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[209.85.221.52]) by smtp.gmail.com with ESMTPSA id d2sm1109363ejo.13.2021.08.12.11.21.47 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Aug 2021 11:21:49 -0700 (PDT) Received: by mail-wr1-f52.google.com with SMTP id h13so9589782wrp.1 for ; Thu, 12 Aug 2021 11:21:47 -0700 (PDT) X-Received: by 2002:a2e:944c:: with SMTP id o12mr3785844ljh.411.1628792497006; Thu, 12 Aug 2021 11:21:37 -0700 (PDT) MIME-Version: 1.0 References: <20210812084348.6521-1-david@redhat.com> <87o8a2d0wf.fsf@disp2133> <60db2e61-6b00-44fa-b718-e4361fcc238c@www.fastmail.com> <87lf56bllc.fsf@disp2133> <87lf56edgz.fsf@oldenburg.str.redhat.com> In-Reply-To: <87lf56edgz.fsf@oldenburg.str.redhat.com> From: Linus Torvalds Date: Thu, 12 Aug 2021 08:21:20 -1000 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v1 0/7] Remove in-tree usage of MAP_DENYWRITE To: Florian Weimer Cc: "Eric W. Biederman" , Andy Lutomirski , David Hildenbrand , Linux Kernel Mailing List , Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Al Viro , Alexey Dobriyan , Steven Rostedt , "Peter Zijlstra (Intel)" , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Petr Mladek , Sergey Senozhatsky , Andy Shevchenko , Rasmus Villemoes , Kees Cook , Greg Ungerer , Geert Uytterhoeven , Mike Rapoport , Vlastimil Babka , Vincenzo Frascino , Chinwen Chang , Michel Lespinasse , Catalin Marinas , "Matthew Wilcox (Oracle)" , Huang Ying , Jann Horn , Feng Tang , Kevin Brodsky , Michael Ellerman , Shawn Anastasio , Steven Price , Nicholas Piggin , Christian Brauner , Jens Axboe , Gabriel Krisman Bertazi , Peter Xu , Suren Baghdasaryan , Shakeel Butt , Marco Elver , Daniel Jordan , Nicolas Viennot , Thomas Cedeno , Collin Fijalkovich , Michal Hocko , Miklos Szeredi , Chengguang Xu , =?UTF-8?Q?Christian_K=C3=B6nig?= , linux-unionfs@vger.kernel.org, Linux API , "the arch/x86 maintainers" , linux-fsdevel , Linux-MM Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org On Thu, Aug 12, 2021 at 8:16 AM Florian Weimer wrote: > > I think this is called MAP_COPY: > > Please don't even consider the crazy notions that GNU Hurd did. It's a fundamental design mistake. The Hurd VM was horrendous, and MAP_COPY was a prime example of the kinds of horrors it had. I'm not sure how much of the mis-designs were due to Hurd, and how much of it due to Mach 3. But please don't point to Hurd VM documentation except possibly to warn people. We want people to _forget_ those mistakes, not repeat them. Linus