[1/2] powerpc/64: Fix checksum folding in csum_tcpudp_nofold and ip_fast_csum_nofold

[Michael Ellerman]

On Thu, 2016-11-03 at 05:10:55 UTC, Paul Mackerras wrote:
> These functions compute an IP checksum by computing a 64-bit sum and
> folding it to 32 bits (the "nofold" in their names refers to folding
> down to 16 bits).  However, doing (u32) (s + (s >> 32)) is not
> sufficient to fold a 64-bit sum to 32 bits correctly.  The addition
> can produce a carry out from bit 31, which needs to be added in to
> the sum to produce the correct result.
> 
> To fix this, we copy the from64to32() function from lib/checksum.c
> and use that.
> 
> Signed-off-by: Paul Mackerras <paulus at ozlabs.org>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/b492f7e4e07a28e706db26cf4943bb

cheers