Adding upstream version 4.19.249.upstream/4.19.249

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

1 files changed, 3238 insertions, 0 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
new file mode 100644
index 000000000..ae70b4809
--- /dev/null
+++ b/block/blk-mq.c
@@ -0,0 +1,3238 @@
+/*
+ * Block multiqueue core code
+ *
+ * Copyright (C) 2013-2014 Jens Axboe
+ * Copyright (C) 2013-2014 Christoph Hellwig
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/backing-dev.h>
+#include <linux/bio.h>
+#include <linux/blkdev.h>
+#include <linux/kmemleak.h>
+#include <linux/mm.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+#include <linux/smp.h>
+#include <linux/llist.h>
+#include <linux/list_sort.h>
+#include <linux/cpu.h>
+#include <linux/cache.h>
+#include <linux/sched/sysctl.h>
+#include <linux/sched/topology.h>
+#include <linux/sched/signal.h>
+#include <linux/delay.h>
+#include <linux/crash_dump.h>
+#include <linux/prefetch.h>
+
+#include <trace/events/block.h>
+
+#include <linux/blk-mq.h>
+#include "blk.h"
+#include "blk-mq.h"
+#include "blk-mq-debugfs.h"
+#include "blk-mq-tag.h"
+#include "blk-stat.h"
+#include "blk-mq-sched.h"
+#include "blk-rq-qos.h"
+
+static bool blk_mq_poll(struct request_queue *q, blk_qc_t cookie);
+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, bytes, bucket;
+
+	ddir = rq_data_dir(rq);
+	bytes = blk_rq_bytes(rq);
+
+	bucket = ddir + 2*(ilog2(bytes) - 9);
+
+	if (bucket < 0)
+		return -1;
+	else if (bucket >= BLK_MQ_POLL_STATS_BKTS)
+		return ddir + BLK_MQ_POLL_STATS_BKTS - 2;
+
+	return bucket;
+}
+
+/*
+ * Check if any of the ctx's 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)
+{
+	if (!sbitmap_test_bit(&hctx->ctx_map, ctx->index_hw))
+		sbitmap_set_bit(&hctx->ctx_map, ctx->index_hw);
+}
+
+static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
+				      struct blk_mq_ctx *ctx)
+{
+	sbitmap_clear_bit(&hctx->ctx_map, ctx->index_hw);
+}
+
+struct mq_inflight {
+	struct hd_struct *part;
+	unsigned int *inflight;
+};
+
+static void blk_mq_check_inflight(struct blk_mq_hw_ctx *hctx,
+				  struct request *rq, void *priv,
+				  bool reserved)
+{
+	struct mq_inflight *mi = priv;
+
+	/*
+	 * index[0] counts the specific partition that was asked for. index[1]
+	 * counts the ones that are active on the whole device, so increment
+	 * that if mi->part is indeed a partition, and not a whole device.
+	 */
+	if (rq->part == mi->part)
+		mi->inflight[0]++;
+	if (mi->part->partno)
+		mi->inflight[1]++;
+}
+
+void blk_mq_in_flight(struct request_queue *q, struct hd_struct *part,
+		      unsigned int inflight[2])
+{
+	struct mq_inflight mi = { .part = part, .inflight = inflight, };
+
+	inflight[0] = inflight[1] = 0;
+	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
+}
+
+static void blk_mq_check_inflight_rw(struct blk_mq_hw_ctx *hctx,
+				     struct request *rq, void *priv,
+				     bool reserved)
+{
+	struct mq_inflight *mi = priv;
+
+	if (rq->part == mi->part)
+		mi->inflight[rq_data_dir(rq)]++;
+}
+
+void blk_mq_in_flight_rw(struct request_queue *q, struct hd_struct *part,
+			 unsigned int inflight[2])
+{
+	struct mq_inflight mi = { .part = part, .inflight = inflight, };
+
+	inflight[0] = inflight[1] = 0;
+	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight_rw, &mi);
+}
+
+void blk_freeze_queue_start(struct request_queue *q)
+{
+	int freeze_depth;
+
+	freeze_depth = atomic_inc_return(&q->mq_freeze_depth);
+	if (freeze_depth == 1) {
+		percpu_ref_kill(&q->q_usage_counter);
+		if (q->mq_ops)
+			blk_mq_run_hw_queues(q, false);
+	}
+}
+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);
+	if (!q->mq_ops)
+		blk_drain_queue(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)
+{
+	int freeze_depth;
+
+	freeze_depth = atomic_dec_return(&q->mq_freeze_depth);
+	WARN_ON_ONCE(freeze_depth < 0);
+	if (!freeze_depth) {
+		percpu_ref_reinit(&q->q_usage_counter);
+		wake_up_all(&q->mq_freeze_wq);
+	}
+}
+EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);
+
+/*
+ * FIXME: replace the scsi_internal_device_*block_nowait() calls in the
+ * mpt3sas driver such that this function can be removed.
+ */
+void blk_mq_quiesce_queue_nowait(struct request_queue *q)
+{
+	blk_queue_flag_set(QUEUE_FLAG_QUIESCED, q);
+}
+EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
+
+/**
+ * blk_mq_quiesce_queue() - wait until all ongoing dispatches have finished
+ * @q: request queue.
+ *
+ * Note: this function does not prevent that the struct request end_io()
+ * callback function is invoked. Once this function is returned, we make
+ * sure no dispatch can happen until the queue is unquiesced via
+ * blk_mq_unquiesce_queue().
+ */
+void blk_mq_quiesce_queue(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned int i;
+	bool rcu = false;
+
+	blk_mq_quiesce_queue_nowait(q);
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (hctx->flags & BLK_MQ_F_BLOCKING)
+			synchronize_srcu(hctx->srcu);
+		else
+			rcu = true;
+	}
+	if (rcu)
+		synchronize_rcu();
+}
+EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue);
+
+/*
+ * blk_mq_unquiesce_queue() - counterpart of blk_mq_quiesce_queue()
+ * @q: request queue.
+ *
+ * This function recovers queue into the state before quiescing
+ * which is done by blk_mq_quiesce_queue.
+ */
+void blk_mq_unquiesce_queue(struct request_queue *q)
+{
+	blk_queue_flag_clear(QUEUE_FLAG_QUIESCED, q);
+
+	/* dispatch requests which are inserted during quiescing */
+	blk_mq_run_hw_queues(q, true);
+}
+EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue);
+
+void blk_mq_wake_waiters(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned int i;
+
+	queue_for_each_hw_ctx(q, hctx, i)
+		if (blk_mq_hw_queue_mapped(hctx))
+			blk_mq_tag_wakeup_all(hctx->tags, true);
+}
+
+bool blk_mq_can_queue(struct blk_mq_hw_ctx *hctx)
+{
+	return blk_mq_has_free_tags(hctx->tags);
+}
+EXPORT_SYMBOL(blk_mq_can_queue);
+
+static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
+		unsigned int tag, unsigned int op)
+{
+	struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
+	struct request *rq = tags->static_rqs[tag];
+	req_flags_t rq_flags = 0;
+
+	if (data->flags & BLK_MQ_REQ_INTERNAL) {
+		rq->tag = -1;
+		rq->internal_tag = tag;
+	} else {
+		if (data->hctx->flags & BLK_MQ_F_TAG_SHARED) {
+			rq_flags = RQF_MQ_INFLIGHT;
+			atomic_inc(&data->hctx->nr_active);
+		}
+		rq->tag = tag;
+		rq->internal_tag = -1;
+		data->hctx->tags->rqs[rq->tag] = rq;
+	}
+
+	/* csd/requeue_work/fifo_time is initialized before use */
+	rq->q = data->q;
+	rq->mq_ctx = data->ctx;
+	rq->rq_flags = rq_flags;
+	rq->cpu = -1;
+	rq->cmd_flags = op;
+	if (data->flags & BLK_MQ_REQ_PREEMPT)
+		rq->rq_flags |= RQF_PREEMPT;
+	if (blk_queue_io_stat(data->q))
+		rq->rq_flags |= RQF_IO_STAT;
+	INIT_LIST_HEAD(&rq->queuelist);
+	INIT_HLIST_NODE(&rq->hash);
+	RB_CLEAR_NODE(&rq->rb_node);
+	rq->rq_disk = NULL;
+	rq->part = NULL;
+	rq->start_time_ns = ktime_get_ns();
+	rq->io_start_time_ns = 0;
+	rq->nr_phys_segments = 0;
+#if defined(CONFIG_BLK_DEV_INTEGRITY)
+	rq->nr_integrity_segments = 0;
+#endif
+	rq->special = NULL;
+	/* tag was already set */
+	rq->extra_len = 0;
+	rq->__deadline = 0;
+
+	INIT_LIST_HEAD(&rq->timeout_list);
+	rq->timeout = 0;
+
+	rq->end_io = NULL;
+	rq->end_io_data = NULL;
+	rq->next_rq = NULL;
+
+#ifdef CONFIG_BLK_CGROUP
+	rq->rl = NULL;
+#endif
+
+	data->ctx->rq_dispatched[op_is_sync(op)]++;
+	refcount_set(&rq->ref, 1);
+	return rq;
+}
+
+static struct request *blk_mq_get_request(struct request_queue *q,
+		struct bio *bio, unsigned int op,
+		struct blk_mq_alloc_data *data)
+{
+	struct elevator_queue *e = q->elevator;
+	struct request *rq;
+	unsigned int tag;
+	bool put_ctx_on_error = false;
+
+	blk_queue_enter_live(q);
+	data->q = q;
+	if (likely(!data->ctx)) {
+		data->ctx = blk_mq_get_ctx(q);
+		put_ctx_on_error = true;
+	}
+	if (likely(!data->hctx))
+		data->hctx = blk_mq_map_queue(q, data->ctx->cpu);
+	if (op & REQ_NOWAIT)
+		data->flags |= BLK_MQ_REQ_NOWAIT;
+
+	if (e) {
+		data->flags |= BLK_MQ_REQ_INTERNAL;
+
+		/*
+		 * Flush requests are special and go directly to the
+		 * dispatch list. Don't include reserved tags in the
+		 * limiting, as it isn't useful.
+		 */
+		if (!op_is_flush(op) && e->type->ops.mq.limit_depth &&
+		    !(data->flags & BLK_MQ_REQ_RESERVED))
+			e->type->ops.mq.limit_depth(op, data);
+	} else {
+		blk_mq_tag_busy(data->hctx);
+	}
+
+	tag = blk_mq_get_tag(data);
+	if (tag == BLK_MQ_TAG_FAIL) {
+		if (put_ctx_on_error) {
+			blk_mq_put_ctx(data->ctx);
+			data->ctx = NULL;
+		}
+		blk_queue_exit(q);
+		return NULL;
+	}
+
+	rq = blk_mq_rq_ctx_init(data, tag, op);
+	if (!op_is_flush(op)) {
+		rq->elv.icq = NULL;
+		if (e && e->type->ops.mq.prepare_request) {
+			if (e->type->icq_cache && rq_ioc(bio))
+				blk_mq_sched_assign_ioc(rq, bio);
+
+			e->type->ops.mq.prepare_request(rq, bio);
+			rq->rq_flags |= RQF_ELVPRIV;
+		}
+	}
+	data->hctx->queued++;
+	return rq;
+}
+
+struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op,
+		blk_mq_req_flags_t flags)
+{
+	struct blk_mq_alloc_data alloc_data = { .flags = flags };
+	struct request *rq;
+	int ret;
+
+	ret = blk_queue_enter(q, flags);
+	if (ret)
+		return ERR_PTR(ret);
+
+	rq = blk_mq_get_request(q, NULL, op, &alloc_data);
+	blk_queue_exit(q);
+
+	if (!rq)
+		return ERR_PTR(-EWOULDBLOCK);
+
+	blk_mq_put_ctx(alloc_data.ctx);
+
+	rq->__data_len = 0;
+	rq->__sector = (sector_t) -1;
+	rq->bio = rq->biotail = NULL;
+	return rq;
+}
+EXPORT_SYMBOL(blk_mq_alloc_request);
+
+struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
+	unsigned int op, blk_mq_req_flags_t flags, unsigned int hctx_idx)
+{
+	struct blk_mq_alloc_data alloc_data = { .flags = flags };
+	struct request *rq;
+	unsigned int cpu;
+	int ret;
+
+	/*
+	 * 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)))
+		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.
+	 */
+	alloc_data.hctx = q->queue_hw_ctx[hctx_idx];
+	if (!blk_mq_hw_queue_mapped(alloc_data.hctx)) {
+		blk_queue_exit(q);
+		return ERR_PTR(-EXDEV);
+	}
+	cpu = cpumask_first_and(alloc_data.hctx->cpumask, cpu_online_mask);
+	alloc_data.ctx = __blk_mq_get_ctx(q, cpu);
+
+	rq = blk_mq_get_request(q, NULL, op, &alloc_data);
+	blk_queue_exit(q);
+
+	if (!rq)
+		return ERR_PTR(-EWOULDBLOCK);
+
+	return rq;
+}
+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 = blk_mq_map_queue(q, ctx->cpu);
+	const int sched_tag = rq->internal_tag;
+
+	if (rq->tag != -1)
+		blk_mq_put_tag(hctx, hctx->tags, ctx, rq->tag);
+	if (sched_tag != -1)
+		blk_mq_put_tag(hctx, hctx->sched_tags, ctx, sched_tag);
+	blk_mq_sched_restart(hctx);
+	blk_queue_exit(q);
+}
+
+void blk_mq_free_request(struct request *rq)
+{
+	struct request_queue *q = rq->q;
+	struct elevator_queue *e = q->elevator;
+	struct blk_mq_ctx *ctx = rq->mq_ctx;
+	struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
+
+	if (rq->rq_flags & RQF_ELVPRIV) {
+		if (e && e->type->ops.mq.finish_request)
+			e->type->ops.mq.finish_request(rq);
+		if (rq->elv.icq) {
+			put_io_context(rq->elv.icq->ioc);
+			rq->elv.icq = NULL;
+		}
+	}
+
+	ctx->rq_completed[rq_is_sync(rq)]++;
+	if (rq->rq_flags & RQF_MQ_INFLIGHT)
+		atomic_dec(&hctx->nr_active);
+
+	if (unlikely(laptop_mode && !blk_rq_is_passthrough(rq)))
+		laptop_io_completion(q->backing_dev_info);
+
+	rq_qos_done(q, rq);
+
+	if (blk_rq_rl(rq))
+		blk_put_rl(blk_rq_rl(rq));
+
+	WRITE_ONCE(rq->state, MQ_RQ_IDLE);
+	if (refcount_dec_and_test(&rq->ref))
+		__blk_mq_free_request(rq);
+}
+EXPORT_SYMBOL_GPL(blk_mq_free_request);
+
+inline void __blk_mq_end_request(struct request *rq, blk_status_t error)
+{
+	u64 now = ktime_get_ns();
+
+	if (rq->rq_flags & RQF_STATS) {
+		blk_mq_poll_stats_start(rq->q);
+		blk_stat_add(rq, now);
+	}
+
+	blk_account_io_done(rq, now);
+
+	if (rq->end_io) {
+		rq_qos_done(rq->q, rq);
+		rq->end_io(rq, error);
+	} else {
+		if (unlikely(blk_bidi_rq(rq)))
+			blk_mq_free_request(rq->next_rq);
+		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);
+
+static void __blk_mq_complete_request_remote(void *data)
+{
+	struct request *rq = data;
+
+	rq->q->softirq_done_fn(rq);
+}
+
+static void __blk_mq_complete_request(struct request *rq)
+{
+	struct blk_mq_ctx *ctx = rq->mq_ctx;
+	bool shared = false;
+	int cpu;
+
+	if (!blk_mq_mark_complete(rq))
+		return;
+	if (rq->internal_tag != -1)
+		blk_mq_sched_completed_request(rq);
+
+	if (!test_bit(QUEUE_FLAG_SAME_COMP, &rq->q->queue_flags)) {
+		rq->q->softirq_done_fn(rq);
+		return;
+	}
+
+	cpu = get_cpu();
+	if (!test_bit(QUEUE_FLAG_SAME_FORCE, &rq->q->queue_flags))
+		shared = cpus_share_cache(cpu, ctx->cpu);
+
+	if (cpu != ctx->cpu && !shared && cpu_online(ctx->cpu)) {
+		rq->csd.func = __blk_mq_complete_request_remote;
+		rq->csd.info = rq;
+		rq->csd.flags = 0;
+		smp_call_function_single_async(ctx->cpu, &rq->csd);
+	} else {
+		rq->q->softirq_done_fn(rq);
+	}
+	put_cpu();
+}
+
+static void hctx_unlock(struct blk_mq_hw_ctx *hctx, int srcu_idx)
+	__releases(hctx->srcu)
+{
+	if (!(hctx->flags & BLK_MQ_F_BLOCKING))
+		rcu_read_unlock();
+	else
+		srcu_read_unlock(hctx->srcu, srcu_idx);
+}
+
+static void hctx_lock(struct blk_mq_hw_ctx *hctx, int *srcu_idx)
+	__acquires(hctx->srcu)
+{
+	if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
+		/* shut up gcc false positive */
+		*srcu_idx = 0;
+		rcu_read_lock();
+	} else
+		*srcu_idx = srcu_read_lock(hctx->srcu);
+}
+
+/**
+ * blk_mq_complete_request - end I/O on a request
+ * @rq:		the request being processed
+ *
+ * Description:
+ *	Ends all I/O on a request. It does not handle partial completions.
+ *	The actual completion happens out-of-order, through a IPI handler.
+ **/
+void blk_mq_complete_request(struct request *rq)
+{
+	if (unlikely(blk_should_fake_timeout(rq->q)))
+		return;
+	__blk_mq_complete_request(rq);
+}
+EXPORT_SYMBOL(blk_mq_complete_request);
+
+int blk_mq_request_started(struct request *rq)
+{
+	return blk_mq_rq_state(rq) != MQ_RQ_IDLE;
+}
+EXPORT_SYMBOL_GPL(blk_mq_request_started);
+
+void blk_mq_start_request(struct request *rq)
+{
+	struct request_queue *q = rq->q;
+
+	blk_mq_sched_started_request(rq);
+
+	trace_block_rq_issue(q, rq);
+
+	if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags)) {
+		rq->io_start_time_ns = ktime_get_ns();
+#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
+		rq->throtl_size = blk_rq_sectors(rq);
+#endif
+		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);
+
+	if (q->dma_drain_size && blk_rq_bytes(rq)) {
+		/*
+		 * Make sure space for the drain appears.  We know we can do
+		 * this because max_hw_segments has been adjusted to be one
+		 * fewer than the device can handle.
+		 */
+		rq->nr_phys_segments++;
+	}
+}
+EXPORT_SYMBOL(blk_mq_start_request);
+
+static void __blk_mq_requeue_request(struct request *rq)
+{
+	struct request_queue *q = rq->q;
+
+	blk_mq_put_driver_tag(rq);
+
+	trace_block_rq_requeue(q, rq);
+	rq_qos_requeue(q, rq);
+
+	if (blk_mq_request_started(rq)) {
+		WRITE_ONCE(rq->state, MQ_RQ_IDLE);
+		rq->rq_flags &= ~RQF_TIMED_OUT;
+		if (q->dma_drain_size && blk_rq_bytes(rq))
+			rq->nr_phys_segments--;
+	}
+}
+
+void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list)
+{
+	__blk_mq_requeue_request(rq);
+
+	/* this request will be re-inserted to io scheduler queue */
+	blk_mq_sched_requeue_request(rq);
+
+	BUG_ON(blk_queued_rq(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);
+		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);
+}
+EXPORT_SYMBOL(blk_mq_add_to_requeue_list);
+
+void blk_mq_kick_requeue_list(struct request_queue *q)
+{
+	kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work, 0);
+}
+EXPORT_SYMBOL(blk_mq_kick_requeue_list);
+
+void blk_mq_delay_kick_requeue_list(struct request_queue *q,
+				    unsigned long msecs)
+{
+	kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work,
+				    msecs_to_jiffies(msecs));
+}
+EXPORT_SYMBOL(blk_mq_delay_kick_requeue_list);
+
+struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
+{
+	if (tag < tags->nr_tags) {
+		prefetch(tags->rqs[tag]);
+		return tags->rqs[tag];
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL(blk_mq_tag_to_rq);
+
+static void blk_mq_rq_timed_out(struct request *req, bool reserved)
+{
+	req->rq_flags |= RQF_TIMED_OUT;
+	if (req->q->mq_ops->timeout) {
+		enum blk_eh_timer_return ret;
+
+		ret = req->q->mq_ops->timeout(req, reserved);
+		if (ret == BLK_EH_DONE)
+			return;
+		WARN_ON_ONCE(ret != BLK_EH_RESET_TIMER);
+	}
+
+	blk_add_timer(req);
+}
+
+static bool blk_mq_req_expired(struct request *rq, unsigned long *next)
+{
+	unsigned long deadline;
+
+	if (blk_mq_rq_state(rq) != MQ_RQ_IN_FLIGHT)
+		return false;
+	if (rq->rq_flags & RQF_TIMED_OUT)
+		return false;
+
+	deadline = blk_rq_deadline(rq);
+	if (time_after_eq(jiffies, deadline))
+		return true;
+
+	if (*next == 0)
+		*next = deadline;
+	else if (time_after(*next, deadline))
+		*next = deadline;
+	return false;
+}
+
+static void blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
+		struct request *rq, void *priv, bool reserved)
+{
+	unsigned long *next = priv;
+
+	/*
+	 * Just do a quick check if it is expired before locking the request in
+	 * so we're not unnecessarilly synchronizing across CPUs.
+	 */
+	if (!blk_mq_req_expired(rq, next))
+		return;
+
+	/*
+	 * We have reason to believe the request may be expired. Take a
+	 * reference on the request to lock this request lifetime into its
+	 * currently allocated context to prevent it from being reallocated in
+	 * the event the completion by-passes this timeout handler.
+	 *
+	 * If the reference was already released, then the driver beat the
+	 * timeout handler to posting a natural completion.
+	 */
+	if (!refcount_inc_not_zero(&rq->ref))
+		return;
+
+	/*
+	 * The request is now locked and cannot be reallocated underneath the
+	 * timeout handler's processing. Re-verify this exact request is truly
+	 * expired; if it is not expired, then the request was completed and
+	 * reallocated as a new request.
+	 */
+	if (blk_mq_req_expired(rq, next))
+		blk_mq_rq_timed_out(rq, reserved);
+
+	if (is_flush_rq(rq, hctx))
+		rq->end_io(rq, 0);
+	else if (refcount_dec_and_test(&rq->ref))
+		__blk_mq_free_request(rq);
+}
+
+static void blk_mq_timeout_work(struct work_struct *work)
+{
+	struct request_queue *q =
+		container_of(work, struct request_queue, timeout_work);
+	unsigned long next = 0;
+	struct blk_mq_hw_ctx *hctx;
+	int 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;
+
+	blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &next);
+
+	if (next != 0) {
+		mod_timer(&q->timeout, 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];
+
+	spin_lock(&ctx->lock);
+	list_splice_tail_init(&ctx->rq_list, 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];
+
+	spin_lock(&ctx->lock);
+	if (!list_empty(&ctx->rq_list)) {
+		dispatch_data->rq = list_entry_rq(ctx->rq_list.next);
+		list_del_init(&dispatch_data->rq->queuelist);
+		if (list_empty(&ctx->rq_list))
+			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 : 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 inline unsigned int queued_to_index(unsigned int queued)
+{
+	if (!queued)
+		return 0;
+
+	return min(BLK_MQ_MAX_DISPATCH_ORDER - 1, ilog2(queued) + 1);
+}
+
+bool blk_mq_get_driver_tag(struct request *rq)
+{
+	struct blk_mq_alloc_data data = {
+		.q = rq->q,
+		.hctx = blk_mq_map_queue(rq->q, rq->mq_ctx->cpu),
+		.flags = BLK_MQ_REQ_NOWAIT,
+	};
+	bool shared;
+
+	if (rq->tag != -1)
+		goto done;
+
+	if (blk_mq_tag_is_reserved(data.hctx->sched_tags, rq->internal_tag))
+		data.flags |= BLK_MQ_REQ_RESERVED;
+
+	shared = blk_mq_tag_busy(data.hctx);
+	rq->tag = blk_mq_get_tag(&data);
+	if (rq->tag >= 0) {
+		if (shared) {
+			rq->rq_flags |= RQF_MQ_INFLIGHT;
+			atomic_inc(&data.hctx->nr_active);
+		}
+		data.hctx->tags->rqs[rq->tag] = rq;
+	}
+
+done:
+	return rq->tag != -1;
+}
+
+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);
+	list_del_init(&wait->entry);
+	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 wait_queue_head *wq;
+	wait_queue_entry_t *wait;
+	bool ret;
+
+	if (!(hctx->flags & BLK_MQ_F_TAG_SHARED)) {
+		if (!test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
+			set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
+
+		/*
+		 * 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;
+
+	wq = &bt_wait_ptr(&hctx->tags->bitmap_tags, 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;
+	}
+
+	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);
+	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;
+
+	if (hctx->queue->elevator)
+		return;
+
+	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);
+}
+
+/*
+ * Returns true if we did some work AND can potentially do more.
+ */
+bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
+			     bool got_budget)
+{
+	struct blk_mq_hw_ctx *hctx;
+	struct request *rq, *nxt;
+	bool no_tag = false;
+	int errors, queued;
+	blk_status_t ret = BLK_STS_OK;
+
+	if (list_empty(list))
+		return false;
+
+	WARN_ON(!list_is_singular(list) && got_budget);
+
+	/*
+	 * 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);
+
+		hctx = blk_mq_map_queue(rq->q, rq->mq_ctx->cpu);
+		if (!got_budget && !blk_mq_get_dispatch_budget(hctx))
+			break;
+
+		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)) {
+				blk_mq_put_dispatch_budget(hctx);
+				/*
+				 * For non-shared tags, the RESTART check
+				 * will suffice.
+				 */
+				if (hctx->flags & BLK_MQ_F_TAG_SHARED)
+					no_tag = true;
+				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);
+		}
+
+		ret = q->mq_ops->queue_rq(hctx, &bd);
+		if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE) {
+			blk_mq_handle_dev_resource(rq, list);
+			break;
+		}
+
+		if (unlikely(ret != BLK_STS_OK)) {
+			errors++;
+			blk_mq_end_request(rq, BLK_STS_IOERR);
+			continue;
+		}
+
+		queued++;
+	} while (!list_empty(list));
+
+	hctx->dispatched[queued_to_index(queued)]++;
+
+	/*
+	 * 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;
+
+		spin_lock(&hctx->lock);
+		list_splice_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.
+		 */
+		needs_restart = blk_mq_sched_needs_restart(hctx);
+		if (!needs_restart ||
+		    (no_tag && list_empty_careful(&hctx->dispatch_wait.entry)))
+			blk_mq_run_hw_queue(hctx, true);
+		else if (needs_restart && (ret == BLK_STS_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);
+
+	/*
+	 * If the host/device is unable to accept more work, inform the
+	 * caller of that.
+	 */
+	if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
+		return false;
+
+	return (queued + errors) != 0;
+}
+
+static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
+{
+	int srcu_idx;
+
+	/*
+	 * We should be running this queue from one of the CPUs that
+	 * are mapped to it.
+	 *
+	 * There are at least two related races now between setting
+	 * hctx->next_cpu from blk_mq_hctx_next_cpu() and running
+	 * __blk_mq_run_hw_queue():
+	 *
+	 * - hctx->next_cpu is found offline in blk_mq_hctx_next_cpu(),
+	 *   but later it becomes online, then this warning is harmless
+	 *   at all
+	 *
+	 * - hctx->next_cpu is found online in blk_mq_hctx_next_cpu(),
+	 *   but later it becomes offline, then the warning can't be
+	 *   triggered, and we depend on blk-mq timeout handler to
+	 *   handle dispatched requests to this hctx
+	 */
+	if (!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
+		cpu_online(hctx->next_cpu)) {
+		printk(KERN_WARNING "run queue from wrong CPU %d, hctx %s\n",
+			raw_smp_processor_id(),
+			cpumask_empty(hctx->cpumask) ? "inactive": "active");
+		dump_stack();
+	}
+
+	/*
+	 * We can't run the queue inline with ints disabled. Ensure that
+	 * we catch bad users of this early.
+	 */
+	WARN_ON_ONCE(in_interrupt());
+
+	might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
+
+	hctx_lock(hctx, &srcu_idx);
+	blk_mq_sched_dispatch_requests(hctx);
+	hctx_unlock(hctx, srcu_idx);
+}
+
+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;
+}
+
+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)) {
+		int cpu = get_cpu();
+		if (cpumask_test_cpu(cpu, hctx->cpumask)) {
+			__blk_mq_run_hw_queue(hctx);
+			put_cpu();
+			return;
+		}
+
+		put_cpu();
+	}
+
+	kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work,
+				    msecs_to_jiffies(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);
+
+bool blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
+{
+	int srcu_idx;
+	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.
+	 */
+	hctx_lock(hctx, &srcu_idx);
+	need_run = !blk_queue_quiesced(hctx->queue) &&
+		blk_mq_hctx_has_pending(hctx);
+	hctx_unlock(hctx, srcu_idx);
+
+	if (need_run) {
+		__blk_mq_delay_run_hw_queue(hctx, async, 0);
+		return true;
+	}
+
+	return false;
+}
+EXPORT_SYMBOL(blk_mq_run_hw_queue);
+
+void blk_mq_run_hw_queues(struct request_queue *q, bool async)
+{
+	struct blk_mq_hw_ctx *hctx;
+	int i;
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (blk_mq_hctx_stopped(hctx))
+			continue;
+
+		blk_mq_run_hw_queue(hctx, async);
+	}
+}
+EXPORT_SYMBOL(blk_mq_run_hw_queues);
+
+/**
+ * blk_mq_queue_stopped() - check whether one or more hctxs have been stopped
+ * @q: request queue.
+ *
+ * The caller is responsible for serializing this function against
+ * blk_mq_{start,stop}_hw_queue().
+ */
+bool blk_mq_queue_stopped(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	int i;
+
+	queue_for_each_hw_ctx(q, hctx, i)
+		if (blk_mq_hctx_stopped(hctx))
+			return true;
+
+	return false;
+}
+EXPORT_SYMBOL(blk_mq_queue_stopped);
+
+/*
+ * 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;
+	int 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;
+	int 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;
+	int 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 (test_bit(BLK_MQ_S_STOPPED, &hctx->state))
+		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;
+
+	lockdep_assert_held(&ctx->lock);
+
+	trace_block_rq_insert(hctx->queue, rq);
+
+	if (at_head)
+		list_add(&rq->queuelist, &ctx->rq_list);
+	else
+		list_add_tail(&rq->queuelist, &ctx->rq_list);
+}
+
+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);
+}
+
+/*
+ * 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 run_queue)
+{
+	struct blk_mq_ctx *ctx = rq->mq_ctx;
+	struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(rq->q, ctx->cpu);
+
+	spin_lock(&hctx->lock);
+	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;
+
+	/*
+	 * 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(hctx->queue, rq);
+	}
+
+	spin_lock(&ctx->lock);
+	list_splice_tail_init(list, &ctx->rq_list);
+	blk_mq_hctx_mark_pending(hctx, ctx);
+	spin_unlock(&ctx->lock);
+}
+
+static int plug_ctx_cmp(void *priv, struct list_head *a, struct list_head *b)
+{
+	struct request *rqa = container_of(a, struct request, queuelist);
+	struct request *rqb = container_of(b, struct request, queuelist);
+
+	return !(rqa->mq_ctx < rqb->mq_ctx ||
+		 (rqa->mq_ctx == rqb->mq_ctx &&
+		  blk_rq_pos(rqa) < blk_rq_pos(rqb)));
+}
+
+void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
+{
+	struct blk_mq_ctx *this_ctx;
+	struct request_queue *this_q;
+	struct request *rq;
+	LIST_HEAD(list);
+	LIST_HEAD(ctx_list);
+	unsigned int depth;
+
+	list_splice_init(&plug->mq_list, &list);
+
+	list_sort(NULL, &list, plug_ctx_cmp);
+
+	this_q = NULL;
+	this_ctx = NULL;
+	depth = 0;
+
+	while (!list_empty(&list)) {
+		rq = list_entry_rq(list.next);
+		list_del_init(&rq->queuelist);
+		BUG_ON(!rq->q);
+		if (rq->mq_ctx != this_ctx) {
+			if (this_ctx) {
+				trace_block_unplug(this_q, depth, !from_schedule);
+				blk_mq_sched_insert_requests(this_q, this_ctx,
+								&ctx_list,
+								from_schedule);
+			}
+
+			this_ctx = rq->mq_ctx;
+			this_q = rq->q;
+			depth = 0;
+		}
+
+		depth++;
+		list_add_tail(&rq->queuelist, &ctx_list);
+	}
+
+	/*
+	 * If 'this_ctx' is set, we know we have entries to complete
+	 * on 'ctx_list'. Do those.
+	 */
+	if (this_ctx) {
+		trace_block_unplug(this_q, depth, !from_schedule);
+		blk_mq_sched_insert_requests(this_q, this_ctx, &ctx_list,
+						from_schedule);
+	}
+}
+
+static void blk_mq_bio_to_request(struct request *rq, struct bio *bio)
+{
+	blk_init_request_from_bio(rq, bio);
+
+	blk_rq_set_rl(rq, blk_get_rl(rq->q, bio));
+
+	blk_account_io_start(rq, true);
+}
+
+static blk_qc_t request_to_qc_t(struct blk_mq_hw_ctx *hctx, struct request *rq)
+{
+	if (rq->tag != -1)
+		return blk_tag_to_qc_t(rq->tag, hctx->queue_num, false);
+
+	return blk_tag_to_qc_t(rq->internal_tag, hctx->queue_num, true);
+}
+
+static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
+					    struct request *rq,
+					    blk_qc_t *cookie)
+{
+	struct request_queue *q = rq->q;
+	struct blk_mq_queue_data bd = {
+		.rq = rq,
+		.last = true,
+	};
+	blk_qc_t new_cookie;
+	blk_status_t ret;
+
+	new_cookie = request_to_qc_t(hctx, rq);
+
+	/*
+	 * 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);
+		*cookie = new_cookie;
+		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);
+		*cookie = BLK_QC_T_NONE;
+		break;
+	}
+
+	return ret;
+}
+
+static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
+						struct request *rq,
+						blk_qc_t *cookie,
+						bool bypass_insert)
+{
+	struct request_queue *q = rq->q;
+	bool run_queue = true;
+
+	/*
+	 * 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 (q->elevator && !bypass_insert)
+		goto insert;
+
+	if (!blk_mq_get_dispatch_budget(hctx))
+		goto insert;
+
+	if (!blk_mq_get_driver_tag(rq)) {
+		blk_mq_put_dispatch_budget(hctx);
+		goto insert;
+	}
+
+	return __blk_mq_issue_directly(hctx, rq, cookie);
+insert:
+	if (bypass_insert)
+		return BLK_STS_RESOURCE;
+
+	blk_mq_request_bypass_insert(rq, run_queue);
+	return BLK_STS_OK;
+}
+
+static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
+		struct request *rq, blk_qc_t *cookie)
+{
+	blk_status_t ret;
+	int srcu_idx;
+
+	might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
+
+	hctx_lock(hctx, &srcu_idx);
+
+	ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false);
+	if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
+		blk_mq_request_bypass_insert(rq, true);
+	else if (ret != BLK_STS_OK)
+		blk_mq_end_request(rq, ret);
+
+	hctx_unlock(hctx, srcu_idx);
+}
+
+blk_status_t blk_mq_request_issue_directly(struct request *rq)
+{
+	blk_status_t ret;
+	int srcu_idx;
+	blk_qc_t unused_cookie;
+	struct blk_mq_ctx *ctx = rq->mq_ctx;
+	struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(rq->q, ctx->cpu);
+
+	hctx_lock(hctx, &srcu_idx);
+	ret = __blk_mq_try_issue_directly(hctx, rq, &unused_cookie, true);
+	hctx_unlock(hctx, srcu_idx);
+
+	return ret;
+}
+
+void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
+		struct list_head *list)
+{
+	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);
+		if (ret != BLK_STS_OK) {
+			if (ret == BLK_STS_RESOURCE ||
+					ret == BLK_STS_DEV_RESOURCE) {
+				blk_mq_request_bypass_insert(rq,
+							list_empty(list));
+				break;
+			}
+			blk_mq_end_request(rq, ret);
+		}
+	}
+}
+
+static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
+{
+	const int is_sync = op_is_sync(bio->bi_opf);
+	const int is_flush_fua = op_is_flush(bio->bi_opf);
+	struct blk_mq_alloc_data data = { .flags = 0 };
+	struct request *rq;
+	unsigned int request_count = 0;
+	struct blk_plug *plug;
+	struct request *same_queue_rq = NULL;
+	blk_qc_t cookie;
+
+	blk_queue_bounce(q, &bio);
+
+	blk_queue_split(q, &bio);
+
+	if (!bio_integrity_prep(bio))
+		return BLK_QC_T_NONE;
+
+	if (!is_flush_fua && !blk_queue_nomerges(q) &&
+	    blk_attempt_plug_merge(q, bio, &request_count, &same_queue_rq))
+		return BLK_QC_T_NONE;
+
+	if (blk_mq_sched_bio_merge(q, bio))
+		return BLK_QC_T_NONE;
+
+	rq_qos_throttle(q, bio, NULL);
+
+	trace_block_getrq(q, bio, bio->bi_opf);
+
+	rq = blk_mq_get_request(q, bio, bio->bi_opf, &data);
+	if (unlikely(!rq)) {
+		rq_qos_cleanup(q, bio);
+		if (bio->bi_opf & REQ_NOWAIT)
+			bio_wouldblock_error(bio);
+		return BLK_QC_T_NONE;
+	}
+
+	rq_qos_track(q, rq, bio);
+
+	cookie = request_to_qc_t(data.hctx, rq);
+
+	plug = current->plug;
+	if (unlikely(is_flush_fua)) {
+		blk_mq_put_ctx(data.ctx);
+		blk_mq_bio_to_request(rq, bio);
+
+		/* bypass scheduler for flush rq */
+		blk_insert_flush(rq);
+		blk_mq_run_hw_queue(data.hctx, true);
+	} else if (plug && q->nr_hw_queues == 1) {
+		struct request *last = NULL;
+
+		blk_mq_put_ctx(data.ctx);
+		blk_mq_bio_to_request(rq, bio);
+
+		/*
+		 * @request_count may become stale because of schedule
+		 * out, so check the list again.
+		 */
+		if (list_empty(&plug->mq_list))
+			request_count = 0;
+		else if (blk_queue_nomerges(q))
+			request_count = blk_plug_queued_count(q);
+
+		if (!request_count)
+			trace_block_plug(q);
+		else
+			last = list_entry_rq(plug->mq_list.prev);
+
+		if (request_count >= BLK_MAX_REQUEST_COUNT || (last &&
+		    blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
+			blk_flush_plug_list(plug, false);
+			trace_block_plug(q);
+		}
+
+		list_add_tail(&rq->queuelist, &plug->mq_list);
+	} else if (plug && !blk_queue_nomerges(q)) {
+		blk_mq_bio_to_request(rq, bio);
+
+		/*
+		 * We do limited plugging. If the bio can be merged, do that.
+		 * Otherwise the existing request in the plug list will be
+		 * issued. So the plug list will have one request at most
+		 * The plug list might get flushed before this. If that happens,
+		 * the plug list is empty, and same_queue_rq is invalid.
+		 */
+		if (list_empty(&plug->mq_list))
+			same_queue_rq = NULL;
+		if (same_queue_rq)
+			list_del_init(&same_queue_rq->queuelist);
+		list_add_tail(&rq->queuelist, &plug->mq_list);
+
+		blk_mq_put_ctx(data.ctx);
+
+		if (same_queue_rq) {
+			data.hctx = blk_mq_map_queue(q,
+					same_queue_rq->mq_ctx->cpu);
+			blk_mq_try_issue_directly(data.hctx, same_queue_rq,
+					&cookie);
+		}
+	} else if ((q->nr_hw_queues > 1 && is_sync) || (!q->elevator &&
+			!data.hctx->dispatch_busy)) {
+		blk_mq_put_ctx(data.ctx);
+		blk_mq_bio_to_request(rq, bio);
+		blk_mq_try_issue_directly(data.hctx, rq, &cookie);
+	} else {
+		blk_mq_put_ctx(data.ctx);
+		blk_mq_bio_to_request(rq, bio);
+		blk_mq_sched_insert_request(rq, false, true, true);
+	}
+
+	return cookie;
+}
+
+void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
+		     unsigned int hctx_idx)
+{
+	struct page *page;
+
+	if (tags->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;
+		}
+	}
+
+	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_init_rq_map().
+		 */
+		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);
+}
+
+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)
+{
+	struct blk_mq_tags *tags;
+	int node;
+
+	node = blk_mq_hw_queue_to_node(set->mq_map, hctx_idx);
+	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 size_t order_to_size(unsigned int order)
+{
+	return (size_t)PAGE_SIZE << order;
+}
+
+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;
+}
+
+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;
+	size_t rq_size, left;
+	int node;
+
+	node = blk_mq_hw_queue_to_node(set->mq_map, hctx_idx);
+	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;
+}
+
+/*
+ * '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);
+
+	hctx = hlist_entry_safe(node, struct blk_mq_hw_ctx, cpuhp_dead);
+	ctx = __blk_mq_get_ctx(hctx->queue, cpu);
+
+	spin_lock(&ctx->lock);
+	if (!list_empty(&ctx->rq_list)) {
+		list_splice_init(&ctx->rq_list, &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)
+{
+	cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_DEAD,
+					    &hctx->cpuhp_dead);
+}
+
+/* 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)
+{
+	blk_mq_debugfs_unregister_hctx(hctx);
+
+	if (blk_mq_hw_queue_mapped(hctx))
+		blk_mq_tag_idle(hctx);
+
+	if (set->ops->exit_request)
+		set->ops->exit_request(set, hctx->fq->flush_rq, hctx_idx);
+
+	if (set->ops->exit_hctx)
+		set->ops->exit_hctx(hctx, hctx_idx);
+
+	blk_mq_remove_cpuhp(hctx);
+}
+
+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 int 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)
+{
+	int node;
+
+	node = hctx->numa_node;
+	if (node == NUMA_NO_NODE)
+		node = hctx->numa_node = set->numa_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_SHARED;
+
+	cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD, &hctx->cpuhp_dead);
+
+	hctx->tags = set->tags[hctx_idx];
+
+	/*
+	 * Allocate space for all possible cpus to avoid allocation at
+	 * runtime
+	 */
+	hctx->ctxs = kmalloc_array_node(nr_cpu_ids, sizeof(void *),
+			GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY, node);
+	if (!hctx->ctxs)
+		goto unregister_cpu_notifier;
+
+	if (sbitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8),
+				GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY, node))
+		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);
+
+	if (set->ops->init_hctx &&
+	    set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
+		goto free_bitmap;
+
+	hctx->fq = blk_alloc_flush_queue(q, hctx->numa_node, set->cmd_size,
+			GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY);
+	if (!hctx->fq)
+		goto exit_hctx;
+
+	if (blk_mq_init_request(set, hctx->fq->flush_rq, hctx_idx, node))
+		goto free_fq;
+
+	if (hctx->flags & BLK_MQ_F_BLOCKING)
+		init_srcu_struct(hctx->srcu);
+
+	blk_mq_debugfs_register_hctx(q, hctx);
+
+	return 0;
+
+ free_fq:
+	blk_free_flush_queue(hctx->fq);
+ exit_hctx:
+	if (set->ops->exit_hctx)
+		set->ops->exit_hctx(hctx, hctx_idx);
+ free_bitmap:
+	sbitmap_free(&hctx->ctx_map);
+ free_ctxs:
+	kfree(hctx->ctxs);
+ unregister_cpu_notifier:
+	blk_mq_remove_cpuhp(hctx);
+	return -1;
+}
+
+static void blk_mq_init_cpu_queues(struct request_queue *q,
+				   unsigned int nr_hw_queues)
+{
+	unsigned int i;
+
+	for_each_possible_cpu(i) {
+		struct blk_mq_ctx *__ctx = per_cpu_ptr(q->queue_ctx, i);
+		struct blk_mq_hw_ctx *hctx;
+
+		__ctx->cpu = i;
+		spin_lock_init(&__ctx->lock);
+		INIT_LIST_HEAD(&__ctx->rq_list);
+		__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
+		 */
+		hctx = blk_mq_map_queue(q, i);
+		if (nr_hw_queues > 1 && hctx->numa_node == NUMA_NO_NODE)
+			hctx->numa_node = local_memory_node(cpu_to_node(i));
+	}
+}
+
+static bool __blk_mq_alloc_rq_map(struct blk_mq_tag_set *set, int hctx_idx)
+{
+	int ret = 0;
+
+	set->tags[hctx_idx] = blk_mq_alloc_rq_map(set, hctx_idx,
+					set->queue_depth, set->reserved_tags);
+	if (!set->tags[hctx_idx])
+		return false;
+
+	ret = blk_mq_alloc_rqs(set, set->tags[hctx_idx], hctx_idx,
+				set->queue_depth);
+	if (!ret)
+		return true;
+
+	blk_mq_free_rq_map(set->tags[hctx_idx]);
+	set->tags[hctx_idx] = NULL;
+	return false;
+}
+
+static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set,
+					 unsigned int hctx_idx)
+{
+	if (set->tags[hctx_idx]) {
+		blk_mq_free_rqs(set, set->tags[hctx_idx], hctx_idx);
+		blk_mq_free_rq_map(set->tags[hctx_idx]);
+		set->tags[hctx_idx] = NULL;
+	}
+}
+
+static void blk_mq_map_swqueue(struct request_queue *q)
+{
+	unsigned int i, hctx_idx;
+	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) {
+		hctx_idx = q->mq_map[i];
+		/* unmapped hw queue can be remapped after CPU topo changed */
+		if (!set->tags[hctx_idx] &&
+		    !__blk_mq_alloc_rq_map(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
+			 */
+			q->mq_map[i] = 0;
+		}
+
+		ctx = per_cpu_ptr(q->queue_ctx, i);
+		hctx = blk_mq_map_queue(q, i);
+
+		cpumask_set_cpu(i, hctx->cpumask);
+		ctx->index_hw = hctx->nr_ctx;
+		hctx->ctxs[hctx->nr_ctx++] = ctx;
+	}
+
+	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 && set->tags[i])
+				blk_mq_free_map_and_requests(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;
+	int i;
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (shared)
+			hctx->flags |= BLK_MQ_F_TAG_SHARED;
+		else
+			hctx->flags &= ~BLK_MQ_F_TAG_SHARED;
+	}
+}
+
+static void blk_mq_update_tag_set_depth(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_rcu(&q->tag_set_list);
+	if (list_is_singular(&set->tag_list)) {
+		/* just transitioned to unshared */
+		set->flags &= ~BLK_MQ_F_TAG_SHARED;
+		/* update existing queue */
+		blk_mq_update_tag_set_depth(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)
+{
+	q->tag_set = set;
+
+	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_SHARED)) {
+		set->flags |= BLK_MQ_F_TAG_SHARED;
+		/* update existing queue */
+		blk_mq_update_tag_set_depth(set, true);
+	}
+	if (set->flags & BLK_MQ_F_TAG_SHARED)
+		queue_set_hctx_shared(q, true);
+	list_add_tail_rcu(&q->tag_set_list, &set->tag_list);
+
+	mutex_unlock(&set->tag_list_lock);
+}
+
+/*
+ * 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;
+	unsigned int i;
+
+	/* hctx kobj stays in hctx */
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (!hctx)
+			continue;
+		kobject_put(&hctx->kobj);
+	}
+
+	q->mq_map = NULL;
+
+	kfree(q->queue_hw_ctx);
+
+	/*
+	 * release .mq_kobj and sw queue's kobject now because
+	 * both share lifetime with request queue.
+	 */
+	blk_mq_sysfs_deinit(q);
+
+	free_percpu(q->queue_ctx);
+}
+
+struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
+{
+	struct request_queue *uninit_q, *q;
+
+	uninit_q = blk_alloc_queue_node(GFP_KERNEL, set->numa_node, NULL);
+	if (!uninit_q)
+		return ERR_PTR(-ENOMEM);
+
+	q = blk_mq_init_allocated_queue(set, uninit_q);
+	if (IS_ERR(q))
+		blk_cleanup_queue(uninit_q);
+
+	return q;
+}
+EXPORT_SYMBOL(blk_mq_init_queue);
+
+static int blk_mq_hw_ctx_size(struct blk_mq_tag_set *tag_set)
+{
+	int hw_ctx_size = sizeof(struct blk_mq_hw_ctx);
+
+	BUILD_BUG_ON(ALIGN(offsetof(struct blk_mq_hw_ctx, srcu),
+			   __alignof__(struct blk_mq_hw_ctx)) !=
+		     sizeof(struct blk_mq_hw_ctx));
+
+	if (tag_set->flags & BLK_MQ_F_BLOCKING)
+		hw_ctx_size += sizeof(struct srcu_struct);
+
+	return hw_ctx_size;
+}
+
+static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
+						struct request_queue *q)
+{
+	int i, j;
+	struct blk_mq_hw_ctx **hctxs = q->queue_hw_ctx;
+
+	blk_mq_sysfs_unregister(q);
+
+	/* protect against switching io scheduler  */
+	mutex_lock(&q->sysfs_lock);
+	for (i = 0; i < set->nr_hw_queues; i++) {
+		int node;
+
+		if (hctxs[i])
+			continue;
+
+		node = blk_mq_hw_queue_to_node(q->mq_map, i);
+		hctxs[i] = kzalloc_node(blk_mq_hw_ctx_size(set),
+				GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
+				node);
+		if (!hctxs[i])
+			break;
+
+		if (!zalloc_cpumask_var_node(&hctxs[i]->cpumask,
+					GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
+					node)) {
+			kfree(hctxs[i]);
+			hctxs[i] = NULL;
+			break;
+		}
+
+		atomic_set(&hctxs[i]->nr_active, 0);
+		hctxs[i]->numa_node = node;
+		hctxs[i]->queue_num = i;
+
+		if (blk_mq_init_hctx(q, set, hctxs[i], i)) {
+			free_cpumask_var(hctxs[i]->cpumask);
+			kfree(hctxs[i]);
+			hctxs[i] = NULL;
+			break;
+		}
+		blk_mq_hctx_kobj_init(hctxs[i]);
+	}
+	for (j = i; j < q->nr_hw_queues; j++) {
+		struct blk_mq_hw_ctx *hctx = hctxs[j];
+
+		if (hctx) {
+			if (hctx->tags)
+				blk_mq_free_map_and_requests(set, j);
+			blk_mq_exit_hctx(q, set, hctx, j);
+			kobject_put(&hctx->kobj);
+			hctxs[j] = NULL;
+
+		}
+	}
+	q->nr_hw_queues = i;
+	mutex_unlock(&q->sysfs_lock);
+	blk_mq_sysfs_register(q);
+}
+
+struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
+						  struct request_queue *q)
+{
+	/* 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;
+
+	q->queue_ctx = alloc_percpu(struct blk_mq_ctx);
+	if (!q->queue_ctx)
+		goto err_exit;
+
+	/* init q->mq_kobj and sw queues' kobjects */
+	blk_mq_sysfs_init(q);
+
+	q->queue_hw_ctx = kcalloc_node(nr_cpu_ids, sizeof(*(q->queue_hw_ctx)),
+						GFP_KERNEL, set->numa_node);
+	if (!q->queue_hw_ctx)
+		goto err_percpu;
+
+	q->mq_map = set->mq_map;
+
+	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->nr_queues = nr_cpu_ids;
+
+	q->queue_flags |= QUEUE_FLAG_MQ_DEFAULT;
+
+	if (!(set->flags & BLK_MQ_F_SG_MERGE))
+		queue_flag_set_unlocked(QUEUE_FLAG_NO_SG_MERGE, q);
+
+	q->sg_reserved_size = INT_MAX;
+
+	INIT_DELAYED_WORK(&q->requeue_work, blk_mq_requeue_work);
+	INIT_LIST_HEAD(&q->requeue_list);
+	spin_lock_init(&q->requeue_lock);
+
+	blk_queue_make_request(q, blk_mq_make_request);
+	if (q->mq_ops->poll)
+		q->poll_fn = blk_mq_poll;
+
+	/*
+	 * Do this after blk_queue_make_request() overrides it...
+	 */
+	q->nr_requests = set->queue_depth;
+
+	/*
+	 * Default to classic polling
+	 */
+	q->poll_nsec = -1;
+
+	if (set->ops->complete)
+		blk_queue_softirq_done(q, set->ops->complete);
+
+	blk_mq_init_cpu_queues(q, set->nr_hw_queues);
+	blk_mq_add_queue_tag_set(set, q);
+	blk_mq_map_swqueue(q);
+
+	if (!(set->flags & BLK_MQ_F_NO_SCHED)) {
+		int ret;
+
+		ret = elevator_init_mq(q);
+		if (ret)
+			return ERR_PTR(ret);
+	}
+
+	return q;
+
+err_hctxs:
+	kfree(q->queue_hw_ctx);
+err_percpu:
+	free_percpu(q->queue_ctx);
+err_exit:
+	q->mq_ops = NULL;
+	return ERR_PTR(-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);
+}
+
+/* Basically redo blk_mq_init_queue with queue frozen */
+static void blk_mq_queue_reinit(struct request_queue *q)
+{
+	WARN_ON_ONCE(!atomic_read(&q->mq_freeze_depth));
+
+	blk_mq_debugfs_unregister_hctxs(q);
+	blk_mq_sysfs_unregister(q);
+
+	/*
+	 * redo blk_mq_init_cpu_queues and blk_mq_init_hw_queues. FIXME: maybe
+	 * we should change hctx numa_node according to the new topology (this
+	 * involves freeing and re-allocating memory, worth doing?)
+	 */
+	blk_mq_map_swqueue(q);
+
+	blk_mq_sysfs_register(q);
+	blk_mq_debugfs_register_hctxs(q);
+}
+
+static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
+{
+	int i;
+
+	for (i = 0; i < set->nr_hw_queues; i++)
+		if (!__blk_mq_alloc_rq_map(set, i))
+			goto out_unwind;
+
+	return 0;
+
+out_unwind:
+	while (--i >= 0)
+		blk_mq_free_rq_map(set->tags[i]);
+
+	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_rq_maps(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 int blk_mq_update_queue_map(struct blk_mq_tag_set *set)
+{
+	if (set->ops->map_queues) {
+		/*
+		 * 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->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.
+		 */
+		blk_mq_clear_mq_map(set);
+
+		return set->ops->map_queues(set);
+	} else
+		return blk_mq_map_queues(set);
+}
+
+/*
+ * 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 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 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->queue_depth = min(64U, set->queue_depth);
+	}
+	/*
+	 * There is no use for more h/w queues than cpus.
+	 */
+	if (set->nr_hw_queues > nr_cpu_ids)
+		set->nr_hw_queues = nr_cpu_ids;
+
+	set->tags = kcalloc_node(nr_cpu_ids, sizeof(struct blk_mq_tags *),
+				 GFP_KERNEL, set->numa_node);
+	if (!set->tags)
+		return -ENOMEM;
+
+	ret = -ENOMEM;
+	set->mq_map = kcalloc_node(nr_cpu_ids, sizeof(*set->mq_map),
+				   GFP_KERNEL, set->numa_node);
+	if (!set->mq_map)
+		goto out_free_tags;
+
+	ret = blk_mq_update_queue_map(set);
+	if (ret)
+		goto out_free_mq_map;
+
+	ret = blk_mq_alloc_rq_maps(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:
+	kfree(set->mq_map);
+	set->mq_map = NULL;
+out_free_tags:
+	kfree(set->tags);
+	set->tags = NULL;
+	return ret;
+}
+EXPORT_SYMBOL(blk_mq_alloc_tag_set);
+
+void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
+{
+	int i;
+
+	for (i = 0; i < nr_cpu_ids; i++)
+		blk_mq_free_map_and_requests(set, i);
+
+	kfree(set->mq_map);
+	set->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 i, ret;
+
+	if (!set)
+		return -EINVAL;
+
+	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->tags, nr,
+							false);
+		} else {
+			ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
+							nr, true);
+		}
+		if (ret)
+			break;
+		if (q->elevator && q->elevator->type->ops.mq.depth_updated)
+			q->elevator->type->ops.mq.depth_updated(hctx);
+	}
+
+	if (!ret)
+		q->nr_requests = 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;
+
+	INIT_LIST_HEAD(&qe->node);
+	qe->q = q;
+	qe->type = q->elevator->type;
+	list_add(&qe->node, head);
+
+	mutex_lock(&q->sysfs_lock);
+	/*
+	 * After elevator_switch_mq, 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_mq(q, NULL);
+	mutex_unlock(&q->sysfs_lock);
+
+	return true;
+}
+
+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 = NULL;
+
+	list_for_each_entry(qe, head, node)
+		if (qe->q == q) {
+			t = qe->type;
+			break;
+		}
+
+	if (!t)
+		return;
+
+	list_del(&qe->node);
+	kfree(qe);
+
+	mutex_lock(&q->sysfs_lock);
+	elevator_switch_mq(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);
+
+	lockdep_assert_held(&set->tag_list_lock);
+
+	if (nr_hw_queues > nr_cpu_ids)
+		nr_hw_queues = nr_cpu_ids;
+	if (nr_hw_queues < 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);
+	/*
+	 * Sync with blk_mq_queue_tag_busy_iter.
+	 */
+	synchronize_rcu();
+	/*
+	 * 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;
+
+	set->nr_hw_queues = nr_hw_queues;
+	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_queue_reinit(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 (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags) ||
+	    blk_queue_flag_test_and_set(QUEUE_FLAG_POLL_STATS, q))
+		return true;
+	blk_stat_add_callback(q, q->poll_cb);
+	return false;
+}
+
+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 (!test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags) ||
+	    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 blk_mq_hw_ctx *hctx,
+				       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_sleep(struct request_queue *q,
+				     struct blk_mq_hw_ctx *hctx,
+				     struct request *rq)
+{
+	struct hrtimer_sleeper hs;
+	enum hrtimer_mode mode;
+	unsigned int nsecs;
+	ktime_t kt;
+
+	if (rq->rq_flags & RQF_MQ_POLL_SLEPT)
+		return false;
+
+	/*
+	 * poll_nsec can be:
+	 *
+	 * -1:	don't ever hybrid sleep
+	 *  0:	use half of prev avg
+	 * >0:	use this specific value
+	 */
+	if (q->poll_nsec == -1)
+		return false;
+	else if (q->poll_nsec > 0)
+		nsecs = q->poll_nsec;
+	else
+		nsecs = blk_mq_poll_nsecs(q, hctx, 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_on_stack(&hs.timer, CLOCK_MONOTONIC, mode);
+	hrtimer_set_expires(&hs.timer, kt);
+
+	hrtimer_init_sleeper(&hs, current);
+	do {
+		if (blk_mq_rq_state(rq) == MQ_RQ_COMPLETE)
+			break;
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		hrtimer_start_expires(&hs.timer, 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);
+	return true;
+}
+
+static bool __blk_mq_poll(struct blk_mq_hw_ctx *hctx, struct request *rq)
+{
+	struct request_queue *q = hctx->queue;
+	long state;
+
+	/*
+	 * 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.
+	 */
+	if (blk_mq_poll_hybrid_sleep(q, hctx, rq))
+		return true;
+
+	hctx->poll_considered++;
+
+	state = current->state;
+	while (!need_resched()) {
+		int ret;
+
+		hctx->poll_invoked++;
+
+		ret = q->mq_ops->poll(hctx, rq->tag);
+		if (ret > 0) {
+			hctx->poll_success++;
+			set_current_state(TASK_RUNNING);
+			return true;
+		}
+
+		if (signal_pending_state(state, current))
+			set_current_state(TASK_RUNNING);
+
+		if (current->state == TASK_RUNNING)
+			return true;
+		if (ret < 0)
+			break;
+		cpu_relax();
+	}
+
+	__set_current_state(TASK_RUNNING);
+	return false;
+}
+
+static bool blk_mq_poll(struct request_queue *q, blk_qc_t cookie)
+{
+	struct blk_mq_hw_ctx *hctx;
+	struct request *rq;
+
+	if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
+		return false;
+
+	hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)];
+	if (!blk_qc_t_is_internal(cookie))
+		rq = blk_mq_tag_to_rq(hctx->tags, blk_qc_t_to_tag(cookie));
+	else {
+		rq = blk_mq_tag_to_rq(hctx->sched_tags, blk_qc_t_to_tag(cookie));
+		/*
+		 * With scheduling, if the request has completed, we'll
+		 * get a NULL return here, as we clear the sched tag when
+		 * that happens. The request still remains valid, like always,
+		 * so we should be safe with just the NULL check.
+		 */
+		if (!rq)
+			return false;
+	}
+
+	return __blk_mq_poll(hctx, rq);
+}
+
+static int __init blk_mq_init(void)
+{
+	cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL,
+				blk_mq_hctx_notify_dead);
+	return 0;
+}
+subsys_initcall(blk_mq_init);