block/blk-mq-tag.c - third_party/kernel - Git at Google

 // 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"

 bool blk_mq_has_free_tags(struct blk_mq_tags *tags)
 {
 	if (!tags)
 		return true;

 	return sbitmap_any_bit_clear(&tags->bitmap_tags.sb);
 }

 /*
  * 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 (!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;

 	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);
 }

 /*
  * For shared tag users, we track the number of currently active users
  * and attempt to provide a fair share of the tag depth for each of them.
  */
 static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
 				  struct sbitmap_queue *bt)
 {
 	unsigned int depth, users;

 	if (!hctx || !(hctx->flags & BLK_MQ_F_TAG_SHARED))
 		return true;
 	if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
 		return true;

 	/*
 	 * Don't try dividing an ant
 	 */
 	if (bt->sb.depth == 1)
 		return true;

 	users = atomic_read(&hctx->tags->active_queues);
 	if (!users)
 		return true;

 	/*
 	 * Allow at least some tags
 	 */
 	depth = max((bt->sb.depth + users - 1) / users, 4U);
 	return atomic_read(&hctx->nr_active) < depth;
 }

 static int __blk_mq_get_tag(struct blk_mq_alloc_data *data,
 			    struct sbitmap_queue *bt)
 {
 	if (!(data->flags & BLK_MQ_REQ_INTERNAL) &&
 	    !hctx_may_queue(data->hctx, bt))
 		return -1;
 	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_TAG_FAIL;
 		}
 		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 != -1)
 		goto found_tag;

 	if (data->flags & BLK_MQ_REQ_NOWAIT)
 		return BLK_MQ_TAG_FAIL;

 	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 != -1)
 			break;

 		sbitmap_prepare_to_wait(bt, ws, &wait, TASK_UNINTERRUPTIBLE);

 		tag = __blk_mq_get_tag(data, bt);
 		if (tag != -1)
 			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:
 	return tag + tag_offset;
 }

 void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, 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 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;

 	if (!reserved)
 		bitnr += tags->nr_reserved_tags;
 	rq = tags->rqs[bitnr];

 	/*
 	 * We can hit rq == NULL here, because the tagging functions
 	 * test and set the bit before assigning ->rqs[].
 	 */
 	if (rq && rq->q == hctx->queue)
 		return iter_data->fn(hctx, rq, iter_data->data, reserved);
 	return true;
 }

 /**
  * 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;
 	bool reserved;
 };

 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->reserved;
 	struct request *rq;

 	if (!reserved)
 		bitnr += tags->nr_reserved_tags;

 	/*
 	 * We can hit rq == NULL here, because the tagging functions
 	 * test and set the bit before assining ->rqs[].
 	 */
 	rq = tags->rqs[bitnr];
 	if (rq && blk_mq_request_started(rq))
 		return iter_data->fn(rq, iter_data->data, reserved);

 	return true;
 }

 /**
  * 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.
  * @reserved:	Indicates whether @bt is the breserved_tags member or the
  *		bitmap_tags member of struct blk_mq_tags.
  */
 static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt,
 			     busy_tag_iter_fn *fn, void *data, bool reserved)
 {
 	struct bt_tags_iter_data iter_data = {
 		.tags = tags,
 		.fn = fn,
 		.data = data,
 		.reserved = reserved,
 	};

 	if (tags->rqs)
 		sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data);
 }

 /**
  * blk_mq_all_tag_busy_iter - iterate over all started requests in a tag map
  * @tags:	Tag map 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.
  */
 static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
 		busy_tag_iter_fn *fn, void *priv)
 {
 	if (tags->nr_reserved_tags)
 		bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true);
 	bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false);
 }

 /**
  * 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.
  */
 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_busy_iter(tagset->tags[i], fn, priv);
 	}
 }
 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. __blk_mq_update_nr_hw_queues() uses
 	 * synchronize_rcu() to ensure this function left the critical section
 	 * below.
 	 */
 	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 struct blk_mq_tags *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))
 		goto free_tags;
 	if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, round_robin,
 		     node))
 		goto free_bitmap_tags;

 	return tags;
 free_bitmap_tags:
 	sbitmap_queue_free(&tags->bitmap_tags);
 free_tags:
 	kfree(tags);
 	return NULL;
 }

 struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 				     unsigned int reserved_tags,
 				     int node, int alloc_policy)
 {
 	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;

 	return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
 }

 void blk_mq_free_tags(struct blk_mq_tags *tags)
 {
 	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;
 		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);
 		if (!new)
 			return -ENOMEM;
 		ret = blk_mq_alloc_rqs(set, new, hctx->queue_num, tdepth);
 		if (ret) {
 			blk_mq_free_rq_map(new);
 			return -ENOMEM;
 		}

 		blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
 		blk_mq_free_rq_map(*tagsptr);
 		*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;
 }

 /**
  * 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);
	// 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"

	bool blk_mq_has_free_tags(struct blk_mq_tags *tags)
	{
	if (!tags)
	return true;

	return sbitmap_any_bit_clear(&tags->bitmap_tags.sb);
	}

	/*
	* 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 (!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;

	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);
	}

	/*
	* For shared tag users, we track the number of currently active users
	* and attempt to provide a fair share of the tag depth for each of them.
	*/
	static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
	struct sbitmap_queue *bt)
	{
	unsigned int depth, users;

	if (!hctx \|\| !(hctx->flags & BLK_MQ_F_TAG_SHARED))
	return true;
	if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
	return true;

	/*
	* Don't try dividing an ant
	*/
	if (bt->sb.depth == 1)
	return true;

	users = atomic_read(&hctx->tags->active_queues);
	if (!users)
	return true;

	/*
	* Allow at least some tags
	*/
	depth = max((bt->sb.depth + users - 1) / users, 4U);
	return atomic_read(&hctx->nr_active) < depth;
	}

	static int __blk_mq_get_tag(struct blk_mq_alloc_data *data,
	struct sbitmap_queue *bt)
	{
	if (!(data->flags & BLK_MQ_REQ_INTERNAL) &&
	!hctx_may_queue(data->hctx, bt))
	return -1;
	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_TAG_FAIL;
	}
	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 != -1)
	goto found_tag;

	if (data->flags & BLK_MQ_REQ_NOWAIT)
	return BLK_MQ_TAG_FAIL;

	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 != -1)
	break;

	sbitmap_prepare_to_wait(bt, ws, &wait, TASK_UNINTERRUPTIBLE);

	tag = __blk_mq_get_tag(data, bt);
	if (tag != -1)
	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:
	return tag + tag_offset;
	}

	void blk_mq_put_tag(struct blk_mq_hw_ctx hctx, 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 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;

	if (!reserved)
	bitnr += tags->nr_reserved_tags;
	rq = tags->rqs[bitnr];

	/*
	* We can hit rq == NULL here, because the tagging functions
	* test and set the bit before assigning ->rqs[].
	*/
	if (rq && rq->q == hctx->queue)
	return iter_data->fn(hctx, rq, iter_data->data, reserved);
	return true;
	}

	/**
	* 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;
	bool reserved;
	};

	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->reserved;
	struct request *rq;

	if (!reserved)
	bitnr += tags->nr_reserved_tags;

	/*
	* We can hit rq == NULL here, because the tagging functions
	* test and set the bit before assining ->rqs[].
	*/
	rq = tags->rqs[bitnr];
	if (rq && blk_mq_request_started(rq))
	return iter_data->fn(rq, iter_data->data, reserved);

	return true;
	}

	/**
	* 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.
	* @reserved: Indicates whether @bt is the breserved_tags member or the
	* bitmap_tags member of struct blk_mq_tags.
	*/
	static void bt_tags_for_each(struct blk_mq_tags tags, struct sbitmap_queue bt,
	busy_tag_iter_fn fn, void data, bool reserved)
	{
	struct bt_tags_iter_data iter_data = {
	.tags = tags,
	.fn = fn,
	.data = data,
	.reserved = reserved,
	};

	if (tags->rqs)
	sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data);
	}

	/**
	* blk_mq_all_tag_busy_iter - iterate over all started requests in a tag map
	* @tags: Tag map 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.
	*/
	static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags,
	busy_tag_iter_fn fn, void priv)
	{
	if (tags->nr_reserved_tags)
	bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true);
	bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false);
	}

	/**
	* 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.
	*/
	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_busy_iter(tagset->tags[i], fn, priv);
	}
	}
	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. __blk_mq_update_nr_hw_queues() uses
	* synchronize_rcu() to ensure this function left the critical section
	* below.
	*/
	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 struct blk_mq_tags 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))
	goto free_tags;
	if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, round_robin,
	node))
	goto free_bitmap_tags;

	return tags;
	free_bitmap_tags:
	sbitmap_queue_free(&tags->bitmap_tags);
	free_tags:
	kfree(tags);
	return NULL;
	}

	struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
	unsigned int reserved_tags,
	int node, int alloc_policy)
	{
	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;

	return blk_mq_init_bitmap_tags(tags, node, alloc_policy);
	}

	void blk_mq_free_tags(struct blk_mq_tags *tags)
	{
	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;
	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);
	if (!new)
	return -ENOMEM;
	ret = blk_mq_alloc_rqs(set, new, hctx->queue_num, tdepth);
	if (ret) {
	blk_mq_free_rq_map(new);
	return -ENOMEM;
	}

	blk_mq_free_rqs(set, *tagsptr, hctx->queue_num);
	blk_mq_free_rq_map(*tagsptr);
	*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;
	}

	/**
	* 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);