From: Jonathan Brassow <jbrassow@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
drivers/md/dm-log-userspace-transfer.c | 1 +
include/linux/dm-log-userspace.h | 13 ++++++++++++-
2 files changed, 13 insertions(+), 1 deletions(-)
diff --git a/drivers/md/dm-log-userspace-transfer.c b/drivers/md/dm-log-userspace-transfer.c
index 075cbcf..049eaf1 100644
--- a/drivers/md/dm-log-userspace-transfer.c
+++ b/drivers/md/dm-log-userspace-transfer.c
@@ -198,6 +198,7 @@ resend:
memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - sizeof(struct cn_msg));
memcpy(tfr->uuid, uuid, DM_UUID_LEN);
+ tfr->version = DM_ULOG_REQUEST_VERSION;
tfr->luid = luid;
tfr->seq = dm_ulog_seq++;
diff --git a/include/linux/dm-log-userspace.h b/include/linux/dm-log-userspace.h
index 0c3c3a2..eeace7d 100644
--- a/include/linux/dm-log-userspace.h
+++ b/include/linux/dm-log-userspace.h
@@ -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 */
--
1.7.2.3
--
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