block/blk-mq.c

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