[linux.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 (!prepare_flush_fn && (ordered & (QUEUE_ORDERED_DO_PREFLUSH |
					     QUEUE_ORDERED_DO_POSTFLUSH))) {
		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;
}

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_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 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_RW;
		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 = blk_fs_request(rq) && blk_barrier_rq(rq);

	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 (!blk_fs_request(rq) &&
	    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);
	}

	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.
 */
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);
	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 blk_rq_pos(rq).
	 */
	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 > queue_max_hw_sectors(q)) {
			bio->bi_size = queue_max_hw_sectors(q) << 9;
			nr_sects -= queue_max_hw_sectors(q);
			sector += queue_max_hw_sectors(q);
		} 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	{
313e4299 TH	27	if (!prepare_flush_fn && (ordered & (QUEUE_ORDERED_DO_PREFLUSH \|
313e4299 TH	28	QUEUE_ORDERED_DO_POSTFLUSH))) {
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
8f11b3e9	91	bool blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error)
86db1e29 JA	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)
8f11b3e9	102	return false;
86db1e29 JA	103
	104	/*
	105	* Okay, sequence complete.
	106	*/
	107	q->ordseq = 0;
	108	rq = q->orig_bar_rq;
40cbbb78	109	__blk_end_request_all(rq, q->orderr);
8f11b3e9	110	return true;
86db1e29 JA	111	}
	112
	113	static void pre_flush_end_io(struct request *rq, int error)
	114	{
	115	elv_completed_request(rq->q, rq);
	116	blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
	117	}
	118
	119	static void bar_end_io(struct request *rq, int error)
	120	{
	121	elv_completed_request(rq->q, rq);
	122	blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
	123	}
	124
	125	static void post_flush_end_io(struct request *rq, int error)
	126	{
	127	elv_completed_request(rq->q, rq);
	128	blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
	129	}
	130
	131	static void queue_flush(struct request_queue *q, unsigned which)
	132	{
	133	struct request *rq;
	134	rq_end_io_fn *end_io;
	135
313e4299	136	if (which == QUEUE_ORDERED_DO_PREFLUSH) {
86db1e29 JA	137	rq = &q->pre_flush_rq;
	138	end_io = pre_flush_end_io;
	139	} else {
	140	rq = &q->post_flush_rq;
	141	end_io = post_flush_end_io;
	142	}
	143
2a4aa30c	144	blk_rq_init(q, rq);
1afb20f3	145	rq->cmd_flags = REQ_HARDBARRIER;
86db1e29 JA	146	rq->rq_disk = q->bar_rq.rq_disk;
	147	rq->end_io = end_io;
	148	q->prepare_flush_fn(q, rq);
	149
	150	elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
	151	}
	152
8f11b3e9	153	static inline bool start_ordered(struct request_queue q, struct request *rqp)
86db1e29	154	{
8f11b3e9 TH	155	struct request rq = rqp;
	156	unsigned skip = 0;
	157
86db1e29 JA	158	q->orderr = 0;
	159	q->ordered = q->next_ordered;
	160	q->ordseq \|= QUEUE_ORDSEQ_STARTED;
	161
58eea927 TH	162	/*
	163	* For an empty barrier, there's no actual BAR request, which
	164	* in turn makes POSTFLUSH unnecessary. Mask them off.
	165	*/
5b93629b	166	if (!blk_rq_sectors(rq)) {
58eea927 TH	167	q->ordered &= ~(QUEUE_ORDERED_DO_BAR \|
58eea927 TH	168	QUEUE_ORDERED_DO_POSTFLUSH);
a185eb4b TH	169	/*
	170	* Empty barrier on a write-through device w/ ordered
	171	* tag has no command to issue and without any command
	172	* to issue, ordering by tag can't be used. Drain
	173	* instead.
	174	*/
	175	if ((q->ordered & QUEUE_ORDERED_BY_TAG) &&
	176	!(q->ordered & QUEUE_ORDERED_DO_PREFLUSH)) {
	177	q->ordered &= ~QUEUE_ORDERED_BY_TAG;
	178	q->ordered \|= QUEUE_ORDERED_BY_DRAIN;
	179	}
	180	}
58eea927	181
f671620e	182	/* stash away the original request */
9934c8c0	183	blk_dequeue_request(rq);
86db1e29	184	q->orig_bar_rq = rq;
f671620e	185	rq = NULL;
86db1e29 JA	186
	187	/*
	188	* Queue ordered sequence. As we stack them at the head, we
	189	* need to queue in reverse order. Note that we rely on that
	190	* no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
58eea927	191	* request gets inbetween ordered sequence.
86db1e29	192	*/
58eea927	193	if (q->ordered & QUEUE_ORDERED_DO_POSTFLUSH) {
313e4299	194	queue_flush(q, QUEUE_ORDERED_DO_POSTFLUSH);
f671620e TH	195	rq = &q->post_flush_rq;
f671620e TH	196	} else
8f11b3e9	197	skip \|= QUEUE_ORDSEQ_POSTFLUSH;
86db1e29	198
f671620e TH	199	if (q->ordered & QUEUE_ORDERED_DO_BAR) {
	200	rq = &q->bar_rq;
	201
	202	/* initialize proxy request and queue it */
	203	blk_rq_init(q, rq);
	204	if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
	205	rq->cmd_flags \|= REQ_RW;
	206	if (q->ordered & QUEUE_ORDERED_DO_FUA)
	207	rq->cmd_flags \|= REQ_FUA;
	208	init_request_from_bio(rq, q->orig_bar_rq->bio);
	209	rq->end_io = bar_end_io;
	210
	211	elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
	212	} else
8f11b3e9	213	skip \|= QUEUE_ORDSEQ_BAR;
86db1e29	214
313e4299 TH	215	if (q->ordered & QUEUE_ORDERED_DO_PREFLUSH) {
313e4299 TH	216	queue_flush(q, QUEUE_ORDERED_DO_PREFLUSH);
86db1e29 JA	217	rq = &q->pre_flush_rq;
86db1e29 JA	218	} else
8f11b3e9	219	skip \|= QUEUE_ORDSEQ_PREFLUSH;
86db1e29	220
0a7ae2ff	221	if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && queue_in_flight(q))
86db1e29	222	rq = NULL;
f671620e	223	else
8f11b3e9	224	skip \|= QUEUE_ORDSEQ_DRAIN;
86db1e29	225
8f11b3e9 TH	226	*rqp = rq;
	227
	228	/*
	229	* Complete skipped sequences. If whole sequence is complete,
	230	* return false to tell elevator that this request is gone.
	231	*/
	232	return !blk_ordered_complete_seq(q, skip, 0);
86db1e29 JA	233	}
86db1e29 JA	234
8f11b3e9	235	bool blk_do_ordered(struct request_queue q, struct request *rqp)
86db1e29 JA	236	{
	237	struct request rq = rqp;
	238	const int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
	239
	240	if (!q->ordseq) {
	241	if (!is_barrier)
8f11b3e9	242	return true;
86db1e29	243
8f11b3e9 TH	244	if (q->next_ordered != QUEUE_ORDERED_NONE)
	245	return start_ordered(q, rqp);
	246	else {
86db1e29	247	/*
a7384677 TH	248	* Queue ordering not supported. Terminate
a7384677 TH	249	* with prejudice.
86db1e29	250	*/
9934c8c0	251	blk_dequeue_request(rq);
40cbbb78	252	__blk_end_request_all(rq, -EOPNOTSUPP);
86db1e29	253	*rqp = NULL;
8f11b3e9	254	return false;
86db1e29 JA	255	}
	256	}
	257
	258	/*
	259	* Ordered sequence in progress
	260	*/
	261
	262	/* Special requests are not subject to ordering rules. */
	263	if (!blk_fs_request(rq) &&
	264	rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
8f11b3e9	265	return true;
86db1e29	266
313e4299	267	if (q->ordered & QUEUE_ORDERED_BY_TAG) {
86db1e29 JA	268	/* Ordered by tag. Blocking the next barrier is enough. */
	269	if (is_barrier && rq != &q->bar_rq)
	270	*rqp = NULL;
	271	} else {
	272	/* Ordered by draining. Wait for turn. */
	273	WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
	274	if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
	275	*rqp = NULL;
	276	}
	277
8f11b3e9	278	return true;
86db1e29 JA	279	}
	280
	281	static void bio_end_empty_barrier(struct bio *bio, int err)
	282	{
cc66b451 JA	283	if (err) {
	284	if (err == -EOPNOTSUPP)
	285	set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
86db1e29	286	clear_bit(BIO_UPTODATE, &bio->bi_flags);
cc66b451	287	}
86db1e29 JA	288
	289	complete(bio->bi_private);
	290	}
	291
	292	/**
	293	* blkdev_issue_flush - queue a flush
	294	* @bdev: blockdev to issue flush for
	295	* @error_sector: error sector
	296	*
	297	* Description:
	298	* Issue a flush for the block device in question. Caller can supply
	299	* room for storing the error offset in case of a flush error, if they
dbdac9b7	300	* wish to.
86db1e29 JA	301	*/
	302	int blkdev_issue_flush(struct block_device bdev, sector_t error_sector)
	303	{
	304	DECLARE_COMPLETION_ONSTACK(wait);
	305	struct request_queue *q;
	306	struct bio *bio;
	307	int ret;
	308
	309	if (bdev->bd_disk == NULL)
	310	return -ENXIO;
	311
	312	q = bdev_get_queue(bdev);
	313	if (!q)
	314	return -ENXIO;
	315
	316	bio = bio_alloc(GFP_KERNEL, 0);
86db1e29 JA	317	bio->bi_end_io = bio_end_empty_barrier;
	318	bio->bi_private = &wait;
	319	bio->bi_bdev = bdev;
2ebca85a	320	submit_bio(WRITE_BARRIER, bio);
86db1e29 JA	321
	322	wait_for_completion(&wait);
	323
	324	/*
	325	* The driver must store the error location in ->bi_sector, if
	326	* it supports it. For non-stacked drivers, this should be copied
83096ebf	327	* from blk_rq_pos(rq).
86db1e29 JA	328	*/
	329	if (error_sector)
	330	*error_sector = bio->bi_sector;
	331
	332	ret = 0;
cc66b451 JA	333	if (bio_flagged(bio, BIO_EOPNOTSUPP))
	334	ret = -EOPNOTSUPP;
	335	else if (!bio_flagged(bio, BIO_UPTODATE))
86db1e29 JA	336	ret = -EIO;
	337
	338	bio_put(bio);
	339	return ret;
	340	}
86db1e29	341	EXPORT_SYMBOL(blkdev_issue_flush);
fb2dce86 DW	342
	343	static void blkdev_discard_end_io(struct bio *bio, int err)
	344	{
	345	if (err) {
	346	if (err == -EOPNOTSUPP)
	347	set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
	348	clear_bit(BIO_UPTODATE, &bio->bi_flags);
	349	}
	350
	351	bio_put(bio);
	352	}
	353
	354	/**
	355	* blkdev_issue_discard - queue a discard
	356	* @bdev: blockdev to issue discard for
	357	* @sector: start sector
	358	* @nr_sects: number of sectors to discard
3e6053d7	359	* @gfp_mask: memory allocation flags (for bio_alloc)
fb2dce86 DW	360	*
	361	* Description:
	362	* Issue a discard request for the sectors in question. Does not wait.
	363	*/
3e6053d7 HD	364	int blkdev_issue_discard(struct block_device *bdev,
3e6053d7 HD	365	sector_t sector, sector_t nr_sects, gfp_t gfp_mask)
fb2dce86 DW	366	{
	367	struct request_queue *q;
	368	struct bio *bio;
	369	int ret = 0;
	370
	371	if (bdev->bd_disk == NULL)
	372	return -ENXIO;
	373
	374	q = bdev_get_queue(bdev);
	375	if (!q)
	376	return -ENXIO;
	377
	378	if (!q->prepare_discard_fn)
	379	return -EOPNOTSUPP;
	380
	381	while (nr_sects && !ret) {
3e6053d7	382	bio = bio_alloc(gfp_mask, 0);
fb2dce86 DW	383	if (!bio)
	384	return -ENOMEM;
	385
	386	bio->bi_end_io = blkdev_discard_end_io;
	387	bio->bi_bdev = bdev;
	388
	389	bio->bi_sector = sector;
	390
ae03bf63 MP	391	if (nr_sects > queue_max_hw_sectors(q)) {
	392	bio->bi_size = queue_max_hw_sectors(q) << 9;
	393	nr_sects -= queue_max_hw_sectors(q);
	394	sector += queue_max_hw_sectors(q);
fb2dce86 DW	395	} else {
	396	bio->bi_size = nr_sects << 9;
	397	nr_sects = 0;
	398	}
	399	bio_get(bio);
e17fc0a1	400	submit_bio(DISCARD_BARRIER, bio);
fb2dce86 DW	401
	402	/* Check if it failed immediately */
	403	if (bio_flagged(bio, BIO_EOPNOTSUPP))
	404	ret = -EOPNOTSUPP;
	405	else if (!bio_flagged(bio, BIO_UPTODATE))
	406	ret = -EIO;
	407	bio_put(bio);
	408	}
	409	return ret;
	410	}
	411	EXPORT_SYMBOL(blkdev_issue_discard);