linux-kernel - Re: [PATCH v7 1/1] mm/page_alloc.c: refactor initialization of struct page for holes in memory layout

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Message-ID: <20210225180935.GI1854360@linux.ibm.com>
Date:   Thu, 25 Feb 2021 20:09:35 +0200
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     David Hildenbrand <david@...hat.com>,
        Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Baoquan He <bhe@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Łukasz Majczak <lma@...ihalf.com>,
        Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...nel.org>,
        Qian Cai <cai@....pw>,
        "Sarvela, Tomi P" <tomi.p.sarvela@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vlastimil Babka <vbabka@...e.cz>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>, stable <stable@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH v7 1/1] mm/page_alloc.c: refactor initialization of
 struct page for holes in memory layout

On Thu, Feb 25, 2021 at 09:54:34AM -0800, Linus Torvalds wrote:
> On Thu, Feb 25, 2021 at 9:07 AM Mike Rapoport <rppt@...ux.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?

Can't happen because this code runs before any allocation is possible and
it is single threaded.
 
> 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)

Ok, I'll do another pass on the comments in the code.

>           Linus

-- 
Sincerely yours,
Mike.