Merge branch 'topic/pcm-estrpipe-in-pm' into for-linus

[pandora-kernel.git] / include / linux / dm-log-userspace.h

diff --git a/include/linux/dm-log-userspace.h b/include/linux/dm-log-userspace.h
index 642e301..8a1f972 100644 (file)
--- 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 */