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[2003:cb:c735:f200:cb49:cb8f:88fc:9446]) by smtp.gmail.com with ESMTPSA id j6-20020a5d6046000000b003259b068ba6sm7972412wrt.7.2023.10.02.07.42.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 Oct 2023 07:42:51 -0700 (PDT) Message-ID: <27f177c9-1035-3277-cd62-dc81c12acec4@redhat.com> Date: Mon, 2 Oct 2023 16:42:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH v2 1/3] userfaultfd: UFFDIO_REMAP: rmap preparation 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: <20230923013148.1390521-1-surenb@google.com> <20230923013148.1390521-2-surenb@google.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230923013148.1390521-2-surenb@google.com> 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 X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: E4F40140008 X-Stat-Signature: mpjtzgpw65dkgbukpggkb13bwrzgsfos X-Rspam-User: X-HE-Tag: 1696257776-594049 X-HE-Meta: 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 MENN8vHv fboXylTiCOwfqIzGqJ449A79Ifkp25Q5l9qZ69Fb877PcO0xUGyddtrAWrx/xidAHrVYjky5GlypYvRH1miJcC0fA5uHBrpu6IgLCk0cgN2OgKdCXE3eTmZt1iw13bwiC0Rxo0Vhyw/2zyYzD2Zm+o9/Bho+nu/Lg2BghMAOO1bvnCHKDRn1d2v4p+XLlrUXVOxDQI9YeF+jbY7ix+Jm5zaznImUGpsuXI4HNTt+yEdoGzJg8bBsRGgdG7ZGQhTqDlotBEViHekdpBJGKlOj3T2YxL/SPQp1XBr5a0thN69DPsdWso0RlleK8TU0H2Zte9PptgH4aWrHdsnWRiLKg7sxVUvSgyFiMFyHJIGPk2kbzt5gV9d5+g1qo+mNQSpPKpkSqoYke74hx261+flvHmemIFjfXBgejDlA8D9zs7wBCukCj/IGPYQxjGTCJVWFMDXI5AFHEEKJrcqbti3DHAqnZ4KPKYkWuU4mx X-Bogosity: Ham, tests=bogofilter, spamicity=0.000199, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 23.09.23 03:31, Suren Baghdasaryan wrote: > From: Andrea Arcangeli > > As far as the rmap code is concerned, UFFDIO_REMAP only alters the > page->mapping and page->index. It does it while holding the page > lock. However folio_referenced() is doing rmap walks without taking the > folio lock first, so folio_lock_anon_vma_read() must be updated to > re-check that the folio->mapping didn't change after we obtained the > anon_vma read lock. I'm curious: why don't we need this for existing users of page_move_anon_rmap()? What's special about UFFDIO_REMAP? -- Cheers, David / dhildenb