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Date:   Mon, 24 Jan 2022 17:13:23 +0800
From:   Peter Xu <peterx@redhat.com>
To:     Hugh Dickins <hughd@google.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        David Hildenbrand <david@redhat.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Yang Shi <shy828301@gmail.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alistair Popple <apopple@nvidia.com>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH RFC v2 1/2] mm: Don't skip swap entry even if zap_details
 specified
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On Sun, Jan 23, 2022 at 10:51:57PM -0800, Hugh Dickins wrote:
> I don't know of any problem that needs fixing with the zero page:
> how do you suppose the zero page gets into a truncatable or hole-punchable
> mapping?  We use it for read faults in anonymous mappings.  And I told the
> story of how once-upon-a-time it could get inserted into any mapping by
> reading from /dev/zero, but that odd case was dropped years ago.  And I
> am open to (even encouraging) a change to make use of zero page for read
> faults of holes in shmem: but that's potential future work, which would
> require some changes elsewhere (though perhaps none here: the zero page
> could never be used for the result of a COW).
> 
> Please explain the zero page problem you hope to fix here.

After I tried to learn the old/new worlds of zero page somehow I thought there
can be zero pfns installed, but it seems not at all..

Please ignore above, sorry for the noise.

-- 
Peter Xu