+/* ki_hint changed from enum to u16, make sure rw_hint fits into u16 */

I don't think this comment is very useful.

+static inline u16 ki_hint_valid(enum rw_hint hint)

I'd call this ki_hint_validate.

+{
+	if (hint > MAX_KI_HINT)
+		return 0;
+
+	return hint;

Nit: kill the empty line.