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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.googlemail.com with ESMTPSA id r19-20020a17090638d300b006d6e4fc047bsm5886872ejd.11.2022.03.08.04.17.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Mar 2022 04:17:04 -0800 (PST) Sender: Paolo Bonzini Message-ID: <800a68f8-fbe0-5980-4290-bdc0ed4d05bd@redhat.com> Date: Tue, 8 Mar 2022 13:17:02 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH v4 01/12] mm/shmem: Introduce F_SEAL_INACCESSIBLE Content-Language: en-US To: Chao Peng , Andy Lutomirski Cc: Steven Price , kvm list , Linux Kernel Mailing List , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, qemu-devel@nongnu.org, Linux API , Jonathan Corbet , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , the arch/x86 maintainers , "H. Peter Anvin" , Hugh Dickins , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Yu Zhang , "Kirill A. Shutemov" , "Nakajima, Jun" , Dave Hansen , Andi Kleen , David Hildenbrand References: <20220118132121.31388-1-chao.p.peng@linux.intel.com> <20220118132121.31388-2-chao.p.peng@linux.intel.com> <619547ad-de96-1be9-036b-a7b4e99b09a6@kernel.org> <20220217130631.GB32679@chaop.bj.intel.com> <2ca78dcb-61d9-4c9d-baa9-955b6f4298bb@www.fastmail.com> <20220223114935.GA53733@chaop.bj.intel.com> <71a06402-6743-bfd2-bbd4-997f8e256554@arm.com> <7cc65bbd-e323-eabb-c576-b5656a3355ac@kernel.org> <20220307132602.GA58690@chaop.bj.intel.com> From: Paolo Bonzini In-Reply-To: <20220307132602.GA58690@chaop.bj.intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/7/22 14:26, Chao Peng wrote: >> In pseudo-Rust, this is the difference between: >> >> fn convert_to_private(in: &mut Memfd) >> >> and >> >> fn convert_to_private(in: Memfd) -> PrivateMemoryFd >> >> This doesn't map particularly nicely to the kernel, though. > I understand this Rust semantics and the difficulty to handle races. > Probably we should not expose F_SEAL_INACCESSIBLE to userspace, instead > we can use a new in-kernel flag to indicate the same thing. That flag > should be set only when the memfd is created with MFD_INACCESSIBLE. Yes, I like this. Paolo