Commit 169e2cc2 authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm: allow error target to replace bio-based and request-based targets 



It may be useful to switch a request-based table to the "error" target.
Enhance the DM core to allow a hybrid target_type which is capable of
handling either bios (via .map) or requests (via .map_rq).

Add a request-based map function (.map_rq) to the "error" target_type;
making it DM's first hybrid target.  Train dm_table_set_type() to prefer
the mapped device's established type (request-based or bio-based).  If
the mapped device doesn't have an established type default to making the
table with the hybrid target(s) bio-based.

Tested 'dmsetup wipe_table' to work on both bio-based and request-based
devices.

Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarJoe Jin <joe.jin@oracle.com>
Signed-off-by: default avatarJun'ichi Nomura <j-nomura@ce.jp.nec.com>
Acked-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent eb18cba7

drivers/md/dm-table.c

+20 −2
Original line number Diff line number Diff line
@@ -860,14 +860,17 @@ EXPORT_SYMBOL(dm_consume_args); 
static int dm_table_set_type(struct dm_table *t)

{

	unsigned i;

	unsigned bio_based = 0, request_based = 0;

	unsigned bio_based = 0, request_based = 0, hybrid = 0;

	struct dm_target *tgt;

	struct dm_dev_internal *dd;

	struct list_head *devices;

	unsigned live_md_type;



	for (i = 0; i < t->num_targets; i++) {

		tgt = t->targets + i;

		if (dm_target_request_based(tgt))

		if (dm_target_hybrid(tgt))

			hybrid = 1;

		else if (dm_target_request_based(tgt))

			request_based = 1;

		else

			bio_based = 1;
@@ -879,6 +882,21 @@ static int dm_table_set_type(struct dm_table *t) 
		}

	}



	if (hybrid && !bio_based && !request_based) {

		/*

		 * The targets can work either way.

		 * Determine the type from the live device.

		 * Default to bio-based if device is new.

		 */

		dm_lock_md_type(t->md);

		live_md_type = dm_get_md_type(t->md);

		dm_unlock_md_type(t->md);

		if (live_md_type == DM_TYPE_REQUEST_BASED)

			request_based = 1;

		else

			bio_based = 1;

	}



	if (bio_based) {

		/* We must use this table as bio-based */

		t->type = DM_TYPE_BIO_BASED;

drivers/md/dm-target.c

+8 −1
Original line number Diff line number Diff line
@@ -131,12 +131,19 @@ static int io_err_map(struct dm_target *tt, struct bio *bio) 
	return -EIO;

}



static int io_err_map_rq(struct dm_target *ti, struct request *clone,

			 union map_info *map_context)

{

	return -EIO;

}



static struct target_type error_target = {

	.name = "error",

	.version = {1, 1, 0},

	.version = {1, 2, 0},

	.ctr  = io_err_ctr,

	.dtr  = io_err_dtr,

	.map  = io_err_map,

	.map_rq = io_err_map_rq,

};



int __init dm_target_init(void)

drivers/md/dm.h

+11 −0
Original line number Diff line number Diff line
@@ -88,11 +88,22 @@ int dm_setup_md_queue(struct mapped_device *md); 
 */

#define dm_target_is_valid(t) ((t)->table)



/*

 * To check whether the target type is bio-based or not (request-based).

 */

#define dm_target_bio_based(t) ((t)->type->map != NULL)



/*

 * To check whether the target type is request-based or not (bio-based).

 */

#define dm_target_request_based(t) ((t)->type->map_rq != NULL)



/*

 * To check whether the target type is a hybrid (capable of being

 * either request-based or bio-based).

 */

#define dm_target_hybrid(t) (dm_target_bio_based(t) && dm_target_request_based(t))



/*-----------------------------------------------------------------

 * A registry of target types.

 *---------------------------------------------------------------*/

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