calculate the number of blocks in a metadata device properly

math_utils.h

@@ -9,6 +9,13 @@ namespace base {
 	T div_up(T const &v, T const &divisor) {
 		return (v + (divisor - 1)) / divisor;
 	}
+
+	// Seemingly pointless function, but it coerces the arguments
+	// nicely.
+	template <typename T>
+	T div_down(T const &v, T const &divisor) {
+		return v / divisor;
+	}
 }
 
 //----------------------------------------------------------------