Re: [v4][PATCH 2/2] fix large pages in pagemap

[Dave Hansen <dave@linux.vnet.ibm.com>]

On Wed, 2008-06-11 at 14:53 -0500, Matt Mackall wrote:
> 
> > I don't get it.   Why can't we just stick a
> > 
> >       if (pmd_huge(pmd))
> >               continue;
> > 
> > into pagemap_pte_range()?  Or something like that.
> 
> That's certainly what you'd hope to be able to do, yes.
> 
> If I recall the earlier discussion, some arches with huge pages can
> only
> identify them via a VMA. Obviously, any arch with hardware that walks
> our pagetables directly must be able to identify huge pages directly
> from those tables, but I think PPC and a couple others that don't have
> hardware TLB fill fail to store such a bit in the tables at all.

Yeah, the ppc (and more) huge pmd entries are just the address of the
huge page.  I would love to get all of them converted so we could use
pmd_huge() on them, eventually.  But, that's a much bigger undertaking.

-- Dave

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