Re: [PATCH RESEND] memory hotplug: fix a double register sectioninfo bug

[Andrew Morton]

On Fri, 14 Sep 2012 20:00:09 +0900
Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx> wrote:

> > @@ -187,9 +184,10 @@ void register_page_bootmem_info_node(struct pglist_data *pgdat)
> >   	end_pfn = pfn + pgdat->node_spanned_pages;
> >
> >   	/* register_section info */
> > -	for (; pfn < end_pfn; pfn += PAGES_PER_SECTION)
> > -		register_page_bootmem_info_section(pfn);
> > -
> > +	for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
> > +		if (pfn_valid(pfn) && (pfn_to_nid(pfn) == node))
> 
> I cannot judge whether your configuration is correct or not.
> Thus if it is correct, I want a comment of why the node check is
> needed. In usual configuration, a node does not span the other one.
> So it is natural that "pfn_to_nid(pfn) is same as "pgdat->node_id".
> Thus we may remove the node check in the future.

yup.  How does this look?

--- a/mm/memory_hotplug.c~memory-hotplug-fix-a-double-register-section-info-bug-fix
+++ a/mm/memory_hotplug.c
@@ -185,6 +185,12 @@ void register_page_bootmem_info_node(str
 
 	/* register_section info */
 	for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
+		/*
+		 * Some platforms can assign the same pfn to multiple nodes - on
+		 * node0 as well as nodeN.  To avoid registering a pfn against
+		 * multiple nodes we check that this pfn does not already
+		 * reside in some other node.
+		 */
 		if (pfn_valid(pfn) && (pfn_to_nid(pfn) == node))
 			register_page_bootmem_info_section(pfn);
 	}
_

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/