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[2003:cb:c708:db00:6510:da8d:df40:abbb]) by smtp.gmail.com with ESMTPSA id n10-20020a5d420a000000b0023682011c1dsm9563940wrq.104.2022.11.08.01.29.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Nov 2022 01:29:19 -0800 (PST) Message-ID: Date: Tue, 8 Nov 2022 10:29:17 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.0 Subject: Re: [PATCH RFC 00/19] mm/gup: remove FOLL_FORCE usage from drivers (reliable R/O long-term pinning) To: Linus Torvalds Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, linux-kselftest@vger.kernel.org, Andrew Morton , Jason Gunthorpe , John Hubbard , Peter Xu , Greg Kroah-Hartman , Andrea Arcangeli , Hugh Dickins , Nadav Amit , Vlastimil Babka , Matthew Wilcox , Mike Kravetz , Muchun Song , Lucas Stach , David Airlie , Oded Gabbay , Arnd Bergmann References: <20221107161740.144456-1-david@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1667899770; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=G/IvXa3Gtc42ocSwbE6e2PTXEI1xHOCM/WDymiGQVjk=; b=uhvynL5oMa6XM3AClcb87WSYdVLqGp/k35fFPHie0MEvwNpKoTSWlF9f5uTDw7a+xfEnhk L8XdKVKBVNg3AlWoI90+7CHwKgtUk3N5LpYYft4ZJFRNZBONE3dKKR9Riq77jeaY4gpU2u BGn4IZ7p/c3XyjowVDJKxEHQqPNcmCc= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=VHE7BTJ1; spf=pass (imf21.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1667899770; a=rsa-sha256; cv=none; b=fkTatQBjWC6dMQrTwSGJ15cVbmfjvSX29aTSe57axXuLCcMQ+4AaOCW45lY79Jd7LZ4RZ+ Mjn1UqTeq/XTRf+pj2zeXgu9tdTdLFxS5qZ4Vj01cvTvufceFX6iXYoFZWXweAeyXHrIRz yi/DkmS4uWIO1y75s9LbZM6BR97qBXo= Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=VHE7BTJ1; spf=pass (imf21.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: A26D71C000A X-Stat-Signature: pxk5pbnkgt1c3a56zeise7ct8e8ar3hu X-HE-Tag: 1667899770-944834 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 07.11.22 18:27, Linus Torvalds wrote: > On Mon, Nov 7, 2022 at 8:18 AM David Hildenbrand wrote: >> >> So instead, make R/O long-term pinning work as expected, by breaking COW >> in a COW mapping early, such that we can remove any FOLL_FORCE usage from >> drivers. > > Nothing makes me unhappy from a quick scan through these patches. > > And I'd really love to just have this long saga ended, and FOLL_FORCE > finally relegated to purely ptrace accesses. > > So an enthusiastic Ack from me. Thanks Linus! My hope is that we can remove it from all drivers and not have to leave it in for some corner cases; so far it looks promising. -- Thanks, David / dhildenb