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>
This commit is contained in:
Jonathan Brassow 2011-01-13 19:59:52 +00:00 committed by Alasdair G Kergon
parent 085ae0651b
commit 86a54a4802
3 changed files with 17 additions and 3 deletions

View file

@ -370,6 +370,16 @@
#define DM_ULOG_REQUEST_TYPE(request_type) \
(DM_ULOG_REQUEST_MASK & (request_type))
/*
* DM_ULOG_REQUEST_VERSION is incremented when there is a
* change to the way information is passed between kernel
* and userspace. This could be a structure change of
* dm_ulog_request or a change in the way requests are
* issued/handled. Changes are outlined here:
* version 1: Initial implementation
*/
#define DM_ULOG_REQUEST_VERSION 1
struct dm_ulog_request {
/*
* The local unique identifier (luid) and the universally unique
@ -383,8 +393,9 @@ struct dm_ulog_request {
*/
uint64_t luid;
char uuid[DM_UUID_LEN];
char padding[7]; /* Padding because DM_UUID_LEN = 129 */
char padding[3]; /* Padding because DM_UUID_LEN = 129 */
uint32_t version; /* See DM_ULOG_REQUEST_VERSION */
int32_t error; /* Used to report back processing errors */
uint32_t seq; /* Sequence number for request */