[GitHub/mt8127/android_kernel_alcatel_ttab.git] / block / blk-barrier.c

/*
 * Functions related to barrier IO handling
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/blkdev.h>

#include "blk.h"

/**
 * blk_queue_ordered - does this queue support ordered writes
 * @q:        the request queue
 * @ordered:  one of QUEUE_ORDERED_*
 * @prepare_flush_fn: rq setup helper for cache flush ordered writes
 *
 * Description:
 *   For journalled file systems, doing ordered writes on a commit
 *   block instead of explicitly doing wait_on_buffer (which is bad
 *   for performance) can be a big win. Block drivers supporting this
 *   feature should call this function and indicate so.
 *
 **/
int blk_queue_ordered(struct request_queue *q, unsigned ordered,
		      prepare_flush_fn *prepare_flush_fn)
{
	if (ordered & (QUEUE_ORDERED_PREFLUSH | QUEUE_ORDERED_POSTFLUSH) &&
	    prepare_flush_fn == NULL) {
		printk(KERN_ERR "%s: prepare_flush_fn required\n", __func__);
		return -EINVAL;
	}

	if (ordered != QUEUE_ORDERED_NONE &&
	    ordered != QUEUE_ORDERED_DRAIN &&
	    ordered != QUEUE_ORDERED_DRAIN_FLUSH &&
	    ordered != QUEUE_ORDERED_DRAIN_FUA &&
	    ordered != QUEUE_ORDERED_TAG &&
	    ordered != QUEUE_ORDERED_TAG_FLUSH &&
	    ordered != QUEUE_ORDERED_TAG_FUA) {
		printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered);
		return -EINVAL;
	}

	q->ordered = ordered;
	q->next_ordered = ordered;
	q->prepare_flush_fn = prepare_flush_fn;

	return 0;
}
EXPORT_SYMBOL(blk_queue_ordered);

/*
 * Cache flushing for ordered writes handling
 */
unsigned blk_ordered_cur_seq(struct request_queue *q)
{
	if (!q->ordseq)
		return 0;
	return 1 << ffz(q->ordseq);
}

unsigned blk_ordered_req_seq(struct request *rq)
{
	struct request_queue *q = rq->q;

	BUG_ON(q->ordseq == 0);

	if (rq == &q->pre_flush_rq)
		return QUEUE_ORDSEQ_PREFLUSH;
	if (rq == &q->bar_rq)
		return QUEUE_ORDSEQ_BAR;
	if (rq == &q->post_flush_rq)
		return QUEUE_ORDSEQ_POSTFLUSH;

	/*
	 * !fs requests don't need to follow barrier ordering.  Always
	 * put them at the front.  This fixes the following deadlock.
	 *
	 * http://thread.gmane.org/gmane.linux.kernel/537473
	 */
	if (!blk_fs_request(rq))
		return QUEUE_ORDSEQ_DRAIN;

	if ((rq->cmd_flags & REQ_ORDERED_COLOR) ==
	    (q->orig_bar_rq->cmd_flags & REQ_ORDERED_COLOR))
		return QUEUE_ORDSEQ_DRAIN;
	else
		return QUEUE_ORDSEQ_DONE;
}

void blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error)
{
	struct request *rq;

	if (error && !q->orderr)
		q->orderr = error;

	BUG_ON(q->ordseq & seq);
	q->ordseq |= seq;

	if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE)
		return;

	/*
	 * Okay, sequence complete.
	 */
	q->ordseq = 0;
	rq = q->orig_bar_rq;

	if (__blk_end_request(rq, q->orderr, blk_rq_bytes(rq)))
		BUG();
}

static void pre_flush_end_io(struct request *rq, int error)
{
	elv_completed_request(rq->q, rq);
	blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
}

static void bar_end_io(struct request *rq, int error)
{
	elv_completed_request(rq->q, rq);
	blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
}

static void post_flush_end_io(struct request *rq, int error)
{
	elv_completed_request(rq->q, rq);
	blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
}

static void queue_flush(struct request_queue *q, unsigned which)
{
	struct request *rq;
	rq_end_io_fn *end_io;

	if (which == QUEUE_ORDERED_PREFLUSH) {
		rq = &q->pre_flush_rq;
		end_io = pre_flush_end_io;
	} else {
		rq = &q->post_flush_rq;
		end_io = post_flush_end_io;
	}

	blk_rq_init(q, rq);
	rq->cmd_flags = REQ_HARDBARRIER;
	rq->rq_disk = q->bar_rq.rq_disk;
	rq->end_io = end_io;
	q->prepare_flush_fn(q, rq);

	elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
}

static inline struct request *start_ordered(struct request_queue *q,
					    struct request *rq)
{
	q->orderr = 0;
	q->ordered = q->next_ordered;
	q->ordseq |= QUEUE_ORDSEQ_STARTED;

	/*
	 * Prep proxy barrier request.
	 */
	blkdev_dequeue_request(rq);
	q->orig_bar_rq = rq;
	rq = &q->bar_rq;
	blk_rq_init(q, rq);
	if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
		rq->cmd_flags |= REQ_RW;
	if (q->ordered & QUEUE_ORDERED_FUA)
		rq->cmd_flags |= REQ_FUA;
	init_request_from_bio(rq, q->orig_bar_rq->bio);
	rq->end_io = bar_end_io;

	/*
	 * Queue ordered sequence.  As we stack them at the head, we
	 * need to queue in reverse order.  Note that we rely on that
	 * no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
	 * request gets inbetween ordered sequence. If this request is
	 * an empty barrier, we don't need to do a postflush ever since
	 * there will be no data written between the pre and post flush.
	 * Hence a single flush will suffice.
	 */
	if ((q->ordered & QUEUE_ORDERED_POSTFLUSH) && !blk_empty_barrier(rq))
		queue_flush(q, QUEUE_ORDERED_POSTFLUSH);
	else
		q->ordseq |= QUEUE_ORDSEQ_POSTFLUSH;

	elv_insert(q, rq, ELEVATOR_INSERT_FRONT);

	if (q->ordered & QUEUE_ORDERED_PREFLUSH) {
		queue_flush(q, QUEUE_ORDERED_PREFLUSH);
		rq = &q->pre_flush_rq;
	} else
		q->ordseq |= QUEUE_ORDSEQ_PREFLUSH;

	if ((q->ordered & QUEUE_ORDERED_TAG) || q->in_flight == 0)
		q->ordseq |= QUEUE_ORDSEQ_DRAIN;
	else
		rq = NULL;

	return rq;
}

int blk_do_ordered(struct request_queue *q, struct request **rqp)
{
	struct request *rq = *rqp;
	const int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);

	if (!q->ordseq) {
		if (!is_barrier)
			return 1;

		if (q->next_ordered != QUEUE_ORDERED_NONE) {
			*rqp = start_ordered(q, rq);
			return 1;
		} else {
			/*
			 * This can happen when the queue switches to
			 * ORDERED_NONE while this request is on it.
			 */
			blkdev_dequeue_request(rq);
			if (__blk_end_request(rq, -EOPNOTSUPP,
					      blk_rq_bytes(rq)))
				BUG();
			*rqp = NULL;
			return 0;
		}
	}

	/*
	 * Ordered sequence in progress
	 */

	/* Special requests are not subject to ordering rules. */
	if (!blk_fs_request(rq) &&
	    rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
		return 1;

	if (q->ordered & QUEUE_ORDERED_TAG) {
		/* Ordered by tag.  Blocking the next barrier is enough. */
		if (is_barrier && rq != &q->bar_rq)
			*rqp = NULL;
	} else {
		/* Ordered by draining.  Wait for turn. */
		WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
		if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
			*rqp = NULL;
	}

	return 1;
}

static void bio_end_empty_barrier(struct bio *bio, int err)
{
	if (err) {
		if (err == -EOPNOTSUPP)
			set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
		clear_bit(BIO_UPTODATE, &bio->bi_flags);
	}

	complete(bio->bi_private);
}

/**
 * blkdev_issue_flush - queue a flush
 * @bdev:	blockdev to issue flush for
 * @error_sector:	error sector
 *
 * Description:
 *    Issue a flush for the block device in question. Caller can supply
 *    room for storing the error offset in case of a flush error, if they
 *    wish to.  Caller must run wait_for_completion() on its own.
 */
int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
{
	DECLARE_COMPLETION_ONSTACK(wait);
	struct request_queue *q;
	struct bio *bio;
	int ret;

	if (bdev->bd_disk == NULL)
		return -ENXIO;

	q = bdev_get_queue(bdev);
	if (!q)
		return -ENXIO;

	bio = bio_alloc(GFP_KERNEL, 0);
	if (!bio)
		return -ENOMEM;

	bio->bi_end_io = bio_end_empty_barrier;
	bio->bi_private = &wait;
	bio->bi_bdev = bdev;
	submit_bio(WRITE_BARRIER, bio);

	wait_for_completion(&wait);

	/*
	 * The driver must store the error location in ->bi_sector, if
	 * it supports it. For non-stacked drivers, this should be copied
	 * from rq->sector.
	 */
	if (error_sector)
		*error_sector = bio->bi_sector;

	ret = 0;
	if (bio_flagged(bio, BIO_EOPNOTSUPP))
		ret = -EOPNOTSUPP;
	else if (!bio_flagged(bio, BIO_UPTODATE))
		ret = -EIO;

	bio_put(bio);
	return ret;
}
EXPORT_SYMBOL(blkdev_issue_flush);

static void blkdev_discard_end_io(struct bio *bio, int err)
{
	if (err) {
		if (err == -EOPNOTSUPP)
			set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
		clear_bit(BIO_UPTODATE, &bio->bi_flags);
	}

	bio_put(bio);
}

/**
 * blkdev_issue_discard - queue a discard
 * @bdev:	blockdev to issue discard for
 * @sector:	start sector
 * @nr_sects:	number of sectors to discard
 * @gfp_mask:	memory allocation flags (for bio_alloc)
 *
 * Description:
 *    Issue a discard request for the sectors in question. Does not wait.
 */
int blkdev_issue_discard(struct block_device *bdev,
			 sector_t sector, sector_t nr_sects, gfp_t gfp_mask)
{
	struct request_queue *q;
	struct bio *bio;
	int ret = 0;

	if (bdev->bd_disk == NULL)
		return -ENXIO;

	q = bdev_get_queue(bdev);
	if (!q)
		return -ENXIO;

	if (!q->prepare_discard_fn)
		return -EOPNOTSUPP;

	while (nr_sects && !ret) {
		bio = bio_alloc(gfp_mask, 0);
		if (!bio)
			return -ENOMEM;

		bio->bi_end_io = blkdev_discard_end_io;
		bio->bi_bdev = bdev;

		bio->bi_sector = sector;

		if (nr_sects > q->max_hw_sectors) {
			bio->bi_size = q->max_hw_sectors << 9;
			nr_sects -= q->max_hw_sectors;
			sector += q->max_hw_sectors;
		} else {
			bio->bi_size = nr_sects << 9;
			nr_sects = 0;
		}
		bio_get(bio);
		submit_bio(DISCARD_BARRIER, bio);

		/* Check if it failed immediately */
		if (bio_flagged(bio, BIO_EOPNOTSUPP))
			ret = -EOPNOTSUPP;
		else if (!bio_flagged(bio, BIO_UPTODATE))
			ret = -EIO;
		bio_put(bio);
	}
	return ret;
}
EXPORT_SYMBOL(blkdev_issue_discard);
Commit	Line	Data
86db1e29 JA	1	/*
	2	* Functions related to barrier IO handling
	3	*/
	4	#include <linux/kernel.h>
	5	#include <linux/module.h>
	6	#include <linux/bio.h>
	7	#include <linux/blkdev.h>
	8
	9	#include "blk.h"
	10
	11	/**
	12	* blk_queue_ordered - does this queue support ordered writes
	13	* @q: the request queue
	14	* @ordered: one of QUEUE_ORDERED_*
	15	* @prepare_flush_fn: rq setup helper for cache flush ordered writes
	16	*
	17	* Description:
	18	* For journalled file systems, doing ordered writes on a commit
	19	* block instead of explicitly doing wait_on_buffer (which is bad
	20	* for performance) can be a big win. Block drivers supporting this
	21	* feature should call this function and indicate so.
	22	*
	23	**/
	24	int blk_queue_ordered(struct request_queue *q, unsigned ordered,
	25	prepare_flush_fn *prepare_flush_fn)
	26	{
	27	if (ordered & (QUEUE_ORDERED_PREFLUSH \| QUEUE_ORDERED_POSTFLUSH) &&
	28	prepare_flush_fn == NULL) {
24c03d47	29	printk(KERN_ERR "%s: prepare_flush_fn required\n", __func__);
86db1e29 JA	30	return -EINVAL;
	31	}
	32
	33	if (ordered != QUEUE_ORDERED_NONE &&
	34	ordered != QUEUE_ORDERED_DRAIN &&
	35	ordered != QUEUE_ORDERED_DRAIN_FLUSH &&
	36	ordered != QUEUE_ORDERED_DRAIN_FUA &&
	37	ordered != QUEUE_ORDERED_TAG &&
	38	ordered != QUEUE_ORDERED_TAG_FLUSH &&
	39	ordered != QUEUE_ORDERED_TAG_FUA) {
	40	printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered);
	41	return -EINVAL;
	42	}
	43
	44	q->ordered = ordered;
	45	q->next_ordered = ordered;
	46	q->prepare_flush_fn = prepare_flush_fn;
	47
	48	return 0;
	49	}
86db1e29 JA	50	EXPORT_SYMBOL(blk_queue_ordered);
	51
	52	/*
	53	* Cache flushing for ordered writes handling
	54	*/
6f6a036e	55	unsigned blk_ordered_cur_seq(struct request_queue *q)
86db1e29 JA	56	{
	57	if (!q->ordseq)
	58	return 0;
	59	return 1 << ffz(q->ordseq);
	60	}
	61
	62	unsigned blk_ordered_req_seq(struct request *rq)
	63	{
	64	struct request_queue *q = rq->q;
	65
	66	BUG_ON(q->ordseq == 0);
	67
	68	if (rq == &q->pre_flush_rq)
	69	return QUEUE_ORDSEQ_PREFLUSH;
	70	if (rq == &q->bar_rq)
	71	return QUEUE_ORDSEQ_BAR;
	72	if (rq == &q->post_flush_rq)
	73	return QUEUE_ORDSEQ_POSTFLUSH;
	74
	75	/*
	76	* !fs requests don't need to follow barrier ordering. Always
	77	* put them at the front. This fixes the following deadlock.
	78	*
	79	* http://thread.gmane.org/gmane.linux.kernel/537473
	80	*/
	81	if (!blk_fs_request(rq))
	82	return QUEUE_ORDSEQ_DRAIN;
	83
	84	if ((rq->cmd_flags & REQ_ORDERED_COLOR) ==
	85	(q->orig_bar_rq->cmd_flags & REQ_ORDERED_COLOR))
	86	return QUEUE_ORDSEQ_DRAIN;
	87	else
	88	return QUEUE_ORDSEQ_DONE;
	89	}
	90
	91	void blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error)
	92	{
	93	struct request *rq;
	94
	95	if (error && !q->orderr)
	96	q->orderr = error;
	97
	98	BUG_ON(q->ordseq & seq);
	99	q->ordseq \|= seq;
	100
	101	if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE)
	102	return;
	103
	104	/*
	105	* Okay, sequence complete.
	106	*/
	107	q->ordseq = 0;
	108	rq = q->orig_bar_rq;
	109
	110	if (__blk_end_request(rq, q->orderr, blk_rq_bytes(rq)))
	111	BUG();
	112	}
	113
	114	static void pre_flush_end_io(struct request *rq, int error)
	115	{
	116	elv_completed_request(rq->q, rq);
	117	blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
	118	}
	119
120	static void bar_end_io(struct request *rq, int error)
121	{
122	elv_completed_request(rq->q, rq);
123	blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
124	}
125
126	static void post_flush_end_io(struct request *rq, int error)
127	{
128	elv_completed_request(rq->q, rq);
129	blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
130	}
131
132	static void queue_flush(struct request_queue *q, unsigned which)
133	{
134	struct request *rq;
135	rq_end_io_fn *end_io;
136
137	if (which == QUEUE_ORDERED_PREFLUSH) {
138	rq = &q->pre_flush_rq;
139	end_io = pre_flush_end_io;
140	} else {
141	rq = &q->post_flush_rq;
142	end_io = post_flush_end_io;
143	}
144
2a4aa30c	145	blk_rq_init(q, rq);
1afb20f3	146	rq->cmd_flags = REQ_HARDBARRIER;
86db1e29 JA	147	rq->rq_disk = q->bar_rq.rq_disk;
	148	rq->end_io = end_io;
	149	q->prepare_flush_fn(q, rq);
	150
	151	elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
	152	}
	153
	154	static inline struct request start_ordered(struct request_queue q,
	155	struct request *rq)
	156	{
	157	q->orderr = 0;
	158	q->ordered = q->next_ordered;
	159	q->ordseq \|= QUEUE_ORDSEQ_STARTED;
	160
	161	/*
	162	* Prep proxy barrier request.
	163	*/
	164	blkdev_dequeue_request(rq);
	165	q->orig_bar_rq = rq;
	166	rq = &q->bar_rq;
2a4aa30c	167	blk_rq_init(q, rq);
86db1e29 JA	168	if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
	169	rq->cmd_flags \|= REQ_RW;
	170	if (q->ordered & QUEUE_ORDERED_FUA)
	171	rq->cmd_flags \|= REQ_FUA;
86db1e29 JA	172	init_request_from_bio(rq, q->orig_bar_rq->bio);
	173	rq->end_io = bar_end_io;
	174
	175	/*
	176	* Queue ordered sequence. As we stack them at the head, we
	177	* need to queue in reverse order. Note that we rely on that
	178	* no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
	179	* request gets inbetween ordered sequence. If this request is
	180	* an empty barrier, we don't need to do a postflush ever since
	181	* there will be no data written between the pre and post flush.
	182	* Hence a single flush will suffice.
	183	*/
	184	if ((q->ordered & QUEUE_ORDERED_POSTFLUSH) && !blk_empty_barrier(rq))
	185	queue_flush(q, QUEUE_ORDERED_POSTFLUSH);
	186	else
	187	q->ordseq \|= QUEUE_ORDSEQ_POSTFLUSH;
	188
	189	elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
	190
	191	if (q->ordered & QUEUE_ORDERED_PREFLUSH) {
	192	queue_flush(q, QUEUE_ORDERED_PREFLUSH);
	193	rq = &q->pre_flush_rq;
	194	} else
	195	q->ordseq \|= QUEUE_ORDSEQ_PREFLUSH;
	196
	197	if ((q->ordered & QUEUE_ORDERED_TAG) \|\| q->in_flight == 0)
	198	q->ordseq \|= QUEUE_ORDSEQ_DRAIN;
	199	else
	200	rq = NULL;
	201
	202	return rq;
	203	}
	204
	205	int blk_do_ordered(struct request_queue q, struct request *rqp)
	206	{
	207	struct request rq = rqp;
	208	const int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
	209
	210	if (!q->ordseq) {
	211	if (!is_barrier)
	212	return 1;
	213
	214	if (q->next_ordered != QUEUE_ORDERED_NONE) {
	215	*rqp = start_ordered(q, rq);
	216	return 1;
	217	} else {
	218	/*
	219	* This can happen when the queue switches to
	220	* ORDERED_NONE while this request is on it.
	221	*/
	222	blkdev_dequeue_request(rq);
	223	if (__blk_end_request(rq, -EOPNOTSUPP,
	224	blk_rq_bytes(rq)))
	225	BUG();
	226	*rqp = NULL;
	227	return 0;
	228	}
	229	}
	230
	231	/*
	232	* Ordered sequence in progress
	233	*/
	234
	235	/* Special requests are not subject to ordering rules. */
236	if (!blk_fs_request(rq) &&
237	rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
238	return 1;
239
240	if (q->ordered & QUEUE_ORDERED_TAG) {
241	/* Ordered by tag. Blocking the next barrier is enough. */
242	if (is_barrier && rq != &q->bar_rq)
243	*rqp = NULL;
244	} else {
245	/* Ordered by draining. Wait for turn. */
246	WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
247	if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
248	*rqp = NULL;
249	}
250
251	return 1;
252	}
253
254	static void bio_end_empty_barrier(struct bio *bio, int err)
255	{
cc66b451 JA	256	if (err) {
	257	if (err == -EOPNOTSUPP)
	258	set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
86db1e29	259	clear_bit(BIO_UPTODATE, &bio->bi_flags);
cc66b451	260	}
86db1e29 JA	261
	262	complete(bio->bi_private);
	263	}
	264
	265	/**
	266	* blkdev_issue_flush - queue a flush
	267	* @bdev: blockdev to issue flush for
	268	* @error_sector: error sector
	269	*
	270	* Description:
	271	* Issue a flush for the block device in question. Caller can supply
	272	* room for storing the error offset in case of a flush error, if they
	273	* wish to. Caller must run wait_for_completion() on its own.
	274	*/
	275	int blkdev_issue_flush(struct block_device bdev, sector_t error_sector)
	276	{
	277	DECLARE_COMPLETION_ONSTACK(wait);
	278	struct request_queue *q;
	279	struct bio *bio;
	280	int ret;
	281
	282	if (bdev->bd_disk == NULL)
	283	return -ENXIO;
	284
	285	q = bdev_get_queue(bdev);
	286	if (!q)
	287	return -ENXIO;
	288
	289	bio = bio_alloc(GFP_KERNEL, 0);
	290	if (!bio)
	291	return -ENOMEM;
	292
	293	bio->bi_end_io = bio_end_empty_barrier;
	294	bio->bi_private = &wait;
	295	bio->bi_bdev = bdev;
2ebca85a	296	submit_bio(WRITE_BARRIER, bio);
86db1e29 JA	297
	298	wait_for_completion(&wait);
	299
	300	/*
	301	* The driver must store the error location in ->bi_sector, if
	302	* it supports it. For non-stacked drivers, this should be copied
	303	* from rq->sector.
	304	*/
	305	if (error_sector)
	306	*error_sector = bio->bi_sector;
	307
	308	ret = 0;
cc66b451 JA	309	if (bio_flagged(bio, BIO_EOPNOTSUPP))
	310	ret = -EOPNOTSUPP;
	311	else if (!bio_flagged(bio, BIO_UPTODATE))
86db1e29 JA	312	ret = -EIO;
	313
	314	bio_put(bio);
	315	return ret;
	316	}
86db1e29	317	EXPORT_SYMBOL(blkdev_issue_flush);
fb2dce86 DW	318
	319	static void blkdev_discard_end_io(struct bio *bio, int err)
	320	{
	321	if (err) {
	322	if (err == -EOPNOTSUPP)
	323	set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
	324	clear_bit(BIO_UPTODATE, &bio->bi_flags);
	325	}
	326
	327	bio_put(bio);
	328	}
	329
	330	/**
	331	* blkdev_issue_discard - queue a discard
	332	* @bdev: blockdev to issue discard for
	333	* @sector: start sector
	334	* @nr_sects: number of sectors to discard
3e6053d7	335	* @gfp_mask: memory allocation flags (for bio_alloc)
fb2dce86 DW	336	*
	337	* Description:
	338	* Issue a discard request for the sectors in question. Does not wait.
	339	*/
3e6053d7 HD	340	int blkdev_issue_discard(struct block_device *bdev,
3e6053d7 HD	341	sector_t sector, sector_t nr_sects, gfp_t gfp_mask)
fb2dce86 DW	342	{
	343	struct request_queue *q;
	344	struct bio *bio;
	345	int ret = 0;
	346
	347	if (bdev->bd_disk == NULL)
	348	return -ENXIO;
	349
	350	q = bdev_get_queue(bdev);
	351	if (!q)
	352	return -ENXIO;
	353
	354	if (!q->prepare_discard_fn)
	355	return -EOPNOTSUPP;
	356
	357	while (nr_sects && !ret) {
3e6053d7	358	bio = bio_alloc(gfp_mask, 0);
fb2dce86 DW	359	if (!bio)
	360	return -ENOMEM;
	361
	362	bio->bi_end_io = blkdev_discard_end_io;
	363	bio->bi_bdev = bdev;
	364
	365	bio->bi_sector = sector;
	366
	367	if (nr_sects > q->max_hw_sectors) {
	368	bio->bi_size = q->max_hw_sectors << 9;
	369	nr_sects -= q->max_hw_sectors;
	370	sector += q->max_hw_sectors;
	371	} else {
	372	bio->bi_size = nr_sects << 9;
	373	nr_sects = 0;
	374	}
	375	bio_get(bio);
e17fc0a1	376	submit_bio(DISCARD_BARRIER, bio);
fb2dce86 DW	377
	378	/* Check if it failed immediately */
	379	if (bio_flagged(bio, BIO_EOPNOTSUPP))
	380	ret = -EOPNOTSUPP;
	381	else if (!bio_flagged(bio, BIO_UPTODATE))
	382	ret = -EIO;
	383	bio_put(bio);
	384	}
	385	return ret;
	386	}
	387	EXPORT_SYMBOL(blkdev_issue_discard);