On Tuesday, 4 of November 2008, Nigel Cunningham wrote:

Hi.

On Mon, 2008-11-03 at 14:34 -0800, Dave Hansen wrote:

quoted

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