Re: [RFC][PATCH] introduce ptr_diff()

Matthew Wilcox
2010-08-19T12:40:21Z

On Thu, Aug 19, 2010 at 02:23:09PM +0200, Andi Kleen wrote:
> IMHO it would be better to simply disable the warning in sparse instead
> of uglying the code just to work around sparse bogosity. It doesnt' seem
> to make much sense. A subtraction followed by a shift is not expensive.

What makes you think it's a shift? struct page isn't necessarily a
power of two in size. The original poster said "allyesconfig" which is
going to add in KMEMCHECK and WANT_PAGE_DEBUG_FLAGS. I think that makes
it 76 bytes on x86-32, so sparse is right to warn.

--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."