git.oblomov.eu Git - linux-2.6/blob - 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@suse.de>
   8  */
   9 #include <linux/kernel.h>
  10 #include <linux/fs.h>
  11 #include <linux/blkdev.h>
  12 #include <linux/elevator.h>
  13 #include <linux/bio.h>
  14 #include <linux/config.h>
  15 #include <linux/module.h>
  16 #include <linux/slab.h>
  17 #include <linux/init.h>
  18 #include <linux/compiler.h>
  19 #include <linux/hash.h>
  20 #include <linux/rbtree.h>
  21 #include <linux/mempool.h>
  22 #include <linux/ioprio.h>
  23 #include <linux/writeback.h>
  24
  25 /*
  26  * tunables
  27  */
  28 static const int cfq_quantum = 4;               /* max queue in one round of service */
  29 static const int cfq_queued = 8;                /* minimum rq allocate limit per-queue*/
  30 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
  31 static const int cfq_back_max = 16 * 1024;      /* maximum backwards seek, in KiB */
  32 static const int cfq_back_penalty = 2;          /* penalty of a backwards seek */
  33
  34 static const int cfq_slice_sync = HZ / 10;
  35 static int cfq_slice_async = HZ / 25;
  36 static const int cfq_slice_async_rq = 2;
  37 static int cfq_slice_idle = HZ / 100;
  38
  39 #define CFQ_IDLE_GRACE          (HZ / 10)
  40 #define CFQ_SLICE_SCALE         (5)
  41
  42 #define CFQ_KEY_ASYNC           (0)
  43 #define CFQ_KEY_ANY             (0xffff)
  44
  45 /*
  46  * disable queueing at the driver/hardware level
  47  */
  48 static const int cfq_max_depth = 2;
  49
  50 static DEFINE_RWLOCK(cfq_exit_lock);
  51
  52 /*
  53  * for the hash of cfqq inside the cfqd
  54  */
  55 #define CFQ_QHASH_SHIFT         6
  56 #define CFQ_QHASH_ENTRIES       (1 << CFQ_QHASH_SHIFT)
  57 #define list_entry_qhash(entry) hlist_entry((entry), struct cfq_queue, cfq_hash)
  58
  59 /*
  60  * for the hash of crq inside the cfqq
  61  */
  62 #define CFQ_MHASH_SHIFT         6
  63 #define CFQ_MHASH_BLOCK(sec)    ((sec) >> 3)
  64 #define CFQ_MHASH_ENTRIES       (1 << CFQ_MHASH_SHIFT)
  65 #define CFQ_MHASH_FN(sec)       hash_long(CFQ_MHASH_BLOCK(sec), CFQ_MHASH_SHIFT)
  66 #define rq_hash_key(rq)         ((rq)->sector + (rq)->nr_sectors)
  67 #define list_entry_hash(ptr)    hlist_entry((ptr), struct cfq_rq, hash)
  68
  69 #define list_entry_cfqq(ptr)    list_entry((ptr), struct cfq_queue, cfq_list)
  70 #define list_entry_fifo(ptr)    list_entry((ptr), struct request, queuelist)
  71
  72 #define RQ_DATA(rq)             (rq)->elevator_private
  73
  74 /*
  75  * rb-tree defines
  76  */
  77 #define RB_NONE                 (2)
  78 #define RB_EMPTY(node)          ((node)->rb_node == NULL)
  79 #define RB_CLEAR_COLOR(node)    (node)->rb_color = RB_NONE
  80 #define RB_CLEAR(node)          do {    \
  81         (node)->rb_parent = NULL;       \
  82         RB_CLEAR_COLOR((node));         \
  83         (node)->rb_right = NULL;        \
  84         (node)->rb_left = NULL;         \
  85 } while (0)
  86 #define RB_CLEAR_ROOT(root)     ((root)->rb_node = NULL)
  87 #define rb_entry_crq(node)      rb_entry((node), struct cfq_rq, rb_node)
  88 #define rq_rb_key(rq)           (rq)->sector
  89
  90 static kmem_cache_t *crq_pool;
  91 static kmem_cache_t *cfq_pool;
  92 static kmem_cache_t *cfq_ioc_pool;
  93
  94 static atomic_t ioc_count = ATOMIC_INIT(0);
  95 static struct completion *ioc_gone;
  96
  97 #define CFQ_PRIO_LISTS          IOPRIO_BE_NR
  98 #define cfq_class_idle(cfqq)    ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
  99 #define cfq_class_be(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_BE)
 100 #define cfq_class_rt(cfqq)      ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
 101
 102 #define ASYNC                   (0)
 103 #define SYNC                    (1)
 104
 105 #define cfq_cfqq_dispatched(cfqq)       \
 106         ((cfqq)->on_dispatch[ASYNC] + (cfqq)->on_dispatch[SYNC])
 107
 108 #define cfq_cfqq_class_sync(cfqq)       ((cfqq)->key != CFQ_KEY_ASYNC)
 109
 110 #define cfq_cfqq_sync(cfqq)             \
 111         (cfq_cfqq_class_sync(cfqq) || (cfqq)->on_dispatch[SYNC])
 112
 113 /*
 114  * Per block device queue structure
 115  */
 116 struct cfq_data {
 117         request_queue_t *queue;
 118
 119         /*
 120          * rr list of queues with requests and the count of them
 121          */
 122         struct list_head rr_list[CFQ_PRIO_LISTS];
 123         struct list_head busy_rr;
 124         struct list_head cur_rr;
 125         struct list_head idle_rr;
 126         unsigned int busy_queues;
 127
 128         /*
 129          * non-ordered list of empty cfqq's
 130          */
 131         struct list_head empty_list;
 132
 133         /*
 134          * cfqq lookup hash
 135          */
 136         struct hlist_head *cfq_hash;
 137
 138         /*
 139          * global crq hash for all queues
 140          */
 141         struct hlist_head *crq_hash;
 142
 143         unsigned int max_queued;
 144
 145         mempool_t *crq_pool;
 146
 147         int rq_in_driver;
 148
 149         /*
 150          * schedule slice state info
 151          */
 152         /*
 153          * idle window management
 154          */
 155         struct timer_list idle_slice_timer;
 156         struct work_struct unplug_work;
 157
 158         struct cfq_queue *active_queue;
 159         struct cfq_io_context *active_cic;
 160         int cur_prio, cur_end_prio;
 161         unsigned int dispatch_slice;
 162
 163         struct timer_list idle_class_timer;
 164
 165         sector_t last_sector;
 166         unsigned long last_end_request;
 167
 168         unsigned int rq_starved;
 169
 170         /*
 171          * tunables, see top of file
 172          */
 173         unsigned int cfq_quantum;
 174         unsigned int cfq_queued;
 175         unsigned int cfq_fifo_expire[2];
 176         unsigned int cfq_back_penalty;
 177         unsigned int cfq_back_max;
 178         unsigned int cfq_slice[2];
 179         unsigned int cfq_slice_async_rq;
 180         unsigned int cfq_slice_idle;
 181         unsigned int cfq_max_depth;
 182
 183         struct list_head cic_list;
 184 };
 185
 186 /*
 187  * Per process-grouping structure
 188  */
 189 struct cfq_queue {
 190         /* reference count */
 191         atomic_t ref;
 192         /* parent cfq_data */
 193         struct cfq_data *cfqd;
 194         /* cfqq lookup hash */
 195         struct hlist_node cfq_hash;
 196         /* hash key */
 197         unsigned int key;
 198         /* on either rr or empty list of cfqd */
 199         struct list_head cfq_list;
 200         /* sorted list of pending requests */
 201         struct rb_root sort_list;
 202         /* if fifo isn't expired, next request to serve */
 203         struct cfq_rq *next_crq;
 204         /* requests queued in sort_list */
 205         int queued[2];
 206         /* currently allocated requests */
 207         int allocated[2];
 208         /* fifo list of requests in sort_list */
 209         struct list_head fifo;
 210
 211         unsigned long slice_start;
 212         unsigned long slice_end;
 213         unsigned long slice_left;
 214         unsigned long service_last;
 215
 216         /* number of requests that are on the dispatch list */
 217         int on_dispatch[2];
 218
 219         /* io prio of this group */
 220         unsigned short ioprio, org_ioprio;
 221         unsigned short ioprio_class, org_ioprio_class;
 222
 223         /* various state flags, see below */
 224         unsigned int flags;
 225 };
 226
 227 struct cfq_rq {
 228         struct rb_node rb_node;
 229         sector_t rb_key;
 230         struct request *request;
 231         struct hlist_node hash;
 232
 233         struct cfq_queue *cfq_queue;
 234         struct cfq_io_context *io_context;
 235
 236         unsigned int crq_flags;
 237 };
 238
 239 enum cfqq_state_flags {
 240         CFQ_CFQQ_FLAG_on_rr = 0,
 241         CFQ_CFQQ_FLAG_wait_request,
 242         CFQ_CFQQ_FLAG_must_alloc,
 243         CFQ_CFQQ_FLAG_must_alloc_slice,
 244         CFQ_CFQQ_FLAG_must_dispatch,
 245         CFQ_CFQQ_FLAG_fifo_expire,
 246         CFQ_CFQQ_FLAG_idle_window,
 247         CFQ_CFQQ_FLAG_prio_changed,
 248 };
 249
 250 #define CFQ_CFQQ_FNS(name)                                              \
 251 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
 252 {                                                                       \
 253         cfqq->flags |= (1 << CFQ_CFQQ_FLAG_##name);                     \
 254 }                                                                       \
 255 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
 256 {                                                                       \
 257         cfqq->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                    \
 258 }                                                                       \
 259 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
 260 {                                                                       \
 261         return (cfqq->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;        \
 262 }
 263
 264 CFQ_CFQQ_FNS(on_rr);
 265 CFQ_CFQQ_FNS(wait_request);
 266 CFQ_CFQQ_FNS(must_alloc);
 267 CFQ_CFQQ_FNS(must_alloc_slice);
 268 CFQ_CFQQ_FNS(must_dispatch);
 269 CFQ_CFQQ_FNS(fifo_expire);
 270 CFQ_CFQQ_FNS(idle_window);
 271 CFQ_CFQQ_FNS(prio_changed);
 272 #undef CFQ_CFQQ_FNS
 273
 274 enum cfq_rq_state_flags {
 275         CFQ_CRQ_FLAG_is_sync = 0,
 276 };
 277
 278 #define CFQ_CRQ_FNS(name)                                               \
 279 static inline void cfq_mark_crq_##name(struct cfq_rq *crq)              \
 280 {                                                                       \
 281         crq->crq_flags |= (1 << CFQ_CRQ_FLAG_##name);                   \
 282 }                                                                       \
 283 static inline void cfq_clear_crq_##name(struct cfq_rq *crq)             \
 284 {                                                                       \
 285         crq->crq_flags &= ~(1 << CFQ_CRQ_FLAG_##name);                  \
 286 }                                                                       \
 287 static inline int cfq_crq_##name(const struct cfq_rq *crq)              \
 288 {                                                                       \
 289         return (crq->crq_flags & (1 << CFQ_CRQ_FLAG_##name)) != 0;      \
 290 }
 291
 292 CFQ_CRQ_FNS(is_sync);
 293 #undef CFQ_CRQ_FNS
 294
 295 static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short);
 296 static void cfq_dispatch_insert(request_queue_t *, struct cfq_rq *);
 297 static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk, gfp_t gfp_mask);
 298
 299 #define process_sync(tsk)       ((tsk)->flags & PF_SYNCWRITE)
 300
 301 /*
 302  * lots of deadline iosched dupes, can be abstracted later...
 303  */
 304 static inline void cfq_del_crq_hash(struct cfq_rq *crq)
 305 {
 306         hlist_del_init(&crq->hash);
 307 }
 308
 309 static inline void cfq_add_crq_hash(struct cfq_data *cfqd, struct cfq_rq *crq)
 310 {
 311         const int hash_idx = CFQ_MHASH_FN(rq_hash_key(crq->request));
 312
 313         hlist_add_head(&crq->hash, &cfqd->crq_hash[hash_idx]);
 314 }
 315
 316 static struct request *cfq_find_rq_hash(struct cfq_data *cfqd, sector_t offset)
 317 {
 318         struct hlist_head *hash_list = &cfqd->crq_hash[CFQ_MHASH_FN(offset)];
 319         struct hlist_node *entry, *next;
 320
 321         hlist_for_each_safe(entry, next, hash_list) {
 322                 struct cfq_rq *crq = list_entry_hash(entry);
 323                 struct request *__rq = crq->request;
 324
 325                 if (!rq_mergeable(__rq)) {
 326                         cfq_del_crq_hash(crq);
 327                         continue;
 328                 }
 329
 330                 if (rq_hash_key(__rq) == offset)
 331                         return __rq;
 332         }
 333
 334         return NULL;
 335 }
 336
 337 /*
 338  * scheduler run of queue, if there are requests pending and no one in the
 339  * driver that will restart queueing
 340  */
 341 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
 342 {
 343         if (cfqd->busy_queues)
 344                 kblockd_schedule_work(&cfqd->unplug_work);
 345 }
 346
 347 static int cfq_queue_empty(request_queue_t *q)
 348 {
 349         struct cfq_data *cfqd = q->elevator->elevator_data;
 350
 351         return !cfqd->busy_queues;
 352 }
 353
 354 /*
 355  * Lifted from AS - choose which of crq1 and crq2 that is best served now.
 356  * We choose the request that is closest to the head right now. Distance
 357  * behind the head are penalized and only allowed to a certain extent.
 358  */
 359 static struct cfq_rq *
 360 cfq_choose_req(struct cfq_data *cfqd, struct cfq_rq *crq1, struct cfq_rq *crq2)
 361 {
 362         sector_t last, s1, s2, d1 = 0, d2 = 0;
 363         int r1_wrap = 0, r2_wrap = 0;   /* requests are behind the disk head */
 364         unsigned long back_max;
 365
 366         if (crq1 == NULL || crq1 == crq2)
 367                 return crq2;
 368         if (crq2 == NULL)
 369                 return crq1;
 370
 371         if (cfq_crq_is_sync(crq1) && !cfq_crq_is_sync(crq2))
 372                 return crq1;
 373         else if (cfq_crq_is_sync(crq2) && !cfq_crq_is_sync(crq1))
 374                 return crq2;
 375
 376         s1 = crq1->request->sector;
 377         s2 = crq2->request->sector;
 378
 379         last = cfqd->last_sector;
 380
 381         /*
 382          * by definition, 1KiB is 2 sectors
 383          */
 384         back_max = cfqd->cfq_back_max * 2;
 385
 386         /*
 387          * Strict one way elevator _except_ in the case where we allow
 388          * short backward seeks which are biased as twice the cost of a
 389          * similar forward seek.
 390          */
 391         if (s1 >= last)
 392                 d1 = s1 - last;
 393         else if (s1 + back_max >= last)
 394                 d1 = (last - s1) * cfqd->cfq_back_penalty;
 395         else
 396                 r1_wrap = 1;
 397
 398         if (s2 >= last)
 399                 d2 = s2 - last;
 400         else if (s2 + back_max >= last)
 401                 d2 = (last - s2) * cfqd->cfq_back_penalty;
 402         else
 403                 r2_wrap = 1;
 404
 405         /* Found required data */
 406         if (!r1_wrap && r2_wrap)
 407                 return crq1;
 408         else if (!r2_wrap && r1_wrap)
 409                 return crq2;
 410         else if (r1_wrap && r2_wrap) {
 411                 /* both behind the head */
 412                 if (s1 <= s2)
 413                         return crq1;
 414                 else
 415                         return crq2;
 416         }
 417
 418         /* Both requests in front of the head */
 419         if (d1 < d2)
 420                 return crq1;
 421         else if (d2 < d1)
 422                 return crq2;
 423         else {
 424                 if (s1 >= s2)
 425                         return crq1;
 426                 else
 427                         return crq2;
 428         }
 429 }
 430
 431 /*
 432  * would be nice to take fifo expire time into account as well
 433  */
 434 static struct cfq_rq *
 435 cfq_find_next_crq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 436                   struct cfq_rq *last)
 437 {
 438         struct cfq_rq *crq_next = NULL, *crq_prev = NULL;
 439         struct rb_node *rbnext, *rbprev;
 440
 441         if (!(rbnext = rb_next(&last->rb_node))) {
 442                 rbnext = rb_first(&cfqq->sort_list);
 443                 if (rbnext == &last->rb_node)
 444                         rbnext = NULL;
 445         }
 446
 447         rbprev = rb_prev(&last->rb_node);
 448
 449         if (rbprev)
 450                 crq_prev = rb_entry_crq(rbprev);
 451         if (rbnext)
 452                 crq_next = rb_entry_crq(rbnext);
 453
 454         return cfq_choose_req(cfqd, crq_next, crq_prev);
 455 }
 456
 457 static void cfq_update_next_crq(struct cfq_rq *crq)
 458 {
 459         struct cfq_queue *cfqq = crq->cfq_queue;
 460
 461         if (cfqq->next_crq == crq)
 462                 cfqq->next_crq = cfq_find_next_crq(cfqq->cfqd, cfqq, crq);
 463 }
 464
 465 static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
 466 {
 467         struct cfq_data *cfqd = cfqq->cfqd;
 468         struct list_head *list, *entry;
 469
 470         BUG_ON(!cfq_cfqq_on_rr(cfqq));
 471
 472         list_del(&cfqq->cfq_list);
 473
 474         if (cfq_class_rt(cfqq))
 475                 list = &cfqd->cur_rr;
 476         else if (cfq_class_idle(cfqq))
 477                 list = &cfqd->idle_rr;
 478         else {
 479                 /*
 480                  * if cfqq has requests in flight, don't allow it to be
 481                  * found in cfq_set_active_queue before it has finished them.
 482                  * this is done to increase fairness between a process that
 483                  * has lots of io pending vs one that only generates one
 484                  * sporadically or synchronously
 485                  */
 486                 if (cfq_cfqq_dispatched(cfqq))
 487                         list = &cfqd->busy_rr;
 488                 else
 489                         list = &cfqd->rr_list[cfqq->ioprio];
 490         }
 491
 492         /*
 493          * if queue was preempted, just add to front to be fair. busy_rr
 494          * isn't sorted.
 495          */
 496         if (preempted || list == &cfqd->busy_rr) {
 497                 list_add(&cfqq->cfq_list, list);
 498                 return;
 499         }
 500
 501         /*
 502          * sort by when queue was last serviced
 503          */
 504         entry = list;
 505         while ((entry = entry->prev) != list) {
 506                 struct cfq_queue *__cfqq = list_entry_cfqq(entry);
 507
 508                 if (!__cfqq->service_last)
 509                         break;
 510                 if (time_before(__cfqq->service_last, cfqq->service_last))
 511                         break;
 512         }
 513
 514         list_add(&cfqq->cfq_list, entry);
 515 }
 516
 517 /*
 518  * add to busy list of queues for service, trying to be fair in ordering
 519  * the pending list according to last request service
 520  */
 521 static inline void
 522 cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 523 {
 524         BUG_ON(cfq_cfqq_on_rr(cfqq));
 525         cfq_mark_cfqq_on_rr(cfqq);
 526         cfqd->busy_queues++;
 527
 528         cfq_resort_rr_list(cfqq, 0);
 529 }
 530
 531 static inline void
 532 cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 533 {
 534         BUG_ON(!cfq_cfqq_on_rr(cfqq));
 535         cfq_clear_cfqq_on_rr(cfqq);
 536         list_move(&cfqq->cfq_list, &cfqd->empty_list);
 537
 538         BUG_ON(!cfqd->busy_queues);
 539         cfqd->busy_queues--;
 540 }
 541
 542 /*
 543  * rb tree support functions
 544  */
 545 static inline void cfq_del_crq_rb(struct cfq_rq *crq)
 546 {
 547         struct cfq_queue *cfqq = crq->cfq_queue;
 548         struct cfq_data *cfqd = cfqq->cfqd;
 549         const int sync = cfq_crq_is_sync(crq);
 550
 551         BUG_ON(!cfqq->queued[sync]);
 552         cfqq->queued[sync]--;
 553
 554         cfq_update_next_crq(crq);
 555
 556         rb_erase(&crq->rb_node, &cfqq->sort_list);
 557         RB_CLEAR_COLOR(&crq->rb_node);
 558
 559         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY(&cfqq->sort_list))
 560                 cfq_del_cfqq_rr(cfqd, cfqq);
 561 }
 562
 563 static struct cfq_rq *
 564 __cfq_add_crq_rb(struct cfq_rq *crq)
 565 {
 566         struct rb_node **p = &crq->cfq_queue->sort_list.rb_node;
 567         struct rb_node *parent = NULL;
 568         struct cfq_rq *__crq;
 569
 570         while (*p) {
 571                 parent = *p;
 572                 __crq = rb_entry_crq(parent);
 573
 574                 if (crq->rb_key < __crq->rb_key)
 575                         p = &(*p)->rb_left;
 576                 else if (crq->rb_key > __crq->rb_key)
 577                         p = &(*p)->rb_right;
 578                 else
 579                         return __crq;
 580         }
 581
 582         rb_link_node(&crq->rb_node, parent, p);
 583         return NULL;
 584 }
 585
 586 static void cfq_add_crq_rb(struct cfq_rq *crq)
 587 {
 588         struct cfq_queue *cfqq = crq->cfq_queue;
 589         struct cfq_data *cfqd = cfqq->cfqd;
 590         struct request *rq = crq->request;
 591         struct cfq_rq *__alias;
 592
 593         crq->rb_key = rq_rb_key(rq);
 594         cfqq->queued[cfq_crq_is_sync(crq)]++;
 595
 596         /*
 597          * looks a little odd, but the first insert might return an alias.
 598          * if that happens, put the alias on the dispatch list
 599          */
 600         while ((__alias = __cfq_add_crq_rb(crq)) != NULL)
 601                 cfq_dispatch_insert(cfqd->queue, __alias);
 602
 603         rb_insert_color(&crq->rb_node, &cfqq->sort_list);
 604
 605         if (!cfq_cfqq_on_rr(cfqq))
 606                 cfq_add_cfqq_rr(cfqd, cfqq);
 607
 608         /*
 609          * check if this request is a better next-serve candidate
 610          */
 611         cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
 612 }
 613
 614 static inline void
 615 cfq_reposition_crq_rb(struct cfq_queue *cfqq, struct cfq_rq *crq)
 616 {
 617         rb_erase(&crq->rb_node, &cfqq->sort_list);
 618         cfqq->queued[cfq_crq_is_sync(crq)]--;
 619
 620         cfq_add_crq_rb(crq);
 621 }
 622
 623 static struct request *cfq_find_rq_rb(struct cfq_data *cfqd, sector_t sector)
 624
 625 {
 626         struct cfq_queue *cfqq = cfq_find_cfq_hash(cfqd, current->pid, CFQ_KEY_ANY);
 627         struct rb_node *n;
 628
 629         if (!cfqq)
 630                 goto out;
 631
 632         n = cfqq->sort_list.rb_node;
 633         while (n) {
 634                 struct cfq_rq *crq = rb_entry_crq(n);
 635
 636                 if (sector < crq->rb_key)
 637                         n = n->rb_left;
 638                 else if (sector > crq->rb_key)
 639                         n = n->rb_right;
 640                 else
 641                         return crq->request;
 642         }
 643
 644 out:
 645         return NULL;
 646 }
 647
 648 static void cfq_activate_request(request_queue_t *q, struct request *rq)
 649 {
 650         struct cfq_data *cfqd = q->elevator->elevator_data;
 651
 652         cfqd->rq_in_driver++;
 653 }
 654
 655 static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
 656 {
 657         struct cfq_data *cfqd = q->elevator->elevator_data;
 658
 659         WARN_ON(!cfqd->rq_in_driver);
 660         cfqd->rq_in_driver--;
 661 }
 662
 663 static void cfq_remove_request(struct request *rq)
 664 {
 665         struct cfq_rq *crq = RQ_DATA(rq);
 666
 667         list_del_init(&rq->queuelist);
 668         cfq_del_crq_rb(crq);
 669         cfq_del_crq_hash(crq);
 670 }
 671
 672 static int
 673 cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
 674 {
 675         struct cfq_data *cfqd = q->elevator->elevator_data;
 676         struct request *__rq;
 677         int ret;
 678
 679         __rq = cfq_find_rq_hash(cfqd, bio->bi_sector);
 680         if (__rq && elv_rq_merge_ok(__rq, bio)) {
 681                 ret = ELEVATOR_BACK_MERGE;
 682                 goto out;
 683         }
 684
 685         __rq = cfq_find_rq_rb(cfqd, bio->bi_sector + bio_sectors(bio));
 686         if (__rq && elv_rq_merge_ok(__rq, bio)) {
 687                 ret = ELEVATOR_FRONT_MERGE;
 688                 goto out;
 689         }
 690
 691         return ELEVATOR_NO_MERGE;
 692 out:
 693         *req = __rq;
 694         return ret;
 695 }
 696
 697 static void cfq_merged_request(request_queue_t *q, struct request *req)
 698 {
 699         struct cfq_data *cfqd = q->elevator->elevator_data;
 700         struct cfq_rq *crq = RQ_DATA(req);
 701
 702         cfq_del_crq_hash(crq);
 703         cfq_add_crq_hash(cfqd, crq);
 704
 705         if (rq_rb_key(req) != crq->rb_key) {
 706                 struct cfq_queue *cfqq = crq->cfq_queue;
 707
 708                 cfq_update_next_crq(crq);
 709                 cfq_reposition_crq_rb(cfqq, crq);
 710         }
 711 }
 712
 713 static void
 714 cfq_merged_requests(request_queue_t *q, struct request *rq,
 715                     struct request *next)
 716 {
 717         cfq_merged_request(q, rq);
 718
 719         /*
 720          * reposition in fifo if next is older than rq
 721          */
 722         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
 723             time_before(next->start_time, rq->start_time))
 724                 list_move(&rq->queuelist, &next->queuelist);
 725
 726         cfq_remove_request(next);
 727 }
 728
 729 static inline void
 730 __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 731 {
 732         if (cfqq) {
 733                 /*
 734                  * stop potential idle class queues waiting service
 735                  */
 736                 del_timer(&cfqd->idle_class_timer);
 737
 738                 cfqq->slice_start = jiffies;
 739                 cfqq->slice_end = 0;
 740                 cfqq->slice_left = 0;
 741                 cfq_clear_cfqq_must_alloc_slice(cfqq);
 742                 cfq_clear_cfqq_fifo_expire(cfqq);
 743         }
 744
 745         cfqd->active_queue = cfqq;
 746 }
 747
 748 /*
 749  * current cfqq expired its slice (or was too idle), select new one
 750  */
 751 static void
 752 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 753                     int preempted)
 754 {
 755         unsigned long now = jiffies;
 756
 757         if (cfq_cfqq_wait_request(cfqq))
 758                 del_timer(&cfqd->idle_slice_timer);
 759
 760         if (!preempted && !cfq_cfqq_dispatched(cfqq)) {
 761                 cfqq->service_last = now;
 762                 cfq_schedule_dispatch(cfqd);
 763         }
 764
 765         cfq_clear_cfqq_must_dispatch(cfqq);
 766         cfq_clear_cfqq_wait_request(cfqq);
 767
 768         /*
 769          * store what was left of this slice, if the queue idled out
 770          * or was preempted
 771          */
 772         if (time_after(cfqq->slice_end, now))
 773                 cfqq->slice_left = cfqq->slice_end - now;
 774         else
 775                 cfqq->slice_left = 0;
 776
 777         if (cfq_cfqq_on_rr(cfqq))
 778                 cfq_resort_rr_list(cfqq, preempted);
 779
 780         if (cfqq == cfqd->active_queue)
 781                 cfqd->active_queue = NULL;
 782
 783         if (cfqd->active_cic) {
 784                 put_io_context(cfqd->active_cic->ioc);
 785                 cfqd->active_cic = NULL;
 786         }
 787
 788         cfqd->dispatch_slice = 0;
 789 }
 790
 791 static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted)
 792 {
 793         struct cfq_queue *cfqq = cfqd->active_queue;
 794
 795         if (cfqq)
 796                 __cfq_slice_expired(cfqd, cfqq, preempted);
 797 }
 798
 799 /*
 800  * 0
 801  * 0,1
 802  * 0,1,2
 803  * 0,1,2,3
 804  * 0,1,2,3,4
 805  * 0,1,2,3,4,5
 806  * 0,1,2,3,4,5,6
 807  * 0,1,2,3,4,5,6,7
 808  */
 809 static int cfq_get_next_prio_level(struct cfq_data *cfqd)
 810 {
 811         int prio, wrap;
 812
 813         prio = -1;
 814         wrap = 0;
 815         do {
 816                 int p;
 817
 818                 for (p = cfqd->cur_prio; p <= cfqd->cur_end_prio; p++) {
 819                         if (!list_empty(&cfqd->rr_list[p])) {
 820                                 prio = p;
 821                                 break;
 822                         }
 823                 }
 824
 825                 if (prio != -1)
 826                         break;
 827                 cfqd->cur_prio = 0;
 828                 if (++cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
 829                         cfqd->cur_end_prio = 0;
 830                         if (wrap)
 831                                 break;
 832                         wrap = 1;
 833                 }
 834         } while (1);
 835
 836         if (unlikely(prio == -1))
 837                 return -1;
 838
 839         BUG_ON(prio >= CFQ_PRIO_LISTS);
 840
 841         list_splice_init(&cfqd->rr_list[prio], &cfqd->cur_rr);
 842
 843         cfqd->cur_prio = prio + 1;
 844         if (cfqd->cur_prio > cfqd->cur_end_prio) {
 845                 cfqd->cur_end_prio = cfqd->cur_prio;
 846                 cfqd->cur_prio = 0;
 847         }
 848         if (cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
 849                 cfqd->cur_prio = 0;
 850                 cfqd->cur_end_prio = 0;
 851         }
 852
 853         return prio;
 854 }
 855
 856 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
 857 {
 858         struct cfq_queue *cfqq = NULL;
 859
 860         /*
 861          * if current list is non-empty, grab first entry. if it is empty,
 862          * get next prio level and grab first entry then if any are spliced
 863          */
 864         if (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1)
 865                 cfqq = list_entry_cfqq(cfqd->cur_rr.next);
 866
 867         /*
 868          * if we have idle queues and no rt or be queues had pending
 869          * requests, either allow immediate service if the grace period
 870          * has passed or arm the idle grace timer
 871          */
 872         if (!cfqq && !list_empty(&cfqd->idle_rr)) {
 873                 unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE;
 874
 875                 if (time_after_eq(jiffies, end))
 876                         cfqq = list_entry_cfqq(cfqd->idle_rr.next);
 877                 else
 878                         mod_timer(&cfqd->idle_class_timer, end);
 879         }
 880
 881         __cfq_set_active_queue(cfqd, cfqq);
 882         return cfqq;
 883 }
 884
 885 static int cfq_arm_slice_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 886
 887 {
 888         unsigned long sl;
 889
 890         WARN_ON(!RB_EMPTY(&cfqq->sort_list));
 891         WARN_ON(cfqq != cfqd->active_queue);
 892
 893         /*
 894          * idle is disabled, either manually or by past process history
 895          */
 896         if (!cfqd->cfq_slice_idle)
 897                 return 0;
 898         if (!cfq_cfqq_idle_window(cfqq))
 899                 return 0;
 900         /*
 901          * task has exited, don't wait
 902          */
 903         if (cfqd->active_cic && !cfqd->active_cic->ioc->task)
 904                 return 0;
 905
 906         cfq_mark_cfqq_must_dispatch(cfqq);
 907         cfq_mark_cfqq_wait_request(cfqq);
 908
 909         sl = min(cfqq->slice_end - 1, (unsigned long) cfqd->cfq_slice_idle);
 910         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
 911         return 1;
 912 }
 913
 914 static void cfq_dispatch_insert(request_queue_t *q, struct cfq_rq *crq)
 915 {
 916         struct cfq_data *cfqd = q->elevator->elevator_data;
 917         struct cfq_queue *cfqq = crq->cfq_queue;
 918
 919         cfqq->next_crq = cfq_find_next_crq(cfqd, cfqq, crq);
 920         cfq_remove_request(crq->request);
 921         cfqq->on_dispatch[cfq_crq_is_sync(crq)]++;
 922         elv_dispatch_sort(q, crq->request);
 923 }
 924
 925 /*
 926  * return expired entry, or NULL to just start from scratch in rbtree
 927  */
 928 static inline struct cfq_rq *cfq_check_fifo(struct cfq_queue *cfqq)
 929 {
 930         struct cfq_data *cfqd = cfqq->cfqd;
 931         struct request *rq;
 932         struct cfq_rq *crq;
 933
 934         if (cfq_cfqq_fifo_expire(cfqq))
 935                 return NULL;
 936
 937         if (!list_empty(&cfqq->fifo)) {
 938                 int fifo = cfq_cfqq_class_sync(cfqq);
 939
 940                 crq = RQ_DATA(list_entry_fifo(cfqq->fifo.next));
 941                 rq = crq->request;
 942                 if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo])) {
 943                         cfq_mark_cfqq_fifo_expire(cfqq);
 944                         return crq;
 945                 }
 946         }
 947
 948         return NULL;
 949 }
 950
 951 /*
 952  * Scale schedule slice based on io priority. Use the sync time slice only
 953  * if a queue is marked sync and has sync io queued. A sync queue with async
 954  * io only, should not get full sync slice length.
 955  */
 956 static inline int
 957 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 958 {
 959         const int base_slice = cfqd->cfq_slice[cfq_cfqq_sync(cfqq)];
 960
 961         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
 962
 963         return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - cfqq->ioprio));
 964 }
 965
 966 static inline void
 967 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 968 {
 969         cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
 970 }
 971
 972 static inline int
 973 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 974 {
 975         const int base_rq = cfqd->cfq_slice_async_rq;
 976
 977         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
 978
 979         return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
 980 }
 981
 982 /*
 983  * get next queue for service
 984  */
 985 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
 986 {
 987         unsigned long now = jiffies;
 988         struct cfq_queue *cfqq;
 989
 990         cfqq = cfqd->active_queue;
 991         if (!cfqq)
 992                 goto new_queue;
 993
 994         /*
 995          * slice has expired
 996          */
 997         if (!cfq_cfqq_must_dispatch(cfqq) && time_after(now, cfqq->slice_end))
 998                 goto expire;
 999
1000         /*
1001          * if queue has requests, dispatch one. if not, check if
1002          * enough slice is left to wait for one
1003          */
1004         if (!RB_EMPTY(&cfqq->sort_list))
1005                 goto keep_queue;
1006         else if (cfq_cfqq_class_sync(cfqq) &&
1007                  time_before(now, cfqq->slice_end)) {
1008                 if (cfq_arm_slice_timer(cfqd, cfqq))
1009                         return NULL;
1010         }
1011
1012 expire:
1013         cfq_slice_expired(cfqd, 0);
1014 new_queue:
1015         cfqq = cfq_set_active_queue(cfqd);
1016 keep_queue:
1017         return cfqq;
1018 }
1019
1020 static int
1021 __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1022                         int max_dispatch)
1023 {
1024         int dispatched = 0;
1025
1026         BUG_ON(RB_EMPTY(&cfqq->sort_list));
1027
1028         do {
1029                 struct cfq_rq *crq;
1030
1031                 /*
1032                  * follow expired path, else get first next available
1033                  */
1034                 if ((crq = cfq_check_fifo(cfqq)) == NULL)
1035                         crq = cfqq->next_crq;
1036
1037                 /*
1038                  * finally, insert request into driver dispatch list
1039                  */
1040                 cfq_dispatch_insert(cfqd->queue, crq);
1041
1042                 cfqd->dispatch_slice++;
1043                 dispatched++;
1044
1045                 if (!cfqd->active_cic) {
1046                         atomic_inc(&crq->io_context->ioc->refcount);
1047                         cfqd->active_cic = crq->io_context;
1048                 }
1049
1050                 if (RB_EMPTY(&cfqq->sort_list))
1051                         break;
1052
1053         } while (dispatched < max_dispatch);
1054
1055         /*
1056          * if slice end isn't set yet, set it. if at least one request was
1057          * sync, use the sync time slice value
1058          */
1059         if (!cfqq->slice_end)
1060                 cfq_set_prio_slice(cfqd, cfqq);
1061
1062         /*
1063          * expire an async queue immediately if it has used up its slice. idle
1064          * queue always expire after 1 dispatch round.
1065          */
1066         if ((!cfq_cfqq_sync(cfqq) &&
1067             cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1068             cfq_class_idle(cfqq))
1069                 cfq_slice_expired(cfqd, 0);
1070
1071         return dispatched;
1072 }
1073
1074 static int
1075 cfq_forced_dispatch_cfqqs(struct list_head *list)
1076 {
1077         int dispatched = 0;
1078         struct cfq_queue *cfqq, *next;
1079         struct cfq_rq *crq;
1080
1081         list_for_each_entry_safe(cfqq, next, list, cfq_list) {
1082                 while ((crq = cfqq->next_crq)) {
1083                         cfq_dispatch_insert(cfqq->cfqd->queue, crq);
1084                         dispatched++;
1085                 }
1086                 BUG_ON(!list_empty(&cfqq->fifo));
1087         }
1088         return dispatched;
1089 }
1090
1091 static int
1092 cfq_forced_dispatch(struct cfq_data *cfqd)
1093 {
1094         int i, dispatched = 0;
1095
1096         for (i = 0; i < CFQ_PRIO_LISTS; i++)
1097                 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]);
1098
1099         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->busy_rr);
1100         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr);
1101         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr);
1102
1103         cfq_slice_expired(cfqd, 0);
1104
1105         BUG_ON(cfqd->busy_queues);
1106
1107         return dispatched;
1108 }
1109
1110 static int
1111 cfq_dispatch_requests(request_queue_t *q, int force)
1112 {
1113         struct cfq_data *cfqd = q->elevator->elevator_data;
1114         struct cfq_queue *cfqq;
1115
1116         if (!cfqd->busy_queues)
1117                 return 0;
1118
1119         if (unlikely(force))
1120                 return cfq_forced_dispatch(cfqd);
1121
1122         cfqq = cfq_select_queue(cfqd);
1123         if (cfqq) {
1124                 int max_dispatch;
1125
1126                 /*
1127                  * if idle window is disabled, allow queue buildup
1128                  */
1129                 if (!cfq_cfqq_idle_window(cfqq) &&
1130                     cfqd->rq_in_driver >= cfqd->cfq_max_depth)
1131                         return 0;
1132
1133                 cfq_clear_cfqq_must_dispatch(cfqq);
1134                 cfq_clear_cfqq_wait_request(cfqq);
1135                 del_timer(&cfqd->idle_slice_timer);
1136
1137                 max_dispatch = cfqd->cfq_quantum;
1138                 if (cfq_class_idle(cfqq))
1139                         max_dispatch = 1;
1140
1141                 return __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
1142         }
1143
1144         return 0;
1145 }
1146
1147 /*
1148  * task holds one reference to the queue, dropped when task exits. each crq
1149  * in-flight on this queue also holds a reference, dropped when crq is freed.
1150  *
1151  * queue lock must be held here.
1152  */
1153 static void cfq_put_queue(struct cfq_queue *cfqq)
1154 {
1155         struct cfq_data *cfqd = cfqq->cfqd;
1156
1157         BUG_ON(atomic_read(&cfqq->ref) <= 0);
1158
1159         if (!atomic_dec_and_test(&cfqq->ref))
1160                 return;
1161
1162         BUG_ON(rb_first(&cfqq->sort_list));
1163         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1164         BUG_ON(cfq_cfqq_on_rr(cfqq));
1165
1166         if (unlikely(cfqd->active_queue == cfqq))
1167                 __cfq_slice_expired(cfqd, cfqq, 0);
1168
1169         /*
1170          * it's on the empty list and still hashed
1171          */
1172         list_del(&cfqq->cfq_list);
1173         hlist_del(&cfqq->cfq_hash);
1174         kmem_cache_free(cfq_pool, cfqq);
1175 }
1176
1177 static inline struct cfq_queue *
1178 __cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned int prio,
1179                     const int hashval)
1180 {
1181         struct hlist_head *hash_list = &cfqd->cfq_hash[hashval];
1182         struct hlist_node *entry, *next;
1183
1184         hlist_for_each_safe(entry, next, hash_list) {
1185                 struct cfq_queue *__cfqq = list_entry_qhash(entry);
1186                 const unsigned short __p = IOPRIO_PRIO_VALUE(__cfqq->org_ioprio_class, __cfqq->org_ioprio);
1187
1188                 if (__cfqq->key == key && (__p == prio || prio == CFQ_KEY_ANY))
1189                         return __cfqq;
1190         }
1191
1192         return NULL;
1193 }
1194
1195 static struct cfq_queue *
1196 cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned short prio)
1197 {
1198         return __cfq_find_cfq_hash(cfqd, key, prio, hash_long(key, CFQ_QHASH_SHIFT));
1199 }
1200
1201 static void cfq_free_io_context(struct cfq_io_context *cic)
1202 {
1203         struct cfq_io_context *__cic;
1204         struct list_head *entry, *next;
1205         int freed = 1;
1206
1207         list_for_each_safe(entry, next, &cic->list) {
1208                 __cic = list_entry(entry, struct cfq_io_context, list);
1209                 kmem_cache_free(cfq_ioc_pool, __cic);
1210                 freed++;
1211         }
1212
1213         kmem_cache_free(cfq_ioc_pool, cic);
1214         if (atomic_sub_and_test(freed, &ioc_count) && ioc_gone)
1215                 complete(ioc_gone);
1216 }
1217
1218 static void cfq_trim(struct io_context *ioc)
1219 {
1220         ioc->set_ioprio = NULL;
1221         if (ioc->cic)
1222                 cfq_free_io_context(ioc->cic);
1223 }
1224
1225 /*
1226  * Called with interrupts disabled
1227  */
1228 static void cfq_exit_single_io_context(struct cfq_io_context *cic)
1229 {
1230         struct cfq_data *cfqd = cic->key;
1231         request_queue_t *q;
1232
1233         if (!cfqd)
1234                 return;
1235
1236         q = cfqd->queue;
1237
1238         WARN_ON(!irqs_disabled());
1239
1240         spin_lock(q->queue_lock);
1241
1242         if (cic->cfqq[ASYNC]) {
1243                 if (unlikely(cic->cfqq[ASYNC] == cfqd->active_queue))
1244                         __cfq_slice_expired(cfqd, cic->cfqq[ASYNC], 0);
1245                 cfq_put_queue(cic->cfqq[ASYNC]);
1246                 cic->cfqq[ASYNC] = NULL;
1247         }
1248
1249         if (cic->cfqq[SYNC]) {
1250                 if (unlikely(cic->cfqq[SYNC] == cfqd->active_queue))
1251                         __cfq_slice_expired(cfqd, cic->cfqq[SYNC], 0);
1252                 cfq_put_queue(cic->cfqq[SYNC]);
1253                 cic->cfqq[SYNC] = NULL;
1254         }
1255
1256         cic->key = NULL;
1257         list_del_init(&cic->queue_list);
1258         spin_unlock(q->queue_lock);
1259 }
1260
1261 /*
1262  * Another task may update the task cic list, if it is doing a queue lookup
1263  * on its behalf. cfq_cic_lock excludes such concurrent updates
1264  */
1265 static void cfq_exit_io_context(struct cfq_io_context *cic)
1266 {
1267         struct cfq_io_context *__cic;
1268         struct list_head *entry;
1269         unsigned long flags;
1270
1271         local_irq_save(flags);
1272
1273         /*
1274          * put the reference this task is holding to the various queues
1275          */
1276         read_lock(&cfq_exit_lock);
1277         list_for_each(entry, &cic->list) {
1278                 __cic = list_entry(entry, struct cfq_io_context, list);
1279                 cfq_exit_single_io_context(__cic);
1280         }
1281
1282         cfq_exit_single_io_context(cic);
1283         read_unlock(&cfq_exit_lock);
1284         local_irq_restore(flags);
1285 }
1286
1287 static struct cfq_io_context *
1288 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1289 {
1290         struct cfq_io_context *cic = kmem_cache_alloc(cfq_ioc_pool, gfp_mask);
1291
1292         if (cic) {
1293                 INIT_LIST_HEAD(&cic->list);
1294                 cic->cfqq[ASYNC] = NULL;
1295                 cic->cfqq[SYNC] = NULL;
1296                 cic->key = NULL;
1297                 cic->last_end_request = jiffies;
1298                 cic->ttime_total = 0;
1299                 cic->ttime_samples = 0;
1300                 cic->ttime_mean = 0;
1301                 cic->dtor = cfq_free_io_context;
1302                 cic->exit = cfq_exit_io_context;
1303                 INIT_LIST_HEAD(&cic->queue_list);
1304                 atomic_inc(&ioc_count);
1305         }
1306
1307         return cic;
1308 }
1309
1310 static void cfq_init_prio_data(struct cfq_queue *cfqq)
1311 {
1312         struct task_struct *tsk = current;
1313         int ioprio_class;
1314
1315         if (!cfq_cfqq_prio_changed(cfqq))
1316                 return;
1317
1318         ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
1319         switch (ioprio_class) {
1320                 default:
1321                         printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1322                 case IOPRIO_CLASS_NONE:
1323                         /*
1324                          * no prio set, place us in the middle of the BE classes
1325                          */
1326                         cfqq->ioprio = task_nice_ioprio(tsk);
1327                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1328                         break;
1329                 case IOPRIO_CLASS_RT:
1330                         cfqq->ioprio = task_ioprio(tsk);
1331                         cfqq->ioprio_class = IOPRIO_CLASS_RT;
1332                         break;
1333                 case IOPRIO_CLASS_BE:
1334                         cfqq->ioprio = task_ioprio(tsk);
1335                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1336                         break;
1337                 case IOPRIO_CLASS_IDLE:
1338                         cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1339                         cfqq->ioprio = 7;
1340                         cfq_clear_cfqq_idle_window(cfqq);
1341                         break;
1342         }
1343
1344         /*
1345          * keep track of original prio settings in case we have to temporarily
1346          * elevate the priority of this queue
1347          */
1348         cfqq->org_ioprio = cfqq->ioprio;
1349         cfqq->org_ioprio_class = cfqq->ioprio_class;
1350
1351         if (cfq_cfqq_on_rr(cfqq))
1352                 cfq_resort_rr_list(cfqq, 0);
1353
1354         cfq_clear_cfqq_prio_changed(cfqq);
1355 }
1356
1357 static inline void changed_ioprio(struct cfq_io_context *cic)
1358 {
1359         struct cfq_data *cfqd = cic->key;
1360         struct cfq_queue *cfqq;
1361         if (cfqd) {
1362                 spin_lock(cfqd->queue->queue_lock);
1363                 cfqq = cic->cfqq[ASYNC];
1364                 if (cfqq) {
1365                         struct cfq_queue *new_cfqq;
1366                         new_cfqq = cfq_get_queue(cfqd, CFQ_KEY_ASYNC,
1367                                                 cic->ioc->task, GFP_ATOMIC);
1368                         if (new_cfqq) {
1369                                 cic->cfqq[ASYNC] = new_cfqq;
1370                                 cfq_put_queue(cfqq);
1371                         }
1372                 }
1373                 cfqq = cic->cfqq[SYNC];
1374                 if (cfqq) {
1375                         cfq_mark_cfqq_prio_changed(cfqq);
1376                         cfq_init_prio_data(cfqq);
1377                 }
1378                 spin_unlock(cfqd->queue->queue_lock);
1379         }
1380 }
1381
1382 /*
1383  * callback from sys_ioprio_set, irqs are disabled
1384  */
1385 static int cfq_ioc_set_ioprio(struct io_context *ioc, unsigned int ioprio)
1386 {
1387         struct cfq_io_context *cic;
1388
1389         write_lock(&cfq_exit_lock);
1390
1391         cic = ioc->cic;
1392
1393         changed_ioprio(cic);
1394
1395         list_for_each_entry(cic, &cic->list, list)
1396                 changed_ioprio(cic);
1397
1398         write_unlock(&cfq_exit_lock);
1399
1400         return 0;
1401 }
1402
1403 static struct cfq_queue *
1404 cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk,
1405               gfp_t gfp_mask)
1406 {
1407         const int hashval = hash_long(key, CFQ_QHASH_SHIFT);
1408         struct cfq_queue *cfqq, *new_cfqq = NULL;
1409         unsigned short ioprio;
1410
1411 retry:
1412         ioprio = tsk->ioprio;
1413         cfqq = __cfq_find_cfq_hash(cfqd, key, ioprio, hashval);
1414
1415         if (!cfqq) {
1416                 if (new_cfqq) {
1417                         cfqq = new_cfqq;
1418                         new_cfqq = NULL;
1419                 } else if (gfp_mask & __GFP_WAIT) {
1420                         spin_unlock_irq(cfqd->queue->queue_lock);
1421                         new_cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
1422                         spin_lock_irq(cfqd->queue->queue_lock);
1423                         goto retry;
1424                 } else {
1425                         cfqq = kmem_cache_alloc(cfq_pool, gfp_mask);
1426                         if (!cfqq)
1427                                 goto out;
1428                 }
1429
1430                 memset(cfqq, 0, sizeof(*cfqq));
1431
1432                 INIT_HLIST_NODE(&cfqq->cfq_hash);
1433                 INIT_LIST_HEAD(&cfqq->cfq_list);
1434                 RB_CLEAR_ROOT(&cfqq->sort_list);
1435                 INIT_LIST_HEAD(&cfqq->fifo);
1436
1437                 cfqq->key = key;
1438                 hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
1439                 atomic_set(&cfqq->ref, 0);
1440                 cfqq->cfqd = cfqd;
1441                 cfqq->service_last = 0;
1442                 /*
1443                  * set ->slice_left to allow preemption for a new process
1444                  */
1445                 cfqq->slice_left = 2 * cfqd->cfq_slice_idle;
1446                 cfq_mark_cfqq_idle_window(cfqq);
1447                 cfq_mark_cfqq_prio_changed(cfqq);
1448                 cfq_init_prio_data(cfqq);
1449         }
1450
1451         if (new_cfqq)
1452                 kmem_cache_free(cfq_pool, new_cfqq);
1453
1454         atomic_inc(&cfqq->ref);
1455 out:
1456         WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
1457         return cfqq;
1458 }
1459
1460 /*
1461  * Setup general io context and cfq io context. There can be several cfq
1462  * io contexts per general io context, if this process is doing io to more
1463  * than one device managed by cfq. Note that caller is holding a reference to
1464  * cfqq, so we don't need to worry about it disappearing
1465  */
1466 static struct cfq_io_context *
1467 cfq_get_io_context(struct cfq_data *cfqd, pid_t pid, gfp_t gfp_mask)
1468 {
1469         struct io_context *ioc = NULL;
1470         struct cfq_io_context *cic;
1471
1472         might_sleep_if(gfp_mask & __GFP_WAIT);
1473
1474         ioc = get_io_context(gfp_mask);
1475         if (!ioc)
1476                 return NULL;
1477
1478 restart:
1479         if ((cic = ioc->cic) == NULL) {
1480                 cic = cfq_alloc_io_context(cfqd, gfp_mask);
1481
1482                 if (cic == NULL)
1483                         goto err;
1484
1485                 /*
1486                  * manually increment generic io_context usage count, it
1487                  * cannot go away since we are already holding one ref to it
1488                  */
1489                 cic->ioc = ioc;
1490                 cic->key = cfqd;
1491                 read_lock(&cfq_exit_lock);
1492                 ioc->set_ioprio = cfq_ioc_set_ioprio;
1493                 ioc->cic = cic;
1494                 list_add(&cic->queue_list, &cfqd->cic_list);
1495                 read_unlock(&cfq_exit_lock);
1496         } else {
1497                 struct cfq_io_context *__cic;
1498
1499                 /*
1500                  * the first cic on the list is actually the head itself
1501                  */
1502                 if (cic->key == cfqd)
1503                         goto out;
1504
1505                 if (unlikely(!cic->key)) {
1506                         read_lock(&cfq_exit_lock);
1507                         if (list_empty(&cic->list))
1508                                 ioc->cic = NULL;
1509                         else
1510                                 ioc->cic = list_entry(cic->list.next,
1511                                                       struct cfq_io_context,
1512                                                       list);
1513                         read_unlock(&cfq_exit_lock);
1514                         kmem_cache_free(cfq_ioc_pool, cic);
1515                         atomic_dec(&ioc_count);
1516                         goto restart;
1517                 }
1518
1519                 /*
1520                  * cic exists, check if we already are there. linear search
1521                  * should be ok here, the list will usually not be more than
1522                  * 1 or a few entries long
1523                  */
1524                 list_for_each_entry(__cic, &cic->list, list) {
1525                         /*
1526                          * this process is already holding a reference to
1527                          * this queue, so no need to get one more
1528                          */
1529                         if (__cic->key == cfqd) {
1530                                 cic = __cic;
1531                                 goto out;
1532                         }
1533                         if (unlikely(!__cic->key)) {
1534                                 read_lock(&cfq_exit_lock);
1535                                 list_del(&__cic->list);
1536                                 read_unlock(&cfq_exit_lock);
1537                                 kmem_cache_free(cfq_ioc_pool, __cic);
1538                                 atomic_dec(&ioc_count);
1539                                 goto restart;
1540                         }
1541                 }
1542
1543                 /*
1544                  * nope, process doesn't have a cic assoicated with this
1545                  * cfqq yet. get a new one and add to list
1546                  */
1547                 __cic = cfq_alloc_io_context(cfqd, gfp_mask);
1548                 if (__cic == NULL)
1549                         goto err;
1550
1551                 __cic->ioc = ioc;
1552                 __cic->key = cfqd;
1553                 read_lock(&cfq_exit_lock);
1554                 list_add(&__cic->list, &cic->list);
1555                 list_add(&__cic->queue_list, &cfqd->cic_list);
1556                 read_unlock(&cfq_exit_lock);
1557                 cic = __cic;
1558         }
1559
1560 out:
1561         return cic;
1562 err:
1563         put_io_context(ioc);
1564         return NULL;
1565 }
1566
1567 static void
1568 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1569 {
1570         unsigned long elapsed, ttime;
1571
1572         /*
1573          * if this context already has stuff queued, thinktime is from
1574          * last queue not last end
1575          */
1576 #if 0
1577         if (time_after(cic->last_end_request, cic->last_queue))
1578                 elapsed = jiffies - cic->last_end_request;
1579         else
1580                 elapsed = jiffies - cic->last_queue;
1581 #else
1582                 elapsed = jiffies - cic->last_end_request;
1583 #endif
1584
1585         ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1586
1587         cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1588         cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1589         cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1590 }
1591
1592 #define sample_valid(samples)   ((samples) > 80)
1593
1594 /*
1595  * Disable idle window if the process thinks too long or seeks so much that
1596  * it doesn't matter
1597  */
1598 static void
1599 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1600                        struct cfq_io_context *cic)
1601 {
1602         int enable_idle = cfq_cfqq_idle_window(cfqq);
1603
1604         if (!cic->ioc->task || !cfqd->cfq_slice_idle)
1605                 enable_idle = 0;
1606         else if (sample_valid(cic->ttime_samples)) {
1607                 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1608                         enable_idle = 0;
1609                 else
1610                         enable_idle = 1;
1611         }
1612
1613         if (enable_idle)
1614                 cfq_mark_cfqq_idle_window(cfqq);
1615         else
1616                 cfq_clear_cfqq_idle_window(cfqq);
1617 }
1618
1619
1620 /*
1621  * Check if new_cfqq should preempt the currently active queue. Return 0 for
1622  * no or if we aren't sure, a 1 will cause a preempt.
1623  */
1624 static int
1625 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1626                    struct cfq_rq *crq)
1627 {
1628         struct cfq_queue *cfqq = cfqd->active_queue;
1629
1630         if (cfq_class_idle(new_cfqq))
1631                 return 0;
1632
1633         if (!cfqq)
1634                 return 1;
1635
1636         if (cfq_class_idle(cfqq))
1637                 return 1;
1638         if (!cfq_cfqq_wait_request(new_cfqq))
1639                 return 0;
1640         /*
1641          * if it doesn't have slice left, forget it
1642          */
1643         if (new_cfqq->slice_left < cfqd->cfq_slice_idle)
1644                 return 0;
1645         if (cfq_crq_is_sync(crq) && !cfq_cfqq_sync(cfqq))
1646                 return 1;
1647
1648         return 0;
1649 }
1650
1651 /*
1652  * cfqq preempts the active queue. if we allowed preempt with no slice left,
1653  * let it have half of its nominal slice.
1654  */
1655 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1656 {
1657         struct cfq_queue *__cfqq, *next;
1658
1659         list_for_each_entry_safe(__cfqq, next, &cfqd->cur_rr, cfq_list)
1660                 cfq_resort_rr_list(__cfqq, 1);
1661
1662         if (!cfqq->slice_left)
1663                 cfqq->slice_left = cfq_prio_to_slice(cfqd, cfqq) / 2;
1664
1665         cfqq->slice_end = cfqq->slice_left + jiffies;
1666         __cfq_slice_expired(cfqd, cfqq, 1);
1667         __cfq_set_active_queue(cfqd, cfqq);
1668 }
1669
1670 /*
1671  * should really be a ll_rw_blk.c helper
1672  */
1673 static void cfq_start_queueing(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1674 {
1675         request_queue_t *q = cfqd->queue;
1676
1677         if (!blk_queue_plugged(q))
1678                 q->request_fn(q);
1679         else
1680                 __generic_unplug_device(q);
1681 }
1682
1683 /*
1684  * Called when a new fs request (crq) is added (to cfqq). Check if there's
1685  * something we should do about it
1686  */
1687 static void
1688 cfq_crq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1689                  struct cfq_rq *crq)
1690 {
1691         struct cfq_io_context *cic;
1692
1693         cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);
1694
1695         /*
1696          * we never wait for an async request and we don't allow preemption
1697          * of an async request. so just return early
1698          */
1699         if (!cfq_crq_is_sync(crq))
1700                 return;
1701
1702         cic = crq->io_context;
1703
1704         cfq_update_io_thinktime(cfqd, cic);
1705         cfq_update_idle_window(cfqd, cfqq, cic);
1706
1707         cic->last_queue = jiffies;
1708
1709         if (cfqq == cfqd->active_queue) {
1710                 /*
1711                  * if we are waiting for a request for this queue, let it rip
1712                  * immediately and flag that we must not expire this queue
1713                  * just now
1714                  */
1715                 if (cfq_cfqq_wait_request(cfqq)) {
1716                         cfq_mark_cfqq_must_dispatch(cfqq);
1717                         del_timer(&cfqd->idle_slice_timer);
1718                         cfq_start_queueing(cfqd, cfqq);
1719                 }
1720         } else if (cfq_should_preempt(cfqd, cfqq, crq)) {
1721                 /*
1722                  * not the active queue - expire current slice if it is
1723                  * idle and has expired it's mean thinktime or this new queue
1724                  * has some old slice time left and is of higher priority
1725                  */
1726                 cfq_preempt_queue(cfqd, cfqq);
1727                 cfq_mark_cfqq_must_dispatch(cfqq);
1728                 cfq_start_queueing(cfqd, cfqq);
1729         }
1730 }
1731
1732 static void cfq_insert_request(request_queue_t *q, struct request *rq)
1733 {
1734         struct cfq_data *cfqd = q->elevator->elevator_data;
1735         struct cfq_rq *crq = RQ_DATA(rq);
1736         struct cfq_queue *cfqq = crq->cfq_queue;
1737
1738         cfq_init_prio_data(cfqq);
1739
1740         cfq_add_crq_rb(crq);
1741
1742         list_add_tail(&rq->queuelist, &cfqq->fifo);
1743
1744         if (rq_mergeable(rq))
1745                 cfq_add_crq_hash(cfqd, crq);
1746
1747         cfq_crq_enqueued(cfqd, cfqq, crq);
1748 }
1749
1750 static void cfq_completed_request(request_queue_t *q, struct request *rq)
1751 {
1752         struct cfq_rq *crq = RQ_DATA(rq);
1753         struct cfq_queue *cfqq = crq->cfq_queue;
1754         struct cfq_data *cfqd = cfqq->cfqd;
1755         const int sync = cfq_crq_is_sync(crq);
1756         unsigned long now;
1757
1758         now = jiffies;
1759
1760         WARN_ON(!cfqd->rq_in_driver);
1761         WARN_ON(!cfqq->on_dispatch[sync]);
1762         cfqd->rq_in_driver--;
1763         cfqq->on_dispatch[sync]--;
1764
1765         if (!cfq_class_idle(cfqq))
1766                 cfqd->last_end_request = now;
1767
1768         if (!cfq_cfqq_dispatched(cfqq)) {
1769                 if (cfq_cfqq_on_rr(cfqq)) {
1770                         cfqq->service_last = now;
1771                         cfq_resort_rr_list(cfqq, 0);
1772                 }
1773                 cfq_schedule_dispatch(cfqd);
1774         }
1775
1776         if (cfq_crq_is_sync(crq))
1777                 crq->io_context->last_end_request = now;
1778 }
1779
1780 static struct request *
1781 cfq_former_request(request_queue_t *q, struct request *rq)
1782 {
1783         struct cfq_rq *crq = RQ_DATA(rq);
1784         struct rb_node *rbprev = rb_prev(&crq->rb_node);
1785
1786         if (rbprev)
1787                 return rb_entry_crq(rbprev)->request;
1788
1789         return NULL;
1790 }
1791
1792 static struct request *
1793 cfq_latter_request(request_queue_t *q, struct request *rq)
1794 {
1795         struct cfq_rq *crq = RQ_DATA(rq);
1796         struct rb_node *rbnext = rb_next(&crq->rb_node);
1797
1798         if (rbnext)
1799                 return rb_entry_crq(rbnext)->request;
1800
1801         return NULL;
1802 }
1803
1804 /*
1805  * we temporarily boost lower priority queues if they are holding fs exclusive
1806  * resources. they are boosted to normal prio (CLASS_BE/4)
1807  */
1808 static void cfq_prio_boost(struct cfq_queue *cfqq)
1809 {
1810         const int ioprio_class = cfqq->ioprio_class;
1811         const int ioprio = cfqq->ioprio;
1812
1813         if (has_fs_excl()) {
1814                 /*
1815                  * boost idle prio on transactions that would lock out other
1816                  * users of the filesystem
1817                  */
1818                 if (cfq_class_idle(cfqq))
1819                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1820                 if (cfqq->ioprio > IOPRIO_NORM)
1821                         cfqq->ioprio = IOPRIO_NORM;
1822         } else {
1823                 /*
1824                  * check if we need to unboost the queue
1825                  */
1826                 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
1827                         cfqq->ioprio_class = cfqq->org_ioprio_class;
1828                 if (cfqq->ioprio != cfqq->org_ioprio)
1829                         cfqq->ioprio = cfqq->org_ioprio;
1830         }
1831
1832         /*
1833          * refile between round-robin lists if we moved the priority class
1834          */
1835         if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio) &&
1836             cfq_cfqq_on_rr(cfqq))
1837                 cfq_resort_rr_list(cfqq, 0);
1838 }
1839
1840 static inline pid_t cfq_queue_pid(struct task_struct *task, int rw)
1841 {
1842         if (rw == READ || process_sync(task))
1843                 return task->pid;
1844
1845         return CFQ_KEY_ASYNC;
1846 }
1847
1848 static inline int
1849 __cfq_may_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1850                 struct task_struct *task, int rw)
1851 {
1852 #if 1
1853         if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
1854             !cfq_cfqq_must_alloc_slice(cfqq)) {
1855                 cfq_mark_cfqq_must_alloc_slice(cfqq);
1856                 return ELV_MQUEUE_MUST;
1857         }
1858
1859         return ELV_MQUEUE_MAY;
1860 #else
1861         if (!cfqq || task->flags & PF_MEMALLOC)
1862                 return ELV_MQUEUE_MAY;
1863         if (!cfqq->allocated[rw] || cfq_cfqq_must_alloc(cfqq)) {
1864                 if (cfq_cfqq_wait_request(cfqq))
1865                         return ELV_MQUEUE_MUST;
1866
1867                 /*
1868                  * only allow 1 ELV_MQUEUE_MUST per slice, otherwise we
1869                  * can quickly flood the queue with writes from a single task
1870                  */
1871                 if (rw == READ || !cfq_cfqq_must_alloc_slice(cfqq)) {
1872                         cfq_mark_cfqq_must_alloc_slice(cfqq);
1873                         return ELV_MQUEUE_MUST;
1874                 }
1875
1876                 return ELV_MQUEUE_MAY;
1877         }
1878         if (cfq_class_idle(cfqq))
1879                 return ELV_MQUEUE_NO;
1880         if (cfqq->allocated[rw] >= cfqd->max_queued) {
1881                 struct io_context *ioc = get_io_context(GFP_ATOMIC);
1882                 int ret = ELV_MQUEUE_NO;
1883
1884                 if (ioc && ioc->nr_batch_requests)
1885                         ret = ELV_MQUEUE_MAY;
1886
1887                 put_io_context(ioc);
1888                 return ret;
1889         }
1890
1891         return ELV_MQUEUE_MAY;
1892 #endif
1893 }
1894
1895 static int cfq_may_queue(request_queue_t *q, int rw, struct bio *bio)
1896 {
1897         struct cfq_data *cfqd = q->elevator->elevator_data;
1898         struct task_struct *tsk = current;
1899         struct cfq_queue *cfqq;
1900
1901         /*
1902          * don't force setup of a queue from here, as a call to may_queue
1903          * does not necessarily imply that a request actually will be queued.
1904          * so just lookup a possibly existing queue, or return 'may queue'
1905          * if that fails
1906          */
1907         cfqq = cfq_find_cfq_hash(cfqd, cfq_queue_pid(tsk, rw), tsk->ioprio);
1908         if (cfqq) {
1909                 cfq_init_prio_data(cfqq);
1910                 cfq_prio_boost(cfqq);
1911
1912                 return __cfq_may_queue(cfqd, cfqq, tsk, rw);
1913         }
1914
1915         return ELV_MQUEUE_MAY;
1916 }
1917
1918 static void cfq_check_waiters(request_queue_t *q, struct cfq_queue *cfqq)
1919 {
1920         struct cfq_data *cfqd = q->elevator->elevator_data;
1921         struct request_list *rl = &q->rq;
1922
1923         if (cfqq->allocated[READ] <= cfqd->max_queued || cfqd->rq_starved) {
1924                 smp_mb();
1925                 if (waitqueue_active(&rl->wait[READ]))
1926                         wake_up(&rl->wait[READ]);
1927         }
1928
1929         if (cfqq->allocated[WRITE] <= cfqd->max_queued || cfqd->rq_starved) {
1930                 smp_mb();
1931                 if (waitqueue_active(&rl->wait[WRITE]))
1932                         wake_up(&rl->wait[WRITE]);
1933         }
1934 }
1935
1936 /*
1937  * queue lock held here
1938  */
1939 static void cfq_put_request(request_queue_t *q, struct request *rq)
1940 {
1941         struct cfq_data *cfqd = q->elevator->elevator_data;
1942         struct cfq_rq *crq = RQ_DATA(rq);
1943
1944         if (crq) {
1945                 struct cfq_queue *cfqq = crq->cfq_queue;
1946                 const int rw = rq_data_dir(rq);
1947
1948                 BUG_ON(!cfqq->allocated[rw]);
1949                 cfqq->allocated[rw]--;
1950
1951                 put_io_context(crq->io_context->ioc);
1952
1953                 mempool_free(crq, cfqd->crq_pool);
1954                 rq->elevator_private = NULL;
1955
1956                 cfq_check_waiters(q, cfqq);
1957                 cfq_put_queue(cfqq);
1958         }
1959 }
1960
1961 /*
1962  * Allocate cfq data structures associated with this request.
1963  */
1964 static int
1965 cfq_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
1966                 gfp_t gfp_mask)
1967 {
1968         struct cfq_data *cfqd = q->elevator->elevator_data;
1969         struct task_struct *tsk = current;
1970         struct cfq_io_context *cic;
1971         const int rw = rq_data_dir(rq);
1972         pid_t key = cfq_queue_pid(tsk, rw);
1973         struct cfq_queue *cfqq;
1974         struct cfq_rq *crq;
1975         unsigned long flags;
1976         int is_sync = key != CFQ_KEY_ASYNC;
1977
1978         might_sleep_if(gfp_mask & __GFP_WAIT);
1979
1980         cic = cfq_get_io_context(cfqd, key, gfp_mask);
1981
1982         spin_lock_irqsave(q->queue_lock, flags);
1983
1984         if (!cic)
1985                 goto queue_fail;
1986
1987         if (!cic->cfqq[is_sync]) {
1988                 cfqq = cfq_get_queue(cfqd, key, tsk, gfp_mask);
1989                 if (!cfqq)
1990                         goto queue_fail;
1991
1992                 cic->cfqq[is_sync] = cfqq;
1993         } else
1994                 cfqq = cic->cfqq[is_sync];
1995
1996         cfqq->allocated[rw]++;
1997         cfq_clear_cfqq_must_alloc(cfqq);
1998         cfqd->rq_starved = 0;
1999         atomic_inc(&cfqq->ref);
2000         spin_unlock_irqrestore(q->queue_lock, flags);
2001
2002         crq = mempool_alloc(cfqd->crq_pool, gfp_mask);
2003         if (crq) {
2004                 RB_CLEAR(&crq->rb_node);
2005                 crq->rb_key = 0;
2006                 crq->request = rq;
2007                 INIT_HLIST_NODE(&crq->hash);
2008                 crq->cfq_queue = cfqq;
2009                 crq->io_context = cic;
2010
2011                 if (is_sync)
2012                         cfq_mark_crq_is_sync(crq);
2013                 else
2014                         cfq_clear_crq_is_sync(crq);
2015
2016                 rq->elevator_private = crq;
2017                 return 0;
2018         }
2019
2020         spin_lock_irqsave(q->queue_lock, flags);
2021         cfqq->allocated[rw]--;
2022         if (!(cfqq->allocated[0] + cfqq->allocated[1]))
2023                 cfq_mark_cfqq_must_alloc(cfqq);
2024         cfq_put_queue(cfqq);
2025 queue_fail:
2026         if (cic)
2027                 put_io_context(cic->ioc);
2028         /*
2029          * mark us rq allocation starved. we need to kickstart the process
2030          * ourselves if there are no pending requests that can do it for us.
2031          * that would be an extremely rare OOM situation
2032          */
2033         cfqd->rq_starved = 1;
2034         cfq_schedule_dispatch(cfqd);
2035         spin_unlock_irqrestore(q->queue_lock, flags);
2036         return 1;
2037 }
2038
2039 static void cfq_kick_queue(void *data)
2040 {
2041         request_queue_t *q = data;
2042         struct cfq_data *cfqd = q->elevator->elevator_data;
2043         unsigned long flags;
2044
2045         spin_lock_irqsave(q->queue_lock, flags);
2046
2047         if (cfqd->rq_starved) {
2048                 struct request_list *rl = &q->rq;
2049
2050                 /*
2051                  * we aren't guaranteed to get a request after this, but we
2052                  * have to be opportunistic
2053                  */
2054                 smp_mb();
2055                 if (waitqueue_active(&rl->wait[READ]))
2056                         wake_up(&rl->wait[READ]);
2057                 if (waitqueue_active(&rl->wait[WRITE]))
2058                         wake_up(&rl->wait[WRITE]);
2059         }
2060
2061         blk_remove_plug(q);
2062         q->request_fn(q);
2063         spin_unlock_irqrestore(q->queue_lock, flags);
2064 }
2065
2066 /*
2067  * Timer running if the active_queue is currently idling inside its time slice
2068  */
2069 static void cfq_idle_slice_timer(unsigned long data)
2070 {
2071         struct cfq_data *cfqd = (struct cfq_data *) data;
2072         struct cfq_queue *cfqq;
2073         unsigned long flags;
2074
2075         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2076
2077         if ((cfqq = cfqd->active_queue) != NULL) {
2078                 unsigned long now = jiffies;
2079
2080                 /*
2081                  * expired
2082                  */
2083                 if (time_after(now, cfqq->slice_end))
2084                         goto expire;
2085
2086                 /*
2087                  * only expire and reinvoke request handler, if there are
2088                  * other queues with pending requests
2089                  */
2090                 if (!cfqd->busy_queues) {
2091                         cfqd->idle_slice_timer.expires = min(now + cfqd->cfq_slice_idle, cfqq->slice_end);
2092                         add_timer(&cfqd->idle_slice_timer);
2093                         goto out_cont;
2094                 }
2095
2096                 /*
2097                  * not expired and it has a request pending, let it dispatch
2098                  */
2099                 if (!RB_EMPTY(&cfqq->sort_list)) {
2100                         cfq_mark_cfqq_must_dispatch(cfqq);
2101                         goto out_kick;
2102                 }
2103         }
2104 expire:
2105         cfq_slice_expired(cfqd, 0);
2106 out_kick:
2107         cfq_schedule_dispatch(cfqd);
2108 out_cont:
2109         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2110 }
2111
2112 /*
2113  * Timer running if an idle class queue is waiting for service
2114  */
2115 static void cfq_idle_class_timer(unsigned long data)
2116 {
2117         struct cfq_data *cfqd = (struct cfq_data *) data;
2118         unsigned long flags, end;
2119
2120         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2121
2122         /*
2123          * race with a non-idle queue, reset timer
2124          */
2125         end = cfqd->last_end_request + CFQ_IDLE_GRACE;
2126         if (!time_after_eq(jiffies, end)) {
2127                 cfqd->idle_class_timer.expires = end;
2128                 add_timer(&cfqd->idle_class_timer);
2129         } else
2130                 cfq_schedule_dispatch(cfqd);
2131
2132         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2133 }
2134
2135 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2136 {
2137         del_timer_sync(&cfqd->idle_slice_timer);
2138         del_timer_sync(&cfqd->idle_class_timer);
2139         blk_sync_queue(cfqd->queue);
2140 }
2141
2142 static void cfq_exit_queue(elevator_t *e)
2143 {
2144         struct cfq_data *cfqd = e->elevator_data;
2145         request_queue_t *q = cfqd->queue;
2146
2147         cfq_shutdown_timer_wq(cfqd);
2148         write_lock(&cfq_exit_lock);
2149         spin_lock_irq(q->queue_lock);
2150         if (cfqd->active_queue)
2151                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
2152         while(!list_empty(&cfqd->cic_list)) {
2153                 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2154                                                         struct cfq_io_context,
2155                                                         queue_list);
2156                 if (cic->cfqq[ASYNC]) {
2157                         cfq_put_queue(cic->cfqq[ASYNC]);
2158                         cic->cfqq[ASYNC] = NULL;
2159                 }
2160                 if (cic->cfqq[SYNC]) {
2161                         cfq_put_queue(cic->cfqq[SYNC]);
2162                         cic->cfqq[SYNC] = NULL;
2163                 }
2164                 cic->key = NULL;
2165                 list_del_init(&cic->queue_list);
2166         }
2167         spin_unlock_irq(q->queue_lock);
2168         write_unlock(&cfq_exit_lock);
2169
2170         cfq_shutdown_timer_wq(cfqd);
2171
2172         mempool_destroy(cfqd->crq_pool);
2173         kfree(cfqd->crq_hash);
2174         kfree(cfqd->cfq_hash);
2175         kfree(cfqd);
2176 }
2177
2178 static int cfq_init_queue(request_queue_t *q, elevator_t *e)
2179 {
2180         struct cfq_data *cfqd;
2181         int i;
2182
2183         cfqd = kmalloc(sizeof(*cfqd), GFP_KERNEL);
2184         if (!cfqd)
2185                 return -ENOMEM;
2186
2187         memset(cfqd, 0, sizeof(*cfqd));
2188
2189         for (i = 0; i < CFQ_PRIO_LISTS; i++)
2190                 INIT_LIST_HEAD(&cfqd->rr_list[i]);
2191
2192         INIT_LIST_HEAD(&cfqd->busy_rr);
2193         INIT_LIST_HEAD(&cfqd->cur_rr);
2194         INIT_LIST_HEAD(&cfqd->idle_rr);
2195         INIT_LIST_HEAD(&cfqd->empty_list);
2196         INIT_LIST_HEAD(&cfqd->cic_list);
2197
2198         cfqd->crq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_MHASH_ENTRIES, GFP_KERNEL);
2199         if (!cfqd->crq_hash)
2200                 goto out_crqhash;
2201
2202         cfqd->cfq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL);
2203         if (!cfqd->cfq_hash)
2204                 goto out_cfqhash;
2205
2206         cfqd->crq_pool = mempool_create(BLKDEV_MIN_RQ, mempool_alloc_slab, mempool_free_slab, crq_pool);
2207         if (!cfqd->crq_pool)
2208                 goto out_crqpool;
2209
2210         for (i = 0; i < CFQ_MHASH_ENTRIES; i++)
2211                 INIT_HLIST_HEAD(&cfqd->crq_hash[i]);
2212         for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
2213                 INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
2214
2215         e->elevator_data = cfqd;
2216
2217         cfqd->queue = q;
2218
2219         cfqd->max_queued = q->nr_requests / 4;
2220         q->nr_batching = cfq_queued;
2221
2222         init_timer(&cfqd->idle_slice_timer);
2223         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2224         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2225
2226         init_timer(&cfqd->idle_class_timer);
2227         cfqd->idle_class_timer.function = cfq_idle_class_timer;
2228         cfqd->idle_class_timer.data = (unsigned long) cfqd;
2229
2230         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue, q);
2231
2232         cfqd->cfq_queued = cfq_queued;
2233         cfqd->cfq_quantum = cfq_quantum;
2234         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2235         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2236         cfqd->cfq_back_max = cfq_back_max;
2237         cfqd->cfq_back_penalty = cfq_back_penalty;
2238         cfqd->cfq_slice[0] = cfq_slice_async;
2239         cfqd->cfq_slice[1] = cfq_slice_sync;
2240         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2241         cfqd->cfq_slice_idle = cfq_slice_idle;
2242         cfqd->cfq_max_depth = cfq_max_depth;
2243
2244         return 0;
2245 out_crqpool:
2246         kfree(cfqd->cfq_hash);
2247 out_cfqhash:
2248         kfree(cfqd->crq_hash);
2249 out_crqhash:
2250         kfree(cfqd);
2251         return -ENOMEM;
2252 }
2253
2254 static void cfq_slab_kill(void)
2255 {
2256         if (crq_pool)
2257                 kmem_cache_destroy(crq_pool);
2258         if (cfq_pool)
2259                 kmem_cache_destroy(cfq_pool);
2260         if (cfq_ioc_pool)
2261                 kmem_cache_destroy(cfq_ioc_pool);
2262 }
2263
2264 static int __init cfq_slab_setup(void)
2265 {
2266         crq_pool = kmem_cache_create("crq_pool", sizeof(struct cfq_rq), 0, 0,
2267                                         NULL, NULL);
2268         if (!crq_pool)
2269                 goto fail;
2270
2271         cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0,
2272                                         NULL, NULL);
2273         if (!cfq_pool)
2274                 goto fail;
2275
2276         cfq_ioc_pool = kmem_cache_create("cfq_ioc_pool",
2277                         sizeof(struct cfq_io_context), 0, 0, NULL, NULL);
2278         if (!cfq_ioc_pool)
2279                 goto fail;
2280
2281         return 0;
2282 fail:
2283         cfq_slab_kill();
2284         return -ENOMEM;
2285 }
2286
2287 /*
2288  * sysfs parts below -->
2289  */
2290 struct cfq_fs_entry {
2291         struct attribute attr;
2292         ssize_t (*show)(struct cfq_data *, char *);
2293         ssize_t (*store)(struct cfq_data *, const char *, size_t);
2294 };
2295
2296 static ssize_t
2297 cfq_var_show(unsigned int var, char *page)
2298 {
2299         return sprintf(page, "%d\n", var);
2300 }
2301
2302 static ssize_t
2303 cfq_var_store(unsigned int *var, const char *page, size_t count)
2304 {
2305         char *p = (char *) page;
2306
2307         *var = simple_strtoul(p, &p, 10);
2308         return count;
2309 }
2310
2311 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
2312 static ssize_t __FUNC(struct cfq_data *cfqd, char *page)                \
2313 {                                                                       \
2314         unsigned int __data = __VAR;                                    \
2315         if (__CONV)                                                     \
2316                 __data = jiffies_to_msecs(__data);                      \
2317         return cfq_var_show(__data, (page));                            \
2318 }
2319 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2320 SHOW_FUNCTION(cfq_queued_show, cfqd->cfq_queued, 0);
2321 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2322 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2323 SHOW_FUNCTION(cfq_back_max_show, cfqd->cfq_back_max, 0);
2324 SHOW_FUNCTION(cfq_back_penalty_show, cfqd->cfq_back_penalty, 0);
2325 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2326 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2327 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2328 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2329 SHOW_FUNCTION(cfq_max_depth_show, cfqd->cfq_max_depth, 0);
2330 #undef SHOW_FUNCTION
2331
2332 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
2333 static ssize_t __FUNC(struct cfq_data *cfqd, const char *page, size_t count)    \
2334 {                                                                       \
2335         unsigned int __data;                                            \
2336         int ret = cfq_var_store(&__data, (page), count);                \
2337         if (__data < (MIN))                                             \
2338                 __data = (MIN);                                         \
2339         else if (__data > (MAX))                                        \
2340                 __data = (MAX);                                         \
2341         if (__CONV)                                                     \
2342                 *(__PTR) = msecs_to_jiffies(__data);                    \
2343         else                                                            \
2344                 *(__PTR) = __data;                                      \
2345         return ret;                                                     \
2346 }
2347 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2348 STORE_FUNCTION(cfq_queued_store, &cfqd->cfq_queued, 1, UINT_MAX, 0);
2349 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1);
2350 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1);
2351 STORE_FUNCTION(cfq_back_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2352 STORE_FUNCTION(cfq_back_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0);
2353 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2354 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2355 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2356 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0);
2357 STORE_FUNCTION(cfq_max_depth_store, &cfqd->cfq_max_depth, 1, UINT_MAX, 0);
2358 #undef STORE_FUNCTION
2359
2360 static struct cfq_fs_entry cfq_quantum_entry = {
2361         .attr = {.name = "quantum", .mode = S_IRUGO | S_IWUSR },
2362         .show = cfq_quantum_show,
2363         .store = cfq_quantum_store,
2364 };
2365 static struct cfq_fs_entry cfq_queued_entry = {
2366         .attr = {.name = "queued", .mode = S_IRUGO | S_IWUSR },
2367         .show = cfq_queued_show,
2368         .store = cfq_queued_store,
2369 };
2370 static struct cfq_fs_entry cfq_fifo_expire_sync_entry = {
2371         .attr = {.name = "fifo_expire_sync", .mode = S_IRUGO | S_IWUSR },
2372         .show = cfq_fifo_expire_sync_show,
2373         .store = cfq_fifo_expire_sync_store,
2374 };
2375 static struct cfq_fs_entry cfq_fifo_expire_async_entry = {
2376         .attr = {.name = "fifo_expire_async", .mode = S_IRUGO | S_IWUSR },
2377         .show = cfq_fifo_expire_async_show,
2378         .store = cfq_fifo_expire_async_store,
2379 };
2380 static struct cfq_fs_entry cfq_back_max_entry = {
2381         .attr = {.name = "back_seek_max", .mode = S_IRUGO | S_IWUSR },
2382         .show = cfq_back_max_show,
2383         .store = cfq_back_max_store,
2384 };
2385 static struct cfq_fs_entry cfq_back_penalty_entry = {
2386         .attr = {.name = "back_seek_penalty", .mode = S_IRUGO | S_IWUSR },
2387         .show = cfq_back_penalty_show,
2388         .store = cfq_back_penalty_store,
2389 };
2390 static struct cfq_fs_entry cfq_slice_sync_entry = {
2391         .attr = {.name = "slice_sync", .mode = S_IRUGO | S_IWUSR },
2392         .show = cfq_slice_sync_show,
2393         .store = cfq_slice_sync_store,
2394 };
2395 static struct cfq_fs_entry cfq_slice_async_entry = {
2396         .attr = {.name = "slice_async", .mode = S_IRUGO | S_IWUSR },
2397         .show = cfq_slice_async_show,
2398         .store = cfq_slice_async_store,
2399 };
2400 static struct cfq_fs_entry cfq_slice_async_rq_entry = {
2401         .attr = {.name = "slice_async_rq", .mode = S_IRUGO | S_IWUSR },
2402         .show = cfq_slice_async_rq_show,
2403         .store = cfq_slice_async_rq_store,
2404 };
2405 static struct cfq_fs_entry cfq_slice_idle_entry = {
2406         .attr = {.name = "slice_idle", .mode = S_IRUGO | S_IWUSR },
2407         .show = cfq_slice_idle_show,
2408         .store = cfq_slice_idle_store,
2409 };
2410 static struct cfq_fs_entry cfq_max_depth_entry = {
2411         .attr = {.name = "max_depth", .mode = S_IRUGO | S_IWUSR },
2412         .show = cfq_max_depth_show,
2413         .store = cfq_max_depth_store,
2414 };
2415
2416 static struct attribute *default_attrs[] = {
2417         &cfq_quantum_entry.attr,
2418         &cfq_queued_entry.attr,
2419         &cfq_fifo_expire_sync_entry.attr,
2420         &cfq_fifo_expire_async_entry.attr,
2421         &cfq_back_max_entry.attr,
2422         &cfq_back_penalty_entry.attr,
2423         &cfq_slice_sync_entry.attr,
2424         &cfq_slice_async_entry.attr,
2425         &cfq_slice_async_rq_entry.attr,
2426         &cfq_slice_idle_entry.attr,
2427         &cfq_max_depth_entry.attr,
2428         NULL,
2429 };
2430
2431 #define to_cfq(atr) container_of((atr), struct cfq_fs_entry, attr)
2432
2433 static ssize_t
2434 cfq_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
2435 {
2436         elevator_t *e = container_of(kobj, elevator_t, kobj);
2437         struct cfq_fs_entry *entry = to_cfq(attr);
2438
2439         if (!entry->show)
2440                 return -EIO;
2441
2442         return entry->show(e->elevator_data, page);
2443 }
2444
2445 static ssize_t
2446 cfq_attr_store(struct kobject *kobj, struct attribute *attr,
2447                const char *page, size_t length)
2448 {
2449         elevator_t *e = container_of(kobj, elevator_t, kobj);
2450         struct cfq_fs_entry *entry = to_cfq(attr);
2451
2452         if (!entry->store)
2453                 return -EIO;
2454
2455         return entry->store(e->elevator_data, page, length);
2456 }
2457
2458 static struct sysfs_ops cfq_sysfs_ops = {
2459         .show   = cfq_attr_show,
2460         .store  = cfq_attr_store,
2461 };
2462
2463 static struct kobj_type cfq_ktype = {
2464         .sysfs_ops      = &cfq_sysfs_ops,
2465         .default_attrs  = default_attrs,
2466 };
2467
2468 static struct elevator_type iosched_cfq = {
2469         .ops = {
2470                 .elevator_merge_fn =            cfq_merge,
2471                 .elevator_merged_fn =           cfq_merged_request,
2472                 .elevator_merge_req_fn =        cfq_merged_requests,
2473                 .elevator_dispatch_fn =         cfq_dispatch_requests,
2474                 .elevator_add_req_fn =          cfq_insert_request,
2475                 .elevator_activate_req_fn =     cfq_activate_request,
2476                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
2477                 .elevator_queue_empty_fn =      cfq_queue_empty,
2478                 .elevator_completed_req_fn =    cfq_completed_request,
2479                 .elevator_former_req_fn =       cfq_former_request,
2480                 .elevator_latter_req_fn =       cfq_latter_request,
2481                 .elevator_set_req_fn =          cfq_set_request,
2482                 .elevator_put_req_fn =          cfq_put_request,
2483                 .elevator_may_queue_fn =        cfq_may_queue,
2484                 .elevator_init_fn =             cfq_init_queue,
2485                 .elevator_exit_fn =             cfq_exit_queue,
2486                 .trim =                         cfq_trim,
2487         },
2488         .elevator_ktype =       &cfq_ktype,
2489         .elevator_name =        "cfq",
2490         .elevator_owner =       THIS_MODULE,
2491 };
2492
2493 static int __init cfq_init(void)
2494 {
2495         int ret;
2496
2497         /*
2498          * could be 0 on HZ < 1000 setups
2499          */
2500         if (!cfq_slice_async)
2501                 cfq_slice_async = 1;
2502         if (!cfq_slice_idle)
2503                 cfq_slice_idle = 1;
2504
2505         if (cfq_slab_setup())
2506                 return -ENOMEM;
2507
2508         ret = elv_register(&iosched_cfq);
2509         if (ret)
2510                 cfq_slab_kill();
2511
2512         return ret;
2513 }
2514
2515 static void __exit cfq_exit(void)
2516 {
2517         DECLARE_COMPLETION(all_gone);
2518         elv_unregister(&iosched_cfq);
2519         ioc_gone = &all_gone;
2520         barrier();
2521         if (atomic_read(&ioc_count))
2522                 complete(ioc_gone);
2523         synchronize_rcu();
2524         cfq_slab_kill();
2525 }
2526
2527 module_init(cfq_init);
2528 module_exit(cfq_exit);
2529
2530 MODULE_AUTHOR("Jens Axboe");
2531 MODULE_LICENSE("GPL");
2532 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");