linux/block/cfq-iosched.c
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   1/*
   2 *  CFQ, or complete fairness queueing, disk scheduler.
   3 *
   4 *  Based on ideas from a previously unfinished io
   5 *  scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
   6 *
   7 *  Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
   8 */
   9#include <linux/module.h>
  10#include <linux/blkdev.h>
  11#include <linux/elevator.h>
  12#include <linux/rbtree.h>
  13#include <linux/ioprio.h>
  14#include <linux/blktrace_api.h>
  15
  16/*
  17 * tunables
  18 */
  19/* max queue in one round of service */
  20static const int cfq_quantum = 4;
  21static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
  22/* maximum backwards seek, in KiB */
  23static const int cfq_back_max = 16 * 1024;
  24/* penalty of a backwards seek */
  25static const int cfq_back_penalty = 2;
  26static const int cfq_slice_sync = HZ / 10;
  27static int cfq_slice_async = HZ / 25;
  28static const int cfq_slice_async_rq = 2;
  29static int cfq_slice_idle = HZ / 125;
  30
  31/*
  32 * offset from end of service tree
  33 */
  34#define CFQ_IDLE_DELAY          (HZ / 5)
  35
  36/*
  37 * below this threshold, we consider thinktime immediate
  38 */
  39#define CFQ_MIN_TT              (2)
  40
  41#define CFQ_SLICE_SCALE         (5)
  42#define CFQ_HW_QUEUE_MIN        (5)
  43
  44#define RQ_CIC(rq)              \
  45        ((struct cfq_io_context *) (rq)->elevator_private)
  46#define RQ_CFQQ(rq)             (struct cfq_queue *) ((rq)->elevator_private2)
  47
  48static struct kmem_cache *cfq_pool;
  49static struct kmem_cache *cfq_ioc_pool;
  50
  51static DEFINE_PER_CPU(unsigned long, ioc_count);
  52static struct completion *ioc_gone;
  53static DEFINE_SPINLOCK(ioc_gone_lock);
  54
  55#define CFQ_PRIO_LISTS          IOPRIO_BE_NR
  56#define cfq_class_idle(cfqq)    ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
  57#define cfq_class_rt(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
  58
  59#define ASYNC                   (0)
  60#define SYNC                    (1)
  61
  62#define sample_valid(samples)   ((samples) > 80)
  63
  64/*
  65 * Most of our rbtree usage is for sorting with min extraction, so
  66 * if we cache the leftmost node we don't have to walk down the tree
  67 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
  68 * move this into the elevator for the rq sorting as well.
  69 */
  70struct cfq_rb_root {
  71        struct rb_root rb;
  72        struct rb_node *left;
  73};
  74#define CFQ_RB_ROOT     (struct cfq_rb_root) { RB_ROOT, NULL, }
  75
  76/*
  77 * Per block device queue structure
  78 */
  79struct cfq_data {
  80        struct request_queue *queue;
  81
  82        /*
  83         * rr list of queues with requests and the count of them
  84         */
  85        struct cfq_rb_root service_tree;
  86        unsigned int busy_queues;
  87
  88        int rq_in_driver;
  89        int sync_flight;
  90
  91        /*
  92         * queue-depth detection
  93         */
  94        int rq_queued;
  95        int hw_tag;
  96        int hw_tag_samples;
  97        int rq_in_driver_peak;
  98
  99        /*
 100         * idle window management
 101         */
 102        struct timer_list idle_slice_timer;
 103        struct work_struct unplug_work;
 104
 105        struct cfq_queue *active_queue;
 106        struct cfq_io_context *active_cic;
 107
 108        /*
 109         * async queue for each priority case
 110         */
 111        struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
 112        struct cfq_queue *async_idle_cfqq;
 113
 114        sector_t last_position;
 115        unsigned long last_end_request;
 116
 117        /*
 118         * tunables, see top of file
 119         */
 120        unsigned int cfq_quantum;
 121        unsigned int cfq_fifo_expire[2];
 122        unsigned int cfq_back_penalty;
 123        unsigned int cfq_back_max;
 124        unsigned int cfq_slice[2];
 125        unsigned int cfq_slice_async_rq;
 126        unsigned int cfq_slice_idle;
 127
 128        struct list_head cic_list;
 129};
 130
 131/*
 132 * Per process-grouping structure
 133 */
 134struct cfq_queue {
 135        /* reference count */
 136        atomic_t ref;
 137        /* various state flags, see below */
 138        unsigned int flags;
 139        /* parent cfq_data */
 140        struct cfq_data *cfqd;
 141        /* service_tree member */
 142        struct rb_node rb_node;
 143        /* service_tree key */
 144        unsigned long rb_key;
 145        /* sorted list of pending requests */
 146        struct rb_root sort_list;
 147        /* if fifo isn't expired, next request to serve */
 148        struct request *next_rq;
 149        /* requests queued in sort_list */
 150        int queued[2];
 151        /* currently allocated requests */
 152        int allocated[2];
 153        /* fifo list of requests in sort_list */
 154        struct list_head fifo;
 155
 156        unsigned long slice_end;
 157        long slice_resid;
 158
 159        /* pending metadata requests */
 160        int meta_pending;
 161        /* number of requests that are on the dispatch list or inside driver */
 162        int dispatched;
 163
 164        /* io prio of this group */
 165        unsigned short ioprio, org_ioprio;
 166        unsigned short ioprio_class, org_ioprio_class;
 167
 168        pid_t pid;
 169};
 170
 171enum cfqq_state_flags {
 172        CFQ_CFQQ_FLAG_on_rr = 0,        /* on round-robin busy list */
 173        CFQ_CFQQ_FLAG_wait_request,     /* waiting for a request */
 174        CFQ_CFQQ_FLAG_must_alloc,       /* must be allowed rq alloc */
 175        CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
 176        CFQ_CFQQ_FLAG_must_dispatch,    /* must dispatch, even if expired */
 177        CFQ_CFQQ_FLAG_fifo_expire,      /* FIFO checked in this slice */
 178        CFQ_CFQQ_FLAG_idle_window,      /* slice idling enabled */
 179        CFQ_CFQQ_FLAG_prio_changed,     /* task priority has changed */
 180        CFQ_CFQQ_FLAG_queue_new,        /* queue never been serviced */
 181        CFQ_CFQQ_FLAG_slice_new,        /* no requests dispatched in slice */
 182        CFQ_CFQQ_FLAG_sync,             /* synchronous queue */
 183};
 184
 185#define CFQ_CFQQ_FNS(name)                                              \
 186static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
 187{                                                                       \
 188        (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name);                   \
 189}                                                                       \
 190static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
 191{                                                                       \
 192        (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                  \
 193}                                                                       \
 194static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
 195{                                                                       \
 196        return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;      \
 197}
 198
 199CFQ_CFQQ_FNS(on_rr);
 200CFQ_CFQQ_FNS(wait_request);
 201CFQ_CFQQ_FNS(must_alloc);
 202CFQ_CFQQ_FNS(must_alloc_slice);
 203CFQ_CFQQ_FNS(must_dispatch);
 204CFQ_CFQQ_FNS(fifo_expire);
 205CFQ_CFQQ_FNS(idle_window);
 206CFQ_CFQQ_FNS(prio_changed);
 207CFQ_CFQQ_FNS(queue_new);
 208CFQ_CFQQ_FNS(slice_new);
 209CFQ_CFQQ_FNS(sync);
 210#undef CFQ_CFQQ_FNS
 211
 212#define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
 213        blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
 214#define cfq_log(cfqd, fmt, args...)     \
 215        blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
 216
 217static void cfq_dispatch_insert(struct request_queue *, struct request *);
 218static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
 219                                       struct io_context *, gfp_t);
 220static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
 221                                                struct io_context *);
 222
 223static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
 224                                            int is_sync)
 225{
 226        return cic->cfqq[!!is_sync];
 227}
 228
 229static inline void cic_set_cfqq(struct cfq_io_context *cic,
 230                                struct cfq_queue *cfqq, int is_sync)
 231{
 232        cic->cfqq[!!is_sync] = cfqq;
 233}
 234
 235/*
 236 * We regard a request as SYNC, if it's either a read or has the SYNC bit
 237 * set (in which case it could also be direct WRITE).
 238 */
 239static inline int cfq_bio_sync(struct bio *bio)
 240{
 241        if (bio_data_dir(bio) == READ || bio_sync(bio))
 242                return 1;
 243
 244        return 0;
 245}
 246
 247/*
 248 * scheduler run of queue, if there are requests pending and no one in the
 249 * driver that will restart queueing
 250 */
 251static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
 252{
 253        if (cfqd->busy_queues) {
 254                cfq_log(cfqd, "schedule dispatch");
 255                kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
 256        }
 257}
 258
 259static int cfq_queue_empty(struct request_queue *q)
 260{
 261        struct cfq_data *cfqd = q->elevator->elevator_data;
 262
 263        return !cfqd->busy_queues;
 264}
 265
 266/*
 267 * Scale schedule slice based on io priority. Use the sync time slice only
 268 * if a queue is marked sync and has sync io queued. A sync queue with async
 269 * io only, should not get full sync slice length.
 270 */
 271static inline int cfq_prio_slice(struct cfq_data *cfqd, int sync,
 272                                 unsigned short prio)
 273{
 274        const int base_slice = cfqd->cfq_slice[sync];
 275
 276        WARN_ON(prio >= IOPRIO_BE_NR);
 277
 278        return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
 279}
 280
 281static inline int
 282cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 283{
 284        return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
 285}
 286
 287static inline void
 288cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 289{
 290        cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
 291        cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
 292}
 293
 294/*
 295 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
 296 * isn't valid until the first request from the dispatch is activated
 297 * and the slice time set.
 298 */
 299static inline int cfq_slice_used(struct cfq_queue *cfqq)
 300{
 301        if (cfq_cfqq_slice_new(cfqq))
 302                return 0;
 303        if (time_before(jiffies, cfqq->slice_end))
 304                return 0;
 305
 306        return 1;
 307}
 308
 309/*
 310 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
 311 * We choose the request that is closest to the head right now. Distance
 312 * behind the head is penalized and only allowed to a certain extent.
 313 */
 314static struct request *
 315cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2)
 316{
 317        sector_t last, s1, s2, d1 = 0, d2 = 0;
 318        unsigned long back_max;
 319#define CFQ_RQ1_WRAP    0x01 /* request 1 wraps */
 320#define CFQ_RQ2_WRAP    0x02 /* request 2 wraps */
 321        unsigned wrap = 0; /* bit mask: requests behind the disk head? */
 322
 323        if (rq1 == NULL || rq1 == rq2)
 324                return rq2;
 325        if (rq2 == NULL)
 326                return rq1;
 327
 328        if (rq_is_sync(rq1) && !rq_is_sync(rq2))
 329                return rq1;
 330        else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
 331                return rq2;
 332        if (rq_is_meta(rq1) && !rq_is_meta(rq2))
 333                return rq1;
 334        else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
 335                return rq2;
 336
 337        s1 = rq1->sector;
 338        s2 = rq2->sector;
 339
 340        last = cfqd->last_position;
 341
 342        /*
 343         * by definition, 1KiB is 2 sectors
 344         */
 345        back_max = cfqd->cfq_back_max * 2;
 346
 347        /*
 348         * Strict one way elevator _except_ in the case where we allow
 349         * short backward seeks which are biased as twice the cost of a
 350         * similar forward seek.
 351         */
 352        if (s1 >= last)
 353                d1 = s1 - last;
 354        else if (s1 + back_max >= last)
 355                d1 = (last - s1) * cfqd->cfq_back_penalty;
 356        else
 357                wrap |= CFQ_RQ1_WRAP;
 358
 359        if (s2 >= last)
 360                d2 = s2 - last;
 361        else if (s2 + back_max >= last)
 362                d2 = (last - s2) * cfqd->cfq_back_penalty;
 363        else
 364                wrap |= CFQ_RQ2_WRAP;
 365
 366        /* Found required data */
 367
 368        /*
 369         * By doing switch() on the bit mask "wrap" we avoid having to
 370         * check two variables for all permutations: --> faster!
 371         */
 372        switch (wrap) {
 373        case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
 374                if (d1 < d2)
 375                        return rq1;
 376                else if (d2 < d1)
 377                        return rq2;
 378                else {
 379                        if (s1 >= s2)
 380                                return rq1;
 381                        else
 382                                return rq2;
 383                }
 384
 385        case CFQ_RQ2_WRAP:
 386                return rq1;
 387        case CFQ_RQ1_WRAP:
 388                return rq2;
 389        case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
 390        default:
 391                /*
 392                 * Since both rqs are wrapped,
 393                 * start with the one that's further behind head
 394                 * (--> only *one* back seek required),
 395                 * since back seek takes more time than forward.
 396                 */
 397                if (s1 <= s2)
 398                        return rq1;
 399                else
 400                        return rq2;
 401        }
 402}
 403
 404/*
 405 * The below is leftmost cache rbtree addon
 406 */
 407static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
 408{
 409        if (!root->left)
 410                root->left = rb_first(&root->rb);
 411
 412        if (root->left)
 413                return rb_entry(root->left, struct cfq_queue, rb_node);
 414
 415        return NULL;
 416}
 417
 418static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
 419{
 420        if (root->left == n)
 421                root->left = NULL;
 422
 423        rb_erase(n, &root->rb);
 424        RB_CLEAR_NODE(n);
 425}
 426
 427/*
 428 * would be nice to take fifo expire time into account as well
 429 */
 430static struct request *
 431cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 432                  struct request *last)
 433{
 434        struct rb_node *rbnext = rb_next(&last->rb_node);
 435        struct rb_node *rbprev = rb_prev(&last->rb_node);
 436        struct request *next = NULL, *prev = NULL;
 437
 438        BUG_ON(RB_EMPTY_NODE(&last->rb_node));
 439
 440        if (rbprev)
 441                prev = rb_entry_rq(rbprev);
 442
 443        if (rbnext)
 444                next = rb_entry_rq(rbnext);
 445        else {
 446                rbnext = rb_first(&cfqq->sort_list);
 447                if (rbnext && rbnext != &last->rb_node)
 448                        next = rb_entry_rq(rbnext);
 449        }
 450
 451        return cfq_choose_req(cfqd, next, prev);
 452}
 453
 454static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
 455                                      struct cfq_queue *cfqq)
 456{
 457        /*
 458         * just an approximation, should be ok.
 459         */
 460        return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) -
 461                       cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
 462}
 463
 464/*
 465 * The cfqd->service_tree holds all pending cfq_queue's that have
 466 * requests waiting to be processed. It is sorted in the order that
 467 * we will service the queues.
 468 */
 469static void cfq_service_tree_add(struct cfq_data *cfqd,
 470                                    struct cfq_queue *cfqq, int add_front)
 471{
 472        struct rb_node **p, *parent;
 473        struct cfq_queue *__cfqq;
 474        unsigned long rb_key;
 475        int left;
 476
 477        if (cfq_class_idle(cfqq)) {
 478                rb_key = CFQ_IDLE_DELAY;
 479                parent = rb_last(&cfqd->service_tree.rb);
 480                if (parent && parent != &cfqq->rb_node) {
 481                        __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
 482                        rb_key += __cfqq->rb_key;
 483                } else
 484                        rb_key += jiffies;
 485        } else if (!add_front) {
 486                rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
 487                rb_key += cfqq->slice_resid;
 488                cfqq->slice_resid = 0;
 489        } else
 490                rb_key = 0;
 491
 492        if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
 493                /*
 494                 * same position, nothing more to do
 495                 */
 496                if (rb_key == cfqq->rb_key)
 497                        return;
 498
 499                cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
 500        }
 501
 502        left = 1;
 503        parent = NULL;
 504        p = &cfqd->service_tree.rb.rb_node;
 505        while (*p) {
 506                struct rb_node **n;
 507
 508                parent = *p;
 509                __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
 510
 511                /*
 512                 * sort RT queues first, we always want to give
 513                 * preference to them. IDLE queues goes to the back.
 514                 * after that, sort on the next service time.
 515                 */
 516                if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq))
 517                        n = &(*p)->rb_left;
 518                else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq))
 519                        n = &(*p)->rb_right;
 520                else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq))
 521                        n = &(*p)->rb_left;
 522                else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
 523                        n = &(*p)->rb_right;
 524                else if (rb_key < __cfqq->rb_key)
 525                        n = &(*p)->rb_left;
 526                else
 527                        n = &(*p)->rb_right;
 528
 529                if (n == &(*p)->rb_right)
 530                        left = 0;
 531
 532                p = n;
 533        }
 534
 535        if (left)
 536                cfqd->service_tree.left = &cfqq->rb_node;
 537
 538        cfqq->rb_key = rb_key;
 539        rb_link_node(&cfqq->rb_node, parent, p);
 540        rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb);
 541}
 542
 543/*
 544 * Update cfqq's position in the service tree.
 545 */
 546static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 547{
 548        /*
 549         * Resorting requires the cfqq to be on the RR list already.
 550         */
 551        if (cfq_cfqq_on_rr(cfqq))
 552                cfq_service_tree_add(cfqd, cfqq, 0);
 553}
 554
 555/*
 556 * add to busy list of queues for service, trying to be fair in ordering
 557 * the pending list according to last request service
 558 */
 559static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 560{
 561        cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
 562        BUG_ON(cfq_cfqq_on_rr(cfqq));
 563        cfq_mark_cfqq_on_rr(cfqq);
 564        cfqd->busy_queues++;
 565
 566        cfq_resort_rr_list(cfqd, cfqq);
 567}
 568
 569/*
 570 * Called when the cfqq no longer has requests pending, remove it from
 571 * the service tree.
 572 */
 573static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 574{
 575        cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
 576        BUG_ON(!cfq_cfqq_on_rr(cfqq));
 577        cfq_clear_cfqq_on_rr(cfqq);
 578
 579        if (!RB_EMPTY_NODE(&cfqq->rb_node))
 580                cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
 581
 582        BUG_ON(!cfqd->busy_queues);
 583        cfqd->busy_queues--;
 584}
 585
 586/*
 587 * rb tree support functions
 588 */
 589static void cfq_del_rq_rb(struct request *rq)
 590{
 591        struct cfq_queue *cfqq = RQ_CFQQ(rq);
 592        struct cfq_data *cfqd = cfqq->cfqd;
 593        const int sync = rq_is_sync(rq);
 594
 595        BUG_ON(!cfqq->queued[sync]);
 596        cfqq->queued[sync]--;
 597
 598        elv_rb_del(&cfqq->sort_list, rq);
 599
 600        if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
 601                cfq_del_cfqq_rr(cfqd, cfqq);
 602}
 603
 604static void cfq_add_rq_rb(struct request *rq)
 605{
 606        struct cfq_queue *cfqq = RQ_CFQQ(rq);
 607        struct cfq_data *cfqd = cfqq->cfqd;
 608        struct request *__alias;
 609
 610        cfqq->queued[rq_is_sync(rq)]++;
 611
 612        /*
 613         * looks a little odd, but the first insert might return an alias.
 614         * if that happens, put the alias on the dispatch list
 615         */
 616        while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
 617                cfq_dispatch_insert(cfqd->queue, __alias);
 618
 619        if (!cfq_cfqq_on_rr(cfqq))
 620                cfq_add_cfqq_rr(cfqd, cfqq);
 621
 622        /*
 623         * check if this request is a better next-serve candidate
 624         */
 625        cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq);
 626        BUG_ON(!cfqq->next_rq);
 627}
 628
 629static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
 630{
 631        elv_rb_del(&cfqq->sort_list, rq);
 632        cfqq->queued[rq_is_sync(rq)]--;
 633        cfq_add_rq_rb(rq);
 634}
 635
 636static struct request *
 637cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
 638{
 639        struct task_struct *tsk = current;
 640        struct cfq_io_context *cic;
 641        struct cfq_queue *cfqq;
 642
 643        cic = cfq_cic_lookup(cfqd, tsk->io_context);
 644        if (!cic)
 645                return NULL;
 646
 647        cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
 648        if (cfqq) {
 649                sector_t sector = bio->bi_sector + bio_sectors(bio);
 650
 651                return elv_rb_find(&cfqq->sort_list, sector);
 652        }
 653
 654        return NULL;
 655}
 656
 657static void cfq_activate_request(struct request_queue *q, struct request *rq)
 658{
 659        struct cfq_data *cfqd = q->elevator->elevator_data;
 660
 661        cfqd->rq_in_driver++;
 662        cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
 663                                                cfqd->rq_in_driver);
 664
 665        cfqd->last_position = rq->hard_sector + rq->hard_nr_sectors;
 666}
 667
 668static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
 669{
 670        struct cfq_data *cfqd = q->elevator->elevator_data;
 671
 672        WARN_ON(!cfqd->rq_in_driver);
 673        cfqd->rq_in_driver--;
 674        cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
 675                                                cfqd->rq_in_driver);
 676}
 677
 678static void cfq_remove_request(struct request *rq)
 679{
 680        struct cfq_queue *cfqq = RQ_CFQQ(rq);
 681
 682        if (cfqq->next_rq == rq)
 683                cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
 684
 685        list_del_init(&rq->queuelist);
 686        cfq_del_rq_rb(rq);
 687
 688        cfqq->cfqd->rq_queued--;
 689        if (rq_is_meta(rq)) {
 690                WARN_ON(!cfqq->meta_pending);
 691                cfqq->meta_pending--;
 692        }
 693}
 694
 695static int cfq_merge(struct request_queue *q, struct request **req,
 696                     struct bio *bio)
 697{
 698        struct cfq_data *cfqd = q->elevator->elevator_data;
 699        struct request *__rq;
 700
 701        __rq = cfq_find_rq_fmerge(cfqd, bio);
 702        if (__rq && elv_rq_merge_ok(__rq, bio)) {
 703                *req = __rq;
 704                return ELEVATOR_FRONT_MERGE;
 705        }
 706
 707        return ELEVATOR_NO_MERGE;
 708}
 709
 710static void cfq_merged_request(struct request_queue *q, struct request *req,
 711                               int type)
 712{
 713        if (type == ELEVATOR_FRONT_MERGE) {
 714                struct cfq_queue *cfqq = RQ_CFQQ(req);
 715
 716                cfq_reposition_rq_rb(cfqq, req);
 717        }
 718}
 719
 720static void
 721cfq_merged_requests(struct request_queue *q, struct request *rq,
 722                    struct request *next)
 723{
 724        /*
 725         * reposition in fifo if next is older than rq
 726         */
 727        if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
 728            time_before(next->start_time, rq->start_time))
 729                list_move(&rq->queuelist, &next->queuelist);
 730
 731        cfq_remove_request(next);
 732}
 733
 734static int cfq_allow_merge(struct request_queue *q, struct request *rq,
 735                           struct bio *bio)
 736{
 737        struct cfq_data *cfqd = q->elevator->elevator_data;
 738        struct cfq_io_context *cic;
 739        struct cfq_queue *cfqq;
 740
 741        /*
 742         * Disallow merge of a sync bio into an async request.
 743         */
 744        if (cfq_bio_sync(bio) && !rq_is_sync(rq))
 745                return 0;
 746
 747        /*
 748         * Lookup the cfqq that this bio will be queued with. Allow
 749         * merge only if rq is queued there.
 750         */
 751        cic = cfq_cic_lookup(cfqd, current->io_context);
 752        if (!cic)
 753                return 0;
 754
 755        cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
 756        if (cfqq == RQ_CFQQ(rq))
 757                return 1;
 758
 759        return 0;
 760}
 761
 762static void __cfq_set_active_queue(struct cfq_data *cfqd,
 763                                   struct cfq_queue *cfqq)
 764{
 765        if (cfqq) {
 766                cfq_log_cfqq(cfqd, cfqq, "set_active");
 767                cfqq->slice_end = 0;
 768                cfq_clear_cfqq_must_alloc_slice(cfqq);
 769                cfq_clear_cfqq_fifo_expire(cfqq);
 770                cfq_mark_cfqq_slice_new(cfqq);
 771                cfq_clear_cfqq_queue_new(cfqq);
 772        }
 773
 774        cfqd->active_queue = cfqq;
 775}
 776
 777/*
 778 * current cfqq expired its slice (or was too idle), select new one
 779 */
 780static void
 781__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 782                    int timed_out)
 783{
 784        cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
 785
 786        if (cfq_cfqq_wait_request(cfqq))
 787                del_timer(&cfqd->idle_slice_timer);
 788
 789        cfq_clear_cfqq_must_dispatch(cfqq);
 790        cfq_clear_cfqq_wait_request(cfqq);
 791
 792        /*
 793         * store what was left of this slice, if the queue idled/timed out
 794         */
 795        if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
 796                cfqq->slice_resid = cfqq->slice_end - jiffies;
 797                cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
 798        }
 799
 800        cfq_resort_rr_list(cfqd, cfqq);
 801
 802        if (cfqq == cfqd->active_queue)
 803                cfqd->active_queue = NULL;
 804
 805        if (cfqd->active_cic) {
 806                put_io_context(cfqd->active_cic->ioc);
 807                cfqd->active_cic = NULL;
 808        }
 809}
 810
 811static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out)
 812{
 813        struct cfq_queue *cfqq = cfqd->active_queue;
 814
 815        if (cfqq)
 816                __cfq_slice_expired(cfqd, cfqq, timed_out);
 817}
 818
 819/*
 820 * Get next queue for service. Unless we have a queue preemption,
 821 * we'll simply select the first cfqq in the service tree.
 822 */
 823static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
 824{
 825        if (RB_EMPTY_ROOT(&cfqd->service_tree.rb))
 826                return NULL;
 827
 828        return cfq_rb_first(&cfqd->service_tree);
 829}
 830
 831/*
 832 * Get and set a new active queue for service.
 833 */
 834static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
 835{
 836        struct cfq_queue *cfqq;
 837
 838        cfqq = cfq_get_next_queue(cfqd);
 839        __cfq_set_active_queue(cfqd, cfqq);
 840        return cfqq;
 841}
 842
 843static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
 844                                          struct request *rq)
 845{
 846        if (rq->sector >= cfqd->last_position)
 847                return rq->sector - cfqd->last_position;
 848        else
 849                return cfqd->last_position - rq->sector;
 850}
 851
 852static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq)
 853{
 854        struct cfq_io_context *cic = cfqd->active_cic;
 855
 856        if (!sample_valid(cic->seek_samples))
 857                return 0;
 858
 859        return cfq_dist_from_last(cfqd, rq) <= cic->seek_mean;
 860}
 861
 862static int cfq_close_cooperator(struct cfq_data *cfq_data,
 863                                struct cfq_queue *cfqq)
 864{
 865        /*
 866         * We should notice if some of the queues are cooperating, eg
 867         * working closely on the same area of the disk. In that case,
 868         * we can group them together and don't waste time idling.
 869         */
 870        return 0;
 871}
 872
 873#define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024))
 874
 875static void cfq_arm_slice_timer(struct cfq_data *cfqd)
 876{
 877        struct cfq_queue *cfqq = cfqd->active_queue;
 878        struct cfq_io_context *cic;
 879        unsigned long sl;
 880
 881        /*
 882         * SSD device without seek penalty, disable idling. But only do so
 883         * for devices that support queuing, otherwise we still have a problem
 884         * with sync vs async workloads.
 885         */
 886        if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
 887                return;
 888
 889        WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
 890        WARN_ON(cfq_cfqq_slice_new(cfqq));
 891
 892        /*
 893         * idle is disabled, either manually or by past process history
 894         */
 895        if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq))
 896                return;
 897
 898        /*
 899         * still requests with the driver, don't idle
 900         */
 901        if (cfqd->rq_in_driver)
 902                return;
 903
 904        /*
 905         * task has exited, don't wait
 906         */
 907        cic = cfqd->active_cic;
 908        if (!cic || !atomic_read(&cic->ioc->nr_tasks))
 909                return;
 910
 911        /*
 912         * See if this prio level has a good candidate
 913         */
 914        if (cfq_close_cooperator(cfqd, cfqq) &&
 915            (sample_valid(cic->ttime_samples) && cic->ttime_mean > 2))
 916                return;
 917
 918        cfq_mark_cfqq_must_dispatch(cfqq);
 919        cfq_mark_cfqq_wait_request(cfqq);
 920
 921        /*
 922         * we don't want to idle for seeks, but we do want to allow
 923         * fair distribution of slice time for a process doing back-to-back
 924         * seeks. so allow a little bit of time for him to submit a new rq
 925         */
 926        sl = cfqd->cfq_slice_idle;
 927        if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
 928                sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT));
 929
 930        mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
 931        cfq_log(cfqd, "arm_idle: %lu", sl);
 932}
 933
 934/*
 935 * Move request from internal lists to the request queue dispatch list.
 936 */
 937static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
 938{
 939        struct cfq_data *cfqd = q->elevator->elevator_data;
 940        struct cfq_queue *cfqq = RQ_CFQQ(rq);
 941
 942        cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
 943
 944        cfq_remove_request(rq);
 945        cfqq->dispatched++;
 946        elv_dispatch_sort(q, rq);
 947
 948        if (cfq_cfqq_sync(cfqq))
 949                cfqd->sync_flight++;
 950}
 951
 952/*
 953 * return expired entry, or NULL to just start from scratch in rbtree
 954 */
 955static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
 956{
 957        struct cfq_data *cfqd = cfqq->cfqd;
 958        struct request *rq;
 959        int fifo;
 960
 961        if (cfq_cfqq_fifo_expire(cfqq))
 962                return NULL;
 963
 964        cfq_mark_cfqq_fifo_expire(cfqq);
 965
 966        if (list_empty(&cfqq->fifo))
 967                return NULL;
 968
 969        fifo = cfq_cfqq_sync(cfqq);
 970        rq = rq_entry_fifo(cfqq->fifo.next);
 971
 972        if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))
 973                rq = NULL;
 974
 975        cfq_log_cfqq(cfqd, cfqq, "fifo=%p", rq);
 976        return rq;
 977}
 978
 979static inline int
 980cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 981{
 982        const int base_rq = cfqd->cfq_slice_async_rq;
 983
 984        WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
 985
 986        return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
 987}
 988
 989/*
 990 * Select a queue for service. If we have a current active queue,
 991 * check whether to continue servicing it, or retrieve and set a new one.
 992 */
 993static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
 994{
 995        struct cfq_queue *cfqq;
 996
 997        cfqq = cfqd->active_queue;
 998        if (!cfqq)
 999                goto new_queue;
1000
1001        /*
1002         * The active queue has run out of time, expire it and select new.
1003         */
1004        if (cfq_slice_used(cfqq))
1005                goto expire;
1006
1007        /*
1008         * The active queue has requests and isn't expired, allow it to
1009         * dispatch.
1010         */
1011        if (!RB_EMPTY_ROOT(&cfqq->sort_list))
1012                goto keep_queue;
1013
1014        /*
1015         * No requests pending. If the active queue still has requests in
1016         * flight or is idling for a new request, allow either of these
1017         * conditions to happen (or time out) before selecting a new queue.
1018         */
1019        if (timer_pending(&cfqd->idle_slice_timer) ||
1020            (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) {
1021                cfqq = NULL;
1022                goto keep_queue;
1023        }
1024
1025expire:
1026        cfq_slice_expired(cfqd, 0);
1027new_queue:
1028        cfqq = cfq_set_active_queue(cfqd);
1029keep_queue:
1030        return cfqq;
1031}
1032
1033/*
1034 * Dispatch some requests from cfqq, moving them to the request queue
1035 * dispatch list.
1036 */
1037static int
1038__cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1039                        int max_dispatch)
1040{
1041        int dispatched = 0;
1042
1043        BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
1044
1045        do {
1046                struct request *rq;
1047
1048                /*
1049                 * follow expired path, else get first next available
1050                 */
1051                rq = cfq_check_fifo(cfqq);
1052                if (rq == NULL)
1053                        rq = cfqq->next_rq;
1054
1055                /*
1056                 * finally, insert request into driver dispatch list
1057                 */
1058                cfq_dispatch_insert(cfqd->queue, rq);
1059
1060                dispatched++;
1061
1062                if (!cfqd->active_cic) {
1063                        atomic_inc(&RQ_CIC(rq)->ioc->refcount);
1064                        cfqd->active_cic = RQ_CIC(rq);
1065                }
1066
1067                if (RB_EMPTY_ROOT(&cfqq->sort_list))
1068                        break;
1069
1070        } while (dispatched < max_dispatch);
1071
1072        /*
1073         * expire an async queue immediately if it has used up its slice. idle
1074         * queue always expire after 1 dispatch round.
1075         */
1076        if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
1077            dispatched >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1078            cfq_class_idle(cfqq))) {
1079                cfqq->slice_end = jiffies + 1;
1080                cfq_slice_expired(cfqd, 0);
1081        }
1082
1083        return dispatched;
1084}
1085
1086static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
1087{
1088        int dispatched = 0;
1089
1090        while (cfqq->next_rq) {
1091                cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
1092                dispatched++;
1093        }
1094
1095        BUG_ON(!list_empty(&cfqq->fifo));
1096        return dispatched;
1097}
1098
1099/*
1100 * Drain our current requests. Used for barriers and when switching
1101 * io schedulers on-the-fly.
1102 */
1103static int cfq_forced_dispatch(struct cfq_data *cfqd)
1104{
1105        struct cfq_queue *cfqq;
1106        int dispatched = 0;
1107
1108        while ((cfqq = cfq_rb_first(&cfqd->service_tree)) != NULL)
1109                dispatched += __cfq_forced_dispatch_cfqq(cfqq);
1110
1111        cfq_slice_expired(cfqd, 0);
1112
1113        BUG_ON(cfqd->busy_queues);
1114
1115        cfq_log(cfqd, "forced_dispatch=%d\n", dispatched);
1116        return dispatched;
1117}
1118
1119static int cfq_dispatch_requests(struct request_queue *q, int force)
1120{
1121        struct cfq_data *cfqd = q->elevator->elevator_data;
1122        struct cfq_queue *cfqq;
1123        int dispatched;
1124
1125        if (!cfqd->busy_queues)
1126                return 0;
1127
1128        if (unlikely(force))
1129                return cfq_forced_dispatch(cfqd);
1130
1131        dispatched = 0;
1132        while ((cfqq = cfq_select_queue(cfqd)) != NULL) {
1133                int max_dispatch;
1134
1135                max_dispatch = cfqd->cfq_quantum;
1136                if (cfq_class_idle(cfqq))
1137                        max_dispatch = 1;
1138
1139                if (cfqq->dispatched >= max_dispatch) {
1140                        if (cfqd->busy_queues > 1)
1141                                break;
1142                        if (cfqq->dispatched >= 4 * max_dispatch)
1143                                break;
1144                }
1145
1146                if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
1147                        break;
1148
1149                cfq_clear_cfqq_must_dispatch(cfqq);
1150                cfq_clear_cfqq_wait_request(cfqq);
1151                del_timer(&cfqd->idle_slice_timer);
1152
1153                dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
1154        }
1155
1156        cfq_log(cfqd, "dispatched=%d", dispatched);
1157        return dispatched;
1158}
1159
1160/*
1161 * task holds one reference to the queue, dropped when task exits. each rq
1162 * in-flight on this queue also holds a reference, dropped when rq is freed.
1163 *
1164 * queue lock must be held here.
1165 */
1166static void cfq_put_queue(struct cfq_queue *cfqq)
1167{
1168        struct cfq_data *cfqd = cfqq->cfqd;
1169
1170        BUG_ON(atomic_read(&cfqq->ref) <= 0);
1171
1172        if (!atomic_dec_and_test(&cfqq->ref))
1173                return;
1174
1175        cfq_log_cfqq(cfqd, cfqq, "put_queue");
1176        BUG_ON(rb_first(&cfqq->sort_list));
1177        BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1178        BUG_ON(cfq_cfqq_on_rr(cfqq));
1179
1180        if (unlikely(cfqd->active_queue == cfqq)) {
1181                __cfq_slice_expired(cfqd, cfqq, 0);
1182                cfq_schedule_dispatch(cfqd);
1183        }
1184
1185        kmem_cache_free(cfq_pool, cfqq);
1186}
1187
1188/*
1189 * Must always be called with the rcu_read_lock() held
1190 */
1191static void
1192__call_for_each_cic(struct io_context *ioc,
1193                    void (*func)(struct io_context *, struct cfq_io_context *))
1194{
1195        struct cfq_io_context *cic;
1196        struct hlist_node *n;
1197
1198        hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
1199                func(ioc, cic);
1200}
1201
1202/*
1203 * Call func for each cic attached to this ioc.
1204 */
1205static void
1206call_for_each_cic(struct io_context *ioc,
1207                  void (*func)(struct io_context *, struct cfq_io_context *))
1208{
1209        rcu_read_lock();
1210        __call_for_each_cic(ioc, func);
1211        rcu_read_unlock();
1212}
1213
1214static void cfq_cic_free_rcu(struct rcu_head *head)
1215{
1216        struct cfq_io_context *cic;
1217
1218        cic = container_of(head, struct cfq_io_context, rcu_head);
1219
1220        kmem_cache_free(cfq_ioc_pool, cic);
1221        elv_ioc_count_dec(ioc_count);
1222
1223        if (ioc_gone) {
1224                /*
1225                 * CFQ scheduler is exiting, grab exit lock and check
1226                 * the pending io context count. If it hits zero,
1227                 * complete ioc_gone and set it back to NULL
1228                 */
1229                spin_lock(&ioc_gone_lock);
1230                if (ioc_gone && !elv_ioc_count_read(ioc_count)) {
1231                        complete(ioc_gone);
1232                        ioc_gone = NULL;
1233                }
1234                spin_unlock(&ioc_gone_lock);
1235        }
1236}
1237
1238static void cfq_cic_free(struct cfq_io_context *cic)
1239{
1240        call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
1241}
1242
1243static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
1244{
1245        unsigned long flags;
1246
1247        BUG_ON(!cic->dead_key);
1248
1249        spin_lock_irqsave(&ioc->lock, flags);
1250        radix_tree_delete(&ioc->radix_root, cic->dead_key);
1251        hlist_del_rcu(&cic->cic_list);
1252        spin_unlock_irqrestore(&ioc->lock, flags);
1253
1254        cfq_cic_free(cic);
1255}
1256
1257/*
1258 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
1259 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
1260 * and ->trim() which is called with the task lock held
1261 */
1262static void cfq_free_io_context(struct io_context *ioc)
1263{
1264        /*
1265         * ioc->refcount is zero here, or we are called from elv_unregister(),
1266         * so no more cic's are allowed to be linked into this ioc.  So it
1267         * should be ok to iterate over the known list, we will see all cic's
1268         * since no new ones are added.
1269         */
1270        __call_for_each_cic(ioc, cic_free_func);
1271}
1272
1273static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1274{
1275        if (unlikely(cfqq == cfqd->active_queue)) {
1276                __cfq_slice_expired(cfqd, cfqq, 0);
1277                cfq_schedule_dispatch(cfqd);
1278        }
1279
1280        cfq_put_queue(cfqq);
1281}
1282
1283static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
1284                                         struct cfq_io_context *cic)
1285{
1286        struct io_context *ioc = cic->ioc;
1287
1288        list_del_init(&cic->queue_list);
1289
1290        /*
1291         * Make sure key == NULL is seen for dead queues
1292         */
1293        smp_wmb();
1294        cic->dead_key = (unsigned long) cic->key;
1295        cic->key = NULL;
1296
1297        if (ioc->ioc_data == cic)
1298                rcu_assign_pointer(ioc->ioc_data, NULL);
1299
1300        if (cic->cfqq[ASYNC]) {
1301                cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]);
1302                cic->cfqq[ASYNC] = NULL;
1303        }
1304
1305        if (cic->cfqq[SYNC]) {
1306                cfq_exit_cfqq(cfqd, cic->cfqq[SYNC]);
1307                cic->cfqq[SYNC] = NULL;
1308        }
1309}
1310
1311static void cfq_exit_single_io_context(struct io_context *ioc,
1312                                       struct cfq_io_context *cic)
1313{
1314        struct cfq_data *cfqd = cic->key;
1315
1316        if (cfqd) {
1317                struct request_queue *q = cfqd->queue;
1318                unsigned long flags;
1319
1320                spin_lock_irqsave(q->queue_lock, flags);
1321                __cfq_exit_single_io_context(cfqd, cic);
1322                spin_unlock_irqrestore(q->queue_lock, flags);
1323        }
1324}
1325
1326/*
1327 * The process that ioc belongs to has exited, we need to clean up
1328 * and put the internal structures we have that belongs to that process.
1329 */
1330static void cfq_exit_io_context(struct io_context *ioc)
1331{
1332        call_for_each_cic(ioc, cfq_exit_single_io_context);
1333}
1334
1335static struct cfq_io_context *
1336cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1337{
1338        struct cfq_io_context *cic;
1339
1340        cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
1341                                                        cfqd->queue->node);
1342        if (cic) {
1343                cic->last_end_request = jiffies;
1344                INIT_LIST_HEAD(&cic->queue_list);
1345                INIT_HLIST_NODE(&cic->cic_list);
1346                cic->dtor = cfq_free_io_context;
1347                cic->exit = cfq_exit_io_context;
1348                elv_ioc_count_inc(ioc_count);
1349        }
1350
1351        return cic;
1352}
1353
1354static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
1355{
1356        struct task_struct *tsk = current;
1357        int ioprio_class;
1358
1359        if (!cfq_cfqq_prio_changed(cfqq))
1360                return;
1361
1362        ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
1363        switch (ioprio_class) {
1364        default:
1365                printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1366        case IOPRIO_CLASS_NONE:
1367                /*
1368                 * no prio set, inherit CPU scheduling settings
1369                 */
1370                cfqq->ioprio = task_nice_ioprio(tsk);
1371                cfqq->ioprio_class = task_nice_ioclass(tsk);
1372                break;
1373        case IOPRIO_CLASS_RT:
1374                cfqq->ioprio = task_ioprio(ioc);
1375                cfqq->ioprio_class = IOPRIO_CLASS_RT;
1376                break;
1377        case IOPRIO_CLASS_BE:
1378                cfqq->ioprio = task_ioprio(ioc);
1379                cfqq->ioprio_class = IOPRIO_CLASS_BE;
1380                break;
1381        case IOPRIO_CLASS_IDLE:
1382                cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1383                cfqq->ioprio = 7;
1384                cfq_clear_cfqq_idle_window(cfqq);
1385                break;
1386        }
1387
1388        /*
1389         * keep track of original prio settings in case we have to temporarily
1390         * elevate the priority of this queue
1391         */
1392        cfqq->org_ioprio = cfqq->ioprio;
1393        cfqq->org_ioprio_class = cfqq->ioprio_class;
1394        cfq_clear_cfqq_prio_changed(cfqq);
1395}
1396
1397static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
1398{
1399        struct cfq_data *cfqd = cic->key;
1400        struct cfq_queue *cfqq;
1401        unsigned long flags;
1402
1403        if (unlikely(!cfqd))
1404                return;
1405
1406        spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1407
1408        cfqq = cic->cfqq[ASYNC];
1409        if (cfqq) {
1410                struct cfq_queue *new_cfqq;
1411                new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc, GFP_ATOMIC);
1412                if (new_cfqq) {
1413                        cic->cfqq[ASYNC] = new_cfqq;
1414                        cfq_put_queue(cfqq);
1415                }
1416        }
1417
1418        cfqq = cic->cfqq[SYNC];
1419        if (cfqq)
1420                cfq_mark_cfqq_prio_changed(cfqq);
1421
1422        spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1423}
1424
1425static void cfq_ioc_set_ioprio(struct io_context *ioc)
1426{
1427        call_for_each_cic(ioc, changed_ioprio);
1428        ioc->ioprio_changed = 0;
1429}
1430
1431static struct cfq_queue *
1432cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
1433                     struct io_context *ioc, gfp_t gfp_mask)
1434{
1435        struct cfq_queue *cfqq, *new_cfqq = NULL;
1436        struct cfq_io_context *cic;
1437
1438retry:
1439        cic = cfq_cic_lookup(cfqd, ioc);
1440        /* cic always exists here */
1441        cfqq = cic_to_cfqq(cic, is_sync);
1442
1443        if (!cfqq) {
1444                if (new_cfqq) {
1445                        cfqq = new_cfqq;
1446                        new_cfqq = NULL;
1447                } else if (gfp_mask & __GFP_WAIT) {
1448                        /*
1449                         * Inform the allocator of the fact that we will
1450                         * just repeat this allocation if it fails, to allow
1451                         * the allocator to do whatever it needs to attempt to
1452                         * free memory.
1453                         */
1454                        spin_unlock_irq(cfqd->queue->queue_lock);
1455                        new_cfqq = kmem_cache_alloc_node(cfq_pool,
1456                                        gfp_mask | __GFP_NOFAIL | __GFP_ZERO,
1457                                        cfqd->queue->node);
1458                        spin_lock_irq(cfqd->queue->queue_lock);
1459                        goto retry;
1460                } else {
1461                        cfqq = kmem_cache_alloc_node(cfq_pool,
1462                                        gfp_mask | __GFP_ZERO,
1463                                        cfqd->queue->node);
1464                        if (!cfqq)
1465                                goto out;
1466                }
1467
1468                RB_CLEAR_NODE(&cfqq->rb_node);
1469                INIT_LIST_HEAD(&cfqq->fifo);
1470
1471                atomic_set(&cfqq->ref, 0);
1472                cfqq->cfqd = cfqd;
1473
1474                cfq_mark_cfqq_prio_changed(cfqq);
1475                cfq_mark_cfqq_queue_new(cfqq);
1476
1477                cfq_init_prio_data(cfqq, ioc);
1478
1479                if (is_sync) {
1480                        if (!cfq_class_idle(cfqq))
1481                                cfq_mark_cfqq_idle_window(cfqq);
1482                        cfq_mark_cfqq_sync(cfqq);
1483                }
1484                cfqq->pid = current->pid;
1485                cfq_log_cfqq(cfqd, cfqq, "alloced");
1486        }
1487
1488        if (new_cfqq)
1489                kmem_cache_free(cfq_pool, new_cfqq);
1490
1491out:
1492        WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
1493        return cfqq;
1494}
1495
1496static struct cfq_queue **
1497cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
1498{
1499        switch (ioprio_class) {
1500        case IOPRIO_CLASS_RT:
1501                return &cfqd->async_cfqq[0][ioprio];
1502        case IOPRIO_CLASS_BE:
1503                return &cfqd->async_cfqq[1][ioprio];
1504        case IOPRIO_CLASS_IDLE:
1505                return &cfqd->async_idle_cfqq;
1506        default:
1507                BUG();
1508        }
1509}
1510
1511static struct cfq_queue *
1512cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
1513              gfp_t gfp_mask)
1514{
1515        const int ioprio = task_ioprio(ioc);
1516        const int ioprio_class = task_ioprio_class(ioc);
1517        struct cfq_queue **async_cfqq = NULL;
1518        struct cfq_queue *cfqq = NULL;
1519
1520        if (!is_sync) {
1521                async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
1522                cfqq = *async_cfqq;
1523        }
1524
1525        if (!cfqq) {
1526                cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
1527                if (!cfqq)
1528                        return NULL;
1529        }
1530
1531        /*
1532         * pin the queue now that it's allocated, scheduler exit will prune it
1533         */
1534        if (!is_sync && !(*async_cfqq)) {
1535                atomic_inc(&cfqq->ref);
1536                *async_cfqq = cfqq;
1537        }
1538
1539        atomic_inc(&cfqq->ref);
1540        return cfqq;
1541}
1542
1543/*
1544 * We drop cfq io contexts lazily, so we may find a dead one.
1545 */
1546static void
1547cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
1548                  struct cfq_io_context *cic)
1549{
1550        unsigned long flags;
1551
1552        WARN_ON(!list_empty(&cic->queue_list));
1553
1554        spin_lock_irqsave(&ioc->lock, flags);
1555
1556        BUG_ON(ioc->ioc_data == cic);
1557
1558        radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
1559        hlist_del_rcu(&cic->cic_list);
1560        spin_unlock_irqrestore(&ioc->lock, flags);
1561
1562        cfq_cic_free(cic);
1563}
1564
1565static struct cfq_io_context *
1566cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
1567{
1568        struct cfq_io_context *cic;
1569        unsigned long flags;
1570        void *k;
1571
1572        if (unlikely(!ioc))
1573                return NULL;
1574
1575        rcu_read_lock();
1576
1577        /*
1578         * we maintain a last-hit cache, to avoid browsing over the tree
1579         */
1580        cic = rcu_dereference(ioc->ioc_data);
1581        if (cic && cic->key == cfqd) {
1582                rcu_read_unlock();
1583                return cic;
1584        }
1585
1586        do {
1587                cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
1588                rcu_read_unlock();
1589                if (!cic)
1590                        break;
1591                /* ->key must be copied to avoid race with cfq_exit_queue() */
1592                k = cic->key;
1593                if (unlikely(!k)) {
1594                        cfq_drop_dead_cic(cfqd, ioc, cic);
1595                        rcu_read_lock();
1596                        continue;
1597                }
1598
1599                spin_lock_irqsave(&ioc->lock, flags);
1600                rcu_assign_pointer(ioc->ioc_data, cic);
1601                spin_unlock_irqrestore(&ioc->lock, flags);
1602                break;
1603        } while (1);
1604
1605        return cic;
1606}
1607
1608/*
1609 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
1610 * the process specific cfq io context when entered from the block layer.
1611 * Also adds the cic to a per-cfqd list, used when this queue is removed.
1612 */
1613static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
1614                        struct cfq_io_context *cic, gfp_t gfp_mask)
1615{
1616        unsigned long flags;
1617        int ret;
1618
1619        ret = radix_tree_preload(gfp_mask);
1620        if (!ret) {
1621                cic->ioc = ioc;
1622                cic->key = cfqd;
1623
1624                spin_lock_irqsave(&ioc->lock, flags);
1625                ret = radix_tree_insert(&ioc->radix_root,
1626                                                (unsigned long) cfqd, cic);
1627                if (!ret)
1628                        hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
1629                spin_unlock_irqrestore(&ioc->lock, flags);
1630
1631                radix_tree_preload_end();
1632
1633                if (!ret) {
1634                        spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1635                        list_add(&cic->queue_list, &cfqd->cic_list);
1636                        spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1637                }
1638        }
1639
1640        if (ret)
1641                printk(KERN_ERR "cfq: cic link failed!\n");
1642
1643        return ret;
1644}
1645
1646/*
1647 * Setup general io context and cfq io context. There can be several cfq
1648 * io contexts per general io context, if this process is doing io to more
1649 * than one device managed by cfq.
1650 */
1651static struct cfq_io_context *
1652cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1653{
1654        struct io_context *ioc = NULL;
1655        struct cfq_io_context *cic;
1656
1657        might_sleep_if(gfp_mask & __GFP_WAIT);
1658
1659        ioc = get_io_context(gfp_mask, cfqd->queue->node);
1660        if (!ioc)
1661                return NULL;
1662
1663        cic = cfq_cic_lookup(cfqd, ioc);
1664        if (cic)
1665                goto out;
1666
1667        cic = cfq_alloc_io_context(cfqd, gfp_mask);
1668        if (cic == NULL)
1669                goto err;
1670
1671        if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
1672                goto err_free;
1673
1674out:
1675        smp_read_barrier_depends();
1676        if (unlikely(ioc->ioprio_changed))
1677                cfq_ioc_set_ioprio(ioc);
1678
1679        return cic;
1680err_free:
1681        cfq_cic_free(cic);
1682err:
1683        put_io_context(ioc);
1684        return NULL;
1685}
1686
1687static void
1688cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1689{
1690        unsigned long elapsed = jiffies - cic->last_end_request;
1691        unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1692
1693        cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1694        cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1695        cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1696}
1697
1698static void
1699cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
1700                       struct request *rq)
1701{
1702        sector_t sdist;
1703        u64 total;
1704
1705        if (cic->last_request_pos < rq->sector)
1706                sdist = rq->sector - cic->last_request_pos;
1707        else
1708                sdist = cic->last_request_pos - rq->sector;
1709
1710        /*
1711         * Don't allow the seek distance to get too large from the
1712         * odd fragment, pagein, etc
1713         */
1714        if (cic->seek_samples <= 60) /* second&third seek */
1715                sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
1716        else
1717                sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
1718
1719        cic->seek_samples = (7*cic->seek_samples + 256) / 8;
1720        cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
1721        total = cic->seek_total + (cic->seek_samples/2);
1722        do_div(total, cic->seek_samples);
1723        cic->seek_mean = (sector_t)total;
1724}
1725
1726/*
1727 * Disable idle window if the process thinks too long or seeks so much that
1728 * it doesn't matter
1729 */
1730static void
1731cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1732                       struct cfq_io_context *cic)
1733{
1734        int old_idle, enable_idle;
1735
1736        /*
1737         * Don't idle for async or idle io prio class
1738         */
1739        if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
1740                return;
1741
1742        enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
1743
1744        if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
1745            (cfqd->hw_tag && CIC_SEEKY(cic)))
1746                enable_idle = 0;
1747        else if (sample_valid(cic->ttime_samples)) {
1748                if (cic->ttime_mean > cfqd->cfq_slice_idle)
1749                        enable_idle = 0;
1750                else
1751                        enable_idle = 1;
1752        }
1753
1754        if (old_idle != enable_idle) {
1755                cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
1756                if (enable_idle)
1757                        cfq_mark_cfqq_idle_window(cfqq);
1758                else
1759                        cfq_clear_cfqq_idle_window(cfqq);
1760        }
1761}
1762
1763/*
1764 * Check if new_cfqq should preempt the currently active queue. Return 0 for
1765 * no or if we aren't sure, a 1 will cause a preempt.
1766 */
1767static int
1768cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1769                   struct request *rq)
1770{
1771        struct cfq_queue *cfqq;
1772
1773        cfqq = cfqd->active_queue;
1774        if (!cfqq)
1775                return 0;
1776
1777        if (cfq_slice_used(cfqq))
1778                return 1;
1779
1780        if (cfq_class_idle(new_cfqq))
1781                return 0;
1782
1783        if (cfq_class_idle(cfqq))
1784                return 1;
1785
1786        /*
1787         * if the new request is sync, but the currently running queue is
1788         * not, let the sync request have priority.
1789         */
1790        if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
1791                return 1;
1792
1793        /*
1794         * So both queues are sync. Let the new request get disk time if
1795         * it's a metadata request and the current queue is doing regular IO.
1796         */
1797        if (rq_is_meta(rq) && !cfqq->meta_pending)
1798                return 1;
1799
1800        if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
1801                return 0;
1802
1803        /*
1804         * if this request is as-good as one we would expect from the
1805         * current cfqq, let it preempt
1806         */
1807        if (cfq_rq_close(cfqd, rq))
1808                return 1;
1809
1810        return 0;
1811}
1812
1813/*
1814 * cfqq preempts the active queue. if we allowed preempt with no slice left,
1815 * let it have half of its nominal slice.
1816 */
1817static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1818{
1819        cfq_log_cfqq(cfqd, cfqq, "preempt");
1820        cfq_slice_expired(cfqd, 1);
1821
1822        /*
1823         * Put the new queue at the front of the of the current list,
1824         * so we know that it will be selected next.
1825         */
1826        BUG_ON(!cfq_cfqq_on_rr(cfqq));
1827
1828        cfq_service_tree_add(cfqd, cfqq, 1);
1829
1830        cfqq->slice_end = 0;
1831        cfq_mark_cfqq_slice_new(cfqq);
1832}
1833
1834/*
1835 * Called when a new fs request (rq) is added (to cfqq). Check if there's
1836 * something we should do about it
1837 */
1838static void
1839cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1840                struct request *rq)
1841{
1842        struct cfq_io_context *cic = RQ_CIC(rq);
1843
1844        cfqd->rq_queued++;
1845        if (rq_is_meta(rq))
1846                cfqq->meta_pending++;
1847
1848        cfq_update_io_thinktime(cfqd, cic);
1849        cfq_update_io_seektime(cfqd, cic, rq);
1850        cfq_update_idle_window(cfqd, cfqq, cic);
1851
1852        cic->last_request_pos = rq->sector + rq->nr_sectors;
1853
1854        if (cfqq == cfqd->active_queue) {
1855                /*
1856                 * if we are waiting for a request for this queue, let it rip
1857                 * immediately and flag that we must not expire this queue
1858                 * just now
1859                 */
1860                if (cfq_cfqq_wait_request(cfqq)) {
1861                        cfq_mark_cfqq_must_dispatch(cfqq);
1862                        del_timer(&cfqd->idle_slice_timer);
1863                        blk_start_queueing(cfqd->queue);
1864                }
1865        } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
1866                /*
1867                 * not the active queue - expire current slice if it is
1868                 * idle and has expired it's mean thinktime or this new queue
1869                 * has some old slice time left and is of higher priority
1870                 */
1871                cfq_preempt_queue(cfqd, cfqq);
1872                cfq_mark_cfqq_must_dispatch(cfqq);
1873                blk_start_queueing(cfqd->queue);
1874        }
1875}
1876
1877static void cfq_insert_request(struct request_queue *q, struct request *rq)
1878{
1879        struct cfq_data *cfqd = q->elevator->elevator_data;
1880        struct cfq_queue *cfqq = RQ_CFQQ(rq);
1881
1882        cfq_log_cfqq(cfqd, cfqq, "insert_request");
1883        cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
1884
1885        cfq_add_rq_rb(rq);
1886
1887        list_add_tail(&rq->queuelist, &cfqq->fifo);
1888
1889        cfq_rq_enqueued(cfqd, cfqq, rq);
1890}
1891
1892/*
1893 * Update hw_tag based on peak queue depth over 50 samples under
1894 * sufficient load.
1895 */
1896static void cfq_update_hw_tag(struct cfq_data *cfqd)
1897{
1898        if (cfqd->rq_in_driver > cfqd->rq_in_driver_peak)
1899                cfqd->rq_in_driver_peak = cfqd->rq_in_driver;
1900
1901        if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
1902            cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
1903                return;
1904
1905        if (cfqd->hw_tag_samples++ < 50)
1906                return;
1907
1908        if (cfqd->rq_in_driver_peak >= CFQ_HW_QUEUE_MIN)
1909                cfqd->hw_tag = 1;
1910        else
1911                cfqd->hw_tag = 0;
1912
1913        cfqd->hw_tag_samples = 0;
1914        cfqd->rq_in_driver_peak = 0;
1915}
1916
1917static void cfq_completed_request(struct request_queue *q, struct request *rq)
1918{
1919        struct cfq_queue *cfqq = RQ_CFQQ(rq);
1920        struct cfq_data *cfqd = cfqq->cfqd;
1921        const int sync = rq_is_sync(rq);
1922        unsigned long now;
1923
1924        now = jiffies;
1925        cfq_log_cfqq(cfqd, cfqq, "complete");
1926
1927        cfq_update_hw_tag(cfqd);
1928
1929        WARN_ON(!cfqd->rq_in_driver);
1930        WARN_ON(!cfqq->dispatched);
1931        cfqd->rq_in_driver--;
1932        cfqq->dispatched--;
1933
1934        if (cfq_cfqq_sync(cfqq))
1935                cfqd->sync_flight--;
1936
1937        if (!cfq_class_idle(cfqq))
1938                cfqd->last_end_request = now;
1939
1940        if (sync)
1941                RQ_CIC(rq)->last_end_request = now;
1942
1943        /*
1944         * If this is the active queue, check if it needs to be expired,
1945         * or if we want to idle in case it has no pending requests.
1946         */
1947        if (cfqd->active_queue == cfqq) {
1948                if (cfq_cfqq_slice_new(cfqq)) {
1949                        cfq_set_prio_slice(cfqd, cfqq);
1950                        cfq_clear_cfqq_slice_new(cfqq);
1951                }
1952                if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
1953                        cfq_slice_expired(cfqd, 1);
1954                else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list))
1955                        cfq_arm_slice_timer(cfqd);
1956        }
1957
1958        if (!cfqd->rq_in_driver)
1959                cfq_schedule_dispatch(cfqd);
1960}
1961
1962/*
1963 * we temporarily boost lower priority queues if they are holding fs exclusive
1964 * resources. they are boosted to normal prio (CLASS_BE/4)
1965 */
1966static void cfq_prio_boost(struct cfq_queue *cfqq)
1967{
1968        if (has_fs_excl()) {
1969                /*
1970                 * boost idle prio on transactions that would lock out other
1971                 * users of the filesystem
1972                 */
1973                if (cfq_class_idle(cfqq))
1974                        cfqq->ioprio_class = IOPRIO_CLASS_BE;
1975                if (cfqq->ioprio > IOPRIO_NORM)
1976                        cfqq->ioprio = IOPRIO_NORM;
1977        } else {
1978                /*
1979                 * check if we need to unboost the queue
1980                 */
1981                if (cfqq->ioprio_class != cfqq->org_ioprio_class)
1982                        cfqq->ioprio_class = cfqq->org_ioprio_class;
1983                if (cfqq->ioprio != cfqq->org_ioprio)
1984                        cfqq->ioprio = cfqq->org_ioprio;
1985        }
1986}
1987
1988static inline int __cfq_may_queue(struct cfq_queue *cfqq)
1989{
1990        if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
1991            !cfq_cfqq_must_alloc_slice(cfqq)) {
1992                cfq_mark_cfqq_must_alloc_slice(cfqq);
1993                return ELV_MQUEUE_MUST;
1994        }
1995
1996        return ELV_MQUEUE_MAY;
1997}
1998
1999static int cfq_may_queue(struct request_queue *q, int rw)
2000{
2001        struct cfq_data *cfqd = q->elevator->elevator_data;
2002        struct task_struct *tsk = current;
2003        struct cfq_io_context *cic;
2004        struct cfq_queue *cfqq;
2005
2006        /*
2007         * don't force setup of a queue from here, as a call to may_queue
2008         * does not necessarily imply that a request actually will be queued.
2009         * so just lookup a possibly existing queue, or return 'may queue'
2010         * if that fails
2011         */
2012        cic = cfq_cic_lookup(cfqd, tsk->io_context);
2013        if (!cic)
2014                return ELV_MQUEUE_MAY;
2015
2016        cfqq = cic_to_cfqq(cic, rw & REQ_RW_SYNC);
2017        if (cfqq) {
2018                cfq_init_prio_data(cfqq, cic->ioc);
2019                cfq_prio_boost(cfqq);
2020
2021                return __cfq_may_queue(cfqq);
2022        }
2023
2024        return ELV_MQUEUE_MAY;
2025}
2026
2027/*
2028 * queue lock held here
2029 */
2030static void cfq_put_request(struct request *rq)
2031{
2032        struct cfq_queue *cfqq = RQ_CFQQ(rq);
2033
2034        if (cfqq) {
2035                const int rw = rq_data_dir(rq);
2036
2037                BUG_ON(!cfqq->allocated[rw]);
2038                cfqq->allocated[rw]--;
2039
2040                put_io_context(RQ_CIC(rq)->ioc);
2041
2042                rq->elevator_private = NULL;
2043                rq->elevator_private2 = NULL;
2044
2045                cfq_put_queue(cfqq);
2046        }
2047}
2048
2049/*
2050 * Allocate cfq data structures associated with this request.
2051 */
2052static int
2053cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
2054{
2055        struct cfq_data *cfqd = q->elevator->elevator_data;
2056        struct cfq_io_context *cic;
2057        const int rw = rq_data_dir(rq);
2058        const int is_sync = rq_is_sync(rq);
2059        struct cfq_queue *cfqq;
2060        unsigned long flags;
2061
2062        might_sleep_if(gfp_mask & __GFP_WAIT);
2063
2064        cic = cfq_get_io_context(cfqd, gfp_mask);
2065
2066        spin_lock_irqsave(q->queue_lock, flags);
2067
2068        if (!cic)
2069                goto queue_fail;
2070
2071        cfqq = cic_to_cfqq(cic, is_sync);
2072        if (!cfqq) {
2073                cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
2074
2075                if (!cfqq)
2076                        goto queue_fail;
2077
2078                cic_set_cfqq(cic, cfqq, is_sync);
2079        }
2080
2081        cfqq->allocated[rw]++;
2082        cfq_clear_cfqq_must_alloc(cfqq);
2083        atomic_inc(&cfqq->ref);
2084
2085        spin_unlock_irqrestore(q->queue_lock, flags);
2086
2087        rq->elevator_private = cic;
2088        rq->elevator_private2 = cfqq;
2089        return 0;
2090
2091queue_fail:
2092        if (cic)
2093                put_io_context(cic->ioc);
2094
2095        cfq_schedule_dispatch(cfqd);
2096        spin_unlock_irqrestore(q->queue_lock, flags);
2097        cfq_log(cfqd, "set_request fail");
2098        return 1;
2099}
2100
2101static void cfq_kick_queue(struct work_struct *work)
2102{
2103        struct cfq_data *cfqd =
2104                container_of(work, struct cfq_data, unplug_work);
2105        struct request_queue *q = cfqd->queue;
2106        unsigned long flags;
2107
2108        spin_lock_irqsave(q->queue_lock, flags);
2109        blk_start_queueing(q);
2110        spin_unlock_irqrestore(q->queue_lock, flags);
2111}
2112
2113/*
2114 * Timer running if the active_queue is currently idling inside its time slice
2115 */
2116static void cfq_idle_slice_timer(unsigned long data)
2117{
2118        struct cfq_data *cfqd = (struct cfq_data *) data;
2119        struct cfq_queue *cfqq;
2120        unsigned long flags;
2121        int timed_out = 1;
2122
2123        cfq_log(cfqd, "idle timer fired");
2124
2125        spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2126
2127        cfqq = cfqd->active_queue;
2128        if (cfqq) {
2129                timed_out = 0;
2130
2131                /*
2132                 * expired
2133                 */
2134                if (cfq_slice_used(cfqq))
2135                        goto expire;
2136
2137                /*
2138                 * only expire and reinvoke request handler, if there are
2139                 * other queues with pending requests
2140                 */
2141                if (!cfqd->busy_queues)
2142                        goto out_cont;
2143
2144                /*
2145                 * not expired and it has a request pending, let it dispatch
2146                 */
2147                if (!RB_EMPTY_ROOT(&cfqq->sort_list)) {
2148                        cfq_mark_cfqq_must_dispatch(cfqq);
2149                        goto out_kick;
2150                }
2151        }
2152expire:
2153        cfq_slice_expired(cfqd, timed_out);
2154out_kick:
2155        cfq_schedule_dispatch(cfqd);
2156out_cont:
2157        spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2158}
2159
2160static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2161{
2162        del_timer_sync(&cfqd->idle_slice_timer);
2163        kblockd_flush_work(&cfqd->unplug_work);
2164}
2165
2166static void cfq_put_async_queues(struct cfq_data *cfqd)
2167{
2168        int i;
2169
2170        for (i = 0; i < IOPRIO_BE_NR; i++) {
2171                if (cfqd->async_cfqq[0][i])
2172                        cfq_put_queue(cfqd->async_cfqq[0][i]);
2173                if (cfqd->async_cfqq[1][i])
2174                        cfq_put_queue(cfqd->async_cfqq[1][i]);
2175        }
2176
2177        if (cfqd->async_idle_cfqq)
2178                cfq_put_queue(cfqd->async_idle_cfqq);
2179}
2180
2181static void cfq_exit_queue(elevator_t *e)
2182{
2183        struct cfq_data *cfqd = e->elevator_data;
2184        struct request_queue *q = cfqd->queue;
2185
2186        cfq_shutdown_timer_wq(cfqd);
2187
2188        spin_lock_irq(q->queue_lock);
2189
2190        if (cfqd->active_queue)
2191                __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
2192
2193        while (!list_empty(&cfqd->cic_list)) {
2194                struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2195                                                        struct cfq_io_context,
2196                                                        queue_list);
2197
2198                __cfq_exit_single_io_context(cfqd, cic);
2199        }
2200
2201        cfq_put_async_queues(cfqd);
2202
2203        spin_unlock_irq(q->queue_lock);
2204
2205        cfq_shutdown_timer_wq(cfqd);
2206
2207        kfree(cfqd);
2208}
2209
2210static void *cfq_init_queue(struct request_queue *q)
2211{
2212        struct cfq_data *cfqd;
2213
2214        cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
2215        if (!cfqd)
2216                return NULL;
2217
2218        cfqd->service_tree = CFQ_RB_ROOT;
2219        INIT_LIST_HEAD(&cfqd->cic_list);
2220
2221        cfqd->queue = q;
2222
2223        init_timer(&cfqd->idle_slice_timer);
2224        cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2225        cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2226
2227        INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
2228
2229        cfqd->last_end_request = jiffies;
2230        cfqd->cfq_quantum = cfq_quantum;
2231        cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2232        cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2233        cfqd->cfq_back_max = cfq_back_max;
2234        cfqd->cfq_back_penalty = cfq_back_penalty;
2235        cfqd->cfq_slice[0] = cfq_slice_async;
2236        cfqd->cfq_slice[1] = cfq_slice_sync;
2237        cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2238        cfqd->cfq_slice_idle = cfq_slice_idle;
2239        cfqd->hw_tag = 1;
2240
2241        return cfqd;
2242}
2243
2244static void cfq_slab_kill(void)
2245{
2246        /*
2247         * Caller already ensured that pending RCU callbacks are completed,
2248         * so we should have no busy allocations at this point.
2249         */
2250        if (cfq_pool)
2251                kmem_cache_destroy(cfq_pool);
2252        if (cfq_ioc_pool)
2253                kmem_cache_destroy(cfq_ioc_pool);
2254}
2255
2256static int __init cfq_slab_setup(void)
2257{
2258        cfq_pool = KMEM_CACHE(cfq_queue, 0);
2259        if (!cfq_pool)
2260                goto fail;
2261
2262        cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
2263        if (!cfq_ioc_pool)
2264                goto fail;
2265
2266        return 0;
2267fail:
2268        cfq_slab_kill();
2269        return -ENOMEM;
2270}
2271
2272/*
2273 * sysfs parts below -->
2274 */
2275static ssize_t
2276cfq_var_show(unsigned int var, char *page)
2277{
2278        return sprintf(page, "%d\n", var);
2279}
2280
2281static ssize_t
2282cfq_var_store(unsigned int *var, const char *page, size_t count)
2283{
2284        char *p = (char *) page;
2285
2286        *var = simple_strtoul(p, &p, 10);
2287        return count;
2288}
2289
2290#define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
2291static ssize_t __FUNC(elevator_t *e, char *page)                        \
2292{                                                                       \
2293        struct cfq_data *cfqd = e->elevator_data;                       \
2294        unsigned int __data = __VAR;                                    \
2295        if (__CONV)                                                     \
2296                __data = jiffies_to_msecs(__data);                      \
2297        return cfq_var_show(__data, (page));                            \
2298}
2299SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2300SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2301SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2302SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
2303SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
2304SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2305SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2306SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2307SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2308#undef SHOW_FUNCTION
2309
2310#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
2311static ssize_t __FUNC(elevator_t *e, const char *page, size_t count)    \
2312{                                                                       \
2313        struct cfq_data *cfqd = e->elevator_data;                       \
2314        unsigned int __data;                                            \
2315        int ret = cfq_var_store(&__data, (page), count);                \
2316        if (__data < (MIN))                                             \
2317                __data = (MIN);                                         \
2318        else if (__data > (MAX))                                        \
2319                __data = (MAX);                                         \
2320        if (__CONV)                                                     \
2321                *(__PTR) = msecs_to_jiffies(__data);                    \
2322        else                                                            \
2323                *(__PTR) = __data;                                      \
2324        return ret;                                                     \
2325}
2326STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2327STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
2328                UINT_MAX, 1);
2329STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
2330                UINT_MAX, 1);
2331STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2332STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
2333                UINT_MAX, 0);
2334STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2335STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2336STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2337STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
2338                UINT_MAX, 0);
2339#undef STORE_FUNCTION
2340
2341#define CFQ_ATTR(name) \
2342        __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2343
2344static struct elv_fs_entry cfq_attrs[] = {
2345        CFQ_ATTR(quantum),
2346        CFQ_ATTR(fifo_expire_sync),
2347        CFQ_ATTR(fifo_expire_async),
2348        CFQ_ATTR(back_seek_max),
2349        CFQ_ATTR(back_seek_penalty),
2350        CFQ_ATTR(slice_sync),
2351        CFQ_ATTR(slice_async),
2352        CFQ_ATTR(slice_async_rq),
2353        CFQ_ATTR(slice_idle),
2354        __ATTR_NULL
2355};
2356
2357static struct elevator_type iosched_cfq = {
2358        .ops = {
2359                .elevator_merge_fn =            cfq_merge,
2360                .elevator_merged_fn =           cfq_merged_request,
2361                .elevator_merge_req_fn =        cfq_merged_requests,
2362                .elevator_allow_merge_fn =      cfq_allow_merge,
2363                .elevator_dispatch_fn =         cfq_dispatch_requests,
2364                .elevator_add_req_fn =          cfq_insert_request,
2365                .elevator_activate_req_fn =     cfq_activate_request,
2366                .elevator_deactivate_req_fn =   cfq_deactivate_request,
2367                .elevator_queue_empty_fn =      cfq_queue_empty,
2368                .elevator_completed_req_fn =    cfq_completed_request,
2369                .elevator_former_req_fn =       elv_rb_former_request,
2370                .elevator_latter_req_fn =       elv_rb_latter_request,
2371                .elevator_set_req_fn =          cfq_set_request,
2372                .elevator_put_req_fn =          cfq_put_request,
2373                .elevator_may_queue_fn =        cfq_may_queue,
2374                .elevator_init_fn =             cfq_init_queue,
2375                .elevator_exit_fn =             cfq_exit_queue,
2376                .trim =                         cfq_free_io_context,
2377        },
2378        .elevator_attrs =       cfq_attrs,
2379        .elevator_name =        "cfq",
2380        .elevator_owner =       THIS_MODULE,
2381};
2382
2383static int __init cfq_init(void)
2384{
2385        /*
2386         * could be 0 on HZ < 1000 setups
2387         */
2388        if (!cfq_slice_async)
2389                cfq_slice_async = 1;
2390        if (!cfq_slice_idle)
2391                cfq_slice_idle = 1;
2392
2393        if (cfq_slab_setup())
2394                return -ENOMEM;
2395
2396        elv_register(&iosched_cfq);
2397
2398        return 0;
2399}
2400
2401static void __exit cfq_exit(void)
2402{
2403        DECLARE_COMPLETION_ONSTACK(all_gone);
2404        elv_unregister(&iosched_cfq);
2405        ioc_gone = &all_gone;
2406        /* ioc_gone's update must be visible before reading ioc_count */
2407        smp_wmb();
2408
2409        /*
2410         * this also protects us from entering cfq_slab_kill() with
2411         * pending RCU callbacks
2412         */
2413        if (elv_ioc_count_read(ioc_count))
2414                wait_for_completion(&all_gone);
2415        cfq_slab_kill();
2416}
2417
2418module_init(cfq_init);
2419module_exit(cfq_exit);
2420
2421MODULE_AUTHOR("Jens Axboe");
2422MODULE_LICENSE("GPL");
2423MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");
2424
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