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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 25 Feb 2021 09:54:34 -0800
Message-ID: <CAHk-=wj-0TeNTNhn+r8c9n76uy8ZiYw03AnXz3hyDZ_rQu35Uw@mail.gmail.com>
Subject: Re: [PATCH v7 1/1] mm/page_alloc.c: refactor initialization of struct
 page for holes in memory layout
To:     Mike Rapoport <rppt@linux.ibm.com>
Cc:     David Hildenbrand <david@redhat.com>,
        Mike Rapoport <rppt@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Baoquan He <bhe@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Chris Wilson <chris@chris-wilson.co.uk>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        =?UTF-8?Q?=C5=81ukasz_Majczak?= <lma@semihalf.com>,
        Mel Gorman <mgorman@suse.de>, Michal Hocko <mhocko@kernel.org>,
        Qian Cai <cai@lca.pw>,
        "Sarvela, Tomi P" <tomi.p.sarvela@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vlastimil Babka <vbabka@suse.cz>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>, stable <stable@vger.kernel.org>,
        "the arch/x86 maintainers" <x86@kernel.org>
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On Thu, Feb 25, 2021 at 9:07 AM Mike Rapoport <rppt@linux.ibm.com> wrote:
>
> >
> > We might still double-initialize PFNs when two zones overlap within a
> > section, correct?
>
> You mean that a section crosses zones boundary?
> I don't think it's that important.

What if there was a memory allocation in between that could allocate
the once-initialized page?

Maybe it can't happen, or is not an issue for some other reason, but
this code has been fragile and had a ton of subtle issues, so maybe
worth documenting (or explaining here why it's just not relevant)

          Linus