/*
 * Functions related to tagged command queuing
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/slab.h>

#include "blk.h"

/**
 * blk_queue_find_tag - find a request by its tag and queue
 * @q:	 The request queue for the device
 * @tag: The tag of the request
 *
 * Notes:
 *    Should be used when a device returns a tag and you want to match
 *    it with a request.
 *
 *    no locks need be held.
 **/
struct request *blk_queue_find_tag(struct request_queue *q, int tag)
{
	return blk_map_queue_find_tag(q->queue_tags, tag);
}
EXPORT_SYMBOL(blk_queue_find_tag);

/**
 * __blk_free_tags - release a given set of tag maintenance info
 * @bqt:	the tag map to free
 *
 * Tries to free the specified @bqt.  Returns true if it was
 * actually freed and false if there are still references using it
 */
static int __blk_free_tags(struct blk_queue_tag *bqt)
{
	int retval;

	retval = atomic_dec_and_test(&bqt->refcnt);
	if (retval) {
		BUG_ON(find_first_bit(bqt->tag_map, bqt->max_depth) <
							bqt->max_depth);

		kfree(bqt->tag_index);
		bqt->tag_index = NULL;

		kfree(bqt->tag_map);
		bqt->tag_map = NULL;

		kfree(bqt);
	}

	return retval;
}

/**
 * __blk_queue_free_tags - release tag maintenance info
 * @q:  the request queue for the device
 *
 *  Notes:
 *    blk_cleanup_queue() will take care of calling this function, if tagging
 *    has been used. So there's no need to call this directly.
 **/
void __blk_queue_free_tags(struct request_queue *q)
{
	struct blk_queue_tag *bqt = q->queue_tags;

	if (!bqt)
		return;

	__blk_free_tags(bqt);

	q->queue_tags = NULL;
	queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
}

/**
 * blk_free_tags - release a given set of tag maintenance info
 * @bqt:	the tag map to free
 *
 * For externally managed @bqt frees the map.  Callers of this
 * function must guarantee to have released all the queues that
 * might have been using this tag map.
 */
void blk_free_tags(struct blk_queue_tag *bqt)
{
	if (unlikely(!__blk_free_tags(bqt)))
		BUG();
}
EXPORT_SYMBOL(blk_free_tags);

/**
 * blk_queue_free_tags - release tag maintenance info
 * @q:  the request queue for the device
 *
 *  Notes:
 *	This is used to disable tagged queuing to a device, yet leave
 *	queue in function.
 **/
void blk_queue_free_tags(struct request_queue *q)
{
	queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
}
EXPORT_SYMBOL(blk_queue_free_tags);

static int
init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
{
	struct request **tag_index;
	unsigned long *tag_map;
	int nr_ulongs;

	if (q && depth > q->nr_requests * 2) {
		depth = q->nr_requests * 2;
		printk(KERN_ERR "%s: adjusted depth to %d\n",
		       __func__, depth);
	}

	tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
	if (!tag_index)
		goto fail;

	nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
	tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
	if (!tag_map)
		goto fail;

	tags->real_max_depth = depth;
	tags->max_depth = depth;
	tags->tag_index = tag_index;
	tags->tag_map = tag_map;

	return 0;
fail:
	kfree(tag_index);
	return -ENOMEM;
}

static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
						   int depth)
{
	struct blk_queue_tag *tags;

	tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
	if (!tags)
		goto fail;

	if (init_tag_map(q, tags, depth))
		goto fail;

	atomic_set(&tags->refcnt, 1);
	return tags;
fail:
	kfree(tags);
	return NULL;
}

/**
 * blk_init_tags - initialize the tag info for an external tag map
 * @depth:	the maximum queue depth supported
 **/
struct blk_queue_tag *blk_init_tags(int depth)
{
	return __blk_queue_init_tags(NULL, depth);
}
EXPORT_SYMBOL(blk_init_tags);

/**
 * blk_queue_init_tags - initialize the queue tag info
 * @q:  the request queue for the device
 * @depth:  the maximum queue depth supported
 * @tags: the tag to use
 *
 * Queue lock must be held here if the function is called to resize an
 * existing map.
 **/
int blk_queue_init_tags(struct request_queue *q, int depth,
			struct blk_queue_tag *tags)
{
	int rc;

	BUG_ON(tags && q->queue_tags && tags != q->queue_tags);

	if (!tags && !q->queue_tags) {
		tags = __blk_queue_init_tags(q, depth);

		if (!tags)
			return -ENOMEM;

	} else if (q->queue_tags) {
		rc = blk_queue_resize_tags(q, depth);
		if (rc)
			return rc;
		queue_flag_set(QUEUE_FLAG_QUEUED, q);
		return 0;
	} else
		atomic_inc(&tags->refcnt);

	/*
	 * assign it, all done
	 */
	q->queue_tags = tags;
	queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q);
	INIT_LIST_HEAD(&q->tag_busy_list);
	return 0;
}
EXPORT_SYMBOL(blk_queue_init_tags);

/**
 * blk_queue_resize_tags - change the queueing depth
 * @q:  the request queue for the device
 * @new_depth: the new max command queueing depth
 *
 *  Notes:
 *    Must be called with the queue lock held.
 **/
int blk_queue_resize_tags(struct request_queue *q, int new_depth)
{
	struct blk_queue_tag *bqt = q->queue_tags;
	struct request **tag_index;
	unsigned long *tag_map;
	int max_depth, nr_ulongs;

	if (!bqt)
		return -ENXIO;

	/*
	 * if we already have large enough real_max_depth.  just
	 * adjust max_depth.  *NOTE* as requests with tag value
	 * between new_depth and real_max_depth can be in-flight, tag
	 * map can not be shrunk blindly here.
	 */
	if (new_depth <= bqt->real_max_depth) {
		bqt->max_depth = new_depth;
		return 0;
	}

	/*
	 * Currently cannot replace a shared tag map with a new
	 * one, so error out if this is the case
	 */
	if (atomic_read(&bqt->refcnt) != 1)