linux-kernel - Re: [PATCH v1 1/4] mm/memory_hotplug: use "unsigned long" for PFN in zone_for_pfn

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Message-Id: <20210715111238.a557aec31381646d5cd71ef2@linux-foundation.org>
Date:   Thu, 15 Jul 2021 11:12:38 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     Heiko Carstens <hca@...ux.ibm.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Vitaly Kuznetsov <vkuznets@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Pankaj Gupta <pankaj.gupta.linux@...il.com>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>,
        Oscar Salvador <osalvador@...e.de>,
        Michal Hocko <mhocko@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mike Rapoport <rppt@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Catalin Marinas <catalin.marinas@....com>,
        virtualization@...ts.linux-foundation.org,
        linux-acpi@...r.kernel.org, Andy Lutomirski <luto@...nel.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Anton Blanchard <anton@...abs.org>,
        Ard Biesheuvel <ardb@...nel.org>, Baoquan He <bhe@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Borislav Petkov <bp@...en8.de>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Christophe Leroy <christophe.leroy@....fr>,
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        Jia He <justin.he@....com>, Joe Perches <joe@...ches.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        Michel Lespinasse <michel@...pinasse.org>,
        Nathan Lynch <nathanl@...ux.ibm.com>,
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        Paul Mackerras <paulus@...ba.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Pierre Morel <pmorel@...ux.ibm.com>,
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        Rich Felker <dalias@...c.org>,
        Scott Cheloha <cheloha@...ux.ibm.com>,
        Sergei Trofimovich <slyfox@...too.org>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Will Deacon <will@...nel.org>,
        Yoshinori Sato <ysato@...rs.osdn.me>
Subject: Re: [PATCH v1 1/4] mm/memory_hotplug: use "unsigned long" for PFN
 in zone_for_pfn_range()

On Thu, 15 Jul 2021 11:42:21 +0200 David Hildenbrand <david@...hat.com> wrote:

> > I'd propose to add Cc: <stable@...r.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@...r.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.