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Mon, 23 Oct 2023 12:01:43 -0700 (PDT) MIME-Version: 1.0 References: <20231009064230.2952396-1-surenb@google.com> <20231009064230.2952396-3-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Mon, 23 Oct 2023 12:01:32 -0700 Message-ID: Subject: Re: [PATCH v3 2/3] userfaultfd: UFFDIO_MOVE uABI To: Peter Xu Cc: akpm@linux-foundation.org, viro@zeniv.linux.org.uk, brauner@kernel.org, shuah@kernel.org, aarcange@redhat.com, lokeshgidra@google.com, david@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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 4A2AA1C0033 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: e7tqsebx1a3duzei656t4jyh7tnrxfkw X-HE-Tag: 1698087705-604642 X-HE-Meta: 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 9GXsSKHJ VwYOn/HG961ILYcmh3L84w0IsxEdxOgnzJWXcc0/ecIYI/b4zMPq064LeQycupDPJnYQvk84ptMqcgNwd6y3vfCgwaD3381MVRT5qNfKi0CqvTS7OkPCIwraiWYZL9XPrvg1xfnJi6fA5xF7Wm+iVHLhyFo6GOZjPZChrmJj9YO1Tg6zOYYw1ZEBlrw0fQnJ+f1D8jMQmwvhfiELmHpS6n7gRTDJkZr+Z3FuJ1LiqzSxrolLWNDE3SL8X2x1CbMAHueHslRqcMTlpxWBkljC1KAHLODGXvixLhZViDKoXxLmMPZY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000558, 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 Mon, Oct 23, 2023 at 11:37=E2=80=AFAM Peter Xu wrote= : > > On Mon, Oct 23, 2023 at 10:43:49AM -0700, Suren Baghdasaryan wrote: > > > Maybe we should follow what it does with mremap()? Then your current= code > > > is fine. Maybe that's the better start. > > > > I think that was the original intention, basically treating remapping > > as a write operation. Maybe I should add a comment here to make it > > more clear? > > Please avoid mention "emulate as a write" - this is not a write, e.g., we > move a swap entry over without faulting in the page. We also keep the pa= ge > states, e.g. on hotness. A write will change all of that. Understood. > > Now rethinking with the recently merged WP_ASYNC: we ignore uffd-wp, whic= h > means dirty from uffd-wp async tracking POV, that matches with soft-dirty > always set. Looks all good. > > Perhaps something like "Follow mremap() behavior; ignore uffd-wp for now" > should work? Sounds good. Will add in the next version. Thanks! > > -- > Peter Xu >