Re: AZFS file system proposal

[Arnd Bergmann <arnd@arndb.de>]

On Monday 07 July 2008, Maxim Shchetynin wrote:
> > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if=
 (copy_to_user(target, (void*) pin, size)) {
> > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0rc =3D -EFAULT;
> > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0goto out;
> > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0}
> >=20
> > Question to the powerpc folks: is copy_to_user safe for an __iomem sour=
ce?
> > Should there be two copies (memcpy_fromio and copy_to_user) instead?
>=20
> I leave this question open.
>=20

Cc:'ing some more people that might have more of a clue on this question.
_memcpy_fromio does a "sync" at the start and an "eieio" at the end.
IFAICT, neither are needed here because the source is always memory.

It also handles unaligned memory accesses, which copy_to_user should
also do correctly, so it *looks* like it should work with just a
copy_to_user, but it still feels wrong to use an __iomem pointer
as the source for a copy_to_user.

Any ideas?

	Arnd <><