block/mq-deadline.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  MQ Deadline i/o scheduler - adaptation of the legacy deadline scheduler,
   4  *  for the blk-mq scheduling framework
   5  *
   6  *  Copyright (C) 2016 Jens Axboe <axboe@kernel.dk>
   7  */
   8 #include <linux/kernel.h>
   9 #include <linux/fs.h>
  10 #include <linux/blkdev.h>
  11 #include <linux/bio.h>
  12 #include <linux/module.h>
  13 #include <linux/slab.h>
  14 #include <linux/init.h>
  15 #include <linux/compiler.h>
  16 #include <linux/rbtree.h>
  17 #include <linux/sbitmap.h>
  18
  19 #include <trace/events/block.h>
  20
  21 #include "elevator.h"
  22 #include "blk.h"
  23 #include "blk-mq.h"
  24 #include "blk-mq-debugfs.h"
  25 #include "blk-mq-sched.h"
  26
  27 /*
  28  * See Documentation/block/deadline-iosched.rst
  29  */
  30 static const int read_expire = HZ / 2;  /* max time before a read is submitted. */
  31 static const int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */
  32 /*
  33  * Time after which to dispatch lower priority requests even if higher
  34  * priority requests are pending.
  35  */
  36 static const int prio_aging_expire = 10 * HZ;
  37 static const int writes_starved = 2;    /* max times reads can starve a write */
  38 static const int fifo_batch = 16;       /* # of sequential requests treated as one
  39                                      by the above parameters. For throughput. */
  40
  41 enum dd_data_dir {
  42         DD_READ         = READ,
  43         DD_WRITE        = WRITE,
  44 };
  45
  46 enum { DD_DIR_COUNT = 2 };
  47
  48 enum dd_prio {
  49         DD_RT_PRIO      = 0,
  50         DD_BE_PRIO      = 1,
  51         DD_IDLE_PRIO    = 2,
  52         DD_PRIO_MAX     = 2,
  53 };
  54
  55 enum { DD_PRIO_COUNT = 3 };
  56
  57 /*
  58  * I/O statistics per I/O priority. It is fine if these counters overflow.
  59  * What matters is that these counters are at least as wide as
  60  * log2(max_outstanding_requests).
  61  */
  62 struct io_stats_per_prio {
  63         uint32_t inserted;
  64         uint32_t merged;
  65         uint32_t dispatched;
  66         atomic_t completed;
  67 };
  68
  69 /*
  70  * Deadline scheduler data per I/O priority (enum dd_prio). Requests are
  71  * present on both sort_list[] and fifo_list[].
  72  */
  73 struct dd_per_prio {
  74         struct list_head dispatch;
  75         struct rb_root sort_list[DD_DIR_COUNT];
  76         struct list_head fifo_list[DD_DIR_COUNT];
  77         /* Next request in FIFO order. Read, write or both are NULL. */
  78         struct request *next_rq[DD_DIR_COUNT];
  79         struct io_stats_per_prio stats;
  80 };
  81
  82 struct deadline_data {
  83         /*
  84          * run time data
  85          */
  86
  87         struct dd_per_prio per_prio[DD_PRIO_COUNT];
  88
  89         /* Data direction of latest dispatched request. */
  90         enum dd_data_dir last_dir;
  91         unsigned int batching;          /* number of sequential requests made */
  92         unsigned int starved;           /* times reads have starved writes */
  93
  94         /*
  95          * settings that change how the i/o scheduler behaves
  96          */
  97         int fifo_expire[DD_DIR_COUNT];
  98         int fifo_batch;
  99         int writes_starved;
 100         int front_merges;
 101         u32 async_depth;
 102         int prio_aging_expire;
 103
 104         spinlock_t lock;
 105         spinlock_t zone_lock;
 106 };
 107
 108 /* Maps an I/O priority class to a deadline scheduler priority. */
 109 static const enum dd_prio ioprio_class_to_prio[] = {
 110         [IOPRIO_CLASS_NONE]     = DD_BE_PRIO,
 111         [IOPRIO_CLASS_RT]       = DD_RT_PRIO,
 112         [IOPRIO_CLASS_BE]       = DD_BE_PRIO,
 113         [IOPRIO_CLASS_IDLE]     = DD_IDLE_PRIO,
 114 };
 115
 116 static inline struct rb_root *
 117 deadline_rb_root(struct dd_per_prio *per_prio, struct request *rq)
 118 {
 119         return &per_prio->sort_list[rq_data_dir(rq)];
 120 }
 121
 122 /*
 123  * Returns the I/O priority class (IOPRIO_CLASS_*) that has been assigned to a
 124  * request.
 125  */
 126 static u8 dd_rq_ioclass(struct request *rq)
 127 {
 128         return IOPRIO_PRIO_CLASS(req_get_ioprio(rq));
 129 }
 130
 131 /*
 132  * get the request before `rq' in sector-sorted order
 133  */
 134 static inline struct request *
 135 deadline_earlier_request(struct request *rq)
 136 {
 137         struct rb_node *node = rb_prev(&rq->rb_node);
 138
 139         if (node)
 140                 return rb_entry_rq(node);
 141
 142         return NULL;
 143 }
 144
 145 /*
 146  * get the request after `rq' in sector-sorted order
 147  */
 148 static inline struct request *
 149 deadline_latter_request(struct request *rq)
 150 {
 151         struct rb_node *node = rb_next(&rq->rb_node);
 152
 153         if (node)
 154                 return rb_entry_rq(node);
 155
 156         return NULL;
 157 }
 158
 159 static void
 160 deadline_add_rq_rb(struct dd_per_prio *per_prio, struct request *rq)
 161 {
 162         struct rb_root *root = deadline_rb_root(per_prio, rq);
 163
 164         elv_rb_add(root, rq);
 165 }
 166
 167 static inline void
 168 deadline_del_rq_rb(struct dd_per_prio *per_prio, struct request *rq)
 169 {
 170         const enum dd_data_dir data_dir = rq_data_dir(rq);
 171
 172         if (per_prio->next_rq[data_dir] == rq)
 173                 per_prio->next_rq[data_dir] = deadline_latter_request(rq);
 174
 175         elv_rb_del(deadline_rb_root(per_prio, rq), rq);
 176 }
 177
 178 /*
 179  * remove rq from rbtree and fifo.
 180  */
 181 static void deadline_remove_request(struct request_queue *q,
 182                                     struct dd_per_prio *per_prio,
 183                                     struct request *rq)
 184 {
 185         list_del_init(&rq->queuelist);
 186
 187         /*
 188          * We might not be on the rbtree, if we are doing an insert merge
 189          */
 190         if (!RB_EMPTY_NODE(&rq->rb_node))
 191                 deadline_del_rq_rb(per_prio, rq);
 192
 193         elv_rqhash_del(q, rq);
 194         if (q->last_merge == rq)
 195                 q->last_merge = NULL;
 196 }
 197
 198 static void dd_request_merged(struct request_queue *q, struct request *req,
 199                               enum elv_merge type)
 200 {
 201         struct deadline_data *dd = q->elevator->elevator_data;
 202         const u8 ioprio_class = dd_rq_ioclass(req);
 203         const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
 204         struct dd_per_prio *per_prio = &dd->per_prio[prio];
 205
 206         /*
 207          * if the merge was a front merge, we need to reposition request
 208          */
 209         if (type == ELEVATOR_FRONT_MERGE) {
 210                 elv_rb_del(deadline_rb_root(per_prio, req), req);
 211                 deadline_add_rq_rb(per_prio, req);
 212         }
 213 }
 214
 215 /*
 216  * Callback function that is invoked after @next has been merged into @req.
 217  */
 218 static void dd_merged_requests(struct request_queue *q, struct request *req,
 219                                struct request *next)
 220 {
 221         struct deadline_data *dd = q->elevator->elevator_data;
 222         const u8 ioprio_class = dd_rq_ioclass(next);
 223         const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
 224
 225         lockdep_assert_held(&dd->lock);
 226
 227         dd->per_prio[prio].stats.merged++;
 228
 229         /*
 230          * if next expires before rq, assign its expire time to rq
 231          * and move into next position (next will be deleted) in fifo
 232          */
 233         if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
 234                 if (time_before((unsigned long)next->fifo_time,
 235                                 (unsigned long)req->fifo_time)) {
 236                         list_move(&req->queuelist, &next->queuelist);
 237                         req->fifo_time = next->fifo_time;
 238                 }
 239         }
 240
 241         /*
 242          * kill knowledge of next, this one is a goner
 243          */
 244         deadline_remove_request(q, &dd->per_prio[prio], next);
 245 }
 246
 247 /*
 248  * move an entry to dispatch queue
 249  */
 250 static void
 251 deadline_move_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
 252                       struct request *rq)
 253 {
 254         const enum dd_data_dir data_dir = rq_data_dir(rq);
 255
 256         per_prio->next_rq[data_dir] = deadline_latter_request(rq);
 257
 258         /*
 259          * take it off the sort and fifo list
 260          */
 261         deadline_remove_request(rq->q, per_prio, rq);
 262 }
 263
 264 /* Number of requests queued for a given priority level. */
 265 static u32 dd_queued(struct deadline_data *dd, enum dd_prio prio)
 266 {
 267         const struct io_stats_per_prio *stats = &dd->per_prio[prio].stats;
 268
 269         lockdep_assert_held(&dd->lock);
 270
 271         return stats->inserted - atomic_read(&stats->completed);
 272 }
 273
 274 /*
 275  * deadline_check_fifo returns 0 if there are no expired requests on the fifo,
 276  * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
 277  */
 278 static inline int deadline_check_fifo(struct dd_per_prio *per_prio,
 279                                       enum dd_data_dir data_dir)
 280 {
 281         struct request *rq = rq_entry_fifo(per_prio->fifo_list[data_dir].next);
 282
 283         /*
 284          * rq is expired!
 285          */
 286         if (time_after_eq(jiffies, (unsigned long)rq->fifo_time))
 287                 return 1;
 288
 289         return 0;
 290 }
 291
 292 /*
 293  * Check if rq has a sequential request preceding it.
 294  */
 295 static bool deadline_is_seq_write(struct deadline_data *dd, struct request *rq)
 296 {
 297         struct request *prev = deadline_earlier_request(rq);
 298
 299         if (!prev)
 300                 return false;
 301
 302         return blk_rq_pos(prev) + blk_rq_sectors(prev) == blk_rq_pos(rq);
 303 }
 304
 305 /*
 306  * Skip all write requests that are sequential from @rq, even if we cross
 307  * a zone boundary.
 308  */
 309 static struct request *deadline_skip_seq_writes(struct deadline_data *dd,
 310                                                 struct request *rq)
 311 {
 312         sector_t pos = blk_rq_pos(rq);
 313         sector_t skipped_sectors = 0;
 314
 315         while (rq) {
 316                 if (blk_rq_pos(rq) != pos + skipped_sectors)
 317                         break;
 318                 skipped_sectors += blk_rq_sectors(rq);
 319                 rq = deadline_latter_request(rq);
 320         }
 321
 322         return rq;
 323 }
 324
 325 /*
 326  * For the specified data direction, return the next request to
 327  * dispatch using arrival ordered lists.
 328  */
 329 static struct request *
 330 deadline_fifo_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
 331                       enum dd_data_dir data_dir)
 332 {
 333         struct request *rq;
 334         unsigned long flags;
 335
 336         if (list_empty(&per_prio->fifo_list[data_dir]))
 337                 return NULL;
 338
 339         rq = rq_entry_fifo(per_prio->fifo_list[data_dir].next);
 340         if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q))
 341                 return rq;
 342
 343         /*
 344          * Look for a write request that can be dispatched, that is one with
 345          * an unlocked target zone. For some HDDs, breaking a sequential
 346          * write stream can lead to lower throughput, so make sure to preserve
 347          * sequential write streams, even if that stream crosses into the next
 348          * zones and these zones are unlocked.
 349          */
 350         spin_lock_irqsave(&dd->zone_lock, flags);
 351         list_for_each_entry(rq, &per_prio->fifo_list[DD_WRITE], queuelist) {
 352                 if (blk_req_can_dispatch_to_zone(rq) &&
 353                     (blk_queue_nonrot(rq->q) ||
 354                      !deadline_is_seq_write(dd, rq)))
 355                         goto out;
 356         }
 357         rq = NULL;
 358 out:
 359         spin_unlock_irqrestore(&dd->zone_lock, flags);
 360
 361         return rq;
 362 }
 363
 364 /*
 365  * For the specified data direction, return the next request to
 366  * dispatch using sector position sorted lists.
 367  */
 368 static struct request *
 369 deadline_next_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
 370                       enum dd_data_dir data_dir)
 371 {
 372         struct request *rq;
 373         unsigned long flags;
 374
 375         rq = per_prio->next_rq[data_dir];
 376         if (!rq)
 377                 return NULL;
 378
 379         if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q))
 380                 return rq;
 381
 382         /*
 383          * Look for a write request that can be dispatched, that is one with
 384          * an unlocked target zone. For some HDDs, breaking a sequential
 385          * write stream can lead to lower throughput, so make sure to preserve
 386          * sequential write streams, even if that stream crosses into the next
 387          * zones and these zones are unlocked.
 388          */
 389         spin_lock_irqsave(&dd->zone_lock, flags);
 390         while (rq) {
 391                 if (blk_req_can_dispatch_to_zone(rq))
 392                         break;
 393                 if (blk_queue_nonrot(rq->q))
 394                         rq = deadline_latter_request(rq);
 395                 else
 396                         rq = deadline_skip_seq_writes(dd, rq);
 397         }
 398         spin_unlock_irqrestore(&dd->zone_lock, flags);
 399
 400         return rq;
 401 }
 402
 403 /*
 404  * Returns true if and only if @rq started after @latest_start where
 405  * @latest_start is in jiffies.
 406  */
 407 static bool started_after(struct deadline_data *dd, struct request *rq,
 408                           unsigned long latest_start)
 409 {
 410         unsigned long start_time = (unsigned long)rq->fifo_time;
 411
 412         start_time -= dd->fifo_expire[rq_data_dir(rq)];
 413
 414         return time_after(start_time, latest_start);
 415 }
 416
 417 /*
 418  * deadline_dispatch_requests selects the best request according to
 419  * read/write expire, fifo_batch, etc and with a start time <= @latest_start.
 420  */
 421 static struct request *__dd_dispatch_request(struct deadline_data *dd,
 422                                              struct dd_per_prio *per_prio,
 423                                              unsigned long latest_start)
 424 {
 425         struct request *rq, *next_rq;
 426         enum dd_data_dir data_dir;
 427         enum dd_prio prio;
 428         u8 ioprio_class;
 429
 430         lockdep_assert_held(&dd->lock);
 431
 432         if (!list_empty(&per_prio->dispatch)) {
 433                 rq = list_first_entry(&per_prio->dispatch, struct request,
 434                                       queuelist);
 435                 if (started_after(dd, rq, latest_start))
 436                         return NULL;
 437                 list_del_init(&rq->queuelist);
 438                 goto done;
 439         }
 440
 441         /*
 442          * batches are currently reads XOR writes
 443          */
 444         rq = deadline_next_request(dd, per_prio, dd->last_dir);
 445         if (rq && dd->batching < dd->fifo_batch)
 446                 /* we have a next request are still entitled to batch */
 447                 goto dispatch_request;
 448
 449         /*
 450          * at this point we are not running a batch. select the appropriate
 451          * data direction (read / write)
 452          */
 453
 454         if (!list_empty(&per_prio->fifo_list[DD_READ])) {
 455                 BUG_ON(RB_EMPTY_ROOT(&per_prio->sort_list[DD_READ]));
 456
 457                 if (deadline_fifo_request(dd, per_prio, DD_WRITE) &&
 458                     (dd->starved++ >= dd->writes_starved))
 459                         goto dispatch_writes;
 460
 461                 data_dir = DD_READ;
 462
 463                 goto dispatch_find_request;
 464         }
 465
 466         /*
 467          * there are either no reads or writes have been starved
 468          */
 469
 470         if (!list_empty(&per_prio->fifo_list[DD_WRITE])) {
 471 dispatch_writes:
 472                 BUG_ON(RB_EMPTY_ROOT(&per_prio->sort_list[DD_WRITE]));
 473
 474                 dd->starved = 0;
 475
 476                 data_dir = DD_WRITE;
 477
 478                 goto dispatch_find_request;
 479         }
 480
 481         return NULL;
 482
 483 dispatch_find_request:
 484         /*
 485          * we are not running a batch, find best request for selected data_dir
 486          */
 487         next_rq = deadline_next_request(dd, per_prio, data_dir);
 488         if (deadline_check_fifo(per_prio, data_dir) || !next_rq) {
 489                 /*
 490                  * A deadline has expired, the last request was in the other
 491                  * direction, or we have run out of higher-sectored requests.
 492                  * Start again from the request with the earliest expiry time.
 493                  */
 494                 rq = deadline_fifo_request(dd, per_prio, data_dir);
 495         } else {
 496                 /*
 497                  * The last req was the same dir and we have a next request in
 498                  * sort order. No expired requests so continue on from here.
 499                  */
 500                 rq = next_rq;
 501         }
 502
 503         /*
 504          * For a zoned block device, if we only have writes queued and none of
 505          * them can be dispatched, rq will be NULL.
 506          */
 507         if (!rq)
 508                 return NULL;
 509
 510         dd->last_dir = data_dir;
 511         dd->batching = 0;
 512
 513 dispatch_request:
 514         if (started_after(dd, rq, latest_start))
 515                 return NULL;
 516
 517         /*
 518          * rq is the selected appropriate request.
 519          */
 520         dd->batching++;
 521         deadline_move_request(dd, per_prio, rq);
 522 done:
 523         ioprio_class = dd_rq_ioclass(rq);
 524         prio = ioprio_class_to_prio[ioprio_class];
 525         dd->per_prio[prio].stats.dispatched++;
 526         /*
 527          * If the request needs its target zone locked, do it.
 528          */
 529         blk_req_zone_write_lock(rq);
 530         rq->rq_flags |= RQF_STARTED;
 531         return rq;
 532 }
 533
 534 /*
 535  * Check whether there are any requests with priority other than DD_RT_PRIO
 536  * that were inserted more than prio_aging_expire jiffies ago.
 537  */
 538 static struct request *dd_dispatch_prio_aged_requests(struct deadline_data *dd,
 539                                                       unsigned long now)
 540 {
 541         struct request *rq;
 542         enum dd_prio prio;
 543         int prio_cnt;
 544
 545         lockdep_assert_held(&dd->lock);
 546
 547         prio_cnt = !!dd_queued(dd, DD_RT_PRIO) + !!dd_queued(dd, DD_BE_PRIO) +
 548                    !!dd_queued(dd, DD_IDLE_PRIO);
 549         if (prio_cnt < 2)
 550                 return NULL;
 551
 552         for (prio = DD_BE_PRIO; prio <= DD_PRIO_MAX; prio++) {
 553                 rq = __dd_dispatch_request(dd, &dd->per_prio[prio],
 554                                            now - dd->prio_aging_expire);
 555                 if (rq)
 556                         return rq;
 557         }
 558
 559         return NULL;
 560 }
 561
 562 /*
 563  * Called from blk_mq_run_hw_queue() -> __blk_mq_sched_dispatch_requests().
 564  *
 565  * One confusing aspect here is that we get called for a specific
 566  * hardware queue, but we may return a request that is for a
 567  * different hardware queue. This is because mq-deadline has shared
 568  * state for all hardware queues, in terms of sorting, FIFOs, etc.
 569  */
 570 static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
 571 {
 572         struct deadline_data *dd = hctx->queue->elevator->elevator_data;
 573         const unsigned long now = jiffies;
 574         struct request *rq;
 575         enum dd_prio prio;
 576
 577         spin_lock(&dd->lock);
 578         rq = dd_dispatch_prio_aged_requests(dd, now);
 579         if (rq)
 580                 goto unlock;
 581
 582         /*
 583          * Next, dispatch requests in priority order. Ignore lower priority
 584          * requests if any higher priority requests are pending.
 585          */
 586         for (prio = 0; prio <= DD_PRIO_MAX; prio++) {
 587                 rq = __dd_dispatch_request(dd, &dd->per_prio[prio], now);
 588                 if (rq || dd_queued(dd, prio))
 589                         break;
 590         }
 591
 592 unlock:
 593         spin_unlock(&dd->lock);
 594
 595         return rq;
 596 }
 597
 598 /*
 599  * Called by __blk_mq_alloc_request(). The shallow_depth value set by this
 600  * function is used by __blk_mq_get_tag().
 601  */
 602 static void dd_limit_depth(blk_opf_t opf, struct blk_mq_alloc_data *data)
 603 {
 604         struct deadline_data *dd = data->q->elevator->elevator_data;
 605
 606         /* Do not throttle synchronous reads. */
 607         if (op_is_sync(opf) && !op_is_write(opf))
 608                 return;
 609
 610         /*
 611          * Throttle asynchronous requests and writes such that these requests
 612          * do not block the allocation of synchronous requests.
 613          */
 614         data->shallow_depth = dd->async_depth;
 615 }
 616
 617 /* Called by blk_mq_update_nr_requests(). */
 618 static void dd_depth_updated(struct blk_mq_hw_ctx *hctx)
 619 {
 620         struct request_queue *q = hctx->queue;
 621         struct deadline_data *dd = q->elevator->elevator_data;
 622         struct blk_mq_tags *tags = hctx->sched_tags;
 623
 624         dd->async_depth = max(1UL, 3 * q->nr_requests / 4);
 625
 626         sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, dd->async_depth);
 627 }
 628
 629 /* Called by blk_mq_init_hctx() and blk_mq_init_sched(). */
 630 static int dd_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
 631 {
 632         dd_depth_updated(hctx);
 633         return 0;
 634 }
 635
 636 static void dd_exit_sched(struct elevator_queue *e)
 637 {
 638         struct deadline_data *dd = e->elevator_data;
 639         enum dd_prio prio;
 640
 641         for (prio = 0; prio <= DD_PRIO_MAX; prio++) {
 642                 struct dd_per_prio *per_prio = &dd->per_prio[prio];
 643                 const struct io_stats_per_prio *stats = &per_prio->stats;
 644                 uint32_t queued;
 645
 646                 WARN_ON_ONCE(!list_empty(&per_prio->fifo_list[DD_READ]));
 647                 WARN_ON_ONCE(!list_empty(&per_prio->fifo_list[DD_WRITE]));
 648
 649                 spin_lock(&dd->lock);
 650                 queued = dd_queued(dd, prio);
 651                 spin_unlock(&dd->lock);
 652
 653                 WARN_ONCE(queued != 0,
 654                           "statistics for priority %d: i %u m %u d %u c %u\n",
 655                           prio, stats->inserted, stats->merged,
 656                           stats->dispatched, atomic_read(&stats->completed));
 657         }
 658
 659         kfree(dd);
 660 }
 661
 662 /*
 663  * initialize elevator private data (deadline_data).
 664  */
 665 static int dd_init_sched(struct request_queue *q, struct elevator_type *e)
 666 {
 667         struct deadline_data *dd;
 668         struct elevator_queue *eq;
 669         enum dd_prio prio;
 670         int ret = -ENOMEM;
 671
 672         eq = elevator_alloc(q, e);
 673         if (!eq)
 674                 return ret;
 675
 676         dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node);
 677         if (!dd)
 678                 goto put_eq;
 679
 680         eq->elevator_data = dd;
 681
 682         for (prio = 0; prio <= DD_PRIO_MAX; prio++) {
 683                 struct dd_per_prio *per_prio = &dd->per_prio[prio];
 684
 685                 INIT_LIST_HEAD(&per_prio->dispatch);
 686                 INIT_LIST_HEAD(&per_prio->fifo_list[DD_READ]);
 687                 INIT_LIST_HEAD(&per_prio->fifo_list[DD_WRITE]);
 688                 per_prio->sort_list[DD_READ] = RB_ROOT;
 689                 per_prio->sort_list[DD_WRITE] = RB_ROOT;
 690         }
 691         dd->fifo_expire[DD_READ] = read_expire;
 692         dd->fifo_expire[DD_WRITE] = write_expire;
 693         dd->writes_starved = writes_starved;
 694         dd->front_merges = 1;
 695         dd->last_dir = DD_WRITE;
 696         dd->fifo_batch = fifo_batch;
 697         dd->prio_aging_expire = prio_aging_expire;
 698         spin_lock_init(&dd->lock);
 699         spin_lock_init(&dd->zone_lock);
 700
 701         /* We dispatch from request queue wide instead of hw queue */
 702         blk_queue_flag_set(QUEUE_FLAG_SQ_SCHED, q);
 703
 704         q->elevator = eq;
 705         return 0;
 706
 707 put_eq:
 708         kobject_put(&eq->kobj);
 709         return ret;
 710 }
 711
 712 /*
 713  * Try to merge @bio into an existing request. If @bio has been merged into
 714  * an existing request, store the pointer to that request into *@rq.
 715  */
 716 static int dd_request_merge(struct request_queue *q, struct request **rq,
 717                             struct bio *bio)
 718 {
 719         struct deadline_data *dd = q->elevator->elevator_data;
 720         const u8 ioprio_class = IOPRIO_PRIO_CLASS(bio->bi_ioprio);
 721         const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
 722         struct dd_per_prio *per_prio = &dd->per_prio[prio];
 723         sector_t sector = bio_end_sector(bio);
 724         struct request *__rq;
 725
 726         if (!dd->front_merges)
 727                 return ELEVATOR_NO_MERGE;
 728
 729         __rq = elv_rb_find(&per_prio->sort_list[bio_data_dir(bio)], sector);
 730         if (__rq) {
 731                 BUG_ON(sector != blk_rq_pos(__rq));
 732
 733                 if (elv_bio_merge_ok(__rq, bio)) {
 734                         *rq = __rq;
 735                         if (blk_discard_mergable(__rq))
 736                                 return ELEVATOR_DISCARD_MERGE;
 737                         return ELEVATOR_FRONT_MERGE;
 738                 }
 739         }
 740
 741         return ELEVATOR_NO_MERGE;
 742 }
 743
 744 /*
 745  * Attempt to merge a bio into an existing request. This function is called
 746  * before @bio is associated with a request.
 747  */
 748 static bool dd_bio_merge(struct request_queue *q, struct bio *bio,
 749                 unsigned int nr_segs)
 750 {
 751         struct deadline_data *dd = q->elevator->elevator_data;
 752         struct request *free = NULL;
 753         bool ret;
 754
 755         spin_lock(&dd->lock);
 756         ret = blk_mq_sched_try_merge(q, bio, nr_segs, &free);
 757         spin_unlock(&dd->lock);
 758
 759         if (free)
 760                 blk_mq_free_request(free);
 761
 762         return ret;
 763 }
 764
 765 /*
 766  * add rq to rbtree and fifo
 767  */
 768 static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
 769                               blk_insert_t flags)
 770 {
 771         struct request_queue *q = hctx->queue;
 772         struct deadline_data *dd = q->elevator->elevator_data;
 773         const enum dd_data_dir data_dir = rq_data_dir(rq);
 774         u16 ioprio = req_get_ioprio(rq);
 775         u8 ioprio_class = IOPRIO_PRIO_CLASS(ioprio);
 776         struct dd_per_prio *per_prio;
 777         enum dd_prio prio;
 778         LIST_HEAD(free);
 779
 780         lockdep_assert_held(&dd->lock);
 781
 782         /*
 783          * This may be a requeue of a write request that has locked its
 784          * target zone. If it is the case, this releases the zone lock.
 785          */
 786         blk_req_zone_write_unlock(rq);
 787
 788         prio = ioprio_class_to_prio[ioprio_class];
 789         per_prio = &dd->per_prio[prio];
 790         if (!rq->elv.priv[0]) {
 791                 per_prio->stats.inserted++;
 792                 rq->elv.priv[0] = (void *)(uintptr_t)1;
 793         }
 794
 795         if (blk_mq_sched_try_insert_merge(q, rq, &free)) {
 796                 blk_mq_free_requests(&free);
 797                 return;
 798         }
 799
 800         trace_block_rq_insert(rq);
 801
 802         if (flags & BLK_MQ_INSERT_AT_HEAD) {
 803                 list_add(&rq->queuelist, &per_prio->dispatch);
 804                 rq->fifo_time = jiffies;
 805         } else {
 806                 deadline_add_rq_rb(per_prio, rq);
 807
 808                 if (rq_mergeable(rq)) {
 809                         elv_rqhash_add(q, rq);
 810                         if (!q->last_merge)
 811                                 q->last_merge = rq;
 812                 }
 813
 814                 /*
 815                  * set expire time and add to fifo list
 816                  */
 817                 rq->fifo_time = jiffies + dd->fifo_expire[data_dir];
 818                 list_add_tail(&rq->queuelist, &per_prio->fifo_list[data_dir]);
 819         }
 820 }
 821
 822 /*
 823  * Called from blk_mq_insert_request() or blk_mq_dispatch_plug_list().
 824  */
 825 static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
 826                                struct list_head *list,
 827                                blk_insert_t flags)
 828 {
 829         struct request_queue *q = hctx->queue;
 830         struct deadline_data *dd = q->elevator->elevator_data;
 831
 832         spin_lock(&dd->lock);
 833         while (!list_empty(list)) {
 834                 struct request *rq;
 835
 836                 rq = list_first_entry(list, struct request, queuelist);
 837                 list_del_init(&rq->queuelist);
 838                 dd_insert_request(hctx, rq, flags);
 839         }
 840         spin_unlock(&dd->lock);
 841 }
 842
 843 /* Callback from inside blk_mq_rq_ctx_init(). */
 844 static void dd_prepare_request(struct request *rq)
 845 {
 846         rq->elv.priv[0] = NULL;
 847 }
 848
 849 static bool dd_has_write_work(struct blk_mq_hw_ctx *hctx)
 850 {
 851         struct deadline_data *dd = hctx->queue->elevator->elevator_data;
 852         enum dd_prio p;
 853
 854         for (p = 0; p <= DD_PRIO_MAX; p++)
 855                 if (!list_empty_careful(&dd->per_prio[p].fifo_list[DD_WRITE]))
 856                         return true;
 857
 858         return false;
 859 }
 860
 861 /*
 862  * Callback from inside blk_mq_free_request().
 863  *
 864  * For zoned block devices, write unlock the target zone of
 865  * completed write requests. Do this while holding the zone lock
 866  * spinlock so that the zone is never unlocked while deadline_fifo_request()
 867  * or deadline_next_request() are executing. This function is called for
 868  * all requests, whether or not these requests complete successfully.
 869  *
 870  * For a zoned block device, __dd_dispatch_request() may have stopped
 871  * dispatching requests if all the queued requests are write requests directed
 872  * at zones that are already locked due to on-going write requests. To ensure
 873  * write request dispatch progress in this case, mark the queue as needing a
 874  * restart to ensure that the queue is run again after completion of the
 875  * request and zones being unlocked.
 876  */
 877 static void dd_finish_request(struct request *rq)
 878 {
 879         struct request_queue *q = rq->q;
 880         struct deadline_data *dd = q->elevator->elevator_data;
 881         const u8 ioprio_class = dd_rq_ioclass(rq);
 882         const enum dd_prio prio = ioprio_class_to_prio[ioprio_class];
 883         struct dd_per_prio *per_prio = &dd->per_prio[prio];
 884
 885         /*
 886          * The block layer core may call dd_finish_request() without having
 887          * called dd_insert_requests(). Skip requests that bypassed I/O
 888          * scheduling. See also blk_mq_request_bypass_insert().
 889          */
 890         if (!rq->elv.priv[0])
 891                 return;
 892
 893         atomic_inc(&per_prio->stats.completed);
 894
 895         if (blk_queue_is_zoned(q)) {
 896                 unsigned long flags;
 897
 898                 spin_lock_irqsave(&dd->zone_lock, flags);
 899                 blk_req_zone_write_unlock(rq);
 900                 spin_unlock_irqrestore(&dd->zone_lock, flags);
 901
 902                 if (dd_has_write_work(rq->mq_hctx))
 903                         blk_mq_sched_mark_restart_hctx(rq->mq_hctx);
 904         }
 905 }
 906
 907 static bool dd_has_work_for_prio(struct dd_per_prio *per_prio)
 908 {
 909         return !list_empty_careful(&per_prio->dispatch) ||
 910                 !list_empty_careful(&per_prio->fifo_list[DD_READ]) ||
 911                 !list_empty_careful(&per_prio->fifo_list[DD_WRITE]);
 912 }
 913
 914 static bool dd_has_work(struct blk_mq_hw_ctx *hctx)
 915 {
 916         struct deadline_data *dd = hctx->queue->elevator->elevator_data;
 917         enum dd_prio prio;
 918
 919         for (prio = 0; prio <= DD_PRIO_MAX; prio++)
 920                 if (dd_has_work_for_prio(&dd->per_prio[prio]))
 921                         return true;
 922
 923         return false;
 924 }
 925
 926 /*
 927  * sysfs parts below
 928  */
 929 #define SHOW_INT(__FUNC, __VAR)                                         \
 930 static ssize_t __FUNC(struct elevator_queue *e, char *page)             \
 931 {                                                                       \
 932         struct deadline_data *dd = e->elevator_data;                    \
 933                                                                         \
 934         return sysfs_emit(page, "%d\n", __VAR);                         \
 935 }
 936 #define SHOW_JIFFIES(__FUNC, __VAR) SHOW_INT(__FUNC, jiffies_to_msecs(__VAR))
 937 SHOW_JIFFIES(deadline_read_expire_show, dd->fifo_expire[DD_READ]);
 938 SHOW_JIFFIES(deadline_write_expire_show, dd->fifo_expire[DD_WRITE]);
 939 SHOW_JIFFIES(deadline_prio_aging_expire_show, dd->prio_aging_expire);
 940 SHOW_INT(deadline_writes_starved_show, dd->writes_starved);
 941 SHOW_INT(deadline_front_merges_show, dd->front_merges);
 942 SHOW_INT(deadline_async_depth_show, dd->async_depth);
 943 SHOW_INT(deadline_fifo_batch_show, dd->fifo_batch);
 944 #undef SHOW_INT
 945 #undef SHOW_JIFFIES
 946
 947 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)                 \
 948 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
 949 {                                                                       \
 950         struct deadline_data *dd = e->elevator_data;                    \
 951         int __data, __ret;                                              \
 952                                                                         \
 953         __ret = kstrtoint(page, 0, &__data);                            \
 954         if (__ret < 0)                                                  \
 955                 return __ret;                                           \
 956         if (__data < (MIN))                                             \
 957                 __data = (MIN);                                         \
 958         else if (__data > (MAX))                                        \
 959                 __data = (MAX);                                         \
 960         *(__PTR) = __CONV(__data);                                      \
 961         return count;                                                   \
 962 }
 963 #define STORE_INT(__FUNC, __PTR, MIN, MAX)                              \
 964         STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, )
 965 #define STORE_JIFFIES(__FUNC, __PTR, MIN, MAX)                          \
 966         STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, msecs_to_jiffies)
 967 STORE_JIFFIES(deadline_read_expire_store, &dd->fifo_expire[DD_READ], 0, INT_MAX);
 968 STORE_JIFFIES(deadline_write_expire_store, &dd->fifo_expire[DD_WRITE], 0, INT_MAX);
 969 STORE_JIFFIES(deadline_prio_aging_expire_store, &dd->prio_aging_expire, 0, INT_MAX);
 970 STORE_INT(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX);
 971 STORE_INT(deadline_front_merges_store, &dd->front_merges, 0, 1);
 972 STORE_INT(deadline_async_depth_store, &dd->async_depth, 1, INT_MAX);
 973 STORE_INT(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX);
 974 #undef STORE_FUNCTION
 975 #undef STORE_INT
 976 #undef STORE_JIFFIES
 977
 978 #define DD_ATTR(name) \
 979         __ATTR(name, 0644, deadline_##name##_show, deadline_##name##_store)
 980
 981 static struct elv_fs_entry deadline_attrs[] = {
 982         DD_ATTR(read_expire),
 983         DD_ATTR(write_expire),
 984         DD_ATTR(writes_starved),
 985         DD_ATTR(front_merges),
 986         DD_ATTR(async_depth),
 987         DD_ATTR(fifo_batch),
 988         DD_ATTR(prio_aging_expire),
 989         __ATTR_NULL
 990 };
 991
 992 #ifdef CONFIG_BLK_DEBUG_FS
 993 #define DEADLINE_DEBUGFS_DDIR_ATTRS(prio, data_dir, name)               \
 994 static void *deadline_##name##_fifo_start(struct seq_file *m,           \
 995                                           loff_t *pos)                  \
 996         __acquires(&dd->lock)                                           \
 997 {                                                                       \
 998         struct request_queue *q = m->private;                           \
 999         struct deadline_data *dd = q->elevator->elevator_data;          \
1000         struct dd_per_prio *per_prio = &dd->per_prio[prio];             \
1001                                                                         \
1002         spin_lock(&dd->lock);                                           \
1003         return seq_list_start(&per_prio->fifo_list[data_dir], *pos);    \
1004 }                                                                       \
1005                                                                         \
1006 static void *deadline_##name##_fifo_next(struct seq_file *m, void *v,   \
1007                                          loff_t *pos)                   \
1008 {                                                                       \
1009         struct request_queue *q = m->private;                           \
1010         struct deadline_data *dd = q->elevator->elevator_data;          \
1011         struct dd_per_prio *per_prio = &dd->per_prio[prio];             \
1012                                                                         \
1013         return seq_list_next(v, &per_prio->fifo_list[data_dir], pos);   \
1014 }                                                                       \
1015                                                                         \
1016 static void deadline_##name##_fifo_stop(struct seq_file *m, void *v)    \
1017         __releases(&dd->lock)                                           \
1018 {                                                                       \
1019         struct request_queue *q = m->private;                           \
1020         struct deadline_data *dd = q->elevator->elevator_data;          \
1021                                                                         \
1022         spin_unlock(&dd->lock);                                         \
1023 }                                                                       \
1024                                                                         \
1025 static const struct seq_operations deadline_##name##_fifo_seq_ops = {   \
1026         .start  = deadline_##name##_fifo_start,                         \
1027         .next   = deadline_##name##_fifo_next,                          \
1028         .stop   = deadline_##name##_fifo_stop,                          \
1029         .show   = blk_mq_debugfs_rq_show,                               \
1030 };                                                                      \
1031                                                                         \
1032 static int deadline_##name##_next_rq_show(void *data,                   \
1033                                           struct seq_file *m)           \
1034 {                                                                       \
1035         struct request_queue *q = data;                                 \
1036         struct deadline_data *dd = q->elevator->elevator_data;          \
1037         struct dd_per_prio *per_prio = &dd->per_prio[prio];             \
1038         struct request *rq = per_prio->next_rq[data_dir];               \
1039                                                                         \
1040         if (rq)                                                         \
1041                 __blk_mq_debugfs_rq_show(m, rq);                        \
1042         return 0;                                                       \
1043 }
1044
1045 DEADLINE_DEBUGFS_DDIR_ATTRS(DD_RT_PRIO, DD_READ, read0);
1046 DEADLINE_DEBUGFS_DDIR_ATTRS(DD_RT_PRIO, DD_WRITE, write0);
1047 DEADLINE_DEBUGFS_DDIR_ATTRS(DD_BE_PRIO, DD_READ, read1);
1048 DEADLINE_DEBUGFS_DDIR_ATTRS(DD_BE_PRIO, DD_WRITE, write1);
1049 DEADLINE_DEBUGFS_DDIR_ATTRS(DD_IDLE_PRIO, DD_READ, read2);
1050 DEADLINE_DEBUGFS_DDIR_ATTRS(DD_IDLE_PRIO, DD_WRITE, write2);
1051 #undef DEADLINE_DEBUGFS_DDIR_ATTRS
1052
1053 static int deadline_batching_show(void *data, struct seq_file *m)
1054 {
1055         struct request_queue *q = data;
1056         struct deadline_data *dd = q->elevator->elevator_data;
1057
1058         seq_printf(m, "%u\n", dd->batching);
1059         return 0;
1060 }
1061
1062 static int deadline_starved_show(void *data, struct seq_file *m)
1063 {
1064         struct request_queue *q = data;
1065         struct deadline_data *dd = q->elevator->elevator_data;
1066
1067         seq_printf(m, "%u\n", dd->starved);
1068         return 0;
1069 }
1070
1071 static int dd_async_depth_show(void *data, struct seq_file *m)
1072 {
1073         struct request_queue *q = data;
1074         struct deadline_data *dd = q->elevator->elevator_data;
1075
1076         seq_printf(m, "%u\n", dd->async_depth);
1077         return 0;
1078 }
1079
1080 static int dd_queued_show(void *data, struct seq_file *m)
1081 {
1082         struct request_queue *q = data;
1083         struct deadline_data *dd = q->elevator->elevator_data;
1084         u32 rt, be, idle;
1085
1086         spin_lock(&dd->lock);
1087         rt = dd_queued(dd, DD_RT_PRIO);
1088         be = dd_queued(dd, DD_BE_PRIO);
1089         idle = dd_queued(dd, DD_IDLE_PRIO);
1090         spin_unlock(&dd->lock);
1091
1092         seq_printf(m, "%u %u %u\n", rt, be, idle);
1093
1094         return 0;
1095 }
1096
1097 /* Number of requests owned by the block driver for a given priority. */
1098 static u32 dd_owned_by_driver(struct deadline_data *dd, enum dd_prio prio)
1099 {
1100         const struct io_stats_per_prio *stats = &dd->per_prio[prio].stats;
1101
1102         lockdep_assert_held(&dd->lock);
1103
1104         return stats->dispatched + stats->merged -
1105                 atomic_read(&stats->completed);
1106 }
1107
1108 static int dd_owned_by_driver_show(void *data, struct seq_file *m)
1109 {
1110         struct request_queue *q = data;
1111         struct deadline_data *dd = q->elevator->elevator_data;
1112         u32 rt, be, idle;
1113
1114         spin_lock(&dd->lock);
1115         rt = dd_owned_by_driver(dd, DD_RT_PRIO);
1116         be = dd_owned_by_driver(dd, DD_BE_PRIO);
1117         idle = dd_owned_by_driver(dd, DD_IDLE_PRIO);
1118         spin_unlock(&dd->lock);
1119
1120         seq_printf(m, "%u %u %u\n", rt, be, idle);
1121
1122         return 0;
1123 }
1124
1125 #define DEADLINE_DISPATCH_ATTR(prio)                                    \
1126 static void *deadline_dispatch##prio##_start(struct seq_file *m,        \
1127                                              loff_t *pos)               \
1128         __acquires(&dd->lock)                                           \
1129 {                                                                       \
1130         struct request_queue *q = m->private;                           \
1131         struct deadline_data *dd = q->elevator->elevator_data;          \
1132         struct dd_per_prio *per_prio = &dd->per_prio[prio];             \
1133                                                                         \
1134         spin_lock(&dd->lock);                                           \
1135         return seq_list_start(&per_prio->dispatch, *pos);               \
1136 }                                                                       \
1137                                                                         \
1138 static void *deadline_dispatch##prio##_next(struct seq_file *m,         \
1139                                             void *v, loff_t *pos)       \
1140 {                                                                       \
1141         struct request_queue *q = m->private;                           \
1142         struct deadline_data *dd = q->elevator->elevator_data;          \
1143         struct dd_per_prio *per_prio = &dd->per_prio[prio];             \
1144                                                                         \
1145         return seq_list_next(v, &per_prio->dispatch, pos);              \
1146 }                                                                       \
1147                                                                         \
1148 static void deadline_dispatch##prio##_stop(struct seq_file *m, void *v) \
1149         __releases(&dd->lock)                                           \
1150 {                                                                       \
1151         struct request_queue *q = m->private;                           \
1152         struct deadline_data *dd = q->elevator->elevator_data;          \
1153                                                                         \
1154         spin_unlock(&dd->lock);                                         \
1155 }                                                                       \
1156                                                                         \
1157 static const struct seq_operations deadline_dispatch##prio##_seq_ops = { \
1158         .start  = deadline_dispatch##prio##_start,                      \
1159         .next   = deadline_dispatch##prio##_next,                       \
1160         .stop   = deadline_dispatch##prio##_stop,                       \
1161         .show   = blk_mq_debugfs_rq_show,                               \
1162 }
1163
1164 DEADLINE_DISPATCH_ATTR(0);
1165 DEADLINE_DISPATCH_ATTR(1);
1166 DEADLINE_DISPATCH_ATTR(2);
1167 #undef DEADLINE_DISPATCH_ATTR
1168
1169 #define DEADLINE_QUEUE_DDIR_ATTRS(name)                                 \
1170         {#name "_fifo_list", 0400,                                      \
1171                         .seq_ops = &deadline_##name##_fifo_seq_ops}
1172 #define DEADLINE_NEXT_RQ_ATTR(name)                                     \
1173         {#name "_next_rq", 0400, deadline_##name##_next_rq_show}
1174 static const struct blk_mq_debugfs_attr deadline_queue_debugfs_attrs[] = {
1175         DEADLINE_QUEUE_DDIR_ATTRS(read0),
1176         DEADLINE_QUEUE_DDIR_ATTRS(write0),
1177         DEADLINE_QUEUE_DDIR_ATTRS(read1),
1178         DEADLINE_QUEUE_DDIR_ATTRS(write1),
1179         DEADLINE_QUEUE_DDIR_ATTRS(read2),
1180         DEADLINE_QUEUE_DDIR_ATTRS(write2),
1181         DEADLINE_NEXT_RQ_ATTR(read0),
1182         DEADLINE_NEXT_RQ_ATTR(write0),
1183         DEADLINE_NEXT_RQ_ATTR(read1),
1184         DEADLINE_NEXT_RQ_ATTR(write1),
1185         DEADLINE_NEXT_RQ_ATTR(read2),
1186         DEADLINE_NEXT_RQ_ATTR(write2),
1187         {"batching", 0400, deadline_batching_show},
1188         {"starved", 0400, deadline_starved_show},
1189         {"async_depth", 0400, dd_async_depth_show},
1190         {"dispatch0", 0400, .seq_ops = &deadline_dispatch0_seq_ops},
1191         {"dispatch1", 0400, .seq_ops = &deadline_dispatch1_seq_ops},
1192         {"dispatch2", 0400, .seq_ops = &deadline_dispatch2_seq_ops},
1193         {"owned_by_driver", 0400, dd_owned_by_driver_show},
1194         {"queued", 0400, dd_queued_show},
1195         {},
1196 };
1197 #undef DEADLINE_QUEUE_DDIR_ATTRS
1198 #endif
1199
1200 static struct elevator_type mq_deadline = {
1201         .ops = {
1202                 .depth_updated          = dd_depth_updated,
1203                 .limit_depth            = dd_limit_depth,
1204                 .insert_requests        = dd_insert_requests,
1205                 .dispatch_request       = dd_dispatch_request,
1206                 .prepare_request        = dd_prepare_request,
1207                 .finish_request         = dd_finish_request,
1208                 .next_request           = elv_rb_latter_request,
1209                 .former_request         = elv_rb_former_request,
1210                 .bio_merge              = dd_bio_merge,
1211                 .request_merge          = dd_request_merge,
1212                 .requests_merged        = dd_merged_requests,
1213                 .request_merged         = dd_request_merged,
1214                 .has_work               = dd_has_work,
1215                 .init_sched             = dd_init_sched,
1216                 .exit_sched             = dd_exit_sched,
1217                 .init_hctx              = dd_init_hctx,
1218         },
1219
1220 #ifdef CONFIG_BLK_DEBUG_FS
1221         .queue_debugfs_attrs = deadline_queue_debugfs_attrs,
1222 #endif
1223         .elevator_attrs = deadline_attrs,
1224         .elevator_name = "mq-deadline",
1225         .elevator_alias = "deadline",
1226         .elevator_features = ELEVATOR_F_ZBD_SEQ_WRITE,
1227         .elevator_owner = THIS_MODULE,
1228 };
1229 MODULE_ALIAS("mq-deadline-iosched");
1230
1231 static int __init deadline_init(void)
1232 {
1233         return elv_register(&mq_deadline);
1234 }
1235
1236 static void __exit deadline_exit(void)
1237 {
1238         elv_unregister(&mq_deadline);
1239 }
1240
1241 module_init(deadline_init);
1242 module_exit(deadline_exit);
1243
1244 MODULE_AUTHOR("Jens Axboe, Damien Le Moal and Bart Van Assche");
1245 MODULE_LICENSE("GPL");
1246 MODULE_DESCRIPTION("MQ deadline IO scheduler");