block/blk-mq.c

   1 /*
   2  * Block multiqueue core code
   3  *
   4  * Copyright (C) 2013-2014 Jens Axboe
   5  * Copyright (C) 2013-2014 Christoph Hellwig
   6  */
   7 #include <linux/kernel.h>
   8 #include <linux/module.h>
   9 #include <linux/backing-dev.h>
  10 #include <linux/bio.h>
  11 #include <linux/blkdev.h>
  12 #include <linux/kmemleak.h>
  13 #include <linux/mm.h>
  14 #include <linux/init.h>
  15 #include <linux/slab.h>
  16 #include <linux/workqueue.h>
  17 #include <linux/smp.h>
  18 #include <linux/llist.h>
  19 #include <linux/list_sort.h>
  20 #include <linux/cpu.h>
  21 #include <linux/cache.h>
  22 #include <linux/sched/sysctl.h>
  23 #include <linux/delay.h>
  24 #include <linux/crash_dump.h>
  25 #include <linux/prefetch.h>
  26
  27 #include <trace/events/block.h>
  28
  29 #include <linux/blk-mq.h>
  30 #include "blk.h"
  31 #include "blk-mq.h"
  32 #include "blk-mq-tag.h"
  33 #include "blk-stat.h"
  34 #include "blk-wbt.h"
  35
  36 static DEFINE_MUTEX(all_q_mutex);
  37 static LIST_HEAD(all_q_list);
  38
  39 /*
  40  * Check if any of the ctx's have pending work in this hardware queue
  41  */
  42 static bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx)
  43 {
  44         return sbitmap_any_bit_set(&hctx->ctx_map);
  45 }
  46
  47 /*
  48  * Mark this ctx as having pending work in this hardware queue
  49  */
  50 static void blk_mq_hctx_mark_pending(struct blk_mq_hw_ctx *hctx,
  51                                      struct blk_mq_ctx *ctx)
  52 {
  53         if (!sbitmap_test_bit(&hctx->ctx_map, ctx->index_hw))
  54                 sbitmap_set_bit(&hctx->ctx_map, ctx->index_hw);
  55 }
  56
  57 static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
  58                                       struct blk_mq_ctx *ctx)
  59 {
  60         sbitmap_clear_bit(&hctx->ctx_map, ctx->index_hw);
  61 }
  62
  63 void blk_mq_freeze_queue_start(struct request_queue *q)
  64 {
  65         int freeze_depth;
  66
  67         freeze_depth = atomic_inc_return(&q->mq_freeze_depth);
  68         if (freeze_depth == 1) {
  69                 percpu_ref_kill(&q->q_usage_counter);
  70                 blk_mq_run_hw_queues(q, false);
  71         }
  72 }
  73 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_start);
  74
  75 static void blk_mq_freeze_queue_wait(struct request_queue *q)
  76 {
  77         wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->q_usage_counter));
  78 }
  79
  80 /*
  81  * Guarantee no request is in use, so we can change any data structure of
  82  * the queue afterward.
  83  */
  84 void blk_freeze_queue(struct request_queue *q)
  85 {
  86         /*
  87          * In the !blk_mq case we are only calling this to kill the
  88          * q_usage_counter, otherwise this increases the freeze depth
  89          * and waits for it to return to zero.  For this reason there is
  90          * no blk_unfreeze_queue(), and blk_freeze_queue() is not
  91          * exported to drivers as the only user for unfreeze is blk_mq.
  92          */
  93         blk_mq_freeze_queue_start(q);
  94         blk_mq_freeze_queue_wait(q);
  95 }
  96
  97 void blk_mq_freeze_queue(struct request_queue *q)
  98 {
  99         /*
 100          * ...just an alias to keep freeze and unfreeze actions balanced
 101          * in the blk_mq_* namespace
 102          */
 103         blk_freeze_queue(q);
 104 }
 105 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);
 106
 107 void blk_mq_unfreeze_queue(struct request_queue *q)
 108 {
 109         int freeze_depth;
 110
 111         freeze_depth = atomic_dec_return(&q->mq_freeze_depth);
 112         WARN_ON_ONCE(freeze_depth < 0);
 113         if (!freeze_depth) {
 114                 percpu_ref_reinit(&q->q_usage_counter);
 115                 wake_up_all(&q->mq_freeze_wq);
 116         }
 117 }
 118 EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);
 119
 120 /**
 121  * blk_mq_quiesce_queue() - wait until all ongoing queue_rq calls have finished
 122  * @q: request queue.
 123  *
 124  * Note: this function does not prevent that the struct request end_io()
 125  * callback function is invoked. Additionally, it is not prevented that
 126  * new queue_rq() calls occur unless the queue has been stopped first.
 127  */
 128 void blk_mq_quiesce_queue(struct request_queue *q)
 129 {
 130         struct blk_mq_hw_ctx *hctx;
 131         unsigned int i;
 132         bool rcu = false;
 133
 134         blk_mq_stop_hw_queues(q);
 135
 136         queue_for_each_hw_ctx(q, hctx, i) {
 137                 if (hctx->flags & BLK_MQ_F_BLOCKING)
 138                         synchronize_srcu(&hctx->queue_rq_srcu);
 139                 else
 140                         rcu = true;
 141         }
 142         if (rcu)
 143                 synchronize_rcu();
 144 }
 145 EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue);
 146
 147 void blk_mq_wake_waiters(struct request_queue *q)
 148 {
 149         struct blk_mq_hw_ctx *hctx;
 150         unsigned int i;
 151
 152         queue_for_each_hw_ctx(q, hctx, i)
 153                 if (blk_mq_hw_queue_mapped(hctx))
 154                         blk_mq_tag_wakeup_all(hctx->tags, true);
 155
 156         /*
 157          * If we are called because the queue has now been marked as
 158          * dying, we need to ensure that processes currently waiting on
 159          * the queue are notified as well.
 160          */
 161         wake_up_all(&q->mq_freeze_wq);
 162 }
 163
 164 bool blk_mq_can_queue(struct blk_mq_hw_ctx *hctx)
 165 {
 166         return blk_mq_has_free_tags(hctx->tags);
 167 }
 168 EXPORT_SYMBOL(blk_mq_can_queue);
 169
 170 static void blk_mq_rq_ctx_init(struct request_queue *q, struct blk_mq_ctx *ctx,
 171                                struct request *rq, unsigned int op)
 172 {
 173         INIT_LIST_HEAD(&rq->queuelist);
 174         /* csd/requeue_work/fifo_time is initialized before use */
 175         rq->q = q;
 176         rq->mq_ctx = ctx;
 177         rq->cmd_flags = op;
 178         if (blk_queue_io_stat(q))
 179                 rq->rq_flags |= RQF_IO_STAT;
 180         /* do not touch atomic flags, it needs atomic ops against the timer */
 181         rq->cpu = -1;
 182         INIT_HLIST_NODE(&rq->hash);
 183         RB_CLEAR_NODE(&rq->rb_node);
 184         rq->rq_disk = NULL;
 185         rq->part = NULL;
 186         rq->start_time = jiffies;
 187 #ifdef CONFIG_BLK_CGROUP
 188         rq->rl = NULL;
 189         set_start_time_ns(rq);
 190         rq->io_start_time_ns = 0;
 191 #endif
 192         rq->nr_phys_segments = 0;
 193 #if defined(CONFIG_BLK_DEV_INTEGRITY)
 194         rq->nr_integrity_segments = 0;
 195 #endif
 196         rq->special = NULL;
 197         /* tag was already set */
 198         rq->errors = 0;
 199
 200         rq->cmd = rq->__cmd;
 201
 202         rq->extra_len = 0;
 203         rq->sense_len = 0;
 204         rq->resid_len = 0;
 205         rq->sense = NULL;
 206
 207         INIT_LIST_HEAD(&rq->timeout_list);
 208         rq->timeout = 0;
 209
 210         rq->end_io = NULL;
 211         rq->end_io_data = NULL;
 212         rq->next_rq = NULL;
 213
 214         ctx->rq_dispatched[op_is_sync(op)]++;
 215 }
 216
 217 static struct request *
 218 __blk_mq_alloc_request(struct blk_mq_alloc_data *data, unsigned int op)
 219 {
 220         struct request *rq;
 221         unsigned int tag;
 222
 223         tag = blk_mq_get_tag(data);
 224         if (tag != BLK_MQ_TAG_FAIL) {
 225                 rq = data->hctx->tags->rqs[tag];
 226
 227                 if (blk_mq_tag_busy(data->hctx)) {
 228                         rq->rq_flags = RQF_MQ_INFLIGHT;
 229                         atomic_inc(&data->hctx->nr_active);
 230                 }
 231
 232                 rq->tag = tag;
 233                 blk_mq_rq_ctx_init(data->q, data->ctx, rq, op);
 234                 return rq;
 235         }
 236
 237         return NULL;
 238 }
 239
 240 struct request *blk_mq_alloc_request(struct request_queue *q, int rw,
 241                 unsigned int flags)
 242 {
 243         struct blk_mq_ctx *ctx;
 244         struct blk_mq_hw_ctx *hctx;
 245         struct request *rq;
 246         struct blk_mq_alloc_data alloc_data;
 247         int ret;
 248
 249         ret = blk_queue_enter(q, flags & BLK_MQ_REQ_NOWAIT);
 250         if (ret)
 251                 return ERR_PTR(ret);
 252
 253         ctx = blk_mq_get_ctx(q);
 254         hctx = blk_mq_map_queue(q, ctx->cpu);
 255         blk_mq_set_alloc_data(&alloc_data, q, flags, ctx, hctx);
 256         rq = __blk_mq_alloc_request(&alloc_data, rw);
 257         blk_mq_put_ctx(ctx);
 258
 259         if (!rq) {
 260                 blk_queue_exit(q);
 261                 return ERR_PTR(-EWOULDBLOCK);
 262         }
 263
 264         rq->__data_len = 0;
 265         rq->__sector = (sector_t) -1;
 266         rq->bio = rq->biotail = NULL;
 267         return rq;
 268 }
 269 EXPORT_SYMBOL(blk_mq_alloc_request);
 270
 271 struct request *blk_mq_alloc_request_hctx(struct request_queue *q, int rw,
 272                 unsigned int flags, unsigned int hctx_idx)
 273 {
 274         struct blk_mq_hw_ctx *hctx;
 275         struct blk_mq_ctx *ctx;
 276         struct request *rq;
 277         struct blk_mq_alloc_data alloc_data;
 278         int ret;
 279
 280         /*
 281          * If the tag allocator sleeps we could get an allocation for a
 282          * different hardware context.  No need to complicate the low level
 283          * allocator for this for the rare use case of a command tied to
 284          * a specific queue.
 285          */
 286         if (WARN_ON_ONCE(!(flags & BLK_MQ_REQ_NOWAIT)))
 287                 return ERR_PTR(-EINVAL);
 288
 289         if (hctx_idx >= q->nr_hw_queues)
 290                 return ERR_PTR(-EIO);
 291
 292         ret = blk_queue_enter(q, true);
 293         if (ret)
 294                 return ERR_PTR(ret);
 295
 296         /*
 297          * Check if the hardware context is actually mapped to anything.
 298          * If not tell the caller that it should skip this queue.
 299          */
 300         hctx = q->queue_hw_ctx[hctx_idx];
 301         if (!blk_mq_hw_queue_mapped(hctx)) {
 302                 ret = -EXDEV;
 303                 goto out_queue_exit;
 304         }
 305         ctx = __blk_mq_get_ctx(q, cpumask_first(hctx->cpumask));
 306
 307         blk_mq_set_alloc_data(&alloc_data, q, flags, ctx, hctx);
 308         rq = __blk_mq_alloc_request(&alloc_data, rw);
 309         if (!rq) {
 310                 ret = -EWOULDBLOCK;
 311                 goto out_queue_exit;
 312         }
 313
 314         return rq;
 315
 316 out_queue_exit:
 317         blk_queue_exit(q);
 318         return ERR_PTR(ret);
 319 }
 320 EXPORT_SYMBOL_GPL(blk_mq_alloc_request_hctx);
 321
 322 static void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx,
 323                                   struct blk_mq_ctx *ctx, struct request *rq)
 324 {
 325         const int tag = rq->tag;
 326         struct request_queue *q = rq->q;
 327
 328         if (rq->rq_flags & RQF_MQ_INFLIGHT)
 329                 atomic_dec(&hctx->nr_active);
 330
 331         wbt_done(q->rq_wb, &rq->issue_stat);
 332         rq->rq_flags = 0;
 333
 334         clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
 335         clear_bit(REQ_ATOM_POLL_SLEPT, &rq->atomic_flags);
 336         blk_mq_put_tag(hctx, ctx, tag);
 337         blk_queue_exit(q);
 338 }
 339
 340 void blk_mq_free_hctx_request(struct blk_mq_hw_ctx *hctx, struct request *rq)
 341 {
 342         struct blk_mq_ctx *ctx = rq->mq_ctx;
 343
 344         ctx->rq_completed[rq_is_sync(rq)]++;
 345         __blk_mq_free_request(hctx, ctx, rq);
 346
 347 }
 348 EXPORT_SYMBOL_GPL(blk_mq_free_hctx_request);
 349
 350 void blk_mq_free_request(struct request *rq)
 351 {
 352         blk_mq_free_hctx_request(blk_mq_map_queue(rq->q, rq->mq_ctx->cpu), rq);
 353 }
 354 EXPORT_SYMBOL_GPL(blk_mq_free_request);
 355
 356 inline void __blk_mq_end_request(struct request *rq, int error)
 357 {
 358         blk_account_io_done(rq);
 359
 360         if (rq->end_io) {
 361                 wbt_done(rq->q->rq_wb, &rq->issue_stat);
 362                 rq->end_io(rq, error);
 363         } else {
 364                 if (unlikely(blk_bidi_rq(rq)))
 365                         blk_mq_free_request(rq->next_rq);
 366                 blk_mq_free_request(rq);
 367         }
 368 }
 369 EXPORT_SYMBOL(__blk_mq_end_request);
 370
 371 void blk_mq_end_request(struct request *rq, int error)
 372 {
 373         if (blk_update_request(rq, error, blk_rq_bytes(rq)))
 374                 BUG();
 375         __blk_mq_end_request(rq, error);
 376 }
 377 EXPORT_SYMBOL(blk_mq_end_request);
 378
 379 static void __blk_mq_complete_request_remote(void *data)
 380 {
 381         struct request *rq = data;
 382
 383         rq->q->softirq_done_fn(rq);
 384 }
 385
 386 static void blk_mq_ipi_complete_request(struct request *rq)
 387 {
 388         struct blk_mq_ctx *ctx = rq->mq_ctx;
 389         bool shared = false;
 390         int cpu;
 391
 392         if (!test_bit(QUEUE_FLAG_SAME_COMP, &rq->q->queue_flags)) {
 393                 rq->q->softirq_done_fn(rq);
 394                 return;
 395         }
 396
 397         cpu = get_cpu();
 398         if (!test_bit(QUEUE_FLAG_SAME_FORCE, &rq->q->queue_flags))
 399                 shared = cpus_share_cache(cpu, ctx->cpu);
 400
 401         if (cpu != ctx->cpu && !shared && cpu_online(ctx->cpu)) {
 402                 rq->csd.func = __blk_mq_complete_request_remote;
 403                 rq->csd.info = rq;
 404                 rq->csd.flags = 0;
 405                 smp_call_function_single_async(ctx->cpu, &rq->csd);
 406         } else {
 407                 rq->q->softirq_done_fn(rq);
 408         }
 409         put_cpu();
 410 }
 411
 412 static void blk_mq_stat_add(struct request *rq)
 413 {
 414         if (rq->rq_flags & RQF_STATS) {
 415                 /*
 416                  * We could rq->mq_ctx here, but there's less of a risk
 417                  * of races if we have the completion event add the stats
 418                  * to the local software queue.
 419                  */
 420                 struct blk_mq_ctx *ctx;
 421
 422                 ctx = __blk_mq_get_ctx(rq->q, raw_smp_processor_id());
 423                 blk_stat_add(&ctx->stat[rq_data_dir(rq)], rq);
 424         }
 425 }
 426
 427 static void __blk_mq_complete_request(struct request *rq)
 428 {
 429         struct request_queue *q = rq->q;
 430
 431         blk_mq_stat_add(rq);
 432
 433         if (!q->softirq_done_fn)
 434                 blk_mq_end_request(rq, rq->errors);
 435         else
 436                 blk_mq_ipi_complete_request(rq);
 437 }
 438
 439 /**
 440  * blk_mq_complete_request - end I/O on a request
 441  * @rq:         the request being processed
 442  *
 443  * Description:
 444  *      Ends all I/O on a request. It does not handle partial completions.
 445  *      The actual completion happens out-of-order, through a IPI handler.
 446  **/
 447 void blk_mq_complete_request(struct request *rq, int error)
 448 {
 449         struct request_queue *q = rq->q;
 450
 451         if (unlikely(blk_should_fake_timeout(q)))
 452                 return;
 453         if (!blk_mark_rq_complete(rq)) {
 454                 rq->errors = error;
 455                 __blk_mq_complete_request(rq);
 456         }
 457 }
 458 EXPORT_SYMBOL(blk_mq_complete_request);
 459
 460 int blk_mq_request_started(struct request *rq)
 461 {
 462         return test_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
 463 }
 464 EXPORT_SYMBOL_GPL(blk_mq_request_started);
 465
 466 void blk_mq_start_request(struct request *rq)
 467 {
 468         struct request_queue *q = rq->q;
 469
 470         trace_block_rq_issue(q, rq);
 471
 472         rq->resid_len = blk_rq_bytes(rq);
 473         if (unlikely(blk_bidi_rq(rq)))
 474                 rq->next_rq->resid_len = blk_rq_bytes(rq->next_rq);
 475
 476         if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags)) {
 477                 blk_stat_set_issue_time(&rq->issue_stat);
 478                 rq->rq_flags |= RQF_STATS;
 479                 wbt_issue(q->rq_wb, &rq->issue_stat);
 480         }
 481
 482         blk_add_timer(rq);
 483
 484         /*
 485          * Ensure that ->deadline is visible before set the started
 486          * flag and clear the completed flag.
 487          */
 488         smp_mb__before_atomic();
 489
 490         /*
 491          * Mark us as started and clear complete. Complete might have been
 492          * set if requeue raced with timeout, which then marked it as
 493          * complete. So be sure to clear complete again when we start
 494          * the request, otherwise we'll ignore the completion event.
 495          */
 496         if (!test_bit(REQ_ATOM_STARTED, &rq->atomic_flags))
 497                 set_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
 498         if (test_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags))
 499                 clear_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags);
 500
 501         if (q->dma_drain_size && blk_rq_bytes(rq)) {
 502                 /*
 503                  * Make sure space for the drain appears.  We know we can do
 504                  * this because max_hw_segments has been adjusted to be one
 505                  * fewer than the device can handle.
 506                  */
 507                 rq->nr_phys_segments++;
 508         }
 509 }
 510 EXPORT_SYMBOL(blk_mq_start_request);
 511
 512 static void __blk_mq_requeue_request(struct request *rq)
 513 {
 514         struct request_queue *q = rq->q;
 515
 516         trace_block_rq_requeue(q, rq);
 517         wbt_requeue(q->rq_wb, &rq->issue_stat);
 518
 519         if (test_and_clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags)) {
 520                 if (q->dma_drain_size && blk_rq_bytes(rq))
 521                         rq->nr_phys_segments--;
 522         }
 523 }
 524
 525 void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list)
 526 {
 527         __blk_mq_requeue_request(rq);
 528
 529         BUG_ON(blk_queued_rq(rq));
 530         blk_mq_add_to_requeue_list(rq, true, kick_requeue_list);
 531 }
 532 EXPORT_SYMBOL(blk_mq_requeue_request);
 533
 534 static void blk_mq_requeue_work(struct work_struct *work)
 535 {
 536         struct request_queue *q =
 537                 container_of(work, struct request_queue, requeue_work.work);
 538         LIST_HEAD(rq_list);
 539         struct request *rq, *next;
 540         unsigned long flags;
 541
 542         spin_lock_irqsave(&q->requeue_lock, flags);
 543         list_splice_init(&q->requeue_list, &rq_list);
 544         spin_unlock_irqrestore(&q->requeue_lock, flags);
 545
 546         list_for_each_entry_safe(rq, next, &rq_list, queuelist) {
 547                 if (!(rq->rq_flags & RQF_SOFTBARRIER))
 548                         continue;
 549
 550                 rq->rq_flags &= ~RQF_SOFTBARRIER;
 551                 list_del_init(&rq->queuelist);
 552                 blk_mq_insert_request(rq, true, false, false);
 553         }
 554
 555         while (!list_empty(&rq_list)) {
 556                 rq = list_entry(rq_list.next, struct request, queuelist);
 557                 list_del_init(&rq->queuelist);
 558                 blk_mq_insert_request(rq, false, false, false);
 559         }
 560
 561         blk_mq_run_hw_queues(q, false);
 562 }
 563
 564 void blk_mq_add_to_requeue_list(struct request *rq, bool at_head,
 565                                 bool kick_requeue_list)
 566 {
 567         struct request_queue *q = rq->q;
 568         unsigned long flags;
 569
 570         /*
 571          * We abuse this flag that is otherwise used by the I/O scheduler to
 572          * request head insertation from the workqueue.
 573          */
 574         BUG_ON(rq->rq_flags & RQF_SOFTBARRIER);
 575
 576         spin_lock_irqsave(&q->requeue_lock, flags);
 577         if (at_head) {
 578                 rq->rq_flags |= RQF_SOFTBARRIER;
 579                 list_add(&rq->queuelist, &q->requeue_list);
 580         } else {
 581                 list_add_tail(&rq->queuelist, &q->requeue_list);
 582         }
 583         spin_unlock_irqrestore(&q->requeue_lock, flags);
 584
 585         if (kick_requeue_list)
 586                 blk_mq_kick_requeue_list(q);
 587 }
 588 EXPORT_SYMBOL(blk_mq_add_to_requeue_list);
 589
 590 void blk_mq_kick_requeue_list(struct request_queue *q)
 591 {
 592         kblockd_schedule_delayed_work(&q->requeue_work, 0);
 593 }
 594 EXPORT_SYMBOL(blk_mq_kick_requeue_list);
 595
 596 void blk_mq_delay_kick_requeue_list(struct request_queue *q,
 597                                     unsigned long msecs)
 598 {
 599         kblockd_schedule_delayed_work(&q->requeue_work,
 600                                       msecs_to_jiffies(msecs));
 601 }
 602 EXPORT_SYMBOL(blk_mq_delay_kick_requeue_list);
 603
 604 void blk_mq_abort_requeue_list(struct request_queue *q)
 605 {
 606         unsigned long flags;
 607         LIST_HEAD(rq_list);
 608
 609         spin_lock_irqsave(&q->requeue_lock, flags);
 610         list_splice_init(&q->requeue_list, &rq_list);
 611         spin_unlock_irqrestore(&q->requeue_lock, flags);
 612
 613         while (!list_empty(&rq_list)) {
 614                 struct request *rq;
 615
 616                 rq = list_first_entry(&rq_list, struct request, queuelist);
 617                 list_del_init(&rq->queuelist);
 618                 rq->errors = -EIO;
 619                 blk_mq_end_request(rq, rq->errors);
 620         }
 621 }
 622 EXPORT_SYMBOL(blk_mq_abort_requeue_list);
 623
 624 struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
 625 {
 626         if (tag < tags->nr_tags) {
 627                 prefetch(tags->rqs[tag]);
 628                 return tags->rqs[tag];
 629         }
 630
 631         return NULL;
 632 }
 633 EXPORT_SYMBOL(blk_mq_tag_to_rq);
 634
 635 struct blk_mq_timeout_data {
 636         unsigned long next;
 637         unsigned int next_set;
 638 };
 639
 640 void blk_mq_rq_timed_out(struct request *req, bool reserved)
 641 {
 642         struct blk_mq_ops *ops = req->q->mq_ops;
 643         enum blk_eh_timer_return ret = BLK_EH_RESET_TIMER;
 644
 645         /*
 646          * We know that complete is set at this point. If STARTED isn't set
 647          * anymore, then the request isn't active and the "timeout" should
 648          * just be ignored. This can happen due to the bitflag ordering.
 649          * Timeout first checks if STARTED is set, and if it is, assumes
 650          * the request is active. But if we race with completion, then
 651          * we both flags will get cleared. So check here again, and ignore
 652          * a timeout event with a request that isn't active.
 653          */
 654         if (!test_bit(REQ_ATOM_STARTED, &req->atomic_flags))
 655                 return;
 656
 657         if (ops->timeout)
 658                 ret = ops->timeout(req, reserved);
 659
 660         switch (ret) {
 661         case BLK_EH_HANDLED:
 662                 __blk_mq_complete_request(req);
 663                 break;
 664         case BLK_EH_RESET_TIMER:
 665                 blk_add_timer(req);
 666                 blk_clear_rq_complete(req);
 667                 break;
 668         case BLK_EH_NOT_HANDLED:
 669                 break;
 670         default:
 671                 printk(KERN_ERR "block: bad eh return: %d\n", ret);
 672                 break;
 673         }
 674 }
 675
 676 static void blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
 677                 struct request *rq, void *priv, bool reserved)
 678 {
 679         struct blk_mq_timeout_data *data = priv;
 680
 681         if (!test_bit(REQ_ATOM_STARTED, &rq->atomic_flags)) {
 682                 /*
 683                  * If a request wasn't started before the queue was
 684                  * marked dying, kill it here or it'll go unnoticed.
 685                  */
 686                 if (unlikely(blk_queue_dying(rq->q))) {
 687                         rq->errors = -EIO;
 688                         blk_mq_end_request(rq, rq->errors);
 689                 }
 690                 return;
 691         }
 692
 693         if (time_after_eq(jiffies, rq->deadline)) {
 694                 if (!blk_mark_rq_complete(rq))
 695                         blk_mq_rq_timed_out(rq, reserved);
 696         } else if (!data->next_set || time_after(data->next, rq->deadline)) {
 697                 data->next = rq->deadline;
 698                 data->next_set = 1;
 699         }
 700 }
 701
 702 static void blk_mq_timeout_work(struct work_struct *work)
 703 {
 704         struct request_queue *q =
 705                 container_of(work, struct request_queue, timeout_work);
 706         struct blk_mq_timeout_data data = {
 707                 .next           = 0,
 708                 .next_set       = 0,
 709         };
 710         int i;
 711
 712         /* A deadlock might occur if a request is stuck requiring a
 713          * timeout at the same time a queue freeze is waiting
 714          * completion, since the timeout code would not be able to
 715          * acquire the queue reference here.
 716          *
 717          * That's why we don't use blk_queue_enter here; instead, we use
 718          * percpu_ref_tryget directly, because we need to be able to
 719          * obtain a reference even in the short window between the queue
 720          * starting to freeze, by dropping the first reference in
 721          * blk_mq_freeze_queue_start, and the moment the last request is
 722          * consumed, marked by the instant q_usage_counter reaches
 723          * zero.
 724          */
 725         if (!percpu_ref_tryget(&q->q_usage_counter))
 726                 return;
 727
 728         blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &data);
 729
 730         if (data.next_set) {
 731                 data.next = blk_rq_timeout(round_jiffies_up(data.next));
 732                 mod_timer(&q->timeout, data.next);
 733         } else {
 734                 struct blk_mq_hw_ctx *hctx;
 735
 736                 queue_for_each_hw_ctx(q, hctx, i) {
 737                         /* the hctx may be unmapped, so check it here */
 738                         if (blk_mq_hw_queue_mapped(hctx))
 739                                 blk_mq_tag_idle(hctx);
 740                 }
 741         }
 742         blk_queue_exit(q);
 743 }
 744
 745 /*
 746  * Reverse check our software queue for entries that we could potentially
 747  * merge with. Currently includes a hand-wavy stop count of 8, to not spend
 748  * too much time checking for merges.
 749  */
 750 static bool blk_mq_attempt_merge(struct request_queue *q,
 751                                  struct blk_mq_ctx *ctx, struct bio *bio)
 752 {
 753         struct request *rq;
 754         int checked = 8;
 755
 756         list_for_each_entry_reverse(rq, &ctx->rq_list, queuelist) {
 757                 int el_ret;
 758
 759                 if (!checked--)
 760                         break;
 761
 762                 if (!blk_rq_merge_ok(rq, bio))
 763                         continue;
 764
 765                 el_ret = blk_try_merge(rq, bio);
 766                 if (el_ret == ELEVATOR_BACK_MERGE) {
 767                         if (bio_attempt_back_merge(q, rq, bio)) {
 768                                 ctx->rq_merged++;
 769                                 return true;
 770                         }
 771                         break;
 772                 } else if (el_ret == ELEVATOR_FRONT_MERGE) {
 773                         if (bio_attempt_front_merge(q, rq, bio)) {
 774                                 ctx->rq_merged++;
 775                                 return true;
 776                         }
 777                         break;
 778                 }
 779         }
 780
 781         return false;
 782 }
 783
 784 struct flush_busy_ctx_data {
 785         struct blk_mq_hw_ctx *hctx;
 786         struct list_head *list;
 787 };
 788
 789 static bool flush_busy_ctx(struct sbitmap *sb, unsigned int bitnr, void *data)
 790 {
 791         struct flush_busy_ctx_data *flush_data = data;
 792         struct blk_mq_hw_ctx *hctx = flush_data->hctx;
 793         struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
 794
 795         sbitmap_clear_bit(sb, bitnr);
 796         spin_lock(&ctx->lock);
 797         list_splice_tail_init(&ctx->rq_list, flush_data->list);
 798         spin_unlock(&ctx->lock);
 799         return true;
 800 }
 801
 802 /*
 803  * Process software queues that have been marked busy, splicing them
 804  * to the for-dispatch
 805  */
 806 static void flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list)
 807 {
 808         struct flush_busy_ctx_data data = {
 809                 .hctx = hctx,
 810                 .list = list,
 811         };
 812
 813         sbitmap_for_each_set(&hctx->ctx_map, flush_busy_ctx, &data);
 814 }
 815
 816 static inline unsigned int queued_to_index(unsigned int queued)
 817 {
 818         if (!queued)
 819                 return 0;
 820
 821         return min(BLK_MQ_MAX_DISPATCH_ORDER - 1, ilog2(queued) + 1);
 822 }
 823
 824 bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list)
 825 {
 826         struct request_queue *q = hctx->queue;
 827         struct request *rq;
 828         LIST_HEAD(driver_list);
 829         struct list_head *dptr;
 830         int queued, ret = BLK_MQ_RQ_QUEUE_OK;
 831
 832         /*
 833          * Start off with dptr being NULL, so we start the first request
 834          * immediately, even if we have more pending.
 835          */
 836         dptr = NULL;
 837
 838         /*
 839          * Now process all the entries, sending them to the driver.
 840          */
 841         queued = 0;
 842         while (!list_empty(list)) {
 843                 struct blk_mq_queue_data bd;
 844
 845                 rq = list_first_entry(list, struct request, queuelist);
 846                 list_del_init(&rq->queuelist);
 847
 848                 bd.rq = rq;
 849                 bd.list = dptr;
 850                 bd.last = list_empty(list);
 851
 852                 ret = q->mq_ops->queue_rq(hctx, &bd);
 853                 switch (ret) {
 854                 case BLK_MQ_RQ_QUEUE_OK:
 855                         queued++;
 856                         break;
 857                 case BLK_MQ_RQ_QUEUE_BUSY:
 858                         list_add(&rq->queuelist, list);
 859                         __blk_mq_requeue_request(rq);
 860                         break;
 861                 default:
 862                         pr_err("blk-mq: bad return on queue: %d\n", ret);
 863                 case BLK_MQ_RQ_QUEUE_ERROR:
 864                         rq->errors = -EIO;
 865                         blk_mq_end_request(rq, rq->errors);
 866                         break;
 867                 }
 868
 869                 if (ret == BLK_MQ_RQ_QUEUE_BUSY)
 870                         break;
 871
 872                 /*
 873                  * We've done the first request. If we have more than 1
 874                  * left in the list, set dptr to defer issue.
 875                  */
 876                 if (!dptr && list->next != list->prev)
 877                         dptr = &driver_list;
 878         }
 879
 880         hctx->dispatched[queued_to_index(queued)]++;
 881
 882         /*
 883          * Any items that need requeuing? Stuff them into hctx->dispatch,
 884          * that is where we will continue on next queue run.
 885          */
 886         if (!list_empty(list)) {
 887                 spin_lock(&hctx->lock);
 888                 list_splice(list, &hctx->dispatch);
 889                 spin_unlock(&hctx->lock);
 890
 891                 /*
 892                  * the queue is expected stopped with BLK_MQ_RQ_QUEUE_BUSY, but
 893                  * it's possible the queue is stopped and restarted again
 894                  * before this. Queue restart will dispatch requests. And since
 895                  * requests in rq_list aren't added into hctx->dispatch yet,
 896                  * the requests in rq_list might get lost.
 897                  *
 898                  * blk_mq_run_hw_queue() already checks the STOPPED bit
 899                  **/
 900                 blk_mq_run_hw_queue(hctx, true);
 901         }
 902
 903         return ret != BLK_MQ_RQ_QUEUE_BUSY;
 904 }
 905
 906 /*
 907  * Run this hardware queue, pulling any software queues mapped to it in.
 908  * Note that this function currently has various problems around ordering
 909  * of IO. In particular, we'd like FIFO behaviour on handling existing
 910  * items on the hctx->dispatch list. Ignore that for now.
 911  */
 912 static void blk_mq_process_rq_list(struct blk_mq_hw_ctx *hctx)
 913 {
 914         LIST_HEAD(rq_list);
 915         LIST_HEAD(driver_list);
 916
 917         if (unlikely(blk_mq_hctx_stopped(hctx)))
 918                 return;
 919
 920         hctx->run++;
 921
 922         /*
 923          * Touch any software queue that has pending entries.
 924          */
 925         flush_busy_ctxs(hctx, &rq_list);
 926
 927         /*
 928          * If we have previous entries on our dispatch list, grab them
 929          * and stuff them at the front for more fair dispatch.
 930          */
 931         if (!list_empty_careful(&hctx->dispatch)) {
 932                 spin_lock(&hctx->lock);
 933                 if (!list_empty(&hctx->dispatch))
 934                         list_splice_init(&hctx->dispatch, &rq_list);
 935                 spin_unlock(&hctx->lock);
 936         }
 937
 938         blk_mq_dispatch_rq_list(hctx, &rq_list);
 939 }
 940
 941 static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
 942 {
 943         int srcu_idx;
 944
 945         WARN_ON(!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
 946                 cpu_online(hctx->next_cpu));
 947
 948         if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
 949                 rcu_read_lock();
 950                 blk_mq_process_rq_list(hctx);
 951                 rcu_read_unlock();
 952         } else {
 953                 srcu_idx = srcu_read_lock(&hctx->queue_rq_srcu);
 954                 blk_mq_process_rq_list(hctx);
 955                 srcu_read_unlock(&hctx->queue_rq_srcu, srcu_idx);
 956         }
 957 }
 958
 959 /*
 960  * It'd be great if the workqueue API had a way to pass
 961  * in a mask and had some smarts for more clever placement.
 962  * For now we just round-robin here, switching for every
 963  * BLK_MQ_CPU_WORK_BATCH queued items.
 964  */
 965 static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
 966 {
 967         if (hctx->queue->nr_hw_queues == 1)
 968                 return WORK_CPU_UNBOUND;
 969
 970         if (--hctx->next_cpu_batch <= 0) {
 971                 int next_cpu;
 972
 973                 next_cpu = cpumask_next(hctx->next_cpu, hctx->cpumask);
 974                 if (next_cpu >= nr_cpu_ids)
 975                         next_cpu = cpumask_first(hctx->cpumask);
 976
 977                 hctx->next_cpu = next_cpu;
 978                 hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
 979         }
 980
 981         return hctx->next_cpu;
 982 }
 983
 984 void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
 985 {
 986         if (unlikely(blk_mq_hctx_stopped(hctx) ||
 987                      !blk_mq_hw_queue_mapped(hctx)))
 988                 return;
 989
 990         if (!async && !(hctx->flags & BLK_MQ_F_BLOCKING)) {
 991                 int cpu = get_cpu();
 992                 if (cpumask_test_cpu(cpu, hctx->cpumask)) {
 993                         __blk_mq_run_hw_queue(hctx);
 994                         put_cpu();
 995                         return;
 996                 }
 997
 998                 put_cpu();
 999         }
1000
1001         kblockd_schedule_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work);
1002 }
1003
1004 void blk_mq_run_hw_queues(struct request_queue *q, bool async)
1005 {
1006         struct blk_mq_hw_ctx *hctx;
1007         int i;
1008
1009         queue_for_each_hw_ctx(q, hctx, i) {
1010                 if ((!blk_mq_hctx_has_pending(hctx) &&
1011                     list_empty_careful(&hctx->dispatch)) ||
1012                     blk_mq_hctx_stopped(hctx))
1013                         continue;
1014
1015                 blk_mq_run_hw_queue(hctx, async);
1016         }
1017 }
1018 EXPORT_SYMBOL(blk_mq_run_hw_queues);
1019
1020 /**
1021  * blk_mq_queue_stopped() - check whether one or more hctxs have been stopped
1022  * @q: request queue.
1023  *
1024  * The caller is responsible for serializing this function against
1025  * blk_mq_{start,stop}_hw_queue().
1026  */
1027 bool blk_mq_queue_stopped(struct request_queue *q)
1028 {
1029         struct blk_mq_hw_ctx *hctx;
1030         int i;
1031
1032         queue_for_each_hw_ctx(q, hctx, i)
1033                 if (blk_mq_hctx_stopped(hctx))
1034                         return true;
1035
1036         return false;
1037 }
1038 EXPORT_SYMBOL(blk_mq_queue_stopped);
1039
1040 void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx)
1041 {
1042         cancel_work(&hctx->run_work);
1043         cancel_delayed_work(&hctx->delay_work);
1044         set_bit(BLK_MQ_S_STOPPED, &hctx->state);
1045 }
1046 EXPORT_SYMBOL(blk_mq_stop_hw_queue);
1047
1048 void blk_mq_stop_hw_queues(struct request_queue *q)
1049 {
1050         struct blk_mq_hw_ctx *hctx;
1051         int i;
1052
1053         queue_for_each_hw_ctx(q, hctx, i)
1054                 blk_mq_stop_hw_queue(hctx);
1055 }
1056 EXPORT_SYMBOL(blk_mq_stop_hw_queues);
1057
1058 void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx)
1059 {
1060         clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
1061
1062         blk_mq_run_hw_queue(hctx, false);
1063 }
1064 EXPORT_SYMBOL(blk_mq_start_hw_queue);
1065
1066 void blk_mq_start_hw_queues(struct request_queue *q)
1067 {
1068         struct blk_mq_hw_ctx *hctx;
1069         int i;
1070
1071         queue_for_each_hw_ctx(q, hctx, i)
1072                 blk_mq_start_hw_queue(hctx);
1073 }
1074 EXPORT_SYMBOL(blk_mq_start_hw_queues);
1075
1076 void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
1077 {
1078         if (!blk_mq_hctx_stopped(hctx))
1079                 return;
1080
1081         clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
1082         blk_mq_run_hw_queue(hctx, async);
1083 }
1084 EXPORT_SYMBOL_GPL(blk_mq_start_stopped_hw_queue);
1085
1086 void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async)
1087 {
1088         struct blk_mq_hw_ctx *hctx;
1089         int i;
1090
1091         queue_for_each_hw_ctx(q, hctx, i)
1092                 blk_mq_start_stopped_hw_queue(hctx, async);
1093 }
1094 EXPORT_SYMBOL(blk_mq_start_stopped_hw_queues);
1095
1096 static void blk_mq_run_work_fn(struct work_struct *work)
1097 {
1098         struct blk_mq_hw_ctx *hctx;
1099
1100         hctx = container_of(work, struct blk_mq_hw_ctx, run_work);
1101
1102         __blk_mq_run_hw_queue(hctx);
1103 }
1104
1105 static void blk_mq_delay_work_fn(struct work_struct *work)
1106 {
1107         struct blk_mq_hw_ctx *hctx;
1108
1109         hctx = container_of(work, struct blk_mq_hw_ctx, delay_work.work);
1110
1111         if (test_and_clear_bit(BLK_MQ_S_STOPPED, &hctx->state))
1112                 __blk_mq_run_hw_queue(hctx);
1113 }
1114
1115 void blk_mq_delay_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
1116 {
1117         if (unlikely(!blk_mq_hw_queue_mapped(hctx)))
1118                 return;
1119
1120         kblockd_schedule_delayed_work_on(blk_mq_hctx_next_cpu(hctx),
1121                         &hctx->delay_work, msecs_to_jiffies(msecs));
1122 }
1123 EXPORT_SYMBOL(blk_mq_delay_queue);
1124
1125 static inline void __blk_mq_insert_req_list(struct blk_mq_hw_ctx *hctx,
1126                                             struct request *rq,
1127                                             bool at_head)
1128 {
1129         struct blk_mq_ctx *ctx = rq->mq_ctx;
1130
1131         trace_block_rq_insert(hctx->queue, rq);
1132
1133         if (at_head)
1134                 list_add(&rq->queuelist, &ctx->rq_list);
1135         else
1136                 list_add_tail(&rq->queuelist, &ctx->rq_list);
1137 }
1138
1139 static void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx,
1140                                     struct request *rq, bool at_head)
1141 {
1142         struct blk_mq_ctx *ctx = rq->mq_ctx;
1143
1144         __blk_mq_insert_req_list(hctx, rq, at_head);
1145         blk_mq_hctx_mark_pending(hctx, ctx);
1146 }
1147
1148 void blk_mq_insert_request(struct request *rq, bool at_head, bool run_queue,
1149                            bool async)
1150 {
1151         struct blk_mq_ctx *ctx = rq->mq_ctx;
1152         struct request_queue *q = rq->q;
1153         struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
1154
1155         spin_lock(&ctx->lock);
1156         __blk_mq_insert_request(hctx, rq, at_head);
1157         spin_unlock(&ctx->lock);
1158
1159         if (run_queue)
1160                 blk_mq_run_hw_queue(hctx, async);
1161 }
1162
1163 static void blk_mq_insert_requests(struct request_queue *q,
1164                                      struct blk_mq_ctx *ctx,
1165                                      struct list_head *list,
1166                                      int depth,
1167                                      bool from_schedule)
1168
1169 {
1170         struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
1171
1172         trace_block_unplug(q, depth, !from_schedule);
1173
1174         /*
1175          * preemption doesn't flush plug list, so it's possible ctx->cpu is
1176          * offline now
1177          */
1178         spin_lock(&ctx->lock);
1179         while (!list_empty(list)) {
1180                 struct request *rq;
1181
1182                 rq = list_first_entry(list, struct request, queuelist);
1183                 BUG_ON(rq->mq_ctx != ctx);
1184                 list_del_init(&rq->queuelist);
1185                 __blk_mq_insert_req_list(hctx, rq, false);
1186         }
1187         blk_mq_hctx_mark_pending(hctx, ctx);
1188         spin_unlock(&ctx->lock);
1189
1190         blk_mq_run_hw_queue(hctx, from_schedule);
1191 }
1192
1193 static int plug_ctx_cmp(void *priv, struct list_head *a, struct list_head *b)
1194 {
1195         struct request *rqa = container_of(a, struct request, queuelist);
1196         struct request *rqb = container_of(b, struct request, queuelist);
1197
1198         return !(rqa->mq_ctx < rqb->mq_ctx ||
1199                  (rqa->mq_ctx == rqb->mq_ctx &&
1200                   blk_rq_pos(rqa) < blk_rq_pos(rqb)));
1201 }
1202
1203 void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
1204 {
1205         struct blk_mq_ctx *this_ctx;
1206         struct request_queue *this_q;
1207         struct request *rq;
1208         LIST_HEAD(list);
1209         LIST_HEAD(ctx_list);
1210         unsigned int depth;
1211
1212         list_splice_init(&plug->mq_list, &list);
1213
1214         list_sort(NULL, &list, plug_ctx_cmp);
1215
1216         this_q = NULL;
1217         this_ctx = NULL;
1218         depth = 0;
1219
1220         while (!list_empty(&list)) {
1221                 rq = list_entry_rq(list.next);
1222                 list_del_init(&rq->queuelist);
1223                 BUG_ON(!rq->q);
1224                 if (rq->mq_ctx != this_ctx) {
1225                         if (this_ctx) {
1226                                 blk_mq_insert_requests(this_q, this_ctx,
1227                                                         &ctx_list, depth,
1228                                                         from_schedule);
1229                         }
1230
1231                         this_ctx = rq->mq_ctx;
1232                         this_q = rq->q;
1233                         depth = 0;
1234                 }
1235
1236                 depth++;
1237                 list_add_tail(&rq->queuelist, &ctx_list);
1238         }
1239
1240         /*
1241          * If 'this_ctx' is set, we know we have entries to complete
1242          * on 'ctx_list'. Do those.
1243          */
1244         if (this_ctx) {
1245                 blk_mq_insert_requests(this_q, this_ctx, &ctx_list, depth,
1246                                        from_schedule);
1247         }
1248 }
1249
1250 static void blk_mq_bio_to_request(struct request *rq, struct bio *bio)
1251 {
1252         init_request_from_bio(rq, bio);
1253
1254         blk_account_io_start(rq, true);
1255 }
1256
1257 static inline bool hctx_allow_merges(struct blk_mq_hw_ctx *hctx)
1258 {
1259         return (hctx->flags & BLK_MQ_F_SHOULD_MERGE) &&
1260                 !blk_queue_nomerges(hctx->queue);
1261 }
1262
1263 static inline bool blk_mq_merge_queue_io(struct blk_mq_hw_ctx *hctx,
1264                                          struct blk_mq_ctx *ctx,
1265                                          struct request *rq, struct bio *bio)
1266 {
1267         if (!hctx_allow_merges(hctx) || !bio_mergeable(bio)) {
1268                 blk_mq_bio_to_request(rq, bio);
1269                 spin_lock(&ctx->lock);
1270 insert_rq:
1271                 __blk_mq_insert_request(hctx, rq, false);
1272                 spin_unlock(&ctx->lock);
1273                 return false;
1274         } else {
1275                 struct request_queue *q = hctx->queue;
1276
1277                 spin_lock(&ctx->lock);
1278                 if (!blk_mq_attempt_merge(q, ctx, bio)) {
1279                         blk_mq_bio_to_request(rq, bio);
1280                         goto insert_rq;
1281                 }
1282
1283                 spin_unlock(&ctx->lock);
1284                 __blk_mq_free_request(hctx, ctx, rq);
1285                 return true;
1286         }
1287 }
1288
1289 static struct request *blk_mq_map_request(struct request_queue *q,
1290                                           struct bio *bio,
1291                                           struct blk_mq_alloc_data *data)
1292 {
1293         struct blk_mq_hw_ctx *hctx;
1294         struct blk_mq_ctx *ctx;
1295         struct request *rq;
1296
1297         blk_queue_enter_live(q);
1298         ctx = blk_mq_get_ctx(q);
1299         hctx = blk_mq_map_queue(q, ctx->cpu);
1300
1301         trace_block_getrq(q, bio, bio->bi_opf);
1302         blk_mq_set_alloc_data(data, q, 0, ctx, hctx);
1303         rq = __blk_mq_alloc_request(data, bio->bi_opf);
1304
1305         data->hctx->queued++;
1306         return rq;
1307 }
1308
1309 static void blk_mq_try_issue_directly(struct request *rq, blk_qc_t *cookie)
1310 {
1311         int ret;
1312         struct request_queue *q = rq->q;
1313         struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, rq->mq_ctx->cpu);
1314         struct blk_mq_queue_data bd = {
1315                 .rq = rq,
1316                 .list = NULL,
1317                 .last = 1
1318         };
1319         blk_qc_t new_cookie = blk_tag_to_qc_t(rq->tag, hctx->queue_num);
1320
1321         if (blk_mq_hctx_stopped(hctx))
1322                 goto insert;
1323
1324         /*
1325          * For OK queue, we are done. For error, kill it. Any other
1326          * error (busy), just add it to our list as we previously
1327          * would have done
1328          */
1329         ret = q->mq_ops->queue_rq(hctx, &bd);
1330         if (ret == BLK_MQ_RQ_QUEUE_OK) {
1331                 *cookie = new_cookie;
1332                 return;
1333         }
1334
1335         __blk_mq_requeue_request(rq);
1336
1337         if (ret == BLK_MQ_RQ_QUEUE_ERROR) {
1338                 *cookie = BLK_QC_T_NONE;
1339                 rq->errors = -EIO;
1340                 blk_mq_end_request(rq, rq->errors);
1341                 return;
1342         }
1343
1344 insert:
1345         blk_mq_insert_request(rq, false, true, true);
1346 }
1347
1348 /*
1349  * Multiple hardware queue variant. This will not use per-process plugs,
1350  * but will attempt to bypass the hctx queueing if we can go straight to
1351  * hardware for SYNC IO.
1352  */
1353 static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
1354 {
1355         const int is_sync = op_is_sync(bio->bi_opf);
1356         const int is_flush_fua = bio->bi_opf & (REQ_PREFLUSH | REQ_FUA);
1357         struct blk_mq_alloc_data data;
1358         struct request *rq;
1359         unsigned int request_count = 0, srcu_idx;
1360         struct blk_plug *plug;
1361         struct request *same_queue_rq = NULL;
1362         blk_qc_t cookie;
1363         unsigned int wb_acct;
1364
1365         blk_queue_bounce(q, &bio);
1366
1367         if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) {
1368                 bio_io_error(bio);
1369                 return BLK_QC_T_NONE;
1370         }
1371
1372         blk_queue_split(q, &bio, q->bio_split);
1373
1374         if (!is_flush_fua && !blk_queue_nomerges(q) &&
1375             blk_attempt_plug_merge(q, bio, &request_count, &same_queue_rq))
1376                 return BLK_QC_T_NONE;
1377
1378         wb_acct = wbt_wait(q->rq_wb, bio, NULL);
1379
1380         rq = blk_mq_map_request(q, bio, &data);
1381         if (unlikely(!rq)) {
1382                 __wbt_done(q->rq_wb, wb_acct);
1383                 return BLK_QC_T_NONE;
1384         }
1385
1386         wbt_track(&rq->issue_stat, wb_acct);
1387
1388         cookie = blk_tag_to_qc_t(rq->tag, data.hctx->queue_num);
1389
1390         if (unlikely(is_flush_fua)) {
1391                 blk_mq_bio_to_request(rq, bio);
1392                 blk_insert_flush(rq);
1393                 goto run_queue;
1394         }
1395
1396         plug = current->plug;
1397         /*
1398          * If the driver supports defer issued based on 'last', then
1399          * queue it up like normal since we can potentially save some
1400          * CPU this way.
1401          */
1402         if (((plug && !blk_queue_nomerges(q)) || is_sync) &&
1403             !(data.hctx->flags & BLK_MQ_F_DEFER_ISSUE)) {
1404                 struct request *old_rq = NULL;
1405
1406                 blk_mq_bio_to_request(rq, bio);
1407
1408                 /*
1409                  * We do limited plugging. If the bio can be merged, do that.
1410                  * Otherwise the existing request in the plug list will be
1411                  * issued. So the plug list will have one request at most
1412                  */
1413                 if (plug) {
1414                         /*
1415                          * The plug list might get flushed before this. If that
1416                          * happens, same_queue_rq is invalid and plug list is
1417                          * empty
1418                          */
1419                         if (same_queue_rq && !list_empty(&plug->mq_list)) {
1420                                 old_rq = same_queue_rq;
1421                                 list_del_init(&old_rq->queuelist);
1422                         }
1423                         list_add_tail(&rq->queuelist, &plug->mq_list);
1424                 } else /* is_sync */
1425                         old_rq = rq;
1426                 blk_mq_put_ctx(data.ctx);
1427                 if (!old_rq)
1428                         goto done;
1429
1430                 if (!(data.hctx->flags & BLK_MQ_F_BLOCKING)) {
1431                         rcu_read_lock();
1432                         blk_mq_try_issue_directly(old_rq, &cookie);
1433                         rcu_read_unlock();
1434                 } else {
1435                         srcu_idx = srcu_read_lock(&data.hctx->queue_rq_srcu);
1436                         blk_mq_try_issue_directly(old_rq, &cookie);
1437                         srcu_read_unlock(&data.hctx->queue_rq_srcu, srcu_idx);
1438                 }
1439                 goto done;
1440         }
1441
1442         if (!blk_mq_merge_queue_io(data.hctx, data.ctx, rq, bio)) {
1443                 /*
1444                  * For a SYNC request, send it to the hardware immediately. For
1445                  * an ASYNC request, just ensure that we run it later on. The
1446                  * latter allows for merging opportunities and more efficient
1447                  * dispatching.
1448                  */
1449 run_queue:
1450                 blk_mq_run_hw_queue(data.hctx, !is_sync || is_flush_fua);
1451         }
1452         blk_mq_put_ctx(data.ctx);
1453 done:
1454         return cookie;
1455 }
1456
1457 /*
1458  * Single hardware queue variant. This will attempt to use any per-process
1459  * plug for merging and IO deferral.
1460  */
1461 static blk_qc_t blk_sq_make_request(struct request_queue *q, struct bio *bio)
1462 {
1463         const int is_sync = op_is_sync(bio->bi_opf);
1464         const int is_flush_fua = bio->bi_opf & (REQ_PREFLUSH | REQ_FUA);
1465         struct blk_plug *plug;
1466         unsigned int request_count = 0;
1467         struct blk_mq_alloc_data data;
1468         struct request *rq;
1469         blk_qc_t cookie;
1470         unsigned int wb_acct;
1471
1472         blk_queue_bounce(q, &bio);
1473
1474         if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) {
1475                 bio_io_error(bio);
1476                 return BLK_QC_T_NONE;
1477         }
1478
1479         blk_queue_split(q, &bio, q->bio_split);
1480
1481         if (!is_flush_fua && !blk_queue_nomerges(q)) {
1482                 if (blk_attempt_plug_merge(q, bio, &request_count, NULL))
1483                         return BLK_QC_T_NONE;
1484         } else
1485                 request_count = blk_plug_queued_count(q);
1486
1487         wb_acct = wbt_wait(q->rq_wb, bio, NULL);
1488
1489         rq = blk_mq_map_request(q, bio, &data);
1490         if (unlikely(!rq)) {
1491                 __wbt_done(q->rq_wb, wb_acct);
1492                 return BLK_QC_T_NONE;
1493         }
1494
1495         wbt_track(&rq->issue_stat, wb_acct);
1496
1497         cookie = blk_tag_to_qc_t(rq->tag, data.hctx->queue_num);
1498
1499         if (unlikely(is_flush_fua)) {
1500                 blk_mq_bio_to_request(rq, bio);
1501                 blk_insert_flush(rq);
1502                 goto run_queue;
1503         }
1504
1505         /*
1506          * A task plug currently exists. Since this is completely lockless,
1507          * utilize that to temporarily store requests until the task is
1508          * either done or scheduled away.
1509          */
1510         plug = current->plug;
1511         if (plug) {
1512                 struct request *last = NULL;
1513
1514                 blk_mq_bio_to_request(rq, bio);
1515
1516                 /*
1517                  * @request_count may become stale because of schedule
1518                  * out, so check the list again.
1519                  */
1520                 if (list_empty(&plug->mq_list))
1521                         request_count = 0;
1522                 if (!request_count)
1523                         trace_block_plug(q);
1524                 else
1525                         last = list_entry_rq(plug->mq_list.prev);
1526
1527                 blk_mq_put_ctx(data.ctx);
1528
1529                 if (request_count >= BLK_MAX_REQUEST_COUNT || (last &&
1530                     blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
1531                         blk_flush_plug_list(plug, false);
1532                         trace_block_plug(q);
1533                 }
1534
1535                 list_add_tail(&rq->queuelist, &plug->mq_list);
1536                 return cookie;
1537         }
1538
1539         if (!blk_mq_merge_queue_io(data.hctx, data.ctx, rq, bio)) {
1540                 /*
1541                  * For a SYNC request, send it to the hardware immediately. For
1542                  * an ASYNC request, just ensure that we run it later on. The
1543                  * latter allows for merging opportunities and more efficient
1544                  * dispatching.
1545                  */
1546 run_queue:
1547                 blk_mq_run_hw_queue(data.hctx, !is_sync || is_flush_fua);
1548         }
1549
1550         blk_mq_put_ctx(data.ctx);
1551         return cookie;
1552 }
1553
1554 static void blk_mq_free_rq_map(struct blk_mq_tag_set *set,
1555                 struct blk_mq_tags *tags, unsigned int hctx_idx)
1556 {
1557         struct page *page;
1558
1559         if (tags->rqs && set->ops->exit_request) {
1560                 int i;
1561
1562                 for (i = 0; i < tags->nr_tags; i++) {
1563                         if (!tags->rqs[i])
1564                                 continue;
1565                         set->ops->exit_request(set->driver_data, tags->rqs[i],
1566                                                 hctx_idx, i);
1567                         tags->rqs[i] = NULL;
1568                 }
1569         }
1570
1571         while (!list_empty(&tags->page_list)) {
1572                 page = list_first_entry(&tags->page_list, struct page, lru);
1573                 list_del_init(&page->lru);
1574                 /*
1575                  * Remove kmemleak object previously allocated in
1576                  * blk_mq_init_rq_map().
1577                  */
1578                 kmemleak_free(page_address(page));
1579                 __free_pages(page, page->private);
1580         }
1581
1582         kfree(tags->rqs);
1583
1584         blk_mq_free_tags(tags);
1585 }
1586
1587 static size_t order_to_size(unsigned int order)
1588 {
1589         return (size_t)PAGE_SIZE << order;
1590 }
1591
1592 static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set,
1593                 unsigned int hctx_idx)
1594 {
1595         struct blk_mq_tags *tags;
1596         unsigned int i, j, entries_per_page, max_order = 4;
1597         size_t rq_size, left;
1598
1599         tags = blk_mq_init_tags(set->queue_depth, set->reserved_tags,
1600                                 set->numa_node,
1601                                 BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags));
1602         if (!tags)
1603                 return NULL;
1604
1605         INIT_LIST_HEAD(&tags->page_list);
1606
1607         tags->rqs = kzalloc_node(set->queue_depth * sizeof(struct request *),
1608                                  GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY,
1609                                  set->numa_node);
1610         if (!tags->rqs) {
1611                 blk_mq_free_tags(tags);
1612                 return NULL;
1613         }
1614
1615         /*
1616          * rq_size is the size of the request plus driver payload, rounded
1617          * to the cacheline size
1618          */
1619         rq_size = round_up(sizeof(struct request) + set->cmd_size,
1620                                 cache_line_size());
1621         left = rq_size * set->queue_depth;
1622
1623         for (i = 0; i < set->queue_depth; ) {
1624                 int this_order = max_order;
1625                 struct page *page;
1626                 int to_do;
1627                 void *p;
1628
1629                 while (this_order && left < order_to_size(this_order - 1))
1630                         this_order--;
1631
1632                 do {
1633                         page = alloc_pages_node(set->numa_node,
1634                                 GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY | __GFP_ZERO,
1635                                 this_order);
1636                         if (page)
1637                                 break;
1638                         if (!this_order--)
1639                                 break;
1640                         if (order_to_size(this_order) < rq_size)
1641                                 break;
1642                 } while (1);
1643
1644                 if (!page)
1645                         goto fail;
1646
1647                 page->private = this_order;
1648                 list_add_tail(&page->lru, &tags->page_list);
1649
1650                 p = page_address(page);
1651                 /*
1652                  * Allow kmemleak to scan these pages as they contain pointers
1653                  * to additional allocations like via ops->init_request().
1654                  */
1655                 kmemleak_alloc(p, order_to_size(this_order), 1, GFP_KERNEL);
1656                 entries_per_page = order_to_size(this_order) / rq_size;
1657                 to_do = min(entries_per_page, set->queue_depth - i);
1658                 left -= to_do * rq_size;
1659                 for (j = 0; j < to_do; j++) {
1660                         tags->rqs[i] = p;
1661                         if (set->ops->init_request) {
1662                                 if (set->ops->init_request(set->driver_data,
1663                                                 tags->rqs[i], hctx_idx, i,
1664                                                 set->numa_node)) {
1665                                         tags->rqs[i] = NULL;
1666                                         goto fail;
1667                                 }
1668                         }
1669
1670                         p += rq_size;
1671                         i++;
1672                 }
1673         }
1674         return tags;
1675
1676 fail:
1677         blk_mq_free_rq_map(set, tags, hctx_idx);
1678         return NULL;
1679 }
1680
1681 /*
1682  * 'cpu' is going away. splice any existing rq_list entries from this
1683  * software queue to the hw queue dispatch list, and ensure that it
1684  * gets run.
1685  */
1686 static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node)
1687 {
1688         struct blk_mq_hw_ctx *hctx;
1689         struct blk_mq_ctx *ctx;
1690         LIST_HEAD(tmp);
1691
1692         hctx = hlist_entry_safe(node, struct blk_mq_hw_ctx, cpuhp_dead);
1693         ctx = __blk_mq_get_ctx(hctx->queue, cpu);
1694
1695         spin_lock(&ctx->lock);
1696         if (!list_empty(&ctx->rq_list)) {
1697                 list_splice_init(&ctx->rq_list, &tmp);
1698                 blk_mq_hctx_clear_pending(hctx, ctx);
1699         }
1700         spin_unlock(&ctx->lock);
1701
1702         if (list_empty(&tmp))
1703                 return 0;
1704
1705         spin_lock(&hctx->lock);
1706         list_splice_tail_init(&tmp, &hctx->dispatch);
1707         spin_unlock(&hctx->lock);
1708
1709         blk_mq_run_hw_queue(hctx, true);
1710         return 0;
1711 }
1712
1713 static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx)
1714 {
1715         cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_DEAD,
1716                                             &hctx->cpuhp_dead);
1717 }
1718
1719 /* hctx->ctxs will be freed in queue's release handler */
1720 static void blk_mq_exit_hctx(struct request_queue *q,
1721                 struct blk_mq_tag_set *set,
1722                 struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
1723 {
1724         unsigned flush_start_tag = set->queue_depth;
1725
1726         blk_mq_tag_idle(hctx);
1727
1728         if (set->ops->exit_request)
1729                 set->ops->exit_request(set->driver_data,
1730                                        hctx->fq->flush_rq, hctx_idx,
1731                                        flush_start_tag + hctx_idx);
1732
1733         if (set->ops->exit_hctx)
1734                 set->ops->exit_hctx(hctx, hctx_idx);
1735
1736         if (hctx->flags & BLK_MQ_F_BLOCKING)
1737                 cleanup_srcu_struct(&hctx->queue_rq_srcu);
1738
1739         blk_mq_remove_cpuhp(hctx);
1740         blk_free_flush_queue(hctx->fq);
1741         sbitmap_free(&hctx->ctx_map);
1742 }
1743
1744 static void blk_mq_exit_hw_queues(struct request_queue *q,
1745                 struct blk_mq_tag_set *set, int nr_queue)
1746 {
1747         struct blk_mq_hw_ctx *hctx;
1748         unsigned int i;
1749
1750         queue_for_each_hw_ctx(q, hctx, i) {
1751                 if (i == nr_queue)
1752                         break;
1753                 blk_mq_exit_hctx(q, set, hctx, i);
1754         }
1755 }
1756
1757 static void blk_mq_free_hw_queues(struct request_queue *q,
1758                 struct blk_mq_tag_set *set)
1759 {
1760         struct blk_mq_hw_ctx *hctx;
1761         unsigned int i;
1762
1763         queue_for_each_hw_ctx(q, hctx, i)
1764                 free_cpumask_var(hctx->cpumask);
1765 }
1766
1767 static int blk_mq_init_hctx(struct request_queue *q,
1768                 struct blk_mq_tag_set *set,
1769                 struct blk_mq_hw_ctx *hctx, unsigned hctx_idx)
1770 {
1771         int node;
1772         unsigned flush_start_tag = set->queue_depth;
1773
1774         node = hctx->numa_node;
1775         if (node == NUMA_NO_NODE)
1776                 node = hctx->numa_node = set->numa_node;
1777
1778         INIT_WORK(&hctx->run_work, blk_mq_run_work_fn);
1779         INIT_DELAYED_WORK(&hctx->delay_work, blk_mq_delay_work_fn);
1780         spin_lock_init(&hctx->lock);
1781         INIT_LIST_HEAD(&hctx->dispatch);
1782         hctx->queue = q;
1783         hctx->queue_num = hctx_idx;
1784         hctx->flags = set->flags & ~BLK_MQ_F_TAG_SHARED;
1785
1786         cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD, &hctx->cpuhp_dead);
1787
1788         hctx->tags = set->tags[hctx_idx];
1789
1790         /*
1791          * Allocate space for all possible cpus to avoid allocation at
1792          * runtime
1793          */
1794         hctx->ctxs = kmalloc_node(nr_cpu_ids * sizeof(void *),
1795                                         GFP_KERNEL, node);
1796         if (!hctx->ctxs)
1797                 goto unregister_cpu_notifier;
1798
1799         if (sbitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8), GFP_KERNEL,
1800                               node))
1801                 goto free_ctxs;
1802
1803         hctx->nr_ctx = 0;
1804
1805         if (set->ops->init_hctx &&
1806             set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
1807                 goto free_bitmap;
1808
1809         hctx->fq = blk_alloc_flush_queue(q, hctx->numa_node, set->cmd_size);
1810         if (!hctx->fq)
1811                 goto exit_hctx;
1812
1813         if (set->ops->init_request &&
1814             set->ops->init_request(set->driver_data,
1815                                    hctx->fq->flush_rq, hctx_idx,
1816                                    flush_start_tag + hctx_idx, node))
1817                 goto free_fq;
1818
1819         if (hctx->flags & BLK_MQ_F_BLOCKING)
1820                 init_srcu_struct(&hctx->queue_rq_srcu);
1821
1822         return 0;
1823
1824  free_fq:
1825         kfree(hctx->fq);
1826  exit_hctx:
1827         if (set->ops->exit_hctx)
1828                 set->ops->exit_hctx(hctx, hctx_idx);
1829  free_bitmap:
1830         sbitmap_free(&hctx->ctx_map);
1831  free_ctxs:
1832         kfree(hctx->ctxs);
1833  unregister_cpu_notifier:
1834         blk_mq_remove_cpuhp(hctx);
1835         return -1;
1836 }
1837
1838 static void blk_mq_init_cpu_queues(struct request_queue *q,
1839                                    unsigned int nr_hw_queues)
1840 {
1841         unsigned int i;
1842
1843         for_each_possible_cpu(i) {
1844                 struct blk_mq_ctx *__ctx = per_cpu_ptr(q->queue_ctx, i);
1845                 struct blk_mq_hw_ctx *hctx;
1846
1847                 memset(__ctx, 0, sizeof(*__ctx));
1848                 __ctx->cpu = i;
1849                 spin_lock_init(&__ctx->lock);
1850                 INIT_LIST_HEAD(&__ctx->rq_list);
1851                 __ctx->queue = q;
1852                 blk_stat_init(&__ctx->stat[BLK_STAT_READ]);
1853                 blk_stat_init(&__ctx->stat[BLK_STAT_WRITE]);
1854
1855                 /* If the cpu isn't online, the cpu is mapped to first hctx */
1856                 if (!cpu_online(i))
1857                         continue;
1858
1859                 hctx = blk_mq_map_queue(q, i);
1860
1861                 /*
1862                  * Set local node, IFF we have more than one hw queue. If
1863                  * not, we remain on the home node of the device
1864                  */
1865                 if (nr_hw_queues > 1 && hctx->numa_node == NUMA_NO_NODE)
1866                         hctx->numa_node = local_memory_node(cpu_to_node(i));
1867         }
1868 }
1869
1870 static void blk_mq_map_swqueue(struct request_queue *q,
1871                                const struct cpumask *online_mask)
1872 {
1873         unsigned int i;
1874         struct blk_mq_hw_ctx *hctx;
1875         struct blk_mq_ctx *ctx;
1876         struct blk_mq_tag_set *set = q->tag_set;
1877
1878         /*
1879          * Avoid others reading imcomplete hctx->cpumask through sysfs
1880          */
1881         mutex_lock(&q->sysfs_lock);
1882
1883         queue_for_each_hw_ctx(q, hctx, i) {
1884                 cpumask_clear(hctx->cpumask);
1885                 hctx->nr_ctx = 0;
1886         }
1887
1888         /*
1889          * Map software to hardware queues
1890          */
1891         for_each_possible_cpu(i) {
1892                 /* If the cpu isn't online, the cpu is mapped to first hctx */
1893                 if (!cpumask_test_cpu(i, online_mask))
1894                         continue;
1895
1896                 ctx = per_cpu_ptr(q->queue_ctx, i);
1897                 hctx = blk_mq_map_queue(q, i);
1898
1899                 cpumask_set_cpu(i, hctx->cpumask);
1900                 ctx->index_hw = hctx->nr_ctx;
1901                 hctx->ctxs[hctx->nr_ctx++] = ctx;
1902         }
1903
1904         mutex_unlock(&q->sysfs_lock);
1905
1906         queue_for_each_hw_ctx(q, hctx, i) {
1907                 /*
1908                  * If no software queues are mapped to this hardware queue,
1909                  * disable it and free the request entries.
1910                  */
1911                 if (!hctx->nr_ctx) {
1912                         if (set->tags[i]) {
1913                                 blk_mq_free_rq_map(set, set->tags[i], i);
1914                                 set->tags[i] = NULL;
1915                         }
1916                         hctx->tags = NULL;
1917                         continue;
1918                 }
1919
1920                 /* unmapped hw queue can be remapped after CPU topo changed */
1921                 if (!set->tags[i])
1922                         set->tags[i] = blk_mq_init_rq_map(set, i);
1923                 hctx->tags = set->tags[i];
1924                 WARN_ON(!hctx->tags);
1925
1926                 /*
1927                  * Set the map size to the number of mapped software queues.
1928                  * This is more accurate and more efficient than looping
1929                  * over all possibly mapped software queues.
1930                  */
1931                 sbitmap_resize(&hctx->ctx_map, hctx->nr_ctx);
1932
1933                 /*
1934                  * Initialize batch roundrobin counts
1935                  */
1936                 hctx->next_cpu = cpumask_first(hctx->cpumask);
1937                 hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
1938         }
1939 }
1940
1941 static void queue_set_hctx_shared(struct request_queue *q, bool shared)
1942 {
1943         struct blk_mq_hw_ctx *hctx;
1944         int i;
1945
1946         queue_for_each_hw_ctx(q, hctx, i) {
1947                 if (shared)
1948                         hctx->flags |= BLK_MQ_F_TAG_SHARED;
1949                 else
1950                         hctx->flags &= ~BLK_MQ_F_TAG_SHARED;
1951         }
1952 }
1953
1954 static void blk_mq_update_tag_set_depth(struct blk_mq_tag_set *set, bool shared)
1955 {
1956         struct request_queue *q;
1957
1958         list_for_each_entry(q, &set->tag_list, tag_set_list) {
1959                 blk_mq_freeze_queue(q);
1960                 queue_set_hctx_shared(q, shared);
1961                 blk_mq_unfreeze_queue(q);
1962         }
1963 }
1964
1965 static void blk_mq_del_queue_tag_set(struct request_queue *q)
1966 {
1967         struct blk_mq_tag_set *set = q->tag_set;
1968
1969         mutex_lock(&set->tag_list_lock);
1970         list_del_init(&q->tag_set_list);
1971         if (list_is_singular(&set->tag_list)) {
1972                 /* just transitioned to unshared */
1973                 set->flags &= ~BLK_MQ_F_TAG_SHARED;
1974                 /* update existing queue */
1975                 blk_mq_update_tag_set_depth(set, false);
1976         }
1977         mutex_unlock(&set->tag_list_lock);
1978 }
1979
1980 static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
1981                                      struct request_queue *q)
1982 {
1983         q->tag_set = set;
1984
1985         mutex_lock(&set->tag_list_lock);
1986
1987         /* Check to see if we're transitioning to shared (from 1 to 2 queues). */
1988         if (!list_empty(&set->tag_list) && !(set->flags & BLK_MQ_F_TAG_SHARED)) {
1989                 set->flags |= BLK_MQ_F_TAG_SHARED;
1990                 /* update existing queue */
1991                 blk_mq_update_tag_set_depth(set, true);
1992         }
1993         if (set->flags & BLK_MQ_F_TAG_SHARED)
1994                 queue_set_hctx_shared(q, true);
1995         list_add_tail(&q->tag_set_list, &set->tag_list);
1996
1997         mutex_unlock(&set->tag_list_lock);
1998 }
1999
2000 /*
2001  * It is the actual release handler for mq, but we do it from
2002  * request queue's release handler for avoiding use-after-free
2003  * and headache because q->mq_kobj shouldn't have been introduced,
2004  * but we can't group ctx/kctx kobj without it.
2005  */
2006 void blk_mq_release(struct request_queue *q)
2007 {
2008         struct blk_mq_hw_ctx *hctx;
2009         unsigned int i;
2010
2011         /* hctx kobj stays in hctx */
2012         queue_for_each_hw_ctx(q, hctx, i) {
2013                 if (!hctx)
2014                         continue;
2015                 kfree(hctx->ctxs);
2016                 kfree(hctx);
2017         }
2018
2019         q->mq_map = NULL;
2020
2021         kfree(q->queue_hw_ctx);
2022
2023         /* ctx kobj stays in queue_ctx */
2024         free_percpu(q->queue_ctx);
2025 }
2026
2027 struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
2028 {
2029         struct request_queue *uninit_q, *q;
2030
2031         uninit_q = blk_alloc_queue_node(GFP_KERNEL, set->numa_node);
2032         if (!uninit_q)
2033                 return ERR_PTR(-ENOMEM);
2034
2035         q = blk_mq_init_allocated_queue(set, uninit_q);
2036         if (IS_ERR(q))
2037                 blk_cleanup_queue(uninit_q);
2038
2039         return q;
2040 }
2041 EXPORT_SYMBOL(blk_mq_init_queue);
2042
2043 static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
2044                                                 struct request_queue *q)
2045 {
2046         int i, j;
2047         struct blk_mq_hw_ctx **hctxs = q->queue_hw_ctx;
2048
2049         blk_mq_sysfs_unregister(q);
2050         for (i = 0; i < set->nr_hw_queues; i++) {
2051                 int node;
2052
2053                 if (hctxs[i])
2054                         continue;
2055
2056                 node = blk_mq_hw_queue_to_node(q->mq_map, i);
2057                 hctxs[i] = kzalloc_node(sizeof(struct blk_mq_hw_ctx),
2058                                         GFP_KERNEL, node);
2059                 if (!hctxs[i])
2060                         break;
2061
2062                 if (!zalloc_cpumask_var_node(&hctxs[i]->cpumask, GFP_KERNEL,
2063                                                 node)) {
2064                         kfree(hctxs[i]);
2065                         hctxs[i] = NULL;
2066                         break;
2067                 }
2068
2069                 atomic_set(&hctxs[i]->nr_active, 0);
2070                 hctxs[i]->numa_node = node;
2071                 hctxs[i]->queue_num = i;
2072
2073                 if (blk_mq_init_hctx(q, set, hctxs[i], i)) {
2074                         free_cpumask_var(hctxs[i]->cpumask);
2075                         kfree(hctxs[i]);
2076                         hctxs[i] = NULL;
2077                         break;
2078                 }
2079                 blk_mq_hctx_kobj_init(hctxs[i]);
2080         }
2081         for (j = i; j < q->nr_hw_queues; j++) {
2082                 struct blk_mq_hw_ctx *hctx = hctxs[j];
2083
2084                 if (hctx) {
2085                         if (hctx->tags) {
2086                                 blk_mq_free_rq_map(set, hctx->tags, j);
2087                                 set->tags[j] = NULL;
2088                         }
2089                         blk_mq_exit_hctx(q, set, hctx, j);
2090                         free_cpumask_var(hctx->cpumask);
2091                         kobject_put(&hctx->kobj);
2092                         kfree(hctx->ctxs);
2093                         kfree(hctx);
2094                         hctxs[j] = NULL;
2095
2096                 }
2097         }
2098         q->nr_hw_queues = i;
2099         blk_mq_sysfs_register(q);
2100 }
2101
2102 struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
2103                                                   struct request_queue *q)
2104 {
2105         /* mark the queue as mq asap */
2106         q->mq_ops = set->ops;
2107
2108         q->queue_ctx = alloc_percpu(struct blk_mq_ctx);
2109         if (!q->queue_ctx)
2110                 goto err_exit;
2111
2112         q->queue_hw_ctx = kzalloc_node(nr_cpu_ids * sizeof(*(q->queue_hw_ctx)),
2113                                                 GFP_KERNEL, set->numa_node);
2114         if (!q->queue_hw_ctx)
2115                 goto err_percpu;
2116
2117         q->mq_map = set->mq_map;
2118
2119         blk_mq_realloc_hw_ctxs(set, q);
2120         if (!q->nr_hw_queues)
2121                 goto err_hctxs;
2122
2123         INIT_WORK(&q->timeout_work, blk_mq_timeout_work);
2124         blk_queue_rq_timeout(q, set->timeout ? set->timeout : 30 * HZ);
2125
2126         q->nr_queues = nr_cpu_ids;
2127
2128         q->queue_flags |= QUEUE_FLAG_MQ_DEFAULT;
2129
2130         if (!(set->flags & BLK_MQ_F_SG_MERGE))
2131                 q->queue_flags |= 1 << QUEUE_FLAG_NO_SG_MERGE;
2132
2133         q->sg_reserved_size = INT_MAX;
2134
2135         INIT_DELAYED_WORK(&q->requeue_work, blk_mq_requeue_work);
2136         INIT_LIST_HEAD(&q->requeue_list);
2137         spin_lock_init(&q->requeue_lock);
2138
2139         if (q->nr_hw_queues > 1)
2140                 blk_queue_make_request(q, blk_mq_make_request);
2141         else
2142                 blk_queue_make_request(q, blk_sq_make_request);
2143
2144         /*
2145          * Do this after blk_queue_make_request() overrides it...
2146          */
2147         q->nr_requests = set->queue_depth;
2148
2149         /*
2150          * Default to classic polling
2151          */
2152         q->poll_nsec = -1;
2153
2154         if (set->ops->complete)
2155                 blk_queue_softirq_done(q, set->ops->complete);
2156
2157         blk_mq_init_cpu_queues(q, set->nr_hw_queues);
2158
2159         get_online_cpus();
2160         mutex_lock(&all_q_mutex);
2161
2162         list_add_tail(&q->all_q_node, &all_q_list);
2163         blk_mq_add_queue_tag_set(set, q);
2164         blk_mq_map_swqueue(q, cpu_online_mask);
2165
2166         mutex_unlock(&all_q_mutex);
2167         put_online_cpus();
2168
2169         return q;
2170
2171 err_hctxs:
2172         kfree(q->queue_hw_ctx);
2173 err_percpu:
2174         free_percpu(q->queue_ctx);
2175 err_exit:
2176         q->mq_ops = NULL;
2177         return ERR_PTR(-ENOMEM);
2178 }
2179 EXPORT_SYMBOL(blk_mq_init_allocated_queue);
2180
2181 void blk_mq_free_queue(struct request_queue *q)
2182 {
2183         struct blk_mq_tag_set   *set = q->tag_set;
2184
2185         mutex_lock(&all_q_mutex);
2186         list_del_init(&q->all_q_node);
2187         mutex_unlock(&all_q_mutex);
2188
2189         wbt_exit(q);
2190
2191         blk_mq_del_queue_tag_set(q);
2192
2193         blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);
2194         blk_mq_free_hw_queues(q, set);
2195 }
2196
2197 /* Basically redo blk_mq_init_queue with queue frozen */
2198 static void blk_mq_queue_reinit(struct request_queue *q,
2199                                 const struct cpumask *online_mask)
2200 {
2201         WARN_ON_ONCE(!atomic_read(&q->mq_freeze_depth));
2202
2203         blk_mq_sysfs_unregister(q);
2204
2205         /*
2206          * redo blk_mq_init_cpu_queues and blk_mq_init_hw_queues. FIXME: maybe
2207          * we should change hctx numa_node according to new topology (this
2208          * involves free and re-allocate memory, worthy doing?)
2209          */
2210
2211         blk_mq_map_swqueue(q, online_mask);
2212
2213         blk_mq_sysfs_register(q);
2214 }
2215
2216 /*
2217  * New online cpumask which is going to be set in this hotplug event.
2218  * Declare this cpumasks as global as cpu-hotplug operation is invoked
2219  * one-by-one and dynamically allocating this could result in a failure.
2220  */
2221 static struct cpumask cpuhp_online_new;
2222
2223 static void blk_mq_queue_reinit_work(void)
2224 {
2225         struct request_queue *q;
2226
2227         mutex_lock(&all_q_mutex);
2228         /*
2229          * We need to freeze and reinit all existing queues.  Freezing
2230          * involves synchronous wait for an RCU grace period and doing it
2231          * one by one may take a long time.  Start freezing all queues in
2232          * one swoop and then wait for the completions so that freezing can
2233          * take place in parallel.
2234          */
2235         list_for_each_entry(q, &all_q_list, all_q_node)
2236                 blk_mq_freeze_queue_start(q);
2237         list_for_each_entry(q, &all_q_list, all_q_node)
2238                 blk_mq_freeze_queue_wait(q);
2239
2240         list_for_each_entry(q, &all_q_list, all_q_node)
2241                 blk_mq_queue_reinit(q, &cpuhp_online_new);
2242
2243         list_for_each_entry(q, &all_q_list, all_q_node)
2244                 blk_mq_unfreeze_queue(q);
2245
2246         mutex_unlock(&all_q_mutex);
2247 }
2248
2249 static int blk_mq_queue_reinit_dead(unsigned int cpu)
2250 {
2251         cpumask_copy(&cpuhp_online_new, cpu_online_mask);
2252         blk_mq_queue_reinit_work();
2253         return 0;
2254 }
2255
2256 /*
2257  * Before hotadded cpu starts handling requests, new mappings must be
2258  * established.  Otherwise, these requests in hw queue might never be
2259  * dispatched.
2260  *
2261  * For example, there is a single hw queue (hctx) and two CPU queues (ctx0
2262  * for CPU0, and ctx1 for CPU1).
2263  *
2264  * Now CPU1 is just onlined and a request is inserted into ctx1->rq_list
2265  * and set bit0 in pending bitmap as ctx1->index_hw is still zero.
2266  *
2267  * And then while running hw queue, flush_busy_ctxs() finds bit0 is set in
2268  * pending bitmap and tries to retrieve requests in hctx->ctxs[0]->rq_list.
2269  * But htx->ctxs[0] is a pointer to ctx0, so the request in ctx1->rq_list
2270  * is ignored.
2271  */
2272 static int blk_mq_queue_reinit_prepare(unsigned int cpu)
2273 {
2274         cpumask_copy(&cpuhp_online_new, cpu_online_mask);
2275         cpumask_set_cpu(cpu, &cpuhp_online_new);
2276         blk_mq_queue_reinit_work();
2277         return 0;
2278 }
2279
2280 static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
2281 {
2282         int i;
2283
2284         for (i = 0; i < set->nr_hw_queues; i++) {
2285                 set->tags[i] = blk_mq_init_rq_map(set, i);
2286                 if (!set->tags[i])
2287                         goto out_unwind;
2288         }
2289
2290         return 0;
2291
2292 out_unwind:
2293         while (--i >= 0)
2294                 blk_mq_free_rq_map(set, set->tags[i], i);
2295
2296         return -ENOMEM;
2297 }
2298
2299 /*
2300  * Allocate the request maps associated with this tag_set. Note that this
2301  * may reduce the depth asked for, if memory is tight. set->queue_depth
2302  * will be updated to reflect the allocated depth.
2303  */
2304 static int blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
2305 {
2306         unsigned int depth;
2307         int err;
2308
2309         depth = set->queue_depth;
2310         do {
2311                 err = __blk_mq_alloc_rq_maps(set);
2312                 if (!err)
2313                         break;
2314
2315                 set->queue_depth >>= 1;
2316                 if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN) {
2317                         err = -ENOMEM;
2318                         break;
2319                 }
2320         } while (set->queue_depth);
2321
2322         if (!set->queue_depth || err) {
2323                 pr_err("blk-mq: failed to allocate request map\n");
2324                 return -ENOMEM;
2325         }
2326
2327         if (depth != set->queue_depth)
2328                 pr_info("blk-mq: reduced tag depth (%u -> %u)\n",
2329                                                 depth, set->queue_depth);
2330
2331         return 0;
2332 }
2333
2334 /*
2335  * Alloc a tag set to be associated with one or more request queues.
2336  * May fail with EINVAL for various error conditions. May adjust the
2337  * requested depth down, if if it too large. In that case, the set
2338  * value will be stored in set->queue_depth.
2339  */
2340 int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
2341 {
2342         int ret;
2343
2344         BUILD_BUG_ON(BLK_MQ_MAX_DEPTH > 1 << BLK_MQ_UNIQUE_TAG_BITS);
2345
2346         if (!set->nr_hw_queues)
2347                 return -EINVAL;
2348         if (!set->queue_depth)
2349                 return -EINVAL;
2350         if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN)
2351                 return -EINVAL;
2352
2353         if (!set->ops->queue_rq)
2354                 return -EINVAL;
2355
2356         if (set->queue_depth > BLK_MQ_MAX_DEPTH) {
2357                 pr_info("blk-mq: reduced tag depth to %u\n",
2358                         BLK_MQ_MAX_DEPTH);
2359                 set->queue_depth = BLK_MQ_MAX_DEPTH;
2360         }
2361
2362         /*
2363          * If a crashdump is active, then we are potentially in a very
2364          * memory constrained environment. Limit us to 1 queue and
2365          * 64 tags to prevent using too much memory.
2366          */
2367         if (is_kdump_kernel()) {
2368                 set->nr_hw_queues = 1;
2369                 set->queue_depth = min(64U, set->queue_depth);
2370         }
2371         /*
2372          * There is no use for more h/w queues than cpus.
2373          */
2374         if (set->nr_hw_queues > nr_cpu_ids)
2375                 set->nr_hw_queues = nr_cpu_ids;
2376
2377         set->tags = kzalloc_node(nr_cpu_ids * sizeof(struct blk_mq_tags *),
2378                                  GFP_KERNEL, set->numa_node);
2379         if (!set->tags)
2380                 return -ENOMEM;
2381
2382         ret = -ENOMEM;
2383         set->mq_map = kzalloc_node(sizeof(*set->mq_map) * nr_cpu_ids,
2384                         GFP_KERNEL, set->numa_node);
2385         if (!set->mq_map)
2386                 goto out_free_tags;
2387
2388         if (set->ops->map_queues)
2389                 ret = set->ops->map_queues(set);
2390         else
2391                 ret = blk_mq_map_queues(set);
2392         if (ret)
2393                 goto out_free_mq_map;
2394
2395         ret = blk_mq_alloc_rq_maps(set);
2396         if (ret)
2397                 goto out_free_mq_map;
2398
2399         mutex_init(&set->tag_list_lock);
2400         INIT_LIST_HEAD(&set->tag_list);
2401
2402         return 0;
2403
2404 out_free_mq_map:
2405         kfree(set->mq_map);
2406         set->mq_map = NULL;
2407 out_free_tags:
2408         kfree(set->tags);
2409         set->tags = NULL;
2410         return ret;
2411 }
2412 EXPORT_SYMBOL(blk_mq_alloc_tag_set);
2413
2414 void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
2415 {
2416         int i;
2417
2418         for (i = 0; i < nr_cpu_ids; i++) {
2419                 if (set->tags[i])
2420                         blk_mq_free_rq_map(set, set->tags[i], i);
2421         }
2422
2423         kfree(set->mq_map);
2424         set->mq_map = NULL;
2425
2426         kfree(set->tags);
2427         set->tags = NULL;
2428 }
2429 EXPORT_SYMBOL(blk_mq_free_tag_set);
2430
2431 int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
2432 {
2433         struct blk_mq_tag_set *set = q->tag_set;
2434         struct blk_mq_hw_ctx *hctx;
2435         int i, ret;
2436
2437         if (!set || nr > set->queue_depth)
2438                 return -EINVAL;
2439
2440         ret = 0;
2441         queue_for_each_hw_ctx(q, hctx, i) {
2442                 if (!hctx->tags)
2443                         continue;
2444                 ret = blk_mq_tag_update_depth(hctx->tags, nr);
2445                 if (ret)
2446                         break;
2447         }
2448
2449         if (!ret)
2450                 q->nr_requests = nr;
2451
2452         return ret;
2453 }
2454
2455 void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
2456 {
2457         struct request_queue *q;
2458
2459         if (nr_hw_queues > nr_cpu_ids)
2460                 nr_hw_queues = nr_cpu_ids;
2461         if (nr_hw_queues < 1 || nr_hw_queues == set->nr_hw_queues)
2462                 return;
2463
2464         list_for_each_entry(q, &set->tag_list, tag_set_list)
2465                 blk_mq_freeze_queue(q);
2466
2467         set->nr_hw_queues = nr_hw_queues;
2468         list_for_each_entry(q, &set->tag_list, tag_set_list) {
2469                 blk_mq_realloc_hw_ctxs(set, q);
2470
2471                 if (q->nr_hw_queues > 1)
2472                         blk_queue_make_request(q, blk_mq_make_request);
2473                 else
2474                         blk_queue_make_request(q, blk_sq_make_request);
2475
2476                 blk_mq_queue_reinit(q, cpu_online_mask);
2477         }
2478
2479         list_for_each_entry(q, &set->tag_list, tag_set_list)
2480                 blk_mq_unfreeze_queue(q);
2481 }
2482 EXPORT_SYMBOL_GPL(blk_mq_update_nr_hw_queues);
2483
2484 static unsigned long blk_mq_poll_nsecs(struct request_queue *q,
2485                                        struct blk_mq_hw_ctx *hctx,
2486                                        struct request *rq)
2487 {
2488         struct blk_rq_stat stat[2];
2489         unsigned long ret = 0;
2490
2491         /*
2492          * If stats collection isn't on, don't sleep but turn it on for
2493          * future users
2494          */
2495         if (!blk_stat_enable(q))
2496                 return 0;
2497
2498         /*
2499          * We don't have to do this once per IO, should optimize this
2500          * to just use the current window of stats until it changes
2501          */
2502         memset(&stat, 0, sizeof(stat));
2503         blk_hctx_stat_get(hctx, stat);
2504
2505         /*
2506          * As an optimistic guess, use half of the mean service time
2507          * for this type of request. We can (and should) make this smarter.
2508          * For instance, if the completion latencies are tight, we can
2509          * get closer than just half the mean. This is especially
2510          * important on devices where the completion latencies are longer
2511          * than ~10 usec.
2512          */
2513         if (req_op(rq) == REQ_OP_READ && stat[BLK_STAT_READ].nr_samples)
2514                 ret = (stat[BLK_STAT_READ].mean + 1) / 2;
2515         else if (req_op(rq) == REQ_OP_WRITE && stat[BLK_STAT_WRITE].nr_samples)
2516                 ret = (stat[BLK_STAT_WRITE].mean + 1) / 2;
2517
2518         return ret;
2519 }
2520
2521 static bool blk_mq_poll_hybrid_sleep(struct request_queue *q,
2522                                      struct blk_mq_hw_ctx *hctx,
2523                                      struct request *rq)
2524 {
2525         struct hrtimer_sleeper hs;
2526         enum hrtimer_mode mode;
2527         unsigned int nsecs;
2528         ktime_t kt;
2529
2530         if (test_bit(REQ_ATOM_POLL_SLEPT, &rq->atomic_flags))
2531                 return false;
2532
2533         /*
2534          * poll_nsec can be:
2535          *
2536          * -1:  don't ever hybrid sleep
2537          *  0:  use half of prev avg
2538          * >0:  use this specific value
2539          */
2540         if (q->poll_nsec == -1)
2541                 return false;
2542         else if (q->poll_nsec > 0)
2543                 nsecs = q->poll_nsec;
2544         else
2545                 nsecs = blk_mq_poll_nsecs(q, hctx, rq);
2546
2547         if (!nsecs)
2548                 return false;
2549
2550         set_bit(REQ_ATOM_POLL_SLEPT, &rq->atomic_flags);
2551
2552         /*
2553          * This will be replaced with the stats tracking code, using
2554          * 'avg_completion_time / 2' as the pre-sleep target.
2555          */
2556         kt = ktime_set(0, nsecs);
2557
2558         mode = HRTIMER_MODE_REL;
2559         hrtimer_init_on_stack(&hs.timer, CLOCK_MONOTONIC, mode);
2560         hrtimer_set_expires(&hs.timer, kt);
2561
2562         hrtimer_init_sleeper(&hs, current);
2563         do {
2564                 if (test_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags))
2565                         break;
2566                 set_current_state(TASK_UNINTERRUPTIBLE);
2567                 hrtimer_start_expires(&hs.timer, mode);
2568                 if (hs.task)
2569                         io_schedule();
2570                 hrtimer_cancel(&hs.timer);
2571                 mode = HRTIMER_MODE_ABS;
2572         } while (hs.task && !signal_pending(current));
2573
2574         __set_current_state(TASK_RUNNING);
2575         destroy_hrtimer_on_stack(&hs.timer);
2576         return true;
2577 }
2578
2579 static bool __blk_mq_poll(struct blk_mq_hw_ctx *hctx, struct request *rq)
2580 {
2581         struct request_queue *q = hctx->queue;
2582         long state;
2583
2584         /*
2585          * If we sleep, have the caller restart the poll loop to reset
2586          * the state. Like for the other success return cases, the
2587          * caller is responsible for checking if the IO completed. If
2588          * the IO isn't complete, we'll get called again and will go
2589          * straight to the busy poll loop.
2590          */
2591         if (blk_mq_poll_hybrid_sleep(q, hctx, rq))
2592                 return true;
2593
2594         hctx->poll_considered++;
2595
2596         state = current->state;
2597         while (!need_resched()) {
2598                 int ret;
2599
2600                 hctx->poll_invoked++;
2601
2602                 ret = q->mq_ops->poll(hctx, rq->tag);
2603                 if (ret > 0) {
2604                         hctx->poll_success++;
2605                         set_current_state(TASK_RUNNING);
2606                         return true;
2607                 }
2608
2609                 if (signal_pending_state(state, current))
2610                         set_current_state(TASK_RUNNING);
2611
2612                 if (current->state == TASK_RUNNING)
2613                         return true;
2614                 if (ret < 0)
2615                         break;
2616                 cpu_relax();
2617         }
2618
2619         return false;
2620 }
2621
2622 bool blk_mq_poll(struct request_queue *q, blk_qc_t cookie)
2623 {
2624         struct blk_mq_hw_ctx *hctx;
2625         struct blk_plug *plug;
2626         struct request *rq;
2627
2628         if (!q->mq_ops || !q->mq_ops->poll || !blk_qc_t_valid(cookie) ||
2629             !test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
2630                 return false;
2631
2632         plug = current->plug;
2633         if (plug)
2634                 blk_flush_plug_list(plug, false);
2635
2636         hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)];
2637         rq = blk_mq_tag_to_rq(hctx->tags, blk_qc_t_to_tag(cookie));
2638
2639         return __blk_mq_poll(hctx, rq);
2640 }
2641 EXPORT_SYMBOL_GPL(blk_mq_poll);
2642
2643 void blk_mq_disable_hotplug(void)
2644 {
2645         mutex_lock(&all_q_mutex);
2646 }
2647
2648 void blk_mq_enable_hotplug(void)
2649 {
2650         mutex_unlock(&all_q_mutex);
2651 }
2652
2653 static int __init blk_mq_init(void)
2654 {
2655         cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL,
2656                                 blk_mq_hctx_notify_dead);
2657
2658         cpuhp_setup_state_nocalls(CPUHP_BLK_MQ_PREPARE, "block/mq:prepare",
2659                                   blk_mq_queue_reinit_prepare,
2660                                   blk_mq_queue_reinit_dead);
2661         return 0;
2662 }
2663 subsys_initcall(blk_mq_init);