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Commit 3791e2fc authored by Alasdair G Kergon's avatar Alasdair G Kergon
Browse files

dm table: add singleton feature 



Introduce the concept of a singleton table which contains exactly one target.

If a target type sets the DM_TARGET_SINGLETON feature bit device-mapper
will ensure that any table that includes that target contains no others.

The thin provisioning pool target uses this.

Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 7f069653

drivers/md/dm-table.c

+16 −0
Original line number Diff line number Diff line
@@ -55,6 +55,7 @@ struct dm_table { 
	struct dm_target *targets;



	unsigned integrity_supported:1;

	unsigned singleton:1;



	/*

	 * Indicates the rw permissions for the new logical
@@ -740,6 +741,12 @@ int dm_table_add_target(struct dm_table *t, const char *type, 
	char **argv;

	struct dm_target *tgt;



	if (t->singleton) {

		DMERR("%s: target type %s must appear alone in table",

		      dm_device_name(t->md), t->targets->type->name);

		return -EINVAL;

	}



	if ((r = check_space(t)))

		return r;
@@ -758,6 +765,15 @@ int dm_table_add_target(struct dm_table *t, const char *type, 
		return -EINVAL;

	}



	if (dm_target_needs_singleton(tgt->type)) {

		if (t->num_targets) {

			DMERR("%s: target type %s must appear alone in table",

			      dm_device_name(t->md), type);

			return -EINVAL;

		}

		t->singleton = 1;

	}



	tgt->table = t;

	tgt->begin = start;

	tgt->len = len;

include/linux/device-mapper.h

+10 −4
Original line number Diff line number Diff line
@@ -128,10 +128,6 @@ void dm_put_device(struct dm_target *ti, struct dm_dev *d); 
 * Information about a target type

 */



/*

 * Target features

 */



struct target_type {

	uint64_t features;

	const char *name;
@@ -160,6 +156,16 @@ struct target_type { 
	struct list_head list;

};



/*

 * Target features

 */



/*

 * Any table that contains an instance of this target must have only one.

 */

#define DM_TARGET_SINGLETON		0x00000001

#define dm_target_needs_singleton(type)	((type)->features & DM_TARGET_SINGLETON)



struct dm_target {

	struct dm_table *table;

	struct target_type *type;