[linux.git] / block / blk-tag.c

/*
 * 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
 *
 * Drop the reference count on @bqt and frees it when the last reference
 * is dropped.
 */
void blk_free_tags(struct blk_queue_tag *bqt)
{
	if (atomic_dec_and_test(&bqt->refcnt)) {
		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);
	}
}
EXPORT_SYMBOL(blk_free_tags);

/**
 * __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_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) {
		switch (max_depth) {
		case 2:
			max_depth = 1;
			break;
		case 3:
			max_depth = 2;
			break;
		default:
			max_depth -= 2;
		}
		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);
Commit	Line	Data
8324aa91 JA	1	/*
	2	* Functions related to tagged command queuing
	3	*/
	4	#include <linux/kernel.h>
	5	#include <linux/module.h>
	6	#include <linux/bio.h>
	7	#include <linux/blkdev.h>
5a0e3ad6	8	#include <linux/slab.h>
8324aa91	9
278caf01 AB	10	#include "blk.h"
278caf01 AB	11
8324aa91 JA	12	/**
	13	* blk_queue_find_tag - find a request by its tag and queue
	14	* @q: The request queue for the device
	15	* @tag: The tag of the request
	16	*
	17	* Notes:
	18	* Should be used when a device returns a tag and you want to match
	19	* it with a request.
	20	*
	21	* no locks need be held.
	22	**/
	23	struct request blk_queue_find_tag(struct request_queue q, int tag)
	24	{
	25	return blk_map_queue_find_tag(q->queue_tags, tag);
	26	}
8324aa91 JA	27	EXPORT_SYMBOL(blk_queue_find_tag);
	28
	29	/**
d45b3279	30	* blk_free_tags - release a given set of tag maintenance info
8324aa91 JA	31	* @bqt: the tag map to free
8324aa91 JA	32	*
d45b3279 CH	33	* Drop the reference count on @bqt and frees it when the last reference
d45b3279 CH	34	* is dropped.
8324aa91	35	*/
d45b3279	36	void blk_free_tags(struct blk_queue_tag *bqt)
8324aa91	37	{
d45b3279	38	if (atomic_dec_and_test(&bqt->refcnt)) {
0e3eb45e MW	39	BUG_ON(find_first_bit(bqt->tag_map, bqt->max_depth) <
0e3eb45e MW	40	bqt->max_depth);
8324aa91 JA	41
	42	kfree(bqt->tag_index);
	43	bqt->tag_index = NULL;
	44
	45	kfree(bqt->tag_map);
	46	bqt->tag_map = NULL;
	47
	48	kfree(bqt);
	49	}
8324aa91	50	}
d45b3279	51	EXPORT_SYMBOL(blk_free_tags);
8324aa91 JA	52
	53	/**
	54	* __blk_queue_free_tags - release tag maintenance info
	55	* @q: the request queue for the device
	56	*
	57	* Notes:
	58	* blk_cleanup_queue() will take care of calling this function, if tagging
	59	* has been used. So there's no need to call this directly.
	60	**/
	61	void __blk_queue_free_tags(struct request_queue *q)
	62	{
	63	struct blk_queue_tag *bqt = q->queue_tags;
	64
	65	if (!bqt)
	66	return;
	67
d45b3279	68	blk_free_tags(bqt);
8324aa91 JA	69
8324aa91 JA	70	q->queue_tags = NULL;
aa94b537	71	queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
8324aa91 JA	72	}
8324aa91 JA	73
8324aa91 JA	74	/**
	75	* blk_queue_free_tags - release tag maintenance info
	76	* @q: the request queue for the device
	77	*
	78	* Notes:
710027a4	79	* This is used to disable tagged queuing to a device, yet leave
8324aa91 JA	80	* queue in function.
	81	**/
	82	void blk_queue_free_tags(struct request_queue *q)
	83	{
aa94b537	84	queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
8324aa91	85	}
8324aa91 JA	86	EXPORT_SYMBOL(blk_queue_free_tags);
	87
	88	static int
	89	init_tag_map(struct request_queue q, struct blk_queue_tag tags, int depth)
	90	{
	91	struct request **tag_index;
	92	unsigned long *tag_map;
	93	int nr_ulongs;
	94
	95	if (q && depth > q->nr_requests * 2) {
	96	depth = q->nr_requests * 2;
	97	printk(KERN_ERR "%s: adjusted depth to %d\n",
24c03d47	98	__func__, depth);
8324aa91 JA	99	}
	100
	101	tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
	102	if (!tag_index)
	103	goto fail;
	104
	105	nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
	106	tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
	107	if (!tag_map)
	108	goto fail;
	109
	110	tags->real_max_depth = depth;
	111	tags->max_depth = depth;
	112	tags->tag_index = tag_index;
	113	tags->tag_map = tag_map;
	114
	115	return 0;
	116	fail:
	117	kfree(tag_index);
	118	return -ENOMEM;
	119	}
	120
	121	static struct blk_queue_tag __blk_queue_init_tags(struct request_queue q,
	122	int depth)
	123	{
	124	struct blk_queue_tag *tags;
	125
	126	tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
	127	if (!tags)
	128	goto fail;
	129
	130	if (init_tag_map(q, tags, depth))
	131	goto fail;
	132
8324aa91 JA	133	atomic_set(&tags->refcnt, 1);
	134	return tags;
	135	fail:
	136	kfree(tags);
	137	return NULL;
	138	}
	139
	140	/**
	141	* blk_init_tags - initialize the tag info for an external tag map
	142	* @depth: the maximum queue depth supported
8324aa91 JA	143	**/
	144	struct blk_queue_tag *blk_init_tags(int depth)
	145	{
	146	return __blk_queue_init_tags(NULL, depth);
	147	}
	148	EXPORT_SYMBOL(blk_init_tags);
	149
	150	/**
	151	* blk_queue_init_tags - initialize the queue tag info
	152	* @q: the request queue for the device
	153	* @depth: the maximum queue depth supported
	154	* @tags: the tag to use
aa94b537 JA	155	*
	156	* Queue lock must be held here if the function is called to resize an
	157	* existing map.
8324aa91 JA	158	**/
	159	int blk_queue_init_tags(struct request_queue *q, int depth,
	160	struct blk_queue_tag *tags)
	161	{
	162	int rc;
	163
	164	BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
	165
	166	if (!tags && !q->queue_tags) {
	167	tags = __blk_queue_init_tags(q, depth);
	168
	169	if (!tags)
d41570b7 PST	170	return -ENOMEM;
d41570b7 PST	171
8324aa91	172	} else if (q->queue_tags) {
6728cb0e JA	173	rc = blk_queue_resize_tags(q, depth);
6728cb0e JA	174	if (rc)
8324aa91	175	return rc;
75ad23bc	176	queue_flag_set(QUEUE_FLAG_QUEUED, q);
8324aa91 JA	177	return 0;
	178	} else
	179	atomic_inc(&tags->refcnt);
	180
	181	/*
	182	* assign it, all done
	183	*/
	184	q->queue_tags = tags;
aa94b537	185	queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q);
8324aa91 JA	186	INIT_LIST_HEAD(&q->tag_busy_list);
8324aa91 JA	187	return 0;
8324aa91	188	}
8324aa91 JA	189	EXPORT_SYMBOL(blk_queue_init_tags);
	190
	191	/**
	192	* blk_queue_resize_tags - change the queueing depth
	193	* @q: the request queue for the device
	194	* @new_depth: the new max command queueing depth
	195	*
	196	* Notes:
	197	* Must be called with the queue lock held.
	198	**/
	199	int blk_queue_resize_tags(struct request_queue *q, int new_depth)
	200	{
	201	struct blk_queue_tag *bqt = q->queue_tags;
	202	struct request **tag_index;
	203	unsigned long *tag_map;
	204	int max_depth, nr_ulongs;
	205
	206	if (!bqt)
	207	return -ENXIO;
	208
	209	/*
	210	* if we already have large enough real_max_depth. just
	211	* adjust max_depth. NOTE as requests with tag value
	212	* between new_depth and real_max_depth can be in-flight, tag
	213	* map can not be shrunk blindly here.
	214	*/
	215	if (new_depth <= bqt->real_max_depth) {
	216	bqt->max_depth = new_depth;
	217	return 0;
	218	}
	219
	220	/*
	221	* Currently cannot replace a shared tag map with a new
	222	* one, so error out if this is the case
	223	*/
	224	if (atomic_read(&bqt->refcnt) != 1)
	225	return -EBUSY;
	226
	227	/*
	228	* save the old state info, so we can copy it back
	229	*/
	230	tag_index = bqt->tag_index;
	231	tag_map = bqt->tag_map;
	232	max_depth = bqt->real_max_depth;
	233
	234	if (init_tag_map(q, bqt, new_depth))
	235	return -ENOMEM;
	236
	237	memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
	238	nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
	239	memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
	240
	241	kfree(tag_index);
	242	kfree(tag_map);
	243	return 0;
	244	}
8324aa91 JA	245	EXPORT_SYMBOL(blk_queue_resize_tags);
	246
	247	/**
	248	* blk_queue_end_tag - end tag operations for a request
	249	* @q: the request queue for the device
	250	* @rq: the request that has completed
	251	*
	252	* Description:
710027a4	253	* Typically called when end_that_request_first() returns %0, meaning
8324aa91 JA	254	* all transfers have been done for a request. It's important to call
	255	* this function before end_that_request_last(), as that will put the
	256	* request back on the free list thus corrupting the internal tag list.
	257	*
	258	* Notes:
	259	* queue lock must be held.
	260	**/
	261	void blk_queue_end_tag(struct request_queue q, struct request rq)
	262	{
	263	struct blk_queue_tag *bqt = q->queue_tags;
f2b20d43	264	unsigned tag = rq->tag; /* negative tags invalid */
8324aa91	265
f2b20d43	266	BUG_ON(tag >= bqt->real_max_depth);
8324aa91 JA	267
	268	list_del_init(&rq->queuelist);
	269	rq->cmd_flags &= ~REQ_QUEUED;
	270	rq->tag = -1;
	271
	272	if (unlikely(bqt->tag_index[tag] == NULL))
	273	printk(KERN_ERR "%s: tag %d is missing\n",
24c03d47	274	__func__, tag);
8324aa91 JA	275
	276	bqt->tag_index[tag] = NULL;
	277
	278	if (unlikely(!test_bit(tag, bqt->tag_map))) {
	279	printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
24c03d47	280	__func__, tag);
8324aa91 JA	281	return;
	282	}
	283	/*
	284	* The tag_map bit acts as a lock for tag_index[bit], so we need
	285	* unlock memory barrier semantics.
	286	*/
	287	clear_bit_unlock(tag, bqt->tag_map);
8324aa91	288	}
8324aa91 JA	289	EXPORT_SYMBOL(blk_queue_end_tag);
	290
	291	/**
	292	* blk_queue_start_tag - find a free tag and assign it
	293	* @q: the request queue for the device
	294	* @rq: the block request that needs tagging
	295	*
	296	* Description:
	297	* This can either be used as a stand-alone helper, or possibly be
	298	* assigned as the queue &prep_rq_fn (in which case &struct request
	299	* automagically gets a tag assigned). Note that this function
	300	* assumes that any type of request can be queued! if this is not
	301	* true for your device, you must check the request type before
	302	* calling this function. The request will also be removed from
	303	* the request queue, so it's the drivers responsibility to readd
	304	* it if it should need to be restarted for some reason.
	305	*
	306	* Notes:
	307	* queue lock must be held.
	308	**/
	309	int blk_queue_start_tag(struct request_queue q, struct request rq)
	310	{
	311	struct blk_queue_tag *bqt = q->queue_tags;
0a7ae2ff	312	unsigned max_depth;
8324aa91 JA	313	int tag;
	314
	315	if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
6728cb0e	316	printk(KERN_ERR
8324aa91	317	"%s: request %p for device [%s] already tagged %d",
24c03d47	318	__func__, rq,
8324aa91 JA	319	rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
	320	BUG();
	321	}
	322
	323	/*
	324	* Protect against shared tag maps, as we may not have exclusive
	325	* access to the tag map.
e3ba9ae5 JA	326	*
	327	* We reserve a few tags just for sync IO, since we don't want
	328	* to starve sync IO on behalf of flooding async IO.
8324aa91	329	*/
e3ba9ae5	330	max_depth = bqt->max_depth;
0a7ae2ff	331	if (!rq_is_sync(rq) && max_depth > 1) {
a6b3f761 JK	332	switch (max_depth) {
a6b3f761 JK	333	case 2:
0a7ae2ff	334	max_depth = 1;
a6b3f761 JK	335	break;
	336	case 3:
	337	max_depth = 2;
	338	break;
	339	default:
	340	max_depth -= 2;
	341	}
1b59dd51	342	if (q->in_flight[BLK_RW_ASYNC] > max_depth)
0a7ae2ff JA	343	return 1;
0a7ae2ff JA	344	}
e3ba9ae5	345
8324aa91	346	do {
0a7ae2ff	347	tag = find_first_zero_bit(bqt->tag_map, max_depth);
e3ba9ae5	348	if (tag >= max_depth)
8324aa91 JA	349	return 1;
	350
	351	} while (test_and_set_bit_lock(tag, bqt->tag_map));
	352	/*
	353	* We need lock ordering semantics given by test_and_set_bit_lock.
	354	* See blk_queue_end_tag for details.
	355	*/
	356
	357	rq->cmd_flags \|= REQ_QUEUED;
	358	rq->tag = tag;
	359	bqt->tag_index[tag] = rq;
9934c8c0	360	blk_start_request(rq);
8324aa91	361	list_add(&rq->queuelist, &q->tag_busy_list);
8324aa91 JA	362	return 0;
8324aa91 JA	363	}
8324aa91 JA	364	EXPORT_SYMBOL(blk_queue_start_tag);
	365
	366	/**
	367	* blk_queue_invalidate_tags - invalidate all pending tags
	368	* @q: the request queue for the device
	369	*
	370	* Description:
	371	* Hardware conditions may dictate a need to stop all pending requests.
	372	* In this case, we will safely clear the block side of the tag queue and
	373	* readd all requests to the request queue in the right order.
	374	*
	375	* Notes:
	376	* queue lock must be held.
	377	**/
	378	void blk_queue_invalidate_tags(struct request_queue *q)
	379	{
	380	struct list_head tmp, n;
	381
	382	list_for_each_safe(tmp, n, &q->tag_busy_list)
	383	blk_requeue_request(q, list_entry_rq(tmp));
	384	}
8324aa91	385	EXPORT_SYMBOL(blk_queue_invalidate_tags);