Re: [PATCH] asm-generic/bitops/fls64.h

Andrew Morton
2008-05-13T15:31:31Z

On Tue, 13 May 2008 14:43:43 +0400 Nickolay Vinogradov <nickolay@protei.ru> wrote:

> Andrew Morton __________:
> > On Sun, 04 May 2008 22:58:50 +0400
> > ____________________ ______________ ____________________ <nickolay@protei.ru> wrote:
> >
> >> bugfix in fls64 on a big endian systems(against 2.6.25).
> >>
> >> Signed-off-by: Nickolay Vinogradov <nickolay@protei.ru>
> >>
> >> --
> >>
> >> diff --git a/include/asm-generic/bitops/fls64.h
> >> b/include/asm-generic/bitops/fls64.h
> >> index 1b6b17c..2eedb6f 100644
> >> --- a/include/asm-generic/bitops/fls64.h
> >> +++ b/include/asm-generic/bitops/fls64.h
> >> @@ -8,7 +8,7 @@ static inline int fls64(__u64 x)
> >> __u32 h = x >> 32;
> >> if (h)
> >> return fls(h) + 32;
> >> - return fls(x);
> >> + return fls((__u32)x);
> >> }
> >>
> >> #endif /* _ASM_GENERIC_BITOPS_FLS64_H_ */
> >
> > Please describe the bug which you are fixing?
> >
> > Perhaps a more robust fix to <whatever the bug is> would be to
> > repair fls() so that it works correctly when passed a u64. Perhaps.
>
> Repair fls64() so that it works correctly when passed a u64.
>

Yes, but what's wrong with it now?

The fls() in include/asm-generic/bitops/fls.h takes an int.

The fls() in include/asm-x86/bitops.h takes an int.

So both of these will already trucate the incoming argument to 32-bits.

It seems that you are using a version of fls() which doesn't do this.
Why? Which architecture are you using? Would it not be more robust to
fix fls()?