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[209.85.208.48]) by smtp.gmail.com with ESMTPSA id w11sm1329870edv.65.2021.12.17.19.39.06 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 17 Dec 2021 19:39:06 -0800 (PST) Received: by mail-ed1-f48.google.com with SMTP id b7so15036472edd.6 for ; Fri, 17 Dec 2021 19:39:06 -0800 (PST) X-Received: by 2002:a05:6000:10d2:: with SMTP id b18mr3943603wrx.193.1639798735711; Fri, 17 Dec 2021 19:38:55 -0800 (PST) MIME-Version: 1.0 References: <20211217113049.23850-1-david@redhat.com> <20211217113049.23850-7-david@redhat.com> <54c492d7-ddcd-dcd0-7209-efb2847adf7c@redhat.com> <20211217204705.GF6385@nvidia.com> <2E28C79D-F79C-45BE-A16C-43678AD165E9@vmware.com> <20211218030509.GA1432915@nvidia.com> <5C0A673F-8326-4484-B976-DA844298DB29@vmware.com> In-Reply-To: <5C0A673F-8326-4484-B976-DA844298DB29@vmware.com> From: Linus Torvalds Date: Fri, 17 Dec 2021 19:38:39 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v1 06/11] mm: support GUP-triggered unsharing via FAULT_FLAG_UNSHARE (!hugetlb) To: Nadav Amit Cc: Jason Gunthorpe , David Hildenbrand , Linux Kernel Mailing List , Andrew Morton , Hugh Dickins , David Rientjes , Shakeel Butt , John Hubbard , Mike Kravetz , Mike Rapoport , Yang Shi , "Kirill A . Shutemov" , Matthew Wilcox , Vlastimil Babka , Jann Horn , Michal Hocko , Rik van Riel , Roman Gushchin , Andrea Arcangeli , Peter Xu , Donald Dutile , Christoph Hellwig , Oleg Nesterov , Jan Kara , Linux-MM , "open list:KERNEL SELFTEST FRAMEWORK" , "open list:DOCUMENTATION" Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: AEB4C18003A X-Stat-Signature: usnxhmdu5fc4drxqrxmhoht9o9tj5tot Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b="AAZ+me/h"; dmarc=none; spf=pass (imf24.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.208.44 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org X-HE-Tag: 1639798744-387515 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: On Fri, Dec 17, 2021 at 7:30 PM Nadav Amit wrote: > > In such a case, I do think it makes sense to fail uffd-wp (when > page_count() > 1), and in a prototype I am working on I do something > like that. Ack. If uddf-wp finds a page that is pinned, just skip it as not write-protectable. Because some of the pinners might be writing to it, of course - just not through the page tables. So that sounds like the right thing to do. I _think_ we discussed this the last time this came up. I have some dim memory of that. Jason, ring a bell? Linus