[net-next-2.6.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 <linux/gfp.h>

#include "blk.h"

/**
 * blk_queue_ordered - does this queue support ordered writes
 * @q:        the request queue
 * @ordered:  one of QUEUE_ORDERED_*
 *
 * 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)
{
	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;

	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 (rq->cmd_type != REQ_TYPE_FS)
		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;
}

bool 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 false;

	/*
	 * Okay, sequence complete.
	 */
	q->ordseq = 0;
	rq = q->orig_bar_rq;
	__blk_end_request_all(rq, q->orderr);
	return true;
}

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_DO_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_type = REQ_TYPE_FS;
	rq->cmd_flags = REQ_HARDBARRIER | REQ_FLUSH;
	rq->rq_disk = q->orig_bar_rq->rq_disk;
	rq->end_io = end_io;

	elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
}

static inline bool start_ordered(struct request_queue *q, struct request **rqp)
{
	struct request *rq = *rqp;
	unsigned skip = 0;

	q->orderr = 0;
	q->ordered = q->next_ordered;
	q->ordseq |= QUEUE_ORDSEQ_STARTED;

	/*
	 * For an empty barrier, there's no actual BAR request, which
	 * in turn makes POSTFLUSH unnecessary.  Mask them off.
	 */
	if (!blk_rq_sectors(rq)) {
		q->ordered &= ~(QUEUE_ORDERED_DO_BAR |
				QUEUE_ORDERED_DO_POSTFLUSH);
		/*
		 * Empty barrier on a write-through device w/ ordered
		 * tag has no command to issue and without any command
		 * to issue, ordering by tag can't be used.  Drain
		 * instead.
		 */
		if ((q->ordered & QUEUE_ORDERED_BY_TAG) &&
		    !(q->ordered & QUEUE_ORDERED_DO_PREFLUSH)) {
			q->ordered &= ~QUEUE_ORDERED_BY_TAG;
			q->ordered |= QUEUE_ORDERED_BY_DRAIN;
		}
	}

	/* stash away the original request */
	blk_dequeue_request(rq);
	q->orig_bar_rq = rq;
	rq = NULL;

	/*
	 * 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 (q->ordered & QUEUE_ORDERED_DO_POSTFLUSH) {
		queue_flush(q, QUEUE_ORDERED_DO_POSTFLUSH);
		rq = &q->post_flush_rq;
	} else
		skip |= QUEUE_ORDSEQ_POSTFLUSH;

	if (q->ordered & QUEUE_ORDERED_DO_BAR) {
		rq = &q->bar_rq;

		/* initialize proxy request and queue it */
		blk_rq_init(q, rq);
		if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
			rq->cmd_flags |= REQ_WRITE;
		if (q->ordered & QUEUE_ORDERED_DO_FUA)
			rq->cmd_flags |= REQ_FUA;
		init_request_from_bio(rq, q->orig_bar_rq->bio);
		rq->end_io = bar_end_io;

		elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
	} else
		skip |= QUEUE_ORDSEQ_BAR;

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

	if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && queue_in_flight(q))
		rq = NULL;
	else
		skip |= QUEUE_ORDSEQ_DRAIN;

	*rqp = rq;

	/*
	 * Complete skipped sequences.  If whole sequence is complete,
	 * return false to tell elevator that this request is gone.
	 */
	return !blk_ordered_complete_seq(q, skip, 0);
}

bool blk_do_ordered(struct request_queue *q, struct request **rqp)
{
	struct request *rq = *rqp;
	const int is_barrier = rq->cmd_type == REQ_TYPE_FS &&
				(rq->cmd_flags & REQ_HARDBARRIER);

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

		if (q->next_ordered != QUEUE_ORDERED_NONE)
			return start_ordered(q, rqp);
		else {
			/*
			 * Queue ordering not supported.  Terminate
			 * with prejudice.
			 */
			blk_dequeue_request(rq);
			__blk_end_request_all(rq, -EOPNOTSUPP);
			*rqp = NULL;
			return false;
		}
	}

	/*
	 * Ordered sequence in progress
	 */

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

	if (q->ordered & QUEUE_ORDERED_BY_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 true;
}

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);
	}
	if (bio->bi_private)
		complete(bio->bi_private);
	bio_put(bio);
}

/**
 * blkdev_issue_flush - queue a flush
 * @bdev:	blockdev to issue flush for
 * @gfp_mask:	memory allocation flags (for bio_alloc)
 * @error_sector:	error sector
 * @flags:	BLKDEV_IFL_* flags to control behaviour
 *
 * 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. If WAIT flag is not passed then caller may check only what
 *    request was pushed in some internal queue for later handling.
 */
int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask,
		sector_t *error_sector, unsigned long flags)
{
	DECLARE_COMPLETION_ONSTACK(wait);
	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;

	/*
	 * some block devices may not have their queue correctly set up here
	 * (e.g. loop device without a backing file) and so issuing a flush
	 * here will panic. Ensure there is a request function before issuing
	 * the barrier.
	 */
	if (!q->make_request_fn)
		return -ENXIO;

	bio = bio_alloc(gfp_mask, 0);
	bio->bi_end_io = bio_end_empty_barrier;
	bio->bi_bdev = bdev;
	if (test_bit(BLKDEV_WAIT, &flags))
		bio->bi_private = &wait;

	bio_get(bio);
	submit_bio(WRITE_BARRIER, bio);
	if (test_bit(BLKDEV_WAIT, &flags)) {
		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 blk_rq_pos(rq).
		 */
		if (error_sector)
			*error_sector = bio->bi_sector;
	}

	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);
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>
5a0e3ad6	8	#include <linux/gfp.h>
86db1e29 JA	9
	10	#include "blk.h"
	11
	12	/**
	13	* blk_queue_ordered - does this queue support ordered writes
	14	* @q: the request queue
	15	* @ordered: one of QUEUE_ORDERED_*
86db1e29 JA	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	**/
00fff265	24	int blk_queue_ordered(struct request_queue *q, unsigned ordered)
86db1e29	25	{
86db1e29 JA	26	if (ordered != QUEUE_ORDERED_NONE &&
	27	ordered != QUEUE_ORDERED_DRAIN &&
	28	ordered != QUEUE_ORDERED_DRAIN_FLUSH &&
	29	ordered != QUEUE_ORDERED_DRAIN_FUA &&
	30	ordered != QUEUE_ORDERED_TAG &&
	31	ordered != QUEUE_ORDERED_TAG_FLUSH &&
	32	ordered != QUEUE_ORDERED_TAG_FUA) {
	33	printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered);
	34	return -EINVAL;
	35	}
	36
	37	q->ordered = ordered;
	38	q->next_ordered = ordered;
86db1e29 JA	39
	40	return 0;
	41	}
86db1e29 JA	42	EXPORT_SYMBOL(blk_queue_ordered);
	43
	44	/*
	45	* Cache flushing for ordered writes handling
	46	*/
6f6a036e	47	unsigned blk_ordered_cur_seq(struct request_queue *q)
86db1e29 JA	48	{
	49	if (!q->ordseq)
	50	return 0;
	51	return 1 << ffz(q->ordseq);
	52	}
	53
	54	unsigned blk_ordered_req_seq(struct request *rq)
	55	{
	56	struct request_queue *q = rq->q;
	57
	58	BUG_ON(q->ordseq == 0);
	59
	60	if (rq == &q->pre_flush_rq)
	61	return QUEUE_ORDSEQ_PREFLUSH;
	62	if (rq == &q->bar_rq)
	63	return QUEUE_ORDSEQ_BAR;
	64	if (rq == &q->post_flush_rq)
	65	return QUEUE_ORDSEQ_POSTFLUSH;
	66
	67	/*
	68	* !fs requests don't need to follow barrier ordering. Always
	69	* put them at the front. This fixes the following deadlock.
	70	*
	71	* http://thread.gmane.org/gmane.linux.kernel/537473
	72	*/
33659ebb	73	if (rq->cmd_type != REQ_TYPE_FS)
86db1e29 JA	74	return QUEUE_ORDSEQ_DRAIN;
	75
	76	if ((rq->cmd_flags & REQ_ORDERED_COLOR) ==
	77	(q->orig_bar_rq->cmd_flags & REQ_ORDERED_COLOR))
	78	return QUEUE_ORDSEQ_DRAIN;
	79	else
	80	return QUEUE_ORDSEQ_DONE;
	81	}
	82
8f11b3e9	83	bool blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error)
86db1e29 JA	84	{
	85	struct request *rq;
	86
	87	if (error && !q->orderr)
	88	q->orderr = error;
	89
	90	BUG_ON(q->ordseq & seq);
	91	q->ordseq \|= seq;
	92
	93	if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE)
8f11b3e9	94	return false;
86db1e29 JA	95
	96	/*
	97	* Okay, sequence complete.
	98	*/
	99	q->ordseq = 0;
	100	rq = q->orig_bar_rq;
40cbbb78	101	__blk_end_request_all(rq, q->orderr);
8f11b3e9	102	return true;
86db1e29 JA	103	}
	104
	105	static void pre_flush_end_io(struct request *rq, int error)
	106	{
	107	elv_completed_request(rq->q, rq);
	108	blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
	109	}
	110
	111	static void bar_end_io(struct request *rq, int error)
	112	{
	113	elv_completed_request(rq->q, rq);
	114	blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
	115	}
	116
	117	static void post_flush_end_io(struct request *rq, int error)
	118	{
	119	elv_completed_request(rq->q, rq);
	120	blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
	121	}
	122
	123	static void queue_flush(struct request_queue *q, unsigned which)
	124	{
	125	struct request *rq;
	126	rq_end_io_fn *end_io;
	127
313e4299	128	if (which == QUEUE_ORDERED_DO_PREFLUSH) {
86db1e29 JA	129	rq = &q->pre_flush_rq;
	130	end_io = pre_flush_end_io;
	131	} else {
	132	rq = &q->post_flush_rq;
	133	end_io = post_flush_end_io;
	134	}
	135
2a4aa30c	136	blk_rq_init(q, rq);
28e18d01	137	rq->cmd_type = REQ_TYPE_FS;
8749534f	138	rq->cmd_flags = REQ_HARDBARRIER \| REQ_FLUSH;
16f2319f	139	rq->rq_disk = q->orig_bar_rq->rq_disk;
86db1e29	140	rq->end_io = end_io;
86db1e29 JA	141
	142	elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
	143	}
	144
8f11b3e9	145	static inline bool start_ordered(struct request_queue q, struct request *rqp)
86db1e29	146	{
8f11b3e9 TH	147	struct request rq = rqp;
	148	unsigned skip = 0;
	149
86db1e29 JA	150	q->orderr = 0;
	151	q->ordered = q->next_ordered;
	152	q->ordseq \|= QUEUE_ORDSEQ_STARTED;
	153
58eea927 TH	154	/*
	155	* For an empty barrier, there's no actual BAR request, which
	156	* in turn makes POSTFLUSH unnecessary. Mask them off.
	157	*/
5b93629b	158	if (!blk_rq_sectors(rq)) {
58eea927 TH	159	q->ordered &= ~(QUEUE_ORDERED_DO_BAR \|
58eea927 TH	160	QUEUE_ORDERED_DO_POSTFLUSH);
a185eb4b TH	161	/*
	162	* Empty barrier on a write-through device w/ ordered
	163	* tag has no command to issue and without any command
	164	* to issue, ordering by tag can't be used. Drain
	165	* instead.
	166	*/
	167	if ((q->ordered & QUEUE_ORDERED_BY_TAG) &&
	168	!(q->ordered & QUEUE_ORDERED_DO_PREFLUSH)) {
	169	q->ordered &= ~QUEUE_ORDERED_BY_TAG;
	170	q->ordered \|= QUEUE_ORDERED_BY_DRAIN;
	171	}
	172	}
58eea927	173
f671620e	174	/* stash away the original request */
9934c8c0	175	blk_dequeue_request(rq);
86db1e29	176	q->orig_bar_rq = rq;
f671620e	177	rq = NULL;
86db1e29 JA	178
	179	/*
	180	* Queue ordered sequence. As we stack them at the head, we
	181	* need to queue in reverse order. Note that we rely on that
	182	* no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
58eea927	183	* request gets inbetween ordered sequence.
86db1e29	184	*/
58eea927	185	if (q->ordered & QUEUE_ORDERED_DO_POSTFLUSH) {
313e4299	186	queue_flush(q, QUEUE_ORDERED_DO_POSTFLUSH);
f671620e TH	187	rq = &q->post_flush_rq;
f671620e TH	188	} else
8f11b3e9	189	skip \|= QUEUE_ORDSEQ_POSTFLUSH;
86db1e29	190
f671620e TH	191	if (q->ordered & QUEUE_ORDERED_DO_BAR) {
	192	rq = &q->bar_rq;
	193
	194	/* initialize proxy request and queue it */
	195	blk_rq_init(q, rq);
	196	if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
7b6d91da	197	rq->cmd_flags \|= REQ_WRITE;
f671620e TH	198	if (q->ordered & QUEUE_ORDERED_DO_FUA)
	199	rq->cmd_flags \|= REQ_FUA;
	200	init_request_from_bio(rq, q->orig_bar_rq->bio);
	201	rq->end_io = bar_end_io;
	202
	203	elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
	204	} else
8f11b3e9	205	skip \|= QUEUE_ORDSEQ_BAR;
86db1e29	206
313e4299 TH	207	if (q->ordered & QUEUE_ORDERED_DO_PREFLUSH) {
313e4299 TH	208	queue_flush(q, QUEUE_ORDERED_DO_PREFLUSH);
86db1e29 JA	209	rq = &q->pre_flush_rq;
86db1e29 JA	210	} else
8f11b3e9	211	skip \|= QUEUE_ORDSEQ_PREFLUSH;
86db1e29	212
0a7ae2ff	213	if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && queue_in_flight(q))
86db1e29	214	rq = NULL;
f671620e	215	else
8f11b3e9	216	skip \|= QUEUE_ORDSEQ_DRAIN;
86db1e29	217
8f11b3e9 TH	218	*rqp = rq;
	219
	220	/*
	221	* Complete skipped sequences. If whole sequence is complete,
	222	* return false to tell elevator that this request is gone.
	223	*/
	224	return !blk_ordered_complete_seq(q, skip, 0);
86db1e29 JA	225	}
86db1e29 JA	226
8f11b3e9	227	bool blk_do_ordered(struct request_queue q, struct request *rqp)
86db1e29 JA	228	{
86db1e29 JA	229	struct request rq = rqp;
33659ebb CH	230	const int is_barrier = rq->cmd_type == REQ_TYPE_FS &&
33659ebb CH	231	(rq->cmd_flags & REQ_HARDBARRIER);
86db1e29 JA	232
	233	if (!q->ordseq) {
	234	if (!is_barrier)
8f11b3e9	235	return true;
86db1e29	236
8f11b3e9 TH	237	if (q->next_ordered != QUEUE_ORDERED_NONE)
	238	return start_ordered(q, rqp);
	239	else {
86db1e29	240	/*
a7384677 TH	241	* Queue ordering not supported. Terminate
a7384677 TH	242	* with prejudice.
86db1e29	243	*/
9934c8c0	244	blk_dequeue_request(rq);
40cbbb78	245	__blk_end_request_all(rq, -EOPNOTSUPP);
86db1e29	246	*rqp = NULL;
8f11b3e9	247	return false;
86db1e29 JA	248	}
	249	}
	250
	251	/*
	252	* Ordered sequence in progress
	253	*/
	254
	255	/* Special requests are not subject to ordering rules. */
33659ebb	256	if (rq->cmd_type != REQ_TYPE_FS &&
86db1e29	257	rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
8f11b3e9	258	return true;
86db1e29	259
313e4299	260	if (q->ordered & QUEUE_ORDERED_BY_TAG) {
86db1e29 JA	261	/* Ordered by tag. Blocking the next barrier is enough. */
	262	if (is_barrier && rq != &q->bar_rq)
	263	*rqp = NULL;
	264	} else {
	265	/* Ordered by draining. Wait for turn. */
	266	WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
	267	if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
	268	*rqp = NULL;
	269	}
	270
8f11b3e9	271	return true;
86db1e29 JA	272	}
	273
	274	static void bio_end_empty_barrier(struct bio *bio, int err)
	275	{
cc66b451 JA	276	if (err) {
	277	if (err == -EOPNOTSUPP)
	278	set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
86db1e29	279	clear_bit(BIO_UPTODATE, &bio->bi_flags);
cc66b451	280	}
f17e232e DM	281	if (bio->bi_private)
	282	complete(bio->bi_private);
	283	bio_put(bio);
86db1e29 JA	284	}
	285
	286	/**
	287	* blkdev_issue_flush - queue a flush
	288	* @bdev: blockdev to issue flush for
fbd9b09a	289	* @gfp_mask: memory allocation flags (for bio_alloc)
86db1e29	290	* @error_sector: error sector
fbd9b09a	291	* @flags: BLKDEV_IFL_* flags to control behaviour
86db1e29 JA	292	*
	293	* Description:
	294	* Issue a flush for the block device in question. Caller can supply
	295	* room for storing the error offset in case of a flush error, if they
f17e232e DM	296	* wish to. If WAIT flag is not passed then caller may check only what
f17e232e DM	297	* request was pushed in some internal queue for later handling.
86db1e29	298	*/
fbd9b09a DM	299	int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask,
fbd9b09a DM	300	sector_t *error_sector, unsigned long flags)
86db1e29 JA	301	{
	302	DECLARE_COMPLETION_ONSTACK(wait);
	303	struct request_queue *q;
	304	struct bio *bio;
fbd9b09a	305	int ret = 0;
86db1e29 JA	306
	307	if (bdev->bd_disk == NULL)
	308	return -ENXIO;
	309
	310	q = bdev_get_queue(bdev);
	311	if (!q)
	312	return -ENXIO;
	313
f10d9f61 DC	314	/*
	315	* some block devices may not have their queue correctly set up here
	316	* (e.g. loop device without a backing file) and so issuing a flush
	317	* here will panic. Ensure there is a request function before issuing
	318	* the barrier.
	319	*/
	320	if (!q->make_request_fn)
	321	return -ENXIO;
	322
fbd9b09a	323	bio = bio_alloc(gfp_mask, 0);
86db1e29	324	bio->bi_end_io = bio_end_empty_barrier;
86db1e29	325	bio->bi_bdev = bdev;
f17e232e DM	326	if (test_bit(BLKDEV_WAIT, &flags))
f17e232e DM	327	bio->bi_private = &wait;
86db1e29	328
f17e232e DM	329	bio_get(bio);
	330	submit_bio(WRITE_BARRIER, bio);
	331	if (test_bit(BLKDEV_WAIT, &flags)) {
	332	wait_for_completion(&wait);
	333	/*
	334	* The driver must store the error location in ->bi_sector, if
	335	* it supports it. For non-stacked drivers, this should be
	336	* copied from blk_rq_pos(rq).
	337	*/
	338	if (error_sector)
	339	*error_sector = bio->bi_sector;
	340	}
86db1e29	341
cc66b451 JA	342	if (bio_flagged(bio, BIO_EOPNOTSUPP))
	343	ret = -EOPNOTSUPP;
	344	else if (!bio_flagged(bio, BIO_UPTODATE))
86db1e29 JA	345	ret = -EIO;
	346
	347	bio_put(bio);
	348	return ret;
	349	}
86db1e29	350	EXPORT_SYMBOL(blkdev_issue_flush);