DM_TARGET_MSG_CMD 1689 drivers/md/dm-ioctl.c 		{DM_TARGET_MSG_CMD, 0, target_message},
DM_TARGET_MSG_CMD  271 include/uapi/linux/dm-ioctl.h #define DM_TARGET_MSG	 _IOWR(DM_IOCTL, DM_TARGET_MSG_CMD, struct dm_ioctl)