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_queue *cfqq = RQ_CFQQ(rq);
 871
 872         cfq_remove_request(rq);
 873         cfqq->on_dispatch[rq_is_sync(rq)]++;
 874         elv_dispatch_sort(q, rq);
 875 }
 876
 877 /*
 878  * return expired entry, or NULL to just start from scratch in rbtree
 879  */
 880 static inline struct request *cfq_check_fifo(struct cfq_queue *cfqq)
 881 {
 882         struct cfq_data *cfqd = cfqq->cfqd;
 883         struct request *rq;
 884         int fifo;
 885
 886         if (cfq_cfqq_fifo_expire(cfqq))
 887                 return NULL;
 888
 889         cfq_mark_cfqq_fifo_expire(cfqq);
 890
 891         if (list_empty(&cfqq->fifo))
 892                 return NULL;
 893
 894         fifo = cfq_cfqq_class_sync(cfqq);
 895         rq = rq_entry_fifo(cfqq->fifo.next);
 896
 897         if (time_after(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))
 898                 return rq;
 899
 900         return NULL;
 901 }
 902
 903 static inline int
 904 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 905 {
 906         const int base_rq = cfqd->cfq_slice_async_rq;
 907
 908         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
 909
 910         return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
 911 }
 912
 913 /*
 914  * get next queue for service
 915  */
 916 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
 917 {
 918         struct cfq_queue *cfqq;
 919
 920         cfqq = cfqd->active_queue;
 921         if (!cfqq)
 922                 goto new_queue;
 923
 924         /*
 925          * slice has expired
 926          */
 927         if (!cfq_cfqq_must_dispatch(cfqq) && cfq_slice_used(cfqq))
 928                 goto expire;
 929
 930         /*
 931          * if queue has requests, dispatch one. if not, check if
 932          * enough slice is left to wait for one
 933          */
 934         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
 935                 goto keep_queue;
 936         else if (cfq_cfqq_slice_new(cfqq) || cfq_cfqq_dispatched(cfqq)) {
 937                 cfqq = NULL;
 938                 goto keep_queue;
 939         } else if (cfq_cfqq_class_sync(cfqq)) {
 940                 if (cfq_arm_slice_timer(cfqd))
 941                         return NULL;
 942         }
 943
 944 expire:
 945         cfq_slice_expired(cfqd, 0, 0);
 946 new_queue:
 947         cfqq = cfq_set_active_queue(cfqd);
 948 keep_queue:
 949         return cfqq;
 950 }
 951
 952 static int
 953 __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 954                         int max_dispatch)
 955 {
 956         int dispatched = 0;
 957
 958         BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
 959
 960         do {
 961                 struct request *rq;
 962
 963                 /*
 964                  * follow expired path, else get first next available
 965                  */
 966                 if ((rq = cfq_check_fifo(cfqq)) == NULL)
 967                         rq = cfqq->next_rq;
 968
 969                 /*
 970                  * finally, insert request into driver dispatch list
 971                  */
 972                 cfq_dispatch_insert(cfqd->queue, rq);
 973
 974                 cfqd->dispatch_slice++;
 975                 dispatched++;
 976
 977                 if (!cfqd->active_cic) {
 978                         atomic_inc(&RQ_CIC(rq)->ioc->refcount);
 979                         cfqd->active_cic = RQ_CIC(rq);
 980                 }
 981
 982                 if (RB_EMPTY_ROOT(&cfqq->sort_list))
 983                         break;
 984
 985         } while (dispatched < max_dispatch);
 986
 987         /*
 988          * expire an async queue immediately if it has used up its slice. idle
 989          * queue always expire after 1 dispatch round.
 990          */
 991         if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
 992             cfqd->dispatch_slice >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
 993             cfq_class_idle(cfqq))) {
 994                 cfqq->slice_end = jiffies + 1;
 995                 cfq_slice_expired(cfqd, 0, 0);
 996         }
 997
 998         return dispatched;
 999 }
1000
1001 static int
1002 cfq_forced_dispatch_cfqqs(struct list_head *list)
1003 {
1004         struct cfq_queue *cfqq, *next;
1005         int dispatched;
1006
1007         dispatched = 0;
1008         list_for_each_entry_safe(cfqq, next, list, cfq_list) {
1009                 while (cfqq->next_rq) {
1010                         cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
1011                         dispatched++;
1012                 }
1013                 BUG_ON(!list_empty(&cfqq->fifo));
1014         }
1015
1016         return dispatched;
1017 }
1018
1019 static int
1020 cfq_forced_dispatch(struct cfq_data *cfqd)
1021 {
1022         int i, dispatched = 0;
1023
1024         for (i = 0; i < CFQ_PRIO_LISTS; i++)
1025                 dispatched += cfq_forced_dispatch_cfqqs(&cfqd->rr_list[i]);
1026
1027         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->busy_rr);
1028         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->cur_rr);
1029         dispatched += cfq_forced_dispatch_cfqqs(&cfqd->idle_rr);
1030
1031         cfq_slice_expired(cfqd, 0, 0);
1032
1033         BUG_ON(cfqd->busy_queues);
1034
1035         return dispatched;
1036 }
1037
1038 static int
1039 cfq_dispatch_requests(request_queue_t *q, int force)
1040 {
1041         struct cfq_data *cfqd = q->elevator->elevator_data;
1042         struct cfq_queue *cfqq, *prev_cfqq;
1043         int dispatched;
1044
1045         if (!cfqd->busy_queues)
1046                 return 0;
1047
1048         if (unlikely(force))
1049                 return cfq_forced_dispatch(cfqd);
1050
1051         dispatched = 0;
1052         prev_cfqq = NULL;
1053         while ((cfqq = cfq_select_queue(cfqd)) != NULL) {
1054                 int max_dispatch;
1055
1056                 if (cfqd->busy_queues > 1) {
1057                         /*
1058                          * Don't repeat dispatch from the previous queue.
1059                          */
1060                         if (prev_cfqq == cfqq)
1061                                 break;
1062
1063                         /*
1064                          * So we have dispatched before in this round, if the
1065                          * next queue has idling enabled (must be sync), don't
1066                          * allow it service until the previous have continued.
1067                          */
1068                         if (cfqd->rq_in_driver && cfq_cfqq_idle_window(cfqq))
1069                                 break;
1070                 }
1071
1072                 cfq_clear_cfqq_must_dispatch(cfqq);
1073                 cfq_clear_cfqq_wait_request(cfqq);
1074                 del_timer(&cfqd->idle_slice_timer);
1075
1076                 max_dispatch = cfqd->cfq_quantum;
1077                 if (cfq_class_idle(cfqq))
1078                         max_dispatch = 1;
1079
1080                 dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
1081                 prev_cfqq = cfqq;
1082         }
1083
1084         return dispatched;
1085 }
1086
1087 /*
1088  * task holds one reference to the queue, dropped when task exits. each rq
1089  * in-flight on this queue also holds a reference, dropped when rq is freed.
1090  *
1091  * queue lock must be held here.
1092  */
1093 static void cfq_put_queue(struct cfq_queue *cfqq)
1094 {
1095         struct cfq_data *cfqd = cfqq->cfqd;
1096
1097         BUG_ON(atomic_read(&cfqq->ref) <= 0);
1098
1099         if (!atomic_dec_and_test(&cfqq->ref))
1100                 return;
1101
1102         BUG_ON(rb_first(&cfqq->sort_list));
1103         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1104         BUG_ON(cfq_cfqq_on_rr(cfqq));
1105
1106         if (unlikely(cfqd->active_queue == cfqq)) {
1107                 __cfq_slice_expired(cfqd, cfqq, 0, 0);
1108                 cfq_schedule_dispatch(cfqd);
1109         }
1110
1111         /*
1112          * it's on the empty list and still hashed
1113          */
1114         list_del(&cfqq->cfq_list);
1115         hlist_del(&cfqq->cfq_hash);
1116         kmem_cache_free(cfq_pool, cfqq);
1117 }
1118
1119 static struct cfq_queue *
1120 __cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned int prio,
1121                     const int hashval)
1122 {
1123         struct hlist_head *hash_list = &cfqd->cfq_hash[hashval];
1124         struct hlist_node *entry;
1125         struct cfq_queue *__cfqq;
1126
1127         hlist_for_each_entry(__cfqq, entry, hash_list, cfq_hash) {
1128                 const unsigned short __p = IOPRIO_PRIO_VALUE(__cfqq->org_ioprio_class, __cfqq->org_ioprio);
1129
1130                 if (__cfqq->key == key && (__p == prio || !prio))
1131                         return __cfqq;
1132         }
1133
1134         return NULL;
1135 }
1136
1137 static struct cfq_queue *
1138 cfq_find_cfq_hash(struct cfq_data *cfqd, unsigned int key, unsigned short prio)
1139 {
1140         return __cfq_find_cfq_hash(cfqd, key, prio, hash_long(key, CFQ_QHASH_SHIFT));
1141 }
1142
1143 static void cfq_free_io_context(struct io_context *ioc)
1144 {
1145         struct cfq_io_context *__cic;
1146         struct rb_node *n;
1147         int freed = 0;
1148
1149         while ((n = rb_first(&ioc->cic_root)) != NULL) {
1150                 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1151                 rb_erase(&__cic->rb_node, &ioc->cic_root);
1152                 kmem_cache_free(cfq_ioc_pool, __cic);
1153                 freed++;
1154         }
1155
1156         elv_ioc_count_mod(ioc_count, -freed);
1157
1158         if (ioc_gone && !elv_ioc_count_read(ioc_count))
1159                 complete(ioc_gone);
1160 }
1161
1162 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1163 {
1164         if (unlikely(cfqq == cfqd->active_queue)) {
1165                 __cfq_slice_expired(cfqd, cfqq, 0, 0);
1166                 cfq_schedule_dispatch(cfqd);
1167         }
1168
1169         cfq_put_queue(cfqq);
1170 }
1171
1172 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
1173                                          struct cfq_io_context *cic)
1174 {
1175         list_del_init(&cic->queue_list);
1176         smp_wmb();
1177         cic->key = NULL;
1178
1179         if (cic->cfqq[ASYNC]) {
1180                 cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]);
1181                 cic->cfqq[ASYNC] = NULL;
1182         }
1183
1184         if (cic->cfqq[SYNC]) {
1185                 cfq_exit_cfqq(cfqd, cic->cfqq[SYNC]);
1186                 cic->cfqq[SYNC] = NULL;
1187         }
1188 }
1189
1190
1191 /*
1192  * Called with interrupts disabled
1193  */
1194 static void cfq_exit_single_io_context(struct cfq_io_context *cic)
1195 {
1196         struct cfq_data *cfqd = cic->key;
1197
1198         if (cfqd) {
1199                 request_queue_t *q = cfqd->queue;
1200
1201                 spin_lock_irq(q->queue_lock);
1202                 __cfq_exit_single_io_context(cfqd, cic);
1203                 spin_unlock_irq(q->queue_lock);
1204         }
1205 }
1206
1207 static void cfq_exit_io_context(struct io_context *ioc)
1208 {
1209         struct cfq_io_context *__cic;
1210         struct rb_node *n;
1211
1212         /*
1213          * put the reference this task is holding to the various queues
1214          */
1215
1216         n = rb_first(&ioc->cic_root);
1217         while (n != NULL) {
1218                 __cic = rb_entry(n, struct cfq_io_context, rb_node);
1219
1220                 cfq_exit_single_io_context(__cic);
1221                 n = rb_next(n);
1222         }
1223 }
1224
1225 static struct cfq_io_context *
1226 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1227 {
1228         struct cfq_io_context *cic;
1229
1230         cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask, cfqd->queue->node);
1231         if (cic) {
1232                 memset(cic, 0, sizeof(*cic));
1233                 cic->last_end_request = jiffies;
1234                 INIT_LIST_HEAD(&cic->queue_list);
1235                 cic->dtor = cfq_free_io_context;
1236                 cic->exit = cfq_exit_io_context;
1237                 elv_ioc_count_inc(ioc_count);
1238         }
1239
1240         return cic;
1241 }
1242
1243 static void cfq_init_prio_data(struct cfq_queue *cfqq)
1244 {
1245         struct task_struct *tsk = current;
1246         int ioprio_class;
1247
1248         if (!cfq_cfqq_prio_changed(cfqq))
1249                 return;
1250
1251         ioprio_class = IOPRIO_PRIO_CLASS(tsk->ioprio);
1252         switch (ioprio_class) {
1253                 default:
1254                         printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1255                 case IOPRIO_CLASS_NONE:
1256                         /*
1257                          * no prio set, place us in the middle of the BE classes
1258                          */
1259                         cfqq->ioprio = task_nice_ioprio(tsk);
1260                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1261                         break;
1262                 case IOPRIO_CLASS_RT:
1263                         cfqq->ioprio = task_ioprio(tsk);
1264                         cfqq->ioprio_class = IOPRIO_CLASS_RT;
1265                         break;
1266                 case IOPRIO_CLASS_BE:
1267                         cfqq->ioprio = task_ioprio(tsk);
1268                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1269                         break;
1270                 case IOPRIO_CLASS_IDLE:
1271                         cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1272                         cfqq->ioprio = 7;
1273                         cfq_clear_cfqq_idle_window(cfqq);
1274                         break;
1275         }
1276
1277         /*
1278          * keep track of original prio settings in case we have to temporarily
1279          * elevate the priority of this queue
1280          */
1281         cfqq->org_ioprio = cfqq->ioprio;
1282         cfqq->org_ioprio_class = cfqq->ioprio_class;
1283
1284         cfq_resort_rr_list(cfqq, 0);
1285         cfq_clear_cfqq_prio_changed(cfqq);
1286 }
1287
1288 static inline void changed_ioprio(struct cfq_io_context *cic)
1289 {
1290         struct cfq_data *cfqd = cic->key;
1291         struct cfq_queue *cfqq;
1292         unsigned long flags;
1293
1294         if (unlikely(!cfqd))
1295                 return;
1296
1297         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1298
1299         cfqq = cic->cfqq[ASYNC];
1300         if (cfqq) {
1301                 struct cfq_queue *new_cfqq;
1302                 new_cfqq = cfq_get_queue(cfqd, CFQ_KEY_ASYNC, cic->ioc->task,
1303                                          GFP_ATOMIC);
1304                 if (new_cfqq) {
1305                         cic->cfqq[ASYNC] = new_cfqq;
1306                         cfq_put_queue(cfqq);
1307                 }
1308         }
1309
1310         cfqq = cic->cfqq[SYNC];
1311         if (cfqq)
1312                 cfq_mark_cfqq_prio_changed(cfqq);
1313
1314         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1315 }
1316
1317 static void cfq_ioc_set_ioprio(struct io_context *ioc)
1318 {
1319         struct cfq_io_context *cic;
1320         struct rb_node *n;
1321
1322         ioc->ioprio_changed = 0;
1323
1324         n = rb_first(&ioc->cic_root);
1325         while (n != NULL) {
1326                 cic = rb_entry(n, struct cfq_io_context, rb_node);
1327
1328                 changed_ioprio(cic);
1329                 n = rb_next(n);
1330         }
1331 }
1332
1333 static struct cfq_queue *
1334 cfq_get_queue(struct cfq_data *cfqd, unsigned int key, struct task_struct *tsk,
1335               gfp_t gfp_mask)
1336 {
1337         const int hashval = hash_long(key, CFQ_QHASH_SHIFT);
1338         struct cfq_queue *cfqq, *new_cfqq = NULL;
1339         unsigned short ioprio;
1340
1341 retry:
1342         ioprio = tsk->ioprio;
1343         cfqq = __cfq_find_cfq_hash(cfqd, key, ioprio, hashval);
1344
1345         if (!cfqq) {
1346                 if (new_cfqq) {
1347                         cfqq = new_cfqq;
1348                         new_cfqq = NULL;
1349                 } else if (gfp_mask & __GFP_WAIT) {
1350                         /*
1351                          * Inform the allocator of the fact that we will
1352                          * just repeat this allocation if it fails, to allow
1353                          * the allocator to do whatever it needs to attempt to
1354                          * free memory.
1355                          */
1356                         spin_unlock_irq(cfqd->queue->queue_lock);
1357                         new_cfqq = kmem_cache_alloc_node(cfq_pool, gfp_mask|__GFP_NOFAIL, cfqd->queue->node);
1358                         spin_lock_irq(cfqd->queue->queue_lock);
1359                         goto retry;
1360                 } else {
1361                         cfqq = kmem_cache_alloc_node(cfq_pool, gfp_mask, cfqd->queue->node);
1362                         if (!cfqq)
1363                                 goto out;
1364                 }
1365
1366                 memset(cfqq, 0, sizeof(*cfqq));
1367
1368                 INIT_HLIST_NODE(&cfqq->cfq_hash);
1369                 INIT_LIST_HEAD(&cfqq->cfq_list);
1370                 INIT_LIST_HEAD(&cfqq->fifo);
1371
1372                 cfqq->key = key;
1373                 hlist_add_head(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
1374                 atomic_set(&cfqq->ref, 0);
1375                 cfqq->cfqd = cfqd;
1376
1377                 if (key != CFQ_KEY_ASYNC)
1378                         cfq_mark_cfqq_idle_window(cfqq);
1379
1380                 cfq_mark_cfqq_prio_changed(cfqq);
1381                 cfq_mark_cfqq_queue_new(cfqq);
1382                 cfq_init_prio_data(cfqq);
1383         }
1384
1385         if (new_cfqq)
1386                 kmem_cache_free(cfq_pool, new_cfqq);
1387
1388         atomic_inc(&cfqq->ref);
1389 out:
1390         WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
1391         return cfqq;
1392 }
1393
1394 static void
1395 cfq_drop_dead_cic(struct io_context *ioc, struct cfq_io_context *cic)
1396 {
1397         WARN_ON(!list_empty(&cic->queue_list));
1398         rb_erase(&cic->rb_node, &ioc->cic_root);
1399         kmem_cache_free(cfq_ioc_pool, cic);
1400         elv_ioc_count_dec(ioc_count);
1401 }
1402
1403 static struct cfq_io_context *
1404 cfq_cic_rb_lookup(struct cfq_data *cfqd, struct io_context *ioc)
1405 {
1406         struct rb_node *n;
1407         struct cfq_io_context *cic;
1408         void *k, *key = cfqd;
1409
1410 restart:
1411         n = ioc->cic_root.rb_node;
1412         while (n) {
1413                 cic = rb_entry(n, struct cfq_io_context, rb_node);
1414                 /* ->key must be copied to avoid race with cfq_exit_queue() */
1415                 k = cic->key;
1416                 if (unlikely(!k)) {
1417                         cfq_drop_dead_cic(ioc, cic);
1418                         goto restart;
1419                 }
1420
1421                 if (key < k)
1422                         n = n->rb_left;
1423                 else if (key > k)
1424                         n = n->rb_right;
1425                 else
1426                         return cic;
1427         }
1428
1429         return NULL;
1430 }
1431
1432 static inline void
1433 cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
1434              struct cfq_io_context *cic)
1435 {
1436         struct rb_node **p;
1437         struct rb_node *parent;
1438         struct cfq_io_context *__cic;
1439         unsigned long flags;
1440         void *k;
1441
1442         cic->ioc = ioc;
1443         cic->key = cfqd;
1444
1445 restart:
1446         parent = NULL;
1447         p = &ioc->cic_root.rb_node;
1448         while (*p) {
1449                 parent = *p;
1450                 __cic = rb_entry(parent, struct cfq_io_context, rb_node);
1451                 /* ->key must be copied to avoid race with cfq_exit_queue() */
1452                 k = __cic->key;
1453                 if (unlikely(!k)) {
1454                         cfq_drop_dead_cic(ioc, __cic);
1455                         goto restart;
1456                 }
1457
1458                 if (cic->key < k)
1459                         p = &(*p)->rb_left;
1460                 else if (cic->key > k)
1461                         p = &(*p)->rb_right;
1462                 else
1463                         BUG();
1464         }
1465
1466         rb_link_node(&cic->rb_node, parent, p);
1467         rb_insert_color(&cic->rb_node, &ioc->cic_root);
1468
1469         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1470         list_add(&cic->queue_list, &cfqd->cic_list);
1471         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1472 }
1473
1474 /*
1475  * Setup general io context and cfq io context. There can be several cfq
1476  * io contexts per general io context, if this process is doing io to more
1477  * than one device managed by cfq.
1478  */
1479 static struct cfq_io_context *
1480 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1481 {
1482         struct io_context *ioc = NULL;
1483         struct cfq_io_context *cic;
1484
1485         might_sleep_if(gfp_mask & __GFP_WAIT);
1486
1487         ioc = get_io_context(gfp_mask, cfqd->queue->node);
1488         if (!ioc)
1489                 return NULL;
1490
1491         cic = cfq_cic_rb_lookup(cfqd, ioc);
1492         if (cic)
1493                 goto out;
1494
1495         cic = cfq_alloc_io_context(cfqd, gfp_mask);
1496         if (cic == NULL)
1497                 goto err;
1498
1499         cfq_cic_link(cfqd, ioc, cic);
1500 out:
1501         smp_read_barrier_depends();
1502         if (unlikely(ioc->ioprio_changed))
1503                 cfq_ioc_set_ioprio(ioc);
1504
1505         return cic;
1506 err:
1507         put_io_context(ioc);
1508         return NULL;
1509 }
1510
1511 static void
1512 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1513 {
1514         unsigned long elapsed = jiffies - cic->last_end_request;
1515         unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1516
1517         cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1518         cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1519         cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1520 }
1521
1522 static void
1523 cfq_update_io_seektime(struct cfq_io_context *cic, struct request *rq)
1524 {
1525         sector_t sdist;
1526         u64 total;
1527
1528         if (cic->last_request_pos < rq->sector)
1529                 sdist = rq->sector - cic->last_request_pos;
1530         else
1531                 sdist = cic->last_request_pos - rq->sector;
1532
1533         /*
1534          * Don't allow the seek distance to get too large from the
1535          * odd fragment, pagein, etc
1536          */
1537         if (cic->seek_samples <= 60) /* second&third seek */
1538                 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
1539         else
1540                 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
1541
1542         cic->seek_samples = (7*cic->seek_samples + 256) / 8;
1543         cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
1544         total = cic->seek_total + (cic->seek_samples/2);
1545         do_div(total, cic->seek_samples);
1546         cic->seek_mean = (sector_t)total;
1547 }
1548
1549 /*
1550  * Disable idle window if the process thinks too long or seeks so much that
1551  * it doesn't matter
1552  */
1553 static void
1554 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1555                        struct cfq_io_context *cic)
1556 {
1557         int enable_idle = cfq_cfqq_idle_window(cfqq);
1558
1559         if (!cic->ioc->task || !cfqd->cfq_slice_idle ||
1560             (cfqd->hw_tag && CIC_SEEKY(cic)))
1561                 enable_idle = 0;
1562         else if (sample_valid(cic->ttime_samples)) {
1563                 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1564                         enable_idle = 0;
1565                 else
1566                         enable_idle = 1;
1567         }
1568
1569         if (enable_idle)
1570                 cfq_mark_cfqq_idle_window(cfqq);
1571         else
1572                 cfq_clear_cfqq_idle_window(cfqq);
1573 }
1574
1575 /*
1576  * Check if new_cfqq should preempt the currently active queue. Return 0 for
1577  * no or if we aren't sure, a 1 will cause a preempt.
1578  */
1579 static int
1580 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1581                    struct request *rq)
1582 {
1583         struct cfq_queue *cfqq = cfqd->active_queue;
1584         sector_t dist;
1585
1586         if (cfq_class_idle(new_cfqq))
1587                 return 0;
1588
1589         if (!cfqq)
1590                 return 0;
1591
1592         if (cfq_class_idle(cfqq))
1593                 return 1;
1594
1595         /*
1596          * if the new request is sync, but the currently running queue is
1597          * not, let the sync request have priority.
1598          */
1599         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
1600                 return 1;
1601
1602         /*
1603          * So both queues are sync. Let the new request get disk time if
1604          * it's a metadata request and the current queue is doing regular IO.
1605          */
1606         if (rq_is_meta(rq) && !cfqq->meta_pending)
1607                 return 1;
1608
1609         if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
1610                 return 0;
1611
1612         /*
1613          * if this request is as-good as one we would expect from the
1614          * current cfqq, let it preempt
1615          */
1616         if (rq->sector > cfqd->last_sector)
1617                 dist = rq->sector - cfqd->last_sector;
1618         else
1619                 dist = cfqd->last_sector - rq->sector;
1620
1621         if (dist <= cfqd->active_cic->seek_mean)
1622                 return 1;
1623
1624         return 0;
1625 }
1626
1627 /*
1628  * cfqq preempts the active queue. if we allowed preempt with no slice left,
1629  * let it have half of its nominal slice.
1630  */
1631 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1632 {
1633         cfq_slice_expired(cfqd, 1, 1);
1634
1635         /*
1636          * Put the new queue at the front of the of the current list,
1637          * so we know that it will be selected next.
1638          */
1639         BUG_ON(!cfq_cfqq_on_rr(cfqq));
1640         list_move(&cfqq->cfq_list, &cfqd->cur_rr);
1641
1642         cfqq->slice_end = 0;
1643         cfq_mark_cfqq_slice_new(cfqq);
1644 }
1645
1646 /*
1647  * Called when a new fs request (rq) is added (to cfqq). Check if there's
1648  * something we should do about it
1649  */
1650 static void
1651 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1652                 struct request *rq)
1653 {
1654         struct cfq_io_context *cic = RQ_CIC(rq);
1655
1656         if (rq_is_meta(rq))
1657                 cfqq->meta_pending++;
1658
1659         /*
1660          * we never wait for an async request and we don't allow preemption
1661          * of an async request. so just return early
1662          */
1663         if (!rq_is_sync(rq)) {
1664                 /*
1665                  * sync process issued an async request, if it's waiting
1666                  * then expire it and kick rq handling.
1667                  */
1668                 if (cic == cfqd->active_cic &&
1669                     del_timer(&cfqd->idle_slice_timer)) {
1670                         cfq_slice_expired(cfqd, 0, 0);
1671                         blk_start_queueing(cfqd->queue);
1672                 }
1673                 return;
1674         }
1675
1676         cfq_update_io_thinktime(cfqd, cic);
1677         cfq_update_io_seektime(cic, rq);
1678         cfq_update_idle_window(cfqd, cfqq, cic);
1679
1680         cic->last_request_pos = rq->sector + rq->nr_sectors;
1681
1682         if (cfqq == cfqd->active_queue) {
1683                 /*
1684                  * if we are waiting for a request for this queue, let it rip
1685                  * immediately and flag that we must not expire this queue
1686                  * just now
1687                  */
1688                 if (cfq_cfqq_wait_request(cfqq)) {
1689                         cfq_mark_cfqq_must_dispatch(cfqq);
1690                         del_timer(&cfqd->idle_slice_timer);
1691                         blk_start_queueing(cfqd->queue);
1692                 }
1693         } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
1694                 /*
1695                  * not the active queue - expire current slice if it is
1696                  * idle and has expired it's mean thinktime or this new queue
1697                  * has some old slice time left and is of higher priority
1698                  */
1699                 cfq_preempt_queue(cfqd, cfqq);
1700                 cfq_mark_cfqq_must_dispatch(cfqq);
1701                 blk_start_queueing(cfqd->queue);
1702         }
1703 }
1704
1705 static void cfq_insert_request(request_queue_t *q, struct request *rq)
1706 {
1707         struct cfq_data *cfqd = q->elevator->elevator_data;
1708         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1709
1710         cfq_init_prio_data(cfqq);
1711
1712         cfq_add_rq_rb(rq);
1713
1714         list_add_tail(&rq->queuelist, &cfqq->fifo);
1715
1716         cfq_rq_enqueued(cfqd, cfqq, rq);
1717 }
1718
1719 static void cfq_completed_request(request_queue_t *q, struct request *rq)
1720 {
1721         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1722         struct cfq_data *cfqd = cfqq->cfqd;
1723         const int sync = rq_is_sync(rq);
1724         unsigned long now;
1725
1726         now = jiffies;
1727
1728         WARN_ON(!cfqd->rq_in_driver);
1729         WARN_ON(!cfqq->on_dispatch[sync]);
1730         cfqd->rq_in_driver--;
1731         cfqq->on_dispatch[sync]--;
1732         cfqq->service_last = now;
1733
1734         cfqd->last_sector = rq->hard_sector + rq->hard_nr_sectors;
1735
1736         if (!cfq_class_idle(cfqq))
1737                 cfqd->last_end_request = now;
1738
1739         cfq_resort_rr_list(cfqq, 0);
1740
1741         if (sync)
1742                 RQ_CIC(rq)->last_end_request = now;
1743
1744         /*
1745          * If this is the active queue, check if it needs to be expired,
1746          * or if we want to idle in case it has no pending requests.
1747          */
1748         if (cfqd->active_queue == cfqq) {
1749                 if (cfq_cfqq_slice_new(cfqq)) {
1750                         cfq_set_prio_slice(cfqd, cfqq);
1751                         cfq_clear_cfqq_slice_new(cfqq);
1752                 }
1753                 if (cfq_slice_used(cfqq))
1754                         cfq_slice_expired(cfqd, 0, 1);
1755                 else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list)) {
1756                         if (!cfq_arm_slice_timer(cfqd))
1757                                 cfq_schedule_dispatch(cfqd);
1758                 }
1759         }
1760 }
1761
1762 /*
1763  * we temporarily boost lower priority queues if they are holding fs exclusive
1764  * resources. they are boosted to normal prio (CLASS_BE/4)
1765  */
1766 static void cfq_prio_boost(struct cfq_queue *cfqq)
1767 {
1768         const int ioprio_class = cfqq->ioprio_class;
1769         const int ioprio = cfqq->ioprio;
1770
1771         if (has_fs_excl()) {
1772                 /*
1773                  * boost idle prio on transactions that would lock out other
1774                  * users of the filesystem
1775                  */
1776                 if (cfq_class_idle(cfqq))
1777                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1778                 if (cfqq->ioprio > IOPRIO_NORM)
1779                         cfqq->ioprio = IOPRIO_NORM;
1780         } else {
1781                 /*
1782                  * check if we need to unboost the queue
1783                  */
1784                 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
1785                         cfqq->ioprio_class = cfqq->org_ioprio_class;
1786                 if (cfqq->ioprio != cfqq->org_ioprio)
1787                         cfqq->ioprio = cfqq->org_ioprio;
1788         }
1789
1790         /*
1791          * refile between round-robin lists if we moved the priority class
1792          */
1793         if ((ioprio_class != cfqq->ioprio_class || ioprio != cfqq->ioprio))
1794                 cfq_resort_rr_list(cfqq, 0);
1795 }
1796
1797 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
1798 {
1799         if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
1800             !cfq_cfqq_must_alloc_slice(cfqq)) {
1801                 cfq_mark_cfqq_must_alloc_slice(cfqq);
1802                 return ELV_MQUEUE_MUST;
1803         }
1804
1805         return ELV_MQUEUE_MAY;
1806 }
1807
1808 static int cfq_may_queue(request_queue_t *q, int rw)
1809 {
1810         struct cfq_data *cfqd = q->elevator->elevator_data;
1811         struct task_struct *tsk = current;
1812         struct cfq_queue *cfqq;
1813         unsigned int key;
1814
1815         key = cfq_queue_pid(tsk, rw, rw & REQ_RW_SYNC);
1816
1817         /*
1818          * don't force setup of a queue from here, as a call to may_queue
1819          * does not necessarily imply that a request actually will be queued.
1820          * so just lookup a possibly existing queue, or return 'may queue'
1821          * if that fails
1822          */
1823         cfqq = cfq_find_cfq_hash(cfqd, key, tsk->ioprio);
1824         if (cfqq) {
1825                 cfq_init_prio_data(cfqq);
1826                 cfq_prio_boost(cfqq);
1827
1828                 return __cfq_may_queue(cfqq);
1829         }
1830
1831         return ELV_MQUEUE_MAY;
1832 }
1833
1834 /*
1835  * queue lock held here
1836  */
1837 static void cfq_put_request(struct request *rq)
1838 {
1839         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1840
1841         if (cfqq) {
1842                 const int rw = rq_data_dir(rq);
1843
1844                 BUG_ON(!cfqq->allocated[rw]);
1845                 cfqq->allocated[rw]--;
1846
1847                 put_io_context(RQ_CIC(rq)->ioc);
1848
1849                 rq->elevator_private = NULL;
1850                 rq->elevator_private2 = NULL;
1851
1852                 cfq_put_queue(cfqq);
1853         }
1854 }
1855
1856 /*
1857  * Allocate cfq data structures associated with this request.
1858  */
1859 static int
1860 cfq_set_request(request_queue_t *q, struct request *rq, gfp_t gfp_mask)
1861 {
1862         struct cfq_data *cfqd = q->elevator->elevator_data;
1863         struct task_struct *tsk = current;
1864         struct cfq_io_context *cic;
1865         const int rw = rq_data_dir(rq);
1866         const int is_sync = rq_is_sync(rq);
1867         pid_t key = cfq_queue_pid(tsk, rw, is_sync);
1868         struct cfq_queue *cfqq;
1869         unsigned long flags;
1870
1871         might_sleep_if(gfp_mask & __GFP_WAIT);
1872
1873         cic = cfq_get_io_context(cfqd, gfp_mask);
1874
1875         spin_lock_irqsave(q->queue_lock, flags);
1876
1877         if (!cic)
1878                 goto queue_fail;
1879
1880         if (!cic->cfqq[is_sync]) {
1881                 cfqq = cfq_get_queue(cfqd, key, tsk, gfp_mask);
1882                 if (!cfqq)
1883                         goto queue_fail;
1884
1885                 cic->cfqq[is_sync] = cfqq;
1886         } else
1887                 cfqq = cic->cfqq[is_sync];
1888
1889         cfqq->allocated[rw]++;
1890         cfq_clear_cfqq_must_alloc(cfqq);
1891         atomic_inc(&cfqq->ref);
1892
1893         spin_unlock_irqrestore(q->queue_lock, flags);
1894
1895         rq->elevator_private = cic;
1896         rq->elevator_private2 = cfqq;
1897         return 0;
1898
1899 queue_fail:
1900         if (cic)
1901                 put_io_context(cic->ioc);
1902
1903         cfq_schedule_dispatch(cfqd);
1904         spin_unlock_irqrestore(q->queue_lock, flags);
1905         return 1;
1906 }
1907
1908 static void cfq_kick_queue(struct work_struct *work)
1909 {
1910         struct cfq_data *cfqd =
1911                 container_of(work, struct cfq_data, unplug_work);
1912         request_queue_t *q = cfqd->queue;
1913         unsigned long flags;
1914
1915         spin_lock_irqsave(q->queue_lock, flags);
1916         blk_start_queueing(q);
1917         spin_unlock_irqrestore(q->queue_lock, flags);
1918 }
1919
1920 /*
1921  * Timer running if the active_queue is currently idling inside its time slice
1922  */
1923 static void cfq_idle_slice_timer(unsigned long data)
1924 {
1925         struct cfq_data *cfqd = (struct cfq_data *) data;
1926         struct cfq_queue *cfqq;
1927         unsigned long flags;
1928         int timed_out = 1;
1929
1930         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1931
1932         if ((cfqq = cfqd->active_queue) != NULL) {
1933                 timed_out = 0;
1934
1935                 /*
1936                  * expired
1937                  */
1938                 if (cfq_slice_used(cfqq))
1939                         goto expire;
1940
1941                 /*
1942                  * only expire and reinvoke request handler, if there are
1943                  * other queues with pending requests
1944                  */
1945                 if (!cfqd->busy_queues)
1946                         goto out_cont;
1947
1948                 /*
1949                  * not expired and it has a request pending, let it dispatch
1950                  */
1951                 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) {
1952                         cfq_mark_cfqq_must_dispatch(cfqq);
1953                         goto out_kick;
1954                 }
1955         }
1956 expire:
1957         cfq_slice_expired(cfqd, 0, timed_out);
1958 out_kick:
1959         cfq_schedule_dispatch(cfqd);
1960 out_cont:
1961         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1962 }
1963
1964 /*
1965  * Timer running if an idle class queue is waiting for service
1966  */
1967 static void cfq_idle_class_timer(unsigned long data)
1968 {
1969         struct cfq_data *cfqd = (struct cfq_data *) data;
1970         unsigned long flags, end;
1971
1972         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1973
1974         /*
1975          * race with a non-idle queue, reset timer
1976          */
1977         end = cfqd->last_end_request + CFQ_IDLE_GRACE;
1978         if (!time_after_eq(jiffies, end))
1979                 mod_timer(&cfqd->idle_class_timer, end);
1980         else
1981                 cfq_schedule_dispatch(cfqd);
1982
1983         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1984 }
1985
1986 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
1987 {
1988         del_timer_sync(&cfqd->idle_slice_timer);
1989         del_timer_sync(&cfqd->idle_class_timer);
1990         blk_sync_queue(cfqd->queue);
1991 }
1992
1993 static void cfq_exit_queue(elevator_t *e)
1994 {
1995         struct cfq_data *cfqd = e->elevator_data;
1996         request_queue_t *q = cfqd->queue;
1997
1998         cfq_shutdown_timer_wq(cfqd);
1999
2000         spin_lock_irq(q->queue_lock);
2001
2002         if (cfqd->active_queue)
2003                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0, 0);
2004
2005         while (!list_empty(&cfqd->cic_list)) {
2006                 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2007                                                         struct cfq_io_context,
2008                                                         queue_list);
2009
2010                 __cfq_exit_single_io_context(cfqd, cic);
2011         }
2012
2013         spin_unlock_irq(q->queue_lock);
2014
2015         cfq_shutdown_timer_wq(cfqd);
2016
2017         kfree(cfqd->cfq_hash);
2018         kfree(cfqd);
2019 }
2020
2021 static void *cfq_init_queue(request_queue_t *q)
2022 {
2023         struct cfq_data *cfqd;
2024         int i;
2025
2026         cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL, q->node);
2027         if (!cfqd)
2028                 return NULL;
2029
2030         memset(cfqd, 0, sizeof(*cfqd));
2031
2032         for (i = 0; i < CFQ_PRIO_LISTS; i++)
2033                 INIT_LIST_HEAD(&cfqd->rr_list[i]);
2034
2035         INIT_LIST_HEAD(&cfqd->busy_rr);
2036         INIT_LIST_HEAD(&cfqd->cur_rr);
2037         INIT_LIST_HEAD(&cfqd->idle_rr);
2038         INIT_LIST_HEAD(&cfqd->cic_list);
2039
2040         cfqd->cfq_hash = kmalloc_node(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL, q->node);
2041         if (!cfqd->cfq_hash)
2042                 goto out_free;
2043
2044         for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
2045                 INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);
2046
2047         cfqd->queue = q;
2048
2049         init_timer(&cfqd->idle_slice_timer);
2050         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2051         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2052
2053         init_timer(&cfqd->idle_class_timer);
2054         cfqd->idle_class_timer.function = cfq_idle_class_timer;
2055         cfqd->idle_class_timer.data = (unsigned long) cfqd;
2056
2057         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
2058
2059         cfqd->cfq_quantum = cfq_quantum;
2060         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2061         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2062         cfqd->cfq_back_max = cfq_back_max;
2063         cfqd->cfq_back_penalty = cfq_back_penalty;
2064         cfqd->cfq_slice[0] = cfq_slice_async;
2065         cfqd->cfq_slice[1] = cfq_slice_sync;
2066         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2067         cfqd->cfq_slice_idle = cfq_slice_idle;
2068
2069         return cfqd;
2070 out_free:
2071         kfree(cfqd);
2072         return NULL;
2073 }
2074
2075 static void cfq_slab_kill(void)
2076 {
2077         if (cfq_pool)
2078                 kmem_cache_destroy(cfq_pool);
2079         if (cfq_ioc_pool)
2080                 kmem_cache_destroy(cfq_ioc_pool);
2081 }
2082
2083 static int __init cfq_slab_setup(void)
2084 {
2085         cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0,
2086                                         NULL, NULL);
2087         if (!cfq_pool)
2088                 goto fail;
2089
2090         cfq_ioc_pool = kmem_cache_create("cfq_ioc_pool",
2091                         sizeof(struct cfq_io_context), 0, 0, NULL, NULL);
2092         if (!cfq_ioc_pool)
2093                 goto fail;
2094
2095         return 0;
2096 fail:
2097         cfq_slab_kill();
2098         return -ENOMEM;
2099 }
2100
2101 /*
2102  * sysfs parts below -->
2103  */
2104
2105 static ssize_t
2106 cfq_var_show(unsigned int var, char *page)
2107 {
2108         return sprintf(page, "%d\n", var);
2109 }
2110
2111 static ssize_t
2112 cfq_var_store(unsigned int *var, const char *page, size_t count)
2113 {
2114         char *p = (char *) page;
2115
2116         *var = simple_strtoul(p, &p, 10);
2117         return count;
2118 }
2119
2120 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
2121 static ssize_t __FUNC(elevator_t *e, char *page)                        \
2122 {                                                                       \
2123         struct cfq_data *cfqd = e->elevator_data;                       \
2124         unsigned int __data = __VAR;                                    \
2125         if (__CONV)                                                     \
2126                 __data = jiffies_to_msecs(__data);                      \
2127         return cfq_var_show(__data, (page));                            \
2128 }
2129 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2130 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2131 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2132 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
2133 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
2134 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2135 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2136 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2137 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2138 #undef SHOW_FUNCTION
2139
2140 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
2141 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count)    \
2142 {                                                                       \
2143         struct cfq_data *cfqd = e->elevator_data;                       \
2144         unsigned int __data;                                            \
2145         int ret = cfq_var_store(&__data, (page), count);                \
2146         if (__data < (MIN))                                             \
2147                 __data = (MIN);                                         \
2148         else if (__data > (MAX))                                        \
2149                 __data = (MAX);                                         \
2150         if (__CONV)                                                     \
2151                 *(__PTR) = msecs_to_jiffies(__data);                    \
2152         else                                                            \
2153                 *(__PTR) = __data;                                      \
2154         return ret;                                                     \
2155 }
2156 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2157 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1);
2158 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1);
2159 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2160 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0);
2161 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2162 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2163 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2164 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0);
2165 #undef STORE_FUNCTION
2166
2167 #define CFQ_ATTR(name) \
2168         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2169
2170 static struct elv_fs_entry cfq_attrs[] = {
2171         CFQ_ATTR(quantum),
2172         CFQ_ATTR(fifo_expire_sync),
2173         CFQ_ATTR(fifo_expire_async),
2174         CFQ_ATTR(back_seek_max),
2175         CFQ_ATTR(back_seek_penalty),
2176         CFQ_ATTR(slice_sync),
2177         CFQ_ATTR(slice_async),
2178         CFQ_ATTR(slice_async_rq),
2179         CFQ_ATTR(slice_idle),
2180         __ATTR_NULL
2181 };
2182
2183 static struct elevator_type iosched_cfq = {
2184         .ops = {
2185                 .elevator_merge_fn =            cfq_merge,
2186                 .elevator_merged_fn =           cfq_merged_request,
2187                 .elevator_merge_req_fn =        cfq_merged_requests,
2188                 .elevator_allow_merge_fn =      cfq_allow_merge,
2189                 .elevator_dispatch_fn =         cfq_dispatch_requests,
2190                 .elevator_add_req_fn =          cfq_insert_request,
2191                 .elevator_activate_req_fn =     cfq_activate_request,
2192                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
2193                 .elevator_queue_empty_fn =      cfq_queue_empty,
2194                 .elevator_completed_req_fn =    cfq_completed_request,
2195                 .elevator_former_req_fn =       elv_rb_former_request,
2196                 .elevator_latter_req_fn =       elv_rb_latter_request,
2197                 .elevator_set_req_fn =          cfq_set_request,
2198                 .elevator_put_req_fn =          cfq_put_request,
2199                 .elevator_may_queue_fn =        cfq_may_queue,
2200                 .elevator_init_fn =             cfq_init_queue,
2201                 .elevator_exit_fn =             cfq_exit_queue,
2202                 .trim =                         cfq_free_io_context,
2203         },
2204         .elevator_attrs =       cfq_attrs,
2205         .elevator_name =        "cfq",
2206         .elevator_owner =       THIS_MODULE,
2207 };
2208
2209 static int __init cfq_init(void)
2210 {
2211         int ret;
2212
2213         /*
2214          * could be 0 on HZ < 1000 setups
2215          */
2216         if (!cfq_slice_async)
2217                 cfq_slice_async = 1;
2218         if (!cfq_slice_idle)
2219                 cfq_slice_idle = 1;
2220
2221         if (cfq_slab_setup())
2222                 return -ENOMEM;
2223
2224         ret = elv_register(&iosched_cfq);
2225         if (ret)
2226                 cfq_slab_kill();
2227
2228         return ret;
2229 }
2230
2231 static void __exit cfq_exit(void)
2232 {
2233         DECLARE_COMPLETION_ONSTACK(all_gone);
2234         elv_unregister(&iosched_cfq);
2235         ioc_gone = &all_gone;
2236         /* ioc_gone's update must be visible before reading ioc_count */
2237         smp_wmb();
2238         if (elv_ioc_count_read(ioc_count))
2239                 wait_for_completion(ioc_gone);
2240         synchronize_rcu();
2241         cfq_slab_kill();
2242 }
2243
2244 module_init(cfq_init);
2245 module_exit(cfq_exit);
2246
2247 MODULE_AUTHOR("Jens Axboe");
2248 MODULE_LICENSE("GPL");
2249 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");