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dm table: add singleton feature

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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: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Alasdair G Kergon
2011-10-31 20:19:00 +00:00
parent 7f06965390
commit 3791e2fc0e
2 changed files with 26 additions and 4 deletions
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16
drivers/md/dm-table.c
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@ -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;