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 static inline void
 538 cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
 539 {
 540         elv_rb_del(&cfqq->sort_list, rq);
 541         cfqq->queued[rq_is_sync(rq)]--;
 542         cfq_add_rq_rb(rq);
 543 }
 544
 545 static struct request *
 546 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
 547 {
 548         struct task_struct *tsk = current;
 549         pid_t key = cfq_queue_pid(tsk, bio_data_dir(bio), bio_sync(bio));
 550         struct cfq_queue *cfqq;
 551
 552         cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
 553         if (cfqq) {
 554                 sector_t sector = bio->bi_sector + bio_sectors(bio);
 555
 556                 return elv_rb_find(&cfqq->sort_list, sector);
 557         }
 558
 559         return NULL;
 560 }
 561
 562 static void cfq_activate_request(request_queue_t *q, struct request *rq)
 563 {
 564         struct cfq_data *cfqd = q->elevator->elevator_data;
 565
 566         cfqd->rq_in_driver++;
 567
 568         /*
 569          * If the depth is larger 1, it really could be queueing. But lets
 570          * make the mark a little higher - idling could still be good for
 571          * low queueing, and a low queueing number could also just indicate
 572          * a SCSI mid layer like behaviour where limit+1 is often seen.
 573          */
 574         if (!cfqd->hw_tag && cfqd->rq_in_driver > 4)
 575                 cfqd->hw_tag = 1;
 576 }
 577
 578 static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
 579 {
 580         struct cfq_data *cfqd = q->elevator->elevator_data;
 581
 582         WARN_ON(!cfqd->rq_in_driver);
 583         cfqd->rq_in_driver--;
 584 }
 585
 586 static void cfq_remove_request(struct request *rq)
 587 {
 588         struct cfq_queue *cfqq = RQ_CFQQ(rq);
 589
 590         if (cfqq->next_rq == rq)
 591                 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
 592
 593         list_del_init(&rq->queuelist);
 594         cfq_del_rq_rb(rq);
 595
 596         if (rq_is_meta(rq)) {
 597                 WARN_ON(!cfqq->meta_pending);
 598                 cfqq->meta_pending--;
 599         }
 600 }
 601
 602 static int
 603 cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
 604 {
 605         struct cfq_data *cfqd = q->elevator->elevator_data;
 606         struct request *__rq;
 607
 608         __rq = cfq_find_rq_fmerge(cfqd, bio);
 609         if (__rq && elv_rq_merge_ok(__rq, bio)) {
 610                 *req = __rq;
 611                 return ELEVATOR_FRONT_MERGE;
 612         }
 613
 614         return ELEVATOR_NO_MERGE;
 615 }
 616
 617 static void cfq_merged_request(request_queue_t *q, struct request *req,
 618                                int type)
 619 {
 620         if (type == ELEVATOR_FRONT_MERGE) {
 621                 struct cfq_queue *cfqq = RQ_CFQQ(req);
 622
 623                 cfq_reposition_rq_rb(cfqq, req);
 624         }
 625 }
 626
 627 static void
 628 cfq_merged_requests(request_queue_t *q, struct request *rq,
 629                     struct request *next)
 630 {
 631         /*
 632          * reposition in fifo if next is older than rq
 633          */
 634         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
 635             time_before(next->start_time, rq->start_time))
 636                 list_move(&rq->queuelist, &next->queuelist);
 637
 638         cfq_remove_request(next);
 639 }
 640
 641 static int cfq_allow_merge(request_queue_t *q, struct request *rq,
 642                            struct bio *bio)
 643 {
 644         struct cfq_data *cfqd = q->elevator->elevator_data;
 645         const int rw = bio_data_dir(bio);
 646         struct cfq_queue *cfqq;
 647         pid_t key;
 648
 649         /*
 650          * Disallow merge of a sync bio into an async request.
 651          */
 652         if ((bio_data_dir(bio) == READ || bio_sync(bio)) && !rq_is_sync(rq))
 653                 return 0;
 654
 655         /*
 656          * Lookup the cfqq that this bio will be queued with. Allow
 657          * merge only if rq is queued there.
 658          */
 659         key = cfq_queue_pid(current, rw, bio_sync(bio));
 660         cfqq = cfq_find_cfq_hash(cfqd, key, current->ioprio);
 661
 662         if (cfqq == RQ_CFQQ(rq))
 663                 return 1;
 664
 665         return 0;
 666 }
 667
 668 static inline void
 669 __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 670 {
 671         if (cfqq) {
 672                 /*
 673                  * stop potential idle class queues waiting service
 674                  */
 675                 del_timer(&cfqd->idle_class_timer);
 676
 677                 cfqq->slice_end = 0;
 678                 cfq_clear_cfqq_must_alloc_slice(cfqq);
 679                 cfq_clear_cfqq_fifo_expire(cfqq);
 680                 cfq_mark_cfqq_slice_new(cfqq);
 681         }
 682
 683         cfqd->active_queue = cfqq;
 684 }
 685
 686 /*
 687  * current cfqq expired its slice (or was too idle), select new one
 688  */
 689 static void
 690 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 691                     int preempted, int timed_out)
 692 {
 693         if (cfq_cfqq_wait_request(cfqq))
 694                 del_timer(&cfqd->idle_slice_timer);
 695
 696         if (!preempted && !cfq_cfqq_dispatched(cfqq))
 697                 cfq_schedule_dispatch(cfqd);
 698
 699         cfq_clear_cfqq_must_dispatch(cfqq);
 700         cfq_clear_cfqq_wait_request(cfqq);
 701         cfq_clear_cfqq_queue_new(cfqq);
 702
 703         /*
 704          * store what was left of this slice, if the queue idled out
 705          * or was preempted
 706          */
 707         if (timed_out && !cfq_cfqq_slice_new(cfqq))
 708                 cfqq->slice_resid = cfqq->slice_end - jiffies;
 709
 710         cfq_resort_rr_list(cfqq, preempted);
 711
 712         if (cfqq == cfqd->active_queue)
 713                 cfqd->active_queue = NULL;
 714
 715         if (cfqd->active_cic) {
 716                 put_io_context(cfqd->active_cic->ioc);
 717                 cfqd->active_cic = NULL;
 718         }
 719
 720         cfqd->dispatch_slice = 0;
 721 }
 722
 723 static inline void cfq_slice_expired(struct cfq_data *cfqd, int preempted,
 724                                      int timed_out)
 725 {
 726         struct cfq_queue *cfqq = cfqd->active_queue;
 727
 728         if (cfqq)
 729                 __cfq_slice_expired(cfqd, cfqq, preempted, timed_out);
 730 }
 731
 732 /*
 733  * 0
 734  * 0,1
 735  * 0,1,2
 736  * 0,1,2,3
 737  * 0,1,2,3,4
 738  * 0,1,2,3,4,5
 739  * 0,1,2,3,4,5,6
 740  * 0,1,2,3,4,5,6,7
 741  */
 742 static int cfq_get_next_prio_level(struct cfq_data *cfqd)
 743 {
 744         int prio, wrap;
 745
 746         prio = -1;
 747         wrap = 0;
 748         do {
 749                 int p;
 750
 751                 for (p = cfqd->cur_prio; p <= cfqd->cur_end_prio; p++) {
 752                         if (!list_empty(&cfqd->rr_list[p])) {
 753                                 prio = p;
 754                                 break;
 755                         }
 756                 }
 757
 758                 if (prio != -1)
 759                         break;
 760                 cfqd->cur_prio = 0;
 761                 if (++cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
 762                         cfqd->cur_end_prio = 0;
 763                         if (wrap)
 764                                 break;
 765                         wrap = 1;
 766                 }
 767         } while (1);
 768
 769         if (unlikely(prio == -1))
 770                 return -1;
 771
 772         BUG_ON(prio >= CFQ_PRIO_LISTS);
 773
 774         list_splice_init(&cfqd->rr_list[prio], &cfqd->cur_rr);
 775
 776         cfqd->cur_prio = prio + 1;
 777         if (cfqd->cur_prio > cfqd->cur_end_prio) {
 778                 cfqd->cur_end_prio = cfqd->cur_prio;
 779                 cfqd->cur_prio = 0;
 780         }
 781         if (cfqd->cur_end_prio == CFQ_PRIO_LISTS) {
 782                 cfqd->cur_prio = 0;
 783                 cfqd->cur_end_prio = 0;
 784         }
 785
 786         return prio;
 787 }
 788
 789 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
 790 {
 791         struct cfq_queue *cfqq = NULL;
 792
 793         if (!list_empty(&cfqd->cur_rr) || cfq_get_next_prio_level(cfqd) != -1) {
 794                 /*
 795                  * if current list is non-empty, grab first entry. if it is
 796                  * empty, get next prio level and grab first entry then if any
 797                  * are spliced
 798                  */
 799                 cfqq = list_entry_cfqq(cfqd->cur_rr.next);
 800         } else if (!list_empty(&cfqd->busy_rr)) {
 801                 /*
 802                  * If no new queues are available, check if the busy list has
 803                  * some before falling back to idle io.
 804                  */
 805                 cfqq = list_entry_cfqq(cfqd->busy_rr.next);
 806         } else if (!list_empty(&cfqd->idle_rr)) {
 807                 /*
 808                  * if we have idle queues and no rt or be queues had pending
 809                  * requests, either allow immediate service if the grace period
 810                  * has passed or arm the idle grace timer
 811                  */
 812                 unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE;
 813
 814                 if (time_after_eq(jiffies, end))
 815                         cfqq = list_entry_cfqq(cfqd->idle_rr.next);
 816                 else
 817                         mod_timer(&cfqd->idle_class_timer, end);
 818         }
 819
 820         __cfq_set_active_queue(cfqd, cfqq);
 821         return cfqq;
 822 }
 823
 824 #define CIC_SEEKY(cic) ((cic)->seek_mean > (128 * 1024))
 825
 826 static int cfq_arm_slice_timer(struct cfq_data *cfqd)
 827 {
 828         struct cfq_queue *cfqq = cfqd->active_queue;
 829         struct cfq_io_context *cic;
 830         unsigned long sl;
 831
 832         WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
 833
 834         /*
 835          * idle is disabled, either manually or by past process history
 836          */
 837         if (!cfqd->cfq_slice_idle)
 838                 return 0;
 839         if (!cfq_cfqq_idle_window(cfqq))
 840                 return 0;
 841         /*
 842          * task has exited, don't wait
 843          */
 844         cic = cfqd->active_cic;
 845         if (!cic || !cic->ioc->task)
 846                 return 0;
 847
 848         cfq_mark_cfqq_must_dispatch(cfqq);
 849         cfq_mark_cfqq_wait_request(cfqq);
 850
 851         sl = min(cfqq->slice_end - 1, (unsigned long) cfqd->cfq_slice_idle);
 852
 853         /*
 854          * we don't want to idle for seeks, but we do want to allow
 855          * fair distribution of slice time for a process doing back-to-back
 856          * seeks. so allow a little bit of time for him to submit a new rq
 857          */
 858         if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
 859                 sl = min(sl, msecs_to_jiffies(2));
 860
 861         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
 862         return 1;
 863 }
 864
 865 static void cfq_dispatch_insert(request_queue_t *q, struct request *rq)
 866 {
 867         struct cfq_data *cfqd = q->elevator->elevator_data;
 868         struct cfq_queue *cfqq = RQ_CFQQ(rq);
 869
 870         cfq_remove_request(rq);
 871         cfqq->on_dispatch[rq_is_sync(rq)]++;
 872         elv_dispatch_sort(q, rq);
 873
 874         rq = list_entry(q->queue_head.prev, struct request, queuelist);
 875         cfqd->last_sector = rq->sector + rq->nr_sectors;
 876 }
 877
 878 /*
 879  * return expired entry, or NULL to just start from scratch in rbtree
 880  */
 881 static inline struct request *cfq_check_fifo(struct cfq_queue *cfqq)
 882 {
 883         struct cfq_data *cfqd = cfqq->cfqd;
 884         struct request *rq;
 885         int fifo;
 886
 887         if (cfq_cfqq_fifo_expire(cfqq))
 888                 return NULL;
 889
 890         cfq_mark_cfqq_fifo_expire(cfqq);
 891
 892         if (list_empty(&cfqq->fifo))
 893                 return NULL;
 894
 895         fifo = cfq_cfqq_class_sync(cfqq);
 896         rq = rq_entry_fifo(cfqq->fifo.next);
 897
 898         if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))
 899                 return rq;
 900
 901         return NULL;
 902 }
 903
 904 static inline int
 905 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 906 {
 907         const int base_rq = cfqd->cfq_slice_async_rq;
 908
 909         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
 910
 911         return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
 912 }
 913
 914 /*
 915  * get next queue for service
 916  */
 917 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
 918 {
 919         struct cfq_queue *cfqq;
 920
 921         cfqq = cfqd->active_queue;
 922         if (!cfqq)
 923                 goto new_queue;
 924
 925         /*
 926          * slice has expired
 927          */
 928         if (!cfq_cfqq_must_dispatch(cfqq) && cfq_slice_used(cfqq))
 929                 goto expire;
 930
 931         /*
 932          * if queue has requests, dispatch one. if not, check if
 933          * enough slice is left to wait for one
 934          */
 935         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
 936                 goto keep_queue;
 937         else if (cfq_cfqq_slice_new(cfqq) || cfq_cfqq_dispatched(cfqq)) {
 938                 cfqq = NULL;
 939                 goto keep_queue;
 940         } else if (cfq_cfqq_class_sync(cfqq)) {
 941                 if (cfq_arm_slice_timer(cfqd))
 942                         return NULL;
 943         }
 944
 945 expire:
 946         cfq_slice_expired(cfqd, 0, 0);
 947 new_queue:
 948         cfqq = cfq_set_active_queue(cfqd);
 949 keep_queue:
 950         return cfqq;
 951 }
 952
 953 static int
 954 __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 955                         int max_dispatch)
 956 {
 957         int dispatched = 0;
 958
 959         BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
 960
 961         do {
 962                 struct request *rq;
 963
 964                 /*
 965                  * follow expired path, else get first next available
 966                  */
 967                 if ((rq = cfq_check_fifo(cfqq)) == NULL)
 968                         rq = cfqq->next_rq;
 969
 970                 /*
 971                  * finally, insert request into driver dispatch list
 972                  */
 973                 cfq_dispatch_insert(cfqd->queue, rq);
 974
 975                 cfqd->dispatch_slice++;
 976                 dispatched++;
 977
 978                 if (!cfqd->active_cic) {
 979                         atomic_inc(&RQ_CIC(rq)->ioc->refcount);
 980                         cfqd->active_cic = RQ_CIC(rq);
 981                 }
 982
 983                 if (RB_EMPTY_ROOT(&cfqq->sort_list))
 984                         break;
 985
 986         } while (dispatched < max_dispatch);
 987
 988         /*
 989          * expire an async queue immediately if it has used up its slice. idle
 990          * queue always expire after 1 dispatch round.
 991          */
 992         if ((!cfq_cfqq_sync(cfqq) &&
 993             cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
 994             cfq_class_idle(cfqq)) {
 995                 cfqq->slice_end = jiffies + 1;
 996                 cfq_slice_expired(cfqd, 0, 0);
 997         }
 998
 999         return dispatched;
1000 }
1001
1002 static int
1003 cfq_forced_dispatch_cfqqs(struct list_head *list)
1004 {
1005         struct cfq_queue *cfqq, *next;
1006         int dispatched;
1007
1008         dispatched = 0;
1009         list_for_each_entry_safe(cfqq, next, list, cfq_list) {
1010                 while (cfqq->next_rq) {
1011                         cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
1012                         dispatched++;
1013                 }
1014                 BUG_ON(!list_empty(&cfqq->fifo));
1015         }
1016
1017         return dispatched;
1018 }
1019
1020 static int
1021 cfq_forced_dispatch(struct cfq_data *cfqd)
1022 {
1023         int i, dispatched = 0;
1024
1025         for (i = 0; i < CFQ_PRIO_LISTS; i++)
1026                 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]);
1027
1028         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->busy_rr);
1029         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr);
1030         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr);
1031
1032         cfq_slice_expired(cfqd, 0, 0);
1033
1034         BUG_ON(cfqd->busy_queues);
1035
1036         return dispatched;
1037 }
1038
1039 static int
1040 cfq_dispatch_requests(request_queue_t *q, int force)
1041 {
1042         struct cfq_data *cfqd = q->elevator->elevator_data;
1043         struct cfq_queue *cfqq, *prev_cfqq;
1044         int dispatched;
1045
1046         if (!cfqd->busy_queues)
1047                 return 0;
1048
1049         if (unlikely(force))
1050                 return cfq_forced_dispatch(cfqd);
1051
1052         dispatched = 0;
1053         prev_cfqq = NULL;
1054         while ((cfqq = cfq_select_queue(cfqd)) != NULL) {
1055                 int max_dispatch;
1056
1057                 /*
1058                  * Don't repeat dispatch from the previous queue.
1059                  */
1060                 if (prev_cfqq == cfqq)
1061                         break;
1062
1063                 cfq_clear_cfqq_must_dispatch(cfqq);
1064                 cfq_clear_cfqq_wait_request(cfqq);
1065                 del_timer(&cfqd->idle_slice_timer);
1066
1067                 max_dispatch = cfqd->cfq_quantum;
1068                 if (cfq_class_idle(cfqq))
1069                         max_dispatch = 1;
1070
1071                 dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
1072
1073                 /*
1074                  * If the dispatch cfqq has idling enabled and is still
1075                  * the active queue, break out.
1076                  */
1077                 if (cfq_cfqq_idle_window(cfqq) && cfqd->active_queue)
1078                         break;
1079
1080                 prev_cfqq = cfqq;
1081         }
1082
1083         return dispatched;
1084 }
1085
1086 /*
1087  * task holds one reference to the queue, dropped when task exits. each rq
1088  * in-flight on this queue also holds a reference, dropped when rq is freed.
1089  *
1090  * queue lock must be held here.
1091  */
1092 static void cfq_put_queue(struct cfq_queue *cfqq)
1093 {
1094         struct cfq_data *cfqd = cfqq->cfqd;
1095
1096         BUG_ON(atomic_read(&cfqq->ref) <= 0);
1097
1098         if (!atomic_dec_and_test(&cfqq->ref))
1099                 return;
1100
1101         BUG_ON(rb_first(&cfqq->sort_list));
1102         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1103         BUG_ON(cfq_cfqq_on_rr(cfqq));
1104
1105         if (unlikely(cfqd->active_queue == cfqq))
1106                 __cfq_slice_expired(cfqd, cfqq, 0, 0);
1107
1108         /*
1109          * it's on the empty list and still hashed
1110          */
1111         list_del(&cfqq->cfq_list);
1112         hlist_del(&cfqq->cfq_hash);
1113         kmem_cache_free(cfq_pool, cfqq);
1114 }
1115
1116 static struct cfq_queue *
1117 __cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned int prio,
1118                     const int hashval)
1119 {
1120         struct hlist_head *hash_list = &cfqd->cfq_hash[hashval];
1121         struct hlist_node *entry;
1122         struct cfq_queue *__cfqq;
1123
1124         hlist_for_each_entry(__cfqq, entry, hash_list, cfq_hash) {
1125                 const unsigned short __p = IOPRIO_PRIO_VALUE(__cfqq->org_ioprio_class, __cfqq->org_ioprio);
1126
1127                 if (__cfqq->key == key && (__p == prio || !prio))
1128                         return __cfqq;
1129         }
1130
1131         return NULL;
1132 }
1133
1134 static struct cfq_queue *
1135 cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned short prio)
1136 {
1137         return __cfq_find_cfq_hash(cfqd, key, prio, hash_long(key, CFQ_QHASH_SHIFT));
1138 }
1139
1140 static void cfq_free_io_context(struct io_context *ioc)
1141 {
1142         struct cfq_io_context *__cic;
1143         struct rb_node *n;
1144         int freed = 0;
1145
1146         while ((n = rb_first(&ioc->cic_root)) != NULL) {
1147                 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1148                 rb_erase(&__cic->rb_node, &ioc->cic_root);
1149                 kmem_cache_free(cfq_ioc_pool, __cic);
1150                 freed++;
1151         }
1152
1153         elv_ioc_count_mod(ioc_count, -freed);
1154
1155         if (ioc_gone && !elv_ioc_count_read(ioc_count))
1156                 complete(ioc_gone);
1157 }
1158
1159 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1160 {
1161         if (unlikely(cfqq == cfqd->active_queue))
1162                 __cfq_slice_expired(cfqd, cfqq, 0, 0);
1163
1164         cfq_put_queue(cfqq);
1165 }
1166
1167 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
1168                                          struct cfq_io_context *cic)
1169 {
1170         list_del_init(&cic->queue_list);
1171         smp_wmb();
1172         cic->key = NULL;
1173
1174         if (cic->cfqq[ASYNC]) {
1175                 cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]);
1176                 cic->cfqq[ASYNC] = NULL;
1177         }
1178
1179         if (cic->cfqq[SYNC]) {
1180                 cfq_exit_cfqq(cfqd, cic->cfqq[SYNC]);
1181                 cic->cfqq[SYNC] = NULL;
1182         }
1183 }
1184
1185
1186 /*
1187  * Called with interrupts disabled
1188  */
1189 static void cfq_exit_single_io_context(struct cfq_io_context *cic)
1190 {
1191         struct cfq_data *cfqd = cic->key;
1192
1193         if (cfqd) {
1194                 request_queue_t *q = cfqd->queue;
1195
1196                 spin_lock_irq(q->queue_lock);
1197                 __cfq_exit_single_io_context(cfqd, cic);
1198                 spin_unlock_irq(q->queue_lock);
1199         }
1200 }
1201
1202 static void cfq_exit_io_context(struct io_context *ioc)
1203 {
1204         struct cfq_io_context *__cic;
1205         struct rb_node *n;
1206
1207         /*
1208          * put the reference this task is holding to the various queues
1209          */
1210
1211         n = rb_first(&ioc->cic_root);
1212         while (n != NULL) {
1213                 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1214
1215                 cfq_exit_single_io_context(__cic);
1216                 n = rb_next(n);
1217         }
1218 }
1219
1220 static struct cfq_io_context *
1221 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1222 {
1223         struct cfq_io_context *cic;
1224
1225         cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask, cfqd->queue->node);
1226         if (cic) {
1227                 memset(cic, 0, sizeof(*cic));
1228                 cic->last_end_request = jiffies;
1229                 INIT_LIST_HEAD(&cic->queue_list);
1230                 cic->dtor = cfq_free_io_context;
1231                 cic->exit = cfq_exit_io_context;
1232                 elv_ioc_count_inc(ioc_count);
1233         }
1234
1235         return cic;
1236 }
1237
1238 static void cfq_init_prio_data(struct cfq_queue *cfqq)
1239 {
1240         struct task_struct *tsk = current;
1241         int ioprio_class;
1242
1243         if (!cfq_cfqq_prio_changed(cfqq))
1244                 return;
1245
1246         ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
1247         switch (ioprio_class) {
1248                 default:
1249                         printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1250                 case IOPRIO_CLASS_NONE:
1251                         /*
1252                          * no prio set, place us in the middle of the BE classes
1253                          */
1254                         cfqq->ioprio = task_nice_ioprio(tsk);
1255                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1256                         break;
1257                 case IOPRIO_CLASS_RT:
1258                         cfqq->ioprio = task_ioprio(tsk);
1259                         cfqq->ioprio_class = IOPRIO_CLASS_RT;
1260                         break;
1261                 case IOPRIO_CLASS_BE:
1262                         cfqq->ioprio = task_ioprio(tsk);
1263                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1264                         break;
1265                 case IOPRIO_CLASS_IDLE:
1266                         cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1267                         cfqq->ioprio = 7;
1268                         cfq_clear_cfqq_idle_window(cfqq);
1269                         break;
1270         }
1271
1272         /*
1273          * keep track of original prio settings in case we have to temporarily
1274          * elevate the priority of this queue
1275          */
1276         cfqq->org_ioprio = cfqq->ioprio;
1277         cfqq->org_ioprio_class = cfqq->ioprio_class;
1278
1279         cfq_resort_rr_list(cfqq, 0);
1280         cfq_clear_cfqq_prio_changed(cfqq);
1281 }
1282
1283 static inline void changed_ioprio(struct cfq_io_context *cic)
1284 {
1285         struct cfq_data *cfqd = cic->key;
1286         struct cfq_queue *cfqq;
1287         unsigned long flags;
1288
1289         if (unlikely(!cfqd))
1290                 return;
1291
1292         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1293
1294         cfqq = cic->cfqq[ASYNC];
1295         if (cfqq) {
1296                 struct cfq_queue *new_cfqq;
1297                 new_cfqq = cfq_get_queue(cfqd, CFQ_KEY_ASYNC, cic->ioc->task,
1298                                          GFP_ATOMIC);
1299                 if (new_cfqq) {
1300                         cic->cfqq[ASYNC] = new_cfqq;
1301                         cfq_put_queue(cfqq);
1302                 }
1303         }
1304
1305         cfqq = cic->cfqq[SYNC];
1306         if (cfqq)
1307                 cfq_mark_cfqq_prio_changed(cfqq);
1308
1309         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1310 }
1311
1312 static void cfq_ioc_set_ioprio(struct io_context *ioc)
1313 {
1314         struct cfq_io_context *cic;
1315         struct rb_node *n;
1316
1317         ioc->ioprio_changed = 0;
1318
1319         n = rb_first(&ioc->cic_root);
1320         while (n != NULL) {
1321                 cic = rb_entry(n, struct cfq_io_context, rb_node);
1322
1323                 changed_ioprio(cic);
1324                 n = rb_next(n);
1325         }
1326 }
1327
1328 static struct cfq_queue *
1329 cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk,
1330               gfp_t gfp_mask)
1331 {
1332         const int hashval = hash_long(key, CFQ_QHASH_SHIFT);
1333         struct cfq_queue *cfqq, *new_cfqq = NULL;
1334         unsigned short ioprio;
1335
1336 retry:
1337         ioprio = tsk->ioprio;
1338         cfqq = __cfq_find_cfq_hash(cfqd, key, ioprio, hashval);
1339
1340         if (!cfqq) {
1341                 if (new_cfqq) {
1342                         cfqq = new_cfqq;
1343                         new_cfqq = NULL;
1344                 } else if (gfp_mask & __GFP_WAIT) {
1345                         /*
1346                          * Inform the allocator of the fact that we will
1347                          * just repeat this allocation if it fails, to allow
1348                          * the allocator to do whatever it needs to attempt to
1349                          * free memory.
1350                          */
1351                         spin_unlock_irq(cfqd->queue->queue_lock);
1352                         new_cfqq = kmem_cache_alloc_node(cfq_pool, gfp_mask|__GFP_NOFAIL, cfqd->queue->node);
1353                         spin_lock_irq(cfqd->queue->queue_lock);
1354                         goto retry;
1355                 } else {
1356                         cfqq = kmem_cache_alloc_node(cfq_pool, gfp_mask, cfqd->queue->node);
1357                         if (!cfqq)
1358                                 goto out;
1359                 }
1360
1361                 memset(cfqq, 0, sizeof(*cfqq));
1362
1363                 INIT_HLIST_NODE(&cfqq->cfq_hash);
1364                 INIT_LIST_HEAD(&cfqq->cfq_list);
1365                 INIT_LIST_HEAD(&cfqq->fifo);
1366
1367                 cfqq->key = key;
1368                 hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
1369                 atomic_set(&cfqq->ref, 0);
1370                 cfqq->cfqd = cfqd;
1371
1372                 cfq_mark_cfqq_idle_window(cfqq);
1373                 cfq_mark_cfqq_prio_changed(cfqq);
1374                 cfq_mark_cfqq_queue_new(cfqq);
1375                 cfq_init_prio_data(cfqq);
1376         }
1377
1378         if (new_cfqq)
1379                 kmem_cache_free(cfq_pool, new_cfqq);
1380
1381         atomic_inc(&cfqq->ref);
1382 out:
1383         WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
1384         return cfqq;
1385 }
1386
1387 static void
1388 cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)
1389 {
1390         WARN_ON(!list_empty(&cic->queue_list));
1391         rb_erase(&cic->rb_node, &ioc->cic_root);
1392         kmem_cache_free(cfq_ioc_pool, cic);
1393         elv_ioc_count_dec(ioc_count);
1394 }
1395
1396 static struct cfq_io_context *
1397 cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
1398 {
1399         struct rb_node *n;
1400         struct cfq_io_context *cic;
1401         void *k, *key = cfqd;
1402
1403 restart:
1404         n = ioc->cic_root.rb_node;
1405         while (n) {
1406                 cic = rb_entry(n, struct cfq_io_context, rb_node);
1407                 /* ->key must be copied to avoid race with cfq_exit_queue() */
1408                 k = cic->key;
1409                 if (unlikely(!k)) {
1410                         cfq_drop_dead_cic(ioc, cic);
1411                         goto restart;
1412                 }
1413
1414                 if (key < k)
1415                         n = n->rb_left;
1416                 else if (key > k)
1417                         n = n->rb_right;
1418                 else
1419                         return cic;
1420         }
1421
1422         return NULL;
1423 }
1424
1425 static inline void
1426 cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
1427              struct cfq_io_context *cic)
1428 {
1429         struct rb_node **p;
1430         struct rb_node *parent;
1431         struct cfq_io_context *__cic;
1432         unsigned long flags;
1433         void *k;
1434
1435         cic->ioc = ioc;
1436         cic->key = cfqd;
1437
1438 restart:
1439         parent = NULL;
1440         p = &ioc->cic_root.rb_node;
1441         while (*p) {
1442                 parent = *p;
1443                 __cic = rb_entry(parent, struct cfq_io_context, rb_node);
1444                 /* ->key must be copied to avoid race with cfq_exit_queue() */
1445                 k = __cic->key;
1446                 if (unlikely(!k)) {
1447                         cfq_drop_dead_cic(ioc, __cic);
1448                         goto restart;
1449                 }
1450
1451                 if (cic->key < k)
1452                         p = &(*p)->rb_left;
1453                 else if (cic->key > k)
1454                         p = &(*p)->rb_right;
1455                 else
1456                         BUG();
1457         }
1458
1459         rb_link_node(&cic->rb_node, parent, p);
1460         rb_insert_color(&cic->rb_node, &ioc->cic_root);
1461
1462         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1463         list_add(&cic->queue_list, &cfqd->cic_list);
1464         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1465 }
1466
1467 /*
1468  * Setup general io context and cfq io context. There can be several cfq
1469  * io contexts per general io context, if this process is doing io to more
1470  * than one device managed by cfq.
1471  */
1472 static struct cfq_io_context *
1473 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1474 {
1475         struct io_context *ioc = NULL;
1476         struct cfq_io_context *cic;
1477
1478         might_sleep_if(gfp_mask & __GFP_WAIT);
1479
1480         ioc = get_io_context(gfp_mask, cfqd->queue->node);
1481         if (!ioc)
1482                 return NULL;
1483
1484         cic = cfq_cic_rb_lookup(cfqd, ioc);
1485         if (cic)
1486                 goto out;
1487
1488         cic = cfq_alloc_io_context(cfqd, gfp_mask);
1489         if (cic == NULL)
1490                 goto err;
1491
1492         cfq_cic_link(cfqd, ioc, cic);
1493 out:
1494         smp_read_barrier_depends();
1495         if (unlikely(ioc->ioprio_changed))
1496                 cfq_ioc_set_ioprio(ioc);
1497
1498         return cic;
1499 err:
1500         put_io_context(ioc);
1501         return NULL;
1502 }
1503
1504 static void
1505 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1506 {
1507         unsigned long elapsed = jiffies - cic->last_end_request;
1508         unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1509
1510         cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1511         cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1512         cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1513 }
1514
1515 static void
1516 cfq_update_io_seektime(struct cfq_io_context *cic, struct request *rq)
1517 {
1518         sector_t sdist;
1519         u64 total;
1520
1521         if (cic->last_request_pos < rq->sector)
1522                 sdist = rq->sector - cic->last_request_pos;
1523         else
1524                 sdist = cic->last_request_pos - rq->sector;
1525
1526         /*
1527          * Don't allow the seek distance to get too large from the
1528          * odd fragment, pagein, etc
1529          */
1530         if (cic->seek_samples <= 60) /* second&third seek */
1531                 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
1532         else
1533                 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
1534
1535         cic->seek_samples = (7*cic->seek_samples + 256) / 8;
1536         cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
1537         total = cic->seek_total + (cic->seek_samples/2);
1538         do_div(total, cic->seek_samples);
1539         cic->seek_mean = (sector_t)total;
1540 }
1541
1542 /*
1543  * Disable idle window if the process thinks too long or seeks so much that
1544  * it doesn't matter
1545  */
1546 static void
1547 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1548                        struct cfq_io_context *cic)
1549 {
1550         int enable_idle = cfq_cfqq_idle_window(cfqq);
1551
1552         if (!cic->ioc->task || !cfqd->cfq_slice_idle ||
1553             (cfqd->hw_tag && CIC_SEEKY(cic)))
1554                 enable_idle = 0;
1555         else if (sample_valid(cic->ttime_samples)) {
1556                 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1557                         enable_idle = 0;
1558                 else
1559                         enable_idle = 1;
1560         }
1561
1562         if (enable_idle)
1563                 cfq_mark_cfqq_idle_window(cfqq);
1564         else
1565                 cfq_clear_cfqq_idle_window(cfqq);
1566 }
1567
1568
1569 /*
1570  * Check if new_cfqq should preempt the currently active queue. Return 0 for
1571  * no or if we aren't sure, a 1 will cause a preempt.
1572  */
1573 static int
1574 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1575                    struct request *rq)
1576 {
1577         struct cfq_queue *cfqq = cfqd->active_queue;
1578
1579         if (cfq_class_idle(new_cfqq))
1580                 return 0;
1581
1582         if (!cfqq)
1583                 return 0;
1584
1585         if (cfq_class_idle(cfqq))
1586                 return 1;
1587         if (!cfq_cfqq_wait_request(new_cfqq))
1588                 return 0;
1589         /*
1590          * if the new request is sync, but the currently running queue is
1591          * not, let the sync request have priority.
1592          */
1593         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
1594                 return 1;
1595         /*
1596          * So both queues are sync. Let the new request get disk time if
1597          * it's a metadata request and the current queue is doing regular IO.
1598          */
1599         if (rq_is_meta(rq) && !cfqq->meta_pending)
1600                 return 1;
1601
1602         return 0;
1603 }
1604
1605 /*
1606  * cfqq preempts the active queue. if we allowed preempt with no slice left,
1607  * let it have half of its nominal slice.
1608  */
1609 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1610 {
1611         cfq_slice_expired(cfqd, 1, 1);
1612
1613         /*
1614          * Put the new queue at the front of the of the current list,
1615          * so we know that it will be selected next.
1616          */
1617         BUG_ON(!cfq_cfqq_on_rr(cfqq));
1618         list_move(&cfqq->cfq_list, &cfqd->cur_rr);
1619
1620         cfqq->slice_end = 0;
1621         cfq_mark_cfqq_slice_new(cfqq);
1622 }
1623
1624 /*
1625  * Called when a new fs request (rq) is added (to cfqq). Check if there's
1626  * something we should do about it
1627  */
1628 static void
1629 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1630                 struct request *rq)
1631 {
1632         struct cfq_io_context *cic = RQ_CIC(rq);
1633
1634         if (rq_is_meta(rq))
1635                 cfqq->meta_pending++;
1636
1637         /*
1638          * check if this request is a better next-serve candidate)) {
1639          */
1640         cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq);
1641         BUG_ON(!cfqq->next_rq);
1642
1643         /*
1644          * we never wait for an async request and we don't allow preemption
1645          * of an async request. so just return early
1646          */
1647         if (!rq_is_sync(rq)) {
1648                 /*
1649                  * sync process issued an async request, if it's waiting
1650                  * then expire it and kick rq handling.
1651                  */
1652                 if (cic == cfqd->active_cic &&
1653                     del_timer(&cfqd->idle_slice_timer)) {
1654                         cfq_slice_expired(cfqd, 0, 0);
1655                         blk_start_queueing(cfqd->queue);
1656                 }
1657                 return;
1658         }
1659
1660         cfq_update_io_thinktime(cfqd, cic);
1661         cfq_update_io_seektime(cic, rq);
1662         cfq_update_idle_window(cfqd, cfqq, cic);
1663
1664         cic->last_request_pos = rq->sector + rq->nr_sectors;
1665
1666         if (cfqq == cfqd->active_queue) {
1667                 /*
1668                  * if we are waiting for a request for this queue, let it rip
1669                  * immediately and flag that we must not expire this queue
1670                  * just now
1671                  */
1672                 if (cfq_cfqq_wait_request(cfqq)) {
1673                         cfq_mark_cfqq_must_dispatch(cfqq);
1674                         del_timer(&cfqd->idle_slice_timer);
1675                         blk_start_queueing(cfqd->queue);
1676                 }
1677         } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
1678                 /*
1679                  * not the active queue - expire current slice if it is
1680                  * idle and has expired it's mean thinktime or this new queue
1681                  * has some old slice time left and is of higher priority
1682                  */
1683                 cfq_preempt_queue(cfqd, cfqq);
1684                 cfq_mark_cfqq_must_dispatch(cfqq);
1685                 blk_start_queueing(cfqd->queue);
1686         }
1687 }
1688
1689 static void cfq_insert_request(request_queue_t *q, struct request *rq)
1690 {
1691         struct cfq_data *cfqd = q->elevator->elevator_data;
1692         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1693
1694         cfq_init_prio_data(cfqq);
1695
1696         cfq_add_rq_rb(rq);
1697
1698         list_add_tail(&rq->queuelist, &cfqq->fifo);
1699
1700         cfq_rq_enqueued(cfqd, cfqq, rq);
1701 }
1702
1703 static void cfq_completed_request(request_queue_t *q, struct request *rq)
1704 {
1705         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1706         struct cfq_data *cfqd = cfqq->cfqd;
1707         const int sync = rq_is_sync(rq);
1708         unsigned long now;
1709
1710         now = jiffies;
1711
1712         WARN_ON(!cfqd->rq_in_driver);
1713         WARN_ON(!cfqq->on_dispatch[sync]);
1714         cfqd->rq_in_driver--;
1715         cfqq->on_dispatch[sync]--;
1716         cfqq->service_last = now;
1717
1718         if (!cfq_class_idle(cfqq))
1719                 cfqd->last_end_request = now;
1720
1721         cfq_resort_rr_list(cfqq, 0);
1722
1723         if (sync)
1724                 RQ_CIC(rq)->last_end_request = now;
1725
1726         /*
1727          * If this is the active queue, check if it needs to be expired,
1728          * or if we want to idle in case it has no pending requests.
1729          */
1730         if (cfqd->active_queue == cfqq) {
1731                 if (cfq_cfqq_slice_new(cfqq)) {
1732                         cfq_set_prio_slice(cfqd, cfqq);
1733                         cfq_clear_cfqq_slice_new(cfqq);
1734                 }
1735                 if (cfq_slice_used(cfqq))
1736                         cfq_slice_expired(cfqd, 0, 1);
1737                 else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1738                         if (!cfq_arm_slice_timer(cfqd))
1739                                 cfq_schedule_dispatch(cfqd);
1740                 }
1741         }
1742 }
1743
1744 /*
1745  * we temporarily boost lower priority queues if they are holding fs exclusive
1746  * resources. they are boosted to normal prio (CLASS_BE/4)
1747  */
1748 static void cfq_prio_boost(struct cfq_queue *cfqq)
1749 {
1750         const int ioprio_class = cfqq->ioprio_class;
1751         const int ioprio = cfqq->ioprio;
1752
1753         if (has_fs_excl()) {
1754                 /*
1755                  * boost idle prio on transactions that would lock out other
1756                  * users of the filesystem
1757                  */
1758                 if (cfq_class_idle(cfqq))
1759                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1760                 if (cfqq->ioprio > IOPRIO_NORM)
1761                         cfqq->ioprio = IOPRIO_NORM;
1762         } else {
1763                 /*
1764                  * check if we need to unboost the queue
1765                  */
1766                 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
1767                         cfqq->ioprio_class = cfqq->org_ioprio_class;
1768                 if (cfqq->ioprio != cfqq->org_ioprio)
1769                         cfqq->ioprio = cfqq->org_ioprio;
1770         }
1771
1772         /*
1773          * refile between round-robin lists if we moved the priority class
1774          */
1775         if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio))
1776                 cfq_resort_rr_list(cfqq, 0);
1777 }
1778
1779 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
1780 {
1781         if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
1782             !cfq_cfqq_must_alloc_slice(cfqq)) {
1783                 cfq_mark_cfqq_must_alloc_slice(cfqq);
1784                 return ELV_MQUEUE_MUST;
1785         }
1786
1787         return ELV_MQUEUE_MAY;
1788 }
1789
1790 static int cfq_may_queue(request_queue_t *q, int rw)
1791 {
1792         struct cfq_data *cfqd = q->elevator->elevator_data;
1793         struct task_struct *tsk = current;
1794         struct cfq_queue *cfqq;
1795         unsigned int key;
1796
1797         key = cfq_queue_pid(tsk, rw, rw & REQ_RW_SYNC);
1798
1799         /*
1800          * don't force setup of a queue from here, as a call to may_queue
1801          * does not necessarily imply that a request actually will be queued.
1802          * so just lookup a possibly existing queue, or return 'may queue'
1803          * if that fails
1804          */
1805         cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
1806         if (cfqq) {
1807                 cfq_init_prio_data(cfqq);
1808                 cfq_prio_boost(cfqq);
1809
1810                 return __cfq_may_queue(cfqq);
1811         }
1812
1813         return ELV_MQUEUE_MAY;
1814 }
1815
1816 /*
1817  * queue lock held here
1818  */
1819 static void cfq_put_request(struct request *rq)
1820 {
1821         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1822
1823         if (cfqq) {
1824                 const int rw = rq_data_dir(rq);
1825
1826                 BUG_ON(!cfqq->allocated[rw]);
1827                 cfqq->allocated[rw]--;
1828
1829                 put_io_context(RQ_CIC(rq)->ioc);
1830
1831                 rq->elevator_private = NULL;
1832                 rq->elevator_private2 = NULL;
1833
1834                 cfq_put_queue(cfqq);
1835         }
1836 }
1837
1838 /*
1839  * Allocate cfq data structures associated with this request.
1840  */
1841 static int
1842 cfq_set_request(request_queue_t *q, struct request *rq, gfp_t gfp_mask)
1843 {
1844         struct cfq_data *cfqd = q->elevator->elevator_data;
1845         struct task_struct *tsk = current;
1846         struct cfq_io_context *cic;
1847         const int rw = rq_data_dir(rq);
1848         const int is_sync = rq_is_sync(rq);
1849         pid_t key = cfq_queue_pid(tsk, rw, is_sync);
1850         struct cfq_queue *cfqq;
1851         unsigned long flags;
1852
1853         might_sleep_if(gfp_mask & __GFP_WAIT);
1854
1855         cic = cfq_get_io_context(cfqd, gfp_mask);
1856
1857         spin_lock_irqsave(q->queue_lock, flags);
1858
1859         if (!cic)
1860                 goto queue_fail;
1861
1862         if (!cic->cfqq[is_sync]) {
1863                 cfqq = cfq_get_queue(cfqd, key, tsk, gfp_mask);
1864                 if (!cfqq)
1865                         goto queue_fail;
1866
1867                 cic->cfqq[is_sync] = cfqq;
1868         } else
1869                 cfqq = cic->cfqq[is_sync];
1870
1871         cfqq->allocated[rw]++;
1872         cfq_clear_cfqq_must_alloc(cfqq);
1873         atomic_inc(&cfqq->ref);
1874
1875         spin_unlock_irqrestore(q->queue_lock, flags);
1876
1877         rq->elevator_private = cic;
1878         rq->elevator_private2 = cfqq;
1879         return 0;
1880
1881 queue_fail:
1882         if (cic)
1883                 put_io_context(cic->ioc);
1884
1885         cfq_schedule_dispatch(cfqd);
1886         spin_unlock_irqrestore(q->queue_lock, flags);
1887         return 1;
1888 }
1889
1890 static void cfq_kick_queue(struct work_struct *work)
1891 {
1892         struct cfq_data *cfqd =
1893                 container_of(work, struct cfq_data, unplug_work);
1894         request_queue_t *q = cfqd->queue;
1895         unsigned long flags;
1896
1897         spin_lock_irqsave(q->queue_lock, flags);
1898         blk_start_queueing(q);
1899         spin_unlock_irqrestore(q->queue_lock, flags);
1900 }
1901
1902 /*
1903  * Timer running if the active_queue is currently idling inside its time slice
1904  */
1905 static void cfq_idle_slice_timer(unsigned long data)
1906 {
1907         struct cfq_data *cfqd = (struct cfq_data *) data;
1908         struct cfq_queue *cfqq;
1909         unsigned long flags;
1910         int timed_out = 1;
1911
1912         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1913
1914         if ((cfqq = cfqd->active_queue) != NULL) {
1915                 timed_out = 0;
1916
1917                 /*
1918                  * expired
1919                  */
1920                 if (cfq_slice_used(cfqq))
1921                         goto expire;
1922
1923                 /*
1924                  * only expire and reinvoke request handler, if there are
1925                  * other queues with pending requests
1926                  */
1927                 if (!cfqd->busy_queues)
1928                         goto out_cont;
1929
1930                 /*
1931                  * not expired and it has a request pending, let it dispatch
1932                  */
1933                 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) {
1934                         cfq_mark_cfqq_must_dispatch(cfqq);
1935                         goto out_kick;
1936                 }
1937         }
1938 expire:
1939         cfq_slice_expired(cfqd, 0, timed_out);
1940 out_kick:
1941         cfq_schedule_dispatch(cfqd);
1942 out_cont:
1943         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1944 }
1945
1946 /*
1947  * Timer running if an idle class queue is waiting for service
1948  */
1949 static void cfq_idle_class_timer(unsigned long data)
1950 {
1951         struct cfq_data *cfqd = (struct cfq_data *) data;
1952         unsigned long flags, end;
1953
1954         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1955
1956         /*
1957          * race with a non-idle queue, reset timer
1958          */
1959         end = cfqd->last_end_request + CFQ_IDLE_GRACE;
1960         if (!time_after_eq(jiffies, end))
1961                 mod_timer(&cfqd->idle_class_timer, end);
1962         else
1963                 cfq_schedule_dispatch(cfqd);
1964
1965         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1966 }
1967
1968 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
1969 {
1970         del_timer_sync(&cfqd->idle_slice_timer);
1971         del_timer_sync(&cfqd->idle_class_timer);
1972         blk_sync_queue(cfqd->queue);
1973 }
1974
1975 static void cfq_exit_queue(elevator_t *e)
1976 {
1977         struct cfq_data *cfqd = e->elevator_data;
1978         request_queue_t *q = cfqd->queue;
1979
1980         cfq_shutdown_timer_wq(cfqd);
1981
1982         spin_lock_irq(q->queue_lock);
1983
1984         if (cfqd->active_queue)
1985                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0, 0);
1986
1987         while (!list_empty(&cfqd->cic_list)) {
1988                 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
1989                                                         struct cfq_io_context,
1990                                                         queue_list);
1991
1992                 __cfq_exit_single_io_context(cfqd, cic);
1993         }
1994
1995         spin_unlock_irq(q->queue_lock);
1996
1997         cfq_shutdown_timer_wq(cfqd);
1998
1999         kfree(cfqd->cfq_hash);
2000         kfree(cfqd);
2001 }
2002
2003 static void *cfq_init_queue(request_queue_t *q)
2004 {
2005         struct cfq_data *cfqd;
2006         int i;
2007
2008         cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL, q->node);
2009         if (!cfqd)
2010                 return NULL;
2011
2012         memset(cfqd, 0, sizeof(*cfqd));
2013
2014         for (i = 0; i < CFQ_PRIO_LISTS; i++)
2015                 INIT_LIST_HEAD(&cfqd->rr_list[i]);
2016
2017         INIT_LIST_HEAD(&cfqd->busy_rr);
2018         INIT_LIST_HEAD(&cfqd->cur_rr);
2019         INIT_LIST_HEAD(&cfqd->idle_rr);
2020         INIT_LIST_HEAD(&cfqd->cic_list);
2021
2022         cfqd->cfq_hash = kmalloc_node(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL, q->node);
2023         if (!cfqd->cfq_hash)
2024                 goto out_free;
2025
2026         for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
2027                 INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
2028
2029         cfqd->queue = q;
2030
2031         init_timer(&cfqd->idle_slice_timer);
2032         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2033         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2034
2035         init_timer(&cfqd->idle_class_timer);
2036         cfqd->idle_class_timer.function = cfq_idle_class_timer;
2037         cfqd->idle_class_timer.data = (unsigned long) cfqd;
2038
2039         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
2040
2041         cfqd->cfq_quantum = cfq_quantum;
2042         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2043         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2044         cfqd->cfq_back_max = cfq_back_max;
2045         cfqd->cfq_back_penalty = cfq_back_penalty;
2046         cfqd->cfq_slice[0] = cfq_slice_async;
2047         cfqd->cfq_slice[1] = cfq_slice_sync;
2048         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2049         cfqd->cfq_slice_idle = cfq_slice_idle;
2050
2051         return cfqd;
2052 out_free:
2053         kfree(cfqd);
2054         return NULL;
2055 }
2056
2057 static void cfq_slab_kill(void)
2058 {
2059         if (cfq_pool)
2060                 kmem_cache_destroy(cfq_pool);
2061         if (cfq_ioc_pool)
2062                 kmem_cache_destroy(cfq_ioc_pool);
2063 }
2064
2065 static int __init cfq_slab_setup(void)
2066 {
2067         cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0,
2068                                         NULL, NULL);
2069         if (!cfq_pool)
2070                 goto fail;
2071
2072         cfq_ioc_pool = kmem_cache_create("cfq_ioc_pool",
2073                         sizeof(struct cfq_io_context), 0, 0, NULL, NULL);
2074         if (!cfq_ioc_pool)
2075                 goto fail;
2076
2077         return 0;
2078 fail:
2079         cfq_slab_kill();
2080         return -ENOMEM;
2081 }
2082
2083 /*
2084  * sysfs parts below -->
2085  */
2086
2087 static ssize_t
2088 cfq_var_show(unsigned int var, char *page)
2089 {
2090         return sprintf(page, "%d\n", var);
2091 }
2092
2093 static ssize_t
2094 cfq_var_store(unsigned int *var, const char *page, size_t count)
2095 {
2096         char *p = (char *) page;
2097
2098         *var = simple_strtoul(p, &p, 10);
2099         return count;
2100 }
2101
2102 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
2103 static ssize_t __FUNC(elevator_t *e, char *page)                        \
2104 {                                                                       \
2105         struct cfq_data *cfqd = e->elevator_data;                       \
2106         unsigned int __data = __VAR;                                    \
2107         if (__CONV)                                                     \
2108                 __data = jiffies_to_msecs(__data);                      \
2109         return cfq_var_show(__data, (page));                            \
2110 }
2111 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2112 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2113 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2114 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
2115 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
2116 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2117 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2118 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2119 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2120 #undef SHOW_FUNCTION
2121
2122 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
2123 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count)    \
2124 {                                                                       \
2125         struct cfq_data *cfqd = e->elevator_data;                       \
2126         unsigned int __data;                                            \
2127         int ret = cfq_var_store(&__data, (page), count);                \
2128         if (__data < (MIN))                                             \
2129                 __data = (MIN);                                         \
2130         else if (__data > (MAX))                                        \
2131                 __data = (MAX);                                         \
2132         if (__CONV)                                                     \
2133                 *(__PTR) = msecs_to_jiffies(__data);                    \
2134         else                                                            \
2135                 *(__PTR) = __data;                                      \
2136         return ret;                                                     \
2137 }
2138 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2139 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1);
2140 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1);
2141 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2142 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0);
2143 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2144 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2145 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2146 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0);
2147 #undef STORE_FUNCTION
2148
2149 #define CFQ_ATTR(name) \
2150         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2151
2152 static struct elv_fs_entry cfq_attrs[] = {
2153         CFQ_ATTR(quantum),
2154         CFQ_ATTR(fifo_expire_sync),
2155         CFQ_ATTR(fifo_expire_async),
2156         CFQ_ATTR(back_seek_max),
2157         CFQ_ATTR(back_seek_penalty),
2158         CFQ_ATTR(slice_sync),
2159         CFQ_ATTR(slice_async),
2160         CFQ_ATTR(slice_async_rq),
2161         CFQ_ATTR(slice_idle),
2162         __ATTR_NULL
2163 };
2164
2165 static struct elevator_type iosched_cfq = {
2166         .ops = {
2167                 .elevator_merge_fn =            cfq_merge,
2168                 .elevator_merged_fn =           cfq_merged_request,
2169                 .elevator_merge_req_fn =        cfq_merged_requests,
2170                 .elevator_allow_merge_fn =      cfq_allow_merge,
2171                 .elevator_dispatch_fn =         cfq_dispatch_requests,
2172                 .elevator_add_req_fn =          cfq_insert_request,
2173                 .elevator_activate_req_fn =     cfq_activate_request,
2174                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
2175                 .elevator_queue_empty_fn =      cfq_queue_empty,
2176                 .elevator_completed_req_fn =    cfq_completed_request,
2177                 .elevator_former_req_fn =       elv_rb_former_request,
2178                 .elevator_latter_req_fn =       elv_rb_latter_request,
2179                 .elevator_set_req_fn =          cfq_set_request,
2180                 .elevator_put_req_fn =          cfq_put_request,
2181                 .elevator_may_queue_fn =        cfq_may_queue,
2182                 .elevator_init_fn =             cfq_init_queue,
2183                 .elevator_exit_fn =             cfq_exit_queue,
2184                 .trim =                         cfq_free_io_context,
2185         },
2186         .elevator_attrs =       cfq_attrs,
2187         .elevator_name =        "cfq",
2188         .elevator_owner =       THIS_MODULE,
2189 };
2190
2191 static int __init cfq_init(void)
2192 {
2193         int ret;
2194
2195         /*
2196          * could be 0 on HZ < 1000 setups
2197          */
2198         if (!cfq_slice_async)
2199                 cfq_slice_async = 1;
2200         if (!cfq_slice_idle)
2201                 cfq_slice_idle = 1;
2202
2203         if (cfq_slab_setup())
2204                 return -ENOMEM;
2205
2206         ret = elv_register(&iosched_cfq);
2207         if (ret)
2208                 cfq_slab_kill();
2209
2210         return ret;
2211 }
2212
2213 static void __exit cfq_exit(void)
2214 {
2215         DECLARE_COMPLETION_ONSTACK(all_gone);
2216         elv_unregister(&iosched_cfq);
2217         ioc_gone = &all_gone;
2218         /* ioc_gone's update must be visible before reading ioc_count */
2219         smp_wmb();
2220         if (elv_ioc_count_read(ioc_count))
2221                 wait_for_completion(ioc_gone);
2222         synchronize_rcu();
2223         cfq_slab_kill();
2224 }
2225
2226 module_init(cfq_init);
2227 module_exit(cfq_exit);
2228
2229 MODULE_AUTHOR("Jens Axboe");
2230 MODULE_LICENSE("GPL");
2231 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");