block/cfq-iosched.c

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