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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 15 Jul 2020 14:51:32 -0700
Message-ID: <CAHk-=whonY2feAuw4sZaRbm97Myt47_eRepd+bnc449miUvrow@mail.gmail.com>
Subject: Re: [PATCHv2] mm: Fix warning in move_normal_pmd()
To:     "Kirill A. Shutemov" <kirill@shutemov.name>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux-MM <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Naresh Kamboju <naresh.kamboju@linaro.org>,
        Joel Fernandes <joel@joelfernandes.org>,
        William Kucharski <william.kucharski@oracle.com>
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On Wed, Jul 15, 2020 at 2:35 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> The stack relocation only moves down.

.. and that may not be true on a grow-up stack. Christ, that code is
hard to read. But I think Kirill is right, and I'm wrong.

So that "try to expand" code is only ok when non-overlapping, or when
moving down.

Naresh - from a testing standpoint, that doesn't make any difference:
I'd still like you to test on x86. We always shift the stack down
there.

          Linus