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b=AEyu1jAqTBA3Y+j0Enju/9w3c9UuvNiY6+tq559Ep/80dmGxuYI7eW0hrNZ4YvhiC 3hOJuxrEVHZubR2oRPxjnCAh3afBfBTXqEHx28mUB9Y2Q1v0n7ztPtHMcj3JPypYAW kRsH667rNpQy0ceIp0gEvuP/Dr/AvMglSw0pcY0A= Date: Tue, 25 Jun 2024 15:38:23 -0700 From: Andrew Morton To: Kefeng Wang Cc: David Hildenbrand , Helge Deller , Daniel Vetter , Matthew Wilcox , , Jonathan Corbet Subject: Re: [PATCH 1/4] fs/proc/task_mmu: use folio API in pte_is_pinned() Message-Id: <20240625153823.b59bbee937fc3cde28bddbab@linux-foundation.org> In-Reply-To: References: <20240604114822.2089819-1-wangkefeng.wang@huawei.com> <20240604114822.2089819-2-wangkefeng.wang@huawei.com> <70ce5e9a-ddd7-4e21-9ca9-cd0e72e1df60@redhat.com> <5ec7f8b0-777c-44d2-874f-9332432129b4@huawei.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 1362340019 X-Stat-Signature: hnujpchuyxygcyg73j9e7rfk1p7qpztg X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1719355105-638452 X-HE-Meta: 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 UleoI+X1 LmmM2ShIlrgsvzZtpbC45xAd76CcU2FbUxqSOTnk+U5s9hneCS45+9IwJbIziT0Yd4ZWWAEgI/+HW+wTF4wJigu6Jj0J3xmj/kKO+Mb4sKXtN60UZdQUChEVhQ1OShVLkyxbVGZUhKTT1khX1KUyXz1AFSEQs0BrYtq5oU6yMUpVoGepVxxYUwZwZPpj3Gn34znfvPwIyoUvIPXKqWdC+dIP8/cGNtCU0MqXWfxKVf1/sFwOx2OIFDZdEwr8MDlv9nd/dGcyqEmKQRl+VMt18K+6DLR6GdKDy4CyXjXQohRkD/ajAdnwm+tjigBHnbjPQp2Ix X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 5 Jun 2024 09:30:59 +0800 Kefeng Wang = wrote: > > =A0=A0=A0 protection to catch successive writes (mprotect, uffd-wp) --= and=20 > > they all > > =A0=A0=A0 face the same issue regarding R/W access via GUP (FOLL_PIN a= nd > > =A0=A0=A0 FOLL_GET). > > =A0=A0=A0 User space better be aware that using read-protection to cat= ch=20 > > writes to > > =A0=A0=A0 a page can miss writes via GUP. Softdirt tracking cannot rel= iably=20 > > catch > > =A0=A0=A0 modifications via GUP after clearing softdirty and returning= to user > > =A0=A0=A0 space. > >=20 > > But I understand if you want to be careful :) So I might send that patc= h=20 > > out at > > some point myself ... > >=20 >=20 > Thank for your detail explanation, let's wait it out. Did we wait long enough? Should we move ahead with this change or should we drop it and have another run at it?