Re: [linux-pm] [PATCH] hibernation should work ok with memory hotplug

Rafael J. Wysocki
2008-11-04T07:08:35Z

On Tuesday, 4 of November 2008, Nigel Cunningham wrote:
> Hi.
>
> On Mon, 2008-11-03 at 14:34 -0800, Dave Hansen wrote:
> > A node might have a node_start_pfn=0 and a node_end_pfn=100 (and it may
> > have only one zone). But, there may be another node with
> > node_start_pfn=10 and a node_end_pfn=20. This loop:
> >
> > for_each_zone(zone) {
> > ...
> > for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
> > if (page_is_saveable(zone, pfn))
> > memory_bm_set_bit(orig_bm, pfn);
> > }
> >
> > will walk over the smaller node's pfn range multiple times. Is this OK?
> >
> > I think all you have to do to fix it is check page_zone(page) == zone
> > and skip out if they don't match.
>
> So pfn 10 in the first node refers to the same memory as pfn 10 in the
> second node?

A pfn always refers to specific page frame and/or struct page, so yes.
However, in one of the nodes these pfns are sort of "invalid" (they point
to struct pages belonging to other zones). AFAICS.

Thanks,
Rafael