Re: [RFC][PATCH] vmemmap on sparsemem v2 [1/5] generic vmemmap on sparsemem

[Heiko Carstens <heiko.carstens@de.ibm.com>]

On Wed, Dec 06, 2006 at 10:17:04AM -0800, Christoph Lameter wrote:
> On Wed, 6 Dec 2006, Heiko Carstens wrote:
> 
> > > +	vmap_start = (unsigned long)pfn_to_page(section_nr_to_pfn(section));
> > > +	vmap_end = vmap_start + PAGES_PER_SECTION * sizeof(struct page);
> > > +
> > > +	for (vmap = vmap_start;
> > > +	     vmap != vmap_end;
> > > +	     vmap += PAGE_SIZE)
> > > +	{
> >
> > Hmm.. maybe I'm just too tired. But why does this work? Why is vmap_start
> > PAGE_SIZE aligned and why is vmap_end PAGE_SIZE aligned too?
> 
> vmap_start is page aligned because pfn_to_page returns a page address.
> Pages are page aligned.

I must be dreaming... I always though pfn_to_page return the address to
the beloging 'struct page'... and indeed it does. So there is nothing
that guarantees that this is page aligned.

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