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[99.254.144.39]) by smtp.gmail.com with ESMTPSA id n17-20020a0ce491000000b0065af657de01sm4900886qvl.115.2023.09.28.09.28.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Sep 2023 09:28:54 -0700 (PDT) Date: Thu, 28 Sep 2023 12:28:51 -0400 From: Peter Xu To: Suren Baghdasaryan Cc: David Hildenbrand , Jann Horn , akpm@linux-foundation.org, viro@zeniv.linux.org.uk, brauner@kernel.org, shuah@kernel.org, aarcange@redhat.com, lokeshgidra@google.com, hughd@google.com, mhocko@suse.com, axelrasmussen@google.com, rppt@kernel.org, willy@infradead.org, Liam.Howlett@oracle.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 Subject: Re: [PATCH v2 2/3] userfaultfd: UFFDIO_REMAP uABI Message-ID: References: <20230923013148.1390521-1-surenb@google.com> <20230923013148.1390521-3-surenb@google.com> <03f95e90-82bd-6ee2-7c0d-d4dc5d3e15ee@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Queue-Id: 07D3640017 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: zfsnwpj8ynh169aujtbozy4xkrnggoff X-HE-Tag: 1695918537-493349 X-HE-Meta: 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 6kUODf41 txyXfOX9hMhYNUlCRBExFg81EDmqsInDOY2apCAKUM9a8dRHJxp5dDmomYgpdEaWnTuASffNgS9SpDJKWRYA4N689fmvO4WKxecTNnb8UfV59p3hKQf5JqX10ViVDmRneh/watgoG3ge707l235KmWPwdF9cV52wcCLGTMibrQ/kIRzOkMnovASV4VoliMpHR/wgkI3IflmVYD8swnim+6tZMuY5Fg4ys9bih3xsIxAGOa/yhxSOwF3MOzyxP92dSZEMU8n0Xrmn024+fjfOrb6bt9bf8DApXx+k/vHsP5bFYjk9ii+TUrsXKdUZVFDfEjvHz+mMMSRMMpXOyu2jT32JFOdj17/cEPRtFTwFoeS4bMsz9/BSHxDZg0En0TX4EL2siRSFktbXucBWdyaCA5EMlmLaGpK/MEdp4 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Sep 27, 2023 at 11:25:22AM -0700, Suren Baghdasaryan wrote: > For uffd_remap can_change_pte_writable() would fail it VM_WRITE is not > set, but we want remapping to work for RO memory as well. Is there an use case that we want remap to work on RO? The thing is, either removing a page or installing a new one with valid content imply VM_WRITE to me on either side.. Thanks, -- Peter Xu