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

[Yasuaki Ishimatsu]

2012/09/15 5:14, Andrew Morton wrote:
> 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?

Looks good to me.

Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>

> --- 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);
>   	}
> _
>
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