linux-kernel - Re: [PATCH 11/11] mm/thp: another PVMW_SYNC fix in page_vma_mapped

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Message-ID: <3f16d6ce-44ec-6d9e-d64-d7f750dc632@google.com>
Date:   Fri, 11 Jun 2021 11:29:31 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Hugh Dickins <hughd@...gle.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yang Shi <shy828301@...il.com>,
        Wang Yugui <wangyugui@...-tech.com>,
        Matthew Wilcox <willy@...radead.org>,
        Alistair Popple <apopple@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>, Zi Yan <ziy@...dia.com>,
        Peter Xu <peterx@...hat.com>, Will Deacon <will@...nel.org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 11/11] mm/thp: another PVMW_SYNC fix in
 page_vma_mapped_walk()

On Thu, 10 Jun 2021, Kirill A. Shutemov wrote:
> On Wed, Jun 09, 2021 at 11:54:46PM -0700, Hugh Dickins wrote:
> > Aha!  Shouldn't that quick scan over pte_none()s make sure that it holds
> > ptlock in the PVMW_SYNC case?  That too might have been responsible for
> > BUGs or WARNs in split_huge_page_to_list() or its unmap_page(), though
> > I've never seen any.
> > 
> > Fixes: ace71a19cec5 ("mm: introduce page_vma_mapped_walk()")
> > Signed-off-by: Hugh Dickins <hughd@...gle.com>
> > Cc: <stable@...r.kernel.org>
> 
> Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

Thanks Kirill.

And Wang Yugui has now reported the good news, that this afterthought
patch finally fixes the unmap_page() BUGs they were hitting on 5.10.

Andrew, please add a link to
https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/
and
Tested-by: Wang Yugui <wangyugui@...-tech.com>

Thanks,
Hugh