On Monday May 29, bluca@xxxxxxxxxx wrote:
> On Mon, May 29, 2006 at 12:08:25PM +1000, Neil Brown wrote:
> >On Sunday May 28, bluca@xxxxxxxxxx wrote:
> >Thanks for the patches. They are greatly appreciated.
> You're welcome
> >>
> >> - mdadm-2.3.1-kernel-byteswap-include-fix.patch
> >> reverts a change introduced with mdadm 2.3.1 for redhat compatibility
> >> asm/byteorder.h is an architecture dependent file and does more
> >> stuff than a call to the linux/byteorder/XXX_endian.h
> >> the fact that not calling asm/byteorder.h does not define
> >> __BYTEORDER_HAS_U64__ is just an example of issues that might arise.
> >> if redhat is broken it should be worked around differently than breaking
> >> mdadm.
> >
> >I don't understand the problem here. What exactly breaks with the
> >code currently in 2.5? mdadm doesn't need __BYTEORDER_HAS_U64__, so
> >why does not having id defined break anything?
> >The coomment from the patch says:
> > > not including asm/byteorder.h will not define __BYTEORDER_HAS_U64__
> > > causing __fswab64 to be undefined and failure compiling mdadm on
> > > big_endian architectures like PPC
> >
> >But again, mdadm doesn't use __fswab64 ....
> >More details please.
> you use __cpu_to_le64 (ie in super0.c line 987)
>
> bms->sync_size = __cpu_to_le64(size);
>
> which in byteorder/big_endian.h is defined as
>
> #define __cpu_to_le64(x) ((__force __le64)__swab64((x)))
>
> but __swab64 is defined in byteorder/swab.h (included by
> byteorder/big_endian.h) as
>
> #if defined(__GNUC__) && (__GNUC__ >= 2) && defined(__OPTIMIZE__)
> # define __swab64(x) \
> (__builtin_constant_p((__u64)(x)) ? \
> ___swab64((x)) : \
> __fswab64((x)))
> #else
> # define __swab64(x) __fswab64(x)
> #endif /* OPTIMIZE */
Grrr......
Thanks for the details. I think I'll just give up and do it myself.
e.g.
short swap16(short in)
{
int i;
short out=0;
for (i=0; i<4; i++) {
out = out<<8 | (in&255);
in = in >> 8;
}
return out;
}
I don't need top performance and at least this should be portable...
NeilBrown
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