linux-kernel - Re: WARNING: at mm/mremap.c:211 move_page

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Date:   Sat, 11 Jul 2020 11:21:43 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Naresh Kamboju <naresh.kamboju@...aro.org>
Cc:     Joel Fernandes <joel@...lfernandes.org>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        William Kucharski <william.kucharski@...cle.com>,
        linux- stable <stable@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>, Michal Hocko <mhocko@...nel.org>,
        lkft-triage@...ts.linaro.org, Chris Down <chris@...isdown.name>,
        Michel Lespinasse <walken@...gle.com>,
        Fan Yang <Fan_Yang@...u.edu.cn>,
        Brian Geffon <bgeffon@...gle.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>, pugaowei@...il.com,
        Jerome Glisse <jglisse@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Hugh Dickins <hughd@...gle.com>,
        Al Viro <viro@...iv.linux.org.uk>, Tejun Heo <tj@...nel.org>,
        Sasha Levin <sashal@...nel.org>,
        Oleg Nesterov <oleg@...hat.com>
Subject: Re: WARNING: at mm/mremap.c:211 move_page_tables in i386

On Sat, Jul 11, 2020 at 11:12 AM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> The fact that it seems to happen with
>
>     https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/mem/thp/thp01.c
>
> makes me think it's somehow related to THP mappings, but I don't see
> why those would matter. All the same pmd freeing should still have
> happened, afaik.

No, I think the only reason it happens with that test-case is simply
because that test-case tests many different argument sizes, and as
part of that it ends up then hitting the "stack is exactly one pmd in
size" case when the stack alignment is right too.

So the THP part is almost certainly a red herring.

Maybe. Considering that I don't see what's wrong, anything is possible.

                Linus