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From:   Yang Shi <shy828301@gmail.com>
Date:   Tue, 17 Jan 2023 10:57:47 -0800
Message-ID: <CAHbLzkrgz3mV=nt_m6b4MV7bWz2-woOjf27sY0+xB9iFunuBsw@mail.gmail.com>
Subject: Re: [PATCH] mm/khugepaged: Fix ->anon_vma race
To:     "Kirill A. Shutemov" <kirill@shutemov.name>
Cc:     Jann Horn <jannh@google.com>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        "Zach O'Keefe" <zokeefe@google.com>, linux-kernel@vger.kernel.org,
        David Hildenbrand <david@redhat.com>
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On Sun, Jan 15, 2023 at 11:07 AM Kirill A. Shutemov
<kirill@shutemov.name> wrote:
>
> On Fri, Jan 13, 2023 at 08:28:59PM +0100, Jann Horn wrote:
> > No, that lockdep assert has to be there. Page table traversal is
> > allowed under any one of the mmap lock, the anon_vma lock (if the VMA
> > is associated with an anon_vma), and the mapping lock (if the VMA is
> > associated with a mapping); and so to be able to remove page tables,
> > we must hold all three of them.
>
> Okay, that's fair. I agree with the patch now. Maybe adjust the commit
> message a bit?

Yeah, the explanation makes sense to me too. Reviewed-by: Yang Shi
<shy828301@gmail.com>

>
> Anyway:
>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@intel.linux.com>
>
> BTW, I've noticied that you recently added tlb_remove_table_sync_one().
> I'm not sure why it is needed. Why IPI in pmdp_collapse_flush() in not
> good enough to serialize against GUP fast?
>
> --
>   Kiryl Shutsemau / Kirill A. Shutemov