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Date:   Thu, 15 Jul 2021 11:12:38 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     David Hildenbrand <david@redhat.com>
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Subject: Re: [PATCH v1 1/4] mm/memory_hotplug: use "unsigned long" for PFN
 in zone_for_pfn_range()
Message-Id: <20210715111238.a557aec31381646d5cd71ef2@linux-foundation.org>
In-Reply-To: <99c59db8-4c3d-6bee-9acc-41a8f76899ef@redhat.com>
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        <20210712124052.26491-2-david@redhat.com>
        <YO9FWrT9h21e/G8X@osiris>
        <99c59db8-4c3d-6bee-9acc-41a8f76899ef@redhat.com>
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On Thu, 15 Jul 2021 11:42:21 +0200 David Hildenbrand <david@redhat.com> wrote:

> > I'd propose to add Cc: <stable@vger.kernel.org> since I actually had
> > the fun to try to debug something like this a couple of years ago:
> > 6cdb18ad98a4 ("mm/vmstat: fix overflow in mod_zone_page_state()")
> > 
> 
> Good point, and thinking again what can go wrong, I tend to agree. We 
> are trying to keep zones contiguous and it could happen that we end up 
> with something like ZONE_DMA here (via default_kernel_zone_for_pfn()) 
> and would consequently online something to ZONE_DMA that doesn't belong 
> there, resulting in crashes.
> 
> @Andrew can you add  Cc: <stable@vger.kernel.org> and
> 
> "As we will search for a fitting zone using the wrong pfn, we might end 
> up onlining memory to one of the special kernel zones, such as ZONE_DMA, 
> which can end badly as the onlined memory does not satisfy properties of 
> these zones."

Yep, all done.