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[209.85.208.43]) by smtp.gmail.com with ESMTPSA id p14-20020a170906a00e00b008b1b644c9fbsm2325714ejy.103.2023.03.04.11.02.53 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 04 Mar 2023 11:02:54 -0800 (PST) Received: by mail-ed1-f43.google.com with SMTP id j11so3514731edq.4 for ; Sat, 04 Mar 2023 11:02:53 -0800 (PST) X-Received: by 2002:a17:906:d041:b0:877:747d:4a82 with SMTP id bo1-20020a170906d04100b00877747d4a82mr2787706ejb.0.1677956573508; Sat, 04 Mar 2023 11:02:53 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Linus Torvalds Date: Sat, 4 Mar 2023 11:02:36 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 2/2] vfs: avoid duplicating creds in faccessat if possible To: Yury Norov Cc: Mateusz Guzik , Alexander Potapenko , Al Viro , Kees Cook , Eric Biggers , Christian Brauner , serge@hallyn.com, paul@paul-moore.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 3, 2023 at 9:51=E2=80=AFPM Yury Norov wr= ote: > > At that time you was OK with CONFIG_FORCE_NR_CPUS, only suggested to > hide it behind CONFIG_EXPERT: I think there was a mis-communication. I as violently *not* ok with that question at all. I think our Kconfig phase is really annoying and nasty, and we should not ask people questions that they don't know what they mean. So putting it behind EXPERT was a "at that point, the question is gone", and I'm ok with the config variable existing. But.. I am *not* ok with you then thinking that "oh, the config variable exists, so our default code generation can be complete crap". The kernel should do well by default. No amount of "but you could go into magic config variables and then force options that might be ok for embedded systems to make it generate ok code". I think it's completely crazy that the distros enable MAXSMP. But that's their choice. A *sane* distro should not do that, and then we limit the normal kernel to something sane like a couple of hundreds of CPUs rather than thousands of them (and the associated huge overhead). At that point, things like cpumap_clear() should be a couple of stores - not a call-out to a variable-sized memset(). Notice? Simple and understandable Kconfig questions like "do you *really* need to support thousands of CPU's" Not that FORCE_NR_CPUS that is _completely_ useless to any distribution and thus completely unacceptable as a regular question. See the difference? Linus