cmirrord now returns log name to kernel in CTR so it can be registered

Version 2 of the userspace log protocol accepts return information during the
DM_ULOG_CTR exchange.  The return information contains the name of the log
device that is being used (if there is one).  The kernel can then register the
device via 'dm_get_device'.  Amoung other things, this allows for userspace to
assemble a correct dependency tree of devices - critical for LVM handling of
suspend/resume calls.

Also, update dm-log-userspace.h to match the kernel header associated with
this protocol change.  (Includes a version inc.)

1 files changed, 13 insertions, 5 deletions

diff --git a/libdm/misc/dm-log-userspace.h b/libdm/misc/dm-log-userspace.h
index b723e355..33179386 100644
--- a/libdm/misc/dm-log-userspace.h
+++ b/libdm/misc/dm-log-userspace.h
@@ -52,15 +52,20 @@
  * Payload-to-userspace:
  *	A single string containing all the argv arguments separated by ' 's
  * Payload-to-kernel:
- *	None.  ('data_size' in the dm_ulog_request struct should be 0.)
+ *	The name of the device that is used as the backing store for the log
+ *      data.  'dm_get_device' will be called on this device.  ('dm_put_device'
+ *      will be called on this device automatically after calling DM_ULOG_DTR.)
+ *      If there is no device needed for log data, 'data_size' in the
+ *      dm_ulog_request struct should be 0.
  *
  * The UUID contained in the dm_ulog_request structure is the reference that
  * will be used by all request types to a specific log.  The constructor must
- * record this assotiation with instance created.
+ * record this assotiation with the instance created.
  *
  * When the request has been processed, user-space must return the
- * dm_ulog_request to the kernel - setting the 'error' field and
- * 'data_size' appropriately.
+ * dm_ulog_request to the kernel - setting the 'error' field, filling the
+ * data field with the log device if necessary, and setting 'data_size'
+ * appropriately.
  */
 #define DM_ULOG_CTR                    1
 
@@ -377,8 +382,11 @@
  * dm_ulog_request or a change in the way requests are
  * issued/handled.  Changes are outlined here:
  *	version 1:  Initial implementation
+ *	version 2:  DM_ULOG_CTR allowed to return a string containing a
+ *	            device name that is to be registered with DM via
+ *	            'dm_get_device'.
  */
-#define DM_ULOG_REQUEST_VERSION 1
+#define DM_ULOG_REQUEST_VERSION 2
 
 struct dm_ulog_request {
 	/*