block/blk-mq-sched.c

   1 /*
   2  * blk-mq scheduling framework
   3  *
   4  * Copyright (C) 2016 Jens Axboe
   5  */
   6 #include <linux/kernel.h>
   7 #include <linux/module.h>
   8 #include <linux/blk-mq.h>
   9
  10 #include <trace/events/block.h>
  11
  12 #include "blk.h"
  13 #include "blk-mq.h"
  14 #include "blk-mq-debugfs.h"
  15 #include "blk-mq-sched.h"
  16 #include "blk-mq-tag.h"
  17 #include "blk-wbt.h"
  18
  19 void blk_mq_sched_free_hctx_data(struct request_queue *q,
  20                                  void (*exit)(struct blk_mq_hw_ctx *))
  21 {
  22         struct blk_mq_hw_ctx *hctx;
  23         int i;
  24
  25         queue_for_each_hw_ctx(q, hctx, i) {
  26                 if (exit && hctx->sched_data)
  27                         exit(hctx);
  28                 kfree(hctx->sched_data);
  29                 hctx->sched_data = NULL;
  30         }
  31 }
  32 EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
  33
  34 static void __blk_mq_sched_assign_ioc(struct request_queue *q,
  35                                       struct request *rq,
  36                                       struct bio *bio,
  37                                       struct io_context *ioc)
  38 {
  39         struct io_cq *icq;
  40
  41         spin_lock_irq(q->queue_lock);
  42         icq = ioc_lookup_icq(ioc, q);
  43         spin_unlock_irq(q->queue_lock);
  44
  45         if (!icq) {
  46                 icq = ioc_create_icq(ioc, q, GFP_ATOMIC);
  47                 if (!icq)
  48                         return;
  49         }
  50
  51         rq->elv.icq = icq;
  52         if (!blk_mq_sched_get_rq_priv(q, rq, bio)) {
  53                 rq->rq_flags |= RQF_ELVPRIV;
  54                 get_io_context(icq->ioc);
  55                 return;
  56         }
  57
  58         rq->elv.icq = NULL;
  59 }
  60
  61 static void blk_mq_sched_assign_ioc(struct request_queue *q,
  62                                     struct request *rq, struct bio *bio)
  63 {
  64         struct io_context *ioc;
  65
  66         ioc = rq_ioc(bio);
  67         if (ioc)
  68                 __blk_mq_sched_assign_ioc(q, rq, bio, ioc);
  69 }
  70
  71 /*
  72  * Mark a hardware queue as needing a restart. For shared queues, maintain
  73  * a count of how many hardware queues are marked for restart.
  74  */
  75 static void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx)
  76 {
  77         if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
  78                 return;
  79
  80         if (hctx->flags & BLK_MQ_F_TAG_SHARED) {
  81                 struct request_queue *q = hctx->queue;
  82
  83                 if (!test_and_set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
  84                         atomic_inc(&q->shared_hctx_restart);
  85         } else
  86                 set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
  87 }
  88
  89 static bool blk_mq_sched_restart_hctx(struct blk_mq_hw_ctx *hctx)
  90 {
  91         if (!test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
  92                 return false;
  93
  94         if (hctx->flags & BLK_MQ_F_TAG_SHARED) {
  95                 struct request_queue *q = hctx->queue;
  96
  97                 if (test_and_clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
  98                         atomic_dec(&q->shared_hctx_restart);
  99         } else
 100                 clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
 101
 102         if (blk_mq_hctx_has_pending(hctx)) {
 103                 blk_mq_run_hw_queue(hctx, true);
 104                 return true;
 105         }
 106
 107         return false;
 108 }
 109
 110 struct request *blk_mq_sched_get_request(struct request_queue *q,
 111                                          struct bio *bio,
 112                                          unsigned int op,
 113                                          struct blk_mq_alloc_data *data)
 114 {
 115         struct elevator_queue *e = q->elevator;
 116         struct request *rq;
 117
 118         blk_queue_enter_live(q);
 119         data->q = q;
 120         if (likely(!data->ctx))
 121                 data->ctx = blk_mq_get_ctx(q);
 122         if (likely(!data->hctx))
 123                 data->hctx = blk_mq_map_queue(q, data->ctx->cpu);
 124
 125         if (e) {
 126                 data->flags |= BLK_MQ_REQ_INTERNAL;
 127
 128                 /*
 129                  * Flush requests are special and go directly to the
 130                  * dispatch list.
 131                  */
 132                 if (!op_is_flush(op) && e->type->ops.mq.get_request) {
 133                         rq = e->type->ops.mq.get_request(q, op, data);
 134                         if (rq)
 135                                 rq->rq_flags |= RQF_QUEUED;
 136                 } else
 137                         rq = __blk_mq_alloc_request(data, op);
 138         } else {
 139                 rq = __blk_mq_alloc_request(data, op);
 140         }
 141
 142         if (rq) {
 143                 if (!op_is_flush(op)) {
 144                         rq->elv.icq = NULL;
 145                         if (e && e->type->icq_cache)
 146                                 blk_mq_sched_assign_ioc(q, rq, bio);
 147                 }
 148                 data->hctx->queued++;
 149                 return rq;
 150         }
 151
 152         blk_queue_exit(q);
 153         return NULL;
 154 }
 155
 156 void blk_mq_sched_put_request(struct request *rq)
 157 {
 158         struct request_queue *q = rq->q;
 159         struct elevator_queue *e = q->elevator;
 160
 161         if (rq->rq_flags & RQF_ELVPRIV) {
 162                 blk_mq_sched_put_rq_priv(rq->q, rq);
 163                 if (rq->elv.icq) {
 164                         put_io_context(rq->elv.icq->ioc);
 165                         rq->elv.icq = NULL;
 166                 }
 167         }
 168
 169         if ((rq->rq_flags & RQF_QUEUED) && e && e->type->ops.mq.put_request)
 170                 e->type->ops.mq.put_request(rq);
 171         else
 172                 blk_mq_finish_request(rq);
 173 }
 174
 175 void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
 176 {
 177         struct request_queue *q = hctx->queue;
 178         struct elevator_queue *e = q->elevator;
 179         const bool has_sched_dispatch = e && e->type->ops.mq.dispatch_request;
 180         bool did_work = false;
 181         LIST_HEAD(rq_list);
 182
 183         if (unlikely(blk_mq_hctx_stopped(hctx)))
 184                 return;
 185
 186         hctx->run++;
 187
 188         /*
 189          * If we have previous entries on our dispatch list, grab them first for
 190          * more fair dispatch.
 191          */
 192         if (!list_empty_careful(&hctx->dispatch)) {
 193                 spin_lock(&hctx->lock);
 194                 if (!list_empty(&hctx->dispatch))
 195                         list_splice_init(&hctx->dispatch, &rq_list);
 196                 spin_unlock(&hctx->lock);
 197         }
 198
 199         /*
 200          * Only ask the scheduler for requests, if we didn't have residual
 201          * requests from the dispatch list. This is to avoid the case where
 202          * we only ever dispatch a fraction of the requests available because
 203          * of low device queue depth. Once we pull requests out of the IO
 204          * scheduler, we can no longer merge or sort them. So it's best to
 205          * leave them there for as long as we can. Mark the hw queue as
 206          * needing a restart in that case.
 207          */
 208         if (!list_empty(&rq_list)) {
 209                 blk_mq_sched_mark_restart_hctx(hctx);
 210                 did_work = blk_mq_dispatch_rq_list(q, &rq_list);
 211         } else if (!has_sched_dispatch) {
 212                 blk_mq_flush_busy_ctxs(hctx, &rq_list);
 213                 blk_mq_dispatch_rq_list(q, &rq_list);
 214         }
 215
 216         /*
 217          * We want to dispatch from the scheduler if we had no work left
 218          * on the dispatch list, OR if we did have work but weren't able
 219          * to make progress.
 220          */
 221         if (!did_work && has_sched_dispatch) {
 222                 do {
 223                         struct request *rq;
 224
 225                         rq = e->type->ops.mq.dispatch_request(hctx);
 226                         if (!rq)
 227                                 break;
 228                         list_add(&rq->queuelist, &rq_list);
 229                 } while (blk_mq_dispatch_rq_list(q, &rq_list));
 230         }
 231 }
 232
 233 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
 234                             struct request **merged_request)
 235 {
 236         struct request *rq;
 237
 238         switch (elv_merge(q, &rq, bio)) {
 239         case ELEVATOR_BACK_MERGE:
 240                 if (!blk_mq_sched_allow_merge(q, rq, bio))
 241                         return false;
 242                 if (!bio_attempt_back_merge(q, rq, bio))
 243                         return false;
 244                 *merged_request = attempt_back_merge(q, rq);
 245                 if (!*merged_request)
 246                         elv_merged_request(q, rq, ELEVATOR_BACK_MERGE);
 247                 return true;
 248         case ELEVATOR_FRONT_MERGE:
 249                 if (!blk_mq_sched_allow_merge(q, rq, bio))
 250                         return false;
 251                 if (!bio_attempt_front_merge(q, rq, bio))
 252                         return false;
 253                 *merged_request = attempt_front_merge(q, rq);
 254                 if (!*merged_request)
 255                         elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
 256                 return true;
 257         default:
 258                 return false;
 259         }
 260 }
 261 EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
 262
 263 bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
 264 {
 265         struct elevator_queue *e = q->elevator;
 266
 267         if (e->type->ops.mq.bio_merge) {
 268                 struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
 269                 struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
 270
 271                 blk_mq_put_ctx(ctx);
 272                 return e->type->ops.mq.bio_merge(hctx, bio);
 273         }
 274
 275         return false;
 276 }
 277
 278 bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq)
 279 {
 280         return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq);
 281 }
 282 EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge);
 283
 284 void blk_mq_sched_request_inserted(struct request *rq)
 285 {
 286         trace_block_rq_insert(rq->q, rq);
 287 }
 288 EXPORT_SYMBOL_GPL(blk_mq_sched_request_inserted);
 289
 290 static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx,
 291                                        struct request *rq)
 292 {
 293         if (rq->tag == -1) {
 294                 rq->rq_flags |= RQF_SORTED;
 295                 return false;
 296         }
 297
 298         /*
 299          * If we already have a real request tag, send directly to
 300          * the dispatch list.
 301          */
 302         spin_lock(&hctx->lock);
 303         list_add(&rq->queuelist, &hctx->dispatch);
 304         spin_unlock(&hctx->lock);
 305         return true;
 306 }
 307
 308 /**
 309  * list_for_each_entry_rcu_rr - iterate in a round-robin fashion over rcu list
 310  * @pos:    loop cursor.
 311  * @skip:   the list element that will not be examined. Iteration starts at
 312  *          @skip->next.
 313  * @head:   head of the list to examine. This list must have at least one
 314  *          element, namely @skip.
 315  * @member: name of the list_head structure within typeof(*pos).
 316  */
 317 #define list_for_each_entry_rcu_rr(pos, skip, head, member)             \
 318         for ((pos) = (skip);                                            \
 319              (pos = (pos)->member.next != (head) ? list_entry_rcu(      \
 320                         (pos)->member.next, typeof(*pos), member) :     \
 321               list_entry_rcu((pos)->member.next->next, typeof(*pos), member)), \
 322              (pos) != (skip); )
 323
 324 /*
 325  * Called after a driver tag has been freed to check whether a hctx needs to
 326  * be restarted. Restarts @hctx if its tag set is not shared. Restarts hardware
 327  * queues in a round-robin fashion if the tag set of @hctx is shared with other
 328  * hardware queues.
 329  */
 330 void blk_mq_sched_restart(struct blk_mq_hw_ctx *const hctx)
 331 {
 332         struct blk_mq_tags *const tags = hctx->tags;
 333         struct blk_mq_tag_set *const set = hctx->queue->tag_set;
 334         struct request_queue *const queue = hctx->queue, *q;
 335         struct blk_mq_hw_ctx *hctx2;
 336         unsigned int i, j;
 337
 338         if (set->flags & BLK_MQ_F_TAG_SHARED) {
 339                 /*
 340                  * If this is 0, then we know that no hardware queues
 341                  * have RESTART marked. We're done.
 342                  */
 343                 if (!atomic_read(&queue->shared_hctx_restart))
 344                         return;
 345
 346                 rcu_read_lock();
 347                 list_for_each_entry_rcu_rr(q, queue, &set->tag_list,
 348                                            tag_set_list) {
 349                         queue_for_each_hw_ctx(q, hctx2, i)
 350                                 if (hctx2->tags == tags &&
 351                                     blk_mq_sched_restart_hctx(hctx2))
 352                                         goto done;
 353                 }
 354                 j = hctx->queue_num + 1;
 355                 for (i = 0; i < queue->nr_hw_queues; i++, j++) {
 356                         if (j == queue->nr_hw_queues)
 357                                 j = 0;
 358                         hctx2 = queue->queue_hw_ctx[j];
 359                         if (hctx2->tags == tags &&
 360                             blk_mq_sched_restart_hctx(hctx2))
 361                                 break;
 362                 }
 363 done:
 364                 rcu_read_unlock();
 365         } else {
 366                 blk_mq_sched_restart_hctx(hctx);
 367         }
 368 }
 369
 370 /*
 371  * Add flush/fua to the queue. If we fail getting a driver tag, then
 372  * punt to the requeue list. Requeue will re-invoke us from a context
 373  * that's safe to block from.
 374  */
 375 static void blk_mq_sched_insert_flush(struct blk_mq_hw_ctx *hctx,
 376                                       struct request *rq, bool can_block)
 377 {
 378         if (blk_mq_get_driver_tag(rq, &hctx, can_block)) {
 379                 blk_insert_flush(rq);
 380                 blk_mq_run_hw_queue(hctx, true);
 381         } else
 382                 blk_mq_add_to_requeue_list(rq, false, true);
 383 }
 384
 385 void blk_mq_sched_insert_request(struct request *rq, bool at_head,
 386                                  bool run_queue, bool async, bool can_block)
 387 {
 388         struct request_queue *q = rq->q;
 389         struct elevator_queue *e = q->elevator;
 390         struct blk_mq_ctx *ctx = rq->mq_ctx;
 391         struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
 392
 393         if (rq->tag == -1 && op_is_flush(rq->cmd_flags)) {
 394                 blk_mq_sched_insert_flush(hctx, rq, can_block);
 395                 return;
 396         }
 397
 398         if (e && blk_mq_sched_bypass_insert(hctx, rq))
 399                 goto run;
 400
 401         if (e && e->type->ops.mq.insert_requests) {
 402                 LIST_HEAD(list);
 403
 404                 list_add(&rq->queuelist, &list);
 405                 e->type->ops.mq.insert_requests(hctx, &list, at_head);
 406         } else {
 407                 spin_lock(&ctx->lock);
 408                 __blk_mq_insert_request(hctx, rq, at_head);
 409                 spin_unlock(&ctx->lock);
 410         }
 411
 412 run:
 413         if (run_queue)
 414                 blk_mq_run_hw_queue(hctx, async);
 415 }
 416
 417 void blk_mq_sched_insert_requests(struct request_queue *q,
 418                                   struct blk_mq_ctx *ctx,
 419                                   struct list_head *list, bool run_queue_async)
 420 {
 421         struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
 422         struct elevator_queue *e = hctx->queue->elevator;
 423
 424         if (e) {
 425                 struct request *rq, *next;
 426
 427                 /*
 428                  * We bypass requests that already have a driver tag assigned,
 429                  * which should only be flushes. Flushes are only ever inserted
 430                  * as single requests, so we shouldn't ever hit the
 431                  * WARN_ON_ONCE() below (but let's handle it just in case).
 432                  */
 433                 list_for_each_entry_safe(rq, next, list, queuelist) {
 434                         if (WARN_ON_ONCE(rq->tag != -1)) {
 435                                 list_del_init(&rq->queuelist);
 436                                 blk_mq_sched_bypass_insert(hctx, rq);
 437                         }
 438                 }
 439         }
 440
 441         if (e && e->type->ops.mq.insert_requests)
 442                 e->type->ops.mq.insert_requests(hctx, list, false);
 443         else
 444                 blk_mq_insert_requests(hctx, ctx, list);
 445
 446         blk_mq_run_hw_queue(hctx, run_queue_async);
 447 }
 448
 449 static void blk_mq_sched_free_tags(struct blk_mq_tag_set *set,
 450                                    struct blk_mq_hw_ctx *hctx,
 451                                    unsigned int hctx_idx)
 452 {
 453         if (hctx->sched_tags) {
 454                 blk_mq_free_rqs(set, hctx->sched_tags, hctx_idx);
 455                 blk_mq_free_rq_map(hctx->sched_tags);
 456                 hctx->sched_tags = NULL;
 457         }
 458 }
 459
 460 static int blk_mq_sched_alloc_tags(struct request_queue *q,
 461                                    struct blk_mq_hw_ctx *hctx,
 462                                    unsigned int hctx_idx)
 463 {
 464         struct blk_mq_tag_set *set = q->tag_set;
 465         int ret;
 466
 467         hctx->sched_tags = blk_mq_alloc_rq_map(set, hctx_idx, q->nr_requests,
 468                                                set->reserved_tags);
 469         if (!hctx->sched_tags)
 470                 return -ENOMEM;
 471
 472         ret = blk_mq_alloc_rqs(set, hctx->sched_tags, hctx_idx, q->nr_requests);
 473         if (ret)
 474                 blk_mq_sched_free_tags(set, hctx, hctx_idx);
 475
 476         return ret;
 477 }
 478
 479 static void blk_mq_sched_tags_teardown(struct request_queue *q)
 480 {
 481         struct blk_mq_tag_set *set = q->tag_set;
 482         struct blk_mq_hw_ctx *hctx;
 483         int i;
 484
 485         queue_for_each_hw_ctx(q, hctx, i)
 486                 blk_mq_sched_free_tags(set, hctx, i);
 487 }
 488
 489 int blk_mq_sched_init_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,
 490                            unsigned int hctx_idx)
 491 {
 492         struct elevator_queue *e = q->elevator;
 493         int ret;
 494
 495         if (!e)
 496                 return 0;
 497
 498         ret = blk_mq_sched_alloc_tags(q, hctx, hctx_idx);
 499         if (ret)
 500                 return ret;
 501
 502         if (e->type->ops.mq.init_hctx) {
 503                 ret = e->type->ops.mq.init_hctx(hctx, hctx_idx);
 504                 if (ret) {
 505                         blk_mq_sched_free_tags(q->tag_set, hctx, hctx_idx);
 506                         return ret;
 507                 }
 508         }
 509
 510         blk_mq_debugfs_register_sched_hctx(q, hctx);
 511
 512         return 0;
 513 }
 514
 515 void blk_mq_sched_exit_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx,
 516                             unsigned int hctx_idx)
 517 {
 518         struct elevator_queue *e = q->elevator;
 519
 520         if (!e)
 521                 return;
 522
 523         blk_mq_debugfs_unregister_sched_hctx(hctx);
 524
 525         if (e->type->ops.mq.exit_hctx && hctx->sched_data) {
 526                 e->type->ops.mq.exit_hctx(hctx, hctx_idx);
 527                 hctx->sched_data = NULL;
 528         }
 529
 530         blk_mq_sched_free_tags(q->tag_set, hctx, hctx_idx);
 531 }
 532
 533 int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
 534 {
 535         struct blk_mq_hw_ctx *hctx;
 536         struct elevator_queue *eq;
 537         unsigned int i;
 538         int ret;
 539
 540         if (!e) {
 541                 q->elevator = NULL;
 542                 return 0;
 543         }
 544
 545         /*
 546          * Default to 256, since we don't split into sync/async like the
 547          * old code did. Additionally, this is a per-hw queue depth.
 548          */
 549         q->nr_requests = 2 * BLKDEV_MAX_RQ;
 550
 551         queue_for_each_hw_ctx(q, hctx, i) {
 552                 ret = blk_mq_sched_alloc_tags(q, hctx, i);
 553                 if (ret)
 554                         goto err;
 555         }
 556
 557         ret = e->ops.mq.init_sched(q, e);
 558         if (ret)
 559                 goto err;
 560
 561         blk_mq_debugfs_register_sched(q);
 562
 563         queue_for_each_hw_ctx(q, hctx, i) {
 564                 if (e->ops.mq.init_hctx) {
 565                         ret = e->ops.mq.init_hctx(hctx, i);
 566                         if (ret) {
 567                                 eq = q->elevator;
 568                                 blk_mq_exit_sched(q, eq);
 569                                 kobject_put(&eq->kobj);
 570                                 return ret;
 571                         }
 572                 }
 573                 blk_mq_debugfs_register_sched_hctx(q, hctx);
 574         }
 575
 576         return 0;
 577
 578 err:
 579         blk_mq_sched_tags_teardown(q);
 580         q->elevator = NULL;
 581         return ret;
 582 }
 583
 584 void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e)
 585 {
 586         struct blk_mq_hw_ctx *hctx;
 587         unsigned int i;
 588
 589         queue_for_each_hw_ctx(q, hctx, i) {
 590                 blk_mq_debugfs_unregister_sched_hctx(hctx);
 591                 if (e->type->ops.mq.exit_hctx && hctx->sched_data) {
 592                         e->type->ops.mq.exit_hctx(hctx, i);
 593                         hctx->sched_data = NULL;
 594                 }
 595         }
 596         blk_mq_debugfs_unregister_sched(q);
 597         if (e->type->ops.mq.exit_sched)
 598                 e->type->ops.mq.exit_sched(e);
 599         blk_mq_sched_tags_teardown(q);
 600         q->elevator = NULL;
 601 }
 602
 603 int blk_mq_sched_init(struct request_queue *q)
 604 {
 605         int ret;
 606
 607         mutex_lock(&q->sysfs_lock);
 608         ret = elevator_init(q, NULL);
 609         mutex_unlock(&q->sysfs_lock);
 610
 611         return ret;
 612 }