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 */ 30static const int read_expire = HZ / 2; /* max time before a read is submitted. */ 31static 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 */ 36static const int prio_aging_expire = 10 * HZ; 37static const int writes_starved = 2; /* max times reads can starve a write */ 38static const int fifo_batch = 16; /* # of sequential requests treated as one 39 by the above parameters. For throughput. */ 40 41enum dd_data_dir { 42 DD_READ = READ, 43 DD_WRITE = WRITE, 44}; 45 46enum { DD_DIR_COUNT = 2 }; 47 48enum dd_prio { 49 DD_RT_PRIO = 0, 50 DD_BE_PRIO = 1, 51 DD_IDLE_PRIO = 2, 52 DD_PRIO_MAX = 2, 53}; 54 55enum { 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 */ 62struct 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 */ 73struct 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 /* Position of the most recently dispatched request. */ 78 sector_t latest_pos[DD_DIR_COUNT]; 79 struct io_stats_per_prio stats; 80}; 81 82struct 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. */ 109static 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 116static inline struct rb_root * 117deadline_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 */ 126static 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 */ 134static inline struct request * 135deadline_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 */ 148static inline struct request * 149deadline_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/* 160 * Return the first request for which blk_rq_pos() >= @pos. For zoned devices, 161 * return the first request after the start of the zone containing @pos. 162 */ 163static inline struct request *deadline_from_pos(struct dd_per_prio *per_prio, 164 enum dd_data_dir data_dir, sector_t pos) 165{ 166 struct rb_node *node = per_prio->sort_list[data_dir].rb_node; 167 struct request *rq, *res = NULL; 168 169 if (!node) 170 return NULL; 171 172 rq = rb_entry_rq(node); 173 /* 174 * A zoned write may have been requeued with a starting position that 175 * is below that of the most recently dispatched request. Hence, for 176 * zoned writes, start searching from the start of a zone. 177 */ 178 if (blk_rq_is_seq_zoned_write(rq)) 179 pos = round_down(pos, rq->q->limits.chunk_sectors); 180 181 while (node) { 182 rq = rb_entry_rq(node); 183 if (blk_rq_pos(rq) >= pos) { 184 res = rq; 185 node = node->rb_left; 186 } else { 187 node = node->rb_right; 188 } 189 } 190 return res; 191} 192 193static void 194deadline_add_rq_rb(struct dd_per_prio *per_prio, struct request *rq) 195{ 196 struct rb_root *root = deadline_rb_root(per_prio, rq); 197 198 elv_rb_add(root, rq); 199} 200 201static inline void 202deadline_del_rq_rb(struct dd_per_prio *per_prio, struct request *rq) 203{ 204 elv_rb_del(deadline_rb_root(per_prio, rq), rq); 205} 206 207/* 208 * remove rq from rbtree and fifo. 209 */ 210static void deadline_remove_request(struct request_queue *q, 211 struct dd_per_prio *per_prio, 212 struct request *rq) 213{ 214 list_del_init(&rq->queuelist); 215 216 /* 217 * We might not be on the rbtree, if we are doing an insert merge 218 */ 219 if (!RB_EMPTY_NODE(&rq->rb_node)) 220 deadline_del_rq_rb(per_prio, rq); 221 222 elv_rqhash_del(q, rq); 223 if (q->last_merge == rq) 224 q->last_merge = NULL; 225} 226 227static void dd_request_merged(struct request_queue *q, struct request *req, 228 enum elv_merge type) 229{ 230 struct deadline_data *dd = q->elevator->elevator_data; 231 const u8 ioprio_class = dd_rq_ioclass(req); 232 const enum dd_prio prio = ioprio_class_to_prio[ioprio_class]; 233 struct dd_per_prio *per_prio = &dd->per_prio[prio]; 234 235 /* 236 * if the merge was a front merge, we need to reposition request 237 */ 238 if (type == ELEVATOR_FRONT_MERGE) { 239 elv_rb_del(deadline_rb_root(per_prio, req), req); 240 deadline_add_rq_rb(per_prio, req); 241 } 242} 243 244/* 245 * Callback function that is invoked after @next has been merged into @req. 246 */ 247static void dd_merged_requests(struct request_queue *q, struct request *req, 248 struct request *next) 249{ 250 struct deadline_data *dd = q->elevator->elevator_data; 251 const u8 ioprio_class = dd_rq_ioclass(next); 252 const enum dd_prio prio = ioprio_class_to_prio[ioprio_class]; 253 254 lockdep_assert_held(&dd->lock); 255 256 dd->per_prio[prio].stats.merged++; 257 258 /* 259 * if next expires before rq, assign its expire time to rq 260 * and move into next position (next will be deleted) in fifo 261 */ 262 if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) { 263 if (time_before((unsigned long)next->fifo_time, 264 (unsigned long)req->fifo_time)) { 265 list_move(&req->queuelist, &next->queuelist); 266 req->fifo_time = next->fifo_time; 267 } 268 } 269 270 /* 271 * kill knowledge of next, this one is a goner 272 */ 273 deadline_remove_request(q, &dd->per_prio[prio], next); 274} 275 276/* 277 * move an entry to dispatch queue 278 */ 279static void 280deadline_move_request(struct deadline_data *dd, struct dd_per_prio *per_prio, 281 struct request *rq) 282{ 283 /* 284 * take it off the sort and fifo list 285 */ 286 deadline_remove_request(rq->q, per_prio, rq); 287} 288 289/* Number of requests queued for a given priority level. */ 290static u32 dd_queued(struct deadline_data *dd, enum dd_prio prio) 291{ 292 const struct io_stats_per_prio *stats = &dd->per_prio[prio].stats; 293 294 lockdep_assert_held(&dd->lock); 295 296 return stats->inserted - atomic_read(&stats->completed); 297} 298 299/* 300 * deadline_check_fifo returns true if and only if there are expired requests 301 * in the FIFO list. Requires !list_empty(&dd->fifo_list[data_dir]). 302 */ 303static inline bool deadline_check_fifo(struct dd_per_prio *per_prio, 304 enum dd_data_dir data_dir) 305{ 306 struct request *rq = rq_entry_fifo(per_prio->fifo_list[data_dir].next); 307 308 return time_is_before_eq_jiffies((unsigned long)rq->fifo_time); 309} 310 311/* 312 * Check if rq has a sequential request preceding it. 313 */ 314static bool deadline_is_seq_write(struct deadline_data *dd, struct request *rq) 315{ 316 struct request *prev = deadline_earlier_request(rq); 317 318 if (!prev) 319 return false; 320 321 return blk_rq_pos(prev) + blk_rq_sectors(prev) == blk_rq_pos(rq); 322} 323 324/* 325 * Skip all write requests that are sequential from @rq, even if we cross 326 * a zone boundary. 327 */ 328static struct request *deadline_skip_seq_writes(struct deadline_data *dd, 329 struct request *rq) 330{ 331 sector_t pos = blk_rq_pos(rq); 332 333 do { 334 pos += blk_rq_sectors(rq); 335 rq = deadline_latter_request(rq); 336 } while (rq && blk_rq_pos(rq) == pos); 337 338 return rq; 339} 340 341/* 342 * For the specified data direction, return the next request to 343 * dispatch using arrival ordered lists. 344 */ 345static struct request * 346deadline_fifo_request(struct deadline_data *dd, struct dd_per_prio *per_prio, 347 enum dd_data_dir data_dir) 348{ 349 struct request *rq, *rb_rq, *next; 350 unsigned long flags; 351 352 if (list_empty(&per_prio->fifo_list[data_dir])) 353 return NULL; 354 355 rq = rq_entry_fifo(per_prio->fifo_list[data_dir].next); 356 if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q)) 357 return rq; 358 359 /* 360 * Look for a write request that can be dispatched, that is one with 361 * an unlocked target zone. For some HDDs, breaking a sequential 362 * write stream can lead to lower throughput, so make sure to preserve 363 * sequential write streams, even if that stream crosses into the next 364 * zones and these zones are unlocked. 365 */ 366 spin_lock_irqsave(&dd->zone_lock, flags); 367 list_for_each_entry_safe(rq, next, &per_prio->fifo_list[DD_WRITE], 368 queuelist) { 369 /* Check whether a prior request exists for the same zone. */ 370 rb_rq = deadline_from_pos(per_prio, data_dir, blk_rq_pos(rq)); 371 if (rb_rq && blk_rq_pos(rb_rq) < blk_rq_pos(rq)) 372 rq = rb_rq; 373 if (blk_req_can_dispatch_to_zone(rq) && 374 (blk_queue_nonrot(rq->q) || 375 !deadline_is_seq_write(dd, rq))) 376 goto out; 377 } 378 rq = NULL; 379out: 380 spin_unlock_irqrestore(&dd->zone_lock, flags); 381 382 return rq; 383} 384 385/* 386 * For the specified data direction, return the next request to 387 * dispatch using sector position sorted lists. 388 */ 389static struct request * 390deadline_next_request(struct deadline_data *dd, struct dd_per_prio *per_prio, 391 enum dd_data_dir data_dir) 392{ 393 struct request *rq; 394 unsigned long flags; 395 396 rq = deadline_from_pos(per_prio, data_dir, 397 per_prio->latest_pos[data_dir]); 398 if (!rq) 399 return NULL; 400 401 if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q)) 402 return rq; 403 404 /* 405 * Look for a write request that can be dispatched, that is one with 406 * an unlocked target zone. For some HDDs, breaking a sequential 407 * write stream can lead to lower throughput, so make sure to preserve 408 * sequential write streams, even if that stream crosses into the next 409 * zones and these zones are unlocked. 410 */ 411 spin_lock_irqsave(&dd->zone_lock, flags); 412 while (rq) { 413 if (blk_req_can_dispatch_to_zone(rq)) 414 break; 415 if (blk_queue_nonrot(rq->q)) 416 rq = deadline_latter_request(rq); 417 else 418 rq = deadline_skip_seq_writes(dd, rq); 419 } 420 spin_unlock_irqrestore(&dd->zone_lock, flags); 421 422 return rq; 423} 424 425/* 426 * Returns true if and only if @rq started after @latest_start where 427 * @latest_start is in jiffies. 428 */ 429static bool started_after(struct deadline_data *dd, struct request *rq, 430 unsigned long latest_start) 431{ 432 unsigned long start_time = (unsigned long)rq->fifo_time; 433 434 start_time -= dd->fifo_expire[rq_data_dir(rq)]; 435 436 return time_after(start_time, latest_start); 437} 438 439/* 440 * deadline_dispatch_requests selects the best request according to 441 * read/write expire, fifo_batch, etc and with a start time <= @latest_start. 442 */ 443static struct request *__dd_dispatch_request(struct deadline_data *dd, 444 struct dd_per_prio *per_prio, 445 unsigned long latest_start) 446{ 447 struct request *rq, *next_rq; 448 enum dd_data_dir data_dir; 449 enum dd_prio prio; 450 u8 ioprio_class; 451 452 lockdep_assert_held(&dd->lock); 453 454 if (!list_empty(&per_prio->dispatch)) { 455 rq = list_first_entry(&per_prio->dispatch, struct request, 456 queuelist); 457 if (started_after(dd, rq, latest_start)) 458 return NULL; 459 list_del_init(&rq->queuelist); 460 data_dir = rq_data_dir(rq); 461 goto done; 462 } 463 464 /* 465 * batches are currently reads XOR writes 466 */ 467 rq = deadline_next_request(dd, per_prio, dd->last_dir); 468 if (rq && dd->batching < dd->fifo_batch) { 469 /* we have a next request and are still entitled to batch */ 470 data_dir = rq_data_dir(rq); 471 goto dispatch_request; 472 } 473 474 /* 475 * at this point we are not running a batch. select the appropriate 476 * data direction (read / write) 477 */ 478 479 if (!list_empty(&per_prio->fifo_list[DD_READ])) { 480 BUG_ON(RB_EMPTY_ROOT(&per_prio->sort_list[DD_READ])); 481 482 if (deadline_fifo_request(dd, per_prio, DD_WRITE) && 483 (dd->starved++ >= dd->writes_starved)) 484 goto dispatch_writes; 485 486 data_dir = DD_READ; 487 488 goto dispatch_find_request; 489 } 490 491 /* 492 * there are either no reads or writes have been starved 493 */ 494 495 if (!list_empty(&per_prio->fifo_list[DD_WRITE])) { 496dispatch_writes: 497 BUG_ON(RB_EMPTY_ROOT(&per_prio->sort_list[DD_WRITE])); 498 499 dd->starved = 0; 500 501 data_dir = DD_WRITE; 502 503 goto dispatch_find_request; 504 } 505 506 return NULL; 507 508dispatch_find_request: 509 /* 510 * we are not running a batch, find best request for selected data_dir 511 */ 512 next_rq = deadline_next_request(dd, per_prio, data_dir); 513 if (deadline_check_fifo(per_prio, data_dir) || !next_rq) { 514 /* 515 * A deadline has expired, the last request was in the other 516 * direction, or we have run out of higher-sectored requests. 517 * Start again from the request with the earliest expiry time. 518 */ 519 rq = deadline_fifo_request(dd, per_prio, data_dir); 520 } else { 521 /* 522 * The last req was the same dir and we have a next request in 523 * sort order. No expired requests so continue on from here. 524 */ 525 rq = next_rq; 526 } 527 528 /* 529 * For a zoned block device, if we only have writes queued and none of 530 * them can be dispatched, rq will be NULL. 531 */ 532 if (!rq) 533 return NULL; 534 535 dd->last_dir = data_dir; 536 dd->batching = 0; 537 538dispatch_request: 539 if (started_after(dd, rq, latest_start)) 540 return NULL; 541 542 /* 543 * rq is the selected appropriate request. 544 */ 545 dd->batching++; 546 deadline_move_request(dd, per_prio, rq); 547done: 548 ioprio_class = dd_rq_ioclass(rq); 549 prio = ioprio_class_to_prio[ioprio_class]; 550 dd->per_prio[prio].latest_pos[data_dir] = blk_rq_pos(rq); 551 dd->per_prio[prio].stats.dispatched++; 552 /* 553 * If the request needs its target zone locked, do it. 554 */ 555 blk_req_zone_write_lock(rq); 556 rq->rq_flags |= RQF_STARTED; 557 return rq; 558} 559 560/* 561 * Check whether there are any requests with priority other than DD_RT_PRIO 562 * that were inserted more than prio_aging_expire jiffies ago. 563 */ 564static struct request *dd_dispatch_prio_aged_requests(struct deadline_data *dd, 565 unsigned long now) 566{ 567 struct request *rq; 568 enum dd_prio prio; 569 int prio_cnt; 570 571 lockdep_assert_held(&dd->lock); 572 573 prio_cnt = !!dd_queued(dd, DD_RT_PRIO) + !!dd_queued(dd, DD_BE_PRIO) + 574 !!dd_queued(dd, DD_IDLE_PRIO); 575 if (prio_cnt < 2) 576 return NULL; 577 578 for (prio = DD_BE_PRIO; prio <= DD_PRIO_MAX; prio++) { 579 rq = __dd_dispatch_request(dd, &dd->per_prio[prio], 580 now - dd->prio_aging_expire); 581 if (rq) 582 return rq; 583 } 584 585 return NULL; 586} 587 588/* 589 * Called from blk_mq_run_hw_queue() -> __blk_mq_sched_dispatch_requests(). 590 * 591 * One confusing aspect here is that we get called for a specific 592 * hardware queue, but we may return a request that is for a 593 * different hardware queue. This is because mq-deadline has shared 594 * state for all hardware queues, in terms of sorting, FIFOs, etc. 595 */ 596static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx) 597{ 598 struct deadline_data *dd = hctx->queue->elevator->elevator_data; 599 const unsigned long now = jiffies; 600 struct request *rq; 601 enum dd_prio prio; 602 603 spin_lock(&dd->lock); 604 rq = dd_dispatch_prio_aged_requests(dd, now); 605 if (rq) 606 goto unlock; 607 608 /* 609 * Next, dispatch requests in priority order. Ignore lower priority 610 * requests if any higher priority requests are pending. 611 */ 612 for (prio = 0; prio <= DD_PRIO_MAX; prio++) { 613 rq = __dd_dispatch_request(dd, &dd->per_prio[prio], now); 614 if (rq || dd_queued(dd, prio)) 615 break; 616 } 617 618unlock: 619 spin_unlock(&dd->lock); 620 621 return rq; 622} 623 624/* 625 * Called by __blk_mq_alloc_request(). The shallow_depth value set by this 626 * function is used by __blk_mq_get_tag(). 627 */ 628static void dd_limit_depth(blk_opf_t opf, struct blk_mq_alloc_data *data) 629{ 630 struct deadline_data *dd = data->q->elevator->elevator_data; 631 632 /* Do not throttle synchronous reads. */ 633 if (op_is_sync(opf) && !op_is_write(opf)) 634 return; 635 636 /* 637 * Throttle asynchronous requests and writes such that these requests 638 * do not block the allocation of synchronous requests. 639 */ 640 data->shallow_depth = dd->async_depth; 641} 642 643/* Called by blk_mq_update_nr_requests(). */ 644static void dd_depth_updated(struct blk_mq_hw_ctx *hctx) 645{ 646 struct request_queue *q = hctx->queue; 647 struct deadline_data *dd = q->elevator->elevator_data; 648 struct blk_mq_tags *tags = hctx->sched_tags; 649 650 dd->async_depth = max(1UL, 3 * q->nr_requests / 4); 651 652 sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, dd->async_depth); 653} 654 655/* Called by blk_mq_init_hctx() and blk_mq_init_sched(). */ 656static int dd_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx) 657{ 658 dd_depth_updated(hctx); 659 return 0; 660} 661 662static void dd_exit_sched(struct elevator_queue *e) 663{ 664 struct deadline_data *dd = e->elevator_data; 665 enum dd_prio prio; 666 667 for (prio = 0; prio <= DD_PRIO_MAX; prio++) { 668 struct dd_per_prio *per_prio = &dd->per_prio[prio]; 669 const struct io_stats_per_prio *stats = &per_prio->stats; 670 uint32_t queued; 671 672 WARN_ON_ONCE(!list_empty(&per_prio->fifo_list[DD_READ])); 673 WARN_ON_ONCE(!list_empty(&per_prio->fifo_list[DD_WRITE])); 674 675 spin_lock(&dd->lock); 676 queued = dd_queued(dd, prio); 677 spin_unlock(&dd->lock); 678 679 WARN_ONCE(queued != 0, 680 "statistics for priority %d: i %u m %u d %u c %u\n", 681 prio, stats->inserted, stats->merged, 682 stats->dispatched, atomic_read(&stats->completed)); 683 } 684 685 kfree(dd); 686} 687 688/* 689 * initialize elevator private data (deadline_data). 690 */ 691static int dd_init_sched(struct request_queue *q, struct elevator_type *e) 692{ 693 struct deadline_data *dd; 694 struct elevator_queue *eq; 695 enum dd_prio prio; 696 int ret = -ENOMEM; 697 698 eq = elevator_alloc(q, e); 699 if (!eq) 700 return ret; 701 702 dd = kzalloc_node(sizeof(*dd), GFP_KERNEL, q->node); 703 if (!dd) 704 goto put_eq; 705 706 eq->elevator_data = dd; 707 708 for (prio = 0; prio <= DD_PRIO_MAX; prio++) { 709 struct dd_per_prio *per_prio = &dd->per_prio[prio]; 710 711 INIT_LIST_HEAD(&per_prio->dispatch); 712 INIT_LIST_HEAD(&per_prio->fifo_list[DD_READ]); 713 INIT_LIST_HEAD(&per_prio->fifo_list[DD_WRITE]); 714 per_prio->sort_list[DD_READ] = RB_ROOT; 715 per_prio->sort_list[DD_WRITE] = RB_ROOT; 716 } 717 dd->fifo_expire[DD_READ] = read_expire; 718 dd->fifo_expire[DD_WRITE] = write_expire; 719 dd->writes_starved = writes_starved; 720 dd->front_merges = 1; 721 dd->last_dir = DD_WRITE; 722 dd->fifo_batch = fifo_batch; 723 dd->prio_aging_expire = prio_aging_expire; 724 spin_lock_init(&dd->lock); 725 spin_lock_init(&dd->zone_lock); 726 727 /* We dispatch from request queue wide instead of hw queue */ 728 blk_queue_flag_set(QUEUE_FLAG_SQ_SCHED, q); 729 730 q->elevator = eq; 731 return 0; 732 733put_eq: 734 kobject_put(&eq->kobj); 735 return ret; 736} 737 738/* 739 * Try to merge @bio into an existing request. If @bio has been merged into 740 * an existing request, store the pointer to that request into *@rq. 741 */ 742static int dd_request_merge(struct request_queue *q, struct request **rq, 743 struct bio *bio) 744{ 745 struct deadline_data *dd = q->elevator->elevator_data; 746 const u8 ioprio_class = IOPRIO_PRIO_CLASS(bio->bi_ioprio); 747 const enum dd_prio prio = ioprio_class_to_prio[ioprio_class]; 748 struct dd_per_prio *per_prio = &dd->per_prio[prio]; 749 sector_t sector = bio_end_sector(bio); 750 struct request *__rq; 751 752 if (!dd->front_merges) 753 return ELEVATOR_NO_MERGE; 754 755 __rq = elv_rb_find(&per_prio->sort_list[bio_data_dir(bio)], sector); 756 if (__rq) { 757 BUG_ON(sector != blk_rq_pos(__rq)); 758 759 if (elv_bio_merge_ok(__rq, bio)) { 760 *rq = __rq; 761 if (blk_discard_mergable(__rq)) 762 return ELEVATOR_DISCARD_MERGE; 763 return ELEVATOR_FRONT_MERGE; 764 } 765 } 766 767 return ELEVATOR_NO_MERGE; 768} 769 770/* 771 * Attempt to merge a bio into an existing request. This function is called 772 * before @bio is associated with a request. 773 */ 774static bool dd_bio_merge(struct request_queue *q, struct bio *bio, 775 unsigned int nr_segs) 776{ 777 struct deadline_data *dd = q->elevator->elevator_data; 778 struct request *free = NULL; 779 bool ret; 780 781 spin_lock(&dd->lock); 782 ret = blk_mq_sched_try_merge(q, bio, nr_segs, &free); 783 spin_unlock(&dd->lock); 784 785 if (free) 786 blk_mq_free_request(free); 787 788 return ret; 789} 790 791/* 792 * add rq to rbtree and fifo 793 */ 794static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, 795 blk_insert_t flags, struct list_head *free) 796{ 797 struct request_queue *q = hctx->queue; 798 struct deadline_data *dd = q->elevator->elevator_data; 799 const enum dd_data_dir data_dir = rq_data_dir(rq); 800 u16 ioprio = req_get_ioprio(rq); 801 u8 ioprio_class = IOPRIO_PRIO_CLASS(ioprio); 802 struct dd_per_prio *per_prio; 803 enum dd_prio prio; 804 805 lockdep_assert_held(&dd->lock); 806 807 /* 808 * This may be a requeue of a write request that has locked its 809 * target zone. If it is the case, this releases the zone lock. 810 */ 811 blk_req_zone_write_unlock(rq); 812 813 prio = ioprio_class_to_prio[ioprio_class]; 814 per_prio = &dd->per_prio[prio]; 815 if (!rq->elv.priv[0]) { 816 per_prio->stats.inserted++; 817 rq->elv.priv[0] = (void *)(uintptr_t)1; 818 } 819 820 if (blk_mq_sched_try_insert_merge(q, rq, free)) 821 return; 822 823 trace_block_rq_insert(rq); 824 825 if (flags & BLK_MQ_INSERT_AT_HEAD) { 826 list_add(&rq->queuelist, &per_prio->dispatch); 827 rq->fifo_time = jiffies; 828 } else { 829 struct list_head *insert_before; 830 831 deadline_add_rq_rb(per_prio, rq); 832 833 if (rq_mergeable(rq)) { 834 elv_rqhash_add(q, rq); 835 if (!q->last_merge) 836 q->last_merge = rq; 837 } 838 839 /* 840 * set expire time and add to fifo list 841 */ 842 rq->fifo_time = jiffies + dd->fifo_expire[data_dir]; 843 insert_before = &per_prio->fifo_list[data_dir]; 844#ifdef CONFIG_BLK_DEV_ZONED 845 /* 846 * Insert zoned writes such that requests are sorted by 847 * position per zone. 848 */ 849 if (blk_rq_is_seq_zoned_write(rq)) { 850 struct request *rq2 = deadline_latter_request(rq); 851 852 if (rq2 && blk_rq_zone_no(rq2) == blk_rq_zone_no(rq)) 853 insert_before = &rq2->queuelist; 854 } 855#endif 856 list_add_tail(&rq->queuelist, insert_before); 857 } 858} 859 860/* 861 * Called from blk_mq_insert_request() or blk_mq_dispatch_plug_list(). 862 */ 863static void dd_insert_requests(struct blk_mq_hw_ctx *hctx, 864 struct list_head *list, 865 blk_insert_t flags) 866{ 867 struct request_queue *q = hctx->queue; 868 struct deadline_data *dd = q->elevator->elevator_data; 869 LIST_HEAD(free); 870 871 spin_lock(&dd->lock); 872 while (!list_empty(list)) { 873 struct request *rq; 874 875 rq = list_first_entry(list, struct request, queuelist); 876 list_del_init(&rq->queuelist); 877 dd_insert_request(hctx, rq, flags, &free); 878 } 879 spin_unlock(&dd->lock); 880 881 blk_mq_free_requests(&free); 882} 883 884/* Callback from inside blk_mq_rq_ctx_init(). */ 885static void dd_prepare_request(struct request *rq) 886{ 887 rq->elv.priv[0] = NULL; 888} 889 890static bool dd_has_write_work(struct blk_mq_hw_ctx *hctx) 891{ 892 struct deadline_data *dd = hctx->queue->elevator->elevator_data; 893 enum dd_prio p; 894 895 for (p = 0; p <= DD_PRIO_MAX; p++) 896 if (!list_empty_careful(&dd->per_prio[p].fifo_list[DD_WRITE])) 897 return true; 898 899 return false; 900} 901 902/* 903 * Callback from inside blk_mq_free_request(). 904 * 905 * For zoned block devices, write unlock the target zone of 906 * completed write requests. Do this while holding the zone lock 907 * spinlock so that the zone is never unlocked while deadline_fifo_request() 908 * or deadline_next_request() are executing. This function is called for 909 * all requests, whether or not these requests complete successfully. 910 * 911 * For a zoned block device, __dd_dispatch_request() may have stopped 912 * dispatching requests if all the queued requests are write requests directed 913 * at zones that are already locked due to on-going write requests. To ensure 914 * write request dispatch progress in this case, mark the queue as needing a 915 * restart to ensure that the queue is run again after completion of the 916 * request and zones being unlocked. 917 */ 918static void dd_finish_request(struct request *rq) 919{ 920 struct request_queue *q = rq->q; 921 struct deadline_data *dd = q->elevator->elevator_data; 922 const u8 ioprio_class = dd_rq_ioclass(rq); 923 const enum dd_prio prio = ioprio_class_to_prio[ioprio_class]; 924 struct dd_per_prio *per_prio = &dd->per_prio[prio]; 925 926 /* 927 * The block layer core may call dd_finish_request() without having 928 * called dd_insert_requests(). Skip requests that bypassed I/O 929 * scheduling. See also blk_mq_request_bypass_insert(). 930 */ 931 if (!rq->elv.priv[0]) 932 return; 933 934 atomic_inc(&per_prio->stats.completed); 935 936 if (blk_queue_is_zoned(q)) { 937 unsigned long flags; 938 939 spin_lock_irqsave(&dd->zone_lock, flags); 940 blk_req_zone_write_unlock(rq); 941 spin_unlock_irqrestore(&dd->zone_lock, flags); 942 943 if (dd_has_write_work(rq->mq_hctx)) 944 blk_mq_sched_mark_restart_hctx(rq->mq_hctx); 945 } 946} 947 948static bool dd_has_work_for_prio(struct dd_per_prio *per_prio) 949{ 950 return !list_empty_careful(&per_prio->dispatch) || 951 !list_empty_careful(&per_prio->fifo_list[DD_READ]) || 952 !list_empty_careful(&per_prio->fifo_list[DD_WRITE]); 953} 954 955static bool dd_has_work(struct blk_mq_hw_ctx *hctx) 956{ 957 struct deadline_data *dd = hctx->queue->elevator->elevator_data; 958 enum dd_prio prio; 959 960 for (prio = 0; prio <= DD_PRIO_MAX; prio++) 961 if (dd_has_work_for_prio(&dd->per_prio[prio])) 962 return true; 963 964 return false; 965} 966 967/* 968 * sysfs parts below 969 */ 970#define SHOW_INT(__FUNC, __VAR) \ 971static ssize_t __FUNC(struct elevator_queue *e, char *page) \ 972{ \ 973 struct deadline_data *dd = e->elevator_data; \ 974 \ 975 return sysfs_emit(page, "%d\n", __VAR); \ 976} 977#define SHOW_JIFFIES(__FUNC, __VAR) SHOW_INT(__FUNC, jiffies_to_msecs(__VAR)) 978SHOW_JIFFIES(deadline_read_expire_show, dd->fifo_expire[DD_READ]); 979SHOW_JIFFIES(deadline_write_expire_show, dd->fifo_expire[DD_WRITE]); 980SHOW_JIFFIES(deadline_prio_aging_expire_show, dd->prio_aging_expire); 981SHOW_INT(deadline_writes_starved_show, dd->writes_starved); 982SHOW_INT(deadline_front_merges_show, dd->front_merges); 983SHOW_INT(deadline_async_depth_show, dd->async_depth); 984SHOW_INT(deadline_fifo_batch_show, dd->fifo_batch); 985#undef SHOW_INT 986#undef SHOW_JIFFIES 987 988#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ 989static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ 990{ \ 991 struct deadline_data *dd = e->elevator_data; \ 992 int __data, __ret; \ 993 \ 994 __ret = kstrtoint(page, 0, &__data); \ 995 if (__ret < 0) \ 996 return __ret; \ 997 if (__data < (MIN)) \ 998 __data = (MIN); \ 999 else if (__data > (MAX)) \ 1000 __data = (MAX); \ 1001 *(__PTR) = __CONV(__data); \ 1002 return count; \ 1003} 1004#define STORE_INT(__FUNC, __PTR, MIN, MAX) \ 1005 STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, ) 1006#define STORE_JIFFIES(__FUNC, __PTR, MIN, MAX) \ 1007 STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, msecs_to_jiffies) 1008STORE_JIFFIES(deadline_read_expire_store, &dd->fifo_expire[DD_READ], 0, INT_MAX); 1009STORE_JIFFIES(deadline_write_expire_store, &dd->fifo_expire[DD_WRITE], 0, INT_MAX); 1010STORE_JIFFIES(deadline_prio_aging_expire_store, &dd->prio_aging_expire, 0, INT_MAX); 1011STORE_INT(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX); 1012STORE_INT(deadline_front_merges_store, &dd->front_merges, 0, 1); 1013STORE_INT(deadline_async_depth_store, &dd->async_depth, 1, INT_MAX); 1014STORE_INT(deadline_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX); 1015#undef STORE_FUNCTION 1016#undef STORE_INT 1017#undef STORE_JIFFIES 1018 1019#define DD_ATTR(name) \ 1020 __ATTR(name, 0644, deadline_##name##_show, deadline_##name##_store) 1021 1022static struct elv_fs_entry deadline_attrs[] = { 1023 DD_ATTR(read_expire), 1024 DD_ATTR(write_expire), 1025 DD_ATTR(writes_starved), 1026 DD_ATTR(front_merges), 1027 DD_ATTR(async_depth), 1028 DD_ATTR(fifo_batch), 1029 DD_ATTR(prio_aging_expire), 1030 __ATTR_NULL 1031}; 1032 1033#ifdef CONFIG_BLK_DEBUG_FS 1034#define DEADLINE_DEBUGFS_DDIR_ATTRS(prio, data_dir, name) \ 1035static void *deadline_##name##_fifo_start(struct seq_file *m, \ 1036 loff_t *pos) \ 1037 __acquires(&dd->lock) \ 1038{ \ 1039 struct request_queue *q = m->private; \ 1040 struct deadline_data *dd = q->elevator->elevator_data; \ 1041 struct dd_per_prio *per_prio = &dd->per_prio[prio]; \ 1042 \ 1043 spin_lock(&dd->lock); \ 1044 return seq_list_start(&per_prio->fifo_list[data_dir], *pos); \ 1045} \ 1046 \ 1047static void *deadline_##name##_fifo_next(struct seq_file *m, void *v, \ 1048 loff_t *pos) \ 1049{ \ 1050 struct request_queue *q = m->private; \ 1051 struct deadline_data *dd = q->elevator->elevator_data; \ 1052 struct dd_per_prio *per_prio = &dd->per_prio[prio]; \ 1053 \ 1054 return seq_list_next(v, &per_prio->fifo_list[data_dir], pos); \ 1055} \ 1056 \ 1057static void deadline_##name##_fifo_stop(struct seq_file *m, void *v) \ 1058 __releases(&dd->lock) \ 1059{ \ 1060 struct request_queue *q = m->private; \ 1061 struct deadline_data *dd = q->elevator->elevator_data; \ 1062 \ 1063 spin_unlock(&dd->lock); \ 1064} \ 1065 \ 1066static const struct seq_operations deadline_##name##_fifo_seq_ops = { \ 1067 .start = deadline_##name##_fifo_start, \ 1068 .next = deadline_##name##_fifo_next, \ 1069 .stop = deadline_##name##_fifo_stop, \ 1070 .show = blk_mq_debugfs_rq_show, \ 1071}; \ 1072 \ 1073static int deadline_##name##_next_rq_show(void *data, \ 1074 struct seq_file *m) \ 1075{ \ 1076 struct request_queue *q = data; \ 1077 struct deadline_data *dd = q->elevator->elevator_data; \ 1078 struct dd_per_prio *per_prio = &dd->per_prio[prio]; \ 1079 struct request *rq; \ 1080 \ 1081 rq = deadline_from_pos(per_prio, data_dir, \ 1082 per_prio->latest_pos[data_dir]); \ 1083 if (rq) \ 1084 __blk_mq_debugfs_rq_show(m, rq); \ 1085 return 0; \ 1086} 1087 1088DEADLINE_DEBUGFS_DDIR_ATTRS(DD_RT_PRIO, DD_READ, read0); 1089DEADLINE_DEBUGFS_DDIR_ATTRS(DD_RT_PRIO, DD_WRITE, write0); 1090DEADLINE_DEBUGFS_DDIR_ATTRS(DD_BE_PRIO, DD_READ, read1); 1091DEADLINE_DEBUGFS_DDIR_ATTRS(DD_BE_PRIO, DD_WRITE, write1); 1092DEADLINE_DEBUGFS_DDIR_ATTRS(DD_IDLE_PRIO, DD_READ, read2); 1093DEADLINE_DEBUGFS_DDIR_ATTRS(DD_IDLE_PRIO, DD_WRITE, write2); 1094#undef DEADLINE_DEBUGFS_DDIR_ATTRS 1095 1096static int deadline_batching_show(void *data, struct seq_file *m) 1097{ 1098 struct request_queue *q = data; 1099 struct deadline_data *dd = q->elevator->elevator_data; 1100 1101 seq_printf(m, "%u\n", dd->batching); 1102 return 0; 1103} 1104 1105static int deadline_starved_show(void *data, struct seq_file *m) 1106{ 1107 struct request_queue *q = data; 1108 struct deadline_data *dd = q->elevator->elevator_data; 1109 1110 seq_printf(m, "%u\n", dd->starved); 1111 return 0; 1112} 1113 1114static int dd_async_depth_show(void *data, struct seq_file *m) 1115{ 1116 struct request_queue *q = data; 1117 struct deadline_data *dd = q->elevator->elevator_data; 1118 1119 seq_printf(m, "%u\n", dd->async_depth); 1120 return 0; 1121} 1122 1123static int dd_queued_show(void *data, struct seq_file *m) 1124{ 1125 struct request_queue *q = data; 1126 struct deadline_data *dd = q->elevator->elevator_data; 1127 u32 rt, be, idle; 1128 1129 spin_lock(&dd->lock); 1130 rt = dd_queued(dd, DD_RT_PRIO); 1131 be = dd_queued(dd, DD_BE_PRIO); 1132 idle = dd_queued(dd, DD_IDLE_PRIO); 1133 spin_unlock(&dd->lock); 1134 1135 seq_printf(m, "%u %u %u\n", rt, be, idle); 1136 1137 return 0; 1138} 1139 1140/* Number of requests owned by the block driver for a given priority. */ 1141static u32 dd_owned_by_driver(struct deadline_data *dd, enum dd_prio prio) 1142{ 1143 const struct io_stats_per_prio *stats = &dd->per_prio[prio].stats; 1144 1145 lockdep_assert_held(&dd->lock); 1146 1147 return stats->dispatched + stats->merged - 1148 atomic_read(&stats->completed); 1149} 1150 1151static int dd_owned_by_driver_show(void *data, struct seq_file *m) 1152{ 1153 struct request_queue *q = data; 1154 struct deadline_data *dd = q->elevator->elevator_data; 1155 u32 rt, be, idle; 1156 1157 spin_lock(&dd->lock); 1158 rt = dd_owned_by_driver(dd, DD_RT_PRIO); 1159 be = dd_owned_by_driver(dd, DD_BE_PRIO); 1160 idle = dd_owned_by_driver(dd, DD_IDLE_PRIO); 1161 spin_unlock(&dd->lock); 1162 1163 seq_printf(m, "%u %u %u\n", rt, be, idle); 1164 1165 return 0; 1166} 1167 1168#define DEADLINE_DISPATCH_ATTR(prio) \ 1169static void *deadline_dispatch##prio##_start(struct seq_file *m, \ 1170 loff_t *pos) \ 1171 __acquires(&dd->lock) \ 1172{ \ 1173 struct request_queue *q = m->private; \ 1174 struct deadline_data *dd = q->elevator->elevator_data; \ 1175 struct dd_per_prio *per_prio = &dd->per_prio[prio]; \ 1176 \ 1177 spin_lock(&dd->lock); \ 1178 return seq_list_start(&per_prio->dispatch, *pos); \ 1179} \ 1180 \ 1181static void *deadline_dispatch##prio##_next(struct seq_file *m, \ 1182 void *v, loff_t *pos) \ 1183{ \ 1184 struct request_queue *q = m->private; \ 1185 struct deadline_data *dd = q->elevator->elevator_data; \ 1186 struct dd_per_prio *per_prio = &dd->per_prio[prio]; \ 1187 \ 1188 return seq_list_next(v, &per_prio->dispatch, pos); \ 1189} \ 1190 \ 1191static void deadline_dispatch##prio##_stop(struct seq_file *m, void *v) \ 1192 __releases(&dd->lock) \ 1193{ \ 1194 struct request_queue *q = m->private; \ 1195 struct deadline_data *dd = q->elevator->elevator_data; \ 1196 \ 1197 spin_unlock(&dd->lock); \ 1198} \ 1199 \ 1200static const struct seq_operations deadline_dispatch##prio##_seq_ops = { \ 1201 .start = deadline_dispatch##prio##_start, \ 1202 .next = deadline_dispatch##prio##_next, \ 1203 .stop = deadline_dispatch##prio##_stop, \ 1204 .show = blk_mq_debugfs_rq_show, \ 1205} 1206 1207DEADLINE_DISPATCH_ATTR(0); 1208DEADLINE_DISPATCH_ATTR(1); 1209DEADLINE_DISPATCH_ATTR(2); 1210#undef DEADLINE_DISPATCH_ATTR 1211 1212#define DEADLINE_QUEUE_DDIR_ATTRS(name) \ 1213 {#name "_fifo_list", 0400, \ 1214 .seq_ops = &deadline_##name##_fifo_seq_ops} 1215#define DEADLINE_NEXT_RQ_ATTR(name) \ 1216 {#name "_next_rq", 0400, deadline_##name##_next_rq_show} 1217static const struct blk_mq_debugfs_attr deadline_queue_debugfs_attrs[] = { 1218 DEADLINE_QUEUE_DDIR_ATTRS(read0), 1219 DEADLINE_QUEUE_DDIR_ATTRS(write0), 1220 DEADLINE_QUEUE_DDIR_ATTRS(read1), 1221 DEADLINE_QUEUE_DDIR_ATTRS(write1), 1222 DEADLINE_QUEUE_DDIR_ATTRS(read2), 1223 DEADLINE_QUEUE_DDIR_ATTRS(write2), 1224 DEADLINE_NEXT_RQ_ATTR(read0), 1225 DEADLINE_NEXT_RQ_ATTR(write0), 1226 DEADLINE_NEXT_RQ_ATTR(read1), 1227 DEADLINE_NEXT_RQ_ATTR(write1), 1228 DEADLINE_NEXT_RQ_ATTR(read2), 1229 DEADLINE_NEXT_RQ_ATTR(write2), 1230 {"batching", 0400, deadline_batching_show}, 1231 {"starved", 0400, deadline_starved_show}, 1232 {"async_depth", 0400, dd_async_depth_show}, 1233 {"dispatch0", 0400, .seq_ops = &deadline_dispatch0_seq_ops}, 1234 {"dispatch1", 0400, .seq_ops = &deadline_dispatch1_seq_ops}, 1235 {"dispatch2", 0400, .seq_ops = &deadline_dispatch2_seq_ops}, 1236 {"owned_by_driver", 0400, dd_owned_by_driver_show}, 1237 {"queued", 0400, dd_queued_show}, 1238 {}, 1239}; 1240#undef DEADLINE_QUEUE_DDIR_ATTRS 1241#endif 1242 1243static struct elevator_type mq_deadline = { 1244 .ops = { 1245 .depth_updated = dd_depth_updated, 1246 .limit_depth = dd_limit_depth, 1247 .insert_requests = dd_insert_requests, 1248 .dispatch_request = dd_dispatch_request, 1249 .prepare_request = dd_prepare_request, 1250 .finish_request = dd_finish_request, 1251 .next_request = elv_rb_latter_request, 1252 .former_request = elv_rb_former_request, 1253 .bio_merge = dd_bio_merge, 1254 .request_merge = dd_request_merge, 1255 .requests_merged = dd_merged_requests, 1256 .request_merged = dd_request_merged, 1257 .has_work = dd_has_work, 1258 .init_sched = dd_init_sched, 1259 .exit_sched = dd_exit_sched, 1260 .init_hctx = dd_init_hctx, 1261 }, 1262 1263#ifdef CONFIG_BLK_DEBUG_FS 1264 .queue_debugfs_attrs = deadline_queue_debugfs_attrs, 1265#endif 1266 .elevator_attrs = deadline_attrs, 1267 .elevator_name = "mq-deadline", 1268 .elevator_alias = "deadline", 1269 .elevator_features = ELEVATOR_F_ZBD_SEQ_WRITE, 1270 .elevator_owner = THIS_MODULE, 1271}; 1272MODULE_ALIAS("mq-deadline-iosched"); 1273 1274static int __init deadline_init(void) 1275{ 1276 return elv_register(&mq_deadline); 1277} 1278 1279static void __exit deadline_exit(void) 1280{ 1281 elv_unregister(&mq_deadline); 1282} 1283 1284module_init(deadline_init); 1285module_exit(deadline_exit); 1286 1287MODULE_AUTHOR("Jens Axboe, Damien Le Moal and Bart Van Assche"); 1288MODULE_LICENSE("GPL"); 1289MODULE_DESCRIPTION("MQ deadline IO scheduler"); 1290