block/deadline-iosched.c

   1 /*
   2  *  Deadline i/o scheduler.
   3  *
   4  *  Copyright (C) 2002 Jens Axboe <axboe@suse.de>
   5  */
   6 #include <linux/kernel.h>
   7 #include <linux/fs.h>
   8 #include <linux/blkdev.h>
   9 #include <linux/elevator.h>
  10 #include <linux/bio.h>
  11 #include <linux/config.h>
  12 #include <linux/module.h>
  13 #include <linux/slab.h>
  14 #include <linux/init.h>
  15 #include <linux/compiler.h>
  16 #include <linux/hash.h>
  17 #include <linux/rbtree.h>
  18
  19 /*
  20  * See Documentation/block/deadline-iosched.txt
  21  */
  22 static const int read_expire = HZ / 2;  /* max time before a read is submitted. */
  23 static const int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */
  24 static const int writes_starved = 2;    /* max times reads can starve a write */
  25 static const int fifo_batch = 16;       /* # of sequential requests treated as one
  26                                      by the above parameters. For throughput. */
  27
  28 static const int deadline_hash_shift = 5;
  29 #define DL_HASH_BLOCK(sec)      ((sec) >> 3)
  30 #define DL_HASH_FN(sec)         (hash_long(DL_HASH_BLOCK((sec)), deadline_hash_shift))
  31 #define DL_HASH_ENTRIES         (1 << deadline_hash_shift)
  32 #define rq_hash_key(rq)         ((rq)->sector + (rq)->nr_sectors)
  33 #define list_entry_hash(ptr)    list_entry((ptr), struct deadline_rq, hash)
  34 #define ON_HASH(drq)            (drq)->on_hash
  35
  36 struct deadline_data {
  37         /*
  38          * run time data
  39          */
  40
  41         /*
  42          * requests (deadline_rq s) are present on both sort_list and fifo_list
  43          */
  44         struct rb_root sort_list[2];
  45         struct list_head fifo_list[2];
  46
  47         /*
  48          * next in sort order. read, write or both are NULL
  49          */
  50         struct deadline_rq *next_drq[2];
  51         struct list_head *hash;         /* request hash */
  52         unsigned int batching;          /* number of sequential requests made */
  53         sector_t last_sector;           /* head position */
  54         unsigned int starved;           /* times reads have starved writes */
  55
  56         /*
  57          * settings that change how the i/o scheduler behaves
  58          */
  59         int fifo_expire[2];
  60         int fifo_batch;
  61         int writes_starved;
  62         int front_merges;
  63
  64         mempool_t *drq_pool;
  65 };
  66
  67 /*
  68  * pre-request data.
  69  */
  70 struct deadline_rq {
  71         /*
  72          * rbtree index, key is the starting offset
  73          */
  74         struct rb_node rb_node;
  75         sector_t rb_key;
  76
  77         struct request *request;
  78
  79         /*
  80          * request hash, key is the ending offset (for back merge lookup)
  81          */
  82         struct list_head hash;
  83         char on_hash;
  84
  85         /*
  86          * expire fifo
  87          */
  88         struct list_head fifo;
  89         unsigned long expires;
  90 };
  91
  92 static void deadline_move_request(struct deadline_data *dd, struct deadline_rq *drq);
  93
  94 static kmem_cache_t *drq_pool;
  95
  96 #define RQ_DATA(rq)     ((struct deadline_rq *) (rq)->elevator_private)
  97
  98 /*
  99  * the back merge hash support functions
 100  */
 101 static inline void __deadline_del_drq_hash(struct deadline_rq *drq)
 102 {
 103         drq->on_hash = 0;
 104         list_del_init(&drq->hash);
 105 }
 106
 107 static inline void deadline_del_drq_hash(struct deadline_rq *drq)
 108 {
 109         if (ON_HASH(drq))
 110                 __deadline_del_drq_hash(drq);
 111 }
 112
 113 static inline void
 114 deadline_add_drq_hash(struct deadline_data *dd, struct deadline_rq *drq)
 115 {
 116         struct request *rq = drq->request;
 117
 118         BUG_ON(ON_HASH(drq));
 119
 120         drq->on_hash = 1;
 121         list_add(&drq->hash, &dd->hash[DL_HASH_FN(rq_hash_key(rq))]);
 122 }
 123
 124 /*
 125  * move hot entry to front of chain
 126  */
 127 static inline void
 128 deadline_hot_drq_hash(struct deadline_data *dd, struct deadline_rq *drq)
 129 {
 130         struct request *rq = drq->request;
 131         struct list_head *head = &dd->hash[DL_HASH_FN(rq_hash_key(rq))];
 132
 133         if (ON_HASH(drq) && drq->hash.prev != head) {
 134                 list_del(&drq->hash);
 135                 list_add(&drq->hash, head);
 136         }
 137 }
 138
 139 static struct request *
 140 deadline_find_drq_hash(struct deadline_data *dd, sector_t offset)
 141 {
 142         struct list_head *hash_list = &dd->hash[DL_HASH_FN(offset)];
 143         struct list_head *entry, *next = hash_list->next;
 144
 145         while ((entry = next) != hash_list) {
 146                 struct deadline_rq *drq = list_entry_hash(entry);
 147                 struct request *__rq = drq->request;
 148
 149                 next = entry->next;
 150
 151                 BUG_ON(!ON_HASH(drq));
 152
 153                 if (!rq_mergeable(__rq)) {
 154                         __deadline_del_drq_hash(drq);
 155                         continue;
 156                 }
 157
 158                 if (rq_hash_key(__rq) == offset)
 159                         return __rq;
 160         }
 161
 162         return NULL;
 163 }
 164
 165 /*
 166  * rb tree support functions
 167  */
 168 #define RB_NONE         (2)
 169 #define RB_EMPTY(root)  ((root)->rb_node == NULL)
 170 #define ON_RB(node)     ((node)->rb_color != RB_NONE)
 171 #define RB_CLEAR(node)  ((node)->rb_color = RB_NONE)
 172 #define rb_entry_drq(node)      rb_entry((node), struct deadline_rq, rb_node)
 173 #define DRQ_RB_ROOT(dd, drq)    (&(dd)->sort_list[rq_data_dir((drq)->request)])
 174 #define rq_rb_key(rq)           (rq)->sector
 175
 176 static struct deadline_rq *
 177 __deadline_add_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
 178 {
 179         struct rb_node **p = &DRQ_RB_ROOT(dd, drq)->rb_node;
 180         struct rb_node *parent = NULL;
 181         struct deadline_rq *__drq;
 182
 183         while (*p) {
 184                 parent = *p;
 185                 __drq = rb_entry_drq(parent);
 186
 187                 if (drq->rb_key < __drq->rb_key)
 188                         p = &(*p)->rb_left;
 189                 else if (drq->rb_key > __drq->rb_key)
 190                         p = &(*p)->rb_right;
 191                 else
 192                         return __drq;
 193         }
 194
 195         rb_link_node(&drq->rb_node, parent, p);
 196         return NULL;
 197 }
 198
 199 static void
 200 deadline_add_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
 201 {
 202         struct deadline_rq *__alias;
 203
 204         drq->rb_key = rq_rb_key(drq->request);
 205
 206 retry:
 207         __alias = __deadline_add_drq_rb(dd, drq);
 208         if (!__alias) {
 209                 rb_insert_color(&drq->rb_node, DRQ_RB_ROOT(dd, drq));
 210                 return;
 211         }
 212
 213         deadline_move_request(dd, __alias);
 214         goto retry;
 215 }
 216
 217 static inline void
 218 deadline_del_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
 219 {
 220         const int data_dir = rq_data_dir(drq->request);
 221
 222         if (dd->next_drq[data_dir] == drq) {
 223                 struct rb_node *rbnext = rb_next(&drq->rb_node);
 224
 225                 dd->next_drq[data_dir] = NULL;
 226                 if (rbnext)
 227                         dd->next_drq[data_dir] = rb_entry_drq(rbnext);
 228         }
 229
 230         BUG_ON(!ON_RB(&drq->rb_node));
 231         rb_erase(&drq->rb_node, DRQ_RB_ROOT(dd, drq));
 232         RB_CLEAR(&drq->rb_node);
 233 }
 234
 235 static struct request *
 236 deadline_find_drq_rb(struct deadline_data *dd, sector_t sector, int data_dir)
 237 {
 238         struct rb_node *n = dd->sort_list[data_dir].rb_node;
 239         struct deadline_rq *drq;
 240
 241         while (n) {
 242                 drq = rb_entry_drq(n);
 243
 244                 if (sector < drq->rb_key)
 245                         n = n->rb_left;
 246                 else if (sector > drq->rb_key)
 247                         n = n->rb_right;
 248                 else
 249                         return drq->request;
 250         }
 251
 252         return NULL;
 253 }
 254
 255 /*
 256  * deadline_find_first_drq finds the first (lowest sector numbered) request
 257  * for the specified data_dir. Used to sweep back to the start of the disk
 258  * (1-way elevator) after we process the last (highest sector) request.
 259  */
 260 static struct deadline_rq *
 261 deadline_find_first_drq(struct deadline_data *dd, int data_dir)
 262 {
 263         struct rb_node *n = dd->sort_list[data_dir].rb_node;
 264
 265         for (;;) {
 266                 if (n->rb_left == NULL)
 267                         return rb_entry_drq(n);
 268
 269                 n = n->rb_left;
 270         }
 271 }
 272
 273 /*
 274  * add drq to rbtree and fifo
 275  */
 276 static void
 277 deadline_add_request(struct request_queue *q, struct request *rq)
 278 {
 279         struct deadline_data *dd = q->elevator->elevator_data;
 280         struct deadline_rq *drq = RQ_DATA(rq);
 281
 282         const int data_dir = rq_data_dir(drq->request);
 283
 284         deadline_add_drq_rb(dd, drq);
 285         /*
 286          * set expire time (only used for reads) and add to fifo list
 287          */
 288         drq->expires = jiffies + dd->fifo_expire[data_dir];
 289         list_add_tail(&drq->fifo, &dd->fifo_list[data_dir]);
 290
 291         if (rq_mergeable(rq))
 292                 deadline_add_drq_hash(dd, drq);
 293 }
 294
 295 /*
 296  * remove rq from rbtree, fifo, and hash
 297  */
 298 static void deadline_remove_request(request_queue_t *q, struct request *rq)
 299 {
 300         struct deadline_rq *drq = RQ_DATA(rq);
 301         struct deadline_data *dd = q->elevator->elevator_data;
 302
 303         list_del_init(&drq->fifo);
 304         deadline_del_drq_rb(dd, drq);
 305         deadline_del_drq_hash(drq);
 306 }
 307
 308 static int
 309 deadline_merge(request_queue_t *q, struct request **req, struct bio *bio)
 310 {
 311         struct deadline_data *dd = q->elevator->elevator_data;
 312         struct request *__rq;
 313         int ret;
 314
 315         /*
 316          * see if the merge hash can satisfy a back merge
 317          */
 318         __rq = deadline_find_drq_hash(dd, bio->bi_sector);
 319         if (__rq) {
 320                 BUG_ON(__rq->sector + __rq->nr_sectors != bio->bi_sector);
 321
 322                 if (elv_rq_merge_ok(__rq, bio)) {
 323                         ret = ELEVATOR_BACK_MERGE;
 324                         goto out;
 325                 }
 326         }
 327
 328         /*
 329          * check for front merge
 330          */
 331         if (dd->front_merges) {
 332                 sector_t rb_key = bio->bi_sector + bio_sectors(bio);
 333
 334                 __rq = deadline_find_drq_rb(dd, rb_key, bio_data_dir(bio));
 335                 if (__rq) {
 336                         BUG_ON(rb_key != rq_rb_key(__rq));
 337
 338                         if (elv_rq_merge_ok(__rq, bio)) {
 339                                 ret = ELEVATOR_FRONT_MERGE;
 340                                 goto out;
 341                         }
 342                 }
 343         }
 344
 345         return ELEVATOR_NO_MERGE;
 346 out:
 347         if (ret)
 348                 deadline_hot_drq_hash(dd, RQ_DATA(__rq));
 349         *req = __rq;
 350         return ret;
 351 }
 352
 353 static void deadline_merged_request(request_queue_t *q, struct request *req)
 354 {
 355         struct deadline_data *dd = q->elevator->elevator_data;
 356         struct deadline_rq *drq = RQ_DATA(req);
 357
 358         /*
 359          * hash always needs to be repositioned, key is end sector
 360          */
 361         deadline_del_drq_hash(drq);
 362         deadline_add_drq_hash(dd, drq);
 363
 364         /*
 365          * if the merge was a front merge, we need to reposition request
 366          */
 367         if (rq_rb_key(req) != drq->rb_key) {
 368                 deadline_del_drq_rb(dd, drq);
 369                 deadline_add_drq_rb(dd, drq);
 370         }
 371 }
 372
 373 static void
 374 deadline_merged_requests(request_queue_t *q, struct request *req,
 375                          struct request *next)
 376 {
 377         struct deadline_data *dd = q->elevator->elevator_data;
 378         struct deadline_rq *drq = RQ_DATA(req);
 379         struct deadline_rq *dnext = RQ_DATA(next);
 380
 381         BUG_ON(!drq);
 382         BUG_ON(!dnext);
 383
 384         /*
 385          * reposition drq (this is the merged request) in hash, and in rbtree
 386          * in case of a front merge
 387          */
 388         deadline_del_drq_hash(drq);
 389         deadline_add_drq_hash(dd, drq);
 390
 391         if (rq_rb_key(req) != drq->rb_key) {
 392                 deadline_del_drq_rb(dd, drq);
 393                 deadline_add_drq_rb(dd, drq);
 394         }
 395
 396         /*
 397          * if dnext expires before drq, assign its expire time to drq
 398          * and move into dnext position (dnext will be deleted) in fifo
 399          */
 400         if (!list_empty(&drq->fifo) && !list_empty(&dnext->fifo)) {
 401                 if (time_before(dnext->expires, drq->expires)) {
 402                         list_move(&drq->fifo, &dnext->fifo);
 403                         drq->expires = dnext->expires;
 404                 }
 405         }
 406
 407         /*
 408          * kill knowledge of next, this one is a goner
 409          */
 410         deadline_remove_request(q, next);
 411 }
 412
 413 /*
 414  * move request from sort list to dispatch queue.
 415  */
 416 static inline void
 417 deadline_move_to_dispatch(struct deadline_data *dd, struct deadline_rq *drq)
 418 {
 419         request_queue_t *q = drq->request->q;
 420
 421         deadline_remove_request(q, drq->request);
 422         elv_dispatch_add_tail(q, drq->request);
 423 }
 424
 425 /*
 426  * move an entry to dispatch queue
 427  */
 428 static void
 429 deadline_move_request(struct deadline_data *dd, struct deadline_rq *drq)
 430 {
 431         const int data_dir = rq_data_dir(drq->request);
 432         struct rb_node *rbnext = rb_next(&drq->rb_node);
 433
 434         dd->next_drq[READ] = NULL;
 435         dd->next_drq[WRITE] = NULL;
 436
 437         if (rbnext)
 438                 dd->next_drq[data_dir] = rb_entry_drq(rbnext);
 439
 440         dd->last_sector = drq->request->sector + drq->request->nr_sectors;
 441
 442         /*
 443          * take it off the sort and fifo list, move
 444          * to dispatch queue
 445          */
 446         deadline_move_to_dispatch(dd, drq);
 447 }
 448
 449 #define list_entry_fifo(ptr)    list_entry((ptr), struct deadline_rq, fifo)
 450
 451 /*
 452  * deadline_check_fifo returns 0 if there are no expired reads on the fifo,
 453  * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
 454  */
 455 static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
 456 {
 457         struct deadline_rq *drq = list_entry_fifo(dd->fifo_list[ddir].next);
 458
 459         /*
 460          * drq is expired!
 461          */
 462         if (time_after(jiffies, drq->expires))
 463                 return 1;
 464
 465         return 0;
 466 }
 467
 468 /*
 469  * deadline_dispatch_requests selects the best request according to
 470  * read/write expire, fifo_batch, etc
 471  */
 472 static int deadline_dispatch_requests(request_queue_t *q, int force)
 473 {
 474         struct deadline_data *dd = q->elevator->elevator_data;
 475         const int reads = !list_empty(&dd->fifo_list[READ]);
 476         const int writes = !list_empty(&dd->fifo_list[WRITE]);
 477         struct deadline_rq *drq;
 478         int data_dir;
 479
 480         /*
 481          * batches are currently reads XOR writes
 482          */
 483         if (dd->next_drq[WRITE])
 484                 drq = dd->next_drq[WRITE];
 485         else
 486                 drq = dd->next_drq[READ];
 487
 488         if (drq) {
 489                 /* we have a "next request" */
 490
 491                 if (dd->last_sector != drq->request->sector)
 492                         /* end the batch on a non sequential request */
 493                         dd->batching += dd->fifo_batch;
 494
 495                 if (dd->batching < dd->fifo_batch)
 496                         /* we are still entitled to batch */
 497                         goto dispatch_request;
 498         }
 499
 500         /*
 501          * at this point we are not running a batch. select the appropriate
 502          * data direction (read / write)
 503          */
 504
 505         if (reads) {
 506                 BUG_ON(RB_EMPTY(&dd->sort_list[READ]));
 507
 508                 if (writes && (dd->starved++ >= dd->writes_starved))
 509                         goto dispatch_writes;
 510
 511                 data_dir = READ;
 512
 513                 goto dispatch_find_request;
 514         }
 515
 516         /*
 517          * there are either no reads or writes have been starved
 518          */
 519
 520         if (writes) {
 521 dispatch_writes:
 522                 BUG_ON(RB_EMPTY(&dd->sort_list[WRITE]));
 523
 524                 dd->starved = 0;
 525
 526                 data_dir = WRITE;
 527
 528                 goto dispatch_find_request;
 529         }
 530
 531         return 0;
 532
 533 dispatch_find_request:
 534         /*
 535          * we are not running a batch, find best request for selected data_dir
 536          */
 537         if (deadline_check_fifo(dd, data_dir)) {
 538                 /* An expired request exists - satisfy it */
 539                 dd->batching = 0;
 540                 drq = list_entry_fifo(dd->fifo_list[data_dir].next);
 541
 542         } else if (dd->next_drq[data_dir]) {
 543                 /*
 544                  * The last req was the same dir and we have a next request in
 545                  * sort order. No expired requests so continue on from here.
 546                  */
 547                 drq = dd->next_drq[data_dir];
 548         } else {
 549                 /*
 550                  * The last req was the other direction or we have run out of
 551                  * higher-sectored requests. Go back to the lowest sectored
 552                  * request (1 way elevator) and start a new batch.
 553                  */
 554                 dd->batching = 0;
 555                 drq = deadline_find_first_drq(dd, data_dir);
 556         }
 557
 558 dispatch_request:
 559         /*
 560          * drq is the selected appropriate request.
 561          */
 562         dd->batching++;
 563         deadline_move_request(dd, drq);
 564
 565         return 1;
 566 }
 567
 568 static int deadline_queue_empty(request_queue_t *q)
 569 {
 570         struct deadline_data *dd = q->elevator->elevator_data;
 571
 572         return list_empty(&dd->fifo_list[WRITE])
 573                 && list_empty(&dd->fifo_list[READ]);
 574 }
 575
 576 static struct request *
 577 deadline_former_request(request_queue_t *q, struct request *rq)
 578 {
 579         struct deadline_rq *drq = RQ_DATA(rq);
 580         struct rb_node *rbprev = rb_prev(&drq->rb_node);
 581
 582         if (rbprev)
 583                 return rb_entry_drq(rbprev)->request;
 584
 585         return NULL;
 586 }
 587
 588 static struct request *
 589 deadline_latter_request(request_queue_t *q, struct request *rq)
 590 {
 591         struct deadline_rq *drq = RQ_DATA(rq);
 592         struct rb_node *rbnext = rb_next(&drq->rb_node);
 593
 594         if (rbnext)
 595                 return rb_entry_drq(rbnext)->request;
 596
 597         return NULL;
 598 }
 599
 600 static void deadline_exit_queue(elevator_t *e)
 601 {
 602         struct deadline_data *dd = e->elevator_data;
 603
 604         BUG_ON(!list_empty(&dd->fifo_list[READ]));
 605         BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
 606
 607         mempool_destroy(dd->drq_pool);
 608         kfree(dd->hash);
 609         kfree(dd);
 610 }
 611
 612 /*
 613  * initialize elevator private data (deadline_data), and alloc a drq for
 614  * each request on the free lists
 615  */
 616 static void *deadline_init_queue(request_queue_t *q, elevator_t *e)
 617 {
 618         struct deadline_data *dd;
 619         int i;
 620
 621         if (!drq_pool)
 622                 return NULL;
 623
 624         dd = kmalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
 625         if (!dd)
 626                 return NULL;
 627         memset(dd, 0, sizeof(*dd));
 628
 629         dd->hash = kmalloc_node(sizeof(struct list_head)*DL_HASH_ENTRIES,
 630                                 GFP_KERNEL, q->node);
 631         if (!dd->hash) {
 632                 kfree(dd);
 633                 return NULL;
 634         }
 635
 636         dd->drq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
 637                                         mempool_free_slab, drq_pool, q->node);
 638         if (!dd->drq_pool) {
 639                 kfree(dd->hash);
 640                 kfree(dd);
 641                 return NULL;
 642         }
 643
 644         for (i = 0; i < DL_HASH_ENTRIES; i++)
 645                 INIT_LIST_HEAD(&dd->hash[i]);
 646
 647         INIT_LIST_HEAD(&dd->fifo_list[READ]);
 648         INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
 649         dd->sort_list[READ] = RB_ROOT;
 650         dd->sort_list[WRITE] = RB_ROOT;
 651         dd->fifo_expire[READ] = read_expire;
 652         dd->fifo_expire[WRITE] = write_expire;
 653         dd->writes_starved = writes_starved;
 654         dd->front_merges = 1;
 655         dd->fifo_batch = fifo_batch;
 656         return dd;
 657 }
 658
 659 static void deadline_put_request(request_queue_t *q, struct request *rq)
 660 {
 661         struct deadline_data *dd = q->elevator->elevator_data;
 662         struct deadline_rq *drq = RQ_DATA(rq);
 663
 664         mempool_free(drq, dd->drq_pool);
 665         rq->elevator_private = NULL;
 666 }
 667
 668 static int
 669 deadline_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
 670                      gfp_t gfp_mask)
 671 {
 672         struct deadline_data *dd = q->elevator->elevator_data;
 673         struct deadline_rq *drq;
 674
 675         drq = mempool_alloc(dd->drq_pool, gfp_mask);
 676         if (drq) {
 677                 memset(drq, 0, sizeof(*drq));
 678                 RB_CLEAR(&drq->rb_node);
 679                 drq->request = rq;
 680
 681                 INIT_LIST_HEAD(&drq->hash);
 682                 drq->on_hash = 0;
 683
 684                 INIT_LIST_HEAD(&drq->fifo);
 685
 686                 rq->elevator_private = drq;
 687                 return 0;
 688         }
 689
 690         return 1;
 691 }
 692
 693 /*
 694  * sysfs parts below
 695  */
 696
 697 static ssize_t
 698 deadline_var_show(int var, char *page)
 699 {
 700         return sprintf(page, "%d\n", var);
 701 }
 702
 703 static ssize_t
 704 deadline_var_store(int *var, const char *page, size_t count)
 705 {
 706         char *p = (char *) page;
 707
 708         *var = simple_strtol(p, &p, 10);
 709         return count;
 710 }
 711
 712 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
 713 static ssize_t __FUNC(elevator_t *e, char *page)                        \
 714 {                                                                       \
 715         struct deadline_data *dd = e->elevator_data;                    \
 716         int __data = __VAR;                                             \
 717         if (__CONV)                                                     \
 718                 __data = jiffies_to_msecs(__data);                      \
 719         return deadline_var_show(__data, (page));                       \
 720 }
 721 SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
 722 SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
 723 SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
 724 SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
 725 SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
 726 #undef SHOW_FUNCTION
 727
 728 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
 729 static ssize_t __FUNC(elevator_t *e, const char *page, size_t count)    \
 730 {                                                                       \
 731         struct deadline_data *dd = e->elevator_data;                    \
 732         int __data;                                                     \
 733         int ret = deadline_var_store(&__data, (page), count);           \
 734         if (__data < (MIN))                                             \
 735                 __data = (MIN);                                         \
 736         else if (__data > (MAX))                                        \
 737                 __data = (MAX);                                         \
 738         if (__CONV)                                                     \
 739                 *(__PTR) = msecs_to_jiffies(__data);                    \
 740         else                                                            \
 741                 *(__PTR) = __data;                                      \
 742         return ret;                                                     \
 743 }
 744 STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
 745 STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
 746 STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
 747 STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
 748 STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
 749 #undef STORE_FUNCTION
 750
 751 #define DD_ATTR(name) \
 752         __ATTR(name, S_IRUGO|S_IWUSR, deadline_##name##_show, \
 753                                       deadline_##name##_store)
 754
 755 static struct elv_fs_entry deadline_attrs[] = {
 756         DD_ATTR(read_expire),
 757         DD_ATTR(write_expire),
 758         DD_ATTR(writes_starved),
 759         DD_ATTR(front_merges),
 760         DD_ATTR(fifo_batch),
 761         __ATTR_NULL
 762 };
 763
 764 static struct elevator_type iosched_deadline = {
 765         .ops = {
 766                 .elevator_merge_fn =            deadline_merge,
 767                 .elevator_merged_fn =           deadline_merged_request,
 768                 .elevator_merge_req_fn =        deadline_merged_requests,
 769                 .elevator_dispatch_fn =         deadline_dispatch_requests,
 770                 .elevator_add_req_fn =          deadline_add_request,
 771                 .elevator_queue_empty_fn =      deadline_queue_empty,
 772                 .elevator_former_req_fn =       deadline_former_request,
 773                 .elevator_latter_req_fn =       deadline_latter_request,
 774                 .elevator_set_req_fn =          deadline_set_request,
 775                 .elevator_put_req_fn =          deadline_put_request,
 776                 .elevator_init_fn =             deadline_init_queue,
 777                 .elevator_exit_fn =             deadline_exit_queue,
 778         },
 779
 780         .elevator_attrs = deadline_attrs,
 781         .elevator_name = "deadline",
 782         .elevator_owner = THIS_MODULE,
 783 };
 784
 785 static int __init deadline_init(void)
 786 {
 787         int ret;
 788
 789         drq_pool = kmem_cache_create("deadline_drq", sizeof(struct deadline_rq),
 790                                      0, 0, NULL, NULL);
 791
 792         if (!drq_pool)
 793                 return -ENOMEM;
 794
 795         ret = elv_register(&iosched_deadline);
 796         if (ret)
 797                 kmem_cache_destroy(drq_pool);
 798
 799         return ret;
 800 }
 801
 802 static void __exit deadline_exit(void)
 803 {
 804         kmem_cache_destroy(drq_pool);
 805         elv_unregister(&iosched_deadline);
 806 }
 807
 808 module_init(deadline_init);
 809 module_exit(deadline_exit);
 810
 811 MODULE_AUTHOR("Jens Axboe");
 812 MODULE_LICENSE("GPL");
 813 MODULE_DESCRIPTION("deadline IO scheduler");