Subject: Re: FW: [PATCH] powerpc/mm: Export HPAGE_SHIFT

From: [email-masked]
Date: Wed, 4 Feb 2009 16:00:37 -0500

On Wed, Feb 04, 2009 at 11:11:22AM -0800, Roland Dreier wrote:
> Heh.  Looking into the implementation, it seems that I could actually do
> 	PAGE_SIZE << compound_order(page)
> directly (since there's no reason to go from size to hstate and back to
> size.  I don't know all the details of these VM internals, but that
> seems to only work on the first (small) page of a giant page?  Which
> causes problems for what we're trying to do here...

You should be able to find the head of a compound page using the
compound_head() inline, so try

	PAGE_SIZE << compound_order(compound_head(page))

-- wli