This is fine in principle, but qmin() is the wrong function to use. uio_resid is not of quad_t type. Use normal comparision operations there.

Hm, the rest of this function assumes that "total" fits in an int.

It will fit indeed, because len is int. Just that the comparision should use unclipped value of uio_resid.

quad_t encompasses all values ssize_t can have, on current platforms. It's too bad we don't have type-safe min/max macros like Linux.

By normal comparison operations, you mean trinary operator?

So... uqmin...?

sys/sys/libkern.h:static __inline u_quad_t uqmin(u_quad_t a, u_quad_t b) { return (a < b ? a : b); }

Actually, szmin?

static __inline ssize_t szmin(ssize_t a, ssize_t b) { return (a < b ? a : b); }

It does not matter what quad_t current domain is.

I mean, use normal C comparision operators like <, be it used in ?: or if is not important. Normal integer promotion rules make it correct.

It also makes an allowance for confusion.