Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4981 insertions, 0 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
new file mode 100644
index 000000000..b3f99dda4
--- /dev/null
+++ b/block/blk-mq.c
@@ -0,0 +1,4981 @@
+// 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/blk-integrity.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/interrupt.h>
+#include <linux/llist.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 <linux/part_stat.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"
+#include "blk-ioprio.h"
+
+static DEFINE_PER_CPU(struct llist_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;
+}
+
+#define BLK_QC_T_SHIFT		16
+#define BLK_QC_T_INTERNAL	(1U << 31)
+
+static inline struct blk_mq_hw_ctx *blk_qc_to_hctx(struct request_queue *q,
+		blk_qc_t qc)
+{
+	return xa_load(&q->hctx_table,
+			(qc & ~BLK_QC_T_INTERNAL) >> BLK_QC_T_SHIFT);
+}
+
+static inline struct request *blk_qc_to_rq(struct blk_mq_hw_ctx *hctx,
+		blk_qc_t qc)
+{
+	unsigned int tag = qc & ((1U << BLK_QC_T_SHIFT) - 1);
+
+	if (qc & BLK_QC_T_INTERNAL)
+		return blk_mq_tag_to_rq(hctx->sched_tags, tag);
+	return blk_mq_tag_to_rq(hctx->tags, tag);
+}
+
+static inline blk_qc_t blk_rq_to_qc(struct request *rq)
+{
+	return (rq->mq_hctx->queue_num << BLK_QC_T_SHIFT) |
+		(rq->tag != -1 ?
+		 rq->tag : (rq->internal_tag | BLK_QC_T_INTERNAL));
+}
+
+/*
+ * 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 block_device *part;
+	unsigned int inflight[2];
+};
+
+static bool blk_mq_check_inflight(struct request *rq, void *priv)
+{
+	struct mq_inflight *mi = priv;
+
+	if (rq->part && blk_do_io_stat(rq) &&
+	    (!mi->part->bd_partno || rq->part == mi->part) &&
+	    blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT)
+		mi->inflight[rq_data_dir(rq)]++;
+
+	return true;
+}
+
+unsigned int blk_mq_in_flight(struct request_queue *q,
+		struct block_device *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 block_device *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, bool force_atomic)
+{
+	mutex_lock(&q->mq_freeze_lock);
+	if (force_atomic)
+		q->q_usage_counter.data->force_atomic = true;
+	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);
+}
+
+void blk_mq_unfreeze_queue(struct request_queue *q)
+{
+	__blk_mq_unfreeze_queue(q, false);
+}
+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)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&q->queue_lock, flags);
+	if (!q->quiesce_depth++)
+		blk_queue_flag_set(QUEUE_FLAG_QUIESCED, q);
+	spin_unlock_irqrestore(&q->queue_lock, flags);
+}
+EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
+
+/**
+ * blk_mq_wait_quiesce_done() - wait until in-progress quiesce is done
+ * @q: request queue.
+ *
+ * Note: it is driver's responsibility for making sure that quiesce has
+ * been started.
+ */
+void blk_mq_wait_quiesce_done(struct request_queue *q)
+{
+	if (blk_queue_has_srcu(q))
+		synchronize_srcu(q->srcu);
+	else
+		synchronize_rcu();
+}
+EXPORT_SYMBOL_GPL(blk_mq_wait_quiesce_done);
+
+/**
+ * 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)
+{
+	blk_mq_quiesce_queue_nowait(q);
+	blk_mq_wait_quiesce_done(q);
+}
+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)
+{
+	unsigned long flags;
+	bool run_queue = false;
+
+	spin_lock_irqsave(&q->queue_lock, flags);
+	if (WARN_ON_ONCE(q->quiesce_depth <= 0)) {
+		;
+	} else if (!--q->quiesce_depth) {
+		blk_queue_flag_clear(QUEUE_FLAG_QUIESCED, q);
+		run_queue = true;
+	}
+	spin_unlock_irqrestore(&q->queue_lock, flags);
+
+	/* dispatch requests which are inserted during quiescing */
+	if (run_queue)
+		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 long i;
+
+	queue_for_each_hw_ctx(q, hctx, i)
+		if (blk_mq_hw_queue_mapped(hctx))
+			blk_mq_tag_wakeup_all(hctx->tags, true);
+}
+
+void blk_rq_init(struct request_queue *q, struct request *rq)
+{
+	memset(rq, 0, sizeof(*rq));
+
+	INIT_LIST_HEAD(&rq->queuelist);
+	rq->q = q;
+	rq->__sector = (sector_t) -1;
+	INIT_HLIST_NODE(&rq->hash);
+	RB_CLEAR_NODE(&rq->rb_node);
+	rq->tag = BLK_MQ_NO_TAG;
+	rq->internal_tag = BLK_MQ_NO_TAG;
+	rq->start_time_ns = ktime_get_ns();
+	rq->part = NULL;
+	blk_crypto_rq_set_defaults(rq);
+}
+EXPORT_SYMBOL(blk_rq_init);
+
+static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
+		struct blk_mq_tags *tags, unsigned int tag, u64 alloc_time_ns)
+{
+	struct blk_mq_ctx *ctx = data->ctx;
+	struct blk_mq_hw_ctx *hctx = data->hctx;
+	struct request_queue *q = data->q;
+	struct request *rq = tags->static_rqs[tag];
+
+	rq->q = q;
+	rq->mq_ctx = ctx;
+	rq->mq_hctx = hctx;
+	rq->cmd_flags = data->cmd_flags;
+
+	if (data->flags & BLK_MQ_REQ_PM)
+		data->rq_flags |= RQF_PM;
+	if (blk_queue_io_stat(q))
+		data->rq_flags |= RQF_IO_STAT;
+	rq->rq_flags = data->rq_flags;
+
+	if (!(data->rq_flags & RQF_ELV)) {
+		rq->tag = tag;
+		rq->internal_tag = BLK_MQ_NO_TAG;
+	} else {
+		rq->tag = BLK_MQ_NO_TAG;
+		rq->internal_tag = tag;
+	}
+	rq->timeout = 0;
+
+	if (blk_mq_need_time_stamp(rq))
+		rq->start_time_ns = ktime_get_ns();
+	else
+		rq->start_time_ns = 0;
+	rq->part = NULL;
+#ifdef CONFIG_BLK_RQ_ALLOC_TIME
+	rq->alloc_time_ns = alloc_time_ns;
+#endif
+	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
+	rq->end_io = NULL;
+	rq->end_io_data = NULL;
+
+	blk_crypto_rq_set_defaults(rq);
+	INIT_LIST_HEAD(&rq->queuelist);
+	/* tag was already set */
+	WRITE_ONCE(rq->deadline, 0);
+	req_ref_set(rq, 1);
+
+	if (rq->rq_flags & RQF_ELV) {
+		struct elevator_queue *e = data->q->elevator;
+
+		INIT_HLIST_NODE(&rq->hash);
+		RB_CLEAR_NODE(&rq->rb_node);
+
+		if (!op_is_flush(data->cmd_flags) &&
+		    e->type->ops.prepare_request) {
+			e->type->ops.prepare_request(rq);
+			rq->rq_flags |= RQF_ELVPRIV;
+		}
+	}
+
+	return rq;
+}
+
+static inline struct request *
+__blk_mq_alloc_requests_batch(struct blk_mq_alloc_data *data,
+		u64 alloc_time_ns)
+{
+	unsigned int tag, tag_offset;
+	struct blk_mq_tags *tags;
+	struct request *rq;
+	unsigned long tag_mask;
+	int i, nr = 0;
+
+	tag_mask = blk_mq_get_tags(data, data->nr_tags, &tag_offset);
+	if (unlikely(!tag_mask))
+		return NULL;
+
+	tags = blk_mq_tags_from_data(data);
+	for (i = 0; tag_mask; i++) {
+		if (!(tag_mask & (1UL << i)))
+			continue;
+		tag = tag_offset + i;
+		prefetch(tags->static_rqs[tag]);
+		tag_mask &= ~(1UL << i);
+		rq = blk_mq_rq_ctx_init(data, tags, tag, alloc_time_ns);
+		rq_list_add(data->cached_rq, rq);
+		nr++;
+	}
+	/* caller already holds a reference, add for remainder */
+	percpu_ref_get_many(&data->q->q_usage_counter, nr - 1);
+	data->nr_tags -= nr;
+
+	return rq_list_pop(data->cached_rq);
+}
+
+static struct request *__blk_mq_alloc_requests(struct blk_mq_alloc_data *data)
+{
+	struct request_queue *q = data->q;
+	u64 alloc_time_ns = 0;
+	struct request *rq;
+	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 (q->elevator) {
+		struct elevator_queue *e = q->elevator;
+
+		data->rq_flags |= RQF_ELV;
+
+		/*
+		 * Flush/passthrough 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) &&
+		    !blk_op_is_passthrough(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->rq_flags & RQF_ELV))
+		blk_mq_tag_busy(data->hctx);
+
+	if (data->flags & BLK_MQ_REQ_RESERVED)
+		data->rq_flags |= RQF_RESV;
+
+	/*
+	 * Try batched alloc if we want more than 1 tag.
+	 */
+	if (data->nr_tags > 1) {
+		rq = __blk_mq_alloc_requests_batch(data, alloc_time_ns);
+		if (rq)
+			return rq;
+		data->nr_tags = 1;
+	}
+
+	/*
+	 * 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 CPU, and thus off the hctx that
+		 * is going away.
+		 */
+		msleep(3);
+		goto retry;
+	}
+
+	return blk_mq_rq_ctx_init(data, blk_mq_tags_from_data(data), tag,
+					alloc_time_ns);
+}
+
+static struct request *blk_mq_rq_cache_fill(struct request_queue *q,
+					    struct blk_plug *plug,
+					    blk_opf_t opf,
+					    blk_mq_req_flags_t flags)
+{
+	struct blk_mq_alloc_data data = {
+		.q		= q,
+		.flags		= flags,
+		.cmd_flags	= opf,
+		.nr_tags	= plug->nr_ios,
+		.cached_rq	= &plug->cached_rq,
+	};
+	struct request *rq;
+
+	if (blk_queue_enter(q, flags))
+		return NULL;
+
+	plug->nr_ios = 1;
+
+	rq = __blk_mq_alloc_requests(&data);
+	if (unlikely(!rq))
+		blk_queue_exit(q);
+	return rq;
+}
+
+static struct request *blk_mq_alloc_cached_request(struct request_queue *q,
+						   blk_opf_t opf,
+						   blk_mq_req_flags_t flags)
+{
+	struct blk_plug *plug = current->plug;
+	struct request *rq;
+
+	if (!plug)
+		return NULL;
+	if (rq_list_empty(plug->cached_rq)) {
+		if (plug->nr_ios == 1)
+			return NULL;
+		rq = blk_mq_rq_cache_fill(q, plug, opf, flags);
+		if (rq)
+			goto got_it;
+		return NULL;
+	}
+	rq = rq_list_peek(&plug->cached_rq);
+	if (!rq || rq->q != q)
+		return NULL;
+
+	if (blk_mq_get_hctx_type(opf) != rq->mq_hctx->type)
+		return NULL;
+	if (op_is_flush(rq->cmd_flags) != op_is_flush(opf))
+		return NULL;
+
+	plug->cached_rq = rq_list_next(rq);
+got_it:
+	rq->cmd_flags = opf;
+	INIT_LIST_HEAD(&rq->queuelist);
+	return rq;
+}
+
+struct request *blk_mq_alloc_request(struct request_queue *q, blk_opf_t opf,
+		blk_mq_req_flags_t flags)
+{
+	struct request *rq;
+
+	rq = blk_mq_alloc_cached_request(q, opf, flags);
+	if (!rq) {
+		struct blk_mq_alloc_data data = {
+			.q		= q,
+			.flags		= flags,
+			.cmd_flags	= opf,
+			.nr_tags	= 1,
+		};
+		int ret;
+
+		ret = blk_queue_enter(q, flags);
+		if (ret)
+			return ERR_PTR(ret);
+
+		rq = __blk_mq_alloc_requests(&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,
+	blk_opf_t opf, blk_mq_req_flags_t flags, unsigned int hctx_idx)
+{
+	struct blk_mq_alloc_data data = {
+		.q		= q,
+		.flags		= flags,
+		.cmd_flags	= opf,
+		.nr_tags	= 1,
+	};
+	u64 alloc_time_ns = 0;
+	struct request *rq;
+	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)) ||
+	    WARN_ON_ONCE(!(flags & 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 = xa_load(&q->hctx_table, hctx_idx);
+	if (!blk_mq_hw_queue_mapped(data.hctx))
+		goto out_queue_exit;
+	cpu = cpumask_first_and(data.hctx->cpumask, cpu_online_mask);
+	if (cpu >= nr_cpu_ids)
+		goto out_queue_exit;
+	data.ctx = __blk_mq_get_ctx(q, cpu);
+
+	if (!q->elevator)
+		blk_mq_tag_busy(data.hctx);
+	else
+		data.rq_flags |= RQF_ELV;
+
+	if (flags & BLK_MQ_REQ_RESERVED)
+		data.rq_flags |= RQF_RESV;
+
+	ret = -EWOULDBLOCK;
+	tag = blk_mq_get_tag(&data);
+	if (tag == BLK_MQ_NO_TAG)
+		goto out_queue_exit;
+	rq = blk_mq_rq_ctx_init(&data, blk_mq_tags_from_data(&data), tag,
+					alloc_time_ns);
+	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(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->rq_flags & RQF_MQ_INFLIGHT)
+		__blk_mq_dec_active_requests(hctx);
+
+	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;
+
+	if ((rq->rq_flags & RQF_ELVPRIV) &&
+	    q->elevator->type->ops.finish_request)
+		q->elevator->type->ops.finish_request(rq);
+
+	if (unlikely(laptop_mode && !blk_rq_is_passthrough(rq)))
+		laptop_io_completion(q->disk->bdi);
+
+	rq_qos_done(q, rq);
+
+	WRITE_ONCE(rq->state, MQ_RQ_IDLE);
+	if (req_ref_put_and_test(rq))
+		__blk_mq_free_request(rq);
+}
+EXPORT_SYMBOL_GPL(blk_mq_free_request);
+
+void blk_mq_free_plug_rqs(struct blk_plug *plug)
+{
+	struct request *rq;
+
+	while ((rq = rq_list_pop(&plug->cached_rq)) != NULL)
+		blk_mq_free_request(rq);
+}
+
+void blk_dump_rq_flags(struct request *rq, char *msg)
+{
+	printk(KERN_INFO "%s: dev %s: flags=%llx\n", msg,
+		rq->q->disk ? rq->q->disk->disk_name : "?",
+		(__force unsigned long long) rq->cmd_flags);
+
+	printk(KERN_INFO "  sector %llu, nr/cnr %u/%u\n",
+	       (unsigned long long)blk_rq_pos(rq),
+	       blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
+	printk(KERN_INFO "  bio %p, biotail %p, len %u\n",
+	       rq->bio, rq->biotail, blk_rq_bytes(rq));
+}
+EXPORT_SYMBOL(blk_dump_rq_flags);
+
+static void req_bio_endio(struct request *rq, struct bio *bio,
+			  unsigned int nbytes, blk_status_t error)
+{
+	if (unlikely(error)) {
+		bio->bi_status = error;
+	} else if (req_op(rq) == REQ_OP_ZONE_APPEND) {
+		/*
+		 * Partial zone append completions cannot be supported as the
+		 * BIO fragments may end up not being written sequentially.
+		 */
+		if (bio->bi_iter.bi_size != nbytes)
+			bio->bi_status = BLK_STS_IOERR;
+		else
+			bio->bi_iter.bi_sector = rq->__sector;
+	}
+
+	bio_advance(bio, nbytes);
+
+	if (unlikely(rq->rq_flags & RQF_QUIET))
+		bio_set_flag(bio, BIO_QUIET);
+	/* don't actually finish bio if it's part of flush sequence */
+	if (bio->bi_iter.bi_size == 0 && !(rq->rq_flags & RQF_FLUSH_SEQ))
+		bio_endio(bio);
+}
+
+static void blk_account_io_completion(struct request *req, unsigned int bytes)
+{
+	if (req->part && blk_do_io_stat(req)) {
+		const int sgrp = op_stat_group(req_op(req));
+
+		part_stat_lock();
+		part_stat_add(req->part, sectors[sgrp], bytes >> 9);
+		part_stat_unlock();
+	}
+}
+
+static void blk_print_req_error(struct request *req, blk_status_t status)
+{
+	printk_ratelimited(KERN_ERR
+		"%s error, dev %s, sector %llu op 0x%x:(%s) flags 0x%x "
+		"phys_seg %u prio class %u\n",
+		blk_status_to_str(status),
+		req->q->disk ? req->q->disk->disk_name : "?",
+		blk_rq_pos(req), (__force u32)req_op(req),
+		blk_op_str(req_op(req)),
+		(__force u32)(req->cmd_flags & ~REQ_OP_MASK),
+		req->nr_phys_segments,
+		IOPRIO_PRIO_CLASS(req->ioprio));
+}
+
+/*
+ * Fully end IO on a request. Does not support partial completions, or
+ * errors.
+ */
+static void blk_complete_request(struct request *req)
+{
+	const bool is_flush = (req->rq_flags & RQF_FLUSH_SEQ) != 0;
+	int total_bytes = blk_rq_bytes(req);
+	struct bio *bio = req->bio;
+
+	trace_block_rq_complete(req, BLK_STS_OK, total_bytes);
+
+	if (!bio)
+		return;
+
+#ifdef CONFIG_BLK_DEV_INTEGRITY
+	if (blk_integrity_rq(req) && req_op(req) == REQ_OP_READ)
+		req->q->integrity.profile->complete_fn(req, total_bytes);
+#endif
+
+	/*
+	 * Upper layers may call blk_crypto_evict_key() anytime after the last
+	 * bio_endio().  Therefore, the keyslot must be released before that.
+	 */
+	blk_crypto_rq_put_keyslot(req);
+
+	blk_account_io_completion(req, total_bytes);
+
+	do {
+		struct bio *next = bio->bi_next;
+
+		/* Completion has already been traced */
+		bio_clear_flag(bio, BIO_TRACE_COMPLETION);
+
+		if (req_op(req) == REQ_OP_ZONE_APPEND)
+			bio->bi_iter.bi_sector = req->__sector;
+
+		if (!is_flush)
+			bio_endio(bio);
+		bio = next;
+	} while (bio);
+
+	/*
+	 * Reset counters so that the request stacking driver
+	 * can find how many bytes remain in the request
+	 * later.
+	 */
+	if (!req->end_io) {
+		req->bio = NULL;
+		req->__data_len = 0;
+	}
+}
+
+/**
+ * blk_update_request - Complete multiple bytes without completing the request
+ * @req:      the request being processed
+ * @error:    block status code
+ * @nr_bytes: number of bytes to complete for @req
+ *
+ * Description:
+ *     Ends I/O on a number of bytes attached to @req, but doesn't complete
+ *     the request structure even if @req doesn't have leftover.
+ *     If @req has leftover, sets it up for the next range of segments.
+ *
+ *     Passing the result of blk_rq_bytes() as @nr_bytes guarantees
+ *     %false return from this function.
+ *
+ * Note:
+ *	The RQF_SPECIAL_PAYLOAD flag is ignored on purpose in this function
+ *      except in the consistency check at the end of this function.
+ *
+ * Return:
+ *     %false - this request doesn't have any more data
+ *     %true  - this request has more data
+ **/
+bool blk_update_request(struct request *req, blk_status_t error,
+		unsigned int nr_bytes)
+{
+	int total_bytes;
+
+	trace_block_rq_complete(req, error, nr_bytes);
+
+	if (!req->bio)
+		return false;
+
+#ifdef CONFIG_BLK_DEV_INTEGRITY
+	if (blk_integrity_rq(req) && req_op(req) == REQ_OP_READ &&
+	    error == BLK_STS_OK)
+		req->q->integrity.profile->complete_fn(req, nr_bytes);
+#endif
+
+	/*
+	 * Upper layers may call blk_crypto_evict_key() anytime after the last
+	 * bio_endio().  Therefore, the keyslot must be released before that.
+	 */
+	if (blk_crypto_rq_has_keyslot(req) && nr_bytes >= blk_rq_bytes(req))
+		__blk_crypto_rq_put_keyslot(req);
+
+	if (unlikely(error && !blk_rq_is_passthrough(req) &&
+		     !(req->rq_flags & RQF_QUIET)) &&
+		     !test_bit(GD_DEAD, &req->q->disk->state)) {
+		blk_print_req_error(req, error);
+		trace_block_rq_error(req, error, nr_bytes);
+	}
+
+	blk_account_io_completion(req, nr_bytes);
+
+	total_bytes = 0;
+	while (req->bio) {
+		struct bio *bio = req->bio;
+		unsigned bio_bytes = min(bio->bi_iter.bi_size, nr_bytes);
+
+		if (bio_bytes == bio->bi_iter.bi_size)
+			req->bio = bio->bi_next;
+
+		/* Completion has already been traced */
+		bio_clear_flag(bio, BIO_TRACE_COMPLETION);
+		req_bio_endio(req, bio, bio_bytes, error);
+
+		total_bytes += bio_bytes;
+		nr_bytes -= bio_bytes;
+
+		if (!nr_bytes)
+			break;
+	}
+
+	/*
+	 * completely done
+	 */
+	if (!req->bio) {
+		/*
+		 * Reset counters so that the request stacking driver
+		 * can find how many bytes remain in the request
+		 * later.
+		 */
+		req->__data_len = 0;
+		return false;
+	}
+
+	req->__data_len -= total_bytes;
+
+	/* update sector only for requests with clear definition of sector */
+	if (!blk_rq_is_passthrough(req))
+		req->__sector += total_bytes >> 9;
+
+	/* mixed attributes always follow the first bio */
+	if (req->rq_flags & RQF_MIXED_MERGE) {
+		req->cmd_flags &= ~REQ_FAILFAST_MASK;
+		req->cmd_flags |= req->bio->bi_opf & REQ_FAILFAST_MASK;
+	}
+
+	if (!(req->rq_flags & RQF_SPECIAL_PAYLOAD)) {
+		/*
+		 * If total number of sectors is less than the first segment
+		 * size, something has gone terribly wrong.
+		 */
+		if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
+			blk_dump_rq_flags(req, "request botched");
+			req->__data_len = blk_rq_cur_bytes(req);
+		}
+
+		/* recalculate the number of segments */
+		req->nr_phys_segments = blk_recalc_rq_segments(req);
+	}
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(blk_update_request);
+
+static void __blk_account_io_done(struct request *req, u64 now)
+{
+	const int sgrp = op_stat_group(req_op(req));
+
+	part_stat_lock();
+	update_io_ticks(req->part, jiffies, true);
+	part_stat_inc(req->part, ios[sgrp]);
+	part_stat_add(req->part, nsecs[sgrp], now - req->start_time_ns);
+	part_stat_unlock();
+}
+
+static inline void blk_account_io_done(struct request *req, u64 now)
+{
+	/*
+	 * Account IO completion.  flush_rq isn't accounted as a
+	 * normal IO on queueing nor completion.  Accounting the
+	 * containing request is enough.
+	 */
+	if (blk_do_io_stat(req) && req->part &&
+	    !(req->rq_flags & RQF_FLUSH_SEQ))
+		__blk_account_io_done(req, now);
+}
+
+static void __blk_account_io_start(struct request *rq)
+{
+	/*
+	 * All non-passthrough requests are created from a bio with one
+	 * exception: when a flush command that is part of a flush sequence
+	 * generated by the state machine in blk-flush.c is cloned onto the
+	 * lower device by dm-multipath we can get here without a bio.
+	 */
+	if (rq->bio)
+		rq->part = rq->bio->bi_bdev;
+	else
+		rq->part = rq->q->disk->part0;
+
+	part_stat_lock();
+	update_io_ticks(rq->part, jiffies, false);
+	part_stat_unlock();
+}
+
+static inline void blk_account_io_start(struct request *req)
+{
+	if (blk_do_io_stat(req))
+		__blk_account_io_start(req);
+}
+
+static inline void __blk_mq_end_request_acct(struct request *rq, u64 now)
+{
+	if (rq->rq_flags & RQF_STATS) {
+		blk_mq_poll_stats_start(rq->q);
+		blk_stat_add(rq, now);
+	}
+
+	blk_mq_sched_completed_request(rq, now);
+	blk_account_io_done(rq, now);
+}
+
+inline void __blk_mq_end_request(struct request *rq, blk_status_t error)
+{
+	if (blk_mq_need_time_stamp(rq))
+		__blk_mq_end_request_acct(rq, ktime_get_ns());
+
+	if (rq->end_io) {
+		rq_qos_done(rq->q, rq);
+		if (rq->end_io(rq, error) == RQ_END_IO_FREE)
+			blk_mq_free_request(rq);
+	} 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);
+
+#define TAG_COMP_BATCH		32
+
+static inline void blk_mq_flush_tag_batch(struct blk_mq_hw_ctx *hctx,
+					  int *tag_array, int nr_tags)
+{
+	struct request_queue *q = hctx->queue;
+
+	/*
+	 * All requests should have been marked as RQF_MQ_INFLIGHT, so
+	 * update hctx->nr_active in batch
+	 */
+	if (hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)
+		__blk_mq_sub_active_requests(hctx, nr_tags);
+
+	blk_mq_put_tags(hctx->tags, tag_array, nr_tags);
+	percpu_ref_put_many(&q->q_usage_counter, nr_tags);
+}
+
+void blk_mq_end_request_batch(struct io_comp_batch *iob)
+{
+	int tags[TAG_COMP_BATCH], nr_tags = 0;
+	struct blk_mq_hw_ctx *cur_hctx = NULL;
+	struct request *rq;
+	u64 now = 0;
+
+	if (iob->need_ts)
+		now = ktime_get_ns();
+
+	while ((rq = rq_list_pop(&iob->req_list)) != NULL) {
+		prefetch(rq->bio);
+		prefetch(rq->rq_next);
+
+		blk_complete_request(rq);
+		if (iob->need_ts)
+			__blk_mq_end_request_acct(rq, now);
+
+		rq_qos_done(rq->q, rq);
+
+		/*
+		 * If end_io handler returns NONE, then it still has
+		 * ownership of the request.
+		 */
+		if (rq->end_io && rq->end_io(rq, 0) == RQ_END_IO_NONE)
+			continue;
+
+		WRITE_ONCE(rq->state, MQ_RQ_IDLE);
+		if (!req_ref_put_and_test(rq))
+			continue;
+
+		blk_crypto_free_request(rq);
+		blk_pm_mark_last_busy(rq);
+
+		if (nr_tags == TAG_COMP_BATCH || cur_hctx != rq->mq_hctx) {
+			if (cur_hctx)
+				blk_mq_flush_tag_batch(cur_hctx, tags, nr_tags);
+			nr_tags = 0;
+			cur_hctx = rq->mq_hctx;
+		}
+		tags[nr_tags++] = rq->tag;
+	}
+
+	if (nr_tags)
+		blk_mq_flush_tag_batch(cur_hctx, tags, nr_tags);
+}
+EXPORT_SYMBOL_GPL(blk_mq_end_request_batch);
+
+static void blk_complete_reqs(struct llist_head *list)
+{
+	struct llist_node *entry = llist_reverse_order(llist_del_all(list));
+	struct request *rq, *next;
+
+	llist_for_each_entry_safe(rq, next, entry, ipi_list)
+		rq->q->mq_ops->complete(rq);
+}
+
+static __latent_entropy void blk_done_softirq(struct softirq_action *h)
+{
+	blk_complete_reqs(this_cpu_ptr(&blk_cpu_done));
+}
+
+static int blk_softirq_cpu_dead(unsigned int cpu)
+{
+	blk_complete_reqs(&per_cpu(blk_cpu_done, cpu));
+	return 0;
+}
+
+static void __blk_mq_complete_request_remote(void *data)
+{
+	__raise_softirq_irqoff(BLOCK_SOFTIRQ);
+}
+
+static inline bool blk_mq_complete_need_ipi(struct request *rq)
+{
+	int cpu = raw_smp_processor_id();
+
+	if (!IS_ENABLED(CONFIG_SMP) ||
+	    !test_bit(QUEUE_FLAG_SAME_COMP, &rq->q->queue_flags))
+		return false;
+	/*
+	 * With force threaded interrupts enabled, raising softirq from an SMP
+	 * function call will always result in waking the ksoftirqd thread.
+	 * This is probably worse than completing the request on a different
+	 * cache domain.
+	 */
+	if (force_irqthreads())
+		return false;
+
+	/* same CPU or cache domain?  Complete locally */
+	if (cpu == rq->mq_ctx->cpu ||
+	    (!test_bit(QUEUE_FLAG_SAME_FORCE, &rq->q->queue_flags) &&
+	     cpus_share_cache(cpu, rq->mq_ctx->cpu)))
+		return false;
+
+	/* don't try to IPI to an offline CPU */
+	return cpu_online(rq->mq_ctx->cpu);
+}
+
+static void blk_mq_complete_send_ipi(struct request *rq)
+{
+	struct llist_head *list;
+	unsigned int cpu;
+
+	cpu = rq->mq_ctx->cpu;
+	list = &per_cpu(blk_cpu_done, cpu);
+	if (llist_add(&rq->ipi_list, list)) {
+		INIT_CSD(&rq->csd, __blk_mq_complete_request_remote, rq);
+		smp_call_function_single_async(cpu, &rq->csd);
+	}
+}
+
+static void blk_mq_raise_softirq(struct request *rq)
+{
+	struct llist_head *list;
+
+	preempt_disable();
+	list = this_cpu_ptr(&blk_cpu_done);
+	if (llist_add(&rq->ipi_list, list))
+		raise_softirq(BLOCK_SOFTIRQ);
+	preempt_enable();
+}
+
+bool blk_mq_complete_request_remote(struct request *rq)
+{
+	WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);
+
+	/*
+	 * For request which hctx has only one ctx mapping,
+	 * or a polled request, always complete locally,
+	 * it's pointless to redirect the completion.
+	 */
+	if (rq->mq_hctx->nr_ctx == 1 ||
+		rq->cmd_flags & REQ_POLLED)
+		return false;
+
+	if (blk_mq_complete_need_ipi(rq)) {
+		blk_mq_complete_send_ipi(rq);
+		return true;
+	}
+
+	if (rq->q->nr_hw_queues == 1) {
+		blk_mq_raise_softirq(rq);
+		return true;
+	}
+	return false;
+}
+EXPORT_SYMBOL_GPL(blk_mq_complete_request_remote);
+
+/**
+ * blk_mq_complete_request - end I/O on a request
+ * @rq:		the request being processed
+ *
+ * Description:
+ *	Complete a request by scheduling the ->complete_rq operation.
+ **/
+void blk_mq_complete_request(struct request *rq)
+{
+	if (!blk_mq_complete_request_remote(rq))
+		rq->q->mq_ops->complete(rq);
+}
+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(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
+	if (rq->bio && rq->bio->bi_opf & REQ_POLLED)
+	        WRITE_ONCE(rq->bio->bi_cookie, blk_rq_to_qc(rq));
+}
+EXPORT_SYMBOL(blk_mq_start_request);
+
+/*
+ * Allow 2x BLK_MAX_REQUEST_COUNT requests on plug queue for multiple
+ * queues. This is important for md arrays to benefit from merging
+ * requests.
+ */
+static inline unsigned short blk_plug_max_rq_count(struct blk_plug *plug)
+{
+	if (plug->multiple_queues)
+		return BLK_MAX_REQUEST_COUNT * 2;
+	return BLK_MAX_REQUEST_COUNT;
+}
+
+static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
+{
+	struct request *last = rq_list_peek(&plug->mq_list);
+
+	if (!plug->rq_count) {
+		trace_block_plug(rq->q);
+	} else if (plug->rq_count >= blk_plug_max_rq_count(plug) ||
+		   (!blk_queue_nomerges(rq->q) &&
+		    blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
+		blk_mq_flush_plug_list(plug, false);
+		last = NULL;
+		trace_block_plug(rq->q);
+	}
+
+	if (!plug->multiple_queues && last && last->q != rq->q)
+		plug->multiple_queues = true;
+	if (!plug->has_elevator && (rq->rq_flags & RQF_ELV))
+		plug->has_elevator = true;
+	rq->rq_next = NULL;
+	rq_list_add(&plug->mq_list, rq);
+	plug->rq_count++;
+}
+
+/**
+ * blk_execute_rq_nowait - insert a request to I/O scheduler for execution
+ * @rq:		request to insert
+ * @at_head:    insert request at head or tail of queue
+ *
+ * Description:
+ *    Insert a fully prepared request at the back of the I/O scheduler queue
+ *    for execution.  Don't wait for completion.
+ *
+ * Note:
+ *    This function will invoke @done directly if the queue is dead.
+ */
+void blk_execute_rq_nowait(struct request *rq, bool at_head)
+{
+	WARN_ON(irqs_disabled());
+	WARN_ON(!blk_rq_is_passthrough(rq));
+
+	blk_account_io_start(rq);
+
+	/*
+	 * As plugging can be enabled for passthrough requests on a zoned
+	 * device, directly accessing the plug instead of using blk_mq_plug()
+	 * should not have any consequences.
+	 */
+	if (current->plug && !at_head)
+		blk_add_rq_to_plug(current->plug, rq);
+	else
+		blk_mq_sched_insert_request(rq, at_head, true, false);
+}
+EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);
+
+struct blk_rq_wait {
+	struct completion done;
+	blk_status_t ret;
+};
+
+static enum rq_end_io_ret blk_end_sync_rq(struct request *rq, blk_status_t ret)
+{
+	struct blk_rq_wait *wait = rq->end_io_data;
+
+	wait->ret = ret;
+	complete(&wait->done);
+	return RQ_END_IO_NONE;
+}
+
+bool blk_rq_is_poll(struct request *rq)
+{
+	if (!rq->mq_hctx)
+		return false;
+	if (rq->mq_hctx->type != HCTX_TYPE_POLL)
+		return false;
+	return true;
+}
+EXPORT_SYMBOL_GPL(blk_rq_is_poll);
+
+static void blk_rq_poll_completion(struct request *rq, struct completion *wait)
+{
+	do {
+		blk_mq_poll(rq->q, blk_rq_to_qc(rq), NULL, 0);
+		cond_resched();
+	} while (!completion_done(wait));
+}
+
+/**
+ * blk_execute_rq - insert a request into queue for execution
+ * @rq:		request to insert
+ * @at_head:    insert request at head or tail of queue
+ *
+ * Description:
+ *    Insert a fully prepared request at the back of the I/O scheduler queue
+ *    for execution and wait for completion.
+ * Return: The blk_status_t result provided to blk_mq_end_request().
+ */
+blk_status_t blk_execute_rq(struct request *rq, bool at_head)
+{
+	struct blk_rq_wait wait = {
+		.done = COMPLETION_INITIALIZER_ONSTACK(wait.done),
+	};
+
+	WARN_ON(irqs_disabled());
+	WARN_ON(!blk_rq_is_passthrough(rq));
+
+	rq->end_io_data = &wait;
+	rq->end_io = blk_end_sync_rq;
+
+	blk_account_io_start(rq);
+	blk_mq_sched_insert_request(rq, at_head, true, false);
+
+	if (blk_rq_is_poll(rq)) {
+		blk_rq_poll_completion(rq, &wait.done);
+	} else {
+		/*
+		 * Prevent hang_check timer from firing at us during very long
+		 * I/O
+		 */
+		unsigned long hang_check = sysctl_hung_task_timeout_secs;
+
+		if (hang_check)
+			while (!wait_for_completion_io_timeout(&wait.done,
+					hang_check * (HZ/2)))
+				;
+		else
+			wait_for_completion_io(&wait.done);
+	}
+
+	return wait.ret;
+}
+EXPORT_SYMBOL(blk_execute_rq);
+
+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(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);
+
+	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);
+
+static bool blk_is_flush_data_rq(struct request *rq)
+{
+	return (rq->rq_flags & RQF_FLUSH_SEQ) && !is_flush_rq(rq);
+}
+
+static bool blk_mq_rq_inflight(struct request *rq, void *priv)
+{
+	/*
+	 * If we find a request that isn't idle we know the queue is busy
+	 * as it's checked in the iter.
+	 * Return false to stop the iteration.
+	 *
+	 * In case of queue quiesce, if one flush data request is completed,
+	 * don't count it as inflight given the flush sequence is suspended,
+	 * and the original flush data request is invisible to driver, just
+	 * like other pending requests because of quiesce
+	 */
+	if (blk_mq_request_started(rq) && !(blk_queue_quiesced(rq->q) &&
+				blk_is_flush_data_rq(rq) &&
+				blk_mq_request_completed(rq))) {
+		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)
+{
+	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);
+		if (ret == BLK_EH_DONE)
+			return;
+		WARN_ON_ONCE(ret != BLK_EH_RESET_TIMER);
+	}
+
+	blk_add_timer(req);
+}
+
+struct blk_expired_data {
+	bool has_timedout_rq;
+	unsigned long next;
+	unsigned long timeout_start;
+};
+
+static bool blk_mq_req_expired(struct request *rq, struct blk_expired_data *expired)
+{
+	unsigned long deadline;
+
+	if (blk_mq_rq_state(rq) != MQ_RQ_IN_FLIGHT)
+		return false;
+	if (rq->rq_flags & RQF_TIMED_OUT)
+		return false;
+
+	deadline = READ_ONCE(rq->deadline);
+	if (time_after_eq(expired->timeout_start, deadline))
+		return true;
+
+	if (expired->next == 0)
+		expired->next = deadline;
+	else if (time_after(expired->next, deadline))
+		expired->next = deadline;
+	return false;
+}
+
+void blk_mq_put_rq_ref(struct request *rq)
+{
+	if (is_flush_rq(rq)) {
+		if (rq->end_io(rq, 0) == RQ_END_IO_FREE)
+			blk_mq_free_request(rq);
+	} else if (req_ref_put_and_test(rq)) {
+		__blk_mq_free_request(rq);
+	}
+}
+
+static bool blk_mq_check_expired(struct request *rq, void *priv)
+{
+	struct blk_expired_data *expired = priv;
+
+	/*
+	 * blk_mq_queue_tag_busy_iter() has locked the request, so it cannot
+	 * be reallocated underneath the timeout handler's processing, then
+	 * the expire check is reliable. If the request is not expired, then
+	 * it was completed and reallocated as a new request after returning
+	 * from blk_mq_check_expired().
+	 */
+	if (blk_mq_req_expired(rq, expired)) {
+		expired->has_timedout_rq = true;
+		return false;
+	}
+	return true;
+}
+
+static bool blk_mq_handle_expired(struct request *rq, void *priv)
+{
+	struct blk_expired_data *expired = priv;
+
+	if (blk_mq_req_expired(rq, expired))
+		blk_mq_rq_timed_out(rq);
+	return true;
+}
+
+static void blk_mq_timeout_work(struct work_struct *work)
+{
+	struct request_queue *q =
+		container_of(work, struct request_queue, timeout_work);
+	struct blk_expired_data expired = {
+		.timeout_start = jiffies,
+	};
+	struct blk_mq_hw_ctx *hctx;
+	unsigned long i;
+
+	/* A deadlock might occur if a request is stuck requiring a
+	 * timeout at the same time a queue freeze is waiting
+	 * completion, since the timeout code would not be able to
+	 * acquire the queue reference here.
+	 *
+	 * That's why we don't use blk_queue_enter here; instead, we use
+	 * percpu_ref_tryget directly, because we need to be able to
+	 * obtain a reference even in the short window between the queue
+	 * starting to freeze, by dropping the first reference in
+	 * blk_freeze_queue_start, and the moment the last request is
+	 * consumed, marked by the instant q_usage_counter reaches
+	 * zero.
+	 */
+	if (!percpu_ref_tryget(&q->q_usage_counter))
+		return;
+
+	/* check if there is any timed-out request */
+	blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &expired);
+	if (expired.has_timedout_rq) {
+		/*
+		 * Before walking tags, we must ensure any submit started
+		 * before the current time has finished. Since the submit
+		 * uses srcu or rcu, wait for a synchronization point to
+		 * ensure all running submits have finished
+		 */
+		blk_mq_wait_quiesce_done(q);
+
+		expired.next = 0;
+		blk_mq_queue_tag_busy_iter(q, blk_mq_handle_expired, &expired);
+	}
+
+	if (expired.next != 0) {
+		mod_timer(&q->timeout, expired.next);
+	} else {
+		/*
+		 * Request timeouts are handled as a forward rolling timer. If
+		 * we end up here it means that no requests are pending and
+		 * also that no request has been pending for a while. Mark
+		 * each hctx as idle.
+		 */
+		queue_for_each_hw_ctx(q, hctx, i) {
+			/* the hctx may be unmapped, so check it here */
+			if (blk_mq_hw_queue_mapped(hctx))
+				blk_mq_tag_idle(hctx);
+		}
+	}
+	blk_queue_exit(q);
+}
+
+struct flush_busy_ctx_data {
+	struct blk_mq_hw_ctx *hctx;
+	struct list_head *list;
+};
+
+static bool flush_busy_ctx(struct sbitmap *sb, unsigned int bitnr, void *data)
+{
+	struct flush_busy_ctx_data *flush_data = data;
+	struct blk_mq_hw_ctx *hctx = flush_data->hctx;
+	struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
+	enum hctx_type type = hctx->type;
+
+	spin_lock(&ctx->lock);
+	list_splice_tail_init(&ctx->rq_lists[type], flush_data->list);
+	sbitmap_clear_bit(sb, bitnr);
+	spin_unlock(&ctx->lock);
+	return true;
+}
+
+/*
+ * Process software queues that have been marked busy, splicing them
+ * to the for-dispatch
+ */
+void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list)
+{
+	struct flush_busy_ctx_data data = {
+		.hctx = hctx,
+		.list = list,
+	};
+
+	sbitmap_for_each_set(&hctx->ctx_map, flush_busy_ctx, &data);
+}
+EXPORT_SYMBOL_GPL(blk_mq_flush_busy_ctxs);
+
+struct dispatch_rq_data {
+	struct blk_mq_hw_ctx *hctx;
+	struct request *rq;
+};
+
+static bool dispatch_rq_from_ctx(struct sbitmap *sb, unsigned int bitnr,
+		void *data)
+{
+	struct dispatch_rq_data *dispatch_data = data;
+	struct blk_mq_hw_ctx *hctx = dispatch_data->hctx;
+	struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
+	enum hctx_type type = hctx->type;
+
+	spin_lock(&ctx->lock);
+	if (!list_empty(&ctx->rq_lists[type])) {
+		dispatch_data->rq = list_entry_rq(ctx->rq_lists[type].next);
+		list_del_init(&dispatch_data->rq->queuelist);
+		if (list_empty(&ctx->rq_lists[type]))
+			sbitmap_clear_bit(sb, bitnr);
+	}
+	spin_unlock(&ctx->lock);
+
+	return !dispatch_data->rq;
+}
+
+struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx,
+					struct blk_mq_ctx *start)
+{
+	unsigned off = start ? start->index_hw[hctx->type] : 0;
+	struct dispatch_rq_data data = {
+		.hctx = hctx,
+		.rq   = NULL,
+	};
+
+	__sbitmap_for_each_set(&hctx->ctx_map, off,
+			       dispatch_rq_from_ctx, &data);
+
+	return data.rq;
+}
+
+static bool __blk_mq_alloc_driver_tag(struct request *rq)
+{
+	struct sbitmap_queue *bt = &rq->mq_hctx->tags->bitmap_tags;
+	unsigned int tag_offset = rq->mq_hctx->tags->nr_reserved_tags;
+	int tag;
+
+	blk_mq_tag_busy(rq->mq_hctx);
+
+	if (blk_mq_tag_is_reserved(rq->mq_hctx->sched_tags, rq->internal_tag)) {
+		bt = &rq->mq_hctx->tags->breserved_tags;
+		tag_offset = 0;
+	} else {
+		if (!hctx_may_queue(rq->mq_hctx, bt))
+			return false;
+	}
+
+	tag = __sbitmap_queue_get(bt);
+	if (tag == BLK_MQ_NO_TAG)
+		return false;
+
+	rq->tag = tag + tag_offset;
+	return true;
+}
+
+bool __blk_mq_get_driver_tag(struct blk_mq_hw_ctx *hctx, struct request *rq)
+{
+	if (rq->tag == BLK_MQ_NO_TAG && !__blk_mq_alloc_driver_tag(rq))
+		return false;
+
+	if ((hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED) &&
+			!(rq->rq_flags & RQF_MQ_INFLIGHT)) {
+		rq->rq_flags |= RQF_MQ_INFLIGHT;
+		__blk_mq_inc_active_requests(hctx);
+	}
+	hctx->tags->rqs[rq->tag] = rq;
+	return true;
+}
+
+static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode,
+				int flags, void *key)
+{
+	struct blk_mq_hw_ctx *hctx;
+
+	hctx = container_of(wait, struct blk_mq_hw_ctx, dispatch_wait);
+
+	spin_lock(&hctx->dispatch_wait_lock);
+	if (!list_empty(&wait->entry)) {
+		struct sbitmap_queue *sbq;
+
+		list_del_init(&wait->entry);
+		sbq = &hctx->tags->bitmap_tags;
+		atomic_dec(&sbq->ws_active);
+	}
+	spin_unlock(&hctx->dispatch_wait_lock);
+
+	blk_mq_run_hw_queue(hctx, true);
+	return 1;
+}
+
+/*
+ * Mark us waiting for a tag. For shared tags, this involves hooking us into
+ * the tag wakeups. For non-shared tags, we can simply mark us needing a
+ * restart. For both cases, take care to check the condition again after
+ * marking us as waiting.
+ */
+static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx,
+				 struct request *rq)
+{
+	struct sbitmap_queue *sbq;
+	struct wait_queue_head *wq;
+	wait_queue_entry_t *wait;
+	bool ret;
+
+	if (!(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED) &&
+	    !(blk_mq_is_shared_tags(hctx->flags))) {
+		blk_mq_sched_mark_restart_hctx(hctx);
+
+		/*
+		 * It's possible that a tag was freed in the window between the
+		 * allocation failure and adding the hardware queue to the wait
+		 * queue.
+		 *
+		 * Don't clear RESTART here, someone else could have set it.
+		 * At most this will cost an extra queue run.
+		 */
+		return blk_mq_get_driver_tag(rq);
+	}
+
+	wait = &hctx->dispatch_wait;
+	if (!list_empty_careful(&wait->entry))
+		return false;
+
+	if (blk_mq_tag_is_reserved(rq->mq_hctx->sched_tags, rq->internal_tag))
+		sbq = &hctx->tags->breserved_tags;
+	else
+		sbq = &hctx->tags->bitmap_tags;
+	wq = &bt_wait_ptr(sbq, hctx)->wait;
+
+	spin_lock_irq(&wq->lock);
+	spin_lock(&hctx->dispatch_wait_lock);
+	if (!list_empty(&wait->entry)) {
+		spin_unlock(&hctx->dispatch_wait_lock);
+		spin_unlock_irq(&wq->lock);
+		return false;
+	}
+
+	atomic_inc(&sbq->ws_active);
+	wait->flags &= ~WQ_FLAG_EXCLUSIVE;
+	__add_wait_queue(wq, wait);
+
+	/*
+	 * It's possible that a tag was freed in the window between the
+	 * allocation failure and adding the hardware queue to the wait
+	 * queue.
+	 */
+	ret = blk_mq_get_driver_tag(rq);
+	if (!ret) {
+		spin_unlock(&hctx->dispatch_wait_lock);
+		spin_unlock_irq(&wq->lock);
+		return false;
+	}
+
+	/*
+	 * We got a tag, remove ourselves from the wait queue to ensure
+	 * someone else gets the wakeup.
+	 */
+	list_del_init(&wait->entry);
+	atomic_dec(&sbq->ws_active);
+	spin_unlock(&hctx->dispatch_wait_lock);
+	spin_unlock_irq(&wq->lock);
+
+	return true;
+}
+
+#define BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT  8
+#define BLK_MQ_DISPATCH_BUSY_EWMA_FACTOR  4
+/*
+ * Update dispatch busy with the Exponential Weighted Moving Average(EWMA):
+ * - EWMA is one simple way to compute running average value
+ * - weight(7/8 and 1/8) is applied so that it can decrease exponentially
+ * - take 4 as factor for avoiding to get too small(0) result, and this
+ *   factor doesn't matter because EWMA decreases exponentially
+ */
+static void blk_mq_update_dispatch_busy(struct blk_mq_hw_ctx *hctx, bool busy)
+{
+	unsigned int ewma;
+
+	ewma = hctx->dispatch_busy;
+
+	if (!ewma && !busy)
+		return;
+
+	ewma *= BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT - 1;
+	if (busy)
+		ewma += 1 << BLK_MQ_DISPATCH_BUSY_EWMA_FACTOR;
+	ewma /= BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT;
+
+	hctx->dispatch_busy = ewma;
+}
+
+#define BLK_MQ_RESOURCE_DELAY	3		/* ms units */
+
+static void blk_mq_handle_dev_resource(struct request *rq,
+				       struct list_head *list)
+{
+	struct request *next =
+		list_first_entry_or_null(list, struct request, queuelist);
+
+	/*
+	 * If an I/O scheduler has been configured and we got a driver tag for
+	 * the next request already, free it.
+	 */
+	if (next)
+		blk_mq_put_driver_tag(next);
+
+	list_add(&rq->queuelist, list);
+	__blk_mq_requeue_request(rq);
+}
+
+static void blk_mq_handle_zone_resource(struct request *rq,
+					struct list_head *zone_list)
+{
+	/*
+	 * If we end up here it is because we cannot dispatch a request to a
+	 * specific zone due to LLD level zone-write locking or other zone
+	 * related resource not being available. In this case, set the request
+	 * aside in zone_list for retrying it later.
+	 */
+	list_add(&rq->queuelist, zone_list);
+	__blk_mq_requeue_request(rq);
+}
+
+enum prep_dispatch {
+	PREP_DISPATCH_OK,
+	PREP_DISPATCH_NO_TAG,
+	PREP_DISPATCH_NO_BUDGET,
+};
+
+static enum prep_dispatch blk_mq_prep_dispatch_rq(struct request *rq,
+						  bool need_budget)
+{
+	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
+	int budget_token = -1;
+
+	if (need_budget) {
+		budget_token = blk_mq_get_dispatch_budget(rq->q);
+		if (budget_token < 0) {
+			blk_mq_put_driver_tag(rq);
+			return PREP_DISPATCH_NO_BUDGET;
+		}
+		blk_mq_set_rq_budget_token(rq, budget_token);
+	}
+
+	if (!blk_mq_get_driver_tag(rq)) {
+		/*
+		 * The initial allocation attempt failed, so we need to
+		 * rerun the hardware queue when a tag is freed. The
+		 * waitqueue takes care of that. If the queue is run
+		 * before we add this entry back on the dispatch list,
+		 * we'll re-run it below.
+		 */
+		if (!blk_mq_mark_tag_wait(hctx, rq)) {
+			/*
+			 * All budgets not got from this function will be put
+			 * together during handling partial dispatch
+			 */
+			if (need_budget)
+				blk_mq_put_dispatch_budget(rq->q, budget_token);
+			return PREP_DISPATCH_NO_TAG;
+		}
+	}
+
+	return PREP_DISPATCH_OK;
+}
+
+/* release all allocated budgets before calling to blk_mq_dispatch_rq_list */
+static void blk_mq_release_budgets(struct request_queue *q,
+		struct list_head *list)
+{
+	struct request *rq;
+
+	list_for_each_entry(rq, list, queuelist) {
+		int budget_token = blk_mq_get_rq_budget_token(rq);
+
+		if (budget_token >= 0)
+			blk_mq_put_dispatch_budget(q, budget_token);
+	}
+}
+
+/*
+ * Returns true if we did some work AND can potentially do more.
+ */
+bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
+			     unsigned int nr_budgets)
+{
+	enum prep_dispatch prep;
+	struct request_queue *q = hctx->queue;
+	struct request *rq, *nxt;
+	int errors, queued;
+	blk_status_t ret = BLK_STS_OK;
+	LIST_HEAD(zone_list);
+	bool needs_resource = false;
+
+	if (list_empty(list))
+		return false;
+
+	/*
+	 * Now process all the entries, sending them to the driver.
+	 */
+	errors = queued = 0;
+	do {
+		struct blk_mq_queue_data bd;
+
+		rq = list_first_entry(list, struct request, queuelist);
+
+		WARN_ON_ONCE(hctx != rq->mq_hctx);
+		prep = blk_mq_prep_dispatch_rq(rq, !nr_budgets);
+		if (prep != PREP_DISPATCH_OK)
+			break;
+
+		list_del_init(&rq->queuelist);
+
+		bd.rq = rq;
+
+		/*
+		 * Flag last if we have no more requests, or if we have more
+		 * but can't assign a driver tag to it.
+		 */
+		if (list_empty(list))
+			bd.last = true;
+		else {
+			nxt = list_first_entry(list, struct request, queuelist);
+			bd.last = !blk_mq_get_driver_tag(nxt);
+		}
+
+		/*
+		 * once the request is queued to lld, no need to cover the
+		 * budget any more
+		 */
+		if (nr_budgets)
+			nr_budgets--;
+		ret = q->mq_ops->queue_rq(hctx, &bd);
+		switch (ret) {
+		case BLK_STS_OK:
+			queued++;
+			break;
+		case BLK_STS_RESOURCE:
+			needs_resource = true;
+			fallthrough;
+		case BLK_STS_DEV_RESOURCE:
+			blk_mq_handle_dev_resource(rq, list);
+			goto out;
+		case BLK_STS_ZONE_RESOURCE:
+			/*
+			 * Move the request to zone_list and keep going through
+			 * the dispatch list to find more requests the drive can
+			 * accept.
+			 */
+			blk_mq_handle_zone_resource(rq, &zone_list);
+			needs_resource = true;
+			break;
+		default:
+			errors++;
+			blk_mq_end_request(rq, ret);
+		}
+	} while (!list_empty(list));
+out:
+	if (!list_empty(&zone_list))
+		list_splice_tail_init(&zone_list, list);
+
+	/* If we didn't flush the entire list, we could have told the driver
+	 * there was more coming, but that turned out to be a lie.
+	 */
+	if ((!list_empty(list) || errors || needs_resource ||
+	     ret == BLK_STS_DEV_RESOURCE) && q->mq_ops->commit_rqs && queued)
+		q->mq_ops->commit_rqs(hctx);
+	/*
+	 * Any items that need requeuing? Stuff them into hctx->dispatch,
+	 * that is where we will continue on next queue run.
+	 */
+	if (!list_empty(list)) {
+		bool needs_restart;
+		/* For non-shared tags, the RESTART check will suffice */
+		bool no_tag = prep == PREP_DISPATCH_NO_TAG &&
+			((hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED) ||
+			blk_mq_is_shared_tags(hctx->flags));
+
+		if (nr_budgets)
+			blk_mq_release_budgets(q, list);
+
+		spin_lock(&hctx->lock);
+		list_splice_tail_init(list, &hctx->dispatch);
+		spin_unlock(&hctx->lock);
+
+		/*
+		 * Order adding requests to hctx->dispatch and checking
+		 * SCHED_RESTART flag. The pair of this smp_mb() is the one
+		 * in blk_mq_sched_restart(). Avoid restart code path to
+		 * miss the new added requests to hctx->dispatch, meantime
+		 * SCHED_RESTART is observed here.
+		 */
+		smp_mb();
+
+		/*
+		 * If SCHED_RESTART was set by the caller of this function and
+		 * it is no longer set that means that it was cleared by another
+		 * thread and hence that a queue rerun is needed.
+		 *
+		 * If 'no_tag' is set, that means that we failed getting
+		 * a driver tag with an I/O scheduler attached. If our dispatch
+		 * waitqueue is no longer active, ensure that we run the queue
+		 * AFTER adding our entries back to the list.
+		 *
+		 * If no I/O scheduler has been configured it is possible that
+		 * the hardware queue got stopped and restarted before requests
+		 * were pushed back onto the dispatch list. Rerun the queue to
+		 * avoid starvation. Notes:
+		 * - blk_mq_run_hw_queue() checks whether or not a queue has
+		 *   been stopped before rerunning a queue.
+		 * - Some but not all block drivers stop a queue before
+		 *   returning BLK_STS_RESOURCE. Two exceptions are scsi-mq
+		 *   and dm-rq.
+		 *
+		 * If driver returns BLK_STS_RESOURCE and SCHED_RESTART
+		 * bit is set, run queue after a delay to avoid IO stalls
+		 * that could otherwise occur if the queue is idle.  We'll do
+		 * similar if we couldn't get budget or couldn't lock a zone
+		 * and SCHED_RESTART is set.
+		 */
+		needs_restart = blk_mq_sched_needs_restart(hctx);
+		if (prep == PREP_DISPATCH_NO_BUDGET)
+			needs_resource = true;
+		if (!needs_restart ||
+		    (no_tag && list_empty_careful(&hctx->dispatch_wait.entry)))
+			blk_mq_run_hw_queue(hctx, true);
+		else if (needs_resource)
+			blk_mq_delay_run_hw_queue(hctx, BLK_MQ_RESOURCE_DELAY);
+
+		blk_mq_update_dispatch_busy(hctx, true);
+		return false;
+	} else
+		blk_mq_update_dispatch_busy(hctx, false);
+
+	return (queued + errors) != 0;
+}
+
+/**
+ * __blk_mq_run_hw_queue - Run a hardware queue.
+ * @hctx: Pointer to the hardware queue to run.
+ *
+ * Send pending requests to the hardware.
+ */
+static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
+{
+	/*
+	 * We can't run the queue inline with ints disabled. Ensure that
+	 * we catch bad users of this early.
+	 */
+	WARN_ON_ONCE(in_interrupt());
+
+	blk_mq_run_dispatch_ops(hctx->queue,
+			blk_mq_sched_dispatch_requests(hctx));
+}
+
+static inline int blk_mq_first_mapped_cpu(struct blk_mq_hw_ctx *hctx)
+{
+	int cpu = cpumask_first_and(hctx->cpumask, cpu_online_mask);
+
+	if (cpu >= nr_cpu_ids)
+		cpu = cpumask_first(hctx->cpumask);
+	return cpu;
+}
+
+/*
+ * It'd be great if the workqueue API had a way to pass
+ * in a mask and had some smarts for more clever placement.
+ * For now we just round-robin here, switching for every
+ * BLK_MQ_CPU_WORK_BATCH queued items.
+ */
+static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
+{
+	bool tried = false;
+	int next_cpu = hctx->next_cpu;
+
+	if (hctx->queue->nr_hw_queues == 1)
+		return WORK_CPU_UNBOUND;
+
+	if (--hctx->next_cpu_batch <= 0) {
+select_cpu:
+		next_cpu = cpumask_next_and(next_cpu, hctx->cpumask,
+				cpu_online_mask);
+		if (next_cpu >= nr_cpu_ids)
+			next_cpu = blk_mq_first_mapped_cpu(hctx);
+		hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
+	}
+
+	/*
+	 * Do unbound schedule if we can't find a online CPU for this hctx,
+	 * and it should only happen in the path of handling CPU DEAD.
+	 */
+	if (!cpu_online(next_cpu)) {
+		if (!tried) {
+			tried = true;
+			goto select_cpu;
+		}
+
+		/*
+		 * Make sure to re-select CPU next time once after CPUs
+		 * in hctx->cpumask become online again.
+		 */
+		hctx->next_cpu = next_cpu;
+		hctx->next_cpu_batch = 1;
+		return WORK_CPU_UNBOUND;
+	}
+
+	hctx->next_cpu = next_cpu;
+	return next_cpu;
+}
+
+/**
+ * __blk_mq_delay_run_hw_queue - Run (or schedule to run) a hardware queue.
+ * @hctx: Pointer to the hardware queue to run.
+ * @async: If we want to run the queue asynchronously.
+ * @msecs: Milliseconds of delay to wait before running the queue.
+ *
+ * If !@async, try to run the queue now. Else, run the queue asynchronously and
+ * with a delay of @msecs.
+ */
+static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async,
+					unsigned long msecs)
+{
+	if (unlikely(blk_mq_hctx_stopped(hctx)))
+		return;
+
+	if (!async && !(hctx->flags & BLK_MQ_F_BLOCKING)) {
+		if (cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask)) {
+			__blk_mq_run_hw_queue(hctx);
+			return;
+		}
+	}
+
+	kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work,
+				    msecs_to_jiffies(msecs));
+}
+
+/**
+ * blk_mq_delay_run_hw_queue - Run a hardware queue asynchronously.
+ * @hctx: Pointer to the hardware queue to run.
+ * @msecs: Milliseconds of delay to wait before running the queue.
+ *
+ * Run a hardware queue asynchronously with a delay of @msecs.
+ */
+void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
+{
+	__blk_mq_delay_run_hw_queue(hctx, true, msecs);
+}
+EXPORT_SYMBOL(blk_mq_delay_run_hw_queue);
+
+/**
+ * blk_mq_run_hw_queue - Start to run a hardware queue.
+ * @hctx: Pointer to the hardware queue to run.
+ * @async: If we want to run the queue asynchronously.
+ *
+ * Check if the request queue is not in a quiesced state and if there are
+ * pending requests to be sent. If this is true, run the queue to send requests
+ * to hardware.
+ */
+void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
+{
+	bool need_run;
+
+	/*
+	 * When queue is quiesced, we may be switching io scheduler, or
+	 * updating nr_hw_queues, or other things, and we can't run queue
+	 * any more, even __blk_mq_hctx_has_pending() can't be called safely.
+	 *
+	 * And queue will be rerun in blk_mq_unquiesce_queue() if it is
+	 * quiesced.
+	 */
+	__blk_mq_run_dispatch_ops(hctx->queue, false,
+		need_run = !blk_queue_quiesced(hctx->queue) &&
+		blk_mq_hctx_has_pending(hctx));
+
+	if (need_run)
+		__blk_mq_delay_run_hw_queue(hctx, async, 0);
+}
+EXPORT_SYMBOL(blk_mq_run_hw_queue);
+
+/*
+ * Return prefered queue to dispatch from (if any) for non-mq aware IO
+ * scheduler.
+ */
+static struct blk_mq_hw_ctx *blk_mq_get_sq_hctx(struct request_queue *q)
+{
+	struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
+	/*
+	 * If the IO scheduler does not respect hardware queues when
+	 * dispatching, we just don't bother with multiple HW queues and
+	 * dispatch from hctx for the current CPU since running multiple queues
+	 * just causes lock contention inside the scheduler and pointless cache
+	 * bouncing.
+	 */
+	struct blk_mq_hw_ctx *hctx = ctx->hctxs[HCTX_TYPE_DEFAULT];
+
+	if (!blk_mq_hctx_stopped(hctx))
+		return hctx;
+	return NULL;
+}
+
+/**
+ * blk_mq_run_hw_queues - Run all hardware queues in a request queue.
+ * @q: Pointer to the request queue to run.
+ * @async: If we want to run the queue asynchronously.
+ */
+void blk_mq_run_hw_queues(struct request_queue *q, bool async)
+{
+	struct blk_mq_hw_ctx *hctx, *sq_hctx;
+	unsigned long i;
+
+	sq_hctx = NULL;
+	if (blk_queue_sq_sched(q))
+		sq_hctx = blk_mq_get_sq_hctx(q);
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (blk_mq_hctx_stopped(hctx))
+			continue;
+		/*
+		 * Dispatch from this hctx either if there's no hctx preferred
+		 * by IO scheduler or if it has requests that bypass the
+		 * scheduler.
+		 */
+		if (!sq_hctx || sq_hctx == hctx ||
+		    !list_empty_careful(&hctx->dispatch))
+			blk_mq_run_hw_queue(hctx, async);
+	}
+}
+EXPORT_SYMBOL(blk_mq_run_hw_queues);
+
+/**
+ * blk_mq_delay_run_hw_queues - Run all hardware queues asynchronously.
+ * @q: Pointer to the request queue to run.
+ * @msecs: Milliseconds of delay to wait before running the queues.
+ */
+void blk_mq_delay_run_hw_queues(struct request_queue *q, unsigned long msecs)
+{
+	struct blk_mq_hw_ctx *hctx, *sq_hctx;
+	unsigned long i;
+
+	sq_hctx = NULL;
+	if (blk_queue_sq_sched(q))
+		sq_hctx = blk_mq_get_sq_hctx(q);
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (blk_mq_hctx_stopped(hctx))
+			continue;
+		/*
+		 * If there is already a run_work pending, leave the
+		 * pending delay untouched. Otherwise, a hctx can stall
+		 * if another hctx is re-delaying the other's work
+		 * before the work executes.
+		 */
+		if (delayed_work_pending(&hctx->run_work))
+			continue;
+		/*
+		 * Dispatch from this hctx either if there's no hctx preferred
+		 * by IO scheduler or if it has requests that bypass the
+		 * scheduler.
+		 */
+		if (!sq_hctx || sq_hctx == hctx ||
+		    !list_empty_careful(&hctx->dispatch))
+			blk_mq_delay_run_hw_queue(hctx, msecs);
+	}
+}
+EXPORT_SYMBOL(blk_mq_delay_run_hw_queues);
+
+/*
+ * This function is often used for pausing .queue_rq() by driver when
+ * there isn't enough resource or some conditions aren't satisfied, and
+ * BLK_STS_RESOURCE is usually returned.
+ *
+ * We do not guarantee that dispatch can be drained or blocked
+ * after blk_mq_stop_hw_queue() returns. Please use
+ * blk_mq_quiesce_queue() for that requirement.
+ */
+void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx)
+{
+	cancel_delayed_work(&hctx->run_work);
+
+	set_bit(BLK_MQ_S_STOPPED, &hctx->state);
+}
+EXPORT_SYMBOL(blk_mq_stop_hw_queue);
+
+/*
+ * This function is often used for pausing .queue_rq() by driver when
+ * there isn't enough resource or some conditions aren't satisfied, and
+ * BLK_STS_RESOURCE is usually returned.
+ *
+ * We do not guarantee that dispatch can be drained or blocked
+ * after blk_mq_stop_hw_queues() returns. Please use
+ * blk_mq_quiesce_queue() for that requirement.
+ */
+void blk_mq_stop_hw_queues(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned long i;
+
+	queue_for_each_hw_ctx(q, hctx, i)
+		blk_mq_stop_hw_queue(hctx);
+}
+EXPORT_SYMBOL(blk_mq_stop_hw_queues);
+
+void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx)
+{
+	clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
+
+	blk_mq_run_hw_queue(hctx, false);
+}
+EXPORT_SYMBOL(blk_mq_start_hw_queue);
+
+void blk_mq_start_hw_queues(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned long i;
+
+	queue_for_each_hw_ctx(q, hctx, i)
+		blk_mq_start_hw_queue(hctx);
+}
+EXPORT_SYMBOL(blk_mq_start_hw_queues);
+
+void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
+{
+	if (!blk_mq_hctx_stopped(hctx))
+		return;
+
+	clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
+	blk_mq_run_hw_queue(hctx, async);
+}
+EXPORT_SYMBOL_GPL(blk_mq_start_stopped_hw_queue);
+
+void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned long i;
+
+	queue_for_each_hw_ctx(q, hctx, i)
+		blk_mq_start_stopped_hw_queue(hctx, async);
+}
+EXPORT_SYMBOL(blk_mq_start_stopped_hw_queues);
+
+static void blk_mq_run_work_fn(struct work_struct *work)
+{
+	struct blk_mq_hw_ctx *hctx;
+
+	hctx = container_of(work, struct blk_mq_hw_ctx, run_work.work);
+
+	/*
+	 * If we are stopped, don't run the queue.
+	 */
+	if (blk_mq_hctx_stopped(hctx))
+		return;
+
+	__blk_mq_run_hw_queue(hctx);
+}
+
+static inline void __blk_mq_insert_req_list(struct blk_mq_hw_ctx *hctx,
+					    struct request *rq,
+					    bool at_head)
+{
+	struct blk_mq_ctx *ctx = rq->mq_ctx;
+	enum hctx_type type = hctx->type;
+
+	lockdep_assert_held(&ctx->lock);
+
+	trace_block_rq_insert(rq);
+
+	if (at_head)
+		list_add(&rq->queuelist, &ctx->rq_lists[type]);
+	else
+		list_add_tail(&rq->queuelist, &ctx->rq_lists[type]);
+}
+
+void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
+			     bool at_head)
+{
+	struct blk_mq_ctx *ctx = rq->mq_ctx;
+
+	lockdep_assert_held(&ctx->lock);
+
+	__blk_mq_insert_req_list(hctx, rq, at_head);
+	blk_mq_hctx_mark_pending(hctx, ctx);
+}
+
+/**
+ * blk_mq_request_bypass_insert - Insert a request at dispatch list.
+ * @rq: Pointer to request to be inserted.
+ * @at_head: true if the request should be inserted at the head of the list.
+ * @run_queue: If we should run the hardware queue after inserting the request.
+ *
+ * Should only be used carefully, when the caller knows we want to
+ * bypass a potential IO scheduler on the target device.
+ */
+void blk_mq_request_bypass_insert(struct request *rq, bool at_head,
+				  bool run_queue)
+{
+	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
+
+	spin_lock(&hctx->lock);
+	if (at_head)
+		list_add(&rq->queuelist, &hctx->dispatch);
+	else
+		list_add_tail(&rq->queuelist, &hctx->dispatch);
+	spin_unlock(&hctx->lock);
+
+	if (run_queue)
+		blk_mq_run_hw_queue(hctx, false);
+}
+
+void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
+			    struct list_head *list)
+
+{
+	struct request *rq;
+	enum hctx_type type = hctx->type;
+
+	/*
+	 * preemption doesn't flush plug list, so it's possible ctx->cpu is
+	 * offline now
+	 */
+	list_for_each_entry(rq, list, queuelist) {
+		BUG_ON(rq->mq_ctx != ctx);
+		trace_block_rq_insert(rq);
+	}
+
+	spin_lock(&ctx->lock);
+	list_splice_tail_init(list, &ctx->rq_lists[type]);
+	blk_mq_hctx_mark_pending(hctx, ctx);
+	spin_unlock(&ctx->lock);
+}
+
+static void blk_mq_commit_rqs(struct blk_mq_hw_ctx *hctx, int *queued,
+			      bool from_schedule)
+{
+	if (hctx->queue->mq_ops->commit_rqs) {
+		trace_block_unplug(hctx->queue, *queued, !from_schedule);
+		hctx->queue->mq_ops->commit_rqs(hctx);
+	}
+	*queued = 0;
+}
+
+static void blk_mq_bio_to_request(struct request *rq, struct bio *bio,
+		unsigned int nr_segs)
+{
+	int err;
+
+	if (bio->bi_opf & REQ_RAHEAD)
+		rq->cmd_flags |= REQ_FAILFAST_MASK;
+
+	rq->__sector = bio->bi_iter.bi_sector;
+	blk_rq_bio_prep(rq, bio, nr_segs);
+
+	/* This can't fail, since GFP_NOIO includes __GFP_DIRECT_RECLAIM. */
+	err = blk_crypto_rq_bio_prep(rq, bio, GFP_NOIO);
+	WARN_ON_ONCE(err);
+
+	blk_account_io_start(rq);
+}
+
+static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
+					    struct request *rq, bool last)
+{
+	struct request_queue *q = rq->q;
+	struct blk_mq_queue_data bd = {
+		.rq = rq,
+		.last = last,
+	};
+	blk_status_t ret;
+
+	/*
+	 * For OK queue, we are done. For error, caller may kill it.
+	 * Any other error (busy), just add it to our list as we
+	 * previously would have done.
+	 */
+	ret = q->mq_ops->queue_rq(hctx, &bd);
+	switch (ret) {
+	case BLK_STS_OK:
+		blk_mq_update_dispatch_busy(hctx, false);
+		break;
+	case BLK_STS_RESOURCE:
+	case BLK_STS_DEV_RESOURCE:
+		blk_mq_update_dispatch_busy(hctx, true);
+		__blk_mq_requeue_request(rq);
+		break;
+	default:
+		blk_mq_update_dispatch_busy(hctx, false);
+		break;
+	}
+
+	return ret;
+}
+
+static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
+						struct request *rq,
+						bool bypass_insert, bool last)
+{
+	struct request_queue *q = rq->q;
+	bool run_queue = true;
+	int budget_token;
+
+	/*
+	 * RCU or SRCU read lock is needed before checking quiesced flag.
+	 *
+	 * When queue is stopped or quiesced, ignore 'bypass_insert' from
+	 * blk_mq_request_issue_directly(), and return BLK_STS_OK to caller,
+	 * and avoid driver to try to dispatch again.
+	 */
+	if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)) {
+		run_queue = false;
+		bypass_insert = false;
+		goto insert;
+	}
+
+	if ((rq->rq_flags & RQF_ELV) && !bypass_insert)
+		goto insert;
+
+	budget_token = blk_mq_get_dispatch_budget(q);
+	if (budget_token < 0)
+		goto insert;
+
+	blk_mq_set_rq_budget_token(rq, budget_token);
+
+	if (!blk_mq_get_driver_tag(rq)) {
+		blk_mq_put_dispatch_budget(q, budget_token);
+		goto insert;
+	}
+
+	return __blk_mq_issue_directly(hctx, rq, last);
+insert:
+	if (bypass_insert)
+		return BLK_STS_RESOURCE;
+
+	blk_mq_sched_insert_request(rq, false, run_queue, false);
+
+	return BLK_STS_OK;
+}
+
+/**
+ * blk_mq_try_issue_directly - Try to send a request directly to device driver.
+ * @hctx: Pointer of the associated hardware queue.
+ * @rq: Pointer to request to be sent.
+ *
+ * If the device has enough resources to accept a new request now, send the
+ * request directly to device driver. Else, insert at hctx->dispatch queue, so
+ * we can try send it another time in the future. Requests inserted at this
+ * queue have higher priority.
+ */
+static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
+		struct request *rq)
+{
+	blk_status_t ret =
+		__blk_mq_try_issue_directly(hctx, rq, false, true);
+
+	if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
+		blk_mq_request_bypass_insert(rq, false, true);
+	else if (ret != BLK_STS_OK)
+		blk_mq_end_request(rq, ret);
+}
+
+static blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last)
+{
+	return __blk_mq_try_issue_directly(rq->mq_hctx, rq, true, last);
+}
+
+static void blk_mq_plug_issue_direct(struct blk_plug *plug, bool from_schedule)
+{
+	struct blk_mq_hw_ctx *hctx = NULL;
+	struct request *rq;
+	int queued = 0;
+	int errors = 0;
+
+	while ((rq = rq_list_pop(&plug->mq_list))) {
+		bool last = rq_list_empty(plug->mq_list);
+		blk_status_t ret;
+
+		if (hctx != rq->mq_hctx) {
+			if (hctx)
+				blk_mq_commit_rqs(hctx, &queued, from_schedule);
+			hctx = rq->mq_hctx;
+		}
+
+		ret = blk_mq_request_issue_directly(rq, last);
+		switch (ret) {
+		case BLK_STS_OK:
+			queued++;
+			break;
+		case BLK_STS_RESOURCE:
+		case BLK_STS_DEV_RESOURCE:
+			blk_mq_request_bypass_insert(rq, false, true);
+			blk_mq_commit_rqs(hctx, &queued, from_schedule);
+			return;
+		default:
+			blk_mq_end_request(rq, ret);
+			errors++;
+			break;
+		}
+	}
+
+	/*
+	 * If we didn't flush the entire list, we could have told the driver
+	 * there was more coming, but that turned out to be a lie.
+	 */
+	if (errors)
+		blk_mq_commit_rqs(hctx, &queued, from_schedule);
+}
+
+static void __blk_mq_flush_plug_list(struct request_queue *q,
+				     struct blk_plug *plug)
+{
+	if (blk_queue_quiesced(q))
+		return;
+	q->mq_ops->queue_rqs(&plug->mq_list);
+}
+
+static void blk_mq_dispatch_plug_list(struct blk_plug *plug, bool from_sched)
+{
+	struct blk_mq_hw_ctx *this_hctx = NULL;
+	struct blk_mq_ctx *this_ctx = NULL;
+	struct request *requeue_list = NULL;
+	struct request **requeue_lastp = &requeue_list;
+	unsigned int depth = 0;
+	LIST_HEAD(list);
+
+	do {
+		struct request *rq = rq_list_pop(&plug->mq_list);
+
+		if (!this_hctx) {
+			this_hctx = rq->mq_hctx;
+			this_ctx = rq->mq_ctx;
+		} else if (this_hctx != rq->mq_hctx || this_ctx != rq->mq_ctx) {
+			rq_list_add_tail(&requeue_lastp, rq);
+			continue;
+		}
+		list_add(&rq->queuelist, &list);
+		depth++;
+	} while (!rq_list_empty(plug->mq_list));
+
+	plug->mq_list = requeue_list;
+	trace_block_unplug(this_hctx->queue, depth, !from_sched);
+	blk_mq_sched_insert_requests(this_hctx, this_ctx, &list, from_sched);
+}
+
+void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
+{
+	struct request *rq;
+
+	/*
+	 * We may have been called recursively midway through handling
+	 * plug->mq_list via a schedule() in the driver's queue_rq() callback.
+	 * To avoid mq_list changing under our feet, clear rq_count early and
+	 * bail out specifically if rq_count is 0 rather than checking
+	 * whether the mq_list is empty.
+	 */
+	if (plug->rq_count == 0)
+		return;
+	plug->rq_count = 0;
+
+	if (!plug->multiple_queues && !plug->has_elevator && !from_schedule) {
+		struct request_queue *q;
+
+		rq = rq_list_peek(&plug->mq_list);
+		q = rq->q;
+
+		/*
+		 * Peek first request and see if we have a ->queue_rqs() hook.
+		 * If we do, we can dispatch the whole plug list in one go. We
+		 * already know at this point that all requests belong to the
+		 * same queue, caller must ensure that's the case.
+		 *
+		 * Since we pass off the full list to the driver at this point,
+		 * we do not increment the active request count for the queue.
+		 * Bypass shared tags for now because of that.
+		 */
+		if (q->mq_ops->queue_rqs &&
+		    !(rq->mq_hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) {
+			blk_mq_run_dispatch_ops(q,
+				__blk_mq_flush_plug_list(q, plug));
+			if (rq_list_empty(plug->mq_list))
+				return;
+		}
+
+		blk_mq_run_dispatch_ops(q,
+				blk_mq_plug_issue_direct(plug, false));
+		if (rq_list_empty(plug->mq_list))
+			return;
+	}
+
+	do {
+		blk_mq_dispatch_plug_list(plug, from_schedule);
+	} while (!rq_list_empty(plug->mq_list));
+}
+
+void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
+		struct list_head *list)
+{
+	int queued = 0;
+	int errors = 0;
+
+	while (!list_empty(list)) {
+		blk_status_t ret;
+		struct request *rq = list_first_entry(list, struct request,
+				queuelist);
+
+		list_del_init(&rq->queuelist);
+		ret = blk_mq_request_issue_directly(rq, list_empty(list));
+		if (ret != BLK_STS_OK) {
+			errors++;
+			if (ret == BLK_STS_RESOURCE ||
+					ret == BLK_STS_DEV_RESOURCE) {
+				blk_mq_request_bypass_insert(rq, false,
+							list_empty(list));
+				break;
+			}
+			blk_mq_end_request(rq, ret);
+		} else
+			queued++;
+	}
+
+	/*
+	 * If we didn't flush the entire list, we could have told
+	 * the driver there was more coming, but that turned out to
+	 * be a lie.
+	 */
+	if ((!list_empty(list) || errors) &&
+	     hctx->queue->mq_ops->commit_rqs && queued)
+		hctx->queue->mq_ops->commit_rqs(hctx);
+}
+
+static bool blk_mq_attempt_bio_merge(struct request_queue *q,
+				     struct bio *bio, unsigned int nr_segs)
+{
+	if (!blk_queue_nomerges(q) && bio_mergeable(bio)) {
+		if (blk_attempt_plug_merge(q, bio, nr_segs))
+			return true;
+		if (blk_mq_sched_bio_merge(q, bio, nr_segs))
+			return true;
+	}
+	return false;
+}
+
+static struct request *blk_mq_get_new_requests(struct request_queue *q,
+					       struct blk_plug *plug,
+					       struct bio *bio,
+					       unsigned int nsegs)
+{
+	struct blk_mq_alloc_data data = {
+		.q		= q,
+		.nr_tags	= 1,
+		.cmd_flags	= bio->bi_opf,
+	};
+	struct request *rq;
+
+	if (blk_mq_attempt_bio_merge(q, bio, nsegs))
+		return NULL;
+
+	rq_qos_throttle(q, bio);
+
+	if (plug) {
+		data.nr_tags = plug->nr_ios;
+		plug->nr_ios = 1;
+		data.cached_rq = &plug->cached_rq;
+	}
+
+	rq = __blk_mq_alloc_requests(&data);
+	if (rq)
+		return rq;
+	rq_qos_cleanup(q, bio);
+	if (bio->bi_opf & REQ_NOWAIT)
+		bio_wouldblock_error(bio);
+	return NULL;
+}
+
+/* return true if this @rq can be used for @bio */
+static bool blk_mq_can_use_cached_rq(struct request *rq, struct blk_plug *plug,
+		struct bio *bio)
+{
+	enum hctx_type type = blk_mq_get_hctx_type(bio->bi_opf);
+	enum hctx_type hctx_type = rq->mq_hctx->type;
+
+	WARN_ON_ONCE(rq_list_peek(&plug->cached_rq) != rq);
+
+	if (type != hctx_type &&
+	    !(type == HCTX_TYPE_READ && hctx_type == HCTX_TYPE_DEFAULT))
+		return false;
+	if (op_is_flush(rq->cmd_flags) != op_is_flush(bio->bi_opf))
+		return false;
+
+	/*
+	 * If any qos ->throttle() end up blocking, we will have flushed the
+	 * plug and hence killed the cached_rq list as well. Pop this entry
+	 * before we throttle.
+	 */
+	plug->cached_rq = rq_list_next(rq);
+	rq_qos_throttle(rq->q, bio);
+
+	rq->cmd_flags = bio->bi_opf;
+	INIT_LIST_HEAD(&rq->queuelist);
+	return true;
+}
+
+static void bio_set_ioprio(struct bio *bio)
+{
+	/* Nobody set ioprio so far? Initialize it based on task's nice value */
+	if (IOPRIO_PRIO_CLASS(bio->bi_ioprio) == IOPRIO_CLASS_NONE)
+		bio->bi_ioprio = get_current_ioprio();
+	blkcg_set_ioprio(bio);
+}
+
+/**
+ * blk_mq_submit_bio - Create and send a request to block device.
+ * @bio: Bio pointer.
+ *
+ * Builds up a request structure from @q and @bio and send to the device. The
+ * request may not be queued directly to hardware if:
+ * * This request can be merged with another one
+ * * We want to place request at plug queue for possible future merging
+ * * There is an IO scheduler active at this queue
+ *
+ * It will not queue the request if there is an error with the bio, or at the
+ * request creation.
+ */
+void blk_mq_submit_bio(struct bio *bio)
+{
+	struct request_queue *q = bdev_get_queue(bio->bi_bdev);
+	struct blk_plug *plug = blk_mq_plug(bio);
+	const int is_sync = op_is_sync(bio->bi_opf);
+	struct request *rq = NULL;
+	unsigned int nr_segs = 1;
+	blk_status_t ret;
+
+	bio = blk_queue_bounce(bio, q);
+	bio_set_ioprio(bio);
+
+	if (plug) {
+		rq = rq_list_peek(&plug->cached_rq);
+		if (rq && rq->q != q)
+			rq = NULL;
+	}
+	if (rq) {
+		if (unlikely(bio_may_exceed_limits(bio, &q->limits))) {
+			bio = __bio_split_to_limits(bio, &q->limits, &nr_segs);
+			if (!bio)
+				return;
+		}
+		if (!bio_integrity_prep(bio))
+			return;
+		if (blk_mq_attempt_bio_merge(q, bio, nr_segs))
+			return;
+		if (blk_mq_can_use_cached_rq(rq, plug, bio))
+			goto done;
+		percpu_ref_get(&q->q_usage_counter);
+	} else {
+		if (unlikely(bio_queue_enter(bio)))
+			return;
+		if (unlikely(bio_may_exceed_limits(bio, &q->limits))) {
+			bio = __bio_split_to_limits(bio, &q->limits, &nr_segs);
+			if (!bio)
+				goto fail;
+		}
+		if (!bio_integrity_prep(bio))
+			goto fail;
+	}
+
+	rq = blk_mq_get_new_requests(q, plug, bio, nr_segs);
+	if (unlikely(!rq)) {
+fail:
+		blk_queue_exit(q);
+		return;
+	}
+
+done:
+	trace_block_getrq(bio);
+
+	rq_qos_track(q, rq, bio);
+
+	blk_mq_bio_to_request(rq, bio, nr_segs);
+
+	ret = blk_crypto_rq_get_keyslot(rq);
+	if (ret != BLK_STS_OK) {
+		bio->bi_status = ret;
+		bio_endio(bio);
+		blk_mq_free_request(rq);
+		return;
+	}
+
+	if (op_is_flush(bio->bi_opf)) {
+		blk_insert_flush(rq);
+		return;
+	}
+
+	if (plug)
+		blk_add_rq_to_plug(plug, rq);
+	else if ((rq->rq_flags & RQF_ELV) ||
+		 (rq->mq_hctx->dispatch_busy &&
+		  (q->nr_hw_queues == 1 || !is_sync)))
+		blk_mq_sched_insert_request(rq, false, true, true);
+	else
+		blk_mq_run_dispatch_ops(rq->q,
+				blk_mq_try_issue_directly(rq->mq_hctx, rq));
+}
+
+#ifdef CONFIG_BLK_MQ_STACKING
+/**
+ * blk_insert_cloned_request - Helper for stacking drivers to submit a request
+ * @rq: the request being queued
+ */
+blk_status_t blk_insert_cloned_request(struct request *rq)
+{
+	struct request_queue *q = rq->q;
+	unsigned int max_sectors = blk_queue_get_max_sectors(q, req_op(rq));
+	blk_status_t ret;
+
+	if (blk_rq_sectors(rq) > max_sectors) {
+		/*
+		 * SCSI device does not have a good way to return if
+		 * Write Same/Zero is actually supported. If a device rejects
+		 * a non-read/write command (discard, write same,etc.) the
+		 * low-level device driver will set the relevant queue limit to
+		 * 0 to prevent blk-lib from issuing more of the offending
+		 * operations. Commands queued prior to the queue limit being
+		 * reset need to be completed with BLK_STS_NOTSUPP to avoid I/O
+		 * errors being propagated to upper layers.
+		 */
+		if (max_sectors == 0)
+			return BLK_STS_NOTSUPP;
+
+		printk(KERN_ERR "%s: over max size limit. (%u > %u)\n",
+			__func__, blk_rq_sectors(rq), max_sectors);
+		return BLK_STS_IOERR;
+	}
+
+	/*
+	 * The queue settings related to segment counting may differ from the
+	 * original queue.
+	 */
+	rq->nr_phys_segments = blk_recalc_rq_segments(rq);
+	if (rq->nr_phys_segments > queue_max_segments(q)) {
+		printk(KERN_ERR "%s: over max segments limit. (%hu > %hu)\n",
+			__func__, rq->nr_phys_segments, queue_max_segments(q));
+		return BLK_STS_IOERR;
+	}
+
+	if (q->disk && should_fail_request(q->disk->part0, blk_rq_bytes(rq)))
+		return BLK_STS_IOERR;
+
+	if (blk_crypto_insert_cloned_request(rq))
+		return BLK_STS_IOERR;
+
+	blk_account_io_start(rq);
+
+	/*
+	 * Since we have a scheduler attached on the top device,
+	 * bypass a potential scheduler on the bottom device for
+	 * insert.
+	 */
+	blk_mq_run_dispatch_ops(q,
+			ret = blk_mq_request_issue_directly(rq, true));
+	if (ret)
+		blk_account_io_done(rq, ktime_get_ns());
+	return ret;
+}
+EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
+
+/**
+ * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
+ * @rq: the clone request to be cleaned up
+ *
+ * Description:
+ *     Free all bios in @rq for a cloned request.
+ */
+void blk_rq_unprep_clone(struct request *rq)
+{
+	struct bio *bio;
+
+	while ((bio = rq->bio) != NULL) {
+		rq->bio = bio->bi_next;
+
+		bio_put(bio);
+	}
+}
+EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
+
+/**
+ * blk_rq_prep_clone - Helper function to setup clone request
+ * @rq: the request to be setup
+ * @rq_src: original request to be cloned
+ * @bs: bio_set that bios for clone are allocated from
+ * @gfp_mask: memory allocation mask for bio
+ * @bio_ctr: setup function to be called for each clone bio.
+ *           Returns %0 for success, non %0 for failure.
+ * @data: private data to be passed to @bio_ctr
+ *
+ * Description:
+ *     Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
+ *     Also, pages which the original bios are pointing to are not copied
+ *     and the cloned bios just point same pages.
+ *     So cloned bios must be completed before original bios, which means
+ *     the caller must complete @rq before @rq_src.
+ */
+int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
+		      struct bio_set *bs, gfp_t gfp_mask,
+		      int (*bio_ctr)(struct bio *, struct bio *, void *),
+		      void *data)
+{
+	struct bio *bio, *bio_src;
+
+	if (!bs)
+		bs = &fs_bio_set;
+
+	__rq_for_each_bio(bio_src, rq_src) {
+		bio = bio_alloc_clone(rq->q->disk->part0, bio_src, gfp_mask,
+				      bs);
+		if (!bio)
+			goto free_and_out;
+
+		if (bio_ctr && bio_ctr(bio, bio_src, data))
+			goto free_and_out;
+
+		if (rq->bio) {
+			rq->biotail->bi_next = bio;
+			rq->biotail = bio;
+		} else {
+			rq->bio = rq->biotail = bio;
+		}
+		bio = NULL;
+	}
+
+	/* Copy attributes of the original request to the clone request. */
+	rq->__sector = blk_rq_pos(rq_src);
+	rq->__data_len = blk_rq_bytes(rq_src);
+	if (rq_src->rq_flags & RQF_SPECIAL_PAYLOAD) {
+		rq->rq_flags |= RQF_SPECIAL_PAYLOAD;
+		rq->special_vec = rq_src->special_vec;
+	}
+	rq->nr_phys_segments = rq_src->nr_phys_segments;
+	rq->ioprio = rq_src->ioprio;
+
+	if (rq->bio && blk_crypto_rq_bio_prep(rq, rq->bio, gfp_mask) < 0)
+		goto free_and_out;
+
+	return 0;
+
+free_and_out:
+	if (bio)
+		bio_put(bio);
+	blk_rq_unprep_clone(rq);
+
+	return -ENOMEM;
+}
+EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
+#endif /* CONFIG_BLK_MQ_STACKING */
+
+/*
+ * Steal bios from a request and add them to a bio list.
+ * The request must not have been partially completed before.
+ */
+void blk_steal_bios(struct bio_list *list, struct request *rq)
+{
+	if (rq->bio) {
+		if (list->tail)
+			list->tail->bi_next = rq->bio;
+		else
+			list->head = rq->bio;
+		list->tail = rq->biotail;
+
+		rq->bio = NULL;
+		rq->biotail = NULL;
+	}
+
+	rq->__data_len = 0;
+}
+EXPORT_SYMBOL_GPL(blk_steal_bios);
+
+static size_t order_to_size(unsigned int order)
+{
+	return (size_t)PAGE_SIZE << order;
+}
+
+/* called before freeing request pool in @tags */
+static void blk_mq_clear_rq_mapping(struct blk_mq_tags *drv_tags,
+				    struct blk_mq_tags *tags)
+{
+	struct page *page;
+	unsigned long flags;
+
+	/*
+	 * There is no need to clear mapping if driver tags is not initialized
+	 * or the mapping belongs to the driver tags.
+	 */
+	if (!drv_tags || drv_tags == tags)
+		return;
+
+	list_for_each_entry(page, &tags->page_list, lru) {
+		unsigned long start = (unsigned long)page_address(page);
+		unsigned long end = start + order_to_size(page->private);
+		int i;
+
+		for (i = 0; i < drv_tags->nr_tags; i++) {
+			struct request *rq = drv_tags->rqs[i];
+			unsigned long rq_addr = (unsigned long)rq;
+
+			if (rq_addr >= start && rq_addr < end) {
+				WARN_ON_ONCE(req_ref_read(rq) != 0);
+				cmpxchg(&drv_tags->rqs[i], rq, NULL);
+			}
+		}
+	}
+
+	/*
+	 * Wait until all pending iteration is done.
+	 *
+	 * Request reference is cleared and it is guaranteed to be observed
+	 * after the ->lock is released.
+	 */
+	spin_lock_irqsave(&drv_tags->lock, flags);
+	spin_unlock_irqrestore(&drv_tags->lock, flags);
+}
+
+void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
+		     unsigned int hctx_idx)
+{
+	struct blk_mq_tags *drv_tags;
+	struct page *page;
+
+	if (list_empty(&tags->page_list))
+		return;
+
+	if (blk_mq_is_shared_tags(set->flags))
+		drv_tags = set->shared_tags;
+	else
+		drv_tags = set->tags[hctx_idx];
+
+	if (tags->static_rqs && set->ops->exit_request) {
+		int i;
+
+		for (i = 0; i < tags->nr_tags; i++) {
+			struct request *rq = tags->static_rqs[i];
+
+			if (!rq)
+				continue;
+			set->ops->exit_request(set, rq, hctx_idx);
+			tags->static_rqs[i] = NULL;
+		}
+	}
+
+	blk_mq_clear_rq_mapping(drv_tags, tags);
+
+	while (!list_empty(&tags->page_list)) {
+		page = list_first_entry(&tags->page_list, struct page, lru);
+		list_del_init(&page->lru);
+		/*
+		 * Remove kmemleak object previously allocated in
+		 * blk_mq_alloc_rqs().
+		 */
+		kmemleak_free(page_address(page));
+		__free_pages(page, page->private);
+	}
+}
+
+void blk_mq_free_rq_map(struct blk_mq_tags *tags)
+{
+	kfree(tags->rqs);
+	tags->rqs = NULL;
+	kfree(tags->static_rqs);
+	tags->static_rqs = NULL;
+
+	blk_mq_free_tags(tags);
+}
+
+static enum hctx_type hctx_idx_to_type(struct blk_mq_tag_set *set,
+		unsigned int hctx_idx)
+{
+	int i;
+
+	for (i = 0; i < set->nr_maps; i++) {
+		unsigned int start = set->map[i].queue_offset;
+		unsigned int end = start + set->map[i].nr_queues;
+
+		if (hctx_idx >= start && hctx_idx < end)
+			break;
+	}
+
+	if (i >= set->nr_maps)
+		i = HCTX_TYPE_DEFAULT;
+
+	return i;
+}
+
+static int blk_mq_get_hctx_node(struct blk_mq_tag_set *set,
+		unsigned int hctx_idx)
+{
+	enum hctx_type type = hctx_idx_to_type(set, hctx_idx);
+
+	return blk_mq_hw_queue_to_node(&set->map[type], hctx_idx);
+}
+
+static struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
+					       unsigned int hctx_idx,
+					       unsigned int nr_tags,
+					       unsigned int reserved_tags)
+{
+	int node = blk_mq_get_hctx_node(set, hctx_idx);
+	struct blk_mq_tags *tags;
+
+	if (node == NUMA_NO_NODE)
+		node = set->numa_node;
+
+	tags = blk_mq_init_tags(nr_tags, reserved_tags, node,
+				BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags));
+	if (!tags)
+		return NULL;
+
+	tags->rqs = kcalloc_node(nr_tags, sizeof(struct request *),
+				 GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
+				 node);
+	if (!tags->rqs) {
+		blk_mq_free_tags(tags);
+		return NULL;
+	}
+
+	tags->static_rqs = kcalloc_node(nr_tags, sizeof(struct request *),
+					GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
+					node);
+	if (!tags->static_rqs) {
+		kfree(tags->rqs);
+		blk_mq_free_tags(tags);
+		return NULL;
+	}
+
+	return tags;
+}
+
+static int blk_mq_init_request(struct blk_mq_tag_set *set, struct request *rq,
+			       unsigned int hctx_idx, int node)
+{
+	int ret;
+
+	if (set->ops->init_request) {
+		ret = set->ops->init_request(set, rq, hctx_idx, node);
+		if (ret)
+			return ret;
+	}
+
+	WRITE_ONCE(rq->state, MQ_RQ_IDLE);
+	return 0;
+}
+
+static int blk_mq_alloc_rqs(struct blk_mq_tag_set *set,
+			    struct blk_mq_tags *tags,
+			    unsigned int hctx_idx, unsigned int depth)
+{
+	unsigned int i, j, entries_per_page, max_order = 4;
+	int node = blk_mq_get_hctx_node(set, hctx_idx);
+	size_t rq_size, left;
+
+	if (node == NUMA_NO_NODE)
+		node = set->numa_node;
+
+	INIT_LIST_HEAD(&tags->page_list);
+
+	/*
+	 * rq_size is the size of the request plus driver payload, rounded
+	 * to the cacheline size
+	 */
+	rq_size = round_up(sizeof(struct request) + set->cmd_size,
+				cache_line_size());
+	left = rq_size * depth;
+
+	for (i = 0; i < depth; ) {
+		int this_order = max_order;
+		struct page *page;
+		int to_do;
+		void *p;
+
+		while (this_order && left < order_to_size(this_order - 1))
+			this_order--;
+
+		do {
+			page = alloc_pages_node(node,
+				GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY | __GFP_ZERO,
+				this_order);
+			if (page)
+				break;
+			if (!this_order--)
+				break;
+			if (order_to_size(this_order) < rq_size)
+				break;
+		} while (1);
+
+		if (!page)
+			goto fail;
+
+		page->private = this_order;
+		list_add_tail(&page->lru, &tags->page_list);
+
+		p = page_address(page);
+		/*
+		 * Allow kmemleak to scan these pages as they contain pointers
+		 * to additional allocations like via ops->init_request().
+		 */
+		kmemleak_alloc(p, order_to_size(this_order), 1, GFP_NOIO);
+		entries_per_page = order_to_size(this_order) / rq_size;
+		to_do = min(entries_per_page, depth - i);
+		left -= to_do * rq_size;
+		for (j = 0; j < to_do; j++) {
+			struct request *rq = p;
+
+			tags->static_rqs[i] = rq;
+			if (blk_mq_init_request(set, rq, hctx_idx, node)) {
+				tags->static_rqs[i] = NULL;
+				goto fail;
+			}
+
+			p += rq_size;
+			i++;
+		}
+	}
+	return 0;
+
+fail:
+	blk_mq_free_rqs(set, tags, hctx_idx);
+	return -ENOMEM;
+}
+
+struct rq_iter_data {
+	struct blk_mq_hw_ctx *hctx;
+	bool has_rq;
+};
+
+static bool blk_mq_has_request(struct request *rq, void *data)
+{
+	struct rq_iter_data *iter_data = data;
+
+	if (rq->mq_hctx != iter_data->hctx)
+		return true;
+	iter_data->has_rq = true;
+	return false;
+}
+
+static bool blk_mq_hctx_has_requests(struct blk_mq_hw_ctx *hctx)
+{
+	struct blk_mq_tags *tags = hctx->sched_tags ?
+			hctx->sched_tags : hctx->tags;
+	struct rq_iter_data data = {
+		.hctx	= hctx,
+	};
+
+	blk_mq_all_tag_iter(tags, blk_mq_has_request, &data);
+	return data.has_rq;
+}
+
+static inline bool blk_mq_last_cpu_in_hctx(unsigned int cpu,
+		struct blk_mq_hw_ctx *hctx)
+{
+	if (cpumask_first_and(hctx->cpumask, cpu_online_mask) != cpu)
+		return false;
+	if (cpumask_next_and(cpu, hctx->cpumask, cpu_online_mask) < nr_cpu_ids)
+		return false;
+	return true;
+}
+
+static int blk_mq_hctx_notify_offline(unsigned int cpu, struct hlist_node *node)
+{
+	struct blk_mq_hw_ctx *hctx = hlist_entry_safe(node,
+			struct blk_mq_hw_ctx, cpuhp_online);
+
+	if (!cpumask_test_cpu(cpu, hctx->cpumask) ||
+	    !blk_mq_last_cpu_in_hctx(cpu, hctx))
+		return 0;
+
+	/*
+	 * Prevent new request from being allocated on the current hctx.
+	 *
+	 * The smp_mb__after_atomic() Pairs with the implied barrier in
+	 * test_and_set_bit_lock in sbitmap_get().  Ensures the inactive flag is
+	 * seen once we return from the tag allocator.
+	 */
+	set_bit(BLK_MQ_S_INACTIVE, &hctx->state);
+	smp_mb__after_atomic();
+
+	/*
+	 * Try to grab a reference to the queue and wait for any outstanding
+	 * requests.  If we could not grab a reference the queue has been
+	 * frozen and there are no requests.
+	 */
+	if (percpu_ref_tryget(&hctx->queue->q_usage_counter)) {
+		while (blk_mq_hctx_has_requests(hctx))
+			msleep(5);
+		percpu_ref_put(&hctx->queue->q_usage_counter);
+	}
+
+	return 0;
+}
+
+static int blk_mq_hctx_notify_online(unsigned int cpu, struct hlist_node *node)
+{
+	struct blk_mq_hw_ctx *hctx = hlist_entry_safe(node,
+			struct blk_mq_hw_ctx, cpuhp_online);
+
+	if (cpumask_test_cpu(cpu, hctx->cpumask))
+		clear_bit(BLK_MQ_S_INACTIVE, &hctx->state);
+	return 0;
+}
+
+/*
+ * 'cpu' is going away. splice any existing rq_list entries from this
+ * software queue to the hw queue dispatch list, and ensure that it
+ * gets run.
+ */
+static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node)
+{
+	struct blk_mq_hw_ctx *hctx;
+	struct blk_mq_ctx *ctx;
+	LIST_HEAD(tmp);
+	enum hctx_type type;
+
+	hctx = hlist_entry_safe(node, struct blk_mq_hw_ctx, cpuhp_dead);
+	if (!cpumask_test_cpu(cpu, hctx->cpumask))
+		return 0;
+
+	ctx = __blk_mq_get_ctx(hctx->queue, cpu);
+	type = hctx->type;
+
+	spin_lock(&ctx->lock);
+	if (!list_empty(&ctx->rq_lists[type])) {
+		list_splice_init(&ctx->rq_lists[type], &tmp);
+		blk_mq_hctx_clear_pending(hctx, ctx);
+	}
+	spin_unlock(&ctx->lock);
+
+	if (list_empty(&tmp))
+		return 0;
+
+	spin_lock(&hctx->lock);
+	list_splice_tail_init(&tmp, &hctx->dispatch);
+	spin_unlock(&hctx->lock);
+
+	blk_mq_run_hw_queue(hctx, true);
+	return 0;
+}
+
+static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx)
+{
+	if (!(hctx->flags & BLK_MQ_F_STACKING))
+		cpuhp_state_remove_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE,
+						    &hctx->cpuhp_online);
+	cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_DEAD,
+					    &hctx->cpuhp_dead);
+}
+
+/*
+ * Before freeing hw queue, clearing the flush request reference in
+ * tags->rqs[] for avoiding potential UAF.
+ */
+static void blk_mq_clear_flush_rq_mapping(struct blk_mq_tags *tags,
+		unsigned int queue_depth, struct request *flush_rq)
+{
+	int i;
+	unsigned long flags;
+
+	/* The hw queue may not be mapped yet */
+	if (!tags)
+		return;
+
+	WARN_ON_ONCE(req_ref_read(flush_rq) != 0);
+
+	for (i = 0; i < queue_depth; i++)
+		cmpxchg(&tags->rqs[i], flush_rq, NULL);
+
+	/*
+	 * Wait until all pending iteration is done.
+	 *
+	 * Request reference is cleared and it is guaranteed to be observed
+	 * after the ->lock is released.
+	 */
+	spin_lock_irqsave(&tags->lock, flags);
+	spin_unlock_irqrestore(&tags->lock, flags);
+}
+
+/* hctx->ctxs will be freed in queue's release handler */
+static void blk_mq_exit_hctx(struct request_queue *q,
+		struct blk_mq_tag_set *set,
+		struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
+{
+	struct request *flush_rq = hctx->fq->flush_rq;
+
+	if (blk_mq_hw_queue_mapped(hctx))
+		blk_mq_tag_idle(hctx);
+
+	if (blk_queue_init_done(q))
+		blk_mq_clear_flush_rq_mapping(set->tags[hctx_idx],
+				set->queue_depth, flush_rq);
+	if (set->ops->exit_request)
+		set->ops->exit_request(set, flush_rq, hctx_idx);
+
+	if (set->ops->exit_hctx)
+		set->ops->exit_hctx(hctx, hctx_idx);
+
+	blk_mq_remove_cpuhp(hctx);
+
+	xa_erase(&q->hctx_table, hctx_idx);
+
+	spin_lock(&q->unused_hctx_lock);
+	list_add(&hctx->hctx_list, &q->unused_hctx_list);
+	spin_unlock(&q->unused_hctx_lock);
+}
+
+static void blk_mq_exit_hw_queues(struct request_queue *q,
+		struct blk_mq_tag_set *set, int nr_queue)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned long i;
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (i == nr_queue)
+			break;
+		blk_mq_exit_hctx(q, set, hctx, i);
+	}
+}
+
+static int blk_mq_init_hctx(struct request_queue *q,
+		struct blk_mq_tag_set *set,
+		struct blk_mq_hw_ctx *hctx, unsigned hctx_idx)
+{
+	hctx->queue_num = hctx_idx;
+
+	if (!(hctx->flags & BLK_MQ_F_STACKING))
+		cpuhp_state_add_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE,
+				&hctx->cpuhp_online);
+	cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD, &hctx->cpuhp_dead);
+
+	hctx->tags = set->tags[hctx_idx];
+
+	if (set->ops->init_hctx &&
+	    set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
+		goto unregister_cpu_notifier;
+
+	if (blk_mq_init_request(set, hctx->fq->flush_rq, hctx_idx,
+				hctx->numa_node))
+		goto exit_hctx;
+
+	if (xa_insert(&q->hctx_table, hctx_idx, hctx, GFP_KERNEL))
+		goto exit_flush_rq;
+
+	return 0;
+
+ exit_flush_rq:
+	if (set->ops->exit_request)
+		set->ops->exit_request(set, hctx->fq->flush_rq, hctx_idx);
+ exit_hctx:
+	if (set->ops->exit_hctx)
+		set->ops->exit_hctx(hctx, hctx_idx);
+ unregister_cpu_notifier:
+	blk_mq_remove_cpuhp(hctx);
+	return -1;
+}
+
+static struct blk_mq_hw_ctx *
+blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set,
+		int node)
+{
+	struct blk_mq_hw_ctx *hctx;
+	gfp_t gfp = GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY;
+
+	hctx = kzalloc_node(sizeof(struct blk_mq_hw_ctx), gfp, node);
+	if (!hctx)
+		goto fail_alloc_hctx;
+
+	if (!zalloc_cpumask_var_node(&hctx->cpumask, gfp, node))
+		goto free_hctx;
+
+	atomic_set(&hctx->nr_active, 0);
+	if (node == NUMA_NO_NODE)
+		node = set->numa_node;
+	hctx->numa_node = node;
+
+	INIT_DELAYED_WORK(&hctx->run_work, blk_mq_run_work_fn);
+	spin_lock_init(&hctx->lock);
+	INIT_LIST_HEAD(&hctx->dispatch);
+	hctx->queue = q;
+	hctx->flags = set->flags & ~BLK_MQ_F_TAG_QUEUE_SHARED;
+
+	INIT_LIST_HEAD(&hctx->hctx_list);
+
+	/*
+	 * Allocate space for all possible cpus to avoid allocation at
+	 * runtime
+	 */
+	hctx->ctxs = kmalloc_array_node(nr_cpu_ids, sizeof(void *),
+			gfp, node);
+	if (!hctx->ctxs)
+		goto free_cpumask;
+
+	if (sbitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8),
+				gfp, node, false, false))
+		goto free_ctxs;
+	hctx->nr_ctx = 0;
+
+	spin_lock_init(&hctx->dispatch_wait_lock);
+	init_waitqueue_func_entry(&hctx->dispatch_wait, blk_mq_dispatch_wake);
+	INIT_LIST_HEAD(&hctx->dispatch_wait.entry);
+
+	hctx->fq = blk_alloc_flush_queue(hctx->numa_node, set->cmd_size, gfp);
+	if (!hctx->fq)
+		goto free_bitmap;
+
+	blk_mq_hctx_kobj_init(hctx);
+
+	return hctx;
+
+ free_bitmap:
+	sbitmap_free(&hctx->ctx_map);
+ free_ctxs:
+	kfree(hctx->ctxs);
+ free_cpumask:
+	free_cpumask_var(hctx->cpumask);
+ free_hctx:
+	kfree(hctx);
+ fail_alloc_hctx:
+	return NULL;
+}
+
+static void blk_mq_init_cpu_queues(struct request_queue *q,
+				   unsigned int nr_hw_queues)
+{
+	struct blk_mq_tag_set *set = q->tag_set;
+	unsigned int i, j;
+
+	for_each_possible_cpu(i) {
+		struct blk_mq_ctx *__ctx = per_cpu_ptr(q->queue_ctx, i);
+		struct blk_mq_hw_ctx *hctx;
+		int k;
+
+		__ctx->cpu = i;
+		spin_lock_init(&__ctx->lock);
+		for (k = HCTX_TYPE_DEFAULT; k < HCTX_MAX_TYPES; k++)
+			INIT_LIST_HEAD(&__ctx->rq_lists[k]);
+
+		__ctx->queue = q;
+
+		/*
+		 * Set local node, IFF we have more than one hw queue. If
+		 * not, we remain on the home node of the device
+		 */
+		for (j = 0; j < set->nr_maps; j++) {
+			hctx = blk_mq_map_queue_type(q, j, i);
+			if (nr_hw_queues > 1 && hctx->numa_node == NUMA_NO_NODE)
+				hctx->numa_node = cpu_to_node(i);
+		}
+	}
+}
+
+struct blk_mq_tags *blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
+					     unsigned int hctx_idx,
+					     unsigned int depth)
+{
+	struct blk_mq_tags *tags;
+	int ret;
+
+	tags = blk_mq_alloc_rq_map(set, hctx_idx, depth, set->reserved_tags);
+	if (!tags)
+		return NULL;
+
+	ret = blk_mq_alloc_rqs(set, tags, hctx_idx, depth);
+	if (ret) {
+		blk_mq_free_rq_map(tags);
+		return NULL;
+	}
+
+	return tags;
+}
+
+static bool __blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set,
+				       int hctx_idx)
+{
+	if (blk_mq_is_shared_tags(set->flags)) {
+		set->tags[hctx_idx] = set->shared_tags;
+
+		return true;
+	}
+
+	set->tags[hctx_idx] = blk_mq_alloc_map_and_rqs(set, hctx_idx,
+						       set->queue_depth);
+
+	return set->tags[hctx_idx];
+}
+
+void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
+			     struct blk_mq_tags *tags,
+			     unsigned int hctx_idx)
+{
+	if (tags) {
+		blk_mq_free_rqs(set, tags, hctx_idx);
+		blk_mq_free_rq_map(tags);
+	}
+}
+
+static void __blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,
+				      unsigned int hctx_idx)
+{
+	if (!blk_mq_is_shared_tags(set->flags))
+		blk_mq_free_map_and_rqs(set, set->tags[hctx_idx], hctx_idx);
+
+	set->tags[hctx_idx] = NULL;
+}
+
+static void blk_mq_map_swqueue(struct request_queue *q)
+{
+	unsigned int j, hctx_idx;
+	unsigned long i;
+	struct blk_mq_hw_ctx *hctx;
+	struct blk_mq_ctx *ctx;
+	struct blk_mq_tag_set *set = q->tag_set;
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		cpumask_clear(hctx->cpumask);
+		hctx->nr_ctx = 0;
+		hctx->dispatch_from = NULL;
+	}
+
+	/*
+	 * Map software to hardware queues.
+	 *
+	 * If the cpu isn't present, the cpu is mapped to first hctx.
+	 */
+	for_each_possible_cpu(i) {
+
+		ctx = per_cpu_ptr(q->queue_ctx, i);
+		for (j = 0; j < set->nr_maps; j++) {
+			if (!set->map[j].nr_queues) {
+				ctx->hctxs[j] = blk_mq_map_queue_type(q,
+						HCTX_TYPE_DEFAULT, i);
+				continue;
+			}
+			hctx_idx = set->map[j].mq_map[i];
+			/* unmapped hw queue can be remapped after CPU topo changed */
+			if (!set->tags[hctx_idx] &&
+			    !__blk_mq_alloc_map_and_rqs(set, hctx_idx)) {
+				/*
+				 * If tags initialization fail for some hctx,
+				 * that hctx won't be brought online.  In this
+				 * case, remap the current ctx to hctx[0] which
+				 * is guaranteed to always have tags allocated
+				 */
+				set->map[j].mq_map[i] = 0;
+			}
+
+			hctx = blk_mq_map_queue_type(q, j, i);
+			ctx->hctxs[j] = hctx;
+			/*
+			 * If the CPU is already set in the mask, then we've
+			 * mapped this one already. This can happen if
+			 * devices share queues across queue maps.
+			 */
+			if (cpumask_test_cpu(i, hctx->cpumask))
+				continue;
+
+			cpumask_set_cpu(i, hctx->cpumask);
+			hctx->type = j;
+			ctx->index_hw[hctx->type] = hctx->nr_ctx;
+			hctx->ctxs[hctx->nr_ctx++] = ctx;
+
+			/*
+			 * If the nr_ctx type overflows, we have exceeded the
+			 * amount of sw queues we can support.
+			 */
+			BUG_ON(!hctx->nr_ctx);
+		}
+
+		for (; j < HCTX_MAX_TYPES; j++)
+			ctx->hctxs[j] = blk_mq_map_queue_type(q,
+					HCTX_TYPE_DEFAULT, i);
+	}
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		/*
+		 * If no software queues are mapped to this hardware queue,
+		 * disable it and free the request entries.
+		 */
+		if (!hctx->nr_ctx) {
+			/* Never unmap queue 0.  We need it as a
+			 * fallback in case of a new remap fails
+			 * allocation
+			 */
+			if (i)
+				__blk_mq_free_map_and_rqs(set, i);
+
+			hctx->tags = NULL;
+			continue;
+		}
+
+		hctx->tags = set->tags[i];
+		WARN_ON(!hctx->tags);
+
+		/*
+		 * Set the map size to the number of mapped software queues.
+		 * This is more accurate and more efficient than looping
+		 * over all possibly mapped software queues.
+		 */
+		sbitmap_resize(&hctx->ctx_map, hctx->nr_ctx);
+
+		/*
+		 * Initialize batch roundrobin counts
+		 */
+		hctx->next_cpu = blk_mq_first_mapped_cpu(hctx);
+		hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
+	}
+}
+
+/*
+ * Caller needs to ensure that we're either frozen/quiesced, or that
+ * the queue isn't live yet.
+ */
+static void queue_set_hctx_shared(struct request_queue *q, bool shared)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned long i;
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (shared) {
+			hctx->flags |= BLK_MQ_F_TAG_QUEUE_SHARED;
+		} else {
+			blk_mq_tag_idle(hctx);
+			hctx->flags &= ~BLK_MQ_F_TAG_QUEUE_SHARED;
+		}
+	}
+}
+
+static void blk_mq_update_tag_set_shared(struct blk_mq_tag_set *set,
+					 bool shared)
+{
+	struct request_queue *q;
+
+	lockdep_assert_held(&set->tag_list_lock);
+
+	list_for_each_entry(q, &set->tag_list, tag_set_list) {
+		blk_mq_freeze_queue(q);
+		queue_set_hctx_shared(q, shared);
+		blk_mq_unfreeze_queue(q);
+	}
+}
+
+static void blk_mq_del_queue_tag_set(struct request_queue *q)
+{
+	struct blk_mq_tag_set *set = q->tag_set;
+
+	mutex_lock(&set->tag_list_lock);
+	list_del(&q->tag_set_list);
+	if (list_is_singular(&set->tag_list)) {
+		/* just transitioned to unshared */
+		set->flags &= ~BLK_MQ_F_TAG_QUEUE_SHARED;
+		/* update existing queue */
+		blk_mq_update_tag_set_shared(set, false);
+	}
+	mutex_unlock(&set->tag_list_lock);
+	INIT_LIST_HEAD(&q->tag_set_list);
+}
+
+static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
+				     struct request_queue *q)
+{
+	mutex_lock(&set->tag_list_lock);
+
+	/*
+	 * Check to see if we're transitioning to shared (from 1 to 2 queues).
+	 */
+	if (!list_empty(&set->tag_list) &&
+	    !(set->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) {
+		set->flags |= BLK_MQ_F_TAG_QUEUE_SHARED;
+		/* update existing queue */
+		blk_mq_update_tag_set_shared(set, true);
+	}
+	if (set->flags & BLK_MQ_F_TAG_QUEUE_SHARED)
+		queue_set_hctx_shared(q, true);
+	list_add_tail(&q->tag_set_list, &set->tag_list);
+
+	mutex_unlock(&set->tag_list_lock);
+}
+
+/* All allocations will be freed in release handler of q->mq_kobj */
+static int blk_mq_alloc_ctxs(struct request_queue *q)
+{
+	struct blk_mq_ctxs *ctxs;
+	int cpu;
+
+	ctxs = kzalloc(sizeof(*ctxs), GFP_KERNEL);
+	if (!ctxs)
+		return -ENOMEM;
+
+	ctxs->queue_ctx = alloc_percpu(struct blk_mq_ctx);
+	if (!ctxs->queue_ctx)
+		goto fail;
+
+	for_each_possible_cpu(cpu) {
+		struct blk_mq_ctx *ctx = per_cpu_ptr(ctxs->queue_ctx, cpu);
+		ctx->ctxs = ctxs;
+	}
+
+	q->mq_kobj = &ctxs->kobj;
+	q->queue_ctx = ctxs->queue_ctx;
+
+	return 0;
+ fail:
+	kfree(ctxs);
+	return -ENOMEM;
+}
+
+/*
+ * It is the actual release handler for mq, but we do it from
+ * request queue's release handler for avoiding use-after-free
+ * and headache because q->mq_kobj shouldn't have been introduced,
+ * but we can't group ctx/kctx kobj without it.
+ */
+void blk_mq_release(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx, *next;
+	unsigned long i;
+
+	queue_for_each_hw_ctx(q, hctx, i)
+		WARN_ON_ONCE(hctx && list_empty(&hctx->hctx_list));
+
+	/* all hctx are in .unused_hctx_list now */
+	list_for_each_entry_safe(hctx, next, &q->unused_hctx_list, hctx_list) {
+		list_del_init(&hctx->hctx_list);
+		kobject_put(&hctx->kobj);
+	}
+
+	xa_destroy(&q->hctx_table);
+
+	/*
+	 * release .mq_kobj and sw queue's kobject now because
+	 * both share lifetime with request queue.
+	 */
+	blk_mq_sysfs_deinit(q);
+}
+
+static struct request_queue *blk_mq_init_queue_data(struct blk_mq_tag_set *set,
+		void *queuedata)
+{
+	struct request_queue *q;
+	int ret;
+
+	q = blk_alloc_queue(set->numa_node, set->flags & BLK_MQ_F_BLOCKING);
+	if (!q)
+		return ERR_PTR(-ENOMEM);
+	q->queuedata = queuedata;
+	ret = blk_mq_init_allocated_queue(set, q);
+	if (ret) {
+		blk_put_queue(q);
+		return ERR_PTR(ret);
+	}
+	return q;
+}
+
+struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
+{
+	return blk_mq_init_queue_data(set, NULL);
+}
+EXPORT_SYMBOL(blk_mq_init_queue);
+
+/**
+ * blk_mq_destroy_queue - shutdown a request queue
+ * @q: request queue to shutdown
+ *
+ * This shuts down a request queue allocated by blk_mq_init_queue() and drops
+ * the initial reference.  All future requests will failed with -ENODEV.
+ *
+ * Context: can sleep
+ */
+void blk_mq_destroy_queue(struct request_queue *q)
+{
+	WARN_ON_ONCE(!queue_is_mq(q));
+	WARN_ON_ONCE(blk_queue_registered(q));
+
+	might_sleep();
+
+	blk_queue_flag_set(QUEUE_FLAG_DYING, q);
+	blk_queue_start_drain(q);
+	blk_freeze_queue(q);
+
+	blk_sync_queue(q);
+	blk_mq_cancel_work_sync(q);
+	blk_mq_exit_queue(q);
+
+	/* @q is and will stay empty, shutdown and put */
+	blk_put_queue(q);
+}
+EXPORT_SYMBOL(blk_mq_destroy_queue);
+
+struct gendisk *__blk_mq_alloc_disk(struct blk_mq_tag_set *set, void *queuedata,
+		struct lock_class_key *lkclass)
+{
+	struct request_queue *q;
+	struct gendisk *disk;
+
+	q = blk_mq_init_queue_data(set, queuedata);
+	if (IS_ERR(q))
+		return ERR_CAST(q);
+
+	disk = __alloc_disk_node(q, set->numa_node, lkclass);
+	if (!disk) {
+		blk_mq_destroy_queue(q);
+		return ERR_PTR(-ENOMEM);
+	}
+	set_bit(GD_OWNS_QUEUE, &disk->state);
+	return disk;
+}
+EXPORT_SYMBOL(__blk_mq_alloc_disk);
+
+struct gendisk *blk_mq_alloc_disk_for_queue(struct request_queue *q,
+		struct lock_class_key *lkclass)
+{
+	struct gendisk *disk;
+
+	if (!blk_get_queue(q))
+		return NULL;
+	disk = __alloc_disk_node(q, NUMA_NO_NODE, lkclass);
+	if (!disk)
+		blk_put_queue(q);
+	return disk;
+}
+EXPORT_SYMBOL(blk_mq_alloc_disk_for_queue);
+
+static struct blk_mq_hw_ctx *blk_mq_alloc_and_init_hctx(
+		struct blk_mq_tag_set *set, struct request_queue *q,
+		int hctx_idx, int node)
+{
+	struct blk_mq_hw_ctx *hctx = NULL, *tmp;
+
+	/* reuse dead hctx first */
+	spin_lock(&q->unused_hctx_lock);
+	list_for_each_entry(tmp, &q->unused_hctx_list, hctx_list) {
+		if (tmp->numa_node == node) {
+			hctx = tmp;
+			break;
+		}
+	}
+	if (hctx)
+		list_del_init(&hctx->hctx_list);
+	spin_unlock(&q->unused_hctx_lock);
+
+	if (!hctx)
+		hctx = blk_mq_alloc_hctx(q, set, node);
+	if (!hctx)
+		goto fail;
+
+	if (blk_mq_init_hctx(q, set, hctx, hctx_idx))
+		goto free_hctx;
+
+	return hctx;
+
+ free_hctx:
+	kobject_put(&hctx->kobj);
+ fail:
+	return NULL;
+}
+
+static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
+						struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned long i, j;
+
+	/* protect against switching io scheduler  */
+	mutex_lock(&q->sysfs_lock);
+	for (i = 0; i < set->nr_hw_queues; i++) {
+		int old_node;
+		int node = blk_mq_get_hctx_node(set, i);
+		struct blk_mq_hw_ctx *old_hctx = xa_load(&q->hctx_table, i);
+
+		if (old_hctx) {
+			old_node = old_hctx->numa_node;
+			blk_mq_exit_hctx(q, set, old_hctx, i);
+		}
+
+		if (!blk_mq_alloc_and_init_hctx(set, q, i, node)) {
+			if (!old_hctx)
+				break;
+			pr_warn("Allocate new hctx on node %d fails, fallback to previous one on node %d\n",
+					node, old_node);
+			hctx = blk_mq_alloc_and_init_hctx(set, q, i, old_node);
+			WARN_ON_ONCE(!hctx);
+		}
+	}
+	/*
+	 * Increasing nr_hw_queues fails. Free the newly allocated
+	 * hctxs and keep the previous q->nr_hw_queues.
+	 */
+	if (i != set->nr_hw_queues) {
+		j = q->nr_hw_queues;
+	} else {
+		j = i;
+		q->nr_hw_queues = set->nr_hw_queues;
+	}
+
+	xa_for_each_start(&q->hctx_table, j, hctx, j)
+		blk_mq_exit_hctx(q, set, hctx, j);
+	mutex_unlock(&q->sysfs_lock);
+}
+
+static void blk_mq_update_poll_flag(struct request_queue *q)
+{
+	struct blk_mq_tag_set *set = q->tag_set;
+
+	if (set->nr_maps > HCTX_TYPE_POLL &&
+	    set->map[HCTX_TYPE_POLL].nr_queues)
+		blk_queue_flag_set(QUEUE_FLAG_POLL, q);
+	else
+		blk_queue_flag_clear(QUEUE_FLAG_POLL, q);
+}
+
+int blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
+		struct request_queue *q)
+{
+	WARN_ON_ONCE(blk_queue_has_srcu(q) !=
+			!!(set->flags & BLK_MQ_F_BLOCKING));
+
+	/* mark the queue as mq asap */
+	q->mq_ops = set->ops;
+
+	q->poll_cb = blk_stat_alloc_callback(blk_mq_poll_stats_fn,
+					     blk_mq_poll_stats_bkt,
+					     BLK_MQ_POLL_STATS_BKTS, q);
+	if (!q->poll_cb)
+		goto err_exit;
+
+	if (blk_mq_alloc_ctxs(q))
+		goto err_poll;
+
+	/* init q->mq_kobj and sw queues' kobjects */
+	blk_mq_sysfs_init(q);
+
+	INIT_LIST_HEAD(&q->unused_hctx_list);
+	spin_lock_init(&q->unused_hctx_lock);
+
+	xa_init(&q->hctx_table);
+
+	blk_mq_realloc_hw_ctxs(set, q);
+	if (!q->nr_hw_queues)
+		goto err_hctxs;
+
+	INIT_WORK(&q->timeout_work, blk_mq_timeout_work);
+	blk_queue_rq_timeout(q, set->timeout ? set->timeout : 30 * HZ);
+
+	q->tag_set = set;
+
+	q->queue_flags |= QUEUE_FLAG_MQ_DEFAULT;
+	blk_mq_update_poll_flag(q);
+
+	INIT_DELAYED_WORK(&q->requeue_work, blk_mq_requeue_work);
+	INIT_LIST_HEAD(&q->requeue_list);
+	spin_lock_init(&q->requeue_lock);
+
+	q->nr_requests = set->queue_depth;
+
+	/*
+	 * Default to classic polling
+	 */
+	q->poll_nsec = BLK_MQ_POLL_CLASSIC;
+
+	blk_mq_init_cpu_queues(q, set->nr_hw_queues);
+	blk_mq_add_queue_tag_set(set, q);
+	blk_mq_map_swqueue(q);
+	return 0;
+
+err_hctxs:
+	blk_mq_release(q);
+err_poll:
+	blk_stat_free_callback(q->poll_cb);
+	q->poll_cb = NULL;
+err_exit:
+	q->mq_ops = NULL;
+	return -ENOMEM;
+}
+EXPORT_SYMBOL(blk_mq_init_allocated_queue);
+
+/* tags can _not_ be used after returning from blk_mq_exit_queue */
+void blk_mq_exit_queue(struct request_queue *q)
+{
+	struct blk_mq_tag_set *set = q->tag_set;
+
+	/* Checks hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED. */
+	blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);
+	/* May clear BLK_MQ_F_TAG_QUEUE_SHARED in hctx->flags. */
+	blk_mq_del_queue_tag_set(q);
+}
+
+static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
+{
+	int i;
+
+	if (blk_mq_is_shared_tags(set->flags)) {
+		set->shared_tags = blk_mq_alloc_map_and_rqs(set,
+						BLK_MQ_NO_HCTX_IDX,
+						set->queue_depth);
+		if (!set->shared_tags)
+			return -ENOMEM;
+	}
+
+	for (i = 0; i < set->nr_hw_queues; i++) {
+		if (!__blk_mq_alloc_map_and_rqs(set, i))
+			goto out_unwind;
+		cond_resched();
+	}
+
+	return 0;
+
+out_unwind:
+	while (--i >= 0)
+		__blk_mq_free_map_and_rqs(set, i);
+
+	if (blk_mq_is_shared_tags(set->flags)) {
+		blk_mq_free_map_and_rqs(set, set->shared_tags,
+					BLK_MQ_NO_HCTX_IDX);
+	}
+
+	return -ENOMEM;
+}
+
+/*
+ * Allocate the request maps associated with this tag_set. Note that this
+ * may reduce the depth asked for, if memory is tight. set->queue_depth
+ * will be updated to reflect the allocated depth.
+ */
+static int blk_mq_alloc_set_map_and_rqs(struct blk_mq_tag_set *set)
+{
+	unsigned int depth;
+	int err;
+
+	depth = set->queue_depth;
+	do {
+		err = __blk_mq_alloc_rq_maps(set);
+		if (!err)
+			break;
+
+		set->queue_depth >>= 1;
+		if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN) {
+			err = -ENOMEM;
+			break;
+		}
+	} while (set->queue_depth);
+
+	if (!set->queue_depth || err) {
+		pr_err("blk-mq: failed to allocate request map\n");
+		return -ENOMEM;
+	}
+
+	if (depth != set->queue_depth)
+		pr_info("blk-mq: reduced tag depth (%u -> %u)\n",
+						depth, set->queue_depth);
+
+	return 0;
+}
+
+static void blk_mq_update_queue_map(struct blk_mq_tag_set *set)
+{
+	/*
+	 * blk_mq_map_queues() and multiple .map_queues() implementations
+	 * expect that set->map[HCTX_TYPE_DEFAULT].nr_queues is set to the
+	 * number of hardware queues.
+	 */
+	if (set->nr_maps == 1)
+		set->map[HCTX_TYPE_DEFAULT].nr_queues = set->nr_hw_queues;
+
+	if (set->ops->map_queues && !is_kdump_kernel()) {
+		int i;
+
+		/*
+		 * transport .map_queues is usually done in the following
+		 * way:
+		 *
+		 * for (queue = 0; queue < set->nr_hw_queues; queue++) {
+		 * 	mask = get_cpu_mask(queue)
+		 * 	for_each_cpu(cpu, mask)
+		 * 		set->map[x].mq_map[cpu] = queue;
+		 * }
+		 *
+		 * When we need to remap, the table has to be cleared for
+		 * killing stale mapping since one CPU may not be mapped
+		 * to any hw queue.
+		 */
+		for (i = 0; i < set->nr_maps; i++)
+			blk_mq_clear_mq_map(&set->map[i]);
+
+		set->ops->map_queues(set);
+	} else {
+		BUG_ON(set->nr_maps > 1);
+		blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
+	}
+}
+
+static int blk_mq_realloc_tag_set_tags(struct blk_mq_tag_set *set,
+				  int cur_nr_hw_queues, int new_nr_hw_queues)
+{
+	struct blk_mq_tags **new_tags;
+
+	if (cur_nr_hw_queues >= new_nr_hw_queues)
+		return 0;
+
+	new_tags = kcalloc_node(new_nr_hw_queues, sizeof(struct blk_mq_tags *),
+				GFP_KERNEL, set->numa_node);
+	if (!new_tags)
+		return -ENOMEM;
+
+	if (set->tags)
+		memcpy(new_tags, set->tags, cur_nr_hw_queues *
+		       sizeof(*set->tags));
+	kfree(set->tags);
+	set->tags = new_tags;
+	set->nr_hw_queues = new_nr_hw_queues;
+
+	return 0;
+}
+
+static int blk_mq_alloc_tag_set_tags(struct blk_mq_tag_set *set,
+				int new_nr_hw_queues)
+{
+	return blk_mq_realloc_tag_set_tags(set, 0, new_nr_hw_queues);
+}
+
+/*
+ * Alloc a tag set to be associated with one or more request queues.
+ * May fail with EINVAL for various error conditions. May adjust the
+ * requested depth down, if it's too large. In that case, the set
+ * value will be stored in set->queue_depth.
+ */
+int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
+{
+	int i, ret;
+
+	BUILD_BUG_ON(BLK_MQ_MAX_DEPTH > 1 << BLK_MQ_UNIQUE_TAG_BITS);
+
+	if (!set->nr_hw_queues)
+		return -EINVAL;
+	if (!set->queue_depth)
+		return -EINVAL;
+	if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN)
+		return -EINVAL;
+
+	if (!set->ops->queue_rq)
+		return -EINVAL;
+
+	if (!set->ops->get_budget ^ !set->ops->put_budget)
+		return -EINVAL;
+
+	if (set->queue_depth > BLK_MQ_MAX_DEPTH) {
+		pr_info("blk-mq: reduced tag depth to %u\n",
+			BLK_MQ_MAX_DEPTH);
+		set->queue_depth = BLK_MQ_MAX_DEPTH;
+	}
+
+	if (!set->nr_maps)
+		set->nr_maps = 1;
+	else if (set->nr_maps > HCTX_MAX_TYPES)
+		return -EINVAL;
+
+	/*
+	 * If a crashdump is active, then we are potentially in a very
+	 * memory constrained environment. Limit us to 1 queue and
+	 * 64 tags to prevent using too much memory.
+	 */
+	if (is_kdump_kernel()) {
+		set->nr_hw_queues = 1;
+		set->nr_maps = 1;
+		set->queue_depth = min(64U, set->queue_depth);
+	}
+	/*
+	 * There is no use for more h/w queues than cpus if we just have
+	 * a single map
+	 */
+	if (set->nr_maps == 1 && set->nr_hw_queues > nr_cpu_ids)
+		set->nr_hw_queues = nr_cpu_ids;
+
+	if (blk_mq_alloc_tag_set_tags(set, set->nr_hw_queues) < 0)
+		return -ENOMEM;
+
+	ret = -ENOMEM;
+	for (i = 0; i < set->nr_maps; i++) {
+		set->map[i].mq_map = kcalloc_node(nr_cpu_ids,
+						  sizeof(set->map[i].mq_map[0]),
+						  GFP_KERNEL, set->numa_node);
+		if (!set->map[i].mq_map)
+			goto out_free_mq_map;
+		set->map[i].nr_queues = is_kdump_kernel() ? 1 : set->nr_hw_queues;
+	}
+
+	blk_mq_update_queue_map(set);
+
+	ret = blk_mq_alloc_set_map_and_rqs(set);
+	if (ret)
+		goto out_free_mq_map;
+
+	mutex_init(&set->tag_list_lock);
+	INIT_LIST_HEAD(&set->tag_list);
+
+	return 0;
+
+out_free_mq_map:
+	for (i = 0; i < set->nr_maps; i++) {
+		kfree(set->map[i].mq_map);
+		set->map[i].mq_map = NULL;
+	}
+	kfree(set->tags);
+	set->tags = NULL;
+	return ret;
+}
+EXPORT_SYMBOL(blk_mq_alloc_tag_set);
+
+/* allocate and initialize a tagset for a simple single-queue device */
+int blk_mq_alloc_sq_tag_set(struct blk_mq_tag_set *set,
+		const struct blk_mq_ops *ops, unsigned int queue_depth,
+		unsigned int set_flags)
+{
+	memset(set, 0, sizeof(*set));
+	set->ops = ops;
+	set->nr_hw_queues = 1;
+	set->nr_maps = 1;
+	set->queue_depth = queue_depth;
+	set->numa_node = NUMA_NO_NODE;
+	set->flags = set_flags;
+	return blk_mq_alloc_tag_set(set);
+}
+EXPORT_SYMBOL_GPL(blk_mq_alloc_sq_tag_set);
+
+void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
+{
+	int i, j;
+
+	for (i = 0; i < set->nr_hw_queues; i++)
+		__blk_mq_free_map_and_rqs(set, i);
+
+	if (blk_mq_is_shared_tags(set->flags)) {
+		blk_mq_free_map_and_rqs(set, set->shared_tags,
+					BLK_MQ_NO_HCTX_IDX);
+	}
+
+	for (j = 0; j < set->nr_maps; j++) {
+		kfree(set->map[j].mq_map);
+		set->map[j].mq_map = NULL;
+	}
+
+	kfree(set->tags);
+	set->tags = NULL;
+}
+EXPORT_SYMBOL(blk_mq_free_tag_set);
+
+int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
+{
+	struct blk_mq_tag_set *set = q->tag_set;
+	struct blk_mq_hw_ctx *hctx;
+	int ret;
+	unsigned long i;
+
+	if (!set)
+		return -EINVAL;
+
+	if (q->nr_requests == nr)
+		return 0;
+
+	blk_mq_freeze_queue(q);
+	blk_mq_quiesce_queue(q);
+
+	ret = 0;
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (!hctx->tags)
+			continue;
+		/*
+		 * If we're using an MQ scheduler, just update the scheduler
+		 * queue depth. This is similar to what the old code would do.
+		 */
+		if (hctx->sched_tags) {
+			ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
+						      nr, true);
+		} else {
+			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
+						      false);
+		}
+		if (ret)
+			break;
+		if (q->elevator && q->elevator->type->ops.depth_updated)
+			q->elevator->type->ops.depth_updated(hctx);
+	}
+	if (!ret) {
+		q->nr_requests = nr;
+		if (blk_mq_is_shared_tags(set->flags)) {
+			if (q->elevator)
+				blk_mq_tag_update_sched_shared_tags(q);
+			else
+				blk_mq_tag_resize_shared_tags(set, nr);
+		}
+	}
+
+	blk_mq_unquiesce_queue(q);
+	blk_mq_unfreeze_queue(q);
+
+	return ret;
+}
+
+/*
+ * request_queue and elevator_type pair.
+ * It is just used by __blk_mq_update_nr_hw_queues to cache
+ * the elevator_type associated with a request_queue.
+ */
+struct blk_mq_qe_pair {
+	struct list_head node;
+	struct request_queue *q;
+	struct elevator_type *type;
+};
+
+/*
+ * Cache the elevator_type in qe pair list and switch the
+ * io scheduler to 'none'
+ */
+static bool blk_mq_elv_switch_none(struct list_head *head,
+		struct request_queue *q)
+{
+	struct blk_mq_qe_pair *qe;
+
+	if (!q->elevator)
+		return true;
+
+	qe = kmalloc(sizeof(*qe), GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY);
+	if (!qe)
+		return false;
+
+	/* q->elevator needs protection from ->sysfs_lock */
+	mutex_lock(&q->sysfs_lock);
+
+	INIT_LIST_HEAD(&qe->node);
+	qe->q = q;
+	qe->type = q->elevator->type;
+	list_add(&qe->node, head);
+
+	/*
+	 * After elevator_switch, the previous elevator_queue will be
+	 * released by elevator_release. The reference of the io scheduler
+	 * module get by elevator_get will also be put. So we need to get
+	 * a reference of the io scheduler module here to prevent it to be
+	 * removed.
+	 */
+	__module_get(qe->type->elevator_owner);
+	elevator_switch(q, NULL);
+	mutex_unlock(&q->sysfs_lock);
+
+	return true;
+}
+
+static struct blk_mq_qe_pair *blk_lookup_qe_pair(struct list_head *head,
+						struct request_queue *q)
+{
+	struct blk_mq_qe_pair *qe;
+
+	list_for_each_entry(qe, head, node)
+		if (qe->q == q)
+			return qe;
+
+	return NULL;
+}
+
+static void blk_mq_elv_switch_back(struct list_head *head,
+				  struct request_queue *q)
+{
+	struct blk_mq_qe_pair *qe;
+	struct elevator_type *t;
+
+	qe = blk_lookup_qe_pair(head, q);
+	if (!qe)
+		return;
+	t = qe->type;
+	list_del(&qe->node);
+	kfree(qe);
+
+	mutex_lock(&q->sysfs_lock);
+	elevator_switch(q, t);
+	mutex_unlock(&q->sysfs_lock);
+}
+
+static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
+							int nr_hw_queues)
+{
+	struct request_queue *q;
+	LIST_HEAD(head);
+	int prev_nr_hw_queues;
+
+	lockdep_assert_held(&set->tag_list_lock);
+
+	if (set->nr_maps == 1 && nr_hw_queues > nr_cpu_ids)
+		nr_hw_queues = nr_cpu_ids;
+	if (nr_hw_queues < 1)
+		return;
+	if (set->nr_maps == 1 && nr_hw_queues == set->nr_hw_queues)
+		return;
+
+	list_for_each_entry(q, &set->tag_list, tag_set_list)
+		blk_mq_freeze_queue(q);
+	/*
+	 * Switch IO scheduler to 'none', cleaning up the data associated
+	 * with the previous scheduler. We will switch back once we are done
+	 * updating the new sw to hw queue mappings.
+	 */
+	list_for_each_entry(q, &set->tag_list, tag_set_list)
+		if (!blk_mq_elv_switch_none(&head, q))
+			goto switch_back;
+
+	list_for_each_entry(q, &set->tag_list, tag_set_list) {
+		blk_mq_debugfs_unregister_hctxs(q);
+		blk_mq_sysfs_unregister_hctxs(q);
+	}
+
+	prev_nr_hw_queues = set->nr_hw_queues;
+	if (blk_mq_realloc_tag_set_tags(set, set->nr_hw_queues, nr_hw_queues) <
+	    0)
+		goto reregister;
+
+	set->nr_hw_queues = nr_hw_queues;
+fallback:
+	blk_mq_update_queue_map(set);
+	list_for_each_entry(q, &set->tag_list, tag_set_list) {
+		blk_mq_realloc_hw_ctxs(set, q);
+		blk_mq_update_poll_flag(q);
+		if (q->nr_hw_queues != set->nr_hw_queues) {
+			int i = prev_nr_hw_queues;
+
+			pr_warn("Increasing nr_hw_queues to %d fails, fallback to %d\n",
+					nr_hw_queues, prev_nr_hw_queues);
+			for (; i < set->nr_hw_queues; i++)
+				__blk_mq_free_map_and_rqs(set, i);
+
+			set->nr_hw_queues = prev_nr_hw_queues;
+			blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
+			goto fallback;
+		}
+		blk_mq_map_swqueue(q);
+	}
+
+reregister:
+	list_for_each_entry(q, &set->tag_list, tag_set_list) {
+		blk_mq_sysfs_register_hctxs(q);
+		blk_mq_debugfs_register_hctxs(q);
+	}
+
+switch_back:
+	list_for_each_entry(q, &set->tag_list, tag_set_list)
+		blk_mq_elv_switch_back(&head, q);
+
+	list_for_each_entry(q, &set->tag_list, tag_set_list)
+		blk_mq_unfreeze_queue(q);
+}
+
+void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
+{
+	mutex_lock(&set->tag_list_lock);
+	__blk_mq_update_nr_hw_queues(set, nr_hw_queues);
+	mutex_unlock(&set->tag_list_lock);
+}
+EXPORT_SYMBOL_GPL(blk_mq_update_nr_hw_queues);
+
+/* Enable polling stats and return whether they were already enabled. */
+static bool blk_poll_stats_enable(struct request_queue *q)
+{
+	if (q->poll_stat)
+		return true;
+
+	return blk_stats_alloc_enable(q);
+}
+
+static void blk_mq_poll_stats_start(struct request_queue *q)
+{
+	/*
+	 * We don't arm the callback if polling stats are not enabled or the
+	 * callback is already active.
+	 */
+	if (!q->poll_stat || blk_stat_is_active(q->poll_cb))
+		return;
+
+	blk_stat_activate_msecs(q->poll_cb, 100);
+}
+
+static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb)
+{
+	struct request_queue *q = cb->data;
+	int bucket;
+
+	for (bucket = 0; bucket < BLK_MQ_POLL_STATS_BKTS; bucket++) {
+		if (cb->stat[bucket].nr_samples)
+			q->poll_stat[bucket] = cb->stat[bucket];
+	}
+}
+
+static unsigned long blk_mq_poll_nsecs(struct request_queue *q,
+				       struct request *rq)
+{
+	unsigned long ret = 0;
+	int bucket;
+
+	/*
+	 * If stats collection isn't on, don't sleep but turn it on for
+	 * future users
+	 */
+	if (!blk_poll_stats_enable(q))
+		return 0;
+
+	/*
+	 * As an optimistic guess, use half of the mean service time
+	 * for this type of request. We can (and should) make this smarter.
+	 * For instance, if the completion latencies are tight, we can
+	 * get closer than just half the mean. This is especially
+	 * important on devices where the completion latencies are longer
+	 * than ~10 usec. We do use the stats for the relevant IO size
+	 * if available which does lead to better estimates.
+	 */
+	bucket = blk_mq_poll_stats_bkt(rq);
+	if (bucket < 0)
+		return ret;
+
+	if (q->poll_stat[bucket].nr_samples)
+		ret = (q->poll_stat[bucket].mean + 1) / 2;
+
+	return ret;
+}
+
+static bool blk_mq_poll_hybrid(struct request_queue *q, blk_qc_t qc)
+{
+	struct blk_mq_hw_ctx *hctx = blk_qc_to_hctx(q, qc);
+	struct request *rq = blk_qc_to_rq(hctx, qc);
+	struct hrtimer_sleeper hs;
+	enum hrtimer_mode mode;
+	unsigned int nsecs;
+	ktime_t kt;
+
+	/*
+	 * If a request has completed on queue that uses an I/O scheduler, we
+	 * won't get back a request from blk_qc_to_rq.
+	 */
+	if (!rq || (rq->rq_flags & RQF_MQ_POLL_SLEPT))
+		return false;
+
+	/*
+	 * If we get here, hybrid polling is enabled. Hence poll_nsec can be:
+	 *
+	 *  0:	use half of prev avg
+	 * >0:	use this specific value
+	 */
+	if (q->poll_nsec > 0)
+		nsecs = q->poll_nsec;
+	else
+		nsecs = blk_mq_poll_nsecs(q, rq);
+
+	if (!nsecs)
+		return false;
+
+	rq->rq_flags |= RQF_MQ_POLL_SLEPT;
+
+	/*
+	 * This will be replaced with the stats tracking code, using
+	 * 'avg_completion_time / 2' as the pre-sleep target.
+	 */
+	kt = nsecs;
+
+	mode = HRTIMER_MODE_REL;
+	hrtimer_init_sleeper_on_stack(&hs, CLOCK_MONOTONIC, mode);
+	hrtimer_set_expires(&hs.timer, kt);
+
+	do {
+		if (blk_mq_rq_state(rq) == MQ_RQ_COMPLETE)
+			break;
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		hrtimer_sleeper_start_expires(&hs, mode);
+		if (hs.task)
+			io_schedule();
+		hrtimer_cancel(&hs.timer);
+		mode = HRTIMER_MODE_ABS;
+	} while (hs.task && !signal_pending(current));
+
+	__set_current_state(TASK_RUNNING);
+	destroy_hrtimer_on_stack(&hs.timer);
+
+	/*
+	 * If we sleep, have the caller restart the poll loop to reset the
+	 * state.  Like for the other success return cases, the caller is
+	 * responsible for checking if the IO completed.  If the IO isn't
+	 * complete, we'll get called again and will go straight to the busy
+	 * poll loop.
+	 */
+	return true;
+}
+
+static int blk_mq_poll_classic(struct request_queue *q, blk_qc_t cookie,
+			       struct io_comp_batch *iob, unsigned int flags)
+{
+	struct blk_mq_hw_ctx *hctx = blk_qc_to_hctx(q, cookie);
+	long state = get_current_state();
+	int ret;
+
+	do {
+		ret = q->mq_ops->poll(hctx, iob);
+		if (ret > 0) {
+			__set_current_state(TASK_RUNNING);
+			return ret;
+		}
+
+		if (signal_pending_state(state, current))
+			__set_current_state(TASK_RUNNING);
+		if (task_is_running(current))
+			return 1;
+
+		if (ret < 0 || (flags & BLK_POLL_ONESHOT))
+			break;
+		cpu_relax();
+	} while (!need_resched());
+
+	__set_current_state(TASK_RUNNING);
+	return 0;
+}
+
+int blk_mq_poll(struct request_queue *q, blk_qc_t cookie, struct io_comp_batch *iob,
+		unsigned int flags)
+{
+	if (!(flags & BLK_POLL_NOSLEEP) &&
+	    q->poll_nsec != BLK_MQ_POLL_CLASSIC) {
+		if (blk_mq_poll_hybrid(q, cookie))
+			return 1;
+	}
+	return blk_mq_poll_classic(q, cookie, iob, flags);
+}
+
+unsigned int blk_mq_rq_cpu(struct request *rq)
+{
+	return rq->mq_ctx->cpu;
+}
+EXPORT_SYMBOL(blk_mq_rq_cpu);
+
+void blk_mq_cancel_work_sync(struct request_queue *q)
+{
+	if (queue_is_mq(q)) {
+		struct blk_mq_hw_ctx *hctx;
+		unsigned long i;
+
+		cancel_delayed_work_sync(&q->requeue_work);
+
+		queue_for_each_hw_ctx(q, hctx, i)
+			cancel_delayed_work_sync(&hctx->run_work);
+	}
+}
+
+static int __init blk_mq_init(void)
+{
+	int i;
+
+	for_each_possible_cpu(i)
+		init_llist_head(&per_cpu(blk_cpu_done, i));
+	open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);
+
+	cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD,
+				  "block/softirq:dead", NULL,
+				  blk_softirq_cpu_dead);
+	cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL,
+				blk_mq_hctx_notify_dead);
+	cpuhp_setup_state_multi(CPUHP_AP_BLK_MQ_ONLINE, "block/mq:online",
+				blk_mq_hctx_notify_online,
+				blk_mq_hctx_notify_offline);
+	return 0;
+}
+subsys_initcall(blk_mq_init);