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dm table: add immutable feature

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Introduce DM_TARGET_IMMUTABLE to indicate that the target type cannot be mixed
with any other target type, and once loaded into a device, it cannot be
replaced with a table containing a different type.

The thin provisioning pool device will use this.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Alasdair G Kergon 2011-10-31 20:19:04 +00:00
parent cc6cbe141a
commit 36a0456fbf
6 changed files with 52 additions and 2 deletions
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9
drivers/md/dm.c
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@ -140,6 +140,8 @@ struct mapped_device {
/* Protect queue and type against concurrent access. */
struct mutex type_lock;
struct target_type *immutable_target_type;
struct gendisk *disk;
char name[16];
@ -2096,6 +2098,8 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
write_lock_irqsave(&md->map_lock, flags);
old_map = md->map;
md->map = t;
md->immutable_target_type = dm_table_get_immutable_target_type(t);
dm_table_set_restrictions(t, q, limits);
if (merge_is_optional)
set_bit(DMF_MERGE_IS_OPTIONAL, &md->flags);
@ -2166,6 +2170,11 @@ unsigned dm_get_md_type(struct mapped_device *md)
return md->type;
}
struct target_type *dm_get_immutable_target_type(struct mapped_device *md)
{
return md->immutable_target_type;
}
/*
* Fully initialize a request-based queue (->elevator, ->request_fn, etc).
*/