block/mq-deadline.c

   1 /*
   2  *  MQ Deadline i/o scheduler - adaptation of the legacy deadline scheduler,
   3  *  for the blk-mq scheduling framework
   4  *
   5  *  Copyright (C) 2016 Jens Axboe <axboe@kernel.dk>
   6  */
   7 #include <linux/kernel.h>
   8 #include <linux/fs.h>
   9 #include <linux/blkdev.h>
  10 #include <linux/blk-mq.h>
  11 #include <linux/elevator.h>
  12 #include <linux/bio.h>
  13 #include <linux/module.h>
  14 #include <linux/slab.h>
  15 #include <linux/init.h>
  16 #include <linux/compiler.h>
  17 #include <linux/rbtree.h>
  18 #include <linux/sbitmap.h>
  19
  20 #include "blk.h"
  21 #include "blk-mq.h"
  22 #include "blk-mq-debugfs.h"
  23 #include "blk-mq-tag.h"
  24 #include "blk-mq-sched.h"
  25
  26 /*
  27  * See Documentation/block/deadline-iosched.txt
  28  */
  29 static const int read_expire = HZ / 2;  /* max time before a read is submitted. */
  30 static const int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */
  31 static const int writes_starved = 2;    /* max times reads can starve a write */
  32 static const int fifo_batch = 16;       /* # of sequential requests treated as one
  33                                      by the above parameters. For throughput. */
  34
  35 struct deadline_data {
  36         /*
  37          * run time data
  38          */
  39
  40         /*
  41          * requests (deadline_rq s) are present on both sort_list and fifo_list
  42          */
  43         struct rb_root sort_list[2];
  44         struct list_head fifo_list[2];
  45
  46         /*
  47          * next in sort order. read, write or both are NULL
  48          */
  49         struct request *next_rq[2];
  50         unsigned int batching;          /* number of sequential requests made */
  51         unsigned int starved;           /* times reads have starved writes */
  52
  53         /*
  54          * settings that change how the i/o scheduler behaves
  55          */
  56         int fifo_expire[2];
  57         int fifo_batch;
  58         int writes_starved;
  59         int front_merges;
  60
  61         spinlock_t lock;
  62         struct list_head dispatch;
  63 };
  64
  65 static inline struct rb_root *
  66 deadline_rb_root(struct deadline_data *dd, struct request *rq)
  67 {
  68         return &dd->sort_list[rq_data_dir(rq)];
  69 }
  70
  71 /*
  72  * get the request after `rq' in sector-sorted order
  73  */
  74 static inline struct request *
  75 deadline_latter_request(struct request *rq)
  76 {
  77         struct rb_node *node = rb_next(&rq->rb_node);
  78
  79         if (node)
  80                 return rb_entry_rq(node);
  81
  82         return NULL;
  83 }
  84
  85 static void
  86 deadline_add_rq_rb(struct deadline_data *dd, struct request *rq)
  87 {
  88         struct rb_root *root = deadline_rb_root(dd, rq);
  89
  90         elv_rb_add(root, rq);
  91 }
  92
  93 static inline void
  94 deadline_del_rq_rb(struct deadline_data *dd, struct request *rq)
  95 {
  96         const int data_dir = rq_data_dir(rq);
  97
  98         if (dd->next_rq[data_dir] == rq)
  99                 dd->next_rq[data_dir] = deadline_latter_request(rq);
 100
 101         elv_rb_del(deadline_rb_root(dd, rq), rq);
 102 }
 103
 104 /*
 105  * remove rq from rbtree and fifo.
 106  */
 107 static void deadline_remove_request(struct request_queue *q, struct request *rq)
 108 {
 109         struct deadline_data *dd = q->elevator->elevator_data;
 110
 111         list_del_init(&rq->queuelist);
 112
 113         /*
 114          * We might not be on the rbtree, if we are doing an insert merge
 115          */
 116         if (!RB_EMPTY_NODE(&rq->rb_node))
 117                 deadline_del_rq_rb(dd, rq);
 118
 119         elv_rqhash_del(q, rq);
 120         if (q->last_merge == rq)
 121                 q->last_merge = NULL;
 122 }
 123
 124 static void dd_request_merged(struct request_queue *q, struct request *req,
 125                               enum elv_merge type)
 126 {
 127         struct deadline_data *dd = q->elevator->elevator_data;
 128
 129         /*
 130          * if the merge was a front merge, we need to reposition request
 131          */
 132         if (type == ELEVATOR_FRONT_MERGE) {
 133                 elv_rb_del(deadline_rb_root(dd, req), req);
 134                 deadline_add_rq_rb(dd, req);
 135         }
 136 }
 137
 138 static void dd_merged_requests(struct request_queue *q, struct request *req,
 139                                struct request *next)
 140 {
 141         /*
 142          * if next expires before rq, assign its expire time to rq
 143          * and move into next position (next will be deleted) in fifo
 144          */
 145         if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
 146                 if (time_before((unsigned long)next->fifo_time,
 147                                 (unsigned long)req->fifo_time)) {
 148                         list_move(&req->queuelist, &next->queuelist);
 149                         req->fifo_time = next->fifo_time;
 150                 }
 151         }
 152
 153         /*
 154          * kill knowledge of next, this one is a goner
 155          */
 156         deadline_remove_request(q, next);
 157 }
 158
 159 /*
 160  * move an entry to dispatch queue
 161  */
 162 static void
 163 deadline_move_request(struct deadline_data *dd, struct request *rq)
 164 {
 165         const int data_dir = rq_data_dir(rq);
 166
 167         dd->next_rq[READ] = NULL;
 168         dd->next_rq[WRITE] = NULL;
 169         dd->next_rq[data_dir] = deadline_latter_request(rq);
 170
 171         /*
 172          * take it off the sort and fifo list
 173          */
 174         deadline_remove_request(rq->q, rq);
 175 }
 176
 177 /*
 178  * deadline_check_fifo returns 0 if there are no expired requests on the fifo,
 179  * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
 180  */
 181 static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
 182 {
 183         struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
 184
 185         /*
 186          * rq is expired!
 187          */
 188         if (time_after_eq(jiffies, (unsigned long)rq->fifo_time))
 189                 return 1;
 190
 191         return 0;
 192 }
 193
 194 /*
 195  * deadline_dispatch_requests selects the best request according to
 196  * read/write expire, fifo_batch, etc
 197  */
 198 static struct request *__dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
 199 {
 200         struct deadline_data *dd = hctx->queue->elevator->elevator_data;
 201         struct request *rq;
 202         bool reads, writes;
 203         int data_dir;
 204
 205         if (!list_empty(&dd->dispatch)) {
 206                 rq = list_first_entry(&dd->dispatch, struct request, queuelist);
 207                 list_del_init(&rq->queuelist);
 208                 goto done;
 209         }
 210
 211         reads = !list_empty(&dd->fifo_list[READ]);
 212         writes = !list_empty(&dd->fifo_list[WRITE]);
 213
 214         /*
 215          * batches are currently reads XOR writes
 216          */
 217         if (dd->next_rq[WRITE])
 218                 rq = dd->next_rq[WRITE];
 219         else
 220                 rq = dd->next_rq[READ];
 221
 222         if (rq && dd->batching < dd->fifo_batch)
 223                 /* we have a next request are still entitled to batch */
 224                 goto dispatch_request;
 225
 226         /*
 227          * at this point we are not running a batch. select the appropriate
 228          * data direction (read / write)
 229          */
 230
 231         if (reads) {
 232                 BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
 233
 234                 if (writes && (dd->starved++ >= dd->writes_starved))
 235                         goto dispatch_writes;
 236
 237                 data_dir = READ;
 238
 239                 goto dispatch_find_request;
 240         }
 241
 242         /*
 243          * there are either no reads or writes have been starved
 244          */
 245
 246         if (writes) {
 247 dispatch_writes:
 248                 BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
 249
 250                 dd->starved = 0;
 251
 252                 data_dir = WRITE;
 253
 254                 goto dispatch_find_request;
 255         }
 256
 257         return NULL;
 258
 259 dispatch_find_request:
 260         /*
 261          * we are not running a batch, find best request for selected data_dir
 262          */
 263         if (deadline_check_fifo(dd, data_dir) || !dd->next_rq[data_dir]) {
 264                 /*
 265                  * A deadline has expired, the last request was in the other
 266                  * direction, or we have run out of higher-sectored requests.
 267                  * Start again from the request with the earliest expiry time.
 268                  */
 269                 rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
 270         } else {
 271                 /*
 272                  * The last req was the same dir and we have a next request in
 273                  * sort order. No expired requests so continue on from here.
 274                  */
 275                 rq = dd->next_rq[data_dir];
 276         }
 277
 278         dd->batching = 0;
 279
 280 dispatch_request:
 281         /*
 282          * rq is the selected appropriate request.
 283          */
 284         dd->batching++;
 285         deadline_move_request(dd, rq);
 286 done:
 287         rq->rq_flags |= RQF_STARTED;
 288         return rq;
 289 }
 290
 291 static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
 292 {
 293         struct deadline_data *dd = hctx->queue->elevator->elevator_data;
 294         struct request *rq;
 295
 296         spin_lock(&dd->lock);
 297         rq = __dd_dispatch_request(hctx);
 298         spin_unlock(&dd->lock);
 299
 300         return rq;
 301 }
 302
 303 static void dd_exit_queue(struct elevator_queue *e)
 304 {
 305         struct deadline_data *dd = e->elevator_data;
 306
 307         BUG_ON(!list_empty(&dd->fifo_list[READ]));
 308         BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
 309
 310         kfree(dd);
 311 }
 312
 313 /*
 314  * initialize elevator private data (deadline_data).
 315  */
 316 static int dd_init_queue(struct request_queue *q, struct elevator_type *e)
 317 {
 318         struct deadline_data *dd;
 319         struct elevator_queue *eq;
 320
 321         eq = elevator_alloc(q, e);
 322         if (!eq)
 323                 return -ENOMEM;
 324
 325         dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
 326         if (!dd) {
 327                 kobject_put(&eq->kobj);
 328                 return -ENOMEM;
 329         }
 330         eq->elevator_data = dd;
 331
 332         INIT_LIST_HEAD(&dd->fifo_list[READ]);
 333         INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
 334         dd->sort_list[READ] = RB_ROOT;
 335         dd->sort_list[WRITE] = RB_ROOT;
 336         dd->fifo_expire[READ] = read_expire;
 337         dd->fifo_expire[WRITE] = write_expire;
 338         dd->writes_starved = writes_starved;
 339         dd->front_merges = 1;
 340         dd->fifo_batch = fifo_batch;
 341         spin_lock_init(&dd->lock);
 342         INIT_LIST_HEAD(&dd->dispatch);
 343
 344         q->elevator = eq;
 345         return 0;
 346 }
 347
 348 static int dd_request_merge(struct request_queue *q, struct request **rq,
 349                             struct bio *bio)
 350 {
 351         struct deadline_data *dd = q->elevator->elevator_data;
 352         sector_t sector = bio_end_sector(bio);
 353         struct request *__rq;
 354
 355         if (!dd->front_merges)
 356                 return ELEVATOR_NO_MERGE;
 357
 358         __rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
 359         if (__rq) {
 360                 BUG_ON(sector != blk_rq_pos(__rq));
 361
 362                 if (elv_bio_merge_ok(__rq, bio)) {
 363                         *rq = __rq;
 364                         return ELEVATOR_FRONT_MERGE;
 365                 }
 366         }
 367
 368         return ELEVATOR_NO_MERGE;
 369 }
 370
 371 static bool dd_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio)
 372 {
 373         struct request_queue *q = hctx->queue;
 374         struct deadline_data *dd = q->elevator->elevator_data;
 375         struct request *free = NULL;
 376         bool ret;
 377
 378         spin_lock(&dd->lock);
 379         ret = blk_mq_sched_try_merge(q, bio, &free);
 380         spin_unlock(&dd->lock);
 381
 382         if (free)
 383                 blk_mq_free_request(free);
 384
 385         return ret;
 386 }
 387
 388 /*
 389  * add rq to rbtree and fifo
 390  */
 391 static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
 392                               bool at_head)
 393 {
 394         struct request_queue *q = hctx->queue;
 395         struct deadline_data *dd = q->elevator->elevator_data;
 396         const int data_dir = rq_data_dir(rq);
 397
 398         if (blk_mq_sched_try_insert_merge(q, rq))
 399                 return;
 400
 401         blk_mq_sched_request_inserted(rq);
 402
 403         if (at_head || blk_rq_is_passthrough(rq)) {
 404                 if (at_head)
 405                         list_add(&rq->queuelist, &dd->dispatch);
 406                 else
 407                         list_add_tail(&rq->queuelist, &dd->dispatch);
 408         } else {
 409                 deadline_add_rq_rb(dd, rq);
 410
 411                 if (rq_mergeable(rq)) {
 412                         elv_rqhash_add(q, rq);
 413                         if (!q->last_merge)
 414                                 q->last_merge = rq;
 415                 }
 416
 417                 /*
 418                  * set expire time and add to fifo list
 419                  */
 420                 rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
 421                 list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
 422         }
 423 }
 424
 425 static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
 426                                struct list_head *list, bool at_head)
 427 {
 428         struct request_queue *q = hctx->queue;
 429         struct deadline_data *dd = q->elevator->elevator_data;
 430
 431         spin_lock(&dd->lock);
 432         while (!list_empty(list)) {
 433                 struct request *rq;
 434
 435                 rq = list_first_entry(list, struct request, queuelist);
 436                 list_del_init(&rq->queuelist);
 437                 dd_insert_request(hctx, rq, at_head);
 438         }
 439         spin_unlock(&dd->lock);
 440 }
 441
 442 static bool dd_has_work(struct blk_mq_hw_ctx *hctx)
 443 {
 444         struct deadline_data *dd = hctx->queue->elevator->elevator_data;
 445
 446         return !list_empty_careful(&dd->dispatch) ||
 447                 !list_empty_careful(&dd->fifo_list[0]) ||
 448                 !list_empty_careful(&dd->fifo_list[1]);
 449 }
 450
 451 /*
 452  * sysfs parts below
 453  */
 454 static ssize_t
 455 deadline_var_show(int var, char *page)
 456 {
 457         return sprintf(page, "%d\n", var);
 458 }
 459
 460 static void
 461 deadline_var_store(int *var, const char *page)
 462 {
 463         char *p = (char *) page;
 464
 465         *var = simple_strtol(p, &p, 10);
 466 }
 467
 468 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV)                            \
 469 static ssize_t __FUNC(struct elevator_queue *e, char *page)             \
 470 {                                                                       \
 471         struct deadline_data *dd = e->elevator_data;                    \
 472         int __data = __VAR;                                             \
 473         if (__CONV)                                                     \
 474                 __data = jiffies_to_msecs(__data);                      \
 475         return deadline_var_show(__data, (page));                       \
 476 }
 477 SHOW_FUNCTION(deadline_read_expire_show, dd->fifo_expire[READ], 1);
 478 SHOW_FUNCTION(deadline_write_expire_show, dd->fifo_expire[WRITE], 1);
 479 SHOW_FUNCTION(deadline_writes_starved_show, dd->writes_starved, 0);
 480 SHOW_FUNCTION(deadline_front_merges_show, dd->front_merges, 0);
 481 SHOW_FUNCTION(deadline_fifo_batch_show, dd->fifo_batch, 0);
 482 #undef SHOW_FUNCTION
 483
 484 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
 485 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
 486 {                                                                       \
 487         struct deadline_data *dd = e->elevator_data;                    \
 488         int __data;                                                     \
 489         deadline_var_store(&__data, (page));                            \
 490         if (__data < (MIN))                                             \
 491                 __data = (MIN);                                         \
 492         else if (__data > (MAX))                                        \
 493                 __data = (MAX);                                         \
 494         if (__CONV)                                                     \
 495                 *(__PTR) = msecs_to_jiffies(__data);                    \
 496         else                                                            \
 497                 *(__PTR) = __data;                                      \
 498         return count;                                                   \
 499 }
 500 STORE_FUNCTION(deadline_read_expire_store, &dd->fifo_expire[READ], 0, INT_MAX, 1);
 501 STORE_FUNCTION(deadline_write_expire_store, &dd->fifo_expire[WRITE], 0, INT_MAX, 1);
 502 STORE_FUNCTION(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX, 0);
 503 STORE_FUNCTION(deadline_front_merges_store, &dd->front_merges, 0, 1, 0);
 504 STORE_FUNCTION(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX, 0);
 505 #undef STORE_FUNCTION
 506
 507 #define DD_ATTR(name) \
 508         __ATTR(name, S_IRUGO|S_IWUSR, deadline_##name##_show, \
 509                                       deadline_##name##_store)
 510
 511 static struct elv_fs_entry deadline_attrs[] = {
 512         DD_ATTR(read_expire),
 513         DD_ATTR(write_expire),
 514         DD_ATTR(writes_starved),
 515         DD_ATTR(front_merges),
 516         DD_ATTR(fifo_batch),
 517         __ATTR_NULL
 518 };
 519
 520 #ifdef CONFIG_BLK_DEBUG_FS
 521 #define DEADLINE_DEBUGFS_DDIR_ATTRS(ddir, name)                         \
 522 static void *deadline_##name##_fifo_start(struct seq_file *m,           \
 523                                           loff_t *pos)                  \
 524         __acquires(&dd->lock)                                           \
 525 {                                                                       \
 526         struct request_queue *q = m->private;                           \
 527         struct deadline_data *dd = q->elevator->elevator_data;          \
 528                                                                         \
 529         spin_lock(&dd->lock);                                           \
 530         return seq_list_start(&dd->fifo_list[ddir], *pos);              \
 531 }                                                                       \
 532                                                                         \
 533 static void *deadline_##name##_fifo_next(struct seq_file *m, void *v,   \
 534                                          loff_t *pos)                   \
 535 {                                                                       \
 536         struct request_queue *q = m->private;                           \
 537         struct deadline_data *dd = q->elevator->elevator_data;          \
 538                                                                         \
 539         return seq_list_next(v, &dd->fifo_list[ddir], pos);             \
 540 }                                                                       \
 541                                                                         \
 542 static void deadline_##name##_fifo_stop(struct seq_file *m, void *v)    \
 543         __releases(&dd->lock)                                           \
 544 {                                                                       \
 545         struct request_queue *q = m->private;                           \
 546         struct deadline_data *dd = q->elevator->elevator_data;          \
 547                                                                         \
 548         spin_unlock(&dd->lock);                                         \
 549 }                                                                       \
 550                                                                         \
 551 static const struct seq_operations deadline_##name##_fifo_seq_ops = {   \
 552         .start  = deadline_##name##_fifo_start,                         \
 553         .next   = deadline_##name##_fifo_next,                          \
 554         .stop   = deadline_##name##_fifo_stop,                          \
 555         .show   = blk_mq_debugfs_rq_show,                               \
 556 };                                                                      \
 557                                                                         \
 558 static int deadline_##name##_next_rq_show(void *data,                   \
 559                                           struct seq_file *m)           \
 560 {                                                                       \
 561         struct request_queue *q = data;                                 \
 562         struct deadline_data *dd = q->elevator->elevator_data;          \
 563         struct request *rq = dd->next_rq[ddir];                         \
 564                                                                         \
 565         if (rq)                                                         \
 566                 __blk_mq_debugfs_rq_show(m, rq);                        \
 567         return 0;                                                       \
 568 }
 569 DEADLINE_DEBUGFS_DDIR_ATTRS(READ, read)
 570 DEADLINE_DEBUGFS_DDIR_ATTRS(WRITE, write)
 571 #undef DEADLINE_DEBUGFS_DDIR_ATTRS
 572
 573 static int deadline_batching_show(void *data, struct seq_file *m)
 574 {
 575         struct request_queue *q = data;
 576         struct deadline_data *dd = q->elevator->elevator_data;
 577
 578         seq_printf(m, "%u\n", dd->batching);
 579         return 0;
 580 }
 581
 582 static int deadline_starved_show(void *data, struct seq_file *m)
 583 {
 584         struct request_queue *q = data;
 585         struct deadline_data *dd = q->elevator->elevator_data;
 586
 587         seq_printf(m, "%u\n", dd->starved);
 588         return 0;
 589 }
 590
 591 static void *deadline_dispatch_start(struct seq_file *m, loff_t *pos)
 592         __acquires(&dd->lock)
 593 {
 594         struct request_queue *q = m->private;
 595         struct deadline_data *dd = q->elevator->elevator_data;
 596
 597         spin_lock(&dd->lock);
 598         return seq_list_start(&dd->dispatch, *pos);
 599 }
 600
 601 static void *deadline_dispatch_next(struct seq_file *m, void *v, loff_t *pos)
 602 {
 603         struct request_queue *q = m->private;
 604         struct deadline_data *dd = q->elevator->elevator_data;
 605
 606         return seq_list_next(v, &dd->dispatch, pos);
 607 }
 608
 609 static void deadline_dispatch_stop(struct seq_file *m, void *v)
 610         __releases(&dd->lock)
 611 {
 612         struct request_queue *q = m->private;
 613         struct deadline_data *dd = q->elevator->elevator_data;
 614
 615         spin_unlock(&dd->lock);
 616 }
 617
 618 static const struct seq_operations deadline_dispatch_seq_ops = {
 619         .start  = deadline_dispatch_start,
 620         .next   = deadline_dispatch_next,
 621         .stop   = deadline_dispatch_stop,
 622         .show   = blk_mq_debugfs_rq_show,
 623 };
 624
 625 #define DEADLINE_QUEUE_DDIR_ATTRS(name)                                         \
 626         {#name "_fifo_list", 0400, .seq_ops = &deadline_##name##_fifo_seq_ops}, \
 627         {#name "_next_rq", 0400, deadline_##name##_next_rq_show}
 628 static const struct blk_mq_debugfs_attr deadline_queue_debugfs_attrs[] = {
 629         DEADLINE_QUEUE_DDIR_ATTRS(read),
 630         DEADLINE_QUEUE_DDIR_ATTRS(write),
 631         {"batching", 0400, deadline_batching_show},
 632         {"starved", 0400, deadline_starved_show},
 633         {"dispatch", 0400, .seq_ops = &deadline_dispatch_seq_ops},
 634         {},
 635 };
 636 #undef DEADLINE_QUEUE_DDIR_ATTRS
 637 #endif
 638
 639 static struct elevator_type mq_deadline = {
 640         .ops.mq = {
 641                 .insert_requests        = dd_insert_requests,
 642                 .dispatch_request       = dd_dispatch_request,
 643                 .next_request           = elv_rb_latter_request,
 644                 .former_request         = elv_rb_former_request,
 645                 .bio_merge              = dd_bio_merge,
 646                 .request_merge          = dd_request_merge,
 647                 .requests_merged        = dd_merged_requests,
 648                 .request_merged         = dd_request_merged,
 649                 .has_work               = dd_has_work,
 650                 .init_sched             = dd_init_queue,
 651                 .exit_sched             = dd_exit_queue,
 652         },
 653
 654         .uses_mq        = true,
 655 #ifdef CONFIG_BLK_DEBUG_FS
 656         .queue_debugfs_attrs = deadline_queue_debugfs_attrs,
 657 #endif
 658         .elevator_attrs = deadline_attrs,
 659         .elevator_name = "mq-deadline",
 660         .elevator_owner = THIS_MODULE,
 661 };
 662 MODULE_ALIAS("mq-deadline-iosched");
 663
 664 static int __init deadline_init(void)
 665 {
 666         return elv_register(&mq_deadline);
 667 }
 668
 669 static void __exit deadline_exit(void)
 670 {
 671         elv_unregister(&mq_deadline);
 672 }
 673
 674 module_init(deadline_init);
 675 module_exit(deadline_exit);
 676
 677 MODULE_AUTHOR("Jens Axboe");
 678 MODULE_LICENSE("GPL");
 679 MODULE_DESCRIPTION("MQ deadline IO scheduler");