From: Jonathan Brassow 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 Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon --- drivers/md/dm-log-userspace-base.c | 6 ++++-- drivers/md/dm-log-userspace-transfer.c | 1 + include/linux/dm-log-userspace.h | 13 ++++++++++++- 3 files changed, 17 insertions(+), 3 deletions(-) Index: linux-2.6.37/drivers/md/dm-log-userspace-base.c =================================================================== --- linux-2.6.37.orig/drivers/md/dm-log-userspace-base.c +++ linux-2.6.37/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_in 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_e dm_ulog_tfr_exit(); mempool_destroy(flush_entry_pool); - DMINFO("version 1.0.0 unloaded"); + DMINFO("version " DM_LOG_USERSPACE_VSN " unloaded"); return; } Index: linux-2.6.37/drivers/md/dm-log-userspace-transfer.c =================================================================== --- linux-2.6.37.orig/drivers/md/dm-log-userspace-transfer.c +++ linux-2.6.37/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++; Index: linux-2.6.37/include/linux/dm-log-userspace.h =================================================================== --- linux-2.6.37.orig/include/linux/dm-log-userspace.h +++ linux-2.6.37/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 */