linux/block/blk-mq.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Block multiqueue core code
   4 *
   5 * Copyright (C) 2013-2014 Jens Axboe
   6 * Copyright (C) 2013-2014 Christoph Hellwig
   7 */
   8#include <linux/kernel.h>
   9#include <linux/module.h>
  10#include <linux/backing-dev.h>
  11#include <linux/bio.h>
  12#include <linux/blkdev.h>
  13#include <linux/kmemleak.h>
  14#include <linux/mm.h>
  15#include <linux/init.h>
  16#include <linux/slab.h>
  17#include <linux/workqueue.h>
  18#include <linux/smp.h>
  19#include <linux/llist.h>
  20#include <linux/list_sort.h>
  21#include <linux/cpu.h>
  22#include <linux/cache.h>
  23#include <linux/sched/sysctl.h>
  24#include <linux/sched/topology.h>
  25#include <linux/sched/signal.h>
  26#include <linux/delay.h>
  27#include <linux/crash_dump.h>
  28#include <linux/prefetch.h>
  29#include <linux/blk-crypto.h>
  30
  31#include <trace/events/block.h>
  32
  33#include <linux/blk-mq.h>
  34#include <linux/t10-pi.h>
  35#include "blk.h"
  36#include "blk-mq.h"
  37#include "blk-mq-debugfs.h"
  38#include "blk-mq-tag.h"
  39#include "blk-pm.h"
  40#include "blk-stat.h"
  41#include "blk-mq-sched.h"
  42#include "blk-rq-qos.h"
  43
  44static DEFINE_PER_CPU(struct llist_head, blk_cpu_done);
  45
  46static void blk_mq_poll_stats_start(struct request_queue *q);
  47static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb);
  48
  49static int blk_mq_poll_stats_bkt(const struct request *rq)
  50{
  51        int ddir, sectors, bucket;
  52
  53        ddir = rq_data_dir(rq);
  54        sectors = blk_rq_stats_sectors(rq);
  55
  56        bucket = ddir + 2 * ilog2(sectors);
  57
  58        if (bucket < 0)
  59                return -1;
  60        else if (bucket >= BLK_MQ_POLL_STATS_BKTS)
  61                return ddir + BLK_MQ_POLL_STATS_BKTS - 2;
  62
  63        return bucket;
  64}
  65
  66/*
  67 * Check if any of the ctx, dispatch list or elevator
  68 * have pending work in this hardware queue.
  69 */
  70static bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx)
  71{
  72        return !list_empty_careful(&hctx->dispatch) ||
  73                sbitmap_any_bit_set(&hctx->ctx_map) ||
  74                        blk_mq_sched_has_work(hctx);
  75}
  76
  77/*
  78 * Mark this ctx as having pending work in this hardware queue
  79 */
  80static void blk_mq_hctx_mark_pending(struct blk_mq_hw_ctx *hctx,
  81                                     struct blk_mq_ctx *ctx)
  82{
  83        const int bit = ctx->index_hw[hctx->type];
  84
  85        if (!sbitmap_test_bit(&hctx->ctx_map, bit))
  86                sbitmap_set_bit(&hctx->ctx_map, bit);
  87}
  88
  89static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
  90                                      struct blk_mq_ctx *ctx)
  91{
  92        const int bit = ctx->index_hw[hctx->type];
  93
  94        sbitmap_clear_bit(&hctx->ctx_map, bit);
  95}
  96
  97struct mq_inflight {
  98        struct block_device *part;
  99        unsigned int inflight[2];
 100};
 101
 102static bool blk_mq_check_inflight(struct blk_mq_hw_ctx *hctx,
 103                                  struct request *rq, void *priv,
 104                                  bool reserved)
 105{
 106        struct mq_inflight *mi = priv;
 107
 108        if ((!mi->part->bd_partno || rq->part == mi->part) &&
 109            blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT)
 110                mi->inflight[rq_data_dir(rq)]++;
 111
 112        return true;
 113}
 114
 115unsigned int blk_mq_in_flight(struct request_queue *q,
 116                struct block_device *part)
 117{
 118        struct mq_inflight mi = { .part = part };
 119
 120        blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
 121
 122        return mi.inflight[0] + mi.inflight[1];
 123}
 124
 125void blk_mq_in_flight_rw(struct request_queue *q, struct block_device *part,
 126                unsigned int inflight[2])
 127{
 128        struct mq_inflight mi = { .part = part };
 129
 130        blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
 131        inflight[0] = mi.inflight[0];
 132        inflight[1] = mi.inflight[1];
 133}
 134
 135void blk_freeze_queue_start(struct request_queue *q)
 136{
 137        mutex_lock(&q->mq_freeze_lock);
 138        if (++q->mq_freeze_depth == 1) {
 139                percpu_ref_kill(&q->q_usage_counter);
 140                mutex_unlock(&q->mq_freeze_lock);
 141                if (queue_is_mq(q))
 142                        blk_mq_run_hw_queues(q, false);
 143        } else {
 144                mutex_unlock(&q->mq_freeze_lock);
 145        }
 146}
 147EXPORT_SYMBOL_GPL(blk_freeze_queue_start);
 148
 149void blk_mq_freeze_queue_wait(struct request_queue *q)
 150{
 151        wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->q_usage_counter));
 152}
 153EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait);
 154
 155int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
 156                                     unsigned long timeout)
 157{
 158        return wait_event_timeout(q->mq_freeze_wq,
 159                                        percpu_ref_is_zero(&q->q_usage_counter),
 160                                        timeout);
 161}
 162EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait_timeout);
 163
 164/*
 165 * Guarantee no request is in use, so we can change any data structure of
 166 * the queue afterward.
 167 */
 168void blk_freeze_queue(struct request_queue *q)
 169{
 170        /*
 171         * In the !blk_mq case we are only calling this to kill the
 172         * q_usage_counter, otherwise this increases the freeze depth
 173         * and waits for it to return to zero.  For this reason there is
 174         * no blk_unfreeze_queue(), and blk_freeze_queue() is not
 175         * exported to drivers as the only user for unfreeze is blk_mq.
 176         */
 177        blk_freeze_queue_start(q);
 178        blk_mq_freeze_queue_wait(q);
 179}
 180
 181void blk_mq_freeze_queue(struct request_queue *q)
 182{
 183        /*
 184         * ...just an alias to keep freeze and unfreeze actions balanced
 185         * in the blk_mq_* namespace
 186         */
 187        blk_freeze_queue(q);
 188}
 189EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);
 190
 191void __blk_mq_unfreeze_queue(struct request_queue *q, bool force_atomic)
 192{
 193        mutex_lock(&q->mq_freeze_lock);
 194        if (force_atomic)
 195                q->q_usage_counter.data->force_atomic = true;
 196        q->mq_freeze_depth--;
 197        WARN_ON_ONCE(q->mq_freeze_depth < 0);
 198        if (!q->mq_freeze_depth) {
 199                percpu_ref_resurrect(&q->q_usage_counter);
 200                wake_up_all(&q->mq_freeze_wq);
 201        }
 202        mutex_unlock(&q->mq_freeze_lock);
 203}
 204
 205void blk_mq_unfreeze_queue(struct request_queue *q)
 206{
 207        __blk_mq_unfreeze_queue(q, false);
 208}
 209EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);
 210
 211/*
 212 * FIXME: replace the scsi_internal_device_*block_nowait() calls in the
 213 * mpt3sas driver such that this function can be removed.
 214 */
 215void blk_mq_quiesce_queue_nowait(struct request_queue *q)
 216{
 217        blk_queue_flag_set(QUEUE_FLAG_QUIESCED, q);
 218}
 219EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
 220
 221/**
 222 * blk_mq_quiesce_queue() - wait until all ongoing dispatches have finished
 223 * @q: request queue.
 224 *
 225 * Note: this function does not prevent that the struct request end_io()
 226 * callback function is invoked. Once this function is returned, we make
 227 * sure no dispatch can happen until the queue is unquiesced via
 228 * blk_mq_unquiesce_queue().
 229 */
 230void blk_mq_quiesce_queue(struct request_queue *q)
 231{
 232        struct blk_mq_hw_ctx *hctx;
 233        unsigned int i;
 234        bool rcu = false;
 235
 236        blk_mq_quiesce_queue_nowait(q);
 237
 238        queue_for_each_hw_ctx(q, hctx, i) {
 239                if (hctx->flags & BLK_MQ_F_BLOCKING)
 240                        synchronize_srcu(hctx->srcu);
 241                else
 242                        rcu = true;
 243        }
 244        if (rcu)
 245                synchronize_rcu();
 246}
 247EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue);
 248
 249/*
 250 * blk_mq_unquiesce_queue() - counterpart of blk_mq_quiesce_queue()
 251 * @q: request queue.
 252 *
 253 * This function recovers queue into the state before quiescing
 254 * which is done by blk_mq_quiesce_queue.
 255 */
 256void blk_mq_unquiesce_queue(struct request_queue *q)
 257{
 258        blk_queue_flag_clear(QUEUE_FLAG_QUIESCED, q);
 259
 260        /* dispatch requests which are inserted during quiescing */
 261        blk_mq_run_hw_queues(q, true);
 262}
 263EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue);
 264
 265void blk_mq_wake_waiters(struct request_queue *q)
 266{
 267        struct blk_mq_hw_ctx *hctx;
 268        unsigned int i;
 269
 270        queue_for_each_hw_ctx(q, hctx, i)
 271                if (blk_mq_hw_queue_mapped(hctx))
 272                        blk_mq_tag_wakeup_all(hctx->tags, true);
 273}
 274
 275/*
 276 * Only need start/end time stamping if we have iostat or
 277 * blk stats enabled, or using an IO scheduler.
 278 */
 279static inline bool blk_mq_need_time_stamp(struct request *rq)
 280{
 281        return (rq->rq_flags & (RQF_IO_STAT | RQF_STATS)) || rq->q->elevator;
 282}
 283
 284static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
 285                unsigned int tag, u64 alloc_time_ns)
 286{
 287        struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
 288        struct request *rq = tags->static_rqs[tag];
 289
 290        if (data->q->elevator) {
 291                rq->tag = BLK_MQ_NO_TAG;
 292                rq->internal_tag = tag;
 293        } else {
 294                rq->tag = tag;
 295                rq->internal_tag = BLK_MQ_NO_TAG;
 296        }
 297
 298        /* csd/requeue_work/fifo_time is initialized before use */
 299        rq->q = data->q;
 300        rq->mq_ctx = data->ctx;
 301        rq->mq_hctx = data->hctx;
 302        rq->rq_flags = 0;
 303        rq->cmd_flags = data->cmd_flags;
 304        if (data->flags & BLK_MQ_REQ_PM)
 305                rq->rq_flags |= RQF_PM;
 306        if (blk_queue_io_stat(data->q))
 307                rq->rq_flags |= RQF_IO_STAT;
 308        INIT_LIST_HEAD(&rq->queuelist);
 309        INIT_HLIST_NODE(&rq->hash);
 310        RB_CLEAR_NODE(&rq->rb_node);
 311        rq->rq_disk = NULL;
 312        rq->part = NULL;
 313#ifdef CONFIG_BLK_RQ_ALLOC_TIME
 314        rq->alloc_time_ns = alloc_time_ns;
 315#endif
 316        if (blk_mq_need_time_stamp(rq))
 317                rq->start_time_ns = ktime_get_ns();
 318        else
 319                rq->start_time_ns = 0;
 320        rq->io_start_time_ns = 0;
 321        rq->stats_sectors = 0;
 322        rq->nr_phys_segments = 0;
 323#if defined(CONFIG_BLK_DEV_INTEGRITY)
 324        rq->nr_integrity_segments = 0;
 325#endif
 326        blk_crypto_rq_set_defaults(rq);
 327        /* tag was already set */
 328        WRITE_ONCE(rq->deadline, 0);
 329
 330        rq->timeout = 0;
 331
 332        rq->end_io = NULL;
 333        rq->end_io_data = NULL;
 334
 335        data->ctx->rq_dispatched[op_is_sync(data->cmd_flags)]++;
 336        refcount_set(&rq->ref, 1);
 337
 338        if (!op_is_flush(data->cmd_flags)) {
 339                struct elevator_queue *e = data->q->elevator;
 340
 341                rq->elv.icq = NULL;
 342                if (e && e->type->ops.prepare_request) {
 343                        if (e->type->icq_cache)
 344                                blk_mq_sched_assign_ioc(rq);
 345
 346                        e->type->ops.prepare_request(rq);
 347                        rq->rq_flags |= RQF_ELVPRIV;
 348                }
 349        }
 350
 351        data->hctx->queued++;
 352        return rq;
 353}
 354
 355static struct request *__blk_mq_alloc_request(struct blk_mq_alloc_data *data)
 356{
 357        struct request_queue *q = data->q;
 358        struct elevator_queue *e = q->elevator;
 359        u64 alloc_time_ns = 0;
 360        unsigned int tag;
 361
 362        /* alloc_time includes depth and tag waits */
 363        if (blk_queue_rq_alloc_time(q))
 364                alloc_time_ns = ktime_get_ns();
 365
 366        if (data->cmd_flags & REQ_NOWAIT)
 367                data->flags |= BLK_MQ_REQ_NOWAIT;
 368
 369        if (e) {
 370                /*
 371                 * Flush/passthrough requests are special and go directly to the
 372                 * dispatch list. Don't include reserved tags in the
 373                 * limiting, as it isn't useful.
 374                 */
 375                if (!op_is_flush(data->cmd_flags) &&
 376                    !blk_op_is_passthrough(data->cmd_flags) &&
 377                    e->type->ops.limit_depth &&
 378                    !(data->flags & BLK_MQ_REQ_RESERVED))
 379                        e->type->ops.limit_depth(data->cmd_flags, data);
 380        }
 381
 382retry:
 383        data->ctx = blk_mq_get_ctx(q);
 384        data->hctx = blk_mq_map_queue(q, data->cmd_flags, data->ctx);
 385        if (!e)
 386                blk_mq_tag_busy(data->hctx);
 387
 388        /*
 389         * Waiting allocations only fail because of an inactive hctx.  In that
 390         * case just retry the hctx assignment and tag allocation as CPU hotplug
 391         * should have migrated us to an online CPU by now.
 392         */
 393        tag = blk_mq_get_tag(data);
 394        if (tag == BLK_MQ_NO_TAG) {
 395                if (data->flags & BLK_MQ_REQ_NOWAIT)
 396                        return NULL;
 397
 398                /*
 399                 * Give up the CPU and sleep for a random short time to ensure
 400                 * that thread using a realtime scheduling class are migrated
 401                 * off the CPU, and thus off the hctx that is going away.
 402                 */
 403                msleep(3);
 404                goto retry;
 405        }
 406        return blk_mq_rq_ctx_init(data, tag, alloc_time_ns);
 407}
 408
 409struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op,
 410                blk_mq_req_flags_t flags)
 411{
 412        struct blk_mq_alloc_data data = {
 413                .q              = q,
 414                .flags          = flags,
 415                .cmd_flags      = op,
 416        };
 417        struct request *rq;
 418        int ret;
 419
 420        ret = blk_queue_enter(q, flags);
 421        if (ret)
 422                return ERR_PTR(ret);
 423
 424        rq = __blk_mq_alloc_request(&data);
 425        if (!rq)
 426                goto out_queue_exit;
 427        rq->__data_len = 0;
 428        rq->__sector = (sector_t) -1;
 429        rq->bio = rq->biotail = NULL;
 430        return rq;
 431out_queue_exit:
 432        blk_queue_exit(q);
 433        return ERR_PTR(-EWOULDBLOCK);
 434}
 435EXPORT_SYMBOL(blk_mq_alloc_request);
 436
 437struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
 438        unsigned int op, blk_mq_req_flags_t flags, unsigned int hctx_idx)
 439{
 440        struct blk_mq_alloc_data data = {
 441                .q              = q,
 442                .flags          = flags,
 443                .cmd_flags      = op,
 444        };
 445        u64 alloc_time_ns = 0;
 446        unsigned int cpu;
 447        unsigned int tag;
 448        int ret;
 449
 450        /* alloc_time includes depth and tag waits */
 451        if (blk_queue_rq_alloc_time(q))
 452                alloc_time_ns = ktime_get_ns();
 453
 454        /*
 455         * If the tag allocator sleeps we could get an allocation for a
 456         * different hardware context.  No need to complicate the low level
 457         * allocator for this for the rare use case of a command tied to
 458         * a specific queue.
 459         */
 460        if (WARN_ON_ONCE(!(flags & (BLK_MQ_REQ_NOWAIT | BLK_MQ_REQ_RESERVED))))
 461                return ERR_PTR(-EINVAL);
 462
 463        if (hctx_idx >= q->nr_hw_queues)
 464                return ERR_PTR(-EIO);
 465
 466        ret = blk_queue_enter(q, flags);
 467        if (ret)
 468                return ERR_PTR(ret);
 469
 470        /*
 471         * Check if the hardware context is actually mapped to anything.
 472         * If not tell the caller that it should skip this queue.
 473         */
 474        ret = -EXDEV;
 475        data.hctx = q->queue_hw_ctx[hctx_idx];
 476        if (!blk_mq_hw_queue_mapped(data.hctx))
 477                goto out_queue_exit;
 478        cpu = cpumask_first_and(data.hctx->cpumask, cpu_online_mask);
 479        data.ctx = __blk_mq_get_ctx(q, cpu);
 480
 481        if (!q->elevator)
 482                blk_mq_tag_busy(data.hctx);
 483
 484        ret = -EWOULDBLOCK;
 485        tag = blk_mq_get_tag(&data);
 486        if (tag == BLK_MQ_NO_TAG)
 487                goto out_queue_exit;
 488        return blk_mq_rq_ctx_init(&data, tag, alloc_time_ns);
 489
 490out_queue_exit:
 491        blk_queue_exit(q);
 492        return ERR_PTR(ret);
 493}
 494EXPORT_SYMBOL_GPL(blk_mq_alloc_request_hctx);
 495
 496static void __blk_mq_free_request(struct request *rq)
 497{
 498        struct request_queue *q = rq->q;
 499        struct blk_mq_ctx *ctx = rq->mq_ctx;
 500        struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
 501        const int sched_tag = rq->internal_tag;
 502
 503        blk_crypto_free_request(rq);
 504        blk_pm_mark_last_busy(rq);
 505        rq->mq_hctx = NULL;
 506        if (rq->tag != BLK_MQ_NO_TAG)
 507                blk_mq_put_tag(hctx->tags, ctx, rq->tag);
 508        if (sched_tag != BLK_MQ_NO_TAG)
 509                blk_mq_put_tag(hctx->sched_tags, ctx, sched_tag);
 510        blk_mq_sched_restart(hctx);
 511        blk_queue_exit(q);
 512}
 513
 514void blk_mq_free_request(struct request *rq)
 515{
 516        struct request_queue *q = rq->q;
 517        struct elevator_queue *e = q->elevator;
 518        struct blk_mq_ctx *ctx = rq->mq_ctx;
 519        struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
 520
 521        if (rq->rq_flags & RQF_ELVPRIV) {
 522                if (e && e->type->ops.finish_request)
 523                        e->type->ops.finish_request(rq);
 524                if (rq->elv.icq) {
 525                        put_io_context(rq->elv.icq->ioc);
 526                        rq->elv.icq = NULL;
 527                }
 528        }
 529
 530        ctx->rq_completed[rq_is_sync(rq)]++;
 531        if (rq->rq_flags & RQF_MQ_INFLIGHT)
 532                __blk_mq_dec_active_requests(hctx);
 533
 534        if (unlikely(laptop_mode && !blk_rq_is_passthrough(rq)))
 535                laptop_io_completion(q->disk->bdi);
 536
 537        rq_qos_done(q, rq);
 538
 539        WRITE_ONCE(rq->state, MQ_RQ_IDLE);
 540        if (refcount_dec_and_test(&rq->ref))
 541                __blk_mq_free_request(rq);
 542}
 543EXPORT_SYMBOL_GPL(blk_mq_free_request);
 544
 545inline void __blk_mq_end_request(struct request *rq, blk_status_t error)
 546{
 547        u64 now = 0;
 548
 549        if (blk_mq_need_time_stamp(rq))
 550                now = ktime_get_ns();
 551
 552        if (rq->rq_flags & RQF_STATS) {
 553                blk_mq_poll_stats_start(rq->q);
 554                blk_stat_add(rq, now);
 555        }
 556
 557        blk_mq_sched_completed_request(rq, now);
 558
 559        blk_account_io_done(rq, now);
 560
 561        if (rq->end_io) {
 562                rq_qos_done(rq->q, rq);
 563                rq->end_io(rq, error);
 564        } else {
 565                blk_mq_free_request(rq);
 566        }
 567}
 568EXPORT_SYMBOL(__blk_mq_end_request);
 569
 570void blk_mq_end_request(struct request *rq, blk_status_t error)
 571{
 572        if (blk_update_request(rq, error, blk_rq_bytes(rq)))
 573                BUG();
 574        __blk_mq_end_request(rq, error);
 575}
 576EXPORT_SYMBOL(blk_mq_end_request);
 577
 578static void blk_complete_reqs(struct llist_head *list)
 579{
 580        struct llist_node *entry = llist_reverse_order(llist_del_all(list));
 581        struct request *rq, *next;
 582
 583        llist_for_each_entry_safe(rq, next, entry, ipi_list)
 584                rq->q->mq_ops->complete(rq);
 585}
 586
 587static __latent_entropy void blk_done_softirq(struct softirq_action *h)
 588{
 589        blk_complete_reqs(this_cpu_ptr(&blk_cpu_done));
 590}
 591
 592static int blk_softirq_cpu_dead(unsigned int cpu)
 593{
 594        blk_complete_reqs(&per_cpu(blk_cpu_done, cpu));
 595        return 0;
 596}
 597
 598static void __blk_mq_complete_request_remote(void *data)
 599{
 600        __raise_softirq_irqoff(BLOCK_SOFTIRQ);
 601}
 602
 603static inline bool blk_mq_complete_need_ipi(struct request *rq)
 604{
 605        int cpu = raw_smp_processor_id();
 606
 607        if (!IS_ENABLED(CONFIG_SMP) ||
 608            !test_bit(QUEUE_FLAG_SAME_COMP, &rq->q->queue_flags))
 609                return false;
 610        /*
 611         * With force threaded interrupts enabled, raising softirq from an SMP
 612         * function call will always result in waking the ksoftirqd thread.
 613         * This is probably worse than completing the request on a different
 614         * cache domain.
 615         */
 616        if (force_irqthreads())
 617                return false;
 618
 619        /* same CPU or cache domain?  Complete locally */
 620        if (cpu == rq->mq_ctx->cpu ||
 621            (!test_bit(QUEUE_FLAG_SAME_FORCE, &rq->q->queue_flags) &&
 622             cpus_share_cache(cpu, rq->mq_ctx->cpu)))
 623                return false;
 624
 625        /* don't try to IPI to an offline CPU */
 626        return cpu_online(rq->mq_ctx->cpu);
 627}
 628
 629static void blk_mq_complete_send_ipi(struct request *rq)
 630{
 631        struct llist_head *list;
 632        unsigned int cpu;
 633
 634        cpu = rq->mq_ctx->cpu;
 635        list = &per_cpu(blk_cpu_done, cpu);
 636        if (llist_add(&rq->ipi_list, list)) {
 637                INIT_CSD(&rq->csd, __blk_mq_complete_request_remote, rq);
 638                smp_call_function_single_async(cpu, &rq->csd);
 639        }
 640}
 641
 642static void blk_mq_raise_softirq(struct request *rq)
 643{
 644        struct llist_head *list;
 645
 646        preempt_disable();
 647        list = this_cpu_ptr(&blk_cpu_done);
 648        if (llist_add(&rq->ipi_list, list))
 649                raise_softirq(BLOCK_SOFTIRQ);
 650        preempt_enable();
 651}
 652
 653bool blk_mq_complete_request_remote(struct request *rq)
 654{
 655        WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);
 656
 657        /*
 658         * For a polled request, always complete locallly, it's pointless
 659         * to redirect the completion.
 660         */
 661        if (rq->cmd_flags & REQ_HIPRI)
 662                return false;
 663
 664        if (blk_mq_complete_need_ipi(rq)) {
 665                blk_mq_complete_send_ipi(rq);
 666                return true;
 667        }
 668
 669        if (rq->q->nr_hw_queues == 1) {
 670                blk_mq_raise_softirq(rq);
 671                return true;
 672        }
 673        return false;
 674}
 675EXPORT_SYMBOL_GPL(blk_mq_complete_request_remote);
 676
 677/**
 678 * blk_mq_complete_request - end I/O on a request
 679 * @rq:         the request being processed
 680 *
 681 * Description:
 682 *      Complete a request by scheduling the ->complete_rq operation.
 683 **/
 684void blk_mq_complete_request(struct request *rq)
 685{
 686        if (!blk_mq_complete_request_remote(rq))
 687                rq->q->mq_ops->complete(rq);
 688}
 689EXPORT_SYMBOL(blk_mq_complete_request);
 690
 691static void hctx_unlock(struct blk_mq_hw_ctx *hctx, int srcu_idx)
 692        __releases(hctx->srcu)
 693{
 694        if (!(hctx->flags & BLK_MQ_F_BLOCKING))
 695                rcu_read_unlock();
 696        else
 697                srcu_read_unlock(hctx->srcu, srcu_idx);
 698}
 699
 700static void hctx_lock(struct blk_mq_hw_ctx *hctx, int *srcu_idx)
 701        __acquires(hctx->srcu)
 702{
 703        if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
 704                /* shut up gcc false positive */
 705                *srcu_idx = 0;
 706                rcu_read_lock();
 707        } else
 708                *srcu_idx = srcu_read_lock(hctx->srcu);
 709}
 710
 711/**
 712 * blk_mq_start_request - Start processing a request
 713 * @rq: Pointer to request to be started
 714 *
 715 * Function used by device drivers to notify the block layer that a request
 716 * is going to be processed now, so blk layer can do proper initializations
 717 * such as starting the timeout timer.
 718 */
 719void blk_mq_start_request(struct request *rq)
 720{
 721        struct request_queue *q = rq->q;
 722
 723        trace_block_rq_issue(rq);
 724
 725        if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags)) {
 726                rq->io_start_time_ns = ktime_get_ns();
 727                rq->stats_sectors = blk_rq_sectors(rq);
 728                rq->rq_flags |= RQF_STATS;
 729                rq_qos_issue(q, rq);
 730        }
 731
 732        WARN_ON_ONCE(blk_mq_rq_state(rq) != MQ_RQ_IDLE);
 733
 734        blk_add_timer(rq);
 735        WRITE_ONCE(rq->state, MQ_RQ_IN_FLIGHT);
 736
 737#ifdef CONFIG_BLK_DEV_INTEGRITY
 738        if (blk_integrity_rq(rq) && req_op(rq) == REQ_OP_WRITE)
 739                q->integrity.profile->prepare_fn(rq);
 740#endif
 741}
 742EXPORT_SYMBOL(blk_mq_start_request);
 743
 744static void __blk_mq_requeue_request(struct request *rq)
 745{
 746        struct request_queue *q = rq->q;
 747
 748        blk_mq_put_driver_tag(rq);
 749
 750        trace_block_rq_requeue(rq);
 751        rq_qos_requeue(q, rq);
 752
 753        if (blk_mq_request_started(rq)) {
 754                WRITE_ONCE(rq->state, MQ_RQ_IDLE);
 755                rq->rq_flags &= ~RQF_TIMED_OUT;
 756        }
 757}
 758
 759void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list)
 760{
 761        __blk_mq_requeue_request(rq);
 762
 763        /* this request will be re-inserted to io scheduler queue */
 764        blk_mq_sched_requeue_request(rq);
 765
 766        BUG_ON(!list_empty(&rq->queuelist));
 767        blk_mq_add_to_requeue_list(rq, true, kick_requeue_list);
 768}
 769EXPORT_SYMBOL(blk_mq_requeue_request);
 770
 771static void blk_mq_requeue_work(struct work_struct *work)
 772{
 773        struct request_queue *q =
 774                container_of(work, struct request_queue, requeue_work.work);
 775        LIST_HEAD(rq_list);
 776        struct request *rq, *next;
 777
 778        spin_lock_irq(&q->requeue_lock);
 779        list_splice_init(&q->requeue_list, &rq_list);
 780        spin_unlock_irq(&q->requeue_lock);
 781
 782        list_for_each_entry_safe(rq, next, &rq_list, queuelist) {
 783                if (!(rq->rq_flags & (RQF_SOFTBARRIER | RQF_DONTPREP)))
 784                        continue;
 785
 786                rq->rq_flags &= ~RQF_SOFTBARRIER;
 787                list_del_init(&rq->queuelist);
 788                /*
 789                 * If RQF_DONTPREP, rq has contained some driver specific
 790                 * data, so insert it to hctx dispatch list to avoid any
 791                 * merge.
 792                 */
 793                if (rq->rq_flags & RQF_DONTPREP)
 794                        blk_mq_request_bypass_insert(rq, false, false);
 795                else
 796                        blk_mq_sched_insert_request(rq, true, false, false);
 797        }
 798
 799        while (!list_empty(&rq_list)) {
 800                rq = list_entry(rq_list.next, struct request, queuelist);
 801                list_del_init(&rq->queuelist);
 802                blk_mq_sched_insert_request(rq, false, false, false);
 803        }
 804
 805        blk_mq_run_hw_queues(q, false);
 806}
 807
 808void blk_mq_add_to_requeue_list(struct request *rq, bool at_head,
 809                                bool kick_requeue_list)
 810{
 811        struct request_queue *q = rq->q;
 812        unsigned long flags;
 813
 814        /*
 815         * We abuse this flag that is otherwise used by the I/O scheduler to
 816         * request head insertion from the workqueue.
 817         */
 818        BUG_ON(rq->rq_flags & RQF_SOFTBARRIER);
 819
 820        spin_lock_irqsave(&q->requeue_lock, flags);
 821        if (at_head) {
 822                rq->rq_flags |= RQF_SOFTBARRIER;
 823                list_add(&rq->queuelist, &q->requeue_list);
 824        } else {
 825                list_add_tail(&rq->queuelist, &q->requeue_list);
 826        }
 827        spin_unlock_irqrestore(&q->requeue_lock, flags);
 828
 829        if (kick_requeue_list)
 830                blk_mq_kick_requeue_list(q);
 831}
 832
 833void blk_mq_kick_requeue_list(struct request_queue *q)
 834{
 835        kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work, 0);
 836}
 837EXPORT_SYMBOL(blk_mq_kick_requeue_list);
 838
 839void blk_mq_delay_kick_requeue_list(struct request_queue *q,
 840                                    unsigned long msecs)
 841{
 842        kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work,
 843                                    msecs_to_jiffies(msecs));
 844}
 845EXPORT_SYMBOL(blk_mq_delay_kick_requeue_list);
 846
 847struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
 848{
 849        if (tag < tags->nr_tags) {
 850                prefetch(tags->rqs[tag]);
 851                return tags->rqs[tag];
 852        }
 853
 854        return NULL;
 855}
 856EXPORT_SYMBOL(blk_mq_tag_to_rq);
 857
 858static bool blk_mq_rq_inflight(struct blk_mq_hw_ctx *hctx, struct request *rq,
 859                               void *priv, bool reserved)
 860{
 861        /*
 862         * If we find a request that isn't idle and the queue matches,
 863         * we know the queue is busy. Return false to stop the iteration.
 864         */
 865        if (blk_mq_request_started(rq) && rq->q == hctx->queue) {
 866                bool *busy = priv;
 867
 868                *busy = true;
 869                return false;
 870        }
 871
 872        return true;
 873}
 874
 875bool blk_mq_queue_inflight(struct request_queue *q)
 876{
 877        bool busy = false;
 878
 879        blk_mq_queue_tag_busy_iter(q, blk_mq_rq_inflight, &busy);
 880        return busy;
 881}
 882EXPORT_SYMBOL_GPL(blk_mq_queue_inflight);
 883
 884static void blk_mq_rq_timed_out(struct request *req, bool reserved)
 885{
 886        req->rq_flags |= RQF_TIMED_OUT;
 887        if (req->q->mq_ops->timeout) {
 888                enum blk_eh_timer_return ret;
 889
 890                ret = req->q->mq_ops->timeout(req, reserved);
 891                if (ret == BLK_EH_DONE)
 892                        return;
 893                WARN_ON_ONCE(ret != BLK_EH_RESET_TIMER);
 894        }
 895
 896        blk_add_timer(req);
 897}
 898
 899static bool blk_mq_req_expired(struct request *rq, unsigned long *next)
 900{
 901        unsigned long deadline;
 902
 903        if (blk_mq_rq_state(rq) != MQ_RQ_IN_FLIGHT)
 904                return false;
 905        if (rq->rq_flags & RQF_TIMED_OUT)
 906                return false;
 907
 908        deadline = READ_ONCE(rq->deadline);
 909        if (time_after_eq(jiffies, deadline))
 910                return true;
 911
 912        if (*next == 0)
 913                *next = deadline;
 914        else if (time_after(*next, deadline))
 915                *next = deadline;
 916        return false;
 917}
 918
 919void blk_mq_put_rq_ref(struct request *rq)
 920{
 921        if (is_flush_rq(rq))
 922                rq->end_io(rq, 0);
 923        else if (refcount_dec_and_test(&rq->ref))
 924                __blk_mq_free_request(rq);
 925}
 926
 927static bool blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
 928                struct request *rq, void *priv, bool reserved)
 929{
 930        unsigned long *next = priv;
 931
 932        /*
 933         * blk_mq_queue_tag_busy_iter() has locked the request, so it cannot
 934         * be reallocated underneath the timeout handler's processing, then
 935         * the expire check is reliable. If the request is not expired, then
 936         * it was completed and reallocated as a new request after returning
 937         * from blk_mq_check_expired().
 938         */
 939        if (blk_mq_req_expired(rq, next))
 940                blk_mq_rq_timed_out(rq, reserved);
 941        return true;
 942}
 943
 944static void blk_mq_timeout_work(struct work_struct *work)
 945{
 946        struct request_queue *q =
 947                container_of(work, struct request_queue, timeout_work);
 948        unsigned long next = 0;
 949        struct blk_mq_hw_ctx *hctx;
 950        int i;
 951
 952        /* A deadlock might occur if a request is stuck requiring a
 953         * timeout at the same time a queue freeze is waiting
 954         * completion, since the timeout code would not be able to
 955         * acquire the queue reference here.
 956         *
 957         * That's why we don't use blk_queue_enter here; instead, we use
 958         * percpu_ref_tryget directly, because we need to be able to
 959         * obtain a reference even in the short window between the queue
 960         * starting to freeze, by dropping the first reference in
 961         * blk_freeze_queue_start, and the moment the last request is
 962         * consumed, marked by the instant q_usage_counter reaches
 963         * zero.
 964         */
 965        if (!percpu_ref_tryget(&q->q_usage_counter))
 966                return;
 967
 968        blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &next);
 969
 970        if (next != 0) {
 971                mod_timer(&q->timeout, next);
 972        } else {
 973                /*
 974                 * Request timeouts are handled as a forward rolling timer. If
 975                 * we end up here it means that no requests are pending and
 976                 * also that no request has been pending for a while. Mark
 977                 * each hctx as idle.
 978                 */
 979                queue_for_each_hw_ctx(q, hctx, i) {
 980                        /* the hctx may be unmapped, so check it here */
 981                        if (blk_mq_hw_queue_mapped(hctx))
 982                                blk_mq_tag_idle(hctx);
 983                }
 984        }
 985        blk_queue_exit(q);
 986}
 987
 988struct flush_busy_ctx_data {
 989        struct blk_mq_hw_ctx *hctx;
 990        struct list_head *list;
 991};
 992
 993static bool flush_busy_ctx(struct sbitmap *sb, unsigned int bitnr, void *data)
 994{
 995        struct flush_busy_ctx_data *flush_data = data;
 996        struct blk_mq_hw_ctx *hctx = flush_data->hctx;
 997        struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
 998        enum hctx_type type = hctx->type;
 999
1000        spin_lock(&ctx->lock);
1001        list_splice_tail_init(&ctx->rq_lists[type], flush_data->list);
1002        sbitmap_clear_bit(sb, bitnr);
1003        spin_unlock(&ctx->lock);
1004        return true;
1005}
1006
1007/*
1008 * Process software queues that have been marked busy, splicing them
1009 * to the for-dispatch
1010 */
1011void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list)
1012{
1013        struct flush_busy_ctx_data data = {
1014                .hctx = hctx,
1015                .list = list,
1016        };
1017
1018        sbitmap_for_each_set(&hctx->ctx_map, flush_busy_ctx, &data);
1019}
1020EXPORT_SYMBOL_GPL(blk_mq_flush_busy_ctxs);
1021
1022struct dispatch_rq_data {
1023        struct blk_mq_hw_ctx *hctx;
1024        struct request *rq;
1025};
1026
1027static bool dispatch_rq_from_ctx(struct sbitmap *sb, unsigned int bitnr,
1028                void *data)
1029{
1030        struct dispatch_rq_data *dispatch_data = data;
1031        struct blk_mq_hw_ctx *hctx = dispatch_data->hctx;
1032        struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
1033        enum hctx_type type = hctx->type;
1034
1035        spin_lock(&ctx->lock);
1036        if (!list_empty(&ctx->rq_lists[type])) {
1037                dispatch_data->rq = list_entry_rq(ctx->rq_lists[type].next);
1038                list_del_init(&dispatch_data->rq->queuelist);
1039                if (list_empty(&ctx->rq_lists[type]))
1040                        sbitmap_clear_bit(sb, bitnr);
1041        }
1042        spin_unlock(&ctx->lock);
1043
1044        return !dispatch_data->rq;
1045}
1046
1047struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx,
1048                                        struct blk_mq_ctx *start)
1049{
1050        unsigned off = start ? start->index_hw[hctx->type] : 0;
1051        struct dispatch_rq_data data = {
1052                .hctx = hctx,
1053                .rq   = NULL,
1054        };
1055
1056        __sbitmap_for_each_set(&hctx->ctx_map, off,
1057                               dispatch_rq_from_ctx, &data);
1058
1059        return data.rq;
1060}
1061
1062static inline unsigned int queued_to_index(unsigned int queued)
1063{
1064        if (!queued)
1065                return 0;
1066
1067        return min(BLK_MQ_MAX_DISPATCH_ORDER - 1, ilog2(queued) + 1);
1068}
1069
1070static bool __blk_mq_get_driver_tag(struct request *rq)
1071{
1072        struct sbitmap_queue *bt = rq->mq_hctx->tags->bitmap_tags;
1073        unsigned int tag_offset = rq->mq_hctx->tags->nr_reserved_tags;
1074        int tag;
1075
1076        blk_mq_tag_busy(rq->mq_hctx);
1077
1078        if (blk_mq_tag_is_reserved(rq->mq_hctx->sched_tags, rq->internal_tag)) {
1079                bt = rq->mq_hctx->tags->breserved_tags;
1080                tag_offset = 0;
1081        } else {
1082                if (!hctx_may_queue(rq->mq_hctx, bt))
1083                        return false;
1084        }
1085
1086        tag = __sbitmap_queue_get(bt);
1087        if (tag == BLK_MQ_NO_TAG)
1088                return false;
1089
1090        rq->tag = tag + tag_offset;
1091        return true;
1092}
1093
1094bool blk_mq_get_driver_tag(struct request *rq)
1095{
1096        struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
1097
1098        if (rq->tag == BLK_MQ_NO_TAG && !__blk_mq_get_driver_tag(rq))
1099                return false;
1100
1101        if ((hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED) &&
1102                        !(rq->rq_flags & RQF_MQ_INFLIGHT)) {
1103                rq->rq_flags |= RQF_MQ_INFLIGHT;
1104                __blk_mq_inc_active_requests(hctx);
1105        }
1106        hctx->tags->rqs[rq->tag] = rq;
1107        return true;
1108}
1109
1110static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode,
1111                                int flags, void *key)
1112{
1113        struct blk_mq_hw_ctx *hctx;
1114
1115        hctx = container_of(wait, struct blk_mq_hw_ctx, dispatch_wait);
1116
1117        spin_lock(&hctx->dispatch_wait_lock);
1118        if (!list_empty(&wait->entry)) {
1119                struct sbitmap_queue *sbq;
1120
1121                list_del_init(&wait->entry);
1122                sbq = hctx->tags->bitmap_tags;
1123                atomic_dec(&sbq->ws_active);
1124        }
1125        spin_unlock(&hctx->dispatch_wait_lock);
1126
1127        blk_mq_run_hw_queue(hctx, true);
1128        return 1;
1129}
1130
1131/*
1132 * Mark us waiting for a tag. For shared tags, this involves hooking us into
1133 * the tag wakeups. For non-shared tags, we can simply mark us needing a
1134 * restart. For both cases, take care to check the condition again after
1135 * marking us as waiting.
1136 */
1137static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx,
1138                                 struct request *rq)
1139{
1140        struct sbitmap_queue *sbq = hctx->tags->bitmap_tags;
1141        struct wait_queue_head *wq;
1142        wait_queue_entry_t *wait;
1143        bool ret;
1144
1145        if (!(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) {
1146                blk_mq_sched_mark_restart_hctx(hctx);
1147
1148                /*
1149                 * It's possible that a tag was freed in the window between the
1150                 * allocation failure and adding the hardware queue to the wait
1151                 * queue.
1152                 *
1153                 * Don't clear RESTART here, someone else could have set it.
1154                 * At most this will cost an extra queue run.
1155                 */
1156                return blk_mq_get_driver_tag(rq);
1157        }
1158
1159        wait = &hctx->dispatch_wait;
1160        if (!list_empty_careful(&wait->entry))
1161                return false;
1162
1163        wq = &bt_wait_ptr(sbq, hctx)->wait;
1164
1165        spin_lock_irq(&wq->lock);
1166        spin_lock(&hctx->dispatch_wait_lock);
1167        if (!list_empty(&wait->entry)) {
1168                spin_unlock(&hctx->dispatch_wait_lock);
1169                spin_unlock_irq(&wq->lock);
1170                return false;
1171        }
1172
1173        atomic_inc(&sbq->ws_active);
1174        wait->flags &= ~WQ_FLAG_EXCLUSIVE;
1175        __add_wait_queue(wq, wait);
1176
1177        /*
1178         * It's possible that a tag was freed in the window between the
1179         * allocation failure and adding the hardware queue to the wait
1180         * queue.
1181         */
1182        ret = blk_mq_get_driver_tag(rq);
1183        if (!ret) {
1184                spin_unlock(&hctx->dispatch_wait_lock);
1185                spin_unlock_irq(&wq->lock);
1186                return false;
1187        }
1188
1189        /*
1190         * We got a tag, remove ourselves from the wait queue to ensure
1191         * someone else gets the wakeup.
1192         */
1193        list_del_init(&wait->entry);
1194        atomic_dec(&sbq->ws_active);
1195        spin_unlock(&hctx->dispatch_wait_lock);
1196        spin_unlock_irq(&wq->lock);
1197
1198        return true;
1199}
1200
1201#define BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT  8
1202#define BLK_MQ_DISPATCH_BUSY_EWMA_FACTOR  4
1203/*
1204 * Update dispatch busy with the Exponential Weighted Moving Average(EWMA):
1205 * - EWMA is one simple way to compute running average value
1206 * - weight(7/8 and 1/8) is applied so that it can decrease exponentially
1207 * - take 4 as factor for avoiding to get too small(0) result, and this
1208 *   factor doesn't matter because EWMA decreases exponentially
1209 */
1210static void blk_mq_update_dispatch_busy(struct blk_mq_hw_ctx *hctx, bool busy)
1211{
1212        unsigned int ewma;
1213
1214        ewma = hctx->dispatch_busy;
1215
1216        if (!ewma && !busy)
1217                return;
1218
1219        ewma *= BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT - 1;
1220        if (busy)
1221                ewma += 1 << BLK_MQ_DISPATCH_BUSY_EWMA_FACTOR;
1222        ewma /= BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT;
1223
1224        hctx->dispatch_busy = ewma;
1225}
1226
1227#define BLK_MQ_RESOURCE_DELAY   3               /* ms units */
1228
1229static void blk_mq_handle_dev_resource(struct request *rq,
1230                                       struct list_head *list)
1231{
1232        struct request *next =
1233                list_first_entry_or_null(list, struct request, queuelist);
1234
1235        /*
1236         * If an I/O scheduler has been configured and we got a driver tag for
1237         * the next request already, free it.
1238         */
1239        if (next)
1240                blk_mq_put_driver_tag(next);
1241
1242        list_add(&rq->queuelist, list);
1243        __blk_mq_requeue_request(rq);
1244}
1245
1246static void blk_mq_handle_zone_resource(struct request *rq,
1247                                        struct list_head *zone_list)
1248{
1249        /*
1250         * If we end up here it is because we cannot dispatch a request to a
1251         * specific zone due to LLD level zone-write locking or other zone
1252         * related resource not being available. In this case, set the request
1253         * aside in zone_list for retrying it later.
1254         */
1255        list_add(&rq->queuelist, zone_list);
1256        __blk_mq_requeue_request(rq);
1257}
1258
1259enum prep_dispatch {
1260        PREP_DISPATCH_OK,
1261        PREP_DISPATCH_NO_TAG,
1262        PREP_DISPATCH_NO_BUDGET,
1263};
1264
1265static enum prep_dispatch blk_mq_prep_dispatch_rq(struct request *rq,
1266                                                  bool need_budget)
1267{
1268        struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
1269        int budget_token = -1;
1270
1271        if (need_budget) {
1272                budget_token = blk_mq_get_dispatch_budget(rq->q);
1273                if (budget_token < 0) {
1274                        blk_mq_put_driver_tag(rq);
1275                        return PREP_DISPATCH_NO_BUDGET;
1276                }
1277                blk_mq_set_rq_budget_token(rq, budget_token);
1278        }
1279
1280        if (!blk_mq_get_driver_tag(rq)) {
1281                /*
1282                 * The initial allocation attempt failed, so we need to
1283                 * rerun the hardware queue when a tag is freed. The
1284                 * waitqueue takes care of that. If the queue is run
1285                 * before we add this entry back on the dispatch list,
1286                 * we'll re-run it below.
1287                 */
1288                if (!blk_mq_mark_tag_wait(hctx, rq)) {
1289                        /*
1290                         * All budgets not got from this function will be put
1291                         * together during handling partial dispatch
1292                         */
1293                        if (need_budget)
1294                                blk_mq_put_dispatch_budget(rq->q, budget_token);
1295                        return PREP_DISPATCH_NO_TAG;
1296                }
1297        }
1298
1299        return PREP_DISPATCH_OK;
1300}
1301
1302/* release all allocated budgets before calling to blk_mq_dispatch_rq_list */
1303static void blk_mq_release_budgets(struct request_queue *q,
1304                struct list_head *list)
1305{
1306        struct request *rq;
1307
1308        list_for_each_entry(rq, list, queuelist) {
1309                int budget_token = blk_mq_get_rq_budget_token(rq);
1310
1311                if (budget_token >= 0)
1312                        blk_mq_put_dispatch_budget(q, budget_token);
1313        }
1314}
1315
1316/*
1317 * Returns true if we did some work AND can potentially do more.
1318 */
1319bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
1320                             unsigned int nr_budgets)
1321{
1322        enum prep_dispatch prep;
1323        struct request_queue *q = hctx->queue;
1324        struct request *rq, *nxt;
1325        int errors, queued;
1326        blk_status_t ret = BLK_STS_OK;
1327        LIST_HEAD(zone_list);
1328        bool needs_resource = false;
1329
1330        if (list_empty(list))
1331                return false;
1332
1333        /*
1334         * Now process all the entries, sending them to the driver.
1335         */
1336        errors = queued = 0;
1337        do {
1338                struct blk_mq_queue_data bd;
1339
1340                rq = list_first_entry(list, struct request, queuelist);
1341
1342                WARN_ON_ONCE(hctx != rq->mq_hctx);
1343                prep = blk_mq_prep_dispatch_rq(rq, !nr_budgets);
1344                if (prep != PREP_DISPATCH_OK)
1345                        break;
1346
1347                list_del_init(&rq->queuelist);
1348
1349                bd.rq = rq;
1350
1351                /*
1352                 * Flag last if we have no more requests, or if we have more
1353                 * but can't assign a driver tag to it.
1354                 */
1355                if (list_empty(list))
1356                        bd.last = true;
1357                else {
1358                        nxt = list_first_entry(list, struct request, queuelist);
1359                        bd.last = !blk_mq_get_driver_tag(nxt);
1360                }
1361
1362                /*
1363                 * once the request is queued to lld, no need to cover the
1364                 * budget any more
1365                 */
1366                if (nr_budgets)
1367                        nr_budgets--;
1368                ret = q->mq_ops->queue_rq(hctx, &bd);
1369                switch (ret) {
1370                case BLK_STS_OK:
1371                        queued++;
1372                        break;
1373                case BLK_STS_RESOURCE:
1374                        needs_resource = true;
1375                        fallthrough;
1376                case BLK_STS_DEV_RESOURCE:
1377                        blk_mq_handle_dev_resource(rq, list);
1378                        goto out;
1379                case BLK_STS_ZONE_RESOURCE:
1380                        /*
1381                         * Move the request to zone_list and keep going through
1382                         * the dispatch list to find more requests the drive can
1383                         * accept.
1384                         */
1385                        blk_mq_handle_zone_resource(rq, &zone_list);
1386                        needs_resource = true;
1387                        break;
1388                default:
1389                        errors++;
1390                        blk_mq_end_request(rq, ret);
1391                }
1392        } while (!list_empty(list));
1393out:
1394        if (!list_empty(&zone_list))
1395                list_splice_tail_init(&zone_list, list);
1396
1397        hctx->dispatched[queued_to_index(queued)]++;
1398
1399        /* If we didn't flush the entire list, we could have told the driver
1400         * there was more coming, but that turned out to be a lie.
1401         */
1402        if ((!list_empty(list) || errors) && q->mq_ops->commit_rqs && queued)
1403                q->mq_ops->commit_rqs(hctx);
1404        /*
1405         * Any items that need requeuing? Stuff them into hctx->dispatch,
1406         * that is where we will continue on next queue run.
1407         */
1408        if (!list_empty(list)) {
1409                bool needs_restart;
1410                /* For non-shared tags, the RESTART check will suffice */
1411                bool no_tag = prep == PREP_DISPATCH_NO_TAG &&
1412                        (hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED);
1413
1414                if (nr_budgets)
1415                        blk_mq_release_budgets(q, list);
1416
1417                spin_lock(&hctx->lock);
1418                list_splice_tail_init(list, &hctx->dispatch);
1419                spin_unlock(&hctx->lock);
1420
1421                /*
1422                 * Order adding requests to hctx->dispatch and checking
1423                 * SCHED_RESTART flag. The pair of this smp_mb() is the one
1424                 * in blk_mq_sched_restart(). Avoid restart code path to
1425                 * miss the new added requests to hctx->dispatch, meantime
1426                 * SCHED_RESTART is observed here.
1427                 */
1428                smp_mb();
1429
1430                /*
1431                 * If SCHED_RESTART was set by the caller of this function and
1432                 * it is no longer set that means that it was cleared by another
1433                 * thread and hence that a queue rerun is needed.
1434                 *
1435                 * If 'no_tag' is set, that means that we failed getting
1436                 * a driver tag with an I/O scheduler attached. If our dispatch
1437                 * waitqueue is no longer active, ensure that we run the queue
1438                 * AFTER adding our entries back to the list.
1439                 *
1440                 * If no I/O scheduler has been configured it is possible that
1441                 * the hardware queue got stopped and restarted before requests
1442                 * were pushed back onto the dispatch list. Rerun the queue to
1443                 * avoid starvation. Notes:
1444                 * - blk_mq_run_hw_queue() checks whether or not a queue has
1445                 *   been stopped before rerunning a queue.
1446                 * - Some but not all block drivers stop a queue before
1447                 *   returning BLK_STS_RESOURCE. Two exceptions are scsi-mq
1448                 *   and dm-rq.
1449                 *
1450                 * If driver returns BLK_STS_RESOURCE and SCHED_RESTART
1451                 * bit is set, run queue after a delay to avoid IO stalls
1452                 * that could otherwise occur if the queue is idle.  We'll do
1453                 * similar if we couldn't get budget or couldn't lock a zone
1454                 * and SCHED_RESTART is set.
1455                 */
1456                needs_restart = blk_mq_sched_needs_restart(hctx);
1457                if (prep == PREP_DISPATCH_NO_BUDGET)
1458                        needs_resource = true;
1459                if (!needs_restart ||
1460                    (no_tag && list_empty_careful(&hctx->dispatch_wait.entry)))
1461                        blk_mq_run_hw_queue(hctx, true);
1462                else if (needs_restart && needs_resource)
1463                        blk_mq_delay_run_hw_queue(hctx, BLK_MQ_RESOURCE_DELAY);
1464
1465                blk_mq_update_dispatch_busy(hctx, true);
1466                return false;
1467        } else
1468                blk_mq_update_dispatch_busy(hctx, false);
1469
1470        return (queued + errors) != 0;
1471}
1472
1473/**
1474 * __blk_mq_run_hw_queue - Run a hardware queue.
1475 * @hctx: Pointer to the hardware queue to run.
1476 *
1477 * Send pending requests to the hardware.
1478 */
1479static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
1480{
1481        int srcu_idx;
1482
1483        /*
1484         * We can't run the queue inline with ints disabled. Ensure that
1485         * we catch bad users of this early.
1486         */
1487        WARN_ON_ONCE(in_interrupt());
1488
1489        might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
1490
1491        hctx_lock(hctx, &srcu_idx);
1492        blk_mq_sched_dispatch_requests(hctx);
1493        hctx_unlock(hctx, srcu_idx);
1494}
1495
1496static inline int blk_mq_first_mapped_cpu(struct blk_mq_hw_ctx *hctx)
1497{
1498        int cpu = cpumask_first_and(hctx->cpumask, cpu_online_mask);
1499
1500        if (cpu >= nr_cpu_ids)
1501                cpu = cpumask_first(hctx->cpumask);
1502        return cpu;
1503}
1504
1505/*
1506 * It'd be great if the workqueue API had a way to pass
1507 * in a mask and had some smarts for more clever placement.
1508 * For now we just round-robin here, switching for every
1509 * BLK_MQ_CPU_WORK_BATCH queued items.
1510 */
1511static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
1512{
1513        bool tried = false;
1514        int next_cpu = hctx->next_cpu;
1515
1516        if (hctx->queue->nr_hw_queues == 1)
1517                return WORK_CPU_UNBOUND;
1518
1519        if (--hctx->next_cpu_batch <= 0) {
1520select_cpu:
1521                next_cpu = cpumask_next_and(next_cpu, hctx->cpumask,
1522                                cpu_online_mask);
1523                if (next_cpu >= nr_cpu_ids)
1524                        next_cpu = blk_mq_first_mapped_cpu(hctx);
1525                hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
1526        }
1527
1528        /*
1529         * Do unbound schedule if we can't find a online CPU for this hctx,
1530         * and it should only happen in the path of handling CPU DEAD.
1531         */
1532        if (!cpu_online(next_cpu)) {
1533                if (!tried) {
1534                        tried = true;
1535                        goto select_cpu;
1536                }
1537
1538                /*
1539                 * Make sure to re-select CPU next time once after CPUs
1540                 * in hctx->cpumask become online again.
1541                 */
1542                hctx->next_cpu = next_cpu;
1543                hctx->next_cpu_batch = 1;
1544                return WORK_CPU_UNBOUND;
1545        }
1546
1547        hctx->next_cpu = next_cpu;
1548        return next_cpu;
1549}
1550
1551/**
1552 * __blk_mq_delay_run_hw_queue - Run (or schedule to run) a hardware queue.
1553 * @hctx: Pointer to the hardware queue to run.
1554 * @async: If we want to run the queue asynchronously.
1555 * @msecs: Milliseconds of delay to wait before running the queue.
1556 *
1557 * If !@async, try to run the queue now. Else, run the queue asynchronously and
1558 * with a delay of @msecs.
1559 */
1560static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async,
1561                                        unsigned long msecs)
1562{
1563        if (unlikely(blk_mq_hctx_stopped(hctx)))
1564                return;
1565
1566        if (!async && !(hctx->flags & BLK_MQ_F_BLOCKING)) {
1567                int cpu = get_cpu();
1568                if (cpumask_test_cpu(cpu, hctx->cpumask)) {
1569                        __blk_mq_run_hw_queue(hctx);
1570                        put_cpu();
1571                        return;
1572                }
1573
1574                put_cpu();
1575        }
1576
1577        kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work,
1578                                    msecs_to_jiffies(msecs));
1579}
1580
1581/**
1582 * blk_mq_delay_run_hw_queue - Run a hardware queue asynchronously.
1583 * @hctx: Pointer to the hardware queue to run.
1584 * @msecs: Milliseconds of delay to wait before running the queue.
1585 *
1586 * Run a hardware queue asynchronously with a delay of @msecs.
1587 */
1588void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
1589{
1590        __blk_mq_delay_run_hw_queue(hctx, true, msecs);
1591}
1592EXPORT_SYMBOL(blk_mq_delay_run_hw_queue);
1593
1594/**
1595 * blk_mq_run_hw_queue - Start to run a hardware queue.
1596 * @hctx: Pointer to the hardware queue to run.
1597 * @async: If we want to run the queue asynchronously.
1598 *
1599 * Check if the request queue is not in a quiesced state and if there are
1600 * pending requests to be sent. If this is true, run the queue to send requests
1601 * to hardware.
1602 */
1603void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
1604{
1605        int srcu_idx;
1606        bool need_run;
1607
1608        /*
1609         * When queue is quiesced, we may be switching io scheduler, or
1610         * updating nr_hw_queues, or other things, and we can't run queue
1611         * any more, even __blk_mq_hctx_has_pending() can't be called safely.
1612         *
1613         * And queue will be rerun in blk_mq_unquiesce_queue() if it is
1614         * quiesced.
1615         */
1616        hctx_lock(hctx, &srcu_idx);
1617        need_run = !blk_queue_quiesced(hctx->queue) &&
1618                blk_mq_hctx_has_pending(hctx);
1619        hctx_unlock(hctx, srcu_idx);
1620
1621        if (need_run)
1622                __blk_mq_delay_run_hw_queue(hctx, async, 0);
1623}
1624EXPORT_SYMBOL(blk_mq_run_hw_queue);
1625
1626/*
1627 * Is the request queue handled by an IO scheduler that does not respect
1628 * hardware queues when dispatching?
1629 */
1630static bool blk_mq_has_sqsched(struct request_queue *q)
1631{
1632        struct elevator_queue *e = q->elevator;
1633
1634        if (e && e->type->ops.dispatch_request &&
1635            !(e->type->elevator_features & ELEVATOR_F_MQ_AWARE))
1636                return true;
1637        return false;
1638}
1639
1640/*
1641 * Return prefered queue to dispatch from (if any) for non-mq aware IO
1642 * scheduler.
1643 */
1644static struct blk_mq_hw_ctx *blk_mq_get_sq_hctx(struct request_queue *q)
1645{
1646        struct blk_mq_hw_ctx *hctx;
1647
1648        /*
1649         * If the IO scheduler does not respect hardware queues when
1650         * dispatching, we just don't bother with multiple HW queues and
1651         * dispatch from hctx for the current CPU since running multiple queues
1652         * just causes lock contention inside the scheduler and pointless cache
1653         * bouncing.
1654         */
1655        hctx = blk_mq_map_queue_type(q, HCTX_TYPE_DEFAULT,
1656                                     raw_smp_processor_id());
1657        if (!blk_mq_hctx_stopped(hctx))
1658                return hctx;
1659        return NULL;
1660}
1661
1662/**
1663 * blk_mq_run_hw_queues - Run all hardware queues in a request queue.
1664 * @q: Pointer to the request queue to run.
1665 * @async: If we want to run the queue asynchronously.
1666 */
1667void blk_mq_run_hw_queues(struct request_queue *q, bool async)
1668{
1669        struct blk_mq_hw_ctx *hctx, *sq_hctx;
1670        int i;
1671
1672        sq_hctx = NULL;
1673        if (blk_mq_has_sqsched(q))
1674                sq_hctx = blk_mq_get_sq_hctx(q);
1675        queue_for_each_hw_ctx(q, hctx, i) {
1676                if (blk_mq_hctx_stopped(hctx))
1677                        continue;
1678                /*
1679                 * Dispatch from this hctx either if there's no hctx preferred
1680                 * by IO scheduler or if it has requests that bypass the
1681                 * scheduler.
1682                 */
1683                if (!sq_hctx || sq_hctx == hctx ||
1684                    !list_empty_careful(&hctx->dispatch))
1685                        blk_mq_run_hw_queue(hctx, async);
1686        }
1687}
1688EXPORT_SYMBOL(blk_mq_run_hw_queues);
1689
1690/**
1691 * blk_mq_delay_run_hw_queues - Run all hardware queues asynchronously.
1692 * @q: Pointer to the request queue to run.
1693 * @msecs: Milliseconds of delay to wait before running the queues.
1694 */
1695void blk_mq_delay_run_hw_queues(struct request_queue *q, unsigned long msecs)
1696{
1697        struct blk_mq_hw_ctx *hctx, *sq_hctx;
1698        int i;
1699
1700        sq_hctx = NULL;
1701        if (blk_mq_has_sqsched(q))
1702                sq_hctx = blk_mq_get_sq_hctx(q);
1703        queue_for_each_hw_ctx(q, hctx, i) {
1704                if (blk_mq_hctx_stopped(hctx))
1705                        continue;
1706                /*
1707                 * Dispatch from this hctx either if there's no hctx preferred
1708                 * by IO scheduler or if it has requests that bypass the
1709                 * scheduler.
1710                 */
1711                if (!sq_hctx || sq_hctx == hctx ||
1712                    !list_empty_careful(&hctx->dispatch))
1713                        blk_mq_delay_run_hw_queue(hctx, msecs);
1714        }
1715}
1716EXPORT_SYMBOL(blk_mq_delay_run_hw_queues);
1717
1718/**
1719 * blk_mq_queue_stopped() - check whether one or more hctxs have been stopped
1720 * @q: request queue.
1721 *
1722 * The caller is responsible for serializing this function against
1723 * blk_mq_{start,stop}_hw_queue().
1724 */
1725bool blk_mq_queue_stopped(struct request_queue *q)
1726{
1727        struct blk_mq_hw_ctx *hctx;
1728        int i;
1729
1730        queue_for_each_hw_ctx(q, hctx, i)
1731                if (blk_mq_hctx_stopped(hctx))
1732                        return true;
1733
1734        return false;
1735}
1736EXPORT_SYMBOL(blk_mq_queue_stopped);
1737
1738/*
1739 * This function is often used for pausing .queue_rq() by driver when
1740 * there isn't enough resource or some conditions aren't satisfied, and
1741 * BLK_STS_RESOURCE is usually returned.
1742 *
1743 * We do not guarantee that dispatch can be drained or blocked
1744 * after blk_mq_stop_hw_queue() returns. Please use
1745 * blk_mq_quiesce_queue() for that requirement.
1746 */
1747void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx)
1748{
1749        cancel_delayed_work(&hctx->run_work);
1750
1751        set_bit(BLK_MQ_S_STOPPED, &hctx->state);
1752}
1753EXPORT_SYMBOL(blk_mq_stop_hw_queue);
1754
1755/*
1756 * This function is often used for pausing .queue_rq() by driver when
1757 * there isn't enough resource or some conditions aren't satisfied, and
1758 * BLK_STS_RESOURCE is usually returned.
1759 *
1760 * We do not guarantee that dispatch can be drained or blocked
1761 * after blk_mq_stop_hw_queues() returns. Please use
1762 * blk_mq_quiesce_queue() for that requirement.
1763 */
1764void blk_mq_stop_hw_queues(struct request_queue *q)
1765{
1766        struct blk_mq_hw_ctx *hctx;
1767        int i;
1768
1769        queue_for_each_hw_ctx(q, hctx, i)
1770                blk_mq_stop_hw_queue(hctx);
1771}
1772EXPORT_SYMBOL(blk_mq_stop_hw_queues);
1773
1774void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx)
1775{
1776        clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
1777
1778        blk_mq_run_hw_queue(hctx, false);
1779}
1780EXPORT_SYMBOL(blk_mq_start_hw_queue);
1781
1782void blk_mq_start_hw_queues(struct request_queue *q)
1783{
1784        struct blk_mq_hw_ctx *hctx;
1785        int i;
1786
1787        queue_for_each_hw_ctx(q, hctx, i)
1788                blk_mq_start_hw_queue(hctx);
1789}
1790EXPORT_SYMBOL(blk_mq_start_hw_queues);
1791
1792void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
1793{
1794        if (!blk_mq_hctx_stopped(hctx))
1795                return;
1796
1797        clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
1798        blk_mq_run_hw_queue(hctx, async);
1799}
1800EXPORT_SYMBOL_GPL(blk_mq_start_stopped_hw_queue);
1801
1802void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async)
1803{
1804        struct blk_mq_hw_ctx *hctx;
1805        int i;
1806
1807        queue_for_each_hw_ctx(q, hctx, i)
1808                blk_mq_start_stopped_hw_queue(hctx, async);
1809}
1810EXPORT_SYMBOL(blk_mq_start_stopped_hw_queues);
1811
1812static void blk_mq_run_work_fn(struct work_struct *work)
1813{
1814        struct blk_mq_hw_ctx *hctx;
1815
1816        hctx = container_of(work, struct blk_mq_hw_ctx, run_work.work);
1817
1818        /*
1819         * If we are stopped, don't run the queue.
1820         */
1821        if (blk_mq_hctx_stopped(hctx))
1822                return;
1823
1824        __blk_mq_run_hw_queue(hctx);
1825}
1826
1827static inline void __blk_mq_insert_req_list(struct blk_mq_hw_ctx *hctx,
1828                                            struct request *rq,
1829                                            bool at_head)
1830{
1831        struct blk_mq_ctx *ctx = rq->mq_ctx;
1832        enum hctx_type type = hctx->type;
1833
1834        lockdep_assert_held(&ctx->lock);
1835
1836        trace_block_rq_insert(rq);
1837
1838        if (at_head)
1839                list_add(&rq->queuelist, &ctx->rq_lists[type]);
1840        else
1841                list_add_tail(&rq->queuelist, &ctx->rq_lists[type]);
1842}
1843
1844void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
1845                             bool at_head)
1846{
1847        struct blk_mq_ctx *ctx = rq->mq_ctx;
1848
1849        lockdep_assert_held(&ctx->lock);
1850
1851        __blk_mq_insert_req_list(hctx, rq, at_head);
1852        blk_mq_hctx_mark_pending(hctx, ctx);
1853}
1854
1855/**
1856 * blk_mq_request_bypass_insert - Insert a request at dispatch list.
1857 * @rq: Pointer to request to be inserted.
1858 * @at_head: true if the request should be inserted at the head of the list.
1859 * @run_queue: If we should run the hardware queue after inserting the request.
1860 *
1861 * Should only be used carefully, when the caller knows we want to
1862 * bypass a potential IO scheduler on the target device.
1863 */
1864void blk_mq_request_bypass_insert(struct request *rq, bool at_head,
1865                                  bool run_queue)
1866{
1867        struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
1868
1869        spin_lock(&hctx->lock);
1870        if (at_head)
1871                list_add(&rq->queuelist, &hctx->dispatch);
1872        else
1873                list_add_tail(&rq->queuelist, &hctx->dispatch);
1874        spin_unlock(&hctx->lock);
1875
1876        if (run_queue)
1877                blk_mq_run_hw_queue(hctx, false);
1878}
1879
1880void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
1881                            struct list_head *list)
1882
1883{
1884        struct request *rq;
1885        enum hctx_type type = hctx->type;
1886
1887        /*
1888         * preemption doesn't flush plug list, so it's possible ctx->cpu is
1889         * offline now
1890         */
1891        list_for_each_entry(rq, list, queuelist) {
1892                BUG_ON(rq->mq_ctx != ctx);
1893                trace_block_rq_insert(rq);
1894        }
1895
1896        spin_lock(&ctx->lock);
1897        list_splice_tail_init(list, &ctx->rq_lists[type]);
1898        blk_mq_hctx_mark_pending(hctx, ctx);
1899        spin_unlock(&ctx->lock);
1900}
1901
1902static int plug_rq_cmp(void *priv, const struct list_head *a,
1903                       const struct list_head *b)
1904{
1905        struct request *rqa = container_of(a, struct request, queuelist);
1906        struct request *rqb = container_of(b, struct request, queuelist);
1907
1908        if (rqa->mq_ctx != rqb->mq_ctx)
1909                return rqa->mq_ctx > rqb->mq_ctx;
1910        if (rqa->mq_hctx != rqb->mq_hctx)
1911                return rqa->mq_hctx > rqb->mq_hctx;
1912
1913        return blk_rq_pos(rqa) > blk_rq_pos(rqb);
1914}
1915
1916void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
1917{
1918        LIST_HEAD(list);
1919
1920        if (list_empty(&plug->mq_list))
1921                return;
1922        list_splice_init(&plug->mq_list, &list);
1923
1924        if (plug->rq_count > 2 && plug->multiple_queues)
1925                list_sort(NULL, &list, plug_rq_cmp);
1926
1927        plug->rq_count = 0;
1928
1929        do {
1930                struct list_head rq_list;
1931                struct request *rq, *head_rq = list_entry_rq(list.next);
1932                struct list_head *pos = &head_rq->queuelist; /* skip first */
1933                struct blk_mq_hw_ctx *this_hctx = head_rq->mq_hctx;
1934                struct blk_mq_ctx *this_ctx = head_rq->mq_ctx;
1935                unsigned int depth = 1;
1936
1937                list_for_each_continue(pos, &list) {
1938                        rq = list_entry_rq(pos);
1939                        BUG_ON(!rq->q);
1940                        if (rq->mq_hctx != this_hctx || rq->mq_ctx != this_ctx)
1941                                break;
1942                        depth++;
1943                }
1944
1945                list_cut_before(&rq_list, &list, pos);
1946                trace_block_unplug(head_rq->q, depth, !from_schedule);
1947                blk_mq_sched_insert_requests(this_hctx, this_ctx, &rq_list,
1948                                                from_schedule);
1949        } while(!list_empty(&list));
1950}
1951
1952static void blk_mq_bio_to_request(struct request *rq, struct bio *bio,
1953                unsigned int nr_segs)
1954{
1955        int err;
1956
1957        if (bio->bi_opf & REQ_RAHEAD)
1958                rq->cmd_flags |= REQ_FAILFAST_MASK;
1959
1960        rq->__sector = bio->bi_iter.bi_sector;
1961        rq->write_hint = bio->bi_write_hint;
1962        blk_rq_bio_prep(rq, bio, nr_segs);
1963
1964        /* This can't fail, since GFP_NOIO includes __GFP_DIRECT_RECLAIM. */
1965        err = blk_crypto_rq_bio_prep(rq, bio, GFP_NOIO);
1966        WARN_ON_ONCE(err);
1967
1968        blk_account_io_start(rq);
1969}
1970
1971static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
1972                                            struct request *rq,
1973                                            blk_qc_t *cookie, bool last)
1974{
1975        struct request_queue *q = rq->q;
1976        struct blk_mq_queue_data bd = {
1977                .rq = rq,
1978                .last = last,
1979        };
1980        blk_qc_t new_cookie;
1981        blk_status_t ret;
1982
1983        new_cookie = request_to_qc_t(hctx, rq);
1984
1985        /*
1986         * For OK queue, we are done. For error, caller may kill it.
1987         * Any other error (busy), just add it to our list as we
1988         * previously would have done.
1989         */
1990        ret = q->mq_ops->queue_rq(hctx, &bd);
1991        switch (ret) {
1992        case BLK_STS_OK:
1993                blk_mq_update_dispatch_busy(hctx, false);
1994                *cookie = new_cookie;
1995                break;
1996        case BLK_STS_RESOURCE:
1997        case BLK_STS_DEV_RESOURCE:
1998                blk_mq_update_dispatch_busy(hctx, true);
1999                __blk_mq_requeue_request(rq);
2000                break;
2001        default:
2002                blk_mq_update_dispatch_busy(hctx, false);
2003                *cookie = BLK_QC_T_NONE;
2004                break;
2005        }
2006
2007        return ret;
2008}
2009
2010static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
2011                                                struct request *rq,
2012                                                blk_qc_t *cookie,
2013                                                bool bypass_insert, bool last)
2014{
2015        struct request_queue *q = rq->q;
2016        bool run_queue = true;
2017        int budget_token;
2018
2019        /*
2020         * RCU or SRCU read lock is needed before checking quiesced flag.
2021         *
2022         * When queue is stopped or quiesced, ignore 'bypass_insert' from
2023         * blk_mq_request_issue_directly(), and return BLK_STS_OK to caller,
2024         * and avoid driver to try to dispatch again.
2025         */
2026        if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)) {
2027                run_queue = false;
2028                bypass_insert = false;
2029                goto insert;
2030        }
2031
2032        if (q->elevator && !bypass_insert)
2033                goto insert;
2034
2035        budget_token = blk_mq_get_dispatch_budget(q);
2036        if (budget_token < 0)
2037                goto insert;
2038
2039        blk_mq_set_rq_budget_token(rq, budget_token);
2040
2041        if (!blk_mq_get_driver_tag(rq)) {
2042                blk_mq_put_dispatch_budget(q, budget_token);
2043                goto insert;
2044        }
2045
2046        return __blk_mq_issue_directly(hctx, rq, cookie, last);
2047insert:
2048        if (bypass_insert)
2049                return BLK_STS_RESOURCE;
2050
2051        blk_mq_sched_insert_request(rq, false, run_queue, false);
2052
2053        return BLK_STS_OK;
2054}
2055
2056/**
2057 * blk_mq_try_issue_directly - Try to send a request directly to device driver.
2058 * @hctx: Pointer of the associated hardware queue.
2059 * @rq: Pointer to request to be sent.
2060 * @cookie: Request queue cookie.
2061 *
2062 * If the device has enough resources to accept a new request now, send the
2063 * request directly to device driver. Else, insert at hctx->dispatch queue, so
2064 * we can try send it another time in the future. Requests inserted at this
2065 * queue have higher priority.
2066 */
2067static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
2068                struct request *rq, blk_qc_t *cookie)
2069{
2070        blk_status_t ret;
2071        int srcu_idx;
2072
2073        might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
2074
2075        hctx_lock(hctx, &srcu_idx);
2076
2077        ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false, true);
2078        if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
2079                blk_mq_request_bypass_insert(rq, false, true);
2080        else if (ret != BLK_STS_OK)
2081                blk_mq_end_request(rq, ret);
2082
2083        hctx_unlock(hctx, srcu_idx);
2084}
2085
2086blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last)
2087{
2088        blk_status_t ret;
2089        int srcu_idx;
2090        blk_qc_t unused_cookie;
2091        struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
2092
2093        hctx_lock(hctx, &srcu_idx);
2094        ret = __blk_mq_try_issue_directly(hctx, rq, &unused_cookie, true, last);
2095        hctx_unlock(hctx, srcu_idx);
2096
2097        return ret;
2098}
2099
2100void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
2101                struct list_head *list)
2102{
2103        int queued = 0;
2104        int errors = 0;
2105
2106        while (!list_empty(list)) {
2107                blk_status_t ret;
2108                struct request *rq = list_first_entry(list, struct request,
2109                                queuelist);
2110
2111                list_del_init(&rq->queuelist);
2112                ret = blk_mq_request_issue_directly(rq, list_empty(list));
2113                if (ret != BLK_STS_OK) {
2114                        if (ret == BLK_STS_RESOURCE ||
2115                                        ret == BLK_STS_DEV_RESOURCE) {
2116                                blk_mq_request_bypass_insert(rq, false,
2117                                                        list_empty(list));
2118                                break;
2119                        }
2120                        blk_mq_end_request(rq, ret);
2121                        errors++;
2122                } else
2123                        queued++;
2124        }
2125
2126        /*
2127         * If we didn't flush the entire list, we could have told
2128         * the driver there was more coming, but that turned out to
2129         * be a lie.
2130         */
2131        if ((!list_empty(list) || errors) &&
2132             hctx->queue->mq_ops->commit_rqs && queued)
2133                hctx->queue->mq_ops->commit_rqs(hctx);
2134}
2135
2136static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
2137{
2138        list_add_tail(&rq->queuelist, &plug->mq_list);
2139        plug->rq_count++;
2140        if (!plug->multiple_queues && !list_is_singular(&plug->mq_list)) {
2141                struct request *tmp;
2142
2143                tmp = list_first_entry(&plug->mq_list, struct request,
2144                                                queuelist);
2145                if (tmp->q != rq->q)
2146                        plug->multiple_queues = true;
2147        }
2148}
2149
2150/*
2151 * Allow 4x BLK_MAX_REQUEST_COUNT requests on plug queue for multiple
2152 * queues. This is important for md arrays to benefit from merging
2153 * requests.
2154 */
2155static inline unsigned short blk_plug_max_rq_count(struct blk_plug *plug)
2156{
2157        if (plug->multiple_queues)
2158                return BLK_MAX_REQUEST_COUNT * 4;
2159        return BLK_MAX_REQUEST_COUNT;
2160}
2161
2162/**
2163 * blk_mq_submit_bio - Create and send a request to block device.
2164 * @bio: Bio pointer.
2165 *
2166 * Builds up a request structure from @q and @bio and send to the device. The
2167 * request may not be queued directly to hardware if:
2168 * * This request can be merged with another one
2169 * * We want to place request at plug queue for possible future merging
2170 * * There is an IO scheduler active at this queue
2171 *
2172 * It will not queue the request if there is an error with the bio, or at the
2173 * request creation.
2174 *
2175 * Returns: Request queue cookie.
2176 */
2177blk_qc_t blk_mq_submit_bio(struct bio *bio)
2178{
2179        struct request_queue *q = bio->bi_bdev->bd_disk->queue;
2180        const int is_sync = op_is_sync(bio->bi_opf);
2181        const int is_flush_fua = op_is_flush(bio->bi_opf);
2182        struct blk_mq_alloc_data data = {
2183                .q              = q,
2184        };
2185        struct request *rq;
2186        struct blk_plug *plug;
2187        struct request *same_queue_rq = NULL;
2188        unsigned int nr_segs;
2189        blk_qc_t cookie;
2190        blk_status_t ret;
2191        bool hipri;
2192
2193        blk_queue_bounce(q, &bio);
2194        __blk_queue_split(&bio, &nr_segs);
2195
2196        if (!bio_integrity_prep(bio))
2197                goto queue_exit;
2198
2199        if (!is_flush_fua && !blk_queue_nomerges(q) &&
2200            blk_attempt_plug_merge(q, bio, nr_segs, &same_queue_rq))
2201                goto queue_exit;
2202
2203        if (blk_mq_sched_bio_merge(q, bio, nr_segs))
2204                goto queue_exit;
2205
2206        rq_qos_throttle(q, bio);
2207
2208        hipri = bio->bi_opf & REQ_HIPRI;
2209
2210        data.cmd_flags = bio->bi_opf;
2211        rq = __blk_mq_alloc_request(&data);
2212        if (unlikely(!rq)) {
2213                rq_qos_cleanup(q, bio);
2214                if (bio->bi_opf & REQ_NOWAIT)
2215                        bio_wouldblock_error(bio);
2216                goto queue_exit;
2217        }
2218
2219        trace_block_getrq(bio);
2220
2221        rq_qos_track(q, rq, bio);
2222
2223        cookie = request_to_qc_t(data.hctx, rq);
2224
2225        blk_mq_bio_to_request(rq, bio, nr_segs);
2226
2227        ret = blk_crypto_init_request(rq);
2228        if (ret != BLK_STS_OK) {
2229                bio->bi_status = ret;
2230                bio_endio(bio);
2231                blk_mq_free_request(rq);
2232                return BLK_QC_T_NONE;
2233        }
2234
2235        plug = blk_mq_plug(q, bio);
2236        if (unlikely(is_flush_fua)) {
2237                /* Bypass scheduler for flush requests */
2238                blk_insert_flush(rq);
2239                blk_mq_run_hw_queue(data.hctx, true);
2240        } else if (plug && (q->nr_hw_queues == 1 ||
2241                   blk_mq_is_sbitmap_shared(rq->mq_hctx->flags) ||
2242                   q->mq_ops->commit_rqs || !blk_queue_nonrot(q))) {
2243                /*
2244                 * Use plugging if we have a ->commit_rqs() hook as well, as
2245                 * we know the driver uses bd->last in a smart fashion.
2246                 *
2247                 * Use normal plugging if this disk is slow HDD, as sequential
2248                 * IO may benefit a lot from plug merging.
2249                 */
2250                unsigned int request_count = plug->rq_count;
2251                struct request *last = NULL;
2252
2253                if (!request_count)
2254                        trace_block_plug(q);
2255                else
2256                        last = list_entry_rq(plug->mq_list.prev);
2257
2258                if (request_count >= blk_plug_max_rq_count(plug) || (last &&
2259                    blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
2260                        blk_flush_plug_list(plug, false);
2261                        trace_block_plug(q);
2262                }
2263
2264                blk_add_rq_to_plug(plug, rq);
2265        } else if (q->elevator) {
2266                /* Insert the request at the IO scheduler queue */
2267                blk_mq_sched_insert_request(rq, false, true, true);
2268        } else if (plug && !blk_queue_nomerges(q)) {
2269                /*
2270                 * We do limited plugging. If the bio can be merged, do that.
2271                 * Otherwise the existing request in the plug list will be
2272                 * issued. So the plug list will have one request at most
2273                 * The plug list might get flushed before this. If that happens,
2274                 * the plug list is empty, and same_queue_rq is invalid.
2275                 */
2276                if (list_empty(&plug->mq_list))
2277                        same_queue_rq = NULL;
2278                if (same_queue_rq) {
2279                        list_del_init(&same_queue_rq->queuelist);
2280                        plug->rq_count--;
2281                }
2282                blk_add_rq_to_plug(plug, rq);
2283                trace_block_plug(q);
2284
2285                if (same_queue_rq) {
2286                        data.hctx = same_queue_rq->mq_hctx;
2287                        trace_block_unplug(q, 1, true);
2288                        blk_mq_try_issue_directly(data.hctx, same_queue_rq,
2289                                        &cookie);
2290                }
2291        } else if ((q->nr_hw_queues > 1 && is_sync) ||
2292                        !data.hctx->dispatch_busy) {
2293                /*
2294                 * There is no scheduler and we can try to send directly
2295                 * to the hardware.
2296                 */
2297                blk_mq_try_issue_directly(data.hctx, rq, &cookie);
2298        } else {
2299                /* Default case. */
2300                blk_mq_sched_insert_request(rq, false, true, true);
2301        }
2302
2303        if (!hipri)
2304                return BLK_QC_T_NONE;
2305        return cookie;
2306queue_exit:
2307        blk_queue_exit(q);
2308        return BLK_QC_T_NONE;
2309}
2310
2311static size_t order_to_size(unsigned int order)
2312{
2313        return (size_t)PAGE_SIZE << order;
2314}
2315
2316/* called before freeing request pool in @tags */
2317static void blk_mq_clear_rq_mapping(struct blk_mq_tag_set *set,
2318                struct blk_mq_tags *tags, unsigned int hctx_idx)
2319{
2320        struct blk_mq_tags *drv_tags = set->tags[hctx_idx];
2321        struct page *page;
2322        unsigned long flags;
2323
2324        list_for_each_entry(page, &tags->page_list, lru) {
2325                unsigned long start = (unsigned long)page_address(page);
2326                unsigned long end = start + order_to_size(page->private);
2327                int i;
2328
2329                for (i = 0; i < set->queue_depth; i++) {
2330                        struct request *rq = drv_tags->rqs[i];
2331                        unsigned long rq_addr = (unsigned long)rq;
2332
2333                        if (rq_addr >= start && rq_addr < end) {
2334                                WARN_ON_ONCE(refcount_read(&rq->ref) != 0);
2335                                cmpxchg(&drv_tags->rqs[i], rq, NULL);
2336                        }
2337                }
2338        }
2339
2340        /*
2341         * Wait until all pending iteration is done.
2342         *
2343         * Request reference is cleared and it is guaranteed to be observed
2344         * after the ->lock is released.
2345         */
2346        spin_lock_irqsave(&drv_tags->lock, flags);
2347        spin_unlock_irqrestore(&drv_tags->lock, flags);
2348}
2349
2350void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
2351                     unsigned int hctx_idx)
2352{
2353        struct page *page;
2354
2355        if (tags->rqs && set->ops->exit_request) {
2356                int i;
2357
2358                for (i = 0; i < tags->nr_tags; i++) {
2359                        struct request *rq = tags->static_rqs[i];
2360
2361                        if (!rq)
2362                                continue;
2363                        set->ops->exit_request(set, rq, hctx_idx);
2364                        tags->static_rqs[i] = NULL;
2365                }
2366        }
2367
2368        blk_mq_clear_rq_mapping(set, tags, hctx_idx);
2369
2370        while (!list_empty(&tags->page_list)) {
2371                page = list_first_entry(&tags->page_list, struct page, lru);
2372                list_del_init(&page->lru);
2373                /*
2374                 * Remove kmemleak object previously allocated in
2375                 * blk_mq_alloc_rqs().
2376                 */
2377                kmemleak_free(page_address(page));
2378                __free_pages(page, page->private);
2379        }
2380}
2381
2382void blk_mq_free_rq_map(struct blk_mq_tags *tags, unsigned int flags)
2383{
2384        kfree(tags->rqs);
2385        tags->rqs = NULL;
2386        kfree(tags->static_rqs);
2387        tags->static_rqs = NULL;
2388
2389        blk_mq_free_tags(tags, flags);
2390}
2391
2392struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
2393                                        unsigned int hctx_idx,
2394                                        unsigned int nr_tags,
2395                                        unsigned int reserved_tags,
2396                                        unsigned int flags)
2397{
2398        struct blk_mq_tags *tags;
2399        int node;
2400
2401        node = blk_mq_hw_queue_to_node(&set->map[HCTX_TYPE_DEFAULT], hctx_idx);
2402        if (node == NUMA_NO_NODE)
2403                node = set->numa_node;
2404
2405        tags = blk_mq_init_tags(nr_tags, reserved_tags, node, flags);
2406        if (!tags)
2407                return NULL;
2408
2409        tags->rqs = kcalloc_node(nr_tags, sizeof(struct request *),
2410                                 GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
2411                                 node);
2412        if (!tags->rqs) {
2413                blk_mq_free_tags(tags, flags);
2414                return NULL;
2415        }
2416
2417        tags->static_rqs = kcalloc_node(nr_tags, sizeof(struct request *),
2418                                        GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
2419                                        node);
2420        if (!tags->static_rqs) {
2421                kfree(tags->rqs);
2422                blk_mq_free_tags(tags, flags);
2423                return NULL;
2424        }
2425
2426        return tags;
2427}
2428
2429static int blk_mq_init_request(struct blk_mq_tag_set *set, struct request *rq,
2430                               unsigned int hctx_idx, int node)
2431{
2432        int ret;
2433
2434        if (set->ops->init_request) {
2435                ret = set->ops->init_request(set, rq, hctx_idx, node);
2436                if (ret)
2437                        return ret;
2438        }
2439
2440        WRITE_ONCE(rq->state, MQ_RQ_IDLE);
2441        return 0;
2442}
2443
2444int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
2445                     unsigned int hctx_idx, unsigned int depth)
2446{
2447        unsigned int i, j, entries_per_page, max_order = 4;
2448        size_t rq_size, left;
2449        int node;
2450
2451        node = blk_mq_hw_queue_to_node(&set->map[HCTX_TYPE_DEFAULT], hctx_idx);
2452        if (node == NUMA_NO_NODE)
2453                node = set->numa_node;
2454
2455        INIT_LIST_HEAD(&tags->page_list);
2456
2457        /*
2458         * rq_size is the size of the request plus driver payload, rounded
2459         * to the cacheline size
2460         */
2461        rq_size = round_up(sizeof(struct request) + set->cmd_size,
2462                                cache_line_size());
2463        left = rq_size * depth;
2464
2465        for (i = 0; i < depth; ) {
2466                int this_order = max_order;
2467                struct page *page;
2468                int to_do;
2469                void *p;
2470
2471                while (this_order && left < order_to_size(this_order - 1))
2472                        this_order--;
2473
2474                do {
2475                        page = alloc_pages_node(node,
2476                                GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY | __GFP_ZERO,
2477                                this_order);
2478                        if (page)
2479                                break;
2480                        if (!this_order--)
2481                                break;
2482                        if (order_to_size(this_order) < rq_size)
2483                                break;
2484                } while (1);
2485
2486                if (!page)
2487                        goto fail;
2488
2489                page->private = this_order;
2490                list_add_tail(&page->lru, &tags->page_list);
2491
2492                p = page_address(page);
2493                /*
2494                 * Allow kmemleak to scan these pages as they contain pointers
2495                 * to additional allocations like via ops->init_request().
2496                 */
2497                kmemleak_alloc(p, order_to_size(this_order), 1, GFP_NOIO);
2498                entries_per_page = order_to_size(this_order) / rq_size;
2499                to_do = min(entries_per_page, depth - i);
2500                left -= to_do * rq_size;
2501                for (j = 0; j < to_do; j++) {
2502                        struct request *rq = p;
2503
2504                        tags->static_rqs[i] = rq;
2505                        if (blk_mq_init_request(set, rq, hctx_idx, node)) {
2506                                tags->static_rqs[i] = NULL;
2507                                goto fail;
2508                        }
2509
2510                        p += rq_size;
2511                        i++;
2512                }
2513        }
2514        return 0;
2515
2516fail:
2517        blk_mq_free_rqs(set, tags, hctx_idx);
2518        return -ENOMEM;
2519}
2520
2521struct rq_iter_data {
2522        struct blk_mq_hw_ctx *hctx;
2523        bool has_rq;
2524};
2525
2526static bool blk_mq_has_request(struct request *rq, void *data, bool reserved)
2527{
2528        struct rq_iter_data *iter_data = data;
2529
2530        if (rq->mq_hctx != iter_data->hctx)
2531                return true;
2532        iter_data->has_rq = true;
2533        return false;
2534}
2535
2536static bool blk_mq_hctx_has_requests(struct blk_mq_hw_ctx *hctx)
2537{
2538        struct blk_mq_tags *tags = hctx->sched_tags ?
2539                        hctx->sched_tags : hctx->tags;
2540        struct rq_iter_data data = {
2541                .hctx   = hctx,
2542        };
2543
2544        blk_mq_all_tag_iter(tags, blk_mq_has_request, &data);
2545        return data.has_rq;
2546}
2547
2548static inline bool blk_mq_last_cpu_in_hctx(unsigned int cpu,
2549                struct blk_mq_hw_ctx *hctx)
2550{
2551        if (cpumask_next_and(-1, hctx->cpumask, cpu_online_mask) != cpu)
2552                return false;
2553        if (cpumask_next_and(cpu, hctx->cpumask, cpu_online_mask) < nr_cpu_ids)
2554                return false;
2555        return true;
2556}
2557
2558static int blk_mq_hctx_notify_offline(unsigned int cpu, struct hlist_node *node)
2559{
2560        struct blk_mq_hw_ctx *hctx = hlist_entry_safe(node,
2561                        struct blk_mq_hw_ctx, cpuhp_online);
2562
2563        if (!cpumask_test_cpu(cpu, hctx->cpumask) ||
2564            !blk_mq_last_cpu_in_hctx(cpu, hctx))
2565                return 0;
2566
2567        /*
2568         * Prevent new request from being allocated on the current hctx.
2569         *
2570         * The smp_mb__after_atomic() Pairs with the implied barrier in
2571         * test_and_set_bit_lock in sbitmap_get().  Ensures the inactive flag is
2572         * seen once we return from the tag allocator.
2573         */
2574        set_bit(BLK_MQ_S_INACTIVE, &hctx->state);
2575        smp_mb__after_atomic();
2576
2577        /*
2578         * Try to grab a reference to the queue and wait for any outstanding
2579         * requests.  If we could not grab a reference the queue has been
2580         * frozen and there are no requests.
2581         */
2582        if (percpu_ref_tryget(&hctx->queue->q_usage_counter)) {
2583                while (blk_mq_hctx_has_requests(hctx))
2584                        msleep(5);
2585                percpu_ref_put(&hctx->queue->q_usage_counter);
2586        }
2587
2588        return 0;
2589}
2590
2591static int blk_mq_hctx_notify_online(unsigned int cpu, struct hlist_node *node)
2592{
2593        struct blk_mq_hw_ctx *hctx = hlist_entry_safe(node,
2594                        struct blk_mq_hw_ctx, cpuhp_online);
2595
2596        if (cpumask_test_cpu(cpu, hctx->cpumask))
2597                clear_bit(BLK_MQ_S_INACTIVE, &hctx->state);
2598        return 0;
2599}
2600
2601/*
2602 * 'cpu' is going away. splice any existing rq_list entries from this
2603 * software queue to the hw queue dispatch list, and ensure that it
2604 * gets run.
2605 */
2606static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node)
2607{
2608        struct blk_mq_hw_ctx *hctx;
2609        struct blk_mq_ctx *ctx;
2610        LIST_HEAD(tmp);
2611        enum hctx_type type;
2612
2613        hctx = hlist_entry_safe(node, struct blk_mq_hw_ctx, cpuhp_dead);
2614        if (!cpumask_test_cpu(cpu, hctx->cpumask))
2615                return 0;
2616
2617        ctx = __blk_mq_get_ctx(hctx->queue, cpu);
2618        type = hctx->type;
2619
2620        spin_lock(&ctx->lock);
2621        if (!list_empty(&ctx->rq_lists[type])) {
2622                list_splice_init(&ctx->rq_lists[type], &tmp);
2623                blk_mq_hctx_clear_pending(hctx, ctx);
2624        }
2625        spin_unlock(&ctx->lock);
2626
2627        if (list_empty(&tmp))
2628                return 0;
2629
2630        spin_lock(&hctx->lock);
2631        list_splice_tail_init(&tmp, &hctx->dispatch);
2632        spin_unlock(&hctx->lock);
2633
2634        blk_mq_run_hw_queue(hctx, true);
2635        return 0;
2636}
2637
2638static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx)
2639{
2640        if (!(hctx->flags & BLK_MQ_F_STACKING))
2641                cpuhp_state_remove_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE,
2642                                                    &hctx->cpuhp_online);
2643        cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_DEAD,
2644                                            &hctx->cpuhp_dead);
2645}
2646
2647/*
2648 * Before freeing hw queue, clearing the flush request reference in
2649 * tags->rqs[] for avoiding potential UAF.
2650 */
2651static void blk_mq_clear_flush_rq_mapping(struct blk_mq_tags *tags,
2652                unsigned int queue_depth, struct request *flush_rq)
2653{
2654        int i;
2655        unsigned long flags;
2656
2657        /* The hw queue may not be mapped yet */
2658        if (!tags)
2659                return;
2660
2661        WARN_ON_ONCE(refcount_read(&flush_rq->ref) != 0);
2662
2663        for (i = 0; i < queue_depth; i++)
2664                cmpxchg(&tags->rqs[i], flush_rq, NULL);
2665
2666        /*
2667         * Wait until all pending iteration is done.
2668         *
2669         * Request reference is cleared and it is guaranteed to be observed
2670         * after the ->lock is released.
2671         */
2672        spin_lock_irqsave(&tags->lock, flags);
2673        spin_unlock_irqrestore(&tags->lock, flags);
2674}
2675
2676/* hctx->ctxs will be freed in queue's release handler */
2677static void blk_mq_exit_hctx(struct request_queue *q,
2678                struct blk_mq_tag_set *set,
2679                struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
2680{
2681        struct request *flush_rq = hctx->fq->flush_rq;
2682
2683        if (blk_mq_hw_queue_mapped(hctx))
2684                blk_mq_tag_idle(hctx);
2685
2686        blk_mq_clear_flush_rq_mapping(set->tags[hctx_idx],
2687                        set->queue_depth, flush_rq);
2688        if (set->ops->exit_request)
2689                set->ops->exit_request(set, flush_rq, hctx_idx);
2690
2691        if (set->ops->exit_hctx)
2692                set->ops->exit_hctx(hctx, hctx_idx);
2693
2694        blk_mq_remove_cpuhp(hctx);
2695
2696        spin_lock(&q->unused_hctx_lock);
2697        list_add(&hctx->hctx_list, &q->unused_hctx_list);
2698        spin_unlock(&q->unused_hctx_lock);
2699}
2700
2701static void blk_mq_exit_hw_queues(struct request_queue *q,
2702                struct blk_mq_tag_set *set, int nr_queue)
2703{
2704        struct blk_mq_hw_ctx *hctx;
2705        unsigned int i;
2706
2707        queue_for_each_hw_ctx(q, hctx, i) {
2708                if (i == nr_queue)
2709                        break;
2710                blk_mq_debugfs_unregister_hctx(hctx);
2711                blk_mq_exit_hctx(q, set, hctx, i);
2712        }
2713}
2714
2715static int blk_mq_hw_ctx_size(struct blk_mq_tag_set *tag_set)
2716{
2717        int hw_ctx_size = sizeof(struct blk_mq_hw_ctx);
2718
2719        BUILD_BUG_ON(ALIGN(offsetof(struct blk_mq_hw_ctx, srcu),
2720                           __alignof__(struct blk_mq_hw_ctx)) !=
2721                     sizeof(struct blk_mq_hw_ctx));
2722
2723        if (tag_set->flags & BLK_MQ_F_BLOCKING)
2724                hw_ctx_size += sizeof(struct srcu_struct);
2725
2726        return hw_ctx_size;
2727}
2728
2729static int blk_mq_init_hctx(struct request_queue *q,
2730                struct blk_mq_tag_set *set,
2731                struct blk_mq_hw_ctx *hctx, unsigned hctx_idx)
2732{
2733        hctx->queue_num = hctx_idx;
2734
2735        if (!(hctx->flags & BLK_MQ_F_STACKING))
2736                cpuhp_state_add_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE,
2737                                &hctx->cpuhp_online);
2738        cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD, &hctx->cpuhp_dead);
2739
2740        hctx->tags = set->tags[hctx_idx];
2741
2742        if (set->ops->init_hctx &&
2743            set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
2744                goto unregister_cpu_notifier;
2745
2746        if (blk_mq_init_request(set, hctx->fq->flush_rq, hctx_idx,
2747                                hctx->numa_node))
2748                goto exit_hctx;
2749        return 0;
2750
2751 exit_hctx:
2752        if (set->ops->exit_hctx)
2753                set->ops->exit_hctx(hctx, hctx_idx);
2754 unregister_cpu_notifier:
2755        blk_mq_remove_cpuhp(hctx);
2756        return -1;
2757}
2758
2759static struct blk_mq_hw_ctx *
2760blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set,
2761                int node)
2762{
2763        struct blk_mq_hw_ctx *hctx;
2764        gfp_t gfp = GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY;
2765
2766        hctx = kzalloc_node(blk_mq_hw_ctx_size(set), gfp, node);
2767        if (!hctx)
2768                goto fail_alloc_hctx;
2769
2770        if (!zalloc_cpumask_var_node(&hctx->cpumask, gfp, node))
2771                goto free_hctx;
2772
2773        atomic_set(&hctx->nr_active, 0);
2774        if (node == NUMA_NO_NODE)
2775                node = set->numa_node;
2776        hctx->numa_node = node;
2777
2778        INIT_DELAYED_WORK(&hctx->run_work, blk_mq_run_work_fn);
2779        spin_lock_init(&hctx->lock);
2780        INIT_LIST_HEAD(&hctx->dispatch);
2781        hctx->queue = q;
2782        hctx->flags = set->flags & ~BLK_MQ_F_TAG_QUEUE_SHARED;
2783
2784        INIT_LIST_HEAD(&hctx->hctx_list);
2785
2786        /*
2787         * Allocate space for all possible cpus to avoid allocation at
2788         * runtime
2789         */
2790        hctx->ctxs = kmalloc_array_node(nr_cpu_ids, sizeof(void *),
2791                        gfp, node);
2792        if (!hctx->ctxs)
2793                goto free_cpumask;
2794
2795        if (sbitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8),
2796                                gfp, node, false, false))
2797                goto free_ctxs;
2798        hctx->nr_ctx = 0;
2799
2800        spin_lock_init(&hctx->dispatch_wait_lock);
2801        init_waitqueue_func_entry(&hctx->dispatch_wait, blk_mq_dispatch_wake);
2802        INIT_LIST_HEAD(&hctx->dispatch_wait.entry);
2803
2804        hctx->fq = blk_alloc_flush_queue(hctx->numa_node, set->cmd_size, gfp);
2805        if (!hctx->fq)
2806                goto free_bitmap;
2807
2808        if (hctx->flags & BLK_MQ_F_BLOCKING)
2809                init_srcu_struct(hctx->srcu);
2810        blk_mq_hctx_kobj_init(hctx);
2811
2812        return hctx;
2813
2814 free_bitmap:
2815        sbitmap_free(&hctx->ctx_map);
2816 free_ctxs:
2817        kfree(hctx->ctxs);
2818 free_cpumask:
2819        free_cpumask_var(hctx->cpumask);
2820 free_hctx:
2821        kfree(hctx);
2822 fail_alloc_hctx:
2823        return NULL;
2824}
2825
2826static void blk_mq_init_cpu_queues(struct request_queue *q,
2827                                   unsigned int nr_hw_queues)
2828{
2829        struct blk_mq_tag_set *set = q->tag_set;
2830        unsigned int i, j;
2831
2832        for_each_possible_cpu(i) {
2833                struct blk_mq_ctx *__ctx = per_cpu_ptr(q->queue_ctx, i);
2834                struct blk_mq_hw_ctx *hctx;
2835                int k;
2836
2837                __ctx->cpu = i;
2838                spin_lock_init(&__ctx->lock);
2839                for (k = HCTX_TYPE_DEFAULT; k < HCTX_MAX_TYPES; k++)
2840                        INIT_LIST_HEAD(&__ctx->rq_lists[k]);
2841
2842                __ctx->queue = q;
2843
2844                /*
2845                 * Set local node, IFF we have more than one hw queue. If
2846                 * not, we remain on the home node of the device
2847                 */
2848                for (j = 0; j < set->nr_maps; j++) {
2849                        hctx = blk_mq_map_queue_type(q, j, i);
2850                        if (nr_hw_queues > 1 && hctx->numa_node == NUMA_NO_NODE)
2851                                hctx->numa_node = cpu_to_node(i);
2852                }
2853        }
2854}
2855
2856static bool __blk_mq_alloc_map_and_request(struct blk_mq_tag_set *set,
2857                                        int hctx_idx)
2858{
2859        unsigned int flags = set->flags;
2860        int ret = 0;
2861
2862        set->tags[hctx_idx] = blk_mq_alloc_rq_map(set, hctx_idx,
2863                                        set->queue_depth, set->reserved_tags, flags);
2864        if (!set->tags[hctx_idx])
2865                return false;
2866
2867        ret = blk_mq_alloc_rqs(set, set->tags[hctx_idx], hctx_idx,
2868                                set->queue_depth);
2869        if (!ret)
2870                return true;
2871
2872        blk_mq_free_rq_map(set->tags[hctx_idx], flags);
2873        set->tags[hctx_idx] = NULL;
2874        return false;
2875}
2876
2877static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set,
2878                                         unsigned int hctx_idx)
2879{
2880        unsigned int flags = set->flags;
2881
2882        if (set->tags && set->tags[hctx_idx]) {
2883                blk_mq_free_rqs(set, set->tags[hctx_idx], hctx_idx);
2884                blk_mq_free_rq_map(set->tags[hctx_idx], flags);
2885                set->tags[hctx_idx] = NULL;
2886        }
2887}
2888
2889static void blk_mq_map_swqueue(struct request_queue *q)
2890{
2891        unsigned int i, j, hctx_idx;
2892        struct blk_mq_hw_ctx *hctx;
2893        struct blk_mq_ctx *ctx;
2894        struct blk_mq_tag_set *set = q->tag_set;
2895
2896        queue_for_each_hw_ctx(q, hctx, i) {
2897                cpumask_clear(hctx->cpumask);
2898                hctx->nr_ctx = 0;
2899                hctx->dispatch_from = NULL;
2900        }
2901
2902        /*
2903         * Map software to hardware queues.
2904         *
2905         * If the cpu isn't present, the cpu is mapped to first hctx.
2906         */
2907        for_each_possible_cpu(i) {
2908
2909                ctx = per_cpu_ptr(q->queue_ctx, i);
2910                for (j = 0; j < set->nr_maps; j++) {
2911                        if (!set->map[j].nr_queues) {
2912                                ctx->hctxs[j] = blk_mq_map_queue_type(q,
2913                                                HCTX_TYPE_DEFAULT, i);
2914                                continue;
2915                        }
2916                        hctx_idx = set->map[j].mq_map[i];
2917                        /* unmapped hw queue can be remapped after CPU topo changed */
2918                        if (!set->tags[hctx_idx] &&
2919                            !__blk_mq_alloc_map_and_request(set, hctx_idx)) {
2920                                /*
2921                                 * If tags initialization fail for some hctx,
2922                                 * that hctx won't be brought online.  In this
2923                                 * case, remap the current ctx to hctx[0] which
2924                                 * is guaranteed to always have tags allocated
2925                                 */
2926                                set->map[j].mq_map[i] = 0;
2927                        }
2928
2929                        hctx = blk_mq_map_queue_type(q, j, i);
2930                        ctx->hctxs[j] = hctx;
2931                        /*
2932                         * If the CPU is already set in the mask, then we've
2933                         * mapped this one already. This can happen if
2934                         * devices share queues across queue maps.
2935                         */
2936                        if (cpumask_test_cpu(i, hctx->cpumask))
2937                                continue;
2938
2939                        cpumask_set_cpu(i, hctx->cpumask);
2940                        hctx->type = j;
2941                        ctx->index_hw[hctx->type] = hctx->nr_ctx;
2942                        hctx->ctxs[hctx->nr_ctx++] = ctx;
2943
2944                        /*
2945                         * If the nr_ctx type overflows, we have exceeded the
2946                         * amount of sw queues we can support.
2947                         */
2948                        BUG_ON(!hctx->nr_ctx);
2949                }
2950
2951                for (; j < HCTX_MAX_TYPES; j++)
2952                        ctx->hctxs[j] = blk_mq_map_queue_type(q,
2953                                        HCTX_TYPE_DEFAULT, i);
2954        }
2955
2956        queue_for_each_hw_ctx(q, hctx, i) {
2957                /*
2958                 * If no software queues are mapped to this hardware queue,
2959                 * disable it and free the request entries.
2960                 */
2961                if (!hctx->nr_ctx) {
2962                        /* Never unmap queue 0.  We need it as a
2963                         * fallback in case of a new remap fails
2964                         * allocation
2965                         */
2966                        if (i && set->tags[i])
2967                                blk_mq_free_map_and_requests(set, i);
2968
2969                        hctx->tags = NULL;
2970                        continue;
2971                }
2972
2973                hctx->tags = set->tags[i];
2974                WARN_ON(!hctx->tags);
2975
2976                /*
2977                 * Set the map size to the number of mapped software queues.
2978                 * This is more accurate and more efficient than looping
2979                 * over all possibly mapped software queues.
2980                 */
2981                sbitmap_resize(&hctx->ctx_map, hctx->nr_ctx);
2982
2983                /*
2984                 * Initialize batch roundrobin counts
2985                 */
2986                hctx->next_cpu = blk_mq_first_mapped_cpu(hctx);
2987                hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
2988        }
2989}
2990
2991/*
2992 * Caller needs to ensure that we're either frozen/quiesced, or that
2993 * the queue isn't live yet.
2994 */
2995static void queue_set_hctx_shared(struct request_queue *q, bool shared)
2996{
2997        struct blk_mq_hw_ctx *hctx;
2998        int i;
2999
3000        queue_for_each_hw_ctx(q, hctx, i) {
3001                if (shared) {
3002                        hctx->flags |= BLK_MQ_F_TAG_QUEUE_SHARED;
3003                } else {
3004                        blk_mq_tag_idle(hctx);
3005                        hctx->flags &= ~BLK_MQ_F_TAG_QUEUE_SHARED;
3006                }
3007        }
3008}
3009
3010static void blk_mq_update_tag_set_shared(struct blk_mq_tag_set *set,
3011                                         bool shared)
3012{
3013        struct request_queue *q;
3014
3015        lockdep_assert_held(&set->tag_list_lock);
3016
3017        list_for_each_entry(q, &set->tag_list, tag_set_list) {
3018                blk_mq_freeze_queue(q);
3019                queue_set_hctx_shared(q, shared);
3020                blk_mq_unfreeze_queue(q);
3021        }
3022}
3023
3024static void blk_mq_del_queue_tag_set(struct request_queue *q)
3025{
3026        struct blk_mq_tag_set *set = q->tag_set;
3027
3028        mutex_lock(&set->tag_list_lock);
3029        list_del(&q->tag_set_list);
3030        if (list_is_singular(&set->tag_list)) {
3031                /* just transitioned to unshared */
3032                set->flags &= ~BLK_MQ_F_TAG_QUEUE_SHARED;
3033                /* update existing queue */
3034                blk_mq_update_tag_set_shared(set, false);
3035        }
3036        mutex_unlock(&set->tag_list_lock);
3037        INIT_LIST_HEAD(&q->tag_set_list);
3038}
3039
3040static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
3041                                     struct request_queue *q)
3042{
3043        mutex_lock(&set->tag_list_lock);
3044
3045        /*
3046         * Check to see if we're transitioning to shared (from 1 to 2 queues).
3047         */
3048        if (!list_empty(&set->tag_list) &&
3049            !(set->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) {
3050                set->flags |= BLK_MQ_F_TAG_QUEUE_SHARED;
3051                /* update existing queue */
3052                blk_mq_update_tag_set_shared(set, true);
3053        }
3054        if (set->flags & BLK_MQ_F_TAG_QUEUE_SHARED)
3055                queue_set_hctx_shared(q, true);
3056        list_add_tail(&q->tag_set_list, &set->tag_list);
3057
3058        mutex_unlock(&set->tag_list_lock);
3059}
3060
3061/* All allocations will be freed in release handler of q->mq_kobj */
3062static int blk_mq_alloc_ctxs(struct request_queue *q)
3063{
3064        struct blk_mq_ctxs *ctxs;
3065        int cpu;
3066
3067        ctxs = kzalloc(sizeof(*ctxs), GFP_KERNEL);
3068        if (!ctxs)
3069                return -ENOMEM;
3070
3071        ctxs->queue_ctx = alloc_percpu(struct blk_mq_ctx);
3072        if (!ctxs->queue_ctx)
3073                goto fail;
3074
3075        for_each_possible_cpu(cpu) {
3076                struct blk_mq_ctx *ctx = per_cpu_ptr(ctxs->queue_ctx, cpu);
3077                ctx->ctxs = ctxs;
3078        }
3079
3080        q->mq_kobj = &ctxs->kobj;
3081        q->queue_ctx = ctxs->queue_ctx;
3082
3083        return 0;
3084 fail:
3085        kfree(ctxs);
3086        return -ENOMEM;
3087}
3088
3089/*
3090 * It is the actual release handler for mq, but we do it from
3091 * request queue's release handler for avoiding use-after-free
3092 * and headache because q->mq_kobj shouldn't have been introduced,
3093 * but we can't group ctx/kctx kobj without it.
3094 */
3095void blk_mq_release(struct request_queue *q)
3096{
3097        struct blk_mq_hw_ctx *hctx, *next;
3098        int i;
3099
3100        queue_for_each_hw_ctx(q, hctx, i)
3101                WARN_ON_ONCE(hctx && list_empty(&hctx->hctx_list));
3102
3103        /* all hctx are in .unused_hctx_list now */
3104        list_for_each_entry_safe(hctx, next, &q->unused_hctx_list, hctx_list) {
3105                list_del_init(&hctx->hctx_list);
3106                kobject_put(&hctx->kobj);
3107        }
3108
3109        kfree(q->queue_hw_ctx);
3110
3111        /*
3112         * release .mq_kobj and sw queue's kobject now because
3113         * both share lifetime with request queue.
3114         */
3115        blk_mq_sysfs_deinit(q);
3116}
3117
3118static struct request_queue *blk_mq_init_queue_data(struct blk_mq_tag_set *set,
3119                void *queuedata)
3120{
3121        struct request_queue *q;
3122        int ret;
3123
3124        q = blk_alloc_queue(set->numa_node);
3125        if (!q)
3126                return ERR_PTR(-ENOMEM);
3127        q->queuedata = queuedata;
3128        ret = blk_mq_init_allocated_queue(set, q);
3129        if (ret) {
3130                blk_cleanup_queue(q);
3131                return ERR_PTR(ret);
3132        }
3133        return q;
3134}
3135
3136struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
3137{
3138        return blk_mq_init_queue_data(set, NULL);
3139}
3140EXPORT_SYMBOL(blk_mq_init_queue);
3141
3142struct gendisk *__blk_mq_alloc_disk(struct blk_mq_tag_set *set, void *queuedata,
3143                struct lock_class_key *lkclass)
3144{
3145        struct request_queue *q;
3146        struct gendisk *disk;
3147
3148        q = blk_mq_init_queue_data(set, queuedata);
3149        if (IS_ERR(q))
3150                return ERR_CAST(q);
3151
3152        disk = __alloc_disk_node(q, set->numa_node, lkclass);
3153        if (!disk) {
3154                blk_cleanup_queue(q);
3155                return ERR_PTR(-ENOMEM);
3156        }
3157        return disk;
3158}
3159EXPORT_SYMBOL(__blk_mq_alloc_disk);
3160
3161static struct blk_mq_hw_ctx *blk_mq_alloc_and_init_hctx(
3162                struct blk_mq_tag_set *set, struct request_queue *q,
3163                int hctx_idx, int node)
3164{
3165        struct blk_mq_hw_ctx *hctx = NULL, *tmp;
3166
3167        /* reuse dead hctx first */
3168        spin_lock(&q->unused_hctx_lock);
3169        list_for_each_entry(tmp, &q->unused_hctx_list, hctx_list) {
3170                if (tmp->numa_node == node) {
3171                        hctx = tmp;
3172                        break;
3173                }
3174        }
3175        if (hctx)
3176                list_del_init(&hctx->hctx_list);
3177        spin_unlock(&q->unused_hctx_lock);
3178
3179        if (!hctx)
3180                hctx = blk_mq_alloc_hctx(q, set, node);
3181        if (!hctx)
3182                goto fail;
3183
3184        if (blk_mq_init_hctx(q, set, hctx, hctx_idx))
3185                goto free_hctx;
3186
3187        return hctx;
3188
3189 free_hctx:
3190        kobject_put(&hctx->kobj);
3191 fail:
3192        return NULL;
3193}
3194
3195static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
3196                                                struct request_queue *q)
3197{
3198        int i, j, end;
3199        struct blk_mq_hw_ctx **hctxs = q->queue_hw_ctx;
3200
3201        if (q->nr_hw_queues < set->nr_hw_queues) {
3202                struct blk_mq_hw_ctx **new_hctxs;
3203
3204                new_hctxs = kcalloc_node(set->nr_hw_queues,
3205                                       sizeof(*new_hctxs), GFP_KERNEL,
3206                                       set->numa_node);
3207                if (!new_hctxs)
3208                        return;
3209                if (hctxs)
3210                        memcpy(new_hctxs, hctxs, q->nr_hw_queues *
3211                               sizeof(*hctxs));
3212                q->queue_hw_ctx = new_hctxs;
3213                kfree(hctxs);
3214                hctxs = new_hctxs;
3215        }
3216
3217        /* protect against switching io scheduler  */
3218        mutex_lock(&q->sysfs_lock);
3219        for (i = 0; i < set->nr_hw_queues; i++) {
3220                int node;
3221                struct blk_mq_hw_ctx *hctx;
3222
3223                node = blk_mq_hw_queue_to_node(&set->map[HCTX_TYPE_DEFAULT], i);
3224                /*
3225                 * If the hw queue has been mapped to another numa node,
3226                 * we need to realloc the hctx. If allocation fails, fallback
3227                 * to use the previous one.
3228                 */
3229                if (hctxs[i] && (hctxs[i]->numa_node == node))
3230                        continue;
3231
3232                hctx = blk_mq_alloc_and_init_hctx(set, q, i, node);
3233                if (hctx) {
3234                        if (hctxs[i])
3235                                blk_mq_exit_hctx(q, set, hctxs[i], i);
3236                        hctxs[i] = hctx;
3237                } else {
3238                        if (hctxs[i])
3239                                pr_warn("Allocate new hctx on node %d fails,\
3240                                                fallback to previous one on node %d\n",
3241                                                node, hctxs[i]->numa_node);
3242                        else
3243                                break;
3244                }
3245        }
3246        /*
3247         * Increasing nr_hw_queues fails. Free the newly allocated
3248         * hctxs and keep the previous q->nr_hw_queues.
3249         */
3250        if (i != set->nr_hw_queues) {
3251                j = q->nr_hw_queues;
3252                end = i;
3253        } else {
3254                j = i;
3255                end = q->nr_hw_queues;
3256                q->nr_hw_queues = set->nr_hw_queues;
3257        }
3258
3259        for (; j < end; j++) {
3260                struct blk_mq_hw_ctx *hctx = hctxs[j];
3261
3262                if (hctx) {
3263                        if (hctx->tags)
3264                                blk_mq_free_map_and_requests(set, j);
3265                        blk_mq_exit_hctx(q, set, hctx, j);
3266                        hctxs[j] = NULL;
3267                }
3268        }
3269        mutex_unlock(&q->sysfs_lock);
3270}
3271
3272int blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
3273                struct request_queue *q)
3274{
3275        /* mark the queue as mq asap */
3276        q->mq_ops = set->ops;
3277
3278        q->poll_cb = blk_stat_alloc_callback(blk_mq_poll_stats_fn,
3279                                             blk_mq_poll_stats_bkt,
3280                                             BLK_MQ_POLL_STATS_BKTS, q);
3281        if (!q->poll_cb)
3282                goto err_exit;
3283
3284        if (blk_mq_alloc_ctxs(q))
3285                goto err_poll;
3286
3287        /* init q->mq_kobj and sw queues' kobjects */
3288        blk_mq_sysfs_init(q);
3289
3290        INIT_LIST_HEAD(&q->unused_hctx_list);
3291        spin_lock_init(&q->unused_hctx_lock);
3292
3293        blk_mq_realloc_hw_ctxs(set, q);
3294        if (!q->nr_hw_queues)
3295                goto err_hctxs;
3296
3297        INIT_WORK(&q->timeout_work, blk_mq_timeout_work);
3298        blk_queue_rq_timeout(q, set->timeout ? set->timeout : 30 * HZ);
3299
3300        q->tag_set = set;
3301
3302        q->queue_flags |= QUEUE_FLAG_MQ_DEFAULT;
3303        if (set->nr_maps > HCTX_TYPE_POLL &&
3304            set->map[HCTX_TYPE_POLL].nr_queues)
3305                blk_queue_flag_set(QUEUE_FLAG_POLL, q);
3306
3307        INIT_DELAYED_WORK(&q->requeue_work, blk_mq_requeue_work);
3308        INIT_LIST_HEAD(&q->requeue_list);
3309        spin_lock_init(&q->requeue_lock);
3310
3311        q->nr_requests = set->queue_depth;
3312
3313        /*
3314         * Default to classic polling
3315         */
3316        q->poll_nsec = BLK_MQ_POLL_CLASSIC;
3317
3318        blk_mq_init_cpu_queues(q, set->nr_hw_queues);
3319        blk_mq_add_queue_tag_set(set, q);
3320        blk_mq_map_swqueue(q);
3321        return 0;
3322
3323err_hctxs:
3324        kfree(q->queue_hw_ctx);
3325        q->nr_hw_queues = 0;
3326        blk_mq_sysfs_deinit(q);
3327err_poll:
3328        blk_stat_free_callback(q->poll_cb);
3329        q->poll_cb = NULL;
3330err_exit:
3331        q->mq_ops = NULL;
3332        return -ENOMEM;
3333}
3334EXPORT_SYMBOL(blk_mq_init_allocated_queue);
3335
3336/* tags can _not_ be used after returning from blk_mq_exit_queue */
3337void blk_mq_exit_queue(struct request_queue *q)
3338{
3339        struct blk_mq_tag_set *set = q->tag_set;
3340
3341        /* Checks hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED. */
3342        blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);
3343        /* May clear BLK_MQ_F_TAG_QUEUE_SHARED in hctx->flags. */
3344        blk_mq_del_queue_tag_set(q);
3345}
3346
3347static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
3348{
3349        int i;
3350
3351        for (i = 0; i < set->nr_hw_queues; i++) {
3352                if (!__blk_mq_alloc_map_and_request(set, i))
3353                        goto out_unwind;
3354                cond_resched();
3355        }
3356
3357        return 0;
3358
3359out_unwind:
3360        while (--i >= 0)
3361                blk_mq_free_map_and_requests(set, i);
3362
3363        return -ENOMEM;
3364}
3365
3366/*
3367 * Allocate the request maps associated with this tag_set. Note that this
3368 * may reduce the depth asked for, if memory is tight. set->queue_depth
3369 * will be updated to reflect the allocated depth.
3370 */
3371static int blk_mq_alloc_map_and_requests(struct blk_mq_tag_set *set)
3372{
3373        unsigned int depth;
3374        int err;
3375
3376        depth = set->queue_depth;
3377        do {
3378                err = __blk_mq_alloc_rq_maps(set);
3379                if (!err)
3380                        break;
3381
3382                set->queue_depth >>= 1;
3383                if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN) {
3384                        err = -ENOMEM;
3385                        break;
3386                }
3387        } while (set->queue_depth);
3388
3389        if (!set->queue_depth || err) {
3390                pr_err("blk-mq: failed to allocate request map\n");
3391                return -ENOMEM;
3392        }
3393
3394        if (depth != set->queue_depth)
3395                pr_info("blk-mq: reduced tag depth (%u -> %u)\n",
3396                                                depth, set->queue_depth);
3397
3398        return 0;
3399}
3400
3401static int blk_mq_update_queue_map(struct blk_mq_tag_set *set)
3402{
3403        /*
3404         * blk_mq_map_queues() and multiple .map_queues() implementations
3405         * expect that set->map[HCTX_TYPE_DEFAULT].nr_queues is set to the
3406         * number of hardware queues.
3407         */
3408        if (set->nr_maps == 1)
3409                set->map[HCTX_TYPE_DEFAULT].nr_queues = set->nr_hw_queues;
3410
3411        if (set->ops->map_queues && !is_kdump_kernel()) {
3412                int i;
3413
3414                /*
3415                 * transport .map_queues is usually done in the following
3416                 * way:
3417                 *
3418                 * for (queue = 0; queue < set->nr_hw_queues; queue++) {
3419                 *      mask = get_cpu_mask(queue)
3420                 *      for_each_cpu(cpu, mask)
3421                 *              set->map[x].mq_map[cpu] = queue;
3422                 * }
3423                 *
3424                 * When we need to remap, the table has to be cleared for
3425                 * killing stale mapping since one CPU may not be mapped
3426                 * to any hw queue.
3427                 */
3428                for (i = 0; i < set->nr_maps; i++)
3429                        blk_mq_clear_mq_map(&set->map[i]);
3430
3431                return set->ops->map_queues(set);
3432        } else {
3433                BUG_ON(set->nr_maps > 1);
3434                return blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
3435        }
3436}
3437
3438static int blk_mq_realloc_tag_set_tags(struct blk_mq_tag_set *set,
3439                                  int cur_nr_hw_queues, int new_nr_hw_queues)
3440{
3441        struct blk_mq_tags **new_tags;
3442
3443        if (cur_nr_hw_queues >= new_nr_hw_queues)
3444                return 0;
3445
3446        new_tags = kcalloc_node(new_nr_hw_queues, sizeof(struct blk_mq_tags *),
3447                                GFP_KERNEL, set->numa_node);
3448        if (!new_tags)
3449                return -ENOMEM;
3450
3451        if (set->tags)
3452                memcpy(new_tags, set->tags, cur_nr_hw_queues *
3453                       sizeof(*set->tags));
3454        kfree(set->tags);
3455        set->tags = new_tags;
3456        set->nr_hw_queues = new_nr_hw_queues;
3457
3458        return 0;
3459}
3460
3461static int blk_mq_alloc_tag_set_tags(struct blk_mq_tag_set *set,
3462                                int new_nr_hw_queues)
3463{
3464        return blk_mq_realloc_tag_set_tags(set, 0, new_nr_hw_queues);
3465}
3466
3467/*
3468 * Alloc a tag set to be associated with one or more request queues.
3469 * May fail with EINVAL for various error conditions. May adjust the
3470 * requested depth down, if it's too large. In that case, the set
3471 * value will be stored in set->queue_depth.
3472 */
3473int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
3474{
3475        int i, ret;
3476
3477        BUILD_BUG_ON(BLK_MQ_MAX_DEPTH > 1 << BLK_MQ_UNIQUE_TAG_BITS);
3478
3479        if (!set->nr_hw_queues)
3480                return -EINVAL;
3481        if (!set->queue_depth)
3482                return -EINVAL;
3483        if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN)
3484                return -EINVAL;
3485
3486        if (!set->ops->queue_rq)
3487                return -EINVAL;
3488
3489        if (!set->ops->get_budget ^ !set->ops->put_budget)
3490                return -EINVAL;
3491
3492        if (set->queue_depth > BLK_MQ_MAX_DEPTH) {
3493                pr_info("blk-mq: reduced tag depth to %u\n",
3494                        BLK_MQ_MAX_DEPTH);
3495                set->queue_depth = BLK_MQ_MAX_DEPTH;
3496        }
3497
3498        if (!set->nr_maps)
3499                set->nr_maps = 1;
3500        else if (set->nr_maps > HCTX_MAX_TYPES)
3501                return -EINVAL;
3502
3503        /*
3504         * If a crashdump is active, then we are potentially in a very
3505         * memory constrained environment. Limit us to 1 queue and
3506         * 64 tags to prevent using too much memory.
3507         */
3508        if (is_kdump_kernel()) {
3509                set->nr_hw_queues = 1;
3510                set->nr_maps = 1;
3511                set->queue_depth = min(64U, set->queue_depth);
3512        }
3513        /*
3514         * There is no use for more h/w queues than cpus if we just have
3515         * a single map
3516         */
3517        if (set->nr_maps == 1 && set->nr_hw_queues > nr_cpu_ids)
3518                set->nr_hw_queues = nr_cpu_ids;
3519
3520        if (blk_mq_alloc_tag_set_tags(set, set->nr_hw_queues) < 0)
3521                return -ENOMEM;
3522
3523        ret = -ENOMEM;
3524        for (i = 0; i < set->nr_maps; i++) {
3525                set->map[i].mq_map = kcalloc_node(nr_cpu_ids,
3526                                                  sizeof(set->map[i].mq_map[0]),
3527                                                  GFP_KERNEL, set->numa_node);
3528                if (!set->map[i].mq_map)
3529                        goto out_free_mq_map;
3530                set->map[i].nr_queues = is_kdump_kernel() ? 1 : set->nr_hw_queues;
3531        }
3532
3533        ret = blk_mq_update_queue_map(set);
3534        if (ret)
3535                goto out_free_mq_map;
3536
3537        ret = blk_mq_alloc_map_and_requests(set);
3538        if (ret)
3539                goto out_free_mq_map;
3540
3541        if (blk_mq_is_sbitmap_shared(set->flags)) {
3542                atomic_set(&set->active_queues_shared_sbitmap, 0);
3543
3544                if (blk_mq_init_shared_sbitmap(set)) {
3545                        ret = -ENOMEM;
3546                        goto out_free_mq_rq_maps;
3547                }
3548        }
3549
3550        mutex_init(&set->tag_list_lock);
3551        INIT_LIST_HEAD(&set->tag_list);
3552
3553        return 0;
3554
3555out_free_mq_rq_maps:
3556        for (i = 0; i < set->nr_hw_queues; i++)
3557                blk_mq_free_map_and_requests(set, i);
3558out_free_mq_map:
3559        for (i = 0; i < set->nr_maps; i++) {
3560                kfree(set->map[i].mq_map);
3561                set->map[i].mq_map = NULL;
3562        }
3563        kfree(set->tags);
3564        set->tags = NULL;
3565        return ret;
3566}
3567EXPORT_SYMBOL(blk_mq_alloc_tag_set);
3568
3569/* allocate and initialize a tagset for a simple single-queue device */
3570int blk_mq_alloc_sq_tag_set(struct blk_mq_tag_set *set,
3571                const struct blk_mq_ops *ops, unsigned int queue_depth,
3572                unsigned int set_flags)
3573{
3574        memset(set, 0, sizeof(*set));
3575        set->ops = ops;
3576        set->nr_hw_queues = 1;
3577        set->nr_maps = 1;
3578        set->queue_depth = queue_depth;
3579        set->numa_node = NUMA_NO_NODE;
3580        set->flags = set_flags;
3581        return blk_mq_alloc_tag_set(set);
3582}
3583EXPORT_SYMBOL_GPL(blk_mq_alloc_sq_tag_set);
3584
3585void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
3586{
3587        int i, j;
3588
3589        for (i = 0; i < set->nr_hw_queues; i++)
3590                blk_mq_free_map_and_requests(set, i);
3591
3592        if (blk_mq_is_sbitmap_shared(set->flags))
3593                blk_mq_exit_shared_sbitmap(set);
3594
3595        for (j = 0; j < set->nr_maps; j++) {
3596                kfree(set->map[j].mq_map);
3597                set->map[j].mq_map = NULL;
3598        }
3599
3600        kfree(set->tags);
3601        set->tags = NULL;
3602}
3603EXPORT_SYMBOL(blk_mq_free_tag_set);
3604
3605int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
3606{
3607        struct blk_mq_tag_set *set = q->tag_set;
3608        struct blk_mq_hw_ctx *hctx;
3609        int i, ret;
3610
3611        if (!set)
3612                return -EINVAL;
3613
3614        if (q->nr_requests == nr)
3615                return 0;
3616
3617        blk_mq_freeze_queue(q);
3618        blk_mq_quiesce_queue(q);
3619
3620        ret = 0;
3621        queue_for_each_hw_ctx(q, hctx, i) {
3622                if (!hctx->tags)
3623                        continue;
3624                /*
3625                 * If we're using an MQ scheduler, just update the scheduler
3626                 * queue depth. This is similar to what the old code would do.
3627                 */
3628                if (!hctx->sched_tags) {
3629                        ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
3630                                                        false);
3631                        if (!ret && blk_mq_is_sbitmap_shared(set->flags))
3632                                blk_mq_tag_resize_shared_sbitmap(set, nr);
3633                } else {
3634                        ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
3635                                                        nr, true);
3636                        if (blk_mq_is_sbitmap_shared(set->flags)) {
3637                                hctx->sched_tags->bitmap_tags =
3638                                        &q->sched_bitmap_tags;
3639                                hctx->sched_tags->breserved_tags =
3640                                        &q->sched_breserved_tags;
3641                        }
3642                }
3643                if (ret)
3644                        break;
3645                if (q->elevator && q->elevator->type->ops.depth_updated)
3646                        q->elevator->type->ops.depth_updated(hctx);
3647        }
3648        if (!ret) {
3649                q->nr_requests = nr;
3650                if (q->elevator && blk_mq_is_sbitmap_shared(set->flags))
3651                        sbitmap_queue_resize(&q->sched_bitmap_tags,
3652                                             nr - set->reserved_tags);
3653        }
3654
3655        blk_mq_unquiesce_queue(q);
3656        blk_mq_unfreeze_queue(q);
3657
3658        return ret;
3659}
3660
3661/*
3662 * request_queue and elevator_type pair.
3663 * It is just used by __blk_mq_update_nr_hw_queues to cache
3664 * the elevator_type associated with a request_queue.
3665 */
3666struct blk_mq_qe_pair {
3667        struct list_head node;
3668        struct request_queue *q;
3669        struct elevator_type *type;
3670};
3671
3672/*
3673 * Cache the elevator_type in qe pair list and switch the
3674 * io scheduler to 'none'
3675 */
3676static bool blk_mq_elv_switch_none(struct list_head *head,
3677                struct request_queue *q)
3678{
3679        struct blk_mq_qe_pair *qe;
3680
3681        if (!q->elevator)
3682                return true;
3683
3684        qe = kmalloc(sizeof(*qe), GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY);
3685        if (!qe)
3686                return false;
3687
3688        INIT_LIST_HEAD(&qe->node);
3689        qe->q = q;
3690        qe->type = q->elevator->type;
3691        list_add(&qe->node, head);
3692
3693        mutex_lock(&q->sysfs_lock);
3694        /*
3695         * After elevator_switch_mq, the previous elevator_queue will be
3696         * released by elevator_release. The reference of the io scheduler
3697         * module get by elevator_get will also be put. So we need to get
3698         * a reference of the io scheduler module here to prevent it to be
3699         * removed.
3700         */
3701        __module_get(qe->type->elevator_owner);
3702        elevator_switch_mq(q, NULL);
3703        mutex_unlock(&q->sysfs_lock);
3704
3705        return true;
3706}
3707
3708static void blk_mq_elv_switch_back(struct list_head *head,
3709                struct request_queue *q)
3710{
3711        struct blk_mq_qe_pair *qe;
3712        struct elevator_type *t = NULL;
3713
3714        list_for_each_entry(qe, head, node)
3715                if (qe->q == q) {
3716                        t = qe->type;
3717                        break;
3718                }
3719
3720        if (!t)
3721                return;
3722
3723        list_del(&qe->node);
3724        kfree(qe);
3725
3726        mutex_lock(&q->sysfs_lock);
3727        elevator_switch_mq(q, t);
3728        mutex_unlock(&q->sysfs_lock);
3729}
3730
3731static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
3732                                                        int nr_hw_queues)
3733{
3734        struct request_queue *q;
3735        LIST_HEAD(head);
3736        int prev_nr_hw_queues;
3737
3738        lockdep_assert_held(&set->tag_list_lock);
3739
3740        if (set->nr_maps == 1 && nr_hw_queues > nr_cpu_ids)
3741                nr_hw_queues = nr_cpu_ids;
3742        if (nr_hw_queues < 1)
3743                return;
3744        if (set->nr_maps == 1 && nr_hw_queues == set->nr_hw_queues)
3745                return;
3746
3747        list_for_each_entry(q, &set->tag_list, tag_set_list)
3748                blk_mq_freeze_queue(q);
3749        /*
3750         * Switch IO scheduler to 'none', cleaning up the data associated
3751         * with the previous scheduler. We will switch back once we are done
3752         * updating the new sw to hw queue mappings.
3753         */
3754        list_for_each_entry(q, &set->tag_list, tag_set_list)
3755                if (!blk_mq_elv_switch_none(&head, q))
3756                        goto switch_back;
3757
3758        list_for_each_entry(q, &set->tag_list, tag_set_list) {
3759                blk_mq_debugfs_unregister_hctxs(q);
3760                blk_mq_sysfs_unregister(q);
3761        }
3762
3763        prev_nr_hw_queues = set->nr_hw_queues;
3764        if (blk_mq_realloc_tag_set_tags(set, set->nr_hw_queues, nr_hw_queues) <
3765            0)
3766                goto reregister;
3767
3768        set->nr_hw_queues = nr_hw_queues;
3769fallback:
3770        blk_mq_update_queue_map(set);
3771        list_for_each_entry(q, &set->tag_list, tag_set_list) {
3772                blk_mq_realloc_hw_ctxs(set, q);
3773                if (q->nr_hw_queues != set->nr_hw_queues) {
3774                        pr_warn("Increasing nr_hw_queues to %d fails, fallback to %d\n",
3775                                        nr_hw_queues, prev_nr_hw_queues);
3776                        set->nr_hw_queues = prev_nr_hw_queues;
3777                        blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
3778                        goto fallback;
3779                }
3780                blk_mq_map_swqueue(q);
3781        }
3782
3783reregister:
3784        list_for_each_entry(q, &set->tag_list, tag_set_list) {
3785                blk_mq_sysfs_register(q);
3786                blk_mq_debugfs_register_hctxs(q);
3787        }
3788
3789switch_back:
3790        list_for_each_entry(q, &set->tag_list, tag_set_list)
3791                blk_mq_elv_switch_back(&head, q);
3792
3793        list_for_each_entry(q, &set->tag_list, tag_set_list)
3794                blk_mq_unfreeze_queue(q);
3795}
3796
3797void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
3798{
3799        mutex_lock(&set->tag_list_lock);
3800        __blk_mq_update_nr_hw_queues(set, nr_hw_queues);
3801        mutex_unlock(&set->tag_list_lock);
3802}
3803EXPORT_SYMBOL_GPL(blk_mq_update_nr_hw_queues);
3804
3805/* Enable polling stats and return whether they were already enabled. */
3806static bool blk_poll_stats_enable(struct request_queue *q)
3807{
3808        if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags) ||
3809            blk_queue_flag_test_and_set(QUEUE_FLAG_POLL_STATS, q))
3810                return true;
3811        blk_stat_add_callback(q, q->poll_cb);
3812        return false;
3813}
3814
3815static void blk_mq_poll_stats_start(struct request_queue *q)
3816{
3817        /*
3818         * We don't arm the callback if polling stats are not enabled or the
3819         * callback is already active.
3820         */
3821        if (!test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags) ||
3822            blk_stat_is_active(q->poll_cb))
3823                return;
3824
3825        blk_stat_activate_msecs(q->poll_cb, 100);
3826}
3827
3828static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb)
3829{
3830        struct request_queue *q = cb->data;
3831        int bucket;
3832
3833        for (bucket = 0; bucket < BLK_MQ_POLL_STATS_BKTS; bucket++) {
3834                if (cb->stat[bucket].nr_samples)
3835                        q->poll_stat[bucket] = cb->stat[bucket];
3836        }
3837}
3838
3839static unsigned long blk_mq_poll_nsecs(struct request_queue *q,
3840                                       struct request *rq)
3841{
3842        unsigned long ret = 0;
3843        int bucket;
3844
3845        /*
3846         * If stats collection isn't on, don't sleep but turn it on for
3847         * future users
3848         */
3849        if (!blk_poll_stats_enable(q))
3850                return 0;
3851
3852        /*
3853         * As an optimistic guess, use half of the mean service time
3854         * for this type of request. We can (and should) make this smarter.
3855         * For instance, if the completion latencies are tight, we can
3856         * get closer than just half the mean. This is especially
3857         * important on devices where the completion latencies are longer
3858         * than ~10 usec. We do use the stats for the relevant IO size
3859         * if available which does lead to better estimates.
3860         */
3861        bucket = blk_mq_poll_stats_bkt(rq);
3862        if (bucket < 0)
3863                return ret;
3864
3865        if (q->poll_stat[bucket].nr_samples)
3866                ret = (q->poll_stat[bucket].mean + 1) / 2;
3867
3868        return ret;
3869}
3870
3871static bool blk_mq_poll_hybrid_sleep(struct request_queue *q,
3872                                     struct request *rq)
3873{
3874        struct hrtimer_sleeper hs;
3875        enum hrtimer_mode mode;
3876        unsigned int nsecs;
3877        ktime_t kt;
3878
3879        if (rq->rq_flags & RQF_MQ_POLL_SLEPT)
3880                return false;
3881
3882        /*
3883         * If we get here, hybrid polling is enabled. Hence poll_nsec can be:
3884         *
3885         *  0:  use half of prev avg
3886         * >0:  use this specific value
3887         */
3888        if (q->poll_nsec > 0)
3889                nsecs = q->poll_nsec;
3890        else
3891                nsecs = blk_mq_poll_nsecs(q, rq);
3892
3893        if (!nsecs)
3894                return false;
3895
3896        rq->rq_flags |= RQF_MQ_POLL_SLEPT;
3897
3898        /*
3899         * This will be replaced with the stats tracking code, using
3900         * 'avg_completion_time / 2' as the pre-sleep target.
3901         */
3902        kt = nsecs;
3903
3904        mode = HRTIMER_MODE_REL;
3905        hrtimer_init_sleeper_on_stack(&hs, CLOCK_MONOTONIC, mode);
3906        hrtimer_set_expires(&hs.timer, kt);
3907
3908        do {
3909                if (blk_mq_rq_state(rq) == MQ_RQ_COMPLETE)
3910                        break;
3911                set_current_state(TASK_UNINTERRUPTIBLE);
3912                hrtimer_sleeper_start_expires(&hs, mode);
3913                if (hs.task)
3914                        io_schedule();
3915                hrtimer_cancel(&hs.timer);
3916                mode = HRTIMER_MODE_ABS;
3917        } while (hs.task && !signal_pending(current));
3918
3919        __set_current_state(TASK_RUNNING);
3920        destroy_hrtimer_on_stack(&hs.timer);
3921        return true;
3922}
3923
3924static bool blk_mq_poll_hybrid(struct request_queue *q,
3925                               struct blk_mq_hw_ctx *hctx, blk_qc_t cookie)
3926{
3927        struct request *rq;
3928
3929        if (q->poll_nsec == BLK_MQ_POLL_CLASSIC)
3930                return false;
3931
3932        if (!blk_qc_t_is_internal(cookie))
3933                rq = blk_mq_tag_to_rq(hctx->tags, blk_qc_t_to_tag(cookie));
3934        else {
3935                rq = blk_mq_tag_to_rq(hctx->sched_tags, blk_qc_t_to_tag(cookie));
3936                /*
3937                 * With scheduling, if the request has completed, we'll
3938                 * get a NULL return here, as we clear the sched tag when
3939                 * that happens. The request still remains valid, like always,
3940                 * so we should be safe with just the NULL check.
3941                 */
3942                if (!rq)
3943                        return false;
3944        }
3945
3946        return blk_mq_poll_hybrid_sleep(q, rq);
3947}
3948
3949/**
3950 * blk_poll - poll for IO completions
3951 * @q:  the queue
3952 * @cookie: cookie passed back at IO submission time
3953 * @spin: whether to spin for completions
3954 *
3955 * Description:
3956 *    Poll for completions on the passed in queue. Returns number of
3957 *    completed entries found. If @spin is true, then blk_poll will continue
3958 *    looping until at least one completion is found, unless the task is
3959 *    otherwise marked running (or we need to reschedule).
3960 */
3961int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin)
3962{
3963        struct blk_mq_hw_ctx *hctx;
3964        unsigned int state;
3965
3966        if (!blk_qc_t_valid(cookie) ||
3967            !test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
3968                return 0;
3969
3970        if (current->plug)
3971                blk_flush_plug_list(current->plug, false);
3972
3973        hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)];
3974
3975        /*
3976         * If we sleep, have the caller restart the poll loop to reset
3977         * the state. Like for the other success return cases, the
3978         * caller is responsible for checking if the IO completed. If
3979         * the IO isn't complete, we'll get called again and will go
3980         * straight to the busy poll loop. If specified not to spin,
3981         * we also should not sleep.
3982         */
3983        if (spin && blk_mq_poll_hybrid(q, hctx, cookie))
3984                return 1;
3985
3986        hctx->poll_considered++;
3987
3988        state = get_current_state();
3989        do {
3990                int ret;
3991
3992                hctx->poll_invoked++;
3993
3994                ret = q->mq_ops->poll(hctx);
3995                if (ret > 0) {
3996                        hctx->poll_success++;
3997                        __set_current_state(TASK_RUNNING);
3998                        return ret;
3999                }
4000
4001                if (signal_pending_state(state, current))
4002                        __set_current_state(TASK_RUNNING);
4003
4004                if (task_is_running(current))
4005                        return 1;
4006                if (ret < 0 || !spin)
4007                        break;
4008                cpu_relax();
4009        } while (!need_resched());
4010
4011        __set_current_state(TASK_RUNNING);
4012        return 0;
4013}
4014EXPORT_SYMBOL_GPL(blk_poll);
4015
4016unsigned int blk_mq_rq_cpu(struct request *rq)
4017{
4018        return rq->mq_ctx->cpu;
4019}
4020EXPORT_SYMBOL(blk_mq_rq_cpu);
4021
4022static int __init blk_mq_init(void)
4023{
4024        int i;
4025
4026        for_each_possible_cpu(i)
4027                init_llist_head(&per_cpu(blk_cpu_done, i));
4028        open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
4029
4030        cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD,
4031                                  "block/softirq:dead", NULL,
4032                                  blk_softirq_cpu_dead);
4033        cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL,
4034                                blk_mq_hctx_notify_dead);
4035        cpuhp_setup_state_multi(CPUHP_AP_BLK_MQ_ONLINE, "block/mq:online",
4036                                blk_mq_hctx_notify_online,
4037                                blk_mq_hctx_notify_offline);
4038        return 0;
4039}
4040subsys_initcall(blk_mq_init);
4041