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[2003:cb:c738:1900:b6ea:5b9:62c0:34e]) by smtp.gmail.com with ESMTPSA id c1-20020adfa301000000b00323287186aasm8094491wrb.32.2023.10.23.08.53.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Oct 2023 08:53:25 -0700 (PDT) Message-ID: <045c35ba-7872-40a7-bd86-e37771076b88@redhat.com> Date: Mon, 23 Oct 2023 17:53:23 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/3] userfaultfd: UFFDIO_MOVE uABI From: David Hildenbrand To: Suren Baghdasaryan , akpm@linux-foundation.org Cc: viro@zeniv.linux.org.uk, brauner@kernel.org, shuah@kernel.org, aarcange@redhat.com, lokeshgidra@google.com, peterx@redhat.com, hughd@google.com, mhocko@suse.com, axelrasmussen@google.com, rppt@kernel.org, willy@infradead.org, Liam.Howlett@oracle.com, jannh@google.com, zhangpeng362@huawei.com, bgeffon@google.com, kaleshsingh@google.com, ngeoffray@google.com, jdduke@google.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, kernel-team@android.com References: <20231009064230.2952396-1-surenb@google.com> <20231009064230.2952396-3-surenb@google.com> <721366d0-7909-45c9-ae49-f652c8369b9d@redhat.com> Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: DE45818000C X-Stat-Signature: u7nxsoord4ik51zyozyzoo5exx5oyjbu X-Rspam-User: X-HE-Tag: 1698076409-807640 X-HE-Meta: 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 mz/yYbjN 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 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: List-Subscribe: List-Unsubscribe: On 23.10.23 14:29, David Hildenbrand wrote: >> + >> + /* Only allow remapping if both are mlocked or both aren't */ >> + if ((src_vma->vm_flags & VM_LOCKED) != (dst_vma->vm_flags & VM_LOCKED)) >> + return -EINVAL; >> + >> + if (!(src_vma->vm_flags & VM_WRITE) || !(dst_vma->vm_flags & VM_WRITE)) >> + return -EINVAL; > > Why does one of both need VM_WRITE? If one really needs it, then the > destination (where we're moving stuff to). Just realized that we want both to be writable. If you have this in place, there is no need to use maybe*_mkwrite(), you can use the non-maybe variants. I recall that for UFFDIO_COPY we even support PROT_NONE VMAs, is there any reason why we want to have different semantics here? -- Cheers, David / dhildenb