32(cfqq->seek_history) > 32/8)
  56
  57 #define RQ_CIC(rq)              icq_to_cic((rq)->elv.icq)
  58 #define RQ_CFQQ(rq)             (struct cfq_queue *) ((rq)->elv.priv[0])
  59 #define RQ_CFQG(rq)             (struct cfq_group *) ((rq)->elv.priv[1])
  60
  61 static struct kmem_cache *cfq_pool;
  62
  63 #define CFQ_PRIO_LISTS          IOPRIO_BE_NR
  64 #define cfq_class_idle(cfqq)    ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
  65 #define cfq_class_rt(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
  66
  67 #define sample_valid(samples)   ((samples) > 80)
  68 #define rb_entry_cfqg(node)     rb_entry((node), struct cfq_group, rb_node)
  69
  70 struct cfq_ttime {
  71         unsigned long last_end_request;
  72
  73         unsigned long ttime_total;
  74         unsigned long ttime_samples;
  75         unsigned long ttime_mean;
  76 };
  77
  78 /*
  79  * Most of our rbtree usage is for sorting with min extraction, so
  80  * if we cache the leftmost node we don't have to walk down the tree
  81  * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
  82  * move this into the elevator for the rq sorting as well.
  83  */
  84 struct cfq_rb_root {
  85         struct rb_root rb;
  86         struct rb_node *left;
  87         unsigned count;
  88         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  */
  98 struct 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  */
 158 enum wl_class_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  */
 168 enum wl_type_t {
 169         ASYNC_WORKLOAD = 0,
 170         SYNC_NOIDLE_WORKLOAD = 1,
 171         SYNC_WORKLOAD = 2
 172 };
 173
 174 struct 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 */
 217 struct 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
 227         /*
 228          * There are two weights - (internal) weight is the weight of this
 229          * cfqg against the sibling cfqgs.  leaf_weight is the wight of
 230          * this cfqg against the child cfqgs.  For the root cfqg, both
 231          * weights are kept in sync for backward compatibility.
 232          */
 233         unsigned int weight;
 234         unsigned int new_weight;
 235         unsigned int dev_weight;
 236
 237         unsigned int leaf_weight;
 238         unsigned int new_leaf_weight;
 239         unsigned int dev_leaf_weight;
 240
 241         /* number of cfqq currently on this group */
 242         int nr_cfqq;
 243
 244         /*
 245          * Per group busy queues average. Useful for workload slice calc. We
 246          * create the array for each prio class but at run time it is used
 247          * only for RT and BE class and slot for IDLE class remains unused.
 248          * This is primarily done to avoid confusion and a gcc warning.
 249          */
 250         unsigned int busy_queues_avg[CFQ_PRIO_NR];
 251         /*
 252          * rr lists of queues with requests. We maintain service trees for
 253          * RT and BE classes. These trees are subdivided in subclasses
 254          * of SYNC, SYNC_NOIDLE and ASYNC based on workload type. For IDLE
 255          * class there is no subclassification and all the cfq queues go on
 256          * a single tree service_tree_idle.
 257          * Counts are embedded in the cfq_rb_root
 258          */
 259         struct cfq_rb_root service_trees[2][3];
 260         struct cfq_rb_root service_tree_idle;
 261
 262         unsigned long saved_wl_slice;
 263         enum wl_type_t saved_wl_type;
 264         enum wl_class_t saved_wl_class;
 265
 266         /* number of requests that are on the dispatch list or inside driver */
 267         int dispatched;
 268         struct cfq_ttime ttime;
 269         struct cfqg_stats stats;
 270 };
 271
 272 struct cfq_io_cq {
 273         struct io_cq            icq;            /* must be the first member */
 274         struct cfq_queue        *cfqq[2];
 275         struct cfq_ttime        ttime;
 276         int                     ioprio;         /* the current ioprio */
 277 #ifdef CONFIG_CFQ_GROUP_IOSCHED
 278         uint64_t                blkcg_id;       /* the current blkcg ID */
 279 #endif
 280 };
 281
 282 /*
 283  * Per block device queue structure
 284  */
 285 struct cfq_data {
 286         struct request_queue *queue;
 287         /* Root service tree for cfq_groups */
 288         struct cfq_rb_root grp_service_tree;
 289         struct cfq_group *root_group;
 290
 291         /*
 292          * The priority currently being served
 293          */
 294         enum wl_class_t serving_wl_class;
 295         enum wl_type_t serving_wl_type;
 296         unsigned long workload_expires;
 297         struct cfq_group *serving_group;
 298
 299         /*
 300          * Each priority tree is sorted by next_request position.  These
 301          * trees are used when determining if two or more queues are
 302          * interleaving requests (see cfq_close_cooperator).
 303          */
 304         struct rb_root prio_trees[CFQ_PRIO_LISTS];
 305
 306         unsigned int busy_queues;
 307         unsigned int busy_sync_queues;
 308
 309         int rq_in_driver;
 310         int rq_in_flight[2];
 311
 312         /*
 313          * queue-depth detection
 314          */
 315         int rq_queued;
 316         int hw_tag;
 317         /*
 318          * hw_tag can be
 319          * -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
 320          *  1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
 321          *  0 => no NCQ
 322          */
 323         int hw_tag_est_depth;
 324         unsigned int hw_tag_samples;
 325
 326         /*
 327          * idle window management
 328          */
 329         struct timer_list idle_slice_timer;
 330         struct work_struct unplug_work;
 331
 332         struct cfq_queue *active_queue;
 333         struct cfq_io_cq *active_cic;
 334
 335         /*
 336          * async queue for each priority case
 337          */
 338         struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
 339         struct cfq_queue *async_idle_cfqq;
 340
 341         sector_t last_position;
 342
 343         /*
 344          * tunables, see top of file
 345          */
 346         unsigned int cfq_quantum;
 347         unsigned int cfq_fifo_expire[2];
 348         unsigned int cfq_back_penalty;
 349         unsigned int cfq_back_max;
 350         unsigned int cfq_slice[2];
 351         unsigned int cfq_slice_async_rq;
 352         unsigned int cfq_slice_idle;
 353         unsigned int cfq_group_idle;
 354         unsigned int cfq_latency;
 355         unsigned int cfq_target_latency;
 356
 357         /*
 358          * Fallback dummy cfqq for extreme OOM conditions
 359          */
 360         struct cfq_queue oom_cfqq;
 361
 362         unsigned long last_delayed_sync;
 363 };
 364
 365 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
 366
 367 static struct cfq_rb_root *st_for(struct cfq_group *cfqg,
 368                                             enum wl_class_t class,
 369                                             enum wl_type_t type)
 370 {
 371         if (!cfqg)
 372                 return NULL;
 373
 374         if (class == IDLE_WORKLOAD)
 375                 return &cfqg->service_tree_idle;
 376
 377         return &cfqg->service_trees[class][type];
 378 }
 379
 380 enum cfqq_state_flags {
 381         CFQ_CFQQ_FLAG_on_rr = 0,        /* on round-robin busy list */
 382         CFQ_CFQQ_FLAG_wait_request,     /* waiting for a request */
 383         CFQ_CFQQ_FLAG_must_dispatch,    /* must be allowed a dispatch */
 384         CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
 385         CFQ_CFQQ_FLAG_fifo_expire,      /* FIFO checked in this slice */
 386         CFQ_CFQQ_FLAG_idle_window,      /* slice idling enabled */
 387         CFQ_CFQQ_FLAG_prio_changed,     /* task priority has changed */
 388         CFQ_CFQQ_FLAG_slice_new,        /* no requests dispatched in slice */
 389         CFQ_CFQQ_FLAG_sync,             /* synchronous queue */
 390         CFQ_CFQQ_FLAG_coop,             /* cfqq is shared */
 391         CFQ_CFQQ_FLAG_split_coop,       /* shared cfqq will be splitted */
 392         CFQ_CFQQ_FLAG_deep,             /* sync cfqq experienced large depth */
 393         CFQ_CFQQ_FLAG_wait_busy,        /* Waiting for next request */
 394 };
 395
 396 #define CFQ_CFQQ_FNS(name)                                              \
 397 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
 398 {                                                                       \
 399         (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name);                   \
 400 }                                                                       \
 401 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
 402 {                                                                       \
 403         (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                  \
 404 }                                                                       \
 405 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
 406 {                                                                       \
 407         return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;      \
 408 }
 409
 410 CFQ_CFQQ_FNS(on_rr);
 411 CFQ_CFQQ_FNS(wait_request);
 412 CFQ_CFQQ_FNS(must_dispatch);
 413 CFQ_CFQQ_FNS(must_alloc_slice);
 414 CFQ_CFQQ_FNS(fifo_expire);
 415 CFQ_CFQQ_FNS(idle_window);
 416 CFQ_CFQQ_FNS(prio_changed);
 417 CFQ_CFQQ_FNS(slice_new);
 418 CFQ_CFQQ_FNS(sync);
 419 CFQ_CFQQ_FNS(coop);
 420 CFQ_CFQQ_FNS(split_coop);
 421 CFQ_CFQQ_FNS(deep);
 422 CFQ_CFQQ_FNS(wait_busy);
 423 #undef CFQ_CFQQ_FNS
 424
 425 static inline struct cfq_group *pd_to_cfqg(struct blkg_policy_data *pd)
 426 {
 427         return pd ? container_of(pd, struct cfq_group, pd) : NULL;
 428 }
 429
 430 static inline struct blkcg_gq *cfqg_to_blkg(struct cfq_group *cfqg)
 431 {
 432         return pd_to_blkg(&cfqg->pd);
 433 }
 434
 435 #if defined(CONFIG_CFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
 436
 437 /* cfqg stats flags */
 438 enum cfqg_stats_flags {
 439         CFQG_stats_waiting = 0,
 440         CFQG_stats_idling,
 441         CFQG_stats_empty,
 442 };
 443
 444 #define CFQG_FLAG_FNS(name)                                             \
 445 static inline void cfqg_stats_mark_##name(struct cfqg_stats *stats)     \
 446 {                                                                       \
 447         stats->flags |= (1 << CFQG_stats_##name);                       \
 448 }                                                                       \
 449 static inline void cfqg_stats_clear_##name(struct cfqg_stats *stats)    \
 450 {                                                                       \
 451         stats->flags &= ~(1 << CFQG_stats_##name);                      \
 452 }                                                                       \
 453 static inline int cfqg_stats_##name(struct cfqg_stats *stats)           \
 454 {                                                                       \
 455         return (stats->flags & (1 << CFQG_stats_##name)) != 0;          \
 456 }                                                                       \
 457
 458 CFQG_FLAG_FNS(waiting)
 459 CFQG_FLAG_FNS(idling)
 460 CFQG_FLAG_FNS(empty)
 461 #undef CFQG_FLAG_FNS
 462
 463 /* This should be called with the queue_lock held. */
 464 static void cfqg_stats_update_group_wait_time(struct cfqg_stats *stats)
 465 {
 466         unsigned long long now;
 467
 468         if (!cfqg_stats_waiting(stats))
 469                 return;
 470
 471         now = sched_clock();
 472         if (time_after64(now, stats->start_group_wait_time))
 473                 blkg_stat_add(&stats->group_wait_time,
 474                               now - stats->start_group_wait_time);
 475         cfqg_stats_clear_waiting(stats);
 476 }
 477
 478 /* This should be called with the queue_lock held. */
 479 static void cfqg_stats_set_start_group_wait_time(struct cfq_group *cfqg,
 480                                                  struct cfq_group *curr_cfqg)
 481 {
 482         struct cfqg_stats *stats = &cfqg->stats;
 483
 484         if (cfqg_stats_waiting(stats))
 485                 return;
 486         if (cfqg == curr_cfqg)
 487                 return;
 488         stats->start_group_wait_time = sched_clock();
 489         cfqg_stats_mark_waiting(stats);
 490 }
 491
 492 /* This should be called with the queue_lock held. */
 493 static void cfqg_stats_end_empty_time(struct cfqg_stats *stats)
 494 {
 495         unsigned long long now;
 496
 497         if (!cfqg_stats_empty(stats))
 498                 return;
 499
 500         now = sched_clock();
 501         if (time_after64(now, stats->start_empty_time))
 502                 blkg_stat_add(&stats->empty_time,
 503                               now - stats->start_empty_time);
 504         cfqg_stats_clear_empty(stats);
 505 }
 506
 507 static void cfqg_stats_update_dequeue(struct cfq_group *cfqg)
 508 {
 509         blkg_stat_add(&cfqg->stats.dequeue, 1);
 510 }
 511
 512 static void cfqg_stats_set_start_empty_time(struct cfq_group *cfqg)
 513 {
 514         struct cfqg_stats *stats = &cfqg->stats;
 515
 516         if (blkg_rwstat_sum(&stats->queued))
 517                 return;
 518
 519         /*
 520          * group is already marked empty. This can happen if cfqq got new
 521          * request in parent group and moved to this group while being added
 522          * to service tree. Just ignore the event and move on.
 523          */
 524         if (cfqg_stats_empty(stats))
 525                 return;
 526
 527         stats->start_empty_time = sched_clock();
 528         cfqg_stats_mark_empty(stats);
 529 }
 530
 531 static void cfqg_stats_update_idle_time(struct cfq_group *cfqg)
 532 {
 533         struct cfqg_stats *stats = &cfqg->stats;
 534
 535         if (cfqg_stats_idling(stats)) {
 536                 unsigned long long now = sched_clock();
 537
 538                 if (time_after64(now, stats->start_idle_time))
 539                         blkg_stat_add(&stats->idle_time,
 540                                       now - stats->start_idle_time);
 541                 cfqg_stats_clear_idling(stats);
 542         }
 543 }
 544
 545 static void cfqg_stats_set_start_idle_time(struct cfq_group *cfqg)
 546 {
 547         struct cfqg_stats *stats = &cfqg->stats;
 548
 549         BUG_ON(cfqg_stats_idling(stats));
 550
 551         stats->start_idle_time = sched_clock();
 552         cfqg_stats_mark_idling(stats);
 553 }
 554
 555 static void cfqg_stats_update_avg_queue_size(struct cfq_group *cfqg)
 556 {
 557         struct cfqg_stats *stats = &cfqg->stats;
 558
 559         blkg_stat_add(&stats->avg_queue_size_sum,
 560                       blkg_rwstat_sum(&stats->queued));
 561         blkg_stat_add(&stats->avg_queue_size_samples, 1);
 562         cfqg_stats_update_group_wait_time(stats);
 563 }
 564
 565 #else   /* CONFIG_CFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
 566
 567 static inline void cfqg_stats_set_start_group_wait_time(struct cfq_group *cfqg, struct cfq_group *curr_cfqg) { }
 568 static inline void cfqg_stats_end_empty_time(struct cfqg_stats *stats) { }
 569 static inline void cfqg_stats_update_dequeue(struct cfq_group *cfqg) { }
 570 static inline void cfqg_stats_set_start_empty_time(struct cfq_group *cfqg) { }
 571 static inline void cfqg_stats_update_idle_time(struct cfq_group *cfqg) { }
 572 static inline void cfqg_stats_set_start_idle_time(struct cfq_group *cfqg) { }
 573 static inline void cfqg_stats_update_avg_queue_size(struct cfq_group *cfqg) { }
 574
 575 #endif  /* CONFIG_CFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
 576
 577 #ifdef CONFIG_CFQ_GROUP_IOSCHED
 578
 579 static struct blkcg_policy blkcg_policy_cfq;
 580
 581 static inline struct cfq_group *blkg_to_cfqg(struct blkcg_gq *blkg)
 582 {
 583         return pd_to_cfqg(blkg_to_pd(blkg, &blkcg_policy_cfq));
 584 }
 585
 586 static inline void cfqg_get(struct cfq_group *cfqg)
 587 {
 588         return blkg_get(cfqg_to_blkg(cfqg));
 589 }
 590
 591 static inline void cfqg_put(struct cfq_group *cfqg)
 592 {
 593         return blkg_put(cfqg_to_blkg(cfqg));
 594 }
 595
 596 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  do {                    \
 597         char __pbuf[128];                                               \
 598                                                                         \
 599         blkg_path(cfqg_to_blkg((cfqq)->cfqg), __pbuf, sizeof(__pbuf));  \
 600         blk_add_trace_msg((cfqd)->queue, "cfq%d%c%c %s " fmt, (cfqq)->pid, \
 601                         cfq_cfqq_sync((cfqq)) ? 'S' : 'A',              \
 602                         cfqq_type((cfqq)) == SYNC_NOIDLE_WORKLOAD ? 'N' : ' ',\
 603                           __pbuf, ##args);                              \
 604 } while (0)
 605
 606 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)  do {                    \
 607         char __pbuf[128];                                               \
 608                                                                         \
 609         blkg_path(cfqg_to_blkg(cfqg), __pbuf, sizeof(__pbuf));          \
 610         blk_add_trace_msg((cfqd)->queue, "%s " fmt, __pbuf, ##args);    \
 611 } while (0)
 612
 613 static inline void cfqg_stats_update_io_add(struct cfq_group *cfqg,
 614                                             struct cfq_group *curr_cfqg, int rw)
 615 {
 616         blkg_rwstat_add(&cfqg->stats.queued, rw, 1);
 617         cfqg_stats_end_empty_time(&cfqg->stats);
 618         cfqg_stats_set_start_group_wait_time(cfqg, curr_cfqg);
 619 }
 620
 621 static inline void cfqg_stats_update_timeslice_used(struct cfq_group *cfqg,
 622                         unsigned long time, unsigned long unaccounted_time)
 623 {
 624         blkg_stat_add(&cfqg->stats.time, time);
 625 #ifdef CONFIG_DEBUG_BLK_CGROUP
 626         blkg_stat_add(&cfqg->stats.unaccounted_time, unaccounted_time);
 627 #endif
 628 }
 629
 630 static inline void cfqg_stats_update_io_remove(struct cfq_group *cfqg, int rw)
 631 {
 632         blkg_rwstat_add(&cfqg->stats.queued, rw, -1);
 633 }
 634
 635 static inline void cfqg_stats_update_io_merged(struct cfq_group *cfqg, int rw)
 636 {
 637         blkg_rwstat_add(&cfqg->stats.merged, rw, 1);
 638 }
 639
 640 static inline void cfqg_stats_update_dispatch(struct cfq_group *cfqg,
 641                                               uint64_t bytes, int rw)
 642 {
 643         blkg_stat_add(&cfqg->stats.sectors, bytes >> 9);
 644         blkg_rwstat_add(&cfqg->stats.serviced, rw, 1);
 645         blkg_rwstat_add(&cfqg->stats.service_bytes, rw, bytes);
 646 }
 647
 648 static inline void cfqg_stats_update_completion(struct cfq_group *cfqg,
 649                         uint64_t start_time, uint64_t io_start_time, int rw)
 650 {
 651         struct cfqg_stats *stats = &cfqg->stats;
 652         unsigned long long now = sched_clock();
 653
 654         if (time_after64(now, io_start_time))
 655                 blkg_rwstat_add(&stats->service_time, rw, now - io_start_time);
 656         if (time_after64(io_start_time, start_time))
 657                 blkg_rwstat_add(&stats->wait_time, rw,
 658                                 io_start_time - start_time);
 659 }
 660
 661 static void cfq_pd_reset_stats(struct blkcg_gq *blkg)
 662 {
 663         struct cfq_group *cfqg = blkg_to_cfqg(blkg);
 664         struct cfqg_stats *stats = &cfqg->stats;
 665
 666         /* queued stats shouldn't be cleared */
 667         blkg_rwstat_reset(&stats->service_bytes);
 668         blkg_rwstat_reset(&stats->serviced);
 669         blkg_rwstat_reset(&stats->merged);
 670         blkg_rwstat_reset(&stats->service_time);
 671         blkg_rwstat_reset(&stats->wait_time);
 672         blkg_stat_reset(&stats->time);
 673 #ifdef CONFIG_DEBUG_BLK_CGROUP
 674         blkg_stat_reset(&stats->unaccounted_time);
 675         blkg_stat_reset(&stats->avg_queue_size_sum);
 676         blkg_stat_reset(&stats->avg_queue_size_samples);
 677         blkg_stat_reset(&stats->dequeue);
 678         blkg_stat_reset(&stats->group_wait_time);
 679         blkg_stat_reset(&stats->idle_time);
 680         blkg_stat_reset(&stats->empty_time);
 681 #endif
 682 }
 683
 684 #else   /* CONFIG_CFQ_GROUP_IOSCHED */
 685
 686 static inline void cfqg_get(struct cfq_group *cfqg) { }
 687 static inline void cfqg_put(struct cfq_group *cfqg) { }
 688
 689 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
 690         blk_add_trace_msg((cfqd)->queue, "cfq%d%c%c " fmt, (cfqq)->pid, \
 691                         cfq_cfqq_sync((cfqq)) ? 'S' : 'A',              \
 692                         cfqq_type((cfqq)) == SYNC_NOIDLE_WORKLOAD ? 'N' : ' ',\
 693                                 ##args)
 694 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)          do {} while (0)
 695
 696 static inline void cfqg_stats_update_io_add(struct cfq_group *cfqg,
 697                         struct cfq_group *curr_cfqg, int rw) { }
 698 static inline void cfqg_stats_update_timeslice_used(struct cfq_group *cfqg,
 699                         unsigned long time, unsigned long unaccounted_time) { }
 700 static inline void cfqg_stats_update_io_remove(struct cfq_group *cfqg, int rw) { }
 701 static inline void cfqg_stats_update_io_merged(struct cfq_group *cfqg, int rw) { }
 702 static inline void cfqg_stats_update_dispatch(struct cfq_group *cfqg,
 703                                               uint64_t bytes, int rw) { }
 704 static inline void cfqg_stats_update_completion(struct cfq_group *cfqg,
 705                         uint64_t start_time, uint64_t io_start_time, int rw) { }
 706
 707 #endif  /* CONFIG_CFQ_GROUP_IOSCHED */
 708
 709 #define cfq_log(cfqd, fmt, args...)     \
 710         blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
 711
 712 /* Traverses through cfq group service trees */
 713 #define for_each_cfqg_st(cfqg, i, j, st) \
 714         for (i = 0; i <= IDLE_WORKLOAD; i++) \
 715                 for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
 716                         : &cfqg->service_tree_idle; \
 717                         (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
 718                         (i == IDLE_WORKLOAD && j == 0); \
 719                         j++, st = i < IDLE_WORKLOAD ? \
 720                         &cfqg->service_trees[i][j]: NULL) \
 721
 722 static inline bool cfq_io_thinktime_big(struct cfq_data *cfqd,
 723         struct cfq_ttime *ttime, bool group_idle)
 724 {
 725         unsigned long slice;
 726         if (!sample_valid(ttime->ttime_samples))
 727                 return false;
 728         if (group_idle)
 729                 slice = cfqd->cfq_group_idle;
 730         else
 731                 slice = cfqd->cfq_slice_idle;
 732         return ttime->ttime_mean > slice;
 733 }
 734
 735 static inline bool iops_mode(struct cfq_data *cfqd)
 736 {
 737         /*
 738          * If we are not idling on queues and it is a NCQ drive, parallel
 739          * execution of requests is on and measuring time is not possible
 740          * in most of the cases until and unless we drive shallower queue
 741          * depths and that becomes a performance bottleneck. In such cases
 742          * switch to start providing fairness in terms of number of IOs.
 743          */
 744         if (!cfqd->cfq_slice_idle && cfqd->hw_tag)
 745                 return true;
 746         else
 747                 return false;
 748 }
 749
 750 static inline enum wl_class_t cfqq_class(struct cfq_queue *cfqq)
 751 {
 752         if (cfq_class_idle(cfqq))
 753                 return IDLE_WORKLOAD;
 754         if (cfq_class_rt(cfqq))
 755                 return RT_WORKLOAD;
 756         return BE_WORKLOAD;
 757 }
 758
 759
 760 static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
 761 {
 762         if (!cfq_cfqq_sync(cfqq))
 763                 return ASYNC_WORKLOAD;
 764         if (!cfq_cfqq_idle_window(cfqq))
 765                 return SYNC_NOIDLE_WORKLOAD;
 766         return SYNC_WORKLOAD;
 767 }
 768
 769 static inline int cfq_group_busy_queues_wl(enum wl_class_t wl_class,
 770                                         struct cfq_data *cfqd,
 771                                         struct cfq_group *cfqg)
 772 {
 773         if (wl_class == IDLE_WORKLOAD)
 774                 return cfqg->service_tree_idle.count;
 775
 776         return cfqg->service_trees[wl_class][ASYNC_WORKLOAD].count +
 777                 cfqg->service_trees[wl_class][SYNC_NOIDLE_WORKLOAD].count +
 778                 cfqg->service_trees[wl_class][SYNC_WORKLOAD].count;
 779 }
 780
 781 static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
 782                                         struct cfq_group *cfqg)
 783 {
 784         return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count +
 785                 cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
 786 }
 787
 788 static void cfq_dispatch_insert(struct request_queue *, struct request *);
 789 static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, bool is_sync,
 790                                        struct cfq_io_cq *cic, struct bio *bio,
 791                                        gfp_t gfp_mask);
 792
 793 static inline struct cfq_io_cq *icq_to_cic(struct io_cq *icq)
 794 {
 795         /* cic->icq is the first member, %NULL will convert to %NULL */
 796         return container_of(icq, struct cfq_io_cq, icq);
 797 }
 798
 799 static inline struct cfq_io_cq *cfq_cic_lookup(struct cfq_data *cfqd,
 800                                                struct io_context *ioc)
 801 {
 802         if (ioc)
 803                 return icq_to_cic(ioc_lookup_icq(ioc, cfqd->queue));
 804         return NULL;
 805 }
 806
 807 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_cq *cic, bool is_sync)
 808 {
 809         return cic->cfqq[is_sync];
 810 }
 811
 812 static inline void cic_set_cfqq(struct cfq_io_cq *cic, struct cfq_queue *cfqq,
 813                                 bool is_sync)
 814 {
 815         cic->cfqq[is_sync] = cfqq;
 816 }
 817
 818 static inline struct cfq_data *cic_to_cfqd(struct cfq_io_cq *cic)
 819 {
 820         return cic->icq.q->elevator->elevator_data;
 821 }
 822
 823 /*
 824  * We regard a request as SYNC, if it's either a read or has the SYNC bit
 825  * set (in which case it could also be direct WRITE).
 826  */
 827 static inline bool cfq_bio_sync(struct bio *bio)
 828 {
 829         return bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC);
 830 }
 831
 832 /*
 833  * scheduler run of queue, if there are requests pending and no one in the
 834  * driver that will restart queueing
 835  */
 836 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
 837 {
 838         if (cfqd->busy_queues) {
 839                 cfq_log(cfqd, "schedule dispatch");
 840                 kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
 841         }
 842 }
 843
 844 /*
 845  * Scale schedule slice based on io priority. Use the sync time slice only
 846  * if a queue is marked sync and has sync io queued. A sync queue with async
 847  * io only, should not get full sync slice length.
 848  */
 849 static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
 850                                  unsigned short prio)
 851 {
 852         const int base_slice = cfqd->cfq_slice[sync];
 853
 854         WARN_ON(prio >= IOPRIO_BE_NR);
 855
 856         return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
 857 }
 858
 859 static inline int
 860 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 861 {
 862         return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
 863 }
 864
 865 static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
 866 {
 867         u64 d = delta << CFQ_SERVICE_SHIFT;
 868
 869         d = d * CFQ_WEIGHT_DEFAULT;
 870         do_div(d, cfqg->weight);
 871         return d;
 872 }
 873
 874 static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
 875 {
 876         s64 delta = (s64)(vdisktime - min_vdisktime);
 877         if (delta > 0)
 878                 min_vdisktime = vdisktime;
 879
 880         return min_vdisktime;
 881 }
 882
 883 static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
 884 {
 885         s64 delta = (s64)(vdisktime - min_vdisktime);
 886         if (delta < 0)
 887                 min_vdisktime = vdisktime;
 888
 889         return min_vdisktime;
 890 }
 891
 892 static void update_min_vdisktime(struct cfq_rb_root *st)
 893 {
 894         struct cfq_group *cfqg;
 895
 896         if (st->left) {
 897                 cfqg = rb_entry_cfqg(st->left);
 898                 st->min_vdisktime = max_vdisktime(st->min_vdisktime,
 899                                                   cfqg->vdisktime);
 900         }
 901 }
 902
 903 /*
 904  * get averaged number of queues of RT/BE priority.
 905  * average is updated, with a formula that gives more weight to higher numbers,
 906  * to quickly follows sudden increases and decrease slowly
 907  */
 908
 909 static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
 910                                         struct cfq_group *cfqg, bool rt)
 911 {
 912         unsigned min_q, max_q;
 913         unsigned mult  = cfq_hist_divisor - 1;
 914         unsigned round = cfq_hist_divisor / 2;
 915         unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
 916
 917         min_q = min(cfqg->busy_queues_avg[rt], busy);
 918         max_q = max(cfqg->busy_queues_avg[rt], busy);
 919         cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
 920                 cfq_hist_divisor;
 921         return cfqg->busy_queues_avg[rt];
 922 }
 923
 924 static inline unsigned
 925 cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
 926 {
 927         struct cfq_rb_root *st = &cfqd->grp_service_tree;
 928
 929         return cfqd->cfq_target_latency * cfqg->weight / st->total_weight;
 930 }
 931
 932 static inline unsigned
 933 cfq_scaled_cfqq_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 934 {
 935         unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
 936         if (cfqd->cfq_latency) {
 937                 /*
 938                  * interested queues (we consider only the ones with the same
 939                  * priority class in the cfq group)
 940                  */
 941                 unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
 942                                                 cfq_class_rt(cfqq));
 943                 unsigned sync_slice = cfqd->cfq_slice[1];
 944                 unsigned expect_latency = sync_slice * iq;
 945                 unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
 946
 947                 if (expect_latency > group_slice) {
 948                         unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
 949                         /* scale low_slice according to IO priority
 950                          * and sync vs async */
 951                         unsigned low_slice =
 952                                 min(slice, base_low_slice * slice / sync_slice);
 953                         /* the adapted slice value is scaled to fit all iqs
 954                          * into the target latency */
 955                         slice = max(slice * group_slice / expect_latency,
 956                                     low_slice);
 957                 }
 958         }
 959         return slice;
 960 }
 961
 962 static inline void
 963 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 964 {
 965         unsigned slice = cfq_scaled_cfqq_slice(cfqd, cfqq);
 966
 967         cfqq->slice_start = jiffies;
 968         cfqq->slice_end = jiffies + slice;
 969         cfqq->allocated_slice = slice;
 970         cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
 971 }
 972
 973 /*
 974  * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
 975  * isn't valid until the first request from the dispatch is activated
 976  * and the slice time set.
 977  */
 978 static inline bool cfq_slice_used(struct cfq_queue *cfqq)
 979 {
 980         if (cfq_cfqq_slice_new(cfqq))
 981                 return false;
 982         if (time_before(jiffies, cfqq->slice_end))
 983                 return false;
 984
 985         return true;
 986 }
 987
 988 /*
 989  * Lifted from AS - choose which of rq1 and rq2 that is best served now.
 990  * We choose the request that is closest to the head right now. Distance
 991  * behind the head is penalized and only allowed to a certain extent.
 992  */
 993 static struct request *
 994 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
 995 {
 996         sector_t s1, s2, d1 = 0, d2 = 0;
 997         unsigned long back_max;
 998 #define CFQ_RQ1_WRAP    0x01 /* request 1 wraps */
 999 #define CFQ_RQ2_WRAP    0x02 /* request 2 wraps */
1000         unsigned wrap = 0; /* bit mask: requests behind the disk head? */
1001
1002         if (rq1 == NULL || rq1 == rq2)
1003                 return rq2;
1004         if (rq2 == NULL)
1005                 return rq1;
1006
1007         if (rq_is_sync(rq1) != rq_is_sync(rq2))
1008                 return rq_is_sync(rq1) ? rq1 : rq2;
1009
1010         if ((rq1->cmd_flags ^ rq2->cmd_flags) & REQ_PRIO)
1011                 return rq1->cmd_flags & REQ_PRIO ? rq1 : rq2;
1012
1013         s1 = blk_rq_pos(rq1);
1014         s2 = blk_rq_pos(rq2);
1015
1016         /*
1017          * by definition, 1KiB is 2 sectors
1018          */
1019         back_max = cfqd->cfq_back_max * 2;
1020
1021         /*
1022          * Strict one way elevator _except_ in the case where we allow
1023          * short backward seeks which are biased as twice the cost of a
1024          * similar forward seek.
1025          */
1026         if (s1 >= last)
1027                 d1 = s1 - last;
1028         else if (s1 + back_max >= last)
1029                 d1 = (last - s1) * cfqd->cfq_back_penalty;
1030         else
1031                 wrap |= CFQ_RQ1_WRAP;
1032
1033         if (s2 >= last)
1034                 d2 = s2 - last;
1035         else if (s2 + back_max >= last)
1036                 d2 = (last - s2) * cfqd->cfq_back_penalty;
1037         else
1038                 wrap |= CFQ_RQ2_WRAP;
1039
1040         /* Found required data */
1041
1042         /*
1043          * By doing switch() on the bit mask "wrap" we avoid having to
1044          * check two variables for all permutations: --> faster!
1045          */
1046         switch (wrap) {
1047         case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
1048                 if (d1 < d2)
1049                         return rq1;
1050                 else if (d2 < d1)
1051                         return rq2;
1052                 else {
1053                         if (s1 >= s2)
1054                                 return rq1;
1055                         else
1056                                 return rq2;
1057                 }
1058
1059         case CFQ_RQ2_WRAP:
1060                 return rq1;
1061         case CFQ_RQ1_WRAP:
1062                 return rq2;
1063         case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
1064         default:
1065                 /*
1066                  * Since both rqs are wrapped,
1067                  * start with the one that's further behind head
1068                  * (--> only *one* back seek required),
1069                  * since back seek takes more time than forward.
1070                  */
1071                 if (s1 <= s2)
1072                         return rq1;
1073                 else
1074                         return rq2;
1075         }
1076 }
1077
1078 /*
1079  * The below is leftmost cache rbtree addon
1080  */
1081 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
1082 {
1083         /* Service tree is empty */
1084         if (!root->count)
1085                 return NULL;
1086
1087         if (!root->left)
1088                 root->left = rb_first(&root->rb);
1089
1090         if (root->left)
1091                 return rb_entry(root->left, struct cfq_queue, rb_node);
1092
1093         return NULL;
1094 }
1095
1096 static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
1097 {
1098         if (!root->left)
1099                 root->left = rb_first(&root->rb);
1100
1101         if (root->left)
1102                 return rb_entry_cfqg(root->left);
1103
1104         return NULL;
1105 }
1106
1107 static void rb_erase_init(struct rb_node *n, struct rb_root *root)
1108 {
1109         rb_erase(n, root);
1110         RB_CLEAR_NODE(n);
1111 }
1112
1113 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
1114 {
1115         if (root->left == n)
1116                 root->left = NULL;
1117         rb_erase_init(n, &root->rb);
1118         --root->count;
1119 }
1120
1121 /*
1122  * would be nice to take fifo expire time into account as well
1123  */
1124 static struct request *
1125 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1126                   struct request *last)
1127 {
1128         struct rb_node *rbnext = rb_next(&last->rb_node);
1129         struct rb_node *rbprev = rb_prev(&last->rb_node);
1130         struct request *next = NULL, *prev = NULL;
1131
1132         BUG_ON(RB_EMPTY_NODE(&last->rb_node));
1133
1134         if (rbprev)
1135                 prev = rb_entry_rq(rbprev);
1136
1137         if (rbnext)
1138                 next = rb_entry_rq(rbnext);
1139         else {
1140                 rbnext = rb_first(&cfqq->sort_list);
1141                 if (rbnext && rbnext != &last->rb_node)
1142                         next = rb_entry_rq(rbnext);
1143         }
1144
1145         return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
1146 }
1147
1148 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
1149                                       struct cfq_queue *cfqq)
1150 {
1151         /*
1152          * just an approximation, should be ok.
1153          */
1154         return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
1155                        cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
1156 }
1157
1158 static inline s64
1159 cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
1160 {
1161         return cfqg->vdisktime - st->min_vdisktime;
1162 }
1163
1164 static void
1165 __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
1166 {
1167         struct rb_node **node = &st->rb.rb_node;
1168         struct rb_node *parent = NULL;
1169         struct cfq_group *__cfqg;
1170         s64 key = cfqg_key(st, cfqg);
1171         int left = 1;
1172
1173         while (*node != NULL) {
1174                 parent = *node;
1175                 __cfqg = rb_entry_cfqg(parent);
1176
1177                 if (key < cfqg_key(st, __cfqg))
1178                         node = &parent->rb_left;
1179                 else {
1180                         node = &parent->rb_right;
1181                         left = 0;
1182                 }
1183         }
1184
1185         if (left)
1186                 st->left = &cfqg->rb_node;
1187
1188         rb_link_node(&cfqg->rb_node, parent, node);
1189         rb_insert_color(&cfqg->rb_node, &st->rb);
1190 }
1191
1192 static void
1193 cfq_update_group_weight(struct cfq_group *cfqg)
1194 {
1195         BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
1196
1197         if (cfqg->new_weight) {
1198                 cfqg->weight = cfqg->new_weight;
1199                 cfqg->new_weight = 0;
1200         }
1201
1202         if (cfqg->new_leaf_weight) {
1203                 cfqg->leaf_weight = cfqg->new_leaf_weight;
1204                 cfqg->new_leaf_weight = 0;
1205         }
1206 }
1207
1208 static void
1209 cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
1210 {
1211         BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
1212
1213         cfq_update_group_weight(cfqg);
1214         __cfq_group_service_tree_add(st, cfqg);
1215         st->total_weight += cfqg->weight;
1216 }
1217
1218 static void
1219 cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
1220 {
1221         struct cfq_rb_root *st = &cfqd->grp_service_tree;
1222         struct cfq_group *__cfqg;
1223         struct rb_node *n;
1224
1225         cfqg->nr_cfqq++;
1226         if (!RB_EMPTY_NODE(&cfqg->rb_node))
1227                 return;
1228
1229         /*
1230          * Currently put the group at the end. Later implement something
1231          * so that groups get lesser vtime based on their weights, so that
1232          * if group does not loose all if it was not continuously backlogged.
1233          */
1234         n = rb_last(&st->rb);
1235         if (n) {
1236                 __cfqg = rb_entry_cfqg(n);
1237                 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
1238         } else
1239                 cfqg->vdisktime = st->min_vdisktime;
1240         cfq_group_service_tree_add(st, cfqg);
1241 }
1242
1243 static void
1244 cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg)
1245 {
1246         st->total_weight -= cfqg->weight;
1247         if (!RB_EMPTY_NODE(&cfqg->rb_node))
1248                 cfq_rb_erase(&cfqg->rb_node, st);
1249 }
1250
1251 static void
1252 cfq_group_notify_queue_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
1253 {
1254         struct cfq_rb_root *st = &cfqd->grp_service_tree;
1255
1256         BUG_ON(cfqg->nr_cfqq < 1);
1257         cfqg->nr_cfqq--;
1258
1259         /* If there are other cfq queues under this group, don't delete it */
1260         if (cfqg->nr_cfqq)
1261                 return;
1262
1263         cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
1264         cfq_group_service_tree_del(st, cfqg);
1265         cfqg->saved_wl_slice = 0;
1266         cfqg_stats_update_dequeue(cfqg);
1267 }
1268
1269 static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq,
1270                                                 unsigned int *unaccounted_time)
1271 {
1272         unsigned int slice_used;
1273
1274         /*
1275          * Queue got expired before even a single request completed or
1276          * got expired immediately after first request completion.
1277          */
1278         if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
1279                 /*
1280                  * Also charge the seek time incurred to the group, otherwise
1281                  * if there are mutiple queues in the group, each can dispatch
1282                  * a single request on seeky media and cause lots of seek time
1283                  * and group will never know it.
1284                  */
1285                 slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
1286                                         1);
1287         } else {
1288                 slice_used = jiffies - cfqq->slice_start;
1289                 if (slice_used > cfqq->allocated_slice) {
1290                         *unaccounted_time = slice_used - cfqq->allocated_slice;
1291                         slice_used = cfqq->allocated_slice;
1292                 }
1293                 if (time_after(cfqq->slice_start, cfqq->dispatch_start))
1294                         *unaccounted_time += cfqq->slice_start -
1295                                         cfqq->dispatch_start;
1296         }
1297
1298         return slice_used;
1299 }
1300
1301 static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
1302                                 struct cfq_queue *cfqq)
1303 {
1304         struct cfq_rb_root *st = &cfqd->grp_service_tree;
1305         unsigned int used_sl, charge, unaccounted_sl = 0;
1306         int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
1307                         - cfqg->service_tree_idle.count;
1308
1309         BUG_ON(nr_sync < 0);
1310         used_sl = charge = cfq_cfqq_slice_usage(cfqq, &unaccounted_sl);
1311
1312         if (iops_mode(cfqd))
1313                 charge = cfqq->slice_dispatch;
1314         else if (!cfq_cfqq_sync(cfqq) && !nr_sync)
1315                 charge = cfqq->allocated_slice;
1316
1317         /* Can't update vdisktime while group is on service tree */
1318         cfq_group_service_tree_del(st, cfqg);
1319         cfqg->vdisktime += cfq_scale_slice(charge, cfqg);
1320         /* If a new weight was requested, update now, off tree */
1321         cfq_group_service_tree_add(st, cfqg);
1322
1323         /* This group is being expired. Save the context */
1324         if (time_after(cfqd->workload_expires, jiffies)) {
1325                 cfqg->saved_wl_slice = cfqd->workload_expires
1326                                                 - jiffies;
1327                 cfqg->saved_wl_type = cfqd->serving_wl_type;
1328                 cfqg->saved_wl_class = cfqd->serving_wl_class;
1329         } else
1330                 cfqg->saved_wl_slice = 0;
1331
1332         cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
1333                                         st->min_vdisktime);
1334         cfq_log_cfqq(cfqq->cfqd, cfqq,
1335                      "sl_used=%u disp=%u charge=%u iops=%u sect=%lu",
1336                      used_sl, cfqq->slice_dispatch, charge,
1337                      iops_mode(cfqd), cfqq->nr_sectors);
1338         cfqg_stats_update_timeslice_used(cfqg, used_sl, unaccounted_sl);
1339         cfqg_stats_set_start_empty_time(cfqg);
1340 }
1341
1342 /**
1343  * cfq_init_cfqg_base - initialize base part of a cfq_group
1344  * @cfqg: cfq_group to initialize
1345  *
1346  * Initialize the base part which is used whether %CONFIG_CFQ_GROUP_IOSCHED
1347  * is enabled or not.
1348  */
1349 static void cfq_init_cfqg_base(struct cfq_group *cfqg)
1350 {
1351         struct cfq_rb_root *st;
1352         int i, j;
1353
1354         for_each_cfqg_st(cfqg, i, j, st)
1355                 *st = CFQ_RB_ROOT;
1356         RB_CLEAR_NODE(&cfqg->rb_node);
1357
1358         cfqg->ttime.last_end_request = jiffies;
1359 }
1360
1361 #ifdef CONFIG_CFQ_GROUP_IOSCHED
1362 static void cfq_pd_init(struct blkcg_gq *blkg)
1363 {
1364         struct cfq_group *cfqg = blkg_to_cfqg(blkg);
1365
1366         cfq_init_cfqg_base(cfqg);
1367         cfqg->weight = blkg->blkcg->cfq_weight;
1368         cfqg->leaf_weight = blkg->blkcg->cfq_leaf_weight;
1369 }
1370
1371 /*
1372  * Search for the cfq group current task belongs to. request_queue lock must
1373  * be held.
1374  */
1375 static struct cfq_group *cfq_lookup_create_cfqg(struct cfq_data *cfqd,
1376                                                 struct blkcg *blkcg)
1377 {
1378         struct request_queue *q = cfqd->queue;
1379         struct cfq_group *cfqg = NULL;
1380
1381         /* avoid lookup for the common case where there's no blkcg */
1382         if (blkcg == &blkcg_root) {
1383                 cfqg = cfqd->root_group;
1384         } else {
1385                 struct blkcg_gq *blkg;
1386
1387                 blkg = blkg_lookup_create(blkcg, q);
1388                 if (!IS_ERR(blkg))
1389                         cfqg = blkg_to_cfqg(blkg);
1390         }
1391
1392         return cfqg;
1393 }
1394
1395 static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
1396 {
1397         /* Currently, all async queues are mapped to root group */
1398         if (!cfq_cfqq_sync(cfqq))
1399                 cfqg = cfqq->cfqd->root_group;
1400
1401         cfqq->cfqg = cfqg;
1402         /* cfqq reference on cfqg */
1403         cfqg_get(cfqg);
1404 }
1405
1406 static u64 cfqg_prfill_weight_device(struct seq_file *sf,
1407                                      struct blkg_policy_data *pd, int off)
1408 {
1409         struct cfq_group *cfqg = pd_to_cfqg(pd);
1410
1411         if (!cfqg->dev_weight)
1412                 return 0;
1413         return __blkg_prfill_u64(sf, pd, cfqg->dev_weight);
1414 }
1415
1416 static int cfqg_print_weight_device(struct cgroup *cgrp, struct cftype *cft,
1417                                     struct seq_file *sf)
1418 {
1419         blkcg_print_blkgs(sf, cgroup_to_blkcg(cgrp),
1420                           cfqg_prfill_weight_device, &blkcg_policy_cfq, 0,
1421                           false);
1422         return 0;
1423 }
1424
1425 static u64 cfqg_prfill_leaf_weight_device(struct seq_file *sf,
1426                                           struct blkg_policy_data *pd, int off)
1427 {
1428         struct cfq_group *cfqg = pd_to_cfqg(pd);
1429
1430         if (!cfqg->dev_leaf_weight)
1431                 return 0;
1432         return __blkg_prfill_u64(sf, pd, cfqg->dev_leaf_weight);
1433 }
1434
1435 static int cfqg_print_leaf_weight_device(struct cgroup *cgrp,
1436                                          struct cftype *cft,
1437                                          struct seq_file *sf)
1438 {
1439         blkcg_print_blkgs(sf, cgroup_to_blkcg(cgrp),
1440                           cfqg_prfill_leaf_weight_device, &blkcg_policy_cfq, 0,
1441                           false);
1442         return 0;
1443 }
1444
1445 static int cfq_print_weight(struct cgroup *cgrp, struct cftype *cft,
1446                             struct seq_file *sf)
1447 {
1448         seq_printf(sf, "%u\n", cgroup_to_blkcg(cgrp)->cfq_weight);
1449         return 0;
1450 }
1451
1452 static int cfq_print_leaf_weight(struct cgroup *cgrp, struct cftype *cft,
1453                                  struct seq_file *sf)
1454 {
1455         seq_printf(sf, "%u\n",
1456                    cgroup_to_blkcg(cgrp)->cfq_leaf_weight);
1457         return 0;
1458 }
1459
1460 static int __cfqg_set_weight_device(struct cgroup *cgrp, struct cftype *cft,
1461                                     const char *buf, bool is_leaf_weight)
1462 {
1463         struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
1464         struct blkg_conf_ctx ctx;
1465         struct cfq_group *cfqg;
1466         int ret;
1467
1468         ret = blkg_conf_prep(blkcg, &blkcg_policy_cfq, buf, &ctx);
1469         if (ret)
1470                 return ret;
1471
1472         ret = -EINVAL;
1473         cfqg = blkg_to_cfqg(ctx.blkg);
1474         if (!ctx.v || (ctx.v >= CFQ_WEIGHT_MIN && ctx.v <= CFQ_WEIGHT_MAX)) {
1475                 if (!is_leaf_weight) {
1476                         cfqg->dev_weight = ctx.v;
1477                         cfqg->new_weight = ctx.v ?: blkcg->cfq_weight;
1478                 } else {
1479                         cfqg->dev_leaf_weight = ctx.v;
1480                         cfqg->new_leaf_weight = ctx.v ?: blkcg->cfq_leaf_weight;
1481                 }
1482                 ret = 0;
1483         }
1484
1485         blkg_conf_finish(&ctx);
1486         return ret;
1487 }
1488
1489 static int cfqg_set_weight_device(struct cgroup *cgrp, struct cftype *cft,
1490                                   const char *buf)
1491 {
1492         return __cfqg_set_weight_device(cgrp, cft, buf, false);
1493 }
1494
1495 static int cfqg_set_leaf_weight_device(struct cgroup *cgrp, struct cftype *cft,
1496                                        const char *buf)
1497 {
1498         return __cfqg_set_weight_device(cgrp, cft, buf, true);
1499 }
1500
1501 static int __cfq_set_weight(struct cgroup *cgrp, struct cftype *cft, u64 val,
1502                             bool is_leaf_weight)
1503 {
1504         struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
1505         struct blkcg_gq *blkg;
1506         struct hlist_node *n;
1507
1508         if (val < CFQ_WEIGHT_MIN || val > CFQ_WEIGHT_MAX)
1509                 return -EINVAL;
1510
1511         spin_lock_irq(&blkcg->lock);
1512
1513         if (!is_leaf_weight)
1514                 blkcg->cfq_weight = val;
1515         else
1516                 blkcg->cfq_leaf_weight = val;
1517
1518         hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
1519                 struct cfq_group *cfqg = blkg_to_cfqg(blkg);
1520
1521                 if (!cfqg)
1522                         continue;
1523
1524                 if (!is_leaf_weight) {
1525                         if (!cfqg->dev_weight)
1526                                 cfqg->new_weight = blkcg->cfq_weight;
1527                 } else {
1528                         if (!cfqg->dev_leaf_weight)
1529                                 cfqg->new_leaf_weight = blkcg->cfq_leaf_weight;
1530                 }
1531         }
1532
1533         spin_unlock_irq(&blkcg->lock);
1534         return 0;
1535 }
1536
1537 static int cfq_set_weight(struct cgroup *cgrp, struct cftype *cft, u64 val)
1538 {
1539         return __cfq_set_weight(cgrp, cft, val, false);
1540 }
1541
1542 static int cfq_set_leaf_weight(struct cgroup *cgrp, struct cftype *cft, u64 val)
1543 {
1544         return __cfq_set_weight(cgrp, cft, val, true);
1545 }
1546
1547 static int cfqg_print_stat(struct cgroup *cgrp, struct cftype *cft,
1548                            struct seq_file *sf)
1549 {
1550         struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
1551
1552         blkcg_print_blkgs(sf, blkcg, blkg_prfill_stat, &blkcg_policy_cfq,
1553                           cft->private, false);
1554         return 0;
1555 }
1556
1557 static int cfqg_print_rwstat(struct cgroup *cgrp, struct cftype *cft,
1558                              struct seq_file *sf)
1559 {
1560         struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
1561
1562         blkcg_print_blkgs(sf, blkcg, blkg_prfill_rwstat, &blkcg_policy_cfq,
1563                           cft->private, true);
1564         return 0;
1565 }
1566
1567 #ifdef CONFIG_DEBUG_BLK_CGROUP
1568 static u64 cfqg_prfill_avg_queue_size(struct seq_file *sf,
1569                                       struct blkg_policy_data *pd, int off)
1570 {
1571         struct cfq_group *cfqg = pd_to_cfqg(pd);
1572         u64 samples = blkg_stat_read(&cfqg->stats.avg_queue_size_samples);
1573         u64 v = 0;
1574
1575         if (samples) {
1576                 v = blkg_stat_read(&cfqg->stats.avg_queue_size_sum);
1577                 do_div(v, samples);
1578         }
1579         __blkg_prfill_u64(sf, pd, v);
1580         return 0;
1581 }
1582
1583 /* print avg_queue_size */
1584 static int cfqg_print_avg_queue_size(struct cgroup *cgrp, struct cftype *cft,
1585                                      struct seq_file *sf)
1586 {
1587         struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
1588
1589         blkcg_print_blkgs(sf, blkcg, cfqg_prfill_avg_queue_size,
1590                           &blkcg_policy_cfq, 0, false);
1591         return 0;
1592 }
1593 #endif  /* CONFIG_DEBUG_BLK_CGROUP */
1594
1595 static struct cftype cfq_blkcg_files[] = {
1596         {
1597                 .name = "weight_device",
1598                 .read_seq_string = cfqg_print_weight_device,
1599                 .write_string = cfqg_set_weight_device,
1600                 .max_write_len = 256,
1601         },
1602         {
1603                 .name = "weight",
1604                 .read_seq_string = cfq_print_weight,
1605                 .write_u64 = cfq_set_weight,
1606         },
1607
1608         /* on root, leaf_weight is mapped to weight */
1609         {
1610                 .name = "leaf_weight_device",
1611                 .flags = CFTYPE_ONLY_ON_ROOT,
1612                 .read_seq_string = cfqg_print_weight_device,
1613                 .write_string = cfqg_set_weight_device,
1614                 .max_write_len = 256,
1615         },
1616         {
1617                 .name = "leaf_weight",
1618                 .flags = CFTYPE_ONLY_ON_ROOT,
1619                 .read_seq_string = cfq_print_weight,
1620                 .write_u64 = cfq_set_weight,
1621         },
1622
1623         /* no such mapping necessary for !roots */
1624         {
1625                 .name = "leaf_weight_device",
1626                 .flags = CFTYPE_NOT_ON_ROOT,
1627                 .read_seq_string = cfqg_print_leaf_weight_device,
1628                 .write_string = cfqg_set_leaf_weight_device,
1629                 .max_write_len = 256,
1630         },
1631         {
1632                 .name = "leaf_weight",
1633                 .flags = CFTYPE_NOT_ON_ROOT,
1634                 .read_seq_string = cfq_print_leaf_weight,
1635                 .write_u64 = cfq_set_leaf_weight,
1636         },
1637
1638         {
1639                 .name = "time",
1640                 .private = offsetof(struct cfq_group, stats.time),
1641                 .read_seq_string = cfqg_print_stat,
1642         },
1643         {
1644                 .name = "sectors",
1645                 .private = offsetof(struct cfq_group, stats.sectors),
1646                 .read_seq_string = cfqg_print_stat,
1647         },
1648         {
1649                 .name = "io_service_bytes",
1650                 .private = offsetof(struct cfq_group, stats.service_bytes),
1651                 .read_seq_string = cfqg_print_rwstat,
1652         },
1653         {
1654                 .name = "io_serviced",
1655                 .private = offsetof(struct cfq_group, stats.serviced),
1656                 .read_seq_string = cfqg_print_rwstat,
1657         },
1658         {
1659                 .name = "io_service_time",
1660                 .private = offsetof(struct cfq_group, stats.service_time),
1661                 .read_seq_string = cfqg_print_rwstat,
1662         },
1663         {
1664                 .name = "io_wait_time",
1665                 .private = offsetof(struct cfq_group, stats.wait_time),
1666                 .read_seq_string = cfqg_print_rwstat,
1667         },
1668         {
1669                 .name = "io_merged",
1670                 .private = offsetof(struct cfq_group, stats.merged),
1671                 .read_seq_string = cfqg_print_rwstat,
1672         },
1673         {
1674                 .name = "io_queued",
1675                 .private = offsetof(struct cfq_group, stats.queued),
1676                 .read_seq_string = cfqg_print_rwstat,
1677         },
1678 #ifdef CONFIG_DEBUG_BLK_CGROUP
1679         {
1680                 .name = "avg_queue_size",
1681                 .read_seq_string = cfqg_print_avg_queue_size,
1682         },
1683         {
1684                 .name = "group_wait_time",
1685                 .private = offsetof(struct cfq_group, stats.group_wait_time),
1686                 .read_seq_string = cfqg_print_stat,
1687         },
1688         {
1689                 .name = "idle_time",
1690                 .private = offsetof(struct cfq_group, stats.idle_time),
1691                 .read_seq_string = cfqg_print_stat,
1692         },
1693         {
1694                 .name = "empty_time",
1695                 .private = offsetof(struct cfq_group, stats.empty_time),
1696                 .read_seq_string = cfqg_print_stat,
1697         },
1698         {
1699                 .name = "dequeue",
1700                 .private = offsetof(struct cfq_group, stats.dequeue),
1701                 .read_seq_string = cfqg_print_stat,
1702         },
1703         {
1704                 .name = "unaccounted_time",
1705                 .private = offsetof(struct cfq_group, stats.unaccounted_time),
1706                 .read_seq_string = cfqg_print_stat,
1707         },
1708 #endif  /* CONFIG_DEBUG_BLK_CGROUP */
1709         { }     /* terminate */
1710 };
1711 #else /* GROUP_IOSCHED */
1712 static struct cfq_group *cfq_lookup_create_cfqg(struct cfq_data *cfqd,
1713                                                 struct blkcg *blkcg)
1714 {
1715         return cfqd->root_group;
1716 }
1717
1718 static inline void
1719 cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
1720         cfqq->cfqg = cfqg;
1721 }
1722
1723 #endif /* GROUP_IOSCHED */
1724
1725 /*
1726  * The cfqd->service_trees holds all pending cfq_queue's that have
1727  * requests waiting to be processed. It is sorted in the order that
1728  * we will service the queues.
1729  */
1730 static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1731                                  bool add_front)
1732 {
1733         struct rb_node **p, *parent;
1734         struct cfq_queue *__cfqq;
1735         unsigned long rb_key;
1736         struct cfq_rb_root *st;
1737         int left;
1738         int new_cfqq = 1;
1739
1740         st = st_for(cfqq->cfqg, cfqq_class(cfqq), cfqq_type(cfqq));
1741         if (cfq_class_idle(cfqq)) {
1742                 rb_key = CFQ_IDLE_DELAY;
1743                 parent = rb_last(&st->rb);
1744                 if (parent && parent != &cfqq->rb_node) {
1745                         __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1746                         rb_key += __cfqq->rb_key;
1747                 } else
1748                         rb_key += jiffies;
1749         } else if (!add_front) {
1750                 /*
1751                  * Get our rb key offset. Subtract any residual slice
1752                  * value carried from last service. A negative resid
1753                  * count indicates slice overrun, and this should position
1754                  * the next service time further away in the tree.
1755                  */
1756                 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
1757                 rb_key -= cfqq->slice_resid;
1758                 cfqq->slice_resid = 0;
1759         } else {
1760                 rb_key = -HZ;
1761                 __cfqq = cfq_rb_first(st);
1762                 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
1763         }
1764
1765         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1766                 new_cfqq = 0;
1767                 /*
1768                  * same position, nothing more to do
1769                  */
1770                 if (rb_key == cfqq->rb_key && cfqq->service_tree == st)
1771                         return;
1772
1773                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1774                 cfqq->service_tree = NULL;
1775         }
1776
1777         left = 1;
1778         parent = NULL;
1779         cfqq->service_tree = st;
1780         p = &st->rb.rb_node;
1781         while (*p) {
1782                 parent = *p;
1783                 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
1784
1785                 /*
1786                  * sort by key, that represents service time.
1787                  */
1788                 if (time_before(rb_key, __cfqq->rb_key))
1789                         p = &parent->rb_left;
1790                 else {
1791                         p = &parent->rb_right;
1792                         left = 0;
1793                 }
1794         }
1795
1796         if (left)
1797                 st->left = &cfqq->rb_node;
1798
1799         cfqq->rb_key = rb_key;
1800         rb_link_node(&cfqq->rb_node, parent, p);
1801         rb_insert_color(&cfqq->rb_node, &st->rb);
1802         st->count++;
1803         if (add_front || !new_cfqq)
1804                 return;
1805         cfq_group_notify_queue_add(cfqd, cfqq->cfqg);
1806 }
1807
1808 static struct cfq_queue *
1809 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
1810                      sector_t sector, struct rb_node **ret_parent,
1811                      struct rb_node ***rb_link)
1812 {
1813         struct rb_node **p, *parent;
1814         struct cfq_queue *cfqq = NULL;
1815
1816         parent = NULL;
1817         p = &root->rb_node;
1818         while (*p) {
1819                 struct rb_node **n;
1820
1821                 parent = *p;
1822                 cfqq = rb_entry(parent, struct cfq_queue, p_node);
1823
1824                 /*
1825                  * Sort strictly based on sector.  Smallest to the left,
1826                  * largest to the right.
1827                  */
1828                 if (sector > blk_rq_pos(cfqq->next_rq))
1829                         n = &(*p)->rb_right;
1830                 else if (sector < blk_rq_pos(cfqq->next_rq))
1831                         n = &(*p)->rb_left;
1832                 else
1833                         break;
1834                 p = n;
1835                 cfqq = NULL;
1836         }
1837
1838         *ret_parent = parent;
1839         if (rb_link)
1840                 *rb_link = p;
1841         return cfqq;
1842 }
1843
1844 static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1845 {
1846         struct rb_node **p, *parent;
1847         struct cfq_queue *__cfqq;
1848
1849         if (cfqq->p_root) {
1850                 rb_erase(&cfqq->p_node, cfqq->p_root);
1851                 cfqq->p_root = NULL;
1852         }
1853
1854         if (cfq_class_idle(cfqq))
1855                 return;
1856         if (!cfqq->next_rq)
1857                 return;
1858
1859         cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
1860         __cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
1861                                       blk_rq_pos(cfqq->next_rq), &parent, &p);
1862         if (!__cfqq) {
1863                 rb_link_node(&cfqq->p_node, parent, p);
1864                 rb_insert_color(&cfqq->p_node, cfqq->p_root);
1865         } else
1866                 cfqq->p_root = NULL;
1867 }
1868
1869 /*
1870  * Update cfqq's position in the service tree.
1871  */
1872 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1873 {
1874         /*
1875          * Resorting requires the cfqq to be on the RR list already.
1876          */
1877         if (cfq_cfqq_on_rr(cfqq)) {
1878                 cfq_service_tree_add(cfqd, cfqq, 0);
1879                 cfq_prio_tree_add(cfqd, cfqq);
1880         }
1881 }
1882
1883 /*
1884  * add to busy list of queues for service, trying to be fair in ordering
1885  * the pending list according to last request service
1886  */
1887 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1888 {
1889         cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
1890         BUG_ON(cfq_cfqq_on_rr(cfqq));
1891         cfq_mark_cfqq_on_rr(cfqq);
1892         cfqd->busy_queues++;
1893         if (cfq_cfqq_sync(cfqq))
1894                 cfqd->busy_sync_queues++;
1895
1896         cfq_resort_rr_list(cfqd, cfqq);
1897 }
1898
1899 /*
1900  * Called when the cfqq no longer has requests pending, remove it from
1901  * the service tree.
1902  */
1903 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1904 {
1905         cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
1906         BUG_ON(!cfq_cfqq_on_rr(cfqq));
1907         cfq_clear_cfqq_on_rr(cfqq);
1908
1909         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
1910                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
1911                 cfqq->service_tree = NULL;
1912         }
1913         if (cfqq->p_root) {
1914                 rb_erase(&cfqq->p_node, cfqq->p_root);
1915                 cfqq->p_root = NULL;
1916         }
1917
1918         cfq_group_notify_queue_del(cfqd, cfqq->cfqg);
1919         BUG_ON(!cfqd->busy_queues);
1920         cfqd->busy_queues--;
1921         if (cfq_cfqq_sync(cfqq))
1922                 cfqd->busy_sync_queues--;
1923 }
1924
1925 /*
1926  * rb tree support functions
1927  */
1928 static void cfq_del_rq_rb(struct request *rq)
1929 {
1930         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1931         const int sync = rq_is_sync(rq);
1932
1933         BUG_ON(!cfqq->queued[sync]);
1934         cfqq->queued[sync]--;
1935
1936         elv_rb_del(&cfqq->sort_list, rq);
1937
1938         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1939                 /*
1940                  * Queue will be deleted from service tree when we actually
1941                  * expire it later. Right now just remove it from prio tree
1942                  * as it is empty.
1943                  */
1944                 if (cfqq->p_root) {
1945                         rb_erase(&cfqq->p_node, cfqq->p_root);
1946                         cfqq->p_root = NULL;
1947                 }
1948         }
1949 }
1950
1951 static void cfq_add_rq_rb(struct request *rq)
1952 {
1953         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1954         struct cfq_data *cfqd = cfqq->cfqd;
1955         struct request *prev;
1956
1957         cfqq->queued[rq_is_sync(rq)]++;
1958
1959         elv_rb_add(&cfqq->sort_list, rq);
1960
1961         if (!cfq_cfqq_on_rr(cfqq))
1962                 cfq_add_cfqq_rr(cfqd, cfqq);
1963
1964         /*
1965          * check if this request is a better next-serve candidate
1966          */
1967         prev = cfqq->next_rq;
1968         cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
1969
1970         /*
1971          * adjust priority tree position, if ->next_rq changes
1972          */
1973         if (prev != cfqq->next_rq)
1974                 cfq_prio_tree_add(cfqd, cfqq);
1975
1976         BUG_ON(!cfqq->next_rq);
1977 }
1978
1979 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
1980 {
1981         elv_rb_del(&cfqq->sort_list, rq);
1982         cfqq->queued[rq_is_sync(rq)]--;
1983         cfqg_stats_update_io_remove(RQ_CFQG(rq), rq->cmd_flags);
1984         cfq_add_rq_rb(rq);
1985         cfqg_stats_update_io_add(RQ_CFQG(rq), cfqq->cfqd->serving_group,
1986                                  rq->cmd_flags);
1987 }
1988
1989 static struct request *
1990 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
1991 {
1992         struct task_struct *tsk = current;
1993         struct cfq_io_cq *cic;
1994         struct cfq_queue *cfqq;
1995
1996         cic = cfq_cic_lookup(cfqd, tsk->io_context);
1997         if (!cic)
1998                 return NULL;
1999
2000         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
2001         if (cfqq) {
2002                 sector_t sector = bio->bi_sector + bio_sectors(bio);
2003
2004                 return elv_rb_find(&cfqq->sort_list, sector);
2005         }
2006
2007         return NULL;
2008 }
2009
2010 static void cfq_activate_request(struct request_queue *q, struct request *rq)
2011 {
2012         struct cfq_data *cfqd = q->elevator->elevator_data;
2013
2014         cfqd->rq_in_driver++;
2015         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
2016                                                 cfqd->rq_in_driver);
2017
2018         cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
2019 }
2020
2021 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
2022 {
2023         struct cfq_data *cfqd = q->elevator->elevator_data;
2024
2025         WARN_ON(!cfqd->rq_in_driver);
2026         cfqd->rq_in_driver--;
2027         cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
2028                                                 cfqd->rq_in_driver);
2029 }
2030
2031 static void cfq_remove_request(struct request *rq)
2032 {
2033         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2034
2035         if (cfqq->next_rq == rq)
2036                 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
2037
2038         list_del_init(&rq->queuelist);
2039         cfq_del_rq_rb(rq);
2040
2041         cfqq->cfqd->rq_queued--;
2042         cfqg_stats_update_io_remove(RQ_CFQG(rq), rq->cmd_flags);
2043         if (rq->cmd_flags & REQ_PRIO) {
2044                 WARN_ON(!cfqq->prio_pending);
2045                 cfqq->prio_pending--;
2046         }
2047 }
2048
2049 static int cfq_merge(struct request_queue *q, struct request **req,
2050                      struct bio *bio)
2051 {
2052         struct cfq_data *cfqd = q->elevator->elevator_data;
2053         struct request *__rq;
2054
2055         __rq = cfq_find_rq_fmerge(cfqd, bio);
2056         if (__rq && elv_rq_merge_ok(__rq, bio)) {
2057                 *req = __rq;
2058                 return ELEVATOR_FRONT_MERGE;
2059         }
2060
2061         return ELEVATOR_NO_MERGE;
2062 }
2063
2064 static void cfq_merged_request(struct request_queue *q, struct request *req,
2065                                int type)
2066 {
2067         if (type == ELEVATOR_FRONT_MERGE) {
2068                 struct cfq_queue *cfqq = RQ_CFQQ(req);
2069
2070                 cfq_reposition_rq_rb(cfqq, req);
2071         }
2072 }
2073
2074 static void cfq_bio_merged(struct request_queue *q, struct request *req,
2075                                 struct bio *bio)
2076 {
2077         cfqg_stats_update_io_merged(RQ_CFQG(req), bio->bi_rw);
2078 }
2079
2080 static void
2081 cfq_merged_requests(struct request_queue *q, struct request *rq,
2082                     struct request *next)
2083 {
2084         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2085         struct cfq_data *cfqd = q->elevator->elevator_data;
2086
2087         /*
2088          * reposition in fifo if next is older than rq
2089          */
2090         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
2091             time_before(rq_fifo_time(next), rq_fifo_time(rq)) &&
2092             cfqq == RQ_CFQQ(next)) {
2093                 list_move(&rq->queuelist, &next->queuelist);
2094                 rq_set_fifo_time(rq, rq_fifo_time(next));
2095         }
2096
2097         if (cfqq->next_rq == next)
2098                 cfqq->next_rq = rq;
2099         cfq_remove_request(next);
2100         cfqg_stats_update_io_merged(RQ_CFQG(rq), next->cmd_flags);
2101
2102         cfqq = RQ_CFQQ(next);
2103         /*
2104          * all requests of this queue are merged to other queues, delete it
2105          * from the service tree. If it's the active_queue,
2106          * cfq_dispatch_requests() will choose to expire it or do idle
2107          */
2108         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list) &&
2109             cfqq != cfqd->active_queue)
2110                 cfq_del_cfqq_rr(cfqd, cfqq);
2111 }
2112
2113 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
2114                            struct bio *bio)
2115 {
2116         struct cfq_data *cfqd = q->elevator->elevator_data;
2117         struct cfq_io_cq *cic;
2118         struct cfq_queue *cfqq;
2119
2120         /*
2121          * Disallow merge of a sync bio into an async request.
2122          */
2123         if (cfq_bio_sync(bio) && !rq_is_sync(rq))
2124                 return false;
2125
2126         /*
2127          * Lookup the cfqq that this bio will be queued with and allow
2128          * merge only if rq is queued there.
2129          */
2130         cic = cfq_cic_lookup(cfqd, current->io_context);
2131         if (!cic)
2132                 return false;
2133
2134         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
2135         return cfqq == RQ_CFQQ(rq);
2136 }
2137
2138 static inline void cfq_del_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2139 {
2140         del_timer(&cfqd->idle_slice_timer);
2141         cfqg_stats_update_idle_time(cfqq->cfqg);
2142 }
2143
2144 static void __cfq_set_active_queue(struct cfq_data *cfqd,
2145                                    struct cfq_queue *cfqq)
2146 {
2147         if (cfqq) {
2148                 cfq_log_cfqq(cfqd, cfqq, "set_active wl_class:%d wl_type:%d",
2149                                 cfqd->serving_wl_class, cfqd->serving_wl_type);
2150                 cfqg_stats_update_avg_queue_size(cfqq->cfqg);
2151                 cfqq->slice_start = 0;
2152                 cfqq->dispatch_start = jiffies;
2153                 cfqq->allocated_slice = 0;
2154                 cfqq->slice_end = 0;
2155                 cfqq->slice_dispatch = 0;
2156                 cfqq->nr_sectors = 0;
2157
2158                 cfq_clear_cfqq_wait_request(cfqq);
2159                 cfq_clear_cfqq_must_dispatch(cfqq);
2160                 cfq_clear_cfqq_must_alloc_slice(cfqq);
2161                 cfq_clear_cfqq_fifo_expire(cfqq);
2162                 cfq_mark_cfqq_slice_new(cfqq);
2163
2164                 cfq_del_timer(cfqd, cfqq);
2165         }
2166
2167         cfqd->active_queue = cfqq;
2168 }
2169
2170 /*
2171  * current cfqq expired its slice (or was too idle), select new one
2172  */
2173 static void
2174 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2175                     bool timed_out)
2176 {
2177         cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
2178
2179         if (cfq_cfqq_wait_request(cfqq))
2180                 cfq_del_timer(cfqd, cfqq);
2181
2182         cfq_clear_cfqq_wait_request(cfqq);
2183         cfq_clear_cfqq_wait_busy(cfqq);
2184
2185         /*
2186          * If this cfqq is shared between multiple processes, check to
2187          * make sure that those processes are still issuing I/Os within
2188          * the mean seek distance.  If not, it may be time to break the
2189          * queues apart again.
2190          */
2191         if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq))
2192                 cfq_mark_cfqq_split_coop(cfqq);
2193
2194         /*
2195          * store what was left of this slice, if the queue idled/timed out
2196          */
2197         if (timed_out) {
2198                 if (cfq_cfqq_slice_new(cfqq))
2199                         cfqq->slice_resid = cfq_scaled_cfqq_slice(cfqd, cfqq);
2200                 else
2201                         cfqq->slice_resid = cfqq->slice_end - jiffies;
2202                 cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
2203         }
2204
2205         cfq_group_served(cfqd, cfqq->cfqg, cfqq);
2206
2207         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
2208                 cfq_del_cfqq_rr(cfqd, cfqq);
2209
2210         cfq_resort_rr_list(cfqd, cfqq);
2211
2212         if (cfqq == cfqd->active_queue)
2213                 cfqd->active_queue = NULL;
2214
2215         if (cfqd->active_cic) {
2216                 put_io_context(cfqd->active_cic->icq.ioc);
2217                 cfqd->active_cic = NULL;
2218         }
2219 }
2220
2221 static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
2222 {
2223         struct cfq_queue *cfqq = cfqd->active_queue;
2224
2225         if (cfqq)
2226                 __cfq_slice_expired(cfqd, cfqq, timed_out);
2227 }
2228
2229 /*
2230  * Get next queue for service. Unless we have a queue preemption,
2231  * we'll simply select the first cfqq in the service tree.
2232  */
2233 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
2234 {
2235         struct cfq_rb_root *st = st_for(cfqd->serving_group,
2236                         cfqd->serving_wl_class, cfqd->serving_wl_type);
2237
2238         if (!cfqd->rq_queued)
2239                 return NULL;
2240
2241         /* There is nothing to dispatch */
2242         if (!st)
2243                 return NULL;
2244         if (RB_EMPTY_ROOT(&st->rb))
2245                 return NULL;
2246         return cfq_rb_first(st);
2247 }
2248
2249 static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
2250 {
2251         struct cfq_group *cfqg;
2252         struct cfq_queue *cfqq;
2253         int i, j;
2254         struct cfq_rb_root *st;
2255
2256         if (!cfqd->rq_queued)
2257                 return NULL;
2258
2259         cfqg = cfq_get_next_cfqg(cfqd);
2260         if (!cfqg)
2261                 return NULL;
2262
2263         for_each_cfqg_st(cfqg, i, j, st)
2264                 if ((cfqq = cfq_rb_first(st)) != NULL)
2265                         return cfqq;
2266         return NULL;
2267 }
2268
2269 /*
2270  * Get and set a new active queue for service.
2271  */
2272 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
2273                                               struct cfq_queue *cfqq)
2274 {
2275         if (!cfqq)
2276                 cfqq = cfq_get_next_queue(cfqd);
2277
2278         __cfq_set_active_queue(cfqd, cfqq);
2279         return cfqq;
2280 }
2281
2282 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
2283                                           struct request *rq)
2284 {
2285         if (blk_rq_pos(rq) >= cfqd->last_position)
2286                 return blk_rq_pos(rq) - cfqd->last_position;
2287         else
2288                 return cfqd->last_position - blk_rq_pos(rq);
2289 }
2290
2291 static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
2292                                struct request *rq)
2293 {
2294         return cfq_dist_from_last(cfqd, rq) <= CFQQ_CLOSE_THR;
2295 }
2296
2297 static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
2298                                     struct cfq_queue *cur_cfqq)
2299 {
2300         struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
2301         struct rb_node *parent, *node;
2302         struct cfq_queue *__cfqq;
2303         sector_t sector = cfqd->last_position;
2304
2305         if (RB_EMPTY_ROOT(root))
2306                 return NULL;
2307
2308         /*
2309          * First, if we find a request starting at the end of the last
2310          * request, choose it.
2311          */
2312         __cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
2313         if (__cfqq)
2314                 return __cfqq;
2315
2316         /*
2317          * If the exact sector wasn't found, the parent of the NULL leaf
2318          * will contain the closest sector.
2319          */
2320         __cfqq = rb_entry(parent, struct cfq_queue, p_node);
2321         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
2322                 return __cfqq;
2323
2324         if (blk_rq_pos(__cfqq->next_rq) < sector)
2325                 node = rb_next(&__cfqq->p_node);
2326         else
2327                 node = rb_prev(&__cfqq->p_node);
2328         if (!node)
2329                 return NULL;
2330
2331         __cfqq = rb_entry(node, struct cfq_queue, p_node);
2332         if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
2333                 return __cfqq;
2334
2335         return NULL;
2336 }
2337
2338 /*
2339  * cfqd - obvious
2340  * cur_cfqq - passed in so that we don't decide that the current queue is
2341  *            closely cooperating with itself.
2342  *
2343  * So, basically we're assuming that that cur_cfqq has dispatched at least
2344  * one request, and that cfqd->last_position reflects a position on the disk
2345  * associated with the I/O issued by cur_cfqq.  I'm not sure this is a valid
2346  * assumption.
2347  */
2348 static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
2349                                               struct cfq_queue *cur_cfqq)
2350 {
2351         struct cfq_queue *cfqq;
2352
2353         if (cfq_class_idle(cur_cfqq))
2354                 return NULL;
2355         if (!cfq_cfqq_sync(cur_cfqq))
2356                 return NULL;
2357         if (CFQQ_SEEKY(cur_cfqq))
2358                 return NULL;
2359
2360         /*
2361          * Don't search priority tree if it's the only queue in the group.
2362          */
2363         if (cur_cfqq->cfqg->nr_cfqq == 1)
2364                 return NULL;
2365
2366         /*
2367          * We should notice if some of the queues are cooperating, eg
2368          * working closely on the same area of the disk. In that case,
2369          * we can group them together and don't waste time idling.
2370          */
2371         cfqq = cfqq_close(cfqd, cur_cfqq);
2372         if (!cfqq)
2373                 return NULL;
2374
2375         /* If new queue belongs to different cfq_group, don't choose it */
2376         if (cur_cfqq->cfqg != cfqq->cfqg)
2377                 return NULL;
2378
2379         /*
2380          * It only makes sense to merge sync queues.
2381          */
2382         if (!cfq_cfqq_sync(cfqq))
2383                 return NULL;
2384         if (CFQQ_SEEKY(cfqq))
2385                 return NULL;
2386
2387         /*
2388          * Do not merge queues of different priority classes
2389          */
2390         if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
2391                 return NULL;
2392
2393         return cfqq;
2394 }
2395
2396 /*
2397  * Determine whether we should enforce idle window for this queue.
2398  */
2399
2400 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2401 {
2402         enum wl_class_t wl_class = cfqq_class(cfqq);
2403         struct cfq_rb_root *st = cfqq->service_tree;
2404
2405         BUG_ON(!st);
2406         BUG_ON(!st->count);
2407
2408         if (!cfqd->cfq_slice_idle)
2409                 return false;
2410
2411         /* We never do for idle class queues. */
2412         if (wl_class == IDLE_WORKLOAD)
2413                 return false;
2414
2415         /* We do for queues that were marked with idle window flag. */
2416         if (cfq_cfqq_idle_window(cfqq) &&
2417            !(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag))
2418                 return true;
2419
2420         /*
2421          * Otherwise, we do only if they are the last ones
2422          * in their service tree.
2423          */
2424         if (st->count == 1 && cfq_cfqq_sync(cfqq) &&
2425            !cfq_io_thinktime_big(cfqd, &st->ttime, false))
2426                 return true;
2427         cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d", st->count);
2428         return false;
2429 }
2430
2431 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
2432 {
2433         struct cfq_queue *cfqq = cfqd->active_queue;
2434         struct cfq_io_cq *cic;
2435         unsigned long sl, group_idle = 0;
2436
2437         /*
2438          * SSD device without seek penalty, disable idling. But only do so
2439          * for devices that support queuing, otherwise we still have a problem
2440          * with sync vs async workloads.
2441          */
2442         if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
2443                 return;
2444
2445         WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
2446         WARN_ON(cfq_cfqq_slice_new(cfqq));
2447
2448         /*
2449          * idle is disabled, either manually or by past process history
2450          */
2451         if (!cfq_should_idle(cfqd, cfqq)) {
2452                 /* no queue idling. Check for group idling */
2453                 if (cfqd->cfq_group_idle)
2454                         group_idle = cfqd->cfq_group_idle;
2455                 else
2456                         return;
2457         }
2458
2459         /*
2460          * still active requests from this queue, don't idle
2461          */
2462         if (cfqq->dispatched)
2463                 return;
2464
2465         /*
2466          * task has exited, don't wait
2467          */
2468         cic = cfqd->active_cic;
2469         if (!cic || !atomic_read(&cic->icq.ioc->active_ref))
2470                 return;
2471
2472         /*
2473          * If our average think time is larger than the remaining time
2474          * slice, then don't idle. This avoids overrunning the allotted
2475          * time slice.
2476          */
2477         if (sample_valid(cic->ttime.ttime_samples) &&
2478             (cfqq->slice_end - jiffies < cic->ttime.ttime_mean)) {
2479                 cfq_log_cfqq(cfqd, cfqq, "Not idling. think_time:%lu",
2480                              cic->ttime.ttime_mean);
2481                 return;
2482         }
2483
2484         /* There are other queues in the group, don't do group idle */
2485         if (group_idle && cfqq->cfqg->nr_cfqq > 1)
2486                 return;
2487
2488         cfq_mark_cfqq_wait_request(cfqq);
2489
2490         if (group_idle)
2491                 sl = cfqd->cfq_group_idle;
2492         else
2493                 sl = cfqd->cfq_slice_idle;
2494
2495         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
2496         cfqg_stats_set_start_idle_time(cfqq->cfqg);
2497         cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu group_idle: %d", sl,
2498                         group_idle ? 1 : 0);
2499 }
2500
2501 /*
2502  * Move request from internal lists to the request queue dispatch list.
2503  */
2504 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
2505 {
2506         struct cfq_data *cfqd = q->elevator->elevator_data;
2507         struct cfq_queue *cfqq = RQ_CFQQ(rq);
2508
2509         cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
2510
2511         cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
2512         cfq_remove_request(rq);
2513         cfqq->dispatched++;
2514         (RQ_CFQG(rq))->dispatched++;
2515         elv_dispatch_sort(q, rq);
2516
2517         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
2518         cfqq->nr_sectors += blk_rq_sectors(rq);
2519         cfqg_stats_update_dispatch(cfqq->cfqg, blk_rq_bytes(rq), rq->cmd_flags);
2520 }
2521
2522 /*
2523  * return expired entry, or NULL to just start from scratch in rbtree
2524  */
2525 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
2526 {
2527         struct request *rq = NULL;
2528
2529         if (cfq_cfqq_fifo_expire(cfqq))
2530                 return NULL;
2531
2532         cfq_mark_cfqq_fifo_expire(cfqq);
2533
2534         if (list_empty(&cfqq->fifo))
2535                 return NULL;
2536
2537         rq = rq_entry_fifo(cfqq->fifo.next);
2538         if (time_before(jiffies, rq_fifo_time(rq)))
2539                 rq = NULL;
2540
2541         cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
2542         return rq;
2543 }
2544
2545 static inline int
2546 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2547 {
2548         const int base_rq = cfqd->cfq_slice_async_rq;
2549
2550         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
2551
2552         return 2 * base_rq * (IOPRIO_BE_NR - cfqq->ioprio);
2553 }
2554
2555 /*
2556  * Must be called with the queue_lock held.
2557  */
2558 static int cfqq_process_refs(struct cfq_queue *cfqq)
2559 {
2560         int process_refs, io_refs;
2561
2562         io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
2563         process_refs = cfqq->ref - io_refs;
2564         BUG_ON(process_refs < 0);
2565         return process_refs;
2566 }
2567
2568 static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
2569 {
2570         int process_refs, new_process_refs;
2571         struct cfq_queue *__cfqq;
2572
2573         /*
2574          * If there are no process references on the new_cfqq, then it is
2575          * unsafe to follow the ->new_cfqq chain as other cfqq's in the
2576          * chain may have dropped their last reference (not just their
2577          * last process reference).
2578          */
2579         if (!cfqq_process_refs(new_cfqq))
2580                 return;
2581
2582         /* Avoid a circular list and skip interim queue merges */
2583         while ((__cfqq = new_cfqq->new_cfqq)) {
2584                 if (__cfqq == cfqq)
2585                         return;
2586                 new_cfqq = __cfqq;
2587         }
2588
2589         process_refs = cfqq_process_refs(cfqq);
2590         new_process_refs = cfqq_process_refs(new_cfqq);
2591         /*
2592          * If the process for the cfqq has gone away, there is no
2593          * sense in merging the queues.
2594          */
2595         if (process_refs == 0 || new_process_refs == 0)
2596                 return;
2597
2598         /*
2599          * Merge in the direction of the lesser amount of work.
2600          */
2601         if (new_process_refs >= process_refs) {
2602                 cfqq->new_cfqq = new_cfqq;
2603                 new_cfqq->ref += process_refs;
2604         } else {
2605                 new_cfqq->new_cfqq = cfqq;
2606                 cfqq->ref += new_process_refs;
2607         }
2608 }
2609
2610 static enum wl_type_t cfq_choose_wl_type(struct cfq_data *cfqd,
2611                         struct cfq_group *cfqg, enum wl_class_t wl_class)
2612 {
2613         struct cfq_queue *queue;
2614         int i;
2615         bool key_valid = false;
2616         unsigned long lowest_key = 0;
2617         enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
2618
2619         for (i = 0; i <= SYNC_WORKLOAD; ++i) {
2620                 /* select the one with lowest rb_key */
2621                 queue = cfq_rb_first(st_for(cfqg, wl_class, i));
2622                 if (queue &&
2623                     (!key_valid || time_before(queue->rb_key, lowest_key))) {
2624                         lowest_key = queue->rb_key;
2625                         cur_best = i;
2626                         key_valid = true;
2627                 }
2628         }
2629
2630         return cur_best;
2631 }
2632
2633 static void
2634 choose_wl_class_and_type(struct cfq_data *cfqd, struct cfq_group *cfqg)
2635 {
2636         unsigned slice;
2637         unsigned count;
2638         struct cfq_rb_root *st;
2639         unsigned group_slice;
2640         enum wl_class_t original_class = cfqd->serving_wl_class;
2641
2642         /* Choose next priority. RT > BE > IDLE */
2643         if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
2644                 cfqd->serving_wl_class = RT_WORKLOAD;
2645         else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
2646                 cfqd->serving_wl_class = BE_WORKLOAD;
2647         else {
2648                 cfqd->serving_wl_class = IDLE_WORKLOAD;
2649                 cfqd->workload_expires = jiffies + 1;
2650                 return;
2651         }
2652
2653         if (original_class != cfqd->serving_wl_class)
2654                 goto new_workload;
2655
2656         /*
2657          * For RT and BE, we have to choose also the type
2658          * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
2659          * expiration time
2660          */
2661         st = st_for(cfqg, cfqd->serving_wl_class, cfqd->serving_wl_type);
2662         count = st->count;
2663
2664         /*
2665          * check workload expiration, and that we still have other queues ready
2666          */
2667         if (count && !time_after(jiffies, cfqd->workload_expires))
2668                 return;
2669
2670 new_workload:
2671         /* otherwise select new workload type */
2672         cfqd->serving_wl_type = cfq_choose_wl_type(cfqd, cfqg,
2673                                         cfqd->serving_wl_class);
2674         st = st_for(cfqg, cfqd->serving_wl_class, cfqd->serving_wl_type);
2675         count = st->count;
2676
2677         /*
2678          * the workload slice is computed as a fraction of target latency
2679          * proportional to the number of queues in that workload, over
2680          * all the queues in the same priority class
2681          */
2682         group_slice = cfq_group_slice(cfqd, cfqg);
2683
2684         slice = group_slice * count /
2685                 max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_wl_class],
2686                       cfq_group_busy_queues_wl(cfqd->serving_wl_class, cfqd,
2687                                         cfqg));
2688
2689         if (cfqd->serving_wl_type == ASYNC_WORKLOAD) {
2690                 unsigned int tmp;
2691
2692                 /*
2693                  * Async queues are currently system wide. Just taking
2694                  * proportion of queues with-in same group will lead to higher
2695                  * async ratio system wide as generally root group is going
2696                  * to have higher weight. A more accurate thing would be to
2697                  * calculate system wide asnc/sync ratio.
2698                  */
2699                 tmp = cfqd->cfq_target_latency *
2700                         cfqg_busy_async_queues(cfqd, cfqg);
2701                 tmp = tmp/cfqd->busy_queues;
2702                 slice = min_t(unsigned, slice, tmp);
2703
2704                 /* async workload slice is scaled down according to
2705                  * the sync/async slice ratio. */
2706                 slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
2707         } else
2708                 /* sync workload slice is at least 2 * cfq_slice_idle */
2709                 slice = max(slice, 2 * cfqd->cfq_slice_idle);
2710
2711         slice = max_t(unsigned, slice, CFQ_MIN_TT);
2712         cfq_log(cfqd, "workload slice:%d", slice);
2713         cfqd->workload_expires = jiffies + slice;
2714 }
2715
2716 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
2717 {
2718         struct cfq_rb_root *st = &cfqd->grp_service_tree;
2719         struct cfq_group *cfqg;
2720
2721         if (RB_EMPTY_ROOT(&st->rb))
2722                 return NULL;
2723         cfqg = cfq_rb_first_group(st);
2724         update_min_vdisktime(st);
2725         return cfqg;
2726 }
2727
2728 static void cfq_choose_cfqg(struct cfq_data *cfqd)
2729 {
2730         struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
2731
2732         cfqd->serving_group = cfqg;
2733
2734         /* Restore the workload type data */
2735         if (cfqg->saved_wl_slice) {
2736                 cfqd->workload_expires = jiffies + cfqg->saved_wl_slice;
2737                 cfqd->serving_wl_type = cfqg->saved_wl_type;
2738                 cfqd->serving_wl_class = cfqg->saved_wl_class;
2739         } else
2740                 cfqd->workload_expires = jiffies - 1;
2741
2742         choose_wl_class_and_type(cfqd, cfqg);
2743 }
2744
2745 /*
2746  * Select a queue for service. If we have a current active queue,
2747  * check whether to continue servicing it, or retrieve and set a new one.
2748  */
2749 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
2750 {
2751         struct cfq_queue *cfqq, *new_cfqq = NULL;
2752
2753         cfqq = cfqd->active_queue;
2754         if (!cfqq)
2755                 goto new_queue;
2756
2757         if (!cfqd->rq_queued)
2758                 return NULL;
2759
2760         /*
2761          * We were waiting for group to get backlogged. Expire the queue
2762          */
2763         if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list))
2764                 goto expire;
2765
2766         /*
2767          * The active queue has run out of time, expire it and select new.
2768          */
2769         if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) {
2770                 /*
2771                  * If slice had not expired at the completion of last request
2772                  * we might not have turned on wait_busy flag. Don't expire
2773                  * the queue yet. Allow the group to get backlogged.
2774                  *
2775                  * The very fact that we have used the slice, that means we
2776                  * have been idling all along on this queue and it should be
2777                  * ok to wait for this request to complete.
2778                  */
2779                 if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list)
2780                     && cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
2781                         cfqq = NULL;
2782                         goto keep_queue;
2783                 } else
2784                         goto check_group_idle;
2785         }
2786
2787         /*
2788          * The active queue has requests and isn't expired, allow it to
2789          * dispatch.
2790          */
2791         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
2792                 goto keep_queue;
2793
2794         /*
2795          * If another queue has a request waiting within our mean seek
2796          * distance, let it run.  The expire code will check for close
2797          * cooperators and put the close queue at the front of the service
2798          * tree.  If possible, merge the expiring queue with the new cfqq.
2799          */
2800         new_cfqq = cfq_close_cooperator(cfqd, cfqq);
2801         if (new_cfqq) {
2802                 if (!cfqq->new_cfqq)
2803                         cfq_setup_merge(cfqq, new_cfqq);
2804                 goto expire;
2805         }
2806
2807         /*
2808          * No requests pending. If the active queue still has requests in
2809          * flight or is idling for a new request, allow either of these
2810          * conditions to happen (or time out) before selecting a new queue.
2811          */
2812         if (timer_pending(&cfqd->idle_slice_timer)) {
2813                 cfqq = NULL;
2814                 goto keep_queue;
2815         }
2816
2817         /*
2818          * This is a deep seek queue, but the device is much faster than
2819          * the queue can deliver, don't idle
2820          **/
2821         if (CFQQ_SEEKY(cfqq) && cfq_cfqq_idle_window(cfqq) &&
2822             (cfq_cfqq_slice_new(cfqq) ||
2823             (cfqq->slice_end - jiffies > jiffies - cfqq->slice_start))) {
2824                 cfq_clear_cfqq_deep(cfqq);
2825                 cfq_clear_cfqq_idle_window(cfqq);
2826         }
2827
2828         if (cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
2829                 cfqq = NULL;
2830                 goto keep_queue;
2831         }
2832
2833         /*
2834          * If group idle is enabled and there are requests dispatched from
2835          * this group, wait for requests to complete.
2836          */
2837 check_group_idle:
2838         if (cfqd->cfq_group_idle && cfqq->cfqg->nr_cfqq == 1 &&
2839             cfqq->cfqg->dispatched &&
2840             !cfq_io_thinktime_big(cfqd, &cfqq->cfqg->ttime, true)) {
2841                 cfqq = NULL;
2842                 goto keep_queue;
2843         }
2844
2845 expire:
2846         cfq_slice_expired(cfqd, 0);
2847 new_queue:
2848         /*
2849          * Current queue expired. Check if we have to switch to a new
2850          * service tree
2851          */
2852         if (!new_cfqq)
2853                 cfq_choose_cfqg(cfqd);
2854
2855         cfqq = cfq_set_active_queue(cfqd, new_cfqq);
2856 keep_queue:
2857         return cfqq;
2858 }
2859
2860 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
2861 {
2862         int dispatched = 0;
2863
2864         while (cfqq->next_rq) {
2865                 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
2866                 dispatched++;
2867         }
2868
2869         BUG_ON(!list_empty(&cfqq->fifo));
2870
2871         /* By default cfqq is not expired if it is empty. Do it explicitly */
2872         __cfq_slice_expired(cfqq->cfqd, cfqq, 0);
2873         return dispatched;
2874 }
2875
2876 /*
2877  * Drain our current requests. Used for barriers and when switching
2878  * io schedulers on-the-fly.
2879  */
2880 static int cfq_forced_dispatch(struct cfq_data *cfqd)
2881 {
2882         struct cfq_queue *cfqq;
2883         int dispatched = 0;
2884
2885         /* Expire the timeslice of the current active queue first */
2886         cfq_slice_expired(cfqd, 0);
2887         while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) {
2888                 __cfq_set_active_queue(cfqd, cfqq);
2889                 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
2890         }
2891
2892         BUG_ON(cfqd->busy_queues);
2893
2894         cfq_log(cfqd, "forced_dispatch=%d", dispatched);
2895         return dispatched;
2896 }
2897
2898 static inline bool cfq_slice_used_soon(struct cfq_data *cfqd,
2899         struct cfq_queue *cfqq)
2900 {
2901         /* the queue hasn't finished any request, can't estimate */
2902         if (cfq_cfqq_slice_new(cfqq))
2903                 return true;
2904         if (time_after(jiffies + cfqd->cfq_slice_idle * cfqq->dispatched,
2905                 cfqq->slice_end))
2906                 return true;
2907
2908         return false;
2909 }
2910
2911 static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
2912 {
2913         unsigned int max_dispatch;
2914
2915         /*
2916          * Drain async requests before we start sync IO
2917          */
2918         if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_flight[BLK_RW_ASYNC])
2919                 return false;
2920
2921         /*
2922          * If this is an async queue and we have sync IO in flight, let it wait
2923          */
2924         if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq))
2925                 return false;
2926
2927         max_dispatch = max_t(unsigned int, cfqd->cfq_quantum / 2, 1);
2928         if (cfq_class_idle(cfqq))
2929                 max_dispatch = 1;
2930
2931         /*
2932          * Does this cfqq already have too much IO in flight?
2933          */
2934         if (cfqq->dispatched >= max_dispatch) {
2935                 bool promote_sync = false;
2936                 /*
2937                  * idle queue must always only have a single IO in flight
2938                  */
2939                 if (cfq_class_idle(cfqq))
2940                         return false;
2941
2942                 /*
2943                  * If there is only one sync queue
2944                  * we can ignore async queue here and give the sync
2945                  * queue no dispatch limit. The reason is a sync queue can
2946                  * preempt async queue, limiting the sync queue doesn't make
2947                  * sense. This is useful for aiostress test.
2948                  */
2949                 if (cfq_cfqq_sync(cfqq) && cfqd->busy_sync_queues == 1)
2950                         promote_sync = true;
2951
2952                 /*
2953                  * We have other queues, don't allow more IO from this one
2954                  */
2955                 if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq) &&
2956                                 !promote_sync)
2957                         return false;
2958
2959                 /*
2960                  * Sole queue user, no limit
2961                  */
2962                 if (cfqd->busy_queues == 1 || promote_sync)
2963                         max_dispatch = -1;
2964                 else
2965                         /*
2966                          * Normally we start throttling cfqq when cfq_quantum/2
2967                          * requests have been dispatched. But we can drive
2968                          * deeper queue depths at the beginning of slice
2969                          * subjected to upper limit of cfq_quantum.
2970                          * */
2971                         max_dispatch = cfqd->cfq_quantum;
2972         }
2973
2974         /*
2975          * Async queues must wait a bit before being allowed dispatch.
2976          * We also ramp up the dispatch depth gradually for async IO,
2977          * based on the last sync IO we serviced
2978          */
2979         if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
2980                 unsigned long last_sync = jiffies - cfqd->last_delayed_sync;
2981                 unsigned int depth;
2982
2983                 depth = last_sync / cfqd->cfq_slice[1];
2984                 if (!depth && !cfqq->dispatched)
2985                         depth = 1;
2986                 if (depth < max_dispatch)
2987                         max_dispatch = depth;
2988         }
2989
2990         /*
2991          * If we're below the current max, allow a dispatch
2992          */
2993         return cfqq->dispatched < max_dispatch;
2994 }
2995
2996 /*
2997  * Dispatch a request from cfqq, moving them to the request queue
2998  * dispatch list.
2999  */
3000 static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3001 {
3002         struct request *rq;
3003
3004         BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
3005
3006         if (!cfq_may_dispatch(cfqd, cfqq))
3007                 return false;
3008
3009         /*
3010          * follow expired path, else get first next available
3011          */
3012         rq = cfq_check_fifo(cfqq);
3013         if (!rq)
3014                 rq = cfqq->next_rq;
3015
3016         /*
3017          * insert request into driver dispatch list
3018          */
3019         cfq_dispatch_insert(cfqd->queue, rq);
3020
3021         if (!cfqd->active_cic) {
3022                 struct cfq_io_cq *cic = RQ_CIC(rq);
3023
3024                 atomic_long_inc(&cic->icq.ioc->refcount);
3025                 cfqd->active_cic = cic;
3026         }
3027
3028         return true;
3029 }
3030
3031 /*
3032  * Find the cfqq that we need to service and move a request from that to the
3033  * dispatch list
3034  */
3035 static int cfq_dispatch_requests(struct request_queue *q, int force)
3036 {
3037         struct cfq_data *cfqd = q->elevator->elevator_data;
3038         struct cfq_queue *cfqq;
3039
3040         if (!cfqd->busy_queues)
3041                 return 0;
3042
3043         if (unlikely(force))
3044                 return cfq_forced_dispatch(cfqd);
3045
3046         cfqq = cfq_select_queue(cfqd);
3047         if (!cfqq)
3048                 return 0;
3049
3050         /*
3051          * Dispatch a request from this cfqq, if it is allowed
3052          */
3053         if (!cfq_dispatch_request(cfqd, cfqq))
3054                 return 0;
3055
3056         cfqq->slice_dispatch++;
3057         cfq_clear_cfqq_must_dispatch(cfqq);
3058
3059         /*
3060          * expire an async queue immediately if it has used up its slice. idle
3061          * queue always expire after 1 dispatch round.
3062          */
3063         if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
3064             cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
3065             cfq_class_idle(cfqq))) {
3066                 cfqq->slice_end = jiffies + 1;
3067                 cfq_slice_expired(cfqd, 0);
3068         }
3069
3070         cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
3071         return 1;
3072 }
3073
3074 /*
3075  * task holds one reference to the queue, dropped when task exits. each rq
3076  * in-flight on this queue also holds a reference, dropped when rq is freed.
3077  *
3078  * Each cfq queue took a reference on the parent group. Drop it now.
3079  * queue lock must be held here.
3080  */
3081 static void cfq_put_queue(struct cfq_queue *cfqq)
3082 {
3083         struct cfq_data *cfqd = cfqq->cfqd;
3084         struct cfq_group *cfqg;
3085
3086         BUG_ON(cfqq->ref <= 0);
3087
3088         cfqq->ref--;
3089         if (cfqq->ref)
3090                 return;
3091
3092         cfq_log_cfqq(cfqd, cfqq, "put_queue");
3093         BUG_ON(rb_first(&cfqq->sort_list));
3094         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
3095         cfqg = cfqq->cfqg;
3096
3097         if (unlikely(cfqd->active_queue == cfqq)) {
3098                 __cfq_slice_expired(cfqd, cfqq, 0);
3099                 cfq_schedule_dispatch(cfqd);
3100         }
3101
3102         BUG_ON(cfq_cfqq_on_rr(cfqq));
3103         kmem_cache_free(cfq_pool, cfqq);
3104         cfqg_put(cfqg);
3105 }
3106
3107 static void cfq_put_cooperator(struct cfq_queue *cfqq)
3108 {
3109         struct cfq_queue *__cfqq, *next;
3110
3111         /*
3112          * If this queue was scheduled to merge with another queue, be
3113          * sure to drop the reference taken on that queue (and others in
3114          * the merge chain).  See cfq_setup_merge and cfq_merge_cfqqs.
3115          */
3116         __cfqq = cfqq->new_cfqq;
3117         while (__cfqq) {
3118                 if (__cfqq == cfqq) {
3119                         WARN(1, "cfqq->new_cfqq loop detected\n");
3120                         break;
3121                 }
3122                 next = __cfqq->new_cfqq;
3123                 cfq_put_queue(__cfqq);
3124                 __cfqq = next;
3125         }
3126 }
3127
3128 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3129 {
3130         if (unlikely(cfqq == cfqd->active_queue)) {
3131                 __cfq_slice_expired(cfqd, cfqq, 0);
3132                 cfq_schedule_dispatch(cfqd);
3133         }
3134
3135         cfq_put_cooperator(cfqq);
3136
3137         cfq_put_queue(cfqq);
3138 }
3139
3140 static void cfq_init_icq(struct io_cq *icq)
3141 {
3142         struct cfq_io_cq *cic = icq_to_cic(icq);
3143
3144         cic->ttime.last_end_request = jiffies;
3145 }
3146
3147 static void cfq_exit_icq(struct io_cq *icq)
3148 {
3149         struct cfq_io_cq *cic = icq_to_cic(icq);
3150         struct cfq_data *cfqd = cic_to_cfqd(cic);
3151
3152         if (cic->cfqq[BLK_RW_ASYNC]) {
3153                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
3154                 cic->cfqq[BLK_RW_ASYNC] = NULL;
3155         }
3156
3157         if (cic->cfqq[BLK_RW_SYNC]) {
3158                 cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
3159                 cic->cfqq[BLK_RW_SYNC] = NULL;
3160         }
3161 }
3162
3163 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct cfq_io_cq *cic)
3164 {
3165         struct task_struct *tsk = current;
3166         int ioprio_class;
3167
3168         if (!cfq_cfqq_prio_changed(cfqq))
3169                 return;
3170
3171         ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
3172         switch (ioprio_class) {
3173         default:
3174                 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
3175         case IOPRIO_CLASS_NONE:
3176                 /*
3177                  * no prio set, inherit CPU scheduling settings
3178                  */
3179                 cfqq->ioprio = task_nice_ioprio(tsk);
3180                 cfqq->ioprio_class = task_nice_ioclass(tsk);
3181                 break;
3182         case IOPRIO_CLASS_RT:
3183                 cfqq->ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
3184                 cfqq->ioprio_class = IOPRIO_CLASS_RT;
3185                 break;
3186         case IOPRIO_CLASS_BE:
3187                 cfqq->ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
3188                 cfqq->ioprio_class = IOPRIO_CLASS_BE;
3189                 break;
3190         case IOPRIO_CLASS_IDLE:
3191                 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
3192                 cfqq->ioprio = 7;
3193                 cfq_clear_cfqq_idle_window(cfqq);
3194                 break;
3195         }
3196
3197         /*
3198          * keep track of original prio settings in case we have to temporarily
3199          * elevate the priority of this queue
3200          */
3201         cfqq->org_ioprio = cfqq->ioprio;
3202         cfq_clear_cfqq_prio_changed(cfqq);
3203 }
3204
3205 static void check_ioprio_changed(struct cfq_io_cq *cic, struct bio *bio)
3206 {
3207         int ioprio = cic->icq.ioc->ioprio;
3208         struct cfq_data *cfqd = cic_to_cfqd(cic);
3209         struct cfq_queue *cfqq;
3210
3211         /*
3212          * Check whether ioprio has changed.  The condition may trigger
3213          * spuriously on a newly created cic but there's no harm.
3214          */
3215         if (unlikely(!cfqd) || likely(cic->ioprio == ioprio))
3216                 return;
3217
3218         cfqq = cic->cfqq[BLK_RW_ASYNC];
3219         if (cfqq) {
3220                 struct cfq_queue *new_cfqq;
3221                 new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic, bio,
3222                                          GFP_ATOMIC);
3223                 if (new_cfqq) {
3224                         cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
3225                         cfq_put_queue(cfqq);
3226                 }
3227         }
3228
3229         cfqq = cic->cfqq[BLK_RW_SYNC];
3230         if (cfqq)
3231                 cfq_mark_cfqq_prio_changed(cfqq);
3232
3233         cic->ioprio = ioprio;
3234 }
3235
3236 static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3237                           pid_t pid, bool is_sync)
3238 {
3239         RB_CLEAR_NODE(&cfqq->rb_node);
3240         RB_CLEAR_NODE(&cfqq->p_node);
3241         INIT_LIST_HEAD(&cfqq->fifo);
3242
3243         cfqq->ref = 0;
3244         cfqq->cfqd = cfqd;
3245
3246         cfq_mark_cfqq_prio_changed(cfqq);
3247
3248         if (is_sync) {
3249                 if (!cfq_class_idle(cfqq))
3250                         cfq_mark_cfqq_idle_window(cfqq);
3251                 cfq_mark_cfqq_sync(cfqq);
3252         }
3253         cfqq->pid = pid;
3254 }
3255
3256 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3257 static void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio)
3258 {
3259         struct cfq_data *cfqd = cic_to_cfqd(cic);
3260         struct cfq_queue *sync_cfqq;
3261         uint64_t id;
3262
3263         rcu_read_lock();
3264         id = bio_blkcg(bio)->id;
3265         rcu_read_unlock();
3266
3267         /*
3268          * Check whether blkcg has changed.  The condition may trigger
3269          * spuriously on a newly created cic but there's no harm.
3270          */
3271         if (unlikely(!cfqd) || likely(cic->blkcg_id == id))
3272                 return;
3273
3274         sync_cfqq = cic_to_cfqq(cic, 1);
3275         if (sync_cfqq) {
3276                 /*
3277                  * Drop reference to sync queue. A new sync queue will be
3278                  * assigned in new group upon arrival of a fresh request.
3279                  */
3280                 cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
3281                 cic_set_cfqq(cic, NULL, 1);
3282                 cfq_put_queue(sync_cfqq);
3283         }
3284
3285         cic->blkcg_id = id;
3286 }
3287 #else
3288 static inline void check_blkcg_changed(struct cfq_io_cq *cic, struct bio *bio) { }
3289 #endif  /* CONFIG_CFQ_GROUP_IOSCHED */
3290
3291 static struct cfq_queue *
3292 cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
3293                      struct bio *bio, gfp_t gfp_mask)
3294 {
3295         struct blkcg *blkcg;
3296         struct cfq_queue *cfqq, *new_cfqq = NULL;
3297         struct cfq_group *cfqg;
3298
3299 retry:
3300         rcu_read_lock();
3301
3302         blkcg = bio_blkcg(bio);
3303         cfqg = cfq_lookup_create_cfqg(cfqd, blkcg);
3304         cfqq = cic_to_cfqq(cic, is_sync);
3305
3306         /*
3307          * Always try a new alloc if we fell back to the OOM cfqq
3308          * originally, since it should just be a temporary situation.
3309          */
3310         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3311                 cfqq = NULL;
3312                 if (new_cfqq) {
3313                         cfqq = new_cfqq;
3314                         new_cfqq = NULL;
3315                 } else if (gfp_mask & __GFP_WAIT) {
3316                         rcu_read_unlock();
3317                         spin_unlock_irq(cfqd->queue->queue_lock);
3318                         new_cfqq = kmem_cache_alloc_node(cfq_pool,
3319                                         gfp_mask | __GFP_ZERO,
3320                                         cfqd->queue->node);
3321                         spin_lock_irq(cfqd->queue->queue_lock);
3322                         if (new_cfqq)
3323                                 goto retry;
3324                 } else {
3325                         cfqq = kmem_cache_alloc_node(cfq_pool,
3326                                         gfp_mask | __GFP_ZERO,
3327                                         cfqd->queue->node);
3328                 }
3329
3330                 if (cfqq) {
3331                         cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
3332                         cfq_init_prio_data(cfqq, cic);
3333                         cfq_link_cfqq_cfqg(cfqq, cfqg);
3334                         cfq_log_cfqq(cfqd, cfqq, "alloced");
3335                 } else
3336                         cfqq = &cfqd->oom_cfqq;
3337         }
3338
3339         if (new_cfqq)
3340                 kmem_cache_free(cfq_pool, new_cfqq);
3341
3342         rcu_read_unlock();
3343         return cfqq;
3344 }
3345
3346 static struct cfq_queue **
3347 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
3348 {
3349         switch (ioprio_class) {
3350         case IOPRIO_CLASS_RT:
3351                 return &cfqd->async_cfqq[0][ioprio];
3352         case IOPRIO_CLASS_NONE:
3353                 ioprio = IOPRIO_NORM;
3354                 /* fall through */
3355         case IOPRIO_CLASS_BE:
3356                 return &cfqd->async_cfqq[1][ioprio];
3357         case IOPRIO_CLASS_IDLE:
3358                 return &cfqd->async_idle_cfqq;
3359         default:
3360                 BUG();
3361         }
3362 }
3363
3364 static struct cfq_queue *
3365 cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
3366               struct bio *bio, gfp_t gfp_mask)
3367 {
3368         const int ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
3369         const int ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
3370         struct cfq_queue **async_cfqq = NULL;
3371         struct cfq_queue *cfqq = NULL;
3372
3373         if (!is_sync) {
3374                 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
3375                 cfqq = *async_cfqq;
3376         }
3377
3378         if (!cfqq)
3379                 cfqq = cfq_find_alloc_queue(cfqd, is_sync, cic, bio, gfp_mask);
3380
3381         /*
3382          * pin the queue now that it's allocated, scheduler exit will prune it
3383          */
3384         if (!is_sync && !(*async_cfqq)) {
3385                 cfqq->ref++;
3386                 *async_cfqq = cfqq;
3387         }
3388
3389         cfqq->ref++;
3390         return cfqq;
3391 }
3392
3393 static void
3394 __cfq_update_io_thinktime(struct cfq_ttime *ttime, unsigned long slice_idle)
3395 {
3396         unsigned long elapsed = jiffies - ttime->last_end_request;
3397         elapsed = min(elapsed, 2UL * slice_idle);
3398
3399         ttime->ttime_samples = (7*ttime->ttime_samples + 256) / 8;
3400         ttime->ttime_total = (7*ttime->ttime_total + 256*elapsed) / 8;
3401         ttime->ttime_mean = (ttime->ttime_total + 128) / ttime->ttime_samples;
3402 }
3403
3404 static void
3405 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3406                         struct cfq_io_cq *cic)
3407 {
3408         if (cfq_cfqq_sync(cfqq)) {
3409                 __cfq_update_io_thinktime(&cic->ttime, cfqd->cfq_slice_idle);
3410                 __cfq_update_io_thinktime(&cfqq->service_tree->ttime,
3411                         cfqd->cfq_slice_idle);
3412         }
3413 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3414         __cfq_update_io_thinktime(&cfqq->cfqg->ttime, cfqd->cfq_group_idle);
3415 #endif
3416 }
3417
3418 static void
3419 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3420                        struct request *rq)
3421 {
3422         sector_t sdist = 0;
3423         sector_t n_sec = blk_rq_sectors(rq);
3424         if (cfqq->last_request_pos) {
3425                 if (cfqq->last_request_pos < blk_rq_pos(rq))
3426                         sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
3427                 else
3428                         sdist = cfqq->last_request_pos - blk_rq_pos(rq);
3429         }
3430
3431         cfqq->seek_history <<= 1;
3432         if (blk_queue_nonrot(cfqd->queue))
3433                 cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT);
3434         else
3435                 cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
3436 }
3437
3438 /*
3439  * Disable idle window if the process thinks too long or seeks so much that
3440  * it doesn't matter
3441  */
3442 static void
3443 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3444                        struct cfq_io_cq *cic)
3445 {
3446         int old_idle, enable_idle;
3447
3448         /*
3449          * Don't idle for async or idle io prio class
3450          */
3451         if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
3452                 return;
3453
3454         enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
3455
3456         if (cfqq->queued[0] + cfqq->queued[1] >= 4)
3457                 cfq_mark_cfqq_deep(cfqq);
3458
3459         if (cfqq->next_rq && (cfqq->next_rq->cmd_flags & REQ_NOIDLE))
3460                 enable_idle = 0;
3461         else if (!atomic_read(&cic->icq.ioc->active_ref) ||
3462                  !cfqd->cfq_slice_idle ||
3463                  (!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
3464                 enable_idle = 0;
3465         else if (sample_valid(cic->ttime.ttime_samples)) {
3466                 if (cic->ttime.ttime_mean > cfqd->cfq_slice_idle)
3467                         enable_idle = 0;
3468                 else
3469                         enable_idle = 1;
3470         }
3471
3472         if (old_idle != enable_idle) {
3473                 cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
3474                 if (enable_idle)
3475                         cfq_mark_cfqq_idle_window(cfqq);
3476                 else
3477                         cfq_clear_cfqq_idle_window(cfqq);
3478         }
3479 }
3480
3481 /*
3482  * Check if new_cfqq should preempt the currently active queue. Return 0 for
3483  * no or if we aren't sure, a 1 will cause a preempt.
3484  */
3485 static bool
3486 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
3487                    struct request *rq)
3488 {
3489         struct cfq_queue *cfqq;
3490
3491         cfqq = cfqd->active_queue;
3492         if (!cfqq)
3493                 return false;
3494
3495         if (cfq_class_idle(new_cfqq))
3496                 return false;
3497
3498         if (cfq_class_idle(cfqq))
3499                 return true;
3500
3501         /*
3502          * Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice.
3503          */
3504         if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq))
3505                 return false;
3506
3507         /*
3508          * if the new request is sync, but the currently running queue is
3509          * not, let the sync request have priority.
3510          */
3511         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
3512                 return true;
3513
3514         if (new_cfqq->cfqg != cfqq->cfqg)
3515                 return false;
3516
3517         if (cfq_slice_used(cfqq))
3518                 return true;
3519
3520         /* Allow preemption only if we are idling on sync-noidle tree */
3521         if (cfqd->serving_wl_type == SYNC_NOIDLE_WORKLOAD &&
3522             cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
3523             new_cfqq->service_tree->count == 2 &&
3524             RB_EMPTY_ROOT(&cfqq->sort_list))
3525                 return true;
3526
3527         /*
3528          * So both queues are sync. Let the new request get disk time if
3529          * it's a metadata request and the current queue is doing regular IO.
3530          */
3531         if ((rq->cmd_flags & REQ_PRIO) && !cfqq->prio_pending)
3532                 return true;
3533
3534         /*
3535          * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
3536          */
3537         if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
3538                 return true;
3539
3540         /* An idle queue should not be idle now for some reason */
3541         if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq))
3542                 return true;
3543
3544         if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
3545                 return false;
3546
3547         /*
3548          * if this request is as-good as one we would expect from the
3549          * current cfqq, let it preempt
3550          */
3551         if (cfq_rq_close(cfqd, cfqq, rq))
3552                 return true;
3553
3554         return false;
3555 }
3556
3557 /*
3558  * cfqq preempts the active queue. if we allowed preempt with no slice left,
3559  * let it have half of its nominal slice.
3560  */
3561 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3562 {
3563         enum wl_type_t old_type = cfqq_type(cfqd->active_queue);
3564
3565         cfq_log_cfqq(cfqd, cfqq, "preempt");
3566         cfq_slice_expired(cfqd, 1);
3567
3568         /*
3569          * workload type is changed, don't save slice, otherwise preempt
3570          * doesn't happen
3571          */
3572         if (old_type != cfqq_type(cfqq))
3573                 cfqq->cfqg->saved_wl_slice = 0;
3574
3575         /*
3576          * Put the new queue at the front of the of the current list,
3577          * so we know that it will be selected next.
3578          */
3579         BUG_ON(!cfq_cfqq_on_rr(cfqq));
3580
3581         cfq_service_tree_add(cfqd, cfqq, 1);
3582
3583         cfqq->slice_end = 0;
3584         cfq_mark_cfqq_slice_new(cfqq);
3585 }
3586
3587 /*
3588  * Called when a new fs request (rq) is added (to cfqq). Check if there's
3589  * something we should do about it
3590  */
3591 static void
3592 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
3593                 struct request *rq)
3594 {
3595         struct cfq_io_cq *cic = RQ_CIC(rq);
3596
3597         cfqd->rq_queued++;
3598         if (rq->cmd_flags & REQ_PRIO)
3599                 cfqq->prio_pending++;
3600
3601         cfq_update_io_thinktime(cfqd, cfqq, cic);
3602         cfq_update_io_seektime(cfqd, cfqq, rq);
3603         cfq_update_idle_window(cfqd, cfqq, cic);
3604
3605         cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
3606
3607         if (cfqq == cfqd->active_queue) {
3608                 /*
3609                  * Remember that we saw a request from this process, but
3610                  * don't start queuing just yet. Otherwise we risk seeing lots
3611                  * of tiny requests, because we disrupt the normal plugging
3612                  * and merging. If the request is already larger than a single
3613                  * page, let it rip immediately. For that case we assume that
3614                  * merging is already done. Ditto for a busy system that
3615                  * has other work pending, don't risk delaying until the
3616                  * idle timer unplug to continue working.
3617                  */
3618                 if (cfq_cfqq_wait_request(cfqq)) {
3619                         if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
3620                             cfqd->busy_queues > 1) {
3621                                 cfq_del_timer(cfqd, cfqq);
3622                                 cfq_clear_cfqq_wait_request(cfqq);
3623                                 __blk_run_queue(cfqd->queue);
3624                         } else {
3625                                 cfqg_stats_update_idle_time(cfqq->cfqg);
3626                                 cfq_mark_cfqq_must_dispatch(cfqq);
3627                         }
3628                 }
3629         } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
3630                 /*
3631                  * not the active queue - expire current slice if it is
3632                  * idle and has expired it's mean thinktime or this new queue
3633                  * has some old slice time left and is of higher priority or
3634                  * this new queue is RT and the current one is BE
3635                  */
3636                 cfq_preempt_queue(cfqd, cfqq);
3637                 __blk_run_queue(cfqd->queue);
3638         }
3639 }
3640
3641 static void cfq_insert_request(struct request_queue *q, struct request *rq)
3642 {
3643         struct cfq_data *cfqd = q->elevator->elevator_data;
3644         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3645
3646         cfq_log_cfqq(cfqd, cfqq, "insert_request");
3647         cfq_init_prio_data(cfqq, RQ_CIC(rq));
3648
3649         rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
3650         list_add_tail(&rq->queuelist, &cfqq->fifo);
3651         cfq_add_rq_rb(rq);
3652         cfqg_stats_update_io_add(RQ_CFQG(rq), cfqd->serving_group,
3653                                  rq->cmd_flags);
3654         cfq_rq_enqueued(cfqd, cfqq, rq);
3655 }
3656
3657 /*
3658  * Update hw_tag based on peak queue depth over 50 samples under
3659  * sufficient load.
3660  */
3661 static void cfq_update_hw_tag(struct cfq_data *cfqd)
3662 {
3663         struct cfq_queue *cfqq = cfqd->active_queue;
3664
3665         if (cfqd->rq_in_driver > cfqd->hw_tag_est_depth)
3666                 cfqd->hw_tag_est_depth = cfqd->rq_in_driver;
3667
3668         if (cfqd->hw_tag == 1)
3669                 return;
3670
3671         if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
3672             cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
3673                 return;
3674
3675         /*
3676          * If active queue hasn't enough requests and can idle, cfq might not
3677          * dispatch sufficient requests to hardware. Don't zero hw_tag in this
3678          * case
3679          */
3680         if (cfqq && cfq_cfqq_idle_window(cfqq) &&
3681             cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
3682             CFQ_HW_QUEUE_MIN && cfqd->rq_in_driver < CFQ_HW_QUEUE_MIN)
3683                 return;
3684
3685         if (cfqd->hw_tag_samples++ < 50)
3686                 return;
3687
3688         if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
3689                 cfqd->hw_tag = 1;
3690         else
3691                 cfqd->hw_tag = 0;
3692 }
3693
3694 static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq)
3695 {
3696         struct cfq_io_cq *cic = cfqd->active_cic;
3697
3698         /* If the queue already has requests, don't wait */
3699         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
3700                 return false;
3701
3702         /* If there are other queues in the group, don't wait */
3703         if (cfqq->cfqg->nr_cfqq > 1)
3704                 return false;
3705
3706         /* the only queue in the group, but think time is big */
3707         if (cfq_io_thinktime_big(cfqd, &cfqq->cfqg->ttime, true))
3708                 return false;
3709
3710         if (cfq_slice_used(cfqq))
3711                 return true;
3712
3713         /* if slice left is less than think time, wait busy */
3714         if (cic && sample_valid(cic->ttime.ttime_samples)
3715             && (cfqq->slice_end - jiffies < cic->ttime.ttime_mean))
3716                 return true;
3717
3718         /*
3719          * If think times is less than a jiffy than ttime_mean=0 and above
3720          * will not be true. It might happen that slice has not expired yet
3721          * but will expire soon (4-5 ns) during select_queue(). To cover the
3722          * case where think time is less than a jiffy, mark the queue wait
3723          * busy if only 1 jiffy is left in the slice.
3724          */
3725         if (cfqq->slice_end - jiffies == 1)
3726                 return true;
3727
3728         return false;
3729 }
3730
3731 static void cfq_completed_request(struct request_queue *q, struct request *rq)
3732 {
3733         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3734         struct cfq_data *cfqd = cfqq->cfqd;
3735         const int sync = rq_is_sync(rq);
3736         unsigned long now;
3737
3738         now = jiffies;
3739         cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d",
3740                      !!(rq->cmd_flags & REQ_NOIDLE));
3741
3742         cfq_update_hw_tag(cfqd);
3743
3744         WARN_ON(!cfqd->rq_in_driver);
3745         WARN_ON(!cfqq->dispatched);
3746         cfqd->rq_in_driver--;
3747         cfqq->dispatched--;
3748         (RQ_CFQG(rq))->dispatched--;
3749         cfqg_stats_update_completion(cfqq->cfqg, rq_start_time_ns(rq),
3750                                      rq_io_start_time_ns(rq), rq->cmd_flags);
3751
3752         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
3753
3754         if (sync) {
3755                 struct cfq_rb_root *st;
3756
3757                 RQ_CIC(rq)->ttime.last_end_request = now;
3758
3759                 if (cfq_cfqq_on_rr(cfqq))
3760                         st = cfqq->service_tree;
3761                 else
3762                         st = st_for(cfqq->cfqg, cfqq_class(cfqq),
3763                                         cfqq_type(cfqq));
3764
3765                 st->ttime.last_end_request = now;
3766                 if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
3767                         cfqd->last_delayed_sync = now;
3768         }
3769
3770 #ifdef CONFIG_CFQ_GROUP_IOSCHED
3771         cfqq->cfqg->ttime.last_end_request = now;
3772 #endif
3773
3774         /*
3775          * If this is the active queue, check if it needs to be expired,
3776          * or if we want to idle in case it has no pending requests.
3777          */
3778         if (cfqd->active_queue == cfqq) {
3779                 const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
3780
3781                 if (cfq_cfqq_slice_new(cfqq)) {
3782                         cfq_set_prio_slice(cfqd, cfqq);
3783                         cfq_clear_cfqq_slice_new(cfqq);
3784                 }
3785
3786                 /*
3787                  * Should we wait for next request to come in before we expire
3788                  * the queue.
3789                  */
3790                 if (cfq_should_wait_busy(cfqd, cfqq)) {
3791                         unsigned long extend_sl = cfqd->cfq_slice_idle;
3792                         if (!cfqd->cfq_slice_idle)
3793                                 extend_sl = cfqd->cfq_group_idle;
3794                         cfqq->slice_end = jiffies + extend_sl;
3795                         cfq_mark_cfqq_wait_busy(cfqq);
3796                         cfq_log_cfqq(cfqd, cfqq, "will busy wait");
3797                 }
3798
3799                 /*
3800                  * Idling is not enabled on:
3801                  * - expired queues
3802                  * - idle-priority queues
3803                  * - async queues
3804                  * - queues with still some requests queued
3805                  * - when there is a close cooperator
3806                  */
3807                 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
3808                         cfq_slice_expired(cfqd, 1);
3809                 else if (sync && cfqq_empty &&
3810                          !cfq_close_cooperator(cfqd, cfqq)) {
3811                         cfq_arm_slice_timer(cfqd);
3812                 }
3813         }
3814
3815         if (!cfqd->rq_in_driver)
3816                 cfq_schedule_dispatch(cfqd);
3817 }
3818
3819 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
3820 {
3821         if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
3822                 cfq_mark_cfqq_must_alloc_slice(cfqq);
3823                 return ELV_MQUEUE_MUST;
3824         }
3825
3826         return ELV_MQUEUE_MAY;
3827 }
3828
3829 static int cfq_may_queue(struct request_queue *q, int rw)
3830 {
3831         struct cfq_data *cfqd = q->elevator->elevator_data;
3832         struct task_struct *tsk = current;
3833         struct cfq_io_cq *cic;
3834         struct cfq_queue *cfqq;
3835
3836         /*
3837          * don't force setup of a queue from here, as a call to may_queue
3838          * does not necessarily imply that a request actually will be queued.
3839          * so just lookup a possibly existing queue, or return 'may queue'
3840          * if that fails
3841          */
3842         cic = cfq_cic_lookup(cfqd, tsk->io_context);
3843         if (!cic)
3844                 return ELV_MQUEUE_MAY;
3845
3846         cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
3847         if (cfqq) {
3848                 cfq_init_prio_data(cfqq, cic);
3849
3850                 return __cfq_may_queue(cfqq);
3851         }
3852
3853         return ELV_MQUEUE_MAY;
3854 }
3855
3856 /*
3857  * queue lock held here
3858  */
3859 static void cfq_put_request(struct request *rq)
3860 {
3861         struct cfq_queue *cfqq = RQ_CFQQ(rq);
3862
3863         if (cfqq) {
3864                 const int rw = rq_data_dir(rq);
3865
3866                 BUG_ON(!cfqq->allocated[rw]);
3867                 cfqq->allocated[rw]--;
3868
3869                 /* Put down rq reference on cfqg */
3870                 cfqg_put(RQ_CFQG(rq));
3871                 rq->elv.priv[0] = NULL;
3872                 rq->elv.priv[1] = NULL;
3873
3874                 cfq_put_queue(cfqq);
3875         }
3876 }
3877
3878 static struct cfq_queue *
3879 cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_cq *cic,
3880                 struct cfq_queue *cfqq)
3881 {
3882         cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
3883         cic_set_cfqq(cic, cfqq->new_cfqq, 1);
3884         cfq_mark_cfqq_coop(cfqq->new_cfqq);
3885         cfq_put_queue(cfqq);
3886         return cic_to_cfqq(cic, 1);
3887 }
3888
3889 /*
3890  * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
3891  * was the last process referring to said cfqq.
3892  */
3893 static struct cfq_queue *
3894 split_cfqq(struct cfq_io_cq *cic, struct cfq_queue *cfqq)
3895 {
3896         if (cfqq_process_refs(cfqq) == 1) {
3897                 cfqq->pid = current->pid;
3898                 cfq_clear_cfqq_coop(cfqq);
3899                 cfq_clear_cfqq_split_coop(cfqq);
3900                 return cfqq;
3901         }
3902
3903         cic_set_cfqq(cic, NULL, 1);
3904
3905         cfq_put_cooperator(cfqq);
3906
3907         cfq_put_queue(cfqq);
3908         return NULL;
3909 }
3910 /*
3911  * Allocate cfq data structures associated with this request.
3912  */
3913 static int
3914 cfq_set_request(struct request_queue *q, struct request *rq, struct bio *bio,
3915                 gfp_t gfp_mask)
3916 {
3917         struct cfq_data *cfqd = q->elevator->elevator_data;
3918         struct cfq_io_cq *cic = icq_to_cic(rq->elv.icq);
3919         const int rw = rq_data_dir(rq);
3920         const bool is_sync = rq_is_sync(rq);
3921         struct cfq_queue *cfqq;
3922
3923         might_sleep_if(gfp_mask & __GFP_WAIT);
3924
3925         spin_lock_irq(q->queue_lock);
3926
3927         check_ioprio_changed(cic, bio);
3928         check_blkcg_changed(cic, bio);
3929 new_queue:
3930         cfqq = cic_to_cfqq(cic, is_sync);
3931         if (!cfqq || cfqq == &cfqd->oom_cfqq) {
3932                 cfqq = cfq_get_queue(cfqd, is_sync, cic, bio, gfp_mask);
3933                 cic_set_cfqq(cic, cfqq, is_sync);
3934         } else {
3935                 /*
3936                  * If the queue was seeky for too long, break it apart.
3937                  */
3938                 if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) {
3939                         cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
3940                         cfqq = split_cfqq(cic, cfqq);
3941                         if (!cfqq)
3942                                 goto new_queue;
3943                 }
3944
3945                 /*
3946                  * Check to see if this queue is scheduled to merge with
3947                  * another, closely cooperating queue.  The merging of
3948                  * queues happens here as it must be done in process context.
3949                  * The reference on new_cfqq was taken in merge_cfqqs.
3950                  */
3951                 if (cfqq->new_cfqq)
3952                         cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
3953         }
3954
3955         cfqq->allocated[rw]++;
3956
3957         cfqq->ref++;
3958         cfqg_get(cfqq->cfqg);
3959         rq->elv.priv[0] = cfqq;
3960         rq->elv.priv[1] = cfqq->cfqg;
3961         spin_unlock_irq(q->queue_lock);
3962         return 0;
3963 }
3964
3965 static void cfq_kick_queue(struct work_struct *work)
3966 {
3967         struct cfq_data *cfqd =
3968                 container_of(work, struct cfq_data, unplug_work);
3969         struct request_queue *q = cfqd->queue;
3970
3971         spin_lock_irq(q->queue_lock);
3972         __blk_run_queue(cfqd->queue);
3973         spin_unlock_irq(q->queue_lock);
3974 }
3975
3976 /*
3977  * Timer running if the active_queue is currently idling inside its time slice
3978  */
3979 static void cfq_idle_slice_timer(unsigned long data)
3980 {
3981         struct cfq_data *cfqd = (struct cfq_data *) data;
3982         struct cfq_queue *cfqq;
3983         unsigned long flags;
3984         int timed_out = 1;
3985
3986         cfq_log(cfqd, "idle timer fired");
3987
3988         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
3989
3990         cfqq = cfqd->active_queue;
3991         if (cfqq) {
3992                 timed_out = 0;
3993
3994                 /*
3995                  * We saw a request before the queue expired, let it through
3996                  */
3997                 if (cfq_cfqq_must_dispatch(cfqq))
3998                         goto out_kick;
3999
4000                 /*
4001                  * expired
4002                  */
4003                 if (cfq_slice_used(cfqq))
4004                         goto expire;
4005
4006                 /*
4007                  * only expire and reinvoke request handler, if there are
4008                  * other queues with pending requests
4009                  */
4010                 if (!cfqd->busy_queues)
4011                         goto out_cont;
4012
4013                 /*
4014                  * not expired and it has a request pending, let it dispatch
4015                  */
4016                 if (!RB_EMPTY_ROOT(&cfqq->sort_list))
4017                         goto out_kick;
4018
4019                 /*
4020                  * Queue depth flag is reset only when the idle didn't succeed
4021                  */
4022                 cfq_clear_cfqq_deep(cfqq);
4023         }
4024 expire:
4025         cfq_slice_expired(cfqd, timed_out);
4026 out_kick:
4027         cfq_schedule_dispatch(cfqd);
4028 out_cont:
4029         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
4030 }
4031
4032 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
4033 {
4034         del_timer_sync(&cfqd->idle_slice_timer);
4035         cancel_work_sync(&cfqd->unplug_work);
4036 }
4037
4038 static void cfq_put_async_queues(struct cfq_data *cfqd)
4039 {
4040         int i;
4041
4042         for (i = 0; i < IOPRIO_BE_NR; i++) {
4043                 if (cfqd->async_cfqq[0][i])
4044                         cfq_put_queue(cfqd->async_cfqq[0][i]);
4045                 if (cfqd->async_cfqq[1][i])
4046                         cfq_put_queue(cfqd->async_cfqq[1][i]);
4047         }
4048
4049         if (cfqd->async_idle_cfqq)
4050                 cfq_put_queue(cfqd->async_idle_cfqq);
4051 }
4052
4053 static void cfq_exit_queue(struct elevator_queue *e)
4054 {
4055         struct cfq_data *cfqd = e->elevator_data;
4056         struct request_queue *q = cfqd->queue;
4057
4058         cfq_shutdown_timer_wq(cfqd);
4059
4060         spin_lock_irq(q->queue_lock);
4061
4062         if (cfqd->active_queue)
4063                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
4064
4065         cfq_put_async_queues(cfqd);
4066
4067         spin_unlock_irq(q->queue_lock);
4068
4069         cfq_shutdown_timer_wq(cfqd);
4070
4071 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4072         blkcg_deactivate_policy(q, &blkcg_policy_cfq);
4073 #else
4074         kfree(cfqd->root_group);
4075 #endif
4076         kfree(cfqd);
4077 }
4078
4079 static int cfq_init_queue(struct request_queue *q)
4080 {
4081         struct cfq_data *cfqd;
4082         struct blkcg_gq *blkg __maybe_unused;
4083         int i, ret;
4084
4085         cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
4086         if (!cfqd)
4087                 return -ENOMEM;
4088
4089         cfqd->queue = q;
4090         q->elevator->elevator_data = cfqd;
4091
4092         /* Init root service tree */
4093         cfqd->grp_service_tree = CFQ_RB_ROOT;
4094
4095         /* Init root group and prefer root group over other groups by default */
4096 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4097         ret = blkcg_activate_policy(q, &blkcg_policy_cfq);
4098         if (ret)
4099                 goto out_free;
4100
4101         cfqd->root_group = blkg_to_cfqg(q->root_blkg);
4102 #else
4103         ret = -ENOMEM;
4104         cfqd->root_group = kzalloc_node(sizeof(*cfqd->root_group),
4105                                         GFP_KERNEL, cfqd->queue->node);
4106         if (!cfqd->root_group)
4107                 goto out_free;
4108
4109         cfq_init_cfqg_base(cfqd->root_group);
4110 #endif
4111         cfqd->root_group->weight = 2 * CFQ_WEIGHT_DEFAULT;
4112         cfqd->root_group->leaf_weight = 2 * CFQ_WEIGHT_DEFAULT;
4113
4114         /*
4115          * Not strictly needed (since RB_ROOT just clears the node and we
4116          * zeroed cfqd on alloc), but better be safe in case someone decides
4117          * to add magic to the rb code
4118          */
4119         for (i = 0; i < CFQ_PRIO_LISTS; i++)
4120                 cfqd->prio_trees[i] = RB_ROOT;
4121
4122         /*
4123          * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
4124          * Grab a permanent reference to it, so that the normal code flow
4125          * will not attempt to free it.  oom_cfqq is linked to root_group
4126          * but shouldn't hold a reference as it'll never be unlinked.  Lose
4127          * the reference from linking right away.
4128          */
4129         cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
4130         cfqd->oom_cfqq.ref++;
4131
4132         spin_lock_irq(q->queue_lock);
4133         cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, cfqd->root_group);
4134         cfqg_put(cfqd->root_group);
4135         spin_unlock_irq(q->queue_lock);
4136
4137         init_timer(&cfqd->idle_slice_timer);
4138         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
4139         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
4140
4141         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
4142
4143         cfqd->cfq_quantum = cfq_quantum;
4144         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
4145         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
4146         cfqd->cfq_back_max = cfq_back_max;
4147         cfqd->cfq_back_penalty = cfq_back_penalty;
4148         cfqd->cfq_slice[0] = cfq_slice_async;
4149         cfqd->cfq_slice[1] = cfq_slice_sync;
4150         cfqd->cfq_target_latency = cfq_target_latency;
4151         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
4152         cfqd->cfq_slice_idle = cfq_slice_idle;
4153         cfqd->cfq_group_idle = cfq_group_idle;
4154         cfqd->cfq_latency = 1;
4155         cfqd->hw_tag = -1;
4156         /*
4157          * we optimistically start assuming sync ops weren't delayed in last
4158          * second, in order to have larger depth for async operations.
4159          */
4160         cfqd->last_delayed_sync = jiffies - HZ;
4161         return 0;
4162
4163 out_free:
4164         kfree(cfqd);
4165         return ret;
4166 }
4167
4168 /*
4169  * sysfs parts below -->
4170  */
4171 static ssize_t
4172 cfq_var_show(unsigned int var, char *page)
4173 {
4174         return sprintf(page, "%d\n", var);
4175 }
4176
4177 static ssize_t
4178 cfq_var_store(unsigned int *var, const char *page, size_t count)
4179 {
4180         char *p = (char *) page;
4181
4182         *var = simple_strtoul(p, &p, 10);
4183         return count;
4184 }
4185
4186 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
4187 static ssize_t __FUNC(struct elevator_queue *e, char *page)             \
4188 {                                                                       \
4189         struct cfq_data *cfqd = e->elevator_data;                       \
4190         unsigned int __data = __VAR;                                    \
4191         if (__CONV)                                                     \
4192                 __data = jiffies_to_msecs(__data);                      \
4193         return cfq_var_show(__data, (page));                            \
4194 }
4195 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
4196 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
4197 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
4198 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
4199 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
4200 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
4201 SHOW_FUNCTION(cfq_group_idle_show, cfqd->cfq_group_idle, 1);
4202 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
4203 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
4204 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
4205 SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
4206 SHOW_FUNCTION(cfq_target_latency_show, cfqd->cfq_target_latency, 1);
4207 #undef SHOW_FUNCTION
4208
4209 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
4210 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
4211 {                                                                       \
4212         struct cfq_data *cfqd = e->elevator_data;                       \
4213         unsigned int __data;                                            \
4214         int ret = cfq_var_store(&__data, (page), count);                \
4215         if (__data < (MIN))                                             \
4216                 __data = (MIN);                                         \
4217         else if (__data > (MAX))                                        \
4218                 __data = (MAX);                                         \
4219         if (__CONV)                                                     \
4220                 *(__PTR) = msecs_to_jiffies(__data);                    \
4221         else                                                            \
4222                 *(__PTR) = __data;                                      \
4223         return ret;                                                     \
4224 }
4225 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
4226 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
4227                 UINT_MAX, 1);
4228 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
4229                 UINT_MAX, 1);
4230 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
4231 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
4232                 UINT_MAX, 0);
4233 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
4234 STORE_FUNCTION(cfq_group_idle_store, &cfqd->cfq_group_idle, 0, UINT_MAX, 1);
4235 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
4236 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
4237 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
4238                 UINT_MAX, 0);
4239 STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
4240 STORE_FUNCTION(cfq_target_latency_store, &cfqd->cfq_target_latency, 1, UINT_MAX, 1);
4241 #undef STORE_FUNCTION
4242
4243 #define CFQ_ATTR(name) \
4244         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
4245
4246 static struct elv_fs_entry cfq_attrs[] = {
4247         CFQ_ATTR(quantum),
4248         CFQ_ATTR(fifo_expire_sync),
4249         CFQ_ATTR(fifo_expire_async),
4250         CFQ_ATTR(back_seek_max),
4251         CFQ_ATTR(back_seek_penalty),
4252         CFQ_ATTR(slice_sync),
4253         CFQ_ATTR(slice_async),
4254         CFQ_ATTR(slice_async_rq),
4255         CFQ_ATTR(slice_idle),
4256         CFQ_ATTR(group_idle),
4257         CFQ_ATTR(low_latency),
4258         CFQ_ATTR(target_latency),
4259         __ATTR_NULL
4260 };
4261
4262 static struct elevator_type iosched_cfq = {
4263         .ops = {
4264                 .elevator_merge_fn =            cfq_merge,
4265                 .elevator_merged_fn =           cfq_merged_request,
4266                 .elevator_merge_req_fn =        cfq_merged_requests,
4267                 .elevator_allow_merge_fn =      cfq_allow_merge,
4268                 .elevator_bio_merged_fn =       cfq_bio_merged,
4269                 .elevator_dispatch_fn =         cfq_dispatch_requests,
4270                 .elevator_add_req_fn =          cfq_insert_request,
4271                 .elevator_activate_req_fn =     cfq_activate_request,
4272                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
4273                 .elevator_completed_req_fn =    cfq_completed_request,
4274                 .elevator_former_req_fn =       elv_rb_former_request,
4275                 .elevator_latter_req_fn =       elv_rb_latter_request,
4276                 .elevator_init_icq_fn =         cfq_init_icq,
4277                 .elevator_exit_icq_fn =         cfq_exit_icq,
4278                 .elevator_set_req_fn =          cfq_set_request,
4279                 .elevator_put_req_fn =          cfq_put_request,
4280                 .elevator_may_queue_fn =        cfq_may_queue,
4281                 .elevator_init_fn =             cfq_init_queue,
4282                 .elevator_exit_fn =             cfq_exit_queue,
4283         },
4284         .icq_size       =       sizeof(struct cfq_io_cq),
4285         .icq_align      =       __alignof__(struct cfq_io_cq),
4286         .elevator_attrs =       cfq_attrs,
4287         .elevator_name  =       "cfq",
4288         .elevator_owner =       THIS_MODULE,
4289 };
4290
4291 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4292 static struct blkcg_policy blkcg_policy_cfq = {
4293         .pd_size                = sizeof(struct cfq_group),
4294         .cftypes                = cfq_blkcg_files,
4295
4296         .pd_init_fn             = cfq_pd_init,
4297         .pd_reset_stats_fn      = cfq_pd_reset_stats,
4298 };
4299 #endif
4300
4301 static int __init cfq_init(void)
4302 {
4303         int ret;
4304
4305         /*
4306          * could be 0 on HZ < 1000 setups
4307          */
4308         if (!cfq_slice_async)
4309                 cfq_slice_async = 1;
4310         if (!cfq_slice_idle)
4311                 cfq_slice_idle = 1;
4312
4313 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4314         if (!cfq_group_idle)
4315                 cfq_group_idle = 1;
4316
4317         ret = blkcg_policy_register(&blkcg_policy_cfq);
4318         if (ret)
4319                 return ret;
4320 #else
4321         cfq_group_idle = 0;
4322 #endif
4323
4324         ret = -ENOMEM;
4325         cfq_pool = KMEM_CACHE(cfq_queue, 0);
4326         if (!cfq_pool)
4327                 goto err_pol_unreg;
4328
4329         ret = elv_register(&iosched_cfq);
4330         if (ret)
4331                 goto err_free_pool;
4332
4333         return 0;
4334
4335 err_free_pool:
4336         kmem_cache_destroy(cfq_pool);
4337 err_pol_unreg:
4338 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4339         blkcg_policy_unregister(&blkcg_policy_cfq);
4340 #endif
4341         return ret;
4342 }
4343
4344 static void __exit cfq_exit(void)
4345 {
4346 #ifdef CONFIG_CFQ_GROUP_IOSCHED
4347         blkcg_policy_unregister(&blkcg_policy_cfq);
4348 #endif
4349         elv_unregister(&iosched_cfq);
4350         kmem_cache_destroy(cfq_pool);
4351 }
4352
4353 module_init(cfq_init);
4354 module_exit(cfq_exit);
4355
4356 MODULE_AUTHOR("Jens Axboe");
4357 MODULE_LICENSE("GPL");
4358 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");