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[209.85.128.51]) by smtp.gmail.com with ESMTPSA id b7sm5878266edj.24.2021.12.19.14.12.31 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 19 Dec 2021 14:12:31 -0800 (PST) Received: by mail-wm1-f51.google.com with SMTP id p27-20020a05600c1d9b00b0033bf8532855so5462296wms.3 for ; Sun, 19 Dec 2021 14:12:31 -0800 (PST) X-Received: by 2002:a05:600c:1e01:: with SMTP id ay1mr9481320wmb.152.1639951940498; Sun, 19 Dec 2021 14:12:20 -0800 (PST) MIME-Version: 1.0 References: <4D97206A-3B32-4818-9980-8F24BC57E289@vmware.com> <5A7D771C-FF95-465E-95F6-CD249FE28381@vmware.com> In-Reply-To: From: Linus Torvalds Date: Sun, 19 Dec 2021 14:12:04 -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: Matthew Wilcox Cc: David Hildenbrand , Nadav Amit , Jason Gunthorpe , Linux Kernel Mailing List , Andrew Morton , Hugh Dickins , David Rientjes , Shakeel Butt , John Hubbard , Mike Kravetz , Mike Rapoport , Yang Shi , "Kirill A . Shutemov" , 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" Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=NdJgcvEj; dmarc=none; spf=pass (imf09.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.208.54 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 21D7A140035 X-Stat-Signature: a8zqjfwkdqgbq45fsfsfh15h1gcm54gm X-HE-Tag: 1639951948-747498 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 Sun, Dec 19, 2021 at 2:02 PM Matthew Wilcox wrote: > > I'd like to get rid of ->mapcount for file pages too. And those are > definitely never mapped in the majority of cases. Fair enough. You'd probably be better off checking "is this mapping mapped" though. Because otherwise you have to get the page lock to serialize each page. Linus