Adding upstream version 5.10.209.upstream/5.10.209

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

1 files changed, 643 insertions, 0 deletions

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
new file mode 100644
index 000000000..16ad9e656
--- /dev/null
+++ b/block/blk-mq-tag.c
@@ -0,0 +1,643 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Tag allocation using scalable bitmaps. Uses active queue tracking to support
+ * fairer distribution of tags between multiple submitters when a shared tag map
+ * is used.
+ *
+ * Copyright (C) 2013-2014 Jens Axboe
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#include <linux/blk-mq.h>
+#include <linux/delay.h>
+#include "blk.h"
+#include "blk-mq.h"
+#include "blk-mq-tag.h"
+
+/*
+ * If a previously inactive queue goes active, bump the active user count.
+ * We need to do this before try to allocate driver tag, then even if fail
+ * to get tag when first time, the other shared-tag users could reserve
+ * budget for it.
+ */
+bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
+{
+	if (blk_mq_is_sbitmap_shared(hctx->flags)) {
+		struct request_queue *q = hctx->queue;
+		struct blk_mq_tag_set *set = q->tag_set;
+
+		if (!test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags) &&
+		    !test_and_set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
+			atomic_inc(&set->active_queues_shared_sbitmap);
+	} else {
+		if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) &&
+		    !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
+			atomic_inc(&hctx->tags->active_queues);
+	}
+
+	return true;
+}
+
+/*
+ * Wakeup all potentially sleeping on tags
+ */
+void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve)
+{
+	sbitmap_queue_wake_all(tags->bitmap_tags);
+	if (include_reserve)
+		sbitmap_queue_wake_all(tags->breserved_tags);
+}
+
+/*
+ * If a previously busy queue goes inactive, potential waiters could now
+ * be allowed to queue. Wake them up and check.
+ */
+void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
+{
+	struct blk_mq_tags *tags = hctx->tags;
+	struct request_queue *q = hctx->queue;
+	struct blk_mq_tag_set *set = q->tag_set;
+
+	if (blk_mq_is_sbitmap_shared(hctx->flags)) {
+		if (!test_and_clear_bit(QUEUE_FLAG_HCTX_ACTIVE,
+					&q->queue_flags))
+			return;
+		atomic_dec(&set->active_queues_shared_sbitmap);
+	} else {
+		if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
+			return;
+		atomic_dec(&tags->active_queues);
+	}
+
+	blk_mq_tag_wakeup_all(tags, false);
+}
+
+static int __blk_mq_get_tag(struct blk_mq_alloc_data *data,
+			    struct sbitmap_queue *bt)
+{
+	if (!data->q->elevator && !(data->flags & BLK_MQ_REQ_RESERVED) &&
+			!hctx_may_queue(data->hctx, bt))
+		return BLK_MQ_NO_TAG;
+
+	if (data->shallow_depth)
+		return __sbitmap_queue_get_shallow(bt, data->shallow_depth);
+	else
+		return __sbitmap_queue_get(bt);
+}
+
+unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
+{
+	struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
+	struct sbitmap_queue *bt;
+	struct sbq_wait_state *ws;
+	DEFINE_SBQ_WAIT(wait);
+	unsigned int tag_offset;
+	int tag;
+
+	if (data->flags & BLK_MQ_REQ_RESERVED) {
+		if (unlikely(!tags->nr_reserved_tags)) {
+			WARN_ON_ONCE(1);
+			return BLK_MQ_NO_TAG;
+		}
+		bt = tags->breserved_tags;
+		tag_offset = 0;
+	} else {
+		bt = tags->bitmap_tags;
+		tag_offset = tags->nr_reserved_tags;
+	}
+
+	tag = __blk_mq_get_tag(data, bt);
+	if (tag != BLK_MQ_NO_TAG)
+		goto found_tag;
+
+	if (data->flags & BLK_MQ_REQ_NOWAIT)
+		return BLK_MQ_NO_TAG;
+
+	ws = bt_wait_ptr(bt, data->hctx);
+	do {
+		struct sbitmap_queue *bt_prev;
+
+		/*
+		 * We're out of tags on this hardware queue, kick any
+		 * pending IO submits before going to sleep waiting for
+		 * some to complete.
+		 */
+		blk_mq_run_hw_queue(data->hctx, false);
+
+		/*
+		 * Retry tag allocation after running the hardware queue,
+		 * as running the queue may also have found completions.
+		 */
+		tag = __blk_mq_get_tag(data, bt);
+		if (tag != BLK_MQ_NO_TAG)
+			break;
+
+		sbitmap_prepare_to_wait(bt, ws, &wait, TASK_UNINTERRUPTIBLE);
+
+		tag = __blk_mq_get_tag(data, bt);
+		if (tag != BLK_MQ_NO_TAG)
+			break;
+
+		bt_prev = bt;
+		io_schedule();
+
+		sbitmap_finish_wait(bt, ws, &wait);
+
+		data->ctx = blk_mq_get_ctx(data->q);
+		data->hctx = blk_mq_map_queue(data->q, data->cmd_flags,
+						data->ctx);
+		tags = blk_mq_tags_from_data(data);
+		if (data->flags & BLK_MQ_REQ_RESERVED)
+			bt = tags->breserved_tags;
+		else
+			bt = tags->bitmap_tags;
+
+		/*
+		 * If destination hw queue is changed, fake wake up on
+		 * previous queue for compensating the wake up miss, so
+		 * other allocations on previous queue won't be starved.
+		 */
+		if (bt != bt_prev)
+			sbitmap_queue_wake_up(bt_prev);
+
+		ws = bt_wait_ptr(bt, data->hctx);
+	} while (1);
+
+	sbitmap_finish_wait(bt, ws, &wait);
+
+found_tag:
+	/*
+	 * Give up this allocation if the hctx is inactive.  The caller will
+	 * retry on an active hctx.
+	 */
+	if (unlikely(test_bit(BLK_MQ_S_INACTIVE, &data->hctx->state))) {
+		blk_mq_put_tag(tags, data->ctx, tag + tag_offset);
+		return BLK_MQ_NO_TAG;
+	}
+	return tag + tag_offset;
+}
+
+void blk_mq_put_tag(struct blk_mq_tags *tags, struct blk_mq_ctx *ctx,
+		    unsigned int tag)
+{
+	if (!blk_mq_tag_is_reserved(tags, tag)) {
+		const int real_tag = tag - tags->nr_reserved_tags;
+
+		BUG_ON(real_tag >= tags->nr_tags);
+		sbitmap_queue_clear(tags->bitmap_tags, real_tag, ctx->cpu);
+	} else {
+		BUG_ON(tag >= tags->nr_reserved_tags);
+		sbitmap_queue_clear(tags->breserved_tags, tag, ctx->cpu);
+	}
+}
+
+struct bt_iter_data {
+	struct blk_mq_hw_ctx *hctx;
+	busy_iter_fn *fn;
+	void *data;
+	bool reserved;
+};
+
+static struct request *blk_mq_find_and_get_req(struct blk_mq_tags *tags,
+		unsigned int bitnr)
+{
+	struct request *rq;
+	unsigned long flags;
+
+	spin_lock_irqsave(&tags->lock, flags);
+	rq = tags->rqs[bitnr];
+	if (!rq || rq->tag != bitnr || !refcount_inc_not_zero(&rq->ref))
+		rq = NULL;
+	spin_unlock_irqrestore(&tags->lock, flags);
+	return rq;
+}
+
+static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
+{
+	struct bt_iter_data *iter_data = data;
+	struct blk_mq_hw_ctx *hctx = iter_data->hctx;
+	struct blk_mq_tags *tags = hctx->tags;
+	bool reserved = iter_data->reserved;
+	struct request *rq;
+	bool ret = true;
+
+	if (!reserved)
+		bitnr += tags->nr_reserved_tags;
+	/*
+	 * We can hit rq == NULL here, because the tagging functions
+	 * test and set the bit before assigning ->rqs[].
+	 */
+	rq = blk_mq_find_and_get_req(tags, bitnr);
+	if (!rq)
+		return true;
+
+	if (rq->q == hctx->queue && rq->mq_hctx == hctx)
+		ret = iter_data->fn(hctx, rq, iter_data->data, reserved);
+	blk_mq_put_rq_ref(rq);
+	return ret;
+}
+
+/**
+ * bt_for_each - iterate over the requests associated with a hardware queue
+ * @hctx:	Hardware queue to examine.
+ * @bt:		sbitmap to examine. This is either the breserved_tags member
+ *		or the bitmap_tags member of struct blk_mq_tags.
+ * @fn:		Pointer to the function that will be called for each request
+ *		associated with @hctx that has been assigned a driver tag.
+ *		@fn will be called as follows: @fn(@hctx, rq, @data, @reserved)
+ *		where rq is a pointer to a request. Return true to continue
+ *		iterating tags, false to stop.
+ * @data:	Will be passed as third argument to @fn.
+ * @reserved:	Indicates whether @bt is the breserved_tags member or the
+ *		bitmap_tags member of struct blk_mq_tags.
+ */
+static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt,
+			busy_iter_fn *fn, void *data, bool reserved)
+{
+	struct bt_iter_data iter_data = {
+		.hctx = hctx,
+		.fn = fn,
+		.data = data,
+		.reserved = reserved,
+	};
+
+	sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data);
+}
+
+struct bt_tags_iter_data {
+	struct blk_mq_tags *tags;
+	busy_tag_iter_fn *fn;
+	void *data;
+	unsigned int flags;
+};
+
+#define BT_TAG_ITER_RESERVED		(1 << 0)
+#define BT_TAG_ITER_STARTED		(1 << 1)
+#define BT_TAG_ITER_STATIC_RQS		(1 << 2)
+
+static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
+{
+	struct bt_tags_iter_data *iter_data = data;
+	struct blk_mq_tags *tags = iter_data->tags;
+	bool reserved = iter_data->flags & BT_TAG_ITER_RESERVED;
+	struct request *rq;
+	bool ret = true;
+	bool iter_static_rqs = !!(iter_data->flags & BT_TAG_ITER_STATIC_RQS);
+
+	if (!reserved)
+		bitnr += tags->nr_reserved_tags;
+
+	/*
+	 * We can hit rq == NULL here, because the tagging functions
+	 * test and set the bit before assigning ->rqs[].
+	 */
+	if (iter_static_rqs)
+		rq = tags->static_rqs[bitnr];
+	else
+		rq = blk_mq_find_and_get_req(tags, bitnr);
+	if (!rq)
+		return true;
+
+	if (!(iter_data->flags & BT_TAG_ITER_STARTED) ||
+	    blk_mq_request_started(rq))
+		ret = iter_data->fn(rq, iter_data->data, reserved);
+	if (!iter_static_rqs)
+		blk_mq_put_rq_ref(rq);
+	return ret;
+}
+
+/**
+ * bt_tags_for_each - iterate over the requests in a tag map
+ * @tags:	Tag map to iterate over.
+ * @bt:		sbitmap to examine. This is either the breserved_tags member
+ *		or the bitmap_tags member of struct blk_mq_tags.
+ * @fn:		Pointer to the function that will be called for each started
+ *		request. @fn will be called as follows: @fn(rq, @data,
+ *		@reserved) where rq is a pointer to a request. Return true
+ *		to continue iterating tags, false to stop.
+ * @data:	Will be passed as second argument to @fn.
+ * @flags:	BT_TAG_ITER_*
+ */
+static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
+			     busy_tag_iter_fn *fn, void *data, unsigned int flags)
+{
+	struct bt_tags_iter_data iter_data = {
+		.tags = tags,
+		.fn = fn,
+		.data = data,
+		.flags = flags,
+	};
+
+	if (tags->rqs)
+		sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data);
+}
+
+static void __blk_mq_all_tag_iter(struct blk_mq_tags *tags,
+		busy_tag_iter_fn *fn, void *priv, unsigned int flags)
+{
+	WARN_ON_ONCE(flags & BT_TAG_ITER_RESERVED);
+
+	if (tags->nr_reserved_tags)
+		bt_tags_for_each(tags, tags->breserved_tags, fn, priv,
+				 flags | BT_TAG_ITER_RESERVED);
+	bt_tags_for_each(tags, tags->bitmap_tags, fn, priv, flags);
+}
+
+/**
+ * blk_mq_all_tag_iter - iterate over all requests in a tag map
+ * @tags:	Tag map to iterate over.
+ * @fn:		Pointer to the function that will be called for each
+ *		request. @fn will be called as follows: @fn(rq, @priv,
+ *		reserved) where rq is a pointer to a request. 'reserved'
+ *		indicates whether or not @rq is a reserved request. Return
+ *		true to continue iterating tags, false to stop.
+ * @priv:	Will be passed as second argument to @fn.
+ *
+ * Caller has to pass the tag map from which requests are allocated.
+ */
+void blk_mq_all_tag_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn,
+		void *priv)
+{
+	__blk_mq_all_tag_iter(tags, fn, priv, BT_TAG_ITER_STATIC_RQS);
+}
+
+/**
+ * blk_mq_tagset_busy_iter - iterate over all started requests in a tag set
+ * @tagset:	Tag set to iterate over.
+ * @fn:		Pointer to the function that will be called for each started
+ *		request. @fn will be called as follows: @fn(rq, @priv,
+ *		reserved) where rq is a pointer to a request. 'reserved'
+ *		indicates whether or not @rq is a reserved request. Return
+ *		true to continue iterating tags, false to stop.
+ * @priv:	Will be passed as second argument to @fn.
+ *
+ * We grab one request reference before calling @fn and release it after
+ * @fn returns.
+ */
+void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
+		busy_tag_iter_fn *fn, void *priv)
+{
+	int i;
+
+	for (i = 0; i < tagset->nr_hw_queues; i++) {
+		if (tagset->tags && tagset->tags[i])
+			__blk_mq_all_tag_iter(tagset->tags[i], fn, priv,
+					      BT_TAG_ITER_STARTED);
+	}
+}
+EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
+
+static bool blk_mq_tagset_count_completed_rqs(struct request *rq,
+		void *data, bool reserved)
+{
+	unsigned *count = data;
+
+	if (blk_mq_request_completed(rq))
+		(*count)++;
+	return true;
+}
+
+/**
+ * blk_mq_tagset_wait_completed_request - wait until all completed req's
+ * complete funtion is run
+ * @tagset:	Tag set to drain completed request
+ *
+ * Note: This function has to be run after all IO queues are shutdown
+ */
+void blk_mq_tagset_wait_completed_request(struct blk_mq_tag_set *tagset)
+{
+	while (true) {
+		unsigned count = 0;
+
+		blk_mq_tagset_busy_iter(tagset,
+				blk_mq_tagset_count_completed_rqs, &count);
+		if (!count)
+			break;
+		msleep(5);
+	}
+}
+EXPORT_SYMBOL(blk_mq_tagset_wait_completed_request);
+
+/**
+ * blk_mq_queue_tag_busy_iter - iterate over all requests with a driver tag
+ * @q:		Request queue to examine.
+ * @fn:		Pointer to the function that will be called for each request
+ *		on @q. @fn will be called as follows: @fn(hctx, rq, @priv,
+ *		reserved) where rq is a pointer to a request and hctx points
+ *		to the hardware queue associated with the request. 'reserved'
+ *		indicates whether or not @rq is a reserved request.
+ * @priv:	Will be passed as third argument to @fn.
+ *
+ * Note: if @q->tag_set is shared with other request queues then @fn will be
+ * called for all requests on all queues that share that tag set and not only
+ * for requests associated with @q.
+ */
+void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
+		void *priv)
+{
+	struct blk_mq_hw_ctx *hctx;
+	int i;
+
+	/*
+	 * __blk_mq_update_nr_hw_queues() updates nr_hw_queues and queue_hw_ctx
+	 * while the queue is frozen. So we can use q_usage_counter to avoid
+	 * racing with it.
+	 */
+	if (!percpu_ref_tryget(&q->q_usage_counter))
+		return;
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		struct blk_mq_tags *tags = hctx->tags;
+
+		/*
+		 * If no software queues are currently mapped to this
+		 * hardware queue, there's nothing to check
+		 */
+		if (!blk_mq_hw_queue_mapped(hctx))
+			continue;
+
+		if (tags->nr_reserved_tags)
+			bt_for_each(hctx, tags->breserved_tags, fn, priv, true);
+		bt_for_each(hctx, tags->bitmap_tags, fn, priv, false);
+	}
+	blk_queue_exit(q);
+}
+
+static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
+		    bool round_robin, int node)
+{
+	return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL,
+				       node);
+}
+
+static int blk_mq_init_bitmap_tags(struct blk_mq_tags *tags,
+				   int node, int alloc_policy)
+{
+	unsigned int depth = tags->nr_tags - tags->nr_reserved_tags;
+	bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
+
+	if (bt_alloc(&tags->__bitmap_tags, depth, round_robin, node))
+		return -ENOMEM;
+	if (bt_alloc(&tags->__breserved_tags, tags->nr_reserved_tags,
+		     round_robin, node))
+		goto free_bitmap_tags;
+
+	tags->bitmap_tags = &tags->__bitmap_tags;
+	tags->breserved_tags = &tags->__breserved_tags;
+
+	return 0;
+free_bitmap_tags:
+	sbitmap_queue_free(&tags->__bitmap_tags);
+	return -ENOMEM;
+}
+
+int blk_mq_init_shared_sbitmap(struct blk_mq_tag_set *set, unsigned int flags)
+{
+	unsigned int depth = set->queue_depth - set->reserved_tags;
+	int alloc_policy = BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags);
+	bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR;
+	int i, node = set->numa_node;
+
+	if (bt_alloc(&set->__bitmap_tags, depth, round_robin, node))
+		return -ENOMEM;
+	if (bt_alloc(&set->__breserved_tags, set->reserved_tags,
+		     round_robin, node))
+		goto free_bitmap_tags;
+
+	for (i = 0; i < set->nr_hw_queues; i++) {
+		struct blk_mq_tags *tags = set->tags[i];
+
+		tags->bitmap_tags = &set->__bitmap_tags;
+		tags->breserved_tags = &set->__breserved_tags;
+	}
+
+	return 0;
+free_bitmap_tags:
+	sbitmap_queue_free(&set->__bitmap_tags);
+	return -ENOMEM;
+}
+
+void blk_mq_exit_shared_sbitmap(struct blk_mq_tag_set *set)
+{
+	sbitmap_queue_free(&set->__bitmap_tags);
+	sbitmap_queue_free(&set->__breserved_tags);
+}
+
+struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
+				     unsigned int reserved_tags,
+				     int node, unsigned int flags)
+{
+	int alloc_policy = BLK_MQ_FLAG_TO_ALLOC_POLICY(flags);
+	struct blk_mq_tags *tags;
+
+	if (total_tags > BLK_MQ_TAG_MAX) {
+		pr_err("blk-mq: tag depth too large\n");
+		return NULL;
+	}
+
+	tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node);
+	if (!tags)
+		return NULL;
+
+	tags->nr_tags = total_tags;
+	tags->nr_reserved_tags = reserved_tags;
+	spin_lock_init(&tags->lock);
+
+	if (flags & BLK_MQ_F_TAG_HCTX_SHARED)
+		return tags;
+
+	if (blk_mq_init_bitmap_tags(tags, node, alloc_policy) < 0) {
+		kfree(tags);
+		return NULL;
+	}
+	return tags;
+}
+
+void blk_mq_free_tags(struct blk_mq_tags *tags, unsigned int flags)
+{
+	if (!(flags & BLK_MQ_F_TAG_HCTX_SHARED)) {
+		sbitmap_queue_free(tags->bitmap_tags);
+		sbitmap_queue_free(tags->breserved_tags);
+	}
+	kfree(tags);
+}
+
+int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
+			    struct blk_mq_tags **tagsptr, unsigned int tdepth,
+			    bool can_grow)
+{
+	struct blk_mq_tags *tags = *tagsptr;
+
+	if (tdepth <= tags->nr_reserved_tags)
+		return -EINVAL;
+
+	/*
+	 * If we are allowed to grow beyond the original size, allocate
+	 * a new set of tags before freeing the old one.
+	 */
+	if (tdepth > tags->nr_tags) {
+		struct blk_mq_tag_set *set = hctx->queue->tag_set;
+		/* Only sched tags can grow, so clear HCTX_SHARED flag  */
+		unsigned int flags = set->flags & ~BLK_MQ_F_TAG_HCTX_SHARED;
+		struct blk_mq_tags *new;
+		bool ret;
+
+		if (!can_grow)
+			return -EINVAL;
+
+		/*
+		 * We need some sort of upper limit, set it high enough that
+		 * no valid use cases should require more.
+		 */
+		if (tdepth > 16 * BLKDEV_MAX_RQ)
+			return -EINVAL;
+
+		new = blk_mq_alloc_rq_map(set, hctx->queue_num, tdepth,
+				tags->nr_reserved_tags, flags);
+		if (!new)
+			return -ENOMEM;
+		ret = blk_mq_alloc_rqs(set, new, hctx->queue_num, tdepth);
+		if (ret) {
+			blk_mq_free_rq_map(new, flags);
+			return -ENOMEM;
+		}
+
+		blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
+		blk_mq_free_rq_map(*tagsptr, flags);
+		*tagsptr = new;
+	} else {
+		/*
+		 * Don't need (or can't) update reserved tags here, they
+		 * remain static and should never need resizing.
+		 */
+		sbitmap_queue_resize(tags->bitmap_tags,
+				tdepth - tags->nr_reserved_tags);
+	}
+
+	return 0;
+}
+
+void blk_mq_tag_resize_shared_sbitmap(struct blk_mq_tag_set *set, unsigned int size)
+{
+	sbitmap_queue_resize(&set->__bitmap_tags, size - set->reserved_tags);
+}
+
+/**
+ * blk_mq_unique_tag() - return a tag that is unique queue-wide
+ * @rq: request for which to compute a unique tag
+ *
+ * The tag field in struct request is unique per hardware queue but not over
+ * all hardware queues. Hence this function that returns a tag with the
+ * hardware context index in the upper bits and the per hardware queue tag in
+ * the lower bits.
+ *
+ * Note: When called for a request that is queued on a non-multiqueue request
+ * queue, the hardware context index is set to zero.
+ */
+u32 blk_mq_unique_tag(struct request *rq)
+{
+	return (rq->mq_hctx->queue_num << BLK_MQ_UNIQUE_TAG_BITS) |
+		(rq->tag & BLK_MQ_UNIQUE_TAG_MASK);
+}
+EXPORT_SYMBOL(blk_mq_unique_tag);