Re: [PATCH v3 2/2] kexec: Use min_t to simplify logic

Andrew Morton
2013-02-26T08:54:04Z

On Tue, 26 Feb 2013 16:49:02 +0800 Zhang Yanfei <zhangyanfei@cn.fujitsu.com> wrote:

> >> diff --git a/kernel/kexec.c b/kernel/kexec.c
> > []
> >> @@ -822,13 +822,9 @@ static int kimage_load_normal_segment(struct kimage *image,
> > []
> >> + mchunk = min_t(size_t, mbytes,
> >> + (size_t)(PAGE_SIZE - (maddr & ~PAGE_MASK)));
> >
> > #define min_t(type, x, y) ({ \
> > type __min1 = (x); \
> > type __min2 = (y); \
> > __min1 < __min2 ? __min1: __min2; })
> >
> >
> >
>
> Hmm, from the definition, the cast is redundant.
>
> Maybe I misunderstood what Andrew meant in the mail related to v2:
>
> "The types of PAGE_SIZE and PAGE_MASK are vague - iirc they once had
> different types on different architectures, so some form of casting is
> unavoidable here."
>
> Andrew, could you please explain the casting you meant above?

I mean that a cast (or min_t, which is a cast) will be needed.
The code you have here casts the same thing two times, which isn't
necessary.