(DM_ULOG_REQUEST_MASK & (request_type))
struct dm_ulog_request {
- char uuid[DM_UUID_LEN]; /* Ties a request to a specific mirror log */
+ /*
+ * The local unique identifier (luid) and the universally unique
+ * identifier (uuid) are used to tie a request to a specific
+ * mirror log. A single machine log could probably make due with
+ * just the 'luid', but a cluster-aware log must use the 'uuid' and
+ * the 'luid'. The uuid is what is required for node to node
+ * communication concerning a particular log, but the 'luid' helps
+ * differentiate between logs that are being swapped and have the
+ * same 'uuid'. (Think "live" and "inactive" device-mapper tables.)
+ */
+ uint64_t luid;
+ char uuid[DM_UUID_LEN];
char padding[7]; /* Padding because DM_UUID_LEN = 129 */
int32_t error; /* Used to report back processing errors */