block/blk-tag.c - maze/linux - Git at Google

 /*
  * 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)
 		return -EBUSY;

 	/*
 	 * save the old state info, so we can copy it back
 	 */
 	tag_index = bqt->tag_index;
 	tag_map = bqt->tag_map;
 	max_depth = bqt->real_max_depth;

 	if (init_tag_map(q, bqt, new_depth))
 		return -ENOMEM;

 	memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
 	nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
 	memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));

 	kfree(tag_index);
 	kfree(tag_map);
 	return 0;
 }
 EXPORT_SYMBOL(blk_queue_resize_tags);

 /**
  * blk_queue_end_tag - end tag operations for a request
  * @q:  the request queue for the device
  * @rq: the request that has completed
  *
  *  Description:
  *    Typically called when end_that_request_first() returns %0, meaning
  *    all transfers have been done for a request. It's important to call
  *    this function before end_that_request_last(), as that will put the
  *    request back on the free list thus corrupting the internal tag list.
  *
  *  Notes:
  *   queue lock must be held.
  **/
 void blk_queue_end_tag(struct request_queue *q, struct request *rq)
 {
 	struct blk_queue_tag *bqt = q->queue_tags;
 	unsigned tag = rq->tag; /* negative tags invalid */

 	BUG_ON(tag >= bqt->real_max_depth);

 	list_del_init(&rq->queuelist);
 	rq->cmd_flags &= ~REQ_QUEUED;
 	rq->tag = -1;

 	if (unlikely(bqt->tag_index[tag] == NULL))
 		printk(KERN_ERR "%s: tag %d is missing\n",
 		       __func__, tag);

 	bqt->tag_index[tag] = NULL;

 	if (unlikely(!test_bit(tag, bqt->tag_map))) {
 		printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
 		       __func__, tag);
 		return;
 	}
 	/*
 	 * The tag_map bit acts as a lock for tag_index[bit], so we need
 	 * unlock memory barrier semantics.
 	 */
 	clear_bit_unlock(tag, bqt->tag_map);
 }
 EXPORT_SYMBOL(blk_queue_end_tag);

 /**
  * blk_queue_start_tag - find a free tag and assign it
  * @q:  the request queue for the device
  * @rq:  the block request that needs tagging
  *
  *  Description:
  *    This can either be used as a stand-alone helper, or possibly be
  *    assigned as the queue &prep_rq_fn (in which case &struct request
  *    automagically gets a tag assigned). Note that this function
  *    assumes that any type of request can be queued! if this is not
  *    true for your device, you must check the request type before
  *    calling this function.  The request will also be removed from
  *    the request queue, so it's the drivers responsibility to readd
  *    it if it should need to be restarted for some reason.
  *
  *  Notes:
  *   queue lock must be held.
  **/
 int blk_queue_start_tag(struct request_queue *q, struct request *rq)
 {
 	struct blk_queue_tag *bqt = q->queue_tags;
 	unsigned max_depth;
 	int tag;

 	if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
 		printk(KERN_ERR
 		       "%s: request %p for device [%s] already tagged %d",
 		       __func__, rq,
 		       rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
 		BUG();
 	}

 	/*
 	 * Protect against shared tag maps, as we may not have exclusive
 	 * access to the tag map.
 	 *
 	 * We reserve a few tags just for sync IO, since we don't want
 	 * to starve sync IO on behalf of flooding async IO.
 	 */
 	max_depth = bqt->max_depth;
 	if (!rq_is_sync(rq) && max_depth > 1) {
 		max_depth -= 2;
 		if (!max_depth)
 			max_depth = 1;
 		if (q->in_flight[BLK_RW_ASYNC] > max_depth)
 			return 1;
 	}

 	do {
 		tag = find_first_zero_bit(bqt->tag_map, max_depth);
 		if (tag >= max_depth)
 			return 1;

 	} while (test_and_set_bit_lock(tag, bqt->tag_map));
 	/*
 	 * We need lock ordering semantics given by test_and_set_bit_lock.
 	 * See blk_queue_end_tag for details.
 	 */

 	rq->cmd_flags |= REQ_QUEUED;
 	rq->tag = tag;
 	bqt->tag_index[tag] = rq;
 	blk_start_request(rq);
 	list_add(&rq->queuelist, &q->tag_busy_list);
 	return 0;
 }
 EXPORT_SYMBOL(blk_queue_start_tag);

 /**
  * blk_queue_invalidate_tags - invalidate all pending tags
  * @q:  the request queue for the device
  *
  *  Description:
  *   Hardware conditions may dictate a need to stop all pending requests.
  *   In this case, we will safely clear the block side of the tag queue and
  *   readd all requests to the request queue in the right order.
  *
  *  Notes:
  *   queue lock must be held.
  **/
 void blk_queue_invalidate_tags(struct request_queue *q)
 {
 	struct list_head *tmp, *n;

 	list_for_each_safe(tmp, n, &q->tag_busy_list)
 		blk_requeue_request(q, list_entry_rq(tmp));
 }
 EXPORT_SYMBOL(blk_queue_invalidate_tags);
	/*
	* 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)
	return -EBUSY;

	/*
	* save the old state info, so we can copy it back
	*/
	tag_index = bqt->tag_index;
	tag_map = bqt->tag_map;
	max_depth = bqt->real_max_depth;

	if (init_tag_map(q, bqt, new_depth))
	return -ENOMEM;

	memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
	nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
	memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));

	kfree(tag_index);
	kfree(tag_map);
	return 0;
	}
	EXPORT_SYMBOL(blk_queue_resize_tags);

	/**
	* blk_queue_end_tag - end tag operations for a request
	* @q: the request queue for the device
	* @rq: the request that has completed
	*
	* Description:
	* Typically called when end_that_request_first() returns %0, meaning
	* all transfers have been done for a request. It's important to call
	* this function before end_that_request_last(), as that will put the
	* request back on the free list thus corrupting the internal tag list.
	*
	* Notes:
	* queue lock must be held.
	**/
	void blk_queue_end_tag(struct request_queue q, struct request rq)
	{
	struct blk_queue_tag *bqt = q->queue_tags;
	unsigned tag = rq->tag; /* negative tags invalid */

	BUG_ON(tag >= bqt->real_max_depth);

	list_del_init(&rq->queuelist);
	rq->cmd_flags &= ~REQ_QUEUED;
	rq->tag = -1;

	if (unlikely(bqt->tag_index[tag] == NULL))
	printk(KERN_ERR "%s: tag %d is missing\n",
	__func__, tag);

	bqt->tag_index[tag] = NULL;

	if (unlikely(!test_bit(tag, bqt->tag_map))) {
	printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
	__func__, tag);
	return;
	}
	/*
	* The tag_map bit acts as a lock for tag_index[bit], so we need
	* unlock memory barrier semantics.
	*/
	clear_bit_unlock(tag, bqt->tag_map);
	}
	EXPORT_SYMBOL(blk_queue_end_tag);

	/**
	* blk_queue_start_tag - find a free tag and assign it
	* @q: the request queue for the device
	* @rq: the block request that needs tagging
	*
	* Description:
	* This can either be used as a stand-alone helper, or possibly be
	* assigned as the queue &prep_rq_fn (in which case &struct request
	* automagically gets a tag assigned). Note that this function
	* assumes that any type of request can be queued! if this is not
	* true for your device, you must check the request type before
	* calling this function. The request will also be removed from
	* the request queue, so it's the drivers responsibility to readd
	* it if it should need to be restarted for some reason.
	*
	* Notes:
	* queue lock must be held.
	**/
	int blk_queue_start_tag(struct request_queue q, struct request rq)
	{
	struct blk_queue_tag *bqt = q->queue_tags;
	unsigned max_depth;
	int tag;

	if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
	printk(KERN_ERR
	"%s: request %p for device [%s] already tagged %d",
	__func__, rq,
	rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
	BUG();
	}

	/*
	* Protect against shared tag maps, as we may not have exclusive
	* access to the tag map.
	*
	* We reserve a few tags just for sync IO, since we don't want
	* to starve sync IO on behalf of flooding async IO.
	*/
	max_depth = bqt->max_depth;
	if (!rq_is_sync(rq) && max_depth > 1) {
	max_depth -= 2;
	if (!max_depth)
	max_depth = 1;
	if (q->in_flight[BLK_RW_ASYNC] > max_depth)
	return 1;
	}

	do {
	tag = find_first_zero_bit(bqt->tag_map, max_depth);
	if (tag >= max_depth)
	return 1;

	} while (test_and_set_bit_lock(tag, bqt->tag_map));
	/*
	* We need lock ordering semantics given by test_and_set_bit_lock.
	* See blk_queue_end_tag for details.
	*/

	rq->cmd_flags \|= REQ_QUEUED;
	rq->tag = tag;
	bqt->tag_index[tag] = rq;
	blk_start_request(rq);
	list_add(&rq->queuelist, &q->tag_busy_list);
	return 0;
	}
	EXPORT_SYMBOL(blk_queue_start_tag);

	/**
	* blk_queue_invalidate_tags - invalidate all pending tags
	* @q: the request queue for the device
	*
	* Description:
	* Hardware conditions may dictate a need to stop all pending requests.
	* In this case, we will safely clear the block side of the tag queue and
	* readd all requests to the request queue in the right order.
	*
	* Notes:
	* queue lock must be held.
	**/
	void blk_queue_invalidate_tags(struct request_queue *q)
	{
	struct list_head tmp, n;

	list_for_each_safe(tmp, n, &q->tag_busy_list)
	blk_requeue_request(q, list_entry_rq(tmp));
	}
	EXPORT_SYMBOL(blk_queue_invalidate_tags);