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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <246ba813-698b-8696-7f4d-400034a3380b@redhat.com> References: <246ba813-698b-8696-7f4d-400034a3380b@redhat.com> <20230120175556.3556978-1-dhowells@redhat.com> <20230120175556.3556978-3-dhowells@redhat.com> To: David Hildenbrand Cc: dhowells@redhat.com, Al Viro , Christoph Hellwig , Matthew Wilcox , Jens Axboe , Jan Kara , Jeff Layton , Logan Gunthorpe , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig , John Hubbard , linux-mm@kvack.org Subject: Re: [PATCH v7 2/8] iov_iter: Add a function to extract a page list from an iterator MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <3814748.1674474663.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Date: Mon, 23 Jan 2023 11:51:03 +0000 Message-ID: <3814749.1674474663@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: D5D5B40008 X-Stat-Signature: 3b1iefqjsozgwt1w1ofxqneh4huuqs8c X-HE-Tag: 1674474669-781405 X-HE-Meta: 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 TX2hX7kx WmdN151FYg4cquW/KzR5A4WuX9KYwf+PH32kJH3VrpFRCMyhmINPisOp1esAyBaK2lAsMWUZwkbYODp0KinzuoWVROkApYtuyj9+lHUs4ElPzNtKnZ23jbAC9JKwsurJruzwlhT8ZIdcOQs9u0CFu9xJmjMP7RsAxwvi5sVtp1iAenawClDvIj1br6TWXmX5a0HI70ZrNj3pgLG5VLaD4ILg1PTx/PhT46tL4bWeRTVbZK6GrqtkRyiUDt+uGhpJkBEVY13YwmIAg1PF0fmkIzFXDGrnb5M435W3H03+3KGQkW0/ZMdiwyL5Faw== 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: David Hildenbrand wrote: > How does this work align with the goal of no longer using FOLL_GET for > O_DIRECT? We should get rid of any FOLL_GET usage for accessing page con= tent. Would that run the risk of changes being made by the child being visible t= o the a DIO write if the parent changes the buffer first? PARENT CHILD =3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D start-DIO-write fork() =3D pid fork() =3D 0 alter-buffer CoW happens page copied original page retained alter-buffer David