Activating dependent Logical Volumes

• If there are several dependent LVs to activate, this may impose restrictions on the sequence in which we perform the ioctls.

• • For example, if the table of device LV1 references LV2, then we must perform DM_DEV_CREATE for LV2 before DM_TABLE_LOAD for LV1.
  • libdevmapper handles this with a tree of device dependencies.

• If we get a failure during DM_DEV_CREATE or DM_TABLE_LOAD it is easy to back out the operations: We are not committed to the change until we resume the devices. This is one reason why we try to do as much as possible up front and make the resume operation cheap and unlikely to fail.