dm table: add immutable feature
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>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 2fe3017..9836324 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -140,6 +140,8 @@
/* 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 @@
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 @@
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).
*/