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Date:   Sun, 9 Jul 2023 21:25:30 +0800
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Subject: Re: [RFC PATCH 0/3] support large folio for mlock
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To:     Matthew Wilcox <willy@infradead.org>
CC:     David Hildenbrand <david@redhat.com>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>, <yuzhao@google.com>,
        <ryan.roberts@arm.com>, <shy828301@gmail.com>,
        <akpm@linux-foundation.org>
References: <20230707165221.4076590-1-fengwei.yin@intel.com>
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From:   "Yin, Fengwei" <fengwei.yin@intel.com>
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On 7/8/2023 12:02 PM, Matthew Wilcox wrote:
> I would be tempted to allocate memory & copy to the new mlocked VMA.
> The old folio will go on the deferred_list and be split later, or its
> valid parts will be written to swap and then it can be freed.
If the large folio splitting failure is because of GUP pages, can we
do copy here?

Let's say, if the GUP page is target of DMA operation and DMA operation
is ongoing. We allocated a new page and copy GUP page content to the
new page, the data in the new page can be corrupted.


Regards
Yin, Fengwei