drivers/block/cfq-iosched.c

   1 /*
   2  *  linux/drivers/block/cfq-iosched.c
   3  *
   4  *  CFQ, or complete fairness queueing, disk scheduler.
   5  *
   6  *  Based on ideas from a previously unfinished io
   7  *  scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
   8  *
   9  *  Copyright (C) 2003 Jens Axboe <axboe@suse.de>
  10  */
  11 #include <linux/kernel.h>
  12 #include <linux/fs.h>
  13 #include <linux/blkdev.h>
  14 #include <linux/elevator.h>
  15 #include <linux/bio.h>
  16 #include <linux/config.h>
  17 #include <linux/module.h>
  18 #include <linux/slab.h>
  19 #include <linux/init.h>
  20 #include <linux/compiler.h>
  21 #include <linux/hash.h>
  22 #include <linux/rbtree.h>
  23 #include <linux/mempool.h>
  24
  25 /*
  26  * tunables
  27  */
  28 static int cfq_quantum = 4;
  29 static int cfq_queued = 8;
  30
  31 #define CFQ_QHASH_SHIFT         6
  32 #define CFQ_QHASH_ENTRIES       (1 << CFQ_QHASH_SHIFT)
  33 #define list_entry_qhash(entry) list_entry((entry), struct cfq_queue, cfq_hash)
  34
  35 #define CFQ_MHASH_SHIFT         8
  36 #define CFQ_MHASH_BLOCK(sec)    ((sec) >> 3)
  37 #define CFQ_MHASH_ENTRIES       (1 << CFQ_MHASH_SHIFT)
  38 #define CFQ_MHASH_FN(sec)       (hash_long(CFQ_MHASH_BLOCK((sec)),CFQ_MHASH_SHIFT))
  39 #define ON_MHASH(crq)           !list_empty(&(crq)->hash)
  40 #define rq_hash_key(rq)         ((rq)->sector + (rq)->nr_sectors)
  41 #define list_entry_hash(ptr)    list_entry((ptr), struct cfq_rq, hash)
  42
  43 #define list_entry_cfqq(ptr)    list_entry((ptr), struct cfq_queue, cfq_list)
  44
  45 #define RQ_DATA(rq)             ((struct cfq_rq *) (rq)->elevator_private)
  46
  47 static kmem_cache_t *crq_pool;
  48 static kmem_cache_t *cfq_pool;
  49 static mempool_t *cfq_mpool;
  50
  51 struct cfq_data {
  52         struct list_head rr_list;
  53         struct list_head *dispatch;
  54         struct list_head *cfq_hash;
  55
  56         struct list_head *crq_hash;
  57
  58         unsigned int busy_queues;
  59         unsigned int max_queued;
  60
  61         mempool_t *crq_pool;
  62
  63         request_queue_t *queue;
  64
  65         /*
  66          * tunables
  67          */
  68         unsigned int cfq_quantum;
  69         unsigned int cfq_queued;
  70 };
  71
  72 struct cfq_queue {
  73         struct list_head cfq_hash;
  74         struct list_head cfq_list;
  75         struct rb_root sort_list;
  76         int pid;
  77         int queued[2];
  78 #if 0
  79         /*
  80          * with a simple addition like this, we can do io priorities. almost.
  81          * does need a split request free list, too.
  82          */
  83         int io_prio
  84 #endif
  85 };
  86
  87 struct cfq_rq {
  88         struct rb_node rb_node;
  89         sector_t rb_key;
  90
  91         struct request *request;
  92
  93         struct cfq_queue *cfq_queue;
  94
  95         struct list_head hash;
  96 };
  97
  98 static void cfq_put_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq);
  99 static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *cfqd, int pid);
 100 static void cfq_dispatch_sort(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 101                               struct cfq_rq *crq);
 102
 103 /*
 104  * lots of deadline iosched dupes, can be abstracted later...
 105  */
 106 static inline void __cfq_del_crq_hash(struct cfq_rq *crq)
 107 {
 108         list_del_init(&crq->hash);
 109 }
 110
 111 static inline void cfq_del_crq_hash(struct cfq_rq *crq)
 112 {
 113         if (ON_MHASH(crq))
 114                 __cfq_del_crq_hash(crq);
 115 }
 116
 117 static void cfq_remove_merge_hints(request_queue_t *q, struct cfq_rq *crq)
 118 {
 119         cfq_del_crq_hash(crq);
 120
 121         if (q->last_merge == crq->request)
 122                 q->last_merge = NULL;
 123 }
 124
 125 static inline void cfq_add_crq_hash(struct cfq_data *cfqd, struct cfq_rq *crq)
 126 {
 127         struct request *rq = crq->request;
 128
 129         BUG_ON(ON_MHASH(crq));
 130
 131         list_add(&crq->hash, &cfqd->crq_hash[CFQ_MHASH_FN(rq_hash_key(rq))]);
 132 }
 133
 134 static struct request *cfq_find_rq_hash(struct cfq_data *cfqd, sector_t offset)
 135 {
 136         struct list_head *hash_list = &cfqd->crq_hash[CFQ_MHASH_FN(offset)];
 137         struct list_head *entry, *next = hash_list->next;
 138
 139         while ((entry = next) != hash_list) {
 140                 struct cfq_rq *crq = list_entry_hash(entry);
 141                 struct request *__rq = crq->request;
 142
 143                 next = entry->next;
 144
 145                 BUG_ON(!ON_MHASH(crq));
 146
 147                 if (!rq_mergeable(__rq)) {
 148                         __cfq_del_crq_hash(crq);
 149                         continue;
 150                 }
 151
 152                 if (rq_hash_key(__rq) == offset)
 153                         return __rq;
 154         }
 155
 156         return NULL;
 157 }
 158
 159 /*
 160  * rb tree support functions
 161  */
 162 #define RB_NONE         (2)
 163 #define RB_EMPTY(node)  ((node)->rb_node == NULL)
 164 #define RB_CLEAR(node)  ((node)->rb_color = RB_NONE)
 165 #define RB_CLEAR_ROOT(root)     ((root)->rb_node = NULL)
 166 #define ON_RB(node)     ((node)->rb_color != RB_NONE)
 167 #define rb_entry_crq(node)      rb_entry((node), struct cfq_rq, rb_node)
 168 #define rq_rb_key(rq)           (rq)->sector
 169
 170 static inline void cfq_del_crq_rb(struct cfq_queue *cfqq, struct cfq_rq *crq)
 171 {
 172         if (ON_RB(&crq->rb_node)) {
 173                 cfqq->queued[rq_data_dir(crq->request)]--;
 174                 rb_erase(&crq->rb_node, &cfqq->sort_list);
 175                 crq->cfq_queue = NULL;
 176         }
 177 }
 178
 179 static struct cfq_rq *
 180 __cfq_add_crq_rb(struct cfq_queue *cfqq, struct cfq_rq *crq)
 181 {
 182         struct rb_node **p = &cfqq->sort_list.rb_node;
 183         struct rb_node *parent = NULL;
 184         struct cfq_rq *__crq;
 185
 186         while (*p) {
 187                 parent = *p;
 188                 __crq = rb_entry_crq(parent);
 189
 190                 if (crq->rb_key < __crq->rb_key)
 191                         p = &(*p)->rb_left;
 192                 else if (crq->rb_key > __crq->rb_key)
 193                         p = &(*p)->rb_right;
 194                 else
 195                         return __crq;
 196         }
 197
 198         rb_link_node(&crq->rb_node, parent, p);
 199         return 0;
 200 }
 201
 202 static void
 203 cfq_add_crq_rb(struct cfq_data *cfqd, struct cfq_queue *cfqq,struct cfq_rq *crq)
 204 {
 205         struct request *rq = crq->request;
 206         struct cfq_rq *__alias;
 207
 208         crq->rb_key = rq_rb_key(rq);
 209         cfqq->queued[rq_data_dir(rq)]++;
 210 retry:
 211         __alias = __cfq_add_crq_rb(cfqq, crq);
 212         if (!__alias) {
 213                 rb_insert_color(&crq->rb_node, &cfqq->sort_list);
 214                 crq->cfq_queue = cfqq;
 215                 return;
 216         }
 217
 218         cfq_dispatch_sort(cfqd, cfqq, __alias);
 219         goto retry;
 220 }
 221
 222 static struct request *
 223 cfq_find_rq_rb(struct cfq_data *cfqd, sector_t sector)
 224 {
 225         struct cfq_queue *cfqq = cfq_find_cfq_hash(cfqd, current->tgid);
 226         struct rb_node *n;
 227
 228         if (!cfqq)
 229                 goto out;
 230
 231         n = cfqq->sort_list.rb_node;
 232         while (n) {
 233                 struct cfq_rq *crq = rb_entry_crq(n);
 234
 235                 if (sector < crq->rb_key)
 236                         n = n->rb_left;
 237                 else if (sector > crq->rb_key)
 238                         n = n->rb_right;
 239                 else
 240                         return crq->request;
 241         }
 242
 243 out:
 244         return NULL;
 245 }
 246
 247 static void cfq_remove_request(request_queue_t *q, struct request *rq)
 248 {
 249         struct cfq_data *cfqd = q->elevator.elevator_data;
 250         struct cfq_rq *crq = RQ_DATA(rq);
 251
 252         if (crq) {
 253                 struct cfq_queue *cfqq = crq->cfq_queue;
 254
 255                 cfq_remove_merge_hints(q, crq);
 256                 list_del_init(&rq->queuelist);
 257
 258                 if (cfqq) {
 259                         cfq_del_crq_rb(cfqq, crq);
 260
 261                         if (RB_EMPTY(&cfqq->sort_list))
 262                                 cfq_put_queue(cfqd, cfqq);
 263                 }
 264         }
 265 }
 266
 267 static int
 268 cfq_merge(request_queue_t *q, struct request **req, struct bio *bio)
 269 {
 270         struct cfq_data *cfqd = q->elevator.elevator_data;
 271         struct request *__rq;
 272         int ret;
 273
 274         ret = elv_try_last_merge(q, bio);
 275         if (ret != ELEVATOR_NO_MERGE) {
 276                 __rq = q->last_merge;
 277                 goto out_insert;
 278         }
 279
 280         __rq = cfq_find_rq_hash(cfqd, bio->bi_sector);
 281         if (__rq) {
 282                 BUG_ON(__rq->sector + __rq->nr_sectors != bio->bi_sector);
 283
 284                 if (elv_rq_merge_ok(__rq, bio)) {
 285                         ret = ELEVATOR_BACK_MERGE;
 286                         goto out;
 287                 }
 288         }
 289
 290         __rq = cfq_find_rq_rb(cfqd, bio->bi_sector + bio_sectors(bio));
 291         if (__rq) {
 292                 if (elv_rq_merge_ok(__rq, bio)) {
 293                         ret = ELEVATOR_FRONT_MERGE;
 294                         goto out;
 295                 }
 296         }
 297
 298         return ELEVATOR_NO_MERGE;
 299 out:
 300         q->last_merge = __rq;
 301 out_insert:
 302         *req = __rq;
 303         return ret;
 304 }
 305
 306 static void cfq_merged_request(request_queue_t *q, struct request *req)
 307 {
 308         struct cfq_data *cfqd = q->elevator.elevator_data;
 309         struct cfq_rq *crq = RQ_DATA(req);
 310
 311         cfq_del_crq_hash(crq);
 312         cfq_add_crq_hash(cfqd, crq);
 313
 314         if (ON_RB(&crq->rb_node) && (rq_rb_key(req) != crq->rb_key)) {
 315                 struct cfq_queue *cfqq = crq->cfq_queue;
 316
 317                 cfq_del_crq_rb(cfqq, crq);
 318                 cfq_add_crq_rb(cfqd, cfqq, crq);
 319         }
 320
 321         q->last_merge = req;
 322 }
 323
 324 static void
 325 cfq_merged_requests(request_queue_t *q, struct request *req,
 326                     struct request *next)
 327 {
 328         cfq_merged_request(q, req);
 329         cfq_remove_request(q, next);
 330 }
 331
 332 static void
 333 cfq_dispatch_sort(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 334                   struct cfq_rq *crq)
 335 {
 336         struct list_head *head = cfqd->dispatch, *entry = head;
 337         struct request *__rq;
 338
 339         cfq_del_crq_rb(cfqq, crq);
 340         cfq_remove_merge_hints(cfqd->queue, crq);
 341
 342         if (!list_empty(head)) {
 343                 __rq = list_entry_rq(head->next);
 344
 345                 if (crq->request->sector < __rq->sector) {
 346                         entry = head->prev;
 347                         goto link;
 348                 }
 349         }
 350
 351         while ((entry = entry->prev) != head) {
 352                 __rq = list_entry_rq(entry);
 353
 354                 if (crq->request->sector <= __rq->sector)
 355                         break;
 356         }
 357
 358 link:
 359         list_add_tail(&crq->request->queuelist, entry);
 360 }
 361
 362 static inline void
 363 __cfq_dispatch_requests(request_queue_t *q, struct cfq_data *cfqd,
 364                         struct cfq_queue *cfqq)
 365 {
 366         struct cfq_rq *crq = rb_entry_crq(rb_first(&cfqq->sort_list));
 367
 368         cfq_dispatch_sort(cfqd, cfqq, crq);
 369 }
 370
 371 static int cfq_dispatch_requests(request_queue_t *q, struct cfq_data *cfqd)
 372 {
 373         struct cfq_queue *cfqq;
 374         struct list_head *entry, *tmp;
 375         int ret, queued, good_queues;
 376
 377         if (list_empty(&cfqd->rr_list))
 378                 return 0;
 379
 380         queued = ret = 0;
 381 restart:
 382         good_queues = 0;
 383         list_for_each_safe(entry, tmp, &cfqd->rr_list) {
 384                 cfqq = list_entry_cfqq(cfqd->rr_list.next);
 385
 386                 BUG_ON(RB_EMPTY(&cfqq->sort_list));
 387
 388                 __cfq_dispatch_requests(q, cfqd, cfqq);
 389
 390                 if (RB_EMPTY(&cfqq->sort_list))
 391                         cfq_put_queue(cfqd, cfqq);
 392                 else
 393                         good_queues++;
 394
 395                 queued++;
 396                 ret = 1;
 397         }
 398
 399         if ((queued < cfqd->cfq_quantum) && good_queues)
 400                 goto restart;
 401
 402         return ret;
 403 }
 404
 405 static struct request *cfq_next_request(request_queue_t *q)
 406 {
 407         struct cfq_data *cfqd = q->elevator.elevator_data;
 408         struct request *rq;
 409
 410         if (!list_empty(cfqd->dispatch)) {
 411                 struct cfq_rq *crq;
 412 dispatch:
 413                 rq = list_entry_rq(cfqd->dispatch->next);
 414
 415                 crq = RQ_DATA(rq);
 416                 if (crq)
 417                         cfq_remove_merge_hints(q, crq);
 418
 419                 return rq;
 420         }
 421
 422         if (cfq_dispatch_requests(q, cfqd))
 423                 goto dispatch;
 424
 425         return NULL;
 426 }
 427
 428 static inline struct cfq_queue *
 429 __cfq_find_cfq_hash(struct cfq_data *cfqd, int pid, const int hashval)
 430 {
 431         struct list_head *hash_list = &cfqd->cfq_hash[hashval];
 432         struct list_head *entry;
 433
 434         list_for_each(entry, hash_list) {
 435                 struct cfq_queue *__cfqq = list_entry_qhash(entry);
 436
 437                 if (__cfqq->pid == pid)
 438                         return __cfqq;
 439         }
 440
 441         return NULL;
 442 }
 443
 444 static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *cfqd, int pid)
 445 {
 446         const int hashval = hash_long(current->tgid, CFQ_QHASH_SHIFT);
 447
 448         return __cfq_find_cfq_hash(cfqd, pid, hashval);
 449 }
 450
 451 static void cfq_put_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 452 {
 453         cfqd->busy_queues--;
 454         list_del(&cfqq->cfq_list);
 455         list_del(&cfqq->cfq_hash);
 456         mempool_free(cfqq, cfq_mpool);
 457 }
 458
 459 static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, int pid)
 460 {
 461         const int hashval = hash_long(current->tgid, CFQ_QHASH_SHIFT);
 462         struct cfq_queue *cfqq = __cfq_find_cfq_hash(cfqd, pid, hashval);
 463
 464         if (!cfqq) {
 465                 cfqq = mempool_alloc(cfq_mpool, GFP_NOIO);
 466
 467                 INIT_LIST_HEAD(&cfqq->cfq_hash);
 468                 INIT_LIST_HEAD(&cfqq->cfq_list);
 469                 RB_CLEAR_ROOT(&cfqq->sort_list);
 470
 471                 cfqq->pid = pid;
 472                 cfqq->queued[0] = cfqq->queued[1] = 0;
 473                 list_add(&cfqq->cfq_hash, &cfqd->cfq_hash[hashval]);
 474         }
 475
 476         return cfqq;
 477 }
 478
 479 static void cfq_enqueue(struct cfq_data *cfqd, struct cfq_rq *crq)
 480 {
 481         struct cfq_queue *cfqq;
 482
 483         cfqq = cfq_get_queue(cfqd, current->tgid);
 484
 485         cfq_add_crq_rb(cfqd, cfqq, crq);
 486
 487         if (list_empty(&cfqq->cfq_list)) {
 488                 list_add(&cfqq->cfq_list, &cfqd->rr_list);
 489                 cfqd->busy_queues++;
 490         }
 491 }
 492
 493 static void
 494 cfq_insert_request(request_queue_t *q, struct request *rq, int where)
 495 {
 496         struct cfq_data *cfqd = q->elevator.elevator_data;
 497         struct cfq_rq *crq = RQ_DATA(rq);
 498
 499         switch (where) {
 500                 case ELEVATOR_INSERT_BACK:
 501                         while (cfq_dispatch_requests(q, cfqd))
 502                                 ;
 503                         list_add_tail(&rq->queuelist, cfqd->dispatch);
 504                         break;
 505                 case ELEVATOR_INSERT_FRONT:
 506                         list_add(&rq->queuelist, cfqd->dispatch);
 507                         break;
 508                 case ELEVATOR_INSERT_SORT:
 509                         BUG_ON(!blk_fs_request(rq));
 510                         cfq_enqueue(cfqd, crq);
 511                         break;
 512                 default:
 513                         printk("%s: bad insert point %d\n", __FUNCTION__,where);
 514                         return;
 515         }
 516
 517         if (rq_mergeable(rq)) {
 518                 cfq_add_crq_hash(cfqd, crq);
 519
 520                 if (!q->last_merge)
 521                         q->last_merge = rq;
 522         }
 523 }
 524
 525 static int cfq_queue_empty(request_queue_t *q)
 526 {
 527         struct cfq_data *cfqd = q->elevator.elevator_data;
 528
 529         if (list_empty(cfqd->dispatch) && list_empty(&cfqd->rr_list))
 530                 return 1;
 531
 532         return 0;
 533 }
 534
 535 static struct request *
 536 cfq_former_request(request_queue_t *q, struct request *rq)
 537 {
 538         struct cfq_rq *crq = RQ_DATA(rq);
 539         struct rb_node *rbprev = rb_prev(&crq->rb_node);
 540
 541         if (rbprev)
 542                 return rb_entry_crq(rbprev)->request;
 543
 544         return NULL;
 545 }
 546
 547 static struct request *
 548 cfq_latter_request(request_queue_t *q, struct request *rq)
 549 {
 550         struct cfq_rq *crq = RQ_DATA(rq);
 551         struct rb_node *rbnext = rb_next(&crq->rb_node);
 552
 553         if (rbnext)
 554                 return rb_entry_crq(rbnext)->request;
 555
 556         return NULL;
 557 }
 558
 559 static int cfq_may_queue(request_queue_t *q, int rw)
 560 {
 561         struct cfq_data *cfqd = q->elevator.elevator_data;
 562         struct cfq_queue *cfqq;
 563         int ret = 1;
 564
 565         if (!cfqd->busy_queues)
 566                 goto out;
 567
 568         cfqq = cfq_find_cfq_hash(cfqd, current->tgid);
 569         if (cfqq) {
 570                 int limit = (q->nr_requests - cfqd->cfq_queued) / cfqd->busy_queues;
 571
 572                 if (limit < 3)
 573                         limit = 3;
 574                 else if (limit > cfqd->max_queued)
 575                         limit = cfqd->max_queued;
 576
 577                 if (cfqq->queued[rw] > limit)
 578                         ret = 0;
 579         }
 580 out:
 581         return ret;
 582 }
 583
 584 static void cfq_put_request(request_queue_t *q, struct request *rq)
 585 {
 586         struct cfq_data *cfqd = q->elevator.elevator_data;
 587         struct cfq_rq *crq = RQ_DATA(rq);
 588         struct request_list *rl;
 589         int other_rw;
 590
 591         if (crq) {
 592                 BUG_ON(q->last_merge == rq);
 593                 BUG_ON(ON_MHASH(crq));
 594
 595                 mempool_free(crq, cfqd->crq_pool);
 596                 rq->elevator_private = NULL;
 597         }
 598
 599         /*
 600          * work-around for may_queue "bug": if a read gets issued and refused
 601          * to queue because writes ate all the allowed slots and no other
 602          * reads are pending for this queue, it could get stuck infinitely
 603          * since freed_request() only checks the waitqueue for writes when
 604          * freeing them. or vice versa for a single write vs many reads.
 605          * so check here whether "the other" data direction might be able
 606          * to queue and wake them
 607          */
 608         rl = &q->rq;
 609         other_rw = rq_data_dir(rq) ^ 1;
 610         if (rl->count[other_rw] <= q->nr_requests) {
 611                 smp_mb();
 612                 if (waitqueue_active(&rl->wait[other_rw]))
 613                         wake_up(&rl->wait[other_rw]);
 614         }
 615 }
 616
 617 static int cfq_set_request(request_queue_t *q, struct request *rq, int gfp_mask)
 618 {
 619         struct cfq_data *cfqd = q->elevator.elevator_data;
 620         struct cfq_rq *crq = mempool_alloc(cfqd->crq_pool, gfp_mask);
 621
 622         if (crq) {
 623                 RB_CLEAR(&crq->rb_node);
 624                 crq->request = rq;
 625                 crq->cfq_queue = NULL;
 626                 INIT_LIST_HEAD(&crq->hash);
 627                 rq->elevator_private = crq;
 628                 return 0;
 629         }
 630
 631         return 1;
 632 }
 633
 634 static void cfq_exit(request_queue_t *q, elevator_t *e)
 635 {
 636         struct cfq_data *cfqd = e->elevator_data;
 637
 638         e->elevator_data = NULL;
 639         mempool_destroy(cfqd->crq_pool);
 640         kfree(cfqd->crq_hash);
 641         kfree(cfqd->cfq_hash);
 642         kfree(cfqd);
 643 }
 644
 645 static int cfq_init(request_queue_t *q, elevator_t *e)
 646 {
 647         struct cfq_data *cfqd;
 648         int i;
 649
 650         cfqd = kmalloc(sizeof(*cfqd), GFP_KERNEL);
 651         if (!cfqd)
 652                 return -ENOMEM;
 653
 654         memset(cfqd, 0, sizeof(*cfqd));
 655         INIT_LIST_HEAD(&cfqd->rr_list);
 656
 657         cfqd->crq_hash = kmalloc(sizeof(struct list_head) * CFQ_MHASH_ENTRIES, GFP_KERNEL);
 658         if (!cfqd->crq_hash)
 659                 goto out_crqhash;
 660
 661         cfqd->cfq_hash = kmalloc(sizeof(struct list_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL);
 662         if (!cfqd->cfq_hash)
 663                 goto out_cfqhash;
 664
 665         cfqd->crq_pool = mempool_create(BLKDEV_MIN_RQ, mempool_alloc_slab, mempool_free_slab, crq_pool);
 666         if (!cfqd->crq_pool)
 667                 goto out_crqpool;
 668
 669         for (i = 0; i < CFQ_MHASH_ENTRIES; i++)
 670                 INIT_LIST_HEAD(&cfqd->crq_hash[i]);
 671         for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
 672                 INIT_LIST_HEAD(&cfqd->cfq_hash[i]);
 673
 674         cfqd->dispatch = &q->queue_head;
 675         e->elevator_data = cfqd;
 676         cfqd->queue = q;
 677
 678         /*
 679          * just set it to some high value, we want anyone to be able to queue
 680          * some requests. fairness is handled differently
 681          */
 682         cfqd->max_queued = q->nr_requests;
 683         q->nr_requests = 8192;
 684
 685         cfqd->cfq_queued = cfq_queued;
 686         cfqd->cfq_quantum = cfq_quantum;
 687
 688         return 0;
 689 out_crqpool:
 690         kfree(cfqd->cfq_hash);
 691 out_cfqhash:
 692         kfree(cfqd->crq_hash);
 693 out_crqhash:
 694         kfree(cfqd);
 695         return -ENOMEM;
 696 }
 697
 698 static int __init cfq_slab_setup(void)
 699 {
 700         crq_pool = kmem_cache_create("crq_pool", sizeof(struct cfq_rq), 0, 0,
 701                                         NULL, NULL);
 702
 703         if (!crq_pool)
 704                 panic("cfq_iosched: can't init crq pool\n");
 705
 706         cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0,
 707                                         NULL, NULL);
 708
 709         if (!cfq_pool)
 710                 panic("cfq_iosched: can't init cfq pool\n");
 711
 712         cfq_mpool = mempool_create(64, mempool_alloc_slab, mempool_free_slab, cfq_pool);
 713
 714         if (!cfq_mpool)
 715                 panic("cfq_iosched: can't init cfq mpool\n");
 716
 717         return 0;
 718 }
 719
 720 subsys_initcall(cfq_slab_setup);
 721
 722 /*
 723  * sysfs parts below -->
 724  */
 725 struct cfq_fs_entry {
 726         struct attribute attr;
 727         ssize_t (*show)(struct cfq_data *, char *);
 728         ssize_t (*store)(struct cfq_data *, const char *, size_t);
 729 };
 730
 731 static ssize_t
 732 cfq_var_show(unsigned int var, char *page)
 733 {
 734         return sprintf(page, "%d\n", var);
 735 }
 736
 737 static ssize_t
 738 cfq_var_store(unsigned int *var, const char *page, size_t count)
 739 {
 740         char *p = (char *) page;
 741
 742         *var = simple_strtoul(p, &p, 10);
 743         return count;
 744 }
 745
 746 #define SHOW_FUNCTION(__FUNC, __VAR)                                    \
 747 static ssize_t __FUNC(struct cfq_data *cfqd, char *page)                \
 748 {                                                                       \
 749         return cfq_var_show(__VAR, (page));                             \
 750 }
 751 SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum);
 752 SHOW_FUNCTION(cfq_queued_show, cfqd->cfq_queued);
 753 #undef SHOW_FUNCTION
 754
 755 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX)                         \
 756 static ssize_t __FUNC(struct cfq_data *cfqd, const char *page, size_t count)    \
 757 {                                                                       \
 758         int ret = cfq_var_store(__PTR, (page), count);                  \
 759         if (*(__PTR) < (MIN))                                           \
 760                 *(__PTR) = (MIN);                                       \
 761         else if (*(__PTR) > (MAX))                                      \
 762                 *(__PTR) = (MAX);                                       \
 763         return ret;                                                     \
 764 }
 765 STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, INT_MAX);
 766 STORE_FUNCTION(cfq_queued_store, &cfqd->cfq_queued, 1, INT_MAX);
 767 #undef STORE_FUNCTION
 768
 769 static struct cfq_fs_entry cfq_quantum_entry = {
 770         .attr = {.name = "quantum", .mode = S_IRUGO | S_IWUSR },
 771         .show = cfq_quantum_show,
 772         .store = cfq_quantum_store,
 773 };
 774 static struct cfq_fs_entry cfq_queued_entry = {
 775         .attr = {.name = "queued", .mode = S_IRUGO | S_IWUSR },
 776         .show = cfq_queued_show,
 777         .store = cfq_queued_store,
 778 };
 779
 780 static struct attribute *default_attrs[] = {
 781         &cfq_quantum_entry.attr,
 782         &cfq_queued_entry.attr,
 783         NULL,
 784 };
 785
 786 #define to_cfq(atr) container_of((atr), struct cfq_fs_entry, attr)
 787
 788 static ssize_t
 789 cfq_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
 790 {
 791         elevator_t *e = container_of(kobj, elevator_t, kobj);
 792         struct cfq_fs_entry *entry = to_cfq(attr);
 793
 794         if (!entry->show)
 795                 return 0;
 796
 797         return entry->show(e->elevator_data, page);
 798 }
 799
 800 static ssize_t
 801 cfq_attr_store(struct kobject *kobj, struct attribute *attr,
 802                const char *page, size_t length)
 803 {
 804         elevator_t *e = container_of(kobj, elevator_t, kobj);
 805         struct cfq_fs_entry *entry = to_cfq(attr);
 806
 807         if (!entry->store)
 808                 return -EINVAL;
 809
 810         return entry->store(e->elevator_data, page, length);
 811 }
 812
 813 static struct sysfs_ops cfq_sysfs_ops = {
 814         .show   = cfq_attr_show,
 815         .store  = cfq_attr_store,
 816 };
 817
 818 struct kobj_type cfq_ktype = {
 819         .sysfs_ops      = &cfq_sysfs_ops,
 820         .default_attrs  = default_attrs,
 821 };
 822
 823 elevator_t iosched_cfq = {
 824         .elevator_name =                "cfq",
 825         .elevator_ktype =               &cfq_ktype,
 826         .elevator_merge_fn =            cfq_merge,
 827         .elevator_merged_fn =           cfq_merged_request,
 828         .elevator_merge_req_fn =        cfq_merged_requests,
 829         .elevator_next_req_fn =         cfq_next_request,
 830         .elevator_add_req_fn =          cfq_insert_request,
 831         .elevator_remove_req_fn =       cfq_remove_request,
 832         .elevator_queue_empty_fn =      cfq_queue_empty,
 833         .elevator_former_req_fn =       cfq_former_request,
 834         .elevator_latter_req_fn =       cfq_latter_request,
 835         .elevator_set_req_fn =          cfq_set_request,
 836         .elevator_put_req_fn =          cfq_put_request,
 837         .elevator_may_queue_fn =        cfq_may_queue,
 838         .elevator_init_fn =             cfq_init,
 839         .elevator_exit_fn =             cfq_exit,
 840 };
 841
 842 EXPORT_SYMBOL(iosched_cfq);