diff options
Diffstat (limited to 'include/linux/dm-log-userspace.h')
| -rw-r--r-- | include/linux/dm-log-userspace.h | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/include/linux/dm-log-userspace.h b/include/linux/dm-log-userspace.h index 642e3017b51f..8a1f972c0fe9 100644 --- a/include/linux/dm-log-userspace.h +++ b/include/linux/dm-log-userspace.h @@ -371,7 +371,18 @@ (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 */ |