dlm_unlock_lock
#define DLM_UNLOCK_LOCK_MAX_LEN (sizeof(struct dlm_unlock_lock)+DLM_LVB_LEN)
struct dlm_unlock_lock unlock;
vec[0].iov_len = sizeof(struct dlm_unlock_lock);
struct dlm_unlock_lock *unlock = (struct dlm_unlock_lock *)msg->buf;