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Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , linux-fsdevel@vger.kernel.org Subject: Re: [RFC PATCH 3/6] mm: nommu: fix an issue on map request to /dev/zero Message-ID: References: <20260813063401.1786548-1-thehajime@gmail.com> <20260813063401.1786548-4-thehajime@gmail.com> <2026081355-remold-sterility-84f9@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: BDF1240008 X-Rspamd-Server: rspam10 X-Rspam-User: X-Stat-Signature: k9p1kt1ox7imo5th9sb6zhp36sa8x6a8 X-HE-Tag: 1786627799-845669 X-HE-Meta: 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 xtCs0qF0 PH9hoaXfN0n3Ulbpe1CUFZBmvXUckpRZfG9rYXeIw5+SU9jh9rkt4uJ2e7YSTY6PZqyPKcshn3d8Jy0G0fcSpnfoeno87bjZRHBBL4HstIa9bJyhV+MCvZoDDwaVc2DZTfhAe+KQFvNkoXGOAShNbR8UjjPwiyHyDU5g3owWIg4iGmVKGOK9NYnRhP9bmaDLOounQZbUt1U3BPQcIM/lqc7f7TTcGh7DQfZGBnhhjngoAU0m8EYNa3fBrwzIpU2gL0uLXwB20JEDJX13Ai2K4lbekce6TiaduJHP4d53JaEdse7s1GJJonNktcWBZVg9+gPn1xOR8xHuKbpst3e5B6OSAhg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Aug 13, 2026 at 09:43:37PM +0900, Daniel Palmer wrote: > Hi Greg, > > On Thu, 13 Aug 2026 at 21:26, Greg Kroah-Hartman > wrote: > > > Given the age of this issue, I don't think anyone uses no-mmu systems > > anymore :( > > There are a few of us using it for hobby stuff[0][1] and there are > apparently people using it for actual commercial stuff. > There was a session about this at LPC 2025... > > One of the big problems for nommu seems to be that everyone is > convinced it is completely unused and totally broken. :) No, the issue is that nobody seems to do any testing or contribute any code aside from at least Hajime (thanks Haijme :), and possibly others (forgive me if I am missing people's names here!) There's been situtions where nommu has been broken for a year and _nobody noticed_. And yet whenever nommu comes up people always seem to pop up and say how important it is, then mention a talk etc. Well if it's important, test it. Test the tip kernel. Report bugs. Contribute code. Any or all of it :) Meanwhile we in mm have to _constantly_ fix stuff up in nommu because it's a total mess and has real maintenance overhead. Having to account for legacy systems that make no sense in 2026 when you're trying to make improvements to systems people use, or not being able to do certain things, really grates after a while. I mean if you don't believe me git log mm/nommu.c. This overhead reason is why I now co-maintain it. So I'm honestly a bit tired of people popping up when the whole 'why nommu' thing comes up, then disappearing when there's work to be done. In general - it's not really for those not doing the work to dictate terms to those who do, IMO. So while I appreciate you confirming there are users (yes we know :) frankly that's not the question. The question is - why isn't a downstream kernel enough for you? Last time I brought this up I basically got radio silence, a couple times before that I was told 'nommu has no maintenance overhead and is perfectly good code and we have products' by somebody who contributes little to nothing in terms of code and nothing no testing. So bah humbug. AFAIC it needs to go and we should never have allowed risc v to add a new nommu arch. > > Cheers, > > Daniel > > 0 - Really good example(s) of the 68000 port > https://github.com/crmaykish/mackerel-68k > 1 - https://github.com/LinuxMD/linuxmd my version of the 68000 code > with devicetree like those fancy ARM things running on a sega > megadrive. -- Cheers, Lorenzo