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SubjectRe: [PATCH] Use correct page frame number to grab page zone lock
Disregard.  It appears that Gerald Schaefer submitted a patch to fix
this already.

http://lkml.org/lkml/2008/10/29/142

-Nathan

Nathan Fontenot wrote:
> There are situations in which the 'pfn' variable used to calculate the
> page zone can be invalid. One case is in the hotplug memory remove path
> where we are trying to remove memory the last valid page frame for the
> system. Passing an invalid page frame number to the pfn_to_page() macro
> will cause the system to oops.
>
> Additionally I think this also solves an issue where we may be grabbing
> the wrong zone->lock. This would occur when 'pfn' refers to a page
> frame beyond what we are examining and lies in a different zone.
>
> Using the starting page frame number passed in appears to resolve
> both of these issues. This patch also removes the redundant
> initialization of 'pfn', it is set explicitly and then again in the for
> loop.
>
>
> Signed-off-by: Nathan Fontenot <nfont@austin.ibm.com>
> ---
>
> Index: linux-2.6/mm/page_isolation.c
> ===================================================================
> --- linux-2.6.orig/mm/page_isolation.c 2008-10-13 12:00:46.000000000
> -0500
> +++ linux-2.6/mm/page_isolation.c 2008-10-29 11:18:39.000000000 -0500
> @@ -119,7 +119,6 @@
> struct zone *zone;
> int ret;
>
> - pfn = start_pfn;
> /*
> * Note: pageblock_nr_page != MAX_ORDER. Then, chunks of free page
> * is not aligned to pageblock_nr_pages.
> @@ -133,7 +132,7 @@
> if (pfn < end_pfn)
> return -EBUSY;
> /* Check all pages are free or Marked as ISOLATED */
> - zone = page_zone(pfn_to_page(pfn));
> + zone = page_zone(pfn_to_page(start_pfn));
> spin_lock_irqsave(&zone->lock, flags);
> ret = __test_page_isolated_in_pageblock(start_pfn, end_pfn);
> spin_unlock_irqrestore(&zone->lock, flags);
> --
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