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

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Message-Id: <1225771353.6755.16.camel@nigel-laptop>
Date:	Tue, 04 Nov 2008 15:02:33 +1100
From:	Nigel Cunningham <ncunningham@...a.org.au>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Matt Tolentino <matthew.e.tolentino@...el.com>,
	linux-pm@...ts.osdl.org, Dave Hansen <haveblue@...ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, pavel@...e.cz,
	Mel Gorman <mel@...net.ie>, Andy Whitcroft <apw@...dowen.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [linux-pm] [PATCH] hibernation should work ok with memory
	hotplug

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?

Regards,

Nigel

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