blk-mq.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Block multiqueue core code
 *
 * Copyright (C) 2013-2014 Jens Axboe
 * Copyright (C) 2013-2014 Christoph Hellwig
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/backing-dev.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/kmemleak.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <linux/smp.h>
#include <linux/llist.h>
#include <linux/list_sort.h>
#include <linux/cpu.h>
#include <linux/cache.h>
#include <linux/sched/sysctl.h>
#include <linux/sched/topology.h>
#include <linux/sched/signal.h>
#include <linux/delay.h>
#include <linux/crash_dump.h>
#include <linux/prefetch.h>
#include <linux/blk-crypto.h>

#include <trace/events/block.h>

#include <linux/blk-mq.h>
#include <linux/t10-pi.h>
#include "blk.h"
#include "blk-mq.h"
#include "blk-mq-debugfs.h"
#include "blk-mq-tag.h"
#include "blk-pm.h"
#include "blk-stat.h"
#include "blk-mq-sched.h"
#include "blk-rq-qos.h"

static DEFINE_PER_CPU(struct list_head, blk_cpu_done);

static void blk_mq_poll_stats_start(struct request_queue *q);
static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb);

static int blk_mq_poll_stats_bkt(const struct request *rq)
{
	int ddir, sectors, bucket;

	ddir = rq_data_dir(rq);
	sectors = blk_rq_stats_sectors(rq);

	bucket = ddir + 2 * ilog2(sectors);

	if (bucket < 0)
		return -1;
	else if (bucket >= BLK_MQ_POLL_STATS_BKTS)
		return ddir + BLK_MQ_POLL_STATS_BKTS - 2;

	return bucket;
}

/*
 * Check if any of the ctx, dispatch list or elevator
 * have pending work in this hardware queue.
 */
static bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx)
{
	return !list_empty_careful(&hctx->dispatch) ||
		sbitmap_any_bit_set(&hctx->ctx_map) ||
			blk_mq_sched_has_work(hctx);
}

/*
 * Mark this ctx as having pending work in this hardware queue
 */
static void blk_mq_hctx_mark_pending(struct blk_mq_hw_ctx *hctx,
				     struct blk_mq_ctx *ctx)
{
	const int bit = ctx->index_hw[hctx->type];

	if (!sbitmap_test_bit(&hctx->ctx_map, bit))
		sbitmap_set_bit(&hctx->ctx_map, bit);
}

static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
				      struct blk_mq_ctx *ctx)
{
	const int bit = ctx->index_hw[hctx->type];

	sbitmap_clear_bit(&hctx->ctx_map, bit);
}

struct mq_inflight {
	struct hd_struct *part;
	unsigned int inflight[2];
};

static bool blk_mq_check_inflight(struct blk_mq_hw_ctx *hctx,
				  struct request *rq, void *priv,
				  bool reserved)
{
	struct mq_inflight *mi = priv;

	if (rq->part == mi->part)
		mi->inflight[rq_data_dir(rq)]++;

	return true;
}

unsigned int blk_mq_in_flight(struct request_queue *q, struct hd_struct *part)
{
	struct mq_inflight mi = { .part = part };

	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);

	return mi.inflight[0] + mi.inflight[1];
}

void blk_mq_in_flight_rw(struct request_queue *q, struct hd_struct *part,
			 unsigned int inflight[2])
{
	struct mq_inflight mi = { .part = part };

	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
	inflight[0] = mi.inflight[0];
	inflight[1] = mi.inflight[1];
}

void blk_freeze_queue_start(struct request_queue *q)
{
	mutex_lock(&q->mq_freeze_lock);
	if (++q->mq_freeze_depth == 1) {
		percpu_ref_kill(&q->q_usage_counter);
		mutex_unlock(&q->mq_freeze_lock);
		if (queue_is_mq(q))
			blk_mq_run_hw_queues(q, false);
	} else {
		mutex_unlock(&q->mq_freeze_lock);
	}
}
EXPORT_SYMBOL_GPL(blk_freeze_queue_start);

void blk_mq_freeze_queue_wait(struct request_queue *q)
{
	wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->q_usage_counter));
}
EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait);

int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
				     unsigned long timeout)
{
	return wait_event_timeout(q->mq_freeze_wq,
					percpu_ref_is_zero(&q->q_usage_counter),
					timeout);
}
EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait_timeout);

/*
 * Guarantee no request is in use, so we can change any data structure of
 * the queue afterward.
 */
void blk_freeze_queue(struct request_queue *q)
{
	/*
	 * In the !blk_mq case we are only calling this to kill the
	 * q_usage_counter, otherwise this increases the freeze depth
	 * and waits for it to return to zero.  For this reason there is
	 * no blk_unfreeze_queue(), and blk_freeze_queue() is not
	 * exported to drivers as the only user for unfreeze is blk_mq.
	 */
	blk_freeze_queue_start(q);
	blk_mq_freeze_queue_wait(q);
}

void blk_mq_freeze_queue(struct request_queue *q)
{
	/*
	 * ...just an alias to keep freeze and unfreeze actions balanced
	 * in the blk_mq_* namespace
	 */
	blk_freeze_queue(q);
}
EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);

void blk_mq_unfreeze_queue(struct request_queue *q)
{
	mutex_lock(&q->mq_freeze_lock);
	q->mq_freeze_depth--;
	WARN_ON_ONCE(q->mq_freeze_depth < 0);
	if (!q->mq_freeze_depth) {
		percpu_ref_resurrect(&q->q_usage_counter);
		wake_up_all(&q->mq_freeze_wq);
	}
	mutex_unlock(&q->mq_freeze_lock);
}
EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);

/*
 * FIXME: replace the scsi_internal_device_*block_nowait() calls in the
 * mpt3sas driver such that this function can be removed.
 */
void blk_mq_quiesce_queue_nowait(struct request_queue *q)
{
	blk_queue_flag_set(QUEUE_FLAG_QUIESCED, q);
}
EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);

/**
 * blk_mq_quiesce_queue() - wait until all ongoing dispatches have finished
 * @q: request queue.
 *
 * Note: this function does not prevent that the struct request end_io()
 * callback function is invoked. Once this function is returned, we make
 * sure no dispatch can happen until the queue is unquiesced via
 * blk_mq_unquiesce_queue().
 */
void blk_mq_quiesce_queue(struct request_queue *q)
{
	struct blk_mq_hw_ctx *hctx;
	unsigned int i;
	bool rcu = false;

	blk_mq_quiesce_queue_nowait(q);

	queue_for_each_hw_ctx(q, hctx, i) {
		if (hctx->flags & BLK_MQ_F_BLOCKING)
			synchronize_srcu(hctx->srcu);
		else
			rcu = true;
	}
	if (rcu)
		synchronize_rcu();
}
EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue);

/*
 * blk_mq_unquiesce_queue() - counterpart of blk_mq_quiesce_queue()
 * @q: request queue.
 *
 * This function recovers queue into the state before quiescing
 * which is done by blk_mq_quiesce_queue.
 */
void blk_mq_unquiesce_queue(struct request_queue *q)
{
	blk_queue_flag_clear(QUEUE_FLAG_QUIESCED, q);

	/* dispatch requests which are inserted during quiescing */
	blk_mq_run_hw_queues(q, true);
}
EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue);

void blk_mq_wake_waiters(struct request_queue *q)
{
	struct blk_mq_hw_ctx *hctx;
	unsigned int i;

	queue_for_each_hw_ctx(q, hctx, i)
		if (blk_mq_hw_queue_mapped(hctx))
			blk_mq_tag_wakeup_all(hctx->tags, true);
}

/*
 * Only need start/end time stamping if we have iostat or
 * blk stats enabled, or using an IO scheduler.
 */
static inline bool blk_mq_need_time_stamp(struct request *rq)
{
	return (rq->rq_flags & (RQF_IO_STAT | RQF_STATS)) || rq->q->elevator;
}

static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
		unsigned int tag, u64 alloc_time_ns)
{
	struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
	struct request *rq = tags->static_rqs[tag];
	req_flags_t rq_flags = 0;

	if (data->flags & BLK_MQ_REQ_INTERNAL) {
		rq->tag = BLK_MQ_NO_TAG;
		rq->internal_tag = tag;
	} else {
		if (data->hctx->flags & BLK_MQ_F_TAG_SHARED) {
			rq_flags = RQF_MQ_INFLIGHT;
			atomic_inc(&data->hctx->nr_active);
		}
		rq->tag = tag;
		rq->internal_tag = BLK_MQ_NO_TAG;
		data->hctx->tags->rqs[rq->tag] = rq;
	}

	/* csd/requeue_work/fifo_time is initialized before use */
	rq->q = data->q;
	rq->mq_ctx = data->ctx;
	rq->mq_hctx = data->hctx;
	rq->rq_flags = rq_flags;
	rq->cmd_flags = data->cmd_flags;
	if (data->flags & BLK_MQ_REQ_PREEMPT)
		rq->rq_flags |= RQF_PREEMPT;
	if (blk_queue_io_stat(data->q))
		rq->rq_flags |= RQF_IO_STAT;
	INIT_LIST_HEAD(&rq->queuelist);
	INIT_HLIST_NODE(&rq->hash);
	RB_CLEAR_NODE(&rq->rb_node);
	rq->rq_disk = NULL;
	rq->part = NULL;
#ifdef CONFIG_BLK_RQ_ALLOC_TIME
	rq->alloc_time_ns = alloc_time_ns;
#endif
	if (blk_mq_need_time_stamp(rq))
		rq->start_time_ns = ktime_get_ns();
	else
		rq->start_time_ns = 0;
	rq->io_start_time_ns = 0;
	rq->stats_sectors = 0;
	rq->nr_phys_segments = 0;
#if defined(CONFIG_BLK_DEV_INTEGRITY)
	rq->nr_integrity_segments = 0;
#endif
	blk_crypto_rq_set_defaults(rq);
	/* tag was already set */
	WRITE_ONCE(rq->deadline, 0);

	rq->timeout = 0;

	rq->end_io = NULL;
	rq->end_io_data = NULL;

	data->ctx->rq_dispatched[op_is_sync(data->cmd_flags)]++;
	refcount_set(&rq->ref, 1);

	if (!op_is_flush(data->cmd_flags)) {
		struct elevator_queue *e = data->q->elevator;

		rq->elv.icq = NULL;
		if (e && e->type->ops.prepare_request) {
			if (e->type->icq_cache)
				blk_mq_sched_assign_ioc(rq);

			e->type->ops.prepare_request(rq);
			rq->rq_flags |= RQF_ELVPRIV;
		}
	}

	data->hctx->queued++;
	return rq;
}

static struct request *__blk_mq_alloc_request(struct blk_mq_alloc_data *data)
{
	struct request_queue *q = data->q;
	struct elevator_queue *e = q->elevator;
	u64 alloc_time_ns = 0;
	unsigned int tag;

	/* alloc_time includes depth and tag waits */
	if (blk_queue_rq_alloc_time(q))
		alloc_time_ns = ktime_get_ns();

	if (data->cmd_flags & REQ_NOWAIT)
		data->flags |= BLK_MQ_REQ_NOWAIT;

	if (e) {
		data->flags |= BLK_MQ_REQ_INTERNAL;

		/*
		 * Flush requests are special and go directly to the
		 * dispatch list. Don't include reserved tags in the
		 * limiting, as it isn't useful.
		 */
		if (!op_is_flush(data->cmd_flags) &&
		    e->type->ops.limit_depth &&
		    !(data->flags & BLK_MQ_REQ_RESERVED))
			e->type->ops.limit_depth(data->cmd_flags, data);
	}

retry:
	data->ctx = blk_mq_get_ctx(q);
	data->hctx = blk_mq_map_queue(q, data->cmd_flags, data->ctx);
	if (!(data->flags & BLK_MQ_REQ_INTERNAL))
		blk_mq_tag_busy(data->hctx);

	/*
	 * Waiting allocations only fail because of an inactive hctx.  In that
	 * case just retry the hctx assignment and tag allocation as CPU hotplug
	 * should have migrated us to an online CPU by now.
	 */
	tag = blk_mq_get_tag(data);
	if (tag == BLK_MQ_NO_TAG) {
		if (data->flags & BLK_MQ_REQ_NOWAIT)
			return NULL;

		/*
		 * Give up the CPU and sleep for a random short time to ensure
		 * that thread using a realtime scheduling class are migrated
		 * off the the CPU, and thus off the hctx that is going away.
		 */
		msleep(3);
		goto retry;
	}
	return blk_mq_rq_ctx_init(data, tag, alloc_time_ns);
}

struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op,
		blk_mq_req_flags_t flags)
{
	struct blk_mq_alloc_data data = {
		.q		= q,
		.flags		= flags,
		.cmd_flags	= op,
	};
	struct request *rq;
	int ret;

	ret = blk_queue_enter(q, flags);
	if (ret)
		return ERR_PTR(ret);

	rq = __blk_mq_alloc_request(&data);
	if (!rq)
		goto out_queue_exit;
	rq->__data_len = 0;
	rq->__sector = (sector_t) -1;
	rq->bio = rq->biotail = NULL;
	return rq;
out_queue_exit:
	blk_queue_exit(q);
	return ERR_PTR(-EWOULDBLOCK);
}
EXPORT_SYMBOL(blk_mq_alloc_request);

struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
	unsigned int op, blk_mq_req_flags_t flags, unsigned int hctx_idx)
{
	struct blk_mq_alloc_data data = {
		.q		= q,
		.flags		= flags,
		.cmd_flags	= op,
	};
	u64 alloc_time_ns = 0;
	unsigned int cpu;
	unsigned int tag;
	int ret;

	/* alloc_time includes depth and tag waits */
	if (blk_queue_rq_alloc_time(q))
		alloc_time_ns = ktime_get_ns();

	/*
	 * If the tag allocator sleeps we could get an allocation for a
	 * different hardware context.  No need to complicate the low level
	 * allocator for this for the rare use case of a command tied to
	 * a specific queue.
	 */
	if (WARN_ON_ONCE(!(flags & (BLK_MQ_REQ_NOWAIT | BLK_MQ_REQ_RESERVED))))
		return ERR_PTR(-EINVAL);

	if (hctx_idx >= q->nr_hw_queues)
		return ERR_PTR(-EIO);

	ret = blk_queue_enter(q, flags);
	if (ret)
		return ERR_PTR(ret);

	/*
	 * Check if the hardware context is actually mapped to anything.
	 * If not tell the caller that it should skip this queue.
	 */
	ret = -EXDEV;
	data.hctx = q->queue_hw_ctx[hctx_idx];
	if (!blk_mq_hw_queue_mapped(data.hctx))
		goto out_queue_exit;
	cpu = cpumask_first_and(data.hctx->cpumask, cpu_online_mask);
	data.ctx = __blk_mq_get_ctx(q, cpu);

	if (q->elevator)
		data.flags |= BLK_MQ_REQ_INTERNAL;
	else
		blk_mq_tag_busy(data.hctx);

	ret = -EWOULDBLOCK;
	tag = blk_mq_get_tag(&data);
	if (tag == BLK_MQ_NO_TAG)
		goto out_queue_exit;
	return blk_mq_rq_ctx_init(&data, tag, alloc_time_ns);

out_queue_exit:
	blk_queue_exit(q);
	return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(blk_mq_alloc_request_hctx);

static void __blk_mq_free_request(struct request *rq)
{
	struct request_queue *q = rq->q;
	struct blk_mq_ctx *ctx = rq->mq_ctx;
	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
	const int sched_tag = rq->internal_tag;

	blk_crypto_free_request(rq);
	blk_pm_mark_last_busy(rq);
	rq->mq_hctx = NULL;
	if (rq->tag != BLK_MQ_NO_TAG)
		blk_mq_put_tag(hctx->tags, ctx, rq->tag);
	if (sched_tag != BLK_MQ_NO_TAG)
		blk_mq_put_tag(hctx->sched_tags, ctx, sched_tag);
	blk_mq_sched_restart(hctx);
	blk_queue_exit(q);
}

void blk_mq_free_request(struct request *rq)
{
	struct request_queue *q = rq->q;
	struct elevator_queue *e = q->elevator;
	struct blk_mq_ctx *ctx = rq->mq_ctx;
	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;

	if (rq->rq_flags & RQF_ELVPRIV) {
		if (e && e->type->ops.finish_request)
			e->type->ops.finish_request(rq);
		if (rq->elv.icq) {
			put_io_context(rq->elv.icq->ioc);
			rq->elv.icq = NULL;
		}
	}

	ctx->rq_completed[rq_is_sync(rq)]++;
	if (rq->rq_flags & RQF_MQ_INFLIGHT)
		atomic_dec(&hctx->nr_active);

	if (unlikely(laptop_mode && !blk_rq_is_passthrough(rq)))
		laptop_io_completion(q->backing_dev_info);

	rq_qos_done(q, rq);

	WRITE_ONCE(rq->state, MQ_RQ_IDLE);
	if (refcount_dec_and_test(&rq->ref))
		__blk_mq_free_request(rq);
}
EXPORT_SYMBOL_GPL(blk_mq_free_request);

inline void __blk_mq_end_request(struct request *rq, blk_status_t error)
{
	u64 now = 0;

	if (blk_mq_need_time_stamp(rq))
		now = ktime_get_ns();

	if (rq->rq_flags & RQF_STATS) {
		blk_mq_poll_stats_start(rq->q);
		blk_stat_add(rq, now);
	}

	if (rq->internal_tag != BLK_MQ_NO_TAG)
		blk_mq_sched_completed_request(rq, now);

	blk_account_io_done(rq, now);

	if (rq->end_io) {
		rq_qos_done(rq->q, rq);
		rq->end_io(rq, error);
	} else {
		blk_mq_free_request(rq);
	}
}
EXPORT_SYMBOL(__blk_mq_end_request);

void blk_mq_end_request(struct request *rq, blk_status_t error)
{
	if (blk_update_request(rq, error, blk_rq_bytes(rq)))
		BUG();
	__blk_mq_end_request(rq, error);
}
EXPORT_SYMBOL(blk_mq_end_request);

/*
 * Softirq action handler - move entries to local list and loop over them
 * while passing them to the queue registered handler.
 */
static __latent_entropy void blk_done_softirq(struct softirq_action *h)
{
	struct list_head *cpu_list, local_list;

	local_irq_disable();
	cpu_list = this_cpu_ptr(&blk_cpu_done);
	list_replace_init(cpu_list, &local_list);
	local_irq_enable();

	while (!list_empty(&local_list)) {
		struct request *rq;

		rq = list_entry(local_list.next, struct request, ipi_list);
		list_del_init(&rq->ipi_list);
		rq->q->mq_ops->complete(rq);
	}
}

#ifdef CONFIG_SMP
static void trigger_softirq(void *data)
{
	struct request *rq = data;
	struct list_head *list;

	list = this_cpu_ptr(&blk_cpu_done);
	list_add_tail(&rq->ipi_list, list);

	if (list->next == &rq->ipi_list)
		raise_softirq_irqoff(BLOCK_SOFTIRQ);
}

/*
 * Setup and invoke a run of 'trigger_softirq' on the given cpu.
 */
static int raise_blk_irq(int cpu, struct request *rq)
{
	if (cpu_online(cpu)) {
		call_single_data_t *data = &rq->csd;

		data->func = trigger_softirq;
		data->info = rq;
		data->flags = 0;

		smp_call_function_single_async(cpu, data);
		return 0;
	}

	return 1;
}
#else /* CONFIG_SMP */
static int raise_blk_irq(int cpu, struct request *rq)
{
	return 1;
}
#endif

static int blk_softirq_cpu_dead(unsigned int cpu)
{
	/*
	 * If a CPU goes away, splice its entries to the current CPU
	 * and trigger a run of the softirq
	 */
	local_irq_disable();
	list_splice_init(&per_cpu(blk_cpu_done, cpu),
			 this_cpu_ptr(&blk_cpu_done));
	raise_softirq_irqoff(BLOCK_SOFTIRQ);
	local_irq_enable();

	return 0;
}

static void __blk_complete_request(struct request *req)
{
	struct request_queue *q = req->q;
	int cpu, ccpu = req->mq_ctx->cpu;
	unsigned long flags;
	bool shared = false;

	BUG_ON(!q->mq_ops->complete);

	local_irq_save(flags);
	cpu = smp_processor_id();

	/*
	 * Select completion CPU
	 */
	if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) && ccpu != -1) {
		if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
			shared = cpus_share_cache(cpu, ccpu);
	} else
		ccpu = cpu;

	/*
	 * If current CPU and requested CPU share a cache, run the softirq on
	 * the current CPU. One might concern this is just like
	 * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
	 * running in interrupt handler, and currently I/O controller doesn't
	 * support multiple interrupts, so current CPU is unique actually. This
	 * avoids IPI sending from current CPU to the first CPU of a group.
	 */
	if (ccpu == cpu || shared) {
		struct list_head *list;
do_local:
		list = this_cpu_ptr(&blk_cpu_done);
		list_add_tail(&req->ipi_list, list);

		/*
		 * if the list only contains our just added request,
		 * signal a raise of the softirq. If there are already
		 * entries there, someone already raised the irq but it
		 * hasn't run yet.
		 */
		if (list->next == &req->ipi_list)
			raise_softirq_irqoff(BLOCK_SOFTIRQ);
	} else if (raise_blk_irq(ccpu, req))
		goto do_local;

	local_irq_restore(flags);
}

static void __blk_mq_complete_request_remote(void *data)
{
	struct request *rq = data;
	struct request_queue *q = rq->q;

	q->mq_ops->complete(rq);
}

/**
 * blk_mq_force_complete_rq() - Force complete the request, bypassing any error
 * 				injection that could drop the completion.
 * @rq: Request to be force completed
 *
 * Drivers should use blk_mq_complete_request() to complete requests in their
 * normal IO path. For timeout error recovery, drivers may call this forced
 * completion routine after they've reclaimed timed out requests to bypass
 * potentially subsequent fake timeouts.
 */
void blk_mq_force_complete_rq(struct request *rq)
{
	struct blk_mq_ctx *ctx = rq->mq_ctx;
	struct request_queue *q = rq->q;
	bool shared = false;
	int cpu;

	WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);
	/*
	 * Most of single queue controllers, there is only one irq vector
	 * for handling IO completion, and the only irq's affinity is set
	 * as all possible CPUs. On most of ARCHs, this affinity means the
	 * irq is handled on one specific CPU.
	 *
	 * So complete IO reqeust in softirq context in case of single queue
	 * for not degrading IO performance by irqsoff latency.
	 */
	if (q->nr_hw_queues == 1) {
		__blk_complete_request(rq);
		return;
	}

	/*
	 * For a polled request, always complete locallly, it's pointless
	 * to redirect the completion.
	 */
	if ((rq->cmd_flags & REQ_HIPRI) ||
	    !test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags)) {
		q->mq_ops->complete(rq);
		return;
	}

	cpu = get_cpu();
	if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
		shared = cpus_share_cache(cpu, ctx->cpu);

	if (cpu != ctx->cpu && !shared && cpu_online(ctx->cpu)) {
		rq->csd.func = __blk_mq_complete_request_remote;
		rq->csd.info = rq;
		rq->csd.flags = 0;
		smp_call_function_single_async(ctx->cpu, &rq->csd);
	} else {
		q->mq_ops->complete(rq);
	}
	put_cpu();
}
EXPORT_SYMBOL_GPL(blk_mq_force_complete_rq);

static void hctx_unlock(struct blk_mq_hw_ctx *hctx, int srcu_idx)
	__releases(hctx->srcu)
{
	if (!(hctx->flags & BLK_MQ_F_BLOCKING))
		rcu_read_unlock();
	else
		srcu_read_unlock(hctx->srcu, srcu_idx);
}

static void hctx_lock(struct blk_mq_hw_ctx *hctx, int *srcu_idx)
	__acquires(hctx->srcu)
{
	if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
		/* shut up gcc false positive */
		*srcu_idx = 0;
		rcu_read_lock();
	} else
		*srcu_idx = srcu_read_lock(hctx->srcu);
}

/**
 * blk_mq_complete_request - end I/O on a request
 * @rq:		the request being processed
 *
 * Description:
 *	Ends all I/O on a request. It does not handle partial completions.
 *	The actual completion happens out-of-order, through a IPI handler.
 **/
bool blk_mq_complete_request(struct request *rq)
{
	if (unlikely(blk_should_fake_timeout(rq->q)))
		return false;
	blk_mq_force_complete_rq(rq);
	return true;
}
EXPORT_SYMBOL(blk_mq_complete_request);

/**
 * blk_mq_start_request - Start processing a request
 * @rq: Pointer to request to be started
 *
 * Function used by device drivers to notify the block layer that a request
 * is going to be processed now, so blk layer can do proper initializations
 * such as starting the timeout timer.
 */
void blk_mq_start_request(struct request *rq)
{
	struct request_queue *q = rq->q;

	trace_block_rq_issue(q, rq);

	if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags)) {
		rq->io_start_time_ns = ktime_get_ns();
		rq->stats_sectors = blk_rq_sectors(rq);
		rq->rq_flags |= RQF_STATS;
		rq_qos_issue(q, rq);
	}

	WARN_ON_ONCE(blk_mq_rq_state(rq) != MQ_RQ_IDLE);

	blk_add_timer(rq);
	WRITE_ONCE(rq->state, MQ_RQ_IN_FLIGHT);

#ifdef CONFIG_BLK_DEV_INTEGRITY
	if (blk_integrity_rq(rq) && req_op(rq) == REQ_OP_WRITE)
		q->integrity.profile->prepare_fn(rq);
#endif
}
EXPORT_SYMBOL(blk_mq_start_request);

static void __blk_mq_requeue_request(struct request *rq)
{
	struct request_queue *q = rq->q;

	blk_mq_put_driver_tag(rq);

	trace_block_rq_requeue(q, rq);
	rq_qos_requeue(q, rq);

	if (blk_mq_request_started(rq)) {
		WRITE_ONCE(rq->state, MQ_RQ_IDLE);
		rq->rq_flags &= ~RQF_TIMED_OUT;
	}
}

void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list)
{
	__blk_mq_requeue_request(rq);

	/* this request will be re-inserted to io scheduler queue */
	blk_mq_sched_requeue_request(rq);

	BUG_ON(!list_empty(&rq->queuelist));
	blk_mq_add_to_requeue_list(rq, true, kick_requeue_list);
}
EXPORT_SYMBOL(blk_mq_requeue_request);

static void blk_mq_requeue_work(struct work_struct *work)
{
	struct request_queue *q =
		container_of(work, struct request_queue, requeue_work.work);
	LIST_HEAD(rq_list);
	struct request *rq, *next;

	spin_lock_irq(&q->requeue_lock);
	list_splice_init(&q->requeue_list, &rq_list);
	spin_unlock_irq(&q->requeue_lock);

	list_for_each_entry_safe(rq, next, &rq_list, queuelist) {
		if (!(rq->rq_flags & (RQF_SOFTBARRIER | RQF_DONTPREP)))
			continue;

		rq->rq_flags &= ~RQF_SOFTBARRIER;
		list_del_init(&rq->queuelist);
		/*
		 * If RQF_DONTPREP, rq has contained some driver specific
		 * data, so insert it to hctx dispatch list to avoid any
		 * merge.
		 */
		if (rq->rq_flags & RQF_DONTPREP)
			blk_mq_request_bypass_insert(rq, false, false);
		else
			blk_mq_sched_insert_request(rq, true, false, false);
	}

	while (!list_empty(&rq_list)) {
		rq = list_entry(rq_list.next, struct request, queuelist);
		list_del_init(&rq->queuelist);
		blk_mq_sched_insert_request(rq, false, false, false);
	}

	blk_mq_run_hw_queues(q, false);
}

void blk_mq_add_to_requeue_list(struct request *rq, bool at_head,
				bool kick_requeue_list)
{
	struct request_queue *q = rq->q;
	unsigned long flags;

	/*
	 * We abuse this flag that is otherwise used by the I/O scheduler to
	 * request head insertion from the workqueue.
	 */
	BUG_ON(rq->rq_flags & RQF_SOFTBARRIER);

	spin_lock_irqsave(&q->requeue_lock, flags);
	if (at_head) {
		rq->rq_flags |= RQF_SOFTBARRIER;
		list_add(&rq->queuelist, &q->requeue_list);
	} else {
		list_add_tail(&rq->queuelist, &q->requeue_list);
	}
	spin_unlock_irqrestore(&q->requeue_lock, flags);

	if (kick_requeue_list)
		blk_mq_kick_requeue_list(q);
}

void blk_mq_kick_requeue_list(struct request_queue *q)
{
	kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work, 0);
}
EXPORT_SYMBOL(blk_mq_kick_requeue_list);

void blk_mq_delay_kick_requeue_list(struct request_queue *q,
				    unsigned long msecs)
{
	kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work,
				    msecs_to_jiffies(msecs));
}
EXPORT_SYMBOL(blk_mq_delay_kick_requeue_list);

struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
{
	if (tag < tags->nr_tags) {
		prefetch(tags->rqs[tag]);
		return tags->rqs[tag];
	}

	return NULL;
}
EXPORT_SYMBOL(blk_mq_tag_to_rq);

static bool blk_mq_rq_inflight(struct blk_mq_hw_ctx *hctx, struct request *rq,
			       void *priv, bool reserved)
{
	/*
	 * If we find a request that is inflight and the queue matches,
	 * we know the queue is busy. Return false to stop the iteration.
	 */
	if (rq->state == MQ_RQ_IN_FLIGHT && rq->q == hctx->queue) {
		bool *busy = priv;

		*busy = true;
		return false;
	}

	return true;
}

bool blk_mq_queue_inflight(struct request_queue *q)
{
	bool busy = false;

	blk_mq_queue_tag_busy_iter(q, blk_mq_rq_inflight, &busy);
	return busy;
}
EXPORT_SYMBOL_GPL(blk_mq_queue_inflight);

static void blk_mq_rq_timed_out(struct request *req, bool reserved)
{
	req->rq_flags |= RQF_TIMED_OUT;
	if (req->q->mq_ops->timeout) {
		enum blk_eh_timer_return ret;

		ret = req->q->mq_ops->timeout(req, reserved);
		if (ret == BLK_EH_DONE)
			return;
		WARN_ON_ONCE(ret != BLK_EH_RESET_TIMER);
	}

	blk_add_timer(req);
}

static bool blk_mq_req_expired(struct request *rq, unsigned long *next)
{
	unsigned long deadline;

	if (blk_mq_rq_state(rq) != MQ_RQ_IN_FLIGHT)
		return false;
	if (rq->rq_flags & RQF_TIMED_OUT)