dm log userspace: add version number to comms

This patch adds a 'version' field to the 'dm_ulog_request'
structure.

The 'version' field is taken from a portion of the unused
'padding' field in the 'dm_ulog_request' structure.  This
was done to avoid changing the size of the structure and
possibly disrupting backwards compatibility.

The version number will help notify user-space daemons
when a change has been made to the kernel/userspace
log API.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-log-userspace-base.c b/drivers/md/dm-log-userspace-base.c
index 31e1687..aa2e0c3 100644
--- a/drivers/md/dm-log-userspace-base.c
+++ b/drivers/md/dm-log-userspace-base.c
@@ -12,6 +12,8 @@
 
 #include "dm-log-userspace-transfer.h"
 
+#define DM_LOG_USERSPACE_VSN "1.1.0"
+
 struct flush_entry {
 	int type;
 	region_t region;
@@ -765,7 +767,7 @@
 		return r;
 	}
 
-	DMINFO("version 1.0.0 loaded");
+	DMINFO("version " DM_LOG_USERSPACE_VSN " loaded");
 	return 0;
 }
 
@@ -775,7 +777,7 @@
 	dm_ulog_tfr_exit();
 	mempool_destroy(flush_entry_pool);
 
-	DMINFO("version 1.0.0 unloaded");
+	DMINFO("version " DM_LOG_USERSPACE_VSN " unloaded");
 	return;
 }