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>

2 files changed, 5 insertions, 2 deletions

diff --git a/drivers/md/dm-log-userspace-base.c b/drivers/md/dm-log-userspace-base.c
index 31e1687e7bf6..aa2e0c374ab3 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 @@ static int __init userspace_dirty_log_init(void)
                 return r;
         }
 
-        DMINFO("version 1.0.0 loaded");
+        DMINFO("version " DM_LOG_USERSPACE_VSN " loaded");
         return 0;
 }
 
@@ -775,7 +777,7 @@ static void __exit userspace_dirty_log_exit(void)
         dm_ulog_tfr_exit();
         mempool_destroy(flush_entry_pool);
 
-        DMINFO("version 1.0.0 unloaded");
+        DMINFO("version " DM_LOG_USERSPACE_VSN " unloaded");
         return;
 }
 
diff --git a/drivers/md/dm-log-userspace-transfer.c b/drivers/md/dm-log-userspace-transfer.c
index 075cbcf8a9f5..049eaf12aaab 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++;