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From:   Joel Fernandes <joel@joelfernandes.org>
Date:   Tue, 14 Jul 2020 14:12:33 -0400
Message-ID: <CAEXW_YRTnCb-z6TeboA3OCYv8eoX8UiCNn7K1hGMX+41Zdz8Og@mail.gmail.com>
Subject: Re: WARNING: at mm/mremap.c:211 move_page_tables in i386
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     "Kirill A. Shutemov" <kirill@shutemov.name>,
        Naresh Kamboju <naresh.kamboju@linaro.org>,
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        open list <linux-kernel@vger.kernel.org>,
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On Tue, Jul 14, 2020 at 12:11 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Tue, Jul 14, 2020 at 9:08 AM Joel Fernandes <joel@joelfernandes.org> wrote:
> >
> > I was thinking we should not call move_page_tables() with overlapping ranges
> > at all, just to keep things simple.
>
> No, we're not breaking the existing stack movement code just to keep
> things simple.
>
> The rule is "make it as simple as possible, but no simpler".
>
> And "as possible" in the case of Linux means "no breaking of old
> interfaces". The stack randomization movement most certainly counts.

Hi Linus,
I think you misunderstood me. I was not advocating breaking the stack
movement code or breaking stack randomization, I was going to try to
see if I could keep that working while not having to do an overlapping
move. That would be what I would do in the future patch (until which
as you mentioned, you would switch the WARN_ON to WARN_ON_ONCE).

I agree with you that we keep things as simple as possible while not
breaking functionality.

Cheers,

 - Joel