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SubjectRe: [PATCH] hugetlb: Provide a default HPAGE_SHIFT if !CONFIG_HUGETLB_PAGE
On Wed, 16 Nov 2011, David Daney wrote:

> > > This is required now to get MIPS kernels to compile with
> > > !CONFIG_HUGETLB_PAGE.
> > >
> >
> > Why?
>
> I should have been more specific. The failure is in Ralf's
> mips-for-linux-next branch.
>

I can't find that branch (it's not in Ralf's tree at git.kernel.org), so
I'm looking at next-20111116. It doesn't compile for mips for other
reasons related to arch/mips/sgi-ip22/ip22-gio.c.

> > This is definitely the wrong fix, anyway, and it would require a change to
> > arch/mips/include/asm/page.h instead since it's localized to mips,
>
> No, all we are doing is supplying a dummy definition for HPAGE_SHIFT as we
> currently have for HPAGE_SIZE and HPAGE_MASK.
>

Which is wrong. MIPS code should not be using HPAGE_SHIFT without
CONFIG_HUGETLB_PAGE and in fact defines it itself for such a configuration
in arch/mips/include/asm/page.h. The only generic uses are in
page_alloc.c where we need CONFIG_HUGETLB_PAGE_SIZE_VARIABLE, which isn't
available on mips, and in mm/hugetlb.c which requires CONFIG_HUGETLB_PAGE
by way of CONFIG_HUGETLBFS.

So feel free to show the actual compile error this time and I'll suggest a
mips fix for it.

> > so nack.
> >
> > > Signed-off-by: David Daney<david.daney@cavium.com>
> > > ---
> > > include/linux/hugetlb.h | 1 +
> > > 1 files changed, 1 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> > > index 19644e0..746d543 100644
> > > --- a/include/linux/hugetlb.h
> > > +++ b/include/linux/hugetlb.h
> > > @@ -113,6 +113,7 @@ static inline void copy_huge_page(struct page *dst,
> > > struct page *src)
> > > #ifndef HPAGE_MASK
> > > #define HPAGE_MASK PAGE_MASK /* Keep the compiler
> > > happy */
> > > #define HPAGE_SIZE PAGE_SIZE
>
> Why didn't you NACK the addition of these two lines too?
>
> Following your logic, we should remove these and patch up all the architecture
> specific files instead.
>

I think it's a worthwhile goal to remove these as well, yes.


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