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Mon, 23 Oct 2023 10:33:53 -0700 (PDT) MIME-Version: 1.0 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> <96899aa6-700b-41b9-ab11-2cae48d75549@redhat.com> In-Reply-To: <96899aa6-700b-41b9-ab11-2cae48d75549@redhat.com> From: Suren Baghdasaryan Date: Mon, 23 Oct 2023 10:33:40 -0700 Message-ID: Subject: Re: [PATCH v3 2/3] userfaultfd: UFFDIO_MOVE uABI To: David Hildenbrand Cc: Peter Xu , 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 5E17C40012 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: 3a1g5gqr7u3zimc4a8ybf9nnnw9sqogg X-HE-Tag: 1698082435-903573 X-HE-Meta: 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 ydae/nSo z+vpFL+ZXedrNchkJYGXZQYSaFo+lMrCL3BvW9iAeyPxr/BxRW8Essrj0KSShlfjyHo6byU4iJuPh0TXTmohj56Yr5ehem0k43DwGOO+9BSlI7AJG2RoIHZmyYP9ufhp5/eqCUCQ5egpSMw+6i972hwkinVrHL6q69vhNX7a+kW1Xp4PP/xNc72A40w0QvoeDeKbDHbIznVwMkRQCUN07rdayl2gFZQSY+f/i2g6j5vmwbkBf+SQuZRDFNnPrRf+Fpw0h4CFQ8W7QIroffWPhLAweT3CkRSJP+c18SnlF4AfzWsU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000595, 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 9:36=E2=80=AFAM David Hildenbrand wrote: > > 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, co= uld > >>> 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 stil= l > >> prefer to rename it, which I'm totally fine with. > >> > >> The 2nd question is wrong from your interpretation. That's not my poi= nt, > >> at least not starting from a few replies already. What I was asking f= or is > >> why such page movement between mm is dangerous. I don't think I get s= olid > >> answers even until now. > >> > >> Noticing "memcg is missing" is not an argument for "cross-mm is danger= ous", > >> it's a review comment. Suren can address that. > >> > >> You'll propose a new feature that may tag an mm is not an argument eit= her, > >> 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. A= nyone > >> 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] Thanks for the discussion, folks! I think posting the single-mm first and then following up with cross-mm and its test would help us move forward. That will provide functionality that is needed today quickly without unnecessary distractions and will give us more time to discuss cross-mm support. Also we will be able to test single-mm in isolation and make it more solid before moving onto cross-mm. I'll try to post the next version sometime this week. Thanks, Suren. > > -- > Cheers, > > David / dhildenb >