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[2003:cb:c738:1900:b6ea:5b9:62c0:34e]) by smtp.gmail.com with ESMTPSA id x22-20020a05600c189600b004083a105f27sm14361777wmp.26.2023.10.23.09.36.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Oct 2023 09:36:18 -0700 (PDT) Message-ID: <96899aa6-700b-41b9-ab11-2cae48d75549@redhat.com> Date: Mon, 23 Oct 2023 18:36:16 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/3] userfaultfd: UFFDIO_MOVE uABI From: David Hildenbrand To: Peter Xu Cc: Suren Baghdasaryan , Lokesh Gidra , akpm@linux-foundation.org, viro@zeniv.linux.org.uk, brauner@kernel.org, shuah@kernel.org, aarcange@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: <12588295-2616-eb11-43d2-96a3c62bd181@redhat.com> <8d187891-f131-4912-82d8-13112125b210@redhat.com> <81cf0943-e258-494c-812a-0c00b11cf807@redhat.com> <1156ad46-1952-4892-8092-bfbb8588c3f3@redhat.com> Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: BBB174000A X-Stat-Signature: e9gdn6yt43kz6mji15nhne4t3t9jgmg4 X-HE-Tag: 1698078992-852435 X-HE-Meta: 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 h8rSWDRV zd2s0Ru+jCbfET+Y/7tiqcIwbFfmfi4kUvY5FSCLHsUJSGcySuZN5919nGbNWqp6DhDOt+GRlrVZR9IsYmCNUAtoVnmCBKxlLQ1LqllDaU+EteKEpTnbkLX38BkD2WW00F6MScUxD1ZpOt+2uOibIPbCkUGbHeJPari7Yj8mzIkdrF/4X8/1cnmFC2OIPaW0mFpxVxX3rPg756RJ1IPKFZd2ybW+pDKq1gXyRWiIou3hOg0za4kHPWGVTRKSUFOIMV01LH7I5CQ8mnoKXHNPeQN5oOc6+490CWPTHLTOHxquxiNlUdg40pEM81nVnEAm3r39FmPdaAZW5OUJMGVxGgPyTYM8CVBxgP5uCzTv+aXrDKcXQGpAlS7SCAMjzXl8/9NSi1tQ0G0tclMd14Vnd0eZWSa4EknRQy56CAitwRrY43nwv8E35Y3svs6NVMfcSYBJ9SDFKQzgH5PMMOX282HUR/Q== 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 14:03, David Hildenbrand wrote: > On 22.10.23 17:46, Peter Xu wrote: >> On Fri, Oct 20, 2023 at 07:16:19PM +0200, David Hildenbrand wrote: >>> These are rather the vibes I'm getting from Peter. "Why rename it, could >>> confuse people because the original patches are old", "Why exclude it if it >>> has been included in the original patches". Not the kind of reasoning I can >>> relate to when it comes to upstreaming some patches. >> >> You can't blame anyone if you misunderstood and biased the question. >> >> The first question is definitely valid, even until now. You guys still >> prefer to rename it, which I'm totally fine with. >> >> The 2nd question is wrong from your interpretation. That's not my point, >> at least not starting from a few replies already. What I was asking for is >> why such page movement between mm is dangerous. I don't think I get solid >> answers even until now. >> >> Noticing "memcg is missing" is not an argument for "cross-mm is dangerous", >> it's a review comment. Suren can address that. >> >> You'll propose a new feature that may tag an mm is not an argument either, >> if it's not merged yet. We can also address that depending on what it is, >> also on which lands earlier. >> >> It'll be good to discuss these details even in a single-mm support. Anyone >> would like to add that can already refer to discussion in this thread. >> >> I hope I'm clear. >> > > I said everything I had to say, go read what I wrote. Re-read your message after flying over first couple of paragraphs previously a bit quick too quickly (can easily happen when I'm told that I misunderstand questions and read them in a "biased" way). I'll happy to discuss cross-mm support once we actually need it. I just don't see the need to spend any energy on that right now, without any users on the horizon. [(a) I didn't blame anybody, I said that I don't understand the reasoning. (b) I hope I made it clear that this is added complexity (and not just currently dangerous) and so far I haven't heard a compelling argument why we should do any of that or even spend our time discussing that. (c) I never used "memcg is missing" as an argument for "cross-mm is dangerous", all about added complexity without actual users. (d) "it easily shows that there are cases where this will require extra work -- without any current benefits" -- is IMHO a perfectly fine argument against complexity that currently nobody needs] -- Cheers, David / dhildenb