linux-kernel - Re: [PATCH v4 1/4] mm/shmem: Unconditionally set pte dirty in mfill_atomic_install

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Message-Id: <20211104143440.d0056137ee07d3e96d6b56ec@linux-foundation.org>
Date:   Thu, 4 Nov 2021 14:34:40 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Peter Xu <peterx@...hat.com>
Cc:     Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrea Arcangeli <aarcange@...hat.com>,
        Liam Howlett <liam.howlett@...cle.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Yang Shi <shy828301@...il.com>,
        David Hildenbrand <david@...hat.com>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Jerome Glisse <jglisse@...hat.com>,
        Alistair Popple <apopple@...dia.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Matthew Wilcox <willy@...radead.org>,
        Axel Rasmussen <axelrasmussen@...gle.com>
Subject: Re: [PATCH v4 1/4] mm/shmem: Unconditionally set pte dirty in
 mfill_atomic_install_pte

On Tue, 28 Sep 2021 17:37:31 -0400 Peter Xu <peterx@...hat.com> wrote:

> > How about a compromise (if you really want to continue with this patch):
> > you leave the SetPageDirty(page) in shmem_mfill_atomic_pte(), where I
> > feel a responsibility for it; but you do whatever works for you with
> > pte_mkdirty() at the mm/userfaultfd.c end?
> 
> Sure.  Duplicating dirty bit is definitely fine to me as it achieves the same
> goal as I hoped - we're still 100% clear we won't free a uffd page without
> being noticed, then that's enough to me for the goal of this patch.  I won't
> initiate that NACK myself since I still think duplicating is unnecessary no
> matter it resides in shmem or uffd code, but please go ahead doing that and
> I'll be fine with it, just in case Andrew didn't follow the details.

I think Hugh was asking you to implement this...

I guess I'll send this patch upstream.  But it does sound like Hugh
would prefer a followon patch for this kernel release which makes the
above change, please.