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