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/rbtree.h>
  13 #include <linux/ioprio.h>
  14
  15 /*
  16  * tunables
  17  */
  18 /* max queue in one round of service */
  19 static const int cfq_quantum = 4;
  20 static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
  21 /* maximum backwards seek, in KiB */
  22 static const int cfq_back_max = 16 * 1024;
  23 /* penalty of a backwards seek */
  24 static const int cfq_back_penalty = 2;
  25 static const int cfq_slice_sync = HZ / 10;
  26 static int cfq_slice_async = HZ / 25;
  27 static const int cfq_slice_async_rq = 2;
  28 static int cfq_slice_idle = HZ / 125;
  29
  30 /*
  31  * offset from end of service tree
  32  */
  33 #define CFQ_IDLE_DELAY          (HZ / 5)
  34
  35 /*
  36  * below this threshold, we consider thinktime immediate
  37  */
  38 #define CFQ_MIN_TT              (2)
  39
  40 #define CFQ_SLICE_SCALE         (5)
  41
  42 #define RQ_CIC(rq)              \
  43         ((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 sample_valid(samples)   ((samples) > 80)
  60
  61 /*
  62  * Most of our rbtree usage is for sorting with min extraction, so
  63  * if we cache the leftmost node we don't have to walk down the tree
  64  * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
  65  * move this into the elevator for the rq sorting as well.
  66  */
  67 struct cfq_rb_root {
  68         struct rb_root rb;
  69         struct rb_node *left;
  70 };
  71 #define CFQ_RB_ROOT     (struct cfq_rb_root) { RB_ROOT, NULL, }
  72
  73 /*
  74  * Per block device queue structure
  75  */
  76 struct cfq_data {
  77         struct request_queue *queue;
  78
  79         /*
  80          * rr list of queues with requests and the count of them
  81          */
  82         struct cfq_rb_root service_tree;
  83         unsigned int busy_queues;
  84
  85         int rq_in_driver;
  86         int sync_flight;
  87         int hw_tag;
  88
  89         /*
  90          * idle window management
  91          */
  92         struct timer_list idle_slice_timer;
  93         struct work_struct unplug_work;
  94
  95         struct cfq_queue *active_queue;
  96         struct cfq_io_context *active_cic;
  97
  98         /*
  99          * async queue for each priority case
 100          */
 101         struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
 102         struct cfq_queue *async_idle_cfqq;
 103
 104         sector_t last_position;
 105         unsigned long last_end_request;
 106
 107         /*
 108          * tunables, see top of file
 109          */
 110         unsigned int cfq_quantum;
 111         unsigned int cfq_fifo_expire[2];
 112         unsigned int cfq_back_penalty;
 113         unsigned int cfq_back_max;
 114         unsigned int cfq_slice[2];
 115         unsigned int cfq_slice_async_rq;
 116         unsigned int cfq_slice_idle;
 117
 118         struct list_head cic_list;
 119 };
 120
 121 /*
 122  * Per process-grouping structure
 123  */
 124 struct cfq_queue {
 125         /* reference count */
 126         atomic_t ref;
 127         /* parent cfq_data */
 128         struct cfq_data *cfqd;
 129         /* service_tree member */
 130         struct rb_node rb_node;
 131         /* service_tree key */
 132         unsigned long rb_key;
 133         /* sorted list of pending requests */
 134         struct rb_root sort_list;
 135         /* if fifo isn't expired, next request to serve */
 136         struct request *next_rq;
 137         /* requests queued in sort_list */
 138         int queued[2];
 139         /* currently allocated requests */
 140         int allocated[2];
 141         /* pending metadata requests */
 142         int meta_pending;
 143         /* fifo list of requests in sort_list */
 144         struct list_head fifo;
 145
 146         unsigned long slice_end;
 147         long slice_resid;
 148
 149         /* number of requests that are on the dispatch list or inside driver */
 150         int dispatched;
 151
 152         /* io prio of this group */
 153         unsigned short ioprio, org_ioprio;
 154         unsigned short ioprio_class, org_ioprio_class;
 155
 156         /* various state flags, see below */
 157         unsigned int flags;
 158 };
 159
 160 enum cfqq_state_flags {
 161         CFQ_CFQQ_FLAG_on_rr = 0,        /* on round-robin busy list */
 162         CFQ_CFQQ_FLAG_wait_request,     /* waiting for a request */
 163         CFQ_CFQQ_FLAG_must_alloc,       /* must be allowed rq alloc */
 164         CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
 165         CFQ_CFQQ_FLAG_must_dispatch,    /* must dispatch, even if expired */
 166         CFQ_CFQQ_FLAG_fifo_expire,      /* FIFO checked in this slice */
 167         CFQ_CFQQ_FLAG_idle_window,      /* slice idling enabled */
 168         CFQ_CFQQ_FLAG_prio_changed,     /* task priority has changed */
 169         CFQ_CFQQ_FLAG_queue_new,        /* queue never been serviced */
 170         CFQ_CFQQ_FLAG_slice_new,        /* no requests dispatched in slice */
 171         CFQ_CFQQ_FLAG_sync,             /* synchronous queue */
 172 };
 173
 174 #define CFQ_CFQQ_FNS(name)                                              \
 175 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq)         \
 176 {                                                                       \
 177         (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name);                   \
 178 }                                                                       \
 179 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq)        \
 180 {                                                                       \
 181         (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name);                  \
 182 }                                                                       \
 183 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)         \
 184 {                                                                       \
 185         return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;      \
 186 }
 187
 188 CFQ_CFQQ_FNS(on_rr);
 189 CFQ_CFQQ_FNS(wait_request);
 190 CFQ_CFQQ_FNS(must_alloc);
 191 CFQ_CFQQ_FNS(must_alloc_slice);
 192 CFQ_CFQQ_FNS(must_dispatch);
 193 CFQ_CFQQ_FNS(fifo_expire);
 194 CFQ_CFQQ_FNS(idle_window);
 195 CFQ_CFQQ_FNS(prio_changed);
 196 CFQ_CFQQ_FNS(queue_new);
 197 CFQ_CFQQ_FNS(slice_new);
 198 CFQ_CFQQ_FNS(sync);
 199 #undef CFQ_CFQQ_FNS
 200
 201 static void cfq_dispatch_insert(struct request_queue *, struct request *);
 202 static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
 203                                        struct io_context *, gfp_t);
 204 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
 205                                                 struct io_context *);
 206
 207 static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
 208                                             int is_sync)
 209 {
 210         return cic->cfqq[!!is_sync];
 211 }
 212
 213 static inline void cic_set_cfqq(struct cfq_io_context *cic,
 214                                 struct cfq_queue *cfqq, int is_sync)
 215 {
 216         cic->cfqq[!!is_sync] = cfqq;
 217 }
 218
 219 /*
 220  * We regard a request as SYNC, if it's either a read or has the SYNC bit
 221  * set (in which case it could also be direct WRITE).
 222  */
 223 static inline int cfq_bio_sync(struct bio *bio)
 224 {
 225         if (bio_data_dir(bio) == READ || bio_sync(bio))
 226                 return 1;
 227
 228         return 0;
 229 }
 230
 231 /*
 232  * scheduler run of queue, if there are requests pending and no one in the
 233  * driver that will restart queueing
 234  */
 235 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
 236 {
 237         if (cfqd->busy_queues)
 238                 kblockd_schedule_work(&cfqd->unplug_work);
 239 }
 240
 241 static int cfq_queue_empty(struct request_queue *q)
 242 {
 243         struct cfq_data *cfqd = q->elevator->elevator_data;
 244
 245         return !cfqd->busy_queues;
 246 }
 247
 248 /*
 249  * Scale schedule slice based on io priority. Use the sync time slice only
 250  * if a queue is marked sync and has sync io queued. A sync queue with async
 251  * io only, should not get full sync slice length.
 252  */
 253 static inline int cfq_prio_slice(struct cfq_data *cfqd, int sync,
 254                                  unsigned short prio)
 255 {
 256         const int base_slice = cfqd->cfq_slice[sync];
 257
 258         WARN_ON(prio >= IOPRIO_BE_NR);
 259
 260         return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
 261 }
 262
 263 static inline int
 264 cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 265 {
 266         return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
 267 }
 268
 269 static inline void
 270 cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 271 {
 272         cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
 273 }
 274
 275 /*
 276  * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
 277  * isn't valid until the first request from the dispatch is activated
 278  * and the slice time set.
 279  */
 280 static inline int cfq_slice_used(struct cfq_queue *cfqq)
 281 {
 282         if (cfq_cfqq_slice_new(cfqq))
 283                 return 0;
 284         if (time_before(jiffies, cfqq->slice_end))
 285                 return 0;
 286
 287         return 1;
 288 }
 289
 290 /*
 291  * Lifted from AS - choose which of rq1 and rq2 that is best served now.
 292  * We choose the request that is closest to the head right now. Distance
 293  * behind the head is penalized and only allowed to a certain extent.
 294  */
 295 static struct request *
 296 cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2)
 297 {
 298         sector_t last, s1, s2, d1 = 0, d2 = 0;
 299         unsigned long back_max;
 300 #define CFQ_RQ1_WRAP    0x01 /* request 1 wraps */
 301 #define CFQ_RQ2_WRAP    0x02 /* request 2 wraps */
 302         unsigned wrap = 0; /* bit mask: requests behind the disk head? */
 303
 304         if (rq1 == NULL || rq1 == rq2)
 305                 return rq2;
 306         if (rq2 == NULL)
 307                 return rq1;
 308
 309         if (rq_is_sync(rq1) && !rq_is_sync(rq2))
 310                 return rq1;
 311         else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
 312                 return rq2;
 313         if (rq_is_meta(rq1) && !rq_is_meta(rq2))
 314                 return rq1;
 315         else if (rq_is_meta(rq2) && !rq_is_meta(rq1))
 316                 return rq2;
 317
 318         s1 = rq1->sector;
 319         s2 = rq2->sector;
 320
 321         last = cfqd->last_position;
 322
 323         /*
 324          * by definition, 1KiB is 2 sectors
 325          */
 326         back_max = cfqd->cfq_back_max * 2;
 327
 328         /*
 329          * Strict one way elevator _except_ in the case where we allow
 330          * short backward seeks which are biased as twice the cost of a
 331          * similar forward seek.
 332          */
 333         if (s1 >= last)
 334                 d1 = s1 - last;
 335         else if (s1 + back_max >= last)
 336                 d1 = (last - s1) * cfqd->cfq_back_penalty;
 337         else
 338                 wrap |= CFQ_RQ1_WRAP;
 339
 340         if (s2 >= last)
 341                 d2 = s2 - last;
 342         else if (s2 + back_max >= last)
 343                 d2 = (last - s2) * cfqd->cfq_back_penalty;
 344         else
 345                 wrap |= CFQ_RQ2_WRAP;
 346
 347         /* Found required data */
 348
 349         /*
 350          * By doing switch() on the bit mask "wrap" we avoid having to
 351          * check two variables for all permutations: --> faster!
 352          */
 353         switch (wrap) {
 354         case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
 355                 if (d1 < d2)
 356                         return rq1;
 357                 else if (d2 < d1)
 358                         return rq2;
 359                 else {
 360                         if (s1 >= s2)
 361                                 return rq1;
 362                         else
 363                                 return rq2;
 364                 }
 365
 366         case CFQ_RQ2_WRAP:
 367                 return rq1;
 368         case CFQ_RQ1_WRAP:
 369                 return rq2;
 370         case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
 371         default:
 372                 /*
 373                  * Since both rqs are wrapped,
 374                  * start with the one that's further behind head
 375                  * (--> only *one* back seek required),
 376                  * since back seek takes more time than forward.
 377                  */
 378                 if (s1 <= s2)
 379                         return rq1;
 380                 else
 381                         return rq2;
 382         }
 383 }
 384
 385 /*
 386  * The below is leftmost cache rbtree addon
 387  */
 388 static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
 389 {
 390         if (!root->left)
 391                 root->left = rb_first(&root->rb);
 392
 393         if (root->left)
 394                 return rb_entry(root->left, struct cfq_queue, rb_node);
 395
 396         return NULL;
 397 }
 398
 399 static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
 400 {
 401         if (root->left == n)
 402                 root->left = NULL;
 403
 404         rb_erase(n, &root->rb);
 405         RB_CLEAR_NODE(n);
 406 }
 407
 408 /*
 409  * would be nice to take fifo expire time into account as well
 410  */
 411 static struct request *
 412 cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 413                   struct request *last)
 414 {
 415         struct rb_node *rbnext = rb_next(&last->rb_node);
 416         struct rb_node *rbprev = rb_prev(&last->rb_node);
 417         struct request *next = NULL, *prev = NULL;
 418
 419         BUG_ON(RB_EMPTY_NODE(&last->rb_node));
 420
 421         if (rbprev)
 422                 prev = rb_entry_rq(rbprev);
 423
 424         if (rbnext)
 425                 next = rb_entry_rq(rbnext);
 426         else {
 427                 rbnext = rb_first(&cfqq->sort_list);
 428                 if (rbnext && rbnext != &last->rb_node)
 429                         next = rb_entry_rq(rbnext);
 430         }
 431
 432         return cfq_choose_req(cfqd, next, prev);
 433 }
 434
 435 static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
 436                                       struct cfq_queue *cfqq)
 437 {
 438         /*
 439          * just an approximation, should be ok.
 440          */
 441         return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) -
 442                        cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
 443 }
 444
 445 /*
 446  * The cfqd->service_tree holds all pending cfq_queue's that have
 447  * requests waiting to be processed. It is sorted in the order that
 448  * we will service the queues.
 449  */
 450 static void cfq_service_tree_add(struct cfq_data *cfqd,
 451                                     struct cfq_queue *cfqq, int add_front)
 452 {
 453         struct rb_node **p, *parent;
 454         struct cfq_queue *__cfqq;
 455         unsigned long rb_key;
 456         int left;
 457
 458         if (cfq_class_idle(cfqq)) {
 459                 rb_key = CFQ_IDLE_DELAY;
 460                 parent = rb_last(&cfqd->service_tree.rb);
 461                 if (parent && parent != &cfqq->rb_node) {
 462                         __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
 463                         rb_key += __cfqq->rb_key;
 464                 } else
 465                         rb_key += jiffies;
 466         } else if (!add_front) {
 467                 rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
 468                 rb_key += cfqq->slice_resid;
 469                 cfqq->slice_resid = 0;
 470         } else
 471                 rb_key = 0;
 472
 473         if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
 474                 /*
 475                  * same position, nothing more to do
 476                  */
 477                 if (rb_key == cfqq->rb_key)
 478                         return;
 479
 480                 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
 481         }
 482
 483         left = 1;
 484         parent = NULL;
 485         p = &cfqd->service_tree.rb.rb_node;
 486         while (*p) {
 487                 struct rb_node **n;
 488
 489                 parent = *p;
 490                 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
 491
 492                 /*
 493                  * sort RT queues first, we always want to give
 494                  * preference to them. IDLE queues goes to the back.
 495                  * after that, sort on the next service time.
 496                  */
 497                 if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq))
 498                         n = &(*p)->rb_left;
 499                 else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq))
 500                         n = &(*p)->rb_right;
 501                 else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq))
 502                         n = &(*p)->rb_left;
 503                 else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
 504                         n = &(*p)->rb_right;
 505                 else if (rb_key < __cfqq->rb_key)
 506                         n = &(*p)->rb_left;
 507                 else
 508                         n = &(*p)->rb_right;
 509
 510                 if (n == &(*p)->rb_right)
 511                         left = 0;
 512
 513                 p = n;
 514         }
 515
 516         if (left)
 517                 cfqd->service_tree.left = &cfqq->rb_node;
 518
 519         cfqq->rb_key = rb_key;
 520         rb_link_node(&cfqq->rb_node, parent, p);
 521         rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb);
 522 }
 523
 524 /*
 525  * Update cfqq's position in the service tree.
 526  */
 527 static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 528 {
 529         /*
 530          * Resorting requires the cfqq to be on the RR list already.
 531          */
 532         if (cfq_cfqq_on_rr(cfqq))
 533                 cfq_service_tree_add(cfqd, cfqq, 0);
 534 }
 535
 536 /*
 537  * add to busy list of queues for service, trying to be fair in ordering
 538  * the pending list according to last request service
 539  */
 540 static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 541 {
 542         BUG_ON(cfq_cfqq_on_rr(cfqq));
 543         cfq_mark_cfqq_on_rr(cfqq);
 544         cfqd->busy_queues++;
 545
 546         cfq_resort_rr_list(cfqd, cfqq);
 547 }
 548
 549 /*
 550  * Called when the cfqq no longer has requests pending, remove it from
 551  * the service tree.
 552  */
 553 static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 554 {
 555         BUG_ON(!cfq_cfqq_on_rr(cfqq));
 556         cfq_clear_cfqq_on_rr(cfqq);
 557
 558         if (!RB_EMPTY_NODE(&cfqq->rb_node))
 559                 cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
 560
 561         BUG_ON(!cfqd->busy_queues);
 562         cfqd->busy_queues--;
 563 }
 564
 565 /*
 566  * rb tree support functions
 567  */
 568 static void cfq_del_rq_rb(struct request *rq)
 569 {
 570         struct cfq_queue *cfqq = RQ_CFQQ(rq);
 571         struct cfq_data *cfqd = cfqq->cfqd;
 572         const int sync = rq_is_sync(rq);
 573
 574         BUG_ON(!cfqq->queued[sync]);
 575         cfqq->queued[sync]--;
 576
 577         elv_rb_del(&cfqq->sort_list, rq);
 578
 579         if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
 580                 cfq_del_cfqq_rr(cfqd, cfqq);
 581 }
 582
 583 static void cfq_add_rq_rb(struct request *rq)
 584 {
 585         struct cfq_queue *cfqq = RQ_CFQQ(rq);
 586         struct cfq_data *cfqd = cfqq->cfqd;
 587         struct request *__alias;
 588
 589         cfqq->queued[rq_is_sync(rq)]++;
 590
 591         /*
 592          * looks a little odd, but the first insert might return an alias.
 593          * if that happens, put the alias on the dispatch list
 594          */
 595         while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
 596                 cfq_dispatch_insert(cfqd->queue, __alias);
 597
 598         if (!cfq_cfqq_on_rr(cfqq))
 599                 cfq_add_cfqq_rr(cfqd, cfqq);
 600
 601         /*
 602          * check if this request is a better next-serve candidate
 603          */
 604         cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq);
 605         BUG_ON(!cfqq->next_rq);
 606 }
 607
 608 static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
 609 {
 610         elv_rb_del(&cfqq->sort_list, rq);
 611         cfqq->queued[rq_is_sync(rq)]--;
 612         cfq_add_rq_rb(rq);
 613 }
 614
 615 static struct request *
 616 cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
 617 {
 618         struct task_struct *tsk = current;
 619         struct cfq_io_context *cic;
 620         struct cfq_queue *cfqq;
 621
 622         cic = cfq_cic_lookup(cfqd, tsk->io_context);
 623         if (!cic)
 624                 return NULL;
 625
 626         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
 627         if (cfqq) {
 628                 sector_t sector = bio->bi_sector + bio_sectors(bio);
 629
 630                 return elv_rb_find(&cfqq->sort_list, sector);
 631         }
 632
 633         return NULL;
 634 }
 635
 636 static void cfq_activate_request(struct request_queue *q, struct request *rq)
 637 {
 638         struct cfq_data *cfqd = q->elevator->elevator_data;
 639
 640         cfqd->rq_in_driver++;
 641
 642         /*
 643          * If the depth is larger 1, it really could be queueing. But lets
 644          * make the mark a little higher - idling could still be good for
 645          * low queueing, and a low queueing number could also just indicate
 646          * a SCSI mid layer like behaviour where limit+1 is often seen.
 647          */
 648         if (!cfqd->hw_tag && cfqd->rq_in_driver > 4)
 649                 cfqd->hw_tag = 1;
 650
 651         cfqd->last_position = rq->hard_sector + rq->hard_nr_sectors;
 652 }
 653
 654 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
 655 {
 656         struct cfq_data *cfqd = q->elevator->elevator_data;
 657
 658         WARN_ON(!cfqd->rq_in_driver);
 659         cfqd->rq_in_driver--;
 660 }
 661
 662 static void cfq_remove_request(struct request *rq)
 663 {
 664         struct cfq_queue *cfqq = RQ_CFQQ(rq);
 665
 666         if (cfqq->next_rq == rq)
 667                 cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
 668
 669         list_del_init(&rq->queuelist);
 670         cfq_del_rq_rb(rq);
 671
 672         if (rq_is_meta(rq)) {
 673                 WARN_ON(!cfqq->meta_pending);
 674                 cfqq->meta_pending--;
 675         }
 676 }
 677
 678 static int cfq_merge(struct request_queue *q, struct request **req,
 679                      struct bio *bio)
 680 {
 681         struct cfq_data *cfqd = q->elevator->elevator_data;
 682         struct request *__rq;
 683
 684         __rq = cfq_find_rq_fmerge(cfqd, bio);
 685         if (__rq && elv_rq_merge_ok(__rq, bio)) {
 686                 *req = __rq;
 687                 return ELEVATOR_FRONT_MERGE;
 688         }
 689
 690         return ELEVATOR_NO_MERGE;
 691 }
 692
 693 static void cfq_merged_request(struct request_queue *q, struct request *req,
 694                                int type)
 695 {
 696         if (type == ELEVATOR_FRONT_MERGE) {
 697                 struct cfq_queue *cfqq = RQ_CFQQ(req);
 698
 699                 cfq_reposition_rq_rb(cfqq, req);
 700         }
 701 }
 702
 703 static void
 704 cfq_merged_requests(struct request_queue *q, struct request *rq,
 705                     struct request *next)
 706 {
 707         /*
 708          * reposition in fifo if next is older than rq
 709          */
 710         if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
 711             time_before(next->start_time, rq->start_time))
 712                 list_move(&rq->queuelist, &next->queuelist);
 713
 714         cfq_remove_request(next);
 715 }
 716
 717 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
 718                            struct bio *bio)
 719 {
 720         struct cfq_data *cfqd = q->elevator->elevator_data;
 721         struct cfq_io_context *cic;
 722         struct cfq_queue *cfqq;
 723
 724         /*
 725          * Disallow merge of a sync bio into an async request.
 726          */
 727         if (cfq_bio_sync(bio) && !rq_is_sync(rq))
 728                 return 0;
 729
 730         /*
 731          * Lookup the cfqq that this bio will be queued with. Allow
 732          * merge only if rq is queued there.
 733          */
 734         cic = cfq_cic_lookup(cfqd, current->io_context);
 735         if (!cic)
 736                 return 0;
 737
 738         cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
 739         if (cfqq == RQ_CFQQ(rq))
 740                 return 1;
 741
 742         return 0;
 743 }
 744
 745 static void __cfq_set_active_queue(struct cfq_data *cfqd,
 746                                    struct cfq_queue *cfqq)
 747 {
 748         if (cfqq) {
 749                 cfqq->slice_end = 0;
 750                 cfq_clear_cfqq_must_alloc_slice(cfqq);
 751                 cfq_clear_cfqq_fifo_expire(cfqq);
 752                 cfq_mark_cfqq_slice_new(cfqq);
 753                 cfq_clear_cfqq_queue_new(cfqq);
 754         }
 755
 756         cfqd->active_queue = cfqq;
 757 }
 758
 759 /*
 760  * current cfqq expired its slice (or was too idle), select new one
 761  */
 762 static void
 763 __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 764                     int timed_out)
 765 {
 766         if (cfq_cfqq_wait_request(cfqq))
 767                 del_timer(&cfqd->idle_slice_timer);
 768
 769         cfq_clear_cfqq_must_dispatch(cfqq);
 770         cfq_clear_cfqq_wait_request(cfqq);
 771
 772         /*
 773          * store what was left of this slice, if the queue idled/timed out
 774          */
 775         if (timed_out && !cfq_cfqq_slice_new(cfqq))
 776                 cfqq->slice_resid = cfqq->slice_end - jiffies;
 777
 778         cfq_resort_rr_list(cfqd, cfqq);
 779
 780         if (cfqq == cfqd->active_queue)
 781                 cfqd->active_queue = NULL;
 782
 783         if (cfqd->active_cic) {
 784                 put_io_context(cfqd->active_cic->ioc);
 785                 cfqd->active_cic = NULL;
 786         }
 787 }
 788
 789 static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out)
 790 {
 791         struct cfq_queue *cfqq = cfqd->active_queue;
 792
 793         if (cfqq)
 794                 __cfq_slice_expired(cfqd, cfqq, timed_out);
 795 }
 796
 797 /*
 798  * Get next queue for service. Unless we have a queue preemption,
 799  * we'll simply select the first cfqq in the service tree.
 800  */
 801 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
 802 {
 803         if (RB_EMPTY_ROOT(&cfqd->service_tree.rb))
 804                 return NULL;
 805
 806         return cfq_rb_first(&cfqd->service_tree);
 807 }
 808
 809 /*
 810  * Get and set a new active queue for service.
 811  */
 812 static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd)
 813 {
 814         struct cfq_queue *cfqq;
 815
 816         cfqq = cfq_get_next_queue(cfqd);
 817         __cfq_set_active_queue(cfqd, cfqq);
 818         return cfqq;
 819 }
 820
 821 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
 822                                           struct request *rq)
 823 {
 824         if (rq->sector >= cfqd->last_position)
 825                 return rq->sector - cfqd->last_position;
 826         else
 827                 return cfqd->last_position - rq->sector;
 828 }
 829
 830 static inline int cfq_rq_close(struct cfq_data *cfqd, struct request *rq)
 831 {
 832         struct cfq_io_context *cic = cfqd->active_cic;
 833
 834         if (!sample_valid(cic->seek_samples))
 835                 return 0;
 836
 837         return cfq_dist_from_last(cfqd, rq) <= cic->seek_mean;
 838 }
 839
 840 static int cfq_close_cooperator(struct cfq_data *cfq_data,
 841                                 struct cfq_queue *cfqq)
 842 {
 843         /*
 844          * We should notice if some of the queues are cooperating, eg
 845          * working closely on the same area of the disk. In that case,
 846          * we can group them together and don't waste time idling.
 847          */
 848         return 0;
 849 }
 850
 851 #define CIC_SEEKY(cic) ((cic)->seek_mean > (8 * 1024))
 852
 853 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
 854 {
 855         struct cfq_queue *cfqq = cfqd->active_queue;
 856         struct cfq_io_context *cic;
 857         unsigned long sl;
 858
 859         WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
 860         WARN_ON(cfq_cfqq_slice_new(cfqq));
 861
 862         /*
 863          * idle is disabled, either manually or by past process history
 864          */
 865         if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq))
 866                 return;
 867
 868         /*
 869          * task has exited, don't wait
 870          */
 871         cic = cfqd->active_cic;
 872         if (!cic || !atomic_read(&cic->ioc->nr_tasks))
 873                 return;
 874
 875         /*
 876          * See if this prio level has a good candidate
 877          */
 878         if (cfq_close_cooperator(cfqd, cfqq) &&
 879             (sample_valid(cic->ttime_samples) && cic->ttime_mean > 2))
 880                 return;
 881
 882         cfq_mark_cfqq_must_dispatch(cfqq);
 883         cfq_mark_cfqq_wait_request(cfqq);
 884
 885         /*
 886          * we don't want to idle for seeks, but we do want to allow
 887          * fair distribution of slice time for a process doing back-to-back
 888          * seeks. so allow a little bit of time for him to submit a new rq
 889          */
 890         sl = cfqd->cfq_slice_idle;
 891         if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
 892                 sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT));
 893
 894         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
 895 }
 896
 897 /*
 898  * Move request from internal lists to the request queue dispatch list.
 899  */
 900 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
 901 {
 902         struct cfq_data *cfqd = q->elevator->elevator_data;
 903         struct cfq_queue *cfqq = RQ_CFQQ(rq);
 904
 905         cfq_remove_request(rq);
 906         cfqq->dispatched++;
 907         elv_dispatch_sort(q, rq);
 908
 909         if (cfq_cfqq_sync(cfqq))
 910                 cfqd->sync_flight++;
 911 }
 912
 913 /*
 914  * return expired entry, or NULL to just start from scratch in rbtree
 915  */
 916 static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
 917 {
 918         struct cfq_data *cfqd = cfqq->cfqd;
 919         struct request *rq;
 920         int fifo;
 921
 922         if (cfq_cfqq_fifo_expire(cfqq))
 923                 return NULL;
 924
 925         cfq_mark_cfqq_fifo_expire(cfqq);
 926
 927         if (list_empty(&cfqq->fifo))
 928                 return NULL;
 929
 930         fifo = cfq_cfqq_sync(cfqq);
 931         rq = rq_entry_fifo(cfqq->fifo.next);
 932
 933         if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))
 934                 return NULL;
 935
 936         return rq;
 937 }
 938
 939 static inline int
 940 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 941 {
 942         const int base_rq = cfqd->cfq_slice_async_rq;
 943
 944         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
 945
 946         return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
 947 }
 948
 949 /*
 950  * Select a queue for service. If we have a current active queue,
 951  * check whether to continue servicing it, or retrieve and set a new one.
 952  */
 953 static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
 954 {
 955         struct cfq_queue *cfqq;
 956
 957         cfqq = cfqd->active_queue;
 958         if (!cfqq)
 959                 goto new_queue;
 960
 961         /*
 962          * The active queue has run out of time, expire it and select new.
 963          */
 964         if (cfq_slice_used(cfqq))
 965                 goto expire;
 966
 967         /*
 968          * The active queue has requests and isn't expired, allow it to
 969          * dispatch.
 970          */
 971         if (!RB_EMPTY_ROOT(&cfqq->sort_list))
 972                 goto keep_queue;
 973
 974         /*
 975          * No requests pending. If the active queue still has requests in
 976          * flight or is idling for a new request, allow either of these
 977          * conditions to happen (or time out) before selecting a new queue.
 978          */
 979         if (timer_pending(&cfqd->idle_slice_timer) ||
 980             (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) {
 981                 cfqq = NULL;
 982                 goto keep_queue;
 983         }
 984
 985 expire:
 986         cfq_slice_expired(cfqd, 0);
 987 new_queue:
 988         cfqq = cfq_set_active_queue(cfqd);
 989 keep_queue:
 990         return cfqq;
 991 }
 992
 993 /*
 994  * Dispatch some requests from cfqq, moving them to the request queue
 995  * dispatch list.
 996  */
 997 static int
 998 __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 999                         int max_dispatch)
1000 {
1001         int dispatched = 0;
1002
1003         BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
1004
1005         do {
1006                 struct request *rq;
1007
1008                 /*
1009                  * follow expired path, else get first next available
1010                  */
1011                 rq = cfq_check_fifo(cfqq);
1012                 if (rq == NULL)
1013                         rq = cfqq->next_rq;
1014
1015                 /*
1016                  * finally, insert request into driver dispatch list
1017                  */
1018                 cfq_dispatch_insert(cfqd->queue, rq);
1019
1020                 dispatched++;
1021
1022                 if (!cfqd->active_cic) {
1023                         atomic_inc(&RQ_CIC(rq)->ioc->refcount);
1024                         cfqd->active_cic = RQ_CIC(rq);
1025                 }
1026
1027                 if (RB_EMPTY_ROOT(&cfqq->sort_list))
1028                         break;
1029
1030         } while (dispatched < max_dispatch);
1031
1032         /*
1033          * expire an async queue immediately if it has used up its slice. idle
1034          * queue always expire after 1 dispatch round.
1035          */
1036         if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
1037             dispatched >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
1038             cfq_class_idle(cfqq))) {
1039                 cfqq->slice_end = jiffies + 1;
1040                 cfq_slice_expired(cfqd, 0);
1041         }
1042
1043         return dispatched;
1044 }
1045
1046 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
1047 {
1048         int dispatched = 0;
1049
1050         while (cfqq->next_rq) {
1051                 cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
1052                 dispatched++;
1053         }
1054
1055         BUG_ON(!list_empty(&cfqq->fifo));
1056         return dispatched;
1057 }
1058
1059 /*
1060  * Drain our current requests. Used for barriers and when switching
1061  * io schedulers on-the-fly.
1062  */
1063 static int cfq_forced_dispatch(struct cfq_data *cfqd)
1064 {
1065         struct cfq_queue *cfqq;
1066         int dispatched = 0;
1067
1068         while ((cfqq = cfq_rb_first(&cfqd->service_tree)) != NULL)
1069                 dispatched += __cfq_forced_dispatch_cfqq(cfqq);
1070
1071         cfq_slice_expired(cfqd, 0);
1072
1073         BUG_ON(cfqd->busy_queues);
1074
1075         return dispatched;
1076 }
1077
1078 static int cfq_dispatch_requests(struct request_queue *q, int force)
1079 {
1080         struct cfq_data *cfqd = q->elevator->elevator_data;
1081         struct cfq_queue *cfqq;
1082         int dispatched;
1083
1084         if (!cfqd->busy_queues)
1085                 return 0;
1086
1087         if (unlikely(force))
1088                 return cfq_forced_dispatch(cfqd);
1089
1090         dispatched = 0;
1091         while ((cfqq = cfq_select_queue(cfqd)) != NULL) {
1092                 int max_dispatch;
1093
1094                 max_dispatch = cfqd->cfq_quantum;
1095                 if (cfq_class_idle(cfqq))
1096                         max_dispatch = 1;
1097
1098                 if (cfqq->dispatched >= max_dispatch) {
1099                         if (cfqd->busy_queues > 1)
1100                                 break;
1101                         if (cfqq->dispatched >= 4 * max_dispatch)
1102                                 break;
1103                 }
1104
1105                 if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))
1106                         break;
1107
1108                 cfq_clear_cfqq_must_dispatch(cfqq);
1109                 cfq_clear_cfqq_wait_request(cfqq);
1110                 del_timer(&cfqd->idle_slice_timer);
1111
1112                 dispatched += __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
1113         }
1114
1115         return dispatched;
1116 }
1117
1118 /*
1119  * task holds one reference to the queue, dropped when task exits. each rq
1120  * in-flight on this queue also holds a reference, dropped when rq is freed.
1121  *
1122  * queue lock must be held here.
1123  */
1124 static void cfq_put_queue(struct cfq_queue *cfqq)
1125 {
1126         struct cfq_data *cfqd = cfqq->cfqd;
1127
1128         BUG_ON(atomic_read(&cfqq->ref) <= 0);
1129
1130         if (!atomic_dec_and_test(&cfqq->ref))
1131                 return;
1132
1133         BUG_ON(rb_first(&cfqq->sort_list));
1134         BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
1135         BUG_ON(cfq_cfqq_on_rr(cfqq));
1136
1137         if (unlikely(cfqd->active_queue == cfqq)) {
1138                 __cfq_slice_expired(cfqd, cfqq, 0);
1139                 cfq_schedule_dispatch(cfqd);
1140         }
1141
1142         kmem_cache_free(cfq_pool, cfqq);
1143 }
1144
1145 /*
1146  * Call func for each cic attached to this ioc. Returns number of cic's seen.
1147  */
1148 static unsigned int
1149 call_for_each_cic(struct io_context *ioc,
1150                   void (*func)(struct io_context *, struct cfq_io_context *))
1151 {
1152         struct cfq_io_context *cic;
1153         struct hlist_node *n;
1154         int called = 0;
1155
1156         rcu_read_lock();
1157         hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list) {
1158                 func(ioc, cic);
1159                 called++;
1160         }
1161         rcu_read_unlock();
1162
1163         return called;
1164 }
1165
1166 static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
1167 {
1168         unsigned long flags;
1169
1170         BUG_ON(!cic->dead_key);
1171
1172         spin_lock_irqsave(&ioc->lock, flags);
1173         radix_tree_delete(&ioc->radix_root, cic->dead_key);
1174         hlist_del_rcu(&cic->cic_list);
1175         spin_unlock_irqrestore(&ioc->lock, flags);
1176
1177         kmem_cache_free(cfq_ioc_pool, cic);
1178 }
1179
1180 static void cfq_free_io_context(struct io_context *ioc)
1181 {
1182         int freed;
1183
1184         /*
1185          * ioc->refcount is zero here, so no more cic's are allowed to be
1186          * linked into this ioc. So it should be ok to iterate over the known
1187          * list, we will see all cic's since no new ones are added.
1188          */
1189         freed = call_for_each_cic(ioc, cic_free_func);
1190
1191         elv_ioc_count_mod(ioc_count, -freed);
1192
1193         if (ioc_gone && !elv_ioc_count_read(ioc_count))
1194                 complete(ioc_gone);
1195 }
1196
1197 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1198 {
1199         if (unlikely(cfqq == cfqd->active_queue)) {
1200                 __cfq_slice_expired(cfqd, cfqq, 0);
1201                 cfq_schedule_dispatch(cfqd);
1202         }
1203
1204         cfq_put_queue(cfqq);
1205 }
1206
1207 static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
1208                                          struct cfq_io_context *cic)
1209 {
1210         list_del_init(&cic->queue_list);
1211
1212         /*
1213          * Make sure key == NULL is seen for dead queues
1214          */
1215         smp_wmb();
1216         cic->dead_key = (unsigned long) cic->key;
1217         cic->key = NULL;
1218
1219         if (cic->cfqq[ASYNC]) {
1220                 cfq_exit_cfqq(cfqd, cic->cfqq[ASYNC]);
1221                 cic->cfqq[ASYNC] = NULL;
1222         }
1223
1224         if (cic->cfqq[SYNC]) {
1225                 cfq_exit_cfqq(cfqd, cic->cfqq[SYNC]);
1226                 cic->cfqq[SYNC] = NULL;
1227         }
1228 }
1229
1230 static void cfq_exit_single_io_context(struct io_context *ioc,
1231                                        struct cfq_io_context *cic)
1232 {
1233         struct cfq_data *cfqd = cic->key;
1234
1235         if (cfqd) {
1236                 struct request_queue *q = cfqd->queue;
1237                 unsigned long flags;
1238
1239                 spin_lock_irqsave(q->queue_lock, flags);
1240                 __cfq_exit_single_io_context(cfqd, cic);
1241                 spin_unlock_irqrestore(q->queue_lock, flags);
1242         }
1243 }
1244
1245 /*
1246  * The process that ioc belongs to has exited, we need to clean up
1247  * and put the internal structures we have that belongs to that process.
1248  */
1249 static void cfq_exit_io_context(struct io_context *ioc)
1250 {
1251         rcu_assign_pointer(ioc->ioc_data, NULL);
1252         call_for_each_cic(ioc, cfq_exit_single_io_context);
1253 }
1254
1255 static struct cfq_io_context *
1256 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1257 {
1258         struct cfq_io_context *cic;
1259
1260         cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
1261                                                         cfqd->queue->node);
1262         if (cic) {
1263                 cic->last_end_request = jiffies;
1264                 INIT_LIST_HEAD(&cic->queue_list);
1265                 INIT_HLIST_NODE(&cic->cic_list);
1266                 cic->dtor = cfq_free_io_context;
1267                 cic->exit = cfq_exit_io_context;
1268                 elv_ioc_count_inc(ioc_count);
1269         }
1270
1271         return cic;
1272 }
1273
1274 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
1275 {
1276         struct task_struct *tsk = current;
1277         int ioprio_class;
1278
1279         if (!cfq_cfqq_prio_changed(cfqq))
1280                 return;
1281
1282         ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
1283         switch (ioprio_class) {
1284         default:
1285                 printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
1286         case IOPRIO_CLASS_NONE:
1287                 /*
1288                  * no prio set, place us in the middle of the BE classes
1289                  */
1290                 cfqq->ioprio = task_nice_ioprio(tsk);
1291                 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1292                 break;
1293         case IOPRIO_CLASS_RT:
1294                 cfqq->ioprio = task_ioprio(ioc);
1295                 cfqq->ioprio_class = IOPRIO_CLASS_RT;
1296                 break;
1297         case IOPRIO_CLASS_BE:
1298                 cfqq->ioprio = task_ioprio(ioc);
1299                 cfqq->ioprio_class = IOPRIO_CLASS_BE;
1300                 break;
1301         case IOPRIO_CLASS_IDLE:
1302                 cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
1303                 cfqq->ioprio = 7;
1304                 cfq_clear_cfqq_idle_window(cfqq);
1305                 break;
1306         }
1307
1308         /*
1309          * keep track of original prio settings in case we have to temporarily
1310          * elevate the priority of this queue
1311          */
1312         cfqq->org_ioprio = cfqq->ioprio;
1313         cfqq->org_ioprio_class = cfqq->ioprio_class;
1314         cfq_clear_cfqq_prio_changed(cfqq);
1315 }
1316
1317 static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
1318 {
1319         struct cfq_data *cfqd = cic->key;
1320         struct cfq_queue *cfqq;
1321         unsigned long flags;
1322
1323         if (unlikely(!cfqd))
1324                 return;
1325
1326         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1327
1328         cfqq = cic->cfqq[ASYNC];
1329         if (cfqq) {
1330                 struct cfq_queue *new_cfqq;
1331                 new_cfqq = cfq_get_queue(cfqd, ASYNC, cic->ioc, GFP_ATOMIC);
1332                 if (new_cfqq) {
1333                         cic->cfqq[ASYNC] = new_cfqq;
1334                         cfq_put_queue(cfqq);
1335                 }
1336         }
1337
1338         cfqq = cic->cfqq[SYNC];
1339         if (cfqq)
1340                 cfq_mark_cfqq_prio_changed(cfqq);
1341
1342         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1343 }
1344
1345 static void cfq_ioc_set_ioprio(struct io_context *ioc)
1346 {
1347         call_for_each_cic(ioc, changed_ioprio);
1348         ioc->ioprio_changed = 0;
1349 }
1350
1351 static struct cfq_queue *
1352 cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
1353                      struct io_context *ioc, gfp_t gfp_mask)
1354 {
1355         struct cfq_queue *cfqq, *new_cfqq = NULL;
1356         struct cfq_io_context *cic;
1357
1358 retry:
1359         cic = cfq_cic_lookup(cfqd, ioc);
1360         /* cic always exists here */
1361         cfqq = cic_to_cfqq(cic, is_sync);
1362
1363         if (!cfqq) {
1364                 if (new_cfqq) {
1365                         cfqq = new_cfqq;
1366                         new_cfqq = NULL;
1367                 } else if (gfp_mask & __GFP_WAIT) {
1368                         /*
1369                          * Inform the allocator of the fact that we will
1370                          * just repeat this allocation if it fails, to allow
1371                          * the allocator to do whatever it needs to attempt to
1372                          * free memory.
1373                          */
1374                         spin_unlock_irq(cfqd->queue->queue_lock);
1375                         new_cfqq = kmem_cache_alloc_node(cfq_pool,
1376                                         gfp_mask | __GFP_NOFAIL | __GFP_ZERO,
1377                                         cfqd->queue->node);
1378                         spin_lock_irq(cfqd->queue->queue_lock);
1379                         goto retry;
1380                 } else {
1381                         cfqq = kmem_cache_alloc_node(cfq_pool,
1382                                         gfp_mask | __GFP_ZERO,
1383                                         cfqd->queue->node);
1384                         if (!cfqq)
1385                                 goto out;
1386                 }
1387
1388                 RB_CLEAR_NODE(&cfqq->rb_node);
1389                 INIT_LIST_HEAD(&cfqq->fifo);
1390
1391                 atomic_set(&cfqq->ref, 0);
1392                 cfqq->cfqd = cfqd;
1393
1394                 cfq_mark_cfqq_prio_changed(cfqq);
1395                 cfq_mark_cfqq_queue_new(cfqq);
1396
1397                 cfq_init_prio_data(cfqq, ioc);
1398
1399                 if (is_sync) {
1400                         if (!cfq_class_idle(cfqq))
1401                                 cfq_mark_cfqq_idle_window(cfqq);
1402                         cfq_mark_cfqq_sync(cfqq);
1403                 }
1404         }
1405
1406         if (new_cfqq)
1407                 kmem_cache_free(cfq_pool, new_cfqq);
1408
1409 out:
1410         WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
1411         return cfqq;
1412 }
1413
1414 static struct cfq_queue **
1415 cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
1416 {
1417         switch (ioprio_class) {
1418         case IOPRIO_CLASS_RT:
1419                 return &cfqd->async_cfqq[0][ioprio];
1420         case IOPRIO_CLASS_BE:
1421                 return &cfqd->async_cfqq[1][ioprio];
1422         case IOPRIO_CLASS_IDLE:
1423                 return &cfqd->async_idle_cfqq;
1424         default:
1425                 BUG();
1426         }
1427 }
1428
1429 static struct cfq_queue *
1430 cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
1431               gfp_t gfp_mask)
1432 {
1433         const int ioprio = task_ioprio(ioc);
1434         const int ioprio_class = task_ioprio_class(ioc);
1435         struct cfq_queue **async_cfqq = NULL;
1436         struct cfq_queue *cfqq = NULL;
1437
1438         if (!is_sync) {
1439                 async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
1440                 cfqq = *async_cfqq;
1441         }
1442
1443         if (!cfqq) {
1444                 cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
1445                 if (!cfqq)
1446                         return NULL;
1447         }
1448
1449         /*
1450          * pin the queue now that it's allocated, scheduler exit will prune it
1451          */
1452         if (!is_sync && !(*async_cfqq)) {
1453                 atomic_inc(&cfqq->ref);
1454                 *async_cfqq = cfqq;
1455         }
1456
1457         atomic_inc(&cfqq->ref);
1458         return cfqq;
1459 }
1460
1461 static void cfq_cic_free(struct cfq_io_context *cic)
1462 {
1463         kmem_cache_free(cfq_ioc_pool, cic);
1464         elv_ioc_count_dec(ioc_count);
1465
1466         if (ioc_gone && !elv_ioc_count_read(ioc_count))
1467                 complete(ioc_gone);
1468 }
1469
1470 /*
1471  * We drop cfq io contexts lazily, so we may find a dead one.
1472  */
1473 static void
1474 cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
1475                   struct cfq_io_context *cic)
1476 {
1477         unsigned long flags;
1478
1479         WARN_ON(!list_empty(&cic->queue_list));
1480
1481         spin_lock_irqsave(&ioc->lock, flags);
1482
1483         if (ioc->ioc_data == cic)
1484                 rcu_assign_pointer(ioc->ioc_data, NULL);
1485
1486         radix_tree_delete(&ioc->radix_root, (unsigned long) cfqd);
1487         hlist_del_rcu(&cic->cic_list);
1488         spin_unlock_irqrestore(&ioc->lock, flags);
1489
1490         cfq_cic_free(cic);
1491 }
1492
1493 static struct cfq_io_context *
1494 cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
1495 {
1496         struct cfq_io_context *cic;
1497         void *k;
1498
1499         if (unlikely(!ioc))
1500                 return NULL;
1501
1502         /*
1503          * we maintain a last-hit cache, to avoid browsing over the tree
1504          */
1505         cic = rcu_dereference(ioc->ioc_data);
1506         if (cic && cic->key == cfqd)
1507                 return cic;
1508
1509         do {
1510                 rcu_read_lock();
1511                 cic = radix_tree_lookup(&ioc->radix_root, (unsigned long) cfqd);
1512                 rcu_read_unlock();
1513                 if (!cic)
1514                         break;
1515                 /* ->key must be copied to avoid race with cfq_exit_queue() */
1516                 k = cic->key;
1517                 if (unlikely(!k)) {
1518                         cfq_drop_dead_cic(cfqd, ioc, cic);
1519                         continue;
1520                 }
1521
1522                 rcu_assign_pointer(ioc->ioc_data, cic);
1523                 break;
1524         } while (1);
1525
1526         return cic;
1527 }
1528
1529 /*
1530  * Add cic into ioc, using cfqd as the search key. This enables us to lookup
1531  * the process specific cfq io context when entered from the block layer.
1532  * Also adds the cic to a per-cfqd list, used when this queue is removed.
1533  */
1534 static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
1535                         struct cfq_io_context *cic, gfp_t gfp_mask)
1536 {
1537         unsigned long flags;
1538         int ret;
1539
1540         ret = radix_tree_preload(gfp_mask);
1541         if (!ret) {
1542                 cic->ioc = ioc;
1543                 cic->key = cfqd;
1544
1545                 spin_lock_irqsave(&ioc->lock, flags);
1546                 ret = radix_tree_insert(&ioc->radix_root,
1547                                                 (unsigned long) cfqd, cic);
1548                 if (!ret)
1549                         hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
1550                 spin_unlock_irqrestore(&ioc->lock, flags);
1551
1552                 radix_tree_preload_end();
1553
1554                 if (!ret) {
1555                         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
1556                         list_add(&cic->queue_list, &cfqd->cic_list);
1557                         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
1558                 }
1559         }
1560
1561         if (ret)
1562                 printk(KERN_ERR "cfq: cic link failed!\n");
1563
1564         return ret;
1565 }
1566
1567 /*
1568  * Setup general io context and cfq io context. There can be several cfq
1569  * io contexts per general io context, if this process is doing io to more
1570  * than one device managed by cfq.
1571  */
1572 static struct cfq_io_context *
1573 cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
1574 {
1575         struct io_context *ioc = NULL;
1576         struct cfq_io_context *cic;
1577
1578         might_sleep_if(gfp_mask & __GFP_WAIT);
1579
1580         ioc = get_io_context(gfp_mask, cfqd->queue->node);
1581         if (!ioc)
1582                 return NULL;
1583
1584         cic = cfq_cic_lookup(cfqd, ioc);
1585         if (cic)
1586                 goto out;
1587
1588         cic = cfq_alloc_io_context(cfqd, gfp_mask);
1589         if (cic == NULL)
1590                 goto err;
1591
1592         if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
1593                 goto err_free;
1594
1595 out:
1596         smp_read_barrier_depends();
1597         if (unlikely(ioc->ioprio_changed))
1598                 cfq_ioc_set_ioprio(ioc);
1599
1600         return cic;
1601 err_free:
1602         cfq_cic_free(cic);
1603 err:
1604         put_io_context(ioc);
1605         return NULL;
1606 }
1607
1608 static void
1609 cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
1610 {
1611         unsigned long elapsed = jiffies - cic->last_end_request;
1612         unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
1613
1614         cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
1615         cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
1616         cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
1617 }
1618
1619 static void
1620 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
1621                        struct request *rq)
1622 {
1623         sector_t sdist;
1624         u64 total;
1625
1626         if (cic->last_request_pos < rq->sector)
1627                 sdist = rq->sector - cic->last_request_pos;
1628         else
1629                 sdist = cic->last_request_pos - rq->sector;
1630
1631         /*
1632          * Don't allow the seek distance to get too large from the
1633          * odd fragment, pagein, etc
1634          */
1635         if (cic->seek_samples <= 60) /* second&third seek */
1636                 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*1024);
1637         else
1638                 sdist = min(sdist, (cic->seek_mean * 4) + 2*1024*64);
1639
1640         cic->seek_samples = (7*cic->seek_samples + 256) / 8;
1641         cic->seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
1642         total = cic->seek_total + (cic->seek_samples/2);
1643         do_div(total, cic->seek_samples);
1644         cic->seek_mean = (sector_t)total;
1645 }
1646
1647 /*
1648  * Disable idle window if the process thinks too long or seeks so much that
1649  * it doesn't matter
1650  */
1651 static void
1652 cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1653                        struct cfq_io_context *cic)
1654 {
1655         int enable_idle;
1656
1657         /*
1658          * Don't idle for async or idle io prio class
1659          */
1660         if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
1661                 return;
1662
1663         enable_idle = cfq_cfqq_idle_window(cfqq);
1664
1665         if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
1666             (cfqd->hw_tag && CIC_SEEKY(cic)))
1667                 enable_idle = 0;
1668         else if (sample_valid(cic->ttime_samples)) {
1669                 if (cic->ttime_mean > cfqd->cfq_slice_idle)
1670                         enable_idle = 0;
1671                 else
1672                         enable_idle = 1;
1673         }
1674
1675         if (enable_idle)
1676                 cfq_mark_cfqq_idle_window(cfqq);
1677         else
1678                 cfq_clear_cfqq_idle_window(cfqq);
1679 }
1680
1681 /*
1682  * Check if new_cfqq should preempt the currently active queue. Return 0 for
1683  * no or if we aren't sure, a 1 will cause a preempt.
1684  */
1685 static int
1686 cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
1687                    struct request *rq)
1688 {
1689         struct cfq_queue *cfqq;
1690
1691         cfqq = cfqd->active_queue;
1692         if (!cfqq)
1693                 return 0;
1694
1695         if (cfq_slice_used(cfqq))
1696                 return 1;
1697
1698         if (cfq_class_idle(new_cfqq))
1699                 return 0;
1700
1701         if (cfq_class_idle(cfqq))
1702                 return 1;
1703
1704         /*
1705          * if the new request is sync, but the currently running queue is
1706          * not, let the sync request have priority.
1707          */
1708         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
1709                 return 1;
1710
1711         /*
1712          * So both queues are sync. Let the new request get disk time if
1713          * it's a metadata request and the current queue is doing regular IO.
1714          */
1715         if (rq_is_meta(rq) && !cfqq->meta_pending)
1716                 return 1;
1717
1718         if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
1719                 return 0;
1720
1721         /*
1722          * if this request is as-good as one we would expect from the
1723          * current cfqq, let it preempt
1724          */
1725         if (cfq_rq_close(cfqd, rq))
1726                 return 1;
1727
1728         return 0;
1729 }
1730
1731 /*
1732  * cfqq preempts the active queue. if we allowed preempt with no slice left,
1733  * let it have half of its nominal slice.
1734  */
1735 static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
1736 {
1737         cfq_slice_expired(cfqd, 1);
1738
1739         /*
1740          * Put the new queue at the front of the of the current list,
1741          * so we know that it will be selected next.
1742          */
1743         BUG_ON(!cfq_cfqq_on_rr(cfqq));
1744
1745         cfq_service_tree_add(cfqd, cfqq, 1);
1746
1747         cfqq->slice_end = 0;
1748         cfq_mark_cfqq_slice_new(cfqq);
1749 }
1750
1751 /*
1752  * Called when a new fs request (rq) is added (to cfqq). Check if there's
1753  * something we should do about it
1754  */
1755 static void
1756 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
1757                 struct request *rq)
1758 {
1759         struct cfq_io_context *cic = RQ_CIC(rq);
1760
1761         if (rq_is_meta(rq))
1762                 cfqq->meta_pending++;
1763
1764         cfq_update_io_thinktime(cfqd, cic);
1765         cfq_update_io_seektime(cfqd, cic, rq);
1766         cfq_update_idle_window(cfqd, cfqq, cic);
1767
1768         cic->last_request_pos = rq->sector + rq->nr_sectors;
1769
1770         if (cfqq == cfqd->active_queue) {
1771                 /*
1772                  * if we are waiting for a request for this queue, let it rip
1773                  * immediately and flag that we must not expire this queue
1774                  * just now
1775                  */
1776                 if (cfq_cfqq_wait_request(cfqq)) {
1777                         cfq_mark_cfqq_must_dispatch(cfqq);
1778                         del_timer(&cfqd->idle_slice_timer);
1779                         blk_start_queueing(cfqd->queue);
1780                 }
1781         } else if (cfq_should_preempt(cfqd, cfqq, rq)) {
1782                 /*
1783                  * not the active queue - expire current slice if it is
1784                  * idle and has expired it's mean thinktime or this new queue
1785                  * has some old slice time left and is of higher priority
1786                  */
1787                 cfq_preempt_queue(cfqd, cfqq);
1788                 cfq_mark_cfqq_must_dispatch(cfqq);
1789                 blk_start_queueing(cfqd->queue);
1790         }
1791 }
1792
1793 static void cfq_insert_request(struct request_queue *q, struct request *rq)
1794 {
1795         struct cfq_data *cfqd = q->elevator->elevator_data;
1796         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1797
1798         cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
1799
1800         cfq_add_rq_rb(rq);
1801
1802         list_add_tail(&rq->queuelist, &cfqq->fifo);
1803
1804         cfq_rq_enqueued(cfqd, cfqq, rq);
1805 }
1806
1807 static void cfq_completed_request(struct request_queue *q, struct request *rq)
1808 {
1809         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1810         struct cfq_data *cfqd = cfqq->cfqd;
1811         const int sync = rq_is_sync(rq);
1812         unsigned long now;
1813
1814         now = jiffies;
1815
1816         WARN_ON(!cfqd->rq_in_driver);
1817         WARN_ON(!cfqq->dispatched);
1818         cfqd->rq_in_driver--;
1819         cfqq->dispatched--;
1820
1821         if (cfq_cfqq_sync(cfqq))
1822                 cfqd->sync_flight--;
1823
1824         if (!cfq_class_idle(cfqq))
1825                 cfqd->last_end_request = now;
1826
1827         if (sync)
1828                 RQ_CIC(rq)->last_end_request = now;
1829
1830         /*
1831          * If this is the active queue, check if it needs to be expired,
1832          * or if we want to idle in case it has no pending requests.
1833          */
1834         if (cfqd->active_queue == cfqq) {
1835                 if (cfq_cfqq_slice_new(cfqq)) {
1836                         cfq_set_prio_slice(cfqd, cfqq);
1837                         cfq_clear_cfqq_slice_new(cfqq);
1838                 }
1839                 if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
1840                         cfq_slice_expired(cfqd, 1);
1841                 else if (sync && RB_EMPTY_ROOT(&cfqq->sort_list))
1842                         cfq_arm_slice_timer(cfqd);
1843         }
1844
1845         if (!cfqd->rq_in_driver)
1846                 cfq_schedule_dispatch(cfqd);
1847 }
1848
1849 /*
1850  * we temporarily boost lower priority queues if they are holding fs exclusive
1851  * resources. they are boosted to normal prio (CLASS_BE/4)
1852  */
1853 static void cfq_prio_boost(struct cfq_queue *cfqq)
1854 {
1855         if (has_fs_excl()) {
1856                 /*
1857                  * boost idle prio on transactions that would lock out other
1858                  * users of the filesystem
1859                  */
1860                 if (cfq_class_idle(cfqq))
1861                         cfqq->ioprio_class = IOPRIO_CLASS_BE;
1862                 if (cfqq->ioprio > IOPRIO_NORM)
1863                         cfqq->ioprio = IOPRIO_NORM;
1864         } else {
1865                 /*
1866                  * check if we need to unboost the queue
1867                  */
1868                 if (cfqq->ioprio_class != cfqq->org_ioprio_class)
1869                         cfqq->ioprio_class = cfqq->org_ioprio_class;
1870                 if (cfqq->ioprio != cfqq->org_ioprio)
1871                         cfqq->ioprio = cfqq->org_ioprio;
1872         }
1873 }
1874
1875 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
1876 {
1877         if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
1878             !cfq_cfqq_must_alloc_slice(cfqq)) {
1879                 cfq_mark_cfqq_must_alloc_slice(cfqq);
1880                 return ELV_MQUEUE_MUST;
1881         }
1882
1883         return ELV_MQUEUE_MAY;
1884 }
1885
1886 static int cfq_may_queue(struct request_queue *q, int rw)
1887 {
1888         struct cfq_data *cfqd = q->elevator->elevator_data;
1889         struct task_struct *tsk = current;
1890         struct cfq_io_context *cic;
1891         struct cfq_queue *cfqq;
1892
1893         /*
1894          * don't force setup of a queue from here, as a call to may_queue
1895          * does not necessarily imply that a request actually will be queued.
1896          * so just lookup a possibly existing queue, or return 'may queue'
1897          * if that fails
1898          */
1899         cic = cfq_cic_lookup(cfqd, tsk->io_context);
1900         if (!cic)
1901                 return ELV_MQUEUE_MAY;
1902
1903         cfqq = cic_to_cfqq(cic, rw & REQ_RW_SYNC);
1904         if (cfqq) {
1905                 cfq_init_prio_data(cfqq, cic->ioc);
1906                 cfq_prio_boost(cfqq);
1907
1908                 return __cfq_may_queue(cfqq);
1909         }
1910
1911         return ELV_MQUEUE_MAY;
1912 }
1913
1914 /*
1915  * queue lock held here
1916  */
1917 static void cfq_put_request(struct request *rq)
1918 {
1919         struct cfq_queue *cfqq = RQ_CFQQ(rq);
1920
1921         if (cfqq) {
1922                 const int rw = rq_data_dir(rq);
1923
1924                 BUG_ON(!cfqq->allocated[rw]);
1925                 cfqq->allocated[rw]--;
1926
1927                 put_io_context(RQ_CIC(rq)->ioc);
1928
1929                 rq->elevator_private = NULL;
1930                 rq->elevator_private2 = NULL;
1931
1932                 cfq_put_queue(cfqq);
1933         }
1934 }
1935
1936 /*
1937  * Allocate cfq data structures associated with this request.
1938  */
1939 static int
1940 cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
1941 {
1942         struct cfq_data *cfqd = q->elevator->elevator_data;
1943         struct cfq_io_context *cic;
1944         const int rw = rq_data_dir(rq);
1945         const int is_sync = rq_is_sync(rq);
1946         struct cfq_queue *cfqq;
1947         unsigned long flags;
1948
1949         might_sleep_if(gfp_mask & __GFP_WAIT);
1950
1951         cic = cfq_get_io_context(cfqd, gfp_mask);
1952
1953         spin_lock_irqsave(q->queue_lock, flags);
1954
1955         if (!cic)
1956                 goto queue_fail;
1957
1958         cfqq = cic_to_cfqq(cic, is_sync);
1959         if (!cfqq) {
1960                 cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
1961
1962                 if (!cfqq)
1963                         goto queue_fail;
1964
1965                 cic_set_cfqq(cic, cfqq, is_sync);
1966         }
1967
1968         cfqq->allocated[rw]++;
1969         cfq_clear_cfqq_must_alloc(cfqq);
1970         atomic_inc(&cfqq->ref);
1971
1972         spin_unlock_irqrestore(q->queue_lock, flags);
1973
1974         rq->elevator_private = cic;
1975         rq->elevator_private2 = cfqq;
1976         return 0;
1977
1978 queue_fail:
1979         if (cic)
1980                 put_io_context(cic->ioc);
1981
1982         cfq_schedule_dispatch(cfqd);
1983         spin_unlock_irqrestore(q->queue_lock, flags);
1984         return 1;
1985 }
1986
1987 static void cfq_kick_queue(struct work_struct *work)
1988 {
1989         struct cfq_data *cfqd =
1990                 container_of(work, struct cfq_data, unplug_work);
1991         struct request_queue *q = cfqd->queue;
1992         unsigned long flags;
1993
1994         spin_lock_irqsave(q->queue_lock, flags);
1995         blk_start_queueing(q);
1996         spin_unlock_irqrestore(q->queue_lock, flags);
1997 }
1998
1999 /*
2000  * Timer running if the active_queue is currently idling inside its time slice
2001  */
2002 static void cfq_idle_slice_timer(unsigned long data)
2003 {
2004         struct cfq_data *cfqd = (struct cfq_data *) data;
2005         struct cfq_queue *cfqq;
2006         unsigned long flags;
2007         int timed_out = 1;
2008
2009         spin_lock_irqsave(cfqd->queue->queue_lock, flags);
2010
2011         cfqq = cfqd->active_queue;
2012         if (cfqq) {
2013                 timed_out = 0;
2014
2015                 /*
2016                  * expired
2017                  */
2018                 if (cfq_slice_used(cfqq))
2019                         goto expire;
2020
2021                 /*
2022                  * only expire and reinvoke request handler, if there are
2023                  * other queues with pending requests
2024                  */
2025                 if (!cfqd->busy_queues)
2026                         goto out_cont;
2027
2028                 /*
2029                  * not expired and it has a request pending, let it dispatch
2030                  */
2031                 if (!RB_EMPTY_ROOT(&cfqq->sort_list)) {
2032                         cfq_mark_cfqq_must_dispatch(cfqq);
2033                         goto out_kick;
2034                 }
2035         }
2036 expire:
2037         cfq_slice_expired(cfqd, timed_out);
2038 out_kick:
2039         cfq_schedule_dispatch(cfqd);
2040 out_cont:
2041         spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
2042 }
2043
2044 static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
2045 {
2046         del_timer_sync(&cfqd->idle_slice_timer);
2047         kblockd_flush_work(&cfqd->unplug_work);
2048 }
2049
2050 static void cfq_put_async_queues(struct cfq_data *cfqd)
2051 {
2052         int i;
2053
2054         for (i = 0; i < IOPRIO_BE_NR; i++) {
2055                 if (cfqd->async_cfqq[0][i])
2056                         cfq_put_queue(cfqd->async_cfqq[0][i]);
2057                 if (cfqd->async_cfqq[1][i])
2058                         cfq_put_queue(cfqd->async_cfqq[1][i]);
2059         }
2060
2061         if (cfqd->async_idle_cfqq)
2062                 cfq_put_queue(cfqd->async_idle_cfqq);
2063 }
2064
2065 static void cfq_exit_queue(elevator_t *e)
2066 {
2067         struct cfq_data *cfqd = e->elevator_data;
2068         struct request_queue *q = cfqd->queue;
2069
2070         cfq_shutdown_timer_wq(cfqd);
2071
2072         spin_lock_irq(q->queue_lock);
2073
2074         if (cfqd->active_queue)
2075                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
2076
2077         while (!list_empty(&cfqd->cic_list)) {
2078                 struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
2079                                                         struct cfq_io_context,
2080                                                         queue_list);
2081
2082                 __cfq_exit_single_io_context(cfqd, cic);
2083         }
2084
2085         cfq_put_async_queues(cfqd);
2086
2087         spin_unlock_irq(q->queue_lock);
2088
2089         cfq_shutdown_timer_wq(cfqd);
2090
2091         kfree(cfqd);
2092 }
2093
2094 static void *cfq_init_queue(struct request_queue *q)
2095 {
2096         struct cfq_data *cfqd;
2097
2098         cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
2099         if (!cfqd)
2100                 return NULL;
2101
2102         cfqd->service_tree = CFQ_RB_ROOT;
2103         INIT_LIST_HEAD(&cfqd->cic_list);
2104
2105         cfqd->queue = q;
2106
2107         init_timer(&cfqd->idle_slice_timer);
2108         cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
2109         cfqd->idle_slice_timer.data = (unsigned long) cfqd;
2110
2111         INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
2112
2113         cfqd->last_end_request = jiffies;
2114         cfqd->cfq_quantum = cfq_quantum;
2115         cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
2116         cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
2117         cfqd->cfq_back_max = cfq_back_max;
2118         cfqd->cfq_back_penalty = cfq_back_penalty;
2119         cfqd->cfq_slice[0] = cfq_slice_async;
2120         cfqd->cfq_slice[1] = cfq_slice_sync;
2121         cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
2122         cfqd->cfq_slice_idle = cfq_slice_idle;
2123
2124         return cfqd;
2125 }
2126
2127 static void cfq_slab_kill(void)
2128 {
2129         if (cfq_pool)
2130                 kmem_cache_destroy(cfq_pool);
2131         if (cfq_ioc_pool)
2132                 kmem_cache_destroy(cfq_ioc_pool);
2133 }
2134
2135 static int __init cfq_slab_setup(void)
2136 {
2137         cfq_pool = KMEM_CACHE(cfq_queue, 0);
2138         if (!cfq_pool)
2139                 goto fail;
2140
2141         cfq_ioc_pool = KMEM_CACHE(cfq_io_context, SLAB_DESTROY_BY_RCU);
2142         if (!cfq_ioc_pool)
2143                 goto fail;
2144
2145         return 0;
2146 fail:
2147         cfq_slab_kill();
2148         return -ENOMEM;
2149 }
2150
2151 /*
2152  * sysfs parts below -->
2153  */
2154 static ssize_t
2155 cfq_var_show(unsigned int var, char *page)
2156 {
2157         return sprintf(page, "%d\n", var);
2158 }
2159
2160 static ssize_t
2161 cfq_var_store(unsigned int *var, const char *page, size_t count)
2162 {
2163         char *p = (char *) page;
2164
2165         *var = simple_strtoul(p, &p, 10);
2166         return count;
2167 }
2168
2169 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
2170 static ssize_t __FUNC(elevator_t *e, char *page)                        \
2171 {                                                                       \
2172         struct cfq_data *cfqd = e->elevator_data;                       \
2173         unsigned int __data = __VAR;                                    \
2174         if (__CONV)                                                     \
2175                 __data = jiffies_to_msecs(__data);                      \
2176         return cfq_var_show(__data, (page));                            \
2177 }
2178 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
2179 SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
2180 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
2181 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
2182 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
2183 SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
2184 SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
2185 SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
2186 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
2187 #undef SHOW_FUNCTION
2188
2189 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
2190 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count)    \
2191 {                                                                       \
2192         struct cfq_data *cfqd = e->elevator_data;                       \
2193         unsigned int __data;                                            \
2194         int ret = cfq_var_store(&__data, (page), count);                \
2195         if (__data < (MIN))                                             \
2196                 __data = (MIN);                                         \
2197         else if (__data > (MAX))                                        \
2198                 __data = (MAX);                                         \
2199         if (__CONV)                                                     \
2200                 *(__PTR) = msecs_to_jiffies(__data);                    \
2201         else                                                            \
2202                 *(__PTR) = __data;                                      \
2203         return ret;                                                     \
2204 }
2205 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
2206 STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
2207                 UINT_MAX, 1);
2208 STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
2209                 UINT_MAX, 1);
2210 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
2211 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
2212                 UINT_MAX, 0);
2213 STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
2214 STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
2215 STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
2216 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
2217                 UINT_MAX, 0);
2218 #undef STORE_FUNCTION
2219
2220 #define CFQ_ATTR(name) \
2221         __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
2222
2223 static struct elv_fs_entry cfq_attrs[] = {
2224         CFQ_ATTR(quantum),
2225         CFQ_ATTR(fifo_expire_sync),
2226         CFQ_ATTR(fifo_expire_async),
2227         CFQ_ATTR(back_seek_max),
2228         CFQ_ATTR(back_seek_penalty),
2229         CFQ_ATTR(slice_sync),
2230         CFQ_ATTR(slice_async),
2231         CFQ_ATTR(slice_async_rq),
2232         CFQ_ATTR(slice_idle),
2233         __ATTR_NULL
2234 };
2235
2236 static struct elevator_type iosched_cfq = {
2237         .ops = {
2238                 .elevator_merge_fn =            cfq_merge,
2239                 .elevator_merged_fn =           cfq_merged_request,
2240                 .elevator_merge_req_fn =        cfq_merged_requests,
2241                 .elevator_allow_merge_fn =      cfq_allow_merge,
2242                 .elevator_dispatch_fn =         cfq_dispatch_requests,
2243                 .elevator_add_req_fn =          cfq_insert_request,
2244                 .elevator_activate_req_fn =     cfq_activate_request,
2245                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
2246                 .elevator_queue_empty_fn =      cfq_queue_empty,
2247                 .elevator_completed_req_fn =    cfq_completed_request,
2248                 .elevator_former_req_fn =       elv_rb_former_request,
2249                 .elevator_latter_req_fn =       elv_rb_latter_request,
2250                 .elevator_set_req_fn =          cfq_set_request,
2251                 .elevator_put_req_fn =          cfq_put_request,
2252                 .elevator_may_queue_fn =        cfq_may_queue,
2253                 .elevator_init_fn =             cfq_init_queue,
2254                 .elevator_exit_fn =             cfq_exit_queue,
2255                 .trim =                         cfq_free_io_context,
2256         },
2257         .elevator_attrs =       cfq_attrs,
2258         .elevator_name =        "cfq",
2259         .elevator_owner =       THIS_MODULE,
2260 };
2261
2262 static int __init cfq_init(void)
2263 {
2264         /*
2265          * could be 0 on HZ < 1000 setups
2266          */
2267         if (!cfq_slice_async)
2268                 cfq_slice_async = 1;
2269         if (!cfq_slice_idle)
2270                 cfq_slice_idle = 1;
2271
2272         if (cfq_slab_setup())
2273                 return -ENOMEM;
2274
2275         elv_register(&iosched_cfq);
2276
2277         return 0;
2278 }
2279
2280 static void __exit cfq_exit(void)
2281 {
2282         DECLARE_COMPLETION_ONSTACK(all_gone);
2283         elv_unregister(&iosched_cfq);
2284         ioc_gone = &all_gone;
2285         /* ioc_gone's update must be visible before reading ioc_count */
2286         smp_wmb();
2287         if (elv_ioc_count_read(ioc_count))
2288                 wait_for_completion(ioc_gone);
2289         synchronize_rcu();
2290         cfq_slab_kill();
2291 }
2292
2293 module_init(cfq_init);
2294 module_exit(cfq_exit);
2295
2296 MODULE_AUTHOR("Jens Axboe");
2297 MODULE_LICENSE("GPL");
2298 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");