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([2001:b07:6468:f312:9af8:e5f5:7516:fa89]) by smtp.googlemail.com with ESMTPSA id b11-20020a17090630cb00b0072b36cbcdaasm1809391ejb.92.2022.08.05.10.55.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 05 Aug 2022 10:55:42 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <472207cf-ff71-563b-7b66-0c7bea9ea8ad@redhat.com> Date: Fri, 5 Aug 2022 19:55:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v7 01/14] mm: Add F_SEAL_AUTO_ALLOCATE seal to memfd Content-Language: en-US To: David Hildenbrand , Chao Peng , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-doc@vger.kernel.org, qemu-devel@nongnu.org, linux-kselftest@vger.kernel.org Cc: Jonathan Corbet , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , Hugh Dickins , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Shuah Khan , Mike Rapoport , Steven Price , "Maciej S . Szmigiero" , Vlastimil Babka , Vishal Annapurve , Yu Zhang , "Kirill A . Shutemov" , luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com, aarcange@redhat.com, ddutile@redhat.com, dhildenb@redhat.com, Quentin Perret , Michael Roth , mhocko@suse.com, Muchun Song References: <20220706082016.2603916-1-chao.p.peng@linux.intel.com> <20220706082016.2603916-2-chao.p.peng@linux.intel.com> From: Paolo Bonzini In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On 7/21/22 11:44, David Hildenbrand wrote: > > Also, I*think* you can place pages via userfaultfd into shmem. Not > sure if that would count "auto alloc", but it would certainly bypass > fallocate(). Yeah, userfaultfd_register would probably have to forbid this for F_SEAL_AUTO_ALLOCATE vmas. Maybe the memfile_node can be reused for this, adding a new MEMFILE_F_NO_AUTO_ALLOCATE flags? Then userfault_register would do something like memfile_node_get_flags(vma->vm_file) and check the result. This means moving this patch later, after "mm: Introduce memfile_notifier". Thanks, Paolo